A tractor multi-stage priority system, hydraulic system and tractor

Abstract

The present application relates to a tractor multi-stage priority system, a hydraulic system and a tractor, wherein the tractor multi-stage priority system comprises a steering priority valve, a multi-stage reversing valve, a liquid filling valve, a solenoid valve, a unloading valve and a shuttle valve group, the steering priority valve being connected to the shuttle valve group; the multi-stage reversing valve is connected to the liquid filling valve; the liquid filling valve can be switched to be connected to the shuttle valve group; the shuttle valve group can be switched to be connected to the steering priority valve, or be switched to be connected to the liquid filling valve, or be switched to be connected to the liquid filling valve and the outlet of the liquid filling valve at the same time. By using the technical scheme of the present application, the priority can be dynamically adjusted by optimizing the flow distribution and the unloading control in the starting stage during the working process of the tractor, and the priority of the steering system is ensured to be the highest, and the load starting is avoided when the engine starts, thereby providing reliable guarantee for the stable operation of the tractor.

Description

Technical Field

[0001] This invention relates to the field of agricultural machinery technology, and in particular to a multi-level priority system for tractors, a hydraulic system, and a tractor. Background Technology

[0002] The hydraulic system of a tractor often needs to drive multiple loads simultaneously, such as the steering system, braking system, and multiple output system. Among these, the steering system and braking system have the highest priority, followed by other actuators or systems (such as multiple output and lifting systems).

[0003] In existing technologies, multi-stage priority valves are commonly used in various systems to achieve flow distribution and load management. However, relying solely on multi-stage priority valves to accomplish these functions has certain limitations. Priority valves in existing solutions typically employ fixed priority allocation, which cannot be dynamically adjusted according to actual operating conditions. This can lead to insufficient flow or uneven flow distribution when steering and hydraulic output occur simultaneously. For example, when steering is performed simultaneously with lifting, the system will prioritize steering, resulting in insufficient flow or uneven flow distribution during the lifting action.

[0004] On the other hand, during the tractor's startup phase, the engine needs to overcome the initial resistance and load of the system to start smoothly. If there is a large load in the hydraulic system at this time, the engine may have difficulty starting due to excessive load, and in severe cases, it may even lead to starting failure or damage to the engine. Summary of the Invention

[0005] This invention provides a multi-level priority system for tractors, a hydraulic system, and a tractor. During the tractor's operation, it can dynamically adjust priorities by optimizing flow distribution and unloading control during the start-up phase, ensuring that the steering system has the highest priority. At the same time, it avoids starting the engine under load, providing a reliable guarantee for the stable operation of the tractor.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a multi-stage priority system for a tractor, comprising an inlet P port for connecting to the outlet of a variable displacement pump, a bidirectional oil port LS OUT port for connecting to the feedback port of the variable displacement pump, an ST port for connecting to the steering system, a signal feedback LS ST port for receiving steering LS feedback signals, a signal feedback LS TB port for receiving trailer LS feedback signals, a TB port for connecting to the trailer braking system, an R port for connecting to the braking system and an accumulator, an X port for connecting to the parking brake system, a return oil port T port for connecting to the oil tank, and an EF port for connecting to other actuators. The system includes a steering priority valve, a multi-stage directional valve, a filling valve, a solenoid valve, an unloading valve, and a shuttle valve assembly, wherein:

[0008] The oil inlet of the steering priority valve is connected to port P, and its oil outlet is connected to port ST, port LS ST and the oil inlet of the shuttle valve assembly.

[0009] The inlet of the multi-stage reversing valve is connected to port P, and can be switched to connect its outlet to port EF, or to connect its outlet to the inlet of the filling valve, or to connect its outlet to port TB.

[0010] The filling valve can be switched to a state in which its oil inlet and its oil outlet are connected, and its oil outlet is connected to the R port and the oil inlet of the shuttle valve assembly, or switched to a state in which its oil inlet and its oil outlet are disconnected.

