JP2004157330A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image in a determined area of paper at all times by adjusting an image forming position on the paper even if an environmental change occurs. <P>SOLUTION: The image forming apparatus having an image carrier belt 2 which circulates via the image forming position where a toner image is formed, and carries the toner image formed at the image forming position is provided with: a displacement amount detection part 20 which detects an amount of displacement of the image carrier belt 2 in the width direction of the belt 2 which crosses the direction of the movement of the belt 2 and in a transfer position where the toner image is transferred onto a recording medium; and an alignment adjustment part 30 which adjusts the image forming position on a recording medium in the width direction thereof on the basis of the amount of displacement detected by the displacement amount detection part 20. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus capable of adjusting the alignment of an image formed on a sheet using an endless belt such as an intermediate transfer belt or a photosensitive belt.
[0002]
[Prior art]
2. Description of the Related Art Image forming apparatuses that transfer a toner image carried by a moving endless belt onto a sheet are widely used because there are many types of sheets that can be used.
[0003]
For example, image formation in which a single-color toner image formed on a plurality of photosensitive drums is sequentially multiplex-transferred to a circulating intermediate transfer belt and the formed multi-color toner image is transferred onto a sheet to form a color image 2. Description of the Related Art There are known apparatuses and image forming apparatuses that form a color image by transferring a multicolor toner image formed by repeating exposure and development on a circulating photosensitive belt to a sheet.
[0004]
In such an image forming apparatus, if the circulating movement speed of the endless belt fluctuates, or if the distance between the image forming positions where the monochromatic toner images are formed is shifted, the multicolor toner images formed on the endless belt are colored. Since the displacement may occur, the displacement of the multi-color toner image carried by the endless belt is avoided by controlling the moving speed of the endless belt or controlling the interval between the image forming positions with high accuracy. .
[0005]
Also, the members constituting the image forming apparatus may expand or contract due to environmental fluctuations, or may cause color misregistration due to deformation or the like due to external force.Therefore, by forming a registration mark and detecting it with a detector, Image position deviation, scanning line inclination, magnification error deviation, and the like in the sub-scanning direction and the main scanning direction are corrected by adjusting the image writing timing and the like.
[0006]
However, if the image forming process is paused and the registration correction is executed, the image forming efficiency is reduced. Therefore, the registration correction is controlled based on the environmental temperature information so that unnecessary registration correction is not performed. (See Patent Document 1).
[0007]
On the other hand, since the endless belt is stretched around a plurality of rolls including a driving roll and circulates, the endless belt is affected by tolerances such as a belt size, a roll diameter, and a roll mounting angle, and displaces the endless belt in the roll axis direction. Force acts. For this reason, the endless belt meanders in the roll axis direction to find a stable position where the force is balanced. This meandering movement is performed when multiple transfer of each color toner image formed on the photosensitive drum to the intermediate transfer belt, or when the multiple transferred multiple color toner image is transferred to paper, or when multiple transfer is performed on the photosensitive belt. When a color toner image is formed, or when the multi-color toner image is transferred onto a sheet, a color shift occurs in the main scanning direction. If the meandering movement becomes severe, the belt may be damaged.
In addition, when the edge position of the endless belt is detected by the displacement sensor and the roll inclination is controlled based on the detection result, the error due to the edge shape of the endless belt is removed to improve the accuracy. Some are also available (see Patent Document 2).
[0008]
[Patent Document 1]
Patent No. 2625130 (Solution problem, solution, FIG. 1)
[Patent Document 2]
JP-A-11-295948 (paragraph numbers 0026 to 0035, figures, paragraph numbers 0042 to 0045, FIGS. 7 to 9)
[0009]
[Problems to be solved by the invention]
The image position on the paper is adjusted at the time of shipment, and is in a desired alignment state. However, since the size of the endless belt and the diameter of the tension roll change due to changes in the environmental temperature and humidity, color shift adjustment and steering control are performed to form a multicolor toner image without color shift on the endless belt. However, at the transfer position where the multicolor toner image is transferred onto the paper, the endless belt may pass through a position deviated from the initial expected position, and the multicolor toner image is transferred to one end of the paper with a bias. However, there is a problem that the alignment changes.
[0010]
That is, at a position where the monochromatic toner images are sequentially superimposed on the endless belt and transferred, or at a position where the toner images are sequentially superimposed and formed, the steering control is performed in the vicinity, so that the endless belt moves straight. However, at the transfer position to the paper, which is a distance from the position where the steering control is performed, if the environmental temperature and humidity change, the belt is deformed. The image is transferred to a position shifted in the width direction.
