Valve

Abstract

The valve comprises a valve seat and a valve element rotationally arranged in the valve seat, the valve seat is provided with a plurality of valve ports, the valve element is provided with a connector, the connector is used for selectively communicating at least two valve ports, and a sealing piece is arranged between the valve seat and the valve element. The sealing part is provided with an opening corresponding to each valve port, the periphery of each opening of the sealing part protrudes to form a first lip edge, the peripheries of all the first lip edges of the sealing part protrude to form a second lip edge, the outer ends of the first lip edges and the outer ends of the second lip edges elastically abut against the valve seat, torque generated by compression deformation during assembly is small, and the sealing part is not prone to deformation. And during use, the valve element can be further deformed to buffer high pressure of fluid, and an excellent sealing effect is formed between the valve element and the valve seat.

Description

Technical Field

[0001] The present application relates to the technical field of pipeline accessories, and in particular to a valve. Background Art

[0002] Valves are often used in piping systems to adjust the flow direction and / or flow rate of fluids. For example, they are used in thermal management systems for electric vehicles to control the flow of heat exchange media in various circuits, such as the traction motor circuit, battery circuit, and passenger compartment temperature control circuit, to meet the heat exchange requirements of multiple working conditions.

[0003] The existing valve structure is usually composed of a valve seat and a valve core that can rotate relative to the valve seat. The valve core rotates to connect different valve ports of the valve seat, so that different circuits connected to it are connected or disconnected, so as to meet the use requirements of different working conditions. However, there is usually leakage between the valve core and the valve port, so that a small amount of liquid may still flow in the valve port that should be closed, affecting the operation of the entire thermal management system. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a valve that can effectively avoid internal liquid leakage.

[0005] A valve comprises a valve seat and a valve core rotatably arranged in the valve seat, the valve seat is provided with a plurality of valve ports, the valve core is provided with an interface, the interface is used to selectively connect at least two of the valve ports, a sealing member is provided between the valve seat and the valve core, the sealing member is provided with an opening corresponding to each of the valve ports, the sealing member protrudes from the periphery of each opening to form a first lip edge and protrudes from the periphery of all the first lips edges to form a second lip edge, and the outer ends of the first lip edge and the second lip edge elastically abut against the valve seat.

[0006] Compared with the prior art, the valve of the present application has a sealing member disposed between its valve seat and valve core. The sealing member protrudes outward to form a first lip and a second lip. The first lip and the second lip elastically abut against the valve seat. The torque generated by the compression deformation of the sealing member during assembly is small. During use, the sealing member can be further deformed to buffer the high pressure of the fluid, thereby forming an excellent sealing effect between the valve core and the valve seat, and effectively solving the problem of internal leakage of the valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a schematic structural diagram of a valve according to an embodiment of the present application.

[0008] Figure 2 for Figure 1 Axial section view of the valve shown.

[0009] Figure 3 for Figure 1 Radial section view of the valve shown.

[0010] Figure 4 for Figure 1 Exploded view of the valve shown.

[0011] Figure 5 for Figure 4 Another angle view of the valve seat of the middle valve.

[0012] Figure 6 for Figure 4 Further exploded view of the seal of the valve.

[0013] Figure 7 for Figure 6 Another angled view of the seal shown.

[0014] Figure 8 for Figure 4 Further exploded view of the balance part of the valve.

[0015] Fig. 9 for Figure 8 Another angle view of the balance member shown.

[0016] Fig.10 for Figure 1 Schematic diagram of another state of the valve shown.

[0017] Description of Figure Numbers:

[0018] 100, valve; 20, valve seat; 22, valve port; 24, substrate; 26, side plate; 261, first positioning portion; 263, second positioning portion; 28, cover plate; 281, shaft hole; 29, sealing ring; 30, valve core; 32, interface; 34, shaft rod; 40, sealing member; 42, opening; 4 balancing member; 52, first sheet; 54, second sheet; 56, third lip. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. One or more embodiments of the present application are exemplarily given in the drawings to make the understanding of the technical solution disclosed in the present application more accurate and thorough. However, it should be understood that the present application can be implemented in a variety of different forms and is not limited to the embodiments described below.

