CN116653899A - Pressure relief structure of a brake valve - Google Patents

Abstract

The invention provides a pressure relief structure of a brake valve, which belongs to the technical field of brake valves. It solves the technical problem of unstable pressure relief of the existing booster brake valve. The pressure relief structure of the brake valve, the pressure relief structure includes a confluence section located on the end surface of the balance piston close to the main piston, an oil drain hole located on the outer peripheral surface of the balance piston, and an oil discharge hole located between the balance piston and the main piston and blocking the confluence. A one-way assembly in the state of communicating with the oil inlet hole. There are several oil drain holes and they are all connected to the converging section. The balance piston is slidably connected with a movable rod that runs through the balance piston. One end is always located in the confluence section and can move axially towards the one-way assembly and push up the one-way assembly. There are several oil drain holes, and the port communicating with the oil drain hole and the confluence section surrounds the The movable rods are arranged at intervals in the circumferential direction. The brake valve is beneficial to ensure a stable pressure relief state.

Description

Pressure relief structure of a brake valve

technical field

The invention belongs to the technical field of brake valves, and relates to a pressure relief structure of a brake valve.

Background technique

Automobile brake valves are divided into air brake valves and hydraulic brake valves. The normal operation of the brake valve is of great significance to the driving brake, and it provides technical support for the smooth braking of the car. The development of this technology is of great significance to automobile manufacturing and road traffic safety.

For example, the Chinese patent with the application number CN200920306571.2 discloses a full hydraulic brake valve, which includes a valve body with an inner cavity, and the valve body has an oil inlet hole communicated with the oil tank and a working oil hole communicated with the brake. It is equipped with a piston assembly that controls the flow of oil and a linkage piston connected to the brake pedal. When the driver steps on the brake pedal, the linkage piston can drive the piston assembly to move to achieve braking. In order to make the braking easier and ensure sufficient braking force, a brake valve with booster is designed, which is usually provided with a pressurizing mechanism, which pressurizes the working area during braking, and resets after braking.

However, the pressure relief valve of the existing brake valve is often easily affected by interference when the pressure relief is triggered, which makes it difficult to maintain a stable position in the working state of the pressure relief valve and poor pressure relief stability. For this reason, those of ordinary skill in the art can easily consider such as: 1. Arrange the pressure relief structure at a fixed position relative to the piston; 2. Design the parts around the pressure relief structure to be relatively stable in position relative to the pressure relief structure, so as to avoid the influence of changes in the position of the components on the pressure relief. The structure itself causes the pressure relief to be unstable.

Contents of the invention

The present invention aims at the above-mentioned problems existing in the prior art, and provides a pressure relief structure of a brake valve. The technical problem to be solved by the present invention is: the pressure relief of the existing booster brake valve is unstable.

The purpose of the present invention can be achieved through the following technical solutions:

A pressure relief structure for a brake valve. The brake valve includes a valve body provided with an oil inlet hole, and a main piston and a balance piston are slidably connected to each other in the valve body. It is characterized in that the pressure relief structure includes a The confluence section on the end surface close to the main piston, the oil drain hole located on the outer peripheral surface of the balance piston, and the one-way assembly located between the balance piston and the main piston and blocking the communication between the confluence section and the oil inlet hole, the oil drain There are several holes and all of them communicate with the confluence section. A movable rod passing through the balance piston is slidably connected in the balance piston. One end of the movable rod is always located in the confluence section and can move axially toward the The one-way assembly moves and pushes up the one-way assembly. There are several oil drain holes, and the ports communicating between the oil drain holes and the confluence section are arranged at intervals around the circumference of the movable rod.

