JP2001078419A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance stopping accuracy through easy and accurate positioning of a yoke. SOLUTION: This stepping motor is structured with the inclusion of a rotor 4, having a cylindrical permanent magnet 3 multipole-magnetized in the circumferential direction, a plurality of yokes 5 to 8 having comb-tooth type magnetic poles 5b, 6b, 7b, 8b provided opposing the rotor 4 o the same axis, an excitation coil 9 loaded at the external circumference of the comb-tooth magnetic poles of the stator yokes 5 to 8 and a cylindrical yoke 10 surrounding the excitation coil 9 and stator yokes 5 to 8. In this case, the relative angular positions of the comb-tooth type magnetic poles 5b to 8b of the stator yokes 5 to 8 are determined by providing a projection 16 for the positioning to the internal surface of the frame yoke 10 and also by engaging a cutout portion 15 for the positioning formed at the circumference of the stator yokes 5 to 8 with the projection 16 for the positioning.

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 an improvement in a positioning mechanism for a relative positional relationship of a stator yoke in a claw pole type stepping motor.

[0002]

2. Description of the Related Art Claw-pole type stepping motors
It is used as a drive source of OA equipment such as paper feed of a printer and drive of a print head. As a conventional structure of such a claw-pole type stepping motor, for example, there is one as shown in FIG.

As shown in FIG. 1, a rotor 4 (rotor) is formed by integrally fixing a cylindrical permanent magnet 3 around a shaft 1. The outer periphery of the permanent magnet 3 is magnetized in a large number in the circumferential direction. Although not shown, a resin connecting member may be inserted between the shaft 1 and the permanent magnet 3 in order to reduce the weight.

[0004] Around this rotor 4, the first to fourth stator yokes 5 to 8 are concentrically arranged because of the two-phase type in this example. More specifically, the first and second stator yokes 5 and 6 constitute a first phase, and the third and fourth stator yokes 7 and 8 constitute a second phase. Each of the stator yokes 5 to 8 has a comb-shaped magnetic pole portion 5b to 8b formed by bending the inner circumference of a flat ring-shaped flange portion 5a to 8a in a predetermined direction by 90 degrees. The pair of stator yokes (5, 6, 7 and 8) face the tip sides of the comb-tooth-shaped magnetic pole portions 5b and 6b, 7b and 8b, and each tooth of the comb-tooth-shaped magnetic pole portions. Insert and place at the unformed site.

Further, the stator yoke pair (5 and 6,
An excitation coil 9 composed of a coil portion 9b wound around a coil bobbin 9a is mounted around the outer periphery of 7 and 8). Thereby, the exciting coil 9 is interposed between the flange portions (5a and 6a, 7a and 8a). The coil bobbin 9a has a disc-shaped flange 9a at both ends of the coil winding portion, and an outer peripheral edge of the flange 9a 'is substantially circular.

The rotor 4, stator yoke 5
A concentric bottomed cup-shaped frame yoke 10 is disposed around the outer periphery of the excitation coil 9 so as to surround the excitation coil 9. In other words, the above components are inserted and arranged in the frame yoke 10. In this state, the open side of the frame yoke 10 is covered with the cap 11.

[0007] Both ends of the shaft 1 are inserted through through holes 10a, 11a formed in the center of the bottom surface of the frame yoke 10 and the center of the cap 11, and protrude to the outside. Function as

By the way, in order to smoothly step-drive at equal intervals (at the same rotation angle), the stator yoke 5 is required.
The relative angles of the comb tooth-shaped magnetic pole portions 5b, 6b, 7b, and 8b need to be set in a desired positional relationship. That is, the comb-teeth-shaped magnetic pole portions 5b and 6b of the first and second stator yokes 5 and 6 forming the same phase are shifted so as to have an interval of [360 ° / n / 2] °. Here, n is the number of poles (number of teeth) of the comb-shaped magnetic pole portion. The same applies between the comb-teeth-shaped magnetic pole portions 7b and 8b of the third and fourth stator yokes 7, 8 constituting the same phase. As a result, each comb tooth-shaped magnetic pole portion is located at an intermediate point between the adjacent comb tooth-shaped magnetic pole portions. Further, the electrical angle of the first phase side and the second phase side is 9
It is shifted by 0 degrees (mechanically shifted by [360 ° / n / 4] °).

