JP2008216415A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing deterioration of image quality caused by discontinuation of the main scanning line. <P>SOLUTION: The image forming apparatus includes a substrate; an optical head in which n-number (n is a natural number that is equal to or greater than 3) of lines of light-emitting elements arranged so that a straight line in the lengthwise direction of the substrate are arranged in the widthwise direction of the substrate; an image carrier on which a latent image is formed by light emitted by the light-emitting elements comprising the optical head; an image carrier rotating angle detecting means for detecting the rotation angle of the image carrier and generating a pulse. The timing of emitting at least the first line of light-emitting elements and the timing of emitting the n-th line of light-emitting elements are synchronized with the pulses of the image carrier rotating angle detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as an electrophotographic, electrostatic copying machine, printer or facsimile, and in particular, an optical head used as an exposure means for forming an electrostatic latent image on an image carrier. The present invention relates to an image forming apparatus using. The present invention also relates to an image forming method using such an optical head.

  In general, an electrophotographic toner image forming unit includes a photosensitive member as an image bearing member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a uniform charging unit using the charging unit. An exposure unit that selectively exposes the outer peripheral surface charged to form an electrostatic latent image, and a toner as a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image ( Developing means for forming a toner image).

  As a tandem type image forming apparatus for forming a color image, a plurality (for example, four) of toner image forming means as described above are arranged on the intermediate transfer belt. The toner image on the photosensitive member by the single color toner image forming unit is sequentially transferred to the intermediate transfer belt, and the toner images of a plurality of colors (for example, yellow, cyan, magenta, and black (black)) are superimposed on the intermediate transfer belt. There is an intermediate transfer belt type that obtains a color image on an intermediate transfer belt.

In a tandem color image forming apparatus (printer), a technique using a light emitter array as the exposure means (optical head) is known. For example, Patent Document 1 describes an example in which a latent image is formed by magnifying output light of a light emitting element arranged two-dimensionally in a light emitter array with a single lens and irradiating the photosensitive drum. . Further, in Patent Document 2, as shown in FIG. 5, a light source 204 in which LED chips 208 of respective colors are arranged in a two-dimensional rectangular shape is provided. In FIG. 8A, it is described that generation of density unevenness is suppressed by overlappingly forming the print dots 451 formed by the light source in the main scanning direction.
JP 2001-63139 A Japanese Patent No. 3741812

  In an image forming apparatus using this type of optical head, a large discontinuous point is generated in the main scanning line, and the discontinuous point becomes a conspicuous streak and image quality may deteriorate. Such discontinuous points include rotational fluctuations of a motor that is a driving source of the image carrier (photosensitive drum), speed fluctuations caused by gears used in a driving force transmission path to the image carrier (photosensitive drum), This is caused by fluctuations in the rotational speed of the image carrier (photosensitive drum) or the like due to vibration of the image forming apparatus main body. However, there is a problem that image quality deterioration cannot be resolved.

  SUMMARY An advantage of some aspects of the invention is that an image forming apparatus according to the present invention includes a substrate and a light emitting element row including a plurality of light emitting elements arranged in the longitudinal direction of the substrate in the substrate width direction. an optical head arranged on the substrate so as to have n rows (where n is a natural number of 3 or more), an image carrier on which a latent image is formed by light emission of a light emitting element constituting the optical head, and the image Image carrier rotation angle detection means for detecting a rotation angle of the carrier to generate a pulse, and at least light emission timing of the first light emitting element row and light emission timing of the nth light emitting element row Is synchronized with the pulse of the image carrier rotation angle detecting means.

  The image forming apparatus according to the present invention is characterized in that a gradient index rod lens is provided between the light emitting element and the image carrier.

  The image forming apparatus according to the present invention is characterized in that the light emitting element is an organic EL element.

  The image forming apparatus according to the present invention is characterized in that the light emitting element is an LED.

