JP3778216B2 - Hybrid type stepping motor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an improvement of a hybrid type stepping motor used in an actuator for office automation equipment such as a laser beam printer.
[0002]
[Prior art]
The content and configuration of the prior art will be described with reference to FIGS.
FIG. 5A is a longitudinal front view including a rotary shaft 3 that serves as an output shaft of a conventional hybrid stepping motor. FIG. 5B is a cross-sectional view taken along the line XX ′ of FIG.
In FIGS. 5A and 5B, reference numeral 1 denotes a stator core. In the case of a two-phase winding, an 8-pole system of magnetic poles 1-1 to 1-8 is generally used, and a plurality of tips of each magnetic pole ( There are 5 small teeth in this figure. Reference numeral 5 denotes an exciting coil, which is wound around each 8-pole magnetic pole 1-1 to 1-8 in the form of windings 5-1 to 5-8 as shown in FIG.
Reference numeral 6 denotes a housing, which is fitted to the front and rear brackets 7 and 7 ', and these brackets 7 and 7' rotatably support the rotary shaft 3 via bearings 8 and 8 '. Reference numeral 2 denotes a permanent magnet, and a rotor R is formed by sandwiching the permanent magnet 2 with two rotor magnetic poles 2A and 2B. Magnetic teeth shown in FIG. Is provided. The permanent magnet 2 is magnetized to two poles of N and S as shown in FIG.
[0003]
FIG. 6 shows that the number of the small teeth of the magnetic poles 1-1 to 1-8 shown in FIG. 5 is one, and the magnetic teeth formed on the outer periphery of the rotor magnetic poles 2A and 2B of the rotor R are also shown. It is the figure simplified and shown from 50 pieces to 10 pieces, and the exciting coil is shown with the same numerals as FIG.
6A is a cross-sectional view taken along the line XX ′ of FIG. 5A, and FIG. 6B is a cross-sectional view taken along the line YY ′ of FIG. 5A. As can be seen from FIGS. 6A and 6B, the magnetic pole positions of the rotor magnetic poles 2A and 2B of the rotor R are shifted by 1/2 pitch.
FIG. 7 is a diagram showing the stator small teeth and the magnetic teeth of the rotor magnetic poles according to the prior art arranged so as to face each other with their center lines coinciding with each other, showing the case where there are three small teeth on the stator It is.
When a direct current flows through the exciting coil 5 and the magnetic pole 1-1 is magnetized, a rotor having a polarity opposite to that of the magnetic pole 1-1 faces as shown in FIG.
At this time, the width of the small teeth of the stator and the width of the magnetic teeth of the rotor magnetic pole are 1: 1, or the magnetic teeth of the rotor magnetic pole are designed to be slightly smaller. FIG. 7 is a diagram at 1: 1.
FIG. 8 is a diagram in which the stator and the rotor of FIGS. 6A and 6B are linearly developed in the circumferential direction of the air gap. In FIG. 8, the magnetic pole 1 of FIG. −3 and 1-7 are denoted by Aφ, and magnetic poles 1-1 and 1-5 excited by the opposite polarity are denoted by −Aφ.
Similarly, the polarities of the magnetic poles 1-2 and 1-6 are denoted by Bφ, and the polarities of the magnetic poles 1-8 and 1-4 having the opposite polarity are denoted by −Bφ.
FIG. 8 shows a state of one-phase excitation, when the magnetic pole 1-3 (1-7) is excited to Aφ (at this time, the magnetic pole 1-1 (1-5) is excited to −Aφ of reverse polarity. However, if the stator tooth width and the rotor magnetic teeth are designed to be 1: 1, the magnetic poles 1-3 (1-7) and magnetic poles 1-1 (1-5) have both sides of each tooth. The edge is coincident with the edge of the rotor magnetic teeth, and a fringing effect that tries to hold the rotor in a state where the edge coincides works.
