Hydraulic system with pressure compensation function

Abstract

An open-close combined hydraulic system with pressure compensation function is suitable for engineering machinery with a hoist system. The hydraulic system has: a hoist ascending mode, in which a first main hoist valve and a second main hoist valve are at respective first valve positions, a first pump and a second pump are both operated in a pump working condition, a hoist motor is operated in a motor working condition, an open circuit is formed between the first pump and the motor, and an open circuit is also formed between the second pump and the motor; and a hoist descending mode, in which the first main hoist valve and the second main hoist valve are at respective second valve positions, the first pump is operated in the pump working condition, the second pump is operated in the motor working condition, the hoist motor is operated in the pump working condition, and a closed circuit is formed between the first pump, the second pump and the motor.

Description

Technical Field

[0001] This application relates to a combined hydraulic system for engineering machinery with a hoisting system, which can switch between open-loop and closed-loop hydraulic circuits and has a pressure compensation function. Background Technology

[0002] In construction machinery with winch systems, such as rotary drilling rigs, closed-loop hydraulic systems are typically used to drive the main winch to lift and lower the load. When the winch lowers the load, the energy generated during the lowering process can be recovered using the closed-loop hydraulic system. However, recovering this energy requires additional hardware for the closed-loop hydraulic system, increasing costs. According to existing technology, a scheme using two pumps to drive the winch motor has been proposed. When the winch descends, one pump supplies oil to the winch motor, and the high-pressure oil flowing from the motor flows into the other pump on the same shaft, causing it to operate as a motor and recover the load's potential energy. Such schemes usually involve complex hydraulic piping. Summary of the Invention

[0003] The purpose of this application is to provide a combined hydraulic system with pressure compensation function for engineering machinery, which can flexibly switch between open-loop hydraulic circuits and closed-loop circuits with a simple structure.

[0004] Therefore, this application provides, in one aspect, an open-close combination hydraulic system with pressure compensation function, suitable for engineering machinery with a winch system, especially rotary drilling rigs, etc., the hydraulic system comprising:

[0005] The hoist motor has its high-pressure port connected to the high-pressure oil circuit and its low-pressure port connected to the low-pressure oil circuit.

[0006] The first pump and the second pump are connected. The input port of the first pump is connected to the oil tank. The second pump is a two-quadrant pump that can operate in both pump and motor modes. The first port of the second pump is connected to the input port of the first pump.

[0007] The first main winding valve, equipped with a first main winding pressure compensation valve, is arranged between the output port of the first pump and the high-pressure oil circuit and the low-pressure oil circuit. In the first valve position, the output port of the first pump is connected to the high-pressure oil circuit and the low-pressure oil circuit is connected to the oil tank by means of the first main winding pressure compensation valve. In the second valve position, the output port of the first pump is connected to the low-pressure oil circuit by means of the first main winding pressure compensation valve.

[0008] The second main winding valve, equipped with a second main winding pressure compensation valve, is arranged between the second port of the second pump and the high-pressure oil circuit and the low-pressure oil circuit. In the first valve position, the second port of the second pump is connected to the high-pressure oil circuit and the low-pressure oil circuit is connected to the oil tank by means of the second main winding pressure compensation valve. In the second valve position, the second port of the second pump is connected to the high-pressure oil circuit.

[0009] The hydraulic system has the following features:

[0010] In the hoisting rising mode, the first main hoist valve and the second main hoist valve are in their respective first valve positions, the first pump and the second pump are both operating in pump mode, the hoisting motor is operating in motor mode, an open circuit is formed between the first pump and the motor, and an open circuit is also formed between the second pump and the motor.

[0011] In the hoisting lowering mode, the first main hoist valve and the second main hoist valve are in their respective second valve positions, the first pump operates in pump mode, the second pump operates in motor mode, the hoisting motor operates in pump mode, and a closed loop is formed between the first pump, the second pump and the motor.

[0012] In one embodiment, the opening and closing combined hydraulic system further includes:

[0013] A check valve installed in a high-pressure oil circuit is oriented to allow hydraulic oil in the high-pressure oil circuit to flow toward the winch motor and to prevent reverse flow.

[0014] The balance valve is set in parallel with the check valve, and its two oil ports are connected to the high-pressure oil circuit upstream and downstream of the check valve, respectively; in the original position of the balance valve, the two oil ports are cut off; in the working position of the balance valve, the two oil ports are connected.

[0015] In the hoisting upward mode, the balance valve is in its original position, and in the hoisting downward mode, the balance valve is in its working position.

[0016] In one embodiment, when the balance valve is in its operating position, the two ports are connected without throttling.

[0017] In one embodiment, the valve position of the balance valve is controlled by the control terminal oil pressure, which is taken from the low-pressure oil circuit.

[0018] In one embodiment, the opening and closing combined hydraulic system further includes:

[0019] First hydraulic actuator;

[0020] The first main valve is equipped with a first main valve pressure compensation valve, which is configured to control the on / off connection between the output port of the first pump and the first hydraulic actuator by means of the first main valve pressure compensation valve.

[0021] In one embodiment, the first control end pressure of both the first main winding pressure compensation valve and the first main valve pressure compensation valve is taken from the output pressure of the first pump, and the second control end pressure is taken from the common first load sensing oil circuit.

[0022] In one embodiment, the opening and closing combined hydraulic system further includes:

[0023] Second hydraulic actuator;

[0024] The second main valve is equipped with a second main valve pressure compensation valve, which is configured to control the on / off connection between the second port of the second pump and the second hydraulic actuator by means of the second main valve pressure compensation valve.

[0025] In one embodiment, the first control end pressure of both the second main winding pressure compensation valve and the second main valve pressure compensation valve is taken from the output pressure of the second pump, and the second control end pressure is taken from the common second load sensing oil circuit.

[0026] In one embodiment, the hydraulic system has a first winch lowering composite mode, wherein the first main winch valve and the second main winch valve are in their respective second valve positions, the first pump operates in pump mode, the second pump operates in motor mode, the winch motor operates in pump mode, the second port of the second pump is connected to the second hydraulic actuator through the second main valve, thereby also connecting the high-pressure oil circuit to the second hydraulic actuator, and a portion of the hydraulic oil returning from the winch motor drives the second pump and the other portion drives the second hydraulic actuator.

[0027] In one embodiment, the hydraulic system has a second winch lowering composite mode, wherein the first main winch valve and the second main winch valve are in their respective second valve positions, the first pump operates in pump mode, the second pump operates in pump mode, the winch motor operates in pump mode, and the second port of the second pump is connected to the second hydraulic actuator through the second main valve, thereby also connecting the high-pressure oil circuit to the second hydraulic actuator. The hydraulic oil returning from the winch motor and the hydraulic oil output from the second pump jointly drive the second hydraulic actuator.

