JPH04109836A - Step motor - Google Patents

Abstract

PURPOSE:To suppress cogging torque, to realize constant speed rotation and to suppress fluctuation of output torque by arranging the outer yoke of any one of two stator units arranged in the axial direction asymmetrically such that each pole tooth of the outer yoke is shifted in specific direction from the central position between the pole teeth of the inner yoke. CONSTITUTION:In a first phase stator unit 50, pole teeth 22A, 23A of inner and outer yokes are arranged symmetrically at the central positions between the counterpart pole teeth but in a second phase stator unit 60, pole teeth 25A of the outer yoke are arranged asymmetrically such that they are shifted by specific angles clockwise from the central position between the pole teeth 24A of the inner yoke when viewed from the inner yoke side. Curve A corresponds to clockwise driving of motor whereas curve B corresponds to counterclockwise driving of motor. As can be seen from the curves, cogging torque can be suppressed when the shift angle is in the range of 30'-1 deg.30'.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of a stepping motor, and more specifically, the present invention relates to the structure of a stepping motor. This invention relates to a stepping motor having a structure in which two motors are arranged.

[Conventional technology]

A stepping motor is constructed by axially arranging a plurality of stator units (usually two phases) consisting of a yoke and a coil around a rotor having magnetic poles.

This stepping motor includes a stator unit consisting of an inner yoke and an outer yoke having a plurality of pole teeth formed at a predetermined pitch in the circumferential direction around a rotor having magnetic poles, and a coil installed between these yokes.
A structure in which two pieces are arranged in the axial direction is widely used.

In conventional stepping motors of this type, the inner and outer yokes of each stator unit are configured so that the intervals between their pole teeth in the circumferential direction are uniform.

[Technical problem to be solved by the invention] However, in such a conventional stepping motor structure, due to the influence of magnetic interference from other adjacent stator units,
There is a problem in that the fluctuating torque for each step angle, that is, the cogging torque becomes large, which hinders uniform rotation.

Furthermore, since the cogging torque is large, there is also a problem in that the output torque tends to fluctuate.

The present invention has been made in view of such conventional technical problems, and an object of the present invention is to provide a stepping motor that can rotate at a constant speed and eliminate fluctuations in output torque by reducing cogging torque. With the goal.

[Means for Solving the Problems] The present invention provides an inner yoke and an outer yoke having a plurality of pole teeth formed at a predetermined pitch in the circumferential direction around a rotor having magnetic poles, and a coil mounted between these yokes. In a stepping motor having a structure in which two stator units are arranged in the axial direction, the outer yoke of one of the stator units is positioned such that each pole tooth of the outer yoke is located from the center position between each pole tooth of the inner yoke. To provide a stepping motor that can reduce cogging torque, enable constant speed rotation, and eliminate fluctuations in output torque by having a structure that is assembled asymmetrically so as to shift in a specific direction.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a longitudinal sectional view showing an embodiment of a stepping motor according to the present invention.

In FIG. 2, the motor case 10 consists of a drum-shaped aperture part with one end open.
An opening 11 is formed in the center of the wall end face of the bearing 1, and a bearing 15 is fixed to the opening by press fitting or the like.

Further, a mounting plate 12 is fixed to the open end surface of the motor case 10 by fixing means such as caulking 13, and the mounting is carried out through an opening 14 formed at the motor shaft center of the plate 12.
Another bearing 16 is fixed by press-fitting or the like.

The mounting plate 12 also serves as an end plate for sealing the open end surface of the motor case 10.

The motor shaft 17 is rotatably supported by the two bearings 15 and 16.

A rotor 18 is press-fitted into the motor case 10 at a position on the motor shaft 17, and rotor magnets 19 are formed on the outer periphery of the rotor 8, magnetized to N and S poles at predetermined pitches in the circumferential direction. has been done.

Inside the motor, which is formed by a motor case 10 and a mounting plate 12, are two stator units 50 and 60 having pole teeth facing the rotor magnet 19.
are arranged side by side in the axial direction.

Each stator unit 50.60 has a structure in which an excitation coil 20.21 is housed between inner and outer yokes having pole teeth, and constitutes the excitation phase of the motor. Therefore, the illustrated motor has two Equipped with an excitation phase.

The excitation coil 20 and the inner and outer yokes 22 and 23 constitute a first phase stator unit 50, and the excitation coil 21 and the inner and outer yokes 24 and 25 constitute a second phase stator unit 60.

Therefore, in the illustrated example, the first phase outer yoke 22 is fixed to the end surface of the motor case 10, the first phase inner yoke 23 and the second phase inner yoke 24 are joined back to back, and the first phase inner yoke 22 is fixed to the end surface of the motor case 10. The two-phase outer yoke 25 is installed Fi12
is fixed.

