Load sensing control loop based on load sensing pump and Vaivistor valve

Abstract

The present invention discloses a load-sensitive control circuit based on a load-sensing pump and a Vaivistor valve, belonging to the technical field of load-sensitive control of excavators, including an electric oil pump connected to an oil tank and one or more hydraulic cylinders and hydraulic motors connected to the electric oil pump, and also includes a load-sensitive variable controller for controlling the electric oil pump, which is composed of a variable piston, a hydraulically controlled reversing valve, a relief valve, and a two-position electromagnetic reversing valve; and also includes two speed regulating valves, which are arranged in parallel at the outlet of the electric oil pump and act on the hydraulic cylinder and the hydraulic motor respectively, and a single speed regulating valve is composed of a proportional pilot valve, a differential pressure reducing valve, a throttle valve, and a plug-in arranged from top to bottom. The nozzle-sensitive control circuit of the present invention can solve the problems of large power loss and poor controllability when the pressure difference is reduced in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of excavator load-sensing control, and in particular relates to a load-sensing control loop based on a load-sensing pump and a Vaivistor valve. Background Art

[0002] Excavator loads involve the extension and rotation of the boom, which involves the movement of a hydraulic motor and multiple hydraulic cylinders. However, conventional excavator load-sensing systems typically utilize a multi-way valve for control, with a differential pressure reducing valve placed before and after the multi-way valve, typically setting a fixed pressure differential of 2 MPa. However, this design suffers from a drawback: high system flow often results in significant power loss. To minimize this power loss, the pressure differential must be reduced. However, conventional multi-way valves exhibit poor control characteristics when the pressure differential is reduced. Therefore, research is necessary to address the high system flow caused by the simultaneous movement of the cylinders and motors in excavators. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a load-sensing control loop based on a load-sensing pump and a Vaivistor valve to solve the problems in the prior art of large power loss and poor controllability when the pressure difference decreases.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a load-sensing control circuit based on a load-sensing pump and a Vaivistor valve, comprising an electric oil pump connected to an oil tank and one or more hydraulic cylinders and hydraulic motors connected to the electric oil pump. The invention also includes a load-sensing variable controller for controlling the electric oil pump, comprising a variable piston, a hydraulically controlled reversing valve, a relief valve, and a two-position electromagnetic reversing valve. The variable piston is connected to a swash plate of the electric oil pump, to which a hydraulically controlled reversing valve is connected. The hydraulically controlled reversing valve is also connected to the relief valve and the two-position electromagnetic reversing valve. The invention also includes two speed regulating valves, which are arranged in parallel at the outlet of the electric oil pump and act on the hydraulic cylinder and the hydraulic motor respectively. A single speed regulating valve is composed of a proportional pilot valve, a differential pressure reducing valve, a throttle valve, and a plug-in arranged from top to bottom.

[0006] Furthermore, the flow rate Q of the speed control valve is: Where: C d is the valve port flow coefficient; A is the area of ​​the valve port opening, m 2 ;Δp is the pressure difference between the front and back of the valve, Pa; ρ is the density, kg / m 3 .

[0007] Furthermore, the speed regulating valve connected to the hydraulic cylinder is connected to the rod chamber and rodless chamber of the hydraulic cylinder through a directional control valve respectively, and the speed regulating valve connected to the hydraulic motor is connected to the left chamber and right chamber of the hydraulic motor through another directional control valve respectively. The single directional control valve includes a three-position solenoid reversing valve and two two-way cartridge valves.

[0008] Furthermore, a shuttle valve is provided on a two-way cartridge valve in the directional control valve.

[0009] Furthermore, the rod chamber and rodless chamber of the hydraulic cylinder, and the left chamber and right chamber of the hydraulic motor are respectively connected to the oil tank through a one-way relief valve, which is composed of a one-way valve and a relief valve.

[0010] Furthermore, a balancing valve is provided on each of the oil return branches of the hydraulic cylinder and the hydraulic motor connected to the oil tank.

[0011] Furthermore, a filter is provided on the oil return main line connected to the oil tank.

[0012] Furthermore, a shuttle valve is provided between the rodless chamber of the hydraulic cylinder and the left chamber of the hydraulic motor, and a shuttle valve is also provided between the rod chamber of the hydraulic cylinder and the right chamber of the hydraulic motor. The load-sensitive variable controller is connected to the two shuttle valves through another shuttle valve.

