JPH0787679B2 - Toroidal motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a toroidal motor, and in particular,
The present invention relates to a toroidal motor that uses a fluid bearing or a sliding bearing as its radial bearing.

(Prior Art) A motor requires a bearing that supports the rotor (rotor) in the radial direction (hereinafter referred to as a radial bearing) and a bearing that supports the thrust direction (hereinafter referred to as a thrust bearing). When a rolling bearing having balls or rollers is used as the radial bearing, the rolling bearing may also have the function of the thrust bearing depending on the rotational speed of the motor and the load.

On the other hand, when a dynamic pressure type or static pressure type hydrodynamic bearing is used as a radial bearing like a motor applied to a laser beam printer or the like, a thrust bearing using a hydrodynamic bearing or the like is required.

However, as is well known, in the hydrodynamic bearing, it is necessary to form a groove for pressure generation in at least one of the rotor and the support of the rotor. Therefore, the fluid bearing
It is generally more cumbersome to manufacture and more expensive than other types of bearings.

In particular, when the fluid bearing is applied to the thrust bearing, the squareness of the end face and the side face of the rotor must be set extremely strictly, and when the rotor end face is molded into a spherical surface and supported, the spherical surface of the spherical surface is used. Since the degree of precision and the degree of sphericity of the support surface that supports the spherical surface require high precision, their fabrication is extremely troublesome.

Therefore, as the thrust bearing, a slot type, coreless type, or synchronous type motor to which a magnetic bearing is applied has been proposed. The motor includes first permanent magnets fixed to both ends of the rotor, and second permanent magnets fixed to the inner wall of the casing so that the same magnetic pole faces as the first permanent magnets face each other. There is.

As described above, when the magnetic bearing is applied as the thrust bearing, the configuration of the motor is simplified and the motor can be easily manufactured.

(Problems to be Solved by the Invention) The above-described conventional technique has the following problems.

When a magnetic bearing is used as the thrust bearing, a part of the magnetic circuit of the magnetic bearing coincides with the magnetic circuit of magnetic force lines generated between the rotor and the stator (stator).

However, with this configuration, when an alternating magnetic field is generated by the biasing of the stator coil, the strength of the magnetic field generated in the magnetic bearing during rotation of the rotor changes, and the rotor may vibrate (cogging) in the thrust direction. In addition, the cogging in the thrust direction may cause the rotor to cogging in the radial direction.

Further, since the magnetic attraction force generated between the rotor and the stator also changes with the rotation of the rotor, the radial vibration of the rotor may be promoted.

The present invention has been made to solve the above problems.

(Means and Actions for Solving Problems) In order to solve the problems described above, the present invention provides a radial body including a cylindrical rotating body and a cylindrical magnet attached to at least a part of the outer periphery thereof. A rotor whose direction is supported by a fluid bearing or a slide bearing, and an annular toroidal core, which is arranged on the outer peripheral portion of the magnet and has a cylindrical surface on the inner periphery and a plurality of protrusions on the outer periphery, A structural feature is that the core includes a plurality of toroidal coils wound around a core and a stator formed of a yoke arranged so as to come into contact with the protrusions.

Further, according to the present invention, as described above, the annular toroidal core has a shape in which the inner circumference is a cylindrical surface and has a plurality of protrusions on the outer periphery, and the yoke arranged on the outer periphery abuts on each protrusion. Since they are in contact with each other, almost all the magnetic fluxes generated from the plurality of toroidal coils pass through the yoke having a small magnetic resistance, and are prevented from leaking between the magnet of the rotor and the toroidal core of the stator. Can be prevented. Therefore, the magnetic resistance between the rotor and the stator becomes uniform over the circumferential direction, and the magnetic attraction force does not change even when the rotating body rotates. Therefore, the rotor does not cogging in the radial direction and the thrust direction during rotation.

(Example) Hereinafter, the present invention will be described in detail with reference to an example in which it is applied to an optical deflector used in a laser beam printer.

FIG. 1 is a schematic vertical sectional view of an optical deflector to which the first embodiment of the present invention is applied, and FIG. 2 is a stator shown in FIG. 1 and a magnet yoke 11 fixed to a rotary sleeve 2.
2 is a schematic front view of the magnet 3 and FIG. 3 is a sectional view of FIG. In FIGS. 1 and 3, the toroidal coil wound around the toroidal core 4 forming the stator is omitted for clarity.

In each figure, the main shaft 1 is horizontally supported with its both ends fixed to a housing 6 that constitutes the housing of the optical deflector.

