JP2006058415A - Printer engine and color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the quality of color images to be formed by preventing the misregistration of transfer positions of toner images of respective colors when the color images are formed by superposing the toner images of a plurality of colors and transferring the same. <P>SOLUTION: In case of the occurrence of the misregistration of the transfer positions of the toner images of the respective colors formed on respective photoreceptors 7, the number of revolutions of a driving section 28 for driving the photoreceptors 7 is adjusted so as to maintain the fixed linear speeds of the photoreceptors 7 according to the amounts of the misregistration. As a result, the misregistration of the transfer positions of the toner images on the photoreceptors 7 can be eliminated and the high-quality color images obviating the misregistration of the transfer positions of the toner images on the photoreceptors 7 can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printer engine and a color image forming apparatus using the printer engine.

  In a color image forming apparatus that forms an image by electrophotography, such as a color copying machine or a color printer, a plurality of photoconductors for forming toner images of different colors, and toners formed on these photoconductors 2. Description of the Related Art There is known a printer engine that includes an intermediate transfer belt to which an image is transferred or a transfer and conveyance belt that holds and conveys a recording medium to which a toner image formed on a photoreceptor is transferred.

  In such a color image forming apparatus, when a toner image of each color formed on each photoconductor is transferred to a recording medium that is held and conveyed by an intermediate transfer belt or a transfer conveyance belt, the transfer position of the toner image of each color is transferred. When the position shift occurs, the color image formed by superimposing the toner images of the respective colors is in a state where the color is blurred, and the image quality is deteriorated.

  Such misalignment of the transfer positions of the toner images of the respective colors occurs due to variations in the linear velocity of the photoconductor. Variations in the linear velocity of the photosensitive member are caused by variations in the diameter of the photosensitive member, variations in the component size of the driving force transmission system that transmits the rotational driving force to the photosensitive member, and the like.

  For this reason, conventionally, a detection pattern toner image is formed on each photoconductor, and these detection pattern toner images are transferred onto a recording medium conveyed by an intermediate transfer belt or a transfer conveyance belt, and the transferred detection pattern toner is transferred. By measuring the interval between the images and changing the exposure timing of the photosensitive member so that the interval is constant, the positional deviation of the toner image at the transfer position is corrected.

  However, when correcting the misregistration of each color toner image transferred by varying the exposure timing of the photoconductor, the minimum misalignment amount that can be corrected is the dot diameter of the light beam that exposes the photoconductor. For example, it is 42 μm.

  For this reason, the amount of misregistration cannot be corrected with a size smaller than the dot diameter of the light beam, and there is a limit to the correction of the misregistration of the toner image of each color.

  The object of the present invention is to prevent the positional shift of the transfer position of each color toner image and to improve the quality of the formed color image when a color image is formed by superimposing and transferring a plurality of color toner images. Is to increase.

  According to a first aspect of the present invention, the printer engine of the present invention is rotationally driven and has a plurality of photoconductors on which toner images are formed on the outer peripheral surface, and is arranged to face the outer peripheral surface of the photoconductor, and is transferred from the photoconductor. An endless belt that carries a toner image or travels while holding a recording medium on which the toner image on the photoconductor is transferred, and a toner image that is formed on the photoconductor are overlaid to overlap the endless belt or the A means for forming a detection pattern toner image on the photoconductor for detecting a displacement amount of a transfer position of each color toner image when transferred to a recording medium held by an endless belt; and forming on the photoconductor Means for transferring the detected detection pattern toner image onto the endless belt or a recording medium held on the endless belt, and on the endless belt or Means for detecting the detection pattern toner image transferred onto the recording medium held by the endless belt, and the position of the transfer position of the detection pattern toner image of each color based on the detection result of the means for detecting the detection pattern toner image Based on the judgment result of the means for judging the deviation amount and the means for judging the positional deviation amount of the transfer position, the number of rotations of the drive unit for driving the photosensitive body is adjusted so as to match the linear velocity of the photosensitive body. Means.

  According to a second aspect of the present invention, in the printer engine according to the first aspect, the driving units are individually connected to the plurality of the photosensitive members.

  According to a third aspect of the present invention, in the printer engine according to the first aspect, as the photosensitive member, a photosensitive member on which a black toner image is formed, a photosensitive member on which a yellow toner image is formed, and a cyan toner image. A photosensitive member on which a magenta toner image is formed, the photosensitive member on which a yellow toner image is formed, and the photosensitive member and a magenta toner on which a cyan toner image is formed. The photoconductor on which an image is formed is connected to the common drive unit, and the photoconductor on which a black toner image is formed is connected to the other drive unit.

  According to a fourth aspect of the present invention, in the printer engine according to the second aspect, a plurality of gears connected to the photoconductor to transmit a rotational driving force to each photoconductor, and a detected portion provided in each of the gears. A plurality of sensors for detecting the detected portion; means for detecting a rotational phase shift between the gears based on a detection result by the sensor; and the means detected by the means for detecting a rotational phase shift. When the means for determining that the rotational phase between the gears has deviated by a certain angle and the means for determining that the rotational phase between the gears has deviated by a certain angle, the position where the rotational phase difference between the gears is eliminated. Means for driving the drive unit to rotate the gear.

  According to a fifth aspect of the present invention, in the printer engine according to the third aspect, the gear is connected to the photosensitive member on which a black toner image is formed and transmits a rotational driving force to the photosensitive member. A gear connected to any one of the photoreceptors on which toner images of yellow, cyan, and magenta are formed and transmitting a rotational driving force to the photoreceptor, and a detected portion provided in each of the gears; Two sensors for detecting the detected portion, means for detecting a rotational phase shift between the gears based on a detection result by the sensor, and the gear detected by the means for detecting a rotational phase shift Means for determining that the rotational phase between them is shifted by a certain angle, and when the means determines that the rotational phase between the gears is shifted by a certain angle, yellow, cyan, The gear that transmits a rotational driving force to the photoconductor that forms each toner image of zenter is rotated to a position where there is no shift in rotational phase with the gear that is connected to the photoconductor that forms a black toner image. Means.

