JP5594054B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a digital multifunction machine having at least two of these functions.

  In recent years, electrophotographic color image forming apparatuses using an intermediate transfer belt have become mainstream. Among them, the “tandem method”, which has a photoconductor for each color and sequentially superimposes it on the intermediate transfer belt, transfers the primary transfer image of each color onto the intermediate transfer belt, and then intermediates the transfer material in synchronization with the timing. This is a system in which a primary transfer image is transferred from a transfer belt onto a recording sheet, and a secondary transfer image is transferred to the recording paper.

  However, since the full-color image must be superimposed on the intermediate transfer belt at one time and each color toner image must be placed at an accurate position without color misregistration, it is very high especially for the conveyance speed and surface undulation of the intermediate transfer belt. Accuracy is required. In order to keep the transfer speed of the intermediate transfer belt constant, the outer diameter accuracy of the support roller and drive roller provided inside the intermediate transfer belt, the friction coefficient, and the belt tension of the intermediate transfer belt itself are kept constant. Rotation control technology for high-precision driving, shift prevention technology, etc. are required. Also, in order to suppress the undulation of the surface of the intermediate transfer belt, the belt is hardened while keeping the shape of the inner roller by placing the intermediate transfer belt in a state where tension is applied to the intermediate transfer unit. ”Was a major issue.

  If an endless belt that is wound around two or more rollers is left in tension for a long time, the endless belt portion of the roller will be curled due to the curvature of the roller. The state (level) differs depending on the material of the endless belt to be used, the roller diameter, the winding angle around the roller, and the like. In particular, in a tandem-type color image forming apparatus, a pattern for adjusting the position of each color is created for color matching by using the surface of an endless belt, and a pattern for adjusting image density is created. The toner density on the paper is adjusted, but if the endless belt has large curl wrinkles and the pattern position and the curled part match, the pattern is read with a sensor. As a result, various correction accuracy deteriorates, and color misregistration and density variation may occur.

  As a method for preventing the occurrence of curl wrinkles, for example, Patent Document 1 is configured such that an endless belt wound around a plurality of rollers when an image is not formed can be rotated in a reverse direction to that when an image is formed, and a return regulation position is set. A method of reducing the tension of the endless belt between the return drive position and the return restriction position by providing another roller that is configured to be defined and cannot be rotated in reverse is disclosed. However, even if the tension of the endless belt can be somewhat reduced, depending on the belt material, when the endless belt is left for a long period of time or a small diameter roller is used, the occurrence of curl wrinkles cannot be completely prevented. Further, when a large tension reduction mechanism is provided, the mechanism becomes complicated, the manufacturing cost increases, and the apparatus cannot be downsized.

  In the image forming apparatus disclosed in Patent Document 2, the curl correction roller that corrects the curl wrinkles contacts and pressurizes the intermediate transfer roller from the outside only for a predetermined time after the intermediate transfer belt is allowed to stand to correct the curl wrinkles. It is characterized by performing. However, when there are a plurality of curl wrinkles, it is difficult to correct all the curl wrinkles in a short time. Further, since it is necessary to provide a curl correction roller driven by a solenoid outside the intermediate transfer belt, the manufacturing cost increases.

  Patent Document 3 proposes a method of separating the secondary transfer roller from the secondary transfer belt when the secondary transfer belt is left for a long period of time in order to suppress the occurrence of curl wrinkles. Occurrence of curling of the secondary transfer belt caused by the roller and the driven roller in the secondary transfer belt in the vicinity thereof is suppressed. However, in this method, as in Patent Document 2, no consideration is given to curl wrinkles on the secondary transfer belt that may be caused by other driven roller portions. In addition, it is necessary to provide a proximity separation mechanism for the secondary transfer roller.

  Therefore, in view of these conventional techniques, the present invention provides an image forming apparatus in which erroneous detection and correction variations do not occur when reading various adjustment patterns by a sensor even when the endless belt is curled. Let it be an issue.

According to the present invention, the present invention provides an image carrier that carries a toner image such as a position adjustment pattern and a density adjustment pattern for color matching created by the toner image forming unit, and at least two rollers. A rotatable endless belt wound around, a transfer means for transferring a toner image on the image carrier onto the surface of the endless belt, a curl portion of the endless belt formed by the roller, and the transfer means. Detecting means for detecting the position adjusting pattern and / or the density adjusting pattern transferred on the surface of the endless belt, and the curling by the detecting means by rotating the endless belt at least once. When the curled portion is detected, the position adjustment pattern and / or the curling portion is not overlapped with the curled portion. Create a serial density adjustment pattern, the at the time of the endless belt stopped, the curled portion and to stop the endless belt so that the position of the rollers forming this match, the while the endless belt is rotated 1 When the curled portion is not detected, the position adjusting pattern and / or the density adjusting pattern is created at an arbitrary position of the endless belt, and when the endless belt is stopped, the endless belt is hung around each roller before starting rotation. The problem can be solved by stopping the endless belt so that the place where it has been moved deviates from each roller .

