JPH1028367A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve lower pow consumption or downsizing of a stepping motor. SOLUTION: In a stepping motor 1, made up of a rotor 2 comprising a permanent tow-pole magnet 8, a platelike two-pole stator 3 having a structure which causes a holding torque around a rotor hole 6 where the rotor 2 is put into and magnetically connected to the rotor 2, and a coil 4 fixed to the stator 4, the stator 3 consists of a torque holding part 5, including the structure which causes the holding torque and a yoke part 3a excluding the torque holding part 5. The torque holding part 5 is designed to have a part thinner than the yoke part 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a step motor used for driving an electronic device such as a timepiece.

[0002]

2. Description of the Related Art In a timepiece, in particular, a stepping motor is used to step-drive a hand. However, in order to increase the battery life or downsize the timepiece, the power consumption of the stepping motor is further reduced. Alternatively, miniaturization is desired.

First, the structure of a conventional step motor will be described. FIG. 5 shows a conventional step motor.
(A) is a plan view thereof, and (b) is a sectional view taken along line EE of (a). FIG. 7 shows a holding torque curve and an excitation torque curve. The conventional step motor 30 shown in FIG.
Is a rotor 3 composed of a permanent magnet 37 having two poles and a diameter d0.
1, a plate-shaped two-pole stator 32 having a rotor hole 35 of a diameter D0 into which the rotor 31 enters and magnetically coupled to the rotor 31, and a coil 33 fixed to the stator 32 by two screws 36. Consists of

Further, in order to generate a holding torque curve 70 having static stability points 73 and 74 at every 180 degrees as shown in FIG. 7, the rotor holes 35 are mutually perpendicular to the straight line EE. It is composed of two substantially semicircles 35a and 35b having centers shifted in the directions. FIG. 5 (b)
As shown in the figure, the thickness t of the stator 32 is constant over the entire plate.

FIG. 6 shows another conventional step motor.
(A) is a plan view thereof, and (b) is a sectional view taken along line FF of (a). The conventional step motor 40 shown in FIG.
A rotor 31 comprising a permanent magnet 37 having a pole and a diameter d0;
A plate-shaped two-pole stator 42 having a rotor hole 45 with a diameter D0 into which the rotor 31 enters and magnetically coupled to the rotor 31
And the coil 33 fixed to the stator 42 by two screws 36.

[0006] Further, in order to generate a holding torque curve 70 having static stable points 73 and 74 at every 180 degrees as shown in FIG. 42, two notches 47 formed at positions facing each other. As shown in FIG. 6B, the thickness t of the stator 42 is constant over the entire plate.

Here, the operation of the conventional step motor will be described with reference to FIG. Since the operations of the step motors 30 and 40 are the same, the operation of the step motor 30 will be described. First, the rotor 31 is set at a static stable point of the holding torque (a point 73 at 0 degrees or a point 7 at 180 degrees shown in FIG. 7).
4) It is stationary. Here, when an exciting current for generating an exciting torque indicated by an exciting torque curve 71 or 72 shown in FIG. 7 is applied to the coil 33 every second for a predetermined time, the rotor 31 causes the valley 75 of the holding torque curve 70 or After turning over clock 76 and rotating 180 degrees, another static stable point of holding torque (18
It rests at the 0 degree point 74 or the 0 degree point 73). By repeating this operation every second, the hands of the clock can be moved. According to the above description, since the rotor 31 is driven by the exciting torque and can rotate over the valley 75 or 76 of the holding torque curve 70, the torque peak value Te1 of the exciting torque curves 71 and 72 and the valley 75 of the holding torque curve 70. , 76, the clock hands can be easily operated by increasing the ratio Te1 / Td1 of the torque peak value Td1.

FIG. 8 shows a curve of a torque peak value of a conventional step motor with respect to a permanent magnet diameter. The holding torque peak value curve 80 and the excitation torque peak value curve 81 are obtained when the diameter of the rotor hole is D0. When the permanent magnet diameter increases from d0 to d1 in the holding torque peak value curve 80, the coordinate point changes from 80a to 80b. The torque peak value increases from Td1 to Td2. In the excitation torque peak value curve 81, when the diameter of the permanent magnet increases from d0 to d1, the coordinate point moves from 81a to 81b, and the torque peak value increases from Te1 to Te2.