  According to a sixth aspect of the present invention, in the printer engine according to any one of the first to fifth aspects, a rotation shaft that is driven to rotate about a center line is provided, and the photoreceptor can be inserted into and removed from the rotation shaft. And an engaging portion that rotates integrally with the rotating shaft is provided on the rotating shaft, and the photosensitive member is slid along the center line direction of the rotating shaft to engage with the engaging portion. An engaging portion that is detachably engaged is provided.

  According to a seventh aspect of the present invention, in the printer engine according to any one of the first to sixth aspects, at least the photosensitive member and charging means for uniformly charging the outer peripheral surface of the photosensitive member are housed in a case. The process cartridge is unitized and detachably mounted in the main body case.

  According to an eighth aspect of the present invention, in the printer engine according to any one of the first to seventh aspects, the endless belt is an intermediate transfer belt.

  According to a ninth aspect of the present invention, in the printer engine according to any one of the first to seventh aspects, the endless belt is a transfer conveyance belt.

  A color image forming apparatus according to a tenth aspect of the present invention is a printer engine according to any one of the first to ninth aspects, a recording medium storage portion that stores a recording medium supplied to the printer engine, and the recording A fixing device that fixes the color toner image transferred onto the medium; and a recording medium discharge unit that discharges the recording medium on which the toner image is fixed.

  According to the first aspect of the present invention, when the transfer position of each color toner image formed on each photoconductor is misaligned, the linear velocity of the photoconductor becomes constant according to the misalignment amount. By adjusting the number of rotations of the drive unit that drives the photosensitive member, it is possible to eliminate the displacement of the transfer position of the toner image on each photosensitive member, and the high-quality that the transfer position of the toner image of each color is not displaced. Color images can be obtained.

  According to the second aspect of the present invention, the linear velocities of the plurality of photoconductors can be individually adjusted, the linear velocities of the respective photoconductors can be matched with high accuracy, and the transfer positions of the toner images of the respective colors can be adjusted. Positioning can be performed with high accuracy.

  According to the third aspect of the present invention, the number of drive units used for alignment of the transfer positions of the toner images on the four photoconductors can be reduced to two, and the number of drive units used is reduced. be able to.

  According to the fourth aspect of the present invention, the gear connected to the photosensitive member may be formed with the center shifted, and the linear speed of the photosensitive member is periodically changed per one rotation of the gear by shifting the center of the gear. As described above, the rotational phase between the gears connected to each photoconductor is shifted by adjusting the rotational speed of the drive unit that drives each photoconductor as in the invention of claim 2 described above. Due to the rotational phase shift, the transfer position of each color toner image is shifted. Therefore, when the rotational phase between the gears is deviated by a certain angle, the toner image is caused by the gear being shifted by rotating the gear to a position where the rotational phase deviation between the gears is eliminated. It is possible to prevent the displacement of the transfer position.

  According to the fifth aspect of the present invention, there is a case where the gear connected to the photosensitive member is formed with the center shifted, and the linear velocity of the photosensitive member is periodically changed per one rotation of the gear by shifting the center of the gear. And a gear connected to the photoconductor on which a black toner image is formed by adjusting the number of rotations of the drive unit that drives each photoconductor as in the invention of claim 3 described above. The rotational phase between the gear connected to the photoconductor on which the toner image of the other color is formed is shifted, and the black toner image and the toner image of the other color are caused by the rotational phase shift. Misalignment of the transfer position occurs. Therefore, when the rotation phase between the gear connected to the photoconductor on which the black toner image is formed and the gear connected to the photoconductor on which another color toner image is formed is deviated by a certain angle. In addition, by rotating the gear to a position where there is no rotational phase shift between the gears, it is possible to prevent the positional shift of the toner image transfer position caused by the shift of the center of the gear.

  According to the invention described in claim 6, the photosensitive member is slid in the direction of the center line of the rotating shaft, and the engaging portion provided on the rotating shaft and the engaging portion provided on the photosensitive member are engaged / disengaged. The photoconductor can be easily replaced.

  According to the seventh aspect of the invention, by attaching / detaching the process cartridge to / from the main body case, at least the photosensitive member and the charging means can be exchanged together, and the exchange work can be easily performed.

  According to the eighth aspect of the present invention, when transferring the toner image formed on each photoconductor onto the intermediate transfer belt, it is possible to prevent the displacement of the transferred toner image.

  According to the ninth aspect of the present invention, when the toner image formed on each photoconductor is transferred to the recording medium which is held and transferred by the transfer conveyance belt, the positional deviation of the transferred toner image is prevented. be able to.

  According to the tenth aspect of the present invention, since this color image forming apparatus has the printer engine according to any one of the first to eighth aspects, a high-quality color in which the transferred toner image of each color does not cause a color shift. A recording medium on which an image is formed can be output.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a longitudinal side view schematically showing a color printer which is a color image forming apparatus. In the main body case 2 of the color printer 1, a printer engine 3, an optical writing device 4 that emits a light beam, a paper feed cassette 5 that is a recording medium storage unit that stores the recording medium P, and a recording in which a toner image is transferred. A fixing device 6 for fixing the medium P is provided.