In this way, by installing the first excitation coil 20 wound around the bobbin 26 inside the first inner and outer yokes 22 and 23, the first phase stator unit 50 is constructed. A second phase stator unit 60 is configured by mounting the second excitation coil 21 wound around the pobbin 27 inside the yokes 24 and 25.

Each yoke 22, 23, 24, 25 is provided with a plurality of pole teeth 22A, 23A, 24A, 25A formed at a predetermined pitch in the circumferential direction so as to face the rotor magnet 19 with a predetermined gap. It is being

A rotational force extraction means 30 such as a pulley is fixed to the output side protrusion of the motor shaft 17.

The bobbins 26 and 27 are made of plasti, for example.

Parts 26A and 27A of the motor case 10 protrude slightly outward from the surface of the motor case 10 through a cutout 31 formed on the side surface of the motor case 10.
The protrusion has a bobbin terminal (or motor terminal) 28. around which the winding end of each exciting coil 20.21 is wound.
29 is fixed by embedding.

Two bobbin terminals 28 and 29 are provided each in the case of unifier winding, and three bobbin terminals 28 and 29 are provided each in the case of pie filer winding.

The winding end portions of each exciting coil 20.21 are wound around the base portions of these bobbin terminals 28.29, and are fixed by soldering or the like.

A circuit board 35 for connection to a motor control section is fixed to the tip of each bobbin terminal 28, 29 in an electrically connected state by soldering or the like.

FIG. 1 shows the pole teeth 22A to 25A of each of the yokes 22 to 25.
FIG.

In FIG. 1, each yoke 22 to 25 has a plurality of yokes (for example, 12
2) of pole teeth 22A to 25A are formed.

When assembling the motor, the first phase inner and outer yokes 22.
23 are assembled so that their pole teeth 22A, 23A are arranged in a staggered manner between the opposing pole teeth, and the second phase inner and outer yokes 24, 25 are assembled with their pole teeth 22A, 23A.
They are assembled so that A is arranged in a staggered manner between the opposing pole teeth.

Therefore, in the stator unit 50 of the first phase, each pole tooth 22A, 23A of the inner and outer yokes 22, 23 is assembled symmetrically so that it is located at the center of the spacing between the opposing pole teeth. In the stator unit 60, each pole tooth 25A of the outer yoke 25 is assembled asymmetrically so that it is shifted by a predetermined angle clockwise from the center position between the pole teeth 24 of the inner yoke when viewed from the inner yoke 24 side. ing.

The angle of deviation of each pole tooth 25A of the outer yoke 25 is set, for example, to approximately 30 minutes to 1 degree and 30 minutes.

That is, in FIG. 1, the outer yoke 2 in the first phase
The inner yoke 2 is located at the center of the pole tooth 22A of 2 and on both sides thereof.
The distance between the pole teeth 23A and 23A of the inner yoke 24 in the second phase is a and b, and the distance between the center of the pole tooth 24A of the inner yoke 24 and the pole teeth 25A and 25A of the outer yoke 25 located on both sides thereof in the second phase is c, d, and furthermore, the pole tooth spacing between the first phase outer yoke 22 and the second phase inner yoke 24 is e, and the second phase inner yoke 24 is
The pole tooth spacing between and the first phase inner yoke 23 is f, the pole tooth spacing between the first phase inner yoke 23 and the second phase outer yoke 25 is g,
When the pole tooth spacing between the second phase outer yoke 25 and the first phase outer yoke 22 is h, the relationship is as follows.

a=b≠C≠d ・・−・−(1)c>a
= b > d −−−・・・・−・−(2) g
>e=f>h−−・−−−−−・−(3) From the above,
A stator unit consisting of an inner yoke and an outer yoke having a plurality of pole teeth formed at a predetermined pitch in the circumferential direction around a rotor 18 having a magnetic pole 19, and a coil installed between these yokes is axially moved. In a stepping motor having a structure in which two stator units are arranged, which one connects the outer yoke 25 of one stator unit 60 with each pole tooth 25A of the outer yoke from the inner yoke side from the center position between each pole tooth 24A of the inner yoke 24. The stepping motor is assembled asymmetrically so that it shifts clockwise when viewed.

In the above configuration, each pole tooth 25A of the outer yoke 25
It is preferable that the deviation angle is set to approximately 30 minutes to 1 degree and 30 minutes.

In the above embodiment, the outer yoke 25 of the second phase stator unit 60 was assembled asymmetrically, but instead of this, the outer yoke 22 of the first phase stator unit 50 was assembled asymmetrically.
may be assembled asymmetrically so that each pole tooth 22A of the outer yoke 22 is shifted clockwise from the center position between the pole teeth 23A of the inner yoke 23 when viewed from the inner yoke 23 side. good.

FIG. 3 shows that the outer yoke 25 of the second phase is shifted by a predetermined angle in a specific direction (in the above embodiment, clockwise when viewed from the inner yoke side) from a symmetrical position (position with a deviation angle of −0). 3 is a graph showing measured values of cogging torque in the case of FIG.

