Power transmission device

Abstract

To miniaturize an oil pump.SOLUTION: A torque converter includes a lock-up device, an energizing member, a cover, an impeller, a turbine, a first hydraulic chamber, and a second hydraulic chamber. The lock-up device includes a clutch and a piston. The energizing member energizes the piston toward the clutch. A first oil passage communicates with the first hydraulic chamber. A second oil passage communicates with the second hydraulic chamber. A switching device switches between a first position and a second position. When the switching device is at the first position, hydraulic fluid is supplied to the first hydraulic chamber through the first oil passage. When the switching device is at the second position, the hydraulic fluid is supplied to the second hydraulic chamber through the second oil passage. The piston presses the clutch when the hydraulic fluid is supplied into the first hydraulic chamber, and releases the pressing on the clutch when the hydraulic fluid is supplied into the second hydraulic chamber.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power transmission device.

Background Art

[0002] In order to improve fuel efficiency, torque converters having a lock-up device have become widespread. For example, the torque converter disclosed in Patent Document 1 has a normal close type lock-up device. That is, in the neutral state, the lock-up device of the torque converter is in a locked state (lock-up state). The torque converter has a coil spring for biasing the lock-up device into the lock-up state. The lock-up device is in the lock-up state when the coil spring presses the piston against the cover.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the torque converter as described above, in order to release the lock-up state of the lock-up device, the oil pump is operated to supply hydraulic oil to the torque converter, and the piston is moved so as to resist the biasing force of the coil spring. There is a desire to miniaturize the oil pump for supplying this hydraulic oil. Therefore, an object of the present invention is to provide a power transmission device capable of miniaturizing the oil pump.

Means for Solving the Problems

[0005] The power transmission device according to the first aspect includes a torque converter, a first oil passage, a second oil passage, and a switching device. The torque converter has a lock-up device, a biasing member, a cover, an impeller, a turbine, a first hydraulic chamber, and a second hydraulic chamber. The lock-up device has a clutch portion and a piston. The biasing member biases the piston toward the clutch portion. The first oil passage communicates with the first hydraulic chamber. The second oil passage communicates with the second hydraulic chamber. The switching device is configured to switch between a first position and a second position. When the switching device is in the first position, hydraulic oil is supplied to the first hydraulic chamber through the first oil passage. When the switching device is in the second position, hydraulic oil is supplied to the second hydraulic chamber through the second oil passage. The piston is configured to press the clutch portion when hydraulic oil is supplied into the first hydraulic chamber, and to release the pressing of the clutch portion when hydraulic oil is supplied into the second hydraulic chamber.

[0006] According to this configuration, since the biasing member biases the piston toward the clutch portion, the lock-up device is in the lock-up state in the neutral state. That is, the lock-up device transmits torque between the cover and the turbine in the neutral state. Also, by supplying hydraulic oil into the first hydraulic chamber, the piston presses the clutch portion. That is, the piston presses the clutch portion not only by the biasing force of the biasing member but also by the hydraulic pressure in the first hydraulic chamber. For this reason, the biasing force by the biasing member can be reduced. As a result, the hydraulic pressure for releasing the lock-up state of the lock-up device can be reduced. For this reason, the oil pump can be miniaturized.

[0007] The power transmission device according to the second aspect is configured as follows in the power transmission device according to the first aspect. The first hydraulic chamber is defined by the cover and the piston. The second hydraulic chamber is defined by the turbine and the piston.

[0008] The power transmission device according to the third aspect is configured as follows in the power transmission device according to the second aspect. The clutch portion is disposed between the piston and the turbine.

[0009] The power transmission device according to the fourth aspect is configured as follows in the power transmission device according to any one of the first to third aspects. The torque converter has a communication hole that communicates the first hydraulic chamber and the second hydraulic chamber.

