JP4640784B2 - Power unit provided with belt type transmission - Google Patents

Description

  The present invention relates to a power unit including an internal combustion engine and a belt-type transmission, and more particularly to a cooling structure for the power unit. The power unit is mounted on a vehicle, for example.

In a belt-type transmission that transmits the power of an internal combustion engine, in order to suppress the temperature rise of components such as a belt and a pulley due to heat transmitted from the internal combustion engine and frictional heat generated between the belt and a pulley. Then, forced cooling is performed by cooling air introduced from the outside into the case of the transmission. For example, in an engine unit composed of an engine and a V-belt type automatic transmission mounted on a motorcycle disclosed in Patent Document 1, a crankshaft is disposed in the transmission case, and is disposed on a side of the transmission case. A drive pulley, a driven pulley, and a V belt of the automatic transmission are housed in the belt chamber of the arranged belt case. Then, the outside air introduced into the belt chamber is cooled by the cooling fan constituted by the driven pulley and the driving pulley in which the fins are formed.
Japanese Patent Laid-Open No. 2002-21988 (FIG. 4)

  By the way, in the prior art, the belt case is formed with an opening through which a crankshaft having one end provided with a drive pulley passes, and the air that has cooled each part in the belt chamber is discharged to the outside through the opening. . The exhaust air from the opening is deflected by hitting a bearing portion that supports the crankshaft in the transmission case (corresponding to the crankcase), and then flows between the transmission case and the belt case.

  However, since the gap between the drive pulley and the transmission case and the gap between the transmission case and the belt case are both narrow, the air in the belt chamber is difficult to be discharged from the opening, and the exhaust air hits the transmission case. Since the portion is limited to the bearing portion that is an inner portion that is relatively close to the rotation center line of the crankshaft, an outer portion that is relatively far from the rotation center line of the crankshaft in the crankcase is effectively removed by the exhaust air. It is difficult to cool down.

  In addition, the outer portion is a portion where the oil blown by the rotating crankshaft adheres or the oil is stored and the oil in the crank chamber comes into contact. It is preferable to do.

The present invention has been made in view of such circumstances, and the inventions according to claims 1 to 4 are characterized in that the outer side of the crankcase or the outside of the crankcase is exhausted by the exhaust air discharged from the transmission case of the belt-type transmission device. The purpose is to cool the part and to promote the cooling of the oil in the crank chamber , and further to promote the cooling of the clutch in the transmission case. The invention according to claim 4, further aims to reduce the size of the power unit in the axial direction.

An invention according to claim 1 is an internal combustion engine including a crankcase that forms a crank chamber in which a crankshaft is housed in an atmosphere containing oil, and a drive pulley provided on a drive shaft driven by the crankshaft. A belt-type transmission device including a transmission case that forms a transmission chamber in which a driven pulley provided on a driven shaft, the drive pulley, and an endless belt stretched over the driven pulley are housed, and the transmission case In the power unit provided with the exhaust port for discharging the cooling air introduced into the transmission chamber to the outside, the clutch is housed in the transmission chamber with a rotation center line parallel to the rotation center line of the crankshaft. The clutch is opposed to the crankcase in the radial direction through the exhaust port, and the radial gap between the exhaust port and the clutch is in the axial direction. Wherein a small power unit than the width of the air discharge port.

According to this, the crankcase is cooled by the exhaust air from the exhaust port . In addition, since the clutch is disposed in the vicinity of the air exhaust port, and the air exhaust port is opened so that the crankcase can be seen in the radial direction, the clutch is cooled by the cooling air flowing toward the air exhaust port. The cooled cooling air is immediately discharged out of the transmission chamber through the air exhaust port. Furthermore, the discharge of the cooling air is promoted by the air flow having the swirl component generated by the rotation of the clutch, and the amount of exhaust air increases.

According to a second aspect of the present invention, in the power plant according to the first aspect, the crankcase has an outer portion positioned radially outward from a maximum rotation locus of the crankshaft in a side view, and The outlet of the wind port is a power unit that faces the outer portion in the flow direction of the exhaust air at the outlet .

According to this, the outer portion is a portion where the oil blown by the rotating crankshaft adheres or the oil is stored, so that the oil in the crank chamber comes into contact. The indoor oil is cooled.

According to a third aspect of the present invention, in the power plant according to the first or second aspect, the outlet of the exhaust port is located at a position not overlapping the driving pulley having the same rotation center line as the crankshaft in a side view. And facing the crankcase in the flow direction of the exhaust air at the outlet .

