JP4862291B2 - Image forming apparatus and gear eccentricity detection method in the apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image using an image forming station in which a structure in which a latent image carrier and a latent image carrier gear are integrally formed is attached to a cartridge body, and a gear eccentricity detection method in the apparatus. Is.

  As an image forming apparatus using a line head in which light emitting elements such as light emitting diodes (LEDs) are arranged in a line, there is an image forming apparatus described in Patent Document 1, for example. In this apparatus, a latent image carrier such as a photosensitive drum is rotationally driven in the sub-scanning direction. A line head is disposed opposite to the photosensitive drum. In this line head, a plurality of light emitting elements are arranged in a line in the main scanning direction substantially orthogonal to the sub-scanning direction, and ON / OFF control is performed according to the image signal. As a result, a line latent image corresponding to the image signal is formed on the photosensitive drum. In this way, a line latent image is written by driving the light emitting element for each image signal for one line while rotating the photosensitive drum. As a result, a two-dimensional latent image is formed on the photosensitive drum. The two-dimensional latent image is developed with toner to form an image.

  In addition, there is a configuration in which a line head is configured by a plurality of organic EL (electroluminescence) elements (Patent Document 2). In this line head, a plurality of organic EL elements are arranged in a row (two rows in a staggered manner) in the main scanning direction substantially orthogonal to the sub-scanning direction, and ON / OFF control is performed according to the image signal. As a result, a line latent image corresponding to the image signal is formed on the photosensitive drum.

JP-A-6-177431 (FIGS. 9 and 10) Japanese Unexamined Patent Publication No. 2003-19826 (FIGS. 1, 7, and 8)

  In order to rotationally drive the latent image carrier such as the photosensitive drum in this way, the latent image carrier gear is integrally formed on the latent image carrier, and this structure is attached to the cartridge body to form a cartridge. . This cartridge is configured to be detachable from the apparatus main body. Then, with the cartridge mounted, the rotational driving force of the motor provided on the apparatus main body side is transmitted to the latent image carrier via the latent image carrier gear, and the latent image carrier rotates in the sub-scanning direction. Accordingly, the rotational speed of the latent image carrier may periodically vary due to the eccentricity of the latent image carrier gear, and this periodic variation is one of the causes of image quality degradation.

  A so-called tandem color image forming apparatus is known as an apparatus for forming a color image. In this image forming apparatus, a plurality of image forming stations that form toner images of different colors are arranged along the moving direction of a transfer medium such as an intermediate transfer belt. In each image forming station, as described above, the latent image carrier is rotated by applying a rotational driving force via the latent image carrier gear, and the line latent image is placed on the latent image carrier by the line head. It is formed. Further, the toner images formed on the latent image carriers are superimposed on the transfer medium to form a color image. In such an apparatus, the rotational phase relationship in each latent image carrier is adjusted, thereby suppressing periodic color misregistration and improving image quality. However, in this apparatus, the color misregistration correction is performed on the assumption that the eccentricity of the latent image carrier gears is the same between the image forming stations. Therefore, when the eccentricity of the latent image carrier gears is different from each other, a sufficient effect cannot be obtained, resulting in a reduction in image quality. Further, when each image forming station is made into a cartridge, the latent image carrier gear is directly connected to the rotation shaft of the latent image carrier and integrated, so that the above phase adjustment cannot be performed. .

  In order to solve these problems, it is conceivable to detect the eccentric characteristics of all of the cartridge mounted on the apparatus main body and the latent image carrier gear incorporated in the image forming station. As described above, it is ideal to execute the processing for obtaining the eccentricity characteristic for all the latent image carrier gears in order to suppress the influence of the eccentricity. However, gears are not so-called one-piece products, but are manufactured industrially with a certain amount as a unit. For gear groups manufactured at the same time under certain conditions, the eccentricity characteristics are the same or approximate. Become. Therefore, in consideration of this point, it is inefficient to execute the processing for uniformly obtaining the eccentric characteristics for each of the latent image carrier gears having the same or similar eccentric characteristics. On the other hand, if an image is formed without accurately grasping the eccentricity characteristics of each latent image carrier gear, the above-described problems occur.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and forms an image using an image forming station in which a structure in which a latent image carrier and a latent image carrier gear are integrally formed is attached to a cartridge body. Therefore, it is an object to efficiently and accurately obtain the eccentric characteristics of the latent image carrier gear, and to improve the image quality by suppressing the influence of the eccentricity of the latent image carrier gear.

  According to the present invention, an image forming station, in which a structure in which a latent image carrier and a latent image carrier gear are integrally formed, is attached to a cartridge body, is mounted on the apparatus body, and a motor provided on the apparatus body side is rotated. The driving force is transmitted to the latent image carrier via the latent image carrier gear to rotate the latent image carrier in the sub-scanning direction, while the image writing unit almost perpendicularly crosses the sub-scanning direction on the latent image carrier. The present invention relates to an image forming apparatus that writes a line latent image extending in the main scanning direction and further develops the latent image with toner to form an image, and a gear eccentricity detection method in the apparatus. It is configured as follows.

The image forming apparatus according to the present invention forms eccentricity characteristics of the latent image carrier gear based on a signal obtained by forming a plurality of phase detection marks by an image forming station and detecting the plurality of phase detection marks. Phase data calculation processing for obtaining phase data can be executed, and a cartridge side memory storing gear information indicating manufacturing conditions and manufacturing timing of the latent image carrier gear is attached to the cartridge body, while the apparatus body side In addition, the main body side memory for storing the gear information and the phase data in association with each other and the gear information stored in the cartridge side memory are compared with the gear information stored in the main body side memory to execute the phase data calculation process. whether and a control unit is provided to determine, gear information is produced at the same time the same or similar at a constant production conditions It is characterized and Turkey different from each other for each latent image carrier gear group having an eccentric characteristic that.

The gear eccentricity detection method in the image forming apparatus according to the present invention includes a step of storing gear information indicating manufacturing conditions and manufacturing timing of the latent image carrier gear in a cartridge side memory attached to the cartridge main body, and the apparatus main body. A step of storing the gear information and the phase data indicating the eccentric characteristic of the latent image carrier gear specified by the gear information in association with the provided main body side memory, and with the image forming station mounted on the apparatus main body Reading gear information from the cartridge side memory and determining whether the gear information is stored in the main body side memory; forming a plurality of phase detection marks by the image forming station; and Phase data calculation processing to obtain the phase data of the latent image carrier gear based on the signal obtained by detecting the mark And a step of determining in accordance with whether or not the determination result performed, gear information that different from each other for each latent image carrier gear group having an eccentric property of the same or similar are produced at the same time at a constant production conditions It is characterized a call.

