Transfer unit for a motor vehicle

A transfer includes: an input shaft; a motor; first and second output shafts; first and second planetary gear devices; an input switching unit; a transmission switching unit; and a distribution switching unit. Further, connection states of the input shaft, the first and the second planetary gear devices, the first and the second output shafts can be switched to a plurality of modes including first, second, and third modes by the input switching unit, the transmission switching unit, and the distribution switching unit.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2020-027576 filed in Japan on Feb. 20, 2020.

BACKGROUND

The present disclosure relates to a transfer.

As a power transmission device mounted on a four-wheel-drive vehicle, a transfer to distribute and transmit power from an engine to front wheels and rear wheels has been known. The transfer has a front wheel-side output member to transmit power to the front wheels, and a rear wheel-side output member to transmit power to the rear wheels, and can establish a two-wheel driving state in which power is output from only one output member and a four-wheel driving state in which power is output from both of the output members.

Also, in a transfer case, the transfer includes a planetary gear device as a transmission unit that outputs a rotation of the engine while changing a speed thereof. With respect to three rotational elements included in this planetary gear device, a rotational element to which the power of the engine is input and a rotational element fixed to the transfer case (fixing member) are different rotational elements. Then, the transfer can be switched between a state in which a rotation of the engine is output with a speed thereof not being changed, and a state in which the rotation of the engine is output with the speed thereof being changed by the planetary gear device.

International Publication No. WO 2010/141682 discloses a transfer including a motor functioning as a power source inside a transfer case. In this transfer, when power of an engine is transmitted to drive wheels, power of the motor can be transmitted to the drive wheels via a planetary gear device.

SUMMARY

There is a need for providing a transfer capable of transmitting power from a motor to drive wheels via a planetary gear device in a state in which one rotational element is fixed to a fixing member.

A transfer includes: an input shaft that inputs power from a first power source; a motor that functions as a second power source; a first output shaft that transmits power to main drive wheels; a second output shaft that transmits power to auxiliary drive wheels; a first planetary gear device having a first rotational element coupled to the motor, a second rotational element, and a third rotational element; a second planetary gear device having a fourth rotational element coupled to the second rotational element, a fifth rotational element, and a sixth rotational element; an input switching unit that selectively switches a connection destination of the input shaft; a transmission switching unit that switches a speed-changing state in which a rotation of the first rotational element is output with a speed thereof being changed by the first planetary gear device, and a non-speed-changing state in which a rotation of the first rotational element is output with a speed thereof not being changed by the first planetary gear device; and a distribution switching unit that switches a distribution state in which power is transmitted to the first output shaft and the second output shaft, and a non-distribution state in which power is transmitted only to the first output shaft between the first output shaft and the second output shaft. Further, connection states of the input shaft, the first planetary gear device, the second planetary gear device, the first output shaft, and the second output shaft can be switched to a plurality of modes by the input switching unit, the transmission switching unit, and the distribution switching unit, and the plurality of modes includes a first mode in which the input shaft is in a state of being directly coupled to the first output shaft and the distribution switching unit is in the non-distribution state, a second mode in which the input shaft is in a state of being directly coupled to the first output shaft, the distribution switching unit is in the distribution state, and the three rotational elements in the second planetary gear device can make differential motions in a state of being respectively coupled to the motor, the first output shaft, and the second output shaft, and a third mode in which the input shaft is in a state of being coupled to the first rotational element of the first planetary gear device, the distribution switching unit is in the distribution state, the transmission switching unit is in the speed-changing state in which the third rotational elements are fixed to a fixing member, and the three rotational elements are integrally rotatable in the second planetary gear device in a state in which two rotational elements are coupled to each other and any one of the rotational elements is coupled to the first output shaft.

DETAILED DESCRIPTION

In the related art, in a configuration described in International Publication No. WO 2010/141682, a rotational element fixed to a fixing member and a rotational element, to which power of a motor is input, among three rotational elements included in a planetary gear device are the same rotational element. Thus, when the power of the motor is transmitted to drive wheels via the planetary gear device, the planetary gear device cannot function as a transmission unit in a state in which one rotational element is fixed. Also, in a case where one rotational element is fixed and the planetary gear device is made to function as a transmission unit, the power of the motor cannot be transmitted to the drive wheels via the planetary gear device.

In the following, a transfer in an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to embodiments described in the following.

FIG. 1is a skeleton diagram schematically illustrating a vehicle equipped with a transfer according to a first embodiment. A vehicle1includes an engine2as a power source, left and right front wheels3L and3R, left and right rear wheels4L and4R, and a power transmission device10to respectively transmit power of the engine2to front wheels3and rear wheels4. This vehicle1is a four-wheel-drive vehicle based on front-engine rear-wheel drive. The rear wheels4are main drive wheels that become drive wheels during traveling in a two-wheel driving state and during traveling in a four-wheel driving state. On the one hand, the front wheels3are auxiliary drive wheels that become driven wheels during traveling in the two-wheel driving state and that become drive wheels during traveling in the four-wheel driving state.

The power transmission device10includes a transmission11coupled to the engine2, a transfer12that is a front/rear wheel power distribution device coupled to the transmission11, a front propeller shaft13and rear propeller shaft14that are respectively coupled to the transfer12, a front-wheel differential gear mechanism15coupled to the front propeller shaft13, a rear-wheel differential gear mechanism16coupled to the rear propeller shaft14, left and right front wheel axles17L and17R coupled to the front-wheel differential gear mechanism15, and left and right rear wheel axles18L and18R coupled to the rear-wheel differential gear mechanism16. Note that wheels and axles are described as front wheels3, rear wheels4, front wheel axles17, and rear wheel axles18with the reference signs L and R being omitted in a case where the left and right thereof are not specifically distinguished.

The power output from the engine2is transmitted to the transfer12via the transmission11. Then, the power transmitted to the transfer12is transmitted from the transfer12to the rear wheels4serially through a rear wheel-side power transmission path of the rear propeller shaft14, the rear-wheel differential gear mechanism16, and the rear wheel axles18. Also, a part of the power transmitted to a side of the rear wheels4is distributed to a side of the front wheels3by the transfer12, and is transmitted to the front wheels3serially through a front wheel-side power transmission path of the front propeller shaft13, the front-wheel differential gear mechanism15, and the front wheel axles17.

As illustrated inFIG. 2, the transfer12of the first embodiment includes a transfer case20that is a non-rotational member. Inside the transfer case20, the transfer12includes an input shaft21, a rear wheel-side output shaft22as a first output shaft to output power to the rear wheels4that are main drive wheels, a front wheel-side output shaft23as a second output shaft to output power to the front wheels3that are auxiliary drive wheels, a first planetary gear device24that functions as a transmission unit, and a second planetary gear device25that functions as a power distribution unit. Also, inside the transfer case20, the transfer12includes, as rotational members to form a power transmission path on the side of the front wheels, a transmitting unit26that functions as an input member for the side of the front wheels, a drive gear27that outputs power to the front wheel-side output shaft23, a driven gear28that is provided integrally with the front wheel-side output shaft23, and a front-wheel drive chain29that couples the drive gear27and the driven gear28. Furthermore, the transfer12includes, inside the transfer case20, a motor30as a power source, and a connection switching device40that switches connection states of the rotational members.