[0028] According to this application, in the open-closed combined hydraulic system, one of the two working pumps is a two-quadrant pump. The hydraulic system can flexibly switch between open-loop and closed-loop hydraulic circuits, thus enabling both dual-pump drive of the winch upwards via an open hydraulic circuit and full recovery of the load's gravitational potential energy during closed-loop winch lowering. Simultaneously, this hydraulic system has a pressure compensation function, achieving independent flow distribution for each circuit regardless of load size during complex operations, which helps simplify the control logic. Attached Figure Description

[0029] The foregoing and other aspects of this application will be more fully understood and appreciated through the following detailed description with reference to the accompanying drawings, in which:

[0030] Figure 1 This is the overall structural diagram of the opening and closing combined hydraulic system according to this application;

[0031] Figure 2 yes Figure 1 A schematic diagram showing the port configuration of the control main valve used in the hydraulic system.

[0032] Figure 3 yes Figure 1 A schematic diagram showing the port configuration of the pressure compensation valve used in the hydraulic system.

[0033] Figure 4 yes Figure 1 A hydraulic schematic diagram of an exemplary embodiment of a hydraulic system in a [the document / model].

[0034] Figure 5 yes Figure 4 A schematic diagram of the hoisting mode of the hydraulic system in the image;

[0035] Figure 6 yes Figure 4 A schematic diagram of the winch-lifting composite mode of the hydraulic system in the image;

[0036] Figure 7 yes Figure 4 A schematic diagram of the winch lowering mode of the hydraulic system in the middle;

[0037] Figure 8 yes Figure 4 A schematic diagram of one of the combined winch lowering modes of the hydraulic system in the diagram;

[0038] Figure 9 yes Figure 4 A schematic diagram of the second hybrid mode of the winch lowering in the hydraulic system. Detailed Implementation

[0039] This application generally relates to a hydraulic system for engineering machinery (such as rotary drilling rigs) with a hoisting system.

[0040] The overall layout of the hydraulic system suitable for adopting the solution of this application is as follows: Figure 1 This is a schematic representation. The hydraulic system is powered by engine E, which serves as the power source for the construction machinery, thereby driving the various working devices of the machinery.

[0041] The hydraulic system includes a first pump (main pump) P1, a second pump (auxiliary pump) P2, and a third pump P3 driven by engine E. These three pumps can be coaxially arranged and interconnected, and kinematically connected to the output end of engine E, for example, via a transfer case (not shown). Alternatively, each of the three pumps can be kinematically connected to the output end of engine E via a reduction gear.

[0042] The first pump P1 and the second pump P2 are mainly used to drive the hoist motor (main hoist motor) M. The third pump P3 is used for other functions of the hoisting system.

[0043] The first pump, P1, is a unidirectional variable pump, such as an electro-proportional adjustable variable pump.

[0044] The second pump P2 is a two-quadrant pump (over-center pump). As referred to in the art, hydraulic pumps can have four-quadrant characteristics based on the pressure and flow direction they withstand during operation. The second pump P2 used in this application has the following two-quadrant characteristics: first quadrant, positive displacement (positive oscillation angle), where the second pump P2 normally functions as a hydraulic pump; second quadrant, negative displacement (negative oscillation angle), where the second pump P2 functions as a motor to convert hydraulic energy into mechanical energy. The second pump P2 is also a variable displacement pump, such as an electro-proportional adjustable variable displacement pump.

[0045] The hoist motor M is a variable displacement motor with both high-pressure and low-pressure ports.

[0046] The input port of the first pump P1 is connected to the oil tank, and the input port of the second pump P2 is connected to the input port of the first pump P1.

[0047] The output port of the first pump P1 is connected on one side to the first main winding valve Vm1 equipped with a pressure compensation valve (first main winding pressure compensation valve) Vh1, and on the other side to the first main valve Vc1 equipped with a pressure compensation valve (first main valve pressure compensation valve) Vf1. The output port of the second pump P2 is connected on one side to the second main winding valve Vm2 equipped with a pressure compensation valve (second main winding pressure compensation valve) Vh2, and on the other side to the second main valve Vc2 equipped with a pressure compensation valve (second main valve pressure compensation valve) Vf2.

[0048] The working port of the first main valve Vc1 is connected to a first hydraulic actuator (not shown) of the construction machinery, for supplying hydraulic oil to the first hydraulic actuator. The working port of the second main valve Vc2 is connected to a second hydraulic actuator (not shown) of the construction machinery, for supplying hydraulic oil to the second hydraulic actuator.

[0049] The first working port of the first main winding valve Vm1 is connected to the high-pressure port of the winch motor M, and the second working port is connected to the low-pressure port of the winch motor M. The first working port of the second main winding valve Vm2 is also connected to the high-pressure port of the winch motor M, and the second working port is also connected to the low-pressure port of the winch motor M.

[0050] The hydraulic system can achieve at least the following operating modes:

[0051] In the hoisting lifting mode, the first pump P1 and the second pump P2 participate in the driving of the hoisting motor M to achieve hoisting lifting.

[0052] In the winch lifting compound mode, the first pump P1 and the second pump P2 participate in the driving of the winch motor M, and the first pump P1 and the second pump P2 also participate in the driving of the first and second hydraulic actuators respectively, realizing the compound action of winch lifting plus other actions.

[0053] In the winch lowering mode, the first pump P1 is in pump mode, the second pump P2 is in motor mode, and the load drives the winch motor M to be in pump mode, thereby realizing the winch lowering.

[0054] In the winch lowering composite mode, the first pump P1 is in pump mode, the second pump P2 is in motor mode or pump mode based on the required flow rate, and the load drives the winch motor M to be in pump mode, thus realizing the composite action of winch lowering plus other actions.

[0055] In each composite mode, the valve positions of pressure compensation valves Vf1 and Vh1 depend on the maximum load pressure from the first hydraulic actuator and the hoisting motor M, thus forming a LUDV (Load Independent Flow Distribution) system. This ensures that the flow supplied to the first hydraulic actuator and the hoisting motor M is only related to the orifice areas of the first main valve Vc1 and the first main hoisting valve Vm1, respectively, and is independent of their respective load sizes, achieving two independent flow distributions. On the other hand, the valve positions of pressure compensation valves Vf2 and Vh2 depend on the maximum load pressure from the second hydraulic actuator and the hoisting motor M, also forming a LUDV system. This ensures that the flow supplied to the second hydraulic actuator and the hoisting motor M is only related to the orifice areas of the second main valve Vc2 and the second main hoisting valve Vm2, respectively, and is independent of their respective load sizes, achieving two independent flow distributions.

