JP2011179410A - Crankcase structure of motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a crankcase structure of a motorcycle, having extremely low possibilities of damaging a press-fitting opening for an oil seal keeping liquid-tightness of a cam chain chamber, easy to install and remove a cam chain and also improving ease of work in replacement of the oil seal. <P>SOLUTION: The crankcase structure of the motorcycle 1 includes: a partition wall 113 having an opening 112 for bringing the cam chain chamber 69, in which the cam chain 64 is contained, in communication with a transmission chamber 111 in which a belt type transmission 72 is contained; a crankshaft 49 extending from the cam chain chamber 69 to the transmission chamber 111 through the opening 112; a lid member 116 having an opening 114 for insertion of the crankshaft 49 and covering the opening 112; a seal ring 118 held between the partition wall 113 and the lid member 116 and providing liquid-tight partition between the cam chain chamber 69 and the transmission chamber 111; and the oil seal 119 provided in the hole 114 and slidingly contacted with the outer peripheral face of the crank shaft 49. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a crankcase structure for a motorcycle.

  For example, a scooter type motorcycle includes a power unit having an engine, a continuously variable transmission, and a deceleration transmission mechanism. This power unit drives the drive wheels by transmitting power in the order of the engine, continuously variable transmission, and deceleration transmission mechanism.

  The continuously variable transmission includes a drive pulley provided integrally with a crankshaft of an engine, a driven pulley provided integrally with a driven shaft that transmits torque to a drive wheel, and a drive pulley and a driven pulley. A belt wound endlessly, and transmits the torque of the drive pulley to the driven pulley by the frictional force between the belt and each pulley. The continuously variable transmission is housed in a transmission case provided integrally with the crankcase of the engine. In order for the continuously variable transmission that transmits the driving force by the frictional force between the belt and each pulley to function normally, the sealing property of the lubricating oil between the transmission case and the crankcase must be sufficiently ensured. is there.

  On the other hand, the engine includes a cam chain that transmits power from the crankshaft to the valve operating mechanism in order to drive the intake valve and the exhaust valve. The cam chain is accommodated in a cam chain chamber defined across the crankcase, the cylinder, and the cylinder head.

  From the viewpoint of engine downsizing and cooling efficiency around the cylinder and cylinder head, a crankcase structure of a motorcycle having a cam chain chamber defined between the cylinder and the continuously variable transmission is known. (For example, refer to Patent Document 1). When the cam chain is arranged in the cam chain chamber partitioned between the cylinder and the continuously variable transmission like this crankcase structure, there is a problem in workability in assembling and maintaining the cam chain. In view of this, the crankcase structure described in Patent Document 1 has a workability that is set by appropriately increasing the outer diameter of the oil seal that keeps the liquid-tightness between the crankcase and the transmission case widened. Has improved.

JP-A-9-144599

The crankcase structure of a motorcycle that performs maintenance of the cam chain by removing the oil seal that keeps the fluid tightness between the crankcase and the transmission case from the pressure inlet damages the pressure inlet during the removal and installation of the cam chain. There is a risk that. If the pressure inlet is damaged, the lubricating oil filled in the crankcase leaks from the cam chain chamber into the transmission case.
Also, the work of attaching and detaching the oil seal at the pressure inlet is very poor in workability and is not desirable from the viewpoint of maintainability in the market.

  Therefore, the present invention has a very low possibility of damaging the oil seal pressure inlet that keeps the fluid tightness of the cam chain chamber, can easily attach and detach the cam chain, and can also improve the workability of the oil seal replacement work. A crankcase structure for a motorcycle is proposed.

  In order to solve the above problems, a crankcase structure of a motorcycle according to the present invention includes a partition wall having an opening for communicating a cam chain chamber in which a cam chain is accommodated with a transmission chamber in which a continuously variable transmission is accommodated. A crankshaft extending from the cam chain chamber to the transmission chamber via the opening, a lid member having a hole through which the crankshaft can be inserted, and covering the opening; and between the partition wall and the lid member A seal ring that is sandwiched between the cam chain chamber and the transmission chamber in a liquid-tight manner, and a shaft seal that is provided in the hole and is in sliding contact with the outer peripheral surface of the crankshaft. Features.

