JP2003188014A - Electromagnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnet that can suppress an attractive power drop at the position where strokes are small in a stator core and a moving core, and improve attraction at the position where the stroke is large for them. <P>SOLUTION: A circular projection 19C is provided at the axial ends of the moving core 19 with a circular recess 17A made on the axial end of the stator core 17. The outer diameter 19D of the circular projection 19C is gradually reduced toward the top of the projection with the inner diameter 19E increasing in the same manner. The circular recess 17A reduces its outer diameter 17B gradually toward the bottom of the recess with its outer diameter 17C gradually increased. The bottom of the recess is formed so as to match the inclination of the projection 19C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic valve in which a movable iron core is axially moved and attracted to a fixed iron core by an attractive force generated by energization, and more particularly to an electromagnet suitable for use in the electromagnetic valve.

[0002]

2. Description of the Related Art An electromagnet of this type is provided with a movable iron core movably in the axial direction so as to face a fixed iron core arranged in a coil body, and the movable iron core has a small diameter at an axial end portion facing the fixed iron core. A step convex portion and a step convex portion having a medium diameter larger than this step convex portion are formed, and a small diameter step convex portion is fitted to the fixed core at an axial end portion facing the movable core. A small-diameter stepped concave portion slightly larger than the small-diameter stepped convex portion and a medium-diameter stepped concave portion slightly larger than the medium-diameter stepped convex portion are formed to fit the medium-diameter stepped convex portion. , At the position where the stroke between the fixed iron core and the movable iron core is large, the magnetic flux flows between the tip side ridge of the small-diameter step convex portion and the opening side ridge of the small-diameter step concave portion and the medium-diameter step. The magnetic flux flowing between the tip side ridge of the convex portion and the opening side ridge of the medium-diameter stepped concave portion to eliminate saturation of the magnetic flux and improve the attractive force. I am trying. (For example, JP-A-9
-306731).

[0003]

However, in such a conventional electromagnet, at the position where the strokes of the fixed iron core and the movable iron core are small, the small-diameter step convex portion fits into the small-diameter step concave portion and the medium-diameter step portion. Since the convex projection fits into the medium-diameter stepped recess, between the outer peripheral surface of the small-diameter stepped projection and the inner peripheral surface of the small-diameter stepped recess, and the outer peripheral surface of the medium-diameter stepped projection. Magnetic flux flows in a radial direction perpendicular to the axial direction between the inner peripheral surface of the stepped recess of medium diameter, and a radial attractive force is generated, reducing the attractive force for axially attracting the movable iron core. I will end up.

The present invention provides an electromagnet which suppresses the reduction of the attractive force in the axial direction at the position where the stroke of the fixed iron core and the movable iron core is small, and improves the attractive force at the position where the stroke of the fixed iron core and the movable iron core is large. Is an issue.

[0005]

Therefore, in the present invention,
A fixed iron core is placed inside the coil body around which the coil is wound, and a movable iron core is provided in the coil body so as to be movable in the axial direction so as to face the fixed iron core. The movable iron core is fixed by the attraction force generated by energizing the coil. An electromagnet that is attracted to a fixed core and a movable core, and one of the axially opposite end portions of the fixed iron core and the movable iron core is formed with an annular projection protruding in the axial direction, and the other is provided with an annular recess into which the annular projection fits. It is formed by recessing in the axial direction, and the annular convex portion is formed as an inclined surface whose outer peripheral surface is successively reduced in diameter or whose inner peripheral surface is gradually enlarged toward the protruding tip side. The outer peripheral surface is successively reduced in diameter or the inner peripheral surface is gradually increased in diameter toward the bottom side which is depressed to correspond to the inclined surface. In this case, the annular convex portion is formed as an inclined surface whose outer peripheral surface is gradually reduced in diameter toward the protruding tip side and whose inner peripheral surface is gradually enlarged, and the annular concave portion is formed so as to correspond to the inclined surface of the annular convex portion. It is desirable that the outer peripheral surface is gradually reduced in diameter toward the bottom side and the inner peripheral surface is formed into an inclined surface in which the diameter is gradually increased.

