JP2002034194A - Rotating body fitting base - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation of the reference surface of a fitting base for assembling a rotating polygon mirror. SOLUTION: The rotating polygon mirror 1 is pushed with an elastic mechanism 6 to a base surface 4c of the fitting base 4 and is coupled integrally with a rotor 5 of a motor. In the process for depositing a rotating shaft 2 which is supported to rotate with radial bearings 3a to an engaging hole 4a of the fitting base 4 by the methods such as shrinkage fit and pressurized insertion, an escaping route by a pair of large diametric portions 4e, 4f is provided at the upper and lower portions of the center portion 4d for tightening fit of an engaging hole 4a in order to prevent deformation of the fitting base 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating body mounting base for fixing a rotating body such as a rotary polygon mirror of a deflection scanning device used in an image forming apparatus such as a laser beam printer to a rotating shaft.

[0002]

2. Description of the Related Art FIG. 9 shows a main part of a conventional deflection scanning apparatus. This comprises a rotating polygon mirror 101 having a plurality of reflecting surfaces 101a and a rotating shaft 1 rotating integrally therewith.
02, a radial bearing 103 for rotatably supporting the rotating shaft 102, and the like. A mounting pedestal 104 made of a metal such as aluminum or brass is fixed to the upper portion of the rotating shaft 102 by shrink fitting or press-fitting, and a rotor 105 including a yoke 105a and a rotor magnet 105b is mounted on the outer periphery of the mounting pedestal 104. Is fixed. The rotating polygon mirror 101 on the mounting base 104 is pressed by an elastic pressing mechanism 106 including a leaf spring 106a, a washer 106b, and a C-ring 106c, and is integrated with the rotating shaft 102.

[0003] On a substrate 107 fixed on a bearing housing of the radial bearing 103, a coil 108a and a core 1 are mounted.
The stator 108 including the coil 08b is disposed so as to face the rotor 105, and the two constitute a driving motor.

The mounting pedestal 104 of the rotary polygon mirror 101 is fixed to the rotary shaft 102 by shrink-fitting or press-fitting.
02 is a tight fit of several μm to several tens μm of interference, and after the shrink fitting or press fitting, the mounting base 104 is fitted.
Easily deformed.

When such deformation exceeds the allowable value, it is difficult for the reflecting surface 101a of the rotating polygon mirror 101 attached thereto to be parallel to the rotating shaft 102.

Incidentally, the deflection scanning device is a rotary polygon mirror 10 for rotating a light beam generated from a semiconductor laser at a high speed.
The light is irradiated on the first reflection surface 101a, and the reflected light passes through a toric lens or the like, and scans the surface of the photosensitive drum to form an image. Current laser beam printers and digital copiers that use this as the heart part have increased the resolution to 1200 dpi or 2400 dpi or more in order to improve the image quality, and a rotating polygonal surface that greatly affects the irradiation position of the light beam. The mirror 101 is required to be assembled with very high accuracy.

A particularly important mounting portion of the mounting pedestal 104 for mounting the rotary polygon mirror 101 to the rotary shaft 102 is a fitting surface 104b with which the inner wall of the center hole 101b of the rotary polygon mirror 101 contacts, and a mounting surface of the rotary polygon mirror 101. A seating surface 10 that contacts the lower surface of the rotating polygon mirror 101 to determine the vertical position.
4c and the like, and these dimensions are strictly controlled.

[0008] Such important attachment parts 104b, 10b
4c deforms beyond the design tolerance, the rotating polygon mirror 10
1 is decentered, the reflecting surface 101a is tilted, or the rotational balance is changed. Each of these causes a shift of the irradiation position of the light beam on the photosensitive drum surface,
This is an issue that we want to solve in order to realize a high-quality laser beam printer and digital copier.

Therefore, in the prior art, as a measure for preventing deformation due to shrink-fitting or press-fitting of the mounting pedestal to the rotary shaft, the interference (particularly, the value of the fitting hole diameter of the mounting pedestal is subtracted from the value of the rotary shaft at room temperature). Value) is designed to be as large as a maximum of tens of μm, and after shrink-fitting or press-fitting, the inclination and distortion of the reference surface of the mounting portion of the mounting base are corrected by cutting to keep it within the design tolerance. Was.

