JPH089621A - Stepping motor - Google Patents

Abstract

PURPOSE:To improve holding torque of a stepping motor without lowering the rotational torque of the motor by assembling each stator core so that the rotational angle at which the torque generated by stator cores magnetized in a paired state becomes zero can be shifted from the rotational angle at which the torque generated by other stator cores which are also magnetized in a paired state by a prescribed amount. CONSTITUTION:Paired pole teeth 12 and 13 constituted of stator cores 20 and 21 are arranged against a permanent magnet in which N and S poles are formed at a pole width of 2W so that their midpoint can be aligned with the boundary between the poles of the magnet 5. Then paired pole teeth 14 and 15 composed of stator cores 22 and 23 are arranged so that they can be shifted from the center of each pole of the magnet 5 by (w). Therefore, a large torque can be maintained without lowering the holding torque of a rotor which is the resultant torque of the torques generated by the stator cores in such a state the maximum holding torque does not drop much as compared with the maximum generated torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a PM-type stepping motor that holds accurately and uniformly and strongly and has a large holding torque.

[0002]

2. Description of the Related Art In a step motor of another known PM, the pole teeth of the stator core are not energized by the exciting coil wound around the stator core during non-energization.
A magnetic circuit passing through the stator core and the like is established by the magnetomotive force of the permanent magnet formed on the outer circumference of the rotor. This magnetic circuit moves the rotor to a magnetically stable position,
Holding torque is generated between the rotor and the stator core.

Conventionally, in such a stepping motor, as shown in FIGS. 3 (a) and 3 (b), each stator core 2 is provided for each permanent magnet 5 having a pole of width 2W.
0 to 23 are arranged. The stator cores 20 to 21 are provided with pole teeth 12 to 15 so as to face the permanent magnets 5, respectively.
Are formed. The pole teeth 12 of the stator cores 20 and 21
And 13 are arranged so that their centers coincide with the boundaries of the poles of the permanent magnet 5. In addition, the stator cores 13, 1
The pole teeth 14 and 15 of No. 4 are arranged at positions facing the poles of the permanent magnet 5 and at positions displaced from the pole teeth 12 and 13 by the distance W.

In each of the stator cores 20 to 23 thus arranged, a magnetic circuit is formed in each of the two stator cores 20 and 21 and the two stator cores 22 and 23 when the step motor is not energized. . With each magnetic circuit, (c) and
The torque shown in (d) is generated. Here, the pole teeth 12, 1
3 and the pole teeth 14 and 15 are displaced from each other by the width W, the cycle of generation of each torque includes the width W at the rotation angle.
A phase difference W corresponding to is generated. Thus, the phase difference is W
In this case, the generated torque becomes 0 when the rotation angle is 0, W, 2W ... In both the set of the stator cores 20 and 21 and the set of the stator cores 22 and 23. When these torques are combined, (e) in FIG.
A synthetic torque as shown in is generated. This combined torque is a holding torque that holds the rotor stationary.

However, when such a PM type step motor is used for valve adjustment for controlling the intake air amount of an engine, for example, the rotor may rotate due to vibration or the like when the step motor is stopped. Figure 3
As shown in (e) of (1), when the torques generated by the sets of the stator cores are combined, the generated torques cancel each other and the maximum torque decreases. Therefore, the inventors of the present application have devised a stepping motor having an increased holding torque and applied for it first. For example, a step motor disclosed in Japanese Patent Laid-Open No. 60-43059, or Japanese Patent Laid-Open No. 60-4
The step motor disclosed in Japanese Patent No. 3060 can be mentioned. In these step motors, in the former, the width of the teeth formed on one of the stator cores in the stator core that establishes a magnetic circuit with two sheets is made uneven. In the latter case, the widths of the north and south poles of the permanent magnets arranged on the rotor are made uneven.
With such respective configurations, the holding torque of the rotor can be increased. Since the conventional configuration is described in detail in the above-mentioned publication, detailed description is omitted here.

