JP6485088B2 - Transmission case - Google Patents

Description

  The present invention relates to a transmission case of a unit swing type engine unit provided in a straddle-type vehicle such as a scooter.

  A straddle type vehicle such as a scooter includes a unit swing type engine unit (see Patent Document 1). The engine unit is a unit of an engine, a belt-type continuously variable transmission, a centrifugal clutch, a gear box, and the like, and further has a function as a swing arm that supports a rear wheel. The engine unit is attached to the body frame of the saddle riding type vehicle so as to be swingable in the vertical direction.

  The unit swing type engine unit includes a transmission case, and a belt type continuously variable transmission and a centrifugal clutch are accommodated in the transmission case. The transmission case is configured by attaching a transmission case cover to the transmission case body. The transmission case body is integrated with the engine crankcase. Specifically, the front part of the transmission case body forms a part of the crankcase. Further, a gear box is attached to the rear part of the transmission case main body.

  The belt-type continuously variable transmission includes a drive pulley mounted on a crankshaft, a driven pulley mounted on a driven shaft, and a belt hung on the drive pulley and the driven pulley. A crankshaft insertion hole is formed in a side wall portion of the saddle riding type vehicle that faces inward in the vehicle width direction at the front part of the transmission case body, and the crankshaft enters the transmission case body through the crankshaft insertion hole. A drive pulley is attached to the end of the crankshaft in the case body. In addition, a driven shaft insertion hole is formed in a side wall portion of the saddle type vehicle facing inward in the vehicle width direction at the rear portion of the transmission case main body, and the driven shaft is inserted into the driven shaft insertion hole. A driven pulley is attached to the shaft. In the transmission case body, a belt is stretched between the drive pulley and the driven pulley. Further, a centrifugal clutch is provided on the driven shaft in the transmission case body. The driven shaft enters the gear box from the transmission case through the driven shaft insertion hole, and is connected to the rear wheel axle through the gear in the gear box.

  In the belt type continuously variable transmission, the belt generates heat due to friction with each pulley, and the centrifugal clutch also generates heat due to friction. For this reason, the belt type continuously variable transmission has a cooling structure for cooling the belt and the centrifugal clutch. Specifically, an air inlet is formed at the front of the transmission case, an air outlet is formed at the rear of the transmission case, and a cooling fan is provided on the crankshaft in the transmission case. When the cooling fan rotates together with the crankshaft, the air taken in from the air intake port becomes the cooling air and flows in the transmission case from the front part to the rear part and is discharged from the air exhaust port. As a result, the belt and the centrifugal clutch are cooled.

JP2013-257010A

  By the way, many transmission case bodies according to the prior art have a rib structure. Specifically, in the transmission case body, on the inner surface of the side wall portion located on the inner side in the vehicle width direction of the saddle riding type vehicle, a number of ribs rising in a direction orthogonal to the surface are formed. Are arranged in a radial or grid pattern.

  FIG. 4 of Patent Document 1 discloses a rib structure in which a large number of ribs are arranged radially. This rib structure is formed not on the transmission case body but on the transmission case cover, but there are many transmission cases in which a rib structure similar to this is formed on the inner surface of the side wall portion of the transmission case body.

  Forming a rib structure on the inner surface of the side wall portion of the transmission case body has the following advantages. That is, in the transmission case, it is possible to ensure rigidity that can withstand a load generated by power transmission or shift by the belt-type continuously variable transmission. Further, it is possible to suppress the vibration of the side wall portion of the transmission case main body caused by the transmission of the engine vibration, and to reduce the noise caused by the vibration of the side wall portion of the transmission case main body.

  However, forming the rib structure on the inner surface of the side wall portion of the transmission case main body has the following problems. That is, the transmission case becomes heavy by forming the rib structure. Certainly, by adopting a method that increases the rigidity of the transmission case body by increasing the overall thickness of the side wall part by adopting a method that increases the rigidity of the transmission case body by forming a rib structure on the side wall part. The transmission case can be made lighter as compared with the present invention, but today, it is desired to further reduce the weight of the transmission case.