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

[0014] 1. This load-sensitive control circuit uses a Valvistor valve and a speed control valve in combination with a differential pressure reducing valve. It has good linear flow amplification and speed regulation performance. A smaller control voltage can be used to control the proportional pilot valve to indirectly control the entire main valve core, eliminating the pilot oil circuit and simplifying the structure.

[0015] 2. This load-sensing control circuit uses a load-sensing pump group, so that the outlet pressure of the electric oil pump can track the maximum load changes very well, and can always maintain the set pressure difference ΔP = 10Mpa. Compared with the traditional load-sensing system, the pressure loss on the control valve is smaller. The flow of each branch changes according to the valve opening of the speed control valve and does not affect each other, which has good energy-saving effect and operability.

[0016] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0018] Figure 1 The schematic diagram of the Valvistor valve in the prior art shows the following: valve inlet 1'; valve outlet 2'; main valve core upper cavity 3'; control cover plate 4'; throttling slot 5'; valve seat 6'.

[0019] Figure 2 This is the schematic diagram of the control circuit. The reference numerals are: oil tank 1; electric oil pump 2; variable piston 3; hydraulically controlled reversing valve 4; relief valve 5; two-position solenoid reversing valve 6; filter 7; shuttle valves 8, 21, and 22; speed regulating valves 9 and 11; balancing valves 10 and 12; one-way relief valves 13, 16, 17, and 20; directional control valves 14, 15, 18, and 19; hydraulic cylinder 23; and hydraulic motor 24.

[0020] Figure 3 for Figure 2 The figure marks are: proportional pilot valve 25, differential pressure reducing valve 26, throttle valve 27, plug-in 28.

[0021] Figure 4 for Figure 2 The enlarged view of the directional control valve in part b is shown in FIG. The reference numerals are: three-position electromagnetic reversing valve 29; two-way cartridge valves 30 and 31; and shuttle valve 32. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only and are schematic, not actual, representations. They should not be construed as limiting this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the drawings.

[0023] The Valvistor valve mentioned in this case, namely the Vaivistor type hydraulic cartridge valve, has a throttle port set on the valve core inside the valve to provide hydraulic flow and displacement feedback, so that the displacement and flow of the main valve change with the displacement and flow of the pilot valve. Therefore, this valve can also be called a flow amplifier. It has a simple structure and can achieve the function of continuous proportional control of the main valve displacement that ordinary cartridge valves do not have without setting up a separate control oil channel. It can also be easily combined with pilot valves with different functions to form throttling, speed regulation, pressure and other control valves. The principle of the Valvistor valve is as follows Figure 1As shown, two different structures are available, depending on the inlet and outlet ports. A narrow throttling slot 5' is provided on the valve core. As the main valve core position changes, the opening of the throttling slot also changes, providing internal position feedback. When the main valve core is closed, the throttling slot leaves only a small throttling opening, allowing oil to flow through the control chamber. As the main valve core opens, the area of ​​the throttling slot increases. When the control cover 4' (pilot valve) is closed, no control flow passes through the throttling slot. At this time, the pressure at the valve inlet 1' equals the pressure in the upper chamber 3' of the main valve core. However, due to the larger area of ​​the upper chamber of the main valve core, the main valve core is tightly pressed against the valve seat 6' by the pressure differential between the valve inlet 1' and the valve outlet 2'. When the control cover 4' (pilot valve) is opened, the pressure in the upper chamber of the main valve core decreases, causing the main valve core to lose force and move away from its seat. The throttling slot now opens, allowing flow to flow through the control circuit. The flow through the control cover 4' equals the flow through the throttling slot plus the flow discharged due to the opening movement of the main valve core. When the flow rates through the throttle slot and the control cover plate are equal, the pressure drop across the throttle slot and the control cover plate 4' maintains balance between the main valve core. When the valve opening of the control cover plate 4' (pilot valve) decreases, the flow rate through the control cover plate 4' decreases. Due to the change in pressure drop, the main valve core loses balance and begins to move downward until the area of ​​the throttle slot is reduced to the appropriate size, restoring force balance.

