JP2684986B2 - Stepping motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-diameter stepping motor suitable for watches, cameras, medical equipment, and the like.
The present invention relates to an improvement for improving motor assemblability and rotation angle accuracy.

[0002]

2. Description of the Related Art As a technique for reducing the outer diameter of a stepping motor, the present inventors have previously proposed a stepping motor having a structure as shown in FIG. This motor is characterized in that bobbins 4 around which coils 6A and 6B are wound are arranged on both sides in the axial direction of a magnet 2 fixed coaxially to a shaft 1, whereby a coil is provided on the outer periphery of the magnet. The outer diameter can be reduced as compared with the conventional stepping motor arranged.

[0003] At both ends of each bobbin 4, U-shaped yokes 8A, 10A, 8B, and 10B are fixed with both side plates (corresponding to pole teeth) facing the outer periphery of the magnet 2. ing. Long pole yoke 8A (8B) and short pole yoke 10A fixed to the same bobbin 4
(10B) is 90 ° out of phase with respect to each other, and the pole teeth of the yokes opposed in the axial direction are 45 ° out of phase with each other. By energizing the coils 6A and 6B alternately while changing the direction of the current, the magnet 2
And the rotor composed of shaft 1 is driven stepwise by 45 °.

When the stepping motor is actually used, a cylindrical case (not shown) for accommodating the above-mentioned parts is provided.
And fixing the yokes 8A, 10A, 8B, 10B to the inner surface of the case with an adhesive or the like, and attaching a pair of support members so as to close both ends of the case. Metal bearings are previously fixed to these support members, and these metal bearings rotatably support both ends of the shaft 1.

[0005]

However, in the stepping motor having the above structure, the yokes 8A, 10A, 8A are not provided.
Since the bobbin 4 is positioned by fixing B and 10B to the inner surface of the case, the accuracy of axial alignment between the bobbin 4 and the bearing and the shaft 1 is poor, and the coils 6A and 6B and the yokes 8A, 10A and 8B. , 10B magnet 2
It was difficult to position it accurately. For this reason, there is a problem in that an error in the rotor stop position due to an error in the pole tooth position and a non-uniform magnetic balance due to an error in the coil position are likely to occur, and it is difficult to improve the rotor rotation accuracy.

Further, the yokes 8A, 10A, 8B, 10B
Is small, and its assembly requires high precision for the above-mentioned reasons, so that careful attention must be paid to the assembling work, and the productivity is low.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a stepping motor which can improve the coaxiality of the bobbin and the shaft and the positioning accuracy of the pole teeth with each other, and can improve the productivity. It is an issue.

[0008]

In order to solve the above problems, a stepping motor according to the present invention comprises a shaft to which a magnet is coaxially fixed, and a pair of shafts arranged coaxially with the shaft on both sides in the axial direction of the magnet. Bobbin, the A-phase coil and the B-phase coil respectively wound on these bobbins, one end of which is magnetically coupled to the magnet-side end of each bobbin and the other end of which is one of the outer peripheral surface of the magnet. Portion and a long pole tooth whose one end is magnetically coupled to the end of each bobbin opposite to the magnet and whose other end faces another part of the outer peripheral surface of the magnet. A pair of support members coaxially arranged adjacent to the ends of the bobbins opposite to the magnets, and a cylindrical case fixed between the support members to accommodate the parts. A press-fitting convex portion is coaxially formed at an end portion of each bobbin on the side of the support member, and the press-fitting concave portion is coaxially formed at the end portion of each support member. The bobbin and the supporting member are positioned relative to each other by press-fitting the projecting portions, and a bearing that supports the shaft is provided coaxially with the supporting member as a reference. Characterize.

Further, in the stepping motor according to the present invention, the press-fitting convex portions formed on the respective bobbins have an annular shape, and the bearing accommodating portion is formed inside the press-fitting convex portions.
The bearing is coaxially fixed in the bearing accommodating portion. In the stepping motor according to a third aspect of the present invention, the bearing accommodating portions are further formed in the inner portions of the press-fitting recesses of the support members, and the bearings are coaxially fixed in the bearing accommodating portions.

According to a fourth aspect of the present invention, the stepping motor is characterized in that each of the supporting members is formed with a positioning engaging portion for restricting the direction around the axis of the bobbin. Further, in the stepping motor according to claim 5, all of the pole teeth are separable from the corresponding bobbins, and are fixed to a cylindrical non-magnetic body which is coaxially arranged to surround the rotor. It is characterized by being

[0011]

In the stepping motor according to the present invention, each bobbin and each supporting member are supported by pressing the press-fitting convex portion formed at the end portion of each bobbin into the press-fitting concave portion formed at the end portion of each supporting member. Since the bearings for positioning the members relative to each other are provided coaxially with each of the supporting members as a reference, and the cylindrical case is fixed between the supporting members, each bobbin and the supporting member are provided. Are aligned with each other, and the respective support members are aligned with each other via the case.

