JP2957929B2 - Method of manufacturing stator yoke for motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a stator yoke for a small motor. More specifically, a magnetic plate is formed into a cylindrical body having an end face closed structure by drawing, and the cylindrical body is formed. The present invention relates to a method of cutting out a pole piece by punching a closed end face of a body and axially shearing a peripheral wall portion, and shaping the pole piece by bending a distal end portion. This technique is useful, for example, for manufacturing a stator yoke for an inner rotor type stepper motor having a structure in which a plurality of toothed magnetic pole pieces are arranged side by side on an inner peripheral portion.

[0002]

2. Description of the Related Art As is well known, an inner rotor type stepper motor comprises a combination of a stator portion and a rotor portion rotatably supported inside the stator portion. In a typical example, the stator portion mainly includes an outer yoke, an inner yoke, and an annular coil interposed therebetween, and two sets of these are connected. The inner yoke has a structure in which a plurality of tooth-shaped magnetic pole pieces are protruded from the inner peripheral edge of the annular plate-shaped portion in parallel to the axial direction at equal intervals, and are continuously integrated. The outer yoke has an outer peripheral cylindrical portion that is continuous with the outer peripheral edge of the annular plate-shaped portion,
Further, a plurality of tooth-shaped magnetic pole pieces are protruded from the inner peripheral edge of the annular plate-shaped portion in parallel to the axial direction at equal intervals, and are continuously integrated. The inner yoke and outer yoke are joined in such a way that their toothed pole pieces stagger
A coil is sandwiched between them. The two sets are combined such that the inner yokes are back-to-back and their toothed pole pieces are displaced by 1/4 of the angle between the pole pieces. The rotor portion rotatable by a bearing in the stator portion includes a shaft, a multi-pole magnetized annular permanent magnet fixed to the shaft, and the like. The stepper motor is configured to be stepwise rotated and displaced by a magnetomotive force generated by supplying a pulse current to a coil.

[0003] The simplest method for manufacturing a stator yoke in which a plurality of tooth-shaped magnetic pole pieces protrude in the axial direction on the inner peripheral edge of the annular plate-shaped portion as described above is the pull-out method. This is a method in which a plate-like body made of a magnetic material is punched into the shape of a toothed pole piece and then bent at a substantially right angle so as to cause it. However, this method has a problem that the tooth-shaped magnetic pole piece cannot be made longer than the motor inner diameter (in other words, the inner diameter of the annular plate-shaped portion).

Accordingly, various methods have been developed for producing long pole pieces. For example, a plate-shaped body is formed into a cylindrical body having an end face closed structure by expanding a central portion by drawing, and the entire end face is removed to form a cylindrical body having an open end face, and then the peripheral wall portion of the cylindrical body is formed. There is a method of cutting out a long rectangular magnetic pole piece by shearing in the axial direction (see Japanese Patent Application Laid-Open No. 56-86054). As still another example, after performing a swelling process on a plate-like body in a trapezoidal or hemispherical shape, the swelling formed portion is punched to punch out corresponding to the formation of the tapered pole piece, and the punched portion is bent. (Japanese Unexamined Patent Publication No. 57-21)
No. 1964).

[0005]

SUMMARY OF THE INVENTION Among the above prior arts,
In the former method, since the shearing is performed over the entire length of the long pole piece, a high-level technique is required, and the processing time per piece is long, and there is a problem that only a rectangular tooth-shaped pole piece can be obtained. On the other hand, the latter method is excellent in terms of productivity, but can be formed by bulging only to the extent that punching is possible, and there is a limit to lengthening the tooth-shaped magnetic pole piece.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor stator yoke in which the length of a pole piece with respect to the motor inner diameter can be made as long as necessary, and the shape of the tip of the pole piece can be arbitrarily changed. It is to provide a manufacturing method.

[0007]

SUMMARY OF THE INVENTION The present invention provides a motor for a motor having a structure in which a plurality of tooth-shaped magnetic pole pieces are protruded from an inner peripheral edge of an annular plate-shaped portion in parallel to an axial direction and are continuously integrated. This is a method for manufacturing a stator yoke. Here, the feature of the present invention is a step of forming a cylindrical body having an end face closed structure by expanding a central portion of the plate made of a magnetic material by drawing, and punching a closed end face of the cylindrical body. Forming the tip of a plurality of pole pieces, and subjecting the peripheral wall of the cylindrical body to axial shearing to form a base of the pole piece that is continuous with the tip of the pole piece formed in the previous step. It is characterized in that, in this order, the step of cutting out and the step of shaping the pole piece by bending at a substantially right angle so as to raise the tip of the pole piece.

