Special vehicle electric drive throttling composite control system and method

Abstract

The application provides a special vehicle electric drive throttling composite control system and method, which comprises a three-position six-way throttling reversing valve, a throttling area, a throttling back oil oil channel and an inlet back oil oil channel are included in the reversing valve core; when the reversing valve core is in the front half area of the reversing position, the oil enters the throttling area of the reversing valve core from the P port of the three-position six-way throttling reversing valve, and the oil in the rod cavity of the oil cylinder flows back to the oil tank through the throttling back oil oil channel; when the reversing valve core is in the rear half area of the reversing position, the oil enters the inlet back oil oil channel of the reversing valve core from the P port of the three-position six-way throttling reversing valve; the valve core displacement sensor is used for monitoring the displacement signal of the reversing valve core, and is connected with the reversing valve core of the three-position six-way throttling reversing valve; the pressure sensor is used for monitoring the outlet pressure of the quantitative pump; the variable speed motor and the controller. The speed control system combining the electric drive variable speed with the valve control throttling variable speed guarantees the accurate control of the system at low speed and the energy saving effect of the system at high speed.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic technology and is applicable to special vehicles with intermittent motion, especially aerial work platforms and truck-mounted cranes. It relates to a special vehicle electric drive throttling composite control system and method. Background Technology

[0002] The pressure-regulating speed circuit is a fundamental circuit in hydraulic systems for adjusting and controlling the speed of actuators. It allows the actuator to switch between different speeds according to working conditions, playing a decisive role in the overall performance of the hydraulic system and the selection of other circuits. While electric motor-driven special-purpose vehicles experience relatively low power usage throughout the entire working cycle, to ensure system power matching, the motor is often selected based on a slightly higher load condition. Traditional methods typically employ throttle valves or load-sensitive valves in conjunction with a constant-speed hydraulic pump for throttling speed regulation, resulting in significant pressure loss and heat generation, making it difficult to meet energy-saving requirements.

[0003] The variable speed motor and constant power variable pump scheme in CN 106499614B controls the motor speed in segments by collecting pressure. However, due to the use of a variable pump and a variable speed motor, the variable mechanism is complex and costly, and the flow rate is not stable at low speeds.

[0004] The servo motor driven variable speed pump control system of CN 111255756B uses dual servo motors and dual pump speed regulation. The control accuracy and response speed of this electro-hydraulic servo system are not as high as those of the hydraulic valve control system. Under low-speed and heavy-load conditions, the speed of the actuator is unstable and the leakage is large. Summary of the Invention

[0005] The purpose of this invention is to provide a composite control system and method for electric drive throttling in special vehicles. In the low-speed stage, valve-controlled throttling speed regulation is performed, and in the high-speed stage, pump-controlled electric drive speed regulation is performed by controlling the motor speed. The composite speed regulation control of the system achieves the control requirements of rapid response and energy saving.

[0006] A special vehicle electric drive throttling composite control system includes:

[0007] The three-position six-way throttling valve 7 has a throttling valve core including a throttling zone, a throttling return oil passage, and an inlet and return oil passage; the throttling zone includes an unloading oil passage and an inlet oil passage;

[0008] The unloading oil passage connects the oil tank 1 and the P port of the three-position six-way throttle valve 7; the oil inlet oil passage connects to the A1 port of the three-position six-way throttle valve 7, and the A1 port connects to the rodless chamber of the oil cylinder 8.

[0009] The throttling return oil passage connects the B1 port of the three-position six-way throttling directional valve 7 to the oil tank 1, and the B1 port connects to the rod chamber of the oil cylinder 8.

[0010] When the reversing valve core is in the first half of the reversing position, the oil flows out from the fixed displacement pump 3 and enters the throttling area of ​​the reversing valve core through the P port of the three-position six-way throttling reversing valve 7. The oil in the rod chamber of the oil cylinder 8 flows back to the oil tank 1 through the throttling return oil passage.

[0011] When the reversing valve core is in the second half of the reversing position, the oil flows out from the fixed displacement pump 3 and enters the inlet and return oil passage of the reversing valve core through the P port of the three-position six-way throttling reversing valve 7; the oil in the rod chamber of the oil cylinder 8 flows back to the oil tank 1 through the inlet and return oil passage.

