Traction control system for automotive vehicles

• US 5,407,257 A
• Filed: 08/11/1994
• Issued: 04/18/1995
• Est. Priority Date: 01/07/1992
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Iwata, Toru
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): Young, Lee W.
• Application Number:
  US08/288,752
• Time in Patent Office: 250 Days
• Field of Search: 303/92, 303/110, 303/100, 303/113.2, 303/113.3, 303/116.2, 303/114.1, 303/119.1, 364/426.02, 364/426.03
• US Class Current: 303/122.09
• 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 8/48 connecting the brake actuator to an alternative or additional source of fluid pressure , e.g. traction control systems
• CPC Class Codes: B60T 8/4872 pump-back systems
• CPC Class Codes: F16H 63/40 comprising signals other than signals for actuating the final output mechanisms

Abstract

An automotive traction control system comprises a master cylinder, an external brake fluid pressure source, a brake fluid pressure control actuator being applied commonly to an acceleration-slip control and a deceleration-slip control, a first switching valve for establishing and blocking a communication between the master cylinder and the pressure control actuator, a second switching valve for establishing and blocking a communication between the external brake fluid pressure source and the pressure control actuator, and a control unit for deriving a pressure reducing control time necessary to reduce the wheel cylinder pressure to a designated brake fluid pressure, based on a pressure intensifying control time, during the acceleration-slip control. The control unit is arranged for switching the second switching valve just after the pressure reducing control time has elapsed, and for switching the first switching valve and a pressure intensifying valve and a pressure reducing valve both included in the pressure control actuator with a predetermined time lag after shifting of the second switching valve, in a transient state transiting from the acceleration-slip control mode to the normal braking operational mode.

Claims

1. An automotive traction control system comprising:

a master cylinder for generating a master cylinder pressure based on a movement of a brake pedal;

at least one wheel cylinder activated by the master cylinder pressure generated by said master cylinder;

an external brake fluid pressure source for generating a brake fluid pressure, regardless of depression of the brake pedal;

a brake fluid pressure control actuator being applied commonly to an acceleration-slip control and a deceleration-slip control, for controlling a wheel cylinder pressure in said at least one wheel cylinder;

a first switching valve for establishing and blocking a fluid communication between said master cylinder and said pressure control actuator;

a second switching valve for establishing and blocking a fluid communication between said external brake fluid pressure source and said pressure control actuator;

means for deriving a pressure reducing control time duration necessary to reduce said wheel cylinder pressure to a designated brake fluid pressure, as a function of a previous pressure intensifying control time duration when said pressure control actuator operates at a pressure intensifying mode, during said accelerations-slip control according to which said first switching valve is shifted to a valve closed state to block the communication between said master cylinder and said pressure control actuator and said second switching valve is shifted to a valve open state to establish the communication between said external brake fluid pressure source and said pressure control actuator; and

a first normal braking operation recovery control means for shifting said second switching valve to a valve closed state just after said pressure reducing control time has elapsed, and for shifting said first switching valve to a valve open state with a predetermined time lag after shifting of said second switching valve to said valve closed state, and for recovering said pressure control actuator to a normal braking operational mode, in a transient state wherein a brake control mode is shifted from the acceleration-slip control mode to the normal braking operational mode at which said wheel cylinder pressure is adjusted depending on the magnitude of said master-cylinder pressure.

2. The automotive traction control system as set forth in claim 1, wherein said brake fluid pressure control actuator includes a plurality of pairs of pressure intensifying valve and pressure reducing valve, each pair being associated with either one of the wheel cylinders, and said pair of pressure intensifying valve and pressure reducing valve is cooperative with each other during said acceleration-slip control in a manner so as to operate at three modes among the pressure intensifying mode wherein the wheel cylinder pressure in the associated wheel cylinder is intensified by the brake fluid pressure introduced thereinto through said external brake fluid pressure source for said pressure intensifying control time, a pressure holding mode wherein the wheel cylinder pressure is held unchanged, and the pressure reducing mode wherein the wheel cylinder pressure is reduced for said pressure reducing control time.