However, for example, as shown in FIG. 9, in addition to the magnetic pole 1-3 (1-7), the magnetic pole 1-2 (1-6) is also excited and excited so that the polarities of Aφ and Bφ are generated. In this state, the edges of the stator small teeth and the rotor magnetic teeth do not match, and the fringing effect cannot be exhibited. In this case, the magnetic poles 1-1 (1-5) and 1-8 (1-4) having opposite polarities to Aφ and Bφ are also excited so as to have the polarities of −Aφ and −Bφ, respectively. is there.
In such a case, for example, if there is variation in the air gap, the rotor is brought close to a phase with a small air gap, and the stationary position accuracy is also deteriorated.
Further, the detent torque, which is a non-excited torque when the excitation coil 5 of the stator is not energized, is a state in which the stator is not magnetized in the diagrams of FIGS. 8 and 9, and the stator of FIGS. FIG. 8 and FIG. 9 each have a balance point at the relative position between the stator and the rotor. In FIG. 8 and FIG. Since π / 4 is shifted, it can be seen that the detent torque of the conventional two-phase hybrid stepping motor is a cycle waveform having a balance point (stable point) every π / 4. The relationship between this conventional detent torque, stator position and rotor position is shown in FIG.
When the rotor (rotor) is in the relative position of FIG. 10 with respect to the stator (stator), the detent torque is zero because of the stable point, but the rotor moves relative to the stator. And every π / 4 as shown in FIG. 10, a detent torque is generated with a torque of π / 2 in a cycle of zero. This is because the pitch of the rotor teeth is 2π, and the holding torque when one phase is excited is 2π, whereas it is 4 times the frequency and added to the waveform of the holding torque, resulting in a distorted waveform from the sine wave. For example, in the case of a two-phase stepping motor, the step angle is π / 2 (1/4 of the tooth pitch) in electrical angle display, the three-phase stepping motor is π / 3, and the P-phase motor is π / P. Thus, when the input pulse of the stepping motor is f per second, the conventional motor has the characteristic that the step angle and the period of the detent torque coincide.
[0004]
[Problems to be solved by the invention]
In the conventional configuration as described above, when the stepping motor is driven at f pulses per second, the amount of change in the detent torque described above becomes the vibration component of the f cycle because the period coincides with the step angle. Shake the motor.
For this reason, there is a problem that the noise of the f-cycle becomes particularly large when the stepping motor is attached to the chassis or when the output shaft is connected to the load.
[0005]
[Means for Solving the Problems]
In the hybrid type stepping motor of the present invention, the plurality of small magnetic pole teeth are respectively provided at the inner tips of the stator magnetic poles having the excitation winding made of a plurality of radially arranged magnetic bodies. Hybrid stepping motor having a rotor having a permanent magnet magnetized in the direction of the rotation axis by two rotor magnetic poles having magnetic pole teeth arranged opposite to the small magnetic pole teeth through a gap In
When the magnetic pole tooth pitch of each of the rotor magnetic poles is 2π, the angle of the small magnetic pole tooth width of the stator is approximately π, and the angle of the magnetic pole tooth width of the rotor magnetic pole is approximately π / 2. characterized in that was.
According to a second aspect of the present invention, in the outer rotor type hybrid stepping motor, the stator is disposed on the inner side, and the rotor is disposed so as to rotate through a gap on the outer periphery of the stator. When the magnetic pole tooth pitch of the rotor magnetic pole of the rotor is 2π, the combination of the small magnetic pole tooth width of the stator is approximately π and the angle of the magnetic pole tooth width of the rotor magnetic pole is approximately π / 2. characterized by comprising.
In this case, as described in claim 3, both end portions of the stator magnetic poles in a range of approximately ± [pi Shi pair core wire in the teeth of both ends of the plurality of small pole teeth formed on the stator magnetic pole It is desirable to form it symmetrically.
[0006]
[Action]
In the present invention, the ratio between the teeth width of the stator small teeth and the pole teeth of the rotor magnetic poles and the valley width is set to a specific one as described above, and even if the stepping motor is driven at f pulses per second, Since the step angle of the angle display and the period of the detent torque are greatly different from each other, the change in the detent torque does not appear as a component of the f cycle unlike the conventional case, unlike the phase change frequency f.
