Power transmission device

Abstract

To suppress a centrifugal oil pressure acting on a piston without increasing in size of a clutch mechanism.SOLUTION: In a power transmission device, an advancing clutch mechanism 25 includes: a clutch case 26; a rotor disc 27 which rotates integrally with an advancing rotor 19; a clutch disc 28 which rotates integrally with the clutch case 26; and a clutch piston 30 which moves according to a pressure of a hydraulic oil supplied to a clutch oil chamber 29 to cause the rotor disc 27 and the clutch disc 28 to engage with each other frictionally. Further, the power transmission device includes: a cancel oil chamber 37 which is arranged aligned with the clutch oil chamber 29 in an axial direction; a cancel piston 38 which is disposed in the cancel oil chamber 37, aligned with the clutch piston 30 in the axial direction and moved in a direction away from the clutch piston 30 by a lubrication oil supplied to the cancel oil chamber 37; and a connecting rod 41 which connects the clutch piston 30 with the cancel piston 38.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a power transmission device that is mounted on a work vehicle such as a wheel loader and transmits rotation of a power source to an output shaft for traveling. [Background technology]

[0002] Wheeled work vehicles, such as wheel loaders, generally have a power transmission between the torque converter and the axle, and the rotation of the engine is transmitted to the wheels via the torque converter and the power transmission. This allows the work vehicle to travel on a road or the like, and the forward travel, reverse travel, travel speed, etc. of the work vehicle are switched by the power transmission.

[0003] The power transmission device is equipped with a hydraulic multi-plate clutch mechanism for switching between forward travel, reverse travel, travel speed, etc. of the work vehicle. The clutch mechanism has multiple discs provided between the rotating body and the driven body, and a piston that connects and disconnects these multiple discs. The piston is movably inserted into an oil chamber, and hydraulic oil or other oil is supplied to the oil chamber to press the multiple discs into frictional engagement with each other. This integrates the rotating body and the driven body via the multiple discs, and the clutch mechanism is in an engaged state.

[0004] Here, the pressing force of the piston against the disc is set by the oil fluid supplied into the oil chamber, but the oil fluid supplied into the oil chamber is subjected to centrifugal force due to the rotation of the rotating body and the driven body. As a result, the piston is subjected not only to pressing force from the oil fluid supplied into the oil chamber, but also to pressing force from the oil fluid subjected to centrifugal force in the oil chamber (centrifugal oil pressure), which creates the problem that it is difficult to control the pressing force acting on the piston by the oil fluid supplied into the oil chamber.

[0005] In particular, when releasing the frictional engagement between the rotor and driven member to disengage the clutch mechanism, it is necessary to cut off the oil supply to the oil chamber and separate the frictionally engaged discs using the return spring. In this case, centrifugal force acts on the oil remaining in the oil chamber, and the centrifugal oil pressure from the oil subjected to this centrifugal force acts on the piston. This causes a problem of delay in the operation of the return spring to separate the discs.

[0006] In response to this, a power transmission device has been proposed in which a cancel chamber is provided on the opposite side of the oil chamber to which oil is supplied to drive the piston (Patent Document 1). In this power transmission device, centrifugal force acts on the oil supplied to the cancel chamber, causing centrifugal oil pressure to act on the piston in a direction away from the disc. This causes the centrifugal oil pressure acting on the piston from the oil in the oil chamber to cancel out the centrifugal oil pressure acting on the piston from the oil in the cancel chamber. As a result, when the supply of oil to the oil chamber is cut off, the frictional engagement of the multiple discs is quickly released by the return spring, allowing the clutch mechanism to be quickly disengaged. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-180751 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the power transmission device disclosed in Patent Document 1, the oil supplied to the oil chamber and the oil supplied to the cancel chamber come into contact with both axial end faces of a single piston, pressing the piston in opposite directions. Therefore, the piston has a radially continuous portion (pressing portion) that presses multiple discs and a portion (pressure-receiving portion) that receives centrifugal oil pressure from the oil supplied to the oil chamber and the cancel chamber, and the pressure-receiving portion extends significantly radially inward from the pressing portion. Thus, the power transmission device disclosed in Patent Document 1 has a problem in that the piston of the clutch mechanism becomes large, resulting in an increase in the size of the entire device.

[0009] The present invention has been made in consideration of the above-mentioned problems of the conventional technology, and has an object to provide a power transmission device that can suppress the centrifugal oil pressure acting on the piston without increasing the size of the clutch mechanism. [Means for solving the problem]

[0010] The present invention provides a power transmission device comprising: a rotating body; a driven body rotatably arranged coaxially with the rotating body; and a clutch mechanism connecting or disconnecting the rotating body and the driven body, wherein the clutch mechanism comprises a clutch case integral with the driven body; a rotating body disk movably engaged with the rotating body and rotating integrally with the rotating body; a clutch disk movably engaged with the clutch case and rotating integrally with the clutch case; and a clutch piston that moves axially relative to the clutch case in response to the pressure of oil fluid supplied to a clutch oil chamber, thereby engaging the rotating body disk and the clutch disk. The power transmission device further comprises: a cancel oil chamber that is separated from the clutch oil chamber and is arranged axially side by side with the clutch oil chamber; a cancel piston that is axially movably arranged in the cancel oil chamber and is arranged axially side by side with the clutch piston, and that moves in a direction away from the clutch piston when oil fluid is supplied to the cancel oil chamber; and a connecting member that connects the clutch piston and the cancel piston. [Effects of the Invention]

[0011] According to the present invention, the centrifugal oil pressure acting on the clutch piston from the oil fluid supplied to the clutch oil chamber can be suppressed by the centrifugal oil pressure acting on the cancel piston from the oil fluid supplied to the cancel oil chamber. Moreover, by arranging the clutch piston and the cancel piston side by side in the axial direction, the clutch mechanism can be configured compactly. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a left side view showing a wheel loader equipped with a power transmission device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a left side view showing the power transmission device with a part cut away. [Figure 3] 1 is a cross-sectional view showing a clutch mechanism of a power transmission device according to a first embodiment in an engaged state. [Figure 4] FIG. 2 is a cross-sectional view showing the clutch mechanism of the power transmission device in a disengaged state. [Figure 5] FIG. 4 is a front view showing the piston in FIG. 3 alone. [Figure 6] 6 is a cross-sectional view of the piston as seen from the direction of arrows VI-VI in FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view showing a clutch mechanism of a power transmission device according to a second embodiment in an engaged state. [Figure 8] FIG. 2 is a cross-sectional view showing the clutch mechanism of the power transmission device in a disengaged state. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of a power transmission device according to the present invention will be described in detail with reference to the accompanying drawings, taking as an example an example a case where the power transmission device is mounted on a wheel loader. Note that in the embodiment, the traveling direction of the wheel loader is defined as the front-rear direction, and the direction perpendicular to the traveling direction is defined as the left-right direction.

