Lifting hydraulic control system and vehicle

Abstract

The utility model relates to the field of vehicle technology, and in particular to a lifting hydraulic control system and a vehicle. The lifting hydraulic control system includes a lifting cylinder, a first proportional flow valve block, a reversing valve, a second proportional flow valve and a first overflow valve. When the piston rod of the lifting cylinder rises or falls, the oil in the rodless chamber and the rod chamber of the lifting cylinder can be flow-controlled through the first proportional flow valve and the second proportional flow valve respectively because the oil passes through the first proportional flow valve and the second proportional flow valve. Since the flow is controllable, the lifting speed and the lowering speed of the lifting cylinder can be controlled. The first overflow valve is used to ensure that when the oil in the rodless chamber of the lifting cylinder flows into the oil tank, the oil circuit pressure is kept constant to avoid the increase in oil circuit pressure caused by the sudden increase in oil flow, thereby achieving precise control of the lifting and lowering of the auxiliary tool.

Description

Technical Field

[0001] The utility model relates to the technical field of vehicles, in particular to a lifting hydraulic control system and a vehicle. Background Art

[0002] With the continuous development of the domestic agricultural industry, the demand for agricultural automation is also increasing, which requires tractors to accurately control the lowering and lifting of attachments. The tractor cylinder lifting control system can control the lifting cylinder of the tractor to control the lifting, lowering or floating of the tractor's attachments.

[0003] Chinese patent document CN218882626U proposes a tractor hydraulic system, which includes a hydraulic oil tank, a gear pump, a priority valve, a steering control valve group, a lifting control valve group, a steering cylinder, a multi-way valve control valve group and a lifting cylinder. The gear pump is connected to the spline in the spline shaft engine gear chamber, the oil inlet of the gear pump is connected to the hydraulic oil tank, the oil outlet of the gear pump is connected to the oil inlet of the priority valve, the AF port of the priority valve is connected to the P1 port of the steering control valve group, the BF port of the priority valve is connected to the P2 port of the lifting control valve group, and the CF port of the priority valve is connected to the P2 port of the steering control valve group. The port is connected to the ES port of the steering control valve group, the L port of the steering control valve group is connected to the L port of the steering cylinder, the R port of the steering control valve group is connected to the R port of the steering cylinder, the P3 port of the lifting control valve group is connected to the P2 port of the multi-way valve control valve group, the T1 port of the lifting control valve group is connected to the T2 port of the multi-way valve control valve group, the output link of the multi-way valve control valve group is connected to the quick-change connector, the DF port of the lifting control valve is connected to the rodless chamber of the lifting cylinder, the EF port of the lifting control valve group is connected to the rod chamber of the lifting cylinder, and the T2 port of the multi-way valve control valve group is connected to the hydraulic oil tank.

[0004] Although the above patent documents can realize the lifting, lowering or floating action of the tractor auxiliary implement, the tractor hydraulic system cannot accurately control the lifting and lowering of the auxiliary implement, that is, the tractor hydraulic system cannot accurately control the auxiliary implement.

[0005] Therefore, there is an urgent need for a lifting hydraulic control system to solve the above technical problems. Utility Model Content

[0006] The utility model aims to provide a lifting hydraulic control system and a vehicle, which can control the lifting speed and the lowering speed of the oil cylinder.

[0007] To achieve this purpose, the utility model adopts the following technical solutions:

[0008] On the one hand, a lifting hydraulic control system is provided, comprising:

[0009] Lifting cylinder;

[0010] A first proportional flow valve, used to control the lifting speed and lowering speed of the lifting cylinder;

[0011] The reversing valve is used to control the oil inlet of the first proportional flow valve to selectively connect to the rod chamber or the rodless chamber of the lifting cylinder.

[0012] A second proportional flow valve is used to control the oil return speed of the rodless chamber of the lifting cylinder;

[0013] A first relief valve, used to control the automatic pressurization of the lifting cylinder;

[0014] The reversing valve is respectively connected to the first proportional flow valve and the lifting cylinder, the second proportional flow valve is respectively connected to the lifting cylinder and the reversing valve, and the first overflow valve is connected to the lifting cylinder and the reversing valve.

[0015] As a preferred technical solution of the above-mentioned lifting hydraulic control system, the first relief valve is a proportional relief valve.