The oil inlet hole can be connected with the oil cup to supply oil for the brake valve. The main piston installed in the valve body can drive the balance piston to slide synchronously under the action of oil pressure. At this time, the end of the balance piston can form a gap with the inner wall of the valve. In the working chamber, the end face of the main piston can form an oil supply chamber separated from the working chamber with the outer periphery of the balance piston and the inner wall of the valve. The oil supply chamber can be connected with the working chamber during braking as a source of pressure supplement for the working chamber, which is beneficial To ensure sufficient braking force, the oil drain hole and the converging section set in the balance piston are used to connect the oil supply chamber and the oil inlet hole to relieve the pressure of the oil supply chamber after the pressure supplement is completed, so that the balance piston can continue to slide and participate in braking. Before the end of the brake pressure supplement, the confluence section is closed by the one-way component to avoid the failure of the pressure supplement. After the brake pressure supplement is completed, the pressure in the working chamber is completed and as the balance piston continues to move, the pressure will gradually be higher than that in the oil supply chamber. The pressure of the movable rod is affected by the limiting part, and one end is always located in the confluence section and is subjected to the pressure of the oil supply chamber. The movable rod runs through the balance piston, which can be connected with the existing driving mechanism or its outer periphery can form a sealed fit with the balance piston. , so that the movable rod can be driven by the driving mechanism to lift the one-way assembly or be moved by the pressure difference between the two ends and overcome the preset resistance of the one-way assembly to trigger the opening of the one-way assembly, and the confluence section communicates with the oil inlet hole , so that the oil in the oil supply chamber can leak out so that the balance piston can continue to slide; in this way, by setting a plurality of oil discharge holes and ports connected to the confluence section at intervals in the circumferential direction, the fluid can pass through multiple outlets when the oil supply chamber is depressurized. The oil drain holes arranged around the movable rod flow, so that the pressurized fluid in different oil drain holes can disperse the impact force of the movable rod against the one-way assembly from the surroundings, reducing the risk of the movable rod being shaken or even shifted by impact. phenomenon, which in turn makes the opening state and position of the one-way component more stable, ensuring stable pressure relief.

In the above-mentioned pressure relief structure of the brake valve, the oil drain hole is inclined from outside to inside along the radial direction of the balance piston toward the side where the one-way assembly is located. In this way, the fluid passing through the oil drain hole has a flow velocity conforming to the setting direction of the movable rod, which is beneficial to reduce the direct impact of the fluid passing through the oil drain hole on the movable rod, thereby reducing the probability that the shaking of the movable rod will affect the opening state of the one-way assembly.

In the above-mentioned pressure relief structure of the brake valve, the ports where the oil drain holes communicate with the confluence section are evenly spaced around the circumference of the movable rod. This is beneficial to make the movable rod more evenly distributed by the impact of the fluid passing through the oil drain hole, and further ensure the stability of the movable rod and the one-way assembly in the open state.

In the above-mentioned pressure relief structure of the brake valve, the outer circumference of the middle section of the movable rod or the outer circumference of the other end of the movable rod is in sealing fit with the balance piston. In this way, the pressure difference effect on the two ends of the movable rod can be guaranteed to be stable and continuous, and the reliability of sliding triggering of the movable rod can be improved.

In the above pressure relief structure of the brake valve, the end surface of the balance piston has a boss-shaped connecting portion, the confluence section is located on the end surface of the connecting portion, the end surface of the main piston has a bottom and the inlet A positioning groove communicating with the oil hole, the connecting portion is positioned and embedded in the positioning groove and is sealingly engaged with the circumferential inner wall of the positioning groove. In this way, the position of the end of the balance piston can be fully restrained by the inner wall of the positioning groove through the cooperation of the connecting part and the positioning groove, and at the same time, it is beneficial to prevent the fluid in the oil supply chamber from invading the other side of the one-way assembly and ensure the blocking and sealing of the one-way assembly. The effect is conducive to ensuring the stability of pressure relief.

In the above-mentioned pressure relief structure of the brake valve, an annular support is fixedly connected to the side wall of the inner chamber of the valve body, and one end of the main piston abutting against the balance piston is positioned and inserted in the support. By fixing the ring-shaped support on the inner wall of the valve, the ends of the main piston and the balance piston are slidably fitted in the support. At the same time, considering that the end of the balance piston is inserted into the main piston, and the one-way assembly is set At the junction of the main piston and the balance piston, the end of the balance piston is positioned in the main piston, and the end of the main piston is limited by the fixed support, so that the position of the one-way assembly is more stable and will not Affected by the sway of the balance piston, the working state of the one-way component is guaranteed to be undisturbed, thereby achieving stable pressure relief.

