Vehicle axle device

A differential case (23) is therein provided with a plurality of rotating discs (38) that are spline-coupled to an outer peripheral side of aright side gear (35), and a plurality of non-rotating discs (39) that are respectively arranged between the respective rotating discs (38) and are non-rotatable relative to the differential case (23) and are movable in a left-right direction. A pressure ring (43) that presses the non-rotating discs (39) toward the rotating discs (38) is disposed between a right retainer (41) positioned in the right side gear (35)-side and the non-rotating disc (39). The right retainer (41) is therein provided with a piston accommodating part (41D) in a position facing the pressure ring (43) in the left-right direction. The piston accommodating part (41D) is therein provided with a piston (46) that is displaced by hydraulic pressure to press the non-rotating discs (39) against the rotating discs (38) through the pressure ring (43).

TECHNICAL FIELD

The present invention relates to a vehicle axle device to be used suitably for a wheel type construction machine such as a wheel loader and a wheel type hydraulic excavator, for example.

BACKGROUND ART

In general, for example, there is known a wheel loader as a representative example of a wheel type construction machine. In this wheel loader, a front vehicle body is coupled to the front side of a rear vehicle body to be capable of swinging in a left-right direction, and a working mechanism composed of an arm, a bucket and the like is mounted to the front vehicle body. On the other hand, an engine as a drive source, a torque converter, a transmission, a hydraulic pump and the like are mounted on the rear vehicle body of the wheel loader. Power of the engine is transmitted to the transmission through the torque converter.

Axle devices are mounted on the front vehicle body and the rear vehicle body respectively to drive and rotate left and right wheels. This axle device is connected via a propeller shaft to an output shaft of the transmission to transmit a rotational force of the engine to the left and right wheels. Here, the axle device is provided with left and right axle shafts, a hollow differential body, and a differential mechanism. The differential body is disposed between left and right axle tubes accommodating therein the left and right axle shafts. The differential mechanism is disposed in the differential body to distribute the rotational force of the engine to the left and right wheels. Mount parts are disposed respectively on left and right axle tubes in a front axle device. The front axle device is attached via the left and right mount parts to the front vehicle body. On the other hand, a rear axle device is attached via an axle support to the rear vehicle body.

Incidentally, when a wheel loader travels in the sand, in the mud or the like, for example, in a case where a ground road surface state of the left wheel differs from that of the right wheel, one of the left and right wheels possibly runs idle by the differential mechanism. For this reason, there is known a limited slip differential mechanism. The limited slip differential mechanism temporarily locks the differential mechanism in response to a condition. As a result, the rotational force of the engine is transmitted to the left and right wheels without one thereof running idle.

The limited slip differential mechanism is provided with a differential case that rotates with an engine, and pinion gears, left and right side gears, left and right transmission shafts, non-rotating discs, and rotating discs, which are arranged in the differential case. The left and right side gears are engaged with the pinion gears in the differential case. The left and right transmission shafts are connected to the left and right side gears to transmit rotation of the differential case to the axle shafts. The non-rotating disc is disposed in the differential case in a non-rotating state relative to the differential case. The rotating disc is disposed in the differential case in an axial overlapping state with the non-rotating disc to rotate together with the left and right side gears. In addition, the limited slip differential mechanism of a hydraulic clutch type is provided with a piston that axially moves by supply of a hydraulic force. This piston presses the non-rotating disc to be made in frictional contact with the rotating disc. Thereby, when a torque difference between the left and right axle shafts is below a torque capacity of a clutch, the differential mechanism becomes in a lock state (a differential lock state). As a result, the left and right side gears rotate together with the differential case to cause the left and right transmission shafts to be connected to each other. Thereby, the torque is transmitted to each of the left and right axle shafts (Refer to Patent Document 1).

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Incidentally, partition walls are disposed inside of the differential body configuring part of the axle device, and a gear room for accommodating the differential mechanism is defined by the partition walls. There are two kinds of differential bodies, one being of a one-piece structure in which a section forming the gear room and the partition walls are integrally formed, and the other being of a two-piece structure in which the section forming the gear room and the partition walls are separately formed. The differential body of the one-piece structure can cut down more on the number of components and the assembly man-hours as compared to those of the two-piece structure, therefore to simplify the axle device. The axle device according to Patent Document 1 has the differential body of the two-piece structure, wherein a piston is disposed in a piston accommodating part disposed on a surface of the partition wall in a gear room side.

However, since partitions are arranged on both the left and right sides in the gear room in the differential body of the one-piece structure, a space of the gear room is made narrower in accordance therewith, causing a processing work in the gear room to be difficult. Accordingly, the differential body of the one-piece structure can reduce the number of components and the assembly man-hours and on the other hand, has a problem with difficulty of forming the piston accommodating section on the surface of the partition wall in the gear room side.

The present invention is made in view of the aforementioned problems in the conventional technology, and an object of the present invention is to provide a vehicle axle device that can simplify the configuration of a differential body.

The present invention is applied to a vehicle axle device, comprising: left and right axle shafts to which left and right wheels are respectively attached; a hollow differential body that is disposed between left and right axle tubes accommodating the left and right axle shafts and in both sides of a left-right direction of which partition walls each having a through hole penetrating in the left-right direction are respectively arranged; and a differential mechanism that is disposed between the left and right partition walls of the differential body to transmit a rotational force of a drive source to the left and right axle shafts, wherein the differential mechanism includes: a differential case that is rotatably supported through bearings on left and right retainers respectively attached in the through holes of the left and right partition walls and is rotated by the drive source; a plurality of pinion gears that are arranged in the differential case and rotate together with the differential case; left and right side gears that are arranged in the differential case and are respectively engaged with the respective pinion gears; and left and right transmission shafts that are connected to the respective side gears to transmit the rotation of the differential case to the left and right axle shafts.