According to the present invention, the movable iron core is attracted to the fixed iron core by the attraction force generated by energizing the coil,
At the position where the stroke between the fixed iron core and the movable iron core is large,
The magnetic flux flows between the outer peripheral surface opening side ridge of the annular concave portion and the outer peripheral surface tip side ridge of the annular convex portion, and the inner peripheral surface opening side ridge of the annular concave portion and the inner peripheral surface tip side of the annular convex portion. Disperses in the magnetic flux flowing between the ridge and the ridge to eliminate saturation of the magnetic flux and improve the attractive force. Further, at a position where the stroke between the fixed iron core and the movable iron core is small, the annular convex portion fits into the annular concave portion, and is formed between the outer peripheral surface of the annular concave portion and the outer peripheral surface of the annular convex portion and the inner peripheral surface of the annular concave portion. A magnetic flux flows between the convex portion and the inner peripheral surface, and the magnetic flux flows between the outer peripheral surface formed on the inclined surface or between the inner peripheral surfaces in a direction according to the inclination angle of the inclined surface and is orthogonal to the axial direction. The flow in the radial direction is reduced to suppress the reduction of the suction force in the axial direction. Therefore, it is possible to suppress the reduction of the suction force in the axial direction at the position where the stroke of the fixed iron core and the movable iron core is small, and to improve the suction force at the position where the stroke of the fixed iron core and the movable iron core is large.

[0007]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention in which an electromagnet is applied to a solenoid valve will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a valve body of an electromagnetic valve, which has a substantially rectangular parallelepiped shape, and a fitting insertion hole 3 into which a spool-shaped valve body 2 is slidably fitted in an axial direction is formed so as to penetrate therethrough. Female threaded portions are threaded on both ends of the fitting insertion hole 3 that is open on both side surfaces of the plug 1.
A supply passage P for supplying a pressure fluid is opened at a substantially central portion in the axial direction of the fitting hole 3, and a fluid actuator (not shown) is provided with a gap on both axial sides of a connection portion of the supply passage P. No)
Two load flow passages A and B which communicate with each other, and further open exhaust flow passages R1 and R2 which communicate with the low pressure side with a gap outward in the axial direction of both load flow passages A and B, respectively. The discharge channels R1 and R2 communicate with each other by an arch-shaped communication channel 4 formed inside the valve body 1 and are connected to the external low pressure side. The valve body 2 has a central land portion 2A at a substantially central portion in the axial direction.
And a first load land portion 2B and a second load land portion 2C with a gap on both sides in the axial direction of the central land portion 2A, and further to the outside in the axial direction of both load land portions 2B, 2C. A first discharge land portion 2D and a second discharge land portion 2E are provided with a gap. In the neutral position shown in the upper half of FIG. 1, the valve body 2 closes both load flow passages A and B with both load land portions 2B and 2C, respectively, and connects between the supply flow passage P and the discharge flow passages R1 and R2. Is provided so as to communicate with the valve body 2 through the communication holes 2F and 2J provided. Further, in one of the switching positions shown in the lower half of FIG.
Between the load passage A and the load passage A, the first load land portion 2B between the load passage A and the discharge passage R1, and the second load land portion 2C between the supply passage P and the load passage B. The second discharge land portion 2
E cuts off between the load flow passage B and the discharge flow passage R2, respectively, switches the communication between the supply flow passage P and the load flow passage B through the communication hole 2J, and the load flow passage A and the discharge flow passage. It is provided so as to switch and communicate with R1 via a communication hole 2F.

A terminal box 5 is mounted on the upper surface of the valve body 1, and electromagnets S1 and S2 are mounted on both side surfaces of the valve body 1, respectively. Hereinafter, since the electromagnets S1 and S2 have the same configuration, the electromagnet S1 will be described as a representative. In the electromagnet S1, a tube body 7 is arranged inside the coil body 6, and the coil body 6 and the tube body 7 are fixed by a cap body 8. The coil body 6 is composed of a coil bobbin 10 around which a coil 9 is wound, a disk-shaped yoke 11 and 12 and a cylindrical yoke 13 which are integrally molded by molding with a resin material such as epoxy resin. And has an insertion hole 6A penetrating in the axial direction. The coil bobbin 10 is provided with a connection pin 15 that extends radially outwardly from one of the flanges formed at both ends in the axial direction and is electrically connected to the coil 9. The connection pin 15 is provided so as to project axially outwardly from the case 14. ing. Disc-shaped yoke 1
Nos. 1 and 12 are arranged adjacent to the other flange of the coil bobbin 10 which is not provided with the connecting pin 15 and are stacked in the axial direction. The cylindrical yoke 13 has a notch that radially penetrates one flange of the coil bobbin 10 to cover the outer circumference of the coil bobbin 10, and has one axial end connected to the disc-shaped yoke 11 and the other axial direction. The ends are arranged to be exposed on the surface of the case 14.

