Hydraulic pump apparatus

Abstract: A hydraulic apparatus as used for providing fluid to a steering gear of an automotive vehicle includes a housing (10) having a valve bore (14) housing a relief valve spool (94) disposed therein and slidable between a first and second position. A discharge connector (88) is disposed on a first end of the valve bore(14) and forms a fluid passage for communicating fluid through the first end of the valve bore to a power steering actuator. An annular retainer (90) is disposed in the valve bore between the first position of the spool valve (94) and the discharge connector (88). The annular retainer includes an outer periphery (130) sized for interference fit engagement with said valve bore (14) for retaining the spool valve (94) within the valve bore (14) when the discharge connector (88) is removed from the first end of the valve bore.

Description: This invention relates a hydraulic apparatus comprising a housing having a valve bore with first and second ends, a spool valve disposed in the valve bore and slidable between a first and second position, and a discharge connector having threads on an outer circumference thereof for engaging internal threads disposed on said first end of said valve bore, said discharge connector forming a fluid passage for communicating fluid through said first end of said valve bore. Though applicable to many different forms of hydraulic apparatus, amongst them pumps, suspension actuators and hydraulic brake devices, the invention will be described by particular reference to a hydraulic steering pump as described in EP-A-0 505 033 which is believed to constitute an example of the closest prior art to the present invention. Hydraulic pumps are well known to those skilled in the hydraulics art, as are many forms of actuators having sliding valves therein. Commonly these valves are used to control fluid flow within the pump, actuator etc. The valve in EP-A-0 505 033, in common with the present invention, serves to relieve the pressure at the discharge connector that leads to the steering gear. The valves are commonly located within a valve bore and are free to slide between at least two predetermined positions. Additionally, the bore is generally manufactured to allow the valve to slide completely out at least one end of the bore. This accommodates assembly, and where necessary, service of the valve assembly. It was recently observed that in certain circumstances, it is desirable to orient power steering pumps such that a longitudinal axis the bore is generally aligned parallel to the vertical axis as installed in the vehicle. It was further observed that during service of hydraulic lines and connectors attaching to the pump, the valve could be displaced from the bore inadvertently. Thus necessitating service of the valve assembly where not necessarily required. The present invention therefore seeks to provide a hydraulic apparatus that can be oriented to have a vertical valve bore yet would not require service of the valve assembly during servicing as a result of its inadvertent removal. According to the present invention, in a hydraulic apparatus as described initially, an annular retainer is disposed in the valve bore between the first position of said spool valve and the discharge connector, the annular retainer having an outer periphery sized for interference fit engagement with said valve bore for retaining the spool valve within the valve bore when the discharge connector is removed from said first end of said valve bore. The annular retainer positively retains the spool valve within the valve bore in the absence of the discharge connector, allowing service of the discharge connector and any associated components, such as fluid line and couplings, without requiring inadvertent service of the spool valve. The preferred embodiment of the invention further comprises a discharge port nozzle attached to the discharge connector, the annular retainer having an inner periphery sized for interference fit with the discharge port nozzle. Conveniently, the outer periphery of the annular retainer includes a plurality of protuberances projecting outward to engage said valve bore, thereby creating said interference fit. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric exploded view of a power steering pump, Figure 2 is a cut away view of the power steering relief valve and adjacent housing area of the power steering pump with the components disposed in the low speed position; Figure 3 is a partial cross section view taken along line 3-3 from Figure 2 of an annular retainer; Figure 4 is a partial sectional view taken along line 4-4 from Figure 3 of an annular retainer; Figure 5 is a partial sectional view taken along line 5-5 from Figure 3 showing the details of an annular retainer; Figure 6 is a partial sectional view taken along line 6-6 from Figure 4 of an annular retainer; and Figure 7 is a cross section through the power steering relief valve and adjacent housing area of the power steering pump with the components disposed in the high speed position. Referring now to Figures 1 and 2, the invention will now be described as applied to a power steering pump of the type described in EP-A-0 505 033, to