CN111550575B

CN111550575B - Double-pilot-operated type slide valve

Info

Publication number: CN111550575B
Application number: CN202010409872.9A
Authority: CN
Inventors: 陆定华; 王庆灏
Original assignee: Weishi Xi Zhejiang Fluid Technology Co ltd
Current assignee: Weishi Xi Zhejiang Fluid Technology Co ltd
Priority date: 2020-05-14
Filing date: 2020-05-14
Publication date: 2021-09-28
Anticipated expiration: 2040-05-14
Also published as: CN111550575A

Abstract

The invention provides a double-pilot type slide valve, because a piston assembly with a reset function is used, the functions of a traditional piston and a traditional return spring are integrated on the piston assembly, so that the return spring and a mounting cavity of the traditional three-position valve can be removed, only a pilot structure is reserved, the pilot structure of the embodiment has no obvious change in size with the traditional pilot structure, and the piston assembly is mounted in a piston cavity of the pilot structure, so the size of the slide valve is greatly reduced in the length direction.

Description

Double-pilot-operated type slide valve

Technical Field

The present invention relates to a spool valve that opens and closes a flow path between a plurality of ports by a valve element that slides in a valve hole, and more particularly to a dual pilot type spool valve.

Background

A known three-position switching valve is configured such that pistons are disposed at both ends of a spool valve slidably housed in a valve hole, and a spring force of a return spring is applied to the spool, and if a pilot fluid pressure is applied to one piston by one pilot valve, the spool is moved in one direction to be switched to a first switching position, and if the pilot fluid pressure is applied to the other piston by the other pilot valve, the spool is moved in the opposite direction to be switched to a second switching position, and if both the pilot valves are closed and both the pistons are released from the application of the pilot fluid pressure, the spool is switched to a neutral switching position by the return spring. Sometimes, two return springs are arranged and respectively arranged at two ends of the spool valve of the slide valve, sometimes, one return spring is arranged, and the spool valve of the slide valve can be switched to a neutral switching position. For example, a CN205101602U three-position five-way middle seal type solenoid valve and a CN204061998U normally closed three-position five-way solenoid valve are indispensable, but a mounting cavity is required to mount the return spring.

One drawback of the three-position switching valves described above is that the piston and return spring arranged along the length of the valve body of the switching valve make it difficult to reduce the length of the switching valve, especially when the installation space is limited, in which the three-position switching valve is difficult to install due to its excessive length.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a double-pilot type slide valve, aiming at reducing the length size of a valve body and eliminating the defects in the prior art.

A dual pilot operated spool valve comprising: a main valve body having ports for input, output, and discharge, and a valve hole formed inside the main valve body so as to communicate with the ports;

a spool valve body that is housed in the valve hole so as to be slidable in an axial direction, and that has three switching positions, namely a first switching position for moving toward one end side of the valve hole, a second switching position for moving toward the other end side, and a neutral switching position between the first switching position and the second switching position; the slide valve core can selectively open or close the ports for input, output and discharge;

a first piston and a second piston which are arranged at one end and the other end of the spool valve and receive the action of the pressure of the pilot fluid to switch the spool valve of the spool valve to the first switching position and the second switching position,

the first piston and/or the second piston is a piston assembly including an elastic portion, and the piston assembly is compressible by the spool valve, and is capable of returning the spool valve to a neutral switching position when the pilot fluid pressure is not applied to the first piston and the second piston, and capable of pushing the spool valve by the pilot fluid pressure.

The first pilot valve portion and the second pilot valve portion are provided on both sides of the main valve body portion, and the first pilot valve portion and the second pilot valve portion act on the first piston and the second piston in the piston chamber thereof, respectively, using a propulsive force generated by the pilot fluid pressure supplied from the input port.

The piston assembly comprises a first shell, a second shell and an inner cavity formed by the first shell and the second shell in a surrounding mode, the elastic part is arranged in the inner cavity and can be compressed by the first shell and/or the second shell and rebound after pressure is released, and the first shell is sleeved with the sealing ring.

The outer surface of the first shell is provided with a top column, and the top column can at least partially enter the valve hole of the main valve body and push the spool of the sliding valve.

The inner wall of the first shell is provided with a fixing column, the inner wall of the second shell is provided with a positioning seat, the elastic part comprises a first spring, and two ends of the first spring are positioned by the fixing column and the positioning seat respectively.