3. The automotive traction control system as set forth in claim 2, wherein said predetermined time lag is set at approximately 30 msec.

4. An automotive traction control system comprising:

a master cylinder for generating a master cylinder pressure based on a movement of a brake pedal;

at least one wheel cylinder activated by the master cylinder pressure generated by said master cylinder;

an external brake fluid pressure source for generating a brake fluid pressure, regardless of depression of the brake pedal;

a brake fluid pressure control actuator being applied commonly to an acceleration-slip control and a deceleration-slip control, for controlling a wheel cylinder pressure in said at least one wheel cylinder;

a first switching valve for establishing and blocking a fluid communication between said master cylinder and said pressure control actuator;

a second switching valve for establishing and blocking a fluid communication between said external brake fluid pressure source and said pressure control actuator;

means for monitoring occurrence of a stop instruction for an acceleration requirement, a malfunction of the system, or a deceleration-slip requirement according to which an anti-skid brake control starts, in a transient state wherein a normal braking operation recovers after termination of said acceleration-slip control according to which said first switching valve is shifted to a valve closed state to block the communication between said master cylinder and said pressure control actuator and said second switching valve is shifted to a valve open state to establish the communication between said external brake fluid pressure source and said pressure control actuator and said second switching valve is shifted to a valve open state to establish the communication between said external brake fluid pressure source and said pressure control actuator; and

a second normal braking operation recovery control means for shifting said second switching valve to a valve closed state substantially at a time of occurrence of said stop instruction for an acceleration requirement, said malfunction of the system, or said deceleration-slip requirement, and for shifting said first switching valve to a valve open state with a predetermined time lag after shifting said second switching valve to said valve closed state, and for recovering said pressure control actuator to a normal braking operational mode, in said transient state.

5. An automotive traction control system comprising:

a master cylinder for generating a master cylinder pressure based on a movement of a brake pedal;

at least one wheel cylinder activated by the master cylinder pressure generated by said master cylinder;

an external brake fluid pressure source for generating brake fluid pressure, regardless of depression of the brake pedal;

a brake fluid pressure control actuator being applied commonly to an acceleration-slip control and a deceleration-slip control, for controlling a wheel cylinder pressure in said at least one wheel cylinder;

a first switching valve for establishing and blocking a fluid communication between said master cylinder and said pressure control actuator;

a second switching valve for establishing and blocking a fluid communication between said external brake fluid pressure source and said pressure control actuator;

means for deriving a pressure reducing control time duration necessary to reduce said wheel cylinder pressure to a designated brake fluid pressure, as a function of a previous pressure intensifying control time duration when said pressure control actuator operates at a pressure intensifying mode, during said acceleration-slip control according to which said first switching valve is shifted to a valve closed state to block the communication between said master cylinder and said pressure control actuator and said second switching valve is shifted to a valve open state to establish the communication between said external brake fluid pressure source and said pressure control actuator;

a first normal braking operation recovery control means for shifting said second switching valve to a valve closed state just after said pressure reducing control time has elapsed, and for shifting said first switching valve to a valve open state with a predetermined time lag after shifting said second switching valve to said valve closed state, and for recovering said pressure control actuator to a normal raking operational mode, in a transient state wherein a brake control mode is shifted from the acceleration-slip control mode to the normal braking operational mode at which said wheel cylinder pressure is adjusted depending on the magnitude of said master-cylinder pressure;

means for monitoring occurrence of a stop instruction for an acceleration requirement, a malfunction of the system, or a deceleration-slip requirement according to which an anti-skid brake control starts, in said transient state; and

a second normal braking operation recovery control means for shifting said second switching valve to the valve closed state substantially at a time of occurrence of said stop instruction for an acceleration requirement, said malfunction of the system, or said deceleration-slip requirement, and for shifting said first switching valve to the valve open state with a predetermined time lag after shifting said second switching valve to said valve closed state, and for recovering said pressure control actuator to the normal braking operational mode, in said transient state;

wherein a command generated by said second normal braking operation recovery control means gets priority over a command generated by said first normal braking operation recover control means.