CN111828429B

CN111828429B - Oil hydraulic cylinder with buffer rear cover

Info

Publication number: CN111828429B
Application number: CN201910379996.4A
Authority: CN
Inventors: 朱冏昇
Original assignee: Ashun Fluid Power Co ltd
Current assignee: Ashun Fluid Power Co ltd
Priority date: 2019-04-15
Filing date: 2019-05-08
Publication date: 2023-01-06
Anticipated expiration: 2039-05-08
Also published as: TW202040014A; CN111828429A; TWI697626B

Abstract

The invention provides an oil hydraulic cylinder with a buffering rear cover, which comprises a cylinder body and a rear cylinder cover, wherein the rear cylinder cover is provided with a fixed seat, a buffer tube and an elastic component. The fixing seat is fixed in a rear buffer groove of the rear cylinder cover and is provided with a through hole and a small flow passage. The buffer tube passes through the through hole of the fixed seat. The elastic component is arranged on the rear cylinder cover and used for accumulating an elastic force when the buffer tube moves backwards and pushing the buffer tube to move forwards by utilizing the elastic force.

Description

Oil hydraulic cylinder with buffer rear cover

Technical Field

The present invention relates to a hydraulic cylinder, and more particularly, to a hydraulic cylinder with a buffering rear cover.

Background

Fig. 10 and 11 show a conventional structure of a cushion type hydraulic cylinder, which includes a cylinder body 11 made of metal, a front cylinder head 12, a rear cylinder head 13, a piston 14, a piston rod 15, and a cushion bush 16 made of rubber. The front cylinder head 12 has a buffer groove 121 and a front oil inlet and outlet hole 122 communicating with each other, and the rear cylinder head 13 has a buffer groove 131 and a rear oil inlet and outlet hole 132 communicating with each other.

As shown in fig. 10, during a forward stroke, oil from an oil tank (not shown) enters from the rear oil inlet/outlet hole 132 and pushes the piston 14 to advance from a point adjacent to the rear cylinder head 13 toward the front cylinder head 12, and the advance of the piston 14 pushes the oil in the cylinder 11 to be discharged from the front oil inlet/outlet hole 122 and to flow back to the oil tank. When the piston 14 is about to reach an end point adjacent to the front cylinder head 12, the buffer bush 16 is inserted into the buffer groove 121 (as shown by a chain line of two dots in the figure) to decrease the discharge flow rate of the oil, so that the advancing speed of the piston 14 is decreased, and the piston 14 is prevented from violently impacting the front cylinder head 12 at the end point, thereby achieving a buffer effect. Fig. 11 shows that the piston 14 has reached this end and the cushion bush 16 has been inserted into the cushion groove 121.

As shown in fig. 11, in a backward stroke, oil from the oil tank enters from the forward oil inlet and outlet hole 122 and pushes the piston 14 backward from the end adjacent to the front cylinder head 12 toward the rear cylinder head 13, and the backward movement of the piston 14 pushes the oil in the cylinder 11 to be discharged from the backward oil inlet and outlet hole 132 and to flow back to the oil tank. When the piston 14 is about to reach the starting point adjacent to the rear cylinder head 13, a rear rod section 152 of the piston rod 15 is inserted into the buffer groove 121 (as shown by a chain line with two points in the figure) to decrease the discharge flow rate of the oil, so that the retreating speed of the piston 14 is decreased accordingly, and the piston 14 is prevented from violently impacting the rear cylinder head 13 at the end point, thereby achieving the buffer effect. Fig. 10 shows that the piston 14 has reached this starting point and the rear rod section 152 of the piston rod 15 has been inserted into the buffer groove 131.

In order to align the rear rod section 152 of the piston rod 15 with the buffer groove 131, the rear rod section 152 must be precisely cut in order to prevent the rear rod section 152 from being hard-pushed into the buffer groove 131 in a skewed posture and even colliding with the vicinity of an inlet 131A of the buffer groove 131 due to excessive skew, and the buffer groove 131 must be precisely cut so that they have good concentricity after assembly, so that the rear rod section 152 can be aligned with the buffer groove 131 as desired. However, the precision of the precision cutting is difficult to control accurately, and it is not ensured that the rear rod section 152 of each piston rod 15 is concentric and circular without any error, and the buffer groove 131 of the rear cylinder cover 13 has the same problem, and these errors will cause the rear rod section 152 to be prone to the skew, and cause the rear rod section 152 to be hard-pushed into the buffer groove 131 or collide with the buffer groove 131.