The present invention is characterized in that: the differential case is therein provided with a plurality of rotating discs that are spline-coupled to an outer peripheral side of one side gear of the left and right side gears and a plurality of non-rotating discs that are arranged between the plurality of rotating discs and are non-rotatable relative to the differential case and movable in the left-right direction; a pressure ring is disposed between one retainer of the left and right retainers positioned in the one side gear-side and the non-rotating disc to press the non-rotating disc against the rotating disc; a piton accommodating part is disposed in the one retainer in a position facing the pressure ring in the left-right direction; and a piston is disposed in the piston accommodating part of the one retainer, the piston being displaced by hydraulic pressures to press the non-rotating disc via the pressure ring against the rotating disc and couple the left and right transmission shafts.

According to the present invention, the piston accommodating part is disposed in the one retainer of the left and right retainers and the piston can be disposed in the piston accommodating part disposed in the one retainer. Thereby, only by attaching the one retainer into the through hole in the partition wall, the piston can be incorporated in the differential mechanism accommodated in the differential body. Accordingly, for example, as compared to a case of forming the piston accommodating part on the partition wall of the differential body, the structure of the differential body can be more simplified.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, descriptions will be in detail made by taking a case where vehicle axle devices according to an embodiment in the present invention are mounted on a wheel loader, as an example with reference toFIG. 1toFIG. 14.

InFIG. 1, a wheel loader1includes a rear vehicle body2, a front vehicle body3, rear wheels4, front wheels5, a working mechanism6that is disposed on the front side of the front vehicle body3, and axle devices11,12to be described later. The front vehicle body3is coupled to the front side of the rear vehicle body2to be capable of swinging in a left-right direction. The rear wheels4are arranged in both sides of the rear vehicle body2in the left-right direction, and the front wheels5are arranged in both sides of the front vehicle body3in the left-right direction.

Here, the rear vehicle body2is provided with an engine7as a drive source, a torque converter8, a transmission9, a hydraulic pump (unillustrated) and the like, which are mounted thereon. The transmission9is connected to the rear axle device11through a propeller shaft9A extending in a front-rear direction and is connected to the front axle device12through a propeller shaft9B. A cab10in which an operator gets is disposed on the upper side of the rear vehicle body2.

The rear axle device11is disposed to be positioned on the lower side of the rear vehicle body2. The rear axle device11is formed to extend in the left-right direction, and the rear wheels4are respectively mounted to both end parts of the rear axle device11in the left-right direction.

The front axle device12is disposed to be positioned on the lower side of the front vehicle body3. The front axle device12is formed to extend in the left-right direction as similar to the rear axle device11, and the front wheels5are respectively mounted to both end parts of the front axle device12in the left-right direction.

Here, the rear axle device11and the front axle device12are configured in the same way with each other except for a point where a connection position between the propeller shafts9A,9B differs therebetween. Therefore, in the present embodiment, an explanation will be in detail made of the configuration of the front axle device12, and an explanation of the configuration of the rear axle device11is to be omitted.

The front axle device12is connected to the propeller shaft9B to drive/rotate the left and right front wheels5. The front axle device12includes, as illustrated inFIG. 2andFIG. 3, a casing13, left and right axle shafts19L,19R, a differential mechanism20, left and right planetary gear reduction mechanisms51L,51R, left and right brake mechanisms55L,55R, which will be described later, and the like.

The casing13configures an outer shell of the front axle device12. The casing13is provided with a hollow differential body14positioned in an immediate part in the left-right direction, and left and right axle tubes15L,15R positioned in both sides of the differential body14in the left-right direction. The differential mechanism20and the left and right brake mechanisms55L,55R are accommodated in the differential body14. The left and right axle shafts19L,19R are respectively supported in the left and right axle tubes15L,15R to be rotatable therein. The front wheels5are respectively attached to the front end sides of the left and right axle shafts19L,19R.

As illustrated inFIG. 3andFIG. 4, the differential body14is composed of a cylindrical tubular body centering at an axis A—A extending in the left-right direction (axially), and has a one-piece structure in which a left partition wall14B and a right partition wall14C, which will be described later, are integrally formed. Both ends of the differential body14in the left-right direction are respectively formed as opening ends14A. The left and right partition walls14B,14C are respectively arranged integrally with both ends of the differential body14in the left-right direction. The left and right partition walls14B,14C each extend from an inner peripheral surface of a section deeper than the opening end14A to the radial inward. Through holes14D respectively smaller in diameter than the opening ends14A are formed in the left and right partition walls14B,14C to penetrate therethrough in the left-right direction (axially).

The inside of the differential body14is sectioned into a gear room14E positioned between the left and right partition walls14B,14C, and left and right brake rooms14F,14G arranged in both of the left side and the right side across the gear room14E. The differential mechanism20is accommodated in the gear room14E, the brake mechanism55L is accommodated in the left brake room14F, and the brake mechanism55R is accommodated in the right brake room14G. A projecting tube14H is disposed on the rear side of the differential body14(in the rear axle device11-side) to project toward the transmission9. The projecting tube14H opens to the gear room14E, and a later-described input shaft17is supported in the projecting tube14H to be rotatable therein.

Base end sides of the left and right axle tubes15L,15R are formed as shorter cylindrical parts15A each having a radial dimension equal to each of both ends of the differential body14in the left-right direction. The insides of the left and right cylindrical parts15A are formed as reduction gear rooms15B, and the later-described planetary gear reduction mechanisms51L,51R are respectively accommodated in the left and right reduction gear rooms15B. Front end sides of the left and right axle tubes15L,15R each are formed in an angular, tubular shape and extend outwards in the left-right direction from the cylindrical part15A. The cylindrical parts15A of the left and right axle tubes15L,15R are attached to the opening ends14A of the differential body14by using a plurality of bolts16. The left and right axle tubes15L,15R extend to be smaller in diameter toward both sides thereof in the left-right direction from the differential body14.

