JP2534724B2 - Vehicle drive force distribution control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applied to a transfer device of a four-wheel drive vehicle and a limited slip differential control device of a vehicle, and is variable according to a clutch engagement force applied from the outside. The present invention relates to a vehicle driving force distribution control device including a friction clutch element that generates a transmission torque (driving force distribution torque or differential limiting torque).

(Prior Art) Conventionally, as a driving force distribution control device for a four-wheel drive vehicle equipped with a multi-plate friction clutch that generates a variable driving force distribution torque according to an externally applied hydraulic pressure, for example, Japanese Unexamined Patent Publication No. 61
The thing described in -157438 gazette etc. is known.

This device uses the difference between the front and rear wheel rotation speeds as control input information, and increases the clutch engagement pressure as the difference between the front and rear wheel rotation speeds increases to the four-wheel drive side.

Further, as a vehicle differential limiting control device equipped with a multi-disc friction clutch that generates a variable differential limiting torque in accordance with an externally applied hydraulic pressure, for example, described in JP-A-62-103227 What has been done is known.

This conventional device uses the difference between the left and right wheel rotation speeds as control input information, and increases the clutch engagement pressure as the difference between the left and right wheel rotation speeds increases to provide a large differential limiting force.

(Problems to be Solved by the Invention) However, in such a conventional device, the clutch hydraulic pressure is set to zero when there is no difference in rotational speed between the front and rear wheels or the left and right wheels. When the rotational speed difference suddenly starts from zero, due to the delay in hydraulic response,
The timing at which the transmission torque is generated by the multi-plate friction clutch is delayed with respect to the pressurized oil supply timing, so that the expected effect cannot be obtained.

Therefore, the present applicant has filed a Japanese Patent Application No. 61-109
No. 868 proposes that the initial fastening pressure is applied when the front-rear wheel rotation speed difference is equal to or less than a predetermined value including zero.

However, in this prior application, although the responsiveness is enhanced, the initial fastening pressure is wasted when the vehicle continues to run without a difference in the front and rear wheel rotation speeds, and the current consumption and oil pump Loss and noise become problems.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the problems described above, and in order to achieve this object, the present invention has the following solution means. The solution means of the present invention will be described with reference to the conceptual diagram of the claims shown in FIG. In a vehicle drive force distribution control device including a friction clutch element e that generates a variable transmission torque according to an applied clutch engagement force, a rotational speed difference ΔN between front and rear wheels or left and right wheels is detected and the rotational speed difference is detected. When ΔN is less than or equal to the set rotational speed difference ΔNo, the initial engaging force to the friction clutch element e is set to zero,
It is characterized in that an initial engaging force control means f is provided for applying a predetermined initial engaging force to the friction clutch element e for a certain period of time when the set rotational speed difference ΔNo is exceeded.

(Operation) When the vehicle is running straight at a low speed on a high friction coefficient road and the rotational speed difference ΔN between the front and rear wheels or the left and right wheels continues to be equal to or smaller than the set rotational speed difference ΔNo, the frictional clutch element e is controlled by the initial engagement force control means f. Zero initial tightening force is maintained.

When the set rotational speed difference ΔNo is exceeded due to changes in road surface conditions or running conditions, the initial fastening force control means f
As a result, a predetermined initial engaging force is applied to the friction clutch element e for a certain period of time.

Even if the rotational speed difference ΔN becomes less than or equal to the set rotational speed difference ΔNo or reciprocates back and forth during the fixed time during which the initial fastening force is applied, the initial fastening force applied state is maintained as it is. A fixed time becomes a control delay time to prevent the occurrence of hunting.

Therefore, by controlling the initial engagement force with a delay time using the rotational speed difference ΔN as a parameter, while preventing control hunting, current consumption, pump loss and noise can be prevented by limiting the timing at which the clutch engagement force is generated. It is possible to achieve both the generation of transmission torque and the improvement of responsiveness.

(Example) Hereinafter, the Example of this invention is described based on drawing.

 First, the configuration will be described.

The drive force distribution control device A for the four-wheel drive vehicle of the embodiment is the second
As shown in the figure, it is adapted to a four-wheel drive vehicle with a rear-wheel drive base, in which the driving force from the engine 1 is directly transmitted to the rear wheels 2, and to the front wheels 3 a multi-disc friction clutch 4 (friction clutch). Element).

