CN223165113U - Three-stage pressure regulating relief valve - Google Patents

Abstract

The utility model discloses a three-stage pressure-regulating overflow valve, and belongs to the technical field of overflow valves. The three-stage pressure regulating overflow valve comprises a valve seat, a valve core and an adjusting assembly, wherein a valve port, a liquid inlet and a liquid outlet are respectively arranged on the valve seat, the valve core is in sliding fit in the valve seat, a first cavity communicated with the liquid inlet is formed in the valve core, the adjusting assembly comprises a buffer piston, an adjusting sleeve and a piston sleeve, the adjusting sleeve is arranged in the valve seat, at least part of the piston sleeve is arranged in the adjusting sleeve, the buffer piston is in sliding fit in the adjusting sleeve, a second cavity is formed between the buffer piston and the adjusting sleeve, a third cavity is formed between the buffer piston and the piston sleeve, the second cavity and the third cavity are both communicated with the first cavity, the adjusting sleeve is provided with a first damping hole, one end of the first damping hole is communicated with the second cavity, the other end of the first damping hole can be communicated with the liquid outlet, and the buffer piston can open or close the first damping hole. The three-stage pressure-regulating overflow valve is provided with the first damping hole, so that the established first pressure is lower, and the pressure can be quickly established.

Description

Three-stage pressure-regulating overflow valve

Technical Field

The utility model relates to the technical field of overflow valves, in particular to a three-stage pressure-regulating overflow valve.

Background

At present, two pressure building processes are usually involved in the overflow valve, so that a certain buffering effect can be achieved, however, as shown in fig. 1, the back pressure of the valve core 2 'is easy to be high due to less oil flowing between the inner part of the valve core 2' and the buffer piston 1', so that the built-up first pressure is high, the pressure of the oil in the liquid inlet 3' of the overflow valve needs to be high to instantly open the valve port 4', and the oil pressure on the first wall 11' and the second wall 12 'opposite to each other of the buffer piston 1' is identical, so that the time required for building up the second pressure is long, and the second pressure cannot be built up quickly.

In view of the above, a three-stage pressure-regulating relief valve is needed to solve the above problems.

Disclosure of utility model

The utility model aims to provide a three-stage pressure regulating overflow valve, wherein a first damping hole is formed in an adjusting sleeve, so that the oil pressure in a second cavity on the right side of a buffer piston is smaller than that in a third cavity on the left side of the buffer piston, the established first pressure is lower, the time required for establishing the second pressure and the third pressure is shorter, and the pressure can be established quickly.

To achieve the purpose, the utility model adopts the following technical scheme:

a three-stage pressure regulating relief valve comprising:

the valve seat is provided with a valve port, a liquid inlet and a liquid outlet respectively;

The valve core is in sliding fit in the valve seat so as to enable the valve core to open or close the valve port, and a first cavity communicated with the liquid inlet is arranged in the valve core;

The adjusting assembly comprises a buffer piston, an adjusting sleeve and a piston sleeve, wherein the adjusting sleeve is arranged in the valve seat, at least part of the piston sleeve is arranged in the adjusting sleeve, the buffer piston is in sliding fit with the adjusting sleeve, a second cavity is formed between the buffer piston and the adjusting sleeve, a third cavity is formed between the buffer piston and the piston sleeve, the second cavity and the third cavity are communicated with the first cavity, the adjusting sleeve is provided with a first damping hole, one end of the first damping hole is communicated with the second cavity, the other end of the first damping hole can be communicated with the liquid outlet, and the buffer piston can be opened or blocked by the first damping hole.

As an alternative scheme, the buffer piston is provided with a second damping hole, the second damping hole is respectively communicated with the second cavity and the first cavity, the minimum aperture of the first damping hole is defined as R1, and the minimum aperture of the second damping hole is R2, and R1 is less than or equal to R2.

Alternatively, the minimum aperture R1 of the first damping hole is not greater than 0.2mm.

Alternatively, the adjusting sleeve comprises a first wall, the buffer piston comprises a second wall, the buffer piston comprises a first position and a second position, the buffer piston is located at the first position, the second cavity is formed between the first wall and the second wall, the first damping hole is provided with a first opening in the first wall, and the second wall abuts against the first wall when the buffer piston is located at the second position, so that the second wall seals the first opening.

