Power steering pump relief system filter

Abstract

Accordingly, the present invention provides a power steering pump having a filter that removes contaminants from fluid flowing through the relief system of the power steering pump. The power steering pump includes a housing having a longitudinal bore communicating with a fluid outlet. A fluid discharge port communicates with the bore and a fluid bypass port also communicates with the bore. A flow control member is situated in the bore and forms a outlet passage communicating with the fluid outlet. A flow control valve is slidably received in the bore. The flow control valve operates to open and allow communication between the fluid discharge port and the outlet passage in the flow control member. When the fluid flow from the fluid discharge port reaches a suitable pressure, the valve opens further to allow fluid flow from the fluid discharge port to the bypass port. A fluid pressure passage communicates pressure from the fluid outlet to a pressure sensing chamber forming part of the flow control valve assembly. A filter located downstream from the flow control member operates to filter fluid passing through the fluid pressure passage, and thereby, prevents contamination from entering the relief system of the power steering pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section through the power steering relief valve and adjacent housing area.

FIG. 2 is a perspective view of a flow control member including a filter.

FIG. 3 is an enlarged cross-section area of the flow control member as illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a partial view of a power steering pump, seen generally at 10, according to a preferred embodiment of the present invention. The power steering pump 10 supplies pressurized fluid for a power steering system used with an automobile. The pump comprises a housing 12 containing a pump element such as a rotor that rotates in a cam chamber. Such power steering pumps are well known and include a discharge port 14 carrying pressurized fluid from the cam chamber in the direction of the arrow 16. The housing 12 also includes a suction passage, not shown, for delivering fluid to the cam chamber. During operation, fluid is drawn into the cam chamber through the suction passage and is pumped under pressure to the discharge port 14 and ultimately through a fluid output 18 forward of an outlet fitting or adapter 20 that connects the power steering pump 10 to the rotary valve and steering gear of the power steering system. Fluid is returned to a return line (not shown) connected to the suction passage and is, in turn, drawn back into the cam chamber. Accordingly, the power steering pump operates in a known manner to supply the steering gear of the power steering system with pressurized fluid.

The volume of the pressurized fluid exiting the outlet fitting or adapter 20 is controlled by recycling a portion of the fluid through a bypass port 22 located in the housing 12. The bypass port 22 is connected to the suction passage whereby fluid traveling through the bypass port 22 flows into the section passage and correspondingly flows into the cam chamber. A flow control valve assembly 24 operates to control the flow of fluid to the bypass port 22. As shown, the flow control valve 24 slides or moves in a reciprocal manner to open and close the bypass port 22 and thereby maintain the fluid flow output from the pump 10 to the steering system at a relatively constant level.

As illustrated, the housing 12 includes a bore 26, that communicates with the fluid discharge port 14 and the bypass port 22. The flow control valve assembly 24 is slidably disposed within the bore 26. The control valve assembly 24 includes a valve body 30. A spring 28 biases the valve body 30 in a closed position whereby a valve face 32 engages an orifice 34 which controls and regulates the fluid flow through the bore 26 and ultimately out of the housing 12 through the outlet fitting or adapter 20 in the direction shown by the arrow 36. The orifice 34 is part of a flow control member 38 seated in the bore 26. Accordingly, the valve assembly 24 operates in a known manner whereby fluid flow through the discharge port 14 enters the fluid flow chamber 40 to a point where pressure in the fluid flow chamber 40 acts on the valve body 30 and correspondingly the spring 28 to move the valve body 30 away from the orifice 34 whereby the fluid in the fluid flow chamber 40 flows through the orifice 34 and the outlet fitting or adapter 20 to the power steering system.

As illustrated in FIGS. 1-3, the flow control member 38 includes a reduced diameter flow control portion 42 having an outlet passage 44 adjacent to the orifice 34. As illustrated, the reduced diameter flow control portion 42 cooperates with the bore 26 to form the annular fluid flow chamber 40. The flow control member 38 further includes a body portion 46 circumferentially sized to fit in and sealingly engage the bore 26. The outer circumferential surface 48 of the body portion 46 includes a knurled or raised surface 50, see FIG. 1, that engages and secures the flow control member 38 within the bore 26. In the preferred embodiment, the flow control member 38 is press fit or driven into the bore 26. The flow control member 38 further includes a reduced diameter outlet end 52 opposite the reduced diameter flow control portion 42. The reduced diameter outlet end 52 includes an outer surface 53 that cooperates an inner surface 27 of with the bore 26 to form an annular fluid pressure chamber 54.