[0014] Figures 1 to 6 show a first embodiment of the present invention. In the figures, the wheel loader 1 is configured as an articulated work vehicle in which a front body 3, on which left and right front wheels 2 are mounted, and a rear body 5, on which left and right rear wheels 4 are mounted, are connected via a connecting mechanism 6 so that they can bend left and right. A steering cylinder 7 is provided between the front body 3 and the rear body 5, and by extending and contracting this steering cylinder 7, the front body 3 and the rear body 5 bend left and right, allowing the wheel loader 1 to be steered while traveling.

[0015] A work implement 8 equipped with a loader bucket 8A is mounted on the front body 3 of the wheel loader 1 so that it can be raised and lowered. The rear body 5 of the wheel loader 1 is provided with a cab 9 that defines the operator's compartment, an engine 10 as a prime mover, a power transmission device 15 (described later), and the like.

[0016] Furthermore, a front axle 11 extending in the left-right direction is provided below the front vehicle body 3, and front wheels 2 are attached to both the left and right sides of the front axle 11. A rear axle 12 extending in the left-right direction is provided below the rear vehicle body 5, and rear wheels 4 are attached to both the left and right sides of the rear axle 12. The front axle 11 is connected to an output shaft 18 of a power transmission device 15 via a propeller shaft 13, and the rear axle 12 is connected to the output shaft 18 of the power transmission device 15 via a propeller shaft 14.

[0017] Next, a power transmission according to the first embodiment will be described.

[0018] The power transmission device 15 is mounted on the rear body 5 of the wheel loader 1, and transmits the output of the engine 10 to the front axle 11 and the rear axle 12 after reducing the power output. The power transmission device 15 has a casing 16 that forms an outer shell, and the casing 16 houses a forward rotating body 19, a forward shaft 20, a forward clutch mechanism 25, a reverse rotating body, a reverse shaft, a reverse clutch mechanism, an intermediate shaft, a speed change rotating body, a speed change shaft, a speed change clutch mechanism, a brake mechanism, and the like (all of which are not shown), which will be described below. An input shaft 17 is arranged on the upper side of the casing 16, and the input shaft 17 is connected to the output shaft of the engine 10. An output shaft 18 is arranged on the lower side of the casing 16, and the output shaft 18 is connected to the propeller shafts 13, 14.

[0019] The power transmission device 15 transmits the output of the engine 10 to the intermediate shaft via one of the forward shaft 20 and the reverse shaft, causing the intermediate shaft to rotate in the forward or reverse direction. The power transmission device 15 then reduces the speed of the rotational output of the intermediate shaft using the speed change shaft, and outputs this reduced rotation to the output shaft 18. The rotation of the output shaft 18 is transmitted to the front axle 11 via the propeller shaft 13, and is also transmitted to the rear axle 12 via the propeller shaft 14. This causes the front wheels 2 and rear wheels 4 to rotate simultaneously, allowing the wheel loader 1 to travel forward or reverse at the desired gear position.

[0020] Here, the casing 16 is provided with a shaft support portion 16A that supports one axial side of the forward shaft 20, and a shaft support portion 16B that supports the other axial side of the forward shaft 20. The shaft support portion 16A opens to the outside of the casing 16, and the opening of this shaft support portion 16A is covered with a cover body 16C. The outer peripheral surface of one axial side (the shaft support portion 16A side) of the forward shaft 20 is slidably fitted with the inner peripheral surface of the cover body 16C. In addition, the cover body 16C is provided with a hydraulic oil introduction passage 16D that introduces hydraulic oil to a clutch pressure passage 35, which will be described later, and a lubricating oil introduction passage 16E that introduces lubricating oil to a lubricating oil passage 36, which will be described later.

[0021] Next, the forward rotor 19, forward shaft 20, and forward clutch mechanism 25 provided in the casing 16 will be described with reference to FIGS. 3 and 4. FIG.

[0022] The forward rotor 19, which serves as a rotor, is rotatably provided within the casing 16 and is rotationally driven by the engine 10. The forward rotor 19 is formed in a stepped cylindrical shape having a hollow, disc-shaped input gear 19A and a cylindrical portion 19B. The input gear 19A is disposed on the shaft support portion 16A side of the casing 16. The cylindrical portion 19B is formed integrally with the input gear 19A and extends from the input gear 19A toward the shaft support portion 16B side of the casing 16. An inner peripheral surface 19C of the input gear 19A is supported by the forward shaft 20 via a needle bearing 23 (described later) so as to be relatively rotatable. A drive gear (neither of which is shown) provided on a drive shaft driven by the engine 10 meshes with the input gear 19A. A spline portion 19D is formed on the outer periphery of the cylindrical portion 19B, and the inner periphery of a rotor disk 27 (described later) is spline-fitted with the spline portion 19D.

[0023] The advance shaft 20, which serves as a driven body, is disposed on the inner peripheral side of the advance rotor 19 and extends in the axial direction of the advance rotor 19. One axial end of the advance shaft 20 forms a one-end mounting portion 20A, and the other axial end of the advance shaft 20 forms an other-end mounting portion 20B. The one-end mounting portion 20A is supported by the shaft support portion 16A of the casing 16 via a roller bearing 21, and the other-end mounting portion 20B is supported by the shaft support portion 16B of the casing 16 via a roller bearing 22.

[0024] The forward shaft 20 has a small-diameter shaft portion 20C adjacent to the one-end mounting portion 20A, a large-diameter shaft portion 20D adjacent to the other-end mounting portion 20B, and an intermediate shaft portion 20E located between the small-diameter shaft portion 20C and the large-diameter shaft portion 20D. The intermediate shaft portion 20E has a radial dimension (shaft diameter) larger than that of the small-diameter shaft portion 20C but smaller than that of the large-diameter shaft portion 20D, and is disposed on the inner circumferential side of the cylindrical portion 19B of the forward rotor 19. A step portion 20F is formed at the boundary between the small-diameter shaft portion 20C and the intermediate shaft portion 20E. A shaft retaining ring 20G is attached to the outer circumferential surface of the small-diameter shaft portion 20C on the one-end mounting portion 20A side. A clutch pressure passage 35 and a lubricating oil passage 36 are provided inside the forward shaft 20 and extend axially.

