Electric proportional power reversing valve group for tractor

Abstract

The application discloses a tractor electric proportional power reversing valve group, which comprises a valve body, an overflow valve, a reversing electromagnetic valve and a cut-off electromagnetic valve arranged on the valve body; the cut-off electromagnetic valve oil inlet is connected with an oil inlet channel; the cut-off electromagnetic valve oil outlet, the reversing electromagnetic valve oil inlet and the overflow valve oil inlet are connected in parallel through an oil inlet channel two; the reversing electromagnetic valve forward gear oil outlet is connected with a working oil channel one; the reversing electromagnetic valve backward gear oil outlet is connected with a working oil channel two; the overflow valve oil outlet is connected with an oil return channel four; the reversing electromagnetic valve oil return and the cut-off electromagnetic valve oil return are connected in parallel to an oil return channel two. Through the interaction between the overflow valve and the proportional electromagnetic valve, the proportional electromagnetic valve is provided with different currents in different time periods, adjustable working oil pressure is provided for the clutch oil filling, the process from the clutch oil filling to mutual engagement and tightness of the clutch internal friction plate is soft and free of impact, and the mechanical transmission effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic valve assembly technology, specifically to an electric proportional power directional valve assembly for tractors. Background Technology

[0002] As an important component of tractors, the power unit is crucial to the tractor's farming efficiency and the successful transformation of agricultural modernization.

[0003] Currently, most tractors in China use mechanical hydraulic control for their power units. During gear shifting, especially when switching directly from forward to reverse or vice versa, there is a noticeable shock. A pause in neutral is necessary between the two gears to mitigate this shock. This increased shifting time is particularly pronounced when the tractor is frequently reversing direction in the field, affecting rapid tillage efficiency. Furthermore, both forward and reverse gear hydraulic circuits require additional buffer devices, resulting in a large footprint, complex structure, and difficult maintenance. Frequent mechanical gear shifting also increases labor intensity, and the existing design cannot meet user needs. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide an electro-proportional power reversing valve group for tractors, which uses electro-proportional control technology to distribute the electro-hydraulic ratio of gear shifting and adjust the stepless speed change, enabling the tractor power unit to achieve smooth and shock-free gear shifting.

[0005] Therefore, the present invention proposes an electric proportional power reversing valve assembly for tractors, including a valve body and an overflow valve, a reversing solenoid valve and a shut-off solenoid valve disposed on the valve body; it also includes an oil inlet circuit one, an oil inlet circuit two, an oil return circuit four, an oil return circuit two, a working oil circuit one and a working oil circuit two.

[0006] The inlet of the shut-off solenoid valve is connected to the first oil inlet circuit. The outlet of the shut-off solenoid valve, the inlet of the reversing solenoid valve, and the inlet of the overflow valve are connected in parallel through the second oil inlet circuit. The forward gear outlet of the reversing solenoid valve is connected to the first working oil circuit. The reverse gear outlet of the reversing solenoid valve is connected to the second working oil circuit. In addition, the outlet of the overflow valve is connected to the fourth return oil circuit. The return oil ports of the reversing solenoid valve and the return oil ports of the shut-off solenoid valve are connected in parallel to the second return oil circuit. The back pressure end of the overflow valve is connected to a control unit, which is used to control the oil pressure in the second oil inlet circuit leading to the inlet of the reversing solenoid valve to increase slowly, so as to realize smooth and gentle, shock-free gear shifting of the tractor.

[0007] Furthermore, the valve body is also equipped with a proportional solenoid valve, the oil inlet of the proportional solenoid valve is connected to the first oil inlet circuit, the oil outlet of the proportional solenoid valve is connected to the back pressure port of the overflow valve through the back pressure oil circuit, and the oil return port of the proportional solenoid valve is externally connected to the third oil return circuit.

[0008] Furthermore, the proportional solenoid valve is a normally closed two-position three-way valve. When power is lost, the oil inlet of the proportional solenoid valve is closed, and the oil outlet of the proportional solenoid valve is connected to the oil return port; when power is supplied, the oil inlet of the proportional solenoid valve is connected to the oil outlet of the proportional solenoid valve.