On the other hand, the holding torque peak value curve 82 and the excitation torque peak value curve 83 are obtained when the diameter of the rotor hole is D2 smaller than D0, and the permanent magnet diameter is from d0 to d2.
2 When the permanent magnet diameter increases from d2 to d0 in the holding torque peak value curve 82, the coordinate point moves from 82a to 82b, and the torque peak value becomes Td3.
To Td4. Excitation torque peak value curve 83
In, when the diameter of the permanent magnet increases from d2 to d0, the coordinate point moves from 83a to 83b, and the torque peak value increases from Te1 to Te3. Here, the permanent magnet diameter d2 at the rotor hole diameter D2 is the torque peak value at the permanent magnet diameter d2 in the exciting torque peak value curve 83 and the torque peak value at the permanent magnet diameter d0 in the exciting torque peak value curve 81. It is set to be Te1.

In the conventional stepping motor, the permanent magnet diameter of the rotor is set to d0, and the diameter of the rotor hole is set to D0. As shown in FIG. 7, the holding torque peak value is Td.
1. The excitation torque peak value is Te1.

[0011]

Since the exciting torque peak value is proportional to the exciting current, the permanent magnet diameter of the rotor is increased with the diameter of the rotor hole being D0, and the exciting torque peak value is increased. If an attempt is made to reduce the power consumption by increasing the value and decreasing the exciting current in accordance with the increase in the exciting torque peak value, the following problem occurs.
That is, as can be seen from the change in the torque peak value of the holding torque peak value curve 80 and the excitation torque peak value curve 81 shown in FIG. 8 due to the permanent magnet diameter, the increase in the holding torque peak value is greater than the increase in the excitation torque peak value. Is larger, Te1 when the permanent magnet diameter of the rotor is d0
And Td1, the ratio Te2 / Td2 of Te2 and Td2 when the permanent magnet diameter of the rotor is d1 compared to the ratio Te1 / Td1.
By making the permanent magnet diameter of the rotor d1 larger than d0, it is possible to rotate the rotor beyond the holding torque valley unless the excitation current is increased and the excitation torque peak value is increased, instead of reducing the excitation current. Disappears.

In order to reduce the holding torque peak value Td2 when the diameter of the permanent magnet of the rotor is d1, in the conventional stepping motor shown in FIG. 5, two substantially semicircles 35a and 35b for determining the holding torque are set. Deviation e between centers of
1. In the conventional stepping motor shown in FIG. 6, it is conceivable to reduce the diameter e2 of the notch 47, which determines the holding torque. However, since these values are several μ and several tens μ, respectively, they cannot be handled in mass production due to processing accuracy. . As described above, by setting the permanent magnet diameter of the rotor to d1 which is larger than d0, other means for preventing the holding torque peak value from increasing even if the excitation torque peak value is increased is required.

If it is attempted to reduce the size of the stepping motor by changing the diameter of the permanent magnet from d0 to d2, the ratio Te1 / Td3 of the peak value Te1 of the exciting torque and the peak value Td3 of the holding torque when the permanent magnet diameter is d2 in FIG.
Is the peak value Te of the exciting torque when the permanent magnet diameter is d0.
Since the ratio is smaller than the ratio Te1 / Td1 of 1 and the holding torque peak value Td1, the step motor cannot rotate normally unless the exciting current is increased, and it is difficult to reduce the size of the step motor.

An object of the present invention is to provide means for reducing the power consumption or reducing the size of a step motor used for driving electronic equipment such as a timepiece.

[0015]

Means for solving the above problem is to provide a rotor comprising a permanent magnet having two poles and a structure for generating a holding torque in the vicinity of a rotor hole in which the rotor enters. In a step motor comprising a plate-shaped two-pole stator to be coupled and a coil fixed to the stator, the stator comprises a holding torque portion including a structure for generating the holding torque, and a yoke portion excluding the holding torque portion. The holding torque portion has a portion thinner than the yoke portion.

