Pumps – With condition responsive pumped fluid control – Driven pump part speed responsive
Patent
1982-04-16
1987-12-22
Freeh, William L.
Pumps
With condition responsive pumped fluid control
Driven pump part speed responsive
417310, 417300, 180142, 180143, F04B 4902, F04B 4900
Patent
active
047144130
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
My invention comprises improvements in a positive displacement power steering pump of the kind shown in U.S. Pat. No. 4,199,304, which issued on Apr. 22, 1980 to the assignee of my invention. Such pumps are used in power steering systems for motor vehicles.
BACKGROUND ART
I am aware of certain prior art patents that describe flow control valves for pumps that are speed sensitive, one being U.S. Pat. No. 4,244,389. That patent comprises a flow control valve having a variable orifice, the effective area of the orifice depending upon the position of the spool valve as seen in FIGS. 1 and 2 of the drawings for that patent. The valve moves, however, in accordance with pump speed or engine speed to vary the flow of fluid to the steering gear. The valve has no road speed sensitive function for eliminating the power assist at a selected design speed as in the present disclosure.
U.S. Pat. No. 3,314,495 shows a well known flow control valve having a so-called drooper pin, best seen in FIG. 6 of that patent. The drooper pin is located in a flow control orifice that communicates with the fluid supply passage for a power steering gear. As the valve spool moves, the metering pin also moves; and its tapered area registers with the orifice to provide a variable effective orifice restriction. As the pump speed changes, the pressure of the fluid in the spring chamber for spring 34C for the construction of FIG. 6 of that patent is reduced by the venturi effect of the increased flow upon an increase in pump speed.
Power steering gear valves, as distinct from power steering pump valves, are shown in U.S. Pats. Nos. 3,690,400 and 3,692,137. These control the magnitude of the pressure in a reaction chamber for a power steering gear. They sense a speed signal, but they are effective only to influence the magnitude of the torque reaction during steering maneuvers and are not effective to reduce pump horsepower loss of the associated power steering pump and to eliminate the power assist at high speeds.
Another power steering system valve shown in U.S. Pat. No. 4,085,657 comprises a differential pressure operated valve that acts in a power steering gear fluid circuit to alter the fluid flow to the steering gear thus changing as desired the characteristic relationship of pressure to steering effort.
DISCLOSURE OF THE INVENTION
The power steering pump shown in U.S. Pat. No. 4,199,304 comprises a rotor assembly having multiple slipper pump elements that register with cam surfaces formed in a cam ring secured to the pump housing. The rotor is drivably connected to an engine driven pump drive shaft.
The cam ring cooperates with the rotor to define two crescent pump cavities spaced in 180.degree. relative angular disposition. An inlet port and an outlet port are provided for each cavity so that two pumping strokes occur for each revolution of the rotor. The outlet ports supply a common flow control valve which maintains a constant flow in a flow delivery passage that communicates with a power steering fluid motor. The flow control valve comprises a valve spool that controls the degree of communication between each fluid outlet port and bypass flow passage communicating with the inlet side of the pump.
In the particular embodiment described in this specification the valve is located in a pump valve plate in which the valve porting is formed. The valve plate is situated against an end plate that registers with one side of the rotor and the side of the cam ring. The opposite side of the rotor and cam ring is engaged by a second end plate. Fluid pressure and spring force urge the end plates, the cam ring and the valve plate into stacked registry.
The valve spool is subjected to a calibrated spring force and to the pressure developed at the outlet ports. It is subjected also to a venturi pressure force that is developed by a flow venturi located in the flow distribution passage. The pressure at the throat of the venturi acts on the side of the pump engaged by the valve spring while the upstream side of the venturi corre
REFERENCES:
patent: 1847229 (1932-03-01), Swanson et al.
patent: 3314495 (1967-04-01), Clark et al.
patent: 3690400 (1972-09-01), Uchiyama et al.
patent: 3692137 (1972-09-01), Inoue
patent: 3744515 (1973-07-01), Inoue
patent: 4085657 (1978-04-01), Keruagoret
patent: 4119172 (1978-10-01), Yanagishima et al.
patent: 4199304 (1980-04-01), Strikis et al.
patent: 4244389 (1981-01-01), Shimoura et al.
patent: 4300650 (1981-11-01), Weber
patent: 4320812 (1982-03-01), Takaoka et al.
Ford Motor Company
Freeh William L.
Harrington Donald J.
Zerschling Keith L.
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