JP2012051505A - Working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt type continuously variable transmission capable of achieving high maintenability by favorably opening a case without causing the complexity of a cooling system.SOLUTION: A transmission case 64 of a belt type continuously variable transmission 32 is composed of a case body 64A supported by a vehicle body and a cover body 64B detachably supported by the case body 64A. On the case body 64A, there is provided a swelling portion 64D formed by swelling a part of wall to the vehicle body side. A discharge section 64F for delivering cooling wind incorporated into the transmission case 64 is formed in such a posture as to deliver cooling wind from the swelling portion 64D to the rear side of the vehicle body.

Description

  The present invention relates to a work vehicle including a belt continuously variable transmission in which an endless belt is wound around a driving pulley capable of changing a belt winding diameter and a driven pulley capable of changing a belt winding diameter. Specifically, the present invention relates to a technique for cooling a belt continuously variable transmission.

  As a work vehicle configured as described above, Patent Document 1 discloses a configuration in which a cover of a belt continuously variable transmission (a belt converter in the document) is attached to an engine side wall. Also, a cooling air suction fan is attached to the outer end position of the drive pulley, an intake port is formed on the outer end side of the drive pulley in the cover, and a discharge port is formed on the engine side wall near the driven pulley on the engine side wall It is shown.

  In this Patent Document 1, a configuration including a connection pipe for sending cooling air from the outlet to the rear of the vehicle body is described. The cooling air is sucked from the intake port by the suction force of the fan, and this cooling air is sent to the outlet port. The structure which guides and discharges the cooling air sent to this discharge port to a vehicle body back via a connection pipe is shown.

  Further, in Patent Document 1, the cover has a structure in which a cylindrical portion that is bolt-connected to the engine side wall portion and a side surface portion that is bolt-connected to the cylindrical portion, and each is separable. The configuration supported in the above is described.

  Further, as a working vehicle configured as described above, Patent Document 2 discloses a configuration in which a belt converter cover that accommodates a drive pulley and a driven pulley is attached to the outer wall surfaces of an engine and a transmission with screws. The belt converter cover includes an inner belt converter cover connected to the outer wall surface described above and an outer belt converter cover connected to the inner belt converter cover.

  In Patent Document 2, an intake duct for supplying cooling air to an air introduction chamber inside the belt converter cover is connected to the inner belt converter cover, and an exhaust port for discharging cooling air from the belt converter cover is formed in the outer belt converter cover. A configuration in which an exhaust duct is connected to the discharge port is shown. The exhaust duct is formed so as to be inclined obliquely upward, and has a shape that extends downward from the belt converter cover between the transmission and the rear wheel by bending the front portion.

Japanese Patent No. 2971870 Japanese Patent No. 4472475

  As shown in the patent document, the belt continuously variable transmission includes a case that accommodates a drive pulley and a driven pulley, thereby protecting the transmission and suppressing adhesion of rainwater and dust to the pulley and the belt. Proper operation is achieved.

  The belt continuously variable transmission requires a configuration for supplying and discharging cooling air from the outside to the case in order to remove heat generated by contact between the pulley and the belt.

  Further, considering the workability at the time of maintenance of the belt continuously variable transmission, it is desirable that the case be configured to be removable so that the portions of the drive pulley and the driven pulley can be exposed greatly. However, when the belt converter cover is provided with a discharge port as described in Patent Document 2, when the belt converter cover is removed, the exhaust duct is also removed integrally, which makes it difficult to handle and improves. There is room for.

  Therefore, as described in Patent Document 1, it is effective to improve the handling of the cover when the belt converter cover is removed by forming a discharge port on the vehicle body side. However, in this patent document 1, since the cooling air is directed from the discharge port toward the inside of the vehicle body, a connection pipe is connected to the discharge port in order to turn the discharge direction of the cooling air backward, which increases the number of parts. It was connected.

  An object of the present invention is to rationally configure a belt continuously variable transmission that can open a case satisfactorily and exhibit good maintainability without complicating a cooling system.

The present invention is characterized in that a belt continuously variable transmission in which an endless belt is wound around a driving pulley capable of changing the belt winding diameter and a driven pulley capable of changing the belt winding diameter is provided. A car,
A speed change case that accommodates the drive pulley, the driven pulley, and the endless belt includes a case body that is supported on the vehicle body side, and a cover body that is detachably supported with respect to the case body.
A bulging portion is formed by bulging a part of the wall portion of the case main body on the side opposite to the cover body, and a discharge portion for sending cooling air taken into the transmission case is disposed on the rear side of the vehicle body from the bulging portion. It is in the point formed with the attitude | position which sends out a cooling air to.

