Priority valve, hydraulic system and loader

Abstract

The present invention relates to the field of loaders, and discloses a priority valve, a hydraulic system, and a loader. The priority valve includes a valve body and an auxiliary oil cylinder, the auxiliary oil cylinder includes a cylinder body and a piston rod, the cylinder body is connected to the priority valve body, the rod chamber of the cylinder body is communicated with the spring chamber of the priority valve body, the return spring abuts between the second end of the priority valve core and the piston rod, and a control oil port K is provided on the cylinder body, and the control oil port K is communicated with the rodless chamber of the cylinder body. By adding an auxiliary oil cylinder, the piston rod can be further compressed to compress the return spring by passing oil to the control oil port K, thereby increasing the back pressure of the oil inlet P to adapt to individual working conditions, and can maintain a low back pressure of the oil inlet P in other working conditions to reduce throttling losses, thereby realizing two-stage control of the priority valve. The hydraulic system includes the above-mentioned priority valve, which not only eliminates the pilot pump and saves costs, but also solves the problem of low pilot pressure and inability to achieve floating action due to insufficient main pressure when working on a straight floating flat ground.

Description

Technical Field

[0001] The present invention relates to the technical field of loaders, and in particular to a priority valve, a hydraulic system and a loader. Background Art

[0002] At present, the pilot control hydraulic system and the main working hydraulic system of the pilot control loader are generally supplied with oil by different hydraulic pumps. Figure 1 As shown, the pilot control system is generally composed of a pilot pump 1', a pilot oil source valve 2', a pilot filter 3' and a pilot handle 4', etc., which is relatively expensive.

[0003] There are some cost reduction solutions for pilot control hydraulic system, such as Figure 2 As shown, the general approach is to remove the pilot pump and use a main oil circuit high-pressure oil pressure reducing valve. This solution saves a pilot pump to achieve the goal of reducing costs. However, this solution has a major drawback and cannot adapt to all loader operating conditions, such as the loader's straight-line floating and level ground operating conditions.

[0004] When the loader is working normally, due to the pressure of the priority valve spool spring, the oil inlet P of the priority valve always maintains a back pressure of 10.3 Bar. At this time, the pilot oil source valve also has a pressure input of 10.3 Bar. Since the pressure does not reach the set pressure of 35 Bar of the pilot oil source valve, the pilot oil source valve does not reduce the pressure and directly inputs the pilot pressure of 10.3 Bar to the pilot handle.

[0005] When the driver operates the pilot handle but not the steering gear, the P port of the priority valve is connected to the EF port of the priority valve, and the pilot pressure of 10.3 Bar is input to the pilot oil port of the multi-way valve through the pilot oil source valve and the pilot handle. This pressure can make the valve core of the multi-way valve half-open (the pressure for the valve core of the multi-way valve to fully switch direction is generally around 22 Bar at present). After the valve core is half-open, the main oil circuit can establish high pressure according to the load, and the P port of the steering pump can establish high pressure. The pilot oil source valve can ensure a stable 35 Bar pilot oil source by reducing pressure and combining with the auxiliary effect of the accumulator.

[0006] When the driver operates the steering gear, the LS load pressure of the steering gear is fed back to the LS port of the priority valve. At this time, the oil at the P port of the steering pump is supplied to the steering gear through the CF port of the priority valve. At this time, the P port of the steering pump can directly establish high pressure (steering pressure). Similarly, the pilot oil source valve can ensure a stable pilot oil output of 35Bar.

[0007] When the operator performs a straight-line floating leveling maneuver, the boom linkage of the multi-way valve must be in the leftmost floating position. The multi-way valve's floating control pressure is generally between 25 and 35 bar. This means the multi-way valve can only enter the floating position when the pilot pressure reaches 25 bar or above. In this floating position, the multi-way valve's P port, the boom cylinder's large and small chamber oil ports, are all connected to the hydraulic tank. At this point, no load can be established on the multi-way valve side. Because the maneuver is on straight-line leveling, there's no steering action, and no load can be established in the steering oil circuit. This means no high-pressure load can be established at the steering pump's P port. At this point, the pilot oil source valve's P port can only input 10.3 bar of pressure, which falls short of the 25 bar minimum floating pressure required by the boom linkage of the multi-way valve. Consequently, the entire machine cannot reliably perform the straight-line floating leveling maneuver.

