JP4422920B2 - Optical deflection scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflection scanning apparatus having a rotary polygon mirror for scanning a laser beam on a photosensitive member in an image forming apparatus using a laser beam.
[0002]
[Prior art]
Conventionally, in an image forming apparatus using a laser beam, an optical deflection scanning apparatus using a dynamic pressure air bearing is used for high speed and high durability. For example, in Japanese Patent Application Laid-Open No. 2000-231072, a permanent magnet is attached to the lower end of the rotating shaft, and another permanent magnet is arranged outside the permanent magnet so as to attract each other. A dynamic pressure air bearing having a configuration to be held has been proposed.
[0003]
FIG. 3 is a cross-sectional view of an optical deflection scanning apparatus using a dynamic pressure air bearing disclosed in Japanese Patent Laid-Open No. 2000-231072.
[0004]
In the optical deflection scanning apparatus shown in FIG. 3, a fixed sleeve 107 made of a ceramic material is fixed to a housing 115 of a drive motor, and a rotary shaft 101 is rotatably fitted and held on the fixed sleeve 107, thereby radial. A hydrodynamic air bearing that is axially supported is formed. A metal member 103 is attached and fixed to the outer periphery of the rotary shaft 101 by shrink fitting. A rotating polygon mirror 102 is attached to the metal member 103, and a rotor 104 constituting a part of the drive motor is fixed to the outer peripheral portion thereof.
[0005]
Furthermore, a stator 106 is attached to a substrate 116 fixed on the housing 115, and a coil 105 is wound around the stator 106, and the stator 106 is disposed so as to face the drive magnet 114, thereby driving motor. The rotating polygon mirror 102 is rotated at a high speed by this drive motor, and the laser beam is scanned.
[0006]
Next, the configuration of the thrust bearing will be described below.
[0007]
A ring-shaped first magnet 108 is fixed to the lower end of the rotating shaft 101 with an ultraviolet curable adhesive. The adhesive effect is enhanced by applying an adhesive to the inside of the ring-shaped first magnet 108. Then, the ring-shaped second magnet 109 is fixed to the lower end portion of the sleeve 107 with an ultraviolet curable adhesive, and the rotary shaft 101 is levitated and supported by the attractive force of both the magnets 108 and 109.
[0008]
[Problems to be solved by the invention]
However, the conventional optical deflection scanning apparatus has the following problems.
[0009]
That is, since the second magnet 109 is fixed by applying an adhesive to the housing 115 , if the applied adhesive is not sufficiently cured, the adhesive flows into the gap between the rotating shaft 101 and the sleeve 107, The rotating shaft 101 and the sleeve 107 are fixed.
[0010]
Further, since the lid 118 for making the lower end of the bearing a sealed space 119 is fixed by applying an adhesive to the lower end of the housing 115, if the adhesive is not sufficiently cured, the adhesive will rotate. 101 flows into the gap between the sleeve 101 and the sleeve 107, and the rotary shaft 101 and the sleeve 107 are fixed. The rotary shaft 101 and the sleeve 107 have a gap of only a few μm. When the adhesive flows into the gap, the rotary shaft 101 is fixed to the sleeve 107, and the rotary shaft 101 stops rotating and functions as an optical deflection scanning device. Will not be fulfilled.
[0011]
Furthermore, the lid 118 cannot be abutted against the second magnet 109 due to the tolerance of the second magnet 109 that is bonded and fixed to the lower end portion of the sleeve 107. For this reason, when the rotating shaft 101 descends, air escapes into the gap between the second magnet 109 and the lid 118, and the pressure in the sealed space 119 does not increase. Therefore, the effect as an air damper is weakened, the rotating shaft 101 also vibrates in response to external vibration and impact, and the rotating polygon mirror 102 attached to the rotating shaft 101 moves up and down to scan the laser beam. This causes a problem of lowering.
[0012]
Accordingly, an object of the present invention is to provide an optical deflection scanning apparatus capable of performing stable scanning while preventing the rotation shaft and the fixed sleeve from sticking.