The flow control member 38 further includes an annular cavity 56 extending to the rear end 58 of the flow control member 38 on one side and communicating with the outlet passage 44 on the opposite side. The annular cavity 56 has a diameter greater than the outlet passage 44 and correspondingly forms a ledge or seat 74 at the interface or junction of the cavity 56 and outlet passage 44. The flow control member 38 also includes at least one aperture 60 extending through the sidewall 62 of the outlet end 52. Accordingly, the aperture 60 provides for fluid flow or communication between the cavity 56 and the fluid pressure chamber 54.

A filter 64 is disposed within the annular cavity 56 and filters the fluid passing from the cavity 56 through the aperture 60 and into the fluid pressure chamber 54. In the present embodiment, the filter 64 is a cylindrically shaped screen 66 sized to fit within the annular cavity 56. Accordingly, depending upon the size of the particulate matter to be filtered, the screen size is selected accordingly. As illustrated, the screen 66 sits on the ledge or seat 74 and extends to a point slightly past the rear end 58 of the flow control member 38 and into the passageway 68 formed in the outlet fitting or adapter 20.

As illustrated, a fluid pressure passageway 70 transmits fluid from the fluid pressure chamber 54 to a pressure sensing chamber 72 located at the end of the flow control valve assembly 24 housing the spring 28. The fluid pressure passageway 70 functions as a pressure regulating mechanism and fluid relief system. For example, the flow rate through the fluid discharge port 14 and into the fluid flow chamber 40 is proportional to the speed of the engine driving the pump. When the engine is operating at low speeds, the spring 28 biases the valve body 30 to a closed position whereby the bypass port 22 is closed and the fluid output pressure downstream of the orifice 34 is communicated through the fluid pressure passage 70 to the pressure sensing chamber 72 which adds to the spring force on the valve body 30. In this manner, the entire output from the rotor or pumping element flows through the outlet passage 44 and to the outlet fitting or adapter 20. As the pump speed increases, the pressure in the fluid flow chamber 40 correspondingly increases and forces the valve body 30 against the spring 28 to a position opening the bypass port 22 and enabling fluid flow through the bypass port 22 to the suction passageway or fluid reservoir. In addition, fluid from the pressure sensing chamber 72 then travels through the fluid pressure passageway 70 into the fluid pressure chamber 54. Accordingly, as the valve body 30 moves within the bore 26, the volume of fluid in the fluid pressure sensing chamber 72 changes, this change is accommodated by fluid flow through the fluid pressure passage 70.

One advantage of the present invention is that the filter 64 is disposed such that the flow of the fluid through the cavity 56 and through the outlet fitting or adapter 20 in the direction of the arrow 36 makes the filter self- cleaning. For example, as the fluid exits through the cavity 56 contamination that builds up on the screen 66 is washed away. Further, the hydraulic or pumping action occurring as the valve body 30 moves reciprocally within the valve bore 26, will also help to dislodge any contaminants from the screen in the area of the aperture 60 whereby the fluid flow through the cavity 56 will wash the contamination away.

Further, since the reduced diameter rear end 58 creates an annular fluid pressure chamber 54, the flow control member 38 does not necessarily have to be located within the bore 26 such that the aperture 60 is adjacent to the fluid flow pressure passage 70. In operation, the fluid flows into and out of the cavity 56 from the fluid flow pressure passageway 70 through the aperture 60 and the screen 66 located in the rear end 52 of the flow control member 38. The fluid in the annular fluid pressure chamber 54 which communicates with the fluid pressure passage 70. Thus, any contaminants are trapped on the screen 66 adjacent the aperture 60. In addition, as shown in FIG. 3, an annular space 76 is created between the screen 66 and the inner surface 56a of the cavity 56 to increase the surface area of the screen 66 acting as a filter. Whereby filtered fluid passing through the screen 66 at any point travels through the annular gap 74 between the screen 66 and the inner surface 56a of the cavity 56 and exits through the aperture 60. Since only filtered fluid travels through the fluid pressure passage 70 to the fluid pressure chamber 54, the likelihood of any contaminants causing sticking or preventing proper valve body 30 operation is greatly reduced.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims

1. A power steering pump comprising: a housing having a bore having a longitudinal axis;a fluid discharge port communicating with the bore;a fluid bypass port communicating with the bore;a flow control valve slidably received in the bore, said bore further including a pressure sensing chamber located on one side of said flow control valve and a fluid outlet located on another side of said flow control valve;said housing further including a fluid pressure passageway communicating with and extending between said fluid outlet and said pressure sensing chamber; anda filter disposed in said bore and filtering fluid traveling through said passageway.

