Steering valve group, rear wheel steering system and sprayer

Abstract

The present invention discloses a steering valve group, a rear wheel steering system and a sprayer, the steering valve group includes a three-position six-way valve, a two-position eight-way valve and a two-position three-way solenoid valve; the two-position three-way solenoid valve has an oil inlet, an oil return port, a working oil port and a pilot oil port; the two-position eight-way valve has eight oil ports and two pilot oil ports; the three-position six-way valve has six oil ports and two pilot oil ports; the pilot oil port of the two-position three-way solenoid valve is connected to its oil return port, one oil port of the two-position eight-way valve is connected to the pilot oil port at its right end, and the working oil port of the two-position three-way solenoid valve is connected to the pilot oil port at the left end of the two-position eight-way valve; the two-position eight-way valve and the three-position six-way valve are connected to each other, so that the two-position eight-way valve is opened or closed under the control of the two-position three-way solenoid valve, and when the two-position eight-way valve is in the open state, its oil supply flow is controlled by the three-position six-way valve, so that the steering amount can be accurately controlled.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic steering, and in particular relates to a steering valve group, a rear wheel steering system and a sprayer. Background Art

[0002] Conventional sprayers have two-wheel steering (mainly using two front wheels for steering), but their turning radius is large, and most of them use a mechanical linkage type with a front and rear axle structure. In addition, their steering mode is single, and in particular, they cannot achieve crab steering. The steering systems disclosed in document No. CN112997992B "A Crab Steering Hydraulic System for a High-Gap Sprayer" and document No. CN112983903B "A Full Hydraulic Steering System for a High-Gap Sprayer with Automatic Steering Function" can achieve four-wheel steering, but their hydraulic systems are complex and the steering accuracy cannot achieve high-precision rear-wheel steering. Summary of the Invention

[0003] In order to solve the above technical problems, one of the objectives of the present invention is to provide a steering valve group that can accurately control the steering angle of the rear wheels.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows: a steering valve group, including a three-position six-way valve, a two-position eight-way valve and a two-position three-way solenoid valve;

[0005] The two-position three-way solenoid valve has an oil inlet, an oil return port, a working oil port and a pilot oil port;

[0006] The two-position eight-way valve has eight oil ports and two pilot oil ports. The eight oil ports of the two-position eight-way valve are oil port A, oil port B, oil port C, oil port D, oil port E, oil port F, oil port G and oil port H. When the two-position eight-way valve is in the left position, oil port A is connected to oil port E, oil port B is connected to oil port F, and oil port C is connected to oil port G. When the two-position eight-way valve is in the right position, oil port A, oil port D and oil port G are connected.

[0007] The three-position six-way valve has six oil ports and two pilot oil ports. The six oil ports of the three-position six-way valve are oil port I, oil port J, oil port K, oil port L, oil port M and oil port N. When the three-position six-way valve is in the left position, oil port I, oil port K and oil port L are connected, and oil port J and oil port M are connected; when the three-position six-way valve is in the middle position, oil port K, oil port M and oil port N are connected; when the three-position six-way valve is in the right position, oil port J, oil port L and oil port N are connected, and oil port I and oil port M are connected;

[0008] The pilot oil port of the two-position three-way solenoid valve is connected to its oil return port, the oil port D of the two-position eight-way valve is connected to the pilot oil port at its right end, and the working oil port of the two-position three-way solenoid valve is connected to the pilot oil port at the left end of the two-position eight-way valve;

[0009] The oil port I is communicated with the oil port H, and the oil port J is communicated with the oil port G.

[0010] The beneficial effect of the above technical solution is that the two-position eight-way valve is opened or closed under the control of the two-position three-way solenoid valve, and when the two-position eight-way valve is in the open state, the flow at its oil port B and oil port C is controlled by the three-position six-way valve, so that the steering amount can be accurately controlled.

[0011] The above technical solution also includes a pressure reducing valve. The oil port E and the oil inlet of the two-position three-way solenoid valve are merged and the pressure reducing valve is provided at the confluence.

