JP3040052B2 - Transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for a four-wheel drive vehicle, and more particularly, to a transfer device in which a multi-plate clutch for transmitting drive torque by an actuator driven by a motor is connected and disconnected.

[0002]

2. Description of the Related Art As a transfer device for a four-wheel drive vehicle,
Two-wheel drive (2W
D) and four-wheel drive (4WD).
A method of controlling a multi-plate clutch is disclosed in Japanese Patent Application Laid-Open No. 1-141125.
There is a hydraulically controlled vehicle driving force distribution clutch device that controls the hydraulic pressure supplied to a piston that operates based on the hydraulic pressure to interrupt the driving torque as disclosed in Japanese Patent Application Publication No. A drive transfer device was filed by the present applicant on October 17, 1990 as a utility model registration application (Japanese Utility Model Application No. 2-108607).

FIG. 12 shows a conventional transfer device, in which a transfer motor 12 is connected to a prime mover (not shown) and is non-coupled to and supported on the outer periphery of an input shaft 1 to which a driving torque is input. Drive sprocket 2
And a plurality of clutch disks 3A coupled to the drive sprocket 2, a plurality of pressure plates 3B for transmitting drive torque by making surface contact with the clutch disks 3A, a pressure plate 3B and the clutch disks 3A. One end is connected to the transfer case 12 by a clutch housing 5 provided continuously with the rear wheel output shaft 4 provided on the shaft 1, a pressing member 6 pressing the pressure plate 3B against the clutch disk 3A, and a support portion 7B. It has a lever 7 which is supported and whose movable end is pressed by a clutch actuator 8, and a needle bearing 7A is provided between the pressing member 6 and the lever 7.

The drive sprocket 2 is connected via a chain 9 to a driven sprocket 11, which is provided in connection with a front wheel output shaft 10, and has an input shaft 1, a drive sprocket 2, a rear wheel output shaft 4, and a push. The member 6 and the front wheel output shaft 10 are supported by the transfer case 12 by bearings 13.

The clutch actuator 8 has a guide 8A fixed to the transfer case 12, and a hydraulic piston 8C housed in the guide 8A and pressing the movable end of the lever 7 based on the hydraulic pressure supplied to the hydraulic chamber 8B. The hydraulic chamber 8B is connected to a pipe 14 for supplying the hydraulic pressure generated in the hydraulic unit 15.

The hydraulic unit 15 generates a hydraulic pressure,
For example, a selected 2WD mode or 4WD mode includes a pressurizing means constituted by a motor, an oil pump and the like, and a valve device such as a solenoid valve for supplying a hydraulic pressure generated by the pressurizing means by opening and closing a valve mechanism. Is connected to a controller 16 that outputs a hydraulic pressure supply signal based on the

In the above transfer apparatus, 2WD
When switching from the mode to the 4WD mode is selected,
The controller 16 outputs a hydraulic pressure supply signal to the hydraulic pressure unit 15, and the hydraulic pressure unit 15 supplies a hydraulic pressure to the hydraulic pressure chamber 8B based on the hydraulic pressure supply signal.

When the internal pressure of the hydraulic chamber 8B increases based on the supply of hydraulic pressure, the hydraulic piston 8C moves in the direction of the lever 7,
The lever 7 is provided with a pressing member 6 via a needle bearing 7A.
Press. Due to this pressing, the pressure plate 3B accommodated in the clutch housing 5 is brought into surface contact with the clutch disc 3A and coupled thereto. As a result, the driving torque is transmitted to the drive sprocket 2 via the multi-plate clutch. The driving torque transmitted to the drive sprocket 2 is transmitted to the driven sprocket 11 via the chain 9 to drive the front wheel output shaft 10.

Next, when the switching from the 4WD mode to the 2WD mode is selected, the controller 16 stops the output of the hydraulic supply signal to the hydraulic unit 15, and the controller 16 stops outputting the hydraulic supply signal. When the internal pressure of the hydraulic chamber 8B decreases, the pressing force of the hydraulic piston 8C that has pressed the lever 7 decreases.