Therefore, the axial center of each bobbin and the shaft can be easily aligned, and the rotor stop position error and the magnetic balance nonuniformity caused by the pole tooth position error do not occur, and the rotor rotation accuracy can be improved. Furthermore, since the bobbin can be easily positioned, the productivity of the assembly work can be improved and the production cost can be reduced.

[0013]

1 is a vertical sectional view showing an embodiment of a stepping motor according to the present invention. In the figure, reference numeral 20 denotes a shaft. At the center of the shaft 20, a cylindrical magnet 22 magnetized in four poles in the circumferential direction is coaxially fixed. A pair of bobbins 26A (A phase) and 26B (B phase) adjacent to both sides of the magnet 22 and having the same shape as each other.
Are arranged coaxially with the shaft 20, respectively. As shown in FIG. 2, these bobbins 26A and 26B include a cylindrical winding portion 36 having an inner diameter larger than the outer diameter of the shaft 20, and flange portions 30 integrally formed at both ends of the winding portion 36. 32 and a press-fitting convex portion 28 formed at the end opposite to the magnet 22, and are integrally formed of a soft magnetic material such as pure iron.

Coils 38A and 38B are wound around the respective winding portions 36 of the bobbins 26A and 26B (not shown in FIGS. 2 and 3). Press-fitting convex portion 28
Has a cylindrical shape with a diameter larger than that of the winding portion 36 and coaxial therewith,
As shown in FIG. 5, bearings 24, such as annular metal bearings, are coaxially press-fitted therein, and both ends of the shaft 20 are rotatably supported by these bearings 24.

As shown in FIG. 2, each of the flange portions 30 and 32 has a shape in which both sides of the disk are notched in parallel, and as shown in FIG. 6, the angles about the axis are deviated from each other by 90 °. Is formed in. And the flange portion 30
A pair of pole tooth contact surfaces 30A with which the long pole teeth 48A and 48B abut are formed at both ends of the flange portion 32, while step portions 34 that engage with the short pole teeth 50A and 50B are provided at both ends of the flange portion 32.
Are formed. The bobbins 26A and 26B are arranged such that the flange portions 30 and 32 thereof are offset from each other by 45 °.

As shown in FIG. 1, support members 40A and 40B are arranged outside the bobbins 26A and 26B (on the side opposite to the magnet 22). These support members 40A, 40B have a columnar shape having a center hole, and a press-fitting concave portion 42 is formed on the side facing the bobbins 26A, 26B coaxially with the center line. The press-fit projections 28 of the bobbins 26A, 26B are press-fitted into these press-fit recesses 42, and the support members 40A, 40B and the bobbins 26A, 2
6B are positioned coaxially. In the support members 40A and 40B of this example, as shown in FIG. 5, a bearing accommodating portion 45 into which the bearing 24 can be press-fitted is coaxially formed inside the press-fitting recess 42. This is a consideration so that the position of the bearing 24 can be selected as described later.

Bobbins 26A of the support members 40A and 40B,
A pair of positioning projections 41 are formed on the end surface on the side of 26B, and the side surfaces of the positioning projections 41 abut the side surfaces of the flange portion 30 as shown in FIG. The angle around the axis is precisely defined. Further, the outer peripheral surfaces of the positioning convex portions 41 are stepped portions having a relatively small diameter in order to facilitate insertion into the end portion of the case 44.

As shown in FIG. 4, a pair of grooves 43 for passing the covered wire 39 of the coils 38A and 38B are formed on the outer peripheral surfaces of the support members 40A and 40B. Further, as shown in FIG. 8, terminals 54A and 54B are respectively embedded in the other end surfaces of the support members 40A and 40B, and the covered wires 39 are connected to these terminals, respectively, and the terminals 54A and 54B are as shown in FIG. Is bent on the same side. This is for fixing all the terminals 54A and 54B to a common printed circuit board.

On the other hand, on the outer circumference of the magnet 22, a cylindrical member 46 is arranged coaxially without contact. The tubular member 46 is composed of two sets of long pole teeth 48A and 48B, two sets of short pole teeth 50A and 50B, and a cylindrical non-magnetic body 52 that fixes the ends of these pole teeth to each other. The pole teeth 48A and 50A form a magnetic circuit on the A phase side, and the pole teeth 48B and 50B form a B phase side magnetic circuit. The outer diameter of the non-magnetic body 52 is substantially equal to the inner diameter of the case 44, and the tubular member 46 is supported in the case 44 without rattling.