According to this configuration, even if the cover body is removed for maintenance, the cover body can be easily removed because the discharge portion is not formed on the cover body. Further, since the discharge portion is formed at the bulging portion, it is possible to send the cooling air directly toward the rear of the vehicle body, and ducts for setting the direction of sending the cooling air are not required. In particular, the bulging part has a structure in which a part of the case body is bulged on the side opposite to the cover body, so that it is possible to form a wide space apart from the pulley and the endless belt, and the cooling air is discharged from the discharge part. In this case, the cooling air can be discharged from a wide space without being obstructed by the pulley or the endless belt.
As a result, a belt continuously variable transmission that smoothly discharges the cooling air without complicating the cooling structure, satisfactorily opens the case, and exhibits good maintainability has been configured.

  In the present invention, a cylindrical exhaust duct may be connected to the discharge portion, and a throttle portion for reducing the discharge path may be formed at an intermediate position of the exhaust duct.

  According to this, when the cooling air is discharged from the discharge part to the exhaust duct, the flow of the cooling air is suppressed in the throttle part, so that the internal pressure of the case rises and the case body and the cover body are connected. This prevents inconvenience of rainwater and dust from entering the case.

  The present invention includes a centrifugal clutch that transmits the driving force of the crankshaft to the output shaft when the rotational speed of the crankshaft of the engine exceeds a set value, and a clutch case that houses the centrifugal clutch is provided between the engine and the transmission case. An air intake portion that is disposed in the middle and receives cooling air in the clutch case may be formed, and a cooling air inlet that guides the cooling air from the clutch case to the transmission case may be formed in the case body.

  According to this, the cooling air is guided from the intake portion to the inside of the clutch case, and the cooling air inside the clutch case is guided from the cooling air inlet of the case body to the inside of the transmission case. As described above, since the air intake portion is not formed in the cover body, the cover body can be easily removed even if the cover body is removed for maintenance.

It is a side view of a work vehicle. It is a top view which shows the transmission structure of a working vehicle. It is a perspective view which shows a frame structure. It is a side view which shows the structure of the suspension of a rear wheel. It is a side view which shows arrangement | positioning of an engine, a belt continuously variable transmission, etc. It is a perspective view which shows arrangement | positioning of an engine, a belt continuously variable transmission, etc. It is a top view which shows arrangement | positioning of an engine, a belt continuously variable transmission, etc. It is a figure which shows the flow of the cooling air in a belt continuously variable transmission planarly. It is a figure which shows the flow of the cooling air in a belt continuously variable transmission in a side view.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
〔overall structure〕
As shown in FIGS. 1 and 2, a vehicle body 3 is provided with a pair of left and right front wheels 1 and a pair of left and right rear wheels 2 that can be steered, and a driving unit 10 is provided at the center of the vehicle body 3. 3 is provided with a loading platform 4, and a driving unit 30 is provided at a position below the loading platform 4 with a driving unit 30.

  This work vehicle is configured as a four-wheel drive type that transmits the driving force from the prime mover 30 to the front wheels 1 and the rear wheels 2, and is used for multi-purpose work such as farm work and transport work. A protective frame 11 that protects the driving unit 10 is provided at a position surrounding the driving unit 10.

  The loading platform 4 has a function of raising the front end side and discharging the load in a dumping manner, and its rear end position is supported by the vehicle body 3 so as to be swingable about the axis. Further, a hydraulic actuator (not shown) that moves up and down the front end side of the loading platform 4 is provided.

  The driving unit 10 includes a driver seat 12 on which a driver is seated, a steering wheel 13 that steers the front wheel 1, a speed change lever 14, an accelerator pedal 15 that controls traveling speed, the front wheel 1 and the rear wheel. A brake pedal 16 for operating the brake device 17 of the wheel 2 is provided. A passenger seat is disposed adjacent to the driver seat 12, and the driver 10 is provided with a bench seat composed of a horizontally long single seat base and a horizontally long single seat back. It has been.

  The shift lever 14 realizes setting of the traveling speed and switching between forward and reverse by a single lever operation. For example, a lever for shifting and a forward / backward lever for switching between forward and reverse The operating unit 10 may be provided with two levers.

  As shown in FIG. 3, the vehicle body frame constituting the vehicle body 3 has a pair of left and right main frames 21 in a front-rear orientation that passes from the front end of the vehicle body below the driving unit 10 and reaches the driving unit 30. A plurality of cross frames 22 for connecting the frames 21 are provided. The protective frame 11 includes a pair of left and right side frames 11A and a plurality of horizontal frames 11B connecting the left and right side frames 11A. The protective frame 11 is connected to a pair of left and right main frames 21 via an intermediate frame or the like.