For this reason, the engagement of the multi-plate clutch is released by releasing the pressing member 6 which has pressed the pressure plate 3B against the clutch disk 3A by the repulsive force of the spring 6A. Therefore, the driving torque input to the input shaft 1 is transmitted to the rear wheel output shaft 4.

[0011]

However, according to the conventional transfer device, since the multiple disc clutch is intermittently controlled by controlling the hydraulic pressure, a hydraulic source and a valve mechanism for supplying a predetermined hydraulic pressure are provided. A hydraulic circuit is required and the configuration becomes complicated. In addition, when the hydraulic pressure is generated and controlled by an electric mechanism, there is a problem that the time for energizing the hydraulic pressure source and the valve mechanism is long, and the power consumption is large. Furthermore, since the viscosity of the hydraulic oil changes due to a change in temperature, there is an inconvenience that the responsiveness when switching between 2WD and 4WD is not constant. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a transfer device which can be formed in a simple and compact structure, consumes less power during operation, and has excellent responsiveness.

[0012]

SUMMARY OF THE INVENTION The present invention provides a drive mode between two-wheel drive and rigid four-wheel drive in order to provide a simple and compact structure, low power consumption during operation, and excellent responsiveness. Control that outputs a rotation signal according to the distribution ratio of drive torque transmitted to the rear wheels or front wheels according to the
Circuit, a linear motor between the supplied drive current and the generated rotational torque, an electric motor that generates a rotational torque according to the drive current based on the rotational signal input from the control circuit, and an input from the electric motor. Provided is a transfer device having a displacement member that moves forward or backward based on a rotational torque to push or release a multi-plate clutch to a pressing unit.

[0013]

When the control means outputs a rotation signal to the motor based on the selected drive mode (4WD, 2WD), a rotation torque corresponding to the control signal is generated in the motor. This rotational torque has a linearity with the supplied drive current, and is converted into a linear motion in a direction in which the pressing means is pressed and released by the rotary motion converting means which is screw-engaged with the displacement member. . When each drive mode is selected, the amount of movement of the displacement member is appropriately set based on the rotational torque of the motor, so that a predetermined pressing force is applied to the pressing means, and as a result, the multi-plate clutch has a coupling degree corresponding to the drive mode. In combination, the drive torque is distributed to the front and rear wheels at a predetermined distribution ratio. And control means multi-plate clutch is coupled stops output of the rotation signal, the braking means brakes the rotation shaft of the motor, and holds on the basis of the stop of the rotation signal.

[0014]

Embodiment 1 The transfer device of the present invention will be described in detail below with reference to embodiments. Portions having the same configuration and function as those of the related art are denoted by the same reference numerals and symbols, and duplicate description will be omitted.

FIG. 1 shows an embodiment of the transfer apparatus according to the present invention. A transfer actuator 12 has a clutch actuator 17 for pressing the lever 7 inside the transfer case 12.

The clutch actuator 17 is a guide 1
7A nut 17B, spring 17C, piston 17
The guide 17A has a stopper 17a at one end thereof for preventing the nut 17B from falling off.
The spring 17C is held between the nut 17B and the piston 17D. The nut 17B is threadedly engaged with a feed screw 18 that has passed through the transfer case 12 and is taken out to the outside, and moves in the length direction of the guide 17A based on the rotation of the feed screw 18. The feed screw 18 is rotatably supported at one end of a guide 17A by a bearing 17b, and further has a reduction gear 19A at the shaft end taken out.

The reduction gear 19A is connected to the transfer case 1
2 is engaged with a reduction gear 19 </ b> B fixed to a rotation shaft of a motor 20 provided outside the transmission gear 2, and transmits the rotation torque of the motor 20 to the feed screw 18. The motor 20 is provided with a brake 20A that brakes and holds the rotation of the rotating shaft. Motor 20 and brake 20A are 2WD or 4WD
It is connected to a controller 21 that outputs a rotation signal in the forward or reverse direction according to the mode.

