Title of Invention

"CRANKCASE STRUCTURE OF FOUR STROKE INTERNAL COMBUSTION ENGINE"

Abstract

To block between a cam chain chamber and a belt-type continuously variable transmission chamber tightly with a small number of parts and provide the crankcase structure of a four-cycle internal combustion engine which facilitates the attachment and detachment of a cam chain in maintenance. [MEANS TO SOLVE] Internal structure of a crankcase of a four-cycle internal combustion engine wherein a crankshaft 40 pierces the partition wall 71 of the crankcase for partitioning a cam chain chamber 52 and a belt-type continuously variable transmission chamber 70 and in the four-cycle internal combustion engine 30 in which a sealing member 72 blocks a through hole 71a piercing the partition wall, the circular sealing member 72 with a larger outside diameter than the maximum outside diameter in a state in which a cam chain 51 is wound on a cam chain driving sprocket 55 engaged with the crankshaft blocks the through hole 7la. [SELECTED DRAWING] Fig. 4

Full Text

[DETAILED DESCRIPTION OF THE INVENTION] [Technical Field of the Invention] The present invention relates to the crankcase Structure of a fourinternal combustion engine adopting a cam chain system for operating a valve and provided with a belt-type continuously variable transmission. [Prior Art] In this type of four-cycle internal combustion engine, as a crankshaft pierces the partition wall of a crankcase for partitioning a belt-type continuously variable transmission chamber off a cam chain chamber in which lubricating oil is used, a sealing member is pressfitted into the through hole of the crankshaft through the partition wall to prevent the oil from leaking into the belt-type continuously variable transmission chamber. Such structure is also disclosed in Japanese published examined patent application No. Hei 5-47437 and in this patent application, a circular hole with a large diameter is formed through the partition wall for partitioning the cam chain chamber and the belt-type continuously variable transmission chamber, a hollow disclike capping member blocks the circular hole and is fixed by a screw, and the crankshaft pierces the central through hole of the capping member. The sealing member blocks a through hole a little larger than the diameter of the crankshaft through this capping member. Therefore, as a large opening is open through the partition wall by removing this capping member" in the maintenance of the internal combustion engine, the cam chain wound on a driving sprocket can be detached through the opening. [Problems to be Solved by the Invention] However, as such a capping member which is different from a partition wall is required and a fixture such as a screw for attaching the capping member is required, the mechanism is complicated and the number of parts is increased. In the case of the conventional internal combustion engine which does not use such a capping member, a method of dividing a crankcase into which right and left parts are integrated into the right and left parts is only one method to detach a cam chain for maintenance and the work is extremely troublesome. The present invention is made to solve such problems and the object is to provide the crankcase structure of a four-cycle internal combustion engine wherein a belt-type continuously variable transmission chamber is blocked tightly off a cam chain chamber with a small number of parts and the cam chain can be readily attached or detached in maintenance. [Means to Solve the Problems] To achieve the above-described object, the present invention provides the crankcase structure of a four-cycle internal combustion engine wherein in the four-cycle internal combustion engine in which a crankshaft pierces a partition wall of a crankcase for partitioning a cam chain chamber and a belt-type continuously variable transmission chamber and a sealing member blocks the through hole, the circular sealing member with a larger outside diameter than the maximum outside diameter in a state in which a cam chain is wound on a cam chain driving sprocket engaged with the crankshaft blocks the through hole. As a through hole with a larger outside diameter than the maximum outside diameter in a state in which the cam chain is wound on the cam chain driving sprocket is open by removing the circular sealing member for blocking the through hole through the partition wall of the crankcase if the cam chain is detached from the cam chain driving sprocket in maintenance, the cam chain can be readily