JP4181051B2 - engine - Google Patents

Description

  According to the present invention, the first driven shaft and the second driven shaft, for example, the lubricating oil pump shaft and the balancer shaft are driven to rotate by the first driving gear and the second driving gear mounted on the crank shaft, respectively, or the above-mentioned by the kick shaft, for example. The present invention relates to an engine in which a crankshaft is rotationally driven via a first drive gear.

  For example, in a motorcycle engine, for example, a lubricating oil pump and a balancer shaft are typically driven to rotate by a plurality of drive gears mounted on a crankshaft (see, for example, JP-A-8-189323). In this case, each driving gear is set to an outer diameter corresponding to the purpose of the driven component. For example, the lubricating oil pump is driven at a rotational speed obtained by reducing the engine speed, and the balancer shaft is driven at the same rotational speed as the engine speed. Therefore, the lubricating oil pump driving gear has a small diameter and the balancer shaft driving gear has a large diameter. Generally, it is set to.

 The crankshaft is equipped with crankshaft components such as a generator and a cam sprocket together with the plurality of drive gears so that these gears and crankshaft components are as compact as possible, power transmission is reliable, and maintenance is easy. It is necessary to install.

  However, when the plurality of drive gears are simply arranged in parallel to the crankshaft, it is necessary to increase the axial thickness of each drive gear in order to firmly attach the drive gear to the crankshaft. There's a problem. Further, when the drive gears are attached by press fitting, there is a concern that maintenance such as replacement of these drive gears becomes difficult.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to provide an engine that can avoid an increase in the crankshaft length and can be easily maintained such as replacement of a drive gear.

According to the first aspect of the present invention, the crankshaft is supported by a crankcase divided into two in the crankshaft direction via a crank journal bearing, and the crankshaft is interposed between the crankshaft and the first and second driven shafts. In the engine in which the rotational force is transmitted via the first drive gear and second drive gear on the shaft side and the first driven gear and second driven gear on the first and second driven shaft sides, the first driving gears are those external teeth (external gear) is cylindrical formed on the outer circumferential surface, is fixed by press-fitting to the crank shaft, the second drive gear, on the inner peripheral surface internal teeth ( the inner gear) are of annular outer peripheral teeth (external gear) are formed respectively on the outer circumferential surface, detachably fitted to inner peripheral teeth engaged portion of the outer peripheral teeth of said first driving gear The rotational force between the crankshaft and the first driven shaft. Transmission is performed directly between the first drive gear and the first driven gear, and transmission of rotational force between the crankshaft and the second driven shaft is performed via the second drive gear. Between the first drive gear and the second driven gear, the first drive gear is positioned axially outside the crank journal bearing, and the outer diameter of the first drive gear is the crank journal. The diameter is set to be smaller than the inner diameter of the outer edge of the crankcase support hole of the bearing, and the crankcase support hole is fitted to the crank journal bearing from the outside in the crankshaft direction with the second drive gear removed. It is characterized by being able to combine.

According to a second aspect of the present invention, the crankshaft is supported by a crankcase divided into two in the crankshaft direction via a crank journal bearing, and the crankshaft is interposed between the crankshaft and the first and second driven shafts. In the engine in which the rotational force is transmitted via the first drive gear and second drive gear on the shaft side and the first driven gear and second driven gear on the first and second driven shaft sides, the first The drive gear has a cylindrical shape having outer peripheral teeth (external gears) and an outer spline following the outer peripheral surface, and is fixed to the crankshaft by press-fitting. The second drive gear has an inner peripheral the internal splines on the face, is of annular each having outer peripheral teeth (external gear) on the outer peripheral surface, the inner spline is fitted detachably on said outer splines of said first drive gear, the crank shaft And the first driven shaft The transmission of the rotational force between the first drive gear and the first driven gear is directly performed, and the transmission of the rotational force between the crankshaft and the second driven shaft is performed with the second drive gear. Is interposed between the first drive gear and the second driven gear, and the first drive gear is located axially outside the crank journal bearing, and the outer diameter of the first drive gear Is set smaller than the inner diameter of the outer edge of the crankcase support hole of the crank journal bearing, and the crankcase support hole is connected to the crank journal bearing in the crankshaft direction with the second drive gear removed. It is characterized in that it can be fitted from the outside to the inside .

  According to a third aspect of the present invention, in the first or second aspect, a crankshaft component is detachably attached to the outside of the first and second drive gears of the crankshaft, and the crankshaft component is removed. The second drive gear is removable from the crankshaft.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the first drive gear is engaged with a kick gear train that transmits the rotation of the kick shaft to the crankshaft, and the second drive gear is coupled with the first drive gear. The balancer gear train for transmitting the rotation of the crankshaft to the balancer shaft is engaged.

  According to a fifth aspect of the present invention, in the fourth aspect, the first drive gear includes a pump gear train that transmits the rotation of the crankshaft to the lubricating oil pump, and the kick gear train that transmits the rotation of the kick shaft to the crankshaft. The kick gear train and a part of the pump gear train are shared.

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

FIG. 3 is a cross-sectional plan view of the continuously variable transmission mechanism and the 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 cross-sectional rear view of the crankcase (cross-sectional view taken along line VIII-VIII in FIG. 5).

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

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

FIG. 11 is a cross-sectional front view showing the 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 cross-sectional view of a main part of the centrifugal clutch mechanism.

FIG. 16 is a cross-sectional view of a conventional general driven pulley.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 to FIG. 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 on which the engine of the present embodiment is mounted, and FIG. FIG. 3 is a sectional plan view of the engine continuously variable transmission mechanism and centrifugal clutch mechanism, FIG. 4 and FIG. 5 are right side views of the engine, 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 crank case, and FIG. 8 is a sectional plan view of the crank case (VIII in FIG. 5). -VIII sectional view), FIG. 9 is a sectional plan view of the engine kick device (sectional view taken along line IX-IX in FIG. 5), FIG. 10 is a sectional plan view around the kick axis, and FIG. Cross-sectional plan view, FIG. 12 and FIG. Sectional view of the clutch mechanism, a side view, FIG. 14, FIG. 15 is an enlarged sectional view of a main part of the centrifugal clutch mechanism. Note that front and rear and left and right as used in this embodiment mean front and rear and left and right as viewed in a seated state.

