Drive unit and speed change gear

Abstract

To reduce energy consumption.SOLUTION: A drive unit includes an electric motor, a planetary gear mechanism, an input member, an output member, a first clutch, a fixed member, a second clutch, and a first energizing member. The planetary gear mechanism includes a sun gear, a planetary gear, a ring gear, and a planetary carrier. The input member connects one of the ring gear and the sun gear with the electric motor. The output member is connected to the planetary carrier. The first clutch connects the input member and the output member in such a manner that they can be cut off. The fixed member is arranged in an unrotatable manner. The second clutch connects the other of the ring gear and the sun gear with the fixed member in such a manner that they can be cut off. The first energizing member energizes the second clutch so as to be in a connection state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a drive unit and a transmission. [Background technology]

[0002] The transmission described in Patent Document 1 is configured to transmit power from an internal combustion engine to drive wheels by changing the rotational speed. Specifically, the transmission has a first clutch, a second clutch, and a planetary gear mechanism. The gear ratio of the transmission is changed by hydraulically switching the states of the first clutch and the second clutch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-210149 Summary of the Invention [Problem to be solved by the invention]

[0004] When a transmission configured as described above is employed in a drive unit using an electric motor as a drive source, it is desirable to reduce energy consumption. Therefore, an object of the present invention is to reduce energy consumption. [Means for solving the problem]

[0005] A drive unit according to a first aspect includes an electric motor, a planetary gear mechanism, an input member, an output member, a first clutch, a fixed member, a second clutch, and a first biasing member. The planetary gear mechanism has a sun gear, planet gears, a ring gear, and a planet carrier. The input member connects one of the ring gear and the sun gear to the electric motor. The output member is connected to the planet carrier. The first clutch connects the input member and the output member in a disengageable manner. The fixed member is arranged non-rotatably. The second clutch connects the other of the ring gear and the sun gear to the fixed member in a disengageable manner. The first biasing member biases the second clutch to an engaged state.

[0006] With this configuration, the second clutch is engaged by the first biasing member. That is, when traveling at low speeds, hydraulic pressure for engaging the second clutch is not required, thereby reducing energy consumption.

[0007] A drive unit according to a second aspect is the drive unit according to the first aspect, further comprising a one-way clutch, which allows the other of the ring gear and the sun gear to rotate in the forward rotation direction.

[0008] A drive unit according to a third aspect is the drive unit according to the first or second aspect, further comprising a second biasing member. The second biasing member biases the first clutch to the disengaged state.

[0009] A drive unit according to a fourth aspect is the drive unit according to any one of the first to third aspects, configured as follows: The first clutch is a centrifugal clutch.

[0010] A drive unit according to a fifth aspect is the drive unit according to the fourth aspect, and is configured as follows: the input member is disposed radially outward from the output member; the first clutch has a centrifugal element and an engagement groove; the centrifugal element rotates integrally with the output member; the centrifugal element is disposed radially movable relative to the output member; the engagement groove is formed on the inner circumferential surface of the input member; and the engagement groove is configured to engage with the centrifugal element.

[0011] A drive unit according to a sixth aspect is the drive unit according to the fifth aspect, and is configured as follows: The first clutch further includes a magnet. The magnet is disposed radially inward of the centrifugal element and attracts the centrifugal element by magnetic force.

[0012] A drive unit according to a seventh aspect is the drive unit according to the fifth or sixth aspect, and is configured as follows: The engagement groove has a pair of inner wall surfaces that face each other in the circumferential direction, and at least one of the pair of inner wall surfaces is inclined radially inward so as to move away from the other inner wall surface.

[0013] A drive unit according to an eighth aspect is the drive unit according to any one of the first to seventh aspects, configured as follows: The input member has a first input portion, a second input portion, and an elastic member that elastically connects the first input portion and the second input portion.

