JP2001178107A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of a stepping motor. SOLUTION: A stepping motor 1 has a rotor 2, that is made of a dipole permanent magnet 8, a plate-shaped dipole stator 3 that has structure for generating a retention torque near a rotor hole 6 where the rotor 2 enters and is magnetically coupled to the rotor 2, and a coil 4 that is fixed to the stator 3. The stator 3 consists of a retention torque part 5, including structure for generating the retention torque, and a yoke 3a excluding the retention torque part 5. Also, the retention torque part 5 is thicker than the yoke 3a. In the stepping motor 1, the thickness of the retention torque is larger than 0 micron and is smaller than 100 micron.

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 and a driving method thereof, and more particularly to a stator.

[0002]

2. Description of the Related Art In electronic devices, especially timepieces, a stepping motor is used to step-drive a hand.
In order to increase the battery life, further reduction in power consumption of the step motor is desired.

[0003] The present applicant has disclosed in Japanese Patent Application Laid-Open
The technology disclosed in Japanese Patent No. 28367 was filed. The structure of the conventional step motor disclosed in Japanese Patent Application Laid-Open No. 10-28367 will be described. 3A and 3B show a conventional stepping motor, wherein FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view taken along line CC of FIG. A conventional stepping motor 11 shown in FIG. 3 includes a rotor 2 composed of a permanent magnet 8 having two poles and a diameter d, and a holding torque portion 50 (having semicircles 60a and 60b and a center 6c having a structure for generating a holding torque). (A hatched portion surrounded by a circle 60d) and a yoke portion 30a excluding the holding torque portion, a plate-shaped two-pole stator 30 having a rotor hole 60 in which the rotor 2 enters, and magnetically coupled to the rotor 2; It comprises a coil 4 fixed to the stator 30 by two screws 7.

The rotor hole 60 is composed of two semicircles 60a and 60b perpendicular to the straight line CC and having centers deviated from each other in a direction perpendicular to the straight line CC in order to generate a holding torque. 50b), and a structure that generates a holding torque that deviates from a perfect circle (a holding torque in the rotation direction of the rotor 2 does not occur when the shape is a perfect circle). Equal).

Further, as shown in FIG. 3 (b), the inner periphery is the outer periphery 60a, 60b of the rotor hole 60, and the outer periphery is the same as the center of the rotor hole 60 (also the center of the rotor 2). A circle having a diameter D3 having a radius of 60
And the semi-circle 60a or the semi-circle 60b).
That is, the thickness is smaller than the thickness t of the yoke portion 30a of the stator 30. Note that 90a and 90b are the stators 3
0 is the edge of the joint 90.

[0006] The structure of another conventional stepping motor disclosed in Japanese Patent Application Laid-Open No. 10-28367 will be described. 4A and 4B show another conventional step motor, in which FIG. 4A is a plan view, and FIG. 4B is a sectional view taken along line EE of FIG. Another conventional step motor 110 shown in a plan view (a) is:
A rotor 2 composed of a permanent magnet 8 having two poles and a diameter d, a holding torque portion 140 including a structure for generating a holding torque (a hatched portion surrounded by circles 150a and 150b having a center of 6c) and the holding torque portion And a rotor hole 150 into which the rotor 2 is inserted.
And a coil 4 fixed to the stator 120 with two screws 7.

The rotor hole 150 of this stepping motor is
Is composed of two notches 140a and 140b formed at positions facing each other at about 45 degrees from the straight line EE to generate a holding torque. No holding torque in the rotational direction is generated), and a structure (consisting of two notches) that generates a holding torque deviated from the above is formed.

A center 6c whose inner periphery is the outer periphery 150a of the rotor hole 150 and whose outer periphery is the same as the center of the rotor hole 150 (also the center of the rotor 2) is indicated by the hatched portion in FIG. As shown in FIG. 4B, the thickness t2 of the holding torque portion 140, which is a circle 150b having a diameter D4 (which is a circle in contact with the notches 140a and 140b), has a thickness t2 of the yoke portion 120a of the stator 120. It is thinner than. Incidentally, 92 shown in FIG. 4A is a narrow portion of the stator 120.