  In the figure, reference numeral 1 denotes a motorcycle on which the engine 2 of the present embodiment is mounted, which rotates a front fork 5 on which a front wheel 4 is pivotally supported by a head pipe 3 fixed to a front end of a vehicle body frame 1a. The rear arm 8 pivotally supported by the rear arm bracket 6 fixed to the central portion is pivotally supported so that the rear wheel 7 can be pivoted up and down, and a driver seat 9a is provided on the upper portion of the vehicle body frame 1a. It has a schematic structure in which a seat 9 composed of a rear passenger seat portion 9b is arranged.

  The vehicle body frame 1a includes a left and right down tube 1b extending obliquely downward from the head pipe 3, a left and right upper tube 1c extending obliquely upward following the rear end of each down tube 1b, a down tube 1b and an upper. It consists of left and right seat rails 1d that are bridged and joined to the tube 1c in the front-rear direction. The vehicle body frame 1a is surrounded by a resin vehicle body cover 10 including a front cover 10a, a leg shield 10b, a side cover 10c, and the like.

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 four-cycle single-cylinder engine, and is suspended and supported at a rear lower part of the down tube 1b with a 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.

  The engine body 15 has a cylinder head 20 connected to the upper joint surface of the cylinder block 19, a head cover 21 provided on the upper side of the cylinder head 20, and a crankshaft 28 stored in the lower joint surface of the cylinder block 19. It has a schematic structure in which a crankcase 22 is connected.

  An intake port 20b communicating with the combustion recess 20a is opened on the rear surface of the cylinder head 20, and a carburetor 23 is connected to the intake port 20b via an intake pipe 23a. 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 obliquely downward to the right of the engine 2, extends below the transmission case 45 to be described later, and extends obliquely rearward and upward through the right side of the bulging portion 22 b of the lubricating oil chamber 95. The muffler 25 is connected to the right side of the wheel 7. A spark plug 30 is inserted into the combustion recess 20a.

  A chain chamber 19a that connects the crankcase 22 and the cylinder head 20 is formed on the left side of the cylinder block 19, and a timing at which the camshaft 31 is rotationally driven by the crankshaft 28 in the chain chamber 19a. A chain 34 is provided, and the cam shaft 31 opens and closes the intake valve 32 and the exhaust valve 33.

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

  A transmission shaft 47 is arranged behind the crankshaft 28 in parallel with the crankshaft 28, and an output shaft 48 is arranged coaxially on the left side in the axial direction of the transmission shaft 47. A drive sprocket 49 is attached to the left end portion of the output shaft 48, and the drive sprocket 49 is connected to the driven sprocket 51 of the rear wheel 7 through a chain 50.

  A generator 42 is attached to the left end of the crankshaft 28. The generator 42 has a structure in which a rotor 42a is fixed to a sleeve 43 that is taper-fitted to the crankshaft 28, and a stator 42b that faces the rotor 42a is fixed to a generator case 44.

  The crankcase 22 is divided into a first case 40 on the left side in the crankshaft direction and a second case 41 on the right side. A generator case 44 that houses the generator 42 is detachably mounted on the outer side in the crankshaft direction of the first case 40, and the continuously variable transmission mechanism 16 is housed on the outer side in the crankshaft direction of the second case 41. A transmission case 45 is mounted.

  The dividing line B of the first and second cases 40 and 41 is slightly deviated to the left of the cylinder axis A. The first and second cases 40 and 41 have first and second support walls 40b and 41b that support the crankshaft 28 inside first and second outer peripheral walls 40a and 41a that are open outward in the crankshaft direction. Are integrally formed.

  The first support wall 40b of the first case 40 includes 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 the first crank support wall portion 40c. On the other hand, it has a speed reduction mechanism support wall portion 40d formed in a stepped shape on the left side in the crankshaft direction.

  The second support wall 41b of the second case 41 includes a second crank support wall portion 41c that supports the right crank journal portion 28d of the crankshaft 28 via the right journal bearing 36, and the second crank support wall portion 41c. On the other hand, it has a clutch support wall 41d bulging and formed on the left side in the crankshaft direction.

  The crank arms 28a and 28b and the crank pin 29 of the crankshaft 28 are accommodated in a crank chamber 37 formed by the first and second crank support walls 40c 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 by the crank chamber 37.

  Further, the reduction gear mechanism 18 is accommodated in a reduction chamber 39 formed by the reduction mechanism support 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 has a reduction shaft 52 installed between the support wall portions 40d and 41d in parallel with the transmission shaft 47, and the right side portion of the reduction shaft 52 is connected to the clutch support wall portion 41d via a reduction bearing 53. The left end portion is pivotally supported via a reduction bearing 54 by a recess 40e formed in the reduction mechanism support wall portion 40d. Further, a primary reduction small gear 74 is mounted on the transmission shaft 47 located in the clutch chamber 38 so as to be relatively rotatable, and a primary reduction large gear 75 meshed with the primary reduction small gear 74 is coupled to the reduction shaft 52 by key fitting. The secondary reduction small gear 52a is integrally formed on the reduction shaft 52 located in the reduction chamber 39, and the secondary reduction large gear 48a meshed with the secondary reduction small gear 52a is integrally formed on the output shaft 48. It has become.

  The output shaft 48 is disposed on the same axis as the transmission shaft 47. A support hole 48b into which the left end portion of the transmission shaft 47 is inserted is recessed in the right end portion of the output shaft 48, and the right end of the output shaft 48 is interposed through a bearing 76 mounted in the support hole 48b. The part is supported by a transmission shaft 47. The left end portion of the output shaft 48 passes through the speed reduction mechanism support wall portion 40d of the first case 40, and is supported by the support wall portion 40d via a bearing 77. The drive sprocket 49 is fixed to the projecting end of the output shaft 48.

  The V-belt type continuously variable transmission mechanism 16 has a drive pulley 55 attached to the right outer end portion of the crankshaft 28 and a driven pulley 56 attached to the right outer end portion of the transmission shaft 47. , 56 are connected by winding a V belt 57.

  The V belt 57 is made of a resin having heat resistance and durability, and has the following structure in detail. For example, a large number of resin blocks 57a formed by mixing carbon fiber or aramid fiber into polyamide resin and forming 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. Concatenated.

