Drive unit

A drive unit includes an electric motor, first and second torque transmission paths, a torque converter, first and second gear trains, and a first switch mechanism. The first and second torque transmission paths are provided parallel to each other. The torque converter is disposed in the first torque transmission path. The torque converter amplifies a torque outputted from the motor when the torque is directed in a first rotational direction. The first gear train is disposed in the first torque transmission path. The first gear train is disposed downstream with respect to the torque converter. The second gear train is disposed in the second torque transmission path. The first switch mechanism switches between the first torque transmission path and the second torque transmission path as a path for transmitting the torque outputted from the motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2021-180365 filed Nov. 4, 2021. The entire contents of that application are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a drive unit.

BACKGROUND ART

Electric cars travel using an electric motor as a drive source. The electric cars move forward by forwardly rotating the electric motor and move backward by reversely rotating the electric motor. There has been proposed a type of electric car in which a torque converter is installed in order to amplify a torque outputted from the electric motor (e.g., Publication of Japan Patent No. 5370233).

It has been demanded that torque transmission is made efficiently in the electric car configured as described above. In view of this, it is an object of the present invention to provide a drive unit whereby torque transmission can be made efficiently.

BRIEF SUMMARY

A drive unit according to an aspect of the present invention includes an electric motor, a first torque transmission path, a second torque transmission path, a torque converter, a first gear train, a second gear train, and a first switch mechanism. The first torque transmission path is configured to transmit a torque outputted from the electric motor to an output unit. The second torque transmission path is provided parallel to the first torque transmission path. The second torque transmission path is configured to transmit the torque outputted from the electric motor to the output unit. The torque converter is disposed in the first torque transmission path. The torque converter is configured to amplify the torque outputted from the electric motor when the torque is directed in the first rotational direction. The first gear train is disposed in the first torque transmission path. The first gear train is disposed downstream with respect to the torque converter. The second gear train is disposed in the second torque transmission path. The first switch mechanism is configured to switch between the first torque transmission path and the second torque transmission path as a path for transmitting the torque outputted from the electric motor.

According to this configuration, when rotation of the torque converter is not required (e.g., when the electric motor is rotated in a second rotational direction), the path for transmission the torque outputted from the electric motor can be switched to the second torque transmission path by the first switch mechanism. Thus, when rotation of the torque converter is not required, torque transmission can be made without through the torque converter; hence, torque transmission can be made efficiently.

The second gear train can be made higher in reduction ratio than the first gear train.

The first gear train can be made higher in reduction ratio than the second gear train.

Preferably, the drive unit further includes a controller. The controller controls the electric motor and the first switch mechanism.

Preferably, the controller executes a first reverse moving mode. When executing the first reverse moving mode, the controller controls and causes the electric motor to be rotated in a second rotational direction. Besides, when executing the first reverse moving mode, the controller controls the first switch mechanism such that transmission of the torque outputted from the electric motor is made through the second torque transmission path.

Preferably, the controller executes a first forward moving mode. When executing the first forward moving mode, the controller controls and causes the electric motor to be rotated in the first rotational direction. Besides, when executing the first forward moving mode, the controller controls the first switch mechanism such that transmission of the torque outputted from the electric motor is made through the first torque transmission path.

Preferably, the controller executes a second forward moving mode. When executing the second forward moving mode, the controller controls and causes the electric motor to be rotated in the first rotational direction. Besides, when executing the second forward moving mode, the controller controls the first switch mechanism such that transmission of the torque outputted from the electric motor is made through the second torque transmission path.

Preferably, the drive unit further includes a third gear train and a second switch mechanism. The third gear train is disposed in the first torque transmission path. The third gear train is configured to receive the torque transmitted thereto from the torque converter. The second switch mechanism is configured to switch between the first gear train and the third gear train as the path for transmitting the torque after the torque is outputted from the torque converter. The controller controls the second switch mechanism.

Preferably, the third gear train is configured to output the torque in a reverse rotational direction to when the torque is outputted from the first gear train.

Preferably, the second switch mechanism is settable to a neutral position without selecting both the first and third gear trains so as to block transmission of the torque outputted from the torque converter.

Preferably, the controller controls and causes the second switch mechanism to be set to the neutral position when executing the second forward moving mode.

Preferably, the drive unit further includes a first clutch. The torque converter includes an input part and an output part. The input part is configured to receive the torque inputted thereto after the torque is outputted from the electric motor. The output part is configured to receive the torque transmitted thereto from the input part through a fluid. The first clutch is configured to allow and block transmission of the torque between the input part and the output part.

Preferably, the first clutch is a one-way clutch. The first clutch is configured to allow transmission of the torque outputted from the electric motor when the torque is directed in the second rotational direction and block transmission of the torque outputted from the electric motor when the torque is directed in the first rotational direction.

Preferably, the drive unit further includes a second clutch. The second clutch is disposed downstream with respect to the torque converter in the first torque transmission path. The second clutch is configured to allow and block transmission of the torque.

Preferably, the second clutch is a one-way clutch. The second clutch is configured to allow transmission of the torque outputted from the torque converter to a downstream side and block transmission of the torque from the downstream side to the torque converter.

Preferably, the drive unit further includes a fourth gear train. The fourth gear train is disposed upstream with respect to the torque converter in the first torque transmission path.

