JP2011053343A - Optical scanner and image forming apparatus equipped with the same - Google Patents

Abstract

An optical scanning device capable of effectively utilizing a space in an image forming apparatus, compactly installing a plurality of laser light sources, a polygon mirror and a BD sensor, and reducing a load of a laser light source for black, and an image provided with the same A forming apparatus is provided.
A plurality of laser diodes LD1 to LD4 for irradiating laser light, a polygon mirror 14 for reflecting and deflecting laser light from each laser diode on the same surface, and polygons respectively corresponding to a plurality of photosensitive drums 3a to 3d. A plurality of mirrors 43 for irradiating the laser light deflected by the mirror 14; a BD sensor 15 for detecting the laser light reflected by the polygon mirror 14 and guided by the plurality of mirrors 43 and outputting a horizontal synchronizing signal; The BD sensor 15 is disposed above the polygon mirror 14 and is concentrated in the vicinity of the photosensitive drum 3a to be printed first.
[Selection] Figure 2

Description

  The present invention relates to an optical scanning device and an image forming apparatus including the optical scanning device. For example, the optical scanning device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus including the optical scanning device. Relates to the device.

  In color image forming apparatuses such as digital copying machines and laser printers, a tandem type apparatus in which a plurality of photoconductors are arranged in tandem has been put into practical use as the speed thereof increases. Here, for example, four photosensitive drums are arranged in the recording paper conveyance direction, and a scanning optical system corresponding to each of these photosensitive drums simultaneously exposes these photosensitive members to form a latent image. Are visualized with a developing device using developers of different colors such as yellow, magenta, cyan, and black. Then, these visualized toner images are sequentially superimposed and transferred onto the same recording paper to obtain a color image.

  In addition, such a color image forming apparatus employs an intermediate transfer method, and in order to shorten the time required for printing the first recording sheet, a plurality of photosensitive drums and optical scanning are provided below the intermediate transfer belt. Equipment.

  The optical scanning device is configured to scan laser light emitted from a plurality of light sources with a rotating polygon mirror (polygon mirror), and to expose photosensitive drums for yellow, magenta, cyan, and black. In such an optical scanning device, the writing start timing on the photosensitive drum in the main scanning direction is synchronized by detecting the BD signal. That is, the optical scanning device has a BD sensor (horizontal synchronization sensor) for detecting laser light as a synchronization detection beam outside the image forming area in order to synchronize the timing of writing start in the main scanning direction. .

  The BD sensor as described above is provided only on the optical path of the black laser beam, for example, and only the black laser beam among the four laser beams is supported, and this is applied to the laser beams for other colors. By making the reference, scanning is started at a predetermined writing start timing of the image data.

  The tandem method in which a plurality of photoconductors are exposed simultaneously is advantageous for high-speed printing because colors and monochrome images can be output at the same speed as a method in which images of each color are sequentially formed on one photoconductor. On the other hand, a scanning optical system corresponding to a plurality of photoconductors is required. In order to configure such a scanning optical system, in the image forming apparatus, a large number of optical elements such as lenses and mirrors are respectively arranged at optimum positions. These optical elements are arranged at appropriate positions for guiding the optical path of the laser light emitted from the light emitting element by the laser diode, and adjusting the shape of the laser light to irradiate the photosensitive member with high accuracy.

  For example, in the configuration of Patent Document 1, a black photosensitive drum is disposed in the vicinity of a transfer position to a recording sheet in order to shorten the time required for printing the first recording sheet, and a plurality of laser light sources and polygons are arranged. The mirror is also arranged in the vicinity of the position for transfer to the recording paper.

JP 2007-171493 A

  However, if the black photosensitive drum is arranged in the vicinity of the position where the toner image on the recording paper is transferred, it is necessary to make a large space for installing a plurality of laser light sources, polygon mirrors, and BD sensors. The wiring of the wire line used when supplying the optical scanning device becomes complicated for a long time, which causes an increase in size and weight of the optical scanning device.

  In addition, since it is configured to obtain a synchronization signal using only the black laser beam during color printing and monochrome printing, the load on the black laser light source increases and the product life of the black laser light source is shortened. There is a problem of becoming.

  The present invention has been made in view of the above-described circumstances. The space in the image forming apparatus is effectively used, a plurality of laser light sources, a polygon mirror, and a BD sensor are installed in a compact manner. An object of the present invention is to provide an optical scanning device capable of reducing the load and an image forming apparatus including the same.

  In order to solve the above-described problems, each configuration of the optical scanning device according to the present invention and the image forming apparatus including the same is as follows.

  The optical scanning device of the present invention includes a plurality of light sources that emit laser light, a rotating polygon mirror that reflects and deflects the laser light from the light source on the same surface, and the rotating polygon mirror that respectively corresponds to a plurality of photosensitive members. An optical system for irradiating the laser light deflected by the optical system, and a horizontal synchronizing signal generating means for detecting the laser light reflected by the rotary polygon mirror and guided by the optical system and outputting a horizontal synchronizing signal; The horizontal synchronizing signal generating means is disposed above the rotary polygon mirror.

  The optical system may be a plurality of lenses that condense and deflect the laser light and a mirror that reflects or transmits the laser light.

  Further, the optical scanning device is arranged in the vicinity of the photoconductor that is farthest from the position where the recording sheet is transferred, in which the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are concentrated. It is characterized by that.

  Further, the horizontal synchronizing signal generation means of the optical scanning device is one of the plurality of laser beams emitted from the plurality of light sources, and detects the laser beam used for the photoconductor to be printed first. The horizontal synchronizing signal is output.

  The optical scanning device includes: a plurality of light receiving elements that detect the intensity of the laser light emitted from the laser light source and output a light amount signal; and a plurality of laser light amount control units that control the light amount of the laser light; Based on the light quantity signals detected and generated by the plurality of light receiving elements, the laser light quantity control means distributes and feeds back to the corresponding laser light quantity control means, and the laser light quantity control means sends a control signal to The automatic output control is performed based on the light amount signal from the element.

