Loader hydraulic system and loader

Abstract

The present invention relates to a loader hydraulic system and a loader, belonging to the technical field of engineering machinery, comprising a hydraulic oil tank, a double gear pump, a third hydraulic pump, a working hydraulic cylinder and a steering hydraulic cylinder; the double gear pump comprises a first hydraulic pump and a second hydraulic pump, the first hydraulic pump, the second hydraulic pump and the third hydraulic pump are all connected to the hydraulic oil tank, the steering hydraulic cylinder is connected to a steering gear, and the third hydraulic pump is connected to the working hydraulic cylinder through a multi-way valve; the priority valve is connected to the multi-way valve, and a priority unloading valve is also connected between the double gear pump and the priority valve; the purpose of the present invention is to overcome the deficiencies in the prior art, to provide a loader hydraulic system and a loader, to avoid the heavy idle speed and excessive energy loss of the engine at low speed, to ensure the power of the engine and the operating efficiency of the whole machine, to reduce the complexity of the hydraulic system, and to make manufacturing, maintenance and care more convenient.

Description

Technical Field

[0001] The invention relates to a loader hydraulic system and a loader, belonging to the technical field of engineering machinery. Background Art

[0002] The hydraulic system of a loader is generally composed of a working hydraulic system and a steering hydraulic system. The working hydraulic system is generally composed of a working pump, a multi-way valve, a working hydraulic cylinder and its pipelines; the steering hydraulic system is generally composed of a steering pump, a priority valve, a steering gear and its pipelines;

[0003] In the prior art, there are generally five solutions for the hydraulic system of a loader:

[0004] The first solution is a dual-pump non-confluent system, that is, the working pump supplies the working hydraulic cylinder in the working device alone, and the steering pump supplies the steering cylinder alone;

[0005] The second solution is a dual-pump merging system, where the steering pump supplies the steering cylinder alone, and the excess flow is combined with the working pump to supply the working hydraulic cylinder in the working device;

[0006] The third solution is a three-pump system, with the steering system using a merge-split flow technique and the working system using a separate supply to the working device;

[0007] The fourth type is a fixed-variable combined hydraulic system, where the steering system uses a variable system and the working system uses a quantitative system;

[0008] The fifth type uses a fully variable hydraulic system. The working system uses a load sensing variable to provide the best matching flow for the working hydraulic system. The steering system also uses a variable system to achieve the flow required by the steering system.

[0009] Among the above five solutions, the hydraulic systems of Solution 4 and Solution 5 are relatively complex, and the manufacturing, maintenance and upkeep costs are relatively high;

[0010] Solution 1: The hydraulic system is simple, but the pump displacement will be large, the hydraulic system will occupy a large amount of power, and the power loss will be large;

[0011] Solution 2 is to solve the problem of heavy steering when the engine is idling. The displacement of the steering pump cannot be too small, but when the engine is running at high speed, the energy loss will be relatively large.

[0012] Solution three solves the problems of heavy idle speed and energy loss at low engine speeds, but existing users are increasingly overloading and have higher and higher requirements for overall machine operating efficiency. However, due to engine power limitations, it is difficult to make further improvements. Summary of the invention

[0013] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a loader hydraulic system and a loader, which avoid the heavy idle speed and excessive energy loss of the engine at low speed, ensure the power of the engine and the operating efficiency of the whole machine, reduce the complexity of the hydraulic system, and make manufacturing, maintenance and care more convenient.

[0014] To achieve the above object, the present invention adopts the following technical solution:

[0015] A loader hydraulic system comprises a hydraulic oil tank, a double gear pump, a third hydraulic pump, a working hydraulic cylinder and a steering hydraulic cylinder;

[0016] The double gear pump comprises a first hydraulic pump and a second hydraulic pump, the first hydraulic pump, the second hydraulic pump and the third hydraulic pump are all connected to the hydraulic oil tank, the steering hydraulic cylinder is connected to a steering gear, and the steering gear is connected to the double gear pump through a priority valve;

[0017] The third hydraulic pump is connected to the working hydraulic cylinder through a multi-way valve; the priority valve is connected to the multi-way valve and can provide hydraulic fluid to the working hydraulic cylinder through the multi-way valve;

[0018] A priority unloading valve is also connected between the double gear pump and the priority valve, the oil return port of the priority unloading valve is connected to the hydraulic oil tank, the priority unloading valve is connected to the steering gear, and the priority unloading valve is connected to the multi-way valve;

[0019] There are multiple working hydraulic cylinders, and the multi-way valve is provided with multiple working ports, which are respectively connected to the corresponding working hydraulic cylinders.