The operation of the conventional step motor will now be described with reference to a conventional step motor shown in FIG.
The operation of the conventional step motor is described in detail in the patent application by the present applicant, and thus will only be briefly described.

In order to reduce the power consumption of the step motor, first, the magnetic coupling between the rotor 2, the stator 30, and the coil 4 must be increased. By increasing the magnetic coupling, the driving torque per unit driving current flowing through the coil 4 increases. Since the driving torque increases in proportion to the reciprocal of the diameter of the rotor hole 60, one method for reducing the diameter of the rotor hole 60 while keeping the outer shape of the magnet 8 is one for the structure of the stepping motor. Conceivable.

Second, the holding torque must be maintained. Eccentricity 50a and 5 of structure that generates holding torque
If the dimension of 0b is left as it is, the holding torque increases in proportion to the cube of the reciprocal of the diameter of the rotor hole 60.
As a result of the reduction in the diameter of the rotor hole 6, the holding torque becomes very large, and the rotor 2 becomes difficult to rotate, so that low power consumption cannot be expected.

Therefore, in order to maintain the holding torque, the dimensions of the eccentricities 50a and 50b of the structure that generates the holding torque must be reduced from the current level of about 30 μ to about several μ (in the step motor 110 shown in FIG. Notch 14
The radius of 0a and 140b is several tens of μ from the current 150μ.
It is difficult to accurately process the eccentricities 50a and 50b of this size with the current processing technology.

Therefore, focusing on the fact that the holding torque is proportional to the thickness t2 of the holding torque portion 50 while keeping the eccentricity or the size of the notch as it is, the thickness t2 of the holding torque portion 50 is maintained in order to maintain the holding torque. The thickness of the yoke portion 30a is made smaller than the thickness t of the yoke portion 30a by the increased torque.

[0014]

However, in order to further reduce the power consumption, the rotor 2 and the stator 30 must be connected.
It is necessary to increase the magnetic coupling between the coil and the coil 4 as much as possible. As a result, the holding torque also increases, but it is not disclosed how far the thickness t2 of the holding torque portion 50 should be reduced in order to maintain the holding torque.

Further, as the diameter D3 of the rotor hole 60 becomes smaller, unnecessary torque generated due to the processing deviation of the circle 60d from the true circle also increases, and the torque is reduced by the eccentricities 50a and 50b and the holding torque. This is added to the holding torque determined by the thickness t2 of the portion 50, thereby distorting the total holding torque.

Furthermore, as a result of the increase in the magnetic coupling between the rotor 2, the stator 30, and the coil 4, the radial attraction force generated by the eccentricity of the rotor 2 during machining or assembly increases, and the axial friction of the rotor 2 increases. This results in an increase in torque, which hinders low power consumption.

Further, a method of driving the step motor 11 has not been disclosed.

An object of the present invention is to provide an optimal structure and a driving method for reducing the power consumption of a step motor used for driving an electronic device such as a timepiece.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is to provide a rotor comprising a two-pole permanent magnet,
A plate-shaped two-pole stator magnetically coupled to the rotor and having a structure for generating a holding torque near a rotor hole into which the rotor enters, and a coil fixed to the stator;
The stator includes a holding torque portion including a structure for generating the holding torque and a yoke portion excluding the holding torque portion. Further, in the step motor having a thickness smaller than that of the yoke portion, the holding torque portion is Is characterized by a thickness greater than 0 microns and less than 100 microns.

The inner periphery of the holding torque portion is the outer periphery of the rotor hole, and the outer periphery of the holding torque portion is a circle having the same center as the center of the rotor hole and larger than the maximum outer periphery of the rotor hole. It is characterized by.

The structure for generating the holding torque is an eccentric or notch structure.

The above-mentioned stator is characterized in that it is a stator formed of one single-layer plate or two or more laminated plates (hereinafter referred to as an integral stator).

The step motor is driven by a chopper.

