Skid control arrangement of a automotive braking system

Claim 2

A skid control arrangement for use in an automotive vehicle including a master cylinder to produce a braking fluid pressure, a wheel cylinder to receive the braking fluid pressure, a source of an operating fluid pressure having a first predetermined fixed level and a second predetermined fixed level lower than the first predetermined fixed level, which control arrangement comprises main braking fluid passage means connecting the master cylinder and the wheel cylinder and acted upon by the braking fluid pressure and the operating fluid pressure in relation to one another, the main braking fluid passage means being operative to open for feeding the braking fluid pressure produced at the master cylinder to the wheel cylinder, while being operative to reduce the braking fluid pressure to be supplied to the cylinder for providing a skid control when the operating fluid pressure is at a level which is higher than said first predetermined fixed level or which is lower than the first predetermined fixed level and higher than a variable level which is predetermined in relation to a given braking fluid pressure, and by-pass braking fluid passage means connecting the master cylinder and wheel cylinder in parallel with the main braking fluid passage means and acted upon by the braking fluid pressure and operating fluid pressure in relation to one another, the by-pass passage means being operative to open for feeding the braking fluid pressure produced at the master cylinder to the wheel cylinder for cancelling the skid control when the operating fluid pressure is at a level which is lower than a second variable level predetermined in relation to the given braking fluid pressure and higher than the first variable level or which is lower than said second predetermined fixed level.

Claim 3

A skid control arrangement for use in an automotive hydraulic brake system including a master cylinder to produce a braking fluid pressure, a wheel cylinder to receive the braking fluid pressure and a source of an operating fluid pressure having a first predetermined fixed level and a second predetermined fixed level lower than the first predetermined fixed level, which control arrangement comprises a housing formed with a first chamber in constant communication with the master cylinder, a second chamber to communicate with the first chamber through a first passage means, a third chamber to communicate with the source of the operating fluid pressure, a fourth chamber in constant communication with the source of the operating fluid pressure, a fifth chamber in constant communication with the first chamber, a first bore in constant communication with the second chamber, and a second bore which is in constant communication with the wheel cylinder and which is to communicate with the first bore through a second passage means or with the first chamber through a third passage means; a first valve means for opening or closing the first passage means; a plunger movable in the second chamber and connected to the first valve means; a first piston movable in the third chamber, connected to the first plunger and larger in pressure, receiving area than the first plunger; the first plunger being acted upon by the braking fluid pressure when the first valve means is in a position to open the first passage means and the first piston being acted upon by the operating fluid pressure when the third chamber is in communication with the source of the operating fluid; the first plunger and the first piston being moved to cause the first valve means to open the first passage means when the operating fluid pressure acting upon the first piston is at a level which is higher than said first predetermined fixed level or which is lower than the first predetermined fixed level and higher than a first variable level which is predetermined in relation to a given braking fluid pressure; a second plunger movable in the first bore; a second piston movable in the fourth chamber and connected to the second plunger; the second piston being constantly acted upon the operating fluid pressure; a third plunger movable in the second bore; a third piston movable in the fifth chamber and connected to the third plunger; and a second valve means connected to the second plunger and movable in the second bore between a first position to open the second passage means and close the third passage means and a second position to close the second passage means and open the third passage means; the second and third plungers being movable between respective first positions to move the second valve means to said first position thereof and respective second positions thereof to move the second valve means to said second piston thereof; the second and third plungers being moved to the respective first positions thereof when the operating fluid pressure is at a level which is higher than a second variable level higher than said first variable level and predetermined in relation to said given braking fluid pressure and which is higher than said second predetermined fixed level and to the respective second positions thereof when the operating fluid pressure is at a level which is lower than said second variable level or than said second predetermined fixed level.