  Further, the rib structure prevents the cooling air flowing in the transmission case, and the cooling effect of the belt or the centrifugal clutch is reduced. Specifically, the flow of the cooling air is in the front-rear direction in the saddle riding type vehicle. On the other hand, among the ribs arranged in a radial pattern or a grid pattern, there are ribs extending in the vertical direction in the saddle riding type vehicle. For this reason, the cooling air blows against the rib extending in the vertical direction, and the flow of the cooling air is hindered. As a result, the belt or the centrifugal clutch may not be sufficiently cooled.

  The present invention has been made in view of, for example, the above-described problems, and a first problem of the present invention is a transmission case capable of reducing the weight while ensuring the rigidity of the transmission case and reducing noise. Is to provide.

  Further, the second problem of the present invention is to create a smooth flow of cooling air while ensuring the rigidity of the transmission case and reducing noise, and to enhance the cooling effect of the stored items such as the belt or the centrifugal clutch. The purpose is to provide a transmission case.

  In order to solve the above problems, the present invention is a unit swing type provided in a straddle-type vehicle and having an engine, a belt-type continuously variable transmission that transmits power of the engine to an axle of a rear wheel, and a gear box. A power transmission case for housing the belt-type continuously variable transmission in the front wall portion, the upper wall portion, the rear wall portion, the lower wall portion, and the inner side in the vehicle width direction of the saddle riding type vehicle. A case body having a crankshaft insertion hole through which the crankshaft is inserted at the front portion and a side wall portion having a driven shaft insertion hole formed at the rear portion through which the driven shaft is inserted, the outer side in the vehicle width direction being open And a side of the side wall portion facing inward in the vehicle width direction, in a region where the crankshaft insertion hole is formed in the front portion of the side wall portion, and the crankcase of the engine A crankcase forming part that forms a part, a surface side of the side wall part facing inward in the vehicle width direction, and formed in a region where the driven shaft insertion hole is formed in the rear part of the side wall part; A gear box mounting portion for mounting a box, and in the side wall portion, between the crankcase forming portion and the gear box mounting portion, the side wall portion itself draws a wave traveling upward or downward. And a corrugated portion that is repeatedly bent or bent is formed.

  By forming the corrugated portion on the side wall portion of the case main body in this manner, it is possible to ensure rigidity or strength that can withstand a load generated by power transmission by the belt-type continuously variable transmission or a shift in the transmission case. Further, by forming the corrugated portion on the side wall portion of the case main body, the vibration of the side wall portion of the case main body caused by the transmission of engine vibration can be suppressed, and the noise caused by the vibration of the case main body can be reduced. . In addition, by forming the corrugated portion on the side wall portion of the case main body, the above-described configuration can be achieved without forming ribs on the side wall portion of the case main body or greatly reducing the number of ribs formed on the side wall portion of the case main body. Thus, it is possible to ensure the rigidity of the transmission case and reduce the noise. Therefore, the transmission case can be lightened by not forming ribs on the side wall portions of the case main body or by greatly reducing the number of ribs formed on the side wall portions of the case main body.

Furthermore, the transmission case according to the present invention includes a cover that covers a portion of the case main body that is open to the outside in the vehicle width direction, and a surface of the side wall portion facing outward in the vehicle width direction has the vehicle width direction. There are provided at least two columnar or cylindrical cover support portions that extend outward and support the cover on the front end side, and are adjacent to each other on the surface of the side wall portion facing outward in the vehicle width direction. Between the cover support portions, plate-like reinforcement portions that rise toward the outside in the vehicle width direction are provided, and each of the cover support portions and the reinforcement portions are formed on wave peaks or troughs in the corrugated portion of the side wall portion. Are arranged along.

By arranging the cover support structure that supports the cover on the case body, such as each cover support part and the reinforcement part, along the wave peaks or valleys in the corrugated part of the side wall part, the flow of cooling air is prevented by the cover support structure. Can be suppressed. Further, the rigidity of the transmission case can be increased by the reinforcing portion.

In the transmission case of the present invention, it is preferable that the wave peaks and valleys in the corrugated portion of the side wall portion extend linearly in the front-rear direction of the saddle riding type vehicle.

