JP5483185B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus provided with a plurality of image forming units that form a plurality of color images including black on an image carrier corresponding to each color (for example, Patent Document 1).

  The image forming apparatus described in Patent Document 1 includes a direct transfer position for directly transferring a black image formed by a black image forming unit onto a recording medium, and a primary image from the remaining other color image forming units onto an intermediate transfer belt. There is a secondary transfer position where the transferred other color image is secondarily transferred from the intermediate transfer belt to the recording medium. This secondary transfer position is located upstream of the direct transfer position in the recording medium conveyance direction. The intermediate transfer belt is rotatably stretched by a plurality of roller members, and the intermediate transfer belt is rotated by a driving roller which is one of the plurality of roller members. Further, there is provided a recording medium conveyance belt which is rotatably stretched by a plurality of roller members and carries the recording medium so as to pass through the secondary transfer position and the direct transfer position. In the image forming apparatus described in Patent Document 1, the recording medium is transferred from the secondary transfer position onto the recording medium by passing the recording medium through the secondary transfer position and the direct transfer position by the recording medium conveyance belt. A color image and a black image transferred onto the recording medium from the direct transfer position are superimposed on the recording medium to form a full-color image on the recording medium. Further, by carrying and transporting the recording medium by the recording medium transport belt, fluctuations in the recording medium transport path between the secondary transfer position and the direct transfer position can be suppressed, and the secondary transfer position and the direct transfer can be suppressed. The recording medium can be stably conveyed between the positions.

  In the image forming apparatus described in Patent Document 1, a plurality of image carriers, an intermediate transfer belt, and a recording medium transport belt are driven by a motor as a drive source. In such a configuration, if all the objects to be driven are driven by different motors, a considerable number of motors are required, leading to problems such as high costs and an increase in the size of the image forming apparatus.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that can be reduced in cost and size.

In order to achieve the above object, the invention of claim 1 is directed to an intermediate transfer belt that is rotatably stretched around a plurality of roller members, and a first surface disposed opposite to the front surface of the intermediate transfer belt. One image carrier, first image forming means for forming an image on the first image carrier, and primary transfer of the image formed on the first image carrier onto the intermediate transfer belt Primary transfer means, secondary transfer means for secondary transfer of the image transferred on the intermediate transfer belt onto the recording medium, and secondary transfer of the image from the intermediate transfer belt onto the recording medium. A second image carrier provided upstream or downstream of the transfer position in the recording medium conveyance direction, a second image forming unit for forming an image on the second image carrier, and the second image carrier. A direct transfer means for directly transferring an image formed on the image carrier onto a recording medium; and the second image carrier. A recording medium transported by a plurality of roller members rotatably supported so as to carry and transport the recording medium so as to pass through a direct transfer position where an image is directly transferred onto the recording medium from the secondary transfer position. an image forming apparatus comprising a belt, a, one of the driving source and the same der intermediate transfer said recording medium conveying belt and the driving source of the belt is, the plurality of roller members for stretching the intermediate transfer belt There is an intermediate transfer belt drive roller that rotates from the drive source to drive the intermediate transfer belt to rotate, and one of a plurality of roller members that stretch the intermediate transfer belt, and is driven by the rotation of the intermediate transfer belt. An intermediate transfer belt driven roller, intermediate transfer belt speed detecting means provided on the intermediate transfer belt driven roller for detecting the rotational speed of the intermediate transfer belt, and the intermediate transfer bell Feedback control means for performing feedback control on the drive source using the detection result detected by the speed detection means, and an interval between the direct transfer position and the secondary transfer position in the recording medium conveyance belt rotation direction. Is a natural number multiple of the circumferential length of the intermediate transfer belt drive roller, and is a natural number multiple of the circumferential length of the intermediate transfer belt driven roller .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus further includes a driving force transmitting member that is rotatably supported and transmits a driving force from the driving source to the intermediate transfer belt driving roller. The distance between the direct transfer position and the secondary transfer position in the conveyance belt rotation direction is a natural number multiple of one rotation period of the driving force transmission member.
According to a third aspect of the present invention, there is provided an intermediate transfer belt that is rotatably stretched around a plurality of roller members, and a first image carrier that is disposed to face the front surface of the intermediate transfer belt. A first image forming unit that forms an image on the first image carrier, and a primary transfer unit that primarily transfers the image formed on the first image carrier onto the intermediate transfer belt; Secondary transfer means for secondary transfer of the image transferred on the intermediate transfer belt onto the recording medium, and the recording medium more than the secondary transfer position where the image is secondarily transferred from the intermediate transfer belt onto the recording medium Second image carrier provided upstream or downstream in the conveying direction, second image forming means for forming an image on the second image carrier, and formed on the second image carrier A direct transfer means for directly transferring the recorded image onto the recording medium, and an image on the recording medium from the second image carrier. A recording medium conveying belt that is rotatably stretched by a plurality of roller members and carries the recording medium so as to pass through the direct transfer position where the image is directly transferred and the secondary transfer position. in the image forming apparatus, wherein a drive source of the intermediate transfer belt and the driving source of the paper conveyance belt is identical, the one of a plurality of roller members for stretching the recording medium conveyance belt drive from the drive source Is transmitted to the recording medium conveying belt, and the recording medium conveying belt driving roller is rotated. The recording medium conveying belt is one of a plurality of roller members that stretch the recording medium conveying belt and is rotated by the rotation of the recording medium conveying belt. A medium conveying belt driven roller; a recording medium conveying belt speed detecting means provided on the recording medium conveying belt driven roller for detecting a rotation speed of the recording medium conveying belt; Feedback control means for performing feedback control on the drive source using the detection result detected by the recording medium conveyance belt speed detection means, and from above the first image carrier in the rotation direction of the intermediate transfer belt. The interval between the primary transfer position where the image is primarily transferred onto the intermediate transfer belt and the secondary transfer position is a natural number times the circumferential length of the recording medium conveyance belt drive roller, and the recording medium conveyance belt driven roller It is characterized by being a natural number times the circumferential length of.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect of the present invention, the image forming apparatus includes a driving force transmitting member that is rotatably supported and transmits a driving force from the driving source to the recording medium conveying belt driving roller. The interval between the primary transfer position and the secondary transfer position in the transfer belt rotation direction is a natural number multiple of one rotation period of the drive transmission member.

  In the present invention, since the drive source of the intermediate transfer belt and the drive source of the recording medium transport belt are the same, image formation can be performed as compared with the case where a separate drive source is provided for each of the intermediate transfer belt and the recording medium transport belt. The number of drive sources provided in the apparatus can be reduced. Therefore, the cost and size of the image forming apparatus can be reduced accordingly.

As described above, according to the present invention, there is an excellent effect that the cost and size of the image forming apparatus can be reduced.

The figure which shows the drive arrangement | sequence in an image formation cross section. 1 is a schematic configuration diagram illustrating a printer according to an embodiment. Sectional drawing which expanded only the image formation part. The figure which extracted only the drive system. FIG. 3 is a detailed view of a gear unit that drives the photosensitive member. FIG. 4 is an explanatory diagram regarding control of driving of an intermediate transfer belt. FIG. 3 is a block diagram illustrating an example of a schematic configuration of a rotation drive control device in an intermediate transfer unit. FIG. 6A is a waveform diagram used for explaining the positional deviation of each image on the intermediate transfer belt. FIG. 6B is a waveform diagram used for explaining the positional deviation of each image on the recording paper conveyance belt. FIG. 4C is a waveform diagram used for explaining the positional deviation between a K toner image and a color (Y, M, C) toner image. FIG. 2 is a schematic configuration diagram of a printer when a K direct transfer nip is disposed downstream of a secondary transfer nip in a recording paper conveyance direction. FIG. 2 is a schematic configuration diagram of a printer when photoconductors 11Y, 11M, and 11C are disposed below an intermediate transfer belt. FIG. 2 is a schematic configuration diagram of a printer when there is a single image forming unit facing an intermediate transfer belt. Sectional drawing which expanded only the image formation part. The figure which shows the drive arrangement | sequence in an image formation cross section. The figure which extracted only the drive system. The block diagram which shows an example of schematic structure of the rotational drive control apparatus in a direct transfer unit.