[0020] Further, the priority unloading valve includes a first reversing valve, a second reversing valve, a first check valve and a second check valve, the first working port of the priority unloading valve is connected to the oil inlet of the priority valve through the first check valve, the second working port of the priority unloading valve is connected to the oil inlet of the multi-way valve through the second check valve, and the oil return port of the priority unloading valve is connected to the hydraulic oil tank through the second reversing valve; the first reversing valve can control the flow of the first working port and the second working port of the priority unloading valve; the second reversing valve can control the flow of the second working port and the oil return port of the priority unloading valve.

[0021] Further, the first reversing valve has a first position and a second position, the right end of the first reversing valve is provided with a first control oil circuit of the first reversing valve and a first spring, the left end of the first reversing valve is provided with a first control oil circuit of the first reversing valve, the steering gear is provided with a steering gear feedback oil circuit, the first control oil circuit of the first reversing valve is connected to the steering gear feedback oil circuit; the second control oil circuit of the first reversing valve is connected to the first hydraulic pump.

[0022] Furthermore, a damper is provided at the left end of the first reversing valve, and the damper can slow down the conversion of the first reversing valve from the first position to the second position.

[0023] Furthermore, the second reversing valve has a third position and a fourth position, the upper end of the second reversing valve is connected to the second working port of the priority unloading valve, and the lower end of the second reversing valve is provided with a second spring. When the pressure of the second working port of the priority unloading valve is greater than the elastic force of the second spring, the hydraulic fluid of the second hydraulic pump can flow to the hydraulic oil tank through the oil outlet of the second reversing valve, thereby unloading the second hydraulic pump.

[0024] Further, the above-mentioned loader hydraulic system also includes a pilot oil source valve and a pilot valve, the pilot oil source valve is connected to the first hydraulic pump, the pilot oil source valve is connected to the third hydraulic pump, the oil outlet of the pilot oil source valve is connected to the oil inlet of the pilot valve, and the oil return port of the pilot oil source valve is connected to the hydraulic oil tank;

[0025] The pilot valve is provided with a plurality of oil outlets which are respectively communicated with corresponding pilot oil outlets on the multi-way valve.

[0026] Furthermore, the pilot valve is a hydraulically controlled pilot valve, the multi-way valve is an open center multi-way valve, and the steering gear is a load sensing full hydraulic steering gear.

[0027] Further, the first working port of the priority unloading valve is communicated with the first working port of the priority valve.

[0028] Furthermore, the return port of the multi-way valve is connected to the hydraulic oil tank via a multi-way valve return pipeline, and a radiator and an oil return filter are arranged in the multi-way valve return pipeline.

[0029] A loader comprises the above-mentioned loader hydraulic system.

[0030] This technical solution reduces the complexity of the hydraulic system and makes manufacturing, maintenance and servicing more convenient.

[0031] This technical solution adopts a priority unloading valve, which can detect the pressure of the corresponding oil port under different working conditions of the working system, and can use the engine power with maximum efficiency in overload conditions to ensure the joint operation efficiency of the whole machine and the traction of the whole vehicle;

[0032] This technical solution adopts a priority unloading valve to solve the problems in the prior art that when the loader load steering hydraulic system is idling, the steering pump flow is insufficient, resulting in heavy steering when turning at low speed, and the steering pump energy is wasted and inefficient when the engine is running at high speed.

[0033] This technical solution is equipped with a radiator and an oil return filter, which can ensure operational stability and safety; it can reduce the entry of impurities into the oil tank and hydraulic system, ensuring operational safety and equipment life. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The schematic diagram of the hydraulic system of a loader provided by the embodiment of the present invention is Figure 1 ;

[0035] Figure 2 It is a structural schematic diagram of a priority unloading valve of a loader hydraulic system provided by an embodiment of the present invention;

[0036] Figure 3 The schematic diagram of the hydraulic system of a loader provided by the embodiment of the present invention is Figure 2 .