Mount parts15C, each formed in a rectangular shape, are arranged on the top surface sides of the left and right axle tubes15L,15R to be adjacent to the cylindrical parts15A. The left and right mount parts15C are attached to the front vehicle body3of the wheel loader1. That is, the front axle device12is an inboard type of an axle device in which the differential mechanism20, the left and right planetary gear reduction mechanisms51L,51R and the left and right brake mechanisms55L,55R are arranged between the mount parts15C of the left and right axle tubes15L,15R. It should be noted that the rear axle device11is attached via an axle support (unillustrated) to the rear vehicle body2.

The input shaft17is disposed through two bearings18in the projecting tube14H of the differential body14to be rotatable therein. A connection flange17A is attached to one end, which projects outside of the projecting tube14H, of the input shaft17, and this connection flange17A is connected to the propeller shaft9B. A drive pinion17B composed of a bevel gear is formed on the other end, which projects into the gear room14E of the differential body14, of the input shaft17, and this drive pinion17B is engaged with a later-described ring gear30.

The left axle shaft19L is disposed to axially extend in the left axle tube15L, and the right axle shaft19R is disposed to axially extend in the right axle tube15R. The left and right axle shafts19L,19R are arranged on the axis A-A. The base end side of the axle shaft19L is spline-coupled to a carrier54of the later-described planetary gear reduction mechanism51L. The front end side of the axle shaft19L projects from the axle tube15L, and the front wheel5is attached to the front end thereof. The base end side of the axle shaft19R is spline-coupled to a carrier54of the later-described planetary gear reduction mechanism51R. The front end side of the axle shaft19R projects from the axle tube15R, and the front wheel5is attached to the front end thereof.

Next, an explanation will be made of the differential mechanism20according to the present embodiment.

The differential mechanism20is disposed in the gear room14E in the differential body14. The differential mechanism20distributes and transmits the drive force (rotational force) of the engine7as a drive source to the left and right front wheels5through the left and right axle shafts19L,19R. Here, the differential mechanism20is configured of a limited slip differential mechanism that temporarily becomes in a lock state (in a differential lock state) in association with a condition. The differential mechanism20includes a differential case23, the ring gear30, a plurality of pinion gears33, left and right side gears34,35, left and right transmission shafts36,37, a plurality of rotating discs38, a plurality of non-rotating discs39, a piston46, which will be described later, and the like.

A cylindrical left retainer21having a collar part21A is attached into the through hole14D of the left partition wall14B configuring part of the differential body14, and the collar part21A of the left retainer21is fixed on the left partition wall14B by using bolts22. In addition, a later-described right retainer41is attached into the through hole14D of the right partition wall14C configuring part of the differential body14, and the right retainer41is fixed on the right partition wall14C by using bolts22.

The differential case23is disposed in the gear room14E of the differential body14. The differential case23is supported through bearings24on the left retainer21and the right retainer41to be rotatable on the axis A-A. The differential case23is formed as an outer shell of the differential mechanism20, and is configured of a first differential case25, a second differential case26, and a third differential case27.

As illustrated inFIG. 4andFIG. 6, the first differential case25is a stepped cylindrical body having a small-diameter cylindrical part25A and a large-diameter cylindrical part25B, wherein a shaft insert hole25C is formed at the center part to penetrate in the left-right direction. A disc-shaped collar part25D in a large diameter is disposed between the small-diameter cylindrical part25A and the large-diameter cylindrical part25B. The small-diameter cylindrical part25A is supported through the bearing24on the left retainer21. A plurality of bolt insert holes25E are formed in the collar part25D over an entire periphery thereof. A plurality of screw holes (female screw holes)25G are formed on an axial end surface25F of the large-diameter cylindrical part25B over an entire periphery thereof. In addition, four recessed parts25H in a semicircle shape are formed on the axial end surface25F of the large-diameter cylindrical part25B at angular intervals of 90 degrees.

As illustrated inFIG. 4andFIG. 7, the second differential case26is formed as a hollow stepped cylindrical body having a small-diameter cylindrical part26A and a large-diameter cylindrical part26B. The small-diameter cylindrical part26A has an outer diameter dimension and a thickness equal to those of the large-diameter cylindrical part25B of the first differential case25. A plurality of bolt insert holes26C are formed in the small-diameter cylindrical part26A over an entire periphery thereof to penetrate in the left-right direction. Each of the bolt insert holes26C corresponds to each of the screw holes25G of the first differential case25. Four recessed parts26E in a semicircle shape are formed on the axial end surface26D of the small-diameter cylindrical part26A at angular intervals of 90 degrees. Each of the recessed parts26E corresponds to each of the recessed parts25H of the first differential case25. A plurality of screw holes26G are formed on an axial end surface26F of the large-diameter cylindrical part26B over an entire periphery thereof. Four rectangular recessed parts26H are formed on the axial end surface26F at angular intervals of 90 degrees. A screw hole26J is formed on the bottom part of each of the recessed parts26H. Further, a plurality of (for example, eight) recessed grooves26L in a semicircle shape in cross section axially extending are formed on an inner peripheral surface26K of the large-diameter cylindrical part26B at equal angular intervals. Each of projecting parts39A of the non-rotating discs39to be described later is engaged to each of the recessed grooves26L.