[0009] Furthermore, the proportional solenoid valve includes a valve seat, an inlet valve, an unloading valve, a spring, a valve core, an electromagnet, and a coil; the valve core is installed in the cavity of the valve seat, the spring is disposed at both ends of the valve core, the electromagnet is disposed outside one end of the valve core, and the coil is located outside the circumference of the electromagnet; the inlet valve and the unloading valve are provided on the cavity of the valve seat.

[0010] Furthermore, the shut-off solenoid valve is a normally open two-position four-way solenoid valve. When de-energized, the oil inlet of the shut-off solenoid valve is connected to the oil outlet of the shut-off solenoid valve; when energized, the oil outlet of the shut-off solenoid valve is connected to the oil return port of the shut-off solenoid valve.

[0011] Furthermore, the shut-off solenoid valve includes a screw plug, a spring, a spring seat, a first return oil valve, a second return oil valve, a slide valve, an inlet valve, an electromagnetic push rod, and a coil; the slide valve is located inside the valve cavity, and both ends of the slide valve are provided with the spring and the spring seat, the screw plug is located outside one of the springs, and the electromagnetic push rod is located outside the other spring.

[0012] Furthermore, the reversing solenoid valve is a normally closed three-position five-way solenoid valve. When de-energized, the oil inlet of the reversing solenoid valve is closed, and both the forward and reverse oil outlets of the reversing solenoid valve are connected to the return oil circuit. When energized, the oil inlet of the reversing solenoid valve is connected to either the forward or reverse oil outlet of the reversing solenoid valve.

[0013] Furthermore, the reversing solenoid valve includes a slide valve and a valve seat. One end of the slide valve is provided with a coil one, an electromagnet one, a spring and a spring seat; the other end of the slide valve is provided with an electromagnet two, a coil two, a spring and a spring seat; the cavity of the valve seat has a return oil valve one, a reverse gear valve, a forward gear valve and a return oil valve two arranged sequentially along the axial direction.

[0014] Furthermore, the overflow valve is a hydraulically controlled direct-acting structure, including a valve core, an oil drain port, a spring, a back pressure piston, a throttling orifice, and a valve seat; the valve core is installed in the valve seat, the oil inlet and outlet of the overflow valve are connected through the oil drain port, the back pressure piston is connected to the rear end of the valve core, the back pressure piston and the valve seat form an inner cavity, and the inner cavity is connected to the back pressure oil port of the overflow valve through the throttling orifice.

[0015] The electric proportional power reversing valve group for tractors provided by this invention interacts with the overflow valve and the proportional solenoid valve. By setting different currents for different time periods in the coil of the proportional solenoid valve, an adjustable working oil pressure is provided for the clutch oil filling. This makes the process of the friction plates inside the clutch from oil filling to mutual engagement and clamping smooth and without shock, thus achieving a mechanical transmission effect.

[0016] During cultivation, the electro-hydraulic ratio is adjusted according to the cultivation environment and needs to control the flow rate of oil filling / draining of the clutch, achieving smooth and shock-free gear shifting. The valve assembly integrates valve blocks with different functions into a single unit, simplifying the structure, making it small, lightweight, and easy to install. This valve assembly can improve operational performance, reduce the labor intensity of the driver, and increase cultivation efficiency.

[0017] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figures 1a-1c This is a schematic diagram of the electric proportional power reversing valve assembly for the tractor power unit of the present invention.

[0020] Figure 2 This is a schematic diagram of the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0021] Figure 3 This is a cross-sectional view of the shut-off solenoid valve in the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0022] Figure 4 This is a cross-sectional view of the overflow valve in the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0023] Figure 5 This is a cross-sectional view of the proportional solenoid valve in the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0024] Figure 6 This is a cross-sectional view of the reversing solenoid valve in the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0025] Figure 7 This is a characteristic curve diagram of the proportional solenoid valve in the electric proportional power reversing valve group for the tractor power unit of the present invention.

