Hydraulic brake protection device booster

Abstract

The present invention provides a hydraulic brake protection device booster, which belongs to the field of mechanical technology. It solves the problem of low working efficiency of existing hydraulic booster cylinders. The hydraulic brake protection device booster includes a cylinder body, a piston 1, and a pusher extending into the cylinder body at the inner end. The piston 1 has a columnar inner cavity, an oil inlet hole, and an oil return hole. The cylinder body is also provided with a piston 2 extending into the inner cavity. A reset spring is provided in the inner cavity. The side of the piston 2 has a sealing part 2. The piston 2 can move under the action of the reset spring and make the sealing part 2 block the oil inlet hole. The oil return hole is connected to the side of the inner cavity away from the pusher. The piston 2 also has an oil passage, and the inlet and outlet of the oil passage are respectively located on both sides of the sealing part 2. When the pusher moves into the cylinder body, it can abut against the piston 2 and block the oil passage. The hydraulic brake protection device booster has the advantage of easier operation.

Description

Technical Field

[0001] The invention belongs to the technical field of machinery and relates to a booster for a hydraulic brake protection device. Background Art

[0002] The structure of a hydraulic booster cylinder generally includes a cylinder body, a piston disposed in the cylinder body, and a push rod whose outer end is used to connect to the vehicle pedal. The piston separates the cylinder body into an oil inlet chamber, an oil return chamber, and an oil outlet chamber. The cylinder body is provided with an oil inlet, an oil return, and an oil outlet that are respectively connected to the oil inlet chamber, the oil return chamber, and the oil outlet chamber. The piston is also provided with an oil passage that connects the oil inlet chamber and the oil return chamber. When in use, the push rod is pushed into the cylinder body and the oil passage is blocked. The oil inlet chamber is continuously supplied with oil through an external oil supply device. The piston is pushed to move with the assistance of oil pressure, providing assistance for the piston push.

[0003] For example, the applicant has designed a hydraulic booster cylinder and applied for a Chinese patent (its application number is: 201711263536.2; its publication number is: CN107830081A). The hydraulic booster cylinder includes a cylinder body with a liquid inlet and a liquid return port, a piston arranged in the cylinder body, and a rod-shaped pushing member. The liquid inlet and the liquid return port can be connected through a liquid passage opened on the piston. The piston has a columnar liquid passage cavity. The liquid passage includes a liquid inlet channel opened on the side wall of the liquid passage cavity and can connect the liquid passage cavity with the liquid inlet. The inner end of the pushing member has a liquid passage portion extending into the liquid passage cavity. The liquid passage portion can translate axially in the liquid passage cavity. When the liquid passage portion is in different positions, the side of the liquid passage portion can partially block the liquid inlet channel to varying degrees or not block the liquid inlet channel. When the hydraulic booster cylinder is in use, a pushing member is pushed into the cylinder body to partially block the liquid inlet channel, so that the liquid inlet speed is faster than the liquid outlet speed. The excess oil will generate a boosting force at the oil inlet chamber to assist the piston in pushing.

[0004] However, under the conditions of the same external oil supply equipment, when the above-mentioned hydraulic booster cylinder is in use, the oil pressure in the oil inlet chamber increases slightly slowly, that is, the working efficiency is relatively low. It can meet the use requirements of some equipment, but cannot meet the use requirements of equipment with higher requirements on work efficiency. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems existing in the prior art and propose a hydraulic brake protection device booster to solve the problem of low working efficiency of the existing hydraulic booster cylinder.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The booster of a hydraulic brake protection device comprises a cylinder body with an oil inlet and an oil return port, a piston 1 arranged in the cylinder body and a pushing member whose inner end extends into the cylinder body, the piston 1 having a columnar inner cavity, an oil inlet hole that can connect the oil inlet and the inner cavity, and an oil return hole that connects the inner cavity and the oil return port, and is characterized in that the cylinder body is also provided with a piston 2 that extends into the inner cavity, a return spring is arranged in the inner cavity, a side portion of the piston 2 has a sealing portion 2, the piston 2 can move under the action of the return spring and make the sealing portion 2 block the oil inlet hole, the oil return hole is connected with a side of the inner cavity away from the pushing member, the piston 2 also has an oil passage, and the inlet and outlet of the oil passage are respectively located on both sides of the sealing portion 2, and the pushing member can abut against the piston 2 and block the oil passage when moving into the cylinder body.