  The printer engine 3 is a part that forms a toner image and transfers the formed toner image to the recording medium P. The printer engine 3 is arranged around four photoconductors 7 (7Y, 7C, 7M, and 7K). The charging roller 8 is a charging unit, the developing device 9, the cleaning device 10, the primary transfer roller 11, the intermediate transfer belt 12 that is an endless belt, the secondary transfer roller 13, the cleaning device 14, and the like. Here, in the description of the present specification and drawings, Y, C, M, and K subscripts indicate yellow, cyan, magenta, and black colors, respectively, and these subscripts are omitted as necessary. .

  The photoconductor 7 is formed in a cylindrical shape and is connected to a drive motor which will be described later, and rotates around the center line by the drive force from the drive motor. A photosensitive layer on which an electrostatic latent image is formed is provided on the outer peripheral surface of the photoreceptor 7.

  The charging roller 8 is disposed in contact with the outer peripheral surface of the photoconductor 7 or is disposed with a small gap from the outer peripheral surface of the photoconductor 7. When a voltage is applied to the charging roller 8 from a power supply unit (not shown), corona discharge is generated between the charging roller 8 and the photoconductor 7, and the outer peripheral surface of the photoconductor 7 is made uniform. Charged.

  The optical writing device 4 emits a light beam corresponding to the image data, and exposes the outer peripheral surface of the uniformly charged photoreceptor 7. By this exposure, an electrostatic latent image corresponding to the image data is formed on the outer peripheral surface of the photoreceptor 7.

  The developing device 9 supplies toner to the photoreceptor 7. The supplied toner adheres to the electrostatic latent image formed on the outer peripheral surface of the photoconductor 7, and the electrostatic latent image on the outer peripheral surface of the photoconductor 7 is visualized as a toner image.

  The intermediate transfer belt 12 is a loop belt formed with a resin film or rubber as a base, wound around a driving roller 15, an entrance roller 16, and a tension roller 17, and connected to a driving motor described later. The drive roller 15 is driven to rotate and travels in the direction of arrow A. The entrance roller 16 and the tension roller 17 are driven to rotate by the frictional force with the intermediate transfer belt 12 as the intermediate transfer belt 12 travels in the direction of arrow A.

  The primary transfer roller 11 is disposed on the inner peripheral surface side (inside the loop) of the intermediate transfer belt 12, and the toner image on each photoconductor 7 is transferred by applying a transfer voltage to the primary transfer roller 11. The image is transferred onto the intermediate transfer belt 12. The toner images formed on the respective photoconductors 7 are sequentially transferred and superimposed on the intermediate transfer belt 12 by the operation of the transfer rollers 11, and a color toner image is formed on the intermediate transfer belt 12.

  The cleaning device 10 cleans the outer peripheral surface of the photoreceptor 7 after the toner image is transferred to the intermediate transfer belt 12. This cleaning removes toner, paper dust, and the like remaining on the outer peripheral surface of the photoreceptor 7 after the toner image is transferred to the intermediate transfer belt 12.

  The color toner image formed on the intermediate transfer belt 12 is transferred to the secondary transfer roller 13 at the timing when the recording medium P is sent to the transfer position where the intermediate transfer belt 12 and the secondary transfer roller 13 are in contact with each other. When the working voltage is applied, it is transferred to the recording medium P. The recording medium P is fed from the sheet feeding cassette 5 and conveyed by the conveying roller 18 and the registration roller 19, and is transferred to the fixing device 6 after the toner image is transferred. The recording medium P to which the toner image has been transferred is subjected to fixing processing by applying heat and pressure in the fixing device 6, and the toner image melted by this fixing processing is fixed to the recording medium P. The recording medium P for which the fixing process has been completed is discharged onto a discharge tray 20 which is a recording medium discharge portion formed on the upper surface portion of the main body case 2.

  The cleaning device 14 cleans the outer peripheral surface of the intermediate transfer belt 12 after the color toner image is transferred to the recording medium P. This cleaning removes toner, paper dust, and the like remaining on the outer peripheral surface of the intermediate transfer belt 12 after the toner image is transferred.

FIG. 2 is a schematic side view showing a driving structure of the photoconductor 7 and the intermediate transfer belt 12 in the printer engine 3.
A roller gear 22 fixed to the roller shaft 21 of the drive roller 15 is provided on one end side of the drive roller 15. The roller gear 22 meshes with a motor gear 25 fixed to the motor shaft 24 of the drive motor 23, and transmits a rotational driving force from the drive motor 23 to the drive roller 15.

  Each photoconductor 7 is detachably attached to a rotary shaft 26, and a photoconductor gear 27 (27Y, 27C, 27M, 27K) is fixed to an end of the rotary shaft 26. These photoconductor gears 27 are motor gears 30 (30Y, 30C,...) Fixed to a motor shaft 29 of a drive motor 28 (28Y, 28C, 28M, 28K) which is a drive unit provided corresponding to each photoconductor 7. 30M, 30K), and a rotational driving force is transmitted from each drive motor 28 to each photoconductor 7. As the drive motor 28 and the drive motor 23 for driving the intermediate transfer belt 12, a stepping motor capable of controlling the rotational speed with high accuracy is used.

  The traveling speed of the intermediate transfer belt 12 in the direction of the arrow A is set slightly faster than the linear speed of the outer peripheral surface of each photoconductor 7, whereby the deflection of the intermediate transfer belt 12 between the photoconductors 7. Is prevented.

  FIG. 3 is a longitudinal sectional front view showing the attachment / detachment structure of the photoconductor 7. The attachment / detachment structure of each photoconductor 7 is the same for all photoconductors 7, and only one photoconductor 7 is shown and described. One end of the rotating shaft 26 to which the photoreceptor 7 is detachably attached is held by a holding portion 31, and this holding portion 31 is held by a holding plate 32 provided in the main body case 2.