The piston sleeve comprises a fourth wall, the third wall and the fourth wall can be in butt joint or form the third cavity, a through hole is further formed in the buffer piston, the through hole is communicated with the first cavity and the third cavity, and the minimum aperture of at least part of the second damping hole is smaller than the minimum aperture of the through hole.

Alternatively, the acting area of the oil in the second cavity acting on the second wall is smaller than the acting area of the oil in the third cavity acting on the third wall.

As an alternative, at least two first damping holes are arranged in the inner circumference of the adjusting sleeve.

As an alternative scheme, a third damping hole is arranged in the valve core, the third damping hole is communicated with the liquid inlet and the first cavity, and the aperture of at least part of the third damping hole is smaller than the caliber of the liquid inlet.

As an alternative, the three-stage pressure-regulating relief valve further includes:

The elastic piece is sleeved on the valve core and is positioned in the valve seat, one end of the elastic piece is abutted to the limiting table of the valve core, a fourth cavity is formed between the elastic piece and the valve seat, and the fourth cavity is communicated with the first damping hole and the liquid outlet;

The base is sleeved on the valve core in a sliding mode and is arranged opposite to the limiting table, the other end of the elastic piece is abutted to the base, the buffer piston can push the base along a first direction to compress the elastic piece, the elastic piece pushes the valve core to move along the first direction, and the first direction is the axial direction of the valve core and the direction close to the valve port.

The beneficial effects of the utility model are as follows:

The second cavity is formed between the buffer piston and the adjusting sleeve, the third cavity is formed between the buffer piston and the piston sleeve, the second cavity and the third cavity are respectively communicated with the first cavity in the valve core, meanwhile, the adjusting sleeve is provided with a first damping hole, one end of the first damping hole is communicated with the second cavity, the other end of the first damping hole can be communicated with the liquid outlet, and the buffer piston can open or close the first damping hole; when the first pressure is built up, the oil in the liquid inlet is not available and acts on the buffer piston through the first cavity, so that the oil pressure of the liquid inlet directly acts on the wall surface of the valve core, which is close to the valve port, to push the valve core to instantly open the valve port, and meanwhile, the oil in the liquid inlet can flow into the second cavity and the third cavity respectively through the first cavity when the valve port is instantly opened, and the oil in the second cavity can flow out to the liquid outlet through the first damping hole, so that the oil pressure in the valve core is reduced, the oil pressure in the first cavity is reduced, the back pressure acting on the valve core is reduced, the valve core can be pushed to instantly open the valve port by smaller oil pressure, and the built-up first pressure is lower.

Then, when the second pressure is built, because of the throttling and depressurization effect of the first damping hole, the oil pressure in the first cavity and the second cavity is smaller, and the oil pressure in the third cavity is larger than the oil pressure in the second cavity, so that at the moment, the buffer piston can rapidly move towards the direction close to the valve port, so that the valve core can rapidly move towards the valve port through the push of the buffer piston, the valve core can reseal the valve port, the valve opening pressure at the liquid inlet is increased, the second pressure can be rapidly built, and the time required for building the second pressure is ensured to be shorter.

Then, when the third pressure is built, the buffer piston can not move towards the direction close to the valve port due to the blocking effect of the adjusting sleeve on the buffer piston, meanwhile, the buffer piston can block the first damping hole, so that oil can not flow to the liquid outlet through the first damping hole, at the moment, the pressure of the oil in the first cavity can be quickly increased, the back pressure of the oil in the first cavity acting on the valve core is quickly increased, the valve opening pressure at the liquid inlet is further increased, the third pressure can be quickly built, the time required by the third pressure building is short, three-time adjustment of the oil pressure at the liquid inlet can be realized through the pressure building process, and therefore, the good buffering effect of the three-stage pressure regulating overflow valve can be ensured.

Drawings

FIG. 1 is a cross-sectional view of a prior art relief valve;

FIG. 2 is a cross-sectional view of a three-stage pressure regulating relief valve provided by the present utility model;

Fig. 3 is a partially enlarged schematic structural view at C in fig. 2.