Similar problems occur in the cushion bushing 16, that is, in order to align the cushion bushing 16 with the cushion groove 121, prevent the cushion bushing 16 from being hard-pressed into the cushion groove 121 in a skewed posture, and even collide with the vicinity of an inlet 121A of the cushion groove 121 due to excessive skew, a rod section 151 of the piston rod 15 corresponding to the cushion bushing 16 must be precisely machined, and the cushion groove 121 must also be precisely machined so that they have good concentricity after assembly, so that the cushion bushing 16 fitted over the rod section 151 can be aligned with the cushion groove 121 as desired. However, as described above, the precision of the precision cutting process is difficult to control accurately, and it is not possible to ensure that the rod segment 151 of each piston rod 15 is concentric and perfect, and there is no error in the damping groove 121 of the front cylinder head 12, which will cause the damping bush 16 to be prone to the skew, and the damping bush 16 to be hard-pushed into the damping groove 131 or collide with the damping groove 131.

Disclosure of Invention

In view of the above problems of the piston rod and the rear cylinder head of the conventional cushion type hydraulic cylinder, the present invention provides a hydraulic cylinder with a cushion rear cover. In view of the above problems of the piston rod and the front cylinder head of the conventional cushion type hydraulic cylinder, the present invention further provides a floating type cushion bushing instead of the conventional cushion bushing, which is described in detail below.

The oil hydraulic cylinder with a buffer rear cover comprises: a cylinder body; a front cylinder cover arranged at the front end of the cylinder body and provided with a shaft hole and a front oil inlet and outlet hole; a piston movably disposed in the cylinder; the piston rod is connected with the piston and penetrates through the shaft hole of the front cylinder cover; the piston rod is provided with a rod section and a front rod section, the front rod section extends from the rod section to the front cylinder cover, and the front rod section is thicker than the rod section, so that a step is formed at the junction of the front rod section and the rod section; a rear cylinder cover, which is arranged at the rear end of the cylinder body and is provided with a flow passage, a rear oil inlet and outlet hole and a rear buffer groove which are communicated with each other, wherein the inner diameter of the rear buffer groove is smaller than that of the cylinder body, the rear cylinder cover is provided with a ring groove facing to the front end surface of the piston, the ring groove surrounds a notch of the rear buffer groove, the diameter of the ring groove is larger than the maximum inner diameter of the rear buffer groove, and the flow passage is communicated with the ring groove and the rear oil inlet and outlet hole; the fixed seat is fixed in the rear buffer groove of the rear cylinder cover and is provided with a through hole which penetrates through the rear cylinder cover from front to back, and the fixed seat is also provided with a small flow passage which communicates the interior of the cylinder body with the rear buffer groove; a buffer tube which can move forwards and backwards and passes through the through hole of the fixed seat, a front end of the buffer tube facing the piston and a rear end of the buffer tube are directly communicated and are respectively positioned in the cylinder body and the rear buffer groove, wherein the inner diameter of the buffer tube is larger than the small flow passage; and an elastic component, which is arranged on the rear cylinder cover and is used for accumulating an elastic force when the buffer tube moves backwards and pushing the buffer tube to move forwards by utilizing the elastic force; the buffer bush is sleeved on a rod section of the piston rod and positioned between the piston and the front cylinder cover, and can be plugged into the front buffer groove along with the advance of the piston rod, an inner wall of the buffer bush surrounds the rod section, the step of the piston rod is blocked in front of the buffer bush, a front gap is formed between the front end of the buffer bush and the step, and a rear gap is formed between the rear end of the buffer bush and the step; a support assembly disposed on the rod section and supporting the inner wall of the cushion collar to form the gap; the rod section of the piston rod is provided with a ring groove, the support component is an annular body sleeved in the ring groove, the annular body is partially embedded in the ring groove, and the annular body is partially positioned outside the ring groove; the inner wall of the buffer lining is supported by the part of the annular body outside the ring groove, so that a first gap and a second gap which are bound by the annular body are formed between the inner wall of the buffer lining and the rod section, and the buffer lining can swing back and forth by taking the annular body as a fulcrum.