  Flange 33 is fitted to both ends of the photoconductor 7, and through holes 34 are formed in these flanges 33 so that the rotary shaft 26 can be inserted and removed. A plurality of grooves 35 serving as engaging portions are formed along the circumferential direction on the inner peripheral portion of one flange 33 positioned on the holding portion 31 side when the photosensitive member 7 is attached to the rotating shaft 26. On the other hand, a joint 36 is fitted to the end of the rotating shaft 26 that is held by the holding portion 31. The joint 36 rotates integrally with the rotation shaft 26, is slidable in the axial direction of the rotation shaft 26, and is urged toward the distal end of the rotation shaft 26 by a spring 37. A plurality of claws 38 that are engaging portions are formed in the joint 36 along the circumferential direction. When the photosensitive member 7 is attached to the rotating shaft 26, the claws 38 engage with the grooves 35, and the rotating shaft 26 and the photosensitive member are engaged. 7 can be rotated together.

  In the photoconductor 7, the rotation shaft 26 is inserted through the central portion of the photoconductor 7, and by engaging the claw 38 and the groove 35, the rotational driving force can be transmitted from the rotation shaft 26 to the photoconductor 7. Further, by sliding the photoconductor 7 along the center line direction of the rotary shaft 26 toward the tip of the rotary shaft 26, the engagement between the claw 38 and the groove 35 can be released and the photoconductor 7 can be removed. As a result, the photoconductor 7 can be easily replaced, and operability and serviceability can be improved.

  FIG. 4 is a block diagram schematically showing the electrical connection of each part provided in the color printer 1. The color printer 1 includes a controller 40 for controlling each unit. The controller 40 centrally controls each unit (CPU) 41, and a ROM (various memory) that stores various programs executed by the CPU 41. A read only memory (RAM) 42 and a RAM (Random Access Memory) 43 functioning as a work area for the CPU 41 are connected by a bus line 44.

  The CPU 41 is connected to a drive motor 23 via a motor control unit 23a, a drive motor 28 (28Y, 28C, 28M, 28K) via a motor control unit 28a, a reflective sensor 45, a timer 46, and the like. . The reflection type sensor 45 detects a detection pattern toner image for detecting the amount of misalignment of the transfer position of each color toner image when the toner images formed on the photoreceptor 7 are superimposed and transferred to the intermediate transfer belt 12. When the detection pattern toner image formed on the photosensitive member 7 is transferred onto the intermediate transfer belt 12, it functions as a means for detecting the detection pattern toner image transferred onto the intermediate transfer belt 12.

  FIG. 5 shows the amount of displacement of the transfer position when the detection pattern toner image formed on each photoconductor 7 is transferred to the intermediate transfer belt 12, and eliminates the displacement of the transfer position according to the detection result. 6 is a flowchart for explaining control for adjusting the linear velocity of the photosensitive member 7 in the manner described above.

  First, a detection pattern toner image is formed on each photoconductor 7 at a preset timing such as immediately after power-on or after a predetermined number of images have been formed (step S1). A means for forming an image on the photoreceptor 7 is executed. The detection pattern toner image is formed by the same process as that for forming a normal toner image. The surface of the photoconductor 7 is charged, and the light beam is emitted from the optical writing device 4 to statically form the surface of the photoconductor 7. An electrostatic latent image is formed, and the electrostatic latent image is developed with toner supplied from the developing device 9.

  The detection pattern toner image formed on each photoconductor 7 is transferred onto the intermediate transfer belt 12 at the same timing (step S2), and the detection pattern toner image formed on each photoconductor 7 is transferred to the intermediate transfer belt 12 here. A means for transferring onto the belt 12 is executed. The detection pattern toner images of the respective colors transferred onto the intermediate transfer belt 12 are arranged on the straight line along the running direction of the intermediate transfer belt 12 with a predetermined interval.

  The detection pattern toner image transferred onto the intermediate transfer belt 12 passes through a position facing the reflective sensor 45 as the intermediate transfer belt 12 travels, and is detected by the reflective sensor 45 during this passage (step S3). ).

  Based on the detection result of the detection pattern toner image of each color by the reflective sensor 45, whether or not the deviation amount of the detection interval of each detection pattern toner image is within the set range, that is, the detection pattern toner images are transferred in an overlapping manner. At this time, it is determined whether or not the amount of misregistration of the transfer position of each color is greater than or equal to a set range (step S4). The

  If the displacement amount determined in step S4 is equal to or greater than the set range, the rotational speed of the drive motor 28 that rotationally drives the photosensitive member 7 is adjusted so as to eliminate the displacement amount (step S5). As the rotational speed of the motor 28 is adjusted, the linear speeds of the respective photoconductors 7 are adjusted to coincide with each other. Here, means for adjusting the rotational speed of the drive motor 28 so that the linear speeds of the respective photoconductors 7 coincide with each other. Is executed. In the present embodiment, the adjustment of the linear velocity of the photoconductor 7 in step S5 is performed by using three photosensitivities on which toner images of other colors are formed on the basis of the linear velocity of the photoconductor 7K on which a black toner image is formed. For each of the bodies 7Y, 7C, 7M. The linear speeds of the three photoconductors 7Y, 7C, and 7M are adjusted by independently adjusting the rotational speeds of the drive motors 28Y, 28C, and 28M that rotationally drive the photoconductors 7Y, 7C, and 7M. .

  In this way, by adjusting the number of rotations of the drive motor 28 so that the linear speeds of the respective photoconductors 7 coincide with each other, the transfer position of each color toner image formed on each photoconductor 7 is transferred. Misalignment can be prevented. As a result, the positional shift of the toner image transfer position caused by the difference in the linear speed of each photoconductor 7 can be eliminated, and a high-quality color image in which the transfer position is not shifted during the transfer of the toner image of each color can be obtained. Obtainable.

