Title of Invention

"STRUCTURE FOR LUBRICATING FORWARD TILTING ENGINE"

Abstract

[Object] To provide an engine lubricating structure suitable for a motorcycle. [Solving Means] In a comparative example shown in Fig. 15(a), oil flows in an engine lubricating structure 171 through an oil passing hole 172 and eventually the engine lubricating structure 171 is filled with the oil. In an embodiment shown in Fig. 15(b), oil flows in the engine lubricating structure 171 through the oil passing hole 172; however, since the oil in the engine lubricating structure 171 is discharged through an oil escape groove 178, it is not accumulated in the engine lubricating structure 171 so much. [Effect] Even for an engine having a structure in which a cylinder axis is disposed substantially in the horizontal direction and oil is liable to be accumulated in an engine lubricating structure, the oil in the engine lubricating structure can be effectively escaped through an oil escape groove. As a result, a valve mechanism of the engine can be continuously smoothly operated.-

Full Text

The present invention relates to a structure for lubricating a forward tilting engine, particularly to an engine lubricating structure suitable for a hybrid type motorcycle including an electric motor in addition to an engine. -.[00 02-] [Related Art] Vehicles of a type using gasoline engine as a drive source are mainly available at present; however, vehicles of a type using an electric motor as a drive source are required at locations where occurrence of exhaust gas must be avoided. A motor-driven vehicle, however, has an inconvenience in the increased body weight and the shortened running distance. To cope with such an inconvenience, it has been increasingly required to develop a hybrid type vehicle including an electric motor in addition to an engine. [0003] For example, Japanese Patent Laid-open No. Hei 8-1 175477 discloses a hybrid type motorcycle entitled "Device for Switching Engine Power to/from Motor Power in Motorcycle or the Like". In the above document, an engine 10 is a simple air-cooled two cycle engine. [0004] A motorcycle, however, is required to mount a four cycle engine in consideration of fuel consumption and emission. In this case, since a four cycle engine is higher in vehicle height than a two cycle engine, it is preferably designed such that a cylinder axis tilts forward for lowering the center of gravity of the vehicle. [0005] Fig. 16 is a view showing an essential portion of a related art valve mechanism. Referring to Fig. 16, a valve guide 203 is disposed to face an exhaust port 202 of a cylinder head 201 and a stem 205 of a valve 204 is slidably inserted in the valve guide 203. A retainer 206 is mounted at a leading end portion of the stem 205, and a valve spring 207 is provided such that one end thereof is in contact with the retainer 206 for biasing the valve 204 in the valve closing direction. The valve 204 is pushed out in the valve opening direction by a cam 208 through a bucket 209 of the lifter and is returned in the valve closing direction by the valve spring 207. [0006] Reference numeral 211 indicates an oil passing hole through which oil mist is supplied into an engine lubricating structure 212 for lubricating the bucket 209 reciprocating through the engine lubricating structure 212 and the valve spring 207. Further, to further improve power consumption, it is required to make friction (frictional resistance) as small as possible. From this viewpoint, a valve chamber for containing a valve drive mechanism is desired to be formed into a closed space isolated from engine oil for keeping the valve chamber in a dry state thereby eliminating friction of the engine oil. [Problem to be Solved by the Invention] As the cylinder axis tilts forward, an angle of a lower valve may tilt downward with respect to a horizontal axis. In this case, an engine including a valve lifter may cause a problem that oil is less escaped from the oil passing hole 211 and is accumulated in the engine lubricating structure 212, so that new oil is difficult to flow in the engine lubricating structure 212, thereby exerting adverse effect on valve operation. The engine structure in which the valve chamber is formed into a closed space not allowing permeation of engine oil causes a problem that it is difficult for engine oil supplied to a cylinder head to return to an oil pan. Accordingly, an object of the present invention is to provide an engine lubricating structure suitable for a hybrid type power unit in which the center of gravity is lowered. To achieve the above object, according to an invention described in claim 1, there is provided a structure for lubricating a forward tilting engine in which a valve is driven by a cam shaft through a valve lifter; a cylinder axis tilts forward and a valve axis tilts downward from a horizontal axis; and an engine lubricating structure for containing said valve lifter is provided in a