[0056] In an exemplary embodiment, the various control master valves (first master valve Vm1, first master valve Vc1, second master valve Vm2, and second master valve Vc2) used in the hydraulic system are pilot oil pressure controlled and are in the form of three-position seven-way valves. Figure 2 Taking the first main valve Vm1 as an example, its various oil ports are shown: P port (oil inlet), A port (first working oil port), B port (second working oil port), C port (valve position oil port), D port (first intermediate oil port), E port (second intermediate oil port), and T port (drain port). Other control main valves also have these seven oil ports. (The rest of the text is incomplete and requires further context.) Figures 4-9 Due to space limitations in the drawing, these port letters are not shown. Furthermore, each main control valve has three positions: neutral, first, and second.

[0057] Back Figure 2 In the neutral valve position, all ports of the first main valve Vm1 are disconnected. In the first valve position, port P is connected to port C (with throttling effect), port D is connected to port A (without throttling effect), port B is connected to port T (without throttling effect), and port E is disconnected. In the second valve position, port P is connected to port C (with throttling effect), port E is connected to port B (without throttling effect), and ports D, A, and T are disconnected.

[0058] Although not shown separately, but combined Figures 4-9The connectivity of each valve position of the other control main valves can be observed. In the neutral valve position and the first valve position, the connectivity between the ports of the first main valve Vc1, the second main valve Vm2, and the second main valve Vc2 is the same as that of the first main valve Vm1 described earlier.

[0059] In the second valve position, the E port of the second main valve Vm2 is connected to the P port (with throttling effect), the A port is connected to the D port (without throttling effect), and the C port, B port, and T port are all cut off.

[0060] In the second valve position, the first main valve Vc1 and the second main valve Vc2 are connected to port P and port C (with throttling effect), port A and port T (without throttling effect), port E and port B (without throttling effect), and port D is cut off.

[0061] Furthermore, in the exemplary embodiment, the various pressure compensation valves used in the hydraulic system are hydraulically controlled and are in the form of three-position three-way valves. Figure 3 The pressure compensation valve Vh1 is shown as an example, illustrating its various ports: S port (inlet), U port (outlet), and V port (diverter port). The pressure compensation valve Vh1 has three positions: closed, first position (normal operating position), and second position (transition position).

[0062] In the closed position, the S, U, and V ports of the pressure compensation valve Vh1 are all cut off. In the first position, the S port is connected to the U port (no throttling effect) and also connected to the V port (throttling effect). In the second position, the S port is connected to the U port (throttling effect), and the V port is cut off.

[0063] The remaining pressure compensation valves Vh2, Vf1, and Vf2 have the same oil ports and valve positions as pressure compensation valve Vh1, as well as the oil port connection relationships under each valve position.

[0064] Figure 1 A hydraulic schematic diagram of an exemplary embodiment of the hydraulic system shown is provided in [reference needed]. Figure 4 .

[0065] See Figure 4 A first valve block Vb1 is provided for the first pump P1. Correspondingly, a first main valve Vm1 and its pressure compensation valve Vh1, and a first main valve Vc1 and its pressure compensation valve Vf1 are disposed within the first valve block Vb1. The valve cores of these valves are assembled within the valve body of the first valve block Vb1, and the valve body of the first valve block Vb1 provides an adjustable bidirectional stroke limiting structure for these valve cores. A first pressure oil circuit Lp1, a first load sensing oil circuit Lc1, and a first return oil circuit Lr1 are formed within the first valve block Vb1.

[0066] A second valve block Vb2 is provided for the second pump P2. Correspondingly, the second main valve Vm2 and its pressure compensation valve Vh2, and the second main valve Vc2 and its pressure compensation valve Vf2 are disposed within the second valve block Vb2. The valve cores of these valves are assembled within the valve body of the second valve block Vb2, and the valve body of the second valve block Vb2 provides an adjustable bidirectional stroke limiting structure for these valve cores. A second pressure oil circuit Lp2, a second load sensing oil circuit Lc2, and a second return oil circuit Lr2 are formed within the second valve block Vb2.

[0067] The output port of the first pump P1 is connected to the first pressure oil circuit Lp1. The input port of the second pump P2 (i.e., the input port of the second pump P2 in hydraulic pump mode, also referred to as the first port of the second pump P2) is connected to the input port of the first pump P1 through the bidirectional oil circuit Lp3 (and thus connected to the oil tank). The output port of the second pump P2 (i.e., the output port of the second pump P2 in hydraulic pump mode, also referred to as the second port of the second pump P2) is connected to the second pressure oil circuit Lp2.

[0068] Both the first return oil circuit Lr1 and the second return oil circuit Lr2 lead to the oil tank.

[0069] The high-pressure port of the hoist motor M is connected to the high-pressure oil circuit La, and the low-pressure port is connected to the low-pressure oil circuit Lb.

[0070] In the high-pressure oil circuit La, there is a one-way valve (high-pressure side one-way valve) V1. The one-way valve V1 is oriented to allow the hydraulic oil in the high-pressure oil circuit La to flow toward the high-pressure port of the motor M, and does not allow reverse flow.

[0071] A balancing valve V2 is arranged in parallel with the check valve V1. The balancing valve V2 has at least two positions and at least two ports. The two ports are connected to the high-pressure oil circuit La upstream and downstream of the check valve V1, respectively. In its normal home position, the two ports are disconnected; in the working position reached after controlled actuation, the two ports are connected. In the working position, the balancing valve V2 is preferably unobstructed and unrestricted. Between the home and working positions, the orifice area of ​​the balancing valve V2 depends on the specific position of its valve core. The valve position of the balancing valve V2 can be controlled by control-end oil pressure. The control-end oil pressure of the balancing valve V2 can be derived from the low-pressure oil circuit Lb by the control oil circuit Lv, as shown in the figure; that is, one end of the control oil circuit Lv is connected to the low-pressure oil circuit Lb, and the other end is connected to the control end of the balancing valve V2. Alternatively, the control-end oil pressure of the balancing valve V2 can be taken from an additionally set pilot oil pressure. Alternatively, the valve position of the balancing valve V2 can be electrically controlled.

[0072] A parallel dual-way valve assembly V3 is set in the control oil circuit Lv. Each branch of the dual-way valve assembly V3 is equipped with a check valve and a throttle, and the check valves in the two branches are oriented in opposite directions.

[0073] In addition, near the motor M, the high-pressure oil circuit La and the low-pressure oil circuit Lb are respectively connected to a relief valve (not shown) to prevent hydraulic shock and a check valve (not shown) to prevent air suction.

