JP6911535B2 - Image forming device and program - Google Patents

Description

The present invention relates to an image forming apparatus and a program for executing a control method thereof.

In recent years, in the printing industry, an image forming apparatus such as an electrophotographic printer has been widely used in place of the conventional offset printing apparatus.

In such an image forming apparatus, in order to stabilize the image to be formed, a scanner is arranged on the downstream side of the image forming portion of the paper transport path, and the image data obtained by reading the scanner is used as an image. There is an image forming apparatus that detects the density and the image forming position and thereby feeds back to the image forming conditions and the image forming timing (for example, Patent Document 1).

On the other hand, in the image forming unit of such an electrophotographic image forming apparatus, a toner image is formed on an image carrier such as a photoconductor drum, and the toner image is transferred to the transferred paper at a transfer position, and the transferred toner is transferred. By heating the image with a fixing roller having a heater arranged inside on the downstream side, the toner image is fixed on the paper.

It is difficult to keep the outer diameter of the roller constant due to variations in the production of the fixing roller, expansion due to temperature rise, and the like. Therefore, it is difficult to completely match the paper transport speed by the fixing roller with the paper transport speed at the transfer position, and there is often a slight speed difference. Due to the influence of this speed difference, excessive deflection (loop) or tension occurs in the paper conveyed between the fixing roller and the transfer position. When excessive deflection is formed, contact with a member provided in the transport path causes image stains and damage to the paper. In addition, when tension occurs, image shift occurs during transfer. In particular, when long paper longer than the standard paper is used, the influence of the speed difference between the transfer position and the fixing roller becomes large. To solve such a problem, conventionally, there is a device in which a sensor for detecting deflection is provided on the front side of the fixing roller and the transport speed of the fixing roller is variably controlled by the detection output (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-191779

In the image forming apparatus disclosed in Patent Document 1, it is necessary to keep the paper conveying speed at the reading position constant during the reading period in which the paper conveyed by the scanner is read, in order to ensure the reading accuracy. ..

However, when the paper transfer speed at the reading position is constant, there is a speed difference between the paper transfer speed and the transfer speed of the variably controlled fixing roller on the upstream side. Therefore, the paper conveyed between the fixing roller and the reading position may be damaged due to excessive deflection or tension, and the accuracy at the time of reading cannot be ensured. There is a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent damage to the conveyed paper while ensuring reading accuracy by a scanner.

The above object of the present invention is achieved by the following means.

(1) Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A scanner that is placed directly downstream of the first roller and reads the image on the paper to be conveyed,
A detector that detects the amount of paper deflection formed between the transfer position and the fixing roller, and
During the image forming period for forming an image, the rotation of the fixing roller is controlled and the rotation of the fixing roller is controlled according to the paper transport state between the transfer position and the fixing roller.
During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the deflection formed in the paper conveyed between the fixing roller and the first roller. A control unit that controls the rotation of the second roller so that the amount is within a predetermined range is provided.
The control unit variably controls the paper transport speed Vf by the fixing roller between a predetermined maximum transport speed Vfmax and a minimum transport speed Vfmin according to the output of the detection unit.
Until the reading is started, the transport speeds of the first roller and the second roller are variably controlled so as to be the same as the transport speed of the fixing roller.
Wherein during reading period, the first to set the conveying speed of the roller in the conveying speed Vfmin, the transport speed of the second roller the conveying speed Vf hereinafter, is controlled by the transport speed Vfmin above, images forming device.

(2) Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A scanner that is placed directly downstream of the first roller and reads the image on the paper to be conveyed,
A detector that detects the amount of paper deflection formed between the transfer position and the fixing roller, and
During the image forming period for forming an image, the rotation of the fixing roller is controlled and the rotation of the fixing roller is controlled according to the paper transport state between the transfer position and the fixing roller.
During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the deflection formed in the paper conveyed between the fixing roller and the first roller. A control unit that controls the rotation of the second roller so that the amount is within a predetermined range is provided.
The control unit variably controls the paper transport speed Vf by the fixing roller between a predetermined maximum transport speed Vfmax and a minimum transport speed Vfmin according to the output of the detection unit.
Until the reading is started, the transport speeds of the first roller and the second roller are both controlled at a speed slower than the transport speed Vf of the fixing roller, and between the fixing roller and the first roller. Form a deflection in the paper to be transported,
Wherein during reading period, the first to set the conveying speed of the roller in the conveying speed VFmax, wherein the conveying speed of the second roller the conveying speed VFmax below, controlled by the transport speed Vf or more, images forming device.

( 3 ) Among the first roller, one or more of the second rollers, and the plurality of rollers of the fixing roller, the amount of deflection formed between adjacent rollers is controlled to be equal to or less than a predetermined amount. (1), or the image forming apparatus according to (2) above.

(4) during said reading period, all deflection amount formed between the adjacent rollers, when it is determined to exceed the predetermined amount, stops the reading of the running, according to the above (3) Image forming device.

( 5 ) A detection unit for detecting the amount of deflection formed between the adjacent rollers is provided, and the amount of deflection formed between the adjacent rollers during the reading period is determined according to the output of the detection unit. , The image forming apparatus according to (3 ) or ( 4) above.

( 6 ) The amount of deflection formed between the adjacent rollers is calculated from the difference in transport speed between the adjacent rollers to be controlled and the duration, and the amount of deflection formed between the adjacent rollers is calculated according to the calculation result of the amount of deflection between the adjacent rollers. The image forming apparatus according to the above (3 ) or the above ( 4 ), which determines the amount of deflection formed in the above.

( 7 ) The image forming apparatus according to any one of (3 ) to ( 6 ) above, wherein the predetermined amount is set to a different value for each adjacent roller.