[0024]

FIG. 1 shows an eccentric integrated stator type stepping motor according to a first embodiment of the present invention.
(A) is a plan view, and (b) is a cross-sectional view taken along a line AA of (a). An embodiment of the present invention will be described with reference to FIG. FIG.
The step motor 1 of the present invention shown in FIG. 1 has a rotor 2 composed of a permanent magnet 8 having two poles and a diameter d, and a holding torque portion 5 (half circles 6a and 6b and a circle having a center 6c) including a structure for generating a holding torque. 6d) and a yoke portion 3a excluding the holding torque portion. The yoke portion 3a has a rotor hole 6 into which the rotor 2 enters, and is formed of one single-layer plate magnetically coupled to the rotor 2. It comprises a two-pole stator 3 and a coil 4 fixed to the stator 3 by two screws 7.

In order to generate a holding torque, the center of the rotor hole 6 is perpendicular to the straight line AA.
On the other hand, a structure (including eccentricities 5a and 5b) composed of two semicircles 6a and 6b having centers deviated in the opposite directions to each other (see FIG. 1 (a)). ) Is formed (equivalent to the inner circumference of the holding torque portion 5).

The feature of this embodiment is that, first, as shown in FIG. 1B, the thickness t of the yoke portion 3a (5 in this embodiment).
00 μ), the thickness t0 of the holding torque portion 5 is 1
That is, it is smaller than 00 μ.

The outer diameter D0 of the holding torque portion 5 is larger than the maximum dimension D formed by the semicircle 6a and the semicircle 6b. In this embodiment, D0 is 12
00μ and the D is 1125μ. In addition, eccentricity 5a, 5
The dimension of b is 25 μ.

FIGS. 2A and 2B show a notch integrated stator type stepping motor according to a second 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. FIG.
An embodiment of the present invention will be described below. A stepping 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 d, and a holding torque portion 14 (15a having a center of 6c) including a structure for generating a holding torque. (A hatched portion surrounded by a circle 15b) and a yoke portion 12a excluding the holding torque portion.

A plate-shaped two-pole integral stator 12 having a rotor hole 15 into which the rotor 2 is inserted and magnetically coupled to the rotor 2
And a step motor comprising a coil 4 fixed to the stator 12 with two screws 7.
5 is approximately 4 from the straight line BB to generate the holding torque.
It is composed of two notches 14a and 14b formed at positions facing each other at 5 degrees, and forms a structure that generates a holding torque that deviates from a perfect circle.

The feature of this embodiment is that, as shown in FIG. 2B, the thickness t0 of the holding torque portion 14 is smaller than 100 μm.

The outer diameter D2 of the holding torque portion 14 is larger than the diameter D1 of the circumscribed circle of the notches 14a and 14b. However, in order to make the motor performance of the step motor 10 equal to that of the step motor 1, the outer diameter D2 cannot be larger than the diameter D1 than the outer diameter D0. Because usually notch 14
This is because the dimensions of a and 14b (the radial dimension of the rotor hole 15) are larger by about 100 μ than the dimensions of the eccentricities 5a and 5b of the step motor 1 shown in FIG.

Therefore, in order not to change the holding torque, the holding torque is proportional to the area of the notches 14a and 14b. Therefore, the circumferential size of the rotor holes 15 of the notches 14a and 14b is made about twice as large as the normal size. The size of the eccentricity 5a, 5b is set to about 50μ compared to the size of the eccentricity 5a, 5b. As a result, while the outer diameter D2 of the holding torque portion 14 is 1200 μm, the diameter D1 of the circumscribed circle of the notches 14 a and 14 b is determined in consideration of the processing position accuracy (about 10 μm) of the outer periphery of the holding torque portion 14. Even so, the dimension of the outer periphery of the holding torque portion 14 does not cover the notches 14a and 14b.

The operation of the first eccentric integrated stator type step motor of the present invention shown in FIG. 1 will be described. As described above, in order to maximize the power consumption, it is necessary to increase the magnetic coupling between the rotor 2, the stator 3, and the coil 4 as much as possible in order to increase the driving torque. As a result, the holding torque also increases, and the remaining power, which is the amount of torque that can rotate the rotor 2, increases. However, power dissipation also increases. Must be reduced.

