A buffer structure for a power shift control valve

Abstract

This invention provides a buffer structure for a power shift control valve, belonging to the field of hydraulic technology. It solves the problem of poor smoothness during the engagement process of existing gear shift friction plates. The buffer structure of this power shift control valve includes a valve body with a shift valve chamber, a return oil passage, a buffer valve chamber, and an inlet oil passage and a working oil passage, both connected to the buffer valve chamber. A buffer valve core and a buffer piston are slidably connected within the buffer valve chamber. A buffer spring 1 acts between the buffer valve core and the buffer piston, and a second buffer spring is also provided between the buffer valve core and the buffer piston. The length of the second buffer spring is less than the length of the first buffer spring. The working oil passage has control oil passages connected to pressure chamber 1 and pressure chamber 2 respectively. A throttling orifice is provided on the control oil passage connected to pressure chamber 2. The cross-sectional area of ​​the top of the buffer piston is larger than the cross-sectional area of ​​the top of the buffer valve core. The shift valve chamber can connect pressure chamber 2 and the return oil passage. The buffer structure of this power shift control valve has the advantage of improving shift smoothness.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic technology and relates to a buffer structure for a power shift control valve. Background Technology

[0002] The power shift control valve is the core hydraulic control component of the transmission. It integrates multiple functional modules such as the shift valve, micro-motion control valve, and safety start valve. By precisely adjusting the flow and pressure of hydraulic oil, it controls the engagement and disengagement of the clutches within the transmission, thereby enabling gear shifting while the vehicle is in motion.

[0003] Currently, gear shifting control is highly intelligent, mostly using electronic or electro-hydraulic proportional control. However, electronic control systems require matching controllers, which are costly. Electro-proportional valves have poor resistance to contamination and require high oil cleanliness. If users do not maintain the oil in a timely manner, it can easily cause tractor gear failure. Traditional mechanical control relies on a handle, connecting rod, or cable to directly drive the clutch engagement. The control is reliable, but there is no buffer or hydraulic / pneumatic flexible transition. The engagement force and speed are entirely controlled manually by the driver. If the handle is pushed too fast or too hard, the clutch will engage instantly, which can easily cause shock, vibration, abnormal noise, or even damage to gears, drive shafts, or external equipment. If the operation is too slow, it will lead to an excessively long clutch half-engagement time, which will aggravate the wear of the friction plates. This is the technical problem of poor smoothness of the gear shift friction plate engagement process. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a buffer structure for a power shift control valve, ensuring buffer reliability and simultaneously solving the problem of poor smoothness during gear shifting friction plate engagement.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A buffer structure for a power shift control valve includes a valve body. The valve body has a shift valve chamber, a return oil passage, a buffer valve chamber, and an inlet oil passage and a working oil passage, both of which are connected to the buffer valve chamber. A buffer valve core and a buffer piston are slidably connected within the buffer valve chamber. A buffer spring 1 acts between the buffer valve core and the buffer piston. The buffer spring 2 is further provided between the buffer valve core and the buffer piston, and the length of the buffer spring 2 is less than the length of the buffer spring 1. A pressure chamber 1 is located between the top of the buffer valve core and the valve body, and a pressure chamber 2 is located between the top of the buffer piston and the valve body. The working oil passage has a control oil passage connected to both pressure chamber 1 and pressure chamber 2, and a control oil passage connected to pressure chamber 2. A throttling orifice is provided on the connected control oil circuit. The cross-sectional area of ​​the top of the buffer piston is larger than that of the top of the buffer valve core. The shift valve chamber can connect the pressure chamber two and the return oil circuit. Under the action of the buffer spring one, the top of the buffer valve core and the top of the buffer piston respectively abut against the inner wall of the valve body, and the inlet oil circuit is connected to the working oil circuit. When the oil pressure in the pressure chamber one increases, the buffer valve core overcomes the elastic force of the buffer spring one and moves towards the buffer piston, and blocks the connection between the inlet oil circuit and the working oil circuit. When the oil pressure in the pressure chamber two increases, the buffer piston moves towards the buffer valve core and compresses the buffer spring two. When the oil pressure in the pressure chamber two continues to increase, the buffer piston drives the buffer valve core to move back, and the inlet oil circuit is connected to the working oil circuit.

