JP2010152280A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress speed variation caused by eccentricity of a photoreceptor gear in each of three photoreceptors for Y, M and C, while sharing one color driving motor by the photoreceptors in a constitution so set that the disposing pitch of the photoreceptor does not coincide with an integral multiple of peripheral length of the photoreceptor. <P>SOLUTION: Respective gears are assembled so that meshing timing of a maximum diameter spot due to the eccentricity of the photoreceptor gear 202C for C with a motor shaft gear of a color driving motor 90YMC synchronizes with the meshing timing of a maximum diameter spot due to the eccentricity of the photoreceptor gear 202M for M with the motor shaft gear thereof. A control means controls driving of the color driving motor 90YMC so as to suppress the speed variation of one rotation cycle in the photoreceptor 1C for C caused by the eccentricity of the photoreceptor gear 202C for C and speed variation of one rotation cycle in the photoreceptor 1M for M, caused by the eccentricity in the photoreceptor gear 202M for M, based on the detected result by a color gear sensor 91YMC. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, at least the visible image formed on the rotating surface of the first image carrier and the visible image formed on the rotating surface of the second image carrier are moved endlessly by the endless moving body. The present invention relates to an image forming apparatus that superimposes and transfers images on a surface or a recording member held on the surface.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus in which a photosensitive member as an image carrier is driven to rotate by the configuration shown in FIG. In the figure, a photoconductor gear 602 is disposed on the inner side of the drum-shaped photoconductor 601 in the direction perpendicular to the drawing sheet. The photoconductor gear 602 has a larger diameter than the photoconductor 601 and is supported by a bearing (not shown) so as to rotate on the same rotation axis as the photoconductor 601. The photoconductor gear 602 and the photoconductor 601 are connected in the axial direction by a coupling (not shown). A drive motor 603 that meshes its own motor shaft gear 603 a with the photoconductor gear 602 is disposed in the vicinity of the photoconductor gear 602. When the motor shaft gear 603 a of the drive motor 603 rotates, the rotational driving force is transmitted to the photoconductor 601 through the photoconductor gear 602. In such a configuration, the gear pitch of the meshing portion between the gear and the motor shaft gear 603a varies due to the eccentricity of the photosensitive gear 602 having a relatively large diameter. Then, a periodic speed fluctuation as shown in FIG. This is a speed fluctuation of a characteristic that draws a sine curve for one cycle per one rotation of the photosensitive member. When such a speed variation occurs in the transfer nip caused by contact between the photoconductor 601 and a transfer member (not shown), the diameter of dots transferred from the photoconductor 601 to the transfer member in the sub-scanning direction (photoconductor surface movement direction). Fluctuates. Specifically, dots transferred when the surface of the photoconductor 601 is moving at a higher linear velocity than the standard (above the center line of the illustrated fluctuation curve) have a diameter in the sub-scanning direction that is smaller than the standard. Is also shortened. On the other hand, dots transferred when the surface of the photoconductor 601 moves at a linear velocity slower than the standard (below the center line of the illustrated fluctuation curve) have a diameter in the sub-scanning direction that is smaller than the standard. Also gets longer.

  When such a variation in dot diameter occurs individually in each of the plurality of photoconductors in the image forming apparatus having the configuration shown in FIG. 3, for example, dot overlay deviation occurs. Specifically, in the same figure, four photoconductors 601Y, M, C, and K are disposed above a belt member 610 that is stretched endlessly in the clockwise direction while being stretched by a plurality of support rollers. Has been. These photoreceptors 601Y, M, C, and K are for forming toner images of Y (yellow), M (magenta), C (cyan), and K (black), respectively, by a known electrophotographic process. And are arranged at a predetermined arrangement pitch P along the belt surface. Then, Y, M, C, and K transfer nips are formed in contact with the belt members, respectively. Y, M, C, and K toner images (not shown) formed on the photoreceptors 601Y, M, C, and K are transferred to the surface of the belt member 610 or the belt surface in the transfer nip for Y, M, C, and K. It is transferred onto the recording paper that is held in a superimposed manner. In such a configuration, when the above-described fluctuations in the dot diameter occur separately, misalignment of each color toner image occurs.

As a method for suppressing the occurrence of such misalignment, there is known a method of adjusting the meshing timing between the photoconductor gears of the respective colors and the motor shaft gears of the Y, M, C, and K drive motors individually corresponding thereto. ing. Specifically, the dots transferred when the fluctuation value in the speed fluctuation curve shown in FIG. 2 is at the positive peak (P ₁ ) per rotation of the photosensitive member are originally larger in diameter in the sub-scanning direction. Becomes shorter (hereinafter referred to as short-diameter dots). On the other hand, the dot transferred when the fluctuation value is at the negative peak (P ₂ ) has a longer diameter in the sub-scanning direction (hereinafter referred to as a long diameter dot). In the configuration of FIG. 3, it is assumed that the arrangement pitch P of each photoconductor is set to the same length as the circumferential length of the photoconductor. Then, the Y dots transferred from the Y photoconductor 601Y to the surface of the belt member 610 (or the recording paper) at the Y transfer nip are moved to the adjacent M by rotating the Y photoconductor 601Y exactly once. Enter the transfer nip. Similarly, the M dot and the C dot enter the adjacent transfer nip when the photoconductor rotates once after the transfer. In such a case, as shown in FIG. 4, if the phases of speed fluctuations in the Y, M, C, and K photoconductors are completely matched with each other, the shortest diameter dots or the longest diameter dots between the colors are used. By overlaying each other, overlay displacement can be suppressed.