  In the invention thus configured (image forming apparatus and gear eccentricity detection method in the apparatus), in order to detect the eccentricity characteristics of the latent image carrier gear, a plurality of phase detection marks are formed by the image forming station. Processing for obtaining phase data indicating the eccentric characteristics of the latent image carrier gear based on signals obtained by detecting the plurality of phase detection marks, that is, phase data calculation processing can be executed. However, the phase data calculation process is selectively executed as needed based on the gear information, instead of uniformly obtaining the phase data by the above process for all the latent image carrier gears. That is, a plurality of latent image carrier gears are classified based on gear information indicating the identity of gears such as manufacturing lot numbers, and the latent image carrier gear groups having the same gear information have the same or approximate eccentricity characteristics. The execution of the phase data calculation process is omitted. More specifically, in each image forming station, the gear information of the latent image carrier gear is stored in the cartridge-side memory attached to the cartridge body, while the gear information and the gear information are stored in the body-side memory provided in the apparatus body. Is stored in association with phase data indicating the eccentricity characteristics of the latent image carrier gear specified in (1). The phase data calculation process is executed only when the gear information stored in the cartridge side memory of the image forming station mounted on the apparatus main body is not stored in the main body side memory. Thus, since the necessity of the phase data calculation process is determined using the gear information, the eccentricity characteristic of the latent image carrier gear can be obtained efficiently. Further, when the latent image carrier gear having gear information other than the gear information stored in the main body side memory is equipped, the phase data calculation process is executed, so that the eccentric characteristics of the latent image carrier gear are Can be obtained accurately.

  In the image forming apparatus, in order to rotationally drive a latent image carrier such as a photosensitive drum, the latent image carrier and the latent image carrier gear are integrally formed, and this structure is attached to the cartridge body to form a cartridge. May be used. In the apparatus configured in this way, it is affected by the eccentricity of the latent image carrier gear. Therefore, the inventor of the present application considered the influence of the eccentricity of the latent image carrier gear, and examined a specific embodiment for suppressing the influence. In the following, embodiments of the present invention will be described after describing the effects of the eccentricity of the latent image carrier gear and considerations regarding countermeasures.

A. Effects and countermeasures of the eccentricity of the latent image carrier gear The influence of the eccentricity of the latent image carrier gear appears in the rotation speed of the latent image carrier. More specifically, the rotational speed fluctuates periodically. As a result, the position of the actually formed image deviates from a predesigned position, so-called ideal position, and the image quality is degraded. In order to clarify this point, a case where a plurality of phase detection marks are formed at equal intervals over the circumference of the latent image carrier will be considered.

  FIG. 1 is a diagram showing the relationship between the measured position of the phase detection mark and the ideal position when the latent image carrier gear is decentered. Here, a rectangular phase detection mark having a length of 7 mm in the main scanning direction x and a length of 1 mm in the sub-scanning direction y based on a synchronization signal output at a constant cycle (standard cycle) is an intermediate transfer belt. Formed on the transfer medium 16. Further, since the circumference of the latent image carrier used here is about 78 mm, 27 phase detection marks MK (1), MK (2),..., MK (27) are set to 2 mm in the sub-scanning direction y. Formed at intervals. When the latent image carrier gear is not decentered, the phase detection marks MK (1), MK (2),... Are formed at so-called ideal positions, and the interval between adjacent marks is constant. Become. However, in the actual apparatus, the eccentricity of the latent image carrier gear is unavoidable, and the phase detection mark may be formed at a position shifted from the ideal position by a positional error as shown in FIG. . Further, when the fluctuation of the position error is considered on the basis of the interval of the synchronization signal, it means that the interval of the synchronization signal, that is, the synchronization period varies due to the eccentricity of the latent image carrier gear. These position errors can be detected by detecting the phase detection marks MK (1), MK (2),... By the mark detection sensor 18 and analyzing the mark detection signal output from the sensor 18. An example of the detection result is the graph shown in FIG.

  FIG. 2 is a graph showing the position error from the ideal position of the phase detection mark accompanying the eccentricity of the latent image carrier gear. In the figure, for the first mark MK (1), the ideal position and the measured position are made to coincide, and the position errors (= ideal position−measured position) for the other marks MK (2) to MK (27). Seeking. Then, the position error of each of the marks MK (2) to MK (27) was plotted according to the distance from the mark MK (1) on the transfer medium. As can be seen from the figure, the eccentricity characteristic of the latent image carrier gear can be specified by the amplitude and the phase. That is, in the actual measurement example shown in the figure, the average value of the position error is about (−42 μm), the amplitude is about 40 μm, and the phase (phase angle) in terms of angle is about 235 °. Thus, the eccentricity characteristic of the latent image carrier gear can be specified by the amplitude and the phase angle. When this eccentricity characteristic is examined in more detail, the following can be understood from the eccentricity characteristic of FIG. That is, in a region where the distance from the mark MK (1) is short (distance: 0 to 20 mm), the position error gradually increases. As shown in FIG. 1B, the mark pitches P12, P23, P34, … Is getting bigger. In the next area (distance: 20 to 40 mm), the fluctuation of the position error becomes small, and the mark pitch becomes the standard pitch in the vicinity of the maximum amplitude position (distance: about 30 mm). Is also getting smaller. After that, it is the same as above. As is clear from these facts, the positional relationship between adjacent marks is clarified by converting the eccentricity characteristics of FIG. 2 into pitch characteristics. That is, a pitch characteristic is obtained by performing a differentiation process on the eccentric characteristic in FIG. 2 (curve in FIG. 3). In addition, the straight line in the figure is a standard pitch.

  As described above, since the pitch of the marks MK (1), MK (2),... Changes due to the eccentricity of the latent image carrier gear, the inventor of the present application has devised control according to the change. That is, the inventor of the present application has obtained the knowledge that the eccentricity of the latent image carrier gear can be canceled and the position error can be suppressed by controlling the period of the synchronization signal in the direction opposite to the change. More specifically, the period of the synchronizing signal was changed with a characteristic (curve in FIG. 4) in which the pitch characteristic was inverted. Then, the phase detection marks MK (1) to MK (27) were formed while changing the period of the synchronization signal with the characteristics shown by the curve in FIG. As a result, as shown in FIG. 5, the position error could be greatly suppressed.

  Therefore, in the present invention, phase data (amplitude and phase angle) indicating the eccentricity characteristic of the latent image carrier gear is detected, and the period of the synchronization signal is corrected based on the phase data, thereby causing the latent image carrier The image writing position is adjusted to improve the image quality. Hereinafter, the contents of the present invention will be described in more detail by showing specific embodiments.

B. Embodiment FIG. 6 is a diagram showing an embodiment of an image forming apparatus according to the present invention. The apparatus 1 includes a color printing process for forming a full color image by superposing four color toners (developers) of black (K), cyan (C), magenta (M), and yellow (Y), and black (K ) To selectively execute monochromatic printing processing for forming a monochrome image using only toner. In this image forming apparatus 1, when an image forming command (printing command) is given to a main controller (not shown) from an external device such as a host computer, an engine controller (not shown) is operated in accordance with the command from the main controller. Each part EG is controlled to execute a predetermined image forming operation, and an image corresponding to the image forming command is formed on a sheet (recording material) S such as a copy sheet, a transfer sheet, a sheet, and an OHP transparent sheet.

  6, an image forming apparatus 1 according to the present embodiment includes a housing main body (apparatus main body) 2, a first opening / closing member 3 that is attached to the front surface of the housing main body 2 (right-hand side surface in the same figure) so as to be openable and closable. A second opening / closing member (also serving as a paper discharge tray) 4 is mounted on the upper surface of the housing body 2 so as to be freely opened and closed. The first opening / closing member 3 is provided with an opening / closing lid 3 a that can be opened and closed on the front surface of the housing body 2. The opening / closing lid 3a can be opened / closed in conjunction with or independently of the first opening / closing member 3.

