JP2005121771A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which color shift can securely be corrected according to changes in temperature and humidity in the apparatus and transfer paper can stably be conveyed. <P>SOLUTION: A temperature/humidity sensor 30 transmits the measurement values of the temperature and humidity in the apparatus to a CPU 28 via an AD converter 27. The CPU 28 determines how much degree the transmitted measurement value of the temperature in the apparatus has changed from the previous correction. When the degree is not smaller than a predetermined amount, a correction cycle is carried out. First, signals indicating the start of the correction are transmitted to image forming parts Pa to Pd by the CPU 28. Then, each of the image forming parts Pa to Pd forms a correction patch image onto a conveying belt. The timing of the formation of the image, or the formation of the correction patch image, is detected by a detection sensor 9 and transmitted to the CPU 28. On the basis of the detected timing, the CPU 28 calculates a change in the speed of the conveying belt from its reference speed, and determines a correction value for the rotating speed of a drive roller 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using a rotationally driven conveyance belt or an intermediate transfer belt, and in particular, a color image that performs color misregistration correction by sampling a color misregistration detection pattern formed on the conveyance belt or the intermediate transfer belt. The present invention relates to a forming apparatus.

  The image forming process of the conventional image forming apparatus will be described with reference to FIG. FIG. 8 is a schematic diagram showing the configuration of the color image forming apparatus. In the color image forming apparatus main body, four image forming portions Pa, Pb, Pc and Pd are located upstream of the conveying belt 8 (right side in FIG. 8). Are arranged in order. These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  Photosensitive drums 1a, 1b, 1c, and 1d that carry visible images (toner images) of the respective colors are disposed in the image forming portions Pa to Pd, and are formed on the photosensitive drums 1a to 1d. The transferred toner image is transferred onto a transfer paper 6 carried and conveyed by a conveyor belt 8 that moves adjacent to each image forming unit, and further fixed on the transfer paper 6 by a fixing unit 7. It is configured to be discharged from the main body. While the photosensitive drums 1a to 1d are rotated clockwise in FIG. 8, an image forming process for the photosensitive drums 1a to 1d is executed.

  Next, the image forming units Pa to Pd will be described. Around and around the photosensitive drums 1a to 1d rotatably arranged, image information is supplied to the chargers 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d and the photosensitive drums 1a to 1d. LED heads 17a, 17b, 17c and 17d to be exposed, developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and a developer remaining on the photosensitive drums 1a to 1d ( Cleaning portions 5a, 5b, 5c and 5d for removing toner are provided.

  First, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, then irradiated with light by the LED heads 17a to 17d, and electrostatic charges corresponding to the image signals are applied to the photosensitive drums 1a to 1d. A latent image is formed. Each of the developing devices 3a to 3d is filled with a predetermined amount of cyan, magenta, yellow, and black toner by a replenishing device (not shown). The toner is supplied onto the photosensitive drums 1a to 1d by the developing units 3a to 3d and electrostatically attached to the toner corresponding to the electrostatic latent images formed by exposure from the LED heads 17a to 17d. An image is formed.

  The transfer paper 6 onto which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is supplied onto the conveyor belt 8 via a paper feed roller 13a and a registration roller 13b, and the photosensitive drums 1a to 1d. It is conveyed to the position. A sheet made of dielectric resin is used for the conveyor belt 8, and a belt in which both ends thereof are overlapped and joined to form an endless shape or a seamless belt is used.

  The conveyor belt 8 is stretched between an upstream conveyor roller 10 and a downstream drive roller 11. The conveyor belt 8 rotates counterclockwise as the drive roller 11 is rotated by a drive motor (not shown). When the rotation is started, the transfer paper 6 is transported from the registration roller 13b onto the transport belt 8. At this time, the image writing signal is turned ON, and an image is formed on the uppermost photosensitive drum 1a at a predetermined timing. The cyan toner image on the photosensitive drum 1a is transferred onto the transfer paper 6 by applying an electric field to the lower portion of the photosensitive drum 1a with the transfer roller 4a to which a predetermined transfer voltage is applied. This transfer paper 6 is held on the conveyor belt 8 by electrostatic attraction force, and then is conveyed to the next image forming portion Pb. Similarly to the above, a magenta toner image is now formed by the photosensitive drum 1b. Transcribed.