As a result, the direction of the cooling air flowing in the transmission case can be matched with the direction in which the wave peaks and valleys in the corrugated portion extend, so that the cooling air can flow smoothly.

Further, in the transmission case of the present invention, the crests and troughs of the corrugated portion of the side wall portion are the rotation center of the drive pulley provided on the crankshaft and the rotation of the driven pulley provided on the driven shaft. It is desirable to extend parallel to the straight line connecting the center points.

Thereby, the direction of the cooling air flowing in the transmission case can be matched with the direction in which the wave peaks and valleys in the corrugated portion extend, and the cooling air can flow smoothly.

Further, in the transmission case of the present invention, the crankcase forming portion is formed in a substantially cylindrical shape extending inward in the vehicle width direction, and a portion of the peripheral wall portion of the crankcase forming portion facing rearward is the peripheral wall portion. Wave portions that are repeatedly bent or bent so as to draw a wave that progresses upward or downward are formed, and wave peaks and valleys in the corrugated portion of the side wall portion and wave peaks in the corrugated portion of the peripheral wall portion. And the valley are preferably connected to each other.

In this way, the corrugated portion is formed in a wide range from the portion between the crankcase forming portion and the gear box mounting portion in the side wall portion of the case body to the portion facing the rear in the peripheral wall portion of the crankcase forming portion. By doing so, the rigidity of the transmission case can be increased. Accordingly, the rigidity of the transmission case can be further improved and the noise can be further reduced without forming ribs or while greatly reducing the number of ribs.

  According to the present invention, it is possible to reduce the weight of the transmission case while ensuring the rigidity of the transmission case and reducing noise. In addition, according to the present invention, while ensuring the rigidity of the transmission case and reducing noise, a smooth flow of cooling air is created in the transmission case, and the cooling effect of the stored matter such as a belt or a centrifugal clutch is enhanced. Can do.

It is an external appearance perspective view which shows the engine unit provided with the transmission case by embodiment of this invention. It is an external view which shows the left side surface of the engine unit in FIG. FIG. 3 is an explanatory diagram showing a state where a transmission case cover is removed from the engine unit in FIG. 2. It is an external appearance perspective view which mainly shows the left side of the transmission case main body of the transmission case by embodiment of this invention. It is an external appearance perspective view which mainly shows the right side surface of the transmission case main body in FIG. It is sectional drawing of the transmission case main body seen from the arrow VI-VI direction in FIG. It is explanatory drawing which shows the characteristic of the waveform part formed in the transmission case main body of the transmission case by embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the front, rear, left, right, up and down directions are based on the driver sitting on the seat of the saddle type vehicle.

  1 and 2 show a unit swing type engine unit including a transmission case 21 according to an embodiment of the present invention. FIG. 3 shows a state where the transmission case cover 51 is removed from the engine unit 1 in FIG.

  In FIG. 1, an engine unit 1 includes an engine 2, a belt-type continuously variable transmission 11 (see FIG. 3) that transmits the power of the engine 2 to the rear wheel side and performs stepless speed change, and a belt-type continuously variable. This is a unit in which a gear box 61 that transmits the output of the transmission 11 to the rear wheel axle, a centrifugal clutch (not shown), and the like are integrated. The engine unit 1 is attached to a body frame of a straddle-type vehicle such as a scooter so as to be swingable in the vertical direction. A rear wheel is supported at the rear of the engine unit 1. The engine unit 1 also includes a transmission case 21 that houses a belt type continuously variable transmission 11 and a centrifugal clutch.

  The engine 2 is disposed in the front part of the engine unit 1. The engine 2 is, for example, a 4-cycle single cylinder engine. The engine 2 includes a crankcase 3, a cylinder 4, and a cylinder head 5. A crankshaft or the like is provided in the crankcase 3, and a piston or the like is provided in the cylinder 4. The cylinder 4 is greatly inclined forward. A head cover 6 is attached to the head of the cylinder head 5.

