JP2003299334A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of noise caused by contact between a case and a yoke by a simple constitution, in a stepping motor which is assembled by press-fitting a stator into the case. <P>SOLUTION: The stepping motor 102 has a rotor which comprises a permanent magnet, a magnet holder for supporting the permanent magnet, and a shaft penetrating the center of the magnet holder; a stator 31 where the rotor is inserted coaxially and which is equipped with yokes 33a, 33b, 33c, and 33d having a plurality of comb-toothed parts in circumferential directions and in which a magnet wire is wound between the yokes; and a case 14 which is mounted around the stator, and the peripheral face of the case 14 is polygonal. <P>COPYRIGHT: (C)2004,JPO

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, it relates to a stepping motor preferably used for driving a carriage or a paper feed roller of an ink jet recording apparatus.

[0002]

2. Description of the Related Art A stepping motor is a motor that can be driven to rotate intermittently by repulsion of a magnetic pole generated by passing a current through a winding of a magnet wire of a stator and a magnetic pole given by a magnet of a rotor. FIG. 6 is an exploded perspective view showing an example of a conventional stepping motor 100. This stepping motor 100 has 2
A rotor 20 composed of two ring-shaped permanent magnets 45a and 45b, a pair of magnet holders 21a and 21b, and a shaft 50, and a plurality of rotor 20 that are coaxially inserted and that have comb-shaped pole teeth portions 35 in the circumferential direction. The main components are a stator 31 having a yoke 33, and a magnet wire wound (47a, 47b) between the yokes 33, and a case 11 that is exteriorly mounted on the stator 31. Also, the magnet wire windings 47a, 47
b is connected to the harness unit 60.

At the time of assembling the stepping motor, the rotor 20 and the stator 31 are separately assembled, and then the rotor 20 is fitted into the space inside the stator 31 and press-fitted and fixed in the case 11. The shaft 50 of the rotor 20 is inserted into the hole of the flange 10 via the bearing 42, and the pulley 41 is attached to one end of the shaft 50.

FIG. 7 shows a stepping motor 100 shown in FIG.
The internal structure of is shown. The rotor 20 is a magnet holder 2
The magnet holder 21 is provided with ring-shaped magnets 45a and 45b supported on the peripheral portions of 1a and 21b.
The shaft 50 is inserted through the centers of a and 21b. The shaft 50 is the bearing 4 mounted on the flange 10.
2 and a bearing 49 mounted on the stator 31. On the side of the rotor 20, washers 4
3, 44, 46 are provided to fix the position of the rotor 20 between the flange 10 and the stator 31.

The stator 31 includes yokes 33a, 33b, 33c and 33d each having a comb-shaped pole tooth portion 35, and a winding wire 47 composed of a pair of left and right magnet wires.
a and 47b are applied.

The case 11 has a back portion adhered to the flange 10 with the stator 31 having the rotor 20 inserted therein being fitted therein. In this state, the stator 31 is attached to the case 11
A cover 53 is attached so as to be press-fitted therein and expose the coating resin portion 51. Also, the rotor 20 is the washer 4
It is supported so as to be pressed against the bearing 42 of the flange 10 via 3, 44.

The stepping motor 1 having the above structure
00, magnet wire windings 47a, 4
When a current is applied to 7b, a magnetomotive force is generated to move the rotor 20 by a predetermined angle. At this time, the magnetomotive force of the rotor 20 and the rotor 2
Due to the repulsion and suction force of 0, the stator 31 and the rotor 2
The thrust force acts on 0. Further, a suction force is also generated on the comb-shaped pole tooth portion 35, and the stress thereof causes the yokes 33a, 33a.
The outer peripheral portions of b, 33c and 33d are slightly deformed. Therefore, the case 11 and the yokes 33a, 33b, 33c, 33
There was a problem that vibration was generated by the excitation of d. That is, since the yokes 33a, 33b, 33c, 33d are not complete arcs, when the stepping motor 100 is assembled by press-fitting the stator 31 in the case 11, the yoke is placed between the case 11 and the yokes 33a, 33b, 33c, 33d. A slight air gap is generated, and vibration energy is applied to the air gap, whereby the yokes 33a, 33b, 33c, and 33d repeatedly make contact with an indefinite portion of the inner peripheral surface of the case 11, and an offensive noise of a high frequency is generated.

