A pump-controlled electro-hydraulic system for a valve

Abstract

The present invention discloses a pump-controlled electro-hydraulic system for a valve, which includes a motor pump control unit, a servo motor, a bidirectional hydraulic pump, a first pressurizing oil tank, and an actuating cylinder. The motor pump control unit includes a volume compensation valve, a first position locking valve, a second position locking valve, a first overload safety valve, and a second overload safety valve. The servo motor is connected to the bidirectional hydraulic pump. The two ports of the bidirectional hydraulic pump are respectively connected to the first position locking valve and the second position locking valve. The other end of the first position locking valve communicates with the rodless cavity of the actuating cylinder, and the other end of the second position locking valve communicates with the rod cavity of the actuating cylinder. The two ends of the volume compensation valve are respectively connected to the first position locking valve and the first pressurizing oil tank. The two ends of the first overload safety valve are respectively connected to the rodless cavity of the actuating cylinder and the first pressurizing oil tank. The two ends of the second overload safety valve are respectively connected to the rod cavity of the actuating cylinder and the first pressurizing oil tank. The present invention has the advantages of compact volume, large output force, high control precision, high driving efficiency, and intelligence.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic transmission and control, and particularly to a pump-controlled electro-hydraulic system for valves. Background Art

[0002] As a pipeline accessory for opening and closing pipelines and controlling the direction, pressure, and flow rate of fluids in pipelines, valves have extremely wide applications in oil and gas, chemical industry, power generation, and metallurgy. At present, the main valve driving methods are manual, electric, hydraulic, and pneumatic. Manual actuators have low output force and slow execution speed, and are only used in certain emergency situations. Pneumatic actuators have low pressure, large volume, and low load stiffness, making it difficult to improve control accuracy. Due to the inherent characteristics of high speed and low torque of electric motors themselves, electric actuators need to be equipped with a speed reducer when bearing heavy loads, and their volume and weight are also large. Hydraulic actuators have the characteristics of high load stiffness and high power density, so they have the advantages of high control accuracy and compact volume, and are very suitable for driving large-diameter heavy-duty valves. However, there are still the following problems: The large throttling loss of traditional valve control systems causes serious oil heating, and an oil cooling device needs to be configured for long-term operation; the core control components, servo valves / proportional valves, are expensive; the system has poor anti-pollution ability and high maintenance requirements. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a pump-controlled electro-hydraulic system for valves, which has the advantages of compact volume, large output force, high control accuracy, high driving efficiency, and intelligence.

[0004] To achieve the above purpose, the technical solution of the present invention is:

[0005] A pump-controlled electro-hydraulic system for valves includes a motor pump control unit, a servo motor, a bidirectional hydraulic pump, a first booster oil tank, and an actuator. The motor pump control unit includes a volume compensation valve, a first position locking valve, a second position locking valve, a first overloading safety valve, and a second overloading safety valve. The output end of the servo motor is connected to the bidirectional hydraulic pump. The two ports of the bidirectional hydraulic pump are respectively connected to the first position locking valve and the second position locking valve. The other end of the first position locking valve communicates with the rodless cavity of the actuator, and the other end of the second position locking valve communicates with the rod cavity of the actuator. The two ends of the volume compensation valve are respectively connected to the first position locking valve and the first booster oil tank. The two ends of the first overloading safety valve are respectively connected to the rodless cavity of the actuator and the first booster oil tank. The two ends of the second overloading safety valve are respectively connected to the rod cavity of the actuator and the first booster oil tank. The first booster oil tank communicates with the S port and the L port of the bidirectional hydraulic pump.

[0006] A first pressure sensor is installed on the pipeline between the first overloading safety valve and the rodless cavity of the actuator, and a second pressure sensor is installed on the pipeline between the second overloading safety valve and the rod cavity of the actuator.

[0007] The actuator is installed with a displacement sensor.

[0008] It further includes an emergency manual unit, which includes a manual pump, a manual directional control valve, and a first two-way hydraulic lock connected in sequence. The two ports of the first two-way hydraulic lock are respectively communicated with the rod chamber and the rodless chamber of the actuator, and the manual pump is communicated with the first pressurized oil tank.

