JP6601135B2 - Four-cycle engine crankcase structure - Google Patents

Description

  The present invention relates to a crankcase structure of a four-cycle engine that is typically suitable for a motorcycle or the like.

  In a parallel multi-cylinder engine mounted on a vehicle such as a motorcycle, an engine suspension is usually provided at the rear of the engine. For example, the vehicle described in Patent Document 1 has a plurality of engine suspension portions on the upper and lower sides of the crankcase, and is mounted and supported on the vehicle body frame via these engine suspension portions. Since the engine suspension receives the engine driving force, a large load acts particularly on the engine suspension on the lower rear side.

JP 2014-69780 A

  However, in the conventional engine, auxiliary machinery such as an oil pump is disposed in front of the engine suspension portion, and functions as a lubricating oil storage portion, which is a large space. For this reason, it is not easy to secure rigidity around the front portion of the engine suspension, and if it is left as it is, a high load is applied to the crankcase of the engine, which causes deformation. If the crankcase is deformed, there may be an increase in mechanical loss (mechanical loss) in a rotating mechanism or structure disposed inside, or deterioration of shift feeling during gear shift. On the other hand, since a lubricating oil passage, auxiliary machinery, and the like are disposed inside the crankcase, it is not always easy to provide a reinforcing structure due to restrictions due to the relationship with them.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a crankcase structure for a four-cycle engine that can effectively and effectively increase the rigidity.

The crankcase structure of a four-cycle engine according to the present invention includes a crankcase that is vertically divided into an upper case and a lower case, a cylinder block and a cylinder head that are sequentially coupled to the crankcase, and an oil that is coupled below the lower case. In a four-cycle engine including a pan, a reinforcing wall that connects the opening in the front-rear direction of the engine is provided on the side of the opening for attaching the oil pan provided in the lower case, and the reinforcing wall extends in the engine width direction. On the same side as the drive sprocket for driving the rear wheels, the drive sprocket is disposed substantially parallel to the drive sprocket, and is divided into large and small spaces by the reinforcing wall, and the opposite side of the drive sprocket across the reinforcing wall in the lower case. An oil pump is arranged in a large divided space .

  In the crankcase structure of a four-cycle engine according to the present invention, the reinforcing wall connects the opening in the vertical direction of the engine to the main lubricant gallery extending in the engine width direction.

  In the crankcase structure of a four-cycle engine according to the present invention, the reinforcing wall is disposed between crankshaft supporting bearings adjacent to each other in the engine width direction.

  In the crankcase structure of a four-cycle engine according to the present invention, an oil pump is disposed on one side in the engine width direction across the reinforcing wall, and a water pump is disposed on the opposite side, and the oil wall is disposed on the reinforcing wall. A hole through which a rotary shaft connecting the pump and the water pump passes is formed.

  According to the present invention, the reinforcing wall is provided substantially parallel to the driving force or load of the rear wheel. By providing a reinforcing wall in a relatively large space in the lower case, the crankcase, in particular the lower case, is reinforced, and deformation due to the load action is suppressed in the crankcase with enhanced rigidity. It is possible to improve the ring and reduce mechanical loss and noise.

1 is a side view of a motorcycle according to an embodiment of the present invention. It is a front view which shows the engine periphery mounted in the vehicle body in embodiment of this invention. It is a left view of the engine in the embodiment of the present invention. It is a right view which shows the state which removed the clutch cover from the crankcase in embodiment of this invention. It is the top view which looked at the mating surface of the lower case in embodiment of this invention from upper direction. It is a back perspective view of the crankcase in the embodiment of the present invention. It is a downward perspective view of the crankcase which shows the inside of the lower case in the embodiment of the present invention. It is a bottom view of the crankcase showing the inside of the lower case in the embodiment of the present invention.