  In the housing main body 2, an electrical component box 5 containing a power circuit board, a main controller, and an engine controller is provided. An image forming unit 6, a transfer belt unit 9, and a paper feed unit 10 are also disposed in the housing body 2. On the other hand, a fixing unit 12 is disposed on the first opening / closing member 3 side. In this embodiment, the consumables in the image forming unit 6 and the paper feeding unit 10 are configured to be detachable from the housing body 2. The consumables and the transfer belt unit 9 can be removed and repaired or exchanged.

  The transfer belt unit 9 is stretched between the two rollers 14 and 15, a driving roller 14 disposed below the housing body 2, a driven roller 15 disposed obliquely above the driving roller 14. And an intermediate transfer belt 16 that is circulated and driven in the direction indicated by an arrow D16, and a belt cleaner 17 that is in contact with the surface of the intermediate transfer belt 16. The driven roller 15 is disposed obliquely above the drive roller 14 (upward on the left hand in FIG. 6). For this reason, the intermediate transfer belt 16 rotates and moves in the direction D16 while being inclined. Further, the belt surface 16a in which the belt conveyance direction D16 when the intermediate transfer belt 16 is driven is downward (right downward in FIG. 6) is located below. In the present embodiment, the belt surface 16a is a belt tension surface (surface pulled by the drive roller 14) when the belt is driven, and the peripheral speed is lower than the peripheral speed of the photosensitive drum (image carrier) 20 of each color. have. In this way, by setting the peripheral speed of the intermediate transfer belt 16 to be slower than the peripheral speed of each photosensitive drum 20, the photosensitive drum 20 is pulled by the intermediate transfer belt 16 in a direction that suppresses rotation. Is driving.

  The drive roller 14 also serves as a backup roller for the secondary transfer roller 19. A rubber layer having a thickness of about 3 mm and a volume resistivity of 100 kΩ · cm or less is formed on the peripheral surface of the drive roller 14, and secondary transfer is omitted by grounding through a metal shaft. A conductive path of the secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 19 is used. Thus, by providing the driving roller 14 with a rubber layer having high friction and shock absorption, it is difficult for the impact when the sheet S enters the secondary transfer portion to be transmitted to the intermediate transfer belt 16, and deterioration of image quality is prevented. can do.

  In the present embodiment, the diameter of the driving roller 14 is smaller than the diameter of the driven roller 15. Thereby, the sheet S after the secondary transfer can be easily peeled by the elastic force of the sheet S itself. The driven roller 15 is also used as a backup roller for the belt cleaner 17. The belt cleaner 17 is provided on the side of the belt surface 16a facing downward in the transport direction, and includes a cleaning blade 17a that removes residual toner and a toner transport member that transports the removed toner, as shown in FIG. Yes. The cleaning blade 17a contacts the intermediate transfer belt 16 at a portion where the intermediate transfer belt 16 is wound around the driven roller 15, and cleans and removes toner remaining on the surface of the intermediate transfer belt 16 after the secondary transfer.

  The driving roller 14 and the driven roller 15 are rotatably supported by a support frame (not shown) of the transfer belt unit 9. Further, a primary transfer roller 21 is provided on the back surface of the belt surface 16a facing downward in the transport direction of the intermediate transfer belt 16 so as to face the photosensitive drum 20 of each image forming station Y, M, C, K described later. . These four primary transfer rollers 21 are rotatably supported with respect to the support frame, and are electrically connected to a primary transfer bias generator (not shown), and generate the primary transfer bias at an appropriate timing. A primary transfer bias is applied from the portion.

  The support frame is rotatable with respect to the housing body 2 around the drive roller 14 as a rotation center. Then, by actuating an actuator (not shown), the support frame is rotated to face the photosensitive drums 20 of the yellow (Y), magenta (M), and cyan (C) image forming stations Y, M, and C. The primary transfer roller 21 arranged in this manner approaches the photosensitive drum 20 and moves away from the photosensitive drum 20. For this reason, when the primary transfer rollers 21 for yellow, magenta, and cyan are moved closer to the photosensitive drum 20, they are brought into contact with the photosensitive drum 20 with the intermediate transfer belt 16 interposed therebetween (solid line in FIG. 6). This contact position is the primary transfer position, and the toner image is transferred to the intermediate transfer belt 16 at the primary transfer position. Conversely, when the primary transfer rollers 21 for yellow, magenta, and cyan move away from the photosensitive drum 20, the photosensitive drum 20 and the intermediate transfer belt 16 of the image forming stations Y, M, and C are separated from each other (FIG. (Dashed line in 6). On the other hand, the primary transfer roller 21 disposed facing the photosensitive drum 20 of the black (K) image forming station K rotates while being in contact with the photosensitive drum 20 with the intermediate transfer belt 16 interposed therebetween. Is configured to do. Therefore, as shown by the solid line in FIG. 6, the color printing process can be executed by positioning all the primary transfer rollers 21 on the photosensitive drum 20 side. On the other hand, as shown by a broken line in FIG. 5, the intermediate transfer belt is executed while only the monochrome printing process is performed by leaving the primary transfer roller 21 for black and separating the other primary transfer roller 21 from the photosensitive drum 20. 16 is separated from the image forming stations Y, M, and C, and yellow, magenta, and cyan colors can be set to a non-printing state. Note that the primary transfer roller 21 for black may also be configured to move away from the photosensitive drum 20 as necessary.

  A mark detection sensor 18 is installed on the support frame of the transfer belt unit 9 in the vicinity of the driving roller 14. The mark detection sensor 18 is a sensor for positioning each color toner image on the intermediate transfer belt 16, detecting the density of each color toner image, and correcting the color shift and image density of each color image. Further, when obtaining phase data of a latent image carrier gear such as a photoconductor gear as will be described later, the sensor 18 detects a phase detection mark formed on the intermediate transfer belt (transfer medium) 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 (four in this embodiment) of different color images. I have. Each of the image forming stations Y, M, C, and K is provided with a photosensitive drum 20 corresponding to the “latent image carrier” of the present invention. A charging unit 22, an image writing unit 23, a developing unit 24, and a photoconductor cleaner 25 are disposed around each photoconductor drum 20. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. In FIG. 6, since the image forming stations of the image forming unit 6 have the same configuration, for convenience of illustration, only some of the image forming stations are denoted by reference numerals, and the other image forming stations are omitted. . Further, the arrangement order of the image forming stations Y, M, C, and K is arbitrary. Further, in this embodiment, as shown in FIG. 7, in each of the image forming stations Y, M, C, and K, the above-described components are attached to the cartridge main body 32 to form a cartridge, and the stations Y, M, C, and Each K is detachable from the housing body 2 as a cartridge.

  When the image forming stations Y, M, C, and K are mounted on the housing body 2, the photosensitive drum 20 is disposed so as to be in contact with the belt surface 16a facing downward in the transport direction of the intermediate transfer belt 16 at the primary transfer position TR1. Has been. As a result, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left in the drawing with respect to the driving roller 14.