According to this, the air outlet that is not overlapped with the drive pulley in a side view has a diameter larger than that of the outer portion or the crankcase that is relatively far from the rotation center line of the crankshaft in the radial direction with respect to the crankcase. It occupies a position corresponding to the outward direction. The outer portion is a portion that comes into contact with the oil in the crank chamber, for example, the oil blown off by the crankshaft adheres or the oil is stored. For this reason, the outer portion can be cooled by the exhaust air from the exhaust port, and the oil in the crank chamber can be cooled through the outer portion.

According to a fourth aspect of the present invention, in the power unit according to the first or second aspect, in the case portion on the crankcase side of the transmission case, the driven case portion that overlaps the driven pulley in a side view has an axial direction. The drive side case portion that overlaps with the drive pulley as viewed in FIG. 3 protrudes to a position that overlaps the crank chamber at a position in the axial direction, and the exhaust port is provided in the driven case portion or in the axial direction. At a position closer to the crank chamber than the drive side case portion .

According to this, as compared with the case where the driven case portion protrudes on the opposite side of the crankcase side or does not overlap the crank chamber at the axial position, the transmission to the crankcase side with respect to the crankcase is achieved. The amount of protrusion of the case can be reduced. Further, since the air exhaust port exhausts the exhaust air to the external space that is located between the driven case portion and the crankcase in the radial direction and has low fluidity of the outside air, the outside portion or the outside of the crankcase that faces the external space The part is cooled by the exhaust air from the exhaust port.

According to invention of Claim 1, the following effect is show | played. That is, since the clutch is cooled by the cooling air flowing toward the exhaust port, and the cooling air after cooling the clutch is immediately discharged out of the transmission chamber through the exhaust port, the cooling of the clutch is promoted and the amount of air hitting the crankcase is increased. As a result, the cooling of the crankcase and the cooling of the oil are further promoted.

According to invention of Claim 2, the following effect is show | played. In other words, the outer portion of the crankcase is cooled by the exhaust air from the transmission chamber, and further cooling of the oil in the crank chamber is promoted.

According to invention of Claim 3, in addition to the effect of the invention of the cited claim, there exist the following effects. That is, the outer portion of the crankcase is cooled by the exhaust air from the transmission chamber, and further cooling of the oil in the crank chamber is promoted.

According to invention of Claim 4, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, since the amount of projection of the transmission case in the axial direction relative to the crankcase can be reduced, the power unit is reduced in size in the axial direction, and the outer or outer portion of the crankcase faces the external space where the outside air is less fluid Cooling is promoted.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
1 and 2, a power unit P to which the present invention is applied is mounted on a scooter type motorcycle as a vehicle. The power unit P is configured by integrating an internal combustion engine E, a belt type continuously variable transmission M as a belt type transmission device, a centrifugal clutch C as a clutch, and a gear type transmission mechanism as a speed reduction mechanism. The power generated by the internal combustion engine E is a continuously variable transmission M, a centrifugal clutch C, a gear type transmission mechanism R1 as a primary reduction mechanism, and a chain type as a secondary reduction mechanism to which the output of the transmission mechanism R1 is input. The power is transmitted to the rear wheels, which are the driving wheels as driving targets, in the order of the transmission mechanism R2.

  The internal combustion engine E mounted on the motorcycle in a horizontal arrangement in which the rotation center line L0 of the crankshaft 9 is directed in the left-right direction is an OHC type, water-cooled V-type 2-cylinder 4-stroke internal combustion engine, and is V-shaped. A pair of cylinders 1a and 1b arranged, and a crankcase 2 coupled to each cylinder 1a and 1b at the base end in the direction of cylinder axis L1a and L1b (hereinafter simply referred to as “cylinder axis direction”) A pair of cylinder heads 5a and 5b coupled to the cylinders 1a and 1b at the tip in the cylinder axial direction and integrated with the cylinders 1a and 1b, and a pair coupled to the cylinder heads 5a and 5b Provided with an engine body composed of the head covers 6a and 6b.

  In the specification or claims, the axial direction and the radial direction mean the direction of the rotation center line L0 of the crankshaft 9 and the radial direction around the rotation center line L0, respectively, unless otherwise specified. Side view means viewing from the axial direction. Further, in the embodiment, “up / down”, “front / rear”, and “left / right” mean up / down, front / rear, and left / right when the motorcycle is used as a reference, and the left / right direction matches the axial direction.