  According to the present invention, the possibility of damaging the pressure inlet of the oil seal that keeps the fluid tightness of the cam chain chamber is extremely low, the cam chain can be easily attached and detached, and the workability for replacing the oil seal can be improved. A motorcycle crankcase structure can be provided.

1 is a left side perspective view showing a scooter-type motorcycle having a crankcase structure of a motorcycle according to an embodiment of the present invention. The left view which showed the power unit provided with the crankcase structure of the motorcycle concerning the embodiment of the present invention. The top view which showed the power unit provided with the crankcase structure of the motorcycle which concerns on embodiment of this invention. Sectional drawing in the IV-IV line of FIG. 2 which showed the power unit provided with the crankcase structure of the motorcycle which concerns on embodiment of this invention. The partial plane sectional view showing the power unit provided with the crankcase structure of the motorcycle concerning the embodiment of the present invention. The figure which showed the principal part of the crankcase structure of the motorcycle which concerns on embodiment of this invention. The figure which showed the principal part of the crankcase structure of the motorcycle which concerns on embodiment of this invention. The figure which showed the principal part of the crankcase structure of the motorcycle which concerns on embodiment of this invention.

  Embodiments of a crankcase structure for a motorcycle according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a left side perspective view showing a scooter-type motorcycle having a crankcase structure for a motorcycle according to an embodiment of the present invention.

  In describing the structure of the motorcycle 1, the solid arrow F in FIG. 1 is defined as the front, and the solid arrow R in FIG. 1 is defined as the rear. Regarding the left and right, when the rider of the motorcycle 1 looks forward, the left hand side of the rider is defined as the left side of the motorcycle 1 and the opposite side as the right side of the motorcycle 1. With respect to up and down, the rider's head side is defined as the upper side of the motorcycle 1 and the opposite side is defined as the lower side of the motorcycle 1. The direction of each part constituting the motorcycle 1 is the same as that of the motorcycle 1.

  As shown in FIG. 1, the motorcycle 1 includes a steel pipe body frame 3, a front fork 4 that is pivotally supported by the body frame 3 so as to be rotatable left and right, a front wheel 5 that is pivotally supported by the front fork 4, A power unit 6 that is pivotally supported by the body frame 3 so as to be swingable up and down, a rear wheel 7 that is pivotally supported by the power unit 6, a shock absorber 8 that buffers and restores the swing of the power unit 6 and the rear wheel 7, and a power unit 6 An air intake device 9 disposed in the front upper portion of the power unit 6, an air cleaner 11 disposed in the rear upper portion of the power unit 6, a seating seat 12 provided in the vehicle body frame 3, and an article storage box 13 closed by the seating seat 12. The fuel tank 15 disposed behind the article storage box 13, the front frame cover 16 covering the body frame 3, and the rear frame It includes a Mukaba 17, a.

  The vehicle body frame 3 includes a head pipe 21 positioned at the frontal head, a down pipe 22 extending rearward and downward from the head pipe 21, and left and right extending obliquely upward and rearward from the vicinity of the rear end of the down pipe 22. A pair of rear pipes 23, a step frame 24 disposed at a portion where the down pipe 22 is inserted downward, and an engine bracket 25 provided in the vicinity of the joint between the down pipe 22 and the rear pipe 23 are provided. The head pipe 21 pivotally supports the handle bar 27, the head lamp 28, and the front fender 29 so as to be rotatable left and right. The engine bracket 25 is connected to the power unit 6 via a link 31.

  The power unit 6 swings up and down around the pivot shaft 32 installed at the rear end of the link 31 together with the rear wheel 7 and functions as a swing arm of the rear wheel 7.