[0007]
【Example】
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS.
In each of these drawings, the components corresponding to those of the conventional one are indicated by the same reference numerals as those in FIGS.
FIG. 1 shows the relationship between one of the stator poles of a stepping motor according to the first embodiment of the present invention and its small teeth and rotor teeth.
First, generally speaking, the characteristics of the present invention will be described. In FIGS. 5A and 5B, which are the structure of a conventional stepping motor, the tooth width and valley of the stator small teeth and the rotor magnetic pole magnetic teeth. It can be said that there is a structural feature in that the ratio of the width is specified and the step is configured such that 1/2 of the step angle of the electrical angle display is the period of the detent torque.
Next, details of this configuration will be described.
In FIG. 1, the small teeth of the magnetic pole 1-1 are shown by three small teeth. As shown in FIG. 1, in the present invention, when the tooth pitches of the rotor magnetic poles 2A and 2B are 2π (radians), the tooth widths of these rotor magnetic poles 2A and 2B are π / 2, respectively. Each of them is (3/2) π, and the tooth width of the small teeth of the stator magnetic pole is π, so that the valley width is also π.
Further, in addition, the present invention is an invention that has been developed from the invention of Japanese Patent Application No. 58-33751 (Japanese Patent Laid-Open No. 59-159661) relating to the patent application of the same inventor.
That is, in the invention of Japanese Patent Application No. 58-33751, the rotor tooth width for exhibiting the fringing effect was limited for the purpose of improving the stationary angle error when the stator was excited in two phases. In the present invention, the tooth width of the stator is further limited to improve the fringing effect more evenly, and its purpose is to reduce the period of the detent torque to 1/2 that of the prior art. Thus, it is intended to reduce vibration and noise when driving the stepping motor.
FIG. 1 shows that the coil 5 is de-energized, and the rotor is aligned with the right end of the small tooth of the magnetic pole 1-1 so that the fringing effect works and becomes one stable point. . When trying to move the rotor to the left, a force to keep the current position works due to the fringing effect, but if the rotor is moved to the left side by a larger external force, the rotor will then move to the left end of the stator small teeth. A force that acts as a stable point at the position where the edge matches and acts to maintain the position works, and is characterized in that it has two stable points with respect to FIG. 7 described above.
[0008]
FIG. 3 is a diagram showing the relationship of FIG. 9 showing the positional relationship between the stator and the rotor at the time of two-phase excitation according to the prior art, corresponding to the case of the present invention. It can be seen that the magnetic teeth of the rotor magnetic poles do not protrude from the small teeth of the stator as shown in FIG.
[0009]
Next, the reason why the small tooth width of the stator is π and the tooth width of the rotor magnetic pole is π / 2 will be described with reference to FIG. 4, and the period of the detent torque at that time will be described.
FIG. 4 is a diagram for explaining the relationship corresponding to FIG. 10 of the prior art in the case of the present invention.
FIG. 4 shows a state in which the center of the magnetic pole N of the stator magnetic pole and the rotor magnetic pole N with the polarity of Aφ is coincident with the center of the magnetic pole N of the negative polarity -Aφ opposite to this. As shown, since the left and right permeances of each magnetic pole are the same, they form one stable point. This is a portion corresponding to the intersection of the dotted line portion of the detent torque and the angle of the horizontal axis.
When the rotor is displaced from the position of the stator and rotor in FIG. 4 by an external force, the left and right permeances as seen from the magnetic teeth of the rotor magnetic poles are different. For example, the magnetic flux generated from N returns to S facing the small tooth portion of the same Bφ magnetic pole through the small tooth width portion of the magnetic pole stator having the polarity of Bφ, but the current position is stable. Is a point.
Therefore, in this case, a force to return to the current position works, but since it is not a stable point due to the fringing effect, it is indicated by a dotted line. When the rotor is moved to the left from the positional relationship of FIG. 4 and the left end of Aφ and the left end of the N pole of the rotor match, this is the next stable point. This is the relationship between the solid line part of the detent torque and the horizontal axis. Corresponds to the intersection.