[0012] The beneficial effect of the above technical solution is that the oil pressure at the oil inlet of the two-position three-way valve and the oil port E of the two-position eight-way valve can be reduced in pressure (the hydraulic oil at the oil inlet and oil port E of the two-position three-way valve are both control oil circuits, which do not require higher hydraulic pressure) to avoid excessive oil pressure.

[0013] The pressure reducing valve in the above technical solution adopts a four-position three-way valve, which has an oil inlet, an oil return port, two working oil ports and two pilot oil ports. The oil port E and the oil inlet of the two-position three-way solenoid valve are both connected to the working oil port of the pressure reducing valve. The oil inlet of the pressure reducing valve is used to introduce hydraulic oil, and the oil return port of the pressure reducing valve is used to discharge hydraulic oil. The working oil port of the pressure reducing valve is connected to one of its pilot oil ports, and the oil return port of the pressure reducing valve is connected to its other pilot oil port.

[0014] The beneficial effect of the above technical solution is that: a four-position three-way valve is used to replace the pressure reducing valve, which has a good pressure reducing effect and can be turned on or off as needed.

[0015] A second object of the present invention is to provide a rear wheel steering system with a simple structure and high steering precision.

[0016] To achieve the above-mentioned object, the technical solution of the present invention is as follows: a rear wheel steering system comprising an oil supply line, an oil return line, two steering cylinders, an electronically controlled valve group and the steering valve group as described above;

[0017] The electric control valve group has an electric control end, an oil inlet, an oil return port and two working oil ports;

[0018] The steering cylinder is a double-acting cylinder, and the large-cavity oil ports of the two steering cylinders are connected to each other, and the small-cavity oil ports of the two steering cylinders are connected to the oil port B and the oil port C respectively;

[0019] The oil inlet of the electric control valve group is connected to the oil port A, the two working oil ports of the electric control valve group are respectively connected to the two pilot oil ports of the three-position six-way valve, and the sensing end of the electric control valve group is linked to the valve core of the three-position six-way valve;

[0020] The oil inlet of the two-position three-way solenoid valve, the oil port E of the two-position eight-way valve and the oil port L of the three-position six-way valve are all connected to the oil supply pipeline;

[0021] The oil port D, oil port H, oil port K, oil port M, oil port N, the oil return port of the two-position three-way solenoid valve and the oil return port of the electric control valve group are all connected to the oil return pipeline.

[0022] The beneficial effect of the above technical solution is that: in this way, the extension and retraction states of the two steering cylinders are opposite, and the hydraulic oil to the two steering cylinders flows to the two steering cylinders through the three-position six-way valve and the two-position eight-way valve, and the opening and closing amount of oil of the three-position six-way valve is controlled by the electronically controlled valve group, and the electronically controlled valve group is supplied with oil by the two-position eight-way valve, and the two-position eight-way valve is controlled to open and close by the two-position three-way solenoid valve. Therefore, only when the two-position three-way valve is in the open state, the two-position eight-way valve will be opened, and at this time the electronically controlled valve group will control the three-position six-way valve to open and close (the left and right positions of the three-position six-way valve are in the open state, and the middle position is in the closed state), and the extension and retraction of the steering cylinder will be started as a whole.

[0023] In the above technical solution, two return oil pipelines are provided, namely the first return oil pipeline a and the second return oil pipeline b. The oil port D, oil port H, oil port M and the return oil port of the electronically controlled valve group are all connected to the first return oil pipeline a, and the oil port K and oil port N are connected to the second return oil pipeline b.

[0024] The beneficial effect of the above technical solution is that it can prevent the oil pressure in the first oil return line and the second oil return line from being too high, thereby affecting the smoothness of the oil return (this is beneficial to improving the steering sensitivity).

[0025] In the above technical solution, a relief valve is provided at the connection point between the oil port H and the first oil return pipeline a.

[0026] The beneficial effect of the above technical solution is that when the two-position eight-way valve is in the closed state, the hydraulic oil in the oil inlet of the electronically controlled valve group can be preferentially discharged from the oil port D through the first oil return pipe.

[0027] In the above technical solution, a first throttle valve is provided on the second oil return pipeline b.

[0028] The beneficial effect of the above technical solution is that a certain oil discharge back pressure is provided on the second oil return pipeline.

