JP2004226660A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect meandering amount with higher precision than that of detection of a terminal position of an intermediate transfer body in the conventional image forming apparatus and to compensate the meandering amount of the intermediate transfer body based on the detected meandering amount. <P>SOLUTION: The image forming apparatus is provided with a writing optical system which uses a semiconductor LD (laser diode) as a light source, a photosensitive body which forms toner images from an electrostatic latent image formed by a laser beam irradiated from the system, the intermediate transfer body which is oppositely arranged on the photosensitive body and on which the toner images are successively transferred by a transfer device and a device which transfers plurality of colors of toner images successively transferred on the transfer body on transfer paper in a batch, has a slit-like printing part which is preliminarily printed at a main scan end part on a transfer surface as a non-image area of the intermediate transfer body and printed in parallel with a feeding direction of the transfer body and a meandering displacement reader consisting of a transfer slit positional sensor which detects a position of the printing part and compensates an image writing position from the writing optical system based on meandering displacement quantity to be outputted from the reader. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile having an intermediate transfer member capable of overwriting a plurality of colors.
[0002]
[Prior art]
In an image forming apparatus having an intermediate transfer member capable of overwriting a plurality of colors, an endless belt is conventionally used for the intermediate transfer member. The endless belt is stretched over a driving roller and a driven roller, and is disposed with a predetermined tension. The driving roller and the driven roller are driven to rotate by the driving means for rotating the driving roller, and the endless belt is conveyed in a predetermined direction. However, there is uneven rotation and vibration in the motor serving as the driving means, and when the rotation axes of the driving roller and the driven roller do not have uniform rotation axis parallelities, uneven conveyance may occur on the intermediate transfer member. There is.
[0003]
When the transport unevenness as described above occurs in the intermediate transfer body, meandering transport occurs in a direction perpendicular to the transport direction of the intermediate transfer body, that is, in the main scanning direction, and a formation position shift of the transferred toner image occurs. There's a problem. If this is a monochrome monochromatic image forming apparatus, the image forming position on the transfer paper as the final recording medium is only shifted in the main scanning direction, but in a full-color image forming apparatus that forms a plurality of colors, This is a serious problem of causing color shift in the main scanning direction of the four primary colors for forming. For this reason, various attempts have conventionally been made to reduce the meandering conveyance as described above.
[0004]
For example, a sensor (gap sensor, photoelectric sensor, or the like) that detects one end position in the width direction (main scanning direction) perpendicular to the conveyance direction of the intermediate transfer body is provided as an image forming apparatus with such a device. An image forming apparatus has been proposed in which an interval between the sensor and an end of the intermediate transfer body is detected by the sensor, and a meandering of the intermediate transfer body is detected based on a change in the detected interval (for example, Patent Document 1). reference.).
[0005]
In another image forming apparatus, a reference mark for detecting a meandering conveyance is formed on an intermediate transfer member by an image writing control means, and the reference mark is perpendicular to the running direction of the reference mark on the intermediate transfer member (transfer belt). A pixel unit that has a reference mark displacement detection sensor that detects the displacement amount in the direction, that is, the main scanning direction, and that can form an image of the meandering of the intermediate transfer body based on the displacement amount of the reference mark detected by the reference mark displacement detection sensor. An image forming apparatus has been proposed in which the image writing position on the intermediate transfer body is corrected in units of pixels on which an image can be formed (see, for example, Patent Document 2).
[0006]
[Patent Document 1]
JP 2001-75326 A (Claims, page 3-5)
[Patent Document 2]
JP-A-2000-71522 (page 3-12, FIG. 5)
[0007]
[Problems to be solved by the invention]
In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-75326, since the position of the side end of the intermediate transfer body is detected, the detection accuracy is limited by the shape accuracy of the side end of the intermediate transfer body. This causes a problem that the meandering amount can be detected only with low accuracy.
[0008]
In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-71522, the meandering amount of the intermediate transfer body is detected by a reference mark displacement detection sensor at the position of a reference mark on which an image is formed on the intermediate transfer body. ing. Since the detection accuracy of this sensor has a resolution that can be detected in image forming pixel units, there is a problem that the meandering amount of the intermediate transfer body can be detected only in minimum pixel units.
