JP2005202039A - Scanning optical device - Google Patents

Abstract

To provide an inexpensive scanning optical device free from image defects due to displacement of an aperture stop caused by tilting of an inclined pin during molding of an optical box.
An optical box as a housing, a multi-beam light source unit that emits a plurality of laser light beams, a rotary polygon mirror that deflects laser light emitted by the multi-beam light source unit, and a rotary drive of the rotary polygon mirror Motor, a cylindrical lens that forms an image of the laser beam emitted from the multi-beam light source unit on the reflecting surface of the rotary polygon mirror, and is formed integrally with the optical box and disposed between the cylindrical lens and the rotary polygon mirror. In a scanning optical device having an aperture stop and an imaging optical system for condensing the laser beam deflected and scanned by the rotary polygon mirror on the surface to be scanned, a hole is provided in the bottom surface of the optical box near the aperture stop. It is characterized by being.
[Selection] Figure 1

Description

  The present invention relates to a scanning optical device used in an image forming apparatus such as a laser printer or a laser facsimile.

  A scanning optical device used in an image forming apparatus such as a laser beam printer reflects a light beam such as a laser beam by a rotating polygon mirror that rotates at high speed, deflects and scans the light beam, and the obtained scanning light is sensitized on a rotating drum. An electrostatic latent image is formed by forming an image on the body. Next, the electrostatic latent image on the photosensitive member is visualized as a toner image by a developing device, transferred to a recording medium such as recording paper, sent to a fixing device, and the toner on the recording medium is heated and fixed to perform printing. Done.

  In recent years, in order to cope with an increase in the speed of an image forming apparatus, the recording speed has been increased by using a multi-beam scanning optical apparatus that simultaneously writes a plurality of light beams.

  Conventionally, for example, as proposed in Patent Document 1, an aperture stop is provided in the vicinity of the rotating polygon mirror, and the displacement of the imaging position for each light emitting point due to focus fluctuation is reduced without increasing the size of the rotating polygon mirror. It is done. That is, the closer the aperture stop is to the rotary polygon mirror, the more effective it is.

  In order to provide a multi-beam scanning optical apparatus having an aperture stop arranged with high accuracy at a low cost, a multi-beam scanning optical apparatus as disclosed in Patent Document 2 has been proposed. That is, the aperture stop is formed integrally with the optical box, and is arranged close to the rotary polygon mirror with high accuracy.

  FIG. 7 shows the conventional scanning optical apparatus. A collimator lens 102, a cylindrical lens 103, and a rotating polygon mirror 104 are sequentially arranged on the optical path in front of the semiconductor laser 101 having a plurality of light emitting points, and an image is formed on the optical path in the reflection direction of the rotating polygon mirror 104. Lenses 105 are arranged and held by an optical box 110 serving as a housing. An aperture stop 111 formed integrally with the optical box 110 is provided between the cylindrical lens 103 and the rotary polygon mirror 104.

  A plurality of light beams emitted from the semiconductor laser 101 are converted into substantially parallel light by the collimator lens 102, the light beams are shaped by the aperture stop 111, and are condensed linearly on the rotating polygon mirror 104 by the cylindrical lens 103. The rotating polygon mirror 104 deflects and scans in a predetermined direction perpendicular to the rotation axis, and forms an image on a rotating drum-shaped photoconductor through the imaging lens 105. The light beam that forms an image on the photosensitive member forms an electrostatic latent image along with the main scanning by the rotation of the rotary polygon mirror and the sub-scanning by the rotating drum. A part of the light beam scanned by the rotary polygon mirror 104 is introduced into the horizontal synchronization signal detector 109 via the horizontal synchronization detection optical system 107 and the slit 108, and the semiconductor laser 101 performs write modulation by the output signal. Start.

  Here, the material of the optical box 110 is generally a resin for cost reduction, and is manufactured by injection molding. The aperture stop has an opening in a direction orthogonal to the direction in which the mold opens and closes, and since the aperture stop has an undercut shape, a mold having a slide mechanism is used. The aperture stop 111 is formed by embedding a nesting in a mold and performing undercutting by sliding the nesting in a direction perpendicular to the opening / closing direction of the mold using an inclined pin or the like.

