JPH0281782A - Sprocket cover device for engine - Google Patents

Abstract

PURPOSE:To reduce a number of part items and assembly labor hours by integrally forming a sprocket cover with a bearing holding member fixing a sprocket side bearing, supporting an output shaft, to a crown case side. CONSTITUTION:Of the bearings 96A, 96B supporting an output shaft 96, the bearing 96A in a side of a sproket 97 is fitted to a bearing holding member 96C made by casting from an opposite side to the sprocket 97 and fixed by a nut 96D. The bearing holding member 96C is mounted to a right case half unit 50b of crankcase 50. Further the bearing holding member 96C integrally forms a cover 99 coating the front of the sprocket 97 and its diagonally front upper, and the point end of the cover 99, approaching an internal surface 33 rising from a hood board 30, surrounds the sprocket 97. By this constitution, the reduction can be contrived of a number of part items and assembly labor hours.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cover device for covering a sprocket fixed to an output shaft of an engine.

(Background of the Invention) Some vehicle engines that transmit engine output to drive wheels by a chain wrapped around a sprocket fixed to the output shaft of the engine are provided with a cover that covers the sprocket. In this case, conventionally, the engine was made as an independent part by die casting, molding of synthetic resin, press working of sheet metal, etc., and this was fixed to the engine. For this reason, in addition to the cover itself, bolts for fixing it are also required, which is disadvantageous in that the number of parts increases.

(Object of the Invention) The present invention was made in view of the above circumstances, and an object of the present invention is to provide a cover device for an engine sprocket that can reduce the number of parts and the number of assembly steps.

(Structure of the Invention) According to the present invention, in a vehicle engine in which the rotation of a drive sprocket fixed to the output shaft of the engine is transmitted to the drive wheels by a chain, the sprocket side that supports the output shaft is This is achieved by a cover device for an engine sprocket, characterized in that a cover for covering the outer periphery of the sprocket is integrally formed with a bearing holding member that fixes the bearing to the crankcase side.

(Example) Fig. 1 is a developed view of an embodiment of the present invention, Fig. 2 is a right side view, Fig. 3 is a shaft arrangement diagram of a gear group for forward/reverse switching, and Fig. 4 is a small size equipped with this. A side view of the four-wheeled vehicle, FIG. 5 is a side view of the four-wheeled vehicle, and FIG.
The cross-sectional view and FIG. 6 are plan views of the guide plate.

In FIG. 4, reference numeral 10 indicates a pair of left and right front steering wheels, 12 a pair of left and right driving rear wheels, 14 a steering handle, 16 a fuel tank, and 18 a straddle-type seat.

20 is an air-cooled single-cylinder engine mounted between the front and rear wheels 10 and 12, and this engine 20 is equipped with a body cover 22.
The left and right sides are covered. A pair of left and right large openings 24 are formed in this body cover 22, and the engine 20
The cooling performance and maintainability of the engine have been improved. Further, the front and rear portions of this body cover 22 protrude left and right to form a front fender 26 and a rear fender 28, respectively.

The front and rear fenders 26 and 28 and the body cover 22 are connected by a footboard 30.

Next, the engine 20 will be explained based on FIG. 1.2. The engine 20 includes a left and right crankcase 50 and a sill 52, and the crankcase 50 extends rearward and also serves as a part of a transmission case 54. crank case 50
A crankshaft 56 is accommodated in the front portion of the engine 56 horizontally with respect to the vehicle body, and a piston 60 is connected to the crankshaft 56 via a connecting rod 58. In FIG. 1, 62 is an overhead camshaft, 666 is a spark plug to which rotation of the crankshaft 56 is transmitted by a timing chain 64, and 68 is a generator attached to the right end of the crankshaft 56.

The transmission case 54 is made to extend rearward from the left side of the crankcase 50. That is, the crankcase 50 is made of a left case half 50a and a right case half 50b, and a belt continuously variable transmission 72 is housed between a case cover 70 that is placed on the left side of the left case half 50a. The right case half 50b and the left case half 5 extend in a thin plate shape.
A forward/reverse switching device 74 is housed between the right side surface of 0a. The transmission 72 includes a driving pulley 74a attached to the left end of the crankshaft 56, a driven pulley 74b attached to a bobbin shaft 76 located at the rear of the transmission case 54, and a pulley 74b wound around both pulleys 74a and 74b. V-belt 7
4c, the radius of the winding of the driving pulley 74a increases as the engine speed increases, and the radius of the winding of the driven pulley 74b decreases accordingly, which is a known method in which the speed is automatically changed. . Driven side boo IJ 74
The rotation of b is caused by the pulley shaft 7 via a centrifugal automatic clutch 78.
6 The forward/reverse switching device 74 includes a forward/reverse switching gear group 80 held between both case halves 50a and 50b, and this gear group 8.
A forward/reverse switching operation mechanism 82 for performing a switching operation of 0 is provided,
These are located between the crankshaft 56 and the pulley shaft 76.