Therefore, conventionally, there has been adopted a method of tightly fitting the case portion and the yoke portion to deform the case and improve the adhesion between the yoke and the case. But,
If the case portion and the yoke portion are fitted to each other too tightly, plating scraping may occur when the yoke is inserted, or the entire stator may be deformed, which increases the possibility of contact with the rotor. Occurrence of plating scraping and contact with the rotor lead to deterioration in the performance of the stepping motor and failure, so it must be avoided as much as possible. Further, if the case portion and the yoke portion are tightly fitted to each other, the yoke cannot be inserted into the case at the time of manufacturing, resulting in a poor yield and a large decrease in productivity.

On the other hand, Japanese Unexamined Patent Publication No. 10-108448 proposes a stepping motor in which a void is filled with synthetic resin or rubber for the purpose of preventing vibration of the case and the yoke. In addition, Japanese Patent Laid-Open No. 11-235002 proposes a stepping motor in which a coil portion and a case portion are integrally formed of synthetic resin or the like for the same purpose. Further, in Japanese Unexamined Patent Publication No. 6-217519, a case is used in which a strip-shaped plate material is rolled into a C-shaped cross section and processed, so that the case has a spring force to reduce magnetic resistance and reduce noise. Technology is proposed.

However, in the above method, the cost of the filler such as synthetic resin or rubber is added to the material cost as it is, so that the cost is increased. The integral molding by the resin mold is a method unsuitable for mass production because it requires a large investment in equipment cost and accuracy control, and the mold structure becomes complicated. Further, if the dimensional accuracy of the resin is not ensured, the center of the resin is displaced from the rotor, which causes abnormal vibration and abnormal noise. In the above method, the noise reduction effect cannot be obtained when the excitation energy equal to or greater than the spring force is applied.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to prevent generation of noise due to a case and a yoke with a simple structure in a stepping motor assembled by press-fitting a stator in the case.

[0012]

In order to solve the above-mentioned problems, the invention of a stepping motor according to claim 1 has a permanent magnet, a magnet holder that supports the permanent magnet, and a magnet holder that is provided at the center of the magnet holder. And a stator having a plurality of comb-shaped pole teeth in the circumferential direction and having the rotor coaxially inserted therein and having a magnet wire wound between the yokes. A stepping motor having a case that is externally mounted on the peripheral portion of the stator, wherein the peripheral surface of the case has a polygonal shape.

According to this feature, since the yoke is firmly supported in the case by forming the peripheral surface of the case into a polygonal shape, noise is generated due to repeated contact of the yoke with the inner peripheral surface of the case. Can be prevented. That is, by fixing the yoke and the case by making multi-point contact with the polygonal case, the yoke and the case do not come into contact with each other at a portion other than the contact point, and noise due to excitation does not occur. In addition, the polygonal shape of the case increases the rigidity, and as a result of shifting to a mode with a high natural vibration cycle, the difference with the natural vibration cycle based on the start of the stepping motor becomes large. can get. Further, by forming the case into a polygonal shape, even if the yoke is tightly fitted, there are few contact portions, so that problems such as deformation do not occur. Further, the polygonal shape of the case can be formed by using a simple metal processing method with a simple structure, so that the manufacturing cost can be kept low. Therefore, the contact portion between the yoke portion and the case portion can be stably fixed at low cost without using a secondary member such as resin or rubber.

According to a second aspect of the present invention, the stepping motor of the first aspect is characterized in that the stator insertion portion for inserting the stator in the case has a shape which is opened through on both sides. According to this feature, when the stator having the resin coating portion is inserted, the magnetic balance is improved and the driving performance of the stepping motor is improved because the stator insertion portion for inserting the stator in the case has a shape that penetrates and opens on both sides. Can be stabilized. That is, in many current stepping motors, the surface of the stator is coated with resin, so that if the back of the case (the contact surface with the flange in FIG. 6) has a metal portion, the magnetic portion will be taken into consideration. It is necessary to adjust the balance, but if the stator insertion portion of the case has a through opening, it is easy to adjust the magnetic balance and drive performance can be stabilized.

According to a third aspect of the present invention, in the stepping motor of the first or second aspect, the case is formed by bending a strip-shaped plate material into a polygonal shape, and has a substantially C-shaped outer shape. It is characterized by being a case. According to this feature, a case having a substantially C-shaped outer shape, which is formed by bending a strip-shaped plate material into a polygonal shape, has a simple structure and can be easily provided with a polygonal shape. That is, since it is only necessary to bend the strip-shaped sheet metal or the like while defining the angle, it is easy to manufacture, it is easy to maintain the accuracy of the polygonal shape, and the manufacturing cost is low.

