An open center hydraulic system that includes a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port. A first fluid circuit and a
An open center hydraulic system that includes a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port. A first fluid circuit and a second fluid circuit each serve as signal lines with the pump sensing port. During operation of the second fluid circuit, reduced fluid flow from the pump outlet is achieved as a result of the sum of induced fluid pressure reductions of respective controlled pressure reduction devices approaching the predetermined pump fluid pressure differential.
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1. An open center hydraulic system comprising: a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port;a first fluid circuit and a
1. An open center hydraulic system comprising: a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port;a first fluid circuit and a second fluid circuit in selective fluid communication with the pump;a first controlled pressure reduction device in fluid communication with the pump outlet and each of the first fluid circuit and the second fluid circuit;a flow regulating device in fluid communication with the sensing port in each of the first fluid circuit and the second fluid circuit;the first fluid circuit comprising: a second controlled pressure reduction device; anda first maximum pressure limiting device;wherein the second controlled pressure reduction device and the first maximum pressure limiting device in fluid communication with the pump sensing port during operation of the first fluid circuit, the first maximum pressure limiting device configured to permit up to a first predetermined fluid pressure value between the pump sensing port downstream of the second controlled pressure reduction device and the first fluid circuit during operation of the first fluid circuit; andthe second fluid circuit comprising: a third controlled pressure reduction device;a fourth controlled pressure reduction device; anda second maximum pressure limiting device;wherein the third controlled pressure reduction device, the fourth controlled pressure reduction device and the second maximum pressure limiting device in fluid communication with the pump sensing port during operation of the second fluid circuit, the second maximum pressure limiting device configured to permit up to a second predetermined fluid pressure value downstream of the fourth controlled pressure reduction device between the pump sensing port and the second fluid circuit during operation of the second fluid circuit;wherein the first controlled fluid pressure reduction device is configured to introduce a first induced fluid pressure reduction between the pump outlet and the first fluid circuit during operation of the first fluid circuit;wherein the first controlled pressure reduction device is configured to introduce a first induced fluid pressure reduction between the pump outlet and the second fluid circuit during operation of the second fluid circuit;wherein the fourth controlled pressure reduction device is configured to introduce a second induced fluid pressure reduction in the second fluid circuit during operation of the second fluid circuit;wherein during operation of the second fluid circuit, reduced fluid flow from the pump outlet is achieved as a result of the sum of the first induced fluid pressure reduction of the first controlled pressure reduction device and the second induced fluid pressure reduction of the fourth controlled pressure reduction device approaching the predetermined pump fluid pressure differential. 2. The system of claim 1, further comprising a solenoid valve for selectively switching between the first fluid circuit and the second fluid circuit. 3. The system of claim 1, wherein the first controlled pressure reduction device is a valve. 4. The system of claim 3, wherein the valve is an orifice. 5. The system of claim 3, wherein the valve is an adjustable valve. 6. The system of claim 1, wherein each of the second controlled pressure reduction device and the third controlled pressure reduction device is a valve. 7. The system of claim 6, wherein the valve is an orifice. 8. The system of claim 6, wherein the valve is an adjustable valve. 9. The system of claim 1, wherein the fourth controlled pressure reduction device is a valve. 10. The system of claim 9, wherein the valve is a relief valve. 11. The system of claim 9, wherein the valve is an adjustable valve. 12. The system of claim 1, wherein at least one of the first maximum pressure limiting device or the second maximum pressure limiting device is a valve. 13. The system of claim 12, wherein the valve is a relief valve. 14. The system of claim 12, wherein the valve is an adjustable valve. 15. The system of claim 9, wherein the valve is a check valve with a regulated pressure value. 16. The system of claim 11, wherein the flow regulating device is in fluid communication with a reservoir. 17. An open center hydraulic system comprising: a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port;a first fluid circuit and a second fluid circuit in selective fluid communication with the pump;a flow regulating device in fluid communication with the sensing port in each of the first fluid circuit and the second fluid circuit;a solenoid valve for selectively switching between the first fluid circuit and the second fluid circuit;a first controlled pressure reduction device in fluid communication with the pump outlet and each of the first fluid circuit and the second fluid circuit;the first fluid circuit comprising: a second controlled pressure reduction device; anda first maximum pressure limiting device, the second controlled pressure reduction device and the first maximum pressure limiting device in fluid communication with the pump sensing port during operation of the first fluid circuit, the first maximum pressure limiting device configured to permit up to a first predetermined fluid pressure value between the pump sensing port downstream of the second controlled pressure reduction device and the first fluid circuit during operation of the first fluid circuit; andthe second fluid circuit comprising: a third controlled pressure reduction device;a fourth controlled pressure reduction device; anda second maximum pressure limiting device, the third controlled pressure reduction device, the fourth controlled pressure reduction device and the second maximum pressure limiting device in fluid communication with the pump sensing port during operation of the second fluid circuit, the second maximum pressure limiting device configured to permit up to a second predetermined fluid pressure value downstream of the fourth controlled pressure reduction device between the pump sensing port and the second fluid circuit during operation of the second fluid circuit;wherein the first controlled fluid pressure reduction device is configured to introduce a first induced fluid pressure reduction between the pump outlet and the first fluid circuit during operation of the first fluid circuit;wherein the first controlled pressure reduction device is configured to introduce a first induced fluid pressure reduction between the pump outlet and the second fluid circuit during operation of the second fluid circuit;wherein the fourth controlled pressure reduction device is configured to introduce a second induced fluid pressure reduction in the second fluid circuit during operation of the second fluid circuit;wherein during operation of the second fluid circuit, reduced fluid flow from the pump outlet is achieved as a result of the sum of the first induced fluid pressure reduction of the first controlled pressure reduction device and the second induced fluid pressure reduction of the fourth controlled pressure reduction device approaching the predetermined pump fluid pressure differential. 18. The system of claim 17, wherein the first controlled pressure reduction device is a valve. 19. The system of claim 18, wherein the valve is an orifice. 20. The system of claim 17, wherein at least one of the first maximum pressure limiting device or the second maximum pressure limiting device is a relief valve.
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이 특허에 인용된 특허 (11)
Hesse,Horst, Control system and method for supplying pressure means to at least two hydraulic consumers.
Carlson Allen J. (Tecumseh MI) Vander Kaay Henry A. (Ann Arbor MI), Power limiting control apparatus for pressure-flow compensated variable displacement pump assemblies.
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