[0006]

However, in the above-mentioned step motor in which the teeth of the former stator core are uneven, it is necessary to employ two types of stator cores having different shapes, which causes a problem of cost increase. . Further, in the case of making the pole widths of the latter permanent magnets uneven, the magnetomotive force of the permanent magnets decreases in the narrower width of the N pole or the S pole. In this case, the permanent magnet with the reduced magnetomotive force adversely affects the rotational torque when the step motor is energized, and the rotational torque may be reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stepping motor having a simple structure and an improved holding torque when it is not energized while ensuring a rotating torque when it is energized.

[0008]

In order to solve the above problems, a step motor according to the present invention has an N pole and an S pole on the outer peripheral surface.
A rotor, which has a cylindrical permanent magnet in which poles are alternately magnetized, and is rotatably supported by a shaft, is arranged to face the permanent magnet with a predetermined gap, and has pole teeth. In the step motor, a plurality of sets of stator cores that are magnetized in opposite poles and an exciting coil that is wound around the stator core and that is magnetized when the pole teeth of the stator core are energized to rotate the rotor are de-energized. Occasionally, the rotational angle of the rotor where the torque generated by the stator core magnetized to the opposite pole is zero and the rotational angle of the rotor where the torque generated by the other stator core magnetized to the opposite pole is zero are Each of the stator cores is assembled so as to be displaced by a certain amount.

In addition, with respect to the phases of the pole teeth formed on the stator cores magnetized to the opposite poles, the pole teeth formed on the other stator cores magnetized to the opposite poles have a predetermined phase difference. The step motor according to claim 1 may be adopted. Further, the step motors according to claim 1 or 2 may be adopted, wherein the respective stator cores have the same shape.

[0010]

The operation of the step motor constructed as above will be described below. As described above, in the step motor according to the present invention, the rotation angle at which the torque generated by the stator core magnetized to the opposite pole becomes zero and the rotation angle at which the torque generated by the other stator core magnetized at the opposite pole becomes zero. Assemble each stator core so that it is displaced by a predetermined amount. By doing so, a predetermined phase difference occurs in the torque generated by each set of stator cores, and it is possible to reduce the canceling torque when combining the generated torques. Therefore, the holding torque of the rotor can be strongly secured.

[0011]

Embodiment An embodiment of a step motor according to the present invention will be described.
Hereinafter, description will be given with reference to the drawings. FIG. 2 is a configuration diagram showing a configuration of the step motor 100 according to the present invention.
A first housing 1 formed of a magnetic material in a cup shape and a second housing 2 formed in a disk shape.
And are fixed to each other by screws or the like not shown. A lid portion 1a having a bearing 6 is fixed to the upper surface of the housing 1, and the first and second housings 1 and 2 form a casing as a case of the step motor 100. A bearing 7 is fixed to the inside of the housing, and the rotor 6 is fixed by the bearings 6 and 7.
Is rotatably attached to the shaft. A permanent magnet 5 is provided on the outer peripheral portion of the rotor 4. A shaft 8 having the same central axis as the rotor 4 is fixed. Outside the rotor 4, the stator cores 20 to 2 that serve as stator poles are separated by a space 11.
3 is arranged on the inner surface of the housing 1. Pole teeth 12 to 15, which will be described later with reference to FIG. 3, are formed on the inner peripheral surface facing the stator cores 20 to 23. Inside the stator cores 20 to 23, exciting coils 3a and 3b that are insulated by the insulating members 16 and 17 and that excite the stator cores 20 to 23 are wound.

The step motor 1 constructed as described above
FIG. 1 shows the state of torque generation when No. 00 is not energized. 1A and 1B, each stator core 20 is shown.
The relationship between the pole teeth 12 to 15 arranged in each of .about.23 and the permanent magnet 5 is modeled. The rotor 4 is shown in Fig. 1 (b).
It has a permanent magnet in which each N pole and S pole are formed with a pole width of 2 W as shown in FIG. For this permanent magnet 5,
A pair of pole teeth 1 composed of the stator cores 20 and 21
As shown in FIG. 1A, the reference numerals 2 and 13 are arranged so that their centers coincide with the boundary lines of the poles of the permanent magnet 5. On the other hand, the pole teeth 14 and 15 of the set composed of the stator cores 22 and 23 are displaced by the width W so as to face each pole of the permanent magnet 5 as described above with reference to FIG. It is generally arranged in a position. However, in the present invention, the pair of pole teeth 1 formed by the stator cores 22 and 23 is displaced by the width w from the center of each pole of the permanent magnet 5.
Place 4 and 15. In this case, as an example, the rotation angle is shifted by the width w in the positive direction.

