Differential limiting torque control system for automotive vehicles

• US 5,471,390 A
• Filed: 07/05/1994
• Issued: 11/28/1995
• Est. Priority Date: 07/23/1993
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Sasaki, Hiroki
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US08/270,829
• Time in Patent Office: 511 Days
• Field of Search: 364/424.05, 364/426.02, 364/426.03, 303/95, 303/96, 303/97, 303/100, 303/101, 303/112, 303/103, 303/111, 303/104, 303/93, 180/167
• US Class Current: 701/78
• CPC Class Codes: B60K 23/04 for differential gearing
• CPC Class Codes: B60T 2201/14 Electronic locking-differential
• CPC Class Codes: B60T 8/175 Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control safety devices for propulsion unit control responsive to, or preventing, skidding of wheels B60K28/16
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60T 8/3215 Systems characterised by having means acting on components of the drive line, e.g. retarder, clutch or differential gear B60T8/322 takes precedence
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/26 Wheel slip
• CPC Class Codes: Y10S 303/06 Axle differential control

Abstract

A differential limiting torque control system for an automotive vehicle with an anti-skid brake control system (ABS) and a limited slip differential (LSD), comprises sensors for detecting a deceleration, a lateral acceleration, and a drive-wheel speed difference between the right and left drive wheels, and an active LSD controller responsive to both the detected deceleration and the detected lateral-acceleration for deriving a first target torque and responsive to the detected drive-wheel speed difference for deriving a second target torque. The controller adjusts a differential limiting torque applied to the LSD to a higher one of the first and second target torques, only during operation of the ABS.

Claims

1. A differential limiting torque control system for an automotive vehicle with an anti-skid brake control device which operates to suppress wheel lock by adjusting a brake-fluid pressure in a road wheel cylinder during braking, said system comprising:

differential limiting means mounted between right and left drive road wheels, for producing a differential limiting torque through which a differential action is limited;

sensor means for detecting a deceleration of the vehicle, a lateral acceleration exerted on the vehicle, a vehicle speed and a drive-wheel speed difference between said right and left drive road wheels;

first derivation means responsive to both the detected deceleration and the detected lateral-acceleration, for deriving a first target torque having a specified torque characteristic according to which said first target torque is increased in accordance with the detected deceleration;

second derivation means responsive to the detected drive-wheel speed difference, for deriving a second target torque having a specified torque characteristic according to which said second target torque is increased in accordance with the detected drive-wheel speed difference; and

control means for controlling said differential limiting means to adjust said differential limiting torque to a higher one of said first and second target torques, only when said anti-skid brake control device is conditioned in an operative state.

2. A differential limiting torque control system for an automotive vehicle with an anti-skid brake control device which operates to suppress wheel lock by adjusting a brake-fluid pressure in a road wheel cylinder during braking, said system comprising:

differential limiting means mounted between right and left drive road wheels, for producing a differential limiting torque through which a differential action is limited;

sensor means for detecting a deceleration of the vehicle, a lateral acceleration exerted on the vehicle, a vehicle speed and a drive-wheel speed difference between said right and left drive road wheels;

first derivation means responsive to both the detected deceleration and the detected lateral-acceleration, for deriving a first target torque having a specified torque characteristic according to which said first target torque is increased in accordance with the detected deceleration until said first target torque reaches a lateral-acceleration dependent torque limit;

second derivation means responsive to the detected drive-wheel speed difference, for deriving a second target torque having a specified torque characteristic according to which said second target torque is increased in accordance with the detected drive-wheel speed difference until said second target torque reaches a vehicle speed dependent torque limit; and

control means for controlling said differential limiting means to adjust said differential limiting torque to a higher one of said first and second target torques only when said anti-skid brake control device is conditioned in an operative state.