The brake 20A is configured to be excited when the controller 21 is outputting a rotation signal to the motor 20, and to release the holding of the rotating shaft of the motor 20.

When the operator operates a transfer select lever (not shown), the controller 21 distributes the driving torque to the front and rear wheels at a predetermined rate based on the selected position. A rotation signal is output to 20A. The motor 20 is rotated by a rotation signal generated based on the operation mode and the drive torque distribution, and the reduction gears 19A and 19B and the feed screw 18 are rotated.
The nut 17B is moved via. The brake 20A releases the holding of the rotating shaft in response to the input of the rotation signal.

When the distribution of the driving torque is set, the controller 21 stops outputting the rotation signal. When the rotation signal is stopped, the motor 20 is turned off. On the other hand, the brake 20A is de-energized by the stop of the rotation signal, and as a result, the rotation shaft of the motor 20 is braked and held.

The operation will be described below.

When switching from the 2WD mode to the 4WD mode is selected by an operator operating a transfer select lever (not shown), the controller 21 outputs a rotation signal to the motor 20 and the brake 20A.

The brake 20A is excited based on the input of the rotation signal, and releases the holding of the motor rotation shaft. Motor 2
0 rotates based on the input of the rotation signal, and the reduction gear 19B
And 19A, the rotational torque reduced to a predetermined reduction ratio is transmitted to the feed screw 18.

Here, assuming that the rotation direction of the feed screw 18 transmitted from the motor 20 is the normal rotation direction, the nut 17
B is the piston 1 driven by the forward rotation of the feed screw 18.
Move in 7D direction.

Based on the movement of the nut 17B, the spring 17C is pressed against the piston 17D,
7D is a pressure plate 3 housed in the housing 5 by moving the pressing member 6 via the lever 7.
B and the clutch disk 3A are coupled, and the driving torque is transmitted to the front wheel output shaft 10 via the chain 9.

When the driving torque is distributed to the front and rear wheels by the engagement of the clutch, the controller 21 stops outputting the rotation signal, and the motor 20 is turned off. The brake 20A is de-energized by the stop of the rotation signal, and holds and fixes the rotating shaft of the motor 20.

Through the above process, the mode is changed from 2WD mode to 4WD mode.
When the switching operation to the mode is completed, the piston 17D
Has a spring 1 held by a nut 17B.
The engagement of the clutch is maintained by the urging force of 7C. The urging force of the spring 17C is applied to the nut 1 when the clutch is engaged.
It is generated based on the pressing amount of the spring 17C pressed by 7B.

FIG. 2 is a diagram showing the relationship between the current supplied to the motor 20 and the generated motor torque. The motor torque linearly increases based on the current supplied to the motor 20. Since the motor torque is converted into a pressing amount for pressing the nut 17B screw-engaged with the feed screw 18 against the spring 17C, the motor torque is controlled by detecting a current supplied to the motor, The degree of coupling of the clutch can be changed according to the drive mode .

FIG. 3 shows a configuration of a current detection circuit for detecting a current supplied to the motor 20, and a power supply 23 is provided with a switch for reversing the rotation of the motor 20 in the forward or reverse direction according to the drive mode. Circuit 24 is connected, and the switching circuit 24 is connected to the motor coil 20a.
It is connected to the. The motor coil 20a has a detection resistor 25
And is connected to a detection circuit 26 which detects the supplied current while being fixed to the ground potential.

Accordingly, the motor torque required for coupling the clutch is set in consideration of the pitch of the feed screw 18 threadedly engaged with the nut 17B and the spring rate of the spring 17C, and the current value for generating the set motor torque is set. When the output of the rotation signal is detected, the clutch actuator 17 can be operated in a short time with low power consumption.