  Thereafter, yellow and black toner images are transferred by the photosensitive drums 1c and 1d by the same method as described above. These four-color images are formed with a predetermined positional relationship that is predetermined with respect to the transfer paper 6 in order to form a predetermined full-color image. Reference numerals 4b, 4c and 4d denote transfer rollers located below the photosensitive drums 1b to 1d. The transfer paper 6 onto which the four color toner images have been transferred is separated from the transport belt 8 and transported to the fixing unit 7. In addition, the photosensitive drums 1a to 1d after the toner images are transferred are prepared by the cleaning units 5a to 5d in preparation for new electrostatic latent images to be subsequently formed.

  The transfer paper 6 transported from the transport belt 8 to the fixing unit 7 is heated and pressed by the fixing roller 18 so that the toner image is fixed on the surface of the transfer paper 6 and a predetermined full-color image is formed. The transfer paper 6 on which the full color image is formed is then discharged out of the apparatus main body by the discharge roller 19.

  In recent years, there has been an increasing demand for high-speed processing in image forming apparatuses. However, in the tandem type color image forming apparatus as described above, a single image is formed by a plurality of image forming units. If the formation speed is increased, the alignment of the images formed by the image forming units of the respective colors deteriorates, and color misregistration occurs. This is because the position and size of each image forming unit itself or the parts in the image forming unit are subtle due to changes in external temperature and temperature of the color image forming apparatus due to a drive motor that rotates at high speed and heat generated from the fixing unit. Due to the change. For this reason, it has been extremely difficult to achieve both high image quality and high speed in a tandem type color image forming apparatus.

  In particular, the driving roller used to drive the conveying belt that conveys the transfer paper to each image forming unit is arranged close to the fixing unit and the driving motor that generate heat, and thus is easily affected by temperature changes. As a material of the rubber, rubber is often used in order to increase the frictional force with the conveyor belt and realize stable driving of the conveyor belt. In addition, as the material of the conveyor belt, a resin is often used in consideration of cost and function. However, since these rubbers and resins undergo a large volume change due to heat, changes in the driving roller diameter and expansion / contraction of the conveyor belt due to changes in the temperature and humidity inside the machine are likely to occur, and image deterioration due to color misregistration becomes severe. was there.

  In view of this, a method has been proposed in which a deviation in image formation timing in each image forming unit is corrected in accordance with a temperature change inside the apparatus to prevent a color deviation, and Patent Document 1 changes the in-machine temperature by a predetermined temperature. In this case, a color misregistration detection pattern is formed to detect the writing timing of each color, writing start and end address errors in the main scanning direction and sub-scanning direction are corrected, and an accurate image position address is obtained for each image forming unit. Discloses a method of correcting the image formation timing.

  When the diameter of the drive roller changes or the conveyor belt expands or contracts due to changes in temperature and humidity, the speed of the conveyor belt also changes. However, the registration roller that supplies the transfer paper onto the conveyor belt is a driving motor for the fixing unit and conveyor belt. Since it is located on the upstream side (right side in FIG. 8) away from the center, it is not easily affected by heat generated by the fixing unit and drive motor located on the downstream side (left side in FIG. 8). For this reason, a change in temperature and humidity in the apparatus causes a difference between the sheet conveyance speed of the conveyance belt and the sheet supply speed of the registration roller that supplies the transfer sheet onto the conveyance belt.

For example, when the conveyance belt speed is slower than the supply speed of the registration rollers, the transfer paper is bent, and when the conveyance belt speed is increased, the transfer paper is pulled in the belt traveling direction, Smooth conveyance becomes difficult. However, in the method of Patent Document 1, although the image formation timing in each image forming unit is corrected, the conveyance belt speed is not corrected. Therefore, a speed difference between the conveyance belt and the registration roller occurs, so that the transfer paper is stably supplied and conveyed. Color misregistration occurs without being able to. Such a phenomenon also occurs in an image forming apparatus in which each color toner image is sequentially stacked on an intermediate transfer belt to form a color image and then transferred onto a transfer sheet at once. It was.
JP-A-8-286458

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus that can reliably correct color misregistration in accordance with changes in in-machine temperature and humidity and can stably convey transfer paper.