[0024] like Figure 2 The load-sensing control circuit schematic diagram shown in the figure shows a load-sensing control circuit based on a load-sensing pump and a Vaivistor valve provided in this embodiment, comprising a fuel tank 1, an electric oil pump 2, a load-sensing variable controller, a speed control valve, a hydraulic cylinder 23, and a hydraulic motor 24. The electric oil pump 2 is connected to the fuel tank 1. The load-sensing variable controller is used to control the electric oil pump 2 and is composed of a variable piston 3, a hydraulically controlled reversing valve 4, a relief valve 5, and a two-position electromagnetic reversing valve 6. The variable piston 3 is connected to the swash plate of the electric oil pump 2, to which the hydraulically controlled reversing valve 4 is connected. The hydraulically controlled reversing valve 4 is also connected to the relief valve 5 and the two-position electromagnetic reversing valve 6. Two speed control valves 9 and 11 are arranged in parallel at the outlet of the electric oil pump 2 and act on the hydraulic cylinder 23 and the hydraulic motor 24, respectively. The hydraulic cylinder is used for the excavator's boom, bucket and / or stick, and is set as two hydraulic cylinders in the figure. The hydraulic motor is used for the excavator's boom rotation, and is set as one hydraulic motor in the figure. This load-sensitive control circuit is for the two loads, and the hydraulic cylinder and hydraulic motor are sensitively controlled when they work simultaneously. The specific description of the two load sensitivities is as follows.

[0025] 1. Pump outlet pressure changes with load pressure:

[0026] 1) When the load increases, the load-sensing variable speed controller operates in the right position, and the rod chamber of variable speed piston 3 connects to oil tank 1. Therefore, under the action of the spring, the swash plate angle of electric oil pump 2 increases, and the pump displacement increases. Because the opening of the speed control valve 9 or 11 based on the Valvistor valve does not change, the increased pump flow increases the pressure differential ΔP across the speed control valve. Because P = Pl + ΔP, the increase in ΔP increases the pump outlet pressure P until the pump outlet pressure P increases to 10 bar greater than the load pressure. 10 bar is the pressure of the bias spring at the right end of the load-sensing controller, at which point the load-sensing controller is balanced.

[0027] 2) When the load pressure decreases, the load-sensing controller operates in the left position, and the control chamber of variable piston 3 is connected to pressurized oil. Under the action of pressurized oil, variable piston 3 is pushed, reducing the swash plate angle and the pump output flow rate. Similarly, because the opening of the speed control valve does not change, the reduced pump flow rate reduces the pressure differential ΔP across the speed control valve. Because P = Pl + ΔP, the reduction in ΔP reduces the pump outlet pressure P until P = PL + 10 bar.

[0028] Therefore, no matter whether the load pressure increases or decreases, the pressure output by the pump can change with the load pressure and is always 10 bar higher than the load pressure, thus achieving the purpose of energy saving.

[0029] The function of the shuttle valves 8, 21 and 22 is to select the maximum load value to be fed back to the electric oil pump when the hydraulic cylinder 23 and the hydraulic motor 24 are in action simultaneously, so that the pump output pressure is 10 bar greater than the maximum load value.

[0030] 2. Pump output flow changes with the system:

[0031] 1) When the system requires the hydraulic cylinder or hydraulic motor to move quickly, the electrical signal controlling the speed regulating valve 9 or 11 increases, and the opening degree of the valve core increases. The increase in the opening degree reduces the pressure drop ΔP across the valve, and the reduction in ΔP reduces the pump outlet pressure P. When P < PL + 10 bar, the load sensing controller works in the right position, which also increases the displacement of the electric oil pump.

[0032] 2) When the system requires the hydraulic cylinder or hydraulic motor to slow down, the electrical signal controlling the speed control valve decreases, and the valve core opening decreases. The decrease in opening increases the pressure drop ΔP across the valve. The increase in ΔP increases the pump outlet pressure, P>Pl+10bar, and the load sensing controller works in the left position, which reduces the pump displacement.

[0033] Therefore, no matter when the flow rate required by the system increases or decreases, the circuit can control the pump displacement to increase or decrease, so that the flow rate discharged by the pump adapts to the system without unnecessary flow loss.

[0034] The function of the speed control valves 9 and 11 is to ensure that the flow rate through them is not affected by load changes and is only related to the valve opening. This makes the flow rate more stable when multiple actuators are working simultaneously. The differential pressure reducing valve used in the speed control valve can maintain a constant pressure difference between the front and back of the valve, that is, the valve flow rate is only related to the opening degree A. The flow rate Q of the speed control valve is: Where: C d is the valve port flow coefficient; A is the area of ​​the valve port opening, m 2 ;Δp is the pressure difference between the front and back of the valve, Pa; ρ is the density, kg / m 3 .