The multi-disc friction clutch 4 is provided in the middle of the front wheel drive system and has a variable front wheel side transmission torque ΔT according to the clutch engagement pressure Pc applied from an external hydraulic pressure generator 6 (external) having a hydraulic pressure source 5. It is a friction clutch element generated.

The driving force distribution control device A includes a front and rear wheel rotation speed difference Δ
Using Nfr as control input information, the driving force distribution control means for controlling the clutch engagement pressure Pc (front wheel side transmission torque ΔT) and the front and rear wheel rotation speed difference ΔNfr as control input information, the front and rear wheel rotation speed difference ΔNfr is the set rotation. When the speed difference is less than ΔNfro, the initial engagement pressure Pi to the multi-plate friction clutch 4 is set to zero, and when the set rotational speed difference ΔNfro is exceeded, a predetermined initial engagement pressure Pi is applied to the multi-plate friction clutch 4 for a certain period of time. And means.

Structurally, as shown in FIG. 2, a front wheel rotation speed sensor 7 and a rear wheel rotation speed sensor 8 are provided as input means, a control unit 9 is provided as control means, and an electromagnetic control valve 10 is provided as an actuator. There is.

Then, in the control unit 9, ΔNfr (= N
r−Nf), a subtractor 11 for calculating the clutch engagement pressure Pc (determines the front-rear wheel drive force distribution ratio) according to ΔNfr, and outputs it as a hydraulic command current value, and a hydraulic command A current amplification amplifier 13 that amplifies the current value to the valve operating current value level, a level setter 14 that outputs a current value corresponding to the set rotational speed difference ΔNfro, and ΔNfr and ΔN depending on the current value.
A comparator 15 that compares fro, a timer 16 that holds this High for a predetermined delay time when there is a High output from the comparator 15, and a contact side on the drawing when the command from the timer 16 is Low → High Is switched to and the command from timer 16 is High →
Changeover switch 17 that switches to the contact side under the drawing when Low
And

 Next, the operation will be described.

(A) When ΔNfr ≦ ΔNfro When traveling at low speed in a straight line on a high friction coefficient road, etc., when the front and rear wheel rotation speed difference ΔNfr continues to be less than or equal to the set front and rear wheel rotation speed difference ΔNfro, the comparator 15 of the control unit 9 and A low signal is output from the timer 16, and the changeover switch 17 remains switched to the contact on the lower side of the drawing.
The initial engagement pressure command to the multi-disc friction clutch 4 is set to zero, and the non-engaged state of the multi-disc friction clutch 4 is maintained.
At this time, the operation of the hydraulic power source 5 is also stopped.

Therefore, the driving force distribution ratio is as follows: rear wheel: front wheel = 100%:
0% rear-wheel drive.

(B) When ΔNfr> ΔNfro When the front / rear wheel rotation speed difference ΔNfr exceeds the set front / rear wheel rotation speed difference ΔNfro due to changes in road surface conditions or driving conditions,
The signals from the comparator 15 and the timer 16 of the control unit 9 change from Low to High, and the changeover switch 17 is changed over to the contact on the upper side of the drawing.

By this switch switching, the hydraulic pressure command current value from the hydraulic pressure command calculator 12 is amplified by the current amplification amplifier 13, and the electromagnetic control valve 10 is actuated by the valve operating current value by this amplification, and the hydraulic power source 5 causes the multi-disc friction clutch 4 to operate. On the other hand, a predetermined initial engagement pressure Pi is applied for a short period of time set by the timer 16. The hydraulic pressure command calculator 12 is set with an arithmetic expression that obtains the control characteristics shown in FIG. 3, for example, and the front / rear wheel rotation speed difference ΔNfr exceeds the set front / rear wheel rotation speed difference ΔNfro for initial engagement. Even if the front-rear wheel rotational speed difference ΔNfr becomes less than or equal to the set rotational speed difference ΔNfro or the value before and after the set rotational speed difference ΔNfro is reciprocated within a certain time during which the pressure Pi is applied, the initial fastening pressure Pi is applied. The state is maintained as it is, and this constant time becomes the control delay time to prevent the occurrence of hunting.