In an embodiment of the invention, the small flow channel of the fixing base is a gap formed between a flat wall of the fixing base and an inner wall of the rear buffer slot.

In one embodiment, the oil cylinder of the present invention includes a limiting member disposed at the rear end of the buffer tube for preventing the buffer tube from separating from the fixing seat.

In an embodiment of the present invention, the supporting member has elasticity and is pressed by the buffer bushing.

In one embodiment, the support assembly is located at or near a middle position of the cushion sleeve in an axial direction.

In one embodiment, the first gap and the second gap are between 0.1mm and 0.3 mm.

Compared with the prior art, the invention does not need to fill the rear rod section of the piston rod into the rear buffer groove to form the buffer function in the prior art, so the problem that the rear rod section is hard extruded into the buffer groove or collides with the buffer groove in the prior art does not exist, and the rear rod and the rear buffer groove of the piston rod do not need to be precisely processed, thereby achieving the effects of saving the manufacturing cost and improving the production speed.

Furthermore, in other embodiments, the damping bush of the present invention capable of proper yaw motion can be aligned, so that a certain degree of processing error is allowed to exist in the damping grooves of the piston rod and the front cylinder head, and the problem that the conventional damping bush is hard squeezed into the damping groove or collides with the damping groove can be solved. In addition, because the labor time is not needed to eliminate or reduce the processing errors, the manufacturing cost can be saved and the production speed can be improved.

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case.

FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention.

Fig. 2 is a partial exploded view of the preferred embodiment at the rear cylinder head 23.

Fig. 3 to 5 are enlarged partial views of the rear cylinder head 23 of the preferred embodiment to illustrate the operation of the buffer tube 231A on the rear cylinder head 23.

Fig. 6 is a partial exploded view of the preferred embodiment at the cushion bushing 26.

Fig. 7 is an enlarged view of a portion of the preferred embodiment at the cushion bushing 26.

Fig. 8 and 9 are schematic diagrams illustrating the deflection of the buffer bush 26 according to the preferred embodiment.

Fig. 10 and 11 are sectional views of a conventional cushion type hydraulic cylinder.

Description of reference numerals:

11. 21 cylinder body

12. 22 front cylinder cover

121. 131 buffer groove

121A inlet

122. Advancing oil outlet

13. 23 rear cylinder cover

132. Rear oil outlet hole

14. 24 piston

15. 25 piston rod

151. 251 pole segment

16. 26 buffer bush

221. Shaft hole

222. Front buffer slot

223. Advancing oil outlet

232. Rear buffer slot

231. Rear buffer assembly

231A buffer tube

231B elastic component

231C fixing seat

231D, 231E C type elastic retaining ring

232. Buffer tank

233. Rear oil outlet hole

252. Ring groove

253. Front rod segment

254. Step

255. Rear rod segment

27. Support assembly

28. Front buffer adjusting component

29. Rear buffer adjusting component

281. 291 flow passage

G1 Gap

G2 Front clearance

G3 Rear clearance

W flat wall

H through hole

C small runner

Detailed Description

The details of the present invention can be more clearly understood in conjunction with the accompanying drawings and the description of the embodiments of the present invention. However, the specific embodiments of the present invention described herein are for the purpose of illustration only and are not to be construed as limiting the invention in any way. Any possible variations based on the present invention may be conceived by the skilled person in the light of the teachings of the present invention, and these should be considered to fall within the scope of the present invention.