In the above pressure relief structure of the brake valve, the position of the one-way assembly is opposite or approximately opposite to the support member along the radial direction of the main piston. This further ensures that the one-way component is arranged in an area fully constrained by the support, thereby enhancing the stability of the one-way component in its working state.

In the above pressure relief structure of the brake valve, the one-way assembly includes a compression spring and a spherical valve block, the compression spring is arranged along the axial direction of the movable rod and is located in the main piston, the compression spring The two ends respectively act on the main piston and the valve block, and the valve block is located at the joint surface of the main piston and the balance piston, abuts against the balance piston and blocks the confluence section. In this way, while ensuring the sealing effect, the movable rod can effectively lift up the valve block when the pressure is relieved, and when the movable rod is reset after the pressure relief is completed, the valve block can also be stably reset under the action of the compression spring.

In the above-mentioned pressure relief structure of the brake valve, the balance piston also has a balance flow channel, and the two ports of the balance flow channel are respectively located on the outer peripheral surface of the balance piston and the side of the balance piston away from the main piston. The side of the balance piston away from the main piston is connected with a one-way blocking member that only allows the fluid in the balance channel to flow out, and the other end of the movable rod is inserted into the one-way blocking member. In this way, the high-pressure fluid formed by the compression of the oil supply chamber can enter the working chamber through the balance flow channel to produce a pressure supplement effect, thereby increasing the working pressure of the brake. The one-way blocking member can prevent the working chamber from directly releasing pressure, and at the same time, the movable rod can also be obtained. The constraint of the one-way blocking piece ensures the stable position of the movable rod.

In the above-mentioned pressure relief structure of the brake valve, the one-way blocking member includes an annular valve member, a spring member and a support plate fixed relative to the balance piston, and the annular valve member is sleeved on the outer periphery of the movable rod And with the movable rod seal fit, the two ends of the spring member respectively act on the annular valve member and the support plate and make the annular valve member always have a tendency to block the balance channel, the end of the movable rod and the support The plates are against each other. In this way, the annular valve part can prevent the fluid from leaking from the inside of the one-way blocking part, and the movable rod can provide position positioning for the annular valve part, so that the opening and closing state of the one-way blocking part can be stabilized, and the support plate can limit the stroke and position of the movable rod , which is conducive to improving the stability of the position state of the movable rod.

In the pressure relief structure of the above-mentioned brake valve, the movable rod includes a connected push rod section and a connecting section, the diameter of the push rod section is smaller than the diameter of the connecting section, and the push rod section can be connected with the connecting section. The valve blocks are against each other, and the annular valve element is always sheathed on the outer periphery of the connecting section. In this way, the ejector rod section with a smaller diameter is pushed against the valve block, which is beneficial to ensure a sufficient flow cross section of the confluence section, and at the same time reduces the impact force of the fluid in the drain hole on the movable rod, reduces the probability of the movable rod shaking, and improves the stability of pressure relief. sex.

Compared with prior art, advantage of the present invention is as follows:

The pressure relief structure of the above-mentioned brake valve is arranged at intervals in the circumferential direction of the port communicating with the confluence section by setting a plurality of oil drain holes, and the fluid can pass through a plurality of oil drain holes arranged circumferentially around the movable rod when the oil supply chamber is relieved. Hole flow, so that the pressurized fluid in different oil drain holes can disperse the impact force of the movable rod against the one-way component from the surroundings, reduce the phenomenon that the movable rod is shaken or even shifted by the impact, and then make the one-way component in the open state And the position is also more stable, ensuring stable pressure relief.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of the closed state of the confluence section in this embodiment.

Fig. 2 is an enlarged view of part A in Fig. 1 .

Fig. 3 is a schematic cross-sectional structure diagram of the open state of the confluence section in this embodiment.

Fig. 4 is an enlarged view of part B in Fig. 3 .

Fig. 5 is an enlarged view of part C in Fig. 4 .

Fig. 6 is a schematic perspective view of the three-dimensional structure of this embodiment.

