JP2003098455A - Optical scanner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in image quality caused by the influence of diffused light from a light source or the temperature rise of a deflector. SOLUTION: This optical scanner is provided with a light shielding wall 73 formed of ribs arranged nearly radially on the outer wall of the motor housing 59 of the deflector 42 deflecting light from the light source 40 so as to scan a photoreceptor 18. The wall 73 prevents the diffused light emitted from the light source 40 from being made incident on the photoreceptor 18 and is used also as the cooling blade of the deflector 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary drive device for rotating a polygon mirror or the like for scanning a light beam for forming an image on a photoconductor in an electrophotographic copying machine or printer, and manufacturing of the rotary body. The present invention relates to a method and a polygon mirror scanner device.

[0002]

2. Description of the Related Art In order to achieve high-speed printing and high definition of an image to be formed by an electrophotographic digital copying machine, a light beam for forming an image is scanned on a medium to be scanned such as a photoconductor. The polygon mirror is rotated at a very high speed of 40,000 rpm or more with high precision to deflect the light and write on the medium to be scanned. This writing unit is shown in FIG.
As shown in, the light emitted from the light source 40 passes through the imaging optical system 80, is reflected by the folding mirror 81, and is deflected by the deflector 82.
Incident on. The deflector 82 has a polygon mirror 83,
The incident light flux is deflected at a constant angular velocity. The light L deflected by the deflector 82 passes through the fθ lens group 43 and the long lens 44 to form an image spot on the medium 84 to be scanned. This imaging spot scans the medium 84 to be scanned by the rotation of the deflector 82.

The light source 40 of this writing unit is, for example, as shown in the perspective view of FIG. 8, four light emitting points 402, 403, 404 and 405 attached to a radiator 401 and light emitting points 402 to 405. A photodiode 406 for monitoring the output is provided in the laser chip case 407 and emits light corresponding to four channels,
The light emitted from the laser window 408 to the front side is emitted to the deflector 82 to realize high-speed printing and high definition of image quality in a digital copying machine or the like. Further, the light emitted from the rear side is monitored for light emission output by a photodiode 406 for output monitoring.

The light striking the photodiode 406 of this light source is reflected by the surface of the photodiode 406, becomes diffused light in the laser chip case, passes through the laser window, and as shown in FIG. The light becomes G, and the light may be reflected in the optical housing of the writing unit and reach the surface to be scanned of the medium to be scanned 84, causing an abnormal image. The photodiodes are arranged so that the flare light G does not pass near the regular scanning light L.

[0005]

However, since the flare light G is not deflected by the deflector 82, the flare light G continuously hits the same position P on the medium to be scanned 84, and its energy is accumulated on the medium to be scanned even if it is a small amount of light. As a result, the amount of energy is sufficient to form an image, and the image appears as an abnormal image.

Further, the deflector 82 has a motor section for deflecting the polygon mirror 83, a bearing section and a drive control circuit, and rotates the polygon mirror 83 at a high speed. By increasing the number of rotations, the optical scanning speed also increases and high-speed optical scanning becomes possible. However, when rotating at a high speed of 40,000 rpm or more, noise is generated by the wind noise of the polygon mirror 83 and the temperature of the deflector rises, so that the fθ lens group 43 and the like in the vicinity are also affected by the temperature and rise in temperature. In particular, a plastic lens causes a serious problem that the refractive index and the like change to cause an abnormal image on the surface to be scanned. Further, due to this temperature rise, the balance of the rotating bodies such as the polygon mirror and the motor is largely changed, the vibration is increased, and the noise of the main body such as the copying machine is generated. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical scanning device and an image forming apparatus which improve such disadvantages, prevent image quality deterioration due to influence of diffused light from a light source and temperature rise of a deflector, and realize low noise. It is what

[0008]

An optical scanning device according to the present invention deflects light emitted from a light source having a semiconductor laser element by a deflector having a polygon mirror held by a rotation driving means and a dynamic pressure bearing, In an optical scanning device that forms a deflected light beam as a light spot on a surface to be scanned, a light blocking wall that blocks diffused light from the light source is provided between the light source and the deflector, and the diffused light emitted from the light source is a photoconductor or the like. It is possible to prevent an abnormal image from being incident on the surface to be scanned.

