초록 ▼

An electrically actuated, hydraulic power steering system is provided. The steering system includes a hydraulic pump for generating hydraulic pressure, a hydraulic fluid reservoir, a hydraulic cylinder, and a control valve arrangement that selectively connects the hydraulic cylinder to the pump and

An electrically actuated, hydraulic power steering system is provided. The steering system includes a hydraulic pump for generating hydraulic pressure, a hydraulic fluid reservoir, a hydraulic cylinder, and a control valve arrangement that selectively connects the hydraulic cylinder to the pump and the hydraulic fluid reservoir. The control valve arrangement is characterized during the on-center position by a first and a second chamber of the hydraulic cylinder being in fluid communication with each other but not with the fluid reservoir. In one embodiment, the steering system has a steering sensor, a control box, and two pressure accumulators for providing at least two levels of steering assist.

대표청구항 ▼

What is claimed is: 1. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering me

What is claimed is: 1. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump and the reservoir, the control valve arrangement operable in at least a first condition, a second condition, and a third condition; wherein in the first condition the control valve arrangement connects the first chamber with the pump and connects the second chamber with the reservoir for fluid communication therebetween; in the second condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the pump for fluid communication therebetween; and in the third condition the control valve arrangement connects the first and second chambers with each other and disconnects the first and second chambers from the reservoir. 2. The hydraulic power steering system of claim 1, wherein the first condition corresponds to a steering assist operation in a first direction, the second condition corresponds to a steering assist operation in a second direction, and the third condition corresponds to a no steering assist operation. 3. The hydraulic power steering system of claim 1, wherein the control valve arrangement comprises a solenoid activated, three position valve. 4. The hydraulic power steering system of claim 3, wherein the control valve arrangement further comprises a solenoid activated, two position valve in series with the solenoid activated, three position valve. 5. The hydraulic power steering system of claim 1, further comprising: a steering sensor operatively engaged with the steering mechanism; and a control box operable to switch the control valve arrangement between the first, second and third conditions in response, at least in part, to a signal received from the steering sensor. 6. The hydraulic power steering system of claim 5, wherein the steering sensor comprises a torsion bar within a housing and a plurality of electrical contacts spaced circumferentially about the torsion bar so that as the torsion bar winds up relative to said housing, a series of electrical connections are made sequentially. 7. The hydraulic power steering system of claim 5, further comprising an electromagnetic clutch operable to engage the hydraulic pump with a driving motor when the clutch is actuated, wherein the control box is operable to actuate the electromagnetic clutch in response, at least in part, to a signal received from the steering sensor. 8. The hydraulic power steering system of claim 7, further comprising a pressure transducer in fluid communication with the first chamber, wherein the control box is operable to actuate the electromagnetic clutch in response, at least in part, to a signal received from the pressure transducer. 9. The hydraulic power steering system of claim 1, wherein the steering mechanism is a rack and pinion steering mechanism. 10. The hydraulic power steering system of claim 1, wherein the steering mechanism is a recirculating ball steering mechanism. 11. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; a pressure accumulator selectively connected to the hydraulic pump and chargeable to a desired pressure; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump, the pressure accumulator and the reservoir, the control valve arrangement operable in at least a first condition, a second condition, and a third condition; wherein: in the first condition the control valve arrangement connects the first chamber with the pump and connects the second chamber with the reservoir for fluid communication therebetween; in the second condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the pump for fluid communication therebetween; and in the third condition the control valve arrangement connects the first and second chambers with the pressure accumulator and disconnects the first and second chambers from the fluid reservoir. 12. The hydraulic power steering system of claim 11, wherein the desired pressure in the pressure accumulator is in the range of approximately 100 to 1800 psi. 13. The hydraulic power steering system of claim 12, wherein the desired pressure in the pressure accumulator is in the range of approximately 100 to 300 psi. 14. The hydraulic power steering system of claim 11, wherein in the third condition the control valve arrangement further connects the first and second chambers with each other for fluid communication therebetween. 15. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; a pressure accumulator selectively connected to the hydraulic pump and chargeable to a desired pressure; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump, the pressure accumulator and the reservoir, the control valve arrangement operable in a least three conditions, wherein: in the first condition the control valve arrangement connects the first chamber with the pressure accumulator and connects the second chamber with the reservoir for fluid communication therebetween; in the second condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the pressure accumulator for fluid communication therebetween; and in the third condition the control valve arrangement connects the first and second chambers with each other and disconnects the first and second chambers from the reservoir. 16. The hydraulic power steering system of claim 15, wherein the control valve arrangement is further operable in a fourth condition and a fifth condition, wherein in the fourth condition the control valve arrangement connects the first chamber with the pump and connects the second chamber with the reservoir for fluid communication therebetween, and wherein in the fifth condition the control valve arrangement connects the first chamber with the reservoir and the second chamber with the pump for fluid communication therebetween. 17. The hydraulic power steering system of claim 15, wherein the desired pressure in the pressure accumulator is in the range of approximately 400 to 600 psi. 18. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; a first pressure accumulator selectively connected to the hydraulic pump and chargeable to a first pressure; a second pressure accumulator selectively connected to the hydraulic pump and chargeable to a second pressure; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump, the first pressure accumulator, the second pressure accumulator and the reservoir, the control valve arrangement operable in at least four conditions; wherein: in a first condition the control valve arrangement connects the first chamber with the first pressure accumulator and connects the second chamber with the reservoir for fluid communication therebetween; in a second condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the first pressure accumulator for fluid communication therebetween; in a third condition the control valve arrangement connects the first chamber with the second pressure accumulator and connects the second chamber with the reservoir for fluid communication therebetween; and in a fourth condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the second pressure accumulator for fluid communication therebetween. 19. The hydraulic power steering system of claim 18, wherein the second pressure is greater than the first pressure. 20. The hydraulic power steering system of claim 19, wherein the first condition corresponds to a low pressure steering assist operation in a first direction, the second condition corresponds to a low pressure steering assist operation in second direction, the third condition corresponds to a high pressure steering assist operation in the first direction and the fourth condition corresponds to a high pressure steering assist operation in the second direction. 21. The hydraulic power steering system of claim 18, wherein in the first condition the control valve arrangement also disconnects the first chamber from the pump and the second pressure accumulator. 22. The hydraulic power steering system of claim 18, further comprising a third pressure accumulator selectively connected to the hydraulic pump and chargeable to a third pressure, wherein the control valve arrangement is further operable to selectively connect the first and second chambers to the third pressure accumulator for fluid communication therebetween. 23. The hydraulic power steering system of claim 22, wherein the third pressure is greater than the second pressure. 24. The hydraulic power steering system of claim 19 wherein the first pressure is in the range of approximately 400 to 600 psi and the second pressure is in the range of approximately 600 to 1800 psi. 25. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; a first pressure accumulator selectively connected to the hydraulic pump and chargeable to a first pressure; a second pressure accumulator selectively connected to the hydraulic pump and chargeable to a second pressure; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump, the first pressure accumulator, the second pressure accumulator and the reservoir, the control valve arrangement operable in at least three conditions; wherein: in a first condition the control valve arrangement connects the first chamber with the second pressure accumulator and connects the second chamber with the reservoir for fluid communication therebetween; in a second condition the control valve arrangement connects the first chamber with the reservoir and connects the second chamber with the second pressure accumulator for fluid communication therebetween; and in a third condition the control valve arrangement connects the first and second chambers with the first pressure accumulator and disconnects the first and second chambers from the reservoir. 26. The hydraulic power steering system of claim 25, wherein the first pressure is in the range of approximately 100 to 300 psi and the second pressure is in the range of approximately 400 to 1800 psi. 27. A hydraulic power steering system for a motorized vehicle comprising: a pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume and a second chamber of variable volume; a steering mechanism operatively engaged to the hydraulic cylinder; a hydraulic fluid reservoir; a pressure accumulator selectively connected to the hydraulic pump and chargeable to a desired pressure; and a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pressure accumulator and the reservoir; wherein, when no steering assist is required, the control valve arrangement connects the first and second chambers with the pressure accumulator and disconnects the first and second chambers from the fluid reservoir. 28. A hydraulic power steering system for a motorized vehicle comprising: a hydraulic pump for generating hydraulic pressure; a hydraulic cylinder system having a first chamber of variable volume, a second chamber of variable volume, and at least one movable piston; a steering mechanism operatively engaged with the at least one piston of the hydraulic cylinder; a hydraulic fluid reservoir; a first pressure accumulator selectively connected to the hydraulic pump and chargeable to a first pressure; a second pressure accumulator selectively connected to the hydraulic pump and chargeable to a second pressure; a third pressure accumulator selectively connected to the hydraulic pump and chargeable to a third pressure; a steering sensor operatively engaged with the steering mechanism; a control valve arrangement operable to selectively connect the first and second chambers of the hydraulic cylinder to the pump, the first pressure accumulator, the second pressure accumulator, the third pressure accumulator and the reservoir, the control valve arrangement operable in at least seven conditions, wherein: the first condition is characterized by the first chamber being in fluid communication with the pump and the second chamber being in fluid communication with the fluid reservoir; the second condition characterized is by the first chamber being in fluid communication with the fluid reservoir and the second chamber being in fluid communication with the pump; the third condition is characterized by the first chamber being in fluid communication with the second pressure accumulator, and the second chamber being in fluid communication with the fluid reservoir; and the fourth condition is characterized by the first chamber being in fluid communication with the fluid reservoir, and the second chamber is in fluid communication with the second pressure accumulator. the fifth condition is characterized by the first chamber being in fluid communication with the third pressure accumulator, and the second chamber being in fluid communication with the fluid reservoir; the sixth condition is characterized by the first chamber being in fluid communication with the fluid reservoir, and the second chamber being in fluid communication with the third pressure accumulator; and the seventh condition is characterized by the first and second chambers being in fluid communication the first pressure accumulator and each other but not with the fluid reservoir; a control box operable to switch the control valve arrangement between said operating conditions in response, at least in part, to signals received from the steering sensor. 29. The hydraulic power steering system of claim 28, wherein the first pressure is in the range of approximately 100 to 300 psi, the second pressure is in the range of approximately 400 to 600 psi and the third pressure is in the range of approximately 600 to 1800 psi. 30. The hydraulic power steering system of claim 28, further comprising: an electromagnetic clutch operable to engage the hydraulic pump with a driving motor when the clutch is actuated, wherein the control box is operable to actuate the electromagnetic clutch in response, at least in part, to a signal received from the steering sensor.