[0014] A drive unit according to a ninth aspect is the drive unit according to any one of the first to eighth aspects, further comprising a control unit. The control unit has a forward low-speed travel mode, a forward high-speed travel mode, and a reverse travel mode. In the forward low-speed travel mode, the control unit rotates the electric motor in a forward rotation direction, disengages the first clutch, and engages the second clutch. In the forward high-speed travel mode, the control unit rotates the electric motor in a forward rotation direction, engages the first clutch, and disengages the second clutch. In the reverse travel mode, the control unit rotates the electric motor in a reverse rotation direction, disengages the first clutch, and engages the second clutch.

[0015] A drive unit according to a tenth aspect is the drive unit according to the ninth aspect, and is configured as follows: when switching from a low-speed forward traveling mode to a high-speed forward traveling mode, the control unit is configured to disengage the second clutch and then engage the first clutch.

[0016] A transmission according to an eleventh aspect is configured to change the rotational speed of power from an electric motor. The transmission includes a planetary gear mechanism, an input member, an output member, a first clutch, a fixed member, a second clutch, and a first biasing member. The planetary gear mechanism has a sun gear, planet gears, a ring gear, and a planet carrier. The input member connects one of the ring gear and the sun gear to the electric motor. The output member is connected to the planet carrier. The first clutch connects the input member and the output member in a disengageable manner. The fixed member is arranged non-rotatably. The second clutch connects the other of the ring gear and the sun gear to the fixed member in a disengageable manner. The first biasing member biases the second clutch to an engaged state. [Effects of the Invention]

[0017] According to the present invention, energy consumption can be reduced. [Brief explanation of the drawings]

[0018] [Figure 1] Block diagram of a drive unit. [Figure 2] Schematic diagram of a transmission. [Figure 3] FIG. [Figure 4] 4 is a flowchart showing a control method of the control unit. [Figure 5] FIG. 10 is a schematic diagram of a transmission according to a modified example. [Figure 6] FIG. 10 is a schematic diagram of a transmission according to a modified example. [Figure 7] FIG. 10 is an enlarged view of a first clutch (disengaged state) according to a modified example. [Figure 8] FIG. 10 is an enlarged view of a first clutch (engaged state) according to a modified example. [Figure 9] FIG. 10 is a schematic diagram of a transmission according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] The drive unit 100 according to this embodiment will be described below with reference to the drawings. In the following description, the axial direction refers to the direction in which the rotation axis O of the transmission 4 extends. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O, and the radial direction refers to the radial direction of a circle centered on the rotation axis O. The forward rotation direction refers to the direction in which members that transmit torque, such as the electric motor 2 and the transmission 4, rotate when the vehicle on which the drive unit 100 is mounted is driven forward, and the reverse rotation direction refers to the direction in which members that transmit torque, such as the electric motor 2 and the transmission 4, rotate when the vehicle is driven backward.

[0020] [Drive unit] As shown in FIG. 1 , the drive unit 100 includes an electric motor 2, a reducer 3, a transmission 4, and a control unit 5. Torque output by the drive unit 100 is transmitted to drive wheels 102 via a differential gear 101. The drive unit 100 is mounted on, for example, an electric vehicle. Note that the drive unit 100 does not necessarily have to include the reducer 3.

[0021] [Electric motor] The electric motor 2 is configured to rotate in a forward rotation direction and a reverse rotation direction. When the vehicle is driven forward, the electric motor 2 rotates in the forward rotation direction. On the other hand, when the vehicle is driven backward, the electric motor 2 rotates in the reverse rotation direction.

[0022] [Reducer] The reducer 3 is disposed in the torque transmission path between the electric motor 2 and the transmission 4. The reducer 3 is configured to reduce the rotational speed of the power output by the electric motor 2 and output the power to the transmission 4. The reducer 3 has, for example, a plurality of gears (not shown).

[0023] [Transmission] The transmission 4 is configured to change the rotational speed of the power from the electric motor 2 and output it to the drive wheels 102. The transmission 4 is configured to change the gear ratio in stages. In this embodiment, the transmission 4 is configured to change the gear ratio in two stages.