[0011] The solenoid valve can be switched so that its inlet is connected to port R and its outlet is connected to port X, or it can be switched so that its inlet is connected to port X and its outlet is connected to port T.

[0012] The oil inlet of the unloading valve is connected to the LS OUT port, and its oil outlet is connected to the T port.

[0013] The shuttle valve assembly can be switched so that its inlet is connected to the outlet of the steering priority valve and its outlet is connected to the LSOUT port, or it can be switched so that its inlet is connected to the outlet of the filling valve and its outlet is connected to the LSOUT port, or it can be switched so that its inlet is connected to the LSTB port and its outlet is connected to the LSOUT port.

[0014] The beneficial effects of this invention are as follows: After the vehicle is powered on, the unloading valve is energized, connecting the pressure oil at the LS OUT port to the oil tank. At this time, the hydraulic system has no load feedback to the variable pump, making it very easy to start the vehicle when the engine starts. This solves the problems of hydraulic energy waste and the difficulty in starting the engine due to a large load. During the steering process, through the integrated steering priority valve, the steering system load enters through the LS ST port. After comparison by the shuttle valve group, the maximum load is fed back to the variable pump through LS OUT. The variable pump switches from a small displacement working state to a large displacement working state, and the steering priority valve gradually switches to the lower working state. The flow rate to the ST oil circuit increases, while the flow rate to other oil circuits decreases. As the steering system load changes, the variable pump supplies oil to the steering cylinder as needed, thereby ensuring the highest priority of the steering system.

[0015] Based on the above technical solution, the present invention can be further improved as follows.

[0016] Furthermore, the shuttle valve assembly includes a first shuttle valve and a second shuttle valve whose first inlet is connected to the outlet of the first shuttle valve. The second inlet of the second shuttle valve is connected to the outlet of the steering priority valve, and the outlet of the second shuttle valve is connected to the LS OUT port. The first shuttle valve can be switched to its outlet and its first inlet, with its first inlet simultaneously connected to the LS TB port, or switched to its outlet and its second inlet, with its second inlet simultaneously connected to the outlet of the filling valve.

[0017] Furthermore, the multi-stage reversing valve is a five-position three-way valve with five positions from top to bottom. The oil inlets of its first and second positions are connected to the upper and lower oil outlets of the corresponding positions, and the oil inlets of its third and fourth positions are connected to the upper oil outlets of the corresponding positions and disconnected from the lower oil outlets of the corresponding positions. The multi-stage reversing valve can be switched to connect its oil inlet to port P in any position, and can be switched to connect its lower oil outlet to port EF in the first or second position, or to connect its upper oil outlet to the oil inlet of the filling valve in the third or fourth position, or to connect its upper oil outlet to port TB in the third or fourth position.

[0018] Furthermore, a first throttle valve is provided on the pipeline connecting the oil inlet of the first or second position of the multi-stage directional valve to the lower oil outlet of the corresponding position.

[0019] Furthermore, a second throttle valve is provided on the pipeline connecting the oil inlet of the third or fourth position of the multi-stage directional valve to the upper oil outlet of the corresponding position.

[0020] Furthermore, the filling valve is a three-position four-way valve with three positions from top to bottom. In its first position, the lower oil inlet is simultaneously disconnected from its upper left oil outlet, upper right oil outlet, and lower left oil outlet. In its third position, the lower oil inlet is simultaneously connected to both the lower left oil outlet and the upper right oil outlet. The filling valve can be switched so that its lower oil inlet in its first position is connected to the oil outlet of the multi-stage directional valve, its upper left oil outlet is connected to port T, its upper right oil outlet is connected to the oil inlet of the shuttle valve assembly, and its lower left oil outlet is connected to port R. The filling valve can also be switched so that its lower oil inlet in its third position is connected to the oil outlet of the multi-stage directional valve, its lower left oil outlet is connected to port R, and its upper right oil outlet is connected to the oil inlet of the shuttle valve assembly.