detached from the cam chain driving sprocket utilizing the through hole, the work for attachment and detachment is facilitated because only a small number of parts are used and the maintainability can be enhanced. When the circular sealing member blocks the through hole, the crankcase structure of a four-cycle internal combustion engine according to Claim 1 wherein the peripheral edge of the circular sealing member is located close to a cam plate sliding boss provided on the half on the movable side of a pulley of a belt-type continuously variable transmission can be realized and therefore, high maintainability can be kept because the sealing member is not touched to the belt driving pulley. When the crankcase structure of a four-cycle internal combustion engine according to Claim 1 or 2 wherein a difference in level is formed on the peripheral edge of the side of the circular sealing member on the side of the belt-type continuously variable transmission chamber is realized, the sealing member pressfitted into the through hole can be readily detached utilizing the difference in level and work for maintenance can be further facilitated. [Preferred Embodiments of the Invention] An embodiment according to the present invention will be described below referring to Figs. 1 to 4. Accordingly, the present invention relates to the crankcase structure of a four- internal combustion engine wherein a crankshaft pierces the partition wall of a crankcase for partitioning a cam chain chamber and a belt-type continuously variable transmission chamber and a sealing member blocks the through hole, wherein: said circular sealing member with a large outside diameter than the maximum outside diameter in a state in which a cam chain is wound on a cam chain driving sprocket engaged with the crankshaft, blocks said through hole. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS [Fig. 1] Fig. 1 is a general side view showing a scooter-type motorcycle equivalent to an embodiment according to the present invention; [Fig. 2] Fig. 2 is a cross section viewed along a line II-I-I in Fig. 1 showing the internal combustion engine of the scooter-type motorcycle; [Fig. 3] Fig. 3 is a sectional view viewed along a line Ill-Ill in Fig. 2; [Fig. 4] Fig. 4 is a sectional view viewed from along a line IV- IV in Fig. 3; and [Fig. 5] Fig. 5 is a cross section of the main part showing the internal structure of a crankcase equivalent to another embodiment. Fig. 1 is a side view showing a scooter-type motorcycle 1 provided with a swinging internal combustion engine according to the present invention. The front 2 of the body and the rear 3 of the body are coupled via a low floor part 4 and a body frame constituting the bone structure of the body is mostly constituted by a downward tube 6 and a main pipe 7. That is, the downward tube 6 is extended downward from a steering head 5 in the front 2 of the body, is bent horizontally at the lower end, is extended in the lower part of the floor part 4 backward, is coupled to a pair of right and left main pipes 7 at the rear end, each main pipe 7 is raised from the coupled part obliquely backward, is bent horizontally at predetermined height and is extended backward. A fuel tank and a housing box are supported by the main pipe 7 and a seat 8 is arranged over it. In the meantime, in the upper part of the front 2 of the body, a handle 11 is provided with it supported by the steering head 5, a front fork 12 is extended downward and a front wheel 13 is supported at the lower end of the front fork. A bracket 15 is protruded at the lower end of the rising part of the main pipe 7 and a swing unit 17 is coupled and supported to/by the bracket 15 via a link member 16 so that it can be swung. A single cylinder four-cycle internal combustion engine 30 is mounted in the front of the swing unit 17 with a cylinder block 32 greatly tilted forward to be approximately horizontal and the end of a hanger bracket 18 which is protruded forward from the lower end of a portion equivalent to a crankcase of its swing unit case 31 is coupled to the link member 16 via a pivot 19. A belt-type continuously variable transmission 35 is constituted backward from the internal combustion engine 30 and a rear wheel 21 is supported by a speed reducing mechanism 38 provided in its rear. A rear cushion 22 is attached between the upper end of this speed reducing mechanism 38 and the upper bent part of the main pipe 7. In the upper part of the swing unit 17, a carburetor 24 which is connected to an inlet pipe 23 extended from the upper