  In the image forming apparatus according to the present invention, the light emission timings of the light emitting element rows other than the first and nth light emitting element rows are determined by equally dividing the time interval between pulses. .

  The image forming apparatus according to the present invention is characterized in that the light emission timings of the light emitting element rows other than the first and nth light emitting element rows are set after a predetermined time of pulse generation.

In the image forming method according to the present invention, the substrate and the light emitting element rows composed of a plurality of light emitting elements arranged in the longitudinal direction of the substrate are arranged in n rows (where n is a natural number of 3 or more) in the substrate width direction. An optical head arranged on the substrate, an image carrier on which a latent image is formed by light emission of a light emitting element constituting the optical head, and an image carrier that generates a pulse by detecting a rotation angle of the image carrier An image forming apparatus comprising: a body rotation angle detection unit; and at least a light emission timing of a first light emitting element row and a light emission timing of an nth light emitting element row, and a pulse of the image carrier rotation angle detection unit. It controls to synchronize with.
According to the image forming apparatus and the image forming method of the present invention, it is possible to reduce image quality deterioration due to discontinuity of main scanning lines.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a cross section of a tandem type image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 according to the present embodiment includes a case main body 2, a first opening / closing member 3 that is openably / closably attached to the front surface of the case main body 2, and a second open / close attached to the upper surface of the case main body 2. And an opening / closing member (also serving as a paper discharge tray) 4.

  The first opening / closing member 3 includes an opening / closing lid 3 ′ attached to the front surface of the case body 2 so as to be freely opened and closed. In the case main body 2, an electrical component box 5 incorporating a power circuit board and a control circuit board, an image forming unit 6, a blower fan 7, a transfer belt unit 9, and a paper feeding unit 10 are disposed. Further, in the first opening / closing member 3, a secondary transfer unit 11, a fixing unit 12, and a recording medium conveying means 13 are provided.

  The transfer belt unit 9 is disposed below the case body 2 and is driven to rotate by a drive source (not shown), a driven roller 15 disposed obliquely above the drive roller 14, An intermediate stretched between two rollers 14 and 15 and circulated and driven by the drive roller 14 and the driven roller 15 in the direction of the arrow (the contact surface of the primary transfer member 21 is downward in the illustrated example). A transfer belt 16. The cleaning unit 17 is separated and brought into contact with the surface of the intermediate transfer belt 16.

  The image forming unit 6 includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of (four in this embodiment) different color images. I have. Each of the image forming stations Y, M, C, and K includes a photosensitive member (image carrier) 20 including a photosensitive drum, and a charging unit 22 disposed around the photosensitive member (image carrier) 20. It has an optical head 23 which is a latent image forming means (exposure device) and a developing device 100. A primary transfer member 21 made of a leaf spring electrode is brought into contact with the photoreceptor 20 of the image forming stations Y, M, C, and K corresponding to each color by its elastic force, and the primary transfer member 21 has a transfer bias. Applied. A test pattern sensor 18 is installed at a position close to the drive roller 14.

  The photoconductor (image carrier) 20 is rotationally driven in the direction of the arrow (clockwise direction). The charging means 22 is composed of a conductive brush roller connected to a high voltage generation source, and the outer periphery of the brush is in the reverse direction (counterclockwise direction) with respect to the photoconductor (image carrier) 20, and the photoconductor ( The surface of the photosensitive member (image carrier) 20 is uniformly charged by rotating in contact with the photosensitive member (image carrier) 20 at a peripheral speed two to three times that of the image carrier 20. The optical head 23 that is an exposure apparatus is an organic head in which a plurality of organic EL light emitting elements are arranged in an array in the axial direction (main scanning direction) and the width direction (sub-scanning direction) of the photoconductor (image carrier) 20. An EL light emitting element array is used. The optical head 23 using the organic EL light emitting element array has a shorter optical path length than the laser scanning optical system and is compact, and can be disposed close to the photoconductor (image carrier) 20. It has the advantage that the whole can be reduced in size. Further, since the number of parts is not large as in the laser scanning optical system, the configuration is simplified. In addition, as a light emitting element which can be used for the optical head 23, it is not limited to such a light emitting element, LED etc. can also be used. In this embodiment, the photoconductor (image carrier) 20, the charging unit 22, and the optical head 23 of each of the image forming stations Y, M, C, and K are unitized as one photoconductor unit 25.