The third differential case27is attached to the second differential case26to be positioned at the opposite side to the first differential case25in the left-right direction. As illustrated inFIG. 4andFIG. 8, the third differential case27has a cylindrical part27A and a disc-shaped collar part27B larger in diameter than the cylindrical part27A. The collar part27B has an outer diameter dimension equal to that of the large-diameter cylindrical part26B of the second differential case26. A shaft insert hole27C is formed at the center part of the third differential case27to axially penetrate therethrough. The cylindrical part27A is supported through the bearing24on the right retainer41. A plurality of bolt insert holes27D are formed in the collar part27B over an entire periphery thereof. Each of the bolt insert holes27D corresponds to each of the screw holes26G in the second differential case26. In addition, four pin insert holes27E, each smaller in diameter than the bolt insert hole27D, are formed in the collar part27B at angular intervals of 90 degrees. Each of the pin insert holes27E corresponds to each of the screw holes26J in the second differential case26. Further, a plurality of (for example, eight) rectangular holes27F are formed in sections, which are positioned closer to the radial inward than the respective bolt insert holes27D, of the collar part27B to axially penetrate therethrough. Each of rectangular projections43D of a later-described pressure ring43is inserted in each of the rectangular holes27F to be movable relative thereto.

In addition, bolts28are respectively inserted in the respective bolt insert holes26C of the second differential case26. The respective bolts28are threaded into the respective screw holes25G of the first differential case25. Thereby, the second differential case26is fixed to the first differential case25. At this time, the axial end surface25F of the first differential case25abuts on the axial end surface26D of the second differential case26(small-diameter cylindrical part26A). Each of shafts32A of a later-described spider32is engaged between the recessed part25H of the first differential case25and the recessed part26E of the second differential case26. In addition, bolts29are respectively inserted in the respective bolt insert holes27D of the third differential case27. The respective bolts29are threaded into the respective screw holes26G of the second differential case26. Thereby, the third differential case27is fixed to the second differential case26. Thereby, the differential case23composed of the first, second and third differential cases25,26,27is assembled. The spider32, the plurality of pinion gears33, and the left and right side gears34,35are arranged in the inside of the differential case23.

The ring gear30is attached to the differential case23in the gear room14E of the differential body14. The ring gear30is formed of an annular bevel gear. The ring gear30is fixed to the collar part25D of the first differential case25by a plurality of bolts31inserted in the respective bolt insert holes25E of the first differential case25. The ring gear30is engaged with the drive pinion17B of the input shaft17. Accordingly, the rotation of the engine7is transmitted through the transmission9to the input shaft17, and the drive pinion17B is engaged with the ring gear30, thereby causing the differential case23to rotate.

The spider32is disposed within the differential case23. As illustrated inFIG. 5, the spider32has four shafts32A combined in a cross shape at angular intervals of 90 degrees. The front end side of each of the shafts32A is held tightly between the recessed part25H of the first differential case25and the recessed part26E of the second differential case26configuring part of the differential case23. The spider32rotates together with the differential case23.

The plurality of (four) pinion gears33are respectively supported on the four shafts32A arranged in the spider32to be rotatable thereon. The pinion gears33each are composed of a bevel gear and are united by the spider32. The respective pinion gears33are engaged with the left side gear34and the right side gear35within the differential case23.

The left side gear34and the right side gear35are respectively arranged in the differential case23. The left and right side gears34,35are paired in the left-right direction across the spider32. In the present embodiment, the right side gear35configures one side gear of the left and right side gears. The left and right side gears34,35each are composed of a bevel gear, and are engaged with each of the pinion gears33supported by the spider32. A thrust plate34A is disposed between the left side gear34and the first differential case25to reduce abrasion of the first differential case25. A thrust plate35A is disposed between the right side gear35and the third differential case27to reduce abrasion of the third differential case27. In addition, a shaft spline part35B is formed on an outer peripheral surface of the right side gear35.

The left transmission shaft36is connected to the left side gear34, and the right transmission shaft37is connected to the right side gear35. The left and right transmission shafts36,37are arranged to be paired on the axis A-A. The left transmission shaft36transmits the rotation of the differential case23through the planetary gear reduction mechanism51L to the axle shaft19L. The right transmission shaft37transmits the rotation of the differential case23through the planetary gear reduction mechanism51R to the axle shaft19R.

The base end side of the left transmission shaft36is spline-coupled to an inner peripheral side of the left side gear34. The front end side of the left transmission shaft36extends through the left partition wall14B of the differential body14into the axle tube15L. A sun gear36A configuring part of the planetary gear reduction mechanism51L is formed integrally with the front end of the left transmission shaft36. On the other hand, the base end side of the right transmission shaft37is spline-coupled to an inner peripheral side of the right side gear35. The front end side of the right transmission shaft extends through the right partition wall14C of the differential body14into the axle tube15R. A sun gear37A configuring part of the planetary gear reduction mechanism51R is formed integrally with the front end of the right transmission shaft37.

The plurality of rotating discs38and the plurality of non-rotating discs39are arranged between the inner peripheral surface26K of the second differential case26configuring part of the differential case23and the shaft spline part35B of the right side gear35. The respective rotating discs38and the respective non-rotating discs39each are composed of an annular plate body and are arranged to alternately overlap axially.

Each of the rotating discs38is spline-coupled on the inner peripheral side to the shaft spline part35B of the right side gear35. Accordingly, each of the rotating discs38is rotatable relative to the differential case23together with the right side gear35in a state of being movable in an axial direction of the right side gear35. As illustrated in FIG.9, each of the non-rotating discs39has the plurality of (for example, eight) projecting parts39A over an entire periphery on the outer peripheral side. Each of the projecting parts39A is engaged with each of the recessed grooves26L formed on the inner peripheral surface26K of the second differential case26. Accordingly, each of the non-rotating discs39is held in a state of being axially movable relative to the differential case23and being non-rotatable relative to the differential case23.

