JP2008009173A - Image forming apparatus, control method for image forming apparatus, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stopping conveyance of sheet at the timing of easily removing the sheet, when a sheet jam may highly possibly occur. <P>SOLUTION: The image forming apparatus includes: image forming units 7 and 13 for forming a toner image; a transfer unit 8 for transferring the formed image to a sheet; a fixing unit 9 for fixing the transferred image to the sheet; a detection unit 25 disposed upstream of the fixing unit 9 in order to detect the sheet conveyed from the transfer unit 8 to the fixing unit 9; and a control unit 26 that determines whether to stop the conveyance of the sheet based upon a predetermined timing at which the sheet is detected by the detection unit 25, which is calculated from the timing of writing the image on the image forming units 7 and 13, and based upon the timing at which the sheet is actually detected by the detection unit 25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In recent years, tandem systems have been adopted in full-color copying machines, printers, and the like in order to shorten the image formation time on paper. In the image forming apparatus using the tandem method, a photosensitive drum is provided for each of magenta, cyan, yellow, and black dyes, which are sequentially arranged on the intermediate transfer belt. In the tandem image forming apparatus, the toner image formed on each photosensitive drum is primarily transferred and superimposed on the intermediate transfer belt, and the superimposed toner image is secondarily transferred to the sheet. It has been. Further, a registration roller is disposed on the upstream side of the secondary transfer roller to correct the oblique feeding of the paper.

  In such a tandem image forming apparatus, in order to shorten the time, the writing of an image to the upstream photosensitive drum is started before the sheet is conveyed from the sheet feeding cassette and arrives at the registration roller. . Then, for example, upon receiving an image writing signal to the black photosensitive drum, the paper is re-fed from the registration roller, and the leading edge of the paper reaches the secondary transfer roller at a predetermined timing.

  Therefore, for example, when a sheet is fed from a sheet feeding cassette by a sheet feeding roller, if a slippage occurs between the sheet feeding roller and the sheet and a conveyance delay of a predetermined amount or more occurs before reaching the registration roller, the sheet May reach the secondary transfer roller later than the transfer timing. In such a case, there is a possibility that the leading edge margin amount becomes smaller than the minimum leading edge margin amount and the paper is wound around the heat roller.

  On the other hand, conventionally, an image forming apparatus for monochrome printing is provided with a transfer roller facing the photosensitive drum, and a registration roller is disposed in a paper conveyance path on the upstream side of the transfer roller. In such an image forming apparatus, when a signal for starting printing (a start button or a print command from the CPU) is received, the sheet is fed from the sheet feeding cassette to the registration roller, and the sheet is temporarily held by the registration roller. Then, the sheet receives an image writing signal on the photosensitive drum and is conveyed to the transfer roller. Therefore, the delay due to the conveyance of the sheet from the sheet cassette is adjusted by the registration roller.

  However, even in monochrome printing, when the registration roller slips with the paper and a conveyance delay of a predetermined amount or more occurs before reaching the registration roller, the paper reaches the transfer roller later than the transfer timing. In some cases, there is a possibility that the sheet is wound around the heat roller although the frequency is less than that in the case of full color.

In order to detect such a paper jam that occurs when the paper rolls around the heat roller, a sensor is provided to detect the paper downstream of the fixing unit with reference to the paper transport direction, and within a predetermined time. An image forming apparatus that determines that a paper jam has occurred when a sheet is not sent from a fixing unit is disclosed (for example, see Patent Document 1).
JP-A-2005-77420

  However, in the conventional detection method, the sheet is detected after the sheet is wound around the heat roller. Even if the apparatus is stopped after the detection by the sensor, especially in the case of a small size sheet, the sheet is detected up to the end of the sheet. Since it winds on the heat roller, it becomes difficult for the user to easily remove the paper, leading to the generation of a service call.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming apparatus control method capable of suppressing the occurrence of a paper jam leading to a service call.

In order to solve the above problems, the first present invention provides:
An image forming unit for forming a toner image;
A transfer unit for transferring the formed image to a sheet;
A fixing unit for fixing the transferred image to the sheet;
A detection unit disposed upstream of the fixing unit for detecting the sheet conveyed from the transfer unit to the fixing unit;
The sheet is calculated based on a timing at which the sheet is scheduled to be detected by the detection unit, and a timing at which the sheet is actually detected by the detection unit, which is calculated from an image writing timing to the image forming unit. And a control unit for controlling whether to stop the conveyance of the image forming apparatus.

The second aspect of the present invention is
The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined leading margin amount based on a result of the leading margin amount comparison unit. It is an image forming apparatus of the invention.

The third aspect of the present invention
The tip margin amount estimation unit includes:
By calculating the product of the difference between the scheduled timing and the actually detected timing and the conveyance speed of the sheet and reflecting the calculated value on the leading edge margin amount to be formed, It is the image forming apparatus according to the second aspect of the present invention, which estimates the formed leading edge margin.

The fourth aspect of the present invention is
The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner occupancy estimation unit for estimating a toner occupancy in a predetermined area from the leading edge of the sheet;
A toner occupancy comparison unit that compares the toner occupancy with a predetermined toner occupancy determined in advance;
A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner occupancy is larger than the predetermined toner occupancy. The image forming apparatus of the present invention.

The fifth aspect of the present invention relates to
The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner amount estimation unit for estimating a toner amount per unit area in a predetermined region from the leading edge of the sheet;
A toner amount comparison unit that compares the toner amount with a predetermined toner amount,
A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner amount is larger than the predetermined toner amount. It is an image forming apparatus of the invention.

The sixth aspect of the present invention
The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner occupancy calculating unit for acquiring a toner occupancy in a predetermined area from the image leading edge;
A toner occupancy comparison unit that compares the toner occupancy with a predetermined toner occupancy determined in advance;
A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner occupancy is larger than the predetermined toner occupancy. The image forming apparatus of the present invention.

