JP2006014583A - Magnetized pattern for stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetized pattern for a stepping motor minimizing the reduction of driving torque, and also, eliminating troubles, such as vibration and noise by reducing the detent torque. <P>SOLUTION: The N-pole and the S-pole are alternately polarized in a rotor magnet 3 of a stepping motor. Wide magnetized parts 4, 5 are formed at two oppositely arranged places, centered about a rotary shaft of the rotor magnet 3. Magnetized parts 6, 6, ... that are narrower than the magnetized parts 4, 5 are formed at a plurality of the remaining places. A plurality of the magnetized parts 6, 6, ... mutually have equal magnetized width. If the number of all poles of the rotor magnet 3 is set as y, the angle obtained by dividing 360° with the number of all poles y as x°, an arbitrary angle as α°, and the total number of the wide magnetized parts is set as z, the center angle of the wide magnetized parts 4, 5 with respect to the arcuate magnetized width is x°+(y/z-1)α° and that of the narrow magnetized parts to the arcuate magnetized width is (x°-α°); and further, the relations of x°+(y/z-1)α°>(x°-α°) and x°/2>α° are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetizing pattern of a stepping motor, and more particularly to a stepping motor for reducing vibration and noise generated when a motor is driven by breaking the magnetization balance of each magnetic pole in the rotation direction of a rotor magnet. The present invention relates to a magnetization pattern.

  Conventionally, this type of stepping motor is suitably used as an intermittent drive source for various devices such as a printer, a facsimile machine, and a disk drive. Thus, in the stepping motor, a rotor is rotatably disposed inside a stator having pole teeth, and the rotor has a cylindrical rotor magnet made of a permanent magnet on an outer peripheral portion. In addition, the stepping motor sequentially drives energization of the stator magnetic pole to the exciting coil, so that the rotor is rotationally driven with respect to the stator.

  As shown in FIG. 3, the rotor magnet 1 has N poles and S poles alternately magnetized at equal intervals in the circumferential direction, and the plurality of magnetized portions 2, 2,. The arcuate magnetization widths C are equal to each other. In the figure, when the total number of poles of the rotor magnet 1 is y and the central angle of the arc-shaped uniform width C of the magnetized portions 2, 2... Is x.degree., The relation of x.degree. = 360.degree. / Y. Meet.

  As shown in FIG. 4, the stepping motor holds the rotor magnet 1 back to the stable point when the rotor magnet 1 is deviated from the stable point between the rotor magnetic pole and the pole teeth when no power is applied. Torque, that is, detent torque is generated, but in recent years, stepping motors with low detent torque have been demanded as the above-mentioned various devices have been improved in performance. When the detent torque of the motor is large, the torque ripple and rotational speed ripple of the motor increase to cause vibration and noise problems, and when used as a positioning motor, the positioning accuracy decreases.

Therefore, in order to reduce the detent torque, the center of each magnetic pole of the magnetization pattern in the half of the stepping motor in the rotation direction is set to 1 from the center of each magnetic pole of the magnetization pattern of the other half. There is also known a magnetized pattern of a motor formed by / 4 displacement and a non-magnetized discontinuous portion generated near the boundary between the two halves (Patent Document 1).
Japanese Patent Laid-Open No. 2-114848

  The magnetization pattern of the conventional stepping motor can cancel the detent torque by inverting the phase of the detent torque generated in the other half with respect to the phase of the detent torque generated in the other half. . However, since the discontinuous portion generated near the boundary between the two halves is formed without magnetization, the non-magnetization greatly reduces the driving torque at the time of driving, making it unsuitable for practical use. Have.

  Therefore, there is a technical problem to be solved in order to reduce the drive torque and reduce the detent torque so as to eliminate the problems of vibration and noise, and the present invention solves the problem. The purpose is to do.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is directed to a rotor magnet of a stepping motor, wherein the magnetized portion of each magnetic pole in the rotation direction of the rotor magnet is provided. Among them, when the magnetization width of the magnetized portions facing each other around the rotation axis of the rotor magnet is A, and the magnetized width of the magnetized portions magnetized at a plurality of other portions at a uniform width is B, The magnetization width of the magnetized portion provides a magnetization pattern of the stepping motor having a relationship of A> B.