Reference numerals illustrate:

1 '-buffer piston, 11' -first wall, 12 '-second wall, 2' -valve core, 3 '-liquid inlet, 4' -valve port;

1-valve seat, 11-valve port, 12-liquid inlet, 13-liquid outlet and 14-fourth cavity;

2-valve core, 21-third damping hole, 22-first cavity, 23-limit table;

31-a buffer piston, 311-a second wall, 312-a third wall, 313-a second damping hole, 314-a through hole, 315-a second cavity;

32-adjusting sleeve, 321-first damping hole, 322-first wall, 323-fifth wall;

33-piston sleeve 331-fourth wall;

4-elastic piece and 5-base.

Detailed Description

All of the features disclosed in this specification, or all of the steps in a method or process disclosed, may be combined in any combination, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification may be replaced by alternative features serving the same or equivalent purpose, unless expressly stated otherwise. That is, each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise. Like reference numerals refer to like elements throughout the specification.

In order to make the technical problems solved, the technical scheme adopted and the technical effects achieved by the utility model more clear, the technical scheme of the utility model is further described below by a specific embodiment in combination with the attached drawings.

In this embodiment, a tertiary pressure regulating overflow valve is provided, and this tertiary pressure regulating overflow valve can carry out tertiary pressure regulation, and makes the first time pressure of establishing less, can establish secondary pressure and tertiary pressure simultaneously fast, guarantees that secondary pressure and tertiary pressure establish required time is shorter for tertiary pressure regulating overflow valve's cushioning effect is better.

Specifically, as shown in fig. 2 and 3, the three-stage pressure-regulating relief valve comprises a valve seat 1, a valve core 2 and an adjusting assembly, wherein a valve port 11, a liquid inlet 12 and a liquid outlet 13 are respectively arranged on the valve seat 1, the valve core 2 is in sliding fit in the valve seat 1 so that the valve core 2 opens or closes the valve port 11, a first cavity 22 communicated with the liquid inlet 12 is arranged in the valve core 2, the adjusting assembly comprises a buffer piston 31, an adjusting sleeve 32 and a piston sleeve 33, the adjusting sleeve 32 is arranged in the valve seat 1, at least part of the piston sleeve 33 is arranged in the adjusting sleeve 32, the buffer piston 31 is in sliding fit in the adjusting sleeve 32, a second cavity 315 is formed between the buffer piston 31 and the adjusting sleeve 32, a third cavity is formed between the buffer piston 31 and the piston sleeve 33, the second cavity 315 and the third cavity are both communicated with the first cavity 22, a first damping hole 321 is arranged in the adjusting sleeve 32, one end of the first damping hole 321 is communicated with the second cavity 315, the other end of the first damping hole 321 can be communicated with the liquid outlet 13, and the buffer piston 31 can open or block the first damping hole 321.

Compared with the prior art, the three-stage pressure regulating overflow valve in the embodiment is provided with the first damping hole 321 in the regulating sleeve 32, one end of the first damping hole 321 is communicated with the second cavity 315, the other end of the first damping hole 321 can be communicated with the liquid outlet 13, and the buffer piston 31 can open or block the first damping hole 321, so that the first damping hole 321 can provide throttling and depressurization for oil in the first cavity 22, three-time regulation of the oil pressure at the liquid inlet 12 can be realized, and the quick response and the good buffer effect of the three-stage pressure regulating overflow valve can be ensured.

Firstly, when the first pressure is built up, since the oil in the liquid inlet 12 is not yet available and acts on the buffer piston 31 through the first cavity 22, at this time, the oil pressure in the liquid inlet 12 directly acts on the wall surface of the valve core 2, which is close to the valve port 11, so as to push the valve core 2 to move along the second direction to instantly open the valve port 11, and at the same time, the oil in the liquid inlet 12 can flow into the second cavity 315 and the third cavity through the first cavity 22 respectively when instantly opening the valve port 11, and at this time, the oil in the second cavity 315 can flow out to the liquid outlet 13 through the first damping hole 321 so as to flow back to the oil tank through the liquid outlet 13, so that the oil pressure in the second cavity 315 is reduced, the oil pressure in the first cavity 22 is reduced, so that the back pressure acting on the valve core 2 is reduced, the oil pressure in the liquid inlet 12 is smaller, the valve core 2 can be pushed to instantly open the valve port 11, and the smaller pressure at the position of the liquid inlet 12 is opened, so that the built up first pressure is lower. The second direction is the axial direction of the valve core 2 and the direction away from the valve port 11, and the second direction is specifically shown by an arrow B in fig. 2.