[0035] Adopting the above scheme, this load-sensitive control loop adopts a load-sensing variable controller to make the outlet pressure of the electric oil pump always higher than the load pressure by ΔP=10bar; and adopts a speed control valve based on the Valvistor valve, in which the differential pressure reducing valve is connected to both ends of the proportional pilot valve, and the opening of the plug-in main valve core is controlled by the proportional pilot valve. The flow and pressure on the proportional pilot valve are relatively small, which can achieve the purpose of energy saving; the reversing function of the directional control valve is also adopted, which can be achieved by controlling the opening and closing of the cartridge valve through the electromagnetic reversing valve as the pilot valve. When the cartridge valve port is open, the main valve port opening is large, and the pressure drop at the pilot valve is very small.

[0036] like Figure 3 As shown, the Valvistor valve-based speed control valve 9 or 11 can control the flow of the hydraulic system in this control circuit. The valve assembly includes, from top to bottom, a proportional pilot valve 25, a differential pressure reducing valve 26, a throttle valve 27, and a plug-in 28. The proportional pilot valve is equipped with a proportional solenoid that controls the pilot flow, thereby adjusting the opening of the plug-in's main valve core and proportionally regulating the flow through the main valve core. The differential pressure reducing valve and the proportional pilot valve are connected in series to form a speed control structure, which maintains a constant pressure differential across the proportional pilot valve. The pressure differential is selected to be 5 bar. The throttle valve controls the flow direction of the hydraulic oil and can be used for one-way or two-way flow. Here, a one-way throttle valve with a one-way valve is used. The plug-in functions as the flow amplification function of the Valvistor valve, with the flow direction from B to A.

[0037] like Figure 4As mentioned above, the hydraulic system of this control circuit achieves directional switching via directional control valves. Specifically, the speed control valve 9 connected to the hydraulic cylinder 23 is connected to the rod chamber and rodless chamber of the hydraulic cylinder 23 via directional control valves 14 and 15, respectively. The speed control valve 11 connected to the hydraulic motor 24 is connected to the left and right chambers of the hydraulic motor 24 via directional control valves 18 and 19, respectively. A single directional control valve consists of a three-position solenoid reversing valve 29 and two two-way cartridge valves 30 and 31, one of which is equipped with a shuttle valve 32 for selective control. Due to the high flow and pressure in the excavator's hydraulic system, conventional solenoid reversing valves cannot be used for directional switching. Instead, the solenoid reversing valve acts as a pilot valve to control the opening of the two-way cartridge valve. This pilot valve primarily controls the flow and direction of the oil, achieving pilot control of high-power valves. Since the control chamber of the two-way cartridge valve needs to maintain high pressure when the electromagnet in the three-position solenoid directional control valve is in the middle position, the control chamber of the two-way cartridge valve in the middle position is connected to the high-pressure oil circuit, that is, the three-position solenoid directional control valve required is a P-type solenoid directional control valve.

[0038] The control principle of the load-sensing controller in this embodiment is that the pilot control pressure of its internal valve core control chamber is taken from the load pressure point of the hydraulic system of this control loop. Therefore, it can control the output flow of the electric oil pump 2 to meet the requirements of the hydraulic system and maintain the system pressure changing with the load. The control loop has two loads, so the maximum load value is introduced into the pilot control chamber through the shuttle valve. The outlet pressure of the electric oil pump 2 is equal to the pressure of the pilot control chamber of the main valve core plus ΔP. ​​The outlet pressure of the electric oil pump is always ΔP higher than the load. ΔP is factory-set to 10 bar.

[0039] In this embodiment, the balancing valve 10 or 12 in the control circuit prevents load-induced loss of control of the hydraulic cylinder 23 or hydraulic motor 24. Furthermore, each branch circuit is equipped with a one-way relief valve 13, 16, 17, and 20. During excavation, the excavation reaction force generates high pressure on one side of the hydraulic cylinder and negative pressure on the other. High pressure can damage the pipelines. Therefore, a one-way relief valve, consisting of a relief valve and a check valve, is installed on both sides of the hydraulic cylinder inlet and return lines of the boom, arm, and bucket. This allows high-pressure oil to return to the tank through the relief valve, while negative pressure oil is replenished by the check valve.

[0040] In this embodiment, a filter 7 is provided on the oil return line connected to the oil tank 1 to achieve the purpose of oil return filtering.