part of a cylinder head 33 of the internal combustion engine 30 and an air cleaner 25 coupled to the carburetor 24 are arranged. In the meantime, a main stand 26 is attached as a pivot to the hanger bracket 18 protruded in the lower part of the swing unit case 31, the base end of a kick arm 28 is fixed to a kick shaft 27 protruded from a transmission case cover 36 of the belt-type continuously variable transmission 35 and a kick pedal 29 is provided at the end of the kick arm 28. The front 2 of the body is covered with a front cover 9a from the front direction, with a rear cover 9b from the rear direction and with a front lower cover 9c from the right and left directions, and the center of the handle 11 is covered with a handle cover 9d. The floor part 4 is covered with a side c 9e and the rear 3 of the body is covered with a body cover lOa and a tail side cover lOb from the right ai left directions. Fig. 2 is a cross section showing the swin unit 17 in Fig. 1 viewed approximately along a line : II. The swing unit case 31 is constituted by integrating a left unit case 31L and a right unit ca: 31R, the right unit case 31R constitutes the half of crankcase, and the left unit case 31L consists of a front crankcase 31a which is long longitudinally, a central transmission case 31b and a rear speed reduct case 31c. The left open face of this left unit case is covered with a transmission case cover 36, the be. type continuously variable transmission 35 is housed inside, the right open face of the rear speed reduce: case 31c is covered with a speed reducer case 37 and speed reducing mechanism 38 is housed inside. A crankshaft 40 is supported by the right and left main bearings 41, 41 so that it can be rotated inside a so-called crankcase consisting of the crankcase 31a and the right unit case 31R, an AC generator 60 is provided in the right extended part of horizontally extended right and left parts, and a cam chain driving sprocket 55 and a belt driving pulley 76 of the belt-type continuously variable transmission 35 are provided in the left extended part. Inside the internal combustion engine 30, a connecting rod 43 couples a piston 42 and a crank pin 40a of the crankshaft 40 which are reciprocated inside a cylinder liner 44 of the cylinder block 32. This four-cycle internal combustion engine 30 adopts an overhead camshaft (OHC)-type valve system, a valve operating mechanism 50 is provided inside a cylinder head cover 34, a cam chain 51 for transmitting driving force to the valve operating mechanism 50 is suspended between a cam shaft 53 and the crankshaft 40 and a cam chain chamber 52 for the cam chain is provided with it communicating with the crankcase 31a, the cylinder block 32 and the cylinder head 33. That is, the cam chain 51 is suspended between a driven sprocket 54 engaged with the left end of the cam shaft 53 directed horizontally and the driving sprocket 55 engaged with the crankshaft 40 through the cam chain chamber 52. A spark plug 45 is fitted from the reverse side (right side) of the cam chain chamber 52 to a combustion chamber in the cylinder head 33. As shown in Fig. 3, an inlet valve 56 and an exhaust valve 57 are respectively arranged above and below the cam shaft 53 in the valve operating mechanism 50 inside the cylinder head cover 34 because a cylinder is greatly tilted forward up to a state close to a position in which the cylinder is approximately horizontal and rocker arms 59, 59 are respectively attached to the upper and lower rocker shafts 58, 58 as a pivot so that the rocker arms can be swung, the rocker arms 59, 59 are swung by the rotation of the cam of the cam shaft 53 and open or close the inlet valve 56 and the exhaust valve 57 at predetermined timing. An arm-shaped outer rotor 62 of the AC generator 60 provided on the right side of the right unit case 31R is fixed to the end of a crankshaft 30 protruded from a central cylinder 31d inside the right unit case 31R via ACG boss 61 and a stator 64 formed by winding a stator coil 65 inside a magnet 63 arranged on the inner peripheral face of the AC generator is fixed to the central cylinder 31d. A forced air cooling fan 66 is attached to the right side of the outer rotor 62, a fan cover 67 is provided on its right side and a fan shroud 68 is coupled to the fan cover 67 to cover the cylinder block 32 and the cylinder head 33. In the meantime, the cam chain chamber 52 is formed with it partitioned off the crankcase by the main bearings 41 in the crankcase 31a of the swing unit case 31, the left wall of the cam chain chamber 52 