JPH05161332A - Stepping motor - Google Patents

Abstract

PURPOSE:To obtain a stepping motor having less vibrations and noises by rotating a rotor magnet by applying pulses to the coreless coils of the stator in which a plurality of coreless coils having no yolks are arranged in parallel in a ring shape. CONSTITUTION:A stator 12 comprises the main bodies 22a and 22b which are separable into two in the axial direction; a plurality of first coreless coils 24 and second coreless coil 26 arranged in parallel in a ring shape on the outer circumference of the main bodies. Then, when pulses of a given cycle are applied to an odd numbered coreless coil 24 and an even numbered coreless coil 26, the magnetic poles having inverted polarities are generated in a given cycle because the coreless coils 24 and 26 have different winding directions. Further, the polarities of the magnetic poles generated by the adjacent coreless coils 24 and 26 are the inverted polarities. Thus, for the stator 12, N pole and S pole are formed by the coreless coils at equal intervals in the circumferential direction. The magnetic poles are inverted in a given cycle to cause the rotor magnet 14 to rotate, but there are no cores in the coreless coils, hence making it possible to reduce the generation of vibrations and noises.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor, and more particularly to a stepping motor used for driving a lens of a video camera or driving a diaphragm.

[0002]

2. Description of the Related Art Conventionally, as an example of a stepping motor used for driving a lens of a video camera, driving an aperture, etc., there is one disclosed in Japanese Utility Model Laid-Open No. 2-142976. The stator of this stepping motor is made of a resin or the like and is formed into a tubular shape. The bobbin has a U-shaped cross section in the axial direction, and an exciting coil formed by winding a wire around the bobbin.
While being formed in a ring shape using a magnetic material such as iron,
The opening edge at the center has pole teeth (cores) that can enter into the exciting coil, and is composed of a pair of yokes that can sandwich the bobbin from the axial direction. A cylindrical rotor magnet having magnetic poles magnetized in the circumferential direction on the outer peripheral surface is rotatably arranged in the stator. By periodically applying a voltage (pulse) to the exciting coil, magnetic poles that change at a constant cycle are generated in the pole teeth. The magnetic pole magnetized on the outer peripheral surface of the rotor magnet arranged in the stator repeats repulsion and attraction with the magnetic pole generated on the pole teeth, whereby the rotor magnet rotates.

[0003]

However, the above-mentioned conventional stepping motor has the following problems. Since the stator has pole teeth formed of a magnetic material, the magnetic poles magnetized on the outer peripheral surface of the rotor magnet are located at the position closest to the pole teeth forming the stator.
When the attracting force is maximized and no voltage is applied to the exciting coil, the rotor magnet stops rotating and enters a stable state. After entering a certain stable state and moving to the next stable state, the rotor magnet is forced with a force exceeding the maximum attractive force acting between the magnetic poles of the rotor magnet and the pole teeth. Need to rotate. This force is called detent torque (cocking torque in a DC motor or the like). Therefore, when trying to rotate the rotor magnet by periodically applying a voltage to the exciting coil of the stator, it is necessary to apply a force exceeding the detent torque to the rotor magnet in each stable state. The rotation speed of the motor continuously changes, and the fluctuation causes the rotor magnet to vibrate, resulting in noise. Due to this noise, for example, when used in a video camera, there is a problem that the noise is recorded during shooting. Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a stepping motor with less vibration and noise.

[0004]

The present invention has the following constitution in order to achieve the above object. That is, the rotor is provided with a stator formed by arranging a plurality of air-core coils without yokes side by side in a ring shape, and a rotor magnet arranged in the stator, and applying a pulse to the air-core coil to provide the rotor. It is characterized by rotating a magnet.

