CN218267425U - Hydraulic valve - Google Patents

Abstract

A hydraulic valve, comprising: a valve body; a first valve seat fixed in the valve body; a piston located within the valve body, the piston reciprocating in a first direction relative to the first valve seat; the first spring is positioned in the valve body, is fixed with the piston and moves relative to the first valve seat in a telescopic way along a first direction; a first spool located within the valve body that reciprocates in a first direction relative to a first valve seat located between the first spool and a first spring. The hydraulic valve has the advantages of good opening and action stability and high reliability.

Description

Hydraulic valve

Technical Field

The utility model relates to a hydraulic pressure technical field, concretely relates to hydraulic valve.

Background

In a large-sized construction machine, a hydraulic machine is an important component for realizing the mechanical function of the device. When the actuators of a hydraulic machine are stopped, a reliable load holding is often required to keep the actuators in a fixed position. Typically, the stop position of the actuator can be controlled by adjusting the position of a diverter valve that controls the actuation of the actuator. However, since such a structure has a fitting clearance of the shaft hole, a certain amount of fluid leakage inevitably occurs, and the actuator gradually slips, and thus, a reliable load holding cannot be performed. Therefore, in such a mechanical device, a hydraulic valve capable of providing a reliable load holding effect is very important.

Currently, in such mechanical devices, hydraulic locks or counterbalance valves are typically employed to provide reliable load retention. The balance valve adopts a gradual opening mode to open the valve port, but the leakage amount of the valve port is increased along with the rise of load pressure until the valve port is opened in an overflowing mode, so that the capacity of providing a load holding effect is limited, and in addition, the structure of the balance valve is complex and the manufacturing cost is high. The hydraulic lock can provide load holding with a small leakage amount, and the leakage amount cannot be increased along with the increase of the load pressure, but the hydraulic lock has the defect that the valve core of the hydraulic lock only has two states of closing and opening, so that the application of the hydraulic lock is often accompanied with severe impact and noise, and the using effect of the device is influenced.

Therefore, the stability and reliability of the opening and operation of the hydraulic valve still need to be improved in the prior art.

SUMMERY OF THE UTILITY MODEL

The utility model provides a technical problem be, provide a hydraulic valve, hydraulic valve opens better with the stability of action, and the reliability of hydrovalve is higher.

In order to solve the technical problem, the technical proposal of the utility model provides a hydraulic valve, which comprises a valve body; a first valve seat fixed in the valve body; a piston located within the valve body, the piston reciprocating in a first direction relative to the first valve seat; the first spring is positioned in the valve body, is fixed with the piston and moves telescopically relative to the first valve seat along a first direction; a first spool positioned within the valve body that reciprocates in a first direction relative to a first valve seat positioned between the first spool and a first spring.

Optionally, the piston comprises first and second opposing end faces in the first direction.

Optionally, the first valve core has a third end surface and a fourth end surface opposite to each other along the first direction, and the third end surface is in contact with the second end surface.

Optionally, the hydraulic valve further comprises: a second valve seat fixed in the valve body; the second valve core is positioned in the valve body and reciprocates along a first direction relative to the second valve seat, the second valve core is provided with a fifth end surface and a sixth end surface which are opposite along the first direction, and the sixth end surface is in contact with the first end surface.

Optionally, the hydraulic valve further comprises: the first sleeve is fixed in the valve body, a first cavity is formed in the first sleeve, and the first valve core is positioned in the first cavity; and the second sleeve is fixed in the valve body, a second cavity is formed in the second sleeve, and the second valve core is positioned in the second cavity.

Optionally, the first valve seat is fixed to the first sleeve side wall; the second valve seat is fixed on the side wall of the second sleeve.

Optionally, the hydraulic valve further comprises: a second spring located within the first cavity, the second spring connecting the first sleeve and the first spool; a third spring located within the second cavity, the third spring connecting the second sleeve and the second valve spool.

Optionally, the stiffness of the first spring is greater than the stiffness of the second spring; the stiffness of the first spring is greater than the stiffness of the third spring.

