JP2600717B2 - Vehicle driving force distribution control device - Google Patents

Description

The present invention is applied to a transfer device of a four-wheel drive vehicle and an operation restriction control device of a vehicle, and is variably transmitted in accordance with an externally applied clutch engagement force. The present invention relates to a vehicle driving force distribution control device including a friction clutch element that generates torque (driving force distribution torque or operation 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
What is described in -157438 gazette etc. is known.

This device uses the front and rear wheel rotational speed difference as control input information,
The control content is such that the clutch engagement pressure is increased as the difference between the front and rear wheel rotation speeds increases, and the clutch engagement pressure is increased to the four-wheel drive side.

Further, as a vehicle differential control control device provided with a multi-plate friction clutch that generates a variable operation limiting torque in accordance with an externally applied hydraulic pressure, for example, described in JP-A-62-103227. Are known.

This conventional device has a control content in which a difference between left and right wheel rotation speeds is used as control input information, and as the difference between left and right wheel rotation speeds increases, a clutch engagement pressure is increased to apply a large operation limiting force.

(Problems to be Solved by the Invention) However, in such a conventional device, when there is no difference in rotational speed between the front and rear wheels or the left and right wheels, the content of the clutch hydraulic pressure is set to zero, When the rotational speed difference suddenly occurs 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 Japanese Patent Application No.
No. 9868 proposes that the initial fastening pressure be applied when the front and rear wheel rotational speed difference is equal to or less than a predetermined value including zero.

However, in this prior application, although the responsiveness is improved, in a vehicle equipped with a wheel lock prevention device that prevents wheel lock during braking, the initial fastening pressure is applied even when there is no difference in front and rear wheel rotation speed. Therefore, at the time of braking in which the wheel lock prevention device operates, a device interference problem occurs, and the control performance of the wheel lock prevention device deteriorates.

That is, since the braking force generated by the operation of the wheel lock prevention device is distributed to the four wheels by the initial engagement pressure, the braking force becomes insufficient, and the braking stop distance becomes longer due to the inertial force during braking.

(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 means for solving the present invention will be described with reference to the conceptual diagram of the claims shown in FIG. 1. The driving means is provided in the middle of a drive system for transmitting the driving force from the engine to the front and rear wheels or the left and right wheels. And a clutch control means 3 for controlling the increase or decrease of the clutch engagement force based on a detection signal from a predetermined detection means 2. The detection means 2 includes a rotation speed difference detection means 201 for front and rear wheels or left and right wheels and an operation detection means 202 for a wheel lock prevention device at the time of braking. The clutch control means 3 operates the wheel lock prevention device 4 Sometimes, the initial engagement force is removed, the clutch engagement force is reduced to zero, the clutch is completely released, and control is performed to maintain that state until the operation is released. Immediately after the operation of the wheel lock prevention device 4 is switched from the operation to the non-operation, the control for giving the initial engagement force that has been removed is performed. When the wheel lock prevention device 4 is not operating, the clutch engagement force increases as the rotation speed difference increases. In a region where the rotational speed difference is small while the rotational speed difference is small, it is characterized in that it is means for performing control for applying an initial fastening force for generating an initial transmission torque.

(Operation) When the wheel lock prevention device 4 is operated, control is performed such that the initial engagement force is removed, the clutch engagement force is reduced to zero, the clutch is completely released, and the state is maintained until the operation is released.

Therefore, when the wheel lock prevention device 4 is operated at the time of rapid braking or braking on a low μ road, the braking force is not distributed by the initial fastening force, and the wheel lock prevention device 4 is not operated.
The full braking performance is demonstrated.

Immediately after the operation of the wheel lock prevention device 4 is switched from the operation to the non-operation, the control for applying the initial fastening force that has been removed is performed. In the region where the rotational speed difference is small while increasing the coupling force, control is performed to apply the initial coupling force that generates the initial transmission torque.

Therefore, a large difference between the front and rear wheel rotational speeds occurs suddenly due to the drive wheel slip, such as when entering from a high μ road to a low μ road, or a sudden large left and right drive wheel rotation occurs when entering a split μ road. Even in the case where a speed difference occurs, in a region where the rotation speed difference is small, the initial engagement force for generating the initial transmission torque is applied, so that the transmission torque is generated in a high response to the command to increase the clutch engagement force. Thus, the increase in the rotational speed difference is quickly suppressed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

 First, the configuration will be described.

