JP2008260502A - Motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motorcycle capable of preventing deterioration of cooling performance due to deformation of a cooling duct such as a dent thereof and capable of improving direct feeling when starting and accelerating. <P>SOLUTION: An engine unit 8 is supported on a body frame 2 in one part thereof so as to swing around an engine unit support part 47 of the body frame 2, and comprises a cooling duct 60 adapted to communicate cooling air into a belt chamber 8b housing a belt type continuously variable transmission 17 of the engine unit 8, wherein the cooling duct 60 has a flexible portion 67 having flexibility and the cooling duct 60 is connected to the belt chamber 8b through the engine unit 8 in a part near a body frame support part 47 thereof, and further, an opposite side part 66b of the belt chamber 8b relative to the flexible portion 67 is fixed to the body frame 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motorcycle having an engine unit including a belt-type continuously variable transmission mechanism and a vehicle body frame that supports the engine unit so as to be swingable up and down.

  For example, in a scooter type motorcycle, an engine unit in which an engine body and a belt-type continuously variable transmission mechanism are integrated is supported by a body frame so as to be able to swing up and down, and a rear wheel is supported at a rear end portion of the engine unit. In addition, a structure in which a saddle-type seat is mounted on a body frame is common.

  In such a motorcycle, the engine unit is generally supported by the vehicle body frame via a link mechanism from the viewpoint of suppressing transmission of engine vibration to the rider via the vehicle body frame as much as possible (for example, Patent Literature 1).

In Patent Document 1, in order to cool the belt of the continuously variable transmission mechanism, cooling air is introduced into the belt chamber of the engine unit by a cooling duct. In this case, in order to absorb the vertical swing of the engine unit, the cooling duct is connected to the belt chamber via a bellows-like flexible portion.
JP 2003-182673 A

  By the way, when the engine unit is supported by the vehicle body frame via the link mechanism, the swing center of the engine unit is located at the connection portion between the link and the engine unit, and the swing direction of the engine unit is up and down due to its structure. It becomes complicated before and after. Therefore, it is necessary to make the flexible part of the cooling duct have a structure corresponding to the swing direction. However, by simply giving flexibility, deformation such as a dent is likely to occur in the flexible portion due to external force or negative pressure due to suction of the belt chamber, and in some cases, the amount of intake air decreases, and the cooling performance of the belt chamber is reduced. There is concern that it will be damaged.

  In the structure in which the engine unit is supported by the vehicle body frame via the link mechanism, a response delay is likely to occur that the acceleration starts after a one-tempo delay even if the throttle is opened at the start and at the time of acceleration. There is a problem of lack of direct feeling.

  The present invention has been made in view of the above-described conventional situation, and provides a motorcycle capable of preventing deterioration of cooling performance due to deformation of a recess of a cooling duct and the like, and improving direct feeling at start and acceleration. The challenge is to do.

  The present invention is a motorcycle including an engine unit including a belt-type continuously variable transmission mechanism and a vehicle body frame that supports the engine unit so as to swing up and down. The engine unit is an engine of the vehicle body frame. A cooling duct that introduces cooling air into a belt chamber that accommodates the belt-type continuously variable transmission mechanism of the engine unit is partially supported by the vehicle body frame so as to swing around a unit support portion. The cooling duct has a flexible portion having flexibility, passes through the vicinity of the support portion of the engine unit to the vehicle body frame, is connected to the belt chamber, and further sandwiches the flexible portion. The opposite side portion of the belt chamber is fixed to the vehicle body frame.

  Here, in the present invention, “the engine unit is supported by the vehicle body frame so that it swings around the engine unit support part of the vehicle body frame” means that the suspended part of the unit swing type engine of the motorcycle This means that a part of the engine unit is supported by the vehicle body frame without a link mechanism that is normally used. Therefore, the engine unit swings without substantially moving its swing center from the engine unit support portion of the body frame. In this case, “substantially without moving” means that even when there is a movement of the elastic bushing, such as when it is supported via an elastic bushing, it swings without moving. Means to include.