[0016] As a preferred technical solution of the above-mentioned lifting hydraulic control system, the first proportional flow valve is a three-way proportional flow valve; and / or the reversing valve is a three-position four-way solenoid valve.

[0017] As a preferred technical solution of the above-mentioned lifting hydraulic control system, a damping hole is arranged between the working port of the first proportional flow valve and the oil tank, and the aperture of the damping hole is smaller than the aperture of each working oil port of the first proportional flow valve.

[0018] As a preferred technical solution of the above-mentioned lifting hydraulic control system, the oil inlet of the reversing valve is connected to the working oil port of the first proportional flow valve, the oil inlet of the reversing valve is selectively connected to the first working oil port or the second working oil port of the reversing valve, the oil outlet of the reversing valve can be selectively connected to at least one of the first working oil port of the reversing valve and the second working oil port of the reversing valve, the oil outlet of the reversing valve is connected to the oil tank, and the second working oil port of the reversing valve is connected to the rod chamber of the lifting cylinder; and / or,

[0019] The first working oil port of the first relief valve is communicated with the rod chamber of the lifting cylinder and the second working oil port of the reversing valve respectively, and the second working oil port of the first relief valve is communicated with the oil tank.

[0020] As a preferred technical solution of the above-mentioned lifting hydraulic control system, it also includes a second overflow valve, which is used to connect the second proportional flow valve and the oil tank.

[0021] As a preferred technical solution of the above-mentioned lifting hydraulic control system, it also includes a compensation one-way valve, which is used to connect the oil tank and the lifting cylinder. The compensation one-way valve only allows oil to flow from the oil tank to the lifting cylinder.

[0022] As a preferred technical solution of the above-mentioned lifting hydraulic control system, it also includes a third overflow valve and an overflow check valve. The third overflow valve and the overflow check valve are arranged on the connecting oil line between the oil inlet of the first proportional flow valve and the oil tank, and the overflow check valve is arranged downstream of the third overflow valve.

[0023] As a preferred technical solution of the above-mentioned lifting hydraulic control system, the number of the lifting cylinders is two.

[0024] On the other hand, a vehicle is provided, comprising the lifting hydraulic control system described in any of the above schemes.

[0025] The utility model has at least the following beneficial effects:

[0026] When the piston rod of the lifting oil cylinder rises or falls, the oil in the rodless chamber and the rod chamber of the lifting oil cylinder can realize flow controllable through the first proportional flow valve and the second proportional flow valve respectively because the oil passes through the first proportional flow valve and the second proportional flow valve. Since the flow is controllable, the lifting speed and the lowering speed of the lifting oil cylinder can be controlled. The first relief valve is used to ensure that when the oil in the rodless chamber of the lifting oil cylinder flows into the oil tank, the oil circuit pressure is kept constant to avoid the increase of oil circuit pressure caused by the sudden increase of oil flow, thereby realizing the precise control of the lifting and lowering of the auxiliary tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0028] Figure 1 A hydraulic principle diagram of a lifting hydraulic control system provided in an embodiment of the utility model.

[0029] In the figure:

[0030] 1. Lifting cylinder; 2. First proportional flow valve; 21. Proportional flow valve body; 22. Pressure compensation valve; 3. Reversing valve; 4. Second proportional flow valve; 5. First overflow valve; 6. Second overflow valve; 7. Compensation check valve; 8. Damping hole; 9. Third overflow valve; 10. Overflow check valve. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0032] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] In the description of this embodiment, the terms "upper", "lower", "right", etc., are based on the directions or positions shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0035] like Figure 1As shown, this embodiment provides a lifting hydraulic control system, which includes a lifting cylinder 1, an oil tank, a hydraulic pump, a first proportional flow valve 2, a reversing valve 3, a second proportional flow valve 4 and a first overflow valve 5, wherein the piston rod of the lifting cylinder 1 is connected to the actuator to control the actuator to rise, fall or float; the oil tank is used to store oil and provide oil to the lifting cylinder 1; the oil inlet of the hydraulic pump is connected to the oil tank to provide power for the oil, and the first proportional flow valve 2 is used to control the lifting cylinder 1; the reversing valve 3 is used to control the oil inlet of the first proportional flow valve 2 to selectively connect to the rod chamber or the rodless chamber of the lifting cylinder 1, and the second proportional flow valve 4 is used to control the oil return speed of the rodless chamber of the lifting cylinder 1; the first overflow valve 5 is used to control the automatic pressurization of the lifting cylinder 1; wherein the reversing valve 3 is respectively connected to the first proportional flow valve 2 and the lifting cylinder 1, the second proportional flow valve 4 is respectively connected to the lifting cylinder 1 and the reversing valve 3, and the first overflow valve 5 is connected to the lifting cylinder 1 and the reversing valve 3.