This will be described in more detail with reference to FIG. 7, which is a diagram showing a change in the thickness t of the holding torque portion for reducing power consumption and increasing reserve power. The circles and triangles indicate experimental data of low power consumption and increased reserve when the thickness is 50 μm and 100 μm. Thickness t is 100
In the case of μ, low power consumption cannot be achieved at −5%, but the reserve torque is increased by 19% due to the large holding torque. On the other hand, when the thickness t is 50 μm, a 17% reduction in power consumption can be achieved, and the remaining torque is increased by 9% as the holding torque is reduced. The stepping motor used as a comparison object between the low power consumption and the increase in the remaining power is described in Japanese Patent Application Laid-Open No.
This is a conventional stepping motor in which the thickness of the holding torque generating section is the same as the thickness of the stator.

As shown in FIG. 7, when the thickness t0 is 50 μm, there is still a 9% margin in the remaining power.
Thus, it can be seen that the power consumption can be further reduced by reducing the holding torque and the remaining power, that is, by reducing the thickness t0 to less than 50 μm.

Incidentally, for the first eccentric integrated stator type stepping motor of the present invention, the outer diameter of the permanent magnet 8 is 750 μm, the maximum outer diameter D of the rotor hole 6 is 1125 μm, and the eccentricities 5 a and 5 b are 25 μm. And the thickness t of the stator 3 is 500
μ.

First, the outer diameter D0 of the holding torque portion 5
Is larger than the maximum dimension D formed by the semicircle 6a and the semicircle 6b.
Magnetic coupling with the permanent magnet 8 of the holding torque generating portion having a thickness t0 by making the magnetic coupling with the outer diameter D
This is because even if the zero circle deviates from the true circle, the extra torque generated by the deviation is negligibly smaller than the holding torque generated by the holding torque generating part having the thickness t0.

Second, the outer diameter D0 of the holding torque portion 5
Is larger than the maximum dimension D formed by the semicircle 6a and the semicircle 6b because the permanent magnet 8, the stator 3, and the coil 4 form a magnetic circuit even if the circle having the outer diameter D0 is a perfect circle. Therefore, the N and S magnetic poles of the permanent magnet 8 are pulled in parallel to the axial direction of the coil 4, but the force is weakened to a negligible level.
This is so that the rotor 2 can be stopped at the holding torque stationary stable position where the rotor 2 is easily started determined by the holding torque generating section having the thickness t0, and can be rotated with low power consumption. In addition, with respect to the first eccentric integrated stator type step motor of the present invention,
Maximum dimension D11 formed by the semicircle 6a and the semicircle 6b
For 25 μ, the outer diameter D0 of the holding torque portion 5 is 1200
μ.

The reason why the stator 3 is formed as an integral stator is that the generation of magnetic poles on the surface of the narrow portion 9 of the stator 3 is suppressed particularly when the rotor 3 is driven, and the radial attractive force of the rotor 3 is reduced. That's why. As a result, the eccentric rotor 3
, The shaft friction torque generated by the radial suction force can be reduced, and the drive power loss due to the shaft friction torque can be reduced.

The operation of the second notch integrated stator type step motor of the present invention shown in FIG. 2 can be similarly described by replacing the eccentricity with the notch in the description of the operation of the eccentric integrated stator step motor. Therefore, the description is omitted.

FIG. 8 is a sectional view of a step motor according to the third embodiment of the present invention. The yoke 31 having the total thickness t is manufactured by laminating a thin plate having a thickness t0 forming the holding torque portion 51 and one plate having a thickness t1 having the rotor hole 61.

FIG. 5 is a chopper drive pulse diagram during one-second hand movement. This chopper drive pulse is composed of eight chopper pulses having a pulse width of about 0.3 ms, and the pulse width is 4 ms. FIG. 6 is a full drive pulse diagram at the time of one-second hand movement. The pulse width of this full drive pulse is 2 ms.

FIG. 7 is a diagram showing a change in the thickness of the holding torque portion with a reduction in power consumption and an increase in surplus power. The data in the circles is the data of the chopper drive pulse, the data in the triangles is the data of the full drive pulse, and the line segments are used to separate the low power consumption and extra power data into the chopper drive pulse and the full drive pulse. L1 and L2 are connected to line segments L10 and L20. In the data where the thickness t0 of the holding torque portion is 50μ, the power consumption is reduced by 1 with the chopper drive pulse shown in FIG.
It has increased by 7% and reserve by 9% (circled data).