[0011]
FIG. 1 is a schematic front view showing a tandem type image forming apparatus using an intermediate transfer belt.
[0012]
The image forming apparatus shown in FIG. 1 is arranged in series with four photosensitive drums 1 on which toner images are formed, and is stretched over a roll 3 to contact each of the photosensitive drums 1 at a primary transfer position. While circulating in the direction of arrow A to form a nip portion between the intermediate transfer belt 2 on which the toner image is sequentially multiplex-transferred and the intermediate transfer belt by a pair of rolls, and the toner primarily transferred on the intermediate transfer belt. And a secondary transfer device 4 for secondary-transferring an image onto a sheet P. The intermediate transfer belt 2 is controlled by a roll 3 a disposed at a position adjacent to the most downstream photosensitive drum 1 a in the direction of arrow A. Have been.
[0013]
FIG. 2 is a schematic side view showing a portion from the roll position to be controlled by steering to the vicinity of the secondary transfer device in FIG. 1. FIG. 2A shows a state in which the intermediate transfer belt is not deformed. (b) shows a state in which the intermediate transfer belt is deformed due to an environmental change.
[0014]
As shown in FIG. 2A and FIG. 2B, a toner image without color shift is formed on the intermediate transfer belt 2 by color shift adjustment and steering control. The sheet P sent to the secondary transfer position passes through the same position of the pair of rolls in the secondary transfer device 4. However, since the intermediate transfer belt 2 is deformed due to environmental change, the position passing through the pair of rolls is B. Deviate in the direction.
[0015]
FIG. 3 is a diagram showing a formation position of an image formed by the secondary transfer of a toner image onto a sheet. FIG. 3A shows a case where the intermediate transfer belt is not deformed. Indicates a case where the intermediate transfer belt is deformed.
[0016]
When the intermediate transfer belt is not deformed, the image 5 adjusted by the color misregistration adjustment function of the image forming apparatus is formed at a position adjusted by the image position adjustment as shown in FIG. Is done. However, if the intermediate transfer belt is deformed due to environmental changes, the position of the intermediate transfer belt in the axial direction passing through the secondary transfer position is shifted even for an image adjusted by the color shift adjustment function. As shown in FIG. 3B, the alignment of the image 5 is shifted in the direction of the arrow B by the shifted amount.
[0017]
The magnitude of this deviation is experimentally measured to be, for example, about 100 μm with respect to a temperature change of about 10 degrees.
[0018]
In view of the above circumstances, the present invention provides an image using an endless belt that can always form an image at a fixed position on a sheet by adjusting the image forming position on the sheet even if an environmental change occurs. It is an object to provide a forming device.
[0019]
[Means for Solving the Problems]
The image forming apparatus of the present invention that achieves the above object includes an image carrier belt that circulates while passing through an image forming position where a toner image is formed, and carries the toner image formed at the image forming position. An image forming apparatus that forms an image on a recording medium by transferring and fixing the toner image on the image carrier belt onto a recording medium,
A displacement amount detection unit that detects a displacement amount in a width direction intersecting the moving direction of the image carrier belt at a transfer position where the toner image is transferred onto a recording medium;
An alignment adjustment unit that adjusts the formation position of the image formed on the recording medium in the width direction on the recording medium based on the displacement amount detected by the displacement amount detection unit. I do.
[0020]
As described above, the displacement amount in the width direction of the image carrier belt is detected by the displacement amount detection unit, and based on the displacement amount, the position in the width direction of the image transferred and fixed on the recording medium is determined in advance. Since the adjustment is performed, an image can always be formed at a fixed position on the recording medium even if the position in the width direction of the image carrier belt moves due to an environmental change.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the image forming apparatus of the present invention will be described.
(1st Embodiment)
FIG. 4 is a schematic configuration diagram illustrating the image forming apparatus according to the first embodiment.
[0022]
The image forming apparatus shown in FIG. 4 includes four photoconductor drums 1 arranged in series, on which a toner image is formed, and four photoconductor drums stretched over a driving roll 10, a driven roll 11, and an opposing roll 12. The intermediate transfer belt 2 circulates in the direction of arrow A while contacting each of them at a primary transfer position, and the color toner images formed on the four photosensitive drums 1 are sequentially multiplex-transferred; A secondary transfer device 4 that forms a nip portion by sandwiching the sheet P with a pair of rolls, and secondary-transfers the multi-color toner images multiplex-transferred onto the intermediate transfer belt 2 onto the sheet, and a sheet that stores the sheet P A registration roll 7 for correcting the skew of the tray 6 and the paper drawn from the paper tray 6) and sending out the paper P whose skew has been corrected to the nip portion of the secondary transfer device 4 at a predetermined timing; It includes sandwiching a plurality of colors sheet P on which the toner image is transferred, and a fixing device 8 for forming an image by fixing a plurality toner image on the sheet by heating and pressing a plurality of colors toner image by.
