JPH0653468B2 - Transmission torque control device for four-wheel drive vehicle - Google Patents

Description

TECHNICAL FIELD The present invention relates to a four-wheel drive vehicle that controls torque transmitted from a power plant to front wheels and rear wheels via a torque transmission path in a four-wheel drive vehicle. The present invention relates to a transmission torque control device.

(Prior Art) In the field of four-wheel drive vehicles, depending on the running state of the vehicle, four
A so-called part-time four-wheel drive vehicle, which can selectively take a two-wheel drive state and a two-wheel drive state, has been put into practical use.

In such a part-time four-wheel drive vehicle, for the purpose of smoothly switching from the four-wheel drive state to the two-wheel drive state or from the two-wheel drive state to the four-wheel drive state, for example,
As disclosed in Japanese Utility Model Laid-Open No. 56-122630, a wet clutch is interposed in either one of the front-wheel side and rear-wheel side torque transmission paths for transmitting the torque generated by the power plant to the front wheels and the rear wheels. It has been known.

However, in the conventional part-time four-wheel drive vehicle as described above, from the four-wheel drive state to the two-wheel drive state,
Alternatively, the switching from the two-wheel drive state to the four-wheel drive state may be performed by an occupant operating a manual operation switch or the like provided on a shift lever or the like according to the traveling state of the vehicle, road conditions, or the like. Because it is
When the operation is bothersome and the difference in rotational speed between the front wheels and the rear wheels is large, the four-wheel drive state is changed to the two-wheel drive state, or the two-wheel drive state is changed to the four-wheel drive state. There is a problem that a switching shock is likely to occur at the time of switching, and it is difficult to set the switching timing.

Therefore, in order to automatically switch between the four-wheel drive state and the two-wheel drive state, one of the front wheel side and the rear wheel side torque transmission paths is provided with the input side rotation speed and the output side rotation speed. A viscous fluid clutch that changes the transmission torque according to the difference with the rotation speed is interposed, and the front wheel or the rear wheel is changed according to the difference between the front wheel rotation speed and the rear wheel rotation speed (the average rotation speed of the left and right wheels). A transmission torque control device for a four-wheel drive vehicle has been proposed in which the transmission torque to the wheels is changed.

However, as described above, the transmission torque control device for a four-wheel drive vehicle in which the viscous fluid clutch is interposed in the torque transmission path to change the transmission torque to the front wheels or the rear wheels according to the difference in the rotational speeds of the front and rear wheels. However, there are the following problems.

That is, for example, the case where the front wheel and the rear wheel have the same diameter and the viscous fluid clutch is interposed in the rear wheel side torque transmission path that transmits the torque from the power plant to the rear wheel is taken into consideration. In Fig. 4, the transmission torque characteristic of is the difference obtained by subtracting the output side rotation speed (rear wheel rotation speed) from the input side rotation speed (front wheel rotation speed) of the viscous fluid clutch on the horizontal axis (hereinafter, rotation speed difference). Called Δn),
When the transmission torque T is plotted on the vertical axis and the rotational speed difference Δn is positive, positive torque (hereinafter referred to as drive torque) is transmitted to the rear wheels as indicated by the solid line. When the rotational speed difference Δn is negative, negative torque (hereinafter referred to as braking torque) is transmitted to the rear wheels as indicated by the alternate long and short dash line. In this way, when the braking torque is transmitted to the rear wheels, the rear wheels become a running resistance, which causes a disadvantage that fuel consumption and durability of each part are deteriorated.

As one means for solving such inconvenience, a clutch mechanism is arranged in series with the viscous fluid clutch in a torque transmission path in which a viscous fluid clutch is interposed, and this clutch mechanism is based on the running state of the vehicle. Therefore, it is conceivable that the intermittent control is performed such that the connection state is established when the running resistance does not occur in the rear wheels and the connection state is established when the running resistance occurs in the rear wheels.

(Problems to be Solved by the Invention) However, as described above, a clutch mechanism is arranged in the torque transmission path in which the viscous fluid clutch is interposed so as to connect and disconnect the viscous fluid clutch. In a transmission torque control device for a four-wheel drive vehicle, which is controlled on and off based on a two-wheel drive state and a four-wheel drive state automatically.
Although the wheel drive state can be obtained, the two-wheel drive state and the four-wheel drive state cannot be arbitrarily selected. Therefore, for example, when the road surface condition is relatively good, it is not necessary to set the vehicle to the four-wheel drive state and it is convenient to set the two-wheel drive state in order to improve the fuel consumption, and thus the two-wheel drive mode can be achieved. There is an inconvenience that the drive state cannot be selected. Further, for example, when a vehicle needs an emergency escape, or when a great running performance is required, there is a disadvantage that the four-wheel drive state cannot be directly obtained.

