JPH0888115A - Yoke - Google Patents

Abstract

PURPOSE: To prevent a gap in the surface part of a sintered body from being clogging because no machining is performed and to form an effective tri-iron tetroxide film by a steam treatment in a yoke which is manufactured by powder metallurgy. CONSTITUTION: A yoke 1 as a magnetic product has a shape in which one end of an outer circumferential tube part 2 and one end of an inner circumferential tube part 3 are connected by a ringed edge part 4. When the yoke 1 is manufactured, a raw-material powder is compressed, a green compact is molded, and the green compact is then heated and sintered. After that, steaming is executed to a sintered body without executing any machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yoke which is a magnetic component manufactured by powder metallurgy.

[0002]

2. Description of the Related Art A yoke, which is a magnetic component used in electric equipment, is manufactured by powder metallurgy, for example. In powder metallurgy, first, a raw material powder containing a metal as a main component is compressed by a powder molding press to mold a green compact (powder molding step), and then the green compact is heated in a sintering furnace to be sintered. Do (sintering process). Furthermore, for the yoke, finally,
In order to prevent rust, improve hardness, and wear resistance, it is also possible to form a ferric tetroxide coating by steam treatment, which is a chemical surface treatment.

By the way, as a material of the yoke, iron containing 0.2 to 0.8% by weight of phosphorus is used in view of magnetic characteristics. This material is likely to have dimensional variations due to strain associated with sintering. In order to improve the dimensional accuracy against such dimensional variations, for example, a workpiece (sintered body) after sintering is subjected to machining such as cutting.

However, when the work is machined, the voids on the surface of the work are clogged. When the voids on the surface of the work are clogged in this way, it becomes difficult for steam to enter the work, and effective steam treatment cannot be performed. That is, originally, not only the surface of the work, but also the ferrosoferric oxide film is formed near the voids in the work, which makes the film effective.

[0005]

As described above, since the yoke manufactured by powder metallurgy has conventionally been machined after sintering in order to improve the dimensional accuracy, the subsequent steam treatment can be performed well. There was no problem.

The present invention is intended to solve such a problem, and an object thereof is to provide a yoke which has been subjected to a chemical surface treatment such as an effective steam treatment.

[0007]

According to a first aspect of the present invention, in order to achieve the above object, a yoke having a shape in which one ends of an outer peripheral tubular portion and an inner peripheral tubular portion are integrally connected by an annular end surface portion, A raw material powder containing a metal as a main component is compressed, molded, and sintered, and a sintered body is subjected to a chemical surface treatment without machining.

According to a second aspect of the present invention, in the yoke of the first aspect, the chemical surface treatment is steam treatment.

[0009]

According to the first aspect of the invention, when the yoke is manufactured, the raw material powder containing a metal as a main component is compressed to form a green compact,
This green compact is heated and sintered, and then the sintered body is subjected to a chemical surface treatment without machining. Since there is no machining in this way, the voids in the surface portion of the sintered body are not clogged, the effect of the chemical surface treatment reaches the inside of the sintered body, and an effective chemical surface treatment is performed.

According to the second aspect of the invention, since the voids in the surface portion of the sintered body are not clogged, the steam passes into the sintered body during the steam treatment and an effective coating of ferric tetroxide is formed. .

[0011]

EXAMPLE An example of the yoke of the present invention will be described below.
This will be described with reference to the drawings. 1 and 2 show the yoke 1. The yoke 1 has a cylindrical outer peripheral tubular portion 2 and an inner peripheral tubular portion 3 which are coaxially positioned, and one end of each of these tubular portions 2 and 3 is an annular end surface portion 4 orthogonal to these.
It has a shape that is integrally connected by. Further, the axial length of the outer peripheral tubular portion 2 is longer than that of the inner peripheral tubular portion 3. Then, the coil is mounted between the cylindrical portions 2 and 3 without any gap. In such a yoke 1, high accuracy is required for the inner diameter and outer diameter of the tubular portions 2 and 3. In addition,
The yoke 1 has a total diameter of about 5 cm, and the cylindrical portions 2 and 3 have a thickness of about 2 mm. In this way,
3 is fairly thin. The material of the yoke 1 is iron containing 0.2 to 0.8% by weight of phosphorus.

Next, a method for manufacturing the yoke 1 will be described. First, a raw material powder containing iron and phosphorus powder is compressed by a powder molding press to mold a green compact (powder molding step). Next, this work (green compact) is heated and sintered in a sintering furnace (sintering step). Next, the work (sintered body) after the sintering is repressurized by a straightening press to finish to a predetermined size (straightening step). Then, the work is subjected to steam treatment as a chemical surface treatment (steam treatment step). In this steam treatment, the work is heated in a steam treatment furnace to about 500 to 550 ° C. and passed through steam to form a ferric tetroxide film on the surface of the work. Machining such as cutting is not performed up to this steam treatment step.

