JP4463055B2 - Light beam scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention is used in an image forming apparatus such as a printer, a facsimile machine, a copying machine or the like that performs electrophotographic image formation, and a light beam scanning device that irradiates an image carrier with image light based on image data. The present invention relates to an image forming apparatus including a beam scanning device.

  An image forming apparatus that performs electrophotographic image formation includes a light beam scanning device that irradiates the surface of an image carrier with image light modulated by a signal based on image data read from a document or image data input from an external device. I have. The surface of the image carrier is uniformly charged in advance by charging means, and an electrostatic latent image is formed on the surface of the image carrier by irradiation with image light. The electrostatic latent image is visualized as a developer image (toner image) by the developer supplied from the developing means, and then transferred to a recording sheet such as paper directly or via an intermediate transfer carrier. The toner image transferred to the recording sheet is finally fixed on the recording sheet by a fixing unit, and an image formed product is obtained.

  As a light beam scanning device provided in such an image forming apparatus, a laser beam system using image light as a laser beam having a high modulation speed and capable of increasing the scanning speed is widely used.

  In recent years, colorization of image forming apparatuses has progressed, and various light beam scanning apparatuses for forming color images have been developed. A conventional light beam scanning device for forming a color image is provided for each component color. However, the light beam scanning devices for the number of component colors must be arranged in the image forming device. Increases the size, and expensive optical parts are redundantly provided, resulting in an increase in cost.

In view of this, a device having a plurality of laser light sources for each component color in a single light beam scanning device has been proposed. This light beam scanning device accommodates a number of component color mirrors in a single housing together with a laser light source for the number of component colors, a single polygon mirror, and a single fθ lens, and is emitted from each laser light source. The light beam is deflected at a constant angular velocity by a single polygon mirror and at a uniform velocity by a single fθ lens, and then separated toward the image carrier for each component color via a mirror provided for each component color. To distribute light (for example, refer to Patent Document 1 or 2).
JP 2001-235699 A Japanese Patent Laid-Open No. 2001-281487

  However, the light beam scanning devices described in Patent Documents 1 and 2 write the image by scanning the image carrier of the image forming station arranged at a predetermined interval with the light beam. It is necessary to provide a large number of reflection mirrors to guide the image carrier. In addition, when the image carrier is located above the light beam scanning device, a number of reflecting mirrors are arranged above the deflection unit where optical components for deflecting the light beam at equal angular speed and deflecting at a constant speed are arranged. Must. Therefore, it is very difficult to adjust the arrangement position of each optical component in the deflection unit in a state where the light beam scanning device is assembled. In addition, it is difficult to incorporate the deflection unit into the housing of the light beam scanning device in a state where the reflection mirror of the light beam scanning device is assembled.

  SUMMARY OF THE INVENTION An object of the present invention is to guide a light beam scanning device, a deflection unit having a scanning optical member for deflecting a light beam at a constant angular velocity and a constant speed, and a light beam deflected at a constant speed to each image carrier. And a housing unit that supports a reflecting optical member such as a reflecting mirror, and each unit can be assembled and adjusted independently by allowing the deflection unit to be attached to the housing unit from the outside. It is an object of the present invention to provide a light beam scanning apparatus and an image forming apparatus that can realize the efficiency of assembly work and the ease of maintenance work.

  As means for solving the above problems, a light beam scanning apparatus of the present invention has the following configuration.

(1) a light source that emits a light beam, and a deflection unit that supports a scanning optical member that deflects the light beam emitted from the light source at an equal angular velocity and then deflects it at an equal velocity;
The light beam deflected at a constant speed by the scanning optical member is divided into a housing unit that supports a plurality of reflecting optical members that reflect the light beam toward the scanning target supported by the main apparatus, and is configured.
The deflection unit, as the scanning optical member, reflects a light beam emitted from the light source by a reflecting surface and deflects it at a constant angular velocity, and fθ deflects a light beam deflected at a constant angular velocity by the polygon mirror at a constant velocity. A lens, and
The housing unit includes two and structures made of metal plates supporting the deflection unit and the plurality of reflecting optical member disposed in parallel to each other physician in position, said housing the said reflecting optical member A resin exterior covering the two structures,
Further, the deflecting unit is configured such that the structure body is externally provided along the main optical axis plane that is a horizontal plane including a normal direction of a reflecting surface of the polygon mirror that reflects the light beam emitted from the light source . It is characterized by being detachable at a predetermined position.

  In this configuration, a deflection unit that houses a scanning optical member that deflects and scans a light beam and a housing unit that supports a reflective optical member such as a reflecting means for guiding the light beam to a scanned object such as an image carrier. The deflection unit is mounted on the housing unit from the outside. Therefore, the scanning optical member mounting operation and adjusting operation in the deflection unit and the reflecting optical member mounting operation and adjusting operation in the housing unit can be performed separately.

The deflecting unit also serves as a scanning optical member, a polygon mirror that reflects a light beam emitted from a light source by a reflecting surface and deflects it at an equal angular velocity, and an fθ lens that deflects the light beam deflected by the polygon mirror at an equal angular velocity. And having. The deflection unit is positioned and attached to the housing unit along the main optical axis surface of the light beam in the deflection unit. The main optical axis surface referred to here is a horizontal plane including the normal direction of the reflection surface of the polygon mirror that reflects the light beam emitted from the light source. Therefore, the test light can be incident on the inside of the housing unit after the reflection optical member is mounted and before the deflection unit is mounted in the same state as the light beam emitted from the deflection unit from the mounting direction of the deflection unit.

