JP6877991B2 - Stepping motor - Google Patents

Description

The present invention relates to a stepping motor that reduces vibration in the axial direction of the motor rotating shaft.

Generally, a stepping motor is composed of a rotor having a motor rotation shaft (output shaft) and a stator having a plurality of windings. At the time of driving, the stator is excited by switching the current flowing through the winding, the rotor is sequentially attracted, and the rotor can rotate.

However, in a stepping motor, since the rotor is sequentially attracted to the stator in a step-like manner in response to the input pulse, vibration related to the input pulse is generated, and if vibration in the axial direction of the motor rotation shaft is generated, that is the case. It is important to reduce.

In Patent Document 1, a spring is sandwiched between the bearing of the motor rotating shaft and the rotor to urge the rotor in the axial direction to reduce vibration in the axial direction of the motor rotating shaft. Further, in Patent Document 2, the bearing is held by a leaf spring, and the motor rotating shaft is urged in the axial direction.

Japanese Unexamined Patent Publication No. 6-284682 JP-A-11-196559

However, in the configurations shown in Patent Documents 1 and 2 that depend only on the elastic body (spring member), the vibration reduction in the axial direction of the motor rotating shaft is insufficient.

An object of the present invention is to provide a stepping motor in which vibration reduction in the axial direction of a motor rotating shaft (shaft) is sufficiently enhanced.

In order to achieve the above object, the stepping motor according to the present invention includes a rotor having a rotor capable of rotating with the shaft as the center axis of rotation and having N poles and S poles alternately arranged in the rotation direction, and the above. A first stator coil provided with a plurality of first teeth having sides oblique to the rotation center axis when the rotor is viewed along a direction perpendicular to the rotation center axis, and the first teeth. The input pulse signal includes a stator having a second stator coil having a side along the side and provided with a second tooth that is alternately arranged with the first tooth in the rotation direction. A stepping motor in which the rotor rotates with respect to the stator by alternately and sequentially exciting the first stator and the second stator to the north and south poles based on the above. A frame in which bearings are rotatably fitted, a first coiled spring that contacts the frame in the direction of the rotation axis, a second coiled spring that contacts the rotor in the direction of the rotation axis, and the like. A mass body sandwiched between the first spring and the second spring and for reducing the vibration of the rotor in the direction of the rotation axis is provided, and the shaft includes the first spring and the second spring, respectively. It is arranged so as to pass through the inside of the coil, and the mass body is characterized in that an opening through which the shaft is passed is formed.

According to the present invention, it is possible to provide a stepping motor in which vibration reduction in the axial direction of the motor rotating shaft (shaft) is sufficiently enhanced.

It is the schematic perspective view which looked at the stepping motor which concerns on embodiment of this invention from the front side. It is a detailed explanatory view of the internal structure (excluding the vibration damping structure) of the stepping motor which concerns on embodiment of this invention. It is the schematic explanatory drawing at the time of driving of the stepping motor which concerns on embodiment of this invention which compared with the comparative example. It is the schematic perspective view and the side sectional view seen from the back side of the stepping motor which concerns on 1st Embodiment. It is an effect explanatory drawing of the stepping motor which concerns on 1st Embodiment. It is a view seen from the front side and the side sectional view of the stepping motor which concerns on 2nd Embodiment. It is a schematic perspective view seen from the back side of the stepping motor which concerns on 3rd Embodiment. It is a detailed explanatory view of the stepping motor which concerns on 3rd Embodiment.

Hereinafter, the stepping motor having the vibration damping structure according to the embodiment of the present invention will be described in detail with reference to the drawings. This stepping motor is used in a wide range of applications, for example, in an image forming apparatus, as a drive source for moving a loading tray for loading ejected sheets up and down, or in a camera, for example, a lens drive drive source. Used as. Such a stepping motor having a vibration damping structure according to the present embodiment can be used for an image forming apparatus or an apparatus other than a camera.

