JP6233045B2 - Optical scanning apparatus, image forming apparatus, and control program - Google Patents

Description

  The present invention relates to an optical scanning device, an image forming apparatus, and a control program.

  In Patent Document 1, an original image is color-separated by an image reading device, image information is read for each of a plurality of color components, color component image information is converted into recorded image information for each recording color, and based on the recorded image information. In an image forming apparatus in a digital copying machine that reproduces a color image on a transfer paper by recording and energizing each color recording apparatus, an image reading means that scans an original image at a constant speed and separates and reads the color, and a read composition Image processing means for processing the image signal into recording information for each color component; and exposure means for projecting light separated into dots onto an image carrier that moves at a constant speed based on the recording information processed by the image processing means; A developing unit that develops the electrostatic latent image formed by exposure; a transfer unit that transfers the developed visible image to a transfer material that moves at a constant speed; and a fixing unit that fixes an image transferred onto the transfer material. Determine the original image Scanned in degrees, the image bearing member is described an image forming apparatus, wherein a transfer material and a speed switching means such as to move at a constant speed.

  Patent Document 2 discloses a full-color image forming apparatus in which a laser light emitting element is controlled according to an image signal to form an electrostatic latent image on a photosensitive member, and an image is formed on a transfer paper by development, transfer, and fixing. Input means for designating an image forming mode including image formation and monochromatic image formation, process control means for executing an image forming process of the mode designated by the input means, and a mode designated by the input means -Color image formation characterized by comprising a speed setting means for setting a higher image forming process speed and a laser beam scanning speed in a single color image forming mode than in a full color image forming mode. An apparatus is described.

Japanese Patent Laid-Open No. 02-016580 JP 05-330130 A

The present invention
Compared to controlling either the rotational speed of the deflector or the number of light beams according to different image forming speeds, the optical scanning device and image forming can be driven stably according to different image forming speeds. An object is to provide an apparatus and a control program.

To achieve the above object, an optical scanning device according to claim 1 includes a light source including a plurality of light emitting elements and a deflection including a plurality of deflecting surfaces for deflecting light beams emitted from the plurality of light emitting elements while rotating. A latent image forming means for condensing the light beam deflected by the deflector onto the surface of the image carrier of the image forming means and forming a latent image according to an image signal on the surface of the image carrier. The rotation speed of the deflector is set within a predetermined range in accordance with the image forming speed at which the image forming unit forms an image on the recording medium based on the latent image formed on the surface of the image carrier. When the image forming speed is slowed down so that the pixel density of the image becomes a predetermined value, the number of surface skips of the deflector is increased, and the number of light rays emitted from the plurality of light sources is increased. Control to increase, or surface of the deflector Without changing the number of faces of the bridge, and and a control means for controlling to reduce the number of rays of light emitted from the plurality of light sources.

The optical scanning device according to claim 2, in the optical scanning apparatus 12 according to claim 1, wherein, when the image forming speed is faster, reduces the number of surfaces of skipping surface of the deflector And a control for decreasing the number of light beams emitted from the plurality of light sources, or a control for increasing the number of light beams emitted from the plurality of light sources without changing the number of surface skips of the deflector.

The optical scanning device according to claim 3, comprising: a light source including a plurality of light emitting elements; and a deflector including a plurality of deflecting surfaces that deflect light beams emitted from the plurality of light emitting elements while rotating. The light beam deflected by the light beam is condensed on the surface of the image carrier of the image forming unit, and a latent image forming unit that forms a latent image in accordance with an image signal on the surface of the image carrier, and The pixel density of the latent image is determined in advance within a predetermined range of the rotation speed of the deflector according to the image forming speed for forming an image on the recording medium based on the latent image formed on the surface of the holder. When the image forming speed is increased so that the value becomes a control value, the number of surface skipping surfaces of the deflector is decreased and the number of light beams emitted from the plurality of light sources is decreased, or the deflector Without changing the number of skipped faces, One and a control means for performing control for increasing the number of the emitted light from said plurality of light sources.

  The optical scanning device according to claim 4 is the optical scanning device according to any one of claims 1 to 3, wherein the image forming speed, the number of light beams emitted from the plurality of light sources, and the deflection are provided. Information indicating a correspondence relationship between the rotational speed of the device and the number of surface skips of the deflector is stored in a storage unit, and the control unit is based on the correspondence relationship stored in the storage unit. Take control.

  The image forming apparatus according to claim 5 includes an image holding member, and an image forming unit that forms an image on a recording medium based on a latent image formed on the surface of the image holding member; The optical scanning device according to claim 4.

  A control program according to a sixth aspect is a program for causing a computer to function as control means of the optical scanning device according to any one of the first to fourth aspects.

According to the first, fifth, third, and sixth aspects of the invention, as compared with the case where either the rotational speed of the deflector or the number of light beams is controlled according to different image forming speeds. Thus, it can be driven stably according to different image forming speeds.

According to the invention described in claim 2, compared with a case not having the present structure, when the image forming speed becomes slow, the deflector can be stably driven.

  According to the fourth aspect of the present invention, the configuration can be simplified as compared with the case where the present configuration is not provided.

