JP3594892B2 - Stepping motor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stepping motor, and more particularly to an improvement in a stepping motor in which the number of phases of a stator winding can be applied to two.
[0002]
[Prior art]
Conventional hybrid type stepping motors and permanent magnet type stepping motors are predominantly two-phase type stepping motors. The structure of such a stepping motor is, for example, as described in Japanese Patent Application Laid-Open No. 2-1642, as a hybrid type stepping motor. This is shown in FIG. 4 or FIG.
[0003]
FIG. 4 is a vertical sectional side view showing the configuration of the conventional hybrid type stepping motor 10, and FIG. 5 is a sectional view taken along line AA 'of FIG.
4 and 5, 1 is a stator housing, 2 is a stator core, 3-1 to 3-8 are stator windings, 4 and 4 'are front and rear brackets, and the stator core 2 is The poles 2-1 to 2-8 are configured, and 2-10 are pole teeth formed on the inner circumference of each of the main poles 2-1 to 2-8.
Stator windings 3-1 to 3-8 are wound around the main poles 2-1 to 2-8, respectively. The stator S is constituted by the stator housing 1, the stator core 2, and the stator windings 3-1 to 3-8.
[0004]
4, 5 and 5 'are bearings, 6 is a rotor shaft, 7 and 8 are rotor magnetic poles, and 7-10 and 8-10 in FIG. 5 are formed on the outer circumference of the rotor magnetic poles 7 and 8. The pole teeth 7-10 and the pole teeth 8-10 are displaced from each other by a half pitch of each pole tooth pitch. Further, a permanent magnet 9 is sandwiched between the two rotor magnetic poles 7 and 8, and the rotor R is constituted by the rotor shaft 6, the rotor magnetic poles 7 and 8 and the permanent magnet 9.
As described above, the rotor R having the configuration in which the permanent magnets 9 are sandwiched between the two rotor magnetic poles 7, 8 in which the arrangement of the pole teeth 7-10, 8-10 is shifted by １ ／ pitch is called a hybrid type rotor. The conventional stator S and rotor R constitute a conventional two-phase hybrid stepping motor 10.
[0005]
[Problems to be solved by the invention]
Incidentally, a step angle θs is important as an index indicating the performance of the stepping motor. Normally, the step angle θs (unit is degrees; hereinafter, omitted) is determined by the number of phases of the stator winding or the number of phases P of the rotor magnetic poles and the number of pole teeth Zt provided for one magnetic pole of the rotor magnetic poles,
θs = 180 / (P · Zt) (1)
It is expressed as
[0006]
The step angle θs shown in the equation (1) is an angle obtained in the case of one-phase excitation when one-phase winding is sequentially energized, and is unique to the stepping motor. Equation (1) shows that increasing the phase number P and the number of pole teeth Zt of the rotor magnetic poles in the denominator reduces θs.
[0007]
When the number of phases of the conventional rotor magnetic pole is two and the number of pole teeth is Zt, the step angle of the permanent magnet type stepping motor is θs = 180 / (2 · Zt) according to equation (1). In order to reduce the step angle to a very small angle, the number of pole teeth Zt must be increased, that is, the rotor tooth width must be reduced.
[0008]
The two-phase hybrid type stepping motor has large vibration and noise, and it is possible to reduce these by increasing the number of stator main poles and improving the magnetic balance. The number of poles was only 8 or a multiple thereof.
[0009]
For example, in the conventional configuration having the hybrid rotor shown in FIGS. 4 and 5, when the number of stator main poles is 6, the number of rotor teeth is 6n + 5 or 6n + 1 (n is an integer of 1 or more). Therefore, the number of teeth is odd. Therefore, when one-phase excitation is performed, one main phase is composed of two main poles that are 180 ° apart from each other. Therefore, for example, two rotor magnetic poles sandwiching the permanent magnet of the hybrid type rotor are magnetized to have different polarities, and Since the rotor magnetic poles are attracted upward and the other rotor magnetic poles are attracted downward, when driven by one-phase excitation, the rotor shaft rotates while receiving a couple in the axial direction. It was a factor of noise.