[0020] The same or similar numbers in the drawings of the present application correspond to the same or similar parts; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B.

[0022] In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0023] The present application provides a valve used in a pipeline system to adjust the flow direction and / or flow rate of a fluid. Figure 1-4 A specific embodiment of the present application is shown. The valve 100 shown includes a valve seat 20 , a valve core 30 rotatably mounted in the valve seat 20 , and a sealing member 40 disposed between the valve seat 20 and the valve core 30 .

[0024] The valve seat 20 is provided with a plurality of valve ports 22 for connecting with external pipelines. Part of the valve ports 22 are used as inlets of the valve 100, and the number thereof can be single or multiple; part of the valve ports 22 are used as outlets of the valve 100, and the number thereof can also be single or multiple. The valve core 30 is provided with an interface 32 for selectively connecting one or more inlets of the valve 100 with one or more outlets. When the valve core 30 rotates to different positions relative to the valve seat 20, the interface 32 of the valve core 30 connects with and connects different valve ports 22 of the valve ports 22, so that the valve 100 is in different working states, thereby connecting different circuits in the external pipeline system connected thereto.

[0025] Please also see Figure 5The valve seat 20 is a hollow columnar structure as a whole, including a base plate 24, an annular side plate 26 extending vertically from the outer edge of the base plate 24, and a cover plate 28 covering the side plate 26. The base plate 24, the side plate 26, and the cover plate 28 together form a space for assembling the valve core 30. In this embodiment, the base plate 24 and the side plate 26 are an integral structure, and the cover plate 28 is fixedly connected to the side plate 26 by screws or the like. Preferably, a sealing ring 29, such as an O-ring, is provided between the cover plate 28 and the side plate 26 so that the two can be tightly connected. In the illustrated embodiment, the side plate 26 of the valve seat 20 is provided with two upper and lower rows of valve ports 22, and each row of valve ports 22 includes a plurality of valve ports 22 arranged at intervals along the circumference of the side plate 26.

[0026] The valve core 30 is cylindrical as a whole and is arranged in the center of the valve seat 20. A shaft rod 34 is convexly provided in the center of the valve core 30 facing the cover plate 28, and the shaft rod 34 passes through the cover plate 28 and extends out of the valve seat 20. Correspondingly, a through shaft hole 281 is formed in the center of the cover plate 28, due to the penetration of the shaft rod 34. A power mechanism, such as a motor (not shown), is connected to the shaft rod 34 in a transmission manner, driving the valve core 30 to rotate relative to the valve seat 20 to adjust the use state of the valve 100 to adapt to different use requirements. In the illustrated embodiment, the valve core 30 is provided with two upper and lower rows of interfaces 32, each row of interfaces 32 includes a plurality of interfaces 32 arranged at intervals along the circumference of the valve core 30, and each interface 32 can have different spacing distances in the circumferential direction.

[0027] Some interfaces 32 in the same row can be interconnected, so that the valve ports 22 in the same row connected thereto can be connected thereto; some interfaces 32 in different rows can be interconnected, so that the valve ports 22 in different rows connected thereto can be connected thereto. Some interfaces 32 can be one-to-one connected, so that the two valve ports 22 connected thereto can be connected thereto; some interfaces 32 can be one-to-many connected, so that three or more valve ports 22 connected thereto can be connected thereto. It should be understood that the number, position, shape, etc. of the valve ports 22 of the valve seat 20, as well as the number, position, shape, etc. of the interfaces 32 of the valve core 30, can be determined according to the specific application scenario, and are not limited to the specific embodiments shown in the figure.