Preferably, the drive unit further includes a third torque transmission path and a third switch mechanism. The third torque transmission path branches off from the first torque transmission path at a position upstream of the torque converter and merges to the first torque transmission path at a position downstream of the torque converter. The third switch mechanism is configured to switch between the first torque transmission path and the third torque transmission path as the path for transmitting the torque.

Preferably, the torque converter includes a centrifugal lock-up clutch.

Preferably, the first switch mechanism includes a first torque output part, a first torque input part, a second torque input part, and a coupling part. The first torque output part is configured to output the torque outputted from the electric motor. The first torque input part is disposed in the first torque transmission path. The first torque input part is configured to receive the torque inputted thereto after the torque is outputted from the first torque output part. The second torque input part is disposed in the second torque transmission path. The second torque input part is configured to receive the torque inputted thereto after the torque is outputted from the first torque output part. The coupling part is settable to a first coupling state and a second coupling state. When set to the first coupling state, the coupling part couples the first torque output part and the first torque input part therethrough. When set to the second coupling state, the coupling part couples the first torque output part and the second torque input part therethrough.

The first torque output part, the first torque input part, and the second torque input part can be disposed along a rotational axis of the electric motor so as to be aligned from a side closer to the electric motor in an order of the first torque output part, the first torque input part, and the second torque input part.

The first torque output part, the first torque input part, and the second torque input part can be disposed along the rotational axis of the electric motor so as to be aligned from the side closer to the electric motor in an order of the second torque input part, the first torque output part, and the first torque input part.

The first torque output part, the first torque input part, and the second torque input part can be disposed along the rotational axis of the electric motor so as to be aligned from the side closer to the electric motor in an order of the first torque output part, the second torque input part, and the first torque input part.

Overall, according to the present invention, torque transmission can be made efficiently.

DETAILED DESCRIPTION

A drive unit according to the present preferred embodiment will be hereinafter explained with reference to drawings.FIG.1is a block diagram showing torque transmission paths in the drive unit, whereasFIG.2is a schematic diagram of the drive unit. It should be noted that in the following explanation, the term “axial direction” refers to an extending direction of a rotational axis O for both an electric motor2and a torque converter3. On the other hand, the term “circumferential direction” refers to a circumferential direction of an imaginary circle about the rotational axis O, whereas the term “radial direction” refers to a radial direction of the imaginary circle about the rotational axis O. Besides, the term “upstream” and “downstream” mean an upstream side and a downstream side in a direction of transmitting a torque.

As shown inFIGS.1and2, the drive unit (100) is configured to drive an output unit101. The output unit101includes a final gear train102, a differential gear103, a pair of drive shafts105, and a pair of drive wheels110. It should be noted that the output unit101can include only the drive wheels110.

The pair of drive shafts105extends from the differential gear103to the pair of drive wheels110, respectively. The pair of drive shafts105extends parallel to the rotational axis O. When described in detail, the pair of drive shafts105extends parallel to first and second torque transmission shafts41aand42a(to be described). Besides, the pair of drive shafts105extends to be offset (displaced) from the first and second torque transmission shafts41aand42a.

The differential gear103is disposed in the middle of the space between the pair of drive wheels110in the extending direction of the pair of drive shafts105. In other words, the pair of drive shafts105is substantially equal in length to each other.

The drive unit100includes the electric motor2, the torque converter3, first and second torque transmission paths4aand4b, a first switch mechanism5, a first clutch6, a first gear train71, a second gear train72, and a controller9. The drive unit100is installed in, for instance, an electric car.

The electric motor2(hereinafter simply referred to as “motor”) includes a motor casing21, a stator22, a rotor23, and an output shaft24. In the present preferred embodiment, the motor2is a so-called inner rotor motor. The motor2is configured to be rotatable in a first rotational direction and a second rotational direction. It should be noted that the second rotational direction is a rotational direction reverse to the first rotational direction.

The motor casing21is non-rotatable, while being fixed to a body frame of the vehicle or so forth. The stator22is fixed to the inner peripheral surface of the motor casing21. The stator22is non-rotatable. The rotor23is rotated about the rotational axis O. The rotor23is disposed radially inside the stator22. The output shaft24extends from the rotor23in the axial direction. The output shaft24is unitarily rotated with the rotor23.

<First and Second Torque Transmission Paths>

As shown inFIG.1, the first and second torque transmission paths4aand4bare configured to transmit a torque, outputted from the motor2, to the output unit101. Besides, the first and second torque transmission paths4aand4bare provided parallel to each other.

The first torque transmission path4aincludes the first and second torque transmission shafts41aand42a. As shown inFIG.2, the torque, outputted from the motor2, is inputted to the first torque transmission shaft41athrough the first switch mechanism5. The first torque transmission shaft41aextends in the axial direction. The first torque transmission shaft41aextends to be coaxial to the output shaft24of the motor2. The first torque transmission shaft41aextends toward the torque converter3. The rotational axis of the first torque transmission shaft41ais substantially matched with that of the motor2and that of the torque converter3.

The first torque transmission shaft41atransmits the torque, outputted from the motor2, to the torque converter3. The first torque transmission shaft41ais attached at the downstream-side end thereof (the right-side end thereof inFIG.2) to a cover hub313(seeFIG.5) of the torque converter3. The first torque transmission shaft41ais solid.