is a partition wall 71 for partitioning the cam chain chamber 52 off a further left belt-type continuously variable transmission chamber 70, a flat cylindrical through hole 7la with a large diameter for passing the crankshaft 40 through the through hole is formed through the partition wall 71 and a circular sealing member 72 is fitted into the through hole 71a and the crankshaft 40 is passed through the hollow part of the circular sealing member 72. The outer annulus 73a, the inner annulus 73b which are made of rubber material 73 and the outside wall 73c of the circular sealing member 72 are coupled with its section in the shape of a character C, circular space is formed inside, a thin steel sheet is embedded in the outer annulus 73a and the outside wall 73c and a ferrule 74b is fitted to the periphery of the inner annulus 73b. The driving sprocket 55 is engaged with the crankshaft 40 between this sealing member 72 and the main bearing 41, and the outside diameter of the outer annulus 73a of the circular sealing member 72 and the bore diameter of the through hole 7la are larger than the maximum outside diameter of the driving sprocket 55 around which the cam chain 51 is wound. Therefore, as the through hole 71a with a large diameter is open if the circular sealing member 72 is removed from the through hole 71a, the cam chain 51 can be removed or wound from/around the driving sprocket 55 through the opening. The belt-type continuously variable transmission chamber 70 is partitioned off the cam chain chamber 52 by this sealing member 72 tightly and oil is prevented from leaking out into the belt-type continuously variable transmission chamber 70. A belt driving pulley 76 is provided to the crankshaft 40 extended through the sealing member 72 so that it can be rotated. The belt driving pulley 76 consists of a half 77 on the fixed side of the pulley and a half 78 on the movable side of the pulley, the half 77 on the fixed side is fixed to the left end of the crankshaft 40 via a boss 79, the half 78 on the movable side is fitted to the crankshaft 40 via each spline on the right side of the half on the fixed side, the half 78 on the movable side is rotated together with the crankshaft 40, is slid in the direction of the shaft and can approach or be separated from the half 77 on the fixed side, and a V belt 75 is suspended between both halves 77 and 78. A cam plate 80 is provided in a fixed position close to the circular sealing member 72 on the right side of the half 78 on the movable side and a slide piece 80a provided at the peripheral end is fitted to a cam plate sliding boss 78a formed at the peripheral end of the half 78 on the movable side in the axial direction so that the slide piece can be slid. The side face of the half 78 on the movable side of the pulley on the side of the cam plate 80 is tapered toward the side of the cam plate 80 and a dry weight roller 81 is housed inside the tapered face with it put between the half on the movable side and the cam plate 80. Therefore, when the rotational speed of the crankshaft 40 is increased, the dry weight roller 81 which is put between the half 78 on the movable side and the cam plate 80 and rotated together with them is moved by centrifugal force in the centrifugal direction, the half 78 on the movable side is pressed by the dry weight roller 81, moved left and approaches the half 77 on the fixed side, and the V belt 75 between both halves 77 and 78 of the pulley is moved in the centrifugal direction so that the diameter which is formed by the wound belt is extended. A belt driven pulley 86 which is located in the rear part and corresponds to the belt driving pulley 76 consists of both halves 87 and 88, the half 87 on the fixed side is fitted to an inner sleeve 89 supported by a shaft 92 for inputting to a speed reducer in the speed reducing mechanism 38 so that the inner sleeve can be relatively rotated and the half 88 on the movable side is fitted to the an outer sleeve 90 which is located on the left side of the half 87 on the fixed side and supported by the inner sleeve 89 so that the outer sleeve can be slid in the direction of the shaft. The V belt 75 is suspended between both halves 87 and 88. A centrifugal clutch is provided on the left side of the shaft 92 for inputting to the speed reducer and the inner sleeve 89 and the power transmitted to the inner sleeve 89 via the V belt 75 is transmitted to the shaft 92 for inputting to the speed reducer when the rotational speed of the inner sleeve is increased and the centrifugal clutch 91 is