Claim 4

A skid control arrangement for use in an automotive hydraulic brake system including a master cylinder to produce a braking fluid pressure, a wheel cylinder to receive the braking fluid pressure and a source of an operating fluid pressure having a first predetermined fixed level and a second predetermined fixed level lower than the first predetermined fixed level, which control arrangement comprises a housing formed with a first chamber in constant communication with the master cylinder, a second chamber to communicate with the first chamber through a first passage means, a third chamber to communicate with the source of the operating fluid pressure, a fourth chamber in constant communication with the source of the operating fluid pressure, a fifth chamber in constant communication with the first chamber, a first bore in constant communication with the second chamber, and a second bore which is in constant communication with the wheel cylinder and which is to communicate with the first bore through a second passage means or with the first chamber through a third passage means; a first valve means for opening or closing the first passage means; a plunger movable in the second chamber and connected to the first valve means; a first piston movable in the third chamber, connected to the first plunger and larger in pressure, receiving area than the first plunger; the first plunger being acted upon by the braking fluid pressure when the first valve means is in a position to open the first passage means and the first piston being acted upon by the operating fluid pressure when the third chamber is in communication with the source of the operating fluid; the first plunger and the first piston being moved to cause the first valve means to open the first passage means when the operating fluid pressure acting upon the first piston is at a level which is higher than said first predetermined fixed level or which is lower than the first predetermined fixed level and higher than a first variable level which is predetermined in relation to a given braking fluid pressure; a second plunger movable in the first bore; a second piston movable in the fourth chamber and connected to the second plunger; the second piston being constantly acted upon the operating fluid pressure; a third plunger movable in the second bore; a third piston movable in the fifth chamber and connected to the third plunger; and a second valve means connected to the second plunger and movable in the second bore between a first position to open the second passage means and close the third passage means and a second position to close the second passage means and open the third passage means; the second and third plungers being movable between respective first positions to move the second valve means to said first position thereof and respective second positions thereof to move the second valve means to said second piston thereof; the second and third plungers being moved to the respective first positions thereof when the operating fluid pressure is at a level which is higher than a second variable level higher than said first variable level and predetermined in relation to said given braking fluid pressure and which is higher than said second predetermined fixed level and to the respective second positions thereof when the operating fluid pressure is at a level which is lower than said second variable level or than said second predetermined fixed level.

Claim 5

A skid control arrangement as set forth in claim 2, further comprising an electric control module responsive to an impending skid condition of a road wheel for producing an output signal when held operative; a two-way flow-shift valve unit having a fluid inlet port communicating with the source of the operating fluid, a first fluid outlet port communicating with the third chamber, and a second fluid outlet port open to the outside; the two-way flow-shift valve unit being held in a first position to open the first fluid outlet port in the absence of the outlet signal from the control module and a second position to open the second fluid outlet port in response to the output signal from the control module; a first switch responsive to the movement of said third plunger toward said second position thereof; and a second switch responsive to said sEcond predetermined fixed level of the operating fluid pressure; the first and second switches being electrically connected in series to said control module for disabling the control module to produce the output signal when the first switch responds to said movement of the third plunger toward said second position thereof and/or the second switch responds to second predetermined fixed level of the operating fluid pressure.

Claim 6

A skid control arrangement as set forth in claim 2, in which said third passage means is provided by a first passageway interconnecting said first chamber and said second bore and a second passageway formed in said second plunger; leading from the first passageway and terminating at an end of the third plunger.

Claim 7

A skid control arrangement as set forth in claim 4, in which said second valve means is located between said second passage means and the open end of the third plunger for closing either of the second and third passage means as the same is moved by said second plunger.

Claim 8

A skid control arrangement as set forth in claim 2, in which said fifth chamber is in constant communication with said first chamber through a first passageway interconnecting the first chamber and the second bore and a second passageway formed in said third plunger and in said piston for providing communication between said first passageway and said fifth chamber.

Claim 9

A skid control arrangement as set forth in claim 2, in which said second and third pistons have substantially equal pressure working areas.

Claim 10

A skid control arrangement as set forth in claim 7, in which said second and third plungers have substantially equal pressure working areas.

Claim 11

A skid control arrangement as set forth in claim 2, further comprising biasing means operative to urge said second valve means to close said second passage means and to open said third passage means.

Claim 12

A skid control arrangement as set forth in claim 2, further comprising biasing means operative to urge said first valve means to close said first passage means.

Claim 13

A skid control arrangement as set forth in claim 2, further comprising biasing means operative to urge said third plunger to move toward said second position thereof.