  The photoconductor (image carrier) 20 is provided with a rotary encoder (not shown) which is a means for detecting the rotation angle of the photoconductor (image carrier) 20, and a part of the organic EL light emitting elements constituting the optical head 23 emits light. It is configured to synchronize timing.

  Next, details of the developing device 100 will be described using the image forming station K as an example. The developing device 100 includes a case 103 for storing toner (hatched portion in the figure), a toner storage unit 101 formed in the case 103, an agitator 119 disposed in the toner storage unit 101, and a toner storage unit. A toner guide member 133 is formed in the upper portion of 101. Further, the supply roller 105 disposed above the toner guide member 133, the contact portion 143 provided on the toner guide member 133 and in contact with the supply roller 105, the toner guide member 133 and the image carrier 20 are contacted. A developing roller 107 disposed so as to be in contact with each other and a regulation blade 109 that is in contact with the developing roller 107 are provided.

  Next, members provided in the conveyance path of the recording medium PP will be described. The paper feed unit 10 includes a paper feed unit including a paper feed cassette 35 in which the recording media PP are stacked and held, and a pickup roller 36 that feeds the recording media PP one by one from the paper feed cassette 35. In the first opening / closing member 3, a registration roller pair 37 that defines the timing of feeding the recording medium PP to the secondary transfer portion, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. A secondary transfer unit 11, a fixing unit 12, a recording medium conveyance path 13, a discharge roller pair 39, and a duplex printing conveyance path 40 are provided. When performing double-sided printing on a recording medium, the recording medium on which image data has been transferred and fixed on one side is reversely fed from the position of the paper discharge roller pair 39 and conveyed through the double-sided printing conveyance path 40, and again from the registration roller pair 37. It is conveyed by the recording medium conveyance path 13.

  The fixing unit 12 includes a heating roller 45 that includes a heating element such as a halogen heater and is rotatable, a pressure roller 46 that presses and biases the heating roller 45, and is swingable on the pressure roller 46. A belt tension member 47 and a heat-resistant belt 49 stretched between the pressure roller 45 and the belt tension member 47. The color image secondarily transferred to the recording medium is fixed to the recording medium at a predetermined temperature at a nip formed by the heating roller 45 and the heat-resistant belt 49.

Next, the basic configuration of the optical head used in the image forming apparatus of the present invention will be described.
FIG. 2 is a view showing a glass substrate on which light emitting elements and the like of the optical head are formed, FIG. 3 is a partially cutaway perspective view showing the configuration of the optical writing optical head, and FIG. It is sectional drawing taken along the direction (width direction).

  FIG. 2 is a schematic plan view of an optical head used in the image forming apparatus according to the embodiment of the present invention. On the glass substrate 262, four organic EL light emitting element lines 274, 275, 276, and 277 are formed within a distance La in the sub-scanning direction (the width direction of the glass substrate 262). The four lines of light emitting elements form 1x rows, 2x rows,... Nx rows of light emitting element rows in an oblique direction. Reference numeral 271 denotes a drive circuit for each light emitting element 261, which controls each light emitting element 261 by, for example, a TFT. By arranging the light emitting elements obliquely, the arrangement of the power supply wiring connecting the drive circuit 271 and the organic EL light emitting element 261 becomes easy. In the example of FIG. 2, the interval in the sub-scanning direction of the light-emitting elements provided at both ends (274, 277) of the light-emitting element array arranged in the sub-scanning direction is La.