[0005]

In the state where no pulse is applied to the air-core coil, the air-core coil has no core, so the magnetic poles of the rotor magnet do not attract any part of the stator. Therefore, when the pulse is not applied to the air-core coil, there is no force to prevent the rotation of the rotor magnet, so that when the pulse is applied to the air-core coil, the rotor magnet rotates smoothly.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is an assembly diagram showing the configuration of the stepping motor of this embodiment. Figure 2
1A and 1B show the configuration of the stepping motor shown in FIG. 1, in which FIG. 1A is a side sectional view and FIG. 1B is an AA sectional view. First, the configuration will be described. The stepping motor includes a case 10 formed of a magnetic material in a cylindrical shape,
The stator 12 has an outer peripheral surface that is in close contact with the inner wall surface of the case 10 and can be housed in the case 10, and is installed in the stator 12, and a plurality of magnetic poles (N pole and S
Rotor magnet 1 in which poles are magnetized at equal intervals
4 and a bearing 18 and a washer 20 that are coaxially attached to both end surfaces of the stator 12 and that axially support a rotating shaft 16 provided on both end surfaces of the rotor magnet 14.

More specifically, the stator 12 is formed in a cylindrical shape, and the main bodies 22a, 2 are separable into two in the axial direction.
2b, and a plurality of first air-core coils 24 and a plurality of first air-core coils 24, which are arranged side by side in a ring shape on the outer peripheral surface of each body 22a, 22b
Of the air core coil 26. The first air-core coil 24 and the second air-core coil 26 do not have a core made of a magnetic material and have different winding directions. The first air core coil 24 and the second air core coil 26 are formed on a synthetic resin bobbin 28 which is a non-magnetic material. The bobbin 28 is provided with a plurality of winding portions 30 which are arranged at equal intervals in the circumferential direction of the main bodies 22a and 22b so as to correspond to the magnetic poles of the rotor magnet 14 and which are radially outwardly projected. Has been done. The first air-core coil 24 and the second air-core coil 26 are alternately arranged in the circumferential direction around the winding portion 30, the odd-numbered first air-core coil 24 and the even-numbered second air-core coil 26.
It is arranged so that

Next, the operation will be described. Stator 1
A pulse of a predetermined cycle having a rectangular waveform is applied to the odd-numbered first air-core coils 24 and the even-numbered second air-core coils 26 formed in 2. First air core coil 24 and second
Since the air-core coil 26 has different winding directions, magnetic poles whose polarities are inverted at a predetermined cycle are generated in the first air-core coil 24 and the second air-core coil 26. Furthermore, the polarities of the magnetic poles generated in the adjacent first air-core coil 24 and the second air-core coil 26 are opposite to each other. As a result, the N pole and the S pole are formed in the stator 12 at equal intervals in the circumferential direction by the air-core coil, and the magnetic poles thereof are reversed at a predetermined cycle. Therefore, the magnetic pole formed on the outer peripheral surface of the rotor magnet 14 repeats repulsion and attraction with the magnetic pole generated in the stator 12, whereby the rotor magnet 14 rotates. Since the stator 12 is not formed of a magnetic material and pole teeth (cores) are not used for the first air core coil 24 and the second air core coil 26, the first air core coil 24 and the second air core coil 24 are not used. A magnetic pole is formed only by the air-core coil 26. Therefore, the stable state of the rotor magnet 14 described above does not exist. Therefore, when the rotor magnet 14 rotates, it is not necessary to apply a large force that exceeds the detent torque as in the conventional case, so that the continuous rotation speed of the rotor magnet 14 does not fluctuate and the rotor magnet 14 rotates smoothly.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

[0010]

When the stepping motor according to the present invention is used, the air-core coil has no core when no pulse is applied to the air-core coil, so the magnetic poles of the rotor magnet do not attract any part of the stator. .. Therefore,
When no pulse is applied to the air-core coil, there is no force to prevent rotation of the rotor magnet, so when a pulse is applied to the air-core coil, the rotor magnet rotates smoothly, causing vibration and noise. It has the remarkable effect of reducing the

[Brief description of drawings]

FIG. 1 is an assembly diagram showing a configuration of an embodiment of a stepping motor according to the present invention.

2A and 2B show a configuration of the stepping motor of FIG. 1, where FIG. 2A is a side sectional view and FIG. 2B is a sectional view taken along line AA.

[Explanation of symbols]

 12 stator 14 rotor magnet 24 first air-core coil 26 second air-core coil

Claims (1)

[Claims] 1. A stator comprising a plurality of air-core coils without yokes arranged side by side in a ring shape, and a rotor magnet disposed in the stator, wherein a pulse is applied to the air-core coil. A stepping motor for rotating the rotor magnet by means of a.