[0009]
Therefore, the present inventors have conducted intensive studies to solve the above problem, and preliminarily printed on the main scanning end portion on the transfer surface, which is a non-image forming area of the intermediate transfer body, to be parallel to the conveyance direction of the intermediate transfer body. A slit-shaped slit printing section characterized by being printed on, and a transfer slit position sensor for detecting the position of the slit printing section disposed at a position facing the slit printing section, wherein the transfer slit position To develop an image forming device that can detect the meandering amount of the intermediate transfer body based on the amount of displacement of the slit printing unit detected by the sensor, and to transfer the toner image that is the original purpose of use with high image quality, By previously forming the meandering amount detecting section of the intermediate transfer body on the intermediate transfer surface formed with high precision surface accuracy, the meandering position is more than that of the conventional image forming apparatus by detecting the end position of the intermediate transfer body. It found that it is possible to detect with high accuracy, and have completed the present invention according to the claims 1.
[0010]
In addition, the present inventors feed back the displacement amount of the slit printing unit detected with high accuracy by the transfer slit position sensor to the image writing control unit, and converts the displacement amount into a clock signal having a higher frequency than a clock signal used for image formation. Control of the intermediate transfer member can accurately correct the meandering amount of the intermediate transfer member, and the image writing control means starts image writing based on the sensor displacement amount due to the meandering conveyance of the intermediate transfer member. It has been found that by correcting the position, it is possible to correct the vertical line skew in the output image without correcting the drive system as the transfer / conveying unit and changing the control. Was completed.
[0011]
Further, the present inventors correct the image writing start position in the main scanning direction in real time based on the amount of displacement from the meandering displacement reading device that has detected the position of the slit printing unit pre-printed on the intermediate transfer body. The vertical line skew of the image on the transfer paper is corrected in the actual image forming area, and at the same time, the process pattern necessary for process control in the area other than the image forming area, and the color of each color not only in the main scanning direction but also in the sub-scanning direction, It has been found that the image position of the control pattern for correcting the color shift amount can be corrected, and the invention according to claim 3 of the present application has been completed.
[0012]
The present invention is intended to solve the above-described problem, and an image forming apparatus capable of detecting a meandering amount with higher accuracy than detecting the end position of an intermediate transfer body in a conventional image forming apparatus, In particular, the meandering amount of the intermediate transfer body can be corrected with high accuracy, and the vertical line skew in the output image can be corrected without correcting the drive system, which is the transfer conveyance unit, and changing the control. The image forming apparatus can further correct the vertical skew of the image on the transfer paper in the actual image forming area, and at the same time, use only the process pattern necessary for process control outside the image forming area or the main scanning direction. It is another object of the present invention to provide an image forming apparatus capable of correcting an image position of a control pattern for correcting a color shift amount of each color in a sub-scanning direction or the like.
[0013]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes a writing optical system that uses a semiconductor laser diode as a light source, and a toner that forms an electrostatic latent image with a laser beam emitted from the writing optical system, and is visualized from the electrostatic latent image. A photoreceptor for forming an image, an intermediate transfer member disposed opposite to the photoreceptor and sequentially transferring the toner image by a transfer device, and recording a plurality of color toner images sequentially transferred on the intermediate transfer member. An image forming apparatus including a transfer device for batch-transferring to a transfer paper serving as a medium, wherein the intermediate transfer body is pre-printed on a main scanning end portion on a transfer surface, which is a non-image area, in a conveying direction of the intermediate transfer body. And a meandering displacement reading device including a transfer slit position sensor for detecting a position of the slit printing portion. Based on the meandering amount of displacement et output, it is characterized in that to correct the image writing position from the writing optical system.