The seventh aspect of the present invention
The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner amount calculation unit for acquiring a toner amount per unit area in a predetermined region from the leading edge of the image;
A toner amount comparison unit that compares the toner amount with a predetermined toner amount,
A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner amount is larger than the predetermined toner amount. It is an image forming apparatus of the invention.

Further, the eighth aspect of the present invention is
The transfer unit has a secondary transfer roller,
The image forming unit includes:
A plurality of photosensitive drums provided for each color;
An intermediate transfer belt in which toner images formed on the surfaces of the plurality of photosensitive drums are superimposed and pressed against the secondary transfer roller;
A plurality of primary transfer rollers respectively disposed opposite to the plurality of photosensitive drums with the intermediate transfer belt interposed therebetween;
An opposing roller disposed to face the secondary transfer roller across the intermediate transfer belt,
The intermediate transfer belt is the image forming apparatus according to the first aspect of the invention, which is wound around the plurality of primary transfer rollers and the counter roller.

The ninth aspect of the present invention provides
An image forming unit for forming a toner image, a transfer unit for transferring the formed image to a sheet, a fixing unit for fixing the transferred image to the sheet, and the transfer unit to the fixing unit A detection unit arranged on the upstream side of the fixing unit for detecting the sheet conveyed to the image forming apparatus,
The sheet is calculated based on the timing when the sheet is scheduled to be detected by the detection unit, and the timing when the sheet is actually detected by the detection unit, which is calculated from the timing of writing the image to the image forming unit. This is a control method for the image forming apparatus, which has a control step for controlling whether or not to stop the conveyance of the image forming apparatus.

The tenth aspect of the present invention is
In the control method for an image forming apparatus according to the ninth aspect of the present invention, the timing at which the sheet is scheduled to be detected by the detection unit, calculated from the timing of writing the image to the image forming unit, and the sheet is the detection unit Is a program for causing a computer to execute a control process for controlling whether or not to stop the conveyance of the sheet based on the timing actually detected by.

The eleventh aspect of the present invention is
A recording medium on which a program of the tenth aspect of the present invention is recorded, which is a recording medium that can be processed by a computer.

  According to the present invention, it is possible to provide an image forming apparatus and a control method for the image forming apparatus that can suppress the occurrence of a paper jam leading to a service call.

  First, the overall configuration of the copying machine according to the first embodiment will be described.

  FIG. 1 is a front view of a copying machine according to a first embodiment of the present invention. As shown in FIG. 1, the copying machine of the present embodiment includes two paper feed cassettes 2 for storing paper on which images are formed on the bottom of a main body 1. In addition, the copying machine according to the present embodiment includes a document reading unit 16 that reads an image of a document with an exposure lamp, a lens, a mirror, and the like at the top of the main body 1.

  The copier in the present embodiment is a color copier using a tandem system, and includes a black image forming unit 3, a yellow image forming unit 4, a cyan image forming unit 5, and a magenta image forming unit 6. . An intermediate transfer belt 7 that superimposes the images formed by the image forming units 3, 4, 5, and 6 before being transferred onto a sheet is disposed. The basic configuration of the four image forming units 3, 4, 5, and 6 is the same, so that the magenta image forming unit 6 will be described as an example. As shown in FIG. The photosensitive drum 10, the charger 11, the developing device 12, the primary transfer roller 6a, the cleaning unit 39, and the like. For example, a drum using an amorphous silicon photoconductor is used as the photoconductor drum 10.

  The primary transfer rollers of the cyan image forming unit 5, the yellow image forming unit 4 and the black image forming unit 3 are denoted by 5a, 4a and 3a. These primary transfer rollers 3 a, 4 a, 5 a, 6 a are arranged inside the intermediate transfer belt 7 and press the respective photosensitive drums with the intermediate transfer belt 7 interposed therebetween.

  Further, a laser for writing an image and forming an electrostatic latent image by optically scanning the surface of each photosensitive drum charged by each charger of each of the four image forming units 3, 4, 5, 6. A scanner unit (hereinafter referred to as LSU) 38 is arranged below the four image forming units 3, 4, 5, 6.

  A secondary transfer roller 8 is provided for transferring the toner image formed on the intermediate transfer belt 7 onto a sheet fed from the sheet feeding cassette 2. The secondary transfer roller 8 presses a driving roller 13 provided inside the intermediate transfer belt 7 via the intermediate transfer belt 7. Further, a fixing unit 9 is provided for fixing the toner image transferred to the paper. Further, a discharge tray 17 for discharging a sheet on which the toner image is fixed by the fixing unit 9 is provided.

  Next, the roller disposed inside the intermediate transfer belt 7 will be described.

  The surface of the intermediate transfer belt 7 of the present embodiment is formed of a material whose main component is rubber. As shown in FIG. 1, the intermediate transfer belt 7 rotates in the arrow A direction. Also, primary transfer rollers 6 a, 5 a, 4 a, 3 a are sequentially arranged in the rotation direction A inside the intermediate transfer belt 7.

  A driven roller 14 is disposed on the upstream side of the primary transfer roller 6 a, and a tension roller 15 is disposed on the downstream side of the driving roller 13 and the upstream side of the driven roller 14. Since the tension roller 15 is biased by a spring in the direction of arrow B, the expansion and contraction of the intermediate transfer belt 7 due to the temperature is absorbed by the tension roller 15 and the tension of the intermediate transfer belt 7 is maintained.

  Next, the fixing unit 9 will be described.

  FIG. 2 is a partially enlarged view of the copying machine according to the present embodiment. As shown in FIG. 2, the fixing unit 9 includes a pressure roller 21 for applying pressure to the paper and a fixing belt 24 pressed by the pressure roller 21. Further, the fixing unit 9 includes a belt support roller 22 disposed to face the pressure roller 21 via the fixing belt 24, and a heat roller 23 in which a heater is built. The fixing belt 24 is formed of polyimide resin or the like and is wound between the belt support roller 22 and the heat roller 23. The fixing belt 24 is heated by the heat of the heat roller 23, and the toner image is fixed on the sheet passing between the pressure roller 21 and the fixing belt 24 by the pressure from the pressure roller 21 and the heat from the fixing belt 24. The

  A separation claw 40 for separating the paper on which the toner image is fixed from the fixing belt 24 is disposed on the downstream side of the portion of the fixing belt 24 where the pressure roller 21 is pressed.