  Hereinafter, a first embodiment in which the present invention is applied to a color laser printer (hereinafter simply referred to as a printer) which is an electrophotographic image forming apparatus will be described.

  FIG. 2 is a schematic configuration diagram illustrating the printer according to the embodiment. FIG. 3 is an enlarged cross-sectional view of the image forming portion of the printer.

  The printer unit includes four image forming units 1Y, 1M, 1C, and 1K for forming yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K) toner images. The intermediate transfer unit 6 of the printer unit extends in the horizontal direction by a driving roller 8, a tension roller 15, an encoder roller 201, and three primary transfer rollers 26Y, 26M, and 26C disposed inside the belt loop. The intermediate transfer belt 12 is stretched by the belt. The tension roller 15 is pivotally supported so that the tension is applied to the intermediate transfer belt 12 by being biased by a spring 61 from the inner side to the outer side of the intermediate transfer belt. The intermediate transfer belt 12 as an image carrier is moved endlessly in the counterclockwise direction in the drawing by the rotational driving of the driving roller 8. The three image forming units 1Y, 1M, and 1C are arranged along the stretched surface of the intermediate transfer belt 12.

  The image forming units 1Y, 1M, 1C, and 1K include a drum-shaped photoconductor 11Y, 11M, 11C, and 11K, a charging device (not shown), a developing device (not shown), and a drum cleaning device (not shown). The two units are integrally attached to and detached from the casing of the printer unit while being held by a common holder. The charging device uniformly charges the peripheral surfaces of the photoreceptors 11Y, 11M, 11C, and 11K, which are rotationally driven by a driving unit (not shown), in the dark with a polarity opposite to the toner charging polarity.

Optical writing units 2Y, 2M, 2C, and 2K are disposed above the image forming units 1Y, 1M, and 1C and on the left side of the image forming unit 1K. Color image information sent from an external personal computer (not shown) is decomposed into Y, M, C, and K information by an image processing unit (not shown) and then processed in the printer unit. The optical writing unit 2 drives Y, M, C, and K light sources (not shown) by a well-known technique based on Y, M, C, and K color-separated image information. Write light for K is generated. Then, the peripheral surfaces of the photoconductors 11Y, 11M, 11C, and 11K uniformly charged by the charging device are scanned with Y, M, C, and K writing light. Thereby, electrostatic latent images for Y, M, C, and K are formed on the peripheral surfaces of the photoreceptors 11Y, 11M, 11C, and 11K. Examples of the light source for the writing light include laser diodes and LEDs.
The electrostatic latent images formed on the peripheral surfaces of the photoreceptors 11Y, 11M, 11C, and 11K are developed by a developing device that employs a well-known two-component developing system that uses a two-component developer composed of toner and a carrier. , M, C, K toner images. Note that a developing device that employs a well-known one-component developing method using a one-component developer made of toner may be used.

  Of the four photoconductors, Y, M, and C photoconductors 11Y, 11M, and 11C are in contact with the intermediate transfer belt 12 to form primary transfer nips for Y, M, and C. Further, primary transfer rollers 26Y, 26M, and 26C that press the intermediate transfer belt 12 toward the Y, M, and C photoconductors 11Y, 11M, and 11C are disposed inside the loop of the intermediate transfer belt 12. . A primary transfer bias is applied to each of the primary transfer rollers 26Y, 26M, and 26C, whereby a transfer electric field is formed in the primary transfer nip for Y, M, and C. The Y, M, and C toner images formed on the peripheral surfaces of the photoreceptors 11Y, 11M, and 11C are placed on the surface of the intermediate transfer belt 12 at the primary transfer nip for Y, M, and C by the action of the transfer electric field and nip pressure. The image is transferred while being superimposed on the surface (the outer surface of the loop). As a result, a three-color superimposed toner image is formed on the front surface of the intermediate transfer belt 12.

  A direct transfer unit 7 is disposed on the right side of the intermediate transfer belt 12 in the drawing. The direct transfer unit 7 has an endless recording paper conveyance belt 13. The recording paper conveyance belt 13 is stretched in a vertically long posture by the secondary transfer roller 9, the drive roller 14, the tension roller 16, and the K transfer roller 36 </ b> K. It can be moved endlessly in the direction. The tension roller 16 is pivotally supported so that it can be urged by a spring 62 directly from the inside to the outside of the transfer belt to apply tension to the recording paper transport belt 13. Further, a portion where the recording paper conveyance belt 13 is wound around the secondary transfer roller 9 is brought into contact with a portion where the intermediate transfer belt 12 is driven around the driving roller 8 to form a secondary transfer nip. A secondary transfer bias is applied to the secondary transfer roller 9, thereby forming a transfer electric field in the secondary transfer nip. Further, a K direct transfer nip is also formed by bringing the recording paper transport belt 13 around the K transfer roller 36K into contact with the K photoconductor 11K. Similarly to the primary transfer rollers 26Y, 26M, and 26C, a transfer bias is also applied to the transfer roller 36K, thereby forming a transfer electric field in the direct transfer nip for K.

  A first paper feed cassette 3 and a second paper feed cassette 4 are disposed below the housing of the printer unit so as to overlap in the vertical direction. These paper feed cassettes send out the recording paper P accommodated therein to the paper transport path. The fed recording paper P abuts against a registration roller pair 111 disposed in a paper conveyance path extending in the vertical direction in the printer unit and the skew is corrected, and then sandwiched between the rollers of the registration roller pair 111. . Then, the sheet is further sent upward by the registration roller pair 111 at a predetermined timing.

  The recording paper P delivered from the registration roller pair 111 sequentially passes through the K direct transfer nip and the Y, M, and C secondary transfer nips formed in the paper conveyance path. When the recording paper P passes through the K direct transfer nip, the K toner image on the peripheral surface of the photoconductor 11K is transferred onto the recording paper P under the action of a transfer electric field and nip pressure. Further, after that, when the recording paper P passes through the secondary transfer nip, three colors (Y, M, C) on the intermediate transfer belt 12 with respect to the K toner image transferred onto the recording paper P. The superimposed toner image is batch-transferred collectively under the action of a transfer electric field or nip pressure. As a result, a full-color image that is a four-color superimposed toner image of Y, M, C, and K is formed on the surface of the recording paper P.

Transfer residual toner adhering to the surfaces of the photoreceptors 11Y, 11M, 11C, and 11K after passing through the primary transfer nip for Y, M, and C and the direct transfer nip for K is removed by the drum cleaning device. The The drum cleaning device for Y, M, C, and K may be a system that scrapes off toner with a cleaning blade, a system that scrapes off toner with a fur brush roller, or a magnetic brush cleaning system. It may be used.
Above the secondary transfer nip, a fixing device 10 is provided that forms a fixing nip by contact between a heating roller and a pressure roller. The recording paper P that has passed through the secondary transfer nip is sent to a fixing nip in the fixing device 10 and subjected to a fixing process for fixing a full-color image on the recording paper P by heat and pressure. Thereafter, the recording paper P passes through the paper discharge path, passes through the paper discharge roller pair 30, and is discharged and stacked on a paper discharge tray 31 provided on the upper surface of the printer unit housing.