  According to this configuration, the magnetizing width A of the wide magnetized portions of the pair facing the rotor magnet is formed wider than the magnetized portions of the uniform width B at the remaining portion. A local change in magnetic flux distribution occurs in the vicinity region centered on the magnetic part, and the detent torque is reduced as a whole of the magnetized part of the rotor magnet.

  The invention according to claim 2 provides the magnetization pattern of the stepping motor according to claim 1, wherein the total number of the magnetized portions having the magnetization width A is one set.

  According to this configuration, only by providing the wide magnetized portions at two locations, the magnetic flux distribution is formed symmetrically with respect to one axis as the whole rotor magnet, and the minimum value of the detent torque is every half cycle (angle 180 °). Is obtained.

  According to a third aspect of the present invention, the total number of the magnetized portions having the magnetized width A is two sets of four, and the four magnetized portions are equal to 90 degrees in the rotation direction of the rotor magnet. The magnetizing pattern of the stepping motor according to claim 1 arranged at a pitch.

  According to this configuration, since the four wide magnetized portions are arranged at an equal angle of 90 degrees, the entire magnetic flux distribution is formed symmetrically with respect to two orthogonal axes, and the minimum value of the detent torque is 90 degrees. Obtained every °.

  In the invention according to claim 4, the total number of poles of all the magnetized portions formed in the rotor magnet is y, an angle obtained by dividing 360 ° by the total number of poles y is x °, an arbitrary angle is α °, When the total number of magnetized portions having the magnetized width A is z, a central angle A ° with respect to the arc-shaped magnetized width A of the opposed magnetized portions is x ° + (y / z−1) α °, The central angle B ° with respect to the arcuate magnetization width B of the other magnetized portion is (x ° −α °), and x ° + (y / z−1) α °> (x ° −α °). And a magnetization pattern of the stepping motor according to claim 1, 2 or 3 satisfying a relationship of x ° / 2> α °.

  According to this configuration, as long as the above relational expression is satisfied, a certain change occurs in the magnetic flux distribution in the vicinity of the wide magnetized portion, and a desired angle-torque characteristic that reduces detent torque is obtained. can get.

  According to the first aspect of the present invention, since the magnetization width A of the magnetized portions facing each other is formed wider than the magnetized width B of the remaining magnetized portions, the distribution of magnetic flux changes. Since the detent torque is reduced, the drive torque of the stepping motor is hardly reduced, and vibration and noise of the motor can be eliminated. In particular, a smooth motor drive with less vibration can be obtained during low-speed driving.

  According to the invention described in claim 2, since the minimum value of the detent torque is generated every half cycle only by providing the wide magnetized portion at two locations of the rotor magnet, in addition to the effect of the invention described in claim 1 The wide magnetized portion can be easily formed, and torque fluctuation during driving of the stepping motor becomes smooth.

  In the invention described in claim 3, since the minimum value of the detent torque is generated every quarter period, in addition to the effect of the invention described in claim 1, the torque fluctuation of the stepping motor becomes smoother. When used as a motor, the positioning accuracy with respect to the load by the motor is improved accordingly.

  According to a fourth aspect of the present invention, in order to reduce the detent torque of the stepping motor, as long as the above relational expression is satisfied, the total number of poles y of the rotor magnet, the wide magnetized portion, and the narrow magnetized portion Therefore, in addition to the effects of the first, second, and third aspects of the invention, the rotor magnet and the stepping motor can be significantly improved in design freedom.