1 is a configuration diagram illustrating a schematic configuration of an example of an image forming apparatus according to a first embodiment. It is a block diagram showing an example of schematic structure from the light source to a deflector in the optical scanning device of 1st Embodiment. It is a block diagram showing an example of schematic structure ahead from the deflector in the optical scanning device of 1st Embodiment. It is a block diagram which shows an example of a structure of the light source 62 in the optical scanning device of 1st Embodiment. It is a block diagram showing the function which controls formation of an electrostatic latent image by the optical scanning device of a 1st embodiment. 3 is a flowchart illustrating an example of a control process for forming an electrostatic latent image according to a change in process speed by the optical scanning device according to the first embodiment. It is explanatory drawing which showed an example of the correspondence of the process speed in the optical scanning device of 1st Embodiment, the surface skip of a deflector, the light emission number of a light emission point, and the rotation speed. It is explanatory drawing for demonstrating control of the light emission number of the light emission point by the light emission control part of the optical scanning device of 1st Embodiment. 12 is a flowchart illustrating an example of a control process for forming an electrostatic latent image according to a change in process speed by the optical scanning device according to the second embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
First, the image forming apparatus of the present invention will be described. FIG. 1 is a configuration diagram showing a schematic configuration of an example of an image forming apparatus according to the present embodiment.

  The image forming apparatus 10 includes an optical scanning device 12YM corresponding to Y (yellow) and M (magenta), an optical scanning device 12CK corresponding to C (cyan) and K (black), and image forming units 14Y, 14M, 14C, 14K. The image forming apparatus 10 according to the present embodiment includes a secondary transfer device 17, an intermediate transfer body 18, a storage container 20, and a fixing device 22.

  Each of the image forming units 14Y, 14M, 14C, and 14K includes photoconductors 24Y, 24M, 24C, and 24K as examples of image carriers. Around the photoreceptors 24Y, 24M, 24C, and 24K, charging devices 26Y, 26M, 26C, and 26K, developing devices 28Y, 28M, 28C, and 28K, primary transfer devices 16Y, 16M, 16C, and 16K, respectively, Photoconductor cleaners 30Y, 30M, 30C, and 30K are provided. Note that, in the following, when there is no need to distinguish between individual colors, the suffixes Y, M, C, K, YM, and CK are omitted.

  The charging device 26 charges the surface of the photoconductor 24. The optical scanning device 12 performs exposure scanning according to the control of the control unit 70 (see FIG. 2, details will be described later) in order to form an electrostatic latent image on the surface of the charged photoreceptor 24. The developing device 28 develops the electrostatic latent image formed on the surface of the photoreceptor 24 with toner contained in the developer to form a toner image. The primary transfer device 16 includes, for example, a transfer roll, and primarily transfers a toner image to an intermediate transfer member 18 as an example of a transfer target. The photoconductor cleaner 30 removes residual toner adhering to the surface of the photoconductor 24 after transfer.

  In the image forming apparatus 10, first, in the image forming unit 14Y, the photosensitive member 24Y rotates clockwise in FIG. 1, and the surface thereof is charged by the charging device 26Y. Next, an electrostatic latent image of the first color (Y) is formed on the surface of the charged photoconductor 24Y by exposure scanning with the optical scanning device 12YM.

  This electrostatic latent image is developed with toner (a developer containing toner) supplied from the developing device 28Y, and a visualized toner image is formed. The toner image reaches the primary transfer portion by the rotation of the photosensitive member 24Y, and the toner image is primarily transferred to the intermediate transfer member 18 by applying an electric field of reverse polarity to the toner image from the primary transfer device 16Y.

  Similarly, the second color toner image (M), the third color toner image (C), and the fourth color toner image (K) are sequentially formed by the image forming units 14M, 14C, and 14K, and the intermediate transfer member 18 is formed. Are overlapped to form a multiple toner image.

  Next, the multiple toner image transferred to the intermediate transfer body 18 reaches the secondary transfer portion where the secondary transfer device 17 is installed by the rotation of the intermediate transfer body 18. In the secondary transfer unit, a bias (transfer voltage) having the same polarity as the polarity of the toner image is applied between the secondary transfer device 17 and the backup roll 19 disposed so as to face each other with the intermediate transfer member 18 therebetween. The toner image is electrostatically repelled and transferred onto a sheet P that is an example of a recording medium.

  Specifically, the paper P is picked up one by one from the paper bundle stored in the storage container 20 by a pickup roller (not shown), and is fed to the intermediate transfer body 18 of the secondary transfer unit by a feed roll (not shown). It is supplied to the next transfer device 17 at a predetermined timing. The toner image held on the intermediate transfer body 18 is transferred to the supplied paper P by bringing the secondary transfer device 17 and the backup roll 19 into pressure contact and applying a transfer voltage.

  The paper P onto which the toner image has been transferred is conveyed to the fixing device 22 where the toner image is fixed by pressurization / heating to be a permanent image.

  After the transfer of the multiple toner image to the paper P is completed, the toner remaining on the outer peripheral surface is removed by a belt cleaner (not shown) provided downstream of the secondary transfer portion, and the next transfer is performed. Will be prepared. The secondary transfer device 17 is also provided with a cleaning member (not shown) to remove foreign matters such as toner particles and paper dust adhering to the transfer.

  In the case of transfer of a single color image, the primary transferred toner image is secondarily transferred in a single color and conveyed to the fixing device 22. In the case of transfer of a multicolor image by superimposing a plurality of colors, each color toner image is transferred. Are synchronized with each other at the primary transfer portion so that the rotation of the intermediate transfer member 18 and the photosensitive members 24Y, 24M, 24C, and 24K is synchronized so that the toner images of the respective colors do not shift.

  In this way, an image is formed on the paper P in the image forming apparatus 10 according to the present embodiment.

  Next, the configuration of the optical scanning device 12 of the present embodiment will be described with reference to the drawings. FIG. 2 is a configuration diagram illustrating an example of a schematic configuration from the light source 62 to the deflector 40 in the optical scanning device 12 of the present embodiment. FIG. 3 is a configuration diagram illustrating an example of a schematic configuration from the deflector 40 in the optical scanning device 12 according to the present embodiment.