The gear group 80 includes a switching shaft 84 and a reverse shaft 86.
A forward gear 88 that can freely rotate on the switching shaft 84 meshes with the gear 76a of the pulley shaft 76, and a reverse gear 90 that can also freely rotate on the switching shaft 84 meshes with the gear 92 on the reverse shaft 86 (see FIG. 3). It is rotated by the bobbin shaft 76 via the bobbin shaft 76. Therefore gear 88
．． 90 rotate in opposite directions. A sleeve 94 splined on the switching shaft 84 forms a dog clutch with both gears 88, 90, and either gear 88 or 90
selectively transmits the rotation to the switching shaft 84. This switching shaft 84
The rotation is transmitted to the output shaft 96, and this rotation is further transmitted to the axle of the rear wheel 12 via a sprocket 97 and a chain 98 (FIG. 1). Here, the output shaft 96 is a bearing 96A.
, 96B, and a bearing 96A on the sprocket 97 side.
is fitted into a bearing holding member 96G made by casting from the side opposite to the sprocket 97 and fixed to a nut 96D,
In this state, the bearing holding member 96G is attached to the right case half 50b of the crankcase 50. A cover 99 that covers the front side of the sprocket 97 and the diagonally upper front side of the sprocket 97 is integrally formed on this bearing holding member 96C (see FIG. 2). The tip of this cover 99 approaches the inner surface rising from the footboard 30, and the sprocket 97 is surrounded by these.

The switching operation mechanism 82 includes a shifter 102 that slides on a thick shaft 100 to move the sleeve 94, a cylindrical cam drum 104 that engages with the shifter 102, a lever shaft 106 that rotates the drum 104, and a lever shaft 106 that rotates the drum 104. A switching lever 108 attached to a lever shaft 106 is provided. The switching lever 108 is capable of swinging toward the outside of the vehicle body around a pin 110 orthogonal to the lever shaft 106, and is given a tendency to return to the inside of the vehicle body by a torsion spring 112. The switching lever 108 moves within a bent guide hole formed in the guide plate 114 (see Fig. 6), and during switching operation, the switching lever 108 is brought down to the imaginary position shown in Fig. 5 and rotated back and forth. It has become. lever shaft 1
The rotation of 06 is transmitted by a pinion 116 to a pinion 118 rotatably attached to the drum 104. The drum 104 has a torsion spring 120 biased in the opening direction.
Both ends of the spring 120 are engaged with each other with a slight play in the compression direction (see FIG. 1.3), and the two ends are integral with the pinion 118.
Book claws pinch both ends of this spring 120.

Therefore, when the switching lever 108 is tilted outward and rotated back and forth, the small gears 116 and 118 rotate, and the drum 104 is rotated while pushing the claw or spring 120 of one of the small gears 118. This causes the shifter 102 to move to connect or disconnect the sleeve 94 from either gear 88, 90, leaving it in a neutral state. A spring 120 on the drum 104 resiliently presses the sleeve 94 against the gears 88, 90 during this switch to enable smooth engagement.

FIG. 7 is a diagram showing another embodiment of the present invention, in which a bearing 196A that holds the output shaft 96 is fitted into the right case half 50b, and the auclease is held by a bearing holding member 196C made of sheet metal. The bearing 196A is held to restrict movement of the bearing 196A in the axial direction. A cover 199 is integrally formed with this bearing holding member 196C.

(Effects of the Invention) As described above, the present invention is such that the cover covering the drive sprocket fixed to the output shaft of the engine is integrally formed with the bearing holding member of the output shaft, so that an independent cover can be attached. The number of parts is reduced compared to the previous model, and the number of assembly steps can also be reduced.

[Brief explanation of the drawing]

Fig. 1 is an exploded view of an embodiment of the present invention, Fig. 2 is a right side view, Fig. 3 is a diagram of the shaft arrangement of the forward/reverse switching gear group, and Fig. 4 is a diagram of a small four-wheeled vehicle equipped with the same. FIG. 5 is a side view, FIG. 5 is a sectional view taken along the line V-V in FIG. 4 to show the operation of the operating lever, FIG. 6 is a plan view of the guide plate, and FIG. 7 is a diagram showing another embodiment. . 20... Engine, 50... Crankcase, 54... Transmission case, 56... Crankshaft, 96... Sprocket, 96A, 196A... Bearing, 96C1196C... Bearing holding member, 99 .199・
...Cover patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] In a vehicle engine in which the rotation of a drive sprocket fixed to the output shaft of the engine is transmitted to the drive wheels by a chain, a bearing on the sprocket side that supports the output shaft is fixed to the crankcase side. A cover device for an engine sprocket, characterized in that a cover for covering the outer periphery of the sprocket is integrally formed with a bearing holding member.