In view of such a point, the present invention provides a viscous fluid clutch or the like that changes the transmission torque according to the input / output rotational speed difference to either one of the torque transmission paths that transmits the torque from the power plant to the front wheels or the rear wheels. A hydraulic mechanism is interposed, and a clutch mechanism is arranged in series with the hydraulic mechanism in the torque transmission path in which the hydraulic mechanism is interposed, and the clutch mechanism is controlled to be intermittently operated. With this, it is possible to automatically switch from the four-wheel drive state to the two-wheel drive state, or from the two-wheel drive state to the four-wheel drive state.
It is possible to provide a transmission torque control device for a four-wheel drive vehicle that can reduce running resistance when the vehicle is running straight and can arbitrarily select a two-wheel drive state and a four-wheel drive state by a manual operation. To aim.

(Means for Solving Problems) In order to achieve the above-mentioned object, a transmission torque control device for a four-wheel drive vehicle according to the present invention includes a front-wheel-side torque transmission path for transmitting torque generated by a power plant to front wheels. A fluid type transmission means which is interposed in one of the rear wheel side torque transmission paths for transmitting to the rear wheels and which changes the transmission torque according to the difference between the input side rotation speed and the output side rotation speed; A clutch mechanism arranged in series with the fluid type power transmission means in the front wheel side or rear wheel side torque transmission path with the mechanical transmission means interposed, and the rotational speed of the torque transmission shaft in each of the front wheel side and rear wheel side torque transmission paths. And a control means for performing an on / off control of the clutch mechanism on the basis of a signal obtained from the detection means. The manual operation means for holding the contact mechanism in the connected state or the disconnected state is provided and configured.

(Operation) In the transmission torque control device for a four-wheel drive vehicle according to the present invention configured as described above, the control means controls the clutch mechanism according to the traveling state of the vehicle based on the signal obtained from the detection means. Performs intermittent control. At this time, for example, when running resistance occurs on the rear wheels, the clutch mechanism is switched to the disengaged state to bring the vehicle into the two-wheel drive state. As a result, the driving efficiency of the vehicle is improved, and deterioration of fuel efficiency and durability of each part is prevented. Further, for example, when the front wheels slip, the control means switches the clutch mechanism to the connected state. As a result, the torque generated by the para-plant is transmitted to the rear wheels by the amount corresponding to the amount of slip of the front wheels via the hydraulic transmission means, and the vehicle is brought into a four-wheel drive state with great running performance.

On the other hand, when the manual operation means is operated, the on / off control of the clutch mechanism by the control means is prohibited, and the clutch mechanism is forcibly held in the engaged state or the disengaged state. As a result, the two-wheel drive state and the four-wheel drive state of the vehicle are arbitrarily selected.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

FIG. 1 schematically shows an example of a transmission torque control device for a four-wheel drive vehicle according to the present invention, together with a vehicle to which the transmission torque control device is applied. In FIG. 1, the torque generated by the power plant 10 including the engine and the transmission is transmitted to the pair of left and right front wheels 12 via the front wheel side torque transmission path indicated by the one-dot chain line arrow F and the one-dot chain line arrow R. Through the rear wheel side torque transmission path indicated by
It is transmitted to a pair of left and right rear wheels 14 having the same diameter as 2.

The front wheel-side torque transmission path F has a pair of gears 1 having the same number of teeth.
6A and 16B and a final gear unit 18 including a front wheel differential gear and the like are interposed. Here, comprised of a final gear unit 18 and the like, the final reduction ratio of the final reduction mechanism in the front wheel torque transmission path F is set to i _f. On the other hand, in the rear wheel side torque transmission path R, the input side rotary shaft 19 and the output shaft rotary shaft 2 are provided.
1, a viscous fluid clutch 20 serving as a fluid type transmission means for changing its transmission torque, an electromagnetic clutch 22 arranged in series with this viscous fluid clutch 20, and a rear wheel differential gear. And a final gear unit 24 composed of the same.
Here, the final gear unit 24, etc.,
The final reduction ratio of the final reduction mechanism in the rear wheel side torque transmission route R is the final reduction ratio i in the front wheel side torque transmission route F.
It is set to i _r greater than _f .