[0023]
Each of the four photosensitive drums 1 includes a charger (not shown) that uniformly charges the photosensitive drum 1 and a laser beam that modulates input image data for each color component to emit a laser beam to uniformly charge the photosensitive drum 1. An exposing unit 9 for forming an electrostatic latent image by scanning exposure light in the width direction; and a developing unit (not shown) for forming a monochromatic toner image on the photosensitive drum 1 by applying toner to the electrostatic latent image And Each of the developing devices holds yellow (Y), magenta (M), cyan (C), and black (K) toners, and each of the four photosensitive drums 1 has a YMCK color. A single color toner image is formed.
[0024]
The toner images for each of the YMCK colors are sequentially transferred onto the intermediate transfer belt 2 in a multiplex manner, and are also transferred onto a sheet P. The multicolor toner images on the sheet P are further fixed by a fixing device 8 to form a color image. Is done.
[0025]
Here, it is not always necessary to form a toner image on all four photosensitive drums 1; for example, a black and white image can be formed by forming only a K color toner image.
[0026]
The image forming apparatus of the present embodiment includes a color misregistration adjusting unit 15 that adjusts color misregistration of a multicolor toner image formed by multiple transfer on the intermediate transfer belt 2 sequentially. At one end of the shaft of the driven roll 11, a steering control unit (not shown) for adjusting the displacement of the intermediate transfer belt 2 and four photosensitive drums 1 downstream of the photosensitive drum 1a at the most downstream in the direction of arrow A, respectively. And a color misregistration detection sensor 16 for detecting a color misregistration detection toner image transferred from the printer 1 to the intermediate transfer belt 2. Then, a color misregistration detection toner image is formed at a predetermined timing, and the color misregistration detection sensor 16 detects the toner image. Based on the detection result, the timing of the laser beam emitted from the exposure unit 9 to each photosensitive drum 1 is determined. The color misregistration is adjusted by adjusting the color shift.
[0027]
Further, in the image forming apparatus according to the present embodiment, after the color misregistration adjustment unit 15 performs color misregistration adjustment and sequentially transfers the single-color toner images onto the intermediate transfer belt 2, the width of the intermediate transfer belt 2 due to a temperature change or the like. A displacement amount detection unit 20 that detects a change in direction (hereinafter, referred to as a “displacement amount”), and a position in the scanning direction of a monochromatic toner image formed on each photosensitive drum 1 in accordance with the displacement amount. And an alignment adjustment unit 30 that is shifted from each other by the same predetermined amount.
[0028]
The displacement amount detection unit 20 includes an edge sensor 21 for detecting an edge of the intermediate transfer belt on the upstream side of the secondary transfer device in the direction of arrow A, and an edge sensor 21 on the upstream side of the photosensitive drum disposed at the most upstream position in the direction of arrow A. A rotation detection sensor 22 for detecting the rotation by a mark provided on the intermediate transfer belt, and based on the detection result of the edge sensor 21 and the detection result of the rotation detection sensor 22, the intermediate transfer at the secondary transfer position. The amount of displacement of the transfer belt 2 in the width direction is detected.
[0029]
In the present embodiment, the alignment adjusting unit 30 shifts the scanning timing of the exposure light emitted from each exposure unit 9 toward each photosensitive drum 1 in the scanning direction by a fixed amount according to the amount of displacement to thereby adjust each photosensitive unit. The position of the monochromatic toner image formed on the body drum 1 is shifted.
[0030]
Therefore, the color misregistration adjusting unit 15 has a function of individually adjusting the position at which the single-color toner image formed on each photosensitive drum 1 is transferred onto the intermediate transfer belt 2 for each photosensitive drum 1. The difference is that the alignment adjusting unit 30 has a function of shifting the position of the monochromatic toner image formed on each photosensitive drum 1 in the scanning direction by the same predetermined amount.
