JP2003301903A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid an increase in the width and longitudinal length of an engine when arranging a continuously variable transmission mechanism and a centrifugal clutch mechanism on a transmission shaft. <P>SOLUTION: The engine 2 comprises the continuously variable transmission mechanism 16 provided outside a crank case 22 in the direction of a crankshaft. The continuously variable transmission mechanism 16 has a V-belt 57 passed on a driving pulley 55 mounted at one end of the crankshaft 28 and on a driven pulley 56 mounted on a transmission shaft 47 parallel to the crankshaft 28. The driving pulley 55 and the driven pulley 56 consist of respective fixed pulley halves 55a, 56a fixed to the crankshaft 28 and the transmission shaft 47 and respective movable pulley halves 55b, 56b arranged slidably in the axial direction. The movable pulley halves 55b, 56b of the driving pulley 55 and the driven pulley 56 are arranged inside and outside, respectively, in the direction of the crankshaft. The centrifugal clutch mechanism 17 is mounted on the transmission shaft 47 adjacent to the inside of the driven pulley 56 in the direction of the crankshaft. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine equipped with a continuously variable transmission mechanism on the outside of a crankcase in the crankshaft direction, which is suitable for, for example, a motorcycle.

[0002]

2. Description of the Related Art For example, in a motorcycle, a V-belt type continuously variable transmission mechanism is provided outside a crankcase in the crankshaft direction, and an engine having a centrifugal clutch mechanism is provided between the continuously variable transmission mechanism and an output shaft. There is a case.

In such an engine, a V-belt is wound around a drive pulley mounted on a crankshaft and a driven pulley mounted on a speed change shaft parallel to the crankshaft, and the centrifugal force is applied on the speed change shaft. A clutch mechanism may be attached.

By the way, a coil spring for urging the movable pulley half toward the fixed pulley half is required on the movable pulley half side of the driven pulley, but when the movable pulley half is arranged inside the engine, The coil spring will protrude inward of the engine. In such a case, if the centrifugal clutch mechanism is arranged on the shift shaft and the output shaft is arranged coaxially with the centrifugal clutch mechanism, the engine width becomes large. Therefore, a driven pulley may be arranged on one side of the speed change shaft, a centrifugal clutch mechanism may be arranged on the other side, and an output shaft may be arranged on the rear side of the speed change shaft to suppress expansion of the engine width ( For example, Japanese Patent Laid-Open No. 2002-21988
Issue).

[0005]

However, when the structure in which the output shaft is arranged on the rear side of the transmission shaft is adopted as in the above-mentioned conventional case, there is a problem that the front-rear length of the engine becomes large.

The present invention has been made in view of the above conventional circumstances, and provides an engine capable of avoiding an increase in engine width and longitudinal length when a continuously variable transmission mechanism and a centrifugal clutch mechanism are arranged on a transmission shaft. Is intended.

[0007]

According to a first aspect of the present invention, in an engine having a continuously variable transmission mechanism on the outer side of a crankcase in the crankshaft direction, a drive pulley having the continuously variable transmission mechanism attached to one end of the crankshaft. And a driven pulley mounted on a speed change shaft parallel to the crank shaft and a V belt wound around the drive shaft and the driven pulley, and a fixed pulley half body and a shaft fixed to the crank shaft and the speed change shaft. A movable pulley half body that is slidable in the axial direction, the movable pulley half bodies of the drive pulley and the driven pulley are arranged inside and outside in the crankshaft direction, and a centrifugal clutch mechanism is attached to the speed change shaft. It is characterized in that it is mounted so as to be adjacent to the inner side of the driven pulley in the crankshaft direction.

According to a second aspect of the present invention, in the first aspect, the movable pulley half of the driven pulley is urged toward the fixed pulley half by a coil spring arranged outside of the driven pulley in the crankshaft direction. It is characterized in that a nut for attaching the pulley to the speed change shaft is arranged so as to be recessed inward in the crankshaft direction from the outer end of the coil spring.

According to a third aspect of the present invention, in the second aspect, the fixed pulley half body is mounted on the speed change shaft by fixing a cylindrical slide collar to the speed change shaft with a nut, and the coil spring comprises: The slide collar is disposed between the spring receiving member mounted on the outer edge opening edge of the slide collar and the movable pulley half, and the nut is disposed so as to be recessed in the slide collar. It is characterized by being fastened and fixed to.

According to a fourth aspect of the present invention, in the third aspect, the inner diameter of the slide collar is set to be larger than that of the transmission shaft.
It is characterized in that the tip end portion of the transmission shaft is set to have a smaller diameter than the other portions of the transmission shaft.

[0011]

According to the engine of the first aspect of the present invention, the movable pulley half of the driven pulley mounted on the speed change shaft is arranged outside the fixed pulley half in the crankshaft direction, and the speed change shaft has a centrifugal clutch. Since the mechanism is mounted so as to be adjacent to the inside of the driven pulley in the crankshaft direction, it is possible to secure a space for disposing the centrifugal clutch mechanism inside the fixed pulley half of the transmission shaft. As a result, the output shaft can be coaxially arranged on the side of the transmission shaft opposite to the driven pulley, and the front-rear length of the engine can be shortened without increasing the engine width.

According to the second aspect of the present invention, the nut for attaching the driven pulley to the speed change shaft is retracted inward in the crankshaft direction from the outer end of the coil spring, so that the movable pulley half is placed outside the fixed pulley half. It is possible to reduce the protrusion to the outside in the axial direction of the gear shift when arranged, and it is possible to suppress an increase in the length of the engine in the crank axis direction.

Further, since the coil spring is located at the outer end portion of the speed change shaft, it is possible to easily carry out the maintenance and replacement work of the coil spring. That is, when the movable pulley half body is arranged inside the fixed pulley half body, the entire driven pulley must be removed, which is low in workability. However, in the present invention, it is not necessary to remove the entire driven pulley.

According to the third aspect of the present invention, a coil spring is arranged between the spring receiving member attached to the tip of the cylindrical slide collar and the movable pulley half body, and the nut is inserted inside the spring receiving member. Since the slide collar is fastened and fixed to the speed change shaft, the required length of the coil spring can be secured and the protrusion to the outside in the speed change axis direction can be reduced with a simple structure.