  The charging unit 22 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to be driven to rotate in contact with the surface of the photosensitive drum 20 at a charging position, and at a peripheral speed in the driven direction with respect to the photosensitive drum 20 as the photosensitive drum 20 rotates. Followed rotation. The charging roller is connected to a charging bias generator (not shown), and receives the charging bias from the charging bias generator to charge the surface of the photosensitive drum 20 at the charging position.

  The image writing unit 23 includes a line head in which light emitting elements such as a liquid crystal shutter including a light emitting diode and a backlight are arranged in a line in the axial direction of the photosensitive drum 20 (direction perpendicular to the paper surface of FIG. 6). It is used and spaced apart from the photosensitive drum 20. Further, the line head has a shorter optical path length and is more compact than the laser scanning optical system. Therefore, it can be disposed close to the photosensitive drum 20 and has the advantage that the entire apparatus can be downsized. The configuration and drive control of the line head will be described in detail later.

  Next, details of the developing unit 24 will be described on behalf of the image forming station K. The developing unit 24 includes a toner storage container 26 for storing toner, two toner agitation supply members 28 and 29 disposed in the toner storage container 26, and a partition member disposed in proximity to the toner agitation supply member 29. 30, a toner supply roller 31 disposed above the partition member 30, a developing roller 33 that contacts the toner supply roller 31 and the photosensitive drum 20 and rotates in a direction indicated by an arrow at a predetermined peripheral speed, and a developing roller And a regulating blade 34 abutting on the bearing 33.

  In each developing unit 24, the toner stirred and carried by the toner stirring supply member 29 is supplied to the toner supply roller 31 along the upper surface of the partition member 30. The toner thus supplied is supplied to the surface of the developing roller 33 via the supply roller 31. The toner supplied to the developing roller 33 is regulated to a predetermined layer thickness by the regulating blade 34 and is conveyed to the photosensitive drum 20. The charged toner is developed at a developing position where the developing roller 33 and the photosensitive drum 20 come into contact with each other by a developing bias applied to the developing roller 33 from a developing bias generator (not shown) electrically connected to the developing roller 33. Moves from the developing roller 33 to the photosensitive drum 20, and the electrostatic latent image formed by the image writing unit 23 is visualized.

  In this embodiment, a photoreceptor cleaner 25 is provided in contact with the surface of the photoreceptor drum 20 on the downstream side of the primary transfer position TR1 in the rotation direction D20 of the photoreceptor drum 20. The photoconductor cleaner 25 is in contact with the surface of the photoconductor drum 20 to remove the toner remaining on the surface of the photoconductor drum 20 after the primary transfer.

  The sheet feeding unit 10 includes a sheet feeding unit including a sheet feeding cassette 35 in which sheets S are stacked and held, and a pickup roller 36 that feeds the sheets S from the sheet feeding cassette 35 one by one. In the first opening / closing member 3, a registration roller pair 37 that defines the timing of feeding the sheet S to the secondary transfer region TR 2, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. A secondary transfer roller 19, a fixing unit 12, a paper discharge roller pair 39, and a duplex printing conveyance path 40 are provided.

  The secondary transfer roller 19 is provided so as to be able to come into contact with and separate from the intermediate transfer belt 16 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 12 includes a heating roller 45 that includes a heating element such as a halogen heater and is rotatable, and a pressure roller 46 that presses and biases the heating roller 45. The image secondarily transferred to the sheet S is fixed to the sheet S at a predetermined temperature at a nip formed by the heating roller 45 and the pressure roller 46. In the present embodiment, the fixing unit 12 can be disposed in a space formed obliquely above the intermediate transfer belt 16, in other words, in a space opposite to the image forming unit 6 with respect to the intermediate transfer belt 16. Thus, heat transfer to the electrical component box 5, the image forming unit 6, and the intermediate transfer belt 16 can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced.

  Further, the sheet S thus subjected to the fixing process is conveyed to a second opening / closing member (discharge tray) 4 provided on the upper surface portion of the housing body 2 via the discharge roller pair 39. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reverse position behind the pair of discharge rollers 39. The rotation direction of the discharge roller pair 39 is reversed, whereby the sheet S is conveyed along the duplex printing conveyance path 40. Then, it is put on the conveyance path again before the registration roller pair 37. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 16 in the secondary transfer region TR2 is transferred first. It is the opposite side of the surface that was made. In this way, images can be formed on both sides of the sheet S.

  FIG. 8 is a schematic diagram showing the positional relationship between the intermediate transfer belt and the photosensitive drums of the respective colors. In the image forming apparatus 1 according to this embodiment, the photosensitive drums 20 for four colors are provided. However, the driving motor 50K for rotating the photosensitive drum 20K for black, and yellow, magenta, and cyan are used. A drive motor 50CL for rotationally driving the photosensitive drums 20Y, 20M, and 20C is provided. A motor pinion 51K is attached to the rotation shaft of the drive motor 50K, and an idler gear 52K is meshed with the motor pinion 51K. Further, another idler gear 53K is meshed with the idler gear 52K. An idler gear 54K is mounted coaxially with the idler gear 53K. When the rotational driving force of the drive motor 50K is transmitted to the idler gear 53K via the motor pinion 51K and the idler gear 52K, the idler gears 53K and 54K rotate integrally. The motor 50K, the motor pinion 51K, and the gears 52K to 54K are fixedly disposed on the housing body 2. In contrast, the photoconductor gear 55K is movable together with the black image forming station K. That is, in the image forming station K, as shown in FIG. 7 and FIG. 8, the photoconductor gear 55K is attached at the end of the photoconductor drum 20K coaxially with the rotating shaft of the photoconductor drum 20K. When the image forming station K is mounted on the housing main body 2, the photoconductor gear 55K meshes with the idler gear 54K. Therefore, by controlling the drive motor 50K, the rotational driving force generated by the motor 50K is applied to the photosensitive drum 20K, and the photosensitive drum 20K is rotationally driven in the sub-scanning direction D20.

  On the other hand, a motor pinion 51CL is attached to the drive motor 50CL, and an idler gear 52CL is meshed with the motor pinion 51CL. The idler gear 53A is meshed with the idler gear 52CL on the black side (lower right side in FIG. 8) of the idler gear 52CL, and the idler gear 53B is meshed with the idler gear 52CL on the magenta side (upper left side in FIG. 8). ing. An idler gear 54C is coaxially attached to one idler gear 53A. An idler gear 54M is coaxially attached to the other idler gear 53B, and an idler gear 53C is meshed with the idler gear 53B on the yellow side (the upper left side in FIG. 8) of the idler gear 53B. Further, another idler gear 53D is meshed with the idler gear 53C. An idler gear 54Y is coaxially attached to the idler gear 35D. In this way, by forming a train wheel by combining a plurality of gears, the rotational driving force of the drive motor 50CL is simultaneously transmitted to the idler gears 54Y, 54M, and 54C. The motor 50CL, the motor pinion 51CL, and the gear group are also fixedly arranged on the housing body 2 in the same manner as the black side. Further, the yellow, magenta, and cyan photoconductor gears 55Y, 55M, and 55C can be moved together with the image forming stations Y, M, and C similarly to the black side. As described above, in this embodiment, the photoconductor gears 55Y, 55M, 55C, and 55K are directly connected to the photoconductor drums (latent image carriers) 20Y, 20M, 20C, and 20K, respectively. It corresponds to “Body Gear”. Further, the structure in which the photosensitive drum 20 and the photosensitive gear 55 are integrally formed is attached to the cartridge main body 32 as described above to form a cartridge.

