Continuously variable transmission, utility vehicle and CVT case

A continuously variable transmission includes: a CVT mechanism including a driving pulley, a driven pulley, an annular belt wound around the driving pulley and the driven pulley, and a centrifugal fan blade disposed at the driving pulley; and a CVT case that defines an internal space accommodating the CVT mechanism. An inner surface of the CVT case includes: a peripheral surface portion that covers the CVT mechanism from an outer side in a radial direction orthogonal to an axial direction of the driving pulley; and a guide surface portion that projects toward an inner side in the radial direction from the peripheral surface portion.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a continuously variable transmission, a utility vehicle, and a CVT case.

Description of the Related Art

JP2004-316857A discloses an all terrain vehicle including a continuously variable transmission. The continuously variable transmission includes a CVT mechanism and a CVT case that defines an internal space accommodating the CVT mechanism. An intake duct that guides outside air as cooling air to the internal space of the CVT case is connected to the CVT case.

SUMMARY OF THE INVENTION

A continuously variable transmission according to one aspect of the present disclosure includes: a CVT mechanism including a driving pulley, a driven pulley, an annular belt wound around the driving pulley and the driven pulley, and a centrifugal fan blade disposed at the driving pulley; and a CVT case that defines an internal space accommodating the CVT mechanism. An inner surface of the CVT case includes a peripheral surface portion that covers the CVT mechanism from an outer side in a radial direction orthogonal to an axial direction of the driving pulley and a guide surface portion that projects toward an inner side in the radial direction from the peripheral surface portion.

A utility vehicle according to one aspect of the present disclosure includes: a prime mover; and a continuously variable transmission connected to the prime mover. The continuously variable transmission includes: a CVT mechanism including a driving pulley, a driven pulley, an annular belt wound around the driving pulley and the driven pulley, and a centrifugal fan blade disposed at the driving pulley; and a CVT case that defines an internal space accommodating the CVT mechanism. An inner surface of the CVT case includes: a peripheral surface portion that covers the CVT mechanism from an outer side in a radial direction orthogonal to an axial direction of the driving pulley; and a guide surface portion that projects toward an inner side in the radial direction from the peripheral surface portion.

A CVT case according to one aspect of the present disclosure is a CVT case that defines an internal space accommodating a CVT mechanism including a driving pulley, a driven pulley, an annular belt wound around the driving pulley and the driven pulley, and a centrifugal fan blade disposed at the driving pulley. The CVT case includes an inner surface that defines the internal space. The inner surface includes: a peripheral surface portion that covers the CVT mechanism from an outer side in a radial direction orthogonal to an axial direction of the driving pulley; and a guide surface portion that projects toward an inner side in the radial direction from the peripheral surface portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1is a schematic left side view of a utility vehicle1according to the embodiment. As shown inFIG.1, the utility vehicle1includes a vehicle body frame2, a pair of left and right front wheels3supporting a front portion of the vehicle body frame2, and a pair of left and right rear wheels4supporting a rear portion of the vehicle body frame2. Tires of the front wheels3and the rear wheels4are balloon tires for uneven ground traveling. A space between the left and right front wheels3is covered with a hood5from above. A driver's seat6and a passenger seat7are arranged side by side behind the hood5and are supported by the vehicle body frame2.

The vehicle body frame2is a pipe frame including pipes connected to each other. The vehicle body frame2includes, for example, a cabin frame2asurrounding an occupant space C where the driver's seat6and the passenger seat7are arranged. Entrances that are opened or closed by side doors8are open at both sides of the occupant space C. The occupant space C surrounded by the cabin frame2ais exposed to an outside. A dash panel9is arranged in front of the driver's seat6and the passenger seat7. A steering wheel10is located at the dash panel9so as to project toward the driver's seat6.

A cargo bed11defining a hollow loading space that is open to an outside is arranged behind the cabin frame2a. A driving source assembly12is mounted behind the driver's seat6and under the cargo bed11. The driving source assembly12includes a prime mover13and a continuously variable transmission14. The prime mover13may be an internal combustion engine, an electric motor, or a combination thereof. The continuously variable transmission14is cooled in such a manner that outside air as cooling air flows inside the continuously variable transmission14. In a side view of the vehicle1, the continuously variable transmission14is arranged in front of and above the rear wheels4. In the side view of the vehicle1, the continuously variable transmission14is arranged diagonally such that a longitudinal direction of the continuously variable transmission14is directed rearward and upward.