According to a fourth aspect of the invention of the stepping motor, in the first or second aspect, the case is a ring-shaped cylindrical member having a polygonal shape. According to this feature, the case in which the ring-shaped tubular material is provided with the polygonal shape can be easily provided with the polygonal shape by simplifying the structure.

The invention of a stepping motor according to a fifth aspect is based on any one of the first to fourth aspects,
A case cover for accommodating the case is provided. According to this feature, since the case cover for housing the case is provided, the case can be stably held, and the generation of noise can be further reduced.

According to a sixth aspect of the present invention, in the fifth aspect, the case cover has a function of supporting the shaft through a bearing. According to this feature, since the case cover has a function of supporting the shaft through the bearing, the flange (support plate member, reference numeral in FIG. 6) as a case support member that has been essentially provided in the conventional technique. A case cover can be used instead of 10). Further, the case cover makes it possible to easily secure the coaxiality without using a flange. Furthermore, since the case cover can be easily manufactured by molding it with a synthetic resin or the like, the cost can be kept low.

[0019]

1 is a drawing showing an embodiment of a stepping motor 102 of the present invention, which is a partial cross section for showing the internal structure. This stepping motor 1
Since the structure of 02 is substantially the same as that of FIGS.

2 and 3 are perspective views showing an example of an embodiment of a polygonal case used for the stepping motor of the present invention. FIG. 2 shows a case 13 whose outer shape is a ring, and the inside of the ring is a through opening into which the stator 31 is inserted. As described above, the case 13 in which the ring-shaped tubular material is polygonal has a simple structure and can be easily processed by a known metal drawing process or the like.

FIG. 3 shows a case 14 having a substantially C-shaped outer shape.
The inside of the C-shape is a through opening into which the stator 31 is inserted. In this way, the C-shaped case 14
Can be easily processed by simplifying the structure and bending a plate material such as a strip-shaped metal plate to form a polygon.
That is, since it is only necessary to bend the strip-shaped sheet metal or the like while defining the angle, it is easy to manufacture, it is easy to maintain the accuracy of the polygonal shape, and the manufacturing cost is low. Since such a polygonal shape can be formed by using a normal metal working method or the like, the manufacturing cost can be kept low.

The case 14 of FIG. 3 will be described below, but the case 13 of FIG. 2 has the same function. As can be seen from FIG. 3, the polygonal case 14 has a plurality of corners 83. By having the corner portion 83 in this way, a contact point with the stator 31 inserted inside is formed, and the case 14 and the stator 31 are stably fixed. That is, the corners 8 formed on the polygonal case 14
A large number of planes between 3 and the corner portion 83 serve as contact points, and firmly support the yokes 33a, 33b, 33c, 33d. Therefore, the yokes 33a, 33b, 33c, 33
It is possible to prevent the noise from being generated due to the yokes 33a, 33b, 33c, and 33d repeatedly making contact with the inner peripheral surface of the case 14, since the d and the case 14 do not come into contact with each other except the contact point.

Further, by making the case 14 into a polygonal shape, the rigidity is increased and the mode shifts to a mode in which the natural vibration period is high. As a result, the difference from the natural vibration period based on the activation of the stepping motor 102 becomes large. A noise reduction effect can be obtained.

The number of corners 83 in the case 14 can be set as appropriate, but when the number of corners 83 is small (for example, 3 to 4 places), the corners 83 of the case 14 and the yokes 33a, 33 are formed.
The gap between the peripheral portions of b, 33c and 33d becomes large, which may deteriorate the magnetic resistance and cause noise. Further, if the number of corners 83 is increased, the outer shape becomes closer to a circle, so that the overall size can be reduced. However, if the number of corners 83 is too large, the yokes 33a, 33
There are too many surfaces that are contact points with b, 33c, 33d,
The effect of the invention may be impaired and the manufacturing becomes complicated.
It is appropriate to provide the corner portions 83 of about several places. When the corners 83 are formed on the case 14, it is preferable to maintain accuracy so that the contact points between the planes formed between the corners 83 and the peripheral portions of the yokes 33a, 33b, 33c, 33d are concentric. .

Further, the case 14 has a shape in which a stator insertion portion into which the stator 31 is inserted is opened on both sides. As a result, when the stator 31 having the resin coating portion 51 (see FIG. 7) is inserted, the magnetic balance becomes good and the driving performance of the stepping motor 102 can be stabilized. As shown in FIG. 1, the case 14 having a shape having a through opening on both sides is directly fixed to the flange 10 at the joint 90 by means such as resistance welding.

