Title of Invention	CAM CHAIN TENSIONER SYSTEM FOR INTERNAL COMBUSTION ENGINE
Abstract	[Object] To provide a cam chain tensioner system having a simple structure with a small number of components and being manufactured at a low cost. [Solving Means] In a cam chain tensioner system for an internal combustion engine, a guide hole 37 into which a push rod 36 is fitted is formed at a lower portion of a crankcase 2L while opening at least upward. An oil reservoir 40, which is a concave portion being depressed downward and opening upward to a cam chain chamber 2C, is formed integrally in the crankcase 2L. The opening in the upper portion of the guide hole 37 faces the inside of the oil reservoir 40.

Title of Invention

CAM CHAIN TENSIONER SYSTEM FOR INTERNAL COMBUSTION ENGINE

Abstract

[Object] To provide a cam chain tensioner system having a simple structure with a small number of components and being manufactured at a low cost. [Solving Means] In a cam chain tensioner system for an internal combustion engine, a guide hole 37 into which a push rod 36 is fitted is formed at a lower portion of a crankcase 2L while opening at least upward. An oil reservoir 40, which is a concave portion being depressed downward and opening upward to a cam chain chamber 2C, is formed integrally in the crankcase 2L. The opening in the upper portion of the guide hole 37 faces the inside of the oil reservoir 40.