An air cleaner15including an air take-in port15athrough which the outside air is taken in the air cleaner15is arranged in front of the steering wheel10and under the hood5. The air cleaner15is arranged higher than a seat surface6aof the driver's seat6. An intake duct17that is a fluid duct is attached to the continuously variable transmission14. The intake duct17is arranged lower than the seat surface6aof the driver's seat6. An intake pipe16that connects the air cleaner15to the intake duct17extends in a front-rear direction while passing through a position lower than the seat surface6aof the driver's seat6.

FIG.2is a sectional view of the continuously variable transmission14ofFIG.1. As shown inFIG.2, the continuously variable transmission14includes a CVT mechanism20and a CVT case21accommodating the CVT mechanism20. The CVT mechanism20includes an input shaft31, an output shaft32, a driving pulley33, a driven pulley34, and a belt35. An axis X1of the input shaft31and an axis of a driving shaft13aare located on the same straight line. To be specific, the input shaft31is connected to the driving shaft13a(for example, a crank shaft) of the prime mover13on the same axis and receives rotational power from the prime mover13. The output shaft32outputs the rotational power to driving wheels (the front wheels3and/or the rear wheels4). Hereinafter, a direction in which the axis X1extends is referred to as an axial direction X1.

The driving pulley33is disposed at the input shaft31so as to rotate integrally with the input shaft31. The driven pulley34is disposed at the output shaft32so as to rotate integrally with the output shaft32. The belt35having a V shape is wound around the driving pulley33and the driven pulley34. In the present embodiment, the driving shaft13aand the input shaft31are directly coupled to each other, but a centrifugal clutch may be interposed between the driving shaft13aand the input shaft31.

The driving pulley33includes: a fixed sheave41fixed to the input shaft31; a movable sheave42fitted to the input shaft31so as to be movable in the axial direction X1; and a sheave thruster43(for example, a flyweight type). The belt35is sandwiched between pressure surfaces of the fixed sheave41and the movable sheave42. When the movable sheave42moves along the input shaft31, and this changes an interval between the fixed sheave41and the movable sheave42, a position, where the belt35is sandwiched, at the driving pulley33in a radial direction (direction orthogonal to the axis X1) of the driving pulley33changes (i.e., an effective diameter of the driving pulley33changes).

The sheave thruster43mechanically moves the movable sheave42relative to the fixed sheave41in accordance with a rotational frequency of the driving pulley33such that the movable sheave42approaches or separates from the fixed sheave41in the axial direction X1. The sheave thruster43includes a receiving plate51, a coupling arm52, a pressure receiving roller53, and a flyweight54. The receiving plate51is arranged at a back surface side of the movable sheave42and away from the movable sheave42in the axial direction X1. The pressure receiving roller53is supported by the receiving plate51through the coupling arm52. The flyweight54is arranged at the back surface side of the movable sheave42and is supported by the movable sheave42while being in contact with the pressure receiving roller53.

The flyweight54turns in a direction away from the movable sheave42by rotational centrifugal force of the driving pulley33to press the pressure receiving roller53in the axial direction X1and moves the movable sheave42in a direction toward the fixed sheave41by reaction force from the pressure receiving roller53. To be specific, by the rotational centrifugal force of the driving pulley33, the sheave thruster43generates thrust that narrows the interval between the fixed sheave41and the movable sheave42. A centrifugal fan blade44that generates swirling flow is disposed on a back surface of the fixed sheave41.

The driven pulley34includes: a fixed sheave61fixed to the output shaft32; and a movable sheave62fitted to the output shaft32so as to be movable in a direction (may be referred to as an axial direction X2) in which an axis X2of the output shaft32extends. A cam cylinder63including spiral cam grooves is fixed to an outer peripheral surface of the output shaft32. The cam cylinder63and the fixed sheave61rotate together with the output shaft32. A sleeve64is integrally coupled to an inner peripheral end of the movable sheave62. The sleeve64is fitted to an outer peripheral surface of the cam cylinder63so as to be movable in the axial direction X2and supports a roller that is movable along the cam grooves of the cam cylinder63.

The sleeve64is biased toward the fixed sheave61by a pressure regulating spring65, and the movable sheave62is pressed toward the fixed sheave61. When the movable sheave62receives rotational force by tensile force of the belt35, thrust that moves the movable sheave62toward the fixed sheave61is generated by a cam action between the cam cylinder63and the roller.