Claim 14

A skid control arrangement as set forth in claim 2, in which said source of the operating fluid pressure is constituted essentially by a constant-displacement pump, an accumulator unit having a predetermined preload pressure and an unloading valve having a pilot port communicating with the pump and the accumulator unit, wherein said first predetermined fixed level is substantially equal to the cut-in pressure of said unloading valve and said second predetermined fixed level is the preload pressure of said accumulator unit.

Claim 15

In an automotive hydraulic braking system, means adapted to produce an electric skid indicating signal, a source of operating fluid pressure having a first predetermined fixed level and a second predetermined fixed level lower than the first predetermined fixed level, a master cylinder to produce the braking fluid pressure, a wheel cylinder to receive the braking fluid pressure produced at the master cylinder for applying a brake, a main braking fluid passageway connecting the master cylinder and wheel cylinder to feed the wheel cylinder with the braking fluid pressure produced at the master cylinder, a first piston-valve-arrangement disposed in the main braking fluid passageway and operable in response to the braking fluid pressure and the operating fluid pressure acting upon the respective ends thereof for blocking the passageway in response to the skid signal thereby reducing the braking fluid pressure to be supplied to the wheel cylinder a by-pass braking fluid passageway connecting the master cylinder and wheel cylinder in parallel with the main passageway, a second piston-valve-arrangement operable in response to the braking fluid pressure and the operating pressure acting upon the respective ends thereof for normally blocking thE by-pass passageway and displaceable to open the same when the operating fluid pressure produced at the fluid pressure source drops respectively to a first predetermined level and a second predetermined level lower than said first predetermined level both indicating failure in the fluid pressure source for thereby feeding the braking fluid pressure produced at the master cylinder to the wheel cylinder, a first switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the displacement of the second piston-valve-arrangement when the operating fluid pressure drops to the first predetermined level for thereby opening said circuit of the skid signal producing means, and a second switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the operating fluid pressure when the operating fluid pressure drops to the second predetermined level for thereby opening said circuit of the skid signal producing means, wherein the arrangement is provided such that the first predetermined level of the operating fluid pressure is given in relation to a braking fluid pressure within a range lower than the first fixed level and higher than the second fixed level and sufficient to restore the first piston-valve-arrangement from the main passageway blocking position to its opening position, and the second predetermined level of the operating fluid pressure is given independently of the braking fluid pressure within a range higher than the second fixed level and lower than the first predetermined level.

Claim 16

In an automotive hydraulic braking system, means adapted to produce an electric skid indicating signal, a source of operating fluid pressure having a first predetermined fixed level and a second predetermined fixed level lower than the first predetermined fixed level, a master cylinder to produce the braking fluid pressure, a wheel cylinder to receive the braking fluid pressure produced at the master cylinder for applying a brake, a main braking fluid passageway connecting the master cylinder and wheel cylinder to feed the wheel cylinder with the braking fluid pressure produced at the master cylinder, a first piston-valve-arrangement disposed in the main braking fluid passageway and operable in response to the braking fluid pressure and the operating fluid pressure acting upon the respective ends thereof for blocking the passageway in response to the skid signal thereby reducing the braking fluid pressure to be supplied to the wheel cylinder a by-pass braking fluid passageway connecting the master cylinder and wheel cylinder in parallel with the main passageway, a second piston-valve-arrangement operable in response to the braking fluid pressure and the operating pressure acting upon the respective ends thereof for normally blocking thE by-pass passageway and displaceable to open the same when the operating fluid pressure produced at the fluid pressure source drops respectively to a first predetermined level and a second predetermined level lower than said first predetermined level both indicating failure in the fluid pressure source for thereby feeding the braking fluid pressure produced at the master cylinder to the wheel cylinder, a first switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the displacement of the second piston-valve-arrangement when the operating fluid pressure drops to the first predetermined level for thereby opening said circuit of the skid signal producing means, and a second switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the operating fluid pressure when the operating fluid pressure drops to the second predetermined level for thereby opening said circuit of the skid signal producing means, wherein the arrangement is provided such that the first predetermined level of the operating fluid pressure is given in relation to a braking fluid pressure within a range lower than the first fixed level and higher than the second fixed level and sufficient to restore the first piston-valve-arrangement from the main passageway blocking position to its opening position, and the second predetermined level of the operating fluid pressure is given independently of the braking fluid pressure within a range higher than the second fixed level and lower than the first predetermined level.