  The drive pulley 55 includes a fixed pulley half 55a fixed to the right end portion of the crankshaft 28, a crank slidable in the axial direction inside the fixed pulley half 55a in the crankshaft direction and through a slide collar 59. And a movable pulley half 55b arranged to rotate together with the shaft 28. A cam plate 58 and a slide collar 59 are attached to the right end of the crankshaft 28 by spline fitting, and the fixed pulley half 55a is attached to the outer side in the axial direction, and is fastened and fixed by a lock nut 60. A cylindrical weight 61 is disposed between the movable pulley half 55 b and the cam plate 58. As the rotation of the crankshaft 28 increases, the weight 61 moves radially outward by centrifugal force to move the movable pulley half 55b outward in the axial direction, thereby increasing the winding diameter of the pulley and reducing the reduction ratio. Become.

  The driven pulley 56 includes a fixed pulley half 56a fixed to the right outer end portion of the transmission shaft 47, and a movable pulley that is slidable in the axial direction on the outer side in the crankshaft direction of the fixed pulley half 56a. Half body 56b. A cylindrical slide collar 62 fixed to the shaft center of the fixed pulley half 56a is spline-fitted to the transmission shaft 47, and is fixed to the shaft center of the movable pulley half 56b on the slide collar 62. The cylindrical boss portion 63 is mounted so as to be movable in the axial direction. A guide pin 64 planted in the slide collar 62 is slidable in a slide groove 63a formed in a slit shape in the boss portion 63, and the movable pulley half 56b rotates with the fixed pulley half 56a. Match.

  A spring receiving member 65 made of an annular plate is attached to the tip of the slide collar 62 by a circlip 65a, and the movable pulley half is interposed between the spring receiving member 65 and the movable pulley half 56b. A coil spring 67 that constantly urges 56b toward the fixed pulley half 56a is provided.

  The driven pulley 56 is inserted and disposed so as to be immersed in the front end portion 62a of the slide collar 62, and is fixed to the transmission shaft 47 by a lock nut 66 screwed to the front end portion 47a of the transmission shaft 47. Yes.

  Here, the inner diameter of the slide collar 62 is set to be larger in stepped shape than the outer diameter of the transmission shaft 47, and the tip portion 47a of the transmission shaft 47 is set to be smaller in stepped shape. Thus, the lock nut 66 and the washer 66a can be inserted and arranged in the slide collar 62 without any trouble, and in this way, the lock nut 66 can be positioned on the inner side in the crankshaft direction than the spring receiving member 65 of the coil spring 67. It has become.

  According to this embodiment, since the movable pulley half 56b of the driven pulley 56 attached to the transmission shaft 47 is disposed on the outer side in the crankshaft direction of the fixed pulley half 56a, the movable pulley half 56b is disposed on the inner portion of the driven pulley 56 of the transmission shaft 47. An empty space can be secured, and the centrifugal clutch mechanism 17 can be disposed adjacent to the fixed pulley half 56a using the empty space. As a result, the output shaft 48 can be coaxially arranged on the side of the counter-driven pulley 56 of the transmission shaft 47 without increasing the engine width. The engine longitudinal length can be shortened.

  In the present embodiment, the lock nut 66 is arranged so as to be immersed inward in the axial direction from the spring receiving member 65 that supports the coil spring 67 that biases the movable pulley half 56b toward the fixed pulley half 56a. While the required length of the coil spring 67 is ensured, the protrusion to the outside in the transmission shaft direction can be reduced with a simple structure, and the increase in the width of the engine vehicle can be suppressed.

  That is, for example, as shown in FIG. 16, in the case of a structure in which the outer end surface of the slide collar 201 is fastened and fixed to the transmission shaft 200 by the lock nut 203, the transmission case 204 is placed in the vehicle width direction outside by the amount of the lock nut 203. It will stick out. On the other hand, in this embodiment, the lock nut 66 is positioned inward in the axial direction from the outer end of the spring receiving member 65, so that 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 the maintenance or replacement of the coil spring 67 is performed, it is only necessary to remove the circlip 65a, and the work can be easily performed. Incidentally, when the movable pulley half is arranged inside the fixed pulley half, that is, the coil spring is arranged inside in the axial direction, the entire driven pulley has to be removed, resulting in low workability.

  The transmission case 45 has a substantially sealed structure formed independently of the crankcase 22 and is an ellipse that covers most of the upper side of the crankcase 22 when viewed from the right side (see FIG. 4). It has a shape. The transmission case 45 includes a bottomed box-shaped resin case main body 45a that opens outward in the crankshaft direction and an aluminum alloy lid 45b that hermetically closes the opening. The case 41 is fastened together. A gap a is provided between the bottom wall 45c of the case body 45a and the second case 41, and heat from the engine 2 is prevented from being transmitted to the transmission case 45 by the gap a.

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

  The centrifugal clutch mechanism 17 is positioned and clamped by the one-side and other-side clutch bearings 80 and 81 attached to the left end and center of the transmission shaft 47 so as not to move in the axial direction. The one-side clutch bearing 80 is supported by a clutch support wall 41d, and the other-side clutch bearing 81 is supported by the clutch cover 71.

  The clutch support wall 41d that supports the one-side clutch bearing 80 and the reduction bearing 53 is displaced to the left in the crankshaft direction with respect to the second crank support wall 41c that supports the right journal bearing 36, in other words. It is located between the first crank support wall 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 closer to the dividing line B than the cylinder axis A.

  The clutch cover 71 that supports the other-side clutch bearing 81 is located on the right outer side in the crankshaft direction with respect to the second crank support wall 41b that supports the right journal bearing 36. Furthermore, the speed reduction mechanism support wall portion 40d that supports the left bearing 77 of the output shaft 48 is located on the left outer side in the crankshaft direction than 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 drive pulley 55 and the driven pulley 56 is made of resin, the heat resistance and durability of the belt itself can be improved as compared with the rubber belt. And cooling of the V-belt 57 can be eliminated. As a result, the transmission case 45 can have a sealed structure, and water and dust can be prevented from entering.