  The formation of a latent image on the photoconductor 20 in an optical head having a light emitting element array in which four organic EL light emitting element lines are arranged in an oblique direction in the sub-scanning direction as shown in FIG. 2 will be described. First, after the light emitting elements of the light emitting element line 274 of the first line are caused to emit light, the organic EL light emitting elements of the second line 275, the third line 276, and the fourth line 277 are spaced at intervals while rotating the photosensitive member 20. The lines are sequentially emitted to form a row of latent images in the main scanning direction of the photoconductor 20. At that time, due to the speed fluctuation in the rotation direction of the photoconductor 20, the print dots are displaced with a certain width in the sub-scanning direction, and discontinuity of the main scanning line occurs. The speed fluctuation factors causing the discontinuity of the main scanning line are the rotation fluctuation of the motor, the speed fluctuation caused by the gear used for the driving force transmission path, and the fluctuation of the rotation speed of the photoconductor due to the vibration in the apparatus. In addition, the detailed definition of the organic EL light emitting element line and the problems related to the main scanning line discontinuity will be described in detail later.

  FIG. 3 is an enlarged perspective view schematically showing the optical head 23 of the image forming apparatus of the present invention. The optical head 23 is configured such that a glass substrate 262 on which four lines of organic EL light emitting element lines are formed is housed in a housing 260 as shown in the figure.

  The gradient index rod lens array 265 constitutes an imaging optical system, and a gradient index rod lens 266 arranged on the front surface of the light emitting unit 263 is stacked. In the present embodiment, the gradient index rod lens 266 is employed as the imaging optical system, but a micro lens may be employed as the imaging optical system. Such a microlens is a lens having a negative optical magnification (inverted imaging). The housing 260 covers the periphery of the glass substrate 262 and the side facing the photoconductor (image carrier) 20 is open. In this way, the light beam R is emitted from the gradient index rod lens 266 to the photoconductor (image carrier) 20.

  Positioning pins 269 and screw insertion holes 268 are provided in order to accurately position the optical head 23 with respect to the respective photoreceptors 20 attached to the photoreceptor unit 25. The positioning pin 269 is inserted into the opposing positioning hole of the case of the optical head 23 (not shown). The positioning pin 269 and the positioning hole are fitted with a slight gap in the main scanning direction, and the position of the optical head 23 in the main scanning direction is set to be adjustable. Each line head 23 is fixed at a predetermined position by screwing a fixing screw into a screw hole of the case of the optical head 23 through screw insertion holes 268 provided at both ends of the long housing 260.

  FIG. 4 is a longitudinal sectional view of an optical head used in the image forming apparatus according to the embodiment of the present invention, and partially shows the configuration of FIG. The light emitting portion 263 of the organic EL element 261 is placed on the glass substrate 262, and is driven by the TFT 271 (FIG. 3) formed on the same glass substrate 262. The output light is irradiated to the image carrier through the gradient index rod lens 266 disposed in front of the light emitting unit 263. The housing 260 covers the periphery of the glass substrate 262 and the side facing the image carrier 20 is open. The glass substrate 262 is fitted into a receiving hole provided in the long housing 260 and is fixed by a fixing bracket 225 with a back cover 223 covered. The opaque back cover 223 prevents the output light of the light emitting unit 263 from being radiated to the side opposite to the irradiation surface of the image carrier, thereby improving the light emission efficiency.

  The positioning pins 269 provided at both ends of the long housing 260 are fitted into the positioning holes of the opposing image forming apparatus main body, and the fixing screws are inserted through the screw insertion holes 268 provided at both ends of the long housing 260. The optical writing optical head 23 is fixed at a predetermined position by being screwed into the screw hole.

  Next, a rotary encoder serving as a rotation angle detection unit of the photoconductor (image carrier) 20 provided on the photoconductor (image carrier) 20 will be described. FIG. 5 is a diagram showing an external appearance of a rotary encoder connected to a photoconductor (image carrier) of an image forming apparatus according to an embodiment of the present invention, and FIG. 6 is a diagram showing a slit disk of the rotary encoder. FIG. 7 is a view showing a cross section of the rotary encoder.