The input shaft21is an input member that inputs power from the engine2into the transfer12. For example, the input shaft21is spline-fitted to an output member (not illustrated) of the transmission11. The power transmitted from the engine2to the input shaft21via the transmission11is input into the transfer12. A connection destination of the input shaft21is selectively switched by the connection switching device40.

The rear wheel-side output shaft22is an output member that outputs power to the side of the rear wheels4. This rear wheel-side output shaft22is arranged on the same axis as the input shaft21, and is coupled to the rear propeller shaft14in such a manner as to rotate integrally therewith. In the transfer12, the first planetary gear device24, the second planetary gear device25, the transmitting unit26, and the drive gear27are arranged on the same axis as the rear wheel-side output shaft22.

The front wheel-side output shaft23is an output member that outputs power to the side of the front wheels3. This front wheel-side output shaft23is arranged on an axis different from that of the input shaft21and the rear wheel-side output shaft22, and is coupled to the front propeller shaft13in such a manner as to rotate integrally therewith. Also, the front wheel-side output shaft23is constantly connected to the drive gear27via the driven gear28and the front-wheel drive chain29. That is, as the drive gear27rotates, the front wheel-side output shaft23rotates. The drive gear27is coupled to the transmitting unit26in such a manner as to rotate integrally therewith.

The transmitting unit26is a rotational member that transmits power to the front wheel-side output shaft23. This transmitting unit26is arranged on the same axis as the rear wheel-side output shaft22and is arranged in such a manner as to be rotatable relative to the rear wheel-side output shaft22. The transmitting unit26is switched by the connection switching device40between a connection state in which power from the power source is transmitted and a disconnection state in which the power from the power source is not transmitted.

The first planetary gear device24functions as a transmission unit that outputs a rotation of the engine2while changing a speed thereof. This first planetary gear device24can transmit power of the engine2and power of the motor30. The first planetary gear device24can function as a transmission unit (engine transmission unit) that outputs a rotation of the engine2while changing a speed thereof when transmitting the power of the engine2, and can function as a transmission unit (motor transmission unit) that outputs a rotation of the motor30while changing a speed thereof when transmitting the power of the motor30. In the transfer12, by causing the first planetary gear device24to function as a transmission unit, it is possible to establish one of a high speed-side gear position Hi and a low speed-side gear position Lo, and to transmit a rotation of the power source to a following stage while changing a speed thereof.

This first planetary gear device24includes a single pinion-type planetary gear device having three rotational elements. As illustrated inFIG. 2, the first planetary gear device24includes, as the three rotational elements, a first sun gear S1, a first ring gear R1arranged concentrically with the first sun gear S1, and a first carrier C1that rotatably and revolvably supports a plurality of pinion gears that meshes with the first sun gear S1and the first ring gear R1.

The first sun gear S1is a first rotational element that functions as an input element. A first rotational member51that is an input member of the first planetary gear device24is coupled to this first sun gear S1in such a manner as to rotate integrally. Also, the first sun gear S1is constantly connected to the motor30via the first rotational member51in such a manner that transmission of power can be performed. The first carrier C1is a second rotational element that functions as an output element. A second rotational member52that is an output member of the first planetary gear device24is coupled to this first carrier C1in such a manner as to rotate integrally. The first ring gear R1is a third rotational element that functions as a reaction force element. A third rotational member53is coupled to this first ring gear R1in such a manner as to rotate integrally.

The second planetary gear device25functions as a power distribution unit that distributes and transmits the power of the engine2to the front wheels3and the rear wheels4. This second planetary gear device25is arranged side by side in an axial direction with the first planetary gear device24, and is configured to receive an input of the power output from the first planetary gear device24. The second planetary gear device25can transmit the power of the engine2and the power of the motor30. Thus, the second planetary gear device25can distribute power to the front wheels3and the rear wheels4when transmitting the power of the engine2, and can distribute power to the front wheels3and the rear wheels4when transmitting the power of the motor30.

This second planetary gear device25includes a single pinion-type planetary gear device having three rotational elements. As illustrated inFIG. 2, the second planetary gear device25includes, as the three rotational elements, a second sun gear S2, a second ring gear R2arranged concentrically with the second sun gear S2, and a second carrier C2that rotatably and revolvably supports a plurality of pinion gears that meshes with the second sun gear S2and the second ring gear R2.

The second sun gear S2is a fourth rotational element that functions as an input element. A second rotational member52is coupled to this second sun gear S2in such a manner as to rotate integrally. That is, the first carrier C1is coupled to the second sun gear S2, and the second sun gear S2and the first carrier C1rotate integrally. The second carrier C2is a fifth rotational element that functions as an output element. The rear wheel-side output shaft22is coupled to this second carrier C2in such a manner as to rotate integrally. The second carrier C2and the rear wheel-side output shaft22are coupled.

Furthermore, a fourth rotational member54is coupled to the second carrier C2in such a manner as to rotate integrally. The second ring gear R2is a sixth rotational element that functions as an output element. A fifth rotational member55is coupled to this second ring gear R2in such a manner as to rotate integrally.

The motor30is a motor generator (MG) that can function as an electric motor and a generator. The motor30includes a rotor, a stator, and an output shaft rotating integrally with the rotor, and is electrically connected to a battery via an inverter. As illustrated inFIG. 2, a reduction gear31is provided on the output shaft of the motor30. The reduction gear31meshes with a counter gear32. The counter gear32meshes with an input gear33. The input gear33is attached to the first rotational member51in such a manner as to rotate integrally, and is mechanically coupled to the first sun gear S1of the first planetary gear device24in such a manner as to rotate integrally. Then, the reduction gear31, the counter gear32, and the input gear33form a reduction gear train. Thus, when the power output from the motor30is transmitted to the first sun gear S1via this reduction gear train, a rotation of the motor30is transmitted with a speed thereof being changed (reduced).

The connection switching device40functions as an input switching unit, a transmission switching unit, and a distribution switching unit. The connection switching device40is a device that switches connection states of the rotational members included in the transfer12, and switches connection states of the input shaft21, the rear wheel-side output shaft22, the first planetary gear device24, the second planetary gear device25, and the transmitting unit26. The input switching unit selectively switches connection destinations of the input shaft21. This input switching unit switches a direct coupling state in which the input shaft21is directly coupled to the rear wheel-side output shaft22(first input state), and a speed-changing state in which the input shaft21is coupled to the first sun gear S1of the first planetary gear device24(second input state). That is, the input switching unit is a so-called high/low switching unit and also has a function as a transmission switching unit. The transmission switching unit switches a speed-changing state in which a rotation of the first sun gear S1is transmitted to the rear wheel-side output shaft22with a speed thereof being changed, and a non-speed-changing state in which a rotation of the first sun gear S1is transmitted to the rear wheel-side output shaft22with the speed thereof not being changed. The distribution switching unit switches a non-distribution state in which the power output from the power source is transmitted only to the rear wheels4(two-wheel driving state), and a distribution state in which the power output from the power source is distributed and transmitted to the front wheels3and the rear wheels4(four-wheel driving state).