[0029] The electrically controlled valve group in the above technical solution includes an electronic controller, two one-way valves and four two-position, two-way solenoid valves. The four two-position, two-way solenoid valves are connected in sequence to form a closed loop. The electronic controller is electrically connected to the four two-position, two-way solenoid valves. The connection point of two adjacent two-position, two-way solenoid valves forms a connecting port, of which two relatively distributed connecting ports constitute the two working oil ports of the electronically controlled valve group, and the remaining two connecting ports respectively constitute the oil inlet and oil return port of the electronically controlled valve group. Two of the one-way valves are connected in series between the two working oil ports of the electronically controlled valve group. The inlet ends of the two one-way valves face away from each other, and the oil return port of the electronically controlled valve group is connected to the oil outlet ends of the two one-way valves.

[0030] The beneficial effect of the above technical solution is that the four two-position two-way solenoid valves can be flexibly opened and closed in combination to drive the opening and closing state and opening and closing amount of the three-position six-way valve.

[0031] In the above technical solution, an oil filter is provided at the oil inlet of the electric control valve group, and a second throttle valve is provided at the oil return port of the electric control valve group.

[0032] The beneficial effect of the above technical solution is that it can prevent the residue in the hydraulic oil from entering the electric control valve group, thereby affecting the control sensitivity of the electric control valve group.

[0033] A third object of the present invention is to provide a sprayer with a simple structure and capable of rear wheel steering.

[0034] In order to achieve the above object, another technical solution of the present invention is as follows: a sprayer includes the rear wheel steering system as described above.

[0035] The beneficial effects of the above technical solution are: its structure is simple, its front wheels can also match the front wheel steering, and the rear wheel steering function can be opened and closed by the two-position three-way valve. When the two-position three-way valve is in the open state, the hydraulic rear wheel steering system of the sprayer can cooperate with the front wheel steering system to achieve four-wheel steering, which makes the function of the entire sprayer more diverse. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a structural diagram of the steering valve group described in Example 1 of the present invention;

[0037] Figure 2 This is another structural schematic diagram of the steering valve group according to Example 1 of the present invention;

[0038] Figure 3 Schematic diagram of the structure of the rear-wheel steering system according to embodiment 2 of the present invention;

[0039] Figure 4 This is a structural diagram of the electric control valve group described in Example 2 of the present invention.

[0040] In the figure: 1. Steering valve group; 11. Three-position six-way valve; 12. Two-position eight-way valve; 13. Two-position three-way solenoid valve; 14. Pressure reducing valve; 2. Oil supply line; 3. Oil return line; 3a. First oil return line; 3b. Second oil return line; 4. Steering cylinder; 5. Electric control valve group; 51. Electric controller; 52. One-way valve; 53. Two-position two-way solenoid valve; 54. Oil filter; 55. Second throttle valve; 6. Overflow valve; 7. First throttle valve. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. The following paragraphs describe the present invention in more detail by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in exact proportions. They are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a steering valve group, including a three-position six-way valve 11, a two-position eight-way valve 12 and a two-position three-way solenoid valve 13;

[0044] The two-position three-way solenoid valve 13 has an oil inlet, an oil return port, a working oil port and a pilot oil port;

[0045] The two-position eight-way valve 12 has eight oil ports and two pilot oil ports. The eight oil ports of the two-position eight-way valve 12 are oil port A, oil port B, oil port C, oil port D, oil port E, oil port F, oil port G and oil port H. When the two-position eight-way valve 12 is in the left position, oil port A is connected to oil port E, oil port B is connected to oil port F, and oil port C is connected to oil port G. When the two-position eight-way valve 12 is in the right position, oil port A, oil port D and oil port G are connected.