Therefore, positioning between the stator yokes (5, 6, 7 and 8) constituting the same phase is performed by the coil bobbin 9a.
Of the flange 9a '(flanges 5a, 6a, 7a, 8)
The projection 9c provided on the surface of the stator yoke 5, and the holes 5d, 6d, 7d, 8d provided on the flanges 5a, 6a, 7a, 8a of the stator yokes 5, 6, 7, 8 are matched. Performed by That is, both flange portions 9a 'of the coil bobbin 9a
Relative positions of the projections 9c formed in the holes 5d, 6d, 7
By appropriately setting the positional relationship between the d and 8d and the comb-teeth-shaped magnetic pole portions 5b, 6b, 7b and 8b, the hole 5
Just match d, 6d, 7d, 8d with projection 9c,
The corresponding comb-shaped magnetic pole portions 5b and 6b, 7b and 8b are [3
60 ° / n / 2] °.

The positioning of the first and second phase stator yokes is performed by providing projections and holes on the flange portions 6a and 7a of the second and third stator yokes 6 and 7, respectively. Can be positioned.

[0011]

However, the above-mentioned conventional stepping motor has the following problems. That is, the protrusion 9 provided on the coil bobbin 9a
When the position of the comb-teeth-shaped magnetic pole part is determined by c, the accuracy of the position depends on the accuracy of the two coil bobbins 9a, and the position references of the comb-teeth-shaped magnetic pole parts of the four stator yokes 5 to 8 are respectively different. Precise positioning is not possible.

The coil bobbin 9 is usually made of a resin such as PBT for the purpose of insulating the conductor. The projections 9c formed of resin are provided with holes 5d, 6d, and 5d provided in stator yokes 5 to 8 which are usually made of iron such as SEC.
With respect to 7d and 8d, the strength is extremely low. If the strength is not good in the manufacturing process, accurate positioning cannot be performed due to crushing or shaving. Further, depending on the material used, there is also a problem that the dimensional accuracy of the resin is easily affected by the environment and changes over time.

Further, as described above, the coil bobbin 9 is for insulation purpose, and it is preferable to make the wall thickness as thin as possible from the viewpoint of the torque characteristics of the motor.
Make it very thin, about 8 mm or less. The projection 9c for positioning the yoke is constituted by a flange 9a 'of the coil bobbin 9a.
The flange 9a 'of the coil bobbin 9a after winding may be deformed due to its thinness, and the position of the projection 9c naturally changes.

On the other hand, each of the cup-shaped frame yokes 5 to 8 has a cutout portion 10b for leading out a lead wire for energizing the exciting coil 9. In order to position the stator yokes 5 to 8, not only the combination of the projection provided on the bobbin and the hole provided on the yoke as described above, but also the notch 10b of the frame yoke 10 described above is used. Projections 5c, 6 on the 8 side to match the notch 10b
There is also a configuration in which c, 7c, and 8c are provided to determine the position.

Further, there is a configuration in which a notch is provided in a frame yoke for positioning for the purpose of positioning the yoke separately from the notch shown above. The frame yoke is usually produced by drawing a flat steel plate with a press. When a notch is formed in the side surface of the frame yoke after drawing, the stress accumulated by the processing is released, and the inner diameter of the frame yoke is widened. Therefore, since the size of the notch changes depending on the processing stress, it is difficult to stably obtain an accurate position by using the notch for positioning the yoke. Further, if the number of cutouts increases, the rigidity of the frame yoke itself is lost, and similarly, the yoke cannot be accurately and stably positioned.

For the above reasons, in the positioning using a resin member or the positioning using a notch, the yoke cannot be fixed at a stable and accurate position because the variation is large. It gets worse.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to provide a stepping motor which solves the above-mentioned problems, can easily and accurately position the yoke, and has a high stopping accuracy. Is to do.

