JPH0652979B2 - Resin mold type stepping motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor used in office equipment and industrial equipment.

2. Description of the Related Art Generally, in a hybrid type stepping motor, the configurations shown in FIGS. 2 (a) and 2 (b) are known. The configuration will be described below with reference to the drawings.
Is a magnetic pole 2 having a plurality of magnetic pole teeth (not shown) formed on the inner circumference thereof
And a magnetic pole 2 with a synthetic resin insulator 3
The stator winding 4 is wound via the. Reference numeral 5 denotes a pair of housings that support the stator 1, and a holding portion 5a for mounting a bearing 7 that rotatably supports the rotating shaft 6 is formed in the central portion. Reference numeral 8 denotes a rotor fixed to the rotating shaft 6 so as to face the stator 1, and includes a permanent magnet 9 and a rotor core 10 which is located on both sides of the permanent magnet 9 and has a plurality of magnetic pole teeth corresponding to the magnetic pole teeth of the stator. I am configuring. An insulating material 11 covers the stator winding 4 and the housing 5 and covers the stator winding 4.

Problems to be Solved by the Invention However, the above configuration has the following drawbacks.

(1) It was difficult to automate the insulation process after winding the stator winding, which was troublesome.

(2) Since the number of parts to be assembled is large and the coaxiality between the inner circumference of the stator and the rotation axis of the rotor is obtained, it is necessary to improve the processing accuracy of each part, which causes a cost increase.

In recent years, as a solution to these problems, the number of stepping motors adopting a method of encapsulating a stator winding portion with a thermosetting resin (for example, unsaturated polyester, epoxy resin) and integrally molding a part of a housing has been increasing. However, this method using a thermosetting resin has a drawback that productivity is poor and the equipment cost ratio of equipment and dies is high, as is known.

On the other hand, the method using a thermoplastic resin is difficult to put into practical use in a stepping motor using an extremely fine winding coil because the winding coil insulating film is easily damaged or broken due to the resin filling pressure during injection molding. It was

The performance required for coil-encapsulated thermoplastic resin is required as basic performance such as high electrical insulation, dimensional stability, heat shock resistance, and mechanical strength of conventional thermosetting resins. The main point is that the filling pressure is low.

Breaking stress (F) of polyurethane copper wire (linear 0.1 mm) of commonly used stepping motor is F≈3 ×
10 ³ N / m ² (0.3 / 0.06 ² πkg / mm ² ) Stress generated during polymer flow; O = η · dy / dχ (dy / dχ = 4Q / πR ² ) and F
> O is required.

On the other hand, since most of the housing as the motor is made of resin, heat shock resistance and dimensional stability are required. The following table shows usage examples of materials used in conventional mold type stepping motors and examples of various characteristics at that time.

As a result of the above, it is desired to develop a material that satisfies the characteristics shown in Table 1 for the thermoplastic resin.

Means for Solving the Problems To solve the above problems, the present invention provides a thermoplastic polyethylene terephthalate (PET) resin having a low melt viscosity of a material and excellent dimensional stability, a crystallization accelerator, and a low heat shrinkage. Agent, a heat-resistant treatment agent, and a resin that is basically compounded with an impact resistance improver, glass fiber, beads or plate-like filler,
A bearing housing is integrally molded with a stator part from a fiber reinforced polyethylene terephthalate resin in which a heat stabilizer and carbon black are mixed.

Action According to the above configuration, it is possible to enclose the coil of the ultra-fine winding stator with the thermoplastic resin (FR-PET) and integrate the housing, and it is possible to significantly improve the productivity as compared with the method using the thermosetting resin. It will be possible.

Embodiment FIG. 1 shows an embodiment of the present invention. The same components as those of the above-described conventional configuration will be described with the same reference numerals.

In the figure, reference numeral 1 denotes a stator around which a winding 4 is wound, and the winding 4 is insulated from the stator 1 by an insulating frame 3. 1
Reference numeral 2 denotes a boss that supports a bearing 7 that rotatably supports the rotating shaft 6, and is fixed to the stator 1 by a bearing housing 13 that is resin-molded integrally. The resin-molded bearing housing 13 completely seals the winding 4 of the stator 1 and the motor flange 14 with the magnetic shield ring 1.
The structure is such that welding and caulking are performed through the assembly 5. Reference numeral 16 denotes a boss that mounts and holds the bearing 7 of the output-side rotary shaft on the flange 14, and is formed of the same resin as that of the bearing housing 13 and configured to maintain the accuracy of the rotary shaft.

Next, the structure of the bearing housing 13 will be described.

Table 2 shows an example of the basic composition of the resin used for the bearing housing 13. Table 3 summarizes the effects of the resin used in the bearing housing 13 of the present invention and the conventional resin on the moldability and quality.

EFFECTS OF THE INVENTION As is clear from the above description, the present invention has the following effects.

1) Thermoplastic resin can be realized by low-pressure encapsulation molding that does not cause disconnection or rare short even when extra fine wires such as polyurethane copper wires are used for stator windings, which has been considered difficult. The productivity can be remarkably improved as compared with the method described in 1.

2) Since it is a thermoplastic resin, ultrasonic welding and heat welding are possible even in the assembly structure, and auxiliary materials such as adhesives and screws are not required, so that the assembly process can be rationalized.

3) Due to the above advantages, it is possible to provide an inexpensive and high-quality stepping motor.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a resin mold type stepping motor showing an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are a longitudinal sectional view and a transverse sectional view of a conventional hybrid type stepping motor. 1 ... Stator, 4 ... Stator winding, 13 ... Bearing housing.

Claims (1)

[Claims] 1. A resin mold type stepping motor in which a stator housing for forming a rotating magnetic field in which a stator winding is wound around a plurality of magnetic poles and a bearing housing are integrally molded, wherein the molding resin is polyethylene in a weight ratio. Resin with a basic composition consisting of 100 parts of terephthalate, 1 part of crystallization accelerator, 20 parts of low heat shrinkage agent, 20 parts of heat treatment agent, and 5 parts of impact modifier, glass fiber 15%, beads or plate filler 25 %, A heat stabilizer of 0.1%, and a carbon black of 0.3% are mixed, and the resin mold type stepping motor is a thermoplastic plastic fiber reinforced polyethylene terephthalate resin.