On the other hand, when the clutch actuator 17 is not operated, a constant pressing force is generated on the piston 17D by the urging force of the spring 17C incorporated in the guide 17A, so that the selected 2WD or 4WD drive mode is set. Will be maintained.

Next, the clutch actuator 1 described above is used.
7, the driving torque distributed to the front and rear wheels is set to a weak 4WD mode, an intermediate 4WD mode, and a rigid 4WD mode.
The step-by-step control process will be described.

FIG. 4 shows the position of the nut 17B in the clutch actuator 17 in each mode.
In the WD mode, (b) to (d) show a state in which the 4WD mode is selected.

The motor 20 rotates based on the 4WD mode selected by the operator, and the reduction gears 19A, 19B
, The feed screw 18 moves the nut 17B. The moving amount of the nut 17B is set to the weak 4WD mode, the intermediate 4WD.
By changing the mode and the rigid 4WD mode, a coupling force of the clutch is generated based on the pressing amount L of the spring 17C.

[0035] FIG. 4 (b), the pressing amount L ₁ is given to the nut 17B by the feed screw 18, showing the state of being set to the weak 4WD mode. Here, the weak 4WD, wet road surface, in the snow road performs safety of the vehicle (slip), a driving torque distribution to the front and rear wheels to the extent that the dry road surface without causing a tight corner phenomenon, the driving mode If it runs at, it can respond to various road surface conditions.

[0036] FIG. 4 (c), the pressing amount L ₂ is given to the nut 17B by the feed screw 18, showing the state of being set to an intermediate 4WD mode. Pressure plate 3B by arbitrarily changing the pressing amount L ₂ of the nut 17B
The amount of slip generated on the contact surface between the clutch disk 3A and the clutch disk 3A (both not shown) changes, and the drive torque distribution to the front and rear wheels can be set to an arbitrary value.

[0037] FIG. 4 (d), the pressing amount L ₃ is given to the nut 17B by the feed screw 18, showing a state that is set in rigid 4WD mode. In the rigid 4WD mode, since a slip does not occur between the pressure plate 3B and the clutch disk 3A (both not shown), a preset drive torque is transmitted to the front and rear wheels. The relationship among the pressing amounts L ₁ , L ₂ , and L ₃ of the nut 17B in the weak 4WD mode, the intermediate 4WD mode, and the rigid 4WD mode is L ₁ <L ₂ <L ₃ .

FIG. 5 shows the pressing amount L _{1 of} the nut 17B,
FIG. 9 is a diagram illustrating the relationship between the transmission torque of the multi-plate clutch and the front and rear wheel differential rotation in the weak 4WD mode, the intermediate 4WD mode, and the rigid 4WD mode set based on L ₂ and L ₃ . The distribution ratio of the driving torque to the front and rear wheels in each 4WD mode can be arbitrarily set as needed.

Also, the operator changes the mode from 4WD mode to 2
When the mode is switched to the WD mode, the controller 2
Numeral 1 outputs to the motor 20 and the brake 20A a rotation signal in a rotation direction that is reversed from that at the time of switching from the 2WD mode to the 4WD mode described above.

The brake 20A is excited based on the input of the rotation signal in the same manner as when the 4WD mode is selected, and releases the restriction on the motor rotation shaft. The motor 20 rotates in a direction reverse to the above-described normal rotation direction based on the input of the rotation signal, and transmits the rotation torque reduced to a predetermined reduction ratio to the feed screw 18 via the reduction gears 19B and 19A.

The rotation of the feed screw 18 causes the nut 17B to move in the direction of the stopper 17a, whereby the spring 17C compressed between the nut 17B and the piston 17D is released, and the urging force is weakened. Is reduced, and the coupling of the clutch is released.

When the setting operation of the 2WD mode is completed, the controller 21 stops outputting the rotation signal, and
Is in a non-energized state. The brake 20A is de-energized by stopping the rotation signal, and brakes and holds the rotating shaft of the motor 20.