[0014]
In the image forming apparatus according to the present invention, the main scanning is performed based on a displacement amount from a meandering displacement reading device that detects a position of the slit printing unit pre-printed on a transfer surface that is a non-image area of the intermediate transfer body. An image forming apparatus capable of correcting the image writing start position in the direction with an accuracy equal to or smaller than the minimum unit pixel size capable of forming an image is preferable, and the image forming apparatus is printed in advance on a transfer surface that is a non-image area of the intermediate transfer body. An image forming apparatus capable of correcting the image writing start position in the main scanning direction in real time based on the amount of displacement from the meandering displacement reading device that has detected the position of the slit printing unit is also preferable.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.
The image forming apparatus according to the present invention has an intermediate transfer member that uses a laser beam of a semiconductor laser diode (LD) as a light source, irradiates a laser beam onto a photosensitive drum surface, and can overwrite a plurality of colors.
[0016]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus having an intermediate transfer member according to the present invention. In FIG. 1, reference numerals 1K, 1Y, 1M and 1C denote a laser writing device, 2K, 2Y, 2M and 2C denote photosensitive drums, 3 denotes an intermediate transfer belt, 4 denotes an intermediate transfer roller, 5K, 5Y, 5M and 5C denote transfer. A slit position sensor, 7K, 7Y, 7M, and 7C are developing devices, 8 is an intermediate transfer belt cleaning device, 9 is a paper feeding device, 10 is a transfer device, 11 is a fixing device, and 12 is a paper discharging device.
[0017]
When a start switch of an image forming apparatus (not shown) is pressed or a print job start signal from a printer is enabled, laser beams whose timing is controlled are emitted from each of the laser writing devices 1K, 1Y, 1M, and 1C, and each photoconductor is Exposure is performed on the surfaces of the drums 2K, 2Y, 2M and 2C.
[0018]
Next, the corresponding photosensitive drums 2K, 2Y, 2M, and 2C are rotated by the developing devices 7K, 7Y, 7M, and 7C for the respective colors according to the exposed laser beam positions, and the respective drums 2K, 2Y, 2M, and 2C are rotated. A monochrome image of black (K), yellow (Y), magenta (M), and cyan (C) is formed thereon. Then, in parallel with the above operation, the intermediate transfer belt 3 is driven to rotate. One of the three illustrated intermediate transfer rollers 4 is driven to rotate as a driving roller, and the other two intermediate transfer rollers 4 are driven to rotate as driven rollers, thereby conveying the entire intermediate transfer belt 3 in the direction of arrow B. By the developing operation on the photoconductor and the transport operation of the intermediate transfer belt 3, the monochrome images formed on the photoconductor drums 2K, 2Y, 2M, and 2C are sequentially transferred to form a composite color image on the intermediate transfer belt 3. .
[0019]
On the other hand, when the start switch of the image forming apparatus (not shown) is pressed or the print job start signal from the printer is enabled, the photographic paper S is separated from the paper feeding device 9 one by one and fed and conveyed. (Shown) and temporarily stop. Then, the registration roller is rotated in synchronization with the composite color image formed on the intermediate transfer belt 3 as described above, and the photographic paper S is fed between the intermediate transfer body and the transfer device 10 to be transferred. To transfer the composite color image onto the photographic paper S. The transferred photographic paper S is directly sent to the fixing device 11, where the fixing device 11 applies heat and pressure to fix the transferred image, and is discharged by a discharge roller attached to the discharge device 12 to be discharged. Stacked on a tray (not shown).
[0020]
Further, the transfer residual toner remaining on the intermediate transfer belt 3 after transferring the composite color image by the transfer device 10 is removed by the intermediate transfer belt cleaning device 8 to clean the surface of the intermediate transfer belt 3 and to form an image again. It is configured to prepare for.
[0021]
FIG. 2 is a perspective view showing a schematic configuration around an intermediate transfer member of the image forming apparatus according to the present invention. Reference numeral 6 in FIG. 2 denotes a transfer slit printing unit for detecting the amount of meandering of the intermediate transfer belt 3. The transfer slit printing section 6 is printed on a transfer surface corresponding to a non-image area of the intermediate transfer belt 3 in advance, and has a meandering transport when the intermediate transfer belt 3 is transported. Printed in parallel.