[0041] The following takes the two hydraulic circuits of an excavator as an example, namely the two circuits are the boom hydraulic oil circuit and the motor rotation oil circuit.

[0042] Table 1: Electromagnet action sequence table

[0043]

[0044] 1. The hydraulic cylinder extends: the electromagnets YA2, YA4, YA5, and YA11 are energized, and the oil pumped by the electric oil pump 2 passes through the speed regulating valve 9 and the main valve core of the two-way cartridge valve 30 of the directional control valve 14 to enter the rodless chamber of the hydraulic cylinder 23. The return oil is the oil in the rod chamber of the hydraulic cylinder 23 passing through the main valve core of the two-way cartridge valve 31 of the directional control valve 15, the balancing valve 10, and the filter 7 back to the oil tank 1.

[0045] 2. The hydraulic cylinder retracts: the electromagnets YA1, YA3, YA5, and YA11 are energized, and the oil discharged from the electric oil pump passes through the speed regulating valve 9 and the main valve core of the two-way cartridge valve 30 of the directional control valve 15 to enter the rod chamber of the hydraulic cylinder. The return oil is the oil in the rodless chamber of the hydraulic cylinder, which passes through the main valve core of the two-way cartridge valve 31 of the directional control valve 14, the balancing valve 10, the filter 7, and then returns to the oil tank 1.

[0046] In this way, the extension and retraction speed of the hydraulic cylinder can be controlled by the electrical signal of the given proportional electromagnet YA5 in the speed control valve 9 to control the opening degree of the main valve core of its plug-in 28, and then control the flow through the main valve core to control the extension and retraction speed of the hydraulic cylinder.

[0047] 3. The hydraulic motor rotates forward: the electromagnets YA7, YA9, YA10, and YA11 are energized, and the oil discharged from the electric oil pump passes through the speed regulating valve 11 and the main valve core of the two-way cartridge valve 30 of the directional control valve 18 to enter the left chamber of the hydraulic motor 24. The return oil is from the right chamber of the hydraulic motor through the main valve core of the two-way cartridge valve 31 of the directional control valve 19, the balancing valve 12, and the filter 7 back to the oil tank 1.

[0048] 4. Reversal of the hydraulic motor: electromagnets YA6, YA8, YA10, and YA11 are energized, and the oil discharged from the electric oil pump passes through the speed regulating valve 11 and the main valve core of the two-way cartridge valve 30 of the directional control valve 19 into the right chamber of the hydraulic motor. The return oil is from the left chamber of the hydraulic motor through the main valve core of the two-way cartridge valve 31 of the directional control valve 18, the balancing valve 12, and the filter 7 and then returns to the oil tank 1.

[0049] In this way, the speed of the hydraulic motor can be controlled by the electrical signal of the given proportional electromagnet YA10 in the speed control valve 11 to control the opening degree of the main valve core of its plug-in 28, thereby controlling the flow through the main valve core to control the rotation speed of the hydraulic motor.

