JP2002341282A - Rotary polygon mirror driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a bearing part by providing a plurality of projection parts in the circumferential direction of the inner circumferential surface of the stator core of a rotary polygon mirror driving device for a polygon scanner and pressing the stator core into a cylindrical projection part erected at the center part of a housing. SOLUTION: The rotary polygon mirror driving device 1 has a housing 3, a rotor 10, and a stator core 24. The housing 3 has the cylindrical projection part erected at its center part, and the inner circumferential surface of the stator core 24 is engaged with the lower outer circumference of the cylindrical projection part. The rotor 10 holds a rotor magnet 15 arranged opposite to the stator core 24, has a polygon mirror 12a on the outer circumferential surface, and rotates in response to the rotating magnetic field product by the stator core 24. The stator core 24 is pressed and fixed into the cylindrical projection part while the projection parts provided in the circumferential direction of the inner circumferential surface of the stator core 24 are in contact with the outer circumferential surface of the cylindrical projection part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary polygon mirror driving apparatus, and more particularly, to a rotary polygon mirror driving apparatus such as a dynamic air bearing type high-speed polygon scanner mounted on a digital copying machine, a laser printer or the like. It concerns the device.

[0002]

2. Description of the Related Art For example, the invention described in Japanese Patent Application Laid-Open No. Hei 9-131032 (rotating polygon mirror driving device) includes a rotor having a rotating shaft and a rotor magnet, and a rotating polygon mirror fixed thereto, and the rotor magnet. And a stator assembly comprising a stator core on which a stator coil and a magnetic body are stacked, which generate electromagnetic torque in opposition to each other, and a stator assembly section composed of an iron-based stator substrate on which a drive IC is mounted. With a configuration in which the bearing to be supported abuts against the stator substrate and is directly shrink-fitted or press-fitted and fixed to the stator core, the heat generated by the bearing and the drive IC are generated by the air cooling effect of the rotating polygon mirror. The object is to improve reliability by radiating heat from the stator core and the stator substrate.

However, the invention described in the above publication is
The document describes only the effect of fixing the stator core with respect to the heat dissipation effect by heat conduction, but does not disclose a specific method of press-fitting the stator core.
Therefore, since the method of press-fitting the core and the shape of the core have not been optimized, there are problems such as influence of distortion on the bearing, vibration, and noise. This is because the press-fitting of the stator core is in fixed contact with the entire circumferential surface. However, it is difficult to maintain the fixing force uniformly on the entire circumferential surface due to variations in assembly at the time of press-fitting. Due to the fact that

[0004]

For example, with a high-speed printing and a high image quality of a digital copying machine, a laser printer, and the like, a polygon scanner to be mounted is required to have 30,000 r.p.m.
High speed rotation exceeding pm is required. In addition, it is indispensable to shorten the start-up time as well as to increase the speed, and a brushless motor having a winding core for easily increasing the start-up torque is used as the drive motor. On the other hand, the brushless motor is formed by laminating magnetic steel sheets, winding a laminated core (hereinafter referred to as a wound core), and fixed to a motor housing. As a method of fixing the winding core, for example, methods such as bonding, caulking, and press-fitting are known, and various methods are disclosed for the purpose of maintaining the fixing force in each method and the material of the fixing portion, improving the thermal conductivity, and the like. I have.

In order to increase the speed of the polygon scanner, a dynamic pressure air bearing is employed from the viewpoint of extending the life.
The use of an adhesive is generally used to fix the winding core, but the steps of coating and heating and curing are complicated and time-consuming.
In addition, there are methods such as press-fitting, but there are problems such as deformation of the dynamic pressure bearing portion, dust generated when parts are rubbed at the time of press-fitting, enters the dynamic pressure bearing, and bearing lock.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned point, and a convex portion is provided on an inner peripheral surface of a stator core of a driving motor section in a rotary polygon mirror driving device such as a high-speed polygon scanner, and the stator core is provided in a housing. The purpose is to improve the reliability of the bearing portion by press-fitting and fixing it to the side, and to realize cost reduction.

[0007]

According to the first aspect of the present invention, there is provided a housing having a cylindrical projection erected at a central portion, a stator core fitted to an outer periphery of a lower portion of the cylindrical projection,
A rotor magnet disposed opposite to the stator core, holding the rotor magnet, and having a polygon mirror on an outer peripheral surface, and magnetically coupled to the cylindrical projection above and inside the cylindrical projection; In the rotary polygon mirror driving device, which comprises a rotor and the rotor rotates in response to a rotating magnetic field generated by the stator core, fixing of the stator core to the cylindrical protrusion is performed in a circumferential direction of an inner peripheral surface of the stator core. Has a plurality of convex portions, and the convex portions are press-fitted and fixed in contact with the outer peripheral surface of the cylindrical projection.