  Next, the sheet conveyance path 19 will be described.

  A transport path 19 for transporting paper from the paper feed cassette 2 to the discharge tray 17 is formed along the side surface 1 a of the main body 1.

  A pair of paper feed rollers 18 is disposed above the paper feed cassette 2 in order to feed the paper stored in the paper feed cassette 2 to the transport path 19. Further, a registration roller pair 20 for correcting the oblique feeding of the sheet is disposed downstream of the secondary transfer roller 8 disposed in the transport path 19.

  Accordingly, the paper fed from the paper feed cassette 2 is fed by the paper feed roller pair 18, discharged through the conveyance path 19 through the registration roller pair 20, the secondary transfer roller 8, and the fixing unit 9. It is conveyed to the tray 17. In FIG. 1, the conveyance path 19 is indicated by a dotted arrow.

  As shown in FIG. 2, a sensor 25 for detecting paper conveyed from the secondary transfer roller 8 to the fixing unit 9 is provided in the conveyance path 19 between the secondary transfer roller 8 and the fixing unit 9. It has been. The sensor 25 is an optical sensor and detects the presence of a sheet by reflected light.

  Next, the control unit 26 of the copying machine according to the second embodiment will be described.

  FIG. 3 is a configuration diagram of the control unit 26 of the copying machine according to the present embodiment. FIG. 4 is a view showing a sheet on which the toner image is transferred.

  As shown in FIG. 3, the control unit 26 drives the fixing unit 9, the magenta image forming unit 6, the cyan image forming unit 5, the yellow image forming unit 4, the black image forming unit 3, etc. The system 28 is controlled.

  Also, a leading edge margin estimation unit 32 is provided for receiving a detection signal 29 when the sheet is detected by the sensor 25 and estimating a leading margin amount that is a blank portion formed at the leading edge of the sheet. In this embodiment, the leading edge margin amount corresponds to the distance L from the leading edge 30a of the paper 30 shown in FIG. 4 to the leading edge 31a of the formed toner image 31. In FIG. 4, the conveying direction is indicated by an arrow B.

Also, the tip margin amount L (mm) estimated by the tip margin amount estimation unit 32 is compared with a predetermined minimum tip margin amount L _min that needs to be secured at a minimum, and the comparison result is obtained. A tip margin amount comparison unit 33 for outputting is provided.

When the margin amount at the front end of the sheet 30 is small, the toner melted by heat becomes an adhesive, and therefore the sheet 30 may not be separated by the separation claw 40 and the sheet 30 may be wound around the fixing belt 24. Get higher. Therefore, in the copying machine according to the present embodiment, the minimum leading edge margin amount L _min that is required to be secured to the sheet 30 at a minimum is set in advance so that the sheet 30 is not wrapped around the fixing belt 24 at the time of fixing. .

Further, based on the image data 41 created from the document data read by the document reading unit 16, the apparatus setting at the time of copying, and the leading edge margin amount L estimated by the leading edge margin amount estimating unit 32, A toner amount estimation unit 37 for estimating the toner amount V (mg / cm ² ) per unit area in the predetermined region W is provided. In FIG. 4, the tip region W is shown surrounded by a thick solid line.

Further, a toner amount V estimated by the toner amount estimation unit 37 is compared with the allowable amount of toner V _max being the maximum permissible amount of toner comparison unit 34 is provided for outputting the comparison result.

When the amount of toner in the leading end region W of the paper 30 is large, the toner melted by heat becomes an adhesive, so that the paper 30 is not separated by the separation claw 40 and the paper 30 can be wound around the fixing belt 24. Increases nature. For this reason, in the copying machine of the present embodiment, the maximum allowable toner amount V _max allowed for the paper 30 is set in advance so that the paper 30 does not wrap around the fixing belt 24 during fixing.

Furthermore, the operation of the drive system 28 is stopped when L <L _min and V> V _max based on the comparison result output from the tip margin amount comparison unit 33 and the comparison result output from the toner amount comparison unit 34. A stop determination unit 36 that outputs a stop signal 35 is provided. Details of each component of the control unit 26 will be described in detail in the following description of the operation.

  An example of the image forming unit of the present invention includes the magenta image forming unit 6, the cyan image forming unit 5, the yellow image forming unit 4, the black image forming unit 3, the intermediate transfer belt 7, the driving roller 13, and the like. It corresponds to the driven roller 14 and the tension roller 15. An example of the transfer unit of the present invention corresponds to the secondary transfer roller 8 of the present embodiment, a spring member (not shown) that biases the secondary transfer roller 8, and the like. An example of the detection unit of the present invention corresponds to the sensor 25 of the present embodiment.

  In the following, the operation of the copying machine of the present embodiment will be described mainly with reference to FIGS. 1, 2, and 5, and an example of the control method of the image forming apparatus of the present invention will be described at the same time. FIG. 5 is a diagram showing a control flow of the copying machine according to the present embodiment.

  First, in the copier shown in FIG. 1, when a document is read by the document reading unit 16, a print start signal is transmitted to the control unit 26 (S1).

  In response to this print start signal, the control unit 26 feeds the paper from the paper feed cassette 2 to the transport path 19 (S2), and the transported paper is stopped by the registration roller 20 (S3).

  The control unit 26 outputs a write signal upon receiving a print start signal as well as a paper feed operation from the paper feed cassette 2, and writes an image on the photosensitive drum based on the image data created from the read original data. Starts (S4). The timing at which this write signal is output is hereinafter referred to as write timing.

  Next, for example, a secondary paper feed signal is output after a predetermined time has elapsed from the output of the write signal to the black image forming unit 3 (S5), and the paper 30 is fed again from the registration roller 20 (S6).