[0026] Explanation of reference numerals in the attached figures

[0027] 1. Valve body; 2. Relief valve; 3. Reversing solenoid valve; 4. Shut-off solenoid valve; 5. Proportional solenoid valve; 6. Oil inlet circuit 1; 7. Oil inlet circuit 2; 8. Oil return circuit 4; 9. Oil return circuit 3; 10. Oil return circuit 2; 11. Back pressure circuit; 12. Working circuit 1; 13. Working circuit 2; P. Hydraulic pump port; T1. Port 1; T2. Port 2; T3. Port 3; T4. Port 4; F. Forward clutch port; R. Reverse clutch port;

[0028] 14. Return valve one; 15. Return valve two; 16. Spool valve; 17. Inlet valve; 18. Electromagnetic push rod; 19. Coil; 111. Plug; 112. Spring; 113. Spring seat; 21. Valve core; 22. Drain port; 23. Spring; 24. Back pressure piston; 25. Throttling orifice; 26. Inner cavity; 27. Valve seat; 31. Valve seat; 32. Inlet valve; 33. Unloading valve; 34. Spring; 35. Valve core; 36. Electromagnet; 37. Coil; 41. Coil one; 42. Electromagnet one; 43. Spring; 44. Spring seat; 45. Spool valve; 46. Return valve one; 47. Reverse gear valve; 48. Forward gear valve; 49. Return valve two; 410. Electromagnet two; 411. Coil two. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] As shown in Figure 1~ Figure 2 As shown, the tractor electric proportional power reversing valve assembly of the present invention includes a valve body 1 and an overflow valve 2, a reversing solenoid valve 3, a shut-off solenoid valve 4, and a proportional solenoid valve 5 disposed on the valve body; it also includes: an oil inlet path 6 for parallel connection of the oil inlet of the shut-off solenoid valve 4 and the oil inlet of the proportional solenoid valve 5; an oil inlet path 7 for parallel connection of the oil outlet of the shut-off solenoid valve 4, the oil inlet of the reversing solenoid valve 3, and the oil inlet of the overflow valve 2; a return oil path 8 for connecting the oil outlet of the overflow valve 2; a return oil path 9 for connecting the return oil outlet of the proportional solenoid valve 5; a return oil path 10 for parallel connection of the return oil outlet of the reversing solenoid valve 3 and the return oil outlet of the shut-off solenoid valve 4; a back pressure oil path 11 for connecting the back pressure port of the overflow valve 2 and the oil outlet of the proportional solenoid valve 5; a working oil path 12 for connecting the forward gear outlet of the reversing solenoid valve 3; and a working oil path 13 for connecting the reverse gear outlet of the reversing solenoid valve 3.

[0031] In addition, the electric proportional power directional valve assembly also includes: a hydraulic pump port P for connecting to the hydraulic pump, a port T4 for connecting to the return oil circuit 4 8, a port T3 for connecting to the return oil circuit 3 9, a port T2 and a port T1 for connecting to the return oil circuit 2 10, a forward clutch port F for connecting to the forward gear clutch, and a reverse clutch port R for connecting to the reverse gear clutch.

[0032] Specifically, the inlet of the shut-off solenoid valve 4 is connected to the first oil inlet circuit 6, and the outlet of the shut-off solenoid valve 4, the inlet of the reversing solenoid valve 3, and the inlet of the overflow valve 2 are connected in parallel through the second oil inlet circuit 7; the forward gear outlet of the reversing solenoid valve 3 is connected to the first working oil circuit 12; the reverse gear outlet of the reversing solenoid valve 3 is connected to the second working oil circuit 13; in addition, the outlet of the overflow valve 2 is connected to the fourth oil return circuit 8; the return oil ports of the reversing solenoid valve 3 and the shut-off solenoid valve 4 are connected in parallel to the second oil return circuit 10.

[0033] Among them, the oil inlet of the proportional solenoid valve 5 is connected to the oil inlet circuit 6, the oil outlet of the proportional solenoid valve 5 is connected to the back pressure port of the overflow valve 2 through the back pressure oil circuit 11, and the oil return port of the proportional solenoid valve 5 is connected to the return oil circuit 9. The proportional solenoid valve 5 is used to control the oil pressure of the oil inlet circuit 7 leading to the oil inlet of the reversing solenoid valve 3 to increase slowly, so as to realize the smooth and gentle shifting of the tractor without shock.