[0008] When the pusher of the booster of the hydraulic brake protection device is not in motion, the external oil supply device delivers oil to the oil inlet of the cylinder body and enters the oil inlet hole of piston 1. Because piston 2 moves under the elastic force of the return spring and blocks the oil inlet hole through sealing part 2, the oil does not enter the inner cavity of piston 1. When the operator pushes the pusher into the cylinder body, the pusher moves inward until it abuts against piston 2 and blocks the oil passage. The operator continues to apply the pushing force, and the pusher pushes piston 2 to overcome the elastic force of the return spring and move to the end away from the pusher, so that the position of sealing part 2 and the position of the oil inlet hole are staggered, and the oil enters the inner cavity through the oil inlet hole. Because the inner cavity is columnar, the sealing part 2 of piston 2 will always abut and seal against the inner wall of piston 1 during the movement of piston 2, so that the oil cannot flow from the gap between piston 1 and piston 2 to the direction of the return oil hole located on the side of the inner cavity away from the pusher. The oil passage is blocked, and the oil can only accumulate on one side of piston 1 and piston 2. As the oil increases, the oil pressure increases, and the auxiliary operator pushes piston 1 to provide assistance for the use of the booster. When oil leakage is required, piston 1, piston 2 and the pusher are reset, and the oil on one side of piston 1 and piston 2 is returned through the opened oil passage, oil return hole and oil return port, and restored to the initial state.

[0009] During this use, because the external oil supply device is in the oil supply state, the sealing part 2 of the piston 2 blocks the oil inlet hole, so that the oil pressure at the oil inlet hole of the piston 1 connected to the external oil supply device and the oil inlet port of the cylinder body increases. When the sealing part 2 moves and opens the oil inlet hole, under the action of the higher oil pressure, the oil will enter the piston 1 faster, and can also provide assistance for the movement of the piston 1 faster, so that the work efficiency is higher. In addition, the piston 1 and the piston 2 extending into the inner cavity are arranged at the same time, so that when the operator pushes the pusher, the on-off control of the oil circuit can be achieved by pushing the smaller piston 2. Compared with directly pushing the larger piston 1, the driving force required is smaller, the operation is easier, the movement of the pusher is faster, and the working efficiency of the booster is also higher. The push of the piston 1 can be driven by the help of the oil pressure, which makes the push easier and makes the boosting effect of the entire booster better.

[0010] In the above-mentioned hydraulic brake protection device booster, the oil passage includes an axial hole that penetrates along the axial direction of the piston 2 and a side hole 2 that penetrates and is opened on the side wall of the axial hole. The side hole 2 is located between the sealing part 2 and the outer end of the pusher. The side of the inner end of the pusher has a protruding sealing part 3, and the outer side of the sealing part 3 abuts against the side of the axial hole. The oil passage includes an axial hole that penetrates and is opened, so that the hole is easy to open, and the flowable area of ​​the oil passage can be expanded as much as possible while ensuring the strength of the piston 2, thereby increasing the flow rate and flow volume of the oil and improving work efficiency. In addition, the opening of a larger axial hole can also reduce the weight of the piston 2, further reducing the demand for the driving force when the pusher is pushed, and improving the boosting effect.

[0011] In the above-mentioned hydraulic brake protection device booster, a cavity is formed between the side of the sealing part 3 close to the outer end of the pusher and the inner wall of the cylinder body, and a through hole connecting the cavity and the inner cavity is also provided on the piston 2. When the pusher is pushed into the cylinder body, the air in the inner cavity can quickly enter the cavity, avoiding the pushing resistance caused by the complete closure of the cavity, making the pusher move faster and working more efficiently; when the pusher is reset, the oil in the cavity is quickly discharged through the through hole, reducing the oil pressure on the reset side, so that the pusher can be reset quickly, improving the working efficiency of the booster.

[0012] In the above hydraulic brake protection device booster, the inner end of the pusher has a concave hole, and the side wall of the concave hole is penetrated by a side hole 3, and the side hole 3 is located between the sealing part 3 and the inner end of the pusher. The side hole 3 and the concave hole form another channel for oil discharge, which increases the speed of oil discharge and improves work efficiency.