[0025] A needle bearing 23 is provided between the outer peripheral surface of the small diameter shaft portion 20C of the forward shaft 20 and the inner peripheral surface 19C of the input gear 19A of the forward rotor 19. Thrust bearings 24 are provided between the stepped portion 20F of the forward shaft 20 and the input gear 19A, and between the shaft retaining ring 20G of the forward shaft 20 and the input gear 19A. This allows the forward shaft 20 and the forward rotor 19 to rotate relative to each other around the same rotational axis L.

[0026] A forward clutch mechanism 25 serving as a clutch mechanism is provided between the forward rotor 19 and the forward shaft 20. The forward clutch mechanism 25 is made up of a wet multi-plate clutch, and connects or disconnects the forward rotor 19 and the forward shaft 20. The forward clutch mechanism 25 includes a clutch case 26, a plurality of rotor discs 27, a plurality of clutch discs 28, a clutch oil chamber 29, a clutch piston 30, a return spring 34, a clutch pressure passage 35, a lubricating oil passage 36, a cancel oil chamber 37, a cancel piston 38, a connecting rod 41, etc.

[0027] The clutch case 26 is attached to the forward shaft 20. The clutch case 26 is formed in a cylindrical shape overall and has an annular fixed portion 26A and a cylindrical portion 26B extending axially from the outer periphery of the fixed portion 26A. The inner periphery of the fixed portion 26A is fixed to the outer periphery of the large diameter shaft portion 20D of the forward shaft 20 using means such as press fitting. The cylindrical portion 26B surrounds the cylindrical portion 19B of the forward rotor 19 from the outer periphery over the entire circumference. In this way, the clutch case 26 is fixed integrally to the large diameter shaft portion 20D of the forward shaft 20 while surrounding the cylindrical portion 19B of the forward rotor 19 from the outer periphery.

[0028] An output gear 26C is integrally formed on the outer periphery of the other axial side (roller bearing 22 side) of cylindrical portion 26B. Output gear 26C meshes with a gear provided on an intermediate shaft (neither is shown). As a result, rotation of forward shaft 20 is transmitted from output gear 26C of clutch case 26 to output shaft 18 via the intermediate shaft and transmission shaft (neither is shown).

[0029] A spline portion 26D is formed on the inner peripheral side of the cylindrical portion 26B. The spline portion 26D faces radially a spline portion 19D formed on the cylindrical portion 19B of the forward rotation body 19. The outer peripheral sides of multiple clutch discs 28 are spline-fitted to the spline portion 26D. An end plate 26E that restricts axial movement of the rotation body discs 27 and clutch discs 28 is provided on the end of the cylindrical portion 26B opposite the fixed portion 26A.

[0030] The multiple rotor disks 27 are provided on the outer periphery of the advancement rotor 19. The rotor disks 27 are made of an annular plate, and the inner periphery of the rotor disks 27 is spline-fitted to a spline portion 19D formed on the outer periphery of a cylindrical portion 19B that constitutes the advancement rotor 19. As a result, the multiple rotor disks 27 rotate integrally with the advancement rotor 19 while being movable in the axial direction relative to the advancement rotor 19.

[0031] The plurality of clutch discs 28 are provided inside the cylindrical portion 26B of the clutch case 26 so as to overlap the rotor discs 27 alternately in the axial direction. The clutch discs 28 are made of annular plates, and the outer peripheries of the clutch discs 28 are spline-fitted to spline portions 26D formed on the inner periphery of the cylindrical portion 26B that constitutes the clutch case 26. As a result, the clutch discs 28 rotate integrally with the clutch case 26 while being movable axially relative to the clutch case 26.

[0032] The clutch oil chamber 29 is provided between the forward shaft 20 and the clutch case 26. The clutch oil chamber 29 is formed as an annular space surrounded by the end face of one axial side (roller bearing 21 side) of the fixed portion 26A, the inner circumferential surface of the cylindrical portion 26B, and the outer circumferential surface of the large diameter shaft portion 20D of the forward shaft 20, and the clutch piston 30 is slidably inserted into the clutch oil chamber 29. A clutch pressure passage 35 formed in the forward shaft 20 communicates with the clutch oil chamber 29, and hydraulic oil is supplied as hydraulic fluid through the clutch pressure passage 35.

[0033] Clutch piston 30, which serves as a piston, is provided axially movably within clutch oil chamber 29. As shown in FIGS. 5 and 6 , clutch piston 30 is made of a thick-walled annular body, and a spline portion 30A and an outer peripheral fitting portion 30B are formed on the outer peripheral surface of clutch piston 30, and an inner peripheral fitting portion 30C is formed on the inner peripheral surface of clutch piston 30. One axial end face of clutch piston 30 forms an annular pressing surface 30D, which presses rotor disc 27 and clutch disc 28 in the axial direction. The other axial end face of clutch piston 30 forms an annular pressure-receiving surface 30E, which receives pressure from the hydraulic oil supplied to clutch oil chamber 29.

[0034] Clutch piston 30 is inserted into clutch oil chamber 29 with spline portion 30A fitted into spline portion 26D of clutch case 26, and faces rotor disk 27 and clutch disk 28 in the axial direction. In this state, outer peripheral fitting portion 30B of clutch piston 30 slidably fits into the inner peripheral surface of cylindrical portion 26B of clutch case 26, and inner peripheral fitting portion 30C of clutch piston 30 slidably fits into the outer peripheral surface of large diameter shaft portion 20D of forward shaft 20. An outer peripheral O-ring 31 seals between outer peripheral fitting portion 30B of clutch piston 30 and the inner peripheral surface of cylindrical portion 26B, and an inner peripheral O-ring 32 seals between inner peripheral fitting portion 30C of clutch piston 30 and the outer peripheral surface of large diameter shaft portion 20D.