In FIG. 3, the horizontal axis shows the displacement angle of the outer yoke 25, the vertical axis shows the cogging torque (g-C1l), the curve gA shows the cogging torque when the motor is driven clockwise, and the curve B indicates the cogging torque when the motor is driven counterclockwise.

As is clear from this graph, by assembling the outer yoke of one stator unit in an asymmetrical position, compared to the case of a symmetrical position f (shift angle -〇),
The cogging torque could be reduced, and especially when the shift angle was about 30 minutes to about 1 degree and 30 minutes, the cogging torque could be significantly reduced.

According to the embodiment described above, in a stepping motor having two stator units 50, 60 arranged in the axial direction, the outer yoke 25 or 22 of one stator unit is connected to each of the pole teeth 25A or 22 of the outer yoke. 22A is assembled asymmetrically so that it is shifted clockwise from the center position between each pole tooth 24A or 23A of the inner yoke 24 or 23 when viewed from the inner yoke side. When assembling the inner and outer yokes symmetrically, magnetic interference from the mating stator unit can be mechanically corrected to form a magnetically symmetrical stator unit, with low cogging torque and
A stepping motor capable of smooth constant rotation was obtained.

In the above embodiment, one of the outer yokes 25 or 22 was shifted clockwise when viewed from the inner yoke 24 or 23, but depending on the state of magnetic interference between each stator unit 50, 60, the above It is also possible to assemble it asymmetrically by shifting it in the opposite direction to that of the embodiment.

In other words, depending on the interference characteristics specific to each stepping motor, by shifting one of the outer yokes by a predetermined angle counterclockwise when viewed from the inner yoke side, the cogging torque can be reduced compared to when assembled in symmetrical positions. , it is possible to eliminate (or reduce) fluctuations in output torque.

FIG. 4 shows a case where the outer yoke 25 is assembled asymmetrically so that its pole teeth 25A are offset from the center position between the pole teeth 24A of the inner yoke 24 in a counterclockwise direction when viewed from the inner yoke side. FIG. 3 is a partially exploded view showing the arrangement relationship of each pole tooth.

4 differs from the state shown in FIG. 1 only in that the pole tooth 25A is shifted to the same extent in the opposite direction to the pole tooth 24A, and the other parts have the same configuration.

Therefore, in FIG. 4, parts corresponding to those in FIG. 1 are indicated by the same reference numerals, and detailed explanation thereof will be omitted.

Similarly to the case of FIG. 1, the embodiment shown in FIG. 4 also provides a stepping motor that can reduce cogging torque and eliminate (or reduce) fluctuations in output torque.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an inner yoke and an outer yoke having a plurality of pole teeth formed at a predetermined pitch in the circumferential direction are mounted around a rotor having magnetic poles, and between these yokes. In a stepping motor with a structure in which two stator units consisting of coils are arranged in the axial direction, the outer yoke of one of the stator units is connected to the center between each pole tooth of the outer yoke and the center between each pole tooth of the inner yoke. Since the stepping motor is assembled asymmetrically so as to deviate from the position in a specific direction, it is possible to reduce cogging torque, to enable constant speed rotation, and to eliminate fluctuations in output torque.

[Brief explanation of drawings]

FIG. 1 is a partially exploded view showing the arrangement of pole teeth of each yoke of a stepping motor according to an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view showing an embodiment of the stepping motor according to the present invention, and FIG. FIG. 4 is a graph showing the measurement results of the displacement angle of the yoke and the cogging torque, and FIG. 4 is a partially exploded view showing the arrangement of pole teeth of each yoke of a stepping motor according to another embodiment of the present invention. Below, symbols representing main components in the drawings are listed. i o------Motor case, 12・------・Mounting plate, 17・---111 Motor shaft, 18------
-1 rotor, 19...-magnetic pole (rotor), 20-
---1 first phase excitation coil, 21...=...second
Excitation coil of phase, 22-... Outer yoke of first phase, 23
------Inner yoke of the first phase, 24--Inner yoke of the second phase, 25--Outer yoke of the second phase, 22A, 23
A, 24A, 25A...Pole teeth of each yoke, 2
6.27...--Bobbin, 50...--1--1st
Phase stator unit, 60 - - - Second phase stator unit.

Claims (2)

[Claims] (1) A stator unit consisting of an inner yoke and an outer yoke having a plurality of pole teeth formed at a predetermined pitch in the circumferential direction around a rotor having magnetic poles, and a coil installed between these yokes is moved in the axial direction. In a stepping motor with a structure in which two stator units are arranged, the outer yoke of one of the stator units is asymmetrically arranged so that each pole tooth of the outer yoke is shifted in a specific direction from the center position between each pole tooth of the inner yoke. A stepping motor that is characterized by its ability to be assembled. (2) The stepping motor according to claim 1, wherein a deviation angle of each pole tooth of the outer yoke is 30 minutes to 1 degree and 30 minutes.