As illustrated inFIG. 2, the connection switching device40includes a first dog clutch41, a first friction clutch42, a second dog clutch43, a second friction clutch44, and a third dog clutch45.

The first dog clutch41is an engagement device that functions as an input switching unit and a transmission switching unit. As illustrated inFIG. 2, the first dog clutch41is a meshing engagement device that selectively connects the input shaft21to the first sun gear S1and the rear wheel-side output shaft22. This first dog clutch41is switched between a first input state in which the power of the engine2is transmitted to the rear wheel-side output shaft22without the first planetary gear device24(direct coupling state), and a second input state in which the power of the engine2is transmitted to the rear wheel-side output shaft22via the first planetary gear device24(speed-changing state). In other words, the first dog clutch41is switched between the direct coupling state in which a rotation of the engine2is transmitted to the rear wheel-side output shaft22with a speed thereof not being changed (first input state), and the speed-changing state in which a rotation of the engine2is transmitted to the rear wheel-side output shaft22with a speed thereof being changed (second input state).

This first dog clutch41has a first switching sleeve46as an input switching member. The first switching sleeve46has a first gear tooth46athat meshes with a first gear tooth21aof the input shaft21, and a second gear tooth46bthat meshes with a gear tooth22aof the rear wheel-side output shaft22. This second gear tooth46bcan mesh with a gear tooth51aof the first rotational member51. The first switching sleeve46is moved in the axial direction by an actuator of the first dog clutch41. Then, in a state in which the first gear tooth46aconstantly meshes with the input shaft21, the first switching sleeve46is switched in such a manner that a meshing partner of the second gear tooth46bbecomes one of the rear wheel-side output shaft22and the first rotational member51. The first dog clutch41becomes the direct coupling state (first input state) in a case where the second gear tooth46bmeshes with the rear wheel-side output shaft22, and the first dog clutch41becomes the speed-changing state (second input state) in a case where the second gear tooth46bmeshes with the first rotational member51.

The first friction clutch42is an engagement device that functions as a transmission switching unit. The first friction clutch42is a friction engagement device that is operated by a hydraulic actuator and that selectively fixes the first ring gear R1to a fixing member20a. The fixing member20ais the transfer case20itself or a non-rotational member integrated with the transfer case20. Also, in the first friction clutch42, it is possible to control engagement force by controlling a hydraulic pressure.

This first friction clutch42has a first friction engagement element (fixed element) fixed to the fixing member20a, and a second friction engagement element (rotational element) that rotates integrally with the first ring gear R1. For example, this first friction engagement element is spline-fitted to the fixing member20a, and the second friction engagement element is mechanically coupled to the third rotational member53in such a manner as to rotate integrally therewith. Thus, when the first friction clutch42is engaged, the first ring gear R1cannot rotate. On the one hand, when the first friction clutch42is released, the first ring gear R1becomes rotatable.

The second dog clutch43is an engagement device that functions as a transmission switching unit. This second dog clutch43is a meshing engagement device that selectively fixes the first ring gear R1to the fixing member20a. The second dog clutch43is switched between an engaged state in which the first ring gear R1is mechanically fixed and a released state in which the first ring gear R1is released rotatably.

This second dog clutch43has a second switching sleeve47as a transmission switching member. The second switching sleeve47has a first gear tooth47athat meshes with a gear tooth53aof the third rotational member53that rotates integrally with the first ring gear R1, and a second gear tooth47bthat meshes with the fixing member20a. The second switching sleeve47is moved in the axial direction by an actuator of the second dog clutch43. Then, in a state in which the first gear tooth47aconstantly meshes with the third rotational member53, the second switching sleeve47is switched between a case where the second gear tooth47bmeshes with the fixing member20aand a case where there is no meshing thereof. In a case where the second gear tooth47bmeshes with the fixing member20a, the second dog clutch43is in the engaged state. In a case where the second gear tooth47bdoes not mesh with the fixing member20a, the second dog clutch43is in the released state.

For example, when the first ring gear R1is fixed to the fixing member20aby the first friction clutch42and the second dog clutch43, the first friction clutch42is switched from the released state to the engaged state with the second dog clutch43being in the released state. Then, with the first friction clutch42maintained in the engaged state, the second switching sleeve47is moved in the axial direction to switch the second dog clutch43from the released state to the engaged state. Then, the first friction clutch42can be released. Since the first ring gear R1can be fixed by mechanical force when the second dog clutch43is engaged, it is not necessary to supply the hydraulic pressure for generation of the engagement force to the hydraulic actuator of the first friction clutch42. As a result, fuel efficiency corresponding to this hydraulic pressure is improved.

The second friction clutch44is an engagement device that functions as a transmission switching unit. The second friction clutch44is a friction engagement device that is operated by the hydraulic actuator and that selectively engages the first ring gear R1and the first carrier C1. In the second friction clutch44, it is possible to control the engagement force by controlling the hydraulic pressure.

This second friction clutch44has a first friction engagement element that rotates integrally with the first carrier C1, and a second friction engagement element that rotates integrally with the first ring gear R1. For example, this first friction engagement element is spline-fitted to a cylindrical portion52aof the second rotational member52, and the second friction engagement element is spline-fitted to a cylindrical portion of the third rotational member53. When the second friction clutch44is engaged, the first carrier C1and the first ring gear R1are in a state of being integrally rotatable. On the one hand, when the second friction clutch44is released, the first carrier C1is in a state of being rotatable relative to the first ring gear R1. Also, the second rotational member52has a connection portion52bthat extends to a side of the second planetary gear device25and that is coupled to the second sun gear S2. Note that the cylindrical portion52amay be a clutch drum mechanically coupled to the second rotational member52in such a manner as to rotate integrally therewith. Similarly, the cylindrical portion of the third rotational member53may be a clutch drum mechanically coupled to the third rotational member53in such a manner as to rotate integrally therewith.

The third dog clutch45is an engagement device that functions as a distribution switching unit. The third dog clutch45is a meshing engagement device that selectively couples the rear wheel-side output shaft22to the transmitting unit26. This third dog clutch45is switched between a distribution state in which a part of the power transmitted to the rear wheel-side output shaft22is distributed to the front wheel-side output shaft23, and a non-distribution state in which the power transmitted to the rear wheel-side output shaft22is not distributed to the front wheel-side output shaft23.