The light-shielding wall is formed by ribs provided substantially radially with respect to the rotation center of the polygon mirror on the outer wall of the housing that houses the polygon mirror held by the rotary driving means of the deflector and the dynamic pressure bearing. The diffused light emitted from the device is prevented from entering the surface to be scanned such as the photoconductor and used as a cooling blade of the deflector.

Further, the light-shielding wall is formed by a part of the housing that houses the light source and the deflector to prevent diffused light emitted from the light source from entering the surface to be scanned such as the photosensitive member and the housing. It is used as a temperature transfer medium to suppress the temperature rise of the deflector.

Further, the surface of the light shielding wall is subjected to a light absorption treatment, for example, black to prevent stray light reflected from the light shielding wall.

The image forming apparatus of the present invention uses the above optical scanning device to prevent the diffused light emitted from the light source from being incident on the surface to be scanned such as the photosensitive member to form an abnormal image, and to provide a high quality image. To form stably.

[0013]

1 is a block diagram of a digital copying machine according to the present invention. As shown in the figure, the digital copying machine 1 has a copying machine main body 2, an automatic document feeder (hereinafter referred to as ADF) 3, and an automatic sorting device 4. The copying machine main body 2 has a document reading unit 5, a writing unit 6, an engine unit 7, and a paper feeding unit 8. The document reading unit 5 includes a carriage 9 having a light source and a plurality of mirrors, a lens 10 and a CC.
It has a D11 and a buffer 12, and scans and reads the document sent by the ADF3. The writing unit 6 emits a laser beam 13 containing image information to the engine unit 7. The engine unit 7 includes an image forming unit 14, a primary transfer unit 15, and a secondary transfer unit 16 as shown in the configuration diagram of FIG.
And a fixing unit 17. Image forming unit 14
Is a charging charger 19 arranged around the photoconductor 18.
And an irradiation section of the laser beam 13 from the writing unit 5, a rotary color developing section 20 made of cyan (C), magenta (M), yellow (Y), and black (K), and a drum cleaning section 21. An electrostatic latent image is formed by the laser beam 13 on the photoconductor 18 charged by the charging charger 19, and the formed electrostatic latent image is visualized by the color developing unit 20 to form a toner image. The primary transfer unit 15 has an intermediate transfer belt 22, a primary transfer section 23, a tension roller 24, a secondary transfer roller 25, a cleaning section 26, and a reference position sensor 27, and intermediates the toner image formed on the photoconductor 18. The primary transfer is performed on the transfer belt 22. Intermediate transfer belt 2
2 is formed larger than A3 which is the maximum transfer paper size in the digital copying machine 1, and when the transfer paper used is A4 size or smaller, it is possible to hold toner images for two surfaces. The intermediate transfer belt 22 is separated from the surface of the photosensitive member 18 by a contacting / separating mechanism (not shown) except when the toner image on the photosensitive member 18 is primarily transferred, and the photosensitive member 18 is only transferred when the image is primarily transferred to the intermediate transfer belt 22. Pressed against the surface. The secondary transfer unit 16 secondarily transfers the toner image transferred onto the intermediate transfer belt 22 onto a recording sheet. The fixing unit 17 fixes the toner image transferred onto the recording paper with heat and pressure. The paper feeding unit 8 includes a plurality of paper feeding cassettes 2.
8a to 28c, a manual tray 29, and a registration rotor 30a
And conveyance rollers 30b to 30d and jam sensors 31a to 3a
1d, the recording paper is sent to the secondary transfer unit 16. A
The DF 3 sends the document to be read to the document reading unit 5, and collects the document read by the document reading unit 5. The automatic sorting device 4 has a plurality of sorting bins and sorts and discharges the recording paper on which the image is formed.

As shown in the configuration diagram of FIG. 3, the writing unit 6 has a light source 40, a mirror 41, a deflector 42, an fθ lens group 43 and an elongated lens 44. The deflector 42 is provided in an optical housing 45. It is fixed with screws. And light source 4
The light emitted from 0 is reflected by the mirror 41 and is deflected by the deflector 42.
Is incident on the photosensitive member 18 through the fθ lens group 43 and the long lens 44.
An imaging spot is formed at.