In the tube body 7, a fixed iron core 17 is fixed to one end of the tube 16 made of a non-magnetic material in the axial direction, and a stopper member 18 made of a magnetic material is fixed to the other end of the tube 16 in the axial direction by welding to form a fixed iron core 17. The movable iron cores 19 are arranged so as to be opposed to each other and are fitted in the tubes 16 and the stopper members 18 so as to be movable in the axial direction. The fixed iron core 17 has a threaded portion 17A threaded on an axial end portion opposite to the end portion to which the tube 16 is fixed, and a pin 20 for engaging the valve element 2 and the movable iron core 19 is axially slid in the central portion. The pin 20 is movably fitted in and is formed by cutting out two opposing positions on the outer peripheral surface so as to allow the fluid to flow therethrough.
The movable iron core 19 penetrates in the axial direction so as to allow the fluid to flow.
The individual circulation holes 19A and 19B are formed. Stop member 1
8 is a threaded portion on the outer periphery, and a movable iron core 19 is provided on the center.
Is provided with a manual operation pin 21 for manually pushing. The cap body 8 is internally threaded with a female thread portion.

The electromagnet S1 is mounted on one side of the valve body 1 as follows. The male screw portion 17A of the fixed iron core 17 is screwed into the female screw portion of the fitting insertion hole 3 of the valve body 1 to form the tube body 7.
Is attached to the valve body 1, and the opening of the fitting insertion hole 3 is the tube body 7.
Is blocked by. Insertion hole 6A of coil body 6 in tube body 7
To support the coil body 6, and a fixed iron core 17 is disposed in the coil body 6. The coil body 6 is sandwiched between the valve body 1 and the cap body 8 by screwing the female thread portion of the cap member 8 into the male thread portion of the stopper member 18 and tightening the cap body 8, and the surface of the case 14 The other end of the yoke 13 in the axial direction exposed at 1 is in contact with one side surface of the valve body 1, and the connection pin 15 is inserted into the terminal box 5 to electrically connect the coil 9 to an external power source. The magnetic path of the attraction force for attracting the movable iron core 19 generated by the energization of the coil 9 to the fixed iron core 17 includes the valve body 1, the fixed iron core 17, the movable iron core 19, the stop member 18, and the yokes 11, 12, and 13. It consists of. Also, the electromagnet S
2 is attached to the other side surface of the valve body 1 in the same manner as the electromagnet S1. Reference numerals 22A and 22B denote springs for holding the valve body 2 in the neutral position, and are mounted between both axial end portions of the valve body 1 and the fixed iron cores 17 of the electromagnets S1 and S2.

As shown in FIG. 2, an annular convex portion 19C is formed so as to project in the axial direction at the axial end of the movable iron core 19 facing the fixed iron core 17, and the fixed iron core 17 faces the movable iron core 19 in the axial direction. An annular recess 17A, into which the annular projection 19C is fitted, is formed in the end by recessing in the axial direction. Annular protrusion 19
C is an inclined surface in which the outer peripheral surface 19D is gradually reduced in diameter toward the protruding tip side and the inner peripheral surface 19E is sequentially enlarged in diameter.
It has a trapezoidal shape with a vertical cross section with a flat tip. The annular recessed portion 17A is formed such that the outer peripheral surface 17B is successively reduced in diameter toward the bottom portion side that is recessed so as to correspond to the outer peripheral surface 19D of the annular convex portion 19C, and the annular recessed portion 17A is recessed so as to correspond to the inner peripheral surface 19E of the annular protruding portion 19C. The inner peripheral surface 17C is formed to be an inclined surface that gradually increases in diameter toward the bottom, and the bottom portion is flattened to have a trapezoidal shape in a vertical cross section. Reference numeral 17D denotes an annular spacer ring made of a non-magnetic material, which is generated when the movable core 19 is returned to the neutral position by disposing the coil 9 in the non-energized state by being arranged along the outer peripheral edge of the fixed core 17 in the axial direction. This is for reducing the residual magnetism.

