JPH0438125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of manufacturing a plunger for an electromagnetic proportional solenoid.

(Prior art and its problems) It is necessary for an electromagnetic proportional solenoid used in an electromagnetic proportional control valve to accurately displace a plunger that controls the valve opening pressure of a valve body in accordance with the excitation current of the solenoid. Therefore, as shown in FIG. 5, a conventional electromagnetic proportional solenoid usually houses a plunger 4 with a shaft 3 made of a non-magnetic material inserted into a cylindrical part 2 formed in a housing 1, and both ends of the shaft 3 are connected to each other. While being supported slidably in the axial direction by bearings 5 and 6, the inner peripheral surface of the cylindrical portion 2 and the plunger 4
The solenoid 7 wound around the housing 1 is provided with a slight clearance between the solenoid 7 and the outer peripheral surface of the housing 1 to prevent the plunger 4 from adhering to the inner peripheral surface of the cylindrical portion 2.
The displacement of the plunger 4 is accurately controlled according to the excitation current.

However, the electromagnetic proportional solenoid with the above configuration has a large number of parts and a complicated structure. Moreover, the machining accuracy of both bearings 5 and 6 that pivotally support both ends of the shaft 3 and the inner circumferential surface of the cylindrical portion 2 and the plunger 4 are It is necessary to improve the machining accuracy at three points, such as controlling the clearance between the outer circumferential surface and the outer circumferential surface of the disk, which results in problems such as being very expensive and increasing the size.

Further, unlike an electromagnetic proportional solenoid, accurate plunger positioning control is not required. For example, in a device that controls an on-off type valve, a non-magnetic material is plated on the outer peripheral surface of the plunger, or a non-magnetic material formed in a ring shape is press-fitted, cold-fitted, or shrink-fitted. A non-magnetic layer is formed on the outer peripheral surface of the plunger, and the plunger is fitted into the cylindrical portion 2 so as to be slidable in the axial direction, and the shaft 3 is omitted. has been done.

However, the former plating method requires the finishing precision required when the base plunger is completed (after plating is completed), takes a long time, is expensive, and the latter method is non-magnetic. The method of externally fitting the ring member requires high machining accuracy for both the plunger, which is the base material, and the ring member, which is formed from a non-magnetic material, and it is difficult to form the ring member thin.

For this reason, it is difficult to form a plunger for use in an electromagnetic proportional solenoid using each of the above methods in terms of cost and technology.

(Object of the Invention) The present invention has been made in view of the above points, and is directed to manufacturing a plunger for an electromagnetic proportional solenoid in which a non-magnetic layer is easily and precisely formed on the outer peripheral surface of the plunger for an electromagnetic proportional solenoid. The purpose is to provide a method.

(Summary of the invention) In order to achieve the above object, the present invention includes:
An electromagnetic proportional solenoid has a plunger housed movably in the axial direction in a concave portion formed in the housing, and is displaceable in accordance with the excitation current of the solenoid wound around the housing. A hole is bored, a plurality of holes are provided that open radially from a predetermined location on the inner circumferential surface of the hole to the outer circumferential surface, and the plunger is housed in a mold having a predetermined diameter larger than the outer diameter of the plunger. , a non-magnetic material is injected through the hole in the axial direction to form a non-magnetic layer on the outer peripheral surface of the plunger, and the plunger is fitted into the cylindrical part so as to be slidable in the axial direction. This constitutes a method for manufacturing a plunger for a proportional solenoid.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows an electromagnetic proportional control valve to which a plunger for an electromagnetic proportional solenoid formed by the method of manufacturing a plunger for an electromagnetic proportional solenoid according to the present invention is applied.
1. Plunger 12 housed within the housing 11; Solenoid 1 wound around the housing 11;
3. It is composed of a housing 11, a cover 14 for housing the solenoid 13, and the like.

The housing 11 consists of a first yoke 15, a second yoke 16, and an annular member 17 interposed between these yokes 15 and 16. Hole 15b
A through hole 15c is formed at the bottom of the hole 15b.
are concentrically bored, and a flange 15d is provided at the other end.
is formed. The yoke 17 is a cylindrical body with a bottom,
The outer diameter of the yoke 15 is set to be equal to the outer diameter of the main body 15a, and the inner diameter is set to be equal to the inner diameter of the hole 15b. The open ends of the holes 15b of these yokes 15 and the open ends of the yoke 16 are connected via an annular member 17.