Since there is no machining as described above, the voids on the surface of the sintered body, that is, the yoke 1 are not clogged, and an effective coating of ferric tetroxide can be formed by steam treatment. That is, during the steam treatment, steam enters the work, and a coating of ferric tetroxide is formed not only on the surface of the work but also in the vicinity of the voids in the work. As a result, a reliable rust preventive effect can be obtained and hardness and wear resistance can be sufficiently improved.

The structure of the straightening mold used in the straightening step will be described with reference to FIGS. 3 and 4.
This orthodontic mold is uniaxial, and the vertical direction is the axial direction. In FIG. 3, 31 is a die, 32 is a core rod, and 33
Is an upper punch, 34 is a lower first punch, 35 is a lower second punch, 36
Is a lower third punch, and each of these mold members has a substantially cylindrical shape. The die 31 forms the outer peripheral surface of the outer peripheral cylindrical portion 2 of the work 1 which serves as a yoke, and the position is fixed. The core rod 32 forms the inner peripheral surface of the inner peripheral tubular portion 3, is located inside the die 31, and its position is fixed. The upper punch 33 forms the outer end surface of the annular end surface portion 4 and moves up and down to move the die 31 and the core rod 32.
It is fitted between the upper and lower parts so as to be freely inserted and removed. The lower first punch 34 forms the front end surface of the outer peripheral cylindrical portion 2, and
Fitted in 31 so that it can move up and down. The lower second punch 35
The inner peripheral surface of the outer peripheral cylindrical portion 2, the inner end surface of the annular end surface portion 4 and the inner peripheral surface of the inner peripheral cylindrical portion 3 are formed, and are fitted in the lower first punch 34 so as to be vertically movable. The lower third punch 36 forms the front end surface of the inner peripheral tubular portion 3, and is fitted between the lower second punch 35 and the core rod 32 so as to be vertically movable.

The die 31 is fixed to a fixed die plate 41 through a die holder 42 and a die holder 43. The core rod 32 is fixed to the base on the correction press body side via a plurality of joints 46. The upper punch 33 is fixed to the lower side of the upper holding plate 47 via an upper punch holder 48, an upper punch holder 49, and the like. The upper holding plate 47 is mechanically driven in the vertical direction.

The lower third punch 36 is fixed on the first base plate 51 via a lower third punch holder 52. The first base plate 51 is fixed on the first driving body 53 on the correction press body side. This first driver 53
Is mechanically driven in the vertical direction. Also,
A holding plate 55 is fixed on the first base plate 51 via a plurality of rods 54.
The lower first punch 34 is held above the lower first punch presser 56 so as to be vertically movable within a predetermined range. That is, the lower first punch 34 has the flange portion 57 formed at the lower end thereof.
The position where the annular spacer 58 applied to the lower side of the lower plate hits the holding plate 55, and the position where the flange part 57 hits the inward facing flange part 59 formed on the upper inner circumference of the lower first punch presser 56 from below. It can be moved up and down between and. Thus, the lower first punch 34 includes the first base plate 51, the rod.
54, a holding plate 55, and a lower first punch retainer 56, and the like, which can move up and down relative to the lower third punch 36 by a difference in the axial length of both cylinders 2 and 3 of the work 1. It has become. A coil spring as a biasing means is provided between the spacer 58 and the step surface 62 formed around the through hole 61 formed in the holding plate 55 in the vertical direction.
63 is installed. With this spring 63, the lower first
The punch 34 is biased upward with respect to the holding plate 55 and the lower third punch 36.

Further, the lower second punch 35 is fixed on the second base plate 66 by a lower second punch presser 67. The second base plate 66 is fixed on the second driving body 68 on the correction press body side. This second driver 68
Includes an air cylinder (not shown), which is mechanically driven in the vertical direction and is urged upward by air pressure. The lower first
The punch 34 and the rod 54 pass through through holes 69 and 70 formed in the second base plate 66 in the vertical direction. Further, the lower second punch 35 penetrates the through hole 61 of the holding plate 55 and the coil spring 63.

Next, the operation of the straightening die will be described. In the straightening process, the upper punch 33 is the die 31 first.
3B, the work 1 is fed onto the lower first punch 34, the lower second punch 35, and the lower third punch 36 in the raised position. Then, the lower first punch 34, the lower second punch 35, and the lower third punch 36 descend and the work 1 enters the die 31. Then, as shown in FIG. 3A, the work 1 descends between the die 31 and the core rod 32 into the die 31, and the upper punch 33, the lower first punch 34, the lower second punch 35, and the lower punch 35 are inserted. It is pressed and corrected by the third punch 36. At this time, due to the pressurization, the lower first punch 34 is in a position in which the spacer 58 hits the holding plate 55 against the spring 63 and is lowered with respect to the lower third punch 36.