[0024] As shown in FIG. 2, the transmission 4 has a planetary gear mechanism 41, an input member 42, an output member 43, a fixed housing 44 (an example of a fixed member), a first clutch 45, a second clutch 46, a first biasing member 47, a second biasing member 48, and a one-way clutch 49.

[0025] [Planetary gear mechanism] 3 is a front view of the planetary gear mechanism 41. As shown in FIG. 3, the planetary gear mechanism 41 has a sun gear 411, a ring gear 412, a plurality of planet gears 413, and a planet carrier 414. The sun gear 411 is arranged to be rotatable around a rotation axis O. The ring gear 412 is annular. The ring gear 412 is an internal gear. The ring gear 412 is arranged to surround the sun gear 411. The ring gear 412 is arranged to be rotatable around the rotation axis O.

[0026] Each planetary gear 413 is disposed between the sun gear 411 and the ring gear 412 in the radial direction. Each planetary gear 413 is in mesh with the sun gear 411 and the ring gear 412. Each planetary gear 413 is disposed so as to be able to revolve around the rotation axis O. Each planetary gear 413 is also disposed so as to be able to rotate on its own axis. A planetary carrier 414 is attached to each planetary gear 413. The planetary carrier 414 is disposed so as to be rotatable around the rotation axis O.

[0027] [Input member] 2, the input member 42 connects the electric motor 2 and the ring gear 412. More specifically, the input member 42 connects the reducer 3 and the ring gear 412. The input member 42 rotates integrally with the ring gear 412. The input member 42 is configured to receive torque from the electric motor 2. The input member 42 is also configured to transmit the torque to the ring gear 412.

[0028] The input member 42 has a first input portion 421, a second input portion 422, and a plurality of elastic members 423. The first input portion 421 is configured to receive torque from the electric motor 2. The second input portion 422 is configured to transmit torque to the ring gear 412.

[0029] Each elastic member 423 elastically connects the first input portion 421 and the second input portion 422. That is, torque transmission between the first input portion 421 and the second input portion 422 is performed via each elastic member 423.

[0030] [Output member] The output member 43 is connected to the planetary carrier 414. The output member 43 rotates integrally with the planetary carrier 414. The output member 43 is disposed rotatable about a rotation axis O. The output member 43 extends axially through the sun gear 411.

[0031] The output member 43 is configured to transmit the torque received from the planetary gear mechanism 41 to the drive wheels 102. In detail, the output member 43 is configured to transmit the torque to the differential gear 101.

[0032] The fixed housing 44 is arranged so as not to rotate. The fixed housing 44 is fixed to the frame of the vehicle or the like. The fixed housing 44 accommodates the planetary gear mechanism 41, the first clutch 45, the second clutch 46, the first biasing member 47, the second biasing member 48, and the one-way clutch 49.

[0033] [First clutch] The first clutch 45 connects the input member 42 and the output member 43 in a disengageable manner. The first clutch 45 is configured to connect the input member 42 and the output member 43 (hereinafter referred to as the "connected state") and to disconnect the input member 42 and the output member 43 (hereinafter referred to as the "disengaged state"). The first clutch 45 is of a normally open type. That is, in a neutral state where no hydraulic pressure is applied, the first clutch 45 is in a disengaged state.

[0034] When the first clutch 45 is in an engaged state, the input member 42 and the output member 43 are connected and rotate together. On the other hand, when the first clutch 45 is in a disengaged state, the input member 42 and the output member 43 are separated and become capable of relative rotation.

[0035] The first clutch 45 has a plurality of first clutch discs 451, a plurality of second clutch discs 452, and a first piston 453. The first clutch discs 451 and the second clutch discs 452 are arranged alternately in the axial direction. A friction material is arranged between the first clutch discs 451 and the second clutch discs 452. The friction material may be attached to the first clutch discs 451 or the second clutch discs 452.

[0036] The first clutch disc 451 is attached to the input member 42 so as to be movable in the axial direction. The first clutch disc 451 rotates integrally with the input member 42. The second clutch disc 452 is attached to the output member 43 so as to be movable in the axial direction. The second clutch disc 452 rotates integrally with the output member 43.