(8) Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A program for causing an image forming apparatus including a scanner that is arranged immediately downstream of the first roller and reads an image on a sheet to be conveyed to execute a control method.
(A) A step of controlling the rotation of the fixing roller so that the amount of deflection of the paper formed between the transfer position and the fixing roller is within a predetermined range during the image forming period for forming an image. When,
(B) During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the paper is conveyed between the fixing roller and the first roller. Including a step of controlling the rotation of the second roller so that the amount of deflection formed is within a predetermined range.
In step (a), a predetermined maximum transfer speed Vfmax and a minimum transfer speed Vfmin are set according to the output of the detection unit that detects the amount of bending of the paper formed between the transfer position and the fixing roller. Control between
Moreover,
(C) The step of making the transport speeds of the first roller and the second roller the same as the transport speed Vf of the fixing roller until the reading is started is included.
In step (b), the control method is described in which the transport speed of the first roller is set to the transport speed Vfmin, and the transport speed of the second roller is controlled at the transport speed Vf or less and the transport speed Vfmin or more. A program to be executed by an image forming apparatus.

(9) Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A program for causing an image forming apparatus including a scanner that is arranged immediately downstream of the first roller and reads an image on a sheet to be conveyed to execute a control method.
(A) A step of controlling the rotation of the fixing roller so that the amount of deflection of the paper formed between the transfer position and the fixing roller is within a predetermined range during the image forming period for forming an image. When,
(B) During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the paper is conveyed between the fixing roller and the first roller. Including a step of controlling the rotation of the second roller so that the amount of deflection formed is within a predetermined range.
In step (a), a predetermined maximum transfer speed Vfmax and a minimum transfer speed Vfmin are set according to the output of the detection unit that detects the amount of bending of the paper formed between the transfer position and the fixing roller. Control between
Moreover,
(D) The step of controlling the transport speeds of the first roller and the second roller at a speed lower than the transport speed Vf of the fixing roller is included until the reading is started.
In step (b), the control method is described in which the transport speed of the first roller is set to the transport speed Vfmax, and the transport speed of the second roller is controlled at the transport speed Vfmax or less and the transport speed Vf or more. A program to be executed by an image forming apparatus.

The image forming apparatus according to the present invention includes a fixing roller, a second roller, a first roller, and a scanner along a transport path, and paper between the transfer position and the fixing roller during the image forming period. The rotation of the fixing roller is controlled according to the conveying state of the paper, and the first roller is rotated at a constant speed during the scanning period of the scanner, and the paper is formed to be conveyed between the fixing roller and the first roller. The rotation of the second roller is controlled so that the amount of deflection is within a predetermined range. By doing so, it is possible to prevent damage to the conveyed paper while ensuring reading accuracy by the scanner.

It is sectional drawing which shows the schematic structure of the image forming apparatus which concerns on 1st Embodiment. It is a block diagram which shows the hardware structure of an image forming apparatus. It is a schematic diagram explaining the transport speed of a fixing roller and the bending state of a paper. It is a schematic diagram explaining the transport speed of a fixing roller and the bending state of a paper. It is a schematic diagram explaining the transport speed of a fixing roller and the bending state of a paper. It is a schematic diagram explaining the relationship between the setting of the transfer speed of the transfer roller, and the bending state of the paper S. It is a schematic diagram explaining the relationship between the setting of the transfer speed of the transfer roller and the bending state of the paper. It is a schematic diagram explaining the relationship between the setting of the transfer speed of the transfer roller and the bending state of the paper. It is a schematic diagram explaining the relationship between the setting of the transfer speed of the transfer roller and the bending state of the paper. It is sectional drawing which shows the schematic structure of the image forming apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the control method of an image forming apparatus. It is a figure which shows the subroutine of FIG. It is a figure which shows the subroutine of FIG. It is a figure which shows the process which is executed following FIG. 8A. It is a figure which shows the transport state of the paper S in step S105. It is a figure which shows the transport state of the paper S in step S107. It is a figure which shows the transport state of the paper S in step S201. It is a figure which shows how the deflection increases in each section with time series. It is a figure which shows how the deflection increases in each section with time series. It is a figure which shows how the deflection increases in each section with time series. It is a figure which shows how the deflection increases in each section with time series. It is a figure which shows how the deflection increases in each section in another example. It is a figure which shows the state of accumulating the deflection in each section along the time series. It is a figure which shows the state of accumulating the deflection in each section along the time series. It is a figure which shows the state of consuming the deflection accumulated up to that time in each section along the time series. It is a figure which shows the state of consuming the deflection accumulated up to that time in each section along the time series. It is a figure which shows the state of consuming the deflection accumulated up to that time in each section along the time series.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a block diagram showing a hardware configuration of the image forming apparatus.

As shown in FIGS. 1 and 2, the image forming apparatus 100 includes an image forming apparatus main body 110, a paper feeding device 120, and a post-processing apparatus 130. The paper S fed from the image forming apparatus main body 110 or the feeding unit of the feeding device 120 is image-formed by the image forming apparatus main body 110. The post-processing apparatus 130 includes a scanner 70, whereby the image forming apparatus main body 110 reads the image-formed paper to acquire image data.

As shown in FIG. 2, the image forming apparatus 100 includes a control unit 10, a storage unit 20, an image forming unit 30, a fixing unit 40, a paper feed transport unit 50, an operation panel 60, a scanner 70, and a deflection detection sensors 80 and 81. They are interconnected via a bus for exchanging signals. Here, the deflection of the paper (also referred to as "sag" or "loop") is a curved state of the paper according to the difference (mm) in the feed amount caused by the speed difference between the rollers that convey the adjacent paper. To say. The amount of deflection may be defined by the difference in feed amount (mm), and is defined by the amount of change in height (mm) due to the curvature of the paper S from the lower surface guide constituting the transport path 53 in the transport path 53. May be good. In the following, when the deflection detection sensors 80 and 81 are used, they are used in the latter definition (height).

The control unit 10 is a CPU, and controls each unit of the device and performs various arithmetic processes according to a program. Further, the control unit 10 has a function of adjusting the color of the image and the image formation position based on the image data obtained by reading the scanner 70 (hereinafter, simply referred to as “image adjustment”). As the color adjustment of the image, for example, the LUT for color conversion is adjusted from the image data (image signal) obtained by reading the image of the color chart, and the image formation conditions such as the exposure amount of the image forming unit 30 are adjusted. As the image position adjustment, for example, the image formation position is adjusted from the detected edge of the paper or the position of the register mark image (mark image).