Next, the operation of this structure will be described. Figure 1
The upper half shows the non-energized state, and the valve body 2 has springs 22A, 2
2B, the load passages A and B are cut off, and the supply passage P communicates with the discharge passages R1 and R2.

In this state, when the coil 9 of the electromagnet S1 is energized, as shown in the lower half of FIG. 1, the movable iron core 19 is attracted to the fixed iron core 17 by the attraction force generated by the energization and moved in the axial direction, 20 slides the valve body 2 to one switching position against the force of the spring 22B, the valve body 2 switches the communication of the supply flow path P to the load flow path B, and the load flow path A to the discharge flow path. Switch communication with R1.

When the coil 9 of the electromagnet S1 is de-energized, the force of the spring 22B causes the valve element 2, the pin 20, the movable core 1 to move.
9 are returned to the positions shown in the upper half of FIG. When the electromagnet S2 is energized, the valve body 2, the pin 20, and the movable iron core 19 are axially moved rightward from the positions shown in the upper half of FIG. The load flow path B is switched and communicated with the discharge flow path R2 while being switched and communicated with A.

With this operation, when the movable iron core 19 is attracted to the fixed iron core 17 by the attraction force generated by energizing the coil 9 of the electromagnet S1 (S2), the movable iron core 19 and the fixed iron core 17 are attracted.
2, the magnetic flux F1 flows between the outer peripheral surface 17B opening side ridge of the annular recess 17A and the outer peripheral surface 19D tip end side ridge of the annular convex portion 19C, as shown in FIG. The magnetic flux F2 flowing between the inner peripheral surface 17C opening side ridge of the concave portion 17A and the inner peripheral surface 19E front end side ridge of the annular convex portion 19C is dispersed to eliminate saturation of the magnetic flux and improve the attractive force. Then, the movable iron core 19 is attracted by the fixed iron core 17 and moves in the axial direction, and at a position where the stroke between the movable iron core 19 and the fixed iron core 17 is small, the annular convex portion 19C fits into the annular concave portion 17A as shown in FIG. The magnetic fluxes F3 and F4 between the outer peripheral surface 17B of the annular concave portion 17A and the outer peripheral surface 19D of the annular convex portion 19C and between the inner peripheral surface 17C of the annular concave portion 17A and the inner peripheral surface 19E of the annular convex portion 19C, respectively. Flow, and the magnetic fluxes F3 and F4 are formed on the inclined surfaces of the outer peripheral surfaces 17B and 19D.
Between the inner peripheral surfaces 17C and 19E and in the direction corresponding to the inclination angle of the inclined surface, the flow in the radial direction orthogonal to the axial direction is reduced, and the reduction of the suction force in the axial direction is suppressed. Therefore, it is possible to suppress the reduction of the suction force in the axial direction at a position where the strokes of the fixed iron core 17 and the movable iron core 19 are small, and the fixed iron core 1
The suction force can be improved at a position where the stroke between 7 and the movable iron core 19 is large.

FIG. 4 is a graph showing the attraction force characteristic, the attraction force characteristic of the electromagnet corresponding to one embodiment of the present invention shown in FIGS. 1 to 3 is indicated by a solid line A, and the attraction force of the electromagnet corresponding to the prior art is shown. The force characteristics are indicated by broken lines B, and the analysis is performed under the condition that the value of current flowing through the coil is 0.2 amperes. According to this, at the large position where the stroke between the movable iron core and the fixed iron core is 2 mm to 1.2 mm, the solid line A and the broken line B overlap each other, and the attraction force of the electromagnet corresponding to the embodiment and the electromagnet corresponding to the conventional technique. It can be seen that the attractive force is almost the same, and the saturation of magnetic flux is eliminated to improve the attractive force. Further, at a small position where the stroke between the movable iron core and the fixed iron core is 0.5 mm, the attraction force of the electromagnet corresponding to one embodiment is 104 Newton, whereas the attraction force of the electromagnet corresponding to the conventional technique is 94 Newton. There is an opening of 10 Newtons, which means that in the electromagnet corresponding to one embodiment, the magnetic flux flows in a direction according to the inclination angle of the inclined surface to reduce the flow in the radial direction orthogonal to the axial direction,
While suppressing the reduction of the attractive force in the axial direction, in the electromagnet equivalent to the conventional technology, the magnetic flux flows in the radial direction orthogonal to the axial direction to generate the attractive force in the radial direction and reduce the attractive force in the axial direction. Can be judged.

