Fluid-pressure and analogous brake systems – Speed-controlled – Multiple control signal with multiple threshold
Reexamination Certificate
1998-03-06
2001-08-21
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Multiple control signal with multiple threshold
C303S146000, C303S113200
Reexamination Certificate
active
06276766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake system of a vehicle such as an automobile, and more particularly, to a brake system for a behavior control of a vehicle, incorporating a pump for pressurizing a working fluid of the brake system, the pump being started before the start of the behavior control to provide a raised pressure source of the working fluid ready for the behavior control without any substantial accumulator therefor.
2. Description of the Prior Art
By Japanese Patent Application 7-201779 laid open to public as Laid-open Publication 8-150919 and having counterparts in U.S.A. and Germany as U.S. Pat. No. 5,797,663 and German Patent Application No. P19535623.3-21, respectively, there has been proposed a brake system for a behavior control of a vehicle such as an automobile adapted to operate with an automatic control means which controls a pump and a plurality of fluid flow control valves based upon a parameter representing a liability of the vehicle to an unstabilized running behavior, the pump generating a raised pressure source of a working fluid by operation, while the fluid flow control valves dealing with the raised pressure source to supply a raised pressure to selected one or ones of four wheels, so as, for example, to brake a front wheel at the outside of a turn running of the vehicle when it is liable to a spin, wherein the invention resides in that the brake system dispenses with the conventional accumulator for the pressurized working fluid by the pump being started to operate according to a forecast of the vehicle being put into the unstabilized behavior estimated by the automatic control means based upon the above-mentioned parameter approaching to a first predetermined value thereof indicating a probability of the occurrence of the unstabilized behavior so that a raised pressure source of the working fluid is immediately available with no substantial accumulator therefor when the automatic control means decides to supply the working fluid at a raised pressure to a wheel cylinder or cylinders of a particular wheel or wheels for execution of a stability control.
In the above-mentioned prior art, it is proposed to check if a parameter such as the slip angle of the vehicle body representing the liability of the vehicle to a spin has exceeded a first predetermined threshold value thereof to start the operation of the pump and to check if the parameter has exceeded a second predetermined threshold value thereof to start the execution of the stability control, the second threshold value being higher than the first threshold value.
SUMMARY OF THE INVENTION
In the meantime, the present inventor contemplated that, if the parameter for starting the pump operation is selected judiciously to be different from the parameter for starting the execution of the behavior control, a higher flexibility and versatility of the control performance should be available than in the above-mentioned prior art, accomplishing a better adaptation of the time for starting the pump operation to the actual need of a raised pressure source of the working fluid.
In view of the above, it is a primary object of the present invention to provide a brake system operable with no substantial accumulator for the raised pressure source of working fluid for selectively applying a braking to a selected wheel or wheels of a vehicle for the purpose of stabilizing the running behavior thereof with a higher adaptation performance of starting pump operation for providing a raised pressure source of the working fluid to the actual use of the raised pressure source of the working fluid.
According to the present invention, the above-mentioned primary object of the present invention is accomplished by a brake system of a vehicle having a vehicle body and front left, front right, rear left and rear right wheels, comprising a reservoir, a plurality of wheel cylinders each adapted to apply a braking force to a corresponding one of the front left, front right, rear left and rear right wheels when supplied with a working fluid at a raised pressure, an inlet passage means adapted to supply the working fluid to said wheel cylinders, a pump means for pumping the working fluid from said reservoir to said inlet passage means to provide a raised pressure source of the working fluid in said passage means, fluid circuit means including fluid flow control valves for selectively conducting the working fluid from said inlet passage means to each one of said wheel cylinders, and an automatic control means for controlling said pump means and said fluid flow control valves, wherein said automatic control means comprises a first means for obtaining a first parameter related to running of the vehicle, and a second means for obtaining a second parameter different from said first parameter related to running of the vehicle in a time-based changing performance thereof, said first and second parameters each relating to a probable requirement for applying braking force to at least one wheel selected from the front left, front might, rear left and rear might wheels for a stability control of the vehicle by successively reaching first and second threshold values, respectively, in said order according to an increase in need for stability control, said automatic control means controlling said pump means and said fluid flow control valves such that, when said first parameter reaches said first threshold value, said pump means is started for operation thereof so as to provide said raised pressure source in said inlet passage means while said flow control valves deal with said raised pressure source not to supply any of the wheel cylinders with such a raised pressure based upon said raised pressure source as to effect a substantial braking thereby, and when said second parameter reaches said second threshold value, the wheel cylinder or cylinders corresponding to said selected wheel or wheels are supplied with such a raised pressure based upon said raised pressure source as to effect a substantial braking thereby.
By selecting the parameter for starting the pump operation to be different from that for starting the substantial operation of the brake system, it is now possible to start the pump operation based upon a checking of such a parameter that is not indicative of the degree of a movement of the vehicle which leads to an unstabilized behavior of the vehicle but is a more primary factor which induces such a movement of the vehicle.
So in the brake system of the above-mentioned construction, said first parameter may be a longitudinal slip ratio of a rear wheel operating at the inside of a turn running of the vehicle, while said second parameter may be the absolute value of a spin value based upon slip angle of the vehicle body representing a liability of the vehicle to spin, said automatic control means controlling said flow control valves so as to supply said raised pressure to effect said substantial braking to either the front left or front right wheel operating at the outside of the turn running of the vehicle, in order to suppress the vehicle from getting into a spin during a turn running with a braking.
In such a brake system, said automatic control means may stop said pump means once started when a predetermined time lapses after subsidence of the absolute value of said spin value below said second threshold value.
Or, in the brake system of the above-mentioned basic construction, when applied to a front steered vehicle having a front steering system, said first parameter may be the absolute value of a change rate of steering angle of the front steering system, while said second parameter may be the absolute value of a spin value based upon slip angle of the vehicle body representing a liability of the vehicle to spin, said automatic control means controlling said flow control valves so as to supply said raised pressure to effect said substantial braking to either the front left or front right wheel operating at the outside of the turn running of the vehicle, in order to supp
Oliff & Berridg,e PLC
Schwartz Christopher P.
Toyota Jidosha & Kabushiki Kaisha
Williams Thomas J.
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