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An inlet throttle valve for supplying liquid to a high-pressure pump has a fully open start position and an operating range where flow through the valve is determined by a pressure balance of a valving member independent of the pressure of oil supplied to the inlet throttle valve. The valve includes

An inlet throttle valve for supplying liquid to a high-pressure pump has a fully open start position and an operating range where flow through the valve is determined by a pressure balance of a valving member independent of the pressure of oil supplied to the inlet throttle valve. The valve includes a hydraulic stop limiting closing movement of the valving member. The valve may be used to flow low-pressure oil to a high-pressure pump for supplying high-pressure oil to HEUI injectors or other components of an internal combustion engine.

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1. In an internal combustion engine having a hydraulic circuit for supplying high-pressure liquid to hydraulically actuated, electronically controlled components, the circuit including a high-pressure pump to flow high-pressure liquid to the components, a source of low-pressure liquid and an inlet p

1. In an internal combustion engine having a hydraulic circuit for supplying high-pressure liquid to hydraulically actuated, electronically controlled components, the circuit including a high-pressure pump to flow high-pressure liquid to the components, a source of low-pressure liquid and an inlet passage extending from the source of low-pressure liquid to the high-pressure pump, the improvement comprising:an inlet throttle valve in the inlet passage, the valve including a cylindrical valving passage having opposed ends and a wall extending between such ends; an inlet port; an outlet port; both ports opening into said valving passage with one port located in said wall; a valve member located in and slideably moveable along the valving passage, the valve member including a piston facing one valving passage end and a hollow cylindrical body extending from the piston along the valving passage toward the other valving passage end; said cylindrical body moveable across said one port to vary the flow area for the valve; a spring in the valving passage biasing the valve member toward said one valving passage end; a bleed flow passage opening through said wall into the interior of the valving passage, said bleed flow passage located between said one port and said one valving passage end; and a chamber in the valving passage located between said piston and said one valving passage end, wherein said valve having a fully open position with said piston located between said bleed flow passage and said one valving passage end and said cylindrical body and one port defining a large inlet area, and said valve having an operational position with said piston located between said bleed flow passage and said one port to directly communicate the bleed flow passage and the chamber and with said cylindrical body partially obstructing said one port so that the flow area of the valve is reduced. 2. The improvement of claim 1 including a vent passage opening into the valving passage between said one port and said bleed flow passage. 3. The improvement of claim 1 wherein said one port comprises said inlet port. 4. The improvement of claim 3 wherein the inlet port surrounds the valving passage and including flow openings extending through the end of the cylindrical body away from the piston, said flow openings movable across the inlet port to vary the flow area. 5. In an internal combustion engine having a hydraulic circuit for supplying high-pressure liquid to hydraulically actuated, electronically controlled components, the circuit including a high-pressure pump to flow high-pressure liquid to the components, a source of low-pressure liquid and an inlet passage extending from the source of low-pressure liquid to the high-pressure pump, the improvement comprising:an inlet throttle valve in the inlet passage, the valve including a valving passage having opposed ends and a wall extending between such ends; an inlet port opening through the wall into the valving passage; an outlet port opening into said valving passage; a valve member located in and slideably moveable along the valving passage, the valve member including a hydraulic pressure responsive piston facing one valving passage end and a body extending from the piston along the valving passage toward the other valving passage end; said body moveable across said inlet port to vary the flow area for the valve; a spring in the valving passage biasing the valve member toward a position allowing full communication between the said inlet port and the said outlet port, a chamber in the valving passage located between said piston and said one valving passage end; and a flow passage extending into said chamber, wherein the flow area of the valve is determined by a balance position of the valve member in the valving passage determined by the force of the spring and the pressure of the liquid at the outlet port biasing the valving member toward said one valving passage end and the pressure of the liquid in t he chamber biasing the valving member toward said other valving passage end, said balance position determined substantially independently of the pressure of the liquid at the inlet port. 6. The improvement of claim 5 including a vent passage opening into the valving passage between the inlet port and the flow passage. 7. The improvement of claim 5 wherein the valve member body comprises a hollow cylinder and including a plurality of flow openings extending through the end of such body away from the piston, said inlet passage extending around the valving passage. 8. An inlet throttle valve for controlling the flow of liquid from a low-pressure liquid source to a high-pressure pump, the valve including a valve body; a valving passage in the valve body having a passage wall and opposed ends; an inlet port opening into the passage through the passage wall; an outlet port communicating with the interior of the valving passage and located to one side of the inlet port; a spool located in and movable along the passage, the spool including a hydraulic pressure responsive piston located to the other side of the inlet port and facing one valving passage end, and a valving member moveable across the inlet port to vary the flow area of the valve and control flow of low-pressure liquid through the valve and to the high-pressure pump; a spring biasing the spool toward a position allowing full communication between the said inlet port and the said outlet port; and hydraulic pressure means for biasing said piston towards a position of reduced communication between the said inlet port and the said outlet port proportional to desired flow of low-pressure fluid through the valve, wherein the flow area at the valve is determined by a pressure balance position of the spool in the passage made substantially independently of the pressure at the low-pressure source. 