Fluid-pressure and analogous brake systems – Speed-controlled – Front-rear axle apportioning or speed difference
Reexamination Certificate
1999-12-30
2001-02-27
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Front-rear axle apportioning or speed difference
C303S011000, C303S115400, C303S116100, C303S140000, C303S147000
Reexamination Certificate
active
06193331
ABSTRACT:
This application is related to and claims priority from Japanese Patent Application No. Hei-8-105383, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicular brake system. In particular, the present invention relates to a vehicular brake system for generating a wheel brake force greater than a brake force corresponding to depressing a brake pedal.
2. Description of Related Art
Load transfer in a vehicle chassis occurs during braking operations of a vehicle. Load transfer is influenced by the vehicle's deceleration which results in a gradual increase in the load on the front wheels of the vehicle. To deal with such problems, proportional control valves, for example, have been provided in the rear wheels to make pressure applied to the rear wheels lower than the pressure applied on the front wheels so that the brake forces generated on the rear wheels are lower than brake forces generated on the front wheels. These widely known proportional control valves reduce the amount of brake fluid in the direction of the brake fluid flow based on predetermined attenuation ratios.
When such a proportional control valve is provided, even if there is actually a high brake pressure in the master cylinder due to the demand for a high braking force, the brake pressure applied to the wheel cylinders is reduced by the proportional control valve which results in a smaller brake force. Thus, performance efficiency of the brake system declines because a significant amount of brake pressure is wasted when generating a large brake force.
SUMMARY OF THE INVENTION
In view of the foregoing problems in the prior art, the present invention provides a vehicular brake system for generating a brake force by efficiently utilizing brake pressure of a magnitude greater than normal pressure levels.
A first aspect of the present invention provides a vehicular brake system which includes a brake pressure generating unit, a first fluid line, a second fluid line, first wheel brake force generating units, second wheel brake force generating units and a first pressure increasing unit. The brake pressure generating unit is capable of generating a first brake pressure. The first fluid line couples a first wheel and a second wheel of the vehicle with the brake pressure generating unit. The second fluid line couples a third wheel and a fourth wheel of the vehicle with the brake pressure generating unit. The second fluid line has a second fluid line pressure which is in accordance with the first brake pressure. The first wheel brake force generating units are coupled to the first wheel and the second wheel. The first wheel brake force generating units generate a first brake force in the first wheel and the second wheel based on a first fluid line pressure of the first fluid line. The second wheel brake force generating units are coupled to the third wheel and the fourth wheel. The second wheel brake force generating units generate a second brake force in the third wheel and the fourth wheel based on the second fluid line pressure of the second fluid line. The first pressure increasing unit is for increasing the first brake force generated by the first wheel brake force generating units in the first wheel and the second wheel by adjusting the first fluid line pressure to exceed the first brake pressure generated by the brake pressure generating unit so that there is a difference between the first fluid line pressure and the second fluid line pressure.
In this way, with first pressure increasing unit increasing pressure in the first fluid line, the first wheel brake force generating units generate a brake force which is greater than a brake force corresponding to, for example, depression of a brake pedal and which assures reliable brake operation of the vehicle. Also, when the front left and right wheels of the vehicle are set as the first and second wheels, respectively, and the rear left and right wheels are set as the third and fourth wheels, respectively, there is assurance of stable vehicle operations even if load transfer occurs during brake operations because the rear wheels will never look before the front wheels lock. This is due to the fact that the first fluid line pressure is increased to exceed both the first brake pressure and the second fluid line pressure.
Preferably, the brake system has a second pressure adjusting unit that adjusts the second brake force generated by the second wheel brake force generating units in the third wheel and the fourth wheel by adjusting the second fluid line pressure to be no more than the first brake pressure generated by the brake pressure generating unit.
Preferably, the first pressure increasing unit adjusts the first fluid line pressure by drawing brake fluid from the brake pressure generating unit and supplying brake fluid drawn from the brake pressure generating unit to the first fluid line when the brake pressure generating unit is generating the first brake pressure.
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Abe Youichi
Sawada Mamoru
Yonemura Syuichi
Denso Corporation
Oberleitner Robert J.
Pillsbury Madison & Sutro LLP
Siconolfi Robert A.
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