The driving force distribution control device A for the four-wheel drive vehicle of the embodiment
As shown in the figure, this is adapted to a rear-wheel drive-based four-wheel drive vehicle, in which driving force from an engine 10 is directly transmitted to a rear wheel 11, and a multi-plate friction clutch 13 (friction clutch) is transmitted to a front wheel 12. Element).

The multi-plate friction clutch 13 is provided in the middle of the front wheel drive system, and generates a variable front wheel side transmission torque ΔT according to the clutch engagement pressure Pc applied from the external hydraulic pressure generator 15 having the hydraulic pressure source 14. It is a clutch element.

The driving force distribution control device A includes a wheel lock prevention device 16.
When the wheel lock prevention device 16 is not operating, the clutch engagement pressure Pc is kept zero until the operation is released. This device increases Pc and applies a predetermined initial fastening pressure Pi (initial front-rear side transmission torque ΔTi) in a region where the front-rear wheel rotational speed difference ΔN is small.

As shown in FIG. 2, a front wheel rotation speed sensor 17 and a rear wheel rotation speed sensor 18 are provided as input means, a control unit 19 is provided as control means, and an electromagnetic control valve 20 is provided as an actuator.

The control unit 19 includes an input interface 191, a CPU (Central Processing Unit) 192, and a RAM (Random Access Unit) as internal circuits.
A memory 193, a ROM (read only memory) 194, and an output interface 195.

The input interface 191 includes a front wheel rotation speed signal (nf) from the front wheel rotation speed sensor 17, a rear wheel rotation speed signal (nr) from the rear wheel rotation speed sensor 18, and an operation signal from the wheel lock prevention device 16. (S) is input.

In the ROM 194, as shown in FIG. 3, a relationship characteristic between the front-rear wheel rotational speed difference ΔN and the front-wheel-side transmission torque ΔT is stored in advance in the form of an arithmetic expression.

 Next, the operation will be described.

First, the flow of the driving force distribution control operation in the control unit 19 of the embodiment device will be described with reference to the flowchart shown in FIG.

In the control unit 19, the control processing operation is repeated at a predetermined control cycle.

In step 100, it is determined whether control is started,
In step 101, FLAG as an initialization step
= 0 is set.

In step 102, the operation signal (s) from the wheel lock prevention device 16 is read.

In step 103, it is determined whether the operation signal (s) read in step 101 is a signal indicating operation of the wheel lock prevention device 16 or a signal indicating non-operation.

In step 104, a designation signal (i) for setting the front wheel side transmission torque ΔT to zero is output.

In step 105, when FLAG = 0 indicating the non-operation mode of the wheel lock prevention device 16, FLAG = 1 indicating the operation mode of the wheel lock prevention device 16 is rewritten.

 In step 106, it is determined whether FLAG = 1.

In step 107, the initial front wheel side transmission torque ΔTi
Is output.

In step 108, FLAG = 1 is rewritten to FLAG = 0.

In step 109, the front wheel rotation speed Nf and the rear wheel rotation speed Nr
Is read.

In step 110, the front wheel rotation speed Nf and the rear wheel rotation speed Nr
From this, the front and rear wheel rotation speed difference ΔN is obtained by calculation.

 The arithmetic expression is ΔN = Nr−Nf.

In step 111, the front-wheel-side transmission torque ΔT is obtained from the front-rear wheel rotational speed difference ΔN and the characteristics shown in FIG.

In step 112, a command signal (i) for obtaining the clutch engagement pressure Pc corresponding to the front wheel side transmission torque ΔT obtained in step 111 is output.

Next, the driving force distribution control operation will be described separately when the wheel lock prevention device 16 is activated and when the wheel lock prevention device 16 is not activated.

(A) When the wheel lock prevention device is activated When the wheel lock prevention device 16 is activated, steps 100 to
The flow up to step 105 is repeated to reduce the front wheel side transmission torque ΔT (clutch engagement pressure Pc) to zero, and from step 103 to step 106 → step 107 → step 108.
That state is maintained until the operation is released, which is a flow that proceeds to.