  FIG. 8 is a sectional view for explaining an optical box and a mold structure in the conventional scanning optical apparatus. For the sake of explanation, only the cross section near the aperture stop 111 is shown.

  A mold 150 for molding the optical box is composed of a movable mold 151 and a fixed mold 152, and a melted resin material is filled in a space between the molds and cooled inside the mold to have a predetermined shape. The optical box 110 is formed. Further, an ejector plate 153 is provided at a position separated from the fixed mold by a stroke distance S ′, and the optical box 110 formed by a plurality of ejector pins 154 is pushed out.

  Since the vicinity of the aperture stop 110 has an undercut shape as described above, an inclined pin 155 that is a nested type is provided at a position corresponding to the aperture stop 110 of the mold. As shown in the figure, the inclined pin 155 is inclined at an angle θ ′ with respect to the drawing direction. Here, the angle θ ′ is generally about 5 °.

  Next, the manufacturing process of the optical box in the conventional scanning optical apparatus will be described with reference to FIGS.

  First, the melted resin material is poured into a closed mold, and the mold is cooled to a temperature at which the resin is cured, whereby the optical box 110 as a product is formed, and the state shown in FIG. 8 is obtained.

  In order to take out the optical box 110 as a product from the mold, first, the movable mold 151 is moved in the removal direction by a distance T ′ (T ′> S ′) as indicated by an arrow (1) in FIG. . At that time, the optical box 110 is stuck to the fixed mold 152.

  Next, as shown by the arrow (2) in the figure, the ejector plate 153 moves in the pulling direction by the stroke amount S ′, and the optical box 110 is removed from the fixed mold 152 by the ejector pins 154 fixed to the ejector plate 153. Extruded. At this time, as shown in FIG. 9, the inclined pin 155 in a nested shape is interlocked with the movement of the ejector plate 153 in a direction inclined by an angle θ ′ with respect to the extraction direction along the guide hole 152a. Moving. When the ejector plate 153 moves by the stroke amount S, the inclined pin 155 slides relative to the optical box 110 in a direction orthogonal to the pulling direction by Δ ′ = S ′ × tan θ ′. As for the cut-shaped portion, the mold is separated from the optical box 110, and the optical box 110 as a product can be taken out from the mold.

  Components such as an imaging lens are attached to the optical box 110 molded as described above as described with reference to FIG. 7 to complete the scanning optical device.

Japanese Patent No. 2524567 JP 2002-091228 A

  However, according to the above-described conventional scanning optical apparatus, in the mold structure used for molding the optical box, the optical axis height direction of the aperture stop is caused by the backlash of the tilt pin of the slide mechanism for molding the aperture stop portion. As a result, there is a problem that the spot shape on the photosensitive member is broken and the image is deteriorated.

  The above problem will be described with reference to FIG.

  FIG. 10 is an enlarged sectional view showing the vicinity of the aperture stop of the conventional scanning optical device and its mold structure. As described above, the portion of the aperture stop 110 of the optical box 110 is formed by the inclined pin 155 that is nested.

  As described in the section of the prior art, the inclined pin 155 moves in the direction inclined by the angle θ ′ with respect to the drawing direction along the guide hole 152a of the fixed mold 152 in conjunction with the movement of the ejector plate. To do. At this time, in order to smoothly slide the tilt pin 155, it is necessary to provide a clearance ΔP of at least about several tens of μm between the tilt pin 155 and the guide hole 152a. Therefore, in the state where the mold shown in FIG. 8 is closed, the inclined pin 155 has a backlash ΔZ in the Z direction due to the influence of the clearance ΔP, and the height of the aperture stop 111 in the Z direction in the optical box 110 formed as a result. The dimensional accuracy of the position Za ′ is not stable.

