Electromagnetic valve for suspension system

Abstract

The utility model discloses an electromagnetic valve for a suspension system, which relates to the technical field of electromagnetic valves and comprises a shell, a coil arranged in the shell, a yoke piece arranged at one end of the coil, a fixed iron core arranged at the other end of the coil and an armature arranged in an inner hole of the coil, and the yoke piece, the armature, the fixed iron core and the shell form a magnetic loop. And a permanent magnet for increasing electromagnetic force is arranged on the magnetic loop. According to the scheme, the electromagnetic valve generates larger electromagnetic force under the same excitation intensity through the permanent magnet which is economical and simple in structure, compared with the prior art, the number of turns of coils of the electromagnetic valve can be smaller, the size of the electromagnetic valve can be smaller, the weight of the electromagnetic valve is lighter, the cost of the electromagnetic valve is lower, and the requirement of a new energy automobile for light weight of electronic parts is better met.

Description

Technical Field

[0001] The utility model relates to the technical field of electromagnetic valves, and more specifically to the technical field of electromagnetic valves used in suspension systems. Background Art

[0002] The existing common solenoid valve structure is usually composed of a yoke, an armature, a coil, a housing, a spring, a fixed iron core, etc. The working principle is as follows: the yoke, the armature, the fixed iron core and the housing are all made of magnetic conductive materials. When the solenoid valve is energized, the coil is energized to generate a magnetic field. The magnetic flux lines form a magnetic circuit in the yoke, the armature, the fixed iron core, the housing and the permanent magnet and are all magnetized. The armature as a moving part is attracted by the fixed iron core and moves toward the fixed iron core.

[0003] For the solenoid valve used in air suspension, in order to reduce the situation that the moving parts in the solenoid valve are in place due to the large kinetic energy and generate huge noise when the solenoid valve is energized, a minimum closing current will be applied to the solenoid valve from the control point of view during the power-on process. The current size can just ensure that the moving parts of the solenoid valve can overcome the force of the return spring and move to the position or close to the position, and then a larger current will be applied to ensure that the solenoid valve is completely closed. This control logic can achieve that the moving parts of the solenoid valve have only a small impact on the stopper to achieve the effect of reducing or eliminating noise;

[0004] However, the preload force of the spring of this type of solenoid valve is relatively large, and the moving parts of the solenoid valve require a larger electromagnetic force to overcome the spring force. Usually, the electromagnetic force can be increased by increasing the number of coil turns, reducing the magnetic gap, increasing the control current, etc. However, if the electromagnetic force is to be significantly increased, increasing the number of coil turns will increase the coil volume and increase the amount of copper wire used. Reducing the magnetic gap will only have a limited effect on improving the electromagnetic force, and increasing the control current will increase energy consumption. In today's new energy vehicles, which have high requirements for the energy consumption of electronic products, increasing the control current is undoubtedly not in line with the mainstream. Utility Model Content

[0005] The purpose of the utility model is to solve the above technical problems and provide a solenoid valve for a suspension system.

[0006] In order to achieve the above-mentioned purpose, the utility model specifically adopts the following technical solutions:

[0007] The utility model provides an electromagnetic valve for a suspension system, comprising a shell, a coil arranged in the shell, a yoke arranged at one end of the coil, a fixed iron core arranged at the other end of the coil, and an armature arranged in an inner hole of the coil; the yoke, the armature, the fixed iron core and the shell form a magnetic circuit, and a permanent magnet for increasing electromagnetic force is arranged on the magnetic circuit.

[0008] Specifically, this solution uses economical and simply constructed permanent magnets to enable the solenoid valve to generate greater electromagnetic force under the same current control, thereby better meeting the new energy vehicle's demand for low energy consumption of electronic components. Because this solution can more easily obtain a larger electromagnetic force under the same magnetic conductivity, compared with the existing technical solutions, the solenoid valve of this solution can have fewer coil turns and a smaller volume. Fewer coil turns can also make the solenoid valve lighter and less expensive, thereby better meeting the new energy vehicle's demand for lightweight electronic components.