Full Text	[Document Name] Specification [Title of the Invention] CAM CHAIN TENSIONER SYSTEM FOR INTERNAL COMBUSTION ENGINE [Technical Field] [0001] The present invention relates to a tensioner system for applying a required tension to a cam chain that transmits a rotation of a crankshaft in an internal combustion engine to a valve system. [Background Art] [0002] An endless cam chain is looped between a drive sprocket, which is fitted on a crankshaft rotatably supported in a crankcase, and a driven sprocket, which is fitted on a camshaft of a valve system. The cam chain is pressed, at its side, by a cam chain tensioner system so as to be maintained in tension with no slack by a constant tension being applied thereto. [0003] A hydraulic cam chain tensioner system is configured as follows. A push rod that is in pressure contact with a pressing member for pressing a cam chain is advanceably and retreatably fitted into a guide cylinder, so that an oil chamber is formed in the guide cylinder. A control valve is provided which allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber. A compression spring is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. I That is, the push rod of the hydraulic cam chain tensioner system is capable of advancing but incapable of retreating. [0004] If the cam chain is elongated due to aging deterioration or the like, the urging force of the compression spring causes the push rod to advance and press the cam chain with the pressing member therebetween, thereby taking up the slack of the cam chain with a predetermined tension applied thereto. In this event, the control valve allows oil to flow into the oil chamber. If the push rod receives a reaction force from the cam chain, the control valve prevents the oil from flowing out, and thus establishes a locked state in which the push rod is inhibited from retreating. As a result, the cam chain is maintained at a predetermined tension. [0005] An example of the techniques for guiding the oil into the oil chamber in such a hydraulic cam chain tensioner system is to provide a dedicated oil passage. This technique, however, requires a complicated structure and thus is accompanied by cumbersome processes and a high manufacturing cost. Against this problem, there is another example configured so that an oil reservoir is formed in the opening portion in the upper end of the guide cylinder into which the push rod is fitted, so that the oil is caused to flow from the oil reservoir into the oil chamber in the guide cylinder (refer to, for example, Patent Document 1). [0006] [Patent Document 1] Japanese Patent No. 4035226 [0007] In Patent Document 1, an oil separator, which is a separate body from a crankcase, is fastened to a bottom wall of a cam chain chamber of the crankcase. The oil reservoir, which opens upward, and the guide cylinder, into which the push rod is fitted, are integrally formed in the oil separator. [Disclosure of the Invention] [Problems to be Solved by the Invention] [0008] Since the oil reservoir and the guide cylinder are integrally formed in the oil separator, the oil separator has a complicated shape and is not easy to manufacture. In addition, it is also necessary to form a space for housing the oil separator in the crankcase, and thus, the manufacture of the crankcase requires a large amount of man-hours and a high cost. The oil separator is a separate body from the crankcase, and thus increases the number of components including a fastening member for fastening the oil separator to the crankcase, leading to a complicated structure and an increase in cost. [0009] The present invention has been made in view of the above-described circumstances. An object of the present invention is to provide a cam chain tensioner system having a simple structure with a small number of components and being manufactured at a low cost. [Means for Solving the Problems] In order to achieve the above-described object, a first aspect of the present invention provides a cam chain tensioner system for an internal combustion engine. The cam chain tensioner system for an internal combustion engine includes: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. The cam chain tensioner system for an internal combustion engine always applies a predetermined tension to the cam chain. In the cam chain tensioner system for an internal combustion engine, the guide hole is formed in a lower portion of the crankcase while opening at least upward. An oil reservoir is formed integrally in the ^ crankcase. The oil reservoir is a concave portion that is depressed downward and opens upward to the cam chain chamber. The upper opening of the guide hole faces the inside of the oil reservoir. A second aspect of the present invention provides the following characteristics in the cam chain tensioner system Eor an internal combustion engine according to the first aspect. Specifically, the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by front and rear guide walls constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir. The push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls. The left and right openings of the push rod between the front and rear guide walls communicate with the oil reservoir. [0012] A third aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of the first and second aspects. Specifically, in the cam chain tensioner system for an internal combustion engine, an oil guide rib is formed to be inclined below the drive sprocket. The oil guide rib protrudes from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft. In addition, the oil reservoir is located below a lower end of the oil guide rib. [0013] A fourth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of the first to third aspects. Specifically, the oil reservoir has a front oil reservoir and a rear oil reservoir that are formed side by side in a vehicle-body front-rear direction. In addition, the front oil reservoir and the rear oil reservoir conununicate with each other. [0014] A fifth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the fourth aspect. Specifically, the front oil reservoir is located below the lower end of the oil guide rib. A front wall of the front oil reservoir protrudes forward. A bottom surface of the front oil reservoir and a bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear. The upper opening of the guide hole faces the rear oil reservoir. [0015] A sixth aspect of the present invention provides the following characteristic in the cam chain tensioner system for an internal combustion engine according to the fifth aspect. Specifically, the crankcase has an oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir. [0016] A seventh aspect of the present invention provides the following characteristic in the cam chain tensioner system for an internal combustion engine according to any one of the first to sixth aspect. Specifically, one side wall, in a vehicle-body width direction, of the oil reservoir formed in the cranlccase is formed with a contact of a sidewall plate that is a separate body. [0017] An eighth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of the first to seventh aspects. Specifically, the guide hole opens in a side wall of the crankcase, and is formed to be inclined so that a lower end, which is closed by a tensioner bolt, of the guide hole is located forward, in the vehicle body, of an upper end of the guide hole. In addition, a drain bolt for closing a drain bolt hole formed in a bottom wall of the crankcase is provided below the tensioner bolt in a side view of the vehicle body. [0018] A ninth aspect of the present invention provides a cam chain tensioner system for an internal combustion engine. The cam chain tensioner system for an internal combustion engine includes: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. The cam chain tensioner system always applies a predetermined tension to the cam chain. In the cam chain tensioner system for an internal combustion engine, an oil reservoir is formed in a lower portion of the crankcase, and the upper opening of the guide hole faces the inside of the oil reservoir. In addition, the crankcase is partitioned by a partition wall into the cam chain chamber provided with the oil' reservoir and a transmission chamber located behind the cam chain chamber in a vehicle-body front-rear direction. Moreover, a communication opening is formed in a portion of the partition wall, the portion located obliquely upward of the oil reservoir. [0019] A tenth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the first to ninth aspects. Specifically, the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction. In addition, a cell motor and an intermediate gear are disposed in a front lower portion of the crankcase in which the crankshaft is pivotally supported. [0020] An eleventh aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the tenth aspect. Specifically, a cylinder protrudes from a ) front upper portion of the crankcase while being slightly inclined forward. In addition, an engine hanger attachment portion is formed on a front wall of the crankcase at a position below the cylinder and above the cell motor. [Effects of the Invention] [0021] In the cam chain tensioner system for an internal combustion engine according to the first aspect, the guide hole is formed in the lower portion of the crankcase while opening at least upward, and the oil reservoir, which is a concave portion being depressed downward and opening upward to the cam chain chamber, is formed integrally in the crankcase, and the upper opening of the guide hole faces the inside of the oil reservoir. Accordingly, oil is efficiently collected in the oil reservoir formed in the lower portion of the crankcase while opening upward. The oil thus pooled in the oil reservoir flows on the push rod from the upper opening of the guide hole so as to be guided to the lid portion of the push rod, and then is caused to flow into the oil chamber when the control valve is opened. Since the oil reservoir and the guide hole are integrally formed in the crankcase, it is possible to simplify the structure with a small number of components while eliminating the need of any fastener or the like, and thus to reduce the cost. [0022] In the cam chain tensioner system for an internal combustion engine according to the second aspect, the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by the front and rear guide walls constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir. The push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls. The left and right openings of the push rod between the front and rear guide walls coitmiunicate with the oil reservoir. Accordingly, it is possible to stably support the push rod with a simple structure. In addition, since the oil pooled in the oil reservoir is in contact with an outer peripheral surface of the push rod through the left and right openings between the front and rear guide walls, it is possible to cause the oil to flow on the push rod so as to be efficiently guided to the control valve. [0023] In the cam chain tensioner system for an internal combustion engine according to the third aspect, the oil guide rib is formed to be inclined below the drive sprocket, the oil guide rib protruding from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft, while the oil reservoir is located below the lower end of the oil guide rib. Accordingly, the oil guide rib receives oil dripping off the drive sprocket, the cam chain, and the like, as well as oil flowing down on the wall surface, on the cam chain chamber side, of the bearing wall, and then guides the oil to the oil reservoir. In this way, the oil can be efficiently collected in the oil chamber. [0024] In the cam chain tensioner system for an internal combustion engine according to the fourth aspect, the oil reservoir has the front oil reservoir and the rear oil reservoir that are formed side by side in the vehicle-body front-rear direction, and the front oil reservoir and the rear oil reservoir communicate with each other. Accordingly, it is possible to suppress, to a small level, the change in the level of oil pooled in the oil reservoir relative to the forward and rearward movements of the vehicle body, thus to reduce the amount of oil spilling out of the oil reservoir, and eventually to secure the required amount of oil reserved in the oil reservoir at any time. [0025] In the cam chain tensioner system for an internal combustion engine according to the fifth aspect, the front oil reservoir is located below the lower end of the oil guide rib. The front wall of the front oil reservoir protrudes forward. The bottom surface of the front oil reservoir and the bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear. The upper opening of the guide hole faces the rear oil reservoir. Accordingly, oil, which has been guide by the oil guide rib and then flowed down from the lower end thereof, is received by the front oil reservoir, so that the capacity of the oil reservoir is increased. In addition, the upper opening of the guide hole faces the rear oil reservoir, which is deep with the inclined bottom surface and thus has a large capacity for reserving oil. As a result, oil can be stably supplied to the oil chamber inside the guide hole. [0026] In the cam chain tensioner system for an internal combustion engine according to the sixth aspect, the crankcase has the oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir. Accordingly, the oil spilling out of the front oil reservoir flows forward beyond the front wall protruding forward, then flows downward, and directly enters the oil return passage. Consequently, the oil is smoothly returned to a bottom portion of the crankcase. [0027] In the cam chain tensioner system.for an internal combustion engine according to the seventh aspect, the one side wall, in the vehicle-body width direction, of the oil reservoir formed in the crankcase is formed with the contact of the sidewall plate, which is a separate body. Accordingly, the oil reservoir in the crankcase opens at its side, so that the crankcase is easy to cast, thus allowing a reduction in the manufacturing cost. [0028] In the cam chain tensioner system for an internal combustion engine according to the eighth aspect, the guide hole opens in the side wall of the crankcase, and is formed to be inclined so that the lower end, which is closed by the tensioner bolt, of the guide hole is located forward, in the vehicle body, of the upper end of the guide hole. In addition, the drain bolt for closing the drain bolt hole formed in the bottom wall of the crankcase is provided below the tensioner bolt in the side view of the vehicle body. The inclining of the guide hole makes it possible to achieve a compact structure in which the tensioner bolt for closing the lower end of the guide hole and the drain bolt for closing the drain bolt hole below the tensioner bolt are disposed close to each other. In addition, the positions respectively at which the tensioner bolt and the drain bolt are attached are displaced vertically from each other. Moreover, the drain bolt may be attached in a direction different from that of the tensioner bolt. For example, the tensioner bolt is attached obliquely upward while the drain bolt is vertically upward in a general manner. Accordingly, it is possible to avoid such a trouble that an unintended one of the tensioner bolt 46 and the drain bolt 55 is operated wrongly at maintenance. [0029] In the cam chain tensioner system for an internal combustion engine according to the ninth aspect, the oil reservoir is formed in the lower portion of the crankcase, while the upper opening of the guide hole faces the inside of the oil reservoir. In addition, the crankcase is partitioned by a partition wall into the cam chain chamber provided with the oil reservoir and a transmission chamber located behind the cam chain chamber in the vehicle-body front-rear direction. Moreover, the communication opening is formed in the portion, obliquely upward of the oil reservoir, of the partition wall. Despite such a simple structure having a small number of components, oil splashed in the transmission chamber flows into the cam chain chamber through the communication opening in the partition wall, and is thus splashed on the cam chain and supplied for lubrication as well as is efficiently collected in the oil reservoir located obliquely therebelow. [0030] In the cam chain tensioner system for an internal combustion engine according to the tenth aspect, the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction, and the cell motor and the intermediate gear are disposed in the front lower portion of the crankcase in which the crankshaft is pivotally supported. Accordingly, it is possible to lower the center of gravity of the vehicle body, and to dispose the cell motor and the intermediate gear by effectively utilizing an open space below and at the front of the crankshaft, so that an increase in size of the internal combustion engine is avoided. [0031] In the cam chain tensioner system for an internal combustion engine according to the eleventh aspect, the cylinder protrudes from the front upper portion of the crankcase while being slightly inclined forward, and the engine hanger attachment portion is formed on the front wall of the crankcase at the position below the cylinder and above the cell motor. Accordingly, it is possible to provide the engine hanger attachment portion by utilizing an open space between the cylinder and the cell motor therebelow, and also to stably suspend the internal combustion engine. [Best Mode for Carrying Out the Invention] Hereinbelow, an internal combustion engine 1 according to the present invention is a SOHC single-cylinder 4-stroke internal combustion engine. The internal combustion engine 1 is mounted on a motorcycle in such a manner that a crankshaft 10 is directed in a vehicle-body width direction with respect to a vehicle body. The crankshaft 10 of the internal combustion engine 1 is rotatably supported in a crankcase 2, and a transmission case 3 is formed integrally behind the crankcase 2, so that the crankcase 2 and the transmission case 3 constitute a power unit case together. [0033] Referring to Fig. 1, a cylinder block 4 and a cylinder head 5 are placed in this order on an obliquely upper portion of the crankcase 2, and are fastened together. A cylinder head cover 6 is placed on top of the cylinder head 5. The assembly of the cylinder block 4, the cylinder head 5, and the cylinder head cover 6 protrudes from the crankcase 2 while being slightly inclined forward. [0034] Referring to Fig. 2, the crankcase 2 is divided left and right into a left crankcase 2L and a right crankcase 2R, and the crankshaft 10 is rotatably supported by a bearing wall 2Lw of the left crankcase 2L and a bearing wall 2Rw of the right crankcase 2R respectively with main bearings 11, 11 interposed respectively therebetween. Crank webs lOw, lOw of the crankshaft 10 are located in a crank chamber 2S formed between the bearing walls 2Lw and 2Rw. Left and right crankshaft portions 10a, lOa of sides of the bearing walls 2Lw and 2Rw, respectively. The left and right crankshaft portions 10a, 10a are covered from outside by left and right case covers 7, 7, respectively. [0035] A drive sprocket 12 of a valve drive system is fitted on the left crankshaft portion 10a in a vicinity of the main bearing 11. An AC generator 13 is provided on the left end of the left crankshaft portion 10a. A driven gear 14 of a starter mechanism is fitted on the left crankshaft portion 10a between the drive sprocket 12 and the AC generator 13. [0036] A valve mechanism is constituted in the cylinder head 5. A camshaft 20, being directed in the vehicle-body width direction, is rotatably supported at the upper surface of the cylinder head 5 in such a manner as to be sandwiched by a camshaft holder 21. A driven sprocket 22 having a diameter substantially twice the diameter of the drive sprocket 12 of the valve drive system is fitted on the left end of the camshaft 20. [0037] A cam chain 23, which is an endless transmission chain is looped between the driven sprocket 22 fitted on the camshaft 20 and the drive sprocket 12 fitted on the crankshaft 10, so that the rotation of the crankshaft 10 is transmitted to the camshaft 20 while the rotational speed thereof is reduced to the half. The cam chain 23 is disposed in cam chain chambers 2C, 4C, and 5C respectively of the crankcase 2, the cylinder block 4, and the cylinder head 5. [0038] A guide roller 24 is rotatably supported in the cam chain chamber 4C of the cylinder block 4. The guide roller 24 has a diameter in a middle of the diameters of the drive sprocket 12 and the driven sprocket 22, and guides the rotational movement of the cam chain 23 at the front and rear sides. [0039] The cam chain chamber 2C of the left crankcase 2L constitutes a common space with an ACG chamber 7S in which the AC generator 13 is covered by the left case cover 7. The space surrounded by a peripheral wall 2Ls protruding to the left of the crankcase 2 near the left bearing wall 2Lw corresponds to the cam chain chamber 2C. A transmission chamber 3S formed at the rear of the crank chamber 2S is formed to bulge leftward to the rear of the cam chain chamber 2C. [0040] In the cam chain chamber 2C, a guide roller 25 is rotatably supported by the left bearing wall 2Lw at a position obliquely upward and forward of the drive sprocket 12. The guide roller 25 guides the rotational movement of the cam chain 23 at the front side. [0041] Referring to Fig. 3, a tensioner arm 31 of a cam chain tensioner system 30 is pivotally supported at the center thereof by a pivot bolt 32 so as to be swingably provided at the rear of the drive sprocket 12 in the cam chain chamber 2C. A tensioner roller 33 is rotatably supported at a distal end of an upward extending arm portion of the tensioner arm 31, while a contact end 31e is formed at a distal end of a downward extending arm portion of the tensioner arm 31. [0042] A push rod 36 of a tensioner lifter 35 is in contact with the contact end 31e of the tensioner arm 31 so as to urge the tensioner arm 31 with pressure. The tensioner roller 33 at the distal end of the upward extending arm portion thereby presses a rotationally moving portion of the cam chain 23 on the rear side so as to appropriately tension the cam chain 23. [0043] The tensioner lifter 35 is formed below the drive sprocket 12 fitted on the crankshaft 10 rotatably supported in the left crankcase 2L (refer to Figs. 1 and 2). Now, refer to Fig. 4, which is a perspective view of the left crankcase 2L, and Fig. 5, which is an enlarged side view of a chief part of the left crankcase 2L. A guide hole 37 is formed in an inclined portion, below a bearing circular hole llh (the drive sprocket 12), of the peripheral wall- 2Ls protruding leftward from the left bearing wall 2Lw of the left crankcase 2L. Specifically, the guide hole 37 is drilled obliquely in the inclined portion in such a manner that a lower portion, outside the peripheral wall 2Ls, of the guide hole 37 is located at the front of an upper portion, inside the peripheral wall 2Ls, of the guide hole 37. The' guide hall 37 penetrates from the cam chain chamber 2C to the outside. [0044] A portion, above the peripheral wall 2Ls, of the guide hole 37 is formed into an oil receiving portion 39, while a lower half portion of the guide hole 37 is formed into a guide cylinder portion 38 extending obliquely downward from the peripheral wall 2Ls. An opening end surface 38s at a lower end of the guide cylinder portion 38 is located at a slightly higher level than a lowermost bottom wall constituting an oil pan 2p which is a bottom portion of the crank chamber 2S. [0045] The oil receiving portion 