touched to the inner sleeve. The speed reducing mechanism 38 transmits the power transmitted to the shaft 92 for inputting to the speed reducer to a shaft 94 for output via an intermediate shaft 93 and gears in a state in which speed is reduced and the shaft for output 94 rotates a rear wheel 21 by rotating the axles of the rear wheel 21. A drum brake 95 is provided at the hub of the rear wheel 21, a drum brake arm 97 to which a brake cable is connected is fitted to a drum brake shaft 96 and the drum brake 95 is constituted so that the drum brake arm 97 is swung when the brake cable is pulled, the drum brake shaft 96 is rotated and the drum brake 95 is applied. The transmission case cover 36 for covering the belt-type continuously variable transmission chamber 70 from the left side covers from the belt driving pulley 76 in the front to the centrifugal clutch 91 in the rear and is pierced by the kick shaft 27 a little in front from the center of the cover so that the kick shaft can be rotated, a driving helical gear 100 is engaged with the inner end of the kick shaft 27 and pressed by a return spring 101. A sliding shaft 102 is supported on the same axis as the crankshaft 40 by the inner face of the front of the transmission case cover 36 so that the sliding shaft can be rotated and can be slid in the axial direction, a driven helical gear 103 is formed on the sliding shaft 102 and engaged with the driving helical gear 100, a ratchet wheel 104 is fixed at its right end and the entire sliding shaft is pressed left by a friction spring 105. In the meantime, a ratchet 79a is formed opposite to the ratchet wheel 104 on the boss 79 on the side of the crankshaft 40 and both can be touched or separated by sliding of the sliding shaft 102. Therefore, when a kick pedal 29 is worked and the kick shaft 27 is rotated against the return spring 101 via the kick arm 28, the driving helical gear 100 is rotated together with the kick shaft 27, the driven helical gear 103 engaged with the driving helical gear is slid right against the friction spring 105, being rotated together with the sliding shaft 102, the ratchet wheel 104 is engaged with the ratchet 79a of the boss 79, can rotate the crankshaft 40 forcedly and can start up the internal combustion engine 30. In the meantime, referring to this internal combustion engine, a starter motor 110 is arranged in the upper part of the crankcase 31a of the left unit case 31L, a pinion 113 around which the coil 112 of an inner rotor surrounded by the magnet 111 of an outer stator is wound is protruded left in the starter motor 110 as shown in Fig. 4 and a gear 113a is formed at the end of the pinion 113. A plunging gear mechanism 115 located between the crankcase 31a and the transmission case cover 36 is provided between the starter motor 110 and the belt driving pulley 76 with the axis directed horizontally, the pinion gear 113a of the starter motor 110 is engaged with an input gear 116 provided on the right side of the plunging gear mechanism 115 and a plunging gear 117 provided on the left side is engaged with a starter ring gear 77a formed at the peripheral edge of the half 77 on the fixed side of the pulley when the plunging gear is plunged left. Therefore, when the starter motor 110 is driven, the rotation of the pinion 113 is transmitted to the input gear 116 of the plunging gear mechanism 115, the plunging gear 117 is plunged left and engaged with the starter ring gear 77a of the half 77 on the fixed side of the pulley, the half 77 on the fixed side is rotated together with the crankshaft 40 and the internal combustion engine 30 can be started up. When the starter motor 110 is stopped, the plunging gear 117 is retracted and the engagement with the starter ring gear 77a is released. A cooling fan 118 made of rubber is attached by baking it on the side (the left side) reverse to the side between which and one side of the half on the movable side of the pulley the V belt 75 is suspended of the half 77 on the fixed side of the pulley on which the starter ring gear 77a to be engaged with the plunging gear 117 is formed, and the belt-type continuously variable transmission 35 is cooled by rotating the cooling fan 118. As shown in Figs. 1 and 2, a cylindrical air intake duct 36a is formed with it protruded in the front of the transmission case cover 36, a cylindrical exhaust duct 36b is formed approximately in the center in the horizontal direction obliquely vertically along the side wall of the transmission case cover, the rear end of a bellows type hose 14 is connected