JPS6249815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a stator yoke for a small motor, and more specifically, a stator yoke having a structure in which a large number of tooth-like magnetic pole surfaces are arranged in parallel on the inner circumferential side, for example, for an inner rotor type small power motor. The present invention relates to a method of manufacturing a stator yoke of a stepper motor.

This type of inner rotor type stepper motor is well known, and an example thereof will be briefly described. As shown in FIG. 1, the stator section mainly consists of an outer yoke 1, an inner yoke 2, and a coil 3 interposed between them, and two sets of these are coupled together. 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 same applies to the inner yoke. outer yoke 1
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 manner that their magnetic pole pieces are offset from each other. Two sets of such fitting bodies are combined at an angle such that the inner yokes 2 are placed back to back and their magnetic pole pieces are shifted by 1/4 of the magnetic pole piece angle. The rotor part is rotatably housed inside the combination by a bearing 4.
It consists of a shaft 5 and a multi-pole magnetized annular permanent magnet 6 fitted therein, and is displaced in steps by the magnetomotive force generated by supplying pulsed current to the coil 3.

Now, conventionally, all methods of manufacturing a stator yoke having a structure having a large number of tooth-shaped magnetic pole pieces on the inner circumferential side have adopted the extraction and raising method. For example, as shown in Figure 2, the end face of a cup-shaped yoke is punched out so that a plurality of U-shaped gaps are positioned radially, and then pulled inward, or as shown in Figure 3. Another method is to punch out the end face of a cup-shaped yoke into the shape of an internal gear, and then pull it inward.

However, with this method, the length of the magnetic pole piece cannot be made long relative to the outer diameter of the motor, and a motor with a high height and high torque cannot be manufactured. In particular, in the case of the former manufacturing method, the point where the tip surface of the magnetic pole piece of one yoke is opposite the end surface of the other yoke,
In other words, since it is a magnetic plate, magnetic flux leaks to that part, and a decrease in torque is unavoidable. Furthermore, in the former case, since the magnetic flux path between the magnetic pole piece and the yoke body is a part that is not punched out, the distance between the bases of adjacent magnetic pole pieces cannot be made too narrow;
In the latter case, the distance between the bases of adjacent pole pieces will inevitably be large due to the shape after punching.
In any case, it is not possible to obtain a motor with a large number of steps relative to the outer diameter of the motor. Furthermore, in either manufacturing method, since the magnetic pole pieces have a flat plate-like structure, they approach the cylindrical rotor surface like a flat plate, and therefore there is a loss in the magnetic path.

An object of the present invention is to eliminate such drawbacks of the prior art, and to make it possible to increase the length of the toothed magnetic pole piece relative to the motor outer diameter, thereby increasing the torque and reducing the motor outer diameter. It is easy to obtain a large number of steps relative to the diameter, and the magnetic pole pieces are curved along the rotor surface, so that the magnetic field generated by the stator can be effectively applied to the rotor. An object of the present invention is to provide a method for manufacturing a high-performance stator yoke for a small motor having a large number of tooth-shaped magnetic pole pieces on its inner peripheral surface.

Embodiments of the present invention will be described in detail below based on the drawings. Prepare a flat plate (approximately 1.0 mm thick) made of a high permeability magnetic material such as electromagnetic soft iron, and first, as shown in Figure 4A, the diameter is 48 mm and the height is 13 mm.
Draw and draw it into a dish shape of about 100 ml. The diameter of the hole through which the material was extracted is approximately 62 mm. Next, squeeze it into a bowl shape as shown in Figure B. Furthermore, as shown in C, D, and E of the figure, the center of the bottom is gradually raised inward by drawing to form a cylindrical shape. Then, the outer periphery is trimmed, and the central end face is punched out and expanded slightly as shown in FIG. Since such drawing processing and punching may be the same as those commonly used, detailed description thereof will be omitted.

Now, the intermediate molded body 10 made in this way is
A large number of tooth-shaped magnetic pieces are formed on the inner periphery of the punch 11 and die 12 as shown in FIG. The punch 11 is a columnar body with a petal-like cross section with five petals, and the lower part has a small diameter punching blade 13 perpendicular to the axis, and a shearing blade 1 inclined at an angle of about 30 degrees to the axis.
4, and a pilot 15 is attached to the lower end thereof. The outer diameter of the pilot 15 is just large enough to fit into the inner cylinder of the intermediate molded body 10, the thickness of the shearing blade 14 is slightly thicker than that of the inner cylinder, and the height is slightly higher than that of the inner cylinder. Dimensions. The die 12 is a petal-shaped punch 1.
A step portion 16 is formed in the upper part of the hole into which the intermediate molded body 10 is just fitted, and which receives the inner cylindrical end of the intermediate molded body 10. Therefore, the die 12 has a structure in which the end surface of the portion projecting inwardly above the step portion 16 is in close contact with the outer surface of the portion remaining as the tooth-shaped magnetic pole piece of the inner cylinder of the intermediate molded body 10.

