JP2881324B2 - Step motor - Google Patents

Description

The present invention relates to a stepping motor, and more particularly to a hybrid type stepping motor combining functions of both a variable reluctance type and a permanent magnet type with an increased torque characteristic. The present invention relates to a novel improvement for reducing the inertia of a rotor and improving responsiveness.

b. Conventional technology Conventionally, there are various types of stepping motors, but in general, a variable reluctance type, a permanent magnet type, and a hybrid type are employed from the principle of torque generation.

Since the variable reluctance type utilizes the variable reluctance force between the stator and the rotor, no reaction force is generated when the power is turned off.

In the permanent magnet type, the magnet itself is a rotor, and the magnetic field of the magnet interacts with the magnetic field of the coil to generate a force. Generates the force said.

Furthermore, the hybrid type is a combination of the above-mentioned variable reluctance type and permanent magnet type, and the magnetic field of the magnet is guided to the reluctance change between the stator and the rotor, generating a force between the magnetic fields created by the stator windings. doing.

An example of the hybrid type is shown in February 10, 1979.
7 to 9 disclosed in pages 34 and 35 of "Basics and Application of Stepping-Mota" by Sogo Denshi Publishing Co., Ltd. published by Japan can be shown.

That is, what is indicated by reference numeral 1 in the drawing is the front lid.
1a, a rear lid 1b and a peripheral wall 1c. A casing 3 having a stator winding 2 is provided in the peripheral wall 1c of the casing 1.

Rotating shafts 7 having rotors 6 are rotatably provided on bearings 4 and 5 formed on the respective lids 1a and 1b. The rotor 6 has a central hole formed at the center of the shaft of the stator 3. 3a
It is rotatably located inside.

The rotor 6 is composed of a magnet 7a magnetized in the axial direction and a pair of yokes 8.

Accordingly, the magnetic field generated by the magnet 7a is led to a change in reluctance between the stator 3 and the rotor 6, and a force is generated between the magnetic field generated by the stator winding 2 and the magnetic field.

c. Problems to be Solved by the Invention Since the conventional step motor is configured as described above, the following problems exist. That is, a hybrid type step motor has been adopted for a head drive servo mechanism such as a floppy disk or a hard disk of an OA device using the step motor.

This is because the hybrid type is suitable for high resolution with small size, light weight, high response, and reduced step angle.

However, not only by reducing the one-step angle but also by improving the driving and control techniques, a method of further subdividing one step by a name such as half-step or micro-step has been adopted.

That is, this is to cope with a finer track interval and an improvement in access time by increasing the density of FD and HD storage media.

In line with these demands, there is no limit to the demand for increased storage capacity and miniaturization of OA equipment. In response to such demands, higher responsiveness can be achieved with a minor hybrid change of a conventional hybrid step motor. It is impossible to respond.

In other words, high responsiveness is an improvement in the generated force / inertia ratio. To increase the generated force, either increase the shape or increase the magnetic flux or current, but, contrary to miniaturization, Responsiveness at the time of stoppage worsens.

Therefore, in the conventional configuration using a rotor in which the magnet and the yoke are integrated and rotor teeth are formed on the outer periphery, it is impossible to achieve high responsiveness.

As a means for increasing the magnetic flux, high-performance rare earth magnets are already used at present, but it is conceivable to improve the saturation magnetic flux density of the silicon steel sheet used for the rotor teeth.
At present, such materials do not exist and are not feasible.

In addition, the increase in current leads to thermal problems,
Also, it is extremely difficult to increase the inertia characteristics because the specific gravity of the material used is determined.

The present invention has been made in order to solve the above-described problems, and in particular, it has been proposed to increase the torque characteristics and increase the rotor characteristics of a hybrid type step motor that combines both functions of a variable reluctance type and a permanent magnet type. It is an object of the present invention to provide a small-sized and high-performance step motor in which the inertia of the motor is reduced and the responsiveness is improved.

d. Means for Solving the Problems A step motor according to the present invention includes a stator having a stator winding provided on a casing, stator teeth formed on an inner surface of the stator, and a shaft formed on the axis of the stator. A center hole, a rotating shaft having a cup-shaped rotor tooth body rotatably provided in a bearing of the casing,
An inner tooth formed on an inner surface of the rotor tooth body, an outer tooth formed on an outer surface of the rotor tooth body, a ring-shaped first fixed yoke provided on the casing and located between the rotor tooth body and a rotating shaft; A ring-shaped fixed magnet connected to the first fixed yoke and magnetized in the axial direction; a second ring-shaped fixed yoke connected to the fixed magnet; and fixed yoke teeth formed on an outer surface of the fixed yoke. It is a configuration provided.

e. Operation In the stepping motor according to the present invention, only the rotor tooth body having rotor teeth is provided for the rotating shaft, and the yoke and magnet conventionally provided on the rotating shaft are fixed to the casing. In addition, while maintaining the torque characteristics, the mass of the rotating shaft having the rotor teeth is greatly reduced, and the inertia characteristics are improved, and high responsiveness can be obtained. Further, since torque is generated in the outer gap between the stator teeth and the rotor teeth and the inner gap between the rotor teeth and the fixed yoke teeth, twice the torque as compared with the conventional case can be obtained.

f. Embodiment Hereinafter, a preferred embodiment of a step motor according to the present invention will be described in detail with reference to the drawings.

The same or equivalent parts as those in the conventional example will be described using the same reference numerals.