[0010] The power transmission device according to the fifth aspect further includes an oil pump, a pump motor, and a control unit in the power transmission device according to any one of the first to fourth aspects. The oil pump is configured to supply hydraulic oil to the torque converter via the first oil passage or the second oil passage. The pump motor is configured to drive the oil pump. The control unit is configured to control the pump motor and the switching device. The control unit has a first lock-up mode, a second lock-up mode, and a lock-up release mode. In the first lock-up mode, the control unit stops the pump motor. In the second lock-up mode, the control unit controls the switching device to be in the first position and operates the pump motor. In the lock-up release mode, the control unit controls the switching device to be in the second position and operates the pump motor.

[0011] The power transmission device according to the sixth aspect further includes a temperature sensor in the power transmission device according to the fifth aspect. The temperature sensor detects the temperature of the hydraulic oil of the torque converter. The torque converter has a communication hole that communicates the first hydraulic chamber and the second hydraulic chamber. When the control unit determines that the temperature detected by the temperature sensor is equal to or higher than a predetermined value, the control unit is configured to execute the second lock-up mode.

[0012] The power transmission device according to the seventh aspect further includes a drive motor and a branch oil passage in the power transmission device according to any one of the first to sixth aspects. The drive motor is configured to output torque to the torque converter. The branch oil passage is configured to branch from the first oil passage and supply hydraulic oil to the drive motor.

Advantages of the Invention

[0013] According to the present invention, the hydraulic pump can be miniaturized.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0015] Hereinafter, the power transmission device 100 according to the present embodiment will be described with reference to the drawings. In the following description, the axial direction is the direction in which the rotation axis O of the torque converter 3 extends. The circumferential direction is the circumferential direction of a circle centered on the rotation axis O, and the radial direction is the radial direction of a circle centered on the rotation axis O.

[0016] [Power Transmission Device] As shown in FIG. 1, the power transmission device 100 includes a drive motor 2, a torque converter 3, a first oil passage 4a, a second oil passage 4b, a switching device 5, an oil pump 6, a pump motor 7, a temperature sensor 8, and a control unit 9. The power transmission device 100 is mounted on, for example, an electric vehicle.

[0017] [Drive Motor] The drive motor 2 functions as a drive source for a vehicle on which the power transmission device 100 is mounted. The drive motor 2 is an electric motor. The drive motor 2 is, for example, an alternating current synchronous motor. Note that the vehicle on which the power transmission device 100 is mounted has only the drive motor 2 as a drive source. That is, the vehicle on which the power transmission device 100 is mounted does not have an internal combustion engine as a drive source. In the present embodiment, the vehicle does not have an internal combustion engine, but may have an internal combustion engine used for power generation.

[0018] The drive motor 2 has a motor case 21, a motor stator 22, and a rotor 23. The drive motor 2 in the present embodiment is a so-called inner rotor type motor. The drive motor 2 has an inverter (not shown) for controlling the rotational speed of the drive motor 2. The drive motor 2 is configured to output torque to a torque converter 3.

[0019] The motor case 21 is fixed to a vehicle body frame or the like and is non-rotatable. The motor stator 22 and the rotor 23 are housed in the motor case 21.

[0020] The motor stator 22 is fixed to the inner peripheral surface of the motor case 21. The motor stator 22 is non-rotatable. The rotor 23 rotates around the rotation axis O. The rotor 23 is arranged inside the motor stator 22 in the radial direction. The motor stator 22 is arranged at a distance from the rotor 23 in the radial direction.

[0021] [Torque Converter] The torque converter 3 is rotatably arranged. The rotation axis O of the torque converter 3 substantially coincides with the rotation axis O of the drive motor 2. Torque from the drive motor 2 is transmitted to the torque converter 3. The torque converter 3 is configured to amplify the torque output by the drive motor 2. Note that a speed reducer or the like may be interposed between the drive motor 2 and the torque converter 3.