According to a second aspect of the present invention, there is provided a housing having a cylindrical projection standing upright at a center portion, a stator core fitted on an outer periphery of a lower portion of the cylindrical projection, and disposed to face the stator core. And a rotor magnet holding the rotor magnet, having a polygon mirror on the outer peripheral surface, and being magnetically coupled to the cylindrical projection at an upper portion inside the cylindrical projection, generated by the stator core. In the rotary polygon mirror driving device in which the rotor rotates in response to the rotating magnetic field, the fixing of the stator core to the cylindrical protrusion has a plurality of recesses in a circumferential direction of an inner peripheral surface of the stator core, It is characterized by being fixed by inserting a predetermined member between the concave portion and the outer peripheral surface of the cylindrical projection.

According to a third aspect of the present invention, in the first aspect of the present invention, a plurality of convex portions provided on the inner peripheral surface of the stator core have a curved surface at least at the distal end thereof and are arranged at equal intervals in the circumferential direction. It is characterized by being arranged individually.

According to a fourth aspect of the present invention, in the second aspect of the present invention, a plurality of recesses provided on the inner peripheral surface of the stator core are arranged at equal intervals in the circumferential direction, with at least the bottom of the recess being a curved surface. It is characterized by that.

According to a fifth aspect of the present invention, in the first or second aspect of the invention, a magnet for magnetically coupling with the rotor is held on an inner peripheral surface above the cylindrical projection, and a lower portion of the cylindrical projection is provided. It has a fixed shaft fixed to the inner periphery, and the Young's modulus of each member constituting the housing, the stator core, and the fixed shaft has a relationship of fixed shaft> housing and housing <core. It is.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an example of the internal configuration of a rotary polygon mirror driving device to which the present invention is applied. FIG.
1A is a cross-sectional view showing an example of the internal configuration of a dynamic pressure air bearing type polygon scanner. In the figure, reference numeral 1 denotes a dynamic pressure air bearing type polygon scanner. , Drive circuit element 4, rotor 1
0, fixed shaft 20, stator core 24, Hall element 30,
It has a motor substrate 31 and a magnetic body 32. Rotor 10
Has a rotating sleeve 11, a flange 12, a rotating yoke 13 having a projection 13a, an upper plate 14, and a rotor magnet 15. Further, the flange 12 is integrally formed with a polygon mirror 12a on the outer peripheral surface. In addition, the fixed shaft 20
A permanent magnet assembly including a magnet 21 and magnetic plates 21 a and 21 b is arranged, and an air reservoir 22 is formed between the fixed shaft 20 and the rotor 10.

FIG. 1B is a diagram showing an example of the state of the outer peripheral surface of the fixed shaft 20. The outer peripheral surface of the fixed shaft 20 has a dynamic pressure generating groove 23 corresponding to the inner peripheral surface of the rotary sleeve 11. Are formed.

A flange 12 made of an aluminum alloy and having a polygon mirror 12a is shrink-fitted or press-fitted on the outer periphery of a cylindrical rotating sleeve 11 made of ceramic. On the upper part of the rotor 10, a rotating yoke 13 made of a magnetic material constituting a magnetic bearing is fixed to the center of an upper plate 14 made of an aluminum alloy. The upper plate 14 is fixed to the upper part of the flange 12 by press-fitting, shrink-fitting, or bonding, and also has a function of closing the upper end opening of the rotating sleeve 13. A rotor magnet 15 is arranged below the flange 12, and forms an outer rotor type brushless motor together with the stator core 24 facing in the circumferential direction. The fixed shaft 20 constituting the radial dynamic pressure bearing is made of a cylindrical ceramic material similarly to the rotary sleeve 11 described above, and has a herringbone-shaped dynamic pressure generating groove 23 formed on the outer peripheral surface thereof. The clearance of the hydrodynamic bearing formed by the fixed shaft 20 and the inner peripheral surface of the rotary sleeve 11 is several μm.
Are fitted.