  In addition, by adopting a highly durable resin belt 57, it is possible to reduce the outer diameter of the drive and driven pulleys 55 and 56, and the distance between the axes of the drive and driven pulleys 55 and 56 is shortened accordingly. The entire engine can be made compact.

  In this embodiment, since the transmission case 45 has a sealed structure independent of the crankcase 22, the engine heat is blocked by the gap a generated between the cases 22 and 45, and the heat from the engine 2 is Is not easily transmitted to the transmission case 45, and the temperature rise in the belt chamber can be suppressed. In addition, the transmission of heat from the engine side is also suppressed from the point that the case body 45a is made of a resin that is difficult to transmit heat.

  The crankcase 22 is divided into first and second cases 40 and 41 in the crankshaft direction, and the transmission case 45 is disposed outside the second case 41 in the crankshaft direction. Since the centrifugal clutch mechanism 17 is disposed in the vicinity of the inner side, the output shaft 48 can be coaxially disposed on the opposite side of the transmission shaft 47 to the continuously variable transmission mechanism 16, and the longitudinal dimension of the engine 2 can be reduced while suppressing the expansion of the width dimension of the engine 2. Can be small.

  Further, since the centrifugal clutch mechanism 17 is sandwiched between the one-side and other-side clutch bearings 80 and 81 mounted on the transmission shaft 47, the centrifugal clutch mechanism 17 can be positioned and supported in the axial direction with a simple structure without using another part. .

  In the present embodiment, the clutch one-side support wall 41d that supports the one-side clutch bearing 80 is positioned between the first and second crank support walls 40c and 41c that support the left and right journal bearings 35 and 36 of the crankshaft 28. Since the clutch cover (clutch other side support wall) 71 that supports the other side clutch bearing 81 is positioned on the outer side in the crank shaft direction of the second crank support wall 41c that supports the right journal bearing 36, the first crank support wall 40c, the clutch chamber 38 while shortening the inter-shaft distance between the crankshaft 28 and the transmission shaft 47 as compared with the case where the clutch one-side support walls 41d and the second crank support wall 41c and the clutch cover 71 are positioned on the same line. The volume of the engine can be secured, the centrifugal clutch mechanism 17 can be stored compactly, and the engine as a whole can be made compact. It can be.

  Further, 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. Replacement work can be easily performed.

  In the present embodiment, the output shaft 48 is disposed 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. Therefore, the centrifugal clutch mechanism 17, the drive sprocket 49, Can be arranged on the same axis, and the longitudinal dimension of the engine can be reduced.

  The centrifugal clutch mechanism 17 is disposed close to the inside of the driven pulley 56 in the crankshaft direction. This 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 so as to rotate together with the transmission shaft 47, and the outer clutch The inner clutch 84 is coaxially arranged on the inner side in the axial direction of the clutch 83, and the 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.

  In the outer clutch 83, a plurality of outer clutch plates 85 are arranged, and two pressing plates 86, 86 are arranged so as to be positioned at both ends thereof, and both 85, 86 rotate together with the outer clutch 83. The outer clutch 83 is engaged. An inner clutch plate 87 is disposed between the outer clutch plate 85 and the pressing plate 86, and each inner clutch plate 87 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 disposed between the cam surface 83a and the outer pressing plate 86. As the weight 88 moves outward in the radial direction due to the centrifugal force of the outer clutch 83, the weight 88 moves to the left of the drawing in FIG. 12 (clutch connection direction) by the cam surface 83a, and presses and moves the pressing plate 86 to move the outer and inner parts. The clutch plates 85 and 86 are connected to each other. In FIG. 12, the upper side from the axis of the centrifugal clutch mechanism 17 indicates a disconnected state, and the lower side indicates a connected state.

  The centrifugal clutch mechanism 17 is provided with a clutch plate sticking prevention mechanism 90. The sticking prevention mechanism 90 includes a leaf spring 91 that urges the outer clutch plate 85 and the pressing plate 86 in a direction to separate them from each other between the outer clutch plates 85 and between the outer clutch plate 85 and the pressing plate 86. It is comprised through.

  Further, pins 92 for restricting 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 pins are inserted. A coil spring 93 that urges the inner clutch plates 87 in a direction to separate them is mounted.

  In the centrifugal clutch mechanism 17 of the present embodiment, the weight 88 moves outward in the radial direction of the clutch 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 opening the throttle (not shown), the weight 88 presses and moves the pressing plate 86 to press the outer and inner clutch plates 85 and 87 so that the engine rotation is controlled by the transmission shaft 47. Is transmitted to the output shaft 48 through the reduction gear mechanism 18, and the rear wheel 7 is rotationally driven through the drive sprocket 49 and the chain 50 by the rotation of the output shaft 48.

  As the engine speed decreases due to the throttle closing operation, the weight 88 moves radially inward, and when the engine speed falls below a predetermined value, the pressure contact force by the weight 88 is released, and the outer. The inner clutch plates 85 and 87 rotate relative to each other, and the engine rotation is blocked between the transmission shaft 47 and the output shaft 48.

  When the clutch contact is released, when the pressure contact force is released, the outer clutch plate 85 and the pressing plate 86 are separated from each other by the reaction force of the leaf spring 91, and the inner clutch plates 87 are separated from each other by the reaction force of the coil spring 93. To do.

  As a result, the outer and inner clutch plates 85 and 87 can be prevented from sticking with the lubricating oil, and the clutch drag phenomenon can be prevented.

  Further, since the axial movement of the inner clutch plate 87 is regulated by the pins 92, it is possible to prevent the inner crack plate 87 from being tilted when the clutch is disengaged, and from this point also, the clutch drag phenomenon can be prevented.

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

  In this lubricating oil system, the lubricating oil in the lubricating oil chamber 95 formed in the bottom portion 22a of the crankcase 22 is sucked by the oil pump 96, and the crankshaft 28, the bearing portion and the sliding portion of the camshaft 31, etc. are lubricated. The lubricating oil that has been pressure-fed and supplied to the part and lubricated the part to be lubricated is returned to the lubricating oil chamber 95 by natural fall.

  The oil pump 96 is disposed at the lower part of the first case 40 of the crankcase 22 as shown mainly in FIG. 11, and more specifically, is an inner side surface of the lubricating oil chamber 95 located on the side opposite to the transmission case 45. 22c. The oil pump 96 has a structure in which a pump shaft 96a is pivotally supported by a housing 97 having a suction port 97a and a discharge port 97b, and a pump gear 98 is attached to an outer end portion of the pump shaft 96a.

