IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0794965
(2004-03-05)
|
등록번호 |
US-7325398
(2008-02-05)
|
발명자
/ 주소 |
|
출원인 / 주소 |
|
인용정보 |
피인용 횟수 :
7 인용 특허 :
7 |
초록
▼
A closed circuit hydraulic system includes a fluid reservoir, a hydraulic cylinder having a cylinder rod, a bidirectional variable displacement hydraulic pump that pumps fluid to either extend or retract the cylinder rod on demand, a flow control valve for relieving pressure between the variable dis
A closed circuit hydraulic system includes a fluid reservoir, a hydraulic cylinder having a cylinder rod, a bidirectional variable displacement hydraulic pump that pumps fluid to either extend or retract the cylinder rod on demand, a flow control valve for relieving pressure between the variable displacement hydraulic pump and the cylinder, and a low pressure check valve between the variable displacement hydraulic pump and the fluid reservoir. Also included is a charge pump for charging the variable displacement hydraulic pump and an accumulator for saving extra energy and fluid from the hydraulic cylinder during the retraction of an extended cylinder rod and using that fluid and energy during the extension of the hydraulic cylinder to reduce a load on the charge pump. The flow control valve opens on demand to allow floating. The low pressure check valve opens when pressure at an inlet of the variable displacement hydraulic pump is low to provide additional fluid and pressure so as to avoid cavitation. A method for using the closed circuit hydraulic system is also provided.
대표청구항
▼
The invention claimed is : 1. A closed circuit hydraulic system for a work vehicle, comprising: a hydraulic cylinder, the hydraulic cylinder having a first chamber and a second chamber; a bidirectional variable displacement hydraulic pump, the bidirectional variable displacement hydraulic pump in f
The invention claimed is : 1. A closed circuit hydraulic system for a work vehicle, comprising: a hydraulic cylinder, the hydraulic cylinder having a first chamber and a second chamber; a bidirectional variable displacement hydraulic pump, the bidirectional variable displacement hydraulic pump in fluid communication with the hydraulic cylinder, the bidirectional variable displacement hydraulic pump selectively pumping and directing to the first chamber to extend the hydraulic cylinder and to the second chamber to retract the hydraulic cylinder, the hydraulic cylinder extending against a weight, the hydraulic cylinder retracting under the weight; an accumulator in flow communication with the first chamber, the accumulator storing fluid from the first chamber during a retraction of the hydraulic cylinder under the weight and releasing the fluid as a supply to the bidirectional variable displacement hydraulic pump during an extension of the hydraulic cylinder; and at least one flow control valve for relieving hydraulic pressure between the bidirectional variable displacement hydraulic pump and the hydraulic cylinder, wherein the bidirectional variable displacement hydraulic pump is in direct communication with the first chamber and with the second chamber, the bidirectional variable displacement hydraulic pump is in direct communication with the first chamber and with the second chamber and the pressure relief valve includes an electro-hydraulic override. 2. The closed circuit hydraulic system of claim 1, wherein the work vehicle includes a work tool and wherein the electro-hydraulic override opens the at least one flow control valve to enable the work tool to float. 3. The closed circuit hydraulic system of claim 1, further comprising: a fluid reservoir; and an anti-cavitation check valve, the anti-cavitation check valve opening at a predetermined pressure in a fluid supply to the bidirectional variable displacement hydraulic pump, the predetermined pressure being set to reduce the risk of cavitation as fluid pressure on an intake side of the bi-directional variable displacement hydraulic pump approaches a level at which cavitation may occur, the anti-cavitation valve opening to allow fluid from the fluid reservoir to increase the pressure at the intake side of the bidirectional variable displacement hydraulic pump. 4. The closed circuit hydraulic system of claim 1, furthering comprising: a first accumulator flow control valve; and a second accumulator flow control valve, the first accumulator flow control valve in fluid communication with the accumulator and with the first chamber, the second accumulator flow control valve in fluid communication with the accumulator and with an inlet for the bidirectional variable displacement hydraulic pump. 5. The closed circuit hydraulic system of claim 4, wherein the first accumulator flow control valve opens to allow the accumulator to store excess fluid from the first chamber during a retraction of an extended hydraulic cylinder, the second accumulator flow control valve being closed. 6. The closed circuit hydraulic system of claim 5, wherein the second accumulator flow control valve opens to allow the accumulator to release the excess fluid to an inlet side of the bidirectional variable displacement hydraulic pump during an extension of a retracted cylinder, the first accumulator flow control valve being closed. 