JP4860224B2 - Assembly structure of power transmission mechanism - Google Patents

Description

  The present invention relates to an assembly structure of a power transmission mechanism that transmits rotation of a countershaft that is shifted and transmitted by a transmission gear train to a propeller shaft via a bevel gear train.

  A vehicle such as a two-wheeled vehicle travels by transmitting rotation of a crankshaft constituting an internal combustion engine to wheels by a power transmission mechanism. The power transmission mechanism includes, for example, a main shaft and a counter shaft that extend in parallel to the crank shaft, and a propeller shaft that extends substantially orthogonal to the counter shaft, and rotation of the crank shaft is provided on the crank shaft and the main shaft. The transmission is transmitted to the propeller shaft via the primary gear train, the transmission gear train provided on the main shaft and the counter shaft, and the bevel gear train provided on the counter shaft and the propeller shaft (see, for example, Patent Document 1). As shown in Patent Document 1, each shaft is rotatably supported by a bearing attached to a crankcase and a bevel gear case and is housed inside the case.

Japanese Examined Patent Publication No. 62-49495

  According to Patent Document 1, in the conventional engine and power transmission mechanism, the crankcase is vertically divided, and the central axes of the crankshaft and the main shaft are positioned on the vertically divided surface. The countershaft is supported at both ends by bearings provided on the crankcase, and the bearing that supports one end of the countershaft is held by a bearing holder that is positioned in the crankcase. On the other hand, the propeller shaft is supported by a bearing provided in the bevel gear case. Further, the main shaft is supported at both ends by bearings provided in the crankcase.

  As described above, in the conventional assembly structure, the bearing holder is positioned in the crankcase in-situ, so that the distance between the main shaft and the countershaft becomes longer by this positioning structure, and the transmission gear train may be enlarged. there were. Further, since the bearing holder is previously attached to the crankcase, it is necessary to couple the bevel gear case to the crankcase in a state where the counter shaft is fixed to the crankcase side. On the other hand, it is necessary to support the propeller shaft in advance on the side of the bevel gear case, and the bevel gear train must be engaged when the case is joined or after the case is joined.

  In view of such a problem, an object of the present invention is to provide an assembly structure of a power transmission mechanism that can easily assemble a power transmission mechanism while reducing an assembly error.

In order to achieve the above object, the assembly structure of the power transmission mechanism according to the present invention includes a main shaft that rotates when the output rotation of the internal combustion engine is transmitted, a counter shaft that is disposed in parallel to the main shaft, A propeller shaft disposed substantially orthogonal to the counter shaft, a bevel gear train formed by meshing a driving bevel gear provided at the tip of the counter shaft and a driven bevel gear provided at the tip of the propeller shaft; A transmission case (for example, a lower case 4 in the embodiment) that accommodates the main shaft and the counter shaft therein, a bevel gear case that is coupled to the transmission case and accommodates the bevel gear train therein, and the bevel gear case was, bearing supports an end portion of the main shaft and the counter In assembly structure of a power transmission mechanism having a first bearing holding member that holds the first bearing supporting the end of the shaft, the main shaft is supported by said bearings, said countershaft first The shaft is supported by the first bearing holding member via a bearing, and the shafts are fixed to the bevel gear case in advance, and then assembled to the transmission case .

The power transmission mechanism assembly structure according to the present invention includes a transmission gear train formed by meshing a drive gear provided on the main shaft and a driven transmission gear provided on the counter shaft, and an input operation. A shift spindle that rotates, a shift drum that rotates according to the rotation of the shift spindle, a shift fork that moves according to the rotation of the shift drum, and the fork shaft that guides the movement of the shift fork, A shift drum mechanism configured to move a predetermined gear of the drive gear and the driven transmission gear in the axial direction by moving the shift fork and change the transmission gear train, the shift spindle, the shift drum, and the Fork shafts, one end is supported by the bevel gear case and the other end is supported by the transmission case It is preferable.

According to the assembly structure of the power transmission mechanism of the internal combustion engine according to the present invention configured as described above, since many of the components of the power transmission mechanism such as the main shaft and the counter shaft are assembled on the bevel gear case side, It is possible to provide a power transmission mechanism in which assemblability is further improved and assembly errors are small.

More specifically, in the present invention, before coupling the transmission case to the bevel gear case, the bevel gear case is in a state where the main shaft is supported, and the counter shaft is supported through the first bearing. The first bearing holding member can be assembled in advance.
For this reason, the drive bevel gear and the driven bevel gear can be engaged with each other and the bevel gear train can be assembled in advance before being housed in the bevel gear case. Therefore, the assemblability of the bevel gear train is improved, and the assembly error can be reduced. Further, the drive gear and the driven transmission gear can be engaged with each other and the transmission gear train can be assembled in advance and then accommodated in the bevel gear case. Therefore, the transmission gear train can be easily assembled, and the assembly error of the transmission gear train to the bevel gear case can be reduced.
Note that a shift drum mechanism can be assembled in advance to the bevel gear case. According to this, further improvement in assemblability can be expected .

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the figure, the direction of the arrow U is upward, the direction of the arrow F is forward, and the direction of the arrow R is right. 1 to 13 show a power unit PU having a power transmission mechanism assembly structure according to the present invention. The power unit PU includes an engine E and a power transmission mechanism TM, and is disposed in a scooter type motorcycle. By this power unit PU, the output rotation of the engine E is shifted and transmitted to the rear wheels via the power transmission mechanism TM, so that the two-wheeled vehicle can run.