[0008] If other actions are performed first to fill the accumulator with pressure and then float, the action can be completed, but it will be discontinuous. Since the pilot accumulator generally has a small volume, it will not be able to float after leakage.

[0009] If the spring back pressure of the priority valve is adjusted so that the P port of the pilot pump always has a back pressure value of more than 25Bar, although it can ensure that it can adapt to the above working conditions, the steering pump will always have a large flow throttling of 25Bar because it is a gear pump, which will consume energy and generate considerable heat. Summary of the Invention

[0010] An object of the present invention is to provide a priority valve that realizes two-stage control.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] A priority valve, comprising:

[0013] The valve body includes a priority valve body, a priority valve core and a return spring, the priority valve body having a sliding chamber and an oil inlet P, a steering oil port CF and a merging oil port EF connected with the sliding chamber, the priority valve core being slidably arranged in the sliding chamber, the priority valve body further having a screw plug chamber directly opposite to a first end of the priority valve core and a spring chamber directly opposite to a second end of the priority valve core, the screw plug chamber being connected with the steering oil port CF, the priority valve body further having a steering feedback oil port LS connected with the spring chamber, the return spring being arranged in the spring chamber, the priority valve core having a first working position that connects the oil inlet P with the steering oil port CF and a second working position that connects the oil inlet P with the merging oil port EF, and when the priority valve core switches from the second working position to the first working position, the passage between the oil inlet P and the merging oil port EF can be gradually reduced;

[0014] Also includes:

[0015] The auxiliary oil cylinder includes a cylinder body and a piston rod. The cylinder body is connected to the priority valve body, and the rod chamber of the cylinder body is communicated with the spring chamber of the priority valve body. The return spring abuts between the second end of the priority valve core and the piston rod. A control oil port K is provided on the cylinder body, and the control oil port K is communicated with the rodless chamber of the cylinder body.

[0016] As an optimal technical solution for the priority valve, a limiting surface is provided in the rod cavity of the cylinder body, and the limiting surface is used to limit the maximum distance that the piston rod moves in the direction of compressing the return spring.

[0017] As an optimal technical solution for the priority valve, the auxiliary oil cylinder further includes a limit seat, which is connected to the cylinder body and extends into the rodless cavity of the cylinder body. The limit seat can limit the initial position of the piston rod.

[0018] As a preferred technical solution of the priority valve, the second end of the priority valve core is provided with a stage, and one end of the return spring abutting against the priority valve core is sleeved on the stage.

[0019] As an optimal technical solution of the priority valve, the piston rod includes a piston and a connecting rod connected to the piston, and one end of the return spring abutting against the piston rod is sleeved on the connecting rod.

[0020] As an optimal technical solution for the priority valve, a first step portion and a second step portion are arranged at intervals on the priority valve core. The step surface of the first step portion is a straight surface, and the straight surface can open or close the passage between the oil inlet P and the steering oil port CF. The step surface of the second step portion is an inclined surface, and the inclined surface can open the passage between the oil inlet P and the merging oil port EF. In the process from opening to closing of the oil inlet P and the merging oil port EF, the inclined surface can gradually reduce the passage between the oil inlet P and the merging oil port EF.

[0021] Another object of the present invention is to provide a hydraulic system that not only eliminates the pilot pump and saves costs, but also solves the problem of low pilot pressure and inability to achieve floating action due to insufficient main pressure when working on a straight floating flat ground through the two-stage control of the priority valve.

