CN211039226U

CN211039226U - Hydraulic power cylinder with overflow structure

Info

Publication number: CN211039226U
Application number: CN201921982726.4U
Authority: CN
Inventors: 陈灵刚; 刘叶芝; 韩伟玉; 刘叶勇
Original assignee: Yuhuan Aoheng Machinery Co ltd
Current assignee: Yuhuan Aoheng Machinery Co ltd
Priority date: 2019-11-15
Filing date: 2019-11-15
Publication date: 2020-07-17
Anticipated expiration: 2029-11-15

Abstract

The utility model provides a take hydraulic power cylinder of overflow structure belongs to mechanical technical field. It has solved the problem of how pressure release of current hydraulic pressure helping hand jar. The hydraulic power cylinder with the overflow structure comprises a cylinder body with an oil inlet and an oil return port, a push rod and a piston body arranged in the cylinder body, wherein the inner end of the push rod extends into the cylinder body, an oil passing hole capable of communicating the oil inlet with the oil return port is formed in the piston body, an overflow valve core and an overflow spring which are separated from the push rod are arranged in the oil passing hole, a first sealing part is arranged on the hole wall of the oil passing hole, a second sealing part is arranged at the inner end of the push rod and can abut against the first sealing part, an overflow hole is formed in the inner end of the push rod, the overflow valve core is arranged at the inner end of the push rod, the push rod can approach the overflow valve core and push the overflow valve core to compress the. The hydraulic power cylinder with the overflow structure has the advantages of good stability and reliability.

Description

Hydraulic power cylinder with overflow structure

Technical Field

The utility model belongs to the technical field of machinery, a hydraulic power cylinder is related to, especially, relate to a take hydraulic power cylinder of overflow structure.

Background

The existing hydraulic power cylinder generally comprises a cylinder body, a piston arranged in the cylinder body and a push rod of which the outer end is used for being connected with a vehicle pedal, wherein the piston divides the cylinder body into an oil inlet cavity and an oil return cavity, the cylinder body is provided with an oil inlet and an oil return opening which are respectively communicated with the oil inlet cavity and the oil return cavity, the piston is also provided with an oil passage which can communicate the oil inlet cavity with the oil return cavity, the inner end of the push rod extends into the cylinder body, and when the push rod moves inwards, the inner end of the push rod can block the oil passage.

However, when the inner end of the push rod continuously blocks the oil passing channel, the pressure in the oil inlet cavity cannot be released, the oil pressure keeps continuously rising, external oil supply equipment can bear larger and larger load, and the service life of the external oil supply equipment is very easy to shorten and even damage after long-term use.

In the face of this problem, conventional technical means adopted by those skilled in the art include:

an overflow structure is connected between an oil inlet and an oil return port outside a cylinder body, for example, a hydraulic power cylinder (with the application number of 201821990147.X) applied by the applicant, in the patent, the overflow structure is integrated on the outer side of the cylinder body and is used for relieving pressure when the oil pressure in an oil inlet cavity exceeds a critical value so as to solve the problem of overlarge load in the prior art;

secondly, an overflow structure is independently arranged in a piston or a push rod in a cylinder body, for example, a hydraulic power cylinder (the application number is 201820208126.1; the publication number is CN207892921U) with a protection structure in Chinese patent applied by the applicant, in the patent, the overflow structure capable of releasing pressure is additionally arranged in the piston and the push rod in the cylinder body, and the pressure can be released when the oil pressure in an oil inlet cavity exceeds a critical value, so that the problem of overlarge load in the prior art is solved.

The specific structure of the two overflow structures often needs to separately open a pressure relief channel in the piston or the push rod, and a valve core and a spring are arranged in the pressure relief channel, and in a default state, the valve core blocks the pressure relief channel under the action of the elastic force of the spring. At the moment, the spring is in a compressed state, and when the acting force exerted by the pressure difference on the two sides of the pressure relief channel is greater than the elastic force of the spring, the valve core is jacked open, and the pressure relief channel is opened for pressure relief. The working principle of the overflow structure means that when the hydraulic power cylinder is put into use, no matter whether a vehicle pedal is stepped on or not, the spring is always in a compressed state, and even in some equipment with high requirements on pressure relief critical values, the spring still needs to be compressed in a large amount. The long-time compressed spring can cause very big influence to the life of spring self, can lead to the elasticity to become invalid even after long-term the use and make the condition that the pressure release passageway was opened easily, and then influences the normal use of hydraulic pressure helping hand jar.

