JP2005151741A - Permanent magnet type stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PM-type steeping motor improvable in output torque by enlarging a motor size while suppressing the generation of heat at high-speed revolution. <P>SOLUTION: This permanent magnet type stepping motor is provided with a rotor that comprises cylindrical permanent magnets of which the S poles and the N poles are alternately magnetized in the circumferential direction at equal pitches, and a stator constituted such that claw-pole shaped unit stators having coils are juxtaposed in the axial direction. A pair of yoke elements of each unit stator is combined such that pole teeth are alternately arranged at equal pitches. The yoke element 131 is formed by forming the pole teeth 131a by punching damping steel sheets constituted of tow superficial steel sheets S1, S2 that are laminated with damping resin R being an insulating material between, and by vertically bending the pole teeth 131a with respect to surrounding rings 131b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a permanent magnet type (PM type) stepping motor suitable for use in office automation equipment such as printers, high-speed facsimiles, and PPC copying machines.

There are a plurality of types of PM stepping motors having different numbers of phases, such as single phase, two phases, three phases or more.
Single-phase PM type stepping motors are mainly used for driving hands for analog watches, but it is necessary to shift the magnetic permeance and phase between the magnetic poles of the stator and rotor so that the rotation direction of the motor is determined. It is not suitable for equipment that requires high speed rotation and high torque.

Therefore, stepping motors of two or more phases are used in office automation equipment such as printers, high-speed facsimiles, and PPC copying machines.
FIG. 6 is a longitudinal side view of a conventional two-phase PM type stepping motor described in Patent Document 1. In FIG. A two-phase PM type stepping motor 10 shown in FIG. 6 includes two parallel plates 11 and 12 constituting a fixed portion, and a rotor 13 that is rotatably supported in a space surrounded by the plates 11 and 12. And a stator 14 disposed between the plates 11 and 12 so as to surround the rotor 13.
The rotor 13 is integrally fixed to the rotary shaft 13a, a rotary shaft 13a attached via a bearing 11a fixed to the center of the plate 11, a bearing 12a fixed to the center of the plate 12, and It is composed of a cylindrical permanent magnet 13b in which S and N poles are alternately magnetized at the same pitch in the circumferential direction.

  On the other hand, the stator 14 includes two annular unit stators 14a and 14b juxtaposed in the axial direction. Each of the unit stators 14a and 14b is a claw pole type stator, and includes a pair of yoke elements 15 and 16 each having comb-like pole teeth formed at a pitch facing the magnetic poles of the rotor 13. ing.

As shown in part in FIG. 7, the yoke element 15 is formed by punching one steel plate to form pole teeth 15a and bending the pole teeth 15a perpendicularly to the surrounding ring portion 15b. The The other yoke element 16 is formed in the same manner.
As shown in FIG. 8, the yoke elements 15 and 16 formed in this way are opposed to each other so that the pole teeth are alternately arranged at an equal pitch, and are wound around the bobbin 17 inside the pair of opposed yoke elements. The coil 18 is disposed, and a pair of yoke elements 15 and 16 are combined so as to sandwich the coil 18.

Japanese Patent Laid-Open No. 11-55928 FIG.

In order to increase the size of the conventional PM stepping motor described above and improve the output torque, it is necessary to increase the flowing magnetic flux by increasing the thickness of the steel plate forming the yoke elements 15 and 16.
However, when the plate thickness of the conventional yoke element is increased, there is a problem that heat generation increases due to eddy current loss flowing in the steel plate at the comb teeth 15a when driven at a high frequency.
For this reason, when rotating at high speed, it is necessary to take measures against heat generation such as attaching a heat radiating plate, resulting in an increase in cost.
In order to prevent excessive heat generation, the upper limit of the size of the PM type stepping motor is about 70 mm in diameter.

  An object of the present invention is to provide a PM type stepping motor that can increase the output torque by enlarging the motor size while suppressing heat generation during high-speed rotation in view of the above-described problems of the prior art. .

  A PM type stepping motor according to a first aspect of the present invention includes a rotating shaft attached to a fixed portion via a pair of bearings arranged at both ends in the axial direction of the fixed portion, and an S pole in the circumferential direction on the outer peripheral portion. , A rotor configured by integrally fixing cylindrical permanent magnets alternately magnetized with N poles, and an outer periphery of the rotor facing each other with a predetermined gap, and a magnetic pole of the rotor on the inner periphery side A pair of yoke elements having opposing comb-shaped pole teeth are combined so that the pole teeth are alternately arranged, and an annular unit stator configured by arranging coils inside the pair of combined yoke elements is used as a shaft. The yoke element is formed by bending a plurality of steel plates stacked via an insulator. The stator is configured by attaching n (n is an integer of 2 or more) in the direction and being attached to the fixing portion. It is characterized by.