  As shown in FIG. 4, the following method is known as a method for completely matching the phases of the speed fluctuations of the respective photoconductors. That is, in each color photoconductor gear, a non-detection plate is provided at a location where the radius is the longest or shortest due to eccentricity. Further, an optical sensor is provided for optically detecting the non-detecting plate when the rotating photoconductor gears position the non-detecting plate at a predetermined rotation angle. Then, by adjusting the driving of the driving motors of the respective colors so as to synchronize the timing at which the respective optical sensors detect the non-detection plates, the phases of the speed fluctuation curves can be matched as shown in FIG.

  The example in which the arrangement pitch P of the photoreceptors of each color is set to the same length as the circumference of the photoreceptor has been described. However, when the arrangement pitch P is set to an integer multiple of 2 times or more the circumference of the photoreceptor. However, by aligning the phases of the speed fluctuation curves of the photoconductors as shown in FIG. Further, since there is not enough room for the layout so that the arrangement pitch P is the same as the circumference of the photosensitive member, when the arrangement pitch P is shorter than the circumference of the photosensitive member, the following may be performed. . That is, as shown in FIG. 5, the phase of the speed variation curve is shifted by an angle corresponding to the difference between the circumferential length of the photosensitive member and the arrangement pitch P between the photosensitive members of the respective colors. By doing so, it is possible to superimpose short diameter dots or long diameter dots in the transfer nip of each color.

  In the case where two or more photoconductors are driven by one drive motor instead of driving each color photoconductor by an individual drive motor, gear meshing as described in Patent Document 1 is employed. That's fine. For example, FIG. 6 shows an example in which the gear meshing disclosed in Patent Document 1 is applied to a configuration in which the arrangement pitch P of the photoconductor is set to an integral multiple of the circumference of the photoconductor. In the figure, the motor shaft gear 603 of the drive motor 603 is simultaneously meshed with the M photoconductor gear 602M and the C photoconductor gear 602C which are adjacent to each other. Further, the arrangement pitch P of the photoconductors is set to the same value as the circumference of the photoconductor. An arrow A in the figure indicates a portion of the peripheral surface of the M photoconductor gear 602M having the longest radius due to gear eccentricity (hereinafter referred to as the longest diameter portion). An arrow B in the figure indicates the longest diameter portion on the peripheral surface of the C photoconductor gear 602C. When the arrangement pitch P of the photosensitive members is set to an integral multiple of the circumferential length of the photosensitive member, as shown in the drawing, the engagement is performed so that the engagement timing of the longest diameter portion of each photosensitive member gear is synchronized with the motor shaft gear 603a. Should be adopted. By such meshing, the speed fluctuation phase of the M photoconductor 601M and the speed fluctuation phase of the C photoconductor 601C can be matched as shown in FIG.

  FIG. 7 shows an example in which the gear meshing disclosed in Patent Document 1 is applied to a configuration in which the arrangement pitch P of the photoconductor is shorter than the circumferential length of the photoconductor. In the figure, the arrangement pitch P of the photoconductors is set to a value shorter than the circumferential length of the photoconductor. In such a setting, as shown in the drawing, the meshing timing of the longest diameter portion of the photoconductor gear with respect to the motor shaft gear 603a is equivalent to the time (angle) corresponding to the difference between the photoconductor circumferential length and the arrangement pitch P. It is only necessary to adopt a meshing that is shifted by only one. By such meshing, a phase shift of the speed fluctuation curve as shown in FIG. 5 is generated between the M photoconductor 601M and the C photoconductor 601C. It is possible to superimpose dots or long diameter dots.

JP 2005-134732 A

  By the way, the present inventors do not make the phase of the speed fluctuation curve in the photoconductors of the respective colors have a predetermined relationship according to the arrangement pitch P as shown in FIGS. We are investigating controlling the motor drive so as not to generate the noise. Specifically, the drive speed of the drive motor is adjusted so as to generate a speed fluctuation curve having the same amplitude and completely opposite phase with respect to the speed fluctuation curve shown in FIG. This speed fluctuation is offset by the latter speed fluctuation. As a result, the speed fluctuation of the photoreceptor due to the eccentricity of the gear can be almost eliminated.

  However, in the gear meshing shown in FIG. 7, if the drive speed of the drive motor is adjusted in this way, there is a risk that the dot misalignment will be worsened. Specifically, in the meshing of the gear shown in FIG. 7, as shown in FIG. 5, the phase of the speed fluctuation curve on the M photoconductor and the phase of the speed fluctuation curve on the C photoconductor are set. In this case, the arrangement pitch P is shifted by an amount corresponding to the difference between the circumferential length of the photosensitive member and the photosensitive member. In this way, when the phases of the respective speed fluctuation curves are shifted, for example, the driving speed of the drive motor is adjusted so as to generate a speed fluctuation having a phase opposite to that of the speed fluctuation curve in the M photoconductor. . Then, with respect to the photoconductor for M, the former speed fluctuation can be canceled by the latter speed fluctuation, so that the speed fluctuation can be almost eliminated. However, with respect to the C photoconductor, the speed fluctuation cannot be canceled. There is a risk that the amplitude of the curve will be increased.

  The present invention has been made in view of the above background, and an object thereof is to provide the following image forming apparatus. In a configuration in which the image carrier arrangement pitch is set not to be an integral multiple of the image carrier circumference, at least the first image carrier and the second image carrier share one drive motor, This is an image forming apparatus capable of suppressing the speed fluctuation caused by the eccentricity of the drive receiving gear for each of the image carriers.