A rotary sleeve 2 (rotor) having a polygon mirror 7 fixed to the outer periphery thereof is rotatably mounted on the main shaft 1. A pressure generating groove 1A is formed on the outer peripheral surface of the main shaft 1. The groove 1A constitutes a radial fluid bearing of the rotary sleeve 2.

A cylindrical magnet 3 is fixed to the outer peripheral portion of the rotary sleeve 2 via a magnet yoke 11.

The magnet yoke 11 is arranged to form a magnetic path of magnetic force lines generated from the inner surface of the magnet 3 and to increase the magnetic flux density of magnetic force lines generated from the outer surface of the magnet 3, but it is not particularly provided. good. The magnet 3 is divided from the central axis of the main shaft 1 at the same central angle so as to have a plurality of magnetic poles.

An annular stator is fixed to the inner wall of the housing 6 so that the inner surface thereof faces the magnet 3. As shown in FIGS. 2 and 3, the stator has an annular toroidal core 4 having a plurality of protrusions on its outer peripheral surface.
A toroidal coil 5 wound between the protrusions, and an annular yoke formed of a magnetic material and arranged around the toroidal core 4 so as to abut each of the protrusions.
It consists of 4A. The yoke 4A is not necessary when the housing 6 is made of a magnetic material and the protrusions are arranged so as to contact the inner wall of the housing 6.

Reference numeral 10 is a substrate for mounting the Hall IC 9. Hall i
C9 is provided to detect the change in the magnetic field of the magnet 3, that is, the rotation angle of the magnet 3.

A window 12 is formed in the housing 6 for allowing light to enter the polygon mirror 7 and directing the light reflected by the polygon mirror 7 to a photoconductor (not shown) or the like. The cover glass 13 seals the window 12.

Reference numeral 8 denotes a balance adjusting ring for the rotating sleeve 2 and the polygon mirror 7.

In the toroidal motor having the above configuration, when the toroidal coil 5 is urged by a driving means (not shown), the rotary sleeve 2 rotates in a predetermined direction.

Here, the magnetic force lines generated from the toroidal coil 5 circulate in the toroidal core 4 and the yoke 4A, as indicated by the symbol MA in FIG. Therefore, the magnetic force lines hardly leak into the space between the toroidal core 4 and the magnet 3.

On the other hand, the lines of magnetic force generated from the magnet 3 circulate between the toroidal core 4 and the magnet 3 via the air gap, as indicated by the symbol MB in FIG.

As described above, in the toroidal motor, the magnetic field generated between the toroidal core 4 and the magnet 3 is only due to the lines of magnetic force generated by the magnet 3, so that even if the rotating sleeve 2 is rotated, the magnetic flux distribution seen from the magnet 3 is , Stationary without change. In other words, the magnetic field between the toroidal core 4 and the magnet 3 is
It is not affected by the alternating magnetic flux generated from the toroidal coil 5.

Further, since the salient poles are not formed on the inner peripheral surface of the toroidal core 4, the width of the air gap between the toroidal core 4 and the magnet 3 is uniform in the circumferential direction, that is, the toroidal core 4 and the magnet 3 have the same width. The magnetic resistance between them is uniform, and the magnetic attraction force acting between the magnet 3 and the toroidal core 4 is always constant regardless of the rotation angle of the magnet 3.

Therefore, even if the toroidal coil 5 is biased to rotate the rotary sleeve 2, the rotary sleeve 2 does not cogging in the radial direction.

By the way, in the first embodiment of the present invention, a radial fluid bearing is formed between the inner peripheral surface of the rotary sleeve 2 and the outer peripheral surface of the main shaft 1, but the thrust bearing of the rotary sleeve 2 is arranged. It has not been.

However, since the magnetic attraction force is generated between the toroidal core 4 and the magnet 3 fixed to the rotary sleeve 2 as described above, the magnet 3 tries to stay at the central portion of the toroidal core 4. Therefore, unless a large external force is applied to the rotary sleeve 2, the rotary sleeve 2 can be supported in the thrust direction by the magnetic attraction force.

In this case, since the force acting in the thrust direction does not change as in the case where a magnetic bearing is used as the thrust bearing, the rotary sleeve 2 can perform stable rotation without cogging in the thrust direction. .

FIG. 6 is a schematic vertical sectional view of an optical deflector to which the second embodiment of the present invention is applied. In FIG. 6, the same reference numerals as those in FIG. 1 denote the same or equivalent parts, and thus the description thereof will be omitted.

In the first embodiment, an example in which the present invention is applied to a sleeve rotation type toroidal motor is shown.
In the second embodiment, an example in which the present invention is applied to a shaft rotation type toroidal motor is shown.

In FIG. 6, the magnet 3 and the polygon mirror 7
Are fixed to the main shaft 1.