Further , the deflection unit is positioned at the position of the main optical axis surface of the light beam in the housing unit. Therefore, the position of the deflection unit in the direction orthogonal to the main optical axis surface is not easily affected by thermal expansion.

Further, the deflection unit and the reflective optical member are supported on the metal flat plate. Therefore, the positional relationship between the scanning optical member and the reflecting optical member in the deflection unit is not easily affected by environmental conditions.
(2) Prior Symbol reflecting optical element reflecting the light beam on the upper surface of the housing unit, the deflection unit is characterized in that it is arranged on the bottom side of the housing unit.

( 3 ) The deflection unit includes a plurality of light sources and a single scanning optical member.

  In this configuration, a plurality of light beams emitted from a plurality of light sources scan each of a plurality of scanning objects arranged in the main apparatus via each single scanning optical member. Therefore, the position of the scanning line with respect to each scanning object by each light beam is maintained with high accuracy.

( 4 ) The light beam scanning apparatus according to (1) or (2), wherein the structure is exposed to the outside of the exterior body at each of both ends in a direction along the main optical axis plane. Comprising a light beam scanning device comprising
A shaft fixed to the front and back frames and having two shafts that fit into the supported portion. A light beam modulated by image data from the light beam scanning device is photoconductive. It is characterized by irradiating the surface of the image carrier that produces the action.

  This configuration is divided into two parts: a deflection unit that houses a scanning optical member that deflects and scans a light beam, and a housing unit that supports a reflective optical member such as a reflecting means that guides the light beam to a scanned object. The image carrier is irradiated with a light beam modulated by image data from a light beam scanning device mounted from the outside along the main optical axis surface of the light beam in the deflection unit. Therefore, the light beam scanning apparatus in which the scanning optical member mounting work and adjustment work in the deflection unit and the reflective optical member mounting work and adjustment work in the housing unit are individually performed are light beams at appropriate positions with respect to the image carrier. A beam is irradiated.

( 5 ) The light beam scanning apparatus according to ( 3 ), wherein the structure includes a supported portion that is exposed to the outside of the exterior body at each of both end portions in a direction along the main optical axis plane. A scanning device, and a plurality of image carriers that receive each of the light beams emitted by each of the light sources,
Each of a plurality of light beams modulated by image data from the light beam scanning device has two shaft bodies that are fixed to the front side frame and the back side frame and are fitted into the supported portion. Is irradiated on the surface of the image carrier that generates a photoconductive action.

  In this configuration, a plurality of light beams emitted from a plurality of light sources scan each of the plurality of image carriers through each single scanning optical member. Therefore, the position of the scanning line with respect to each image carrier by each light beam is maintained with high accuracy, and an image is formed at a position aligned with each other on each image carrier.

( 6 ) The adjustment member for adjusting the irradiation position of the light beam on the image carrier is provided to be exposed on the surface of the light beam scanning device facing the image carrier.

  In this configuration, the irradiation position of the light beam on the image carrier is adjusted using the adjustment member exposed on the surface facing the image carrier in the light beam scanning device. Therefore, when correcting the scanning position of each light beam with respect to the image carrier in accordance with the positional accuracy of the image carrier, the adjustment member corresponding to the image carrier to be adjusted is easily visually recognized.

  According to the present invention, the following effects can be obtained.

  (1) Since the mounting operation and adjustment operation of the scanning optical member in the deflection unit and the mounting operation and adjustment operation of the reflection optical member in the housing unit can be performed separately, the efficiency of assembly work and maintenance are improved. The work can be facilitated.

  In addition, since the deflection unit and the housing unit are integrated in an individually adjusted state, the respective rough adjustments have been completed. After the deflection unit is mounted on the housing unit, the scanning position is adjusted. It is only necessary to make adjustments, and it is not necessary to perform complicated adjustments after being mounted on the main body device, thereby reducing the adjustment work.

  Furthermore, since the test light can be incident on the inside of the housing unit after the reflection optical member is mounted and before the deflection unit is mounted in the same state as the light beam irradiated by the deflection unit from the mounting direction of the deflection unit, For example, the reflective optical member attached to the housing unit can be easily adjusted using an adjustment jig using a laser beam.

  In addition, it is possible to make it less susceptible to an optical axis deviation error due to an installation error when both units are combined.

  (2) The positional accuracy of the deflection unit in the direction orthogonal to the main optical axis surface can be made less susceptible to thermal expansion, and the optical characteristics against environmental changes can be maintained well.

  (3) The positional relationship between the scanning optical member and the reflecting optical member in the deflection unit can be made less susceptible to environmental conditions, and the optical characteristics can be maintained well.

  (4) The position of the scanning line with respect to each scanning object by each light beam can be maintained with high accuracy.

  (5) A scanning optical member mounting operation and adjustment operation in the deflection unit and a reflection optical member mounting operation and adjustment operation in the housing unit are separately performed from the light beam scanning device to an appropriate position with respect to the image carrier. A light beam can be irradiated, and the image forming state can be maintained satisfactorily.

  (6) The position of the scanning line with respect to each image carrier by each light beam is maintained with high accuracy, images can be formed at positions aligned with each other on each image carrier, and good image quality can be maintained. .