In order to achieve the above object, the invention of claim 1 includes at least first and second image carriers, and first and second image carriers, each carrying a visible image on its rotating surface. The first and second drive receiving gears which individually correspond to each other, receive the driving force on the driving side and rotate on the same rotation axis as the image carrier, and transmit the driving force to the image carrier, An endless moving body that moves the surface endlessly and a visible image formed on the surface of each image carrier are superimposed and transferred onto the surface of the endless moving body or a recording member held on the surface of the endless moving body. A transfer motor, and a drive motor for supplying a driving force to the first image carrier and the second image carrier by engaging its own motor shaft gear with the first drive receiving gear and the second drive receiving gear. At least one of the first image carrier and the second image carrier And an image forming apparatus in which the image carrier arrangement pitch in the direction along the surface of the endless moving body is set to a value that does not coincide with an integral multiple of the circumference of the image carrier. The engagement timing of the maximum diameter portion where the distance from the rotation center is maximum due to the eccentricity of the gear at the periphery of the first drive receiving gear and the motor shaft gear of the drive motor is determined as the second drive receiving gear. The first drive receiving gear, the drive motor and the second drive receiving gear are assembled so as to synchronize with the meshing timing of the maximum diameter portion due to the eccentricity of the gear and the motor shaft gear, and the drive control means includes: Based on the detection result by the phase detection means, the first image carrier is caused by the fluctuation in the speed of one rotation period caused by the eccentricity of the first drive receiving gear, and the second drive receiving gear caused by the eccentricity. Two statues Is characterized in that 1 is for controlling the drive of the drive motor so as to suppress the speed fluctuation of the rotation period in bearing member.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a third image carrier, which is an image carrier different from the first and second image carriers, and a third image carrier. A third drive receiving gear that rotates on the same rotational axis, and a relay gear that simultaneously meshes with the two drive receiving gears so as to relay the driving force from the second drive receiving gear to the third drive receiving gear. And the meshing timing of the relay gear with the minimum diameter portion where the distance from the rotation center is minimized by the eccentricity of the gear at the periphery of the third driving receiving gear is determined by the eccentricity of the second driving receiving gear. The second drive receiving gear, the relay gear, and the third drive receiving gear are assembled so as to be synchronized with the meshing timing of the maximum diameter portion and the relay gear.

In these inventions, since the drive motor shaft gear of the drive motor is meshed with the first drive receiving gear and the second drive receiving gear, respectively, the first image carrier and the second image carrier. Can share one drive motor.
Further, in spite of the configuration in which the image carrier arrangement pitch is set not to coincide with an integral multiple of the image carrier circumferential length, unlike the gear meshing described in Patent Document 1, the motor shaft of the drive motor An engagement is employed in which the meshing timing of the maximum diameter portion of the first drive receiving gear and the meshing timing of the maximum diameter portion of the second drive receiving gear are synchronized with the gear. In such meshing, the first image carrier and the second image carrier are synchronized with each other at the timing at which positive speed fluctuations appear due to gear eccentricity, or due to gear eccentricity. The timings at which negative speed fluctuations appear are synchronized with each other. Then, the drive speed of the drive motor is decreased at the former timing to suppress the positive speed fluctuation of each image carrier at the same time, or the drive speed of the drive motor is increased at the latter timing to reduce the negative speed of each image carrier. It is possible to suppress speed fluctuations at the same time. Therefore, it is possible to suppress the speed fluctuation caused by the eccentricity of the drive receiving gear for each of the image carriers.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described.
First, the basic configuration of the printer will be described. FIG. 8 is a schematic configuration diagram illustrating the printer according to the embodiment. In the drawing, the printer according to the embodiment includes four process units 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). It has. These use Y, M, C, and K toners as image forming substances, but otherwise have the same configuration and are replaced when the lifetime is reached. Taking a process unit 6Y for generating a Y toner image as an example, as shown in FIG. 9, a drum-shaped photoreceptor 1Y, a drum cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, a developing device 5Y, and the like. It has. The process unit 6Y can be attached to and detached from the printer body, so that consumable parts can be replaced at a time.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1 </ b> Y as an image carrier is exposed and scanned by the laser beam L to carry an electrostatic latent image for Y. The electrostatic latent image of Y is developed into a Y toner image by a developing device 5Y using a Y developer containing Y toner and a magnetic carrier. Then, intermediate transfer is performed on an intermediate transfer belt 8 described later. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other color process units (6M, C, K), (M, C, K) toner images are similarly formed on the photoreceptors (1M, C, K), and the intermediate transfer belt 8 is subjected to an intermediate process. Transcribed.

  The developing device 5Y has a developing roll 51Y disposed so as to be partially exposed from the opening of the casing. Further, it also includes two conveying screws 55Y, a doctor blade 52Y, a toner density sensor (hereinafter referred to as T sensor) 56Y, and the like that are arranged in parallel to each other.

  In the casing of the developing device 5Y, a Y developer (not shown) including a magnetic carrier and Y toner is accommodated. The Y developer is frictionally charged while being agitated and conveyed by the two conveying screws 55Y, and is then carried on the surface of the developing roll 51Y. Then, after the layer thickness is regulated by the doctor blade 52Y, the layer is transported to the developing region facing the Y photoreceptor 1Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 1Y. This adhesion forms a Y toner image on the photoreceptor 1Y. In the developing unit 5Y, the Y developer that has consumed Y toner by the development is returned into the casing as the developing roll 51Y rotates.