FIG. 6A shows the paper 30 in a state where the toner image 31 is transferred to a predetermined position based on the image data and the apparatus setting at the time of copying. As shown in FIG. 6 (a), when the toner image 31 is formed at a position which is expected, at a leading end margin amount L ₀ from the distal end 30a of the paper 30, the toner image 31 is transferred It will be. When the leading edge of the toner image 31 and 31a, the distance from the tip 30a to the tip 31a corresponds to the front end margin amount _{L 0.}

  Subsequently, the sheet 30 is re-fed from the registration roller pair 20 and the oblique feeding is corrected, and is sent to the secondary transfer roller 8. The toner image 31 formed on the intermediate transfer belt 7 is transferred onto the paper 30 by the secondary transfer roller 8 (S7).

  The sheet 30 to which the toner image 31 is transferred is further conveyed, and the leading end 30a of the sheet 30 is detected by the sensor 25 (S8). With reference to the writing timing, the time until the timing when the conveyed paper 30 is actually detected by the sensor 25 is T (msec).

With reference to the image writing timing, the time until the timing at which the paper 30 secures the leading edge margin L ₀ (cm) and the image is formed and is detected by the sensor 25 is T ₀ (msec). To do. Further, the conveyance speed of the sheet 30 set so that the sheet 30 is detected by the sensor 25 at the timing T ₀ (msec) is V ₀ (cm / msec).

FIG. 6B is a diagram illustrating the sheet 30 in a state where conveyance is delayed and the formation position of the toner image 31 is shifted. As shown in FIG. 6B, when the conveyance of the paper 30 is delayed from the schedule, the toner image 31 is formed from the leading end 30 a of the paper 30. Therefore, when the leading edge margin amount estimation unit 32 receives the sheet detection signal 29 from the sensor 25, the leading edge margin amount estimation unit 32 calculates V ₀ × (T−T ₀ ), thereby shifting the leading edge 31a of the toner image 31 from the planned position. ΔL can be estimated. Then, the tip margin amount estimation unit 32 can calculate L ₀ −ΔL and estimate the tip margin amount L actually formed (S9).

Then, the tip margin amount comparison unit 33 compares the minimum tip margin amount L _min with the tip margin amount L. Then, the comparison result is output to the stop determination unit 36 (S10).

On the other hand, the toner amount estimation unit 37 estimates the toner amount V (mg / cm ² ) per unit area in the tip region W (cm ² ) from the tip 30 a of the paper 30. In FIG. 6B, when the width of the paper 30 is α (cm), the length of the paper 30 in the predetermined area W is indicated by β (cm).

Specifically, the total toner amount V _ALL in the region of (β−L) (cm) from the tip 31a of the toner image 31 in FIG. _6A is calculated from the image data 41 that is the basis of the writing signal. (See FIG. 6B). This total toner amount V _ALL is formed by superposing four toner amounts of magenta, cyan, yellow, and black, for example, ([toner amount per pixel (value based on image data). )] × [total number of pixels of four colors]).

Next, the toner amount V per unit area can be calculated by dividing the total toner amount V _ALL by W (see FIG. 6B) (S11).

The toner amount comparing unit 34, and the allowable amount of toner V _max, is compared with the toner amount V calculated in S11 are performed. Then, the comparison result is output to the stop determination unit 36 (S12).

Next, the stop determination unit 36 determines whether or not the comparison result satisfies L <L _min and V> V _max (S13). When the condition is satisfied, a stop signal 35 is output to the drive system 28 (S14). The operation of the drive system 28 is stopped by the output of the stop signal.

On the other hand, if L <L _min and V> V _max are not satisfied, the paper 30 is continuously conveyed and the toner image 31 is fixed in the fixing unit 9 (S15). Then, the paper 30 on which the toner image 31 is formed is discharged to the discharge tray 17 (S16).

As the stop threshold, L _min = 0.3 cm and toner amount V _MAX = 120 mg / cm ² can be cited as examples.

  As described above, in this exemplary embodiment, when there is a high possibility that the paper 30 on which the toner image 31 is formed is wound around the fixing belt 24, the conveyance of the paper 30 is stopped before the paper is completely wound around the fixing belt 24. Therefore, it is easy to remove the paper 30.

In this embodiment, it is determined whether or not to stop the drive system 28 in consideration of the toner amount. However, the toner amount estimation unit 37 and the toner amount comparison unit 34 are not provided, and the toner amount V is considered. Instead, control may be performed so that the drive system 28 is stopped when the tip margin amount L is smaller than the minimum tip margin amount L _min .

However, considering the toner amount V, even when the leading edge margin amount L is smaller than the minimum leading edge margin amount L _min , the sheet 30 is wound around the fixing belt 24 when the toner amount V is smaller than V _max. Since there is a low possibility of being attached, it is possible to prevent an unnecessary apparatus from being stopped.

  In this embodiment, the tandem color copier has been described. However, the present invention can also be applied to a one-drum color copier.

  In this embodiment, the fixing unit 9 using the fixing belt 24 is used. However, without using the fixing belt 24, a toner image is formed on the sheet between the pressure roller 21 and the heat roller pressed against the pressure roller 21. A fixing unit configured to fix the image may be used.

  In this embodiment, the secondary paper feed signal is output after a predetermined time has elapsed from the writing timing of the black image forming unit 3 to the photosensitive drum, but the magenta image forming unit 6, the cyan image forming unit 5, In addition, the secondary paper feed signal may be output based on the write signal to the photosensitive drum of the yellow image forming unit 4 and can be appropriately changed depending on the configuration of the apparatus.

  In this embodiment, the fixing unit 9 using the fixing belt 24 is used. However, without using the fixing belt 24, a toner image is formed on the sheet between the pressure roller 21 and the heat roller pressed against the pressure roller 21. A fixing unit configured to fix the image may be used.

(Embodiment 2)
The copier according to the second embodiment of the present invention will be described below. The description will be made with reference to FIGS. 4 and 6 used in the first embodiment.

  FIG. 7 is a schematic side view of the printer according to the second embodiment. The printer of the second embodiment is for monochrome printing.