[0009] In one embodiment, the permanent magnet is located on the magnetic circuit between the yoke and the armature, and the permanent magnet is arranged on the armature.

[0010] In one embodiment, the permanent magnet is arranged on the armature on a side close to the yoke piece and / or on the armature on a side close to the stator core.

[0011] In one embodiment, the permanent magnet is located on the magnetic circuit between the yoke and the housing.

[0012] In one embodiment, the permanent magnet is disposed on a yoke piece close to one side of the housing, and a gap exists between the permanent magnet and the housing.

[0013] In one embodiment, the permanent magnet is disposed on the housing at a side close to the yoke, and a gap exists between the permanent magnet and the yoke.

[0014] In one embodiment, the permanent magnet is located on the magnetic circuit between the stator core and the housing.

[0015] In one embodiment, the permanent magnet is disposed on a fixed iron core close to one side of the housing, and a gap exists between the permanent magnet and the housing.

[0016] In one embodiment, the permanent magnet is disposed on the housing close to a side of the fixed iron core, and a gap exists between the permanent magnet and the fixed iron core.

[0017] In one embodiment, a tubular support body sleeved on the outside of the armature is fixedly disposed in the inner hole of the coil, and accommodating portions for accommodating steel balls are circumferentially distributed on the outer wall of the armature. The steel balls partially extend out of the outer wall of the armature and contact the inner wall of the tubular support body.

[0018] Specifically, at least three axial grooves or at least three radial grooves are distributed circumferentially on the outer wall of the armature, and a steel ball is arranged in each axial groove or each radial groove. The steel ball part extends out of the outer wall of the armature and contacts the inner wall of the tubular support body. Both ends of each axial groove are provided with a closing opening to prevent the corresponding steel ball from slipping out. The length and number of the grooves can be selected according to actual conditions, and the number of steel balls in the axial grooves is determined according to actual conditions.

[0019] In one embodiment, it also includes an armature shaft and a spring. The armature and the fixed iron core are both provided with shaft holes allowing the armature shaft to slide through. The spring is sleeved on the armature shaft between the armature and the fixed iron core. The upper and lower ends of the spring are respectively connected to the bottom of the armature and the top of the fixed iron core.

[0020] Specifically, the fixed iron core is cylindrical, and a secondary stepped conical groove with a diameter larger than the diameter of the armature shaft is provided at the central position of the top of the fixed iron core. The diameter of the primary step groove is larger than the diameter of the secondary step groove, and the shaft hole is located at the center of the secondary step groove; the armature is cylindrical, and a cylindrical protrusion matching the size of the primary step groove is provided at the bottom of the armature. The spring is located in the secondary step groove, the lower end of the spring is fixedly connected to the top of the secondary step groove, and the upper end of the spring is connected to the bottom of the cylindrical protrusion.

[0021] In addition, the solenoid valve also includes a sealing assembly arranged in the movable space inside the bottom of the outer shell (that is, the space below the fixed iron core, which is fixedly installed on the outer shell), and the sealing assembly is sleeved on the end of the armature shaft extending from the bottom of the fixed iron core. A stop component is provided on the inner side of the bottom of the outer shell for blocking the axial travel of the sealing assembly.

[0022] In one embodiment, the yoke, the armature, the fixed iron core and the housing are all made of magnetic conductive materials.

[0023] The beneficial effects of the utility model are as follows:

[0024] 1. This structure uses an economical and simple permanent magnet to enable the solenoid valve to generate greater electromagnetic force under the same current control, which better meets the demand of new energy vehicles for low energy consumption of electronic components;

[0025] 2. Because this structure is easier to obtain a larger electromagnetic force under the same magnetic conductivity, compared with the original solution, the solenoid valve of this structure can have fewer coil turns and a smaller volume. Fewer coil turns can also make the solenoid valve lighter and less expensive, better meeting the demand for lightweight electronic components in new energy vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the solenoid valve used in the suspension system of the utility model when it is not powered;