  The optical scanning device 12YM scans and exposes the photoconductor 24Y and the photoconductor 24M with two light beams L corresponding to Y and M, respectively. The optical scanning device 12CK scans and exposes the photosensitive member 24C and the photosensitive member 24K with light rays L corresponding to C and K, respectively. Note that the diameter of the K photoconductor 24K is larger than the diameters of the other photoconductors 24Y, 24M, and 24C, and only the K photoconductor 24K is deteriorated at an early stage due to the frequent black and white image output. To prevent that.

  The two optical scanning devices 12YM and 12CK use a housing 32YM and a housing 32CK having a common shape. However, the diameters of the photoconductors 24M and 24K are different from each other, so that the space from the housing 32YM to the photoconductor 24M is increased. Since the distance and the distance from the housing 32CK to the photoconductor 24K are different, the optical systems corresponding to M and K are partially different in optical characteristics.

  Since the diameters of the photoconductor 24Y and the photoconductor 24C are the same, the optical characteristics of the optical systems corresponding to Y and C are basically the same. That is, the casing 32YM and the casing 32CK have the same positional relationship relative to the photoreceptor 24Y and the photoreceptor 24C so that the optical system corresponding to Y and the optical system corresponding to C have the same characteristics. They are arranged so as to be.

  First, a schematic configuration from the light source 62 to the deflector 40 in the optical scanning device 12 of the present embodiment will be described with reference to FIG. Each of the optical scanning devices 12YM and 12CK has a light source 62 corresponding to each color, a light source drive unit 74 that drives the light source 62, a light emission control unit 72 that controls light emission of the light source 62 by the light source drive unit 74, a deflector 40, and a deflector drive. Unit 78 and deflector controller 76.

  The light source 62 of the present embodiment is a VCSEL (Vertical Cavity Surface Emitting Laser), and as shown in FIG. 4, the light source 62 is a plurality of two-dimensionally arranged in the main scanning direction and the sub-scanning direction. The light emitting point 63 is provided. As a specific example, in the present embodiment, 32 light emitting points 63 are provided, and the light source 62 includes an array of eight light emitting points arranged along the sub-scanning direction. Are arranged in four rows. The light source driving unit 74 is a so-called driver IC (Integrated Circuit), and drives light emission (on) / non-light emission (off) of a plurality of light emitting points 63 of the light source 62. A light source drive unit 74 is electrically connected to the light emission control unit 72. Light emission (ON) and non-light emission (OFF) of a plurality of light emission points 63 of the light source 62 are independently controlled by the light emission control unit 72 via the light source driving unit 74. The light emission control unit 72 is realized as a computer, ASIC, FPGA, or the like having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, The light source 62 is controlled.

  In FIG. 3, only one light source 62 and light source driving unit 74 are shown, but the light source 62 and the light source driving unit 74 are provided in the housing 32 for each color. In the present embodiment, the light emission control unit 72 includes one light emission control unit 72 for each optical scanning device 12 and is common to Y and M and common to C and K. You may make it prepare separately for every.

  Specifically, a light source 62Y and a light source driving unit 74Y corresponding to Y, and a light source 62M and a light source driving unit 74M corresponding to M are provided in the housing 32YM of the optical scanning device 12YM. The light source 62Y and the light source 62M are arranged so that the light beams LY and LM do not interfere with each other in the thickness direction of the deflector 40 (vertical direction in FIG. 2: rotation axis direction). Similarly, a light source 62C and a light source driving unit 74C corresponding to C, and a light source 62K and a light source driving unit 74K corresponding to K are provided in the housing 32CK of the optical scanning device 12CK. The light source 62C and the light source 62K are arranged so that the light beams LC and LK do not interfere with each other in the thickness direction of the deflector 40 (vertical direction in FIG. 2: rotation axis direction).

  The light beam L emitted from the light source 62 is guided to the deflector 40 through a lens group 64 such as a collimator lens and a cylindrical lens.

  In this embodiment, as shown in FIG. 2, a polygon mirror that is a rotating polygonal mirror is used as an example of the deflector 40. In this embodiment, as shown in FIG. 3, one deflector 40 is provided for each optical scanning device 12, and Y and M are common, and C and K are common. The deflector control unit 76 and the deflector driving unit 78 also include one deflector 40 for each optical scanning device 12, and are common to Y and M and common to C and K.

  The deflector driving unit 78 is a so-called motor or the like, is connected to the rotation shaft of the deflector 40, and rotates the deflector 40 in the direction of arrow A in FIG. A deflector driving unit 78 is electrically connected to the deflector control unit 76. The rotation of the deflector 40 is controlled by the deflector controller 76 via the deflector driver 78. The deflector control unit 76 is realized as a computer, an ASIC, an FPGA, or the like provided with a CPU, a RAM, a ROM, and the like, and controls the deflector 40 by executing a program.

  In the optical scanning device 12 of the present embodiment, the light emission control unit 72 and the deflector control unit 76 are electrically connected to the control unit 70 that controls the entire image forming apparatus 10, and are controlled according to the control of the control unit 70. The light emission control unit 72 controls the light source 62, and the deflector control unit 76 controls the deflector 40. The control unit 70 is realized as a computer, an ASIC, or the like that includes a CPU, a RAM (Random Access Memory), a ROM, and the like. In the control unit 70, the CPU executes a program stored in the ROM, whereby control to the light emission control unit 72 and the deflector control unit 76 is executed.

  The light beam guided to the deflector 40 is deflected in the main scanning direction by the rotating deflector 40. The deflected light beam is irradiated on the surface of the photosensitive member 24 through the Fθ lenses 42 and 44 and the like. In the image forming apparatus 10 of the present embodiment, the direction in which the deflector 40 deflects and scans the light beam is the main scanning direction, and the direction crossing the main scanning direction is the sub-scanning direction.

