Anti-lock brake system for vehicles

• US 4,925,254 A
• Filed: 09/08/1988
• Issued: 05/15/1990
• Est. Priority Date: 09/21/1987
• Status: Expired due to Term

• Current Assignee: Wabco Westinghouse Fahrzeugbremsen GmbH
• Original Assignee: Wabco Westinghouse Fahrzeugbremsen GmbH
• Inventors: Lindemann, Klaus, Kaess, Hans-Harald, Holst, Hans, Petersen, Erwin, Saba, Manfred
• Primary Examiner(s): Kashnikow, Andres
• Assistant Examiner(s): Newholm, Timothy
• Application Number:
  US07/242,027
• Time in Patent Office: 614 Days
• Field of Search: 303/95, 303/96, 303/97, 303/100, 303/103, 303/105, 303/106, 303/110, 303/111, 188/181 A, 188/181 C, 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-lock brake system for vehicles with an electronic system which regulates the braking pressure of a monitored wheel as a function of the wheel speed, so that locking is prevented. The system is designed so that each wheel has its own speed sensor, and both wheels of one axle are pressurized with pressure medium by means of a joint control valve controlled by the electronic system. This arrangement corresponds to that of a select-low regulation. To shorten the extended braking distance on roads with different traction on each side, which occurs with a select-low regulation, the control system is designed so that when a retard signal (-b) occurs, the electronic system does not switch as usual to "remove pressure", but, at least until the occurrence of a slip signal (λ), the control valve is switched to the "maintain pressure" position.

Claims

1. A vehicle anti-lock brake system, said anti-lock brake system comprising:

(a) a solenoid control valve connectable at a fluid pressure inlet port to enable communication of fluid pressure thereto from a source of such fluid pressure, said solenoid control valve being connectable at a fluid pressure outlet port to a predetermined pair of brake cylinders positioned on such vehicle, said solenoid control valve controls communication of such fluid pressure to such predetermined pair of brake cylinders and evacuation of such fluid pressure from such predetermined pair of brake cylinders;

(b) a speed sensing means positionable on such vehicle adjacent each brakeable wheel for each of determining a rotational speed of such brakeable wheel and for generating an electrical signal having a value representative of such rotational speed and for transmitting said electrical signal;

(c) an electronic control system positionable on such vehicle and electrically connectable at an input terminal thereof to each said speed sensing means to enable receiving said electrical signal value generated by said speed sensing means, said electronic control system being electrically connectable at an output terminal thereof to enable transmission of an electrical control signal to an input terminal of said solenoid control valve;

(d) a means disposed in said electronic control system for determining when said electrical signal value received by said electronic control system from each said speed sensing means is representative of a deceleration signal value of a low wheel, said electronic control system in response to said electrical signal value being representative of said deceleration signal value transmits a pressure hold electrical control signal to said input terminal of said solenoid control valve;

(e) a means disposed in said electronic control system for determining when said electrical signal value received by said electronic control system from each said speed sensing means is representative of a slip signal value of a low wheel, said electronic control system in response to said electrical signal value being representative of said slip signal value transmits a pressure decrease electrical control signal to said input terminal of said solenoid control valve;

(f) a means disposed in said electronic control system for determining when said electrical signal value received by said electronic control system from each said speed sensing means is representative of a decrease in said electrical signal value of said slip signal value of such low wheel, said electronic control system in response to said decrease in said electrical signal value representative of said slip signal value of such low wheel transmits a pressure increase electrical control signal to said input terminal of said solenoid control valve;

(g) a switch means disposed in said electronic control system for switching to a select low control mode; and

(h) a timer means disposed in said electronic control system for determining a time duration of an electrical signal value being received by said electronic control system from each said speed sensing means and wherein said switching means in said electronic control system will switch to said select low control mode when said speed sensing means adjacent each of a high wheel and a low wheel transmits an electrical signal value representative of a slip signal value to said input terminal of said electronic control system for a duration of about 100 ms as determined by said timer means.

2. An anti-lock brake system, according to claim 1, wherein said electronic control system further includes a means disposed therein for determining when said electrical signal value received by said electronic control system from each said speed sensing means indicates at least one of a deceleration signal value and a slip signal value from a high wheel, said electronic control system in response to this determination transmits an appropriate electrical control signal to said input terminal of said solenoid control valve to switch said solenoid control valve to a pressure decrease position.