[0022] To achieve this object, the present invention adopts the following technical solutions:

[0023] A hydraulic system comprising:

[0024] A working pump and a multi-way valve, wherein the oil inlet of the working pump is connected to the oil tank, the oil outlet of the working pump is connected to the oil inlet of the multi-way valve, and the oil outlet of the multi-way valve is connected to the working oil cylinder;

[0025] A steering pump, a steering gear, and a priority valve as described in any of the above schemes, wherein the oil inlet of the steering pump is connected to the oil tank, the oil outlet of the steering pump is connected to the oil inlet P of the priority valve, the steering oil port CF of the priority valve is connected to both the oil inlet of the steering gear and the screw plug cavity of the priority valve body, the confluence oil port EF of the priority valve is connected to the oil inlet of the multi-way valve, the feedback oil port of the steering gear is connected to the steering feedback oil port LS of the priority valve, and the oil outlet of the steering gear is connected to the steering cylinder;

[0026] A pilot oil source valve and a pilot handle, the oil inlet of the pilot oil source valve is connected to the oil outlet of the steering pump, the oil outlet of the pilot oil source valve is connected to the oil inlet of the pilot handle, the oil outlet of the pilot handle is connected to the control end of the multi-way valve, and the oil outlet of the pilot handle that controls the multi-way valve to be in the floating working position is also connected to the control oil port K of the priority valve.

[0027] As an optimal technical solution for the hydraulic system, the initial elastic force of the reset spring is set to F, the elastic force generated by the oil inlet from the control oil port K compressing the reset spring again when the pilot handle is executed to switch the multi-way valve to the floating working position is set to F3, and the effective area of ​​the first end of the priority valve core is set to A, then the value of (F+F3) / A is greater than or equal to the minimum floating control pressure of the multi-way valve.

[0028] As a preferred technical solution of the hydraulic system, it further includes an accumulator, and the oil outlet of the pilot oil source valve is also connected to the accumulator.

[0029] Another object of the present invention is to provide a loader comprising the hydraulic system as described in any of the above schemes.

[0030] Beneficial effects of the present invention:

[0031] The present invention provides a priority valve, comprising a valve body and an auxiliary oil cylinder. The auxiliary oil cylinder comprises a cylinder body and a piston rod. The cylinder body is connected to the priority valve body, and the rod chamber of the cylinder body communicates with the spring chamber of the priority valve body. A return spring abuts between the second end of the priority valve core and the piston rod. The cylinder body is provided with a control oil port K, which communicates with the rodless chamber of the cylinder body. By adding the auxiliary oil cylinder, oil can be passed through the control oil port K to cause the piston rod to further compress the return spring, thereby increasing the back pressure at the oil inlet P to adapt to certain operating conditions. In other operating conditions, the back pressure at the oil inlet P can be maintained at a low level to reduce throttling losses, thereby achieving two-stage control of the priority valve.

[0032] The hydraulic system provided by the present invention not only eliminates the pilot pump and saves costs, but also solves the problem of low pilot pressure and inability to achieve floating action due to insufficient main pressure when working on a straight floating flat ground through the two-stage control of the priority valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the principle of a hydraulic system provided by the prior art;

[0034] Figure 2 This is a schematic diagram of the principle of another hydraulic system provided by the prior art;

[0035] Figure 3 It is a structural diagram of a priority valve provided by an embodiment of the present invention;

[0036] Figure 4 It is a schematic diagram of the principle of the hydraulic system provided by an embodiment of the present invention.

[0037] In the picture:

[0038] 1', pilot pump; 2', pilot oil source valve; 3', pilot filter; 4', pilot handle;

[0039] 1. Working pump; 2. Multi-way valve; 3. Steering pump; 4. Priority valve; 5. Steering gear; 6. Pilot oil source valve; 7. Pilot handle; 8. Accumulator; 9. Radiator; 10. Filter;

[0040] 41. Valve body; 411. Priority valve body; 412. Priority valve core; 4121. First step; 4122. Second step; 413. Return spring; 414. Plug; 42. Auxiliary oil cylinder; 421. Cylinder body; 4211. Limiting surface; 422. Piston rod; 423. Limiting seat; 43. Overflow valve. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only show portions relevant to the present invention, not all of them.