  Further, as in the present embodiment, the linear speeds of the photoconductors 7Y, 7C, and 7M are independently performed so as to match the linear speed of the photoconductor 7K. The alignment can be performed with high accuracy.

  A second embodiment of the present invention will be described with reference to FIGS. The same parts as those described in FIGS. 1 to 5 are denoted by the same reference numerals, and description thereof is also omitted (the same applies to the following embodiments).

  FIG. 6 is a schematic side view showing the drive structure of the photoconductor 7 in the printer engine 3A. The basic structure of the printer engine 3A of the present embodiment is the same as that of the printer engine 3 of the first embodiment. The difference of the present embodiment from the first embodiment is that the photoconductor 7 is driven to rotate. This is the point that two drive motors 28 are used. One is a drive motor 28K that rotationally drives the photoreceptor 7K on which a black toner image is formed, and the other is a drive motor 28X that is a drive unit that rotationally drives the photoreceptors 7Y, 7C, and 7M. .

  The motor gear 30K fixed to the motor shaft 29 of the drive motor 28K meshes with the photoconductor gear 27K fixed to the rotating shaft 26 of the photoconductor 7K. The motor gear 30X fixed to the motor shaft 29 of the drive motor 28X meshes with the photoconductor gear 27M fixed to the rotary shaft 26 of the photoconductor 7M and the photoconductor gear 27C fixed to the rotary shaft 26 of the photoconductor 7C. ing. An idler gear 50 meshes with the photoconductor gear 27C and the photoconductor gear 27Y fixed to the rotating shaft 26 of the photoconductor 7Y.

  FIG. 7 shows the amount of displacement of the transfer position when the toner image formed on each photoconductor 7 is transferred to the intermediate transfer belt 12, and the photoconductor 7 is configured to eliminate the position shift according to the detection result. It is a flowchart explaining the control which adjusts this linear velocity.

  First, a detection pattern toner image is formed on each photoconductor 7 at a preset timing such as immediately after power-on or after a predetermined number of images have been formed (step S11). A means for forming an image on the photoreceptor 7 is executed.

  The detection pattern toner image formed on each photoconductor 7 is transferred onto the intermediate transfer belt 12 at the same timing (step S12), and the detection pattern toner image formed on each photoconductor 7 is intermediately transferred thereto. A means for transferring onto the belt 12 is executed. The detection pattern toner images of the respective colors transferred onto the intermediate transfer belt 12 are arranged on the straight line along the running direction of the intermediate transfer belt 12 with a predetermined interval.

  The detection pattern toner image transferred onto the intermediate transfer belt 12 passes through a position facing the reflective sensor 45 as the intermediate transfer belt 12 travels, and is detected by the reflective sensor 45 during this passage (step S13). ).

  Based on the detection result of the detection pattern toner image of each color by the reflective sensor 45, the average value of the detection intervals of the detection pattern toner images is calculated (step S14), that is, whether or not the average value is within the set range. Then, it is determined whether or not the amount of displacement of the transfer position when the detection pattern toner images are transferred in a superimposed manner is greater than or equal to the set range (step S15). Here, the position of the transfer position of the detection pattern toner image of each color is determined. Means for determining the amount of deviation is executed.

  If the amount of displacement determined in step S15 is greater than or equal to the set range, the rotational speed of the drive motor 28 that rotationally drives the photoreceptor 7 is adjusted so as to eliminate the amount of displacement (step S16). As the rotational speed of the motor 28 is adjusted, the linear speeds of the respective photoconductors 7 are adjusted to coincide with each other, and a means for adjusting the linear speeds of the respective photoconductors 7 is executed. In the present embodiment, the adjustment of the rotational speed of the drive motor 28 (adjustment of the linear speed of the photoconductor 7) in step S16 is performed based on the linear speed of the photoconductor 7K on which a black toner image is formed as a reference. This is done by adjusting the number of rotations of the drive motor 28X that integrally rotates the three photoreceptors 7Y, 7C, and 7M on which the toner images are formed.

  In this way, by adjusting the linear velocities of the respective photoconductors 7 so that the toner images of the respective colors formed on the respective photoconductors 7 are transferred, other black toner images are transferred to other black toner images. The transfer position of the color toner image can be prevented from being displaced. As a result, the transfer position of the toner image caused by the difference in linear velocity between the photoconductor 7K that forms a black toner image and the photoconductors 7Y, 7C, and 7M that form toner images of colors other than black is caused. The positional shift can be eliminated, and a high-quality color image can be obtained in which the transfer position does not shift during the transfer of the toner images of the respective colors.

  In the present embodiment, the positional shift of the transfer position cannot be adjusted for each of the three color toner images of yellow, cyan, and magenta, but the black toner of the three color toner images of yellow, cyan, and magenta. It is possible to reduce the average value of positional deviation with respect to the image. As a result, the number of drive motors 28 can be reduced, and the structure for aligning the transfer position of the toner image can be simplified.

A third embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a schematic side view showing a driving structure of the photosensitive member 7 in the printer engine 3B. The basic structure of the printer engine 3B of the present embodiment is the same as that of the printer engine 3 of the first embodiment. In the printer engine 3B of the present embodiment, the printer engine 3B is formed on each photoconductor gear 27 that is a gear. The configuration includes a projection 60 (60Y, 60C, 60M, 60K) that is a detected portion and a sensor 61 (61Y, 61C, 61M, 61K) that is located in the vicinity of the photoconductor gear 27 and detects the projection 60. is there. A reflective sensor or the like is used as the sensor 61, and the sensor 61 is positioned so as to detect the protrusion 60 once per rotation of the photosensitive member 7.