Hereinafter, preferred embodiments of an engine crankcase structure according to the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a configuration example of a main part of a motorcycle 100 as an application example of the present invention, and FIG. 2 is a front view showing the periphery of an engine mounted on a vehicle body. First, the configuration of the main part of the motorcycle 100 will be described with reference to FIG. 1 and FIG. In the drawings used in the following description, including FIG. 1, the front of the vehicle is indicated by an arrow Fr, the rear of the vehicle is indicated by an arrow Rr, and the lateral right side of the vehicle is indicated by an arrow R as necessary. The left side is indicated by an arrow L.

  1 and 2, a motorcycle 100 has a body frame 101 made of steel or aluminum alloy, and the body frame 101 supports components or parts such as an engine. Two front forks 103 are provided at the front of the body frame 101 and are supported by a steering head pipe 102 so as to be turnable left and right. A handle bar is fixed to the upper end of the front fork 103 via a steering bracket. A front wheel 104 is rotatably supported on the lower portion of the front fork 103, and a front fender is attached so as to cover the upper portion of the front wheel 104.

  The vehicle body frame 101 is integrally coupled to the rear portion of the steering head pipe 102, branches into a bifurcated pair of left and right sides, and extends from the steering head pipe 102 while being widened rearward and downward. It is configured as a so-called twin spar type frame composed of 101A and a pivot frame portion 101B which is welded to the main frame portion 101A and extends rearward and downward. The main frame portion 101A and the pivot frame portion 101B are coupled to each other and have a three-dimensional structure in which a space is formed as a whole, and the engine 10 is mounted on the vehicle body frame 101 inside the space.

  A swing arm is coupled via a pivot shaft 105 so as to be swingable in the vertical direction in the middle in the vertical direction of the pivot frame portion 101B of the body frame 101. A rear wheel 106 (partially abbreviated by a two-dot chain line) is rotatably supported at the rear end of the swing arm. A rear shock absorber is mounted between the vehicle body frame 101 and the swing arm. In particular, the lower end side of the rear shock absorber is connected to both the vehicle body frame 101 and the swing arm via a link mechanism. A driven sprocket is pivotally attached to the rear wheel 106, and a power transmission chain is wound between the drive sprocket on the engine 10 side and the driven sprocket of the rear wheel 106. Engine power is transmitted from the drive sprocket to the driven sprocket via the chain, thereby driving the rear wheel 106 to rotate. A rear fender covering the vicinity of the front upper portion is provided in the immediate vicinity of the rear wheel 106.

  Further, from the vicinity of the rear part of the body frame 10 to the upper part of the rear wheel 106, the seat rail 107 extends rearward while being inclined moderately rearward, and the seat (seat seat) is supported by the seat rail 107. A fuel tank covered with a tank cover is mounted on the front side of the seat.

  In the exterior of the vehicle, the front and left and right side portions of the vehicle mainly have cowlings (hereinafter simply referred to as cowls). In this example, the upper cowl, body cowl, and under cowl are integrated to cover the front of the vehicle, Covered by side cowl. A seat cowl is attached around the seat at the rear of the vehicle.

  As shown in FIGS. 1 and 2, the engine 10 is mounted and supported by the vehicle body frame 101 at a substantially vehicle central portion of the motorcycle 100. In this embodiment, the engine 10 is a water-cooled multi-cylinder four-cycle gasoline engine. The engine 10 is a parallel multi-cylinder engine in which cylinders are arranged side by side in the left-right direction (vehicle width direction). Specifically, the engine 10 is a parallel 4-cylinder engine. In the description, they are simply described as “# 1”). FIG. 3 is a left side view of the engine 10 according to the present embodiment. Referring also to FIG. 3, a cylinder block 13 above a crankcase 12 that houses a crankshaft (crankshaft) 11 that is horizontally supported horizontally. The cylinder head 14 and the cylinder head cover 15 are integrally connected so as to overlap each other, and an oil pan 16 is attached to the lower portion of the crankcase 12. It should be noted that the cylinder axis Z of the engine 10 is disposed with a moderate inclination forward. The engine 10 is suspended and supported by a plurality of engine mounts (referred to as an engine suspension portion 10A, see FIGS. 3 and 4, etc.) so as to be integrally coupled and supported inside the vehicle body frame 101. Acts as a rigid member of the frame 101.