According to the invention of claim 4, the inner diameter of the slide collar is large, and the tip of the speed change shaft is small, and the nut is inserted into the slide collar. It can be immersed axially inward.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 15 are views for explaining a motorcycle engine according to an embodiment of the present invention. FIG. 1 is a left side view of a motorcycle equipped with the engine of the present embodiment, and FIG. Is a sectional plan view showing the engine in a deployed state (a sectional view taken along the line II-II in FIG. 6), FIG. 3 is a sectional plan view of the continuously variable transmission mechanism of the engine, a centrifugal clutch mechanism portion, and FIGS. 4 and 5 are right sides of the engine. FIG. 6 is a right side view of the engine with the continuously variable transmission mechanism and the centrifugal clutch mechanism removed, FIG. 7 is a right side view of the crankcase, and FIG. 8 is a sectional plan view of the crankcase (FIG. 5 is a sectional view taken along line VIII-VIII), and FIG. 9 is a sectional plan view of the kick device of the engine (FIG. 5).
IX-IX line cross-sectional view), FIG. 10 is a cross-sectional plan view around the kick axis, FIG. 11 is a cross-sectional plan view showing the lubricating oil path of the engine,
12 and 13 are a sectional view and a side view of the centrifugal clutch mechanism,
14 and 15 are enlarged cross-sectional views of the essential parts of the centrifugal clutch mechanism. The front and rear, and the left and right in the present embodiment mean the front and rear, and the left and right when viewed in a state of sitting on a seat.

In the figure, reference numeral 1 denotes a motorcycle in which an engine 2 of the present embodiment is mounted, which is a front wheel 4 by a head pipe 3 fixed to the front end of a vehicle body frame 1a.
A front fork 5 rotatably supported so as to be rotatable left and right, and a rear arm 8 rotatably supported by a rear wheel 7 is pivotally supported by a rear arm bracket 6 fixed to a central portion so as to be vertically swingable. A driver seat portion 9 is provided on the upper portion of the frame 1a.
It has a schematic structure in which a seat 9 including a and a rear passenger seat portion 9b is arranged.

The body frame 1a includes left and right down tubes 1b extending obliquely downward from the head pipe 3, left and right upper tubes 1c extending obliquely upward following the rear ends of the down tubes 1b, and down tubes. The left and right seat rails 1d are joined to the upper tube 1b and the upper tube 1c in the front-rear direction. The vehicle body frame 1a includes a front cover 10a and a leg shield 1
0b, a side cover 10c, and the like, which are surrounded by a resin-made vehicle body cover 10.

A steering handle 11 is fixed to the upper end of the front fork 5, and the steering handle 11 is surrounded by a handle cover 11a. A rear cushion 12 is installed between the rear arm 8 and the rear arm bracket 6.

The engine 2 is an air-cooled 4-cycle single-cylinder engine, and is suspended and supported at the lower rear portion of the down tube 1b with the cylinder axis A inclined forward by about 45 degrees. The engine 2 includes an engine body 15, a V-belt type continuously variable transmission mechanism 16, a wet multi-plate centrifugal clutch mechanism 17, and a reduction gear mechanism 18.

In the engine body 15, a cylinder head 20 is connected to the upper mating surface of the cylinder block 19, a head cover 21 is provided on the upper side of the cylinder head 20, and a crankshaft 28 is provided on the lower mating surface of the cylinder block 19. It has a schematic structure in which the housed crankcases 22 are connected.

An intake port 20b communicating with the combustion recess 20a is opened on the rear surface of the cylinder head 20.
The carburetor 2 is connected to the intake port 20b via an intake pipe 23a.
3 is connected. An exhaust port 20c communicating with the combustion recess 20a is opened on the front surface of the cylinder head 20, and an exhaust pipe 24 is connected to the exhaust port 20c. The exhaust pipe 24 extends rearward and downward of the engine 2 and then extends obliquely rearward through the right side, and is connected to a muffler 25 arranged on the right side of the rear wheel 7. A spark plug 30 is inserted in the combustion recess 20a.

On the left side of the cylinder block 19, there is formed a chain chamber 19a which communicates the inside of the crankcase 22 with the inside of the cylinder head 20.
A timing chain 34 for rotating and driving a cam shaft 31 by the crank shaft 28 is provided on the shaft 9a. The cam shaft 31 drives the intake valve 32 and the exhaust valve 33 to open and close.

A piston 26 is slidably inserted in the cylinder bore of the cylinder block 19.
A small end 27b of a connecting rod 27 is connected to the piston 26, and a large end 27a of the connecting rod is connected to a crank pin 29 fitted between the left and right crank arms 28a and 28b of the crank shaft 28. .

A transmission shaft 47 is provided behind the crankshaft 28.
Are arranged in parallel with the crankshaft 28, and an output shaft 48 is arranged coaxially with the transmission shaft 47 on the axial left side. A drive sprocket 49 is mounted on the left end portion of the output shaft 48, and the drive sprocket 49 drives the driven sprocket 5 of the rear wheel 7 via a chain 50.
It is connected to 1.

A generator 42 is mounted on the left end of the crankshaft 28. This generator 42 has a crankshaft 2
The rotor 42a is fixed to the sleeve 43 that is taper-fitted to the stator 8 and the stator 4 that faces the rotor 42a.
2b is fixed to the generator case 44.

The crankcase 22 includes a first case 40 on the left side (one side) and a second case 40 on the right side (the other side) in the crankshaft direction.
It is divided into a case 41. A generator case 44 accommodating the generator 42 is detachably mounted on the outer side of the first case 40 in the crank axis direction, and the continuously variable transmission mechanism 16 is accommodated on the outer side of the second case 41 in the crank axis direction. The transmission case 45 is mounted.

The dividing line B of the first and second cases 40, 41 is displaced slightly to the left of the cylinder axis A. The first and second cases 40 and 41 support the crankshaft 28 inside the first and second outer peripheral walls 40a and 41a, which are generally open outward in the crankshaft direction.
It has a schematic structure in which b and 41b are integrally formed.

The first support wall 40b of the first case 40.
Is a first crank support wall portion 40c that supports the left crank journal portion 28c of the crankshaft 28 via a left journal bearing 35, and a stepwise shape on the left side in the crankshaft direction with respect to the first crank support wall portion 40c. It has the deceleration mechanism support wall portion 40d that is bulged.

The second support wall 41 of the second case 41 is also provided.
b is the right crank journal portion 28d of the crankshaft 28
A second crank support wall portion 41c for supporting the right crank journal through a right journal bearing 36, and a clutch support wall portion (clutch that is bulged in a stepwise manner on the left side in the crankshaft direction with respect to the second crank support wall portion 41c). One side support wall) 41d.