[0034] like Figure 2 As shown, the proportional solenoid valve 5 is a normally closed two-position three-way valve. When de-energized, the oil inlet of the proportional solenoid valve 5 is closed, and the oil outlet of the proportional solenoid valve 5 is connected to the oil return port; when energized, the oil inlet and oil outlet of the proportional solenoid valve 5 are connected.

[0035] The shut-off solenoid valve 4 is a normally open two-position four-way solenoid valve. When de-energized, the oil inlet and outlet of the shut-off solenoid valve 4 are connected; when energized, the oil inlet and return port of the shut-off solenoid valve 4 are connected.

[0036] The reversing solenoid valve 3 is a normally closed three-position five-way solenoid valve. When de-energized, the oil inlet of the reversing solenoid valve 3 is closed, and the forward and reverse oil outlets of the reversing solenoid valve 3 are connected to the return oil circuit 10. When energized, the oil inlet of the reversing solenoid valve 3 is connected to either the forward or reverse oil outlet.

[0037] In this case, if Figure 3As shown, the shut-off solenoid valve 4 is a normally open two-position four-way solenoid valve. The shut-off solenoid valve 4 includes a plug 111, a spring 112, a spring seat 113, a first return valve 14, a second return valve 15, a slide valve 16, an inlet valve 17, an electromagnetic push rod 18, and a coil 19. The slide valve 16 is located in the valve cavity, with springs 112 and spring seats 113 at both ends. The plug 111 is located outside one spring 112, and the electromagnetic push rod 18 is located outside the other spring 112. In the valve cavity, the first return valve 14 is connected to the second return port ④, the second return valve 15 is connected to the first return port ③, and the inlet valve 17 is connected to the inlet port ①.

[0038] The switch button of coil 19 is connected to the brake pedal. When coil 19 is de-energized, the springs 112 at both ends keep the slide valve 16 in the center position, with oil inlet 1 and oil outlet 2 connected, and oil return port 1 and oil return port 2 connected. Oil inlet circuit 1 6 is connected to oil inlet circuit 2 7 through oil inlet 1 and oil outlet 2, allowing oil to flow through port P. When the brake pedal is pressed, the switch button of coil 19 of the cut-off solenoid valve 4 is activated, and coil 19 is energized to generate electromagnetic force, which drives the electromagnetic push rod 18 to push the slide valve 16 to move. Oil inlet 1 and oil return port 2 4 are closed, while oil return port 1 3 and oil outlet 2 are connected. Oil inlet circuit 1 6 and oil inlet circuit 2 7 are cut off, and oil does not flow through port P. At the same time, the oil pressure of the forward or reverse gear clutch is unloaded through oil outlet 2 and oil return port 1 3 of the cut-off solenoid valve 4 to oil return circuit 2 10 and then to the oil return tank, so that the tractor achieves the effect of deceleration and stopping.

[0039] like Figure 4 As shown, the hydraulically controlled relief valve 2 is a hydraulically controlled direct-acting structure, including a valve core 21, an oil drain port 22, a spring 23, a back pressure piston 24, a throttle orifice 25, an inner cavity 26, and a valve seat 27. The valve core 21 is installed in the valve seat 27, and the oil inlet ① and the oil outlet ② are connected through the oil drain port 22. The back pressure piston 24 is connected to the rear end of the valve core 21. The back pressure piston 24 and the valve seat 27 form the inner cavity 26, and the inner cavity 26 is connected to the back pressure oil port ③ through the throttle orifice 25.

[0040] When the oil pressure in inlet 7 rises to a certain value, the oil entering the inlet 1 of the relief valve 2 overcomes the spring force of the spring 23, pushing the valve core 21 to move, and the drain port 22 is opened, connecting the inlet 1 and the outlet 2. Part of the oil passes through the inlet 1 and the outlet 2 to the return oil circuit 8 for unloading. The oil pressure in inlet 7 is determined by the spring force of the relief valve 2. At the tail end of the valve core 21, there is also a back pressure piston 24, a valve seat 27, and a back pressure port 3. The back pressure port 3 is connected to the outlet 1 of the proportional solenoid valve 5 through the back pressure oil circuit 11.