[0027] Figure 2 It is a schematic diagram of the structure of the electromagnetic valve used in the suspension system of the utility model when it is powered on;

[0028] Figure 3 It is a structural schematic diagram in which the permanent magnet is arranged outside the fixed iron core close to the outer shell;

[0029] Figure 4 It is a schematic diagram of the structure in which the permanent magnet is arranged outside the yoke and close to the housing;

[0030] Figure 5 It is a structural layout form of the accommodation part;

[0031] Figure 6 It is another structural layout form of the accommodation part;

[0032] Figure numerals: 1-permanent magnet, 2-yoke, 3-armature, 4-coil, 5-housing, 6-spring, 7-fixed iron core, 8-armature shaft, 9-moving component, 10-stop component, 11-tubular support body, 12-steel ball. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0036] In the description of the embodiments of the present invention, it should be noted that the terms "inside", "outside", "upper", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the utility model product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] Example 1

[0038] like Figure 1 to Figure 2As shown, this embodiment provides a solenoid valve for a suspension system, including a housing 5, a coil 4 arranged in the housing 5, a yoke 2 arranged on the top of the coil 4, an armature 3 movably arranged in the inner hole of the coil 4, and a fixed iron core 7 arranged below the coil 4 and cooperating with the armature 3. The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 form a magnetic circuit, and a permanent magnet 1 for increasing the electromagnetic force is arranged on the magnetic circuit.

[0039] The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 are all made of magnetic conductive materials.

[0040] The permanent magnet 1 is located on the magnetic circuit between the yoke 2 and the armature 3 , and the permanent magnet 1 is arranged on the armature 3 .

[0041] The permanent magnet 1 is disposed at one or more positions of the top outer side of the armature 3 , the top inner side of the armature 3 , the bottom outer side of the armature 3 , or the bottom inner side of the armature 3 .

[0042] Specifically, taking the example of the permanent magnet 1 being arranged on the outer side of the top of the armature 3, the installation matching relationship between the permanent magnet 1 and the armature 3 is specifically described: a placement table for placing the permanent magnet 1 is arranged circumferentially on the outer side of the top of the armature 3, and the permanent magnet 1 is fixedly arranged on the placement table, and the outer shape of the permanent magnet 1 is the same as the outer shape of the armature 3. Taking the armature 3 as a cylindrical shape as an example, the shape of the permanent magnet 1 is a circular ring, and the outer diameter of the permanent magnet 1 is the same as or slightly smaller than the armature 3 (generally less than 0.1 mm). The shape of the permanent magnet 1 can also be other shapes that can meet the design requirements, such as a square ring, an elliptical ring, etc.

[0043] When the permanent magnet 1 is arranged on the outside of the bottom of the armature 3, the installation and matching relationship between the permanent magnet 1 and the armature 3 is the same as that when the permanent magnet 1 is arranged on the outside of the top of the armature 3, which will not be repeated.

[0044] Taking the example of the permanent magnet 1 being arranged on the inner side of the top of the armature 3, the installation and matching relationship between the permanent magnet 1 and the armature 3 is specifically explained: an annular placement table for placing the permanent magnet 1 is arranged at the top axial hole of the armature 3, and the permanent magnet 1 is fixedly arranged on the placement table. The external shape of the permanent magnet 1 is the same as the shape of the placement table, and a center hole allowing the armature 3 axis to pass through is arranged in the permanent magnet 1.

[0045] When the permanent magnet 1 is arranged on the inner side of the bottom of the armature 3, the installation and matching relationship between the permanent magnet 1 and the armature 3 is the same as that when the permanent magnet 1 is arranged on the inner side of the top of the armature 3, which will not be repeated.

[0046] Specifically, this solution uses an economical and simple permanent magnet 1 to enable the solenoid valve to generate a greater electromagnetic force under the same current control, which better meets the new energy vehicle's demand for low energy consumption of electronic components. Because this solution is easier to obtain a larger electromagnetic force under the same magnetic conductivity, compared with the prior art solution (excluding the permanent magnet 1), the solenoid valve of this solution can have fewer turns of the coil 4 and a smaller volume. Fewer turns of the coil 4 can also make the solenoid valve lighter and lower in cost, which better meets the new energy vehicle's demand for lightweight electronic components.

