Anti-skid control apparatus for a vehicle braking system

• US 4,979,784 A
• Filed: 06/28/1988
• Issued: 12/25/1990
• Est. Priority Date: 06/30/1987
• Status: Expired due to Fees

• Current Assignee: Bosch Braking Systems Co Ltd (Robert Bosch GmbH)
• Original Assignee: Nippon ABS Ltd.
• Inventors: Arikawa, Tetsuro
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US07/212,517
• Time in Patent Office: 910 Days
• Field of Search: 303/95, 303/96, 303/98, 303/100, 303/103, 303/106, 303/109, 303/110, 303/111, 188/181 C, 188/181 R, 364/426.02
• US Class Current: 303/149
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear

Abstract

An anti-skid control apparatus for a vehicle includes fluid pressure control valve devices arranged between a tandem master cylinder and the front wheels of the vehicle, and a control unit receiving outputs of wheel speed sensors to assess skid conditions of the wheels and to control the valve devices. The apparatus discriminates between "low side" and "high side" of the road by assessing skid conditions of either the rear wheels or the front wheels. The braking pressure of the rear or front wheel that is on the low side and that of the wheel connected diagonally to it are controlled in either a "select-high" or a "select-low" manner, and the pressures of the other diagonally opposite wheels are controlled in the opposite manner. In the alternative, the apparatus may assess the skid condition of the one rear wheel based on the larger of the braking frictional coefficients of the sides of the road, on the basis of the acceleration and slip conditions of the one rear wheel, while it judges the skid condition of the other rear wheel on the smaller one of the braking frictional coefficients of the sides of the road only on the basis of the acceleration condition of the other rear wheel, and the braking pressures of the respective conduit systems are controlled in the select-low manner.

Claims

1. In an anti-skid control apparatus for a vehicle braking system including:

(A) a pair of front wheels and a pair of rear wheels which are diagonally connected with each other;

(B) wheel speed sensors associated with said wheels, respectively;

(C) a first fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of one of said front wheels, arranged between a first fluid pressure generating chamber of a tandem master cylinder and said wheel cylinder of the one front wheel;

(D) a second fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of another of said front wheels, arranged between a second fluid pressure generating chamber of said tandem master cylinder and said wheel cylinder of the other front wheel; and

(E) a control unit comprising a right front wheel speed signal generator (34a) connected to a one of the wheel speed sensors (28a) associated with a right one of the pair of front wheels (6a) to produce a first wheel speed signal;

a left rear wheel speed signal generator (35a) connected to a one of the wheel speed sensors (29b) associated with a left one of the pair of rear wheels (11b) to produce a second wheel speed signal;

a left front wheel speed signal generator (34b) connected to a one of the wheel speed sensors (28b) associated with a left one of the pair of front wheels (6b) to produce a third wheel speed signal;

a right rear wheel speed signal generator (35b) connected to a one of the wheel speed sensors (29a) associated with a right one of the pair of rear wheels (11a) to produce a fourth wheel speed signal;

a first approximate vehicle speed signal generator (36a) connected to the right front wheel speed signal generator (34a) and to the left rear wheel speed signal generator (35a) to produce a first approximate vehicle speed signal;

a second approximate vehicle speed signal generator (36b) connected to the left front wheel speed signal generator (34b) and to the right rear wheel speed signal generator (35b) to produce a second approximate vehicle speed signal;

a first slip measure (37a) connected to the left rear wheel speed signal generator (35a) and toe the first approximate vehicle speed signal generator (36a) to produce a right slip measure signal;

a second slip measure (37b) connected to the right rear wheel speed signal generator (35b) and toe the second approximate vehicle speed signal generator (36b) to produce a left slip measure signal;

a slip comparator (38) connected to the first and second slip measures (37a and 37b) to produce a compared slip signal;

an inverter (48) connected to the slip comparator (38) to produce an inverted compared slip signal;

a first high select (39a) connected to the wheel speed signal generators (34a and 35a) and to the slip comparator (38) to select the higher of the wheel speed signals;

a first low select (40a) connected to the wheel speed signal generators (34a and 35a) and to the inverter (48) to select the lower of the wheel speed signals;