[0042] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0043] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0044] In the description of this embodiment, the terms "upper," "lower," "left," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0045] like Figure 3 As shown, an embodiment of the present invention provides a priority valve 4, including a valve body 41, the valve body 41 includes a priority valve body 411, a priority valve core 412 and a return spring 413, the priority valve body 411 has a sliding cavity and an oil inlet P, a steering oil port CF and a confluence oil port EF connected to the sliding cavity, the priority valve core 412 is slidably arranged in the sliding cavity, the priority valve body 411 also has a screw plug cavity facing the first end of the priority valve core 412 and a spring cavity facing the second end of the priority valve core 412, the priority The first end of the valve core is provided with an oil passage connecting the screw plug cavity and the steering oil port CF. The priority valve body 411 also has a steering feedback oil port LS connected to the spring cavity. A return spring 413 is disposed within the spring cavity. The priority valve core 412 has a first operating position connecting the oil inlet P with the steering oil port CF and a second operating position connecting the oil inlet P with the merging oil port EF. As the priority valve core 412 switches from the second operating position to the first operating position, the passage between the oil inlet P and the merging oil port EF gradually decreases. Preferably, a screw plug 414 is disposed within the screw plug cavity to limit the position of the priority valve core 412.

[0046] Priority valve spool 412 is spaced apart from each other by a first step 4121 and a second step 4122. The first step 4121 is a straight surface that opens or closes the passage between the oil inlet P and the steering port CF. The second step 4122 is an inclined surface that opens the passage between the oil inlet P and the confluence port EF. Furthermore, the inclined surface gradually reduces the passage between the oil inlet P and the confluence port EF during the process of opening and closing the two ports. In other words, the first step 4121 functions as a switch, while the second step 4122 not only functions as a switch, but also as a throttle.

[0047] The priority valve 4 provided in this embodiment of the present invention further includes an auxiliary oil cylinder 42, comprising a cylinder body 421 and a piston rod 422. The cylinder body 421 is connected to the priority valve body 411, and the rod cavity of the cylinder body 421 communicates with the spring cavity of the priority valve body 411. The return spring 413 abuts between the second end of the priority valve core 412 and the piston rod 422. The cylinder body 421 is provided with a control oil port K, which communicates with the rodless cavity of the cylinder body 421. By adding the auxiliary oil cylinder 42, oil can be passed through the control oil port K to cause the piston rod 422 to further compress the return spring 413, thereby increasing the back pressure of the oil inlet P to adapt to certain operating conditions. In other operating conditions, the back pressure of the oil inlet P can be maintained at a low level to reduce throttling losses.

[0048] Preferably, a limiting surface 4211 is provided within the rod cavity of the cylinder body 421. This limiting surface 4211 is used to limit the maximum distance that the piston rod 422 can move in the direction of compressing the return spring 413. This arrangement facilitates control of the compression of the return spring 413 and facilitates calculation of the elastic force of the return spring 413. Furthermore, the auxiliary oil cylinder 42 also includes a limiting seat 423, which is connected to the cylinder body 421 and extends into the rodless cavity of the cylinder body 421. The limiting seat 423 is capable of limiting the initial position of the piston rod 422, thereby controlling the initial compression of the return spring 413 and facilitating calculation of the elastic force of the return spring 413.

[0049] Preferably, the second end of the priority valve core 412 is provided with a stage, and the end of the return spring 413 that contacts the priority valve core 412 is sleeved on the stage. The piston rod 422 includes a piston and a connecting rod connected to the piston, and the end of the return spring 413 that contacts the piston rod 422 is sleeved on the connecting rod. This arrangement facilitates the placement of the return spring 413.

[0050] Preferably, the priority valve 4 further includes a relief valve 43 connected to the steering feedback oil port LS. By providing the relief valve 43 , when the pressure of the hydraulic system is too high, the relief valve 43 can overflow to protect the hydraulic system.