39 constitutes an oil reservoir 40 (illustrated by broken line cross hatching in Figs. 5 and 6), which is a concave portion being depressed downward and opening upward. A bolt boss portion 39f is formed in a front-side wall portion, which protrudes forward, of the oil reservoir 40. A rear-side wall of the oil reservoir 40 is formed with' a rear guide wall 39r in such a manner that a rear inner surface of the guide hole 37 extends. A right-side wall of the oil reservoir 40 is formed by the left bearing wall 2Lw, while a left-side wall thereof is not formed, but instead, a sidewall plate 41 is affixed to the oil reservoir 40 so as to serve as the left¬side wall. [0046] The sidewall plate 41 is, as illustrated in Fig. 4, a plate member having a substantially triangular shape with an acute apex angle. One longer side, which is straight, of the sidewall plate 41 is referred to as an upper side 41a and is maintained horizontally in the front-rear direction. The other longer side, extending obliquely forward from the rear apex portion, of the sidewall plate 41 is referred to as a lower side 41b. A shorter side 41c on the front side of the sidewall plate 41 has a center portion being cut out so as to form a convex and concave contour. The sidewall plate 41 has an attachment hole 41h drilled therein at a position closer to the shorter side 41c. [0047] The sidewall plate 41 is brought into contact with a left side wall of the oil receiving portion 39. Then, a bolt 42 is inserted through the attachment hole 41h with a washer 4 3 interposed therebetween, and is screwed into a bolt hole of the bolt boss portion 39f of the oil receiving portion 39. In this way, the sidewall plate 41 is affixed to the oil receiving portion 39 so as to serve as the left¬side wall of the oil reservoir 40, [0048] A front guide wall 39c protrudes obliquely upward at a center portion of the oil reservoir 40 in the front-rear direction in such a manner that a front inner surface of the inclined guide hole 37 extends. The front guide wall 39c partitions the oil reservoir 40 into a front oil reservoir 40f and a rear oil reservoir 40r. Note that, there is a gap between the front guide wall 39c and the sidewall plate 41 constituting the left¬side wall; thus the front oil reservoir 40f and the rear oil reservoir 40r communicate with each other through the gap (refer to Fig. 6). [0049] The bolt boss portion 39f in the front wall portion of the front oil reservoir 40f protrudes forward, and the bottom surface of the front oil reservoir 40f and the bottom surface of the rear oil reservoir 40r are continuous with each other while being inclined obliquely downward to the rear. [0050] An upper opening of the guide hole 37 faces the rear oil reservoir 40r. The upper opening, which faces the inside of the rear oil reservoir 40r, of the guide hole 37 is formed to open upward as well as to left and right sides by the front guide wall 39c and the rear guide wall 39r constituting the upper portion of the guide hole 37, the front guide wall 39c and the rear guide wall 39r extending to the inside of the rear oil reservoir 40r. The left- and right-sides openings between the front and rear guide walls 39c and 39r communicate with the rear oil reservoir 40r (refer to Fig. 6) . [0051] The push rod 36 is fitted into the guide hole 37 through the upper opening thereof. The push rod 36 is slidably supported by being sandwiched at the front and rear sides thereof by the front and rear guide walls 39c and 39r protruding obliquely upward. Accordingly, the push rod 36 is stably supported over a long length thereof. In addition, since the left and right openings between the front and rear guide walls 39c and 39r face the rear oil reservoir 40r, oil pooled in the rear oil reservoir 40r is in contact with an outer peripheral surface of the push rod 36 through the left and right openings between the front and rear guide walls 39c and 39r. [0052] The push rod 36 is a cylindrical member having an outer diameter slightly smaller than the inner diameter of the guide hole 37. A plurality of circular holes 36h are formed in the cylinder wall of the push rod 36 at necessary portions located along the axial direction thereof- The oil brought into contact with the outer peripheral surface of the push rod 36 can be caused to flow on the outer peripheral surface so as to be supplied to the cylindrical inner portion of the push rod 36 through the circular holes 36h. A head member 44 made of rubber is fitted onto an upper-end opening of the push rod 36. A control valve 4 5 is provided on a lower-end opening of the push rod 36. [0053] The control valve 45 includes: a valve seat 45s having a closed-end cylindrical shape with a circular hole drilled in the bottom wall thereof; a ball 45b; and a valve cap 45c having a closed-end cylindrical shape. The valve seat 45s is fitted slightly deep into the lower-end opening of the push rod 36. The ball 45b is loosely fitted in a cylindrical portion of the valve seat 45s, and the valve cap 45c is attached onto the opening of the valve seat 45s. Thus, while the ball 45b is prevented from falling down, the ball 45b is capable of opening and closing the circular hole of the valve seat 45s. [0054] A female thread is formed in a vicinity of the opening of the guide hole 37 at a lower end of the guide cylinder portion 38. A tensioner bolt 46 having a flange is screwed into the female thread so as to close the lower-end opening of the guide hole 37. As described above, the push rod 36 including the control valve 45 at the lower end is fitted into the guide hole 37 from above. Then, a compression spring 47 is inserted into the guide hole 37 from below, and then the lower-end opening of the guide hole 37 is closed with the tensioner bolt 46. As a result, the push rod 36 is urged obliquely upward by the compression spring 47. [0055] The head member 44 at the upper end of the push rod 36 thus urged obliquely upward by the compression spring 47 is in contact with the contact end 31e of the aforementioned tensioner arm 31 so as to urge the tensioner arm 31 in a manner that the tensioner arm 31 swing in a counterclockwise direction in the side view of Fig. 3. Accordingly, the tensioner roller 33 on the opposite end of the tensioner arm 31 presses the rotationally moving portion of the cam chain 23 on the rear side so as to apply a constant tension to the cam chain 23. [0056] As described above, the oil pooled in the oil reservoir 40 is supplied to the cylindrical inner portion of the push rod 36, the cylindrical inner portion communicating with the oil reservoir 40 through the circular holes 36h of the push rod 36. In this way, the oil is filled in the lower portion of the cylindrical inner portion, and further, in an oil chamber 37a, which is a part, being located below the control valve 45 and having the compression spring 47 set therein, of the guide hole 37 of the guide cylinder portion 38. Accordingly, while the push rod 36 is kept pressed by the tensioner arm 31, the oil inside the oil chamber 37a, below the control valve 45, of the guide hole 37 presses the ball 45b against the circular hole of the valve seat 45s so as to establish a valve-closed state, so that the push rod 36 is inhibited from retreating (descending). [0057] If the cam chain 23 is slacked, the push rod 36 is caused to advance by the urging force of the compression spring 47 so as to swing the tensioner arm 31. The tensioner arm 31 thus swung presses the tensioner roller 33 more deeply against the cam chain 23, so that the tension of the cam chain 23 is maintained. At this time, the control valve 45 opens to allow the oil inside the push rod 36 to flow into the oil chamber 37a below the control valve 45, so that the push rod 36 can advance. The push rod 36, which has thus advanced, is inhibited from retreating by the closing operation of the control valve 45. Accordingly, the cam chain 23 will not be slacked again, and can always be maintained with an appropriate tension being applied thereto. [0058] Referring to Fig. 4, which is the perspective view of the left crankcase 2L, an oil guide rib 50 is formed to protrude leftward from the left bearing wall 2Lw of the crankcase 2 at a position below the guide roller 25 and the drive sprocket 12 in the cam chain chamber 2C. The oil guide rib 50 is inclined obliquely downward to the rear. A front portion of the oil reservoir 40 is located directly below a lower end of the oil guide rib 50. There is a void 51 between the lower end of the oil guide rib 50 and the bolt boss portion 39f, which serves as the front wall of the oil reservoir 40. [0059] On the other hand, a communication opening 52 through which the cam chain chamber 2C and the transmission chamber 3S at the rear thereof communicate with each other is formed behind the oil reservoir 40. Specifically, the communication opening 52 is formed by removing an obliquely upper portion of the peripheral wall 2Ls, which serves as a partition wall dividing the cam chain chamber 2C and the transmission chamber 3S at the rear thereof, of the left crankcase 2L as well as by removing a portion, adjoining the obliquely upper portion, of the left bearing wall 2Ls. A slope 53 extending from a lower end of the communication opening 52 toward the oil reservoir 40 is formed on the peripheral wall 2Ls. [0060] The lowermost portion of the peripheral wall 2Ls is located below the front end of the bolt boss portion 39f of the oil reservoir 40. An opening, which serves as an oil return passage 54, is formed in the lowermost portion and a portion, adjoining the lowermost portion, of the left I bearing wall 2Lw. The oil return passage 54 allows the cam chain chamber 2C and the crank chamber 2S to communicate with each other therethrough, and leads to the oil pan 2p at the bottom portion of the crank chamber 2S. [0061] The left crankcase 2L constituting the cam chain chamber 2C has the above-described structure. The inclined oil guide rib 50 thus receives, and guides downward to the rear, oil which drips off by the rotations of the drive sprocket 12 and the guide roller 25 as well as by the rotational movement of the cam chain 23, and also oil which flows down on the wall surface, on the cam chain chamber side, of the left bearing wall 2Lw. The oil, which is guided by the oil guide rib 50 and then flows down from the lower end thereof, is received by the front oil reservoir 40f, so that the capacity of the oil reservoir 40 is increased. Accordingly, since the oil can be caused to flow from the lower end of the oil guide rib 50 into the front oil chamber 40f therebelow, it is possible to efficiently collect the oil in the oil reservoir 40 (refer to the arrows of broken lines, which indicate the flow of oil, in Fig. 3) . [0062] In addition, part of oil splashed by the rotation of the transmission gear inside the transmission chamber 3S flows into the cam chain chamber 2C through the communication opening 52, which is located obliquely upward and rearward of the oil reservoir 40, and which allows the cam chain chamber 2C and the transmission chamber 3S at the rear thereof to communicate with each other. The part of oil is thus splashed on the cam chain 23 and supplied for lubrication. In addition, oil that has poured on the slope 53 is guided by the slope 53 so as to flow into the oil reservoir 40 located obliquely therebelow, and thereby is efficiently collected therein (refer to the arrows of broken lines, which indicate the flow of oil, in Fig, 3). [0063] In this way, the oil guided by the oil guide rib 50 at the front flows into the oil reservoir 40 from the front side thereof. The oil entering through the communication opening 52 behind the oil reservoir 40 and being guided by the slope 53 also flows into the oil reservoir 40 from the rear side thereof. Moreover, the oil flowing on the left bearing wall 2Lw also flows into the oil reservoir 40 from above, and further, the splashed oil pours into the oil reservoir 40 from above. In this way, the oil is very efficiently collected in the oil reservoir 40. [0064] In the oil reservoir 40, the upper opening of the guide hole 37 faces the rear oil reservoir 40r, which is deep with the inclined bottom surface and thus has a large capacity for reserving oil. The oil pooled in the rear oil reservoir 40r comes into contact with the outer peripheral surface of the push rod 36 through the upper opening of the guide hole 37, that is, through the left and right openings between the front and rear guide walls 39c and 39r. The oil is thus supplied sufficiently to the inside of the push rod 36 through the circular holes 36h in the cylinder wall of the push rod 36. Accordingly, the oil can be stably supplied to the oil chamber 37a when the control valve 45 [0065] Note that the oil reservoir 40 is partitioned by the front guide wall 39c into the front oil reservoir 40f and the rear oil reservoir 40r formed side by side in the vehicle-body front-rear direction, and that the front oil reservoir 40f and the rear oil reservoir 40r communicate with each other. Accordingly, it is possible to suppress, to a small level, the change in the level of oil pooled in the oil reservoir 40 relative to the forward and rearward movements of the vehicle body, thus to reduce the amount of oil spilling out of the oil reservoir 40, and eventually to secure the required amount of oil reserved in the oil reservoir 40 at any time. [0066] As described above, since the oil reservoir 40 is integrally formed in the crankcase 2 together with the guide hole 37, there is no need of any fasteners or the like. Accordingly, it is possible to reduce the number of components and simplify the structure, leading to a reduction in cost. Since one side wall, in the vehicle-body width direction, of the oil reservoir 40 formed in the crankcase 2 is formed with the contact of the sidewall plate 41, which is a separate body, the oil reservoir 40 in the crankcase 2 opens at its side. Accordingly, the crankcase 2 is easy to cast, thus enabling a further reduction in the manufacturing cost. [0067] The oil spilling out of the oil reservoir 40 flows forward beyond the bolt boss portion 39f, which is the front wall protruding forward. The oil then flows downward, passes through the oil return passage 54 below, and thereafter directly enters the crank chamber 2S (refer to the arrows of broken lines in Fig. 3). Consequently, the oil is smoothly returned, to the oil pan 2p at the bottom portion of the crankcase 2. [0068] A drain bolt hole is formed in the lowermost bottom wall of the oil pan 2p. A drain bolt 55 is screwed into the drain bolt hole vertically upward from below, and thus closes the drain bolt hole. In the side view shown in Fig. 3, the drain bolt 55 screwed into the drain bolt hole is attached below and near the tensioner bolt 46, which closes the lower-end opening „ of the guide hole 37 of the guide cylinder portion 38. [0069] As illustrated in Figs. 2 and 3, although the tensioner bolt 46 and the drain bolt 55 are disposed respectively at positions close to each other, the positions respectively at which the tensioner bolt 46 and the drain bolt 55 are attached are displaced vertically from each other. Moreover, the directions respectively in which the tensioner bolt 46 and the drain bolt 55 are attached are different from each other. Specifically, the tensioner bolt 46 is attached obliquely upward, while the drain bolt 55 is attached vertically upward. Accordingly, it is possible to avoid such a trouble that an unintended one of the tensioner bolt 46 and the drain bolt 55 is operated wrongly at maintenance. In the internal combustion engine 1, a cell motor 60 is disposed in a front lower portion of the crankcase 2. As illustrated in Fig. 1, the cell motor 60 is disposed in such a manner that a drive shaft 61 thereof protrudes leftward. A drive gear 61a is formed on a shaft end of the drive shaft 61. An intermediate gear shaft 62 is disposed behind, and in parallel with, the drive shaft 61. A large-diameter intermediate gear 63b and a small-diameter intermediate gear 63s are integrally supported on the intermediate gear shaft 62. [0071] The drive gear 61a of the drive shaft 61 of the cell motor 60 meshes with the large-diameter intermediate gear 62b. The small-diameter intermediate gear 63s, which is integral with the large-diameter intermediate gear 63b, meshes with the driven gear 14 fitted on the crankshaft 10. The starter mechanism is thus constituted. [0072] In the internal combustion engine 1, which is mounted on a vehicle in such a manner that the crankshaft 10 is directed in the vehicle-body width direction, there is room in space in the front lower portion of the crankshaft 10. Since the cell motor 60 as well as the intermediate gears 63b and 63s are disposed by effectively utilizing the space in the front lower portion of the crankcase 2, it is possible to avoid an increase in size of the internal combustion engine 1. [0073] In the internal combustion engine 1, the assembly of the cylinder block 4 and the cylinder head 5 protrudes from the front upper portion of the crankcase 2 while being slightly inclined forward. As illustrated in Fig. 1, an engine hanger attachment portion 70 is formed to protrude on the front wall of the crankcase 2 at a position which is below the front wall of the cylinder block 4 inclined forward and is above the cell motor 60. [0074] The engine hanger attachment portion 70 is provided by utilizing an open space between the cylinder block 4 and the cell motor 60 therebelow. Accordingly, the engine hanger attachment portion 70 does not become bulky, and the internal combustion engine 1 can be stably suspended. [Brief Description of the Drawings] [0075] [Fig. 1] Fig. 1 is a partially omitted side view of an internal combustion engine according to an embodiment of the present invention. [Fig. 2] Fig. 2 is a cross-sectional development view of the internal combustion engine (a cross-sectional view taken along the line II-II in Fig. 3). [Fig. 3] Fig. 3 is a side view showing a chief part of the internal combustion engine in an enlarged manner, as a partial cross-section of the internal combustion engine. [Fig. 4] Fig. 4 is a perspective view of a left crankcase and a sidewall plate. [Fig. 5] Fig. 5 is a side view of the left crankcase. [Fig. 6] Fig. 6 is a cross-sectional view taken along the line VI-VI in Fig. 5. [Explanation of the Reference Numerals] [0076] 1 INTERNAL COMBUSTION ENGINE 2 CRANKCASE 2L LEFT CRANKCASE 2Lw LEFT BEARING WALL 2Ls PERIPHERAL WALL 2C CAM CHAIN CHAMBER 2S CRANK CHAMBER 2R RIGHT CRANKCASE 3 TRANSMISSION CASE 3S TRANSMISSION CHAMBER 4 CYLINDER BLOCK 5 CYLINDER HEAD 6 CYLINDER HEAD COVER 7 CASE COVER 10 CRANKSHAFT 11 MAIN BEARING 12 DRIVE SPROCKET 13 AC GENERATOR 14 DRIVEN GEAR, 20 CAMSHAFT 21 CAMSHAFT HOLDER 22 DRIVEN SPROCKET 23 CAM CHAIN 24 GUIDE ROLLER 25 GUIDE ROLLER 30 CAM CHAIN TENSIONER SYSTEM 31 TENSIONER ARM 32 PIVOT BOLT 33 TENSIONER ROLLER 35 TENSIONER LIFTER 36 PUSH ROD 37 GUIDE HOLE 37a OIL CHAMBER 38 GUIDE CYLINDER PORTION 39 OIL RECEIVING PORTION 39f BOLT BOSS PORTION 39c FRONT GUIDE WALL 39r REAR GUIDE WALL 40 OIL RESERVOIR 41 SIDEWALL PLATE 42 BOLT 4 3 WASHER 44 HEAD MEMBER 4 5 CONTROL VALVE 4 6 TENSIONER BOLT 47 COMPRESSION SPRING 50 OIL GUIDE RIB 51 VOID 52 COMMUNICATION OPENING 53 SLOPE 54 OIL RETURN PASSAGE 55 DRAIN BOLT 60 CELL MOTOR 61a DRIVE GEAR 62 INTERMEDIATE GEAR SHAFT 63b LARGE-DIAMETER INTERMEDIATE GEAR 63s SMALL-DIAMETER INTERMEDIATE GEAR 7 0 ENGINE HANGER ATTACHMENT PORTION [Document Name] Scope of Claims [Claim 1] A cam chain tensioner system for an internal combustion engine, comprising: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out, the cam chain tensioner system always applying a predetermined tension to the cam chain, wherein the guide hole is formed in a lower portion of the crankcase while opening at least upward, an oil reservoir is formed integrally in the crankcase, the oil reservoir being a concave portion that is depressed downward and opens upward to the cam chain chamber, and the upper opening of the guide hole faces the inside of the oil reservoir. [Claim 2] The cam chain tensioner system for an internal combustion engine according to claim 1, wherein the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by front and rear guide walls constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir, the push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls, and the left and right openings of the push rod between the front and rear guide walls communicate with the oil reservoir. [Claim 3] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 and 2, wherein an oil guide rib is formed to be inclined below the drive sprocket, the oil guide rib protruding from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft, and the oil reservoir is located below a lower end of the oil guide rib. [Claim 4] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 3, wherein the oil reservoir has a front oil reservoir and a rear oil reservoir that are formed side by side in a vehicle-body front-rear direction, and the front oil reservoir and the rear oil reservoir communicate with each other. [Claim 5] The cam chain tensioner system for an internal combustion engine according to claim A, wherein the front oil reservoir is located below the lower end of the oil guide rib, a front wall of the front oil reservoir protrudes forward, a bottom surface of the front oil reservoir and a bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear, and the upper opening of the guide hole faces the rear oil reservoir. [Claim 6] The cam chain tensioner system for an internal combustion engine according to claim 5, wherein the crankcase has an oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir. [Claim 7] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 6, wherein one side wall, in a vehicle-body width direction, of the oil reservoir formed in the crankcase is formed with a contact of a sidewall plate that is a separate body. [Claim 8] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 7, wherein the guide hole opens in a side wall of the crankcase, and is formed to be inclined so that a lower end, which is closed by a tensioner bolt, of the guide hole is located forward, in the vehicle body, of an upper end of the guide hole, and a drain bolt for closing a drain bolt hole formed in a bottom wall of the crankcase is provided below the tensioner bolt in a side view of the vehicle body. [Claim 9] A cam chain tensioner system for an internal combustion engine, comprising: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out, the cam chain tensioner system always applying a predetermined tension to the cam chain, wherein an oil reservoir is formed in a lower portion of the crankcase, the upper opening of the guide hole facing the inside of the oil reservoir, the crankcase is partitioned by a partition wall into the cam chain chamber provided with the oil reservoir and a transmission chamber located behind the cam chain chamber in a vehicle-body front-rear direction, and a communication opening is formed in a portion of the partition wall, the portion located obliquely upward of the oil reservoir. [Claim 10] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 9, wherein the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction, and a cell motor and an intermediate gear are disposed in a front lower portion of the crankcase in which the crankshaft is pivotally supported. [Claim 11] The cam chain tensioner system for an internal combustion engine according to claim 10, wherein a cylinder protrudes from a front upper portion of the crankcase while being slightly inclined forward, and an engine hanger attachment portion is formed on a front wall of the crankcase at a position below the cylinder and above the cell motor.