For this reason, the overflow structure in the hydraulic power cylinder needs to be regularly maintained and replaced, and for convenient replacement, technical personnel in the field often more tend to adopt scheme one, namely the overflow structure sets up in the cylinder body outside to reduce the cost of maintenance change. However, although the above conventional technical means currently available to those skilled in the art can solve the technical problem of pressure relief, the overflow structure has a short replacement period of parts, and the effect is still not ideal.

SUMMERY OF THE UTILITY MODEL

The utility model aims at the above-mentioned problem that prior art exists, provide a take hydraulic power cylinder of overflow structure, solved the problem of how to make hydraulic power cylinder pressure release.

The purpose of the utility model can be realized by the following technical proposal:

a hydraulic power cylinder with an overflow structure comprises a cylinder body with an oil inlet and an oil return port, a push rod and a piston body arranged in the cylinder body, wherein the inner end of the push rod extends into the cylinder body, an oil passing hole capable of communicating the oil inlet with the oil return port is formed in the piston body, the hydraulic power cylinder is characterized in that an overflow valve core and an overflow spring which are separated from the push rod are arranged in the oil passing hole, a first sealing part is arranged on the hole wall of the oil passing hole, a second sealing part is arranged at the inner end of the push rod and can abut against the first sealing part, an overflow hole is further formed in the inner end of the push rod, the overflow valve core is arranged at the inner end of the push rod, the push rod can approach the overflow valve core and push the overflow valve core to compress the overflow spring, and the overflow hole can be.

The hydraulic power cylinder with the overflow structure is provided with the overflow hole at the inner end of the push rod, and the position of the overflow valve core is opposite to the inner end of the push rod. When an operator does not step on the pedal, the push rod does not move into the cylinder body, the overflow valve core is separated from the push rod and is not subjected to the acting force of the push rod, the compression amount of the overflow spring is small or even not compressed, and oil fed into the cylinder body from the oil inlet can flow out through the oil hole and the oil return port; when an operator steps on the pedal, the push rod moves axially into the cylinder body, the first sealing part and the second sealing part abut against each other to form sealing and block the oil through hole, in the moving process of the push rod, the inner end of the push rod gradually approaches to the overflow valve core and pushes the overflow valve core to compress the overflow spring, and the overflow valve core extends into and blocks the overflow hole under the elastic action of the overflow spring. At this moment, the oil passing hole and the overflow hole are blocked, and the oil pressure on one side of the piston body can be gradually increased, so that the piston body is assisted to be pushed to move. When the oil pressure on one side of the piston body is too high, the oil pressure acts on the overflow valve core, the overflow valve core is pushed to compress the overflow spring and is separated from the overflow hole, oil can be discharged through the overflow hole, the pressure relief of the hydraulic power cylinder is realized, and the stability of the oil pressure on the oil inlet side of the piston body is kept.

In the working process, when the pedal is not stepped, the push rod does not act, the overflow valve core does not compress the overflow spring, so that the compression amount of the overflow spring is greatly reduced, even the overflow spring is not compressed, namely the elasticity of the overflow spring is far smaller than the pressure relief critical value; when the pedal is stepped on, the overflow valve core is stressed to compress the overflow spring, so that the elastic force of the overflow spring reaches a pressure relief critical value. The overflow spring is in a state of being compressed by a large margin only when the push rod works, and is in a loose state when the push rod does not work, so that the working time of the overflow spring which is compressed continuously is reduced, the use stability and reliability of the overflow spring are improved, the replacement frequency of the overflow spring is reduced, and the maintenance and replacement cost is reduced.

In the hydraulic power cylinder with the overflow structure, the first sealing part is annular, the second sealing part comprises a conical sealing surface located on the outer side of the inner end of the push rod, and the aperture of the first sealing part is larger than the diameter of the small end of the second sealing part and smaller than the diameter of the large end of the second sealing part. The conical sealing surface can provide guidance for the inward movement of the push rod and adjust the position of the inner end of the push rod so that the first sealing part and the second sealing part can better abut against the seal, the accuracy that the positions of the push rod and the overflow valve core are opposite to each other to improve the accuracy that the overflow valve core blocks a pressure relief channel is guaranteed, the situation that the push rod and the overflow valve core are staggered to excessively compress the overflow spring can be avoided, and the use stability and reliability of the overflow spring are guaranteed.