In another method, the inner diameter accuracy of the fitting hole of the mounting base and the outer diameter accuracy of the rotary shaft are strictly designed and processed.
By keeping the interference as small as several μm at the maximum,
Even if the mounting pedestal is deformed after shrink-fitting or press-fitting, the degree of deformation itself is reduced so that the dimensional accuracy of the mounting portion falls within the design allowable value.

[0011]

As described above, in order to solve the problem of the deformation of the mounting pedestal when the mounting pedestal of the rotary polygon mirror is shrink-fitted or press-fitted to the rotary shaft, the prior art shrink-fits and press-fits. This has been achieved by a method of keeping the dimensions of the mounting portion within the design tolerance by a later cutting process, or a method of increasing the accuracy of the inner diameter of the fitting hole of the mounting base and the accuracy of the outer diameter of the rotating shaft.

[0012] However, with respect to a method of making the error of the reference plane within a design allowable value by cutting, the number of steps increases because of the presence of a cutting step and a setup step therefor. There is a problem to be solved.

Further, the method of processing the fitting hole and the rotating shaft of the mounting pedestal with high precision has a problem that the cost is naturally increased due to the high precision processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and has a step of fixing a mounting base for supporting a rotating body such as a rotary polygon mirror to a rotating shaft by shrink fitting or press fitting. An object of the present invention is to provide a rotating body mounting pedestal that reduces the deformation of the mounting pedestal caused by the above, and does not cause the mounting accuracy and rotation balance of a rotating body such as a rotating polygon mirror to be significantly deteriorated by the deformation of the mounting pedestal. It is.

[0015]

In order to achieve the above object, a rotating body mounting pedestal according to the present invention has a supporting surface for supporting a rotating body, a reference surface for positioning the rotating body, and a rotating shaft. A main body having a fitting hole that fits into the main body, the fitting hole being fixed to the rotating shaft by tight fitting, and a pair of large holes that are opened on the upper surface and the lower surface of the main body with the center portion interposed therebetween. It has a diameter part.

An annular groove may be provided instead of at least one of the large diameter portions.

Preferably, the rotating body is a rotary polygon mirror of the deflection scanning device.

[0018]

When the seating surface or reference surface of the rotator mounting pedestal supporting the rotator such as a rotating polygon mirror is deformed in an assembling process such as shrink-fitting or press-fitting which fixes the rotator mounting pedestal to the rotating shaft, the rotating polygon mirror is used. Of the reflecting surface may be caused, or the rotational balance may be deteriorated. In order to avoid this, a pair of large-diameter portions are provided on the upper and lower surfaces of the main body so as to sandwich a center portion of the fitting hole fixed to the rotating shaft by tight fitting.

Since the mounting pedestal can be easily prevented from being deformed in the assembling process with respect to the rotating shaft, it is possible to contribute to the improvement of the optical performance and the cost reduction of the deflection scanning device.

[0020]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment, which comprises a rotating polygon mirror 1 which is a rotating body having a plurality of reflecting surfaces 1a, a rotating shaft 2 rotating integrally therewith, and a rotating shaft 2 And a thrust bearing 3b for rotatably supporting the bearing. A mounting base 4 made of metal such as aluminum or brass having a fitting hole 4a is fixed to the upper part of the rotating shaft 2 by shrink fitting or press-fitting, and a yoke 5a and a rotor are mounted on the outer periphery of the mounting base 4. A rotor 5 composed of a magnet 5b is fixed. The rotating polygon mirror 1 on the mounting base 4 is pressed by an elastic pressing mechanism 6 including a leaf spring 6a, a washer 6b, and a C-ring 6c, and is integrated with the rotating shaft 2.

On a substrate 7 fixed on the bearing housing of the radial bearing 3a, a stator 8 including a coil 8a and a core 8b is disposed so as to face the rotor 5, and a driving motor is constituted by both. I have.