[0041] like Figure 5As shown, the proportional solenoid valve 5 is a two-position, three-normally closed structure, including a valve seat 31, an inlet valve 32, an unloading valve 33, a spring 34, a valve core 35, an electromagnet 36, and a coil 37. The valve core 35 is installed in the cavity of the valve seat 31, the spring 34 is located at both ends of the valve core 35, the electromagnet 36 is located outside one end of the valve core 35, and the coil 37 is located outside the circumference of the electromagnet 36. The cavity of the valve seat 31 is provided with an inlet valve 32 and an unloading valve 33. The inlet valve 32 is connected to the oil inlet port ② of the proportional solenoid valve 5, and the unloading valve 33 is connected to the oil return port ③ of the proportional solenoid valve 5.

[0042] When coil 37 is de-energized, oil inlet ② is closed, and back pressure oil inlet ① and return oil inlet ③ are connected. When coil 37 is energized, electromagnetic force is generated, causing electromagnet 36 to push valve core 35 to move, oil inlet valve 32 is opened, oil in inlet 6 enters from oil inlet ②, passes through oil inlet valve to back pressure oil inlet ①, then passes through back pressure oil circuit 11 to return oil inlet ③ of overflow valve 2, and enters inner cavity 26 through throttle orifice 25, generating back pressure. Back pressure piston 24 pushes valve core 21 to move, oil drain port 22 is closed, and oil pressure in inlet 7 increases.

[0043] The proportional solenoid valve 5 is controlled by an electronic control unit. When the electronic control unit receives a voltage change signal from the sensor of the shift lever, it adjusts the current output to the proportional solenoid valve accordingly, so that it continuously and proportionally regulates the pressure of the back pressure oil circuit. Adjusting the current of the coil 37 of the proportional solenoid valve 5 controls the opening and closing of the inlet valve 32, further controlling the flow rate of the back pressure oil circuit 11, and further controlling the opening and closing of the drain port 22 in the relief valve 2. The oil pressure in the inlet circuit 7 can be high or low. The characteristic curve of the current-pressure relationship in the proportional solenoid valve 5 is shown in Figure 1. Figure 7 As shown.

[0044] The overflow valve 2 and the proportional solenoid valve 5 interact with each other. By setting different currents for each time period of the coil 37 of the proportional solenoid valve 5, an adjustable working oil pressure is provided for the clutch to be filled with oil. This makes the process from filling the friction plates inside the clutch to engaging and clamping each other smooth and without impact, thus achieving a mechanical transmission effect.

[0045] like Figure 6 As shown, the reversing solenoid valve 3 is a normally closed three-position five-way solenoid valve, which controls the tractor to be in three gears: forward, neutral, and reverse. The reversing solenoid valve 3 includes a slide valve 45 and a valve seat. One end of the slide valve 45 is provided with a coil 41, an electromagnet 42, a spring 43, and a spring seat 44; the other end of the slide valve 45 is provided with an electromagnet 410, a coil 411, a spring 43, and a spring seat 44; the cavity of the valve seat has a return valve 46, a reverse gear valve 47, a forward gear valve 48, and a return valve 49 arranged sequentially along the axial direction.

[0046] When coil 1 (41) and coil 2 (411) are de-energized, springs 43 at both ends keep the slide valve 45 in the center position, the oil inlet 3 is closed, the return oil inlet 1 (①) and the reverse gear oil outlet 2 are connected, the forward gear oil outlet 4 and the return oil outlet 2 (⑤) are connected, the working oil circuit 12 of the forward gear clutch and the working oil circuit 23 of the reverse gear clutch are both connected to the return oil circuit 20, and the tractor stops moving.

[0047] When coil 411 is energized, it generates electromagnetic force that drives electromagnet 410 to push the slide valve to the left. The oil inlet ③ and forward gear oil outlet ④ are connected, and the oil return port ① and reverse gear oil outlet ② are connected. The oil in the oil inlet 7 enters the working oil circuit 1 and then fills the forward gear clutch with oil through port F, so that the friction plates engage with each other and drive the tractor to move forward.