Fig. 1 shows a preferred embodiment of the hydraulic cylinder of the present invention, which includes a cylinder body 21, a front cylinder head 22, a rear cylinder head 23, a piston 24, a piston rod 25, and a damping member 231. The front cylinder head 22 is disposed at a front end of the cylinder block 21 and has a shaft hole 221 and a front oil inlet/outlet hole 223. The piston 24 is movably disposed in the cylinder 21. The piston rod 25 is connected to the piston 24 and extends to the outside space of the front cylinder head 22 after passing through the shaft hole 221. The rear cylinder head 23 is disposed at a rear end of the cylinder block 21, and has a rear oil inlet/outlet hole 233 and a rear cushion groove 232 communicating with each other. The rear buffer groove 232 communicates with the inside of the cylinder 21 and has an inner diameter smaller than that of the cylinder 21. The rear cushion 231 is disposed on the rear cylinder head 2 so that the rear cylinder head 23 becomes a cushion rear cover, which will be described in detail later.

The hydraulic cylinder of the present invention may or may not have a front cushion design. In the case of the front cushion design, as shown in fig. 1, the hydraulic cylinder of the present invention further includes a cushion bushing 26, and the front cylinder head 22 further includes a front cushion groove 222. The front buffer groove 222 is coaxial with the shaft hole 221 and communicates with the front oil inlet/outlet hole 223. The front buffer tank 222 is also communicated with the inside of the cylinder 21 and has an inner diameter smaller than that of the cylinder 21. The cushion bushing 26 is sleeved on a rod section 251 of the piston rod 25, is located between the piston 24 and the front cylinder head 22, and can be inserted into the front cushion groove 222 along with the advance of the piston 24. The cooperation of the buffer lining 26 and the front buffer slot 222 can decelerate the advancing piston 24 to achieve the buffering purpose, and can further cooperate with a front buffer adjusting component 28 and the corresponding flow passage 281 to adjust the decreasing speed of the advancing piston 24, which is not necessary and belongs to the prior art, and therefore, the details thereof are not repeated.

As shown in fig. 2 and 3, the rear buffer element 231 includes a fixed seat 231C, a buffer tube 231A and an elastic element 231B. The fixing seat 231C is fixed in the rear cushion groove 232 of the rear cylinder head 23, and has a through hole H penetrating in the front-rear direction. The buffer tube 231A is movably inserted through the through hole H of the fixing seat 231C in the front and rear directions, and a front end and a rear end of the buffer tube 231A are directly communicated with each other and respectively located in the cylinder 21 and the rear buffer groove 232. The elastic member 213B is disposed on the rear cylinder head 23, and accumulates an elastic force when the buffer tube 231A moves backward, and pushes the buffer tube 231A to move forward by the elastic force. The fixing seat 231C further has a small flow passage C communicating the inside of the cylinder 21 with the rear buffer groove 232, and the inner diameter of the buffer tube 231A is larger than the small flow passage C.

In this example, the small flow channel C is a gap formed between a flat wall W of the holder 231C and an inner wall of the rear buffer groove 232. In this example, the fixing seat 231C has three flat walls W distributed at equal angles, so that three gaps can be formed as three small flow passages C. However, the small channel C may be a through hole on the fixing seat 231C.

In this embodiment, a compression spring may be used as the elastic element 213B, but not limited thereto.

In this embodiment, a C-shaped elastic retaining ring 231D may be used to limit the fixing seat 231C to be fixed at a position in the rear buffer slot 232 without being separated from the rear buffer slot 232. However, the fixing manner of the fixing seat 231C is not limited to the above, and for example, a fixing plug may be used to fix the fixing seat 231C in the rear buffer slot 232, or the rear cylinder cover 23 and the fixing seat 231C are integrated into a whole, or the fixing seat 231C is welded in the rear buffer slot 232.

Preferably, the above embodiment further comprises a limiting member, such as another C-shaped elastic buckle 231E. The limiting member is disposed at the rear end of the buffer tube 231A for preventing the buffer tube 231A from being separated from the fixing seat 231C. However, besides the other C-shaped elastic retaining ring 231E, it can also be used to prevent the buffer tube 231A from separating from the fixing seat 231C, for example, a blocking pin is inserted through the rear end of the buffer tube 231A, and both ends of the blocking pin protrude transversely from the rear end.