cylinder head, characterized in that an oil escape groove is provided in a lower wall of said engine lubricating structure, When the valve axis tilts downward with respect to the horizontal axis, oil is liable to be accumulated in the engine lubricating structure; however, according to the present invention, it is possible to effectively escape the oil in the engine lubricating structure through the oil escape groove while keeping the lowering of the center of gravity of the hybrid type power unit. To achieve the above object, according an invention described in claim 2, there is provided a structure for lubricating a forward tilting engine in which a valve drive mechanism is provided in a cylinder head and a valve chamber for containing said valve drive mechanism is provided on a side portion of a cylinder; said valve chamber is formed into a closed space isolated from engine oil; a cylinder axis is disposed substantially in the horizontal direction; and an oil return passage for returning oil in said valve chamber to an oil pan is provided in both said cylinder head and a cylinder block, characterized in that said oil return passage extends downward from a lower portion of said valve chamber, and an air passage extending from said oil pan to an upper portion of said valve chamber is provided in both said cylinder block and said cylinder head. With this configuration, since oil is returned from the valve chamber to the oil pan through the lower oil return passage and air is supplied from the oil pan to the valve chamber through the upper air passage, the oil can be smoothly returned. Accordingly there is provided a structure for lubricating a forward tilting engine in which a valve is driven by a cam shaft through a valve lifter; a cylinder axis tilts forward and a valve axis tilts downward from a horizontal axis; and an engine lubricating structure for containing said valve lifter is provided in a cylinder head in the valve lifter containing recess, characterized in that • an oil escape groove is provided in the axial direction of the valve and in a surface of a lower wall of said valve lifter containing recess, [Brief Description of the Drawings] [Fig. 1] A side view of a motorcycle according to the present invention. [Fig. 2] A sectional side view of a power unit according to the present invention. [Fig. 3] A sectional plan view of the power unit according to the present invention. [Fig. 4] A view showing a configuration and a function of a cone type continuously variable transmission according to the present invention. [Fig. 5] A view showing a configuration and a function of the cone type continuously variable transmission according to the present invention. [Fig. 6] A view illustrating an engine lubricating system according to the present invention. [Fig. 7] A view illustrating a transmission lubricating system according to the present invention. [Fig. 8] A front view of the power unit, showing a cam shaft drive mechanism as a valve system drive mechanism according to the present invention. [Fig. 9] A view showing an arrangement of an AI reed valve and a water pump according to the present invention. [Figs. 10(a) and 10(b)] Sectional views showing the water pump of the present invention and also showing mounting of a common pulley. [Fig. 11] A sectional view taken on line 11-11 of Fig. 9. [Fig. 12] A view showing an essential portion of a valve mechanism according to the present invention. [Fig. 13] An enlarged view of an essential partition shown in Fig. 12. [Fig. 14] A view seen from an arrow 14 of Fig. 12, with a lifter mechanism omitted. [Figs. 15(a) and 15(b)] Views showing a function of an engine lubricating structure according to the present invention. [Fig. 16] A view showing an essential portion of a related art valve mechanism. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. It is to be noted that the drawings should be seen in the direction of reference numerals. Fig. 1 is a side view of a motorcycle according to the present invention. Referring to Fig. 1, a motorcycle 1 has at its lower central portion a box-like main frame 2 serving as a battery containing box. Inverse U-shaped front swing arms 4 extend from a lower front portion of the main frame 2 through a front pivot 3, and a front wheel 5 is rotatably mounted on the front swing arms 4. A head pipe post 7 extends obliquely upward from an upper front portion of the main frame 2 and a head pipe 8 is fixed at a leading end of the head pipe post 7. A handle post 9 is rotatably mounted in the head pipe 8, and a steering arm 11 is mounted on a lower end of the handle post 9. A leading end (lower end) of the steering arm 11 is connected to a knuckle 12 mounted on the front wheel 5. A power-unit 15 is swingably mounted on an upper rear portion of the main frame 2 through a rear pivot 13 functioning as a swing shaft. A rear wheel 16 is mounted on the power unit 15. A rear cushion 17 is disposed in front of the rear