  Further, in the present invention, “a part of which is supported by the vehicle body frame” means not only the case where the crankcase is supported but also the case where the cylinder block or the cylinder head is supported.

  In the motorcycle according to the present invention, the engine unit is supported so as to swing around the engine unit support portion of the vehicle body frame, so that the swing of the engine unit is simple only in the vertical direction. Along with this, the flexible portion of the cooling duct needs only to have a structure that only absorbs the vertical swing. As a result, the flexible portion can be configured with a high strength that can cope with an external force or a suction force of the belt chamber, and thus a sufficient amount of intake air can be secured and the cooling performance of the belt chamber can be enhanced.

  In the present invention, the engine unit is supported so that it swings around the engine unit support portion of the vehicle body frame, in other words, without interposing the link mechanism. The direct feeling at the time of acceleration can be improved. That is, when the link mechanism is interposed between the engine unit and the vehicle body frame, when the throttle opening operation is performed to start running from the stop state, the engine torque is transmitted to the rear wheels first. There is a response delay that is once absorbed by the link mechanism and then transmitted to the rear wheels. As a result, the vehicle starts to move forward one tempo behind the throttle opening operation, and a sufficient direct feeling cannot be obtained particularly at the start. In the present invention, since the link mechanism is not interposed, the above problem can be suppressed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 14 are views for explaining a motorcycle according to an embodiment of the present invention. In the description of the present embodiment, front and rear and left and right mean front and rear and left and right when viewed in a seated state.

  In the figure, reference numeral 1 denotes a scooter type motorcycle. The motorcycle 1 includes a unit swing type engine unit 8 having a belt type continuously variable transmission 17, an underbone body frame 2 that supports the engine unit 8 so as to be swingable up and down, And a saddle-type seat 9 mounted thereon.

  The motorcycle 1 includes a front fork 6 supported by a head pipe 3 positioned at the front end of the body frame 2 so as to be steerable left and right, and a steering handle 5 and a lower end portion disposed at an upper end portion of the front fork 6. And a rear wheel 7 disposed at the rear end of the engine unit 8, and a rear cushion 10 interposed between the engine unit 8 and the vehicle body frame 2.

  The motorcycle 1 includes a front cover 11 that covers the front side of the head pipe 3, a leg shield 12 that covers the rear side of the head pipe 3 and covers the front of the legs of the rider, and a lower periphery of the seat 9. A side cover 13 for covering, a footboard 15 disposed at the lower edge of the leg shield 12, and an undercover 16 for covering the lower portion of the footboard 15 from the side are provided. The foot board 15 is disposed on the upper surface of a foot bracket 29 fixed to the vehicle body frame 2.

  The vehicle body frame 2 extends rearward and downward from the head pipe 3 while expanding outward in the vehicle width direction, and left and right down tubes 20 and 20 extending substantially horizontally rearward from the lower end, and the left and right down tubes. Left and right seat rails 21 and 21 that extend obliquely upward rearward from the middle part of the tube 20 and extend substantially horizontally rearward from the rear end, and vertically extend from the rear ends of the left and right down tubes 20, Upper and lower engine suspension frames 22 and 22 are coupled to the seat rail 21 at the upper end.

  The vehicle body frame 2 extends rearward from the head pipe 3 in a substantially straight line shape, and rear left and right upper tubes 24 and 24 coupled to the seat rail 21 and the left and right engine suspension frames. And left and right seat stays 25, 25 for connecting the seat rail 21 and a cross member 23 for connecting the vicinity of the connecting portion of the engine suspension frame 22 of the left and right seat rails 25 in the vehicle width direction. Have.

  The engine unit 8 is obtained by integrally connecting an engine body 8a and a transmission case 8b in which the belt type continuously variable transmission 17 is accommodated. An air cleaner 36 is fixed to the upper wall surface of the transmission case 8b.