Then, when the second pressure is built up, due to the throttling and depressurization effect of the first damping hole 321, the oil pressure in the first cavity 22 and the second cavity 315 is smaller, and the oil pressure in the third cavity is larger than the oil pressure in the second cavity 315, so that at this time, the buffer piston 31 can rapidly move along the first direction, so that the buffer piston 31 pushes the valve core 2 to rapidly move towards the valve port 11, the valve core 2 can re-close the valve port 11, the valve opening pressure at the liquid inlet 12 is increased, the second pressure can be rapidly built up, and the time required for building up the second pressure is ensured to be shorter. The first direction is the axial direction of the valve core 2 and the direction close to the valve port 11, and the first direction is opposite to the second direction, and the first direction is specifically shown by an arrow a in fig. 2.

Then, when the third pressure is built, because the adjusting sleeve 32 resists the buffer piston 31 at this time, the buffer piston 31 cannot move continuously along the first direction, meanwhile, the buffer piston 31 can block the first damping hole 321, so that the oil cannot flow to the liquid outlet 13 through the first damping hole 321, at this time, the pressure of the oil in the first cavity 22 can be quickly increased, the back pressure of the oil in the first cavity 22 acting on the valve core 2 is quickly increased, the valve opening pressure at the liquid inlet 12 is further increased, the third pressure can be quickly built, and the time required for building the third pressure is ensured to be shorter.

By simulating the two conditions that the first damping hole 321 is not arranged and the first damping hole 321 is arranged respectively, the overflow valve in the prior art has two pressure establishment processes and is slower in pressure establishment process when the first damping hole 321 is not arranged, and in the application, after the first damping hole 321 is arranged, the overflow valve has three pressure establishment processes and the established first pressure is lower, and the second pressure and the third pressure are established faster.

It should be noted that the above-mentioned back pressure of the valve element 2 specifically refers to the pressure of the oil in the first chamber 22 acting on the valve element 2 on the wall surface of the valve element 2 located in the first chamber 22 and close to the valve port 11, so that the back pressure of the valve element 2 directly acts on the valve port 11.

Further, as shown in fig. 3, the buffer piston 31 is provided with a second damping hole 313, the second damping hole 313 is respectively communicated with the second cavity 315 and the first cavity 22, the minimum aperture of the first damping hole 321 is defined as R1, the minimum aperture of the second damping hole 313 is defined as R2, and R1 is less than or equal to R2, so that the throttling effect of the first damping hole 321 is ensured to be more obvious, the built primary pressure is lower, and the pressure in the first cavity 22 is kept, so that the buffer piston 31 is pushed under the action of pressure difference, and the normal service performance of the overflow valve is ensured. Specifically, the minimum aperture R1 of the first damping hole 321 is not greater than 0.2mm, so that the minimum aperture R1 of the first damping hole 321 is not too large, and the throttling and depressurization effect of the first damping hole 321 with smaller aperture can be ensured to be better. Here, the minimum aperture R1 of the first damping hole 321 is not particularly limited as long as it does not exceed 0.2 mm.

In detail, as shown in fig. 2 and 3, the regulating sleeve 32 includes a first wall 322 and a fifth wall 323 disposed opposite to each other, the first orifice 321 has a first opening in the first wall 322, the first orifice 321 has a second opening in the fifth wall 323, the first opening communicates with the second opening, and the second opening communicates with the liquid outlet 13, and the damper piston 31 includes a second wall 311 disposed opposite to the second wall 311 in the axial direction of the spool 2.