  In this printer, in the monochrome mode for forming a monochrome image, the K photoconductor 11K is optically scanned by the optical writing unit 2K based on monochrome image data sent from an external personal computer (not shown). The electrostatic latent image for K thus formed is developed into a K toner image by a K developing device. The K toner image is directly transferred onto the recording paper P by the K direct transfer nip and then fixed on the recording paper P by the fixing device 10.

  In the monochrome mode, the secondary transfer roller 9 in the loop of the recording paper transport belt 13 is moved away from the intermediate transfer belt 12 to separate the recording paper transport belt 13 from the intermediate transfer belt 12. Then, the Y, M, and C image forming units 1Y, 1M, and 1C and the intermediate transfer belt 12 are stopped, and a monochrome image is formed. The image forming units 1Y, 1M, 1C, the intermediate transfer belt 12 and the like can be prevented from being consumed and the life can be extended.

  Alternatively, the driving roller 8 that supports the intermediate transfer belt 12 may be displaced by means (not shown) so that the intermediate transfer belt 12 contacts and separates from the recording paper transport belt 13. In this case, since the transport posture of the recording paper P is not changed, the behavior of the recording paper P between the recording paper transport belt 13 and the fixing device 10 can be stabilized. For this reason, it is possible to suppress the occurrence of wrinkles and image distortion on the recording paper P after being discharged from the fixing device 10.

  In the monochrome mode, the K toner image is directly transferred from the image forming unit 1K to the recording paper P fed from the registration roller pair 111 to the K direct transfer nip, so that the image is added to the image forming units 1Y, 1M, and 1C. The forming unit 1K is also arranged so as to be aligned along the stretched surface of the intermediate transfer belt 12, and the K toner image is transferred onto the recording paper P through the intermediate transfer belt 12 at the secondary transfer nip. Rather than high-speed printing.

  By the way, in the printer configured as described above, the optical characteristics of the photoconductor 11 and the optical writing unit 2 of the printer are caused by various factors such as impact during transportation and installation, vibration during image formation and paper conveyance, and temperature change in the machine. Positional fluctuations occur in the elements, causing image misalignment. Further, the positional deviation of the image is also caused by the eccentricity of the rotating parts such as the photosensitive member 11, the intermediate transfer belt 12, and the recording paper conveying belt 13, and the fluctuation of the rotational driving speed.

  In a printer including a plurality of image forming units 1, the relative misregistration of each color image becomes a color misregistration, and image quality deterioration cannot be avoided.

  Therefore, in the present embodiment, color misregistration detection control for detecting the color misregistration by detecting the pattern image for color matching adjustment by the optical sensor 130 serving as the pattern image detecting means is performed at a predetermined timing. The optical sensor 130 is disposed on the downstream side in the direct transfer belt rotation direction with respect to the direct transfer nip and the secondary transfer nip so as to face the front surface of the recording paper transport belt 13. An optical sensor facing roller 239 that faces the optical sensor 130 with the recording paper transport belt 13 interposed therebetween is provided so as to follow the rotation of the recording paper transport belt 13. As a predetermined timing, when an operation for changing a speed fluctuation pattern such as when an image forming unit is exchanged is performed, or when a print command is issued in a state where the high-quality print mode is selected, the number of sheets to be passed is counted. The number of sheets, for example, when 200 sheets of color paper are passed, a temperature sensor is provided and a predetermined temperature change is performed, for example, 5 deg is changed, a timer is provided, and a predetermined time, for example, 6 hours has elapsed from the previous adjustment time.

  In the color misregistration detection control, drive motors (not shown) that rotate the photoconductors 11Y, 11M, 11C, and 11K are rotated at a constant speed to form pattern images on the photoconductors 11Y, 11M, 11C, and 11K. . Then, the Y, M, C, and K pattern images formed on the photoreceptors 11Y, 11M, 11C, and 11K are finally transferred onto the recording paper conveyance belt 13 without overlapping each pattern image.

  The pattern image for color matching adjustment is transferred onto the recording paper transport belt 13 so that the pattern images of the respective colors are arranged at a predetermined pitch along the recording paper transport belt rotation direction (sub-scanning direction). Further, as the pattern image, a horizontal pattern image orthogonal to the rotation direction of the recording paper conveyance belt and an oblique pattern image intersecting with the rotation direction of the recording paper conveyance belt at 45 degrees are used. Scanning direction) and a direction (main scanning direction) orthogonal to the recording paper conveyance belt rotation direction can be detected.

  Further, by forming a plurality of pattern images in the recording paper conveyance belt rotation direction (sub-scanning direction), it is possible to detect sub-scanning magnification deviations of the respective colors in the recording paper conveyance belt rotation direction (sub-scanning direction). Further, by forming a plurality of pattern images in a direction (main scanning direction) orthogonal to the recording paper conveyance belt rotation direction, the main scanning magnification deviation of each color in the direction orthogonal to the recording paper conveyance belt rotation direction (main scanning direction) Bending and skew deviation can be detected. Furthermore, it is possible to improve the color matching adjustment accuracy by repeating the pattern image detection a plurality of times and averaging the detection results.

  Theoretically, the pattern images are formed on the recording paper transport belt 13 so as to be arranged at a predetermined pitch in the recording paper transport belt rotation direction. An error corresponding to the fluctuation appears in the pitch.

  When the pattern image for color matching adjustment passes immediately below the optical sensor 130 as the recording paper transport belt 13 rotates, the image position is detected by the optical sensor 130. Thereby, the pitch error of the detection time of the pattern image for color matching adjustment of each color is detected. By adjusting the writing timing for writing the latent image on the photoconductor 11 from the detected pitch error, the registration deviation correction in the sub-scanning direction and the main scanning direction is adjusted, and the drive clock of the drive motor that drives the photoconductor 11 to rotate is adjusted. Thus, the registration deviation correction in the sub-scanning direction, the skew deviation correction by adjusting the folding mirror in the optical writing unit 2, the magnification correction in the main scanning direction by adjusting the writing speed, and the like may be performed.

  Next, the drive system of the intermediate transfer belt 12 and the recording paper transport belt 13 will be described with reference to FIGS.

  FIG. 4 is a schematic configuration diagram of the image forming drive unit. FIG. 1 is a diagram showing a driving arrangement in an image forming section in which FIGS. 3 and 4 are overlapped.

  As described above, the intermediate transfer belt 12 is stretched by the drive roller 8, the tension roller 15, and the like, and the recording paper transport belt 13 is stretched by the secondary transfer roller 9, the drive roller 14, the tension roller 16, and the like. .

  The drive roller 8 is driven from a motor output shaft 81 to a gear 82 using a drive motor 80 provided in the printer main body as a drive source. The gear 83 is a gear 83 which is an intermediate transfer belt drive gear coaxial with the drive roller 8. The drive is transmitted to the drive roller 8 from the gear 83 by a coupling (not shown).

  The drive roller 14 is provided in the printer main body and is driven and transmitted from a motor output shaft 81 to a gear 84 which is a recording paper transport belt drive gear coaxial with the drive roller 14 using a drive motor 80 shared with the drive roller 8 as a drive source. Drive is transmitted from the gear 84 to the drive roller 14 by a coupling (not shown).

  The secondary transfer roller 9 and the tension roller 16 are rotated by the rotation of the recording paper transport belt 13 that is rotationally driven by the driving roller 14. A paper adsorbing roller that adsorbs the recording paper P onto the recording paper conveyance belt 13 by electrostatic force when a predetermined voltage is applied from a power source (not shown) to the position opposite the tension roller 16 via the recording paper conveyance belt 13. 17 is disposed. The paper suction roller 17 is in contact with the front surface (loop outer surface) of the recording paper transport belt 13, and the paper suction roller 17 also rotates as the recording paper transport belt 13 rotates.