[0018]

In order to achieve the above-mentioned object, a stepping motor according to the present invention comprises a rotor having a cylindrical permanent magnet which is multipolarly magnetized in a circumferential direction; A plurality of stator yokes each having a comb-shaped magnetic pole portion provided so as to face each other; an exciting coil mounted around the comb-shaped magnetic pole portion of the stator yoke; the exciting coil and the stator yoke portion; It is assumed that a stepping motor includes a surrounding cylindrical frame yoke. A positioning projection is provided on an inner side surface of the frame yoke, and a positioning notch formed on a peripheral edge of the stator yoke and the positioning projection are aligned with each other to form the comb-teeth-shaped magnetic pole portion of each stator yoke. The configuration is such that the relative angular position of is determined.

At least one or more positioning projections are provided on the side surface of the cup-shaped frame yoke so that the inside becomes convex, and the outer periphery of an annular stator yoke having a plurality of comb-shaped magnetic pole portions (pole teeth). Since a notch having a shape to be fitted to the protrusion of the frame yoke is provided in the portion, the position of the rotation angle of the stator yoke is determined by matching the protrusion with the notch.

By providing a projection for positioning the stator yoke on the frame yoke, a plurality of stator yokes serve as the same position reference, and accurate positioning can be performed. Both the frame yoke and the stator yoke are made of a metal magnetic material such as iron, and the position of the pole teeth does not become unstable due to the problem that one of them is easily deformed in terms of strength, and the processing accuracy of the member itself is improved. Processing can be performed with higher precision than resin parts, and changes over time after processing are reduced.

Preferably, the inner shape of the positioning notch is formed in a concave shape, and the side surfaces of the positioning protrusion corresponding to both side edges of the concave are formed as flat flat straight portions. (Claim 2). In this case, the positioning accuracy is further improved.

More preferably, the present invention is a two-phase type stepping motor in which the number of the stator yokes is four, and the positioning projections are provided at three positions on the opening side, the center and the bottom side of the frame yoke. (Claim 3).

By dividing the positioning projections provided on the frame yoke into three locations where four stator yokes are located, for example, the half-punch method may cause the side surfaces (straight portions) of the projections due to abrasion of the mold or erroneous setting. However, even if it is separated from the frame yoke, the strength of the projections is maintained, and there is no worry about deformation.

It is more preferable that the positioning projections provided at the three positions are arranged in a line along the axial direction. By thus forming the three projections in one row, not only the mold structure becomes easy but also the positional accuracy becomes higher. Furthermore, since the notch portion of the yoke and the notch portion of the bobbin are also arranged in one row in the height direction, it is easier to assemble.

Further, a relief portion which is one step lower is provided on the peripheral edge of the bottom of the frame yoke, and when the positioning projection is formed by press working near the relief portion, the peripheral edge of the bottom is raised. (Claim 5).

Further, if the bottommost projection provided on the frame yoke is processed as it is, the bottom of the frame yoke swells outward, so that the flatness of the bottom is impaired or the flatness of the bottom is maintained. In this case, the positioning projection is not formed to the innermost lower portion of the frame yoke, and the inserted stator yoke may not be firmly received and may be lifted. However, a relief portion is provided on the peripheral edge of the bottom of the frame yoke so that the positioning projection projects slightly below the bottom, so that the inserted stator yoke is accommodated and the flatness of the bottom is not impaired.

[0027]

FIG. 2 shows a preferred embodiment of a stepping motor according to the present invention. As shown in the figure, since the basic configuration of the stepping motor of the present embodiment is the same as that of the conventional one shown in FIG. 1, the corresponding members are denoted by the same reference numerals and detailed description thereof will be omitted. .

In the present invention, three yoke positioning projections 16 are provided on the inner surface of the cup-shaped (tubular) frame yoke 10 in the height direction. Then, the flange portions 5a, 6a, 7a, 8 of the annular stator yokes 5 to 8 are formed.
A concave notch 15 for positioning is provided in a part of the outer peripheral edge of a. Then, the outer shape of the positioning protrusion 16 and the inner shape of the notch 15 for positioning substantially match.

