Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
1998-11-13
2001-04-17
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S547300, C060S566000
Reexamination Certificate
active
06216457
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to brake systems for motor vehicles, and in particular to fluid pressure operated boosters for vehicle braking systems.
Conventional vehicle brake systems are constructed such that the braking force developed by the system is generally proportional to the force applied by the vehicle operator on a vehicle brake pedal. The pedal is linked to a piston in a master cylinder which moves to pressurize the fluid of the brake system, and thus actuate the individual wheel brakes. Generally, in order to provide a sufficiently high pressure to operate the wheel brakes without requiring an excessive effort by the operator, most vehicles include a “boosted” power brake system wherein the force applied to the brake pedal by the operator is amplified or boosted before being applied to the master cylinder. In automobiles and light trucks, this is typically accomplished by incorporating either a vacuum or hydraulically operated boost piston assembly between the brake pedal and the master cylinder.
Vacuum operated boost piston assemblies utilize the pressure differences between the atmosphere and the vehicle's engine vacuum to develop a force across a boost piston or diaphragm. The force developed by this differential pressure across the boost piston may be many times that which could be developed by the operator by pressing against the pedal, and is applied to the piston of the master cylinder to actuate the brakes.
Hydraulic boost piston assemblies utilize the pressure developed by a hydraulic system, such as the vehicle's power steering system, to apply a force to a boost piston. The force applied by the hydraulic system to the boost piston, like the vacuum boost system may be many times that which could be applied by the operator of the vehicle without a boost system. The increase force applied to the piston of the master cylinder generates higher braking system operating pressures for a given pedal force input.
SUMMARY OF THE INVENTION
Briefly, the present invention, in a first embodiment thereof, comprises a vehicle hydraulic system including: a hydraulic fluid reservoir; a pressure source supplying pressurized hydraulic fluid to a discharge header; a fluid conduit between the discharge header and the reservoir; a back pressure valve operative in the fluid conduit to maintain a desired pressure in the discharge header; a vehicle braking system having a hydraulically operated boost piston assembly for supplementing a force exerted by a vehicle operator to operate brakes of the vehicle braking system; and a boost pressure control valve responsive to an input signal from the vehicle operator for selectively directing pressurized hydraulic fluid from the discharge header to the boost piston assembly and venting hydraulic fluid from the boost piston assembly to the reservoir.
In a further aspect of this embodiment, the boost pressure control valve may include a housing defining a plurality of ports and a spool movable relative to the housing for selectively directing pressurized hydraulic fluid from the discharge header to the boost piston assembly through the ports and venting hydraulic fluid from the boost piston assembly to the reservoir through the ports, with the spool moving relative to the housing in response to the input signal.
In a further aspect of this embodiment, the input signal to the boost pressure control valve may be a pressure signal generated by a pilot valve, wherein the pilot valve selectively applies pressurized hydraulic fluid from the discharge header to a portion of the spool and vents hydraulic fluid from the portion of the spool to the reservoir to cause the spool to move relative to the housing in response to an operator input to the pilot valve.
In yet a further aspect of this first embodiment of the present invention, the input signal to the boost pressure control valve may comprise an electrical signal to a solenoid having an armature operatively coupled to the spool, such that the forces generated by the electric solenoid are balanced against forces generated by the boost pressure.
In yet a further aspect of the present invention, a second fluid conduit is included for carrying hydraulic fluid therein between the boost pressure control valve and the boost piston assembly, and wherein the back pressure valve controls pressure in the discharge header in response to the pressure of the hydraulic fluid in the second fluid conduit between the boost pressure control valve, and the boost piston assembly.
In yet a further embodiment of the present invention, there is disclosed a vehicle hydraulic system comprising a hydraulic fluid reservoir; a first fluid conduit in fluid communication with the reservoir; a pressure source supplying pressurized hydraulic fluid to the first fluid conduit; a vehicle braking system having a hydraulically operated boost piston assembly for supplementing a force exerted by a vehicle operator to operate brakes of the vehicle braking system; and a boost pressure control valve responsive to an input signal from the vehicle operator for selectively directing pressurized hydraulic fluid at a desired pressure from the first fluid conduit via a boost conduit to the boost piston assembly and venting hydraulic fluid from the boost piston assembly to the reservoir. This embodiment further includes a power steering valve assembly positioned in the first fluid conduit between the reservoir and the boost pressure control valve, wherein operation of the power steering valve assembly generates a back pressure in the first fluid conduit which can be directed to the vehicle braking system by the boost pressure control valve. This embodiment further includes a back pressure valve positioned in the first fluid conduit which can be selectively at least partially closed such that the back pressure valve and the power steering valve assembly, in combination with the pressure source, pressurize the first fluid conduit to a pressure greater than the pressure in the boost conduit in response to driver input.
In yet a further aspect of this embodiment, the system may include an accumulator; and an accumulator valve assembly positioned in the first fluid conduit between the back pressure valve and the boost pressure control valve to hydraulically connect the accumulator to the first fluid conduit when a difference in pressure between the first fluid conduit and the boost conduit drops below a first predetermined value.
In yet a further aspect of this embodiment, the system may include a charging valve assembly connected to the accumulator to cause the accumulator to be automatically charged when hydraulic pressure representative of pressure in the accumulator drops below a second predetermined value.
In yet a further aspect of the present invention, there is disclosed a method for supplying hydraulic fluid to a vehicle braking system comprising: the steps of: supplying pressurized hydraulic fluid to a discharge header; maintaining a desired pressure in the discharge header; supplementing via a boost piston assembly a force exerted by a vehicle operator to operate brakes of the vehicle braking system; and selectively directing a boost pressure, comprising pressurized hydraulic fluid from the discharge header via a boost conduit, to the boost piston assembly and venting hydraulic fluid from the boost piston assembly in response to an input signal.
In a further aspect of this inventive method, the step of selectively directing pressurized hydraulic fluid comprises the step of applying pressurized hydraulic fluid to the boost piston assembly in accordance with a force, F, generated by the input signal and applied to a spool within a boost pressure control valve, the force F being in opposition at least to a force generated within the boost pressure control valve by the boost pressure such that the balance of these forces determines whether the pressurized hydraulic fluid is directed to the boost piston assembly or vented from the boost piston assembly.
In a yet further embodiment of this method, th
Barron Richard J.
Hunnicutt Harry A.
Krawczyk Gregory J.
Lubbers Mark D.
Tang Louis S.
Kelsey-Hayes Company
Lopez F. Daniel
MacMillan Sobanski & Todd LLC
LandOfFree
Electronically controlled hydraulic brake boost pressure... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronically controlled hydraulic brake boost pressure..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronically controlled hydraulic brake boost pressure... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2536385