  As shown in FIG. 7, the printer according to the present embodiment has a paper tray 101 disposed at the bottom of the main body 50 for storing paper to be printed, and an image that forms an image on the paper supplied from the paper tray 101. A forming unit 102, a discharge unit 104 configured by a roller or the like for discharging a sheet on which an image is formed, and a discharge tray 123 disposed on the upper surface of the main body 100 on which the sheet discharged from the discharge unit 104 is placed. I have.

  The paper tray 101 is provided with a paper feeding unit 151 configured with rollers for supplying paper to the image forming unit 102. Further, three rollers for conveying the sheet on which the image is formed on one side by the image forming unit 2 to the discharge unit 104 side and conveying the sheet conveyed to the discharge unit 104 side to the image forming unit 102 side again. A sheet reversing unit 103 composed of 116, 117, 118 and the like is installed.

  Further, a conveyance path through which the sheet is conveyed from the sheet tray 101 through the image forming unit 102 to the discharge tray 123 via the discharge unit 104 is indicated by a solid line arrow as the normal conveyance path 121. On the other hand, a conveyance path through which the sheet is conveyed again from the sheet reversing unit 103 to the image forming unit 102 is illustrated as a reverse conveyance path 122 by a dotted arrow.

  Next, the image forming unit 102 will be described.

  The image forming unit 102 includes an image transfer unit 105 that transfers toner to a sheet, and a fixing unit 106 that fixes toner on the sheet by increasing the temperature. The fixing unit 106 includes a fixing roller 114 having a heater and a pressure roller 115 in pressure contact with the fixing roller 114. A separation claw 140 for separating the sheet from the surface of the fixing path roller 104 is disposed on the downstream side of the fixing roller 114.

  Further, the image transfer unit 105 is charged by applying light to the surface of the photosensitive drum 107, the charging unit 108 for charging the surface of the photosensitive drum 107, and the surface of the photosensitive drum 107 other than the portion where the image is formed. An exposure unit (see arrow 109 in FIG. 2) that removes the electric charge and forms an electrostatic latent image, and a developer that attaches toner to the electrostatic latent image formed on the surface of the photosensitive drum 107 to form a visible image 110. Further, the image transfer unit 105 presses the conveyed paper against the photosensitive drum 107, applies a charge opposite to the toner and transfers the toner onto the paper by electrostatic force, and the surface of the photosensitive drum 107. It has a gradual charger 112 for removing the charge and a cleaning unit 113 for removing the toner remaining on the photosensitive drum 107 without being transferred.

  Further, a registration roller pair 124 that adjusts the sheet conveyance timing and the transfer timing and corrects the oblique sheet feeding is arranged on the forward conveyance path 121 on the upstream side of the transfer roller 111. Further, an optical sensor 125 similar to the sensor 25 of the first embodiment is disposed between the transfer roller 112 and the fixing unit 106, and the optical sensor 125 detects paper.

  Next, the control unit 126 of the printer according to the first embodiment will be described.

  FIG. 8 is a configuration diagram of the control unit 126 of the printer according to the second embodiment. As shown in FIG. 8, the control unit 126 controls the drive system 128 such as the fixing unit 106 and the image forming unit 105 of the copying machine by a control signal 127.

  Also, a leading edge margin estimation unit 132 is provided that receives a detection signal 129 when the sheet is detected by the sensor 125 and estimates a leading margin amount that is a blank portion formed at the leading edge of the sheet. This leading edge margin amount corresponds to the distance L from the leading edge 30a of the paper 30 shown in FIG. 4 to the leading edge 31a of the toner image 31 formed. In FIG. 4, the conveying direction is indicated by an arrow C.

Also, the tip margin amount L (mm) estimated by the tip margin amount estimation unit 132 is compared with a predetermined minimum tip margin amount L _min that needs to be secured at a minimum, and the comparison result is obtained. A leading edge margin comparison unit 133 for output is provided.

When the margin amount at the front end of the paper 30 is small, the toner melted by heat becomes an adhesive, and therefore the paper 30 may be wound around the fixing roller 114 without being separated by the separation claw 140. Get higher. Therefore, in the printer of the present embodiment, the minimum leading edge margin amount L _min that is required to be secured to the sheet 30 at a minimum is set in advance so that the sheet 30 does not wind around the fixing roller 114 at the time of fixing.

  Further, based on the image data 139 transmitted to the printer, the apparatus setting at the time of printing, and the leading edge margin amount L estimated by the leading edge margin amount estimation unit 132, the toner occupancy S in the predetermined area W at the leading edge of the paper is obtained. A toner occupation rate estimation unit 137 for estimating (%) is provided. In FIG. 4, the tip region W is shown surrounded by a thick solid line.

Further, a toner amount comparison unit 134 that compares the toner occupancy S estimated by the toner occupancy estimation unit 137 with the maximum allowable allowable toner occupancy S _max and outputs the comparison result is provided.

Note that when the toner occupancy ratio in the leading edge region W of the paper 30 is large, the toner melted by heat becomes an adhesive, so that the paper 30 is not separated by the separation claw 140 and the paper 30 is wrapped around the fixing roller 114. The possibility increases. For this reason, in the copying machine of the present embodiment, the maximum allowable toner occupancy S _max allowed for the paper 30 is set in advance so that the paper 30 does not wrap around the fixing roller 114 during fixing.

Further, according to the comparison result output from the tip margin amount comparison unit 133 and the comparison result output from the toner occupancy ratio comparison unit 134, the operation of the drive system 128 is performed when L <L _min and S> S _max. A stop determination unit 136 that outputs a stop signal 135 for stopping is provided. Details of each component of the control unit 126 will be described in the following description of the operation.

  The transfer unit of the present invention includes a transfer roller 111 pressing the photosensitive drum 107, a unit for applying a reverse bias to the transfer roller 111, and a spring member for pressing the transfer roller 111 to the photosensitive drum 107. Etc.

  Hereinafter, the operation of the printer of the second embodiment will be described mainly with reference to FIGS. 7 to 9, and an example of the control method of the image forming apparatus of the present invention will be described at the same time. FIG. 9 is a diagram showing a control flow of the copying machine according to the present embodiment.