  The shock absorber 8 is connected between the rear part of the rear pipe 23 and the rear part of the power unit 6.

  The seating sheet 12 is installed above the article storage box 13 so as to close the opening. The seating seat 12 opens the opening of the article storage box 13 by lifting the rear end around the hinge portion 33 at the front end.

  The article storage box 13 is a bottomed box-shaped container that opens upward, and is installed above the rear pipe 23.

  The fuel tank 15 includes an oil supply portion 35 that passes through a tray portion 34 extending rearward from the upper edge of the article storage box 13 and faces upward.

  The front frame cover 16 is a resin cover that covers the front portion of the vehicle body frame 3.

  The rear frame cover 17 is a resin cover that covers the rear portion of the vehicle body frame 3.

  The motorcycle 1 includes a tail lamp 36 provided at the rear end of the rear frame cover 17, a rear fender 37 provided above the rear wheel 7, and a resin step board disposed above the step frame 24. 38.

  The front frame cover 16, the rear frame cover 17, and the step board 38 are continuously connected.

FIG. 2 is a left side view showing a power unit having a crankcase structure for a motorcycle according to an embodiment of the present invention. FIG. 3 is a plan view showing a power unit having a crankcase structure for a motorcycle according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2 showing a power unit having a crankcase structure for a motorcycle according to an embodiment of the present invention.

  As shown in FIGS. 2 to 4, the power unit 6 of the motorcycle 1 includes an integrated engine 41 and a transmission unit 42, and has a general layout for a scooter type motorcycle.

  The engine 41 is, for example, a forced air-cooled four-cycle engine, and includes a crankcase 43, a single-cylinder cylinder assembly 44 that is provided in front of the crankcase 43 and arranged to be inclined substantially horizontally, A transmission unit 42 provided on the left side and extended rearward, and a generator 45 provided on the right side of the crankcase 43 are provided.

  The crankcase 43 is configured by combining a left case half 47 and a right case half 48 which are divided into left and right. The crankcase 43 pivotally supports a crankshaft 49 having a rotation shaft along the vehicle width direction (left-right direction). Both ends of the crankshaft 49 protrude to the left and right of the crankcase 43, respectively.

  The cylinder assembly 44 includes a cylinder block 51 provided in front of the crankcase 43, a cylinder head 52 provided in front of the cylinder block 51, and a head cover 53 provided in front of the cylinder head 52. The cylinder block 51 has an inner peripheral surface that defines a cylinder bore 55, and the cylinder head 52 has an inner peripheral surface that defines a combustion chamber 56 aligned with the cylinder bore 55.

  The cylinder assembly 44 includes a piston 57 that can reciprocate inside the cylinder bore 55, a connecting rod 59 that is connected to the piston 57 and the crank pin 58 of the crankshaft 49, and a combustion chamber 56 that is attached to the cylinder head 52. A spark plug 60 facing the cam shaft 61 supported in the vehicle width direction (left-right direction) inside the cylinder head 52, a cam drive sprocket 62 provided on the crankshaft 49, and a camshaft cam drive 61 A sprocket 63 and an endless cam chain 64 that passes through the cylinder block 51 and the cylinder head 52 and is wound between the cam drive sprocket 62 and the cam driven sprocket 63 are provided.

  The cylinder assembly 44 converts the reciprocating motion of the piston 57 into the rotational motion of the crankshaft 49 by the connecting rod 59.

  The rotation of the crankshaft 49 is decelerated to 1/2 and transmitted to the camshaft 61 by the cam drive sprocket 62 and the cam driven sprocket 63. The rotation of the cam shaft 61 opens and closes an intake valve (not shown) and an exhaust valve (not shown) at predetermined timings via an intake cam 66 and an exhaust cam 67 formed on the cam shaft 61 and a rocker arm 68. Let

  The cam chain 64 is accommodated in a cam chain chamber 69 defined on the left side of the cylinder block 51, the cylinder head 52 and the head cover 53.

