JPH06303757A - Pm type stepping motor - Google Patents

Abstract

PURPOSE:To positively position the axial direction of a rotor magnet by providing a small ball for supporting the load of a shaft in axial direction so that it contacts the end face of a shaft and then fixing it at a bearing part. CONSTITUTION:Bearings 8 and 9 are provided at a mounting plate 6 firmly provided at a stator yoke and a cover 7 in a stator 5 and the stator 5 is supported so that it rotates freely with a shaft 10 supporting a magnet 4 of a rotor 3 at the rotation center as a center. The shaft 10 is supported at an inner hole 11 of the bearing 9 so that it rotates freely but the inner hole 11 has only one opening and then a small ball 12 is laid out at the depth of the inner hole 11, thus supporting an end face 10' of the shaft 10 in contact. Even if a strong force is applied in an axial direction by the shaft 10, the small ball 12 can be supported by the bottom of the inner hole 11, thus preventing the rotor 3 from traveling in axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The PM type stepping motor of the present invention is used in actuators for OA equipment, in-vehicle equipment, home electric appliances and the like.

[0002]

2. Description of the Related Art As a conventional PM type stepping motor, for example, a structure having a longitudinal sectional view shown in FIG. 6 has been known. A stator plate 29, which includes a coil portion 27 and a stator yoke 28 that are excited from the outside, has a mounting plate 30 and a cover 31.
Are fixed, and the mounting plate 30 and the cover 31 have bearings 32, respectively.
Is provided. The shaft 33 that slidably rotates on the inner circumference of the bearing 32 forms a rotor 35 together with the magnet 34, and rotates on the inner circumference of the stator portion 29 to generate torque.

Here, the rotor 35 and the stator yoke 28
The positional relationship between the spacers 36 does not greatly shift in the axial direction of the shaft 33, and in order to suppress vibration, the spacer 36
-37 and the spring washer 38 are inserted and used.

[0004]

As shown in the conventional example, positioning the rotor and the stator in the axial direction of the shaft improves the torque of the stepping motor,
In other words, it is not only necessary for improving efficiency, but also essential for improving rotational position accuracy, which is a characteristic of stepping motors. However, by inserting and using a spacer or a spring washer as in the conventional example, a sliding load due to friction at the contact portion between the spacer and the rotor or the spacer and the bearing not only causes a decrease in the motor torque, but also the rotor. However, there were problems such as an increase in mechanical hysteresis in forward / reverse rotation and a decrease in durability due to sliding friction of spacers and bearings.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide a high-performance and high-accuracy motor with reduced friction sliding load.

[0006]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems, and its construction is such that a small ball for supporting a load in the axial direction of the shaft is provided so as to abut on the end surface of the shaft. It is inserted and fixed in the bearing part.

[0007]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a vertical sectional view showing a first embodiment of a PM type stepping motor of the present invention.

The coil portion 1 energized by receiving an electric input from the outside excites a stator yoke 2 surrounding the coil portion 1 so as to cover the coil portion 1 and generates a torque by magnetism with a magnet 4 constituting a rotor 3. The stator 5 has a mounting plate 6 fixed to the stator yoke, a cover 7, a bearing 8 and a bearing 9.
Is provided for rotatably supporting the shaft 10 that supports the magnet 4 of the rotor 3 at the center of rotation on the inner peripheral surface. The shaft 10 is rotatably supplied to the inner hole 11 of the bearing 9,
The inner hole 11 has only one opening, and a small ball 12 is arranged in the inner part of the inner hole 11 to abut and support the end surface 10 ′ of the shaft 10. There is a gap 13 between the bearing 9 and the magnet 4, and
Since the gap 14 is also present between the magnet 4 and the bearing 8, the sliding load when the rotor 3 rotates is mostly the sliding load of the shaft 10, the bearing 8 and the bearing 9, and the end face 10 ′ of the shaft 10 is. The contact support between the small balls 12 and the small balls 12 is so small that it can be ignored.

FIG. 2 is an enlarged cross-sectional view of the bearing 9 portion of the first embodiment of the present invention.

Since the small ball 12 arranged in the inner hole 11 of the bearing 9 is configured to come into contact with the bottom 11 'of the inner hole 11 over a wide range, the small ball is generated by the rotation torque of the end surface 10' of the shaft 10. There is no such thing as 12 rotating.
Further, even if a strong axial force is applied by the shaft 10, the small balls 12 can be supported by the bottom 11 'of the inner hole 11, so that the rotor 3 does not move in the axial direction.