[0074] The connections of the oil ports of the first main spiral valve Vm1 in the first valve block Vb1 are as follows: Port P is connected to the first pressure oil circuit Lp1; Ports A and B are connected to the valve body surface ports A1 and B1 of the first valve block Vb1, respectively, and ports A1 and B1 are connected to the high-pressure oil circuit La and the low-pressure oil circuit Lb through branch oil circuits L1a and L1b, respectively; Port C is connected to the S port and the first control terminal of the pressure compensation valve Vh1; Port D is connected to the U port of the pressure compensation valve Vh1 through a check valve, and the check valve is oriented to allow hydraulic oil to flow from the U port to the D port and prohibit reverse flow; Port E is connected to the U port of the pressure compensation valve Vh1 through a check valve, and the check valve is oriented to allow hydraulic oil to flow from the U port to the E port and prohibit reverse flow; Port T is connected to the first return oil circuit Lr1.

[0075] The first control terminal of the first main valve Vm1 is connected to the pilot port Xf1 on the valve body surface of the first valve block Vb1 via a one-way throttle valve Vg1 (composed of a one-way valve and a throttle valve connected in parallel). The second control terminal is connected to the pilot port Xc1 on the valve body surface of the first valve block Vb1 via a one-way throttle valve Vk1. Pilot valves (not shown) are connected to the pilot ports Xf1 and Xc1 respectively to provide pilot pressure to the control terminals on both sides of the first main valve Vm1.

[0076] The V port and the second control terminal of the pressure compensation valve Vh1 are both connected to the first load sensing oil circuit Lc1.

[0077] An overflow valve Vi1 is installed between the oil passage between port A and port A1 of the first main valve Vm1 and the first return oil passage Lr1, and an overflow valve Vj1 is installed between the oil passage between port B and port B1 and the first return oil passage Lr1.

[0078] The connections of the oil ports of the first main valve Vc1 in the first valve block Vb1 are as follows: Port P is connected to the first pressure oil circuit Lp1; Ports A and B are respectively connected to ports Xa1 and Xb1 on the valve body surface of the first valve block Vb1, and ports Xa1 and Xb1 lead to the first hydraulic actuator; Port C is connected to the S port and the first control terminal of the pressure compensation valve Vf1; Port D is connected to the U port of the pressure compensation valve Vf1 via a check valve, and the check valve is oriented to allow hydraulic oil to flow from port U to port D and prohibit reverse flow; Port E is connected to the U port of the pressure compensation valve Vf1 via a check valve, and the check valve is oriented to allow hydraulic oil to flow from port U to port E and prohibit reverse flow; Port T is connected to the first return oil circuit Lr1.

[0079] The first control terminal of the first main valve Vc1 is connected to the pilot port Xe1 on the valve body surface of the first valve block Vb1 via a one-way throttle valve Ve1, and the second control terminal is connected to the pilot port Xd1 on the valve body surface of the first valve block Vb1 via a one-way throttle valve Vn1. Pilot valves (not shown) are connected to the pilot ports Xe1 and Xn1 respectively to provide pilot pressure to the control terminals on both sides of the first main valve Vc1.

[0080] The V port of the pressure compensation valve Vf1 is connected to the first load sensing oil circuit Lc1 on one side and to the second control terminal of the pressure compensation valve Vf1 on the other side.

[0081] An overflow valve Vl1 is installed between the oil passage between port A and port Xa1 of the first main valve Vc1 and the first return oil passage Lr1, and an overflow valve Vm1 is installed between the oil passage between port B and port Xb1 and the first return oil passage Lr1.

[0082] If the first pump P1 supplies hydraulic oil to other hydraulic actuators besides the motor M and the first hydraulic actuator, then other control main valves and corresponding pressure compensation valves can be added to the first valve block Vb1.

[0083] When the first pump P1 participates in the combined action, the pressure in the first load sensing oil circuit Lc1 is the maximum load pressure among all loads borne by the first pump P1. The control oil pressure of the first control terminal of the pressure compensation valves Vh1 and Vf1 is taken from port C of the first main valve Vm1, and the control oil pressure of the second control terminal is taken from the first load sensing oil circuit Lc1.

[0084] The connections of the oil ports of the second main winding valve Vm2 in the second valve block Vb2 are as follows: Port P is connected to the second pressure oil circuit Lp2; Ports A and B are connected to ports A2 and B2 on the valve body surface of the second valve block Vb2, respectively. Ports A2 and B2 are connected to the high-pressure oil circuit La and the low-pressure oil circuit Lb through branch oil circuits L2a and L2b, respectively; Port C is connected to the S port and the first control terminal of the pressure compensation valve Vh2; Port D is directly connected to the U port of the pressure compensation valve Vh2; Port E is connected to the U port of the pressure compensation valve Vh2 via a check valve, which is oriented to allow hydraulic oil to flow from port U to port E and prohibits reverse flow; Port T is connected to the second return oil circuit Lr2. It can be seen that there is actually a direct oil circuit between ports D and E of the second main winding valve Vm2, and this oil circuit is equipped with a check valve that allows hydraulic oil to flow from port D to port E and prohibits reverse flow. The function of this oil circuit will be explained later. Figures 7-9 This is reflected in the described operations.

[0085] The first control terminal of the second main valve Vm2 is connected to the pilot port Xf2 on the valve body surface of the second valve block Vb2 via a one-way throttle valve Vg2, and the second control terminal is connected to the pilot port Xc2 on the valve body surface of the second valve block Vb2 via a one-way throttle valve Vk2. Pilot valves (not shown) are connected to the pilot ports Xf2 and Xc2 respectively to provide pilot pressure to the control terminals on both sides of the second main valve Vm2.

[0086] The V port of the pressure compensation valve Vh2 is connected to the second load sensing oil circuit Lc2 on one side and to the second control terminal of the pressure compensation valve Vh2 on the other side.

[0087] An overflow valve Vi2 is installed between the oil passage between port A and port A2 of the second main spiral valve Vm2 and the second return oil passage Lr2, and an overflow valve Vj2 is installed between the oil passage between port B and port B2 and the second return oil passage Lr2.

[0088] The connections of the oil ports of the second main valve Vc2 in the second valve block Vb2 are as follows: Port P is connected to the second pressure oil circuit Lp2; Ports A and B are respectively connected to the valve body surface ports Xa2 and Xb2 of the second valve block Vb2, and ports Xa2 and Xb2 lead to the second hydraulic actuator; Port C is connected to the S port and the first control terminal of the pressure compensation valve Vf2; Port D is connected to the U port of the pressure compensation valve Vf2 via a check valve, and the check valve is oriented to allow hydraulic oil to flow from port U to port D and prohibit reverse flow; Port E is connected to the U port of the pressure compensation valve Vf2 via a check valve, and the check valve is oriented to allow hydraulic oil to flow from port U to port E and prohibit reverse flow; Port T is connected to the second return oil circuit Lr2.