[0028] Please also see Figure 2 and Figure 3, the sealing member 40 is arranged in the valve seat 20 and is directly opposite to the position of the valve port 22. In the radial direction, the sealing member 40 is tightly sandwiched between the inner wall of the side plate 26 of the valve seat 20 and the outer wall of the valve core 30. Corresponding to each valve port 22 of the valve seat 20, the sealing member 40 is provided with an opening 42, and the shape and size of the opening 42 are adapted to the valve port 22, so that the setting of the sealing member 40 does not affect the communication between the valve port 22 and the interface 32 of the valve core 30. In the illustrated embodiment, the sealing member 40 is in the shape of an arc sheet as a whole, which is adapted to the columnar structure of the valve seat 20 and the valve core 30; the sealing member 40 is provided with two upper and lower rows of openings 42, and each row of openings 42 is multiple and arranged at intervals along the circumference of the sealing member 40.

[0029] like Figure 4 As shown, the outer wall of the seal 40 protrudes to form a first lip 44 and a second lip 46, and the outer ends of the first lip 44 and the second lip 46 are elastically abutted against the side plate 26 of the valve seat 20. Specifically, the seal 40 forms a first lip 44 on the periphery of each opening 42 thereof, and forms a second lip 46 on the periphery of all openings 42. The first lip 44 and the second lip 46 are both closed annular structures, and the size of the second lip 46 is much larger than that of the first lip 44, and the second lip 46 is arranged around all the first lips 44. In this way, the solid part of the seal 40 forms a double lip structure, which can have a sufficiently large contact area with the valve seat 20 as a whole to ensure the tightness of the connection; each lip 44, 46 can be relatively smaller in size, and is more likely to deform when subjected to force.

[0030] In the illustrated embodiment, the cross section of the first lip 44 is generally "V"-shaped, and its cross-sectional dimension gradually decreases in the direction toward the valve seat 20; similarly, the cross section of the second lip 46 is generally "V"-shaped, and its cross-sectional dimension gradually decreases in the direction toward the valve seat 20. Between two adjacent openings 42, the two first lips 44 together form a double lip structure, in which the distal ends of the two first lips 44 are spaced a certain distance from each other, and the overall cross section is generally "W"-shaped; at the outer edge of the sealing member 40, the first lip 44 and the second lip 46 adjacent thereto together form a double lip structure, in which the distal ends of the first lip 44 and the distal ends of the second lip 46 are spaced a certain distance from each other, and the overall cross section is also generally "W"-shaped.

[0031] When the seal 40 is assembled with the valve core 30 and the valve seat 20, due to its double lip structure, it can produce a sufficiently large deformation under a small external force, which is not only conducive to the rapid assembly of the product, but also conducive to reducing the torque after deformation, so that the seal 40 can further deform when squeezed by the high-pressure fluid to buffer the pressure of the fluid, avoiding the seal 40 from being damaged under long-term high pressure, causing internal leakage problems, and affecting the normal operation of the entire pipeline system. In addition, since the seal 40 is more easily deformed, even if there is a large tolerance between the valve core 30 and the valve seat 20, it can be compensated by the deformation of the seal 40, and the precision requirements for parts are not high, which is conducive to reducing production costs.

[0032] like Figure 6-7 As shown, in this embodiment, the sealing member 40 includes a first component 48 and a second component 49 which are overlapped in the radial direction, and both the first component 48 and the second component 49 are in the shape of arc-shaped sheets.

[0033] The first component 48 is located on the radially outer side of the seal 40 and is disposed toward the valve seat 20, and the second component 49 is located on the radially inner side of the seal 40 and is disposed toward the valve core 30. The opening 42 penetrates both the first component 48 and the second component 49. The first component 48 has better elasticity than the second component 49. The first lip 44 and the second lip 46 extend outward from the first component 48 as a whole and are in sealing contact with the valve seat 20. The second component 49 has a higher hardness than the first component 48 and is slidably matched with the valve core 30. Preferably, the thickness of the second component 49 in the radial direction is much smaller than the thickness of the first component 48 in the radial direction, so that the size of the second component 49 can be minimized while the overall strength of the seal 40 is improved by the second component 49, that is, the material used for the second component 49 is reduced, and the overall cost of the seal 40 is minimized.