Optionally, the stiffness range of the first spring is 2000N/mm-6000N/mm.

Optionally, the hydraulic valve further comprises: the first limiting end is fixed on the surface of the first valve seat and is positioned between the first valve seat and the first spring.

Optionally, the hydraulic valve further comprises: and the second limiting end is fixed on the surface of the second valve seat and is positioned between the second valve seat and the first spring.

Optionally, the first valve spool includes a first region and a second region adjacent to the first region, the first region being in contact with the piston; the surface of the side wall of the first area is a cylindrical surface, the side wall of the first area is perpendicular to the third end surface, the surface of the side wall of the second area is a conical surface, and the included angle between the surface of the side wall of the second area and the third end surface is larger than 0 and smaller than 90 degrees.

Optionally, a third cavity is formed in the first valve element, and the third cavity is communicated with the first cavity; and the second valve spool is provided with a fourth cavity which is communicated with the second cavity.

Optionally, the hydraulic valve further comprises: the first oil port and the second oil port are positioned in the valve body and communicated with the first sleeve; and the third oil port and the fourth oil port are communicated with the second sleeve.

Compared with the prior art, the utility model discloses technical scheme has following beneficial effect:

the technical scheme of the utility model provide an among the hydrovalve, be fixed with first spring on the piston of hydrovalve. In the opening process of the hydraulic valve, the piston moves towards the direction close to the first valve seat under the action of liquid pressure to jack the first valve core until the first spring abuts against the first limiting end on the first valve seat, and at the moment, a small gap exists between the first valve core and the first valve seat, so that a throttling effect is formed, and the flexible opening of the hydraulic valve is realized. In addition, when the hydraulic oil quantity further increases, because the existence of first spring, the in-process of piston motion is blockked by the elasticity of first spring to drive first case and steadily move gradually, make to have the clearance grow gradually between first case and the first disk seat, in order to realize the flexible action effect of hydrovalve, simultaneously, at this in-process, the clearance size that produces between first case and the first disk seat is positive correlation with the liquid pressure that the piston received, thereby make hydraulic valve opening volume change along with the fuel feeding flow change, consequently, the stability and the reliability of hydrovalve action have been promoted, the repeated oscillation and the noise influence that pressure shock brought have been reduced.

Further, the first valve core comprises a first area and a second area adjacent to the first area, the surface of the side wall of the first area is a cylindrical surface, and the surface of the side wall of the second area is a conical surface. The first area and the second area jointly form a damping taper neck, so that when the hydraulic valve is opened, a gap between the first valve core and the first valve seat is smaller, a throttling effect is formed in the gap between the first valve core and the first valve seat, the load pressure borne by the first valve core is kept, and an actuating mechanism connected with the hydraulic valve starts to move slowly to achieve the flexible opening effect of the hydraulic valve.

Drawings

Fig. 1 to 3 are schematic structural views of a hydraulic valve according to an embodiment of the present invention;

fig. 4 to 6 are schematic structural diagrams of the hydraulic valve in the working process.

Detailed Description

As discussed in the background, in the prior art, a hydraulic lock or a balanced valve is typically employed to provide reliable load retention. The balance valve adopts a gradual opening mode to open the valve port, but the leakage amount of the valve port is increased along with the rise of load pressure until the valve port is opened in an overflowing mode, so that the capacity of providing a load holding effect is limited, and in addition, the structure of the balance valve is complex and the manufacturing cost is high. The hydraulic lock can provide load holding with little leakage amount, and can not increase the leakage amount along with the rise of load pressure, but the valve core of the hydraulic lock only has two states of 'closed' and 'opened', so that the application of the hydraulic lock is often accompanied with violent impact and noise, and the using effect of the device is influenced.

Therefore, in the prior art, the opening stability and reliability of the hydraulic valve are required to be improved.