[0012] Valve core displacement sensor 7.1 is used to monitor the displacement signal of the directional valve core, and it is connected to the directional valve core of the three-position six-way throttling directional valve 7.

[0013] Pressure sensor 6 is used to monitor the outlet pressure of metering pump 3, and it is connected to the outlet of metering pump 3;

[0014] When the reversing valve core is in the first half of the reversing position, the variable speed motor 4 drives the fixed displacement pump 3 at a constant speed in the constant torque range; when the reversing valve core is in the second half of the reversing position, the motor 4 drives the fixed displacement pump 3 at a variable speed in the constant power range.

[0015] The controller 5 is connected to the valve core displacement sensor 7.1, the pressure sensor 6, and the variable speed motor 4.

[0016] Preferably, the unloading oil passage includes ports c'2 and c'5, the oil inlet oil passage includes ports c'1 and c'4, and the throttling return oil passage includes ports c'3 and c'6.

[0017] When the reversing valve core is in the first half of the reversing position, port c'1 and port P are connected by a check valve; port c'4 is connected to port A1; port c'3 is connected to oil tank 1; port c'6 is connected to port B1; port c'2 is connected to port P; and port c'5 is connected to oil tank 1.

[0018] The inlet and outlet oil passages include port C1, port C2, port C3, port C4, and port C5;

[0019] When the reversing valve core is in the second half of the reversing position, port C1 and port P are connected by a check valve; port C4 is connected to port A1, port C6 is connected to port B1, port C3 is connected to oil tank 1; port C2 is connected to port P, port C5 is connected to the oil tank; and ports C2 and C5 are disconnected.

[0020] Preferably, it also includes an overflow valve 2, whose inlet is connected to port P and whose outlet is connected to the oil tank 1.

[0021] A method for combined throttling control of electric drive in a special-purpose vehicle includes the following steps:

[0022] Valve-controlled throttling speed regulation: The oil flows out from the hydraulic pump and enters the throttling area of ​​the reversing valve core through port P. At this time, port c'1 is connected to port c'4, port c'2 is connected to port c'5, and port c'3 is connected to port c'6.

[0023] After entering through port P, the oil is split. One stream returns to the oil tank via unloading oil passages c'2-c'5; the other stream flows from port c'1 to port c'4, then enters the rodless chamber of cylinder 8 through port A1, causing the piston rod to extend. The oil in the rod chamber of cylinder 8 flows from port B1 to port c'6, then merges with the unloading oil through port c'3 and returns to the oil tank 1 through port T.

[0024] At this time, the variable speed motor 4 operates at a constant speed in the constant torque zone. The change in the opening of the throttling groove of the reversing valve core changes the size of the flow cross-sectional area of ​​the throttling port, so that the oil in the throttling zone is under the dual control of the inlet throttling and the bypass throttling unloading oil passage.

[0025] Electric drive speed regulation: The oil flows out from the hydraulic pump and enters the reversing valve core through port P. At this time, port C1 is connected to port C4 and port C3 is connected to port C6.

[0026] The oil enters from port P, flows from port C1 to port C4, and then enters the rodless chamber of cylinder 8 through port A1, causing the piston rod of the cylinder to extend. The oil in the rod chamber of cylinder 8 flows from port B1 to port C6, and then returns to oil tank 1 through port C3 and port T.

[0027] At this time, the variable speed motor 4 drives the fixed displacement pump 3 at different speeds within the constant power range; the throttling function of the reversing valve core is completely closed, and the flow regulation of the system is completely controlled by the variable speed motor 4.

[0028] At this time, the valve core displacement sensor 7.1 will feed back the valve core displacement signal of the three-position six-way throttling valve 7 to the controller 5, and the pressure sensor 6 will feed back the outlet pressure of the hydraulic pump to the controller 5. The controller 5 will adjust the speed of the variable speed motor 4 according to the magnitude of the valve core displacement signal and the magnitude of the pressure sensor signal, and then adjust the output flow.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] (1) The present invention is a speed control system that combines electric drive speed change with valve-controlled throttling speed change, ensuring accurate control at low speed and energy-saving effect at high speed.

[0031] In the first half of the reversing valve core stroke, the motor drives the fixed displacement pump at a constant speed within the constant torque range, and the valve core of the three-position six-way throttling reversing valve is switched to achieve valve-controlled throttling speed regulation.