  The transmission unit 42 includes a transmission case 71 provided on the left side of the left case half 47 and extending rearward, and a belt-type transmission 72 and a reduction transmission mechanism 73 housed in the transmission case 71. The transmission case 71 includes a transmission case main body 74 that is integrally formed with the left case half body 47, and a transmission case cover 75 that closes the left opening of the transmission case main body 74.

  The transmission unit 42 includes a driven shaft 77 that is pivotally supported at the rear of the transmission case body 74 and the transmission case cover 75, and an intermediate shaft 78 that is disposed below the driven shaft 77 and is pivotally supported by the mission cover 97. A rear wheel shaft 79 disposed on the rear upper side of the intermediate shaft 78 and supported by the transmission case main body 74 and the transmission cover 97. The rear wheel shaft 79 protrudes from the right side surface of the mission cover 97. The protruding portion of the rear wheel shaft 79 is fixed to the rear wheel 7 so as to rotate together. The crankshaft 49 also serves as the drive shaft of the transmission unit 42.

  The belt-type transmission 72 is housed in a transmission case 71, and is provided on a drive pulley 81 and a driven shaft 77 provided integrally with the left end of a crankshaft 49 extending inside the transmission case 71. A driven pulley 82, an endless V-belt 83 wound around the pulleys 81, 82, and a centrifugal clutch 84 arranged in parallel on the left side of the driven pulley 82. In the belt-type transmission 72, the drive pulley 81 expands the effective diameter by increasing the centrifugal force accompanying the rotation of the crankshaft 49, while the driven pulley 82 reduces the effective diameter to steplessly rotate the crankshaft 49. Are automatically shifted (accelerated) and transmitted to the driven shaft 77.

  The drive pulley 81 includes a fixed pulley half 86 and a movable pulley half 87 facing each other. The side surfaces of the fixed pulley half 86 and the movable pulley half 87 facing each other form a belt groove.

  The fixed pulley half 86 is formed of steel and is fixed to the crankshaft 49. On the other hand, the movable pulley half 87 is movable in the perspective direction with respect to the fixed pulley half 86. The movable pulley half 87 includes a movable pulley housing 88 having a side surface facing the fixed pulley half 86, a fixed plate 89 positioned on the right side of the movable pulley housing 88 and fixed to the crankshaft 49, and a movable pulley housing. And a weight roller 90 disposed between the fixing plate 89 and the fixing plate 89. The movable pulley housing 88 is configured to be movable in the axial direction of the crankshaft 49. The movable pulley half 87 moves the weight roller 90 to the outer peripheral side of the movable pulley housing 88 and the fixed plate 89 by the centrifugal force generated by the rotation of the crankshaft 49 so that the movable pulley housing 88 approaches the fixed pulley half 86.

  The driven pulley 82 also includes a fixed pulley half 91 and a movable pulley half 92 that face each other. The side surfaces of the fixed pulley half 91 and the movable pulley half 92 facing each other form a belt groove.

  The fixed pulley half 91 is fixed to the driven shaft 77. On the other hand, the movable pulley half 92 is movable in the perspective direction with respect to the fixed pulley half 91.

  When the rotational speed of the driven pulley 82 reaches a predetermined rotational speed or more, the centrifugal clutch 84 causes the driven shaft 77 and the driven pulley 82 to frictionally engage with each other.

  The reduction transmission mechanism 73 includes a primary drive gear 93 provided near the right end of the driven shaft 77, a primary driven gear 94 provided on the intermediate shaft 78 and meshed with the primary drive gear 93, and a second drive gear 93 provided on the intermediate shaft 78. And a secondary driven gear 96 provided on the rear wheel shaft 79 and meshed with the secondary drive gear 95. These four gears 93, 94, 95, and 96 are liquid-tightly isolated by a mission cover 97 attached to the rear portion of the transmission case main body 74 and immersed in lubricating oil.