FIG. 4 is a plan view showing a state in which the case 14 of the present invention is housed in the case cover 15. Also, FIG.
Shows a stepping motor 103 according to a second embodiment of the present invention including the case cover 15,
The state of the cross section is partially shown. The cover 15 is
For example, it is made of a material such as synthetic resin. The inner peripheral surface of the case cover 15 is formed in a polygonal shape so as to correspond to the polygonal shape of the case 14, and the case 14 can be inserted and stored.

In the stepping motor 103 of this embodiment, since the case cover 15 is provided, the case 14
Can be stably held, and the generation of noise can be further reduced. In addition, the case cover 15 has a hole 7
8 and by inserting the bearing 42 into this portion,
The shaft 50 can be supported. Further, the case cover 15 also has holes 79a and 79b for mounting the stepping motor 102.

The case cover 15 has a function of supporting the shaft 50 through the bearing 42. The case cover 15 allows the rotor 20 and the stator 31 to be coaxial with each other easily without using the flange 10. Will be able to secure. In this way, the case cover 15
Can be used in place of the flange 10 (see FIG. 6 and FIG. 7) as a case supporting member which has been indispensably provided in the prior art.

[0029]

According to the present invention, since the yoke is firmly supported in the case by forming the peripheral surface of the case into a polygonal shape, noise generated by repeated contact of the yoke with the inner peripheral surface of the case is reduced. Occurrence can be prevented. That is, by fixing the yoke and the case by making multi-point contact with the polygonal case, the yoke and the case do not come into contact with each other at a portion other than the contact point, and noise due to excitation does not occur. In addition, the polygonal shape of the case increases the rigidity, and as a result of shifting to a mode with a high natural vibration cycle, the difference with the natural vibration cycle based on the start of the stepping motor becomes large. can get. Further, since the case can be formed in a polygonal shape by using a simple metal structure and a usual metal working method, the manufacturing cost can be kept low. Further, it is possible to inexpensively stabilize the contact portion between the yoke portion and the case portion without using a secondary member such as resin or rubber.

[Brief description of drawings]

FIG. 1 is a view for explaining a stepping motor according to an embodiment of the present invention, and partially shows a cross-sectional structure.

FIG. 2 is a perspective view for explaining an embodiment of a case.

FIG. 3 is a perspective view provided for explaining another embodiment of the case.

FIG. 4 is a plan view showing a case cover accommodating a case.

FIG. 5 is a diagram for explaining a stepping motor according to a second embodiment of the present invention, and partially shows a structure of a cross section.

FIG. 6 is an exploded perspective view for explaining a conventional stepping motor.

FIG. 7 is a sectional view for explaining a conventional stepping motor.

[Explanation of symbols]

10 flange 11 cases (conventional) 13, 14 cases (the present invention) 15 Case cover 20 rotor 21a, 21b Magnet holder 31 Stator 33a, 33b, 33c, 33d Yoke 42 bearing 43,44,46 washers 45a, 45b magnet 47a, 47b winding 49 bearings 50 shaft 83 corners 100, 102, 103 Stepping motor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kaaki Shibasaki             Seiko, 3-3-3 Yamato, Suwa City, Nagano Prefecture             -In Epson Corporation F-term (reference) 5H605 AA04 AA05 BB05 BB10 CC01                       CC03 CC10 EA02 GG04

Claims (6)

[Claims] 1. A rotor comprising a permanent magnet, a magnet holder for supporting the permanent magnet, and a shaft penetrating the center of the magnet holder, and a rotor which is coaxially inserted into the rotor and is arranged in a circumferential direction. A stepping motor comprising: a stator having a yoke having a plurality of comb-shaped pole teeth, and winding a magnet wire between the yokes; and a case externally mounted on the periphery of the stator. Characterized by making the peripheral surface polygonal,
Stepping motor. 2. The stepping motor according to claim 1, wherein a stator insertion portion of the case into which the stator is inserted has a shape having a through opening on both sides. 3. The stepping according to claim 1, wherein the case is a case having a substantially C-shaped outline formed by bending a strip-shaped plate material to form a polygon. motor. 4. The stepping motor according to claim 1 or 2, wherein the case is a ring-shaped tubular member having a polygonal shape. 5. The stepping motor according to claim 1, further comprising a case cover that accommodates the case. 6. The stepping motor according to claim 5, wherein the case cover has a function of supporting the shaft via a bearing.