[0010]
Further, in the conventional permanent magnet type stepping motor, as shown in JP-A-6-14514, a winding is wound so that the polarity of the main pole for one phase is the same, and Are excited in the same polarity, there is no different polarity in one phase in the one-phase excitation drive, so that a magnetic path is not sufficiently formed, and the next two phases are excited to the opposite polarity to be different polarity. To form a magnetic path between the two phases, and there is a drawback that only two-phase excitation or more than two-phase excitation is practical.
[0011]
On the other hand, it is conceivable to increase the number of phases P of the stator windings, such as four phases or five phases. there were.
[0012]
The present invention solves the problems (problems) of the conventional stepping motors of this type (permanent magnet type and hybrid type stepping motors) as described above. An object of the present invention is to provide a two-phase hybrid type stepping motor that realizes noise.
[0013]
[Means for Solving the Problems]
The stepping motor according to the present invention has the following configuration in order to solve the problems of the conventional stepping motor.
The two-phase hybrid type stepping motor has a configuration including a stator and a rotor having the following features.
(1) The number of phases of the stator winding is two, and the number of stator main poles is twelve, one of which is composed of six every other phase. A stator that is wound so that it has three N poles and three S poles when excited.
(2) A rotor magnetic pole made of two magnetic materials having a plurality of Zt tooth teeth with gear teeth, and a permanent magnet sandwiched between the two rotor magnetic poles and magnetized in the same direction as the rotation axis. A rotor of a hybrid type having a magnet.
In this case, it is desirable to set the number of pole teeth Zt to Zt = 12n ± 3.
Here, n is an integer of 1 or more. When n is 2 or more, each of the twelve stator main poles has a plurality of pole teeth.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to explain one embodiment of the hybrid type stepping motor of the present invention, for the sake of convenience of explanation, a first and second preliminary stepping motors will be described using a permanent magnet type stepping motor having a similar stator. Give an explanation.
First Preliminary Embodiment First, as a first preliminary embodiment, a configuration of a six-pole three-phase permanent magnet type stepping motor 20 will be described with reference to FIG.
FIG. 1 shows the first preliminary embodiment, in which the number of phases of the rotor magnetic poles is three, the number of main poles of the stator is 6 m, and the number of poles of the rotor Z = m · (12n ± 2), the figure shows a simplified example in which m = 1, six main poles, n = 4, and Z = 50 in this case.
[0015]
The rotor R2 of the permanent magnet type stepping motor 20 of the present embodiment is different from the rotor R of the conventional two-phase stepping motor 10 shown in FIG. 4 and includes a cylindrical permanent magnet 23 as shown in FIG. It is desirable to have a back yoke 24, which is rotatably supported about a rotor shaft 26. The outer peripheral surface of the cylindrical permanent magnet 23 is magnetized such that a total of 50 pole teeth 27-10 and 28-10 are formed so that N poles and S poles are alternately arranged in the rotation direction.
[0016]
Outside the cylindrical permanent magnet 23, the inner peripheral surfaces of the six stator main poles 22-1 to 22-6 face each other via a small gap, and the tips of the stator main poles 22-1 to 22-6 are opposed. On the inner peripheral surface, three pole teeth 22-10 are formed for each main pole. The six stator main poles 22-1 to 22-6 are arranged at an equal pitch of 60 ° to each other, and are wound with stator windings 21-1 to 21-6, respectively. The above-mentioned winding is a three-phase winding, and the stator windings 21-1 and 21-4 form one phase, and when the one phase is DC-excited, the stator main poles 22-1 and 22-4 are formed. Are wound so as to have mutually different polarities.
[0017]
Although the conventional hybrid stepping motor 10 shown in FIGS. 4 and 5 cannot perform one-phase excitation driving, the permanent magnet type stepping motor 20 of the present embodiment always has the same number of different poles in one phase. And one-phase excitation drive becomes possible.
That is, in FIG. 1, the magnetic flux emitted from the N pole of the cylindrical permanent magnet 23 enters the opposite polarity main pole 22-1, interlinks with the winding 21-1, and passes through the annular yoke 25 of the stator S2. And enters the main pole 22-4, interlinks with the winding 21-4, enters the S pole of the cylindrical permanent magnet 23 facing the pole teeth of the main pole 22-4, passes through the back yoke 24, and returns to the original position. Return to the N pole and close the magnetic path. In this manner, one-phase excitation drive is possible.