  A partition wall is provided between the two transport screws 55Y. By this partition wall, the first supply unit 53Y that accommodates the developing roll 51Y, the right conveyance screw 55Y in the drawing, and the like, and the second supply unit 54Y that accommodates the left conveyance screw 55Y in the drawing are separated in the casing. . The right conveying screw 55Y in the drawing is driven to rotate by a driving means (not shown), and supplies the Y developer in the first supply unit 53Y to the developing roll 51Y while being conveyed from the near side to the far side in the drawing. The Y developer conveyed to the vicinity of the end of the first supply unit 53Y by the right conveyance screw 55Y in the drawing enters the second supply unit 54Y through an opening (not shown) provided in the partition wall. In the second supply unit 54Y, the left conveyance screw 55Y in the drawing is driven to rotate by a driving means (not shown), and the Y developer sent from the first supply unit 53Y is the right conveyance screw 55Y in the drawing. Transport in the reverse direction. The Y developer transported to the vicinity of the end of the second supply unit 54Y by the transport screw 55Y on the left side in the drawing passes through the other opening (not shown) provided in the partition wall, and the first supply unit. Return to 53Y.

  The above-described T sensor 56Y composed of a magnetic permeability sensor is provided on the bottom wall of the second supply unit 54Y and outputs a voltage having a value corresponding to the magnetic permeability of the Y developer passing therethrough. Since the magnetic permeability of the two-component developer containing toner and magnetic carrier shows a good correlation with the toner concentration, the T sensor 56Y outputs a voltage corresponding to the Y toner concentration. This output voltage value is sent to a control unit (not shown). This control unit includes a RAM that stores a Vtref for Y that is a target value of an output voltage from the T sensor 56Y. The RAM also stores M Vtref, C Vtref, and K Vtref data, which are target values of output voltages from a T sensor (not shown) mounted in another developing device. The Y Vtref is used for driving control of a Y toner conveying device to be described later. Specifically, the control unit drives and controls a Y toner conveying device (not shown) so that the value of the output voltage from the T sensor 56Y is close to the Y Vtref, and the Y toner in the second supply unit 54Y. To replenish. By this replenishment, the Y toner concentration in the Y developer in the developing device 5Y is maintained within a predetermined range. The same toner replenishment control using the M, C, and K toner conveying devices is performed for the developing units of the other process units.

  8, the optical writing unit 7 is disposed below the process units 6Y, M, C, and K in the drawing. The optical writing unit 7 as a latent image forming unit scans the respective photosensitive members in the process units 6Y, 6M, 6C, and 6K with the laser light L emitted based on the image information. By this scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The optical writing unit 7 passes through a plurality of optical lenses and mirrors while deflecting the laser light (L) emitted from the light source in the main scanning direction by reflection on a polygon mirror that is rotationally driven by a motor. Irradiates the photoconductor.

  On the lower side of the optical writing unit 7 in the figure, paper storage means having a paper feed cassette 26 and a paper feed roller 27 incorporated therein is disposed. The sheet feeding cassette 26 stores a plurality of recording sheets P as sheet-like recording bodies, and a sheet feeding roller 27 is brought into contact with the uppermost recording sheet P. When the paper feed roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P is sent out toward the paper feed path 70.

  A registration roller pair 28 is disposed near the end of the paper feed path 70. The registration roller pair 28 rotates both rollers so as to sandwich the recording paper P, but temporarily stops the rotation as soon as it is sandwiched. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above the process units 6Y, 6M, 6C, and 6K, there is disposed a transfer unit 15 that moves the intermediate transfer belt 8 as an endless moving body endlessly while stretching. This transfer unit 15 includes a secondary transfer bias roller 19 and a cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer bias rollers 9Y, 9M, 9C, 9K, a driving roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved counterclockwise in the figure by the rotational drive of the driving roller 12 while being stretched around these seven rollers. The primary transfer bias rollers 9Y, M, C, and K sandwich the intermediate transfer belt 8 moved endlessly in this manner from the photoreceptors 1Y, M, C, and K to form primary transfer nips, respectively. Yes. In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All of the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, M, C, and K are sequentially transferred. , K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  The driving roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The visible four-color toner image formed on the intermediate transfer belt 8 is transferred onto the recording paper P at the secondary transfer nip. Then, combined with the white color of the recording paper P, a full color toner image is obtained. Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10. The recording paper P on which the four-color toner images are collectively transferred at the secondary transfer nip is sent to the fixing device 20 via the post-transfer conveyance path 71.

  The fixing device 20 forms a fixing nip by a fixing roller 20a having a heat source such as a halogen lamp inside, and a pressure roller 20b that rotates while contacting the roller with a predetermined pressure. The recording paper P fed into the fixing device 20 is sandwiched between the fixing nips so that the unfixed toner image carrying surface is in close contact with the fixing roller 20a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  The recording paper P on which the full-color image has been fixed in the fixing device 20 exits the fixing device 20 and then reaches the branch point between the paper discharge path 72 and the pre-reversal conveyance path 73. A first switching claw 75 is swingably disposed at the branch point, and the path of the recording paper P is switched by the swing. Specifically, the path of the recording paper P is set to the direction toward the paper discharge path 72 by moving the tip of the claw in a direction to approach the pre-reverse feed path 73. Further, by moving the tip of the claw away from the conveyance path 73 before reversal, the path of the recording paper P is changed to the direction toward the conveyance path 73 before reversal.