The storage unit 20 is composed of a ROM for storing various programs and various data in advance, a RAM for temporarily storing programs and data as a work area, a hard disk for storing various programs and various data, and the like. The storage unit 20 stores image data for a color chart in which color patches of a plurality of colors for various evaluations are arranged, an allowable upper limit value for each section of the amount of deflection formed between each roller, which will be described later, and the like. ..

The image forming unit 30 includes an intermediate transfer belt 31, a plurality of developing units, an exposed unit (not shown), and a transfer roller 32 as a secondary transfer unit. The yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photoconductor drum of each developing unit are sequentially transferred onto the intermediate transfer belt 31, and at the transfer position p1. It is transferred onto the paper S by the transfer roller 32. During image formation, the intermediate transfer belt 31 moves in the direction of the arrow in FIG. 1 at a constant moving speed.

The fixing portion 40 includes a hollow heating roller in which a heater is arranged and a pressure roller facing the heating roller. Hereinafter, the heating roller and the heating roller are collectively referred to as "fixing roller 41". Each roller is controlled within a predetermined temperature range by a heater, and the paper is heated and pressurized. Also during image formation. By controlling the rotation speed of the drive motor (not shown) by the control unit 10, the feed speed of the paper S of the fixing roller 41 (hereinafter, also referred to as “conveyance speed”, the same applies to other rollers) is variably controlled.

The paper feed transport unit 50 includes a paper feed tray 51 provided in the image forming apparatus main body 110, and a plurality of transport rollers R0 arranged along the paper feed tray 52, the transport path 53, and the transport path 53 provided in the paper feed device 120. , R1, R2, etc., and a plurality of paper detection sensors for detecting the passage of paper, and a plurality of drive motors (not shown) for driving these transfer rollers. Long paper S is fed from the paper feed tray 52. The transport rollers R1 and R2 function as "first transport rollers" and "second transport rollers," respectively.

The operation panel 60 includes a touch panel, a numeric keypad, a start button, a stop button, and the like, and is used for displaying printing conditions, device status, and inputting various instructions. Further, the user can input the paper information of the paper loaded in the paper feed trays 51 and 52 through the operation panel 60. Paper information includes paper size, paper type (plain paper, coated paper), paper thickness, weight, and the like. The input paper information is stored in the storage unit 20 in association with the paper feed trays 51 and 52.

(scanner)
The scanner 70 reads the paper S conveyed to the reading position p2 on the transfer path 53. The scanner 70 is arranged on the direct downstream side of the transfer roller R1 and on the direct flow side of the transfer roller R0, and its reading position p2 is provided at a substantially intermediate position between the transfer rollers R0 and R1. The transport rollers R0 and R1 rotate at the same rotation speed by being connected to one drive motor or the like. The transport rollers R0 and R1 rotate at a constant speed during the reading period in which the scanner 70 is used for reading, as will be described later.

The scanner 70 includes a sensor array, a lens optical system, an LED (Light Emitting Diode) light source, a housing for accommodating these, and the like. The sensor array is a color line sensor in which a plurality of optical elements (for example, CCD (Charge Coupled Device)) are arranged in a line along the main scanning direction, and the reading area in the width direction corresponds to the entire width of the paper S. .. The optical system is composed of a plurality of mirrors and lenses. The light from the LED light source passes through the original glass and irradiates the surface of the paper S passing through the reading position p2 on the transport path 53. The image of this reading position is guided by the optical system and imaged on the sensor array.

The control unit 10 performs color adjustment and image position adjustment from the image data obtained by the scanner 70. In the example shown in FIG. 1, the post-processing apparatus 130 includes one scanner, but two scanners are arranged along the transport path 53 so that both sides of the paper can be read at the same time. You may.

(Deflection detection sensor)
A plurality of deflection detection sensors 80 and 81 are arranged along the transport path 53 to detect the amount of deflection of the paper S. The deflection detection sensor 80 and the deflection detection sensor 81 have the same configuration, and are, for example, distance measuring sensors that measure the distance to an object by changing the light receiving position of the irradiated light. The deflection detection sensor 80 is arranged between the transfer position p1 and the fixing roller 41, and the plurality of deflection detection sensors 81 are between the fixing roller 41 and the transfer roller R2 and between the transfer roller R2 and the transfer roller R1. It is placed in each section of. The deflection detection sensors 80 and 81 detect the height of the paper S in each section, that is, the amount of deflection. Then, the control unit 10 controls the transport speed of each roller (fixing roller 41, transport rollers R1, R2) or the transport speed difference between adjacent transport rollers by the output of the deflection detection sensors 80 and 81. An actuator method may be adopted as the deflection detection sensors 80 and 81. For example, a movable actuator that comes into contact with a weak load is provided on the back surface side of the paper S that conveys the paper S, and the transfer position (height) of the paper S in the transfer path 53 is determined by an optical sensor that detects the movement of the actuator. The amount of deflection of the paper S is detected by measuring.

(Variable control of fixing roller during image formation period)
Here, the speed control of the fixing roller 41 will be described. 3A to 3C are schematic views for explaining the transport speed of the fixing roller 41 and the bending state of the paper. In the following, the transfer speeds of the paper S by the fixing roller 41, the transfer roller 32, and the transfer rollers R1 and R2 are shown as transfer speeds Vf, Vt, Vr1 and Vr2, respectively.

As shown in FIG. 3A, when the transfer speed Vf <transfer speed Vt, the paper is transferred between the transfer roller 32 and the fixing roller 41 according to the difference in transfer speed and the duration of transfer by both rollers. Deflection of S is formed. When the difference in transport speed is large, or when the length of the paper S is long and the duration is long, the amount of deflection becomes large, and the mechanical parts arranged in the transport path 53 interfere with the paper S to reach the paper S. Problems such as damage and dirt on the paper occur.

On the other hand, as shown in FIG. 3B, when the transport speed Vf> the transport speed Vt, the paper S is pulled between the two rollers. In this case, in general, the fixing roller 41 has a larger conveying force of the paper S than other conveying rollers such as the transfer roller 32. Therefore, when the elongation of the paper S exceeds a predetermined value, the paper S slips at the transfer position p1. It may occur or the paper may be torn. When slip occurs, problems such as transfer position shift occur.