[0007] This application incorporates a buffer structure within the power shift control valve body to control the load pressure of the working oil circuit, preventing hard contact during gear engagement from damaging gears, drive shafts, or external equipment. The specific control principle of the buffer structure is as follows:

[0008] The function of the working oil circuit is to transmit hydraulic energy to drive the actuator. This application sets up a pressure chamber one between the top of the buffer valve core and the valve body, and a pressure chamber two between the top of the buffer piston and the valve body. Both pressure chamber one and pressure chamber two are connected to the working oil circuit through a control oil circuit. Initially, the buffer structure does not participate in the operation; the tops of the buffer valve core and the buffer piston respectively abut against the inner wall of the valve body. At this time, the inlet oil circuit and the working oil circuit are connected. As oil flows in, the pressure in the working oil circuit gradually increases. When the oil supply to the actuator is basically full, the load pressure in the working oil circuit rises rapidly. When the pressure in the oil circuit begins to exceed the force of the first buffer spring, since the pressure in the first pressure chamber is the same as the pressure in the working oil circuit, the buffer valve core moves towards the buffer piston under the action of the oil pressure in the first pressure chamber until the connection between the inlet oil circuit and the working oil circuit is blocked, thus achieving the first stage of buffering. Because the oil entering the second pressure chamber must pass through a throttle orifice, the pressure feedback from the second pressure chamber is delayed, and the oil pressure in the second pressure chamber gradually increases. Even if the connection between the inlet oil circuit and the working oil circuit is blocked, because the working oil circuit in the gear output system is usually connected to a hydraulic cylinder or hydraulic motor, the external load will react on the piston, causing the oil in the working oil circuit to... The pressure will continue to rise. As oil flows into pressure chamber two, the oil pressure in pressure chamber two increases. Because the load-bearing area at the top of the buffer piston is larger than that at the top of the buffer valve core, according to the mechanical principle F=P×A, when the load pressure acting on the buffer piston is greater than the load pressure acting on the buffer valve core, the buffer piston moves towards the buffer valve core. As the oil pressure in pressure chamber two continues to increase, the buffer piston overcomes the force of buffer spring two and continues to move towards the buffer valve core, realizing the second stage of buffering. The length and elastic force of buffer spring two can be selected according to the actual working conditions. As the oil pressure in pressure chamber two further increases... The buffer piston abuts against the buffer valve core and drives the buffer valve core back to its initial position. The buffer valve core reconnects the oil inlet circuit and the working circuit, and the buffering ends. Thus, by controlling the load pressure of pressure chamber one and pressure chamber two, the initial engagement of the clutch is buffered, improving the smoothness of the gear friction plate engagement process during gear shifting. After the connection between the oil inlet circuit and the working circuit is blocked, this application sets the buffer springs to be of different lengths to achieve segmented variable stiffness buffering, overcome the moving inertia of the buffer piston, and extend the effective engagement time of the friction plate, that is, extend the process of the friction plate from approaching to fully contacting, thereby improving the smoothness of gear shifting.

[0009] Furthermore, when the driver frequently shifts gears, the existing technology fails to provide a buffering effect due to the untimely return of the buffer piston. The existing gear shifting passes through the neutral position, such as when shifting forward or reverse. This application can utilize the existing gear shifting mechanism that passes through the neutral position. When shifting gears through the neutral position, the shift valve chamber connects to pressure chamber two and the return oil circuit, causing pressure chamber two to release pressure, thereby improving the timeliness of the buffer piston's return and ensuring the reliability of the buffering function during frequent gear shifting.