The elastic part further comprises a second spring, two ends of the second spring are positioned by the fixing column and the positioning seat respectively and sleeved on the outer side of the first spring, and the second spring has larger elastic force than the first spring.

The first shell and/or the second shell are provided with vent holes, and fluid in the inner cavity can be discharged from the vent holes when the piston assembly is compressed.

When the pilot fluid pressure is not applied to the piston assembly, the first shell is pressed against one end of the spool of the slide valve by the elastic part, and the second shell is pressed against the side wall of the piston cavity by the elastic part.

The slide valve core is equal to the valve hole in length, and when the fluid pressure is not acted on the first piston and the second piston, the slide valve core is kept in the valve hole and is in a neutral switching position.

The first shell comprises a guide cylinder, a positioning flange is arranged at the end part of the guide cylinder, the second shell comprises a limiting flange, and the positioning flange is matched with the limiting flange to prevent the first shell from being separated from the second shell.

The invention has the beneficial effects that:

the invention uses the piston component with the reset function in the three-position electromagnetic slide valve, integrates the functions of the traditional piston and the traditional return spring on the piston component, thus the return spring and the installation cavity of the traditional three-position valve can be removed, only the pilot structure is reserved, and the pilot structure of the embodiment and the traditional pilot structure have no obvious change in size, thereby greatly reducing the size in the length direction of the slide valve. The beneficial effects of specific implementation means are seen in the embodiment section.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a cross-sectional view of a dual pilot operated spool valve of the present invention;

FIG. 2 is a side view of the main valve body portion of FIG. 1 of the present invention;

FIG. 3 is an exploded view of the piston assembly of the present invention;

FIG. 4 is a cross-sectional view of the piston assembly of the present invention;

FIG. 5 is a perspective view of the pilot valve arrangement of the present invention;

FIG. 6 is an exploded view of the pilot valve housing and pilot of the present invention;

FIG. 7 is another perspective view of the pilot valve configuration of the present invention;

fig. 8 is a perspective view of the leader of the present invention;

fig. 9 is a side view of the leader of the present invention;

FIG. 10 is a longitudinal cross-sectional view of the pilot valve construction of the present invention with the piston assembly removed;

FIG. 11 is a side view of the pilot valve housing of the present invention;

FIG. 12 is a longitudinal cross-sectional view of the pilot valve housing of the present invention;

fig. 13 is a horizontal cross-sectional view of the pilot valve housing of the present invention.

Description of the main reference numerals:

100-main valve body part, 11-pilot flow channel, 12-main valve body sealing ring, 13-valve core first end, 14-valve core second end, 15-screw hole, 16-valve core, 200-pilot valve part, 21-pilot valve cover, 210-first inlet, 211-second inlet, 212-second joint face, 213-second side wall, 214-second pilot hole, 215-sealing ring, 216-rib plate, 217-positioning column, 22-pilot piece, 220-positioning sleeve, 221-first pilot hole, 222-first joint face, 223-sealing groove, 224-first side wall, 225-pilot cavity, 226-valve seat, 227-limiting plate, 23-manual valve, 230-manual valve O-shaped ring, 231-manual valve spring, 232-top head, 24-piston component, 240-piston cavity, 241-first shell, 2411-fixed column, 2412-guide cylinder, 2413-sinking groove, 2414-positioning flange, 2415-top column, 242-second shell, 243-vent hole, 244-limiting flange, 245-first spring, 246-sealing ring, 247-positioning seat, 248-deformation groove, 249-second spring, 25-cover plate, 250-plate body, 251-limiting angle, 300-electromagnetic valve part, 301-outer sleeve, 302-iron core, 303-first sealing ring, 304-electromagnetic valve core, 305-second sealing ring, 306-internal valve core, 307-inner sleeve, 308-second return spring, 309-external thread and 310-first return spring.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

A dual pilot operated spool valve according to some embodiments of the present invention is described below with reference to fig. 1 through 13.

Fig. 1 shows a double-pilot type spool in the present embodiment, which is a double-sided pilot type spool having one pilot valve portion 200, and has a main valve body portion 100 and two pilot valve portions 200, in the present embodiment, the main valve body portion 100 has a valve structure as a five-port valve, which is a three-position five-way valve, and the pilot valve portions 200 are provided on both end sides in the longitudinal direction of the main valve body portion 100. The pressure fluid controlled by the main valve body portion 100 is compressed air. It should be clarified that the pilot valve portion 200 of the present embodiment does not need to be fitted with the main valve body portion 100 having a specific number of ports, and the main valve body portion 100 of the three-position five-way valve of the present embodiment should not be construed as a limitation to the pilot valve portion 200.