  The generator 45 includes a stator 98 fixed to the crankcase 43 (the right case half body 48), and a rotor 99 provided integrally with the crankshaft 49 at the right end. The generator 45 generates electricity by rotating the rotor 99 around the stator 98 by the rotation of the crankshaft 49.

  The engine 41 transmits the rotation of the crankshaft 49 due to the operation of the cylinder assembly 44 to the driven shaft 77 through the drive pulley 81, the V belt 83, the driven pulley 82, and the centrifugal clutch 84 in order, and the rotation of the driven shaft 77 is decelerated. The speed is reduced by the mechanism 73 and transmitted to the rear wheel shaft 79 and the rear wheel 7.

  The engine 41 also generates an engine cooling fan 101 that generates cooling air for the cylinder assembly 44, a resin cooling cowling 102 that covers the right side of the cylinder assembly 44 and the crankcase 43, and cooling air for the belt-type transmission 72. A transmission cooling fan 103 (impeller).

  The engine cooling fan 101 is fixed to the right end portion of the crankshaft 49, more specifically, to the rotor 99 of the generator 45, and rotates together with the rotor 99 as the crankshaft 49 rotates.

  The cooling cowling 102 has a cooling air intake port 104 opened on the right side of the engine cooling fan 101, and a cooling air discharge port (not shown) opened below the cylinder assembly 44.

  The transmission cooling fan 103 is juxtaposed to the left end of the crankshaft 49, more specifically the left side of the drive pulley 81, and is fixed to the crankshaft 49, and rotates together with the drive pulley 81 as the crankshaft 49 rotates. .

  The engine 41 rotates the engine cooling fan 101 and sucks air from the cooling air intake port 104, and uses the air discharged from the engine cooling fan 101 as cooling air to flow in the internal space of the cooling cowling 102 so that the cylinder assembly 44 is The cooling air is forcibly cooled and the heated cooling air is discharged from the cooling air outlet. Further, the engine 41 rotates the transmission cooling fan 103 to suck in air from the cooling air suction port 106 opened in the transmission case cover 75, and uses the air discharged from the transmission cooling fan 103 as cooling air for the transmission case. The belt-type transmission 72 is cooled by flowing through the internal space 71, and the warmed cooling air is discharged from the cooling air discharge port 107 opened in the transmission case cover 75.

  FIG. 5 is a partial plan sectional view showing a power unit having a crankcase structure for a motorcycle according to an embodiment of the present invention.

  As shown in FIG. 5, the crankcase 43 has an opening 112 that allows communication between a cam chain chamber 69 in which a cam chain 64 is accommodated and a transmission chamber 111 in which a belt-type transmission 72 (continuously variable transmission) is accommodated. A partition wall 113; a crankshaft 49 extending from the cam chain chamber 69 to the transmission chamber 111 via the opening 112; a lid member 116 having a hole 114 through which the crankshaft 49 can be inserted; A seal ring 118 that is sandwiched between the cam chain chamber 69 and the transmission chamber 111 by being sandwiched between the cover member 113 and the lid member 116, and provided in the hole 114 so as to be in sliding contact with the outer peripheral surface of the crankshaft 49. An oil seal 119 (shaft seal).

  The transmission chamber 111 is a space defined by the transmission case 71 and in which the belt-type transmission device 72 is accommodated.

  The partition wall 113 is a partition wall shared between the crankcase 43 (more specifically, the left case half body 47) and the transmission case main body 74, and exposes one surface to the cam chain chamber 69 and the other surface. Exposed to the transmission chamber 111. The opening 112 of the partition wall 113 is a maintenance hole used when the cam chain 64 is taken out from the cam chain chamber 69 and when the cam chain 64 is introduced into the cam chain chamber 69. A peripheral edge of the opening 112 on the transmission chamber 111 side is a seal surface 121 that can contact the seal ring 118.