  In order to achieve the above object, the present invention provides a plurality of image forming units including a photosensitive drum and a developing device, conveying means for sequentially conveying transfer paper to each image forming unit, and developing on the photosensitive drum. A transfer means for transferring the toner image formed on the transfer paper or the transport means, and a detection means for detecting the temperature and / or humidity inside the apparatus, and the temperature and / or the internal temperature detected by the detection means. Alternatively, when the humidity changes by a predetermined amount, the color shift correction is performed by changing the driving speed of the conveying means.

  The present invention also provides a plurality of image forming units including a photosensitive drum and a developing device, an intermediate transfer unit in which toner images developed on the photosensitive drum are sequentially stacked, and a stack on the intermediate transfer unit. Transfer means for transferring the toner image onto the transfer paper, and detection means for detecting the temperature and / or humidity inside the apparatus, and the temperature and / or humidity inside the apparatus detected by the detection means changes by a predetermined amount. In this case, color misregistration correction is performed by changing the driving speed of the intermediate transfer means.

  According to the present invention, in the image forming apparatus configured as described above, the driving speed of the transport unit or the intermediate transfer unit is set so that the correction patch image formed on the transport unit or the intermediate transfer unit is adjusted by the image forming unit. It is characterized by being changed according to the image formation timing.

  According to the present invention, in the image forming apparatus having the above-described configuration, the conveying unit or the intermediate transfer unit includes a driving roller connected to a driving motor by an endless carrier having both ends of a flexible sheet-like member connected. The detection means is arranged in the vicinity of the drive roller and the drive motor.

  In the image forming apparatus having the above-described configuration, the drive roller is a rubber roller.

  According to the first configuration of the present invention, when the temperature and / or humidity inside the apparatus changes by a predetermined amount, the color shift caused by the temperature change inside the apparatus can be automatically corrected accurately. Further, since the color misregistration correction is performed by changing the conveying belt speed, the conveying belt speed and the registration roller speed can be always matched, and the transfer paper can be smoothly and stably conveyed.

  Further, according to the second configuration of the present invention, in the image forming apparatus of the type in which the toner images on the photosensitive drum are sequentially stacked on the intermediate transfer belt and the stacked color images are transferred onto the transfer paper at a time. Similarly, by changing the intermediate transfer belt speed in accordance with changes in temperature and / or humidity inside the apparatus, it is possible to accurately correct color misregistration caused by environmental changes inside the apparatus.

  Further, according to the third configuration of the present invention, the conveyor belt speed or the intermediate transfer belt speed is changed according to the image forming timing of the correction patch image formed on the conveyor means or the intermediate transfer means. Alternatively, the speed of the intermediate transfer belt can be accurately corrected in accordance with the actual image shift.

  Further, according to the fourth configuration of the present invention, the detecting means is disposed in the vicinity of the driving roller and the driving motor, thereby accurately detecting the temperature in the vicinity of the driving roller that is likely to change in diameter due to a temperature change. Therefore, it is possible to determine the necessity of more appropriate color misregistration correction.

  Further, according to the fifth configuration of the present invention, even when the material of the drive roller is rubber whose volume change is large due to temperature change, highly accurate color misregistration correction can be performed. A stable driving of the belt is realized, and high-quality image formation is possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a color image forming apparatus according to the first embodiment of the present invention. Parts common to FIG. 8 of the conventional example are denoted by the same reference numerals and description thereof is omitted. In FIG. 1, a temperature / humidity sensor 30 for detecting the temperature and humidity inside the image forming apparatus is disposed in the vicinity of the driving roller 11 and a motor (not shown) for driving the driving roller.