which the reader is referred for a fuller description of the pump. It should be stressed, however, as has been earlier mentioned, that the present invention may be employed with similar advantage in many hydraulic devices having internal valve mechanisms and external hydraulic lines, such as suspension actuators, hydraulic brake devices, etc. A rotary vane hydraulic power steering pump supplies pressurized fluid to an automotive vehicle steering gear. The pump includes a housing 10 defining a cylindrical space 12 containing the pumping elements, a bore 14 having first and second ends 15, 17 containing a flow control valve and related components and a diffuser passage 18. The housing includes at least three bosses 20-22, each having a cylindrical hole adapted to receive a mechanical attachment such as a bolt, which can be threaded directly to the engine block of the vehicle. In this way, the conventional bracket usually used to support a power steering pump located in position to be driven by a belt from the engine crankshaft can be eliminated. The components that pump hydraulic fluid from a reservoir to the steering gear are rotatably supported on a shaft 24, driven by an endless drive belt from an engine and rotatably connected by a splined connection to a rotor 26 fixed in position on the shaft by a snap ring 28. The rotor has ten radially sliding vanes 30, held in contact with the inner surface of a cam ring 32 having two arcuate zones extending angularly in rise or inlet quadrants and two zones of lesser radial size extending angularly in fall or outlet quadrants mutually separated by the inlet quadrants. A lower pressure plate 34 and an upper pressure plate 36 are fixed in position radially with respect to the cam 32 by alignment pins 38. Formed through the thickness of the upper pressure plate are arcuate outlet ports 40, 42 communicating with an outlet port opening to the flow control valve bore 14, inlet ports 44, 46 and arcuate passages 48, 50 for use in cold starting priming. The lower pressure plate has inlet ports 56, 54 formed through its thickness, outlet ports 58, 60 and arcuate flow passages 62, 64 hydraulically connected to passages 48, 50. A wire retaining ring 66 seats within a recess at the end of the pump housing to hold in position a pump cover 68. Bushing 70 supports shaft 24 on a recess in the inner surface of the cover. Seal 72 prevents the passage of hydraulic fluid. The opposite end of the rotor shaft is supported rotatably in a bushing 74, which is supported on the housing; a shaft seal 76 prevents flow of hydraulic fluid from the pumping chambers. Located adjacent the lower pressure plate on the opposite side from the cam are an inner seal 78, an outer seal 80, and a Belleville spring 82, which develops an axial force tending to force mutually adjacent surfaces of the various components into abutting contact. Located within bore 14 are a discharge port nozzle 84, integrally formed with a discharge connector 88, a seal 86,and an annular retainer ring 90. The discharge connector 88 has a threaded portion 89 for engagement with a threaded portion 92 of the valve bore 14. Also located within bore 14 is a relief valve spool 94, a coiled compression spring, ball, and ball seat 96 and a larger compression spring 98 urging spool 94 toward a first position where the flow control valve is closed corresponding to low pump speed operation. A seal 100 and plug 102 close the adjacent end of the bore mechanically and hydraulically. A tube assembly 104 connects a tube carrying fluid from the steering gear to the pump housing, through which it passes in suitable ports to the pumping chamber. Referring now to Figures 2 through 6, the annular retainer ring 90 is disposed within the bore 14 between a first position of the valve spool 94 and the inner end of the discharge connector 88. The annular retainer 90 includes an outer periphery 130 sized for interference fit engagement with the bore 14. In the preferred embodiment, the outer periphery of the annular retainer includes a plurality of protuberances 132 projecting radially outward for engagement with the bore 14. The protuberances may be tapered, having a low end 134 of the taper adjacent to the valve spool 94 and the high end 136 adjacent to the discharge connector 88. The annular retainer 90 also includes an inner periphery 140 sized for interference fit engagement with the discharge port nozzle 84. The inner periphery 140 may include flats 142 protruding inwardly from the otherwise circular periphery of the annular retainer. Depending on the amount of interference desired, small flats may be formed just adjacent to the spool valve 94, or if greater interference is desired, larger flats may extend further into the inner periphery 140 of the annular retainer 90. Advantageously, the amount of taper on the protuberances 132 and the size of the flats 142 can be varied so as to create a relationship permitting the removal of the discharge port nozzle without causing the annular retainer to be removed from the bore 14. This is accomplished by the combination of greater surface area contacted by the outer diameter than the inner diameter together with a sufficient taper on the protuberances 132 to create