  First, a print start signal is transmitted to the printer shown in FIG. 7 from the PC or the like together with image data to the control unit 126 (S21).

  Upon receiving this print start signal, the control unit 126 feeds paper from the paper feed cassette 101 to the transport path 121 (S22), and the fed paper is stopped by the registration roller 124 (S23).

  Upon receiving a print start signal from the paper feed cassette 101, the control unit 126 outputs a write signal, and based on the image data 139 transmitted from the PC, the image is written on the photosensitive drum. Start (S24). The timing at which this write signal is output is hereinafter referred to as write timing.

  Next, after a lapse of a predetermined time from the output of the writing signal, a secondary paper feed signal is outputted (S25), and the paper 30 is fed again from the registration roller 124 (S26).

As in the first embodiment, FIG. 6A shows the sheet 30 in which the toner image 31 is transferred to a predetermined position based on the image data 139 and the apparatus setting at the time of copying. As shown in FIG. 6 (a), when the toner image 31 is formed at a position which is expected, at a leading end margin amount L ₀ from the distal end 30a of the paper 30, the toner image 31 is transferred It will be. When the leading end of the toner image 31 and 31a, the distance from the tip 30a to the tip 31a corresponds to the front end margin amount _{L 0.}

  Subsequently, the sheet 30 on which the oblique feeding is formed by the registration roller 124 is sent to the transfer roller 111. Then, the transfer roller 111 transfers the toner image 31 formed on the photosensitive drum 107 onto the paper 30 (S27).

  The sheet 30 to which the toner image 31 is transferred is further conveyed, and the leading edge 30a of the sheet 30 is detected by the sensor 125 (S28). With reference to the writing timing, the time until the timing at which the conveyed paper 30 is actually detected by the sensor 125 is T (msec).

With reference to the image writing timing, the paper 30 has a leading edge margin L ₀ (cm) secured and an image is formed, and the time until the scheduled timing detected by the sensor 125 is T ₀ (msec). To do. Further, the conveyance speed of the sheet 30 set so that the sheet 30 is detected by the sensor 125 at the timing T ₀ (msec) is V ₀ (cm / msec).

FIG. 6B is a diagram illustrating the sheet 30 in a state where conveyance is delayed and the formation position of the toner image 31 is shifted. As shown in FIG. 6B, when the conveyance of the paper 30 is delayed from the schedule, the toner image 31 is formed from the leading end 30 a of the paper 30. Therefore, when the leading edge margin amount estimation unit 132 receives the paper detection signal 129 from the sensor 125, the leading edge margin amount estimation unit 132 calculates V ₀ × (T−T ₀ ), thereby shifting the leading edge 31a of the toner image 31 from the planned position. ΔL can be estimated. Then, the tip margin amount estimation unit 32 can calculate L ₀ −ΔL and estimate the tip margin amount L actually formed (S29).

Then, the tip margin amount comparison unit 33 compares the minimum tip margin amount L _min with the tip margin amount L. Then, the comparison result is output to the stop determination unit 36 (S30).

On the other hand, the toner occupancy rate estimation unit 137 estimates the toner occupancy rate S (%) in the leading edge region W (cm ² ) from the leading edge 30 a of the paper 30. The toner occupancy S is calculated from the image data 139, the apparatus setting at the time of copying, and the estimated leading edge margin amount L (S31).

Specifically, in the toner occupancy rate estimation unit 137, the writing area M (cm ² ) in the region having a length of (β−L) (cm) from the leading end 31a of the image data 31 in FIG. It is calculated from the image data that is the basis of the signal. By dividing this area M by W, the toner occupancy S (%) in the tip region W (cm ² ) is calculated (see FIG. 6B).

Then, the toner occupancy ratio comparison unit 134 compares the allowable toner occupancy ratio S _max with the toner occupancy ratio S of the paper 30 on which the toner image is actually transferred. Then, the comparison result is output to the stop determination unit 136 (S32).

Next, the stop determination unit 136 determines whether or not the comparison result satisfies L <L _min and S> S _max (S33). When the condition is satisfied, a stop signal 135 is output to the drive system 128 (S34). The operation of the drive system 128 is stopped by the output of the stop signal.

On the other hand, when L <L _min and S> S _max are not satisfied, the sheet 30 is continuously conveyed, and the toner image 31 is fixed in the fixing unit 106 (S35). Then, the paper 30 on which the toner image 31 is formed is discharged to the discharge tray 123 (S36).

Examples of the stop threshold include L _min = 0.3 (cm) and toner occupancy S _MAX = 50 (%).

  As described above, in the present embodiment, when there is a high possibility that the paper 30 on which the toner image 31 is formed is wound around the fixing roller 114, the conveyance of the paper 30 is stopped before the paper is completely wound around the fixing roller 114. Therefore, it is easy to remove the paper 30.

In this embodiment, it is determined whether or not to stop the drive system 28 in consideration of the toner occupancy rate. However, the toner occupancy rate estimation unit 137 and the toner occupancy rate comparison unit 134 are not provided, and the toner occupancy rate Control may be performed so that the drive system 128 is stopped when the tip margin amount L is smaller than the minimum tip margin amount L _min without considering the rate S.

However, considering the toner occupancy S, even if the leading edge margin amount L is smaller than the minimum leading edge margin amount L _min , if the toner occupancy S is smaller than S _max , the sheet 30 is fixed to the fixing roller 114. Therefore, it is possible to prevent an unnecessary apparatus from being stopped.

  In the case of the color copying machine described in the first embodiment, since the four color toners overlap, it is preferable to use “toner amount” per unit area as a determination factor for stopping the paper. The “toner occupation ratio” described in the second embodiment may be used.

  In the monochrome printer of the second embodiment, “toner occupancy” is used as a determination element for stopping the paper, but “toner amount” may be used as a determination element.

(Embodiment 3)
The copying machine according to the third embodiment of the present invention will be described below.

  The basic configuration of the copying machine in the third embodiment is the same as that in the first embodiment, but the configuration of the control unit and the control flow are different, and therefore this difference will be mainly described.