The inner periphery of the holding torque portion is the outer periphery of the rotor hole, and the outer periphery is a circle having the same center as the center of the rotor hole.

[0017] The stator is characterized in that it is formed by laminating at least two stator members having different shapes and having rotor holes.

[0018]

1A and 1B show a stepping motor according to the present invention, wherein FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along line AA of FIG. An embodiment of the present invention will be described with reference to FIG. A stepping motor 1 according to the present invention shown in FIG. 1 has a rotor 2 composed of a permanent magnet 8 having two poles and a diameter d1, and a holding torque portion 5 including a structure for generating a holding torque described below.
(A hatched portion surrounded by a substantially semicircle 6a, 6b and a circle 6d whose center is 6c) and a yoke portion 3a excluding the holding torque portion,
It comprises a plate-shaped two-pole stator 3 having a rotor hole 6 (diameter D0) into which the rotor 2 is inserted and magnetically coupled to the rotor 2, and a coil 4 fixed to the stator 3 by two screws 7. The rotor holes 6 are centered at right angles to the line AA and opposite to each other in order to generate a holding torque curve 70 having static stability points 73, 74 at every 180 degrees as shown in FIG. (A holding torque portion 5 shown in FIG. 1 (a)) which generates a holding torque deviated from a perfect circle (a holding torque is not generated when the shape is a perfect circle). (Equivalent to the inner circumference of).

As shown in FIG. 1B, the feature of this embodiment is that the inner periphery is the outer periphery 6a, 6b of the rotor hole 6, and the outer periphery is the center of the rotor hole 6 (also the center of the rotor 2). A circle 6d having the same center 6c (the radius is 6c and 6a
When the thickness t0 of the holding torque portion 5 is experimentally viewed, and when the ratio d1 / d0 of the permanent magnet diameters is 1.2, the yoke of the stator 3 is obtained. This is that t0 / t is as thin as 0.5 as compared with the thickness t of the portion 3a. 9a and 9b are edges of the joint 9 of the stator 3, and the radius of the circle 6d can be increased to a smaller one between 6c and 9a or between 6c and 9b.

FIG. 9 shows a curve of the torque peak value of the step motor according to the present invention with respect to the permanent magnet diameter. However,
When the permanent magnet diameter is d0, it is the torque peak value of the conventional step motor, and is the same as FIG. 8 except for the excitation torque peak value Te4 at the coordinate point 91c of the step motor of the present invention. That is, coordinate point 90a (92a) is coordinate point 8
0a (shown in FIG. 8), and the holding torque peak value is Td.
1, the coordinate point 91a is the same as the coordinate point 81a, the excitation torque peak value is Te1, the coordinate point 93a is the same as the coordinate point 83b, and the excitation torque peak value is Te3. The holding torque peak value curve 90 and the excitation torque peak value curve 91 are obtained when the diameter of the rotor hole is D0. When the permanent magnet diameter increases from d0 to d1 in the holding torque peak value curve 90, the coordinate point changes from 90a to 90b. Although it moves, the torque peak value is not different from Td1. When the permanent magnet diameter increases from d0 to d1 in the excitation torque peak value curve 91, the coordinate point moves from 91a to 91b, and the torque peak value increases from Te1 to Te20.

On the other hand, the holding torque peak value curve 92 and the excitation torque peak value curve 93 are obtained when the diameter of the rotor hole is D2 smaller than D0, and when the permanent magnet diameter increases from d2 to d0 in the holding torque peak value curve 92. The coordinate point moves from 92b to 92a, but the thickness t0 of the holding torque portion is set so that the torque peak value does not change from Td1. Excitation torque peak value curve 93
, The permanent magnet diameter is set to d2 so that the torque peak value when the permanent magnet diameter is d2 becomes the torque peak value Te1 when the rotor hole diameter is D0 and the permanent magnet diameter is d0, and the permanent magnet diameter is set to d2. When the magnet diameter increases from d2 to d0, the coordinate point moves from 93b to 93a, and the torque peak value increases from Te1 to Te3.