  Referring also to FIG. 3, the pair of first and second banks B1 and B2 constituting the V bank are mainly composed of a cylinder 1a and a cylinder 1b, respectively. More specifically, the first bank B1 as the front bank includes a cylinder 1a that has a cylinder axis L1a that is slightly tilted forward and obliquely upward, and is largely tilted forward, a cylinder head 5a, and a head cover 6a. The second bank B2 as the rear bank includes a cylinder 1b having a cylinder axis L1b slightly inclined rearward and obliquely upward, and a cylinder head 5b and a head cover 6b slightly inclined backward.

  A crankshaft 9 to which a piston 7 fitted to each cylinder 1a, 1b so as to be capable of reciprocating movement is connected via a connecting rod 8 is housed in a crank chamber 10 formed by the crankcase 2, and is paired with the crankcase 2. The main bearing 11 is rotatably supported. The crankcase 2 includes first and second crankcase portions 3 and 4 that are divided in the axial direction by a plane orthogonal to the rotation center line L0. In each crankcase portion 3, 4, the bearing portions 3 a, 4 a that support the crankshaft 9 via the main bearing 11 are thick portions that are thicker than the outer portion F (described later) and the outer portion (described later). is there.

  2 and 3, each cylinder head 5a, 5b, which is fastened together with the cylinders 1a, 1b to the crankcase 2 by the head bolt 12, has a combustion chamber 13 facing the piston 75 in the cylinder axial direction, and combustion An intake port 14 having a pair of intake ports opening in the chamber 13 and an exhaust port 15 having a pair of exhaust ports opening in the combustion chamber 13 are formed, and an ignition plug 16 facing the center of the combustion chamber 13 (FIG. 1). Is installed. Further, each cylinder head 5a, 5b is provided with a pair of intake valves 17 and a pair of exhaust valves 18 which open and close the pair of intake ports and the pair of exhaust ports, respectively. Each intake valve 17 and each exhaust valve 18 are respectively predetermined by a valve operating device 20 including a rocker arm 22 that is driven by a valve operating cam provided on a cam shaft 21 that is rotationally driven by the power of the crankshaft 9 to swing. It is opened and closed at the timing.

  Referring to FIGS. 1 and 3, an intake device 25 including a pair of throttle bodies 26 provided with a throttle valve 26 a is disposed in the bank space, and the intake air guided by the intake devices 25 and the throttle body 26 are attached. The air-fuel mixture formed by the fuel supplied from the fuel injection valve 27 is sucked into the combustion chamber 13 through the intake port 14. The combustion gas generated in the combustion chamber 13 drives the piston 7 with the pressure, and then is discharged to the outside as an exhaust gas through an exhaust device having an exhaust pipe (not shown) connected to the exhaust port 15.

  Referring to FIG. 2, the crankcase cover 28 coupled to the left side of the first crankcase part 3 and the first crankcase part 3 include an auxiliary machine room 30 in which the AC generator 29 is housed and the auxiliary machine room. An oil tank 31 is formed adjacent to the rear of 30. A continuously variable transmission M is arranged on the right side of the second crankcase portion 4.

  1 and 2, the lubrication system provided in the internal combustion engine E is a dry sump type equipped with an oil pump 32 including a feed pump (not shown) driven by the power of the crankshaft 9 and a scavenging pump 32a. Each lubrication system is an oil tank 31, a water-cooled oil cooler 33 that cools oil discharged from the feed pump that discharges oil sucked from the oil tank 31, an oil filter 34, and each lubrication of the internal combustion engine E Each scrubbing pump 32a that collects oil after lubricating the parts, each lubricating part of the internal combustion engine E for guiding the oil between these lubricating system members, and from the main gallery 35 into which the oil from the oil filter 34 flows And a number of oil passages for guiding the oil to

  Then, the oil after lubricating each lubricated portion including sliding parts such as the main bearing 11, the piston 7, and the valve gear 20 falls or flows down in the cylinders 1a, 1b or the crankcase 2 to the crank chamber 10. get together. In the crank chamber 10, the oil collects in an oil reservoir 10 b formed by the case bottoms 3 b and 4 b of the crankcase 2, and the oil in the oil reservoir 10 b is collected by the scavenging pump 32 a and stored in the oil tank 31. Therefore, the crank chamber 10 is filled with an atmosphere containing oil.