[0022] Figure 2 is a cross-sectional view of the torque converter 3. As shown in Figure 2, the torque converter 3 has a cover 31, an impeller 32, a turbine 33, a stator 34, an output hub 35, a lock-up device 36, a plurality of biasing members 37, a damper device 38, and a communication hole 39. Further, the torque converter has a first hydraulic chamber H1 and a second hydraulic chamber H2. A working fluid is supplied into the torque converter 3. The working fluid is, for example, hydraulic oil.

[0023] <Cover> Torque is input to the cover 31 from the drive motor 2. The cover 31 rotates by the torque from the drive motor 2. The cover 31 has a first disk portion 311 and a first cylindrical portion 312. The first cylindrical portion 312 extends axially from the outer peripheral end portion of the first disk portion 311. Specifically, the first cylindrical portion 312 extends axially from the first disk portion 311 toward the impeller 32. That is, the first cylindrical portion 312 extends to the first side in the axial direction. A seal member 106 is disposed between the cover 31 and the output shaft 105. The seal member 106 is, for example, a resin seal ring.

[0024] Further, the cover 31 has a housing portion 313 and a hole portion 314. The housing portion 313 is a recess formed on the inner surface of the first disk portion 311, that is, the surface facing the first side in the axial direction of the first disk portion 311. The housing portion 313 is annular and extends in the circumferential direction. The housing portion 313 opens toward the turbine 33. That is, the housing portion 313 opens toward the space between the cover 31 and the turbine 33.

[0025] The hole portion 314 extends radially within the first disk portion 311. The hole portion 314 constitutes a part of a first oil passage 4a described later. The hole portion 314 communicates with the housing portion 313. Specifically, the hole portion 314 communicates with the housing portion 313 at the outer peripheral end portion in the radial direction.

[0026] <Impeller> The impeller 32 rotates integrally with the cover 31. The torque from the drive motor 2 is input to the impeller 32 via the cover 31. The impeller 32 is fixed to the cover 31. Specifically, the impeller 32 is fixed to the first cylindrical portion 312 of the cover 31.

[0027] The impeller 32 has an impeller shell 321, a plurality of impeller blades 322, and an impeller hub 323. The impeller shell 321 is fixed to the cover 31, for example, by welding. The impeller blades 322 are fixed to the inner surface of the impeller shell 321. The impeller hub 323 is fixed to the inner peripheral end portion of the impeller shell 321 by welding or the like.

[0028] <Turbine> The turbine 33 is disposed opposite to the impeller 32. Specifically, the turbine 33 faces the impeller 32 in the axial direction. Torque is transmitted from the impeller 32 to the turbine 33 via the working oil.

[0029] The turbine 33 has a turbine shell 331 and a plurality of turbine blades 332. The turbine blades 332 are fixed to the inner surface of the turbine shell 331 by brazing or the like.

[0030] <Stator> The stator 34 is configured to rectify the working oil returning from the turbine 33 to the impeller 32. The stator 34 is rotatable around the rotation axis O. For example, the stator 34 is supported by a fixed shaft 101 via a one-way clutch 102. Note that the fixed shaft 101 is non-rotatable. The stator 34 is disposed between the impeller 32 and the turbine 33 in the axial direction.

[0031] The one-way clutch 102 is disposed between the fixed shaft 101 and the stator 34. The one-way clutch 102 is configured to enable the stator 34 to rotate in the forward rotation direction. On the other hand, the one-way clutch 102 prevents the stator 34 from rotating in the reverse rotation direction. The torque is amplified by this stator 34 and transmitted from the impeller 32 to the turbine 33.

[0032] The stator 34 has a disk-shaped stator carrier 341 and a plurality of stator blades 342 attached to the outer peripheral surface thereof. A first thrust bearing 103 is disposed between the stator 34 and the impeller 32, and a second thrust bearing 104 is disposed between the stator 34 and the output hub 35.

[0033] [Output hub] The output hub 35 is configured to output the torque transmitted from the turbine 33 to the output shaft 105. The turbine 33 is attached to this output hub 35. Specifically, the turbine shell 331 is attached to the output hub 35 via a rivet or the like. The output hub 35 is formed with a spline hole 353. The output shaft 105 is spline-fitted into this spline hole 353. A third thrust bearing 109 is disposed between the output hub 35 and the cover 31.