  The pair of left and right side frames 11A have a loop structure, and a step 23 made of a plate material is provided at a position where the lower end portion of the side frame 11A and the pair of left and right main frames 21 are connected. Further, a back plate 24 is formed in a region extending from the left and right side frames 11 </ b> A at the rear position of the driver seat 12. Step 23 serves as a boarding surface for the driver, and the back plate 24 supports the seat back of the driver seat 12.

  As shown in FIGS. 2 and 4 to 7, the prime mover 30 includes an air-cooled engine 31, a dry belt continuously variable transmission 32, and a transmission case 33. The transmission case 33 includes a gear transmission mechanism (not shown) and a differential mechanism (not shown). The lower end portion of the transmission case 33 is provided with a pair of left and right rear wheel drive shafts 34 for transmitting the driving force from the differential mechanism to the rear wheels 2 and a rear axle case 35 for housing the rear wheel drive shafts 34. Yes.

  A power take-out shaft 36 that protrudes forward at the lower end of the mission case 33 is provided. An intermediate shaft 37 to which the driving force of the power take-off shaft 36 is transmitted is provided at the lower part of the vehicle body 3, and a differential case 38 to which the driving force of the intermediate shaft 37 is transmitted to the front portion of the vehicle body 3. A front wheel drive shaft 39 that transmits the driving force of the case 38 to the front wheels 1 is provided.

  A universal joint such as a cardan joint is interposed between the power take-out shaft 36 and the intermediate shaft 37 of the transmission case 33, and similarly, between the front and rear intermediate shafts 37 and between the intermediate shaft 37 and the differential case 38. A universal joint is also provided with the input shaft. In addition, a universal joint such as a cardan joint is interposed between the output shaft of the differential case 38 and the front wheel drive shaft 39. Similarly, it can be freely connected between the front wheel drive shaft 39 and the front wheel 1 axle. A joint is interposed.

  Although not shown in the drawing, the transmission case 33 is provided with a clutch mechanism that can be switched between a transmission state for transmitting the driving force to the power take-off shaft 36 and a blocking state for blocking the driving force. This clutch mechanism can be switched by a driver's operation, and by setting the transmission state, a four-wheel drive state in which the rear wheel 2 and the front wheel 1 are driven simultaneously appears, and the clutch mechanism is cut off. By setting the state, a two-wheel drive state in which only the rear wheel 2 is driven appears.

  A brake device 17 is provided at the shaft ends of the pair of left and right front wheel drive shafts 39 and the shaft ends of the pair of left and right rear wheel drive shafts 34. These brake devices 17 function so as to apply a braking force to the front wheels 1 and the rear wheels 2 by operating the brake pedal 16.

  A gear speed change mechanism (not shown) of the transmission case 33 is operated by operating the speed change lever 14. This gear transmission mechanism realizes a change in the traveling speed of the vehicle body 3 and a switching of the traveling direction (switching between forward and reverse) in accordance with the operation of the shift lever 14.

〔suspension〕
The left and right front wheels 1 are mounted on the vehicle body frame by a strut-type independent front suspension. In other words, the base end side of the lower arm (not shown) is swingably supported by the body frame, and the axle of the front wheel 1 is supported on the swing end of the lower arm. A suspension unit 25 (see FIG. 1) including a coil spring and a shock absorber is provided between the lower arm and the vehicle body frame, whereby the front wheel 1 is mounted on the vehicle body.

  With this suspension, the left and right front wheels 1 can move up and down independently according to the undulations of the road surface, and when the up / down operation involves an impact, the suspension unit 25 absorbs the impact.

  As shown in FIGS. 1, 4, and 5, the left and right rear wheels 2 are mounted on a vehicle body frame by a rigid axle suspension. That is, a pair of left and right auxiliary frames 26 are provided for the left and right main frames 21. A rear axle case 35 is supported by the auxiliary frame 26, and a suspension unit 25 including a coil spring and a shock absorber is provided between the rear axle case 35 and the vehicle body frame, whereby the rear wheel 2 is attached to the vehicle body. It is mounted.

  The pair of left and right auxiliary frames 26 includes a pair of left and right side members 26A bent in an L shape, a lower arm 26B that pivotally connects the front end of the pair of left and right side members 26A and the main frame 21, and a pair of left and right sides. An upper arm 26C that pivotably connects the upper end of the side member 26A and the main frame 21 is provided. The pair of left and right side members 26A are connected by a connecting frame 28, and the bottom of the engine 31 is supported by the connecting frame 28 in a connected state.

  As a specific structure, the front end of the lower arm 26B is swingably connected to a bracket 21A on the lower surface of the intermediate portion of the main frame 21 via a rubber bush. The rear end of the lower arm 26B is swingably connected to the bracket 26L at the front end of the side member 26A via a rubber bush. Further, the front end of the upper arm 26C is slidably connected to a bracket 21B on the lower surface of the rear portion of the main frame 21 via a rubber bush. The rear end of the upper arm 26C is swingably connected to the bracket 26H at the rear end of the side member 26A. Further, the left and right side members 26 </ b> A are supported by the main frame 21 by lateral rods 27.