This third dog clutch45has a third switching sleeve48as a distribution switching member. The third switching sleeve48has a first gear tooth48athat meshes with a first gear tooth54aof the fourth rotational member54and a gear tooth55aof the fifth rotational member55, and a second gear tooth48bthat meshes with a first gear tooth26aof the transmitting unit26. The third switching sleeve48is moved in the axial direction by an actuator of the third dog clutch45. Then, the third switching sleeve48is switched among the non-distribution state, a first distribution state, and a second distribution state by selectively changing a coupling target.

In the non-distribution state, the second carrier C2and the second ring gear R2are not coupled to the transmitting unit26, and the second carrier C2and the second ring gear R2are coupled to each other in such a manner as to be integrally rotatable. In the non-distribution state, the first gear tooth48aof the third switching sleeve48meshes with the fourth rotational member54, and the second gear tooth48bmeshes with the fifth rotational member55(seeFIG. 2). In a case where the third switching sleeve48is in the non-distribution state, the transfer12is set to the two-wheel driving state.

The first distribution state is a state in which the second carrier C2and the second ring gear R2can make differential motions and the second ring gear R2is coupled to the transmitting unit26. In the first distribution state, the first gear tooth48aof the third switching sleeve48meshes with the fifth rotational member55, and the second gear tooth48bmeshes with the transmitting unit26(seeFIG. 5described later). In a case where the third switching sleeve48is in the first distribution state, the transfer12is set to the four-wheel driving state in which a differential motion between the rear wheel-side output shaft22and the front wheel-side output shaft23is allowed.

The second distribution state is a state in which the second carrier C2and the second ring gear R2are coupled to each other in a manner of being integrally rotatable and the second carrier C2and the second ring gear R2are coupled to the transmitting unit26. In the second distribution state, the first gear tooth48aof the third switching sleeve48meshes with the fourth rotational member54and the fifth rotational member55, and the second gear tooth48bmeshes with the transmitting unit26(seeFIG. 8andFIG. 10described later). In a case where the third switching sleeve48is in the second distribution state, the transfer12is set to the four-wheel driving state in which a differential motion between the rear wheel-side output shaft22and the front wheel-side output shaft23is limited.

In such a manner, in the distribution state, the second planetary gear device25and the third dog clutch45can be switched between a state in which the rear wheel-side output shaft22and the transmitting unit26can make differential motions (first distribution state) and a state in which the rear wheel-side output shaft22and the transmitting unit26do not make differential motions (second distribution state). That is, when being in the four-wheel driving state, the transfer12can be switched between a differential state in which differential motions between the rear propeller shaft14and the front propeller shaft13are not limited (first distribution state) and a non-differential state in which differential motions therebetween are limited (second distribution state).

Also, as illustrated inFIG. 1, the vehicle1includes an electronic control device100that controls the vehicle1. The electronic control device100outputs a command signal to an actuator that operates the connection switching device40, and controls the operation of the connection switching device40. For example, the electronic control device100includes a microcomputer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input/output interface and the like. The CPU executes various kinds of control by performing signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM.

Sensor signals from various sensors mounted on the vehicle1are input into the electronic control device100. For example, various sensors include an engine speed sensor, a motor rotation angle sensor, a vehicle speed sensor, an accelerator position sensor, a Hi range selection switch to select a high speed-side gear position Hi by an operation by a driver, and a 4WD selection switch to select the four-wheel driving state by an operation by the driver. The electronic control device100executes drive control and the like of the vehicle1on the basis of the input sensor signals. Then, the electronic control device100outputs a command signal to control the engine2, a command signal to control the transmission11, a command signal to control the transfer12and the like. The command signal to control the transfer12includes a command signal to control the motor30and a command signal to control the connection switching device40.

For example, the electronic control device100can control a driving state of the transfer12into a plurality of modes by controlling an operation of the motor30and controlling a connection state of the connection switching device40. More specifically, when the electronic control device100executes switching control of the connection switching device40, connection states of the rotational members included in the transfer12(connection states of the input shaft21, the first planetary gear device24, the second planetary gear device25, the rear wheel-side output shaft22, and the front wheel-side output shaft23) can be switched to a plurality of modes. The plurality of modes includes a first mode, a second mode, and a third mode.

The first mode is the two-wheel driving state and is a connection state in which the third dog clutch45is in the non-distribution state with the input shaft21being in a state of directly coupled to the rear wheel-side output shaft22. Also, in the first mode, an engine traveling mode in which the rear wheels4are driven only by the power of the engine2, an HV mode in which the rear wheels4are driven by the power of the engine2and the power of the motor30, and an EV mode in which the rear wheels4are driven only by the power of the motor30can be set.

The second mode is the four-wheel driving state, and is a connection state in which the third dog clutch45is in the first distribution state with the input shaft21being in a state of directly coupled to the rear wheel-side output shaft22, and in which a differential motion of each rotational element of the second planetary gear device25is possible. The second planetary gear device25also has a function as a distribution switching unit. This second mode is a so-called torque split 4WD mode, and is a mode in which power distribution to the front wheels3and the rear wheels4can be operated by control of an operation of the motor30(front-rear distribution control mode).

The third mode is a four-wheel driving state, and is a connection state in which the third dog clutch45is in the second distribution state and the three rotational elements included in the second planetary gear device25are integrally rotatable. This third mode is a mode in which the power distribution to the front wheels3and the rear wheels4is mechanically fixed (fixed distribution mode) since the rear wheel-side output shaft22and the transmitting unit26are engaged by the third dog clutch45in such a manner as to rotate integrally.

Furthermore, in each of the first mode, the second mode, and the third mode, the first planetary gear device24can be switched between a non-speed-changing state (Hi mode) and a speed-changing state (Lo mode). In a case of the non-speed-changing state, the first planetary gear device24is in a mode in which the three rotational elements including the first sun gear S1, the first carrier C1, and the first ring gear R1can be integrally rotated (Hi mode). Also, in a case of the speed-changing state, the first planetary gear device24is in a mode in which the first sun gear S1and the first ring gear R1can be rotated with the first ring gear R1being in a fixed state (Lo mode). That is, each of the first mode, the second mode, and the third mode described above includes a case of the Hi mode and a case of the Lo mode.

Also, in the third mode, the input shaft21is in a state of being directly coupled to the rear wheel-side output shaft22in a case of the Hi mode, and the input shaft21is in a state of being coupled to the first sun gear S1in a case of the Lo mode.

In such a manner, in the transfer12, switching among a plurality of driving states can be performed by the connection switching device40, the first planetary gear device24, and the second planetary gear device25. The plurality of driving states include a first driving state (Hi mode in the first mode), a second driving state (Lo mode in the first mode), a third driving state (Hi mode in the second mode), a fourth driving state (Lo mode in the second mode), a fifth driving state (Hi mode in the third mode), and a sixth driving state (Lo mode in the third mode).