  A PM type stepping motor according to a second aspect is characterized in that the stator is constituted by three unit stators on the premise of the configuration of the first aspect.

  Furthermore, in the PM type stepping motor according to claim 3, on the premise of the configuration of claim 1 or 2, the yoke element is formed of a damping steel plate in which damping resin is sandwiched between two skin steel plates. It is characterized by.

According to the configuration of the first aspect of the present invention, the yoke element constituting each unit stator is formed by bending a plurality of steel plates stacked with an insulator interposed therebetween, so that eddy current loss can be achieved even during high frequency driving. Can be reduced and heat generation can be reduced.
For this reason, the size of the entire motor can be increased, and the magnetic flux can be increased by increasing the plate thickness of the yoke element while suppressing heat generation, thereby providing a stepping motor having a high rotational speed and a high output torque.

  Further, when n = 3, the configuration of claim 2 is provided, and a three-phase PM stepping motor that generates less heat during high-speed rotation can be provided as compared with a conventional three-phase PM stepping motor.

  Furthermore, if the yoke element is constituted by a damping steel plate in which damping resin is sandwiched between two skin steel plates as in claim 3, the same basic molding characteristics as a single-layer steel plate can be obtained, and Therefore, it is possible to construct a PM type stepping motor with low cost and low heat generation.

  The best mode for carrying out a PM stepping motor according to the present invention will be described below with reference to the drawings. Here, an example of a three-phase PM type stepping motor will be described with n = 3. 1 is a longitudinal side view of a three-phase PM stepping motor 100 according to the present embodiment, FIG. 2 is an exploded perspective view of the PM stepping motor 100 shown in FIG. 1, and FIG. 3 is a PM stepping motor 100 shown in FIG. FIG. 4 is a perspective view showing a part of a yoke element of a unit stator constituting the PM stepping motor 100 shown in FIG. 1, and FIG. 5 is an explanatory view showing the positional relationship between the rotor magnetic poles of the rotor and the pole teeth of the stator. FIG. 5 is a perspective view of a damping steel plate used for the yoke element of FIG. 4.

First, the overall configuration will be described with reference to FIGS. 1 to 3, and then the configuration of the yoke element, which is a feature of the present invention, will be described with reference to FIGS. 4 and 5.
As shown in FIG. 1, the three-phase PM type stepping motor 100 according to the present embodiment includes two parallel plates 111 and 112 constituting a fixed portion, and a space surrounded by the plates 111 and 112. The rotor 120 is rotatably supported, and the stator 130 is disposed between the plates 111 and 112 so as to surround the rotor 120.
The rotor 120 includes a rotating shaft 121 attached via bearings 113 and 114 fixed to both ends of the fixed portion in the axial direction, that is, the center of the plate 111 and the center of the plate 112, and the rotating shaft 121. It is composed of a cylindrical permanent magnet 122 that is fixed integrally and is alternately magnetized with S and N poles at the same pitch in the circumferential direction.

On the other hand, the stator 130 includes n pieces of unit stators 130a, 130b, and 130c arranged in the axial direction, in this example, three annular unit stators 130a, 130b, and 130c. As shown in FIG. 2, the first unit stator 130a is a claw-pole unit stator, and comb-shaped pole teeth 131a and 132a formed at a pitch facing the magnetic poles of the rotor 120, respectively. A pair of yoke elements 131 and 132 having the above structure is combined, and a coil 134 wound around a bobbin 133 is arranged inside the combined pair of yoke elements.
The second and third unit stators 130b and 130c are configured similarly to the unit stator 130a.

  The plates 111 and 112, the rotor 120, and the stator 130 assembled in the state of FIG. 1 are accommodated in a cup-shaped casing 115 shown in FIG. To do. In FIG. 1, the casing 115 and the lid body 116 are not illustrated, and in FIG. 2, the plates 111 and 112 are not illustrated.

  Next, the positional relationship between the pole teeth formed on the yoke elements of the unit stators 130a, 130b, and 130c and the magnetic poles of the permanent magnet 122 formed on the outer periphery of the rotor 120 is based on the developed view of FIG. explain.