[0046] The three-position six-way valve 11 has six oil ports and two pilot oil ports. The six oil ports of the three-position six-way valve 11 are oil port I, oil port J, oil port K, oil port L, oil port M and oil port N. When the three-position six-way valve 11 is in the left position, oil port I, oil port K and oil port L are connected, and oil port J and oil port M are connected; when the three-position six-way valve 11 is in the middle position, oil port K, oil port M and oil port N are connected; when the three-position six-way valve 11 is in the right position, oil port J, oil port L and oil port N are connected, and oil port I and oil port M are connected;

[0047] The pilot oil port of the two-position three-way solenoid valve 13 is connected to its oil return port, the oil port D of the two-position eight-way valve 12 is connected to the pilot oil port at its right end, and the working oil port of the two-position three-way solenoid valve 13 is connected to the pilot oil port at the left end of the two-position eight-way valve 12;

[0048] The oil port I is connected to the oil port H, and the oil port J is connected to the oil port G; in this way, the two-position eight-way valve is opened or closed under the control of the two-position three-way solenoid valve, and when the two-position eight-way valve is in the open state, the flow at its oil ports B and C is controlled by the three-position six-way valve, so that the steering amount can be accurately controlled.

[0049] in, Figure 1 and Figure 2 In the figure, A, B, C, D...M and N represent oil port A, oil port B, oil port C, oil port D...oil port M and oil port N respectively.

[0050] like Figure 2 As shown, the above technical solution also includes a pressure reducing valve 14, the oil port E and the oil inlet of the two-position three-way solenoid valve 13 are merged and the pressure reducing valve 14 is provided at the confluence; in this way, the oil pressure of the oil inlet of the two-position three-way valve and the oil port E of the two-position eight-way valve can be reduced in pressure (the hydraulic oil at the oil inlet of the two-position three-way valve and the oil port E are both control oil circuits, which do not require higher hydraulic pressure) to avoid excessive oil pressure.

[0051] The pressure reducing valve 14 in the above technical solution adopts a four-position three-way valve, which has an oil inlet, an oil return port, two working oil ports and two pilot oil ports. The oil port E and the oil inlet of the two-position three-way solenoid valve 13 are both connected to the working oil port of the pressure reducing valve 14. The oil inlet of the pressure reducing valve 14 is used to introduce hydraulic oil, and the oil return port of the pressure reducing valve 14 is used to discharge hydraulic oil. The working oil port of the pressure reducing valve 14 is connected to one of its pilot oil ports, and the oil return port of the pressure reducing valve 14 is connected to the other pilot oil port; that is, a four-position three-way valve is used to replace the pressure reducing valve, which has a good reduction effect and can also be turned on or off as needed.

[0052] Example 2

[0053] like Figure 3 As shown, this embodiment provides a rear wheel steering system, comprising an oil supply line 2, an oil return line 3, two steering cylinders 4, an electronically controlled valve group 5 and the steering valve group 1 as described in Example 1;

[0054] The electric control valve group 5 has an electric control end, an oil inlet, an oil return port and two working oil ports;

[0055] The steering cylinder 4 is a double-acting cylinder, and the large-cavity oil ports of the two steering cylinders 4 are connected to each other, and the small-cavity oil ports of the two steering cylinders 4 are connected to the oil port B and the oil port C respectively;

[0056] The oil inlet of the electric control valve group 5 is connected to the oil port A, the two working oil ports of the electric control valve group 5 are respectively connected to the two pilot oil ports of the three-position six-way valve 11, and the sensing end of the electric control valve group 5 is linked to the valve core of the three-position six-way valve 11;

[0057] The oil inlet of the two-position three-way solenoid valve 13, the oil port E of the two-position eight-way valve 12 and the oil port L of the three-position six-way valve 11 are all connected to the oil supply pipeline 2;

[0058] The oil port D, oil port H, oil port K, oil port M, oil port N, the return oil port of the two-position three-way solenoid valve 13 and the return oil port of the electronically controlled valve group 5 are all connected to the return oil pipeline 3, so that the extension and contraction states of the two steering cylinders are opposite, and the hydraulic oil to the two steering cylinders flows to the two steering cylinders through the three-position six-way valve and the two-position eight-way valve, and the opening and closing amount of the three-position six-way valve is controlled by the electronically controlled valve group, and the electronically controlled valve group is supplied with oil by the two-position eight-way valve, and the two-position eight-way valve is controlled to open and close by the two-position three-way solenoid valve. Therefore, only when the two-position three-way valve is in the open state, the two-position eight-way valve will be opened, and the electronically controlled valve group will control the three-position six-way valve to open and close (the left and right positions of the three-position six-way valve are in the open state, and the middle position is in the closed state), and the extension and contraction of the steering cylinder will be started as a whole.