[0032] In the latter half of the reversing valve core's stroke, the motor drives the metering pump at variable speed within a constant power range. The speed is related to the displacement of the reversing valve core and the outlet pressure of the metering pump. The controller adjusts the motor speed based on the signals from the valve core displacement sensor and the pump outlet pressure sensor. Changes in the motor speed affect the output flow of the metering pump, thus achieving electric speed regulation.

[0033] (2) By combining pressure feedback and displacement feedback, the over-torque phenomenon of speed regulation lag is avoided, and the speed regulation is made more stable through software tuning algorithm optimization. Attached Figure Description

[0034] Figure 1 A schematic diagram of the hydraulic principle of the electric drive throttling composite control system for special-purpose vehicles;

[0035] Figure 2 This is a schematic diagram of the operating range of a variable speed motor.

[0036] Wherein, 1—oil tank; 2—overflow valve; 3—displacement pump; 4—variable speed motor; 5—controller; 6—pressure sensor; 7—three-position six-way throttling valve; 7.1—valve core displacement sensor; 8—oil cylinder. Detailed Implementation

[0037] The special-purpose vehicle electric drive throttling composite control system and method of the present invention will be described in more detail below with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving the advantageous effects of the invention. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0038] A special vehicle electric drive throttling composite control system, wherein the variable speed motor 4 is directly connected to the fixed displacement pump 3, the oil inlet of the fixed displacement pump 3 is connected to the oil tank 1, and the oil outlet of the fixed displacement pump 3 is split, one path is connected to the P port of the three-position six-way throttling valve 7, and the other path is connected to the oil inlet of the overflow valve 2. The oil return port of the overflow valve 2 is connected to the oil tank 1, and the oil return port T of the three-position six-way throttling valve 7 is connected to the oil tank 1.

[0039] Specifically, it includes:

[0040] The three-position six-way throttling valve 7 has a throttling valve core including a throttling zone, a throttling return oil passage, and an inlet and return oil passage; the throttling zone includes an unloading oil passage and an inlet oil passage;

[0041] The unloading oil passage connects the oil tank 1 and the P port of the three-position six-way throttle valve 7; the oil inlet oil passage connects the A1 port of the three-position six-way throttle valve 7, and the A1 port connects to the rodless chamber of the cylinder 8; the throttle return oil passage connects the B1 port of the three-position six-way throttle valve 7 and the oil tank 1, and the B1 port connects to the rod chamber of the cylinder 8.

[0042] When the reversing valve core is in the first half of the reversing position, the oil flows out from the fixed displacement pump 3 and enters the throttling area of ​​the reversing valve core through the P port of the three-position six-way throttling reversing valve 7. The oil in the rod chamber of the oil cylinder 8 flows back to the oil tank 1 through the throttling return oil passage.

[0043] When the reversing valve core is in the second half of the reversing position, the oil flows out from the fixed displacement pump 3 and enters the inlet and return oil passage of the reversing valve core through the P port of the three-position six-way throttling reversing valve 7; the oil in the rod chamber of the oil cylinder 8 flows back to the oil tank 1 through the inlet and return oil passage.

[0044] The valve core displacement sensor 7.1 is used to monitor the displacement signal of the reversing valve core, and it is connected to the reversing valve core of the three-position six-way throttling reversing valve 7.

[0045] Pressure sensor 6 is used to monitor the outlet pressure of metering pump 3, and it is connected to the outlet of metering pump 3;

[0046] When the reversing valve core is in the first half of the reversing position, the variable speed motor 4 drives the fixed displacement pump 3 at a constant speed in the constant torque range; when the reversing valve core is in the second half of the reversing position, the motor 4 drives the fixed displacement pump 3 at a variable speed in the constant power range.

[0047] Overflow valve 2 has its inlet port connected to port P and its return port connected to oil tank 1.

[0048] The controller 5 is connected to the valve core displacement sensor 7.1, the pressure sensor 6, and the variable speed motor 4. It converts the data into control signals and transmits them to the variable speed motor 4.

[0049] In this embodiment, the unloading oil passage includes ports c'2 and c'5, the oil inlet oil passage includes ports c'1 and c'4, and the throttling return oil passage includes ports c'3 and c'6.