  The crankcase 3 is formed by fixing a pair of crankcase forming portions 31 and 55 together. One crankcase forming portion 31 forms the left portion of the crankcase 3, and the other crankcase forming portion 55 forms the right portion of the crankcase 3. The crankcase forming portion 31 that forms the left portion of the crankcase 3 is formed integrally with the transmission case main body 22 of the transmission case 21.

  As shown in FIG. 3, the belt-type continuously variable transmission 11 is accommodated in a transmission case 21 and disposed on the left side of the engine unit 1. The belt type continuously variable transmission 11 includes a drive pulley 12, a driven shaft (not shown), a driven pulley 13, and a belt 14. The left end side of the crankshaft of the engine 2 enters the transmission case 21 through a crankshaft insertion hole 28 formed in a front portion of a transmission case body 22 to be described later, and the drive pulley 12 is placed in the transmission case 21. It is attached to the left end side of the crankshaft. Further, the left end side of the driven shaft enters the transmission case 21 through the driven shaft insertion hole 29 formed in the rear portion of the transmission case body 22, and the driven pulley 13 is located in the transmission case 21 at the left end of the driven shaft. Is attached to the side. The belt 14 is stretched around the drive pulley 12 and the driven pulley 13. Although not shown, the centrifugal clutch is disposed on the left side of the driven pulley 13 and attached to the driven shaft.

  The belt type continuously variable transmission 11 includes a cooling structure as described below in order to suppress heat generation due to friction of the belt 14 or heat generation due to friction of the centrifugal clutch. That is, as shown in FIG. 2, an air inlet 52 is formed in the front portion of a transmission case cover 51 described later, and a cooling duct 53 is connected to the air inlet 52. As shown in FIG. 3, a cooling fan 15 is provided on the left side of the drive pulley 12 in the transmission case 21. The cooling fan 15 is attached to the left end side of the crankshaft. Further, an outlet 37 is formed at the rear part of the transmission case body 22.

  When the cooling fan 15 rotates together with the crankshaft, air is taken from the outside of the saddle riding type vehicle into the transmission case 21 through the cooling duct 53 and the air inlet 52. The air taken into the transmission case 21 becomes cooling air and flows through the transmission case 21 from the front to the rear as shown by the arrows in FIG. Spill to Cooling air flowing in the transmission case 21 is blown onto the belt 14 and the centrifugal clutch, thereby cooling the belt 14 and the centrifugal clutch. Cooling air that has flowed out of the transmission case 21 from the outlet 37 is discharged to the outside of the saddle-ride type vehicle through an exhaust path 63 and an exhaust port 64 (see FIG. 1) formed in the vicinity of the gear box 61. The

  FIG. 4 mainly shows the left side surface of the transmission case body 22 of the transmission case 21 according to the embodiment of the present invention. FIG. 5 mainly shows the right side surface of the transmission case main body 22. The transmission case 21 is a case that accommodates the belt type continuously variable transmission 11 and the centrifugal clutch. The transmission case 21 is disposed on the left side of the engine unit 1 and behind the engine 2. The transmission case 21 includes a transmission case body 22 and a transmission case cover 51. Both the transmission case main body 22 and the transmission case cover 51 are made of a metal material such as aluminum.

  As shown in FIG. 4, the transmission case body 22 includes a front wall portion 23, an upper wall portion 24, a rear wall portion 25, a lower wall portion 26, and a side wall located on the inner side in the vehicle width direction of the saddle riding type vehicle, that is, on the right side. It has a portion 27 and is formed in a substantially box shape that is open on the outside in the vehicle width direction of the saddle riding type vehicle, that is, on the left side. A crankshaft insertion hole 28 through which the crankshaft is inserted is formed at the front portion of the side wall portion 27, and a driven shaft insertion hole 29 through which the driven shaft is inserted is formed at the rear portion of the side wall portion 27. .

  Further, as shown in FIG. 5, a crankcase forming portion 31 is formed on the right surface side of the side wall portion 27 and in a region where the crankshaft insertion hole 28 is formed in the front portion of the side wall portion 27. The crankcase forming part 31 forms the left part of the crankcase 3 as described above. The crankcase forming portion 31 is formed in a substantially cylindrical shape extending rightward from the side wall portion 27 of the transmission case main body 22. A mating surface 33 is formed at the right end of the crankcase forming portion 31 to be mated with the other crankcase forming 55.