[0089] The first control terminal of the second main valve Vc2 is connected to the pilot port Xe2 on the valve body surface of the second valve block Vb2 via a one-way throttle valve Ve2, and the second control terminal is connected to the pilot port Xd2 on the valve body surface of the second valve block Vb2 via a one-way throttle valve Vn2. Pilot valves (not shown) are connected to pilot ports Xe2 and Xn2 respectively to provide pilot pressure to the control terminals on both sides of the second main valve Vc2.

[0090] The V port and the second control terminal of the pressure compensation valve Vf2 are both connected to the second load sensing oil circuit Lc2.

[0091] An overflow valve Vl2 is installed between the oil passage between port A and port Xa2 of the second main valve Vc2 and the second return oil passage Lr2, and an overflow valve Vm2 is installed between the oil passage between port B and port Xb2 and the second return oil passage Lr2.

[0092] If the second pump P2 supplies hydraulic oil to other hydraulic actuators besides the motor M and the second hydraulic actuator, then other control main valves and corresponding pressure compensation valves can be added to the second valve block Vb2.

[0093] When the second pump P2 participates in the combined action, the pressure in the second load sensing oil circuit Lc2 is the maximum load pressure among all loads borne by the second pump P2. The control oil pressure at the first control terminal of the pressure compensation valves Vh2 and Vf2 is taken from the C port of the second main valve Vm2 and the second main valve Vc2, respectively, and the control oil pressure at the second control terminal is taken from the second load sensing oil circuit Lc2.

[0094] Those skilled in the art will understand that the valve positions and number of ports of the first main valve Vm1, the second main valve Vm2, the first main valve Vc1, and the second main valve Vc2, as well as the on / off relationship of the ports under each valve position, are not necessarily limited to the above forms, as long as they can achieve the function of controlling the connection and disconnection between the corresponding oil circuits as described later.

[0095] The following description Figure 1 , Figure 4 The diagram shows the various operating modes of the hydraulic system.

[0096] First refer to Figure 5 The hoisting lifting mode of the hydraulic system is described, wherein the first pump P1 and the second pump P2 operate to participate in the driving of the hoisting motor M, thereby realizing the hoisting lifting.

[0097] Specifically, the first main valve Vc1 and the second main valve Vc2 are in the neutral position, so the output flow of the first pump P1 and the second pump P2 is not split.

[0098] The balance valve V2 is in its original position, and its two ports are disconnected.

[0099] Both the first pump P1 and the second pump P2 are in pump operation mode, drawing hydraulic oil from the oil tank. The hydraulic oil output by the two pumps enters the first pressure oil circuit Lp1 and the second pressure oil circuit Lp2, respectively.

[0100] The first main valve Vm1 is in the first valve position (open system valve position), so that its P port is connected to the C port, its D port is connected to the A port, and its B port is connected to the T port. The hydraulic oil output from the first pump P1 to the first pressure oil circuit Lp1 is transmitted through the P and C ports of the first main valve Vm1 to the S port and the first control terminal of the pressure compensation valve Vh1. The oil pressure on the first control terminal pushes the pressure compensation valve Vh1 into its first valve position, so that the S port and U port of the pressure compensation valve Vh1 are connected without throttling, and connected with the V port with throttling. The hydraulic oil flows through the S and U ports of the pressure compensation valve Vh1 to the D port of the first main valve Vm1, and then through the A port of the first main valve Vm1 to port A1. From port A1, it is transmitted to the high-pressure oil circuit La through the branch oil circuit L1a.

[0101] The second main winding valve Vm2 is in the first valve position (open system valve position), so that its P port is connected to the C port, its D port is connected to the A port, and its B port is connected to the T port. The hydraulic oil output from the second pump P2 to the second pressure oil circuit Lp2 is transmitted through the P and C ports of the second main winding valve Vm2 to the S port and the first control terminal of the pressure compensation valve Vh2. The oil pressure on the first control terminal pushes the pressure compensation valve Vh2 into its first valve position, so that the S port and U port of the pressure compensation valve Vh2 are connected without throttling, and connected with the V port with throttling. The hydraulic oil flows through the S and U ports of the pressure compensation valve Vh2 to the D port of the second main winding valve Vm2, and then through the A port of the second main winding valve Vm2 to port A2. From port A2, it is transmitted through the branch oil circuit L2a to the high-pressure oil circuit La, where it merges with the hydraulic oil output from the first pump P1 and flows together through the check valve V1 into the high-pressure port of the motor M, driving the motor M to rotate.

[0102] Then, the low-pressure hydraulic oil after work is output from the low-pressure port of motor M through the low-pressure oil circuit Lb, and then branches into branch oil circuits L1b and L2b. The hydraulic oil entering branch oil circuit L1b flows through port B1 to port B of the first main winding valve Vm1, and then flows through port T of the first main winding valve Vm1 into the first return oil circuit Lr1, returning to the oil tank. The hydraulic oil entering branch oil circuit L2b flows through port B2 to port B of the second main winding valve Vm2, and then flows through port T of the second main winding valve Vm2 into the second return oil circuit Lr2, returning to the oil tank.

[0103] Thus, in the hoisting mode, the hydraulic system is in an open system state, with the first pump P1 and the second pump P2 simultaneously driving the hoist motor M. The flow direction of the hydraulic oil in the hydraulic system is shown by the arrows. The first main winding valve Vm1 and the second main winding valve Vm2 are both fully open, and the flow rate to the motor M is controlled by controlling the output flow rate of the first pump P1 and the second pump P2.

[0104] In the hoisting mode described above, if the first pump P1 alone can meet the power and speed requirements for hoisting, and the pressure on the high-pressure side of the hydraulic system represented by the high-pressure oil circuit La is not high (below the set high-pressure side pressure limit), then only the first pump P1 can be activated, with the first main winding valve Vm1 in the first position; while the second pump P2 remains stopped, and the second main winding valve Vm2 is in the neutral position. At this time, the hydraulic system is also in an open system state, with only the first pump P1 participating in the drive of the motor M.

[0105] Next, refer to Figure 6 The hydraulic system is described in a winch-lifting composite mode, in which the first pump P1 and the second pump P2 jointly participate in driving the winch motor M to achieve winch lifting, and at the same time, the first pump P1 and the second pump P2 also participate in driving the first and second hydraulic actuators respectively.

[0106] Specifically, the balance valve V2 is in its original position, with its two ports disconnected. Both the first pump P1 and the second pump P2 are in operation. The first main winch valve Vm1 and the second main winch valve Vm2 are in their respective first valve positions (open system valve positions), allowing a portion of the hydraulic oil output from the first pump P1 and the second pump P2 to enter the motor M, while the hydraulic oil discharged from the motor M returns to the oil tank. This achieves the hoisting operation. This part is related to the previous section. Figure 5 The descriptions are the same, so they will not be repeated.