  In addition, the image forming apparatus of the present invention includes the optical scanning device, the photosensitive member on which an electrostatic latent image is formed by irradiation of the laser light from the optical scanning device, and the electrostatic device formed on the photosensitive member. The image forming apparatus includes: a developing unit that develops the latent image by attaching the latent image to the developer; and a transfer unit that transfers the developer attached by the developing unit to a recording medium.

  In the image forming apparatus, at least the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are concentrated in the vicinity of the photoconductor to be printed first. Is.

  According to the present invention, a plurality of light sources that emit laser light, a rotary polygon mirror that reflects and deflects the laser light from the light source on the same surface, and a deflection by the rotary polygon mirror respectively corresponding to a plurality of photoconductors. An optical system for irradiating the laser beam, and a horizontal synchronization signal generating means for detecting the laser beam reflected by the rotary polygon mirror and guided by the optical system and outputting a horizontal synchronization signal. When the horizontal synchronization signal generating means is disposed above the rotary polygon mirror, the laser beam is reflected / deflected from the rotary polygon mirror, passes through the optical system, and reaches the synchronization generation means. Therefore, the detection delay of the laser beam can be prevented beforehand. In addition, since the horizontal synchronization signal generating means can be effectively used by arranging the horizontal synchronizing signal generation unit in the space on the rotary mirror, it is possible to achieve an excellent effect that the downsizing of the optical scanning device can be realized.

  According to the present invention, the optical system includes a plurality of lenses that collect and deflect the laser light and a mirror that reflects or transmits the laser light, thereby controlling vibration of the optical system related to print quality. Can do.

  According to the invention, in the optical scanning device, the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are arranged in a concentrated manner, and the photosensitive member that is farthest from a position to which a recording sheet is transferred. Therefore, the optical scanning device can be prevented from being enlarged, the wiring of the optical wire can be simplified, and the length of the optical scanning device can be reduced because it does not require a long wire. An excellent effect that it is possible can be achieved.

  According to the present invention, the horizontal synchronization signal generating means of the optical scanning device is one of the plurality of laser beams emitted from the plurality of light sources, and the laser used for the photoconductor to be printed first. By detecting the light and outputting the horizontal synchronizing signal, it is possible to reduce consumption of laser light sources other than the laser light source that emits the laser light used for the photoconductor to be printed first.

  According to the present invention, the optical scanning device detects a light intensity of the laser light emitted from the light source and outputs a light quantity signal, a laser light quantity control means for controlling the light quantity of the laser light, Based on the light quantity signal detected and generated by the light receiving element, and distributes and feeds back to each laser light quantity control means, and the laser light quantity control means sends a control signal to send the light quantity from the light receiving element. By performing automatic output control based on the signal, APC can be performed to adjust the light amount, the laser light emitted from each light source can be stabilized, and the excellent effects of reducing unevenness in the image to be formed can be obtained.

  According to the present invention, the photosensitive member on which an electrostatic latent image is formed by the laser beam irradiation by the optical scanning device and the electrostatic latent image formed on the photosensitive member are attached to a developer. An image forming apparatus comprising: a developing unit that develops the toner by the developing unit; and a transfer unit that transfers the developer adhered by the developing unit to a recording medium. Therefore, it is possible to realize a downsized image forming apparatus that enables good image formation.

  According to the present invention, in the image forming apparatus, at least the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are concentrated in the vicinity of the photoconductor to be printed first. Thus, the space in the image forming apparatus can be effectively used, and the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating means can be installed in a compact manner, thereby realizing a downsized image forming apparatus.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus including an optical scanning device according to an embodiment of the present invention. 1 is an explanatory diagram illustrating a configuration of an optical scanning device of an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view of an optical scanning device of an image forming apparatus according to an embodiment of the present invention. It is a timing chart at the time of producing | generating a horizontal synchronizing signal using the laser beam irradiated from the black (K) laser light source at the time of the conventional color printing. 6 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a yellow (Y) laser light source during color printing according to an embodiment of the present invention. It is a timing chart at the time of producing | generating a horizontal synchronizing signal using the laser beam irradiated from the black (K) laser light source at the time of the conventional monochrome printing. 6 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a yellow (Y) laser light source during monochrome printing according to an embodiment of the present invention. It is a block diagram of the laser light quantity control part which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an image forming apparatus 100 provided with an optical scanning device 1 according to the present embodiment.

  The image forming apparatus 100 according to the present embodiment performs color separation on image information, forms an image for each hue, and outputs a color image or a monochrome image on a predetermined sheet (recording sheet). In general, the image forming apparatus main body 110, the automatic document processing apparatus 120, and the paper feeding unit 200 are included.

  The image forming apparatus main body 110 according to this embodiment includes a photosensitive drum 3 (toner image) that carries a developer image (toner image) formed by a developer (toner) that matches each hue in accordance with color-separated image information. A plurality of process printing units 19 (developing means) having an electrostatic latent image carrier) and laser beams (beams) are radiated onto the respective photosensitive drums 3 for each color based on image information. The recording sheet includes an exposure unit 1 (optical scanning device) that generates an image, an endless intermediate transfer belt unit 6 that constitutes a transfer unit that stacks and transfers a plurality of toner images, and a heat roller 71 and a pressure roller 72. And a fixing unit 7 for thermally fixing the toner image transferred to the toner image.

  A document placing table 92 made of transparent glass on which a document is placed is provided on the upper portion of the image forming apparatus main body 110. An automatic document processing device 120 is provided above the document table 92.

  The automatic document processing device 120 is also mounted so as to be automatically openable and closable, also serving as a document pressing cover made up of a double-sided document automatic reading device using a document moving method. The automatic document processing device 120 is configured to be rotatable in the direction of arrow M in FIG. 1 and is configured such that a document can be manually placed by opening the upper side of the document placing table 92.