[0034] The output hub 35 has a boss portion 351 and a flange portion 352. The boss portion 351 is cylindrical and extends in the axial direction. The boss portion 351 has a spline hole 353. The flange portion 352 extends radially outward from the outer peripheral surface of the boss portion 351. The flange portion 352 is annular and extends in the circumferential direction. The turbine shell 331 is attached to this flange portion 352.

[0035] [Lock-up device] When the lock-up device 36 is in the locked state (lock-up state), the impeller 32 and the turbine 33 are directly connected. Specifically, the lock-up device 36 directly connects the cover 31 and the turbine 33. Also, when the lock-up device 36 is in the unlocked state (lock-up release state), the direct connection between the impeller 32 and the turbine 33 is released. Specifically, the lock-up device 36 releases the direct connection between the cover 31 and the turbine 33.

[0036] Figure 3 is an enlarged cross-sectional view of the torque converter 3. The lock-up device 36 has a clutch portion 361 and a piston 362.

[0037] The clutch portion 361 can be in a clutch-on state and a clutch-off state. For the lock-up device 36 to be in the lock-up state means that the clutch portion 361 is in the clutch-on state. Also, for the lock-up device 36 to be in the lock-up release state means that the clutch portion 361 is in the clutch-off state.

[0038] The clutch portion 361 has a plurality of first clutch disks 361a and a plurality of second clutch disks 361b. Each first clutch disk 361a and each second clutch disk 361b are alternately arranged in the axial direction. A friction material is disposed between the first clutch disk 361a and the second clutch disk 361b. The friction material may be attached to the first clutch disk 361a or may be attached to the second clutch disk 361b.

[0039] The first clutch disk 361a is axially movably attached to the first cylindrical portion 312 of the cover 31. Also, the first clutch disk 361a rotates integrally with the first cylindrical portion 312.

[0040] The second clutch disk 361b is attached to a member that rotates integrally with the turbine 33 or the turbine 33. In this embodiment, the second clutch disk 361b is attached to the damper device 38. The second clutch disk 361b is attached to the damper device 38 so as to be axially movable. Also, the second clutch disk 361b rotates integrally with the damper device 38.

[0041] The piston 362 is axially movably disposed within the accommodating portion 313 of the cover 31. The piston 362 is axially slidably disposed on the inner wall surface defining the accommodating portion 313. The piston 362 is annular and extends in the circumferential direction. Seal members 107, 108 are disposed between the piston 362 and the inner wall surface defining the accommodating portion 313. The seal members 107, 108 are, for example, O-rings. The piston 362 is configured to rotate integrally with the cover 31. Note that the piston 362 may be relatively rotatable with respect to the cover 31.

[0042] When the piston 362 moves axially to the first side, that is, when the piston 362 moves toward the clutch portion 361 and presses the clutch portion 361, the first clutch disk 361a and the second clutch disk 361b frictionally engage with each other. As a result, the lock-up device 36 enters a lock-up state.

[0043] The lock-up device 36 has a pressure receiving member 363. The pressure receiving member 363 is attached to the first cylindrical portion 312. The movement of the pressure receiving member 363 toward the first side in the axial direction is restricted by a stopper ring 364. The clutch portion 361 is disposed between the piston 362 and the pressure receiving member 363. The clutch portion 361 is axially sandwiched between the piston 362 and the pressure receiving member 363.

[0044] [Biasing member] The biasing member 37 biases the piston 362 toward the clutch portion 361. That is, the biasing member 37 biases the piston 362 toward the first side in the axial direction. The biasing member 37 is, for example, a coil spring. The biasing member 37 is disposed between the cover 31 and the piston 362 in a compressed state. The biasing members 37 are arranged at intervals in the circumferential direction.