In the figure, 1, the valve body; 11, the oil inlet hole; 12, the working oil hole;

2. Balance piston; 21. Confluence section; 22. Connecting part; 23. Balance flow channel; 24. Oil drain hole;

3. Main piston; 31. Positioning groove;

4. Working cavity; 5. Oil supply cavity; 6. Support piece;

7. One-way assembly; 71. Pressure spring; 72. Valve block;

8. Movable rod; 81. Push rod section; 82. Connecting section;

9. One-way blocking piece; 91. Annular valve piece; 911. Valve plate; 912. Sealing ring; 9121. Sealing lip; 9122. Annular boss; 913. Spring washer; 92. Spring piece; 93. Support plate;

10. Spring seat; 20. Pedal connecting rod assembly; 30. Control oil hole; 40. Oil return hole; 50. Return spring; 60. Spring base; 70. Guide rod.

Detailed ways

The following are specific embodiments of the present invention and in conjunction with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

As shown in Figure 1, in the pressure relief structure of the brake valve, the brake valve includes a valve body 1 with an oil inlet hole 11 and a working oil hole 12, and the valve body 1 is slidably connected with the main piston 3 and the Balance piston 2, the outer diameter of the main piston 3 is larger than the outer diameter of the balance piston 2, that is, the radial dimension of the inner cavity of the valve body 1 in the sliding area of the main piston 3 is greater than the radial dimension of the inner cavity of the valve body 1 in the sliding area of the balance piston 2 When braking, the working cavity 4 communicating with the working oil hole 12 is formed between the end surface of the balance piston 2 far away from the main piston 3 and the inner wall of the valve body 1, and the outer periphery of the balance piston 2 can pass through the sealing structure and the inner wall of the valve body 1. An oil supply chamber 5 that can replenish pressure for the working chamber 4 is formed between them. The volumes of the oil supply chamber 5 and the working chamber 4 can change with the sliding of the balance piston 2; the oil inlet hole 11 can be connected with the oil cup to supply the brake valve. oil, the working oil hole 12 communicates with the brake and can output oil pressure to control the brake. The main piston 3 and the balance piston 2 arranged in the valve body 1 can be triggered by the driver stepping on the pedal connecting rod assembly 20 to trigger the oil to enter from the control oil hole 30. The oil acts on the end surface of the main piston 3, and the main piston 3 is driven by the oil pressure to drive the balance piston 2 to slide. The oil return hole 40 is used to discharge the fluid acting on the end surface of the main piston 2 after the brake is completed. The working chamber 4 The increase of internal oil pressure can be output directly through the working oil hole 12; the oil supply chamber 5 can supplement the pressure of the working chamber 4 during the braking process to ensure sufficient braking force, and connect the oil supply chamber 5 and the oil inlet hole after the brake pressure supplement 11 Release the pressure on the oil supply chamber 5, so that the balance piston 2 can continue to slide and brake after the pressure supplement is completed, and before the brake supplement pressure is completed, the oil supply chamber 5 and the oil inlet hole 11 are blocked by the one-way assembly 7 , to avoid supplementary pressure failure. The side wall of the inner cavity of the valve body 1 is fixedly connected with an annular support member 6, one end of the main piston 3 facing the balance piston 2 is positioned and inserted in the support member 6, and the end of the balance piston 2 is positioned and inserted in the main piston 3 and At the junction of the two, there is a one-way assembly 7 that blocks the oil supply chamber 5 and the oil inlet hole 11. A movable rod 8 that can reciprocate in the axial direction is slidably connected to the balance piston 2, and the movable rod 8 runs through the balance piston. 2. By fixing the ring-shaped support member 6 on the inner wall of the valve body 1, the end of the main piston 3 and the balance piston 2 are slidably fitted in the support member 6, and at the same time, the end of the balance piston 2 is inserted into the main piston. 3, and the one-way assembly 7 is arranged at the junction of the main piston 3 and the balance piston 2, so that the end of the balance piston 2 is positioned in the main piston 3, and the end of the main piston 3 is supported by the fixed support 6 The limit constraint makes the position of the one-way component 7 more stable without being affected by the shaking of the balance piston 2, and ensures that the working state of the one-way component 7 is not disturbed, thereby achieving stable pressure relief. The balance piston 2 also has a balance channel 23 that can communicate with the oil supply chamber 5 and the working chamber 4. The balance piston 2 is connected with a one-way valve that only allows the fluid in the balance flow channel 23 to enter the working chamber 4 from the oil supply chamber 5. The blocking piece 9 and the one-way blocking piece 9 are located in the working chamber 4 , and the other end of the movable rod 8 is inserted into the one-way blocking piece 9 . In this way, the high-pressure fluid formed after the oil supply chamber 5 is compressed can enter the working chamber 4 through the balance flow channel 23 to generate a supplementary pressure effect, thereby increasing the brake working pressure. Setting the one-way blocking member 9 can avoid the direct pressure release of the working chamber 4, and at the same time The movable rod 8 can also be constrained by the one-way blocking member 9 to ensure the stable position of the movable rod 8 . The working chamber 4 is provided with a spring seat 10 which always abuts against the end face of the balance piston 2. The working chamber 4 is also provided with a return spring 50, a spring base 60 and a guide rod 70. The two ends of the return spring 50 act on the spring seat 10 respectively. On the spring base 60 , the spring base 60 abuts against the bottom surface of the working chamber, and the guide rod 70 is axially connected with the spring base 60 and is slidably connected with the spring base 10 to provide guidance for the movement of the balance piston 2 .