In order to solve the technical problem, the technical scheme of the utility model a hydraulic valve is provided, be fixed with first spring on the piston of hydrovalve. In the process of opening the hydraulic valve, the piston is blocked by the elastic force of the first spring when moving towards the direction close to the first valve seat, so that the piston can be stably and gradually close to the first valve seat, the first valve core is further driven to be stably and gradually far away from the first valve seat, and a gap between the first valve core and the first valve seat is gradually enlarged, so that the flexible opening effect of the hydraulic valve is realized.

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Fig. 1 to 3 are schematic structural diagrams of a hydraulic valve according to an embodiment of the present invention. Wherein, fig. 1 is a schematic diagram of the overall structure of the hydraulic valve, fig. 2 is a schematic diagram of a cross section along the direction AA' of fig. 1, and fig. 3 is an enlarged view of the area B in fig. 2.

Referring to fig. 1 to 3, the hydraulic valve includes: a valve body 100; a first valve seat 131 fixed in the valve body 100; a piston 120 located within the valve body 100, the piston 120 reciprocating in a first direction X relative to a first valve seat 131; a first spring 141 located inside the valve body 100, the first spring 141 being fixed to the piston 120, the first spring 141 moving telescopically relative to the first valve seat 131 in the first direction X; a first spool 133 located within the valve body 100, the first spool 133 reciprocating in the first direction X relative to a first valve seat 131, the first valve seat 131 being located between the first spool 133 and a first spring 141.

In the present embodiment, the valve body 100 serves as a housing of the hydraulic valve, and other components of the hydraulic valve are accommodated and fixed in the valve body 100.

Specifically, a first oil port 101, a second oil port 102, and a first sleeve 111 are fixed in the valve body 100, and the second oil port 102 and the first sleeve 111 are communicated with each other.

In this embodiment, the first sleeve 111 has a first cavity 145 therein, and the first valve spool 133 is located in the first cavity 145.

In this embodiment, the hydraulic valve further includes: a third oil port 103 and a fourth oil port 104 located in the valve body 100; a second valve seat 132 and a second sleeve 112 fixed within the valve body 100; a second spool 134 located within the valve body 100, the second spool 134 reciprocating in the first direction X relative to the second valve seat 132. The second sleeve 112 has a second cavity 146 therein, and the second spool 134 is located in the second cavity 146. The fourth port 104 is in communication with the second sleeve 112.

Specifically, the first oil port 101 is communicated with the first sleeve 111 through a first passage 161 and a second passage 162, and the second oil port 102 is communicated with the first sleeve 111 through a third passage 163; the third oil port 103 is communicated with the second sleeve 112 through a fourth passage 164 and a fifth passage 165, and the fourth oil port 104 is communicated with the second sleeve 112 through a sixth passage 166.

The first oil port 101 and the third oil port 103 are connected with an external hydraulic directional valve, and the second oil port 102 and the fourth oil port 104 are respectively connected with an actuating mechanism, such as an oil port of a hydraulic oil cylinder or a motor. When the hydraulic valve works, the first oil port 101, the second oil port 102, the third oil port 103 and the fourth oil port 104 guide hydraulic oil into or out of the valve body 100, so as to provide a liquid medium for the work of the hydraulic valve.

In the present embodiment, the central axes of the first sleeve 111 and the second sleeve 112 coincide with the central axis of the valve body 100. The first oil port 101 and the second oil port 102 are respectively fixed on the valve body 100 on two sides of the first sleeve 111; the third oil port 103 and the fourth oil port 104 are respectively fixed on the valve body 100 on both sides of the second sleeve 112.

In other embodiments, under the condition that the working effect of the hydraulic valve is not affected, the positions of the first sleeve and the second sleeve relative to the valve body may have other arrangement modes, and the relative positions of the first oil port, the second oil port, the third oil port and the fourth oil port with the first sleeve, the second sleeve and the valve body may also have other arrangement modes.