3. An anti-lock brake system, according to claim 2, wherein said switch means in said electronic control system switches to a select low control mode when said speed sensing means adjacent a high wheel transmits an electrical signal value representative of a slip signal value to said input terminal of said electronic control system.

4. An anti-lock brake system, according to claim 2, wherein said electronic control system further includes a second switching means disposed therein for switching to a select low control mode during a first control cycle of said anti-lock brake system.

5. An anti-lock brake system, according to claim 2, wherein said electronic control system further includes a switching means disposed therein for switching said anti-lock brake system to a select low control mode at a vehicle speed determined by said speed sensing means to be less than about 15 km/hr.

6. An anti-lock brake system, according to claim 1, wherein said switch means in said electronic control system switches to a select low control mode when said speed sensing means adjacent a high wheel transmits an electrical signal value representative of a slip signal value to said input terminal of said electronic control system.

7. An anti-lock brake system, according to claim 6, wherein said electronic control system further includes a second switching means disposed therein for switching to said select low control mode during a first control cycle of said anti-lock brake system.

8. An anti-lock brake system, according to claim 6, wherein said electronic control system further includes a second switching means disposed therein for switching said anti-lock brake system to said select low control mode at a vehicle speed determined by said speed sensing means to be less than about 15 km/hr.

9. An anti-lock brake system, according to claim 1, wherein said electronic control system further includes a second switching means disposed therein for switching to a select low control mode during a first control cycle of said anti-lock brake system.

10. An anti-lock brake system, according to claim 9, wherein said electronic control system further includes a second switching means disposed therein for switching said anti-lock brake system to said select low control mode at a vehicle speed determined by said speed sensing means to be less than about 15 km/hr.

11. An anti-lock brake system, according to claim 1, wherein said electronic control system further includes a switching means disposed therein for switching said anti-lock brake system to a select low control mode at a vehicle speed determined by said speed sensing means to be less than about 15 km/hr.

12. An electronic control apparatus for a vehicle anti-lock brake system, said electronic control apparatus comprising:

(a) a solenoid actuated control valve having a fluid pressure inlet port and a fluid pressure outlet port, said inlet port being connectable to receive fluid pressure from a source of such fluid pressure, said outlet port being connectable to a predetermined pair of brake cylinders positioned on such vehicle, said solenoid actuated control valve controlling both communication of such fluid pressure to such predetermined pair of brake cylinders and for evacuating such fluid pressure from such predetermined pair of brake cylinders;

(b) a speed sensing means positionable on such vehicle in a position adjacent each brakeable wheel for each of determining a rotational speed of an associated brakeable wheel and for generating an electrical signal having a value representative of such rotational speed of such associated brakeable wheel and for transmitting said electrical signal value;

(c) an electronic control system positionable on such vehicle, said electronic control system having at least one input terminal and at least one output terminal, said electronic control system being electrically connectable at said input terminal thereof to each of said speed sensing means to enable receiving said electrical signal value thereat, said electronic control system being electrically connectable at said output terminal thereof to an input terminal of said solenoid actuated control valve to enable transmission of an electrical control signal thereto;

(d) a first means disposed in said electronic control system for determining when said electrical signal value being received by said electronic control system from said each of said speed sensing means is representative of a deceleration signal value of a low wheel, said electronic control system transmitting a pressure hold electrical control signal to said input terminal of said solenoid actuated control valve in response to said electrical signal value being representative of said deceleration signal value of such low wheel;

(e) a second means disposed in said electronic control system for determining when said electrical signal value being received by said electronic control system from said each of said speed sensing means is representative of a slip signal value of such low wheel, said electronic control system transmitting a pressure increase electrical control signal to said input terminal of said solenoid actuated control valve in response to said electrical signal value being representative of said slip signal value of such low wheel;

(f) a third means disposed in said electronic control system for determining when said electrical signal value being received by said electronic control system from said each of said speed sensing means is representative of a decrease in said electrical signal value of said slip signal value of such low wheel, said electronic control system transmitting a pressure increase electrical control signal to said input terminal of said solenoid actuated control valve in response to said decrease in said electrical signal value representative of said slip signal value of such low wheel;

(g) a fourth means disposed in said electronic control system for determining when said electrical signal value being received by said electronic control system from said each of said speed sensing means is representative of at least one of a deceleration signal value and a slip signal value of a high wheel, said electronic control system transmitting a pressure decrease electrical control signal to said input terminal of said solenoid control valve in response to said electrical signal value of such high wheel being representative of said at least one of said deceleration signal value and said slip signal value;

(h) a timer means disposed in said electronic control system for determining a time duration of said electrical signal value being received by said electrical control system from said each of said speed sensing means; and

(i) a microprocessor disposed in said electronic control system for generating appropriate electrical control signals to be transmitted to said input terminal of said solenoid actuated control valve.