[0037] The first piston 453 presses the first clutch disc 451 and the second clutch disc 452 so that the first clutch disc 451 and the second clutch disc 452 are frictionally engaged with each other.

[0038] [Second clutch] The second clutch 46 connects and disconnects the sun gear 411 and the fixed housing 44. The second clutch 46 is configured to connect the sun gear 411 and the fixed housing 44 (hereinafter referred to as the "connected state") and disconnect the sun gear 411 and the fixed housing 44 (hereinafter referred to as the "disconnected state"). The second clutch 46 is of a normally closed type. That is, in a neutral state where no hydraulic pressure is applied, the second clutch 46 is in the connected state.

[0039] When the second clutch 46 is in the engaged state, the sun gear 411 is connected to the fixed housing 44 and is unable to rotate. On the other hand, when the second clutch 46 is in the disengaged state, the sun gear 411 is separated from the fixed housing 44 and is able to rotate.

[0040] The second clutch 46 has a plurality of third clutch discs 461, a plurality of fourth clutch discs 462, and a second piston 463. The third clutch discs 461 and the fourth clutch discs 462 are arranged alternately in the axial direction. A friction material is arranged between the third clutch discs 461 and the fourth clutch discs 462. The friction material may be attached to the third clutch discs 461 or the fourth clutch discs 462.

[0041] The third clutch disc 461 is attached to the fixed housing 44 so as to be movable in the axial direction. The third clutch disc 461 is non-rotatable. The fourth clutch disc 462 is attached to the sun gear 411 so as to be movable in the axial direction. The fourth clutch disc 462 rotates integrally with the sun gear 411.

[0042] The second piston 463 presses the third clutch disc 461 and the fourth clutch disc 462 so that the third clutch disc 461 and the fourth clutch disc 462 are frictionally engaged with each other.

[0043] [First biasing member] The first biasing member 47 biases the second clutch 46 to the engaged state. The first biasing member 47 is, for example, a coil spring. The first biasing member 47 is disposed in a compressed state. The first biasing member 47 presses the second piston 463 in the axial direction toward the third clutch disc 461 and the fourth clutch disc 462. Note that the second clutch 46 is disengaged by hydraulically moving the second piston 463 in the axial direction against the biasing force of the first biasing member 47.

[0044] [Second biasing member] The second biasing member 48 biases the first clutch 45 to put it into a disengaged state. The second biasing member 48 is, for example, a coil spring. The second biasing member 48 presses the first piston 453 in the axial direction so as to move it away from the first clutch disc 451 and the second clutch disc 452. Note that the first clutch 45 is put into an engaged state by hydraulically moving the first piston 453 in the axial direction against the biasing force of the second biasing member 48.

[0045] [One-way clutch] The one-way clutch 49 is configured to permit rotation of the sun gear 411 in a forward rotation direction R1 (see FIG. 3). The one-way clutch 49 prevents rotation of the sun gear 411 in a reverse rotation direction R2 (see FIG. 3). Specifically, the one-way clutch 49 has an inner ring, an outer ring, and sprags. One of the inner ring and the outer ring is fixed to the sun gear 411, and the other of the inner ring and the outer ring is fixed to the fixed housing 44. When the sun gear 411 attempts to rotate in the reverse rotation direction R2, the sprags mesh with each other to transmit torque between the inner ring and the outer ring. As a result, the one-way clutch 49 is unable to rotate, preventing rotation of the sun gear 411 in the reverse rotation direction R2. On the other hand, when the sun gear 411 rotates in the forward rotation direction R1, the sprags are disengaged, causing the inner ring and the outer ring to rotate freely relative to each other. As a result, rotation of the sun gear 411 in the forward rotation direction R1 is permitted.

[0046] [Control Unit] 1 and 2, the control unit 5 is configured to control the electric motor 2, the first clutch 45, and the second clutch 46. Specifically, the control unit 5 controls the first clutch 45 and the second clutch 46 by controlling the hydraulic unit 103. The hydraulic unit 103 includes, for example, a hydraulic pump and a control valve. The hydraulic unit 103 supplies hydraulic pressure to the first clutch 45 via a first oil passage P1, and supplies hydraulic pressure to the second clutch 46 via a second oil passage P2.