[0010] In the aforementioned buffer structure of a power shift control valve, the working oil circuit has a valve chamber working port one and a valve chamber working port two located on the wall of the shift valve chamber, and the inlet oil circuit has a valve chamber inlet located on the wall of the shift valve chamber. The valve chamber working port one, the valve chamber inlet, and the valve chamber working port two are arranged sequentially at intervals along the axial direction. A shift valve rod is slidably connected to the shift valve chamber through one side of the valve body. An oil passage two is formed on the shift valve rod. When the shift valve rod blocks the connection between the oil passage two and the valve chamber inlet and the valve chamber working port two, the shift valve chamber connects to pressure chamber two and the return oil circuit. This structure associates the pressure relief of pressure chamber two with the shifting of the shift valve rod, ensuring the timely return of the buffer piston.

[0011] In the aforementioned buffer structure of a power shift control valve, the return oil circuit has a valve chamber return port located on the wall of the shift valve chamber. The wall of the shift valve chamber also has a valve chamber through port communicating with the pressure chamber. The valve chamber through port and the valve chamber return port are directly opposite each other. An oil groove is formed on the shift valve stem. When the shift valve stem is in neutral, the oil groove connects the valve chamber through port and the valve chamber return port. This structure shortens the oil flow path, improves unloading efficiency, and ensures the timely return of the buffer piston, thereby improving buffer reliability.

[0012] In the aforementioned buffer structure of a power shift control valve, the diameter of the valve chamber return port is the same as the width of the first oil passage groove, while the width of the second oil passage groove is greater than that of the first oil passage groove. The fact that the valve chamber return port has the same diameter as the first oil passage groove increases the pressure relief flow rate per unit time, while the greater width of the second oil passage groove extends the pressure relief time, improving unloading efficiency and ensuring the timely return of the buffer piston, thereby enhancing buffer reliability.

[0013] In the aforementioned buffer structure of a power shift control valve, a clearance hole is provided on the end face of the buffer piston, the buffer valve core has a rod-shaped tail, a buffer spring is sleeved on the tail and acts on the bottom of the clearance hole, a second buffer spring is located inside the clearance hole and sleeved outside the first buffer spring, and the distance between the tail and the bottom of the clearance hole is greater than the distance between the second buffer spring and the buffer valve core. The tail and the clearance hole together support the buffer spring. In the initial state, the second buffer spring is in a free extension and contraction state. The position of the second buffer spring avoids its position deviation in the initial state, and the distance setting ensures that the second buffer spring performs its buffering function.

[0014] In the aforementioned buffer structure of a power shift control valve, a gasket is fitted onto the tail end, and the buffer valve cavity has a stepped surface for the buffer piston to abut against. A countersunk hole is formed on the stepped surface. The gasket is embedded in the countersunk hole under the elastic force of a first buffer spring, and the second buffer spring can abut against the gasket. The diameter of the countersunk hole is slightly larger than the diameter of the gasket. The gasket increases the contact area of ​​the buffer valve core, disperses the force, and avoids local stress concentration in the buffer valve core. The countersunk hole design avoids the gasket occupying the movement stroke of the buffer piston, and on the other hand, the gasket provides a flat and rigid pressure-bearing surface, allowing the spring force to be transmitted axially to the buffer valve core, ensuring buffer reliability.

[0015] In the aforementioned buffer structure of a power shift control valve, the buffer valve core further has a rod-shaped head that divides the buffer valve chamber into a front chamber and a rear chamber. A stepped surface is formed between the front and rear chambers. The head is connected to the tail and has a shoulder. One side of the gasket abuts against the shoulder, and the other side of the gasket abuts against the buffer spring. This structure increases the contact area between the gasket and the buffer valve core, allowing the spring force to be transmitted axially to the buffer valve core, thus ensuring buffer reliability.

[0016] In the aforementioned buffer structure of a power shift control valve, the distance between the buffer piston and the stepped surface is greater than the distance between the tail and the bottom of the clearance hole. A buffer spring acts between the end face of the buffer piston and the stepped surface. The stepped surface defines the maximum stroke of the buffer piston, and the buffer spring extends the buffering time and increases the return speed of the buffer piston at the end of the buffering process.