  (7) When correcting the scanning position of each light beam with respect to the image carrier in accordance with the positional accuracy of the image carrier, the adjustment member corresponding to the image carrier to be adjusted can be easily visually confirmed, and the adjustment work Can be simplified.

  Hereinafter, an image forming apparatus according to the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a simple configuration of an image forming apparatus provided with a light beam scanning apparatus according to an embodiment of the present invention. The image forming apparatus 100, which is a main body apparatus, forms multicolor and single color images on a sheet based on image data transmitted via a network or the like. Therefore, the image forming apparatus 100 includes an exposure unit E, a photosensitive drum 101 (101A to 101D), a developing device 102 (102A to 102D), a charging roller 103 (103A to 103D), a cleaning unit 104 (104A to 104D), Intermediate transfer belt 11, primary transfer roller 13 (13A to 13D), secondary transfer roller 14, fixing device 15, paper transport paths P1, P2, P3, paper feed cassette 16, manual paper feed tray 17, paper discharge tray 18, etc. It has.

  The image forming apparatus 100 applies black (K) and four hues of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of a color image. Image formation is performed in the image forming sections PA to PD using the corresponding image data. The image forming units PA to PD have the same configuration. For example, the black image forming unit PA includes a photosensitive drum 101A, a developing device 102A, a charging roller 103A, a transfer roller 13A, a cleaning unit 104A, and the like. The image forming portions PA to PD are arranged in a line in the moving direction of the intermediate transfer belt 11.

  However, although not shown in FIG. 1, the photosensitive drum 101A has a larger diameter than the photosensitive drums 101B to 101D. The photosensitive drum 101 is an image carrier and a scanned body according to the present invention. In monochrome image formation performed using only the black image forming unit PA, there is a high demand for speeding up, and the frequency of use is higher than color image formation performed using all of the image forming units PA to PD. This is because the photosensitive drum 101A provided in the black image forming portion PA needs to have a longer life than the photosensitive drums 101B to 101D. The photosensitive drums 101B to 101D have the same diameter. For this reason, the interval between the rotation shaft of the photosensitive drum 101A and the rotation shaft of the photosensitive drum 101B is longer than the interval between the rotation shafts between the photosensitive drums 101B to 101D.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101, which is an image carrier as the scanned body of the present invention, to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging charger may be used. An exposure unit E which is a light beam scanning apparatus of the present invention includes a semiconductor laser, a polygon mirror 4, a first reflection mirror 7, a second reflection mirror 8, and the like (not shown), and each hue of black, cyan, magenta and yellow. Each of the photosensitive drums 101A to 101D is irradiated with a laser beam (a light beam according to the present invention) modulated by the image data. On each of the photosensitive drums 101A to 101D, an electrostatic latent image is formed based on image data of each hue of black, cyan, magenta, and yellow. Details of the exposure unit E will be described later.

  The developing device 102 supplies toner to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and visualizes the electrostatic latent image into a developer image. Each of the developing devices 102A to 102D stores toner of each hue of black, cyan, magenta, and yellow, and the electrostatic latent image of each hue formed on each of the photosensitive drums 101A to 101D is black, cyan. The developer images are developed in magenta and yellow hues. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 is stretched between the driving roller 11A and the driven roller 11B to form a loop-shaped moving path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101D, the photosensitive drum 101C, the photosensitive drum 101B, and the photosensitive drum 101A in this order. Primary transfer rollers 13A to 13D are arranged at positions facing the respective photosensitive drums 101A to 101D with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101A to 101D is a primary transfer position.

  In order to transfer the developer images carried on the surfaces of the photosensitive drums 101A to 101D onto the intermediate transfer belt 11, primary transfer biases having a polarity opposite to the charging polarity of the toner are applied to the primary transfer rollers 13A to 13D. Applied by control. As a result, the developer images of the respective colors formed on the photosensitive drum 101 (101A to 101D) are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 11 and transferred onto the outer peripheral surface of the intermediate transfer belt 11. Is formed.

  However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, a part of the four photosensitive drums 101A to 101D corresponding to the hue of the input image data is input. An electrostatic latent image and a developer image are formed only on the photoreceptor 101. For example, when forming a monochrome image, an electrostatic latent image and a developer image are formed only on the photosensitive drum 101A corresponding to the black hue, and only the black developer image is formed on the outer peripheral surface of the intermediate transfer belt 11. Is transcribed.

  Each of the primary transfer rollers 13A to 13D is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, etc.). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material.

  The developer image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is transferred to a secondary transfer position (a transfer position of the present invention) that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. It is transported to. The secondary transfer roller 14 is in pressure contact with the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11A at a predetermined nip pressure during image formation.

  When the paper fed from the paper feed cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, the polarity of the toner charged on the secondary transfer roller 14 is opposite to that of the toner. The high voltage is applied. As a result, the developer image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the sheet.

  Of the toner adhering to the intermediate transfer belt 11 from the photosensitive drum 101, the toner remaining on the intermediate transfer belt 11 without being transferred onto the paper is removed by the cleaning unit 12 in order to prevent color mixing in the next process. Collected.

  The sheet on which the developer image has been transferred is guided to the fixing device 15 and passes between the heating roller 15A and the pressure roller 15B and is heated and pressed. As a result, the developer image is firmly fixed on the surface of the paper. The sheet on which the developer image is fixed is discharged onto the discharge tray 18 by the discharge roller 18A.