  Referring to FIGS. 1 to 3, the crankcase 2 is an outer portion that is a portion located radially outward from the maximum rotation locus of the crankshaft 9 (hereinafter simply referred to as “rotation locus”) in a side view. The portion F includes case bottom portions 3b and 4b below the rotation locus and case rear portions 3c and 4c behind the rotation locus. Here, the rotation locus is a locus defined by the crank web 9a of the crankshaft 9 in this embodiment. Further, the outer portion F is a portion relatively distant from the rotation center line L0 with respect to the bearing portions 3a and 4a constituting the inner portion which is a portion relatively close to the rotation center line L0 in the crankcase 2. This is a part of an outer portion (hereinafter simply referred to as “outer portion”) positioned radially outward from the bearing portions 3a and 4a.

  Case bottom portions 3b and 4b and case rear portions 3c and 4c are most of the portions excluding specific portions such as a boss portion where the crankcase portions 3 and 4 are joined, and are thicker than the bearing portions 3a and 4a. Is a small thin part. The case rear portions 3c and 4c have radial case portions 3c1 and 4c1 that face the crankshaft 9 in the radial direction and define the crank chamber 10 in the radial direction.

  Referring to FIGS. 2 and 3, in the crank chamber 10, the rear part, which is close to the oil tank 31, communicates with an overflow hole 36 provided in the oil tank 31, and the oil overflowing from the oil tank 31 is stored in the oil reservoir 31. An overflow passage 37 leading to 10b is formed integrally with the first and second crankcase portions 3 and 4 between the radial case portions 3c1 and 4c1 and the radial case portions 3c1 and 4c1 and the crankshaft 9 in the radial direction. It is formed between the partition walls 38. Since the overflow passage 37 is formed by the partition wall 38, the generation of power loss due to the collision between the oil overflowing from the oil tank 31 and the crankshaft 9 is prevented. Note that only the overflow hole 36 may be provided without providing the overflow passage 37 and the partition wall 38.

  Thus, in this embodiment, the oil overflowing from the oil tank 31 is in contact with the case rear portions 3c and 4c, and the oil reservoir 10b is formed at the case bottom portions 3b and 4b to store the oil. Furthermore, when the overflow passage 37 and the partition wall 38 are not provided as described above, the oil blown off by the rotating crankshaft 9 adheres to the case rear portions 3c and 4c. Therefore, the case rear portions 3 c and 4 c and the case bottom portions 3 b and 4 b are portions where the oil contacts in the crank chamber 10.

The continuously variable transmission M will be mainly described with reference to FIGS.
The continuously variable transmission M includes a drive shaft 40 that is rotationally driven by the internal combustion engine E, a drive pulley 41 that is drivingly connected to the drive shaft 40 so as to be integrally rotatable, a rotary clutch that is rotatably supported by the driven shaft 42, and a centrifugal clutch. A driven pulley 43 coupled to the driven shaft 42 via C in a rotatable manner; a driving pulley 41; a belt 44 comprising an endless V-belt stretched over the driven pulley 43; and a driving pulley 41 according to the engine rotational speed. And a transmission ratio control means for controlling the transmission ratio by changing the winding radius of the belt 44 in the driven pulley 43, and a transmission case 45 forming the transmission chamber 48.

  The transmission chamber 48 houses a speed change mechanism including a drive shaft 40, a driven shaft 42, both pulleys 41 and 43, a belt 44, and the speed ratio control means, and a centrifugal clutch C. Further, the drive shaft 40 has the same rotation center line as the crankshaft 9, and the rotation center line L2 of the driven shaft 42 is parallel to the rotation center line L0. The driven shaft 42 is rotatably supported by first and second transmission case portions 46 and 47, which will be described later, with the driven pulley 43 and the centrifugal clutch C interposed therebetween. Further, the transmission mechanism R1 is provided between the driven shaft 42 and the first transmission case portion 46. It is rotatably supported by the first crankcase portion 3 with the gear 49 constituting it interposed. As a result, the driven pulley 43 and the centrifugal clutch C are arranged in series in the axial direction with respect to the driven shaft 42 and share the rotation center line L2.

  The drive pulley 41 includes a fixed sheave 41a that is coupled to the drive shaft 40 so as not to move relative to the drive shaft 40, and a movable sheave 41b that is movable in the axial direction with respect to the fixed sheave 41a. A belt 44 is provided on both sheaves 41a and 41b. It is clamped in the axial direction. The driven pulley 43 includes a fixed sheave 43a that can rotate integrally with the driven shaft 42 via the centrifugal clutch C, and a movable sheave 43b that is drivingly connected to the fixed sheave 43a so as to be movable in the axial direction.