7. The closed circuit hydraulic system of claim 1, further comprising: a fluid reservoir; and a charge pump, the charge pump supplying fluid from the fluid reservoir to an intake side of the bidirectional variable displacement hydraulic pump. 8. A closed circuit hydraulic system for a work vehicle, comprising: a fluid reservoir a hydraulic cylinder, the hydraulic cylinder having a first chamber and a second chamber; a bidirectional variable displacement hydraulic pump, the bidirectional variable displacement hydraulic pump in fluid Communication with the hydraulic cylinder, the bidirectional variable displacement hydraulic pump selectively pumping and directing fluid from the fluid reservoir to the first chamber to extend the cylinder rod and to the second chamber to retract the cylinder rod, the hydraulic cylinder extending against a weight, the hydraulic cylinder retracting under the weight; an accumulator in flow communication with the first chamber, the accumulator storing fluid from the first chamber during a retraction of the hydraulic cylinder under the weight and releasing the fluid as a supply to the bidirectional variable displacement hydraulic pump during an extension of the hydraulic cylinder; and an anti-cavitation check valve, the anti-cavitation check valve opening at a predetermined pressure in a fluid supply to the bidirectional variable displacement hydraulic pump, the predetermined pressure being set to reduce the risk of cavitation as fluid pressure on an intake side of the bidirectional variable displacement hydraulic pump approaches a level at which cavitation may occur, the anti-cavitation valve opening to allow fluid from the fluid reservoir to increase the pressure at the intake side of the bidirectional variable displacement hydraulic pump. 9. A work vehicle having at least one implement, the at least one implement being powered by a closed circuit hydraulic system, the closed circuit hydraulic system comprising: a hydraulic cylinder, the hydraulic cylinder having a cylinder rod, the cylinder rod having an extension side and a retraction side; a bidirectional variable displacement hydraulic pump, the bidirectional variable displacement hydraulic pump in fluid communication with the hydraulic cylinder, the bidirectional variable displacement hydraulic pump selectively pumping and directing to the extension side to extend the cylinder rod and to the retraction side to retract the cylinder rod, the hydraulic cylinder extending against a weight, the hydraulic cylinder retracting under the weight; an accumulator in flow communication with the first chamber, the accumulator storing fluid from the extension side during a retraction of the hydraulic cylinder under the weight and releasing the fluid as a supply to the bidirectional variable displacement hydraulic pump during an extension of the hydraulic cylinder; and at least one flow control valve for relieving hydraulic pressure between the bidirectional variable displacement hydraulic pump and the hydraulic cylinders, wherein the bidirectional variable displacement hydraulic pump is in direct communication with the extension side and with the retraction side, the at least one flow control valve comprises a pilot controlled pressure relief valve and the pressure relief valve includes an electro-hydraulic override. 10. The work vehicle of claim 9, wherein the electro-hydraulic override opens the at least one flow control valve to enable the implement to float. 11. The work vehicle of claim 9, further comprising: a fluid reservoir; and an anti-cavitation check valve, the anti-cavitation check valve opening at a predetermined pressure in a fluid supply to the bidirectional variable displacement hydraulic pump, the predetermined pressure being set to reduce the risk of cavitation as fluid pressure on an intake side of the bidirectional variable displacement hydraulic pump approaches a level at which cavitation may occur, the anti-cavitation valve opening to allow fluid from the fluid reservoir to increase the pressure at the intake side of the bidirectional variable displacement hydraulic pump. 12. The work vehicle of claim 9, wherein the closed circuit hydraulic system further comprises: an accumulator; a first accumulator flow control valve; and a second accumulator flow control valve, the first accumulator flow control valve in fluid communication with the accumulator and with the extension side, the second accumulator flow control valve in fluid communication with the accumulator and with an inlet for the bidirectional variable displacement hydraulic pump. 13. The work vehicle of claim 12, wherein the first accumulator flow control valve opens to allow the accumulator to store excess fluid from the extension side during a retraction of an extended cylinder, the second accumulator flow control valve being closed. 14. The work vehicle of claim 13, wherein the second accumulator flow control valve opens to allow the accumulator to release the excess fluid to an inlet side of the bidirectional variable displacement hydraulic pump during an extension of a retracted cylinder, the first accumulator flow control valve being closed. 15. The work vehicle of claim 9, further comprising: a fluid reservoir; and a charge pump, the charge pump supplying fluid from the fluid reservoir to an intake side of the bidirectional variable displacement hydraulic pump. 16. A work vehicle having at least one work tool, the at least one work tool being powered by a closed circuit hydraulic system, the closed circuit hydraulic system comprising: a fluid reservoir; a hydraulic cylinder, the hydraulic cylinder having a cylinder rod, the cylinder rod having an extension side and a retraction side; a bidirectional variable displacement hydraulic pump, the bidirectional variable displacement hydraulic pump in fluid communication with the hydraulic cylinder, the bidirectional variable displacement hydraulic pump selectively pumping and directing fluid to the extension side to extend the cylinder rod and to the retraction side to retract the cylinder rod, the hydraulic cylinder extending against a weight, the hydraulic cylinder retracting under the weight; an accumulator in flow communication with the extension side, the accumulator storing fluid from the extension side during a retraction of the hydraulic cylinder under the weight and releasing the fluid as a supply to the bidirectional variable displacement hydraulic pump during an extension of the hydraulic cylinder; and an anti-cavitation check valve, the anti-cavitation check valve opening at a predetermined pressure in a fluid supply to the bidirectional variable displacement hydraulic pump, the predetermined pressure being set to reduce the risk of cavitation as fluid pressure on an intake side of the pump approaches a level at which cavitation may occur, the anti-cavitation valve opening to allow fluid from the fluid reservoir to increase the pressure at the intake side of the bidirectional variable displacement hydraulic pump.
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