Hydraulic braking system including power-operated pressure source device, and device for controlling pressure output of the pressure source device

1. A braking system comprising:

a power-operated hydraulic pressure source operable to deliver a pressurized working fluid:

a brake including a hydraulically operated brake cylinder;

a manually operable brake operating member;

a master cylinder disposed between said power-operated hydraulic pressure source and said brake cylinder and operable to deliver the pressurized working fluid into said brake cylinder in response to an operation of said manually operable brake operating member; and

a flow-rate changing device disposed between said power-operated hydraulic pressure source and said brake cylinder and including said master cylinder, said flow-rate changing device being operable to change a rate of flow of the pressurized working fluid from said master cylinder into said brake cylinder, which rate corresponds to a given rate at which the pressurized working fluid is delivered into said master cylinder as a result of an operation of said power-operated hydraulic pressure source, said flow-rate changing device being operable to change the rate of flow of the pressurized working fluid from said master cylinder into said brake cylinder during an operation in which a pressure of the working fluid in said brake cylinder is controlled such that the pressure of the working fluid in said brake cylinder changes with a change of an operating amount of said manually operable brake operating member;

wherein said master cylinder includes (a) a housing, and (b) a pressurizing piston fluid-tightly and slidably fitted in said housing, said pressurizing piston having two pressure-receiving surface areas which are different from each other and which respectively partially define a front pressurizing chamber and a rear pressure chamber on front and rear sides of said pressurizing piston, said master cylinder being operable to supply said brake cylinder with the pressurized working fluid delivered from said front pressurizing chamber as said pressurizing piston is advanced,

and wherein said flow-rate changing device includes a switching device having a first state in which the pressurized working fluid is delivered from said power-operated hydraulic pressure source to one of said front pressurizing chamber and said rear pressure chamber which has a smaller one of said two pressure-receiving surface areas, and a second state in which the pressurized working fluid is delivered from said power-operated hydraulic pressure source to the other of said front pressurizing chamber and said rear pressure chamber.

2. A braking system according to claim 1 , wherein said rear pressure chamber has the smaller pressure-receiving surface area, and said flow-rate changing device further includes a discharge-flow inhibiting device operable to inhibit a discharge flow of the pressurized working fluid from said rear pressure chamber while the pressurized working fluid is delivered from said power-operated hydraulic pressure source to said front pressurizing chamber under the control of said switching device.

3. A braking system according to claim 1 , wherein said switching device includes a communication control valve device operable for selective fluid communication of said power-operated hydraulic pressure source with one of at least two fluid chambers of said master cylinder, said at least two fluid chambers including said front pressurizing chamber and said rear pressure chamber.

4. A braking system according to claim 1 , further comprising a pressure control device operable to control a pressure of the pressurized fluid in at least one of at least two fluid chambers of said master cylinder, on the basis of an operation-related amount representative of an operating state of said manually operable brake operating member, said at least two fluid chambers including said front pressurizing chamber and said rear pressure chamber.

5. A braking system according to claim 1 , wherein said flow-rate changing device is operable to change said rate of flow of the pressurized working fluid into said brake cylinder on the basis of a pressure of the pressurized working fluid in said front pressurizing chamber of said master cylinder.

6. A braking system comprising:

a power-operated hydraulic pressure source operable to deliver a pressurized working fluid;

a brake including a hydraulically operated brake cylinder;

a hydraulic cylinder disposed between said power-operated hydraulic pressure source and said brake cylinder, said hydraulic cylinder including (a) a housing, and (b) a pressurizing piston fluid-tightly and slidably fitted in said housing, said pressurizing piston having two pressure-receiving surface areas which are different from each other and which respectively partially define a front pressurizing chamber and a rear pressure chamber on front and rear sides of said pressurizing piston, said hydraulic cylinder being operable to supply said brake cylinder with the pressurized working fluid from said front pressurizing chamber as said pressurizing piston is advanced;

a flow-rate changing device disposed between said power-operated hydraulic pressure source and said brake cylinder and operable to change a rate of flow of the pressurized working fluid into said brake cylinder, which rate corresponds to a given rate at which the pressurized working fluid is delivered from said power-operated hydraulic pressure source, said flow-rate changing device being operable to change the rate of flow of the pressurized working fluid into said brake cylinder during an operation in which a pressure of the working fluid in said brake cylinder is controlled such that the pressure of the working fluid in said brake cylinder changes with a change of an operating amount of said manually operable brake operating member;

said flow-rate changing device including a switching device having a first state in which the pressurized working fluid is delivered from said power-operated hydraulic pressure source to one of said front pressurizing chamber and said rear pressure chamber which has a smaller one of said two pressure-receiving surface areas, and a second state in which the pressurized working fluid is delivered from said power-operated hydraulic pressure source to the other of said front pressurizing chamber and said rear pressure chamber,

said flow-rate changing device further including a discharge-flow inhibiting device operable to inhibit a discharge flow of the pressurized working fluid from said rear pressure chamber while the pressurized working fluid is delivered from said power-operated hydraulic pressure source to said front pressurizing chamber under the control of said switching device; and

a check valve disposed in parallel connection with said discharge-flow inhibiting device, said check valve permitting a flow of the pressurized working fluid in a first direction from said power-operated hydraulic pressure source toward said rear pressure chamber, and inhibiting a flow of the pressurized working fluid in a second direction opposite to said first direction.