[0107] Simultaneously, the first main valve Vc1 is in its first or second valve position (depending on the operating requirements of the first hydraulic actuator). Therefore, a portion of the hydraulic oil output from the first pump P1 is transmitted to the P port of the first main valve Vc1, and then through the C port to the S port of the pressure compensation valve Vf1 and the first control terminal. The oil pressure at the first control terminal pushes the pressure compensation valve Vf1 into its first valve position, so that the S port and U port of the pressure compensation valve Vf1 are connected without throttling, and connected with the V port with throttling. The hydraulic oil flows through the S port and U port of the pressure compensation valve Vh1 to the D port or E port of the first main valve Vc1, and then through the A port or B port of the first main valve Vc1 to the port Xa1 or Xb1 to supply the first hydraulic actuator. The hydraulic oil that has performed work in the first hydraulic actuator returns to the port Xb1 or Xa1, and from the port Xb1 or Xa1 returns to the oil tank through the first return oil circuit Lr1.

[0108] The pressure compensation valve Vf1 can adjust the pressure at port C of the first main valve Vc1 by switching its valve position, making it equal to the pressure (load pressure) in the first load sensing oil circuit Lc1 plus the equivalent pressure of the spring of the pressure compensation valve Vf1. The pressure compensation valve Vh1 can adjust the pressure at port C of the first main valve Vm1 by switching its valve position, making it equal to the pressure (load pressure) in the first load sensing oil circuit Lc1 plus the equivalent pressure of the spring of the pressure compensation valve Vh1, thereby ensuring that the flow between each control main valve in the first valve block Vb1 is distributed according to the opening area of ​​the main valve core.

[0109] The second main valve Vc2 is in either its first or second position (depending on the operating requirements of the first hydraulic actuator) to supply a portion of the hydraulic oil output from the first pump P1 to the second hydraulic actuator. This is similar to the above description of the first pump P1 supplying hydraulic oil to the first hydraulic actuator via the first main valve Vc1, and will not be repeated here. Pressure compensation valves Vf2 and Vh2 can adjust the C-port pressure of the second main valve Vc2 and the second main valve Vm2 by switching their positions, thereby ensuring that the flow rate among the control main valves in the second valve block Vb2 is distributed according to the opening area of ​​the main valve core.

[0110] At this time, the hydraulic system is in an open system state, with the first pump P1 and the second pump P2 simultaneously driving the winch motor M. Simultaneously, the first pump drives the first hydraulic actuator, and the second pump drives the second hydraulic actuator. The flow direction of the hydraulic oil in the hydraulic system is shown by the arrows. The valve port areas of the first main winch valve Vm1, the second main winch valve Vm2, the first main valve Vc1, and the second main valve Vc2 are controlled electro-proportionally to achieve the distribution of the output flow of the first pump P1 between the motor M and the first hydraulic actuator, and the distribution of the output flow of the second pump P2 between the motor M and the second hydraulic actuator.

[0111] In the hoisting composite mode described above, if the first pump P1 alone can meet the power and speed required for hoisting, and the pressure on the high-pressure side of the hydraulic system represented by the high-pressure oil circuit La is not high (below the set high-pressure side pressure limit), then the first main hoisting valve Vm1 can be placed in the first valve position and the second main hoisting valve Vm2 can be placed in the neutral position, so that only the first pump P1 is used to drive the motor M.

[0112] In the hoisting lifting compound mode, the pressure in the first load sensing oil circuit Lc1 is the maximum load pressure borne by the first pump P1 from the motor M and the first hydraulic actuator. Therefore, the pressure at the second control end of the pressure compensation valves Vh1 and Vf1 is the maximum load pressure, so that the flow rate through the first main winch valve Vm1 and the first main valve Vc1 depends only on the valve port area of ​​each of them, and is independent of the actual load pressure of the motor M and the first hydraulic actuator, thus realizing the independent flow distribution of the two circuits.

[0113] Similarly, the pressure in the second load sensing oil circuit Lc2 is the maximum load pressure borne by the second pump P2 from the motor M and the second hydraulic actuator. Therefore, the pressure at the second control end of the pressure compensation valves Vh2 and Vf2 is the maximum load pressure, so that the flow through the second main valve Vm2 and the second main valve Vc2 depends only on the valve port area of ​​each of them, and is independent of the actual load pressure of the motor M and the second hydraulic actuator, thus realizing independent flow distribution of the two circuits.

[0114] Furthermore, by controlling the flow rate Q (valve orifice area A) of each main control valve, based on the flow formula (Q ~ A * ΔP)... 1 / 2 It is easy to control the pressure difference ΔP on the valve core of the main valve.

[0115] Furthermore, in the hoisting composite mode described above, if only one of the first and second hydraulic actuators needs to operate simultaneously during the hoisting operation, while the other does not, the main valve corresponding to the non-operating hydraulic actuator can be placed in the neutral position to cut off the hydraulic oil supply to that actuator. Thus, the operation of one of the first or second hydraulic actuators is achieved simultaneously with the hoisting operation.

[0116] Next, refer to Figure 7 Describe the winch lowering mode of the hydraulic system, wherein the first pump P1 operates in the positive displacement position, the second pump P2 operates in the negative displacement position (motor mode), and the load drives the winch motor M to be in pump mode.

[0117] The first main winding valve Vm1 is in its second valve position (closed system valve position), so that its P port is connected to the C port, its E port is connected to the B port, and its D port, A port, and T port are cut off. The hydraulic oil output from the first pump P1 to the first pressure oil circuit Lp1 is transmitted through the P port and C port of the first main winding valve Vm1 to the S port and the first control terminal of the pressure compensation valve Vh1. The oil pressure on the first control terminal pushes the pressure compensation valve Vh1 into its first valve position, so that the S port and U port of the pressure compensation valve Vh1 are connected without throttling, and connected with the V port with throttling. The hydraulic oil flows through the S port and U port of the pressure compensation valve Vh1 to the E port of the first main winding valve Vm1, and then through the B port of the first main winding valve Vm1 to port B1. From port B1, it is transmitted through the branch oil circuit L1b to the low-pressure oil circuit Lb, and then enters the motor M (pump mode) from the low-pressure port. At the same time, the hydraulic oil pressure in the low-pressure oil circuit Lb is transmitted to the control end of the balance valve V2 through the control oil circuit Lv (via the dual-way valve assembly V3), causing the balance valve V2 to switch to the working valve position and connect its two oil ports (preferably without throttling).

[0118] As the load decreases, it drives the winch motor M. The high-pressure hydraulic oil output from the high-pressure port of motor M (in pump mode) enters the high-pressure oil circuit La. Then, it enters the branch oil circuit L2a through the balance valve V2 (bypassing the check valve V1).