As shown in FIG. 9, long pole teeth 4 in phase
8A (or 48B) and short pole teeth 50A (or 50
In B), the phases are 90 ° out of phase with each other, and a gap having a constant width is provided therebetween. Also, the pole teeth 48 on the A phase side
A, 50A and pole teeth 48B, 50B on the B phase side are 45
° out of phase with a constant gap between them. Then, as shown in FIG. 1, the long pole teeth 48A, 48
B makes contact with the pole tooth contact surfaces 30A of the flange portions 30 of the bobbins 26A, 26B without any gaps, and has short pole teeth 50A,
50B engages with the step portion 34 of the flange portion 32 without any gap. At the same time, long pole teeth 48A,
The tip end of 48B is sandwiched between the pair of positioning projections 41, and the positioning property during assembly is improved.

In this example, the in-phase pole teeth are 4
However, the present invention is not limited to four sheets and may be another number. Further, the case 44 is made of resin, aluminum, or the like so that the structural strength can be sufficiently ensured and the construction method such as caulking, which is necessary for firmly holding the accommodated parts in a predetermined portion, can be easily adopted. Also, it is desirable to be formed of a non-magnetic material such as stainless steel.

According to the stepping motor having the above structure, the press-fitting convex portion 28 formed at the end of each bobbin 26A, 26B is inserted into the press-fitting concave portion 42 formed at the end of each supporting member 40A, 40B. Press-fit each bobbin 26A, 26
B and the respective support members 40A, 40B are positioned relative to each other, the bearing 24 supporting the shaft 20 is press-fitted into the press-fitting convex portion 28 to be coaxially positioned, and the support members 40A, 40B are cylindrically positioned. Since the case 44 having a fixed shape is fixed, each bobbin 26A, 26B and the supporting member 40
A and 40B are accurately aligned with each other, and at the same time, the support members 40A and 40B are aligned with each other via the case 44.

Therefore, it is easy to align the bobbins 26A, 26B and the shaft 20 with high precision, and the air gap between the pole teeth 48A, 48B, 50A, 50B and the magnet 22 is kept uniform. With
Each bobbin 26A, 26B and pole teeth 48A, 48B, 50
By ensuring the connection with A and 50B, nonuniform magnetic balance does not occur, and the rotor rotation accuracy can be improved. Further, since the bobbins 26A and 26B can be easily positioned, the productivity of the assembling work can be improved and the production cost can be reduced.

Also, in this embodiment, the bobbins 26A, 2A
Since the bearing 24 is fixed in the press-fitting convex portion 28 of 6B, it is possible to secure a large distance from the end portion of the stepping motor to the bearing 24, and to reduce the noise and vibration generated by the bearing 24 by that amount. In addition, when the terminals 54A and 54B are soldered, the heat and substances such as soldering paste are less likely to be transmitted to the bearing 24, and the bearing performance is less likely to deteriorate due to the influence of heat and chemical substances such as paste. Further, since the positioning protrusions 41 are formed on the support members 40A and 40B, the angle adjustment of the bobbins 26A and 26B is facilitated, so that the assemblability can be improved from this point as well.

Further, since the press-fitting recesses 42 are formed in the support members 40A, 40B and the bobbins 26A, 26B are press-fitted and fixed in the press-fitting recesses 42,
As compared with the case where the bobbins 26A and 26B are arranged in the cavity of the injection mold as usual, and molten resin is injected into the cavity to mold the support members 40A and 40B, the inside of the cavity is more likely to be molded. Bobbins 26A, 26B
Without any problems such as the difficulty of accurate positioning of
It is possible to improve the accuracy of axial alignment between the bobbins 26A, 26B and the support members 40A, 40B.

Furthermore, in this embodiment, the pole teeth 48
The positions of the pole teeth 48A, 48B, 50A, 50B around the magnet 22 are made by separating the A, 48B, 50A, 50B from the bobbins 26A, 26B and forming the tubular member 46 fixed to each other by the non-magnetic body 52. The accuracy is extremely high, and it is possible to improve the rotor rotation accuracy in synergy with the above effect.

In the above embodiment, the bobbins 26A, 2
The bearing 24 was press-fitted into the press-fitting convex portion 28 of 6B,
Instead, as shown in FIG.
The bearing 24 may be press-fitted and fixed in the 0B bearing housing portion 45. In this way, the distance between the bearings 24 becomes large, so that the rotational stability of the shaft 20 can be improved.