Then, the work 1 is extracted. At this time, the upper punch 33 rises and comes out of the die 31. Further, the lower first punch 3 together with the first driving body 53 and the second driving body 68.
4, the lower second punch 35 and the lower third punch 36 are initially lifted together, and the work 1 is moved to the die 31 and the core rod 32.
Push up. The lower second punch 35 is mechanically driven by the second driving body 68 to move up until the upper end surface thereof coincides with the upper surface of the die 31, and thereafter, is urged upward by air pressure. On the other hand, the lower first punch 34 and the lower third punch 36 continue to move up by the mechanical driving of the first driving body 53, and push up both the tubular portions 2 and 3 of the work 1. And at the upper limit of the mechanical drive,
As shown in FIG. 4, the lower third punch 36 has a die 31 at the upper end surface.
The inner peripheral cylindrical portion 3 of the work 1 is extracted from the die 31 so as to coincide with the upper surface of the die 1. Until then, due to the frictional resistance between the work 1 and the lower first punch 34, the lower first punch 34 and the lower third punch 36 are integrally lifted. )
As shown in, the tension of the spring 63 causes the flange
It moves up with respect to the lower third punch 36 until the 56 hits the inward flange portion 59 of the lower first punch 34. As a result, the work 1
The outer peripheral tube portion 2 of the is removed from the die 31. The lower second punch
As shown in FIG. 4, the frictional resistance between the work piece 35 and the work piece 1 keeps rising even after the upper end surface of the work piece 1 coincides with the top surface of the die 31.
When it comes out of the space, the frictional resistance decreases and it falls.

According to the configuration of the straightening die, the lower punch
34, 35, 36 are made into three pieces, and the outer peripheral cylinder part 2 and the inner peripheral cylinder part 3 having different lengths are pushed out by the lower first punch 34 and the lower third punch 36, which move differently, respectively. Therefore, it is possible to prevent the work 1 from being distorted at the time of extraction. Therefore, even if the work 1 is thin, no damage such as cracks occurs. In addition, it is possible to prevent damage to the mold. This allows mass production.

Further, in order to prevent the work 1 from being distorted, it is not necessary to reduce the frictional resistance between the work 1 and the lower second punch 35 and the core rod 32. Since it can be surely pressed against the lower second punch 35 and the core rod 32,
The dimensional accuracy of the work 1 can be sufficiently secured. Therefore,
There is no need to perform mechanical processing such as cutting as post-processing, which is advantageous in performing steam treatment as described above.

Further, by using the lower first punch holder 56, the lower first punch 34 can be moved up and down with respect to the lower third punch 36, and by the coil spring 63 arranged around the lower second punch 35. Since the lower first punch 34 is biased upward with respect to the lower third punch 36, the orthodontic mold can be made compact despite the fact that there are three lower punches. Also, three lower punches can be incorporated into a straightening press body originally having two lower punches, and the conventional straightening press body can be used as it is.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
The size of the yoke is not limited to that of the above embodiment. However, according to the present invention, the thickness of the tubular portion is 3.7 to
Especially effective for thin yokes of about 5.5%.
Further, the shape of the yoke itself is not limited to the round shape as in the above-mentioned embodiment, and may be a deformed yoke such as a square. Furthermore, the chemical surface treatment is not limited to steam treatment, and black coating or the like is also possible.

[0024]

According to the invention of claim 1, in a yoke having a shape in which one end of the outer peripheral tubular portion and one end of the inner peripheral tubular portion are integrally connected by an annular end face portion, a raw material powder containing a metal as a main component is compressed. Since the sintered body that has been molded and sintered is subjected to a chemical surface treatment without machining, the chemical surface treatment can be performed effectively when the voids on the surface of the sintered body are not clogged. Various chemical surface treatments are possible.

According to the invention of claim 2, the steam treatment can be carried out in a state where the voids in the surface portion of the sintered body are not clogged, and an effective coating of ferric tetroxide can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a yoke of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a cross-sectional view showing an example of a straightening die used for manufacturing the yoke, in which (a) on the left side of the center line shows pressing, and (b) on the right side shows when extraction is completed.

FIG. 4 is a partial cross-sectional view showing a state in the middle of extracting the same as above.

[Explanation of symbols]

 1 Yoke 2 Outer Cylinder 3 Inner Cylinder 4 Annular End Face

Claims (2)

[Claims] 1. In a yoke having a shape in which one ends of an outer peripheral tubular portion and an inner peripheral tubular portion are integrally connected by an annular end surface portion, a raw material powder containing a metal as a main component is compressed, molded and sintered. A yoke characterized by being chemically surface-treated without subjecting the body to machining. 2. The yoke according to claim 1, wherein the chemical surface treatment is steam treatment.