When the stator yokes 5 to 8 are inserted and arranged in the frame yoke 10, the positioning notches 15 and the positioning projections 16 are matched to each other.
The angular positions of the eight comb tooth-shaped magnetic pole portions 5b to 8b are also uniquely determined. Therefore, the relative angular positions between the stator yokes 5 to 8 can be determined with high accuracy by appropriately setting the above angular positions.

Further, as shown in the figure, in the present embodiment, the above-described positioning projection 16 is provided at a position of 180 degrees with respect to the notch 10b for taking out the lead wire of the coil formed on the frame yoke 10 to the outside. I have. This allows
Minimize the effects of stress release. However,
Since the shape of the projection depends on the shape of the mold, the position of the positioning projection 16 is notched.
The position is not limited to the position 180 degrees from b. Also,
A plurality of positioning projections 16 may be provided in the circumferential direction. In that case, a plurality of positioning notches 15 are provided at corresponding positions.

Positioning notch 15 and positioning projection 1
The specific shape of 6 can be, for example, as shown in FIG. That is, the positioning projection 16 provided on the cup-shaped frame yoke 10 is
Both ends (side surfaces) in the circumferential direction of 0 are flat portion-shaped straight portions 16a. At this time, the frame yoke 10
The projection dimension T of the positioning projection 16 is t
≧ T. When the stator yokes 5 to 8 are mounted on the frame yoke 10, the straight portions 16a
Are in contact with both side edges 15a of the inner peripheral surface of the positioning notch 15, are prevented from rotating, and are positioned in the rotation direction (rotation angle).

As shown in section A, the upper and lower end portions 16b of the positioning projections 16 where the stator yokes 5 to 8 do not abut are not so thin (substantially the thickness t). I have. Thereby, the strength of the positioning projection 16 itself is kept strong.

In order to manufacture the positioning projections 16 having such a shape, for example, after squeezing a predetermined position on the side surface of the frame yoke 10 from a flat plate by pressing,
By a method called half-punching, the stator yoke is machined so that a portion fitted with the positioning notch 15 becomes straight. In this method, a straight having a thickness greater than the plate thickness cannot be obtained, but since there is no sagging due to processing or burrs when separated, a straight 16a at a portion to be fitted with the stator yokes 5 to 8 can be secured, and the stator yoke is positioned. The projection has the same shape as the notch.

As shown in FIG. 4, three positioning projections 16 provided so as to be arranged in the height direction
0 are provided near the upper and lower ends and at the center in the height direction. The positioning projection 16 provided at the center position
Is designed so that the two second and third stator yokes 6 and 7 are positioned together, so that the height-direction length of the central positioning projection 16 is also greater than that of the other. Is set long.

Further, the bottom surface 10c of the frame yoke 10
A relief portion 10d having a substantially parallelogram vertical section is provided in the vicinity of the outer peripheral edge of. In the present embodiment, the relief portion 10d is formed in a ring shape over the entire circumference, but may be provided at least inside the region where the positioning projection is formed. The width t1 of the relief portion 10d is set to be longer than the protrusion dimension T of the positioning projection 16. The relief portion 10d is formed before the positioning projection 16 is formed.

That is, as shown in FIG. 5B, when a predetermined position of the side surface of the frame yoke 10 is pressed to form the positioning projection 16 after forming the relief portion 10d as shown in FIG. Even if the meat escapes during the processing of the positioning projections 16, it does not protrude to the outside bottom. As a result, the mounting flange (flat plate member) is normally bonded to the outside of the bottom surface 10c of the frame yoke 10, but it can be projected outward as described above with the processing of the positioning projection 16. Since there is no flange, the flange can be joined easily and reliably.