When the rotational frequency of the input shaft31is low, the effective diameter of the driving pulley33is small, and the effective diameter of the driven pulley34is large (i.e., a reduction ratio is high). When the rotational frequency of the input shaft31increases, the movable sheave42approaches the fixed sheave41by the thrust of the sheave thruster43generated by the increase in centrifugal force, and this increases the effective diameter of the driving pulley33. At the driven pulley34, the tensile force of the belt35increases, and this increases force acting toward a radially inner side of the belt35. Then, the movable sheave62moves in a direction away from the fixed sheave61against spring force of the pressure regulating spring65and cam thrust of the cam cylinder63, and this decreases the effective diameter of the driven pulley34(i.e., the reduction ratio becomes low).FIG.2shows that the movable sheave42is located farthest away from the fixed sheave41at the driving pulley33.

The CVT case21defines an internal space21ain which the CVT mechanism20is arranged. The CVT case21includes a case main body71and a cover72. The case main body71may be made of metal. The cover72may be made of metal or synthetic resin. The case main body71has a recessed section. The case main body71includes an inner peripheral surface71aand an opening71b. The inner peripheral surface71ais opposed to the centrifugal fan blade44from an outer side in a radial direction orthogonal to the axial direction X1. The opening71bis open toward a first side of the driving pulley33in the axial direction X1and is defined by an end edge of the inner peripheral surface71a.

The cover72is attached to the case main body71by fasteners to close the opening71b. The cover72has a recessed section. The cover72includes a bottom wall portion72a, a peripheral wall portion72b, and an opening72c. The bottom wall portion72ais opposed to the CVT mechanism20from the first side in the axial direction X1. The peripheral wall portion72bprojects from the bottom wall portion72atoward the case main body71. The opening72cis open toward a second side in the axial direction X1and is defined by an end edge of the peripheral wall portion72b. The case main body71and the cover72include respective contact surfaces71cand72dthat are in contact with each other.

The bottom wall portion72aincludes a recess72ethat is located in a region opposed to the driving pulley33in the axial direction X1and is recessed toward the first side in the axial direction X1. The sheave thruster43is accommodated in the recess72e. The case main body71includes an inflow opening21b(seeFIG.1) and an outflow opening21c(seeFIG.3) which communicate with the internal space21a. The cooling air from an outside flows through the inflow opening21b(seeFIG.1) into the internal space21a, and the cooling air in the internal space21ais discharged through the outflow opening21c(seeFIG.3) to an outside.

A partition22is disposed in the CVT case21. The partition22extends in the radial direction of the driving pulley33and divides the internal space21ainto a first chamber S1and a second chamber S2. The first chamber S1communicates with the inflow opening21b(seeFIG.1). The second chamber S2communicates with the outflow opening21c(seeFIG.3). The CVT mechanism20is arranged in the second chamber S2. The partition22includes a portion opposed to the centrifugal fan blade44in the axial direction X1. The partition22includes a communication opening H that is opposed to a radially inner portion of the centrifugal fan blade44and makes the first chamber S1communicate with the second chamber S2. The input shaft31passes through the communication opening H.

FIG.3is a sectional view taken along line ofFIG.2. As shown inFIG.3, the inner peripheral surface71aof the case main body71includes an arc-shaped first region71aathat is opposed to the internal space21afrom an opposite side of the axis X2in a direction in which a virtual line V connecting the axis X1and the axis X2extends when viewed from the axial direction X1. The inner peripheral surface71aof the case main body71includes a second region71abthat is located in front of a point P, located farthest from the axis X2, of a radially outer end of the fixed sheave41in a rotational direction D of the fixed sheave41and extends along the virtual line V when viewed from the axial direction X1. When viewed from the axial direction X1, the second region71abextends linearly along the virtual line V.

When the centrifugal fan blade44rotates by the rotation of the driving pulley33(seeFIG.2), the cooling air around the communication opening H is supplied outward in the radial direction. The supplied cooling air flows toward the outflow opening21calong the first region71aaand the second region71abof the inner peripheral surface71aof the case main body71. Then, the cooling air which has cooled the belt35(seeFIG.2) and the like flows out from the outflow opening21c. When the centrifugal fan blade44supplies the cooling air around the communication opening H outward in the radial direction, negative pressure is generated around the communication opening H in the second chamber S2, and the cooling air in the first chamber S1(seeFIG.2) is sucked into the second chamber S2through the communication opening H.

FIG.4is a sectional view taken along line IV-IV ofFIG.2.FIG.5is a perspective view of the cover of the CVT case ofFIG.2.FIG.4shows that the movable sheave42is located closest to the fixed sheave41in the driving pulley33. As shown inFIG.4, the contact surface71cof the case main body71and the contact surface72dof the cover72are arranged at the second side in the axial direction X1beyond a portion of a radially outer end42aof the movable sheave42located closest to the fixed sheave41, the portion being located at the most second side in the axial direction X1.