[0034] In a specific embodiment, the first component 48 may be a rubber component, that is, the first component 48 may be made of rubber, such as EPDM (Ethylene Propylene Diene Monomer) and the like; the second component 49 may be a plastic component, that is, the second component 49 may be made of plastic, such as PTFE (Polytetrafluoroethylene) and the like. PTFE material has good self-lubricating properties and can effectively reduce the friction of the valve core 30 during rotation, so that the valve 100 can have a longer service life. The first component 48 and the second component 49 are preferably an integral structure that cannot be disassembled and can be integrally connected during the molding process by injection molding or the like. In some embodiments, the second component 49 can be constructed as a coating covering the inner wall of the first component 48, and its thickness is almost negligible relative to the overall thickness of the seal 30. Of course, the first component 48 and the second component 49 can also be separately molded and fixedly connected as a whole by bonding or the like.

[0035] Through the elastic first component 48, the seal 40 is more likely to deform when subjected to force, forming an effective seal between the solid part of the valve seat 20 (specifically, the edge of the valve port 22) and the solid part of the valve core 30 (specifically, the edge of the interface 32), so that the fluid can only flow between the valve port 22 of the valve seat 20 through the valve core 30, and will not leak into the gap between the valve seat 20 and the valve core 30 and then flow directly between the valve port 22, thereby avoiding leakage. Through the hard second component 49, not only the overall strength of the seal 40 can be improved, but also the friction between the valve core 30 and the seal 40 when the valve core 30 rotates relative to the valve seat 20 can be effectively reduced, so that the rotation of the valve core 30 is more stable and smooth, and the valve core 30 can be adjusted quickly and accurately as needed, which is more efficient overall.

[0036] like Figure 3 , Figure 5 As shown, the inner wall of the side plate 26 of the valve seat 20 is convexly provided with a first positioning portion 261 for installation and positioning of the seal 40. Preferably, there are two first positioning portions 261 and they are spaced apart in the circumferential direction, and the seal 40 is clamped between the two first positioning portions 261 and positioned in the circumferential direction, so that its opening 42 can correspond to the valve port 22 of the valve seat 20 one by one. Preferably, the outer ends of the two first positioning portions 261 are bent and extended toward each other to form a small hook portion 265, and the hook portion 265 acts on the radial inner wall of the seal 40 to position the seal 40 in the radial direction, so that after being assembled with the valve seat 20, it can remain in a state of being tightly pressed against the side plate 26 and deformed.

[0037] Preferably, the first component 48 has a larger length in the circumferential direction than the second component 49, and the circumferential sides of the first component 48 extend outward relative to the circumferential sides of the second component 49; the first positioning portion 261 is an axially extending convex strip, which elastically abuts against the circumferential side of the first component 48, making the assembly of the seal 40 more convenient.

[0038] In one embodiment of the present application, a balancing member 50 is further disposed between the valve seat 20 and the valve core 30. The balancing member 50 and the sealing member 40 are symmetrically disposed on opposite sides of the valve core 30, so that the valve core 30 can be coaxially disposed with the valve 100. Figure 8-9 As shown, in this embodiment, the balancing member 50 is in an arc-shaped sheet shape as a whole, and includes a first sheet body 52 and a second sheet body 54 stacked in the radial direction. Preferably, the first sheet body 52 and the second sheet body 54 are an integral structure that cannot be disassembled, wherein the first sheet body 52 is located on the radial outer side of the balancing member 50 and elastically abuts against the side plate 26 of the valve seat 20; the second sheet body 54 is located on the radial inner side of the balancing member 50 and slidably cooperates with the valve core 30.

[0039] In a specific embodiment, the first sheet 52 may be a rubber piece, that is, the first sheet 52 may be made of rubber, such as EPDM, etc.; the second sheet 54 may be a plastic piece, that is, the second sheet 54 may be made of plastic, such as PTFE, etc. Preferably, the thickness of the second sheet 54 in the radial direction of the balancing member 50 is much smaller than the thickness of the first sheet 52 in the radial direction, and the length of the second sheet 54 in the circumferential direction is smaller than the length of the first sheet 52 in the circumferential direction, so as to minimize the size of the second sheet 54 and reduce the cost of the balancing member 50. In some embodiments, the second sheet 54 may be constructed as a coating covering the inner wall of the first sheet 52, and its thickness is almost negligible relative to the thickness of the balancing member 50 as a whole. Of course, the first sheet 52 and the second sheet 54 may also be formed separately and then fixedly connected as a whole by bonding or the like.