Further, the present invention is not limited to the above-mentioned respective embodiments, and it goes without saying that the structure may be appropriately changed as necessary.

[0029]

As described above, according to the stepping motor of the present invention, the press-fitting convex portion formed at the end portion of each bobbin into the press-fitting concave portion formed at the end portion of each supporting member. By press-fitting, each bobbin and each supporting member are relatively positioned, and a bearing for supporting the shaft is provided coaxially with each supporting member as a reference, and a cylindrical case is fixed between each supporting member. Because it is a thing,
Each bobbin and the support member are aligned with each other, and the support members are aligned with each other via the case.

Therefore, it is easy to align the axis of each bobbin with the shaft, and the rotor stop position error due to the pole tooth position error and the magnetic balance non-uniformity due to the coil eccentricity do not occur, and the rotor rotation accuracy is improved. Can be increased. Furthermore, since the bobbin can be easily positioned, the productivity of the assembly work can be improved and the production cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a stepping motor according to the present invention.

FIG. 2 is an exploded perspective view showing a pole tooth, a bobbin, and a support member of the embodiment.

FIG. 3 is a perspective view showing an assembled state of the bobbin and the support member of the embodiment.

FIG. 4 is a perspective view showing an assembled state of the pole teeth, the bobbin and the support member of the same embodiment.

FIG. 5 is a longitudinal sectional view of the bobbin and the support member of the embodiment.

FIG. 6 is a front view of the bobbin and the support member of the embodiment.

FIG. 7 is a front view of the support member of the embodiment.

FIG. 8 is a sectional view of the same support member taken along the line VIII-VIII in FIG. 7.

FIG. 9 is a cross-sectional view showing an arrangement state of pole teeth of the embodiment.

FIG. 10 is a front view showing another embodiment in which the fixed position of the bearing is changed.

FIG. 11 is a perspective view showing a conventional stepping motor.

[Explanation of symbols]

 20 Shaft 22 Magnet 24 Bearing 26A, 26B Bobbin 28 Press-fitting convex part 30, 32 Flange part 30A Pole tooth contact surface 38A, 38B Coil 40A, 40B Support member 41 Positioning convex part (positioning engaging part) 42 Press-fitting Recesses 44 Case 45 Bearing press-fitting recesses 46 Cylindrical members 48A, 48B Long pole teeth 50A, 50B Short pole teeth 52 Non-magnetic body 54A, 54B Terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-70609 (JP, A) JP-A-63-39451 (JP, A) JP-A-7-143724 (JP, A) Actual development Sho-57- 34181 (JP, U) Actual flat 6-36381 (JP, U)

Claims (5)

(57) [Claims] 1. A shaft to which a magnet is coaxially fixed, a pair of bobbins arranged coaxially with the shaft on both axial sides of the magnet, and A-phase and B-phase coils wound around these bobbins, respectively. A short pole tooth whose one end is magnetically coupled to the magnet-side end of each bobbin and whose other end faces a part of the outer peripheral surface of the magnet; Long pole teeth, one end of which is magnetically coupled to the end and the other end of which faces the other part of the outer peripheral surface of the magnet, and coaxially adjacent to the end of each bobbin opposite to the magnet. A pair of support members arranged in a space, and a cylindrical case that is fixed between the support members and accommodates the respective parts, and a press-fitting convex portion is provided at an end portion of each bobbin on the support member side. The bobbin and the support member are relatively positioned by press-fitting the press-fitting convex portions formed on the shafts and coaxially formed at the ends of the support members, respectively. The stepping motor is characterized in that a bearing that supports the shaft is provided coaxially with each of the support members as a reference. 2. The press-fitting convex portions formed on each bobbin have an annular shape, and bearing accommodating portions are formed inside the press-fitting convex portions, and the bearings are coaxially fixed in the bearing accommodating portions. The stepping motor according to claim 1, wherein: 3. A bearing accommodating portion is further formed in a deep portion of the press-fitting recess of each of the supporting members, and the bearing is coaxially fixed in the bearing accommodating portion. The described stepping motor. 4. A positioning engagement portion is formed on each of the support members to regulate a direction around an axis of the bobbin fixed to the support member.
Or the stepping motor described in 3. 5. All of the pole teeth are separable from the corresponding bobbins, and are fixed to a cylindrical non-magnetic body that is coaxially arranged to surround the rotor. The stepping motor according to claim 1, 2, 3, or 4.