Integrated carbon tank electromagnetic valve with negative pressure balance design
By employing a negative pressure balance design and a split airflow structure, the noise problem of the integrated carbon canister solenoid valve has been solved, achieving a low-noise and stable-sealing carbon canister solenoid valve design suitable for automotive fuel evaporative emission control systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-24
AI Technical Summary
The integrated carbon canister solenoid valve generates significant noise when the moving iron core moves, and the airflow noise also increases, which existing technologies have not been able to effectively solve.
The negative pressure balance design is adopted. By introducing a balance air passage and a lip seal ring with a specific structure in the carbon canister solenoid valve, the moving iron core assembly is ensured to maintain the connection between the sealing cavity and the air outlet channel under electromagnetic force, reducing the air pressure difference. Combined with the split airflow design, airflow noise is reduced.
This achieves low-noise movement of the moving iron core assembly, reduces knocking noise and airflow noise when the moving iron core stops moving, and ensures sealing stability and space saving.
Smart Images
Figure CN121719967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon canister solenoid valve technology, specifically to an integrated carbon canister solenoid valve with a negative pressure balance design. Background Technology
[0002] In automotive evaporative emission control (EVAP) systems, the carbon canister solenoid valve and the dual one-way valve are two key functional components. The carbon canister solenoid valve is typically installed between the carbon canister and the engine intake manifold, opening or closing according to instructions from the engine control unit (ECU) to control the desorption of fuel vapors adsorbed in the carbon canister and their entry into the engine for combustion. The dual one-way valve is typically installed between the fuel tank and the carbon canister to balance the pressure inside and outside the fuel tank and prevent fuel leakage under certain conditions (such as rollover).
[0003] In traditional technical solutions, the carbon canister solenoid valve and the double check valve are usually designed, manufactured, and installed as two separate components. Integrating the double check valve into the carbon canister solenoid valve reduces connecting pipelines and lowers the risk of leakage. The integrated carbon canister solenoid valve includes a carbon canister solenoid valve unit and a double check valve unit. The moving iron core in the carbon canister solenoid valve controls the connection between its inlet and outlet channels, while the outlet channel connects to the chamber within the double check valve unit. When the moving iron core moves, the pressure imbalance between the upper and lower chambers creates a significant pressure difference, requiring a large electromagnetic force to overcome this difference and drive the moving iron core to open. This results in a loud knocking noise when the moving iron core stops moving. Furthermore, the integrated design of the carbon canister solenoid valve and the double check valve eliminates the natural attenuation effect of traditional pipelines on airflow noise, leading to increased airflow noise. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the present invention aims to provide an integrated carbon canister solenoid valve with a negative pressure balance design, thereby solving the technical problem of excessive noise in existing integrated carbon canister solenoid valves.
[0005] To solve the above-mentioned technical problems, the present invention provides an integrated carbon canister solenoid valve with a negative pressure balance design, comprising: The housing assembly has an air outlet channel at its bottom. The electromagnetic drive unit includes a magnetic yoke assembly, a winding assembly, and a moving iron core assembly. The winding assembly is connected inside the housing assembly and has a through hole arranged in the vertical direction. The through hole includes a sealed cavity and a communicating cavity that are not interconnected. The magnetic yoke assembly is connected inside the sealed cavity. The moving iron core assembly is slidably connected in the vertical direction in the through hole and is located below the magnetic yoke assembly. The upper and lower ends of the moving iron core assembly are located inside the sealed cavity and the communicating cavity, respectively. The moving iron core assembly has a balancing air passage. The sealed cavity is connected to the air outlet passage through the balancing air passage. The moving iron core assembly is used to control the opening and closing of the communicating cavity and the air outlet passage. The double-single-pass housing is connected to the lower end of the housing assembly and has a chamber that communicates with the air outlet channel. The chamber is equipped with a partition, which radially divides the chamber into an air inlet chamber in the middle and a first air outlet chamber and a second air outlet chamber on the left and right sides of the air inlet chamber. The upper end of the air inlet chamber is connected to the air outlet channel. The upper left and right side walls of the partition are respectively provided with a first flow channel and a second flow channel. The air inlet chamber is connected to the first air outlet chamber and the second air outlet chamber through the first flow channel and the second flow channel, respectively. The double-single-pass housing is provided with a main channel located below the partition. The bottom ends of the first air outlet chamber and the second air outlet chamber are both connected to the main channel.