[0021] Furthermore, the solenoid valve is a two-position three-way valve. When the solenoid valve is switched to its first position, port R is connected to port X, or when it is switched to its second position, port X is connected to port T.

[0022] Furthermore, a filter screen is installed on the pipe connecting the oil outlet of the steering priority valve to the oil inlet of the shuttle valve assembly.

[0023] The present invention also provides a hydraulic system comprising a tractor multi-level priority system.

[0024] The present invention also provides a tractor that includes a hydraulic system. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the working principle of the tractor multi-level priority system of the present invention;

[0026] Figure 2 This is a schematic diagram of the tractor multi-level priority system of the present invention during power-on startup.

[0027] Figure 3 This is a schematic diagram of the tractor multi-level priority system of the present invention during steering.

[0028] Figure 4 A schematic diagram illustrating the tractor multi-level priority system of the present invention during fluid filling and / or service braking;

[0029] Figure 5 This is a schematic diagram of the tractor multi-level priority system of the present invention when performing trailer braking;

[0030] Figure 6 For the present invention Figure 5 A magnified view of a portion of the image;

[0031] Figure 7 This is a schematic diagram of the tractor multi-level priority system of the present invention when the parking brake is released.

[0032] Figure 8 This is a schematic diagram of the tractor multi-level priority system of the present invention supplying fluid to other actuators.

[0033] The attached diagram lists the components represented by each number as follows:

[0034] 1. Variable displacement pump; 2. Steering priority valve; 3. Multistage directional valve; 31. First throttle valve; 32. Second throttle valve; 4. Filling valve; 5. Solenoid valve; 6. Unloading valve; 7. First shuttle valve; 8. Second shuttle valve; 9. Filter screen. Detailed Implementation

[0035] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] Example 1

[0037] like Figures 1-8This embodiment 1 provides a multi-stage priority system for a tractor, which includes an inlet P port for connecting to the outlet of a variable pump 1, a bidirectional oil port LS OUT port for connecting to the feedback port of the variable pump 1, an ST port for connecting to the steering system, a signal feedback LS ST port for receiving steering LS feedback signals, a signal feedback LS TB port for receiving trailer LS feedback signals, a TB port for connecting to the trailer braking system, an R port for connecting to the braking system and the accumulator, an X port for connecting to the parking brake system, a return oil port T port for connecting to the oil tank, and an EF port for connecting to other actuators. It includes a steering priority valve 2, a multi-stage directional valve 3, a filling valve 4, a solenoid valve 5, an unloading valve 6, and a shuttle valve assembly, wherein:

[0038] The oil inlet of the steering priority valve 2 is connected to port P, and its oil outlet is connected to port ST, port LS ST and the oil inlet of the shuttle valve assembly;

[0039] The inlet of the multi-stage reversing valve 3 is connected to port P, and can be switched to connect its outlet to port EF, or to connect its outlet to the inlet of the filling valve 4, or to connect its outlet to port TB.

[0040] The filling valve 4 can be switched to a state in which its oil inlet and its oil outlet are connected, and its oil outlet is connected to the R port and the oil inlet of the shuttle valve assembly, or switched to a state in which its oil inlet and its oil outlet are disconnected.

[0041] Solenoid valve 5 can be switched so that its oil inlet is connected to port R and its oil outlet is connected to port X, or it can be switched so that its oil inlet is connected to port X and its oil outlet is connected to port T.

[0042] The oil inlet of the unloading valve 6 is connected to the LS OUT port, and its oil outlet is connected to the T port;

[0043] The shuttle valve assembly can be switched so that its inlet is connected to the outlet of the steering priority valve 2 and its outlet is connected to the LS OUT port, or it can be switched so that its inlet is connected to the outlet of the filling valve 4 and its outlet is connected to the LS OUT port, or it can be switched so that its inlet is simultaneously connected to the LS TB port and its outlet is connected to the LS OUT port.