  The distance between the rollers is preferably larger than the length of the position adjustment pattern and / or the density adjustment pattern in the traveling direction of the endless belt.

  Further, in the detection operation of the curled portion, immediately after the first curled portion is detected, the position adjusting pattern and / or the density adjusting pattern are created so as not to overlap the first curled portion, and the endless pattern is created. When the belt is stopped, it is preferable that the endless belt is stopped so that the position of the first curled portion and the roller forming the same coincide.

Further, from the distance between the detection means and each roller and the linear speed of each roller, a time from when the endless belt starts to rotate until the detection means detects each curled portion is obtained in advance. It is preferable to determine by which of the rollers each detected curled portion is attached by comparing the time until each curled portion is actually detected.
Further, it is preferable that the distances between the rollers are all the same.

In addition, when the endless belt is stopped, it is preferable that the endless belt is stopped so that each curled portion or a portion corresponding to each curled portion coincides with the nearest roller that passes next.
Moreover, it is preferable that the diameter of each roller is the same.

Further, the position adjustment pattern and / or before the image formation after the start-up of the apparatus when the endless belt is left for a long time or before the image formation after the transition to the energy saving mode when the endless belt is left for a long time. Alternatively, when the density adjustment pattern is created and these adjustments are made, it is preferable to perform the curl detection operation.
Further, it is preferable that the detection operation of the curled portion can be switched by a user.

  According to the present invention, the endless belt is rotated at least once to detect the curled portion by the detecting means. When the curled portion is detected, the position adjusting pattern and / or the density adjusting pattern is set so as not to overlap the curled portion. Since the pattern is created, the fluctuation in the output of the pattern reading value of the detecting means due to the influence of the curled portion is also suppressed, the erroneous detection of the pattern is prevented, and as a result, the correction accuracy is improved. In addition, when the endless belt is stopped, the endless belt is stopped so that the positions of the curled portion and the roller forming the curled portion coincide with each other, so that the curled portion can be prevented from being attached to different portions on the endless belt.

1 is a schematic configuration diagram of an indirect transfer tandem color image forming apparatus. FIG. 3 is a schematic diagram illustrating an intermediate transfer member that is an endless belt wound around three rollers. FIG. 6 is a diagram illustrating a relationship between output voltage of a sensor and time on an intermediate transfer body on which a curl wrinkle is formed. FIG. 6 is a diagram illustrating a relationship between the output voltage of a sensor and time when a toner pattern for position adjustment is formed between the curl ridges 504 and the curl ridges 502; It is the schematic which shows another intermediate transfer body hung around four rollers. 5 is a flowchart showing a processing procedure from the start of operation of the intermediate transfer member to the stop of operation of the intermediate transfer member.

FIG. 1 schematically shows an example of an indirect transfer tandem color image forming apparatus 1. First, the image forming apparatus 1 will be described.
In the color image forming apparatus 1, the apparatus main body 100 is placed on a paper feed table 200 as illustrated. A scanner 300 is mounted on the apparatus main body 100, and an automatic document feeder (ADF) 400 is mounted thereon. In the apparatus main body 100, a transfer device having an endless belt-like intermediate transfer member 10 is provided in the approximate center thereof. The intermediate transfer member 10 includes a driving roller 14 driven by a driving source (not shown) and two driven rollers. It is stretched between 15 and 16, and rotates clockwise in FIG.

  The intermediate transfer member 10 used in the present invention may have a multilayer structure or a single layer structure. If it has a multilayer structure, the base layer is made of, for example, a fluororesin with little elongation, a PVDF sheet (polyvinylidene fluoride sheet) or a polyimide resin, and the surface is covered with a smooth coat layer such as a fluorine resin, In the case of a single layer, some materials such as PVDF (polyvinylidene fluoride), PC (polycarbonate), PI (polyimide) are used. In the present invention, it is not necessary to specify the material of the intermediate transfer member 10 in particular.

  The intermediate transfer body 10 is configured such that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15. Yellow (Y), magenta (M), and cyan along the direction of movement of the intermediate transfer member 10 above the linear portion spanned between the driving roller 14 and the driven roller 15 of the intermediate transfer member 10. (D) Four drum-shaped photoconductors 40Y, 40M, 40C, and 40Bk (hereinafter simply referred to as photoconductors 40 if not specified) of black (Bk) are arranged at predetermined intervals. . Further, four primary transfer rollers 58 as transfer means are provided inside the intermediate transfer member 10 so as to sandwich the intermediate transfer member 10 so as to face the respective photosensitive members 40 as image bearing members.