  The power unit PU includes a head cover 1, a cylinder head 2, a cylinder block 3, a lower case 4, a side cover 5, and a bevel gear case 6. These members 1 to 6 are combined to form a housing H. A device, a mechanism, an auxiliary machine, etc. constituting the power unit PU are disposed inside and outside the housing H. As shown in FIGS. 1 and 3, the engine E is a water-cooled, 4-stroke, DOHC, parallel 3-cylinder type composed of a head cover 1, a cylinder head 2, a cylinder block 3, a lower case 4, and a side cover 5. This is an internal combustion engine. As shown in FIG. 4, the power transmission mechanism TM includes a lower case 4, a side cover 5, and a bevel gear case 6.

  First, the engine E will be described. The cylinder block 3 includes a cylinder portion 3A that internally forms three cylinder bores 3a, 3b, and 3c arranged on the left and right sides, and an upper crankcase portion 3B that is an upper case half of the vertically divided crankcase 12A. It is a housing member. The cylinder block 3 is disposed in the two-wheeled vehicle with the cylinder shaft 11A tilted forward, and the cylinder portion 3A is positioned forward and the upper crankcase portion 3B is positioned rearward. A piston 11 is slidably disposed in each cylinder bore 3a to 3c in the direction of the cylinder shaft 11A.

  The lower case 4 is a large housing member in which a lower crankcase portion 4A that is a lower case half of the vertically divided crankcase 12A and a transmission case portion 4B that houses the power transmission mechanism TM are integrated. The lower crankcase portion 4A is joined to the upper crankcase portion 3B and coupled to the rear of the cylinder block 3. As described above, the crankcase 12A of this configuration example includes the upper crankcase portion 3B of the cylinder block 3 and the lower crankcase portion 4A of the lower case 4, and the crankcase 12B is formed inside the crankcase 12A. The crankshaft 12 is accommodated in the chamber 12B and is rotatably supported. The upper crankcase portion 3B of the cylinder block 3, the lower crankcase portion 4A and the transmission case portion 4B of the lower case 4 are open on the right side, and the side cover 5 is coupled to cover the right side. The

  The cylinder block 3 and the lower case 4 are formed such that the joint surface 12C between the cylinder block 3 and the lower case 4 extends in the horizontal direction in the direction in which the cylinder shaft 11A extends in the vertical direction, but in this configuration example, the cylinder shaft 11A is substantially horizontal. As shown in FIG. 2, the joining surface 12C is formed so as to incline from the rear upper side to the front lower side and extend substantially in the vertical direction as shown in FIG. The crankshaft 12 is disposed with a central axis 12d extending in the left-right direction, and the central shaft 12d is disposed on the joint surface 12C.

  As shown in FIG. 3, the crankshaft 12 includes four journals 12a formed integrally with a web 12b, and three crank pins 12c that connect the webs 12b and 12b. The pistons 11 are connected to the corresponding crank pins 12c via connecting rods 13. Thereby, the reciprocating motion of the piston 11 and the rotation of the crankshaft 12 are interlocked, and when the piston 11 reciprocates once, the crankshaft 12 rotates once.

  The cylinder head 2 is coupled to the front portion of the cylinder portion 3 </ b> A of the cylinder block 3. Three combustion chambers 9 corresponding to each of the cylinder bores 3a to 3c are formed surrounded by the inner wall surface of the cylinder head 2, the upper surface of the piston 11, and the inner peripheral surfaces of the cylinder bores 3a to 3c. A spark plug (not shown) is attached to the cylinder head 2 with its tip portion facing each combustion chamber 9.

  The cylinder head 2 is formed with an intake port 21 and an exhaust port 24 that open to each combustion chamber 9. Also, inside the cylinder head 2, an intake passage 22 having one end communicating with the intake port 21 and the other end communicating with the outside, and an exhaust gas with one end communicating with the exhaust port 24 and the other end communicating with the outside. A passage 25 is formed. An intake manifold (not shown) is attached to the external connection port 23 of the intake passage 22. An intake device having a fuel injection valve and an air cleaner are attached to the intake manifold, and an intake system is constituted by the intake manifold, the intake device, and the air cleaner. An exhaust manifold (not shown) is attached to the external connection port 26 of the exhaust passage 25, and communicates with the outside through the exhaust manifold.

  A head cover 1 is coupled to the front portion of the cylinder head 2 and is surrounded by the head cover 1 and the cylinder head 2 to form a valve operating chamber 10. A spark plug is attached from an opening provided at the top of the head cover 1. The valve operating chamber 10 is provided with an intake valve 14 that opens and closes an intake port 21 and an exhaust valve 15 that opens and closes an exhaust port 24. Both valves 14 and 15 are always urged by valve springs 14a and 15a in a direction to close the intake port 21 and the exhaust port 24.

  A camshaft holder 7 is interposed in the valve operating chamber 10 between the cylinder head 2 and the head cover 1. The intake and exhaust camshafts 16 and 17 formed integrally with the cams 18 and 19 are connected to the cylinder head. 2 and the camshaft holder 7 so as to be rotatably supported. The cam 18 of the intake camshaft 16 is in contact with the upper end of the intake valve 14, and the cam 19 of the exhaust camshaft 17 is in contact with the upper end of the exhaust valve 15. When both the camshafts 16 and 17 rotate, the intake and exhaust valves 14 and 15 are pushed down against the urging force of the valve springs 14a and 15a by the cams 18 and 19, and the intake valve 14 opens the intake port 21 and exhausts. The valve 15 opens the exhaust port 24. When the intake port 21 is opened, the air-fuel mixture from the intake system is supplied to the combustion chamber 9, and when the exhaust port 24 is opened, the gas inside the combustion chamber 9 is guided to the exhaust passage 26 and discharged to the outside. .