The die 12 and punch 11 are attached to a conventional punching press to form toothed magnetic pole pieces. As shown in FIG. 7, with the die 12 covered with the intermediate formed body 10, the punch 1 is inserted from above.
I'm going to put down 1. First, the pilot 15 is inserted into the inner cylinder of the intermediate molded body 10, and then the shear blade 14, which has an inclination angle of about 30° with respect to the central axis, is inserted.
comes into contact with the end surface of the intermediate molded body 10. Then, as the punch 11 is gradually press-fitted, the remaining portion is cut off, leaving only five tooth-shaped magnetic pole pieces, and the chips are removed in one lump at each cut-out location. The sheared intermediate state has a shape as shown in FIG. 8A. Subsequently, the punching blade 13 comes into contact with the end surface of the intermediate molded body 10, and that part is punched out. The state thus obtained is the 8th
As shown in Figure B, the shape is such that the space between the bases of adjacent tooth-like pole pieces is hollowed out. After such hollowing is performed, a projection is formed for resistance welding the yokes together or the yoke and the flange, a window for positioning is punched, and the toothed magnetic pole pieces are modified. When such processing is performed, processing distortion remains, so it is preferable to perform annealing in a vacuum.

Formation of the tooth-shaped magnetic pole piece is, in principle, carried out by the punch 11 and die 12 as described above, but the structure of the die actually used is shown in Fig. 9. be. A punch plate 20 is fitted on the upper part of the punch 11, and a rotation lock key 2 is inserted into the punch plate 20.
1, the back plate 22 and bolt 23 are inserted into the back plate 22 and the bolt 23.
It is fixed by. The upper stripper 24 attached to the lower part of the punch 11 is attached to the punch plate 20.
The support bolt 25 is slidably fitted into the support bolt 25 to prevent it from falling off. Upper stripper 24
is the spring 27 fitted in the spring guide 26
As a result, an elastic force acts in a direction away from the punch plate 20, and the punch plate normally remains at a position regulated by the support bolt 25, that is, a position where its lower end surface coincides with the joint surface between the punch 11 and the pilot 15. ing. The lower mold includes a lower stripper 28 that fits around the outer periphery of the die 12, a support bolt 29 that supports the lower stripper 28, and a push-up washer 30.
When the upper mold is pushed down with the intermediate molded body 10 placed on the upper part of the die 12, the upper stripper 24
comes into contact with the upper end surface of the intermediate molded body 10 and pushes down the lower stripper 28, support bolt 29, and push-up washer 30, so that the intermediate molded body 10 is tightly covered with the die 12, as shown in FIG. It becomes a satsuta style. When the upper mold is further pushed down, the upper stripper 2
4 firmly presses the intermediate formed body 10, and punches 1
1 descends and cuts off the inner cylindrical portion in the axial direction as shown in FIG. 8A. This is done by the inclined shearing blades in the lower part of the punch 11. When the upper mold is further pushed down, the bases of adjacent pole pieces are punched out in a shape in which the bases are largely hollowed out, as shown in FIG. 8B. The positional relationship of the molds at that time is shown by imaginary lines in FIG. When the upper mold is pulled up and the push-up washer 30 is pushed up, the lower stripper 28 is slightly raised, and the yoke having a large number of toothed magnetic pole pieces can be easily taken out.

By the way, the yoke consists of an outer yoke and an inner yoke fitted into the outer yoke. Therefore, die 12
For example, as shown in FIG. 10, the upper part of the outer periphery has a smaller diameter by the thickness of the yoke plate, and the height of the smaller diameter portion is lower than the height of the outer yoke to be produced. The outer yoke intermediate molded body 10a has an outer periphery larger than that of the inner yoke intermediate molded body 10b by the thickness of the plate. The magnetic pole pieces of the outer yoke are formed by placing the intermediate molded body 10a over the die 12, as shown in FIG. 11A. Therefore, at this time, there is a gap between the upper outer periphery of the die 12 and the intermediate molded body 10a.
The magnetic pole piece of the inner yoke is formed after the adapter 31 is attached, as shown in FIG. 11B. Since the inner yoke intermediate formed body 10b has a small diameter, there is no gap between it and the upper outer circumference of the die 12, and the outer circumference height is also low. The upper molds may be exactly the same. Therefore, just attach the adapter 31 when using the outer yoke and attach the adapter 31 when using the inner yoke.
Two types of magnetic pole pieces, an outer yoke and an inner yoke, can be cut out without changing other molds or the like. The outer yoke and inner yoke thus manufactured fit together such that their toothed magnetic pole pieces are offset from each other.