[0018]
Next, when the currents in the stator windings 21-1 and 21-4 are cut off and at the same time current is applied to the windings 21-2 and 21-5 for two phases, the magnetic poles of the rotor permanent magnets Since the poles 22-2 and 22-5 are configured to be shifted at a predetermined angle with respect to the pole teeth 22-10, the rotor R2 rotates by the shift. This deviation angle is the step angle θs.
[0019]
Similarly, when the windings 21-3 and 21-6 wound around the main poles 22-3 and 22-6 for three phases are excited, the windings are turned by one step angle θs in the same manner as described above. Thus, the simplest one-phase excitation driving is possible.
[0020]
Further, another excellent point different from the above-mentioned advantage of the first preliminary embodiment is apparent in comparison with the conventional example shown in FIGS. That is, in the state where the stator main poles 22-1 and 22-4 of FIG. 1 are excited, the pole teeth 22-10 of one main pole 22-1 turn the cylindrical permanent magnet 23 constituting the rotor R2. The radial force for attracting and the radial force for attracting the same cylindrical permanent magnet 23 whose pole teeth 22-10 of the other main pole 22-4 attract the same cylindrical permanent magnet 23 have opposite directions and are equal in magnitude, and therefore cancel each other. Therefore, no radial force acts on the bearing member that always supports the rotor shaft 26, and therefore vibration and noise during rotation are reduced.
[0021]
As described above, even in the six-pole structure, in the present embodiment, it is possible to drive with low vibration and low noise, which cannot be obtained by the conventional hybrid type stepping motor.
[0022]
Next, the induction of the number of poles Z of the rotor in the permanent magnet type stepping motor according to the first preliminary embodiment, Z = m · (12n ± 2), will be described.
The step angle θs of the stepping motor is given by the above equation (1). In the stepping motor of this embodiment, since the number of phases of the stator winding is three, if P = 3 in the equation (1), this embodiment In the case of the ring magnet type rotor in which the N pole and the S pole are alternately arranged in the stepping motor 20, the step angle θs is given by Zt = Z / 2.
θs = 180 / {3 · Z · (1/2)} = 120 / Z (2)
It becomes.
[0023]
On the other hand, the stator main pole is equally divided into 360/6 m, and the rotor magnetic pole closest to the pole teeth of the stator main pole is equally divided into {360 / (Z / 2)} · n. At the step angle θs, this is
θs = ± [360 / 6m−360n / {Z · (1/2)}] (3)
It is represented by
[0024]
By solving the equations (2) and (3), Z = m · (12n ± 2) is obtained. At this time, when n is 2 or more, the torque of the stepping motor can be increased by providing a plurality of pole teeth at the tips of the 6 m main poles.
Further, when the number of phases of the stator winding is three, the step angle θs can be reduced even if the number of pole teeth Zt provided on the rotor magnetic poles is the same as shown in the equation (1). Since the resolution of the stepping motor can be increased, it can be seen that the stepping motor of the present embodiment can improve the above-mentioned disadvantages of the conventional technology.
[0025]
Second preliminary embodiment:
Next, a configuration of a 12-pole two-phase permanent magnet type stepping motor 30 according to a second preliminary embodiment will be described with reference to FIG.
The rotor R3 has the same structure as the rotor R2 shown in FIG. 1, and N poles and S poles are alternately multipole magnetized on the outer periphery of the cylindrical permanent magnet 33.
The stator S3 has twelve main poles 32-1 to 32-12 arranged at equal pitches, and is provided with two-phase stator windings 31-1 to 31-12. Of the twelve main poles 32-1 to 32-12, one for each of the 12 phases is six, and when this one phase is DC-excited, the N polarity becomes three in the six main poles alternately. The windings 31-1 to 31-12 are wound so as to have three S polarities.
[0026]
Six main poles for one phase are configured every other twelve stator main poles 32-1 to 32-12, and the six main poles are configured to have alternately different polarities. Is desirable. FIG. 2 shows the polarity of one example of the one-phase winding. With this configuration, as in the example of FIG. 1, the radial force acting on the rotor R3 is always canceled.
[0027]
Further, even in the case of a two-phase machine, the greater the number of stator main poles, the smaller the vibration and noise during driving. Since the stator S3 relating to the stepping motor has 12 main poles, vibration and noise can be reduced.