  FIG. 9 is a block diagram schematically showing an electrical connection of each unit included in the color printer. This color printer has a configuration in which sensors 61Y, 61C, 61M, and 61K are added to the electrical connection structure shown in FIG.

  FIG. 10 is a flowchart for explaining the control for rotating the photoconductor gear 27 to a position where the rotation phase shift is eliminated when the rotation phase shift occurs between the photoconductor gears 27 and the rotation phase shifts by a certain angle. is there.

  First, an image forming operation is started, and the protrusion 60 is detected by the sensor 61 once for each rotation of the photosensitive gear 27 as the photosensitive gear 27 rotates (step S21). The detection of the protrusion 60 is performed independently by each sensor 61 in each photoconductor gear 27.

  By comparing the timings at which the sensors 61 detect the protrusions 60, a rotational phase shift between the photoconductor gears 27 is detected (step S22). Here, based on the detection result by the sensors 61, the photoconductor gears 27 are detected. Means for detecting a shift in rotational phase is executed. Here, the rotational phase shift between the photoconductor gears 27 is a case where the rotational speed of the drive motor 28 is adjusted so that the linear speeds of the photoconductors 7 coincide with each other in order to align the transfer positions of the toner images of the respective colors. In addition, this adjustment is caused by a change in the rotation speed of the photoconductor gear 27. The photoconductor gear 27 formed by molding or the like may be molded with the center shifted, and the linear velocity of the photoconductor 7 connected to the photoconductor gear 27 with the center shifted is the speed of the photoconductor gear 27. The rotation fluctuates periodically for one rotation, and a positional deviation of the transfer position due to the periodic fluctuation occurs, causing a color deviation of the transferred toner image.

  Based on the detected rotational phase shift between the photosensitive gears 27, it is determined whether the rotational phase has shifted by a certain angle (for example, ± 15 °) (step S23). Means for determining that the rotational phase has shifted by a certain angle is executed.

  When the rotational phase between the photoconductor gears 27 is deviated by a certain angle, the image forming operation is temporarily interrupted, and the photoconductor gears 27 are rotationally driven by the drive motor 28 at positions where the rotational phase shifts of the photoconductor gears 27 are eliminated. In step S24, a means for driving the drive motor 28 is executed so as to rotate the photoconductor gear 27 to a position where the rotational phase shift between the photoconductor gears 27 is eliminated. At this time, the rotation of the photoconductor gear 27 may be performed only on the photoconductor gear 27 whose rotational phase is shifted by a certain angle, or may be performed on all the photoconductor gears 27.

  In this way, when the rotational phase of the photoconductor gear 27 is deviated by a certain angle, the photoconductor gear 27 is adjusted so as to eliminate the rotational phase shift, so that the center of the photoconductor gear 27 is deviated. The toner image transfer position can be prevented from being shifted due to the rotational phase shift caused by rotating the toner at different rotational speeds.

A fourth embodiment of the present invention will be described with reference to FIG.
FIG. 11 is a schematic side view showing a driving structure of the photosensitive member 7 in the printer engine 3C. As described in the second embodiment (FIG. 6), the printer engine 3 of the present embodiment has two drive motors 28 that rotate the photosensitive member 7, and one of them is the photosensitive member 7K. A drive motor 28K for rotationally driving, and the other one is a drive motor 28X for rotationally driving the photoreceptors 7Y, 7C, 7M.

  The motor gear 30K fixed to the motor shaft 29 of the drive motor 28K meshes with the photoconductor gear 27K fixed to the rotating shaft 26 of the photoconductor 7K. A motor gear 30X fixed to the motor shaft 29 of the drive motor 28X meshes with a photoconductor gear 27Y fixed to the rotary shaft 26 of the photoconductor 7Y and a photoconductor gear 27C fixed to the rotary shaft 26 of the photoconductor 7C. ing. An idler gear 50 meshes with the photoconductor gear 27C and the photoconductor gear 27M fixed to the rotating shaft 26 of the photoconductor 7M.

  In the present embodiment, protrusions 60 (60K, 60M) that are detected portions are formed only on the photoconductor gear 27K connected to the photoconductor 7K and the photoconductor gear 27M connected to the photoconductor 7M. . Further, two sensors 61 (61K, 61M) for detecting the protrusion 60 are provided in the vicinity of the photoconductor gears 27K, 27M. A reflective sensor or the like is used as the sensor 61, and the sensor 61 is positioned so as to detect the protrusion 60 once per rotation of the photosensitive member 7.

  Here, since the three photoconductor gears 27Y, 27C, and 27M are rotationally driven by the common drive motor 28X, there is no rotational phase shift between the photoconductor gears 27Y, 27C, and 27M. In this embodiment, the rotational phase shift of the photoconductor gear 27 occurs between the three photoconductor gears 27Y, 27C, and 27M and the photoconductor gear 27K.

  In the present embodiment, substantially the same control as in the flowchart shown in FIG. 10 is performed, and therefore the content of the control will be described with reference to FIG. First, an image forming operation is started, and the protrusions 60K and 60M are detected by the sensors 61K and 61M once for each rotation of the photoconductor gears 27K and 27M as the photoconductor gears 27K and 27M rotate (steps). S21).