[0051] like Figure 4 As shown, an embodiment of the present invention further provides a hydraulic system, comprising: a working pump 1, a multi-way valve 2, a steering pump 3, a steering gear 5, a priority valve 4 as described in the above scheme, a pilot oil source valve 6 and a pilot handle 7, wherein the oil inlet of the working pump 1 is connected to the oil tank, the oil outlet of the working pump 1 is connected to the oil inlet of the multi-way valve 2, and the oil outlet of the multi-way valve 2 is connected to the working oil cylinder; the oil inlet of the steering pump 3 is connected to the oil tank, the oil outlet of the steering pump 3 is connected to the oil inlet P of the priority valve 4, and the steering oil port CF of the priority valve 4 is simultaneously connected to the oil inlet of the steering gear 5 and the priority valve body 4 11, the screw plug chamber is connected, the confluence oil port EF of the priority valve 4 is connected with the oil inlet of the multi-way valve 2, the feedback oil port of the steering gear 5 is connected with the steering feedback oil port LS of the priority valve 4, and the oil outlet of the steering gear 5 is connected with the steering cylinder; the oil inlet of the pilot oil source valve 6 is connected with the oil outlet of the steering pump 3, the oil outlet of the pilot oil source valve 6 is connected with the oil inlet of the pilot handle 7, the oil outlet of the pilot handle 7 is connected with the control end of the multi-way valve 2, and the oil outlet of the pilot handle 7 that controls the multi-way valve 2 to be in the floating working position is also connected with the control oil port K of the priority valve 4.

[0052] When the whole machine has no action, there is no pressure input to the steering feedback oil port LS and the control oil port K of the priority valve 4. The priority valve core 412 is in the first working position under the action of the reset spring 413. At this time, the oil inlet P of the priority valve 4 is connected to the steering oil port CF. When oil is input to the oil inlet P of the priority valve 4, the hydraulic oil enters the steering oil port CF and acts on the first end of the priority valve core 412 through the screw plug cavity of the priority valve 4, pushing the priority valve core 412 to move to the second end. Assuming that the reset spring 413 must be overcome when the priority valve core 412 moves to the second working position, the hydraulic oil will not be applied to the steering oil port CF. The elastic force of spring 413 is F. When the pressure of the oil inlet P of the priority valve 4 reaches 10.3 Bar (the control pressure of the priority valve 4), the force F1 of the hydraulic oil acting on the first end of the priority valve core 412 is just equal to the elastic force F of the reset spring 413. At this time, the oil inlet P of the priority valve 4 is connected to the confluent oil port EF. The oil entering from the oil inlet P of the priority valve 4 is returned through the confluent oil port EF of the priority valve 4 and the middle position of the multi-way valve 2, that is, the oil inlet P of the priority valve 4 always maintains a back pressure of 10.3 Bar for oil return.

[0053] When the entire machine is steering, feedback oil from the steering gear 5 is input into the spring chamber of the priority valve 4 through the steering feedback oil port LS of the priority valve 4, acting on the second end of the priority valve core 412. The applied force is set to F2. At this point, the sum of F2 and the elastic force F of the return spring 413 is greater than F1, causing the priority valve core 412 to move to the first working position. The oil inlet P of the priority valve 4 is now connected to the steering oil port CF. High-pressure oil from the steering pump 3 is supplied to the steering cylinder through the priority valve 4 for steering. At this time, the oil inlet P of the priority valve 4 always has a high-pressure oil supply determined by the steering load. The pilot oil source valve 6 can establish a stable pressure of 35 bar.

[0054] When the entire machine is loading, there's no pressure input to the steering feedback port LS and control port K of priority valve 4. The same principle applies as when the entire machine is not operating. The oil inlet P of priority valve 4 is now connected to the confluence port EF. The oil entering through the inlet P of priority valve 4 merges through the confluence port EF and flows into the main oil circuit of multi-way valve 2. At this point, a high-pressure oil level, determined by the machine's workload, flows to the inlet P of priority valve 4. The pilot oil source valve 6 can establish a stable pressure of 35 bar.