[0047] Example 2

[0048] like Figure 4 As shown, this embodiment provides a solenoid valve for a suspension system, including a housing 5, a coil 4 arranged in the housing 5, a yoke 2 arranged on the top of the coil 4, an armature 3 movably arranged in the inner hole of the coil 4, and a fixed iron core 7 arranged below the coil 4 and cooperating with the armature 3. The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 form a magnetic circuit, and a permanent magnet 1 for increasing the electromagnetic force is arranged on the magnetic circuit.

[0049] The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 are all made of magnetic conductive materials.

[0050] The permanent magnet 1 is located on the magnetic circuit between the yoke 2 and the housing 5 .

[0051] The permanent magnet 1 is disposed on the yoke piece 2 on a side close to the housing 5 , and there is a gap between the permanent magnet 1 and the housing 5 .

[0052] Example 3

[0053] like Figure 4 As shown, this embodiment provides a solenoid valve for a suspension system, including a housing 5, a coil 4 arranged in the housing 5, a yoke 2 arranged on the top of the coil 4, an armature 3 movably arranged in the inner hole of the coil 4, and a fixed iron core 7 arranged below the coil 4 and cooperating with the armature 3. The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 form a magnetic circuit, and a permanent magnet 1 for increasing the electromagnetic force is arranged on the magnetic circuit.

[0054] The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 are all made of magnetic conductive materials.

[0055] The permanent magnet 1 is located on the magnetic circuit between the yoke 2 and the housing 5 .

[0056] The permanent magnet 1 is disposed on the housing 5 at a side close to the yoke 2 , and there is a gap between the permanent magnet 1 and the yoke 2 .

[0057] Example 4

[0058] like Figure 3As shown, this embodiment provides a solenoid valve for a suspension system, including a housing 5, a coil 4 arranged in the housing 5, a yoke 2 arranged on the top of the coil 4, an armature 3 movably arranged in the inner hole of the coil 4, and a fixed iron core 7 arranged below the coil 4 and cooperating with the armature 3. The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 form a magnetic circuit, and a permanent magnet 1 for increasing the electromagnetic force is arranged on the magnetic circuit.

[0059] The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 are all made of magnetic conductive materials.

[0060] The permanent magnet 1 is located on the magnetic circuit between the fixed iron core 7 and the housing 5 .

[0061] The permanent magnet 1 is disposed on the fixed iron core 7 close to the housing 5 , and there is a gap between the permanent magnet 1 and the housing 5 .

[0062] Example 5

[0063] like Figure 3 As shown, this embodiment provides a solenoid valve for a suspension system, including a housing 5, a coil 4 arranged in the housing 5, a yoke 2 arranged on the top of the coil 4, an armature 3 movably arranged in the inner hole of the coil 4, and a fixed iron core 7 arranged below the coil 4 and cooperating with the armature 3. The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 form a magnetic circuit, and a permanent magnet 1 for increasing the electromagnetic force is arranged on the magnetic circuit.

[0064] The yoke 2, the armature 3, the fixed iron core 7 and the housing 5 are all made of magnetic conductive materials.

[0065] The permanent magnet 1 is located on the magnetic circuit between the fixed iron core 7 and the housing 5 .

[0066] The permanent magnet 1 is disposed on the housing 5 at a side close to the fixed iron core 7 , and there is a gap between the permanent magnet 1 and the fixed iron core 7 .

[0067] Example 6

[0068] The following optimizations are made based on any one of Embodiments 1 to 3, specifically:

[0069] It also includes an armature 3 shaft and a spring 6. The armature 3 and the fixed iron core 7 are both provided with shaft holes allowing the armature 3 shaft to slide through. The spring 6 is sleeved on the armature 3 shaft between the armature 3 and the fixed iron core 7. The upper and lower ends of the spring 6 are respectively connected to the bottom of the armature 3 and the top of the fixed iron core 7.