[0009] The emergency manual unit includes a 2S2 port, and the manual directional control valve is communicated with the first pressurized oil tank through the 2S2 port.

[0010] It further includes an emergency energy storage unit, which includes a check valve, a second pressurized oil tank, an accumulator, a directional control valve, and a second two-way hydraulic lock. The second pressurized oil tank is communicated with one port of the directional control valve and the first pressurized oil tank. One end of the check valve is communicated with the pipeline between the first position locking valve and the double-direction hydraulic pump, and the other end of the check valve is communicated with the accumulator. The accumulator, the directional control valve, and the second two-way hydraulic lock are connected in sequence. The two ports of the second two-way hydraulic lock are respectively communicated with the rod chamber and the rodless chamber of the actuator.

[0011] The two ports of the second two-way hydraulic lock are connected with speed control valves, and the speed control valves are communicated with the rod chamber and the rodless chamber of the actuator.

[0012] The emergency energy storage unit includes a unloading valve, a pressure sensor, and a pressure setting valve. The unloading valve and the pressure setting valve are distributed in parallel, and both ends of the unloading valve and the pressure setting valve are respectively connected with the second pressurized oil tank and the accumulator. A pressure sensor is installed on the pipeline between the pressure setting valve and the accumulator.

[0013] The beneficial effects of the present invention are as follows:

[0014] 1. The hydraulic rated pressure of the pump-controlled electro-hydraulic system is increased by more than 10 times compared with the traditional pneumatic actuator. Therefore, the volume of the supporting actuator is much smaller than that of the traditional pneumatic actuator under the same output force. At the same time, the hydraulic pressure can be amplified by the actuator, and the torque required for the supporting drive motor is much smaller than that of the direct-drive electric actuator. Therefore, the volume of the supporting motor is much smaller than that of the traditional electric actuator under the same output force. The power-to-weight ratio of the electro-hydraulic system is far better than that of the existing pneumatic and electric actuators, that is, it is compact in volume and large in output force.

[0015] 2. The pump-controlled electro-hydraulic system adopts the configuration of a servo motor driving a fixed-displacement double-direction hydraulic pump, that is, the output flow of the pump is adjusted by controlling the motor speed, so as to control the speed, start and stop of the actuator. This pump-controlled configuration replaces the core control components, servo valves / proportional valves, which can greatly reduce the cost and maintenance requirements and improve the system reliability. Secondly, the pump-controlled configuration replaces the traditional valve-controlled throttle speed control with volumetric speed control, which has high transmission efficiency, small throttle heat consumption, and no need to add a heat dissipation device.

[0016] 3. A volume compensation valve is configured to compensate for the volume difference of the oil caused by the telescopic movement of the actuator. A single-rod cylinder can be directly used as the actuator, which is beneficial to reducing the equipment cost and improving the reliability.

[0017] 4. The pressurized oil tank enables the valve to work properly when installed in any posture, and isolates external pollutants from entering the oil, improving the reliability and service life of the hydraulic components in the device.

[0018] 5. The emergency manual unit and the emergency energy storage unit enable the device to manually / automatically complete the conversion of the valve opening and closing states even under power-off conditions, with high reliability. Adopting a modular design, it can be combined as needed for plug-and-play.

[0019] 6. In the present invention, the emergency energy storage unit is equipped with a pressure detection and compensation function. After detecting a decrease in the energy storage pressure caused by leakage or the like, it can automatically compensate and boost the pressure, with a high degree of intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the hydraulic schematic diagram of the present invention;

[0021] Figure 2 is the hydraulic principle when the actuator of the present invention extends / retracts;

[0022] Figure 3 is the hydraulic schematic diagram of the emergency manual unit of the present invention;

[0023] Figure 4 is the hydraulic schematic diagram of the emergency energy storage unit of the present invention;

[0024] Figure 5 is the flow chart of the program control part of the present invention.

