JPH10333073A - Deflecting scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a bearing rotating and supporting a rotary polygon mirror and to easily execute balance correction. SOLUTION: A rotary polygon mirror 1 is coupled to the upper end part of a rotary shaft 3 by an elastic pressing mechanism 8 and a rotor magnet 5 is fixed to the lower end part of the rotary shaft 3. Then, the intermediate part of the shaft 3 is supported by a sleeve 2 being a dynamic pressure bearing. Since the bearing is disposed between the mirror 1 and the magnet 5, the load of the bearing is reduced by supporting the centroid position of a rotor R including both of the mirror 1 and the magnet 5. Moreover, the balance correction that a weight is attached to balance grooves 10a and 10b is also easily executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device used for an image forming apparatus such as a laser beam printer and a laser facsimile.

[0002]

2. Description of the Related Art A deflection scanning device used in an image forming apparatus such as a laser beam printer or a laser facsimile deflects and scans a light beam such as a laser beam by a rotating polygon mirror rotating at a high speed, and converts the obtained scanning light into a rotating drum. An electrostatic latent image is formed by forming an image on the upper photosensitive member. Next, the electrostatic latent image on the photoreceptor is visualized into a toner image by a developing device, transferred to a recording medium such as recording paper, sent to a fixing device, and printed by heating and fixing the toner on the recording medium ( Print) is performed.

In recent years, the speed of the deflection scanning device has been increased, and a rotating polygon mirror having a rotation speed exceeding 10,000 rpm has been developed.

FIG. 5 shows a main part of a deflection scanning apparatus according to a conventional example, which comprises a rotary shaft 103 supported on an optical box 100 via a bearing 102 such as a ball bearing.
And a yoke 105a and a rotor magnet 10 integrally connected to a washer 104 integrated with the rotating shaft 103.
5 and a stator coil 107 fixed to a motor substrate 106 integral with the bearing housing 102a. The rotating polygon mirror 101 includes a holding spring 108a and a spring holding 10
8b, elastic pressing mechanism 108 including G ring 108c, etc.
Is pressed by the washer 104, and is integrated with the rotating shaft 103 and the rotor magnet 105 via the washer 104.

When the stator coil 107 is excited by a drive current supplied from a drive circuit on the motor substrate 106, the rotor magnet 105 rotates at a high speed together with the rotary polygon mirror 101, and as described above, the rotary polygon mirror 101
Is deflected and scanned by the light beam applied to the.

When the rotary polygon mirror 101 is rotated at a high speed, a dynamic imbalance occurs due to an imbalance in the mass of the entire rotating body including the rotary polygon mirror 101, the rotor magnet 105, the yoke 105a, the washer 104, the elastic pressing mechanism 108, and the like. Is generated, and due to whirling vibration caused by this,
The image quality of the image forming apparatus may be degraded. Therefore,
Balance grooves 109a and 109b are formed on the upper surface of the rotating polygon mirror 101 and the upper surface of the yoke 105a of the rotor magnet 105.
And a weight 110 or the like is adhered thereto to reduce the imbalance of the mass of the rotating body.

The weight 110 is obtained by mixing metal particles, glass beads, or the like with a light-curing adhesive such as an ultraviolet-curing type.
9b is mounted on an appropriate portion, and is cured by irradiating light such as ultraviolet rays, and is adhered to the rotating polygon mirror 101 and the yoke 105a.

[0008]

However, according to the above prior art, the lower half of the rotary shaft is supported by the bearing, and both the rotary polygon mirror and the rotor magnet are assembled to the upper half of the rotary shaft. The bearings support the rotating body, including the rotating polygon mirror and the rotor magnet, at locations distant from the center of gravity of the rotating body, so that the rotating polygon mirror is liable to generate whirling vibration and the like, and a large load is applied to the bearing. Therefore, there is an unsolved problem that the life of the bearing is short.