[0040] like Figure 3 , Figure 5 As shown, the inner wall of the side plate 26 of the valve seat 20 is also convexly provided with a second positioning portion 263, and the second positioning portion 263 is preferably two and spaced apart in the circumferential direction. The balance member 50 is clamped between the two second positioning portions 263 and positioned in the circumferential direction, so that it can be kept in a symmetrical position with the sealing member 40. In the illustrated embodiment, the second positioning portion 263 is an axially extending convex strip, and its outer ends are bent and extended toward each other to form a small hook portion 267. During assembly, the second positioning portion 263 elastically abuts against the circumferential side edge of the first sheet body 52, so that the balance member 50 is positioned in the circumferential direction; the hook portion 267 acts on the radial inner wall of the balance member 50 to position the balance member 50 in the radial direction, so that the balance member 50 can be kept in a state of being tightly pressed against the side plate 26 after being assembled with the valve seat 20 and deformed.

[0041] In some embodiments, the balancing member 50 may have a lip structure similar to the sealing member 40. For example, the outer wall of the first sheet 52 of the balancing member 50 has a third lip structure 56 protruding toward the valve seat 20. The third lip is preferably a double lip structure, which elastically abuts against the valve seat 20 in the radial direction, so that the opposite sides of the valve core 30 are elastically matched with the valve seat 20 through the balancing member 50 and the sealing member 40, respectively, which is conducive to keeping the valve core 30 and the valve seat 20 in a coaxial state.

[0042] In some embodiments, no opening is provided on the balancing member 50, and its overall dimensions, such as the circumferential length and / or the axial height, are smaller than the circumferential length and / or the axial height of the seal 40, so that the overall weight of the balancing member 50 can be equivalent to the seal 40 having an opening 42. In this way, the weights of the opposite sides of the valve seat 20 are consistent, and the overall center of gravity is on its central axis, which is beneficial for the valve core 30 and the valve seat 20 to remain in a coaxial state.

[0043] During assembly, the seal 40 and the balance 50 are first installed on the corresponding positions of the valve seat 20, and then the valve core 30 is assembled to the center of the valve seat 20, so that the second component 49 inside the seal 40 and the second sheet 54 inside the balance 50 are closely abutted against the opposite sides of the outer wall of the valve core 30, and the lips 44, 46 of the first component 48 and the lips 56 of the first sheet 52 are closely abutted against the inner wall of the valve seat 20. Since the lips 44, 46, 56 are easy to deform and the torque is small after assembly, they can be further deformed when squeezed by high-pressure fluid to buffer the pressure of the fluid, so as to avoid the seal 40 from being damaged under long-term high pressure, causing internal leakage problems, and affecting the normal operation of the entire pipeline system. The cooperation between the seal 40 and the balance 50 enables the valve core 30 and the valve seat 20 to maintain a coaxial state, so that the rotation of the valve core 30 is more stable. In some embodiments, there can be multiple balances 50, as long as they can be symmetrically arranged with the seal 40.

[0044] like Figure 3 As shown, when the valve core 30 rotates to the point where its interface 32 docks with some of the valve ports 22 of the valve seat 20, the valve 100 is in a working state. According to the pipeline to be connected, the rotation angle of the valve core 30 is adjusted so that the valve ports 22 corresponding to the pipeline to be connected can be connected by the interface 32 of the valve core 30. According to the settings of the valve ports 22 and the interface 32, the valve 100 can have a variety of different working states, which are not listed here one by one. Fig.10 As shown, when the valve core 30 rotates to the point where its interface 32 is misaligned with the valve port 22 of the valve seat 20, the valve 100 is in a non-operating state, the valve ports 22 of the valve seat 20 cannot be connected, and all pipelines connected thereto are in a disconnected state. The present application achieves sealing between the valve port 22 and the valve seat 20 through a sealing member 40 with a lip edge, thereby preventing direct communication between the valve ports 22. The overall structure is simple, the cost is low, and the elasticity of the sealing member 40 itself can adapt to various valve port structures, and the versatility is good.

