Actuator of antiskid system for vehicle

Claim 2

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit.

Claim 3

An actuator of an antiskid system for a vehicle according to claim 1, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state.

Claim 4

An actuator of an antiskid system for a vehicle according to claim 2, wherein said accumulator is of a gas type.

Claim 5

An actuator of an antiskid system for a vehicle according to claim 3, wherein said second changeover valve further comprises an electromagnetic changeover valve and switch means for controlling the operation of said changeover valve wherein said switch means is actuated in response to pressing of said brake pedal.

Claim 6

An actuator of an antiskid system for a vehicle according to claim 2, wherein said second changeover valve further comprises an electromagnetic changeover valve, the operation of which is controlled by a switch actuated in response to pressing of said brake pedal.

Claim 7

An actuator of an antiskid system for a vehicle according to claim 1, wherein said accumulator is of a gas type.

Claim 8

An actuator of an antiskid system for a vehicle according to claim 6, wherein said second changeover valve further comprises an electromagnetic changeover valve and switch means for controlling the operation of said changeover valve wherein said switch means is actuated in response to pressing of said brake pedal.

Claim 9

An actuator of an antiskid system for a vehicle according to claim 1, wherein said second changeover valve further comprises an electromagnetic changeover valve, the operation of which is controlled by a switch actuated in response to pressing of said brake pedal.

Claim 10

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit wherein said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve, respectively.

Claim 11

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit wherein said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve, respectively.

Claim 12

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state wherein said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve, respectively.

Claim 13

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state wherein said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve, respectively.

Claim 14

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit; wherein said accumulator is of a gas type, and said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve.

Claim 15

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit; wherein said accumulator is of a gas type, and said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve.

Claim 16

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adpated to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state, wherein said accumulator is of a gas type, and said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve.

Claim 17

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adpated to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state, wherein said accumulator is of a gas type, and said second changeover valve further comprises a normally-closed valve disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve; a normally-open valve disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to close and open said normally-open valve and said normally-closed valve.

Claim 18

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 19

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 20

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit; wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 21

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit; wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 22

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said accumulator is of a gas type, and wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 23

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said accumulator is of a gas type, and wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 24

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state, wherein said accumulator is of a gas type, and wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.

Claim 25

An actuator of an antiskid system for a vehicle, comprising: a cut-off valve for selectively dividing a hydraulic pressure circuit connecting together a brake master cylinder and a wheel brake cylinder of said vehicle into a brake master cylinder-side hydraulic pressure circuit portion and a wheel brake cylinder-side hydraulic pressure circuit portion; an accumulator for accumulating a power hydraulic pressure; a piston movable in a first direction by the hydraulic pressure in said wheel brake cylinder-side hydraulic pressure circuit portion as well as movable in a second direction, opposite to said first direction, by said power hydraulic pressure so as to close and open said cut-off valve as well as to increase and restore the volume of said wheel brake cylinder-side hydraulic pressure circuit portion by the movement thereof in the first and second directions; a first changeover valve interposed in a power hydraulic pressure circuit connecting together said accumulator and a fluid chamber which is formed on one of the sides of said piston and to which said power hydraulic pressure is applied, said changeover valve being adapted to remove the power hydraulic pressure in said fluid chamber when a wheel of said vehicle is brought into a state close to a locked stated and to apply the power hydraulic pressure to said fluid chamber when said wheel is in a state other than one close to a locked state; and a second changeover valve interposed in said power hydraulic pressure circuit, said second changeover valve being adapted to open and close said power hydraulic pressure circuit in response to pressing and releasing of a brake pedal such as to remove the power hydraulic pressure in said fluid chamber when closing said power hydraulic pressure circuit, wherein said piston has an area for receiving said wheel brake cylinder-side hydraulic pressure and an area for receiving said power hydraulic pressure which areas are equal to each other, and the power hydraulic pressure accumulated in said accumulator is higher than a maximum value of a brake hydraulic pressure at which said wheel is brought into a state close to a locked state, wherein said accumulator is of a gas type, and wherein said second changeover valve further comprises a normally-closed valve constituted by a fixed valve seat disposed in a hydraulic pressure circuit extending from said accumulator to said first changeover valve, and a movable valve brought into contact with said valve seat by a spring; a normally-open valve constituted by a valve spool which is disposed in a hydraulic pressure circuit extending from said normally-closed valve to said first changeover valve and is adapted to slide so as to lift said valve constituting said normally-closed valve from said valve seat, and a spool which has a passage closed by contact with said valve spool and is lifted from said valve spool by a spring; and a piston slidable against a spring by the hydraulic pressure supplied from said brake master cylinder so as to slide said spool of said normally-open valve toward said valve spool.