[0045] For example, the piston 362 has a plurality of receiving recesses 362a. The receiving recesses 362a are arranged at intervals in the circumferential direction. Each receiving recess 362a opens toward the second side in the axial direction. The biasing member 37 is disposed in the receiving recess 362a.

[0046] The piston 362 presses the clutch portion 361 by the biasing force of the biasing member 37. Therefore, in the neutral state where the power transmission device 100 is not operating, the clutch portion 361 is in the clutch-on state. That is, in the state where the oil pump 6 is not operating and no working oil is supplied into the torque converter 3, the clutch portion 361 is in the clutch-on state. When the power transmission device 100 is in the neutral state, the lock-up device 36 is in the lock-up state. That is, the lock-up device 36 is of the normally-closed type.

[0047] [Damper device] The damper device 38 is disposed between the cover 31 and the turbine 33 in the axial direction. Specifically, the damper device 38 is disposed between the cover 31 and the turbine 33. The damper device 38 is configured to absorb torque fluctuations transmitted from the lock-up device 36 to the output hub 35.

[0048] The damper device 38 is connected to the lock-up device 36 on the input side. Also, the damper device 38 is connected to the output hub 35 on the output side. The damper device 38 is configured to transmit torque from the lock-up device 36 to the output hub 35. The damper device 38 elastically connects the lock-up device 36 and the output hub 35. Specifically, the damper device 38 has a coil spring 381, and connects the lock-up device 36 and the output hub 35 via the coil spring 381.

[0049] [First and Second Hydraulic Chambers] The first hydraulic chamber H1 is defined by the cover 31 and the piston 362. Specifically, the first hydraulic chamber H1 is defined by the bottom surface of the accommodating portion 313, the inner wall surface of the accommodating portion 313, and the second side surface in the axial direction of the piston 362.

[0050] When hydraulic oil is supplied to the first hydraulic chamber H1, the piston 362 moves to the first side in the axial direction. As a result, the piston 362 presses the clutch portion 361. That is, the lock-up device 36 is brought into a lock-up state not only by the biasing force of the biasing member 37 but also by hydraulic pressure.

[0051] The second hydraulic chamber H2 is defined by the turbine 33 and the piston 362. Specifically, the second hydraulic chamber H2 is defined by the cover 31, the turbine 33, the piston 362, and the output hub 35. When hydraulic oil is supplied to the second hydraulic chamber H2, the piston 362 moves to the second side in the axial direction. As a result, the pressing of the clutch portion 361 by the piston 362 is released. That is, the lock-up device 36 is brought into a lock-up released state.

[0052] The clutch portion 361 is disposed in the second hydraulic chamber H2. That is, the clutch portion 361 is disposed between the piston 362 and the turbine 33. Also, the damper device 38 is disposed in the second hydraulic chamber H2. The second hydraulic chamber H2 communicates with the space between the impeller 32 and the turbine 33.

[0053] [First and Second Oil Passages] As shown in FIG. 1, the first oil passage 4a communicates with the first hydraulic chamber H1. Specifically, the first oil passage 4a communicates the oil tank 41 with the first hydraulic chamber H1. As described above, the hole 314 formed in the cover 31 is a part of the first oil passage 4a.

[0054] The second oil passage 4b communicates with the second hydraulic chamber H2. Specifically, the second oil passage 4b communicates the oil tank 41 with the second hydraulic chamber H2. The second oil passage 4b communicates with the second hydraulic chamber H2 through the space between the impeller 32 and the turbine 33.

[0055] The communication hole 39 communicates the first hydraulic chamber H1 with the second hydraulic chamber H2. In this embodiment, the communication hole 39 is formed in the first disk portion 311 of the cover 31. The communication hole 39 extends in the axial direction. The communication hole 39 communicates the first oil passage 4a with the second hydraulic chamber H2. The communication hole 39 communicates the first hydraulic chamber H1 with the second hydraulic chamber H2 through the first oil passage 4a.