[0025] In the figure: motor pump control unit 1, servo motor 11, two-way hydraulic pump 12, first pressurized oil tank 13, volume compensation valve 15, first position locking valve 16a, second position locking valve 16b, first overload safety valve 17a, second overload safety valve 17b, first pressure sensor 18a, second pressure sensor 18b, actuator 19, displacement sensor 191, emergency manual unit 2, manual pump 21, manual reversing valve 22, first two-way hydraulic lock 23, emergency energy storage unit 3, one-way valve 31, unloading valve 32, pressure sensor 33, pressure setting valve 34, second pressurized oil tank 35, speed control valve 36, accumulator 37, reversing valve 38, second two-way hydraulic lock 39. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The technical solutions of the present invention will be further described below through embodiments in conjunction with the drawings.

[0027] As Figure 1As shown in the figure, a pump-controlled electro-hydraulic system for a valve includes a motor pump control unit 1, an emergency manual unit 2, an emergency energy storage unit 3, a servo motor 11, a bidirectional hydraulic pump 12, a first booster oil tank 13, and an actuator 19. The motor pump control unit 1, as the main part of the system, provides hydraulic energy and controls the opening or closing of the valve in the normal state, and can also be used to precisely control the valve opening. The emergency manual unit 2 and the emergency energy storage unit 3 can be additionally installed according to actual needs. The emergency manual unit 2 manually generates hydraulic energy to control the switching state of the valve when power is off. The emergency energy storage unit 3 stores oil and stores energy during normal times, and can quickly complete one or more switching state conversions when power is off.

[0028] Among them, the actuator 19 is installed on the rotating mechanism of the controlled valve. The output end of the servo motor 11 is connected to the bidirectional hydraulic pump 12, and the servo motor 11 and the bidirectional hydraulic pump 12 are connected by a coupling. The servo motor 11 can precisely control the rotation speed of the bidirectional hydraulic pump 12, and can not only simply complete the opening and closing state conversion but also be used to precisely control the valve opening.

[0029] Refer to Figure 2 , the motor pump control unit 1 includes a volume compensation valve 15, a first position locking valve 16a, a second position locking valve 16b, a first overload safety valve 17a, and a second overload safety valve 17b. The two ports of the bidirectional hydraulic pump 12 are respectively connected to the first position locking valve 16a (1A1 port) and the second position locking valve 16b (1B1 port). The other end of the first position locking valve 16a communicates with the rodless cavity of the actuator 19 (the rodless cavity refers to Figure 2 the right cavity in the figure, the rod chamber refers to the left cavity, that is, the cavity with the piston rod is the rod chamber, or it is the 1A4 port), and the other end of the second position locking valve 16b communicates with the rod chamber of the actuator 19 (1B4 port). The two ends of the volume compensation valve 15 are respectively connected to the first position locking valve 16a (1A1 port) and the first booster oil tank 13 (1T1 port). Here, the connection of the volume compensation valve 15 to the first position locking valve 16a is actually the connection of the volume compensation valve 15 to the pipeline between the first position locking valve 16a and the servo motor 11.

[0030] The two ends of the first overload safety valve 17a are respectively connected to the rodless cavity of the actuator 19 and the first booster oil tank 13 (1T1 port). The two ends of the second overload safety valve 17b are respectively connected to the rod chamber of the actuator 19 and the first booster oil tank 13 (1T1 port). The first booster oil tank 13 communicates with the S port and the L port of the bidirectional hydraulic pump 12.

[0031] A first pressure sensor 18a is installed on the pipeline between the first overload safety valve 17a and the rodless cavity of the actuating cylinder 19, and a second pressure sensor 18b is installed on the pipeline between the second overload safety valve 17b and the rod cavity of the actuating cylinder 19. The first pressure sensor 18a and the second pressure sensor 18b are used to monitor the oil pressure in the pipeline.

[0032] The actuating cylinder 19 is equipped with a displacement sensor 191, which is used to detect the piston rod stroke of the actuating cylinder 19.