  In the image forming apparatus 100, a substantially vertical direction for feeding the paper stored in the paper feed cassette 16 to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. Paper transport path P1 is provided.

  In the paper transport path P1, the pickup roller 16A and paper feed roller 16B that feed out the paper in the paper feed cassette 16 one by one into the paper transport path P1, and the uppermost position when a plurality of papers are fed out in a superimposed manner. A paper pad 16C for scooping the paper so that only the paper to be conveyed is transported, and a transport roller R capable of changing the rotational speed for transporting the fed paper along the paper transport path P1 are arranged.

  A paper detector 30 is disposed immediately after the separation pad 16C of the paper transport path P1. The paper detector 30 detects the presence or absence of paper passing between the paper feed roller 16B and the scooping pad 16C. That is, it is detected whether or not one sheet is properly fed from the sheet feeding cassette to the sheet transport path P1 by the pickup roller 16A. Further, the paper detector 30 outputs a detection result to the connected control unit 50.

  In the paper conveyance path P1, a registration roller 19 that guides the conveyed paper between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a paper discharge roller that discharges the paper to the paper discharge tray 18 18A is arranged.

  In the image forming apparatus 100, a sheet conveyance path P <b> 2 is formed between the manual sheet feeding tray 17 and the registration roller 19. Similarly to the configuration of the paper transport path P1, the paper transport path P2 includes a pick-up roller 17A, a paper feed roller 17B, and a separating pad 17C for feeding the papers placed on the manual feed tray 17 one by one into the paper transport path P2. Has been placed.

  Further, a sheet conveyance path P3 is formed between the paper discharge roller 18A and the upstream side of the registration roller 19 in the sheet conveyance path P1. The paper discharge roller 18A is rotatable in both forward and reverse directions. When forming a single-sided image for forming an image on one side of a sheet, and when forming a second-side image in forming a double-sided image for forming an image on both sides of a sheet. Driven in the forward direction, the paper is discharged to the paper discharge tray 18.

  On the other hand, at the time of forming the first surface image in the double-sided image formation, the discharge roller 18A is driven in the normal rotation direction until the rear end of the paper passes through the fixing device 15, and then reversely rotated with the rear end of the paper sandwiched. Driven in the direction, the sheet is guided into the sheet conveyance path P3. As a result, the paper on which the image is formed on only one side when the double-sided image is formed is guided to the paper transport path P1 with the front and back surfaces and the front and rear ends reversed.

  The registration roller 19 performs secondary transfer of paper fed from the paper feed cassette 16 or the manual paper feed tray 17 or transported via the paper transport path P3 at a timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the sheet fed or conveyed prior to the rotation of the intermediate transfer belt 11 has the front end at the registration roller 19. The movement in the sheet conveyance path P1 is stopped in a state of being in contact with (chucked) 19. Thereafter, the registration roller 19 is a position at which the secondary transfer roller 14 and the intermediate transfer belt 11 are in pressure contact with each other, and the front end portion of the sheet and the front end portion of the developer image formed on the intermediate transfer belt 11 face each other. To start rotation.

  At the time of full color image formation in which image formation is performed in all of the image forming portions PA to PD, the primary transfer rollers 13A to 13D press the intermediate transfer belt 11 against all of the photosensitive drums 101A to 101D. On the other hand, during monochrome image formation in which image formation is performed only in the image forming portion PA, only the primary transfer roller 13A presses the intermediate transfer belt 11 against the photosensitive drum 101A.

  FIG. 2 is a schematic front view showing a configuration of an exposure unit which is a light beam scanning apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing an optical path of a light beam in the exposure unit. Hereinafter, in FIG. 2, an arrow XX direction that is a direction parallel to the rotation axis of the photosensitive drum 101 and is a scanning direction of the laser beam is referred to as a main scanning direction. In FIG. 3, 6A is a main optical axis surface that is the center in the vertical direction of the laser beams L1 to L4, and the arrow Y-Y direction that is a direction orthogonal to the main scanning direction in the main optical axis surface 6A. This is called the scanning direction.

  The exposure unit E includes a semiconductor laser 1 (1A to 1D), a collimator lens 2 (2A to 2D), a mirror 3 (3B to 3D), a first cylindrical lens 4, a mirror 5, a polygon mirror 6, a first fθ lens 7, Optical components such as a 2fθ lens 8, a second cylindrical lens 9 (9A to 9D), mirrors 21 to 24, a synchronization lens 10A, and a BD sensor 10 are provided.

  Each of the semiconductor lasers 1A to 1D as the light source of the present invention irradiates laser beams L1 to L4 modulated based on black, cyan, magenta and yellow image data, respectively. The laser beams L1 to L4 are a plurality of light beams of the present invention. Laser beams L1 to L4, which are diffused lights emitted from the semiconductor lasers 1A to 1D, pass through the collimator lenses 2A to 2D, the mirrors 3B to 3D, the first cylindrical lens 4 and the mirror 5, respectively, on the reflection surface of the polygon mirror 6. In the plane including the rotation axis of the polygon mirror 6, the light enters at different incident angles.

  The polygon mirror 6 includes, for example, six reflecting surfaces. The polygon mirror 6 rotates in the direction of the arrow A and deflects the laser beams L1 to L4 at the respective reflecting surfaces in the direction of the arrow B at a constant angular velocity.