  The transmission ratio control means applies a plurality of centrifugal weights 51 whose positions in the axial direction are changed by a cam plate 50 fixed to the drive shaft 40, and a resilient force in a direction in which the belt 44 is fastened to the movable sheave 43b. And a spring 52. In the drive pulley 41, each centrifugal weight 51 is moved in the radial direction by the centrifugal force generated according to the rotational speed of the crankshaft 9, so that the movable sheave 41b pressed by the centrifugal weight 51 is moved in the axial direction. The winding radius is changed. Due to the change in tension of the belt 44 generated at this time, in the driven pulley 43, the movable sheave 43b moves in the axial direction against or against the elastic force of the spring 52, and the winding radius is increased. Be changed. The winding radius of the belt 44 in each pulley 41, 43 is the minimum winding radius in the driving pulley 41 when the engine rotational speed is low, as shown by the solid line in FIG. As the engine rotational speed increases from the maximum winding radius, the maximum winding radius at the driving pulley 41 and the minimum at the driven pulley 43 when the engine rotational speed is high, as shown by a two-dot chain line in FIG. The speed ratio of the continuously variable transmission M is automatically and continuously changed in accordance with the engine rotational speed.

  A transmission case 45 separate from the crankcase 2 is divided in the axial direction into a first transmission case portion 46 coupled to the second crankcase portion 4 by bolts, and to the right of the first transmission case portion 46. It is comprised from the 2nd transmission case part 47 couple | bonded, and both case parts 46 and 47 are couple | bonded by many volt | bolts. The crankshaft 9 penetrates the second crankcase portion 4 and the first transmission case portion 46, and a shaft end portion protruding rightward from the first transmission case portion 46 in the transmission chamber 48 constitutes the drive shaft 40. Thus, the first transmission case portion 46 forming the transmission chamber 48 is a separate member from the second crankcase portion 4 disposed adjacent to the vicinity of the first transmission case portion 46, Since a gap serving as a heat insulation space is formed between the case portions 4 and 46, heat from the crankcase 2 is suppressed from being transmitted to the transmission case 45, and the belt 44 in the transmission chamber 48 and the like. The temperature rise of the speed change mechanism is suppressed, and the durability of the belt 44 and the like is improved.

  The centrifugal clutch C constituting the starting clutch includes a drive plate 61 as an input side rotating member that rotates integrally with the fixed sheave 43a, and a clutch outer 62 as an output side rotating member that is coupled to the driven shaft 42 so as to be integrally rotatable. And a plurality of centrifugal weights 63 supported by the drive plate 62 in a swingable manner. Then, when the driven pulley 43 rotates beyond the rotational speed corresponding to the idling rotational speed of the internal combustion engine E, the centrifugal weight that blows off by the centrifugal force against the elastic force of the clutch spring and presses the clutch outer 62. The drive plate 61 and the clutch outer 62 are connected via 63, and the centrifugal clutch C enters a connected state in which the drive plate 61 and the clutch outer 62 rotate integrally.

  The centrifugal clutch C is disposed so as to overlap the crank chamber 10 and the crankcase 2 at a position in the axial direction. The clutch outer 62 that covers the drive plate 61 and the centrifugal weight 63 radially outwardly about the rotation center line L2 includes a bowl-shaped main body 62a, and an annular member 62b fixed to the outer peripheral surface of the main body 62a. Consists of

Next, the cooling structure of the power unit P will be described.
Referring to FIG. 2, the speed change mechanism and the centrifugal clutch C are forcibly cooled by the cooling fan constituted by the driven pulley 43 using the outside air introduced into the transmission chamber 48 as cooling air. Specifically, the second transmission case portion 47 and the cover 71 coupled to the second transmission case portion 47 form an air guide chamber 72 that guides outside air into the transmission chamber 48. The cover 71 is provided with an intake 71 a for introducing outside air into the air guide chamber 72.

  The stationary sheave 43a and the movable sheave 43b of the driven pulley 43 constitute a radial flow type cooling fan by a large number of fins 43a1 and 43b1 provided on the back surface thereof. Then, due to suction by the fixed sheave 43a, outside air flows into the air guide chamber 72 through the intake port 71a, passes through the filter element 73, and then enters the transmission chamber 48 from the inlet 47a formed in the second transmission case portion 47. Flow into. Further, the cooling sheave in the transmission chamber 48 is pumped toward the drive pulley 41 by the movable sheave 43b.