Then, the first and second crank support wall portions 4
The crank arms 28a and 28b of the crankshaft 28 and the crank pin 29 are housed in a crank chamber 37 formed by 0c and 41c.

The centrifugal clutch mechanism 17 is housed in a clutch chamber 38 formed by the second outer peripheral wall 41a and the clutch support wall portion 41d, and the clutch chamber 38 is defined as the crank chamber 37. There is.

Further, the reduction gear mechanism 18 is housed in a reduction chamber 39 formed by the reduction mechanism supporting wall portion 40d and the clutch support wall portion 41d, and the reduction chamber 39 communicates with the crank chamber 37.

The reduction gear mechanism 18 includes the support wall portion 4
A reduction shaft 52 is installed between 0d and 41d in parallel with the transmission shaft 47, the right side portion of the reduction shaft 52 is axially supported by the clutch support wall portion 41d via a reduction bearing 53, and the left end portion is the reduction mechanism. Recess 40 formed in support wall 40d
By e, the shaft is supported via the reduction bearing 54. A primary reduction small gear 74 is rotatably attached to the transmission shaft 47 located in the clutch chamber 38, and a primary reduction large gear 75 meshing with the primary reduction small gear 74 is connected to the reduction shaft 52 by key fitting. A structure in which a secondary reduction small gear 52a is integrally formed on the reduction shaft 52 located in the reduction chamber 39, and a secondary reduction large gear 48a meshing with the secondary reduction small gear 52a is integrally formed on the output shaft 48. Has become.

The output shaft 48 is arranged on the same axis as the transmission shaft 47. A support hole 48b into which the left end of the speed change shaft 47 is inserted is recessed in the right end of the output shaft 48, and the right end of the output shaft 48 is inserted through a bearing 76 mounted in the support hole 48b. The part is pivotally supported by a speed change shaft 47. Further, the left end portion of the output shaft 48 penetrates the reduction mechanism supporting wall portion 40 d of the first case 40, and the supporting wall portion 40
It is axially supported by a bearing 77 by d. The drive sprocket 49 is fixed to the protruding end of the output shaft 48.

The V-belt type continuously variable transmission mechanism 16 has a drive pulley 55 mounted on the right outer end portion of the crankshaft 28 and a driven pulley 56 on the right outer end portion of the speed change shaft 47.
Is mounted, and both pulleys 55, 56 are connected by winding a V-belt 57.

The V-belt 57 is made of a resin having heat resistance and durability, and specifically has the following structure. For example, a large number of resin blocks 57a formed by mixing carbon fibers or aramid fibers into polyamide resin and forming them in a horizontal H shape are arranged side by side, and these are fitted with a pair of annular connecting members 57b made of super heat resistant rubber. It is a connection.

The drive pulley 55 corresponds to the crankshaft 2
Fixed pulley half 55a fixed to the right end of 8, and axially slidable inward of the fixed pulley half 55a in the axial direction and arranged so as to rotate with the crankshaft 28 via a slide collar 59. And a movable pulley half 55b that has been formed. A cam plate 58 and a slide collar 59 are mounted on the right end of the crankshaft 28 by spline fitting, the fixed pulley half body 55a is mounted on the axially outer side of these, and is fixed by tightening with a lock nut 60. A cylindrical weight 61 is disposed between the movable pulley half body 55b and the cam plate 58. As the rotation of the crankshaft 28 increases, the weight 61 is moved radially outward by the centrifugal force to move the movable pulley half 55b axially outward, thereby increasing the winding diameter of the pulley and reducing the reduction ratio. Become.

The driven pulley 56 is fixed to the right outer end portion of the transmission shaft 47, and a fixed pulley half body 56a and an axially slidable outer side of the fixed pulley half body 56a. And a movable pulley half 56b. A cylindrical slide collar 62 fixed to the shaft center portion of the fixed pulley half body 56a is spline-fitted to the speed change shaft 47, and fixed to the shaft center portion of the movable pulley half body 56b on the slide collar 62. The cylindrical boss portion 63 is attached so as to be movable in the axial direction. A guide pin 64 embedded in the slide collar 62 is slidable in a slide groove 63a formed in a slit shape on the boss portion 63, and the movable pulley half body 56b rotates together with the fixed pulley half body 56a. I am fit.

At the tip of the slide collar 62, a spring receiving member 65 made of an annular plate is provided.
The movable pulley half body 5 is mounted between the spring receiving member 65 and the movable pulley half body 56b.
A coil spring 67 for constantly urging 6b toward the fixed pulley half 56a is provided.

The driven pulley 56 is inserted into the tip end portion 62a of the slide collar 62 so as to be inserted therein, and is attached to the speed change shaft 47 by a lock nut 66 screwed to the tip end portion 47a of the speed change shaft 47. It is fixed.

Here, the inner diameter of the slide collar 62 is set to be larger than the outer diameter of the speed change shaft 47 in a stepwise manner, and the tip portion 47a of the speed change shaft 47 is set to a small diameter in a stepwise manner.
As a result, the lock nut 66 and the washer 66a can be inserted and arranged in the slide collar 62 without any trouble, and thus the lock nut 66 and the coil spring 67 can be arranged.
The spring receiving member 65 can be located on the inner side in the crankshaft direction.

According to this embodiment, since the movable pulley half 56b of the driven pulley 56 mounted on the speed change shaft 47 is arranged outside the fixed pulley half 56a in the crankshaft direction, the driven pulley 56 of the speed change shaft 47 is arranged. An empty space can be secured in the inner portion, and the centrifugal clutch mechanism 17 can be arranged adjacent to the fixed pulley half body 56a by utilizing this empty space. As a result, the anti-following pulley 5 of the transmission shaft 47 is expanded without increasing the engine width.
The output shaft 48 can be coaxially arranged on the 6 side, and as a result, the front-rear length of the engine can be shortened as compared with the conventional output shaft arranged on the rear side of the transmission shaft.

In this embodiment, the lock nut 66 is used.
The movable pulley half 56b to the fixed pulley half 56a.
Since the coil spring 67 for urging the coil spring 67 is disposed so as to be recessed inward in the axial direction with respect to the spring receiving member 65, the coil spring 67 is provided with a simple structure to project outward in the axial direction of the gear shift with a simple structure. Can be smaller,
It is possible to suppress an increase in the width of the engine vehicle.