wheel 16, and an air cleaner 18, an exhaust pipe 19, a muffler 21, and a tail lamp 22 are disposed behind the rear wheel 16. A vehicular body is surrounded by a front fender 25, a front cover 26, a front handle cover 27, a center cowl 28, a rear cowl 29 and a rear fender 31 which are disposed in this order from the front side to the rear side of the vehicular body, -f001 Of In Fig. 1, reference numeral 30 indicates a stem; 32 is a front brake disk; 33 is a caliper; 34 is a resin spring; 35 is a front damper; 36 is a leg shield; 37 is a passenger's step; 38 is a side stand; and 39 is a main stand. On an upper side of Fig. 1, reference numeral 41 indicates a horn; 42 is a front lamp; 43 is a handlebar; 44 is a grip; 45 is a baffle duct; 46 is a radiator; 47 is a fan; 48 is a sheet; 49 is a helmet box; 51 is a helmet; 52 is a tail lamp; and 55 is a power unit case. The power unit case 55 is composed of right and left crank cases 55b and 55a (the right crank case 55b on the back side of the figure is not shown), a transmission case 55c, an electric motor case 55d, and a reduction gear case 55e. [0011] Fig. 2 is a sectional side view of the power unit according to the present invention. As will be fully described with reference to Fig. 8, the power unit 15 includes a four-cycle engine in which an intake cam shaft and an exhaust cam shaft are provided in a cylinder head. The power unit 15 has a crank shaft 56 disposed in a lower portion of the power unit case 55; a clutch shaft 47 disposed in parallel to and higher than the crank shaft 56; and a transmission shaft 58 and an electric motor shaft 59 disposed in such a manner as to extend from one end of the clutch shaft 57 in the longitudinal direction (fore and aft) of the vehicular body. That is to say, the clutch shaft 57, transmission shaft 58, and electric motor shaft 59 are disposed in series and also in parallel to and higher than the crank shaft 56. Since the clutch shaft 57, transmission shaft 58, and electric motor shaft 59 are disposed in series in the longitudinal direction of the vehicular body, the direction of a force applied to the power unit case 55 becomes simple. This facilitates the design of the power unit case 55. Concretely, the power unit., case 55 can be designed such that the rigidity is high in the direction where the force is applied and the rigidity is low in the direction where the force is not applied; and consequently, the power unit case 55 can be reduced in weight and also be made compact as a whole in proportional to simplification of the force applied to the power unit case 55. In Fig. 2, reference numeral 75 indicates an epicycle reduction gear; 76 is a potentiometer for detecting a rotational angle of a transmission control motor 95 to be described later; 121 is a cam shaft drive pulley; 78 is a water pump driven by the pulley 121; 79 is a belt cover; and 103a is an oil pump case disposed at a lower central portion of the figure. A primary drive gear 61, a primary driven gear 62, a centrifugal clutch 67, and a transmission 70, (which are further added with an electric motor shaft 59 when the electric motor 80 is operated for assisting the engine power), constitutes a power transmission system for transmitting a power from the engine; and the electric motor shaft 59 when the electric motor 80 is operated constitutes a power transmission system for transmitting a power from the electric motor.-. The details of components associated with the clutch shaft 57, transmission shaft 58, and electric motor shaft 59 will be fully described with reference to the following figure. 1-0015] • Fig. 3 is a sectional plan view of the power unit according to the present invention. The details of the components associated with the clutch shaft, transmission shaft, and electric motor shaft, and the drive force transmission configuration will be described with reference to this figure. The primary driven gear 62 rotatably mounted on the clutch shaft 57 is driven by the primary drive gear 61 mounted on the crank shaft 56. The primary driven gear 62 drives a clutch outer 64 of a one-way clutch 63 for a starter and a clutch inner 68 of the centrifugal clutch 67 independently from the clutch shaft 57. For this purpose, the primary driven gear 62 is connectable to both the clutch outer 64 of the one-way clutch 63 and the clutch inner 68 of the centrifugal clutch 67 by means of a cylindrical member 66. As the centrifugal clutch inner 68 is rotated at a rotational speed of a specific value or more, a centrifugal clutch outer 69 is rotated together with the centrifugal clutch inner .68, with a result that the clutch shaft 57 starts to be rotated. The above primary drive gear 61 includes a phase difference adjusting sub-gear 61a and a spring 61b for preventing occurrence of gear rattle. The transmission 70, which is of a cone type with its function fully described with reference to another figure, transmits a power in the order of the