to the air intake duct 36a, the bellows type hose 14 is extended forward and its front end is connected to an exhaust pipe 6b formed with it protruded from the bent part of the downward tube 6 . An air intake pipe 6a is formed with it protruded in a location of the downward tube 6 close to the steering head 5 and the inside of the downward tube 6 communicates with the air intake pipe 6a and the exhaust pipe 6b. Therefore, when the cooling fan 118 is rotated by the rotation of the crankshaft 40 in the belt-type continuously variable transmission chamber 70, air is taken in from the air intake pipe 6a of the downward tube 6, enters the bellows type hose 14 from the exhaust pipe 6b through the downward tube 6, is sucked into the belt-type continuously variable transmission chamber 70 from the air intake duct 36a through the bellows type hose 14, cools the belt-type continuously variable transmission 35 and is discharged outside from the exhaust duct 36b. This four-cycle internal combustion engine 30 is constituted as described above, the above-described belt-type continuously variable transmission chamber 70 is partitioned tightly by the circular sealing member 72 with a large diameter to prevent oil from leaking, as the through hole 71a with a large diameter is open by removing the sealing member 72 in the maintenance of the belt-type continuously variable transmission chamber 70, the cam chain 51 can be readily removed and wound from/on the driving sprocket 55, the swing unit case 31 is not required to be disassembled right and left, no special capping member is required, the number of parts is small, the structure is simple and the maintenance is simplified. Though the circular sealing member 72 has a large diameter, it is large to the extent that the peripheral edge of the circular sealing member approaches the cam plate sliding boss 78a with which the slide piece 80a on the periphery of the approaching cam plate 80 is engaged so that the slide piece can be slid and the sealing member 72 can be arranged without being touched to the belt driving pulley 76 so that the maintenance is simplified. Next, an example in which the sealing member is transformed will be described referring to Fig. 5. The structure of an internal combustion engine except this sealing member 120 is the same as that in the above-described embodiment and the same reference numbers are used. Referring to this sealing member 120 pressfitted into a flat cylindrical through hole 71a of a partition wall 71 formed in a crankcase 31a of a left unit case 31L, a steel plate 122a is embedded in an outer annulus 121a and an outside wall 121c of a rubber member 121 consisting of the outer annulus 121a, an inner annulus 121b and the outside wall 121c and a ferrule 122b is fitted on the periphery of the inner annulus 121b substantially as the above-described sealing member 72, however, a difference in level 123 is formed in the bent part ranging from the outside wall 121c to the outer annulus 121a. When such a sealing member 120 is pressfitted into the through hole 71a, the outside wall 121c is protruded outside from the opening of the through hole 71a through the difference in level 123, a hollow disclike falling preventing plate 124 presses the end face of the flat cylindrical through hole 71a and the difference in level 123 from the left direction and the falling preventing plate 124 is fixed on a boss 125 for attaching a screw of a crankcase 31a by a screw 126. The falling preventing plate 124 presses the difference in level 123 with its hollow circular opening reduced by the difference in level 123 of the sealing member 120 and fitted to the periphery of the protruded outside wall 121c to prevent the sealing member 120 from falling. Therefore, as the outside wall 121c of the sealing member 120 is a little protruded and exposed from the through hole 71a if the screw 126 is loosened and the falling preventing plate 124 is detached, the sealing member 120 can be readily detached utilizing this exposed outside wall 121c and the maintenance can be further facilitated. [Effect of the Invention] According to the present invention, as a through hole larger than the maximum outside diameter in a state in which a cam chain is wound on a cam chain driving sprocket is formed when a circular sealing member for blocking a through hole formed through the partition wall of a crankcase is removed if the cam chain is detached from the cam chain driving sprocket in maintenance, the cam chain can be readily detached from the cam chain driving sprocket