[0059] In the above technical solution, two return oil pipelines 3 are provided, namely the first return oil pipeline 3a and the second return oil pipeline 3b. The oil port D, oil port H, oil port M and the return oil port of the electronically controlled valve group 5 are all connected to the first return oil pipeline 3a, and the oil port K and oil port N are connected to the second return oil pipeline 3b. In this way, the first return oil pipeline and the second return oil pipeline can avoid excessive oil pressure affecting the smoothness of the return oil (this is conducive to improving the sensitivity of steering).

[0060] In the above technical solution, an overflow valve 6 is provided at the connection point between the oil port H and the first oil return pipeline 3a, so that when the two-position eight-way valve is in the closed state, the hydraulic oil at the oil inlet of the electronically controlled valve group can be discharged preferentially from the oil port D through the first oil return pipe.

[0061] In the above technical solution, the second oil return pipeline 3b is provided with a first throttle valve 7, so that a certain oil discharge back pressure is generated on the second oil return pipeline.

[0062] Specifically, in this embodiment, the oil port E and the oil inlet of the two-position three-way solenoid valve 13 are both connected to the oil supply pipeline 2 through the pressure reducing valve 14, the oil inlet of the pressure reducing valve 14 is connected to the oil supply pipeline 2, and the oil return port of the pressure reducing valve 14 is connected to the oil return pipeline 3.

[0063] like Figure 4As shown, the electronically controlled valve group 5 in the above technical solution includes an electronic controller 51, two one-way valves 52 and four two-position two-way solenoid valves 53, and the four two-position two-way solenoid valves 53 are connected in sequence to form a closed loop. The electronic controller 51 is electrically connected to the four two-position two-way solenoid valves 53, and the connection point of two adjacent two-position two-way solenoid valves 53 forms a connecting port, wherein two relatively distributed connecting ports constitute the two working oil ports of the electronically controlled valve group 5, and the remaining two connecting ports respectively constitute the oil inlet and oil return port of the electronically controlled valve group 5, and two of the one-way valves 52 are connected in series between the two working oil ports of the electronically controlled valve group 5, the inlet ends of the two one-way valves 52 are away from each other, and the oil return port of the electronically controlled valve group 5 is connected to the oil outlet ends of the two one-way valves 52, so that the four two-position two-way solenoid valves can be flexibly opened and closed to drive the opening and closing state and opening and closing amount of the three-position six-way valve.

[0064] In the above technical solution, an oil filter 54 is provided at the oil inlet of the electric control valve group 5, and a second throttle valve 55 is provided at the oil return port of the electric control valve group 5, so as to prevent the residue in the hydraulic oil from entering the electric control valve group, thereby affecting the sensitivity of the control of the electric control valve group.

[0065] The two-position three-way valve in this embodiment controls the opening or closing of the entire rear-wheel steering system. In the open state, it controls the two-position eight-way valve to be in the left position (open state). At this time, a portion of the hydraulic oil after decompression will flow to the electronic control valve group, and the electronic control valve group is connected to the two pilot oil ports of the three-position six-way valve to realize the control of the opening and closing amount of the three-position six-way valve (and the valve core of the three-position six-way valve is linked due to the sensing end of the electronic controller 51. At this time, a control loop is formed between the three-position six-way valve and the electronic control valve group, that is, the electric controller senses the movement of the valve core of the three-position six-way valve, and the electronic controller receives the steering command and accordingly opens and closes the four two-position two-way valves to drive the valve core of the three-position six-way valve to move). When the three-position six-way valve is in the left position, the two steering cylinders drive the two rear wheels to deflect backward. When the three-position six-way valve is in the right position, the two steering cylinders drive the two rear wheels to deflect to the left. When the three-position six-way valve is in the middle position, the two steering cylinders drive the two rear wheels to maintain the corresponding deflection angle.

[0066] In this embodiment, the electronic controller can accept the front wheel steering angle for linkage, that is, the angle of the front wheel steering is monitored by the angle sensor, and the electronic controller accepts the angle sensed by the angle sensor to adjust the movement of the three-position six-way valve core.