  The lid member 116 is formed by casting an aluminum alloy casting or steel, and covers the opening 112 and overlaps the seal surface 121 on the periphery of the opening 112. The lid member 116 has a seal groove 122 for holding and positioning the seal ring 118 in a portion overlapping the seal surface 121, that is, in the vicinity of the outer peripheral edge thereof. Further, the hole 114 of the lid member 116 is a pressure inlet into which the oil seal 119 is press-fitted, and holds the press-fitted oil seal 119 having an inner diameter slightly smaller than the outer diameter of the oil seal 119.

  The seal ring 118 is configured using a gasket such as a rubber or metal O-ring or a sheet gasket.

  The oil seal 119 has an inner diameter that maintains the fluid tightness of the lubricating oil corresponding to the shaft diameter of the crankshaft 49 and allows the crankshaft 49 to rotate, and an outer diameter that is press-fitted into the hole 114 of the lid member 116. It is the shaft seal of the annular body which has.

  FIGS. 6 and 7 are views showing a main part of the crankcase structure of the motorcycle according to the embodiment of the present invention. FIG. 6 is a diagram in which the belt-type transmission is omitted. FIG. 7 is a diagram in which the belt-type transmission and the lid member are omitted.

  6 and 7, the opening 112 of the partition wall 113 that separates the cam chain chamber 69 of the crankcase 43 (more specifically, the left case half 47) and the transmission chamber 111 of the transmission case main body 74 and its lid member 116. Are formed corresponding to the shapes of the left case half 47 and the transmission case main body 74. Specifically, the opening 112 and the lid member 116 are formed not only in a circular shape concentric with the crankshaft 49 and the oil seal 119 but also in a shape having the chord edges 112a and 116a from which a part of the arc is removed. May be. The opening 112 and the string edge portions 112a and 116a of the lid member 116 secure a space for installing the starter motor 124 that is provided in the transmission case main body 74 and starts the engine 41.

  The lid member 116 is fixed by a fastening member 126 such as a bolt that can be screwed into a bolt hole 125 formed in the partition wall 113. The opening 112 and the chord edge portions 112a and 116a of the lid member 116 are free in shape as long as the surface pressure between the partition wall 113 and the lid member 116 by the fastening member 126 is maintained and the oil seal 119 can be liquid tight. Can be set.

  That is, the opening 112 and the lid member 116 can be formed as large as possible within a range that can be enveloped in the transmission case main body 74. On the other hand, the oil seal 119 press-fitted into the hole 114 of the lid member 116 can be set to an appropriate inner diameter and outer diameter in consideration of its sealing performance regardless of the size of the opening 112 and the lid member 116.

  On the other hand, the partition wall 113 includes a cylindrical knock pin 127 provided so as to protrude from the periphery of the bolt hole 125. As for the knock pin 127, the fastening member 126 is inserted in the hollow part. On the other hand, the lid member 116 has a positioning hole 129 into which the knock pin 127 can be inserted. The partition wall 113 and the lid member 116 ensure the coaxiality between the oil seal 119 provided on the lid member 116 and the crankshaft 49 by the knock pin 127 and the positioning hole 129.

  The crankcase 43 (more specifically, the left case half 47) has a drain hole 131 located in the vicinity of the lower end of the cam chain chamber 69. The drain hole 131 is a hole that allows the cam chain chamber 69 and the crank chamber to communicate with each other, and is used when the lubricating oil that has finished lubricating the cam chain 64 is discharged from the cam chain chamber 69 to the crank chamber. Since the opening 112 is formed as large as possible in the drain hole 131, the lubricating oil can be reliably discharged from the cam chain chamber 69 to the crank chamber.

  FIG. 8 is a view showing a main part of the crankcase structure of the motorcycle according to the embodiment of the present invention.

  As shown in FIG. 8, the fastening member 126 that fastens the lid member 116 to the partition wall 113 that separates the cam chain chamber 69 of the crankcase 43 (more specifically, the left case half body 47) and the transmission chamber 111 of the transmission case main body 74 is provided. The crankshaft 49 is disposed on the radially outer side of the movable pulley half 87 of the drive pulley 81 as viewed in the rotational axis direction of the crankshaft 49. Further, the fastening member 126 is disposed in the vicinity of the inner peripheral edge of the transmission case 71 (more specifically, the transmission case main body 74).