A pressing plate40is disposed between the third differential case27and the non-rotating disc39to be positioned within the differential case23. As illustrated inFIG. 10, the pressing plate40is formed of an annular plate body, and four projecting parts40A are arranged on the outer peripheral side of the pressing plate40to project to the radial outward at angular intervals of 90 degrees. The four projecting parts40A are engaged to the respective recessed parts26H of the second differential case26. Accordingly, the pressing plate40rotates together with differential case23in a state of being axially movable along the respective recessed parts26H. Pin insert holes40B are respectively formed in the respective projecting parts40A of the pressing plate40. Each of the pin insert holes40B corresponds to the screw hole26J formed in each of the recessed parts26H of the second differential case26.

The right retainer41is attached to the through hole14D of the right partition wall14C configuring part of the differential body14. The right retainer41configures one retainer positioned in the right side gear35-side. As illustrated inFIG. 12toFIG. 14, the right retainer41is formed in a stepped cylindrical shape having a cylindrical part41A fitted in the through hole14D, and a collar part41B larger in diameter than the cylindrical part41A. As illustrated inFIG. 14, a plurality of bolt insert holes41C are formed in the collar parts41B of the right retainer41over an entire periphery thereof. Bolt22are inserted in the respective bolt insert holes41C, and each of the bolts22is threaded into each of the screw holes14J arranged in the right partition wall14C of the differential body14. Thereby, the right retainer41is attached to the right partition wall14C in a state where the cylindrical part41A is fitted into the through hole14D.

A piston accommodating part41D having a step part of two steps is formed in a section, which axially faces the non-rotating disc39, of the right retainer41. The piston accommodating part41D is formed by cutting an outer peripheral surface of the cylindrical part41A over an entire periphery thereof. This piston accommodating part41D has a large-diameter step part41E adjacent to the end surface of the cylindrical part41A, and a small-diameter step part41F adjacent to the end surface of the large-diameter step part41E. The later-described piston46is attached to the piston accommodating part41D. O-rings42are respectively attached to outer peripheral surfaces of the large-diameter step part41E and the small-diameter step part41F. The O-ring42maintains liquid-tight sealing between the piston46and the right retainer41(piston accommodating part41D). In addition, a later-described retainer-side oil passage49B opens to an end surface41G of the piston accommodating part41D positioned in a boundary part between the large-diameter step part41E and the small-diameter step part41F. Further, a nut41H is threaded on an inner peripheral side of the right retainer41, and pressures are given to the bearing24between the nut41H and the third differential case27.

The pressure ring43is disposed between the right retainer41and the non-rotating disc39. The pressure ring43is pressed by the piston46to axially move and presses the non-rotating disc39against the rotating disc38via the pressing plate40. As illustrated inFIG. 11, the pressure ring is formed as an annular body having an outer diameter dimension smaller in diameter than the collar part27B of the third differential case27. Four projecting parts43A are arranged on the outer peripheral side of the pressure ring43to project to the radial outward at angular intervals of 90 degrees. Pin insert holes43B are respectively formed in the four projecting parts43A. Each of the pin insert holes43B corresponds to the screw hole26J formed in each of the recessed parts26H of the second differential case26.

A plurality of (for example, eight) rectangular projections43D are arranged to project on an end surface43C, which axially faces the third differential case27, of the pressure ring43. Each of the rectangular projections43D is inserted in each of the rectangular holes27F of the third differential case27. The front end of each of the rectangular projections43D abuts on the pressing plate40.

Four pins44are arranged in the respective recessed parts26H of the second differential case26, and axially extend toward the right retainer41. Each of the pins44has a screw part44A, and this screw part44A is threaded in the screw hole26J formed in each of the recessed parts26H. Each of the pins44projects outside of the differential case23through each of the pin insert holes40B of the pressing plate40and each of the pin insert holes27E of the third differential case27. Each of the pins44projecting outside of the differential case23is inserted in each of pin insert holes43B of the pressure ring43. The pressure ring43axially moves while being guided by each of the pins44. A stop ring44B is attached in a projecting end side of each of the pins44. The pressure ring43is prevented from being axially pulled out by the stop ring44B.

Four return springs45each are arranged on an outer peripherical side of each of the pins44to be positioned between the respective recessed parts26H of the second differential case26and the pressing plate40. Each of the return springs45is composed of a compression spring and urges the pressing plate40to the piston46-side (third differential case27-side).

The piston46is disposed in the piston accommodating part41D of the right retainer41. As illustrated inFIG. 12andFIG. 13, the piston46is formed in a stepped cylindrical shape having a large-diameter cylindrical part46A and a small-diameter cylindrical part46B. An inner-diameter projected part46C in an annular shape is disposed on an inner peripheral side of a boundary part between the large-diameter cylindrical part46A and the small-diameter cylindrical part46B to extend to the radial inward. Here, an outer diameter dimension of the large-diameter cylindrical part46A is set to be equal to that of the cylindrical part41A of the right retainer41. An inner peripheral surface46D of the large-diameter cylindrical part46A is slidably fitted on an outer peripheral surface of the large-diameter step part41E of the right retainer41. An inner peripheral surface46E of the inner-diameter projected part46C is slidably fitted on an outer peripheral surface of the small-diameter step part41F of the right retainer41.

In this way, the right retainer41is provided with the piston accommodating part41D that is smaller in an outer diameter dimension than the cylindrical part41A and is composed of the large-diameter step part41E and the small-diameter step part41F. The piston46is attached in the piston accommodating part41D of the right retainer41. As a result, the outer diameter dimension of the large-diameter cylindrical part46A of the piston46is equal to the cylindrical part41A of the right retainer41. The piston46is inserted in the through hole14D formed in the right partition wall14C of the differential body14in a state of being incorporated in the piston accommodating part41D of the right retainer41. In this state, by fixing the right retainer41on the right partition wall14C, the piston46can be caused to abut on the pressure ring43via a later-described thrust bearing48.