[0047] The control unit 5 is configured by, for example, a computer (for example, a microcomputer) equipped with a CPU (Central Processing Unit) and a ROM (Read Only Memory). The ROM stores programs for performing various calculations. The CPU executes the programs stored in the ROM.

[0048] The control unit 5 has a forward low-speed traveling mode, a forward high-speed traveling mode, and a reverse traveling mode. For example, as shown in Fig. 4, the control unit 5 determines whether or not an instruction to travel forward has been received from the driver (step S1). If the control unit 5 determines that an instruction to travel forward has not been received, that is, that an instruction to travel backward has been received (No in step S1), the control unit 5 executes the reverse traveling mode (step S2).

[0049] On the other hand, when the control unit 5 determines that it has received a command to travel forward (Yes in step S1), it then determines whether or not the rotation speed of the output member 43 is equal to or less than a predetermined value (step S3). If the control unit 5 determines that the rotation speed of the output member 43 is equal to or less than the predetermined value (Yes in step S3), it executes the low-speed forward traveling mode (step S4). If the control unit 5 determines that the rotation speed of the output member 43 is not equal to or less than the predetermined value, that is, that the rotation speed of the output member 43 has exceeded the predetermined value (No in step S3), it executes the high-speed forward traveling mode (step S5).

[0050] In the low-speed forward traveling mode, the control unit 5 rotates the electric motor 2 in the forward rotation direction. The control unit 5 then disengages the first clutch 45 and engages the second clutch 46. Note that because the first clutch 45 is disengaged with no hydraulic pressure applied, the control unit 5 controls the hydraulic unit 103 to stop the supply of hydraulic pressure to the first clutch 45. Also, because the second clutch 46 is engaged with no hydraulic pressure applied, the control unit 5 controls the hydraulic unit 103 to stop the supply of hydraulic pressure to the first clutch 45. In this way, in the low-speed forward traveling mode, there is no need to operate the hydraulic unit 103, and therefore energy consumption can be reduced.

[0051] 3, in the forward low-speed traveling mode, the first clutch 45 is disengaged, so the ring gear 412 and the planetary carrier 414 rotate in the forward rotation direction R1 (clockwise in FIG. 3) while being rotatable relative to each other. Since the second clutch 46 is engaged and the one-way clutch 49 is engaged, the sun gear 411 cannot rotate in the reverse rotation direction R2 (counterclockwise in FIG. 3) and is stationary.

[0052] As described above, the planetary gear mechanism 41 amplifies the torque from the input member 42 and transmits it to the output member 43. Furthermore, the planetary gear mechanism 41 reduces the rotational speed of the power from the input member 42 before transmitting it.

[0053] In the forward high-speed traveling mode, the control unit 5 rotates the electric motor 2 in the forward rotation direction. The control unit 5 then brings the first clutch 45 into an engaged state and the second clutch 46 into a disengaged state. In detail, the control unit 5 controls the hydraulic unit 103 to supply hydraulic pressure to each of the first clutch 45 and the second clutch 46, bringing the first clutch 45 into an engaged state and the second clutch 46 into a disengaged state.

[0054] In the high-speed forward traveling mode, the first clutch 45 is engaged, so the ring gear 412 and the planetary carrier 414 rotate integrally in the forward rotation direction R1. Since the second clutch 46 is disengaged and the one-way clutch 49 rotates freely, the sun gear 411 rotates in the forward rotation direction R1.

[0055] As a result, the planetary gear mechanism 41 transmits the power from the input member 42 to the output member 43 without reducing the rotational speed. When switching from the low-speed forward traveling mode to the high-speed forward traveling mode, the control unit 5 first disengages the second clutch 46 to keep only the one-way clutch 49 engaged, and then engages the first clutch 45. This control automatically and appropriately switches the sun gear 411 from fixed rotation to rotation in the forward rotation direction R1 by the one-way clutch 49, thereby achieving smooth gear switching without shift shock.