That is, for example, as shown in FIG. 16, in the case of the structure in which the outer end surface of the slide collar 201 is fastened and fixed to the speed change shaft 200 by the lock nut 203, the transmission case 204 corresponds to the lock nut 203. It will protrude outside in the width direction. On the other hand, in the present embodiment, since the lock nut 66 is located axially inward of the outer end of the spring receiving member 65, the protrusion of the transmission case 45 can be reduced by t (about 10 mm).

Further, since the coil spring 67 is located on the outer side in the axial direction, when performing maintenance or replacement of the coil spring 67, it suffices to remove the circlip 65a and the work can be performed easily. By the way, when the movable pulley half is arranged inside the fixed pulley half, that is, when the coil spring is arranged inside in the axial direction, the driven pulley as a whole must be removed, resulting in low workability.

The transmission case 45 has a substantially closed structure formed independently of the crankcase 22, and most of the upper side of the crankcase 22 is seen from the right side (see FIG. 4). It has an elliptical shape that covers. The transmission case 45 is composed of a box-shaped case body 45a having a bottom that opens outward in the crankshaft direction, and a lid 45b that hermetically closes the opening, and is fixed to the second case 41 together by bolts 70. ing. A gap a is provided between the bottom wall 45c of the case body 45a and the second case 41, and the gap a prevents heat from the engine 2 from being transmitted to the transmission case 45.

An opening 41e having a size that allows the centrifugal clutch mechanism 17 to be put in and taken out is formed on the outer side in the axial direction of the second outer peripheral wall 41a forming the clutch chamber 38. A clutch cover (clutch other side support wall) 71 is airtightly attached to the opening 41e, and the clutch cover 71 is detachably tightened and fixed to an opening edge portion of the second outer peripheral wall 41a by a bolt 72. . This removes the transmission case 45 together with the driven pulley 56,
By removing the clutch cover 71, the centrifugal clutch mechanism 17 can be removed together with the transmission shaft 47.

The centrifugal clutch mechanism 17 is axially immovably positioned and clamped by the one-side and the other-side clutch bearings 80 and 81 mounted at the axially left end portion and the central portion of the transmission shaft 47. The one-side clutch bearing 80 is supported by the clutch support wall portion 41d, and the other-side clutch bearing 81 is supported by the clutch cover 71.

The clutch support wall portion 41d that supports the one-side clutch bearing 80 and the reduction gear bearing 53 is the second crank support wall portion 41c that supports the right journal bearing 36.
It is further offset to the left in the crankshaft direction, in other words, it is located between the first crank support wall portion 40c that supports the left journal bearing 35 and the second crank support wall 41c. More specifically, it is located on the cylinder axis A or slightly to the dividing line B from the cylinder axis A.

The clutch cover 71 that supports the other side clutch bearing 81 is located on the outer right side in the crankshaft direction with respect to the second crank support wall portion 41b that supports the right journal bearing 36. Furthermore, the reduction mechanism support wall portion 40d that supports the left side bearing 77 of the output shaft 48 is located on the left side in the crankshaft direction with respect to the first crank support wall portion 40c that supports the left journal bearing 35.

According to the present embodiment, since the V belt 57 wound around the driving pulley 55 and the driven pulley 56 is made of resin, the belt itself has higher heat resistance and durability than rubber belts. Therefore, the cooling of the V-belt 57 can be eliminated. As a result, the transmission case 45 can have a closed structure, and water and dust can be prevented from entering.

Further, by adopting the resin belt 57 having high durability, it is possible to reduce the outer diameters of the drive and driven pulleys 55 and 56, and between the axes of the drive and driven pulleys 55 and 56 by that much. The distance can be shortened and the entire engine can be made compact.

In this embodiment, since the transmission case 45 has a closed structure independent of the crankcase 22, the engine heat is cut off by the gap a formed between the two cases 22 and 45. It is difficult to transfer the heat from the transmission case 45 to the transmission case 45, and the temperature rise in the belt chamber can be suppressed.

The crankcase 22 is divided into first and second cases 40 and 41 in the crankshaft direction, and the second case 4
The transmission case 45 is arranged on the outer side in the crankshaft direction of No. 1, and the centrifugal clutch mechanism 17 is arranged near the inner side of the transmission case 45 in the crankshaft direction. The output shaft 48 can be arranged coaxially, and the dimension in the front-rear direction can be reduced while suppressing the expansion of the width dimension of the engine 2.

The centrifugal clutch mechanism 17 is attached to the transmission shaft 4
Since it is sandwiched by the one-side clutch bearings 80 and the other-side clutch bearings 81 mounted on the 7, the centrifugal clutch mechanism 17 can be axially positioned and supported with a simple structure without using separate parts.

In the present embodiment, the clutch one side support wall 41d that supports the one side clutch bearing 80 supports the left and right journal bearings 35 and 36 of the crankshaft 28.
A second clutch supporting the right journal bearing 36 with a clutch cover (clutch other side supporting wall) 71 which is located between the crank supporting walls 40c and 41c and supports the other side clutch bearing 81.
Since it is positioned outside the crank support wall 41c in the crank axis direction, compared with the case where the first crank support wall 40c and the clutch one side support wall 41d are positioned on the same line, and the second crank support wall 41c and the clutch cover 71 are positioned on the same line. As a result, the volume of the clutch chamber 38 can be secured while shortening the axial distance between the crankshaft 28 and the transmission shaft 47, the centrifugal clutch mechanism 17 can be compactly housed, and the entire engine can be made compact.

Since the clutch cover 71 is detachably attached to the opening 41e of the second case 41, the centrifugal clutch mechanism 17 can be removed together with the transmission shaft 47 by removing the transmission case 45 and the clutch cover 71. Maintenance and parts replacement work can be easily performed.

In this embodiment, the output shaft 48 is arranged coaxially with the transmission shaft 47 on the side opposite to the transmission case 45, and the drive sprocket 49 is mounted on the output shaft 48, so that the centrifugal clutch mechanism 17 and the drive shaft are driven. The sprocket 49 and the sprocket 49 can be arranged coaxially, and the front-rear dimension of the engine can be reduced.

