Differential limiting control device for vehicle

Abstract

A differential limiting control device for a vehicle calculates a yaw rate correspondence control amount according to deviation between actual yaw rate and target yaw rate when a vehicle turns, and also judges the vehicle's steering characteristic of the moment and magnitude relation between wheel speeds of right and left front wheels. The differential limiting control device then applies compensation toward an increase or decrease side based on a yaw rate correspondence control amount to a base control amount according to a combination of the steering characteristic and the magnitude relation between the wheel speeds, and controls a differential limiting force between the right and left front wheels based upon a final control amount obtained after the compensation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:

FIG. 1 is a view showing an entire configuration of a differential limiting control device for a vehicle according to one embodiment of the present invention;

FIG. 2 is a control block diagram showing a procedure of setting a control amount of an electronic control type front LSD, which is carried out by an ECU;

FIG. 3 is a pattern diagram showing a control state of a differential limiting force when inner wheel speed is higher than outer wheel speed; and

FIG. 4 is a pattern diagram showing a control state of the differential limiting force when the inner wheel speed is lower than the outer wheel speed.

Claims

1. A differential limiting control device for a vehicle, comprising: differential limiting means capable of regulating a differential limiting force between right and left wheels to which a driving force from a driving source is transmitted;target turning state index determination means for determining a target turning state index on the basis of a driving state of a vehicle;actual turning state index detection means for detecting an actual turning state index of the vehicle;control amount calculating means for calculating a turning correspondence control amount as a compensation amount with respect to the differential limiting force to be applied to between the right and left wheels, based upon the target turning state index and the actual turning state index;steering characteristic judging means for judging a vehicle's steering characteristic of the moment based upon the target turning state index and the actual turning state index;wheel speed detection means for detecting wheel speeds of the right and left wheels; anddifferential limiting control means for reflecting the turning correspondence control amount in the differential limiting force for compensation toward an increase or decrease side according to a combination of the steering characteristic judged by the steering characteristic judging means and magnitude relation between wheel speeds of the right and left wheels detected by the wheel speed detection means, and controlling the differential limiting means according to a differential limiting force after the compensation.

2. The differential limiting control device for a vehicle according to claim 1, wherein: if it is determined that wheel speed of a turning inner wheel is higher than wheel speed of a turning outer wheel, the differential limiting control means applies an increase compensation to the differential limiting force between the right and left wheels according to the turning correspondence control amount when the steering characteristic judged by the steering characteristic judging means is understeer, and applies a decrease compensation to the differential limiting force between the right and left wheels according to the turning correspondence control amount when the steering characteristic is oversteer; andif it is determined that the wheel speed of the turning inner wheel is lower than the wheel speed of the turning outer wheel, the differential limiting control means applies a decrease compensation to the differential limiting force between the right and left wheels according to the turning correspondence control amount when the steering characteristic judged by the steering characteristic judging means is understeer, and applies an increase compensation to the differential limiting force between the right and left wheels according to the turning correspondence control amount when the steering characteristic is oversteer.

3. The differential limiting control device for a vehicle according to claim 1, wherein: the target tuning state index determination means determines target yaw rate of the vehicle as the target turning state index;the actual turning state index detection means detects actual yaw rate of the vehicle as the actual turning state index;the control amount calculating means calculates the turning correspondence control amount based upon the target yaw rate and the actual yaw rate; andthe steering characteristic judging means judges the steering characteristic of the vehicle based upon the target yaw rate and the actual yaw rate.

4. The differential limiting control device for a vehicle according to claim 1, wherein: the differential limiting control means has base control amount calculating means for calculating as a base control amount of the differential limiting force at least one of a revolution difference correspondence control amount based upon difference between the wheel speeds of the right and left wheels, an acceleration correspondence control amount based upon a vehicle acceleration state caused by an accelerating operation, and a deceleration correspondence control amount based upon a vehicle deceleration state caused by a decelerating operation; andthe differential limiting control means applies an increase or decrease compensation to the base control amount calculated by the base control amount calculating means according to the turning correspondence control amount.

5. The differential limiting control device for a vehicle according to claim 1, wherein: the right and left wheels are front wheels of the vehicle.

6. The differential limiting control device for a vehicle according to claim 1, wherein: the vehicle is a four-wheel drive vehicle in which an electronic control coupling that distributes a driving force to the front and rear wheels of the vehicle is installed in between a front differential and a rear differential; andthe differential limiting means is provided only to the front differential.