[0035] The clutch piston 30 is provided with a plurality of (for example, two) bleed valves 33. Each bleed valve 33 is disposed midway through an oil passage 30F that passes through the clutch piston 30 in the axial direction, and has a ball 33A that opens and closes the oil passage 30F. When hydraulic oil is supplied to the clutch oil chamber 29, the ball 33A of the bleed valve 33 closes the oil passage 30F, thereby preventing the hydraulic oil from flowing toward the clutch disc 28. On the other hand, when hydraulic oil is not supplied to the clutch oil chamber 29, the ball 33A of the bleed valve 33 disengages from the oil passage 30F to open the oil passage 30F, thereby allowing the hydraulic oil to flow out of the clutch oil chamber 29. As shown in FIGS. 3 and 5, the two bleed valves 33 are disposed at equal circumferential intervals (180°) on a circumference S of a radius R centered on the rotational axis L of the forward rotor 19.

[0036] Two axially extending bolt holes (internal threaded holes) 30G are formed in the pressure-receiving surface 30E on the other axial side of the clutch piston 30. The bolt holes 30G are formed as bottomed holes, and the externally threaded portion 41B of the connecting rod 41 is screwed into them. These two bolt holes 30G are arranged at an equal circumferential interval (180°) on a circumference S of radius R centered on the rotation axis L of the forward rotation body 19. In this embodiment, the two bolt holes 30G and the two bleed valves 33 are arranged alternately at an equal circumferential interval (90°) on the circumference S of radius R centered on the rotation axis L of the forward rotation body 19.

[0037] The plurality of return springs 34 are located on the outer periphery of the rotor disc 27 and are provided between the plurality of clutch discs 28. The return springs 34 are, for example, wave springs, and are sandwiched between two adjacent clutch discs 28. The return springs 34 bias the plurality of clutch discs 28 in a direction that separates them from the adjacent rotor discs 27.

[0038] Therefore, when hydraulic oil is supplied into the clutch oil chamber 29 through the clutch pressure passage 35, the clutch piston 30 moves toward the clutch disc 28 against the spring force (biasing force) of the return spring 34. As a result, the clutch piston 30 presses the plurality of rotor discs 27 and the plurality of clutch discs 28 in the axial direction, frictionally engaging them with the end plate 26E of the clutch case 26 (see FIG. 3). This brings the forward clutch mechanism 25 into an engaged state, and the cylindrical portion 19B of the forward rotor 19 and the cylindrical portion 26B of the clutch case 26 become integrated. As a result, the rotation of the forward rotor 19 is transmitted to the forward shaft 20 via the clutch case 26, and the forward rotor 19 and the forward shaft 20 rotate integrally about the rotation axis L.

[0039] On the other hand, when the supply of hydraulic oil to the clutch oil chamber 29 is cut off, the spring force of the return spring 34 releases the frictional engagement between the plurality of rotor discs 27 and the plurality of clutch discs 28 (see FIG. 4). This disengages the forward clutch mechanism 25, and the rotation of the forward rotor 19 is not transmitted to the forward shaft 20, allowing only the forward rotor 19 to rotate (spin).

[0040] The clutch pressure passage 35 is provided inside the forward shaft 20 and extends in the axial direction. The clutch pressure passage 35 is an oil passage that guides hydraulic oil discharged from a hydraulic pump 45, which will be described later, to the clutch oil chamber 29. The clutch pressure passage 35 has an annular passage 35A formed on one axial side of the forward shaft 20, an axial passage 35B that extends axially from an end face 20H on one axial side of the forward shaft 20 and communicates with the annular passage 35A, and a radial passage 35C that extends radially from the tip end side of the axial passage 35B and opens to the clutch oil chamber 29.

[0041] The annular passage 35A is formed in an annular shape around the entire outer peripheral surface of the forward shaft 20 and communicates with a hydraulic oil introduction passage 16D formed in the lid body 16C. The axial passage 35B is formed at a position radially eccentric from the rotational axis L of the forward shaft 20 and communicates with the annular passage 35A. The portion of the axial passage 35B that opens to the end face 20H of the forward shaft 20 is closed by a sealing plug 35D. Therefore, the hydraulic oil discharged from the hydraulic pump 45 and introduced into the hydraulic oil introduction passage 16D of the lid body 16C is supplied to the clutch oil chamber 29 via the annular passage 35A, axial passage 35B, and radial passage 35C of the clutch pressure passage 35.

[0042] The lubricating oil passage 36 is provided inside the forward shaft 20 at a position different from the clutch pressure passage 35. The lubricating oil passage 36 guides lubricating oil discharged from a lubricating oil pump 48 (described later) to the rotor disc 27, the clutch disc 28, etc., and also to the cancel oil chamber 37. The lubricating oil passage 36 opens to the end face 20H of the forward shaft 20 and has an axial passage 36A extending axially from the end face 20H to the position of the large diameter shaft portion 20D, a plurality of (e.g., three) bearing radial passages 36B branching radially from the axial passage 36A, a plurality of (e.g., two) clutch radial passages 36C, and an oil chamber radial passage 36D.

[0043] The bearing radial passage 36B branches radially from the axial passage 36A at the position of the small diameter shaft portion 20C and opens to the outer peripheral surface of the small diameter shaft portion 20C. The bearing radial passage 36B supplies lubricating oil to the needle bearing 23 and the thrust bearing 24. The clutch radial passage 36C branches radially from the axial passage 36A at the position of the intermediate shaft portion 20E and opens to the outer peripheral surface of the intermediate shaft portion 20E. The clutch radial passage 36C supplies lubricating oil to the rotor disk 27 and the clutch disk 28. The oil chamber radial passage 36D branches radially from the axial passage 36A at the position of the large diameter shaft portion 20D and opens to the cancel oil chamber 37.

[0044] The cancel oil chamber 37 is disposed between the forward shaft 20 and the clutch case 26, separated from the clutch oil chamber 29. The cancel oil chamber 37 is arranged axially alongside the clutch oil chamber 29, with the fixed portion 26A of the clutch case 26 sandwiched between them. That is, the cancel oil chamber 37 and the clutch oil chamber 29 are arranged axially alongside each other, separated by the fixed portion 26A of the clutch case 26. The cancel oil chamber 37 is formed as an annular space surrounded by the end face on the other axial side (the roller bearing 22 side) of the fixed portion 26A of the clutch case 26, the inner circumferential surface of the cylindrical portion 26B, and the outer circumferential surface of the large-diameter shaft portion 20D of the forward shaft 20, and a cancel piston 38 is slidably inserted into it. The inner circumferential surfaces of the cancel oil chamber 37 and the clutch oil chamber 29, and the outer circumferential surfaces of the cancel oil chamber 37 and the clutch oil chamber 29 are each arranged concentrically with respect to the rotation axis L of the forward rotor 19. The cancel oil chamber 37 is connected to the radial oil chamber passage 36D of the lubricating oil passage 36 formed in the forward shaft 20, and lubricating oil, which is an oil fluid different from the hydraulic oil supplied to the clutch oil chamber 29, is supplied and discharged through the lubricating oil passage 36.