  5 to 7, reference numeral 300 denotes a rotary encoder, 301 denotes a slit disk, 302 denotes a detection unit, 303 denotes a light emitting unit, 304 denotes a light receiving unit, and 305 denotes a photosensitive member (image carrier) axis. The rotary encoder 300 includes a slit disk 301 having a slit formed at a predetermined interval and a detection unit 302. The detection unit 302 includes a light emitting unit 303 such as a light emitting diode and a light receiving unit 304 such as a phototransistor. A signal output from the rotary encoder 300 provided on the photoconductor (image carrier) 20 is used to synchronize the light emission timings of a part of light emitting elements such as an organic EL constituting the optical head 23. Here, in the present embodiment, the reason why the output pulses of the rotary encoder 300 cannot synchronize the light emission timings of all the light emitting elements is due to the detection limit of the rotation angle of the rotary encoder 300. The slits formed in the slit disk 301 of the rotary encoder 300 have processing accuracy limits and cost limitations. For this reason, there is a limit to the accuracy that the rotary encoder 300 can detect. Originally, it would be ideal if the synchronization of the light emission timings of all the light emitting elements of the optical head 23 could be covered by the output pulse of the rotary encoder 300. The signal of the rotary encoder 300 is used to synchronize the light emission timing of a part of the light emitting elements of the optical head 23.

  Next, the definition of the arrangement of light emitting elements and the like of the optical head 23 will be described. 8 to 10 are diagrams schematically showing each component for defining the arrangement of each component of the optical head. The glass substrate 262 of the optical head 23 has a rectangular shape, and has a longitudinal direction indicated by an arrow C and a width direction indicated by an arrow D in the drawing. In the photoconductor (image carrier) 20, the direction indicated by the arrow A in the figure is the main scanning direction, and the direction indicated by the arrow B is the sub-scanning direction. 8 to 10, the illustration of the gradient index rod lens 266 and the like is omitted.

  In the example of the present embodiment, every four organic EL elements are arranged obliquely in the longitudinal direction of the optical head 23. The arrangement of every four organic EL elements has periodicity in the longitudinal direction of the optical head 23. Reference numeral 290 shown on the photoconductor (image carrier) 20 represents a spot which is an irradiation portion formed by light emission of the light emitting element 261. The set of spots 290 forms a latent image on the photoconductor (image carrier) 20. In FIG. 8, a spot 290 is shown when the photosensitive member (image carrier) 20 is seen through, and this is also the case when defining the arrangement related to the spot 290 in the subsequent drawings. It shall be defined based on the drawing.

  Next, the definition of the arrangement of the light emitting elements 261 and the spots 290 will be described with reference to FIGS. 9 and 10. FIG. 9 schematically shows the light emitting element 261 on the glass substrate 262, and FIG. 10 schematically shows the spot 290 on the photoconductor (image carrier) 20. A group of light emitting elements 261 arranged in a straight line in the longitudinal direction of the glass substrate 262 is defined as a light emitting element row. Then, the light emitting element row 1st row to the light emitting element row 4th row are arranged in the order as illustrated. Similarly, a group of spots 290 arranged in a straight line in the longitudinal direction of the photoconductor (image carrier) 20 is defined as a spot row. Similarly, the first row of spot rows to the fourth row of spot rows are arranged in the order shown in the figure.

  Next, the relationship between the light emission timing of the light emitting element 261 and the formation timing of the spot 290 on the photoconductor (image carrier) 20 will be described with reference to FIGS. FIG. 11 to FIG. 14 are diagrams schematically showing the formation process of the spot irradiation part in the photoconductor (image carrier) 20.

  13 to 18, a case where a single linear spot is formed in the main scanning direction of the photoconductor (image carrier) 20 will be described.