  Further, in the drive pulley 41, the fixed sheave 41a forms a radial flow type cooling fan by a large number of fins 41a1 provided on the back surface thereof, and the air passage 41a2 including a large number of through holes in the boss portion of the fixed sheave 41a. (See also FIG. 1). As a result, the air in the transmission chamber 48 sucked into the fixed sheave 41a is guided to the space between the first transmission case portion 46 adjacent to the crankcase 2 and the drive pulley 41 through the air passage 41a2, so that the transmission case 45 Cooling of the fixed sheave 41a, which is the portion of the drive pulley 41 adjacent to the crankcase 2 that is at a higher temperature, is promoted.

  Furthermore, the transmission case 45 is provided with first and second air exhaust ports 80 and 81 for discharging the cooling air in the transmission chamber 48 to the outside as exhaust air. Referring also to FIG. 1, the first air outlet 80 is located between the drive shaft 40 and the driven shaft 42 in a side view and is located in a region surrounded by the belt 44, and both rotation center lines L 0. , L2 at a position that intersects the plane. The second exhaust port 81 is located on the opposite side of the exhaust port 80 with the driven shaft 42 and the centrifugal clutch C interposed therebetween, and discharges cooling air to the outside.

  Referring to FIGS. 1 and 4, the air exhaust port 80 is provided in a portion of the first transmission case portion 46 as a case portion on the crankcase side in the transmission case 45 that is opposed to the second crankcase portion 4 in the radial direction. Then, the air is opened to the external space S between the crankcase 2 and the transmission case 45, and the cooling air after cooling the transmission mechanism is discharged mainly toward the second crankcase portion 4. The outer space S is defined on the one side in the axial direction by the second crankcase portion 3 including the oil tank 31, and is defined by the first transmission case portion 46 on the other side in the axial direction. This is a space that is defined mainly by the radial case portion 4c1 at the front, which is also the direction, and by a rising portion 46c, which will be described later, at the rear, which is also the outside in the radial direction. The radial case portion 4c1 is the case rear portion 4c in which traveling wind does not easily flow when the motorcycle is traveling, and faces the external space S.

  2 and 3, the first transmission case portion 46 includes a drive side case portion 46a that overlaps with the drive pulley 41 when viewed in the axial direction, and a driven side case portion that overlaps with the driven pulley 43 when viewed in the axial direction. 46b. The driven case portion 46b is configured by a protruding portion that protrudes to a position overlapping the crank chamber 10 at a position in the axial direction with respect to the driving side case portion 46a. The air exhaust port 80 is provided in the rising portion 46c with respect to the driving side case portion 46a in the driven side case portion 46b, and therefore is located closer to the crank chamber 10 than the driving side case portion 46a. The rising portion 46c is formed by a cylindrical wall having an axis substantially parallel to the rotation center line L2 in the driven case portion 46b, and is a portion facing the radial case portion 4c1 in the radial direction. Therefore, the air exhaust port 80 is opposed to the radial case portion 4c1 in the radial direction, and the entire air exhaust port 80 is in a position facing the radial case portion 4c1 from the transmission chamber 48 in the radial direction.

  An air exhaust port 80 constituted by a through-hole penetrating the driven case portion 46b in the radial direction is formed between an inlet 80a that is an opening on the transmission chamber 48 side, the crankcase 2 and the first transmission case portion 46. And an outlet 80b that is an opening on the external space S side. The inlet 80a and the outlet 80b are opposed to the radial case portion 4c1 in the flow direction of the exhaust air at the outlet 80b, and do not overlap the drive pulley 41 in a side view and have a diameter relative to the second crankcase portion 4. It is located outward in the direction and further overlaps with the radial case portion 4c1 at the axial position. Here, the flow direction is a main flow direction of exhaust air.

  Referring to FIG. 4, the clutch outer 62, which is the maximum outer diameter portion of the centrifugal clutch C, faces the crankcase 2 through the exhaust port 80 in the radial direction and is disposed in the vicinity of the exhaust port 80. More specifically, the radial interval W1 between the clutch outer 62 and the air exhaust port 80 is smaller than the width W2 of the air exhaust port 80 in the axial direction, and more than the width W3 of the centrifugal clutch C in the axial direction. small. Further, the clutch outer 62 is at a position that partially overlaps the air exhaust port 80 at the position in the axial direction on the side opposite to the driven pulley 43 in the axial direction with respect to the air exhaust port 80. As described above, the clutch outer 62 is disposed in the vicinity of the exhaust port 80, so that the centrifugal clutch C efficiently receives the cooling air toward the exhaust port 80 in the transmission chamber 48. Further, the discharge of the exhaust air is promoted by the air flow having the swirling component that is induced by the rotating clutch outer 62.