  As in this embodiment, the drive source of the drive roller 8 that rotationally drives the intermediate transfer belt 12 and the drive source of the drive roller 14 that rotationally drives the recording paper transport belt 13 are the same drive motor 80. The number of drive motors provided in the printer can be reduced as compared with the case where drive motors serving as drive sources are provided separately for the drive roller 8 and the drive roller 14, respectively. Miniaturization can be achieved.

  Next, the drive system of the photoreceptor will be described. FIG. 5 is a detailed view of a gear unit for driving the photosensitive member.

  The photosensitive member 11K is transmitted from the motor output shaft 251 to the gear 82K that is coaxial with the photosensitive member 11K by using the driving motor 250 as a driving source. A joint portion 121 as shown in FIG. 5A is formed at the tip of the gear 82K, and is engaged with a not-shown photoreceptor 11K side joint to transmit driving.

  The photoreceptors 11Y, 11M, and 11C are driven from the motor output shaft 96 to the gear 82C that is coaxial with the photoreceptor 11C and the gear 82M that is coaxial with the photoreceptor 11M, using the drive motor 95 as a drive source. A joint portion 121 as shown in FIG. 5A is formed at the tip of the gear 82C or the gear 82M, and is engaged with a photoreceptor 11C side joint or a photoreceptor 11M joint (not shown) to transmit driving. .

  An idler gear 99 is fitted to the gear 82M, and driving is transmitted from the idler gear 99 to a gear 82Y coaxial with the photoreceptor 11Y. A joint portion 121 as shown in FIG. 5A is formed at the tip of the gear 82Y, and the gear 82Y and a photoreceptor 11Y side joint (not shown) are fitted through the joint portion 121 so that the gear 82Y. Drive is transmitted to the photoreceptor 11Y.

  As shown in FIG. 5B, a filler 92 serving as a reference position for the photoconductors 11Y, 11M, 11C, and 11K is provided on the gears 82Y, 82M, 82C, and 82K coaxial with the photoconductors 11Y, 11M, 11C, and 11K. The filler 92 is formed in a convex shape for a half circumference of the gears 82Y, 82M, 82C, and 82K, in other words, for a half circumference of the photoconductors 11Y, 11M, 11C, and 11K. Further, a phase sensor 97 for detecting the filler 92 is provided, and phase information in the rotation direction of the photoconductor 11 is obtained during driving. As the phase sensor 97, an optical sensor composed of a light emitting element and a light receiving element provided so as to be opposed to each other with a predetermined interval is used, and light irradiated from the light emitting element to the light receiving element is gears 82Y and 82M. , 82C, 82K is detected by the filler 92 that can pass between the light emitting element and the light receiving element, and phase information in the rotational direction of the photoconductors 11Y, 11M, 11C, 11K is obtained. A configuration can be employed.

  Next, control of driving of the intermediate transfer belt 12 will be described. As shown in FIG. 6, an encoder 208 serving as a detecting unit that detects the rotational angular displacement or the rotational angular velocity of the encoder roller 201 is provided on the same axis as the encoder roller 201. The encoder 208 is not provided on the same axis as the encoder roller 201, but is provided on the same axis as the primary transfer rollers 26 Y, 26 M, 26 C and the tension roller 15 that are driven by the rotation of the intermediate transfer belt 12 as in the encoder roller 201. Also good. However, the tension roller 15 that is driven by the rotation of the intermediate transfer belt 12 in the same manner as the encoder roller 201 or the like is pivotally supported so as to be able to swing while being urged by a spring, so that it easily receives additional fluctuations. The measurement accuracy of the rotational angular displacement or rotational angular velocity of the roller 15 is lower than when the encoder is provided coaxially with other driven rollers such as the primary transfer rollers 26Y, 26M, and 26C. Therefore, it is not preferable to provide the encoder 208 on the same axis as the tension roller 15 because there is a possibility that feedback control described later cannot be performed appropriately.

  FIG. 7 is a block diagram showing an example of a schematic configuration of the rotation drive control device in the intermediate transfer unit 6. The feedback control unit 210 detects the rotational angular displacement or rotational angular velocity detection result of the encoder roller 201 obtained based on the output from the encoder 208 serving as the displacement measuring means, and the rotational speed of the driving motor 80 that drives the driving roller 8 to rotate. To give feedback. Specifically, when the rotational angular displacement or rotational angular velocity of the encoder roller 201 is smaller than the control target value obtained in advance through experiments or the like, the rotation detected by the encoder 208 calculated by the deviation calculating unit 209. The drive motor 80 is feedback-controlled (acceleration control) by the feedback control unit 210 in accordance with the deviation between the angular displacement or rotation angular velocity and the control target value to increase the rotation speed of the drive motor 80, and consequently the rotation speed of the drive roller 8 is increased. Speed up. On the other hand, when the rotational angular displacement or rotational angular velocity of the encoder roller 201 is larger than the control target value, the drive motor 80 is feedback-controlled by the feedback control unit 210 according to the deviation calculated by the deviation calculation unit 209. (Deceleration control) is performed to reduce the rotational speed of the drive motor 80, and consequently the rotational speed of the drive roller 8.

  As described above, in the present embodiment, the drive roller 8 is adjusted so that the rotation angular displacement or the rotation angular velocity of the encoder roller 201 is kept constant based on the detection signal from the encoder 208 provided coaxially with the encoder roller 201. Rotation is driven with feedback control. By this feedback control, it is possible to suppress fluctuations in the speed of one rotation period of the driving roller 8 generated in the intermediate transfer belt 12 due to the eccentricity of the driving roller 8 and the like, and the intermediate transfer belt rotated by the driving roller 8 correspondingly. The rotation speed of 12 can be stabilized.

  However, in terms of control, the fluctuation of the speed of one rotation period of the drive roller 8 generated in the intermediate transfer belt 12 by the feedback control is suppressed, but due to the eccentricity of the encoder roller 201 provided with the encoder 208, the intermediate transfer belt 12 The generated speed fluctuation in one rotation cycle of the encoder roller 201 is not suppressed by the feedback control. That is, if the encoder roller 201 to which the encoder 208 is attached is eccentric, the speed fluctuation component due to the eccentricity of the encoder roller 201 is fed back to the rotational speed of the drive roller 8 and thus the rotational speed of the intermediate transfer belt 12, and the intermediate transfer belt 12. In addition, the speed fluctuation due to the eccentricity of the encoder roller 201 occurs. Therefore, the rotation speed of the intermediate transfer belt 12 has a speed fluctuation of one rotation cycle of the encoder roller 201. If the target speed of the intermediate transfer belt 12 is V0 and the radius of the encoder roller 201 is R1, the speed fluctuates at a cycle of (2πR1) / V0. As a result, the recording paper conveyance belt 13 that is the same drive source also causes a speed fluctuation at a cycle of (2πR1) / V0.

  When the encoder roller 201 is decentered or the encoder 208 is decentered, the displacement of the encoder 20 in one rotation cycle from the ideal position in the three-color image on the intermediate transfer belt 12 is shown in FIG. It occurs as shown in

  Here, in this embodiment, the relationship between the station pitch w, which is the distance between the adjacent photoconductors 11 shown in FIG. 3, and the radius R1 of the encoder roller 201 is set so as to satisfy the relationship of Equation 1. ing. That is, since the station pitch w is set to a natural number multiple of one rotation period (circumferential length) of the encoder roller 201, the speed fluctuation of the intermediate transfer belt 12 in each of the primary transfer nips for Y, M, and C is The speed fluctuation is always in the same phase. As a result, it is possible to suppress the occurrence of color misregistration in the Y, M, and C toner images primarily transferred to the intermediate transfer belt 12.