[0050] When the reversing valve core is in the first half of the reversing position, port c'1 and port P are connected by a check valve; port c'4 is connected to port A1; port c'3 is connected to oil tank 1; port c'6 is connected to port B1; port c'2 is connected to port P; and port c'5 is connected to oil tank 1.

[0051] The inlet and outlet oil passages include port C1, port C2, port C3, port C4, and port C5.

[0052] When the reversing valve core is in the second half of the reversing position, port C1 and port P are connected by a check valve; port C4 is connected to port A1, port C6 is connected to port B1, port C3 is connected to oil tank 1; port C2 is connected to port P, port C5 is connected to the oil tank; and ports C2 and C5 are disconnected.

[0053] Figure 1As shown, when the valve core of the three-position six-way throttling valve is in the neutral position, the oil flows out from the fixed displacement pump 3, enters the directional valve through the P port, and returns directly to the oil tank 1 through the unloading oil passage of the three-position six-way directional valve. At this time, the system is in the unloading state, the oil cylinder 8 does not move, the variable speed motor 4 maintains constant torque mode to output at low speed, and the fixed displacement pump 3 maintains low speed operation.

[0054] (1) Valve-controlled throttling speed regulation:

[0055] When the valve core of the three-position six-way throttling valve 7 switches from the neutral position to the reversing position, and the reversing valve core is in the first half of the reversing position, as shown in region a' of the figure, if the oil pressure does not exceed the set pressure of the relief valve 2:

[0056] The oil flows out of the hydraulic pump and enters the throttling zone of the reversing valve core through port P. At this time, port c'1 is connected to port c'4, port c'2 is connected to port c'5, and port c'3 is connected to port c'6.

[0057] After entering through port P, the oil is split. One stream of oil returns to the oil tank via unloading oil passages c'2-c'5; the other stream flows from port c'1 to port c'4, then enters the rodless chamber of cylinder 8 through port A1, causing the piston rod to extend. The oil in the rod chamber of cylinder 8 flows from port B1 to port c'6, then merges with the unloading oil through port c'3 and returns to the oil tank 1 through port T.

[0058] At this time, the variable speed motor 4 is operating at a constant speed in the constant torque region. Therefore, the speed of the variable speed motor 4 is constant, so the system flow is not controlled by the variable speed motor 4.

[0059] The change in the opening of the throttling groove of the reversing valve core alters the cross-sectional area of ​​the throttling orifice, allowing the oil to be controlled by both inlet throttling and bypass throttling in the throttling zone, thus achieving high-precision and rapid response control.

[0060] (2) Electric drive speed regulation:

[0061] When the valve core of the three-position six-way throttling valve 7 is in the latter half of the reversing position, as shown in region a of the figure, if the oil pressure does not exceed the set pressure of the relief valve 2:

[0062] The oil flows out of the hydraulic pump and enters the reversing valve core through port P. At this time, port C1 is connected to port C4 and port C3 is connected to port C6.

[0063] The oil enters from port P, flows from port C1 to port C4, and then enters the rodless chamber of cylinder 8 through port A1, causing the piston rod of the cylinder to extend. The oil in the rod chamber of cylinder 8 flows from port B1 to port C6, and then returns to oil tank 1 through port C3 and port T.

[0064] At this time, the variable speed motor 4 drives the fixed displacement pump 3 at different speeds within the constant power range; the throttling function of the directional valve core is completely closed, and the flow regulation of the system is completely controlled by the variable speed motor 4.

[0065] At this time, the valve core displacement sensor 7.1 feeds back the valve core displacement signal of the three-position six-way throttling valve 7 to the controller 5, and the pressure sensor 6 feeds back the outlet pressure of the hydraulic pump to the controller 5. The controller 5 adjusts the speed of the variable speed motor 4 according to the magnitude of the valve core displacement signal and the magnitude of the pressure sensor signal, thereby adjusting the output flow rate. That is, if the motor drives the pump speed to increase, the flow rate increases, and vice versa.

[0066] During the movement of cylinder 8, if the hydraulic pressure at port P of the three-position six-way throttle valve 7 exceeds the set pressure of the relief valve 2, the relief valve 2 will open, and the hydraulic oil at port P will enter the inlet of the relief valve 2. The system will be in an overflow state, and cylinder 8 will stop moving. At this time, pressure sensor 6 will feed back the outlet pressure signal of fixed displacement pump 3 to controller 5. Controller 5 will output a signal to slow down the variable speed motor 4, and the fixed displacement pump 3 will maintain low speed operation.