As described above, the present invention is configured to form a cylindrical shape and then shear it in the axial direction to form a large number of tooth-like magnetic pole pieces. The length can be increased, and the stator magnetic field and rotor magnetic field can therefore be used more effectively, which can improve torque. There are effects that can be easily obtained. Furthermore, in the present invention, during the shearing process, the tooth-shaped magnetic pole piece forming portion of the inner cylinder is completely surrounded by the die and punch, and the material constituting the portion is kept in a state where it cannot escape anywhere. , even long tooth-shaped magnetic pole pieces can be formed with extreme precision without stretching or bending. Furthermore, since the punching between the bases of the toothed magnetic pole piece can be formed simply by further press-fitting the same punch following the step of cutting out the toothed magnetic pole piece, there is also the effect of increasing the production speed. Furthermore, when configured as in the present invention,
Since the magnetic pole pieces can be made into an arc shape that follows the outer circumference of the rotor (instead of being shaped like a flat plate in the case of traction), the stator magnetic field acts on the rotor more efficiently, increasing torque and saving power. As a result, the loss in the magnetic path is reduced and the effective magnetic flux linkage is increased, so if the same current as a conventional motor is passed, the torque will be increased. Furthermore, when punching is performed so as to greatly hollow out the bases of adjacent toothed magnetic pole pieces as in the present invention, magnetic material remains in the portion of the other yoke where the tip of the toothed magnetic pole piece of one yoke faces. Therefore, there is less magnetic flux leaking in the axial direction than in the conventional structure, and torque is increased by effectively utilizing the rotor magnetic flux. As described above, the present invention has remarkable effects not found in the prior art, and can significantly improve the performance of the motor as a whole.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a small stepper motor to which the present invention can be applied, Figs. 2 and 3 are explanatory diagrams of a conventional trigger type yoke, and Fig. 4 shows the first half of the process of the method of the present invention. Molding state explanatory diagram,
FIG. 5 is a perspective view showing an example of the punch, intermediate molded body, and die used in the process of forming the magnetic pole piece of the yoke, FIG. 6 is a bottom view of the punch, and FIG. 7 is an enlarged explanatory view showing the state of shearing processing. FIG. 8A is a perspective view showing the yoke after shearing, B is a perspective view showing the yoke after punching, FIG. 9 is a sectional view showing an example of a die installed in an actual press machine, and FIG. 10 is a perspective view of the yoke after shearing. FIG. 11A is a sectional view showing the lower mold structure during processing of the outer yoke, and FIG. 11B is a sectional view showing the lower mold structure during processing of the inner yoke. 10... Intermediate molded body, 11... Punch, 12...
...Die, 13...Punching blade, 14...Shearing blade,
15...Pilot.

Claims (1)

[Claims] 1. A washer-like plate, an outer ring continuous to its outer periphery, and a number of tooth-shaped magnetic pole pieces protruding from the inner edge of the washer-like plate in parallel to its central axis in the same direction as the outer ring are continuous. A method of manufacturing a stator yoke for a small motor with an integrated structure, in which the outer periphery of a plate-shaped body made of magnetic material is bent by drawing, and the central part is bent in the same direction as the outer periphery so that the central part forms a cylindrical shape. a step of punching and forming the protruding end surface of the cylindrical body, a die that closely contacts the outer surface of the tooth-like pole piece forming portion of the cylindrical body, and a cutting edge pointing outward at an acute angle with respect to the central axis. A punch having a plurality of shearing blades arranged around the circumference and having a blade thickness equal to or slightly thicker than the wall thickness of the cylindrical body, and having a pilot at the tip that just fits into the cylindrical body. Using a press, the cylindrical body is sheared along the axial direction from the plate-like surface side, leaving only a large number of tooth-shaped magnetic pole pieces arranged at equal intervals around the central axis, and the rest of the cylindrical body is A small motor having a large number of tooth-shaped magnetic pole pieces on the inner circumferential side, which comprises a step of cutting out a portion of the tooth-shaped magnetic pole pieces, and a step of punching out the base portions of adjacent tooth-shaped magnetic pole pieces into a shape that hollows out the space between the bases of adjacent tooth-shaped magnetic pole pieces. manufacturing method of stator yoke for