  In the first transmission case portion 46, a rib 82 protruding in a bowl shape toward the radial case portion 4c1 is provided on the upper edge of the edge portion defining the air outlet 80. In the portion of the rib 82, the space between the rising portion 46c and the radial case portion 4c1 is reduced in the external space S, so that the upward flow of exhaust air is restricted and the flow of exhaust air downward is promoted. Furthermore, the rib 82 prevents or suppresses the entry of water into the transmission chamber 48 through the air outlet 80.

  Referring to FIGS. 1 and 4, the air exhaust port 80 is located at a position overlapping the outer peripheral edge of the movable sheave 43 b in a side view and when the winding radius of the belt 44 on the driven pulley 43 is maximized, the movable sheave 43 b Is in a position approaching in the axial direction until the distance is substantially equal to the distance W (see the movable sheave 43b indicated by a two-dot chain line in FIG. 4). For this reason, during the high speed operation of the internal combustion engine E in which the heat generation amount of the internal combustion engine E increases and the crankcase 2 becomes higher in temperature, discharge of the cooling air is promoted by the movable sheave 43b, and the cooling air in the transmission chamber 48 is The fluidity of the exhaust air is improved, the amount of exhaust air is further increased, and cooling is promoted.

Next, operations and effects of the embodiment configured as described above will be described.
The outlet 80b of the exhaust outlet 80 provided in the transmission case 45 is opposed to the radial case portion 4c1 of the case rear portion 4c of the crankcase 2 in the flow direction of the exhaust air at the outlet 80b or in a side view. It is positioned so as not to overlap with the drive pulley 41 having the same rotation center line L0 as the crankshaft 9 and faces the crankcase 2 in the flow direction of the exhaust air at the outlet 80b. The direction case portion 4c1 is cooled. Further, the outer portion F including the radial case portion 4c1 is a portion where the oil in the crank chamber 10 comes into contact with the oil blown off by the rotating crankshaft 9 or the oil is stored. Therefore, the oil in the crank chamber 10 is cooled through the radial case portion 4c1. As a result, the outer portion F of the crankcase 2 is cooled by the exhaust air from the transmission chamber 48, and further cooling of the oil in the crank chamber 10 is promoted.

  Moreover, since the bearing portions 3a and 4a are thick portions of the crankcase 2, when exhaust air is applied to the bearing portions 3a and 4a, the oil in the crankcase 2 is cooled through the bearing portions 3a and 4a. Although the effect is low, the outer portion F or the outer portion including the radial case portion 4c1, which is generally thinner than the bearing portions 3a and 4a, is cooled by the exhaust air from the exhaust port 80. Therefore, the oil in the crank chamber 10 is effectively cooled through the outer portion F or the outer portion.

  The driven case portion 46b of the first transmission case portion 46 protrudes to a position overlapping the crank chamber 10 in the axial direction with respect to the drive side case portion 46a, and the exhaust port 80 is provided in the driven case portion 46b. Or provided in a position closer to the crank chamber 10 than the drive side case portion 46a in the axial direction, the driven side case portion 46b protrudes on the opposite side to the crank case side or the crank chamber 10 Compared with the case where it does not overlap with the crankcase 2, the amount of projection of the transmission case 45 to the crankcase side (right side) can be reduced. Further, since the air exhaust port 80 exhausts the exhaust air to the external space S between the driven case portion 46b and the crankcase 2 in the radial direction and having low fluidity of the outside air, the air exhaust port 80 faces the external space S, and The case rear portion 4c including the radial case portion 4c1, which is a portion where the traveling wind is difficult to hit because of the rear portion 4c, is cooled by the exhaust air from the exhaust port 80. As a result, the amount of projection of the transmission case 45 in the axial direction relative to the crankcase 2 can be reduced, so that the power unit P can be reduced in size in the axial direction and Cooling of the case rear portion 4c is promoted. Furthermore, since the oil tank 31 faces the external space S, the oil tank 31 is also cooled by the exhaust air flowing through the external space S.