Further, in this example, the control unit 100 is provided to automatically perform the above-mentioned on / off control of the electromagnetic clutch 22. The control unit 100 includes a front wheel rotation speed sensor 40 for detecting the rotation speed of the input shaft 26 of the final gear unit 18 and the input shaft 2 of the final gear unit 24.
Rotation detection signals Sf and S, which are obtained from a rear wheel side rotation speed sensor 50 that detects the rotation speed of seven wheels, according to the rotation speeds of the front wheel 12 and the rear wheel 14 (both are the average rotation speeds of the left and right wheels).
r is supplied. Further, the control unit 100 receives hold signals Sa and Sb from the control signal source 60, respectively.
It is supplied through manual operation switches 61 and 62 arranged near the driver's seat.

The control unit 100 uses the rotation detection signals Sf and S described above.
The input shaft 26 corresponding to the rotation speed of the front wheel 12 based on r
When the value obtained by subtracting the rotation speed of the input shaft 27 corresponding to the rotation speed of the rear wheel 14 from zero is greater than or equal to zero, an operation signal Cc for connecting the electromagnetic clutch 22 is generated. Then, this is supplied to the electromagnetic clutch 22. As a result, the solenoid of the electromagnetic clutch 22 is excited to bring the electromagnetic clutch 22 into the connected state, the output side rotation shaft 21 and the input shaft 27 are connected, and the viscous fluid clutch 2 is connected.
The output shaft of 0 and the input side of the final gear unit 24 are connected. On the other hand, the control unit 100 supplies the operation signal Cc when the value obtained by subtracting the rotational speed of the input shaft 27 on the rear wheel side from the rotational speed of the input shaft 26 on the front wheel side is less than or equal to zero or a value in the vicinity thereof. Stop. As a result, the solenoid of the electromagnetic clutch 22 is demagnetized.
2 is cut off, and the connection between the output side of the viscous fluid clutch 20 and the input side of the final gear unit 24 is cut off.

When the power plant 10 is operated under the configuration as described above, the torque generated by the power plant 10 is transmitted to the front wheels 12 via the front wheel side torque transmission path F, and the vehicle is put into a traveling state. In this case, when the vehicle is traveling straight ahead, the final reduction ratio i _r in the rear wheel side torque transmission path R is set to be larger than the final reduction ratio i _f in the front wheel side torque transmission path F, and the front wheel side input shaft 26 Becomes lower than the rotation speed of the input shaft 27 on the rear wheel side, and the rotation speed difference Δn becomes a negative value Δn _b as shown in FIG. 4 described above, for example. Therefore, the control unit 10
When 0, the supply of the actuation signal Cc to the electromagnetic clutch 22 is stopped, and the electromagnetic clutch 22 is disengaged. As a result, when the vehicle is traveling straight ahead, the vehicle is in the two-wheel drive state, and the traveling resistance is reduced. As a result, the driving efficiency of the vehicle is improved, and the fuel efficiency and the durability of each part are prevented from being lowered.

Further, when the front wheel 12 slips to some extent while the power plant 10 is operating, the rotational speed difference Δn has a positive value. Therefore, the control unit 100 supplies the actuation signal Cc to the electromagnetic clutch 22 to put it in the connected state. As a result, the torque generated by the power plant 10 is transmitted to the rear wheels 14 via the viscous fluid clutch 20 by an amount corresponding to the slip amount of the front wheels 12. As a result, the vehicle is brought into the four-wheel drive state and has great running performance.

On the other hand, when the vehicle is turning, since the turning radius of the front wheels 12 is larger than the turning radius of the rear wheels 14, the rotation speed of the input shaft 26 on the front wheel side is higher than that of the input shaft 27 on the rear wheel side. Become. Therefore, the control unit 100 supplies the actuation signal Cc to the electromagnetic clutch 22 to bring it into the connected state.

Here, as shown in FIG. 4 which is described above, when the final reduction ratio of the front wheel torque transmission path F and the rear wheel torque transmission path R i _f and i _r are the same, the power plant 10 When the value of the generated torque is T _A , the driving torques transmitted to the front wheels 12 and the rear wheels 14 at this time are values indicated by T _f and T _r , respectively. Then, the reduced torque power plant 10 in such a condition occurs, for example, _'if it is a, T _A' small becomes a value T _A from T _r as the difference T _{f 'braking} torque and T _r It will be transmitted to the front wheels 12.