The centrifugal clutch mechanism 17 includes the driven pulley 5
It is arranged close to the inside of the crankshaft 6 in the crankshaft direction.
The centrifugal clutch mechanism 17 is of a wet multi-plate type, and as shown mainly in FIGS. 12 to 15, the boss 83b of the bowl-shaped outer clutch 83 is spline-fitted to the transmission shaft 47 so as to rotate together, and the outer clutch An inner clutch 84 is coaxially arranged on the inner side of the clutch 83 in the axial direction, and a hub portion 84a of the inner clutch 84 is spline-fitted so as to rotate together with the primary reduction small gear 74. The primary reduction small gear 74 is rotatably mounted on the transmission shaft 47.

A plurality of outer clutch plates 85 are arranged in the outer clutch 83, and two pressing plates 86, 86 are arranged so as to be located at both ends thereof.
Reference numerals 5 and 86 are locked to the outer clutch 83 so as to rotate together with the outer clutch 83. An inner clutch plate 87 is arranged between the outer clutch plate 85 and the pressing plate 86, and each inner clutch plate 87 is
Is locked to the outer periphery of the inner clutch 84 so as to rotate together with the inner clutch 84.

A cam surface 83a is formed inside the outer clutch 83, and a weight 88 is arranged between the cam surface 83a and the outer pressing plate 86. This weight 88 moves to the left side in the drawing of FIG. 12 (clutch connection direction) by the cam surface 83a as it moves radially outward by the centrifugal force of the outer clutch 83.
The pressing plate 86 is moved by pressing to bring the outer and inner clutch plates 85 and 86 into a connected state. Note that FIG.
In the figure, the upper side and the lower side of the axis of the centrifugal clutch mechanism 17 show the disconnected state and the connected state, respectively.

The centrifugal clutch mechanism 17 is provided with a clutch plate sticking prevention mechanism 90. The sticking prevention mechanism 90 is a leaf spring 91 that urges the outer clutch plates 85 and the pressing plate 86 in a direction in which they are separated from each other between the outer clutch plates 85 and between the outer clutch plates 85 and the pressing plate 86. It is configured by interposing.

Further, pins 92 for restricting the axial movement of the inner clutch plates 87 are inserted in the inner clutch plates 87 at intervals in the circumferential direction, and between the inner clutch plates 87 of the pins 92. The inner clutch plate 87
A coil spring 93 that biases the coils in a direction to separate them from each other is attached.

In the centrifugal clutch mechanism 17 of this embodiment,
The weight 88 moves outward in the clutch radial direction by centrifugal force as the engine speed increases, and its axial position is determined by the cam surface 83a. When the engine rotation exceeds a predetermined value by the opening operation of the throttle (not shown), the weight 88 pushes the pressing plate 86 to bring the outer and inner clutch plates 85 and 87 into pressure contact, whereby the engine rotation is changed. To reduction gear mechanism 18
Is transmitted to the output shaft 48 via the drive shaft 48, and the rear wheel 7 is rotationally driven by the rotation of the output shaft 48 via the drive sprocket 49 and the chain 50.

The weight 88 moves inward in the radial direction as the engine speed decreases due to the closing operation of the throttle.
When the engine speed falls below a predetermined value, the pressure contact force of the weight 88 is released, and the outer and inner clutch plates 8 are released.
5, 87 rotate relative to each other, and engine rotation is cut off between the transmission shaft 47 and the output shaft 48.

When the pressure contact force is released when the clutch is disengaged, the outer clutch plate 85 and the pressing plate 86 are separated from each other by the reaction force of the plate spring 91, and the inner clutch plate 87 is generated by the reaction force of the coil spring 93. The two are separated from each other.

As a result, the outer and inner clutch plates 8
It is possible to prevent sticking of the 5,87 to each other due to the lubricating oil and prevent the clutch from dragging.

Further, the inner clutch plate 8 is formed by each pin 92.
Since the axial movement of 7 is restricted, it is possible to prevent the inner crack plate 87 from tilting when the clutch is disengaged.
Also from this point, the clutch drag phenomenon can be prevented.

Next, the lubricating oil system of the engine 2 will be described.

This lubricating oil system is based on the above crankcase 22.
The lubricating oil in the lubricating oil chamber 95 formed in the bottom portion 22a of the above is sucked by the oil pump 96 and pressure-fed to the lubricated portions such as the bearing portion and the sliding portion of the crankshaft 28, the cam shaft 31, and the lubricated portion. The lubricating oil that has been lubricated is returned to the lubricating oil chamber 95 by natural fall.

The oil pump 96 is mainly shown in FIG.
As shown in FIG. 5, the pump shaft 96a is pivotally supported by the housing 97 that is arranged below the first case 40 of the crankcase 22 and has the suction port 97a and the discharge port 97b.
A pump gear 98 is attached to the outer end of the pump shaft 96a.

The first case 40 has the suction port 97a.
A suction passage 40f communicating with the above is formed, and the suction passage 40f is opened on the bottom surface in the lubricating oil chamber 95 via the oil strainer 99. A lubricating oil supply passage 40g communicating with the discharge port 97b is formed in the first case 40. The supply passage 40g communicates with a main supply passage 44a formed in the generator case 44 with an oil filter 100 interposed therebetween, and the downstream end of the main supply passage 44a is on the left end surface of the crankshaft 28. It is connected to the communicating oil chamber 44c.

The oil chamber 44 is provided on the crankshaft 28.
An oil passage 28e communicating with c is formed in the axial direction, and the oil passage 28e is connected to the connecting bearing portion 101 of the crank pin 29 and the connecting rod 27 via a branch passage 29a formed in the crank pin 29. It is open.

The lubricating oil sucked by the oil pump 96 is pressure-fed to the oil passage 28e through the supply passage 40g and the main supply passage 44a, and is supplied from the oil passage 28e to the coupling bearing portion 101 through the branch passage 29a. . The lubricating oil supplied to the coupling bearing portion 101 is scattered into the crank chamber 37 by the supplied hydraulic pressure and the centrifugal force of the crankshaft 28, and a part of the scattered lubricating oil enters the deceleration chamber 39. The secondary reduction small gear 52a and the large gear 48a are lubricated, and then fall into the lubricating oil chamber 95.

A bulging portion 22b is formed integrally with the bottom portion 22a of the crankcase 22 so as to be positioned below the transmission case 45 (FIGS. 8 and 11).
reference). The bulging portion 22b communicates with the lubricating oil chamber 95, and is formed so as to be located within the projection surface of the transmission case 45 when seen in a plan view.

