Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-11-15
2002-07-02
Lavinder, Jack (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S011000, C303S113300
Reexamination Certificate
active
06412882
ABSTRACT:
This application is based on Japanese Patent Application Nos. 11-352104 filed Dec. 10, 1999 and 2000-174029 filed Jun. 9, 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 system for an automotive vehicle, and more particularly to improvements of a vehicle braking system.
2. Discussion of Related Art
The assignee of the present application filed Japanese Patent Application No. 11-184816 (which has not been published at the time the present invention was made), which discloses a braking system for an automotive vehicle, wherein an assisting force other than an operating force acting on a brake operating member is applied to a pressurizing piston of a master cylinder, so that the operating force of the brake operating member is boosted by the assisting force. Described more specifically, the pressurizing piston is fluid-tightly and slidably received in a housing of the master cylinder, and cooperates with the housing to define a pressurizing chamber on the front side of the pressurizing piston, and an assisting chamber on the rear side of the pressurizing piston. A pressurized working fluid is supplied into the assisting chamber, to apply an assisting force to the pressurizing piston, whereby the operating force applied to on the brake operating member is boosted by the assisting force. In this vehicle braking system, the pressure of the fluid to be delivered from the master cylinder can be controlled in relation to the brake operating force, by controlling the pressure of the fluid supplied into the assisting chamber.
In the vehicle braking system described above, the operating stroke of the brake operating member is not controlled in relation to the operating force, and the operating stroke is determined by the operating state in a portion of the braking system between the master cylinder and a wheel brake cylinder. Accordingly, the operating stroke of the brake operating member which corresponds to a given operating force may fluctuate.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a braking system for an automotive vehicle, which is capable of controlling the operating stroke of the brake operating member in relation to the operating force.
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 combinations 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 system for a vehicle having a wheel, comprising:
a master cylinder including a cylinder housing, and a pressurizing piston which is fluid-tightly and slidably received in the cylinder housing and which cooperates with the cylinder housing to define a pressurizing chamber and an assisting chamber on respective front and rear sides of the pressurizing piston;
a brake operating device including a brake operating member manually operable with a brake operating force to apply a pressurizing force based on the brake operating force to the pressurizing piston;
a brake for braking the wheel;
a wheel brake cylinder which is connected to the master cylinder, for activating the brake;
a hydraulic pressure source operable to pressurize a working fluid;
a reservoir;
a first flow control device connected to the assisting chamber, the hydraulic pressure source and the reservoir, and operable to control flows of the fluid between the assisting chamber, and the hydraulic pressure source and the reservoir; and
a second flow control device connected to the pressurizing chamber, the hydraulic pressure source and the reservoir, and operable to control flows of the fluid between the pressurizing chamber, and the hydraulic pressure source and the reservoir.
The brake operating member may be a brake pedal operable by depression by foot of an operator of the vehicle, or a in brake lever operable by hand of the vehicle operator, for instance.
In the braking system constructed according to the above mode (1) of this invention, the fluid pressure in the pressurizing chamber (hereinafter referred to as “master cylinder pressure” where appropriate) and the operating stroke of the brake operating member (hereinafter referred to as “brake operating stroke” where appropriate) can be controlled to suitable values determined in relation to the operating force of the brake pedal (hereinafter referred to as “brake operating force” where appropriate). When the pressurized fluid is supplied from the hydraulic pressure source to the assisting chamber of the master cylinder, the brake operating force is boosted by the fluid pressure in the assisting chamber. When the pressurized fluid is discharged from the assisting chamber to the reservoir, the volume of the assisting chamber is reduced to thereby permit a retracting movement of the pressurizing piston. Therefore, the master cylinder pressure can be controlled to a suitable value determined by the specific brake operating force, by controlling the first flow control device to control the fluid flows to and from the assisting chamber. When the pressurized fluid is supplied from the hydraulic pressure source to the pressurizing chamber, the distance of an advancing movement of the pressurizing piston required to obtain a certain value of the fluid pressure in the pressurizing chamber can be made smaller than when the pressurized fluid is not supplied to the pressurizing chamber. On the other hand, the distance of the advancing movement of the pressurizing piston is increased as the pressurized fluid is discharged from the pressurizing chamber to the reservoir. Therefore, the brake operating stroke can be controlled to a suitable value determined by the brake operating force, by controlling the second flow control device to control the fluid flows to and from the pressurizing chamber. Thus, the three parameters, that is, the brake operating force, the brake operating stroke and the master cylinder pressure can be controlled in predetermined relationships with each other, by suitably controlling the first and second flow control devices to control the fluid flows to and from the assisting chamber and the fluid flows to and from the pressurizing chamber.
The present braking system is further advantageous in that the vehicle wheel can be braked with the fluid pressure in the pressurizing chamber, without an operation of the brake operating member, by controlling the second flow control device to control the fluid flows to and from the pressurizing chamber, namely, to control the fluid pressure in the pressurizing chamber. The master cylinder may be arranged such that when the pressurizing piston is placed at its fully retracted position, the pressurizing chamber is held in communication with the reservoir, generally, through a fluid passage whose cross sectional area is comparatively small. In this arrangement, the first flow control device is preferably activated to supply the assisting chamber with a relatively small amount of the pressurized fluid received from the hydraulic pressure source, in order to advance the pressurizing piston by a distance necessary to disconnect the pressurizing chamber from the reservoir, before the pressurized fluid is supplied from the hydraulic pressure source through the second flow control device.
Further, the wheel can be braked without an operation of the brake operating member and without an operation of the second flow control device. That is, the first flow contr
Isono Hiroshi
Mizutani Yasuji
Lavinder Jack
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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