  Next, with reference to FIG. 3, a schematic configuration beyond the deflector 40 in the optical scanning device 12 of the present embodiment will be described.

  As shown in FIG. 3, in the optical scanning device 12YM, the light beam LY corresponding to Y is deflected by the reflecting surface of the deflector 40, and is scanned on the photosensitive member 24 at a constant speed by the pair of Fθ lenses 42 and 44. Move in the main scanning direction. The light beam LY that has passed through the Fθ lenses 42 and 44 is folded back by the cylindrical mirror 44, the plane mirror 46, and the cylindrical mirror 48, passes through the transmission glass 57, and forms an image on the photoreceptor 24 </ b> Y.

  Similarly, in the optical scanning device 12CK, the light beam LC corresponding to C is deflected by the reflection surface of the deflector 40, and the pair of Fθ lenses 42 and 44 scan the photosensitive member 24 at a constant speed in the main scanning direction. Move in. The light beam LC that has passed through the Fθ lenses 42 and 44 is folded back by the cylindrical mirror 44, the plane mirror 46, and the cylindrical mirror 48, passes through the transmission glass 57, and forms an image on the photoreceptor 24 </ b> C.

  In the optical scanning device 12YM, the light beam LM corresponding to M passes through the Fθ lenses 42 and 44, which are deflected by the reflection surface of the deflector 40, and then the cylindrical mirror 50, the plane mirror 52, the reflection mirror 54, and the like. Each image is folded back by the plane mirror 56 and passes through the transmission glass 58, and then forms an image on the photosensitive member 24M.

  On the other hand, in the optical scanning device 12K, the reflection mirror 54 and the plane mirror 56 are arranged so that the light beam LK corresponding to K has a different optical path length from the light beam LM of the optical scanning device 12YM. Since the diameter of the photosensitive member 24K is larger than the diameters of the other photosensitive members 24Y, 24M, and 24C, the scanning position PK is not located on the same plane as the scanning positions PY, PM, and PC (see FIG. 1). The characteristics of the corresponding optical system and the optical system corresponding to M cannot be made the same. Since only the diameter of the photoconductor 24K is larger than the diameters of the other photoconductors 24Y, 24M, and 24C, the distance from the housing 32CK to the photoconductor 24K is shorter than the distance from the housing 32YM to the photoconductor 24M. Therefore, unless the optical path length of the light beam LK in the housing 32CK is made longer than the light beam LM, a normal image (electrostatic latent image) corresponding to K cannot be formed by the light beam LK. For this reason, in the case 32CK, as shown by the solid line and the two-dot chain line in FIG. 3, the angle of the reflection mirror 54 and the angle of the plane mirror 56 are different from those of the case 32YM. As a result, the difference in optical path length between the light beam LK and the light beam LM is absorbed.

  The image forming apparatus 10 according to the present embodiment is provided with a plurality of modes depending on the type of image formation and the like, and a speed for forming an image (hereinafter referred to as a process speed) is set according to the mode. ing. For example, in the present embodiment, the process speed varies depending on the type of paper P on which an image is formed. In general, the thicker the sheet P, the easier it is for heat to escape when the fixing device 22 fixes the toner image. Therefore, the thicker the paper P, the slower the process speed. In addition, the process speed decreases as the mode in which high-definition image formation is performed. Further, the process speed varies depending on the mode corresponding to the image to be formed, such as characters, drawings, and photographs.

  The control unit 70 of the image forming apparatus 10 controls the rotation speed (the number of rotations) of the photoconductor 24 according to the change in the process speed. When the process speed increases, the rotational speed of the photoconductor 24 increases. When the process speed decreases, the rotational speed of the photoconductor 24 decreases. The formation of the electrostatic latent image by the optical scanning device 12 is controlled so that the image density in the sub-scanning direction of the electrostatic latent image formed on the photosensitive member 24 does not change according to the change in the rotational speed of the photosensitive member 24. Is done. That is, in the image forming apparatus 10 of the present embodiment, the optical scanning device 12 is statically controlled so that the image density of the electrostatic latent image formed on the photoconductor 24 is within a predetermined range regardless of the process speed. Controls the formation of an electrostatic latent image. The predetermined range in which the image density of the electrostatic latent image falls may be obtained in advance by experiments or the like according to the characteristics of the image forming apparatus 10 and the image to be formed.

  In order to drive the deflector 40 stably, a preferable rotation speed (number of rotations) is determined. The preferable rotation speed (number of rotations) is determined by the size and structure of the deflector 40. The larger the deflector 40 is, the more easily affected by the moment of inertia and the range of the rotational speed (number of rotations) at which stable driving is performed becomes narrower. In the optical scanning device 12 of the present embodiment, when the formation of the electrostatic latent image is controlled according to the change in the process speed, the rotation speed (the number of rotations) of the deflector 40 is within a range where stable driving is performed. Control is performed as follows.

  Hereinafter, control of formation of an electrostatic latent image by the optical scanning device 12 according to a change in process speed in the present embodiment will be described.

  FIG. 5 is a block diagram showing the function of controlling the formation of the electrostatic latent image by the optical scanning device 12. FIG. 6 is a flowchart showing an example of a control process for forming an electrostatic latent image by the optical scanning device 12 in accordance with a change in process speed.

  Control processes in the control unit 70, the light emission control unit 72, and the deflector control unit 76 illustrated in FIG. 6 are executed when an image formation instruction is input to the image forming apparatus 10.

  First, the control unit 70 of the image forming apparatus 10 determines whether an image forming mode has been acquired in step S100. For example, when an image formation mode is instructed along with an image formation instruction from a user interface (not shown) or an external personal computer, the image formation mode is acquired. The process waits until the image forming mode is acquired. If acquired, the process proceeds to step S102.