  The engine body 8a is a water-cooled four-cycle single-cylinder engine mounted with the cylinder axis A oriented substantially horizontally, and a crank mechanism 18 including a crankshaft 18b disposed substantially horizontally in the vehicle width direction is accommodated. A cylinder block 8d, a cylinder head 8e, and a head cover 8f are sequentially connected to the front mating surface of the crankcase 8c.

  The belt type continuously variable transmission 17 includes a drive pulley 17a disposed at a left end portion of a crankshaft 18b protruding into the transmission case 8b, a driven pulley 17b disposed at a rear end portion of the transmission case 8b, A V belt 17c wound around the drive pulley 17a and the driven pulley 17b is provided.

  A main shaft 17d and a drive shaft 17e to which the rotation of the driven pulley 17b is transmitted are arranged in the transmission case 8b, and the rear wheel 7 is mounted on the drive shaft 17e.

  The belt type continuously variable transmission 17 can change the belt winding diameter of the drive pulley 17a between the low position and the top position by a controller (not shown) based on the accelerator operation amount of the rider and the engine speed, vehicle speed, and the like. A winding diameter variable mechanism 26 to be controlled is provided (see FIG. 4).

  The winding diameter variable mechanism 26 includes a driving motor 26a, a reciprocating driving gear 26b that changes a winding diameter by moving a movable sheave (not shown) of the driving pulley 17b in the axial direction, and rotation of the driving motor 26a. And a reduction gear group 26c for transmitting the motor to the reciprocating drive gear 26b.

  As shown in FIGS. 5 and 6, the engine unit 8 includes a balancer mechanism 27 including a balancer shaft 27 a that suppresses engine vibration caused by a primary inertia force. The balancer mechanism 27 is configured to rotate in the reverse direction at the same rotational speed as the crankshaft 18b of the crank mechanism 18.

  The balancer mechanism 27 is disposed above the crankshaft 18b in the crankcase 8c, and is formed integrally with a balancer shaft 27a disposed in parallel to the crankshaft 18b so as to extend in a direction perpendicular to the balancer shaft 27a. Balancer weight 27b. The balancer weight 27b extends so as to be positioned between the left and right counterweights 18a and 18a of the crankshaft 18b.

  The left and right ends of the balancer shaft 27a are supported by the crankcase 8c via bearings 28, 28, and a balancer gear 27c is coupled to the inner side of the right bearing 28 of the balancer shaft 27a via a damper member 27d. ing. The balancer gear 27c meshes with a drive gear 18b 'coupled to the crankshaft 18b.

  Here, the primary inertia force generated by the rotation of the crankshaft 18b of the crank mechanism 18 is a rotation component that rotates with a constant magnitude, and a translation that changes in magnitude with the rotation of the crankshaft 18b with a constant direction. And ingredients.

  Further, the balancer mechanism 27 includes an acceleration caused by a couple of forces generated by a rotation component generated by the primary inertial force of the crankshaft 18b balanced with an inertial force generated by the rotation of the balancer shaft 27a, and the crankshaft 18b. The acceleration due to the translational component of the primary inertia force is configured to be substantially opposite to each other and substantially the same in the pivot shaft 51 portion that is the support portion of the engine unit 8.

  In order to make both the accelerations substantially opposite to each other and have the same magnitude, as shown in FIG. 12, the instantaneous rotation center where the vibration due to the primary inertial force F1 of the crank mechanism 18 and the inertial force F2 of the balancer mechanism 27 does not occur. The pivot shaft 51 may be disposed. Hereinafter, a method of arranging the instantaneous rotation center on the pivot shaft 51 will be described.