transmission shaft 58 ->• an inner disk 71 -> a cone 72 -> an outer cup 73. The rotation of the outer cup 73 is transmitted to the electric motor shaft 59 through a one-way clutch 83. The electric motor 80 is of a coreless type, in which a permanent magnet type rotor 81 is mounted on the electric motor shaft 59 and a stator coil 82 is mounted on an electric motor case 55d. When the centrifugal clutch 67 is turned on, a drive force is transmitted in the order of the clutch shaft 57, transmission shaft 58, transmission 70, and electric motor shaft 59, and acts to drive an axle 90 through a multi-disk type torque limiter 84 and a reduction gear mechanism 85 (which is composed of a small gear 86, a large gear 87, a small gear 88, and a large gear 89). [0017] The multi-disk type torque limiter 84 includes a limiter inner 84a rotated together with the electric motor shaft 59, disks 84b and 84c (the disk 84b is mounted on the limiter inner 84a and the disk 84c is mounted on the following limiter outer 84d), a limiter outer 84d, and a spring 84e. The small gear 86 is integrated with the limiter outer 84d. A power is transmitted in the order of the limiter inner 84 -» disk 84b -> disk 84c -> limiter outer 84d -> small gear 86. If an excess torque over a predetermined value is applied, there occurs a slip between the disks 84b and 84c for protecting the components of. the multi-disk torque limiter 84. The predetermined torque can be set by the spring 84e. The one-way clutch outer 64 for a starter acts as a flywheel and has a balance weight 91 for taking an engine balance. The one-way clutch outer 64 constitutes the one¬way clutch 63 for transmitting rotation of a starter in combination with the one-way clutch inner 65. When a starter driven gear 93 is rotated by a starter (not shown), the centrifugal clutch inner 68 is rotated through the one-way clutch inner 65 and the one-way clutch outer 64, to start operation of the engine. And, when the one-way clutch outer 64 is rotated at a higher speed, it is separated from the clutch inner 65 on the low speed side. [0019] In Fig. 3, the cam shaft drive pulley 121 for driving a cam shaft or the like is provided on the other end (front end) of the crank shaft 56. A belt 122 is driven by the pulley 121. The details of these pulley 121 and the belt 122 will be fully described later. Figs . 4 and 5 are views illustrating a configuration and a function of the cone type continuously variable transmission according to the present invention. In the state of the cone 72 shown in Fig. 4, a relationship of R1>R2 is given, where Rl is a distance from the center of a cone supporting shaft 74 to the inner disk 71, that is, a rotational radius of the inner disk 71, and R2 is a distance from the center of a core supporting shaft 74 to the outer cup 73, that is, a rotational radius of the outer cup 73. The cone 72 is rotated at a low speed because a large diameter portion (radius: Rl ) of the cone 72 is rotated by the inner disk 71, and the outer cup 73 is rotated at a low speed because the outer cup 73 is rotated by the small diameter portion (rad-ius: R2 ) of the cone 72. [-4921] When rotation of the outer cup 73 is higher than that of the electric motor shaft 59, a power is transmitted from the outer cup 73 to the electric motor shaft 59 through the one-way clutch 83. Reference numeral 70a indicates a cam ball for pushing the outer cup 73 leftward along with rotation of the outer cup 73. Such a pushing action allows a contact pressure to be applied between the outer cup 73 and the cone 72. Reference numerals 7 Ob, 70c and 70d indicate oil seals. The oil seals 70b and 70c form a closed space for accumulating transmission oil in the transmission 70, and the oil seal 70d cuts off oil on the crank case 55b side (on the left side of the figure). Accordingly, there is no fear that oil in the crank case is mixed with transmission oil. In the state of the cone 72 shown in Fig. 5, a relationship of R3 The cone 72 is rotated at a high speed because the small diameter portion (radius: R3 ) of the cone 72 is rotated by the inner disk 71, and the outer cup 73 is rotated at a high speed because the outer cup 73 is rotated by the large diameter portion (radius: R4 ) of the cone 72. By moving the cone 72 as shown in Figs. 4 and 5, the transmission 70 transmits rotation at a reduced speed, a uniform speed, or an increased speed. .