Each of the four photoconductors 40 can rotate counterclockwise in FIG. 1, and around each photoconductor 40 is a charging device, a developing device 60, the above-described primary transfer roller 58, and the photoconductor. A cleaning device and a static elimination device are provided, and each constitutes an image forming unit 18. A common exposure device 21 is provided above the four image forming units 18.
Each image (toner image) formed on each photoconductor is sequentially transferred onto the intermediate transfer body 10 in a superimposed manner.
On the other hand, on the lower side of the intermediate transfer member 10, a secondary transfer device 22 including a transfer unit that transfers an image on the intermediate transfer member 10 to a sheet as recording paper is provided. The secondary transfer device 22 has a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, 23, and the secondary transfer belt 24 is driven by a driven roller 16 via an intermediate transfer body 10. It comes to be pressed against.

The secondary transfer device 22 collectively transfers the toner images on the intermediate transfer member 10 onto a sheet fed between the secondary transfer belt 24 and the intermediate transfer member 10.
A fixing device 25 for fixing the toner image on the sheet is provided downstream of the secondary transfer device 22 in the sheet conveying direction, and a pressure roller 27 is pressed against the fixing belt 26 which is an endless belt. .
The secondary transfer device 22 also functions to convey the sheet after image transfer to the fixing device 25. Further, the secondary transfer device 22 may be a transfer device using a transfer roller or a non-contact charger. A sheet reversing device 28 is provided below the secondary transfer device 22 for reversing the sheet when images are formed on both sides of the sheet.

As described above, the apparatus main body 100 constitutes an indirect transfer tandem color image forming apparatus 1.
When color copying is performed by the color image forming apparatus 1, a document is set on the document table 30 of the automatic document feeder 400. When the document is manually set, the automatic document feeder 400 is opened, the document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed.

  When a start key (not shown) is pressed, when the document is set on the automatic document feeder 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

  Further, the intermediate transfer body 10 starts to rotate by pressing the start key described above. At the same time, the photoconductors 40Y, 40M, 40C, and 40K start rotating, and yellow (Y), magenta (M), cyan (C), and black (Bk) single color toners are formed on the photoconductors. The operation for forming an image is started. The toner images of the respective colors formed on the respective photoreceptors are sequentially transferred while being superimposed on the intermediate transfer body 10 that rotates clockwise in FIG. 1, and a full-color composite color image is formed there. Is done.

  On the other hand, when the start key is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the sheet is fed out from one selected paper feed cassette 44 in the paper bank 43. Then, it is separated into one sheet by the separation roller 45 and conveyed to the sheet feed path 46. The sheet is conveyed by a conveying roller 47 to a sheet feeding path 48 in the apparatus main body 1, hits a registration roller 49 and temporarily stops.

In the case of manual sheet feeding, the sheet set on the manual tray 51 is fed by the rotation of the sheet feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual sheet feeding path 53. Then, it hits the registration roller 49 and temporarily stops.
The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer body 10, and feeds the temporarily stopped sheet between the intermediate transfer body 10 and the secondary transfer device 22. . Then, a color image is transferred onto the sheet by the secondary transfer device 22.

The sheet on which the color image has been transferred is conveyed to a fixing device 25 by a secondary transfer device 22 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. Thereafter, the sheet is guided to the discharge side by the switching claw 55, is discharged onto the discharge tray 57 by the discharge roller 56, and is stacked there.
When the double-sided copy mode is selected, the sheet on which an image is formed on one side is conveyed to the sheet reversing device 28 side by the switching claw 55, reversed there and led to the transfer position again, and this time the image is formed on the back side. After that, the paper is discharged onto the paper discharge tray 57 by the discharge roller 56.
On the other hand, the residual toner remaining on the intermediate transfer body 10 after the image transfer is removed from the intermediate transfer body 10 after the image transfer by the cleaning device 17 to prepare for re-image formation by the tandem image forming apparatus.

  In addition to the copying operation described above, various adjustments are made to maintain a stable output image in the image forming apparatus. Although these adjustments are conventionally performed and will not be described in detail, for example, regarding color misregistration of the toner images of the respective colors, the photosensitive member 40 which is a position adjusting pattern forming unit for each color is applied onto the intermediate transfer member 10. A pattern for adjusting the position of each color is created, and these are detected by an optical reflective sensor (not shown), which is a detection means arranged opposite to the pattern for position adjustment, and the interval is determined based on the output of the sensor. The degree of deviation from the ideal is calculated and corrected. The position adjustment pattern for each color for color matching is recognized as a pattern when the output voltage of the optical reflective sensor exceeds a certain value. As for image density adjustment, a density adjustment pattern for each color is created on the intermediate transfer body 10 by the photoconductor 40 which is a density adjustment pattern forming unit for each color, and is read by the same or different optical reflective sensor. Based on the output of the sensor, each condition relating to the density is corrected so that a stable density can be maintained. Japanese Patent Application Laid-Open No. 2004-228561 details a method of performing process control using a density correction pattern and a positional deviation correction pattern.