The second torque transmission shaft42areceives the torque inputted thereto from the torque converter3. The second torque transmission shaft42aoutputs the torque, inputted thereto from the torque converter3, to the first gear train71. The second torque transmission shaft42aextends axially toward the motor2from the torque converter3.

The second torque transmission shaft42ahas a cylindrical shape. The first torque transmission shaft41aextends through the interior of the second torque transmission shaft42a. The second torque transmission shaft42ais attached at the upstream-side end thereof (the right-side end thereof inFIG.2) to a turbine33(seeFIG.5) of the torque converter3. On the other hand, the second torque transmission shaft42ais rotatably supported at the downstream-side end thereof (the left-side end thereof inFIG.2) by, for instance, a transmission casing40or so forth through a bearing member and/or so forth.

The second torque transmission path4bis configured to transmit the torque, outputted from the motor2, to the output unit101without the torque passing through the torque converter3.

The first switch mechanism5is configured to switch between the first torque transmission path4aand the second torque transmission path4bas a path for transmitting the torque outputted from the motor2. It should be noted that the first switch mechanism5is controlled by the controller9. The first switch mechanism5is disposed in the interior of the transmission casing40.

As shown inFIGS.3and4, the first switch mechanism5includes a first torque output gear51(exemplary first torque output part), a first torque input gear52(exemplary first torque input part), a second torque input gear53(exemplary second torque input part), and a first ring gear54(exemplary coupling part). Besides, the first switch mechanism5further includes an actuator55causing the first ring gear54to move in the axial direction. The actuator55is controlled by the controller9.

The first torque output gear51is configured to output the torque, outputted from the motor2, to the first or second torque transmission path4a,4b. The first torque output gear51is attached to the distal end of the output shaft24. The first torque output gear51is unitarily rotated with the output shaft24. The first torque output gear51can be provided as a different member separated from the output shaft24, or alternatively, can be provided as a single member integrated with the output shaft24. The first torque output gear51is disposed to be rotatable about the rotational axis O. The first torque output gear51includes a plurality of teeth on the outer peripheral surface thereof.

The first torque input gear52is disposed in the first torque transmission path4a. The first torque input gear52is configured to receive the torque that is inputted thereto after outputted from the first torque output gear51. The first torque input gear52is disposed to be rotatable about the rotational axis O.

The first torque input gear52is attached to the first torque transmission shaft41a. When described in detail, the first torque input gear52is attached to the upstream-side end (the left-side end inFIG.3) of the first torque transmission shaft41a. The first torque input gear52is unitarily rotated with the first torque transmission shaft41a. The first torque input gear52can be provided as a different member separated from the first torque transmission shaft41a, or alternatively, can be provided as a single member integrated with the first torque transmission shaft41a. The first torque input gear52is approximately equal in diameter to the first torque output gear51. The first torque input gear52includes a plurality of teeth on the outer peripheral surface thereof.

The second torque input gear53is disposed in the second torque transmission path4b. The second torque input gear53is configured to receive the torque that is inputted thereto after outputted from the first torque output gear51. The second torque input gear53is disposed to be rotatable about the rotational axis O. The second torque input gear53is approximately equal in diameter to the first torque output gear51. The second torque input gear53includes a plurality of teeth on the outer peripheral surface thereof. The second torque input gear53is supported by the output shaft24, while being rotatable relative thereto.

The first torque output gear51is disposed axially between the first and second torque input gears52and53. The second torque input gear53, the first torque output gear51, and the first torque input gear52are disposed along the rotational axis O, while being aligned in this order from a side closer to the motor2. The first torque output gear51, the first torque input gear52, and the second torque input gear53are disposed to be rotatable relative to each other.

The first ring gear54includes a plurality of teeth on the inner peripheral surface thereof. The first ring gear54is constantly meshed with the first torque output gear51and is unitarily rotated therewith. In other words, the first ring gear54is unitarily rotated with the output shaft24.

The first ring gear54is disposed to be movable in the axial direction. When controlled by the controller9, the first ring gear54is moved in the axial direction. When described in detail, as described above, the actuator55, controlled by the controller9, causes the first ring gear54to move in the axial direction. When moved in the axial direction, the first ring gear54is settable to a first coupling state and a second coupling state. It should be noted thatFIG.3shows the first ring gear54set to the first coupling state, whereasFIG.4shows the first ring gear54set to the second coupling state.

As shown inFIG.3, when set to the first coupling state, the first ring gear54couples the first torque output gear51and the first torque input gear52therethrough. When described in detail, the first ring gear54is meshed with the first torque output gear51, while being meshed with the first torque input gear52.

When the first ring gear54is thus meshed with both the first torque output gear51and the first torque input gear52, the first torque output gear51and the first torque input gear52are coupled to be unitarily rotated with each other. In other words, the output shaft24and the first torque transmission shaft41aare unitarily rotated with each other. As a result, the first switch mechanism5can set the first torque transmission path4aas the path for transmitting the torque outputted from the motor2. It should be noted that when the first ring gear54is set to the first coupling state, the torque outputted from the motor2is not transmitted to the second torque transmission path4b.

As shown inFIG.4, when set to the second coupling state, the first ring gear54couples the first torque output gear51and the second torque input gear53therethrough. When described in detail, the first ring gear54is meshed with the first torque output gear51, while being meshed with the second torque input gear53.