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

  An oil passage 28e communicating with the oil chamber 44c is formed in the crankshaft 28 in the axial direction. The oil passage 28e is connected to the crankpin 29 via a branch passage 29a formed in the crankpin 29. It opens to the connecting bearing portion 101 with the connecting rod 27.

  The lubricating oil sucked in by the oil pump 96 is pumped 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 connecting bearing portion 101 through the branch passage 29a. The lubricating oil supplied to the connecting bearing portion 101 is scattered in the crank chamber 37 by the supply hydraulic pressure and by 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 52 a and the large gear 48 a are lubricated and then dropped into the lubricating oil chamber 95.

  The lubricating oil chamber 95 is formed at the bottom portion 22a of the crankcase 22 so as to be positioned below the crank chamber 37, and further has a bulging portion 22b that bulges so as to be positioned below the transmission case 45. It is integrally formed (see FIGS. 8 and 11). The bulging portion 22b is formed so as to be located in the projection surface of the transmission case 45 as viewed from above, and the center line D in the vehicle width direction of the lubricating oil chamber 95 is from the cylinder axis A to the transmission case 45. It is biased to the side.

  According to the present embodiment, since the bulging portion 22b is formed to bulge at the bottom portion 22a of the crankcase 22 so as to be positioned below the transmission case 45, the empty space below the transmission case 45 is effectively used for lubrication. The amount of lubricating oil in the oil chamber 95 can be increased, and the height of the engine 2 does not need to be increased as compared with the case where the amount of lubricating oil is ensured by deepening the case bottom.

  Further, since the bottom 22a of the crankcase 22 is expanded below the transmission case 45, the surface area of the lubricating oil chamber 95 can be increased, the cooling performance can be increased, and the weight balance of the entire engine is good. Can be.

  Here, in this embodiment, since the V belt 57 is made of resin and the transmission case 45 is independent of the crankcase 22, the heat resistance of the belt itself compared to the case of using a rubber belt, The durability can be enhanced and the thermal influence 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 reduced in size, and an empty space can be provided below the transmission case 45. The portion 22b is formed to increase the lubricating oil capacity.

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

  As shown mainly in FIGS. 3 and 7, the centrifugal clutch mechanism 17 is partially in a region where the lubricating oil scatters from the connecting bearing portion 101 of the connecting rod 27 and the crank pin 29 when viewed in the direction perpendicular to the crankshaft. Are positioned so as to overlap. Specifically, the outer and inner clutch plates 85 and 87 of the centrifugal clutch mechanism 17 are disposed at positions facing the crank chamber 37.

  The second outer peripheral wall 41a that defines the crank chamber 37 and the clutch chamber 38 is formed with an introduction opening 103 for introducing the lubricating oil scattered from the coupling bearing portion 101 into the clutch chamber 38.

  A guide portion 104 extending inward of the clutch chamber 38 is integrally formed with the clutch support wall portion 41d. The guide portion 104 is located on an extension line connecting the crankshaft 28 and the transmission shaft 47, and extends in the longitudinal direction so as to be substantially opposed to the introduction opening 103, and a lower end of the lubricant receiving portion 104a. And a guide portion 104b extending in an arc shape so as to go around the transmission shaft 47. The guide portion 104b is positioned so as to be inserted into a boss portion having a truncated cone shape of the inner clutch 84.

  As a result, the lubricating oil that has entered from the introduction opening 103 is received by the guide portion 104 and guided more to the inner portion than the outer periphery of the centrifugal clutch mechanism 17, and the lubricating oil is caused to flow by the centrifugal force of the clutch mechanism 17 to the outer and inner clutches. While being supplied between the plates 85 and 87, it is 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 lubrication structure of the present embodiment, since the lubricating oil supplied to the coupling bearing portion 101 between the crank pin 29 and the connecting rod large end portion 27a is guided to the centrifugal clutch mechanism 17, the coupling bearing portion 101 is used. Lubricating oil ejected and scattered in a large amount from the engine can be supplied to the centrifugal clutch mechanism 17, it is not necessary to provide a special lubricating oil path, and a sufficient amount of lubricating oil can be supplied to the centrifugal clutch mechanism 17. , 87 can be prevented.

  In the present embodiment, the centrifugal clutch mechanism 17 is located in the clutch chamber 38 defined from the crank chamber 37 and in the lubricating oil scattering region from the connecting bearing portion 101 when viewed in the direction perpendicular to the crankshaft. Since the introduction opening 103 that allows the lubricating oil to enter is formed in the second outer peripheral wall 41a that defines the clutch chamber 38 and the crank chamber 37, the lubricating oil from the crank chamber 37 has a very simple structure. Can be effectively introduced into the clutch chamber 38.

  In the present embodiment, a guide portion 104 extending inward of the clutch chamber 38 is formed integrally with the clutch support wall portion 41d, and the guide portion 104 is positioned on an extension line connecting the crankshaft 28 and the transmission shaft 47, and the introduction opening 103 is provided. And a guide portion 104b extending in a circular arc shape so as to wrap around the lower portion of the transmission shaft 47 following the lower end of the lubricant receiving portion 104a. Lubricating oil can be supplied to the clutch plates 85 and 87 more reliably.

  Next, the kick device of the engine 2 will be described.

  As shown mainly in FIGS. 5, 9, and 10, a kick shaft 110 is disposed in parallel with the output shaft 48 substantially vertically below the output shaft 48. When viewed from a direction perpendicular to the crankshaft, the kick shaft 110 has a boss formed by supporting the inner side of the drive sprocket 49 by the boss portion 40h of the first case 40 and a pair of outer portions formed on the generator cover 44. 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. Further, a return spring 113 is wound around the inner end portion of the kick shaft 110, and the kick shaft 110 is urged to rotate to the depressed position by the return spring 113.

  A main intermediate shaft 114 and a sub intermediate shaft 115 are disposed between the kick shaft 110 and the crank shaft 28 in parallel with the kick shaft 110, respectively. The main intermediate shaft 114 is pivotally supported across the first case 40 and the second case 41, and a main intermediate gear 116 that can mesh with the kick gear 112 is attached to the main intermediate shaft 114.