The states of the generated torque when the stator cores 20 to 23 are arranged in this manner are shown in FIGS. 1 (c) and 1 (d) for each set of stator cores. That is, in FIG. 1C, the pole teeth 12 and 13 in the set formed by the stator cores 20 and 21 are the permanent magnets 5 respectively.
The generated torque generated with is shown. Also, Fig. 1 (d)
Shows the torque generated by the pole teeth 14 and 15 in the set formed by the stator cores 22 and 23 together with the permanent magnet 5. Here, the generated torque shown in FIG. 1 (d) is larger than the generated torque shown in FIG. 1 (c) by the width W +
A phase difference corresponding to the shift of w occurs. Figure 1 (e) shows
The holding torque of the rotor 4 obtained by combining the generated torques is shown. In this holding torque, as shown in FIG. 1 (e), the maximum holding torque can maintain a large torque with almost no decrease as compared with the maximum torque of each generated torque. This is because the generated torques are not offset as much as possible by shifting the phases by a predetermined amount. However, in this case, the cycle in which the maximum holding torque is generated is twice as long as that of the conventional step motor shown in FIG. This causes a situation where the stop position of the rotor becomes rough, but it can be easily dealt with by doubling the number of steps of the step motor 100. The phase difference of each stator core set is adjusted according to the torque generation characteristics of each step motor.

In the step motor constructed and operated as described above, it is possible to increase the holding torque by using each stator core formed in the same shape. Therefore, the cost of the step motor can be suppressed. Moreover, since the size of each pole of the permanent magnet 5 is evenly distributed, it is possible to sufficiently secure the rotational torque when the step motor is energized.

The present invention is not limited to the above embodiment, but can be variously modified as follows. For example, in the above embodiment, the phase difference between the pole teeth 14 and 15 of the set formed by the stator cores 22 and 23 is shifted by the width w in the plus direction with respect to the rotation angle. However, the invention is not limited to this, and the rotation angle may be shifted in the negative direction.

[0016]

As described above, according to the present invention, it is possible to provide a stepping motor which has a simple structure and has an improved holding torque when not energized while ensuring a rotational torque when energized.

[Brief description of drawings]

FIG. 1 is a chart showing a generation state of a holding torque when a step motor according to the present invention is not energized.

FIG. 2 is a configuration diagram showing a simple configuration of a step motor according to the present invention.

FIG. 3 is a chart showing a generation state of a holding torque when a conventional step motor is not energized.

[Explanation of symbols]

 1 Housing 4 Rotor 5 Permanent Magnet 12-15 Pole Teeth 20-23 Stator Core

Claims (3)

[Claims] 1. A rotor having a cylindrical permanent magnet, which is magnetized alternately with N poles and S poles on its outer peripheral surface, and is rotatably axially fixed, and a predetermined gap with respect to the permanent magnet. A plurality of sets of stator cores that are arranged opposite to each other and have pole teeth and are magnetized to the opposite poles; and an exciting coil that is wound around the stator core and that magnetizes the pole teeth of the stator core when energized to rotate the rotor. In the step motor, when the energizing coil is not energized, the rotation angle of the rotor in which the torque generated by the stator core magnetized in the opposite pole is 0 and the torque generated by the other stator core magnetized in the opposite pole are 0. And the stator cores are assembled so that the rotation angle of the rotor deviates by a predetermined amount. 2. A pole tooth formed on each of the other stator cores magnetized to the opposite pole has a predetermined phase difference with respect to a phase of a pole tooth formed on each of the stator cores magnetized to the opposite pole. The step motor according to claim 1, wherein: 3. The step motor according to claim 1, wherein the plurality of stator cores have the same shape.