[0037] Explanation of reference numerals: 1-hydraulic oil tank, 2-dual gear pump, 3-third hydraulic pump, 4-working hydraulic cylinder, 5-steering hydraulic cylinder, 6-first hydraulic pump, 7-second hydraulic pump, 8-steering gear, 9-priority valve, 10-multi-way valve, 11-priority unloading valve, 12-first reversing valve, 13-second reversing valve, 14-first check valve, 15-second check valve, 16-first spring, 17-second spring, 18-pilot oil source valve, 19-pilot valve, 20-radiator, 21-return oil filter, 22-damping. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0041] As attached Figure 1-2 The loader hydraulic system comprises a hydraulic oil tank 1, a double gear pump 2, a third hydraulic pump 3, a working hydraulic cylinder 4 and a steering hydraulic cylinder 5;

[0042] The double gear pump includes a first hydraulic pump 6 and a second hydraulic pump 7. The oil inlets of the first hydraulic pump, the second hydraulic pump and the third hydraulic pump are all connected to the hydraulic oil tank and can obtain hydraulic fluid from the hydraulic oil tank. The steering hydraulic cylinder is connected to a steering gear 8, and the steering gear is connected to the double gear pump through a priority valve 9.

[0043] The third hydraulic pump is connected to the working hydraulic cylinder via a multi-way valve 10; the priority valve is connected to the multi-way valve and can provide hydraulic fluid to the working hydraulic cylinder via the multi-way valve;

[0044] There are multiple working hydraulic cylinders, and the multi-way valve is provided with multiple working ports, which are respectively connected to the corresponding working hydraulic cylinders;

[0045] The specific connections of the above-mentioned multiple components are as follows: the oil inlet port P of the priority valve is connected to the oil outlet port of the first hydraulic pump, the first working oil port CF of the priority valve is connected to the oil inlet port of the steering gear, and the hydraulic fluid is provided to the steering hydraulic cylinder through the steering gear; the second working oil port EF of the priority valve is connected to the oil inlet port of the multi-way valve, and the redundant hydraulic fluid is provided to the working hydraulic cylinder through the multi-way valve;

[0046] The oil outlet of the third hydraulic pump is connected to the oil inlet P of the multi-way valve, and can provide hydraulic fluid to the working hydraulic cylinder;

[0047] The second working port P3 of the second hydraulic pump is connected to the oil inlet P of the multi-way valve, and can provide hydraulic fluid to the working hydraulic cylinder;

[0048] The steering gear is a load sensing fully hydraulic steering gear; the steering gear can extend or retract the piston rod of the steering hydraulic cylinder, such as Figure 1As shown, the rodless chamber of one steering hydraulic cylinder is connected to the R port of the steering gear, and the rod chamber is connected to the L port of the steering gear; the rodless chamber of the other steering hydraulic cylinder is connected to the L port of the steering gear, and the rod chamber is connected to the R port of the steering gear, so that the steering hydraulic cylinders in the chain move in opposite directions synchronously, and when the piston rod of one steering hydraulic cylinder is extended, the piston rod of the other steering hydraulic cylinder is retracted, and the two steering hydraulic cylinders cooperate to drive the wheels to steer, and the speed of the movement of the steering hydraulic cylinders is controlled by the input of the steering gear;

[0049] The multi-way valve is an open center multi-way valve; the multi-way valve has an oil inlet P, a first working port and a second working port, pilot oil ports a1, b1, a2, b2, and a return port T; the first working port of the multi-way valve is connected to the first working hydraulic cylinder. In this embodiment, the second working port of the multi-way valve is connected to the second working hydraulic cylinder, and the return port T of the multi-way valve is connected to the hydraulic oil tank through an oil return pipeline; each working port of the multi-way valve is connected to a corresponding working hydraulic cylinder, and the working hydraulic cylinder is used to drive the working parts to move; so as to realize the loader bucket to perform actions such as raising the arm, lowering the arm, retracting the bucket, and unloading;

[0050] A priority unloading valve 11 is also connected between the double gear pump and the priority valve, the oil return port of the priority unloading valve is connected to the hydraulic oil tank, the priority unloading valve is connected to the steering gear, and the priority unloading valve is connected to the multi-way valve;

[0051] like Figure 2 As shown, an embodiment, the priority unloading valve includes a first reversing valve 12, a second reversing valve 13, a first check valve 14 and a second check valve 15, the first working port P2 of the priority unloading valve is connected to the oil inlet P port of the priority valve through the first check valve, the second working port P3 of the priority unloading valve is connected to the oil inlet port of the multi-way valve through the second check valve, and the oil return port T2 of the priority unloading valve is connected to the hydraulic oil tank through the second reversing valve; the first reversing valve can control the flow of the first working port P2 and the second working port P3 of the priority unloading valve; the second reversing valve can control the flow of the second working port P3 and the oil return port T2 of the priority unloading valve.