As another aspect, in the hydraulic cylinder with an overflow structure, the first sealing portion is annular, the second sealing portion includes a step surface located outside the inner end of the push rod, and the end of the inner end of the push rod can extend into the first sealing portion. The push rod can also be sealed by adopting a step type structure, the small end extends into the first sealing part to be guided and supported, and the large end is used for abutting against the first sealing part for sealing.

In the hydraulic power cylinder with the overflow structure, a liquid inlet hole and a liquid outlet hole are further formed in the hole wall of the oil passing hole, the liquid inlet hole can be communicated with the oil passing hole and the oil inlet, the liquid outlet hole can be communicated with the oil passing hole and the oil return opening, the overflow valve core and the overflow spring are located on one side of the liquid outlet hole, and the liquid inlet hole is located on the other side of the liquid outlet hole. The overflow valve core, the overflow spring and the liquid inlet hole are respectively positioned at two sides of the liquid outlet hole, so that oil can not pass through the overflow valve core when entering the oil through hole from the liquid inlet hole and flowing out of the oil through hole from the liquid outlet hole, the impact and influence on the overflow valve core and the overflow spring are reduced, and the stability and reliability of the overflow spring during subsequent use are ensured.

In the hydraulic cylinder with the overflow structure, the side wall of the oil passing hole is provided with a protruding annular retaining shoulder, the liquid outlet hole is formed in the retaining shoulder, the outer side of the overflow valve core is provided with a protruding annular shoulder, and the protruding shoulder can abut against the retaining shoulder. Through the setting of keeping off shoulder and convex shoulder for overflow valve core can support steadily and lean on keeping off the shoulder, avoids overflow valve core self or take place to rock at fluid flow in-process, can avoid producing the noise, can reduce the influence to overflow spring again, has guaranteed stability and reliability when overflow spring uses.

In the hydraulic power cylinder with the overflow structure, the overflow hole comprises a first pressure release hole and a second pressure release hole, the first pressure release hole penetrates through the side wall of the inner end of the push rod along the radial direction, the second pressure release hole is formed along the axial direction, one end of the second pressure release hole is communicated with the middle of the first pressure release hole, the other end of the second pressure release hole is formed in the end face of the inner end of the push rod, and one end, facing the push rod, of the overflow valve core is opposite to the two positions of the pressure release holes. The arrangement structure of the first pressure relief hole and the second pressure relief hole is convenient to arrange, the oil throughput of the first pressure relief hole can be increased, and the pressure relief process is accelerated.

In the hydraulic power cylinder with the overflow structure, a conical guide surface is arranged on the outer side of one end, facing the push rod, of the overflow valve core, and the end part of the overflow valve core can partially extend into the port of the overflow hole and enables the guide surface to be abutted against and sealed with the inner wall of the overflow hole. The guide surface on the overflow valve core provides guide for the overflow valve core to extend into the port of the overflow hole to realize sealing, sealing accuracy is improved, and the accuracy of the overflow hole sealing by the overflow valve core can be further improved by matching the conical sealing surface at the inner end of the push rod.

As another aspect, in the hydraulic cylinder with the overflow structure described above, the overflow valve core includes a ball core support and a steel ball, the ball core support has a concave spherical recess, and the steel ball is partially disposed in the recess. The steel ball type overflow valve core can be well embedded into the overflow hole and realizes circumferential sealing.

In foretell hydraulic power cylinder of taking overflow structure, the push rod includes sealed case, expanding spring and all is shaft-like pole one and pole two, stretch out the outer end of pole one the cylinder body, the inner cover of pole one is established the outer end outside of pole two, expanding spring set up in between pole one and the pole two, and pole one and pole two can remove in opposite directions and compress expanding spring, sealed case links firmly the inner of pole two and above-mentioned sealing part two and overflow hole all are located on the sealed case.

As another aspect, in the hydraulic cylinder with the overflow structure, the push rod is of an integral structure.

Compared with the prior art, the overflow spring in the hydraulic power cylinder with the overflow structure is only in a state of being greatly compressed when the push rod works, and is in a loose state when the push rod does not work, so that the working time of the overflow spring being continuously compressed is reduced, the use stability and reliability of the overflow spring are improved, the replacement frequency of the overflow spring is reduced, and the maintenance and replacement cost is reduced.

Drawings

Fig. 1 is a schematic sectional view of the hydraulic cylinder with the overflow structure.

Fig. 2 is a partially enlarged view of the hydraulic cylinder with the relief structure.

FIG. 3 is an enlarged view of the push rod of the hydraulic cylinder with overflow structure shown in the figure after moving inward.