  In a multi-beam scanning optical apparatus having an aperture stop, it is very important to make the height position of the aperture stop coincide with the optical axis L. Depending on the characteristics of the optical lens system, the aperture stop can be changed from the optical box reference plane. In general, the positional accuracy of the Z-direction height position Za ′ is required to be about ± 20 μm.

  However, as described above, in the structure in which the undercut-shaped aperture stop is formed using the inclined pin, the backlash of about ± 50 μm is inevitably included due to the effect of the inclination of the inclined pin, including the machining accuracy of the mold. End up. Accordingly, the accuracy of the height position of the aperture stop of the optical box also has an error of about ± 50 μm. As a result, there arises a problem that an image defect occurs due to a collapse of the spot shape on the photosensitive member.

  In order to solve the above problem, for example, it is possible to manufacture the aperture stop with a separate part such as a sheet metal with high accuracy and fix it at a predetermined position of the optical box with a screw or the like, but the number of parts increases. Another problem arises that the assembly tact time becomes longer and the cost of the scanning optical device increases.

  An object of the present invention is to solve the above-mentioned problems and to provide an inexpensive scanning optical device free from image defects due to the displacement of the aperture stop caused by tilted pin backlash when molding an optical box.

  In order to achieve the above object, a scanning optical device according to the present invention deflects laser light emitted by an optical box serving as a housing, a multi-beam light source unit that emits a plurality of laser light beams, and the multi-beam light source unit. The rotating polygon mirror, a motor for driving the rotating polygon mirror, a cylindrical lens for forming an image of the laser beam emitted from the multi-beam light source unit on the reflecting surface of the rotating polygon mirror, and the optical box are formed integrally. In the scanning optical apparatus, comprising: an aperture stop disposed between the cylindrical lens and the rotary polygon mirror; and an imaging optical system for condensing the laser beam deflected and scanned by the rotary polygon mirror on a surface to be scanned. A hole is provided in the bottom surface of the box near the aperture stop.

  Here, it is preferable that the hole provided in the bottom surface of the optical box is provided in a slide space required when the aperture stop is formed by slide molding.

  Furthermore, it is more preferable that the hole provided in the bottom surface of the optical box is provided on the lower side of the rotating substrate of the motor for rotationally driving the rotary polygon mirror.

  According to the present invention, in a multiple beam scanning optical apparatus using a multiple beam light source having a plurality of light emitting points, an aperture stop is integrally formed in an optical box using an inclined pin provided in a mold. By providing a hole in the space, high-definition scanning optical device that is less likely to cause image failure due to deterioration of the spot shape on the photosensitive member due to the displacement of the height of the aperture stop, and that supports high-speed image forming devices Can be provided at low cost.

  Embodiments of the scanning optical apparatus according to the present invention will be described with reference to FIGS.

<Embodiment 1>
The scanning optical apparatus according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a scanning optical apparatus according to the present invention. A collimator lens 2, a cylindrical lens 3, and a rotating polygon mirror 4 are sequentially arranged on the optical path in front of the semiconductor laser 1 having a plurality of emission points, and an image is formed on the optical path in the reflection direction of the rotating polygon mirror 4. Lenses 5 are arranged and held by an optical box 10 serving as a housing. An aperture stop 11 formed integrally with the optical box 10 is provided between the cylindrical lens 3 and the rotary polygon mirror 4.

  A plurality of light beams emitted from the semiconductor laser 1 are converted into substantially parallel light by the collimator lens 2, the light beams are shaped by the aperture stop 11, and are condensed linearly on the rotary polygon mirror 4 by the cylindrical lens 3. Then, it is deflected and scanned by the rotary polygon mirror 4 in a predetermined direction perpendicular to the rotation axis thereof, and passes through the imaging lens 5 to form an image on a rotating drum-shaped photoconductor. The light beam that forms an image on the photosensitive member forms an electrostatic latent image along with the main scanning by the rotation of the rotary polygon mirror and the sub-scanning by the rotating drum. A part of the light beam scanned by the rotary polygon mirror 4 is introduced into the horizontal synchronization signal detector 8 through the horizontal synchronization detection optical system 6 and the slit 7, and the semiconductor laser 1 performs write modulation by the output signal. Start.