[0033] The working principle of the motor pump control unit 1 is as follows: after receiving the extension command, the electromagnets of the first position locking valve 16a and the second position locking valve 16b are energized to connect the oil circuit. The servo motor 11 drives the bidirectional hydraulic pump 12 to rotate, sucks oil from the 1B1 port of the motor pump control unit 1, and supplies oil to the 1A1 port. The oil passes through the first position locking valve 16a and enters the actuating cylinder 19 to build pressure in its rodless cavity to resist the external load force of the valve, causing the actuating cylinder 19 to extend. If the external load force of the valve is too large at this time and the pressure in the rodless cavity exceeds the safety pressure of the system, the oil can overflow from the first overload safety valve 17a back to the first booster tank 13. The oil in the rod cavity of the actuating cylinder 19 flows back to the 1B1 port through the second position locking valve 16b. Due to the area difference between the rod cavity and the rodless cavity, the volume of the oil flowing back to the 1B1 port is smaller than the volume of the oil flowing out of the 1A1 port, resulting in a decrease in the pressure at the 1B1 port. At this time, the built-in one-way valve of the bidirectional hydraulic pump 12 opens, and the oil enters the S port of the bidirectional hydraulic pump 12 from the first booster tank 13 and then enters the 1B1 port through the built-in one-way valve to complete the compensation of the volume difference. After the displacement sensor 191 installed on the actuating cylinder 19 detects that the actuating cylinder 19 reaches the preset position, it sends a signal to stop the rotation of the servo motor 11. At the same time, the electromagnets of the first position locking valve 16a and the second position locking valve 16b are de-energized to lock the oil circuit, so that the actuating cylinder 19 remains in the target position.

[0034] After receiving the retraction instruction, the electromagnets of the first position locking valve 16a and the second position locking valve 16b are energized to connect the oil circuit. The servo motor 11 drives the bidirectional hydraulic pump 12 to rotate, suck oil from the 1A1 port of the motor pump control unit 1, and supply oil to the 1B1 port. The oil passes through the second position locking valve 16b and enters the actuator 19, and builds pressure in its rod chamber to resist the external load force of the valve, causing it to retract. If the external load force of the valve is too large at this time and the pressure in the rodless chamber exceeds the safety pressure of the system, the oil can overflow from the second overload safety valve 17b back to the first booster tank 13. The oil in the rodless chamber of the actuator 19 flows back to the 1A1 port through the first position locking valve 16a. Due to the area difference between the rod chamber and the rodless chamber, the volume of the oil flowing back to the 1A1 port is more than the volume of the oil flowing out of the 1B1 port. At this time, the 1A1 port is at high pressure, entering the pilot control port of the volume compensation valve 15 to open it, so that the excess oil in the 1A1 flows back to the first booster tank 13 to complete the absorption of the volume difference. After the displacement sensor 191 installed on the actuator 19 detects that the actuator 19 reaches the preset position, it sends a signal to stop the rotation of the servo motor 11. At the same time, the electromagnets of the first position locking valve 16a and the second position locking valve 16b are de-energized to lock the oil circuit and keep the actuator 19 at the target position.

[0035] When there is no signal, the actuator 19 needs to be kept locked, and the electromagnets of the first position locking valve 16a and the second position locking valve 16b are de-energized to lock the oil circuit. If the valve suddenly suffers an overload external load force exceeding the safety pressure of the system, the oil in the actuator 19 can overflow from the first overload safety valve 17a and the second overload safety valve 17b back to the first booster tank 13 to avoid mechanical damage and deformation of the structure.

[0036] Refer to Figure 3 , the emergency manual unit 2 includes a manual pump 21, a manual reversing valve 22, and a first two-way hydraulic lock 23 connected in sequence. The two ports (i.e., the 2A2 port and the 2B2 port) of the first two-way hydraulic lock 23 are respectively connected to the rod chamber and the rodless chamber of the actuator 19, and the manual pump 21 is connected to the first booster tank 13 (1T1 port).

[0037] The emergency manual unit 2 includes a 2S2 port, and the manual reversing valve 22 is connected to the first booster tank 13 (1T1 port) through the 2S2 port.