An end surface of the inner-diameter projected part46C of the piston46in the small-diameter cylindrical part46B-side is formed as an annular pressing surface46F pressing the pressure ring43. On the other hand, an entire peripheral groove46G in an annular shape is formed on an end surface of the inner-diameter projected part46C at the opposite side to the pressing surface46F (in the large-diameter cylindrical part46A-side). An annular hydraulic chamber47is formed between the entire peripheral groove46G and the end surface41G of the piston accommodating part41D in the right retainer41over an entire periphery thereof. Accordingly, when pressurized oil is supplied to the hydraulic chamber47, the piston46axially moves to press the pressure ring43.

An annular thrust bearing48is disposed between the pressing surface46F of the piston46and the pressure ring43. The thrust bearing48is disposed on an inner peripheral side of the small-diameter cylindrical part46B of the piston46to be radially positioned. Accordingly, the piston46can press the pressure ring43via the thrust bearing48, thus suppressing friction from being generated between the piston46and the pressure ring43.

An oil passage49is formed in the right partition wall14C of the differential body14and in the right retainer41to perform supply and discharge of pressurized oil (liquid pressure) to and from the hydraulic chamber47. The oil passage49is composed of a partition wall-side oil passage49A formed in the right partition wall14C and a retainer-side oil passage49B formed in the right retainer41. A flow inlet of the partition wall-side oil passage49A opens to the outer peripheral surface of the differential body14. A flow outlet of the retainer-side oil passage49B opens to the end surface41G of the piston accommodating part41D of the right retainer41. A hydraulic source (unillustrated) is connected to the flow inlet of the partition wall-side oil passage49A. The pressurized oil discharged from the hydraulic source is supplied via the partition wall-side oil passage49A and the retainer-side oil passage49B to the hydraulic chamber47.

Thereby, the piston46axially presses the pressure ring43through the thrust bearing48. Each of the rectangular projections43D of the pressure ring43presses the pressing plate40to the non-rotating disc39against a spring force of each of the return springs45. Therefore, the respective non-rotating discs39and the respective rotating discs38are made in frictional contact with each other between the second differential case26and the piston46. Thereby, when a torque difference between the left axle shaft19L and the right axle shaft19R is equal to or less than the torque capacity of the clutch, the differential mechanism20becomes in the lock state (the differential lock state). As a result, the left and right side gears34,35rotate together with the differential case23to transmit the torque to the left and right axle shafts19L,19R respectively.

On the other hand, when the supply of the pressurized oil to the hydraulic chamber47is stopped, the pressing plate and the piston46move in a direction away from the non-rotating discs39by the spring force of each of the return springs45. As a result, the contact state between the respective non-rotating discs39and the respective rotating discs38is released and the right side gear35is made to be rotatable relative to the differential case23to make the differential function effective. As a result, the rotational force of the engine7is distributed to the left front wheel5and the right front wheel5in accordance with a difference in the frictional force between the left and right front wheels5and the road surface.

An air-bleeding passage50is formed in the right partition wall14C of the differential body14and in the right retainer41. The air-bleeding passage50is, at the time of incorporating the piston46to the piston accommodating part41D of the right retainer41, a passage for discharging air in the hydraulic chamber47to an exterior. As illustrated inFIG. 14, the air-bleeding passage50is configured of a partition wall-side passage50A formed in the right partition wall14C and a retainer-side passage50B formed in the right retainer41. One end50A1of the partition wall-side passage50A opens to an end surface, which the collar part41B of the right retainer41abuts on, of the right partition wall14C. The other end50A2of the partition wall-side passage50A opens to the outer peripheral surface of the differential body14. One end50B1of the retainer-side passage50B opens to the piston accommodating part41D. The other end50B2of the retainer-side passage50B opens to an axial end surface of the collar part41B to be communicated with the one end50A1of the partition wall-side passage50A. Thereby, when the piston46is installed in the piston accommodating part41D of the right retainer41, the air in the hydraulic chamber47is discharged through the retainer-side passage50B and the partition wall-side passage50A to an exterior. Accordingly, the piston46can smoothly be installed in the piston accommodating part41D. It should be noted that after installing the piston46, the other end50A2of the partition wall-side passage50A is blocked by a sealing plug (unillustrated).

The left planetary gear reduction mechanism51L is disposed in a reduction gear room15B of the left axle tube15L (refer toFIG. 2). The planetary gear reduction mechanism51L is configured of the sun gear36A formed integrally with the front end side of the left transmission shaft36, a ring gear52, a plurality of planet gears53and a carrier54. The ring gear52is disposed on an inner peripheral side of the axle tube15L (cylindrical part15A). The plurality of planet gears53are engaged with the sun gear36A and the ring gear52. The carrier54rotatably supports each of the planet gears53and is spline-coupled to the axle shaft19L. Accordingly, the rotation of the left transmission shaft36is transmitted to the axle shaft19L in a state of being reduced in speed by the planetary gear reduction mechanism51L.

The right planetary gear reduction mechanism51R is disposed in the reduction gear room15B of the right axle tube15R. The planetary gear reduction mechanism51R is configured of, as similar to the left planetary gear reduction mechanism51L, the sun gear37A formed integrally with the front end side of the right transmission shaft37, the ring gear52, the plurality of planet gears53and the carrier54. The carrier54is spline-coupled to the axle shaft19L. Accordingly, the rotation of the right transmission shaft37is transmitted to the axle shaft19R in a state of being reduced in speed by the planetary gear reduction mechanism51R.

The left brake mechanism55L is disposed in the left brake room14F of the differential body14. This brake mechanism.55L is configured as a wet type multiple-brake mechanism, for example. The brake mechanism55L includes a plurality of brake discs57spline-coupled via a hub56on an outer peripheral side of the left transmission shaft36, a brake plate58, and a brake piston59. Each of the brake discs57rotates together with the left transmission shaft36. The brake plate58is disposed to face the brake disc57and is held in a non-rotating state relative to the differential body14. In addition, the brake piston59pushes the brake plate58against the brake disc57by the hydraulic force from an exterior. Thereby, the braking force is applied to the left transmission shaft36.

