JPS62231821A - Power transmission for four wheel drive vehicle - Google Patents

Abstract

PURPOSE:To prevent a hump phenomenon in a four wheel drive vehicle transmission device provided with a fluid type transmission means, by releasing a direct coupling means for the fluid type transmission means when the fluid temperature in the fluid transmission means is above a predetermined temperature. CONSTITUTION:A control unit 100 receives a signal from a temperature sensor 101 for detecting the temperature of viscous fluid in a viscous fluid clutch 20, and delivers a disable signal to a driver circuit 22a when the temperature 101 of the fluid exceeds a critical temperature at which a hump phenomenon occurs, to deenergize a solenoid of an electromagnetic clutch 22 which is therefore disengaged. With this arrangement, it is possible to cut off torque delivered to the fluid type power transmission means 20 to prevent the hump phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power transmission device for a four-wheel drive vehicle, and more particularly, the present invention relates to a power transmission device for a four-wheel drive vehicle. The present invention relates to a power transmission device for a four-wheel drive vehicle that controls power.

(Prior art) In the field of four-wheel drive vehicles, four-wheel drive vehicles are
2. Description of the Related Art So-called "vert time" four-wheel drive vehicles, which can be selectively operated between a wheel drive state and a two-wheel drive state, are in practical use.

In such a part-time four-wheel drive vehicle, for the purpose of smoothly switching from a four-wheel drive state to a two-wheel drive state, or from a two-wheel drive state to a four-wheel drive state, for example,
It is also shown in Utility Model Application Publication No. 56-122630,
It is known that a wet clutch is interposed in one of the front wheel side and rear wheel side torque transmission paths that transmit the torque generated by the power plant to the front wheels and the rear wheels.

However, in the conventional part-time four-wheel drive vehicle as described above, the transition from four-wheel drive state to two-wheel drive state,
Alternatively, the changeover from a two-wheel drive state to a four-wheel drive state may be performed by a passenger operating a switch or the like provided on a shift lever or the like, depending on the driving state of the vehicle, road conditions, etc. This causes troublesome operation, and when there is a large difference in rotational speed between the front wheels and the rear wheels, changing from 4-wheel drive to 2-wheel drive, or from 2-wheel drive to 4-wheel There are problems in that a switching shock is likely to occur when switching to the drive state, and it is difficult to set the switching timing.

Therefore, in order to enable automatic fishing to switch between the 4-wheel drive state and the 2-wheel drive state, the input side rotation speed and the output side A viscous fluid clutch is interposed that changes the transmission torque according to the difference in rotation speed, and the transmission torque is changed depending on the difference between the front wheel rotation speed and the rear wheel rotation speed (both are the average rotation speed of the left and right wheels). Changed the transmission torque to 4.
Power for wheel drive vehicles (public notice device is being considered.

Note that this viscous fluid clutch is disclosed in West German Patent Publication No. 3436728.

(Problem to be Solved by the Invention) However, as described above, a viscous fluid clutch is interposed in the torque transmission path to change the torque transmitted to the front wheels or the rear wheels according to the difference in rotation speed between the front and rear wheels. I did 4
Power transmission devices for wheel drive vehicles have the following problems.

That is, the viscous fluid clutch is provided with an air chamber of 10 to 20%, but if the wet clutch continues to be directly connected for a long time, the fluid in the viscous fluid clutch expands beyond the volume of the air chamber. A hang phenomenon similar to a seizure phenomenon or damage to the seal due to this expansion may occur, resulting in leakage of this fluid.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a power transmission device for a four-wheel drive vehicle that can prevent the hang phenomenon from occurring in the viscous fluid clutch.

(Means for Solving the Problems) The power transmission device for a four-wheel drive vehicle of the present invention is provided with either a front wheel side torque transmission path or a rear wheel side torque transmission path that transmits torque generated by a power plant to the front wheels and rear wheels. placed in
A fluid type transmission means that changes the transmission torque according to the difference between the input side rotation speed and the output side rotation speed, and the front wheel side or rear wheel side torque transmission path where this fluid type transmission means is arranged is directly connected. A direct connection means arranged in series with the fluid transmission means; a temperature detection means for detecting the temperature of the fluid in the fluid transmission means; The present invention is characterized in that it includes a control means for releasing the direct connection means when the temperature of the indicated fluid exceeds a predetermined temperature.