[0038] The working principle of the emergency manual unit 2 is as follows: In the event of an emergency such as a power failure, the operator first turns the manual reversing valve 22 from the neutral position (locked position) to the right position (extended), manually presses the manual pump 21 to generate high-pressure hydraulic oil. The hydraulic oil in the first pressurizing oil tank 13 enters the 1A2 port of the motor pump control unit 1 through the manual pump 21, the manual reversing valve 22, the first two-way hydraulic lock 23, and the 2A2 port of the emergency manual unit 2, and then enters the rodless cavity of the actuating cylinder 19 to push the actuating cylinder 19 to extend. The hydraulic oil in the rod cavity of the actuating cylinder 19 passes through the 1B2 port of the motor pump control unit 1 and the 2B2 oil port of the emergency manual unit 2, then flows through the manual reversing valve 22, and returns to the first pressurizing oil tank 13 through the 2S2 oil port of the emergency manual unit 2 and the 1S2 oil port of the motor pump control unit 1. When the actuating cylinder 19 needs to retract, the manual reversing valve 22 needs to be turned from the neutral position (locked position) to the left position (retracted), and the manual pump 21 is manually pressed to generate high-pressure hydraulic oil. The hydraulic oil in the first pressurizing oil tank 13 enters the 1B2 port of the motor pump control unit 1 through the manual pump 21, the manual reversing valve 22, the first two-way hydraulic lock 23, and the 2B2 port of the emergency manual unit 2, and then enters the rod cavity of the actuating cylinder 19 to push the actuating cylinder 19 to retract. The hydraulic oil in the rodless cavity of the actuating cylinder 19 passes through the 1A2 port of the motor pump control unit 1 and the 2A2 oil port of the emergency manual unit 2, then flows through the manual reversing valve 22, and returns to the first pressurizing oil tank 13 through the 2S2 oil port of the emergency manual unit 2 and the 1S2 oil port of the motor pump control unit 1. When the actuating cylinder 19 reaches the required position, the manual reversing valve 22 is operated to return to the neutral position (locked position), and the first two-way hydraulic lock 23 can ensure the reliable sealing of the actuating cylinder 19.

[0039] Refer to Figure 4 The emergency energy storage unit 3 includes a one-way valve 31, a second pressurizing oil tank 35, an accumulator 37, a reversing valve 38, a second two-way hydraulic lock 39, a pressure relief valve 32, a pressure sensor 33, and a pressure setting valve 34. One end of the second pressurizing oil tank 35 is connected to one port of the reversing valve 38 and the first pressurizing oil tank 13, that is, the second pressurizing oil tank 35 is connected to the first pressurizing oil tank 13 through the 3T2 port, the 1T2 port, and the 1T1 port. One end (3P2 port) of the one-way valve 31 is connected to the pipeline between the first position locking valve 16a and the two-way hydraulic pump 12 (i.e., the 1A1 port), and the other end of the one-way valve 31 is connected to the accumulator 37. The accumulator 37, the reversing valve 38, and the second two-way hydraulic lock 39 are connected in sequence. The two ports of the second two-way hydraulic lock 39 are respectively connected to the rod cavity and the rodless cavity of the actuating cylinder 19.

[0040] The two ports of the second two-way hydraulic lock 39 are connected to a speed control valve 36, and the speed control valve 36 is connected to the rod cavity and the rodless cavity of the actuating cylinder 19, that is, the 3A3 port is connected to the rodless cavity, and the 3B3 port is connected to the rod cavity.

[0041] The unloading valve 32 and the pressure setting valve 34 are distributed in parallel. Both ends of the unloading valve 32 and the pressure setting valve 34 are respectively connected to the second booster oil tank 35 and the accumulator 37. A pressure sensor 33 is installed in the pipeline between the pressure setting valve 34 and the accumulator 37 to monitor the oil pressure at the accumulator 37 through the pressure sensor 33.