[0045] The cancel piston 38 is provided axially movably within the cancel oil chamber 37. The cancel piston 38 is formed of a thick-walled annular body, and its outer peripheral surface 38A slidably fits within the inner peripheral surface of the cylindrical portion 26B of the clutch case 26, while its inner peripheral surface 38B slidably fits within the outer peripheral surface of the large-diameter shaft portion 20D of the forward shaft 20. One axial end face of the cancel piston 38 forms an annular pressure-receiving surface 38C, which receives pressure from the lubricating oil supplied to the cancel oil chamber 37. The cancel piston 38 is inserted into the cancel oil chamber 37 in a state aligned axially with the clutch piston 30, which is inserted into the clutch oil chamber 29. By arranging the clutch piston 30 and the cancel piston 38 aligned axially in this way, it is possible to prevent the forward clutch mechanism 25 from becoming larger in diameter.

[0046] The gap between the outer peripheral surface 38A of the cancel piston 38 and the inner peripheral surface of the cylindrical portion 26B is sealed by an outer peripheral O-ring 39, and the gap between the inner peripheral surface 38B of the cancel piston 38 and the outer peripheral surface of the large diameter shaft portion 20D is sealed by an inner peripheral O-ring 40. The cancel piston 38 moves in a direction away from the clutch piston 30 as lubricating oil discharged from the lubricating oil pump 48 is supplied to the cancel oil chamber 37 through the lubricating oil passage 36.

[0047] Two rod insertion holes 38D (only one shown) are formed in the cancel piston 38 and penetrate therethrough in the axial direction. These two rod insertion holes 38D are located at positions corresponding to the two bolt holes 30G formed in the clutch piston 30, i.e., are arranged at equal intervals (180°) in the circumferential direction on a circumference S of radius R centered on the rotational axis L of the forward rotation body 19. Two rod insertion holes 26F (only one shown) are also formed in the fixed portion 26A of the clutch case 26 and penetrate therethrough in the axial direction. These two rod insertion holes 26F are also located at positions corresponding to the two bolt holes 30G formed in the clutch piston 30, i.e., are arranged at equal intervals (180°) in the circumferential direction on a circumference S of radius R centered on the rotational axis L of the forward rotation body 19. A shaft portion 41A of a connecting rod 41 is slidably inserted through the rod insertion hole 38D of the cancel piston 38 and the rod insertion hole 26F of the clutch case 26 (fixed portion 26A).

[0048] A plurality of (for example, two) connecting rods 41 serving as connecting members connect the clutch piston 30 and the cancel piston 38 (only one is shown). The connecting rod 41 has a cylindrical shaft portion 41A and a male thread portion 41B that protrudes from one axial end face of the shaft portion 41A toward the clutch piston 30. The shaft portion 41A of the connecting rod 41 is inserted into a rod insertion hole 26F formed in the fixed portion 26A of the clutch case 26 and a rod insertion hole 38D formed in the cancel piston 38. The male thread portion 41B of the connecting rod 41 is threaded into a bolt hole 30G of the clutch piston 30, and one axial end face of the shaft portion 41A abuts against a pressure-receiving surface 30E of the clutch piston 30. As a result, the two connecting rods 41 are arranged at an interval of 180° on a circumference S of radius R centered on the rotation axis L of the forward rotor 19, and connect the clutch piston 30 and the cancel piston 38 at two locations across the fixed part 26A of the clutch case 26. In this case, the two connecting rods 41 and the two bleed valves 33 are arranged alternately at equal intervals (90°) in the circumferential direction on the circumference S of radius R centered on the rotation axis L of the forward rotor 19.

[0049] An O-ring 42 is fitted onto the outer peripheral surface of the shaft portion 41A of the connecting rod 41 at a portion close to the male thread portion 41B. The O-ring 42 provides a seal between the inner peripheral surface of the rod insertion hole 26F formed in the clutch case 26 (fixed portion 26A) and the outer peripheral surface of the shaft portion 41A. The other axial side of the shaft portion 41A of the connecting rod 41 forms a protruding end 41C that protrudes outward from the other axial end face 38E of the cancel piston 38. A stop ring (shaft retaining ring) 43 is attached to the protruding end 41C, and the stop ring 43 prevents the protruding end 41C from entering the rod insertion hole 38D of the cancel piston 38.

[0050] The hydraulic oil passage 44 connects the clutch pressure passage 35 formed in the forward shaft 20 with the hydraulic pump 45. A switching valve 46 is provided in the hydraulic oil passage 44. The switching valve 46 is, for example, a solenoid valve having an electromagnetic pilot unit 46A. When no signal is supplied from a controller (not shown) to the electromagnetic pilot unit 46A, the switching valve 46 holds the valve position (a), and when a signal is supplied to the electromagnetic pilot unit 46A, the switching valve 46 is switched to the valve position (b). When the switching valve 46 holds the valve position (a), the supply of hydraulic oil to the clutch oil chamber 29 is cut off, and the forward clutch mechanism 25 is in a disengaged state (disconnected state) (see FIG. 4). When the switching valve 46 is switched from the valve position (a) to the valve position (b), hydraulic oil discharged from the hydraulic pump 45 is supplied to the clutch oil chamber 29 through the clutch pressure passage 35, and the forward clutch mechanism 25 is in an engaged state (see FIG. 3).

[0051] The lubricating oil passage 47 connects the lubricating oil passage 36 formed in the forward shaft 20 to the lubricating oil pump 48. The discharge pressure of the lubricating oil pump 48 is set lower than the discharge pressure of the hydraulic pump 45. The lubricating oil discharged from the lubricating oil pump 48 is introduced into the lubricating oil passage 36 through the lubricating oil passage 47 and is supplied to the needle bearing 23 and thrust bearing 24, as well as into the cancel oil chamber 37.

[0052] The power transmission device 15 according to the first embodiment has the above-described configuration, and its operation will be described below.