Specifically, the cushion piston 31 has a first position and a second position, the first wall 322 and the second wall 311 form the second chamber 315 therebetween when the cushion piston 31 is in the first position, the cushion piston 31 is in contact with the piston housing 33, the second wall 311 is in contact with the first wall 322 when the cushion piston 31 is in the second position, the second wall 311 closes the first opening, and the third chamber is formed between the cushion piston 31 and the piston housing 33, that is, the first position is a position in which the first damper hole 321 is opened, and the second position is a position in which the first damper hole 321 is closed.

Further, as shown in fig. 2 and 3, the buffer piston 31 further includes a third wall 312, the third wall 312 is disposed opposite to the second wall 311, the piston sleeve 33 includes a fourth wall 331, a third cavity can be abutted or formed between the third wall 312 and the fourth wall 331, a through hole 314 is further disposed on the buffer piston 31, the through hole 314 communicates the first cavity 22 and the third cavity, and at least part of the second damping hole 313 has a minimum aperture smaller than the minimum aperture of the through hole 314, so as to ensure the throttling and depressurization effects of the second damping hole 313.

Specifically, the acting area of the oil in the second cavity 315 acting on the second wall 311 is smaller than the acting area of the oil in the third cavity acting on the third wall 312, and, when the second pressure is established, the oil pressure in the third cavity is greater than the oil pressure in the second cavity 315 due to the throttling and depressurization effect of the first damping hole 321, so that at this time, the oil pressure in the third cavity is far greater than the oil pressure in the second cavity 315, so that the buffer piston 31 can move more rapidly along the first direction, so as to push the valve core 2 to move more rapidly toward the valve port 11 through the buffer piston 31.

Further, as shown in fig. 2 and 3, at least two first damping holes 321 are uniformly arranged in the inner circumference of the adjusting sleeve 32, so that the uniformity of the oil pressure in the second cavity 315 can be ensured through the at least two uniformly arranged first damping holes 321, and the deviation imbalance of the oil pressure in the second cavity 315 is avoided. In this embodiment, two first damping holes 321 are uniformly disposed in the inner circumference of the adjusting sleeve 32. In other embodiments, three first damping holes 321 may be uniformly disposed in the inner circumference of the adjusting sleeve 32, so that the throttling and depressurizing effects on the first cavity 22 can be further ensured through the three first damping holes 321, so that the pressure established for the first time is smaller, and the time required for establishing the second pressure and the third pressure is shorter. Here, the number of the first damping holes 321 is not limited as long as it is possible to ensure that the respective first damping holes 321 are uniformly distributed and all communicate with the second chamber 315.

Further, as shown in fig. 2 and 3, a third damping hole 21 is provided in the valve core 2, the third damping hole 21 communicates the liquid inlet 12 with the first cavity 22, and at least part of the aperture of the third damping hole 21 is smaller than the aperture of the liquid inlet 12, so as to ensure the throttling and depressurization effects of the third damping hole 21.

Specifically, as shown in fig. 2, the three-stage pressure-regulating overflow valve further comprises an elastic member 4 and a base 5, wherein the elastic member 4 is sleeved on the valve core 2 and is positioned in the valve seat 1, one end of the elastic member 4 is abutted to a limiting table 23 of the valve core 2, a fourth cavity 14 is formed between the elastic member 4 and the valve seat 1, the fourth cavity 14 is communicated with a second opening of the first damping hole 321 and the liquid outlet 13, the base 5 is slidably sleeved on the valve core 2 and is opposite to the limiting table 23, the other end of the elastic member 4 is abutted to the base 5, and the buffer piston 31 can push the base 5 in the first direction to compress the elastic member 4 so that the elastic member 4 pushes the valve core 2 to move in the first direction. In this embodiment, the elastic member 4 may be a spring.

The specific working process of the three-stage pressure-regulating overflow valve in the embodiment is as follows:

firstly, the liquid inlet 12 enters the liquid, the liquid pressure of the liquid inlet 12 directly acts on the wall surface, close to the valve port 11, of the valve core 2 to push the valve core 2 to instantaneously open the valve port 11 along the second direction, when the valve port 11 is instantaneously opened, the liquid of the liquid inlet 12 enters the first cavity 22 through the third damping hole 21 and then enters the second cavity 315 through the first cavity 22 and the second damping hole 313, so that the liquid in the second cavity 315 acts on the second wall 311 of the buffer piston 31, and meanwhile, the liquid in the first cavity 22 enters the third cavity through the through hole 314, so that the liquid in the third cavity acts on the third wall 312 of the buffer piston 31.