  As shown in FIG. 13, the primary inertial force F1 of the crank mechanism 18 has a predetermined elliptical shape S1 drawn by a locus for one cycle when the force is displayed as a vector. On the other hand, the inertial force F2 of the balancer mechanism 27 draws a vector locus of a perfect circle shape S2. The balancer shaft 27a and the crankshaft 18b are such that the crank / balancer straight line L2 connecting the two shafts is substantially parallel to the gravity center / target position straight line L1 connecting the gravity center G of the engine unit 8 and the pivot shaft 51. Placed in.

  The major axis of the primary inertial force ellipse of the crank mechanism 18 is arranged substantially parallel to the crank-balancer straight line L2, and the inertial force F2 of the balancer mechanism 27 is the size of the diameter of the perfect circle S2. Is configured to be substantially the same as the major axis of the ellipse of the primary inertia force of the crank mechanism.

  In the vicinity of the pivot shaft 51, the elliptical shape of the primary inertial force of the crank mechanism is controlled so that the acceleration due to the translational force and the acceleration due to the couple are substantially in opposite directions and have the same magnitude. Thus, the instantaneous rotation center can be arranged in the vicinity of the pivot shaft 51.

  In the above description, the crank / balancer straight line L2 connecting the balancer shaft 27a and the crankshaft 18b is substantially the same as the gravity center / target position straight line L1 connecting the gravity center G of the engine unit 8 and the pivot shaft 51. The case where they are arranged in parallel has been described as an example. However, the arrangement of the two shafts is not limited to this. This will be described below.

  The elliptical shape of the primary inertia force by the crank mechanism 18 is controlled by adjusting at least the counterweight 18a of the crank mechanism 18. By adjusting the position and weight of the counterweight 18a, the elliptical shape of the primary inertial force by the crank mechanism 18 can be easily controlled to the predetermined elliptical shape S1.

  Further, by adjusting the position and weight of the balancer weight 27b of the balancer mechanism 27, the shape drawn by the locus for one cycle when the force is vector-displayed for the inertial force F2 of the balancer mechanism 27 has a predetermined size. Can be controlled so as to have a perfect circular shape S2.

  As described above, even when the crank / balancer straight line L2 is not parallel to the center of gravity / target position straight line L1, the instantaneous rotation center can be arranged in the target position, that is, in the vicinity of the pivot shaft 51.

  In this way, it is possible to suppress the vicinity of the pivot shaft 51 from vibrating, so there is no need to provide a link mechanism for suppressing the engine vibration from being transmitted to the vehicle body frame or the like. Thereby, the number of parts can be reduced and the weight can be reduced.

  Reference numeral 77 is an oil pump that pumps the lubricating oil at the bottom of the crankcase 8c to each lubricated portion of the engine body 8a, and 78 is a cooling water pump that pumps the cooling water to each cooling water jacket of the engine body 8a. It is. Reference numeral 79 denotes an alternator.

  A part of the engine unit 8 is supported so as to swing around a pivot member (engine unit support portion) 47 formed on the left and right engine suspension frames 22 and 22 of the body frame 2. Yes. More specifically, the engine unit 8 swings up and down around the axis a of the pivot shaft 51 inserted into the pivot member 47, and the portion below the cylinder axis A directly, that is, a link mechanism. It is supported without intervention. More specifically, it has the following structure.

  The lower ends of the left and right engine suspension frames 22 are integrally connected by a lower side portion 22c. Cylindrical left and right pivot members 47, 47 arranged with their shaft cores facing in the vehicle width direction are fixed near the down tube 20 connection portion of the left and right engine suspension frames 122. Elastic bushes 50 and 50 are inserted and fixed to the left and right pivot members 47. Each elastic bush 50 has a structure in which a rubber member 50c is interposed between the outer cylinder 50a and the inner cylinder 50b. A pivot shaft 51 is inserted and fixed in the left and right inner cylinders 50b.