  Further, in this embodiment, the distance y from the primary transfer nip for C shown in FIG. 3 to the secondary transfer nip in the path along the intermediate transfer belt 12 on the downstream side in the rotational direction of the intermediate transfer belt, and the encoder roller 201 Is set so as to satisfy the relationship of Equation 2.

  As a result, the speed of the intermediate transfer belt 12 between the primary transfer nip C and the secondary transfer nip for C always varies in speed in the same phase. The expansion and contraction of the image in the toner image can be suppressed. In other words, by satisfying the relationship of Equation 2, the position shift component of the encoder roller 201 on the intermediate transfer belt 12 in one rotation cycle can be canceled during the secondary transfer by the action of slip transfer.

  Further, by satisfying the relationship between Equations 1 and 2, the M and Y toner images transferred from the photoconductors 11M and 11Y onto the intermediate transfer belt 12 can also be applied to the encoder roller 201 by the slip transfer. A position shift component of one rotation cycle can be canceled at the time of secondary transfer (see FIG. 8B).

  Here, since the drive source of the recording paper transport belt 13 is the same as the drive source of the intermediate transfer belt 12, the speed fluctuation of one rotation cycle of the encoder roller 201 occurs in the rotational speed of the recording paper transport belt 13.

  Therefore, in the present embodiment, the relationship between the distance x from the K direct transfer nip to the secondary transfer nip shown in FIG. 3 and the radius R1 of the encoder roller 201 is set to satisfy the relationship of Equation 3. Has been.

  As described above, the distance x from the direct transfer nip for K to the secondary transfer nip is set to a natural number times the circumferential length of the encoder roller 201, so that the speed of the recording paper transport belt 13 in the direct transfer nip. The phase of the fluctuation can be matched with the phase of the speed fluctuation of the recording paper conveyance belt 13 in the secondary transfer nip. As a result, as shown in FIG. 8C, on the recording paper conveyance belt 13, the phase of the positional deviation waveform of the K toner image and the color (Y, M, C) toner image is matched, and the encoder roller 201 It is possible to suppress the occurrence of color misregistration between the K toner image and the color (Y, M, C) toner image due to the speed fluctuation in one rotation cycle.

  Further, when feedback control is performed on the drive motor 80 so as to cancel the speed fluctuation in one rotation cycle of the drive roller 8 as described above, the drive roller 8 and the drive roller 14 having the same drive source as the drive roller 8 have the same one. A speed fluctuation of the rotation cycle occurs, and consequently, a speed fluctuation of one rotation period of the driving roller 8 occurs on the recording paper conveyance belt 13.

  Therefore, in this embodiment, the relationship between the distance x from the K direct transfer nip to the secondary transfer nip and the radius R2 of the drive roller 8 is set so as to satisfy the relationship of Equation 4.

  In this way, the distance x from the direct transfer nip for K to the secondary transfer nip is set to a natural number times the circumferential length of the drive roller 8, so that the speed of the recording paper transport belt 13 in the direct transfer nip is increased. The phase of the fluctuation can be matched with the phase of the speed fluctuation of the recording paper conveyance belt 13 in the secondary transfer nip. As a result, on the recording paper transport belt 13, the phase of the misalignment waveform of the K toner image and the color (Y, M, C) toner image is matched, and this is caused by the speed fluctuation of the driving roller 8 in one rotation cycle. Thus, color misregistration between the K toner image and the color (Y, M, C) toner image can be suppressed.

  Similarly, when the feedback control as described above is performed, the recording paper transport belt 13 may be displaced by one rotation period of the gear 82 or the gear 83. In this embodiment, the relationship between the distance x from the K direct transfer nip to the secondary transfer nip and the period R3 given to the recording paper transport belt 13 by the component corresponding to one rotation of the gear 82 and the gear 83 is expressed by the following equation (5). It is set to satisfy the relationship.

  As a result, the phase shift waveform of the K toner image and the color (Y, M, C) toner image are in phase with each other on the recording paper conveyance belt 13, and the rotation speed of the gear 82 and the gear 83 is changed in one rotation cycle. It is possible to suppress color misregistration between the toner image and the color (Y, M, C) toner image.

  Also, as shown in FIG. 9, even if the B image forming unit 1K, in other words, the K direct transfer nip is arranged downstream of the secondary transfer nip in the recording paper conveyance direction, the same as described above. Color shift and image expansion / contraction can be suppressed.

  In this embodiment, the recording paper P is carried and conveyed by the recording paper conveyance belt 13 so as to pass through the direct transfer nip and the secondary transfer nip. As a result, the recording paper P is transferred directly from the secondary transfer nip to the secondary transfer nip by the recording paper transport belt 13 regardless of whether the direct transfer nip is positioned upstream or downstream in the recording paper transport direction. Can be passed. Therefore, there is no reduction in the degree of freedom of layout in the printer, for example, the transfer nip must be positioned directly downstream of the secondary transfer nip in the recording paper conveyance direction.

  In the printer according to the present embodiment, the photoconductors 11Y, 11M, and 11C are positioned above the intermediate transfer belt 12, but the photoconductors 11Y, 11M, and 11C are connected to the intermediate transfer belt as shown in FIG. It may be located below 12.

  In addition, as shown in FIG. 11, the image forming unit 1 (photosensitive member 11) facing the intermediate transfer belt 12 may be single. In FIG. 7, an image forming unit 1 </ b> R that forms a toner image using red (R) toner is disposed to face the intermediate transfer belt 12. In the case of such a configuration, the station pitch w item is eliminated, and the above equation 1 can be ignored.

[Embodiment 2]
A second embodiment in which the present invention is applied to a color laser printer (hereinafter simply referred to as a printer) that is an electrophotographic image forming apparatus will be described below. Note that the basic configuration of the printer according to the present embodiment is substantially the same as that of the image forming apparatus according to the first embodiment, and a description thereof will be omitted.

  FIG. 12 is an enlarged cross-sectional view of the image forming portion of the printer according to this embodiment. The difference between the present embodiment and the first embodiment is that the object to be feedback controlled is not the drive roller 8 that rotationally drives the intermediate transfer belt 12 but the drive roller 14 that rotationally drives the recording paper conveyance belt 13.

  FIG. 14 is a schematic configuration diagram of the image forming drive unit, and FIG. 13 is a diagram showing a drive arrangement in the image forming section.

  The drive roller 14 is driven from a motor output shaft 241 to a gear 242 using a drive motor 240 provided in the printer body as a drive source, and a gear that is a recording paper conveyance belt drive gear coaxial with the drive roller 14. The drive is transmitted to 243, and the drive is transmitted from the gear 243 to the drive roller 14 by a coupling (not shown).

  The secondary transfer roller 9 and the tension roller 16 are rotated by the rotation of the recording paper transport belt 13 that is rotationally driven by the driving roller 14. A paper adsorbing roller that adsorbs the recording paper P onto the recording paper conveyance belt 13 by electrostatic force when a predetermined voltage is applied from a power source (not shown) to the position opposite the tension roller 16 via the recording paper conveyance belt 13. 17 is disposed. The paper suction roller 17 is in contact with the front surface (loop outer surface) of the recording paper transport belt 13, and the paper suction roller 17 also rotates as the recording paper transport belt 13 rotates.

  The drive roller 8 is provided in the printer main body, and a drive motor 80 shared with the drive roller 14 is used as a drive source, and the drive is transmitted from the motor output shaft 241 to a gear 244 that is an intermediate transfer belt drive gear coaxial with the drive roller 8. Drive is transmitted to the gear 244 and the drive roller 8 by a coupling (not shown).