  Further, a gear box mounting portion 35 is formed in a region on the right surface side of the side wall portion 27 of the transmission case main body 22 and the driven shaft insertion hole 29 in the rear portion of the side wall portion 27. The gear box mounting portion 35 is a portion for mounting the gear box 61. A gear box mounting surface 36 for mounting a gear box case 62 (see FIG. 1) that forms the outer shell of the gear box 61 is formed in the gear box mounting portion 35.

  Further, an outlet 37 for allowing the cooling air described above to flow out is formed in the rear part of the side wall part 27 of the transmission case main body 22. Further, on the right side of the side wall portion 27, in the vicinity of the gear box mounting portion 35, a wind exhaust path forming portion 38 is formed. As shown in FIG. 1, when the gear box 61 is attached to the gear box attaching portion 35, the exhaust air path forming portion 38 is covered with a part of the gear box case 62. As a result, a wind exhaust path 63 is formed on the right side of the rear portion of the side wall 27 of the transmission case body 22. In addition, the outlet 37 communicates with the upper end side of the exhaust path 63. Further, an air exhaust port 64 that opens the lower end side of the air exhaust path 63 to the outside of the saddle riding type vehicle is formed in the lower portion of the gear box case 62.

  As shown in FIG. 5, a corrugated portion 41 is formed between the crankcase forming portion 31 and the gear box mounting portion 35 in the side wall portion 27 of the transmission case main body 22. Here, FIG. 6 shows a cross section of the transmission case main body 22 as seen from the direction of arrows VI-VI in FIG. As shown in FIG. 6, in the corrugated portion 41 of the side wall portion 27, the side wall portion 27 itself is repeatedly curved in the left-right direction (vehicle width direction) so as to draw a wave traveling upward or downward. In FIG. 6, when the portion curved to protrude to the left side is referred to as a mountain, and the portion curved to protrude to the right side is referred to as a valley, in this embodiment, five peaks are formed in the corrugated portion 41, Four valleys are formed.

  Moreover, as shown in FIG. 3, the peak and trough of the wave in the waveform portion 41 extend linearly in the front-rear direction of the saddle riding type vehicle. Specifically, the straight line connecting the tops of the wave peaks in the corrugated part 41 and the straight line connecting the bottoms of the wave troughs in the corrugated part 41 extend linearly in the longitudinal direction of the saddle riding type vehicle. . Further, the peaks and valleys of the wave in the corrugated portion 41 extend in parallel with a straight line connecting the rotation center point A of the drive pulley 12 and the rotation center point B of the driven pulley 13. Specifically, the straight line connecting the tops of the wave peaks in the corrugated part 41 and the straight line connecting the bottoms of the wave valleys in the corrugated part 41 are respectively the rotation center A of the drive pulley 12 and the rotation of the driven pulley 13. It extends in parallel with a straight line connecting the center point B of the.

  Further, as shown in FIG. 5, a portion of the peripheral wall portion 32 of the crankcase forming portion 31 facing rearward is repeatedly bent substantially in the front-rear direction so as to draw a wave that the peripheral wall portion 32 itself moves upward or downward. The corrugated portion 42 is formed. And the wave peak in the waveform part 42 of the surrounding wall part 32 of the crankcase formation part 31 and the wave peak in the waveform part 41 of the side wall part 27 of the transmission case main body 22 are mutually connected, and are formed continuously. ing. Similarly, the wave trough in the corrugated portion 42 and the wave trough in the corrugated portion 41 are connected to each other and are formed continuously.

  On the other hand, the transmission case cover 51 shown in FIG. 2 covers a portion opened to the left side in the transmission case main body 22. The transmission case cover 51 is formed with an air inlet 52 for taking the cooling air described above into the transmission case 21.