Therefore, in the present embodiment, as shown in FIG. 3C, the transport speed Vf is variably controlled in the range of Vfmin to Vfmax according to the output of the deflection detection sensor 80. This variable control is performed at least while the paper is being conveyed by both the transfer roller 32 and the fixing roller 41, that is, during image formation. The values of Vfmin and Vfmax are predetermined fixed values in consideration of the dimensional tolerance of the outer diameter of the fixing roller and the thermal expansion during heating, and are stored in the storage unit 20. Even under the conditions of the upper and lower limits of the variation, the deflection is formed at Vfmin, and the deflection is eliminated at Vfmax.

(About the transport speed of the transport roller during the reading period)
The transport speed of the transport rollers R0 to R2 in the aftertreatment device 130 is usually controlled to be the same as the transport speed of the fixing roller 41. That is, when the fixing roller 41 is variably controlled according to the detection output of the deflection detection sensor 80 during the image forming period, the transport rollers R0 to R2 are also variably controlled so as to have the same speed.

However, even during the image formation period, the speed of the transport roller R1 (the same applies to the transport roller R0) is controlled at a constant speed during the reading period in which the scanner 70 reads.

Hereinafter, how the bending state of the paper S changes depending on the transport speeds Vr1 and Vr2 of the transport rollers R1 and R2 during this reading period will be described with reference to the drawings. 4A to 4D are schematic views illustrating the relationship between the setting of the transport speeds Vr1 and Vr2 and the bending state of the paper S.

FIG. 4A shows the paper when the transport speed Vr1 of the transport roller R1 is set to, for example, Vfmax so that the transport speed Vr1> the transport speed Vf is set and the transport speed Vr2 is controlled to be the same as the transport speed Vf. It is a figure which shows the bending state of S.

In this case, as shown in FIG. 4A, the paper S is pulled together without forming any deflection (the amount of deflection is less than zero) between the transport rollers R1 and R2. In this situation, since the conveying force of the fixing roller 41 is larger than the conveying force of the conveying roller R1, there is a possibility that the paper S may slip or the paper may be torn due to this tension. Further, if slip occurs, the reading accuracy of the scanner 70 cannot be ensured.

FIG. 4B shows paper when the transport speed Vr1 of the transport roller R1 is set to, for example, Vfmin so that the transport speed Vr1 <convey speed Vf is set and the transport speed Vr2 is controlled to be the same as the transport speed Vf. It is a figure which shows the bending state of S.

In this case, deflection continues to be formed between the transport rollers R1 and R2 due to the speed difference between the two rollers. If the amount of deflection exceeds the allowable upper limit value depending on the duration, it will interfere with the mechanical parts arranged in the transport path 53. If it interferes with the mechanical parts, the paper S may become dirty or damaged. The allowable upper limit value can be different depending on the arrangement position of the mechanical parts between the adjacent rollers. For example, the allowable upper limit value between the rollers R1 and R2 and the allowable upper limit value between the roller R2 and the fixing roller 41 can take different values.

FIG. 4C shows a bending state of the paper S when the transport speed Vr1 of the transport roller R1 is set to the transport speed Vr1> the transport speed Vf and the transport speed Vr2 of the transport roller R2 is set to the same speed as the transport speed Vr1. It is a figure.

In this case, the paper S is pulled together without forming a deflection between the transport roller R2 and the fixing roller 41. In this situation, since the conveying force of the fixing roller 41 is larger than the total conveying force of the conveying rollers R1 and R2, there is a possibility that the paper S may slip or the paper may be torn due to this tension. be.

FIG. 4D is a diagram showing a bending state of the paper S when the transport speed Vr1 of the transport roller R1 is set to the transport speed Vr1 <the transport speed Vf and the transport speed Vr2 is set to the same speed as the transport speed Vr1.

In this case, if the deflection continues to be formed between the transfer roller R2 and the fixing roller 41 due to the speed difference and the amount of deflection exceeds the allowable upper limit value depending on the duration, the deflection is arranged in the transfer path 53. It will interfere with mechanical parts.

In the present embodiment, under such a situation, the amount of deflection is controlled within a predetermined range (zero or more, allowable upper limit value or less) by performing the control described later, thereby transporting while ensuring the reading accuracy by the scanner. Prevents damage to the paper. Here, before explaining the control, the image forming apparatus according to the second embodiment will be described. FIG. 5 is a cross-sectional view showing a schematic configuration of the image forming apparatus 100b according to the second embodiment. In the second embodiment, the configuration of the post-processing device 130b is different from that of the image forming device 100 according to the first embodiment. Since the other configurations are the same, detailed description thereof will be omitted.

The post-processing device 130b of the image forming device 100b includes a first post-processing unit 131 having a scanner 70 and a second post-processing unit 132 for relay transfer.

The configuration of the first post-processing unit 131 has the same configuration as that of the post-processing device 130 of the first embodiment, and thus the description thereof will be omitted. The second post-processing unit 132 includes a plurality of transport rollers R21, R22, and R23, which function as a “second transport roller”. Although not described in the figure, the second post-processing unit 132 is provided with a transfer path for switchback provided with branch inlets and outlets on the upstream side and the downstream side of the transfer roller R22. Depending on the setting, the paper to be conveyed is turned inside out and conveyed via this transfer path for switchback.

(Paper transport control method)
Hereinafter, a method of controlling paper transport will be described with reference to FIGS. 6 to 8B. Although this control method can be applied to any of the image forming apparatus 100 and 100b of the first and second embodiments, in the following description, it is applied to the image forming apparatus 100b according to the second embodiment. This case will be described.

FIG. 6 is a flowchart showing a paper transport control method executed by the control unit 10 of the image forming apparatus 100b. 7, 8A, and 8B are diagrams showing the subroutine of FIG.

(Step S101)
First, start executing the print job. The control unit 10 starts executing the print job by accepting a print job from the user, for example, through a PC terminal connected to the image forming apparatus 100. During the period when the print job is started to be executed and the image is formed, the transport speed Vf of the fixing roller 41 is set to the detection output of the deflection detection sensor 80 by the control unit 10 as described with reference to FIGS. 3A to 3C. It is variably controlled accordingly.