13. An electronic control apparatus for an anti-lock brake system, according to claim 12, wherein said microprocessor includes a program means loaded therein to switch said anti-lock brake system to a select low control mode when said speed sensing means positioned adjacent a high wheel transmits an electrical signal value representative of a slip signal value to said electronic control system.

14. An electronic control apparatus for an anti-lock brake system, according to claim 13, wherein said program means loaded in said microprocessor switches said anti-lock brake system to said select low control mode when said speed sensing means positioned adjacent each of such high wheel and such low wheel transmits an electrical signal value representative of a slip signal value to said electronic control system for a duration of about 100 ms as determined by said timer means.

15. An electronic control apparatus for an anti-lock brake system, according to claim 14, wherein said program means loaded in said microprocessor switches said anti-lock brake system into said select low control mode during a first control cycle of said anti-lock brake system.

16. An electronic control apparatus for an anti-lock brake system, according to claim 15, wherein said program means loaded in said microprocessor switches said anti-lock brake system into said select low control mode at a vehicle speed determined by said speed sensing means to be less than about 15 km/hr.

17. A control method for a fluid pressure responsive anti-lock brake system positioned on a vehicle, said control method comprising the steps of:

(a) connecting an electrically actuated and electrically controllable solenoid control valve at a fluid pressure medium inlet port thereof to a source of said fluid pressure medium positioned on such vehicle;

(b) connecting a fluid pressure medium outlet port of said electrically actuated and controllable solenoid control valve to a predetermined pair of brake cylinders positioned on such vehicle;

(c) initiating a brake application on such vehicle;

(d) activating said electrically actuated and controllable solenoid control valve substantially at an identical time as said brake application initiated in step (c) by feeding an electrical control signal to an input terminal of said electrically actuated and controllable solenoid control valve from an output terminal of an electronic control system positioned on such vehicle;

(e) communicating said fluid pressure medium to said inlet port of said electrically actuated and controllable solenoid control valve from said source of said fluid pressure medium substantially at an identical time as said electrical control signal is fed to said input terminal of said electrically actuated and controllable solenoid control valve in step (d);

(f) communicating a first predetermined volume of said fluid pressure medium from said outlet port of said electrically actuated and controllable solenoid control valve to each of said predetermined pair of brake cylinders substantially at an identical time as said fluid pressure medium is communicated to said inlet port of said electrically actuated and controllable solenoid control valve in step (e) thereby applying a first predetermined brake pressure on each of a respective brakeable wheel mounted on such vehicle;

(g) determining a rotational speed of each said brakeable wheel with a speed sensing means positioned on such vehicle adjacent a respective one of each said brakeable wheel;

(h) generating an electrical signal value representative of said rotational speed of said each said brakeable wheel determined in step (g);

(i) feeding said electrical signal value generated in step (h) from an output terminal of said speed sensing means to an input terminal of said electronic control system;

(j) determining in said electronic control system when said electrical signal value being fed to said input terminal thereof in step (i) is an electrical signal value representative of a deceleration signal value of a low wheel;

(k) generating a brake pressure hold electrical control signal in said electronic control system in response to a determination in step (j) of said electrical signal value fed to said input terminal of said electronic control system in step (i) being representative of said deceleration signal value of said low wheel;

(l) feeding said brake pressure hold electrical control signal generated in step (k) from said output terminal of said electronic control system to said input terminal of said electrically actuated and controllable solenoid control valve;

(m) maintaining said first predetermined brake pressure on said each of said respective brakeable wheel applied in step (f) in response to said brake pressure hold electrical control signal fed to said input terminal of said electrically actuated and controllable solenoid control valve in step (1);

(n) determining in said electronic control system when said electrical signal value fed to said input terminal thereof in step (i) is an electrical signal value representative of a slip signal value of said low wheel;

(o) generating a brake pressure decrease electrical control signal in said electronic control system in response to a determination in step (n) of said electrical signal value being fed to said input terminal of said electronic control system in step (i) being representative of said slip signal value of said low wheel;

