JPH0950207A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid continuing to discharge a paper sheet which is not enough corrected for curling, by automatically stopping the recording operation on a paper sheet when a recording material (paper sheet) curls to such a degree that curling can not be corrected. SOLUTION: A curling part 501 of a curling correcting part consists of a soft upper roller 502 made of an elastic material such as silicone sponge having a large diameter and a hard lower roller 503 made of a metal having a small diameter. By pressing the metal lower roller 503 to the elastic upper roller 502, a nip part which is convex upward along the outer diameter of the metal lower roller 503 is formed so as to correct positive curling (curling as convex downward) of a paper sheet P which passes through the nip part. The invading amount (x) of the metal lower roller 503 can be adjusted. Whether such a curling state that can not be corrected is generated in a paper sheet P or not is judged according to the processing amt. such as the toner amt. fixed to the paper sheet P when an image is formed. If curling which can not be corrected is produced in the paper sheet P, recording operation is automatically topped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a curl correction function of a recording material on which an image is formed.

[0002]

2. Description of the Related Art For example, in an image forming apparatus using an electrophotographic system, a toner image formed on a photosensitive drum is generally transferred onto a sheet, and a heat roller is used to fix the toner onto the sheet as a recording material. Has been adopted. Further, there is also provided a device that connects a sheet post-processing device such as a sorter to such an image forming apparatus to perform post-processing such as sheet sorting (collapsing) and stapling. When these post-processing devices are used, the curl state of the paper particularly affects the stacking performance and the alignment performance of the paper, and therefore a device using a curl correction device in combination is also proposed.

[0003]

However, conventionally, when a curl that cannot be corrected by the curl correction device is generated on the paper, the paper whose curl correction is insufficient is sent to a post-processing device such as a sorter. There was an occasion. For example, in an image forming apparatus equipped with a general curl correction device capable of correcting only the normal curl (convex downward) of the paper, images on both front and back sides of the paper that may have reverse curl (convex upward) may occur. At the time of formation, there is a possibility that the paper, whose reverse curl is not corrected, is sent to the sorter, which may cause misalignment of the paper, resulting in inaccurate staple position and defective staple. If the curl correction device is configured to correct both the normal curl and the reverse curl, there is a problem in that the image forming apparatus as a whole is increased in size and cost.

An object of the present invention is to prevent the recording operation on the recording material from being stopped in the case where the recording material has a curl that cannot be curled, and to prevent the recording material from being discharged with insufficient curl correction. An object of the present invention is to provide an image forming apparatus capable of performing the above.

[0005]

An image forming apparatus of the present invention comprises an image forming means capable of forming an image on a recording material, and a curl capable of correcting curl of the recording material on which an image is formed by the image forming means. A correction unit, a detection unit that detects a processing amount of the image forming unit that causes a curl of the recording material, and a curl that occurs on the recording material based on a detection result of the detection unit by the curl correction unit. Determination means for determining whether or not correction is possible, and control for stopping the image forming operation by the image forming means in response to the determination by the determination means that the correction by the curl correction means is impossible And means.

According to the present invention, when a curl that cannot be curled is generated on the recording material, the recording operation on the recording material is automatically stopped, and the ejection of the recording material whose curl correction is insufficient is continued. To avoid. Then, for example, it is possible to prevent a defective stacking of recording materials or a defective alignment in a post-processing unit such as a sorter.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic sectional view of a color image forming apparatus as a first embodiment of the present invention.

In this example, a digital color image reader unit 201 (hereinafter abbreviated as "reader unit") is provided at the upper part, a digital color image printer unit 202 (hereinafter abbreviated as "printer unit") at the lower part, a reader unit 201 and a printer. An image processing unit 203 is provided between the units 202.

In the reader unit 201, the original 30 is placed on the original table glass 31 and is exposed and scanned by the exposure lamp 32.
3, the light is condensed on the full-color sensor 34 integrally formed with the RGB three-color separation filter, and a color-separated image analog signal is obtained. The color-separated image analog signal is digitized through an amplifier circuit (not shown), processed by the image processing unit 203, and then sent to the printer unit 202.

In the printer section 202, the photosensitive drum 1 as an image bearing member is rotatably supported in the direction of the arrow, and the pre-exposure lamp 11, the corona charger 2 and the laser exposure optical system 3 are arranged around the photosensitive drum 1. The potential sensor 12, the developing device 4 (developing devices 4y, 4c, 4m, 4Bk), the on-drum light amount detection sensor 13, the transfer device 5, and the cleaning device 6 are arranged.