[0036] In the initial state, the coil S1 of the first proportional flow valve 2 is not energized, and the oil only enters the P1 port through the oil return port of the first proportional flow valve 2 to achieve the purpose of oil return. When lifting, the coil S1 of the first proportional flow valve 2 and the coil Y1 of the reversing valve 3 are energized, and the oil enters the first proportional flow valve 2 through the P port and flows into the reversing valve 3. Since the first proportional flow valve 2 can realize flow control, the lifting speed of the lifting cylinder 1 can be controlled on the basis of flow control, which improves the control accuracy of the system. When forced to descend, the coil Y2 of the reversing valve 3 and the coil S1 of the first proportional flow valve 2 are energized, the left position of the first proportional flow valve 2 is turned on, and the right position of the reversing valve 3 is turned on. The oil enters the rod chamber of the lifting cylinder 1 through the reversing valve 3, and the oil in the rodless chamber of the lifting cylinder 1 flows into the oil tank through the reversing valve 3. At this time, the descending speed of the lifting cylinder 1 is controlled by the second proportional flow valve 4. The first proportional flow valve 2 can realize controllable descending working speed of the lifting cylinder 1 on the basis of controllable flow.

[0037] When the piston rod of the lifting cylinder 1 descends under the action of its own weight, the coil S2 of the second proportional flow valve 4 is energized, the left position of the second proportional flow valve 4 is turned on, and the oil in the rodless chamber of the lifting cylinder 1 enters the oil tank through the second proportional flow valve 4. Since the second proportional flow valve 4 can adjust the outflow flow of the oil in the rodless chamber of the lifting cylinder 1, the descending speed of the piston rod of the lifting cylinder 1 can be adjusted.

[0038] When the floating function of the lifting cylinder 1 is required, the coil S2 of the second proportional flow valve 4 is energized, and the left position of the second proportional flow valve 4 is turned on. At this time, the reversing valve 3 is in the normal position, and the valve core of the second proportional flow valve 4 is fully opened. The oil in the rod chamber and the rodless chamber of the lifting cylinder 1 flows to the oil tank. The lifting cylinder 1 realizes the floating function under the action of the deadweight of the attachment, and the agricultural attachment can float according to the terrain. The first overflow valve 5 is used to ensure that when the oil in the rodless chamber of the lifting cylinder 1 flows into the oil tank, the oil circuit pressure is kept constant to avoid the increase of oil circuit pressure caused by the sudden increase of oil flow.

[0039] In summary, when the piston rod of the lifting cylinder 1 rises or falls, the oil in the rodless chamber and the rod chamber of the lifting cylinder 1 can be flow-controlled through the first proportional flow valve 2 and the second proportional flow valve 4 respectively because the oil passes through the first proportional flow valve 2 and the second proportional flow valve 4. Since the flow is controllable, the lifting speed and the lowering speed of the lifting cylinder 1 can be controlled. The first overflow valve 5 is used to ensure that when the oil in the rodless chamber of the lifting cylinder 1 flows into the oil tank, the oil circuit pressure is kept constant to avoid the increase of the oil circuit pressure caused by the sudden increase of the oil flow, thereby realizing the precise control of the lifting and lowering of the auxiliary tool.

[0040] It should be noted that the second proportional flow valve 4 can selectively make the reversing valve 3 unidirectionally communicate with the rodless chamber of the lifting cylinder 1, or the second proportional flow valve 4 can make the reversing valve 3 communicate with the rodless chamber of the lifting cylinder 1. Specifically, a one-way structure is provided between the first working oil port and the second working oil port of the second proportional flow valve 4, and the one-way structure only allows the oil to flow from the second proportional flow valve 4 to the lifting cylinder 1. The second proportional flow valve 4 can control the load holding of the lifting cylinder 1, control the self-weight descending speed and realize the floating function of the actuator.