The housing of the main valve body 100 has a rectangular block shape having a longitudinal direction, a width direction, and a height direction, and the lower surface thereof is formed with inlet ports P and outlet ports E1 and E2 arranged in the longitudinal direction of the housing. The upper surface is provided with ports A1 and A2 for output, and the arrangement of the five ports is as follows: the first and second output ports a1 and a2 are located on both sides of the central input port P, and the first and second discharge ports E1 and E2 are located on both outer sides of the first and second output ports a1 and a 2.

When the pilot valve portions 200 are alternately turned on and off to alternately supply or discharge pilot gas, thereby switching the spool 16 to the advanced position or the return position, the spool 16 is located at the intermediate position, i.e., the cutoff position, when no fluid is supplied to the input P port of the main valve portion 100, and at this time, the input P and discharge ports E1 and E2 are closed by the spool 16, and the five ports a1 and a2 for output are provided on the upper surface. The on-off engagement of the spool valve with each port in the housing of the main valve body 100 is not a concern of the present invention, and is prior art and will not be described further herein.

The pilot valve portion 200 on one side applies a propulsive force in one direction generated by the pilot gas to the spool 16, and the pilot valve portion 200' on the other side applies a propulsive force to the second end 14 of the spool 16, thereby moving toward the pilot valve portion 200 on one side and supplying a motive force.

The pilot valve unit 200 has a pilot valve cover 21 connected to the housing and a solenoid valve unit 300 driving structure connected to the pilot valve cover 21. A piston chamber 240 leading to an end of the valve hole is formed in the pilot valve cover 21, and a pilot piston 24 applying a thrust force to the spool 16 is slidably accommodated in the piston chamber 240 in the spool axial direction.

A piston seal 246 for sealing between the outer periphery of the piston 24 and the inner periphery of the piston cavity 240 is attached to the outer periphery of the piston 24, and the piston 24 and the piston seal 246 provided thereon partition the piston cavity 240 into a pressure chamber for propulsion to which a pilot gas is supplied from the pilot flow path from the input port P or to which the pilot gas is discharged.

The present embodiment provides a dual pilot operated spool valve, comprising: a main valve body 100 having ports for input, output, and discharge, and a valve hole formed inside the main valve body 100 so as to communicate with the ports; a spool valve body 16 which is housed in the valve hole so as to be slidable in an axial direction, and which has three switching positions, namely a first switching position for moving toward one end side of the valve hole, a second switching position for moving toward the other end side, and a neutral switching position between the first switching position and the second switching position; the slide valve core can selectively open or close the ports for input, output and discharge; and first and second pistons disposed at one end and the other end of the spool valve 16 and adapted to receive a pilot fluid pressure to switch the spool valve 16 to the first and second switching positions, wherein the first and/or second pistons are piston units each including an elastic portion and are compressible by the spool valve 16, and are adapted to return the spool valve 16 to the neutral switching position when the pilot fluid pressure does not act on the first and second pistons and to push the spool valve 16 under the pilot fluid pressure.

Because the piston assembly with the reset function is used, the functions of the traditional piston and the traditional return spring are integrated on the piston assembly, so that the return spring and the installation cavity of the traditional three-position valve can be removed, only the pilot structure is reserved, and the pilot structure and the traditional pilot structure of the embodiment have no obvious change in size, so that the size of the slide valve in the length direction is greatly reduced.

The piston assembly 24 includes a first shell 241, a second shell 242 and an inner cavity formed by the first shell 241 and the second shell 242, wherein the elastic part is arranged in the inner cavity and can be compressed by the first shell 241 and/or the second shell 242 and rebound after the pressure is released, and the first shell 241 is sleeved with a sealing ring 246. That is, the present embodiment creatively integrates the conventional return spring in the piston assembly in the form of the elastic part interposed between the first and second housings of the piston assembly, thereby providing the elastic force.

The first housing 241 has a top pillar 2415 formed on an outer surface thereof, and the top pillar 2415 can enter at least a part of the valve hole of the main valve body 100 and push the spool 16. When the piston assembly is forced toward the spool valve by the pilot fluid pressure, the posts 2415 now extend into the valve openings to push the spool valve 16 toward the other side and compress the piston assembly or other return device on the other side. At this time, the spool valve body 16 is switched to the first switching position or the second switching position.