  In step S102, the control unit 70 selects a process speed corresponding to the image forming mode. The selection method is not particularly limited. For example, the correspondence between the image forming mode and the process speed is stored in advance in a storage unit (not shown) in the image forming apparatus 10 and selected based on the correspondence. A method is mentioned.

  In the next step S104, the control unit 70 instructs the selected process speed to the light emission control unit 72 and the deflector control unit 76, and then ends the present process. The process speed itself may be instructed, or information indicating the process speed (for example, the process speed stage) may be instructed.

  On the other hand, the deflector controller 76 of the optical scanning device 12 is in a standby state until the process speed is acquired in step S130. When the process speed is instructed in step S104 of the control unit 70 described above, the deflector control unit 76 acquires the instructed process speed and proceeds to step S132.

  In step S132, the clock of the deflector driving unit 78 corresponding to the rotational speed corresponding to the process speed is selected from the table 82 with reference to the table 82 indicating the correspondence between the process speed and the rotational speed of the deflector 40.

  Specifically, the table 82 of the present embodiment is configured by information indicating the correspondence between the process speed and the rotation speed (clock) stored in a storage unit such as a memory in the deflector control unit 76. .

  FIG. 7 shows an example of a correspondence relationship between the process speed of the present embodiment, the surface skipping of the deflector 40, the number of light emission of the light emitting point 63, and the number of rotations. In the present embodiment, as a specific example, the process speed 1 corresponds to a speed (A4 / 120 ppm) for printing 120 sheets of A4 paper per minute. The process speed 4 corresponds to a speed (A4 / 40 ppm) for printing 40 sheets of A4 paper per minute. As described above, in the image forming apparatus 10 of the present embodiment, the process speed is determined in advance from the process speed 1 to the process speed 4 so as to sequentially decrease.

  As a method for controlling the formation of the electrostatic latent image formed on the photoconductor 24, a method based on the rotational speed of the deflector 40 and the number of light beams formed on the photoconductor 24 (the number of light emitted from the light emitting point 63). And a method. As a method based on the rotation speed of the deflector 40, there is a method of increasing the rotation speed (rotation speed) as the process speed increases and decreasing the rotation speed (rotation speed) as the process speed decreases. Can be mentioned. Further, as a method based on the rotation speed of the deflector 40, there is a method of performing a surface skip for skipping a deflection surface. When one surface is skipped (one deflection is performed with respect to two deflection surfaces), the formation speed of the electrostatic latent image on the photosensitive member 24 is substantially halved without changing the rotation speed (rotation speed) of the deflector 40. This is substantially equivalent to reducing the rotation speed (number of rotations). On the other hand, as a method based on the number of light beams formed on the photosensitive member 24, the number of light beams (the number of light emission) is increased as the process speed is increased, and the number of light beams is increased as the process speed is decreased. A method of reducing (the number of emitted light) is mentioned.

  Here, when only one of the method based on the rotational speed of the deflector 40 and the method based on the number of light rays imaged on the photoconductor 24 (the number of light emitted from the light emitting point 63) is performed, the rotational speed of the deflector 40 is In some cases, the above-described stable driving may be out of range. In particular, in the optical scanning device 12 of the present embodiment, since the thickness of the deflector 40 is thick, the range of the number of rotations at which the deflector 40 is stably driven is narrow. Therefore, in the optical scanning device 12 of the present embodiment, as a method based on the rotational speed of the deflector 40, the presence / absence of surface skipping and the number of light rays imaged on the photosensitive member 24 (the number of light emission points 63) are combined. Further, by adjusting according to the rotation speed of the deflector 40, the rotation speed of the deflector 40 is set within the range where the above-described stable driving is performed. Accordingly, the rotational speed AArpm at the process speed 1, the rotational speed BBrpm at the process speed 2, the rotational speed CCrpm at the process speed 3, and the rotational speed DDrpm at the process speed 4 shown in FIG. It is a numerical value in.

  As shown in FIG. 7, in the optical scanning device 12, when the process speed is increased, the number of surface skipping of the deflector 40 is decreased (no surface skipping is performed), and the number of light emission at the light emitting point 63 is decreased. Control or control to increase the number of light emission at the light emitting point 63 without changing the number of surfaces of the deflector 40 is performed.

  Further, as shown in FIG. 7, in the optical scanning device 12, when the process speed becomes slow, the number of surface skipping of the deflector 40 is increased (surface skipping is performed) and the number of light emission at the light emitting point 63 is increased. Or the control for reducing the number of light emission at the light emitting point 63 without changing the number of surface skipping surfaces of the deflector 40.

  In the optical scanning device 12 of the present embodiment, such a correspondence relationship is obtained in advance by experiments or the like and stored in the deflector control unit 76, the light emission control unit 72, and the like.

  The table 82 of the present embodiment includes a correspondence relationship between the process speed and the rotation speed in the example of the correspondence relationship shown in FIG. In FIG. 7, the number of rotations (rpm) is shown corresponding to the process speed. Specifically, the frequency of the clock for driving the motor of the deflector driving unit 78 for driving the deflector 40 is shown. Corresponds to the information. As the process speed increases, the clock frequency increases.

  In the next step S134, the deflector controller 76 outputs the selected clock to the deflector driver 78, and then ends this process.

  On the other hand, the light source driving unit 74 of the optical scanning device 12 is in a standby state until the process speed is acquired in step S160. When the process speed is instructed in step S104 of the control unit 70 described above, the light source driving unit 74 acquires the instructed process speed, and proceeds to step S162.

  In step S162, the table 80 showing the correspondence relationship between the process speed and whether or not the deflector 40 skips the surface and the number of light emission of the light emission point 63 is referred to, and the light emission number of the light emission point 63 corresponding to the process speed is determined from the table 80. select.