  When the path to the paper discharge path 72 is selected by the first switching claw 75, the recording paper P is disposed outside the apparatus after passing through the paper discharge roller pair 100 from the paper discharge path 72. Are stacked on a stack 50a provided on the upper surface of the printer housing. On the other hand, when the path toward the conveyance path 73 before reversal is selected by the first switching claw 75, the recording paper P enters the nip of the reversing roller pair 21 via the conveyance path 73 before reversal. The reversing roller pair 21 conveys the recording paper P sandwiched between the rollers toward the stack unit 50a, but reversely rotates the rollers immediately before the trailing edge of the recording paper P enters the nip. Due to this reverse rotation, the recording paper P is transported in the opposite direction, and the rear end side of the recording paper P enters the reverse transport path 74.

  The reverse conveyance path 74 has a shape extending while curving from the upper side to the lower side in the vertical direction, and the first reverse conveyance roller pair 22, the second reverse conveyance roller pair 23, and the third reverse conveyance in the path. A roller pair 24 is provided. The recording paper P is conveyed while sequentially passing through the nips of these roller pairs, so that the recording paper P is turned upside down. The recording paper P that has been turned upside down is returned to the paper feed path 70 and then reaches the secondary transfer nip again. Then, this time, the image transfer surface enters the secondary transfer nip while bringing the non-image carrying surface into close contact with the intermediate transfer belt 8, and the second four-color toner image of the intermediate transfer belt is collectively transferred to the non-image carrying surface. The Thereafter, the sheet is stacked on the stack unit 50a outside the apparatus via the post-transfer conveyance path 71, the fixing device 20, the paper discharge path 72, and the paper discharge roller pair 100. A full color image is formed on both sides of the recording paper P by such reverse conveyance.

  A bottle support portion 31 is disposed between the transfer unit 15 and the stack portion 50a located above the transfer unit 15. The bottle support portion 31 has toner bottles 32Y, 32M, 32C, 32K serving as toner storage portions for storing Y, M, C, and K toners. The toner bottles 32Y, 32M, 32C, and 32K are arranged so as to be arranged at an angle slightly inclined from the horizontal, and the arrangement positions are higher in the order of Y, M, C, and K. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are appropriately replenished to the developing units of the process units 6Y, 6M, 6C, and 6K, respectively, by a toner conveyance device described later. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the printer body independently of the process units 6Y, 6M, 6C, and 6K.

  In the monochrome mode print job, the printer drives only the K photoconductor 1K among the four photoconductors 1Y, 1M, 1C, and 1K. At this time, by adjusting the posture of the transfer unit 15, the intermediate transfer belt 8 is brought into contact with only the K photoconductor 1K among the four photoconductors 1Y, 1M, 1C, and 1K. On the other hand, in the color mode print job, all of the four photoconductors 1Y, 1M, 1C, and 1K are driven. At this time, the intermediate transfer belt 8 is brought into contact with all of the four photosensitive members 1Y, 1M, 1C, and 1K by adjusting the posture of the transfer unit 15.

  FIG. 10 is a perspective view showing a process unit and a photoreceptor driving system. In the printer according to the embodiment, the configuration of the process unit and the photosensitive member driving system for each color is almost the same, and therefore, in FIG. For this reason, the subscripts Y, M, C, and K attached to the end of the reference numerals of these process units and photosensitive member drive systems are omitted.

  In the drawing, a photosensitive member driving system including a coupling 201 and a photosensitive member gear 202 which are a part of connecting means is fixed in a printer main body. On the other hand, the process unit 6 is detachable from the printer body. The photosensitive member 1 of the process unit 6 includes rotating shaft members that protrude from both end surfaces in the rotation axis direction, and the rotating shaft members protrude from the unit housing. Of these two rotating shaft members, a known coupling (not shown), which is a part of the connecting means, is fixed to the rotating shaft member (not shown) existing in the blind spot region in the drawing. A rotary encoder 250 is fixed to the other rotating shaft member. The rotary encoder 250 detects the rotational angular velocity of the photosensitive member 1 and outputs the result to a control unit described later.

  On the printer body side, the photoconductor gear 202 is rotatably supported by a support plate. A coupling 201 is formed at the rotation center of the photoconductor gear 202, and this coupling 201 is connected to a coupling (not shown) fixed to the rotation shaft of the photoconductor 1 in the axial direction. By this connection, the rotational driving force of the photoconductor gear 202 is transmitted to the photoconductor 1 through these two couplings. When the process unit 6 is pulled out from the printer main body, the coupling between the coupling (not shown) fixed to the rotating shaft member of the photosensitive member 1 and the coupling 201 formed on the photosensitive member gear 202 is released. This printer includes the process unit 6 and the photosensitive member driving system shown in FIG. 10 for each of the colors Y, M, C, and K.

  FIG. 11 is an enlarged configuration diagram illustrating a peripheral configuration of the four photosensitive members 1Y, 1M, 1C, and 1K in the printer according to the embodiment. FIG. 12 is a perspective view showing the same peripheral configuration. In these drawings, the K photoconductor gear 202K is engaged with a K motor shaft gear 95 fixed to the motor shaft of the K drive motor 90K. The photoconductor 1K for K is driven to rotate by the rotational driving force of the K driving motor 90K being transmitted by this meshing.