[0070] Specifically, the fixed iron core 7 is cylindrical, and a secondary stepped conical groove with a diameter greater than the diameter of the armature 3 axis is provided at the central position of the top of the fixed iron core 7, the diameter of the primary stepped groove is greater than the diameter of the secondary stepped groove, and the axial hole is located at the center of the secondary stepped groove; the armature 3 is cylindrical, and a cylindrical protrusion matching the size of the primary stepped groove is provided at the bottom of the armature 3, the spring 6 is located in the secondary stepped groove, the lower end of the spring 6 is fixedly connected to the top of the secondary stepped groove, and the upper end of the spring 6 is connected to the bottom of the cylindrical protrusion.

[0071] In addition, the solenoid valve also includes a sealing assembly arranged in the movable space inside the bottom of the outer shell 5 (that is, the space below the fixed iron core 7, and the fixed iron core 7 is fixedly installed on the outer shell 5), and the sealing assembly is sleeved on the end of the armature 3 shaft extending from the bottom of the fixed iron core 7. A stop component 10 is provided on the inner side of the bottom of the outer shell 5 for blocking the axial travel of the sealing assembly.

[0072] Working principle: the yoke 2, armature 3, fixed iron core 7 and housing 5 are all made of magnetic conductive materials. After the solenoid valve is energized, the coil 4 is energized to generate a magnetic field. The magnetic lines of flux form a magnetic circuit in the yoke 2, armature 3, fixed iron core 7, housing 5 and permanent magnet 1 and are all magnetized. The armature 3 as a moving part is attracted by the fixed iron core 7, and the armature 3 moves in the direction of the fixed iron core 7. The armature 3 drives the moving component 9 to move together until the moving component 9 contacts the stop component 10.

[0073] When a small amount of electricity is passed through the coil 4, the coil 4 can only generate a small magnetic field strength, so the armature 3 can only obtain a small electromagnetic force. At this time, the magnetic field of the permanent magnet 1 can increase the magnetic flux in the magnetic circuit of the solenoid valve, so that the armature 3 has a larger electromagnetic force.

[0074] The present invention discloses three arrangements of permanent magnets 1: the permanent magnets 1 are arranged on the armature 3; the permanent magnets 1 are arranged on the armature 3 (such as Figure 1 and Figure 2 ); The permanent magnet 1 is arranged on the fixed core 7 near the housing 5 (such as Figure 3 ); The permanent magnet 1 is arranged outside the yoke 2 and close to the housing 5 (such as Figure 4 ).

[0075] Example 7

[0076] like Figure 5 As shown, this embodiment is based on any one of Embodiments 1 to 4 and is optimized as follows, specifically:

[0077] A tubular support body 11 is fixedly arranged in the inner hole of the coil 4 and is sleeved on the outside of the armature 3. At least three axial slide grooves are distributed circumferentially on the outer wall of the armature 3. Each axial slide groove is provided with a steel ball 12. Each steel ball 12 partially extends out of the outer wall of the armature 3 and contacts the inner wall of the tubular support body 11.

[0078] Specifically, both ends of each axial slide groove are provided with closing ends to prevent the corresponding steel ball 12 from sliding out, and the length and number of the slide grooves can be selected according to actual conditions.

[0079] When the axial slide groove is a through groove that passes through the upper and lower ends of the outer wall of the armature 3, the number of the axial slide grooves can be set to three or other numbers greater than three. Three axial slide grooves are the preferred method, and closing ends are provided at the penetration points at the upper and lower ends of each axial slide groove to prevent the steel balls 12 inside the axial slide groove from falling; when the axial slide groove is a through groove, the number of steel balls 12 in each axial slide groove is at least two. When the number of steel balls 12 is two, there is one at each end of the axial slide groove.