  The table 80 includes a correspondence relationship between the process speed, the presence / absence of surface skipping, and the light emission number of the light emitting point 63 in the example of the correspondence relationship shown in FIG. Specifically, the table 80 according to the present embodiment is information indicating a correspondence relationship between the process speed stored in the storage unit such as the memory in the light source driving unit 74, the presence / absence of surface skipping, and the number of light emission of the light emitting point 63. It is comprised by.

  In the next step S164, with reference to the table 80 showing the correspondence between the process speed, the presence / absence of surface deflection of the deflector 40, and the number of light emission of the light emitting points 63, the presence / absence of surface skipping corresponding to the process speed is selected from the table 80. To do.

  In the next step S166, the number of light emission of the selected light emission point 63 and the presence / absence of surface skipping are output to the light source driving unit 74, and then this process is terminated.

  When the light source driving unit 74 controls the light emission number of the light emitting point 63, as shown in FIG. 8, the light source driving unit 74 changes the light emission number by causing the light emitting point 63 arranged outside to emit no light. In the optical scanning device 12 of the present embodiment, since the optical path is adjusted with the center of the light emitting point 63 at the center of the light source 62 as a reference, the light emitting point 63 provided outside the light source 62 is set as non-light emitting. Yes. As the number of light emission points 63 changes, the number of light beams deflected by the deflector 40 changes.

  In addition, when performing surface skipping, the light source driving unit 74 controls light emission of the light emitting point 63 so as to skip a period corresponding to the number of skipped surfaces.

  As described above, the image forming apparatus 10 of the present embodiment forms an image at a process speed corresponding to a plurality of image forming modes. The optical scanning device 12 controls the formation of an electrostatic latent image on the photoconductor 24 according to the process speed. In the table 80 of the light emission control unit 72 and the table 82 of the deflector control unit 76, the correspondence relationship between the process speed, the surface skipping of the deflector 40, the light emission number of the light emitting point 63, and the rotation number of the deflector 40 is previously stored. It is remembered. The deflector controller 76 selects the number of rotations (clock) of the deflector 40 according to the process speed based on the table 82 and outputs it to the deflector driver 78. The light emission control unit 72 selects the presence / absence of the surface of the deflector 40 according to the process speed based on the table 80 and the light emission number of the light emission point 63, and outputs them to the light source drive unit 74.

  In the optical scanning device 12 of the present embodiment, the deflection is performed so that the pixel density in the sub-scanning direction of the electrostatic latent image formed on the photoreceptor 24 is within a predetermined range regardless of the process speed. The device 40 skips the surface, controls the light emission number of the light emitting point 63 and the rotation speed of the deflector 40. Further, in the optical scanning device 12 according to the present embodiment, the surface of the deflector 40 is skipped within the range in which the rotational speed (the number of rotations) of the deflector 40 is stably driven, and the number of light emitted from the light emitting point 63 and the deflection thereof. The number of rotations of the device 40 is controlled.

  Therefore, in the optical scanning device 12 of the present embodiment, the process speed can be changed over a wider range than when either the rotational speed of the deflector 40 or the number of light emission (number of light rays) of the light emitting point 63 is controlled. Correspondingly, the deflector 40 can be driven stably.

  Thereby, the image forming apparatus 10 can have a plurality of process speeds. Further, since the deflector 40 can be driven stably, the image quality of the formed image can be improved and the speed related to the entire image formation can be suppressed.

  When the optical scanning device 12 is applied to another image forming apparatus 10, the correspondence relationship shown in FIG. 7 and the table 80 and the table 82 corresponding to the image forming apparatus 10 to which the optical scanning device 12 is applied can be stored in advance. Therefore, various image forming apparatuses 10 can be supported.

[Second Embodiment]
In the optical scanning device 12 of the first embodiment, the process speed, the surface skipping of the deflector 40, the number of light emission of the light emitting point 63, and the deflection of the deflector 40 within the range in which the rotational speed of the deflector 40 is stably driven. The case where the correspondence with the rotation speed is stored in advance has been described. On the other hand, in the optical scanning device 12 according to the present embodiment, such a correspondence relationship is not stored in advance, and the surface of the deflector 40 is skipped in accordance with a change from the current process speed (such as an initial value). And the number of light emission of the light emission point 63 is controlled.

  Since the optical scanning device 12 of the present embodiment does not store the correspondence relationship in advance as described above, the light emission control unit 72 does not include the table 80, and the deflector control unit 76 does not include the table 82. The other configurations of the image forming apparatus 10 and the optical scanning device 12 of the present embodiment are substantially the same as the configurations of the image forming apparatus 10 and the optical scanning device 12 of the first embodiment, and thus detailed description thereof is omitted. To do.

  In the optical scanning device 12 of the present embodiment, the control process for forming the electrostatic latent image by the optical scanning device 12 according to the change in the process speed is different from that of the first embodiment. To explain.

  FIG. 9 is a flowchart showing an example of control processing for forming an electrostatic latent image by the light emission control unit 72 and the deflector control unit 76 of the optical scanning device 12 according to the change in the process speed. Note that the control processing (steps S100 to S104 in FIG. 6) by the control unit 70 is the same as that in the first embodiment, and thus detailed description thereof is omitted.

  On the other hand, the deflector controller 76 of the optical scanning device 12 is in a standby state until the process speed is acquired in step S230. When the process speed is instructed in step S104 of the control unit 70 described above in the first embodiment, the deflector control unit 76 acquires the instructed process speed and proceeds to step S232.