[•0023] For this purpose, as shown in Fig. 4, a control gear 97 is shifted by the transmission control motor 95 through gears 96a, 96b and 96c. The control gear 97 has a trapezoid female thread portion 99 formed on its boss portion. The trapezoid female thread portion 99 is meshed with a trapezoid male thread portion 98 fixed on the case 55 side. The control gear 97 is shifted leftward in the figure by spiral motion of the trapezoid female thread portion 99. The leftward shift of the control gear 97 moves the cone 72 leftward in the figure together with the cone supporting shaft 74 into the state shown in Fig. 5. It is important that both the trapezoid male thread portion 98 and the trapezoid female thread portion 99 are provided not on the outer cup 73 side but on the inner disk 71 side. The cone 72 is pushed leftward in the figure by reaction of the outer cup 73. As a result, the control gear 97 is applied with a force in the direction shown by an arrow "1", that is, in the direction from the low speed side to the high speed side. With the configuration in this embodiment, the cone 72 can be shifted to the high speed side with a small torque. This is effective to lower the capacity of the transmission control motor 95. A lubricating system will be described below. Fig. 6 is a view illustrating an engine lubricating system according to the present invention, in which flow of oil is indicated by an arrow. The power unit case 55 has a lower oil tank 101 disposed at its lower portion, and an upper oil tank 102 disposed at its upper portion. A first oil pump 103, a second oil pump 104, and a third oil pump 105 are coaxially disposed on one end side (right end side) of the crank shaft 56. First, oil in the lower oil tank 101 is pumped by the first oil pump 103 through a strainer 106 and a first oil passage 107, and is supplied to the upper oil tank 102 through a second oil passage 108. The oil in the upper oil tank 102 flows to the second oil pump 104 through a third oil passage 109 and is pressurized by the second oil pump 104. The oil thus pressurized lubricates main journal portions 56a, a connecting rod large end portion 56b, and others ( particularly, a valve chamber not shown) through a fourth oil passage 111, a filter 112, and a fifth oil passage 113, and returns to the lower oil tank 101. In this figure, reference numeral 112a indicates a filter cover. Fig. 7 is a view illustrating a transmission lubricating system according to the present invention. Referring to Fig. 7, transmission oil is pumped from a transmission oil tank 115 additionally provided on a lower portion of the power unit case 55 by the third oil pump 105 through a six oil passage 116, being fed to the transmission shaft 58 through a seventh oil passage 117, and is supplied to the transmission 70 through an oil passage 118 in the transmission shaft 58. The oil is then returned to the transmission oil tank 115 in the direction shown by an arrow in the figure, and is pumped by the third oil pump 105 through a strainer 119. Fig. 8 is a front view of the power unit, showing a cam shaft drive mechanism as a--valve drive mechanism according to the present invention. Referring to Fig. 8, the left crank case 55a is mounted on the right side of a cylinder block 129B integrated with the right crank case 55b, and the electric motor 80 is disposed higher than the crank shaft 56. A cylinder head 129H is mounted on the left side of the cylinder block 129B. The muffler 21 is mounted at the leading end of the exhaust pipe 19 extending from the cylinder head 129H. An intake manifold 129M extending from the air cleaner 18 on the upper left side (and on the back side of the figure) is connected to the cylinder head 129H through a carburetor 129C. Reference numeral 129S indicates a starter motor mounting hole. In Fig. 8, since a belt cover 79 is removed, there can be seen, from the front side of the power unit 15, a cam shaft drive mechanism 120 as the valve drive mechanism composed of a cam shaft drive pulley 121, a belt 122, an intake side cam shaft pulley 123, an exhaust side cam shaft pulley 124, and a tensioner 125. The belt 122 may be replaced with a chain, and the pulleys 121, 123 and 124 may be replaced with sprockets, and therefore, the belt 122 may be referred to as a " winding means" represented by a timing belt, V-belt or roller chain; the cam shaft drive pulley 121 may be referred to as a "cam shaft drive rotator" rotated by the winding means; and each of the cam shaft pulleys 123 and 124 may be referred to as a "cam shaft rotator" rotated by the winding means. The means may be selected from any part other than the above chain or sprocket insofar as it exhibits the function described above, f As is apparent from Fig. 8, since the cylinder is disposed in the width direction of the vehicular body with its cylinder axis 126 substantially in the horizontal direction (for example, a tilt angle a with respect to the ground is set at + 10° ) , the center of gravity of the vehicle is lowered and also the cylinder length can be set within the vehicular width. This increases the degree of design of the vehicle. [0030]- In Fig. 8, which is seen in the direction from the front wheel side to the rear wheel side, both the crank shaft 56 and the clutch shaft 57 are disposed on the right side from a body center 127, and the cylinder head 129H is disposed on the left side from the body center 127. Behind the clutch shaft 57 in the figure are disposed the shafts of "the power transmission system"-such