  A transmission case 17 is integrally formed at the rear portion of the crankcase 12, and a counter shaft and a plurality of transmission gears, which will be described later, are disposed in the transmission case 17. The power of the engine 10 is finally transmitted from the crankshaft 11 through the transmission to the drive sprocket which is the output end thereof, and the drive sprocket passes the rear wheel 106 (FIG. 1) through the power transmission chain as described above. Rotating drive.

  Note that the crankcase 12 and the transmission case 17 are integrally connected to each other to constitute a casing assembly of an engine unit including the engine 10 as a whole. A plurality of auxiliary machines including a starter motor for starting the engine, a clutch device, and the like, which will be described later, are mounted or coupled at appropriate positions of the casing assembly, and the entire engine unit including these is supported by the vehicle body frame 101.

  The engine 10 further includes an air intake system that supplies air (intake air) and an air-fuel mixture supplied from an air cleaner and a fuel supply device, an exhaust system that exhausts exhaust gas after combustion from the engine 10, and the engine 10 is cooled. A cooling system that lubricates and a lubrication system that lubricates the movable part of the engine 10 and a control system (ECU; Engine Control Unit) that controls the operation thereof are attached. By controlling the control system, a plurality of functional systems cooperate with the above-mentioned auxiliary machines and the like, and thereby smooth operation of the entire engine unit is performed.

  Each functional system will be described. First, an intake port (intake port) is opened on the rear side of the cylinder head 14 in each cylinder in the intake system, and a throttle body is connected to the intake port via an intake pipe (intake pipe). . The throttle body is provided with a throttle valve that opens and closes an intake flow path or passage formed in the throttle body according to the accelerator opening, and the flow rate of air supplied from the air cleaner is controlled. In this example, the throttle valve shaft of each cylinder is coaxially arranged, and has a valve drive mechanism for driving the throttle valve shaft mechanically, electrically or electromagnetically.

  On the other hand, each throttle body is provided with an injector for fuel injection downstream of the throttle valve, and fuel in the fuel tank is supplied to these injectors by a fuel pump. In this case, each injector is connected to a delivery pipe laid horizontally in the vehicle width direction on the upper side, and fuel is distributed from the delivery pipe connected to the fuel pump. Each injector injects fuel into the intake passage in the throttle body at a predetermined timing under the control of the control system described above, whereby a mixture of a predetermined air-fuel ratio is supplied to the cylinder block 13 of each cylinder.

Next, in each exhaust system, an exhaust port (exhaust port) is opened in front of the cylinder head 14 in each cylinder, and an exhaust pipe (exhaust pipe) 18 is connected to the exhaust port. The exhaust pipe 18 of each cylinder extends downward from the exhaust port, and merges and integrates below the crankcase 12. The exhaust pipe 18 extends rearward, and a muffler 19 is attached to the rear end thereof.
In this case, the exhaust pipe 18 of the # 1 cylinder and the exhaust pipe 18 of the # 2 cylinder join at the joining part 20, and the exhaust pipe 18 of the # 3 cylinder and the exhaust pipe 18 of the # 4 cylinder join at the joining part 21. Further, when the merging portion 20 and the merging portion 21 merge with each other, the four exhaust pipes 18 of the # 1 to # 4 cylinders gather in a single collecting pipe 22 substantially at the lower left of the oil pan 16. The collecting pipe 22 is connected to the muffler 19 via the connection pipe 23.