  FIG. 11 shows a state where a predetermined portion of the photoconductor (image carrier) 20 reaches the position P1. At this time, the fourth light emitting element row emits light, and a latent image is formed by the fourth spot row of the photoconductor (image carrier) 20.

  FIG. 12 shows a state where a predetermined portion of the photoconductor (image carrier) 20 reaches the position P2. At this time, the third light emitting element row emits light, and a latent image is formed by the third spot row of the photoconductor (image carrier) 20. A black circle on the photoconductor (image carrier) 20 indicates a latent image spot formed at the position P1.

  FIG. 13 shows a state where a predetermined portion of the photoconductor (image carrier) 20 reaches the position P3. At this time, the second light emitting element row emits light, and a latent image is formed by the second spot row of the photoconductor (image carrier) 20. The black circles on the photoconductor (image carrier) 20 indicate the latent image spots formed at the positions P1 and P2.

  FIG. 14 shows a state where a predetermined portion of the photoconductor (image carrier) 20 reaches the position P4. At this time, the first light emitting element row emits light, and a latent image is formed by the first spot row of the photoconductor (image carrier) 20. The black circles on the photoconductor (image carrier) 20 indicate the latent image spots formed at the positions P1, P2, and P3.

  Each spot is formed on the optical head 23 at the light emission timing of the light emitting element as described above, and a latent image is formed on the photoconductor (image carrier) 20.

  Next, the problem of discontinuity of the main scanning lines caused by using the optical head having the above basic configuration in the image forming apparatus will be described again. The arrangement of the light emitting elements 261 on the glass substrate 262 is arbitrary, but here, a case where there are the first to fourth light emitting element rows will be described.

  FIGS. 15 and 16 are views showing spots formed on the photoconductor (image carrier) 20. FIG. 15 shows a one-line spot ideally formed on the photoconductor (image carrier) 20 without unevenness in the rotational speed of the photoconductor (image carrier) 20, and FIG. FIG. 10 is a diagram for explaining deterioration in image quality due to discontinuity of main scanning lines in a conventional image forming apparatus. When considering the discontinuity of the main scanning line of the image forming apparatus, for the sake of simplicity, it is considered to form a one-line spot irradiation portion in the main scanning direction on the photoconductor (image carrier) 20. In order to form a one-line spot irradiation part on the photoconductor (image carrier) 20, the fourth light emitting element row → the third light emitting element row → the third light emitting element row → the first line. Spots are formed at the light emission timing of sequentially emitting light from the first light emitting element row.

  Here, if there is a modulation in the mechanism that transmits the driving force to the photoconductor (image carrier) 20 and the rotational speed of the photoconductor (image carrier) 20 is uneven, a 1-line spot irradiation unit is formed. Does not become a straight spot irradiating part, but shifts with the light emission timing of the light emitting element group. Such a shift causes image quality deterioration due to discontinuity of the main scanning line.

  FIG. 16 is a diagram for explaining discontinuity of main scanning lines caused by an image forming apparatus in which a conventional encoder (image carrier) 20 is not provided with a rotary encoder. FIG. 16 shows one line of spots formed when unevenness occurs in the rotational speed of the photoconductor (image carrier) 20. As shown in FIG. 16, when unevenness occurs in the rotation speed of the photoconductor (image carrier) 20, the spot is formed so as to be stepped for each spot row. Such a shift of one line causes deterioration of image quality. In the case of FIG. 16, the most prominent step-like deviation between adjacent spot rows is an accumulated deviation amount corresponding to four light emission timings. Such a noticeable step-like shift between the spot rows makes the deterioration of the image quality noticeable. The present invention proposes an image forming apparatus that minimizes such a step-like shift between adjacent spot rows and suppresses degradation of image quality due to discontinuity of main scanning lines as much as possible.