The inner wall of the first shell 241 is provided with a fixing column 2411, the inner wall of the second shell 242 is provided with a positioning seat 247, the elastic part comprises a first spring 245, and two ends of the first spring 245 are respectively positioned by the fixing column 2411 and the positioning seat 247. The first spring 245 is a hollow cylinder which is spirally wound, and the fixing column 2411 and the positioning seat 247 both extend into the hollow space, so that the first spring 245 can be prevented from dislocating or deviating from the working position.

The elastic portion further includes a second spring 249, two ends of the second spring 249 are respectively positioned by the fixing column 2411 and the positioning seat 247 and sleeved outside the first spring 245, and the second spring 249 has a larger elastic force than the first spring 245. Firstly, because the space of the inner cavity formed by the first shell 241 and the second shell 242 is limited, the length of the spring installed in the inner cavity is also limited, and the restoring force of the spring provided by the spring is not capable of meeting the requirement, two spring sets are adopted to provide restoring elastic force at the same time; second, the second spring 249 having a large elastic force is fitted around the first spring 245, so that the first and

second cases

241 and 242 are more uniformly stressed.

The first case 241 and/or the second case 242 are provided with vent holes 243, and fluid in the inner chamber can be discharged through the vent holes 243 when the piston assembly 24 is compressed. Preferably, the vent 243 is located on the second shell 242 and penetrates through the positioning seat 247. Thus, fluid can axially enter or exit the inner cavity, and the piston assembly cannot be subjected to forces other than the axial direction due to the vent hole positioned on the axial line, so that the piston assembly is prevented from being stuck in the piston cavity.

The main valve body 100 is provided with a first pilot valve portion and a second pilot valve portion on both sides thereof, and the first pilot valve portion and the second pilot valve portion act on a first piston and a second piston in a piston chamber thereof, respectively, using a thrust force generated by a pilot fluid pressure supplied from an input port. When the pilot fluid pressure is not applied to the piston assembly 24, the first case 241 is pressed against one end of the spool 16 by the elastic portion, and the second case 242 is pressed against the sidewall of the piston chamber 240 by the elastic portion. The spool valve 16 is equal in length to the valve hole, and when the pilot fluid pressure is not applied to the first piston and the second piston, the spool valve 16 is held in the valve hole and is in the neutral switching position. The axial displacement of the spool 16 is limited by the length of the top post 2415 extending into the valve bore when the spool 16 is pushed, and in this embodiment, the plane of the first shell 241 surrounding the top post 2415 will act as a stop surface against the end surface of the main valve body 100 when the spool 16 is pushed, thereby precisely determining the length of the top post 2415 extending into the valve bore.

The second shell 242 is at least partially located in the first shell 241 and guided and limited by the first shell, the first shell 241 includes a guide tube 2412, a positioning flange 2414 is provided at an end of the guide tube 2412, the second shell 242 includes a limiting flange 244, and the positioning flange 2414 cooperates with the limiting flange 244 to prevent the first shell 241 from being separated from the second shell 242. The second shell 242 is provided with at least one deformation groove 248, the second shell 242 can enter the guide tube 2412 of the first shell 241 in a state that the deformation groove 248 is contracted, when the second shell 242 enters the guide tube 2412, the compression of the deformation groove 248 can be released, the second shell 242 is unfolded to an unstressed state in the guide tube 2412, and the second shell is guided by the inner wall of the guide tube to move in the axial direction.

In the present embodiment, the pilot valve unit 200 and the solenoid valve unit 300 for controlling the operation state of the pilot valve unit 200 include: the pilot valve housing 21, the second engagement surface 212 in the pilot valve housing 21 divides the pilot valve housing 21 into a piston chamber 240 and a pilot installation chamber, and the piston 24 is installed in the piston chamber 240 for pushing the spool valve 16 of the main valve body portion 100. A lead 22 mounted within the lead mounting cavity and including a lead cavity 225. And a pilot flow path for sequentially connecting the pilot flow passage 11 of the main valve body portion 100, the pilot chamber 225 of the pilot 22, and the piston chamber 240 of the pilot bonnet 21, the pilot flow path being defined inside the pilot bonnet 21 and being formed at least partially surrounded by the second joint surface 212 inside the pilot bonnet and the first joint surface 222 of the pilot 22.