[0048] When line 41 is energized, it generates electromagnetic force that drives electromagnet 42 to push the slide valve to the right. The oil inlet ③ and the reverse gear outlet ② are connected. The oil in the oil inlet 7 enters the working oil inlet 13 through the oil inlet ③ and the reverse gear outlet ②, and then fills the reverse gear clutch with oil through port R, so that the friction plates engage with each other and drive the tractor to move backward.

[0049] The working principle and process of the tractor-use electric proportional power reversing valve assembly of the present invention are briefly described below with reference to the accompanying drawings.

[0050] With the shut-off solenoid valve 4, proportional solenoid valve 5, and directional solenoid valve 3 all de-energized, the hydraulic pump injects oil into inlet P. The oil then splits into two paths: one path flows from inlet path 6 to inlet ② of proportional solenoid valve 5, and the other path passes through ports ① and ② of shut-off solenoid valve 4, entering inlet path 7 and reaching inlet ① of relief valve 2 and inlet ③ of directional solenoid valve 3. The oil pressure in inlet path 7 is controlled by relief valve 2 at a minimum constant pressure, creating conditions for the operation of each valve and protecting the oil pump from lower loads.

[0051] When the reversing solenoid valve 3 coil 411 is energized, the forward gear valve 48 is opened, connecting ports ③ and ④. Oil from inlet circuit 2 7 enters working oil circuit 1 12 through ports ③ and ④, then fills the forward gear clutch via port F. Simultaneously, the proportional solenoid valve 5 coil is energized, and the current gradually increases at different set time intervals, increasing the oil pressure inlet circuit 2 7 leading to the forward gear clutch. This causes the friction plates to move from initial contact to tight engagement, propelling the tractor from a slow start to rapid forward movement. Due to this design, the tractor's start-up and acceleration process is smooth and without any impact.

[0052] When the reversing solenoid valve 3 coil 2 411 is de-energized, coil 1 41 is energized, and the proportional solenoid valve 5 coil 37 is de-energized simultaneously, the forward gear clutch oil pressure is unloaded from the working oil circuit 12 through ports ④ and ⑤ of the reversing solenoid valve 3 to the return oil circuit 10. The pressure in the inlet oil circuit 7 changes from high pressure to low pressure and changes direction, entering the working oil circuit 13 through ports ③ and ② of the reversing solenoid valve 3, and then filling the reverse gear clutch with oil through port R, stopping the tractor from moving forward. When the proportional solenoid valve 5 coil is energized for the second time, the current gradually increases at different set time periods, increasing the oil pressure in the inlet oil circuit 7 leading to the reverse gear clutch. The friction plates go from contacting each other to gripping each other, driving the tractor from a slow start to rapid backward movement. Due to the above design, the tractor can shift smoothly and gently without stopping in neutral during the shift from forward to reverse, without any shock.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tractor-mounted electric proportional power directional valve assembly, characterized in that, It includes a valve body (1) and an overflow valve (2), a reversing solenoid valve (3) and a shut-off solenoid valve (4) installed on the valve body; it also includes an oil inlet circuit 1 (6), an oil inlet circuit 2 (7), an oil return circuit 4 (8), an oil return circuit 2 (10), a working oil circuit 1 (12) and a working oil circuit 2 (13). The valve body (1) is also provided with a proportional solenoid valve (5). The oil inlet of the proportional solenoid valve (5) is connected to the first oil inlet (6). The oil outlet of the proportional solenoid valve (5) is connected to the back pressure port of the overflow valve (2) through the back pressure oil circuit (11). The oil return port of the proportional solenoid valve (5) is connected to the third oil return circuit (9). The proportional solenoid valve (5) is a normally closed two-position three-way valve. When de-energized, the oil inlet of the proportional solenoid valve (5) is closed, and the oil outlet of the proportional solenoid valve (5) is connected to the oil return port. When energized, the oil inlet of the proportional solenoid valve (5) is connected to the oil outlet of the proportional solenoid valve (5). The shut-off solenoid valve (4) is a normally open two-position four-way solenoid valve. The oil inlet of the shut-off solenoid valve (4) is connected to the first oil inlet circuit (6). The oil outlet of the shut-off solenoid valve (4), the oil inlet of the reversing solenoid valve (3), and the oil inlet of the overflow valve (2) are connected in parallel through the second oil inlet circuit (7). The forward gear oil outlet of the reversing solenoid valve (3) is connected to the first working oil circuit (12). The reverse gear oil outlet of the reversing solenoid valve (3) is connected to the second working oil circuit (13). In addition, the oil outlet of the overflow valve (2) is connected to the fourth return oil circuit (8). The return oil outlet of the reversing solenoid valve (3) and the return oil outlet of the shut-off solenoid valve (4) are connected in parallel to the second return oil circuit (10). The back pressure end of the overflow valve (2) is connected to a control unit, which is used to control the oil pressure of the oil inlet of the second oil inlet (7) to the oil inlet of the reversing solenoid valve (3) to increase slowly, so as to realize the smooth and gentle shifting of the tractor without impact.

