Multiple displacement hydraulic pump system with automatic displacement control for brake boosters and the like
OwnerPeter Nortoninventor
Life of this patent
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Abstract
A pump system is disclosed for delivering hydraulic fluid to a load device, such as a hydraulic brake system. The system automatically switches from larger displacement to smaller displacement as pressure at the outlet increases. The pump system comprises one or more lower pressure pumps and a high pressure pump with an actuator driving all pumps simultaneously. An unloading valve is coupled with each lower pressure pump for dumping the output thereof in response to pressure of the fluid delivered to the load device. The actuator comprises an electromagnetic linear motor which imparts an intake stroke to the pumps and stresses a spring which releases stored energy for imparting the pressure stroke to the pumps.
Claims8
A hydraulic brake system for an automotive vehicle comprising:
- a hydraulic booster,
- a pump system for supplying pressurized fluid to said booster from a reservoir,
- said booster including a pressure chamber, an inlet port and an outlet port and including a booster valve adapted to be actuated by a brake pedal and which is movable from a center position to admit pressurized fluid from the inlet port to the pressure chamber or movable from said center position to release pressurized fluid from said pressure chamber to said outlet port,
- said pump system including,
- an electric motor,
- a low pressure pump and a high pressure pump adapted to be driven concurrently by said motor, said pumps having respective inlets adapted to be coupled with the reservoir and having respective outlets,
- a common discharge passage coupled with the outlet of the high pressure pump and coupled through a one-way valve with the outlet of the low pressure pump and coupled with said inlet port of said hydraulic booster,
- and an unloading means coupled with the outlet of the low pressure pump and being operable to enable fluid pumped by the low pressure pump to flow with minimal resistance to said reservoir when fluid pressure in the common discharge passage exceeds a predetermined value,
- said pumps collectively having sufficient pumping capacity to supply the requirement of said brake system without supplementary flow from any other source.
Dependencies are inferred from the claim text.