  Enlarged views in the vicinity of the drive roller 11 in FIG. 1 are shown in FIGS. 2A is a front view of the vicinity of the driving roller 11, and FIG. 2B is a side view of the vicinity of the driving roller 11 as viewed from the fixing unit 7 side (left side of FIG. 1). The drive roller 11 is connected to the drive motor 20 via a drive gear 20a, and the drive roller 11 is also rotated by the rotation of the drive motor 20 to drive the conveyor belt 8 to rotate counterclockwise. The driving roller 11 is disposed in the vicinity of the fixing unit 7 that is the highest temperature inside the image forming apparatus, and the driving motor 20 that drives the driving roller 11 also generates heat by rotation. For this reason, as shown in the figure, the temperature / humidity sensor 30 is installed on the inner side of the apparatus main body front surface 12a so as to be slightly upstream of the drive motor 20, so that the drive roller due to heat generated by the fixing unit 7 and the drive motor 20 is provided. It becomes possible to accurately detect a temperature change near 11. In addition, the installation position of the temperature / humidity sensor 30 is not limited to the above, and may be installed in another position where the temperature change near the driving roller 11 can be accurately detected.

  FIG. 3 is a block diagram showing the configuration of the color image forming apparatus of the first embodiment. In FIG. 3, the color image forming apparatus includes an interface control unit 21, a data analysis unit 22, an output mechanism control unit 23, an operation panel 24, an output mechanism unit 25, and a detection sensor 9. The interface unit 21 is an interface unit that accepts print data from a host device (not shown). The data analysis unit 22 is a part that analyzes the print data sent by the drawing command, converts it into bitmap data, and transmits it to the output mechanism unit 25 via the output mechanism control unit 23. The output mechanism control unit 23 is a part that controls the output mechanism unit 25, and an AD converter 27, a CPU 28, and a DA converter 29 are arranged therein. The output mechanism control unit 23 will be described below.

  The AD converter 27 receives measured values of temperature and humidity inside the apparatus from an after-mentioned temperature / humidity sensor 30 as analog signals, converts them into digital signals, and sends them to the CPU 28. The CPU 28 determines how much the temperature inside the apparatus sent has changed since the previous color misregistration correction, and executes a color misregistration correction cycle if the degree of change is a predetermined amount or more. First, a correction start signal is transmitted to each of the image forming units Pa to Pd, and then each of the image forming units Pa to Pd forms a correction patch image on the conveyance belt. The image forming timing of the formed correction patch image is detected by the detection sensor 9, and the detection result is transmitted to the CPU. The CPU 28 calculates a speed change from the reference conveying belt speed based on the detected image forming timing, and determines a correction value for the rotational speed of the driving roller 11.

  The correction value determined by the CPU 28 is converted again into an analog signal via the DA converter 29 and sent to the output mechanism unit 25. The output mechanism section 25 is a mechanism section that transfers a toner image onto transfer paper based on the control of the output mechanism control section 23, and the temperature / humidity sensor 30, the image forming sections Pa to Pd, the drive motor 20, and the drive roller 11 are arranged. Has been. The correction value set by the output mechanism control unit 23 is sent to the drive motor 20, and the rotational speed of the drive roller 11, that is, the speed of the conveyor belt is corrected, so that a high-quality image without color misregistration can be formed on the transfer paper. Form. The operation panel 24 includes an input unit through which an operator inputs operating conditions to the apparatus, and a display unit that notifies the operator of the operation state of the apparatus.

  As a result, the color misregistration correction cycle is executed in accordance with the temperature and humidity changes in the apparatus, and the optimum speed correction value of the transport belt is set for the correction patch image formation timing shift. Can always match the speed of the registration roller. For this reason, it is possible to provide a color image forming apparatus that can reliably prevent color misregistration due to temperature and humidity changes and can stably and smoothly transfer the transfer paper, thereby forming a higher quality image.