  In the rotor magnet of the stepping motor according to the present invention, the magnetization width of the magnetized portion of the magnetized portion of each magnetic pole in the rotation direction of the rotor magnet facing the rotation axis of the rotor magnet as A And when the magnetization width of the magnetized portions magnetized at a plurality of other locations at a uniform width is B, the magnetized width of each of the magnetized portions has a relationship of A> B, so that the drive The objective of reducing the detent torque and suppressing the generation of vibrations and noises without causing a significant decrease in torque was achieved.

An embodiment of the present invention will be described below with reference to FIGS. In the figure, reference numeral 3 denotes a cylindrical rotor magnet. The rotor magnet 3 is rotatably disposed inside a stator unit (not shown) having a stator magnetic pole, and the core portion of the rotor magnet 3 is , And is integrally fixed to a rotation shaft provided at the center of rotation. Furthermore, the rotor unit is driven to rotate by sequentially exciting the exciting coil of the stator magnetic pole, so that the magnetic pole of the rotor magnet 3 is attracted or repelled by the stator magnetic pole.

  As shown in FIG. 1, the rotor magnet 3 is formed with N-pole magnetized portions and S-pole magnetized portions alternately in multiple poles along the circumferential direction. The magnetized portion of the rotor magnet 3 has a wide magnetized portion 4 and 5 magnetized with a predetermined arcuate magnetizing width A and an arcuate magnetized width B that is uniform at the remaining plural locations. It is composed of a plurality of magnetized portions 6, 6.

  The wide magnetized portions 4 and 5 are a set of two locations facing each other across the rotation center O of the rotor magnet 1, and in the illustrated example, the wide magnetized portions 4 and 5 are provided at two locations in one set. Is provided. In addition, the magnetization width A of the wide magnetized portions 4 and 5 is wider than the magnetized width B of the narrow magnetized portion 6 by a predetermined width.

  Thus, when the wide magnetized portions 4, 5 are formed wider than the narrow magnetized portions 6, 6,..., Unlike the conventional magnetized pattern of FIG. In the vicinity of the magnetic parts 4 and 5, a certain change occurs in the distribution state of the magnetic flux, and so-called detent torque, which is unusual when the rotating shaft is rotated from the outside when there is no excitation, is reduced. That is, the wide magnetized portions 4 and 5 are formed wide so that the balance of the magnetized width of the entire rotor magnet 3 is broken, and particularly in the vicinity of the wide magnetized portions 4 and 5. As a result, the attracting force against the stator side opposite pole that is close to this slightly increases, while the repulsive force against the stator side same pole is also increased, and the detent torque is locally offset. It is considered that the detent torque is reduced by the occurrence of the magnetic flux density distribution that is reduced.

The illustrated example is applied to a PM (Permanent Magnet) type stepping motor in which 48 pole teeth are formed on a stator. More specifically, the wide magnetized portions 4 and 5 and the narrow magnetized portion 6 of the rotor magnet 3 have 24 total poles y and an angle 360 ° divided by the total poles y. This is applied to a motor in which x ° is 15 ° and an arbitrary angle α ° is 0.5 °. Regarding the performance of the motor, the relationship between the rotation angle θ and the detent torque T was examined, and the θ-T characteristic shown in FIG. 2 was obtained.

  As is clear from the figure, the fluctuation range of the detent torque T is reduced to one-half or less as compared with the conventional full uniform width type magnetization pattern (see FIG. 3). According to the magnetized pattern of the present invention, the magnetic flux density distribution changes so as to reduce the detent torque T by forming the magnetized portions 4 and 5 having the wide width A at the two locations of the rotor magnet 3. It means that it was obtained.

  In this case, the formation of the magnetized portions 4 and 5 having the wide width A causes a slight decrease in the driving torque of the stepping motor, but the torque decrease is extremely small as compared with the conventional non-magnetic pole formation type magnetization pattern. It was. Thus, the magnetized pattern of the present invention can reduce the detent torque T to less than half despite the slight decrease in the drive unit torque, and can greatly suppress the vibration and noise of the stepping motor. It was.

  According to the present embodiment, only by forming the magnetized portions 4 and 5 having the wide width A in only two portions of the rotor magnet 3, a magnetized pattern that facilitates torque fluctuation during motor driving can be easily manufactured. .