Further, when performing balance correction for preventing vibration using a balance groove such as a rotary polygon mirror or a yoke of a rotor magnet, dynamic imbalance in the circumferential direction of a rotating body including a rotating shaft is reduced. And circumferential balance correction for
Since it is necessary to perform the axial balance correction individually to reduce the axial dynamic imbalance of the rotating body, the number of steps for the balance correction is large, which increases the assembly cost of the apparatus. Results.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unresolved problems of the prior art, and supports the position of the center of gravity of the entire rotating body including a rotating shaft and a rotating polygon mirror with a dynamic pressure bearing or the like. It is an object of the present invention to provide a deflection scanning device capable of improving the rotation performance of a rotary polygon mirror and greatly simplifying a balance correction process.

[0011]

In order to achieve the above object, a deflection scanning apparatus according to the present invention comprises: a rotating polygon mirror for reflecting a light beam; a rotating shaft integrally connected to the rotating polygon mirror; A motor having a rotor integral with a rotating shaft and a stator opposed thereto, and bearing means for supporting the rotating shaft between the rotating polygon mirror and the rotor are provided.

The bearing means may be a dynamic pressure bearing.

[0013] The bearing means may be a ball bearing.

The rotary shaft may be provided with a step, and the rotary polygon mirror may be directly supported on the step.

[0015]

Since bearing means for rotatingly supporting a rotating shaft integral with the rotating polygon mirror and the rotor are provided,
The rotating polygon mirror and the rotor can be stably supported, and the load on the bearing means can be greatly reduced. As a result, the rotation performance of the rotary polygon mirror can be improved, and the life of the bearing means can be greatly extended.

Since the rotating polygon mirror and the rotor are largely separated from each other with the bearing portion interposed therebetween, if the rotating polygon mirror and the rotor are provided with respective balance grooves, it is extremely easy to correct the balance to prevent vibration of the rotating polygon mirror. Thus, the balance correction in the circumferential direction and the balance correction in the axial direction can be performed simultaneously. This simplifies the balance correction process,
The number of assembly steps of the deflection scanning device can be greatly reduced, and the assembly cost can be reduced.

Further, by providing a step on the rotary shaft and directly supporting the rotary polygon mirror on the step, the number of assembly parts of the apparatus can be reduced. Thereby, the cost reduction of the deflection scanning device can be further promoted.

[0018]

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

FIG. 1 is a schematic sectional view showing a main part of a deflection scanning apparatus according to an embodiment, which comprises a rotary polygon mirror 1 having a plurality of reflecting surfaces on a polygonal columnar side surface, and an optical box described later. A sleeve 2 which is a bearing means (dynamic pressure bearing) supported by a bearing housing 2a integral with the rotary shaft 50, a rotary shaft 3 rotatably supported by the sleeve 2, and a washer 4 fixed to the rotary shaft 3. And a rotor magnet 5 that is a rotor integrally coupled to the lower end of the rotating shaft 3, and a stator coil 7 that is a stator fixed to a motor substrate 6 that is integral with the bearing housing 2 a. Constitutes a motor for rotating the rotary polygon mirror 1 together with the rotor magnet 5. The rotary polygon mirror 1 is pressed against the washer 4 by the elastic pressing mechanism 8 and is integrated with the rotating shaft 3 via the washer 4.

When the stator coil 7 is excited by a drive current supplied from a drive circuit on the motor substrate 6, the rotor magnet 5 rotates together with the rotating shaft 3 and the rotating polygon mirror 1, and the rotating magnet 3 The light beam such as the irradiated laser beam is deflected and scanned.

The washer 4 is made of a metal such as aluminum or brass, and the rotor magnet 5 is a plastic magnet. The sleeve 2 is made of a material having excellent wear resistance, such as a ceramic material, and is fixed to a bracket 2b made of aluminum, brass, plastic, or the like by shrink fitting or bonding. The bracket 2b is fixed to the bearing housing 2a by shrink fitting, bonding, screwing, or the like.

The rotating shaft 3 protrudes from the upper and lower ends of the sleeve 2. A rotating polygon mirror 1 is mounted on the upper end of the rotating shaft 3 via a washer 4, and the lower end of the rotating shaft 3 is shrink-fitted. The rotor magnet 5 is fixed by a method such as bonding or screwing. The washer 4 is fixed to the rotating shaft 3 by shrink-fitting, bonding, or the like, and the rotating polygon mirror 1 includes a pressing spring 8a.
Pressing mechanism 8 consisting of spring presser 8b and G ring 8c
And is integrally pressed with the washer 4.