  In the cooling system, a water jacket is formed around the cylinder block 13 and the cylinder head 14 so that cooling water circulates. A radiator 24 which is a heat exchanger for cooling the cooling water fed to the water jacket is provided. The radiator 24 dissipates the heat of the cooling water flowing through the interior by applying the traveling wind. In this example, the radiator 24 has a substantially horizontally long rectangular shape as viewed from the front, as shown in FIG. From the vicinity of the lower portion of the steering head pipe 102 to the vicinity of the front side of the exhaust pipe 18 in front of the cylinder block 13, the rear end of the steering head pipe 102 is disposed so as to be inclined moderately to the rear. The cylinder block 13 of the engine 10 is substantially covered with a radiator 24 in a front view. The radiator 24 is supported at an appropriate position using the body frame 101 or the like.

  In this example, the cooling system has a water pump 25 on the left side wall portion of the crankcase 12 as shown in FIG. 3, which is driven in conjunction with, for example, an oil pump built in the crankcase 12 as described later. The water pump 25 and the water jacket are connected to each other by a cooling water hose, and the water pump 25 and the radiator 24 are connected to each other by another cooling water hose. Cooled cooling water is supplied from the radiator 24 to the water pump 25 via a cooling water hose. The water pump 25 discharges the cooling water cooled by the radiator 24 and circulates the water jacket, thereby cooling the engine. The cooling water that has circulated in the water jacket is fed to the radiator 24 via the cooling water hose. The radiator 24 cools the cooling water supplied from the engine 10 and supplies it again to the water pump 25 through the cooling water hose, and the cooling water circulation is repeated in the cooling system.

  Further, a lubricating system is configured to supply lubricating oil to the movable parts of the engine unit and lubricate them. This lubrication system includes a valve gear configured around the crankshaft 11 and in the cylinder head 14, and a cam chain, a transmission, and the like that connect them. In the present embodiment, an oil pump that is driven by using the rotational force of the crankshaft 11 directly or indirectly as a drive source is incorporated in the crankcase 12 with respect to the lubrication system. A trochoid pump or the like is used as the oil pump, and the lubricating oil sucked up from the oil pan 16 by this oil pump is supplied to the lubricating system. An oil filter 26 (FIG. 1) is attached to the front lower portion of the crankcase 12, and the lubricating oil is purified by the oil filter 26 before being supplied to the lubrication system.

  A specific configuration example around the crankcase 12 will now be described with reference to FIGS. 4 and 5 as well. 4 is a right side view showing a state in which the clutch cover 27 (see FIG. 1) is removed from the crankcase 12, and FIG. 5 is a mating surface 12A of the lower case 29 among the upper case 28 and the lower case 29 constituting the crankcase 12. It is the top view which looked at from the upper part. In this embodiment, the crankcase 12 is divided into upper and lower parts by an upper case 28 and a lower case 29, and the crank chamber 30 is formed by closing both of them. In this case, the cylinder block 13 is integral with the crankcase 12, that is, integrally formed with the upper case 28. Further, the crankshaft 11 and the countershaft 31 that is a transmission input shaft are pivotally supported by the mating surface 12A of the crankcase 12. The mating surface 12A is set so as to incline backward as shown in FIG.

  In the crank chamber 30 of the crankcase 12, the crankshaft 11 and a crank web 32 integrated with the crankshaft 11 are arranged on the mating surface 12 </ b> A via journal bearings 34 with a plurality (five in this example) of journal portions 33. And is pivotally supported. A connecting rod 35 is connected between the crank webs 32 corresponding to the cylinders via a crank pin. A piston is pivotally attached to the tip (small end) of the connecting rod 35 via a piston pin, and the piston reciprocates up and down in the cylinder bore of the cylinder block 13. The crankshaft 11 is rotationally driven by the reciprocating operation of the piston.