  The first fθ lens 7 and the second fθ lens 8 are parallel to the axial direction of the photoconductive drums 101A to 101D on the respective surfaces of the photoconductive drums 101a to 101d with the laser beams L1 to L4 deflected at a constant angular velocity by the polygon mirror 6. A uniform velocity is deflected in the direction of arrow C in the main scanning direction. As an example, the first fθ lens 7 is composed of an aspheric surface on both the entrance surface and the exit surface. Further, the second fθ lens 8 has an incident surface formed of a free-form surface and an output surface formed of an aspheric surface.

  The polygon mirror 6, the first fθ lens 7, and the second fθ lens 8 are scanning optical members of the present invention.

  The mirrors 21 to 24 are reflection optical members of the present invention, and separate and reflect the laser beams L1 to L4 so as to be distributed on the respective surfaces of the photosensitive drums 101A to 101D. The laser beams L1 to L4 that have passed through the second fθ lens 8 are the mirror 21 and the second cylindrical lens 9A, the mirror 22 (22A to 22C) and the second cylindrical lens 9B, the mirror 23 (23A and 23B), and the second cylindrical lens, respectively. 9C, images are formed on the respective surfaces of the photosensitive drums 101a to 101d via the mirror 24 (24A to 24C) and the second cylindrical lens 9D.

  After passing through the second fθ lens 8, the laser beams L 1 and L 2 and the laser beams L 3 and L 4 are positioned above and below the main optical axis surface 6 A that is a horizontal plane including the normal direction of each reflecting surface of the polygon mirror 6. To do.

  The first fθ lens 7 has an aspheric surface on both the entrance surface and the exit surface, and the second fθ lens 8 has an entrance surface on an aspheric surface and an exit surface on a free curved surface. The first fθ lens 7, the second fθ lens 8, and the second cylindrical lens 9 are plastic molded products in consideration of mass productivity, but glass lenses may be used.

  The BD sensor 10 detects any of the laser beams L1 to L4 outside the effective exposure region in the main scanning direction. That is, any one of the laser beams L1 to L4 reflected by the reflecting surface of the polygon mirror 6 does not reach the surface of the photosensitive drum 101 in the main scanning direction on the light receiving surface of the BD sensor 10 via the synchronization lens 10A. Form an image. When receiving any one of the laser beams L1 to L4, the BD sensor 10 outputs a signal for determining the modulation start timing based on the image data of each of the laser beams L1 to L4 in the semiconductor lasers 1A to 1D.

  In this embodiment, the laser beams L1 to L4 are reflected by the same reflecting surface of the polygon mirror 6 so that all the laser beams are almost overlapped, so that the modulation start timing of all the laser beams is controlled by only one laser beam. It is possible to do. Since the detection is performed by the BD sensor 10 using the laser beam L1 that forms a black image with the least bending distortion of the scanning line, highly accurate detection can be performed.

FIG. 4 is an external view from obliquely above the back side of the exposure unit. The exposure unit E includes a housing main body 31A and a housing lid 31B that are exterior bodies of the present invention, and a support member 61 (not shown in FIG. 4) that is a structural body of the present invention. It is configured. The housing main body 31A and the housing lid body 31B are made of, for example, an inexpensive and lightweight resin such as polycarbonate kneaded with glass fibers and a relatively large linear expansion coefficient (the linear expansion coefficient of polycarbonate kneaded with 30% glass fibers is 2). 7 × 10 ⁻⁵ / ° C.). The housing lid 31B is formed with slits 32A to 32D in the main scanning direction (arrow XX direction) facing the respective photosensitive drums 101A to 101D (not shown). Laser beams L1 to L4 are irradiated to the photosensitive drums 101A to 101D through the slits 32A to 32D, respectively.

  The height of the exposure unit E is smaller in the portion facing the photosensitive drum 101A than in the portion facing the other photosensitive drums 101B to 101D. The photosensitive drum 101A has a larger diameter than the photosensitive drums 101B to 101D, and the bottom surface of the exposure unit E needs to be substantially horizontal in order to avoid interference with other units inside the image forming apparatus 100. Because there is. When the photosensitive drums 101A to 101D have the same diameter, the height of the exposure unit E can be made substantially uniform over the entire width.

  On at least the front side and the back side of the left and right side surfaces of the housing main body 31A, recesses 33, 33 and recesses 34, 34 that are opened outward in the left-right direction are formed. The recesses 33, 33 and the recesses 34, 34 are fitted on shafts 41, 42 that are fixed at both ends to a front frame and a rear frame of the image forming apparatus 100 (not shown). The widths in the vertical direction of the recesses 33 and 33 and the recesses 34 and 34 are larger than the outer diameters of the shaft bodies 41 and 42. Further, with respect to the sub-scanning direction (arrow Y-Y direction), the distance between the center of the arc part of the recesses 33 and 33 and the center of the arc part of the recesses 34 and 34 is the center of the shaft body 41 and the center of the shaft body 42. The distance is shorter than. For this reason, in at least one of the recesses 33 and 33 or the recesses 34 and 34, only the upper surface is in contact with the peripheral surface of the shaft body 41 or 42.