[0044] like Figure 2 After the vehicle is powered on, the unloading valve 6 is energized, connecting the pressure oil at the LS OUT port to the oil tank. At this time, the hydraulic system has no load feedback to the variable pump 1, making it very easy to start the vehicle when the engine starts. This solves the problems of hydraulic energy waste and the difficulty in starting the engine due to a large load. Figure 3During the steering process, the steering system load enters through the LS ST port via the integrated steering priority valve 2. After comparison by the shuttle valve group, the maximum load is fed back to the variable pump 1 via LS OUT. The variable pump 1 switches from a small displacement working state to a large displacement working state, and the steering priority valve 2 gradually switches to the lower position working state. The flow rate to the ST oil circuit increases, while the flow rate of other oil circuits decreases. As the steering system load changes, the variable pump 1 supplies oil to the steering cylinder as needed, thereby ensuring that the steering system has the highest priority.

[0045] like Figure 1 When the engine starts and the engine speed stabilizes, the unloading valve 6 is de-energized. At this time, the maximum load signal of the hydraulic system is compared by the shuttle valve group and fed back to the variable pump 1 through LS OUT to control the pressure and flow of the variable pump 1 to meet the needs of the hydraulic system.

[0046] like Figure 4 When the steering is not engaged, the hydraulic fluid at port P flows through the steering priority valve 2 to the lower position of the multi-stage directional valve 3 and the lower position of the charging valve 4, then provides brake fluid to port R or charges the accumulator. At this time, the load pressure LS is compared by the second shuttle valve 8, and the maximum load pressure is fed back to the variable pump 1. The variable pump 1 operates at high displacement, continuously charging port R (accumulator). When the pressure at port R reaches the spring setting value of charging valve 4, charging valve 4 switches to its uppermost position, and charging ends. Figure 7 When the steering system does not require flow, only a small amount of oil that guides and controls the position of the valve core flows back to the oil tank, while a large amount of oil is supplied to other working oil circuits, resulting in high efficiency.

[0047] like Figure 5 and Figure 6 When there is a need for trailer braking, the tractor depresses the road brake pedal and applies pilot control oil to the trailer control system, which controls the valve switching action in the trailer braking system and feeds back the load signal to variable pump 1. Then, the TB port (connected to the trailer braking system) provides pressure according to the trailer load demand, thereby realizing the trailer braking function.

[0048] like Figure 7 When the tractor is in motion, releasing the handbrake energizes solenoid valve 5 (port R connects to the braking system and accumulator). Oil flows through solenoid valve 5 to the parking brake chamber via port X, releasing the parking brake and allowing the tractor to move. Figure 2 When the tractor stops, the handbrake is pulled up. At this time, the solenoid valve 5 is de-energized, and the oil in the parking brake chamber flows back to the oil tank through the lower position of the solenoid valve 5. At this time, the tractor realizes parking brake.

[0049] In this embodiment 1, the shuttle valve assembly includes a first shuttle valve 7 and a second shuttle valve 8 whose first oil inlet is connected to the oil outlet of the first shuttle valve 7. The second oil inlet of the second shuttle valve 8 is connected to the oil outlet of the steering priority valve 2, and the oil outlet of the second shuttle valve 8 is connected to the LSOUT port. The first shuttle valve 7 can be switched to have its oil outlet and its first oil inlet connected, and its first oil inlet is simultaneously connected to the LS TB port, or it can be switched to have its oil outlet and its second oil inlet connected, and its second oil inlet is simultaneously connected to the oil outlet of the filling valve 4.

[0050] like Figure 3 During steering operations, hydraulic fluid enters the second inlet of the second shuttle valve 8 from the outlet of the steering priority valve 2, and exits from the outlet of the second shuttle valve 8 to the LS OUT port; during filling and / or service braking, hydraulic fluid enters the second inlet of the first shuttle valve 7 from the outlet of the filling valve 4, and then enters the first inlet of the second shuttle valve 8 from the outlet of the first shuttle valve 7, before exiting from the outlet of the second shuttle valve 8 to the LS OUT port; Figure 5 and Figure 6 When the trailer brakes, the oil enters the first inlet of the first shuttle valve 7 from the LS TB port, then enters the first inlet of the second shuttle valve 8 from the outlet of the first shuttle valve 7, and then exits from the outlet of the second shuttle valve 8 to the LS OUT port.