[0022]
On the other hand, reflection type sensors or the like are used for the transfer slit position sensors 5K, 5Y, 5M, and 5C for detecting the transfer slit printing unit 6, and are arranged at positions facing the transfer slit printing unit 6. The transfer slit position sensors 5K, 5Y, 5M, and 5C have light receiving elements arranged in the main scanning direction to detect the position of the transfer slit printing unit 6 in the main scanning direction with respect to the sensor positions. In the reference transport state in which the intermediate transfer belt 3 has no meandering transport, the output from the transfer slit position sensors 5K, 5Y, 5M, and 5C is zero (± 0), that is, the intermediate transfer belt 3 is in a meandering transport. In the reference transport state where the transfer is not performed, the transfer slit position sensors 5K, 5Y, 5M, and 5C are arranged so that the center position in the main scanning direction and the transfer slit printing unit 6 have the same positional relationship. The detection signals from the transfer slit position sensors 5K, 5Y, 5M, and 5C are output to an image writing control unit that controls the driving timing of the laser beam, and are feedback-controlled.
[0023]
FIG. 3 is a diagram showing the positional relationship between the intermediate transfer member, the meandering displacement reading device, and the photosensitive member of the image forming apparatus according to the present invention. FIG. 4 is a schematic view showing an example of meandering conveyance of the intermediate transfer member corresponding to FIG. 3 (a-1), (a-2), and (a) of FIG. 4 show a reference transport state in which the intermediate transfer belt 3 is not transported at all in a meandering manner, and (b-1) of FIG. (B-2) and FIG. 4B show a state where the intermediate transfer belt 3 meanders.
[0024]
The x-axis direction shown in FIG. 3 is the main scanning direction and the meandering direction of the intermediate transfer belt 3, and the illustrated axial direction is the meandering amount of the intermediate transfer body in the positive direction. . On the other hand, the y-axis direction is the transport direction of the intermediate transfer belt 3. In FIG. 4A, which is the reference conveyance state, the transfer slit printing unit 6 always coincides with the center of the transfer slit position sensors 5K, 5Y, 5M, and 5C. , 2Y, 2M, and 2C, the distance to the write start position in the main scanning direction is always constant at A as shown in FIG.
[0025]
On the other hand, in FIG. 4B, which is meandering, the intermediate transfer belt 3 meanders by the meandering amount shown in FIG. 4B, and the meandering amount is transferred to the transfer slit position sensors 5K, 5Y, and 5M. , 5C, as shown in (b-2) of FIG. When the intermediate transfer belt 3 meanders by + Δa displacement in the main scanning direction (x direction in the figure), it is detected as + Δa by the transfer slit position sensors 5K, 5Y, 5M, and 5C. This + Δa is fed back to the image writing control unit as a meandering displacement amount, and the image writing timing in the main scanning direction is changed from the A amount in the reference transport state to the A + Δa amount. By this correction, when the intermediate transfer body is moved in a meandering manner as shown in FIG. 4B, the writing start position of the laser beam to be exposed on the photosensitive drums 2K, 2Y, 2M, and 2C is shifted to the intermediate transfer body. It is controlled to the position changed by the meandering amount. By such control, the output image formed on the photographic paper S, which is the final output, can be corrected without correcting other control timings by correcting the writing start position to be exposed by the meandering conveyance of the intermediate transfer belt 3. Thus, an output image in which the vertical line skew has been corrected can be obtained.
[0026]
In the present invention, an intermediate transfer belt having a slit-shaped transfer slit printing section prepared in advance in a non-image area on the transfer surface of the intermediate transfer belt is used, and a transfer slit position sensor is arranged at a position facing the transfer slit printing section. By detecting the position of the slit printing section in the main scanning direction with this sensor, the amount of meandering displacement of the intermediate transfer belt is detected. Based on the detected amount of displacement, the writing start position is corrected. Problems such as vertical line skew to an output image due to conveyance can be solved. According to the image forming apparatus described in claim 1 of the present application, the above-described effects can be obtained.
[0027]
FIG. 5 is a block diagram illustrating a configuration of a control unit in the image forming apparatus according to the present invention.
