In a hydraulic closed circuit system with hydraulic pumps which maintains a well-balanced flow rate by automatically controlling the flow rate, a first hydraulic pump is connected to a hydraulic cylinder device such that the hydraulic closed circuit is made, a second hydraulic pump is connected at o
In a hydraulic closed circuit system with hydraulic pumps which maintains a well-balanced flow rate by automatically controlling the flow rate, a first hydraulic pump is connected to a hydraulic cylinder device such that the hydraulic closed circuit is made, a second hydraulic pump is connected at one of paired delivery ports to a bottom side of the hydraulic cylinder device and at the other of the ports to a tank, and a prime mover drives the first and second hydraulic pumps and recovers motive power from these pumps. A pump capacity control unit detects a moving direction of the hydraulic cylinder device, and a pressure in a lower-thrust side of the device, and controls a capacity of the second hydraulic pump so that the flow rate during the extension/retraction of the hydraulic cylinder device becomes balanced between the first and second hydraulic pumps and the hydraulic cylinder device.
대표청구항▼
1. A hydraulic closed circuit system, comprising: a hydraulic cylinder device;a first hydraulic pump of a bidirectional delivery type connected to the hydraulic cylinder device in such a manner that a hydraulic closed circuit is made;a second hydraulic pump of a bidirectional delivery and bidirectio
1. A hydraulic closed circuit system, comprising: a hydraulic cylinder device;a first hydraulic pump of a bidirectional delivery type connected to the hydraulic cylinder device in such a manner that a hydraulic closed circuit is made;a second hydraulic pump of a bidirectional delivery and bidirectional variable displacement type, connected at one of paired delivery ports thereof to a bottom side of the hydraulic cylinder device and at the other of the paired delivery ports to a tank;a prime mover that drives the first and second hydraulic pumps and recovers motive power from the first and second hydraulic pumps; anda pump capacity control unit configured to:detect a direction in which the hydraulic cylinder device operates,detect a pressure applied on a lower-thrust side of the hydraulic cylinder device, andcontrol a capacity of the second hydraulic pump such that a flow rate of a hydraulic fluid during extension/retraction of the hydraulic cylinder device becomes balanced between the first and second hydraulic pumps and the hydraulic cylinder device,wherein the pump capacity control unit, during an extending operation of the hydraulic cylinder device, is further configured to: when the pressure on the lower-thrust side of the hydraulic cylinder device is lower than a reference pressure value, increase the capacity of the second hydraulic pump, andwhen the pressure on the lower-thrust side of the hydraulic cylinder device is higher than the reference pressure value, decrease the capacity of the second hydraulic pump, andwherein the pump capacity control unit, during a retracting operation of the hydraulic cylinder device, is further configured to: when the pressure on the lower-thrust side of the hydraulic cylinder device is higher than the reference pressure value, increase the capacity of the second hydraulic pump, andwhen the pressure on the lower-thrust side of the hydraulic cylinder device is lower than the reference pressure value, decrease the capacity of the second hydraulic pump. 2. The hydraulic closed circuit system according to claim 1, wherein the pump capacity control unit includes: an operation detecting device that detects the direction in which the hydraulic cylinder device operates;a first and a second pressure detecting device configured to detect respectively a pressure applied to the bottom side of the hydraulic cylinder device, and a pressure applied to a rod side of the hydraulic cylinder device; anda pump capacity correcting device configured to determine, on the basis of values detected by the operation detecting device and the first and second pressure detecting devices, whether the hydraulic cylinder device is in a power-running operation or in a regenerative operation and whether the hydraulic cylinder device is being extended or retracted, calculate a correction value for the capacity of the second hydraulic pump on the basis of results of the determination, and thereby control the capacity of the second hydraulic pump, andwherein the reference pressure value is expressed as Pref, the bottom-side pressure of the hydraulic cylinder device is expressed as Pb, and the rod-side pressure of the hydraulic cylinder device is expressed as Pr, and the pump capacity correcting device is further configured to:(a) when the hydraulic cylinder device is being extended and is in the power-running operation, increase the correction value as the rod-side pressure Pr decreases relative to the reference pressure value Pref, and reduces the correction value as the rod-side pressure Pr increases;(b) when the hydraulic cylinder device is being extended and is in the regenerative operation, increase the correction value as the bottom-side pressure Pb decreases relative to the reference pressure value Pref, and reduce the correction value as the bottom-side pressure Pb increases;(c) when the hydraulic cylinder device is being retracted and is in the power-running operation, reduce the correction value as the bottom-side pressure Pb decreases relative to the reference pressure value Pref, and increase the correction value as the bottom-side pressure Pb increases; and(d) when the hydraulic cylinder device is being retracted and is in the regenerative operation, reduce the correction value as the rod-side pressure Pr decreases relative to the reference pressure value Pref, and increase the correction value as the rod-side pressure Pr increases. 