Full Text

[Document Name] Specification
[Title of the Invention] CAM CHAIN TENSIONER SYSTEM FOR
INTERNAL COMBUSTION ENGINE
[Technical Field]
[0001]
The present invention relates to a tensioner system for applying a required tension to a cam chain that transmits a rotation of a crankshaft in an internal combustion engine to a valve system. [Background Art] [0002]
An endless cam chain is looped between a drive sprocket, which is fitted on a crankshaft rotatably supported in a crankcase, and a driven sprocket, which is fitted on a camshaft of a valve system. The cam chain is pressed, at its side, by a cam chain tensioner system so as to be maintained in tension with no slack by a constant tension being applied thereto. [0003]
A hydraulic cam chain tensioner system is configured as follows. A push rod that is in pressure contact with a pressing member for pressing a cam chain is advanceably and retreatably fitted into a guide cylinder, so that an oil chamber is formed in the guide cylinder. A control valve is provided which allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber. A compression spring is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. I That is, the push rod of the hydraulic cam chain

tensioner system is capable of advancing but incapable of
retreating.
[0004]
If the cam chain is elongated due to aging deterioration or the like, the urging force of the compression spring causes the push rod to advance and press the cam chain with the pressing member therebetween, thereby taking up the slack of the cam chain with a predetermined tension applied thereto. In this event, the control valve allows oil to flow into the oil chamber. If the push rod receives a reaction force from the cam chain, the control valve prevents the oil from flowing out, and thus establishes a locked state in which the push rod is inhibited from retreating. As a result, the cam chain is maintained at a predetermined tension. [0005]
An example of the techniques for guiding the oil into the oil chamber in such a hydraulic cam chain tensioner system is to provide a dedicated oil passage. This technique, however, requires a complicated structure and thus is accompanied by cumbersome processes and a high manufacturing cost. Against this problem, there is another example configured so that an oil reservoir is formed in the opening portion in the upper end of the guide cylinder into which the push rod is fitted, so that the oil is caused to flow from the oil reservoir into the oil chamber in the guide cylinder (refer to, for example, Patent Document 1). [0006]
[Patent Document 1] Japanese Patent No. 4035226