(Step S102)
Next, it is determined whether or not the scanning process by the scanner 70 is "enabled" in the print settings of the print job. If the scan process is valid (YES), the process proceeds to step S104, and if it is not valid (NO), the process proceeds to step S103.

(Step S103)
Since the scanning process is not performed, while the paper S is being conveyed including during the image formation period, the control unit 10 synchronizes with the transfer speed Vf of the fixing roller 41 which is variably controlled as described above, and each transfer roller. The transport speeds of R1, R21, R22, and R23 are controlled to be the same as the transport speed Vf.

(Step S104)
When the scanning process is performed, the length of the paper S used for printing in the transport direction is larger than the distance L1 (see FIG. 5) between the scanning position p2 of the scanner 70 and the fixing roller 41 (nip position). Judge whether it is long or not. If the length of the paper S> the distance L1 (YES), the process proceeds to step S111, otherwise (NO), the process proceeds to step S105.

(Step S105)
While the paper S to be conveyed is being conveyed by the fixing roller 41, the other transfer rollers R1 to R23 are controlled to the same transfer speed as the transfer speed Vf of the fixing roller 41 in the same manner as in S103 described above.

FIG. 9A is a diagram showing a transport state of the paper S in step S105. Since the length of the paper S is shorter than the distance L1, the transport of the paper S by the fixing roller 41 and the scanning process by the scanner 70 are not performed at the same time.

(Step S106)
Next, it is determined whether or not the rear end of the paper S has passed through the fixing roller 41. This determination is made, for example, by a timer according to the detection signal of the paper detection sensor arranged in the transport path 53 and the drive time of the drive motor. When the rear end of the paper S has passed through the fixing roller 41, the process proceeds to step S107.

(Step S107)
After the paper S has passed through the fixing roller 41, the transport speeds of the transport rollers R1, R21, R22, and R23 are all set to the same constant value. As the constant speed, the transport speed Vf at the time of passing through the fixing roller 41 may be used, or a predetermined default value (for example, an intermediate value between Vfmax and Vfmin) may be applied. After that, the scanning process is performed while conveying the paper S at this constant speed.

FIG. 9B is a diagram showing a transport state of the paper S in step S107. During the reading period, that is, during the period from when the paper S reaches the reading position p2 to when the paper S comes out, the paper S needs to be conveyed at a constant speed from the viewpoint of reading accuracy. During the reading period, each transport roller maintains this constant speed while transporting the paper S.

(Step S111)
Here, the control unit 10 determines the type of the deflection creation mode. The setting of the deflection creation mode is stored in the storage unit 20 in advance. This setting may be changed by the user through the operation panel 60. If the type of the deflection creation mode is the "post-creation mode", the process proceeds to step S112, and if the type is the "pre-creation mode", the process proceeds to step S113.

(Post-creation mode (subroutine of S112))
FIG. 7 is a diagram showing a subroutine in step S112 of FIG. In the post-creation mode shown in FIG. 7, the deflection is not created until the start of scanning, that is, until the tip of the paper S reaches the reading position p2, and the deflection is created after the start of scanning. Is.

(Step S201)
In the post-creation mode, first, the other transport rollers R1 to R23 are controlled to the same transport speed as the transport speed Vf of the fixing roller 41, similarly to the above-mentioned S103.

FIG. 10 is a diagram showing a transport state of the paper S in step S201. As shown in the figure (the same applies to the following figure), the intervals between the adjacent rollers of the transport rollers R1, R21, R22, R23, and the fixing roller 41 are defined as sections 1 to 4, respectively. There is. In addition, the allowable upper limit value of the amount of deflection in each section is schematically represented by the position in the height direction in the figure, and is indicated by a dashed line. In the figure, the allowable upper limit of the amount of deflection in all sections is the same value, but as described above, different values are taken for each section according to the shape and position of the mechanical parts in each section in the transport path 53. obtain.

(Step S202)
Here, the control unit 10 determines whether or not the tip of the paper S has reached immediately before the reading position p2. When it is reached, the process proceeds to the next step. The distance (time) from the reading position p2 to just before this can be appropriately set depending on the timing at which the tip of the paper S reaches the transport roller R1 and the like.

(Step S203)
The transfer speed Vr1 of the transfer roller R1 is set to Vfmin. After that, the transport speed of Vfmin is maintained during the reading period.

(Step S204)
The control unit 10 starts the scanning process by the scanner 70 when the tip of the paper S reaches the reading position p2.

(Step S205)
After that, the control unit 10 sets the transfer speed of the transfer rollers R21, R22, R23 so as to maintain the relationship of the downstream roller ≤ upstream roller between the transfer rollers R1, R21, R22, R23, and the fixing roller 41. Control. Here, the fixing roller 41 is variably controlled, and the transport roller R1 is set to a constant speed in step S203.

(Loop 1 (S211 to S214))
In loop 1, the amount of deflection between all adjacent rollers is checked. Specifically, sections 1 to 4 are checked in order.

When the amount of deflection reaches a predetermined amount in any section (S212: YES), the transfer speeds of the transfer rollers on the upstream side and the downstream side of that section are set to be the same, and after that, the creation of deflection is stopped ( S213). In the present embodiment, this predetermined amount is set to the same value as the allowable upper limit value of each section for each section, but a predetermined margin is added to the allowable upper limit value and set to a value smaller than this. May be good.

(Step S221)
Here, it is determined whether or not the rear end of the paper S has passed through the fixing roller 41. If the rear end of the paper S has passed through the fixing roller 41, the process proceeds to step S226, and if not, the process proceeds to step S222.

(Step S222)
Here, the control unit 10 determines whether all the deflection amounts of the sections 1 to 4 have reached a predetermined amount. If it has been reached, the process proceeds to step S224. On the other hand, if it has not been reached, the process proceeds to step S223.

(Step S222)
Here, the control unit 10 determines whether or not the scanning process is completed. If it is not completed, the process returns to step S205. On the other hand, if the scanning process is completed, the process proceeds to step S225.