Next, the operation of the stepping motor according to the present invention, in which the diameter of the permanent magnet is d1, will be described with reference to FIGS. When increasing the permanent magnet diameter, the thickness t0 of the holding torque portion 5 (when the permanent magnet diameter is d0, the thickness t0 of the holding torque portion 5 is the thickness t of the yoke portion). Thus, the holding torque peak value curve can be made a constant holding torque peak value curve 90. This reduces the thickness t0 of the holding torque portion 5,
This is because the holding torque portion 5 is magnetically saturated with the magnetic flux of the permanent magnet 8 to reduce the contribution of the holding torque portion 5 to the holding torque. Therefore, even if the diameter of the permanent magnet is increased to d1, the holding torque peak value becomes Td1 irrespective of the case where the diameter of the permanent magnet is d0, so that the holding torque curve can be substantially changed to the holding torque curve 70 shown in FIG.

On the other hand, the excitation torque peak value draws an excitation torque peak value curve 91 as the permanent magnet diameter increases from d0 to d1, and the excitation torque peak value changes from Te1 to T1.
e20 (substantially equal to Te2 shown in FIG. 8).
Here, since the excitation torque peak value is proportional to the excitation current, if the excitation current when generating the excitation torque peak value Te20 is reduced to Te1 / Te20, the excitation torque peak value at the excitation current becomes the excitation torque peak value Te1. . Therefore, the excitation torque curves are almost the same as the excitation torque curves 71 and 72 shown in FIG. 7, so that the rotor can be rotated in the same manner as the conventional step motor.

Further, referring to FIG. 9, the diameter of the permanent magnet is d.
The operation of the step motor of the present invention, which is 0, will be described. When the thickness t0 of the holding torque part 5 is set so that the holding torque part is on the verge of magnetic saturation with the magnetic flux of the permanent magnet 8, the holding torque peak value is set to the coordinate point 90a or 92a.
Can be kept as Td1. On the other hand, due to the presence of the holding torque portion 5, the magnetic coupling between the permanent magnet 8 and the coil 4 is equivalently increased, so that the excitation torque peak value becomes T
Te4 indicated by coordinates 91c larger than e1. Therefore, by reducing the excitation current to Te1 / Te4, the excitation torque peak value can be set to the excitation torque peak value Te1 indicated by the coordinate point 91a. Therefore, the holding torque curve and the excitation torque curve become substantially the holding torque curve 70 and the excitation torque curves 71 and 72 shown in FIG. 7, respectively, so that the rotor can be rotated in the same manner as the conventional step motor.

Therefore, according to the above description, the permanent magnet diameter d
1 is Te1 / Te20 compared with the conventional stepping motor having a permanent magnet diameter d0, and the stepping motor having a permanent magnet diameter d0 is d.
It can be seen that a lower power consumption of the exciting current can be achieved in Te1 / Te4 than in the conventional step motor of No. 0.

Next, the downsizing of the step motor of the present invention by changing the diameter of the rotor hole from D0 to D2 will be described with reference to FIG. The holding torque peak value curve 92 of the stepping motor of the present invention is obtained by changing the permanent magnet diameter from d0 to d.
2 and the excitation torque peak value curve 93 is almost the same as the excitation torque peak value curve 83 in FIG. 8, so that the excitation torque peak value and the holding torque peak value at the diameter d2 of the permanent magnet are obtained. Is no different from Te1 / Td1 when the diameter of the permanent magnet is d0, and it can be seen that the stepping motor of the present invention can be driven by the same exciting current as the conventional stepping motor.

From the above description, it can be seen that the diameter of the rotor hole can be reduced to D2 without increasing the power consumption of the step motor, so that the stator can be downsized and the step motor can be downsized.