  The rear axle case 35 is connected to the upper surfaces of the left and right side members 26A by a holder 26E, and the lower end of the suspension unit 25 is connected to the holder 26E. Further, as described above, the bottom of the engine 31 is supported by the connecting frame 28 that connects the left and right side members 26A. With such a structure, the engine 31 and the transmission case 33 are supported by the left and right side members 26A.

  As a result, when the left and right rear wheels 2 are moved up and down in accordance with the road surface undulation, the transmission case 33, the engine 31, and the belt continuously variable transmission 32 are integrally moved up and down as the rear axle case 35 is moved up and down. . If the up / down operation involves an impact, the suspension unit 25 absorbs the impact.

(Moving part)
As shown in FIGS. 4 to 8, the engine 31 is disposed in the driving portion 30 with the crankshaft 31 </ b> C (see FIG. 8) in the horizontal position, and the input shaft 33 </ b> A is set in the horizontal position at a position adjacent to the rear side. A layout is adopted in which a mission case 33 is arranged, a muffler 40 having a long side is arranged behind the mission case 33, and a belt continuously variable transmission 32 is arranged at a side position between the engine 31 and the mission case 33. Has been. The muffler 40 is formed in a horizontally long cylindrical shape, and a lower end side thereof is fixed to a bracket extending from the auxiliary frame 26.

  The engine 31 has a structure in which a cylinder head 31B is connected to a cylinder block 31A on which a crankshaft 31C is supported. The cylinder head 31B is connected to the cylinder block 31A so as to be obliquely forward and upward, thereby reducing the level difference between the upper surface of the cylinder block 31A and the cylinder head 31B and making the entire engine more compact in the vertical direction. It is illustrated.

  Since the engine 31 and the transmission case 33 are disposed adjacent to each other in the front-rear direction, a gap 30A is formed between the upper part of the engine 31 (the upper part of the cylinder block 31A) and the upper part of the transmission case 33. A pair of left and right connecting projections 31D projecting obliquely rearward and upward are formed on the upper surface of the cylinder block 31A, and a pair of left and right connecting projections 33D projecting upward are formed on the upper surface of the mission case 33. A horizontal flat plate-like connecting plate 41 is disposed at a position covering the gap 30A above and above the upper surface of the engine 31 and the upper surface of the transmission case 33, and a plurality of front ends of the connecting plate 41 are provided. The bolt 41A is connected to the horizontal surface portion on the rear end side of the connection protrusion 31D, and the rear end of the connection plate 41 is connected to the horizontal surface portion on the upper end of the connection protrusion 33D by a plurality of bolts 41A. The connecting plate 41 is formed in a shape bent in an inverted V shape in a side view, and has a plurality of front and rear protrusions 41 </ b> C protruding upward on the upper surface side, and a maintenance opening for the transmission case 33 at the rear thereof. A cutout portion 41D that avoids the portion 33E is formed.

  Since the connecting plate 41 is provided in a horizontal posture, the tension of the endless belt 63 of the belt continuously variable transmission 32 may act between the output shaft 65A of the engine 31 and the input shaft 33A of the transmission case 33. In addition, the connecting plate 41 prevents the displacement of the relative positional relationship between the engine 31 and the transmission case 33. That is, the output shaft 65 </ b> A of the engine 31 and the input shaft 33 </ b> A of the mission case 33 are disposed in a lateral orientation at substantially the same level. Therefore, the width direction of the connecting plate 41 substantially coincides with the axial direction of the output shaft 65A and the axial direction of the input shaft 33A.

  As shown in FIG. 8, the belt continuously variable transmission 32 includes a drive pulley 61 on an output shaft 65A, a driven pulley 62 on an input shaft 33A, and an endless belt 63 wound around them. As described above, since the width direction of the connecting plate 41 is substantially coincident with the axial center direction of the output shaft 65A and the axial core direction of the input shaft 33A, the tension acting from the endless belt 63 is applied to each axial core. This acts in the direction of approaching the outer end side, and this tension is received in the lateral width direction of the connecting plate 41. Therefore, displacement of the relative positional relationship between the engine 31 and the transmission case 33 can be prevented by the connecting plate 41.

  Further, if the posture that can receive the force that changes the output shaft 65A and the input shaft 33A in a non-parallel posture is received in the width direction of the plate, the connecting plate 41 has the shaft core of the output shaft 65A and the shaft core of the input shaft 33A. It may be slightly inclined with respect to. As will be described later, the output shaft 65A of the engine 31 is the output shaft 65A of the centrifugal clutch 65 to which the driving force from the engine 31 is transmitted. However, the centrifugal clutch 65 is omitted and the crank shaft 31C of the engine 31 is used as the output shaft. Alternatively, a configuration may be adopted in which the output pulley (crankshaft 31C) is provided with a drive pulley 61 that extends into the transmission case 64.