Let τs be the interval between the pole teeth 131a of one yoke element 131 of each unit stator. The interval between the pole teeth 132a of the other yoke element 132 is also τs. The pair of yoke elements 131 and 132 are combined so that the pole teeth 131a and 132a are alternately arranged at an equal pitch.
That is, in each unit stator, the pole teeth 131a of one yoke element 131 are arranged so as to be shifted from the pole teeth 132a of the other yoke element 132 by τs / 2.

Next, let P be the magnetization pitch angle between the different poles of the rotor 120 (the distance between the N pole and the adjacent S pole). Here, τs = 2P. The n unit stators are arranged such that the pole teeth of each one of the yoke elements are shifted by an angle of 2P / n. In this example, three unit stators 130a, 130b, and 130c are arranged such that the pole teeth 131a of each one of the yoke elements 131 are sequentially shifted by an angle 2P / 3.
Incidentally, since the pole teeth 132a of the other yoke element 132 have the same pitch, the pole teeth of the yoke element 132 are also shifted by an angle of 2P / 3 in order. According to such an arrangement, as shown in FIG. 3, when the pole teeth 131a of one yoke element 131 of the first unit stator 130a are opposed to the N pole of the permanent magnet 122, the first unit fixing is performed. The pole teeth 132a of the other yoke element 132 of the child 130a face the S pole, and the pole teeth of the second and third unit stators 130b and 130c are shifted by P / 3 from the nearest magnetic pole, respectively. It is in.

  At the time of driving, the rotor 120 can be rotated at a step angle of τs / 6 by passing forward and reverse currents sequentially through the coils of the unit stators 130a, 130b, and 130c.

  As shown in FIG. 4, one yoke element 131 constituting each of the unit stators 130a, 130b, and 130c has a plurality of, in this example, two skin steel plates laminated with a damping resin R as an insulator interposed therebetween. It is formed by punching a damping steel plate composed of S1 and S2 to form pole teeth 131a and bending the pole teeth 131a perpendicularly to the surrounding ring portion 131b. The other yoke element 132 is formed in the same manner.

As shown in FIG. 4, the damping steel plate generally has a sandwich structure in which a damping resin R as an intermediate layer is sandwiched between two skin steel plates S1 and S2, and is damped by bending deformation due to solid propagation vibration. The shear deformation energy (shear deformation energy) imparted to the resin R is converted into thermal energy by the viscoelastic property of the resin to attenuate the vibration.
In the present invention, the damping steel plate is not used for such vibration damping, but is used to suppress heat generation due to eddy current loss by reducing the thickness of each of the steel plates S1 and S2 by lamination.
Since the damping steel sheet has good deep drawability and bendability, it can be applied to parts that require bending such as a yoke element of a PM type stepping motor.

In general, motor heat is caused by iron loss generated in an iron core and copper loss generated in a coil. Of these, the iron loss Wf is composed of an eddy current loss caused by a magnetic flux passing through the iron core and a hysteresis loss, as represented by the following equation (1).
Wf = B ² {σ _h (f / 100) + σ _e d ² (f / 100) ² } [W / kg] (1)
Where σ _{h is the} hysteresis loss coefficient,
σ _e : eddy current loss coefficient,
B: Steel plate magnetic flux density (T),
d: the thickness of the steel sheet (mm),
f: frequency (Hz) of the drive current.

In general, in a steel sheet used for a motor, the eddy current loss coefficient σ _e is about 6 times the hysteresis loss coefficient σ _h , and most of the heat generated by iron loss is caused by eddy current loss.
Further, since iron loss due to eddy current loss is proportional to the square of the thickness d of the steel plate, it is necessary to use a thin steel plate to suppress heat generation.
For this reason, in general motors, steel plates rolled into thin plates are used in order to reduce eddy currents and suppress heat generation. The conventional PM type stepping motor uses a single-layer steel plate for the yoke element, and has no idea of using a laminated steel plate, and heat is generated uniformly depending on the thickness of the steel plate. The PM stepping motor 100 of the present embodiment uses a damping steel plate that is a resin composite steel material developed as a noise countermeasure technology with a steel plate used in a housing or the like to reduce eddy current and generate heat. It is suppressed.