On the other hand, when the thickness t0 of the holding torque portion is 100 μm
In the data shown in FIG. 6, the full drive pulse shown in FIG. 6 does not result in low power consumption, but rather increases power consumption by 5% and has a spare power of 1%.
Up 9% (triangle mark data). Here, in each drive pulse, the thickness t0 of the holding torque portion is from 50 μ to 1
The increase in power to 00 μ increases power dissipation and increases spare power due to an increase in holding torque.
The reason why there is not much difference in the residual power data between the chopper and the full driving pulse is that the same driving pulse (not shown) having a wider width is applied after the chopper or the full driving pulse and the measurement is performed. It is.

Here, it is considered that the reduction in power consumption linearly changes with respect to the thickness t0 within each of the line segments L1 and L2. Then, the line segment L of the low power consumption data of the chopper drive pulse is obtained.
The line segment L2 of 1 and the low power consumption data of the full drive pulse is
Crossing at a thickness t01 slightly smaller than 100μ,
At a thickness t0 smaller than the thickness t01, it is considered that the chopper drive pulse has lower power consumption. As described above, in the stepping motor of the present invention in which the thickness t0 of the holding torque portion is smaller than 100 μ (smaller than t01 in the present embodiment), the driving power by the chopper driving pulse is lower than the full driving pulse in the one-second hand operation. It can be seen that electrification is achieved. It is clear that the chopper drive is more suitable for low power consumption even in the drive other than the one-second hand movement.

[0046]

As can be understood from the above description, according to the present invention as set forth in claims 1 to 5, the power consumption of a step motor used for driving an electronic device such as a timepiece can be reduced, and the life of the battery can be reduced. It can be seen that there is an effect that can be extended.

[Brief description of the drawings]

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

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

FIG. 3 is a plan view and a sectional view of a conventional step motor.

FIG. 4 is a plan view and a sectional view of another conventional step motor.

FIG. 5 is a chopper drive pulse diagram during one-second hand movement.

FIG. 6 is a full drive pulse diagram during one-second hand movement.

FIG. 7 is a diagram showing a change in thickness of a holding torque portion in which power consumption is reduced and a surplus power is increased.

FIG. 8 is a sectional view of a step motor according to a third embodiment of the present invention.

[Explanation of symbols]

 1, 10, 11, 110 Step motor 2 Rotor 3, 12, 30, 120 Stator 4 Coil 5, 14, 50, 140 Holding torque portion 3a, 12a, 30a, 120a Yoke portion 5a, 5b, 50a, 50b Eccentricity 14a, 14b, 140a, 140b Notch 9, 91, 92 Stator narrow part 90 Stator joint part t0, t2 Holding torque part thickness D0, D2, D3, D4 Holding torque part outermost diameter

Claims (6)

[Claims] 1. A rotor comprising a permanent magnet having two poles, a plate-shaped stator having a structure for generating a holding torque near a rotor hole in which the rotor enters, and being magnetically coupled to the rotor, and fixed to the stator. A coil, and the stator includes a holding torque portion including a structure for generating the holding torque and a yoke portion excluding the holding torque portion.
A step motor wherein the thickness of the holding torque portion is smaller than that of the yoke portion, wherein the thickness of the holding torque portion is less than 100 microns. 2. An inner circumference of the holding torque portion is an outer circumference of the rotor hole, and an outer circumference of the holding torque portion is a circle having the same center as a center of the rotor hole and larger than a maximum outer circumference of the rotor hole. The step motor according to claim 1, wherein: 3. The step motor according to claim 1, wherein the structure for generating the holding torque is an eccentric or notch structure. 4. The step motor according to claim 1, wherein the stator has two poles. 5. The stator according to claim 1, wherein the stator is a single-layer plate or a single-layer plate.
The step motor according to any one of claims 1 to 4, wherein the step motor is a stator formed of at least two laminated plates. 6. The step motor according to claim 1, wherein the step motor is driven by a chopper.