Here, the first to sixth driving states will be described with reference toFIG. 2toFIG. 11. Note that the motor30is described as “MG”, the engine2is described as “ENG”, the first sun gear S1is described as “S1”, the first carrier C1is described as “C1”, the first ring gear R1is described as “R1”, the second dog clutch43is described as “CL1”, the second sun gear S2is described as “S2”, the second carrier C2is described as “C2”, the second ring gear R2is described as “R2”, and the third dog clutch45is described as “CL2” inFIG. 3,FIG. 4,FIG. 6,FIG. 7,FIG. 9, andFIG. 11.

First, the first driving state (case of the Hi mode in the first mode) will be described with reference toFIG. 2andFIG. 3. In the first driving state, the first planetary gear device24is in the non-speed-changing state in the two-wheel driving state in which the connection switching device40is in the non-distribution state and the power is transmitted only to the rear wheels4. Thus, in the first driving state, when the power of the motor30is transmitted to the rear wheels4, a rotation of the motor30is transmitted to the rear wheel-side output shaft22without a speed thereof being reduced by the transfer12as illustrated inFIG. 3.

As illustrated inFIG. 2, in a case where the transfer12is in the first driving state, the first dog clutch41is in the direct coupling state, the second dog clutch43is in the non-speed-changing state, and the third dog clutch45is in the non-distribution state. More specifically, the first switching sleeve46meshes with the input shaft21and the rear wheel-side output shaft22, whereby the input shaft21is directly coupled to the rear wheel-side output shaft22. The second switching sleeve47does not mesh with the fixing member20a. Also, when the first friction clutch42is released and the second friction clutch44is engaged, the first carrier C1and the first ring gear R1are coupled in such a manner as to rotate integrally in the first planetary gear device24. When the third switching sleeve48meshes with the fourth rotational member54and the fifth rotational member55, the second carrier C2and the second ring gear R2are coupled in such a manner as to rotate integrally in the second planetary gear device25.

In such a manner, since the input shaft21is directly coupled to the rear wheel-side output shaft22in the first driving state, the power of the engine2is transmitted to the rear wheel-side output shaft22without the first planetary gear device24and the second planetary gear device25. That is, a rotation of the input shaft21(rotation of the engine2) is transmitted to the rear wheel-side output shaft22with a speed thereof not being changed. Also, although the motor30is constantly connected to the rear wheel-side output shaft22via the first planetary gear device24and the second planetary gear device25, the first planetary gear device24and the second planetary gear device25are in the non-speed-changing state in the first driving state. Thus, in the first driving state, the six rotational elements included in the first planetary gear device24and the second planetary gear device25have the same rotational speed.

Next, the second driving state (case of Lo mode in the first mode) will be described with reference toFIG. 4. In the second driving state, the first planetary gear device24is in the speed-changing state in the two-wheel driving state in which the connection switching device40is in the non-distribution state and the power is transmitted only to the rear wheels4. Thus, in the second driving state, when the power of the motor30is transmitted to the rear wheels4, a rotation of the motor30is transmitted to the rear wheel-side output shaft22with a speed thereof being reduced by the first planetary gear device24as illustrated inFIG. 4.

In a case where the transfer12is in the second driving state, unlike the first driving state, the second dog clutch43is in the speed-changing state. That is, the second dog clutch43is engaged in a state in which the first friction clutch42is released and the second friction clutch44is released. Accordingly, the first ring gear R1can be mechanically fixed in the first planetary gear device24. Thus, power (motor torque) input into the first sun gear S1can be output from the first carrier C1in a state in which the three rotational elements included in the second planetary gear device25and the first carrier C1have the same rotational speed.

In such a manner, rear wheel-driving can be performed by the engine2and the motor30, and a speed reduction ratio of the motor30can be switched in the first driving state and the second driving state.

Next, the third driving state (case of Hi mode in the second mode) will be described with reference toFIG. 5andFIG. 6. In the third driving state, the first planetary gear device24is in the non-speed-changing state and the second planetary gear device25is in a state of being able to make a differential motion in the four-wheel driving state in which the connection switching device40is in the first distribution state.

As illustrated inFIG. 5, in a case where the transfer12is in the third driving state, the first dog clutch41is in the direct coupling state, the second dog clutch43is in the non-speed-changing state, and the third dog clutch45is in the first distribution state. More specifically, the first switching sleeve46meshes with the input shaft21and the rear wheel-side output shaft22. The second switching sleeve47does not mesh with the fixing member20a. Also, the first friction clutch42is released and the second friction clutch44is engaged. The third switching sleeve48meshes with the fifth rotational member55and the transmitting unit26. Accordingly, the three rotational elements can rotate integrally in the first planetary gear device24, and the second sun gear S2, the second carrier C2, and the second ring gear R2can make differential motions in the second planetary gear device25.

In such a manner, since the input shaft21is directly coupled to the rear wheel-side output shaft22in the third driving state, the power of the engine2is transmitted to the rear wheel-side output shaft22without the first planetary gear device24and the second planetary gear device25. That is, a rotation of the input shaft21(rotation of the engine2) is transmitted to the rear wheel-side output shaft22with a speed thereof not being changed. Also, since the second planetary gear device25is in a state of being able to make a differential motion, the power of the motor30is distributed and transmitted to the transmitting unit26and the rear wheel-side output shaft22via the first planetary gear device24and the second planetary gear device25. Thus, in the third driving state, it becomes possible to control the distribution of the power transmitted to the side of the front wheels and the side of the rear wheels by torque output from the motor30as illustrated inFIG. 6.

Next, the fourth driving state (case of Lo mode in the second mode) will be described with reference toFIG. 7. In the fourth driving state, the first planetary gear device24is in the speed-changing state and the second planetary gear device25is in a state of being able to make a differential motion in the four-wheel driving state in which the connection switching device40is in the first distribution state. Thus, in the fourth driving state, when the power of the engine2and the power of the motor30are transmitted to the front wheels3and the rear wheels4, a rotation of the engine2is transmitted to the rear wheel-side output shaft22with the speed thereof not being reduced by the transfer12, and a rotation of the motor30is transmitted to the rear wheel-side output shaft22with the speed thereof being reduced by the first planetary gear device24as illustrated inFIG. 7. In such a manner, in a case where the transfer12is in the fourth driving state, unlike the third driving state, the second dog clutch43is engaged in a state in which the second friction clutch44is released. Accordingly, the first ring gear R1can be mechanically fixed in the first planetary gear device24. Thus, the power (motor torque) input into the first sun gear S1can be output from the first carrier C1in a state in which differential motions with the three rotational elements included in the second planetary gear device25can be made.

In such a manner, in the third driving state and the fourth driving state, front/rear distribution control can be performed, and a speed reduction ratio of the motor30can be switched.

Next, the fifth driving state (case of Hi mode in the third mode) will be described with reference toFIG. 8andFIG. 9. In the fifth driving state, in the four-wheel driving state in which the connection switching device40is in the second distribution state, the first planetary gear device24is in the non-speed-changing state and the second planetary gear device25is in an integrally rotating state. In the fifth driving state, a fixed distribution 4WD mode in which a rotation of the engine2is output with a speed thereof not being reduced by the transfer12and a power distribution of the front and rear wheels is mechanically fixed is possible.