As shown in Figure 2, the pressure relief structure includes a confluence section 21 and an oil drain hole 24 located in the balance piston 2 and capable of communicating with the oil supply chamber 5 and the oil inlet hole 11, and the two ends of the movable rod 8 are respectively located in the working chamber 4 and the oil inlet hole 11. In the confluence section 21, the movable rod 8 can move axially towards the one-way assembly 7 and lift the one-way assembly 7. There are multiple oil drain holes 24 and they are all connected to the confluence section 21. The oil drain holes 24 are connected to the confluence section 21. The communicating ports of the section 21 are evenly spaced around the outer circumference of the movable rod 8 . Specifically, the end surface of the balance piston 2 has a boss-shaped connecting portion 22, the confluence section 21 is located on the end surface of the connecting portion 22, the end surface of the main piston 3 has a positioning groove 31 communicating with the oil inlet hole 11, and the connecting portion 22 is positioned Embedded in the positioning groove 31 and sealingly matched with the circumferential inner wall of the positioning groove 31 . In this way, the position of the end of the balance piston 2 can be fully restrained by the inner wall of the positioning groove 31 through the cooperation of the connecting portion 22 and the positioning groove 31, and at the same time, the fluid in the oil supply chamber 5 can be prevented from invading the other side of the one-way assembly 7 to ensure one-way The blocking and sealing effect of the component 7 on the confluence section 21 is beneficial to ensure the stability of pressure relief. In this way, fluid can flow through a plurality of drain holes 24 arranged circumferentially around the movable rod 8 when performing pressure relief. The number of drain holes 24 can be two or more, so that the pressure in different drain holes 24 The impact force of the fluid on the movable rod 8 against the one-way component 7 is dispersed, reducing the phenomenon that the movable rod 8 is impacted and shaken or even shifted, thereby making the opening state and position of the one-way component 7 more stable, ensuring stable pressure relief . Preferably, the oil drain hole 24 is arranged obliquely toward the side where the one-way assembly 7 is located from outside to inside along the radial direction of the connecting portion 22 . This helps to reduce the direct impact of the fluid passing through the oil drain hole 24 on the movable rod 8 , thereby reducing the probability that the movable rod 8 shakes and affects the opening state of the one-way assembly 7 . The one-way assembly 7 includes a compression spring 71 and a spherical valve block 72. The compression spring 71 is arranged axially along the movable rod 8. The two ends of the compression spring 71 act on the main piston 3 and the valve block 72 respectively. The valve block 72 It abuts against the balance piston 2 and blocks the confluence section 21 . In this way, while ensuring the sealing effect, the movable rod 8 can effectively lift the valve block 72 during pressure relief, and the valve block 72 can also be stably reset under the action of the stage clip 71 when the movable rod 8 resets after the pressure relief is completed. Specifically, the one-way blocking member 9 includes an annular valve member 91, a spring member 92, and a support plate 93 fixed in position relative to the balance piston 2. The support plate 93 abuts against the spring seat 10, and the annular valve member 91 is sleeved on the movable rod. 8 outer periphery and seal fit with the movable rod 8, the two ends of the spring member 92 respectively act on the annular valve member 91 and the support disc 93 and make the annular valve member 91 always have a tendency to block the balance channel 23, the movable rod 8 The end of the support plate 93 abuts against. In this way, the annular valve member 91 can prevent fluid from leaking from the inside of the one-way sealing member 9, and the movable rod 8 can provide position positioning for the annular valve member 91, so that the opening and closing state of the one-way sealing member 9 is stable, and the support plate 93 can limit The stroke and position of the movable rod 8 are conducive to improving the stability of the position and state of the movable rod 8 . The movable rod 8 includes a connected push rod section 81 and a connection section 82, the diameter of the push rod section 81 is smaller than the diameter of the connection section 82, the push rod section 81 can abut against the valve block 72, and the annular valve member 91 is always sleeved. It is provided on the outer periphery of the connection section 82 . In this way, the push rod section 81 with a smaller diameter and the valve block 72 are leaned against, which is beneficial to ensure a sufficient flow cross section of the confluence section 21, reduces the impact force of the fluid in the drain hole 24 on the movable rod 8, and reduces the shaking of the movable rod 8. Probability, improve pressure relief stability.