[0052] More specifically, the first reversing valve has a first position and a second position, a first reversing valve first control oil circuit LS1 and a ΔP1 first spring 16 are provided at the right end of the first reversing valve, a first reversing valve second control oil circuit LS2 is provided at the left end of the first reversing valve, a steering gear feedback oil circuit LS is provided on the steering gear, the first reversing valve first control oil circuit is connected to the steering gear feedback oil circuit; the first reversing valve second control oil circuit LS2 is connected to the first hydraulic pump;

[0053] In one embodiment, a damper 22 is further provided at the left end of the first reversing valve, and the damper can slow down the conversion of the first reversing valve from the first position to the second position, reduce the impact, and ensure the safety of use and the service life of the components;

[0054] More specifically, the second reversing valve has a third position and a fourth position, the upper end of the second reversing valve is connected to the second working port P3 of the priority unloading valve, and the lower end of the second reversing valve is provided with a △P2 second spring 17. When the pressure of the second working port P3 of the priority unloading valve is greater than the elastic force of the △P2 second spring, the hydraulic fluid of the second hydraulic pump can flow to the hydraulic oil tank through the oil outlet T2 of the second reversing valve, thereby unloading the second hydraulic pump;

[0055] The specific usage of the priority unloading valve is as follows:

[0056] When the steering gear and the working hydraulic cylinder are not in motion, the pressure at the oil outlet of the first hydraulic pump is lower than the elastic force of the first spring △P1, which will cause the first reversing valve to be in the first position. At this time, the hydraulic fluid of the second hydraulic pump enters the priority valve from the first working port P2 of the priority unloading valve, enters the middle position of the multi-way valve from the second working oil port EF of the priority valve, and flows back to the hydraulic oil tank;

[0057] When the steering gear is not in motion and the working hydraulic cylinder is in motion, when the pressure at the oil outlet of the first hydraulic pump is lower than the elastic force of the first spring △P1, the first reversing valve will be in the first position, and the hydraulic fluid of the second hydraulic pump will enter the priority valve from the first working port P2 of the priority unloading valve, and enter the P port of the multi-way valve from the second working oil port EF of the priority valve to provide hydraulic fluid for the working hydraulic cylinder;

[0058] When the load of the working hydraulic cylinder continues to increase, the pressure at the oil outlet of the first hydraulic pump is greater than the elastic force of the first spring △P1 and less than the elastic force of the second spring △P2, the first reversing valve is in the second position, the second reversing valve is in the third position, and the hydraulic fluid of the second hydraulic pump enters the oil inlet port P of the multi-way valve from the second working port P3 of the priority unloading valve to provide hydraulic fluid for the working hydraulic cylinder;

[0059] When the load of the working hydraulic cylinder continues to increase and the load pressure is greater than the elastic force of the second spring △P2, the first reversing valve will be in the second position, and the second reversing valve will be in the fourth position. The hydraulic fluid of the second hydraulic pump will flow from the return oil port T of the priority unloading valve to the hydraulic oil tank, thereby unloading the power of the second hydraulic pump.

[0060] When the steering gear is in motion and the working hydraulic cylinder is not in motion, when the pressure at the oil outlet of the first hydraulic pump is lower than the elastic force of the first spring △P1 plus the pressure of the feedback line LS of the steering gear, the first reversing valve will be in the first position, and the hydraulic fluid of the second hydraulic pump enters the priority valve from the first working port P2 of the priority unloading valve, and the first working oil port CF of the priority valve provides hydraulic fluid for the steering gear. At the same time, since the working hydraulic cylinder is not in motion, the pressure at the oil outlet of the first hydraulic pump will not be greater than the elastic force of the first spring △P1 △P1 plus the pressure of the feedback line LS of the steering gear, but the first reversing valve may be in other positions between the first position and the second position. At this time, part of the hydraulic fluid of the second hydraulic pump enters the priority valve from the first working port P2 of the priority unloading valve, and the first working oil port CF of the priority valve provides hydraulic fluid for the steering gear; the other part flows from the second working port P3 of the priority unloading valve through the middle position of the multi-way valve and returns to the hydraulic oil tank;

[0061] When the steering gear is in motion and the working hydraulic cylinder is in motion at the same time, when the pressure at the oil outlet of the first hydraulic pump is lower than the elastic force of the first spring △P1 plus the pressure of the feedback line LS of the steering gear, the first reversing valve will be in the first position, and the hydraulic fluid of the second hydraulic pump will enter the priority valve from the first working port P2 of the priority unloading valve, and enter the steering gear from the first working oil port CF of the priority valve to provide hydraulic fluid;