As shown in the sectional view of FIG. 4, the deflector 42 has a rotary body 51, a fixed portion 52, and a drive rotary substrate 53. The rotating body 51 has a rotating sleeve 54, a flange 55, a rotor magnet 56, a rotating yoke 57, and a closing member 59. The rotary sleeve 54 is made of a ceramic material and has a cylindrical shape. The flange 55 is made of aluminum alloy,
The cylindrical portion 551 fixed to the rotating sleeve 54 and the cylindrical portion 5
A polygon mirror portion 5 formed of a regular polygon on the outer periphery of 51
52 and a rotor magnet fixing portion 5 formed in a cylindrical shape with a diameter larger than that of the cylindrical portion 551 at the lower end portion of the cylindrical portion 551.
53, and a circumferential groove 554 formed on the upper surface between the cylindrical portion 551 and the polygon mirror portion 552. The cylindrical portion 551 of the flange 55 is fixed to the rotary sleeve 54 by shrink fitting or press fitting to be integrated. The rotor magnet 56 is a bond magnet using a resin such as nylon or epoxy as a binder, and a neodymium-based, samarium-cobalt-based rare earth or ferrite-based magnet material is used. The bond magnet forming the rotor magnet 56 is formed so as to have a thermal expansion coefficient equal to or larger than that of the aluminum alloy forming the flange 55. And the rotor magnet 5
6 is press-fitted and fixed to the inner peripheral surface of the rotor magnet fixing portion 553 of the flange 55. The rotating yoke 57 is made of a magnetic material, and has protrusions 571 provided at a lower portion thereof at regular intervals to form a magnetic bearing. An upper end of the rotating yoke 57 is a disc-shaped closing member made of aluminum alloy. It is fixed to the center of 58. The closing member 58 is a cylindrical portion 55 of the flange 55.
The upper end of the rotary sleeve 54 is fixed to the upper end of the rotary sleeve 54 by shrink fitting or adhesion, and the open upper end of the rotary sleeve 54 is closed. The circumferential groove 554 provided on the flange 55 is attached to the rotary sleeve 54 by a closing member 58.
To prevent stress strain on the polygon mirror portion 552 when fixing the blades or accompanying temperature rise during use.

The fixed portion 52 has a motor housing 59, a fixed shaft portion 60, a magnetic bearing permanent magnet assembly 61, a lower closing member 62, and a stator core 63. A fixed shaft portion 60 is fixed to the motor housing 59. The fixed shaft portion 60 constitutes a radial dynamic pressure bearing of the rotating body 51, is formed of a ceramic material in a cylindrical shape, and has a herringbone dynamic pressure generating groove 601 formed on the outer peripheral surface thereof. The dynamic pressure bearing gap formed between the surface and the inner peripheral surface of the rotary sleeve 54 is formed to be several μm, and the rotary sleeve 54 is fitted therein. The magnetic bearing permanent magnet assembly 61 includes a cylindrical magnet 64 and a magnetic plate 65 provided above and below the magnet 64, and the magnetic plate 64 is the rotating yoke 5.
7 is fixed to the inner peripheral surface of the fixed shaft portion 60 so as to have a constant gap facing the protrusion 571 of the magnetic disk 65 and the magnetic gap between the magnetic plate 65 and the protrusion 571 of the rotary yoke 57. The rotor 51 is supported in the axial direction in a non-contact manner. The lower closing member 62 is the inner peripheral surface of the fixed shaft portion 60,
It is fixed to the lower portion of the magnetic bearing permanent magnet assembly 61, and forms an air reservoir 66 between the fixed shaft portion 60 and the rotating body 51. A fine hole for communicating the air reservoir 66 with the outside of the rotating body 51 is provided in either the rotating yoke 57, the closing member 58, or the lower closing member 62 forming the air reservoir 66, and is used for the rotating yoke 57 and the magnetic bearing. The magnetic bearing formed by the permanent magnet assembly 61 has damping characteristics. The stator core 63 is provided in the motor housing 59 so as to face the rotor magnet 56, and the stator core 63 and the rotor magnet 56 constitute an outer rotor type brushless motor. Further, an upper cover 67 is attached to an upper end portion of the motor housing 59 to substantially seal the rotating body 51 to prevent dust from entering the portion of the rotating body 51 and to rotate the rotating body 51 at a high speed. The wind noise of the polygon mirror section 552 is prevented. Further, the motor housing 59 and the upper cover 67 are formed of a metal material such as an aluminum alloy so that the temperature rise due to the heat generated by the rotation of the rotating body 51 can be quickly transmitted to the optical housing 45.