According to this embodiment, the crankcase 22
Since the bulging portion 22b is formed so as to be located below the transmission case 45 on the bottom portion 22a of the transmission case 45,
The amount of lubricating oil in the lubricating oil chamber 95 can be increased by effectively utilizing the empty space below, and there is no need to increase the height of the engine 2 as compared with the case where the case bottom is deepened to secure the amount of lubricating oil. .

Since the bottom portion 22a of the crankcase 22 is bulged below the transmission case 45, the lubricating oil chamber 95
The surface area of the engine can be increased, the cooling performance can be improved accordingly, and the weight balance of the entire engine can be improved.

In this embodiment, since the V-belt 57 is made of resin and the transmission case 45 is independent of the crankcase 22, the belt itself is different from the case where a rubber belt is used. The heat resistance and durability can be improved, and the heat effect from the engine can be suppressed. As a result, the diameters of the drive and driven pulleys 55 and 56 can be reduced, the transmission case 45 can be downsized, and an empty space can be provided below the transmission case 45. By forming the portion 22b, the lubricating oil capacity can be increased.

Next, the lubricating structure of the centrifugal clutch mechanism 17 will be described.

As shown mainly in FIGS. 3 and 7, the centrifugal clutch mechanism 17 has a coupling bearing portion 1 for connecting the connecting rod 27 and the crank pin 29 when viewed in a direction perpendicular to the crankshaft.
It is located so as to partially overlap the lubricating oil scattering area from 01. Specifically, the outer of the centrifugal clutch mechanism 17 and the inner clutch plates 85 and 87 are arranged at positions facing the crank chamber 37.

Then, the crank chamber 37 and the clutch chamber 3
8 on the second outer peripheral wall 41a defining the connecting bearing portion 1
An introduction opening 103 for introducing the lubricating oil scattered from 01 into the clutch chamber 38 is formed.

A guide portion 104 extending inside the clutch chamber 38 is integrally formed on the clutch support wall portion 41d. The guide portion 104 is located on an extension line connecting the crank shaft 28 and the speed change shaft 47, and the introduction opening 103 is provided.
The lubricating oil receiving portion 104 extending in the longitudinal direction so as to substantially face
a and the lower end of the lubricating oil receiving portion 104a, the transmission shaft 4
Guide portion 1 extending in an arc shape so as to wrap around 7
04b and. The guide portion 104b is positioned so as to be inserted into a boss portion of the inner clutch 84 having a truncated cone shape.

As a result, the lubricating oil that has entered through the introduction opening 103 is received by the guide portion 104, and is guided more to the inside than the outer circumference of the centrifugal clutch mechanism 17, and the lubricating oil is circulated by the centrifugal force of the clutch mechanism 17. , Is supplied between the inner clutch plates 85 and 87, and is also supplied to the meshing portion of the primary reduction large gear 75 and the small gear 74 (see arrows in FIGS. 3 and 7).

According to the centrifugal clutch mechanism lubricating structure of the present embodiment, the lubricating oil supplied to the coupling bearing portion 101 of the crank pin 29 and the connecting rod large end portion 27a is guided to the centrifugal clutch mechanism 17, so that the coupling is performed. A large amount of lubricating oil jetted and scattered from the bearing portion 101 can be supplied to the centrifugal clutch mechanism 17, there is no need to provide a special lubricating oil path, and a sufficient amount of lubricating oil can be supplied to the centrifugal clutch mechanism 17. The seizure of the clutch plates 85 and 87 can be prevented.

In the present embodiment, the centrifugal clutch mechanism 17 is positioned in the clutch chamber 38 defined by the crank chamber 37 and in the lubricating oil scattering region from the coupling bearing portion 101 when viewed in the direction perpendicular to the crankshaft. And the second outer peripheral wall 4 that defines the clutch chamber 38 and the crank chamber 37.
Since the introduction opening 103 for allowing the lubricant oil to enter is formed in the la 1a, the lubricant oil from the crank chamber 37 can be effectively introduced into the clutch chamber 38 with a very simple structure.

In the present embodiment, the clutch support wall portion 41d.
A guide portion 104 extending inside the clutch chamber 38 is integrally formed with the crankshaft 28 and the transmission shaft 4.
7 and a lubricating oil receiving portion 104a extending substantially opposite to the introduction opening 103 and extending downwardly from the lubricating oil receiving portion 104a. Since it is configured with the extending guide portion 104b, the lubricating oil can be more reliably supplied to the outer and inner clutch plates 85 and 87.

Next, the kick device of the engine 2 will be described. Mainly, as shown in FIGS. 5, 9, and 10, a kick shaft 110 is arranged substantially vertically below the output shaft 48 in parallel therewith. When viewed in the direction perpendicular to the crankshaft, the kick shaft 110 is rotatably supported by the boss portion 40h of the first case 40 on the inner side of the drive sprocket 49 and the boss formed on the generator cover 44 on the outer side. It is pivotally supported by the portion 44b.

A kick arm 111 is attached to the outer end of the kick shaft 110. A kick gear 112 is spline-fitted to the inner end of the kick shaft 110 so as to be slidable in the axial direction, and the kick gear 112 is located in the first case 40. A return spring 113 is wound around the inner end of the kick shaft 110, and the return spring 113 urges the kick shaft 110 to pivot to a depressed position.

A main intermediate shaft 114 and a sub intermediate shaft 115 are arranged between the kick shaft 110 and the crank shaft 28 in parallel with the kick shaft 110. This main intermediate shaft 11
4 is rotatably supported by spanning a first case 40 and a second case 41, and the kick gear 1 is attached to the main intermediate shaft 114.
A main intermediate gear 116 capable of meshing with 12 is mounted.

The sub intermediate shaft 115 is rotatably supported by a bearing portion 40j formed in the first case 40, and the inner and outer ends of the sub intermediate shaft 115 project inside and outside the first case 40, respectively. ing. A first intermediate gear 115a that meshes with the main intermediate gear 116 is integrally formed inside the case of the sub intermediate shaft 115, and a second intermediate gear 117 is attached to the outside of the case. This second intermediate gear 11
A first crank gear 121, which will be described later, is meshed with 7.

By depressing the kick arm 111, the kick shaft 110 rotates, and the kick gear 112 axially moves with the rotation and meshes with the main intermediate gear 116, and the first and second intermediate gears 115a, 115a. It is transmitted to the first crank gear 121 via 117, and the crankshaft 28 rotates.

Left journal bearing 3 of the crankshaft 28
5 and the sleeve 43 of the generator 42 in this order from the outside, the one-way clutch 120, the first crank gear 12
1, a cam sprocket 122 is mounted.