  On the other hand, a color motor shaft gear 96 is disposed between the M photoconductor gear 202M and the C photoconductor gear 202C so as to mesh with these photoconductor gears. The color motor shaft gear 96 is fixed to the motor shaft of the color drive motor 90YMC, and transmits the driving force of the color drive motor 90YMC to the M photoconductor gear 202M and the C photoconductor gear 202C. Accordingly, the M photoconductor 1M and the C photoconductor 1C are driven to rotate. An idler gear 97 as a relay gear is disposed between the Y photoconductor gear 202Y and the M photoconductor gear 202M so as to mesh with both photoconductor gears. As a result, the driving force of the color drive motor 90YMC is transmitted to the Y photoconductor 1Y sequentially through the color motor shaft gear 96, the M photoconductor gear 202M, the idler gear 97, and the Y photoconductor gear 202Y. The

  Each of the photoconductor gears 202Y, 202M, 202C, and 202K is manufactured by resin molding using a mold, and the position and amount of eccentricity are determined by the mold. Therefore, if a groove for molding a mark is formed in the mold at the maximum diameter location where the radius is maximum due to gear eccentricity or the minimum diameter location where the radius is minimum, the maximum diameter of each photoconductor gear is obtained. It is possible to form a mark at a place or a place with a minimum diameter.

  The K photoconductor 1K is rotationally driven by a K drive motor 90K which is a drive source different from the other photoconductors. The reason why the driving source is different for the K photoconductor 1K is that the demand for monochrome printing is higher than that for color printing. At the time of high-demand monochrome printing, by driving only the K photoconductor 1K, consumption of other photoconductors 1Y, 1M, 1C, and motors can be suppressed, and energy can be saved. is there.

  FIG. 13 is an enlarged configuration diagram showing the peripheral configuration of the four photoconductors from the opposite side to FIG. In the figure, a K rotating disk 203K is fixed to the end of the coupling 201K of the K photoconductor 1K opposite to the photoconductor gear 202K. The K-rotation disk 203K is integrally formed with a large-diameter portion 204K having a partially increased diameter, which is a transmission type photosensor when the K photoconductor gear 202K is in a predetermined rotational position. Is detected by a K gear sensor 91K.

  On the other hand, a color rotating disk 203YMC is fixed to the end of the coupling 201C of the C photoconductor 1C opposite to the photoconductor gear 202C. The color rotating disk 203YMC is also integrally formed with a large-diameter portion 204YMC having a partially increased diameter, which is such that the Y, M, and C photoconductor gears 202Y, M, and C are in predetermined rotational positions. Is detected by a color gear sensor 91YMC composed of a transmissive photosensor.

  In this printer, the large-diameter portion 204K of the K-rotating disc 203K and the large-diameter portion 204YMC of the color rotating disc 203YMC are attached to the respective rotating discs so as to be positioned at the same rotational angle as the maximum diameter portion of the photoconductor gear. Yes.

  FIG. 14 is a block diagram showing a part of the electric circuit of the printer. In the figure, a bus 94 includes a process unit 6Y, M, C, K, an optical writing unit 7, a paper feed cassette 26, a registration motor 92, a data input port 68, a transfer unit 15, an operation display unit 93, a control unit 150, and the like. Is connected. Further, Y, M, C, K process units 9Y, M, C, K, a K gear sensor 91K, a color gear sensor 91YMC, and the like are also connected.

  The registration motor 92 is a drive source for the registration roller pair 28 described above. The data input port 68 receives image information sent from an external personal computer (not shown) or the like. The control unit 150 controls the entire printer, and includes a CPU 1a, a RAM 1a serving as information storage means, a ROM 1b, and the like. The operation display unit 93 includes a touch panel, a liquid crystal panel, and a plurality of touch keys. The operation display unit 93 displays various information under the control of the control unit 150 and receives input information from the operator. Or send to.

Next, a characteristic configuration of the printer according to the embodiment will be described.
FIG. 15 is a first enlarged schematic view for explaining meshing of the Y, M, and C photoconductor gears 202Y, M, and C. FIG. In the drawing, an arrow A indicates a maximum diameter portion where the radius is maximum on the peripheral surface of the photoconductor gear 202M due to the eccentricity of the photoconductor gear 202M for M. An arrow B indicates the maximum diameter portion on the peripheral surface of the C photoconductor gear 202C. An arrow C indicates the maximum diameter portion of the Y photoconductor gear 202Y. An arrow D indicates a minimum diameter portion where the radius is minimum on the peripheral surface of the photoconductor gear 202Y due to the eccentricity of the Y photoconductor gear 202Y. Not only the Y photoconductor gear 202Y but also the maximum diameter portion and the minimum diameter portion of the gear are positioned in a point-symmetrical relationship of 180 °.

  In this printer, the arrangement pitch P of the photosensitive members 1Y, 1M, 1C, and 1K of each color is set equal. More specifically, the arrangement pitch P is set to a value shorter than the circumferential length of the photoreceptor. In recent years when miniaturization of the printer main body has been promoted, the arrangement pitch P is often set to a value shorter than the circumferential length of the photoconductor as in this printer.

  As shown in the figure, in this printer, the motor shaft gear 96 of the color drive motor 90YMC, the M photoconductor gear 202M, and the C photoconductor gear 202C are meshed as follows. Assemble. That is, the meshing timing of the maximum diameter portion (arrow B) of the C photoconductor gear 202C as the first drive receiving gear and the motor shaft gear 96 is set to the M photoconductor as the second drive receiving gear. This meshing is synchronized with the meshing timing of the maximum diameter portion (arrow A) of the gear 202M and the motor shaft gear 96. In such meshing, the phase of the speed fluctuation caused by the eccentricity of the photoconductor gear 202C in the C photoconductor 1C as the first image carrier and the M photoconductor as the second image carrier. The phase of the speed fluctuation caused by the eccentricity of the photoconductor gear 202M at 1M is synchronized with each other.