The right brake mechanism55R is disposed in the right brake room14G of the differential body14. The brake mechanism55R is configured of, as similar to the left brake mechanism55L, a plurality of brake discs57spline-coupled via a hub56on an outer peripheral side of the right transmission shaft37, a brake plate58, and a brake piston59. In addition, the brake piston59pushes the brake plate58against the brake disc57by the hydraulic force from an exterior. Thereby, the braking force is applied to the right transmission shaft37.

The front axle device12according to the present embodiment has the configuration as described above, and hereinafter, an explanation will be made of the operation of the front axle device12at the traveling of the wheel loader1.

When an operator who has got in the cab10operates the engine7, a rotational force of the engine7is transmitted to the input shaft17through the propeller shaft9B of the transmission9. The rotation of the input shaft17is transmitted from the drive pinion17B to the ring gear30of the differential mechanism20to rotate the differential case23to which the ring gear30is attached.

Each of the shafts32A of the spider32is tightly held between the recessed part25H of the first differential case25and the recessed part26E of the second differential case26configuring part of the differential case23. Accordingly, the spider32rotates together with the differential case23in a state where the four pinion gears33are supported by each of the shafts32A.

Here, in a state where the pressurized oil is not supplied to the hydraulic chamber47formed between the piston accommodating part41D of the right retainer41and the piston46from the hydraulic source, the pressing plate40is urged in the direction away from the non-rotating discs39by the spring forces of the respective return springs45. Thereby, the respective non-rotating discs39and the respective rotating discs38are held in the non-contact state with each other.

When the differential case23rotates together with the respective pinion gears33, the left side gear34and the right side gear35engaged with the respective pinion gears33rotate. The rotation of the left transmission shaft36coupled to the left side gear34is transmitted to the axle shaft19L in a state of being reduced in speed by the planetary gear reduction mechanism51L. Similarly, the rotation of the right transmission shaft37coupled to the right side gear35is transmitted to the axle shaft19R in a state of being reduced in speed by the planetary gear reduction mechanism51R. As a result, the left and right front wheels5are driven and rotated simultaneously.

Here, in a case where a frictional force between the left front wheel5and the road surface is equal to that between the right front wheel5and the road surface at the straight-traveling of the wheel loader1, the left and right side gears34,35rotate together with the differential case23. As a result, the rotational force of the engine7is transmitted to the left and right front wheels5on an equal basis, making it possible to cause the wheel loader1to travel straight.

In addition, in a case where the frictional force between the left front wheel5and the road surface differs from that between the right front wheel5and the road surface at the revolving traveling of the wheel loader1, the left side gear34and right side gear35rotate in rotating speeds different from each other. As a result, the rotational force of the engine7is distributed to the left front wheel5and the right front wheel5in accordance with a difference in the frictional force between the left front wheel5and the road surface and between the right front wheel5and the road surface, and therefore, it is possible to cause the wheel loader1to travel for revolution.

On the other hand, when the wheel loader1travels in the sand, in the mud or the like, for example, there are some cases where a ground road surface state of the left front wheel5differs from a ground road surface state of the right front wheel5. In this case, it is required to avoid one of the left and right front wheels5from possibly running idle due to the differential mechanism20.

In this case, for example, a foot pedal, a manual switch and the like (none of them is illustrated) arranged in the cab are operated. Thereby, the pressurized oil from the hydraulic source is supplied through the partition wall-side oil passage49A in the differential body14and the retainer-side oil passage49B in the right retainer41to the hydraulic chamber47.

Therefore, the piston46axially presses the pressure ring43through the thrust bearing48. Each of the rectangular projections43D of the pressure ring43presses the pressing plate40to the non-rotating disc39against the spring force of each of the return springs45. Accordingly, the respective non-rotating discs39and the respective rotating discs38come in shaft frictional contact with each other between the second differential case26and the piston46. Thereby, when the torque difference between the left axle shaft19L and the right axle shaft19R is equal to or less than the torque capacity of the clutch, the differential mechanism20becomes in the lock state (the differential lock state). As a result, the left and right side gears34,35rotate together with the differential case23to transmit the torque to the left and right axle shafts19L,19R respectively. Accordingly, it is possible to avoid one of the left and right front wheels5from running idle, to cause the wheel loader1to travel.

Here, in a case of incorporating the differential mechanism20according to the present embodiment in the gear room14E of the differential body14, each of the pinion gears33, the left and right side gears34,35, the rotating discs38, the non-rotating discs39and the like are assembled within the differential case23. In addition, the ring gear30is attached to the first differential case25and the pin44is attached in each of the screw holes26J of the second differential case26. In a state where the return spring45is arranged on the outer peripheral side of each of the pins44, each of the pins44is inserted in the pin insert hole27E of the third differential case27. Further, each of the pins44is inserted in the pin through hole43B of the pressure ring43and each of the rectangular projections43D of the pressure ring43is inserted in each of the rectangular holes27F of the third differential case27. In this state, the stop ring44B is attached to the projecting end of each of the pins44.

In addition, the differential case23to which the pressure ring43is attached is inserted into the gear room14E of the differential body14. In this state, the left retainer21is inserted in the through hole14D of the left partition wall14B, and the collar part21A is attached to the left partition wall14B. Thereby, the first differential case25is held via the bearing24by the left retainer21. On the other hand, the piston46is incorporated in the piston accommodating part41D of the right retainer41. In this state, the piston46and the cylindrical part41A of the right retainer41are inserted in the through hole14D formed in the right partition wall14C of the differential body14and the collar part41B is attached to the right partition wall14C. As a result, the third differential case27is held via the bearing24by the right retainer41. At this time, it is possible to cause the piston46to abut on the pressure ring43via the thrust bearing48.