2. A power steering pump as set forth in claim 1 wherein said fluid outlet includes a flow control member, said flow control member having an outlet passageway and a cavity; and said filter disposed within said cavity.

3. A power steering pump as set forth in claim 2 wherein said filter includes a screen.

4. A power steering pump as set forth in claim 1 including said flow control member having a reduced diameter portion adjacent a rear end thereof; said reduced diameter portion having an aperture therein, said aperture communicating with said cavity; andsaid filter located in said cavity and filtering fluid traveling from said cavity through said aperture.

5. A power steering pump as set forth in claim 4 wherein said cavity is cylindrical, said cylindrical cavity having an inner wall, a diameter greater than the diameter of said fluid outlet; and said filter is disposed within said bore and spaced from said inner wall of said cylindrical cavity.

6. A power steering pump as set forth in claim 5 wherein said filter is a cylindrical screen.

7. A power steering pump as set forth in claim 1 including an outlet fitting connected to said housing, said filter extending from said flow control member to said outlet fitting.

8. A power steering pump as set forth in claim 2 including a fluid pressure chamber located between said flow control member and said bore, wherein said fluid pressure passageway communicates with said fluid pressure chamber.

9. A power steering pump as set forth in claim 8 including said flow control member having an aperture, said aperture communicating with said cavity and said fluid pressure chamber.

10. A power steering pump comprising: a housing, said housing having a bore;a fluid outlet, said fluid outlet communicating with said bore;a fluid discharge port communicating with said bore;a fluid bypass port communicating with said bore;a flow control member disposed in said bore, said flow control member having an orifice on one end thereof and an outlet passage, said outlet passage communicating with said orifice and with said fluid outlet;a flow control valve slidably received in said bore and having a fluid delivery chamber on one side thereof and a pressure sensing chamber on an opposite side thereof;a fluid pressure passage extending from a point downstream of said orifice to said pressure sensing chamber; anda filter disposed in said flow control member and filtering fluid traveling through said fluid pressure passage.

11. A power steering pump as set forth in claim 10 wherein said flow control member includes a cavity; and a filter, said filter located in said cavity.

12. A power steering pump as set forth in claim 11 wherein said filter includes a screen.

13. A power steering pump as set forth in claim 10 wherein said filter is located in said flow control member between said outlet passage and said fluid pressure passage to provide uninterrupted fluid flow from said outlet passage in said flow control member to said fluid outlet.

14. A power steering pump as set forth in claim 11 wherein said filter is spaced from an inner surface of said cavity.

15. A filter assembly for use with a power steering pump comprising: a flow control member having a body, a flow control portion having an outlet passage and a rear end, said body portion having a cavity, said cavity extending into said body from said rear end;an aperture extending through a side wall of said relief system end between an outer surface of said rear end and an inner surface thereof as defined by said cavity; anda filter disposed within said cavity.

16. A filter assembly as set forth in claim 15 wherein said filter is a screen member spaced from said inner surface of said cavity.

17. A filter assembly as set forth in claim 16 wherein said screen is seated on a ledge formed at an intersection of said cavity and said outlet passage.

18. A filter assembly as set forth in claim 15 wherein said outlet passage extends from said flow control end to said cavity and forms an uninterrupted fluid flow passage between said flow control end and said rear end, said rear end including an aperture therein and said filter disposed between said uninterrupted flow passage and said aperture.

19. A filter assembly as set forth in claim 15 wherein said body has a cylindrical shape and said rear end further has a cylindrical shape having an outer diameter less than the outer diameter of said cylindrically shaped body; and said cavity having a cylindrically shaped configuration whereby said filter is also cylindrically shaped and located within said cylindrically shaped cavity.

20. A filter assembly as set forth in claim 19 wherein a cylindrically shaped screen is spaced from an inner surface of said cavity and seated on one end on a ledge formed at the intersection of said outlet passage and said cavity, said screen having said opposite end extending outward longitudinally past the rear end of said flow control member.