Hydraulic system and a working machine comprising such a hydraulic system
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
E02F-009/22
F15B-021/14
출원번호
US-0322941
(2009-05-29)
등록번호
US-9074347
(2015-07-07)
국제출원번호
PCT/SE2009/000282
(2009-05-29)
§371/§102 date
20111212
(20111212)
국제공개번호
WO2010/138029
(2010-12-02)
발명자
/ 주소
Vigholm, Bo
Ekvall, Andreas
Heybroek, Kim
출원인 / 주소
Volvo Construction Equipment AB
대리인 / 주소
WRB-IP LLP
인용정보
피인용 횟수 :
2인용 특허 :
7
초록▼
A hydraulic system for a working machine includes at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function. The system furth
A hydraulic system for a working machine includes at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function. The system further includes an arrangement for limiting the pressure of the hydraulic fluid at the return port, which pressure limiting arrangement has a pilot-operated valve adapted to set a maximum allowable pressure at the return port of the control valve unit. The pressure is variable by controlling the pilot-operated valve by a control unit.
대표청구항▼
1. A hydraulic system for a working machine, comprising at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function, and a mean
1. A hydraulic system for a working machine, comprising at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function, and a means for limiting the pressure of the hydraulic fluid at the return port, wherein the pressure limiting means comprises a pilot-operated valve arranged to set a maximum allowable pressure at the return port of the control valve unit, which pressure is variable by controlling the pilot-operated valve by means of a control unit, wherein the maximum allowable pressure at the return port of the control valve unit is continuously variable by means of the pilot-operated valve. 2. The hydraulic system according to claim 1, wherein the pilot-operated valve is connected to the return port and connected in parallel with the recovery unit. 3. The hydraulic system according to claim 1, wherein the pilot-operated valve is electrically controllable. 4. The hydraulic system according to claim 1, wherein the system comprises a pump for providing hydraulic fluid. 5. The hydraulic system according to claim 4, wherein the pump is adapted to provide hydraulic fluid to the at least one work function. 6. The hydraulic system according to claim 5, wherein the system comprises a means for returning energy, recovered from a return flow from the work function, to the pressure side of the pump. 7. The hydraulic system according to claim 6, wherein the pump is adapted to function both as a pump and a hydraulic motor, and the pump is adapted to provide a torque when hydraulic fluid flows from the recovery unit to the pressure side of the pump and further through the pump to the suction side of the pump, at the same time as the pump provides a required pressure on the pressure side for supplying the work function. 8. The hydraulic system according to claim 5, wherein the system comprises a means for returning energy, recovered from a return flow from the work function, to the suction side of the pump. 9. The hydraulic system according to claim 4, wherein the pump is drivable by the driveline of a working machine and is adapted to brake the driveline during deceleration of the working machine, and the system comprises a hydraulic control means for controlling a flow of hydraulic fluid, from the pressure side of the pump to the recovery unit, for recovering energy during deceleration of the working machine. 10. The hydraulic system according to claim 1, wherein the recovery unit comprises a first hydraulic machine and a second hydraulic machine, and the first and second hydraulic machine are mechanically interconnected, and the first hydraulic machine is adapted to be driven by a flow of hydraulic fluid and the second hydraulic machine is adapted to pump hydraulic fluid by being driven by the first hydraulic machine. 11. The hydraulic system according to claim 10, wherein the first hydraulic machine is connected to the return port to be driven by a return flow, and the second hydraulic machine is adapted to pump hydraulic fluid to an accumulator. 12. The hydraulic system according to claim 10, wherein the pump is adapted to provide hydraulic fluid to the at least one work function, and the first hydraulic machine is connected to the return port to be driven by a return flow, and the second hydraulic machine is adapted to pump hydraulic fluid to the pressure side of the pump. 13. The hydraulic system according to claim 10, wherein the pump is adapted to provide hydraulic fluid to the at least one work function, and the first hydraulic machine is connected to the return port to be driven by a return flow, and the second hydraulic machine is adapted to pump hydraulic fluid to the suction side of the pump. 14. The hydraulic system according to claim 1, wherein the at least one work function comprises a hydraulic cylinder provided with a piston for transferring power to a machine component in a working machine. 