  The crankcase structure of the motorcycle 1 is configured such that the fastening member 126 is disposed radially outside the movable pulley half 87 of the drive pulley 81, whereby the rotation shaft of the crankshaft 49 between the bolt head 126 a and the movable pulley half 87. The overlapping in the direction is prevented, the length of the crankshaft 49 in the vehicle width direction is suppressed, and the power unit 6 can be downsized.

  The crankcase structure of the motorcycle 1 configured as described above enables the cam chain 64 in the cam chain chamber 69 to be attached and detached as follows. That is, when the cam chain 64 is taken out from the cam chain chamber 69 and when the cam chain 64 is introduced into the cam chain chamber 69, the fastening member 126 is first extracted from the bolt hole, and then the lid member 116, the seal ring 118, and the oil seal. 119 is integrally moved in the direction of the rotation axis of the crankshaft 49 and removed from the partition wall 113. Then, the opening 112 of the partition wall 113 is opened, and the cam chain 64 can be detached and attached.

  According to the crankcase structure of the motorcycle 1, the space of the crankcase 43 (more specifically, the left case half body 47) and the speed change case 71 (more specifically, the speed change case main body 74) and other equipment such as the starter is spatial. The opening 112 that is the maintenance hole of the cam chain chamber 69 can be opened as much as possible under the constraints.

  Further, according to the crankcase structure of the motorcycle 1, the oil seal 119 that is press-fitted into the hole 114 of the lid member 116 and the seal ring 118 that is disposed in the seal groove 122 of the lid member 116 are used as an opening 112 that is a maintenance hole. In addition, it is not necessary to form the lid member 116 in a circular shape, and the degree of freedom in shape selection is increased.

  Accordingly, the cam chain 64 can be easily taken out from the cam chain chamber 69, and the cam chain 64 can be easily introduced into the cam chain chamber 69 and wound around the cam drive sprocket 62, so that the maintainability of the cam chain 64 is greatly improved.

  Furthermore, according to the crankcase structure of the motorcycle 1, when the cam chain 64 is taken out or introduced from the cam chain chamber 69, the hole 114 of the lid member 116 is not damaged by the cam chain 64. Further, when the cam chain 64 is taken out or introduced from the cam chain chamber 69, it contacts the outer peripheral surface of the crankshaft 49 and the seal surface 121 of the partition wall 113 even if the cam chain 64 may contact the opening edge of the opening 112. The risk of doing so is very low. Furthermore, since the opening 112 has a sufficient width, the outer peripheral surface of the crankshaft 49 and the seal surface 121 of the partition wall 113 can be reliably cured, and damage to each part can be avoided. Thus, damage to the portion sealed by the oil seal 119 and the seal ring 118 can be reliably avoided, and liquid tightness between the transmission chamber 111 and the cam chain chamber 69 can be reliably maintained.

  Furthermore, according to the crankcase structure of the motorcycle 1, since the oil seal 119 is press-fitted into the hole 114 of the cover member 116, the oil seal is press-fitted into the partition wall through the oil seal through the opening. Compared with this structure, the work related to the mounting of the oil seal 119 becomes extremely easy, the press-fit property can be improved and the press-fit dimensions can be visually confirmed, and press-fitting errors such as oblique press-fitting are less likely to occur. Even when the cam chain 64 is removed and introduced in the market, it is not necessary to remove the oil seal 119 directly, and the oil seal 119 and the lid member 116 can be easily attached and detached integrally. Moreover, since the positioning of the lid member 116 and the partition wall 113 is facilitated, the oil seal 119 can be reused without replacement.