3. The hydraulic closed circuit system according to claim 2, wherein the pump capacity correcting device provides a deadband in which the pump capacity correcting device does not correct the capacity of the second hydraulic pump in a predetermined pressure range including the reference pressure value. 4. The hydraulic closed circuit system according to claim 3, wherein the prime mover is an electric motor or a hydraulic motor. 5. The hydraulic closed circuit system according to claim 3, wherein the first and second hydraulic pumps are a pump of a single-pump double-port flow distribution type, and wherein the pump capacity control unit controls the capacity of the second hydraulic pump by changing a flow rate ratio of the hydraulic fluid in two ports of the pump of the single-pump double-port flow distribution type. 6. The hydraulic closed circuit system according to claim 2, wherein the prime mover is an electric motor or a hydraulic motor. 7. The hydraulic closed circuit system according to claim 2, wherein the first and second hydraulic pumps are a pump of a single-pump double-port flow distribution type, and wherein the pump capacity control unit controls the capacity of the second hydraulic pump by changing a flow rate ratio of the hydraulic fluid in two ports of the pump of the single-pump double-port flow distribution type. 8. The hydraulic closed circuit system according to claim 1, wherein the pump capacity control unit includes: an operation detecting device that detects the direction in which the hydraulic cylinder device operates;a lower-thrust-side pressure selecting valve that selects, from pressures inside a bottom-side hydraulic chamber and a rod-side hydraulic chamber of the hydraulic cylinder device, the pressure inside the hydraulic chamber of the lower-thrust side of the hydraulic cylinder device;a pressure detection device that detects the pressure that the lower-thrust-side pressure selecting valve has selected; anda pump capacity correcting device configured to calculate a correction value for the capacity of the second hydraulic pump on the basis of values detected by the operation detecting device and the pressure detection device, and thereby control the capacity of the second hydraulic pump,wherein the pump capacity correcting device includes:a reference data setter that sets the reference pressure value;a first calculating device that calculates, from a differential value between the reference pressure value and the pressure value detected by the pressure detection device, a correction value for the capacity of the second hydraulic pump operative when the hydraulic cylinder device is being extended;a second calculating device that calculates, from a differential value between the reference pressure value and the pressure value detected by the pressure detection device, a correction value for the capacity of the second hydraulic pump operative when the hydraulic cylinder device is being retracted; anda selector that selects one of the first and second calculating devices, depending upon the operating direction of the hydraulic cylinder device that the operation detecting device has detected. 9. The hydraulic closed circuit system according to claim 8, wherein the pump capacity correcting device provides a deadband in which the pump capacity correcting device does not correct the capacity of the second hydraulic pump in a predetermined pressure range including the reference pressure value. 10. The hydraulic closed circuit system according to claim 8, wherein the prime mover is an electric motor or a hydraulic motor. 11. The hydraulic closed circuit system according to claim 8, wherein the first and second hydraulic pumps are a pump of a single-pump double-port flow distribution type, and wherein the pump capacity control unit controls the capacity of the second hydraulic pump by changing a flow rate ratio of the hydraulic fluid in two ports of the pump of the single-pump double-port flow distribution type. 12. The hydraulic closed circuit system according to claim 1, wherein the prime mover is an electric motor or a hydraulic motor. 13. The hydraulic closed circuit system according to claim 1, wherein the first and second hydraulic pumps are a pump of a single-pump double-port flow distribution type, and wherein the pump capacity control unit controls the capacity of the second hydraulic pump by changing a flow rate ratio of the hydraulic fluid in two ports of the pump of the single-pump double-port flow distribution type.
연구과제 타임라인
LOADING...
LOADING...
LOADING...
LOADING...
LOADING...
이 특허에 인용된 특허 (1)
Persson, Bengt-Goran; Vanderlaan, Dale; Kasper, Lew, Flow management system for hydraulic work machine.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.