[0119] The second main winding valve Vm2 is in its second valve position (closed system valve position), so that its E port and P port are throttled and connected, its A port and D port are unthrottled and connected, and its C port, B port, and T port are cut off. Hydraulic oil in branch oil circuit L2a is transmitted through port A2 to port A of the second main winding valve Vm2, then leaves port D of the second main winding valve Vm2, enters the second main winding valve Vm2 through port E via the oil route with a check valve between port D and port E, and then enters the second pressure oil circuit Lp2 through port P of the second main winding valve Vm2. The high-pressure hydraulic oil in the second pressure oil circuit Lp2 enters the second pump P2, driving the second pump P2, which is in motor mode, to do work (absorb load potential energy). The second pump P2 outputs torque to the shaft connected to engine E, driving the first pump P1 and other accessories to recover load potential energy. After leaving the second pump P2, the hydraulic oil flows through the bidirectional oil circuit Lp3 to the input port of the first pump P1 and enters the first pump P1.

[0120] Both port A of the first main winding valve Vm1 and port B of the second main winding valve Vm2 are in the cut-off state, so there is no hydraulic oil flow in the branch oil circuits L1a and L2b.

[0121] This achieves a closed-loop circulation of hydraulic oil between the first pump P1, motor M, and second pump P2. At this time, the hydraulic circuit between the first pump P1, motor M, and second pump P2 is in a closed state, enabling the load lowering operation. By adjusting the displacement of the winch motor M, the first pump P1, and the second pump P2, the winch motor M can reach the speed required for the first pump P1 and the second pump P2 to jointly drive the winch motor M.

[0122] Next, refer to Figure 8 The description of the winch lowering compound mode (I) of the hydraulic system is as follows: the first pump P1 operates in the positive displacement position, the second pump P2 operates in the negative displacement position (motor mode), and the load drives the winch motor M to be in the pump mode.

[0123] The premise of this winch lowering composite mode (I) is that the hydraulic oil flow rate required for the second hydraulic actuator to perform the action is less than the flow rate of the high-pressure hydraulic oil returned by the motor M.

[0124] Specifically, the first main winding valve Vm1 and the second main winding valve Vm2 are in their respective second valve positions (closed system valve positions). The balancing valve V2 is switched to the working valve position. Thus, referring to the previous section... Figure 7 As shown in the description, the hydraulic circuit between the first pump P1, the motor M, and the second pump P2 is in a closed state, realizing the load lowering operation.

[0125] The first main valve Vc1 and the second main valve Vc2 are each in their first or second valve position (depending on the operating requirements of the corresponding hydraulic actuator). In this way, a portion of the output flow from the first pump P1 is supplied to the first hydraulic actuator through the first main valve Vc1, thereby enabling the first hydraulic actuator to operate simultaneously with the load being lowered. The remaining portion of the output flow from the first pump P1 flows through the first main valve Vm1 into the low-pressure oil circuit Lb, and then through Lb into the low-pressure port of the motor M.

[0126] On the other hand, as the load decreases, it drives the winch motor M, which outputs high-pressure hydraulic oil from its high-pressure port into the high-pressure oil circuit La. The oil then enters the second main winch valve Vm2 and is discharged into the second pressure oil circuit Lp2 via the P port of the second main winch valve Vm2. A portion of the high-pressure hydraulic oil in the second pressure oil circuit Lp2 enters the second pump P2, driving the second pump P2, which is in motor operation mode, to perform work (absorbing load potential energy). The other portion of the high-pressure hydraulic oil reaches the second main valve Vc2 and is supplied to the second hydraulic actuator, thus enabling the second hydraulic actuator to operate simultaneously with the load being lowered.

[0127] Next, refer to Figure 9The hydraulic system is described in the second description of the winch lowering compound mode, in which the first pump P1 operates in the positive displacement position, the second pump P2 operates in the positive displacement position, and the load drives the winch motor M to be in the pump operation mode.

[0128] The premise of this winch lowering composite mode (II) is that the hydraulic oil flow rate required for the second hydraulic actuator to perform the action is greater than the flow rate of the high-pressure hydraulic oil returned by the motor M.

[0129] Specifically, the first main winding valve Vm1 and the second main winding valve Vm2 are in their respective second valve positions (closed system valve positions). The balancing valve V2 is switched to the working valve position. Thus, referring to the previous section... Figure 7 As shown in the description, the hydraulic circuit between the first pump P1, the motor M, and the second pump P2 is in a closed state, realizing the load lowering operation.

[0130] The first main valve Vc1 is in either its first or second position (depending on the operating requirements of the corresponding hydraulic actuator). This allows a portion of the output flow from the first pump P1 to be supplied to the first hydraulic actuator via the first main valve Vc1, thereby enabling the first hydraulic actuator to operate simultaneously with the load being lowered. The remaining portion of the output flow from the first pump P1 flows through the first main valve into the low-pressure oil circuit Lb, and then through Lb into the low-pressure port of the motor M.

[0131] On the other hand, as the load decreases, it drives the winch motor M, which outputs high-pressure hydraulic oil from its high-pressure port into the high-pressure oil circuit La. In the high-pressure oil circuit La, the oil flows through the balance valve V2 to the second main winch valve Vm2, and then is discharged into the second pressure oil circuit Lp2 through the P port of the second main winch valve Vm2. Simultaneously, the second pump P2 operates in pump mode (positive displacement), drawing hydraulic oil from the oil tank through the bidirectional oil circuit Lp3 and also discharging it into the second pressure oil circuit Lp2. In the second pressure oil circuit Lp2, the hydraulic oil from the winch motor M and the hydraulic oil from the second pump P2 combine, and then are supplied to the second hydraulic actuator through the second main valve Vc2, thus enabling the second hydraulic actuator to operate simultaneously with the load lowering.

[0132] Understandable, Figure 8 , Figure 9 In the two winch lowering combined modes shown, if the first hydraulic actuator does not need to operate during the winch lowering operation, the first main valve Vc1 can be placed in the neutral position to cut off the supply of hydraulic oil to the first hydraulic actuator.

[0133] exist Figure 8 , Figure 9 In both of the winch lowering composite modes shown, the gravitational potential energy during load descent can be directly used to drive the second hydraulic actuator to do work, without any intermediate steps.

[0134] It is understandable that during the hoisting lowering operation, if the hydraulic oil flow rate required for the second hydraulic actuator to perform the action is exactly equal to the flow rate of the high-pressure hydraulic oil returned by the motor M, then the second pump P2 can be in a zero-displacement state.

