JPH0510022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric motor having a stator integrally molded with synthetic resin.

BACKGROUND ART A step motor will be described below as an example of a conventional electric motor.

In general, a conventional step motor, as shown in Fig. 2, consists of a rotor 4 consisting of a permanent magnet 1, a shaft 2, and a magnetic pole piece 3 having a large number of small teeth on the outer periphery, and a stator 5 surrounding the rotor 4. In the stator 5, a coil 7 is wound around each pole of a stator core 6 made of laminated magnetic thin plates. 8 is a load side frame, and 9 is an anti-load side frame, which are formed of a sintered member, a pressed member, or the like.

The load side frame 8 and the anti-load side frame 9
The steps 10 and 11 on the outer periphery of the stator core 6
It is positioned by making it abut against the outer diameter part 12 of. Furthermore, the two frames 8 and 9 are integrally provided with recesses 13 and 14 for accommodating bearings, and bearings 15 are inserted and housed in the recesses 13 and 14. Shaft 2 is pivotally supported.

With this type of motor, the overall thickness can be reduced, and
When trying to improve assembly workability, Figures 3 and 4
As shown in the figure, it is desirable that the support structure for the rotor 4 be a single-axis structure. In FIG. 3, the load-side frame 16 is formed of an inexpensive press member, and a bent portion 17 for press-fitting and accommodating the bearing 15 is formed in the load-side frame 16 by deep drawing. In FIG. 4, the stator 5 is integrally molded with synthetic resin 18, and the recess 19 for accommodating the bearing is also formed of synthetic resin.

In the step motor configured as described above, it is known that the smaller the gap 22 between the inner diameter part 20 of the stator core 6 and the outer diameter part 21 of the rotor 4, the better the rotational characteristics.

Problems to be Solved by the Invention However, in the conventional structure, in order to reduce the gap 22, the steps 10 of the frames 8, 9,
11 and the inner circumferential portions of the recesses 13 and 14 and the inner diameter portion 20 of the stator core 6, it is necessary to process them with extremely high precision. However, frame 8,
9 and the stator core 6 are each separate pieces, which increases the number of assembly steps, and because they are processed and polished separately before being assembled, the misalignment that occurs during each polishing is added, and the two frames 8, 9
Also, it is very difficult to increase the concentricity between the inner diameter portions 20 of the stator core 6. When the frame 16 is made of a single shaft structure using a press member as shown in FIG.
Since the bearings 15 are press-fitted, the bent portion 17
In order to increase the strength of the frame 16, it is necessary to ensure sufficient wall thickness, but in this case, the material of the frame 16 itself had to be a thick steel plate, and the processing also required advanced technology.

If a thin iron plate is used, sufficient strength for holding the bearing 15 cannot be obtained, and there is a risk that the bent portion 17 may be deformed when the bearing 15 is press-fitted.

On the other hand, when the stator 5 is molded with synthetic resin and the recess 19 into which the bearing 15 is press-fitted is integrally formed with resin as shown in FIG. 4, the synthetic resin has a small restoring force against deformation during press-fitting, so After press-fitting the motor 15, sufficient holding force may not be obtained, and the concave portion 19 may crack or deform during long-term use, or the motor surface may cause problems when used in a floppy disk drive device. It had problems such as large leakage magnetic flux.

The present invention has been made in view of the above problems, and provides an electric motor that does not reduce the concentricity of the stator and rotor, reduces leakage magnetic flux from inside the electric motor, and strengthens the holding force of the bearings. The purpose is to provide.

Means for Solving the Problems A means for solving the above problems is to integrally mold the frame and the stator with synthetic resin, and at the same time, the synthetic resin covers the inner surface of the frame, and at the bent portions of the frame. , which covers the surface opposite to the surface holding the bearing that rotatably supports the rotor.

Effect The effect of this technical means is as follows.
In other words, the frame and stator are integrally molded with synthetic resin, and this synthetic resin covers the inner surface of the frame, and at the bent part of the frame, the side opposite to the surface that holds the bearing that rotatably supports the rotor. By covering the surface of the motor, the strength of the bent part is increased, the frame can be formed from a thin steel plate, and the bent part does not deform even during long-term operation. It is also possible to reduce leakage magnetic flux from.

Embodiment Hereinafter, as an embodiment of the present invention, a step motor will be described based on the accompanying drawings. In FIG. 1, 20 is a stator made of laminated magnetic thin plates, and a coil 21 is wound around the stator. 22 is a frame formed by pressing an iron plate. The stator 20 and frame 22 are integrally molded with synthetic resin 23. The frame 22 is located at the front face of the motor on the output shaft side and is attached to cover the front face of the motor. The synthetic resin 23 is molded over almost the entire surface of the stator 20, and the frame 2
2 and the bent portion 24 formed by drawing the frame 22. The stator inner diameter portion 25 and the bent portion 24 of the frame 22 are cut so as to be concentric.
26 is a rotor. The rotor 26 includes two magnetic pole pieces 27 having a large number of small teeth on the outer periphery, a permanent magnet 28 sandwiched between these two magnetic pole pieces 27, and a shaft 29 that connects the magnetic pole pieces 27 and the permanent magnet 28. The rotor support member 30 is made of non-magnetic resin and is fixed to the rotor support member 30. The rotor 26 is rotatably supported via two bearings 31 that are press-fitted into the bent portion 24 of the frame 22 so as to be rotatable, and has a single-axis structure. 32 is a metal lid attached to the back surface of the motor body.

In the above configuration, the bent portion 2 of the frame 22
Even if 4 becomes a little thin due to the squeezing process, most of the outer circumferential surface of the bent part 24 is integrally molded with the synthetic resin 23, so the bent part 24 is reinforced, and the bent part 24 is easily removed when press-fitting the bearing. There is no fear of deformation, the frame 22 can be made of a thin iron plate, and the motor can be made thinner.

Also, when assembling, the frame 22 and stator 2
0 is securely fixed when the resin 23 is injected, so assembly with high concentricity is possible. On the other hand, since the magnetic flux generated by the permanent magnet 28 provided on the rotor 26 is shielded by the frame 22 and the lid 32, almost no magnetic flux leaks to the outside.

Effects of the Invention As is clear from the above description, the frame and the stator are integrally molded with synthetic resin, and the synthetic resin covers the inner surface of the frame and rotatably supports the rotor at the bent portion of the frame. By covering the surface opposite to the surface that holds the bearing, it is possible to maintain the strength of the bent part even if the frame is made of thin material, and prevent the bent part from deforming due to long-term operation. At the same time, leakage magnetic flux from inside the motor can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a step motor showing an embodiment of the present invention, FIG. 2 is a sectional view of a conventional step motor, and FIGS. 3 and 4 are sectional views of a conventional single-shaft step motor. be. 20...Stator, 22...Frame, 23...
...Synthetic resin, 24...Bending portion.

Claims (1)

[Claims] 1 A rotor, a stator, a bearing that rotatably supports the rotor, and a frame having a bent portion that holds the bearing, the frame and the stator being integrally molded with synthetic resin, An electric motor characterized in that the synthetic resin covers an inner surface of the frame and a surface opposite to a surface holding the bearing at a bent portion of the frame.