a second high select (39b) connected to the wheel speed signal generators (34b and 35b) and to the inverter (48) to select the higher of the wheel speed signals;

a second low select (40b) connected to the wheel speed signal generators (34b and 35b) and to the slip comparator (38) to select the lower of the wheel speed signals;

a first skid signal generator (41a) connected to the first high select (39a), the first approximate vehicle speed signal generator (36a) and the first low select (40a) to produce a first skid signal;

a second skid signal generator (41b) connected to the second high select (39b), the second approximate vehicle speed signal generator (36b) and the second low select (40b) to produce a second skid signal;

a first logic unit (42a) connected to the first skid signal generator (41a) to produce a first logic signal;

a second logic unit (42b) connected to the second skid signal generator (41b) to produce a second logic signal;

a first amplifier (43a) connected to the first logic unit (42a) to produce a signal that is taken to the first fluid pressure control device; and

a second amplifier (43b) connected to the second logic unit (42b) to produce a signal that is taken to the second fluid pressure control device, the control unit receiving outputs of said wheel speed sensors for judging the skid conditions of said front and rear wheels and for generating instructions for controlling said first and second fluid, whereby pressure control valve device, whereby said control unit comprises a discriminating circuit means for discriminating between the frictionally lower one and higher one of the sides of the road on which said wheels are running, on the basis of the judging results of the skid conditions of said rear wheels, and a control circuit means for controlling the braking pressure of the one rear wheel on the low side and of the one front wheel connected diagonally to said one rear wheel in a "select-high" manner, and the braking pressures of the other rear wheel on the high side and of the other front wheel connected diagonally to said other rear wheel in a "select-low" manner.

2. An anti-skid control apparatus according to claim 1, in which said discrimination circuit means judges the one side of the road on which the one of the rear wheels is running in more slip than the other of them, to have a smaller frictional coefficient, and the other side of the road on which the other of the rear wheels is running in less slip than the one of them, to have a larger frictional coefficient.

3. An anti-skid control apparatus according to claim 1, in which the one side of the road on which the one of the rear wheels is running at a lower wheel speed than the other of them, is judged to have a smaller functional coefficient, and the other side of the road on which the other of the rear wheels is running at a higher wheel speed than the one of them, is judged to have a larger frictional coefficient.

4. An anti-skid control apparatus according to claim 1, in which the one side of the road on which the one of the rear wheels to be locked at a lower pressure than the other of them is running, is judged to have a smaller frictional coefficient, and the other side of the road on which the other of the rear wheels to be locked at a higher pressure than the one of them is running, is judged to have a higher frictional coefficient.

5. An anti-skid control apparatus according to claim 1, in which the one side of the road on which the one of the rear wheels, which has generated a control signal sooner than the other of them, is running, is judged to have a smaller frictional coefficient, and the other side of the road on which the other of the rear wheels is running, is judged to have a higher frictional coefficient.

6. In an anti-skid control apparatus for a vehicle braking system including:

(A) a pair of front wheels and a pair of rear wheels which are diagonally connected with each other;

(B) wheel speed sensors associated with said wheels, respectively;

(C) a first fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of one of said front wheels, arranged between a first fluid pressure generating chamber of a tandem master cylinder and said wheel cylinder of the one front wheel;

(D) a second fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of another of said front wheels, arranged between a second fluid pressure generating chamber of said tandem master cylinder and said wheel cylinder of the other front wheel; and

(E) a control unit comprising;

a right front wheel speed signal generator (34a) connected to a one of the wheel speed sensors (28a) associated with a right one of the pair of front wheels (6a) to produce a first wheel speed signal;

a left rear wheel speed signal generator (35a) connected to a one of the wheel speed sensors (29b) associated with al eft one of the pair of rear wheels (11b) to produce a second wheel speed signal;

a left front wheel speed signal generator (34b) connected to a one of the wheel speed sensors (28b) associated with a left one of the pair of front wheels (6b) to produce a third wheel speed signal;