In addition, in this embodiment, a rear rod segment 255 of the piston rod 25 does not protrude from the piston 24 and faces the front end of the buffer tube 231A, but not limited thereto, for example, the rear rod segment 255 may slightly protrude from the piston 24, or the piston 24 covers the rear rod segment 255 so as not to be exposed.

As shown in fig. 3, when the piston 24 is pushed backward, the oil in the cylinder 21 flows through the buffer tube 231A into the rear buffer groove 232, and continues to flow out through the rear oil inlet/outlet hole 233. As shown in fig. 4, when the piston 24 comes to make the rear rod section 255 of the piston rod 25 collide with the front end of the buffer tube 231A, the oil in the cylinder 21 flows through the small flow passage C of the fixing seat 231C into the rear buffer groove 232 and continues to flow out from the rear oil inlet/outlet hole 233, and at this time, the oil flow is greatly reduced, so that the piston 24 starts to decelerate, and the piston 24 is prevented from violently colliding with the rear cylinder head 23, thereby achieving the buffering purpose. As the piston 24 retreats, the buffer tube 231A is pushed by the piston 24 to move backward, and the elastic member 231B is compressed, thereby accumulating the elastic force.

As shown in fig. 5, when the piston 24 is retreated to a final point, the buffer tube 231A is also pushed to the bottom by the piston 24. Once the piston 24 is pushed forward, that is, the oil flowing from the rear oil inlet/outlet hole 233 flows into the cylinder 21 through the small flow passages C of the buffer tube 231A and the fixing seat 231C, respectively, and thus the piston 24 is pushed to move forward, at this time, as the piston 24 moves forward, the buffer tube 231A can move forward by the elastic force accumulated by the elastic element 231B until moving back to the original position.

As can be seen from the above description, the present invention moves the rear cushion design to the rear cylinder cover 23, and there is no need to insert the rear rod section of the piston rod into the rear cushion groove to form the cushion function as in the prior art, so there is no problem that the rear rod section is hard inserted into the cushion groove or collides with the cushion groove in the prior art, and it is needless to say that the rear rod and the rear cushion groove of the piston rod are not required to be precisely machined, so that the effects of saving the manufacturing cost and increasing the production speed can be achieved.

In this embodiment, a rear cushion adjustment assembly 29 and its corresponding flow passage 291 may be further used to adjust the decreasing speed of the piston 24 when it retreats, which is not necessary and is not described in detail in the prior art. In one embodiment, a front end face 230 of the rear cylinder head 23 facing the piston 24 has a ring groove 230A, the ring groove 230A surrounds a notch 232A of the rear cushion groove 232, the diameter of the ring groove 230A is larger than the maximum inner diameter of the rear cushion groove 232, the flow passage 291 is disposed in the rear cylinder head 23, and the flow passage 291 further connects the ring groove 230A with the rear oil inlet/outlet hole 233. The ring groove 230A forms a space between the piston 24 and the rear cylinder head 23, and when the piston 24 retreats to the end of the stroke as shown in fig. 5, some oil is still stored between the piston 24 and the rear cylinder head 23, and when the oil is injected into the cylinder body from the rear oil inlet/outlet hole 233, a part of the oil can be simultaneously injected into the ring groove 230A through the flow passage 291, and pushes the piston 24 together with the oil injected into the buffer tube 231A and the small flow passage C, thereby generating an effect of assisting in pushing away the piston 24.

The cushion bushing 26 of the hydraulic cylinder of the present invention can be a conventional cushion bushing, and can also be the one shown in the figures, that is, as shown in fig. 6 and 7, an inner wall 261 of the cushion bushing 26 surrounds the rod segment 251, and a gap G1 is formed between the inner wall 261 and the rod segment 251. The support member 27 is disposed on the rod segment 251 and supports the inner wall 261 of the cushion bushing 26, such that the gap G1 is formed between the cushion bushing 26 and the rod segment 251.

Since the cushion bushing 26 does not entirely abut against the piston rod 25, but is supported by the piston rod 25 with the gap G1 therebetween and the support member 27, the cushion bushing 26 is floatingly disposed on the piston rod 25, so that the cushion bushing 26 has a moderate yawing capability, as shown in fig. 8 and 9.