  FIG. 4 shows an example of a color misregistration correction patch image. Magenta (M), cyan (C), yellow (Y), and black (B) diagonal lines M1, C1, Y1, and B1 and horizontal lines M2, C2, and Y2 of each color are provided at both ends of the conveyance belt 8. And a patch image composed of B2 is formed. Although not shown in FIG. 1, the detection sensor 9 is disposed on the upstream side of the fixing unit 7, and is positioned in the width direction of the transport belt 8 in accordance with the patch image forming position on the transport belt 8. The positional relationship between the straight lines of these colors is detected by the detection sensor 9 and compared with a predetermined reference position, thereby calculating a timing shift for each color. A correction value for the driving speed of the driving roller 11, that is, the driving speed of the conveyor belt 8, is determined according to the calculated timing shift, and the color shift is corrected. After the color misregistration correction is completed, the correction patch image is removed from the transport belt 8 by a predetermined cleaning method.

  Next, the operation of the image forming apparatus of this embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a color misregistration correction cycle in the color image forming apparatus of this embodiment. The operation at the time of color misregistration correction will be described with reference to FIGS. 1 and 3 according to the steps of FIG.

  First, the temperature and humidity in the machine are detected by the temperature / humidity sensor 30 (step S1). Next, a temperature difference between the temperature detected by the CPU 28 and the temperature inside the machine when the previous correction was performed is calculated (step S2), and it is determined whether or not the temperature difference inside the machine is within an allowable range (step S3). ). If the temperature difference is within the allowable range, the process returns to step S1 for detecting the temperature and humidity in the machine again. On the other hand, if the temperature difference is not within the allowable range, a command for creating a correction patch image is transmitted from the CPU 28 to each of the image forming units Pa to Pd, and a correction patch image is formed on the transport belt (step S4). ). When the correction patch image is formed, the detection sensor 9 detects a shift in image formation timing (step S5), and the detection result is sent to the CPU 28. A correction value for correcting the speed of the conveyor belt is calculated based on the sent detection result (step S6).

  The calculated correction value is output to the drive motor 20 that drives the drive roller 11, whereby the rotation speed of the drive roller 11 that has changed with the temperature change is corrected to the reference speed (step S <b> 7). The speed is corrected so as to match the speed of the registration roller 13b, and the color misregistration correction is completed (step 8).

  In the above embodiment, the temperature and humidity inside the apparatus are detected using the temperature and humidity sensor 30 arranged in the vicinity of the drive roller 11 and the drive motor 20, but a plurality of temperature and humidity sensors are provided, and the temperature and humidity outside the apparatus. It is also possible to determine whether or not color misregistration correction is possible by also detecting the temperature and taking into account the temperature inside and outside the machine. Such an image forming apparatus is shown in FIG. FIG. 6A is a front view of the image forming apparatus according to the second embodiment of the present invention, and FIG. 6B shows the image forming apparatus according to the present embodiment on the fixing unit 7 side (left side of FIG. 6A). It is the side view seen from. In this embodiment, in addition to the temperature / humidity detection sensor 30 that detects the temperature and humidity inside the machine, the temperature / humidity detection sensor 31 that detects the temperature and humidity outside the machine is affected by the heat generated by the fixing unit 7 and the drive motor 20. It is installed inside the apparatus main body rear surface 12b near the intake duct (not shown) in the upper part of the paper cassette 16 which is not easily received.

  When the difference between the in-machine temperature and the outside temperature is large, the in-machine temperature is likely to fluctuate, so color misregistration correction is frequently performed, and so-called downtime in which an image forming operation cannot be performed frequently occurs. However, by providing multiple temperature and humidity sensors in this way and detecting the temperature inside and outside the machine, the temperature outside the machine as well as inside the machine can be reflected in the determination of the necessity of color misregistration correction. Judgment can be made. The place where the temperature / humidity detection sensor 31 is installed is not limited to the above, and the temperature / humidity detection sensor 31 can be installed in another place as long as it is not easily affected by the temperature and humidity inside the apparatus.

  In each of the above embodiments, it is determined whether or not to perform color misregistration correction based on the temperature change detected by the temperature and humidity sensor, but whether or not correction is necessary is determined based on the humidity change instead of the temperature change. Alternatively, the determination can be made based on both the temperature change and the humidity change detected by the temperature / humidity sensor. In addition, when determining whether correction is necessary based on a temperature change or a humidity change, a temperature sensor or a humidity sensor that detects only one of temperature and humidity may be used instead of the temperature / humidity sensor.