Also in this case, Z = 24n ± 6 of the number of poles of the rotor Z is obtained by the same induction as the above-described equations (1) to (3). Here, n is an integer of 1 or more, and when n ≧ 2, it is desirable to provide a plurality of pole teeth 32-20 at the tips of the twelve main poles 31-1 to 31-12.
[0028]
Embodiment of the present invention:
Next, based on the above description of the first and second preliminary embodiments, the configuration of a 12-pole two-phase hybrid type stepping motor 40 according to an embodiment of the present invention will be described with reference to FIG. explain.
The stator S4 has the same configuration as the stator S3 of the second preliminary embodiment, except that the rotor R4 is a hybrid type. The hybrid type is disadvantageous in terms of vibration and noise as compared with the configuration shown in FIG. 2, but the number of main poles is larger than that of the prior art in which the number of main poles is 8 in FIG. The working electromagnetic force is also balanced.
[0029]
The force acting in the radial direction is such that the three main poles 42-1, 42-5, and 42-9 arranged at a pitch of 120 ° have the same polarity and attract different polarities.
cos (0 ゜) −2 · cos (30 ゜) = 0
Will be offset.
[0030]
The advantage of the hybrid type is that, in general, the step angle θs can be made smaller than that obtained by magnetizing the outer peripheral surface of the cylindrical permanent magnet 23 shown in FIG. This is because it is difficult to form a multipole with a desired magnetizing force on the outer peripheral surface of the cylindrical permanent magnet 23. Also in this case, the number of gear-shaped salient poles of the rotor (the number of pole teeth of the rotor) Zt is given as Zt = 12n ± 3 in the same manner as described above.
Here, n is an integer of 1 or more, and when n ≧ 2, it is desirable to provide a plurality of pole teeth 42-20 on each of the twelve main poles 42-1 to 42-12.
[0031]
In the above-described first and second preliminary embodiments and the embodiment of the present invention, the most desirable embodiment in which the stator main poles are arranged symmetrically so as to be equally spaced in the circumferential direction is described. In this case, in the first preliminary embodiment, when the number of stator magnetic poles Z is Z = m · (12n ± 2), and in the second preliminary embodiment, Z = 24n ± 6), and in the embodiment of the present invention, the case where the number of pole teeth Zt of the rotor is Zt = 12n ± 3 has been described.
If the stator main pole is formed in a symmetrical shape in this way, the step angle accuracy is excellent and the characteristics are advantageous, but even if the stator is formed in an asymmetrical shape, the characteristics are slightly lowered, but the effect of the present invention is Since it has an effect, it is practical depending on the use.
[0032]
【The invention's effect】
In the hybrid stepping motor according to the first and second aspects of the present invention, the stator main pole has a 12-pole configuration while being a two-phase machine. Low noise can be realized.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional front view showing a configuration of a three-phase permanent magnet type stepping motor according to a first preliminary embodiment.
FIG. 2 is a longitudinal sectional front view showing a configuration of a permanent magnet type stepping motor having a two-phase 12-pole structure according to a second preliminary embodiment.
FIG. 3 is a longitudinal sectional front view showing an embodiment of a hybrid type stepping motor having a two-phase 12-pole structure according to an embodiment of the present invention.
FIG. 4 is a vertical sectional side view showing a configuration of a conventional two-phase hybrid type stepping motor.
FIG. 5 is a sectional view taken along line AA ′ of FIG. 4;
[Explanation of symbols]
40: Hybrid type stepping motors 41-1 to 41-12: Stator windings 42-1 to 42-12: Stator main pole 42-20: Stator main pole pole teeth

Claims (2)

A hybrid stepping motor comprising a stator and a rotor having the following configuration.
(1) The number of phases of the stator winding is two, and the number of stator main poles is twelve, one of which is composed of six every other phase. A stator that is wound so that three N poles and three S poles are alternately formed when excited.
(2) A rotor magnetic pole composed of two magnetic bodies having a plurality of Zt gear teeth with tooth teeth, and a permanent magnet sandwiched between the two rotor magnetic poles and magnetized in the same direction as the rotation axis. A rotor of a hybrid type having a magnet. 2. The hybrid stepping motor according to claim 1, wherein the number of pole teeth Zt of the rotor is Zt = 12n ± 3.
Here, n is an integer of 1 or more. When n is 2 or more, each of the twelve stator main poles has a plurality of pole teeth.

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