[0028]
In a copying machine of an image forming apparatus, for example, a full-color image forming apparatus, when a job request is received from a scanner unit for reading an image to be copied and a printer driver unit for transferring a job signal from a host, each form is changed. The image signal is transferred to the image writing control unit.
[0029]
The transferred image signal is input to an image signal generation unit constituting an image writing control unit. On the other hand, engine control information (number of processed images, image size, application, etc.), which is job information requested by the engine control unit that controls the operation of the entire image forming apparatus as well as the image writing control unit, is also input to the image writing control unit. Is done.
[0030]
In the image signal generation unit, the input image signal is subjected to image processing by processing according to the engine control information. At this time, in order to actually develop the image on the photographic paper, the image signal generation unit performs processing with a pixel clock signal (wclk) that defines the minimum pixel used for image formation. The pixel clock signal generates a clock signal (wclk) having a predetermined frequency based on information from the engine control unit such as the resolution and the linear speed of the photosensitive drum in the pixel clock generation unit, and sends the clock signal (wclk) to the image signal generation unit and the multiplication circuit unit. Is entered. The real image signal processed by the image signal generation unit is input to the writing position control unit.
[0031]
The writing position control unit includes a synchronization detection signal (DETP) from a synchronization detection unit of the laser writing device, a meandering detection signal (Δa) from a transfer slit position sensor on the intermediate transfer belt, and engine control from the engine control unit. Information is entered.
[0032]
The synchronization detection signal (DETP) is a signal for keeping the writing start position in the main scanning direction constant when exposing the laser beam onto the photosensitive drum. This signal is an output signal from a synchronization detection plate disposed outside the scanning area on the photosensitive drum of the laser beam reflected and deflected by the polygon mirror in the laser writing device. Of light-receiving elements serve as a synchronization detection sensor, and the synchronization detection sensor photoelectrically converts an incident laser beam and outputs a synchronization detection signal (DETP).
[0033]
The meandering detection signal (Δa) is a signal indicating the meandering amount during the conveyance of the intermediate transfer belt, and is a signal obtained by detecting the position of the transfer slit printing portion on the intermediate transfer belt in the main scanning direction by the transfer slit position sensor. The write position control unit combines the synchronization detection signal (DETP) with the actual image signal from the image signal generation unit at a predetermined timing to generate a signal for driving the semiconductor laser as a light source. At this time, the start timing of writing the real image signal from the synchronization detection signal is controlled according to the meandering detection signal (Δa). The meandering correction clock signal (dclk) obtained by multiplying the pixel clock signal (wclk) generated by the pixel clock generation unit is input to the writing position control unit. The meandering correction clock signal (dclk) is a signal having a higher frequency than the pixel clock signal obtained by multiplying the pixel clock signal (wclk) that defines the minimum pixel on which an image can be formed. The meandering correction clock signal (dclk) is a clock signal having a frequency corresponding to the detection resolution of the transfer slit position sensor, and one clock of the meandering correction clock signal (dclk) corresponds to one resolution of the transfer slit position sensor. I have. The meandering detection signal (Δa) from the transfer slit position sensor is detected, and the synchronization detection signal (DETP) and the meandering detection signal (Δa) are input to the writing position control unit. Assuming that A (= N × wclk) is from the synchronization detection signal when the meandering detection signal (Δa) is 0 to the start position of the actual image signal in the main scanning direction, the synchronization detection is performed when Δa> 0 is detected. The delay time from the signal to the actual image writing timing is changed to A + Δa × dclk, and the actual image writing start position is delayed when there is no meandering conveyance. On the other hand, when Δa <0, the delay time is set to A−Δa × dclk, and the actual image writing start timing is relatively advanced.
[0034]
The laser driving signal synthesized by the writing position control unit is input to the laser driving unit. The semiconductor laser mounted on the laser drive unit is repeatedly driven to turn on / off by turning on / off the laser drive signal. A laser beam emitted by driving the semiconductor laser enters a laser writing device, passes through and reflects a plurality of lenses, mirrors, and the like, and travels along an optical path. The laser beam is rotated and deflected by a polygon mirror disposed in the middle of the optical path, and the photosensitive drum is exposed to a laser beam in the main scanning direction. The process from this exposure to obtaining an output image is as described above.