[0056] [Switching Device] The switching device 5 is configured to switch between a first position and a second position. The switching device 5 is, for example, a direction control valve. In FIG. 1, the switching device is in the first position. When the switching device 5 is in the first position, hydraulic oil is supplied to the first hydraulic chamber H1 through the first oil passage 4a. That is, when the switching device 5 is in the first position, the hydraulic oil from the oil tank 41 is supplied to the first hydraulic chamber H1 through the first oil passage 4a.

[0057] In FIG. 4, the switching device 5 is in the second position. When the switching device 5 is in the second position, hydraulic oil is supplied to the second hydraulic chamber H2 through the second oil passage 4b. That is, when the switching device 5 is in the second position, the hydraulic oil from the oil tank 41 is supplied to the second hydraulic chamber H2 through the second oil passage 4b.

[0058] [Oil Pump, Pump Motor, Temperature Sensor] As shown in FIG. 1, the oil pump 6 is configured to supply hydraulic oil to the torque converter 3 via the first oil passage 4a or the second oil passage 4b. The pump motor 7 is configured to drive the oil pump 6.

[0059] The temperature sensor 8 is configured to detect the temperature of the hydraulic oil in the torque converter 3. Specifically, the temperature sensor 8 is configured to detect the temperature of the hydraulic oil in the oil tank 41. Note that the temperature sensor 8 may detect the temperature of the hydraulic oil flowing in the oil passage returning from the torque converter 3 to the oil tank 41. The temperature sensor 8 is configured to output information regarding the detected temperature of the hydraulic oil to the control unit 9.

[0060] [Control Unit] The control unit 9 is configured to control the switching device 5 and the pump motor 7. The control unit 9 is configured to control the switching device 5 and the pump motor 7 based on the vehicle speed, the accelerator opening, and the temperature of the hydraulic oil. Note that the control unit 9 acquires vehicle speed information from a vehicle speed sensor, acquires information regarding the accelerator opening from an accelerator position sensor, etc., and acquires information regarding the temperature of the hydraulic oil from the temperature sensor 8.

[0061] The control unit 9 has a first lock-up mode, a second lock-up mode, and a lock-up release mode. When the control unit 9 executes the first lock-up mode, the control unit 9 stops the pump motor 7. When the pump motor 7 stops in this way, only the biasing force of the biasing member 37 acts on the piston 362. Therefore, the lock-up device 36 is in the lock-up state only by the biasing force of the biasing member 37. In this first lock-up mode, the torque converter 3 transmits torque from the cover 31 to the turbine 33 via the lock-up device 36.

[0062] When the control unit 9 executes the second lock-up mode, it controls the switching device 5 to be in the first position and operates the pump motor 7. As a result, hydraulic oil is supplied to the first hydraulic chamber H1 through the first oil passage 4a. Therefore, in addition to the biasing force of the biasing member 37, the hydraulic pressure of the hydraulic oil supplied to the first hydraulic chamber H1 acts on the piston 362. Accordingly, the lock-up device 36 is in a lock-up state by the biasing force of the biasing member 37 and the hydraulic pressure in the first hydraulic chamber H1.

[0063] The lock-up device 36 can transmit higher torque in the second lock-up mode than in the first lock-up mode. Also, in the second lock-up mode, since the hydraulic oil flows from the first hydraulic chamber H1 to the second hydraulic chamber H2 through the communication hole 39, the hydraulic oil can be circulated. Therefore, the hydraulic oil can be cooled.

[0064] When the control unit 9 executes the lock-up release mode, as shown in FIG. 4, it controls the switching device 5 to be in the second position and operates the pump motor 7. As a result, hydraulic oil is supplied to the second hydraulic chamber H2 through the second oil passage 4b. Therefore, the hydraulic pressure of the hydraulic oil supplied to the second hydraulic chamber H2 acts on the piston 362 so as to oppose the biasing force of the biasing member 37. As a result, the piston 362 moves away from the clutch portion 361, and the clutch portion 361 becomes a clutch-off state. That is, the lock-up device 36 is in a lock-up release state by the hydraulic pressure in the second hydraulic chamber H2. Therefore, the torque converter 3 transmits torque from the impeller 32 to the turbine 33 through the hydraulic oil.