[0062] When the load of the working hydraulic cylinder continues to increase, making the pressure at the oil outlet of the first hydraulic pump greater than the elastic force of the first spring △P1 plus the pressure of the feedback line LS of the steering gear, and less than the elastic force of the second spring △P2, the first reversing valve will be in the second position, the second reversing valve will be in the third position, and the second hydraulic pump will enter the oil inlet P of the multi-way valve from the second working port P3 of the priority unloading valve to provide hydraulic fluid for the working hydraulic cylinder; When the load of the working hydraulic cylinder continues to increase and the load pressure is greater than the elastic force of the second spring △P2, the first reversing valve will be in the second position, and the second reversing valve will be in the fourth position, and the hydraulic fluid of the second hydraulic pump will flow from the return oil port T of the priority unloading valve to the hydraulic oil tank, thereby unloading the power of the second hydraulic pump.

[0063] More specifically, it also includes a pilot oil source valve 18 and a pilot valve 19, wherein the first oil inlet P1 of the pilot oil source valve is connected to the oil outlet of the first hydraulic pump, the second oil inlet P2 of the pilot oil source valve is connected to the oil outlet of the third hydraulic pump, the oil outlet U of the pilot oil source valve is connected to the oil inlet P of the pilot valve, and the oil return port T of the pilot oil source valve is connected to the hydraulic oil tank;

[0064] The pilot valve is a hydraulically controlled pilot valve and is provided with multiple oil outlets, such as 1a, 1b, 2a, 2b, which are respectively connected to the corresponding pilot oil ports a1, b1, a2, b2 on the multi-way valve, and can be used to control the working state of the multi-way valve. The first oil inlet P1 of the pilot oil source valve is provided with hydraulic fluid by the third hydraulic pump, and the second oil inlet P2 of the pilot oil source valve is provided with hydraulic fluid by the first hydraulic pump, which can ensure that the pilot valve has a sufficient source of hydraulic fluid and will not fail to work due to damage to a single hydraulic pump, thereby ensuring stability in use.

[0065] As attached Figure 3 In one embodiment shown, the first working port of the priority unloading valve is in communication with the first working port of the priority valve;

[0066] Relative to Figure 1 The embodiment shown, Figure 3 In the embodiment shown in the figure, only the first working port P2 of the priority unloading valve is changed from being connected to the oil inlet port P of the priority valve to being connected to the first working oil port CF of the priority valve; the specific implementation process is roughly the same, the difference is that: Figure 1 In the embodiment shown, the hydraulic fluid generated by the second hydraulic pump enters the steering gear through the first working port P2 of the priority unloading valve and the priority valve; Figure 3 In the embodiment shown, the hydraulic fluid generated by the second hydraulic pump directly enters the steering gear through the first working port P2 of the priority unloading valve; Figure 1 The embodiment shown has the excellent effect of reducing the pressure loss of the inlet and outlet of the priority valve and reducing energy waste;

[0067] The above two embodiments have the following beneficial effects compared with the prior art:

[0068] The priority unloading valve is used to detect the pressure of the corresponding oil port under different working conditions of the working system. In the overload condition, the engine power can be used with maximum efficiency to ensure the joint operation efficiency of the whole machine and the traction of the whole vehicle.

[0069] The use of a priority unloading valve solves the problems in the prior art of heavy steering when the loader load steering hydraulic system is idling due to insufficient steering pump flow, and energy waste and low efficiency of the steering pump when the engine is running at high speed;

[0070] The following is an explanation of two working conditions that may be encountered in actual operations:

[0071] Working condition 1: When the loader is doing the stacking operation, the whole machine needs forward traction and the boom needs to be lifted when the bucket is full. When the hydraulic system of this technical solution is used, the power of the second hydraulic pump will be unloaded in this working condition, thereby increasing the traction of the whole machine. When the stacking is completed and the material is lifted, the second hydraulic pump will merge into the multi-way valve to improve the operating efficiency of the whole machine.

[0072] Working condition 2, when the engine turns quickly at low speed, the steering gear needs more hydraulic fluid, and the hydraulic fluid flow of the first hydraulic pump cannot meet the demand of the steering gear. At this time, the priority unloading valve is controlled by the steering gear feedback oil circuit LS2 and the first spring, so that the first reversing valve in the priority unloading valve is in the first position, and the hydraulic fluid flowing out of the second hydraulic pump enters the priority valve oil inlet P through the first working port P2 of the priority unloading valve to meet the steering gear flow demand when the engine turns quickly at low speed.