[0007]
In Patent Document 1, an oil separator, which is a separate body from a crankcase, is fastened to a bottom wall of a cam chain chamber of the crankcase. The oil reservoir, which opens upward, and the guide cylinder, into which the push rod is fitted, are integrally formed in the oil separator. [Disclosure of the Invention] [Problems to be Solved by the Invention] [0008]
Since the oil reservoir and the guide cylinder are integrally formed in the oil separator, the oil separator has a complicated shape and is not easy to manufacture. In addition, it is also necessary to form a space for housing the oil separator in the crankcase, and thus, the manufacture of the crankcase requires a large amount of man-hours and a high cost.
The oil separator is a separate body from the crankcase, and thus increases the number of components including a fastening member for fastening the oil separator to the crankcase, leading to a complicated structure and an increase in cost. [0009]
The present invention has been made in view of the above-described circumstances. An object of the present invention is to provide a cam chain tensioner system having a simple structure with a small number of components and being manufactured at a low cost. [Means for Solving the Problems]

In order to achieve the above-described object, a first aspect of the present invention provides a cam chain tensioner system for an internal combustion engine. The cam chain tensioner system for an internal combustion engine includes: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. The cam chain tensioner system for an internal combustion engine always applies a predetermined tension to the cam chain. In the cam chain tensioner system for an internal combustion engine, the guide hole is formed in a lower portion of the crankcase while opening at least upward. An oil reservoir is formed integrally in the ^ crankcase. The oil reservoir is a concave portion that is depressed downward and opens upward to the cam chain chamber. The upper opening of the guide hole faces the inside of the oil reservoir.

A second aspect of the present invention provides the following characteristics in the cam chain tensioner system Eor an internal combustion engine according to the first aspect. Specifically, the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by front and rear guide walls constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir. The push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls. The left and right openings of the push rod between the front and rear guide walls communicate with the oil reservoir. [0012]
A third aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of the first and second aspects. Specifically, in the cam chain tensioner system for an internal combustion engine, an oil guide rib is formed to be inclined below the drive sprocket. The oil guide rib protrudes from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft. In addition, the oil reservoir is located below a lower end of the oil guide rib. [0013]
A fourth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of

the first to third aspects. Specifically, the oil reservoir has a front oil reservoir and a rear oil reservoir that are formed side by side in a vehicle-body front-rear direction. In addition, the front oil reservoir and the rear oil reservoir conununicate with each other. [0014]
A fifth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the fourth aspect. Specifically, the front oil reservoir is located below the lower end of the oil guide rib. A front wall of the front oil reservoir protrudes forward. A bottom surface of the front oil reservoir and a bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear. The upper opening of the guide hole faces the rear oil reservoir. [0015]
A sixth aspect of the present invention provides the following characteristic in the cam chain tensioner system for an internal combustion engine according to the fifth aspect. Specifically, the crankcase has an oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir. [0016]
A seventh aspect of the present invention provides the following characteristic in the cam chain tensioner system for an internal combustion engine according to any one of the first to sixth aspect. Specifically, one side wall, in a vehicle-body width direction, of the oil reservoir formed in the cranlccase is formed with a contact

of a sidewall plate that is a separate body. [0017]
An eighth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to any one of the first to seventh aspects. Specifically, the guide hole opens in a side wall of the crankcase, and is formed to be inclined so that a lower end, which is closed by a tensioner bolt, of the guide hole is located forward, in the vehicle body, of an upper end of the guide hole. In addition, a drain bolt for closing a drain bolt hole formed in a bottom wall of the crankcase is provided below the tensioner bolt in a side view of the vehicle body. [0018]
A ninth aspect of the present invention provides a cam chain tensioner system for an internal combustion engine. The cam chain tensioner system for an internal combustion engine includes: a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system; a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member; an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod; a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and a

compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out. The cam chain tensioner system always applies a predetermined tension to the cam chain. In the cam chain tensioner system for an internal combustion engine, an oil reservoir is formed in a lower portion of the crankcase, and the upper opening of the guide hole faces the inside of the oil reservoir. In addition, the crankcase is partitioned by a partition wall into the cam chain chamber provided with the oil' reservoir and a transmission chamber located behind the cam chain chamber in a vehicle-body front-rear direction. Moreover, a communication opening is formed in a portion of the partition wall, the portion located obliquely upward of the oil reservoir. [0019]
A tenth aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the first to ninth aspects. Specifically, the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction. In addition, a cell motor and an intermediate gear are disposed in a front lower portion of the crankcase in which the crankshaft is pivotally supported. [0020]
An eleventh aspect of the present invention provides the following characteristics in the cam chain tensioner system for an internal combustion engine according to the tenth aspect. Specifically, a cylinder protrudes from a ) front upper portion of the crankcase while being slightly

inclined forward. In addition, an engine hanger attachment portion is formed on a front wall of the crankcase at a position below the cylinder and above the cell motor. [Effects of the Invention] [0021]
In the cam chain tensioner system for an internal combustion engine according to the first aspect, the guide hole is formed in the lower portion of the crankcase while opening at least upward, and the oil reservoir, which is a concave portion being depressed downward and opening upward to the cam chain chamber, is formed integrally in the crankcase, and the upper opening of the guide hole faces the inside of the oil reservoir. Accordingly, oil is efficiently collected in the oil reservoir formed in the lower portion of the crankcase while opening upward. The oil thus pooled in the oil reservoir flows on the push rod from the upper opening of the guide hole so as to be guided to the lid portion of the push rod, and then is caused to flow into the oil chamber when the control valve is opened.
Since the oil reservoir and the guide hole are integrally formed in the crankcase, it is possible to simplify the structure with a small number of components while eliminating the need of any fastener or the like, and thus to reduce the cost. [0022]
In the cam chain tensioner system for an internal combustion engine according to the second aspect, the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by the front and rear guide walls

constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir. The push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls. The left and right openings of the push rod between the front and rear guide walls coitmiunicate with the oil reservoir. Accordingly, it is possible to stably support the push rod with a simple structure. In addition, since the oil pooled in the oil reservoir is in contact with an outer peripheral surface of the push rod through the left and right openings between the front and rear guide walls, it is possible to cause the oil to flow on the push rod so as to be efficiently guided to the control valve. [0023]
In the cam chain tensioner system for an internal combustion engine according to the third aspect, the oil guide rib is formed to be inclined below the drive sprocket, the oil guide rib protruding from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft, while the oil reservoir is located below the lower end of the oil guide rib. Accordingly, the oil guide rib receives oil dripping off the drive sprocket, the cam chain, and the like, as well as oil flowing down on the wall surface, on the cam chain chamber side, of the bearing wall, and then guides the oil to the oil reservoir. In this way, the oil can be efficiently collected in the oil chamber. [0024]

In the cam chain tensioner system for an internal combustion engine according to the fourth aspect, the oil reservoir has the front oil reservoir and the rear oil reservoir that are formed side by side in the vehicle-body front-rear direction, and the front oil reservoir and the rear oil reservoir communicate with each other. Accordingly, it is possible to suppress, to a small level, the change in the level of oil pooled in the oil reservoir relative to the forward and rearward movements of the vehicle body, thus to reduce the amount of oil spilling out of the oil reservoir, and eventually to secure the required amount of oil reserved in the oil reservoir at any time. [0025]
In the cam chain tensioner system for an internal combustion engine according to the fifth aspect, the front oil reservoir is located below the lower end of the oil guide rib. The front wall of the front oil reservoir protrudes forward. The bottom surface of the front oil reservoir and the bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear. The upper opening of the guide hole faces the rear oil reservoir. Accordingly, oil, which has been guide by the oil guide rib and then flowed down from the lower end thereof, is received by the front oil reservoir, so that the capacity of the oil reservoir is increased. In addition, the upper opening of the guide hole faces the rear oil reservoir, which is deep with the inclined bottom surface and thus has a large capacity for reserving oil. As a result, oil can be stably supplied to the oil chamber inside the guide hole.