When the first ring gear54is thus meshed with both the first torque output gear51and the second torque input gear53, the first torque output gear51and the second torque input gear53are coupled to be unitarily rotated with each other. In other words, the output shaft24and the second torque input gear53are unitarily rotated with each other. As a result, the first switch mechanism5can set the second torque transmission path4bas the path for transmitting the torque outputted from the motor2. It should be noted that when the first ring gear54is set to the second coupling state, the torque outputted from the motor2is not transmitted to the first torque transmission path4a.

As shown inFIG.1, the torque converter3is disposed in the first torque transmission path4a. The torque converter3is configured to amplify the torque outputted from the motor2when the torque is directed in the first rotational direction. It should be noted that when directed in the second rotational direction, the torque outputted from the motor2is not amplified by the torque converter3. The torque converter3output the amplified torque to the first gear train71.

As shown inFIG.2, the rotational axis O of the torque converter3is substantially matched with that of the motor2. When torque transmission is made through the first torque transmission path4aby the first switch mechanism5, the torque outputted from the motor2is transmitted to the torque converter3. The torque converter3is disposed axially apart from the motor2at an interval.

The first switch mechanism5is disposed between the torque converter3and the motor2. The motor2, the first switch mechanism5, and the torque converter3are axially aligned in this order. Besides, the first and second gear trains71and72are also disposed between the torque converter3and the motor2.

As shown inFIG.5, the torque converter3includes a cover31, an impeller32, the turbine33, a stator34, and a one-way clutch36. Besides, the torque converter3further includes a lock-up clutch37of a centrifugal type. It should be noted that the cover31and the impeller32correspond to an input part in the present invention, whereas the turbine33corresponds to an output part in the present invention.

The torque converter3is disposed such that the impeller32faces the motor2(the left side inFIG.5), whereas the cover31faces opposite to the motor2(the right side inFIG.5). The torque converter3is accommodated in the interior of a torque converter casing30(seeFIG.2). Hydraulic fluid is supplied to the interior of the torque converter3. The hydraulic fluid is, for instance, hydraulic oil.

The cover31is a component to which the torque, outputted from the motor2, is inputted. The cover31is rotated by the torque inputted thereto from the motor2. The cover31is fixed to the first torque transmission shaft41a. For example, the cover31includes a spline hole to which the first torque transmission shaft41ais spline-coupled. Because of this, the cover31is unitarily rotated with the first torque transmission shaft41a. The cover31is disposed to cover the turbine33.

The cover31includes a disc portion311, a cylindrical portion312, and a cover hub313. The disc portion311includes an opening in the middle thereof. The cylindrical portion312extends from the outer peripheral end of the disc portion311toward the motor2. The disc portion311and the cylindrical portion312are provided as a single member integrated with each other.

The cover hub313is fixed to the inner peripheral end of the disc portion311. In the present preferred embodiment, the cover hub313is provided as a different member separated from the disc portion311. However, the cover hub313can be provided as a single member integrated with the disc portion311.

The cover hub313includes the spline hole to which the first torque transmission shaft41ais spline-coupled. The cover hub313is rotatably supported by the torque converter casing30through a bearing member (not shown in the drawings).

The impeller32is unitarily rotated with the cover31. The impeller32is fixed to the cover31. The impeller32includes an impeller shell321, a plurality of impeller blades322, and an impeller hub323.

The impeller shell321is fixed to the cover31. The plural impeller blades322are attached to the inner surface of the impeller shell321.

The impeller hub323is attached to the inner peripheral end of the impeller shell321. It should be noted that in the present preferred embodiment, the impeller hub323is provided as a single member integrated with the impeller shell321, but alternatively, can be provided as a different member separated from the impeller shell321.

The turbine33is disposed in opposition to the impeller32. When described in detail, the turbine33is axially opposed to the impeller32. The turbine33is a component to which the torque is transmitted from the impeller32through the hydraulic fluid.

The turbine33includes a turbine shell331, a plurality of turbine blades332, and a turbine hub333. The plural turbine blades332are fixed to the inner surface of the turbine shell331.

The turbine hub333is fixed to the inner peripheral end of the turbine shell331. For example, the turbine hub333is fixed to the turbine shell331by rivets. In the present preferred embodiment, the turbine hub333is provided as a different member separated from the turbine shell331. However, the turbine hub333can be provided as a single member integrated with the turbine shell331.

The second torque transmission shaft42ais attached to the turbine hub333. When described in detail, the second torque transmission shaft42ais spline-coupled to the turbine hub333. The turbine hub333is unitarily rotated with the second torque transmission shaft42a. In other words, the torque converter3outputs the amplified torque to the second torque transmission shaft42a.

The stator34is configured to regulate the flow of the hydraulic oil returning from the turbine33to the impeller32. The stator34is rotatable about the rotational axis O. For example, the stator34is supported by a stationary shaft104through the one-way clutch36. The stator34is disposed axially between the impeller32and the turbine33.

It should be noted that the stationary shaft104axially extends through the interior of the impeller hub323. The stationary shaft104has a cylindrical shape and the second torque transmission shaft42aaxially extends through the interior of the stationary shaft104. Besides, the stationary shaft104extends from, for instance, the transmission casing40or the torque converter casing30. The stationary shaft104is non-rotatable.