[0051] like Figures 1-8 The multi-stage directional valve 3 is a five-position three-way valve with five positions from top to bottom. The oil inlets of its first and second positions are connected to the upper and lower oil outlets of the corresponding positions. The oil inlets of its third and fourth positions are connected to the upper oil outlets of the corresponding positions and disconnected from the lower oil outlets of the corresponding positions. The multi-stage directional valve 3 can be switched to connect its oil inlet to port P in any position, and can be switched to connect its lower oil outlet to port EF in its first or second position, or to connect its upper oil outlet to the oil inlet of the filling valve 4 in its third or fourth position, or to connect its upper oil outlet to port TB in its third or fourth position.

[0052] like Figure 4 During fluid filling and / or service braking, the multi-stage directional valve 3 switches to the third or fourth position, connecting its inlet to port P, and then switches to its upper outlet in the third or fourth position, connecting to the inlet of the filling valve 4. This allows fluid to enter from port P into the inlet of the third or fourth position, and then exit from the upper outlet of the corresponding position into the filling valve 4. Figure 5 and Figure 6 When the trailer brakes, the multi-stage directional valve 3 switches to the third or fourth position, connecting its inlet to port P, and then switches to its upper outlet in the third or fourth position, connecting to port TB. This allows oil to enter from port P and enter the inlet in the third or fourth position, and then exit from the upper outlet in the corresponding position to port TB. Figure 8 When supplying oil to other actuators, the multi-stage directional valve 3 switches to the first position and the second position, with the oil inlet connected to port P, and switches to the first position or the second position, with the lower oil outlet connected to port EF. This allows the oil to enter the first position and the second position from port P, and then exit from the corresponding position's upper oil outlet to port EF, and then exit to other actuators.

[0053] Among them, a first throttle valve 31 is configured on the pipeline connecting the oil inlet of the first or second position of the multi-stage directional valve 3 and the lower oil outlet of the corresponding position.

[0054] A first throttle valve 31 is configured between the oil inlet at the first or second position and the corresponding lower oil outlet. When the oil passes through the first or second position where the first throttle valve 31 is installed, the flow rate can be controlled by the first throttle valve 31 to improve the stability of the hydraulic system. When the multi-stage directional valve 3 switches positions, the first throttle valve 31 can prevent system instability caused by sudden changes in flow rate and accurately control the fluid flow rate through the valve. When flow rate control is not required, rapid flow can be achieved through the other position where the first throttle valve 31 is not installed.

[0055] The diagram shows the first throttle valve 31 configured in the second position of the multi-stage directional valve 3. Alternatively, the first throttle valve 31 can be configured in the first position of the multi-stage directional valve 3 as a parallel configuration.

[0056] Among them, a second throttle valve 32 is configured on the pipeline connecting the oil inlet of the third or fourth position of the multi-stage reversing valve 3 and the upper oil outlet of the corresponding position.

[0057] A second throttle valve 32 is configured between the oil inlet in the third or fourth position and the corresponding lower oil outlet. When the oil passes through the third or fourth position where the second throttle valve 32 is configured, the flow rate can be controlled by the second throttle valve 32, thereby improving the stability of the hydraulic system. When the multi-stage directional valve 3 switches positions, the second throttle valve 32 can prevent system instability caused by sudden changes in flow rate and accurately control the fluid flow rate through the valve. When flow rate control is not required, rapid flow can be achieved through the other position where the second throttle valve 32 is not configured.

[0058] The diagram shows a second throttle valve 32 configured in the fourth position of the multi-stage directional valve 3. Alternatively, the second throttle valve 32 can be configured in the third position of the multi-stage directional valve 3 as a parallel configuration.