  Both camshafts 16 and 17 are rotated by the rotation of the crankshaft 12 being transmitted by the cam transmission mechanism 30. As shown in FIGS. 2 and 5, the cam transmission mechanism 30 transmits the rotation of the crankshaft 12 by an idle gear train 33 provided on the idle shaft 32, and further rotates the rotation of the idle gear train 33 by the chain transmission mechanism. It is configured to transmit to the shafts 16 and 17.

  In this configuration example, the idle shaft 32 includes a first idle shaft 34 that is a rotating shaft and a second idle shaft 35 that is a fixed shaft. The idle gear train 33 is provided on the first idle shaft 34 and meshes with the cam drive gear 31, the second idle gear 37 provided on the first idle shaft 34, and the second idle shaft 35. A third idle gear 38 that is rotatably provided on the top and meshes with the second idle gear 37. The chain transmission mechanism includes a cam drive sprocket 39 provided on the second idle shaft 34 and rotating together with the third idle gear 38, cam driven sprockets 40, 41 provided on the cam shafts 16 and 17, respectively, The cam chain 42 is stretched between the two sprockets 39-41.

  The cam transmission mechanism 30 rotates the camshafts 16 and 17 once when the crankshaft 12 rotates twice according to the rotation ratio of the cam drive gear 31, the idle gear train 33, and the three sprockets 39 to 41. The first idle shaft 34 rotates at the same rotational speed as the crankshaft 12, and the rotation of the second idle gear 37 is transmitted to the third idle gear 38 at a half rotational speed. The cam chain 42 is disposed inside the chain chamber 30a that is formed on the right side of the right cylinder bore 3c so as to communicate with the inside of the cylinder block 3 and the cylinder head 2.

  The idle shaft 32 is located below the crankshaft 12, and the second idle shaft 35 is located forward relative to the first idle shaft 34. The crankshaft 12 is rotatably supported with the journal 12a supported by four crank journal portions 12D formed on the joint surface 12C of the crankcase 12A, and the center shaft 12d is positioned on the joint surface 12C. The first idle shaft 34 is supported by idle journal portions 12E formed at the left and right ends of the joint surface 12C of the crankcase 12A and is rotatable, and the central shaft 34d is joined to the joint surface similarly to the crankshaft 12. 12C. Thus, the crankshaft 12 and the first idle shaft 34 are supported by being sandwiched between the upper and lower crankcase portions 3B and 4A.

  A breather chamber 46 communicating with the crank chamber 12B is formed above the chain chamber 30a as shown in FIG. The breather chamber 46 is formed by being surrounded by the rear upper inner wall surface of the cylinder head 2 and the front upper inner wall surface of the cylinder block 3. A rib 48 projects from the upper crankcase portion 3B of the cylinder block 3 and the inner wall surface of the side cover 5. The rib 48 serves as a partition wall to form a zigzag breather passage 47 between the cylinder block 3 and the side wall. It is formed surrounded by a cover 5. In the breather passage 47, one end 47a communicates with the crank chamber 12B and the other end 47b communicates with the breather chamber 46, and the breather chamber 46 and the crank chamber 12B communicate with each other.

  A pipe connection member 49 a is pressed into the cylinder head 2 so as to protrude upward, and the pipe connection member 49 a communicates with the breather chamber 46. One end of a blow-by gas pipe 49 is connected to the pipe connecting member 49a, and the other end of the blow-by gas pipe 49 is connected to an intake system such as an air cleaner. As a result, the blow-by gas inside the crank chamber 12B flows into the breather passage 47 in accordance with the pulsation of the crank chamber 12B, and the oil component adheres to the partition wall 48 and is separated from the gas and liquid. And supplied to the combustion chamber 9.

  As shown in FIG. 5, a starter 50 for starting the engine E is provided in the internal space of the upper crankcase portion 3 </ b> B of the cylinder block 3. The starter 50 has an electric starter motor 51 and is configured to transmit the driving force of the starter motor 51 to the crankshaft 12 by a reduction gear train 52.

  The starter motor 51 is fitted to the cylinder block 3 by being fitted into a motor mounting hole 3 d formed on the left side surface of the cylinder block 3, and the output shaft is positioned inside the cylinder block 3. The reduction gear train 52 includes a starter pinion 53 attached to the output shaft of the starter motor 51, and a starter gear train 54 including a starter drive gear 55, a starter idle gear 56, and a starter driven gear 57. The starter gear train 54 is provided on the first and second idle shafts 34 and 35. The starter driven gear 57 is attached to a one-way clutch 58 provided on the first idle shaft 34.

  According to such a starting device 50, the starter motor 51 is driven by the operation of the cell switch near the handle, the starter pinion 53 is rotated, and the first idle shaft 34 is rotated via the starter gear train 53. When the first idle shaft 34 rotates, the first idle gear 36 and the cam drive gear 31 rotate, and the crankshaft 12 is rotationally driven to start the engine E. When the engine E starts and enters an idle state, the rotation speed of the crankshaft 12 exceeds the rotation speed of the starter-driven gear 57, and the starter-driven gear 57 is idled by the one-way clutch 58.