In the mounting pedestal 4 for assembling the rotary polygon mirror 1, particularly important mounting portions are a fitting surface 4 b, which is a reference surface with which the inner wall of the center hole 1 b of the rotary polygon mirror 1 contacts, and a mounting surface of the rotary polygon mirror 1. The seat surface 4c is a support surface that is in contact with the lower surface of the rotary polygon mirror 1 to determine the vertical position, and these dimensions are strictly controlled.

When such important attachment portions 4b and 4c are deformed beyond the design allowance, the rotary polygon mirror 1 is decentered, falls down, and the rotational balance changes. Any of these causes a shift of the irradiation position of the light beam on the photosensitive surface.

Therefore, in the present embodiment, at the upper and lower ends of the center portion 4d of the fitting hole 4a formed by tight fitting of the mounting pedestal 4, relief is provided by a pair of large diameter portions 4e, 4f that do not contact the rotating shaft 2. Thus, the structure is such that no distortion is generated in the fitting surface 4b and the seat surface 4c, which are the contact portions between the rotary polygon mirror 1 and the mounting base 4.

For example, as shown in FIG.
The dimension of the fitting surface 4b, which is the contact portion between the
0 mm ± 2.5 μm, the runout accuracy of the bearing surface 4 c is 3.5 μm, and the outer diameter of the rotating shaft 2 is 2.998 mm ±.
0.5 μm, and the inner diameter of the center part 4d is 2.9865.
When the rotation shaft 2 and the mounting pedestal 4 are tightly fitted to each other at 7.5 to 15.5 μm with ± 3.5 μm, particularly between the large-diameter portion 4 e above the mounting pedestal 4 and the rotation shaft 2. , About 1 mm in width and about 2 mm in depth.

Although the fitting dimension is ± 2.5 μm and the runout accuracy is 3.5 μm, it is sufficient that the deformation of the fitting surface due to shrink fitting is 2.5 μm or the runout is within 3.5 μm. Not something. This includes the machining accuracy by cutting when creating the mounting pedestal. For example, if the fitting surface is ± 2.5 μm becomes 1.5 μm due to shrink fitting, the machining accuracy by cutting is ± 1.5
It must be within μm. That is, the smaller the deformation of the fitting surface and the bearing surface due to shrink fitting, the better.

Instead of the large-diameter portions 4e and 4f opening at the upper and lower ends shown in FIG. 1, instead of the large-diameter portion 14e above the mounting base 14 and the lower surface of the main body, as shown in FIG. A combination of open annular grooves 14f may be used. Alternatively, as shown in FIG. 3B, a pair of annular grooves 24e and 24f opened on the upper and lower surfaces of the main body of the mounting base 24 may be used.

Next, when the mounting pedestal is shrink-fitted to the rotating shaft using the rotating shaft manufactured with the dimensions shown in FIG. 2 and the mounting pedestal, that is, when the mounting pedestal is provided with a relief portion with a large diameter portion or a groove. And a fitting hole 3 having no relief as shown in FIG.
The results of measuring the deformation of the mounting base 34 having 4a due to shrink fitting are shown in the graphs of FIGS.

In the graph of FIG.
b, the amount of radial displacement of deformation due to shrink fitting of 34b,
The unit is μm, the vertical axis represents the position from the lower end of the fitting surface, and the unit is mm. For the fitting surfaces 4b and 34b, the maximum value of the radial displacement of the deformation due to shrink fitting was used as the evaluation value.

FIG. 6 shows deformation of the seating surfaces 4c and 34c.
In the graph, the vertical axis represents the amount of displacement of the seat surfaces 4c and 34c when the upper surface direction of the mounting base is positive, in units of μm, and the horizontal axis represents the position of the seat surface in the radial direction of the upper surface of the seat in units of mm.

Since the bearing surface has a runout accuracy, the difference between the maximum value and the minimum value of the vertical displacement of the bearing surface was used as the evaluation value. FIG.
6 and FIG. 6 show the measurement results when the interference between the fitting hole of the mounting base and the outer diameter of the rotating shaft is 16 μm, which is larger than the maximum value of 15.5 μm.