  When the document is set on the document tray 93 on which the document is placed, the automatic document processing device 120 picks up the uppermost document by the pickup roller 121 and pulls out the document one by one from the document tray 93 and conveys it. After this document is guided and passed through a contact glass (not shown) provided in the image reading unit 102, the document is discharged to a document discharge tray 94.

  The paper feed unit 200 includes a paper feed cassette 202 and a paper feed tray 201, each of which has a plurality of recording papers.

  Each process printing unit 19 includes a developing device 2, a photosensitive drum 3, a cleaner unit 4, and a charger 5, and forms a latent image corresponding to each color.

  In the present embodiment, four process printing units 19a, 19b, 19c, and 19d corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are used as the process printing unit 19. The belts 61 are sequentially provided along the belt 61.

  The process printing unit 19a in which the transfer of the toner image on the recording paper is first performed, that is, the hue process printing unit 19a arranged at the furthest position from the transfer roller 10e includes yellow hue toner, and includes an intermediate transfer belt 61. First, a yellow toner image is formed. The process printing unit 19b includes a magenta hue toner and forms a magenta toner image. The process printing unit 19c includes a cyan hue toner and forms a cyan toner image. Among the four process printing units, the process printing unit 19d disposed at the position closest to the transfer roller 10e includes a toner of black hue and forms a black toner image.

  The intermediate transfer belt unit 6 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, intermediate transfer rollers 64a, 64b, 64c and 64d, and an intermediate transfer belt cleaning unit 65. The intermediate transfer belt unit 6 is disposed above the photosensitive drums 3a to 3d.

  In the following description, the intermediate transfer rollers 64a, 64b, 64c, and 64c are collectively referred to as the intermediate transfer roller 64 when used. The intermediate transfer roller 64 is provided corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). When the photosensitive drums 3a to 3d are used generically, they are referred to as the photosensitive drum 3.

  The intermediate transfer belt 61 is formed endlessly using a film having a thickness of about 100 μm to 150 μm. As the material of the transfer belt 61, polyimide, polycarbonate, thermoplastic elastomer, alloy, or the like is mainly used.

  Further, the intermediate transfer belt 61 is stretched by an intermediate transfer belt drive roller 62, an intermediate transfer belt driven roller 63, and an intermediate transfer roller 64 so that the surface thereof is in contact with the outer peripheral surface of the photosensitive drum 3, and the intermediate transfer belt 61 It is configured to move in the sub-scanning direction by the driving force of the belt driving roller 62. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 61 by sequentially superimposing and transferring the respective color toner images formed on the photosensitive drum 3 by the process printing unit 65 onto the intermediate transfer belt 61. It is configured to form.

  The intermediate transfer belt driving roller 62 is disposed on one end side of the housing, and is provided so as to convey the recording paper while being pressed against the housing by sandwiching the transfer belt 61 together with the intermediate transfer belt driving roller 62.

  The intermediate transfer roller 64 is disposed at a position shifted to the downstream side in the moving direction of the transfer belt 61 wound around the transfer belt driven roller 63 from the transfer belt driving roller 62, and presses against the inner surface of the transfer belt 61, The outer surface of the transfer belt 61 is provided so as to obtain a predetermined nip amount by winding a part of the outer peripheral surface of the photosensitive drum 3.

  The intermediate transfer roller 64 includes a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and an outer peripheral surface of the metal shaft is covered with a conductive elastic material such as EPDM (ethylene propylene rubber) or urethane foam. Yes. The conductive elastic material can uniformly apply a high voltage to the intermediate transfer belt 61.

  Transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 61 is performed by an intermediate transfer roller 64 that is in contact with the substantially back side of the intermediate transfer belt 61. The intermediate transfer roller 64 configured in this manner is opposite to the high-voltage transfer bias, that is, the toner charging polarity (minus), in order to transfer the toner image formed on the photosensitive drum 3 to the intermediate transfer belt 61. A high voltage of polarity (plus) is applied, and the high voltage is uniformly applied to the intermediate transfer belt 61 by the elastic material.

  In this embodiment, a roller shape is used as the transfer electrode, but a brush-like transfer electrode (transfer brush) may be brought into contact with the back side of the intermediate transfer belt 61 to serve as a transfer unit.

  The toner images (electrostatic images) that have become prominent in accordance with the respective hues on the respective photosensitive drums 3 are laminated by the intermediate transfer belt 61 and become image information input to the apparatus. The image information stacked in this way is transferred onto the recording sheet by the rotation of the intermediate transfer belt 61 by a transfer roller 10e disposed at a contact position between the recording sheet and the intermediate transfer belt 61 described later.

  The transfer unit 10 constituting the transfer unit constitutes a transfer unit that transfers the developer image transferred to the intermediate transfer belt 61 onto a recording sheet. The transfer unit 10 includes a transfer roller 10e, and the transfer roller 10e is the intermediate transfer belt. The drive roller 62 is disposed substantially horizontally and parallel to the drive roller 62 so as to come into pressure contact with the intermediate transfer belt 61 wound around the transfer roller 10e at a predetermined nip.

  The transfer roller 10e is applied with a voltage for transferring a multicolor toner image formed on the intermediate transfer belt 61 onto a recording sheet, that is, a high voltage having a polarity opposite to the toner charging polarity (minus) and a polarity (plus). It is comprised so that.

  One of the transfer roller 10e and the intermediate transfer belt driving roller 62 is made of a hard material (metal or the like), and the other is a soft material (elastic rubber roller or foaming resin roller or the like) on the surface of the core metal. It is composed of a covered elastic roller. As a result, a nip having a predetermined width can be obtained constantly.

  A registration roller 13 is provided below the transfer belt driving roller 62 and the transfer roller 10e. The registration roller 13 is configured to align the leading end of the recording sheet fed from the sheet feeding unit 200 and the leading end of the toner image on the intermediate transfer belt 61 and convey the registration roller to the transfer roller 10e side.