[0013] In the above hydraulic brake protection device booster, the number of the oil return holes is at least two, the inlet of one of the oil return holes is opposite to the end face of the second piston, the inlet of at least one of the oil return holes is opposite to the side of the second piston, and a radial hole is formed through the side of the second piston near the oil return hole. Multiple oil return holes are formed on the first piston, and corresponding radial holes are formed on the second piston to increase the discharge channel of the oil, increase the oil discharge speed, and improve the work efficiency.

[0014] In the above hydraulic brake protection device booster, the end of the piston 1 facing the pusher has a protruding cylindrical support portion, the inner wall of the support portion has a protruding blocking portion, and the piston 2 abuts against the blocking portion under the elastic force of the return spring and makes the sealing portion 2 block the oil inlet hole. The blocking portion limits the position of the piston 2, ensuring that the sealing portion 2 on the piston 2 can block the oil inlet hole without moving.

[0015] In the above hydraulic brake protection device booster, the side of the support portion is also penetrated with a boost hole, through which the oil in the inner cavity can be transported to the outside of the piston one, providing sufficient boost guarantee for the movement of the piston one.

[0016] In the above hydraulic brake protection device booster, the outer wall of the piston 1 is also provided with an annular oil inlet groove, the oil inlet groove is connected to the oil inlet hole, and the axial width of the oil inlet groove is greater than the diameter of the oil inlet hole, and sealing rings are provided between the piston 1 and the inner wall of the cylinder body on both sides of the oil inlet groove. The diameter of the oil inlet hole is relatively small, which is convenient for the sealing of the sealing part 2, and the opening of the oil inlet groove can expand the connecting area between the oil inlet hole and the oil inlet port.

[0017] In the above hydraulic brake protection device booster, a relief valve is connected between the oil inlet and the oil return port on the outside of the cylinder body to release pressure in time to avoid excessive oil pressure at the oil inlet and affect the service life of the external oil supply equipment.

[0018] In the above-mentioned hydraulic brake protection device booster, the cylinder body has two cavities, and the two cavities are both provided with the above-mentioned piston one, piston two and pushing member. The cylinder body is also provided with a balancing hole connecting the two cavities, and the two ends of the balancing hole are respectively located on the sides of the two cavities. Both ends of the balancing hole are provided with balancing valves that can open and close the balancing hole, and the valve core part of the balancing valve extends into the cavity. A cylindrical piston sleeve is also fixed on the piston one, and the piston sleeve can move with the piston one to push the valve core of the balancing valve to retract into the balancing hole and open the balancing hole.

[0019] Compared with the prior art, the hydraulic brake protection device booster has the following advantages:

[0020] 1. The booster of the hydraulic brake protection device adopts a normally closed mode, so that when the pusher is not pushed, the oil accumulates at the oil inlet and does not enter the cylinder for circulation, which increases the oil at the oil inlet, so that when the pusher is pushed, the oil can enter the cylinder faster to provide assistance, and the working efficiency is high.

[0021] 2. By opening an axial hole in the second piston and a concave hole at the inner end of the pusher, the flow area for oil discharge is expanded, the oil discharge speed is increased, and the work efficiency is further improved.

[0022] 3. The booster of the hydraulic brake protection device is provided with a piston 1 and a piston 2 structure for use with a pusher. The piston 2 is small in size and light in weight. The driving force required by the operator to move the piston 2 through the pusher is reduced, and the operation is easier. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a cross-sectional structural schematic diagram of the booster of the hydraulic brake protection device.

[0024] Figure 2 It is a partial enlarged view of the booster of the hydraulic brake protection device.

[0025] Figure 3 It is a partial enlarged view of the booster of the hydraulic brake protection device when in use.

[0026] Figure 4 It is a schematic diagram of the cross-sectional structure of the booster overflow valve of the hydraulic brake protection device.