As shown inFIGS.2and5, an inner surface80of the cover72includes a bottom surface80aand an inner peripheral surface80b. The bottom surface80ais opposed to the CVT mechanism20from the first side in the axial direction X1. The inner peripheral surface80bis opposed to the CVT mechanism20from the outer side in the radial direction orthogonal to the axial direction X1. As shown inFIGS.2and5, the inner peripheral surface80bof the cover72includes a first region80balocated adjacent to the first region71aa(seeFIG.3) of the inner peripheral surface71aof the case main body71in the axial direction X1. To be specific, the first region80baof the inner peripheral surface80bof the cover72is an arc-shaped region that is opposed to the internal space21afrom the opposite side of the axis X2in the direction in which the virtual line V extends when viewed from the axial direction X1.

As shown inFIGS.4and5, the inner peripheral surface80bof the cover72includes a second region80bblocated adjacent to the second region71ab(seeFIG.3) of the inner peripheral surface71aof the case main body71in the axial direction X1. The second region80bbof the inner peripheral surface80bof the cover72is a region that is located in front of the point P (seeFIG.3) in the rotational direction D of the fixed sheave41and extends along the virtual line V when viewed from the axial direction X1. The second region80bbextends linearly along the virtual line V when viewed from the axial direction X1. The inner peripheral surface80bof the cover72has a stair shape at the first region80baand a stair shape at the second region80bb.

As shown inFIGS.2and4, the inner peripheral surface80bof the cover72has such a stair shape that in the first region80ba, the inner peripheral surface80bapproaches the axis X1as the inner peripheral surface80bextends from the opening72ctoward a bottom surface portion86. Specifically, the inner peripheral surface80bof the cover72includes a first peripheral surface portion81, a first guide surface portion82, a second peripheral surface portion83, a second guide surface portion84, and a third peripheral surface portion85. The inner surface80of the cover72includes the bottom surface portion86that is opposed to the driving pulley33in the axial direction X1. The first peripheral surface portion81, the first guide surface portion82, the second peripheral surface portion83, the second guide surface portion84, and the third peripheral surface portion85are lined up in this order from the opening72ctoward the bottom surface portion86.

In the cover72, the first peripheral surface portion81is arranged adjacent to the contact surface72din the axial direction X1. With the cover72fixed to the case main body71, the first peripheral surface portion81is arranged adjacent to the inner peripheral surface71aof the case main body71in the axial direction X1. The first peripheral surface portion81is arranged on an extension of the inner peripheral surface71aof the case main body71in the axial direction X1. The first peripheral surface portion81faces an inner side in the radial direction orthogonal to the axial direction X1so as to cover the CVT mechanism20from the outer side in the radial direction.

The first guide surface portion82projects toward the inner side in the radial direction from an end of the first peripheral surface portion81which end is located at the first side in the axial direction X1. The first guide surface portion82faces the second side in the axial direction X1. As shown inFIG.2, the first guide surface portion82is arranged at the first side in the axial direction X1beyond a portion of a radially outer end41aof the fixed sheave41, the portion being located at the most first side in the axial direction X1. The first guide surface portion82is arranged at the second side in the axial direction X1beyond a portion of the radially outer end42aof the movable sheave42located farthest away from the fixed sheave41, the portion being located at the most second side in the axial direction X1. More specifically, as shown inFIG.4, the first guide surface portion82is arranged at the second side in the axial direction X1beyond a portion of the radially outer end42aof the movable sheave42located closest to the fixed sheave41, the portion being located at the most second side in the axial direction X1.

The second peripheral surface portion83extends from a radially inner end of the first guide surface portion82toward the first side in the axial direction X1. The second peripheral surface portion83faces the inner side in the radial direction so as to cover the CVT mechanism20from the outer side in the radial direction. The second peripheral surface portion83is closer to the axis X1than the first peripheral surface portion81is.

The second guide surface portion84projects toward the inner side in the radial direction from an end of the second peripheral surface portion83which end is located at the first side in the axial direction X1. The second guide surface portion84faces the second side in the axial direction X1. As shown inFIG.4, the second guide surface portion84is arranged at the first side in the axial direction X1beyond a portion of the radially outer end42aof the movable sheave42located closest to the fixed sheave41, the portion being located at the most first side in the axial direction X1.

The third peripheral surface portion85extends from a radially inner end of the second guide surface portion84toward the first side in the axial direction X1. The third peripheral surface portion85faces the inner side in the radial direction so as to cover the CVT mechanism20from the outer side in the radial direction. The third peripheral surface portion85is closer to the axis X1than the second peripheral surface portion83is. The third peripheral surface portion85is connected to the bottom surface portion86at the first side in the axial direction X1.