  The clutch outer 62 of the centrifugal clutch C faces the crankcase 2 in the radial direction through the air exhaust port 80, and the distance W1 between the air exhaust port 80 and the clutch outer 62 in the radial direction is the width W2 of the air exhaust port 80 in the axial direction. Since the centrifugal clutch C is disposed in the vicinity of the air exhaust port 80, and the air exhaust port 80 is open so that the crankcase 2 can be seen in the radial direction, the centrifugal clutch C is directed toward the air exhaust port 80. The centrifugal clutch C is cooled by the flowing cooling air, and the cooling air after cooling the centrifugal clutch C is immediately discharged out of the transmission chamber 48 through the exhaust port 80. Furthermore, discharge of cooling air is promoted by an air flow having a swirl component generated by the rotation of the centrifugal clutch C, and the amount of exhaust air increases. As a result, the cooling of the centrifugal clutch C is promoted, the air volume hitting the case rear portion 4c including the radial case portion 4c1 is increased, and the cooling of the crankcase 2 and the cooling of the oil are further promoted.

  Since the air exhaust port 80 is located in the region surrounded by the belt 44 and is located at a position intersecting the plane including both the rotation center lines L0 and L2, the air exhaust port 80 is in the central portion of the transmission chamber 48. The flow of the cooling air toward the exhaust port 80 becomes smooth, and the cooling effect is further improved.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
A number of fins may be provided on the outer peripheral surface of the clutch outer 62, and the clutch outer 62 may constitute a discharge fan that discharges the cooling air in the transmission chamber 48 radially outward. As a result, the efficiency of exhausting the cooling air in the transmission chamber 48 is improved, so that cooling of the transmission mechanism is promoted and the amount of exhaust air is increased, so that the cooling of the outer portion F and oil is further promoted.
The air exhaust port 80 may be formed by a duct provided in the transmission case 45 instead of the through hole of the transmission case 45.
The internal combustion engine may be a multi-cylinder internal combustion engine other than the V-type two cylinders or a single-cylinder internal combustion engine. The internal combustion engine and the continuously variable transmission may be mounted on a machine other than the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a right side view showing a part in cross section when a part of a transmission case is removed in a power plant to which the present invention is applied, showing an embodiment of the present invention. It is the II-II sectional view taken on the line of FIG. FIG. 2 is a right side view of the internal combustion engine of FIG. 1, showing a part in cross-section when a part of the crankcase is removed. It is a principal part enlarged view centering on the exhaust port of FIG.

Explanation of symbols

2 ... Crank case, 3, 4 ... Crank case part, 4c ... Case rear part, 9 ... Crank shaft, 10 ... Crank chamber, 41 ... Driving pulley, 43 ... Driving pulley, 44 ... Belt, 45 ... Driving case, 46,47 ... transmission case part, 46a ... drive side case part, 46b ... driven side case part, 48 ... transmission chamber, 80, 81 ... air exhaust port, 80b ... outlet, P ... power unit, E ... internal combustion engine, M ... continuously variable transmission Device: C ... Centrifugal clutch, F ... Outer part, S ... External space, W1 ... Space, W2 ... Width.

Claims (4)

An internal combustion engine having a crankcase that forms a crank chamber in which the crankshaft is housed in an atmosphere containing oil, a drive pulley provided on the drive shaft driven by the crankshaft, and a driven pulley provided on the driven shaft And a belt-type transmission device including a transmission case that forms a transmission chamber in which the drive pulley and an endless belt spanned over the driven pulley are housed, and the transmission case is introduced into the transmission chamber. In the power unit provided with the exhaust port for discharging the cooled air to the outside,
The clutch has a rotation center line parallel to the rotation center line of the crankshaft and is accommodated in the transmission chamber, and the clutch is opposed to the crankcase through the exhaust port in the radial direction. The power plant according to claim 1 , wherein a distance between the air exhaust port and the clutch is smaller than a width of the air exhaust port in the axial direction . The crankcase has an outer portion positioned radially outward from the maximum rotation locus of the crankshaft in a side view, and the outlet of the exhaust port is outward in the flow direction of the exhaust air at the outlet. power plant according to claim 1, wherein the facing to the portion. The outlet of the air outlet is located at a position that does not overlap the driving pulley having the same rotation center line as the crankshaft in a side view, and faces the crankcase in the direction of the air flow at the outlet. The power unit according to claim 1 or 2. In the case portion on the crankcase side of the transmission case, the driven case portion that overlaps the driven pulley in a side view is positioned in the axial direction with respect to the drive side case portion that overlaps the drive pulley when viewed in the axial direction. Projecting to a position overlapping with the crank chamber, and the exhaust port is provided in the driven case portion or in a position closer to the crank chamber than the driving side case portion in the axial direction. The power plant according to claim 1 or 2, characterized by the above.

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