The applicant also tried to divide the pilot structure and the electromagnet module into two independent parts to be respectively processed and then assembled into a whole before, namely, the pilot cavity is formed by splicing a part of the electromagnet module and the pilot structure in parallel, and the pilot flow path is formed between the pilot structure and the electromagnet module. Therefore, in this embodiment, the second joint surface 212 in the pilot valve housing 21 divides the pilot valve housing 21 into the piston cavity 240 and the pilot installation cavity, and the applicant integrates the pilot cavity of the electromagnet module with respect to the fluid on-off control into the pilot structure, which greatly improves the precision of the fit between the pilot structure and the pilot containing the pilot cavity, for example, the pilot 22 can be guided by at least one inner wall of the pilot installation cavity of the pilot valve housing 21 during installation, and after the pilot 22 initially enters the pilot installation cavity, the pilot 22 can be combined with other positioning and guiding structures, thereby improving the assembly precision. And the pilot part can more reasonably utilize the space of the pilot structure, and the layout is more compact, so that the overall length of the pilot valve is reduced.

Further, the pilot valve cover 21 is provided with a first inlet 210, the second joint surface 212 is provided with a second side wall 213, and the first inlet 210 and the second side wall 213 communicate with each other at the second inlet 211 to form a part of the pilot flow path.

The pilot 22 includes a first side wall 224 on the first engagement surface 222, a valve seat 226 in the pilot chamber 225, and the first side wall 224 is connected to the pilot chamber 225 through the valve seat 226 and forms a part of the pilot flow path.

The second joint surface 212 of the pilot valve housing 21 is provided with a second pilot hole 214, the pilot member 22 is provided with a first pilot hole 221 on the first joint surface 222, the pilot cavity 225 is communicated with the piston cavity 240 through the first pilot hole and the second pilot hole, and the second joint surface 212 and/or the first joint surface 222 is provided with a seal ring 215 for sealing a fluid passage defined by the second side wall 213 of the pilot valve housing 21 and the first side wall 224 of the pilot member 22 together with the fluid passage formed by the first pilot hole and the second pilot hole.

At least one positioning post 217 is disposed on the second joint surface inside the pilot valve housing 21, the pilot member 22 is provided with a positioning sleeve 220 on the outer surface, and the positioning post 217 can be inserted into the positioning sleeve 220 to position the pilot valve housing 21 and the pilot member 22 relative to each other.

The positioning sleeves 220 of the pilot 22 are multiple and uniformly distributed on the outer surface of the pilot 22, and multiple positioning posts 217 are arranged in the pilot valve cover 21 to fit with the positioning sleeves 220.

The pilot valve portion 200 is further provided with a manual valve 23 for manually opening the valve seat 226, a stem of the manual valve 23 penetrates the pilot valve cover 21 and the pilot member 22, and a top 232 of the stem is capable of engaging with the solenoid 304 of the solenoid valve portion 300 in the pilot chamber 225 to push the solenoid 304 to a position away from the seal valve seat 226, and the stem is externally fitted with a manual valve spring 231 and is restrained by a stopper plate 227 located in the pilot member 22 against pop-up.

The present embodiment also provides a spool valve using the aforementioned pilot valve structure, that is, the spool valve has a main valve portion 100 having: a housing provided with input, output and discharge ports; a valve hole extending in a length direction of the housing inside the housing; and a spool valve body 16 which is inserted into the valve hole so as to be slidable in the axial direction of the valve hole, and which is capable of selectively opening or closing ports for input, output, and discharge; the pilot valve portion 200 causes a propulsive force generated by the pilot fluid supplied from the input port to act on the spool valve 16.

The solenoid valve portion 300 is used to selectively open or close the valve seat 226 of the pilot valve structure, thereby selectively opening or closing the pilot flow path of the pilot valve structure. An electromagnet (not shown) may be secured to the core 302 via external threads 309, and when energized, the solenoid valve element 304 moves toward the core 302. The solenoid valve portion 300 includes an outer casing 301, and as can be seen in fig. 10, the outer casing 301 of the solenoid valve portion 300 is fixed to one end of the pilot 22 by the cover plate 25, a solenoid valve body 304 is movably provided in one end of the outer casing 301, an iron core 302 is fixedly provided in the other end, an inner valve body 306 and a first return spring 310 are provided in an inner cavity of the solenoid valve body 304, the inner valve body 306 is biased toward the valve seat 226 by the first return spring 310, a second return spring 308 is provided between the outer casing 301 and the solenoid valve body 304, and the solenoid valve body 304 is biased toward the valve seat 226 by the second return spring 308. The inner valve core 306 is arranged in the inner cavity of the solenoid valve core 304, so that when an electromagnet (not shown in the figure) loses power, the solenoid valve core 304 moves towards the valve seat 226 under the action of the second return spring 308, and when the inner valve core 306 is in contact with the valve seat 226, the impact force provided by the second return spring 308 can be buffered and absorbed under the action of the first return spring 310, namely, the impact between the inner valve core 306 and the valve seat 226 is reduced, and the service life of the inner valve core 306 can be prolonged.