as the transmission shaft 58 and the electric motor shaft 59, as described with reference to Figs. 2 and 3. Fig. 9 is a view showing an arrangement of an AI reed valve and a water pump according to the present invention . Reference numeral 150 indicates an AI (Air Injection) reed valve, which is a check valve provided in a system for promoting purification of exhaust gas by blowing air into an exhaust port in a suitable amount. The structure of the AI reed valve 150 will be described with reference to Fig. 11. Since the AI reed valve 150 is provided on the front side of the cylinder head 129H, the maintenance of the AI reed valve 150 can be easily performed only by removal of the belt cover just as does inspection of the cam shaft drive mechanism 120. Further, with the above arrangement, the AI reed valve 150 can be usually protected by the belt cover. The common pulley 125 serves as both the above-described tensioner for adjusting tension of the belt 122 and a pump pulley. The common pulley 125 is rotatably mounted on a pump housing 131 of the water pump 78 as will be fully described later. The pump housing 131 not only contains a pump rotor 132 but also has two adjustment slots 133 and 134. Reference numerals 135 indicate a plurality of small screws used for assembly of the pump housing 131. Two projecting ribs 128a project from the cylinder block 129B in parallel to each other, between which a guide groove 128b is provided. _[ cm 2.2-] Figs. 10 (a) and 10 (b) are sectional views showing the water pump according to the present invention and also showing mounting of the common pulley. Referring to Fig. 10 (a), the water pump 78 includes a pump rotor 132; an inner magnet 136 mounted on the pump rotor 132; a rotor supporting shaft 137 for rotatably supporting the pump rotor 132; a housing cover 131a for supporting one end of the rotor supporting shaft 137; a housing base 131b for supporting the other end of the rotor supporting shaft 137; a shaft portion 131c formed on the housing base 131b; a cup 139 mounted on the shaft portion 131c through bearings 138; an outer magnet 141 mounted on an inner peripheral surface of the cup 139; and the common pulley 125 mounted on an outer peripheral surface of the cup 139. The pump housing 131 is composed of the housing cover 131a, housing base 131b, --and- shaft portion 131c. •[0034] When the common pulley 125, cup 139 and outer magnet 141 are rotated by movement of the belt 122, lines of magnetic force of the outer magnet 141 reaches the inner magnet 136 through the housing base 131b, to impart a rotational force to the inner magnet 136, whereby the pump rotor 132 starts to be rotated. Accordingly, the water pump 78 pressurizes water pumped from a suction passage 142 by the pump rotor 132, and supplies the water into a water inlet 146 of the cylinder block through a discharge passage 143 and an eccentric tube fitting 145. The eccentric tube fitting 145 is a fitting in which an inlet is eccentric a distance 6 with respect to an outlet as shown in Fig. 10(b). By rotating 90° the eccentric tube fitting 145 in the state shown in Fig. 10 (a), the water pump 78 can be moved a distance A in parallel to the water inlet 146 of the cylinder block as shown in Fig. 10 (b). Referring to Fig. 9 again, tension of the belt 122 is increased by loosening bolts 147, turning the eccentric tube fitting 145 in the direction shown by an arrow "2", and moving the common pulley 125 in the direction shown by an arrow "3". After the tension of the belt 122 is thus adjusted, the bolts 147 are fastened. The water pump 78, which is supported by shafts portion 131c (see Fig. 10(b)) fitted in the guide groove 128b and by the two bolts 147, are not moved except for the step of adjusting the tension of the belt 122. Fig. 11 is a sectional view taken on line 11-11 of Fig. 9. Referring to Fig. 11, the AI reed valve 150 supplies air, which is blown from the air inlet 151, into the exhaust port through an AI port 153 opened in a reed valve 152 and the cylinder head 129H. When a pressure on the AI port 153 side is increased, the reed valve 152 is closed, so that there is no fear that air or exhaust gas flows backward into the air inlet 151. Fig. 12 is a view showing an essential portion of a valve mechanism according to the present invention. Since intake and exhaust valves are different from each other in terms of shape and material but are similar to each other in the basic configuration, the same reference numerals are used commonly to the intake and exhaust valves . Referring to Fig. 12, a valve guide 163 is disposed to face an intake port 161 or an exhaust port 162 of the cylinder head 129H, and a stem 165 of a valve 164 is slidably inserted in the valve guide 163. A retainer 166 is mounted at a leading end of the stem 165 and a valve spring 167 is provided such that one end thereof is in contact with the retainer 166 for biasing the valve 164 in the valve closing direction. The valve 