  In addition, a generator 42 and a starter motor 43 are disposed as electrical components in the gap 30A, and a connecting plate 41 is disposed at a position covering the upper side thereof. Because of this arrangement, the connection plate 41 prevents the intrusion of water into the generator 42 and the starter motor 43 when the work vehicle is washed or during heavy rain. Note that the electrical components disposed in the gap 30A are not limited to the generator 42 and the starter motor 43, and include, for example, fuses and electrical wiring for engines.

  In this work vehicle, the engine 31 and the transmission case 33 are connected to each other by a connecting plate 41 during assembly work, and an integrated object having a belt continuously variable transmission 32 is mounted on the vehicle body. Moreover, the work in the form which isolate | separates an integrated object from a vehicle body is performed at the time of a maintenance. In order to easily perform such an operation, it is possible to form a mounting portion 41B of a hanging bracket (not shown) for lifting an integrated object on the connecting plate 41. The mounting portion 41B is configured by a screw hole formed in the connecting plate 41, and supports the hanging metal fitting in a form of being screwed into the screw hole. In addition, you may form a simple through-hole as the attaching part 41B. In this case, it is possible to employ a connection structure such as inserting a bolt part into a hanging metal fitting and screwing a nut into this to fix the connection.

  In addition, when lifting an integrated object, in order to realize stable lifting, hanging brackets are attached to a plurality of locations such as the left and right rear axle cases 35, and the lifting brackets are lifted by applying force to the plurality of hanging brackets. Is desirable.

  An engine blower 50 is provided on the side of the engine 31 opposite to the belt continuously variable transmission 32. The engine blower 50 includes a fan 50A that rotates by the driving force of the engine 31 and a case 50B that accommodates the fan 50A. The case 50B includes an intake opening 50C and a lateral portion from the rear side of the gap 30A. A bulging portion 50D bulging out is formed.

  With such a configuration, most of the cooling air sucked from the intake opening 50C of the case 50B is supplied from one end of the case 50B to the cylinder block 31A and the cylinder head 31B as the fan 50A rotates during operation of the engine 31. To do. When cooling air is supplied in this way, a part of the cooling air is supplied from the bulging portion 50D at the other end of the case 50B through the cooling air passage 30R as shown in FIG. 41 is fed into the gap 30A on the lower surface of 41. The cooling air supplied from the cooling air passage 30R to the gap 30A cools the generator 42 and the starter motor 43 as electrical components arranged in the gap 30A.

  As shown in FIGS. 1 and 7, a first air cleaner 45 for intake of the engine 31 and a belt continuously variable transmission 32 are disposed in a space between the operating unit 10 and the loading platform 4 on the back side of the back plate 24. A second air cleaner 46 for cooling air intake is disposed.

  An intake pipe 47 is connected to the cylinder head 31 </ b> B of the engine 31, and the tip of the intake pipe 47 is connected to the first air cleaner 45. An exhaust pipe 48 is connected to the cylinder head 31 </ b> B, and the muffler 40 is connected to the end of the exhaust pipe 48. The muffler 40 has a cylindrical structure, and is arranged at a rear position of the transmission case 33 in a horizontally long posture with the longitudinal direction being along the lateral direction of the vehicle body. A heat shield plate 49 made of metal such as a steel plate is provided at a position surrounding the upper surface of the muffler 40, and a gap is formed between the heat shield plate 49 and the outer surface of the muffler 40. Further, a centrifugal clutch 65 is provided on a side portion of the engine 31, and an intake duct 67 is connected to the intake portion 51 in the vicinity of the centrifugal clutch 65, and a tip of the intake duct 67 is connected to the second air cleaner 46. Yes.

[Driving part: Belt continuously variable transmission]
As shown in FIG. 8, the belt continuously variable transmission 32 includes a rubber endless belt extending over a drive pulley 61 capable of changing the belt winding diameter and a driven pulley 62 capable of changing the belt winding diameter. 63 is wound and these are accommodated in the transmission case 64. A metal belt may be used as the endless belt 63.

  A centrifugal clutch 65 to which rotational driving force is transmitted from the crankshaft 31C of the engine 31 is provided, and an output shaft 65A of the centrifugal clutch 65 is provided with a drive pulley 61. The input shaft 33A of the mission case 33 is provided with a driven pulley 62. The output shaft 65A of the centrifugal clutch 65 is disposed coaxially with the crankshaft 31C, and this is the output shaft 65A of the engine 31.