[0042] The working principle of the emergency energy storage unit 3 is as follows: The emergency energy storage unit 3 works in conjunction with the motor pump control unit 1. When not powered on initially, there is no pressure in the emergency energy storage unit 3. After the system is powered on, the bidirectional hydraulic pump 12 in the motor pump control unit 1 sucks oil from the first booster oil tank 13, and the discharged high-pressure oil enters the accumulator 37 through the 1P2 port of the motor pump control unit 1, the 3P2 port of the emergency energy storage unit 3, and the one-way valve 31. After the pressure in the accumulator 37 reaches the set pressure of the pressure setting valve 34, the excess oil overflows to the second booster oil tank 35 through the unloading valve 32 to prevent the pressure from exceeding the limit. At the same time, the pressure sensor 33 detects that the pressure in the accumulator 37 reaches the limit value and sends a signal to the control system to stop the liquid filling. Due to the locking of the one-way valve 31 and the reversing valve 38, the pressure energy is stored in the accumulator 37. In the case of a complete power failure of the system, the operator releases the stored pressure energy by operating the reversing valve 38 to extend or retract the actuator 19 (this operation is the same as the operation principle of the above-mentioned emergency manual unit 2), and the extension and retraction speed can be adjusted by the speed control valve 36.

[0043] The flowchart of the program control part of this embodiment refers to Figure 5 , and the steps include:

[0044] ① Preset the operating speed V of the servo motor 11: The operator can set the operating speed of the servo motor 11 for equipment startup through the operation interface to control the traveling speed of the actuator 19 during operation.

[0045] ② In the manual mode, the operator can freely control the current motion state of the actuator 19 using three buttons: valve open, valve close, and stop.

[0046] ③ In the automatic mode, the operator needs to give a control command. The control command is the valve opening K, and the range of K is 0% to 100%. Then select to start running the program.

[0047] ④ When the program starts running, the servo motor 11 starts to accelerate, and the target position S is calculated according to the control command in step ③ d : S d = C·K, where C is the digital signal converted from the sensor analog signal.

[0048] ⑤ According to the target position S in step ④ d , the total running time T is obtained, and the motion parameters are calculated:

[0049]

[0050] V C is the current speed, V0 is the initial speed, V t is the terminal speed, t is the current time, and T is the total running time.

[0051] Meanwhile, calculate the deceleration position S m , and the formula for calculating the deceleration position is: S m = (V C - V t )2 / 2a;

[0052] V C is the running speed of the current servo motor 11, V t is the terminal speed, and a is the acceleration.

[0053] ⑥ According to the calculation results of step ⑤, continuously adjust the running speed of the servo motor 11 until the valve opening reaches the preset value K. Before the valve opening position reaches the deceleration position, the servo motor 11 accelerates. After reaching the deceleration position, the servo motor 11 starts to decelerate until it reaches the target position and the servo motor 11 stops rotating, and the program stops running, waiting for the next control signal.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pump-controlled electro-hydraulic system for a valve, characterized in that: It includes a motor pump control unit (1), a servo motor (11), a bi-directional hydraulic pump (12), a first pressurizing oil tank (13), and an actuating cylinder (19). The motor pump control unit (1) includes a volume compensation valve (15), a first position locking valve (16a), a second position locking valve (16b), a first overload safety valve (17a), and a second overload safety valve (17b). The output end of the servo motor (11) is connected to the bi-directional hydraulic pump (12). The two ports of the bi-directional hydraulic pump (12) are respectively connected to the first position locking valve (16a) and the second position locking valve (16b). The other end of the first position locking valve (16a) communicates with the rodless cavity of the actuating cylinder (19). The other end of the second position locking valve (16b) communicates with the rod cavity of the actuating cylinder (19). The two ends of the volume compensation valve (15) are respectively connected to the first position locking valve (16a) and the first pressurizing oil tank (13). The two ends of the first overload safety valve (17a) are respectively connected to the rodless cavity of the actuating cylinder (19) and the first pressurizing oil tank (13). The two ends of the second overload safety valve (17b) are respectively connected to the rod cavity of the actuating cylinder (19) and the first pressurizing oil tank (13). The first pressurizing oil tank (13) communicates with the S port and the L port of the bi-directional hydraulic pump (12). After receiving the extension instruction, the electromagnets of the first position locking valve (16a) and the second position locking valve (16b) are energized to connect the oil circuit. The servo motor (11) drives the bi-directional hydraulic pump (12) to rotate, suck oil from the 1B1 port of the motor pump control unit (1), and supply oil to the 1A1 port. The oil flows into the actuating cylinder (19) through the first position locking valve (16a), causing the actuating cylinder (19) to extend. The oil in the rod cavity of the actuating cylinder (19) flows back to the 1B1 port through the second position locking valve (16b). The volume of the oil flowing back to the 1B1 port is less than the volume of the oil flowing out of the 1A1 port. At this time, the built-in one-way valve of the bi-directional hydraulic pump (12) opens, and the oil flows from the first pressurizing oil tank (13) into the S port of the bi-directional hydraulic pump (12), and then enters the 1B1 port through the built-in one-way valve. After receiving the retraction instruction, the electromagnets of the first position locking valve (16a) and the second position locking valve (16b) are energized to connect the oil circuit. The servo motor (11) drives the bi-directional hydraulic pump (12) to rotate, suck oil from the 1A1 port of the motor pump control unit (1), and supply oil to the 1B1 port. The oil flows into the actuating cylinder (19) through the second position locking valve (16b) to make it retract. The oil in the rodless cavity of the actuating cylinder (19) flows back to the 1A1 port through the first position locking valve (16a). The volume of the oil flowing back to the 1A1 port is more than the volume of the oil flowing out of the 1B1 port. At this time, the 1A1 port is at high pressure, entering the pilot control port of the volume compensation valve (15) to open it, so that the excess oil at the 1A1 port flows back to the first pressurizing oil tank (13).