  In this printer, the photoconductor gears 202Y, M, C, and K for each color are formed by the same mold, and the radius of the maximum diameter portion and the radius of the minimum diameter portion are the same for each color. ing. Therefore, as shown in the figure, when the M photoconductor gear 202M and the C photoconductor gear 202C are assembled so that the meshing timing of the maximum diameter portion with respect to the motor shaft gear 96 is synchronized with each other, the photoconductor speed is increased. The fluctuation is generated as follows. That is, the speed fluctuation waveform caused by the eccentricity of the photoconductor gear 202M in the M photoconductor 1M and the speed fluctuation waveform caused by the eccentricity of the photoconductor gear 202C in the C photoconductor 1C are exactly the same in amplitude. Generate things. Moreover, the phases of each other are completely synchronized. The speed fluctuation waveform having such a relationship can be completely canceled by controlling the driving of the color drive motor 90YCM so as to generate a speed fluctuation waveform having the same amplitude and opposite phase. In this printer, a drive amount change pattern of the color drive motor 90YMC that can generate a speed fluctuation waveform having an opposite phase during the drive period per one rotation of the photoreceptor is stored in advance in the ROM 150c of the control unit 150. Then, based on the timing at which the large-diameter portion 204YMC is detected for each gear revolution by the color gear sensor 91YMC as the phase detection means, and the above-described drive amount change pattern, the color drive motor 90YMC that generates a reverse phase speed fluctuation waveform. The control unit 150 is configured to perform the drive control. As a result, the M photoconductor 1M and the C photoconductor 1C can substantially eliminate the occurrence of speed fluctuations due to the eccentricity of the photoconductor gear.

  Similarly, the K drive motor 90K generates a speed fluctuation waveform having a phase opposite to the speed fluctuation waveform caused by the eccentricity of the photoconductor gear 202K during the driving period per rotation of the K photoconductor. The obtained drive amount change pattern of the K drive motor 90K is stored in the ROM 150c of the control unit 150 in advance. Then, based on the timing at which the large-diameter portion 204K is detected for each gear rotation by the K gear sensor 91K as the phase detection means and the above-described drive amount change pattern, the K drive motor 90K that generates a reverse phase speed fluctuation waveform is generated. The control unit 150 is configured to perform drive control. As a result, the speed fluctuation caused by the eccentricity of the photoconductor gear 202K can be almost eliminated in the K photoconductor 1K.

  FIG. 16 is a second enlarged schematic view for explaining meshing of the Y, M, and C photoconductor gears 202Y, M, and C. FIG. As shown in the figure, in this printer, the Y photoconductor gear 202Y, the idler gear 97, and the M photoconductor gear 202M are assembled so as to realize the following meshing. That is, at the peripheral edge of the Y photoconductor gear 202Y as the third drive receiving gear, the minimum diameter portion (arrow D in the figure) where the distance from the rotation center is minimized by the eccentricity of the gear, the idler gear 97, The meshing timing is synchronized with the meshing timing between the maximum diameter portion (arrow A) due to the eccentricity of the M photoconductor gear 202M and the relay gear.

  The reason for adopting such meshing is as follows. That is, as described above, in this printer, the drive control of the color drive motor 90YMC is performed so as to cancel the speed fluctuation caused by the eccentricity of the photoconductor gear 202M in the photoconductor 1M for M. By such drive control, the M photoconductor gear 202M rotates at a substantially constant rotational angular velocity. As described above, even if the M photoconductor gear 202M rotates at a constant rotational angular speed, the idler gear 97 undergoes a speed fluctuation. This is because the gear pitch variation caused by the eccentricity of the M photoconductor gear 202M occurs at the meshing portion of the M photoconductor gear 202M and the idler gear 97 (hereinafter referred to as "M-idler meshing portion"). When the driving of the color drive motor 90YMC is not controlled in reverse phase, a speed fluctuation generated by superimposing the speed fluctuation caused by the gear pitch fluctuation and the rotational speed fluctuation of the M photoconductor gear 202M is generated in the idler gear 97. However, in this printer, only the former speed fluctuation occurs.

  On the other hand, even if it is assumed that the idler gear 97 rotates at a constant rotational angular speed, the rotational speed fluctuation occurs in the Y photoconductor gear 202Y. This is because a gear pitch error caused by the eccentricity of the Y photoconductor gear 202Y occurs at the meshing portion between the Y photoconductor gear 202Y and the idler gear 97 (hereinafter referred to as "Y-idler meshing portion"). When the Y photoconductor gear 202Y, the idler gear 97, and the M photoconductor gear 202M are meshed as shown in the figure and the M photoconductor gear 202M is rotated at a constant rotational angular velocity, the following is performed. be able to. That is, in the Y photoconductor gear 202Y, the speed fluctuation caused by the fluctuation of the rotation speed of the idler gear 97 due to the gear pitch fluctuation of the “M-idler meshing part” and the gear pitch fluctuation of the “Y-M idler meshing part”. A speed fluctuation is generated by superimposing the speed fluctuation caused by. When the gears are engaged as shown in the figure, the former speed fluctuation waveform and the latter speed fluctuation waveform are in an opposite phase relationship, and the former speed fluctuation is canceled by the latter speed fluctuation. Thereby, the speed fluctuation of the Y photoconductor gear 202Y can be almost eliminated.

  FIG. 17 is an enlarged schematic diagram for explaining the meshing of the Y, M, and C photoconductor gears 202Y, M, and C in a modified example of the printer according to the embodiment. As shown in the figure, in this modification, a motor shaft gear 96 positioned between the Y photoconductor gear 202Y and the M photoconductor gear 202M is engaged with both photoconductor gears. The rotational driving force of the M photoconductor gear 202M is transmitted to the C photoconductor gear 202C through an idler gear 97 meshed with the M photoconductor gear 202M. . In this configuration, the Y photoconductor 1Y functions as the first image carrier, the M photoconductor 1M functions as the second image carrier, and the C photoconductor 1C is the third image carrier. It functions as an image carrier.