  In each of the above-described embodiments, the image forming apparatus has been described in which the transfer paper is transported to each image forming unit by the transport unit and the toner images of the respective colors are sequentially formed on the transfer paper. The same effect can be obtained in an image forming apparatus in which toner images of respective colors are sequentially stacked on an intermediate transfer belt to form a color image and then transferred onto a transfer sheet at a time. In this case, the toner formed on the intermediate transfer belt by changing the intermediate transfer belt speed according to the temperature and / or humidity detected by the temperature / humidity sensor instead of the conveyance belt speed in each of the above embodiments. In addition to preventing color misregistration of the image, smooth transfer onto the transfer paper becomes possible.

  The color misregistration correction in the case where the conveyance belt 8, the drive roller 11, and the transfer rollers 4a to 4d in the image forming apparatus of FIG. 1 have specifications as shown in FIG. 7 will be specifically described. Now, it is assumed that the target value (reference value) of the conveyance belt driving speed is 116.0 mm / s. As shown in the figure, the drive roller 11 is made of rubber (EPDM), so that the thermal expansion is large, and the outer diameter slightly changes due to the surrounding temperature and humidity change. Further, since the conveyor belt 8 is also made of resin (PVDF), it similarly expands and contracts due to changes in the surrounding temperature and humidity, and as a result, the driving speed of the conveyor belt 8 changes from the target value.

  During double-sided continuous printing, the temperature and humidity in the machine changes up to about 45 ° C / 25% at room temperature and normal humidity (23 ° C / 50%). In addition, the internal temperature rises to about 30 ° C. even during single-sided single-sided printing. Therefore, when a predetermined amount of change occurs in the detection value of the temperature / humidity sensor, the conveyance belt speed is automatically detected, and correction is performed so that the conveyance belt drive speed becomes the target value. Specifically, patch images of each color as shown in FIG. 4 are formed on the conveyance belt, and the image formation timing (image position) is detected by the detection sensor. Next, the detected timing is compared with a reference timing (reference position), and the amount of change in the conveyor belt speed is calculated from the timing deviation.

  In the configuration of this embodiment, when the conveying belt speed changes by 0.01%, the color misregistration amount in the magenta and black images changes by 28.5 μm at the maximum. When the in-machine temperature changes by 5 ° C., the belt speed changes by about 0.03%, so the color misregistration amount is about 80 μm at maximum. For this reason, correction is performed here when the in-machine temperature changes by 5 ° C., but the temperature change amount serving as a reference for correction is not limited to this, and can be arbitrarily set according to the allowable range of color misregistration. It can be set. Then, by correcting the driving speed of the driving roller in accordance with the calculated change amount of the conveying belt speed, the conveying belt driving speed is corrected to the target value of 116.0 mm / s, and the color misregistration correction is completed. .

  The present invention provides a plurality of image forming units including a photosensitive drum and a developing device, a conveying unit that conveys transfer paper to each image forming unit, and a toner image developed on the photosensitive drum on the transfer paper or conveying unit. A transfer means for transferring the image on the top and a detection means for detecting the temperature and / or humidity inside the apparatus, and when the temperature and / or humidity inside the apparatus detected by the detection means changes by a predetermined amount, Color misregistration correction is performed by changing the driving speed. Thereby, when the temperature and humidity inside the apparatus change by a predetermined amount, the color shift caused by the temperature change inside the apparatus can be automatically corrected accurately. Furthermore, since color misregistration correction is performed by changing the speed of the conveying means, the driving speed of the conveying means and the registration roller speed can always be matched, and there is no image deterioration due to color misregistration and smooth and stable conveyance of transfer paper. A color image forming apparatus capable of achieving the above is provided.