  The sub intermediate shaft 115 is supported by a bearing portion 40j formed in the first case 40, and the inner and outer end portions of the sub intermediate shaft 115 protrude inside and outside the first case 40, respectively. 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. The second intermediate gear 117 is engaged with a first crank gear 121 described later.

  When the kick arm 111 is stepped on, the kick shaft 110 rotates, and the kick gear 112 moves in the axial direction along with the rotation and meshes with the main intermediate gear 116, via the first and second intermediate gears 115 a and 117. Is transmitted to the first crank gear 121, and the crankshaft 28 rotates.

  Between the left journal bearing 35 of the crankshaft 28 and the sleeve 43 of the generator 42, a one-way clutch 120, the first crank gear (first drive gear) 121, and a cam sprocket 122 are mounted in order from the outside. Yes.

  The one-way clutch 120 is provided with a starting gear 120a, and a driving gear 125a of a starter motor 125 is connected to the starting gear 120a via an idler gear 124. The starter motor 125 is disposed and fixed on the front wall of the crankcase 22 with its motor axis parallel to the crankshaft 28.

  The kick gear 112, the main intermediate gear 116, and the first intermediate gear 115 a are disposed at positions communicating with the lubricating oil chamber 95 inside the first case 40. The second intermediate gear 117, the first crank gear 121, and the cam sprocket 122 are disposed outside the first case 40.

  According to the kick device of the present embodiment, since the kick gear 112, the main intermediate gear 116, and the first intermediate gear 115a are positioned at the portion communicating with the lubricating oil chamber 95, the meshing portions of these gears can be sufficiently lubricated. .

  Further, the main intermediate shaft 115 is penetrated from the inside of the first case 40 to the outside, the rotation of the kick shaft 110 is transmitted from the inside to the outside of the main intermediate shaft 115, and the first crank gear is transmitted from the second intermediate gear 117 on the outside. Since the first crank gear 121 can be disposed outside the crank journal portion 28c, the distance between the crank bearings 35 and 36 can be reduced, and the crankshaft 28 can be bent by the connecting rod 27. It can be pivoted with a small moment. Furthermore, the space for arranging the cam sprocket 122 and 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 crankshaft 28 in the first case 40, a gear is required between the left crank bearing 35 and the left crank arm 28a, and the left and right bearings 35, The interval of 36 becomes wide, which is disadvantageous in the bending moment.

In the present embodiment, since the kick shaft 110 is disposed substantially below the output shaft 48 in the vertical direction, the kick arm 111 can be easily depressed, and the longitudinal dimension of the engine 2 can be reduced.

  Further, the inner side in the vehicle width direction of the rear wheel drive sprocket 49 of the kick shaft 110 is pivotally supported by the first clutch support wall portion 40d of the crankcase 22, and the outer side in the vehicle width direction is pivotally supported by the generator case 44. Since the kick arm 111 is mounted on the outward projecting end of the generator case 44 of the kick shaft 110, the kick shaft 110, and thus the kick arm 111, can be disposed at an optimal stepping position without interfering with the rear wheel drive sprocket 49. it can.

  As shown in FIG. 4, the kick shaft 110 is located in the axial projection plane of the transmission case 45 and in the axial projection plane of the centrifugal clutch mechanism 17 when viewed in the crankshaft direction. . 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 as described above, it is not necessary to secure a space for arranging the kick shaft in the transmission case 45. Therefore, the driving pulley 55 and the driven pulley of the continuously variable transmission mechanism 16 are not required. 56 can be arranged so close that a slight gap b (see FIG. 3) is generated, and the length of the engine in the front-rear direction can be reduced accordingly.

  Further, since the kick shaft 110 is disposed in the projection surface in the crankshaft direction of the transmission case 45, the kick shaft 110 can be disposed at a position close to the crankshaft 28 and easy to step on.

  In the present embodiment, the centrifugal clutch mechanism 17 is disposed in the vicinity of the inside of the driven pulley 56 in the crankshaft direction, and the kick shaft 110 is disposed in the axial projection plane of the centrifugal clutch mechanism 17 and substantially vertically below the transmission shaft 47. Since the kick shaft 110 is disposed, the kick shaft 110 can be disposed at a position where it can be most easily depressed using the empty space in the projection plane of the centrifugal clutch mechanism, and the longitudinal length of the engine 2 can be reduced.

  A balancer shaft 129 is disposed in parallel with the crankshaft 28 above the crankshaft 28. The balancer shaft 129 is pivotally 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 protrudes outward from the first case 40, and a balancer gear 132 is coupled to the protruding portion. A damper member 133 is interposed on the inner peripheral portion of the balancer gear 132.

  Here, the left and right crank arms 28a and 28b of the crankshaft 28 are located in the balancer bearings 130 and 131, and the balancer weight 129a of the balancer shaft 129 is between the left and right crank arms 28a and 28b. In addition, they are arranged close to the crankshaft 28 side so as to overlap the rotation locus of the crankpin 29. As a result, the balancer shaft is compact.

  A second crank gear (second drive gear) 127 is mounted on the first crank gear (first drive gear) 121 press-fitted into the crankshaft 28 so as to rotate together. The balancer gear (second driven gear) 132 meshes with the second crank gear 127. The first crank gear 121 is engaged with a second intermediate gear 117 of a kick gear train that transmits the rotation of the kick shaft 110 to the crank shaft. Furthermore, the pump gear 98 of the lubricating oil pump 96 is engaged with the first crank gear 121 via the second intermediate gear 117. That is, the second intermediate gear 117 is shared as a part of the pump gear train and the kick gear train.

  More specifically, the first crank gear 121 has a cylindrical shape in which outer peripheral teeth (external gears) 121a are formed on the outer peripheral surface, and has a thickness more than twice that of other plate gears. It is firmly press-fitted and fixed to the outer periphery of the shaft 28. The second crank gear 127 has an annular shape in which inner peripheral teeth (internal gears) 127a and outer peripheral teeth (external gears) 127b are formed on the inner peripheral surface and the outer peripheral surface. The second crank gear 127 is mounted so as to cover the engaged portion (right end portion) of the first crank gear 121, and its inner peripheral tooth 127 a is engaged with the outer peripheral tooth 121 a of the first crank gear 121. (See FIG. 6). Thereby, 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.