utilizing the through hole, attachment and detachment can be facilitated because the number of parts is small and the maintainability can be enhanced. When the circular sealing member is attached with it blocking the through hole, the inside of the crankcase is constituted so that the peripheral edge of the circular sealing member is located close to a cam plate sliding boss provided on the half on the movable side of a pulley of a belt-type continuously variable transmission and therefore, the inside of the crankcase can be constituted without the sealing member being touched to a belt driving pulley so that high maintainability is kept. The sealing member pressfitted into the through hole can be readily detached utilizing a difference in level by forming the difference in level on the peripheral edge of the side of the circular sealing member on the side of a belt-type continuously variable transmission chamber and the maintenance can be further facilitated. 30. Internal combustion engine 31. Swing unit case 32. Cylinder block 33. Cylinder head 34. Cylinder head cover 35. Belt-type continuosly variable transmission 36. Transmission cover case 37. Transmission case 38. Speed reducing mechanism 40. Crankshaft 41. Main bearing 42. Piston 43. Connecting rofl 44. Cylinder liner 45. Sparking plug 50. Valve operating mechanism 51. Cam chain 52. Cam chain chamber 53. Cam shaft 54. Driven sprocket 55. Driving sprocket 56. Inlet valve 57. Exhaust valve 58. Rocker shaft 59. Rocker arm 60. AC generator 61. ACG boss 62. Outer rotor 63. Magnet 64. Stator 65. Stator core 66. Pan 67. Fan cover 68. Fan shroud 70. Belt-type continuosly variable transmission chamber 71. Partition wall 72. Sealing member 73. Rubber member 74a. Steel plate 74b. Ferrule 75. V belt 76. Belt driving pulley 77. Half on the fixed side of the pulley 78. Half on the movable side of the pulley 79. Boss 80. Cam plate 81. Dry weight roller 86. Belt driven pulley 87. Half on the fixed side of the pulley 88. Half on the movable side of the pulley 89. Inner sleeve 90. Outer sleeve 91. Centrifugal clutch 92. Shaft for inputting to a speed reducer 93. Intermediate shaft 94. Shaft for output 95. Drum brake 96. Drum brake shaft 97. Drum brake arm 100. Driving helical gear 101. Return spring 102. Sliding shaft 103. Driven helical gear 104. Ratchet wheel 105. Friction spring 110. Starter motor 111. Magnet 112. Coil 113. Pinion 115. Plunging gear mechanism 116. Input gear 117. Plunging gear 118. Cooling fan 120. Sealing member 121. Rubber member 122a. Steel plate 122b. Ferrule 123. Difference in level 124. Falling preventing plate 125. Boss for attaching a screw 126. Screw WE CLAIM: 1. The crankcase structure of a four- internal combustion engine (30) wherein a crankshaft (40) pierces the partition wall (71) of a crankcase (3la) for partitioning a cam chain chamber (52) and a belt-type continuously variable transmission chamber (35) and a sealing member (72) blocks the through hole (71a), characrtered in that said circular sealing member with a large outside diameter than the maximum outside diameter in a state in which a cam chain (51) is wound on a cam chain driving sprocket (55) engaged with the crankshaft (40) blocks said through hole (7la). 2. The crankcase structure of a four- internal combustion engine as claimed in claim 1, wherein: when said circular sealing member blocks said through hole, the peripheral edge of it is located close to a cam plate (80) sliding boss (79) provided on the half on the movable side of a pulley of a belt-type continuously variable transmission chamber. 3. The crankcase structure of a four- internal combustion engine as claimed in claim 1 or 2, wherein a difference in level is formed on the peripheral edge of the side of said circular sealing member on the side of said belt-type continuously variable transmission chamber. 4. The crankcase structure of a four internal combustion engine (30) substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

2146-del-1996-abstract.pdf

2146-del-1996-claims.pdf

2146-del-1996-complete specification (granted).pdf

2146-del-1996-correspondence-others.pdf

2146-del-1996-correspondence-po.pdf

2146-del-1996-description (complete).pdf

2146-del-1996-drawings.pdf

2146-del-1996-form-1.pdf

2146-del-1996-form-13.pdf

2146-del-1996-form-19.pdf

2146-del-1996-form-2.pdf

2146-del-1996-form-3.pdf

2146-del-1996-form-6.pdf

2146-del-1996-form-61.pdf

2146-del-1996-gpa.pdf

2146-del-1996-petition-137.pdf

2146-del-1996-petition-138.pdf

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