  FIG. 5 is an assembly view from obliquely upward on the back side showing the internal structure of the exposure unit. The housing main body 31A includes the mirror 21, the mirror 22 (22A to 22C), the mirror 23 (23A and 23B), the mirror 24 (24A to 24C), the second cylindrical lenses 9A to 9D, and the BD sensor 10 on the front side and the rear side. It accommodates in the inside in the state supported in the supporting members 61 and 61 located in this. Further, on one side of the bottom surface of the housing main body 31A in the sub-scanning direction, the semiconductor lasers 1A to 1D, the collimator lenses 2A to 2D, the mirrors 3B to 3D, the first cylindrical lens 4, the mirror 5, the polygon mirror 6, and the first fθ lens. 7. The deflecting unit 51 holding the second fθ lens 8 is disposed in a state of being supported by the support members 61 and 61. However, the semiconductor lasers 1A to 1D, the collimator lenses 2A to 2D, the mirrors 3B to 3D, the first cylindrical lens 4 and the mirror 5 do not appear in FIG.

The deflection unit 51 is formed of, for example, a material such as BMC having a high strength and a small linear expansion coefficient (the linear expansion coefficient of BMC is 1.8 × 10 ⁻⁵ / ° C.). In the deflection unit 51, the semiconductor lasers 1A to 1D, the collimator lenses 2A to 2D, the mirrors 3B to 3D, the first cylindrical lens 4, the mirror 5, the polygon mirror 6, the first fθ lens 7, and the second fθ lens 8 are in a positional relationship with each other. It is positioned in a strictly prescribed state.

  The front-side and back-side support members 61 and 61 are formed by rolling a rolled steel sheet having a thickness of 0.8 mm to 1.2 mm into a predetermined shape only by punching. Even when processing a plate material such as a rolled steel plate, bending is likely to cause distortion due to dimensional errors and internal stress, and it is difficult to position each part in each support member 61 properly. However, it is difficult to make the dimensions uniform. On the other hand, in the punching process in which the plate material is sandwiched between the molds, the precision of the mold is repeatedly reflected in the plurality of processed products, and the dimensions of the plurality of support members 61 can be made uniform.

  FIG. 6 is a front view of a support member used in the exposure unit. Inside the plate-like support member 61 whose longitudinal direction is the sub-scanning direction (arrow Y-Y direction), square hole-shaped mirror support portions 62A to 62I are formed. Each mirror support part 62A-62I supports each edge part of the mirrors 21 and 22 (22A-22C), 23 (23A, 23B), and 24 (24A-24C).

  Lens support portions 67 </ b> A to 67 </ b> D are formed on the upper end surface of the support member 61. Each lens support part 67A-67D exhibits a rectangular notch shape, and supports each edge part of 2nd cylindrical lens 9A-9D via the adjustment member mentioned later.

  A first supported portion 63 and a second supported portion 64 are formed on the left and right end surfaces of the support member 61. The supported portion 63 and the supported portion 64 are concave portions opened to the outside in the sub-scanning direction. As described above, the supported portions 63 and 64 are externally fitted to the shafts 41 and 42 whose both ends are fixed to the front and back frames of the image forming apparatus 100 (not shown). As a result, the support member 61 is supported by the frame of the image forming apparatus 100 via the shaft bodies 41 and 42.

  The widths of the supported parts 63 and 64 in the vertical direction are larger than the outer diameters of the shaft bodies 41 and 42. Further, with respect to the sub-scanning direction (arrow Y-Y direction), the distance between the center of the arc portion of the supported portions 63 and 64 and the center of the arc portion of the supported portions 63 and 64 is the center of the shaft body 41 and the shaft body. The distance from the center of 42 is shorter. Therefore, only the upper side surfaces of the supported portions 63 and 64 are in contact with the peripheral surfaces of the shaft bodies 41 and 42, and the supported portions 63 and 64 are a predetermined distance in the sub-scanning direction with respect to the shaft bodies 41 and 42. It is only displaceable.

  A fixing hole 65 is formed in a substantially central portion of the support member 61 in the sub-scanning direction. In addition, a rectangular recess 66 is formed in the lower end surface of the support member 61 in the vicinity of the left end portion in the drawing. The support member 61 supports the deflection unit 51 through the fixing hole 65 and the recess 66. The fixing hole 65 is a positioning member of the present invention, and is located in the main optical axis surface 6A of the laser beams L1 to L4 irradiated from the deflection unit 51 supported by the support member 61. For this reason, the position of the deflection unit 51 in the direction orthogonal to the main optical axis surface 6A is hardly affected by thermal expansion, and it is possible to maintain good optical characteristics against environmental changes.

  Further, a fixing hole 68 is formed in the support member 61. In the fixing hole 68, the fixing member 10B that supports the BD sensor 10 and the synchronous lens 10A is fixed to the supporting member 61.

  As shown in FIG. 5, a mounting hole 52 is formed in the vicinity of the right end portion in the drawing on the front and back surfaces of the deflection unit 51, and a support shaft 53 is formed in the vicinity of the left end portion in the drawing. . The support member 61 includes mirrors 21 and 22 (22A to 22C), 23 (23A and 23B), 24 (24A to 24C), the second cylindrical lenses 9A to 9D, and the BD sensor 10 and the synchronous lens 10A. In the state where the outer surface is supported, the outer surface is brought into contact with the inner surfaces of the front and rear wall surfaces of the housing main body 31A and stored in the housing main body 31A.