[0056] In the reverse driving mode, the control unit 5 rotates the electric motor 2 in the reverse rotation direction. The control unit 5 also disengages the first clutch 45 and engages the second clutch 46. In this way, in the reverse driving mode, there is no need to operate the hydraulic unit, which reduces energy consumption.

[0057] In the reverse travel mode, the first clutch 45 is disengaged, so the ring gear 412 and the planetary carrier 414 rotate in the reverse rotation direction R2 while being rotatable relative to each other. In this reverse travel mode, the one-way clutch 49 is in an idling state, so it cannot prevent the sun gear 411 from rotating in the forward rotation direction R1. However, because the second clutch 46 is engaged, the sun gear 411 cannot rotate in the forward rotation direction R1 and is stationary.

[0058] As described above, the planetary gear mechanism 41 amplifies the torque from the input member 42 and transmits it to the output member 43. Furthermore, the planetary gear mechanism 41 reduces the rotational speed of the power from the input member 42 before transmitting it.

[0059] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. Note that the following modifications can basically be applied simultaneously.

[0060] 5, the first clutch 45 may be of a normally closed type. That is, the second biasing member 48 may bias the first clutch 45 so that the first clutch 45 is in the connected state.

[0061] (b) As shown in Fig. 6, the first clutch 45 may be a centrifugal clutch. That is, the first clutch 45 may be configured to engage the input member 42 and the output member 43 by receiving centrifugal force generated by rotation of the output member 43. In this case, the first clutch 45 has a plurality of centrifugal elements 454, a plurality of engagement grooves 455, and a plurality of magnets 456, as shown in Fig. 7.

[0062] More specifically, the input member 42 is disposed radially outward relative to the output member 43. Each engagement groove 455 is formed on the inner circumferential surface of the input member 42. Each engagement groove 455 faces radially inward. Each engagement groove 455 is disposed at intervals from one another in the circumferential direction. Each engagement groove 455 is configured to engage with a centrifugal element 454.

[0063] The pair of inner wall surfaces 455a, 455b that define the engagement groove 455 are inclined radially inward so as to move away from each other. The pair of inner wall surfaces 455a, 455b face each other in the circumferential direction. Note that at least one of the pair of inner wall surfaces 455a, 455b may be inclined.

[0064] The output member 43 has a plurality of accommodating portions 431. Each accommodating portion 431 opens radially outward. That is, each accommodating portion 431 is formed on the outer circumferential surface of the output member 43. The accommodating portions 431 are arranged at intervals from one another in the circumferential direction. The intervals between the accommodating portions 431 are preferably the same as the intervals between the engagement grooves 455.

[0065] Each centrifugal element 454 is housed in the housing portion 431. Each centrifugal element 454 rotates integrally with the output member 43. Each centrifugal element 454 is movable in the radial direction within the housing portion 431. Each centrifugal element 454 is magnetic.

[0066] Of the side surfaces 454a, 454b of each centrifugal element 454 facing in the circumferential direction, the portions that face the inner wall surfaces 455a, 455b when the centrifugal element 454 moves radially outward and engages with the engagement groove 455 are inclined along the inner wall surfaces 455a, 455b.

[0067] Each magnet 456 is disposed radially inward relative to each centrifugal element 454. Each magnet 456 is attached to the output member 43. Each magnet 456 is disposed radially inward relative to each housing portion 431. For example, each magnet 456 is embedded in the output member 43. Each magnet 456 is configured to attract the centrifugal element 454 by magnetic force.

[0068] With the first clutch 45 configured in this manner, when the rotational speed of the output member 43 exceeds a predetermined value, as shown in Fig. 8, each centrifugal element 454 moves radially outward by centrifugal force and engages with each engagement groove 455. As a result, the input member 42 and the output member 43 rotate integrally.