[0041] When the piston rod of the lifting cylinder 1 descends under the action of its own weight, the coil S2 of the second proportional flow valve 4 is energized, the left position of the second proportional flow valve 4 is turned on, and the oil in the rodless chamber of the lifting cylinder 1 enters the oil tank through the second proportional flow valve 4. Since the second proportional flow valve 4 can adjust the outflow flow of the oil in the rodless chamber of the lifting cylinder 1, the descending speed of the piston rod of the lifting cylinder 1 can be adjusted.

[0042] It should be noted that, in some embodiments, the oil inlet of the reversing valve 3 is connected to the oil outlet of the first proportional flow valve 2, the oil inlet of the reversing valve 3 is selectively connected to the first working oil port or the second working oil port of the reversing valve 3, the oil outlet of the reversing valve 3 can be selectively connected to at least one of the first working oil port of the reversing valve 3 and the second working oil port of the reversing valve 3, the oil outlet of the reversing valve 3 is connected to the oil tank, and the second working oil port of the reversing valve 3 is connected to the rod chamber of the lifting cylinder 1. The first working oil port of the first relief valve 5 is respectively connected to the rod chamber of the lifting cylinder 1 and the second working oil port of the reversing valve 3, and the second working oil port of the first relief valve 5 is connected to the oil tank. It can be understood that the first relief valve 5 is used to ensure that when the oil in the rodless chamber of the lifting cylinder 1 flows into the oil tank, the oil circuit pressure is kept constant to avoid the increase of the oil circuit pressure caused by the sudden increase of the oil flow.

[0043] In some embodiments, the lifting hydraulic control system further includes a second relief valve 6, the first working oil port of the second relief valve 6 is connected to the second working oil port of the second proportional flow valve 4 and the rodless chamber of the lifting cylinder 1, the second working oil port of the second relief valve 6 is connected to the oil tank, and the second relief valve 6 is used to prevent the hydraulic oil pressure flowing out of the flow control valve from increasing, and the hydraulic oil pressure entering the rodless chamber of the lifting cylinder 1 suddenly increases, causing the piston rod of the lifting cylinder 1 to extend unstably. Both the first relief valve 5 and the second relief valve 6 can achieve the purpose of protecting the lifting hydraulic control system.

[0044] Furthermore, the first relief valve 5 is a proportional relief valve. The proportional relief valve can adjust its own opening, and when the piston rod (ie, the actuator) of the lifting cylinder 1 is manually forced to descend, the first relief valve 5 can increase the relief pressure, thereby ensuring the safe operation of the system.

[0045] In some embodiments, the first proportional flow valve 2 includes a proportional flow valve body 21 and a pressure compensating valve 22. Specifically, the oil outlet of the hydraulic pump is respectively connected to the oil inlet of the pressure compensating valve 22 and the first oil inlet of the proportional flow valve body 21, the oil outlet of the hydraulic pump is also respectively connected to the first hydraulic control end and the second hydraulic control end of the proportional flow valve body 21, the oil outlet of the proportional flow valve body 21 is connected to the second oil inlet of the pressure compensating valve 22, the oil inlet of the proportional flow valve body 21 is selectively connected or disconnected with the oil outlet of the proportional flow valve body 21, the first oil inlet of the pressure compensating valve 22 is connected to the first hydraulic control end of the pressure compensating valve 22 and the pressure compensating valve 22 The return oil port is connected, the second oil inlet of the pressure compensating valve 22 is connected to the second hydraulic control end, the second oil inlet of the pressure compensating valve 22 is selectively connected or disconnected with the oil outlet of the pressure compensating valve 22, and the first oil inlet of the pressure compensating valve 22 is selectively connected or disconnected with the oil return port of the pressure compensating valve 22; the oil inlet of the reversing valve 3 is connected to the oil outlet of the pressure compensating valve 22, the oil inlet of the reversing valve 3 is selectively connected to the first working oil port or the second working oil port of the reversing valve 3, the oil outlet of the reversing valve 3 can be rotatably connected to at least one of the first working oil port and the second working oil port of the reversing valve 3, and the second working oil port of the reversing valve 3 is connected to the rod chamber of the lifting cylinder 1.

[0046] In the initial state, the coil S1 of the first proportional flow valve 2 shall not be energized, the right position of the first proportional flow valve 2 is turned on, and the oil of the hydraulic pump only passes through the pressure compensation valve 22. Since the first hydraulic control end of the pressure compensation valve 22 is filled with oil, the right position is turned on, and the oil passes through the first oil inlet of the pressure compensation valve 22 and the oil return port of the pressure compensation valve 22 to enter the P1 port to achieve the purpose of oil return.