  Here, the outer diameter of the first crank gear 121 is set to be smaller than the outer edge portion 35 b that contacts the outer race of the support hole 35 a of the left crank journal bearing 35 formed in the first case 40. Thereby, the operation | work at the time of assembling the crankshaft 28 in the crankcase 22 is realizable with a simple structure. That is, with the second crank gear 127 removed, the first case 40 is moved from the left to the right to fit the support hole 35a into the left crank journal bearing 35a, and then the second crank gear 127 is moved to the first. The crank gear 121 is fitted and mounted.

  The one-way clutch 120, the first crank gear 121, and the cam sprocket 122 mounted on the crankshaft 28 are tightened with a nut 123 screwed to the left end portion of the crankshaft 28, thereby the sleeve 43, the journal bearing 35, It is clamped so that it cannot move in the axial direction.

  According to the present embodiment, since the cylindrical first crank gear 121 is press-fitted and fixed to the crankshaft 28, the press-fitting length of the first crank gear 121 to the crankshaft 28 can be sufficiently secured, and the first One crank gear 121 can be firmly fixed to the crankshaft 28.

  Further, the rotation of the crankshaft 28 is transmitted from the first crank gear 121 firmly fixed thereto to the pump gear 98, and the rotation of the kick shaft 110 is transmitted to the crankshaft 28 via the first crank gear 121. Therefore, it is possible to reliably transmit the rotational force between the crankshaft 28, the lubricating oil pump 96, and the kick shaft 110.

  The second crank gear 127 is disposed so as to overlap the engaged portion (right end portion) of the first crank gear 121. Therefore, the first crank gear 121 is formed in a cylindrical shape that can ensure a sufficient press-fitting length. However, the problem that the crankshaft direction length becomes long can be avoided.

  In addition, since the inner peripheral tooth 127a of the second crank gear 127 is detachably fitted to the outer peripheral tooth 121a of the first crank gear 121, the second crank gear 127 can be easily attached and detached.

  Further, since the outer diameter of the first crank gear 121 is set to be smaller than the inner diameter of the outer edge portion 35b of the crankcase side support hole 35a of the adjacent crank journal bearing 35, the crankshaft 28 when the crankcase 22 has a left and right split structure. The crankcase can be easily assembled with a simple structure. That is, when assembling the crankshaft 28, the first case 40 is moved inward in the crankshaft direction with the second crank gear 127 removed, and the bearing support hole 35a is fitted to the crank journal bearing 35. Thereby, the support part of the crankcase 22 and the crankshaft 28 is assembled.

  Further, by removing the generator 42 and the one-way clutch 120 mounted outside the first and second crank gears 121 and 127 of the crankshaft 28, the second crank gear 127 can be removed outward in the axial direction. As described above, the second crank gear 127 can be easily assembled and removed. Since the balancer shaft 129 driven by the second crank gear 127 always rotates at the same speed as the engine rotation, it may become a noise source, but the second crank gear 127 can be easily replaced. It is easy to realize a combination of the second crank gear 127 and the looseness gear 132 with less noise generation.

  Further, since the second intermediate gear 117 meshed with the first crank gear 121 is shared between the case where the rotation of the kick shaft 110 is transmitted to the crank shaft 28 and the case where the rotation of the crank shaft 28 is transmitted to the pump gear 98, only that. The crankshaft length can be shortened, the engine width can be made compact, and the required number of gears and gear shafts can be reduced.

  Further, since the inner peripheral teeth 127a of the second crank gear 127 and the second intermediate gear 117 are engaged with the first crank gear 121 press-fitted into the crankshaft 28, the crank of the first crank gear 121 is engaged. A sufficient press-fitting length to the shaft 28 can be ensured, and the rotation of the crankshaft 28 can be reliably transmitted to the pump gear 98 and the balancer gear 132.

  In the present embodiment, since the structure in which the outer peripheral teeth 121a of the first crank gear 121 and the inner peripheral teeth 127a of the second crank gear 127 are fitted is employed, the second crank gear 127 can be easily assembled and maintenance can be performed. The time can be easily removed. That is, the second crank gear 127 can be easily removed from the first crank gear 121 by removing the nut 123 of the crankshaft 28 and removing the sleeve 43 and the one-way clutch 120.

  Here, in the above embodiment, the first drive gear has outer peripheral teeth (external gears) over its entire length, but the engaged portion of the first drive gear is an external spline, and the second The drive gear may have an inner spline on its inner peripheral surface, and both the splines may be fitted. In this case, the second drive gear can be easily manufactured because the internal gear can be omitted.

    Each axis of the engine 2 of the present embodiment has the following arrangement structure.

  The transmission shaft 47 and the output shaft 48 are disposed on substantially the same 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 crankshaft 28 and the output shaft 48, and the kick shaft 110, the pump shaft 96a, the main and sub intermediate shafts 114, 115 is arranged.

  The kick shaft 110 is disposed substantially vertically below the output shaft 48, and the pump shaft 96a is disposed substantially vertically below the balancer shaft 129. Further, the main and sub intermediate shafts 114 and 115 are arranged on a line connecting the crankshaft 28 and the kick shaft 110.

  According to the present embodiment, the balancer shaft 129 is disposed on the upper side of the horizontal plane C including the crankshaft 28 and the output shaft 48, and the kick shaft 110 and the pump shaft 96a of the oil pump 96 are disposed on the lower side. , Can be placed in a well-balanced position below, avoiding the enlargement of the engine. That is, there is an empty space on the upper side of the horizontal plane C and on the rear side of the cylinder bore, and the balancer shaft 129 is arranged using this space. Since the balancer shaft 129 rotates with a large rotation locus of the weight 129a, the loss horsepower due to the stirring of the lubricating oil increases when immersed in the lubricating oil. However, in this embodiment, the balancer shaft 129 diffuses the lubricating oil. Never do. Further, the reduction shaft 52 is arranged on the upper side of the horizontal plane C by utilizing the empty space between the balancer shaft 129 and the output shaft 48. In this case, although it is located in the upper part where it is difficult to supply the lubricating oil, since 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, there is no problem of insufficient lubrication.