The sleeve 2 constitutes a radial dynamic pressure bearing that supports the rotating shaft 3 in a non-contact manner by an air film formed between the sleeve 2 and the sleeve 2. Also, the first end of the sleeve 2
Is fixed, and faces the second magnet 9b fixed to the lower surface of the washer 4. The first and second magnets 9a and 9b constitute a thrust bearing that stabilizes the axial position (height direction) of the washer 4 and the rotary polygon mirror 1 by an axial biasing force generated between the first and second magnets 9a and 9b. .

When the rotary polygon mirror 1 is rotated at a high speed, a whirling vibration or the like is generated due to a dynamic imbalance of the rotating body R including the rotary polygon mirror 1, the washer 4, the rotor magnet 5, and the like.
For this reason, the image quality of the image forming apparatus may be degraded. Therefore, the upper surface of the rotary polygon mirror 1 and the rotor magnet 5
Annular balance grooves 10 extending in the circumferential direction on the lower surface of the
a, 10b are provided, and a weight is adhered to them to reduce the imbalance of the mass of the rotating body R. The weight is obtained by mixing metal particles, glass beads, or the like into a light-curing adhesive such as an ultraviolet-curing type. The rotating polygon mirror 1 is rotated to measure whirling vibration and the like, and the weight is determined based on the measured value. Select the weight and mounting position of each weight.

According to the present embodiment, the rotary polygon mirror and the rotor magnet are connected to both ends of the rotary shaft, and the central portion therebetween is supported by the dynamic pressure bearing constituted by the sleeve. The dynamic pressure of the dynamic pressure bearing can be configured to act on the position of the center of gravity of the entire rotating body including the rotating polygon mirror, the rotating shaft, and the rotor magnet. Thus, by supporting the position of the center of gravity of the rotating body by the non-contact dynamic pressure bearing, the load on the bearing can be reduced, the rotational performance can be improved, and the life of the bearing can be greatly extended.

When the balance is corrected to prevent the vibration of the rotary polygon mirror, the rotary polygon mirror and the rotor magnet are disposed at both ends of the rotary shaft. If the balance grooves are provided, the axial balance correction and the circumferential balance correction of the rotating body can be performed simultaneously and extremely easily.
By simplifying the number of assembling steps of the apparatus in this way, the cost of assembling the deflection scanning device can be greatly reduced.

As a result, high performance and suitable for high speed
In addition, it is possible to realize a deflection scanning device that requires a long bearing life and low manufacturing cost.

FIG. 2 shows a first modification. In this embodiment, a step 13a is provided at the upper end of the rotating shaft 13, and the rotary polygon mirror 1 is directly supported on the step 13a, thereby omitting the washer 4 of the apparatus shown in FIG.

There is an advantage that the manufacturing cost of the deflection scanning device can be further reduced by reducing the number of assembly parts.

FIG. 3 shows a second modification. This is shown in FIG.
Ball 22a, 22b instead of the sleeve 2 of the device
Using a ball bearing 22 that supports a rotating shaft 23.

The bearing means for supporting the rotating shaft is not limited to the above-described dynamic pressure bearing or ball bearing, but may be another type of bearing.

FIG. 4 shows the entire deflection scanning device, which comprises a light source 51 for generating a light beam such as a laser beam and a cylindrical beam for condensing the laser beam linearly on the reflection surface of the rotary polygon mirror 1. A lens 51a for deflecting and scanning the light beam by the rotation of the rotary polygon mirror 1;
2 and the photoreceptor 5 on the rotating drum via the mirror 53
4 is imaged. The imaging lens 52 is a spherical lens unit 52
a, a toric lens unit 52b, etc., and a so-called fθ function for correcting the scanning speed and the like of a point image formed on the photoconductor 54.