Further, according to the present invention, there is provided an outer cylindrical portion which is continuous with an outer peripheral edge of the annular plate-like portion, and a plurality of tooth-like magnetic pole pieces project from an inner peripheral edge of the annular plate-like portion in parallel to the axial direction. This is a method of manufacturing a motor stator yoke having a structure in which they are continuously integrated. In such a case, the plate-shaped body made of a magnetic material is bent by drawing, and the central part is expanded to form a cylindrical body having a short-side closed structure in the same direction as the peripheral cylindrical part by expanding the central part. . After this drawing step, the tooth-shaped magnetic pole piece is shaped by the same steps as above.

The shape of the tip of the pole piece can be any shape, such as a triangle, a trapezoid, or a semi-ellipse, depending on the shape of the punching die. The base of the pole piece, on the other hand, has a rectangular shape to undergo shearing. The closed end face of the cylindrical body before performing the punching process,
The shape is almost flat.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, of a cylindrical body formed by drawing, both the closed end face and the peripheral wall are used as pole pieces. Since the closed end face is punched, a pole piece tip of any shape can be formed. The peripheral wall of the cylindrical body is sheared in the axial direction and the base of the pole piece is cut out, so that the length is not particularly limited. As long as the cylindrical body can be formed by drawing, a long pole piece base can be obtained. The distance for performing the shearing process is shortened by the amount punched out by the punching process, and the shearing process is facilitated.

[0011]

FIG. 1 is a process explanatory view showing an example of a method for manufacturing a stator yoke for a small motor according to the present invention. This is a stator yoke having a structure in which a plurality of tooth-shaped magnetic pole pieces protrude in parallel with the axial direction from the inner peripheral edge of the annular plate-shaped portion and are continuously integrated with each other (that is, the stator yoke corresponds to the inner yoke shown in the known example) This is a method of manufacturing a stator yoke having the following shape.

First, a plate-like body 10 made of a magnetic material as shown in FIG. 1A is expanded at the center by drawing, and a cylindrical body 12 having an end face closed structure as shown in FIG. 1B is formed. As shown in FIG. 2, the cylindrical body 12 includes a substantially flat closed end face 12a and a peripheral wall 12b. At this stage, the outer periphery of the plate-shaped body 10 is trimmed as needed to form the annular plate-shaped portion 14.

Next, as shown in FIG.
The tip end portions 16a of the plurality of pole pieces are formed by punching the closed end face 12a of the second pole piece 2 in the axial direction. Here, the tip 16a of each pole piece has a triangular shape.
This punching process can be performed accurately and easily by using a mold having a predetermined shape (here, a five-valve flower-shaped punch). Subsequently, as shown in FIG. 1D, the peripheral wall portion 12b of the cylindrical body 12 is subjected to an axial shearing process so that the tip portion 16a of each pole piece punched in the previous step is formed.
The base 16b of the pole piece is cut out so as to be continuous. In this shearing process, a punch having a sharp edge with respect to the central axis is used to push the pole piece from the tip end side toward the annular plate-shaped portion.

Finally, as shown in FIG. 1E, the pole piece 16 is shaped by raising the tip 16a of the pole piece and bending it at substantially right angles to be in the same plane as the base 16b.
Instead of the process shown in FIG. 1B, trimming of the annular plate-shaped portion 14 may be performed at the stage after the pole piece shaping. Thereby, a plurality (five in this case) of tooth-shaped magnetic pole pieces 16 are protruded at equal intervals from the inner peripheral edge of the annular plate-shaped portion 14 in the axial direction, and are continuously integrated. A stator yoke is obtained.

Although the tip of the tooth-shaped magnetic pole piece obtained in the above embodiment has a triangular shape, according to the method of the present invention, an arbitrary magnetic pole can be formed by changing the shape of the die at the time of punching. A one-end shape can be realized. An example is shown in FIG. In the example shown in FIG. 3A, the tip of the pole piece has a trapezoidal shape, and the base has a rectangular shape. In the example shown in FIG. 3B, the tip of the pole piece has a semi-elliptical (semi-elliptical) shape, and the base has a rectangular shape. Not limited to these, it is also possible to manufacture a tooth-shaped magnetic pole piece having an arbitrary tip shape. Such a tapered tip shape is useful for suppressing magnetic saturation at the base of the pole piece and increasing magnetic efficiency.

In the case of manufacturing a stator yoke corresponding to the outer yoke in the above-described well-known example, a process shown in FIG. 4 is performed. First, as shown in FIG. 4A, a plate 20 made of a magnetic material is prepared. Next, this plate is subjected to drawing,
As shown in FIG. 4B, the outer peripheral cylindrical portion 21 is formed and the central portion is expanded to form the cylindrical body 22 having the end face closed structure in the same direction as the outer peripheral cylindrical portion 21. For example, a method in which a plate-shaped body is first drawn into a dish shape, the center portion is further deeply drawn into a bowl shape, and the bottom center is gradually raised inward to form a cylindrical shape. Thereafter, the edge of the outer peripheral cylindrical portion 21 is trimmed as necessary. The cylindrical body 22 formed by this drawing has an end face closed structure including a closed end face 22a and a peripheral wall portion 22b. Thereby, the outer peripheral cylindrical portion 21
An annular plate-shaped portion 24 is formed between the cylindrical body 22 and the central cylindrical body 22.