  In addition, the toner adhering to the intermediate transfer belt 61 due to contact with the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording paper by the transfer roller 10e is mixed with toner in the next step. In order to cause this, it is set to be removed and collected by the intermediate transfer belt cleaning unit 65.

  The intermediate transfer belt cleaning unit 65 is provided in the vicinity of the intermediate transfer belt driven roller 63 and disposed so as to be in contact with (or slidably contact with) the intermediate transfer belt 61. A toner recovery unit (not shown) that temporarily stores the toner (waste toner) scraped off from the residual toner is configured to scrape and recover the residual toner on the intermediate transfer belt 61. .

  Further, the intermediate transfer belt cleaning unit 65 is disposed in the vicinity of the process printing unit 6 on the upstream side of the process printing unit 6 in the moving direction of the intermediate transfer belt 61. The portion of the intermediate transfer belt 61 where the cleaning blade contacts the outer surface is supported by the intermediate transfer driven roller 63 on the inner surface.

  The paper feed unit 200 includes a paper feed tray 201 for storing recording paper used for image formation, and is provided below the optical scanning device 1. Recording paper is supplied from the paper feed tray 201 one by one.

  The paper feed tray 201 is provided below the paper feed unit 200 positioned below the image forming apparatus main body, and a large amount of recording paper having a size defined by the specifications of the image forming apparatus or a size predetermined by the user is provided. The structure which can be accommodated is taken.

  A pickup roller 11 a is provided on one end portion of the paper feed tray 201, and comes into contact with the surface of one end portion of the recording paper at the top of the recording paper set in the paper feed tray 201, so that the frictional resistance of the roller To feed and convey one sheet at a time.

  The paper discharge tray 91 is provided in the upper part of the image forming apparatus main body 110 so that printed recording paper is discharged face down and stacked.

  The paper feed unit 200 includes a substantially vertical paper transport path S for transporting the recording paper in the paper feed tray 201 to the paper discharge tray 91 provided above via the transfer unit 10 and the fixing unit 7. Has been.

  In the vicinity of the paper transport path S from the paper feed tray 201 to the paper discharge tray 91, a pickup roller 11a, a registration roller 13, a transfer unit 10, a fixing unit 7, and a plurality of transport rollers 12a, 12b, 12c, 12d, and the like. It is arranged.

  The conveyance rollers 12a, 12b, 12c, and 12d are small rollers for promoting and assisting conveyance of the recording paper, and a plurality of conveyance rollers 12a, 12b, 12c, and 12d are provided along the paper conveyance path S.

  The pickup roller 11 a is provided near the end of the paper feed cassette 202, picks up recording paper from the paper feed cassette 202 one by one, and supplies it to the paper transport path S. The pickup roller 11b is provided in the vicinity of the end of the manual paper feed cassette 203, and is provided in the vicinity of the end of the manual paper feed cassette 203 which is disposed on the side surface of the image forming apparatus and can manually supply recording paper. Recording sheets are picked up one by one from the sheet feeding cassette 203 and supplied to the sheet conveyance path S.

  The registration roller 13 temporarily stops the recording sheet conveyed by the sheet conveyance path S at a predetermined position and measures the next conveyance timing. It has a function of conveying the recording sheet to the transfer unit 10 at a timing at which the leading edge of the toner image on the intermediate transfer belt 61 is synchronized with the leading edge of the recording sheet.

  The recording paper conveyed from the paper feed tray 201 is conveyed to the registration roller 13 by the conveyance roller conveyance roller 12 a in the conveyance path and temporarily stops. The registration roller 13 then stops the leading edge of the stopped recording paper and the intermediate transfer belt 61. The toner image is conveyed to the transfer unit 10 at a timing for aligning the leading ends of the toner images.

  The transferred recording paper is transferred to the toner image on the intermediate transfer belt 61 by the transfer unit 10 and further transferred to the fixing unit 7 where the unfixed toner on the recording paper is melted by heat and fused to the recording paper. To do. After passing through the fixing unit 7 via the conveying rollers 12c and 12d, the sheet is naturally cooled and fixed on the recording paper. Then, the recording paper is discharged onto the paper discharge roller 91.

  The paper transport path S is for printing on one side of the recording paper. On the other hand, when printing on both sides of the recording paper, when the printing ends on one side and the trailing edge of the recording paper that has passed through the fixing unit 7 is gripped by the conveying roller 12b, the conveying roller 12b rotates in the reverse direction. The recording paper is guided to the transport rollers 12c and 12d. Further, after printing is performed on the back surface of the recording paper through the registration roller 13, the recording paper is discharged to the paper discharge tray 91.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72, and is configured to rotate with a recording sheet interposed therebetween.

  The fixing unit 7 fixes the toner image by controlling the heat roller 71 to a predetermined fixing temperature based on a detection value from a temperature detector (not shown) and maintaining the predetermined temperature (fixing temperature). This is realized by heat-fixing the toner image on the recording paper by heating and pressing the recording paper on which the toner image has been transferred between the heat roller 71 and the pressure roller 72 while being rotated and conveyed. The heat roller 71 is heated by the external heating belt 73.

  The process printing units 19a, 19b, 19c, and 19d are provided in parallel in a substantially horizontal direction (left and right direction in the drawing) in the housing of the image forming apparatus, and the photosensitive drum 3a that is an image carrier for each color. 3b, 3c, and 3d, and chargers (charging means) 5a, 5b, 5c, and 5d for charging the photosensitive drums 3a, 3b, 3c, and 3d, and cleaner units 4a, 4b, 4c, and 4d, respectively.

  Here, the symbols a, b, c, and d attached to the components corresponding to the respective colors correspond to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) in the order of description. However, in the following description, the components provided for each color are collected together in the developing device 2 except for the case where the components corresponding to a specific color are specified and described. The photosensitive drum 3, the cleaner unit 4, and the charged body 5 are described.