In the present embodiment, the piston 120 is located at the center of the valve body 100, and the piston 120 is coaxial with the first valve seat 131 and the second valve seat 132; the first sleeve 111 and the second sleeve 112 are respectively located on two sides of the piston 120 along the first direction X. Specifically, the piston 120 includes a first end surface (not shown) and a second end surface (not shown) opposite to each other along the first direction X. The first spool 133 has a third end surface (not labeled) and a fourth end surface (not labeled) opposite to each other along the first direction X, and the third end surface is in contact with the second end surface. The second spool 134 has a fifth end surface (not labeled) and a sixth end surface (not labeled) opposite to each other along the first direction X, and the sixth end surface is in contact with the first end surface.

In this embodiment, the piston 120 has a piston body (not shown) and two protrusions (not shown) located on both sides of the piston body, and each protrusion is in contact with the first valve spool 133 and the second valve spool 134, respectively.

In this embodiment, the first valve seat 131 is fixed to the sidewall of the first sleeve 111; the second valve seat 132 is fixed to the sidewall of the second sleeve 112. The first valve seat 131 is fixedly connected with the first sleeve 111 through threads, and the second valve seat 132 is fixedly connected with the second sleeve 112 through threads.

In this embodiment, a first position-limiting end 171 is fixed on the surface of the first valve seat 131, and the first position-limiting end 171 is located between the first valve seat 131 and the first spring 141; a second position-limiting end 172 is fixed on the surface of the second valve seat 132, and the second position-limiting end 172 is located between the second valve seat 132 and the first spring 141. The first and second position-limiting ends 171 and 172 are used for controlling the relative positions of the first spring 141 and the piston 120 in the valve body 100.

During the operation of the hydraulic valve, the piston 120 reciprocates relative to the first valve seat 131 and the second valve seat 132 along the first direction X, so as to drive the first spring 141 to perform telescopic motion relative to the first valve seat 131 and the second valve seat 132 along the first direction X until contacting with the first limiting end 171 or the second limiting end 172.

In the process, the piston 120 jacks the first valve core 133 until the first spring 141 abuts against the first limit end 171 on the first valve seat 131, and at this time, a small gap exists between the first valve core 133 and the first valve seat 131, so that the flexible opening of the hydraulic valve is realized. Then, after the hydraulic valve is opened, when the hydraulic oil amount is further increased, due to the existence of the first spring 141 and the stiffness of the first spring 141 is high, the piston 120 is blocked by the elastic force of the first spring 141 in the process of moving towards the direction close to the first valve seat 131, so that the piston 120 smoothly and progressively approaches the first valve seat 131, and further the first valve core 133 is driven to smoothly and progressively leave away from the first valve seat 131, and a gap existing between the first valve core 133 and the first valve seat 131 is gradually increased, so as to achieve the flexible action effect of the hydraulic valve.

In this embodiment, the hydraulic valve further includes: a second spring 142, the second spring 142 being located in the first cavity 145, the second spring 142 connecting the first sleeve 111 and the first spool 133; a third spring 143, the third spring 143 being located within the second cavity 146, the third spring 143 connecting the second sleeve 112 and the second spool 134.

In the present embodiment, the stiffness of the first spring 141 is greater than the stiffness of the second spring 142; the stiffness of the first spring 141 is greater than the stiffness of the third spring 143. Therefore, the approach of the piston 120 to the first valve seat 131 is mainly blocked by the elastic force of the first spring 141, so that the piston 120 moves smoothly and gradually to achieve the flexible action effect of the hydraulic valve.

Specifically, in the present embodiment, the stiffness of the first spring 141 ranges from 2000N/mm to 6000N/mm.

With continued reference to fig. 3, the first spool 133 includes a first region (not labeled) that contacts the piston 120 and a second region (not labeled) adjacent to the first region; the surface of the side wall of the first area is a cylindrical surface, and the side wall of the first area is vertical to the third end surface; the surface of the side wall of the second area is a conical surface, and the included angle between the surface of the side wall of the second area and the third end surface is larger than 0 and smaller than 90 degrees.