2. The pump-controlled electro-hydraulic system for a valve according to claim 1, characterized in that: A first pressure sensor (18a) is installed in the pipeline between the first overload safety valve (17a) and the rodless chamber of the actuating cylinder (19), and a second pressure sensor (18b) is installed in the pipeline between the second overload safety valve (17b) and the rod chamber of the actuating cylinder (19).

3. The pump-controlled electro-hydraulic system for a valve according to claim 1, characterized in that: A displacement sensor (191) is installed on the actuating cylinder (19).

4. The pump-controlled electro-hydraulic system for a valve according to claim 1, characterized in that: It further includes an emergency manual unit (2), and the emergency manual unit (2) includes a manual pump (21), a manual reversing valve (22), and a first two-way hydraulic lock (23) connected in sequence. The two ports of the first two-way hydraulic lock (23) are respectively communicated with the rod chamber and the rodless chamber of the actuating cylinder (19), and the manual pump (21) is communicated with the first booster oil tank (13).

5. The pump-controlled electro-hydraulic system for a valve according to claim 4, characterized in that: The emergency manual unit (2) includes a 2S2 port, and the manual reversing valve (22) is communicated with the first booster oil tank (13) through the 2S2 port.

6. The pump-controlled electro-hydraulic system for a valve according to claim 1, wherein: It further includes an emergency energy storage unit (3), and the emergency energy storage unit (3) includes a check valve (31), a second booster oil tank (35), an accumulator (37), a reversing valve (38), and a second two-way hydraulic lock (39). The second booster oil tank (35) is communicated with one port of the reversing valve (38) and the first booster oil tank (13). One end of the check valve (31) is communicated with the pipeline between the first position locking valve (16a) and the two-way hydraulic pump (12), and the other end of the check valve (31) is communicated with the accumulator (37). The accumulator (37), the reversing valve (38), and the second two-way hydraulic lock (39) are connected in sequence. The two ports of the second two-way hydraulic lock (39) are respectively communicated with the rod chamber and the rodless chamber of the actuating cylinder (19).

7. The pump-controlled electro-hydraulic system for a valve according to claim 6, characterized in that: The two ports of the second two-way hydraulic lock (39) are connected to a speed regulating valve (36), and the speed regulating valve (36) is communicated with the rod chamber and the rodless chamber of the actuating cylinder (19).

8. The pump-controlled electro-hydraulic system for a valve according to claim 6, wherein: The emergency energy storage unit (3) includes a relief valve (32), a pressure sensor (33), and a pressure setting valve (34). The relief valve (32) and the pressure setting valve (34) are distributed in parallel, and both ends of the relief valve (32) and the pressure setting valve (34) are respectively connected to the second booster oil tank (35) and the accumulator (37). A pressure sensor (33) is installed in the pipeline between the pressure setting valve (34) and the accumulator (37).

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