Here, the material of the optical box 10 is generally a resin for cost reduction, and is manufactured by injection molding. The aperture stop has an opening in a direction orthogonal to the direction in which the mold opens and closes, and the aperture stop portion has an undercut shape, so a mold having a slide mechanism is used. The aperture stop 11 is formed by embedding a nesting in a mold and performing undercutting by sliding the nesting in a direction perpendicular to the opening / closing direction of the mold using an inclined pin or the like. Therefore, a slide space 12 is required at a location in contact with the aperture stop 11 on the bottom surface of the optical box 10.

  As shown in FIG. 1, the slide space 12 is provided with a hole 13, and this hole 13 is used for positioning the tilt pin of the mold in the Z direction as will be described later.

  2 is a cross-sectional view for explaining the structure of the optical box and the mold for molding the optical box in the scanning optical apparatus according to the present embodiment, and FIG. 3 is an enlarged view of the vicinity of the aperture stop. For the sake of explanation, only the cross section near the aperture stop 11 is shown.

  A mold 50 for molding the optical box 10 is composed of a movable mold 51 and a fixed mold 52, and a melted resin material is filled in a space between the mold 51 and cooled inside the mold to obtain a predetermined mold. A shaped optical box 10 is formed. In addition, an ejector plate 53 is provided at a position separated from the fixed mold 52 by a stroke distance S in the pulling direction, and the optical box 10 formed by a plurality of ejector pins 54 is pushed out.

  Since the vicinity of the aperture stop 11 has an undercut shape as described above, an inclined pin 55 that is a nested type is provided at a position corresponding to the aperture stop 11 of the mold. As shown in the drawing, the inclined pin 55 is inclined at an angle θ with respect to the pulling direction, and is movable within a guide hole 52 a provided in the fixed mold 52. Here, the angle θ is generally about 5 °. In order to smoothly slide the tilt pin 55, the tilt pin 55 and the guide hole 52a are manufactured to have a predetermined clearance ΔP.

  Here, a pin 51a is provided at a position corresponding to the hole 13 provided in the slide space of the optical box of the movable side mold 51, and an inclined pin whose Z direction position is accurately guaranteed on the end face thereof. A reference surface 51b is provided.

  Next, the manufacturing process of the optical box in the scanning optical apparatus according to the present embodiment will be described with reference to FIGS.

  First, the melted resin material is poured into a closed mold, and the mold is cooled to a temperature at which the resin is cured, whereby the optical box 10 as a product is formed, and the state shown in FIG. 2 is obtained. At this time, the inclined pin 55 is configured to abut against an inclined pin reference surface 51 b provided on the movable mold 51. Therefore, as described above, the clearance ΔP is provided between the inclined pin 55 and the guide hole 52a, but the Z direction position Za of the aperture stop 11 can be ensured with high accuracy without being affected by the clearance ΔP. it can. Explaining with specific numbers, the Z-direction height Z1 of the inclined pin reference surface 51b provided on the movable mold 51 and the distance Z2 from the inclined pin abutting surface to the position corresponding to the aperture stop are as follows. By producing the molds with a dimensional accuracy of about ± 10 μm, it is possible to finish the Z-direction position of the aperture stop 11 of the optical box as a product with an accuracy of about ± 20 μm with respect to the nominal value. Become.

  Then, in order to take out the optical box 10 as a product from the mold, first, the movable mold 51 is moved by a distance T (T> S) in the pulling direction as indicated by the arrow (1) in FIG. At that time, the optical box 10 is stuck to the fixed mold 52.

  Next, the ejector plate 53 moves in the pulling direction by the stroke amount S, and the optical box 10 is pushed out of the fixed mold 52 by the ejector pins 54 fixed to the ejector plate 53. At this time, as shown in FIG. 4, the inclined pin 55 in a nested shape moves in a direction inclined by an angle θ with respect to the extraction direction along the guide hole 52a in conjunction with the movement of the ejector plate 53. . When the ejector plate 53 moves by the stroke amount S, the inclined pin 55 slides by Δ = S × taθ in the direction orthogonal to the pulling direction, and the mold is also used for the undercut shape portion of the aperture stop 111. The optical box 10 which is separated from the product 10 and becomes a product can be taken out from the mold.

