Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-01-07
2001-02-06
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06183049
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brake boosting system for providing intensified braking force by directly boosting master cylinder pressure.
Conventionally, a brake boosting system used in an automobile is provided with a booster, which boosts input to a predetermined magnitude by using hydraulic pressure such as negative pressure or fluid pressure and a master cylinder (hereinafter, sometimes referred to as “MCY”) is actuated by the output of the booster, thereby obtaining large braking force from small leg power on the brake pedal.
Conventionally used in a vacuum brake boosting system provided with a vacuum booster is negative pressure produced in an engine. Recently, however, fuel consumption reduction of an engine is desired, whereas lower negative pressure is produced in the engine. As a result of this, output of a vacuum booster is also reduced. One of measures to cope with this reduction in the output is enlargement of the vacuum booster. However, this enlargement makes it quite difficult to install the vacuum booster in a small engine room.
On the other hand, a fluid pressure brake boosting system provided with a fluid pressure booster has a problem that parts such as a pump and an accumulator are required, thereby increasing the cost.
In such brake boosting systems, it is desired that, in case of emergency braking, the boosting device quickly produces braking force larger than that in case of normal braking.
among inexpert drivers, there must be a person who can not pedal a brake pedal fully so as not to develop large braking force. In this case, it is desired to provide braking assist for ensuring that large braking force is obtained even by such an inexpert driver.
In the conventional brake boosting systems, however, since the servo ratio of the servo control is constant during the output of the braking force, not only braking force larger than that for normal braking can nor be quickly produced for emergency braking, but also no braking assist for ensuring that large braking force is obtained even by the inexpert driver is provided. Therefore, it is difficult to meet the aforementioned demands.
SUMMARY OF THE INVENTION
The object of the present invention provide a brake boosting system with a simple structure which can intensify master cylinder pressure to output large braking force when necessary.
For accomplishing the object, a brake boosting system of the present invention comprises at least: a brake operating member for braking operation; a reservoir for storing brake fluid; a master cylinder for producing master cylinder pressure; and a brake cylinder for producing braking force when the master cylinder pressure is introduced into the brake cylinder, wherein corresponding to the operation of the brake operating member, an input shaft advances to actuate a master cylinder piston, thereby producing the master cylinder pressure. The brake boosting system further comprising: a pressure intensifying chamber facing the rear end of the master cylinder piston; a reaction chamber disposed between the master cylinder piston and the input shaft and always communicating with the pressure intensifying chamber; a fluid pressure source for producing fluid pressure and supplying the fluid pressure into the pressure intensifying chamber; and a communication control means which allows the pressure intensifying chamber and the reaction chamber to communicate with the reservoir when the system is inoperative, and intercepts the pressure intensifying chamber and the reaction chamber from communicating with the reservoir when the input shaft advances.
The brake boosting system of the present invention as structured above may consist of a system of open centre type. When the brake boosting system is inoperative, the pressure intensifying chamber communicates with both the fluid pressure source and the reservoir by the communication control means. During a normal braking operation, because of the advance of the input shaft, the pressure intensifying chamber is shut off from the reservoir by the communication control means. During this normal braking, the fluid pressure of the fluid pressure source is prevented from being supplied to the pressure intensifying chamber not to intensifying the master cylinder pressure of the master cylinder, thereby performing the braking operation at normal braking pressure. Also during the braking operation when braking assist is necessary, the pressure intensifying chamber is shut off from the reservoir by the communication means. In this case where the intensified pressure is required, the fluid pressure of the fluid pressure source is supplied to the pressure intensifying chamber so as to intensify the master cylinder pressure in the master cylinder, thereby performing the braking operation at braking pressure higher than the normal braking pressure. Therefore, the pressure intensifying can be securely obtained when it is required to quickly provide large braking force such as emergency braking.
Further, the present invention further comprises a solenoid control valve disposed between the pressure intensifying chamber and the fluid pressure source for controlling the communication between the pressure intensifying chamber and the fluid pressure source.
In the brake boosting system of the present invention, the supply and discharge of the fluid pressure from the fluid pressure source to the pressure intensifying chamber is controlled by the solenoid control valve. Therefore, when the pressure intensification is necessary, the fluid pressure can be rapidly and securely supplied from the fluid pressure source to the pressure intensifying chamber.
A brake boosting system of the present invention comprises at least: a brake operating member for braking operation; a reservoir for storing brake fluid; a master cylinder for producing master cylinder pressure; and a brake cylinder for producing braking force when the master cylinder pressure is introduced into the brake cylinder, wherein corresponding to the operation of the brake operating member, an input shaft advances to actuate a master cylinder piston, thereby producing the master cylinder pressure. The brake boosting system further comprises: a pressure intensifying chamber facing the rear end of the master cylinder piston; a reaction chamber disposed between the master cylinder piston and the input shaft and always communicating with the pressure intensifying chamber; a fluid pressure source for producing fluid pressure; and a communication control means which allows the pressure intensifying chamber and the reaction chamber to communicate with the reservoir and intercepts the pressure intensifying chamber and the reaction chamber from communicating with the fluid pressure source when the system is inoperative, and blocks the pressure intensifying chamber and the reaction chamber from communicating with the reservoir and allows the pressure intensifying chamber and the reaction chamber to communicate with the fluid pressure source when the input shaft advances.
The brake boosting system of the present invention as structured above may consist of a system of closed centre type. When the brake boosting system is inoperative, the pressure intensifying chamber is shut off from the fluid pressure source and communicates with the reservoir by the communication control means. During a normal braking operation, because of the advance of the input shaft, the pressure intensifying chamber is shut off from the reservoir and is allowed to communicate with the fluid pressure source by the communication control means. During this normal braking operation, the fluid pressure of the fluid pressure source is prevented from being supplied to the pressure intensifying chamber not to intensifying the master cylinder pressure of the master cylinder, thereby performing the braking operation at normal braking pressure. Also during the braking operation when braking assist is necessary, the pressure intensifying chamber is shut off from the reservoir and is allowed to communicate with the flu
Imoto Yuzo
Inoue Hidefumi
Oka Hiroyuki
Sawada Mamoru
Shimada Masahiro
Bartz C. T.
Bosch Braking Systems Co. Ltd.
Kanesaka & Takeuchi
Schwartz Christopher P.
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