(Step S224)
If the amount of deflection in all sections reaches a predetermined amount and further deflection is created between the conveying rollers R1 to the fixing roller 41, the paper S being conveyed may come into contact with mechanical parts and cause damage. There is a risk of receiving it. In order to avoid this, the scanning process is stopped and the process proceeds to step S225.

(Step S225)
At this point, the scanning process has not been performed, so the control unit 10 controls all the transfer rollers R1 to R23 so that the transfer speed is the same as the transfer speed Vf of the fixing roller 41, and the process is shown in FIG. Return (return).

(Step S226)
After the paper S has passed through the fixing roller 41, the transport speeds of the transport rollers R21, R22, and R23 are all set to the same constant value. As a constant speed, for example, the same transfer speed Vfmin as that of the transfer roller R1 is set, and then the process is returned to FIG. 6 (return).

(Transition of the flexed state of the post-creation mode (S112))
Here, with reference to FIGS. 11A to 11D, the transition of the deflection state created in each section in the post-creation mode will be specifically described. In the example shown here, in step S205, the control unit 10 first variably controls the transport speeds of the transport rollers R21, R22, and R23 so as to be the same transport speed as the fixing roller 41.

11A to 11D are diagrams showing how the deflection increases in each section along the time series after FIG. 10.

FIG. 11A shows a state in which the amount of deflection reaches the allowable upper limit value in the section 1. Up to this point, since the transport speeds of the transport rollers R21, R22, and R23 are all controlled at the same transport speed as the fixing roller 41, the deflection is created only in the section 1. At this time, the increase speed of the deflection depends on the transport speed Vf of the fixing roller 41 which is variably controlled. For example, when the fixing roller 41 is controlled at the highest transfer speed Vfmax according to the output of the deflection detection sensor 80, the increase speed of the deflection in the section 1 becomes the fastest. When the amount of deflection reaches the allowable upper limit value in the section 1, the control unit 10 sets the transfer rollers R1 and R21 on the downstream side and the upstream side of the section 1 at the same transfer speed, that is, the transfer speed of the transfer roller R21. Set to Vfmin (S213). As a result, from now on, the deflection is created only in the section 2.

FIG. 11B further shows a state in which the amount of deflection reaches the allowable upper limit value even in the section 2. In the section 2, the control unit 10 transfers the transport rollers R21 and R22 on the downstream side and the upstream side of the section 2 at the same transport speed, that is, the transport speed of the transport roller R22, in response to the amount of deflection reaching the allowable upper limit value. Is set to Vfmin (S213). As a result, from now on, the deflection will be created only in the section 3.

FIG. 11C is a diagram showing a state in which the amount of deflection of the section 3 subsequently reaches the allowable upper limit value. FIG. 11D is a diagram showing a state in which the amount of deflection of the section 4 approaches the allowable upper limit value after the transfer speed of the transfer roller R23 is set to Vfmin.

After FIG. 11D, when the amount of deflection further increases in section 4 and reaches the allowable upper limit value, there is a concern that the paper may be damaged, so the scanning process is immediately stopped (S222, S224). It should be noted that the scan is rarely canceled, and in most cases, the scan process is completed before the amount of deflection reaches the allowable upper limit value in all sections.

In the examples shown in FIGS. 11A to 11D, examples of forming deflections in order from the downstream side to the upstream side section are shown, but the present invention is not limited to this. The deflection may be formed from any section, or may be created simultaneously in several sections. FIG. 12 is a diagram showing an example in which deflection is simultaneously created in all sections. For example, by dividing the difference between the transfer speed Vf of the fixing roller 41 and the transfer speed Vfmin of the transfer roller R1 into four, for example, dividing it into four equal parts and allocating them to each of the transfer rollers R21 to R23, the rate of increase in deflection in each section is uniform. Can be done. In this case, if the allowable upper limit values are not the same, or due to variations in the outer diameter of the transport roller, the amount of deflection in any section may reach the allowable upper limit value first. For example, when the allowable upper limit value is reached in the section 2, the control unit 10 speeds up the transport roller R21 and / or decelerates the transport roller R22 to set the transport speeds of both transport rollers to be the same. .. After that, the amount of deflection in the section 2 is maintained (S213).

As described above, in the "post-creation mode", during the reading period, the control unit 10 fixes the transport roller R1 (first roller) immediately before the reading position p2 to the minimum transport speed Vfmin within the variable range of the fixing roller 41. Set to. Then, the transport speed of the transport rollers R21 to R23 (second roller) between the two rollers is controlled by the transport speed Vf or less and the transport speed Vfmin or more of the fixing roller 41. By transporting the paper at a constant speed during the scanning period, it is possible to perform reading with high accuracy, read with high accuracy, and prevent damage to the transported paper.

(Pre-created mode (subroutine of S113))
8A and 8B are diagrams showing the subroutine of step S113 of FIG. In the pre-creation mode shown in FIGS. 8A and 8B, the deflection is created and accumulated before the start of scanning, and after the start of scanning, the accumulated deflection is gradually consumed.

(S301)
In the pre-creation mode, first, the transfer speeds of the transfer rollers R21, R22, R23 so as to maintain the relationship of downstream roller ≤ upstream roller between the transfer rollers R1, R21, R22, R23, and the fixing roller 41. To control. If this magnitude relationship is satisfied, the transfer speeds of the transfer rollers R1, R21, R22, and R23 can be set to various values. These transport speeds may be slower than normal transport speeds or may be stopped. If the transport speed is slowed down and the speed difference between the fixing roller 41 and the transport speed Vf is increased, a larger amount of deflection can be accumulated. Further, the amount of deflection accumulated before the start of scanning may be set according to the duration of transportation by the fixing roller 41, that is, the length of the paper S during the reading period. If the length of the paper S is not so long, the amount of deflection that accumulates may be small.

13A and 13B are diagrams showing how deflection is accumulated in each section in time series in the pre-creation mode. In the examples shown in FIGS. 13A and 13B, a predetermined amount of deflection is accumulated in order from section 4 to section 1 on the upstream side while the paper is abutted against the stopped transport roller.