a right rear wheel speed signal generator (35b) connected to a one of the wheel speed sensors (29a) associated with a right one of the pair of rear wheels (11a) to produce a fourth wheel speed signal;

a first approximate vehicle speed signal generator (36a) connected to the right front wheel speed signal generator (34a) and to the left rear wheel speed signal generator (35a) to produce a first approximate vehicle speed signal;

a second approximate vehicle speed signal generator (36b) connected to the left front wheel speed signal generator (34b) and to the right rear wheel speed signal generator (35b) to produce a second approximate vehicle speed signal;

a first slip measure (37a) connected to the left rear wheel speed signal generator (35a) and to the first approximate vehicle speed signal generator (36a) to produce a right slip measure signal;

a second slip measure (37b) connected to the right rear wheel speed signal generator (35b) and to the second approximate vehicle speed signal generator (36b) to produce a left slip measure signal;

a slip comparator (38) connected to the first and second slip measures (37a and 37b) to produce a compared slip signal;

an inverter (48) connected to the slip comparator (38) to produce an inverted compared slip signal;

a first high select (39a) connected to the wheel speed signal generators (34a and 35a) and to the inverter (48) to select the higher of the wheel speed signals;

a first low select (40a) connected to the wheel speed signal generators (34a and 35a) and to the slip comparator (38) to select the lower of the wheel speed signals;

a second high select (39b) connected to the wheel speed signal generators (34b and 35b) and to the slip comparator (38) to select the higher of the wheel speed signals;

a second low select (40b) connected to the wheel speed signal generators (34b and 35b) and to the inverter (48) to select the lower of the wheel speed signals;

a first skid signal generator (41a) connected to the first high select (39a), the first approximate vehicle speed signal generator (36a) and the first low select (40a) to produce a first skid signal;

a second skid signal generator (41b) connected to the second high select (39b), the second approximate vehicle speed signal generator (36b) and the second low select (40b) to produce a second skid signal;

a first logic unit (442a) connected to the first skid signal generator (41a) to produce a first logic signal;

a second logic unit (42b) connected to the second skid signal generator (41b) to produce a second logic signal;

a first amplifier (43a) connected to the first logic unit (42a) to produce a signal that is taken to the first fluid pressure control device; and

a second amplifier (43b) connected to the second logic unit (42b) to produce a signal that is taken to the second fluid pressure control device, the control unit receiving outputs of said wheel speed sensors for judging the skid conditions of said front and rear wheels and for generating instructions for controlling said first and second fluid pressure control valve devices, whereby said control unit comprises a discriminating circuit for discriminating between the fictionally lower one and higher one of the sides of the road on which said wheels are running, on the basis of the judging results of the skid conditions of said front wheels, and the braking pressures of the one front wheel on the low side and of the one rear wheel connected diagonally to said one front wheel are controlled in a "select-low" manner, and the braking pressures of the other front wheel on the high side and of the other rear wheel connected diagonally to said other front wheel are controlled in a "select-low" manner.

7. An anti-skid control apparatus according to claim 6, in which said discriminating circuit means judges the one side of the road on which the one of the front wheels is running in more slip than the other of them, to have a smaller frictional coefficient, and the other side of the rod on which the other of the front wheels is running in less slip than the one of them, to have a larger frictional coefficient.

8. An anti-skid control apparatus according to claim 6, in which the one side of the road on which the one of the front wheels is running at a lower wheel speed than the other of them, is judged to have a smaller frictional coefficient, and the other side of the road on which the other of the front wheels is running at a higher wheel speed than the one of them, is judged to have a larger frictional coefficient.

9. An anti-skid control apparatus according to claim 6, in which the one side of the road on which the one of the front wheels to be locked at a lower pressure than the other of them is running, is judged to have a smaller frictional coefficient, and the other side of the road on which the other of the front wheels to be locked at a higher pressure than the one of them is running, is judged to have a higher frictional coefficient.

10. An anti-skid control apparatus according to claim 6, in which the one side of the road on which the one of the front wheels, which has generated a control signal sooner than the other of them, is running, is judged to have a smaller frictional coefficient, and the other side of the road on which the other of the front is running, is judged to have a higher frictional coefficient.