  So far, the printer that superimposes and transfers the Y, M, C, and K toner images on the photoreceptors 1Y, 1M, 1C, and 1K onto the intermediate transfer belt 8 as an endless moving body has been described. The present invention can also be applied to an image forming apparatus configured to superimpose and transfer each color toner image on a recording sheet held on the surface of a member.

FIG. 6 is a configuration diagram showing a photosensitive member gear and a drive motor of a conventional printer. 6 is a graph showing speed variation characteristics of a photoreceptor due to the eccentricity of the photoreceptor gear. FIG. 6 is a configuration diagram showing a plurality of photosensitive members and a belt member in a conventional tandem type image forming apparatus. 6 is a graph for explaining phase alignment of speed fluctuations of each photoconductor in a configuration in which the arrangement pitch of the photoconductors is set to an integral multiple of the photoconductor circumference. 6 is a graph for explaining a phase shift of speed variation of each photoconductor desirably generated in a configuration in which the arrangement pitch of the photoconductor is set to a value different from an integral multiple of the photoconductor circumference. FIG. 9 is a configuration diagram showing an example in which the meshing of gears disclosed in Patent Document 1 is applied to a configuration in which the arrangement pitch P of the photosensitive member is set to an integral multiple of the circumferential length of the photosensitive member. FIG. 6 is a configuration diagram showing an example in which the gear meshing disclosed in Patent Document 1 is applied to a configuration in which the arrangement pitch P of the photoconductor is shorter than the circumferential length of the photoconductor. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram showing a process unit for Y of the printer and its surroundings. The perspective view which shows a process unit and a photoreceptor drive system. FIG. 3 is an enlarged configuration diagram showing a peripheral configuration of four photoconductors in the printer. The perspective view which shows the surrounding structure. FIG. 10 is an enlarged configuration diagram showing a peripheral configuration of four photoconductors from a side opposite to FIG. 9. FIG. 2 is a block diagram showing a part of an electric circuit of the printer. FIG. 3 is a first enlarged schematic diagram for explaining meshing of four photoconductor gears in the printer. FIG. 3 is a second enlarged schematic diagram for explaining the engagement of four photoconductor gears in the printer. FIG. 6 is an enlarged schematic diagram for explaining engagement of four photoconductor gears in a modified example of the printer.

Explanation of symbols

1Y: Photoconductor for Y (third image carrier)
1M: Photoconductor for M (second image carrier)
1C: Photoconductor for C (first image carrier)
6Y, M, C, K: Process unit (part of visible image forming means)
7: Optical writing unit (part of visible image forming means)
8: Intermediate transfer belt (endless moving body)
15: Transfer unit (transfer means)
90YMC: Color drive motor (drive motor)
91YMC: Color gear sensor (phase detection means)
150: Control unit (drive control means)
202Y: Y photoconductor gear (third drive receiving gear)
202M: Photoconductor gear for M (second drive receiving gear)
202C: Photoconductor gear for C (first drive receiving gear)

Claims (2)

At least first and second image carriers that carry a visible image on their rotating surface;
The first and second image carriers individually correspond to the first and second image carriers, respectively, and receive the driving force on the driving side and rotate on the same rotation axis as the image carrier, thereby transmitting the driving force to the image carrier. A second drive receiving gear;
An endless moving body that moves its surface endlessly;
Transfer means for transferring the visible image formed on the surface of each image carrier in a superimposed manner on the surface of the endless moving body or a recording member held on the surface of the endless moving body;
A drive motor that meshes its own motor shaft gear with the first drive receiving gear and the second drive receiving gear and supplies driving force to the first image carrier and the second image carrier;
A phase detection means for detecting at least one of the rotation phases of the first image carrier and the second image carrier;
An image forming apparatus in which the image carrier arrangement pitch in the direction along the surface of the endless moving body is set to a value that does not coincide with an integral multiple of the circumference of the image carrier,
The meshing timing of the maximum diameter portion where the distance from the rotation center is maximum due to the eccentricity of the gear at the periphery of the first drive receiving gear and the motor shaft gear of the drive motor is determined by the second drive receiving gear. The first drive receiving gear, the drive motor, and the second drive receiving gear are assembled so as to be synchronized with the meshing timing between the maximum diameter portion due to eccentricity and the motor shaft gear,
and,
Based on the detection result of the phase detection means, the drive control means changes the speed of one rotation cycle in the first image carrier due to the eccentricity of the first drive receiving gear, and the second drive receiving gear. An image forming apparatus for controlling driving of the drive motor so as to suppress a speed fluctuation in one rotation cycle in the second image carrier due to eccentricity. The image forming apparatus according to claim 1.
A third image carrier that is an image carrier different from the first and second image carriers;
A third drive receiving gear that rotates on the same rotational axis as the third image carrier;
A relay gear that simultaneously meshes with the two drive receiving gears so as to relay the driving force from the second drive receiving gear to the third drive receiving gear;
At the peripheral edge of the third drive receiving gear, the meshing timing of the relay gear with the minimum diameter position where the distance from the rotation center is minimized due to the eccentricity of the gear, the maximum diameter position due to the eccentricity of the second drive receiving gear. An image forming apparatus, wherein the second drive receiving gear, the relay gear, and the third drive receiving gear are assembled so as to be synchronized with the meshing timing of the motor and the relay gear.

Images