In FIG. 13A, the transport roller R23 and all the rollers on the downstream side thereof are stopped. In this state, the tip of the paper S is in contact with the stopped transport roller R23, and a deflection corresponding to the transport amount of the fixing roller 41 is formed. When the amount of deflection in section 4 reaches a predetermined amount rx, the rotation of the transport roller R23 is started while maintaining this amount of deflection. That is, thereafter, the transport speed of the transport roller R23 is set to the same transport speed as the transport speed Vf of the fixing roller 41. Here, the predetermined amount rx of the section 4 that triggers the start of rotation of the transport roller R23 may be set to be the same as the allowable upper limit value, and the allowable upper limit value is added with a margin or multiplied by a predetermined coefficient. , May be set to a value less than this.

FIG. 13B is a diagram showing a state in which the deflection is formed in the section 3 following the section 4. When the amount of deflection in the section 3 reaches a predetermined amount rx, the transport roller R22 is set to the same transport speed as the roller on the upstream side. After that, the deflection of a predetermined amount rx is formed also in the section 2 and the section 1 in the same manner.

(Loop 2 (S311-S314))
In loop 2, the amount of deflection between all adjacent rollers is checked. Specifically, sections 1 to 4 are checked in order.

When the amount of deflection reaches a predetermined amount rx in any section (S312: YES), the transfer speeds of the transfer rollers on the upstream side and the downstream side of that section are set to be the same, and thereafter, the deflection of that section is created. Is stopped (S313). For example, as shown in FIG. 13A described above, when the amount of deflection in the section 4 reaches a predetermined amount rx, the transfer speed Vr23 of the transfer roller R23 is set to the same transfer speed Vf as the fixing roller 41 thereafter.

(Step S321)
Here, the control unit 10 determines whether or not the tip of the paper S has reached immediately before the reading position p2. When it is reached, the process proceeds to the next step. If it has not been reached, the process returns to step S301.

(Step S322)
The transfer speed Vr1 of the transfer roller R1 is set to Vfmax. After that, the transport speed of Vfmax is maintained during the reading period.

(Step S323)
The control unit 10 starts the scanning process by the scanner 70 when the tip of the paper S reaches the reading position p2.

(Step S331)
After that, the control unit 10 sets the transfer speed of the transfer rollers R21, R22, R23 so as to maintain the relationship of downstream roller ≥ upstream roller 41 between the transfer rollers R1, R21, R22, R23, and the fixing roller 41. Control. Here, the fixing roller 41 is variably controlled, and the transport roller R1 is set to a constant speed in step S322. As a result, the amount of deflection accumulated so far is gradually consumed.

14A to 14C are diagrams showing how the deflection accumulated up to that point is consumed in each section along the time series in the pre-creation mode. FIG. 14A shows a state immediately after the start of the scanning process, and in this state, the deflection is hardly consumed. FIG. 14B shows how the amount of deflection was consumed at almost the same rate in all sections. As shown in FIG. 14B, the deflection of each section may be consumed evenly in all sections, or may be consumed upstream or in order from any section. Regarding the setting of each transport roller at this time, the same idea as the deflection creating procedure in step S205 described with reference to FIGS. 12 or 11A to 11D can be applied to the deflection consumption procedure in step S331.

(Step S332)
Here, it is determined whether or not the rear end of the paper S has passed through the fixing roller 41. If the rear end of the paper S has passed through the fixing roller 41, the process proceeds to step S337, and if not, the process proceeds to step S333.

(Step S333)
Here, the control unit 10 determines whether or not all the deflection amounts of the sections 1 to 4 have been consumed. If all is not consumed, the process proceeds to step S334. On the other hand, if all is consumed, the process proceeds to step S335.

(Step S334)
Here, the control unit 10 determines whether or not the scanning process is completed. If it is not completed, the process returns to step S331. On the other hand, if the scanning process is completed, the process proceeds to step S336.

(Step S335)
When all the accumulated deflection amount is consumed and the deflection is further consumed between the transfer rollers R1 to the fixing roller 41, the paper S being conveyed is in a state of being pulled between the adjacent rollers. FIG. 14C is a diagram showing a state in which all the deflection is consumed. Under such a situation, the paper S being read slips, and the reading accuracy cannot be ensured. In order to avoid this, the scanning process is stopped and the process proceeds to step S336.

(Step S336)
At this point, the scanning process has not been performed, so the control unit 10 controls all the transfer rollers R1 to R23 so that the transfer speed is the same as the transfer speed Vf of the fixing roller 41, and the process is shown in FIG. Return (return).

(Step S337)
After the paper S has passed through the fixing roller 41, the transport speeds of the transport rollers R21, R22, and R23 are all set to the same constant value. As a constant speed, for example, the same transfer speed Vfmax as that of the transfer roller R1 is set, and then the process is returned to FIG. 6 (return).

In this way, in the "pre-created mode", the deflection is accumulated before the scanning process is started. During the reading period, the control unit 10 sets the transport roller R1 (first roller) immediately before the reading position p2 to the maximum transport speed Vfmax within the variable range of the fixing roller 41. Then, the transport speed of the transport rollers R21 to R23 (second roller) between the two rollers is controlled by the transport speed Vfmax or less and the transport speed Vf or more of the fixing roller 41. By controlling in this way, it is possible to perform reading with high accuracy by conveying the paper at a constant speed during the reading period, and to prevent damage to the conveyed paper.

The configuration of the image forming apparatus described above is not limited to the above configuration, and various modifications can be made within the scope of the claims, as the main configuration has been described in explaining the features of the above-described embodiment. .. Further, the configuration provided in the general image forming apparatus is not excluded.

In the above-described embodiment, an example of detecting the amount of deflection in each section by the deflection detection sensors 80 and 81 has been shown, but the present invention is not limited to this, and the difference in the transfer speed between the transfer rollers on the upstream side and the downstream side of each section is not limited to this. And, the amount of deflection (difference in feed amount (mm)) may be calculated for each section based on the duration.

Further, the program for operating the image forming apparatus 100 or the like may be provided by a computer-readable recording medium such as a USB memory, a flexible disk, or a CD-ROM, or may be provided online via a network such as the Internet. May be good. In this case, the program recorded on the computer-readable recording medium is usually transferred to a memory, storage, or the like and stored. Further, this program may be provided as a single application software, or may be incorporated into the software of each device as a function of the image forming apparatus 100.