  Here, the conditions of the magnetized pattern according to the present invention will be described in more detail. The angle obtained by dividing the total number of poles of the rotor magnet 3 by y and 360 ° by the total number of poles y is x ° and half of the angle x °. Is a central angle A ° = x ° with respect to the arcuate magnetization width A of the opposed magnetized portions 4 and 5, where α is an arbitrary angle and z is the total number of magnetized portions having the magnetized width A. + (Y / z-1) α ° is larger than the central angle B ° = (x ° −α °) with respect to the arcuate magnetization width B of the narrow magnetized portions 6, 6. Set conditions. That is, the wide antipodal magnetization pattern of the present invention satisfies the following conditional expressions (1), (2) and (3) simultaneously.

x ° + (y / z−1) α °> (x ° −α °) (1)
x ° / 2> α ° (2)
x ° = 360 ° / y (3)
As long as the wide antipodal magnetized pattern satisfies the above three conditional expressions, the wide magnetized portions 4 and 5 cause a change in the magnetic flux density distribution around it, and the detent torque can be reduced. For example, the number of sets of the wide magnetized portions 4 and 5 facing each other across the rotation center O of the rotor magnet 3 is one set of two places facing each other in the vertical direction in FIG. It is also possible to form a total of four sets of two sets by adding one set of two locations. In this case, the two sets of four wide magnetized portions 4 and 5 are arranged at an equal pitch of 90 degrees in the circumferential direction of the rotor magnet 3.

  When two sets of the wide magnetized portions 4 and 5 are arranged on both sides in the right-angle biaxial direction, the change in the magnetic flux density distribution of the rotor magnet 3 occurs on the left-right symmetric axis and the up-down symmetric axis. As compared with the case where the magnetized portions 4 and 5 having the wide width A are formed at two locations in one set, the detent torque reduction effect is further increased, and the torque fluctuation during the operation of the stepping motor becomes smoother.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

The perspective view of the rotor magnet which shows one Embodiment of this invention and demonstrates the magnetization pattern of a stepping motor. Explanatory drawing of the angle-torque characteristic of the stepping motor of FIG. The perspective view of the rotor magnet which shows a prior art example and demonstrates the magnetization pattern of a stepping motor. Explanatory drawing of the angle-torque characteristic of the stepping motor of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor magnet 2 Magnetized part 3 Rotor magnet 4,5 Wide magnetized part 6 Narrow magnetized part A, B Magnetized width

Claims (4)

  In the rotor magnet of the stepping motor, the magnetization width of the magnetized portion facing each other around the rotation axis of the rotor magnet among the magnetized portions of the magnetic poles in the rotation direction of the rotor magnet is A, The stepping motor is characterized in that the magnetization width of each of the magnetized portions has a relationship of A> B, where B is the magnetized width of the magnetized portions magnetized at a uniform width at a plurality of locations. Magnetic pattern.   2. The stepping motor magnetizing pattern according to claim 1, wherein the total number of magnetized portions having the magnetizing width A is two in one set.   The total number of the magnetized portions having the magnetized width A is four in two sets, and the four magnetized portions are arranged at an equal pitch of 90 degrees in the rotation direction of the rotor magnet. 2. A magnetizing pattern for a stepping motor according to claim 1. The total number of poles of all magnetized portions formed on the rotor magnet is y, the angle obtained by dividing 360 ° by the total number of poles y is x °, an arbitrary angle is α °, and the magnetization width is A. When the total number of the parts is z, the central angle A ° with respect to the arcuate magnetization width A of the opposed magnetized parts is x ° + (y / z−1) α °, and the arcuate shapes of the other magnetized parts. The central angle B ° with respect to the magnetization width B is (x ° −α °), and
x ° + (y / z−1) α °> (x ° −α °) and x ° / 2> α °
The magnetization pattern of the stepping motor according to claim 1, wherein the following relationship is satisfied.

Images