  In this embodiment, the photoconductor gear 55 directly connected to the rotation shaft of the photoconductor drum 20 has a smaller diameter than the diameter of the photoconductor drum 20 (20Y, 20M, 20C, 20K), and its outer peripheral portion. A phase detection projection 56 is provided as a phase reference. When the image forming station (Y, M, C, K) is mounted on the housing body 2 as described above, the phase sensor 57 (57Y, 57M, 57C, 57K) fixedly disposed on the housing body 2 is used. It can be detected. Thus, in the present embodiment, the phase detection protrusion 56 functions as the “phase detection reference portion” of the present invention. However, the phase detection reference portion is not limited to the protrusion shape, and for example, a recess may be provided in a part of the photoconductor gear 55 and the recess may function as the phase detection reference portion.

  Each phase sensor 57 receives a light projecting portion that irradiates light toward the rotation locus of the phase detection projection 56 of the photoconductor gear 55 and the light reflected by the phase detection projection 56 and corresponds to the received light amount. And a light receiving section for outputting the signal. For this reason, every time the phase detection projection 56 provided on the photoconductor gear 55 passes through the phase sensor 57, a pulse signal is output to a phase measurement unit provided in the engine controller described below.

  FIG. 9 is a block diagram showing the main electrical configuration of the image forming apparatus of FIG. In the apparatus 1, a main controller 51 and an engine controller 52 are provided. The main controller 51 includes a CPU 511, an image data memory 512, and an exposure control unit 513. In the main controller 51, when an image forming command (printing command) is given from an external device such as a host computer, the CPU 511 gives a control signal corresponding to the image forming command to the engine controller 52 and is included in the image forming command. The stored image data is temporarily stored in the image data memory 512. Further, the exposure control unit 513 receives a synchronization signal Hsync whose period has been corrected as will be described later, and gives the image signal VSG to the image writing unit 23 at a timing according to the synchronization signal Hsync.

  The engine controller 52 includes a CPU 521, a phase measuring unit 522, and a memory 523. Among these components, the CPU 521 controls each part of the engine unit EG in accordance with a command from the CPU 511 of the main controller 51 and executes a predetermined image forming operation. As part of this, the CPU 521 outputs a strobe signal STB to each image writing unit 23 at an appropriate timing to cause the light emitting elements constituting the line head to emit light. In this way, the plurality of light emitting elements are driven almost simultaneously, and the line latent image is written on the photosensitive drum 20. That is, in the line head 231 of each image writing unit 23, as shown in FIG. 10, the plurality of light emitting elements 232 are main-scanned substantially orthogonal to the rotation direction D20 (FIG. 6) of the photosensitive drum 20, that is, the sub-scanning direction. They are arranged in a row in the direction X. The line head 231 is provided with a shift register circuit 233, a latch circuit 234, and an AND circuit 235. The shift register circuit 233 receives an image signal VSG for one line from the exposure control unit 513 in accordance with a clock signal (not shown). The latch circuit 234 takes in the image signal VSG from the shift register circuit 233 according to the latch signal. The AND circuit 235 outputs the image signal VSG to the light emitting element 232 when the strobe signal STB is given from the CPU 521. Therefore, the light emitting elements 232 corresponding to the image signal VSG simultaneously emit light, and a line latent image corresponding to the image signal VSG for one line is formed on the photosensitive drum 20. As described above, in this embodiment, the writing timing of the line latent image can be controlled by controlling the output timing of the image signal VSG from the exposure control unit 513 or the output timing of the strobe signal STB from the CPU 521.

  Returning to FIG. 9, the description will be continued. The CPU 521 is electrically connected to non-volatile memories 61Y, 61M, 61C, 61K provided in the image forming stations Y, M, C, K. That is, each of the memories 61Y, 61M, 61C, 61K is fixed to the side surface of the cartridge main body 32 as shown in FIG. 7, and stores information about the station (including gear information and phase data of the photoconductor gear 55). is doing. Thus, each of the memories 61Y, 61M, 61C, 61K corresponds to the “cartridge side memory” of the present invention. By mounting the station on the housing body 2, information can be transmitted between the memories 61Y, 61M, 61C, 61K and the CPU 521. The electrical connection method between the memories 61Y, 61M, 61C and 61K and the CPU 521 may be a contact method or a wireless method. This also applies to the electrical connection between the CPU 521 and the exposure control unit 513 and each image writing unit 23.

  Further, the phase measuring unit 522 is electrically connected to each phase sensor 57 (57Y, 57M, 57C, 57K) as described above, and can receive the detection signal output from each phase sensor 57. . The phase measurement unit 522 is also electrically connected to the mark detection sensor 18 and can receive an output signal from the sensor 18. Thus, based on the output signals from the two types of sensors, the phase measuring unit 522 detects phase data (amplitude and phase angle) related to the eccentricity of the photoconductor gear 55 and outputs it to the CPU 521.

  Further, the non-volatile memory 523 stores control data for controlling the engine unit EG, and temporarily stores calculation results in the CPU 521 and other data. As one of the stored contents, correction data for periodically correcting the synchronization signal Hsync is stored in the memory 523 as a correction table in association with the phase data of the photoconductor gear 55, and is used as the “main body side memory” of the present invention. It is functioning. That is, in this memory 523, as shown in FIG. 11, correction values (amplitude, phase angle) determined by the amplitude and phase angle constituting the phase data are stored in a data table format. Each of these correction values (amplitude, phase angle) indicates the period of the synchronization signal Hsync output while the photosensitive drum 20 makes one revolution. For example, correction data shown in FIG. 12 as correction values (40, 210). Can be set. Thereby, the writing position of the latent image on the photosensitive drum (latent image carrier) 20 is adjusted to improve the image quality. The operation of the image forming apparatus shown in FIG. 6 will be described below with reference to FIG.

  FIG. 13 is a flowchart showing the operation for adjusting the writing position of the latent image on the photosensitive drum. In this embodiment, when an image forming command (printing command) is given to the main controller 51 from an external device such as a host computer, correction data is obtained based on the phase data of the photoconductor gear 55 for each toner color before image formation. Loaded. Then, an image signal is given to the line head 231 in synchronization with a synchronization signal output in a cycle based on the correction data, and image formation is executed. Therefore, it is necessary to preset the phase data of the photoconductor gear 55 for each of the stations Y, M, C, and K mounted on the housing body 2. Therefore, in this embodiment, it is determined whether or not the station is a new cartridge (step S1). When the cartridge is a new cartridge, the phase data calculation process described below is executed, that is, the phase data of the photoconductor gear 55 installed in the station is obtained and stored in the nonvolatile memory 61 ( Steps S2 to S8). On the other hand, for a station for which phase data has already been obtained, the process proceeds to step S9 without performing phase data calculation processing.

  In step S2 of the phase data calculation process, the motor corresponding to the image forming station determined to be a new cartridge is driven and rotation of the photosensitive drum 20 constituting the station is started. For example, when it is determined that the black station K is a new cartridge, the drive motor 50K is driven, and when it is determined that the yellow, magenta or cyan stations Y, M, and C are new cartridges, the drive motor 50K is driven. The motor 50CL is driven. As described above, steps S2 to S8 are executed for the station that needs to derive the phase data.