  As in this embodiment, the drive source of the drive roller 8 that rotationally drives the intermediate transfer belt 12 and the drive source of the drive roller 14 that rotationally drives the recording paper transport belt 13 are the same drive motor 240. The number of drive motors provided in the printer can be reduced as compared with the case where drive motors serving as drive sources are provided separately for the drive roller 8 and the drive roller 14, respectively. Miniaturization can be achieved.

  Next, the drive control of the recording paper conveyance belt 13 will be described. On the same axis as the encoder roller 219, an encoder 245 (see FIG. 15), which is a detecting means for detecting the rotational angular displacement or rotational angular velocity of the encoder roller 219, is provided. Note that the encoder is not provided on the same axis as the encoder roller 219, but on the same axis as any of the transfer roller 36 K, the tension roller 16, and the optical sensor facing roller 239, which is driven by the rotation of the recording paper conveyance belt 13 as the encoder roller 219. It may be provided. However, the tension roller 16 that is driven by the rotation of the recording paper transport belt 13 in the same manner as the encoder roller 219 is pivotally supported so as to be able to swing while being urged by a spring. The measurement accuracy of the rotational angular displacement or rotational angular velocity of the tension roller 16 is lower than when the encoder is provided coaxially with other driven rollers such as the transfer roller 36K. Therefore, it is not preferable to provide the encoder on the same axis as the tension roller 16 because there is a possibility that feedback control described later cannot be performed appropriately.

  FIG. 15 is a block diagram showing an example of a schematic configuration of the rotation drive control device in the direct transfer unit 7. The feedback control unit 247 detects the rotational angular displacement or rotational angular velocity detection result of the encoder roller 219 obtained based on the output from the encoder 245 that is the displacement measuring means, and the rotational speed of the drive motor 240 that drives the drive roller 14 to rotate. To give feedback. Specifically, when the rotational angular displacement or rotational angular velocity of the encoder roller 219 is smaller than the control target value obtained in advance through experiments or the like, the rotation detected by the encoder 245 calculated by the deviation calculator 246. The drive motor 240 is feedback-controlled (acceleration control) by the feedback control unit 247 according to the deviation between the angular displacement or rotation angular velocity and the control target value to increase the rotation speed of the drive motor 240, and consequently the rotation speed of the drive roller 14 is increased. Speed up. On the other hand, when the rotational angular displacement or rotational angular velocity of the encoder roller 219 is larger than the control target value, the drive motor 240 is feedback controlled by the feedback control unit 247 according to the deviation calculated by the deviation calculating unit 246. (Deceleration control) is performed to slow down the rotational speed of the drive motor 240, and consequently the rotational speed of the drive roller 14.

  Thus, in the present embodiment, the drive roller 14 is controlled so that the rotational angular displacement or rotational angular velocity of the encoder roller 219 is kept constant based on the detection signal from the encoder 245 provided coaxially with the encoder roller 219. Rotation is driven with feedback control. By this feedback control, it is possible to suppress the speed fluctuation of the drive roller 14 in one rotation cycle generated on the recording paper transport belt 13 due to the eccentricity of the drive roller 14, and the recording paper rotated by the drive roller 14 correspondingly. It is possible to stabilize the rotation speed of the conveyor belt 13.

  However, in terms of control, although the speed fluctuation of one rotation period of the drive roller 14 generated in the recording paper conveyance belt 13 by the feedback control is suppressed, the recording paper conveyance belt is caused by the eccentricity of the encoder roller 219 provided with the encoder 245. The speed fluctuation in one rotation cycle of the encoder roller 219 generated at 13 is not suppressed by the feedback control. That is, if the encoder roller 219 to which the encoder 245 is attached is eccentric, the speed fluctuation component due to the eccentricity of the encoder roller 219 is fed back to the rotational speed of the drive roller 14 and consequently the rotational speed of the recording paper transport belt 13, The speed fluctuation due to the eccentricity of the encoder roller 219 occurs on the transport belt 13. Therefore, the rotation speed of the recording paper transport belt 13 has a speed fluctuation of one rotation cycle of the encoder roller 219. If the target speed of the recording paper transport belt 13 is V0 and the radius of the encoder roller 219 is R5, the speed fluctuates at a cycle of (2πR5) / V0. As a result, the intermediate transfer belt, which is the same drive source, also causes a speed fluctuation at a cycle of (2πR5) / V0. Therefore, when the encoder roller 219 of the recording paper transport belt 13 is decentered or the encoder 245 is decentered, the encoder roller 219 is displaced by one rotation period on the intermediate transfer belt 12.

  Here, in the present embodiment, the relationship between the distance x from the K direct transfer nip to the secondary transfer nip shown in FIG. 13 and the radius R5 of the encoder roller 219 satisfies the relationship of Equation 6. Is set.

  As described above, the distance x from the K direct transfer nip to the secondary transfer nip is set to a natural number multiple of the circumferential length of the encoder roller 219, so that the speed of the recording paper transport belt 13 in the direct transfer nip is increased. The phase of the fluctuation can be matched with the phase of the speed fluctuation of the recording paper conveyance belt 13 in the secondary transfer nip. As a result, on the recording paper conveyance belt 13, the phase of the displacement waveform between the K toner image and the color (Y, M, C) toner image is matched, and this is caused by the speed fluctuation of one rotation period of the encoder roller 219. Thus, color misregistration between the K toner image and the color (Y, M, C) toner image can be suppressed.

  Here, since the drive source of the intermediate transfer belt 12 is the same as the drive source of the recording paper transport belt 13, when the feedback control as described above is performed, the speed fluctuation of one rotation cycle of the encoder roller 219 is caused by the intermediate transfer belt 12. It will occur in the rotation speed.

  In this embodiment, the relationship between the station pitch w, which is the distance between adjacent photosensitive members shown in FIG. 13, and the radius R5 of the encoder roller 219 is set so as to satisfy the relationship of Equation 7. That is, since the station pitch w is set to a natural number multiple of one rotation period (circumferential length) of the encoder roller 201, the speed fluctuation of the intermediate transfer belt 12 in each of the primary transfer nips for Y, M, and C is The speed fluctuation is always in the same phase. As a result, it is possible to suppress the occurrence of color misregistration in the Y, M, and C toner images primarily transferred to the intermediate transfer belt 12.

  In the present embodiment, the distance y from the primary transfer nip for C shown in FIG. 13 to the secondary transfer nip in the path along the intermediate transfer belt 12 on the downstream side in the rotation direction of the intermediate transfer belt, and the encoder roller 219 Is set so as to satisfy the relationship of Eq.

  As a result, the speed of the intermediate transfer belt 12 between the primary transfer nip C and the secondary transfer nip for C always varies in speed in the same phase. The expansion and contraction of the image in the toner image can be suppressed. In other words, by satisfying the relationship of Equation 8, the position shift component of one rotation period of the encoder roller 219 on the intermediate transfer belt 12 can be canceled at the time of secondary transfer by the action of slip transfer.

  Further, by satisfying the relationship between Equations 7 and 8, the M and Y toner images transferred from the photoconductors 11M and 11Y onto the intermediate transfer belt 12 can also be applied to the encoder roller 219 by the slip transfer. A position shift component of one rotation cycle can be canceled at the time of secondary transfer.

  Further, when feedback control is performed on the drive motor 240 so as to cancel the speed fluctuation of one rotation cycle of the drive roller 14 as described above, the drive roller 14 is connected to the drive roller 8 having the same drive source as the drive roller 14. A speed fluctuation of one rotation period occurs, and consequently, a speed fluctuation of one rotation period of the driving roller 14 occurs on the intermediate transfer belt 12.