If the front / rear wheel rotation speed difference ΔNfr exceeds the set front / rear wheel rotation speed difference ΔNfro and then rises further, the third
The front-rear wheel driving force distribution control according to the control characteristics shown in the figure is directly transferred.

At this time, since the initial engagement pressure Pi is applied in advance, the front wheel side transmission torque ΔT is generated with high responsiveness to the increase in the clutch engagement pressure Pc in the multi-disc friction clutch 4 without a time delay, and the front and rear wheel rotations are prevented. The drive force distribution is gradually changed from the rear wheel drive state to the four-wheel drive state according to the speed difference ΔNfr, and the optimum front-rear wheel drive force distribution ratio for traveling is obtained.

As described above, in the driving force distribution control device A of the embodiment, the effects described above can be obtained.

Because the initial engagement pressure Pi is controlled with a delay time using the front-rear wheel rotation speed difference ΔNfr as a parameter, control hunting is prevented while current consumption and current consumption are limited by limiting the timing of clutch engagement pressure Pc generation. It is possible to achieve both prevention of pump loss and noise and improvement of generation response of the front wheel side transmission torque ΔT.

Since the system uses the front-rear wheel rotational speed difference ΔNfr as the input control information for the front-rear wheel driving force distribution control and the initial engagement pressure control, the driving force distribution control device A has a simple structure and is inexpensive.

As described above, the embodiments have been described based on the drawings. However, the specific configuration is not limited to the embodiments, and even if there is a design change or the like without departing from the gist of the present invention, it is included in the present invention. .

For example, in the embodiment, the example of application to the driving force distribution control device A for a four-wheel drive vehicle is shown, but it may be applied to the vehicle differential limiting control device shown in the conventional example.

Further, in the embodiment, the multi-plate friction clutch 4 which is hydraulically engaged as the friction clutch element is shown, but a clutch using mechanical or other fluid pressure may be used.

In the embodiment, the front-rear wheel rotational speed difference ΔNfr is used as the input control information for the front-rear wheel driving force distribution control and the initial engagement pressure control, but the driving force distribution control is not limited to the vehicle speed or the accelerator opening degree. Alternatively, the control may be performed based on other input information, and only the initial engagement pressure control may be performed using the rotational speed difference ΔN as the input control information.

(Effects of the Invention) As described above, in the vehicle drive force distribution control device of the present invention, the vehicle drive force distribution control device is provided in the middle of the drive system that transmits the drive force from the engine to the front and rear wheels or the left and right wheels, and In a vehicle drive force distribution control device having a friction clutch element in which a variable transmission torque is generated according to the clutch engagement force applied from, the rotational speed difference between the front and rear wheels or the left and right wheels is detected, and the rotational speed difference is When the rotational speed difference is less than or equal to the set rotational speed, the initial engaging force to the friction clutch element is set to zero,
Since the means is characterized by providing an initial engagement force control means for applying a predetermined initial engagement force to the friction clutch element for a certain period of time when the set rotational speed difference is exceeded, the clutch engagement force of the clutch engagement force can be prevented while preventing control hunting. Preventing current consumption, pump loss and noise by limiting the generation time,
It is possible to obtain the effect that both generation of transmission torque and improvement of response can be achieved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a vehicle driving force distribution control device according to the present invention, FIG. 2 is a block diagram showing a four-wheel drive vehicle driving force distribution control device, and FIG. 3 is an example device. FIG. 6 is a drive force distribution control characteristic diagram of FIG. a ... Engine b ... Front wheel c ... Rear wheel d ... External e ... Friction clutch element f ... Initial engaging force control means

Claims (1)

(57) [Claims] 1. A friction clutch element is provided in the middle of a drive system for transmitting a driving force from an engine to front and rear wheels or left and right wheels, and a variable transmission torque is generated according to a clutch engaging force applied from the outside. In the vehicle driving force distribution control device, the difference in rotational speed between the front and rear wheels or the left and right wheels is detected, and when the rotational speed difference is less than or equal to the set rotational speed difference, the initial engagement force to the friction clutch element is set to zero and the set rotational speed is set. A drive force distribution control device for a vehicle, comprising: an initial engagement force control means for applying a predetermined initial engagement force to a friction clutch element for a certain period of time when a speed difference is exceeded.