Next, a method for processing the stator of the step motor according to the present invention will be described. FIG. 3 is a processing procedure diagram of the step motor 1. Stator blank 20 (FIG. 3A)
3B, a dummy hole 21, a slit 22, and a screw hole 21a are formed in the stator blank 20.
Next, as shown in FIG. 3C, both ends of the slit 22 are joined with a non-magnetic brazing material 23 (joining portion 23a). next,
As shown in FIG. 3D, a thin portion 24 whose outer shape becomes the outer shape of the holding torque portion 5 shown in FIG. 3E is pressed. Finally, as shown in FIG. 3 (e), the rotor hole 6 is press-cut by shaving to form the holding torque portion 5, thereby completing the stator 3.

FIGS. 2A and 2B show a step motor according to another embodiment of the present invention, wherein FIG. 2A is a plan view and FIG. 2B is a sectional view taken along line BB of FIG. An embodiment of the present invention will be described with reference to FIG. The step motor 10 of the present invention shown in a plan view (a) has a rotor 2 composed of a permanent magnet 8 having two poles and a diameter d1, and a holding torque portion 14 (centered at a center) including a structure for generating a holding torque described below. 6c circle 15a and circle 15
c) and a yoke portion 12a excluding the holding torque portion, and has a rotor hole 15 (diameter D0) into which the rotor 2 enters, and is a plate-shaped two-pole stator magnetically coupled to the rotor 2. 12 is a stepping motor comprising a coil 4 fixed to the stator 12 by two screws 7. The rotor hole 15 has a holding torque having a static stable point 73, 74 every 180 degrees as shown in FIG. In order to generate the curve 70, it is composed of two notches 17 formed at positions facing each other at about 45 degrees from the straight line BB, and is a perfect circle (in the case of a perfect circle, no holding torque is generated). A structure (consisting of two notches) that generates a holding torque deviated from the above is formed.

2 (a), the inner circumference is the outer circumference 15a of the rotor hole 15, and the outer circumference is the rotor hole 15a.
Center 6 which is the same as the center (also the center of rotor 2)
The thickness t0 of the holding torque portion 14, which becomes a circle 15c having a c (a circle contacting the notch 17), is shown in FIG. 2B when the ratio d1 / d0 of the permanent magnet diameter is 1.2. Thus, compared to the thickness t of the yoke portion 12a of the stator 12, t0
/ T is as thin as 0.5. 2A shows a narrow portion 91 of the stator 12, 91a and 91b are edges of the narrow portion 91, and the radius of the circle 15c is 6c and 9
The distance can be increased to the smaller one of the distance between 1a or 6c and 91b. The circle 15c may be formed such that the notch 17 is located inside the vicinity of the circumference of the circle 15c.

The method for machining the stator of the step motor 10 according to the present invention is similar to the method for machining the stator of the step motor 1 except that there is no slit machining or slit welding shown in FIGS. 3 (b) and 3 (c). e) two substantially semicircles 6 shown in FIG.
Except that the configuration of a and 6b is replaced by two notches 17, the description is omitted. The operation in FIG. 9 is the same as that of the step motor 1, and the description is omitted.

FIG. 4 shows a stepping motor according to another embodiment of the present invention, wherein (a) and (b) are plan views of stator members having different shapes for forming a stator.
(C) is a plan view of the step motor, and (d) is a cross-sectional view taken along line CC of (c). Referring to FIG. 4, an embodiment of a step motor according to the present invention in which a stator is formed by stacking two stator members having different shapes on each other will be described. Step motor 111 of the present invention shown in FIG.
Is a rotor 2 comprising a permanent magnet 8 having two poles and a diameter d1.
And a yoke portion 1 excluding the holding torque portion 115 including a structure for generating a holding torque described below.
13a and 113b, the diameter of which the rotor 2 enters is D
It comprises a plate-shaped two-pole stator 113 having a zero rotor hole 116 and magnetically coupled to the rotor 2, and a coil 4 fixed to the stator 113 by two screws 7. The rotor holes 116 are centered at right angles to the straight line C-C and opposite to each other in order to generate the holding torque curve 70 shown in FIG. (A holding torque portion 115 shown in FIG. 4 (c)) that generates a holding torque deviating from a perfect circle (a holding torque is not generated when the shape is a perfect circle). (Equivalent to the inner circumference of).