[0035]
By controlling the actual image writing start timing from the synchronization detection signal according to the meandering detection signal as described above, the writing position of the toner image formed on the photosensitive drum is changed, and the toner image is formed on the intermediate transfer belt. Since the color composite image is formed at a position reflecting the meandering amount of the intermediate transfer belt, an output image with corrected vertical line skew can be obtained without correcting other control timings. Further, the actual image writing start timing is controlled by a meandering correction clock signal having a higher frequency than the pixel clock, so that the meandering amount of the intermediate transfer belt can be corrected with high accuracy. According to the image forming apparatus described in claim 2 of the present application, the above effects can be obtained.
[0036]
FIG. 6 is a flowchart illustrating how an image forming position is corrected by meandering conveyance in the image forming apparatus according to the present invention.
[0037]
First, when the start switch of the copy application is pressed or the print operation from the host is enabled to start each print job, the image signal generation unit performs image processing on the actual image signal as described above. At the same time, the intermediate transfer belt is driven to rotate. Before adjusting the timing with the photographic paper, which is the final output, the semiconductor laser is driven to start the writing process in order to detect the synchronization detection signal which is the writing reference position in the main scanning direction. On the intermediate transfer belt, the position of the transfer slit printing section on the intermediate transfer belt is detected by the transfer slit position sensor, and is output to the writing position control section as a meandering detection signal (Δa). On the other hand, in the synchronization detection section, the synchronization detection sensor detects the synchronization detection signal (DETP) and outputs the same to the image signal generation section and the writing position control section. The writing position control unit controls the writing start timing (reference: A) of the actual image signal based on the input meandering detection signal (Δa). When Δa = 0, the laser beam writing is started with the current write start timing (A) because the reference transfer state is such that there is no meandering transfer of the intermediate transfer belt. When Δa> 0, the meandering conveyance of the intermediate transfer belt causes the belt to meander from the front end side in the main scanning direction toward the rear end side. Therefore, the time until the image writing timing for the synchronization detection signal (DETP) is delayed by Δa × dclk from the current state to A + Δa × dclk. Conversely, if Δa <0, the belt is meandering from the rear end to the front end in the main scanning direction due to the meandering conveyance of the intermediate transfer belt. Control to make it faster. That is, A-Δa × dclk is set. By forming this correction loop, the writing position of the toner image formed on the photosensitive drum is meandered, but is formed on the intermediate transfer belt because it matches the meandering property of the intermediate transfer belt. As the toner image, an image without meandering is formed. Further, the correction loop makes it possible to correct a vertical skew caused by a sudden meandering conveyance having no periodicity in real time. According to the image forming apparatus described in claim 3 of the present application, the above effects can be obtained.
[0038]
【The invention's effect】
According to the first aspect of the present invention, in an image forming apparatus having an intermediate transfer body to which toner images are sequentially transferred by a transfer device, slit printing is performed beforehand on a transfer surface that is a non-image forming area of the intermediate transfer body. The position of the portion is detected by a transfer slit position sensor disposed opposite thereto, and the meandering amount of the intermediate transfer body is detected based on the detected amount.
[0039]
The transfer surface of the intermediate transfer body is formed with high precision surface accuracy in order to transfer the original intended toner image with high quality, so the slit printing part on the transfer surface is a conventional image forming device. It is possible to detect the meandering amount with higher accuracy than the detection of the end position of the intermediate transfer member in, and it is possible to correct the meandering amount of the intermediate transfer member based on the detected meandering amount.
[0040]
Further, an image forming process for detection may be added by detecting a portion printed on the intermediate transfer member in advance without forming a new meandering amount detection pattern for detecting the meandering amount of the intermediate transfer belt. Thus, it is possible to provide an image forming apparatus capable of detecting the meandering conveyance of the intermediate transfer member and correcting the meandering conveyance.