A magnet 21 constituting an axial bearing, an upper magnetic plate 21a, a lower magnetic plate 2
1b is disposed. The permanent magnet assembly for a magnetic bearing includes a rotating yoke 13
Has a magnetic gap in the radial direction with the projection 13a of the rotor 10, and supports the rotor 10 in a non-contact manner in the axial direction by using an attractive force acting between the magnetic gaps. Further, a fine hole (not shown) for communicating the air reservoir 22 formed above the fixed shaft 20 with the outside of the rotor 10 by the fixed shaft 20 and the rotor 10 is formed in the rotating yoke 1.
3, or lower closing member (not shown), or upper plate 14
And the like, and is formed on each member forming the air reservoir 22, so that the magnetic bearing has damping characteristics.

The upper and lower portions of the rotor 10 have unbalanced correction portions. On the upper side of the flange 12, an adhesive is applied to a concave portion of the outer peripheral surface of the flange 12 or a part thereof is cut off. An adhesive is applied to the inner peripheral surface of the flange 12 or the rotor magnet 15, or a part of the outer peripheral surface or the lower end surface of the flange 12 is cut off. In order to reduce the vibration at the time of high-speed rotation, the unbalance amount of each of the above portions is kept at 1 mg or less.
The rotor 10 is substantially sealed by the motor housing 3 and the upper cover 2 so as to cover the rotor 10.

When driving the motor, the magnetic field of the rotor magnet 15 causes the Hall element 3 mounted on the motor substrate 31 to be driven.
With reference to the signal output from 0 as a position signal, the drive circuit element 4 switches the excitation of the stator winding and rotates. Here, the rotor magnet 15 is magnetized in the radial direction, and generates rotation torque between the outer circumferences of the stator core 24 to rotate. The rotor magnet 15 in this example is a plastic magnet, and has a structure in which the outer periphery is held by the flange 12 so that destruction by centrifugal force during high-speed rotation does not occur. A metal magnet having a centrifugal proof strength may be used, but it is easy to reduce the wall thickness, and a plastic magnet is preferable if it has an outer diameter holding mechanism.

Further, the rotor magnet 15 has a magnetic path open in the outer diameter and the height direction other than the inner diameter, and the Hall element 30 for switching the excitation of the motor is arranged in the open magnetic path. The magnetic body 32 has a function of shielding magnetic flux leaking from the rotor magnet 15 and prevents eddy current from flowing through the motor housing 3. The reason why the open magnetic path is adopted is that a magnetic body must be provided on the outer diameter of the rotor magnet 15 in order to form a closed magnetic path, the number of parts increases, and the unbalance change increases. 1
In the case where a magnetic body is disposed at the outer diameter of the Hall element 5, the Hall element 3 is used to prevent the magnetic flux of the rotor magnet 15 from leaking in the outer diameter direction.
0 has to be arranged on the inner periphery of the rotor magnet 15 (between the stator core 24 and the rotor magnet 15).

Another problem with high-speed polygon scanners having a speed of 30,000 rpm or more is to reduce the start-up time. A large current flows at the start-up, and the magnetic field of the stator core 24 causes the Hall element 30 to malfunction, resulting in a start-up failure. In view of the above, it is appropriate to use an open magnetic path.

(Embodiment 1) FIG. 2 is a cross-sectional view of HH 'shown in FIG.
FIG. 13 is a cross-sectional view showing an example of a fixed state of the stator core 24 and the motor housing 3 in a radial direction in a cross section.
Is a gap between the stator core 24 and the motor housing 3. The stator core 24 shown in this embodiment has a convex portion 24a on the inner peripheral portion. Here, the winding and the fixed shaft are not shown. The inner peripheral portion of the stator core 24 has a convex portion 24a toward the center.
a is pressed into the outer peripheral portion of the motor housing 3,
The stator core 24 is fixed.

As shown in FIG. 2, it is desirable that a plurality of the protrusions 24a of the stator core 24 be arranged at equal intervals. If they are not singular or at equal intervals, the center axis is likely to shift during press-fitting, and the fixing force varies, making it difficult to perform stable fixing. Further, the shape of the convex portion 24a is more preferably a shape having a rounded tip. For example, if the tip is not round but square, the edge of the square edge is likely to wear out in the die for press punching of the stator core, making it difficult to maintain high precision of the die.

Here, in the conventional method, since the protrusion is not provided and the entire circumference is fitted, the dimensional control of the parts is strict,
Further, even when the parts are strictly controlled, it is not possible to determine where on the circumference the fitting contact will occur due to variations in the roundness of each part, and distortion of the motor housing 3 will occur in various states. In addition, non-contact points due to variations in roundness are likely to be formed, and thus stable fixing cannot be performed. For example, a core generated when exciting a winding coil,
There was a problem of increasing magnetic noise such as coil vibration noise.