There is a great difference especially in the fitting surface between the case where the relief portion is formed by the groove or the large diameter portion and the case where the relief portion is not provided. When no relief is provided, the maximum value of the deformation of the fitting surface is 2.40.
2 μm, which exceeds the design tolerance of ± 2.5 μm.
Neither can the precision of the cutting be included.

On the other hand, when the relief portion is provided, the maximum value of the deformation of the fitting surface is 1.238 μm, which is within the allowable design value, and the precision of the cutting process can be 1.5 μm or more. Become.

On the other hand, the allowable value of the seating surface is 3.5 μm, whereas the allowable value is 0.130 μm when the relief portion is not provided and 0.067 μm when the relief portion is provided. On the other hand, it is a sufficiently small deformation.

The shrink-fitting of the rotary shaft to the mounting base is performed using a shrink-fitting device as shown in FIG. 300 to 350 ° C. in the mounting base positioning table D with the embedded heater
The brass mounting pedestal 4 heated to a temperature causes thermal expansion. In such a heated state, the rotating shaft 2 gripped by the robot hand R is inserted into the fitting hole 4a of the mounting base 4 as the robot hand R descends. The inserted rotating shaft 2 of stainless steel is heated by the mounting base 4 and the heater, and is fixed to the mounting base 4 by thermal expansion. afterwards,
The mounting pedestal 4 fixed to the rotating shaft 2 is cooled.

In this embodiment, the rotary polygon mirror of the deflection scanning device has been described as a rotary body. However, the present invention is not limited to the rotary polygon mirror, but may be applied to a rotary body such as a hard disk rotary device or a CD rotary device. Applicable. Further, a cylindrical sleeve that rotates around a fixed shaft may be used instead of the rotating shaft.

According to the present embodiment, after fixing the mounting base to the rotating shaft, the mounting base is cut or the outer diameter of the rotating shaft and the inner diameter of the mounting base before fixing are processed with high precision. Since there is no need, the manufacturing cost of the deflection scanning device and the like can be significantly reduced.

That is, high quality laser beam printers and digital copiers which do not cause problems such as eccentricity, tilting of the rotary polygon mirror, change in rotational balance, and the like, and have no image quality deterioration due to a shift of the laser irradiation position on the rotating drum. Can be produced at low cost.

FIG. 8 shows the entire deflection scanning apparatus, which is a light source 9 for generating a light beam (light flux) such as a laser beam.
1 and a cylindrical lens 91a for linearly condensing the laser beam on the reflecting surface 1a of the rotary polygon mirror 1, and deflects and scans the light beam by rotation of the rotary polygon mirror 1.
An imaging lens system 92 serving as an imaging optical system and a return mirror 9
The image is formed on the image forming surface of the photoreceptor on the rotating drum D through the step 3. The imaging lens system 92 includes a spherical lens 92a, a toric lens 92b, and the like, and has a so-called fθ function for correcting a scanning speed of a point image formed on the photoconductor.

When the rotary polygon mirror 1 is rotated by the motor, its reflection surface 1a rotates at a constant speed around the axis of the rotary polygon mirror 1. Generated from the light source 91 as described above,
The angle between the optical path of the light beam condensed by the cylindrical lens 91a and the normal to the reflecting surface 1a of the rotating polygon mirror 1, that is, the angle of incidence of the light beam on the reflecting surface 1a, changes with time as the rotating polygon mirror 1 rotates. And the reflection angle also changes, so that the point image formed by condensing the light beam on the photoconductor is in the axial direction of the rotating drum D (main scanning direction).
(Scan).

The imaging lens system 92 focuses the light beam reflected by the rotary polygon mirror 1 on a photosensitive member into a point image having a predetermined spot shape, and controls the scanning speed of the point image in the main scanning direction. It is designed to keep constant speed.

The point image formed on the photoreceptor is formed by the main scanning by the rotation of the rotary polygon mirror 1 and the sub-scanning by the rotation of the rotating drum D having the photoreceptor around its axis. Form an image.