  As such an optical reflective sensor, several types of optical sensors are known, and a reflective sensor in which an LED as a light emitting element and a photodiode (PD) or a phototransistor (PTr) as a light receiving element are combined. Generally known. The sensor configuration includes a type that detects only specularly reflected light (see Patent Document 4), a type that detects only diffusely reflected light (see Patent Documents 5 and 6), and a type that detects both (see Patent Document 7). There are three types.

  By the way, the intermediate transfer member 10 is provided with a roller due to the belt material to be used, the tension of the endless belt by the inner and outer support rollers of the endless belt, or by leaving the endless belt under tension for a long time. The curl will occur at the point where In addition, the case where it is left for a long time means the case where it is left for one week or more, for example. As shown in FIG. 3, when an endless belt portion with a curled wrinkle is read by an optical reflective sensor, the belt surface is curved at this portion, so the direction of reflected light at this portion is the sensor. The reflected light received by the sensor deviates from this light receiving element. Therefore, the output voltage at this location is lower than the background portion of the flat intermediate transfer body 10. In this case, the curled portion is erroneously detected as a pattern, and there is a possibility that appropriate color misregistration correction cannot be performed.

  In addition, when adjusting image density, a method is often used in which toner patches with different levels of density are created on an endless belt, and the output voltage when the sensor is read by a sensor is converted to the amount of adhesion. If it overlaps with the curled part where the output voltage fluctuates, an output voltage on which the fluctuation amount of the background is added is obtained. This may also lead to erroneous detection of the toner adhesion amount. .

  Therefore, as a measure against curl wrinkles, there is a method of arranging a restraining member or a roller inside the endless belt. However, if a fixed pressing member is used, scratches and debris are generated inside the endless belt, and the product The service life is shortened, and there is a possibility that abnormal noise is generated by the vibration of the holding member facing the endless belt. In the case of a curved roller, it is necessary to attach the roller with high accuracy in order to maintain the positional relationship between light emission and light reception of the sensor. Even if a roller is provided, it may not be sufficiently corrected in the case of large curl wrinkles.

  Therefore, in the present invention, a configuration has been devised in which various adjustments using the position adjustment pattern and the density adjustment pattern are performed stably and reliably without being affected even when the intermediate transfer member 10 has a curl wrinkle. . The essence of the present invention is that a pattern is not formed at a portion with a curl ridge, and when the rotation of the intermediate transfer member is stopped, the intermediate transfer member is stopped by matching the curl ridge with the original roller, The curl must not be attached to. Accordingly, it is possible to suppress fluctuations in the output of the read value of the pattern by the sensor without being affected by the curl so as to prevent erroneous detection of the pattern.

  FIG. 2 is a schematic view showing the intermediate transfer member 10 that is an endless belt wound around three rollers 15, 14, and 16. Here, the distance between the axes of the rollers 15 and 14 is A (mm), the distance between the axes of the rollers 14 and 16 is B (mm), and the distance between the axes of the rollers 16 and 15 is C. (Mm), and the distances A, B, and C are different from each other. The distances A, B, and C are larger than the lengths of various adjustment toner pattern groups in the traveling direction of the intermediate transfer member 10. Further, an optical reflective sensor 501 for detecting curl wrinkles is disposed in the vicinity of the roller 14 between the roller 14 and the roller 16 and at a distance of D (mm) from the axis of the roller 16. ing. The sensor 501 also has a function of detecting a position adjustment pattern and a density adjustment pattern. As described above, the intermediate transfer member 10 that is wound around the three rollers 14, 15, and 16 may be curled in the region that is wound around the rollers. Here, reference numeral 502 denotes a curl hook attached by the roller 14, reference numeral 503 denotes a curl hook attached by the roller 15, and reference numeral 504 denotes a curl hook attached by the roller 16.

  Before entering the adjustment operation, as the curl wrinkle detection operation, first, the intermediate transfer member 10 is rotated once in the clockwise direction at a linear velocity V (mm / s), and the curl wrinkle is detected by the sensor 501. At this time, the curl scissors pass through the sensor 501 in the order of the curl scissors 502 attached by the roller 14, the curl scissors 503 attached by the roller 15, and the curl scissors 504 attached by the roller 16. Then, as shown in FIG. 3, since the output voltage of the sensor 501 that has detected the curl wrinkle portion changes, the occurrence of the curl wrinkle can be confirmed from the change in the output voltage. The position of the curl flange portion can be grasped from the elapsed time from the start of the rotation of the body 10.