[0006] With the above structure, the integrated carbon canister solenoid valve with negative pressure balance design of the present invention has the following advantages: the housing assembly serves as the carbon canister solenoid valve unit, and the double one-way housing serves as the double one-way valve unit. The through hole in the winding assembly is divided into a sealed cavity and a connected cavity that are not interconnected. The connected cavity can communicate with the outlet channel to maintain the basic function of the carbon canister solenoid valve, while the sealed cavity is connected to the outlet channel through the balance air passage. When the moving iron core assembly is started by electromagnetic force, the sealed cavity and the outlet channel at both ends of the moving iron core assembly remain connected to achieve negative pressure balance. Only a small electromagnetic force is needed to drive the moving iron core assembly to start, thereby reducing the knocking noise generated when the moving iron core assembly stops moving. In addition, by setting an inlet cavity, a first outlet cavity and a second outlet cavity, the airflow is divided into two paths after entering the inlet cavity and enters the first outlet cavity and the second outlet cavity respectively, which slows down the airflow velocity and makes the cavity act as a resonant cavity, thereby reducing the noise generated by the airflow.
[0007] As an improvement, a lip seal ring is fitted onto the outer wall of the yoke assembly. The lip seal ring includes a cylindrical part and a conical part located below the cylindrical part. The inner diameter of the upper end of the conical part is larger than the inner diameter of the lower end. The cylindrical part seals between the outer wall of the yoke assembly and the inner wall of the through hole, while the lower end of the conical part seals onto the outer wall of the moving iron core assembly. This structure, by setting a lip seal ring with a specific structure, provides a crucial sealing guarantee for the pressure balance design. Its cylindrical part ensures the reliability of the static seal between the yoke assembly and the winding assembly, while its unique conical part can tightly fit against the outer wall of the reciprocating moving iron core assembly to form a dynamic seal. This design ensures the non-communication between the sealing cavity and the connecting cavity, guaranteeing the basic function of the carbon canister solenoid valve.
[0008] As an improvement, the inner wall of the through hole is provided with an annular protrusion, and the cylindrical part abuts between the magnetic yoke assembly, the inner wall of the through hole and the upper end face of the annular protrusion. This structure provides precise axial positioning and support for the cylindrical part of the lip seal, which prevents the lip seal from axially displacing or deforming during air pressure fluctuations or long-term use, and further enhances the sealing stability of the sealing cavity.
[0009] As an improvement, the bottom end of the magnetic yoke assembly is provided with a first conical surface, and the inner wall of the cylindrical part is provided with a second conical surface that matches and seals with the first conical surface. With this structure, the first conical surface at the bottom end of the magnetic yoke assembly matches with the second conical surface on the inner wall of the lip seal to form a conical seal, which has a higher sealing specific pressure and better adaptability.
[0010] As an improvement, the cross-sectional area of the upper end of the moving iron core assembly is the same as the cross-sectional area of the end of the air outlet channel that is closest to the moving iron core assembly. With this structure, by making the cross-sectional area of the upper end of the moving iron core assembly the same as the cross-sectional area of the corresponding end of the air outlet channel, when the pressure on both sides of the air channel is balanced, the resultant force generated by the gas pressure acting on the upper and lower end faces of the moving iron core assembly in the axial direction is zero. In this state, the movement of the moving iron core assembly is completely controlled by electromagnetic force and spring force, thus completely eliminating the adverse effects of air pressure difference.
[0011] As an improvement, the housing assembly includes an upper housing and a lower housing, with the lower housing connected to the lower end of the upper housing, and the air outlet channel located on the lower housing in the vertical direction and passing through the bottom end of the lower housing.
[0012] As an improvement, the double single-pass housing is also provided with an airflow channel located below the chamber. The airflow channel is provided with a one-way valve assembly for controlling the opening and closing of the airflow channel. The airflow channel is connected to the air outlet channel through the chamber.
