Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Reexamination Certificate
1999-09-30
2001-11-06
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
Working member position feedback to motive fluid control
Plural input signal means for single motor valve
Reexamination Certificate
active
06311606
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 10(1998)-278402 filed on Sep. 30, 1998, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to vehicle brake systems. More particularly, the present invention pertains to a vacuum servo unit for a vehicle brake system.
BACKGROUND OF THE INVENTION
It is known that an automatic brake operation is established for purposes of preventing slip of the road-wheels of a vehicle when a rapid acceleration is made. An inter-vehicle distance control also utilizes such an automatic brake operation.
A known vacuum servo unit or booster is disclosed in, for example, U.S. Pat. No. 5,493,946 granted to Schluter. In this disclosed vacuum servo unit, automatic brake operation is established by introducing atmospheric pressure into a variable chamber by opening a valve. The valve is associated with a solenoid and energizing the solenoid causes atmosphere to be introduced into the variable chamber.
However, immediately upon fall opening of the valve, the vacuum servo unit outputs its maximum force. It is thus difficult in this known vacuum servo unit to establish a precise automatic braking operation based on the cause of the booster operation.
A need thus exists for a vacuum servo unit or booster that is not susceptible of the foregoing drawbacks and disadvantages.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a vacuum servo unit for vehicle brake systems includes a housing in which is defined at least one pressure space, a movable wall provided in the housing for movement in an axial direction and dividing the pressure space into a front chamber and a rear chamber, a power piston coupled to the movable wall, an axially movable input member located in the power piston that is movable when an input force is applied by a brake operation member, an atmospheric pressure valve seat movable together with the input member, a negative pressure valve seat formed in the power piston, and a control valve. The control valve includes an atmospheric pressure seal portion and a negative pressure seal portion, with the atmospheric pressure seal portion interrupting fluid communication between the atmosphere and the rear chamber upon engagement with the atmospheric pressure valve seat and establishing fluid communication between the atmosphere and the rear chamber upon disengagement with the atmospheric pressure valve seat, and with the negative pressure seal portion interrupting fluid communication between the negative pressure source and the rear chamber upon engagement with the negative pressure valve seat and establishing fluid communication between the negative pressure source and the rear chamber upon disengagement from the negative pressure valve seat. An output member outputs an advancing force of the power piston outside the housing upon being advanced by the power piston, and a reaction member transmits the advancing force of the power piston and the input force applied to the input member to the output member, with the reaction member providing a reaction force corresponding to the force outputted from the output rod to retract the input member. An actuator provides the advancing force to the power piston by disengaging the atmospheric pressure valve seat from the atmospheric pressure seal portion to cause introduction of atmospheric pressure into the rear chamber. The input member includes a front portion engageable with the reaction member and a rear portion positioned at a rear side of the front portion and movable back and forth relative to the front portion, and the actuator is accommodated in the power piston so as to be movable back and forth. The actuator includes a movable portion engaged with the atmospheric pressure valve seat and engageable with the front portion of the input member, and a moving portion for moving the movable portion. As the actuator is driven, the reaction member retracts at least the front portion of the input member, the atmospheric pressure valve seat becomes engaged with the atmospheric pressure seal portion, and the output force depends on a driving force of the actuator.
According to another aspect of the invention, a vacuum servo unit for vehicle brake systems includes a housing in which is defined at least one pressure space, a movable wall provided in the housing for movement in an axial direction and dividing the pressure space into first and second chambers, a power piston coupled to the movable wall, an axially movable input member located in the power piston and connectable to a brake operation member to be moved upon application of an input force to the brake operation member, a valve mechanism located in the power piston to control pressure within one of said first and second chambers to cause the movable wall to move and thereby apply an advancing force to the power piston, an output member outputting the advancing force applied to the power piston outside the housing, and a deformable reaction member transmitting the advancing force of the power piston and the input force applied to the input member to the output member. The reaction member provides a reaction force corresponding to the force outputted from the output rod to retract the input member. An actuator is connected to the valve mechanism to operate the valve mechanism upon operation of the actuator in a manner causing application of the advancing force to the power piston, and a compressible member is located within the power piston and compressible during operation of the actuator to compensate for temperature changes affecting a degree of deformation of the reaction member.
According to a further aspect of the invention, a vacuum servo unit for vehicle brake systems includes a housing in which is defined at least one pressure space, a movable wall provided in the housing for movement in an axial direction and dividing the pressure space into first and second chambers, a power piston coupled to the movable wall, an axially movable input member located in the power piston and connectable to a brake operation member to be moved upon application of an input force to the brake operation member, a valve mechanism located in the power piston to control pressure within one of said first and second chambers to cause the movable wall to move and thereby apply an advancing force to the power piston, an output member outputting the advancing force applied to the power piston outside the housing, and a deformable reaction member transmitting the advancing force of the power piston and the input force applied to the input member to the output member. The valve mechanism includes an atmospheric pressure valve seat and an atmospheric pressure seal portion that are adapted to engage one another and the reaction member provides a reaction force corresponding to the force outputted from the output rod to retract the input member. An actuator is connected to the valve mechanism to operate the valve mechanism upon operation of the actuator in a manner causing application of the advancing force to the power piston. The input member has an engaging portion for directly engaging the reaction member, and the distance between the engaging portion and the atmospheric pressure valve seat during operation of the actuator varying depending on the driving force of the actuator.
REFERENCES:
patent: 5493946 (1996-02-01), Schlüter
patent: 5845556 (1998-12-01), Tsubouchi et al.
patent: 5857399 (1999-01-01), Tsubouchi et al.
patent: 5943938 (1999-08-01), Okuno et al.
patent: 6082241 (2000-07-01), Kobayashi et al.
patent: 6119577 (2000-09-01), Takasaki et al.
patent: 6135007 (2000-10-01), Tsubouchi
patent: 44 41 910 (1996-05-01), None
patent: 44 41 913 (1996-05-01), None
patent: 199 35 876 (2000-03-01), None
patent: 10-44971 (1998-02-01), None
patent: 98/14358 (1998-04-01), None
Miwa Akihiko
Tsubouchi Kaoru
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Ryznic John E.
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