FIG. 5 shows another embodiment of the present invention. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Only different parts will be described. The annular convex portion 23A formed so as to project from the axial end of the movable iron core 23 has an outer peripheral surface 23B as compared with the annular convex portion 19C of the embodiment shown in FIG.
Has the same diameter as the outer peripheral surface 19D, but the inner peripheral surface 23C has a diameter larger than that of the inner peripheral surface 19E.
The annular recess 24A, which is formed at the axial end of the annular recess 24A, is provided with an outer peripheral surface 24B and an inner peripheral surface 24C corresponding to the outer peripheral surface 23B and the inner peripheral surface 23C so as to fit the annular convex portion 23A. The outer peripheral surface 23 of each of the annular convex portion 23A and the annular concave portion 24A
B and 24B and the respective inner peripheral surfaces 23C and 24C form inclined surfaces at the same inclination angle as in the embodiment. Then, at the axial end of the movable iron core 23, a convex portion 23E is formed so as to project in the axial direction at the center of the annular convex portion 23A on the radially inner side, and the circular convex portion 23E is formed on the outer periphery toward the projecting tip side. The surface 23F is formed as an inclined surface whose diameter is successively reduced, and the tip is flattened to have a trapezoidal shape in a vertical cross section. A concave portion 24E into which the convex portion 23E is fitted is formed by axially denting the fixed iron core 24 at an axial end portion thereof.
Inner peripheral surface 24F toward the bottom side which is depressed to correspond to F
Are formed on an inclined surface of which the diameter is gradually reduced, and the bottom is flattened to have a trapezoidal shape in a vertical cross section.

In such a structure, at a position where the stroke between the movable iron core 23 and the fixed iron core 24 is large, the magnetic flux has an outer peripheral surface 24B of the annular concave portion 24A and a ridge portion on the opening side and the annular convex portion 23A.
Magnetic flux F1 flowing between the outer peripheral surface 23B and the ridge on the tip side,
Inner peripheral surface 24C of the annular recess 24A on the opening side ridge and the annular projection 2
Magnetic flux F2 flowing between the inner peripheral surface 3C of 3A and the ridge on the tip side
In addition to being dispersed into the magnetic flux F5, the magnetic flux F5 flowing between the inner peripheral surface 24F of the recess 24E on the opening side ridge and the outer peripheral surface 23F of the convex portion 23E on the tip side ridge is absorbed to further eliminate saturation of the magnetic flux. Improve power more. Then, at a position where the stroke between the movable iron core 23 and the fixed iron core 24 is small, the annular convex portion 23A
Fit in the annular recess 24A and the protrusion 23E becomes recess 2
4E, and the magnetic flux is formed between the outer peripheral surfaces 24B and 23B and the inner peripheral surfaces 24C and 23C and the inner peripheral surface 2 which are formed on the inclined surfaces.
4F and the outer peripheral surface 23F respectively flow in a direction according to the inclination angle of the inclined surface to reduce the flow in the radial direction orthogonal to the axial direction and suppress the reduction of the suction force in the axial direction, as in the embodiment. To do. Therefore, it is possible to suppress the reduction of the suction force in the axial direction at the position where the stroke of the fixed iron core 24 and the movable iron core 23 is small, and to further improve the suction force at the position where the stroke of the fixed iron core 24 and the movable iron core 23 is large. it can.