  Further, as shown in FIG. 5, the first idle gear 36 provided on the first idle shaft 34 that rotates at the same rotational speed as the crankshaft 12 is asymmetrically shaped and partially thickened. This thick part 36a functions as a balancer weight. Further, a circular hole is formed through the thick portion 36a, and a weight member 36b formed of a material having a large specific gravity (such as tungsten) is attached to the circular hole. As described above, the cam drive gear 31, the first idle gear 36, the first idle shaft 34, and the balancer weights 36a and 36b constitute a balancer mechanism. When the piston 11 reciprocates once, the balancer weights 36a and 36b rotate once. This will cancel the vibration. As described above, the first idle shaft 34 is shared as the shaft of the cam transmission mechanism 30, the starter 50, and the balancer mechanism, and the cam drive gear 31 and the first idle gear 36 are also connected to the crankshaft 12. The engine E is shared as a gear train for power transmission, and a plurality of dedicated shafts and gear trains are omitted for each mechanism, so that the engine E is downsized.

  As shown in FIGS. 2 and 8, an oil pan 8 is attached to the lower portion of the lower case 4 from below, and the internal space of the oil pan 8 communicates with the internal space of the lower case 4. Inside the oil pan 8, lubricating oil for the engine E and the power transmission mechanism TM is stored. An oil pump for supplying this lubricating oil to each lubricating part is provided in the inner space of the lower crankcase 3B.

  As shown in FIGS. 2 and 8, in the inner space of the lower crankcase portion 4A of the lower case 4, the pump shaft 97 extends to the left and right, located below, that is, behind the first idle shaft 34. And is rotatably arranged. The pump shaft 97 is driven by the rotation of the first idle shaft 34 being transmitted via the pump transmission mechanism 98. As shown in FIG. 2, the pump transmission mechanism 98 includes a pump drive sprocket 98a formed integrally with the first idle shaft 34, a pump driven sprocket 98b provided on the pump shaft 97 and rotating integrally with the pump shaft 97, The pump chain 98c spans between the two sprockets 98a and 98b.

  The oil pump 61 is driven by the rotation of the pump shaft 97. When the oil pump 61 is driven, the lubricating oil stored in the oil pan 8 is sucked from the strainer 62 provided in the oil pan 8 and guided to the suction pipe 66. The lubricating oil introduced into the oil pump 61 through the suction pipe 66 is pumped to the pump discharge oil passage, passes through the oil passage formed in the lower case 4 and the cylinder block 3, and the crank journal portion 12 </ b> D and the idle journal portion. It is supplied to each lubrication part such as 12E.

  Further, as shown in FIG. 9, a water pump 81 for supplying cooling water is attached to the right end portion of the pump shaft 97. When the pump shaft 97 rotates and the built-in impeller rotates, the water pump 81 pressure-feeds cooling water from the radiator to the outside from the discharge pipe connecting portion 81a. The pipe connected to the discharge pipe connecting portion 81a is connected to a pipe connecting portion 84 attached to the cylinder portion 3A of the cylinder block 3 as shown in FIG. The pipe connection portion 84 communicates with a cooling water passage 85 formed inside the cylinder block 3, and further communicates with a water jacket 83 via the cooling water passage 85. The cooling water from the water pump 81 passes through the water jacket 83, whereby the engine E is cooled. Thus, in this configuration example, the drive shafts of the oil pump 61 and the water pump 81 are shared, and the engine E is downsized.

  Next, the power transmission mechanism TM will be described. As shown in FIGS. 4 and 13, the power transmission mechanism TM includes a primary gear train 101, a multi-plate clutch 105, a transmission mechanism 110, a bevel gear train 121, and a shaft mounting member 125 that constitutes a propeller shaft. The transmission case 4B of the lower case 4 and the bevel gear case 6 are accommodated. The bevel gear case 6 is coupled to the left side surface of the lower case 4. The transmission mechanism 110 includes a transmission shaft 110a that is rotatably accommodated in the internal space of the transmission case portion 4B. The transmission shaft 110 a includes a main shaft 111 and a counter shaft 112 that are arranged in parallel to the crankshaft 12.

  The primary gear train 101 is configured by meshing a primary drive gear 102 that rotates integrally with the crankshaft 12 and a primary driven gear 103 that is rotatably provided on the main shaft 111. As shown in FIG. 2, the primary drive gear 102 is the same gear as the cam drive gear 31. The cam drive gear 31 functions as the cam transmission mechanism 30 and also functions as the primary gear train 101 of the power transmission mechanism TM, so that the axial direction of the crankshaft 12 is reduced.

  The multi-plate clutch 105 is wet and is attached to the right end of the main shaft 111. The outer clutch 106 is attached to the primary driven gear 102 via a damper and rotates on the main shaft 111 integrally with the primary driven gear 103. The inner clutch 107, which rotates integrally with the main shaft 111, the outer plate 108 provided in the outer clutch 106, and the inner plate 109 provided in the inner clutch 107, are provided by engaging and disengaging both plates 108, 109. The rotation of the outer clutch 106 is transmitted to the inner clutch 107 detachably.

  The multi-plate clutch 105 is provided with a release mechanism 150. The release mechanism 150 is inserted into the shaft hole 111a of the main shaft 111, the right end is connected to the inner clutch 107, the left end protrudes outwardly to the left of the main shaft 111, and the left end of the rod 151 is disposed inside. The release cylinder 152 is housed in the cylinder. The release cylinder 152 is attached to the left end of the rod 151 and is slidably disposed in the release cylinder 152. The release piston 153 is urged to the left by the release spring 154. . Such a release mechanism 150 always engages the plates 108 and 109 with the release piston 153 and the rod 151 positioned to the left by the urging force of the release spring 154, and rotates from the primary gear train 101. It is transmitted to the main shaft 111. When a clutch lever near the handle (not shown) is operated, hydraulic oil is supplied to the oil chamber 152a of the release cylinder 152, and the release piston 153 moves to the right against the urging force of the release spring 154. As a result, the rod 151 moves to the right, the inner clutch 107 is pressed, the plates 108 and 109 are separated, and the transmission of rotation from the primary gear train 101 to the main shaft 111 is cut off.