[0045] In a specific embodiment, the valve 100 can be applied to the thermal management system of an electric vehicle, and the valve port 22 of the valve seat 20 can be connected to the drive circuit of the traction motor of the thermal management system, the temperature control circuit of the battery, the air conditioning circuit of the passenger compartment, etc. When in use, the rotation of the valve core 30 can be controlled according to the temperature of the external environment, including the rotation direction, rotation angle, etc., to adjust the flow direction and / or flow rate of the heat exchange medium in each circuit. The heat exchange medium can be a coolant with high heat exchange efficiency and good fluidity, such as water, so that each circuit can dissipate heat and / or heat in a timely and effective manner, and adapt to the use requirements under various working conditions. Of course, the valve 100 provided in the present application can be used to control the flow of fluid in any pipeline system, and is not limited to use in thermal management systems.

[0046] It should be noted that the above embodiments only express the preferred implementation of the present application, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the present application. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, such as combining different features in various embodiments, etc., which should all fall within the scope of protection of the present application.

Claims

1. A valve, comprising a valve seat and a valve core rotatably disposed in the valve seat, wherein the valve seat is provided with a plurality of valve ports, and the valve core is provided with an interface, wherein the interface is used to selectively connect at least two of the valve ports, characterized in that: A sealing member is arranged between the valve seat and the valve core, and the sealing member is arranged with an opening corresponding to each valve port. The sealing member protrudes from the periphery of each opening to form a first lip and protrudes from the periphery of all first lips to form a second lip. The outer ends of the first lip and the second lip elastically abut against the valve seat.

2. The valve according to claim 1, characterized in that The first lip is in a closed ring shape, and the second lip is in a closed ring shape.

3. The valve according to claim 1, characterized in that The cross section of the first lip is in a "V" shape, and the cross section of the second lip is in a "V" shape; the cross section of two adjacent first lips is in a "W" shape as a whole, and the cross section of the second lip and the first lip adjacent thereto is in a "W" shape as a whole.

4. The valve according to any one of claims 1 to 3, characterized in that: The sealing member comprises a first component and a second component arranged radially inwardly of the first component, the second component slidably cooperates with the valve core, the elasticity of the first component is greater than the elasticity of the second component, and the first lip and the second lip extend outwardly from the first component as a whole.

5. The valve according to claim 4, characterized in that The first component is a rubber component, the second component is a plastic component, and the first component and the second component are integrally connected.

6. The valve according to claim 4, characterized in that The thickness of the second component in the radial direction is smaller than the thickness of the first component in the radial direction.

7. The valve according to any one of claims 1 to 3, characterized in that: A balancing piece is also arranged between the valve core and the valve seat. Both the balancing piece and the sealing piece are arc-shaped sheet structures and are symmetrically arranged on opposite sides of the valve core.

8. The valve according to claim 7, characterized in that The inner wall of the valve seat is provided with two first positioning portions, and the sealing member is sandwiched between the two first positioning portions in the circumferential direction; and / or, the inner wall of the valve seat is provided with two second positioning portions, and the balancing member is sandwiched between the two second positioning portions in the circumferential direction.

9. The valve according to claim 7, characterized in that The balancing member includes a first sheet and a second sheet arranged radially inwardly of the first sheet, the second sheet slidably cooperates with the valve core, the first sheet protrudes to form a third lip, and the third lip elastically abuts against the valve seat.

10. The valve according to claim 9, characterized in that The first sheet is a rubber piece, the second sheet is a plastic piece, and the thickness of the second sheet in the radial direction is smaller than the thickness of the first sheet in the radial direction.

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