15. The hydraulic system according to claim 14, wherein the control valve unit is adapted to control a return flow of hydraulic fluid, optionally from the piston side of the hydraulic cylinder and/or the piston rod side of the hydraulic cylinder, to the recovery unit. 16. The hydraulic system according to claim 14, wherein the system comprises a pressure sensor adapted to measure the pressure of the hydraulic fluid on the piston side of the hydraulic cylinder. 17. The hydraulic system according to claim 14, wherein the system comprises a pressure sensor adapted to measure the pressure of the hydraulic fluid on the piston rod side of the hydraulic cylinder. 18. The hydraulic system according to claim 1, wherein the recovery unit is adapted to dampen a relative movement caused by an external disturbance, at least in one direction, between a work implement and a machine body of the working machine, which work implement is moveable relative to the machine body by means of the work function. 19. The hydraulic system according to claim 18, wherein the system comprises a sensor for determining a reference position for the work implement relative to the machine body. 20. The hydraulic system according to claim 1, wherein the system comprises a plurality of work functions with an associated respective control valve unit, and one the pilot-operated valve is provided for the respective work function. 21. The hydraulic system according to claim 20, wherein the system comprises a check valve which is connected in series with the recovery unit in a position between the return port of the control valve unit and the recovery unit, and the check valve is connected in parallel with the pilot-operated valve in order to block flow in a direction toward the work function, and the system comprises one the check valve arranged for a respective pilot-operated valve, which check valve is connected in series with the recovery unit in a position between the return port of the respective control valve unit and the recovery unit, and connected in parallel with the pilot-operated valve, in order to block flow in a direction toward the respective work function. 22. The hydraulic system according to claim 21, wherein the outlets of the check valves are interconnected upstream of the recovery unit. 23. The hydraulic system according to claim 22, wherein the system comprises a pressure sensor adapted to measure the pressure of the hydraulic fluid in a position located downstream of the check valves and upstream of the recovery unit. 24. The hydraulic system according to claim 20, wherein the system comprises a pressure sensor for the respective pilot-operated valve adapted to measure the pressure of the hydraulic fluid in a position located between the return port of the respective control valve unit and the inlet port of the respective pilot-operated valve. 25. The hydraulic system according to claim 20, wherein the system comprises one the recovery unit for the respective work function. 26. The hydraulic system according to claim 20, wherein the system comprises a control unit for individual control of the pilot-operated valves. 27. A working machine comprising a hydraulic system according to claim 1. 28. A hydraulic system for a working machine, comprising at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function, and a means for limiting the pressure of the hydraulic fluid at the return port, wherein the pressure limiting means comprises a pilot-operated valve arranged to set a maximum allowable pressure at the return port of the control valve unit, which pressure is variable by controlling the pilot-operated valve by means of a control unit, wherein the system comprises a check valve which is connected in series with the recovery unit in a position between the return port of the control valve unit and the recovery unit, and the check valve is connected in parallel with the pilot-operated valve in order to block flow in a direction toward the work function. 29. A hydraulic system for a working machine, comprising at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function, and a means for limiting the pressure of the hydraulic fluid at the return port, wherein the pressure limiting means comprises a pilot-operated valve arranged to set a maximum allowable pressure at the return port of the control valve unit, which pressure is variable by controlling the pilot-operated valve by means of a control unit, wherein the system comprises a pressure sensor adapted to measure the pressure of the hydraulic fluid in a position located between the return port of the control valve unit and the inlet port of the pilot-operated valve. 30. A method for recovering energy in a hydraulic system, wherein the hydraulic system comprises at least one work function and a control valve unit for controlling hydraulic fluid to and from the work function, and a recovery unit connected to a return port of the control valve unit for recovering energy from the work function, comprising continuously controlling a maximum allowable pressure at the return port by a pressure limiting means through receiving signals from a control unit to adapt a maximum energy recovery rate of the recovery unit to an actual operation mode of the work function.
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