Therefore, when the rapid braking is performed during the braking on the low μ road and the wheel lock prevention device 16 is operated, the braking force is not distributed by engaging the clutch, and the braking performance of the wheel lock prevention device 16 is fully exhibited. You.

(B) When the wheel lock prevention device is not activated When the operation of the wheel lock prevention device 16 is released, as described above, the flow proceeds from step 103 to step 106 → step 107 → step 108. In step 107, the initial front wheel side transmission torque ΔTi is given.

When the wheel lock prevention device 16 enters the non-operation state, the flow proceeds to step 103 → step 106 → step 109 → step 110 → step 111 → step 112,
The larger the front and rear wheel rotational speed difference ΔN, the larger the front wheel side transmission torque ΔT
(Clutch engagement pressure Pc) is increased, and a predetermined initial front wheel side transmission torque ΔTi (initial clutch engagement pressure Pci) is applied in a region where the wheel rotational speed difference ΔN is small.

Therefore, even when the front and rear wheel rotational speed difference ΔN suddenly increases due to the drive wheel slip, such as when entering from a high μ road to a low μ road, a predetermined initial value is set in advance in a region where the front and rear wheel rotational speed difference ΔN is small. Since the front wheel side transmission torque ΔTi is applied, a desired front wheel side transmission torque ΔT is generated with a high response to the command to increase the clutch engagement pressure Pc, and the increase in the front and rear wheel rotational speed difference ΔN is quickly suppressed. Shows high running performance.

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, an example of application to the driving force distribution control device A of a four-wheel drive vehicle has been described, but the invention may be applied to the vehicle differential control control device shown in the conventional example.

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

(Effects of the Invention) As described above, in the vehicle driving force distribution control device of the present invention, when the wheel lock prevention device is operated, the clutch control means is deactivated to reduce the initial engagement force to zero. In this state, the clutch is released to the safety release state, and the state is maintained until the operation is released, and immediately after the wheel lock prevention device is switched from the operation to the non-operation, the control for applying the removed initial fastening force is performed. When the wheel lock prevention device is not operated, the clutch engagement force is increased as the rotation speed difference is large, and control is performed to apply the initial engagement force for generating the initial transmission torque in a region where the rotation speed difference is small. Of the braking performance of the wheel lock prevention device at the time of driving, and the control responsiveness in the driving force distribution control corresponding to the rotational speed difference The effect of achieving both improvement and improvement can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a driving force distribution control device for a vehicle according to the present invention, FIG. 2 is a block diagram showing a driving force distribution control device for a four-wheel drive vehicle according to an embodiment, and FIG. FIG. 4 is a flowchart showing a driving force distribution control operation performed by the control unit. DESCRIPTION OF SYMBOLS 1 ... Friction clutch element 2 ... Detection means 201 ... Rotation speed difference detection means of front and rear wheels or right and left wheels 202 ... Operation detection means of wheel lock prevention device 3 ... Clutch control means 4 ... Wheel lock prevention device

Claims (1)

(57) [Claims] 1. A friction clutch element which is provided in a drive system for transmitting a driving force from an engine to front and rear wheels or left and right wheels and generates a variable transmission torque in accordance with an externally applied clutch fastening force; A driving force distribution control device for a vehicle, comprising: a clutch control unit that controls increase / decrease of a clutch engagement force based on a detection signal from a predetermined detection unit; wherein the detection unit detects rotation speed difference between front and rear wheels or left and right wheels. Means for detecting the operation of the wheel lock prevention device at the time of braking, and the clutch control means, when the wheel lock prevention device is operating, removes the initial engagement force to bring the clutch engagement force to zero and completely disengages the clutch. Control to maintain the state until the operation is released is performed, and immediately after the wheel lock prevention device is switched from operation to non-operation, it is removed. When the wheel lock prevention device is not operated, the clutch engagement force is increased as the rotation speed difference increases, and the initial engagement force that generates the initial transmission torque is applied in a region where the rotation speed difference is small when the wheel lock prevention device is not operating. A driving force distribution control device for a vehicle.