However, in this example, the final speed reduction ratio i _r in the rear wheel side torque transmission path R is set to be larger than the final speed reduction ratio _if in the front wheel side torque transmission path F, so the rotational speed difference Δn
Above have been as shown in FIG. 4, the small becomes a value consisting of the value [Delta] n _c when the final reduction ratio i _f and i _r in the front wheel torque transmission path F and the rear wheel torque transmission path R is the same Δn _c ′. Therefore, during turning of the vehicle, even if the torque generated by the power plant 10 is reduced from T _A to T _A ′, the drive torque T _r ′ is transmitted to the rear wheels 14 and the drive torque is transmitted to the front wheels 12. T _f ″
Is transmitted. As a result, when the vehicle is turning, the driving efficiency is improved, the turning radius is suppressed from increasing, and the driving control of the vehicle is facilitated.

As described above, in the present example, the control unit 100 performs the on-off control of the electromagnetic clutch 22 to change from the four-wheel drive state to the two-wheel drive state or from the two-wheel drive state to the four-wheel drive state. The switching is automatically performed, but depending on the timing of this switching, switching shock may occur due to the operating time of the electromagnetic clutch 22.

Therefore, in this example, in order to prevent such a switching shock, the control unit 100 allows the electromagnetic clutch 2 to take into consideration the operating time (time lag) of the electromagnetic clutch 22.
The supply timing and the stop timing of the operation signal Cc to the electromagnetic clutch 22 are controlled in order to switch the connection state 2 from the connection state to the connection state or from the connection state to the connection state.

Assuming that the rotational speed difference Δn changes with time as shown in FIG. 2, the target timing for switching the electromagnetic clutch 22 from the disengaged state to the connected state is that the rotational speed difference Δn is greater than zero. Time t ₂ at which the above-mentioned value Δn _D is reached from a negative value whose absolute value is made larger than the slightly smaller value Δn _D.
The target time to switch the electromagnetic clutch 22 from the connected state to the disconnected state is a positive value whose absolute value is greater than the value Δn _D ′ at which the rotational speed difference Δn is slightly larger than zero. Is a time t _{5 at} which the value Δn _D ′ of In this way, the disengagement timing of the electromagnetic clutch 22 is set to the rotational speed difference Δ.
By making it slightly earlier than the times t ₃ and t ₆ at which n becomes zero, the part between the value Δn _D at the time t ₂ and the Δn _D ′ at the time t ₅ becomes a so-called control dead zone. Thus, when the rotational speed difference Δn slightly fluctuates in this portion, a situation in which the electromagnetic clutch 22 is frequently disengaged is avoided.

Then, as described above, in order to switch the electromagnetic clutch 22 from the disengaged state to the connected state at the time point t ₂ , the operating time t _K when the electromagnetic clutch 22 switches from the disengaged state to the connected state is taken into consideration at the time point t. It is necessary to supply the actuation signal Cc to the electromagnetic clutch 22 at the time point t _{1 which} is earlier than the operation time t _{K by 2;} and in order to switch the electromagnetic clutch 22 from the connected state to the disconnected state at the time point t ₅ , the electromagnetic clutch 22 the operating time t _K when switched to the cutoff state from the connected state _'in anticipation of operating time from the time t ₅ t _K'
It is necessary to stop the supply of the actuation signal Cc to the electromagnetic clutch 22 at time t ₄ , which is only as early as possible. Therefore, the change rate d / dtΔn of the rotation speed difference Δn (in FIG. 2, the change rate d / dtΔn at the time points t ₁ and t ₄ is dN ₁
And _'by multiplying the operating time t _K or t _K' dN ₄ and by operating time and is shown) t _K or t _K calculates a variation amount of the rotation speed difference Δn in a period corresponding to this By adding the amount of change in the calculated rotational speed difference Δn to the rotational speed difference Δn at that time, the rotational speed difference Δn after a period corresponding to the operating time t _K or t _K ′ is predicted, and this predicted value is obtained. when the rotational speed difference [Delta] n is equal to or greater than the value [Delta] n _D, or, when a value [Delta] n _D 'below, the control unit 100 supplies an operation signal Cc to the electromagnetic clutch 22, or the actuation signal C to the electromagnetic clutch 22
The supply of c is stopped.

In addition, in this example, as described above, in addition to being able to automatically obtain the two-wheel drive state and the four-wheel drive state according to the running state of the vehicle, the two-wheel drive state and the four-wheel drive state can be arbitrarily set.
The wheel drive state can be selected.