[0053] For example, when the wheel loader 1 is caused to travel forward, the output of the engine 10 is transmitted to a forward rotor 19 of the power transmission device 15 via a torque converter (not shown). The rotation of the forward rotor 19 is transmitted to a forward shaft 20 and a forward clutch mechanism 25, and then transmitted to an intermediate shaft (not shown) from an output gear 26C provided on a clutch case 26 of the forward clutch mechanism 25, and the intermediate shaft rotates in the forward direction. The power transmission device 15 reduces the speed of the rotation output of the intermediate shaft using a transmission shaft (not shown), and outputs this reduced rotation to an output shaft 18. The rotation of the output shaft 18 is transmitted to the front axle 11 via a propeller shaft 13, and is also transmitted to the rear axle 12 via a propeller shaft 14. As a result, the front wheels 2 and rear wheels 4 rotate simultaneously, allowing the wheel loader 1 to travel forward at the desired gear position.

[0054] Here, when the rotation of the forward rotor 19 is to be transmitted to the forward shaft 20 and the forward clutch mechanism 25, a signal is supplied from a controller (not shown) to the electromagnetic pilot section 46A of the switching valve 46. This switches the switching valve 46 from valve position (a) to valve position (b), and the hydraulic oil discharged from the hydraulic pump 45 is supplied to the clutch oil chamber 29 through the hydraulic oil passage 44, the hydraulic oil introduction passage 16D of the casing 16 (cover body 16C), and the clutch pressure passage 35 of the forward shaft 20.

[0055] When hydraulic oil is supplied into the clutch oil chamber 29, the clutch piston 30 moves toward the clutch disc 28 against the spring force of the return spring 34. As a result, the clutch piston 30 presses the plurality of rotor discs 27 and the plurality of clutch discs 28 in the axial direction, frictionally engaging them with the end plate 26E of the clutch case 26 (see FIG. 3). This brings the forward clutch mechanism 25 into an engaged state, and the cylindrical portion 19B of the forward rotor 19 and the cylindrical portion 26B of the clutch case 26 become integrated. As a result, the rotation of the forward rotor 19 is transmitted to the forward shaft 20 via the clutch case 26, and the forward rotor 19 and the forward shaft 20 rotate integrally about the rotation axis L.

[0056] When the forward clutch mechanism 25 is engaged, in addition to the hydraulic oil pressure (clutch pressure) from the hydraulic oil supplied to the clutch oil chamber 29, centrifugal hydraulic pressure from the hydraulic oil in the clutch oil chamber 29 acts on the clutch piston 30 due to centrifugal force caused by the rotation of the forward shaft 20 and the clutch case 26. For this reason, the timing at which the forward clutch mechanism 25 is engaged is influenced by factors other than the clutch pressure, i.e., the rotation speeds of the forward shaft 20 and the clutch case 26, making it difficult to control the clutch pressure required to engage the forward clutch mechanism 25 at the appropriate timing.

[0057] Meanwhile, lubricating oil discharged from the lubricating oil pump 48 is supplied to the cancel oil chamber 37 through the lubricating oil passage 47, the lubricating oil introduction passage 16E of the casing 16 (lid body 16C), and the lubricating oil passage 36 of the forward shaft 20. The lubricating oil in the cancel oil chamber 37 is subjected to centrifugal force accompanying the rotation of the forward shaft 20 and clutch case 26, and centrifugal oil pressure acts on the cancel piston 38. As a result, the cancel piston 38 moves in a direction away from the clutch piston 30, but the cancel piston 38 and clutch piston 30 are connected via a connecting rod 41.

[0058] Therefore, the centrifugal oil pressure acting on the clutch piston 30 from the hydraulic oil in the clutch oil chamber 29 can be offset by the centrifugal oil pressure acting on the cancel piston 38 from the lubricating oil in the cancel oil chamber 37. As a result, the forward clutch mechanism 25 can be engaged at the appropriate timing by the clutch pressure from the hydraulic oil supplied to the clutch oil chamber 29, regardless of the rotation speeds of the forward shaft 20 and the clutch case 26.

[0059] Next, when the forward clutch mechanism 25 is to be disengaged, the supply of a signal from the controller (not shown) to the electromagnetic pilot section 46A of the switching valve 46 is stopped. This switches the switching valve 46 from valve position (b) to valve position (a), and the supply of hydraulic oil to the clutch oil chamber 29 is cut off. Therefore, the spring force of the return spring 34 releases the frictional engagement between the multiple rotor discs 27 and the multiple clutch discs 28. This disengages the forward clutch mechanism 25, and the rotation of the forward rotor 19 is not transmitted to the forward shaft 20, allowing only the forward rotor 19 to rotate (idle).

[0060] Here, even when the forward clutch mechanism 25 is disengaged, centrifugal force acts on the hydraulic oil remaining in the clutch oil chamber 29, and centrifugal oil pressure from the hydraulic oil subjected to this centrifugal force acts on the clutch piston 30. This may delay the operation of the return spring 34 to release the frictional engagement between the rotor disc 27 and the clutch disc 28.

[0061] On the other hand, because the cancel oil chamber 37 is filled with lubricating oil supplied through the lubricating oil passage 36, centrifugal oil pressure from the lubricating oil subjected to centrifugal force in the cancel oil chamber 37 acts on the cancel piston 38. Because the clutch piston 30 and the cancel piston 38 are connected via a connecting rod 41, the centrifugal oil pressure acting on the clutch piston 30 from the hydraulic oil in the clutch oil chamber 29 can be offset by the centrifugal oil pressure acting on the cancel piston 38 from the lubricating oil in the cancel oil chamber 37.

[0062] As a result, when the supply of hydraulic oil to the clutch oil chamber 29 is cut off, the clutch piston 30 and the cancel piston 38 move together in a direction away from the rotor disc 27 due to the spring force of the return spring 34 (see FIG. 4). In this way, the frictional engagement between the rotor disc 27 and the clutch disc 28 is quickly released by the return spring 34, so that the forward clutch mechanism 25 can be quickly disengaged.

[0063] Moreover, in the power transmission device 15 according to this embodiment, the clutch piston 30 and the cancel piston 38 are arranged side by side in the axial direction, and are connected to each other via a connecting rod 41. This prevents the clutch piston 30 and the cancel piston 38 from becoming large in the radial direction, allows the forward clutch mechanism 25 to be configured compactly, and the power transmission device 15 as a whole to be made smaller.

[0064] Furthermore, the two connecting rods 41 that connect the clutch piston 30 and the cancel piston 38 are arranged at an interval of 180° on a circumference S of radius R centered on the rotational axis L of the forward rotor 19. As a result, the axial movement of the clutch piston 30 is transmitted evenly to the cancel piston 38 via the two connecting rods 41, and the axial movement of the cancel piston 38 is transmitted evenly to the clutch piston 30 via the two connecting rods 41. As a result, the clutch piston 30 and the cancel piston 38 can be moved smoothly in the axial direction in accordance with the supply and discharge of hydraulic oil to and from the clutch oil chamber 29, and the forward clutch mechanism 25 can be engaged and disengaged quickly and accurately.