Meanwhile, the oil in the second cavity 315 can flow out to the liquid outlet 13 through the first damping hole 321 to flow back to the oil tank through the liquid outlet 13, so that the oil in the valve core 2 and between the buffer piston 31 flows, the oil pressure in the second cavity 315 is reduced, the oil pressure in the first cavity 22 is reduced, the back pressure acting on the valve core 2 is reduced, and the pressure of the oil in the liquid inlet 12 needs to overcome the elastic force of the elastic piece 4 and the back pressure of the valve core 2, and the back pressure of the valve core 2 is reduced at the moment, so that the oil pressure of the liquid inlet 12 is smaller, the valve core 2 can be pushed to instantly open the valve port 11, and a smaller pressure valve at the position of the liquid inlet 12 is realized, so that the established first pressure is lower.

Then, since the pressure of the oil in the second chamber 315 is reduced, the acting force of the oil in the second chamber 315 on the second wall 311 is smaller than the acting force of the oil in the third chamber on the third wall 312, and since the acting area of the oil in the second chamber 315 on the second wall 311 is smaller than the acting area of the oil in the third chamber on the third wall 312, the buffer piston 31 moves in the first direction under the action of the oil in the two walls, so that the buffer piston 31 can push the base 5 in the first direction to further compress the elastic member 4, so that the elastic member 4 pushes the valve core 2 to move in the first direction, the acting force of the elastic member 4 on the valve core 2 is increased, and since the pressure of the oil in the inlet 12 needs to overcome the elastic force of the elastic member 4 and the back pressure of the valve core 2, the elastic force of the elastic member 4 is increased, so that the valve opening pressure of the oil in the inlet 12 is increased, and the second pressure is stable until the second wall 311 of the buffer piston 31 abuts against the first wall 322 of the regulating sleeve 32 to seal the first hole 321.

Then, the buffer piston 31 cannot continue to move in the first direction due to the resisting action of the first wall 322 of the adjusting sleeve 32 on the second wall 311 of the buffer piston 31, the buffer piston 31 can block the first damping hole 321 and enable the oil to flow to the liquid outlet 13 through the first damping hole 321, accordingly, the pressure of the oil in the first cavity 22 can be quickly increased, the back pressure of the oil in the first cavity 22 acting on the valve core 2 can be quickly increased, and the back pressure of the valve core 2 can be increased due to the fact that the pressure of the oil in the liquid inlet 12 needs to overcome the elastic force of the elastic piece 4 and the back pressure of the valve core 2, so that the valve opening pressure of the oil in the liquid inlet 12 can be further increased, and the third pressure can be quickly established.

Finally, when the pressure of the oil in the inlet 12 increases to overcome the elastic force of the elastic member 4 and the back pressure of the valve core 2, the pressure of the oil in the inlet 12 pushes the valve core 2 to move in the second direction, so that the valve core 2 reopens the valve port 11, and overflow is opened.

The three-stage pressure regulating relief valve in this embodiment can ensure that the throttling and depressurization effects of the second damping hole 313 and the third damping hole 21 in the pressure building process are low in the built-up primary pressure, and has good buffering effect, meanwhile, the throttling and depressurization effects of the first damping hole 321 can ensure that the oil acting forces respectively acting on the second wall 311 and the third wall 312 of the buffer piston 31 are unequal, so that the buffer piston 31 can be quickly pushed to move along the first direction by the pressure difference between the second wall 311 and the third wall 312 of the buffer piston 31 to compress the elastic piece 4, thereby quickly building the second pressure and shortening the time for building the second pressure, and the second wall 311 of the buffer piston 31 is used for blocking the first damping hole 321, thereby quickly building the third pressure and shortening the time for building the third pressure.

The foregoing is merely exemplary of the present utility model, and those skilled in the art should not be considered as limiting the utility model, since modifications may be made in the specific embodiments and application scope of the utility model in light of the teachings of the present utility model.