In this way, according to the present embodiment, the piston accommodating part41D is formed in the right retainer41to be attached to the right partition wall14C of the differential body14, making it possible to assemble the piston46to the piston accommodating part41D. Accordingly, it is not required to form the piston accommodating part on the surface of the right partition wall14C in the gear room14E-side. Thereby, it is possible to use the differential body14of the one-piece structure in which the left and right partition walls14B,14C defining the gear room14E are integrally formed. Accordingly, as compared to a case where the piston accommodating part is formed on the partition wall of the differential body, it is possible to more simplify the configuration of the differential body14. As a result, it is possible to simplify the configuration of the entire front axle device12to contribute to a reduction in the manufacture cost.

In addition, after inserting the differential case23into the gear room14E of the differential body14, the right retainer41to which the piston46is assembled can be attached to the right partition wall14C. Thereby, it is possible to cause the piston46to abut on the pressure ring43through the thrust bearing48. This result can enhance the workability at the time of assembling the piston46to the differential mechanism20accommodated in the differential body14. In addition, it is not required to perform the assembly work of the piston46in the gear room14E of the differential body14. Therefore, the differential case23disposed in the gear room14E can be structured to be large, increasing the number of the rotating discs38and the non-rotating discs39, for example.

In this way, according to the present embodiment, the front axle device12has the differential mechanism20transmitting the rotational force of the engine7to the left and right axle shafts19L,19R. The differential mechanism20is provided with the differential case23that is rotatably supported through the bearing24by the left and right retainers21,41attached respectively to the through holes14D of the left and right partition walls14B,14C and rotates by the engine7, the plurality of pinion gears33that are arranged in the differential case23and rotate together with the differential case23, the left and right side gears34,35that are arranged in the differential case23and engaged with the respective pinion gears33, and the left and right transmission shafts36,37that are connected to the respective side gears34,35and transmit the rotation of the differential case23to the left and right axle shafts19L,19R.

In addition, the differential case23is provided therein with the plurality of rotating discs38spline-coupled to the outer peripheral side of the right side gear35and the plurality of non-rotating discs39that are arranged between the respective rotating discs38and are non-rotatable relative to the differential case23and movable in the left-right direction, the pressure ring43is disposed between the right retainer41positioned in the right side gear35-side and the non-rotating discs39to press the non-rotating discs39toward the rotating discs38, the piston accommodating part41D is disposed in the right retainer41in a position facing the pressure ring43in the left-right direction, and the piston46is disposed in the piston accommodating part41D, the piston46being displaced by the liquid pressure to press the non-rotating discs39via the pressure ring43against the rotating discs38and connect the left and right transmission shafts36,37.

According to this configuration, since the piston46can be assembled to the piston accommodating part41D formed in the right retainer41, it is not required to form the piston accommodating part on the surface of the right partition wall14C in the gear room14E-side. Thereby, it is possible to use the differential body14of the one-piece structure in which the left and right partition walls14B,14C defining the gear room14E are integrally formed. Accordingly, as compared to a case of forming the piston accommodating part in the partition wall of the differential body, the configuration of the differential body14can be more simplified.

According to the present embodiment, the hydraulic chamber47to which the pressurized oil for pressing the piston46is supplied is formed between the piston46and the piston accommodating part41D of the right retainer41, and the oil passage49for connection between the hydraulic source and the hydraulic chamber47is formed in the right partition wall14C of the differential body14and in the right retainer41. According to this configuration, the pressurized oil from the hydraulic source is supplied through the oil passage49formed in the right partition wall14C and in the right retainer41to the hydraulic chamber47. Accordingly, it is not required to connect a hydraulic line composed of a different component from the right retainer41to the hydraulic chamber47, making it possible to simplify the configuration of the differential mechanism20.

According to the present embodiment, the differential case23includes the first differential case25that is rotatably supported by the left retainer21and in which the ring gear30is disposed on the outer peripheral side and the left side gear34is disposed on the inner peripheral side, the second differential case26that is attached to the first differential case25and in which the right side gear35is disposed on the inner peripheral side and the third differential case27that is attached to the second differential case26to be positioned at the opposite side to the first differential case25in the left-right direction and is rotatably supported on the right retainer41, and the respective rotating discs38and the respective non-rotating discs39are arranged between the inner peripheral side of the second differential case26and the shaft spline part35B of the right side gear35, and the piston46can press the non-rotating discs39via the pressure ring43inserted in the third differential case27.

According to the present embodiment, the pressing plate40is disposed between the non-rotating disc39and the pressure ring43to press the non-rotating discs39when the piston46operates to move the pressure ring43toward the non-rotating disc39, the pin44is disposed between the second differential case26and the pressure ring43to be inserted in the third differential case27and in the pressing plate40, and the return spring45is disposed between the second differential case26and the pressing plate40, the return spring45being located on the outer peripheral side of the pin44to urge the pressing plate40toward the piston46-side.

According to this configuration, when the supply of the pressurized oil to the hydraulic chamber47is stopped, the pressing plate40and the piston46move in a direction away from the non-rotating discs39by the spring force of the return spring45. As a result, the contact state between the respective non-rotating discs39and the respective rotating discs38is released and the right side gear35is made rotatable relative to the differential case23to make the differential function effective. As a result, the rotational force of the engine7can be distributed to the left front wheel5and the right front wheel5in accordance with the difference in frictional force between the left front wheel5and the road surface and between the right front wheel5and the road surface.

It should be noted that in the present embodiment, the wheel loader1is exemplified as the vehicle to which the rear axle device11and the front axle device12are applied. The present invention is, however, not limited thereto, but, for example, may be applied widely to other wheel type construction machines such as a wheel type excavator.

DESCRIPTION OF REFERENCE NUMERALS