  By comparing the timings at which the two sensors 61K and 61M detect the protrusions 60K and 60M, respectively, a rotational phase shift between the two photoconductor gears 27K and 27M is detected (step S22). Based on the detection result by 61M, a means for detecting a rotational phase shift between the photoconductor gears 27K and 27M is executed. The rotational phase shift between the photoconductor gears 27 changes the rotation speed of the photoconductor gears 27 when the rotational speeds of the drive motors 28K and 28X are adjusted so that the linear speeds of the photoconductors 7 coincide with each other. Caused by The photoconductor gear 27 formed by molding or the like may be molded with the center shifted, and the linear velocity of the photoconductor 7 connected to the photoconductor gear 27 with the center shifted is the speed of the photoconductor gear 27. The rotation fluctuates periodically for one rotation, and a positional deviation of the transfer position due to the periodic fluctuation occurs, causing a color deviation of the transferred toner image.

  Based on the detected rotational phase shift between the photoconductor gears 27K and 27M, it is determined whether or not the rotational phase has shifted by a certain angle (for example, ± 15 °) (step S23). , 27M, means for determining that the rotational phase has shifted by a certain angle is executed.

  When the rotational phase between the photoconductor gears 27K and 27M is deviated by a certain angle, the image forming operation is temporarily interrupted, and the photoconductor gear 27 is moved to a position where the rotational phase of the photoconductor gears 27K and 27M is eliminated. (Step S24), and means for driving the drive motor 28 so as to rotate the photoconductor gear 27 to a position where there is no shift in the rotation phase between the photoconductor gears 27 is executed. When the photoconductor gear 27 is rotationally driven so as to eliminate the rotational phase shift, one of the drive motors 28K and 28A may be driven.

  In the present embodiment, since the three photoconductors 7Y, 7C, and 7M are rotationally driven by the common drive motor 28X, the number of sensors 61 for detecting the rotational phase shift of the photoconductor gear 27 is reduced. Thus, the structure for adjusting the rotational phase shift of the photoconductor gear 27 can be simplified.

A fifth embodiment of the present invention will be described with reference to FIG.
FIG. 12 is a longitudinal side view schematically showing a color printer which is a color image forming apparatus. The intermediate transfer belt 12 is used as an endless belt in the printer engine of the color image forming apparatus according to each of the embodiments described above, whereas the transfer engine is used as an endless belt in the printer engine 3D of the color printer 70 of the present embodiment. A belt 71 is used.

  The transfer / conveying belt 71 holds and conveys the recording medium P fed from the inside of the paper feeding cassette 5, and the toner images formed on the respective photoreceptors 7 are sequentially transferred onto the recording medium P to be conveyed, A color toner image is formed on the recording medium P.

  Although not shown, in the present embodiment, as in the first embodiment, a plurality of drive motors that independently rotate and drive each photoconductor 7 are provided and formed on the photoconductor 7. The detection pattern toner image for detecting the amount of misalignment of the transfer position of the toner image of each color when the toner images are superimposed and transferred to the recording medium P which is held by the transfer conveyance belt 71 and conveyed is the photosensitive member 7. Reflective type as means for forming on top, means for transferring the detection pattern toner image formed on each photoreceptor 7 onto the recording medium P, means for detecting the detection pattern toner image transferred on the recording medium P The line of the photoconductor 7 based on the judgment result of the sensor, the means for judging the positional deviation amount of the detection pattern toner image of each color based on the detection result of the detection pattern toner image, and the means for judging the positional deviation amount There means like be adjusted to be constant is provided.

  Further, as described in the third embodiment (FIGS. 8 to 10), the photoconductor gears connected to the photoconductors 7 and transmitting the rotational driving force to the photoconductors 7, and the photoconductor gears. Protrusions that are provided detection parts, sensors that detect the respective protrusions, means for detecting a rotational phase shift between the photoconductor gears based on the detection results by the sensors, and the detected rotation phase between the photoconductor gears Means for determining that there is a certain angle shift, means for rotating the photoconductor gear at a position where there is no shift in the rotation phase between the photoconductor gears when the rotation phase between the photoconductor gears is deviated by a certain angle, and the like are provided. .

A sixth embodiment of the present invention will be described with reference to FIG.
This embodiment is a unit in which the photoconductor 7, the charging roller 8, the developing device 9, and the cleaning device 10 are housed in a case 80 in the printer engine of the color image forming apparatus according to each of the embodiments described above. A process cartridge 81 is used. The process cartridge 81 is detachably mounted in the main body case of the color image forming apparatus. Four process cartridges 81 are provided to form yellow, cyan, magenta, and black toner images, and each is detachably mounted in the main body case.

  By attaching / detaching the process cartridge 81 to / from the main body case, at least the photosensitive member 7, the charging roller 8, the developing device 9, and the cleaning device 10 can be replaced together, and the replacement work can be easily performed. And serviceability can be improved.

  There are various process cartridge configurations. For example, only the photosensitive member 7 and the charging roller 8 are housed in a case to form a unit, and the photosensitive member 7, the charging roller 8, and the cleaning device 10 are included in the case. And a unit in which the photosensitive member 7, the charging roller 8, and the developing device 9 are accommodated in a case. Each process cartridge is included in the main body case of the color image forming apparatus. It is detachably attached.