  In step S232, the clock of the deflector driver 78 is selected. The clock selection method in this embodiment is not particularly limited. For example, when the rotation speed is not changed in order to drive the deflector 40 stably, a predetermined clock (a common value that does not depend on the process speed) may be selected. In addition, for example, when the rotation speed is varied in order to perform fine adjustment according to the process speed, the correspondence relationship between the process speed and the information indicating the clock frequency is stored in advance, for example, as in the first embodiment. In addition, the selection may be made based on the correspondence.

  In the next step S234, the deflector controller 76 outputs the selected clock to the deflector driver 78, and then ends this process.

  On the other hand, the light source driving unit 74 of the optical scanning device 12 is in a standby state until the process speed is acquired in step S260. When the process speed is instructed in step S104 of the control unit 70 described above in the first embodiment, the light source driving unit 74 acquires the instructed process speed and proceeds to step S262.

  In step S262, it is determined whether to change the process speed. If the process speed is not changed from the current value (for example, the initial value), the light emission control of the light emitting point 63 (whether or not the surface is skipped and the number of light emission) is not changed, and thus this processing is terminated. On the other hand, when the process speed is changed from the current value, the process proceeds to step S264.

  In step S264, the light emission control unit 72 determines whether or not the process speed has increased. If it is faster, the process proceeds to step S266. In step S266, it is determined whether or not the process speed before the change is within a predetermined range including a half value of the process speed after the change. That is, it is determined whether or not the process speed after the change is within a predetermined range including a value that is twice the process speed before the change. In the optical scanning device 12 of the present embodiment, since the number of surface skipping is one, the apparent rotational speed (number of rotations) of the deflector 40 is doubled or halved depending on the presence or absence of surface skipping. Become. For this reason, the light emission control unit 72 of the present embodiment performs control so as not to skip the surface when it is included in a predetermined range including a value twice the process speed before the change. The predetermined range may be determined in advance by experiments or the like according to the characteristics of the deflector 40, the characteristics of the image forming apparatus 10, and the like.

  If the determination in step S266 is affirmative, the process proceeds to step S268 to select no surface skipping (no surface skipping is performed). In the next step S270, after selecting to maintain the light emission number of the light emission point 63, the process proceeds to step S290.

  On the other hand, if the result in Step S266 is negative, the process proceeds to Step S272. In step S272, it is determined whether or not to change the presence or absence of surface skipping from the current state. The method for determining whether or not to change the presence or absence of surface skipping from the current state is not particularly limited. For example, when the change amount of the process speed is more than half, that is, when the process speed is more than double, it is preferable to select the change of the surface skipping and not to skip the surface (do not skip the surface). Note that, for example, even when the amount of change in the process speed is less than half (the process speed is less than twice), it is preferable to select the change of the surface skip (for example, the process speed 2 and the process speed 2 in FIG. 7). Process speed 3). The presence or absence of the change may be determined in advance by experiments or the like according to the characteristics of the deflector 40, the characteristics of the image forming apparatus 10, and the like.

  If the determination in step S272 is affirmative, the surface skip is changed, so that the surface skip is not performed, that is, the number of surfaces to be skipped is decreased. If the determination in step S272 is affirmative, the process proceeds to step S274, and after selecting to reduce the number of light emission at the light emission point 63, the process proceeds to step S290.

  On the other hand, if the determination in step S272 is affirmative, the skipping is not changed, the skipping is performed when the current state is skipping, and the skipping is performed when the current state is skipping. If the result in Step S272 is negative, the process proceeds to Step S276, and after selecting to increase the light emission number of the light emitting point 63, the process proceeds to Step S290.

  On the other hand, when the process speed has been reduced from the current state, the result in Step S264 is negative, and the process proceeds to Step S278. In step S278, similarly to step S266 described above, it is determined whether or not the process speed before the change is within a predetermined range including a half value of the process speed after the change. That is, it is determined whether or not the process speed after the change is included in a predetermined range including a value that is half the process speed before the change. In the light emission control unit 72 according to the present embodiment, when it is included in a predetermined range including a value half of the process speed before the change, the light emission control unit 72 performs control so as to perform surface skipping. The predetermined range may be determined in advance by experiments or the like according to the characteristics of the deflector 40, the characteristics of the image forming apparatus 10, and the like.

  If the determination in step S278 is affirmative, the process proceeds to step S280, and the surface skipping is performed (surface skipping is performed). In the next step S282, after selecting to maintain the light emission number of the light emission point 63, the process proceeds to step S290.

  On the other hand, if the result in Step S278 is negative, the process proceeds to Step S284. In step S284, as in step S272 described above, it is determined whether to change the presence / absence of surface skipping from the current state.

  If the determination in step S284 is affirmative, in order to change the surface skipping, surface skipping is performed, that is, the number of surfaces to be skipped is increased. If the determination in step S284 is affirmative, the process proceeds to step S286, and after selecting to increase the light emission number of the light emitting point 63, the process proceeds to step S290.

  On the other hand, if the determination in step S284 is affirmative, the skipping is not changed, the skipping is performed when the current state is skipping, and the skipping is not performed when the current state is skipping. If the result in Step S284 is negative, the process proceeds to Step S288, and the process proceeds to Step S290 after selecting to reduce the number of light emission at the light emission point 63.

  In step S290, the number of light emission points of the selected light emission point 63 and the presence / absence of surface skipping are output to the light source driving unit 74, and then this process ends.

  As described above, in the optical scanning device 12 of the present embodiment, the light emission control unit 72 changes the number of surface skipping of the deflector 40 and the number of light emission of the light emitting point 63 according to the change from the current process speed. Control.