[0067] From the above, we can see that:

[0068] (1) The first half of the reversing valve core stroke is a low-speed zone for valve-controlled throttling speed regulation, i.e., the throttling interval a' or b' shown in the attached figure. At this time, the variable speed motor 4 maintains constant torque and low speed output, and the fixed displacement pump 3 operates at low speed.

[0069] According to the throttling speed regulation characteristic equation Throttling speed regulation is achieved by adjusting the flow rate into the hydraulic cylinder by changing the cross-sectional area of ​​the throttling orifice of the throttling valve core.

[0070] Specific implementation method: When the valve core starts to move to switch the oil circuit, the unloading oil passage of the throttling reversing valve is reduced due to the movement of the valve core, forming a bypass throttling.

[0071] At the same time, the oil inlet circuit of the throttling zone is connected to the working oil circuit (from port c'1 to c'4), and the valve core throttling groove and the valve body channel form an oil inlet throttling.

[0072] The two types of throttling create an equivalent hydraulic resistance mechanical linkage with opposite trends, forming a composite throttling speed regulation with valve control in the first half of the zone.

[0073] (2) The latter half of the reversing valve core stroke is the high-speed zone for electric drive constant power speed regulation. The valve core is located in the electric drive zone a or b shown in the attached figure. The valve core displacement sensor detects the movement stroke of the reversing valve core of the three-position six-way throttling reversing valve 7. The pressure sensor 6 feeds back the outlet pressure signal of the hydraulic pump to the controller 5. The controller 5 filters the pressure signal and calculates the upper limit of the speed of the variable speed motor 4. By comparing it with the outlet pressure in real time, the constant power control of the variable speed motor 4 is realized.

[0074] The combination of multiple speed control methods results in better speed control and stability of the system.

[0075] When the throttling orifice is at a small opening, the throttling speed regulation exhibits good speed stiffness and strong stability, enabling precise micro-motion at low speeds. After the valve core leaves the throttling zone and enters the electric drive zone, the system flow is controlled by the variable speed motor 4, achieving energy-saving effects without overflow throttling losses at high speeds. Automatic control can also be achieved by replacing the control mechanism of the three-position six-way throttling reversing valve 7 from a handle to a proportional electromagnet.

[0076] In electric drive speed control, the greater the displacement of the reversing valve core, the higher the speed of the variable speed motor 4. Simultaneously, a pressure signal feedback is introduced to prevent the torque of the variable speed motor 4 from exceeding its limit. The operating range of the variable speed motor 4 is as follows: Figure 2 As shown, within the speed regulation range from point n to point m, the system performs electric drive speed regulation, and the variable speed motor 4 always maintains constant power output.

[0077] Due to the hysteresis of electric drives and load fluctuations, once the system experiences over-torque overload, such as Figure 2 The Pover point is indicated. At this time, the pressure signal feedback mechanism is activated. Controller 5 will multiply the hydraulic pump outlet pressure detected by pressure sensor 6 by the pump displacement to obtain the pump input torque, and match it with the maximum operating speed corresponding to this load torque. Figure 2 The motor speed is switched from ω1 to ω2 to maintain constant power matching between the motor and the pump (the pump's load power does not exceed the motor's power limit). Figure 2 In the diagram, the horizontal axis represents the motor's angular velocity, and the vertical axis represents the motor's torque.