In the figure, 1, a cylinder body; 11. an oil inlet cavity; 12. an oil return cavity; 13. an oil inlet; 14. an oil return port; 2. a piston body; 21. an oil passing hole; 21a, a liquid inlet hole; 21b, liquid outlet holes; 23. a shoulder block; 23a, a first sealing part; 3. a push rod; 31. an overflow aperture; 31a and a first pressure relief hole; 31b and a second pressure relief hole; 32. a sealing surface; 33. a first rod; 34. a second rod; 35. a tension spring; 36. sealing the valve core; 4. an overflow valve core; 41. a shoulder is formed; 42. a guide surface; 5. and an overflow spring.

Detailed Description

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

As shown in fig. 1 and 2, the hydraulic cylinder with the overflow structure includes a cylinder body 1 having an oil inlet 13 and an oil return port 14, a piston body 2 disposed in the cylinder body 1, and a push rod 3, wherein the piston body 2 separates an oil inlet cavity 11 communicated with the oil inlet 13 and an oil return cavity communicated with the oil return port 14 in the cylinder body 1, and the piston body 2 has an oil passing hole 21 capable of communicating the oil inlet cavity 11 with the oil return cavity 12. The inner end of the push rod 3 extends into the cylinder body 1, the outer end of the push rod extends out of the cylinder body 1, and when the push rod 3 moves towards the cylinder body 1 along the axial direction, the inner end of the push rod 3 can block the oil passing hole 21. In this embodiment, the piston body 2 includes a piston body, a rod-shaped piston rod and a locking cap, the piston rod is inserted into the body and fixed to the body, the oil passing hole 21 is an inner hole axially formed in the piston rod, the inner end of the push rod 3 extends into the piston rod from the outer end of the piston rod, the locking cap is screwed to the inner end of the piston rod, and a seal is formed between the locking cap and the inner end of the piston rod.

An overflow valve core 4 and an overflow spring 5 are arranged in the oil passing hole 21, the overflow valve core 4 is positioned between the overflow spring 5 and the push rod 3, and the overflow valve core 4 is opposite to the inner end of the push rod 3. The hole wall of the oil passing hole 21 is provided with a liquid inlet hole 21a communicated with the oil inlet cavity 11 and a liquid outlet hole 21b communicated with the oil return cavity 12 in a penetrating way, the overflow valve core 4 and the overflow spring 5 are positioned at one side of the liquid outlet hole 21b, and the liquid inlet hole 21a is positioned at the other side of the liquid outlet hole 21 b.

Specifically, a protruding annular retaining shoulder 23 is arranged on the side wall of the oil passing hole 21, the liquid outlet hole 21b is radially arranged in the middle of the retaining shoulder 23, the relief valve element 4 and the push rod 3 are respectively positioned on two sides of the retaining shoulder 23, and one end of the retaining shoulder 23 facing the push rod 3 is a first sealing part 23 a. The outer side of the overflow valve core 4 has a protruding annular shoulder 41, and the shoulder 41 can abut against the end face of one end of the stop shoulder 23. One end part of the overflow valve core 4 facing the push rod 3 penetrates through the retaining shoulder 23, and a gap through which oil can pass is formed between the outer wall of the overflow valve core 4 and the inner wall of the retaining shoulder 23. In the embodiment, one end of the relief valve core 4 facing the relief spring 5 is provided with a cylindrical guide part, the relief spring 5 is sleeved outside the guide part, one end of the relief spring 5 abuts against the piston body 2, and the other end abuts against the shoulder 41; the overflow valve element 4 is cylindrical at its end facing the tappet 3 and has a conical guide surface 42 on its end outside. Of course, the relief valve element 4 may be replaced as needed, for example, the relief valve element 4 includes a ball element holder and a steel ball, the ball element holder has a concave spherical recess, and the steel ball is partially disposed in the recess.

The inner end of the push rod 3 is also provided with an overflow hole 31 which can enable the oil inlet cavity 11 to be communicated with the oil return cavity 12, one port of the overflow hole 31 is opposite to the overflow valve core 4, when the push rod 3 moves towards the cylinder body 1, the overflow valve core 4 can be close to and pushed to compress the overflow spring 5, and the overflow valve core 4 can abut against the port of the overflow hole 31 and block the overflow hole 31.