100, 100b Image forming device 110 Image forming device main body 120 Paper feeding device 130, 130b Post-processing device 131 First post-processing unit 132 Second post-processing unit 10 Control unit 20 Storage unit 30 Image forming unit 32 Transfer roller 40 Fixing unit 41 Fixing roller 50 Paper feed carrier 51, 52 Paper tray 53 Transport path R0, R1, R2, R21, R22, R23 Transport roller 60 Operation panel 70 Scanner 80, 81 Deflection detection sensor (detector)
p1 Transfer position p2 Reading position

Claims (9)

Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A scanner that is placed directly downstream of the first roller and reads the image on the paper to be conveyed,
A detector that detects the amount of paper deflection formed between the transfer position and the fixing roller, and
During the image forming period for forming an image, the rotation of the fixing roller is controlled and the rotation of the fixing roller is controlled according to the paper transport state between the transfer position and the fixing roller.
During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the deflection formed in the paper conveyed between the fixing roller and the first roller. A control unit that controls the rotation of the second roller so that the amount is within a predetermined range is provided .
The control unit variably controls the paper transport speed Vf by the fixing roller between a predetermined maximum transport speed Vfmax and a minimum transport speed Vfmin according to the output of the detection unit.
Until the reading is started, the transport speeds of the first roller and the second roller are variably controlled so as to be the same as the transport speed of the fixing roller.
An image forming apparatus that sets the transport speed of the first roller to the transport speed Vfmin during the reading period, and controls the transport speed of the second roller at the transport speed Vf or less and the transport speed Vfmin or more. Along the transport path for transporting paper, in order from the upstream side
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A scanner that is placed directly downstream of the first roller and reads the image on the paper to be conveyed,
A detector that detects the amount of paper deflection formed between the transfer position and the fixing roller, and
During the image forming period for forming an image, the rotation of the fixing roller is controlled and the rotation of the fixing roller is controlled according to the paper transport state between the transfer position and the fixing roller.
During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the deflection formed in the paper conveyed between the fixing roller and the first roller. A control unit that controls the rotation of the second roller so that the amount is within a predetermined range is provided .
The control unit variably controls the paper transport speed Vf by the fixing roller between a predetermined maximum transport speed Vfmax and a minimum transport speed Vfmin according to the output of the detection unit.
Until the reading is started, the transport speeds of the first roller and the second roller are both controlled at a speed slower than the transport speed Vf of the fixing roller, and between the fixing roller and the first roller. Form a deflection in the paper to be transported,
An image forming apparatus that sets the transport speed of the first roller to the transport speed Vfmax during the reading period, and controls the transport speed of the second roller at the transport speed Vfmax or less and the transport speed Vf or more. 2 . Alternatively, the image forming apparatus according to claim 2. The image forming apparatus according to claim 3 , wherein if it is determined that all of the amount of deflection formed between the adjacent rollers during the reading period exceeds the predetermined amount, the reading during execution is stopped. A claim that includes a detection unit that detects the amount of deflection formed between the adjacent rollers, and determines the amount of deflection formed between the adjacent rollers during the reading period according to the output of the detection unit. 3 or the image forming apparatus according to claim 4. The amount of deflection formed between the adjacent rollers is calculated from the difference in transport speed between the adjacent rollers to be controlled and the duration, and is formed between the adjacent rollers according to the calculation result of the amount of deflection. The image forming apparatus according to claim 3 or 4 , wherein the amount of deflection is determined. The image forming apparatus according to any one of claims 3 to 6 , wherein the predetermined amount is set to a different value for each adjacent roller. Along the conveying path for conveying the sheet, in order from the top stream side,
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A program for causing an image forming apparatus including a scanner that is arranged immediately downstream of the first roller and reads an image on a sheet to be conveyed to execute a control method.
(A) A step of controlling the rotation of the fixing roller so that the amount of deflection of the paper formed between the transfer position and the fixing roller is within a predetermined range during the image forming period for forming an image. When,
(B) During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the paper is conveyed between the fixing roller and the first roller. Including a step of controlling the rotation of the second roller so that the amount of deflection formed is within a predetermined range.
In step (a), a predetermined maximum transfer speed Vfmax and a minimum transfer speed Vfmin are set according to the output of the detection unit that detects the amount of bending of the paper formed between the transfer position and the fixing roller. Control between
Moreover,
(C) The step of making the transport speeds of the first roller and the second roller the same as the transport speed Vf of the fixing roller until the reading is started is included.
In step (b), the control method is described in which the transport speed of the first roller is set to the transport speed Vfmin, and the transport speed of the second roller is controlled at the transport speed Vf or less and the transport speed Vfmin or more. A program to be executed by an image forming apparatus. Along the conveying path for conveying the sheet, in order from the top stream side,
An image forming unit that forms an image and transfers the formed image onto paper at the transfer position,
A fixing roller that heats and fixes the image transferred on the paper,
With one or more second rollers that convey the paper,
The first roller that conveys the paper and
A program for causing an image forming apparatus including a scanner that is arranged immediately downstream of the first roller and reads an image on a sheet to be conveyed to execute a control method.
(A) A step of controlling the rotation of the fixing roller so that the amount of deflection of the paper formed between the transfer position and the fixing roller is within a predetermined range during the image forming period for forming an image. When,
(B) During the scanning period in which the image on the paper is read by the scanner, the first roller is rotated at a constant speed, and the paper is conveyed between the fixing roller and the first roller. Including a step of controlling the rotation of the second roller so that the amount of deflection formed is within a predetermined range.
In step (a), a predetermined maximum transfer speed Vfmax and a minimum transfer speed Vfmin are set according to the output of the detection unit that detects the amount of bending of the paper formed between the transfer position and the fixing roller. Control between
Moreover,
(D) The step of controlling the transport speeds of the first roller and the second roller at a speed lower than the transport speed Vf of the fixing roller is included until the reading is started.
In step (b), the control method is described in which the transport speed of the first roller is set to the transport speed Vfmax, and the transport speed of the second roller is controlled at the transport speed Vfmax or less and the transport speed Vf or more. A program to be executed by an image forming apparatus.

Images