  The photosensitive drum 3 is disposed such that a part of the outer peripheral surface thereof is in contact with the surface of the intermediate transfer belt 61, and the charging device 5, the developing device 2, and the like as an electric field generator along the outer peripheral surface of the drum. A cleaner unit 4 is arranged in close proximity.

  The charger 5 is a charger type charger, and is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. The charger 5 is disposed so as to be in contact with the outer peripheral surface of the photosensitive drum 3 on the substantially opposite side to the position where the intermediate transfer belt unit 6 is disposed across the photosensitive drum 3. In the present embodiment, a charge-type charger is used as the charger 5. However, a roller-type charger, a brush-type charger, or the like may be used instead of the charge-type charger.

  The developing device 2 stores toner of each color of yellow (Y), magenta (M), cyan (C), and black (K) for each developing device 2, and is charged in the rotating direction of the photosensitive drum. 5 is arranged on the downstream side. Then, each color toner is supplied to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 3 to make it noticeable.

  The cleaner unit 4 includes a cleaning blade, and is configured to contact the cleaning blade along the outer peripheral surface of the photosensitive drum 3 to scrape and collect residual toner on the photosensitive drum 3.

  Next, the configuration of the optical scanning device according to the embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a schematic view showing the relationship between the optical scanning device of the image forming apparatus and the intermediate transfer unit according to the embodiment of the present invention. FIG. 3 is a perspective view of the optical scanning device of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a black (K) laser light source during conventional color printing. FIG. 5 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a yellow (Y) laser light source during color printing according to the present invention. FIG. 6 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a black (K) laser light source during conventional monochrome printing. FIG. 7 is a timing chart when a horizontal synchronization signal is generated using laser light emitted from a yellow (Y) laser light source during monochrome printing according to the present invention. FIG. 8 shows a laser light quantity control unit according to the embodiment of the present invention.

  As shown in FIGS. 2 and 3, the optical scanning device 1 according to the present embodiment irradiates a plurality of laser beams corresponding to colors of yellow (Y), magenta (M), cyan (C), and black (K). Laser light source (laser diode unit: LD), a rotary polygon mirror (polygon mirror 14) that reflects and deflects each laser beam on the same surface, and a plurality of photosensitive drums 3 are reflected and deflected by the polygon mirror 14. Further, a reflecting mirror 43 for irradiating each laser beam and a horizontal synchronizing signal generating means (BD sensor) for detecting each laser beam reflected by the polygon mirror 14 and guided by the reflecting mirror 43 and outputting a horizontal synchronizing signal. 15).

  The laser diode unit LD includes a plurality of laser diodes LD (LD1, LD2, LD3, LD4), a collimator lens (not shown), and a cylindrical lens (not shown).

  The collimator lens converts the divergent laser light emitted from each laser diode into parallel laser light (laser beam) and irradiates the polygon mirror 14 with it.

  The cylindrical lens focuses the laser beam only in one axial direction, and makes the laser beam an elongated line image. The laser light emitted from the laser diode diffuses to a non-target, but more stable laser light can be provided by using it in combination with a collimator lens.

  Laser diodes are used in the plurality of laser light sources of this embodiment. Instead, a configuration using a writing head in which light emitting elements such as EL (Electro Luminescence) and LED (Light Emitting Diode) are arranged in an array is used. May be.

  The polygon mirror 14 has a regular polygonal column shape, includes a plurality of reflection surfaces, and is driven to rotate at high speed by a polygon motor (not shown) attached to the bottom surface of the optical scanning device 1. The laser beam transmitted through the half mirror (light deflecting means) is deflected in the main scanning direction.

  As shown in FIG. 2, the optical system that reflects the laser light includes a plurality of reflection mirrors 43 that reflect the laser light, half mirrors 30 and 31 as means for transmitting and polarizing the laser light, the first fθ lens 40, the first It includes a 2fθ lens 41 and four third fθ lenses 42a, 42b, 42c, and 42d.

  The plurality of fθ lenses correct distortion aberration so as to ensure temporal linearity on the photosensitive drum 3.

  The plurality of fθ lenses are long in the main scanning direction and short in the direction perpendicular to the main scanning direction and are formed in a rod shape, and both ends thereof are supported by the optical scanning device main body.

The operation for each laser beam in the optical scanning device 1 will be described below.
The laser light emitted from the laser diode LD1 corresponding to yellow becomes parallel light by the collimator lens, passes through the half mirror 31 (light deflecting means), and further passes through the cylindrical lens. Further, a laser beam having a predetermined diameter enters the polygon mirror 14. The polygon mirror 14 rotates at a high constant angular velocity, and the laser light incident along with the rotation is reflected and polarized as a deflected laser light that continuously changes its angle, and is scanned in the main scanning direction.

  Further, the laser light passes through the first fθ lens 40 and the second fθ lens 41 and is subjected to a condensing function, then is reflected by the reflection mirror and proceeds to the third fθ lens 42a. The focused laser beam is reflected again by another mirror, passes through the third fθ lens 42a, and enters the photosensitive drum 3a corresponding to yellow. The structure is such that the laser light constantly strikes the photosensitive drum 3a perpendicularly. Further, the laser beam reflected again by the another mirror described above is transmitted through another half mirror 30 and diffracted, and then enters the BD sensor 15. The BD sensor 15 will be described later.

  On the other hand, the laser light emitted from the laser diode LD1 corresponding to yellow becomes parallel light by the collimator lens, and part of it is diffracted by the half mirror 31, and enters the laser light quantity control unit 8 shown in FIG. The laser light quantity control unit 8 includes a plurality of photodiodes (light receiving elements) F1-F4 that detect the intensity of the laser light emitted from each laser diode, and detects the laser light by the plurality of photodiodes to automatically Output control is performed. Details of the configuration of the laser light quantity control unit 8 will be described later.