[0013] As an improvement, the airflow channel includes a first airflow channel and a second airflow channel, and the one-way valve assembly includes a first one-way valve assembly and a second one-way valve assembly. The first one-way valve assembly and the second one-way valve assembly are respectively disposed in the first airflow channel and the second airflow channel and are respectively used to control the opening and closing of the first airflow channel and the second airflow channel. The first airflow channel and the second airflow channel are both connected to the chamber, and the main flow channel is connected to the first airflow channel and the second airflow channel.
[0014] As an improvement, the electromagnetic drive unit also includes a spring that abuts against the magnetic yoke assembly and the moving iron core assembly.
[0015] As an improvement, the lower end of the magnetic yoke assembly is provided with a mounting groove. The balancing air passage includes an expanded diameter section and a reduced diameter section located below the expanded diameter section. Both the expanded diameter section and the reduced diameter section are arranged in the vertical direction. The upper end of the expanded diameter section passes through the upper end of the moving iron core assembly and connects to the sealing cavity. The lower end of the reduced diameter section passes through the lower end of the moving iron core assembly and connects to the air outlet passage. The upper and lower ends of the spring are located in the mounting groove and the expanded diameter section, respectively, and abut against the upper end face of the mounting groove and the lower end face of the expanded diameter section. With this structure, the two ends of the spring are respectively accommodated in the mounting groove of the magnetic yoke assembly and the expanded diameter section of the moving iron core assembly, achieving precise centering and stable support of the spring. This layout makes full use of the space of the balancing air passage inside the moving iron core assembly (expanded diameter section), making the spring an integrated structural part of the entire pressure balancing system. It not only ensures the reliability of the spring operation and prevents uneven wear, but also makes the axial structure of the electromagnetic drive unit more compact. While achieving core functions such as pressure balancing and noise reduction, it saves space to the maximum extent, which is conducive to the miniaturization design of the entire integrated module. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of the present invention.
[0017] Figure 2 for Figure 1 Cross-sectional view of section AA.
[0018] Figure 3 for Figure 2 A magnified view of part C in the middle.
[0019] Figure 4 This is a structural schematic diagram from another perspective of the present invention.
[0020] Figure 5 for Figure 4 Cross-sectional view of the middle BB section.
[0021] Reference numerals: 1. Exhaust channel; 2. Magnetic yoke assembly; 3. Winding assembly; 4. Moving iron core assembly; 5. Sealing cavity; 6. Connecting cavity; 7. Balanced air passage; 71. Expanded diameter section; 72. Reduced diameter section; 8. Double single-pass housing; 9. Chamber; 91. Inlet chamber; 92. First exhaust chamber; 93. Second exhaust chamber; 10. Lip seal ring; 101. Cylindrical section; 102. Conical section; 11. Annular protrusion; 12. First conical surface; 13. Second conical surface; 14. Upper housing; 15. Lower housing; 16. First airflow channel; 17. Second airflow channel; 18. First one-way valve assembly; 19. Second one-way valve assembly; 20. Spring; 21. Mounting groove; 22. First flow passage; 23. Second flow passage; 24. Main flow passage; 25. Baffle plate. Detailed Implementation
[0022] The following is a detailed description of an integrated carbon canister solenoid valve with a negative pressure balance design according to the present invention, with reference to the accompanying drawings.
[0023] like Figures 1 to 5 As shown, an integrated carbon canister solenoid valve with negative pressure balance design includes a housing assembly, an electromagnetic drive unit, and a double single-pass housing 8. The bottom end of the housing assembly is provided with an air outlet channel 1. Specifically, the housing assembly includes an upper housing 14 and a lower housing 15. The lower housing 15 is connected to the lower end of the upper housing 14, and the air outlet channel 1 is provided on the lower housing 15 in the vertical direction and passes through the bottom end of the lower housing 15.
