Hydraulic servo unit for automotive braking system

Claim 2

A hydraulic servo valve unit for use in a hydraulic braking system of a motor vehicle having a brake pedal, comprising a housing having formed therein an inlet and an outlet; a first fluid chamber formed in said housing and communicating with said inlet, a second fluid chamber formed in said housing and communicating with said outlet, a power piston slidably accomodated within said housing between said first and second fluid chambers and having formed therein at least one fluid passageway communicating with said first and second fluid chambers, said power piston having formed therein bore means communicating with said inlet, a cone-shapEd valve element for opening and closing said at least one fluid passageway formed in said power piston, an operating rod partially extending into said first fluid chamber of said housing and axially movable by said brake pedal, an actuating plunger integrally connected to said operating rod and axially extending into said first fluid chamber for actuating said cone-shaped valve element, a check valve disposed in said bore means of said power piston and actuated by said actuating plunger for controlling fluid communication between said inlet and said first fluid chamber, a first spring means disposed in said first fluid chamber for biasing said power piston in one direction, a second spring means disposed in said second fluid chamber for biasing said power piston in another direction, and a third spring means disposed in said first fluid chamber for biasing said cone-shaped valve element toward said power piston for closing said fluid passageway of said power piston, the arrangement being such that, when said operating rod and accordingly said actuating plunger are moved in one direction, said actuating plunger causes said cone-shaped valve element to move in a position to close said at lease one fluid passageway formed in said power piston and at the same time opens said check valve to provide fluid communication between said inlet and said first fluid chamber for admitting fluid under pressure into said first fluid chamber whereby the fluid under pressure admitted thereto acts on said power piston to produce an actuating force, whereas, when said actuating plunger is moved in another direction, said actuating plunger closes said check valve to prevent the fluid under pressure from being supplied into said first fluid chamber and at the same time causes said cone-shaped valve element to open said at least one fluid passageway formed in said power piston for discharging the fluid under pressure remaining in said first fluid chamber through said second fluid chamber into said outlet whereby the fluid under pressure is prevented from acting on said power piston.

Claim 3

A hydraulic servo unit as claimed in claim 1, wherein said power piston has formed on its outer periphery an annular recess which forms a third fluid chamber communicating with said inlet and at least one radially extending opening to provide fluid communication between said bore means of said power piston and said third fluid chamber.

Claim 4

A hydraulic servo unit as claimed in claim 1, wherein said actuating plunger includes an axially extending cylindrical portion on which said cone-shaped valve element is slidably mounted, a radially extending annular projection formed at an end portion of said cylindrical portion, said annular projection abutting on said cone-shaped valve element when said actuating plunger is moved in said another direction to open said fluid passageway of said power piston, an actuating member secured to one end of said actuating plunger and causing said check valve to be opened when said actuating plunger is moved in said one direction.

Claim 5

A hydraulic servo unit as claimed in claim 3, wherein said actuating plunger further includes fluid passageways for providing fluid communication between said bore means of said power piston and said first fluid chamber.

Claim 6

A hydraulic servo unit as claimed in claim 2, wherein said power piston also has formed at one end thereof a conical valve seat which said cone-shaped valve element engages to close said fluid passageway of said power piston.

Claim 7

A hydraulic servo unit as claimed in claim 5, wherein the conical angle of said conical valve seat is slightly smaller than that of said cone-shaped valve element.

Claim 8

A hydraulic servo unit as claimed in claim 5, wherein the conical angle of said conical valve seat is slightly larger than that of said cone-shaped valve element, and wherein said power piston is provided with an auxiliary valve surface which said cone-shaped valve element contacts at its outer periphery.