[0073] In one embodiment, the return port of the multi-way valve is connected to the hydraulic oil tank via a multi-way valve return pipeline, and a radiator 20 and an oil return filter 21 are provided in the multi-way valve return pipeline. The radiator can ensure working stability, and the oil return filter can reduce the entry of impurities into the hydraulic system, thereby ensuring safe use.

[0074] A loader comprises the above-mentioned loader hydraulic system.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A loader hydraulic system, characterized in that: It comprises a hydraulic oil tank (1), a double gear pump (2), a third hydraulic pump (3), a working hydraulic cylinder (4) and a steering hydraulic cylinder (5); The double gear pump comprises a first hydraulic pump (6) and a second hydraulic pump (7), the first hydraulic pump, the second hydraulic pump and the third hydraulic pump are all connected to the hydraulic oil tank, the steering hydraulic cylinder is connected to a steering gear (8), and the steering gear is connected to the double gear pump via a priority valve (9); The third hydraulic pump is connected to the working hydraulic cylinder via a multi-way valve (10); the priority valve is connected to the multi-way valve and can provide hydraulic fluid to the working hydraulic cylinder via the multi-way valve; A priority unloading valve (11) is also connected between the double gear pump and the priority valve, the oil return port of the priority unloading valve is connected to the hydraulic oil tank, the priority unloading valve is connected to the steering gear, and the priority unloading valve is connected to the multi-way valve; There are multiple working hydraulic cylinders, and the multi-way valve is provided with multiple working ports, which are respectively connected to the corresponding working hydraulic cylinders; The priority unloading valve comprises a first reversing valve (12), a second reversing valve (13), a first non-return valve (14) and a second non-return valve (15); the first working port of the priority unloading valve is connected to the oil inlet of the priority valve via the first non-return valve; the second working port of the priority unloading valve is connected to the oil inlet of the multi-way valve via the second non-return valve; the oil return port of the priority unloading valve is connected to the hydraulic oil tank via the second reversing valve; the first reversing valve is capable of controlling the flow rates of the first working port and the second working port of the priority unloading valve; and the second reversing valve is capable of controlling the flow rates of the second working port and the oil return port of the priority unloading valve; The first reversing valve has a first position and a second position, a first control oil circuit of the first reversing valve and a first spring (16) are provided at the right end of the first reversing valve, a second control oil circuit of the first reversing valve is provided at the left end of the first reversing valve, a steering gear feedback oil circuit is provided on the steering gear, the first control oil circuit of the first reversing valve is connected to the steering gear feedback oil circuit; the second control oil circuit of the first reversing valve is connected to the first hydraulic pump; The second reversing valve has a third position and a fourth position, the upper end of the second reversing valve is connected to the second working port of the priority unloading valve, and the lower end of the second reversing valve is provided with a second spring (17), when the pressure of the second working port of the priority unloading valve is greater than the elastic force of the second spring, the hydraulic fluid of the second hydraulic pump can flow to the hydraulic oil tank through the oil outlet of the second reversing valve, thereby unloading the second hydraulic pump; It also includes a pilot oil source valve (18) and a pilot valve (19), wherein the pilot oil source valve is connected to the first hydraulic pump, the pilot oil source valve is connected to the third hydraulic pump, the oil outlet of the pilot oil source valve is connected to the oil inlet of the pilot valve, and the oil return port of the pilot oil source valve is connected to the hydraulic oil tank; The pilot valve is provided with a plurality of oil outlets which are respectively communicated with corresponding pilot oil outlets on the multi-way valve.

2. A loader hydraulic system according to claim 1, characterized in that: A damper (22) is also provided at the left end of the first reversing valve, and the damper can slow down the conversion of the first reversing valve from the first position to the second position.

3. A loader hydraulic system according to claim 1, characterized in that: The pilot valve is a hydraulically controlled pilot valve, the multi-way valve is an open center multi-way valve, and the steering gear is a load sensing full hydraulic steering gear.

4. A loader hydraulic system according to claim 1, characterized in that: The first working port of the priority unloading valve is communicated with the first working port of the priority valve.

5. A loader hydraulic system according to claim 1, characterized in that: The return port of the multi-way valve is connected to the hydraulic oil tank via a multi-way valve return pipeline, and a radiator (20) and an oil return filter (21) are provided in the multi-way valve return pipeline.

6. A loader, characterized in that: A loader hydraulic system comprising the following:

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