164 is pushed out in the valve opening direction by a cam (not shown) through a bucket 169 of a lifter, and is returned in the valve closing direction by the valve spring 167. Reference numeral 171 indicates an engine lubricating structure, and 172 is an oil passing hole. [ uu jy^p In the engine of this embodiment, the cylinder axis 126 tilts upward an angle a (about 10°) with respect to a horizontal axis 175, and a stem axis 177 of the lower valve 164 tilts downward an angle /3 (about 7° ) with respect to the horizontal direction. Fig. 13 is an enlarged view showing an essential portion of the valve mechanism shown in Fig. 12. Referring to Fig. 13, an oil escape groove 178 is provided in a floor wall of the engine lubricating structure 171 for containing the bucket 169 of the lifter and the valve spring 167. •f-0 041 f Fig. 14 is a view seen from an arrow 14 of Fig. 12, with the lifter mechanism omitted. Referring to Fig. 14, the oil escape groove 178 is offset from the lowermost position of the lower engine lubricating structure 171 because the oil during discharge is brought in contact with the cam (not shown) at the lowermost position. Accordingly, the oil escape groove 178 is preferably disposed at a position which does not interfere with the cam and which is as low as possible. Figs. 15 (a) and 15 (b) are views showing a function of the engine lubricating structure according to the present invention. Fig. 15 (a) shows a structure of a comparative example in which oil flows in the engine lubricating structure 171 through the oil passing hole 172 and eventually the engine lubricating structure 171 is filled with the oil . Fig. 15 (b) shows a structure in this embodiment in which oil flows in the engine lubricating structure 171 through the oil passing hole 172; however, since the oil in the engine lubricating structure 171 is discharged through the oil escape groove 178, it is not accumulated in the engine lubricating structure 171 so much. The engine lubricating structure of the present invention is suitable for a small-sized engine, and further, it may be applied to a medium-sized or large-sized engine. H3044 ] • [Effect of the Invention] The present invention having the above configuration exhibits the following effects: According to the invention described in claim 1, since the cylinder axis is disposed substantially in the horizontal direction, it is possible to lower the center of gravity of the hybrid type power unit. Further, although the valve axis tilts downward with respect to the horizontal axis, oil is liable to be accumulated in the engine lubricating structure; however, according to the present invention, the oil in the engine lubricating structure can be effectively escaped through the oil escape groove. [Reference Numerals] 1: motorcycle, 15: power unit, 126: cylinder axis, 129H: cylinder head, 164: valve, 171: engine lubricating structure, 172: oil passing hole, 175: horizontal axis, 177: stem axis, 178: oil escape groove WE CLAIM: 1 . A structure for lubricating a forward tilting engine in which a valve is driven by a cam shaft through a valve lifter; a cylinder axis tilts forward and a valve axis tilts downward from a horizontal axis; and an engine lubricating structure for containing said valve lifter is provided in a cylinder head in the valve lifter containing recess, characterized in that an oil escape groove is provided in the axial direction of the valve and in a surface of a lower wall of said valve lifter containing recess, 2. A structure for lubricating a forward tilting engine as claimed in claim 1, wherein a valve drive mechanism is provided in a cylinder head and a valve chamber for containing said valve drive mechanism is provided on a side portion of a cylinder; said valve chamber is formed into a closed space isolated from engine oil; a cylinder axis is disposed in the horizontal direction; and an oil return passage for returning oil in said valve chamber to an oil pan is provided in both-said cylinder head and a cylinder block wherein said oil return extends downward from a lower portion of said valve chamber, and an air passage extending from said oil pan to an upper portion of said valve chamber is provided in both said cylinder block and said cylinder head. 3. A structure for lubricating a forward tilting engine substantially as hereinbefore described with reference to and illustrated in the accompanying drawings.

Documents:

2430-del-1998-abstract.pdf

2430-del-1998-claims.pdf

2430-del-1998-correspondence-others.pdf

2430-del-1998-correspondence-po.pdf

2430-del-1998-description (complete).pdf

2430-del-1998-drawings.pdf

2430-del-1998-form-1.pdf

2430-del-1998-form-13.pdf

2430-del-1998-form-19.pdf

2430-del-1998-form-2.pdf

2430-del-1998-form-3.pdf

2430-del-1998-form-4.pdf

2430-del-1998-form-6.pdf

2430-del-1998-gpa.pdf

2430-del-1998-petition-137.pdf

2430-del-1998-petition-138.pdf

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