A gap is formed between the outer wall of the push rod 3 and the side wall of the oil passing hole 21, the overflow hole 31 comprises a first pressure relief hole 31a which penetrates through the side wall of the inner end of the push rod 3 along the radial direction and a second pressure relief hole 31b which is formed along the axial direction, one end of the second pressure relief hole 31b is communicated with the middle part of the first pressure relief hole 31a, the other end of the second pressure relief hole 31b is formed in the end face of the inner end of the push rod 3, one end, facing the push rod 3, of the overflow valve core 4 is opposite to the second pressure relief hole 31b in position and can partially extend into the second pressure relief hole 31b, and the guide surface 42 is abutted against the inner wall. The outer side of the inner end of the push rod 3 also has a conical sealing surface 32 as a second sealing part, and the sealing surface 32 can abut against the first sealing part 23a of the stop shoulder 23 and form a seal. In this embodiment, the push rod 3 includes a sealing valve core 36, a telescopic spring 35, and a first rod 33 and a second rod 34 both in rod shape, an outer end of the first rod 33 extends out of the cylinder 1, an inner end of the first rod 33 is sleeved outside an outer end of the second rod 34, the telescopic spring 35 is disposed between the first rod 33 and the second rod 34, the first rod 33 and the second rod 34 can move in opposite directions and compress the telescopic spring 35, the sealing valve core 36 is fixedly connected to an inner end of the second rod 34, and the sealing surface 32 and the overflow hole 31 are both located on the sealing valve core 36. If necessary, the push rod 3 can also be designed as a one-piece construction.

After the hydraulic power cylinder with the overflow structure is installed, when an operator does not step on a pedal, the push rod 3 moves outwards under the elastic action of the reset spring, the overflow valve core 4 is separated from the push rod 3, the overflow valve core 4 does not compress the overflow spring 5 under the action of the push rod 3, the compression amount of the overflow spring 5 is small or even not compressed, and the overflow valve core 4 is blocked at one end of the oil passing hole 21 by the blocking shoulder 23. Oil enters the oil inlet cavity 11 from the oil inlet 13 of the cylinder body 1, flows out to the oil return cavity 12 through the liquid inlet hole 21a, the oil passing hole 21 and the liquid outlet hole 21b, and returns to the oil tank from the oil return port 14.

As shown in FIG. 3, when the operator steps on the pedal, the push rod 3 is pushed to move axially into the cylinder 1 until the sealing surface 32 of the inner end of the push rod 3 abuts against the first sealing portion 23a of the stop shoulder 23 to form a seal therebetween, and the oil passing hole 21 is blocked. In the moving process of the push rod 3, the inner end of the push rod 3 gradually approaches to the overflow valve core 4, the end part of the overflow valve core 4 also gradually extends into the second pressure relief hole 31b and is abutted against the inner wall of the second pressure relief hole 31b through the guide surface 42 to form sealing, the push rod 3 is continuously pushed inwards to abut against the stop shoulder 23, at the moment, the overflow valve core 4 is compressed by the acting force applied by the inner end of the push rod 3 to move inwards, the overflow valve core 4 is abutted against the second pressure relief hole 31b of the push rod 3 tightly by means of the elastic force of the overflow spring 5, and sealing and blocking of the overflow hole 31 are achieved. At this time, both the oil passing hole 21 and the spill hole 31 are blocked, and the oil pressure at the side of the oil inlet chamber 11 is gradually increased, thereby assisting in moving the piston body 2.

When the oil pressure on one side of the oil inlet cavity 11 is too high, the oil pressure acts on the overflow valve core 4 through the second pressure relief hole 31b to push the overflow valve core 4 to be separated from the push rod 3 and compress the overflow spring 5, and the oil on one side of the oil inlet cavity 11 can be discharged to the oil return cavity 12 through the overflow hole 31, the oil passing hole 21 and the liquid outlet hole 21b, so that the pressure relief on one side of the oil inlet cavity 11 of the hydraulic power cylinder is realized, and the oil pressure on one side of the oil inlet cavity 11 is kept stable.