[0017] In the aforementioned buffer structure of a power shift control valve, the working oil circuit has a valve chamber working oil port three located on the front chamber wall, and the control oil circuit has a control oil port located on the front chamber wall, the diameter of which is larger than the diameter of the valve chamber working oil port three. This structure ensures timely pressure feedback from the pressure chamber one.

[0018] In the aforementioned buffer structure of a power shift control valve, both the outer end face of the buffer piston and the outer end face of the buffer valve core have bosses. This structure facilitates the flow of oil into pressure chamber one and pressure chamber two.

[0019] Compared with the prior art, the buffer structure of the power shift control valve provided by the present invention has the following advantages:

[0020] 1. A buffer spring with one long and one short is used. In the initial stage of buffering, the movement of the buffer piston only compresses the longer buffer spring one. After the buffer piston moves a certain distance, the buffer spring two is also compressed, which forces the movement speed of the buffer piston to be reduced, prolongs the process of the friction plate from approaching to fully contacting, and improves the smoothness of gear shifting.

[0021] 2. This application utilizes the existing gear shifting mechanism that passes through the neutral position. When the directional valve stem passes through the neutral position, the pressure chamber two is connected to the return oil circuit, causing the pressure chamber two to release pressure. This improves the timely return of the buffer piston and ensures the reliability of the buffer function during frequent gear shifting. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of the power shift control valve in its initial state.

[0023] Figure 2 This is a schematic diagram of the control oil circuit in the power shift control valve.

[0024] Figure 3 yes Figure 1 A magnified view of a portion of the image.

[0025] Figure 4 This is a cross-sectional view of the power shift control valve in the shifting state.

[0026] Figure 5 This is a schematic diagram of the first-stage buffer state of the power shift control valve.

[0027] Figure 6 This is a schematic diagram of the second-stage buffer state of the power shift control valve.

[0028] Figure 7 This is a schematic diagram of the third-stage buffer state of the power shift control valve.

[0029] Figure 8 This is a schematic diagram of the power shift control valve in its end-buffered state.

[0030] In the diagram: 1. Valve body; 11. Oil inlet passage; 111. Valve cavity oil inlet; 12. Working oil passage; 121. Valve cavity working port one; 122. Valve cavity working port two; 123. Valve cavity working port three; 13. Oil return passage; 131. Valve cavity return port; 14. Buffer valve cavity; 141. Stepped surface; 142. Countersunk hole; 143. Front cavity; 144. Rear cavity; 15. Pressure cavity one; 16. Pressure cavity two ; 17. Control oil circuit; 171. Throttling orifice; 172. Control oil port; 18. Shift valve chamber; 181. Valve chamber oil passage port; 2. Buffer valve core; 21. Tail end; 22. Head end; 23. Shoulder; 3. Buffer piston; 31. Displacement hole; 4. Buffer spring one; 5. Buffer spring two; 6. Shift valve rod; 61. Oil passage groove one; 62. Oil passage groove two; 7. Gasket; 8. Buffer spring three; 9. Boss. Detailed Implementation

[0031] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments.