[0026]
In the cam chain tensioner system for an internal combustion engine according to the sixth aspect, the crankcase has the oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir. Accordingly, the oil spilling out of the front oil reservoir flows forward beyond the front wall protruding forward, then flows downward, and directly enters the oil return passage. Consequently, the oil is smoothly returned to a bottom portion of the crankcase. [0027]
In the cam chain tensioner system.for an internal combustion engine according to the seventh aspect, the one side wall, in the vehicle-body width direction, of the oil reservoir formed in the crankcase is formed with the contact of the sidewall plate, which is a separate body. Accordingly, the oil reservoir in the crankcase opens at its side, so that the crankcase is easy to cast, thus allowing a reduction in the manufacturing cost. [0028]
In the cam chain tensioner system for an internal combustion engine according to the eighth aspect, the guide hole opens in the side wall of the crankcase, and is formed to be inclined so that the lower end, which is closed by the tensioner bolt, of the guide hole is located forward, in the vehicle body, of the upper end of the guide hole. In addition, the drain bolt for closing the drain bolt hole formed in the bottom wall of the crankcase is provided below the tensioner bolt in the side view of the vehicle body. The inclining of the guide hole makes it possible to

achieve a compact structure in which the tensioner bolt for closing the lower end of the guide hole and the drain bolt for closing the drain bolt hole below the tensioner bolt are disposed close to each other.
In addition, the positions respectively at which the tensioner bolt and the drain bolt are attached are displaced vertically from each other. Moreover, the drain bolt may be attached in a direction different from that of the tensioner bolt. For example, the tensioner bolt is attached obliquely upward while the drain bolt is vertically upward in a general manner. Accordingly, it is possible to avoid such a trouble that an unintended one of the tensioner bolt 46 and the drain bolt 55 is operated wrongly at maintenance. [0029]
In the cam chain tensioner system for an internal combustion engine according to the ninth aspect, the oil reservoir is formed in the lower portion of the crankcase, while the upper opening of the guide hole faces the inside of the oil reservoir. In addition, the crankcase is partitioned by a partition wall into the cam chain chamber provided with the oil reservoir and a transmission chamber located behind the cam chain chamber in the vehicle-body front-rear direction. Moreover, the communication opening is formed in the portion, obliquely upward of the oil reservoir, of the partition wall. Despite such a simple structure having a small number of components, oil splashed in the transmission chamber flows into the cam chain chamber through the communication opening in the partition wall, and is thus splashed on the cam chain and supplied

for lubrication as well as is efficiently collected in the
oil reservoir located obliquely therebelow.
[0030]
In the cam chain tensioner system for an internal combustion engine according to the tenth aspect, the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction, and the cell motor and the intermediate gear are disposed in the front lower portion of the crankcase in which the crankshaft is pivotally supported. Accordingly, it is possible to lower the center of gravity of the vehicle body, and to dispose the cell motor and the intermediate gear by effectively utilizing an open space below and at the front of the crankshaft, so that an increase in size of the internal combustion engine is avoided. [0031]
In the cam chain tensioner system for an internal combustion engine according to the eleventh aspect, the cylinder protrudes from the front upper portion of the crankcase while being slightly inclined forward, and the engine hanger attachment portion is formed on the front wall of the crankcase at the position below the cylinder and above the cell motor. Accordingly, it is possible to provide the engine hanger attachment portion by utilizing an open space between the cylinder and the cell motor therebelow, and also to stably suspend the internal combustion engine. [Best Mode for Carrying Out the Invention]

Hereinbelow, an internal combustion engine 1 according to the present invention is a SOHC single-cylinder 4-stroke internal combustion engine. The internal combustion engine 1 is mounted on a motorcycle in such a manner that a crankshaft 10 is directed in a vehicle-body width direction with respect to a vehicle body.
The crankshaft 10 of the internal combustion engine 1 is rotatably supported in a crankcase 2, and a transmission case 3 is formed integrally behind the crankcase 2, so that the crankcase 2 and the transmission case 3 constitute a power unit case together. [0033]
Referring to Fig. 1, a cylinder block 4 and a cylinder head 5 are placed in this order on an obliquely upper portion of the crankcase 2, and are fastened together. A cylinder head cover 6 is placed on top of the cylinder head 5. The assembly of the cylinder block 4, the cylinder head 5, and the cylinder head cover 6 protrudes from the crankcase 2 while being slightly inclined forward. [0034]
Referring to Fig. 2, the crankcase 2 is divided left and right into a left crankcase 2L and a right crankcase 2R, and the crankshaft 10 is rotatably supported by a bearing wall 2Lw of the left crankcase 2L and a bearing wall 2Rw of the right crankcase 2R respectively with main bearings 11, 11 interposed respectively therebetween.
Crank webs lOw, lOw of the crankshaft 10 are located in a crank chamber 2S formed between the bearing walls 2Lw and 2Rw. Left and right crankshaft portions 10a, lOa of
sides of the bearing walls 2Lw and 2Rw, respectively. The left and right crankshaft portions 10a, 10a are covered from outside by left and right case covers 7, 7, respectively. [0035]
A drive sprocket 12 of a valve drive system is fitted on the left crankshaft portion 10a in a vicinity of the main bearing 11. An AC generator 13 is provided on the left end of the left crankshaft portion 10a. A driven gear 14 of a starter mechanism is fitted on the left crankshaft portion 10a between the drive sprocket 12 and the AC generator 13. [0036]
A valve mechanism is constituted in the cylinder head 5. A camshaft 20, being directed in the vehicle-body width direction, is rotatably supported at the upper surface of the cylinder head 5 in such a manner as to be sandwiched by a camshaft holder 21. A driven sprocket 22 having a diameter substantially twice the diameter of the drive sprocket 12 of the valve drive system is fitted on the left end of the camshaft 20. [0037]
A cam chain 23, which is an endless transmission chain is looped between the driven sprocket 22 fitted on the camshaft 20 and the drive sprocket 12 fitted on the crankshaft 10, so that the rotation of the crankshaft 10 is transmitted to the camshaft 20 while the rotational speed thereof is reduced to the half.
The cam chain 23 is disposed in cam chain chambers 2C, 4C, and 5C respectively of the crankcase 2, the cylinder

block 4, and the cylinder head 5. [0038]
A guide roller 24 is rotatably supported in the cam chain chamber 4C of the cylinder block 4. The guide roller 24 has a diameter in a middle of the diameters of the drive sprocket 12 and the driven sprocket 22, and guides the rotational movement of the cam chain 23 at the front and rear sides. [0039]
The cam chain chamber 2C of the left crankcase 2L constitutes a common space with an ACG chamber 7S in which the AC generator 13 is covered by the left case cover 7. The space surrounded by a peripheral wall 2Ls protruding to the left of the crankcase 2 near the left bearing wall 2Lw corresponds to the cam chain chamber 2C.
A transmission chamber 3S formed at the rear of the crank chamber 2S is formed to bulge leftward to the rear of the cam chain chamber 2C. [0040]
In the cam chain chamber 2C, a guide roller 25 is rotatably supported by the left bearing wall 2Lw at a position obliquely upward and forward of the drive sprocket 12. The guide roller 25 guides the rotational movement of the cam chain 23 at the front side. [0041]
Referring to Fig. 3, a tensioner arm 31 of a cam chain tensioner system 30 is pivotally supported at the center thereof by a pivot bolt 32 so as to be swingably provided at the rear of the drive sprocket 12 in the cam chain chamber 2C.

A tensioner roller 33 is rotatably supported at a distal end of an upward extending arm portion of the tensioner arm 31, while a contact end 31e is formed at a distal end of a downward extending arm portion of the tensioner arm 31. [0042]
A push rod 36 of a tensioner lifter 35 is in contact with the contact end 31e of the tensioner arm 31 so as to urge the tensioner arm 31 with pressure. The tensioner roller 33 at the distal end of the upward extending arm portion thereby presses a rotationally moving portion of the cam chain 23 on the rear side so as to appropriately tension the cam chain 23. [0043]
The tensioner lifter 35 is formed below the drive sprocket 12 fitted on the crankshaft 10 rotatably supported in the left crankcase 2L (refer to Figs. 1 and 2).
Now, refer to Fig. 4, which is a perspective view of the left crankcase 2L, and Fig. 5, which is an enlarged side view of a chief part of the left crankcase 2L. A guide hole 37 is formed in an inclined portion, below a bearing circular hole llh (the drive sprocket 12), of the peripheral wall- 2Ls protruding leftward from the left bearing wall 2Lw of the left crankcase 2L. Specifically, the guide hole 37 is drilled obliquely in the inclined portion in such a manner that a lower portion, outside the peripheral wall 2Ls, of the guide hole 37 is located at the front of an upper portion, inside the peripheral wall 2Ls, of the guide hole 37. The' guide hall 37 penetrates from the cam chain chamber 2C to the outside.

[0044]
A portion, above the peripheral wall 2Ls, of the guide hole 37 is formed into an oil receiving portion 39, while a lower half portion of the guide hole 37 is formed into a guide cylinder portion 38 extending obliquely downward from the peripheral wall 2Ls. An opening end surface 38s at a lower end of the guide cylinder portion 38 is located at a slightly higher level than a lowermost bottom wall constituting an oil pan 2p which is a bottom portion of the crank chamber 2S. [0045]
The oil receiving portion 39 constitutes an oil reservoir 40 (illustrated by broken line cross hatching in Figs. 5 and 6), which is a concave portion being depressed downward and opening upward. A bolt boss portion 39f is formed in a front-side wall portion, which protrudes forward, of the oil reservoir 40. A rear-side wall of the oil reservoir 40 is formed with' a rear guide wall 39r in such a manner that a rear inner surface of the guide hole 37 extends. A right-side wall of the oil reservoir 40 is formed by the left bearing wall 2Lw, while a left-side wall thereof is not formed, but instead, a sidewall plate 41 is affixed to the oil reservoir 40 so as to serve as the left¬side wall. [0046]
The sidewall plate 41 is, as illustrated in Fig. 4, a plate member having a substantially triangular shape with an acute apex angle. One longer side, which is straight, of the sidewall plate 41 is referred to as an upper side 41a and is maintained horizontally in the front-rear

direction. The other longer side, extending obliquely forward from the rear apex portion, of the sidewall plate 41 is referred to as a lower side 41b. A shorter side 41c on the front side of the sidewall plate 41 has a center portion being cut out so as to form a convex and concave contour.
The sidewall plate 41 has an attachment hole 41h drilled therein at a position closer to the shorter side 41c. [0047]
The sidewall plate 41 is brought into contact with a left side wall of the oil receiving portion 39. Then, a bolt 42 is inserted through the attachment hole 41h with a washer 4 3 interposed therebetween, and is screwed into a bolt hole of the bolt boss portion 39f of the oil receiving portion 39. In this way, the sidewall plate 41 is affixed to the oil receiving portion 39 so as to serve as the left¬side wall of the oil reservoir 40, [0048]
A front guide wall 39c protrudes obliquely upward at a center portion of the oil reservoir 40 in the front-rear direction in such a manner that a front inner surface of the inclined guide hole 37 extends. The front guide wall 39c partitions the oil reservoir 40 into a front oil reservoir 40f and a rear oil reservoir 40r.
Note that, there is a gap between the front guide wall 39c and the sidewall plate 41 constituting the left¬side wall; thus the front oil reservoir 40f and the rear oil reservoir 40r communicate with each other through the gap (refer to Fig. 6).