[0031]
As described above, the displacement amount of the intermediate transfer belt 2 at the secondary transfer position is detected by the displacement amount detection unit 20, and the alignment adjustment unit 30 adjusts the amount of the exposure light applied to each photosensitive drum 1 from each of the exposure units 9. Since the scanning timing in the main scanning direction is simultaneously shifted, the positions of the monochromatic toner images formed on the respective photosensitive drums 1 are mutually shifted by the same predetermined amount (hereinafter, referred to as “alignment adjustment amount”). The positions of the multicolor toner images on the intermediate transfer belt 2 are also shifted by a predetermined amount in the width direction of the intermediate transfer belt 2, and when the images are transferred onto the paper P at the secondary transfer position, the images are arranged at predetermined positions on the paper P can do.
[0032]
In the present embodiment, the case where a color image is formed by a tandem-type image forming apparatus using an intermediate transfer belt has been described.However, the present invention is not limited to the case where a color image is formed. Applied. Further, the image forming apparatus does not need to be limited to an apparatus using an intermediate transfer belt, but is also applicable to an image forming apparatus using a photosensitive belt.
[0033]
FIG. 5 is a block diagram illustrating a configuration of the displacement amount detection unit.
[0034]
As shown in FIG. 5, the displacement amount detection unit 20 includes an edge sensor 21 for detecting an edge of the intermediate transfer belt, a rotation detection sensor 22 for detecting that the intermediate transfer belt has made one rotation, and a reference for the intermediate transfer belt. A belt reference position storage unit 23 that stores a detection value of the edge sensor when acquiring the position, a belt edge detection unit 24 that samples a detection value detected by the edge sensor 21, and a belt edge detection unit 22 that detects the position. A belt average position calculating unit 25 for averaging the detection values sampled by the belt edge detecting unit 24 based on the rotation time of the intermediate transfer belt and calculating an average detected value, and an average calculated by the belt average position calculating unit 25. A belt displacement calculator 26 that calculates a difference between the detected value and the reference detection value stored in the belt reference position storage unit 23 to obtain a displacement amount; A displacement amount calculated by the calculating unit 26 and a correction amount calculation unit 27 that converts the alignment adjustment amount.
[0035]
The alignment adjustment amount converted by the correction amount calculation unit 27 is sent to the alignment adjustment unit 30, and the alignment of the image on the paper is adjusted.
[0036]
Here, the alignment adjustment amount in the present embodiment uses the number of pixels that shifts the position where an electrostatic latent image is written by irradiating a laser beam from the exposure unit to the photosensitive drum, but is not limited to this.
[0037]
FIG. 6 is a diagram illustrating a method of setting a reference detection value stored in a belt reference position storage unit of the displacement amount detection unit.
[0038]
In FIG. 6, when the image forming apparatus is assembled, the position of the image formed on the paper is adjusted in the shipping inspection (S-1). When the image formation position adjustment is completed, the average detection value of the edge sensor is calculated, the reference detection value of the intermediate transfer belt at the secondary transfer position is obtained, and stored in the belt reference position storage unit (S-2). If the image forming apparatus has been used for a long time and parts exchange related to image formation has been performed or maintenance has been performed by a serviceman (S-3), it is determined whether or not image forming position adjustment is necessary (S-4). If the image formation position adjustment is necessary, the image formation position adjustment is performed (S-5). When the image formation position adjustment is completed, the average detection value of the edge sensor is calculated, and the intermediate transfer belt at the secondary transfer position is calculated. Is obtained and stored in the belt reference position storage unit (S-6).
[0039]
On the other hand, when the image forming position adjustment is not necessary, the reference detection value that has been set is maintained as it is (S-7). The reference position can be obtained at an arbitrary timing as long as the adjustment of the color misregistration is completed. For example, when the image forming position is adjusted according to a request of a customer or the like, the reference position may be obtained at that time.
[0040]
7A and 7B are diagrams illustrating an example of an edge sensor. FIG. 7A is a diagram illustrating an edge sensor in which a light source and a light receiving sensor are in the same direction. FIG. 7B is a diagram illustrating a light source and a light receiving sensor. FIG. 3 is a diagram showing an edge sensor in which the directions are different from each other.
[0041]
As shown in FIG. 7, the intermediate transfer belt 2 is stretched around one roll 12 of the secondary transfer device (the other roll is omitted here). An edge sensor 21 that detects the edge of the intermediate transfer belt 2 is provided upstream or downstream of the roll 12.