The main shaft 1 is rotatably supported by a housing 6. On the supporting surface of the main shaft 1 of the housing 6 and / or on the outer peripheral surface of the main shaft 1, pressure generating grooves (not shown) are bored, and these constitute a radial fluid bearing.

Also in this embodiment, the main shaft 1 can be stably supported in the thrust direction only by the magnetic attraction force generated between the magnet 3 and the toroidal core 4 without providing a thrust bearing.

Although the present invention has been described as being applied to the toroidal motor used in the optical deflector in each of the above-described embodiments, the present invention is not particularly limited to this and the optical deflector is not limited thereto. Of course, it may be applied to a toroidal motor applied to other than.

Further, in each of the above-described embodiments, the present invention is described as being applied to a toroidal motor of a type in which the main shaft 1 or the rotating sleeve 6 (that is, the rotor) is supported horizontally, but the present invention is particularly applicable to this. The present invention is not limited to this, and may be applied to a toroidal motor of a type in which a rotor is vertically supported. When the rotor is supported vertically, the weight of the rotor is relatively small, the magnetic attraction between the magnet fixed to the rotor and the toroidal core is strong, and the rotor is like the optical deflector. It is possible to support the rotor in the thrust direction by the magnetic attraction force only for a device to which an external force is not applied.

Further, in each of the above-described embodiments, the present invention is described as being applied to a toroidal motor using a fluid bearing as a radial bearing, but the present invention is not particularly limited to this, and a slide bearing is not limited thereto. Needless to say, it may be applied to a toroidal motor using. When applying a toroidal motor to an optical deflector, a sliding bearing is used as a radial bearing when the rotation speed and rotation accuracy of the polygon mirror are not very high, or when the rotor runout during rotation may be large. be able to.

(Effects of the Invention) As is apparent from the above description, according to the present invention, a magnetic field line generated from a stator having a toroidal coil does not substantially leak into the gap between the magnets of the stator and the rotor. In the motor,
Since the radial direction is supported by the fluid bearing or the slide bearing, the thrust direction of the rotor is supported only by the magnetic attraction force generated between the stator and the rotor without providing the thrust bearing. , The following effects are achieved.

(1) The structure of the toroidal motor can be simplified and the manufacturing cost can be significantly reduced.

(2) Since a pressure generating surface for applying a force in the slite direction is not required, a sleeve rotation type rotor is
The thickness of both ends of the rotor can be reduced, and in the case of an axial rotation type rotor, the rotor can be shortened. As a result, the weight and moment of inertia of the rotor can be significantly reduced, and the motor is lightened. Moreover, since the load applied to the radial bearing is reduced, the life of the motor is extended and the responsiveness is improved.

(3) The magnetic attractive force generated between the rotor and the stator due to the magnetic force lines generated from the rotor is not affected by the alternating magnetic flux generated from the stator, and the magnetic resistance between the stator and the rotor is in the circumferential direction. Since it is uniform over the entire length, the magnetic attraction force does not change even when the rotor rotates. Therefore, when the rotor rotates, the rotor does not cogging in the radial direction and the thrust direction.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an optical deflector to which a first embodiment of the present invention is applied, and FIG. 2 is a schematic front view of a stator and a rotor magnet and a magnet yoke shown in FIG. 3 is a sectional view of FIG. 2, FIGS. 4 and 5 are views showing magnetic lines of force generated by a toroidal coil and a magnet, and FIG. 6 is a schematic vertical section of an optical deflector to which a second embodiment of the present invention is applied. It is a side view. 1 ... Spindle, 1A ... Pressure generating groove, 2 ... Rotating sleeve, 3 ... Magnet, 4 ... Toroidal core, 4A ...
Yoke, 5 ... Toroidal coil, 6 ... Housing,
7 ... Polygon mirror, 9 ... Hall IC, 10 ... Substrate,
11 …… Magnet yoke

Claims (2)

[Claims] 1. A rotor comprising a cylindrical rotating body (2) and a cylindrical magnet (3) mounted on at least a part of its outer circumference, the radial direction of which is supported by a fluid bearing or a sliding bearing. , The outer circumference of the magnet has an inner circumference of a cylindrical surface,
And an annular toroidal core (4) having a plurality of protrusions on the outer periphery, a plurality of toroidal coils (5) wound around the annular toroidal core, and a yoke (4A) arranged so as to contact the protrusions. A toroidal motor, comprising: 2. A yoke (4A) arranged so as to be in contact with each of the protrusions is a housing (6) of the toroidal motor molded from a magnetic material, and each of the protrusions contacts an inner wall of the housing. The toroidal motor according to claim 1, wherein the toroidal motors are arranged so as to be in contact with each other.