  As described above, the image forming apparatus of the present invention includes the rotary encoder 300, and the output pulses from the rotary encoder 300 synchronize the light emission timings of the light emitting elements such as the organic EL constituting the optical head 23. Take. However, the light emission timings of all the light emitting elements of the optical head 23 cannot be synchronized with the output pulse of the rotary encoder 300. Therefore, in the present invention, the light emission timings of some light emitting elements of the optical head 23 are synchronized with the output pulse of the rotary encoder 300.

  FIG. 17 is a diagram showing spots formed by the image forming apparatus of this embodiment. Also here, when considering the discontinuity of the main scanning line of the image forming apparatus for the sake of simplicity, it is necessary to form a spot irradiation portion of one line in the main scanning direction on the photosensitive member (image carrier) 20 for the sake of simplicity. Think about it.

  As described above, in order to form a one-line spot irradiation section on the photoconductor (image carrier) 20, the fourth light emitting element row → the third light emitting element row → the third line. Spots are formed at the light emission timing of sequentially emitting light from the first light emitting element row to the first light emitting element row. In the present invention, the light emission timings of at least the fourth light emitting element row and the first light emitting element row are configured to be synchronized with the output pulse from the rotary encoder 300. Such a spot formed by the present invention is as shown in FIG. 17, and the first and fourth spot rows coincide at least with the discontinuity of the main scanning line. Degradation of image quality can be suppressed.

  So far, the optical head 23 having the first to fourth light emitting element rows has been described as an example. However, the optical head that can be used in the image forming apparatus of the present invention is not limited to this, and a general In other words, the present invention can be applied to an image forming apparatus using an optical head (here, n is a natural number of 3 or more) having light emitting element rows from the first row to the nth row. In such an optical head, the light emission timings of at least the first and nth light emitting element rows are synchronized by the output pulse of the rotary encoder. In such a case, the light emission timings of the light emitting element rows other than the first row and the nth row may be determined by equally dividing the time interval between the output pulses of the rotary encoder, or the rotary You may set so that it may be after the predetermined time of the output pulse of an encoder.

  FIG. 18 is a diagram showing spots formed by the image forming apparatus of this embodiment. A spot of one line on the photosensitive member (image carrier) 20 of the image forming apparatus using the optical head having the light emitting element rows consisting of the first row to the fifth row is shown. In this example as well, the first spot line and the fifth spot line at least coincide with each other, and image quality deterioration due to discontinuity of the main scanning lines can be suppressed.

  As described above, according to the image forming apparatus and the image forming method of the present invention, it is possible to reduce deterioration in image quality due to discontinuity of main scanning lines.