(Operations and Effects of the Invention) In the power transmission device for a four-wheel drive vehicle of the present invention, as described above, the temperature detection means detects the temperature of the fluid in the fluid power transmission means, and when this temperature is equal to or higher than a predetermined temperature, Since the above-mentioned direct coupling means is released when the above-mentioned condition occurs, the above-mentioned fluid type transmission means becomes inactive, thereby preventing the above-mentioned hang phenomenon from occurring, and improving the reliability of the above-mentioned fluid type transmission means. Can be secured.

(Embodiments) Hereinafter, a power transmission system for a four-wheel drive vehicle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

The drawing is a schematic diagram showing an example of a power transmission device for a four-wheel drive vehicle according to the present invention, together with a vehicle to which the same is applied.

In this figure, torque generated by a power plant 10 consisting of an engine and a transmission is transmitted to a pair of left and right front wheels 12 via a front wheel side torque transmission path indicated by a dashed-dotted line arrow F, and is also transmitted to a pair of left and right front wheels 12 indicated by a dashed-dotted line arrow R. The torque is transmitted to a pair of left and right rear wheels 14 having the same diameter as the front wheels 12 through a rear wheel side torque transmission path.

The front wheel side torque transmission path F includes a pair of gears 1 with the same number of teeth.
6A and 16B, and a final gear unit 18 consisting of a front wheel differential gear and the like are interposed. On the other hand, in the rear wheel side torque transmission path R, depending on the rotational speed difference between the input end rotating shaft 19 and the output side rotating shaft 21,
A final gear unit 24 consisting of a viscous fluid clutch 20 as a fluid transmission means for changing the transmitted torque, an electromagnetic clutch 22 arranged in series with the viscous fluid clutch 20, a rear wheel differential gear, etc.
is mediated.

In this example, a control unit 100 is provided to control the driver circuit 22a of the electromagnetic clutch 22 in order to automatically perform the intermittent control of the electromagnetic clutch 22 described above. This control unit 100 is supplied with a temperature signal from a temperature sensor 101 that detects the temperature of the viscous fluid within the viscous fluid clutch 20.

Based on the temperature signal, the control unit 100 determines whether the temperature of the viscous fluid is above a predetermined temperature, that is, close to a dangerous temperature at which a hang phenomenon occurs, and when this determination is YES, the driver circuit 22a is inactivated. supply the signal,
As a result, the driver circuit 22a demagnetizes the solenoid of the electromagnetic clutch 22, and the electromagnetic clutch 22 is disconnected.As a result, when the temperature of the fluid in the viscous fluid clutch 20 reaches a predetermined temperature or higher, an input signal is input to the driver circuit 22a. The viscous fluid clutch 20
This prevents the hang phenomenon, etc.

[Brief explanation of drawings]

The drawing is a schematic diagram showing an example of a power transmission device for a four-wheel drive vehicle according to the present invention, together with a vehicle to which the power transmission device is applied. 10...Power plant, F...Front wheel side torque transmission path, R...
Rear wheel side torque transmission path, 20... Viscous fluid clutch, 22... Electromagnetic clutch, 100... Control unit, 101... Temperature sensor.

Claims (1)

[Claims] It is placed on either the front or rear wheel torque transmission path that transmits the torque generated by the power plant to the front and rear wheels, and changes the transmitted torque according to the difference between the input side rotation speed and the output side rotation speed. a hydraulic transmission means arranged in series with the fluid transmission means so as to directly connect the front wheel side or rear wheel side torque transmission path in which the fluid transmission means is arranged; Temperature detection means for detecting the temperature of the fluid within the transmission means, and control for receiving an output signal from the temperature detection means and releasing the direct coupling means when the temperature of the fluid indicated by the output signal exceeds a predetermined temperature. A power transmission device for a four-wheel drive vehicle equipped with means.