Because the first region and the second region together form a damping taper neck (as shown in region C), when the hydraulic valve is opened, a gap between the first valve element 133 and the first valve seat 131 is small, and a throttling effect is formed in the gap between the first valve element 133 and the first valve seat 131, which is beneficial to maintaining a load pressure on the first valve element 133, so that the actuating structure slowly starts to move, and a flexible opening effect of the hydraulic valve is achieved.

In this embodiment, the first valve core 133 further has a third cavity 148 therein, and the third cavity 148 is communicated with the first cavity 145, so that the hydraulic oil in the first cavity 145 can enter the third cavity 148, thereby being beneficial to maintaining the load pressure on the first valve core 133 in the hydraulic valve load maintaining stage, and further reliably closing the hydraulic valve. The second spool 134 further has a fourth cavity 149 therein, and the fourth cavity 149 is communicated with the second cavity 146.

In this embodiment, the first sleeve 111 and the second sleeve 112 are connected to the second port 102 and the fourth port 104 in a pipe connection manner. The first and third ports 101 and 103 are connected to a first valve seat 131 and a second valve seat 132.

In other embodiments, the first sleeve, the second oil port and the fourth oil port are connected in a tubular manner. The first oil port and the third oil port are connected with the first valve seat and the second valve seat in a plate type connection mode.

Fig. 4 to 6 are schematic structural diagrams of the hydraulic valve in the working process. Fig. 4 and 5 correspond to the view direction of fig. 2, and fig. 6 corresponds to the view direction of fig. 3.

Referring to fig. 4, fig. 4 is a schematic diagram illustrating a load holding stage during operation of the hydraulic valve.

When the hydraulic valve is operating, the external hydraulic directional control valve supplies oil to the third port 103 and from the third port 103 through the fourth passage 164 into the fifth passage 165, where the hydraulic oil contacts the second spool 134. As the hydraulic oil continuously flows in, the oil pressure of the hydraulic oil received by the sixth end surface of the second valve element 134 gradually increases until the oil pressure is greater than the pre-pressure for opening the third spring 143, so that the third spring 143 is compressed, and the second valve element 134 moves in a direction away from the second valve seat 132, so that a gap is formed between the second valve element 134 and the second valve seat 132. The hydraulic oil thus passes through the gap between the second spool 134 and the second valve seat 132, enters the second cavity 146 of the second sleeve 112 and the fourth cavity 149 of the second spool 134, and flows through the gap between the second spool 134 and the second valve seat 132 into the sixth passage 166, flows into the fourth port 104, and enters the actuator (as shown in the oil passage 10).

Then, the actuator introduces hydraulic oil into the second oil port 102, and flows through the third passage 163, and enters the first cavity 145 of the first sleeve 111 and the third cavity 148 of the first valve element 133, so that the first valve element 133 is subjected to the pressure of the hydraulic oil, and the first valve element 133 abuts against the first valve seat 131, thereby closing the valve port. The pressure experienced by the first spool 133, i.e., the load pressure at the second port 102, ensures that the hydraulic valve maintains a reliable and stable load hold (as shown by the oil path 11).

Referring to fig. 5 and 6, fig. 5 and 6 are schematic diagrams illustrating a flexible opening phase of the hydraulic valve during operation.

The amount of the hydraulic oil flowing into the fifth passage 165 from the third port 103 is gradually increased, and the first end surface of the piston 120 is acted by the pressure of the hydraulic oil in the fifth passage 165, so that the piston 120 moves toward the first valve seat 131 and abuts against the first valve element 133. When the pressure of the hydraulic oil in the fifth passage 165 on the piston 120 continuously rises until the pressure is greater than the opening condition of the first valve element 133, the piston 120 opens the first valve element 133, that is, the first valve element 133 is pushed to move in the direction away from the first valve seat 131 until the first spring 141 abuts against the first limit end 171, so that a small gap exists between the first valve element 133 and the first valve seat 131, and the hydraulic valve is opened by a small distance. Specifically, in this embodiment, the hydraulic valve is opened to a position that is one-half of the damping cone neck. At this time, a small gap is formed between the first valve element 133 and the first valve seat 131, and when hydraulic oil enters the small gap, a throttling effect is formed, which is beneficial to maintaining the load pressure on the first valve element 133, so that the actuator slowly starts to move, and a flexible opening effect of the hydraulic valve is realized.