[0013]
Another object of the present invention is to provide an optical deflection scanning device that is highly reliable with respect to vibration and shock and capable of highly accurate scanning.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is provided on a rotating shaft, a fixing sleeve on the outer periphery of the rotating shaft and rotatably fitting the rotating shaft, and on an outer periphery of the fixing sleeve. A housing for supporting the fixed sleeve; a rotary polygon mirror fixed to the rotary shaft; a first permanent magnet fixed to a lower end portion of the rotary shaft to support the rotary shaft in a floating manner; And a second permanent magnet disposed at a position opposite to the permanent magnet, and a cup-shaped lid to which the second permanent magnet is bonded and fixed. Are fitted and fixed to the outer periphery of the housing to form an air pocket between the fixing sleeve and the lower end of the rotating shaft and the lid .
[0017]
Therefore, according to the first aspect of the invention, since the Ru is prevented from uncured adhesive, it prevents the adhesive in the gap of the fixed sleeve and the rotary shaft flows, a rotary shaft by inflow of the adhesive fixing Stable scanning is possible by preventing the sleeve from sticking.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0021]
FIG. 1 is a cross-sectional view of an optical deflection scanning apparatus according to the present invention.
[0022]
In the optical deflection scanning apparatus according to the present invention, a fixed sleeve 2 made of ceramic or metal is fixed to a housing 1 made of metal such as brass or aluminum, and a rotating shaft 3 is rotatably fitted and held on the fixed sleeve 2. Thus, a dynamic pressure air bearing that supports the rotating shaft 3 in the radial direction is configured.
[0023]
A metal member 4 is attached and fixed to the outer periphery of the rotating shaft 3 by shrink fitting. A rotating polygon mirror 5 is attached to the metal member 4, and a drive motor is attached to the outer periphery of the member 4. A part of the rotor 17 is fixed.
[0024]
Further, a stator 9 is attached to the substrate 7 fixed on the housing 1. A coil 8 is wound around the stator 9, and the stator 9 is disposed so as to face the drive magnet 6, thereby forming a drive motor. The drive motor rotates the rotary polygon mirror 5 at a high speed to perform laser driving. Scan the beam. The drive magnet 6 is a so-called bond magnet formed by mixing a magnetic material such as powdered ferrite or the like with rubber or resin.
[0025]
Next, the configuration of the thrust bearing will be described.
[0026]
The first permanent magnet 13 is bonded and fixed to the lower end portion of the rotary shaft 3, and the first permanent magnet 13 is attracted to the inside of the cup-shaped lid 10 formed by cutting a metal such as brass or aluminum. The two permanent magnets 11 are bonded and fixed with a thermosetting or ultraviolet curable adhesive 12. At this time, ultraviolet rays and heat are sufficiently applied to completely cure the bonded portion of the second permanent magnet 11.
[0027]
Next, heat is applied to the entire cup-shaped lid 10 to completely cure the bonded portion that cannot be visually confirmed.
[0028]
By passing through the above process, the uncured adhesive for bonding the second permanent magnet 11 to the inside of the cup-shaped lid 10 can be prevented. The first permanent magnet 13 and the second permanent magnet 11 are so-called bonded magnets configured by mixing powdered rubber or resin with powdered magnetic material such as ferrite.
[0029]
Next, an anaerobic UV curable adhesive 18 is applied to the outer periphery of the housing 1 to fix the cup-shaped lid 10. When the cup-shaped lid 10 is attached to the housing 1, an anaerobic ultraviolet-curing adhesive 18 protrudes, but ultraviolet rays are sufficiently irradiated to cure the portion. The clearance between the housing 1 and the cup-shaped lid 10 is narrowed so that the anaerobic effect of the adhesive is sufficiently exhibited. Further, by applying a primer to the outer periphery of the housing 1 and the cup-shaped lid 10, the curing of the adhesive for fixing the housing 1 and the cup-shaped lid 10 to the adhesive is ensured.
[0030]
By adopting the configuration as described above, the adhesive 18 is prevented from being uncured, and it is not necessary to apply the adhesive to the lower end portion of the fixed sleeve 2. The inflow does not occur, and the rotation shaft 3 and the fixing sleeve 2 can be prevented from being fixed due to the inflow of the adhesive. That is, do not apply the adhesive at a position close to the gap between the rotary shaft 3 and the fixed sleeve 2, and if the adhesive is used at a position close to the gap between the rotary shaft 3 and the fixed sleeve 2, sufficiently cure This prevents the adhesive from flowing into the gap between the rotary shaft 3 and the fixed sleeve 2 and prevents the rotary shaft 3 and the fixed sleeve 2 from sticking to each other.