As shown in FIG.
Fig. 4 (c) shows a laminate of a stator member 26 having a thickness t1 and a stator member 28 having a thickness t0.
A circle 1 having a center 6c whose inner circumferences are the outer circumferences 116a and 116b of the rotor hole 116 and whose outer circumference is the center of the rotor hole 116 (also the center of the rotor 2).
The thickness t0 of the holding torque portion 115, which is 16d, is
As shown in (d), when the permanent magnet diameter ratio d1 / d0 is 1.2, the yoke portions 113a, 113
As compared with the thickness t of 3b, t0 / t is as thin as 0.5. Next, a method of processing and assembling the step motor of the present invention using the stator members 26 and 28 will be described.

FIG. 4A shows a stator member 26 having a rotor hole 25 which forms a circle 116d on the outer periphery of the holding torque portion 115. FIG. 4B shows a stator member 28, A rotor hole 27 made of two substantially semicircles 27a and 27b having centers deviated from each other in a direction perpendicular to a straight line CC which is an inner periphery of the torque portion 115 is cut out by a shaving press. Next, as shown in FIG. 4 (c), the stator member 26 and the stator member 28 are overlapped with the center 25b of the hole 25 for the rotor and the center 27d of the hole 27 for the rotor.
5 is assembled, and the rotor holes 116 are assembled.
Is mounted on the rotor 113, and the coil 4 is fixed to the stator 113 with the screws 7, thereby forming a step motor 111.
Is completed. The thickness t0 of the holding torque portion 115 can be easily and accurately obtained by the stator processing method. The operation in FIG. 9 is the same as that of the step motor 1, and the description is omitted.

FIG. 10 is a sectional view of a step motor according to another embodiment of the present invention. FIG. 1 (b) and FIG. 2 (b)
4 (d), the holding torque portion is provided on one side in the thickness direction of the stator, but may be provided near the center in the thickness direction like the holding torque portion 50 shown in the sectional view of FIG.

FIG. 11 is a sectional view of a step motor according to another embodiment of the present invention. 1 (b), 2 (b) and 4 (d), the sectional shape of the holding torque portion is a step shape, but the holding torque portion 5 shown in the sectional view of FIG.
As shown in FIG. 1, an inclined cross-sectional shape whose thickness continuously increases from t0 to t may be used.

FIG. 12 is a sectional view of a step motor according to another embodiment of the present invention. In FIG. 4D, the holding torque portion 115 is formed by stacking two stator members 26 and 28. However, like the holding torque portion 52 shown in the sectional view of FIG. 53, 54,
55 may be formed by overlapping.

FIGS. 13A and 13B show a stepping motor according to another embodiment of the present invention. FIG. 13A is a plan view of the stepping motor, and FIG. 13B is a sectional view taken along line DD of FIG. FIG.
3, an embodiment of the stepping motor according to the present invention in which the stator is formed by stacking two stator members having different shapes. The step motor 211 of the present invention shown in FIG. 13A has a rotor 2 composed of a permanent magnet 8 having two poles and a diameter d1, a holding torque portion 215 including a structure for generating a holding torque described below, and the holding motor 215. It consists of yoke parts 213a and 213b excluding the torque part,
A plate-shaped two-pole stator 213 having a rotor hole 216 with a diameter D0 into which the rotor 2 enters and magnetically coupled to the rotor 2
And the coil 4 fixed to the stator 213 by two screws 7. The rotor holes 216 are centered at right angles to the line DD and in opposite directions to generate a holding torque curve 70 having static stability points 73, 74 at every 180 degrees, as shown in FIG. (A holding torque portion 215 shown in FIG. 13 (a)) that generates a holding torque deviated from a perfect circle (a holding torque is not generated when the shape is a perfect circle). Is equal to the inner circumference of Here, the step motor shown in FIG. 13 is different from the step motor shown in FIG. 4 in the following points. In other words, the rotor hole 216 of the stator 213 shown in FIG. 13 is composed of a circle having a diameter D0 and two substantially semicircles 216a and 216b having a radius larger than the radius of the circle, whereas FIG. The rotor hole 116 of the stator 113 shown in FIG. 3 is formed by a circle 116d and two substantially semicircles 116a and 116b whose radius is smaller than the radius of the circle.