[0042]
The edge sensor 21 shown in FIG. 7A is of a type in which reflected light of light emitted from the light source 21a toward the intermediate transfer belt 2 is received by a light receiving sensor 21b. When displaced, the amount of received light increases, and when displaced in the direction of arrow C ', the amount of received light decreases. Therefore, the amount of displacement can be detected from the amount of received light.
[0043]
In the edge sensor 21 shown in FIG. 7B, a light source 21a and a light receiving sensor 21b are opposed to each other with the intermediate transfer belt 2 interposed therebetween, and light emitted from the light source 21a toward the intermediate transfer belt 2 is detected by a light receiving sensor 12b. It is of a type that directly receives light, and the amount of received light decreases when the intermediate transfer belt 2 is displaced in the direction of arrow C, and the amount of received light increases when displaced in the direction of arrow C '. Therefore, the amount of displacement can be detected based on the amount of received light.
[0044]
Here, an LED, an LD, or the like can be used as the light source 21a. Further, a CCD, a position sensor (PSD), or the like can be used as the light receiving sensor 21b. Here, an edge sensor is used to determine the amount of displacement of the belt, but for example, a mechanism for detecting a mark position on the belt in the width direction or a mechanism for detecting the position of an image drawn on the belt. Is also good. However, in the latter case, the mechanism for detecting the image is arranged upstream of the secondary transfer position.
[0045]
The edge sensor 21 preferably detects an edge of the intermediate transfer belt 2 at a secondary transfer position where a multicolor toner image on the intermediate transfer belt 2 is transferred onto a sheet. However, since it is difficult to arrange the edge sensor 21 at the secondary transfer position due to space restrictions, the edge sensor 21 is arranged at the upstream side or the downstream side of the secondary transfer position, and the steering control unit is used. When the intermediate transfer belt 2 passes through a driven roller whose widthwise deviation is corrected, the moving distance from the intermediate transfer belt 2 to the secondary transfer position is L1, and the intermediate transfer belt 2 passes through the driven roller. , The movement distance to the position where the edge is detected by the edge sensor 21 is L2, and the detection value of the edge sensor is T2, the detection value T1 of the edge sensor at the secondary transfer position is T1 = T2 It can be obtained by conversion from the relational expression of × L1 / L2.
[0046]
FIG. 8 is a diagram illustrating a specific method for determining the amount of displacement of the intermediate transfer belt.
[0047]
In FIG. 8, the vertical axis represents the edge position of the intermediate transfer belt detected by the edge sensor, and the horizontal axis represents the elapsed time. The left waveform in the figure is used for shipping inspection, parts replacement, and the like. The image forming position adjustment is performed, and the edge position when the reference position at which the intermediate transfer belt passes through the secondary transfer position is set is shown. The waveform in the center in the figure indicates the intermediate transfer during normal image formation. The right waveform in the figure represents the edge position of the belt, and the edge position of the intermediate transfer belt when the temperature change is large.
[0048]
As shown in the figure, the detection value obtained by detecting the edge of the circulating intermediate transfer belt with the edge sensor is not only when the environmental temperature and humidity greatly fluctuate, but also during normal image formation and reference position setting. The detection value generally differs when the detection time differs. Therefore, it is necessary to detect the edge position over at least one rotation of the intermediate transfer belt and average the detected values.
[0049]
For example, a reference mark is provided on the intermediate transfer belt, and the time interval at which the reference mark is detected by the rotation sensor is determined as the rotation time of the intermediate transfer belt. The displacement amount detection unit may calculate the average detection value by sampling the detection value detected by the edge sensor at regular intervals, and averaging the sampled detection value over the orbiting time. it can. In this case, the average may be obtained by excluding the maximum value and the minimum value among the detected values as abnormal values.
[0050]
The displacement amount detection unit obtains a reference average detection value immediately after image formation position adjustment is performed among the calculated average detection values, and stores the reference average detection value in the memory. By calculating the difference between the average detected value in the above-mentioned method and the reference average detected value stored in the memory, the amount of displacement of the intermediate transfer belt can be obtained.
[0051]
Here, the peak-to-peak value of the detection value detected by the edge sensor of the present embodiment is about 100 μm, the displacement is less than 100 μm during normal image formation, and the displacement is 500 μm when the temperature change is large. When the displacement exceeds 100 μm, the adjustment of the formation position of the color image formed on the paper in the width direction of the intermediate transfer belt (hereinafter, referred to as “alignment adjustment”) is performed. However, the present invention is not limited to this.
[0052]
FIG. 9 is a flowchart illustrating the alignment adjustment according to the first embodiment.