As illustrated inFIG. 8, in a case where the transfer12is in the fifth driving state, the first dog clutch41is in the direct coupling state, the second dog clutch43is in the non-speed-changing state, and the third dog clutch45is in the second distribution state. More specifically, the first switching sleeve46meshes with the input shaft21and the rear wheel-side output shaft22. The second switching sleeve47does not mesh with the fixing member20a. Also, the first friction clutch42is released and the second friction clutch44is engaged. When the third switching sleeve48meshes with the fourth rotational member54, the fifth rotational member55, and the transmitting unit26, the second ring gear R2and the second carrier C2are coupled to each other in such a manner as to rotate integrally in the second planetary gear device25, and the second ring gear R2and the second carrier C2are coupled to the transmitting unit26.

In such a manner, since the input shaft21is directly coupled to the rear wheel-side output shaft22in the fifth driving state, the power of the engine2is transmitted to the rear wheel-side output shaft22without the first planetary gear device24and the second planetary gear device25. That is, a rotation of the input shaft21(rotation of the engine2) is transmitted to the rear wheel-side output shaft22with a speed thereof not being changed. Also, since the first planetary gear device24and the second planetary gear device25are in the non-speed-changing state in the fifth driving state, when the power of the motor30is transmitted to the rear wheel-side output shaft22and the front wheel-side output shaft23, the six rotational elements included in the first planetary gear device24and the second planetary gear device25have the same rotational speed as illustrated inFIG. 9.

Next, the sixth driving state (case of Lo mode in the third mode) will be described with reference toFIG. 10andFIG. 11. In the sixth driving state, in the four-wheel driving state in which the connection switching device40is in the second distribution state, the first planetary gear device24is in the speed-changing state and the second planetary gear device25is in the integrally rotating state. In the sixth driving state, a rotation of the engine2can be output with the speed thereof being changed (reduced) by the first planetary gear device24. Furthermore, in the sixth driving state, the rear wheels4can be driven by the power of the motor30even in the Lo mode.

As illustrated inFIG. 10, in a case where the transfer12is in the sixth driving state, the first dog clutch41is in the second input state, the second dog clutch43is in the speed-changing state, and the third dog clutch45is in the second distribution state. More specifically, the first switching sleeve46meshes with the input shaft21and the first rotational member51. The second switching sleeve47meshes with the fixing member20a. Also, the first friction clutch42is released and the second friction clutch44is released. The third switching sleeve48meshes with the fourth rotational member54, the fifth rotational member55, and the transmitting unit26. As a result, the second ring gear R2and the second carrier C2are coupled to each other in such a manner as to rotate integrally in the second planetary gear device25, and the second ring gear R2and the second carrier C2are coupled to the transmitting unit26. Furthermore, in the first planetary gear device24, power input into the first sun gear S1can be output from the first carrier C1in a state in which the first ring gear R1is mechanically fixed.

In such a manner, since the input shaft21is coupled to the first rotational member51in the sixth driving state, the power of the engine2is transmitted to the rear wheel-side output shaft22via the first planetary gear device24and the second planetary gear device25. Also, since the first planetary gear device24is in the speed-changing state, a rotation of the input shaft21(rotation of the engine2) is transmitted to the rear wheel-side output shaft22with the speed thereof being changed by the first planetary gear device24. Thus, in the sixth driving state, when the power of the motor30is transmitted to the rear wheel-side output shaft22, a rotation of the motor30can be transmitted to the rear wheel-side output shaft22with the speed thereof being changed by the first planetary gear device24as illustrated inFIG. 11.

As described above, with respect to the three rotational elements included in the first planetary gear device24, the first ring gear R1fixed to the fixing member20aand the first sun gear S1to which the motor30is constantly connected are different rotational elements. Thus, the power of the motor30can be transmitted to the rear wheel-side output shaft22even in the speed-changing state in which the first ring gear R1is fixed. As a result, in a case where the first planetary gear device24is in the speed-changing state, a rotation of the motor30can be output with the speed thereof being changed by the first planetary gear device24, and the power of the engine2can be transmitted to the drive wheels with the power of the motor30being added thereto.

Also, in the connection state in which the input shaft21is directly coupled to the rear wheel-side output shaft22, a speed reduction ratio applied to the motor30can be arbitrarily switched by the first planetary gear device24.

Note that it is possible to configure a modification example of the above-described first embodiment.

For example, as illustrated inFIG. 12, in a transfer12of a modification example, a connection switching device40includes a fourth dog clutch49that selectively fixes a second ring gear R2of a second planetary gear device25to a fixing member20a. The fourth dog clutch49has a switching sleeve as a transmission switching member. The switching sleeve of the fourth dog clutch49has a first gear tooth49athat meshes with a gear tooth55aof a fifth rotational member55, and a second gear tooth49bthat meshes with the fixing member20a. The second ring gear R2is fixed when the fourth dog clutch49is coupled to the fixing member20a, and the second ring gear R2functions as a reaction force element in the second planetary gear device25. In a case where the fourth dog clutch49is engaged in such a manner, a third switching sleeve48couples a second carrier C2and a transmitting unit26. As a result, the second planetary gear device25becomes a speed-changing state, and a rotation of a second sun gear S2can be output from the second carrier C2with a speed thereof being changed. Also, in a case where the third switching sleeve48meshes with a fourth rotational member54and a fifth rotational member55, the fourth dog clutch49is in a released state.

Furthermore, a driving state illustrated inFIG. 12is a seventh driving state in which a first planetary gear device24is in the non-speed-changing state and the second planetary gear device25is in the speed-changing state in a four-wheel driving state in which the connection switching device40is in a distribution state. In the seventh driving state, a rotation of an engine2is output with a speed thereof not being reduced by the transfer12, a power distribution of front and rear wheels is mechanically fixed, and a rotation of a motor30is output with a speed thereof being changed by the second planetary gear device25. Power of the engine2is directly transmitted from an input shaft21to a rear wheel-side output shaft22. On the one hand, power of the motor30is transmitted to the second planetary gear device25in the speed-changing state via the first planetary gear device24in the non-speed-changing state. This second planetary gear device25is in a state in which the second ring gear R2functions as a reaction force element by mechanical force.

In such a manner, as a modification example of the transfer12, the second planetary gear device25may be configured to switch between the speed-changing state and the non-speed-changing state. Accordingly, when an output from the first planetary gear device24is transmitted to the rear wheel-side output shaft22in a driving state other than the above-described third driving state and fourth driving state, speed reduction can be acquired in the second planetary gear device25in addition to a speed reduction ratio acquired in the first planetary gear device24.