In one embodiment and another embodiment,
The movable cores 19 and 23 are formed with the annular projections 19C and 23A and the fixed iron cores 17 and 24 are formed with the annular recesses 17A and 24A. However, the movable cores are formed with the annular recesses and the fixed cores are formed with the annular projections. May be. Also, the annular protrusions 19C, 23A
And the annular recesses 17A, 24A have outer peripheral surfaces 19D, 23B,
17B, 24B and inner peripheral surfaces 19E, 23C, 17C, 24
Although both C and C are formed on the inclined surface, at least one of the outer peripheral surface and the inner peripheral surface may be formed on the inclined surface.
Further, although the electromagnets S1 and S2 are applied to the solenoid valve, it is needless to say that the electromagnets S1 and S2 may be applied to other devices depending on the application.

[0020]

As described above, according to the invention of claim 1,
An annular convex portion is formed so as to project in the axial direction on one of the axial end portions of the fixed iron core and the movable iron core facing each other, and an annular concave portion to which the annular convex portion fits is formed by being depressed in the axial direction on the other end. , The annular convex portion is formed on the inclined surface whose outer peripheral surface is successively reduced in diameter or whose inner peripheral surface is gradually enlarged toward the protruding tip side, and the annular concave portion is depressed so as to correspond to the inclined surface of the annular convex portion. Since the outer peripheral surface is gradually reduced in diameter toward the bottom side or the inner peripheral surface is formed into an inclined surface that is gradually expanded, the reduction of the suction force in the axial direction is suppressed at the position where the stroke of the fixed core and the movable core is small. As a result, the suction force can be improved at a position where the stroke between the fixed iron core and the movable iron core is large.

Further, in the invention according to claim 2, the annular convex portion is formed as an inclined surface whose outer peripheral surface is successively reduced in diameter toward the protruding tip side and whose inner peripheral surface is successively enlarged, and the annular concave portion is annular. Since the outer peripheral surface is gradually reduced in diameter and the inner peripheral surface is gradually increased in diameter toward the bottom side that is recessed to correspond to the inclined surface of the convex portion, between the outer peripheral surfaces formed on the inclined surface. And between the inner peripheral surface, the magnetic flux can flow in the direction according to the inclination angle of the inclined surface and reduce the flow in the radial direction orthogonal to the axial direction, so that the stroke of the fixed core and the movable core is small. It is possible to further suppress the reduction of the suction force in the axial direction.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention in which an electromagnet is applied to a solenoid valve.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part in an operating state different from that of FIG.

FIG. 4 is a graph showing suction force characteristics.

5 is a cross-sectional view showing another embodiment of the present invention and corresponding to FIG.

[Explanation of symbols]

6 coil body 9 coils 17, 24 Fixed core 19, 23 Movable iron core 19C, 23A annular projection 17A, 24A annular recess 17B, 19D, 23B, 24B outer peripheral surface 17C, 19E, 23C, 24C inner peripheral surface S1 and S2 electromagnets

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3H106 DA23 DB02 DB12 DB23 DB32                       DC09 DD04 EE16 GA13 GA15                 5E048 AA08 AB01 AD04

Claims (2)

[Claims] 1. A fixed iron core is arranged in a coil body around which a coil is wound, a movable iron core is provided in the coil body so as to be movable in the axial direction so as to face the fixed iron core, and a suction force generated by energizing the coil is used. An electromagnet for attracting a movable iron core to a fixed iron core, which is formed by axially projecting an annular convex portion on one of axial ends of the fixed iron core and the movable iron core that face each other.
On the other hand, an annular concave portion to which the annular convex portion fits is formed by being recessed in the axial direction, and the annular convex portion has a slope that gradually reduces the outer peripheral surface toward the protruding tip side or sequentially enlarges the inner peripheral surface. It is characterized in that the annular concave portion is formed on the surface, and the annular concave portion is formed so as to correspond to the inclined surface of the annular convex portion, and the outer peripheral surface is successively reduced in diameter or the inner peripheral surface is gradually enlarged toward the bottom side. And an electromagnet. 2. The annular convex portion is formed as an inclined surface whose outer peripheral surface is gradually reduced in diameter toward the protruding tip side and whose inner peripheral surface is gradually enlarged, and the annular concave portion corresponds to the inclined surface of the annular convex portion. The electromagnet according to claim 1, wherein the outer peripheral surface is formed to be an inclined surface in which the diameter is gradually reduced toward the bottom side and the inner peripheral surface is gradually increased in diameter.