<< First Embodiment >>
(Stepping motor)
FIG. 1 shows a schematic perspective view of a stepping motor (two-phase PM type stepping motor) 20 according to an embodiment of the present invention as viewed from the front side, and FIG. 2 shows an internal structure thereof (excluding a vibration damping structure described later). .. The stepping motor 20 includes a rotor 11 having a permanent magnet in which N poles and S poles as magnetic poles are alternately formed in the circumferential direction, and a rotation shaft (shaft) which is a motor rotation shaft (output shaft) connected to the rotor 11. 12 and a bearing 13 for holding the rotating shaft 12. Further, a stator 14 arranged on the outer periphery of the rotor 11 and having a plurality of teeth, and a coil 15 for magnetizing the stator 14 as a magnetic pole are provided. Then, these are stored (held) in the casing 16.

At the time of driving, the stator 14 is alternately and sequentially excited to the N pole and the S pole by the input pulse signal from the outside. Along with this, the poles of the rotor 11 are attracted to the stator 14, and the rotor 11 can rotate. At this time, the rotor 11 rotates in steps each time the magnetic poles of the stator 14 are switched.

Here, a comparative example (the tooth shape of the stator 14 is parallel to the magnetic pole shape of the rotor 11 as shown in FIG. 3A) and the present embodiment (the tooth shape of the stator 14 is parallel to the rotor 11 as shown in FIG. 3B). Compare with the shape (triangular shape) having sides that are diagonal to the magnetic pole shape of.

When the tooth shape of the stator 14 is parallel (similar) to the magnetic pole shape of the rotor 11 as shown in FIG. 3, the rotor 11 can receive a force only in the rotation direction (circumferential direction). On the other hand, when the tooth shape of the stator 14 has a side oblique to the magnetic pole shape of the rotor 11 as shown in FIG. 3B, the rotor 11 is not only in the rotation direction but also in the thrust direction ( It also receives a force (in the axial direction of the rotating shaft 12). Therefore, every time the magnetic poles of the stator 14 are switched, the rotor 11 repeatedly moves in the thrust direction. This causes vibration and develops into vibration of the entire stepping motor 20.

In order to suppress this vibration, it is common to urge the rotor 11 and the rotating shaft 12 with a spring to suppress the vibration (Patent Documents 1 and 2). However, it is practically difficult to significantly reduce the vibration by urging using only the elastic body (spring member).

(Vibration damping structure using mass body)
In the present embodiment, in order to suppress vibration in the thrust direction of the rotor 11 (axial direction of the rotating shaft 12), a vibration damping method using a dynamic vibration absorber is adopted. A dynamic vibration absorber is a structure that vibrates instead of a vibration damping target and exerts a large vibration damping effect at a specific frequency, and details will be described below.

As shown in FIG. 4, in the stepping motor 20 according to the present embodiment, the mass body 21 is a compression spring A (first elastic member) 22 and a compression spring B (first elastic member) 22 arranged in the axial direction of the rotating shaft 12. It is sandwiched between the elastic members (2) 23, and these play the role of a dynamic vibration absorber. The mass body 21 of the present embodiment is made of brass, but the material of the mass body 21 is not limited to brass.

Further, the compression spring B23 is held by the frame 24 as the first holding member, and the frame 24 is fixed (connected) to the casing 16 as the second holding member by means such as a set screw. In addition, a pressing member 25 is connected to the end of the compression spring A22 and is in contact with the end of the rotating shaft 12. That is, the compression spring A22 is substantially connected to the rotating shaft 12 in the axial direction even if the pressing member 25 is used.