As shown inFIG.5, the inner peripheral surface80bof the cover72includes a first extended guide surface portion87and a second extended guide surface portion88in the second region80bb. The first extended guide surface portion87is continuous with the first guide surface portion82in a circumferential direction of the inner peripheral surface80b. When viewed from the axial direction X1, the first extended guide surface portion87projects toward the virtual line V connecting the axis X1of the driving pulley33and the axis X2of the driven pulley34. The second extended guide surface portion88is continuous with the second guide surface portion84in the circumferential direction of the inner peripheral surface80bof the cover72. The second extended guide surface portion88projects toward the virtual line V when viewed from the axial direction X1.

A projection amount L1of the first extended guide surface portion87decreases as the first extended guide surface portion87extends from the driving pulley33toward the driven pulley34. Similarly, a projection amount L2of the second extended guide surface portion88decreases as the second extended guide surface portion88extends from the driving pulley33toward the driven pulley34. At the same position of the inner peripheral surface80bof the cover72in the circumferential direction, the projection amount L2of the second extended guide surface portion88is larger than the projection amount L1of the first extended guide surface portion87.

According to the above-described configuration, the cooling air which has reached the first peripheral surface portion81of the CVT case21by the centrifugal fan blade44is guided by the first guide surface portion82of the CVT case21and is therefore prevented from flowing in the axial direction X1. On this account, the cooling air supplied by the centrifugal fan blade44is guided so as to flow along the belt35. Thus, the CVT mechanism20including the belt35can be efficiently cooled.

The first guide surface portion82is arranged at the second side in the axial direction X1beyond the radially outer end42aof the movable sheave42located farthest away from the fixed sheave41. More specifically, the first guide surface portion82is arranged at the second side in the axial direction X1beyond the radially outer end42aof the movable sheave42located closest to the fixed sheave41. Therefore, the cooling air supplied by the centrifugal fan blade44is suitably prevented from moving toward the first side in the axial direction X1, and the cooling air flows along the first peripheral surface portion81of the CVT case21at an adequate flow rate. Thus, the belt35can be effectively cooled.

The first guide surface portion82is arranged at the first side in the axial direction X1beyond the position of the radially outer end41aof the fixed sheave41. Therefore, the cooling air supplied by the centrifugal fan blade44is suitably caught by the first guide surface portion82of the CVT case21, and the cooling air flows along the first peripheral surface portion81of the CVT case21at an adequate flow rate. Thus, the belt35can be effectively cooled.

Since the first guide surface portion82is formed on the inner surface80of the cover72, the first guide surface portion82facing the first side in the axial direction X1can be easily formed.

The contact surface71cof the case main body71and the contact surface72dof the cover72are arranged at the second side in the axial direction X1beyond the radially outer end42aof the movable sheave42located closest to the fixed sheave41. Therefore, the first guide surface portion82facing the first side in the axial direction X1can be formed at the cover72.

The second guide surface portion84projecting toward the inner side in the radial direction from the second peripheral surface portion83is disposed at the first side of the second peripheral surface portion83in the axial direction X1. Therefore, the directivity of the cooling air flowing from the driving pulley33toward the driven pulley34further improves, and therefore, the cooling efficiency can be improved. More specifically, the second guide surface portion84is arranged at the first side in the axial direction X1beyond the radially outer end42aof the movable sheave42located closest to the fixed sheave41. Therefore, the movable sheave42can be suitably cooled while improving the directivity of the cooling air.

The inner surface80of the CVT case21includes: the first extended guide surface portion87that is continuous with the first guide surface portion82; and the second extended guide surface portion88that is continuous with the second guide surface portion84. Therefore, the belt35and the driven pulley34can be effectively cooled.

The projection amount L1of the first extended guide surface portion87and the projection amount L2of the second extended guide surface portion88decrease as the first extended guide surface portion87and the second extended guide surface portion88extend from the driving pulley33toward the driven pulley34. Therefore, the driven pulley34can also be suitably cooled by the cooling air.

As above, the embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this and is also applicable to embodiments in which modifications, replacements, additions, omissions and the like are suitably made. Moreover, a new embodiment may be prepared by combining the components described in the above embodiment. For example, some of components or methods in an embodiment may be applied to another embodiment, and some of components in an embodiment may be separated and arbitrarily extracted from the other components in the embodiment. Furthermore, the components shown in the attached drawings and the detailed explanations include not only components essential to solve the problems but also components for exemplifying the above technology and not essential to solve the problems.