[0047] During lifting, the coil S1 of the proportional flow valve body 21 and the coil Y1 of the reversing valve 3 are energized, and the oil enters the oil inlet of the proportional flow valve body 21 through the oil outlet P of the hydraulic pump. The coil S1 is energized, and the left position of the proportional flow valve body 21 is turned on. At the moment of conduction, the pressure at the first hydraulic control end and the second hydraulic control end of the pressure compensation valve 22 are the same. As the control current of the coil S1 of the proportional flow valve body 21 increases, the opening of the proportional flow valve body 21 increases. Before the valve core of the pressure compensation valve 22 is not actuated, the opening of the pressure compensation valve 22 remains unchanged, but the pressure on the upstream side of the pressure compensation valve 22 (that is, the pressure at the oil outlet of the proportional flow valve body 21) increases. This pressure enters the spring side of the pressure compensation valve 22 with the oil and pushes the valve core of the pressure compensation valve 22 to actuate so as to increase the opening of the pressure compensation valve 22. As the pressures before and after the proportional flow valve body 21 and the spring at both ends of the pressure compensation valve 22 reach equilibrium, the flow through the proportional flow valve body 21 can be made independent of the oil outlet pressure of the hydraulic pump. When the control signal of the coil S1 of the proportional flow valve body 21 decreases, the principle is similar and will not be described. The above hydraulic system can better control the lifting cylinder 1, and the oil inlet flow rate can be controlled independently of the load. Since the proportional flow valve body 21 can realize flow control, the lifting speed of the lifting cylinder 1 can be controlled on the basis of flow control, thereby improving the control accuracy of the system.

[0048] When forced to descend, the coil Y2 of the reversing valve 3 and the coil S1 of the proportional flow valve body 21 are energized, the left position of the proportional flow valve body 21 is turned on, the right position of the reversing valve 3 is turned on, and the oil enters the rod chamber of the lifting cylinder 1 through the second working oil port of the reversing valve 3, while the oil in the rodless chamber of the lifting cylinder 1 flows into the oil tank through the first working oil port of the reversing valve 3 and the outlet of the reversing valve 3. The specific principle is similar to the principle of the above-mentioned lifting, and will not be described. On the basis of controllable flow, the controllable descending working speed of the lifting cylinder 1 can be achieved.

[0049] In some embodiments, the lifting hydraulic control system further includes a compensation check valve 7, the oil inlet of the compensation check valve 7 is connected to the oil tank, the compensation check valve 7 is used to connect the oil tank and the lifting cylinder 1, and the compensation check valve 7 only allows oil to flow from the oil tank to the lifting cylinder 1. The oil outlet of the compensation check valve 7 is connected to the rod chamber of the lifting cylinder 1. The function of the compensation check valve 7 is to force the lifting cylinder 1 to return to its initial state when a fault occurs in the proportional flow valve block 2. Since the pressure at the R2 port is greater than the pressure in the rod chamber, the compensation check valve 7 can achieve a rapid descent of the cylinder 1, so that the oil can enter the rod chamber through the compensation check valve 7 after passing through the R2 port.

[0050] In some embodiments, a damping hole 8 is provided between the oil outlet of the first proportional flow valve 2 (i.e., the oil outlet of the pressure compensation valve 22) and the oil tank. Such a setting can ensure that the oil entering from the proportional flow valve body 21 is returned through the oil return port of the pressure compensation valve 22. The aperture of the damping hole 8 is smaller than the aperture of each working oil port of the first proportional flow valve 2. The setting of the damping hole 8 can prevent the P port from being blocked, so as to ensure that energy consumption is reduced.

[0051] In order to ensure that the oil pressure entering the first proportional flow valve 2 is not greater than the allowable pressure of the first proportional flow valve 2, in some embodiments, the lifting hydraulic control system further includes a third relief valve 9 and a relief check valve 10, and the third relief valve 9 and the relief check valve 10 are provided on the connecting oil path between the oil outlet P of the hydraulic pump and the oil tank, and the relief check valve 10 is located downstream of the third relief valve 9. The third relief valve 9 can ensure that the pressure entering the first proportional flow valve 2 is constant, thereby improving the safety of the system, and the relief check valve 10 can prevent the oil in the oil tank from flowing back.