[0043]

Embodiment 2 FIG. 6 shows a second embodiment of the transfer apparatus of the present invention.
FIG. 4 is an explanatory view showing the embodiment, in which a feed screw 18 provided with a reduction gear 19A has a bearing 17b, one end of which is supported by the transfer case 12 and the other end of which is supported by the guide 17A, and a nut 17B inserted into the guide 17A.
And screw engagement.

A plurality of springs 17E are inserted between the nut 17B and the piston 17D. The springs 17E are provided so as to penetrate through a buried portion of a bearing 17b for supporting the feed screw 18.

The rotational force based on the rotation of the motor 20 is transmitted to the feed screw 18 via the reduction gears 19A and 19B. The feed screw 18 moves the nut 17B engaged with the screw in the length direction of the guide 17A according to the rotation direction.

Here, as in the first embodiment, it is assumed that the rotation of the feed screw 18 for moving the nut 17B to compress the spring 17E is the forward rotation direction.

When the feed screw 18 rotates in the normal rotation direction due to the rotation of the motor 20, the plurality of springs 17E are compressed by the nut 17B and pressed against the piston 17D, thereby generating a pressing force on the lever 7 in contact with the piston 17D. Is transmitted to the pressing member 6 via the needle bearing 7A.

With this pressing force, the pressing member 6 presses the pressure plate 3B housed in the housing 5 against the clutch disc 3A to connect the clutch, and from the drive sprocket 2 via the chain 9 and the driven sprocket 11 to the front wheel. The driving torque is transmitted to the output shaft 10.

[0049]

Embodiment 3 FIG. 7 shows a third embodiment of the transfer apparatus according to the present invention.
FIG. 4 is an explanatory view showing the embodiment, and has a clutch actuator 37 that transmits the rotational force of the motor 20 to the feed screw 18 via the worm gear 30 and the worm wheel 31.

The worm gear 30 is provided on the rotating shaft of the motor 20.
The worm gear 30 is arranged so that the rotation axis of the motor 20 and the feed screw 18 are perpendicular to each other by meshing with the worm wheel 31 attached to the end of the feed screw 18.

When the motor 20 is rotated, the worm gear 30 rotates the worm wheel 31, and the feed screw 18 attached to the worm wheel 31 causes the nut 17 B, which is screwed inside the actuator 37, to rotate in the rotation direction of the motor 20. Is moved in the length direction of the guide 17A based on. The operation of the motor 20 and the brake 20A when the 2WD or 4WD mode is selected is the same as in the first and second embodiments.

According to the above configuration, the worm gear 30
In addition, the worm wheel 31 can be made compact, and the degree of freedom of the mounting position of the motor 20 is increased.

[0053]

Fourth Embodiment FIG. 8 shows a fourth embodiment of the output shaft 1 for a front wheel.
FIG. 3 is an explanatory diagram of a transfer device of the present invention having a clutch mechanism on the 0 side.

A clutch disk 3A and a pressure plate 3B are accommodated in a housing 5 provided coaxially with the front wheel output shaft 10, and a piston 32 is applied via a bearing 13 to a pressing member 6 for pressing the pressure plate 3B. In contact. The piston 32 is pressed by the nut 17B via the rod 33.

The nut 17B supports the rod 33 movably in the longitudinal direction, and the rod 33 has a spring 34 provided coaxially on the outer periphery. The feed screw 18 threadedly engaged with the nut 17 </ b> B has one shaft end supported by the transfer case 12, is rotatably supported by the bearing 13, and is taken out through the transfer case 12. The other shaft end has a reduction gear 19A.
Reduction gear 19A is connected to motor 20 via reduction gear 19B.