A charging device for uniformly charging the surface of the photoreceptor, a developing device for visualizing an electrostatic latent image formed on the surface of the photoreceptor into a toner image, Transfer device for transferring the toner image onto recording paper (both not shown)
And the like are arranged, and recording information by a light beam generated from the light source 91 is printed on recording paper or the like.

The detection mirror 94 reflects the light beam on the upstream side in the main scanning direction with respect to the optical path of the light beam incident on the recording information writing start position on the surface of the photosensitive member.
The light is introduced to the light receiving surface of a light receiving element 96 having a photodiode or the like via a condenser lens 95. The light receiving element 96 outputs a scan start signal for detecting a scan start position (write start position) when the light receiving surface is irradiated with the light beam.

The light source 91 generates a light beam corresponding to a signal given from a processing circuit for processing information from the host computer. The signal given to the light source 91 corresponds to information to be written on the photoconductor, and the processing circuit generates a signal representing information corresponding to one scanning line which is a locus formed by a point image formed on the surface of the photoconductor. Light source 91 as one unit
Give to. This information signal is transmitted in synchronization with a scanning start signal given from the light receiving element 96.

The rotating polygon mirror 1, the imaging lens system 92 and the like are housed in an optical box 90, and the light source 91 and the like are mounted on the side wall of the optical box 90. After assembling the rotary polygon mirror 1 and the imaging lens system 92 into the optical box 90, a lid (not shown) is attached to an upper opening of the optical box 90.

[0048]

Since the present invention is configured as described above, the following effects can be obtained.

The deflection scanning device can easily and effectively avoid the distortion of the mounting base body which occurs in the step of fixing the mounting base supporting the rotating body such as the rotary polygon mirror to the rotating shaft by shrink fitting or press fitting. Can contribute to the improvement of optical performance and cost reduction.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of a deflection scanning device according to an embodiment.

FIG. 2 is a diagram illustrating a specific example.

FIG. 3 is a diagram showing two modified examples.

FIG. 4 is a diagram showing a comparative example.

FIG. 5 is a graph showing a measurement result obtained by measuring a deformation of a fitting surface of a mounting base.

FIG. 6 is a graph showing measurement results obtained by measuring the deformation of the seat surface of the mounting base.

FIG. 7 is a view for explaining a shrink-fitting step between the mounting base and the rotary shaft.

FIG. 8 is a diagram illustrating the entire deflection scanning device.

FIG. 9 is a schematic sectional view showing one conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotating polygon mirror 1a reflecting surface 2 rotating shaft 3a radial bearing 3b thrust bearing 4,14,24 mounting pedestal 4a fitting hole 4b fitting surface 4c seating surface 4d central portion 4e, 4f, 14e large diameter portion 5 rotor 8 stator 14f , 24e, 24f Groove

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H02K 21/22 B41J 3/00 DF term (reference) 2C362 BA11 BA12 2H045 AA07 AA14 5H605 AA04 AA08 BB05 BB10 BB14 BB19 CC01 CC02 DD05 DD09 EA02 EA19 GG04 5H607 AA11 AA12 BB01 BB07 BB14 BB17 BB25 CC01 CC05 CC09 DD01 DD03 DD08 DD09 DD14 FF01 GG01 GG02 JJ06 5H621 BB07 GA01 GA04 HH01 JK01 JK08 JK13 JK19

Claims (3)

[Claims] 1. A body having a support surface for supporting a rotating body, a reference surface for positioning the rotating body, and a fitting hole fitted on a rotating shaft, wherein the fitting hole is A rotating body mounting pedestal comprising: a central portion fixedly fitted to a rotating shaft by a close fit; and a pair of large-diameter portions opened on the upper and lower surfaces of the main body with the central portion interposed therebetween. 2. The rotator mounting base according to claim 1, wherein an annular groove is provided instead of at least one of the large-diameter portions. 3. The rotator mounting base according to claim 1, wherein the rotator is a rotary polygon mirror of a deflection scanning device.