  The transmission mechanism 110 includes a main shaft 111 disposed behind the crankshaft 12, a counter shaft 112 disposed below the main shaft 111, and a transmission case portion provided on the main shaft 111 and the counter shaft 112. It is composed of six sets of transmission gear trains G1 to G6 accommodated in the internal space of 4B and a shift drum mechanism 113 for changing the gear position. The transmission gear trains G1 to G6 are composed of drive transmission gears M1 to M6 provided on the main shaft 111 and driven transmission gears C1 to C6 provided on the counter shaft 112. The drive and driven transmission gears are: The gears constituting the transmission gear train are always meshed with each other. The transmission gear trains G1 to G6 are arranged in the order of the first, fifth, fourth, third, sixth, and second transmission gear trains from the right side of the shaft. FIG. 4 shows a neutral state, and only one set of gear trains is rotated integrally with the main shaft 111 and the counter shaft 112 by the operation of the shift drum mechanism 113, and the rotation of the main shaft 111 is changed to the counter shaft 112. introduce.

  The first and second drive transmission gears M1 and M2 are fixed on the main shaft 111 and rotate integrally with the main shaft 111. The fifth and sixth drive transmission gears M5 and M6 and the first, third and fourth driven transmission gears C1, C3 and C4 are fixed on the shaft and are relatively rotatable with respect to the shaft (hereinafter referred to as “the following”). , Referred to as idle gear). The third and fourth drive transmission gears M3 and M4 are integrally formed. The integrated third and fourth drive transmission gears M3 and M4 and the fifth and sixth driven transmission gears C5 and C6 are spline-fitted to the shaft, rotate together with the shaft, and are movable in the axial direction. (Hereinafter referred to as idle gear). Each idle gear is disposed so as to be sandwiched between idle gears, and an engagement projection 119a and a fork groove 119b are formed.

  As shown in FIG. 13, the shift drum mechanism 113 includes a shift spindle 114 that rotates in response to an operation of a shift pedal (not shown), and the rotation of the shift spindle 114 is transmitted via the interlocking mechanism 115, and the main shaft 111 and the counter shaft 112. The shift drum 116 rotates around an axis parallel to the groove 116, and one end of the shift drum 116 engages with a groove 116a formed on the outer peripheral surface of the shift drum 116. The shift fork 117 includes three shift forks 117 that move in the axial direction and a fork shaft 118 that is pivotally connected to guide the shift fork 117. The other end of the shift fork 117 is engaged with a fork groove 119b formed in the idle gear.

  When the shift pedal is operated by such a shift drum mechanism 113, the shift fork 117 moves in the axial direction, and each idle gear moves in the axial direction. As a result, the engagement protrusion 119a formed on the idle gear is engaged with and disengaged from the adjacent idle gear, and the transmission gear train that rotates integrally with the main shaft 111 and the counter shaft 112 is appropriately changed.

  The bevel gear train 121 includes a drive bevel gear 122 formed integrally with the counter shaft 112 at the left end of the counter shaft 112 and a driven bevel gear 123 formed integrally with the shaft attachment member 125 at one end of the shaft attachment member 125. Composed. The bevel gear train 121 is accommodated in the bevel gear case 6.

  The shaft mounting member 125 has a driven bevel gear 123 formed at one end and a spline 125 a formed at the other end, and is rotatably disposed inside the bevel gear case 6. A shaft body (not shown) is attached to the spline 125a to constitute a propeller shaft. The shaft mounting member 125 is rotated integrally with the shaft body by the rotation from the counter shaft 112 transmitted by the bevel gear train 121. The propeller shaft extends rearward in a direction perpendicular to the countershaft 112 and can transmit power to the rear wheels. With the power transmission mechanism TM configured as described above, the rotation of the crankshaft 12 is shifted and transmitted to the rear wheels, so that the two-wheeled vehicle can travel.

  The main shaft 111 is supported by bearings 141 and 142 at both left and right ends, and is rotatable. The bearing 141 that supports the right end is provided in the lower case 4, and the bearing 142 that supports the left end is a bevel gear case. 6 is provided. The counter shaft 112 is supported by bearings 143 and 144 at both left and right ends, and is rotatable. A bearing 143 that supports the right end is provided in the lower case 4, and a bearing 144 that supports the left end is attached to the bevel gear case 6. Provided. The bearing 144 that supports the left end portion of the countershaft 112 is held by the first bearing holder 130.

  The first bearing holder 130 is formed in a cylindrical shape, and two bearings 144 and 144 are accommodated in the cylinder interior 131 from the right opening. A flange 132 projecting inward is formed in the left opening of the cylinder interior 131, and a bearing 144 is brought into contact with the flange 132. Furthermore, a screw-formed nut is screwed onto the outer side surface from the right opening, and the outer ring side of the bearings 144 and 144 is fixed to the cylinder interior 131 of the first bearing holder 130. Similarly, a nut formed by screwing from the right opening to the inner surface is screwed to fix the inner ring side of the bearings 144 and 144 to the counter shaft 112. As a result, the bearings 144 and 144 are held in the cylinder interior 131 of the first bearing holder 130 by being sandwiched in the axial direction by the flange 132 and both nuts.