  In FIG. 2, when the first curl hook 502 reaches below the sensor 501, this is detected by the sensor 501, and it is confirmed that the curl hook 502 is formed by the roller 14. Further, even if the curl ridge 502 is not formed by the roller 14 and the curl 503 of the roller 15 is first detected, this is based on the elapsed time from the start of the rotation of the intermediate transfer body 10. It is possible to determine which of the rollers on which the curl is attached. Similarly, even if the curl ridge 504 of the roller 16 is first detected, it can be determined from the elapsed time that this is the curl ridge 504 of the roller 16.

  In the present invention, since the intermediate transfer body 10 is rotated once, it is possible to grasp which curl wrinkle is formed or not. Accordingly, on the intermediate transfer body 10, the position adjustment pattern for each color and the density adjustment pattern for each color are arranged on the intermediate transfer body 10 so as to avoid the curl defects 502, 503, and 504 based on the position information of the curl defects 502, 503, and 504. The position and density can be corrected. For example, if the first curl wrinkles are detected and the second and third curl wrinkles are not detected, it is sufficient to avoid the first curl wrinkles and form the pattern. A pattern can also be formed in a portion corresponding to the above, the degree of freedom of pattern formation is widened, and the waiting time of the user can be shortened.

  In addition, the intermediate transfer member 10 is not necessarily rotated once, but immediately after any one of the curl wrinkles 502, 503, and 504 is detected by the sensor 501, the curl wrinkle is avoided on the intermediate transfer member 10. Various adjustment patterns may be created. In this case, a pattern is formed between the curl wrinkles detected first and the curl wrinkles that exist in the following cases, but it is not necessary to rotate the intermediate transfer member 10 once, so that the user wait time Can be shortened.

  Then, when the rotation of the intermediate transfer member 10 after the completion of various adjustment operations and the printing operation is stopped, the curl rods 502, 503, and 504 attach the curl rods based on the elapsed time and / or the position information of the curl rod. The intermediate transfer member 10 is controlled to stop again on the same rollers 14, 15, 16. Thereby, it is possible to avoid the curl wrinkles from being attached to different places on the intermediate transfer member 10, and it is possible to reliably create various adjustment patterns between the curl wrinkles. Accordingly, the curl of the intermediate transfer member 10 and various adjustment patterns are prevented from overlapping, the output fluctuation of the sensor reading value due to the influence of the curl of the intermediate transfer member 10 is suppressed, and erroneous detection of various adjustment patterns is prevented. As a result, the correction accuracy is improved.

  Moreover, you may comprise the diameter of each roller 14,15,16 the same. As a result, the size of the curl wrinkles formed becomes uniform, so that the accuracy of detection of the curl wrinkles by the sensor and the superposition of the curl wrinkles and the rollers when the rotation of the intermediate transfer body 10 is stopped is improved.

  Further, from the distances A, B, and C (mm) between the rollers 14, 15, and 16, the distance D (mm) from the roller 16 to the sensor 501, and the linear velocity V (mm / s) of each roller, an intermediate transfer member is obtained. The time until the sensor 501 detects each curl flaw after the start of rotation of the sensor 10 can be calculated in advance. By comparing this time with the time until the curl wrinkle is actually detected, the detected curl is detected. It is possible to reliably determine with which roller the scissors are attached.

  On the other hand, from the distances A, B, and C (mm) between the rollers 14, 15, and 16, the distance D (mm) from the roller 16 to the sensor 501, and the linear velocity V (mm / s) of each roller, an intermediate transfer member. By observing only the elapsed time since the start of rotation of 10, it is possible to grasp the position where each existing curl must be. Therefore, regardless of whether or not the curl wrinkle is detected by the sensor 501, that is, without using the sensor 501, between the curl hook 502 and the curl hook 503, between the curl hook 503 and the curl hook 504, or between the curl hook 504 and the curl hook 504. Various adjustment patterns can be created during 502. Then, when the rotation of the intermediate transfer body 10 is stopped, the portions of the curl ridges 502, 503, and 504 that exist in some cases are stopped again on the original rollers 14, 15, and 16 only based on the elapsed time. The intermediate transfer member 10 may be controlled.

  Further, when curl wrinkles are not detected during one rotation of the intermediate transfer body 10, there is no possibility of erroneous detection due to curl wrinkles. Therefore, the adjustment operation is started by starting the creation of an adjustment pattern at an arbitrary position after one rotation. Is executed normally, and it is possible to continue to maintain high-quality images. In this case, when the intermediate transfer member 10 is stopped, the intermediate transfer member 10 can be stopped at an arbitrary position, and the waiting time of the user is shortened. Furthermore, at the time of this stop, the intermediate transfer member 10 may be stopped based on the elapsed time from the start of rotation so that the portion wound around the roller before the start of rotation of the intermediate transfer member 10 deviates from the roller. As a result, the formation of curled wrinkles at specific locations on the intermediate transfer member 10 can be avoided.