  As shown in FIG. 4, a cover attachment surface 45 is formed on the left end side edge of the transmission case body 22, and the transmission case cover 51 is attached to the cover attachment surface 45 using bolts or the like. The left side surface of the side wall portion 27 of the transmission case main body 22 is provided with two columnar or cylindrical cover support portions 46 extending in the left direction, and the front ends of the cover support portions 46 are connected to the transmission case cover 51. Connect using bolts. The transmission case cover 51 is firmly fixed to the transmission case main body 22 by attaching an edge of the transmission case cover 51 to the cover mounting surface 45 of the transmission case main body 22 and connecting the center portion to each cover support portion 46.

  Further, on the left surface of the side wall 27 of the transmission case main body 22, a plate-shaped reinforcing portion 47 that rises in the left direction is provided between two adjacent cover support portions 46. The reinforcing portion 47 has a function of increasing the rigidity of the transmission case 21 by reinforcing each cover support portion 46. Further, as shown in FIG. 3, the cover support portions 46 and the reinforcing portions 47 are arranged along wave peaks or valleys in the corrugated portion 41 of the side wall portion 27.

  As described above, in the transmission case 21 according to the embodiment of the present invention, the corrugated portion 41 is formed on the side wall portion 27 of the transmission case main body 22. Thereby, the transmission case 21 has the following effects.

  That is, as shown in FIG. 7, when a plate-like member is repeatedly bent in the left-right direction so as to draw a wave traveling upward or downward, the member has a high rigidity in the front-rear direction and a rigidity in the left-right direction. Become. Therefore, by forming the corrugated portion 41 that is repeatedly curved in the left-right direction so as to draw a wave traveling in the upward or downward direction on the side wall portion 27 of the transmission case body 22, the rigidity in the front-rear direction of the transmission case 21 and the left-right direction Stiffness can be increased.

  In the engine unit 1, the cylinder 4 of the engine 2 is greatly inclined forward as shown in FIG. 1, so that the direction of the force that the crankcase 3 receives from the crankshaft is backward. And since the transmission case 21 is arrange | positioned at the back of the engine 2, the force of this back direction is added to the transmission case 21. FIG. In addition, a load generated by power transmission or shift by the belt type continuously variable transmission 11 is applied to the transmission case 21 in the front-rear direction. Since the side wall portion 27 of the transmission case main body 22 in which the corrugated portion 41 is formed has high rigidity in the front-rear direction, it is possible to prevent the transmission case 21 from being deformed by applying such a rearward or front-rear direction force. it can.

  Further, as shown in FIG. 4, the wall surface of the side wall portion 27 of the transmission case body 22 is wider than the wall surface of the other wall portion included in the transmission case 21 or the wall surface of each wall portion included in the crankcase 3. Has an area. Therefore, if the corrugated portion 41 is not formed on the side wall portion 27 and the side wall portion 27 is formed in a simple flat plate shape having a uniformly flat surface, the side wall portion 27 is subjected to the vibration of the engine 2 in the left-right direction. Vibrate. The vibration of the side wall 27 emits a sound as if the drum of the drum vibrates and emits a sound, which becomes noise. However, in the transmission case 21 according to the embodiment of the present invention, since the corrugated portion 41 is formed on the side wall portion 27, the rigidity in the left-right direction is high as described above. Therefore, it is possible to suppress the side wall portion 27 from vibrating in the left-right direction due to the vibration of the engine 2. As a result, noise due to vibration of the side wall portion 27 can be reduced.

  Further, the bending strength in the left-right direction of the transmission case 21 can be increased by the corrugated portion 41 of the side wall portion 27.

  Thus, since the rigidity of the transmission case 21 can be increased by the corrugated portion 41 formed on the side wall portion 27, it is not necessary to form ribs on the transmission case 21, or the number of ribs formed on the transmission case 21 is greatly increased. Can be reduced. As a result, the transmission case 21 can be lightened. Therefore, the weight of the engine unit 1 can be reduced.