  In the transmission case 17, the countershaft 31 is rotatably supported on the mating surface 12 </ b> A in parallel with the rear of the crankshaft 11. The counter shaft 31 is supported via a bearing 36 and the like. One end (right side) of the crankshaft 11 is provided so as to protrude into the clutch chamber, and the primary drive gear 37 is pivotally attached to this end. On the other hand, a primary driven gear 38 that meshes with the primary drive gear 37 is attached to one end (right side) of the counter shaft 31, and the counter shaft 31 can be driven to rotate by rotation of the crankshaft 11. A clutch device 39 is configured at an end portion of the counter shaft 31 that protrudes toward the clutch chamber, and the clutch device 39 connects and disconnects the power between the crankshaft 11 and the counter shaft 31. The clutch shaft of the clutch device 39 is arranged coaxially with the counter shaft 31.

  Further, in the transmission case 17, the counter shaft 31 constitutes a part of a transmission (transmission) accommodated in the transmission case 17. A drive shaft 40 is disposed substantially below the counter shaft 31, and a plurality of transmission gears are arranged in a row on the counter shaft 31 and the drive shaft 40. These transmission gears are selectively set in meshing relationship by a gear shift device, thereby obtaining a desired gear ratio of the transmission. The power of the engine 10 is finally transmitted from the crankshaft 11 through a transmission to a drive sprocket 41 (see FIG. 3) attached to the shaft end of the drive shaft 40. As described above, the drive sprocket 41 rotationally drives the driven sprocket, and hence the rear wheel 106, through the power transmission chain.

  Further, as shown in FIG. 4, in the engine 10, an extension line M connecting the central axes of the crankshaft 11 and the countershaft 31 and the cylinder axis Z of the cylinder block 13 intersect each other at an acute angle θ in a side view of the engine. The cylinder block 13 is disposed to be inclined rearward. The extension line M is on the mating surface 12A of the upper case 28 and the lower case 29 of the crankcase 12, and the cylinder axis Z is set to be inclined backward with respect to the perpendicular P passing through the crankshaft 11 from the mating surface 12A. Is done.

Further, as shown in FIG. 6, a concave shape 43 is formed on the cylinder axis Z (see FIG. 4) side of the cylinder block 13 below the water jacket 42 on the rear surface of the cylinder block 13. A starter motor 44 is disposed in the concave shape 43. As shown in FIG. 6, the concave shape 43 of the cylinder block 13 is provided substantially at the center in the engine width direction, and substantially corresponds to the # 2 cylinder and the # 3 cylinder.
Further, referring also to FIG. 3, a breather chamber 45 is provided behind the starter motor 44 integrally with the upper case 28. The breather chamber 45 has a breather chamber cover 46 (FIG. 3). The introduced blow-by gas is separated into gas and liquid, and the separated gas is returned to the intake system.

  Here, referring to FIG. 5, the output shaft 44 a of the starter motor 44 is disposed in the left-right direction, that is, in parallel with the crankshaft 11 and extends to the right, and between the output shaft 44 a and the crankshaft 11, It meshes with a torque limiter 47 mounted on a driving force transmission shaft 48 extending in parallel. The torque limiter 47 is configured to transmit only the torque from the starter motor 44 to the crankshaft 11 side and to block the torque from the crankshaft 11 side to the starter motor 44 side. The torque limiter 47 is connected to the crankshaft 11 via a plurality of idle gears 49. In this case, the idle gear 49A at the final stage meshes with a one-way clutch 50 that is attached to the right end of the crankshaft 11. When the starter motor 44 is operated, the crankshaft 11 is forcibly rotated via the torque limiter 47, the idle gear 49, and the like, whereby the engine 10 can be started.

  Now, in the engine 10 having the above-described configuration, in the present invention, an opening 51 for attaching the oil pan 16 is provided in the lower case 29 as shown in FIGS. A reinforcing wall 52 is provided on the opening 51 side of the lower case 29, that is, on the lower side of the lower case 29, and connects the opening 51 so as to straddle the engine longitudinal direction. The reinforcing wall 52 is arranged on the same side (left side) in the engine width direction as the drive sprocket 41 attached to the shaft end of the drive shaft 40.