Claims (9)

1. Three-stage pressure regulating overflow valve, its characterized in that includes:

The valve seat (1) is respectively provided with a valve port (11), a liquid inlet (12) and a liquid outlet (13);

The valve core (2) is in sliding fit in the valve seat (1), so that the valve core (2) opens or closes the valve port (11), and a first cavity (22) communicated with the liquid inlet (12) is arranged in the valve core (2);

The adjusting assembly comprises a buffer piston (31), an adjusting sleeve (32) and a piston sleeve (33), wherein the adjusting sleeve (32) is arranged in the valve seat (1), at least part of the piston sleeve (33) is arranged in the adjusting sleeve (32), the buffer piston (31) is in sliding fit with the adjusting sleeve (32), a second cavity (315) is formed between the buffer piston (31) and the adjusting sleeve (32), a third cavity is formed between the buffer piston (31) and the piston sleeve (33), the second cavity (315) and the third cavity are communicated with the first cavity (22), the adjusting sleeve (32) is provided with a first damping hole (321), one end of the first damping hole (321) is communicated with the second cavity (315), the other end of the first damping hole (321) can be communicated with the liquid outlet (13), and the buffer piston (31) can be opened or blocked the first damping hole (321).

2. The three-stage pressure regulating relief valve according to claim 1, wherein said buffer piston (31) is provided with a second damping hole (313), said second damping hole (313) being in communication with said second chamber (315) and said first chamber (22), respectively, defining a minimum aperture of said first damping hole (321) as R1, a minimum aperture of said second damping hole (313) as R2, R1 being less than or equal to R2.

3. The three-stage pressure regulating relief valve according to claim 2, wherein the minimum aperture R1 of said first orifice (321) is not more than 0.2mm.

4. The three-stage pressure regulating relief valve as claimed in claim 2, wherein the regulating sleeve (32) comprises a first wall (322), the buffer piston (31) comprises a second wall (311), the buffer piston (31) has a first position and a second position, the buffer piston (31) is located at the first position, the second cavity (315) is formed between the first wall (322) and the second wall (311), the first damping hole (321) has a first opening in the first wall (322), and the second wall (311) abuts against the first wall (322) when the buffer piston (31) is located at the second position, so that the second wall (311) seals the first opening.

5. The three-stage pressure regulating relief valve as claimed in claim 4, wherein the buffer piston (31) further comprises a third wall (312), the third wall (312) is disposed opposite to the second wall (311), the piston sleeve (33) comprises a fourth wall (331), the third wall (312) and the fourth wall (331) can be abutted against or form the third cavity, a through hole (314) is further disposed on the buffer piston (31), the through hole (314) is communicated with the first cavity (22) and the third cavity, and at least part of the second damping hole (313) has a minimum aperture smaller than the minimum aperture of the through hole (314).

6. The three-stage pressure regulating relief valve of claim 5, wherein an area of action of oil in the second chamber (315) against the second wall (311) is less than an area of action of oil in the third chamber against the third wall (312).

7. The three-stage pressure regulating relief valve according to any of claims 1-6, wherein at least two of said first orifice holes (321) are provided circumferentially within said regulating sleeve (32).

8. The three-stage pressure regulating relief valve according to any of claims 1-6, wherein a third damping hole (21) is provided in said valve core (2), said third damping hole (21) communicates said liquid inlet (12) with said first chamber (22), and at least part of said third damping hole (21) has a smaller aperture than the aperture of said liquid inlet (12).

9. The three-stage pressure regulating relief valve according to any one of claims 1-6, wherein said three-stage pressure regulating relief valve further comprises:

The elastic piece (4) is sleeved on the valve core (2) and is positioned in the valve seat (1), one end of the elastic piece (4) is abutted to a limiting table (23) of the valve core (2), a fourth cavity (14) is formed between the elastic piece (4) and the valve seat (1), and the fourth cavity (14) is communicated with the first damping hole (321) and the liquid outlet (13);

The base (5), the slip cap is located case (2) and with spacing platform (23) set up relatively, the other end butt of elastic component (4) extremely base (5), just buffering piston (31) can be followed the first direction and pushed base (5) are in order to compress elastic component (4), so that elastic component (4) promotes case (2) are followed first direction removes, first direction is the axial of case (2) and be close to the direction of valve port (11).