  Although not shown, the intervals between the rollers may be set to be the same, and the three rollers may be arranged at the positions of the apexes of the regular triangle. In this case, after the intermediate transfer member is rotated once and each curl is detected by the sensor, or any one of the three curls is detected by the sensor, or the curl is not detected. However, an adjustment pattern may be created between the curl ridges and the curl ridges based on only the elapsed time. In this case, when the intermediate transfer member is stopped, it is not necessary to match each curl ridge with each roller forming the curl ridge, and the intermediate transfer member 10 is stopped so that each curl ridge coincides with the nearest roller that passes next. Just do it. At this time, depending on the case, all the existing curl ridges stop at the three roller positions. Thereby, the time for rotating the intermediate transfer member 10 is shortened, and the waiting time for the user is shortened.

FIG. 4 is a diagram showing the relationship between the output voltage of the sensor and the time when a toner pattern for position adjustment is formed between the curl ridge 504 and the curl ridge 502 while avoiding the curl ridge 504.
Although not shown in the drawing, as the toner pattern for position adjustment, four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) extending on the intermediate transfer member 10 in the direction orthogonal to the traveling direction are provided. A horizontal line of four lines and four diagonal lines of yellow (Y), magenta (M), cyan (C), and black (Bk) extending at an angle of 45 ° from the traveling direction are formed at predetermined intervals. In the portion of four horizontal lines (not shown) of each color formed between the curl ridge 504 and the curl ridge 502, the reflected light is considerably less than the background portion of the intermediate transfer body 10, so that the output is as shown in the figure. The voltage is also considerably smaller than the background portion, so that these portions are detected as a pattern. In addition, in the portion of four diagonal lines (not shown) of each color, the output voltage is small although not as long as four horizontal lines.

  On the other hand, since the position of the curl ridges 504 and 502 can be grasped by the elapsed time regardless of the sensor 501 or the sensor 501, the toner pattern group can be formed so as to avoid them. At this time, as described above, the distances A, B, and C are larger than the lengths of the toner pattern groups for various adjustments in the traveling direction of the intermediate transfer member 10, so that the eight toner pattern groups are curled toes 504 and 502. There is no overlap. Further, in the illustrated example, the output voltage of the toner pattern for position adjustment and the output voltage of the curl ridge are shown in an easy-to-understand manner. However, a toner pattern for density adjustment is formed between the curl ridges, or A toner pattern for density adjustment may be formed.

  FIG. 5 is a schematic view showing another intermediate transfer member 10 wound around four rollers 602, 603, 604, and 605. Here, the distance between the axes of the rollers 603 and 602 is A (mm), the distance between the axes of the rollers 602 and 605 is B (mm), and the distance between the axes of the rollers 605 and 604 is C. (Mm), the distance between the axes of the rollers 604 and 603 is D (mm), and the distances A, B, C, and D are different from each other. The distances A, B, C, and D are larger than the lengths of various adjustment toner pattern groups in the traveling direction of the intermediate transfer member 10. An optical reflective sensor 601 for detecting curl wrinkles is disposed in the vicinity of the roller 602 between the rollers 602 and 605 and at a distance of E (mm) from the axis of the roller 605. ing. The sensor 601 also has a function of detecting a position adjustment pattern and a density adjustment pattern. Here, 606 is a curl tack attached by the roller 602, 607 is a curl tack attached by the roller 603, 608 is a curl tack attached by the roller 604, and 609 is a roller 605. It is a curl stick attached by.

  Also in this case, as an operation for detecting curl wrinkles before entering the adjustment operation, first, the intermediate transfer member 10 is rotated once in the clockwise direction at a linear velocity V (mm / s), and the curl wrinkles are detected by the sensor 601. Do. At this time, the curl hooks are in the order of the curl hook 606 attached by the roller 602, the curl hook 607 attached by the roller 603, the curl hook 608 attached by the roller 604, and the curl hook 609 attached by the roller 605. Passes through sensor 601. Then, as in FIG. 3, the output voltage of the sensor 601 that has detected the curl wrinkle portion changes, so that the occurrence of the curl wrinkle portion can be confirmed from the change in the output voltage. The position of the curl flange portion can be grasped from the elapsed time from the start of the rotation of the body 10. In addition, as in the embodiment of FIG. 2, the positional relationship between each roller and the sensor, such as the distances A, B, C, D between the rollers and the sensor distance E from the roller 605, and the belt linear velocity V are grasped. Thus, the position of the intermediate transfer member 10 and the position of each curl can be grasped. Therefore, by grasping the elapsed time from the start of rotation of the intermediate transfer body 10, it is possible to determine which roller the detected curl is attached to.