  The basic configuration and manufacturing process of the mold used in the optical box used in the scanning optical apparatus according to the present embodiment described so far are basically the same as those described in the above-described conventional example. Compared to this, the manufacturing cost of the mold does not increase greatly, and the molding tact time does not increase.

  As described with reference to FIG. 1, a semiconductor laser, lenses, and the like are attached to the optical box manufactured by the method described above, and the scanning optical device is completed.

  As described above, the scanning optical device according to the present embodiment has a configuration in which the tilt pin of the mold is abutted against the tilt pin reference surface provided in the movable side mold at the time of optical box molding. The backlash of the Z-direction height of the tilt pin due to the clearance between the tilt pin and the guide hole can be suppressed, and as a result, the Z-direction height position of the aperture stop from the optical box reference plane can be improved.

  Therefore, by using the scanning optical device according to the present embodiment, it is possible to provide a scanning optical device that is free from image deterioration due to the deterioration of the spot shape on the photosensitive member due to the displacement of the aperture stop.

<Embodiment 2>
5 and 6 show a scanning optical apparatus according to Embodiment 2 of the present invention. Since the basic configuration of the lens and the like inside the scanning optical device is the same as that of the scanning optical device of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof is omitted here.

  FIG. 5 is a perspective view showing the entire scanning optical apparatus according to the present embodiment, and FIG. 6 is a partial sectional view showing the vicinity of the aperture stop 11. Similar to the scanning optical device of the first embodiment, the aperture stop 11 is formed integrally with the optical box 10 by providing a tilting pin that is nested in the mold, and the slide space 12 is provided with a hole 13. ing. The method of using the holes 13 and the manufacturing process for producing the optical box 10 by injection molding are as described in the scanning optical device of the first embodiment, and the detailed description thereof is omitted here.

  FIG. 6 is a partial sectional view showing the vicinity of the aperture stop 11. In this figure, 4M is a motor which is a driving means for rotating the rotary polygon mirror 4. The motor 4M includes a circuit board 4M1, a drive driver 4M2, a bearing 4M3, and the like, and the rotary polygon mirror 4 is fixed on the bearing 4M3. In general, the circuit board 4M1 is often made of a metal such as an iron plate in order to maintain rigidity.

  In the scanning optical apparatus according to the present embodiment, as shown in FIG. 6, the hole 13 provided in the slide space 12 on the bottom of the optical box is provided below the circuit board 4M1 near the bearing 4M3. It has become.

  When the rotary polygon mirror rotates during the operation of the scanning optical device, heat is generated from the motor 4M due to the current consumed by the motor driver 4M2 and the loss in the bearing 4M3. In recent years, the speed of image forming apparatuses has been increased, and a rotating polygon mirror of a scanning optical apparatus is required to rotate at a high speed of tens of thousands rpm. When the rotational speed of the rotary polygon mirror increases, the amount of heat generated from the motor bearing and motor drive IC that rotates the rotary polygon mirror increases, the temperature inside the scanning optical device becomes high, and the durability of the bearing deteriorates. The problem that an image defect occurs due to a change in refractive index or the like is likely to occur.

  In the scanning optical apparatus according to the present embodiment, as described above, the hole 13 provided in the slide space 12 on the bottom surface of the optical box is provided below the circuit board 4M1 near the bearing 4M3. Therefore, the heat generated in the bearing 4M3 passes through the metallic circuit board 4M1 having a high thermal conductivity to the outside of the scanning optical device from the hole 13 provided on the bottom surface of the optical box as shown by the thick arrow in the figure. It is possible to escape. Similarly, the heat generated from the drive driver 4M2 can be released to the outside of the scanning optical device through the hole 13 on the bottom of the optical box through the circuit board 4M1 as shown by the thick arrow in the figure. It is possible to prevent deterioration of the durability of the bearing due to heat generated from the motor when rotated at high speed, and image defects due to a change in the refractive index of the lens.