  A pair of left and right suspension portions (supported portions) 8j and 8j are formed to project forward from the bottom wall front portion 8c 'of the crankcase 8c so as to be positioned below the cylinder axis A of the cylinder block 8d. . The left and right suspension portions 8j are disposed inside the left and right pivot members 47 and are rotatably supported by the pivot shaft 51 via bearings 52 and 52. Thus, the engine unit 8 is suspended and supported by the left and right pivot members 47 through the pivot shaft 51 and the elastic bush 50 so as to be swingable up and down.

  When the engine unit 8 is directly supported by the vehicle body frame 2 in this way, the engine unit 8 is supported via the elastic bushing 50, so that the engine vibration and the vibration from the road surface are transmitted to the rider via the vehicle body frame 2. Can be suppressed.

  A fuel tank 30 is disposed at the front end portion in the vehicle body frame 2, and a radiator 31 is disposed below the fuel tank 30. A resin article storage box 33 that opens upward is disposed behind the fuel tank 30.

  The seat 9 includes a main seat 9a on which a rider sits, and a tandem seat 9b that is formed separately from the main seat 9a and on which a rear passenger sits. A backrest 9c that supports the waist of the rider is disposed at the rear end of the main seat 9a.

  The main seat 9a is supported by the front end portion of the storage box 33 so as to be pivotable forward, and the tandem seat 9b is supported at the rear end portion of the storage box 33 so as to be pivotable rearward. Yes.

  The engine unit 8 is connected to a cooling duct 60 that introduces cooling air into a transmission case 8 b that houses the belt type continuously variable transmission mechanism 17. The cooling duct 60 has a flexible portion having flexibility, passes through the vicinity of the support portion of the engine unit to the vehicle body frame, is connected to the belt chamber, and further sandwiches the flexible portion with the belt. The opposite side of the chamber is fixed to the body frame.

  Specifically, the cooling duct 60 is formed so as to extend substantially linearly along a horizontal portion 20c formed so as to form a substantially straight line in the front-rear direction of the left down tube 20, and the foot It is arranged so as to pass under the board (footrest part) 15 and inside the under cover 16. A maintenance opening 16a is formed in a portion of the under cover 16 facing the cooling duct 60, and the maintenance opening 16a is covered with a lid member 76 so as to be opened and closed.

  The cooling duct 60 includes an element 65 disposed below the footboard 15, an intermediate duct 66 extending rearward from the element 65, and extending rearward from the intermediate duct 66. The intermediate duct 66 and the transmission case 8b. The flexible duct 67 (flexible part) which has the flexibility which connects the inside is connected, and this flexible duct 67 is located in the immediate vicinity of the support part to the vehicle body frame of an engine unit.

  The element 65, the intermediate duct 66, and the flexible duct 67 are detachably fastened by band members 68, 68, 68, respectively.

  The transmission case 8b includes a case main body 8g extending rearward after the left end of the crankcase 8c, and a case cover 8h detachably attached to the left joint surface of the case main body 8g. A space formed by the cover 8h and the case main body 8g is a belt chamber. Here, the drive pulley 17a is formed with a plurality of blades (not shown) for sucking cooling air into the belt chamber by the rotational force of the drive pulley 17a.

  The case cover 8h is divided into a front case 8m fixed to the case main body 8g by a plurality of bolts 73 and a rear case 8n fixed to the case main body 8g by bolting.

  The front case 8m is integrally formed with an air introduction port 8p extending forward in a cylindrical shape, and the flexible duct 67 is detachably fastened to the air introduction port 8p by the band member 68. Therefore, the air introduction port 8p is a belt chamber connecting portion of the cooling duct 60. An air discharge port (not shown) is formed at the rear end of the transmission case 8b.

  The traveling wind that has flowed into the left and right undercovers 16 is filtered by the element 65, passes through the intermediate duct 66 and the flexible duct 67, and is sucked by the drive pulley 17a from the air introduction port 8p into the transmission case 8b. The V belt 17c and the like are discharged to the outside from the rear end portion of the transmission case 8b while cooling.