(p) feeding said brake pressure decrease electrical control signal generated in step (o) from said output terminal of said electronic control system to said input terminal of said electrically actuated and controllable solenoid control valve;

(q) evacuating from said predetermined pair of brake cylinders a predetermined portion of said first predetermined volume of said fluid pressure medium communicated thereto in step (f) thereby decreasing said first predetermined brake pressure being applied in step (f);

(r) determining in said electronic control system when said electrical signal value fed to said input terminal thereof in step (i) is an electrical signal value representative of a decrease in said slip signal value of said low wheel determined in step (n);

(s) generating a brake pressure increase electrical control signal in said electronic control system in response to a determination in step (r) of said electrical signal value fed to said input terminal of said electronic control system in step (i) being representative of said decrease in said slip signal value of said low wheel;

(t) feeding said brake pressure increase electrical control signal generated in step (s) from said output terminal of said electronic control system to said input terminal of said electrically actuated and controllable solenoid control valve;

(u) communicating a second predetermined volume of said fluid pressure medium from said outlet port of said electrically actuated and controllable solenoid control valve to said each of said predetermined pair of brake cylinders thereby applying a second predetermined brake pressure on said each of said respective brakeable wheel;

(v) terminating said brake application initiated in step (c); and

(w) evacuating substantially all of said fluid pressure medium from said each of said predetermined pair of brake cylinders in response to an electrical control signal being fed from said output terminal of said electronic control system to said input terminal of said electrically actuated and controllable solenoid control valve after said brake application has been terminated in step (v).

18. A control method for a fluid pressure responsive anti-lock brake system, according to claim 17, wherein after step (i) and prior to step (v) said control method includes the additional steps of:

(a'"'"') determining in said electronic control system when said electrical signal value being fed to said input terminal thereof in step (i) is an electrical signal value representative of at least one of a deceleration signal value and a slip signal value of a high wheel;

(b'"'"') generating a brake pressure decrease electrical control signal in said electronic control system in response to a determination in step (a'"'"') of said electrical signal value fed to said input terminal of said electronic control system in step (i) being representative of said at least one of said deceleration signal value and said slip signal value of said high wheel;

(c'"'"') feeding said brake pressure decrease electrical control signal generated in step (b'"'"') from said output terminal of said electronic control system to said input terminal of said electrically actuated and controllable solenoid control valve; and

(d'"'"') evacuating from said predetermined pair of brake cylinders a predetermined portion of said first predetermined volume of said fluid pressure medium communicated thereto in step (f) thereby decreasing said first predetermined brake pressure being applied in step (f) to said high wheel.

19. A control method for a fluid pressure responsive anti-lock brake system, according to claim 18, wherein after step (i) and prior to step (v) said control method includes the additional steps of:

(a") determining in said electronic control system when said electrical signal value being fed to said input terminal thereof in step (i) is said electrical signal value representative of said slip signal value of said high wheel;

(b") generating a select low control mode electrical control signal in said electronic control system in response to a determination in step (a") of said electrical signal value fed to said input terminal of said electronic control system in step (i) being representative of said slip signal value of said high wheel;

(c") feeding said select low control mode electrical control signal generated in step (b") from said output terminal of said electronic control system to said anti-lock brake system; and

(d") switching said anti-lock brake system to said select low control mode.

20. A control method for a fluid pressure responsive anti-lock brake system, according to claim 19, wherein during step (i) said control method includes the additional step of determining a time duration in said electronic control system of said electrical signal value being fed to said input terminal thereof being which is representative of said slip signal value of each of said high wheel and said low wheel.

21. A control method for a fluid pressure responsive anti-lock brake system, according to claim 20, wherein said control method includes the additional steps of:

(aa) generating a select low control mode electrical control signal in said electronic control system in response to a determination of said time duration being about 100 ms;

(bb) feeding said select low control mode electrical control signal generated in step (aa) from said output terminal of said electronic control system to said anti-lock brake system; and

(cc) switching said anti-lock brake system to said select low control mode.

22. A control method for a fluid pressure responsive anti-lock brake system, according to claim 21, wherein said control method includes the additional step of switching said anti-lock brake system into said select low control mode during a first control cycle of said anti-lock brake system.

23. A control method for a fluid pressure responsive anti-lock brake system, according to claim 22, wherein said control method includes the additional step of switching said anti-lock brake system into said select low control mode at a vehicle speed determined in said electronic control system of less than about 15 km/hr.