In this case, for example, the left end of the rotor S pole can be matched with the left end of the magnetic pole of −Aφ, and the right end of the S pole can be matched with the right end of the magnetic pole of Bφ. , Bφ coincides with the right end of the magnetic pole and stabilizes. However, if the small tooth width of the stator magnetic pole is made smaller than π, for example, and the tooth width of the rotor magnetic tooth is π / 2, the N and S poles of the rotor are the left end of each magnetic pole that becomes Aφ and −Aφ. Even if the edges can be matched, the right ends of the magnetic poles Bφ and -Bφ cannot be matched, and the fringing effect does not work equally for each phase.
Therefore, it is necessary that the small tooth width of the stator be π.
In the case of FIG. 4, when the rotor position is moved with respect to the stator, as described above, the stable point is the effect of the stator tooth width π and the rotor tooth width π / 2. In this case, the detent torque cycle is halved and the detent torque cycle is halved, resulting in a detent torque waveform as shown in FIG.
For this reason, since the period of the detent torque in the prior art coincides with the step angle as described above, a large vibration and noise component is generated at the same frequency as the drive frequency. However, according to the present invention, the period of the detent torque is reduced to 1 / Therefore, the vibration and noise of the drive frequency component can be greatly reduced.
[0010]
FIG. 2 shows a second embodiment of the present invention. Next, technical considerations of this embodiment will be described in comparison with the first embodiment shown in FIG.
That is, more torque can be obtained by forming the tooth groove (valley) of the magnetic pole 1-1 in FIG. 1 into a circular arc shape having a part of the straight in the radial direction shown in FIG. Because it is used. In this case, in FIG. 1, the fringing effect is in effect at the right ends of the small teeth of the three magnetic poles 1-1, but the right end of the small teeth at the right end of the magnetic pole 1-1 is straight in the radial direction. On the other hand, the right end of each of the center and the left end of the magnetic pole 1-1 has an arc shape, so that the permeance seen from the rotor is increased and the holding torque can be increased.
Those of the second embodiment, an invention in consideration of this point, as shown in FIG. 2, the stator - poles of (stearyl data) For example, both end portions of the magnetic pole 1-1 ', the stator magnetic poles on which is shaped to keep the magnetically symmetrical Shi pairs the center line of teeth at both ends of the small magnetic pole teeth formed on the left and right in a range of approximately ± [pi in the first embodiment of FIG. 1 As in the case of, when the magnetic pole tooth pitch of the rotor magnetic pole of the rotor is 2π, the small magnetic pole tooth width of the stator is approximately π and the magnetic pole tooth width of the rotor magnetic pole is approximately π / 2. Alternatively, the ratio between the teeth width and valley width of the stator small teeth and the rotor magnetic pole magnetic teeth is set so that the stator small magnetic pole tooth width is approximately π / 2 and the magnetic pole tooth width of the rotor magnetic pole is approximately π. It has been identified.
Therefore, if there is enough space in the slot for inserting the coil, the small teeth of the magnetic pole 1-1 'are all symmetrical with respect to the center line as in this embodiment shown in FIG. Compared with the first embodiment , vibration and noise are reduced with frequency components during driving.
[0011]
Furthermore, although not shown in the drawings, the present invention is applied to an outer rotor type hybrid stepping motor in which the stator is arranged on the inner side and the rotor is arranged to rotate on the outer periphery of the stator through a gap. However, in this case, when the magnetic pole tooth pitch of the rotor magnetic pole of the rotor is 2π, the small magnetic pole tooth width of the stator is approximately π, The combination of the rotor magnetic pole teeth width is approximately π / 2, or the stator small magnetic pole teeth width is approximately π / 2, and the rotor magnetic pole teeth width is approximately π.
[0012]
【The invention's effect】
Since the hybrid type stepping motor according to the present invention is configured as described above, it has the following excellent effects.