[0032] like Figures 1-3 As shown, the buffer structure of this power shift control valve includes a valve body 1. The valve body 1 has a shift valve chamber 18, a return oil passage 13, a buffer valve chamber 14, and an inlet oil passage 11 and a working oil passage 12, both of which are connected to the buffer valve chamber 14. A buffer valve core 2 and a buffer piston 3 are slidably connected within the buffer valve chamber 14. A buffer spring 4 acts between the buffer valve core 2 and the buffer piston 3. A second buffer spring 5 is also provided between the buffer valve core 2 and the buffer piston 3. The length of the second buffer spring 5 is less than the length of the first buffer spring 4. A pressure chamber 15 is located between the top of the buffer valve core 2 and the valve body 1, and a pressure chamber 16 is located between the top of the buffer piston 3 and the valve body 1. The working oil passage 12 has a control oil passage 17 that is connected to both the first pressure chamber 15 and the second pressure chamber 16. Figure 2 As shown, the control oil circuit 17, which is connected to the pressure chamber 2 16, is provided with a throttling orifice 171. The cross-sectional area of ​​the top end of the buffer piston 3 is larger than the cross-sectional area of ​​the top end of the buffer valve core 2, as shown. Figure 1 As shown, the shift valve chamber 18 can connect the pressure chamber 16 and the return oil circuit 13, as follows: Figure 3 As shown, under the action of the buffer spring 4, the top of the buffer valve core 2 and the top of the buffer piston 3 respectively abut against the inner wall of the valve body 1, and the oil inlet passage 11 is connected to the working oil passage 12; Figure 5 As shown, when the oil pressure in pressure chamber 15 increases, the buffer valve core 2 overcomes the elastic force of the buffer spring 4 and moves towards the buffer piston 3, thus blocking the connection between the oil inlet passage 11 and the working oil passage 12; Figure 6 and Figure 7 As shown, when the oil pressure in pressure chamber 16 increases, the buffer piston 3 moves toward the buffer valve core 2 and compresses the buffer spring 5; Figure 8 As shown, when the oil pressure in pressure chamber 2 16 continues to increase, the buffer piston 3 drives the buffer valve core 2 to move back, and the oil inlet passage 11 is connected to the working oil passage 12.

[0033] like Figure 1 and Figure 4As shown, the working oil passage 12 has a valve chamber working oil port 121 and a valve chamber working oil port 122 located on the wall of the shift valve chamber 18. The oil inlet passage 11 has a valve chamber inlet 111 located on the wall of the shift valve chamber 18. The valve chamber working oil port 121, the valve chamber inlet 111, and the valve chamber working oil port 122 are arranged sequentially at intervals along the axial direction. A shift valve rod 6 is slidably connected to the shift valve chamber 18 through one side of the valve body 1. An oil groove 62 is formed on the shift valve rod 6. When the shift valve rod 6 blocks the communication between the oil groove 62 and the valve chamber inlet 111 and the valve chamber working oil port 122, the shift occurs. Valve chamber 18 connects pressure chamber 2 16 and return oil passage 13. Return oil passage 13 has a valve chamber return port 131 located on the wall of shift valve chamber 18. The wall of shift valve chamber 18 also has a valve chamber through port 181 communicating with pressure chamber 2 16. The valve chamber through port 181 and valve chamber return oil port 131 are directly opposite each other. A through groove 61 is formed on the shift valve stem 6. When the shift valve stem 6 is in neutral, the through groove 61 connects the valve chamber through port 181 and the valve chamber return oil port 131. The diameter of the valve chamber return oil port 131 is the same as the width of the through groove 61. The width of the through groove 62 is greater than the width of the through groove 61. Figure 1 The image shows the initial position of the shift valve stem 6. When the shift valve stem 6 moves to the left, the oil groove 2 62 connects the working oil port 121 of the valve chamber and the oil inlet 111 of the valve chamber. When the shift valve stem 6 moves to the right, the oil groove 2 62 connects the working oil port 2 122 of the valve chamber and the oil inlet 111 of the valve chamber.

[0034] A relief hole 31 is provided on the end face of the buffer piston 3. The buffer valve core 2 has a rod-shaped head 22 and a tail 21. The head 22 is connected to the tail 21 and forms a shoulder 23. The head 22 divides the buffer valve chamber 14 into a front chamber 143 and a rear chamber 144. The aforementioned stepped surface 141 is formed between the front chamber 143 and the rear chamber 144. A gasket 7 is fitted on the tail 21. One side of the gasket 7 abuts against the shoulder 23. A buffer spring 4 is fitted on the tail 21. One end of the buffer spring 4 abuts against the other side of the gasket 7, and the other end of the buffer spring 4 acts on the bottom of the relief hole 31. A countersunk hole 142 is provided on 141. The gasket 7 is embedded in the countersunk hole 142 under the elastic force of the buffer spring 4. The buffer spring 5 can abut against the gasket 7. The diameter of the countersunk hole 142 is slightly larger than the diameter of the gasket 7. The buffer spring 5 is located in the relief hole 31 and is sleeved outside the buffer spring 4. The distance between the tail 21 and the bottom of the relief hole 31 is greater than the distance between the buffer spring 5 and the buffer valve core 2. The distance between the buffer piston 3 and the stepped surface 141 is greater than the distance between the tail 21 and the bottom of the relief hole 31. A buffer spring 8 acts between the end face of the buffer piston 3 and the stepped surface 141.