  Here, the lower case 29 is provided with an oil pump 53 that is rotationally driven using the rotational force of the crankshaft 11 directly or indirectly as a drive source. In this case, the oil pump 53 has a rotating shaft arranged along the engine width direction (left-right direction), and is coaxially connected to the water pump 25 via the connecting shaft 54. In the power connection relationship between the oil pump 53 and the drive source, the rotational force of the crankshaft 11 can be used directly or indirectly. For example, the rotation shaft of the oil pump 53 is connected to the drive shaft via a chain or the like. The oil pump 53 can be driven by the rotational force. Alternatively, for example, a sprocket is attached to an appropriate position in the middle of the connecting shaft 54, the connecting shaft 54 is connected to the crankshaft 11 through the sprocket and a chain, and the water pump 25 and the oil pump 53 are driven by the power. It may be.

  In the lubrication system, the oil pump 53 sucks up the lubricating oil in the oil pan 16 through the oil strainer and pumps the lubricating oil to each part in the engine that requires lubrication. In this case, the lubricating oil discharged from the oil pump 53 is supplied to the oil cooler through the lubricating oil passage, and the lubricating oil that has passed through the oil cooler is further supplied to the oil filter 26 through the lubricating oil passage. The lubricating oil purified by the oil filter 26 is supplied to the main gallery 55 through a lubricating oil passage formed in the crankcase 12 (lower case 29). As shown in FIGS. 7 and 8, the main gallery 55 extends in the left-right direction of the lower case 29 over substantially the entire width thereof, and is positioned at a predetermined distance upward from the opening 51 of the lower case 29, that is, the opening 51. It is formed in parallel with the crankshaft 11 etc. at a height position higher than the predetermined distance. A plurality of lubricating oil passages branch from the main gallery 55 in order to supply the lubricating oil to a lubricating system including the crankshaft 11 and the valve gear.

  As shown in FIG. 8 and the like, the lower case 29 has a plurality of, in this example, five journal bearings 34 for supporting the journal portion 33 of the crankshaft 11 between the upper case 28 (see also FIG. 5). Are integrally formed. The bearing portion 56 is disposed along the left-right direction (engine width direction) at a cylinder interval of # 1 to # 4 cylinders corresponding to the journal portion 33 of the crankshaft 11. The reinforcing wall 52 is formed so as to connect from the opening 51 to the main gallery 55 of the lubricating oil extending in the engine width direction in the engine vertical direction.

  The reinforcing wall 52 is disposed between the bearing portions 56 for supporting the crankshaft 11 adjacent in the engine width direction. In this example, as shown in FIG. 8 and the like, the reinforcing wall 52 extends in the front-rear direction between the two bearing portions 56 adjacent to each other corresponding to the # 2 cylinder.

  An oil pump 53 is arranged on one side (right side) in the engine width direction across the reinforcing wall 52, and a water pump 25 is arranged on the opposite side (left side). As shown in FIG. 7, a hole 57 through which a connecting shaft 54, which is a rotating shaft that connects the oil pump 53 and the water pump 25, is formed in the reinforcing wall 52.

In the crankcase structure of the engine 10 according to the present invention, first, a reinforcing wall 52 is provided on the opening 51 side of the lower case 29 to connect the opening 51 so as to straddle the engine longitudinal direction.
In the engine 10, as shown in FIG. 7 or FIG. 8, in front of the engine suspension 10A (see FIG. 3, FIG. 4, etc.), the drive sprocket 41 that drives the rear wheel 106 is reinforced substantially parallel to the driving force or load. A wall 52 is provided. By providing the reinforcing wall 52 at a relatively large space in the lower case 29, the crankcase 12, particularly the lower case 29, is reinforced. As a result, the crankcase 12 with enhanced rigidity is prevented from being deformed by a load action, so that it is possible to improve shift feeling and reduce mechanical loss and noise.