  If the process speed before the change is within a predetermined range including the half value of the process speed after the change, the light emission control unit 72 controls the presence or absence of surface skipping. Further, when the process speed is increased, the light emission control unit 72 reduces the number of surface skips of the deflector 40 and reduces the number of light emission of the light emitting points 63, or the number of surface skips of the deflector 40. The control for increasing the number of light emission at the light emitting point 63 is performed without changing. Further, when the process speed becomes slow, the light emission control unit 72 increases the number of surface skips of the deflector 40 and increases the number of light emission of the light emitting points 63, or the surface skip surface of the deflector 40. The number of light emission points 63 is controlled to be decreased without changing the number.

  Therefore, in the optical scanning device 12 of the present embodiment, the process speed can be changed over a wider range than when either the rotational speed of the deflector 40 or the number of light emission (number of light rays) of the light emitting point 63 is controlled. Correspondingly, the deflector 40 can be driven stably.

  Further, since the light emission control unit 72 performs control in accordance with a change from the current process speed, the light emission control unit 72 can appropriately perform control even when the optical scanning device 12 is applied to another image forming apparatus 10.

  As described above, in the optical scanning device 12 of the image forming apparatus 10 according to each of the above-described embodiments, as compared with the case where one of the rotational speed of the deflector 40 and the number of emitted light (number of light beams) of the light emitting point 63 is controlled. The deflector 40 can be stably driven in response to a wide range of process speed changes.

  In each of the above-described embodiments, the case where the present invention is applied to the optical scanning device 12 including one deflector 40 for a plurality of colors (two colors) has been described, but the present invention is not limited thereto. For example, the present invention may be applied to an optical scanning device including one deflector for each color. In the case of the optical scanning device 12 including one deflector 40 for several colors (two colors) as in the present embodiment, when the thickness direction of the deflector 40 is large and the thickness is small. Compared with this, since the range of the rotational speed at which the deflector 40 is stably driven is narrowed, a higher effect can be obtained by applying the present invention.

  In each of the above embodiments, the case where the present invention is applied to the optical scanning device 12 in which the light source 62 is a VCSEL and has 32 light emitting points 63 is described, but the present invention is not limited thereto. For example, the number of 63 light emitting points is not limited to this embodiment, and may be a plurality. Further, the present invention may be applied to an LED print head using a light emitting diode (LED) as a light source.

  In the first embodiment, the case where the light emission control unit 72 includes the table 80 and the deflector control unit 76 includes the table 82 is described. However, the present invention is not limited to this. For example, the light emission control unit 72 and the deflector. The table 80 and the table 82 may be stored in a storage unit provided separately from the control unit 76, or the table 80 and the table 82 are not separately stored, and information indicating the correspondence relationship illustrated in FIG. 7 is stored. You may make it make it.

  Moreover, each said embodiment is an example of this invention, and it cannot be overemphasized that it can change according to a condition within the range which does not deviate from the main point of this invention. The configurations and operations of the image forming apparatus 10, the optical scanning device 12, the light emission control unit 72, the deflector control unit 76, and the like described in the present embodiment are examples, and the situation is within the scope of the present invention. It goes without saying that it can be changed according to the situation.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Optical scanning device 24 Photoconductor 40 Deflector 62 Light source 63 Light emission point 70 Control part 72 Light emission control part 76 Deflector control part 80 Table 82 Table

Claims (6)

A light source including a plurality of light emitting elements and a deflector including a plurality of deflection surfaces for deflecting light beams emitted from the plurality of light emitting elements while rotating the light beams deflected by the deflectors; A latent image forming means for focusing on the surface of the image carrier and forming a latent image according to an image signal on the surface of the image carrier;
In accordance with the image forming speed at which the image forming means forms an image on the recording medium based on the latent image formed on the surface of the image carrier, the latent image is within a predetermined range of the rotation speed of the deflector. When the image forming speed is slowed down so that the pixel density of the pixel becomes a predetermined value, the number of surface skips of the deflector is increased and the number of light rays emitted from the plurality of light sources is increased. Control means for performing control, or control for reducing the number of light beams emitted from the plurality of light sources without changing the number of surface skips of the deflector ;
An optical scanning device comprising: Wherein, when said image forming speed is faster,
Reducing the number of faces skipping surface of said deflector, and controls to reduce the number of rays of light emitted from the plurality of light sources, or without changing the number of faces skipping surface of said deflector, and from the plurality of light sources Control to increase the number of rays emitted,
The optical scanning device according to claim 1. A light source including a plurality of light emitting elements and a deflector including a plurality of deflection surfaces for deflecting light beams emitted from the plurality of light emitting elements while rotating the light beams deflected by the deflectors; A latent image forming means for focusing on the surface of the image carrier and forming a latent image according to an image signal on the surface of the image carrier;
In accordance with the image forming speed at which the image forming means forms an image on the recording medium based on the latent image formed on the surface of the image carrier, the latent image is within a predetermined range of the rotation speed of the deflector. When the image forming speed is increased so that the pixel density of the pixel becomes a predetermined value, the number of surface skipping surfaces of the deflector is decreased and the number of light beams emitted from the plurality of light sources is decreased. Control means for performing control, or control for increasing the number of light beams emitted from the plurality of light sources without changing the number of surface skips of the deflector ;
An optical scanning device comprising: Information representing a correspondence relationship between the image forming speed and the number of light beams emitted from the plurality of light sources, the rotational speed of the deflector, and the number of surface skips of the deflector is stored in a storage unit, The control means performs control based on the correspondence relationship stored in the storage means.
The optical scanning device according to claim 1. An image forming unit that has an image carrier and forms an image on a recording medium based on a latent image formed on the surface of the image carrier;
The optical scanning device according to any one of claims 1 to 4, and
An image forming apparatus.   The control program for functioning a computer as a control means of the optical scanning apparatus of any one of the said Claim 1 to the said Claim 4.