3. A differential limiting torque control system for an automotive vehicle with an at least two-channel type anti-skid brake control device which operates so that two brake-fluid pressures respectively applied to a front driven-wheel side and to a rear drive-wheel side are adjusted independently of each other, said system comprising:

differential limiting means mounted between right and left drive road wheels, for producing a differential limiting torque through which a differential action is limited;

sensor means for detecting a deceleration of the vehicle, a lateral acceleration exerted on the vehicle, a vehicle speed and a drive-wheel speed difference between said right and left drive road wheels;

first derivation means responsive to both the detected deceleration and the detected lateral-acceleration, for deriving a first target torque having a specified torque characteristic according to which said first target torque is increased in accordance with the detected deceleration;

second derivation means responsive to the detected drive-wheel speed difference, for deriving a second target torque having a specified torque characteristic according to which said second target torque is increased in accordance with the detected drive-wheel speed difference;

means for determining whether an anti-skid control of said anti-skid brake control device is executed at least on the rear drive-wheel side during operation of said anti-skid brake control device, and for switching a flag ON when the anti-skid control is executed at least on the rear drive-wheel side; and

control means for controlling said differential limiting means to adjust said differential limiting torque to a higher one of said first and second target torques when said flag is OFF, and to said second target torque when said flag is ON.

4. A differential limiting torque control system for an automotive vehicle with an at least two-channel type anti-skid brake control device which operates so that two brake-fluid pressures respectively applied to a front driven-wheel side and to a rear drive-wheel side are adjusted independently of each other, said system comprising:

differential limiting means mounted between right and left drive road wheels, for producing a differential limiting torque through which a differential action is limited;

sensor means for detecting a deceleration of the vehicle, a lateral acceleration exerted on the vehicle body, a vehicle speed and a drive-wheel speed difference between said right and left drive road wheels;

first derivation means responsive to both the detected deceleration and the detected lateral-acceleration, for deriving a first target torque having a specified torque characteristic according to which said first target torque is increased in accordance with the detected deceleration until said first target torque reaches a lateral-acceleration dependent torque limit;

second derivation means responsive to the detected drive-wheel speed difference, for deriving a second target torque having a specified torque characteristic according to which said second target torque is increased in accordance with the detected drive-wheel speed difference until said second target torque reaches a vehicle speed dependent torque limit;

means for determining whether an anti-skid control of said anti-skid brake control device is executed at least on the rear drive-wheel side during operation of said anti-skid brake control device, and for switching a flag ON when the anti-skid control is executed at least on the rear drive-wheel side; and

control means for controlling said differential limiting means to adjust said differential limiting torque to a higher one of said first and second target torques when said flag is OFF, and to said second target torque when said flag is ON.

5. The differential limiting torque control system as set forth in claim 4, wherein said first target torque is increasingly varied in proportion to the detected vehicle speed.

6. A differential limiting torque control system for an automotive vehicle with an at least two-channel type anti-skid brake control device which operates so that two brake-fluid pressures respectively applied to a front driven-wheel side and to a rear drive-wheel side are adjusted independently of each other, said system comprising:

differential limiting means mounted between right and left drive road wheels, for producing a differential limiting torque through which a differential action is limited;

sensor means for detecting a deceleration of the vehicle, a lateral acceleration exerted on the vehicle body, a vehicle speed and a drive-wheel speed difference between said right and left drive road wheels;

first derivation means responsive to both the detected deceleration and the detected lateral-acceleration, for deriving a first target torque having a specified torque characteristic according to which said first target torque is increased in accordance with the detected deceleration until said first target torque reaches a lateral-acceleration dependent torque limit;

second derivation means responsive to the detected drive-wheel speed difference, for deriving a second target torque having a specified torque characteristic according to which said second target torque is increased in accordance with the detected drive-wheel speed difference until said second target torque reaches a vehicle speed dependent torque limit;

means for determining whether an anti-skid control of said anti-skid brake control device is executed at least on the rear drive-wheel side during operation of said anti-skid brake control device, and for switching a flag ON when the anti-skid control is executed at least on the rear drive-wheel side; and

control means for controlling said differential limiting means to adjust said differential limiting torque to a higher one of said first and second target torques when said flag is OFF, and to said second target torque when said flag is ON,

wherein the specified torque characteristics of said first and second target torques are coordinated with each other, so that the derived first target torque exceeds the derived second target torque during cornering of the vehicle on a high-μ

road surface having a high coefficient of friction with a high lateral acceleration and so that the derived second target torque exceeds the derived first target torque during driving of the vehicle on a low-μ

road surface having a low coefficient of friction or a split-μ

road wherein one of the right and left drive road wheels lies on a high-μ

road surface and the other drive road wheel lies on a low-μ

road surface.