[0067] When the two-position three-way solenoid valve is in the closed state, the two-position eight-way valve is in the right position (closed state). At this time, the electronically controlled valve group does not take in oil, so it cannot operate the three-position six-way valve. At this time, the connection between the hydraulic three-position six-way valve and the steering cylinder is also cut off by the two-position eight-way valve, so the steering cylinder remains stationary.

[0068] In this embodiment, the oil port K and the oil port N both have a throttling function, so that if the two steering cylinders encounter greater resistance during extension and retraction, they have a certain buffering and avoidance function.

[0069] When the two-position three-way valve in this embodiment is in a closed state, the entire sprayer can be steered solely by its front wheel steering system.

[0070] Figure 4 In the figure, X represents the sensing end of the electronic controller; Y and Z represent the two working oil ports of the electronic control valve group. Figure 3 and Figure 4 P in the middle indicates the oil supply end, and T indicates the oil return end. Figure 4 The middle dotted line indicates the electrical connection between the electronic controller and the four two-position two-way valves.

[0071] The operating principle of the electric control valve group in this embodiment can be as follows: Figure 4 For example, four two-position two-way valves are labeled a, b, c, and d respectively. The connection between a and b corresponds to the oil inlet of the electric control valve group, the connection between c and d corresponds to the oil return port of the electric control valve group, and the connection between b and c corresponds to one working oil port of the electric control valve group, and the connection between a and d corresponds to the other working oil port of the electric control valve group. Two one-way valves are arranged between the two working oil ports, and the oil inlet ends of the two one-way valves are close to each other and are connected to the oil return port of the electric control valve group. , and a second throttle valve is set at the return oil port of the electric control valve group. In this way, if the flow of hydraulic oil at the return oil port of the electric control valve group is large (the second throttle valve is holding pressure), the two one-way valves will be pushed open in the opposite direction, so that both of its two working oil ports are pressurized. At this time, the three-position six-way valve returns to the middle position, and ac is opened and bd is closed, then the working oil port (Y) is pressurized. Conversely, bd is opened and ac is closed, then the working oil port (Z) is pressurized. For the specific operating principle of the electric control valve group, please refer to Danfoss's PVES electronic control module.

[0072] Example 3

[0073] This embodiment provides a sprayer, including the rear-wheel steering system as described in Example 2. Its structure is simple, and its front wheels can also match the front-wheel steering. The rear-wheel steering function can be turned on and off by a two-position three-way valve. When the two-position three-way valve is in the open state, the hydraulic rear-wheel steering system of the sprayer can cooperate with the front-wheel steering system to achieve four-wheel steering, which makes the function of the entire sprayer more diverse.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A steering valve group, characterized in that: It includes a three-position six-way valve (11), a two-position eight-way valve (12) and a two-position three-way solenoid valve (13); The two-position three-way solenoid valve (13) has an oil inlet, an oil return port, a working oil port and a pilot oil port; The two-position eight-way valve (12) has eight oil ports and two pilot oil ports, and the eight oil ports of the two-position eight-way valve (12) are oil port A, oil port B, oil port C, oil port D, oil port E, oil port F, oil port G and oil port H; when the two-position eight-way valve (12) is in the left position, oil port A is connected to oil port E, oil port B is connected to oil port F, and oil port C is connected to oil port G; when the two-position eight-way valve (12) is in the right position, oil port A, oil port D and oil port G are connected; The three-position six-way valve (11) has six oil ports and two pilot oil ports, and the six oil ports of the three-position six-way valve (11) are oil port I, oil port J, oil port K, oil port L, oil port M and oil port N respectively; when the three-position six-way valve (11) is in the left position, oil port I, oil port K and oil port L are connected, and oil port J and oil port M are connected; when the three-position six-way valve (11) is in the middle position, oil port K, oil port M and oil port N are connected; when the three-position six-way valve (11) is in the right position, oil port J, oil port L and oil port N are connected, and oil port I and oil port M are connected; The pilot oil port of the two-position three-way solenoid valve (13) is connected to its oil return port, the oil port D of the two-position eight-way valve (12) is connected to the pilot oil port at its right end, and the working oil port of the two-position three-way solenoid valve (13) is connected to the pilot oil port at the left end of the two-position eight-way valve (12); The oil port I is communicated with the oil port H, and the oil port J is communicated with the oil port G.