The stator34includes a stator carrier341having a disc shape and a plurality of stator blades342attached to the outer peripheral surface of the stator carrier341.

The one-way clutch36is disposed between the stationary shaft104and the stator34. The one-way clutch36is configured to make the stator34rotatable in the first rotational direction. By contrast, the one-way clutch36makes the stator34non-rotatable in the second rotational direction. The torque is transmitted from the impeller32to the turbine33, while being amplified by the stator34.

The centrifugal lock-up clutch37is attached to the turbine33. The lock-up clutch37is unitarily rotated with the turbine33. The lock-up clutch37is configured to couple the cover31and the turbine33to each other by a centrifugal force generated in rotation of the turbine33. When described in detail, the lock-up clutch37is configured to transmit the torque from the cover31to the turbine33when the rotational speed of the turbine33becomes greater than or equal to a predetermined value.

The lock-up clutch37includes a plurality of centrifugal elements371and a plurality of friction materials372. The friction materials372are attached to the outer peripheral surfaces of the centrifugal elements371, respectively. The centrifugal elements371are disposed to be radially movable. It should be noted that the centrifugal elements371are disposed to be circumferentially immovable. Because of this, the centrifugal elements371are rotated together with the turbine33and are moved radially outward by centrifugal forces.

When the rotational speed of the turbine33becomes greater than or equal to the predetermined value, the lock-up clutch37is configured such that the centrifugal elements371are moved radially outward and the friction materials372are engaged by friction with the inner peripheral surface of the cylindrical portion312of the cover31. As a result, the lock-up clutch37is turned to an on state, and the torque inputted to the cover31is transmitted therefrom to the turbine33through the lock-up clutch37. It should be noted that even when the lock-up clutch37is turned to the on state, the hydraulic fluid is flowable through the lock-up clutch37.

When the rotational speed of the turbine33becomes less than the predetermined value, the centrifugal elements371are moved radially inward, whereby the friction materials372and the inner peripheral surface of the cylindrical portion312of the cover31, engaged by friction, are disengaged from each other. As a result, the lock-up clutch37is turned to an off state, and the torque inputted to the cover31is not transmitted therefrom to the turbine33through the lock-up clutch37. In other words, the torque inputted to the cover31is transmitted therefrom to the impeller32and is then transmitted to the turbine33through the hydraulic fluid.

The first clutch6is configured to allow and block torque transmission between the input part and the output part in the torque converter3. When described in detail, the first clutch6is configured to allow and block torque transmission between the cover31and the turbine33.

The first clutch6is disposed between the cover31and the turbine33. The first clutch6is a one-way clutch.

The first clutch6blocks transmission of the torque outputted from the motor2when the torque is directed in the first rotational direction. In other words, when the torque, outputted from the motor2so as to be directed in the first rotational direction, is inputted to the first clutch6, the first clutch6makes the cover31rotatable relative to the turbine33. Because of this, when the motor2is rotated in the first rotational direction, the first clutch6does not allow torque transmission from the cover31to the turbine33. As a result, the torque, outputted from the motor2so as to be directed in the first rotational direction, is sequentially transmitted to the cover31, the impeller32, and the turbine33in this order.

By contrast, the first clutch6transmits the torque outputted from the motor2when the torque is directed in the second rotational direction. In other words, when the torque, outputted from the motor2so as to be directed in the second rotational direction, is inputted to the first clutch6, the first clutch6makes the cover31unitarily rotate with the turbine33. Because of this, when the motor2is rotated in the second rotational direction, the first clutch6allows torque transmission from the cover31to the turbine33. The torque, outputted from the motor2so as to be directed in the second rotational direction, is transmitted without through the impeller32and the hydraulic fluid.

<First and Second Gear Trains>

As shown inFIG.2, the first and second gear trains71and72are disposed axially between the motor2and the torque converter3. Besides, the first torque output gear51, the first torque input gear52, and the second torque input gear53in the first clutch mechanism5are disposed axially between the first and second gear trains71and72. The first and second gear trains71and72are accommodated in the transmission casing40.

As shown inFIGS.1and2, the first and second gear trains71and72output the torque toward the output unit101. When described in detail, the first and second gear trains71and72output the torque to the drive wheels110through the final gear train102, the differential gear103, and the drive shafts105.

The first and second gear trains71and72are configured to output the torque, outputted from the motor2so as to be directed in the first rotational direction, as a forward rotation directional torque. In other words, the first and second gear trains71and72are configured to output the torque, outputted from the motor2so as to be directed in the second rotational direction, as a reverse rotation directional torque. Because of this, when the motor2is rotated in the first rotational direction and the torque is outputted therefrom to the drive wheels110through the first or second gear train71,72, the vehicle is moved forward. By contrast, when the motor2is rotated in the second rotational direction and the torque is outputted therefrom to the drive wheels110through the first or second gear train71,72, the vehicle is moved backward.

The first gear train71is disposed in the first torque transmission path4a. The first gear train71is disposed downstream with respect to the torque converter3. Specifically, the first gear train71is attached to the second torque transmission shaft42a.

As shown inFIG.3, the first gear train71includes a first gear71aand a second gear71bthat are meshed with each other. The first gear71ais attached to the downstream-side end of the second torque transmission shaft42a. The first gear71ais unitarily rotated with the second torque transmission shaft42a.