In this embodiment, if the ratio of the area of the first end surface of the piston 120 to the area of the third end surface of the first spool 133 is defined as the pilot ratio Φ, the condition that the first spool 133 is opened is:

the hydraulic oil pressure in the fifth passage 165 is equal to or greater than (the second spring 142 opening pre-pressure + the second oil port 102 load pressure)/the pilot ratio phi, wherein the second spring 142 opening pre-pressure is the minimum pressure for compressing the second spring 142.

Then, when the amount of the hydraulic oil flowing into the fifth passage 165 from the third oil port 103 is further increased, the first end surface of the piston 120 is gradually increased under the pressure action of the hydraulic oil in the fifth passage 165, so as to push the piston 120 to further compress the first spring 141, so that the opening gap between the first valve core 133 and the first valve seat 131 is gradually increased, and meanwhile, because the stiffness of the first spring 141 is relatively high, the opening amount of the hydraulic valve is stably and gradually changed along with the change of the oil supply flow rate, thereby realizing the flexible action effect of the hydraulic valve, improving the stability of the hydraulic valve during the action, and avoiding the problem of shaking and crawling during the action of the hydraulic valve.

During the opening and the operation of the hydraulic valve, the hydraulic oil of the second oil port 102 simultaneously enters the first cavity 145 and the third passage 163, the hydraulic oil of the first cavity 145 continuously fills the third cavity 148 communicated with the first cavity 145, and the hydraulic oil in the first cavity 145 and the third cavity 148 is discharged out of the first cavity 145 and the third cavity 148 through side holes (not marked) formed in the first valve element 133 and reaches the third passage 163 (as shown in the oil passage 30). Meanwhile, the hydraulic oil in the third passage 163 flows through the gap between the first valve element 133 and the first valve seat 131, and then flows through the second passage 162 and the first passage 161 to enter the first oil port 101 (as shown in the oil passage 20), thereby completing the whole flexible opening and flexible action process of the hydraulic valve.

In the flexible action process of the hydraulic valve, because the first spring 141 exists and the stiffness of the first spring 141 is greater than that of the second spring 142, the piston 120 is blocked by the elastic force of the first spring 141 in the process of approaching the first valve seat 131, so that the first valve element 133 is driven to smoothly and progressively leave away from the first valve seat 131, and a gap existing between the first valve element 133 and the first valve seat 131 is gradually enlarged from a small opening, so that the flexible action effect of the hydraulic valve is realized. Meanwhile, in the process, the size of the gap generated between the first valve element 133 and the first valve seat 131 is positively correlated with the pressure of the hydraulic oil received by the piston 120, and when the amount of the hydraulic oil entering the fifth passage 165 from the third oil port 103 is large, the first spring 141 can be further compressed, so that the first valve element 133 is gradually pushed to continue to be away from the first valve seat 131, and the gap between the first valve element 133 and the first valve seat 131 is increased; when the amount of hydraulic oil entering the fifth passage 165 from the third oil port 103 is small, the gap between the first valve element 133 and the first valve seat 131 is also small, so that the opening amount of the hydraulic valve changes along with the change of the oil supply flow, the stability and reliability of the action of the hydraulic valve are improved, and the repeated oscillation and noise influence caused by pressure impact is reduced.

Referring to fig. 6 in conjunction with fig. 5, the first valve element 133 includes a first region (not labeled) and a second region (not labeled) adjacent to the first region, the sidewall surface of the first region is a cylindrical surface, and the sidewall surface of the second region is a conical surface. When the first valve element 133 is opened, the first spring 141 abuts against the first limit end 171, and an opening gap between the first valve element 133 and the first valve seat 131 is small. On this basis, because the first area and the second area jointly form a damping taper neck (as shown in an area C), a gap between the first valve element 133 and the first valve seat 131 is further limited, and hydraulic oil flowing through the gap is subjected to a large resistance, so that a throttling effect is formed in the gap between the first valve element 133 and the first valve seat 131, and thus the load pressure applied to the first valve element 133 is favorably maintained, the actuating mechanism slowly starts to move, a flexible opening effect of the hydraulic valve is realized, and pressure impact and abnormal sound in the working process of the hydraulic valve are reduced.