[0027] In the figure, 1, cylinder body; 1a, cavity; 1b, oil inlet; 1c, oil return port; 2, piston one; 2a, inner cavity; 2b, oil inlet hole; 2c, oil return hole; 2d, supporting part; 2e, power-assisting hole; 2f, oil inlet groove; 3, pushing member; 3a, sealing part three; 3b, recessed hole; 3c, side hole three; 4, reset spring; 5, piston two; 5a, sealing part two; 5b, axial hole; 5c, side hole two; 5d, radial hole; 5e, through hole; 6, blocking part; 7, overflow valve. DETAILED DESCRIPTION

[0028] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0029] The booster of the hydraulic brake protection device includes a cylinder body 1 having an oil inlet 1b, an oil return port 1c and an oil outlet. The cylinder body 1 has two cavities, and piston 1 2, piston 2 5 and a pusher 3 are arranged in the two cavities. A balancing hole connecting the two cavities is also opened in the cylinder body 1. The two ends of the balancing hole are respectively located on the sides of the two cavities. A balancing valve capable of opening and closing the balancing hole is arranged at both ends of the balancing hole, and the valve core of the balancing valve extends into the cavity. A cylindrical piston sleeve is also fixed on the piston 1 2. The piston sleeve can move with the piston 1 2 to push the valve core of the balancing valve to retract into the balancing hole and open the balancing hole. Since the structures at the two cavities in the cylinder body 1 are the same, the structure at one of the cavities is taken as an example for structural description.

[0030] like Figure 1 and Figure 2 As shown, piston 1 2 divides the cavity into an oil inlet cavity, an oil return cavity and an oil outlet cavity. The oil return cavity is connected to the oil return port 1c, and the oil outlet cavity is connected to the oil outlet port. The balance hole is opened on the side of the oil outlet cavity. A spring 1 is arranged in the oil return cavity, and the two ends of the spring 1 are respectively against the inner wall of the cylinder body 1 and the piston 1 2. The piston 2 moves toward the oil inlet cavity under the elastic force of the spring 1.

[0031] The piston 2 has a cylindrical inner cavity 2a, and an oil inlet hole 2b is provided on the side of the inner cavity 2a. A circular oil inlet groove 2f in communication with the oil inlet port 1b is provided on the outer wall of the piston 2. The bottom of the oil inlet groove 2f is connected to the oil inlet hole 2b, and the axial width of the oil inlet groove 2f is greater than the aperture of the oil inlet hole 2b. Sealing rings are provided between the piston 2 and the inner wall of the cylinder body 1 on both sides of the oil inlet groove 2f. Several oil return holes 2c are also provided in the piston 2 to connect the inner cavity 2a with the oil return cavity. The piston 2 has a cylindrical support portion 2d protruding at one end facing the pusher 3. Under the elastic force of the spring 1, the piston 2 can make the end of the support portion 2d abut against the inner wall of the cylinder body 1. Several power-assisting holes 2e are also provided on the side of the support portion 2d to connect the inner cavity 2a with the oil inlet cavity. In this embodiment, the number of oil return holes 2c is at least two, wherein the inlet of one oil return hole 2c is opposite to the end face of the inner cavity 2a, and the inlet of at least one oil return hole 2c is opposite to the side of piston 2 5 extending into piston 1 2.

[0032] The side of the piston 2 5 has a protruding sealing part 2 a, a return spring 4 is arranged between the front end of the piston 2 5 and the piston 1 2, and the inner wall of the support part 2 d has a protruding blocking part 6. Under the elastic force of the return spring 4, the piston 2 5 moves backward to abut against the blocking part 6 and makes the sealing part 2 a block the oil inlet hole 2 b. An axial hole 5 b is opened in the axial direction of the piston 2 5, and a side hole 2 5 c is opened in the side of the piston 2 5. The side hole 2 5 c is located between the sealing part 2 5 a and the rear end of the piston 2 5. The side of the piston 2 5 is also opened between the front end and the sealing part 2 5 a. In this embodiment, the sealing part 2 5 a includes an annular sealing groove opened on the outside of the piston 2 5, and a sealing ring 1 with a circular cross section and a sealing ring 2 with a square cross section are arranged in the sealing groove. The sealing ring 2 is sleeved on the outside of the sealing ring 1 and the outside of the sealing ring 2 is tightly against the side wall of the inner cavity 2 a; the blocking part 6 is an annular retaining ring.