The second gear71bis supported by a drive shaft70. The second gear71bis unitarily rotated with the drive shaft70. The second gear71boutputs the torque, inputted thereto from the first gear71a, to the drive shaft70.

The second gear train72is disposed in the second torque transmission path4b. The second gear train72includes a third gear72aand a fourth gear72bthat are meshed with each other. The number of gears in the second gear train72is equal to that in the first gear train71.

The third gear72ais unitarily rotated with the second torque input gear53. The third gear72ais integrated with the second torque input gear53. The third gear72acan be provided as a single member integrated with the second torque input gear53, or alternatively, can be provided as a different member separated from the second torque input gear53. The third gear72ais supported by the output shaft24, while being rotatable relative thereto.

The fourth gear72bis supported by the drive shaft70. The fourth gear72bis unitarily rotated with the drive shaft70. The fourth gear72boutputs the torque, inputted thereto from the third gear72a, to the drive shaft70.

The first gear train71is different in reduction ratio from the second gear train72. When described in detail, the first gear train71is higher in reduction ratio than the second gear train72.

As shown inFIG.1, the controller9is configured to control the motor2and the first switch mechanism5. For example, a computer (e.g., microcomputer), including a CPU (Central Processing Unit), a ROM (Read Only Memory), and so forth, is provided as the controller9. The ROM stores programs for various computations. The CPU executes the programs stored in the ROM.

The controller9executes any of a first forward moving mode, a second forward moving mode, a first reverse moving mode, and a second reverse moving mode. When the controller9executes the first or second forward moving mode, the drive unit100is actuated to move the vehicle forward. By contrast, when the controller9executes the first or second reverse moving mode, the drive unit100is actuated to move the vehicle backward.

When executing the first forward moving mode, the controller9controls and causes the motor2to be rotated in the first rotational direction. Besides, when executing the first forward moving mode, the controller9controls the first switch mechanism5such that transmission of the torque outputted from the motor2is made through the first torque transmission path4a.

When described in detail, the controller9controls the actuator55such that the first ring gear54is set to the first coupling state. As a result, the first ring gear54couples the first torque output gear51and the first torque input gear52to each other, whereby the torque, outputted from the motor2, is transmitted to the first torque transmission path4a.

It should be noted that when the controller9controls and causes the motor2to be rotated in the first rotational direction, the first clutch6blocks torque transmission. As a result, the torque, outputted from the motor2so as to be directed in the first rotational direction, is transmitted via the torque converter3. It should be noted that when the rotational speed of the turbine33in the torque converter3becomes greater than or equal to a predetermined value, the lock-up clutch37is turned to a lock-up on state, whereby torque transmission is made. In other words, torque transmission is directly made from the cover31to the turbine33without through the hydraulic fluid.

When executing the second forward moving mode, the controller9controls and causes the motor2to be rotated in the first rotational direction. Besides, when executing the second forward moving mode, the controller9controls the first switch mechanism5such that transmission of the torque outputted from the motor2is made through the second torque transmission path4b.

When described in detail, the controller9controls the actuator55such that the first ring gear54is set to the second coupling state. As a result, the first ring gear54couples the first torque output gear51and the second torque input gear53to each other, whereby the torque, outputted from the motor2, is transmitted to the second torque transmission path4b.

In the first forward moving mode, torque amplification is enabled by the torque converter3. Besides, in the first forward moving mode, torque transmission is made through the first gear train71higher in reduction ratio than the second gear train72. Therefore, in the first forward moving mode, the drive unit100is enabled to output a high drive force during traveling at low speed. In other words, the first forward moving mode is suitable for traveling at low speed.

By contrast, in the second forward moving mode, torque transmission is directly made without through the torque converter3; hence, torque transmission can be made efficiently. Besides, in the second forward moving mode, torque transmission is made through the second gear train72lower in reduction ratio than the first gear train71; hence, the motor2can be reduced in rotational speed. The second forward moving mode is suitable for traveling at high speed.

When executing the first reverse moving mode, the controller9controls and causes the motor2to be rotated in the second rotational direction. Besides, when executing the first reverse moving mode, the controller9controls the first switch mechanism5such that transmission of the torque outputted from the motor2is made through the second torque transmission path4b. It should be noted that the method of controlling the first switch mechanism5is identical to that in the second forward moving mode described above.

When executing the second reverse moving mode, the controller9controls and causes the motor2to be rotated in the second rotational direction. Besides, when executing the second reverse moving mode, the controller9controls the first switch mechanism5such that transmission of the torque outputted from the motor2is made through the first torque transmission path4a. It should be noted that the method of controlling the first switch mechanism5is identical to that in the first forward moving mode described above.

Torque transmission is made through the first clutch6in the first torque transmission path4a. In other words, transmission of the torque directed in the second rotational direction is made without through the torque converter3in the first torque transmission path4a.

In the drive unit100configured as described above, the controller9executes either the first forward moving mode or the second forward moving mode when the vehicle is moved forward. It should be noted that either the first forward moving mode or the second forward moving mode can be selected in accordance with operation by a driver or can be selected by the controller9based on at least one traveling condition or so forth.

The controller executes either the first reverse moving mode or the second reverse moving mode when the vehicle is moved backward. In similar manner to the above, either the first reverse moving mode or the second reverse moving mode can be selected in accordance with operation by the driver or can be selected by the controller9based on at least one traveling condition or so forth.