[0050] 5. The hydraulic motor and hydraulic cylinder work at the same time, that is, the hydraulic cylinder extends and the hydraulic motor rotates forward, the hydraulic cylinder extends and the hydraulic motor rotates reversely, the hydraulic cylinder retracts and the hydraulic motor rotates forward, and the hydraulic cylinder retracts and the hydraulic motor reverses. The working process is as described above, so I will not go into details. It just involves the shuttle valve to select the maximum load value to feedback to the electric oil pump when the hydraulic cylinder and hydraulic motor act at the same time.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A load sensing control circuit based on a load sensing pump and a Vaivistor valve, comprising an electric oil pump (2) connected to an oil tank (1) and one or more hydraulic cylinders (23) and hydraulic motors (24) connected to the electric oil pump, characterized in that: It also includes a load-sensitive variable controller for controlling the electric oil pump, which is composed of a variable piston (3), a hydraulically controlled reversing valve (4), a relief valve (5), and a two-position electromagnetic reversing valve (6). The variable piston is connected to the inclined plate of the electric oil pump, the variable piston is connected to the hydraulically controlled reversing valve, and the hydraulically controlled reversing valve is also connected to the relief valve and the two-position electromagnetic reversing valve. It also includes two speed regulating valves (9, 11) which are arranged in parallel at the outlet of the electric oil pump and act on the hydraulic cylinder and the hydraulic motor respectively. The single speed regulating valve is composed of a proportional pilot valve (25), a differential pressure reducing valve (26), a throttle valve (27), and a plug-in (28) arranged from top to bottom, wherein: the proportional pilot valve (25) is provided with a proportional solenoid for controlling the size of the pilot flow to adjust the opening of the main valve core so as to proportionally adjust the flow passing through the main valve core; the differential pressure reducing valve (26) and the proportional pilot valve (25) are connected in series to form a speed regulating structure so that the pressure difference at both ends of the proportional pilot valve is constant; the throttle valve (27) controls the flow direction of the hydraulic oil and is a one-way throttle valve with a one-way valve; the plug-in (28) plays a role in amplifying the flow of the Vaivistor valve; A speed regulating valve (9) connected to the hydraulic cylinder (23) is connected to the rod chamber and the rodless chamber of the hydraulic cylinder (23) via a directional control valve, and a speed regulating valve (11) connected to the hydraulic motor (24) is connected to the left chamber and the right chamber of the hydraulic motor (24) via another directional control valve. The single directional control valve is composed of a three-position electromagnetic reversing valve (29) and two two-way cartridge valves (30, 31), one of the two-way cartridge valves being provided with a first shuttle valve (32); A second shuttle valve (21) is provided between the rodless chamber of the hydraulic cylinder (23) and the left chamber of the hydraulic motor (24), and a third shuttle valve (22) is also provided between the rod chamber of the hydraulic cylinder (23) and the right chamber of the hydraulic motor (24), and the load-sensitive variable controller is connected to the second and third shuttle valves (21, 22) respectively through another shuttle valve (8); When the pump outlet pressure changes with the load pressure: when the load increases, the load-sensitive variable controller works in the right position, the rod chamber of the variable piston (3) is connected to the oil tank (1), and the swash plate angle of the electric oil pump (2) increases under the action of the spring, the pump displacement increases, and the opening degree of the speed control valve (9, 11) based on the Vaivistor valve does not change. The increase in pump flow will increase the pressure difference ΔP across the speed control valve, because P=Pl+ΔP. The increase in ΔP increases the pump outlet pressure P until the pump outlet pressure P increases to 10 bar greater than the load pressure; and when the load pressure decreases, the load The sensitive controller works in the left position, and the variable piston control chamber is connected to the pressure oil. Under the action of the pressure oil, the variable piston is pushed to reduce the swing angle of the swash plate, and the flow rate output by the pump is reduced. The opening degree of the speed regulating valve does not change. The reduction of the pump flow rate reduces the pressure difference ΔP across the speed regulating valve. Because P=PL+ΔP, the reduction of ΔP reduces the pump outlet pressure P until P=PL+10bar; among which, 10bar is the pressure of the bias spring at the right end of the load sensitive controller. At this time, the load sensitive controller is balanced; Pl is the right position pressure of the main valve core pilot control chamber, and PL is the left position pressure of the main valve core pilot control chamber; When the pump output flow rate changes with the system: when the system requires the hydraulic cylinder or hydraulic motor to be fast, the electrical signal controlling the speed regulating valve (9, 11) increases, the valve core opening increases, the increase in opening reduces the pressure drop ΔP across the valve, the reduction in ΔP reduces the pump outlet pressure P, P<PL+10bar, the load sensitive controller works in the right position, so that the displacement of the electric oil pump (2) increases; and when the system requires the hydraulic cylinder or hydraulic motor to be slow, the electrical signal controlling the speed regulating valve decreases, the valve core opening decreases, the reduction in opening increases the pressure drop ΔP across the valve, the increase in ΔP increases the pump outlet pressure, P>Pl+10bar, the load sensitive controller works in the left position, so that the displacement of the electric oil pump decreases.

2. The load sensing control circuit based on a load sensing pump and a Vaivistor valve according to claim 1, characterized in that: The rod chamber and rodless chamber of the hydraulic cylinder and the left chamber and right chamber of the hydraulic motor are respectively connected to the oil tank through a one-way overflow valve (13, 16, 17, 20), and the one-way overflow valve is composed of a one-way valve and an overflow valve.

3. The load sensing control circuit based on a load sensing pump and a Vaivistor valve according to claim 1, characterized in that: The invention also includes a balance valve (10, 12) provided on the oil return branch of the hydraulic cylinder and the hydraulic motor connected to the oil tank, respectively.

4. The load sensing control circuit based on a load sensing pump and a Vaivistor valve according to claim 1, characterized in that: The invention also includes a filter (7) provided on a main oil return line connected to the oil tank.

Images