  A mounting portion 65a is formed on the front wall of the element 65 so as to protrude forward, and the mounting portion 65a spans the left and right down tubes 20 and 20 and is connected to the bracket 70a of the radiator support member 70. Are fixed by bolts 71.

  A front mounting portion 66a and a rear mounting portion (vehicle body side fixing portion) 66b are formed on the front lower edge portion and the rear upper edge portion of the intermediate duct 66 so as to protrude downward and upward, respectively. The front mounting portion 66a is fixed to the bracket 20f connected to the down tube 20 by bolts 72, and the rear mounting portion 66b is fixed to the bracket 22f fixed to the engine suspension frame 22 by bolts 72.

  The element 65 is a cylinder having a triangular cross section, and has a structure in which an element body 65b for filtering air is disposed in an element case 75. The air suction port 75c of the element case 75 and the element main body 65b are arranged to face the inner surface of the under cover 16 with a predetermined gap.

  The intermediate duct 66 has a vertically long elliptical shape, and is disposed so as to pass between the horizontal portion 20c of the down tube 20 and the side stand 44a in the retracted position.

  The cooling duct 60 has a substantially straight shape over its entire length, and extends from the air inlet 8p, which is a belt chamber connecting portion, to the front end portion of the hood board 15 located in front of the vehicle.

  As shown in FIG. 8, the flexible duct 67 is disposed such that the center line B in a side view thereof passes near the upper side of the axis a of the pivot member 47, and the transmission case 8 b sandwiching the flexible duct 67. A rear mounting portion 66 b on the opposite side of the intermediate duct 66 is fixed to the engine suspension frame 22.

  In this way, the flexible duct 67 is shown by a two-dot chain line from the state at the minimum stroke shown by the solid line in FIG. 9 according to the vertical swing stroke of the engine unit 8 around the pivot shaft 51. It is free to bend up to the maximum stroke. In this case, since the flexible duct 67 is disposed in the vicinity of the pivot shaft 51, the bending amount accompanying the stroke change is disposed at a position where the flexible duct 67 is separated from the swing shaft of the engine unit. It is smaller than the case.

  According to the present embodiment, since the engine unit 8 is supported so as to swing about the axis a of the pivot member 47 constituting the engine unit support portion of the vehicle body frame, the swing of the engine unit 8 is in the vertical direction. Accordingly, the flexible duct 67 of the cooling duct 60 can be configured to only absorb the vertical swing. As a result, the flexible duct 67 can be configured with a high strength that can cope with an external force or a suction force of the belt chamber, so that a sufficient intake air amount can be secured and the cooling efficiency of the V-belt 17c can be increased. it can.

  According to the present embodiment, the engine unit 8 is partially supported by the vehicle body frame so as to swing around the axis a of the pivot shaft 51 of the pivot member 47 constituting the engine unit support portion. In other words, the suspension unit of the unit swing type engine is supported without a link mechanism normally used, so that the engine unit 8 can be swung without substantially moving its swing center from the axis a. Can be made. Therefore, the response to the throttle opening operation can be improved as compared with the one having a link mechanism interposed, and the direct feeling at the time of start and acceleration can be improved. That is, when the link mechanism is interposed between the engine unit and the vehicle body frame, when the throttle opening operation is performed to start running from the stop state, the engine torque is transmitted to the rear wheels first. There is a response delay that is once absorbed by the link mechanism and then transmitted to the rear wheels. As a result, the vehicle starts to move forward one tempo behind the throttle opening operation, and a sufficient direct feeling cannot be obtained particularly at the start. In the present embodiment, since the engine unit 8 is directly supported by the vehicle body frame 2 without interposing a link mechanism, the above problem can be suppressed.

  Further, since the engine unit 8 is supported by the pivot member 47 with the elastic bush 50 interposed, transmission of engine vibration to the vehicle body side can be suppressed. Even when the elastic bush 50 is interposed, the swing center of the engine unit 8 is not substantially moved. That is, when viewed microscopically, the swing center moves by the amount of bending of the elastic bush 50, but this amount of movement hardly affects the response delay which is a problem of the present invention. .