That is, when the manual operation switch 61 is turned on and the hold signal Sa is supplied to the control unit 100, the control unit 100 continuously stops the supply of the actuation signal Cc to the electromagnetic clutch 22 to operate the electromagnetic clutch 22. In the cutoff state, the manual operation switch 62 is turned on and the control unit 100 receives the hold signal S.
When b is supplied, the control unit 100 continuously supplies the operation signal Cc to the electromagnetic clutch 22 so that the electromagnetic clutch 2
Hold 2 in the cutoff state. Therefore, when the manual operation switch 61 is turned on, the vehicle is forcibly set to the two-wheel drive state, and when the manual operation switch 62 is turned on, the vehicle is forcibly set to the four-wheel drive state. . Therefore, for example, when the road surface condition is relatively good, by operating the manual operation switch 61 to turn it on, the vehicle can be brought into a two-wheel drive state with less running resistance, thereby reducing the fuel consumption. Can be improved. Further, for example, in a state where the vehicle is required to make an emergency escape from a rough road, the manual operation switch 62 is operated to turn it on to bring the vehicle into a four-wheel drive state with great running performance. be able to.

When both the manual operation switches 61 and 62 are both turned off, the switching control of the electromagnetic clutch 22 according to the running state of the vehicle is performed as described above.

The control as described above is mainly performed based on the operation of the microcomputer incorporated in the control unit 100. An example of the program executed by this microcomputer is shown in a flowchart in FIG.

Hereinafter, the control operation of the control unit 100 will be described with reference to the flowchart of FIG.

The program shown in FIG. 3 starts, for example, when the power plant 10 is operated, and after the start, a rotation detection signal obtained from the front wheel side rotation speed sensor 40 and the rear wheel side rotation speed sensor 50 in process 101. Input Sf and Sr, respectively, and proceed to the decision 102. In the decision 102, it is determined whether or not the hold signal Sa is supplied, that is, whether or not the manual operation switch 61 is turned on, and when it is determined that the hold signal Sa is supplied, the process 111 is executed. After proceeding to stop the supply of the operation signal Cc to the electromagnetic clutch 22,
Return to process 101. As a result, the electromagnetic clutch 22
Is cut off, and the vehicle enters the two-wheel drive state.

On the other hand, if the decision signal 102 determines that the hold signal Sa is not supplied, the process proceeds to the decision 103 to determine whether the hold signal Sb is supplied. When it is determined that the hold signal Sb is supplied, the process proceeds to the process 108 to supply the operation signal Cc to the electromagnetic clutch 22, and then the process 10 is performed.
Return to 1. As a result, the electromagnetic clutch 22 is brought into the connected state and the vehicle is brought into the four-wheel drive state.

If the decision 103 determines that the hold signal Sb is not supplied, the process 104
And the rotation detection signal Sf input in the process 101.
And Sr, the rotational speed difference Δn between the front wheel side input shaft speed Nf of the front wheel side input shaft 26 and the front wheel side input shaft speed Nr of the rear wheel side input shaft 27 is calculated. It is determined whether the rotational speed difference Δn calculated in the process 104 is zero or a negative value, that is, whether the front wheel side input shaft rotational speed Nf is less than or equal to the rear wheel side input shaft rotational speed Nr. Then, when it is determined that the rotation speed difference Δn is zero or a negative value, the process proceeds to the process 106, and conversely, when it is determined that the rotation speed difference Δn is a positive value. , Go to process 109.

In the process 106 that is executed when the decision 105 determines that the rotational speed difference Δn is zero or a negative value, the rotational speed difference Δn is added to the change rate d / dt of the rotational speed difference Δn.
Δn multiplied by the operating time t _K in, by adding the variation amount of the rotation speed difference Δn in a period corresponding to the operation time t _K, the value Δn expected rotational speed difference after a period corresponding to the operation time t _K
After calculating _P , the process proceeds to decision 107. In decision 107 determines whether the value [Delta] n _P is the value [Delta] n _D above, when the value [Delta] n _P is the value [Delta] n _D above, in order to a connected state of the electromagnetic clutch 22 from the cutoff state, the process Proceeding to 108, the operation signal Cc is supplied to the electromagnetic clutch 22 and the process 101 is returned to. Further, when it is determined in the decision 107 that the value Δn _P is not equal to or more than the value Δn _D , the process proceeds to the process 111 in order to maintain the electromagnetic clutch 22 in the disengaged state, and the supply of the operation signal Cc to the electromagnetic clutch 22 is stopped. The state that has been continued is continued and the process 101 is returned to.