When the rotary polygon mirror 1 is rotated by the motor, its reflecting surface rotates at a constant speed around the axis of the rotary polygon mirror 1 as shown by an arrow A. As described above, the light source 51
The angle formed by the optical path of the light beam generated by the cylindrical lens 51a and the normal to the reflecting surface of the rotating polygon mirror 1, that is, the angle of incidence of the light beam on the reflecting surface is determined by the rotation of the rotating polygon mirror 1. And the reflection angle also changes with time, so that the point image formed by condensing the light beam on the photoconductor 54 moves in the direction indicated by the arrow Y (main scanning direction).

The imaging lens 52 condenses the light beam (scanning light) reflected by the rotary polygon mirror 1 on the photosensitive member 54 into a point image having a predetermined spot shape, and also moves the point image in the main scanning direction. Is a complex lens designed to keep the scanning speed of the lens at a constant speed.

The point image formed on the photoreceptor 54 is electrostatically generated by the main scanning by the rotation of the rotary polygon mirror 1 and the sub-scanning by the rotation of the rotating drum having the photoreceptor 54 about its axis. Form a latent image.

A corona discharge device for uniformly charging the surface of the photoreceptor 54 is provided around the photoreceptor 54, and an electrostatic latent image formed on the surface of the photoreceptor 54 is visualized as a toner image. And a transfer corona discharger (both not shown) for transferring the toner image to a recording paper or the like, and recording information by a light beam generated from the light source 51 is printed on the recording paper or the like. .

The detection mirror 55 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 writing start position Y ₁ of the recording information on the photosensitive member 54.
The light is introduced to the light receiving surface of a light receiving element 56b having a photodiode or the like via a condenser lens 56a. Light receiving element 56b
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 condenser lens 56a and the light receiving element 56b are disposed between the imaging lens 52 and the rotary polygon mirror 1, and the detection mirror 55 reflects the light beam below the scanning surface of the scanning light.

The light source 51 generates a light beam corresponding to a signal supplied from a processing circuit 57 for processing information from a host computer. The signal given to the light source 51 is
The processing circuit 57 corresponds to information to be written to the photoconductor 54, and the processing circuit 57 uses the signal representing the information corresponding to one scanning line, which is a locus formed by a point image formed on the surface of the photoconductor 54, as one unit, Give to. This information signal is transmitted in synchronization with a scanning start signal given from the light receiving element 56b through the line 56c.

The rotary polygon mirror 1, the imaging lens 52 and the like are housed in an optical box 50, and the light source 51 and the like are mounted on the side wall of the optical box 50. After assembling the rotary polygon mirror 1 and the imaging lens 52 into the optical box 50, a lid (not shown) is attached to the upper opening of the optical box 50.

[0041]

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

It is very easy to correct the balance to prevent vibration of the rotating polygon mirror, and the assembly cost is low. In addition, it can greatly contribute to extending the life of the bearing and improving the rotational performance.

As a result, an inexpensive deflection scanning device which is high in performance and suitable for high speed operation can be realized. By mounting such a deflection scanning device, it is possible to greatly contribute to higher performance and lower cost of the image forming apparatus.

[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 schematic sectional view showing a first modification.

FIG. 3 is a schematic sectional view showing a second modification.

FIG. 4 is a diagram illustrating the entire deflection scanning device.

FIG. 5 is a schematic cross-sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating polygon mirror 2 Sleeve 3, 13, 23 Rotation axis 5 Rotor magnet 7 Stator coil 10a, 10b Balance groove 22 Ball bearing

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyuki Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Taku Fukita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Akihiro Fukutomi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] A motor having a rotating polygon mirror for reflecting a light beam, a rotating shaft integrally coupled to the rotating polygon mirror, a rotor integrated with the rotating shaft, and a stator opposed thereto; A deflection scanning device having bearing means for supporting the rotating shaft between the rotating polygon mirror and the rotor. 2. The deflection scanning device according to claim 1, wherein the bearing means is a dynamic pressure bearing. 3. The deflection scanning device according to claim 1, wherein the bearing means is a ball bearing. 4. The deflection scanning device according to claim 1, wherein a step is provided on the rotating shaft, and a rotary polygon mirror is directly mounted on the step. 5. The rotating polygon mirror and the rotor are provided with respective balance grooves.
The deflection scanning device according to claim 1.