  Further, since the kick shaft 110 is disposed substantially vertically below the output shaft 48, the longitudinal length of the engine 2 can be reduced and the kick shaft 110 can be disposed at a position where the kick shaft 110 can be easily depressed.

  According to the first aspect of the present invention, the first drive gear is press-fitted and fixed to the crankshaft, and the inner peripheral teeth of the second drive gear are detachably fitted to the end portions of the outer peripheral teeth of the first drive gear. Is transmitted from the first drive gear to the first driven gear and from the first drive gear to the second driven gear via the second drive gear, the fixed length of the first drive gear to the crankshaft More specifically, the press-fitting length can be sufficiently secured, and the rotation of the crankshaft can be reliably transmitted to the first and second driven gears. Further, the second drive gear is arranged so as to overlap with the engaged portion of the first drive gear, and therefore the length in the crankshaft direction becomes long even when the press-fit length of the first drive gear is sufficiently secured. The problem can be avoided.

In addition, since the outer diameter of the first drive gear is set to be smaller than the inner diameter of the crankcase side support hole of the adjacent crank journal bearing, assembly of the crankshaft in the crankcase when the crankcase is divided into the left and right structures is performed. It can be easily performed with a simple structure. That is, when assembling the crankshaft, with the second drive gear removed, the left and right split crankcase is moved in the direction of the crankshaft, and the bearing support hole of the crankcase is fitted to the crank journal bearing. Then, the support part of a crankcase and a crankshaft will be assembled by this.
In the second aspect of the invention, the engaged portion of the first drive gear is an outer spline, the inner spline is formed on the inner peripheral surface of the second drive gear, and both the splines are fitted. It is not necessary to form an internal gear on the inner peripheral surface of the second drive gear, and the second drive gear can be easily manufactured.

  In the third aspect of the invention, the second drive gear can be removed axially outward when the crankshaft component mounted outside the first and second drive gears of the crankshaft is removed. The assembly and removal of the two drive gears are easy. For example, when the noise from the second drive gear is large, the work for replacing it with another one can be easily performed.

  In the invention of claim 4, since the kick gear train is engaged with the first drive gear and the balancer gear train is engaged with the second drive gear, the first drive in which the rotation from the cook shaft is firmly fixed to the crankshaft. It can be reliably transmitted to the crankshaft via the gear. Further, the balancer shaft driven by the second drive gear always rotates at the same speed as the engine rotation, so it may become a noise source. However, since the second drive gear can be easily replaced, the noise during assembly of the engine It is easy to realize a combination of a drive gear and a driven gear that generate less.

  In the invention of claim 5, since both the pump gear train and the kick gear train are meshed with the first drive gear through a partially common gear, the crankshaft length can be shortened accordingly, and the number of necessary gears and The number of gear shafts can be reduced.

Claims (5)

The crankshaft is supported by a crankcase divided into two in the direction of the crankshaft via a crank journal bearing, and the first drive gear on the crankshaft side is interposed between the crankshaft and the first and second driven shafts. In the engine that transmits the rotational force via the second drive gear, the first driven gear on the first and second driven shaft side, and the second driven gear,
The first drive gear has a cylindrical shape with outer peripheral teeth (external gears) formed on the outer peripheral surface, and is fixed to the crankshaft by press-fitting, and the second drive gear is formed on the inner peripheral surface . peripheral teeth (internal gear) may be of annular outer peripheral teeth on the outer peripheral surface (outer gear) is formed respectively, attaching and detaching the inner peripheral teeth engaged portion of the outer peripheral teeth of said first driving gear It is possible to fit,
Transmission of rotational force between the crankshaft and the first driven shaft is performed directly between the first drive gear and the first driven gear, and between the crankshaft and the second driven shaft. Rotational force is transmitted between the first drive gear and the second driven gear with the second drive gear interposed.
The first drive gear is positioned axially outside the crank journal bearing, and the outer diameter of the first drive gear is set smaller than the inner diameter of the outer edge portion of the crankcase side support hole of the crank journal bearing. An engine characterized in that the crankcase support hole can be fitted to the crank journal bearing from the outside in the crankshaft direction to the inside with the second drive gear removed. The crankshaft is supported by a crankcase divided into two in the direction of the crankshaft via a crank journal bearing, and the first drive gear on the crankshaft side is interposed between the crankshaft and the first and second driven shafts. In the engine that transmits the rotational force via the second drive gear, the first driven gear on the first and second driven shaft side, and the second driven gear,
The first drive gear has a cylindrical shape having outer peripheral teeth (external gears) on the outer peripheral surface and an outer spline following the outer peripheral teeth, and is fixed to the crankshaft by press-fitting. The second drive gear is the internal splines on the inner peripheral surface is of a circular, each having an outer peripheral teeth (external gear) on the outer peripheral surface, and fitted detachably on the outer splines of the first driving gear to internal splines,
Transmission of rotational force between the crankshaft and the first driven shaft is performed directly between the first drive gear and the first driven gear, and between the crankshaft and the second driven shaft. Rotational force is transmitted between the first drive gear and the second driven gear with the second drive gear interposed.
The first drive gear is positioned axially outside the crank journal bearing, and the outer diameter of the first drive gear is set smaller than the inner diameter of the outer edge portion of the crankcase side support hole of the crank journal bearing. The engine is characterized in that the crankcase-side support hole can be fitted to the crank journal bearing from the outside in the crankshaft direction to the inside with the second drive gear removed. 3. The crankshaft component according to claim 1 or 2, wherein a crankshaft component is detachably mounted on the outside of the first and second drive gears of the crankshaft, and the second drive gear is in a state where the crankshaft component is detached. An engine characterized by being removable from the crankshaft. 4. The kick gear train for transmitting rotation of the kick shaft to the crankshaft is meshed with the first drive gear, and the rotation of the crankshaft is balanced with the second drive gear. The engine is characterized in that the balancer gear train that is transmitted to the gear is engaged. 5. The kick gear train for transmitting the rotation of the crankshaft to the lubricating oil pump and the kick gear train for transmitting the rotation of the kick shaft to the crankshaft are meshed with the first drive gear. An engine characterized by sharing a train and a part of the pump gear train.

Images