[0135] According to the combined hydraulic system for construction machinery disclosed in this application, flexible switching between open-loop and closed-loop hydraulic circuits can be achieved simply by changing the valve position of the main winch valve, without increasing the complexity and cost of the hydraulic system. This hydraulic system retains the advantages of open hydraulic systems while also utilizing the gravitational potential energy of the load during winch lowering. Simultaneously, the system features pressure compensation, enabling independent flow distribution in compound operations regardless of load size, thus simplifying control logic. Furthermore, each main control valve is equipped with a corresponding pressure compensation valve, forming a load-independent flow distribution system. This ensures that the flow through each main control valve is only related to the valve orifice area and is independent of the load size, achieving independent flow distribution and facilitating control of the differential pressure on the valve core. This is crucial for realizing certain functions of construction machinery.

[0136] While this application has been described herein with reference to specific embodiments, the scope of this application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of this application.

Claims

1. An on / off combined hydraulic system with pressure compensation function, comprising: The hoisting motor (M) has its high-pressure port connected to the high-pressure oil circuit (La) and its low-pressure port connected to the low-pressure oil circuit (Lb). The first pump (P1) and the second pump (P2) are connected to the oil tank. The second pump (P2) is a two-quadrant pump that can operate in both pump and motor modes. The first port of the second pump (P2) is connected to the input port of the first pump (P1). A first main winding valve (Vm1) equipped with a first main winding pressure compensation valve (Vh1) is arranged between the output port of the first pump (P1) and the high-pressure oil circuit (La) and the low-pressure oil circuit (Lb). In the first valve position, the output port of the first pump (P1) is connected to the high-pressure oil circuit (La) and the low-pressure oil circuit (Lb) is connected to the oil tank by means of the first main winding pressure compensation valve (Vh1). In the second valve position, the output port of the first pump (P1) is connected to the low-pressure oil circuit (Lb) by means of the first main winding pressure compensation valve (Vh1). A second main winding valve (Vm2) equipped with a second main winding pressure compensation valve (Vh2) is arranged between the second port of the second pump (P2) and the high-pressure oil circuit (La) and the low-pressure oil circuit (Lb). In the first valve position, the second port of the second pump (P2) is connected to the high-pressure oil circuit (La) and the low-pressure oil circuit (Lb) is connected to the oil tank via the second main winding pressure compensation valve (Vh2). In the second valve position, the second port of the second pump (P2) is connected to the high-pressure oil circuit (La). The hydraulic system has the following features: In the hoisting rising mode, the first main hoist valve (Vm1) and the second main hoist valve (Vm2) are in their respective first valve positions, the first pump (P1) and the second pump (P2) are both operating in pump mode, the hoisting motor (M) is operating in motor mode, an open circuit is formed between the first pump (P1) and the motor (M), and an open circuit is also formed between the second pump (P2) and the motor (M). In the hoisting lowering mode, the first main winding valve (Vm1) and the second main winding valve (Vm2) are in their respective second valve positions. The first pump (P1) operates in pump mode, the second pump (P2) operates in motor mode, and the hoisting motor (M) operates in pump mode. A closed loop is formed between the first pump (P1), the second pump (P2), and the motor (M).

2. The opening and closing combined hydraulic system as described in claim 1, further comprising: A check valve (V1) installed in the high-pressure oil circuit (La) is oriented to allow hydraulic oil in the high-pressure oil circuit (La) to flow toward the winch motor (M) and to prevent reverse flow. A balance valve (V2) is arranged in parallel with the check valve (V1), and its two oil ports are connected to the high-pressure oil circuit (La) upstream and downstream of the check valve (V1), respectively. In the original position of the balance valve (V2), the two oil ports are cut off; in the working position of the balance valve (V2), the two oil ports are connected. In the hoisting upward mode, the balance valve (V2) is in its original position, and in the hoisting downward mode, the balance valve (V2) is in its working position.

3. The opening and closing combined hydraulic system as described in claim 2, wherein, When the balance valve (V2) is in its working position, the two ports are connected without throttling.

4. The opening and closing combined hydraulic system as described in claim 2 or 3, wherein, The valve position of the balance valve (V2) is controlled by the control terminal oil pressure, which is taken from the low-pressure oil circuit (Lb).

5. The opening and closing combined hydraulic system as described in any one of claims 1-4, further comprising: First hydraulic actuator; A first main valve (Vc1) equipped with a first main valve pressure compensation valve (Vf1) is configured to control the on / off connection between the output port of the first pump (P1) and the first hydraulic actuator via the first main valve pressure compensation valve (Vf1).

6. The opening and closing combined hydraulic system as described in claim 5, wherein, The first control end pressure of the first main valve pressure compensation valve (Vh1) and the first main valve pressure compensation valve (Vf1) is taken from the output pressure of the first pump (P1), and the second control end pressure is taken from the common first load sensing oil circuit (Lc1).

7. The opening and closing combined hydraulic system as described in any one of claims 1-6, further comprising: Second hydraulic actuator; The second main valve (Vc2) is equipped with a second main valve pressure compensation valve (Vf2) and is configured to control the on / off connection between the second port of the second pump (P2) and the second hydraulic actuator by means of the second main valve pressure compensation valve (Vf2).

8. The opening and closing combined hydraulic system as described in claim 7, wherein, The first control terminal pressure of the second main valve pressure compensation valve (Vh2) and the second main valve pressure compensation valve (Vf2) is taken from the output pressure of the second pump (P2), and the second control terminal pressure is taken from the common second load sensing oil circuit (Lc2).

9. The opening and closing combined hydraulic system as described in claim 7 or 8, wherein, The hydraulic system has a first winch lowering composite mode, wherein the first main winch valve (Vm1) and the second main winch valve (Vm2) are in their respective second valve positions, the first pump (P1) operates in pump mode, the second pump (P2) operates in motor mode, the winch motor (M) operates in pump mode, and the second port of the second pump (P2) is connected to the second hydraulic actuator through the second main valve (Vc2), thereby also connecting the high-pressure oil circuit (La) to the second hydraulic actuator. A portion of the hydraulic oil returning from the winch motor (M) drives the second pump (P2), and the other portion drives the second hydraulic actuator.

10. The opening and closing combined hydraulic system as described in any one of claims 7-9, wherein, The hydraulic system has a second winch lowering composite mode, wherein the first main winch valve (Vm1) and the second main winch valve (Vm2) are in their respective second valve positions, the first pump (P1) operates in pump mode, the second pump (P2) operates in pump mode, the winch motor (M) operates in pump mode, and the second port of the second pump (P2) is connected to the second hydraulic actuator through the second main valve (Vc2), thereby also connecting the high-pressure oil circuit (La) to the second hydraulic actuator. The hydraulic oil returning from the winch motor (M) and the hydraulic oil output from the second pump (P2) jointly drive the second hydraulic actuator.

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