[0055] When the entire machine is performing linear floating and level operation, the oil inlet P of the priority valve 4 cannot generate high pressure due to the working load and steering load. At this time, the oil inlet P of the priority valve 4 maintains a back pressure of 10.3 Bar. When the pilot handle 7 is operated to switch the multi-way valve 2 to the floating working position, the 10.3 Bar pilot oil output from the corresponding oil outlet of the pilot handle 7 acts on the piston rod 422 through the control oil port K of the priority valve 4, pushing the piston rod 422 in the direction of compressing the return spring 413, compressing the return spring 413 again. The maximum displacement of the piston rod 422 is X within the limit of the limit surface 4211. Let the force generated by the return spring 413 compressing X be F3. At this time, the original spring force F plus the force F3 generated by the compression X will be greater than the force F1 generated by the 10.3 Bar pressure at the first end of the priority valve core 412. The priority valve core 412 will move toward the first end, thereby closing the passage from the oil inlet P to the converging oil port EF. Since the steering oil port CF is now blocked from the outside, and the path from the oil inlet P to the confluence port EF is reduced, the pressure at the oil inlet P of the priority valve 4 increases due to the throttling effect, and F1 increases. When F1 rises to equal the sum of F and F3, the pilot valve core reaches a new balance. At this time, the pressure at the oil inlet P of the priority valve 4 increases, allowing the pilot oil source valve 6 to establish high pressure, thereby helping the entire machine complete the straight-line floating leveling action.

[0056] Furthermore, if the effective area of ​​the first end of the priority valve core 412 is set to A, the value of (F+F3) / A should be greater than or equal to the minimum floating control pressure of the multi-way valve 2. Only when this condition is met can the valve core of the multi-way valve 2 be moved to the floating working position to ensure that the whole machine can stably complete the linear floating flat ground action. Generally, the floating control pressure of the multi-way valve 2 is 25-35Bar, so if the effective area of ​​the first end of the priority valve core 412 is set to A, the value of F+F3 divided by A must be greater than or equal to 25Bar. At this time, the pressure of the P port must reach at least 25Bar to reach a new balance. The pressure of 25Bar can be transmitted to the corresponding pilot port of the multi-way valve 2 through the pilot oil source valve 6 and the pilot handle 7. The pilot pressure of 25Bar can push the valve core of the multi-way valve 2 to move to the floating working position to realize the floating action.

[0057] Preferably, the hydraulic system further includes an accumulator 8, and the oil outlet of the pilot oil source valve 6 is also connected to the accumulator 8. The accumulator 8 can store energy and release it when the system needs it to replenish the system. When the system pressure increases instantaneously, it can absorb this energy to ensure normal pressure in the entire system.

[0058] Preferably, the hydraulic system further includes a filter 10 and a radiator 9, which are arranged on the connecting pipeline between the oil return port of the multi-way valve 2 and the oil tank to filter and dissipate heat of the return oil.

[0059] An embodiment of the present invention further provides a loader, comprising the hydraulic system as described in the above scheme. By adopting the above hydraulic system, it is possible to achieve stable execution of straight-line floating level ground working conditions while ensuring cost reduction (i.e., without using a pilot pump).

[0060] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A priority valve, comprising: The valve body (41) includes a priority valve body (411), a priority valve core (412) and a return spring (413). The priority valve body (411) has a sliding cavity and an oil inlet P, a steering oil port CF and a confluence oil port EF connected to the sliding cavity. The priority valve core (412) is slidably arranged in the sliding cavity. The priority valve body (411) also has a screw plug cavity facing the first end of the priority valve core (412) and a spring cavity facing the second end of the priority valve core (412). The screw plug cavity is connected to the steering oil port C. F is connected, the priority valve body (411) further has a steering feedback oil port LS connected to the spring chamber, the return spring (413) is arranged in the spring chamber, the priority valve core (412) has a first working position that connects the oil inlet P with the steering oil port CF and a second working position that connects the oil inlet P with the merging oil port EF, and when the priority valve core (412) switches from the second working position to the first working position, the passage between the oil inlet P and the merging oil port EF can be gradually reduced; It is characterized by further comprising: The auxiliary oil cylinder (42) includes a cylinder body (421) and a piston rod (422). The cylinder body (421) is connected to the priority valve body (411), and the rod chamber of the cylinder body (421) is communicated with the spring chamber of the priority valve body (411). The return spring (413) abuts between the second end of the priority valve core (412) and the piston rod (422). A control oil port K is provided on the cylinder body (421), and the control oil port K is communicated with the rodless chamber of the cylinder body (421).