The annular member 17 is made of a non-magnetic material, and its outer diameter and inner diameter are set to be the same as the outer diameter and inner diameter of the yoke 16, respectively. This annular member 17 is the yoke 15
and 16, and solenoid 1
The magnetic flux generated by 3 is made to flow through a path of yoke 15, plunger 12, and yoke 16. The main body 15a of the yoke 15, the annular member 17, and the yoke 16 form a cylindrical portion 11a of the housing 11.

The plunger 12 is fitted into the cylindrical portion 11a so as to be slidable in the axial direction, and a through hole 12a is formed in the axial center, and one open end 12a' is stepped and widened to a large diameter. The outer peripheral surface 12b of this plunger 12
A layer 20 of a non-magnetic member having wear resistance, such as ceramic (hereinafter referred to as non-magnetic layer), is uniformly formed with a predetermined thickness over the entire circumference. This nonmagnetic layer 20 is formed as shown in FIGS. 2 to 4.

The outer diameter of the plunger 12 is made smaller than the inner diameter of the cylindrical portion 11a by a predetermined dimension corresponding to the thickness of the non-magnetic layer 20 to be formed, and as shown in FIGS. One end surface 12c
A blind hole 12d with a depth of about 2/3 of the length of the plunger is bored in the axis of the plunger. Then, at approximately the center and near the bottom end surface of this blind hole 12d, a plurality of, for example four, one ends of each blind hole 12d are arranged radially and radially.
Holes 12e to 12h and 12e' to 12h' are formed, which are open on the inner circumferential surface of 2d and whose respective other ends are open on the outer circumferential surface 12b.

This plunger 12 is housed in a mold 30 of an injection molding machine as shown in FIG. This mold 30 includes an outer cylinder 31, end plates 32 that close both ends of the outer cylinder 31,
Consists of 33. The outer cylinder 31 is set to have the same length as the plunger 12, and the cylindrical part 11 is located in the center.
A hole 31a with the same diameter as the inner diameter of the plunger 12 is bored in the center of one end plate 32, and a blind hole 12d of the plunger 12 is formed in the center of one end plate 32.
A hole 32a corresponding to and having the same diameter is bored.

After storing the plunger 12 in this mold 30 with the blind hole 12d of the plunger 12 facing the hole 32a of the end plate 32, the non-magnetic material, that is, ceramic is injected into the blind hole 12d from the hole 32a. . The ceramic injected into this blind hole 12d passes through each hole 12e to 12h, 12e' to 12h' to the outer peripheral surface 12b of the plunger 12 and the hole 31a of the outer cylinder 31.
is injected into the annular space between the inner peripheral surface of the As a result, the ceramic layer 20 is formed concentrically and uniformly on the outer peripheral surface 12b of the plunger 12. Next, the plunger 12 is taken out from the mold 30, and a hole 12a is bored in the shaft center as shown in FIG.

Note that the hole 12a is formed in the ceramic layer 2 as described above.
Alternatively, a through hole may be used instead of the blind hole 12d, a solid rod of a predetermined outer diameter may be loosely fitted into this through hole, and after pouring the ceramic, the hole may be bored. It may also be formed by drawing out a solid rod. Furthermore, the through hole 12a is provided to facilitate sliding within the cylindrical portion 11a of the plunger 12, and therefore is not limited to the axial center position, and may be bored at a position off the axial center. .

This plunger 12 is fitted into the cylindrical portion 11a so as to be slidable in the axial direction. In this state, the inner circumferential surface of the yoke 16 and the outer circumferential surface of the plunger 12 are in contact with each other via the non-magnetic layer 20, and magnetic attraction between the two is prevented.

A coil spring 19 is interposed between the opening end 12a' of the hole 12a of the plunger 12 and the opposing end surface of the yoke 16, and a spacer 21 formed of a non-magnetic material is fitted into the end surface of the hole 15b of the yoke 15. It is set up.