As shown in FIG.
Reference numeral 3 denotes a stator member 221 having a thickness t1 and a thickness t0
FIG.
3 (a), the inner periphery is indicated by the rotor hole 21.
6, the outer circumference of the rotor hole 21
The thickness t0 of the holding torque portion 215, which becomes a circle 216d having a center 6c which is the center of the rotor 6 (also the center of the rotor 2)
Is the ratio d1 of the permanent magnet diameter as shown in FIG.
When / d0 is 1.2, the yoke 213 of the stator 213
As compared with the thickness t of a and 213b, t0 / t is as thin as 0.5.

FIG. 14 is a perspective view showing a part of a step motor according to another embodiment of the present invention in which a notch is formed in a stator. A holding torque portion 316 indicated by a hatched portion of the stator 313 has an inner periphery of a rotor. Outer circumference 315a of hole 315
The center 6 whose outer periphery is the same as the center of the rotor hole 315
A notch 314 having a depth t0 is formed in the stator 313 as a circle 315c having a c (a circle in contact with the notch 314). Here, another notch is formed at a symmetric position of the notch 314 with respect to the center 6c.

[0041]

As can be seen from the above description, according to the present invention as set forth in claims 1, 2 and 3, the power consumption of a step motor used for driving electronic equipment such as a timepiece can be reduced, and It can be seen that there is an effect that the life can be extended. Alternatively, it can be seen that there is an effect that the step motor can be downsized.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of a step motor according to the present invention.

FIG. 2 is a plan view and a sectional view of a step motor according to another embodiment of the present invention.

FIG. 3 is a processing procedure diagram of the step motor of the present invention.

FIG. 4 is a processing procedure diagram, a plan view, and a cross-sectional view of a step motor according to another embodiment of the present invention.

FIG. 5 is a plan view and a sectional view of a conventional step motor.

FIG. 6 is a plan view and a sectional view of another conventional step motor.

FIG. 7 is a torque curve of a step motor.

FIG. 8 is a curve of a torque peak value of a conventional step motor with respect to a permanent magnet diameter.

FIG. 9 is a curve of a torque peak value of a step motor according to the present invention with respect to a permanent magnet diameter.

FIG. 10 is a sectional view of a step motor according to another embodiment of the present invention.

FIG. 11 is a sectional view of a step motor according to another embodiment of the present invention.

FIG. 12 is a sectional view of a step motor according to another embodiment of the present invention.

FIG. 13 is a plan view and a sectional view of a step motor according to another embodiment of the present invention.

FIG. 14 is a perspective view of a part of a step motor having a notch formed therein according to another embodiment of the present invention.

[Explanation of symbols]

1 10 30 40 111 Step motor 2 31 Rotor 3 12 32 42 113 213 313 Stator 4 33 Coil 5 14 50 51 52 115 115 215 316
Holding torque part 3a 12a 113a Yoke part 26 28 53 54 55 220 221 Stator member

Claims (3)

[Claims] 1. A rotor comprising a two-pole permanent magnet, a plate-shaped two-pole stator having a structure for generating a holding torque near a rotor hole into which the rotor enters, and magnetically coupled to the rotor; In a step motor having a fixed coil, the stator includes a holding torque portion including a structure for generating the holding torque and a yoke portion excluding the holding torque portion, and the holding torque portion has a portion thinner than the yoke portion. A step motor. 2. The step motor according to claim 1, wherein an inner circumference of the holding torque portion is an outer circumference of the rotor hole, and an outer circumference is a circle having the same center as the center of the rotor hole. . 3. The step motor according to claim 1, wherein the stator is formed by overlapping at least two stator members having different shapes and having holes for a rotor.