  When the rotation of the photosensitive drum 20 is started, the phase detection projection 56 provided on the photosensitive gear 55 eventually passes through the phase sensor 57 and a pulse signal is output to the phase measurement unit 522. Thereby, the phase detection projection 56 serving as a phase reference is detected (step S3), and a phase detection mark is formed (step S4). In this embodiment, 27 phase detection marks MK (1) to MK (27) are provided in the same manner as the phase detection marks in the section “A. Influence and countermeasures due to eccentricity of latent image carrier gear”. It is formed on the intermediate transfer belt 16 (see FIG. 1). ... Each time these phase detection marks MK (1), MK (2),... Pass through the mark detection sensor 18, a mark detection signal is output from the mark detection sensor 18 to the phase measurement unit 522. Thus, the phase detection marks MK (1) to MK (27) formed between the circumferential lengths of the photosensitive drum 20 are detected, and at the same time, the rotation of the photosensitive drum 20 is stopped (step S6). In this embodiment, the mark formation mode is the same as that described in the section “A. Effect and countermeasures due to eccentricity of latent image carrier gear”, but the number and shape of marks are arbitrary. .

  In the subsequent step S7, the phase measurement unit 522 obtains the phase data of the photoconductor gear 55 based on the detection signal described above. More specifically, the position error (= ideal position−measured position) for the marks MK (2) to MK (27), as described in the section “A. Effect and countermeasures due to eccentricity of latent image carrier gear”. ) Is required. These positional errors are associated with the distance from the mark MK (1) on the intermediate transfer belt 16, and the eccentric characteristic of the photoconductor gear 55 similar to that in FIG. 2 is obtained. Therefore, amplitude information and phase information characterizing the eccentricity characteristic are calculated. The phase data (amplitude information and phase information) obtained in this way is written and stored in the non-volatile memory 61 of the image forming station that is the execution target of the phase data calculation process (step S8). The phase data is also temporarily stored in the memory 523 of the engine controller 52 for image formation.

  Thus, in this embodiment, when the phase data of the photoconductor gear 55 is unknown because it is a new cartridge, the phase detection marks MK (1) to MK (27) are formed, and these The phase data of the photoconductor gear 55 is obtained by reading the marks MK (1) to MK (27). Therefore, the eccentric characteristic of the photoconductor gear 55 can be obtained with certainty. Moreover, since the phase data thus obtained is stored in the nonvolatile memory 61 attached to the cartridge main body 32, the above-described phase data calculation processing (steps S2 to S7) is not necessary thereafter. Of course, when the image forming station is detached from the housing body 2 and then reattached to the original device or attached to another device, the process proceeds to the next step S9 without performing the phase data calculation process. it can.

  When the phase data calculation process is completed, or when “NO” is determined in step S1, the process proceeds to step S9, and the phase data is read from the memory 61 of each image forming station. The phase data includes the amplitude information and the phase information (phase angle) as described above, and the eccentric characteristics of the photoconductor gear 55 are specified by these. Therefore, in this embodiment, as described above, a correction value (amplitude, phase angle) determined by the phase data is extracted as correction data from the correction table in which the correction data for suppressing the influence of eccentricity and the phase data are associated with each other. (Step S10). This correction data indicates the period of the synchronization signal Hsync output while the photosensitive drum 20 makes one revolution. For example, when the amplitude and the phase angle constituting the phase data are “40” and “210”, respectively. For example, correction data shown in FIG. 12 is loaded.

  In the next step S11, all the motors 50K and 50CL are driven, and the rotation of all the photosensitive drums 20 is started. In each station, after the phase detection projection 56 serving as a phase reference is detected (step S12), the synchronization signal Hsync having been subjected to the period correction based on the correction data loaded in step S10 is sent from the CPU 521 to the exposure control unit 513. Is output (step S13). Then, the exposure control unit 513 outputs the image signal VSG for one line to the line head 231 while synchronizing with the cycle-corrected synchronization signal Hsync (step S14). On the other hand, when the line head 231 receives the image signal VSG for one line, it outputs a signal to that effect to the CPU 521. As a result, it is confirmed that the line head 231 holds the image signal for one line. Therefore, a strobe signal STB is output from the CPU 521 to the image writing unit 23, the light emitting elements 232 corresponding to the image signal VSG emit light at the same time, and the light emitting elements 232 are turned off after a certain time, and are lined on the photosensitive drum 20. A latent image is formed. Such line latent image formation processing (steps S13 and S14) is repeated until it is determined in step S15 that the image formation is completed. In this way, a two-dimensional latent image is formed on the photosensitive drum 20 at each image forming station and the latent image is developed to form a toner image. Then, the toner images are mutually transferred on the intermediate transfer belt 16. A color image is formed by superposition. If it is determined in step S15 that the image formation has been completed, the rotation of all the photosensitive drums 20 is stopped (step S16).

  As described above, according to this embodiment, the period of the synchronization signal Hsync is corrected in accordance with the eccentricity of the photoconductor gear 55, thereby adjusting the writing position of the line latent image on the photoconductor drum 20. Therefore, the influence of eccentricity can be suppressed, and as a result, the image quality can be improved. Further, correcting the cycle of the synchronizing signal Hsync is very excellent in further improving the image quality in an apparatus in which the photoconductor gear 55 and the photoconductor drum 20 are integrally configured. That is, in the tandem apparatus using the image forming station in which the photoconductor gear 55 and the photoconductor drum 20 are integrated, the eccentric characteristics of the photoconductor gear 55 may be different between the stations. Even if this invention is used, the image quality may not be improved. On the other hand, in the above-described embodiment, correction based on the phase data of the photoconductor gear 55 is performed for each photoconductor drum 20. Therefore, even in an apparatus in which the eccentric characteristics of the photoconductor gear 55 are different between stations, the influence of the eccentricity of the photoconductor gear 55 can be reliably suppressed.

  Further, the phase data of the photoconductor gear 55 may be measured before the new cartridge is mounted on the apparatus 1 and stored in the nonvolatile memory 61. In this case, the phase data calculation process (steps S2 to S7) is not necessary. However, in order to measure phase data in advance for a single cartridge (image forming station), it is necessary to use a dedicated measuring device, which is inefficient in terms of cost and workability. On the other hand, in the above embodiment, the phase data calculation process (steps S2 to S7) is executed for the new cartridge to automatically obtain the phase data within the apparatus, so that the prior measurement may be omitted. And phase data can be obtained efficiently and accurately.

  In the above embodiment, the phase data is composed of amplitude information and phase information (phase angle), and correction data for suppressing the influence of eccentricity and phase data are associated with each other and stored in the correction table. Then, correction data corresponding to the phase data obtained as described above, that is, correction values (amplitude, phase angle) are extracted. Therefore, correction data can be obtained without following the same procedure as described in the section “A. Effect and countermeasures due to eccentricity of latent image carrier gear”, and the time required for image formation can be shortened. Simplification of control can be achieved.