The following steps may be basically the same as those in the above embodiment. As shown in C of FIG. 4, by the cylindrical body 22 closed end face 22a of the punching processing of (representing the machining position working direction is indicated by an arrow W _1), to form a tip portion 26a of the plurality of pole pieces. Then, as shown in D in FIG. 4, by shearing axially circumferential wall of the cylindrical body (representing the machining position working direction is indicated by an arrow W _2), before the pole pieces punched by the step tip 26a The base 26b of the pole piece continuous with the base piece is cut out. Finally, as shown in FIG. 4E, the pole piece 26 is shaped by raising the tip portion 26a of the pole piece and bending it at a substantially right angle so as to be in the same plane as the end portion 26b. Therefore, after forming into a predetermined shape by drawing, the method of forming the pole piece is exactly the same as that shown in FIG.

[0018] In this manner, the toothed magnetic pole piece having the outer peripheral cylindrical portion continuous with the outer peripheral edge of the annular plate-shaped portion and projecting from the inner peripheral edge of the annular plate-shaped portion in parallel to the axial direction. Set
A stator yoke having a structure in which they are continuously integrated is obtained.

In carrying out the method of the present invention, an independent plate may be prepared one by one and subjected to drawing, punching, shearing and bending, but the elongated plate is used as a raw material. A method may be employed in which drawing, punching, shearing, and bending are sequentially performed without separating the individual yokes, and the individual stator yokes are finally cut and trimmed.

[0020]

As described above, according to the present invention, the pole piece is cut out by combining the punching process and the axial shearing process, so that it is possible to increase the magnetic pole length with respect to the motor inner diameter. Since the length required for the shearing process is shortened by the amount of the punching, the operation becomes easy without requiring a very advanced processing technique, and the processing time per piece can be shortened. In addition, since the tip is stamped, an arbitrary shape such as a triangular or trapezoidal shape can be realized according to the shape of the mold.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one embodiment of the method of the present invention.

FIG. 2 is a sectional view showing a shape of a molded product after drawing.

FIG. 3 is an explanatory view showing an example of the shape of a pole piece obtained by the method of the present invention.

FIG. 4 is a process explanatory view showing another embodiment of the method of the present invention.

[Explanation of symbols]

 10, 20 Plate-shaped body 12, 22 Cylindrical body 12a, 22a Closed end face 12b, 22b Peripheral wall portion 14, 24 Toroidal plate-shaped portion 16, 26 Magnetic pole piece 16a, 26a Tip of magnetic pole piece 16b, 26b Base of magnetic pole piece 21 Outer cylinder

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02K 15/02 H02K 1/12 H02K 1/14 H02K 37/14 535

Claims (3)

(57) [Claims] 1. A method of manufacturing a motor stator yoke having a structure in which a plurality of tooth-shaped magnetic pole pieces are protruded from an inner peripheral edge of an annular plate-shaped portion in parallel with an axial direction and are continuously integrated. A step of forming a cylindrical body having an end face closed structure by expanding a central portion of the plate made of a magnetic material by drawing, and punching out a closed end face of the cylindrical body to form a plurality of magnetic pole pieces. Forming a tip of the pole piece, and cutting the base of the pole piece continuous with the tip of the pole piece formed in the previous step by shearing the peripheral wall of the cylindrical body in the axial direction; A method of manufacturing a stator yoke for a motor, comprising: performing a step of forming a magnetic pole piece by bending at a substantially right angle so as to raise a tip end of the piece in this order. 2. A plurality of tooth-shaped magnetic pole pieces having an outer peripheral cylindrical portion which is continuous with an outer peripheral edge of the annular plate-shaped portion, and projecting from an inner peripheral edge of the annular plate-shaped portion in parallel to an axial direction, A method of manufacturing a stator yoke for a motor having a structure in which they are continuously integrated, wherein a plate-like body made of a magnetic material is formed by drawing to form an outer peripheral cylindrical portion and expand a central portion to form a cylinder having an end face closed structure. Forming the end of the plurality of pole pieces by punching a closed end face of the cylindrical body, and forming the cylindrical wall around the peripheral wall of the cylindrical body. Cutting out the base of the pole piece that is continuous with the tip of the pole piece formed in the previous process by shearing in the direction, and bending the pole piece almost perpendicularly to cause the tip of the pole piece The steps of shaping this order Method of manufacturing a motor stator yoke and performing. 3. The cylindrical body formed by drawing is:
3. The stator yoke for a motor according to claim 1, wherein the closed end face has a substantially flat shape, and the closed end face is punched to form a triangular, trapezoidal, or semi-elliptical pole piece tip. Method.