As shown in Figure 3, it is the structural state of the lower brake valve after the pressure replenishment is completed. The one-way assembly 7 moves and triggers the one-way assembly 7 to open the confluence section 21 , so that the oil inlet hole 11 communicates with the oil supply chamber 5 to relieve pressure.

As shown in FIG. 4 , at this time, the ejector rod section 81 is against the valve block 72 , and the hydraulic oil can flow through the oil drain hole 24 and the confluence section 21 to realize pressure relief and backflow.

As shown in FIG. 5 , the annular valve body 1 includes a valve plate 911 , a sealing ring 912 and a spring washer 913 which abut against in sequence. The valve plate 911 abuts against the working piston and is sheathed on the outer peripheral surface of the movable rod 8 . One end acts on the spring washer 913. The inner edge of the sealing ring 912 has a sealing lip 9121 arranged around the circumference. The sealing lip 9121 is in interference fit with the outer circumference of the connecting section 82, and the sealing lip 9121 has a large end facing the valve plate. The trumpet shape arranged on the side where 911 is located, the sealing lip 9121 is in sealing fit with the outer peripheral surface of the movable rod 8 along the circumferential direction. The inner edge of the sealing ring 912 is provided with a sealing lip 9121 and the outer peripheral surface of the movable rod 8 to form a circumferential linear seal, and the sealing lip 9121 is arranged in a trumpet shape, which is beneficial for the sealing lip 9121 to resist the pressure of the working chamber 4 to maintain contact with the movable rod. The contact of 8 reduces the loss when the movable rod 8 slides relative to the sealing ring 912 while ensuring the sealing effect, which is beneficial to prolong the working life. The sealing ring 912 has an annular boss 9122 protruding toward the side where the support plate 93 is located. The inner wall of the annular boss 9122 is spaced from the outer peripheral surface of the movable rod 8 . The sealing lip 9121 is arranged on the inner wall of the protruding annular boss 9122, and the inner wall of the annular boss 9122 is spaced from the outer peripheral surface of the movable rod 8, so that the area where the sealing lip 9121 is located is more susceptible to the radial pressure of the outer periphery And evenly abut against the movable rod 8, so that even if the sealing lip 9121 wears, it still remains close to the movable rod 8. At the same time, the closer the ring boss 9122 is to the seal ring 912 body, the less likely it is to be deformed by the pressure of the external fluid. A part of the cavity can always be maintained in the annular boss 9122, which is beneficial to ensure the continuous pressure of the external fluid on the annular boss 9122 and prolong the maintenance period.

As shown in FIG. 6 , the pedal link assembly 20 can be an existing assembly part with a pedal, and is connected to the bottom of the valve body 1 .