  Furthermore, in the above embodiment, since the light emission of the light emitting element 232 is controlled using the strobe signal STB, even if the write position of the latent image is adjusted by correcting the period of the synchronization signal Hsync as described above, The light emission time for each line latent image is substantially the same. As a result, density unevenness due to non-uniform light emission time can be reliably prevented, and an image can be formed with excellent quality.

  By the way, in the above embodiment, when it is determined that the image forming station mounted on the housing body 2 is a new cartridge, the phase data calculation process is always executed. However, as explained in the above section “Problems to be Solved by the Invention”, since the gear manufactured industrially is used as the photoconductor gear 55, the gear manufactured at the same time under a certain condition. The eccentricity characteristics of the groups are considered to be the same or similar. Therefore, in the present invention, for example, even if the cartridge is a new cartridge, the new cartridge using the gear having the same eccentric characteristic as the photoconductor gear 55 used in the new cartridge is used for the above phase. Data calculation processing is omitted. Hereinafter, the contents of the present invention will be described in detail with reference to FIGS.

  FIG. 14 is a flowchart showing a gear eccentricity detection method according to the present invention. 15 and 16 are diagrams showing examples of information stored in a memory provided in the image forming apparatus according to the present invention. One of the major differences between this embodiment and the apparatus described above is the memory structure. That is, as shown in FIGS. 15 and 16, the main body memory 523 associates the “manufacturing lot number” and “phase data” of the photoconductor gear 55 with respect to the photoconductor 55 for which phase data has already been obtained. A phase data table is stored. In addition to “unused” and “phase data”, “manufacturing lot number” can be stored in each of the cartridge side memories 61Y, 61M, 61C, 61K. Among these pieces of information, “unused” stores information indicating whether or not the image forming station is a new cartridge, and “1” is stored when the image forming station is not used. "Is memorized. In the “phase data”, phase data (amplitude, phase angle) composed of amplitude information indicating the eccentric characteristics of the photoconductor gear 55 and phase information (phase angle) is stored. In the “manufacturing lot number” added in this embodiment, the manufacturing lot number of the photoconductor gear 55 attached to the cartridge main body 32 is stored. This production lot number is a number that is commonly assigned to gears produced by the production of gears with the same specifications. For gear groups with the same production lot number, the eccentricity characteristics are included. The various characteristics are the same or similar. Thus, in the present embodiment, the production lot number is used as “gear information” of the present invention.

  Next, the operation of the image forming apparatus according to the present invention will be described in detail. In this embodiment, a part of the operation in the embodiment shown in FIG. 13 is changed, and the phase data calculation process (steps S2 to S7), the correction data derivation process, and the line latent image forming process are the same. Hereinafter, the difference will be mainly described. Here, in order to facilitate understanding of the operation, a specific operation in the apparatus in the memory state shown in FIGS. 15 and 16 will be exemplified.

  When an image forming command (printing command) is given to the main controller 51 from an external device such as a host computer, it is determined whether each image forming station is a new cartridge (step S1). For example, in the apparatus in the memory state shown in FIGS. 15 and 16, only the yellow image forming station Y is unused, and the other image forming stations M, C, and K are used at least once. The phase data of each photoconductor gear 55 is also stored on the cartridge side. Therefore, the operation relating to stations other than yellow proceeds to step S9.

  On the other hand, for the station Y determined to be a new cartridge, the process proceeds to step S21, the production lot number stored in the cartridge side memory 61Y is read, and whether or not it is stored in the main body side memory 523 is determined by the engine controller 52. CPU 521 determines the phase data using different methods depending on the determination result.

  For example, in the apparatus in the memory state shown in FIG. 15, “YNMR0002” is stored as the manufacturing lot number, but this manufacturing lot number (gear information) is not stored in the main body side memory 523. That is, by comparing the production lot number, it can be seen that the eccentric characteristic of the photoconductor gear 55 to which the production lot number is attached is unknown. Therefore, in this case (“NO” in step S21), the above-described phase data calculation process (steps S2 to S7) is executed to obtain phase data indicating the eccentric characteristic of the photoconductor gear 55 of the manufacturing lot number. Then, the phase data is written and stored in the cartridge side memory 61Y of the station Y (step S8), and the unused information is rewritten to “0” (step S22). On the other hand, for the main body side, the phase data and the production lot number are additionally stored in the main body side memory 523 in association with each other (step S23). When the phase data regarding the station Y that is new and whose eccentricity characteristics are unknown is thus obtained, the process proceeds to step S9.

  For example, in the apparatus in the memory state shown in FIG. 16, “YNMR0003” is stored as the manufacturing lot number, but this manufacturing lot number (gear information) is stored in the main body side memory 523 and associated with the manufacturing lot number. Phase data is stored. Therefore, if “YES” is determined in the step S21, the CPU 521 reads the phase data (20, 60) corresponding to the production lot number “YNMR0003” (step S24). The phase data (20, 60) is written and stored in the cartridge side memory 61Y of the station Y (step S25), and unused information is rewritten to “0” (step S26). Thus, for the station Y that is a new product but uses the photoconductor gear 55 with the same production lot number, the phase data relating to the station Y is obtained without performing the phase data calculation process (steps S2 to S7). Is obtained, the process proceeds to step S9.

  In step S9 and subsequent steps, phase data reading processing (step S9), correction data extraction (step S10), and image forming processing (steps S11 to S16) are executed in the same manner as in the above embodiment.

  As described above, according to the embodiment shown in FIG. 14, the manufacturing lot number and the phase data are stored in the main body side memory 523 while being associated with each other. Even if the mounted image forming station is a new cartridge, if the phase data corresponding to the manufacturing lot number of the photoconductor gear 55 exists in the main body side memory 523, the phase data calculation process is omitted. Yes. Therefore, the execution frequency of the phase data calculation process can be reduced without reducing the accuracy of the phase data, and the eccentric characteristic of the photoconductor gear 55 can be obtained efficiently. If the mounted image forming station is a new cartridge and the eccentric characteristic of the photoconductor gear 55 is unknown, the phase data calculation process is executed to obtain the phase data of the photoconductor gear 55. . Therefore, the eccentric characteristic of the photoconductor gear 55 can be accurately obtained. Moreover, since the phase data obtained in this way is stored in the nonvolatile memory 61 attached to the cartridge main body 32 of the new cartridge, the above-described phase data calculation processing (steps S2 to S7) is not necessary thereafter. Of course, when the image forming station is detached from the housing body 2 and then reattached to the original apparatus or attached to another apparatus, the process can proceed to step S9 without performing the phase data calculation process. Furthermore, since the phase data obtained by executing the phase data calculation process is additionally stored in the main body side memory 523 in association with the unknown production lot number, the number of production lot numbers with known phase data increases, and the phase data The execution frequency of the data calculation process can be further reduced.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the writing position of the line latent image is adjusted by controlling the cycle of the synchronization signal Hsync, but the writing position is controlled by controlling the cycle of the strobe signal STB instead of the synchronization signal Hsync. You may make it adjust. This is because the line head 231 configured as described above turns on the light emitting element 232 in response to the strobe signal STB.

  In the above embodiment, when the line head 231 receives the image signal VSG for one line, it outputs a signal to that effect to the CPU 521 and confirms that the line head 231 holds the image signal for one line. Yes. Thus, the means for confirming the holding of one line is not limited to this. For example, when the exposure control unit 513 outputs the image signal VSG for one line, it outputs a signal to that effect to the CPU 521 and confirms that the line head 231 holds the image signal for one line. May be.