[0065] Furthermore, the two connecting rods 41 and the two bleed valves 33 are alternately arranged at equal intervals (90°) in the circumferential direction on a circumference S of radius R centered on the rotation axis L of the forward rotor 19. As a result, when the supply of hydraulic oil to the clutch oil chamber 29 is cut off and the clutch piston 30 and the cancel piston 38 move in a direction away from the rotor disc 27 due to the spring force of the return spring 34, hydraulic oil can be made to flow out evenly from the clutch oil chamber 29 through the two bleed valves 33, allowing the clutch piston 30 and the cancel piston 38 to move smoothly in the axial direction.

[0066] Thus, the power transmission device 15 according to the embodiment comprises a forward rotor 19, a forward shaft 20 rotatably provided coaxially with the forward rotor 19, and a forward clutch mechanism 25 that connects or disconnects the forward rotor 19 and the forward shaft 20. The forward clutch mechanism 25 comprises a clutch case 26 provided integrally with the forward shaft 20, a rotor disk 27 that engages with the forward rotor 19 so as to be movable in the axial direction and rotates integrally with the forward rotor 19, a clutch disk 28 that engages with the clutch case 26 so as to be movable in the axial direction and rotates integrally with the clutch case 26, and a clutch that moves in response to the pressure of hydraulic oil supplied to the clutch oil chamber 29. The clutch disc 28 is provided with a clutch piston 30 that moves axially relative to the clutch case 26 and frictionally engages the rotor disc 27 and the clutch disc 28, a cancel oil chamber 37 that is arranged axially alongside the clutch oil chamber 29 while being partitioned off from the clutch oil chamber 29, a cancel piston 38 that is arranged axially movably in the cancel oil chamber 37 while being axially alongside the clutch piston 30, and that moves in a direction away from the clutch piston 30 as lubricating oil is supplied to the cancel oil chamber 37, and a connecting rod 41 that connects the clutch piston 30 and the cancel piston 38.

[0067] With this configuration, the centrifugal hydraulic pressure acting on the clutch piston 30 from the hydraulic oil supplied to the clutch oil chamber 29 can be suppressed by the centrifugal hydraulic pressure acting on the cancel piston 38 from the lubricating oil supplied to the cancel oil chamber 37. As a result, when hydraulic oil is supplied to the clutch oil chamber 29 to engage the forward clutch mechanism 25, the forward clutch mechanism 25 can be engaged at the appropriate timing by the clutch pressure of the hydraulic oil supplied to the clutch oil chamber 29, regardless of the rotation speeds of the forward shaft 20 and the clutch case 26. On the other hand, when the supply of hydraulic oil to the clutch oil chamber 29 is cut off to disengage the forward clutch mechanism 25, the return spring 34 quickly releases the frictional engagement between the rotor disc 27 and the clutch disc 28, regardless of the rotation speeds of the forward shaft 20 and the clutch case 26, and the forward clutch mechanism 25 can be quickly disengaged. Moreover, because the clutch piston 30 and the cancel piston 38 are arranged side by side in the axial direction, the forward clutch mechanism 25 can be configured compactly, and the entire power transmission device 15 can be made smaller.

[0068] In this embodiment, a plurality of connecting rods 41 are provided between the clutch piston 30 and the cancel piston 38, and the plurality of connecting rods 41 are arranged at equal intervals on a circumference S centered on the rotation axis L of the forward rotor 19. With this configuration, the axial movement of the clutch piston 30 is transmitted evenly to the cancel piston 38 via the plurality of connecting rods 41, and the axial movement of the cancel piston 38 is transmitted evenly to the clutch piston 30 via the plurality of connecting rods 41. As a result, the clutch piston 30 and the cancel piston 38 can be moved smoothly in the axial direction in accordance with the supply and discharge of hydraulic oil to and from the clutch oil chamber 29, and the forward clutch mechanism 25 can be engaged and disengaged quickly and accurately.

[0069] In this embodiment, the clutch piston 30 is provided with a plurality of bleed valves 33 that prevent hydraulic oil from flowing out of the clutch oil chamber 29 when hydraulic oil is supplied to the clutch oil chamber 29 and allow hydraulic oil to flow out of the clutch oil chamber 29 when hydraulic oil is not supplied to the clutch oil chamber 29, and the plurality of connecting rods 41 and the plurality of bleed valves 33 are arranged at equal intervals on a circumference S centered on the rotation axis L of the forward rotor 19. With this configuration, when the supply of hydraulic oil to the clutch oil chamber 29 is cut off and the clutch piston 30 and the cancel piston 38 move in a direction away from the rotor disc 27 due to the spring force of the return spring 34, hydraulic oil can be allowed to flow out evenly from the clutch oil chamber 29 through the two bleed valves 33. As a result, the clutch piston 30 and the cancel piston 38 can be moved smoothly in the axial direction.

[0070] 7 and 8 show a second embodiment of the present invention. A feature of this embodiment is that a pressure adjusting device is provided midway through the lubricating oil passage 47 that supplies oil to the cancel oil chamber 37. In this embodiment, the same components as those in the first embodiment are given the same reference numerals, and their description will be omitted.

[0071] Similar to the forward clutch mechanism 25 according to the first embodiment, the forward clutch mechanism 51 according to the present embodiment is configured to include a clutch case 26, a plurality of rotor discs 27, a plurality of clutch discs 28, a clutch oil chamber 29, a clutch piston 30, a return spring 34, a clutch pressure passage 35, a lubricating oil passage 36, a cancel oil chamber 37, a cancel piston 38, and a connecting rod 41. However, the forward clutch mechanism 51 differs from the forward clutch mechanism 25 in that it is provided with a pressure regulating valve 52, which will be described later.

[0072] Pressure regulating valve 52 serving as a pressure adjusting device is provided midway through lubricating oil passage 47, which supplies lubricating oil to cancel oil chamber 37, and hydraulic oil passage 44, which supplies hydraulic oil to clutch oil chamber 29. Pressure regulating valve 52 is, for example, a 4-port 2-position solenoid valve having an electromagnetic pilot unit 52A, and holds valve position (c) when no signal is supplied from a controller (not shown) to electromagnetic pilot unit 52A, and switches to valve position (d) when a signal is supplied to electromagnetic pilot unit 52A.