The rotation of the feed screw 18 causes the nut 17B to rotate.
Is moved in the direction of the piston 32, the spring 34 provided coaxially with the rod 33 is compressed, and the rod 33 is pressed against the piston 32 by the urging force. The pressed piston 32 presses the pressing member 6, and the pressing member 6 presses the pressure plate 3B against the clutch disc 3A.

[0057]

Embodiment 5 FIG. 9 shows a piston 32 according to a fourth embodiment.
2 is a partially enlarged view of a transfer device in which a hydraulic chamber 32A is provided in a section of the transfer device, and control is performed by detecting a pressing force generated in a piston 32 by a rod 33 by a pressure sensor 32B attached to the hydraulic chamber 32A.

The rod 33 urged by the spring 34 based on the movement of the nut 17B presses the piston 32 through the hydraulic chamber 32A. At the time of this pressing, the hydraulic chamber 32A
Since the internal pressure of the controller 2 rises, when a preset internal pressure is detected by the pressure sensor 32B, the controller 2
1 stops the output of the rotation signal to the motor 20.

[0059]

Sixth Embodiment FIG. 10 shows a pressure sensor 32B according to a fifth embodiment.
, A load cell 32C is provided.
3 is a partially enlarged view of a transfer device in which the output of a rotation signal of the motor 20 is controlled by the pressure detection signal of FIG.

FIG. 11 shows a transfer device in which the load cell 32C shown in the fifth embodiment is provided in the second embodiment.

By controlling the operation of the clutch actuator of the transfer device by the motor, the number of parts can be reduced as compared with the case of the hydraulically operated clutch actuator, so that the size can be reduced and the manufacturing cost can be reduced. In addition, since no hydraulic oil is used, the switching operation of the transfer is stable even when the temperature changes, and in particular, ABS (Antilock Brake System) which requires a quick response from the 4WD mode to the 2WD mode is required.
The operation of the ABS is not hindered even in the vehicle equipped with m).

In the case of an ABS-equipped vehicle, the switching from the 4WD mode to the 2WD mode is performed by switching the transfer device based on a slip detection signal of a wheel sensor provided at a rotating portion of each wheel.
The transfer device can be switched without delay based on the detection of the slip.

The above-described clutch actuator is configured to supply current to the motor only during operation, and it is not necessary to correct the torque characteristics by temperature unlike a transfer device using hydraulic pressure, so that the control process is simplified. In addition, power consumption can be reduced.

[0064]

As described above, according to the transfer apparatus of the present invention, the distribution ratio of the drive torque transmitted to the rear wheels or the front wheels according to the drive mode between the two-wheel drive and the rigid four-wheel drive . Control circuit that outputs rotation signal
And an electric motor having a linearity between the supplied drive current and the generated rotation torque, and generating a rotation torque according to the drive current based on the rotation signal input from the control circuit; and a rotation input from the electric motor. With a displacement member that moves forward or backward based on the torque to push or release the multi-plate clutch to the pressing means, the structure can be made simple and compact, and low power consumption during operation and excellent responsiveness are provided. can do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a transfer device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a current supplied to a motor 20 and a generated motor torque in the first embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration of a current detection circuit according to the first embodiment.

FIG. 4 is an explanatory diagram showing a position of a nut 17B in an actuator 17 in the first embodiment.

FIG. 5 is a diagram showing the relationship between the transmission torque of the multiple disc clutch and the differential rotation of the front and rear wheels in the first embodiment.

FIG. 6 is an explanatory diagram of a transfer device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a transfer device showing a third embodiment of the present invention.

FIG. 8 is a partially enlarged view of a transfer device showing a fourth embodiment of the present invention.

FIG. 9 is a partially enlarged view of a transfer device showing a fifth embodiment of the present invention.

FIG. 10 is a partially enlarged view of a transfer device provided with a load cell 32C in the fifth embodiment.

FIG. 11 is an explanatory diagram of a transfer device provided with a load cell 32C in the second embodiment.