  Therefore, after the intermediate transfer member 10 is rotated once and each curl ridge 606, 607, 608, 609 is detected by the sensor, or after any one of the four curl ridges is detected by the sensor, or Based on only the elapsed time without detecting curl wrinkles, an adjustment pattern is created on the intermediate transfer body 10 so as to avoid curl wrinkles from the position information of each curl wrinkle, and the position and density are corrected. Just do it.

  When the rotation of the intermediate transfer member 10 is stopped after various adjustment operations and printing operations, the curl rods 606, 607, 608, and 609 are changed to the curl rods 606, 607, 608, and 609 based on the elapsed time and / or the position information of the curl rods by the sensor. The intermediate transfer member 10 may be controlled to stop again on the same rollers 602, 603, 604, and 605 with ridges.

  If the diameters of the rollers 602, 603, 604, and 605 are configured to be the same, the size of the curl wrinkles formed becomes uniform. Therefore, when the curl wrinkles are detected by the sensor and the intermediate transfer body 10 is stopped. The accuracy of superimposing the curl and roller in the is improved.

  Further, when the curl wrinkle is not detected while the intermediate transfer body 10 makes one rotation, there is no possibility of erroneous detection due to the curl wrinkle. Therefore, the image can be surely started by starting the creation of the adjustment pattern at an arbitrary position after one rotation. It becomes possible to maintain the quality. In this case, when the intermediate transfer member 10 is stopped, the intermediate transfer member 10 can be stopped at an arbitrary position, and the waiting time of the user is shortened. Furthermore, at the time of this stop, the intermediate transfer member 10 may be stopped based on the elapsed time from the start of rotation so that the portion wound around the roller before the start of rotation of the intermediate transfer member 10 deviates from the roller. As a result, the formation of curled wrinkles at specific locations on the intermediate transfer member 10 can be avoided.

  Although not shown, the intervals between the rollers may be set to be the same, and the four rollers may be arranged at the positions of the apexes of the square. In this case, the intermediate transfer member is rotated once and each curl is detected, or any one of the four curls is detected by the sensor, or the curl is not detected. Based on only the time, an adjustment pattern may be created between the curl and the curl and the adjustment may be performed. When the intermediate transfer member is stopped, it is not necessary for each curl to coincide with each roller that forms the curl, and the intermediate transfer member 10 can be stopped so that each curl coincides with the nearest roller that passes next. That's fine. At this time, depending on the case, all the existing curl ridges coincide with the four roller positions and stop. Thereby, the time for rotating the intermediate transfer member 10 is shortened, and the waiting time for the user is shortened.

  The curl detection operation of the present invention is performed when various adjustments are always performed after the start-up of the image forming apparatus and before image formation when the intermediate transfer member is left for a long period of time, for example, one week or more. It is particularly effective when it is executed when adjustment is performed after the transition to the energy saving mode where the intermediate transfer member is left for a long time and before image formation. However, when the device is used frequently and the neglect period is short, it is expected that no curl wrinkles will be formed. In such a case, the curl wrinkle detection itself is set to a switchable mode, and the user, for example, forms an image. Switching from the operation panel of the apparatus may not be executed. Thereby, the waiting time of the user can be further reduced.

FIG. 6 is a flowchart showing a processing procedure from the start to the stop of the operation of the intermediate transfer member in the present invention.
First, the intermediate transfer member is rotated until a time equal to or longer than one rotation of the intermediate transfer member has elapsed, and the position of the curl wrinkle is confirmed by a sensor (step S1). Next, since the position of each curl wrinkle can be grasped from the elapsed time from the start of rotation of the intermediate transfer member and the detection of the curl wrinkle portion by the sensor, various adjustment patterns are created so as not to overlap the detected curl wrinkles. (Step S2). After all, when no curl wrinkles are detected, it is not necessary to avoid the portion wound around the roller before the start of rotation, and a pattern is created at an arbitrary position on the intermediate transfer member. The time t (s) for one rotation of the intermediate transfer member is obtained from the length (mm) of the intermediate transfer member and the linear velocity (mm / s) of the roller. Instead of steps S1 and S2, a pattern may be created immediately after any one of the curl wrinkles is detected and between the curl wrinkles and the existing curl wrinkles in some cases. Further, in place of these steps S1 and S2, a pattern is formed so as to avoid the positions of all the existing curl wrinkles in some cases, without detecting the curl wrinkles by the sensor, without rotating the intermediate transfer member once. You may create it.