  Therefore, in the present embodiment, the relationship between the distance y from the primary transfer nip for C to the secondary transfer nip in the path along the intermediate transfer belt 12 on the downstream side in the rotation direction of the intermediate transfer belt and the radius R4 of the drive roller 14. Is set so as to satisfy the relationship of Equation (9).

  As a result, the speed of the intermediate transfer belt 12 between the primary transfer nip C and the secondary transfer nip for C always varies in speed in the same phase. The expansion and contraction of the image in the toner image can be suppressed. In other words, when the relationship of Equation 9 is satisfied, the position shift component of one rotation cycle of the driving roller 14 on the intermediate transfer belt 12 can be canceled at the time of secondary transfer by the action of slip transfer.

  Similarly, when the feedback control as described above is performed, the intermediate transfer belt 12 may be displaced by one rotation period of the gear 242 or the gear 243. In this embodiment, the distance y from the primary transfer nip for C to the secondary transfer nip in the path along the intermediate transfer belt 12 on the downstream side in the rotation direction of the intermediate transfer belt, and the component for one rotation of the gear 242 and the gear 243 Is set so that the relationship with the period R6 given to the intermediate transfer belt 12 satisfies the relationship of several tens.

  As a result, the one-cycle speed fluctuation of the gear 242 and the gear 243 generated in the intermediate transfer belt 12 is always the speed fluctuation in the same phase in the C primary transfer nip and the secondary transfer nip. It is possible to suppress the occurrence of image expansion and contraction in the C toner image at the primary transfer nip and the secondary transfer nip. In other words, by satisfying the relationship of Formula 10, the position shift component of one rotation period of the driving roller 14 on the intermediate transfer belt 12 can be canceled at the time of secondary transfer by the action of slip transfer.

  Further, even if the K image forming unit 1K, in other words, the K direct transfer nip is arranged downstream of the secondary transfer nip in the recording paper conveyance direction, the color misregistration and the image expansion and contraction are suppressed as described above. can do.

  In this embodiment, the recording paper P is carried and conveyed by the recording paper conveyance belt 13 so as to pass through the direct transfer nip and the secondary transfer nip. As a result, the recording paper P is transferred directly from the secondary transfer nip to the secondary transfer nip by the recording paper transport belt 13 regardless of whether the direct transfer nip is positioned upstream or downstream in the recording paper transport direction. Can be passed. Therefore, there is no reduction in the degree of freedom of layout in the printer, for example, the transfer nip must be positioned directly downstream of the secondary transfer nip in the recording paper conveyance direction.

  In the printer according to the present embodiment, the photoconductors 11Y, 11M, and 11C are positioned above the intermediate transfer belt 12, but the photoconductors 11Y, 11M, and 11C are positioned below the intermediate transfer belt 12. May be. Further, the number of the image forming unit 1 (photosensitive member 11) facing the intermediate transfer belt 12 may be single. In this case, since the station pitch w item is eliminated, the above equation 7 can be ignored.

As described above, in each embodiment, the intermediate transfer belt 12 that is rotatably stretched around a plurality of roller members, and the first image carrier that is disposed to face the front surface of the intermediate transfer belt 12. On the photoreceptors 11Y, 11M, and 11C, the image forming units 1Y, 1M, and 1C as the first image forming units for forming images on the photoreceptors 11Y, 11M, and 11C, and the photoreceptors 11Y, 11M, and 11C. The primary transfer rollers 26Y, 26M, and 26C, which are primary transfer means for primary transfer of the formed image onto the intermediate transfer belt 12, and the image transferred onto the intermediate transfer belt 12 are transferred onto the recording paper P as a recording medium. A secondary transfer roller 9 that is a secondary transfer means for performing the next transfer and a secondary transfer position at which the image is secondarily transferred from the intermediate transfer belt 12 onto the recording paper P, on the upstream side or the downstream side in the recording paper conveyance direction. Provided The image forming unit 1K by the second image forming unit for forming an image on the photoconductor 11K, and the image formed on the photoconductor 11K directly on the recording paper P. A transfer roller 36K, which is a direct transfer means for transferring, and the recording paper P so as to pass through the secondary transfer position and the direct transfer position where the image is directly transferred from the photoreceptor 11K onto the recording paper P. In an image forming apparatus comprising a recording sheet conveying belt 13 that is a recording medium conveying belt that is rotatably stretched by a plurality of roller members, the drive source of the intermediate transfer belt 12 and the recording sheet conveying belt 13 The drive source is the same. As a result, the number of drive motors provided in the image forming apparatus can be reduced as compared with the case where drive motors that are drive sources are separately provided for the intermediate transfer belt 12 and the recording paper transport belt 13. Therefore, the cost and size of the image forming apparatus can be reduced accordingly.
Further, according to the first embodiment, the intermediate transfer belt is one of a plurality of roller members that stretch the intermediate transfer belt 12, and the drive is transmitted from the drive motor 80 that is the driving source to rotate the intermediate transfer belt 12. A driving roller 8 that is a driving roller; an encoder roller 201 that is one of a plurality of roller members that stretch the intermediate transfer belt 12 and that is driven by the rotation of the intermediate transfer belt 12; The encoder 208 is an intermediate transfer belt speed detecting means provided in 201 for detecting the rotational speed of the intermediate transfer belt 12, and a feedback control means for performing feedback control on the drive motor 80 using the detection result detected by the encoder 208. And a feedback control unit 210 for rotating the recording paper transport belt Distance between the secondary transfer position and the direct transfer position in is a natural number times the circumferential length of the driving roller 8, which is a natural number multiple of the circumferential length of the encoder roller 201. Thereby, as described above, the phase of the speed fluctuation of the recording paper conveyance belt 13 caused by one rotation cycle of the drive roller 8 and the encoder roller 201 can be made the same at the direct transfer position and the secondary transfer position. Therefore, it is possible to suppress the occurrence of a color shift in one rotation cycle of the drive roller 8 and the encoder roller 201 between the Y, M, C, and K toner images transferred onto the recording paper P carried on the recording paper conveyance belt 13. can do.
Further, according to the first embodiment, the gear 82 or the gear 83 which is a driving force transmission member that is rotatably supported and transmits a driving force from the driving motor 80 to the driving roller 8 is provided in the rotation direction of the recording paper conveyance belt. The distance between the direct transfer position and the secondary transfer position is a natural number multiple of one rotation period of the gear 82 or the gear 83. Thereby, as described above, the phase of the speed fluctuation of the recording paper transport belt 13 generated in one rotation cycle of the gear 82 and the gear 83 can be made the same at the direct transfer position and the secondary transfer position. Therefore, it is possible to suppress the occurrence of a color shift of one rotation period of the gear 82 or the gear 83 between the Y, M, C, and K toner images transferred onto the recording paper P carried on the recording paper conveyance belt 13. Can do.
Further, according to the second embodiment, the recording paper conveyance belt 13 is one of a plurality of roller members that stretch the recording paper conveyance belt 13, and the drive is transmitted from the drive motor 240 that is the driving source to rotate the recording paper conveyance belt 13. A drive roller 14 that is a medium conveying belt driving roller and an encoder that is one of a plurality of roller members that stretch the recording paper conveying belt 13 and that is a recording medium conveying belt driven roller that rotates following the rotation of the recording paper conveying belt 13 A roller 219, an encoder 245 that is provided on the encoder roller 219 and detects the rotational speed of the recording paper transport belt 13, and a detection medium detected by the encoder 245. A feedback control unit 247 which is feedback control means for feedback control. Thus, the distance between the primary transfer position where the image is primarily transferred from the photoreceptors 11Y, 11M, 11C to the intermediate transfer belt 12 in the rotational direction of the intermediate transfer belt and the secondary transfer position is the circumferential length of the drive roller 14. Is a natural number multiple of the circumferential length of the encoder roller 219. Thereby, as described above, the phase of the speed fluctuation of the intermediate transfer belt 12 caused by one rotation cycle of the drive roller 14 and the encoder roller 219 can be made the same at the primary transfer position and the secondary transfer position. Therefore, the speed fluctuation of the intermediate transfer belt 12 between the primary transfer nip and the secondary transfer nip of Y, M, and C due to one rotation cycle of the drive roller 14 and the encoder roller 219 is always the speed fluctuation in the same phase. Therefore, it is possible to prevent the Y, M, and C toner images from expanding and contracting at the primary transfer nip and the secondary transfer nip. In other words, a position shift component of one rotation cycle of the driving roller 14 and the encoder roller 219 on the intermediate transfer belt 12 can be canceled at the time of secondary transfer by the action of slip transfer.
In addition, according to the second embodiment, the gear 242 or the gear 243 that is a driving force transmission member that is rotatably supported and transmits a driving force from the driving motor 240 to the driving roller 14 is provided, and the above-mentioned in the rotation direction of the intermediate transfer belt. The interval between the primary transfer position and the secondary transfer position is a natural number multiple of one rotation period of the gear 242 or the gear 243. Thereby, as described above, the phase of the speed fluctuation of the intermediate transfer belt 12 generated in one rotation cycle of the gear 242 or the gear 243 can be made the same at the primary transfer position and the secondary transfer position. Therefore, the speed fluctuation of the intermediate transfer belt 12 between the primary transfer nip and the secondary transfer nip of Y, M, and C, which occurs in one rotation cycle of the gear 242 and the gear 243, is always a speed fluctuation in the same phase. It is possible to suppress the occurrence of image expansion and contraction in the Y, M, and C toner images at the primary transfer nip and the secondary transfer nip. In other words, the position shift component of one rotation cycle of the gear 242 and the gear 243 on the intermediate transfer belt 12 can be canceled at the time of secondary transfer by the action of slip transfer.