A drive circuit having a plurality of rotation drive elements 68 is provided on the drive rotation substrate 53, and the motor housing 5 is provided.
It is attached to the lower surface of 9. This drive rotation board 53
The drive circuit of the motor housing 59 through the conductive portion 69.
It is connected to the Hall element 71 of the motor substrate 70 provided inside. The magnetic flux leaking from the rotor magnet 56 is shielded between the motor housing 59 and the motor board 70.
The motor housing 59 has a magnetic body 72 for preventing an eddy current from flowing.

When the rotating body 51 is rotated by the deflector 42 configured as described above, the signal output from the Hall element 71 mounted on the motor substrate 70 by the magnetic field of the rotor magnet 56 is referred to as a position signal. Drive rotation board 5
The drive circuit of 3 switches the excitation of the stator winding to rotate. Here, the rotor magnets 56 are magnetized in the radial direction, and generate rotating torque with the outer circumference of the stator core 63 to rotate the rotating body 51.

In order to reduce the vibration when the rotating body 51 is rotated at a high speed, the balance of the rotating body 51 is corrected. For example, in order to realize low vibration when rotating the rotating body 51 at a high speed of 40,000 rpm or more, the unbalance amount of the rotating body 51 needs to be 10 mg · mm or less. Must achieve 1 mg or less. The balance correction points are two points in the axial direction of the upper part and the lower part of the rotating body 51, and it is desirable to arrange the upper and lower two positions with the center of gravity of the rotating body 51 interposed therebetween. As described above, in order to correct a minute amount of 1 mg or less, it is difficult to control with an adherent such as an adhesive, and when an adhesive or the like is used, the adhesive strength is weak because the amount is small, For example, it peels off and scatters at a high speed of 40,000 rpm or more. Therefore, when the balance of the rotating body 51 is corrected, a part of the components forming the rotating body 51 is deleted by cutting with a drill or laser processing, so that high speed rotation can be stably supported.

On the outer peripheral surface of the motor housing 59 of the deflector 42, as shown in FIG. 3, a plurality of radially arranged rib-shaped light shielding walls 73 are provided. The light-blocking wall 73 is, for example, as shown in the perspective view of FIG.
From 405 to output monitor photodiode 406
The flare light G which is incident on and reflected on the surface to become diffused light is shielded. Since the flare light G is shielded by the light shielding wall 73 in this manner, it is possible to prevent the flare light G from entering the photoconductor 18 for writing an image, and it is possible to stably form a high-quality image.

Further, since the motor housing 59 having the light shielding wall 73 is made of aluminum alloy, the heat dissipation is good and the light shielding wall 73 can be integrally formed by die casting, so that the light shielding wall 73 can be formed at a low cost. Further, by performing black alumite treatment on the surfaces of the motor housing 59 and the light shielding wall 73, the surface area can be increased, further heat dissipation can be improved, and the optical reflectance can be lowered, so that the flare light G can be prevented. At 73, it is possible to prevent stray light after reflection. In addition, the light shielding wall 73 is attached to the motor housing 59.
By forming a rib extending radially on the outer wall of
It can act as a heat radiation fin, and the heat radiation effect of the motor housing 59 can be improved. Therefore, the temperature rise of the deflector 42 can be suppressed, and an inexpensive plastic lens can be used as the fθ lens group 43 and the long lens 44.

In the above description, the case where the light shielding wall 73 for shielding the flare light G is radially provided on the outer wall of the motor housing 59 has been described. However, as shown in the sectional view of FIG. It may be provided on the upper lid 46. In this case, the light shielding wall 73 can be integrally formed by forming the upper lid 46 by aluminum die casting. Further, the temperature inside the optical housing 45 can be absorbed by the light shielding wall 73 and radiated from the upper lid 46, and the temperature rise inside the optical housing 45 can be further suppressed.