2. The steering valve assembly according to claim 1, characterized in that: It also includes a pressure reducing valve (14), the oil port E and the oil inlet of the two-position three-way solenoid valve (13) are merged, and the pressure reducing valve (14) is provided at the merging point.

3. The steering valve assembly according to claim 2, characterized in that: The pressure reducing valve (14) adopts a four-position three-way valve, which has an oil inlet, an oil return port, two working oil ports and two pilot oil ports. The oil port E and the oil inlet of the two-position three-way solenoid valve (13) are both connected to the working oil port of the pressure reducing valve (14). The oil inlet of the pressure reducing valve (14) is used to introduce hydraulic oil, and the oil return port of the pressure reducing valve (14) is used to discharge hydraulic oil. The working oil port of the pressure reducing valve (14) is connected to one of its pilot oil ports, and the oil return port of the pressure reducing valve (14) is connected to the other of its pilot oil ports.

4. A rear wheel steering system, characterized in that: It comprises an oil supply pipeline (2), an oil return pipeline (3), two steering oil cylinders (4), an electric control valve group (5) and a steering valve group (1) according to any one of claims 1 to 3; The electric control valve group (5) has an electric control end, an oil inlet, an oil return port and two working oil ports; The steering oil cylinder (4) is a double-acting oil cylinder, and the large cavity oil ports of the two steering oil cylinders (4) are connected to each other, and the small cavity oil ports of the two steering oil cylinders (4) are connected to the oil port B and the oil port C respectively; The oil inlet of the electric control valve group (5) is connected to the oil port A, the two working oil ports of the electric control valve group (5) are respectively connected to the two pilot oil ports of the three-position six-way valve (11), and the sensing end of the electric control valve group (5) is linked to the valve core of the three-position six-way valve (11); The oil inlet of the two-position three-way solenoid valve (13), the oil port E of the two-position eight-way valve (12), and the oil port L of the three-position six-way valve (11) are all in communication with the oil supply pipeline (2); The oil port D, the oil port H, the oil port K, the oil port M, the oil port N, the oil return port of the two-position three-way solenoid valve (13) and the oil return port of the electric control valve group (5) are all connected to the oil return pipeline (3).

5. The rear wheel steering system according to claim 4, characterized in that: The oil return pipeline (3) is provided with two, namely a first oil return pipeline (3a) and a second oil return pipeline (3b); the oil port D, the oil port H, the oil port M and the oil return port of the electric control valve group (5) are all connected to the first oil return pipeline (3a); the oil port K and the oil port N are connected to the second oil return pipeline (3b).

6. The rear wheel steering system according to claim 5, characterized in that: An overflow valve (6) is provided at the connection point between the oil port H and the first oil return pipeline (3a).

7. The rear wheel steering system according to claim 5, characterized in that: A first throttle valve (7) is provided on the second oil return pipeline (3b).

8. The rear wheel steering system according to claim 4, characterized in that: The electric control valve group (5) comprises an electric controller (51), two one-way valves (52) and four two-position two-way solenoid valves (53). The four two-position two-way solenoid valves (53) are sequentially connected to form a closed loop. The electric controller (51) is electrically connected to the four two-position two-way solenoid valves (53). The connection point of two adjacent two-position two-way solenoid valves (53) forms a connecting port, wherein two relatively distributed connecting ports constitute two working oil ports of the electric control valve group (5), and the remaining two connecting ports respectively constitute the oil inlet and oil return port of the electric control valve group (5). Two one-way valves (52) are connected in series between the two working oil ports of the electric control valve group (5). The inlet ends of the two one-way valves (52) are opposite to each other, and the oil return port of the electric control valve group (5) is connected to the oil outlet ends of the two one-way valves (52).

9. The rear wheel steering system according to claim 4, characterized in that: An oil filter (54) is provided at the oil inlet of the electric control valve group (5), and a second throttle valve (55) is provided at the oil return port of the electric control valve group (5).

10. A sprayer, characterized in that: Comprising a rear wheel steering system as described in any one of claims 4-9.

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