[0053]
In FIG. 9, the edge of the intermediate transfer belt during image formation is detected by the edge sensor, and the detected value is sampled (S-11). Then, by detecting the mark provided on the intermediate transfer belt by the rotation sensor, the rotation time during which the intermediate transfer belt makes one rotation is detected, and the detection values sampled during the rotation time are averaged, and the average detection value is calculated. It is calculated (S-12). Further, the difference between the reference average detection value and the average detection value stored in the memory is calculated, the amount of displacement is obtained (S-13), and the obtained amount of displacement is converted into the number of pixels (S-14). It is determined whether the number of pixels obtained by converting the obtained displacement amount is equal to or more than the correction unit (S-15). If the number of pixels is equal to or larger than the correction unit, the exposure unit irradiates the photosensitive drum with the converted number of pixels. The timing is corrected, the writing position in the main scanning direction is shifted (S-16), a toner image is formed, and the image is output on paper (S-18). If less than the correction unit, the exposure unit does not correct the irradiation timing on the photosensitive drum (S-17), forms a toner image as it is, and outputs the image on paper (S-18). Hereinafter, the same processing is performed until the image formation is completed (S-19).
[0054]
FIG. 10 is a diagram illustrating a method of correcting the scanning timing of the exposure light emitted from the exposure unit to the photosensitive drum.
[0055]
In FIG. 10, a start signal is issued at positions (hereinafter, referred to as "writing positions") P1 and P2 where exposure light is irradiated in a scanning direction intersecting the process direction of the photosensitive drum and an electrostatic latent image is formed. By counting clock pulses based on the time T, writing is always started from a fixed position in the scanning direction of the photosensitive drum. The time during which the clock pulse is ON is a reference for laser lighting, and corresponds to one pixel. Therefore, the displacement detected by the displacement detector is converted into the number of clock pulses, and the number of clock pulses counted is corrected based on the time T at which the start signal is issued, so that the write positions P1 and P2 can be determined. It needs to be shifted.
[0056]
The writing positions P1 and P2 can be shifted in units of pixels, but if it is not necessary to shift in units of pixels, the number of pixels to be corrected is determined to be, for example, 3 pixels or 4 pixels, and the displacement amount is converted. When the value exceeds the number of pixels serving as the correction unit, the writing position may be shifted for each number of pixels serving as the correction unit.
[0057]
In this case, the alignment adjustment unit shifts the positions written from the respective exposure units to the respective photosensitive drums on which the monochromatic toner images of different colors are formed by the same number of pixels.
[0058]
Next, a second embodiment of the present invention will be described.
[0059]
The second embodiment is different from the first embodiment in that the alignment adjustment unit adjusts the alignment by moving the registration roll to shift the sheet delivered to the secondary transfer position in the width direction. Although they differ, the other points are common, and therefore the differences will be described.
[0060]
FIG. 11 is a schematic configuration diagram illustrating an image forming apparatus according to the second embodiment.
[0061]
The image forming apparatus according to the present embodiment includes a driving unit that moves the registration roll in the axial direction as compared with the image forming apparatus according to the first embodiment illustrated in FIG. However, the difference is that the registration roll is moved in the axial direction, but the other points are common. Therefore, the same components are denoted by the same reference numerals, and redundant description will be omitted.
[0062]
The registration roller 7 of the image forming apparatus illustrated in FIG. 11 includes a driving unit (a motor here) (not illustrated) that reciprocates the registration roller 7 in a width direction intersecting the sheet feeding direction. The image forming apparatus further includes a color misregistration adjustment unit 15 that adjusts color misregistration of a multicolor toner image formed by multiple transfer on the intermediate transfer belt 2 sequentially. And a steering control unit (not shown) for adjusting the displacement of the intermediate transfer belt 2, and the four photosensitive drums 1 on the intermediate transfer belt 2 from the four photosensitive drums 1 a downstream of the most downstream photosensitive drum 1 a in the direction of arrow A. A color misregistration detection sensor 16 for detecting the transferred color misregistration detection toner image.
[0063]
Further, in the image forming apparatus of the present embodiment, the displacement amount for detecting the displacement amount of the intermediate transfer belt 2 after the color misregistration adjustment unit 15 performs the color misregistration adjustment and sequentially transfers the monochromatic toner images onto the intermediate transfer belt 2. The image forming apparatus includes a detection unit 20 and an alignment adjustment unit 30 that adjusts a formation position of an image formed on the sheet P by moving the registration roll 7 in the axial direction according to the displacement amount.