In a forward stroke in which the piston 24 is pushed to advance toward the front cylinder head 22, since the cushion bushing 26 has a moderate deflection capability, even if the cushion bushing 26 is not completely aligned with the cushion groove 222 due to machining errors of the rod section 161 and/or the front cushion groove 222, as long as a front end of the cushion bushing 26 contacts any inner wall of the front cushion groove 222, the cushion bushing 26 is aligned, so as to avoid or reduce the probability that the cushion bushing 26 hard impacts the front cushion groove 222 or impacts the front cushion groove 222. In other words, the cushion bushing 26 allows a certain degree of machining error and/or other error between the piston rod 25 and the front cushion groove 222, because the misalignment of the cushion bushing 26 with the front cushion groove 222 caused by these errors can be effectively improved by the feature that the cushion bushing 26 can be aligned.

The supporting member 27 is mainly present for forming the gap G1, and its specific form is not limited, so long as it can achieve the above-mentioned purpose.

In one embodiment, the support member 27 is resilient and is slightly deformed by the cushion bushing 26, as shown in FIG. 7, to provide the cushion bushing 26 with a moderate degree of resilient deflection.

As shown in fig. 6 and 7, the support member 27 is preferably an annular body, such as an O-ring made of rubber, but not limited thereto, for example, the support member 27 may include a plurality of individual spaced-apart surrounding rod segments 251, each of which may be circular, conical or other shape. In addition, the rod segment 251 of the piston rod 25 preferably has a circumferential groove 252, and the annular body is partially embedded in the circumferential groove 252 and partially located outside the circumferential groove 252. The groove 252 is used to fix the support member 27 so that the support member 27 does not move arbitrarily. In one embodiment, the ring groove 252 may not be provided.

As shown in fig. 6 and 7, the piston rod 25 has a front rod segment 253, and the front rod segment 253 extends from the rod segment 251 toward the front cylinder head 22. Wherein the front segment 253 is thicker than the segment 251 such that the front segment 253 and the segment 251 interface to form a step 254. The step 254 stops in front of the cushion bushing 26. A front gap G2 is provided between a front end of the cushion bushing 26 and the step 254. A rear gap G3 is provided between a rear end of the cushion bushing 26 and the piston 24. However, in one embodiment, the outer diameters of the front segment 253 and the segment 251 may be the same, and the step 254 and associated features are absent.

As shown in fig. 7, the supporting component 27 is preferably located at or near a middle position of the cushion bushing 26 in an axial direction, but not limited thereto, such as a forward position or a rearward position.

Preferably, the gap G1 is between 0.1 and 0.3mm, and most preferably about 0.2mm, and the front gap G2 and the rear gap G3 are substantially the same, but not limited thereto.

In the above embodiment, the gap G1 includes a first gap G11 and a second gap G12, the first gap G11 and the second gap G12 are separated by the supporting component 27 without communication, in short, the first gap G11 and the second gap are bound by the supporting component 27. As a result, the entire cushion bushing 26 can be appropriately swung about the support member 27 as a fulcrum, as shown in fig. 4 and 5, in other words, the cushion bushing 26 can be swung back and forth about the support member 27 as a fulcrum, like a seesaw.

As is apparent from the above description of the cushion bush 26, the cushion bush 26 of the present invention has a characteristic of being guided because it has a capability of a moderate yawing motion (i.e., a capability of swinging back and forth with the support member 27 as a fulcrum) by the support member 27 and the gap G1, and this characteristic allows a certain degree of machining error to exist in the cushion groove 222 of the piston rod 25 and the front cylinder head 22, thereby solving the problem that the cushion bush is hard-pushed into the cushion groove or collides with the cushion groove due to these machining errors in the past. In addition, because the machining errors are allowed, the labor time is not needed to eliminate or reduce the machining errors, and the effects of saving the manufacturing cost and improving the production speed are achieved.