  The recess 66 is open on the left side in the figure, and the width in the vertical direction is larger than the radius of the support shaft 53. In addition, the length of the recess 66 is longer than the outer diameter of the support shaft 53 in the sub scanning direction (arrow YY direction). Therefore, only the upper side surface of the recess 66 is in contact with the peripheral surface of the support shaft 53, and the support shaft 53 is displaceable by a predetermined distance in the sub-scanning direction with respect to the recess 66.

  Ribs 35 are formed on the front and rear wall surfaces of the housing main body 31A so as to protrude outward over the entire circumference. For this reason, the front and back wall surfaces of the housing main body 31A are made stronger than the other portions. Accordingly, the support member 61 is reinforced by the wall surface of the housing main body 31A in the main scanning direction which is the thickness direction.

  After housing the support member 61 in the housing main body 31A, the deflection unit 51 is inserted below the housing main body 31A from the left side in FIG. When the support member 61 is stored in the housing main body 31A, the fixing hole 64 of the support member 61 faces the mounting hole 36 of the housing main body 31A. When the support shaft 53 of the deflection unit 51 is fitted into the recess 66 of the support member 61, the mounting hole 52 of the deflection unit 51 faces the fixing hole 36 of the housing main body 31A and the fixing hole 64 of the support member 61.

  In this state, the shaft portion 54A of the fixing member 54 is passed through the fixing hole 36 and the fixing hole 64 sequentially from the outside of the housing main body 31A, and is further fitted into the attachment hole 52. Thereby, the support member 61, the housing main body 31A, and the deflection unit 51 are positioned at one point in the sub-scanning direction.

  The shaft portion 54A of the fixing member 54 is configured by coaxially arranging three portions having different diameters. The shaft portion 54A of the fixing member 54 is fitted in the mounting hole 36 of the housing main body 31A, the fixing hole 64 of the support member 61, and the mounting hole 52 of the deflection unit 51 in each of the three portions. Therefore, the housing main body 31A and the deflection unit 51 are deformed independently of each other, and the deformation generated in the housing main body 31A does not affect the position of the deflection unit 51.

  When assembling the exposure unit E configured as described above, a light source such as the semiconductor laser 1 and a scanning optical member such as the fθ lenses 7 and 8 are attached to the deflection unit 51 while strictly defining their positions. On the other hand, the mirrors 21 to 24, which are reflective optical members, are attached to the support member 61 of the housing unit 31 with the second cylindrical lenses 9A to 9D and the BD sensor 10 strictly defined with respect to each other. Thereafter, the deflection unit 51 is supported by the support member 61 from the outside of the housing unit 31 along the main optical axis surfaces of the laser beams L1 to L4 irradiated by the deflection unit 51.

  As described above, since the mounting operation and adjustment operation of the scanning optical member in the deflection unit 51 and the installation operation and adjustment operation of the reflection optical member in the housing unit 31 can be performed individually, the efficiency of the assembly operation can be improved. In addition, the maintenance work can be facilitated.

  Further, since the deflection unit 51 and the housing unit 31 are integrated in an individually adjusted state, almost rough adjustment has been completed in each, and the scanning position after the deflection unit 51 is mounted on the housing unit 31. It is sufficient to make adjustments to the extent that the image forming apparatus 100 and the image forming apparatus 100 are mounted.

  Further, the test light is irradiated in the same state as the laser beams L1 to L4 irradiated from the deflection unit 31 in the housing unit 31 after the reflection optical member is mounted and before the deflection unit 51 is mounted. Since it can enter, for example, the adjustment of the reflective optical member attached to the housing unit 31 can be easily performed using an adjustment jig using a laser beam.

  In addition, it is possible to make it less susceptible to an optical axis deviation error due to an installation error when both units are combined.

  Further, even after the deflection unit 51 is once mounted on the housing unit 31, the deflection unit 51 can be easily separated from the housing unit 31 simply by removing the fixing member 54. For this reason, the maintenance work of the exposure unit E after being mounted on the image forming apparatus 100 can be easily performed.

  FIG. 7 is a perspective view from obliquely upward on the back side showing the opened state of the exposure unit. FIG. 8 is a view showing a configuration of an adjustment member used in the exposure unit. Second cylindrical lenses 9 </ b> A to 9 </ b> D are arranged at the uppermost part inside the exposure unit E assembled as described above. As described above, the second cylindrical lenses 9 </ b> A to 9 </ b> D are supported by the lens support portions 67 </ b> A to 67 </ b> D formed on the upper end surface of the support member 61 via the adjustment member 71.

  Concave portions 81 </ b> A to 81 </ b> D are formed at positions facing the lens support portions 67 </ b> A to 67 </ b> D of the support member 61 on the upper surface of the front surface side and the back surface side of the housing main body 31 </ b> A. In addition, holes 82A to 82D are formed in the upper surface on the back side of the housing main body 31A in proximity to the recesses 81A to 81D. The recesses 81 </ b> A to 81 </ b> D store the adjustment member 71. A part of the adjustment gear 72 is exposed on the upper surface side from the holes 82A to 82D.

  The adjustment member 71 includes a holder 71A, a holder spring 71B, and a lens spring 71C. Each end of the second cylindrical lenses 9A to 9D is housed in the holder 71A via a lens spring 71C. The holder 71A is accommodated in a recess 81 (81A to 81D) on the back side of the housing main body 31A via a holder spring 71B. In the sub-scanning direction, the width of each recess 81 is longer than the length of the holder 71A.