9. The inlet throttle valve as in claim 8 wherein the spool includes an edge cooperable with the inlet port to vary the flow area. 10. The inlet throttle valve as in claim 9 wherein the edge extends around the spool, and including a circular inlet opening at the edge when the valve is in a fully open position. 11. The inlet throttle valve as in claim 8 wherein the spool and inlet port include one or more openings and an edge relatively moveable across said openings. 12. The inlet throttle valve as in claim 11 wherein said openings are in said spool. 13. The inlet throttle valve as in claim 8 wherein said valving passage is cylindrical and the spool has a hollow cylindrical body with said piston at one end of the body. 14. The inlet throttle valve as in claim 13 wherein said spool comprises a valving edge at the other end of the cylindrical body. 15. The inlet throttle valve as in claim 13 wherein said spool comprises a plurality of openings extending through the spool. 16. The inlet throttle valve as in claim 15 wherein said inlet port surrounds the valving passage and said openings include a plurality of diametrically opposed, axially offset openings. 17. The inlet throttle valve as in claim 8 including a chamber between said piston and said one end of the valving passage, a flow passage opening into said valving passage between the inlet port and said one valving passage end, said valve having a fully open position with said piston located between said flow passage and said one valving passage end and an operating position with said piston located between said flow passage and said inlet port. 18. The inlet throttle valve as in claim 17 including a seepage flow connection between said flow passage and said chamber when the valve is in the fully open position. 19. The inlet throttle valve as in claim 17 including a circular inlet opening at the inlet port when said valve is in said fully open position. 20. The inlet throttle valve as in claim 19 wherein the axial length of the spool along the wall is substantially equal to the distance from the side of the flow passage adjacent said one valving passage end to the side of the inlet port away from said one valving passage end wherein movement of the spool from the fully open position away from said one valving passage end opens the flow passage and closes the circular inlet opening substantially simultaneously. 21. The inlet throttle valve as in claim 8 including a chamber in the valving passage between the piston and said one valving passage end; a flow passage opening into the chamber; and a vent passage opening into the chamber between the inlet port and the flow passage to limit movement of the spool away from said one valving passage end. 22. The inlet throttle valve as in claim 8 including a vent passage opening into the valving passage between the inlet port and said one valving passage end. 23. An inlet throttle valve for controlling the flow of liquid from a low-pressure liquid source to a high-pressure pump, the valve including a valve body; a valving passage in the valve body having a passage wall and opposed ends; an inlet port communicating with the valving passage; an outlet port communicating with the valving passage, one of said ports opening through said wall; a spool located in and movable along the passage, the spool including a hydraulic pressure responsive piston facing one end of the passage, and a valving member moveable across said one port to vary the flow area of the valve and control flow of low-pressure liquid through the valve and to the high-pressure pump; a spring biasing the spool toward said one valving passage end; a chamber between said piston and said one valving passage end; and a flow passage opening into said valving passage between said one port and said one valving passage end, the valve having a fully open position wherein said piston is located between the flow passage and said one valving passage end and an operational position where said piston is located between the flow passage and said one port, wherein when the valve is in the fully open position liquid from the flow passage bleed flows past the piston and into the chamber to move the spool away from said one valving passage end to an operating position. 24. The inlet throttle valve as in claim 23 wherein the spool includes a valving edge cooperable with said one port to vary the flow area of the valve. 25. The inlet throttle valve as in claim 24 wherein the valving edge extends around the spool, and including a circular inlet opening at the edge when the valve is in the fully open position. 26. The inlet throttle valve as in claim 25 wherein the spool and said one port include one or more flow openings and a portion relatively moveable across said openings. 27. The inlet throttle valve as in claim 26 wherein said openings are in the spool. 28. The inlet throttle valve as in claim 23 wherein said one port comprises said inlet port. 29. The inlet throttle valve as in claim 23 including a seepage flow connection between said flow passage and said chamber when the valve is in the fully open position wherein seepage flow into the chamber slowly moves the valve from the fully open position to the operational position. 30. The inlet throttle valve as in claim 23 including a vent passage opening into the valving passage between said one port and the flow passage to limit movement of the spool away from said one end of the valving passage. 31. An inlet throttle valve for controlling the flow of liquid from a low-pressure liquid source to a high-pressure pump, the valve including a valve body; a valving passage in the valve body having a passage wall and opposed ends; an inlet port communicating with the valving passage; an outlet port communicating with the valving passage; one of said ports opening through said wall; a spool located in and moveable along the passage, the spool including a hydraulic pressure responsive piston facing one end of the passage and a valving member moveable across said one port to vary the flow area of the valve and control flow of low-pressur e liquid through the valve and to the high-pressure pump; a spring biasing the spool toward said one valving passage end; a hydraulic fluid chamber located in said valving passage between said piston and said one valving passage end; an inlet flow passage opening into said valving passage adjacent said one valving passage end thereof; and a vent passage opening into said valving passage between said inlet flow passage and said one port to limit movement of the spool away from said one valving passage end. 32. The inlet throttle valve as in claim 31 wherein said piston having a position between said inlet flow passage and said one valving passage end wherein bleed flow from said inlet passage to said chamber slowly moves the piston away from said one valving passage to open said inlet flow passage to said chamber. 33. The inlet throttle valve as in claim 32 wherein said valve has a fully open position and an operating position, and including a circular inlet passage surrounding said wall when the valve is in said fully open position.