Claim 9

A hydraulIc servo unit for use in hydraulic brake system of a motor vehicle having a brake pedal, said servo unit comprising a housing, said housing having formed therein an inlet, and an outlet, a first fluid chamber formed in said housing and communicating with said inlet, a second fluid chamber formed in said housing and communicating with said outlet, a power piston slidably accommodated in said housing between said first and second fluid chambers and including at least one fluid passageway to provide communication between said first and second fluid chambers, bore means formed in said power piston and providing communication between said inlet and said first fluid chamber and a conical valve seat formed at one end of said power piston, a cone-shaped valve element having a conical valve head seated on said conical valve seat of said power piston for closing said at least one fluid passageway of said power piston, a check valve disposed in said bore means of said power piston for controlling fluid communication between said inlet and said first fluid chamber, a control rod mechanically connected to said brake pedal and axially moved thereby, an operating rod cooperating with said control rod, an actuating plunger integrally connected to said operating rod and axially extending through said first fluid chamber into said bore means of said power piston, said actuating plunger including an axially extending cylindrical portion, a radially extending annular projection formed at one end of said cylindrical portion and an actuating member secured to one end of said actuating plunger, said annular projection selectively abutting on said cone-shaped valve element and said actuating member selectively opening said check valve, said actuating plunger also including fluid passageways for providing fluid communication between said bore means of said power piston and said first fluid chamber, a first compression spring disposed in said first fluid chamber for biasing said power piston in one direction, a second compression spring disposed in said second fluid chamber for biasing said power piston in another direction, a third compression spring disposed in said first fluid chamber for biasing said cone-shaped valve element toward said conical valve seat on said power piston, and a push rod fixed to said power piston and axially movable therewith, the arrangement being such that, when said brake pedal is depressed to cause said control rod and accordingly said operating rod to axially move in said one direction, said actuating plunger is moved in the same direction to cause said annular projection to be out of abutting engagement with said cone-shaped valve element for thereby causing said cone-shaped valve element to be seated on said conical valve seat of said power piston by the action of said third compression spring and at the same time causes said actuating member secured to said actuating plunger to open said check valve, whereby fluid under presssure is admitted through said inlet and said bore means of said power piston and said fluid passageways of said actuating plunger into said first fluid chamber and acts on said power piston to move said power piston and accordingly said push rod in said one direction, whereas, when said brake pedal is released said operating rod is moved in said another direction by the action of said second compression spring and the action of the fluid under pressure acting thereon to cause said actuating member to close said check valve to prevent the fluid under pressure from being admitted to said first fluid chamber and at the same time causes said annular projection of said actuating plunger to abut on said cone-shaped valve element thereby to cause the same to unseat from said conical valve seat formed on said power piston thereby to open said fluid passageway of said power piston against the action of said third compression spring, whereby the fluid under pressure remaining in said first fluid chamber is discharged through said second fluid chamber into said outlet.

Claim 10

A hydraulIc servo unit for use in hydraulic brake system of a motor vehicle having a brake pedal, said servo unit comprising a housing, said housing having formed therein an inlet, and an outlet, a first fluid chamber formed in said housing and communicating with said inlet, a second fluid chamber formed in said housing and communicating with said outlet, a power piston slidably accommodated in said housing between said first and second fluid chambers and including at least one fluid passageway to provide communication between said first and second fluid chambers, bore means formed in said power piston and providing communication between said inlet and said first fluid chamber and a conical valve seat formed at one end of said power piston, a cone-shaped valve element having a conical valve head seated on said conical valve seat of said power piston for closing said at least one fluid passageway of said power piston, a check valve disposed in said bore means of said power piston for controlling fluid communication between said inlet and said first fluid chamber, a control rod mechanically connected to said brake pedal and axially moved thereby, an operating rod cooperating with said control rod, an actuating plunger integrally connected to said operating rod and axially extending through said first fluid chamber into said bore means of said power piston, said actuating plunger including an axially extending cylindrical portion, a radially extending annular projection formed at one end of said cylindrical portion and an actuating member secured to one end of said actuating plunger, said annular projection selectively abutting on said cone-shaped valve element and said actuating member selectively opening said check valve, said actuating plunger also including fluid passageways for providing fluid communication between said bore means of said power piston and said first fluid chamber, a first compression spring disposed in said first fluid chamber for biasing said power piston in one direction, a second compression spring disposed in said second fluid chamber for biasing said power piston in another direction, a third compression spring disposed in said first fluid chamber for biasing said cone-shaped valve element toward said conical valve seat on said power piston, and a push rod fixed to said power piston and axially movable therewith, the arrangement being such that, when said brake pedal is depressed to cause said control rod and accordingly said operating rod to axially move in said one direction, said actuating plunger is moved in the same direction to cause said annular projection to be out of abutting engagement with said cone-shaped valve element for thereby causing said cone-shaped valve element to be seated on said conical valve seat of said power piston by the action of said third compression spring and at the same time causes said actuating member secured to said actuating plunger to open said check valve, whereby fluid under presssure is admitted through said inlet and said bore means of said power piston and said fluid passageways of said actuating plunger into said first fluid chamber and acts on said power piston to move said power piston and accordingly said push rod in said one direction, whereas, when said brake pedal is released said operating rod is moved in said another direction by the action of said second compression spring and the action of the fluid under pressure acting thereon to cause said actuating member to close said check valve to prevent the fluid under pressure from being admitted to said first fluid chamber and at the same time causes said annular projection of said actuating plunger to abut on said cone-shaped valve element thereby to cause the same to unseat from said conical valve seat formed on said power piston thereby to open said fluid passageway of said power piston against the action of said third compression spring, whereby the fluid under pressure remaining in said first fluid chamber is discharged through said second fluid chamber into said outlet.

Claim 11

A hydraulic servo unit as claimed in claim 8, wherein said power piston has formed therein a radially extending annular shoulder on which said annular projection of said actuating plunger abuts to transmit a brake pedal pressure to said power piston.