  The centrifugal clutch 65 is in a disconnected state when the rotational speed of the crankshaft 31C is less than a set value, and does not transmit the rotational force of the crankshaft 31C to the output shaft 65A. Further, when the rotational speed of the crankshaft 31C exceeds the set value, the connected state is reached, and the operation of transmitting the rotational force of the crankshaft 31C to the output shaft 65A is performed.

  The drive pulley 61 includes a fixed sheave 61A disposed on the proximal end side (side closer to the engine 31) of the output shaft 65A and a movable sheave 61B disposed on the distal end side of the output shaft 65A. Further, a winding diameter adjusting mechanism 66 for adjusting the position of the movable sheave 61B is provided at the protruding end of the output shaft 65A.

  The winding diameter adjusting mechanism 66 moves the movable sheave 61B in a direction approaching the fixed sheave 61A as the rotational speed of the output shaft 65A increases, thereby increasing the belt winding diameter of the drive pulley 61. On the contrary, as the rotational speed of the output shaft 65A decreases, the movable sheave 61B is moved away from the fixed sheave 61A to reduce the belt winding diameter of the drive pulley 61.

  The driven pulley 62 fixes the movable sheave 62A disposed on the proximal end side of the input shaft 33A (the side close to the transmission case 33), the fixed sheave 62B disposed on the distal end side of the input shaft 33A, and the movable sheave 62A. A coil spring 62C that applies an urging force in a direction to approach the sheave 62B.

  The coil spring 62 </ b> C applies a biasing force for determining the position of the movable sheave 62 </ b> A of the driven pulley 62 corresponding to the tension acting on the endless belt 63. That is, when the belt winding diameter of the drive pulley 61 changes, the tension acting on the endless belt 63 changes. As the tension increases, the movable sheave 62A is moved away from the fixed sheave 62B, and as the tension decreases, the movable sheave 62A approaches the fixed sheave 62B. Therefore, when the belt winding diameter of the drive pulley 61 is small, the belt winding diameter of the driven pulley 62 is set to a large value. On the contrary, when the belt winding diameter of the drive pulley 61 is increased. The belt winding diameter of the driven pulley 62 is set to a small value.

  As shown in FIG. 8, the transmission case 64 includes a case main body 64A supported on the vehicle body side (at least one of the transmission case 33 and the engine 31), and a cover body supported detachably with respect to the case main body 64A. 64B. A cooling air inlet 64C is formed on the engine side of the wall surface of the case main body 64A, and a bulging portion 64D that swells on the side opposite to the cover body 64B (on the transmission case 33 side) is formed on the mission case side of the wall surface. The main flange surface 64E is formed at the outer peripheral position of the case main body 64A. A flat vertical wall surface 64W that is orthogonal to the output shaft 65A is formed on the engine side (front side) of the case main body 64A, and the transmission case side (rear side) of the case main body 64A is longer than the vertical wall surface 64W. A bulging wall 64X that bulges toward the mission case 33 is formed, and the bulging portion 64D is configured by the bulging wall 64X. By thus forming the bulging portion 64D, a wider space is formed on the mission case side than the driven pulley 62.

  As shown in FIG. 9, the cooling air is sent to the bulging portion 64 </ b> D using the wind pressure generated by the rotation of the driven pulley 62, so that the cooling air is sent to the rear side of the vehicle body 3 from the upper part of the outer periphery of the driven pulley 62. A discharge portion 64F is formed on the top. The driven pulley 62 rotates in the direction indicated by the arrow R shown in the figure, and the cooling air taken into the transmission case 64 cools the inside of the transmission case 64 and flows in the direction of the discharge portion 64F. With this configuration, when the cooling air is discharged from the discharge portion 64F, the rear side of the vehicle body 3 in the direction along the tangential line of the substantially horizontal posture contacting the upper portion of the driven pulley 62 as the driven pulley 62 rotates. The wind pressure toward the discharge portion 64F acts on the cooling air, and the cooling air is efficiently discharged from the discharge portion 64F using this wind pressure.

  The cover body 64B has a structure that can accommodate the drive pulley 61, the winding diameter adjusting mechanism 66, and the driven pulley 62, and has a structure in which a sub-flange surface 64G is formed on the outer periphery. In this speed change case 64, the case main body 64A and the cover body 64B are connected by a bolt or the like in such a form that a sealing material such as rubber is sandwiched between the main flange surface 64E and the sub flange surface 64G.