  Each laser diode used as a laser light source is required to have a constant amount of emitted light, but the laser diode emits light due to temperature changes caused by the environment in which the laser diode is placed or the heat generated by the laser diode itself. It has the property that the amount of light varies.

  Therefore, a photodiode is arranged in the vicinity of the laser diode, the light emission amount of the laser diode is detected by a light receiving element (photodiode), and the light emission amount detected by the photodiode is fed back to the laser light amount control means, so that the laser light amount Control is performed so that the light amount of the laser diode is made constant by the control means. Such control is referred to as automatic output control (auto power control, APC).

  APC is performed on all of the plurality of laser light sources (laser diodes LD1 to LD4) provided in the optical scanning device for each scanning line on the photosensitive drum 3 to adjust the light amount. Thereby, in all the laser light sources, the light output can be stabilized, and the density unevenness of the image to be formed can be reduced. Details of the operation of the automatic output control in the present invention will be described later.

  Next, the operation of each laser beam emitted from the laser light sources of other colors will be described below with reference to FIG.

  Laser light emitted from the laser diode LD2 corresponding to magenta becomes parallel light by the collimator lens, passes through the half mirror 31, and further passes through the cylindrical lens. Further, a laser beam having a predetermined diameter enters the polygon mirror 14. The polygon mirror 14 rotates at a high constant angular velocity, and the laser light incident along with the rotation is reflected and polarized as a deflected laser light that continuously changes its angle, and is scanned in the main scanning direction.

  Further, the laser light passes through the first fθ lens 40 and the second fθ lens 41 and is subjected to a condensing function, then is reflected by the reflection mirror and proceeds in the direction of the third fθ lens 42b. The focused laser light is reflected again by another mirror, passes through the third fθ lens 42b, and enters the photosensitive drum 3b corresponding to magenta. The configuration is such that the laser light constantly strikes the photosensitive drum 3b perpendicularly.

  Further, the laser light emitted from the laser diode LD3 corresponding to cyan becomes parallel light by the collimator lens, passes through the half mirror 31, and further passes through the cylindrical lens. Further, a laser beam having a predetermined diameter enters the polygon mirror 14. The polygon mirror 14 rotates at a high constant angular velocity, and the laser light incident along with the rotation is reflected and polarized as a deflected laser light that continuously changes its angle, and is scanned in the main scanning direction.

  Further, the laser light passes through the first fθ lens 40 and the second fθ lens 41 and receives a condensing action, then is reflected by the reflection mirror 43 and proceeds to the third fθ lens 43c. The focused laser beam is reflected again by another mirror, passes through the third fθ lens 43c, and enters the photosensitive drum 3c corresponding to cyan. The structure is such that the laser light constantly strikes the photosensitive drum 3c perpendicularly.

  Further, the laser light emitted from the laser diode LD4 corresponding to black becomes parallel light by the collimator lens, passes through the half mirror 31, and further passes through the cylindrical lens. Further, a laser beam having a predetermined diameter enters the polygon mirror 14. The polygon mirror 14 rotates at a high constant angular velocity, and the laser light incident along with the rotation is reflected and polarized as a deflected laser light that continuously changes its angle, and is scanned in the main scanning direction.

  Further, the laser light passes through the first fθ lens 40 and the second fθ lens 41 and is subjected to a condensing function, then is reflected by the reflection mirror 43 and proceeds to the third fθ lens 42d. The focused laser beam is reflected again by another mirror, passes through the third fθ lens 42d, and enters the photosensitive drum 3d corresponding to black. The structure is such that the laser light constantly strikes the photosensitive drum 3d perpendicularly.

  Each charged photosensitive drum 3 is rotationally driven in the direction of the arrow as shown in FIG. 2, irradiated with laser light, and repeatedly scanned in the main scanning direction. Thereby, an electrostatic latent image is formed on the surface of each photosensitive drum 3. Each color toner is supplied by the developing device 2, and the electrostatic latent image formed on each photosensitive drum 3 becomes noticeable and becomes a toner image. These toner images are transferred onto the recording paper via the intermediate transfer belt 61, and become a color toner image on the recording paper.

  The BD sensor 15 is disposed in the vicinity of the scanning start position for one line of laser light irradiated onto the photosensitive drum 3. The distance between the BD sensor 15 and the polygon mirror 14 is set substantially equal to the distance between the photosensitive drum 3 and the polygon mirror 14. The BD sensor 15 is reflected and polarized by the polygon mirror 14, passes through the first fθ lens 40 and the second fθ lens 41, is reflected by the reflection mirror 43, and detects yellow laser light after being diffracted by the half mirror 30. .

  The detection signal (yellow laser light) of the BD sensor 15 is used as a horizontal synchronization signal (BD signal) for synchronizing the rotation of the polygon mirror (rotating polygon mirror) and the data writing. The control unit (not shown) of the optical scanning device according to the present invention determines the position to start writing an image on the photosensitive member for each scanning line based on the detection signal detected by the BD sensor 15. A signal (BD signal) is generated and output. A BD signal is generated for each line. Furthermore, the timing of writing out the laser beams of other colors is also performed based on the horizontal synchronization signal (BD signal).

  Further, in the present embodiment, the BD sensor 15 is disposed above the polygon mirror 14 and is disposed in the vicinity of the laser diode units LD1 to LD4 so that these components are concentrated in a part of the image forming apparatus. Thus, the space occupied in the image forming apparatus can be used efficiently, and the optical scanning device and the image forming apparatus including the same can be reduced in size.

  When the synchronization signal is generated by the laser light emitted from the black (K) laser light source as in the prior art, as shown in FIG. 3, the vicinity of the black (K) photosensitive drum (indicated by the dotted line in FIG. 3). It is arranged in the enclosed area B1). The plurality of laser diodes, the BD sensor 15 and the polygon mirror 14 operate by being supplied with electricity. However, the wiring of the wire line and the like accompanying this becomes long, and the place where each component of the optical scanning device is installed is limited. Therefore, it is inevitable to increase the size of the optical scanning device and the image forming apparatus including the same.

