JP2003134778A - Electromagnetic rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize rotation of a rotor while intending miniaturization of an electromagnetic rotor in the radial direction. SOLUTION: A brushless electromagnetic rotating machine is equipped with a rotor magnet 20 which is combined and fixed to a rotating shaft 3 via a flange 6 and rotates integrally with the rotating shaft, a bearing member 5 supporting rotatably the rotating shaft, a rotating substrate 4 combined and fixed to the bearing member, and a fixed yoke 1 provided with coils 17. The fixed yoke has inner yokes 1a and outer yokes 1b which face each other in the radial direction and form a gap for arranging the rotor magnet. The outer yokes and the inner yokes face each other, and positioned in plural portions point-symmetrically around the rotating shaft. The respective plural outer yokes are combined in the circumferential direction of the rotating shaft and constituted integrally. In upper end portions of the outer yokes, the respective inner yokes are connected with the outer yokes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic rotating machine, and more particularly to a laser beam printer (hereinafter referred to as LBP).
The present invention relates to a polygon scanner motor used for such purposes.

[0002]

2. Description of the Related Art In recent years, LBP is required to be low-cost, downsized and highly accurate, and a scanner unit which is a main unit is also required to be downsized, low cost and highly accurate. This should improve the rotation accuracy of the motor,
A low center of gravity design is required in which the center of gravity is arranged at a low position with respect to the bearing portion that holds the rotating shaft of the motor rotor.

In order to achieve miniaturization, a motor having a shape in which a stator yoke is extended in the axial direction has been proposed. For example, there is an electromagnetic rotating machine described in Japanese Patent Laid-Open No. 2001-78416.

As shown in FIGS. 3 and 4, this has a shape in which the main parts constituting the electromagnetic rotating machine are extended in the direction of the rotation axis. The fixed yoke 16 includes a pair of inner yokes 16c and outer yokes 16b, extends in the rotation axis direction to form a magnetic gap, and the plurality of magnetic gaps are arranged around the rotation axis. By disposing the inner yoke 16c and the outer yoke 16b in this manner, the size is reduced in the radial direction as compared with the conventional electromagnetic rotating machine.

[0005]

However, the above-mentioned conventional example has the following problems.

An inner yoke and an outer yoke are arranged so as to sandwich the rotor magnet, and this rotary magnet is arranged so as to be arranged from the axially upper direction to the lower direction of the inner yoke and the outer yoke. Therefore, the center of gravity of the rotor including the rotor magnet is set such that the center of gravity is arranged in the axially upper direction with respect to the bearing that holds the shaft that constitutes the rotor, which is a factor that deteriorates the rotation accuracy when the motor rotates.

Further, in the case of the conventional structure, since the member for holding the outer yoke holding member 19 for closing the gap of the outer yoke is required, the number of parts is increased, and the cost is also increased accordingly. Further, since the outer yoke holder is provided on the outside of the yoke, the outer shape of the motor becomes large and it is impossible to achieve a small size.

Therefore, the object of the present invention is to improve the rotational accuracy of the motor and to equip the fixed yoke with the function of the outer yoke retainer, so that the outer yoke retainer can be eliminated, and the compact, low-cost and highly accurate electromagnetic can be achieved. To provide a rotating machine.

[0009]

In order to achieve the above object, an electromagnetic rotating machine according to the present invention includes a rotor magnet fixedly coupled to a rotary shaft via a flange and rotating integrally with the rotary shaft, and the rotary magnet. A bearing member that rotatably supports the shaft, a rotating substrate that is fixedly coupled to the bearing member, and a fixed yoke that includes a coil portion are provided, and the fixed yoke forms a gap in which the rotor magnet is arranged. In the brushless electromagnetic rotating machine, which has an inner yoke and an outer yoke which are opposed to each other in a radial direction, and the outer yoke and the inner yoke are respectively opposed to each other and are arranged in a plurality of points symmetrically around a rotation axis. The outer yoke is integrally formed by connecting the outer yoke in the circumferential direction of the rotary shaft, and the inner yokes are connected at the upper end of the outer yoke (the side opposite to the rotating substrate). Lies in that it has.

In particular, the rotary magnet has a shape that extends from the flange toward the rotary substrate, is folded back, and then extends upward so as to enter the gap.

Further, the fixed yoke is connected to the circuit board at the outer yoke portion.

Therefore, the function of pressing the outer yoke to close the gap between the outer yokes can be provided, and the dustproof function and the rigidity can be added to the yoke.

Further, since the outer yoke pressing member is not necessary, the size in the motor axial direction (radial direction) can be further reduced, and the size can be reduced. Furthermore, it is possible to lower the center of gravity by the structure of the rotor magnet and improve the rotation accuracy of the motor.

Further, the rigidity of the yoke can be improved, which is advantageous for resonance of the yoke.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 and 2 show
1 is a perspective view and a sectional view of an electromagnetic rotating machine according to the present invention, respectively. Reference numeral 1 is a fixed yoke, and the fixed yoke 1 is provided with an inner yoke 1a and an outer yoke 1b in the radial direction, and an air gap is formed between them. A plurality of pairs of yokes and magnetic gaps are arranged around the rotation axis. In the embodiment, the outer yoke 1b is formed integrally by connecting six portions so that six magnetic gaps are formed, and the inner yokes 1a from above are connected together. The fixed yoke 1 is fixed to the circuit board 4 at the final stage.

First, the fixed bearing 5 is fixed to the circuit board 4 by caulking by the caulking portion 5b of the fluid bearing 5. The circuit board 4 is caulked and fixed by three inner peripheral side protrusions 4a to 4c and the caulking portion 5b of the bearing 5.