[0064]
Here, the registration roll 7 of the present embodiment corresponds to the recording medium sending section of the present invention, and has a shift function of being moved by being driven by the driving section. The paper tray may be any as long as it can be moved to a predetermined position, for example, a paper tray provided with a slide mechanism.
[0065]
When the displacement amount detection unit 20 detects a displacement amount exceeding a certain amount, the alignment adjustment unit 30 drives the drive unit to move the registration roll 7 by the amount of displacement of the intermediate transfer belt 2. For this reason, the position of the sheet P sent to the secondary transfer position also moves in accordance with the passing position of the intermediate transfer belt 2, so that the multicolor toner image can be transferred to a predetermined position on the sheet P. .
[0066]
In the present embodiment, the case where a color image is formed by a tandem-type image forming apparatus using an intermediate transfer belt has been described.However, the present invention is not limited to the case where a color image is formed. Applied. Further, the image forming apparatus does not need to be limited to an apparatus using an intermediate transfer belt, but is also applicable to an image forming apparatus using a photosensitive belt.
[0067]
FIG. 12 is a diagram illustrating a method of moving the position of the sheet to be sent to the secondary transfer position.
[0068]
In FIG. 12, the intermediate transfer belt 2 circulates and moves between nips formed by a pair of rolls (one of the rolls is omitted) 12 of the secondary transfer device 4. On the upstream side of the secondary transfer device 4, a registration roller 7 including a pair of rolls and having a side shift mechanism, which is driven by the driving unit 31 and moves in the direction of arrow CC ′, is provided.
[0069]
The skew of the sheet P fed from the sheet tray is corrected by abutting against the registration roll 7 or a side guide, and further, the registration roll 7 is pressed by an arrow C- By sliding in the direction C ', the position of the sheet P is slid in the direction of the arrow CC'. The sliding amount is adjusted by moving the driving unit 31 so as to match the displacement amount of the intermediate transfer belt detected by the displacement amount detecting unit.
[0070]
For example, when a stepping motor is used for the drive unit 31, the displacement is converted into the number of clock pulses of the stepping motor or the number of reference clocks of the timer, and the stepping motor is rotated by the converted number of clocks. It can be adjusted by sliding the registration roll 7.
[0071]
FIG. 13 is a flowchart illustrating the alignment adjustment according to the second embodiment.
[0072]
In FIG. 13, the edge of the intermediate transfer belt during image formation is detected by the edge sensor, and the detected value is sampled (S-21). Then, by detecting the mark provided on the intermediate transfer belt with the rotation sensor, the rotation time during which the intermediate transfer belt makes one rotation is detected, and the detection values sampled during the rotation time are averaged, and the average detection value is calculated. It is calculated (S-22). Further, a difference between the reference average detection value and the average detection value stored in the memory is calculated, a displacement amount is obtained (S-23), and the obtained displacement amount is converted into a reference clock number of the timer (S- 24). It is determined whether the reference clock number obtained by converting the obtained displacement amount is equal to or larger than the correction unit (S-25). If it is equal to or greater than the correction unit, the stepping motor is rotated by the number of converted clocks to slide the registration roll, and at the same time, slide the paper P to send it out to the secondary transfer position (S-26). The color toner image is transferred and an image is output (S-28). If it is less than the correction unit, the paper P is sent out without sliding the registration roll (S-17), and a multi-color toner image is transferred and an image is output (S-28). Hereinafter, the same processing is performed until the image formation is completed (S-29).
Even if a shift in the width direction of the intermediate transfer belt at the secondary transfer position occurs due to an environmental change, the shift amount is detected by the displacement amount detection unit, and the alignment adjustment unit detects the shift amount corresponding to the shift amount. Since the sheet to be sent to the next transfer position can be shifted, when a multicolor toner image is transferred onto the sheet P at the secondary transfer position, an image can be arranged at a predetermined position on the sheet P.
[0073]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the edge of the belt at the secondary transfer position is detected, and the forming position of the image formed on the paper is adjusted based on the detection result. Therefore, the image is always printed at a predetermined position on the sheet even if the position of the belt in the width direction changes due to an environmental change.
[Brief description of the drawings]
FIG. 1 is a schematic front view showing a tandem type image forming apparatus using an intermediate transfer belt.
FIG. 2 is a schematic side view illustrating a portion from a roll position to be subjected to steering control to a vicinity of a secondary transfer device.