[0078] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A special-purpose vehicle electric drive throttling composite control system, characterized in that, include: The three-position six-way throttling valve (7) has a throttling valve core including a throttling zone, a throttling return oil passage and an inlet and return oil passage; the throttling zone includes an unloading oil passage and an inlet oil passage; The unloading oil passage connects the oil tank (1) and the P port of the three-position six-way throttle valve (7); the oil inlet oil passage connects to the A1 port of the three-position six-way throttle valve (7), and the A1 port connects to the rodless chamber of the oil cylinder (8); The throttling return oil passage connects the B1 port of the three-position six-way throttling reversing valve (7) to the oil tank (1), and the B1 port connects to the rod chamber of the oil cylinder (8); The unloading oil passage includes ports c'2 and c'5, the oil inlet oil passage includes ports c'1 and c'4, and the throttling return oil passage includes ports c'3 and c'6. When the reversing valve core is in the first half of the reversing position, port c'1 and port P are connected by a check valve; port c'4 is connected to port A1; port c'3 is connected to the oil tank (1); port c'6 is connected to port B1; port c'2 is connected to port P; and port c'5 is connected to the oil tank (1). The oil inlet and outlet channels include ports C1, C2, C3, C4, C5, and C6. When the reversing valve core is in the second half of the reversing position, port C1 and port P are connected by a check valve; port C4 is connected to port A1, port C6 is connected to port B1, port C3 is connected to the oil tank (1); port C2 is connected to port P, port C5 is connected to the oil tank; port C2 and port C5 are disconnected. When the reversing valve core is in the first half of the reversing position, the oil flows out from the metering pump (3) and enters the throttling area of ​​the reversing valve core through the P port of the three-position six-way throttling reversing valve (7). The oil in the rod chamber of the oil cylinder (8) flows back to the oil tank (1) through the throttling return oil passage. When the reversing valve core is in the second half of the reversing position, the oil flows out from the metering pump (3) and enters the oil inlet and return passage of the reversing valve core through the P port of the three-position six-way throttling reversing valve (7); the oil in the rod chamber of the oil cylinder (8) flows back to the oil tank (1) through the oil inlet and return passage. A valve core displacement sensor (7.1) is used to monitor the displacement signal of the reversing valve core, and it is connected to the reversing valve core of the three-position six-way throttling reversing valve (7). A pressure sensor (6) is used to monitor the outlet pressure of the metering pump (3), and it is connected to the outlet of the metering pump (3); When the reversing valve core is in the first half of the reversing position, the variable speed motor (4) drives the metering pump (3) at a constant speed in the constant torque range; when the reversing valve core is in the second half of the reversing position, the variable speed motor (4) drives the metering pump (3) at a variable speed in the constant power range. The overflow valve (2) has its inlet port connected to port P and its return port connected to the oil tank (1). The controller (5) is connected to the valve core displacement sensor (7.1), pressure sensor (6) and variable speed motor (4) for signal transmission.

2. A method for combined throttling control of electric drive for special-purpose vehicles, the method being based on the combined throttling control system for electric drive of special-purpose vehicles as described in claim 1, characterized in that, Includes the following steps: Valve-controlled throttling speed regulation: The oil flows out from the hydraulic pump and enters the throttling area of ​​the reversing valve core through port P. At this time, port c'1 is connected to port c'4, port c'2 is connected to port c'5, and port c'3 is connected to port c'6. After entering through port P, the oil is split into two streams. One stream returns to the oil tank from unloading oil passages c'2-c'5; the other stream flows from port c'1 to port c'4 and enters the rodless chamber of cylinder (8) through port A1, causing the piston rod of cylinder (8) to extend. The oil in the rod chamber of cylinder (8) flows from port B1 to port c'6 and then merges with the unloading oil through port c'3, returning to the oil tank (1) from port T. At this time, the variable speed motor (4) operates at a constant speed in the constant torque zone. The change in the opening of the throttling groove of the reversing valve core changes the size of the flow cross-sectional area of ​​the throttling port, so that the oil is subject to dual control of inlet throttling and bypass throttling in the throttling zone. Electric drive speed regulation: The oil flows out from the hydraulic pump and enters the reversing valve core through port P. At this time, port C1 is connected to port C4 and port C3 is connected to port C6. The oil enters from port P, flows from port C1 to port C4, and enters the rodless chamber of the cylinder (8) through port A1, causing the piston rod of the cylinder to extend; the oil in the rod chamber of the cylinder (8) flows from port B1 to port C6, and then returns to the oil tank (1) through port C3 and port T. At this time, the variable speed motor (4) drives the fixed displacement pump (3) at a constant power range; the throttling function of the reversing valve core is completely closed, and the flow regulation of the system is completely controlled by the variable speed motor (4) at different speeds; At this time, the valve core displacement sensor (7.1) feeds back the valve core displacement signal of the three-position six-way throttling valve (7) to the controller (5), and the pressure sensor (6) feeds back the outlet pressure of the hydraulic pump to the controller (5). The controller (5) adjusts the speed of the variable speed motor (4) according to the magnitude of the valve core displacement signal and the magnitude of the pressure sensor signal, and then adjusts the output flow.

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