  Therefore, according to the crankcase structure of the motorcycle 1 according to the present embodiment, the possibility of damaging the hole 114 into which the oil seal 119 that keeps the fluid tightness of the cam chain chamber 69 is pressed is extremely low. It can be easily attached and detached, and the workability required for replacing the oil seal 119 can be improved.

DESCRIPTION OF SYMBOLS 1 Motorcycle 3 Body frame 4 Front fork 5 Front wheel 6 Power unit 7 Rear wheel 8 Shock absorber 9 Intake device 11 Air cleaner 12 Seating sheet 13 Article storage box 15 Fuel tank 16 Front frame cover 17 Rear frame cover 21 Head pipe 22 Down pipe 23 Rear pipe 24 Step frame 25 Engine bracket 27 Handle bar 28 Front lamp 29 Front fender 31 Link 32 Pivot shaft 33 Hinge part 34 Tray part 35 Refueling part 36 Tail lamp 37 Rear fender 38 Step board 41 Engine 42 Transmission unit 43 Crankcase 43a Ceiling wall 44 Cylinder assembly 45 Generator 47 Left case half 48 Right case half 49 Crankshaft 51 Cylinder block 52 Cylinder head 53 Head cover 55 Cylinder bore 56 Combustion chamber 57 Piston 58 Crank pin 59 Connecting rod 60 Spark plug 61 Cam shaft 62 Cam drive sprocket 63 Cam driven sprocket 66 Intake cam 67 Exhaust cam 68 Rocker arm 64 Cam chain 69 Cam chain chamber 71 Transmission case 72 Belt transmission 73 Deceleration transmission mechanism 74 Transmission case body 75 Transmission case cover 77 Driven shaft 78 Intermediate shaft 79 Rear wheel shaft 81 Drive pulley 82 Driven pulley 83 V belt 84 Centrifugal clutch 86 Fixed pulley half 86a Starter ring gear 87 Movable Pulley half 88 Movable pulley housing 89 Fixed plate 90 Weight roller 91 Fixed pulley half 91a Anti-belt groove side surface 92 Movable pulley half 93 Primary drive gear 94 Primary driven gear 95 Secondary driven gear 96 Secondary driven gear 97 Mission cover 98 Stator 99 Rotor 99a Outer peripheral surface 99b Projection 101 Engine cooling fan 102 Cooling cowling 103 Transmission cooling fan 105 Transmission cooling fan 104 Cooling air inlet 106 Cooling air inlet 107 Cooling air outlet 111 Shifting chamber 112 Opening 112a String edge 113 Partition wall 114 Hole 116 Lid member 116a String edge 118 Seal ring 119 Oil seal 121 Seal surface 122 Seal groove 124 Starter motor 125 Bolt hole 126 Fastening member 126a Bolt head 127 Knock pin 129 Positioning hole 131 Drain hole

Claims (4)

A partition wall having an opening for communicating the cam chain chamber in which the cam chain is accommodated with the speed change chamber in which the continuously variable transmission is accommodated;
A crankshaft extending from the cam chain chamber to the transmission chamber through the opening;
A lid member having a hole through which the crankshaft can be inserted and covering the opening;
A seal ring that is sandwiched between the partition wall and the lid member to partition the cam chain chamber and the transmission chamber in a liquid-tight manner;
A crankcase structure for a motorcycle, comprising: a shaft seal provided in the hole and in sliding contact with an outer peripheral surface of the crankshaft. The continuously variable transmission includes a drive pulley having a movable pulley half provided on the crankshaft;
2. The automatic according to claim 1, further comprising a fastening member that is disposed radially outside the movable pulley half when viewed in the rotational axis direction of the crankshaft and fixes the lid member to the isolation wall. Crankcase structure for motorcycles. The crankcase structure for a motorcycle according to claim 2, wherein the fastening member is disposed in the vicinity of an inner peripheral edge of a transmission case that partitions the transmission chamber. The crankcase structure for a motorcycle according to any one of claims 1 to 3, further comprising a knock pin for positioning the lid member on the isolation wall.

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