[0035] The working oil circuit 12 has a valve chamber working oil port 3 123 located on the wall of the front chamber 143, and the control oil circuit 17 has a control oil port 172 located on the wall of the front chamber 143. The control oil port 172 is connected to the pressure chamber 15, and the diameter of the control oil port 172 is larger than the diameter of the valve chamber working oil port 3 123. Both the outer end face of the buffer piston 3 and the outer end face of the buffer valve core 2 have bosses 9.

[0036] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0037] Although this article uses a lot of terms such as valve body 1, oil inlet 11, valve cavity inlet 111, working oil passage 12, valve cavity working port one 121, valve cavity working port two 122, valve cavity working port three 123, return oil passage 13, valve cavity return oil port 131, buffer valve cavity 14, stepped surface 141, countersunk hole 142, front cavity 143, rear cavity 144, pressure cavity one 15, pressure cavity two 16, control oil passage 17, throttle orifice 171, control oil port 172, shift valve cavity 18, valve cavity oil passage 181, buffer valve core 2, tail 21, head 22, shoulder 23, buffer piston 3, clearance hole 31, buffer spring one 4, buffer spring two 5, shift valve rod 6, oil groove one 61, oil groove two 62, gasket 7, buffer spring three 8, boss 9, the possibility of using other terms cannot be ruled out. The use of these terms is merely for the convenience of describing and explaining the nature of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

Claims

1. A buffer structure for a power shift control valve, comprising a valve body (1), the valve body (1) having a shift valve chamber (18), a return oil passage (13), a buffer valve chamber (14), and an inlet oil passage (11) and a working oil passage (12) both connected to the buffer valve chamber (14), wherein a buffer valve core (2) and a buffer piston (3) are slidably connected within the buffer valve chamber (14), and a buffer spring (4) acts between the buffer valve core (2) and the buffer piston (3), characterized in that, A second buffer spring (5) is provided between the buffer valve core (2) and the buffer piston (3). The length of the second buffer spring (5) is less than the length of the first buffer spring (4). There is a pressure chamber (15) between the top of the buffer valve core (2) and the valve body (1). There is a second pressure chamber (16) between the top of the buffer piston (3) and the valve body (1). The working oil circuit (12) has a control oil circuit (17) that is connected to the first pressure chamber (15) and the second pressure chamber (16) respectively. A throttling orifice (171) is provided on the control oil circuit (17) that is connected to the second pressure chamber (16). The cross-sectional area of ​​the top of the buffer piston (3) is greater than the cross-sectional area of ​​the top of the buffer valve core (2). The shift valve chamber (18) can connect the second pressure chamber (16) and the return valve. In the oil passage (13), under the action of the buffer spring (4), the top of the buffer valve core (2) and the top of the buffer piston (3) respectively abut against the inner wall of the valve body (1), and the oil inlet passage (11) is connected to the working oil passage (12); when the oil pressure in the pressure chamber (15) increases, the buffer valve core (2) overcomes the elastic force of the buffer spring (4) and moves toward the buffer piston (3), and blocks the connection between the oil inlet passage (11) and the working oil passage (12); when the oil pressure in the pressure chamber (2) increases, the buffer piston (3) moves toward the buffer valve core (2) and compresses the buffer spring (2); when the oil pressure in the pressure chamber (2) continues to increase, the buffer piston (3) drives the buffer valve core (2) to move back, and the oil inlet passage (11) is connected to the working oil passage (12).