  In addition, a tapered surface 133 that is cut from the outer wall toward the cylinder interior 131 is formed in the left opening of the first bearing holder 130. The tapered surface 133 has substantially the same gradient as the outer conical surface 122 a of the bevel drive gear 122, and the counter shaft 122 abuts the bearing 144 held by the first bearing holder 130 at the base end of the bevel drive gear 122. Thus, the left end portion is supported with the bevel drive gear 122 as close to the first bearing holder 130 as possible. Thus, the counter shaft 122 can be reduced in size in the axial direction, and the amount of protrusion of the counter shaft 112 from the bearing 144 toward the drive bevel gear 122 can be reduced, so that the capacity of the internal space of the bevel gear case 6 can be reduced. .

  The right end of the shift spindle 114 is supported by a through hole provided in the lower case, and the left end is supported by a bearing 145 attached to a through hole 6c provided in the bevel gear case 6 so as to be rotatable. The right end portion of the shift drum 116 is supported by a bearing 146 provided in the lower case 4, and the left end portion is accommodated and supported in a boss hole 6 d provided in the bevel gear case 6 so as to be rotatable. The fork shaft 118 has a right end portion supported by a through hole provided in the lower case 4, and a left end portion supported by a boss hole 6 e provided in the bevel gear case 6 as a fixed shaft.

  The shaft attachment member 125 is provided with a fixing hole 125b in the axial direction from the end face of one end. A support shaft 126 is press-fitted into the fixing hole 125b, and the support shaft 126 is supported by a bearing 147 provided in the bevel gear case 6 so that one end portion of the shaft mounting member 125 is supported. The other end of the shaft attachment member 125 is supported by a bearing 148 held by the second bearing holder 135. The second bearing holder 135 is formed in a substantially cylindrical shape like the first bearing holder 130, holds the bearing 148 in the cylinder interior 136, and the bearing 148 is attached to the second bearing holder 135 and the propeller shaft mounting member 125 by a nut. The bearing 148 is clamped in the axial direction by the flange 137 and the nut.

  Here, a procedure for assembling the power transmission mechanism TM will be briefly described. The first bearing holder 130 is assembled to the bevel gear case 6 in a state where the left end portion of the counter shaft 122 is supported by the bearing 133 held by the first bearing holder 130. The bevel gear case 6 is formed with a fitting portion 6h for assembling the first bearing holder 130, and screw holes 6i are provided around the fitting portion 6h at a predetermined interval. Further, a dowel hole 6j is formed in the fitting portion 6h. The first bearing holder 130 is fitted into the fitting portion 6h, and a knock pin (not shown) provided in the axial direction of the bearing 144 held on the left end surface is inserted into the dowel hole 6j of the fitting portion 6h. Positioned with respect to the bevel gear case 6, a bolt is inserted from the right end surface toward the screw hole 6 i and fastened to the bevel gear case 6. As a result, the drive bevel gear 122 is accommodated in the internal space of the bevel gear case 6.

  Further, the other end portion is supported by the bearing 148 held by the second bearing holder 135, and the shaft attachment member 125 in which the shaft member 126 is press-fitted into the fixing hole 125 b is attached to the bevel gear case 6. The second bearing holder 135 formed in a substantially cylindrical shape is fitted into the mounting opening of the bevel gear case 6, and the shaft member 126 is supported by the bearing 147 provided in the bevel gear case 6, so that the shaft mounting member 125 becomes the bevel gear case. 6 and the bevel driven gear 123 is accommodated in the internal space of the bevel gear case 6. In this way, by positioning the first bearing holder 130 and the second bearing holder 135 on the bevel gear case 6 and assembling the counter shaft 122 and the shaft mounting member 125 with respect to the bevel gear case 6, the bevel drive gear 122 and the bevel driven gear are assembled. 123 is meshed to form a bevel gear train 121.

  Further, the left end portion of the main shaft 111 is supported on the bevel gear case 6. The bevel gear case 6 is provided with a release accommodating hole 6f for accommodating the release cylinder 152. With the left end portion of the main shaft 111 supported, the release cylinder 152 is accommodated in the release accommodating hole 6f. 150 is attached. The release mechanism 150 is attached to the left of the bearing 142 that supports the left end portion of the main shaft 111.

  The main shaft 111 and the countershaft 112, each of which is supported at the left end by the bevel gear case 6, are provided with six sets of transmission gear trains G1 to G6, and corresponding drive and driven transmission gears are engaged with each other. Further, the bevel gear case 6 supports the left end portions of the shift spindle 114, the shift drum 116 and the fork shaft 118 of the shift drum mechanism 113. A shift fork 117 is attached to the shift drum 116 and the fork shaft 118, and the other end of the shift fork 117 is engaged with a fork groove 119b of the idle gear.

  Thus, the main shaft 111 and the counter shaft 112, the shift spindle 114, the shift drum 115, the shift fork 117, the fork shaft 118, the transmission gear trains G1 to G6, and the bevel gear train 121 are preliminarily attached to the bevel gear case 6. The shaft mounting member 125, the first and second bearing holders 130 and 135, and the release mechanism 150 are assembled, and most of the constituent members of the power transmission mechanism TM such as the speed change mechanism 110 and the bevel gear train 121 are included in the bevel gear case 6. Assembled on the side. The bevel gear case 6 in which the respective members are assembled in this way is attached so as to cover the attachment opening 4m of the lower case 4.