On the other hand, when the press-fit portion is loosened at a low temperature, the gap 3 between the stator core 24 and the motor housing 3 is reduced.
By applying an adhesive to 3, it is possible to prevent a decrease in fixing force. Here, when the adhesive is applied to the gap 33, it is not necessary to apply the adhesive over the entire circumference because press-in is dominant, and application at a plurality of locations is sufficient.

(Embodiment 2) FIG. 3 is a cross-sectional view showing another example of the fixed state of the stator core 24 and the motor housing 3 in the radial direction shown in FIG. 2, in which 40 is a fixing pin. . The stator core 24 shown in the present embodiment has a concave portion 24b on the inner peripheral portion, and the fixing pin 40 is press-fitted into a gap formed by the concave portion 24b and the concave portion 3b provided on the outer peripheral portion of the motor housing 3. The stator core 24 is fixed. As shown in FIG. 3, it is preferable that a plurality of recesses 24 b of the stator core 24 are equally distributed and arranged, and the fixing pins 40 are press-fitted at a plurality of locations simultaneously. In the case of singular or non-equal distribution, or in the case of press-fitting the fixing pins 40 one by one, the center axis is likely to shift, and the fixing force varies, making it difficult to stably fix. Furthermore, as for the shape of the concave portions 24b and 3b, a shape having a round bottom is more preferable as shown in FIG. When the bottom is square, the edge of the square edge is likely to be worn in a press stamping die for core production, making it difficult to maintain high accuracy of the die.

FIG. 4 is a view showing an example of the shape of the fixing pin 40. 4 (A) is a straight parallel pin, FIG. 4 (B) is a spring pin that generates a restoring force in the outer diameter direction after press-fitting, and FIG. 4 (C) is an axially tapered pin. An example is shown. Among these, the tapered pin shown in FIG. 4C is the most suitable, and has an effect of suppressing the decrease in fixing force as much as possible even if there is a temperature change. Further, by providing knurled irregularities on the outer diameter of the fixing pin 40, there is an effect of further improving the fixing force of the stator core 24.

Although there is no problem in the above fixation even when the outer periphery of the motor housing 3 is a continuous circle and there is no recess 3b, the circumferential positioning of the stator core 24 can be performed by providing the recess 3b at a suitable position in advance. It becomes possible. If the positions of the stator core 24 and the Hall element 30 deviate from the proper positions, it will lead to poor starting and reduced efficiency, so positioning is important.

A problem common to the embodiments shown in FIGS. 2 and 3 is that, when the stator core 24 is press-fitted, the motor housing 3 on the press-fitted side is fixed in the radial direction, that is, as shown in FIG. Distortion is generated on the shaft side. However, since the material of the fixed shaft 20 is ceramic, it has a higher Young's modulus than the aluminum alloy of the motor housing 3 and is less susceptible to press-fit distortion, and does not deteriorate the accuracy of the fixed shaft 20. The materials and Young's modulus used in Examples 1 and 2 are shown below.・ Stator core: Magnetic steel plate (Young's modulus 2.0 × 10
4kg / mm2) ・ Motor housing: Aluminum alloy (Young's modulus 0.7 × 1)
・ 04kg / mm2) ・ Fixed shaft: Ceramic (Young's modulus 3.5 × 1)
04 kg / mm2) Here, the Young's modulus is defined as fixed shaft> motor housing,
In addition, since the relation of motor housing <stator core is satisfied, distortion at the time of press-fitting from stator core 24 is absorbed by motor housing 3 and transmission to fixed shaft 20 can be minimized.

In the above description, the motor type has been described as the outer rotor type. However, the same effect can be obtained with the inner rotor type with respect to the method of fixing the core.
Also, the motor housing does not necessarily need to have a shape surrounding the rotor, and the same effect can be obtained if the place where the bearing component and the stator core are fixed is the same as described above.

[0029]

According to the first aspect of the present invention, a stable fixing force can be obtained by providing a convex portion on the fitting surface of the inner circumferential side of the stator core with the housing and press-fitting and fixing the stator core to the housing side. , It can be realized with simple steps.

According to the second aspect of the present invention, a recess is provided in the fitting surface of the inner periphery of the stator core with the housing, and the stator core is fixed to the housing by press-fitting a fixing pin into the recess. Rubbing dust and the like generated between the parts does not occur outside the stator core, and it is possible to prevent dust and the like from entering the bearing.