  Further, in the transmission case 21 according to the embodiment of the present invention, the wave peaks and valleys in the corrugated portion 41 formed on the side wall portion 27 are linear in the longitudinal direction of the saddle riding type vehicle as shown in FIG. The drive pulley 12 extends parallel to a straight line connecting the rotation center point A of the drive pulley 12 and the rotation center point B of the driven pulley 13. That is, the extending direction of the peak and valley of the wave coincides with the flow direction of the cooling air. Therefore, by setting the extending direction of the wave peaks and valleys in this way, it is possible to suppress the cooling air from hitting the wave peaks or valleys in the corrugated portion 41 to disturb or prevent the flow of the cooling air. And a smooth flow of cooling air can be created. As a result, the cooling effect of the contents in the transmission case 21, that is, the belt 14 and the centrifugal clutch can be enhanced. Thereby, the lifetime of the belt 14 etc. can be extended.

  Further, in the transmission case 21 according to the embodiment of the present invention, as shown in FIG. 5, a corrugated portion 42 is also formed on a part of the peripheral wall portion 32 of the crankcase forming portion 31, and a wave peak in the corrugated portion 42 is formed. The peaks and valleys of the wave in the corrugated portion 41 formed on the side wall portion 27 are connected to each other. Thereby, the rigidity of the crankcase forming part 31 can be increased, and the rigidity of the side wall part 27 can be further increased. Moreover, noise can be further reduced.

  Further, in the transmission case 21 according to the embodiment of the present invention, as shown in FIG. 3, the cover support portions 46 and the reinforcing portions 47 are arranged along wave peaks or valleys in the corrugated portion 41 of the side wall portion 27. Therefore, it can be suppressed that the cooling air blows against the cover support part 46 or the reinforcing part 47 and the flow is hindered. As a result, a smooth flow of cooling air can be ensured, and since the structure for supporting the transmission case cover 51 on the transmission case body 22 is provided, it is possible to prevent the cooling effect of the belt 14 and the centrifugal clutch from being lowered. Can do.

  In the embodiment described above, the case where the corrugated portion 41 (42) is formed by repeatedly curving the side wall portion 27 (the peripheral wall portion 32) is described as an example, but the present invention is not limited to this. The side wall portion 27 (the peripheral wall portion 32) may be bent repeatedly to form the corrugated portion 41 (42). That is, the wave shape of the waveform portion 41 (42) is not limited to a sine wave shape, and may be a rectangular wave shape or a sawtooth wave shape.

  Further, the number of peaks and valleys, the height of peaks and valleys (wave amplitude), and the period of waves in the wave of the waveform section 41 (42) are not limited to those illustrated. Further, the height or period of the peaks or valleys in the wave of the waveform section 41 (42) may not be constant.

  Further, although the wave peaks and valleys in the corrugated portion 41 extend in the front-rear direction, the wave peaks and valleys may extend in the horizontal direction or not in the horizontal direction. Further, as another embodiment of the transmission case of the present invention, the direction of the wave of the corrugated portion 41 and the direction of expansion of the valleys is within a range that does not interfere with the flow of the cooling air, and the rotation center point A of the drive pulley 12 and the driven pulley 13 It is also possible to adopt a configuration in which the tilt is made with respect to a straight line connecting the rotation center point B. However, as described above, the wave and valley extending directions of the corrugated portion 41 are parallel to the straight line connecting the rotation center point A of the drive pulley 12 and the rotation center point B of the driven pulley 13. Thus, a high cooling effect of the belt or the like can be obtained with certainty.

  In the above-described embodiment, the corrugated portion is formed between the crankcase forming portion 31 and the gear box mounting portion 35 in the side wall portion 27 and in the portion facing the rear in the peripheral wall portion of the crankcase forming portion 31. However, the corrugated portion may be formed only between the crankcase forming portion 31 and the gear box mounting portion 35 in the side wall portion 27.

  In the above-described embodiment, the case where two cover support portions 46 and one reinforcing portion 47 are provided in the transmission case main body 22 has been described as an example. However, the cover support portion 46 and The number of reinforcing portions 47 may be increased. In this case, the reinforcing portions 47 are arranged so that the extending direction thereof coincides with the flow direction of the cooling air.