The reinforcing wall 52 is arranged on the same side as the drive sprocket 41 in the engine width direction.
By arranging the reinforcing wall 52 in this way, it is possible to efficiently receive a load with respect to the tension of the power transmission chain for driving the rear wheel 106. Since the reinforcing wall 52 is disposed at a position relatively close to the drive sprocket 41, the moment due to the rear wheel driving load can be suppressed to be small. In this respect as well, deformation of the crankcase 12 is suppressed.

The reinforcing wall 52 is formed so as to connect the opening 51 at the lower end of the lower case 29 to the main gallery 55.
The reinforcing wall 52, in combination with the main gallery 55, can form a box-like three-dimensional structure composed of a surface in a relatively large space, and can greatly improve the rigidity of the lower case 29. it can.

The reinforcing wall 52 is disposed between the bearing portions 56 for supporting the crankshaft.
By providing the reinforcing wall 52 so as not to interfere with the bearing portion 56, the height direction dimension can be ensured to the maximum, and the rigidity of the crankcase 12 can be improved.

Further, holes 57 through which the shaft connecting shafts 54 connected to the oil pump 53 and the water pump 25 disposed on both sides of the reinforcing wall 52 pass are formed.
Even if the reinforcing wall 52 is provided, peripheral accessories and the like can be efficiently arranged, and the space can be effectively used while strengthening the rigidity.

As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention.
In the above embodiment, the example of defining the right or left in the engine width direction with respect to the arrangement relationship of the members has been described. However, the left-right relationship may be reversed from the above case.

10 engine, 10 engine suspension, 11 crankshaft, 12 crankcase, 13 cylinder block, 14 cylinder head, 15 cylinder head cover, 16 oil pan, 17 transmission case, 18 exhaust pipe, 19 muffler, 20, 21 junction, 22 Collecting pipe, 24 radiator, 25 water pump, 26 oil filter, 28 upper case, 29 lower case, 30 crank chamber, 31 counter shaft, 32 crank web, 33 journal part, 34 journal bearing, 35 connecting rod, 37 primary drive gear , 38 Primary driven gear, 39 Clutch device, 40 Drive shaft, 41 Drive sprocket, 42 Water jacket, 43 Concave shape, 44 Starter motor 44a output shaft, 45 breather chamber, 46 breather chamber cover, 47 torque limiter, 49 idle gear, 50 one-way clutch, 51 opening, 52 reinforcement wall, 53 oil pump, 54 connecting shaft, 55 main gallery, 56 bearing portion, 57 hole, 100 motorcycle.

Claims (4)

In a four-cycle engine comprising a crankcase that is divided into an upper case and a lower case, a cylinder block and a cylinder head that are sequentially coupled to the crankcase, and an oil pan that is coupled below the lower case,
On the side of the opening for attaching the oil pan established in the lower case, a reinforcing wall is provided to connect the opening in the longitudinal direction of the engine ,
The reinforcing wall is disposed substantially parallel to the drive sprocket on the same side as the drive sprocket for driving the rear wheels in the engine width direction,
A crank for a four-cycle engine, wherein an oil pump is disposed in a large space separated from the drive sprocket across the reinforcing wall in the lower case divided into large and small spaces by the reinforcing wall. Case structure. The crankcase structure for a four-stroke engine according to claim 1 , wherein the reinforcing wall connects the opening in the vertical direction of the engine to the main lubricant gallery extending in the engine width direction. The crankcase structure for a four-cycle engine according to claim 1 or 2 , wherein the reinforcing wall is disposed between bearings for supporting a crankshaft adjacent to each other in the engine width direction. With arranging the oil pump to one side in the engine width direction across the reinforcing walls, the water pump is disposed on the opposite side, rotating shaft connecting the oil pump and the water pump penetrates the said reinforcing wall The crankcase structure for a four-cycle engine according to any one of claims 1 to 3 , wherein a hole is formed.

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