  In the optical scanning device of the present embodiment, the plurality of laser diodes LD1-LD4, the BD sensor 15, and the polygon mirror 14 are concentrated in the vicinity of the photosensitive drum 3a farthest from the transfer position. In this case, it is possible to simplify the routing of the wire wire, and it is possible to reduce the weight of the image forming apparatus because a long wire wire is unnecessary, and maintenance can be easily performed.

  Next, automatic output control according to the present embodiment will be described in detail. The automatic output control is controlled by the laser light quantity control unit 8.

  A part of the laser light emitted from each laser light source passes through the half mirror 31 (laser light branching means), and the other part of the laser light is diffracted and branched by the half mirror 31 to the laser light quantity control unit 8. Incident.

  The laser light amount control unit 8 includes light receiving elements (photodiodes) F1-F4 that detect the intensity of laser light, a CPU (Central Processing Unit) 81, an image processing unit 82, and four pulse modulation units 83a-83d. Four laser diode control circuits (laser diode drivers) 84a-84d, switches S1-S4, and the like are provided.

  The CPU 81 outputs a control signal to the image processing unit 82 and controls the operation of the image processing unit 82. An image data signal (not shown) and a BD signal are input to the image processing unit 82, and an image data signal electrically processed with a clock (pixel clock) for one pixel to the pulse modulation units 83a to 83d. At the same time, a sample and hold signal (S / H signal) is output to the plurality of laser diode control circuits 84a to 84d, and a light amount signal switching signal is output.

  The output timing of the light quantity signal switching signal is determined by the horizontal synchronization signal (BD signal). When the laser beam is detected by the BD sensor 15, a horizontal synchronization signal (BD signal) is output and input to the image processing unit 82, and a predetermined timing (predetermined number of clocks) based on the horizontal synchronization signal (BD signal). After the elapse), a light amount signal switching signal is output from the image processing unit 82 to the switches S1 to S4.

  The pulse modulation units 83a to 83d for the yellow (Y), magenta (M), cyan (C), and black (K) laser light sources respectively modulate the image data signals input from the image processing unit 82, and respectively modulate them. Output to the corresponding laser diode control circuit 84a-84d.

  Laser diodes LD1 to LD4 are connected to the laser diode control circuits 84a to 84d, respectively, and light amount signals are input from the photodiodes F1 to F4 through the switches S1 to S4 and sampled from the image processing unit 82.・ Hold signal is input. Each laser diode control circuit drives the corresponding laser diode LD1-LD4 based on the pulse width modulated image data signal input from the corresponding pulse modulation unit 83a-83d, and the photodiode F1-F4. Automatic output control is performed based on the light quantity signal.

  The laser light quantity control unit 8 sends out a lighting signal and a light quantity signal switching signal of the laser diodes LD1 to LD4 as control signals from the image processing unit 82 outside the image forming area, and sets the sample and hold signal to the sample state. The light amount signals generated by the photodiodes F1-F4 are fed back to the laser diode control circuits 84a-84d. Thus, each laser diode is controlled to a prescribed light amount value by APC. The sample state indicates a state in which the laser light amount adjustment is performed by feeding back the light amount detected by the photodiodes F1-F4 to the laser light amount control unit 8.

  Next, after performing APC control of the laser diodes LD1 to LD4, the laser light amount control unit 8 turns off the sample signal, the drive signal (lighting signal) of each laser diode, and the light amount signal switching signal. In the image forming region (WR), the sample-and-hold signal sent to each laser diode control circuit 84a-84d is set in the hold state, the output current of each laser diode control circuit 84a-84d is fixed to a constant value, and the laser diode LD1. -A write operation is performed while driving the LD 4 at a constant current.

  By repeating the above operation, the writing operation is performed while performing APC control of each of the laser diodes LD1 to LD4. In addition, although an example of the laser light quantity control part was shown in FIG. 8, a laser light control part is not limited to this.

  As described above, the laser diode control circuit 84a shifts to the sample state based on the sample signal from the image processing and performs light amount adjustment by APC during a period in which writing is not performed outside the image forming area. Furthermore, during the period in which writing is performed in the image forming region (WR), the state shifts to the hold state based on the hold signal from the image processing unit 82, and the drive current of the laser diode LD1 is fixed to the same current value as in the sample state. Constant current driving is performed on the laser diode LD1. This process is repeated for each line, and automatic output control (APC) is intermittently performed on each color laser light source.

  Next, the automatic output control (APC) of each color laser light source during color printing and monochrome printing and the operation of each laser light source (laser diode LD1-LD4) based on the BD signal output by the BD sensor 15 will be described with reference to FIG. Description will be made with reference to each timing chart of FIG.

  First, conventional color printing and monochrome printing will be described with reference to FIGS.

  As shown in FIG. 4, in the case of conventional color printing, automatic output control (APC) performs APC for each color simultaneously, and laser light sources for black (K), magenta (M), cyan (C), and yellow (Y). Turn on (laser diode). 4 to 8, the low signal is active and the high signal is off.

  When the BD sensor 15 detects the laser light, the laser light sources other than black (K) are turned off. During the horizontal synchronization period, the black (K) laser light source is kept on. At the same time when the horizontal synchronization period ends and the BD signal as the horizontal synchronization signal rises, the black (K) laser light source is turned off. The horizontal synchronization signal is a signal related to the operation when returning the scanning line that has reached the right end of the photosensitive member to the left end.

  When the BD signal rises and enters the image forming area (WR) after a predetermined number of clocks, image data is transmitted. Based on the drive signal, the laser light source of each color is turned on and off to blink, and an image for one line is printed. The above process is repeated and printing is performed for each line.