[0065] When moving forward, the control unit 9 determines whether to execute the first lock-up mode or the second lock-up mode or the lock-up release mode based on the vehicle speed and the accelerator opening. For example, in region A of FIG. 5, the control unit 9 executes the lock-up release mode. That is, in region A of FIG. 5, the torque converter 3 transmits torque from the impeller 32 to the turbine 33 through the hydraulic oil and exhibits a torque amplification function.

[0066] On the other hand, in region B of FIG. 5, the control unit 9 executes the first lock-up mode or the second lock-up mode. That is, in region B of FIG. 5, the torque converter 3 transmits torque from the cover 31 to the output hub 35 via the lock-up device 36. The control unit 9 normally executes the first lock-up mode. And when the control unit 9 determines that the temperature detected by the temperature sensor 8 is equal to or higher than a predetermined value, it executes the second lock-up mode. Note that when the control unit 9 determines that the temperature detected by the temperature sensor 8 is less than the predetermined value, it executes the first lock-up mode.

[0067] Also, during reverse travel, the control unit 9 determines whether to execute the first lock-up mode or the second lock-up mode based on the vehicle speed and the accelerator opening. For example, in region A of FIG. 6, the control unit 9 executes the second lock-up mode. That is, when the output torque of the drive motor 2 is equal to or higher than a predetermined value, the control unit 9 executes the second lock-up mode. On the other hand, in region B of FIG. 6, the control unit 9 executes the first lock-up mode. Note that the control unit 9 does not execute the lock-up release mode during reverse travel.

[0068] The control unit 9 is constituted by, for example, a computer (such as a microcomputer) including a CPU (Central Processing Unit) and a ROM (Read Only Memory). Programs for performing various operations are stored in the ROM. The CPU executes the programs stored in the ROM.

[0069] [Control Method] FIG. 7 is a flowchart showing an example of the control method by the control unit 9. Hereinafter, with reference to FIG. 7, the control method of the control unit 9 during forward travel will be described.

[0070] The control unit 9 first determines whether to execute the first or second lock-up mode based on the vehicle speed and the accelerator opening (step S1). Specifically, the control unit 9 has a map showing the relationship between the vehicle speed and the accelerator opening and the mode executed by the control unit 9. Then, the control unit 9 determines whether to execute the first or second lock-up mode based on that map. If the control unit 9 determines not to execute the first or second lock-up mode (No in step S1), it executes the lock-up release mode (step S2).

[0071] If the control unit 9 determines to execute the first or second lock-up mode (Yes in step S1), it then determines whether the accelerator opening is greater than or equal to a predetermined value (step S3). If the control unit 9 determines that the accelerator opening is greater than or equal to the predetermined value (Yes in step S3), it executes the second lock-up mode (step S4). That is, the control unit 9 controls the switching device 5 to be in the first position and operates the pump motor 7.

[0072] On the other hand, if the control unit 9 determines that the accelerator opening is less than the predetermined value (No in step S3), it determines whether the temperature of the hydraulic oil is greater than or equal to a predetermined value (step S5). If the control unit 9 determines that the temperature of the hydraulic oil is greater than or equal to the predetermined value (Yes in step S5), it executes the process of step S4. On the other hand, if the control unit 9 determines that the temperature of the hydraulic oil is less than the predetermined value (No in step S5), it executes the first lock-up mode (step S6). That is, the control unit 9 stops the pump motor 7.

[0073] [Modification Example] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various changes are possible without departing from the spirit of the present invention. Note that the following modification examples can basically be applied simultaneously.

[0074] (a) As shown in FIG. 8, the power transmission device 100 may further include a branch oil passage 4c. The branch oil passage 4c branches from the first oil passage 4a. The branch oil passage 4c is configured to supply hydraulic oil to the drive motor 2. For example, the branch oil passage 4c is configured to supply hydraulic oil into the motor case 21 of the drive motor 2.