[0024] like Figure 2 and Figure 3 As shown, the electromagnetic drive unit is housed within the housing assembly and includes a magnetic yoke assembly 2, a winding assembly 3, a moving iron core assembly 4, and a spring 20. The winding assembly 3 is connected within the housing assembly and has a through hole arranged vertically. The through hole includes a sealed cavity 5 and a connecting cavity 6 that are not interconnected. The sealed cavity 5 is located above the connecting cavity 6. The magnetic yoke assembly 2 is connected within the sealed cavity 5. The moving iron core assembly 4 is slidably connected within the through hole in the vertical direction and is located below the magnetic yoke assembly 2. The upper and lower ends of the moving iron core assembly 4 are located within the sealed cavity 5 and the connecting cavity 6, respectively. Inside, spring 20 abuts against magnetic yoke assembly 2 and moving iron core assembly 4; moving iron core assembly 4 is provided with balance air passage 7, sealing cavity 5 is connected to air outlet channel 1 through balance air passage 7, moving iron core assembly 4 is used to control the opening and closing between connecting cavity 6 and air outlet channel 1, the lower outer diameter of moving iron core assembly 4 is larger than the upper inner diameter of air outlet channel 1 and is used to block air outlet channel 1, upper housing 14 is provided with air inlet channel connected to connecting cavity 6, the specific principle of moving iron core assembly 4 controlling the opening and closing between connecting cavity 6 and air outlet channel 1 is existing technology and will not be described in detail here.
[0025] The double single-pass housing 8 is connected to the lower end of the housing assembly and has a chamber 9 that communicates with the air outlet channel 1. Specifically, it is connected to the lower housing 15 below.
[0026] like Figure 2 and Figure 3 As shown, a lip seal ring 10 is fitted onto the outer wall of the magnetic yoke assembly 2. The lip seal ring 10 includes a cylindrical part 101 and a tapered part 102 located below the cylindrical part 101. The inner diameter of the upper end of the tapered part 102 is larger than the inner diameter of the lower end. The cylindrical part 101 is sealed between the outer wall of the magnetic yoke assembly 2 and the inner wall of the through hole. The lower end of the tapered part 102 is sealed onto the outer wall of the moving iron core assembly 4. The lip seal ring 10 separates the sealing cavity 5 and the connecting cavity 6, thus achieving the separation of the sealing cavity 5 and the connecting cavity 6.
[0027] Continue to refer to Figure 2 and Figure 3The inner wall of the through hole is provided with an annular protrusion 11, and the cylindrical part 101 abuts against the magnetic yoke assembly 2, the inner wall of the through hole and the upper end face of the annular protrusion 11; the bottom end of the magnetic yoke assembly 2 is provided with a first conical surface 12, and the inner wall of the cylindrical part 101 is provided with a second conical surface 13 that matches and seals against the first conical surface 12; the lower end of the magnetic yoke assembly 2 is provided with a mounting groove 21, and the balance air passage 7 includes an expanded diameter part 71 and a reduced diameter part 72 located below the expanded diameter part 71. The expanded diameter part 71 and the reduced diameter part 72 are both arranged in the vertical direction. The upper end of the expanded diameter part 71 passes through the upper end of the moving iron core assembly 4 and connects to the sealing cavity 5, and the lower end of the reduced diameter part 72 passes through the lower end of the moving iron core assembly 4 and connects to the air outlet passage 1. The upper and lower ends of the spring 20 are respectively located in the mounting groove 21 and the expanded diameter part 71 and abut against the upper end face of the mounting groove 21 and the lower end face of the expanded diameter part 71.
[0028] The housing assembly serves as the carbon canister solenoid valve unit, and the double one-way housing 8 serves as the double one-way valve unit. The through hole in the winding assembly 3 is divided into a non-interconnected sealed cavity 5 and a connected cavity 6. The connected cavity 6 can be connected to the air outlet channel 1 to maintain the basic function of the carbon canister solenoid valve, while the sealed cavity 5 is connected to the air outlet channel 1 through the balance air channel 7. When the electromagnetic force drives the moving iron core assembly 4 to start, the sealed cavity 5 and the air outlet channel 1 at the upper and lower ends of the moving iron core assembly 4 are always connected to achieve negative pressure balance. Only a small electromagnetic force is needed to drive the moving iron core assembly 4 to start, thereby reducing the knocking noise generated when the moving iron core assembly 4 stops moving.