One preferred embodiment of the present invention has been explained above. However, the present invention is not limited to the above, and a variety of changes can be made without departing from the gist of the present invention. It should be noted that modifications to be described, excluding part thereof, are applicable simultaneously.

(a) In the preferred embodiment described above, the first gear train71is higher in reduction ratio than the second gear train72. However, the configuration for the first and second gear trains71and72is not limited to the above. For example, as shown inFIG.6, the second gear train72can be higher in reduction ratio than the first gear train71.

(b) As shown inFIG.7, the drive unit100may not include the first clutch6. Besides, the torque converter3may not include the lock-up clutch37.

(c) As shown inFIG.8, the drive unit100can include a second clutch7. The second clutch7is disposed in the first torque transmission path4a. The second clutch7is disposed downstream with respect to the torque converter3. The second clutch7is configured to allow and block torque transmission.

When described in detail, the second clutch7is a one-way clutch. The second clutch7is configured to allow transmitting downstream the torque outputted from the torque converter3and block transmitting the torque from downstream to the torque converter3.

(d) As shown inFIG.9, the drive unit100can include a third gear train73and a second switch mechanism5a. The third gear train73is disposed in the first torque transmission path4a. In other words, two gear trains, composed of the first and third gear trains71and73, are installed in the first torque transmission path4a. Besides, the first and third gear trains71and73are disposed parallel to each other.

The third gear train73is configured to receive the torque transmitted thereto from the torque converter3. The third gear train73is attached to the second torque transmission shaft42a. The third gear train73is configured to output the torque toward the output unit101. When described in detail, the third gear train73outputs the torque to the drive wheels110through the final gear train102, the differential gear103, and the drive shafts105.

The third gear train73outputs the torque in a reverse rotational direction to when the torque is outputted from the first gear train71. When described in detail, the third gear train73is configured to output the torque, outputted from the motor2so as to be directed in the first rotational direction, as a reverse rotation directional torque. In other words, the third gear train73is configured to output the torque, outputted from the motor2so as to be directed in the second rotational direction, as a forward rotation directional torque. Because of this, when the motor2is rotated in the first rotational direction and the torque is outputted therefrom to the output unit101through the third gear train73, the vehicle is moved backward. By contrast, when the motor2is rotated in the second rotational direction and the torque is outputted therefrom to the output unit101through the third gear train73, the vehicle is moved forward.

The controller9is enabled to execute a third reverse moving mode in addition to the first and second reverse moving modes. When executing the third reverse moving mode, the controller9controls and causes the motor2to be rotated in the first rotational direction. Besides, when executing the third reverse moving mode, the controller9controls the first switch mechanism5such that transmission of the torque outputted from the motor2is made through the first torque transmission path4a. Moreover, when executing the third reverse moving mode, the controller9controls the second switch mechanism5asuch that transmission of the torque amplified by the torque converter3is made through the third gear train73.

As shown inFIG.10, the third gear train73includes fifth to seventh gears73ato73c. The fifth gear73ais supported by the second torque transmission shaft42a, while being rotatable relative thereto. By meshing of a second ring gear54a(to be described) in the second switch mechanism5a, the fifth gear73ais unitarily rotated with the second torque transmission shaft42a.

The sixth gear73bis meshed with the fifth gear73a. The sixth gear73bis supported by a countershaft (not shown in the drawings). The sixth gear73bcan be rotated unitarily with or relative to the countershaft.

The seventh gear73cis meshed with the sixth gear73b. The seventh gear73cis supported by the drive shaft70. The seventh gear73cis unitarily rotated with the drive shaft70. The seventh gear73coutputs the torque, transmitted thereto from the fifth gear73a, to the drive shaft70.

Besides, in the present modification, in similar manner to the fifth gear73a, the first gear71ais supported by the second torque transmission shaft42a, while being rotatable relative thereto.

The second switch mechanism5ais configured to switch between the first gear train71and the third gear train73as the path for transmitting the torque after the torque is outputted from the torque converter3. Besides, the second switch mechanism5ais settable to a neutral position without selecting any of the first and third gear trains71and73so as to block transmission of the torque outputted from the torque converter3. For example, when executing the second forward moving mode described above, the controller9controls and causes the second switch mechanism5ato be set to the neutral position.

The second switch mechanism5aincludes a second torque output gear51a, a third torque input gear52a, a fourth torque input gear53a, the second ring gear54a, and a second actuator55a. The second actuator55ais controlled by the controller9. When controlled by the controller9, the second actuator55ais caused to axially move the second ring gear54a.

The second torque output gear51ais attached to the second torque transmission shaft42a. The second torque output gear51ais unitarily rotated with the second torque transmission shaft42a. The second torque output gear51acan be provided as a single member integrated with the second torque transmission shaft42a, or alternatively, can be provided as a different member separated from the second torque transmission shaft42a. The second torque output gear51aincludes a plurality of teeth on the outer peripheral surface thereof.

The third torque input gear52ais supported by the second torque transmission shaft42a, while being rotatable relative thereto. When meshed with the second ring gear54a, the third torque input gear52ais unitarily rotated with the second torque transmission shaft42a. The third torque input gear52ais unitarily rotated with the first gear71ain the first gear train71. It should be noted that the third torque input gear52acan be provided as a single member integrated with the first gear71a, or alternatively, can be provided as a different member separated from the first gear71a.