[0059] like Figures 1-8The filling valve 4 is a three-position four-way valve with three positions from top to bottom. Its first position has its lower oil inlet disconnected from its upper left oil outlet, upper right oil outlet, and lower left oil outlet. Its third position has its lower oil inlet connected to both the lower left oil outlet and the upper right oil outlet. The filling valve 4 can be switched to its first position, with its lower oil inlet connected to the outlet of the multi-stage directional valve 3, its upper left oil outlet connected to port T, its upper right oil outlet connected to the inlet of the shuttle valve assembly, and its lower left oil outlet connected to port R. The filling valve 4 can be switched to its third position, with its lower oil inlet connected to the outlet of the multi-stage directional valve 3, its lower left oil outlet connected to port R, and its upper right oil outlet connected to the inlet of the shuttle valve assembly.

[0060] like Figure 5 and Figure 6 When the trailer brakes, the hydraulic fluid enters the TB port from the outlet of the multi-stage directional valve 3; for example... Figure 4 During the filling and / or service braking process, the filling valve 4 switches to its third position. The oil enters from the outlet of the multi-stage directional valve 3 into the lower inlet of the filling valve 4 at the third position. The oil is discharged from the lower left outlet of the third position to the R port and from the upper right outlet of the third position to the inlet of the shuttle valve assembly.

[0061] like Figures 1-8 Solenoid valve 5 is a two-position three-way valve. When solenoid valve 5 is switched to its first position, port R is connected to port X, or when it is switched to its second position, port X is connected to port T.

[0062] When the tractor is in motion, releasing the handbrake energizes solenoid valve 5, allowing hydraulic fluid to flow through the upper position of solenoid valve 5 and into the parking brake chamber via port X. This releases the parking brake from the tractor. At this time, as... Figure 6 The oil can enter the first position of solenoid valve 5 from port R, and then exit to port X; when the tractor stops and the handbrake is pulled, solenoid valve 5 is de-energized, as... Figure 2 The oil in the parking brake chamber is discharged to port T through the second position of solenoid valve 5 and flows back to the oil tank. At this time, the tractor realizes parking brake.

[0063] like Figures 1-8 A filter screen 9 is installed on the pipeline connecting the oil outlet of the steering priority valve 2 to the oil inlet of the shuttle valve assembly.

[0064] The hydraulic oil is filtered through filter screen 9 to effectively remove impurities and particles from the oil, preventing these impurities from entering the shuttle valve assembly. This avoids wear or jamming of internal components of the valve assembly, ensuring the stability and reliability of the hydraulic system, and also helps to extend the system's maintenance cycle and service life.

[0065] The working principle of the tractor multi-level priority system of the present invention is as follows:

[0066] 1. For example Figure 2After the vehicle is powered on, the unloading valve 6 is energized, connecting the pressurized oil at the LS OUT port to the oil tank. The pressurized oil flows from the LS OUT port through the unloading valve 6 into the T port and is then returned to the oil tank. At this time, the hydraulic system has no load feedback to the variable pump 1. When the engine starts, the vehicle starts very easily, solving the problems of hydraulic energy waste and the difficulty in starting the engine due to a large load. Figure 1 After the engine starts and the engine speed stabilizes, the unloading valve 6 is de-energized. At this time, the maximum load signal of the hydraulic system is compared by the second shuttle valve 8 and fed back to the variable pump through LS OUT to control the pressure and flow of the variable pump 1 to meet the requirements of the hydraulic system.

[0067] 2. To ensure the highest steering priority, a steering priority valve 2 is integrated. The spring force of the priority valve keeps the pressure differential at the main valve port of the steering valve constant. The downstream of steering priority valve 2 is connected to the hydraulic system of other actuators. When the steering system is not working, the ST port is closed. Due to the damping orifice, some oil flows back to the oil tank through the damping orifice and the connected LS circuit. The resulting pressure differential causes the valve core to move. At this time, the opening of other oil circuits increases, while the opening of the ST port in the steering oil circuit decreases. That is, when the steering system does not require flow, only a small amount of oil that guides and controls the position of the valve core flows back to the oil tank, while a large amount of oil is supplied to other working oil circuits, resulting in high efficiency.