  Further, as shown in FIG. 6, in the case of conventional monochrome printing, only the black (K) laser light source is turned on for the APC period, and the horizontal synchronization period is kept on as it is. When the horizontal synchronization period ends, the BD signal rises and at the same time the black (K) laser light source is turned off.

  When the BD signal rises and enters the image forming area (WR) after a predetermined number of clocks, image data is transmitted. Based on the drive signal, the black (K) laser light source is turned off and on to blink, and an image for one line is printed.

  Next, color printing and monochrome printing according to the present embodiment will be described with reference to FIGS. 5 and 7.

  As shown in FIG. 5, when color printing is performed in the image forming apparatus 100 having the optical scanning device 1 of the present invention, automatic output control (APC) is performed simultaneously for each color, and Y, M, C, and K laser light sources. Turn on LD1-LD4. When the BD sensor 15 detects the laser light, the laser light sources LD2-LD4 other than yellow (Y) are turned off. During the horizontal synchronization interval, the yellow (Y) laser light source LD1 is kept on. When the horizontal synchronization interval ends, the BD signal rises and the yellow (Y) laser light source LD1 is turned off.

  When the BD signal rises and enters the image forming area (WR) after a predetermined number of clocks, image data is transmitted. Based on the drive signal, the laser light source LD1 for each color is turned off and on to blink, and an image for one line is printed. Printing is performed by repeating the above process for each line.

  In this way, the BD sensor 15 does not detect the laser light from the black (K) laser light source LD4 and outputs a horizontal synchronization signal, but detects the laser light emitted from the yellow (Y) laser light source LD1 and horizontally. Output sync signal. By not using the black (K) laser light source LD4 when generating and outputting the horizontal synchronization signal, the consumption of the black (K) laser light source LD4 can be reduced.

  When the BD sensor detects the laser light emitted from the yellow (Y) laser light source LD1 and outputs a horizontal synchronization signal, that is, a period in which the horizontal synchronization signal is low active as shown in FIG. 5 (BD period). In the middle, the yellow (Y) laser light source is turned on.

  As shown in FIG. 7, when performing monochrome printing in the image forming apparatus 100 having the optical scanning device 1 of the present invention, only the black (K) and yellow (Y) laser light sources LD1 and LD4 are turned on during the APC period. To do. When the BD sensor detects the laser light, the black (K) laser light source LD4 is turned off. The yellow (Y) laser light source LD1 continues to be on, and when the horizontal synchronization period ends, the BD signal rises, and at the same time, the yellow (Y) laser light source LD1 is turned off.

  When the BD signal rises and enters the image forming area (WR) after a predetermined number of clocks, image data is transmitted. Based on the drive signal, the black (K) laser light source LD4 is turned off and on to blink, and an image for one line is printed. Printing is performed by repeating the above process for each line.

  In this way, the laser light from the laser light source LD4 in black (K) is not emitted from the laser light source LD4 in black (K) during the period in which the horizontal synchronization signal is active (BD period), but in yellow (Y). By using the laser light emitted from the laser light source LD1, the consumption of the black (K) laser light source LD4 can be reduced.

DESCRIPTION OF SYMBOLS 1 Optical scanning device 3a, 3b, 3c, 3d Photosensitive drum 8 Laser light quantity control part 14 Polygon mirror 15 BD sensor 30, 31 Half mirror 40 1st f (theta) lens 41 2nd f (theta) lens 42a, 42b, 42c, 42d 3rd f (theta) lens 43 Multiple Reflection mirror 81 CPU
82 Image processing unit 83a, 83b, 83c, 83d Pulse modulation unit 84a, 84b, 84c, 84d Laser light quantity control circuit F1, F2, F3, F4 Photodiode LD (LD1, LD2, LD3, LD4) Laser diode

Claims (7)

A plurality of light sources for irradiating laser light;
A rotating polygon mirror that reflects and deflects the laser light from the light source on the same surface;
An optical system for irradiating the laser beam deflected by the rotary polygon mirror, corresponding to each of a plurality of photoconductors;
A horizontal synchronization signal generating means for detecting the laser light reflected by the rotary polygon mirror and guided by the optical system and outputting a horizontal synchronization signal;
The optical scanning device according to claim 1, wherein the horizontal synchronization signal generating means is disposed above the rotary polygon mirror.   The optical scanning device according to claim 1, wherein the optical system includes a plurality of lenses that collect and deflect the laser light, and a mirror that reflects or transmits the laser light.   The plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are arranged in a concentrated manner, and are arranged in the vicinity of the photoconductor that is farthest from a position where a recording sheet is transferred. Item 3. The optical scanning device according to Item 1 or 2.   The horizontal synchronization signal generating means is one of the plurality of laser beams emitted from the plurality of light sources, detects the laser beam used for the photoconductor to be printed first, and outputs the horizontal synchronization signal The optical scanning device according to claim 1, wherein: The optical scanning device includes: a plurality of light receiving elements that detect the intensity of the laser light emitted from the light source and output a light amount signal; a plurality of laser light amount control units that control the light amount of the laser light;
With
Based on the light quantity signals detected and generated by the plurality of light receiving elements, the laser light quantity control means distributes and feeds back to the corresponding laser light quantity control means, and the laser light quantity control means sends a control signal to 5. The optical scanning device according to claim 1, wherein automatic output control is performed based on a light amount signal. An optical scanning device according to any one of claims 1 to 5,
The photosensitive member on which an electrostatic latent image is formed by irradiation of the laser beam by the optical scanning device;
Developing means for developing the electrostatic latent image formed on the photoreceptor by attaching it to a developer;
Transfer means for transferring the developer attached by the developing means to a recording medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 6, wherein at least the plurality of light sources, the rotary polygon mirror, and the horizontal synchronization signal generating unit are concentrated in the vicinity of the photoconductor to be printed first. apparatus.

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