FIG. 10 is a configuration diagram of the control unit 46 in the copying machine according to the third embodiment. As shown in FIG. 10, the control unit 46 includes a toner amount calculation unit 47 instead of the toner amount estimation unit 37 described in the first embodiment. The toner amount calculation unit 47 is based on the image data 41 created from the document data read by the document reading unit 16, and the toner amount V ′ (mg / cm ² ) per unit area in the predetermined area W ′ at the leading edge of the image. ) Is calculated. The predetermined area W ′ will be described later.

  Hereinafter, the operation of the copying machine of the third embodiment will be described with reference mainly to the control flow shown in FIG. 11, and an example of the control method of the image forming apparatus of the present invention will be described at the same time. The operation of the copying machine of the third embodiment is basically the same as that of the first embodiment, and the value of the leading edge margin amount L is obtained in the same manner as in the first embodiment. Therefore, a description will be given focusing on a calculation method of the toner amount V ′, which is a difference from the first embodiment.

  FIG. 12 is a diagram illustrating the sheet 30 in a state where the toner image 31 is transferred to a predetermined position.

In the third embodiment, in S11 ′, the toner amount calculation unit 37 causes the toner amount V ′ (per unit area) in the predetermined region W ′ (cm ² ) from the tip 31a of the toner image 31 based on the image data 41. mg / cm ² ) is calculated.

Specifically, the total toner amount V _ALL in the area W ′ in FIG. 12 is calculated from the image data 41 that is the basis of the writing signal. This total toner amount V _ALL is formed by superposing four toner amounts of magenta, cyan, yellow, and black, for example, ([toner amount per pixel (value based on image data). )] × [total number of pixels of four colors]).

Next, the toner amount V per unit area can be calculated by dividing the total toner amount V _ALL by W ′ (S11 ′).

  That is, the toner amount V ′ calculated in the third embodiment is not a value in a predetermined area from the front end 30a of the paper 30 but a value in a predetermined area from the front end 31a of the toner image 31 unlike the first embodiment. Yes, the value does not vary depending on the leading edge margin amount L.

The toner amount comparing unit 34, and the allowable amount of toner _{V max,} is compared with the toner amount V calculated in S11' performed. Then, the comparison result is output to the stop determination unit 36 (S12 ′).

On the other hand, the comparison result between the estimated tip margin amount L and the minimum tip margin amount L _min is output to the stop determination unit 36 as in the first embodiment (S10).

Then, the stop determination unit 36 determines whether or not the comparison result satisfies L <L _min and V ′> V _max (S13 ′). When the condition is satisfied, a stop signal 35 is output to the drive system 28 (S14). The operation of the drive system 28 is stopped by the output of the stop signal.

On the other hand, when L <L _min and V ′> V _max are not satisfied, the sheet 30 is continuously conveyed and the toner image 31 is fixed in the fixing unit 9 (S15). Then, the paper 30 on which the toner image 31 is formed is discharged to the discharge tray 17 (S16).

As the stop threshold, L _min = 0.3 cm and toner amount V _MAX = 120 mg / cm ² can be cited as examples.

  As described above, in this exemplary embodiment, when there is a high possibility that the paper 30 on which the toner image 31 is formed is wound around the fixing belt 24, the conveyance of the paper 30 is stopped before the paper is completely wound around the fixing belt 24. Therefore, it is easy to remove the paper 30.

Note that the method for calculating the toner amount in a predetermined region from the leading edge of the toner image as described in the third embodiment can be applied to the toner occupancy S described in the second embodiment. . That is, based on the image data, the toner occupancy S ′ (%) in the predetermined area W ′ from the leading end 31a of the image data shown in FIG. 12 is calculated. Then, when the toner occupancy S ′ is larger than S _max and the leading edge margin amount L is smaller than the minimum leading edge margin amount L _min , the control is performed so that the drive system 128 is stopped. Application to Form 2 can be realized.

In the third embodiment, the determination is made in S13 ′ using the minimum tip margin amount L _min and the allowable toner amount V _max . However, only the minimum tip margin amount L _min is considered without considering the allowable toner amount V _max. You may determine using.

In the third embodiment, the minimum tip margin amount L _min is a fixed value, but may be a variable value. The variation value can be realized, for example, by providing a table of the minimum tip margin amount L _min corresponding to the toner amount V ′. Using this table, the minimum tip margin amount L _min corresponding to the toner amount V ′ obtained in S11 ′ is determined, and the minimum tip margin amount L _min and the tip margin amount L are compared in S10. A stop signal 35 is output to the drive system 28 when the tip margin amount L is smaller than the minimum tip margin amount L _min . In this way, when the possibility that the paper 30 is wound around the fixing belt 24 is high, the conveyance of the paper 30 can be stopped before the paper 30 is completely wound around the fixing belt 24.

  Further, as an example of the image forming apparatus of the present invention, a copying machine is described in the first and third embodiments and a printer is used in the second embodiment, but both are a printer, a copying machine, a fax, and the like. There may be.

  The program of the present invention is a program for causing a computer to execute the operation of the control process of the above-described control method of the image forming apparatus of the present invention, and is a program that operates in cooperation with the computer.

  The recording medium of the present invention is a recording medium on which a program for causing a computer to execute all or part of the control steps of the above-described image forming apparatus control method of the present invention is readable by the computer. The read program is a recording medium for executing the operation in cooperation with the computer.

  The “process operation” of the present invention means the operation of all or part of the process.

  Further, one use form of the program of the present invention may be an aspect in which the program is recorded on a recording medium such as a ROM readable by a computer and operates in cooperation with the computer.

  Also, one use form of the program of the present invention is an aspect in which the program is transmitted through a transmission medium such as the Internet, a transmission medium such as light, radio wave, and sound wave, read by a computer, and operates in cooperation with the computer. Also good.

  The computer of the present invention described above is not limited to pure hardware such as a CPU, but may include firmware, an OS, and peripheral devices.