[0041]
According to the second aspect of the present invention, in an image forming apparatus having an intermediate transfer body to which a toner image is sequentially transferred by a transfer device, a slit prepared in advance on a transfer surface of a non-image forming area of the intermediate transfer body The displacement of the printing unit is detected with high accuracy by the transfer slit position sensor, fed back to the image writing control unit, and controlled by a clock signal having a higher frequency than the clock signal used for image formation, thereby meandering the intermediate transfer body. It is possible to correct the amount with a high precision of the minimum pixel unit or less. Further, the image writing control unit corrects the image writing start position based on the detected displacement of the sensor due to the meandering conveyance of the intermediate transfer body, so that the vertical position of the output image can be corrected without correcting the driving system such as the transfer conveyance unit. An image forming apparatus capable of correcting a line skew defect can be provided.
[0042]
Still further, according to the third aspect of the present invention, in an image forming apparatus having an intermediate transfer body to which a toner image is sequentially transferred by a transfer device, a meandering detecting a position of a slit printing portion pre-printed on the intermediate transfer body. The meandering detection signal from the displacement reading device is fed back to the image writing control unit that controls the writing position of the actual image in the previous stage, and the image writing start position in the main scanning direction is corrected in real time, so that the image is transferred in the actual image forming area. It is possible to provide an image forming apparatus capable of correcting a vertical line skew of an image on paper and simultaneously correcting an actual image position even when a periodic meandering meandering occurs.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus having an intermediate transfer member according to the present invention.
FIG. 2 is a perspective view showing a schematic configuration around an intermediate transfer member of the image forming apparatus according to the present invention.
FIG. 3 is a diagram illustrating a positional relationship between an intermediate transfer member, a meandering displacement reading device, and a photosensitive member of the image forming apparatus according to the present invention.
FIG. 4 is a schematic diagram illustrating an example of meandering conveyance of an intermediate transfer member corresponding to FIG. 3;
FIG. 5 is a block diagram illustrating a configuration of a control unit in the image forming apparatus according to the present invention.
FIG. 6 is a flowchart showing how an image forming position is corrected by meandering conveyance in the image forming apparatus according to the present invention.
[Explanation of symbols]
1K, 1Y, 1M, 1C laser writing device
2K, 2Y, 2M, 2C Photoconductor drum
3 Intermediate transfer belt
4 Intermediate transfer roller
5K, 5Y, 5M, 5C Transfer slit position sensor
6 Transfer slit printing section
7K, 7Y, 7M, 7C developing device
8 Intermediate transfer belt cleaning device
9 Paper feeder
10 Transfer device
11 Fixing device
12 Paper ejection device
S photographic paper

Claims (3)

A writing optical system using a semiconductor laser diode as a light source, a photoconductor that forms an electrostatic latent image with a laser beam emitted from the writing optical system, and forms a toner image visualized from the electrostatic latent image; An intermediate transfer member that is disposed opposite to the photoreceptor and sequentially transfers the toner images by a transfer device; and collectively transfers a plurality of color toner images sequentially transferred on the intermediate transfer member to a transfer sheet that is a recording medium. An image forming apparatus including a transfer device;
A slit-shaped slit printing unit, which is printed in advance on a main scanning end portion on a transfer surface that is a non-image area of the intermediate transfer body and is printed in parallel with the conveyance direction of the intermediate transfer body, A meandering displacement reading device comprising a transfer slit position sensor for detecting the position,
An image forming apparatus, wherein an image writing position from a writing optical system is corrected based on a meandering displacement amount output from the meandering displacement reading device. The image writing start position in the main scanning direction can be image-formed based on the amount of displacement from the meandering displacement reading device that has detected the position of the slit printing section pre-printed on the transfer surface, which is a non-image area of the intermediate transfer body. 2. The image forming apparatus according to claim 1, wherein the correction is performed with an accuracy equal to or less than a minimum unit pixel size. The image writing start position in the main scanning direction is corrected in real time based on the amount of displacement from the meandering displacement reading device that has detected the position of the slit printing unit pre-printed on the transfer surface that is a non-image area of the intermediate transfer body. The image forming apparatus according to claim 1, wherein:

Images