  Due to such a configuration, when the rotational speed of the engine 31 exceeds the set value due to the operation of the accelerator pedal 15, the centrifugal clutch 65 transmits the driving force of the crankshaft 31C to the output shaft 65A. Since the output shaft 65A rotates at a low speed at the initial stage of this transmission, the winding diameter adjusting mechanism 66 sets the belt winding diameter of the drive pulley 61 to a small value, and in conjunction with this, the belt winding of the driven pulley 62 is set. The rotation diameter is set to a large value. As a result, the driving force of the engine 31 is transmitted to the input shaft 33A of the mission case 33 at a low speed (large reduction ratio). When the rotational speed of the engine 31 further increases, the winding diameter adjusting mechanism 66 increases the belt winding diameter of the drive pulley 61 as the output shaft 65A rotates at a higher speed, and the driven pulley 61 is driven in conjunction with this. The belt winding diameter of the pulley 62 is set to a small value. As a result, the driving force of the engine 31 is transmitted to the input shaft 33A of the mission case 33 at a high speed (low reduction ratio).

[Driving part: Cooling configuration of belt continuously variable transmission]
A clutch case 52 surrounding the centrifugal clutch 65 is connected to the cylinder block 31 </ b> A of the engine 31, and the clutch case 52 is connected to a case main body 64 </ b> A of the transmission case 64. Thereby, the clutch case 52 is disposed at a position sandwiched between the engine 31 and the transmission case 64. An intake portion 51 is formed in the clutch case 52, and the cooling air inlet 64 </ b> C is formed in the case main body 64 </ b> A connected to the clutch case 52, and the cooling air from the second air cleaner 46 is supplied to the intake portion 51. An intake duct 67 to be supplied is connected. With this configuration, the cooling air flows from the intake portion 51 into the clutch case 52 and is sent from the inside of the clutch case 52 to the inside of the transmission case 64 via the cooling air inlet 64C. Will be cooled. The air intake 51 may be formed on the case main body 64A.

  The cooling air inlet 64C described above is formed in a region surrounding the output shaft 65A, and a plurality of intake fins 61C are formed in a portion of the fixed sheave 61A of the drive pulley 61 that faces the cooling air inlet 64C. Yes. The movable sheave 62A and the fixed sheave 62B are formed with a number of reinforcing ribs 62D that can function as exhaust fins.

  As shown in FIGS. 8 and 9, the discharge portion 64F is formed in a cylindrical shape and extends from the upper portion of the rear portion of the case main body 64A so as to be slightly obliquely rearward and upward. 68 is connected. The exhaust duct 68 has a bent portion 68A formed at an intermediate position so that the exhaust direction is directed downward at the base end portion thereof and toward the inner side of the vehicle body, and the cooling air discharge path is reduced at the bent portion 68A. A restrictor 68B (which reduces the cross-sectional area of the discharge path) is provided. Further, the exhaust opening 68C at the end portion (downstream side in the exhaust direction) of the exhaust duct 68 is formed in a shape that expands in the direction along the longitudinal direction of the muffler 40 (lateral direction), and the exhaust direction is located behind the vehicle body 3. The cooling air is discharged to the gap between the muffler 40 and the heat shield plate 49 in a direction orthogonal to the longitudinal direction of the muffler 40 by being directed to the direction. The exhaust duct 68 includes an upper guide surface 68D directed downward in the rear direction for guiding the exhaust gas fed from the discharge portion 64F toward the throttle portion 68B, and a lower portion in the forward downward direction for guiding the exhaust gas from the throttle portion 68B downward. A guide surface 68E and a tip curved surface 68F for guiding the exhaust from the throttle 68B toward the exhaust opening 68C are formed. Note that the exhaust direction need not be horizontal as long as the exhaust is sent from the exhaust opening 68C to the muffler 40 in a direction orthogonal to the longitudinal direction of the muffler 40. For example, the exhaust from the exhaust opening 68C You may spray on the muffler 40 from diagonally upward or diagonally downward.

  With such a configuration, the intake fin 61 </ b> C creates a negative pressure as the drive pulley 61 is driven to rotate, and the outside air sucked by the second air cleaner 46 by this negative pressure serves as the cooling air via the intake duct 67. It is sucked into the inside of the transmission case 64 from 64C. The cooling air sucked in this way flows in the speed change case 64 from the drive pulley 61 to the driven pulley 62, and contacts the drive pulley 61, the driven pulley 62, and the endless belt 63 when flowing in this way. Take away heat and cool them.

  Then, the cooling air that has deprived the heat inside the transmission case 64 flows into the bulging portion 64D formed in the case main body 64A, and from the discharge portion 64F to the transmission case 64 in accordance with the flow of the wind accompanying the rotation of the driven pulley 62. Is discharged outside. Further, when the cooling air is sent from the discharge part 64F to the exhaust duct 68, the flow is suppressed in the throttle part 68B, so that the internal pressure of the transmission case 64 is increased. Thus, since the internal pressure of the transmission case 64 is increased, water and dust can be prevented from entering between the main flange surface 64E of the case body 64A and the sub flange surface 64G of the cover body 64B. Then, the cooling air reaching the end of the exhaust duct 68 is supplied to the gap between the muffler 40 and the heat shield plate 49 from the exhaust opening 68C, and the heat dissipation of the muffler 40 is also realized.