  Furthermore, in the present embodiment, since the balancer mechanism 27 is disposed in the engine unit 8, vibrations by the engine unit 8 can be suppressed, and the engine vibration can be transmitted through the vehicle body frame 2 while directly supporting the engine unit 8 to the vehicle body frame 2. Can be prevented from being transmitted to the rider.

  More specifically, the balancer mechanism 27 includes an acceleration due to a couple generated by a rotation component generated by the primary inertia force of the crankshaft 18b balanced with an inertial force generated by the rotation of the balancer shaft 27a, and the crankshaft. The acceleration due to the translational component of the primary inertial force of the shaft 18b is substantially opposite to and substantially the same in the vicinity of the axis a of the bibot shaft 51 that is the body frame side support portion of the engine unit 8. Since it is comprised, it can suppress that an engine vibration is transmitted to a rider.

  In the present embodiment, since the lower part of the engine unit 8 below the cylinder axis A is suspended and supported by the vehicle body frame 2, the cooling duct connection part of the engine unit 8 in particular compared to the case where it is supported by the upper part of the cylinder axis A. It is possible to reduce the amount of vertical swing of. As a result, the vertical swing amount of the flexible duct 67 is reduced, the structure of the flexible duct 67 can be simplified, and the strength can be increased accordingly.

  Furthermore, since the flexible duct 67 is disposed so as to be positioned in the vicinity of the pivot member 47 of the vehicle body frame 2, the vertical swing amount of the flexible duct 67 can be reduced from this point as well, and the structure of the flexible duct 67 is reduced. Can be further simplified, and it is easy to ensure strength.

  In the present embodiment, since the cooling duct 60 is formed so that the whole including the flexible duct 67 is substantially linear in the vehicle front-rear direction, the air resistance of the cooling air flowing through the cooling duct 60 can be reduced. As a result, it is possible to secure a sufficient amount of intake air into the belt chamber and thus improve the engine responsiveness.

  In the present embodiment, the cooling duct 60 is formed so as to extend from the belt chamber connecting portion of the engine unit 8 to the front end portion of the rider footboard 15 in front of the vehicle, so that the capacity of the cooling duct 60 can be increased. Thereby, the amount of intake air at the time of start and acceleration can be secured, and the cooling performance of the V belt 17c can be improved.

  In addition, the flexible duct 67 is arranged so that the center line B in a side view thereof passes above the axis a of the pivot member 47 that is a support portion of the engine unit 8 to the vehicle body frame. For this reason, the flexure of the bellows-shaped flexible duct 67 can be reduced, and the flow resistance in the duct can be reduced accordingly.

That is, with respect to the stroke of the suspension system of the engine unit 8, normally, as shown in FIG. 14 (a), the stroke S1 from the steady running state to the most compressed state (high load input state) is from the steady running state to the most extended state. It is set larger than the stroke S2.

  When the flexible duct 67 is disposed above the axis a of the engine unit support portion, the flexible duct 67 is compressed as the engine unit 8 strokes to the maximum compression state, and strokes to the maximum extension state. It is extended with. Therefore, the amount of flexure of the bellows of the flexible duct 67 is maximum in the maximum compression state and minimum in the maximum extension state, as shown in FIG. Since the amount of deflection during steady running is close to this minimum amount of deflection, the flow resistance in the duct is also reduced.

  On the other hand, when the flexible duct 67 is arranged below the axis a of the engine unit support portion, the flexible duct 67 is extended as it strokes to the most compressed state, and as it strokes to the most extended state. Compressed. Therefore, the amount of flexure of the bellows of the flexible duct 67 is minimum in the maximum compression state and maximum in the maximum extension state, as shown in FIG. Since the amount of deflection during steady running is close to the maximum amount of deflection, the flow resistance in the duct also increases.