The specific embodiments described herein are only to illustrate the spirit of the present invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (10)

1. A pressure relief structure for a brake valve, the brake valve includes a valve body (1) provided with an oil inlet hole (11), and the valve body (1) is slidably connected with a main piston (3) against it And the balance piston (2), characterized in that the pressure relief structure includes a confluence section (21) located on the end surface of the balance piston (2) close to the main piston (3), an oil drain hole ( 24) and a one-way assembly (7) located between the balance piston (2) and the main piston (3) and blocking the communication between the confluence section (21) and the oil inlet hole (11), the oil drain hole ( 24) There are at least two and both are in communication with the confluence section (21), the balance piston (2) is slidingly connected with a movable rod (8) that runs through the balance piston (2), and the movable rod (8) one end of which is always located in the confluence section (21) and can move axially towards the one-way assembly (7) and lift the one-way assembly (7), the oil drain hole (24) and the confluence section (21) The communicating ports are arranged at intervals around the circumference of the movable rod (8). 2. The pressure relief structure of the brake valve according to claim 1, characterized in that, the oil drain hole (24) faces the one-way assembly from outside to inside along the radial direction of the balance piston (2) (7) The side on which it is located is set obliquely. 3. The pressure relief structure of the brake valve according to claim 1, characterized in that, the ports where several of the oil drain holes (24) communicate with the confluence section (21) go around the circumferential direction of the movable rod (8) Evenly spaced. 4. The pressure relief structure of the brake valve according to claim 1, 2 or 3, characterized in that, the outer circumference of the middle section of the movable rod (8) or the outer circumference of the other end of the movable rod (8) is in contact with the balance piston (2) Seal fit. 5. The pressure relief structure of the brake valve according to claim 1, 2 or 3, characterized in that, the end face of the balance piston (2) has a boss-shaped connecting portion (22), and the confluence section ( 21) Located on the end surface of the connecting part (22), the end surface of the main piston (3) has a positioning groove (31) whose bottom communicates with the oil inlet hole (11), and the connecting part (22) is positioned It is embedded in the positioning groove (31) and sealingly fits with the circumferential inner wall of the positioning groove (31). 6. The pressure relief structure of the brake valve according to claim 1, 2 or 3, characterized in that, the inner chamber side wall of the valve body (1) is fixedly connected with an annular support (6), the One end of the main piston (3) abutting against the balance piston (2) is positioned and inserted in the support (6), and the position of the one-way assembly (7) is along the radial direction of the main piston (3) The supporting member (6) is opposite or approximately opposite to each other. 7. The pressure relief structure of the brake valve according to claim 1, 2 or 3, characterized in that, the one-way assembly (7) includes a compression spring (71) and a spherical valve block (72), the Compression spring (71) is arranged along the axial direction of the movable rod (8) and is located in the main piston (3), and the two ends of the compression spring (71) respectively act on the main piston (3) and the valve block (72), the valve block (72) is located at the joint surface of the main piston (3) and the balance piston (2) and abuts against the balance piston (2) and blocks the confluence section (21) . 8. The pressure relief structure of the brake valve according to claim 1, 2 or 3, characterized in that, the balance piston (2) also has a balance channel (23), and the balance channel (23) The two ports of the balance piston (2) are located on the outer peripheral surface of the balance piston (2) and the side of the balance piston (2) away from the main piston (3), and the side of the balance piston (2) away from the main piston (3) is connected with a A one-way valve (9) through which the fluid in the balance channel (23) flows out, and the other end of the movable rod (8) is inserted into the one-way blocking member (9). 9. The pressure relief structure of the brake valve according to claim 8, characterized in that, the one-way blocking member (9) comprises an annular valve member (91), a spring member (92) and a valve relative to the balance piston. (2) a support plate (93) with a fixed position, the annular valve member (91) is sleeved on the outer periphery of the movable rod (8) and is in sealing fit with the movable rod (8), the spring member (92) The two ends respectively act on the annular valve member (91) and the support disc (93) and make the annular valve member (91) always have a tendency to block the balance channel (23), the end of the movable rod (8) Against the support plate (93). 10. The pressure relief structure of the brake valve according to claim 9, characterized in that, the movable rod (8) comprises a connected push rod segment (81) and a connecting segment (82), and the push rod segment (81) has a diameter smaller than that of the connection section (82), the push rod section (81) can abut against the valve block (72), and the annular valve element (91) is always sleeved on the periphery of the connecting section (82).