[Effect of the embodiment]
As described above, according to the present invention, the cooling air supplied to the transmission case 64 is brought into contact with the drive pulley 61, the driven pulley 62, and the endless belt 63 to achieve cooling. Further, since the cooling air is supplied from the case main body 64A of the transmission case 64 and the cooling air is discharged from the discharge portion 64F of the case main body 64A, the cooling air is also used when the cover body 64B is removed. There is no need to remove the duct to be supplied or the exhaust duct for sending cooling air, so that the operation can be easily performed.

  The case body 64A is formed with a bulging portion 64D that swells on the side opposite to the cover body 64B (on the mission case 33 side), and a discharge portion 64F is formed with respect to the bulging portion 64D. In the discharge part 64F, the wind pressure acting in the tangential direction from the upper part of the driven pulley 62 toward the discharge part 64F is caused to act on the cooling air as the driven pulley 62 rotates, so that the cooling air can be discharged efficiently. I have to. Further, since the bulging portion 64D forms a wide space apart from the driven pulley 62, the cooling air is discharged from the bulging portion 64D to the discharge portion 64F and is obstructed by the pulley and the endless belt. Efficient discharge. Further, when cooling air is sent from the discharge part 64F to the exhaust duct 68, the flow is restricted in the throttle part 68B to increase the internal pressure of the transmission case 64, and from the connection surface between the case body 64A and the cover body 64B. Prevents intrusion of rainwater and dust.

  Further, the cooling air discharged from the exhaust opening 68C of the exhaust duct 68 is sent to a wide area along the longitudinal direction of the muffler 40 from the exhaust opening 68C of the exhaust duct 68, and this cooling air is discharged to the rear side of the vehicle body 3. As a result, the air is supplied to the gap with the heat shield plate 49, so that even when the vehicle body 3 is traveling, it reaches the surface of the muffler 40 without being affected by the air flow from the outside, and the muffler 40 can be cooled well. It becomes.

  In particular, in the belt continuously variable transmission 32, a strong tension acts on the endless belt 63, and this tension acts on the output shaft 65A and the input shaft 33A, so that the output shaft 65A and the input shaft 33A are in a non-parallel posture. A force acts on the engine 31 and the transmission case 33 toward the vehicle. On the other hand, the connection plate 41 is connected to the upper part of the engine 31 and the transmission case 33 in a posture that strongly resists the action of the tension, so that the relative posture between the engine 31 and the transmission case 33 is maintained with high accuracy. it can.

  Further, since the connecting plate 41 is disposed at a position covering the gap 30A between the engine 31 and the transmission case 33, it prevents water from entering the electrical components such as the generator 42 and the starter motor 43 disposed in the space. It will be possible. This eliminates the inconvenience of water intruding into electrical components even when the car is washed at high pressure or during heavy rain.

  The present invention can be used for all work vehicles including a dry belt continuously variable transmission.

31 Engine 31C Crankshaft 51 Intake section 52 Clutch case 61 Drive pulley 62 Driven pulley 63 Endless belt 64 Shift case 65 Centrifugal clutch 65A Output shaft 64A Case body 64B Cover body 64C Cooling air inlet 64D Swelling section 64F Discharge section 68 Exhaust duct 68B Aperture

Claims (3)

A work vehicle comprising a belt continuously variable transmission in which an endless belt is wound around a driving pulley capable of changing a belt winding diameter and a driven pulley capable of changing a belt winding diameter,
A speed change case that accommodates the drive pulley, the driven pulley, and the endless belt includes a case body that is supported on the vehicle body side, and a cover body that is detachably supported with respect to the case body.
A bulging portion is formed by bulging a part of the wall portion of the case main body on the side opposite to the cover body, and a discharge portion for sending cooling air taken into the transmission case is disposed on the rear side of the vehicle body from the bulging portion. A work vehicle that is formed with a posture to send cooling air to the vehicle.   2. The work vehicle according to claim 1, wherein a cylindrical exhaust duct is connected to the discharge portion, and a throttle portion for reducing the discharge path is formed at an intermediate position of the exhaust duct.   A centrifugal clutch is provided that transmits the driving force of the crankshaft to the output shaft when the rotational speed of the crankshaft of the engine exceeds a set value, and a clutch case that houses the centrifugal clutch is disposed between the engine and the transmission case. The work vehicle according to claim 1 or 2, wherein an intake portion for receiving cooling air is formed in the clutch case, and a cooling air inlet for guiding the cooling air from the clutch case to the transmission case is formed in the case body. .

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