[0068] 3. For example Figure 3 When the machine is steering, the steering system load enters the valve through the LS ST port. After comparison by the second shuttle valve 8, the maximum load is fed back to the variable pump 1 via LS OUT. The variable pump 1 switches from a small displacement operating state to a large displacement operating state, and the steering priority valve 2 gradually switches to the lower position operating state. The flow rate to the ST oil circuit increases, while the flow rate to other oil circuits decreases. As the steering system load changes, the variable pump 1 supplies oil to the steering cylinder as needed. Figure 4 When the steering is not working, the oil at port P enters the multi-stage reversing valve 3 and the lower position of the filling valve 4 through the steering priority valve 2, and then provides brake oil to port R or fills the accumulator. At this time, the load LS pressure is compared by the second shuttle valve 8 and the maximum load pressure is output and fed back to the variable pump 1. The variable pump 1 is in the large displacement working state and continuously fills port R (accumulator). When the pressure at port R reaches the spring setting value of filling valve 4, filling valve 4 reverses to the uppermost position and the filling ends.

[0069] 4. For example Figure 5 and Figure 6When there is a trailer braking requirement, the tractor depresses the road brake pedal and applies pilot control oil to the trailer control system, controlling the valve reversing action in the trailer braking system and feeding back the load signal to the variable pump 1. Then, the TB port (connected to the trailer braking system) provides pressure according to the trailer load requirement, thereby realizing the trailer braking function. During this process, the oil at the P port enters the multi-stage reversing valve 3, and enters the TB port through the third or fourth position of the multi-stage reversing valve 3. At the same time, the oil enters the first inlet of the first shuttle valve 7 from the LS TB port, and enters the first inlet of the second shuttle valve 8 through the outlet of the first shuttle valve 7. Then, the oil is guided from the outlet of the second shuttle valve 8 to the LS OUT port, feeding back the load signal to the variable pump 1.

[0070] 5. When the tractor is in motion, release the handbrake, and the solenoid valve 5 is energized (the R port is connected to the braking system and accumulator). The oil flows through the upper position of the solenoid valve 5 and into the parking brake chamber through the X port, and the tractor releases the parking brake state and can be driven. When the tractor stops, pull up the handbrake. At this time, the solenoid valve 5 is de-energized, and the oil in the parking brake chamber flows back to the oil tank through the lower position of the solenoid valve 5. At this time, the tractor realizes the parking brake.

[0071] Example 2

[0072] This embodiment 2 provides a hydraulic system, which includes the tractor multi-level priority system as described in embodiment 1.

[0073] Example 3

[0074] This embodiment 3 provides a tractor that includes the hydraulic system described in embodiment 2.