a higher retaining force than that created by the interference between the flats and the discharge port nozzle. This is particularly advantageous where automated assembly equipment is used and the retainer 90 must stay on the discharge port nozzle until it is assembled into the valve bore. Operation of the relief valve spool 94 will now be described with reference to Figures 2 and 7. Pressurized fluid flows from the outlet ports in the pressure plates through port 112 to bore 14 in which relief valve spool 94 is located. Nozzle 84 has an axially directed passage 114, which continually connects port 112 to the pressure tube 116, which carries high pressure hydraulic fluid to the steering gear from the pump. The flow rate through port 112 is proportional to the speed of the pump shaft 24 and to the speed of the engine to which that shaft is connected. Directing fluid flow into passage 114 produces a pressure drop relative to pressure at port 112. Pressure downstream of aperture 114, the steering system pressure, is fed back in passage 115 to the end of the relief valve spool 94 contacted by spring 98. A force resulting from the feedback pressure adds to the spring force on the spool. When pump speed increases, hydraulic system pressure in port 112 increases, thereby forcing relief valve spool 94, against the effect of compression spring 98 and the feedback pressure, away from the first position toward a second position (as shown in Figure 7) where additional fluid flow is bled back to a fluid reservoir through the diffuser passage 18. This operating condition may also be referred to as the high speed operating mode, as it occurs when the pump operates at high speeds. In the event the discharge connector 88 must be removed, such as to service pressure tube 116, the spring 98 urges the relief valve spool 94 against the annular retainer 90. The annular retainer 90 positively resists sliding of the relief valve spool 94, so as to prevent inadvertent disassembly of the relief valve spool 94. A hooked object may be inserted in bore 14 to forcibly remove the retainer 90 if servicing the relief valve spool 94 is specifically desired.

Claims: A hydraulic apparatus, comprising: a housing (10) having a valve bore (14) therein, said valve bore having first and second ends (15,17); a spool valve (94) disposed in said valve bore (14) and slidable between a first and second position; and a discharge connector (88) having threads on an outer circumference thereof for engaging internal threads disposed on said first end of said valve bore (14), said discharge connector (88) forming a fluid passage for communicating fluid through said first end (15) of said valve bore; characterised by an annular retainer (90) disposed in said valve bore (14) between said first position of said spool valve (94) and said discharge connector (88), said annular retainer (90) having an outer periphery (130) sized for interference fit engagement with said valve bore (14) for retaining said spool valve (94) within said valve bore (14) when said discharge connector (88) is removed from said first end of said valve bore. An apparatus as claimed in claim 1, further comprising a discharge port nozzle (84) attached to said discharge connector (88), said annular retainer (90) having an inner periphery (140) sized for interference fit with said discharge port nozzle (84). An apparatus as claimed in claim 1 or 2, wherein said outer periphery (130) of said annular retainer (90) includes a plurality of protuberances (132) projecting outward to engage said valve bore (14), thereby creating said interference fit. An apparatus as claimed in claim 3, wherein said protuberances (132) include an outward taper having a low end (134) adjacent to said spool valve (94) and a high end (136) adjacent to said discharge connector (88). An apparatus as claimed in claim 2, 3 or 4, wherein said inner periphery (140) of said annular retainer (90) includes at least one flat portion (142) for creating said interference fit with said discharge port nozzle (84). An apparatus as claimed in claim 5, wherein said flat portion (142) only projects inward from said inner periphery (140) adjacent to said spool valve (94). An apparatus as claimed in any of claims 2 to 6, wherein said interference fit between said outer periphery (130) of said annular retainer (90) and said valve bore (14) creates a greater retaining force than said interference fit between said inner periphery (140) of said annular retainer (90) and said discharge port nozzle (84), such that said discharge connector (88) and said discharge port nozzle (84) can be removed from said valve bore (14) without removing said annular retainer (90) from said valve bore (14). A hydraulic pump for providing fluid to a steering gear of an automotive vehicle, comprising an apparatus as claimed in any preceding claim, wherein the said valve spool (94) forms part of a pressure relieve valve to reduce the hydraulic pressure at the discharge connector (88).

Inventors: BLEITZ DANIEL J, MASTROFRANCESCO LUIGI, BLEITZ, DANIEL J., MASTROFRANCESCO, LUIGI
Applicants: FORD GLOBAL TECH LLC, FORD GLOBAL TECHNOLOGIES, LLC
Application year: 1998
Main classification: F04C15
IPC codes: F16K27, F04C14