2. The priority valve according to claim 1, characterized in that A limiting surface (4211) is provided in the rod cavity of the cylinder body (421), and the limiting surface (4211) is used to limit the maximum distance that the piston rod (422) moves in the direction of compressing the return spring (413).

3. The priority valve according to claim 1, characterized in that The auxiliary oil cylinder (42) further includes a limiting seat (423), which is connected to the cylinder body (421) and extends into the rodless cavity of the cylinder body (421). The limiting seat (423) can limit the initial position of the piston rod (422).

4. The priority valve according to claim 1, characterized in that The second end of the priority valve core (412) is provided with a stage, and one end of the return spring (413) abutting against the priority valve core (412) is sleeved on the stage.

5. The priority valve according to claim 1, characterized in that The piston rod (422) comprises a piston and a connecting rod connected to the piston, and one end of the return spring (413) abutting against the piston rod (422) is sleeved on the connecting rod.

6. The priority valve according to claim 1, characterized in that A first step portion (4121) and a second step portion (4122) are arranged at intervals on the priority valve core (412), the step surface of the first step portion (4121) is a straight surface, and the straight surface can open or close the passage between the oil inlet P and the steering oil port CF, the step surface of the second step portion (4122) is an inclined surface, and the inclined surface can open the passage between the oil inlet P and the merging oil port EF, and in the process from opening to closing the oil inlet P and the merging oil port EF, the inclined surface can gradually reduce the passage between the oil inlet P and the merging oil port EF.

7. A hydraulic system, characterized in that: include: A working pump (1) and a multi-way valve (2), wherein the oil inlet of the working pump (1) is connected to the oil tank, the oil outlet of the working pump (1) is connected to the oil inlet of the multi-way valve (2), and the oil outlet of the multi-way valve (2) is connected to the working oil cylinder; A steering pump (3), a steering gear (5) and a priority valve (4) according to any one of claims 1 to 6, wherein the oil inlet of the steering pump (3) is communicated with the oil tank, the oil outlet of the steering pump (3) is communicated with the oil inlet P of the priority valve (4), the steering oil port CF of the priority valve (4) is simultaneously communicated with the oil inlet of the steering gear (5) and the screw plug cavity of the priority valve body (411), the confluence oil port EF of the priority valve (4) is communicated with the oil inlet of the multi-way valve (2), the feedback oil port of the steering gear (5) is communicated with the steering feedback oil port LS of the priority valve (4), and the oil outlet of the steering gear (5) is communicated with the steering oil cylinder; A pilot oil source valve (6) and a pilot handle (7), wherein the oil inlet of the pilot oil source valve (6) is communicated with the oil outlet of the steering pump (3), the oil outlet of the pilot oil source valve (6) is communicated with the oil inlet of the pilot handle (7), the oil outlet of the pilot handle (7) is communicated with the control end of the multi-way valve (2), and the oil outlet of the pilot handle (7) for controlling the multi-way valve (2) to be in a floating working position is also communicated with the control oil port K of the priority valve (4).

8. The hydraulic system according to claim 7, characterized in that: The initial elastic force of the reset spring (413) is set to F, the elastic force generated by the oil inlet from the control oil port K compressing the reset spring (413) again when the pilot handle (7) switches the multi-way valve (2) to the floating working position is set to F3, and the effective area of ​​the first end of the priority valve core (412) is set to A, then the value of (F+F3) / A is greater than or equal to the minimum floating control pressure of the multi-way valve (2).

9. The hydraulic system according to claim 7, characterized in that An accumulator (8) is also included, and the oil outlet of the pilot oil source valve (6) is also communicated with the accumulator (8).

10. A loader, characterized in that: Comprising a hydraulic system as described in any one of claims 7 to 9.

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