1 to 6 show a stepping motor according to the present invention, and FIG.
FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG.
4 is an enlarged cross-sectional view of a main part of FIG. 2, and FIGS. 5 and 6 are partial perspective views showing another embodiment of the rotor tooth body. FIG.

1 to 4, reference numeral 1 denotes a casing including a front lid 1a, a rear lid 1b, and a peripheral wall 1c. A stator winding 2 is provided in the peripheral wall 1c of the casing 1. And stator 3 having stator teeth 3b on its inner surface.
Is provided.

Bearings 4 and 5 formed on the lids 1a and 1b are provided with a rotatable shaft 7 having rotor teeth 6 which are formed at the center of the axis of the stator 3. Is rotatably positioned in the center hole 3a.

The rotor tooth body 6 has a substantially cup-shaped overall shape. The rotor teeth 6b of the rotor tooth body 6, a number of internal teeth 6f formed on the inner surface thereof, and a number of external teeth formed on the outer surface thereof. 6e.

Further, a part of the center hole 3a formed between each tooth 6e, 6f of the rotor tooth body 6 and the rotating shaft 7 has a first fixed member held in a cantilever manner by a rear cover 1b of the casing 1. A yoke 8, a fixed magnet 7a connected to the first fixed yoke 8, and a second fixed yoke 8A connected to the fixed magnet 7a are fixedly provided. Therefore, the first fixed yoke 8, the fixed magnet 7a, and the second fixed yoke 8A are
They are connected in series in the axial direction.

As shown in FIG. 4, fixed yoke teeth 8a are formed on the outer surface of the fixed yoke 8, and an outer gap portion 30 is formed between the external teeth 6e and the stator teeth 3b. An inner gap portion 31 is formed between the teeth 8a.

The step motor according to the present invention is configured as described above, and its operation will be described below.

That is, a predetermined drive pulse is supplied to the stator winding 2, and the magnetic field generated by the fixed magnet 7 a is led to a reluctance change between the stator 3 and the rotor tooth body 6, thereby forming the stator winding 2. A torque is generated in the gaps 30 and 31 between the magnetic field and the magnetic field, and the rotor teeth 6 and the rotating shaft 7 rotate.

5 and 6 show another embodiment of the rotor tooth body 6. The rotor tooth body 6 shown in FIG.
Is a non-magnetic cup body 20 made of a non-magnetic material having a large number of valleys 6bA at predetermined intervals on the peripheral surface, and internal teeth 6f and external teeth made of a rectangular magnetic material embedded in each of the valleys 6bA. By forming the thickness D of the non-magnetic cup body 20 to be thin, an ultra-thin rotor tooth body 6 can be obtained.

g. Effects of the Invention Since the step motor according to the present invention is configured as described above, the following effects can be obtained.

That is, only a rotor tooth body having both external teeth and internal teeth is provided for the rotation shaft, and its mass is extremely small as compared with a conventional rotor, so that inertia can be reduced. By realizing extremely high responsiveness, it is possible to reliably obtain a step operation with a minute rotation angle such as a recent microstep.

In addition, the torque generated in the outer gap and the inner gap formed on the outer surface and the inner surface of the rotor tooth body can obtain twice the torque as compared with the conventional one. High responsiveness can be realized by reducing the mass and improving the torque.

[Brief description of the drawings]

1 to 6 show a stepping motor according to the present invention. FIG. 1 is a sectional view showing the overall structure, FIG. 2 is a sectional view taken along line AA of FIG. 3 is an enlarged perspective view showing the rotor teeth of FIG. 1, FIG. 4 is an enlarged sectional view of a main part of FIG. 2, and FIGS. 5 and 6 show other embodiments of the rotor teeth. 7 to 9 are views showing a conventional hybrid type stepping motor, and FIG. 7 is a cross-sectional view showing the entire structure.
FIG. 8 is a sectional view taken along line AA of FIG. 7, and FIG. 9 is a perspective view showing the rotor. 1 is a casing, 2 is a stator winding, 3 is a stator, 3a
Is a central hole, 3b is a stator tooth, 6 is a rotor tooth body, 6b is a rotor tooth, 6bA is a valley, 6e is an external tooth, 6f is an internal tooth, 7 is a rotating shaft, 7
a is a fixed magnet, 8 is a first fixed yoke, 8A is a second fixed yoke, 8a is a fixed yoke tooth, 30 is an outer gap portion, and 31 is an inner gap portion.

Claims (1)

(57) [Claims] 1. A stator (3) provided on a casing (1) and having a stator winding (2), and said stator (3).
And a center hole (3a) formed in the center of the axis of the stator (3) and a bearing (4, 5) of the casing (1) rotatably provided. A rotating shaft (7) having a cup-shaped rotor tooth body (6), and inner teeth (6f) formed on the inner surface of the rotor tooth body (6) and formed on the outer surface of the rotor tooth body (6). External teeth (6e),
The rotor tooth body (6) provided in the casing (1)
A ring-shaped first fixed yoke (8) positioned between the first fixed yoke (8) and the rotating shaft (7); a ring-shaped fixed magnet (7a) connected to the first fixed yoke (8) and magnetized in the axial direction; An annular second fixed yoke (8) connected to the magnet (7a)
A), fixed yoke teeth (8a) formed on the outer surface of the fixed yoke (8), and an outer gap portion (30) between the stator teeth (3b) and the rotor teeth (6) and the rotor. Inner gap (31) between tooth body (6) and fixed yoke tooth (8a)
A step motor characterized in that a torque is generated in the step motor.