A solenoid 13 is installed in the cylindrical portion 11a of the yoke 11.
The yoke 11 and the solenoid 13 are housed in a substantially bowl-shaped cover 14. The cover 14 is made of a magnetic material, and the outer periphery of the flange 15d of the yoke 15 is fitted into the open end of the cover 14, and the bottom end of the yoke 16 is fitted into a recess provided at the bottom end of the cover, so that the outside It forms a magnetic circuit.

A housing 24 forming a control valve is fixed to the end face of the flange 15d of the yoke 15, and the housing 24 has a hole 24a corresponding to the hole 15c of the yoke 15, and a hole 24b communicating with the hole 24a and housing the valve body 25. , a hole 24c that communicates with the hole 25 and is closed by the valve body 25, and a drain hole 24d that communicates with the hole 24b. The valve body 25 has a hole 24
A coil spring 26 is housed in the hole 15c and closes the hole 24c, and between each opposing end surface of the valve body 25 and the plunger 12 is a coil spring 26 that passes through the hole 15c and biases the valve body 25 in the valve closing direction. It is mediated.

The plunger 12 is attracted in response to the excitation current supplied to the solenoid 13 and slides within the cylindrical portion 11a in the direction of the yoke 15, and accordingly compresses the coil spring 26 to reduce its set load, that is, the valve opening pressure. Control. Incidentally, since the spaces on both sides of the plunger 12 are communicated through the through hole 12a, the plunger 12 can slide smoothly.

In this embodiment, the non-magnetic layer 20 is made of ceramic, but it is not limited to this, and may be made of other materials such as Teflon or other resin materials.

(Effects of the Invention) As explained above, according to the present invention, the plunger, which is housed movably in the axial direction in the cylindrical portion formed in the housing, is displaced in accordance with the excitation current of the solenoid wound around the housing. An axial hole is drilled in one end surface of the plunger of the electromagnetic proportional solenoid, and a plurality of holes are provided that open radially from a predetermined location on the inner circumferential surface of the hole to the outer circumferential surface. The plunger is housed in a mold having a predetermined diameter larger than the outer diameter of the plunger, and a non-magnetic material is injected through the hole in the axial direction to form a non-magnetic material layer on the outer peripheral surface of the plunger, and the plunger is moved to the cylindrical portion. Since the plunger is slidably inserted in the axial direction, there is no need for finishing accuracy on the outer peripheral surface of the plunger, and the surface accuracy after molding is also high, equivalent to that obtained by plating or machining. Moreover, post-processing is unnecessary. Furthermore, by setting the outer diameter of the plunger to a desired value, the thickness of the non-magnetic layer formed on the outer peripheral surface of the plunger can be easily formed to a desired value, and as a result, the manufacturing process is simplified. This has advantages such as making it possible to reduce manufacturing costs significantly.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an electromagnetic proportional solenoid to which a plunger formed by the method of manufacturing a plunger for an electromagnetic proportional solenoid according to the present invention is applied, and FIG. 2 is a longitudinal sectional view showing an embodiment of the plunger according to the present invention. The cross-sectional view shown in FIG. 3 is taken along the arrow line -
4 is a cross-sectional view showing an embodiment of the plunger manufacturing method according to the present invention, and FIG. 5 is a vertical cross-sectional view of a conventional electromagnetic proportional solenoid. 11...Housing, 12...Plunger, 1
3... Solenoid, 14... Cover, 15, 16
... Yoke, 20 ... Nonmagnetic layer, 30 ... Type,
31... Outer cylinder, 32, 33... End plate.

Claims (1)

[Claims] 1. An electromagnetic proportional solenoid has a plunger housed in an inner cylindrical portion formed in a housing so as to be movable in the axial direction, and is displaceable in accordance with the excitation current of a solenoid wound around the housing. a hole is bored, a plurality of holes are provided that open radially from a predetermined location on the inner circumferential surface of the hole to the outer circumferential surface, and the plunger is housed in a predetermined mold larger than the outer diameter of the plunger, A non-magnetic material is injected through the axial hole to form a non-magnetic layer on the outer peripheral surface of the plunger, and the plunger is fitted into the cylindrical portion so as to be slidable in the axial direction. A method of manufacturing a plunger for an electromagnetic proportional solenoid.