Fig. 7 shows the fitting relationship between the cover plate 25 and the pilot valve housing 21, in this embodiment, the cover plate 25 has a plate body 250 and a limiting angle 251 at the angle of the plate body 250, and the limiting angle 251 can be adapted to the notch at the corresponding position of the pilot valve housing 21 to prevent the operator from mistakenly installing the device.

In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless expressly limited otherwise. The terms "mounted," "connected," "fixed," and the like are to be construed broadly, and for example, "connected" may be a fixed connection, a removable connection, or an integral connection; "coupled" may be direct or indirect through an intermediary. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual pilot operated spool valve comprising:

a main valve body (100) having ports for input, output, and discharge, and a valve hole formed inside the main valve body so as to communicate with the ports;

a spool valve (16) that is housed in the valve hole so as to be slidable in an axial direction, and that has three switching positions, namely a first switching position at which the spool valve moves toward one end of the valve hole, a second switching position at which the spool valve moves toward the other end, and a neutral switching position between the first switching position and the second switching position;

the slide valve core can selectively open or close the ports for input, output and discharge; first and second pistons disposed at one end and the other end of the spool (16) and adapted to switch the spool (16) to the first and second switching positions by receiving a pilot fluid pressure, characterized in that: the first piston and/or the second piston are/is a piston assembly comprising an elastic part, the piston assembly can be compressed by the slide valve core, and can reset the slide valve core to a neutral switching position when the prior fluid pressure does not act on the first piston and the second piston and can push the slide valve core under the action of the prior fluid pressure;

the piston assembly (24) comprises a first shell (241), a second shell (242) and an inner cavity formed by the first shell and the second shell in a surrounding mode, an elastic part is arranged in the inner cavity and can be compressed by the first shell and/or the second shell and rebound after pressure is released, a sealing ring (246) is sleeved outside the first shell, and the second shell (242) is at least partially located in the first shell (241) and guided and limited by the first shell;

the inner wall of the first shell (241) is provided with a fixing column (2411), the inner wall of the second shell (242) is provided with a positioning seat (247), the elastic part comprises a first spring (245), and two ends of the first spring (245) are respectively positioned by the fixing column (2411) and the positioning seat (247);

the elastic part further comprises a second spring (249), two ends of the second spring (249) are respectively positioned by the fixing column (2411) and the positioning seat (247) and sleeved on the outer side of the first spring (245), and the second spring has larger elastic force than the first spring;

the first shell (241) comprises a guide cylinder (2412), a positioning flange (2414) is arranged at the end part of the guide cylinder (2412), the second shell (242) comprises a limiting flange (244), and the positioning flange (2414) is matched with the limiting flange (244) to prevent the first shell (241) from being separated from the second shell (242).

2. The dual pilot operated spool valve of claim 1, wherein: a first pilot valve part and a second pilot valve part are respectively arranged on both sides of the main valve body part (100), and the first pilot valve part and the second pilot valve part respectively act on a first piston and a second piston in a piston cavity thereof by using the propelling force generated by the pilot fluid pressure provided by the input port.

3. The dual pilot operated spool valve of claim 1, wherein: the outer surface of the first shell (241) is provided with a top pillar (2415), and the top pillar (2415) can at least partially enter a valve hole of the main valve body (100) and push the spool of the spool valve.

4. The dual pilot operated spool valve of claim 1, wherein: the first shell (241) and/or the second shell (242) are provided with vent holes (243), and when the piston assembly (24) is compressed, fluid in the inner cavity can be discharged from the vent holes (243).

5. The dual pilot operated spool valve of claim 1, wherein: when the pilot fluid pressure is not applied to the piston assembly (24), the first case (241) is pressed against one end of the spool (16) by the elastic portion, and the second case (242) is pressed against the side wall of the piston chamber (240) by the elastic portion.

6. The dual pilot operated spool valve of claim 1, wherein: the slide valve core (16) is equal to the valve hole in length, and when the fluid pressure is not acted on the first piston and the second piston, the slide valve core (16) is kept in the valve hole and is in a neutral switching position.