1 is a longitudinal side view schematically showing a color printer according to a first embodiment of the present invention. FIG. 2 is a schematic side view illustrating a driving structure of a photosensitive member and an intermediate transfer belt in a printer engine. It is a vertical front view which shows the attachment or detachment structure of a photoconductor. It is a block diagram which shows roughly the electrical connection of each part with which a color printer is provided. The detection pattern toner image formed on each photoconductor detects the amount of misalignment of the transfer position when the toner image is transferred to the intermediate transfer belt, and the photoconductor line so as to eliminate the misalignment of the transfer position according to the detection result. It is a flowchart explaining the control which adjusts a speed. FIG. 6 is a schematic side view showing a driving structure of a photosensitive member in a printer engine according to a second embodiment of the present invention. The amount of displacement of the transfer position when the toner image formed on each photoconductor is transferred to the intermediate transfer belt 12 is detected, and the linear velocity of the photoconductor 7 is adjusted so as to eliminate the position shift according to the detection result. It is a flowchart explaining the control to perform. It is a schematic side view which shows the drive structure of the photoreceptor in the printer engine of the 3rd Embodiment of this invention. It is a block diagram which shows roughly the electrical connection of each part with which a color printer is provided. 7 is a flowchart for describing control for rotating a photoconductor gear to a position where the rotation phase shift is eliminated when a rotation phase shift occurs between the photoconductor gears and the rotation phase shifts by a certain angle. It is a schematic side view which shows the drive structure of the photoreceptor in the printer engine of the 4th Embodiment of this invention. It is a vertical side view which shows schematically the color printer of the 5th Embodiment of this invention. It is a vertical side view which shows the process cartridge used as the 6th Embodiment of this invention.

Explanation of symbols

2 Main body case 3, 3A, 3B, 3C, 3D Printer engine 5 Recording medium storage unit 6 Fixing device 7 Photoconductor 8 Charging means 12 Endless belt, intermediate transfer belt 20 Recording medium discharge unit 26 Rotating shaft 27 Gear 28 Drive unit 35 Engagement unit 38 Engagement unit 45 Means for detecting detection pattern toner image 60 Detected unit 61 Sensor 71 Endless belt, transfer conveyance belt 80 Case 81 Process cartridge

Claims (10)

A plurality of photosensitive members that are rotationally driven and have toner images formed on an outer peripheral surface;
An endless belt disposed opposite to the outer peripheral surface of the photosensitive member and carrying a toner image transferred from the photosensitive member or running while holding a recording medium onto which the toner image on the photosensitive member is transferred; ,
A detection pattern for detecting the amount of misalignment of the transfer position of each color toner image when the toner images formed on the photoconductor are superimposed and transferred onto the endless belt or a recording medium held on the endless belt. Means for forming a toner image on the photoreceptor;
Means for transferring a detection pattern toner image formed on each of the photoreceptors onto the endless belt or onto a recording medium held on the endless belt;
Means for detecting a detection pattern toner image transferred on the endless belt or on a recording medium held on the endless belt;
Means for determining the amount of displacement of the transfer position of the detection pattern toner image of each color based on the detection result of the means for detecting the detection pattern toner image;
Means for adjusting the number of rotations of a drive unit for driving the photoconductor so that the linear speeds of the photoconductor coincide with each other based on a determination result of the means for determining a displacement amount of a transfer position;
Having a printer engine.   The printer engine according to claim 1, wherein the driving unit is individually connected to the plurality of photosensitive members. As the photosensitive member, a photosensitive member on which a black toner image is formed, a photosensitive member on which a yellow toner image is formed, a photosensitive member on which a cyan toner image is formed, and a photosensitive member on which a magenta toner image is formed. Having a body,
The photosensitive member on which the yellow toner image is formed, the photosensitive member on which the cyan toner image is formed, and the photosensitive member on which the magenta toner image is formed are connected to the common driving unit, and a black toner image is formed. The printer engine according to claim 1, wherein the photosensitive member on which the toner is formed is connected to the other driving unit. A plurality of gears coupled to the photoconductor to transmit a rotational driving force to each photoconductor;
A detected portion provided in each of the gears;
A plurality of sensors for detecting the detected part;
Means for detecting a rotational phase shift between the gears based on a detection result by the sensor;
Means for determining that the rotational phase between the gears detected by the means for detecting a rotational phase shift has shifted by a certain angle;
Means for driving the drive unit to rotate the gear to a position where the rotational phase shift between the gears disappears when the means determines that the rotational phase between the gears has shifted by a certain angle;
The printer engine according to claim 2. A gear connected to the photosensitive member on which a black toner image is formed and transmitting a rotational driving force to the photosensitive member;
A gear that is rotationally driven by the common drive unit and is connected to any one of the photoconductors on which toner images of yellow, cyan, and magenta are formed, and transmits a rotational driving force to these photoconductors;
A detected portion provided in each of the gears;
Two sensors for detecting the detected portion;
Means for detecting a rotational phase shift between the gears based on a detection result by the sensor;
Means for determining that the rotational phase between the gears detected by the means for detecting a rotational phase shift has shifted by a certain angle;
Means for driving the drive unit to rotate the gear to a position where the rotational phase shift between the gears disappears when the means determines that the rotational phase between the gears has shifted by a certain angle;
The printer engine according to claim 3.   A rotating shaft that is driven to rotate about a center line is provided, and the photosensitive member is detachably attached to the rotating shaft, and an engaging portion that rotates integrally with the rotating shaft is provided on the rotating shaft. 6. An engaging portion that is detachably engaged with the engaging portion by sliding the photosensitive member along a center line direction of the rotation shaft is provided on the photosensitive member. The printer engine described.   7. A process cartridge having at least the photosensitive member and charging means for uniformly charging the outer peripheral surface of the photosensitive member, housed in a case, unitized and detachably mounted in a main body case. The printer engine according to any one of the above.   The printer engine according to claim 1, wherein the endless belt is an intermediate transfer belt.   The printer engine according to claim 1, wherein the endless belt is a transfer conveyance belt. A printer engine according to any one of claims 1 to 9,
A recording medium storage unit for storing a recording medium supplied to the printer engine;
A fixing device for fixing a color toner image transferred onto the recording medium;
A recording medium discharge section for discharging a recording medium on which the toner image is fixed;
A color image forming apparatus comprising:

Images