On the other hand, in the decision 105 described above, the rotational speed difference Δn
Process 109 if is determined to be a positive value
In the same manner as the process 104, the rotational speed difference Δn
, The operation time rate of change d / dtΔn rotational speed difference Δn (<0) _'multiplied by the operating time t _K' t _K by adding the variation amount of the rotation speed difference [Delta] n in the period corresponding to the operating time The expected rotational speed difference value Δn _P ′ after the period corresponding to t _K ′ is calculated, and the process proceeds to decision 110. In decision 110, the [Delta] n P _'is the value [Delta] n _D' is equal to or less than a, when the value [Delta] n P _'is the value [Delta] n _D' is less, to the cutoff state the electromagnetic clutch 22 from the connected state Therefore, the process proceeds to the process 111, the supply of the operation signal Cc to the electromagnetic clutch 22 is stopped, and the process returns to the process 101. If the decision 110 determines that the value Δn _P ′ is not less than or equal to the value Δn _D ′, the process proceeds to the process 108 to maintain the connected state of the electromagnetic clutch 22, and the electromagnetic clutch 2
2 is continued to be supplied with the operation signal Cc, and the process 101 is returned to.

In the above example, the case where the viscous fluid clutch 20 and the electromagnetic clutch 22 are interposed in the rear wheel torque transmission path R has been described, but the present invention is not limited to this, and the front wheel torque transmission path F is not limited to this. Alternatively, the viscous fluid clutch 20 and the electromagnetic clutch 22 may be interposed.

(Effects of the Invention) As is apparent from the above description, according to the transmission torque control device for a four-wheel drive vehicle of the present invention, the fluid type transmission means is provided in either the front wheel side or the rear wheel side torque transmission path. While intervening, a clutch mechanism is arranged in series with it, and the control means controls the clutch mechanism on and off based on the rotational speed difference between the rear wheels and the front wheels, so when the vehicle is in a straight traveling state, A two-wheel drive state with less running resistance is obtained, and a four-wheel drive state with great running performance is obtained when the front wheels of the running vehicle slip. For this reason, the four-wheel drive state and the two-wheel drive state are appropriately selected according to the traveling state of the vehicle, etc., and drive efficiency can be improved without complicated operations, and fuel consumption and fuel consumption can be improved. It is possible to prevent deterioration of durability of each part.

In addition to such effects, according to the transmission torque control device for a four-wheel drive vehicle according to the present invention, the two-wheel drive state and the four-wheel drive state of the vehicle can be arbitrarily changed by operating the manual operation means. As a result, it is possible to further improve the fuel consumption as compared with the one in which the operating state of the clutch mechanism is automatically switched, and the vehicle can be urgently escaped from a bad road. It is possible to sufficiently meet various requirements.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a transmission torque control device for a four-wheel drive vehicle according to the present invention together with a vehicle to which it is applied, and FIG. 2 is provided for explaining the operation of the example shown in FIG. FIG. 3 is a characteristic diagram, FIG. 3 is a flowchart showing an example of an operation program of a microcomputer in an example of the control unit used in the example shown in FIG. 1, and FIG. 4 is a characteristic diagram used for explaining the action of the viscous fluid clutch. Is. In the figure, 10 is a power plant, 12 is a front wheel, 14 is a rear wheel, 18 and 24 are final gear units, 20 is a viscous fluid clutch, 22 is an electromagnetic clutch, 40 is a front wheel side rotation speed sensor, and 50 is a rear wheel side rotation. Number sensor, 60 is a control signal source, 61 and 62 are manually operated switches, 100
Is a control unit.

Claims (1)

[Claims] 1. A difference between an input side rotational speed and an output side rotational speed of the power plant is interposed in either one of a front wheel side and a rear wheel side torque transmission path for transmitting a torque generated by a power plant to a front wheel and a rear wheel. Fluid transmission means for changing the transmission torque in accordance with the above, and the fluid transmission means arranged in series with the fluid transmission means to interrupt the front wheel side or rear wheel side torque transmission path in which the fluid transmission means is interposed. Clutch mechanism, detection means for detecting the number of rotations of the torque transmission shaft in each of the front wheel side and rear wheel side torque transmission paths, and control means for performing on / off control of the clutch mechanism based on a signal obtained from the detection means. And a manual operation means for prohibiting the on / off control of the clutch mechanism by the control means and for holding the clutch mechanism in the engaged state or the disengaged state. Four-wheel drive vehicle of the transmission torque control device.