  In the above-described embodiment, each cover support portion 46 and the reinforcing portion 47 are arranged on the top of the wave peak in the corrugated portion 41 of the side wall portion 27, but each cover support portion 46 and the reinforcing portion 47 are arranged on the corrugated portion 41. You may arrange on the bottom of the wave valley in. By disposing each cover support portion 46 and the reinforcing portion 47 on the bottom of the wave valley in the corrugated portion 41, the rigidity of the transmission case main body 22 can be increased.

  The transmission case of the present invention can be widely applied to scooter type motorcycles, motor tricycles, and the like.

  Further, the present invention can be appropriately changed without departing from the spirit or idea of the invention which can be read from the claims and the entire specification, and a transmission case with such a change is also included in the technical idea of the present invention. included.

DESCRIPTION OF SYMBOLS 1 Engine unit 2 Engine 3 Crankcase 11 Belt type continuously variable transmission 12 Drive pulley 13 Driven pulley 14 Belt 15 Cooling fan 21 Transmission case 22 Transmission case main body (case main body)
23 Front wall part 24 Upper wall part 25 Rear wall part 26 Lower wall part 27 Side wall part 28 Crankshaft insertion hole 29 Driven shaft insertion hole 31, 55 Crankcase forming part 32 Peripheral wall part 35 Gear box attachment part 37 Outlet 41, 42 Corrugated part 46 Cover support part 47 Reinforcement part 51 Transmission case cover (cover)
52 Air intake port 53 Cooling duct 61 Gear box

Claims (4)

In a unit swing type engine unit provided in a straddle-type vehicle and having an engine, a belt-type continuously variable transmission that transmits power of the engine to an axle of a rear wheel, and a gear box, the belt-type continuously variable transmission is A transmission case for housing,
The front wall portion, the upper wall portion, the rear wall portion, the lower wall portion, and a crankshaft insertion hole through which the crankshaft is inserted is formed in the front portion, and is located on the inner side in the vehicle width direction of the saddle riding type vehicle. A case main body having a side wall portion formed with a driven shaft insertion hole through which the driven shaft is inserted, and the vehicle width direction outer side being opened;
A crank that is formed in a region of the side wall portion facing inward in the vehicle width direction and in the region where the crankshaft insertion hole is formed in the front portion of the side wall portion, and forms a part of the crankcase of the engine A case forming part;
A gear box mounting portion for mounting the gear box, formed on the side of the side wall portion facing the vehicle width direction inside and in the region where the driven shaft insertion hole is formed in the rear portion of the side wall portion ;
A cover that covers a portion of the case body that is open to the outside in the vehicle width direction ;
Between the crankcase forming portion and the gear box mounting portion in the side wall portion, a corrugated portion that is repeatedly curved or bent so as to draw a wave that the side wall portion itself proceeds upward or downward is formed ,
A surface of the side wall portion facing outward in the vehicle width direction is provided with at least two columnar or cylindrical cover support portions that extend outward in the vehicle width direction and support the cover on the front end side. ,
A plate-shaped reinforcing portion that rises toward the outside in the vehicle width direction is provided between the two cover support portions adjacent to each other on the surface facing the vehicle width direction outside of the side wall portion,
The cover case and the reinforcing portion are arranged along wave peaks or troughs in the corrugated portion of the side wall portion .   The transmission case according to claim 1, wherein peaks and valleys of waves in the corrugated portion of the side wall portion extend linearly in the front-rear direction of the saddle riding type vehicle.   Wave peaks and valleys in the corrugated portion of the side wall portion are parallel to a straight line connecting a rotation center point of a drive pulley provided on the crankshaft and a rotation center point of a driven pulley provided on the driven shaft. The transmission case according to claim 2, wherein the transmission case extends.   The crankcase forming portion is formed in a substantially cylindrical shape extending inward in the vehicle width direction, and the peripheral wall portion itself advances upward or downward in a portion facing rearward in the peripheral wall portion of the crankcase forming portion. Waveforms that are repeatedly curved or bent so as to draw a wave are formed, and the wave crests and valleys in the corrugated part of the side wall part and the wave peaks and troughs in the corrugated part of the peripheral wall part are connected to each other. The transmission case according to any one of claims 1 to 3.

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