The fourth torque input gear53ais supported by the second torque transmission shaft42a, while being rotatable relative thereto. When meshed with the second ring gear54a, the fourth torque input gear53ais unitarily rotated with the second torque transmission shaft42a. The fourth torque input gear53ais unitarily rotated with the fifth gear73ain the third gear train73. It should be noted that the fourth torque input gear53acan be provided as a single member integrated with the fifth gear73a, or alternatively, can be provided as a different member separated from the fifth gear73a.

The second ring gear54aincludes a plurality of teeth on the inner peripheral surface thereof. The second ring gear54ais constantly meshed with the second torque output gear51aand is unitarily rotated therewith. In other words, the second ring gear54ais unitarily rotated with the second torque transmission shaft42a. The second ring gear54ais disposed to be movable in the axial direction.

The second ring gear54ais meshed with the second torque output gear51aand is also capable of being turned to a state of engagement with the third torque input gear52a. When the second ring gear54ais meshed with the second torque output gear51aand the third torque input gear52aas described above, the torque, transmitted from the second torque transmission shaft42a, is outputted through the first gear train71.

On the other hand, the second ring gear54ais meshed with the second torque output gear51aand is also capable of being turned to a state of engagement with the fourth torque input gear53a. When the second ring gear54ais meshed with the second torque output gear51aand the fourth torque input gear53aas described above, the torque, transmitted from the second torque transmission shaft42a, is outputted through the third gear train73.

By contrast, when the second switch mechanism5ais set to the neutral position, the second ring gear54ais turned to a state of meshing with only the second torque output gear51a. When the second ring gear54ais meshed with only the second torque output gear51awithout being meshed with either the third torque input gear52aor the fourth torque input gear53a, torque transmission can be blocked between the drive shaft70and the second torque transmission shaft42a. With this configuration, the torque converter3and so forth can be prevented from being rotated in conjunction with another component, while the drive unit100is driven in the second forward moving mode.

The second switch mechanism5ais controlled by the controller9. When controlled by the controller9, the second ring gear54ais moved in the axial direction. The axial movement of the second ring gear54aresults in meshing with the second torque output gear51aand the third torque input gear52a, meshing with the second torque output gear Ma and the fourth torque input gear53a, or meshing with only the second torque output gear51a.

(e) As shown inFIG.11, the drive unit100can further include a fourth gear train74. The fourth gear train74is disposed in the first torque transmission path4a. The fourth gear train74is disposed upstream with respect to the torque converter3. The fourth gear train74changes the speed of a torque inputted thereto and outputs the torque changed in speed. The fourth gear train74is, for instance, a planetary gear mechanism.

When the drive unit100includes the fourth gear train74as described above, the first gear train71can be set to be equal in reduction ratio to the second gear train72. For example, the first and third gears71aand72acan be set to be equal in diameter and can be meshed with a single gear attached to the drive shaft70.

(f) As shown inFIG.12, the drive unit100can further include a third torque transmission path4cand a third switch mechanism5b. The third torque transmission path4cbranches off from the first torque transmission path4aat a position upstream of the torque converter3and merges to the first torque transmission path4aat a position downstream of the torque converter3.

The third switch mechanism5bis configured to switch between the first torque transmission path4aand the third torque transmission path4cas the path for transmitting the torque. It should be noted that the third switch mechanism5bcan be configured in similar manner to the first switch mechanism5or the second switch mechanism5a.

(g) In the preferred embodiment described above, the second torque input gear53, the first torque output gear51, and the first torque input gear52are disposed along the rotational axis O, while being aligned in this order from the side closer to the motor2. However, the configuration of the first switch mechanism5is not limited to this.

For example, as shown inFIG.13, the first torque output gear51, the first torque input gear52, and the second torque input gear53can be disposed along the rotational axis O, while being aligned in this order from the side closer to the motor2.

The drive unit100, employing the first switch mechanism5configured as described above, is applicable to, for instance, a motorcycle as shown inFIG.14. In the motorcycle, an output unit does not include any differential gear, but instead, includes a belt108.

(h) As shown inFIG.15, the first torque output gear51, the second torque input gear53, and the first torque input gear52can be disposed along the rotational axis O, while being aligned in this order from the side closer to the motor2.

The drive unit100, employing the first switch mechanism5configured as described above, is applicable to, for instance, a four-wheel drive car as shown inFIG.16.

(i) In the preferred embodiment described above, the first and second gear trains71and72are disposed between the motor2and the torque converter3. However, the configuration of the drive unit100is not limited to this. For example, as shown inFIG.15, the first and second gear trains71and72can be disposed on the opposite side of the motor2with reference to the torque converter3. In other words, the torque converter3can be disposed between the motor2and both the first and second gear trains71and72.

REFERENCE SIGNS LIST

2: Electric motor3: Torque converter4a: First torque transmission path4b: Second torque transmission path4c: Third torque transmission path5: First switch mechanism5a: Second switch mechanism5b: Third switch mechanism6: First clutch7: Second clutch9: Controller37: Lock-up Clutch51: First torque output gear52: First torque input gear53: Second torque input gear54: First ring gear71: First gear train72: Second gear train73: Third gear train74: Fourth gear train100: Drive unit101: Output unit