1 is a cross-sectional view of a tandem type image forming apparatus according to an embodiment of the present invention. It is a figure which shows the glass substrate which forms the light emitting element of an optical head, etc. on it. It is the perspective view which fractured | ruptured a part which shows the structure of an optical writing optical head. It is sectional drawing taken along the subscanning direction (width direction) of the optical head. 1 is a diagram illustrating an external appearance of a rotary encoder connected to a photoconductor (image carrier) of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the slit disc of a rotary encoder. FIG. 7 is a cross-sectional view of the rotary encoder. It is the figure which showed typically each component for the definition of the arrangement | sequence of each component of an optical head. It is the figure which showed typically each component for the definition of the arrangement | sequence of each component of an optical head. It is the figure which showed typically each component for the definition of the arrangement | sequence of each component of an optical head. FIG. 3 is a diagram schematically showing a process of forming a spot irradiating part on a photoreceptor (image carrier) 20. FIG. 3 is a diagram schematically showing a process of forming a spot irradiating part on a photoreceptor (image carrier) 20. FIG. 3 is a diagram schematically showing a process of forming a spot irradiating part on a photoreceptor (image carrier) 20. FIG. 3 is a diagram schematically showing a process of forming a spot irradiating part on a photoreceptor (image carrier) 20. 2 is a diagram showing spots formed on a photoconductor (image carrier) 20. FIG. 2 is a diagram showing spots formed on a photoconductor (image carrier) 20. FIG. It is a figure which shows the spot formed with the image forming apparatus of this embodiment. It is a figure which shows the spot formed with the image forming apparatus of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ...... Case main body, 3rd opening / closing member, 3 '... Opening / closing lid, 4 ... 2nd opening / closing member, 5 ... Electrical component box , 6 ... Image forming unit, 7 ... Blower fan, 9 ... Transfer belt unit, 10 ... Paper feed unit, 11 ... Secondary transfer unit, 12 ... Fixing unit, 13. ..Recording medium conveying means, 14 ... drive roller, 15 ... driven roller, 16 ... intermediate transfer belt, 17 ... cleaning means, 18 ... test pattern sensor, 20 ... photoreceptor (Image carrier), 21 ... primary transfer member, 22 ... charging means, 23 ... optical head, 35 ... paper feed cassette, 36 ... pick-up roller, 37 ... registration roller pair , 39 ... Paper discharge roller pair, 40 ... Carrying for duplex printing Feed path 45... Heating roller 46. Pressure roller 47. Belt stretch member 49. Heat resistant belt 100 Development device 101 Toner container 103 ... Case, 105 ... Supply roller, 107 ... Developing roller, 109 ... Regulator blade, 111 ... Plate spring member, 112 ... Elastic member, 113 ... Toner, 117 ... Rotating shaft, 119 ... agitator, 121 ... arm member, 123 ... stirring fin, 129 ... toner guide surface, 131 ... toner guide space, 133 ... toner guide member, 135 ... Scraper, 137 ... Flat transfer part, 139 ... Temporary storage part, 141 ... Bending part, 143 ... Abutting part, 223 ... Back cover, 225 ... Fixing bracket, 260... Housing 61: Each light emitting element, 262 ... Glass substrate, 263 ... Light emitting part, 266 ... Gradient index rod lens, 269 ... Positioning pin, 268 ... Screw insertion hole, 271 ..Drive circuit, 274, 275, 276, 277 ... organic EL light emitting element line, 300 ... rotary encoder, 301 ... slit disk, 302 ... detector, 303 ... light emitter, 304: light receiving portion, 305: photosensitive member (image carrier) shaft

Claims (7)

An optical head arranged on a substrate and light emitting element rows composed of a plurality of light emitting elements arranged in the longitudinal direction of the substrate so as to be n rows in the substrate width direction (where n is a natural number of 3 or more);
An image carrier on which a latent image is formed by light emission of a light emitting element constituting the optical head;
Image carrier rotation angle detection means for detecting a rotation angle of the image carrier and generating a pulse,
At least the light emission timing of the first light emitting element row and the light emission timing of the nth light emitting element row are synchronized with a pulse of the image carrier rotation angle detecting means. The image forming apparatus according to claim 1, wherein a gradient index rod lens is provided between the light emitting element and the image carrier. The image forming apparatus according to claim 1, wherein the light emitting element is an organic EL element. The image forming apparatus according to claim 1, wherein the light emitting element is an LED. The light emission timing of light emitting element rows other than the first and nth light emitting element rows is determined by equally dividing the time interval between pulses. The image forming apparatus described. 6. The image forming apparatus according to claim 1, wherein the light emission timings of the light emitting element rows other than the first row and the nth light emitting element row are set after a predetermined time after the generation of the pulse. . An optical head arranged on a substrate and light emitting element rows composed of a plurality of light emitting elements arranged in the longitudinal direction of the substrate so as to be n rows in the substrate width direction (where n is a natural number of 3 or more); Image formation comprising: an image carrier on which a latent image is formed by light emission of a light emitting element constituting the optical head; and an image carrier rotation angle detecting means for detecting a rotation angle of the image carrier and generating a pulse. The apparatus controls the light emission timing of at least the first light emitting element row and the light emission timing of the nth light emitting element row so as to be synchronized with the pulse of the image carrier rotation angle detecting means. Image forming method.

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