DESCRIPTION OF SYMBOLS 1 Image formation unit 2 Optical writing unit 3 Paper feed cassette 4 Paper feed cassette 6 Intermediate transfer unit 7 Direct transfer unit 8 Drive roller 9 Secondary transfer roller 10 Fixing device 11 Photoconductor 12 Intermediate transfer belt 13 Recording paper conveyance belt 14 Drive Roller 15 Tension roller 16 Tension roller 17 Paper adsorption roller 26 Primary transfer roller 30 Paper discharge roller pair 31 Paper discharge tray 36K Transfer roller 61 Spring 62 Spring 80 Drive motor 81 Motor output shaft 82 Gear 83 Gear 84 Gear 92 Filler 95 Drive motor 96 Motor output shaft 97 Phase sensor 99 Idler gear 111 Registration roller pair 121 Joint part 201 Encoder roller 208 Encoder 209 Deviation calculation part 210 Feedback control part 219 Encoder low 239 optical sensor opposed roller 240 driving motor 241 motor output shaft 242 gear 243 gear 244 gear 245 encoder 246 error calculator 247 feedback controller 250 driving motor 251 motor output shaft

JP 2006-201743 A

Claims (4)

An intermediate transfer belt rotatably stretched around a plurality of roller members;
A first image carrier disposed opposite to the front surface of the intermediate transfer belt;
First image forming means for forming an image on the first image carrier;
Primary transfer means for primarily transferring an image formed on the first image carrier onto the intermediate transfer belt;
Secondary transfer means for secondary transfer of the image transferred onto the intermediate transfer belt onto a recording medium;
A second image carrier provided on the upstream side or the downstream side in the recording medium conveyance direction from the secondary transfer position where the image is secondarily transferred from the intermediate transfer belt onto the recording medium;
Second image forming means for forming an image on the second image carrier;
Direct transfer means for directly transferring an image formed on the second image carrier onto a recording medium;
A plurality of rotatable roller members that carry and convey a recording medium so as to pass through a direct transfer position where an image is directly transferred from the second image carrier onto the recording medium and the secondary transfer position. In an image forming apparatus comprising a recording medium conveyance belt stretched by
Wherein Ri drive source and the same der of the recording medium conveying belt and the driving source of the intermediate transfer belt,
An intermediate transfer belt drive roller that is one of a plurality of roller members that stretch the intermediate transfer belt and that is driven by the drive source and rotates the intermediate transfer belt;
An intermediate transfer belt driven roller that is one of a plurality of roller members that stretch the intermediate transfer belt and that rotates following the rotation of the intermediate transfer belt;
An intermediate transfer belt speed detecting means provided on the intermediate transfer belt driven roller for detecting the rotational speed of the intermediate transfer belt;
Feedback control means for performing feedback control on the drive source using the detection result detected by the intermediate transfer belt speed detection means,
An interval between the direct transfer position and the secondary transfer position in the rotation direction of the recording medium conveyance belt is a natural number multiple of the circumferential length of the intermediate transfer belt driving roller, and is equal to the circumferential length of the intermediate transfer belt driven roller. An image forming apparatus characterized by being a natural number multiple . The image forming apparatus according to claim 1 .
A driving force transmitting member that is rotatably supported and transmits a driving force from the driving source to the intermediate transfer belt driving roller;
An image forming apparatus, wherein an interval between the direct transfer position and the secondary transfer position in the recording medium conveyance belt rotation direction is a natural number multiple of one rotation period of the driving force transmission member. An intermediate transfer belt rotatably stretched around a plurality of roller members;
A first image carrier disposed opposite to the front surface of the intermediate transfer belt;
First image forming means for forming an image on the first image carrier;
Primary transfer means for primarily transferring an image formed on the first image carrier onto the intermediate transfer belt;
Secondary transfer means for secondary transfer of the image transferred onto the intermediate transfer belt onto a recording medium;
A second image carrier provided on the upstream side or the downstream side in the recording medium conveyance direction from the secondary transfer position where the image is secondarily transferred from the intermediate transfer belt onto the recording medium;
Second image forming means for forming an image on the second image carrier;
Direct transfer means for directly transferring an image formed on the second image carrier onto a recording medium;
A plurality of rotatable roller members that carry and convey a recording medium so as to pass through a direct transfer position where an image is directly transferred from the second image carrier onto the recording medium and the secondary transfer position. In an image forming apparatus comprising a recording medium conveyance belt stretched by
The drive source of the intermediate transfer belt and the drive source of the recording medium transport belt are the same,
A plurality of one of the roller members paper conveyance belt drive roller driven from the drive source rotationally driving the recording medium conveying belt is transmitted for stretching the recording medium conveying belt,
A recording medium conveyance belt driven roller that is one of a plurality of roller members that stretch the recording medium conveyance belt and that is rotated by the rotation of the recording medium conveyance belt;
A recording medium conveyance belt speed detecting means provided on the recording medium conveyance belt driven roller for detecting a rotation speed of the recording medium conveyance belt;
Feedback control means for performing feedback control on the drive source using the detection result detected by the recording medium conveyance belt speed detection means,
The interval between the primary transfer position where the image is primarily transferred from the first image carrier to the intermediate transfer belt in the rotation direction of the intermediate transfer belt and the secondary transfer position is a circle of the recording medium transport belt driving roller. An image forming apparatus characterized in that it is a natural number times the circumference and is a natural number times the circumference of the recording medium transport belt driven roller. The image forming apparatus according to claim 3 .
A driving force transmitting member that is rotatably supported and transmits a driving force from the driving source to the recording medium conveying belt driving roller;
An image forming apparatus, wherein an interval between the primary transfer position and the secondary transfer position in the rotation direction of the intermediate transfer belt is a natural number multiple of one rotation period of the drive transmission member.

Images