The one-way clutch 120 has a starting gear 1
20a is mounted, and a drive gear 125a of a starter motor 125 is connected to the starting gear 120a via an idler gear 124. This starter motor 12
Reference numeral 5 is arranged and fixed to the front wall of the crankcase 22 with the motor axis line parallel to the crankshaft 28.

The kick gear 112, the main intermediate gear 116, and the first intermediate gear 115a are arranged in a position communicating with the lubricating oil chamber 95 inside the first case 40. Further, the second intermediate gear 117 and the first crank gear 1
21 and the cam sprocket 122 are arranged outside the first case 40.

According to the kick device of this embodiment, the kick gear 112, the main intermediate gear 116, and the first intermediate gear 11
Since 5a is located in a portion communicating with the lubricating oil chamber 95,
The meshing portion of these gears can be sufficiently lubricated.

Further, the main intermediate shaft 115 is penetrated from the inner side of the first case 40 to the outer side, the rotation of the kick shaft 110 is transmitted from the inner side of the main intermediate shaft 115 to the outer side of the second intermediate gear 117. Since the power is transmitted to the crankshaft 28 via the first crank gear 121, the first crank gear 121 can be arranged outside the crank journal portion 28c, the interval between the crank bearings 35 and 36 can be narrowed, and the crankshaft 28 can be connected to the connecting rod. The bending moment due to 27 can be reduced to support the shaft. Furthermore, cam sprocket 12
The space for disposing the second crank gear 127 can be secured, and the layout around the crankshaft can be easily performed. That is, when the rotation of the kick shaft 110 is transmitted to the crank shaft 28 within the first case 40, the left crank bearing 35 and the left crank arm 28
A gear is required between the left and right bearings 35, 36, which increases the distance between the left and right bearings 35, 36, which is disadvantageous in terms of the bending moment.

In this embodiment, since the kick shaft 110 is arranged substantially below the output shaft 48 in the vertical direction, the kick arm 111 can be easily depressed, and the engine 2 can be operated easily.
The front and rear dimensions of can be reduced.

The inside of the rear wheel drive sprocket 49 of the kick shaft 110 in the vehicle width direction is the first of the crankcase 22.
The clutch support wall portion 40d is pivotally supported, the vehicle width direction outer side is pivotally supported by the generator case 44, and the kick arm 111 is attached to the outwardly projecting end of the kick shaft 110 of the generator case 44. Axis 110, and eventually kick arm 111
Can be arranged at an optimum stepping position without interfering with the rear wheel drive sprocket 49.

As shown in FIG. 4, the kick shaft 110 has the transmission case 45 when viewed in the crankshaft direction.
Of the centrifugal clutch mechanism 17 in the axial projection plane of (1) and in the axial projection plane of the centrifugal clutch mechanism 17. More specifically, it is arranged so as to be positioned substantially vertically below the driven pulley 56.

Since the kick shaft 110 is arranged on the opposite side of the transmission case 45 in this manner, it is not necessary to secure a space for arranging the kick shaft in the transmission case 45. Therefore, the drive pulley 55 of the continuously variable transmission mechanism 16 is provided. And driven pulley 56
Can be arranged close to each other to the extent that a slight gap b (see FIG. 3) is generated, and the front-rear length of the engine can be reduced accordingly.

The kick shaft 110 is attached to the transmission case 4
Since it is arranged in the projection plane of the crankshaft direction No. 5, the kick shaft 110 can be arranged at a position close to the crank shaft 28 and at a position where it is easy to step on.

In this embodiment, the centrifugal clutch mechanism 1 described above is used.
7 is arranged near the inner side of the driven pulley 56 in the crank axis direction, and the kick shaft 110 is arranged in the axial projection plane of the centrifugal clutch mechanism 17 and substantially vertically below the speed change shaft 47. It is possible to use the empty space in the projection plane of the clutch mechanism, to dispose the clutch mechanism at the position where it is most easy to step on, and to reduce the front-rear length of the engine 2.

A balancer shaft 129 is arranged in parallel with the crankshaft 28 above the crankshaft 28.
The balancer shaft 129 is axially supported by the first and second cases 40 and 41 via balancer bearings 130 and 131.
The left end portion of the balancer shaft 129 projects outward from the first case 40, and the balancer gear 132 is coupled to the projecting portion. A damper member 133 is provided on the inner peripheral portion of the balancer gear 132.

Here, the balancer bearings 130 and 131
The left and right crank arms 28a of the crankshaft 28,
28b and the balancer weight 129a of the balancer shaft 129 is the left and right crank arms 28a, 2
It is arranged close to the crankshaft 28 side so as to overlap the rotation locus of the crankpin 29 between 8b.
This makes it compact around the balancer axis.

A second crank gear (second drive gear) 127 is attached to the first crank gear (first drive gear) 121 press-fitted into the crankshaft 28 so as to rotate together with the second crank gear (second drive gear) 127. The balancer gear (second driven gear) 132 is meshed with the gear 127. More specifically, the inner peripheral teeth 127 are formed on the inner peripheral surface of the second crank gear 127.
a is formed, and the outer peripheral teeth 121a of the first crank gear 121 are fitted to the inner peripheral teeth 127a (see FIG. 6). As a result, the rotation of the crankshaft 28 is transmitted from the first crank gear 121 to the balancer gear 132 via the second crank gear 127.

The first crank gear 12 is connected to the pump gear (first driven gear) 98 via a second intermediate gear 117.
1 is connected. In this way, the first crank gear 121 and the second intermediate gear 117 are commonly used for kick start and oil pump drive. Also, the one-way clutch 120 and the first crank gear 1 mounted on the crankshaft 28.
The cam sprocket 122 and the cam sprocket 122 are held by the sleeve 43 and the journal bearing 35 so as to be immovable in the axial direction by tightening a nut 123 screwed to the left end of the crank shaft 28.

According to this embodiment, the first crank gear 1
When the rotation of the kick shaft 110 is transmitted to the crankshaft 28 by the second intermediate gear 117 meshing with the crankshaft 21,
Since the rotation of 8 is also used for transmitting the rotation to the pump gear 98, the crankshaft length can be shortened and the engine width can be made compact.

Further, the inner peripheral teeth 12 of the second crank gear 127 are fitted to the first crank gear 121 press-fitted into the crank shaft 28.
Since 7a is fitted and the second intermediate gear 117 is meshed, the press-fitting length of the first crank gear 121 into the crankshaft 28 can be sufficiently secured,
The rotation of the crankshaft 28 can be reliably transmitted to the pump gear 98 and the balancer gear 132.