[0075] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0076] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0077] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0078] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0079] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0080] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A tractor multi-level priority system, comprising an inlet P port for communication with the outlet of a variable pump (1), a bidirectional oil port LS OUT port for communication with the feedback port of the variable pump (1), an ST port for communication with the steering system, a signal feedback LS ST port for receiving steering LS feedback signals, a signal feedback LS TB port for receiving trailer LS feedback signals, a TB port for receiving trailer braking signals, an R port for connecting the braking system and an accumulator, an X port for connecting the parking brake system, a return oil port T port for communication with an oil tank, and an EF port for communication with other actuators, characterized in that, This includes a steering priority valve (2), a multi-stage directional valve (3), a filling valve (4), a solenoid valve (5), an unloading valve (6), and a shuttle valve assembly, wherein: The oil inlet of the steering priority valve (2) is connected to the P port, and its oil outlet is connected to the ST port, the LS ST port and the oil inlet of the shuttle valve assembly. The inlet of the multi-stage reversing valve (3) is connected to port P, and can be switched to its outlet to connect to port EF, or to its outlet to connect to the inlet of the filling valve (4), or to its outlet to connect to port TB. The filling valve (4) can be switched to a state in which its oil inlet is connected to its oil outlet and its oil outlet is connected to the R port and the oil inlet of the shuttle valve group, or switched to a state in which its oil inlet is disconnected from its oil outlet. The solenoid valve (5) can be switched to have its inlet port connected to port R and its outlet port connected to port X, or to have its inlet port connected to port X and its outlet port connected to port T. The oil inlet of the unloading valve (6) is connected to the LS OUT port, and its oil outlet is connected to the T port. The shuttle valve assembly can be switched so that its inlet is connected to the outlet of the steering priority valve (2) and its outlet is connected to the LSOUT port, or switched so that its inlet is connected to the outlet of the filling valve (4) and its outlet is connected to the LSOUT port, or switched so that its inlet is connected to the LSTB port and its outlet is connected to the LSOUT port. The shuttle valve assembly includes a first shuttle valve (7) and a second shuttle valve (8) whose first inlet is connected to the outlet of the first shuttle valve (7). The second inlet of the second shuttle valve (8) is connected to the outlet of the steering priority valve (2), and the outlet of the second shuttle valve (8) is connected to the LS OUT port. The first shuttle valve (7) can be switched to have its outlet and its first inlet connected, and its first inlet connected to the LS TB port at the same time, or switched to have its outlet and its second inlet connected, and its second inlet connected to the outlet of the filling valve (4). The multi-stage reversing valve (3) is a five-position three-way valve with five positions from top to bottom. The oil inlets of its first and second positions are connected to the upper and lower oil outlets of the corresponding positions. The oil inlets of its third and fourth positions are connected to the upper oil outlets of the corresponding positions and disconnected from the lower oil outlets of the corresponding positions. The multi-stage reversing valve (3) can be switched to connect its oil inlet to port P at any position, and can be switched to connect its lower oil outlet to port EF at its first or second position, or to connect its upper oil outlet to the oil inlet of the filling valve (4) at its third or fourth position, or to connect its upper oil outlet to port TB at its third or fourth position.

2. The tractor multi-level priority system according to claim 1, characterized in that, A first throttle valve (31) is installed on the pipeline connecting the oil inlet of the first or second position of the multi-stage directional valve (3) to the lower oil outlet of the corresponding position.

3. The tractor multi-level priority system according to claim 1, characterized in that, A second throttle valve (32) is provided on the pipeline connecting the oil inlet of the third or fourth position of the multi-stage reversing valve (3) to the upper oil outlet of the corresponding position.

4. The tractor multi-level priority system according to claim 1, characterized in that, The filling valve (4) is a three-position four-way valve with three positions from top to bottom. Its first position has its lower oil inlet disconnected from its upper left oil outlet, upper right oil outlet and lower left oil outlet. Its third position has its lower oil inlet connected to both the lower left oil outlet and the upper right oil outlet. The filling valve (4) can be switched to its first position with its lower oil inlet connected to the oil outlet of the multi-stage directional valve (3), its upper left oil outlet connected to port T, its upper right oil outlet connected to the oil inlet of the shuttle valve group, and its lower left oil outlet connected to port R. The filling valve (4) can be switched to its third position with its lower oil inlet connected to the oil outlet of the multi-stage directional valve (3), its lower left oil outlet connected to port R, and its upper right oil outlet connected to the oil inlet of the shuttle valve group.

5. A tractor multi-level priority system according to claim 1, characterized in that, The solenoid valve (5) is a two-position three-way valve. When the solenoid valve (5) is switched to its first position, the R port is connected to the X port, or when it is switched to its second position, the X port is connected to the T port.

6. A tractor multi-level priority system according to any one of claims 1-5, characterized in that, A filter screen (9) is installed on the pipeline connecting the oil outlet of the steering priority valve (2) to the oil inlet of the shuttle valve assembly.

7. A hydraulic system, characterized in that, It includes the tractor multi-level priority system as described in any one of claims 1-6.

8. A tractor, characterized in that, It includes the hydraulic system as described in claim 7.

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