(1) As described in claim 1 or 2, when the angle of the magnetic pole tooth pitch of the rotor magnetic pole is 2π, the angle of the small magnetic pole tooth width of the stator is approximately π, so that the position of the rotor Regardless of this, the permeance of the magnetic flux becomes substantially constant, and the detent torque can be reduced. Further, by setting the magnetic pole tooth width of the rotor magnetic pole to approximately π / 2, the period of the remaining detent torque can be reduced to ½ that of the prior art. For example, in the case of two phases, the fourth harmonic can be changed to the eighth harmonic. Therefore , vibration and noise do not appear in the frequency component during driving, and a quiet actuator can be realized while being a stepping motor.
Therefore, it is suitable for OA equipment such as a laser beam printer.
According to the experiment, the dynamic torque decreased by about 7% when driven by 1400pps with a 2-phase motor with a step angle of 1.8 °, but the vibration of the motor was greatly increased from 0.4G to 2G of the conventional technology. It has been confirmed that it can be reduced .
(2) Further, as described in claim 3, both ends of the stator magnetic pole are within a range of approximately ± π with respect to the center lines of the small teeth at both ends of the plurality of small magnetic pole teeth formed on the stator magnetic pole. If it is formed symmetrically, the small tooth shape of each magnetic pole of the stator is completely symmetric in each center line, so that vibration and noise during driving can be greatly reduced, while being a stepping motor, A quieter actuator can be realized.
[Brief description of the drawings]
FIG. 1 is a front view of a main part showing a configuration of a stator and a rotor according to a first embodiment of the present invention.
FIG. 2 is a front view of a main part showing a configuration of a stator and a rotor according to a second embodiment of the present invention.
FIG. 3 is a development view of magnetic poles of a stator and a rotor in a two-phase excitation state according to the present invention.
FIG. 4 is an arrangement view showing a detent torque generation relationship of a stepping motor according to the present invention in a magnetic pole arrangement of a stator and a rotor.
FIGS. 5A and 5B show the structure of a hybrid stepping motor of the prior art, in which FIG. 5A is a longitudinal front view, and FIG. 5B is a cross-sectional view taken along line XX ′ of FIG. .
6A is a simplified view taken along the line XX ′ of FIG. 5A, and FIG. 6B is a simplified view taken along the line YY ′ of FIG. 5A. It is a thing.
FIG. 7 is a front view of a main part showing a configuration of a stator and a rotor of a prior art.
FIG. 8 is a development view of the magnetic poles of the stator and the rotor in the one-phase excitation state of the prior art.
FIG. 9 is a development view of the magnetic poles of the stator and the rotor in the two-phase excitation state of the prior art.
FIG. 10 is an arrangement view showing a detent torque generation relationship of a stepping motor according to the prior art in a magnetic pole arrangement of a stator and a rotor.
[Explanation of symbols]
1-1: Magnetic pole 2A, 2B: Rotor magnetic pole

Claims (3)

A plurality of small magnetic pole teeth are respectively provided at the inner tips of the stator magnetic poles having an exciting winding made of a plurality of radially arranged magnetic bodies, and the magnetic pole teeth are arranged to face the small magnetic pole teeth through a gap. In a hybrid stepping motor having a rotor formed by sandwiching a permanent magnet magnetized in the direction of the rotation axis by two rotor magnetic poles,
When the magnetic pole tooth pitch of each rotor magnetic pole is an angle 2π, the angle of the small magnetic pole tooth width of the stator is approximately π, and the angle of the magnetic pole tooth width of the rotor magnetic pole is approximately π / 2. A hybrid stepping motor characterized by that. In the outer rotor type hybrid stepping motor in which the stator is arranged on the inner side and the rotor is arranged so as to rotate through the gap on the outer periphery of the stator,
When the magnetic pole pitch of the rotor magnetic pole of the rotor is 2π, the angle of the small magnetic pole tooth width of the stator is approximately π, and the angle of the magnetic pole tooth width of the rotor magnetic pole is approximately π / 2. hybrid stepper characterized by comprising a - data. Both end portions of said stator magnetic poles, characterized in that it is formed symmetrically in the range of approximately ± [pi Shi pair core wire in the teeth of both ends of the plurality of small pole teeth formed on said stator poles A hybrid stepping motor according to claim 1 or 2.

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