In this embodiment, the first crank gear 121
Outer peripheral teeth 121a and inner peripheral teeth 1 of the second crank gear 127
Since the structure in which the second crank gear 127 is fitted with the second crank gear 127 is adopted, the second crank gear 127 can be easily assembled and can be easily removed during maintenance. That is, by removing the nut 123 of the crankshaft 28 and removing the sleeve 43 and the one-way clutch 121, the second crank gear 127 can be easily removed from the first crank gear 121.

The arrangement structure of each shaft of the engine 2 is as follows. A shift shaft 47 and an output shaft 48 are arranged on the substantially horizontal plane behind the crankshaft 28 as viewed in the crankshaft direction. The balancer shaft 129 and the reduction shaft 52 are arranged above the horizontal plane C including the axes of the crank shaft 28 and the output shaft 48, and the kick shaft 110, the pump shaft 96a, the main and auxiliary intermediate shafts 114,
115 are arranged.

The kick shaft 110 is arranged substantially vertically below the output shaft 48, and the pump shaft 96a is arranged substantially vertically below the balancer shaft 129. Furthermore, the above main,
The sub intermediate shafts 114 and 115 are the crank shaft 28 and the kick shaft 1.
It is arranged on the line connecting 10 and 10.

According to this embodiment, the balancer shaft 129 is arranged on the upper side of the horizontal plane C including the crank shaft 28 and the output shaft 48, and the kick shaft 110 and the pump shaft 96a of the oil pump 96 are arranged on the lower side. These can be arranged in a well-balanced manner on the upper side and the lower side, and an increase in size of the engine can be avoided. That is, there is an empty space above the horizontal plane C and behind the cylinder bore, and the balancer shaft 129 is arranged by utilizing this empty space. And the balancer shaft 129
Since the weight 129a rotates with a large rotation locus, the loss horsepower due to agitation of the lubricating oil increases when the weight 129a is immersed in the lubricating oil. However, in the present embodiment, the balancer shaft 1
29 does not diffuse the lubricating oil. The horizontal plane C
The reduction shaft 52 is disposed on the upper side of the space utilizing the empty space between the balancer shaft 129 and the output shaft 48. In this case, although the lubricating oil is located in the upper portion where it is difficult to supply, the lubricating oil scattered from the connecting bearing portion 101 of the connecting rod of the crankshaft 28 is supplied to the reduction gear 75 and the like, so there is no problem of insufficient lubrication.

Further, since the kick shaft 110 is arranged substantially vertically below the output shaft 48, the front-rear length of the engine 2 can be reduced and the kick shaft 110 can be arranged at a position where it is easy to step on.

[Brief description of drawings]

FIG. 1 is a left side view of a motorcycle equipped with an engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view (cross-sectional view taken along line II-II in FIG. 6) showing a developed state of the engine.

FIG. 3 is a sectional plan view of a continuously variable transmission mechanism and a centrifugal clutch mechanism portion of the engine.

FIG. 4 is a right side view of the engine.

FIG. 5 is a left side view of the engine.

FIG. 6 is a right side view of the engine with the continuously variable transmission mechanism and the centrifugal clutch mechanism removed.

FIG. 7 is a right side view of the crankcase of the engine.

FIG. 8 is a sectional plan view of the crankcase (VIII in FIG. 5).
-VIII sectional view).

9 is a cross-sectional plan view of the kick device for the engine (FIG. 5).
IX-IX line sectional view).

FIG. 10 is a cross-sectional plan view of the kick device.

FIG. 11 is a cross-sectional plan view showing a lubricating oil path of the engine.

FIG. 12 is a sectional view of the centrifugal clutch mechanism.

FIG. 13 is a side view of the centrifugal clutch mechanism.

FIG. 14 is an enlarged cross-sectional view of a main part of the centrifugal clutch mechanism.

FIG. 15 is an enlarged sectional view of a main part of the centrifugal clutch mechanism.

FIG. 16 is a cross-sectional view of a conventional general centrifugal clutch mechanism.

[Explanation of symbols]

2 engine 16 continuously variable transmission 17 Centrifugal clutch mechanism 22 crankcase 28 crankshaft 47 speed change shaft 55 Drive pulley 55a, 56a Fixed pulley half body 55b, 56b Movable pulley half 56 Driven pulley 57 V belt 62 slide color 65 Spring receiving member 66 lock nuts 67 coil spring

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3D039 AA02 AA04 AB04 AC03 AC34                       AC77 AD53                 3J050 AA03 BA03 BB08 CA02 CC02                       CC07 CD02 DA03

Claims (4)

[Claims] 1. An engine having a continuously variable transmission mechanism on the outer side of a crankcase in the crankshaft direction, wherein the continuously variable transmission mechanism is mounted on a drive pulley mounted on one end of the crankshaft and a transmission shaft parallel to the crankshaft. The driven pulley and the driven pulley are wound around a V-belt, and the drive pulley and the driven pulley are fixed pulley halves fixed to the crankshaft and the speed change shaft and a movable pulley slidably arranged in the axial direction. The driving pulley and the driven pulley, the movable pulley halves are respectively arranged on the inner side and the outer side in the crank shaft direction, and the centrifugal clutch mechanism is adjacent to the shift shaft on the inner side in the crank shaft direction of the driven pulley. An engine characterized by being installed like 2. The movable pulley half of the driven pulley according to claim 1, wherein the movable pulley half is urged toward the fixed pulley half by a coil spring arranged outside of the driven pulley in the crankshaft direction. An engine, wherein a nut for attaching to the engine is arranged so as to be recessed inward in the crankshaft direction from the outer end of the coil spring. 3. The fixed pulley half body according to claim 2, wherein the fixed pulley half body is attached to the speed change shaft by fixing a cylindrical slide collar to the speed change shaft with a nut, and the coil spring is attached to the outside of the slide collar. It is arranged between the spring receiving member mounted on the edge of the end opening and the movable pulley half, and the nut is arranged so as to be immersed in the slide collar, and the slide collar is fastened and fixed to the speed change shaft. An engine characterized by being. 4. The slide collar according to claim 3, wherein an inner diameter of the slide collar is set to be larger than that of the transmission shaft, and a tip portion of the transmission shaft is set to be smaller than other portions of the transmission shaft. Engine to do.