Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2001-02-08
2002-08-13
Lavinder, Jack (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113100, C303S113400, C303S113300, C060S582000
Reexamination Certificate
active
06431662
ABSTRACT:
This application is based on Japanese Patent Applications No. 2000-056295 filed Mar. 1, 2000 and No. 2000-183596 filed Jun. 19, 2000, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a braking pressure source device for an automotive vehicle, and more particularly to a braking pressure source device including a master cylinder wherein a pressurizing piston partially defines a pressurizing chamber and a back-pressure chamber on opposite sides thereof so that the pressure in the back-pressure chamber acts on the pressurizing piston.
2. Discussion of Related Art
Japanese Patent Application No. 10-364575 filed by the assignee of this invention but not laid open at the time the present invention was made discloses one type of a braking pressure source device which includes a master cylinder wherein a pressurizing piston partially defines a back-pressure chamber on a rear side thereof so that a back pressure in the back-pressure chamber acts on the pressurizing piston in an advancing direction of the pressurizing piston. In this type of braking pressure source device, the pressurizing piston is fluid-tightly and slidably received in the cylinder housing of the master cylinder, and cooperates with the cylinder housing to define a pressurizing chamber and the back-pressure chamber on respective front and rear sides thereof, and an input rod is formed integrally with the pressurizing piston fluid-tightly and slidably extends outward through the rear end wall of the cylinder housing which partially defines the back-pressure chamber. In operation, a working fluid in the pressurizing chamber is pressurized by an advancing movement of the pressurizing piston on the basis of a brake operating force acting on a manually operable brake operating member. Further, the pressurizing chamber and the back-pressure chamber are connected to each other through a communication passage, in which is provided a normally closed solenoid-operated shut-off valve.
In the braking pressure source device described above, the back-pressure chamber is supplied with the working fluid pressurized by a power-operated hydraulic pressure source, which includes a pump and an accumulator. The pressure of the pressurized fluid delivered from the pump or accumulator is controlled by a pressure control valve device, and the fluid having the thus controlled pressure is supplied to the back-pressure chamber. The pressurizing piston receives a force based on the brake operating force and a force based on the back pressure, namely, the pressure of the pressurized fluid supplied to the back-pressure chamber, so that the fluid in the pressurizing chamber is pressurized to a pressure higher than a level that is established by only the brake operating force. Thus, the brake operating force is boosted by the pressurized fluid in the back-pressure chamber. When the power-operated hydraulic pressure source becomes defective, for instance, when the accumulator suffers from a fluid leakage preventing a supply of the pressurized fluid from the power-operated hydraulic pressure source to the back-pressure chamber, the back-pressure chamber is disconnected from the power-operated hydraulic pressure source, and the solenoid-operated shut-off valve provided in the communication passage is opened, permitting a flow of the fluid from the back-pressure chamber into the pressurizing chamber. When the pressurizing piston is advanced in this state, the fluid pressurized in the pressurizing chamber is fed into the back-pressure chamber, so that the effective surface area in transverse cross section or effective diameter of the pressurizing piston is reduced to that of the input rod. Accordingly, the pressure in the pressurizing chamber (hereinafter referred to as “master cylinder pressure” where appropriate) corresponding to a given amount of brake operating force acting on the input rod is made higher when the pressurizing chamber and the back-pressure chambers are communicated with each other than when these chambers are not communicated with each other. Thus, the master cylinder pressure generated when the pressurized fluid cannot be delivered from the power-operated hydraulic pressure source to the back-pressure chamber is as high as that when the pressurized fluid is delivered to the back-pressure chamber.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a braking pressure source device including a master cylinder in which a pressurizing chamber and a back-pressure chamber formed on the respective front and rear sides of a pressurizing piston are connected to each other through a communication passage provided with a communication control valve device including a solenoid-operated valve, and wherein the communication control valve device is controlled in a manner different from that in the braking pressure source device described in the above-identified Japanese Patent Application.
The above object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combination thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A braking pressure source device provided in a braking system for an automotive vehicle, the braking system including a brake operating member manually operable with a brake operating force applied thereto, the braking pressure source device comprising:
a master cylinder including a cylinder housing, a pressurizing piston fluid-tightly and slidably received in the cylinder housing and cooperating with the cylinder housing to define a pressurizing chamber and a back-pressure chamber on a front and a rear side of the pressurizing piston, and an input rod which fluid-tightly and slidably extends through a rear end wall of the cylinder housing, the pressurizing piston being advanced by the brake operating force of the brake operating member transmitted thereto through the input rod, to pressurize a working fluid in the pressurizing chamber;
means for defining a communication passage for communication between the pressurizing chamber and the back-pressure chamber;
a first control valve device disposed in the communication passage for controlling the communication between the pressurizing and back-pressure chambers through the communication passage; and
a first control valve control device for controlling the first control valve device,
and wherein the first control valve control device controls the first control valve device on the basis of at least one of an operating state of the brake operating member, a running state of the automotive vehicle and a state of a road surface on which the automotive vehicle is running.
The operating state of the brake operating member includes, for example, an operating force and an operating stroke of the brake operating member, and rates of change of these operating force and stroke. The operating force can be directly detected, or indirectly detected by detecting a physical quantity which changes with the operating force of the brake operating member, such as a fluid pressure in the pressurizing chamber. The state of the road surface includes, for instance, a friction coefficient and a gradient of the road surface, and the presence or absence of recessed, raised and/or stepped areas in the road surface. The running condition of the vehicle includes, for instance, slipping states of the vehicle wheels, and running or turning stability
Isono Hiroshi
Mizutani Yasuji
Lavinder Jack
Oliff & Berridg,e PLC
Sy Mariano
Toyota Jidosha & Kabushiki Kaisha
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