[0031]
If the cup-shaped lid 10 is made of the same material as that of the housing 1, the linear expansion coefficient of the cup-shaped lid 10 and the housing 1 becomes the same. The outer diameter of the housing 1 is always constant, and stress does not act on the adhesive existing therebetween, thereby preventing peeling of the adhesive.
[0032]
Furthermore, a closed space 19 is formed at the bottom of the rotating shaft 3 by attaching the cup-shaped lid 10. The closed space 19 can be regarded as a substantially sealed space because the clearance between the rotating shaft 3 and the fixed sleeve 2 is as narrow as several μm.
[0033]
When the cup-shaped lid 10 is attached to the housing 1, the upper end of the second permanent magnet 11 attached to the cup-shaped lid 10 is abutted against the lower end of the housing 1 to attach the second permanent magnet. There is no gap between the magnet 11 and the fixed sleeve 2. As a result, when the rotating shaft 3 is lowered, the pressure in the sealed space 19 is higher than when the rotating shaft 3 is at the same height when there is a gap. This will be described in detail with reference to FIG.
[0034]
2A is an enlarged view of the sealed space 119 of the conventional example, and FIG. 2B is an enlarged cross-sectional view of the sealed space 19 in the present embodiment.
[0035]
Here, the volumes of the sealed spaces 119 and 19 are V and Vi, and the internal pressures are P and Pi, respectively. At this time, the condition is V> Vi (1)
And
[0036]
From the gas equation of state,
P · V = Pi · Vi (2)
It becomes.
[0037]
From Equation (1) and Equation (2),
P <Pi
It becomes.
[0038]
For this reason, since the sealed space 19 effectively functions as a damper against large vibrations, the vertical movement of the rotating shaft 3 is suppressed against large external vibrations and shocks, and the vertical movement of the rotary polygon mirror 5 is also suppressed. High-precision scanning is possible.
[0039]
【The invention's effect】
As apparent from the above description, according to the first aspect of the present invention, since the Ru is prevented from uncured adhesive, it prevents the adhesive from flowing into the gap of the fixed sleeve and the rotary shaft, the adhesive Stable scanning is possible by preventing the rotation shaft and the fixed sleeve from sticking due to the inflow of.
[0040]
According to the second aspect of the present invention, since the linear expansion coefficient of the lid and the housing is the same, the inner diameter of the lid and the outer diameter of the housing are always constant even when the outside air temperature changes, and the adhesive existing therebetween Stress does not act on the agent, and peeling of the adhesive is prevented.
[0041]
According to the third aspect of the present invention, the pressure of the air reservoir is increased so that the air reservoir effectively functions as a damper against large vibrations, and the vertical movement of the rotating shaft is suppressed against large external vibrations and shocks. Therefore, the vertical movement of the rotary polygon mirror is also suppressed, and highly accurate scanning is possible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical deflection scanning apparatus according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a sealed space according to a conventional example and an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a conventional optical deflection scanning apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Fixed sleeve 3 Rotating shaft 5 Rotating polygon mirror 11 2nd permanent magnets 12 and 18 Adhesive 13 1st permanent magnet 19 Sealed space (air pocket)

Claims (3)

A rotating shaft, a fixed sleeve on the outer periphery of the rotating shaft that rotatably fits and holds the rotating shaft, a housing on the outer periphery of the fixed sleeve that supports the fixed sleeve, and fixed to the rotating shaft A rotating polygonal mirror, a first permanent magnet fixed to the lower end of the rotating shaft for levitating and supporting the rotating shaft, and a second permanent magnet disposed at a position facing the first permanent magnet. An optical deflection scanning device having a magnet,
A cup-shaped lid to which the second permanent magnet is bonded and fixed, and the cup-shaped lid is fitted and fixed to the outer peripheral portion of the housing to thereby fix the fixing sleeve and the rotating shaft. An optical deflection scanning device, wherein an air pocket is formed between a lower end portion and the lid.   2. The optical deflection scanning apparatus according to claim 1, wherein the housing and the lid are made of the same material. Optical deflection scanning apparatus according to claim 1 or 2, wherein said second permanent magnet is adhered and fixed to the lid is abutted against the lower end of the fixed sleeve.

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