[0029] Furthermore, the cross-sectional area of the upper end of the moving iron core assembly 4 is the same as the cross-sectional area of the end of the air outlet channel 1 closest to the moving iron core assembly 4. Specifically, the cross-sectional area of the upper end of the moving iron core assembly 4 is the same as the cross-sectional area of the upper end of the air outlet channel 1. When the balancing air passage 7 connects the pressures on both sides, the resultant force generated axially by the gas pressure acting on the upper and lower end faces of the moving iron core assembly 4 is zero. In this state, the movement of the moving iron core assembly 4 is completely controlled by electromagnetic force and spring force, thus completely eliminating the adverse effects caused by the air pressure difference.
[0030] like Figure 5As shown, the double-one-way housing 8 also has an airflow channel located below the chamber 9. The airflow channel contains a one-way valve assembly for controlling the opening and closing of the airflow channel. The airflow channel is connected to the outlet channel 1 through the chamber 9. The integrated design of the carbon canister solenoid valve and the double one-way valve eliminates the natural attenuation effect of traditional pipelines on airflow noise, leading to increased airflow noise. To reduce airflow noise, a partition 25 is provided inside the chamber 9. The partition 25 radially divides the chamber 9 into an inlet chamber 91 located in the middle and a chamber located to the left of the inlet chamber 91. The first air outlet chamber 92 and the second air outlet chamber 93 on the right sides are connected to the air outlet channel 1 at the upper end of the air inlet chamber 91. The left and right side walls of the upper end of the partition 25 are respectively provided with the first flow channel 22 and the second flow channel 23. The air inlet chamber 91 is connected to the first air outlet chamber 92 and the second air outlet chamber 93 through the first flow channel 22 and the second flow channel 23 respectively. The double single-pass housing 8 is provided with the main flow channel 24 located below the partition 25. The bottom end of the first air outlet chamber 92 and the bottom end of the second air outlet chamber 93 are both connected to the main flow channel 24.
[0031] After entering the intake chamber 91, the airflow is split into two paths and enters the first exhaust chamber 92 and the second exhaust chamber 93 respectively, which slows down the airflow speed and makes the chamber 9 act as a resonant cavity, thereby reducing the noise generated by the airflow.
[0032] The airflow channels include a first airflow channel 16 and a second airflow channel 17. The one-way valve assembly includes a first one-way valve assembly 18 and a second one-way valve assembly 19. The first one-way valve assembly 18 and the second one-way valve assembly 19 are respectively disposed in the first airflow channel 16 and the second airflow channel 17 and are respectively used to control the opening and closing of the first airflow channel 16 and the second airflow channel 17. The first airflow channel 16 and the second airflow channel 17 are both connected to the chamber 9. The main flow channel 24 is connected to the first airflow channel 16 and the second airflow channel 17.
[0033] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiment. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
Claims
1. An integrated carbon canister solenoid valve with a negative pressure balance design, characterized in that, include: A housing assembly, wherein an air outlet channel (1) is provided at the bottom end of the housing assembly. The electromagnetic drive unit includes a magnetic yoke assembly (2), a winding assembly (3), and a moving iron core assembly (4). The winding assembly (3) is connected to the housing assembly. The winding assembly (3) has a through hole arranged in the vertical direction. The through hole includes a sealed cavity (5) and a connecting cavity (6) that are not connected to each other. The magnetic yoke assembly (2) is connected to the sealed cavity (5). The moving iron core assembly (4) is slidably connected in the through hole in the vertical direction and is located below the magnetic yoke assembly (2). The upper and lower ends of the moving iron core assembly (4) are located in the sealed cavity (5) and the connecting cavity (6), respectively. The moving iron core assembly (4) has a balancing air passage (7). The sealed cavity (5) is connected to the air outlet channel (1) through the balancing air passage (7). The moving iron core assembly (4) is used to control the connection and disconnection between the connecting cavity (6) and the air outlet channel (1). A double-single-pass housing (8) is connected to the lower end of the housing assembly and has a chamber (9) communicating with the air outlet channel (1). The chamber (9) is provided with a partition (25), which radially divides the chamber (9) into an air inlet chamber (91) in the middle and a first air outlet chamber (92) and a second air outlet chamber (93) on the left and right sides of the air inlet chamber (91). The upper end of the air inlet chamber (91) is connected to the air outlet channel (1), and the upper left and right sides of the partition (25) are connected to the air outlet channel (1). The wall is provided with a first flow channel (22) and a second flow channel (23). The air inlet chamber (91) is connected to the first air outlet chamber (92) and the second air outlet chamber (93) through the first flow channel (22) and the second flow channel (23) respectively. The double single-pass housing (8) is provided with a main flow channel (24) located below the partition (25). The bottom end of the first air outlet chamber (92) and the bottom end of the second air outlet chamber (93) are both connected to the main flow channel (24).
2. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 1, characterized in that, The outer wall of the magnetic yoke assembly (2) is fitted with a lip seal ring (10). The lip seal ring (10) includes a cylindrical part (101) and a conical part (102) located below the cylindrical part (101). The inner diameter of the upper end of the conical part (102) is larger than the inner diameter of the lower end. The cylindrical part (101) is sealed between the outer wall of the magnetic yoke assembly (2) and the inner wall of the through hole. The lower end of the conical part (102) is sealed on the outer wall of the moving iron core assembly (4).
3. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 2, characterized in that, The inner wall of the through hole is provided with an annular protrusion (11), and the cylindrical part (101) abuts against the magnetic yoke assembly (2), the inner wall of the through hole and the upper end face of the annular protrusion (11).
4. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 2, characterized in that, The bottom end of the magnetic yoke assembly (2) is provided with a first conical surface (12), and the inner wall of the cylindrical part (101) is provided with a second conical surface (13) that matches and seals with the first conical surface (12).
5. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 1, characterized in that, The cross-sectional area of the upper end of the moving iron core assembly (4) is the same as the cross-sectional area of the end of the air outlet channel (1) that is close to the moving iron core assembly (4).
6. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 1, characterized in that, The housing assembly includes an upper housing (14) and a lower housing (15). The lower housing (15) is connected to the lower end of the upper housing (14). The air outlet channel (1) is located on the lower housing (15) in the vertical direction and passes through the bottom end of the lower housing (15).
7. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 1, characterized in that, The double single-pass housing (8) is also provided with an airflow channel located below the chamber (9). The airflow channel is provided with a one-way valve assembly for controlling the opening and closing of the airflow channel. The airflow channel is connected to the air outlet channel (1) through the chamber (9).
8. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 7, characterized in that, The airflow channel includes a first airflow channel (16) and a second airflow channel (17). The one-way valve assembly includes a first one-way valve assembly (18) and a second one-way valve assembly (19). The first one-way valve assembly (18) and the second one-way valve assembly (19) are respectively disposed in the first airflow channel (16) and the second airflow channel (17) and are respectively used to control the opening and closing of the first airflow channel (16) and the second airflow channel (17). The first airflow channel (16) and the second airflow channel (17) are both connected to the chamber (9). The main flow channel (24) connects the first airflow channel (16) and the second airflow channel (17).
9. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 1, characterized in that, The electromagnetic drive unit also includes a spring (20), which abuts against the magnetic yoke assembly (2) and the moving iron core assembly (4).
10. The integrated carbon canister solenoid valve with negative pressure balance design according to claim 9, characterized in that, The lower end of the magnetic yoke assembly (2) is provided with a mounting groove (21). The balance air passage (7) includes an enlarged diameter section (71) and a reduced diameter section (72) located below the enlarged diameter section (71). The enlarged diameter section (71) and the reduced diameter section (72) are both arranged in the vertical direction. The upper end of the enlarged diameter section (71) passes through the upper end of the moving iron core assembly (4) and connects to the sealing cavity (5). The lower end of the reduced diameter section (72) passes through the lower end of the moving iron core assembly (4) and connects to the air outlet passage (1). The upper and lower ends of the spring (20) are located in the mounting groove (21) and the enlarged diameter section (71) respectively and abut against the upper end face of the mounting groove (21) and the lower end face of the enlarged diameter section (71).