Besides the above scheme, the second sealing part at the inner end of the push rod 3 can also comprise a step surface positioned on the outer side of the inner end of the push rod 3, namely, the push rod 3 is of a step-shaped structure with a small inner end and a large outer end, the diameter of the inner end of the push rod 3 is smaller than the bore diameter of the inner bore of the retaining shoulder 23, the outer diameter of the step surface of the push rod 3 is larger than the bore diameter of the inner bore of the retaining shoulder 23, and sealing is realized by abutting the step surface and the.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Claims

1. A hydraulic power cylinder with an overflow structure comprises a cylinder body (1) with an oil inlet (13) and an oil return opening (14), a push rod (3) and a piston body (2) arranged in the cylinder body (1), wherein the inner end of the push rod (3) extends into the cylinder body (1), an oil passing hole (21) capable of communicating the oil inlet (13) with the oil return opening (14) is formed in the piston body (2), the hydraulic power cylinder is characterized in that an overflow valve core (4) and an overflow spring (5) which are separated from the push rod (3) are arranged in the oil passing hole (21), a first sealing part (23a) is arranged on the hole wall of the oil passing hole (21), a second sealing part is arranged at the inner end of the push rod (3) and can abut against the first sealing part (23a), an overflow hole (31) is further formed in the inner end of the push rod (3), and the overflow valve core (4) is arranged at the inner end of the push rod (3), the push rod (3) can approach the overflow valve core (4) and push the overflow valve core (4) to compress the overflow spring (5), and the overflow valve core (4) can block the overflow hole (31).

2. The hydraulic cylinder with the overflow structure according to claim 1, wherein the first sealing portion (23a) is annular, the second sealing portion includes a sealing surface (32) which is conical outside the inner end of the push rod (3), and the first sealing portion (23a) has a hole diameter which is larger than the small end diameter of the second sealing portion and smaller than the large end diameter of the second sealing portion.

3. The hydraulic cylinder with the overflow structure according to claim 1, wherein the first sealing portion (23a) is annular, and the second sealing portion includes a step surface located outside the inner end of the push rod (3), and the end of the inner end of the push rod (3) can extend into the first sealing portion (23 a).

4. The hydraulic cylinder with the overflow structure according to claim 1, 2 or 3, wherein a liquid inlet hole (21a) and a liquid outlet hole (21b) are further formed in a wall of the oil passing hole (21), the liquid inlet hole (21a) can communicate with the oil passing hole (21) and the oil inlet (13), the liquid outlet hole (21b) can communicate with the oil passing hole (21) and the oil return port (14), the overflow valve core (4) and the overflow spring (5) are located on one side of the liquid outlet hole (21b), and the liquid inlet hole (21a) is located on the other side of the liquid outlet hole (21 b).

5. The hydraulic cylinder with the overflow structure as claimed in claim 4, wherein the oil passing hole (21) has a protruding annular shoulder (23) on a side wall thereof, the liquid outlet hole (21b) is opened on the shoulder (23), and the overflow valve spool (4) has a protruding annular shoulder (41) on an outer side thereof, wherein the shoulder (41) can abut against the shoulder (23).

6. The hydraulic cylinder with the overflow structure according to claim 1, 2 or 3, wherein the overflow hole (31) includes a first pressure release hole (31a) radially penetrating through the inner end side wall of the push rod (3) and a second pressure release hole (31b) axially formed therethrough, one end of the second pressure release hole (31b) is communicated with the middle of the first pressure release hole (31a), the other end of the second pressure release hole (31b) is formed in an end surface of the inner end of the push rod (3), and one end of the overflow valve core (4) facing the push rod (3) is opposite to the second pressure release hole (31 b).

7. The hydraulic cylinder with the overflow structure as claimed in claim 1, 2 or 3, characterized in that the overflow valve core (4) has a conical guide surface (42) on the outer side of one end facing the push rod (3), and the end of the overflow valve core (4) can partially extend into the port of the overflow hole (31) and make the guide surface (42) and the inner wall of the overflow hole (31) abut against and seal.

8. The hydraulic power cylinder with the overflow structure as claimed in claim 1, 2 or 3, wherein the overflow valve core (4) comprises a ball core support and a steel ball, the ball core support is provided with a concave spherical concave hole, and the steel ball is partially arranged in the concave hole.

9. The hydraulic power cylinder with the overflow structure as claimed in claim 1, 2 or 3, wherein the push rod (3) comprises a sealing valve core (36), a telescopic spring (35) and a rod I (33) and a rod II (34) which are rod-shaped, the outer end of the rod I (33) extends out of the cylinder body (1), the inner end of the rod I (33) is sleeved outside the outer end of the rod II (34), the telescopic spring (35) is arranged between the rod I (33) and the rod II (34), the rod I (33) and the rod II (34) can move towards each other and compress the telescopic spring (35), the sealing valve core (36) is fixedly connected to the inner end of the rod II (34), and the sealing portion II and the overflow hole (31) are both located on the sealing valve core (36).

10. The hydraulic cylinder with the overflow structure of claim 1, 2 or 3, wherein the push rod (3) is a one-piece structure.