When the hysteresis loss is ignored in the above equation (1), the iron loss Wf is as shown in the following equation (2).
Wf ≈ σ _e B ² d ² (f / 100) ² [W / kg] (2)
That is, it can be seen that by using a damping steel plate having a half thickness, the iron loss Wf is reduced to about ¼ and the heat generation due to the eddy current loss is greatly reduced. That is, when the iron loss when a steel sheet having a certain thickness is used as a single layer is 1, the iron loss generated in the steel sheet having a half thickness is ¼. Therefore, even when two half-thick steel plates are used, if they are insulated, the total iron loss will be halved, and iron loss will be generated while maintaining the amount of flowing magnetic flux. Can be halved.

Table 1 below shows a case where a three-phase PM type stepping motor uses a yoke element composed of a conventional single-layer steel plate (conventional structure) and a yoke element composed of a damping steel plate of the present embodiment. The estimated value of the iron loss in the case of being present (invention structure) is shown.
Here, the outer diameter of the unit stator is 81 mm, the yoke element of the conventional structure is composed of a single-layer steel plate having a thickness of 1.6 mm, and the yoke element of the embodiment is composed of two skin steel plates having a thickness of 0.8 mm. And a damping steel plate laminated with a damping resin having a thickness of about 0.05 to 0.15 mm interposed therebetween. In this case, the frequency f of the drive current is 150 Hz.
In Table 1, loss items (1) and (2) are hysteresis loss and eddy current loss at pole teeth 131a and 132a of yoke elements 131 and 132, and loss items (3) and (4) are yoke elements 131 and 132. Hysteresis loss and eddy current loss, loss items (5) and (6) in portions other than the pole teeth of FIG.

In the above comparison, the total value of iron loss due to the inventive structure is suppressed to about １ ／ of the value due to the conventional structure. Therefore, the heat generation amount can be suppressed to about 1/3, and a PM type stepping motor with high speed rotation and high output torque can be configured without taking any special heat dissipation measures.
Although the case where n = 3 has been described in the embodiment, the present invention can be applied if n is 2 or more.

  In the field of office equipment, industrial equipment, etc., it is particularly suitable for applications requiring high rotational speed and high output torque.

It is a vertical side view of the three-phase PM type stepping motor according to the embodiment of the present invention. It is a disassembled perspective view of the PM type stepping motor shown in FIG. FIG. 2 is a development view showing a positional relationship between pole teeth formed on a yoke element of the PM stepping motor shown in FIG. 1 and magnetic poles of a permanent magnet formed on the outer periphery of a rotor. It is a perspective view which shows the structure of a part of yoke element of the PM type stepping motor shown in FIG. It is a perspective view which shows the structure of the damping steel plate for forming the yoke element shown in FIG. It is a vertical side view which shows the structure of the conventional 2 phase PM type | mold stepping motor. FIG. 7 is a perspective view showing a partial structure of a yoke element of the PM type stepping motor shown in FIG. 6. FIG. 7 is an exploded cross-sectional view showing a structure of a unit stator of the PM type stepping motor shown in FIG. 6.

Explanation of symbols

100: Three-phase PM type stepping motors 111, 112: Plate 120, rotor:
121: rotating shaft 122: permanent magnet 130: stators 130a, 130b, 130c: unit stators 131, 132: yoke elements S1, S2: skin steel plate R: damping resin 131a, 132a: pole teeth 131b: ring portion 133: Bobbin 134: Coil

Claims (3)

A cylindrical permanent magnet in which S and N poles are alternately magnetized in a circumferential direction on an outer peripheral portion on a rotating shaft attached to the fixed portion via a pair of bearings arranged at both ends in the axial direction of the fixed portion. A rotor configured by fixing magnets integrally;
A pair of yoke elements having comb-shaped pole teeth facing the outer circumference of the rotor with a predetermined gap and facing the magnetic poles of the rotor on the inner circumference side are combined so that the pole teeth are alternately arranged. A ring-shaped unit stator constituted by arranging a coil inside a pair of the combined yoke elements is attached to the fixing portion in the axial direction by arranging n pieces (n is an integer of 2 or more). And a stator to be
The permanent magnet type stepping motor, wherein the yoke element is formed by bending a plurality of steel plates laminated via an insulator. The permanent magnet type stepping motor according to claim 1, wherein the stator includes three unit stators. The permanent magnet type stepping motor according to claim 1, wherein the yoke element is formed of a damping steel plate in which damping resin is sandwiched between two skin steel plates.

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