  Next, after completing the pattern reading, various corrections are performed (step S3), and a printing operation is performed (step S4). At this time, the printing operation may not be performed. After the printing operation, if one or more curl defects are detected in step S1, the intermediate transfer member is rotated until each detected curl defect coincides with the original roller, and stopped there (step S5). On the other hand, if the curl has not been detected in step S1 and the pattern has been created after the time of one rotation or more of the intermediate transfer member has elapsed, there is no curl on the intermediate transfer member. Immediately stop at the position (step S6).

  Further, instead of steps S1 and S2, a detection is also made in the case where a pattern is created between this curl crease and an existing curl crease immediately after any one curl crease is detected. The intermediate transfer member may be rotated until the curled wrinkles made coincide with the original rollers and stopped there. Further, in place of steps S1 and S2, a pattern is created so as not to detect the curl wrinkle by the sensor, to avoid the position of all the curl wrinkles that exist in some cases, without rotating the intermediate transfer member once. Even in this case, the intermediate transfer member may be rotated based on the elapsed time until the positions of all curl ridges existing coincide with the original roller and stopped there.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the optical reflective sensor may be attached at a different location, or the intermediate transfer member may be wound around five or more rollers. The configuration of each part of the image forming apparatus is also arbitrary. For example, the image forming apparatus is not limited to the tandem type, and an arbitrary image forming system such as a revolver system can be employed. The present invention can also be applied to a full color machine using three color toners, a multicolor machine using two color toners, or a monochrome apparatus. Of course, the image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile, or a multifunction machine having a plurality of functions.

1 Image forming apparatus 10 Intermediate transfer member (endless belt)
14, 15, 16, 602, 603, 604, 605 Roller 40 Photoconductor (image carrier)
58 Primary transfer roller (transfer means)
501, 601 Sensor (detection means)
502, 503, 504, 606, 607, 608, 609 Curl hook

JP 2001-215809 A JP 2010-66521 A JP 2009-300682 A Japanese Patent Application Laid-Open No. 2001-324840 JP-A-5-249787 Japanese Patent No. 315555 Japanese Patent Application Laid-Open No. 2006-139179

Claims (9)

An image carrier for carrying a toner image such as a position adjustment pattern and a density adjustment pattern for color matching created by the toner image forming means;
A rotatable endless belt wound around at least two rollers;
Transfer means for transferring a toner image on the image carrier onto the endless belt surface;
Image forming comprising: a curl portion of the endless belt formed by the roller; and a detection unit that detects the position adjustment pattern and / or the density adjustment pattern transferred onto the endless belt surface by the transfer unit. In the device
The endless belt is rotated at least once to detect the curled portion by the detecting means. When the curled portion is detected, the position adjustment pattern and / or the density adjustment is performed so as not to overlap the curled portion. Creating a pattern for use, and when the endless belt is stopped, the endless belt is stopped so that the position of the curl portion and the roller that has formed the same coincides ,
When the curled portion is not detected during one rotation of the endless belt, the position adjustment pattern and / or the density adjustment pattern is created at an arbitrary position of the endless belt, and when the endless belt is stopped The image forming apparatus is characterized in that the endless belt is stopped so that a portion hung around each roller before starting rotation is displaced from each roller .   2. The image forming apparatus according to claim 1, wherein a distance between the rollers is greater than a length of the position adjustment pattern and / or the density adjustment pattern in a traveling direction of the endless belt.   In the detection operation of the curled portion, immediately after the first curled portion is detected, the position adjusting pattern and / or the density adjusting pattern is created so as not to overlap the first curled portion, and the endless belt 3. The image forming apparatus according to claim 1, wherein the endless belt is stopped so that the position of the first curled portion coincides with a position of the roller that formed the first curled portion. From the distance between the detection means and each roller and the linear speed of each roller, a time from when the endless belt starts to rotate until the detection means detects each curled portion is obtained in advance, and the time is actually by the curled portion is to compare the time to is detected, one of the claims 1 to 3 in which each curl portion which is detected is characterized in that to determine what attached at any of the rollers one The image forming apparatus described in the item. The image forming apparatus according to any one of claims 1 to 4, the distance between the rollers, characterized in that all the same. 6. The image formation according to claim 5 , wherein when the endless belt is stopped, the endless belt is stopped so that each curled portion or a portion corresponding to each curled portion coincides with a nearest roller that passes next. apparatus. The image forming apparatus according to any one of claims 1 to 6, the diameter of the rollers is equal to or all the same. The position adjustment pattern and / or before the image formation after the start-up of the apparatus when the endless belt is left for a long time or before the image formation after the transition to the energy saving mode when the endless belt is left for a long time when performing these adjustments to create a density adjustment pattern, the image forming apparatus according to any one of claims 1 to 7, characterized in that the detection operation of the curling portion. The image forming apparatus according to any one of claims 1 to 8, the detection operation of the on-off of the curled portion is characterized in that it is switched by the user.

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