FIG. 12 is an explanatory diagram showing a conventional transfer device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input shaft 2 Drive sprocket 3A Clutch disk 3B Pressure plate 4 Rear wheel output shaft 5 Clutch housing 6 Pressing member 6A Spring 7 Lever 7A Needle bearing 7B Support part 8 Clutch actuator 8A Guide 8B, 32A Hydraulic chamber 8C Hydraulic piston 9 Chain 10 Front shaft output shaft 11 Driven sprocket 12 Transfer case 13 Bearing 14 Piping 15 Hydraulic unit 16 Controller 17, 37 Clutch actuator 17A Guide 17a Stopper 17b Bearing 17B Nut 17C, 17E, 34 Spring 17D, 32 Piston 18 Feed screw 19A, 19B Reduction gear Reference Signs List 20 motor 20A brake 20a motor coil 21 controller 23 power supply 24 switching circuit 25 detection resistor 6 detection circuit 30 worm gear 31 worm wheel 32B pressure sensor 32C load cell 33 rod

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60K 17/344

Claims (5)

(57) [Claims] 1. A multi-plate clutch provided in a drive system for transmitting a driving torque to a front wheel or a rear wheel, and a pressing unit for pressing or releasing the multi-plate clutch, and a rear wheel is pressed based on a pressing operation of the pressing unit. In a transfer device for transmitting the driving torque to a wheel or a front wheel, a rotation signal corresponding to a distribution ratio of the driving torque transmitted to the rear wheel or the front wheel according to a driving mode between two-wheel drive and rigid four-wheel drive is provided. A control circuit that outputs, an electric motor that has linearity between the supplied drive current and the generated rotation torque, and generates a rotation torque according to the drive current based on the rotation signal input from the control circuit; A displacement member that advances or retreats based on the rotational torque input from the electric motor and presses or releases the multi-plate clutch to the pressing means. Transfer device, characterized in that the. 2. A multi-plate clutch provided in a drive system for transmitting a driving torque to a front wheel or a rear wheel, and a pressing means for pressing or releasing the multi-plate clutch, and a rear wheel is provided based on a pressing operation of the pressing means. A transfer device that transmits the drive torque to a wheel or a front wheel, a control unit that outputs a rotation signal based on pressing or releasing of the multi-plate clutch, a motor that rotates based on the rotation signal , and the rotation signal. Braking the rotating shaft of the motor based on
Braking means for holding, reduction gear means for reducing and transmitting the rotational torque of the motor, rotational movement conversion means for converting rotational movement based on the rotational torque reduced by the reduction gear means into linear movement, A displacement member that is screw-engaged with the rotational motion converting means and is displaced in the pitch direction of the screw based on the rotational torque, a spring member biased by the displacement member, and the pressing means by a repulsive force of the spring member. and an actuator constituted by the pressing piston, the rotation said control means to press the multi-plate clutch
When a signal is output, the braking means is released and the motor generates the rotational torque for displacing the displacement member in the pressing direction of the multi-plate clutch, and the rotational torque is converted by the rotational motion converting means. The displacement member of the actuator is displaced in the piston direction, and the spring member controls the degree of coupling of the multi-plate clutch by changing the pressing force of the pressing means in accordance with the amount of displacement of the displacement member. A transfer device wherein torque is distributed to front and rear wheels at a predetermined distribution ratio corresponding to the rotation signal . 3. The control means sets the degree of engagement of the multi-plate clutch based on a selected operation mode of two-wheel drive, weak four-wheel drive, intermediate four-wheel drive, or rigid four-wheel drive. 3. The transfer device according to claim 2, wherein the rotation signal for controlling the rotation torque of the motor is output. 4. The transfer apparatus according to claim 2, wherein said braking means is released when said motor is energized, and restrains and holds the rotating shaft of said motor when said motor is not energized. 5. The transfer device according to claim 2, wherein said piston presses said pressing means by a repulsive force of said spring member when said rotating shaft of said motor is held.