According to the third aspect of the present invention, the tips of the protrusions provided on the inner peripheral surface of the stator core are formed in an arc shape and are arranged at equal intervals in the circumferential direction, thereby positioning and fixing the stator core in the rotational direction. And start-up failure and reduction in motor efficiency can be prevented.

According to the fourth aspect of the present invention, the bottom of the concave portion provided on the inner peripheral surface of the stator core is formed in an arc shape, and a plurality of the concave portions are arranged at equal intervals in the circumferential direction, thereby positioning and fixing the stator core in the rotational direction. As a result, it is possible to prevent starting failure and reduction in motor efficiency.

According to the fifth aspect of the invention, the Young's modulus of each member constituting the fixed shaft, the stator core, and the housing is determined by:
By setting the relationship of fixed shaft> housing and housing <stator core, the housing absorbs the distortion from the stator core during press-fitting, and the transmission of the distortion to the fixed shaft can be minimized. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an internal configuration of a rotary polygon mirror driving device to which the present invention is applied.

FIG. 2 is a sectional view showing an example of a fixed state of a stator core and a motor housing in a radial direction in a section taken along line HH ′ shown in FIG. 1;

FIG. 3 is a cross-sectional view showing another example of a fixed state of the radial direction stator core and the motor housing shown in FIG. 2;

FIG. 4 is a view showing an example of the shape of a fixing pin.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Dynamic pressure air bearing type polygon scanner, 2 ... Top cover, 3 ... Motor housing, 4 ... Drive circuit element, 10 ...
Rotor, 11 ... rotating sleeve, 12 ... flange, 13 ...
Rotating yoke, 14 upper plate, 15 rotor magnet, 20 fixed shaft, 21 magnet, 22 air reservoir, 23 dynamic pressure generating groove, 24 stator core, 30 Hall element, 31 motor board, 32 Magnetic material, 33: gap, 40: fixing pin.

Continued on the front page F term (reference) 2C362 BA08 BA09 BA10 2H045 AA14 AA15 AA62 5H605 AA05 BB05 BB14 CC03 CC04 CC10 DD03 DD09 EA06 EB06

Claims (5)

[Claims] 1. A housing having a cylindrical projection erected at the center, a stator core fitted on the outer periphery of a lower part of the cylindrical projection, and a rotor magnet arranged to face the stator core. A rotor that holds the rotor magnet, has a polygon mirror on the outer peripheral surface, and is magnetically coupled to the cylindrical protrusion above and below the cylindrical protrusion; and a rotating magnetic field generated by the stator core. In the rotary polygon mirror driving device in which the rotor rotates correspondingly, fixing of the stator core to the cylindrical protrusion has a plurality of protrusions in a circumferential direction of an inner peripheral surface of the stator core, and the protrusions are A rotary polygon mirror driving device, wherein the driving device is press-fitted and fixed in contact with the outer peripheral surface of the cylindrical projection. 2. A housing having a cylindrical projection erected at the center, a stator core fitted on the outer periphery of a lower portion of the cylindrical projection, and a rotor magnet arranged to face the stator core. A rotor that holds the rotor magnet, has a polygon mirror on the outer peripheral surface, and is magnetically coupled to the cylindrical protrusion at an upper portion of the inside of the cylindrical protrusion; and a rotating magnetic field generated by the stator core. In the rotary polygon mirror driving device in which the rotor rotates correspondingly, fixing of the stator core to the cylindrical projection has a plurality of recesses in a circumferential direction of an inner peripheral surface of the stator core, and the recess and the cylinder A rotary polygon mirror driving device, wherein a fixed member is fixed by inserting a predetermined member between the driving member and the outer peripheral surface of the projection. 3. A plurality of protrusions provided on an inner peripheral surface of the stator core, wherein at least a tip of the protrusion has a curved surface and a plurality of protrusions are arranged at equal intervals in a circumferential direction. 3. The rotary polygon mirror driving device according to claim 1. 4. A plurality of concave portions provided on the inner peripheral surface of the stator core, wherein at least a bottom portion of the concave portion has a curved surface and a plurality of concave portions are arranged at equal intervals in a circumferential direction.
3. The rotary polygon mirror driving device according to claim 1. 5. A housing for holding a magnet for magnetic coupling with the rotor above the cylindrical projection on an inner peripheral surface thereof, having a fixed shaft fixed to an inner periphery below the cylindrical projection. The Young's modulus of each member forming the stator core and the fixed shaft is such that the fixed shaft> housing and the housing <
3. The rotary polygon mirror drive device according to claim 1, wherein the rotary polygon mirror drive device has a core relationship.