The hydraulic valve is of a symmetrical structure, so that in the working process of the hydraulic valve, hydraulic oil can enter the valve body 100 from the first oil port 101, flows into the second oil port 102 through the first valve core 133, flows into the second valve core 134 through the fourth oil port 104 after passing through an external execution mechanism, the flexible opening and action of the hydraulic valve are realized at the second valve core 134 and the second valve seat 132, and finally, the hydraulic oil flows out from the third oil port 103.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention, and the scope of the present invention is defined by the appended claims.

Claims (14)

1. A hydraulic valve, comprising:

a valve body;

a first valve seat fixed in the valve body;

a piston located within the valve body, the piston reciprocating in a first direction relative to the first valve seat;

the first spring is positioned in the valve body, is fixed with the piston and moves telescopically relative to the first valve seat along a first direction;

a first spool positioned within the valve body that reciprocates in a first direction relative to a first valve seat positioned between the first spool and a first spring.

2. The hydraulic valve of claim 1, wherein the piston includes opposing first and second end faces in a first direction.

3. The hydraulic valve of claim 2, wherein the first spool has third and fourth opposing end surfaces in the first direction, the third end surface contacting the second end surface.

4. The hydraulic valve of claim 2, further comprising: a second valve seat fixed in the valve body; the second valve core is positioned in the valve body and reciprocates along a first direction relative to the second valve seat, the second valve core is provided with a fifth end surface and a sixth end surface which are opposite along the first direction, and the sixth end surface is in contact with the first end surface.

5. The hydraulic valve of claim 4, further comprising: the first sleeve is fixed in the valve body, a first cavity is formed in the first sleeve, and the first valve core is positioned in the first cavity; and the second sleeve is fixed in the valve body, a second cavity is formed in the second sleeve, and the second valve core is positioned in the second cavity.

6. The hydraulic valve of claim 5, wherein the first valve seat is fixed to a first sleeve sidewall; the second valve seat is fixed on the side wall of the second sleeve.

7. The hydraulic valve of claim 5, further comprising: a second spring located within the first cavity, the second spring connecting the first sleeve and the first spool; a third spring located within the second cavity, the third spring connecting the second sleeve and the second valve spool.

8. The hydraulic valve of claim 7, wherein the stiffness of the first spring is greater than the stiffness of the second spring; the stiffness of the first spring is greater than the stiffness of the third spring.

9. The hydraulic valve of claim 8, wherein the first spring has a stiffness in the range of 2000N/mm to 6000N/mm.

10. The hydraulic valve of claim 1, further comprising: the first limiting end is fixed on the surface of the first valve seat and is positioned between the first valve seat and the first spring.

11. The hydraulic valve of claim 4, further comprising: and the second limiting end is fixed on the surface of the second valve seat and is positioned between the second valve seat and the first spring.

12. The hydraulic valve of claim 3, wherein the first spool includes a first region and a second region adjacent the first region, the first region being in contact with the piston; the surface of the side wall of the first area is a cylindrical surface, the side wall of the first area is perpendicular to the third end surface, the surface of the side wall of the second area is a conical surface, and the included angle between the surface of the side wall of the second area and the third end surface is larger than 0 and smaller than 90 degrees.

13. The hydraulic valve of claim 5, wherein the first spool has a third cavity therein, the third cavity being in communication with the first cavity; and the second valve core is provided with a fourth cavity which is communicated with the second cavity.

14. The hydraulic valve of claim 5, further comprising: the first oil port and the second oil port are positioned in the valve body and communicated with the first sleeve; and the third oil port and the fourth oil port are communicated with the second sleeve.

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