Also, as another modification example, in a case where a first planetary gear device24is a single pinion type, a combination of an input element, an output element, and a reaction force element is not limited to that of the above-described first embodiment. As an example, a first sun gear S1may be a first rotational element (input element), a first carrier C1may be a third rotational element (reaction force element), and a first ring gear R1may be a second rotational element (output element). Alternatively, a first sun gear S1may be a third rotational element (reaction force element), a first carrier C1may be a second rotational element (output element), and a first ring gear R1may be a first rotational element (input element). Alternatively, a first sun gear S1may be a second rotational element (output element), a first carrier C1may be a third rotational element (reaction force element), and a first ring gear R1may be a first rotational element (input element). In these cases, a first rotational member51is integrally attached to a first rotational element that functions as an input element, and a second rotational member52is attached to a second rotational element, which functions as an output element, in such a manner as to rotate integrally therewith. Also, a first friction clutch42and a second dog clutch43are configured to selectively fix a third rotational element to a fixing member20a.

Also, as another modification example, a first planetary gear device24may include a double pinion-type planetary gear device. In a case where the first planetary gear device24is the double pinion type, a first sun gear S1can be a first rotational element (input element), a first ring gear R1can be a second rotational element (output element), and a first carrier C1can be a third rotational element (reaction force element). Alternatively, a first sun gear S1may be a first rotational element (input element), a first ring gear R1may be a third rotational element (reaction force element), and a first carrier C1may be a second rotational element (output element). Alternatively, a first sun gear S1may be a third rotational element (reaction force element), a first ring gear R1may be a second rotational element (output element), and a first carrier C1may be a first rotational element (input element). Alternatively, a first sun gear S1may be a second rotational element (output element), a first ring gear R1may be a third rotational element (reaction force element), and a first carrier C1may be a first rotational element (input element).

Also, as another modification example, in a case where a second planetary gear device25is a single pinion type, a connection portion52bof a second rotational member52may be coupled to a second ring gear R2. That is, in a case where the second planetary gear device25is the single pinion type, the second ring gear R2may be a fourth rotational element (input element), a second carrier C2may be a fifth rotational element (output element), and a second sun gear S2may be a sixth rotational element. In this case, a fifth rotational member55is attached to the second sun gear S2in such a manner as to rotate integrally. The second sun gear S2is selectively coupled to a transmitting unit26by a third dog clutch45. A third switching sleeve48meshes with a first gear tooth54aof a fourth rotational member54that rotates integrally with the second carrier C2, a gear tooth55aof the fifth rotational member55that rotates integrally with the second sun gear S2, and a first gear tooth26aof the transmitting unit26.

Also, as another modification example, a second planetary gear device25may include a double pinion-type planetary gear device. In a case where the second planetary gear device25is the double pinion type, a second sun gear S2can be a fourth rotational element (input element), a second ring gear R2can be a fifth rotational element (output element), and a second carrier C2can be a sixth rotational element. In this case, a fourth rotational member54and a rear wheel-side output shaft22are coupled to the second ring gear R2in such a manner as to rotate integrally therewith. A fifth rotational member55is coupled to the second carrier C2in such a manner as to rotate integrally.

Also, as another modification example, in a case where a second planetary gear device25is a double pinion type, a connection portion52bof a second rotational member52may be coupled to a second carrier C2. That is, in a case where the second planetary gear device25is the double pinion type, the second carrier C2may be a fourth rotational element (input element), a second ring gear R2may be a fifth rotational element (output element), and a second sun gear S2may be a sixth rotational element.

Furthermore, in the above-described first embodiment and each modification example, an engagement device included in a connection switching device40is not limited to the above-described combination of a dog clutch and a friction clutch. That is, a connection switching device40only needs to realize each kind of required connection, and the number and form (such as dog clutch and friction clutch) thereof can be freely selected. For example, a first dog clutch41and a third dog clutch45may be friction clutches. A second friction clutch44may be a dog clutch. Also, a second dog clutch43may not be provided.

Also, a transfer12may select a connection state, in which a relationship between a rear wheel-side output shaft22and a front wheel-side output shaft23is switched, according to front wheel driving force required for torque splitting, motor characteristics and the like. That is, application to a vehicle in which front wheels3are main drive wheels and rear wheels4are auxiliary drive wheels is also possible. In this case, the above-described rear wheel-side output shaft22becomes an output shaft for the front wheels, and the above-described front wheel-side output shaft23becomes an output shaft for the rear wheels.

Also, when a first planetary gear device24and a second planetary gear device25are in an integrally rotating state, a combination of two rotational elements coupled to each other is not specifically limited. For example, in the first planetary gear device24, a first sun gear S1and a first carrier C1may be coupled, or all three rotational elements may be coupled. Also, in the second planetary gear device25, a second sun gear S2and a second ring gear R2may be coupled, or all three rotational elements may be coupled.

Also, in a case where a first planetary gear device24is in a speed-changing state, a combination of rotational elements only needs to be a combination in which a speed of an output can be reduced (changed) with respect to an input. Thus, a speed reduction ratio in the first planetary gear device24and a rotational direction of an output element are not specifically limited. Note that in the above-described first embodiment, a case where a value of a speed reduction ratio (transmission gear ratio) becomes the largest and a rotational direction of an input element and a rotational direction of an output element do not change has been described with a first sun gear S1as the input element, a first carrier C1as the output element, and a first ring gear R1as a reaction force element.

Also, an arrangement of a motor30and presence or absence of speed reduction at the time of connection (such as reduction gear31), addition of a transmission mechanism to the motor30and the like are not specifically limited. Selection can be made arbitrarily according to specifications of a vehicle1and a motor30.

Next, a transfer12of a second embodiment will be described with reference toFIG. 13. In the second embodiment, unlike the first embodiment, an input switching unit includes a first dog clutch41and a fifth dog clutch50. Note that in the description of the second embodiment, the same reference signs are used for configurations similar to those of the first embodiment, and a description thereof is omitted.

As illustrated inFIG. 13, a connection switching device40in the second embodiment includes, as engagement devices to function as input switching units, two clutches that are a first dog clutch41and a fifth dog clutch50. Also, in a second planetary gear device25, a second carrier C2is arranged in such a manner as to be rotatable relative to a rear wheel-side output shaft22. An input shaft21and the second carrier C2are selectively coupled to the rear wheel-side output shaft22by the fifth dog clutch50. This fifth dog clutch50switches a connection relationship among the input shaft21, the rear wheel-side output shaft22, the second carrier C2, and a transmitting unit26.

The first dog clutch41is switched between a second input state in which the input shaft21is coupled to a first sun gear S1and a disconnection state in which the input shaft21is not coupled to the first sun gear S1. When the first dog clutch41becomes the second input state, a first gear tooth46aof a first switching sleeve46meshes with a first gear tooth21aof the input shaft21, and a second gear tooth46bthereof meshes with a gear tooth51aof a first rotational member51. In a case where the first dog clutch41is in the disconnection state, the first switching sleeve46does not mesh with the first rotational member51.