The present invention is not limited to the above embodiments, and in particular, various features described in different embodiments can be arbitrarily combined with each other to form other embodiments, and the features are understood to be applicable to any embodiment except the explicitly opposite descriptions, and are not limited to the described embodiments.

Claims

1. An oil hydraulic cylinder with a buffer rear cover is characterized by comprising:

a cylinder body;

the front cylinder cover is arranged at the front end of the cylinder body and is provided with a shaft hole and a front oil inlet and outlet hole; the front cylinder cover is provided with a front buffer groove which is coaxial with the shaft hole and communicated with the front oil inlet and outlet hole, the front buffer groove is communicated with the interior of the cylinder body, and the inner diameter of the front buffer groove is smaller than that of the cylinder body;

a piston movably disposed in the cylinder;

the piston rod is connected with the piston and penetrates through the shaft hole of the front cylinder cover; the piston rod is provided with a rod section and a front rod section, the rod section is provided with an annular groove, the front rod section extends from the rod section to the front cylinder cover, and the front rod section is thicker than the rod section, so that a step is formed at the junction of the front rod section and the rod section;

a rear cylinder cover, which is arranged at the rear end of the cylinder body and is provided with a flow passage, a rear oil inlet and outlet hole and a rear buffer groove which are communicated with each other, wherein the inner diameter of the rear buffer groove is smaller than that of the cylinder body, the rear cylinder cover is provided with a ring groove facing to the front end surface of the piston, the ring groove surrounds a notch of the rear buffer groove, the diameter of the ring groove is larger than the maximum inner diameter of the rear buffer groove, and the flow passage is communicated with the ring groove and the rear oil inlet and outlet hole;

the fixed seat is fixed in the rear buffer groove of the rear cylinder cover and is provided with a through hole which penetrates through the rear cylinder cover and the front cylinder cover and a small flow passage which communicates the interior of the cylinder body with the rear buffer groove;

a buffer tube which can move forwards and backwards and passes through the through hole of the fixed seat, a front end of the buffer tube facing the piston and a rear end of the buffer tube are directly communicated and are respectively positioned in the cylinder body and the rear buffer groove, and the inner diameter of the buffer tube is larger than the small flow passage; and

an elastic component arranged on the rear cylinder cover and used for accumulating an elastic force when the buffer tube moves backwards and pushing the buffer tube to move forwards by utilizing the elastic force;

a buffer bush, which is sleeved on a rod section of the piston rod and positioned between the piston and the front cylinder cover, and can be plugged into the front buffer groove along with the advance of the piston rod, an inner wall of the buffer bush surrounds the rod section, the step of the piston rod is blocked in front of the buffer bush, a front gap is arranged between a front end of the buffer bush and the step, and a rear gap is arranged between a rear end of the buffer bush and the step;

a support assembly disposed on the rod segment and supporting the inner wall of the cushion collar; the supporting component is an annular body sleeved in the ring groove, the annular body is partially embedded in the ring groove, and the annular body is partially positioned outside the ring groove;

the inner wall of the buffer lining is supported by the part of the annular body outside the ring groove, so that a first gap and a second gap which are bounded by the annular body are formed between the inner wall of the buffer lining and the rod section, and the buffer lining can swing back and forth by taking the annular body as a fulcrum.

2. The oil hydraulic cylinder with rear buffering cover as claimed in claim 1, wherein the small flow passage of the fixing seat is a gap formed between a flat wall of the fixing seat and an inner wall of the rear buffering groove.

3. The hydraulic cylinder with a rear buffering cover as claimed in claim 1, wherein the hydraulic cylinder includes a limiting member disposed at the rear end of the buffer tube for preventing the buffer tube from being separated from the fixing seat.

4. The hydraulic cylinder with rear buffering cover as claimed in claim 1, wherein the supporting member is elastic and pressed against the buffering bush.

5. The oil hydraulic cylinder with a rear buffering cover as claimed in claim 1 or 4, wherein the supporting member is located at or near a middle position of the buffering bush in an axial direction.

6. The hydraulic cylinder with a rear buffering cover as claimed in claim 5, wherein the first gap and the second gap are between 0.1mm to 0.3 mm.