JPH026302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of assembling a stator for a stepper motor.

Stepper motors are often used in measuring instruments, computer peripherals, office equipment, information equipment, and the like. There are a wide variety of stepper motors of this type, and one example will be briefly explained. FIG. 1 shows an example of an inner rotor type stepper motor. The stator section mainly consists of an outer yoke 1, an inner yoke 2, and a coil 3 interposed between them.
It consists of two sets of these combined. The outer yoke 1 has a shape in which a large number of tooth-shaped magnetic pole pieces protrude from its inner peripheral edge in the axial direction at equal intervals, and the inner yoke 2 has a similar shape. A coil 3 is inserted between the outer yoke 1 and the inner yoke 2, and the outer yoke 1 and the inner yoke 2 are fitted in such a state that their magnetic pole pieces are offset from each other. Two sets of such fitting bodies are connected to the inner yoke 2.
They are placed back to back with a spacer 4 interposed between them, and are combined at an angle such that their magnetic pole pieces are shifted by 1/4 of the distance between the magnetic pole pieces. A rotor part rotatably housed inside the combination by a bearing 5 is
It consists of a shaft 6 and a multi-pole magnetized annular magnet 8 fixed to it by a synthetic resin 7, and is magnetized in a step-like manner by the magnetomotive force generated by supplying a pulse current to the coil 3. It is something that is displaced.

Now, in such a stepper motor,
Stator yoke, i.e. outer yoke 1 and inner yoke 2
It is important to accurately attach the to the mounting plate (for example, flange 10, motor cover 11, spacer 4, etc.). Traditionally, in such cases,
As shown in Fig. 2, protrusions 12 protruding toward the mounting plate are provided on the stator yoke, that is, on the outer yoke 1 and the inner yoke 2, and the stator yoke is attached by spot welding (projection welding). It is common to fix and integrate the mounting plate and the mounting plate. This projection 12 concentrates the current and force and provides good results in normal applications.

However, this method has a problem in that splashes (fine pieces of the welded material, powder, etc.) are likely to occur during welding. This point is particularly important in stepper motors to which the present invention is applied. The reason for this is that the stator yoke, which is the material to be welded, is made of a high magnetic permeability material, and there are permanent magnets inside, so the splash enters the narrow gap between the permanent magnet rotor and the stator, causing them to come into close contact and rotate. Defects may occur, and it is impractical to completely clean all assembled stators after welding, as the shape is complex and the stators are magnetically attached, making it very time-consuming. It is from.

In addition, in the case of such spot welding, it is necessary to provide an engaging part for positioning on the stator yoke and its mounting plate, completely separate from the projection, which complicates the structure and makes the stator yoke and its mounting plate more complicated. Another problem is that if the mounting plate is dirty, the welding will not be completed completely and the weld will likely come off.

The purpose of the present invention is to eliminate the drawbacks of the conventional technology, to fix the stator yoke and the mounting plate firmly and accurately, and to prevent splashes and the like, thereby greatly improving the reliability of the motor. It is an object of the present invention to provide a stator assembly method that can be combined with other manufacturing processes that were completely unrelated to the present invention to reduce the number of steps and equipment.

A stator yoke for a stepper motor requires complex machining such as press molding, drilling holes, and forming a large number of magnetic pole pieces, resulting in residual strain. Particularly in the case of a high-performance stepper motor, the magnetic properties of the yoke will continue to deteriorate due to residual strain, and no improvement in motor performance can be expected. Therefore, after the stator yoke is molded, it is necessary to perform annealing to remove residual strain and restore its magnetic properties.

The present inventors came up with the idea that by making skillful use of this annealing process, it would be possible to simultaneously achieve the fixation of the stator yoke and the mounting plate, and this led to the completion of the present invention. It is.

That is, the present invention provides a method for assembling a stator by fixing a stator yoke for a stepper motor having a large number of magnetic pole pieces to a predetermined position on a mounting plate.
A plurality of positioning reference holes are provided on the part of the stator yoke that faces the mounting plate, and a half-blank protrusion for positioning is formed at a predetermined position on the mounting plate facing the holes, and a brazing material is interposed between the stator yoke and the mounting plate. A method for assembling a stator for a stepper motor, characterized in that the half-blank convex portion is fitted into the reference hole and then sent into a high-temperature atmosphere to simultaneously perform brazing joining and annealing of the stator yoke. .

This will be explained in more detail below. FIG. 3 is an explanatory diagram showing one embodiment of the present invention. The basic shapes of the outer yoke 1 and the inner yoke 2 are almost the same as those of the conventional ones. These are made of high magnetic permeability materials, such as electromagnetic soft iron. A notable difference from the conventional one is that a plurality of (two in this embodiment) positioning reference holes 20 are drilled at predetermined positions in the parts of the outer yoke 1 and the inner yoke 2 that face the mounting plates. It is that you are.

The mounting plate is a general term for the flange 10, the motor cover 11, or the spacer 4, and positioning half-blanked convex portions 21 are formed at predetermined positions thereof toward the opposing outer yoke 1 and inner yoke 2. Therefore, the spacer 4 has two on each side.
This means that individual half-blanked convex portions are formed. These reference holes 20 and half-blanked protrusions 21 function as positioning members that allow each stator yoke to take a predetermined positional relationship with each other when they are fitted, and until they are completely fixed and integrated, It also serves as a temporary fixing function to prevent the stator yoke and the mounting plate from shifting from each other.

Such a stator yoke and a mounting plate are prepared, and a circular thin plate-shaped brazing material 25 is interposed between them.
The half-blanked convex portion 21 is fitted into the reference hole 20. This completes the positioning and sends it into the high-temperature atmosphere as it is.

As the brazing material 25, for example, silver brazing material can be used. In that case, 1 in a vacuum at about 1100℃
By leaving it for ~1.5 hours, the stator yoke and the mounting plate can be brazed together and the stator yoke can be annealed at the same time.

When the stator yoke and mounting plate are joined by conventional projection welding, even a slight deviation in welding conditions causes imbalances in parallelism, welding defects, and frequent splashes, which seriously impede motor performance. According to this method, all such problems can be solved.

In other words, since the present invention is configured as described above, the stator yoke and the mounting plate can be fixed firmly and precisely, and splashes do not occur, so the reliability of the motor is greatly improved, and there is no need to worry about any problems that have arisen in the past. Since it can also be used as an annealing process, it can produce excellent effects such as reducing assembly man-hours and equipment.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an inner rotor type stepper motor, FIG. 2 is an explanatory view of a conventional technique, and FIG. 3 is an explanatory view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Outer yoke, 2... Inner yoke, 4... Spacer, 10... Flange, 11... Motor cover, 20... Reference hole for positioning, 21... Half punched convex portion, 25... Brazing material.

Claims (1)

[Claims] 1. In a method of assembling a stator by fixing a stator yoke for a stepper motor having a large number of magnetic pole pieces to a predetermined position on a mounting plate, a plurality of positioning reference holes are provided in the part of the stator yoke facing the mounting plate, and mounting A half-blank convex portion for positioning is formed at a predetermined position on the plate, a brazing material is interposed between the stator yoke and the mounting plate, and the half-blank convex portion is fitted into the reference hole in a high-temperature atmosphere. A method for assembling a stator for a stepper motor, characterized by simultaneously performing brazing joining and annealing of the stator yoke.