  As shown in FIGS. 11 and 12, bolt insertion holes 4 n and 6 k are provided around the outer peripheral edge of the mounting opening 4 m of the lower case 4 and the outer peripheral edge of the bevel gear case 6 at predetermined intervals. . The bevel gear case 6 is connected to the lower case 4 by being inserted into the bolt insertion holes 6k of the cases 4 and 6 in which the bolts are aligned. The first bearing holder 130 has a dowel hole 130p formed on the right end surface, and a knock pin 161 is inserted into the dowel hole 130p. Thus, the knock pin 161 is provided so as to extend in the axial direction of the bearing 144 to be held. A dowel hole 4p is also formed in the outer peripheral edge of the mounting opening 4m of the lower case 4. The bevel gear case 6 is positioned with respect to the lower case 4 by inserting a knock pin 161 provided in the first bearing holder 130 into the dowel hole 4 p of the lower case 4. Thus, when the bevel gear case 6 is coupled to the lower case 4 by positioning using the first bearing holder 130, the right end portions of the main shaft 111, the counter shaft 112, the shift drum 116, and the fork shaft 118 are supported by the lower case 4, respectively. Is done. Accordingly, the transmission gear trains G1 to G6 are accommodated in the internal space of the transmission case portion 4B of the lower case 4.

  Further, when the bevel gear case 6 is coupled to the lower case 4, an end portion of the transmission supply oil passage 79 formed inside the lower case 4 and through which the lubricating oil discharged from the oil pump 61 flows is formed inside the bevel gear case 6. It communicates with the communication hole 79a of the countershaft supply oil passage 6a. The countershaft supply oil passage 6 a opens into the internal space of the bevel gear case 6 and faces the drive bevel gear 122. A tubular oil joint 162 that connects this opening and the shaft hole 112a of the countershaft 112 is provided. Thereby, the lubricating oil is supplied to the shaft hole 112a of the counter shaft 112. The lubricating oil supplied to the shaft hole 112a is supplied to the driven transmission gear through the oil hole 112b extending in the radial direction. The oil joint 162 is formed with a through hole 162 a that opens into the internal space of the bevel gear case 6. A part of the lubricating oil flowing through the oil joint 162 is ejected from the through hole 162 a into the internal space of the bevel gear case 6 and supplied to the bevel gear train 121.

  As shown in FIGS. 11 and 12, an outer peripheral oil passage 79b formed at the inner peripheral edge of the bevel gear case 6 is connected to the end of the communication hole 79a with the transmission supply oil passage 79. A path 79b communicates with the shaft support hole 6g via a main shaft supply oil path 6b formed inside the bevel gear case 6. The shaft support hole 6g is provided with an oil guide (not shown), and the lubricating oil guided to the shaft support hole 6g is supplied to the shaft hole 111a of the main shaft 111, and the primary driven gear 103, the multi-plate clutch 105, the drive speed change. Supplied to the gear. Note that oil having different properties is used for the hydraulic oil of the release mechanism 150 and the lubricating oil from the oil pan 8 so that the lubricating oil guided to the shaft hole 111 a of the main shaft 111 is not supplied to the release cylinder 152. The shaft support hole 6g is provided with an oil seal 163 located on the left side of the oil guide.

  In this way, the primary driven gear 103 is attached to the right end portion of the main shaft 111 accommodated in the lower case 4 and the bevel gear case 6 to constitute the primary gear train 101, and the multi-plate clutch 105 is attached. Further, an interlocking mechanism 115 is interposed between the shift spindle 114 and the shift drum 116, and the shift drum mechanism 113 is assembled. Then, the side cover 5 is coupled to cover the right side surface of the opened lower case 4.

  As described above, in the power transmission mechanism TM of this configuration example, the first bearing holder 130 that holds the bearing 144 that supports the left end portion of the countershaft 112 is fixed to the bevel gear case 6 via the bolt. Therefore, before the bevel gear case 6 is coupled to the lower case 4, the counter shaft 112 supported by the bearing 144 held by the first bearing holder 130 can be assembled to the bevel gear case 6. The bevel gear train 121 can be meshed in advance and accommodated in the internal space of the bevel gear case 6. Thereby, the assembly property of the bevel gear train 121 is improved, and the power transmission mechanism TM can be easily assembled. Further, the first bearing holder 130 is provided with a knock pin 161 for positioning the bevel gear case 6 with respect to the lower case 4. Thereby, the countershaft 112 fixed to the bevel gear case 6 via the first bearing holder 130 can be assembled to the lower case 4 with high accuracy.

  A bearing 142 that supports the left end portion of the main shaft 111 is provided in the bevel gear case 6, and the main shaft 111 is assembled to the bevel gear case 6 together with the counter shaft 112. As a result, the transmission gear trains G1 to G6 can be assembled on the bevel gear case 6 side before the two cases 4 and 6 are joined, and the assemblability of the transmission gear trains G1 to G6 is improved. Furthermore, the shift drum mechanism 113 is assembled in advance on the bevel gear case 6 side, and many of the components of the power transmission mechanism TM are assembled on the bevel gear case 6 side. Thereby, the assemblability of the power transmission mechanism TM is further improved, and the power transmission mechanism TM with little assembly error can be provided.

  The first bearing holder 130 is positioned by a knock pin provided extending in the axial direction of the bearing 144 to be held and integrated with the bevel gear case 6. The first bearing holder 130 is also positioned by the knock pin 161 and integrated with the lower case 4. Thus, since the inlay positioning is avoided, the inter-axis dimension of the main shaft 111 and the counter shaft 112 can be shortened, the enlargement of the transmission gear trains G1 to G6 is avoided, and the power transmission mechanism TM is reduced in size. Is achieved.