The fifth dog clutch50is a meshing engagement device that has a switching sleeve and that selectively couples the input shaft21to the rear wheel-side output shaft22. The switching sleeve included in the fifth dog clutch50includes a first gear tooth50athat meshes with a second gear tooth21bof the input shaft21and a gear tooth22aof the rear wheel-side output shaft22, and a second gear tooth50bthat meshes with a second gear tooth54bof a fourth rotational member54or a second gear tooth26bof the transmitting unit26.

The fifth dog clutch50is switched between a first input state (direct coupling state) in which the input shaft21is directly coupled to the rear wheel-side output shaft22and the second carrier C2and the rear wheel-side output shaft22are coupled, and a distribution state in which the rear wheel-side output shaft22and the transmitting unit26are coupled. When the fifth dog clutch50is in the first input state, the first gear tooth50ameshes with the second gear tooth21bof the input shaft21and the gear tooth22aof the rear wheel-side output shaft22, and the second gear tooth50bmeshes with the second gear teeth54bof the fourth rotational member54. In a case where the fifth dog clutch50is in the distribution state, the first gear tooth50ameshes with the gear tooth22aof the rear wheel-side output shaft22, and the second gear tooth50bmeshes with the second gear tooth26bof the transmitting unit26.

Also, a driving state illustrated inFIG. 13is a sixth driving state. In this sixth driving state, the first dog clutch41is in the second input state, a first planetary gear device24is in a speed-changing state, the second planetary gear device25is in an integrally rotating state, a third dog clutch45is in a second distribution state, and the fifth dog clutch50is in the distribution state.

Next, a transfer12of a third embodiment will be described with reference toFIG. 14. In the third embodiment, unlike the first embodiment, a second ring gear R2of a second planetary gear device25is coupled to a rear wheel-side output shaft22in such a manner as to integrally rotate therewith. Note that in the description of the second embodiment, the same reference signs are used for configurations similar to those of the first embodiment, and a description thereof is omitted.

As illustrated inFIG. 14, in the transfer12in the third embodiment, a transmitting unit26, a drive gear27, and a front-wheel drive chain29are arranged between a first planetary gear device24and the second planetary gear device25arranged side by side in an axial direction. A third switching sleeve48of a third dog clutch45includes a first gear tooth48athat meshes with a gear tooth55aof a fifth rotational member55, a second gear tooth48bthat meshes with a first gear tooth26aof the transmitting unit26, and a third gear tooth48cthat meshes with a first gear tooth54aof a fourth rotational member54.

The third switching sleeve48is switched between a non-distribution state, a first distribution state, and a second distribution state. In the non-distribution state, the second gear tooth48bof the third switching sleeve48meshes with the fourth rotational member54, and the third gear tooth48cmeshes with the fifth rotational member55. As illustrated inFIG. 14, the first distribution state is a state in which the second carrier C2and the second ring gear R2can make differential motions and the second carrier C2is coupled to the transmitting unit26. In the first distribution state, the second gear tooth48bmeshes with the transmitting unit26and the third gear tooth48cmeshes with the fourth rotational member54in a state in which the first gear tooth48aof the third switching sleeve48does not mesh with the fifth rotational member55. In the second distribution state, the first gear tooth48aof the third switching sleeve48meshes with the fifth rotational member55, the second gear tooth48bmeshes with the transmitting unit26, and the third gear tooth48cmeshes with the fourth rotational member54.

In the present disclosure, in a transfer including a motor, a first planetary gear device, and a second planetary gear device, a third rotational element fixed to a fixing member and a first rotational element to which power of the motor is input among three rotational elements included in the first planetary gear device are different rotational elements. Thus, when the first planetary gear device is made to function as a transmission unit in a state in which one rotational element is fixed to a fixing member, power can be transmitted from the motor to drive wheels via this first planetary gear device.

According to an embodiment, in a transfer including a motor, a first planetary gear device, and a second planetary gear device, a third rotational element fixed to a fixing member and a first rotational element to which power of the motor is input among three rotational elements included in the first planetary gear device are different rotational elements. Thus, when the first planetary gear device is made to function as a transmission unit in a state in which one rotational element is fixed to a fixing member, power can be transmitted from the motor to drive wheels via this first planetary gear device.

According to an embodiment, when main drive wheels are driven by the power of the motor, a rotation of the motor can be output with a speed thereof being changed by the first planetary gear device.

According to an embodiment, when the power from the first power source and the power of the motor are transmitted to the main drive wheels and the auxiliary drive wheels, a rotation of the input shaft and a rotation of the motor can be output with speeds thereof being changed by the first planetary gear device.

According to an embodiment, it is also possible to cause the first planetary gear device to function as a transmission unit in a first mode and a second mode. As a result, when the main drive wheels are driven by the power of the motor in a case of the first mode and the second mode, a rotation of the motor can be output with a speed thereof being changed by the first planetary gear device.

According to an embodiment, in a case where a mode becomes the first mode and the main drive wheels are driven, the power from the first power source can be directly transmitted to the first output shaft, and a rotation of the motor can be output with a speed thereof being changed by the first planetary gear device when the power of the motor is transmitted to the first output shaft.

According to an embodiment, in a case where a mode is in the second mode and the main drive wheels and the auxiliary drive wheels are driven, the power from the first power source can be directly transmitted to the first output shaft, and a rotation of the motor can be output with a speed thereof being changed by the first planetary gear device when the power of the motor is transmitted to the first output shaft and the second output shaft.

According to an embodiment, it is possible to cause the first planetary gear device to function as a transmission unit by bringing the first engagement device into the engaged state. Also, by bringing the second engagement device into the engaged state, it is possible to perform switching into a state in which the rotational elements of the first planetary gear device rotate integrally.

According to an embodiment, the distribution switching member is switched among the first distribution state, the second distribution state, and the non-distribution state, whereby the transfer can be switched to a plurality of driving states.

According to an embodiment, in a case of the first mode and the third mode, it is possible to cause the second planetary gear device to function as a transmission unit by bringing the third engagement device into the engaged state. As a result, in a case where the power of the first power source is transmitted to the drive wheels in the third mode, a rotation of the input shaft can be output with a speed thereof being changed by the first planetary gear device and the second planetary gear device.

According to an embodiment, a connection destination of the input shaft can be selectively switched by the input switching member and the first distribution switching member. Also, a case where power can be transmitted to the transmitting unit by first distribution switching member and the second distribution switching member and a case where the power cannot be transmitted can be switched.

According to an embodiment, in a case of the first mode, the power of the first power source can be transmitted to the main drive wheels in a state in which the input shaft is directly coupled to the first output shaft by the first distribution switching member.

According to an embodiment, in a case of the second mode, in a state in which the input shaft is directly coupled to the first output shaft by the first distribution switching member, the power of the motor is transmitted to the second planetary gear device that is in a state of being able to make a differential motion, whereby it is possible to control a distribution of the power transmitted to the main drive wheels and the auxiliary drive wheels.

According to an embodiment, in a case of the third mode, the second distribution switching member brings the second planetary gear device into an integrally rotatable state.