As a result, the rotating shaft 12 is urged (pressed) by the pressing member 25 by the restoring force of the compression spring A22 and the compression spring B23. There is also some damping effect due to this urging, and it is adjusted so that it becomes a suitable urging force. In this embodiment, the urging force is about 40N. Further, since the pressing member 25 rubs against the end of the rotating shaft 12 as the rotor 11 rotates, it is desirable that the pressing member 25 is made of a highly slidable material such as POM (polyacetal) resin. Although the present embodiment uses a compression spring as the first elastic member and the second elastic member, a tension spring, a leaf spring, or the like may be used.

(Resonance frequency of mass)
When the stepping motor 20 is driven, the rotor 11 rotates at a speed corresponding to the frequency of the input pulse. At this time, the rotor 11 repeats the movement in the thrust direction (the axial direction of the rotating shaft 12) every time the magnetic poles of the stator 14 are sequentially switched between the N pole and the S pole. Therefore, vibration of one cycle is generated by two input pulses.

Therefore, in the present embodiment, the resonance frequency of the mass body is set to 1/2 with respect to the pulse frequency of the input pulse that switches the magnetic poles of the stator in the circumferential direction. That is, when the pulse is input at a speed of 800 pps, a large vibration in the thrust direction is generated at 400 Hz. As a result, according to the present embodiment, the mass body 21 vibrates instead of the rotor 11 due to the dynamic vibration absorption effect. As a result, the vibration of the rotor 11 can be greatly reduced.

Here, when the mass of the mass body 21 is m, the spring constant which is the elastic constant of the compression spring A22 is k ₁ , and the spring constant which is the elastic constant of the compression spring B23 is k ₂ , the resonance frequency f of the mass body 21 is The following conditional expression is satisfied.

_{In this embodiment, the values of m = 6.0 g, k 1} = 19.6 N / mm, and k ₂ = 19.6 N / mm are used so that the resonance frequency f of the mass body 21 is 400 Hz.

Here, FIG. 5 shows a result of comparing the vibration of the casing 16 with the conventional configuration (using only the elastic body (spring member) without using the mass body). The casing 16 has a vibration peak of 400 Hz, which was 2.02 m / s ^{2 in the conventional configuration, but is 0.07 m / s 2} in the present embodiment using the mass body. That is, by the configuration of the present embodiment using the dynamic vibration absorber, it is possible to significantly reduce the vibration of the rotor 11 in the axial direction of the rotating shaft 12.

<< Second Embodiment >>
In the first embodiment , the dynamic vibration absorber is configured on the outside of the casing (frame) 16, but even if the dynamic vibration absorber is configured on the inside (internal space) of the casing 16 and the rotor 11 is directly damped. I do not care. A cross-sectional view in this case is shown in FIG. In this embodiment, the compression spring A (second spring) 22 directly urges the rotor 11. Further, the mass body 21'has a ring shape and is held in a non-contact state with the rotor 11, the rotating shaft 12, and the bearing 13. As a result, the mass body 21'vibrates instead of the rotor 11, and the vibration of the rotor 11 in the axial direction of the rotating shaft 12 can be significantly reduced.

<< Third Embodiment >>
In this embodiment, the same dynamic vibration absorber as in the first embodiment is used to reduce vibration in the axial direction of the motor rotation shaft of the stepping motor, and the resonance frequency f can be easily adjusted. This is what I did. Only the parts different from the first embodiment will be described, and the description of the same configuration will be omitted.

When using a vibration damping method using a dynamic vibration absorber, it is important to set the resonance frequency f. This is because when the resonance frequency f of the dynamic vibration absorber is different from the design value, the vibration damping effect is significantly reduced. However, there is a possibility that the resonance frequency f of the dynamic vibration absorber may change due to the variation within the tolerance of the mass and the spring constant and the change with time. Therefore, it is desirable to have a function of adjusting the resonance frequency f. In the present embodiment, the resonance frequency f of the dynamic vibration absorber can be easily adjusted by changing (variable) the spring constant of the compression spring A22 and the mass of the mass body 21.