[0033] The inner end of the pusher 3 extends into the axial hole 5b of the piston 2 5, and a spring 3 is arranged between the pusher 3 and the piston 2 5. The pusher 3 moves toward the outer end under the elastic force of the spring 3. The side of the inner end of the pusher 3 has a protruding sealing portion 3a, and the outer side of the sealing portion 3a is tightly against the side of the axial hole 5b. The inner end of the pusher 3 has a concave hole 3b, and a side hole 3c is provided on the side wall of the concave hole 3b. The side hole 3c is located between the sealing portion 3a and the inner end of the pusher 3. A cavity 1a is formed between the side of the sealing portion 3a close to the outer end of the pusher 3, the piston 2 5 and the inner wall of the cylinder body 1, and a through hole 5e is also provided on the piston 25 to connect the cavity 1a and the inner cavity 2a. In this embodiment, the structure of the sealing part three 3a is similar to the structure of the sealing part two 5a, including an annular sealing groove, in which a sealing ring one with a circular cross-section and a sealing ring two with a square cross-section are arranged, and the sealing ring two is sleeved on the outside of the sealing ring one and the outside of the sealing ring two is tightly against the inner wall of the axial hole 5b.

[0034] like Figure 4 As shown, a relief valve 7 is connected between the oil inlet 1b and the oil return port 1c on the outside of the cylinder body 1. The valve body of the relief valve 7 is connected to the cylinder body 1 as a whole. When the oil at the oil inlet 1b is too much, the valve core of the relief valve 7 will be pushed open. When the piston 1 2, the piston 2 5 and the pusher 3 do not move, the oil inlet 1b and the oil return port 1c are directly connected to circulate and return the oil to the oil tank. When the oil pressure drops, the relief valve 7 is closed again to maintain a certain oil pressure at the oil inlet 1b.

[0035] When the pusher 3 of the booster of the hydraulic brake protection device is not in motion, the external oil supply device delivers the oil to the oil inlet 1b of the cylinder body 1, and enters the oil inlet hole 2b of the piston 2 through the oil inlet groove 2f. Since the sealing part 2a blocks the oil inlet hole 2b, the oil will not enter the inner cavity 2a of the piston 2. The original oil in the cylinder body 1 will return through the boosting hole 2e, the through hole 5e, the side hole 2 5c, the axial hole 5b, the radial hole 5d, the oil outlet hole 1, the oil return cavity and the oil return port 1c.

[0036] When the operator pushes the push member 3 into the cylinder body 1, Figure 4 As shown, the pusher 3 overcomes the elastic force of the spring 3 and moves inward to abut against the piston 2 5, while the sealing portion 3a blocks the side hole 2 5c. The operator continues to apply the pushing force, and the piston 2 5 moves inward synchronously with the pusher 3 overcoming the elastic force of the return spring 4 until the inner end of the piston 2 5 abuts against the piston 1 2. At this time, the sealing part 2a moves forward and no longer blocks the oil inlet hole 2b. The oil enters the inner cavity 2a through the oil inlet hole 2b. Because the inner cavity 2a is columnar, the sealing part 2a 5a of the piston 2a will always abut against and seal the inner wall of the piston 1 2 during the movement of the piston 2a, so that the oil cannot flow from the gap between the piston 1 2 and the piston 25 to the direction of the return oil hole 2c. The side hole 2c is blocked by the sealing part 3a. The oil can only accumulate in the second half of the inner cavity 2a and flow to the oil inlet cavity through the boosting hole 2e, and flow to the cavity 1a through the through hole 5e. As the oil increases, the oil pressure increases, and the auxiliary operator pushes the piston 1 2, providing assistance for the use of the booster. During the movement of the piston 1 2, the position of the oil inlet hole 2b gradually staggers with the oil inlet port 1b, and the oil inlet connection is achieved by relying on the oil inlet groove 2f. When the piston 1 2 continues to move until the oil inlet groove 2f and the oil inlet port 1b are offset, the oil inlet port 1b can be directly connected to the oil inlet cavity at the rear side of the piston 1 2 to achieve oil inlet assistance. In this embodiment, the spring coefficients of the spring 1, the return spring 4 and the spring 3 are reduced one by one.