[0069] 7, when the rotation speed of the output member 43 falls below a predetermined value, the centrifugal elements 454 move radially inward due to the inclination of the inner wall surfaces 455a, 455b and the magnetic force of the magnets 456, and the engagement between the centrifugal elements 454 and the engagement grooves 455 is released. As a result, the input member 42 and the output member 43 become capable of rotating relative to each other.

[0070] (c) As shown in Fig. 9, the input member 42 may be connected to the sun gear 411. In this case, the second clutch 46 connects the ring gear 412 and the fixed housing 44 in a disengageable manner. In addition, the one-way clutch 49 is configured to permit rotation of the ring gear 412 in the forward rotation direction. [Explanation of symbols]

[0071] 2: Electric motor 4: Transmission 41: Planetary gear mechanism 411: Sun Gear 412: Ring gear 413: Planetary gear 414: Planet carrier 42: Input member 421: First input section 422: Second input section 423: Elastic member 43: Output member 44: Fixed housing 45: First clutch 454: Centrifugal element 455: Engagement groove 455a: Inner wall surface 455b: Inner wall 456: Magnet 46: Second clutch 47: First biasing member 48: Second biasing member 49: One-way clutch 5: Control section 100: Drive unit

Claims

1. an electric motor; a planetary gear mechanism having a sun gear, planet gears, a ring gear, and a planet carrier; an input member connecting one of the ring gear and the sun gear to the electric motor; an output member connected to the planetary carrier; a first clutch that disconnectably connects the input member and the output member; a fixed member arranged non-rotatably; a second clutch that disconnectably connects the other of the ring gear and the sun gear to the fixed member; a first biasing member that biases the second clutch to the engaged state; A drive unit comprising:

2. a one-way clutch that permits rotation of the other of the ring gear and the sun gear in a forward rotation direction; 2. The drive unit according to claim 1.

3. Further provided is a second biasing member that biases the first clutch to a disengaged state.

2. The drive unit according to claim 1.

4. The first clutch is a centrifugal clutch.

2. The drive unit according to claim 1.

5. the input member is disposed radially outward relative to the output member, The first clutch is a centrifugal element that rotates integrally with the output member and is disposed so as to be movable in a radial direction relative to the output member; an engagement groove formed on an inner circumferential surface of the input member and configured to engage with the centrifugal element; having 5. A drive unit according to claim 4.

6. The first clutch further includes a magnet disposed radially inward of the centrifugal element and attracting the centrifugal element by magnetic force.

6. A drive unit according to claim 5.

7. The engagement groove has a pair of inner wall surfaces that face each other in the circumferential direction, At least one of the pair of inner wall surfaces is inclined radially inward so as to move away from the other inner wall surface.

6. A drive unit according to claim 5.

8. The input member has a first input portion, a second input portion, and an elastic member that elastically connects the first input portion and the second input portion.

2. The drive unit according to claim 1.

9. a control unit having a forward low-speed running mode, a forward high-speed running mode, and a reverse running mode; The control unit In the forward low-speed traveling mode, the electric motor is rotated in a forward rotation direction, the first clutch is disengaged, and the second clutch is engaged. In the high-speed forward traveling mode, the electric motor is rotated in a forward rotation direction, the first clutch is engaged, and the second clutch is disengaged. In the reverse driving mode, the electric motor is rotated in a reverse rotation direction, the first clutch is disengaged, and the second clutch is engaged.

2. The drive unit according to claim 1.

10. the control unit is configured to, when switching from the forward low-speed traveling mode to the forward high-speed traveling mode, bring the second clutch into a disengaged state and then bring the first clutch into an engaged state.

10. A drive unit according to claim 9.

11. 1. A transmission configured to vary the rotational speed of power from an electric motor, comprising: a planetary gear mechanism having a sun gear, planet gears, a ring gear, and a planet carrier; an input member connecting one of the ring gear and the sun gear to the electric motor; an output member connected to the planetary carrier; a first clutch that disconnectably connects the input member and the output member; a fixed member arranged non-rotatably; a second clutch that disconnectably connects the other of the ring gear and the sun gear to the fixed member; a first biasing member that biases the second clutch to the engaged state; A transmission comprising:

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