Further, by providing the relief portion 10d, the peripheral edge of the bottom surface 10c of the frame yoke 10 does not rise, and almost the entire bottom surface 10c is flush, and the fourth stator is placed on the flush bottom surface 10c. There is also an advantage that the yoke 8 can be arranged. Moreover, the positioning projection 1
The upper and lower ends 16b of the base 6 are inclined so as not to make the thickness too thin. However, since the lower end can be located on the bottom surface of the escape portion 10d, the vertical surface 16c of the positioning projection 16 can be formed. Can be set at substantially the same height as the bottom surface 10c of the frame yoke 10, or at a slightly higher position (a distance shorter than the plate thickness d of the flange portion 8a of the stator yoke 8). Therefore, the positioning notch 15 of the fourth stator yoke 8 can be brought into contact with the vertical surface 16c.

In the above-described embodiment, the number of the positioning projections 16 and the number of the positioning notches 15 provided in the circumferential direction are the same (one each), but the positioning notches provided on the stator yoke are the same. Many may be set. In such a case, by changing the positioning notch corresponding to the positioning projection, it is possible to use four identical stator yokes.

Further, projections and holes are provided at portions where the stator yokes meet each other, that is, at predetermined positions on the joint surfaces of the flange portions 6a and 7a of the second and third stator yokes 6 and 7, respectively. By matching, further improvement in the positional accuracy of the relative angular positions of the first-phase and second-phase comb-teeth-shaped magnetic pole portions can be expected.

[0040]

As described above, in the stepping motor according to the present invention, since the rotation angle is directly positioned between the stator yoke and the frame yoke, the yoke can be easily and accurately positioned, and the stopping accuracy can be improved. , A stepping motor with a high level can be obtained. And when comprised like Claim 2, positioning accuracy will become still higher.

According to the third aspect of the invention, the strength of each positioning projection is ensured, and the possibility of deformation is suppressed as much as possible. As a result, the positioning accuracy can be ensured. In addition, according to the structure of the fourth aspect, in addition to the above-described effects, processing and assembly can be easily performed.

Further, according to the fifth aspect of the present invention, the positioning protrusion on the bottom side and the positioning notch on the stator yoke positioned on the bottom side are firmly secured while ensuring the flatness of the bottom of the frame yoke. Can be matched.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional example.

FIG. 2 is an exploded perspective view showing a preferred embodiment of a stepping motor according to the present invention.

FIG. 3 is a diagram showing a main part thereof.

FIG. 4 is a longitudinal sectional view showing the outer peripheral edge side.

FIG. 5 is a diagram showing a manufacturing process of a lower positioning projection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft 3 Permanent magnet 4 Rotor 5-8 Stator yoke 5b-8b Comb-shaped magnetic pole part 9 Excitation coil 10 Frame yoke 10d Relief part 15 Notch for positioning 15a Side edge 16 Projection for positioning 16a Straight part

Claims (5)

[Claims] 1. A rotor having a cylindrical permanent magnet multipolarly magnetized in a circumferential direction, and a plurality of stator yokes each having a comb-shaped magnetic pole portion provided coaxially with and facing the rotor. A stepping motor comprising: an excitation coil mounted around the comb-teeth-shaped magnetic pole portion of the stator yoke; and a cylindrical frame yoke surrounding the excitation coil and the stator yoke portion. Positioning projections are provided on the side surfaces, and the positioning notch formed on the peripheral edge of the stator yoke and the positioning projections are matched with each other to determine the relative angular position of the comb-teeth-shaped magnetic pole portion of each stator yoke. A stepping motor characterized in that: 2. The method according to claim 1, wherein an inner shape of the notch for positioning is formed in a concave shape, and a side surface of the positioning protrusion corresponding to both side edges of the concave is a straight flat portion. 2. The stepping motor according to 1. 3. A stepping motor of a two-phase type having four stator yokes, wherein the positioning projections are provided at three positions on an opening side, a center part and a bottom side of the frame yoke. The stepping motor according to claim 1 or 2, wherein 4. The stepping motor according to claim 3, wherein the positioning projections provided at the three positions are arranged in a line along the axial direction. 5. A stepped relief portion is provided at the periphery of the bottom of the frame yoke, and when the positioning projection is formed by press working near the relief, the peripheral portion of the bottom rises. The stepping motor according to claim 1, wherein the stepping motor is suppressed.