[0049]
The bolt boss portion 39f in the front wall portion of the front oil reservoir 40f protrudes forward, and the bottom surface of the front oil reservoir 40f and the bottom surface of the rear oil reservoir 40r are continuous with each other while being inclined obliquely downward to the rear. [0050]
An upper opening of the guide hole 37 faces the rear oil reservoir 40r.
The upper opening, which faces the inside of the rear oil reservoir 40r, of the guide hole 37 is formed to open upward as well as to left and right sides by the front guide wall 39c and the rear guide wall 39r constituting the upper portion of the guide hole 37, the front guide wall 39c and the rear guide wall 39r extending to the inside of the rear oil reservoir 40r. The left- and right-sides openings between the front and rear guide walls 39c and 39r communicate with the rear oil reservoir 40r (refer to Fig. 6) . [0051]
The push rod 36 is fitted into the guide hole 37 through the upper opening thereof. The push rod 36 is slidably supported by being sandwiched at the front and rear sides thereof by the front and rear guide walls 39c and 39r protruding obliquely upward. Accordingly, the push rod 36 is stably supported over a long length thereof.
In addition, since the left and right openings between the front and rear guide walls 39c and 39r face the rear oil reservoir 40r, oil pooled in the rear oil

reservoir 40r is in contact with an outer peripheral surface of the push rod 36 through the left and right openings between the front and rear guide walls 39c and 39r. [0052]
The push rod 36 is a cylindrical member having an outer diameter slightly smaller than the inner diameter of the guide hole 37. A plurality of circular holes 36h are formed in the cylinder wall of the push rod 36 at necessary portions located along the axial direction thereof- The oil brought into contact with the outer peripheral surface of the push rod 36 can be caused to flow on the outer peripheral surface so as to be supplied to the cylindrical inner portion of the push rod 36 through the circular holes 36h.
A head member 44 made of rubber is fitted onto an upper-end opening of the push rod 36.
A control valve 4 5 is provided on a lower-end opening of the push rod 36. [0053]
The control valve 45 includes: a valve seat 45s having a closed-end cylindrical shape with a circular hole drilled in the bottom wall thereof; a ball 45b; and a valve cap 45c having a closed-end cylindrical shape. The valve seat 45s is fitted slightly deep into the lower-end opening of the push rod 36. The ball 45b is loosely fitted in a cylindrical portion of the valve seat 45s, and the valve cap 45c is attached onto the opening of the valve seat 45s. Thus, while the ball 45b is prevented from falling down, the ball 45b is capable of opening and closing the circular hole of the valve seat 45s.

[0054]
A female thread is formed in a vicinity of the opening of the guide hole 37 at a lower end of the guide cylinder portion 38. A tensioner bolt 46 having a flange is screwed into the female thread so as to close the lower-end opening of the guide hole 37.
As described above, the push rod 36 including the control valve 45 at the lower end is fitted into the guide hole 37 from above. Then, a compression spring 47 is inserted into the guide hole 37 from below, and then the lower-end opening of the guide hole 37 is closed with the tensioner bolt 46. As a result, the push rod 36 is urged obliquely upward by the compression spring 47. [0055]
The head member 44 at the upper end of the push rod 36 thus urged obliquely upward by the compression spring 47 is in contact with the contact end 31e of the aforementioned tensioner arm 31 so as to urge the tensioner arm 31 in a manner that the tensioner arm 31 swing in a counterclockwise direction in the side view of Fig. 3. Accordingly, the tensioner roller 33 on the opposite end of the tensioner arm 31 presses the rotationally moving portion of the cam chain 23 on the rear side so as to apply a constant tension to the cam chain 23. [0056]
As described above, the oil pooled in the oil reservoir 40 is supplied to the cylindrical inner portion of the push rod 36, the cylindrical inner portion communicating with the oil reservoir 40 through the circular holes 36h of the push rod 36. In this way, the

oil is filled in the lower portion of the cylindrical inner portion, and further, in an oil chamber 37a, which is a part, being located below the control valve 45 and having the compression spring 47 set therein, of the guide hole 37 of the guide cylinder portion 38.
Accordingly, while the push rod 36 is kept pressed by the tensioner arm 31, the oil inside the oil chamber 37a, below the control valve 45, of the guide hole 37 presses the ball 45b against the circular hole of the valve seat 45s so as to establish a valve-closed state, so that the push rod 36 is inhibited from retreating (descending). [0057]
If the cam chain 23 is slacked, the push rod 36 is caused to advance by the urging force of the compression spring 47 so as to swing the tensioner arm 31. The tensioner arm 31 thus swung presses the tensioner roller 33 more deeply against the cam chain 23, so that the tension of the cam chain 23 is maintained.
At this time, the control valve 45 opens to allow the oil inside the push rod 36 to flow into the oil chamber 37a below the control valve 45, so that the push rod 36 can advance.
The push rod 36, which has thus advanced, is inhibited from retreating by the closing operation of the control valve 45. Accordingly, the cam chain 23 will not be slacked again, and can always be maintained with an appropriate tension being applied thereto. [0058]
Referring to Fig. 4, which is the perspective view of the left crankcase 2L, an oil guide rib 50 is formed to

protrude leftward from the left bearing wall 2Lw of the crankcase 2 at a position below the guide roller 25 and the drive sprocket 12 in the cam chain chamber 2C. The oil guide rib 50 is inclined obliquely downward to the rear.
A front portion of the oil reservoir 40 is located directly below a lower end of the oil guide rib 50. There is a void 51 between the lower end of the oil guide rib 50 and the bolt boss portion 39f, which serves as the front wall of the oil reservoir 40. [0059]
On the other hand, a communication opening 52 through which the cam chain chamber 2C and the transmission chamber 3S at the rear thereof communicate with each other is formed behind the oil reservoir 40. Specifically, the communication opening 52 is formed by removing an obliquely upper portion of the peripheral wall 2Ls, which serves as a partition wall dividing the cam chain chamber 2C and the transmission chamber 3S at the rear thereof, of the left crankcase 2L as well as by removing a portion, adjoining the obliquely upper portion, of the left bearing wall 2Ls.
A slope 53 extending from a lower end of the communication opening 52 toward the oil reservoir 40 is formed on the peripheral wall 2Ls. [0060]
The lowermost portion of the peripheral wall 2Ls is located below the front end of the bolt boss portion 39f of the oil reservoir 40. An opening, which serves as an oil return passage 54, is formed in the lowermost portion and a portion, adjoining the lowermost portion, of the left I bearing wall 2Lw. The oil return passage 54 allows the cam

chain chamber 2C and the crank chamber 2S to communicate with each other therethrough, and leads to the oil pan 2p at the bottom portion of the crank chamber 2S. [0061]
The left crankcase 2L constituting the cam chain chamber 2C has the above-described structure. The inclined oil guide rib 50 thus receives, and guides downward to the rear, oil which drips off by the rotations of the drive sprocket 12 and the guide roller 25 as well as by the rotational movement of the cam chain 23, and also oil which flows down on the wall surface, on the cam chain chamber side, of the left bearing wall 2Lw. The oil, which is guided by the oil guide rib 50 and then flows down from the lower end thereof, is received by the front oil reservoir 40f, so that the capacity of the oil reservoir 40 is increased. Accordingly, since the oil can be caused to flow from the lower end of the oil guide rib 50 into the front oil chamber 40f therebelow, it is possible to efficiently collect the oil in the oil reservoir 40 (refer to the arrows of broken lines, which indicate the flow of oil, in Fig. 3) . [0062]
In addition, part of oil splashed by the rotation of the transmission gear inside the transmission chamber 3S flows into the cam chain chamber 2C through the communication opening 52, which is located obliquely upward and rearward of the oil reservoir 40, and which allows the cam chain chamber 2C and the transmission chamber 3S at the rear thereof to communicate with each other. The part of oil is thus splashed on the cam chain 23 and supplied for

lubrication. In addition, oil that has poured on the slope 53 is guided by the slope 53 so as to flow into the oil reservoir 40 located obliquely therebelow, and thereby is efficiently collected therein (refer to the arrows of broken lines, which indicate the flow of oil, in Fig, 3). [0063]
In this way, the oil guided by the oil guide rib 50 at the front flows into the oil reservoir 40 from the front side thereof. The oil entering through the communication opening 52 behind the oil reservoir 40 and being guided by the slope 53 also flows into the oil reservoir 40 from the rear side thereof. Moreover, the oil flowing on the left bearing wall 2Lw also flows into the oil reservoir 40 from above, and further, the splashed oil pours into the oil reservoir 40 from above. In this way, the oil is very efficiently collected in the oil reservoir 40. [0064]
In the oil reservoir 40, the upper opening of the guide hole 37 faces the rear oil reservoir 40r, which is deep with the inclined bottom surface and thus has a large capacity for reserving oil. The oil pooled in the rear oil reservoir 40r comes into contact with the outer peripheral surface of the push rod 36 through the upper opening of the guide hole 37, that is, through the left and right openings between the front and rear guide walls 39c and 39r. The oil is thus supplied sufficiently to the inside of the push rod 36 through the circular holes 36h in the cylinder wall of the push rod 36. Accordingly, the oil can be stably supplied to the oil chamber 37a when the control valve 45

[0065]
Note that the oil reservoir 40 is partitioned by the front guide wall 39c into the front oil reservoir 40f and the rear oil reservoir 40r formed side by side in the vehicle-body front-rear direction, and that the front oil reservoir 40f and the rear oil reservoir 40r communicate with each other. Accordingly, it is possible to suppress, to a small level, the change in the level of oil pooled in the oil reservoir 40 relative to the forward and rearward movements of the vehicle body, thus to reduce the amount of oil spilling out of the oil reservoir 40, and eventually to secure the required amount of oil reserved in the oil reservoir 40 at any time. [0066]
As described above, since the oil reservoir 40 is integrally formed in the crankcase 2 together with the guide hole 37, there is no need of any fasteners or the like. Accordingly, it is possible to reduce the number of components and simplify the structure, leading to a reduction in cost.
Since one side wall, in the vehicle-body width direction, of the oil reservoir 40 formed in the crankcase 2 is formed with the contact of the sidewall plate 41, which is a separate body, the oil reservoir 40 in the crankcase 2 opens at its side. Accordingly, the crankcase 2 is easy to cast, thus enabling a further reduction in the manufacturing cost. [0067]
The oil spilling out of the oil reservoir 40 flows forward beyond the bolt boss portion 39f, which is the

front wall protruding forward. The oil then flows downward, passes through the oil return passage 54 below, and thereafter directly enters the crank chamber 2S (refer to the arrows of broken lines in Fig. 3). Consequently, the oil is smoothly returned, to the oil pan 2p at the bottom portion of the crankcase 2. [0068]
A drain bolt hole is formed in the lowermost bottom wall of the oil pan 2p. A drain bolt 55 is screwed into the drain bolt hole vertically upward from below, and thus closes the drain bolt hole.
In the side view shown in Fig. 3, the drain bolt 55 screwed into the drain bolt hole is attached below and near the tensioner bolt 46, which closes the lower-end opening „ of the guide hole 37 of the guide cylinder portion 38. [0069]
As illustrated in Figs. 2 and 3, although the tensioner bolt 46 and the drain bolt 55 are disposed respectively at positions close to each other, the positions respectively at which the tensioner bolt 46 and the drain bolt 55 are attached are displaced vertically from each other. Moreover, the directions respectively in which the tensioner bolt 46 and the drain bolt 55 are attached are different from each other. Specifically, the tensioner bolt 46 is attached obliquely upward, while the drain bolt 55 is attached vertically upward. Accordingly, it is possible to avoid such a trouble that an unintended one of the tensioner bolt 46 and the drain bolt 55 is operated wrongly at maintenance.