  The adjustment gear 72 meshes with the adjustment gear 73 on the back surface of the housing main body 31A. The rotation of the adjustment gear 73 is transmitted as a linear motion in the sub-scanning direction to the holder 71A accommodated in the recess 81 via a mechanism (not shown). Thus, by rotating the adjustment gear 72 exposed from the hole 82 (82A to 82D), the end on the back side of the second cylindrical lens 9 (9A to 9D) moves in the sub-scanning direction, and the exposure unit The inclination of the second cylindrical lens 9 in the upper surface of E changes. Thereby, the inclination of the scanning direction of the image light with respect to the surface of the photosensitive drum 101 (101A to 101D) is adjusted.

  As shown in FIG. 7, the adjustment member 71 is exposed at a position corresponding to each of the photosensitive drums 101 </ b> A to 101 </ b> D on the surface facing the photosensitive drum 101 in the exposure unit E. For this reason, the adjustment member 71 corresponding to the photosensitive drum 101 to which the scanning positions of the laser beams L1 to L4 are to be adjusted can be quickly recognized, and the adjustment work of the scanning positions of the laser beams L1 to L4 can be simplified. it can.

  In the above embodiment, the light beam scanning device applied to the image forming apparatus 100 including the four photosensitive drums 101A to 101D in which the four semiconductor lasers 1A to 1D are arranged in the deflection unit 51 is taken as an example. However, the present invention is not limited to this, and the present invention is similarly applied to a light beam scanning apparatus that irradiates at least a single object to be scanned by deflecting light of at least a single light source with equal angular velocity and equal velocity. Can be implemented.

It is explanatory drawing which shows the simple structure of the image forming apparatus provided with the light beam scanning apparatus which concerns on embodiment of this invention. It is the schematic of the front which shows the structure of the exposure unit which is the light beam scanning apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the optical path of the light beam in the said exposure unit. It is an external view from diagonally upward on the back side of the exposure unit. It is an assembly drawing from diagonally upward on the back side showing the internal structure of the exposure unit. It is a front view of the supporting member used for the said exposure unit. It is a perspective view from the slanting upper part of the back side which shows the cover open state of the said exposure unit. It is a figure which shows the structure of the adjustment member used for the said exposure unit.

Explanation of symbols

1 (1A-1D) Semiconductor laser (light source)
6 Polygon mirror (scanning optical member)
7 First fθ lens (scanning optical member)
8 Second fθ lens (scanning optical member)
9 (9A to 9D) Second cylindrical lens 21 to 24 Mirror (reflection optical member)
31 Housing unit 31A Housing body (exterior body)
31B Housing lid (exterior body)
51 Deflection unit 61 Support member (structure)
101 (101A to 101D) Photosensitive drum 10 BD sensor

Claims (6)

A light source that irradiates a light beam, and a deflection unit that supports a scanning optical member that deflects the light beam emitted from the light source at an equal angular velocity and then deflects it at an equal velocity
The light beam deflected at a constant speed by the scanning optical member is divided into a housing unit that supports a plurality of reflecting optical members that reflect the light beam toward the scanning target supported by the main apparatus, and is configured.
The deflection unit, as the scanning optical member, reflects a light beam emitted from the light source by a reflecting surface and deflects the beam at a constant angular velocity, and fθ deflects the light beam deflected by the polygon mirror at a constant velocity. A lens, and
The housing unit includes two and structures made of metal plates supporting the deflection unit and the plurality of reflecting optical member disposed in parallel to each other physician in position, said housing the said reflecting optical member A resin exterior body covering two structures,
Further, the deflecting unit is configured such that the structure body is externally provided along the main optical axis plane that is a horizontal plane including a normal direction of a reflecting surface of the polygon mirror that reflects the light beam emitted from the light source . A light beam scanning device characterized by being detachable at a predetermined position. The light beam scanning apparatus according to claim 1, wherein the reflection optical member reflects the light beam toward an upper surface side of the housing unit, and the deflection unit is disposed on a bottom surface side of the housing unit. The deflection unit, the light beam scanning apparatus according to claim 1 or 2, characterized in that a plurality of light sources and each single scanning optical element. The light beam scanning apparatus according to claim 1, wherein the structure is provided with a supported portion that is exposed to the outside of the exterior body at each of both ends in a direction along the main optical axis surface. Equipped with equipment,
A shaft fixed to the front and back frames and having two shafts that fit into the supported portion. A light beam modulated by image data from the light beam scanning device is photoconductive. An image forming apparatus characterized by irradiating the surface of an image carrier that produces an action. The light beam scanning device according to claim 3 , wherein the structure includes a supported portion that is exposed to the outside of the exterior body at each of both end portions in a direction along the main optical axis surface; A plurality of image carriers that receive each of the light beams emitted by each of the light sources, and
Each of a plurality of light beams modulated by image data from the light beam scanning device has two shaft bodies that are fixed to the front side frame and the back side frame and are fitted into the supported portion. Is applied to the surface of an image carrier that generates a photoconductive action. An adjusting member for adjusting an irradiation position of the light beam with respect to said image bearing member, according to claim 4 or 5, characterized in that provided exposed on a surface facing the image carrier in the optical beam scanning device Image forming apparatus.

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