[0075] (b) In the above embodiment, the piston 362 was accommodated in the accommodation portion 313 of the cover 31, but the configuration of the piston 362 is not limited thereto. For example, the piston 362 may be configured to separate the space between the first disk portion 311 of the cover 31 and the turbine 33. That is, the piston 362 may be disk-shaped with an opening at the center. In this case, the piston 362 slides axially on, for example, the output hub 35.

[0076] (c) In the above embodiment, the clutch portion 361 is disposed on the first side in the axial direction with respect to the piston 362, but the configuration of the lock-up device 36 is not limited thereto. For example, the clutch portion 361 may be disposed on the second side in the axial direction with respect to the piston 362. In this case, the first hydraulic chamber H1 is the space between the piston 362 and the turbine 33, and the second hydraulic chamber H2 is the space between the cover 31 and the piston 362. Further, the biasing member 37 biases the piston 362 toward the second side in the axial direction.

[0077] (d) In the above embodiment, the communication hole 39 was formed in the cover 31, but the configuration of the communication hole 39 is not limited thereto. For example, the communication hole 39 may be formed in the piston 362. In this case, the communication hole 39 directly communicates the first hydraulic chamber H1 and the second hydraulic chamber H2.

Explanation of Reference Numerals

[0078] 2: Drive motor 3: Torque converter 31: Cover 32: Impeller 33: Turbine 36: Lock-up device 361: Clutch part 362: Piston 37: Biasing member 39: Communication hole 4a: First oil passage 4b: Second oil passage 4c: Branch oil passage 5: Switching device 6: Oil pump 7: Pump motor 8: Temperature sensor 9: Control unit 100: Power transmission device H1: First hydraulic chamber H2: Second hydraulic chamber

Claims

1. A lock-up device including a clutch portion and a piston, a biasing member that biases the piston toward the clutch portion, a cover, an impeller, a turbine, a first hydraulic chamber, and a second hydraulic chamber, a torque converter having the same, a first oil passage communicating with the first hydraulic chamber, a second oil passage communicating with the second hydraulic chamber, a switching device configured to switch between a first position where hydraulic oil is supplied to the first hydraulic chamber via the first oil passage and a second position where hydraulic oil is supplied to the second hydraulic chamber via the second oil passage, comprising, the piston is configured to press the clutch portion when hydraulic oil is supplied into the first hydraulic chamber and release the pressing of the clutch portion when hydraulic oil is supplied into the second hydraulic chamber, a power transmission device.

2. the first hydraulic chamber is defined by the cover and the piston, the second hydraulic chamber is defined by the turbine and the piston, The power transmission device according to claim 1.

3. the clutch portion is disposed between the piston and the turbine, The power transmission device according to claim 2.

4. the torque converter has a communication hole that communicates the first hydraulic chamber and the second hydraulic chamber, The power transmission device according to claim 1.

5. an oil pump configured to supply hydraulic oil to the torque converter via the first oil passage or the second oil passage, a pump motor configured to drive the oil pump, a control unit configured to control the pump motor and the switching device, further comprising, the control unit, a first lock-up mode for stopping the pump motor, a second lock-up mode for controlling the switching device to be in the first position and operating the pump motor, a lock-up release mode for controlling the switching device to be in the second position and operating the pump motor, having, The power transmission device according to claim 1.

6. further comprising a temperature sensor that detects the temperature of the hydraulic oil of the torque converter, the torque converter has a communication hole that communicates the first hydraulic chamber and the second hydraulic chamber, the control unit is configured to execute the second lock-up mode when it is determined that the temperature detected by the temperature sensor is equal to or higher than a predetermined value, The power transmission device according to claim 5.

7. A drive motor configured to output torque to the torque converter; A branch oil passage configured to branch from the first oil passage and supply hydraulic oil to the drive motor; The power transmission device according to claim 1, further comprising: The power transmission device according to claim 1.

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