2. The buffer structure of a power shift control valve according to claim 1, characterized in that, The working oil passage (12) has a valve chamber working oil port one (121) and a valve chamber working oil port two (122) located on the wall of the shift valve chamber (18). The oil inlet passage (11) has a valve chamber inlet (111) located on the wall of the shift valve chamber (18). The valve chamber working oil port one (121), the valve chamber inlet (111) and the valve chamber working oil port two (122) are arranged in sequence along the axial direction at intervals. A shift valve rod (6) is slidably connected to the shift valve chamber (18) on one side of the valve body (1). An oil groove two (62) is opened on the shift valve rod (6). When the shift valve rod (6) blocks the connection between the oil groove two (62) and the valve chamber inlet (111) and the valve chamber working oil port two (122), the shift valve chamber (18) is connected to the pressure chamber two (16) and the return oil passage (13).

3. The buffer structure of a power shift control valve according to claim 2, characterized in that, The return oil passage (13) has a valve chamber return oil port (131) located on the cavity wall of the shift valve chamber (18). The cavity wall of the shift valve chamber (18) is also provided with a valve chamber through oil port (181) that communicates with the pressure chamber two (16). The valve chamber through oil port (181) and the valve chamber return oil port (131) are arranged opposite each other. An oil groove (61) is provided on the shift valve rod (6). When the shift valve rod (6) is in neutral, the oil groove (61) connects the valve chamber through oil port (181) and the valve chamber return oil port (131).

4. The buffer structure of a power shift control valve according to claim 3, characterized in that, The diameter of the valve cavity return port (131) is the same as the width of the first oil passage groove (61), and the width of the second oil passage groove (62) is greater than the width of the first oil passage groove (61).

5. The buffer structure of a power shift control valve according to claim 1 or 2, characterized in that, The buffer piston (3) has a relief hole (31) on its end face. The buffer valve core (2) has a rod-shaped tail (21). The first buffer spring (4) is sleeved on the tail (21) and acts on the bottom of the relief hole (31). The second buffer spring (5) is located inside the relief hole (31) and is sleeved outside the first buffer spring (4). The distance between the tail (21) and the bottom of the relief hole (31) is greater than the distance between the second buffer spring (5) and the buffer valve core (2).

6. The buffer structure of a power shift control valve according to claim 5, characterized in that, A gasket (7) is fitted on the tail (21). The buffer valve chamber (14) has a stepped surface (141) for the buffer piston (3) to abut against. A countersunk hole (142) is opened on the stepped surface (141). The gasket (7) is embedded in the countersunk hole (142) under the elastic force of the first buffer spring (4). The diameter of the countersunk hole (142) is slightly larger than the diameter of the gasket (7). The second buffer spring (5) can abut against the gasket (7).

7. The buffer structure of a power shift control valve according to claim 6, characterized in that, The buffer valve core (2) also has a rod-shaped head (22), which divides the buffer valve chamber (14) into a front chamber (143) and a rear chamber (144). The aforementioned stepped surface (141) is formed between the front chamber (143) and the rear chamber (144). The head (22) is connected to the tail (21) and has a shoulder (23). One side of the gasket (7) abuts against the shoulder (23), and the other side of the gasket (7) abuts against the buffer spring (4).

8. The buffer structure of a power shift control valve according to claim 6, characterized in that, The distance between the buffer piston (3) and the step surface (141) is greater than the distance between the tail (21) and the bottom of the relief hole (31). A buffer spring (8) acts between the end face of the buffer piston (3) and the step surface (141).

9. The buffer structure of a power shift control valve according to claim 7, characterized in that, The working oil circuit (12) has a valve chamber working oil port three (123) located on the wall of the front cavity (143), and the control oil circuit (17) has a control oil port (172) located on the wall of the front cavity (143). The diameter of the control oil port (172) is larger than the diameter of the valve chamber working oil port three (123).

10. The buffer structure of a power shift control valve according to claim 1 or 2, characterized in that, Both the outer end face of the buffer piston (3) and the outer end face of the buffer valve core (2) have bosses (9).

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