First, the adjustment of the spring constant of the compression spring B23 will be described. The spring constant k ₂ of the compression spring B23 is a modulus of transverse elasticity of the material G, the wire diameter d, the effective number of turns N _a, if the average coil diameter and is D, can be expressed by the following equation.

In the present embodiment, the spring constant k2 is adjusted by changing the effective number of turns Na. A schematic explanatory view of the present embodiment is shown in FIG. 7, and a detailed explanatory view is shown in FIG. As shown in FIG. 7, a stopper (stopper member , plate ) 26 is sandwiched between the windings of the compression spring B23. The stopper 26 is threaded and is held by screws 27 arranged on the frame 24. When the stopper 26 is at the position shown in FIG. 8A, the spring constant is the same as that of the first embodiment.

In contrast, by rotating the stopper 26, when the position of FIG. 8 (b), a part of the winding is in contact, the effective number of turns N _a of the compression spring B23 is decreased. That is, the spring constant k ₂ changes. Thereby, the resonance frequency f of the dynamic vibration absorber can be adjusted. The means for changing the spring constant is not limited, and other methods may be used. Further, the spring constant of the compression spring A22 may be adjusted instead of the compression spring B23.

Next, the mass adjustment of the mass body 21 will be described. As shown in FIG. 7, the mass body 21 has a plurality of holes (screw holes) on the outer peripheral portion, and the adjusting mass 28 can be attached to one or more screw holes. Thereby, the resonance frequency f of the dynamic vibration absorber can be adjusted. The method of changing the mass of the mass body 21 is not particularly limited to that described above.

In the present embodiment, the spring constant and the mass can be changed, but either the spring constant or the mass may be changed.

(Modification example)
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

(Modification example 1)
In the above-described embodiment, the spring member is shown as the elastic body, but the present invention is not limited to this, and a rubber member or the like may be used.

(Modification 2)
Further, in the above-described embodiment, a side that is oblique to the magnetic pole shape of the rotor is provided, and the tooth shape provided in the axial direction of the rotation axis is a triangular shape having a tapered tip with respect to the base. It can be composed of isosceles triangles and right triangles. Further, the shape is not limited to a triangle shape, and may be a trapezoidal shape, a parallelogram shape, or the like. The lines on each side forming the shape are not limited to straight lines, and at least a part of them may be curved lines.

11 ... rotor, 12 ... rotating shaft, 14 ... stator, 21 ... mass body, 22 ... compression spring A (first elastic member), 23 ... compression spring B (second elastic member), 24 ... Frame (first holding member)

Claims (4)

A rotor that can rotate with the shaft as the center axis of rotation and has magnets in which north and south poles are alternately arranged in the direction of rotation.
A first stator coil provided with a plurality of first teeth having sides oblique to the rotation center axis when the rotor is viewed along a direction perpendicular to the rotation center axis, and the first stator coil. It comprises a stator having a second stator coil having a side along the side of the tooth and provided with a second tooth that alternates with the first tooth in the direction of rotation.
A stepping motor in which the rotor rotates with respect to the stator by alternately and sequentially exciting the first stator and the second stator to the N pole and the S pole based on the input pulse signal. hand,
A frame in which the bearing of the shaft is rotatably fitted, and
A coiled first spring that contacts the frame in the direction of the rotation axis,
A coiled second spring that contacts the rotor in the direction of the rotation axis,
A mass body sandwiched between the first spring and the second spring to reduce vibration of the rotor in the direction of the rotation axis is provided.
The shaft is arranged so as to pass through the inside of each of the first spring and the second spring, and the mass body is formed with an opening through which the shaft is passed. .. The stepping motor according to claim 1, wherein the mass body is annular. The stepping motor according to claim 1 or 2, wherein both the first tooth and the second tooth have a triangular shape. A plate attached to the frame and extending toward at least one of the windings of the first spring and between the windings of the second spring and having a variable position in the direction of the rotation axis. The stepping motor according to any one of claims 1 to 3, wherein the stepping motor is characterized.

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