2. The tractor electric proportional power directional valve assembly according to claim 1, characterized in that, The proportional solenoid valve (5) includes a valve seat (31), an inlet valve (32), an unloading valve (33), a spring (34), a valve core (35), an electromagnet (36), and a coil (37). The valve core (35) is installed in the cavity of the valve seat (31), the spring (34) is located at both ends of the valve core (35), the electromagnet (36) is located outside one end of the valve core (35), and the coil (37) is located outside the circumference of the electromagnet (36). The inlet valve (32) and the unloading valve (33) are provided on the cavity of the valve seat (31).

3. The tractor electric proportional power directional valve assembly according to claim 1, characterized in that, When the shut-off solenoid valve (4) is de-energized, the oil inlet of the shut-off solenoid valve (4) is connected to the oil outlet of the shut-off solenoid valve (4); when energized, the oil outlet of the shut-off solenoid valve (4) is connected to the oil return port of the shut-off solenoid valve (4).

4. The tractor electric proportional power directional valve assembly according to claim 3, characterized in that, The shut-off solenoid valve (4) includes a screw plug (111), a spring (112), a spring seat (113), a return valve one (14), a return valve two (15), a slide valve (16), an inlet valve (17), an electromagnetic push rod (18), and a coil (19). The slide valve (16) is located in the valve cavity. Both ends of the slide valve (16) are provided with the spring (112) and the spring seat (113). The screw plug (111) is located outside one of the springs (112), and the electromagnetic push rod (18) is located outside the other spring (112).

5. The tractor electric proportional power directional valve assembly according to claim 1, characterized in that, The reversing solenoid valve (3) is a normally closed three-position five-way solenoid valve. When de-energized, the oil inlet of the reversing solenoid valve (3) is closed, and the forward gear oil outlet and the reverse gear oil outlet of the reversing solenoid valve (3) are both connected to the return oil circuit two (10). When energized, the oil inlet of the reversing solenoid valve (3) is connected to the forward gear oil outlet or the reverse gear oil outlet of the reversing solenoid valve (3).

6. The tractor electric proportional power directional valve assembly according to claim 5, characterized in that, The reversing solenoid valve (3) includes a slide valve (45) and a valve seat. One end of the slide valve (45) is provided with a coil (41), an electromagnet (42), a spring (43), and a spring seat (44); the other end of the slide valve (45) is provided with an electromagnet (410), a coil (411), a spring (43), and a spring seat (44); the cavity of the valve seat has a return valve (46), a reverse valve (47), a forward valve (48), and a return valve (49) arranged sequentially along the axial direction.

7. The tractor electric proportional power directional valve assembly according to claim 1, characterized in that, The overflow valve (2) is a hydraulically controlled direct-acting structure, including a valve core (21), an oil drain port (22), a spring (23), a back pressure piston (24), a throttle orifice (25), and a valve seat (27). The valve core (21) is installed in the valve seat (27). The oil inlet and outlet of the overflow valve (2) are connected through the oil drain port (22). The back pressure piston (24) is connected to the rear end of the valve core (21). The back pressure piston (24) and the valve seat (27) form an inner cavity (26). The inner cavity (26) is connected to the back pressure oil port of the overflow valve (2) through the throttle orifice (25).

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