[0080] When the axial slide groove is a semi-through groove that passes through the upper end or lower end of the outer wall of the armature 3, the number of the axial slide grooves can be set to three or other numbers greater than three. Three axial slide grooves are the preferred method, and a closing end is provided at the penetration point of each axial slide groove to prevent the steel ball 12 inside the axial slide groove from falling; when the axial slide groove is a semi-through groove, the number of steel balls 12 in each axial slide groove is at least one, and the specific number is determined according to the length of the axial slide groove.

[0081] When the axial groove is a strip groove located in the middle of the outer wall of the armature 3, in order to ensure the stability of the sliding process, the number of axial grooves is at least three, and the number of steel balls 12 in each axial groove is one, and the specific number is determined according to the length of the axial groove.

[0082] Example 8

[0083] Figure 6 As shown, this embodiment is based on any one of Embodiments 1 to 4 and is optimized as follows, specifically:

[0084] A tubular support body 11 sleeved on the outside of the armature 3 is fixedly arranged in the inner hole of the coil 4, and at least three radial grooves are circumferentially distributed on the outer wall of the armature 3, and a steel ball 12 is arranged in each radial groove, and each steel ball 12 partially extends out of the outer wall of the armature 3 and contacts the inner wall of the tubular support body 11. Specifically, when the radial groove is a hole groove located on the outer wall of the armature 3, in order to ensure the stability of the sliding process, the number of radial grooves is at least three, and the number of steel balls 12 in each radial groove is one.

Claims

1. A solenoid valve for a suspension system, characterized in that: The invention comprises a housing (5), a coil (4) arranged in the housing (5), a yoke (2) arranged at one end of the coil (4), a fixed iron core (7) arranged at the other end of the coil (4), and an armature (3) arranged in the inner hole of the coil (4); the yoke (2), the armature (3), the fixed iron core (7) and the housing (5) form a magnetic circuit, and a permanent magnet (1) for increasing electromagnetic force is arranged on the magnetic circuit.

2. The solenoid valve for a suspension system according to claim 1, characterized in that: The permanent magnet (1) is located on a magnetic circuit between the yoke piece (2) and the armature (3), and the permanent magnet (1) is arranged on the armature (3).

3. The solenoid valve for a suspension system according to claim 2, characterized in that: The permanent magnet (1) is arranged on the armature (3) on a side close to the yoke (2) and / or on the armature (3) on a side close to the fixed iron core (7).

4. The solenoid valve for a suspension system according to claim 1, characterized in that: The permanent magnet (1) is located on the magnetic circuit between the yoke (2) and the housing (5).

5. The solenoid valve for a suspension system according to claim 4, characterized in that: The permanent magnet (1) is arranged on the yoke piece (2) on a side close to the housing (5), and a gap exists between the permanent magnet (1) and the housing (5).

6. The solenoid valve for a suspension system according to claim 4, characterized in that: The permanent magnet (1) is arranged on the housing (5) on a side close to the yoke (2), and a gap exists between the permanent magnet (1) and the yoke (2).

7. The solenoid valve for a suspension system according to claim 1, characterized in that: The permanent magnet (1) is located on the magnetic circuit between the fixed iron core (7) and the housing (5).

8. The solenoid valve for a suspension system according to claim 7, characterized in that: The permanent magnet (1) is arranged on the fixed iron core (7) on a side close to the outer shell (5), and a gap exists between the permanent magnet (1) and the outer shell (5).

9. The solenoid valve for a suspension system according to claim 7, characterized in that: The permanent magnet (1) is arranged on the housing (5) at a side close to the fixed iron core (7), and a gap exists between the permanent magnet (1) and the fixed iron core (7).

10. A solenoid valve for a suspension system according to any one of claims 1 to 9, characterized in that: A tubular support body (11) is fixedly arranged in the inner hole of the coil (4) and is sleeved on the outside of the armature (3). Receiving portions for accommodating steel balls are distributed circumferentially on the outer wall of the armature (3). The steel balls partially extend out of the outer wall of the armature (3) and contact the inner wall of the tubular support body (11).

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