  In addition, a plurality of image forming units including a photosensitive drum and a developing device, an intermediate transfer unit in which toner images developed on the photosensitive drum are sequentially stacked, and a toner image stacked on the intermediate transfer unit are transferred. A transfer means for transferring onto the paper and a detection means for detecting the temperature and / or humidity inside the apparatus, and the intermediate transfer means when the temperature and / or humidity inside the apparatus detected by the detection means changes by a predetermined amount The color shift correction is performed by changing the driving speed. As a result, even in an image forming apparatus that transfers a color image sequentially laminated on an intermediate transfer belt at a time, color misregistration due to environmental changes inside the apparatus can be accurately corrected and transferred to a transfer sheet. Can be smoothly transferred.

  Further, the driving speed of the conveying unit or the intermediate transfer unit is changed according to the image forming timing of the correction patch image formed on the conveying unit or the intermediate transfer unit by the image forming unit. Accordingly, the speed of the conveying unit or the intermediate transfer unit can be accurately corrected according to the actual image shift, and a high-quality image without color shift is formed.

  The conveying means or the intermediate transfer means is constituted by rotating an endless carrier having both ends of a flexible sheet-like member connected by a driving roller connected to a driving motor. Since it is arranged in the vicinity of the motor, it is possible to accurately detect the temperature in the vicinity of the driving roller that easily changes in diameter due to a temperature change, and it is possible to determine the necessity of more appropriate color misregistration correction.

  In addition, since the driving roller is a rubber roller, the frictional force with the conveyance belt or the intermediate transfer belt is increased to realize stable driving of the conveyance belt or the intermediate transfer belt, and the material of the driving roller changes in temperature. Even in the case of a rubber whose volume change is large, color misregistration correction can be performed with high accuracy, which contributes to higher image quality of the formed image.

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 4 is an enlarged view of the vicinity of a driving roller of the image forming apparatus of the present embodiment. FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to the present embodiment. FIG. 4 is a schematic diagram illustrating an example of a color misregistration correction patch image. FIG. 5 is a flowchart illustrating an operation at the time of image output in the image forming apparatus of the present embodiment. These are the schematic block diagrams which show the image forming apparatus in other embodiment of this invention. FIG. 4 is a table showing specifications of a conveyance belt, a driving roller, and a transfer roller of the image forming apparatus used in the first embodiment of the present invention. FIG. 1 is a schematic configuration diagram showing a conventional image forming apparatus.

Explanation of symbols

1a-1d. Photosensitive drum Pa to Pd. Image forming unit 4. Transfer roller 8. 8. Conveyor belt Detection sensor 11. Drive roller 20. Drive motor 23. Output mechanism controller 25. Output mechanism section 28. CPU
30, 31 Temperature / humidity sensor

Claims (5)

A plurality of image forming units including a photosensitive drum and a developing device; a conveying unit that sequentially conveys transfer paper to each of the image forming units; and a toner image developed on the photosensitive drum on the transfer paper or the conveying unit A transfer means for transferring the image on the surface; and a detection means for detecting the temperature and / or humidity inside the apparatus,
An image forming apparatus, wherein color misregistration correction is performed by changing a driving speed of the conveying unit when a temperature and / or humidity inside the apparatus detected by the detecting unit changes by a predetermined amount. A plurality of image forming units including a photosensitive drum and a developing device, an intermediate transfer unit in which toner images developed on the photosensitive drum are sequentially stacked, and a toner image stacked on the intermediate transfer unit are transferred. A transfer means for transferring onto the paper, and a detection means for detecting the temperature and / or humidity inside the apparatus,
An image forming apparatus, wherein color misregistration correction is performed by changing a driving speed of the intermediate transfer unit when a predetermined amount of temperature and / or humidity inside the apparatus detected by the detection unit changes.   The driving speed of the transport unit or the intermediate transfer unit is changed according to the image formation timing of a correction patch image formed on the transport unit or the intermediate transfer unit by the image forming unit. The image forming apparatus according to claim 1.   The conveying means or the intermediate transfer means is constituted by rotating an endless carrier having both ends of a flexible sheet-like member connected by a driving roller connected to a driving motor, and the detecting means is the driving The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed in the vicinity of a roller and the drive motor.   The image forming apparatus according to claim 4, wherein the driving roller is a rubber roller.

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