[0052] It is understandable that the first proportional flow valve 2 is a three-way flow valve. In some embodiments, the proportional flow valve body 21 and the second proportional flow valve 4 are both two-position two-way valves, and the pressure compensation valve 22 is a two-position three-way valve.

[0053] In some embodiments, the reversing valve 3 is a three-position four-way solenoid valve.

[0054] In some embodiments, there are two lifting cylinders 1. The two lifting cylinders 1 work together to achieve stable lifting, lowering or floating of the auxiliary tool.

[0055] The embodiment of the utility model further provides a vehicle, which includes the lifting hydraulic control system provided in the above embodiment. For example, the vehicle is a tractor or other agricultural machinery, and the actuator is an auxiliary tool of the tractor.

[0056] Since the vehicle of the embodiment of the present invention includes the above-mentioned lifting hydraulic control system, the vehicle has all the advantages and beneficial effects of the above-mentioned embodiments, which will not be described in detail here.

[0057] In addition, the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. Lifting hydraulic control system, characterized in that: include: Lifting cylinder (1); A first proportional flow valve (2) for controlling the lifting speed and lowering speed of the lifting cylinder (1); The reversing valve (3) is used to control the oil inlet of the first proportional flow valve (2) to selectively connect to the rod chamber or the rodless chamber of the lifting cylinder (1). A second proportional flow valve (4) for controlling the oil return speed of the rodless chamber of the lifting cylinder (1); A first overflow valve (5) for controlling the automatic pressurization of the lifting cylinder (1); The reversing valve (3) is respectively connected to the first proportional flow valve (2) and the lifting cylinder (1); the second proportional flow valve (4) is respectively connected to the lifting cylinder (1) and the reversing valve (3); and the first overflow valve (5) is connected to the lifting cylinder (1) and the reversing valve (3).

2. The lifting hydraulic control system according to claim 1, characterized in that: The first relief valve (5) is a proportional relief valve.

3. The lifting hydraulic control system according to claim 1, characterized in that: The first proportional flow valve (2) is a three-way flow valve; and / or the reversing valve (3) is a three-position four-way solenoid valve.

4. The lifting hydraulic control system according to claim 1, characterized in that: A damping hole (8) is provided between the oil outlet of the first proportional flow valve (2) and the oil tank, and the aperture of the damping hole (8) is smaller than the aperture of each working oil port of the first proportional flow valve (2).

5. The lifting hydraulic control system according to claim 1, characterized in that: The oil inlet of the reversing valve (3) is connected to the working oil port of the first proportional flow valve (2), the oil inlet of the reversing valve (3) is selectively connected to the first working oil port or the second working oil port of the reversing valve (3), the oil outlet of the reversing valve (3) can be selectively connected to at least one of the first working oil port of the reversing valve (3) and the second working oil port of the reversing valve (3), the oil outlet of the reversing valve (3) is connected to the oil tank, and the second working oil port of the reversing valve (3) is connected to the rod chamber of the lifting cylinder (1); and / or, The first working oil port of the first overflow valve (5) is respectively connected to the rod chamber of the lifting cylinder (1) and the second working oil port of the reversing valve (3), and the second working oil port of the first overflow valve (5) is connected to the oil tank.

6. The lifting hydraulic control system according to claim 1, characterized in that: It also comprises a second overflow valve (6), wherein the second overflow valve (6) is used to connect the second proportional flow valve (4) and the oil tank.

7. The lifting hydraulic control system according to claim 1, characterized in that: It also comprises a compensation check valve (7), which is used to connect the oil tank and the lifting cylinder (1), and the compensation check valve (7) only allows oil to flow from the oil tank to the lifting cylinder (1).

8. The lifting hydraulic control system according to claim 1, characterized in that: The invention also comprises a third overflow valve (9) and an overflow check valve (10), wherein the third overflow valve (9) and the overflow check valve (10) are arranged on the oil path connecting the oil inlet of the first proportional flow valve (2) and the oil tank, and the overflow check valve (10) is arranged downstream of the third overflow valve (9).

9. The lifting hydraulic control system according to claim 1, characterized in that: The number of the lifting cylinders (1) is two.

10. A vehicle, characterized in that Comprising a lifting hydraulic control system as described in any one of claims 1-9.

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