After that, a rotor magnet 20 is inserted into the bearing 5 via a flange 6 and fixed to the rotating shaft 3 so as to rotate integrally with the rotating shaft 3. The rotary magnet is magnetized in the circumferential direction corresponding to the inner yoke. Hereinafter, the rotating shaft 3, the flange 6, and the rotor magnet will be referred to as a rotor.

A drive circuit element is also mounted on the rotary substrate 4 (details thereof are omitted), and the rotor 3 is mounted after the bearing 5 is mounted.

The inner yoke 1a of the fixed yoke 1 is provided with a plurality of bobbin coils 17, respectively.
The terminal 17a of the bobbin coil 17 is lightly press-fitted into a.
And 17b are soldered to the flexible printed board 7 for supplying current to the bobbin coil.

After that, the fixed yoke 1 is screwed and fixed to the rotary substrate 4 with screws 8. The flexible printed board 7 is electrically connected to the rotating board. The Hall element that detects the rotation control of the motor is attached to the flexible printed board. Further, it may be attached to the rotating substrate 4.

The operation according to the above configuration is the same as that of the prior art, and therefore detailed description will be omitted.

In the present embodiment, the cogging generated can be controlled by connecting the outer peripheral portions of the outer yoke 1 to each other so as to be integrated.

As shown in FIG. 4, in the conventional example, a rotor magnet 20 sandwiched between a pair of inner and outer yokes 16c and 16b is arranged so that the inner and outer yokes 1a and 1a are arranged from above in the axial direction of the yoke. It was arranged so as to sandwich a magnetic gap in 1b. Therefore, the center of rotation of the rotor magnet 20 is the dynamic pressure generating portion 5a of the bearing 5.
High position against.

However, according to this embodiment, the rotor magnet 20 extends from the flange 6 toward the rotary substrate 4 in the axial direction (thrust direction), is bent and then extends upward, that is, the cross-sectional shape in the rotary axis direction is J. It has a letter shape. Then, the inner yoke 1b of the fixed yoke 1 is configured to be fitted into the recess of the folded portion of the rotary magnet 20 from above. Therefore, the center of gravity of the rotor magnet approaches the dynamic pressure generating portion 5a of the bearing 5, and it becomes possible to configure a rotor having a low center of gravity.

Further, in the structure of this embodiment, since the outer yoke 1b is connected and integrated, the structure is such that foreign matter and the like can be prevented from entering from the outside in the radial direction (radial direction) of the rotating shaft 3, so that the rotor magnet is rotated. It is possible to prevent foreign matter from entering due to some trouble. In addition, even if the rotor magnet is broken during rotation, it is possible to prevent the danger of scattering the fragments of the magnet rotor.

It is also possible to assemble the parts from one direction.

[0027]

As described above, the center of gravity of the rotor magnet can be lowered by adopting the configuration of the present invention. Therefore, the rotation accuracy is improved. In addition, by connecting the outer yoke of the fixed yoke in a circumferential shape and integrating it,
The rigidity of the fixed yoke increases. In addition, foreign matter can be prevented from entering from the outside, and the outer yoke holder, which has been conventionally required, can be eliminated. Therefore, the space in the axial direction is unnecessary, and the size reduction can be achieved. Also, since the assembly direction can be assembled to the rotary substrate from one direction (upper side), the assembly is improved, and the optimum electromagnetic rotary machine can be supplied to the inexpensive polygon scanner motor.

[Brief description of drawings]

FIG. 1 is a perspective view of an electromagnetic rotating machine according to the present invention.

FIG. 2 is a sectional view of an electromagnetic rotating machine according to the present invention.

FIG. 3 is a cross-sectional view of a conventional electromagnetic rotating machine.

FIG. 4 is a perspective view of a conventional electromagnetic rotating machine.

[Explanation of symbols]

1 Fixed yoke 1a Inner yoke 1b Outer yoke 3 Rotating shaft 4 Circuit board 5 Fluid dynamic pressure bearing 5a Dynamic pressure generating portion 6 Flange 7 Flexible printed board 9 Polygon mirror 11 Inside gap 12 formed by outer yoke and rotor magnet of this embodiment Gap formed by yoke and rotor magnet 15 Hall element 16 Fixed yoke 17 of conventional example Bobbin coils 17a and 17b Bobbin terminal 19 Outer yoke retainer 20 Molded rotor magnet 20a Part constituting magnetic circuit

Claims (3)

[Claims] 1. A rotor magnet fixedly coupled to a rotary shaft via a flange and rotating integrally with the rotary shaft, a bearing member for rotatably supporting the rotary shaft, and fixedly coupled to the bearing member. A rotating substrate and a fixed yoke having a coil portion are provided, and the fixed yoke has an inner yoke and an outer yoke which are opposed to each other in a radial direction to form a gap for arranging the rotor magnet, and the inner yoke and the inner yoke. In a brushless electromagnetic rotating machine in which a plurality of yokes are opposed to each other and point-symmetrically around a rotation axis, each of the plurality of outer yokes is integrally formed by being joined in the circumferential direction of the rotation axis. In addition, the electromagnetic rotating machine is characterized in that each inner yoke is formed by connecting the outer yoke and an upper end portion of the outer yoke. 2. The electromagnetic rotating machine according to claim 1, wherein the rotary magnet has a shape that extends from the flange toward the rotary substrate, is folded back, and then extends upward so as to enter the gap. . 3. The fixed yoke is connected to the circuit board at the outer yoke portion.
Electromagnetic rotating machine according to.