Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-04-23
2001-06-12
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C060S397000
Reexamination Certificate
active
06244676
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a negative pressure control apparatus for a brake booster, and particularly to a negative pressure control apparatus for controlling negative pressure in a brake booster in a system which has a function of increasing a brake fluid pressure by increasing the negative pressure of the brake booster.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Laid-Open Patent Application No. 5-208663, a braking apparatus having a brake booster is known. The brake booster is a mechanism which assists a brake operation by using an intake manifold negative pressure as a power source so that a larger braking force can be generated. The above braking apparatus has a function of increasing a master cylinder pressure by increasing negative pressure of the brake booster when a brake operation is not being performed. Hereinafter, this function is referred to as a booster charge function.
The above braking apparatus also has a function of performing an automatic brake control for generating a braking force when an obstacle is detected ahead of the vehicle in a situation where no brake operation is being performed. This automatic brake control is achieved by increasing the master cylinder pressure using the above-mentioned booster charge function. Additionally, the above braking apparatus increases the negative pressure of the brake booster toward a predetermined target value when execution of the automatic brake control is predicted so as to positively perform the brake control.
However, when a temperature of brake fluid is low, a delay occurs in transmitting a fluid pressure to wheel cylinders due to an increase in viscous resistance of the brake fluid. Thus, in the above-mentioned conventional braking apparatus, a response of the automatic brake control controlling the brake fluid pressure may be delayed when the temperature is low.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a negative pressure control apparatus for a brake booster which can always control the brake fluid pressure with a fast response time regardless of the temperature of the brake fluid in a brake system having the booster charge function.
The above-mentioned object can be achieved by a negative pressure control apparatus for a brake booster for controlling a negative pressure in a negative pressure chamber of the brake booster, which apparatus is provided in a system having a booster charge mechanism for generating a fluid pressure by using the negative pressure in the negative pressure chamber and a fluid pressure control mechanism for controlling a brake fluid pressure by using the fluid pressure generated by the booster charge mechanism, the apparatus comprising:
a negative pressure controller for controlling the negative pressure in the negative pressure chamber to be at least a predetermined target negative pressure;
a temperature detector for detecting information relating to a temperature of brake fluid; and
a target negative pressure setting part for setting the predetermined target negative pressure based on the temperature of the brake fluid.
In this invention, the negative pressure controller controls the negative pressure in the negative pressure chamber to be at least a predetermined target value. The booster charge mechanism generates a fluid pressure by using the negative pressure in the negative pressure chamber, and the fluid pressure control mechanism controls a brake fluid pressure by using the fluid pressure generated by the booster charge mechanism. When a temperature of brake fluid is low, a delay may occur in transmission of fluid pressure in the fluid pressure control mechanism due to an increase in viscosity of the brake fluid. When a delay occurs in transmission of fluid pressure, a response of the fluid control mechanism controlling the brake fluid pressure is delayed. According to the present invention, the target negative pressure setting part sets the target value based on the temperature of the brake fluid. In this case, the fluid pressure generated by the booster charge mechanism can be increased in accordance with the increase in viscosity of the brake fluid, and thus the delay in transmission of fluid pressure is compensated for. Therefore, according to the present invention, the brake fluid pressure can be controlled with a fast response time regardless of the temperature.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
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Endo Hiroaki
Watanabe Ryochi
Yamada Yoshihisa
Nguyen Xuan Lan
Oberleitner Robert J.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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