In the internal combustion engine 1, a cell motor 60 is disposed in a front lower portion of the crankcase 2.
As illustrated in Fig. 1, the cell motor 60 is disposed in such a manner that a drive shaft 61 thereof protrudes leftward. A drive gear 61a is formed on a shaft end of the drive shaft 61.
An intermediate gear shaft 62 is disposed behind, and in parallel with, the drive shaft 61. A large-diameter intermediate gear 63b and a small-diameter intermediate gear 63s are integrally supported on the intermediate gear shaft 62. [0071]
The drive gear 61a of the drive shaft 61 of the cell motor 60 meshes with the large-diameter intermediate gear 62b. The small-diameter intermediate gear 63s, which is integral with the large-diameter intermediate gear 63b, meshes with the driven gear 14 fitted on the crankshaft 10. The starter mechanism is thus constituted. [0072]
In the internal combustion engine 1, which is mounted on a vehicle in such a manner that the crankshaft 10 is directed in the vehicle-body width direction, there is room in space in the front lower portion of the crankshaft 10. Since the cell motor 60 as well as the intermediate gears 63b and 63s are disposed by effectively utilizing the space in the front lower portion of the crankcase 2, it is possible to avoid an increase in size of the internal combustion engine 1. [0073]
In the internal combustion engine 1, the assembly of

the cylinder block 4 and the cylinder head 5 protrudes from the front upper portion of the crankcase 2 while being slightly inclined forward. As illustrated in Fig. 1, an engine hanger attachment portion 70 is formed to protrude on the front wall of the crankcase 2 at a position which is below the front wall of the cylinder block 4 inclined forward and is above the cell motor 60. [0074]
The engine hanger attachment portion 70 is provided by utilizing an open space between the cylinder block 4 and the cell motor 60 therebelow. Accordingly, the engine hanger attachment portion 70 does not become bulky, and the internal combustion engine 1 can be stably suspended. [Brief Description of the Drawings] [0075]
[Fig. 1] Fig. 1 is a partially omitted side view of an internal combustion engine according to an embodiment of the present invention.
[Fig. 2] Fig. 2 is a cross-sectional development view of the internal combustion engine (a cross-sectional view taken along the line II-II in Fig. 3).
[Fig. 3] Fig. 3 is a side view showing a chief part of the internal combustion engine in an enlarged manner, as a partial cross-section of the internal combustion engine.
[Fig. 4] Fig. 4 is a perspective view of a left crankcase and a sidewall plate.
[Fig. 5] Fig. 5 is a side view of the left crankcase.
[Fig. 6] Fig. 6 is a cross-sectional view taken

along the line VI-VI in Fig. 5. [Explanation of the Reference Numerals] [0076]
1 INTERNAL COMBUSTION ENGINE
2 CRANKCASE
2L LEFT CRANKCASE
2Lw LEFT BEARING WALL
2Ls PERIPHERAL WALL
2C CAM CHAIN CHAMBER
2S CRANK CHAMBER
2R RIGHT CRANKCASE
3 TRANSMISSION CASE
3S TRANSMISSION CHAMBER
4 CYLINDER BLOCK
5 CYLINDER HEAD
6 CYLINDER HEAD COVER
7 CASE COVER

10 CRANKSHAFT
11 MAIN BEARING
12 DRIVE SPROCKET
13 AC GENERATOR
14 DRIVEN GEAR,

20 CAMSHAFT
21 CAMSHAFT HOLDER
22 DRIVEN SPROCKET
23 CAM CHAIN
24 GUIDE ROLLER
25 GUIDE ROLLER

30 CAM CHAIN TENSIONER SYSTEM
31 TENSIONER ARM

32 PIVOT BOLT
33 TENSIONER ROLLER

35 TENSIONER LIFTER
36 PUSH ROD
37 GUIDE HOLE
37a OIL CHAMBER
38 GUIDE CYLINDER PORTION
39 OIL RECEIVING PORTION
39f BOLT BOSS PORTION
39c FRONT GUIDE WALL
39r REAR GUIDE WALL
40 OIL RESERVOIR
41 SIDEWALL PLATE
42 BOLT
4 3 WASHER
44 HEAD MEMBER
4 5 CONTROL VALVE
4 6 TENSIONER BOLT
47 COMPRESSION SPRING
50 OIL GUIDE RIB
51 VOID
52 COMMUNICATION OPENING
53 SLOPE
54 OIL RETURN PASSAGE
55 DRAIN BOLT
60 CELL MOTOR
61a DRIVE GEAR
62 INTERMEDIATE GEAR SHAFT
63b LARGE-DIAMETER INTERMEDIATE GEAR

63s SMALL-DIAMETER INTERMEDIATE GEAR 7 0 ENGINE HANGER ATTACHMENT PORTION

[Document Name] Scope of Claims
[Claim 1] A cam chain tensioner system for an internal
combustion engine, comprising:
a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system;
a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member;
an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod;
a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and
a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out,
the cam chain tensioner system always applying a predetermined tension to the cam chain, wherein
the guide hole is formed in a lower portion of the crankcase while opening at least upward,
an oil reservoir is formed integrally in the crankcase, the oil reservoir being a concave portion that is depressed downward and opens upward to the cam chain chamber, and the upper opening of the guide hole faces the inside of the oil reservoir. [Claim 2] The cam chain tensioner system for an internal

combustion engine according to claim 1, wherein
the upper opening, which faces the inside of the oil reservoir, of the guide hole is formed to open upward as well as to left and right sides by front and rear guide walls constituting the upper portion of the guide hole, the front and rear guide walls extending to the inside of the oil reservoir,
the push rod is fitted into the guide hole and slidably supported by being sandwiched at front and rear sides thereof by the front and rear guide walls, and
the left and right openings of the push rod between the front and rear guide walls communicate with the oil reservoir.
[Claim 3] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 and 2, wherein
an oil guide rib is formed to be inclined below the drive sprocket, the oil guide rib protruding from a wall surface of a bearing wall of the crankcase, the wall surface being on the cam chain chamber side, the bearing wall being for the crankshaft, and
the oil reservoir is located below a lower end of the oil guide rib.
[Claim 4] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 3, wherein
the oil reservoir has a front oil reservoir and a rear oil reservoir that are formed side by side in a vehicle-body front-rear direction, and
the front oil reservoir and the rear oil reservoir

communicate with each other.
[Claim 5] The cam chain tensioner system for an internal
combustion engine according to claim A, wherein
the front oil reservoir is located below the lower end of the oil guide rib,
a front wall of the front oil reservoir protrudes forward,
a bottom surface of the front oil reservoir and a bottom surface of the rear oil reservoir are continuous with each other while being inclined obliquely downward to the rear, and
the upper opening of the guide hole faces the rear oil reservoir.
[Claim 6] The cam chain tensioner system for an internal combustion engine according to claim 5, wherein
the crankcase has an oil return passage formed therein below the front wall, protruding forward, of the front oil reservoir.
[Claim 7] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 6, wherein
one side wall, in a vehicle-body width direction, of the oil reservoir formed in the crankcase is formed with a contact of a sidewall plate that is a separate body. [Claim 8] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 7, wherein
the guide hole opens in a side wall of the crankcase, and is formed to be inclined so that a lower end, which is closed by a tensioner bolt, of the guide hole is located

forward, in the vehicle body, of an upper end of the guide hole, and
a drain bolt for closing a drain bolt hole formed in a bottom wall of the crankcase is provided below the tensioner bolt in a side view of the vehicle body. [Claim 9] A cam chain tensioner system for an internal combustion engine, comprising:
a pressing member that acts with pressure on an endless cam chain looped between a drive sprocket and a driven sprocket in a cam chain chamber, the drive sprocket being fitted on a crankshaft rotatably supported in a crankcase of an internal combustion engine, the driven sprocket being fitted on a camshaft of a valve system;
a push rod that is slidably fitted into a guide hole and is in pressure contact with the pressing member;
an oil chamber that is formed inside the guide hole while being covered with a lid portion of the push rod;
a control valve that is provided to the lid portion of the push rod, and that allows oil to flow into the oil chamber and inhibits the oil from flowing out of the oil chamber; and
a compression spring that is set in the oil chamber and urges the push rod in a direction in which the push rod protrudes out,
the cam chain tensioner system always applying a predetermined tension to the cam chain, wherein
an oil reservoir is formed in a lower portion of the crankcase, the upper opening of the guide hole facing the inside of the oil reservoir,
the crankcase is partitioned by a partition wall into

the cam chain chamber provided with the oil reservoir and a transmission chamber located behind the cam chain chamber in a vehicle-body front-rear direction, and
a communication opening is formed in a portion of the partition wall, the portion located obliquely upward of the oil reservoir.
[Claim 10] The cam chain tensioner system for an internal combustion engine according to any one of claims 1 to 9, wherein
the internal combustion engine is mounted on a vehicle in such a manner that the crankshaft is directed in the vehicle-body width direction, and
a cell motor and an intermediate gear are disposed in a front lower portion of the crankcase in which the crankshaft is pivotally supported.
[Claim 11] The cam chain tensioner system for an internal combustion engine according to claim 10, wherein
a cylinder protrudes from a front upper portion of the crankcase while being slightly inclined forward, and
an engine hanger attachment portion is formed on a front wall of the crankcase at a position below the cylinder and above the cell motor.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=ZR3C9hN3u3At+IeNHBPCSg==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

278703

Indian Patent Application Number

3112/CHE/2009

PG Journal Number

54/2016

Publication Date

30-Dec-2016

Grant Date

28-Dec-2016

Date of Filing

16-Dec-2009

Name of Patentee

HONDA MOTOR CO., LTD

Applicant Address

1-1, MINAMI-AOYAMA 2-CHOME, MINATO-KU, TOKYO 107-8556

Inventors:

#	Inventor's Name	Inventor's Address
1	KANAE, TAKESHI	C/O HONDA R&D CO., LTD., 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193

PCT International Classification Number

F02B 67/06; F02B 61/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2008-334251	2008-12-26	Japan