Claim 17

In an automotive hydraulic braking system, means adapted to produce an electric skid signal; a source of the operating fluid pressure including a constant-displacement pump, an accumulator unit having a predetermined preload pressure and an unloading valve having a pilot port communicating with the pump and the accumulator unit, the unloading valve having a fixed cutin pressure higher than the preload pressure of the accumulator unit; a master cylinder to produce the braking fluid pressure; a wheel cylinder to receive the braking fluid pressure produced at the master cylinder for applying a brake; a main braking fluid passageway connecting the master cylinder and wheel cylinder to feed the wheel cylinder with the braking fluid pressure produced at the master cylinder; a first piston-valve-arrangement disposed in the main braking fluid passageway and operable in response to the braking fluid pressure and the operating fluid pressure acting upon the opposite ends thereof for blocking the main passageway in response to the skid signal thereby reducing the braking fluid pressure to be supplied to the wheel cylinder; a by-pass braking fluid passageway connecting the master cylinder and wheel cylinder in parallel with the main passageway; a second piston-valve-arrangement operable in response to the braking fluid pressure and the operating fluid pressure acting upon the respective ends thereof for normally blocking the by-pass passageway and displaceable to open the same when the operating fluid pressure produced at the fluid pressure source drops respectively to a first predetermined level indicating failure of the fluid pressure source which is given in relation to the braking fluid pressure with in a range higher than the preload pressure of the accumulator unit and lower than the cut-in pressure of the unloading valve and is sufficient to shift the first piston-valve-arrangement from the main passageway blocking position to its opening position, and to a second predetermined level indicating failure of the fluid pressure source which is given independently of the braking fluid pressure within a range higher than the preload pressure of the accumulator unit and lower than the first predetermined level; a first switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the displacement of the second piston-valve-arrangement when the operating fluid pressure drOps to the first predetermined level for thereby opening said circuit of the skid signal producing means; and a second switch means in series therewith and responsive to the operating fluid pressure when the operating fluid pressure drops to the second predetermined level for thereby opening said circuit of the skid signal producing means.

Claim 18

In an automotive hydraulic braking system, means adapted to produce an electric skid signal; a source of the operating fluid pressure including a constant-displacement pump, an accumulator unit having a predetermined preload pressure and an unloading valve having a pilot port communicating with the pump and the accumulator unit, the unloading valve having a fixed cutin pressure higher than the preload pressure of the accumulator unit; a master cylinder to produce the braking fluid pressure; a wheel cylinder to receive the braking fluid pressure produced at the master cylinder for applying a brake; a main braking fluid passageway connecting the master cylinder and wheel cylinder to feed the wheel cylinder with the braking fluid pressure produced at the master cylinder; a first piston-valve-arrangement disposed in the main braking fluid passageway and operable in response to the braking fluid pressure and the operating fluid pressure acting upon the opposite ends thereof for blocking the main passageway in response to the skid signal thereby reducing the braking fluid pressure to be supplied to the wheel cylinder; a by-pass braking fluid passageway connecting the master cylinder and wheel cylinder in parallel with the main passageway; a second piston-valve-arrangement operable in response to the braking fluid pressure and the operating fluid pressure acting upon the respective ends thereof for normally blocking the by-pass passageway and displaceable to open the same when the operating fluid pressure produced at the fluid pressure source drops respectively to a first predetermined level indicating failure of the fluid pressure source which is given in relation to the braking fluid pressure with in a range higher than the preload pressure of the accumulator unit and lower than the cut-in pressure of the unloading valve and is sufficient to shift the first piston-valve-arrangement from the main passageway blocking position to its opening position, and to a second predetermined level indicating failure of the fluid pressure source which is given independently of the braking fluid pressure within a range higher than the preload pressure of the accumulator unit and lower than the first predetermined level; a first switch means disposed in the circuit of the skid signal producing means in series therewith and responsive to the displacement of the second piston-valve-arrangement when the operating fluid pressure drOps to the first predetermined level for thereby opening said circuit of the skid signal producing means; and a second switch means in series therewith and responsive to the operating fluid pressure when the operating fluid pressure drops to the second predetermined level for thereby opening said circuit of the skid signal producing means.