  In the power unit PU of the present configuration example, the joint surface 12C of the cylinder block 3 and the lower case 4 forming the crankcase 12A extends in a substantially vertical direction in a side view, and the central axis 12d of the crankshaft 12 is connected to the joint surface 12C. The central shaft 34d of the first idle shaft 34, which is located above and shared as the shaft of the cam transmission mechanism 30, the starter 50 and the balancer mechanism, is also located on the joint surface 12C and arranged below the crankshaft 12. Yes. The main shaft 111 is disposed behind the crankshaft 12, that is, behind the interior space of the lower case 4, and the counter shaft 112 is disposed below the main shaft 111.

  The primary gear train 101 is configured so that the primary driven gear 103 has a large diameter and the rotation of the crankshaft 12 is decelerated at a large reduction ratio and transmitted to the main shaft 111. The inter-axis dimension becomes longer. For this reason, a dead space is formed between the first idle shaft 34 disposed below the crankshaft 12 and the counter shaft 112 disposed below the main shaft 111. A pump shaft 97 is disposed in this space, and an oil pump 61 and a water pump 81 are attached to the left and right of the pump shaft 97.

  The pump shaft 97 is disposed below the inner space of the lower case 4, and the oil pump 61 is disposed in the vicinity of the oil pan 8. For this reason, the suction pipe 66 can be made compact. In addition, since the pump shaft 97 is disposed between the first idle shaft 34 and the counter shaft 112, the dimension between the first idle shaft 34 and the pump shaft 97 can be shortened, and the pump shaft 97 is driven. The pump transmission mechanism 98 can be configured compactly. Thus, the dead space is effectively utilized by the shaft arrangement of this configuration example, and the power unit PU can be reduced in size.

  Further, since the second idle shaft 35 is disposed in front of the first idle shaft 34 that positions the central shaft 34d below the joint surface 12C, the cam drive sprocket 39 is positioned in the front lower direction and the chain chamber 30a. The cam drive sprocket 39 side is offset downward. Due to this offset, a dead space is formed above the cam drive sprocket 39 side of the chain chamber 30a, and a breather chamber 46 is formed here. Thereby, dead space can be used effectively and power unit PU can be reduced in size. In particular, it is not necessary to form the breather chamber 46 inside the head cover 1 as in the prior art, and the capacity of the head cover 1 can be reduced. When the cylinder shaft 11A is tilted forward and disposed in the two-wheeled vehicle, the power unit PU can be reduced in size in the front-rear direction.

1 is a right side sectional view showing an engine of a power unit provided with a breather structure for an internal combustion engine according to the present invention. It is a left sectional view of the power unit. It is sectional drawing which looked at the engine from back. It is sectional drawing which looked at the power transmission mechanism of the said power unit from back. It is the front sectional view seen in the arrow VV direction of FIG. It is the figure which looked at the cylinder block in the cylinder axial direction. It is a figure which shows the joint surface of a cylinder block. It is right side sectional drawing of a lower case and a bevel gear case. It is a right sectional view of a cylinder block and a lower case showing a main gallery. It is a left view of the transmission case part of a lower case. It is a right view of a bevel gear case. It is sectional drawing of the bevel gear case seen in the XII-XII direction shown in FIG. It is sectional drawing of a shift drum mechanism.

Explanation of symbols

PU power unit E engine TM power transmission mechanism G1 to G6 transmission gear train M1 to M6 drive transmission gear train C1 to C6 driven transmission gear train H housing 4 lower case 5 side cover 6 bevel gear case 11 piston 12 crankshaft 31 cam drive gear 101 primary gear Row 102 Primary drive gear 103 Primary driven gear 105 Multi-plate clutch 110 Transmission mechanism 111 Main shaft 112 Counter shaft 113 Shift drum mechanism 121 Bevel gear row 122 Drive bevel gear 123 Driven bevel gear 125 Shaft mounting member 130 First bearing holder 135 Second bearing holder 150 Release Mechanism 161 dowel pin

Claims (2)

A main shaft that rotates when the output rotation of the internal combustion engine is transmitted ;
A countershaft arranged in parallel to the main shaft;
A propeller shaft disposed substantially orthogonal to the countershaft;
A bevel gear train formed by meshing a drive bevel gear provided at the tip of the counter shaft and a driven bevel gear provided at the tip of the propeller shaft;
A transmission case that houses the main shaft and the counter shaft therein;
A bevel gear case coupled to the transmission case and containing the bevel gear train therein;
Wherein provided in the bevel gear case, the assembling of the power transmission mechanism having a first bearing holding member that holds the first bearing supporting the end of the bearing and the counter shaft supporting an end portion of the main shaft In structure
The main shaft is supported by the bearing, the counter shaft is supported by the first bearing holding member via the first bearing, and these shafts are fixed to the bevel gear case in advance, and then the transmission An assembly structure of a power transmission mechanism characterized by being assembled to a case . A transmission gear train formed by meshing a drive gear provided on the main shaft and a driven transmission gear provided on the counter shaft;
A shift spindle that rotates according to an input operation, a shift drum that rotates according to the rotation of the shift spindle, a shift fork that moves according to the rotation of the shift drum, and the fork shaft that guides the movement of the shift fork A shift drum mechanism that moves a predetermined gear of the drive gear and the driven transmission gear in the axial direction by movement of the shift fork, and changes the transmission gear train,
The assembly structure of the power transmission mechanism according to claim 1, wherein one end of each of the shift spindle, the shift drum, and the fork shaft is supported by the bevel gear case and the other end is supported by the transmission case .

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