FIG. 3 is a longitudinal sectional view showing a bearing portion of a second embodiment of the PM type stepping motor of the present invention.

The structure of the motor body is similar to that of the first embodiment, but the inner diameter 16A of the inner hole 16 of the bearing 15 is set smaller than the outer diameter 12B of the small ball 12 (φA <φB).
By inserting 2 into the inner hole 16, an inner hole 16 ′ for supporting the shaft 10 in the radial direction is formed. The size of inserting the small ball 12 into the inner hole 16 is determined according to the positions of the rotor 3 and the stator yoke 2.

FIG. 4 is a vertical sectional view showing a third embodiment of the PM type stepping motor of the present invention.

The stator yoke 2, the coil 1, the bearing 9, the small balls 12, the rotor 3, etc. are the same as in the first embodiment, but a rolling bearing is used as the bearing 17, and a spring washer 18 is provided in the axial direction of the rotor 3. Pressurization can be applied by the mounting plate 19 via the. Axial pressure is applied to the bearing 17
It is transmitted to the shaft 10 by the spacer 20 through the inner ring of, and is supported by the bearing 9 by pressing the small ball 12. Here, when a sliding bearing is used for the bearing 17 when applying a pressure in the axial direction, a sliding load in the axial direction increases around the bearing 17 due to the pressure of the spring washer, and a large torque loss occurs. In addition, since the hysteresis due to normal rotation / reverse rotation may increase, the structure of the third embodiment of the present invention is preferable.

FIG. 5 is a vertical sectional view showing a fourth embodiment of the PM type stepping motor of the present invention.

The bobbin 24 and the bobbin 25 provided with the coil portion 22 and the coil portion 23 are fixed to the stator yoke 2, and the bobbin 24 and the bearing portion 24 'and the bearing portion 25' of the bobbin 25 connect the shaft 10 of the rotor 3 to each other. Support rotatably in the radial direction. A small ball 12 is provided in the inner hole 26 of the bearing 25 'to support the shaft 10 in abutment in the axial direction. The bearing portion 24 and the bearing portion 25 'are respectively made of the same material as the bobbin, and are made of resin or the like, for example, but are inferior in high load and durability as compared with the case of being made of metal
The driving sound is quiet, and it is possible to obtain smooth rotation.

[0018]

The present invention has the following great effects.

(1) The bearing portion is provided with a small ball for supporting the axial direction of the shaft, and the shaft in contact with and supporting the shaft surely positions the rotor magnet in the axial direction.
It can also be done easily. Further, even when the axial pressure is applied to the rotor, the small balls and the shaft can be contacted and supported, so that the loss due to the sliding friction of the bearing portion can be reduced.

(2) By using a part of the bobbin as the bearing part, the structure is simplified and the sound pressure generated from the bearing part when the rotor is rotated can be reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a PM type stepping motor of the present invention.

FIG. 2 is an enlarged sectional view of a bearing 9 portion of the first embodiment of the invention.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the PM type stepping motor of the present invention.

FIG. 4 is a vertical sectional view showing a third embodiment of a PM type stepping motor of the present invention.

FIG. 5 is a vertical cross-sectional view showing a fourth embodiment of a PM type stepping motor of the present invention.

FIG. 6 is a longitudinal sectional view showing a conventional PM type stepping motor.

[Explanation of symbols]

 1, 22, 23, 27 Coil part 2, 28 Stator yoke 3, 35 Rotor 4, 34 Magnet 5, 29 Stator 6, 19, 30 Mounting plate 7, 31 Cover 8, 9, 15, 17, 17, 32 Bearing 10, 33 Shaft 10 'End face 11, 16, 16', 26 Inner hole 11 'Bottom 12 Small ball 13,14 Gap 18,38 Spring washer 20, 36, 37 Spacer 24, 25 Bobbin 24', 25 'Bearing part

Claims (4)

[Claims] 1. A cylindrical magnet having a multi-pole magnetized on the outer periphery,
A coil portion excited by supplying an electric current from the outside, a stator for transmitting a magnetomotive force of the coil portion to the rotor to generate torque, a rotor including a magnet and a shaft,
A PM type stepping motor comprising at least a small ball supporting a load of an axial direction of a rotor shaft. 2. A PM type stepping motor according to claim 1, wherein a small ball for supporting a load of the shaft of the rotor in the axial direction is fixed to the bearing portion. 3. The PM type stepping motor according to claim 1, further comprising a mechanism for applying a load in the axial direction to the rotor. 4. The PM according to claim 1, wherein a bearing portion supporting the shaft is integrated with the bobbin of the stator.
Type stepping motor.