  As described above, the configuration of the present invention may be realized by software or hardware.

  According to the present invention, it is possible to suppress the occurrence of a paper jam that leads to a service call, which is useful for an image forming apparatus such as a copying machine, a printer, and a fax.

1 is a front configuration diagram of a copying machine according to a first embodiment of the present invention. Partial enlarged view of the copying machine according to the first embodiment of the present invention. 1 is a configuration diagram of a control unit of a copying machine according to a first embodiment of the present invention. The figure which shows the paper in which the toner image was transcribe | transferred by the copying machine in Embodiment 1 concerning this invention. The figure which shows the control flow of the copying machine in Embodiment 1 concerning this invention. (A) The figure which shows the paper in which the toner image was transcribe | transferred to the position planned by the copying machine in embodiment concerning this invention, (b) A toner image is actually transferred by the copying machine in embodiment concerning this invention. Showing the used paper Side structure diagram of the printer according to the second embodiment of the present invention. Configuration diagram of a printer control unit according to the second embodiment of the present invention. The figure which shows the control flow of the printer in Embodiment 2 concerning this invention. Configuration diagram of a control unit of a copying machine according to a third embodiment of the present invention The figure which shows the control flow of the copying machine in Embodiment 3 concerning this invention. The figure which shows the paper in which the toner image was transcribe | transferred to the position planned by the copying machine in Embodiment 3 concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Transfer roller 9 Fixing unit 13 Drive roller 14 Driven roller 15 Tension roller 19 Conveyance path 20 Registration roller pair 21 Pressure roller 25 Sensor 26 Control unit 27 Control signal 28 Drive system 29 Detection signal 30 Paper 31 Toner image 32 Leading margin amount estimation unit 33 Lead margin amount comparison unit 34 Toner occupancy ratio comparison unit 35 Stop signal 36 Stop determination unit 37 Toner occupancy ratio estimation unit

Claims (11)

An image forming unit for forming a toner image;
A transfer unit for transferring the formed image to a sheet;
A fixing unit for fixing the transferred image to the sheet;
A detection unit disposed upstream of the fixing unit for detecting the sheet conveyed from the transfer unit to the fixing unit;
The sheet is calculated based on a timing at which the sheet is scheduled to be detected by the detection unit, and a timing at which the sheet is actually detected by the detection unit, which is calculated from an image writing timing to the image forming unit. And a control unit for controlling whether to stop the conveyance of the image. The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
2. A stop determination unit that determines stop of the conveyance of the sheet when the leading edge margin amount is smaller than the predetermined leading margin amount based on a result of the leading margin amount comparison unit. Image forming apparatus. The tip margin amount estimation unit includes:
By calculating the product of the difference between the scheduled timing and the actually detected timing and the conveyance speed of the sheet and reflecting the calculated value on the leading edge margin amount to be formed, The image forming apparatus according to claim 2, wherein the formed tip margin is estimated. The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner occupancy estimation unit for estimating a toner occupancy in a predetermined area from the leading edge of the sheet;
A toner occupancy comparison unit that compares the toner occupancy with a predetermined toner occupancy determined in advance;
And a stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner occupancy rate is larger than the predetermined toner occupancy rate. The image forming apparatus according to 1. The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner amount estimation unit for estimating a toner amount per unit area in a predetermined region from the leading edge of the sheet;
A toner amount comparison unit that compares the toner amount with a predetermined toner amount,
2. A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner amount is larger than the predetermined toner amount. Image forming apparatus. The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner occupancy calculating unit for acquiring a toner occupancy in a predetermined area from the image leading edge;
A toner occupancy comparison unit that compares the toner occupancy with a predetermined toner occupancy determined in advance;
And a stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner occupancy rate is larger than the predetermined toner occupancy rate. The image forming apparatus according to 1. The control unit is
A leading edge margin amount estimation unit for estimating a leading edge margin amount from the leading edge of the sheet to a portion where the image is transferred based on the scheduled timing and the actually detected timing;
A tip margin amount comparison unit that compares the tip margin amount estimated by the tip margin amount estimation unit with a predetermined tip margin amount;
A toner amount calculation unit for acquiring a toner amount per unit area in a predetermined region from the leading edge of the image;
A toner amount comparison unit that compares the toner amount with a predetermined toner amount,
2. A stop determination unit that determines stop of conveyance of the sheet when the leading edge margin amount is smaller than the predetermined margin amount and the toner amount is larger than the predetermined toner amount. Image forming apparatus. The transfer unit has a secondary transfer roller,
The image forming unit includes:
A plurality of photosensitive drums provided for each color;
An intermediate transfer belt in which toner images formed on the surfaces of the plurality of photosensitive drums are superimposed and pressed against the secondary transfer roller;
A plurality of primary transfer rollers respectively disposed opposite to the plurality of photosensitive drums with the intermediate transfer belt interposed therebetween;
An opposing roller disposed to face the secondary transfer roller across the intermediate transfer belt,
The image forming apparatus according to claim 1, wherein the intermediate transfer belt is wound around the plurality of primary transfer rollers and the counter roller. An image forming unit for forming a toner image, a transfer unit for transferring the formed image to a sheet, a fixing unit for fixing the transferred image to the sheet, and the transfer unit to the fixing unit A detection unit arranged on the upstream side of the fixing unit for detecting the sheet conveyed to the image forming apparatus,
The sheet is calculated based on a timing at which the sheet is scheduled to be detected by the detection unit, and a timing at which the sheet is actually detected by the detection unit, which is calculated from an image writing timing to the image forming unit. A control method for an image forming apparatus, comprising a control step for controlling whether or not to stop the conveyance of the image forming apparatus.   10. The control method for an image forming apparatus according to claim 9, wherein the sheet is scheduled to be detected by the detection unit, calculated from an image writing timing to the image forming unit, and the sheet is detected by the detection unit. A program for causing a computer to execute a control process for controlling whether or not to stop the conveyance of the sheet based on the timing actually detected. A recording medium on which the program according to claim 10 is recorded, wherein the recording medium can be processed by a computer.

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