[0073] When the forward clutch mechanism 51 is to be engaged, a signal is supplied to the electromagnetic pilot unit 52A, switching the pressure regulating valve 52 to valve position (d) (see FIG. 7). As a result, hydraulic oil discharged from the hydraulic pump 45 is supplied to the clutch oil chamber 29, and lubricating oil discharged from the lubricating oil pump 48 is supplied to the cancel oil chamber 37. As a result, the centrifugal hydraulic pressure acting on the clutch piston 30 from the hydraulic oil in the clutch oil chamber 29 and the centrifugal hydraulic pressure acting on the cancel piston 38 from the lubricating oil in the cancel oil chamber 37 are offset. Therefore, the clutch piston 30 can frictionally engage the rotor disc 27 and the clutch disc 28 by the clutch pressure of the hydraulic oil supplied to the clutch oil chamber 29, without being affected by the centrifugal hydraulic pressure. As a result, the forward clutch mechanism 25 can be engaged at the appropriate timing, regardless of the rotation speeds of the forward shaft 20 and the clutch case 26.

[0074] On the other hand, when the forward clutch mechanism 51 is to be disengaged, the supply of a signal to the electromagnetic pilot unit 52A is cut off, and the pressure regulating valve 52 is switched to valve position (c) (see FIG. 8). This cuts off the supply of hydraulic oil to the clutch oil chamber 29, and the hydraulic oil discharged from the hydraulic pump 45 is supplied to the cancel oil chamber 37. In this way, in response to the cutoff of the supply of hydraulic oil to the clutch oil chamber 29, the pressure regulating valve 52 adjusts the pressure of the oil supplied to the cancel oil chamber 37 by supplying high-pressure hydraulic oil to the cancel oil chamber 37 in place of low-pressure lubricating oil.

[0075] When the supply of hydraulic oil to the clutch oil chamber 29 is cut off, the return spring 34 releases the frictional engagement between the rotor disc 27 and the clutch disc 28, and the forward clutch mechanism 25 is disengaged. At this time, the centrifugal oil pressure acting on the clutch piston 30 due to the hydraulic oil remaining in the clutch oil chamber 29 is offset by the pressure acting on the cancel piston 38 from the hydraulic oil supplied to the cancel oil chamber 37. As a result, the frictional engagement between the rotor disc 27 and the clutch disc 28 is quickly released by the return spring 34, and the forward clutch mechanism 25 can be quickly disengaged.

[0076] Furthermore, for example, when the discharge pressure of the hydraulic pump 45 is increased, the force of the cancel piston 38, which is moved by the hydraulic oil supplied to the cancel oil chamber 37, can move the clutch piston 30 in a direction away from the clutch disc 28. This reduces the spring force of the return spring 34, or makes it possible to eliminate the need for the return spring 34. As a result, lubricating oil can be smoothly circulated between the multiple rotor discs 27 and the multiple clutch discs 28 through the lubricating oil passage 36 (clutch radial passage 36C) formed in the forward shaft 20, and drag torque can be reduced when the forward clutch mechanism 25 is disengaged.

[0077] In the embodiment, the cancel oil chamber 37, the cancel piston 38, the connecting rod 41, etc. are applied to the forward clutch mechanism 25 (51) of the power transmission device 15. However, the present invention is not limited to this, and can also be applied to, for example, a reverse clutch mechanism, a gear change clutch mechanism, etc.

[0078] Furthermore, in the second embodiment, the pressure regulating device is exemplified as pressure regulating valve 52 provided midway through hydraulic oil passage 44 and lubricating oil passage 47. However, the present invention is not limited to this, and for example, the lubricating oil pump may be a variable displacement pump, and the flow rate of lubricating oil supplied to cancel oil chamber 37 may be increased when forward clutch mechanism 25 is disengaged.

[0079] Furthermore, in the embodiment, the clutch piston 30 and the cancel piston 38 are connected by two connecting rods 41. However, the present invention is not limited to this, and may be configured to use, for example, three or more connecting rods. [Explanation of symbols]

[0080] 15 Power transmission device 19 Forward rotating body (rotating body) 20 Advance axis (driven body) 25,51 Forward clutch mechanism (clutch mechanism) 26 Clutch case 27 Rotating disc 28 Clutch disc 29 Clutch oil chamber 30 Clutch piston 33 Bleed valve 37 Cancellation Oil Room 38 Cancel piston 41 Connecting rod (connecting member) 52 Pressure regulating valve (pressure regulating device)

Claims

1. a rotating body, a driven body rotatably provided coaxially with the rotating body, and a clutch mechanism for connecting and disconnecting the rotating body and the driven body, The clutch mechanism includes: a clutch case integrally provided with the driven body; a rotor disk that is axially movably engaged with the rotor and rotates integrally with the rotor; a clutch disc that is axially movably engaged with the clutch case and rotates integrally with the clutch case; a clutch piston that moves axially relative to the clutch case in response to pressure of oil supplied to a clutch oil chamber, and engages the rotor disc and the clutch disc, a cancel oil chamber that is partitioned from the clutch oil chamber and is arranged alongside the clutch oil chamber in the axial direction; a cancel piston that is arranged in the cancel oil chamber so as to be axially movable in a state aligned with the clutch piston in the axial direction, and that moves in a direction away from the clutch piston when oil is supplied to the cancel oil chamber; a connecting member that connects the clutch piston and the cancel piston.

2. 2. The power transmission device according to claim 1, wherein a pressure adjusting device is provided in the oil passage that supplies oil to the cancel oil chamber, and that adjusts the pressure of the oil supplied to the cancel oil chamber in accordance with the oil supplied to the clutch oil chamber.

3. a plurality of the connecting members are provided between the clutch piston and the cancel piston; 2. The power transmission device according to claim 1, wherein the plurality of connecting members are arranged at equal intervals on a circumference centered on the rotation axis of the rotating body.

4. The clutch piston is provided with a plurality of bleed valves that prevent oil from flowing out of the clutch oil chamber when oil is supplied to the clutch oil chamber and that allow oil to flow out of the clutch oil chamber when oil is not supplied to the clutch oil chamber, 4. The power transmission device according to claim 3, wherein the plurality of connecting members and the plurality of bleed valves are arranged at equal intervals on a circumference centered on the rotation axis of the rotating body.

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