  In the above embodiment, the writing position is adjusted by controlling the output timing of the image signal VSG to the line head 231, and the writing position is adjusted by controlling the light emission timing of the light emitting element 232. These output timing and light emission timing are closely related. For example, even if the output timing is controlled, if the strobe signal STB is output while the image signal is not transmitted to the line head 231 for one line, there is a problem that a part of the image is not formed. Therefore, in order to surely prevent such a problem, it is desirable to control both the output timing and the light emission timing in association with the phase data of the photoconductor gear 55.

  In the above embodiment, the line latent image is formed by the image writing unit 23 using a line head in which light emitting diodes (LEDs) are arranged in a line. However, the configuration of the image writing unit 23 is limited to this. Is not to be done. For example, a line head in which a plurality of organic EL (electroluminescence) elements are arranged in a line in the axial direction of the photosensitive drum 20 (direction perpendicular to the paper surface of FIG. 6) may be used.

  Further, in the above embodiment, as described in the section “A. Influence and countermeasures due to eccentricity of latent image carrier gear”, the synchronization signal Hsync is opposite to the change in mark pitch (for example, the pitch characteristic shown in FIG. 3). The period is corrected. That is, although the correction data is set so that the pitch of the mark MK is uniform, the correction data may be set so that the actual measurement mark MK in FIG. 1 is located at the ideal position.

  In the above embodiment, the “manufacturing lot number” is used as the gear information. However, the gear information is not limited to this, and information indicating that the eccentricity characteristics are the same or approximate from a common point in manufacturing. Information used when the eccentric characteristics are classified and arranged by inspection or inspection may be used as gear information.

  Further, in each of the above embodiments, the present invention is applied to an apparatus that forms a color image using toners of four colors of yellow, magenta, cyan, and black. However, a color formation method (tandem method, four-cycle method) The type and number of toner colors are not limited to the above, and can be applied to all image forming apparatuses that form an image using a line head in which a plurality of light emitting elements are arranged in a line.

The figure which shows the relationship between the measurement position of a phase detection mark, and an ideal position. The graph which shows the position error from the ideal position of the mark for phase detection accompanying eccentricity of a latent image carrier gear. The figure which shows the fluctuation | variation of the pitch of the mark for phase detection accompanying eccentricity of a latent image carrier gear. The figure which shows the period of the synchronizing signal suitable in order to suppress eccentricity of a latent image carrier gear. The graph which shows the position error from the ideal position of the mark for phase detection formed in synchronization with the synchronizing signal shown in FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. The perspective view which shows the image forming station with which FIG. 6 is equipped. FIG. 3 is a schematic diagram illustrating an arrangement relationship between an intermediate transfer belt and photosensitive drums of respective colors. FIG. 7 is a block diagram showing a main electrical configuration of the image forming apparatus in FIG. 6. The figure which shows the structure of a line head. The figure which shows the correction table which consists of correction data for correct | amending a synchronizing signal. The figure which shows an example of correction data. 6 is a flowchart showing an operation for adjusting a writing position of a latent image on a photosensitive drum. The flowchart which shows the gear eccentricity detection method concerning this invention. 4 is a diagram showing an example of memory information in the image forming apparatus according to the present invention. FIG. FIG. 10 is a diagram showing another example of memory information in the image forming apparatus according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 20, 20Y, 20M, 20C, 20K ... Photosensitive drum (latent image carrier), 23, 23Y, 23M, 23C, 23K ... Image writing unit, 32 ... Cartridge main body, 55, 55Y, 55M, 55C, 55K ... photosensitive member gear (latent image carrier gear), 61, 61Y, 61M, 61C, 61K ... non-volatile memory (cartridge side memory), 521 ... CPU (control unit), 523 ... non-volatile memory ( Main body side memory), D20 ... sub-scanning direction, Hsync ... synchronization signal, STB ... strobe signal, VSG ... image signal, X, x ... main scanning direction, y ... sub-scanning direction

Claims (5)

An image forming station is mounted on the main body of the apparatus, and a rotational driving force of a motor provided on the main body is mounted on the main body of the cartridge. The latent image carrier is transmitted to the latent image carrier via the latent image carrier gear to rotate and move the latent image carrier in the sub-scanning direction. In an image forming apparatus for writing a line latent image extending in a substantially orthogonal main scanning direction and further developing the latent image with toner to form an image,
Phase data for obtaining phase data indicating eccentricity characteristics of the latent image carrier gear based on signals obtained by forming a plurality of phase detection marks by the image forming station and detecting the plurality of phase detection marks. The calculation process can be executed,
While the cartridge body is mounted with a cartridge-side memory storing gear information indicating the manufacturing conditions and the manufacturing time of the latent image carrier gear,
On the apparatus main body side, the main body side memory that stores the gear information and the phase data in association with each other, and the gear information stored in the cartridge side memory is compared with the gear information stored in the main body side memory. And a control unit for determining whether or not to execute the phase data calculation process,
Gear information image forming apparatus comprising a Turkey different from each other for each latent image carrier gear group having an eccentric property of the same or similar are produced at the same time at a constant production conditions.   The control unit reads phase data corresponding to the gear information from the main body side memory when the gear information stored in the cartridge side memory is stored in the main body side memory. The image forming apparatus according to claim 1, wherein the phase data is calculated by executing phase data calculation processing.   When calculating the phase data by executing the phase data calculation process, the control means associates the phase data with the gear information stored in the cartridge-side memory and associates the phase data with the gear information. The image forming apparatus according to claim 2, further stored in the main body side memory.   When the gear information stored in the cartridge side memory is stored in the main body side memory, the control unit controls the image writing unit based on the read phase data to transfer the latent image carrier to the latent image carrier. While the line latent image writing position is adjusted, the image writing unit is controlled based on the calculated phase data to adjust the line latent image writing position to the latent image carrier when not stored. The image forming apparatus according to claim 2. An image forming station is mounted on the main body of the apparatus, and a rotational driving force of a motor provided on the main body is mounted on the main body of the cartridge. The latent image carrier is transmitted to the latent image carrier via the latent image carrier gear to rotate and move the latent image carrier in the sub-scanning direction. In an image forming apparatus for writing a line latent image extending in a substantially orthogonal main scanning direction and further developing the latent image with toner to form an image,
Storing gear information indicating manufacturing conditions and manufacturing timing of the latent image carrier gear in a cartridge-side memory attached to the cartridge body;
Storing the gear information and phase data indicating the eccentricity characteristics of the latent image carrier gear specified by the gear information in association with each other in a main body side memory provided in the apparatus main body;
Reading gear information from the cartridge-side memory in a state where the image forming station is mounted on the apparatus body, and determining whether the gear information is stored in the body-side memory;
A phase data calculation process is performed in which a plurality of phase detection marks are formed by the image forming station and phase data of the latent image carrier gear is obtained based on signals obtained by detecting the plurality of phase detection marks. Determining whether or not according to the determination result,
Gear information gear eccentricity detection method in an image forming apparatus, wherein the Turkey different from each other for each latent image carrier gear group having an eccentric property of the same or similar are produced at the same time at a constant production conditions.

Images