[0037] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A hydraulic brake protection device booster, comprising a cylinder (1) having an oil inlet (1b) and an oil return port (1c), a piston (2) disposed in the cylinder (1), and a pusher (3) whose inner end extends into the cylinder (1), wherein the piston (2) has a columnar inner cavity (2a), an oil inlet hole (2b) capable of connecting the oil inlet (1b) and the inner cavity (2a), and an oil return hole (2c) connecting the inner cavity (2a) and the oil return port (1c), characterized in that: The cylinder body (1) is also provided with a second piston (5) extending into the inner cavity (2a), and a return spring (4) is provided in the inner cavity (2a). The side of the second piston (5) is provided with a second sealing portion (5a). The second piston (5) can move under the action of the return spring (4) and make the second sealing portion (5a) block the oil inlet hole (2b). The oil return hole (2c) is connected with the side of the inner cavity (2a) away from the push member (3). The second piston (5) is also provided with an oil passage, and the inlet and outlet of the oil passage are respectively located on both sides of the second sealing portion (5a). When the push member (3) moves into the cylinder body (1), it can abut against the second piston (5) and block the oil passage.

2. The hydraulic brake protection device booster according to claim 1, characterized in that: The oil passage comprises an axial hole (5b) extending through the axial direction of the second piston (5) and a side hole (5c) extending through the side wall of the axial hole (5b). The side hole (5c) is located between the second sealing portion (5a) and the outer end of the pusher (3). The side of the inner end of the pusher (3) has a protruding sealing portion (3a), and the outer side of the sealing portion (3a) abuts against the side of the axial hole (5b).

3. The hydraulic brake protection device booster according to claim 2, characterized in that: A cavity (1a) is formed between the side of the sealing portion three (3a) close to the outer end of the pusher (3) and the inner wall of the cylinder body (1), and a through hole (5e) connecting the cavity (1a) and the inner cavity (2a) is also provided on the piston two (5).

4. The hydraulic brake protection device booster according to claim 2 or 3, characterized in that: The inner end of the pusher (3) has an inwardly concave hole (3b), and a side hole three (3c) is formed through the side wall of the concave hole (3b). The side hole three (3c) is located between the sealing portion three (3a) and the inner end of the pusher (3).

5. The hydraulic brake protection device booster according to claim 2 or 3, characterized in that: The number of the oil return holes (2c) is at least two, wherein the inlet of one of the oil return holes (2c) is opposite to the end face of the second piston (5), and the inlet of at least one of the oil return holes (2c) is opposite to the side of the second piston (5), and a radial hole (5d) is formed through the side of the second piston (5) near the oil return hole (2c).

6. The hydraulic brake protection device booster according to claim 1, 2 or 3, characterized in that: The piston 1 (2) has a protruding cylindrical support portion (2d) at one end facing the pusher (3), and the inner wall of the support portion (2d) has a protruding blocking portion (6). Under the elastic force of the return spring (4), the piston 2 (5) abuts against the blocking portion (6) and causes the sealing portion 2 (5a) to block the oil inlet hole (2b).

7. The hydraulic brake protection device booster according to claim 6, characterized in that: The side of the support portion (2d) is also provided with a power-assisting hole (2e).

8. The hydraulic brake protection device booster according to claim 1, 2 or 3, characterized in that: The outer side wall of the piston 1 (2) is also provided with an annular oil inlet groove (2f), the oil inlet groove (2f) is connected to the oil inlet hole (2b), and the axial width of the oil inlet groove (2f) is greater than the hole diameter of the oil inlet hole (2b), and sealing rings are provided between the piston 1 (2) and the inner wall of the cylinder body (1) on both sides of the oil inlet groove (2f).

9. The hydraulic brake protection device booster according to claim 1, 2 or 3, characterized in that: An overflow valve (7) is connected between the oil inlet (1b) and the oil return port (1c) on the outside of the cylinder body (1).

10. The hydraulic brake protection device booster according to claim 1, 2 or 3, characterized in that: The cylinder body (1) has two cavities, and the two cavities are both provided with the above-mentioned piston one (2), piston two (5) and pushing member (3). The cylinder body (1) is also provided with a balancing hole connecting the two cavities, and the two ends of the balancing hole are respectively located at the sides of the two cavities. Both ends of the balancing hole are provided with a balancing valve capable of opening and closing the balancing hole, and the valve core of the balancing valve extends into the cavity. A cylindrical piston sleeve is also fixed on the piston one (2), and the piston sleeve can move with the piston one (2) to push the valve core of the balancing valve to retract into the balancing hole and open the balancing hole.

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