  Therefore, by using the configuration of the present embodiment, there is no image deterioration due to the deterioration of the spot shape on the photoreceptor due to the displacement of the aperture stop, and the heat dissipation performance corresponding to the high-speed rotation of the rotary polygon mirror. An excellent scanning optical device can be provided without increasing the cost.

  Further, in the scanning optical device according to the present embodiment, the hole 13 provided in the slide space 12 on the bottom surface of the optical box is provided below the circuit board 4M1 near the bearing 4M3. The distance between the aperture stop 11 and the rotary polygon mirror 4 can be made closer than that of the conventional scanning optical apparatus.

  As explained in detail in Japanese Patent No. 2524567, the closer the aperture stop is to the rotary polygon mirror, the less the image formation position shift for each light emitting point due to focus variation without increasing the size of the rotary polygon mirror. Can do. In the scanning optical device according to the present embodiment, as described above, the slide space necessary for forming integrally with the optical box using the tilt pin is provided below the circuit board 4M1. Therefore, the distance between the aperture stop and the rotary polygon mirror can be made shorter than that of the conventional scanning optical apparatus. Therefore, by using the configuration of the present embodiment, a scanning optical device capable of suppressing the shift of the imaging position for each light emitting point caused by the focus shift and outputting a high-quality image without increasing the size of the rotary polygon mirror. Can be provided without cost increase.

  As described above, by using the configuration of the present embodiment, there is no image deterioration due to the deterioration of the spot shape on the photoconductor due to the positional displacement of the aperture stop in the height direction, and the light emission caused by the focus positional displacement. It is possible to provide a scanning optical device excellent in heat dissipation with little image formation position shift for each point without increasing the cost.

  The present invention can be applied to a scanning optical device used in an image forming apparatus such as a laser printer or a laser facsimile.

1 is a perspective view showing a scanning optical device according to Embodiment 1 of the present invention. It is a figure which shows the metal mold | die structure which shape | molds the optical box in the scanning optical apparatus which concerns on Embodiment 1 of this invention. It is an enlarged view which shows the metal mold | die structure of an aperture stop vicinity. It is a figure explaining the manufacturing process of the optical box in the scanning optical apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the scanning optical apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the aperture stop vicinity of the scanning optical apparatus concerning Embodiment 2 of this invention. It is a perspective view which shows the conventional scanning optical apparatus. It is a figure which shows the metal mold | die structure which shape | molds the optical box in the conventional scanning optical apparatus. It is a figure explaining the manufacturing process of the optical box in the conventional scanning optical apparatus. It is a figure explaining the problem of the conventional scanning optical apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical box 11 Aperture stop 12 Slide space 13 Hole 51 Movable side metal mold 51a Pin 51b Inclination pin reference surface 52 Fixed side metal mold 53 Ejector plate 54 Ejector pin 55 Inclination pin

Claims (3)

An optical box serving as a housing; a multi-beam light source unit that emits a plurality of laser beams; a rotary polygon mirror that deflects laser light emitted by the multi-beam light source unit; and a motor that rotationally drives the rotary polygon mirror; A cylindrical lens that forms an image of a laser beam emitted from the multi-beam light source unit on a reflecting surface of the rotary polygon mirror, and an aperture stop that is formed integrally with the optical box and disposed between the cylindrical lens and the rotary polygon mirror And a scanning optical device having an imaging optical system for condensing the laser beam deflected and scanned by the rotary polygon mirror on the surface to be scanned,
A scanning optical device, wherein a hole is provided in a bottom surface of the optical box near the aperture stop.   2. The scanning optical apparatus according to claim 1, wherein the hole provided in the bottom surface of the optical box is provided in a slide space required when forming an aperture stop by slide molding.   3. The scanning optical device according to claim 1, wherein the hole provided in the bottom surface of the optical box is provided on a lower side of a rotating substrate of a motor that rotationally drives the rotary polygon mirror.

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