FIG. 3 is a diagram illustrating a formation position of an image formed by secondary transfer of a toner image onto a sheet.
FIG. 4 is a schematic configuration diagram illustrating the image forming apparatus according to the first embodiment.
FIG. 5 is a block diagram illustrating a configuration of a displacement amount detection unit.
FIG. 6 is a diagram illustrating a method of setting a reference detection value stored in a belt reference position storage unit of the displacement amount detection unit.
FIG. 7 is a diagram illustrating an example of an edge sensor.
FIG. 8 is a diagram showing a specific method for determining the amount of displacement of the intermediate transfer belt.
FIG. 9 is a flowchart illustrating alignment adjustment according to the first embodiment.
FIG. 10 is a diagram illustrating a method of correcting the irradiation timing of exposure light irradiated from the exposure unit to the photosensitive drum.
FIG. 11 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment.
FIG. 12 is a diagram illustrating a method of moving a position of a sheet to be sent to a secondary transfer position.
FIG. 13 is a flowchart illustrating alignment adjustment according to the second embodiment.
[Explanation of symbols]
1,1a Photoreceptor drum
2 Intermediate transfer belt
3,3a roll
4 Secondary transfer device
5 images
6 Paper tray
7 cash register roll
8 Fixing device
9 Exposure section
10 Drive roll
11 Follower roll
12 Opposing roll
15 Color shift adjustment unit
16 Color shift detection sensor
20 Displacement detector
21 Edge sensor
22 Orbit detection sensor
23 Belt reference position storage unit
24 Belt edge detector
25 Belt average position calculator
26 Belt displacement calculator
27 Correction amount calculator
30 Alignment adjustment unit
31 Drive unit

Claims (9)

An image carrier belt that circulates while passing through an image forming position where the toner image is formed, and carries the toner image at the image forming position; By transferring and fixing, in an image forming apparatus that forms an image on the recording medium,
A displacement amount detection unit that detects a displacement amount in a width direction intersecting the moving direction of the image carrier belt at a transfer position where the toner image is transferred onto a recording medium,
An image forming apparatus, comprising: an alignment adjustment unit configured to adjust a formation position of the image on a recording medium in the width direction based on the displacement amount detected by the displacement amount detection unit. The image carrier belt circulates while sequentially passing through a plurality of image forming positions, and carries a multi-color toner image in which respective single-color toner images formed at the plurality of image forming positions are sequentially superimposed. And
2. The image according to claim 1, wherein the image forming position further includes a color misregistration adjustment unit that adjusts color misregistration of the multicolor toner images sequentially superimposed on the image carrier belt. Forming equipment. Sending a recording medium to the transfer position, comprising a recording medium sending unit that is movable in a width direction crossing the sending direction of the recording medium,
The alignment adjusting section is configured to adjust the formation position of the image in the width direction on a recording medium by moving the recording medium sending section in the width direction according to the displacement amount. The image forming apparatus according to claim 1. A plurality of image forming units that form each single-color toner image at the plurality of image forming positions,
The alignment adjustment unit shifts the formation position in the width direction of the single color toner image formed by each of the plurality of image forming units with respect to the plurality of image forming units by a predetermined amount according to the displacement amount. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The plurality of image forming units, each having an exposure unit that exposes the charged photoconductor while scanning the exposure light in the width direction,
The image forming apparatus according to claim 4, wherein the alignment adjustment unit shifts the formation position in the width direction by a predetermined amount by shifting a scan timing of exposure light emitted from the exposure unit. . The image forming apparatus according to claim 1, wherein the displacement amount detection unit includes an edge sensor that detects an edge of the image carrier belt. The displacement amount detection unit has an edge sensor that detects an edge of the image carrier belt, and the displacement amount is determined based on a detection value of the edge sensor when an image forming position on a recording medium is adjusted. 3. The image forming apparatus according to claim 2, wherein the image is detected. 7. The displacement amount detection unit according to claim 6, wherein the displacement amount is obtained by averaging detection values detected by the edge sensor during at least one circulation of the image carrier belt. 8. The image forming apparatus according to 7. The color misregistration adjustment unit has a belt position correction unit that corrects the position deviation of the image carrier belt in the width direction,
The displacement amount detector is configured to move the image carrier belt to the transfer position after the image carrier belt passes through the belt position correction unit, and to detect the edge after the image carrier belt passes through the belt position correction unit. The image forming apparatus according to claim 7, wherein the displacement amount is obtained based on a ratio to a distance moved to a position detected by the sensor.

Images