Further, as shown in the sectional view of FIG. 6, the light shielding wall 73 may be provided on the upper cover 67 of the deflector 42. When the upper cover 67 is formed of a thin metal plate material,
By forming the light shielding wall 73 by bending, the upper cover 67 and the light shielding wall 73 can be integrally formed at low cost. Further, when the alumite treatment is performed as the surface treatment, the parts are small in size, so that the surface treatment can be performed in a short time using a small surface treatment device, and the productivity can be improved.

[0024]

As described above, according to the present invention, the light shielding wall for shielding the diffused light from the light source is provided between the light source and the deflector, and the diffused light emitted from the light source is on the surface to be scanned such as the photoconductor. Since the incident light is prevented, it is possible to prevent the abnormal image from being formed by the diffused light emitted from the light source.

Further, the light shielding wall is formed by ribs provided substantially radially with respect to the rotation center of the polygon mirror on the outer wall of the housing which houses the polygon mirror held by the rotation driving means of the deflector and the dynamic pressure bearing. As a result, the diffused light emitted from the light source can be prevented from entering the surface to be scanned such as the photoconductor and can be used as the cooling blade of the deflector, and the temperature rise of the deflector can be suppressed.

Further, the light shielding wall is formed by a part of the housing containing the light source and the deflector, so that the diffused light emitted from the light source is prevented from entering the surface to be scanned such as the photosensitive member. It can be used as a temperature transfer medium for the housing to suppress the temperature rise of the deflector.

Further, stray light reflected from the light-shielding wall can be prevented by applying light absorption treatment to the surface of the light-shielding wall, for example, blackening.

Further, by using this optical scanning device in an image forming apparatus, it is possible to prevent diffused light emitted from a light source from entering a surface to be scanned such as a photosensitive member to form an abnormal image.
A high-quality image can be stably formed.

[Brief description of drawings]

FIG. 1 is a block diagram of a digital copying machine of the present invention.

FIG. 2 is a configuration diagram of an engine unit of a digital copying machine.

FIG. 3 is a plan view showing a configuration of a writing unit.

FIG. 4 is a cross-sectional view showing a configuration of a deflector.

FIG. 5 is a cross-sectional view showing a configuration of a writing unit in which a light shielding wall is provided on an upper lid of an optical housing.

FIG. 6 is a cross-sectional view showing a configuration of a writing unit in which a light shielding wall is provided on an upper cover of a deflector.

FIG. 7 is a configuration diagram of a conventional optical scanning device.

FIG. 8 is a perspective view showing a configuration of a light source of the optical scanning device.

[Explanation of symbols]

1; digital copier, 2; copier body, 3; ADF,
4; automatic sorting device, 5; original reading unit, 6; writing unit, 7; engine section, 8; paper feeding unit, 40;
Light source, 42; Deflector, 43; fθ lens group, 44; Long lens, 45; Optical housing, 51; Rotating body, 52;
Fixed part, 53; drive rotating substrate, 552; polygon mirror part, 59; motor housing, 67; upper cover, 73;
Shading wall.

Continued front page    F-term (reference) 2C362 AA03 BA04 DA27                 2H042 AA09 AA15 AA29                 2H045 AA01 AA33 BA23 BA32 CB63

Claims (5)

[Claims] 1. A light emitted from a light source having a semiconductor laser element is deflected by a deflector having a polygon mirror held by a rotation driving means and a dynamic pressure bearing, and the deflected light beam is formed as a light spot on a surface to be scanned. In the optical scanning device for forming an image, an optical scanning device is characterized in that a light shielding wall for shielding diffused light from the light source is provided between the light source and the deflector. 2. The light shielding wall is formed by a rib provided substantially radially with respect to a rotation center of the polygon mirror on an outer wall of a housing which houses a polygon mirror held by a rotation driving means of a deflector and a dynamic pressure bearing. The optical scanning device according to claim 1. 3. The optical scanning device according to claim 1, wherein the light-shielding wall is formed by a part of a housing that houses a light source and a deflector. 4. The optical scanning device according to claim 1, wherein the surface of the light shielding wall is subjected to light absorption processing. 5. An image forming apparatus comprising the optical scanning device according to claim 1.