1 is a side view of a motorcycle according to an embodiment of the present invention. It is a side view of the body frame of the motorcycle. It is a top view of the said vehicle body frame. It is a side view of the engine unit supported by the above-mentioned body frame so that rocking is possible. It is a side view of the balancer mechanism of the engine unit. It is sectional drawing of the said balancer mechanism. It is a side view of the engine unit. It is a side view of the cooling duct connected to the engine unit. It is a side view of the flexible duct of the said cooling duct. It is sectional drawing (XX sectional drawing of FIG. 8) of the said cooling duct. It is sectional drawing (XI-XI sectional view taken on the line of FIG. 8) of the said cooling duct. It is a section top view of the engine unit support part of the above-mentioned embodiment engine. It is a schematic diagram for demonstrating the structure of the balancer mechanism of the said embodiment engine. It is a figure for demonstrating the effect by the duct arrangement | positioning of the said embodiment engine.

Explanation of symbols

1 Motorcycle 2 Body frame 8 Engine unit 8b Transmission case (belt chamber)
8c Crankcase 8j Suspension part (part of engine unit)
8p Belt room connection 15 Footboard (footrest)
17 Belt type continuously variable transmission mechanism 18 Crank mechanism 18b Crankshaft 27 Balancer mechanism 27a Balancer shaft 47 Pivot member (engine unit support part)
50 Elastic bush (elastic member)
51 Pivot shaft (support to the body frame)
60 Cooling duct 66b Car body side fixing part 67 Flexible duct (flexible part)
A Cylinder axis B Center line of cooling duct

Claims (10)

A motorcycle including an engine unit including a belt-type continuously variable transmission mechanism and a vehicle body frame that supports the engine unit so as to swing up and down.
A part of the engine unit is supported by the body frame so as to swing around an engine unit support portion of the body frame,
A cooling duct for introducing cooling air into a belt chamber that houses the belt-type continuously variable transmission mechanism of the engine unit;
The cooling duct has a flexible portion having flexibility, passes through the vicinity of the support portion of the engine unit to the vehicle body frame, is connected to the belt chamber, and further sandwiches the flexible portion. A motorcycle characterized in that the opposite side of the chamber is fixed to the body frame. 2. The motorcycle according to claim 1, wherein the engine unit includes a balancer mechanism including a balancer shaft that suppresses engine vibration caused by a primary inertia force. 3. The engine unit according to claim 2, further comprising a crank mechanism including a crankshaft, wherein a primary inertia force generated by the rotation of the crankshaft is a rotation component that rotates with a constant magnitude, and a constant direction of the crankshaft. A translational component whose magnitude changes with rotation, and a rotational component of a primary inertial force generated by the rotation of the crankshaft is balanced with an inertial force generated by the rotation of the balancer shaft, The motorcycle according to claim 1, wherein the acceleration due to the translational component of the primary inertial force of the crankshaft is substantially opposite to and substantially the same in the support portion of the engine unit to the body frame. The motorcycle according to claim 1, wherein the engine unit is supported by the body frame via an elastic member. The motorcycle according to claim 1, wherein the supported portion of the engine unit is provided in a crankcase that supports a crankshaft of the engine unit. 2. The motorcycle according to claim 1, wherein the engine unit is supported by a vehicle body frame at a portion below a cylinder axis line arranged in a forward tilt state. 2. The motorcycle according to claim 1, wherein at least a portion between the belt chamber connecting portion and the vehicle body side fixing portion is substantially straight when viewed from the side. 2. The motorcycle according to claim 1, wherein the flexible portion is positioned in the vicinity of a support portion of the engine unit for a vehicle body frame. 2. The motorcycle according to claim 1, wherein the cooling duct extends from the belt chamber connecting portion to a rider footrest portion located in front of the vehicle from the connecting portion. 2. The motorcycle according to claim 1, wherein the cooling duct is disposed such that a center line in a side view passes above a support portion of the engine unit to the body frame.

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