In the laser exposure optical system 3, the reader unit 2
The image signal from 01 is converted into an optical signal by a laser output section (not shown), the converted laser light is reflected by the polygon mirror 3a, passes through the lens 3b and the mirror 3c,
The image is projected on the surface of the photosensitive drum 1.

During image formation by the printer unit 202,
Rotate the photosensitive drum 1 in the direction of the arrow to move the pre-exposure lamp 11
The photosensitive drum 1 after the charge is removed in step 1 is uniformly charged by the charger 2, and then a light image E is emitted for each separated color to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1, and a toner image based on resin is formed on the photosensitive drum 1. The developing device is an eccentric cam 2
By the operations of 4y, 24c, 24m, and 24Bk, the photosensitive drum 1 is selectively approached in accordance with each separated color.

The developed toner image on the photosensitive drum 1 is recorded on the recording material cassettes 7a, 7b, 7c and the intermediate tray 22.
Alternatively, the image is transferred from the recording material tray 7m to the recording material supplied to the position facing the photosensitive drum 1 via the transport system and the transfer device 5. The transfer device 5 of this example includes a transfer roller 5a serving as a recording material holding unit, a transfer charging device 5b, and a suction roller 5 facing a suction charging device 5c for electrostatically sucking a recording material.
g, an inner charging device 5d, and an outer charging device 5e, and a recording material carrying sheet 5f made of a dielectric material is cylindrically integrated in the peripheral opening area of the transfer drum 5a that is rotatably supported. It has been stretched. A dielectric sheet such as a polycarbonate film is used as the recording material carrying sheet 5f (hereinafter referred to as "transfer sheet 5f").

In this embodiment, since electrostatic attraction is used as the recording material carrying means, 1/2 of the entire circumference of the transfer sheet 5f is used.
In the case of the following recording materials (250 mm), images can be formed on two recording materials at the same time. The case of simultaneously forming images on these two recording sheets is referred to as "two-sheet attachment control", and the case of performing image formation by electrostatically attracting one recording material to the transfer sheet 5f is referred to as "one-sheet attachment control". ".

As the drum-shaped transfer device, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum 1 is transferred onto the recording material carried on the transfer sheet 5f by the transfer charger 5b. In this way, the transfer sheet 5
A desired number of color images are transferred to the recording material that is adsorbed and conveyed to f, and a full-color image is formed. In the case of forming a full-color image, the recording material on which the four color toner images have been transferred in this way is separated from the transfer sheet 5f from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b and the separation charger 5h. , Via the heat roller fixing device 9,
The paper is ejected to a paper ejection curl correction unit 500 described later. Then, the recording material has a curl correction unit 5 as a curl correction unit.
After being subjected to curl correction control at 00, the sheet is sent to the sheet discharge post-processing unit 600 shown in FIG. 22, and then desired post-processing such as gathering and stapling is performed. The curl correction unit 500 and the paper discharge post-processing unit 600 will be described later.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming step again after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of the recording material,
After the recording material having an image formed on one surface is discharged from the fixing device 9, the transport path switching guide 19 is immediately driven to guide the recording material through the transport vertical path 20 and then to the reversing path 21a. By the reverse rotation of the reversing roller 21b, the rear end of the fed-in roller is ejected in the direction opposite to the fed-in direction, and the trailing end is stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step. When images are formed on both the front and back sides of the recording material in this way, the first side of the recording material on which the image is first formed is the “first side of both sides”, and the second surface on which the image is formed is the “second side”. Both sides are second side. "

Fur brushes facing each other through the recording material supporting sheet 5f in order to prevent scattering of powder on the recording material supporting sheet 5f of the transfer drum 5a and adhesion of oil described later on the recording material. 14 and a fur backup brush 15, an oil cleaning roller 16 and an oil cleaning backup brush 17 which face each other via the recording material carrying sheet 5f, and a polishing roller 18 and a polishing roller backup brush 19 which face each other via the recording material carrying sheet 5f. Use to clean. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in this example, the eccentric cam 25 is operated at a desired timing and the cam follower 5i integrated with the transfer drum 5a is operated, so that the gap between the recording material carrying sheet 5f and the photosensitive drum 1 is reduced. It has a configuration that can be set arbitrarily. For example, during standby or when the power is off, the interval between the transfer drum 5a and the photosensitive drum 1 is increased.

Next, the toner density control in the developing device 4 will be described. Since each toner in the magenta developing device 4m, the cyan developing device 4c, and the yellow developing device 4y reflects near-infrared light having a wavelength of about 960 nm, its characteristics are used to develop the inside of each developing device. The reflected light is detected by the developer concentration detecting unit 780 (see FIG. 2) arranged in the printer, converted into a toner concentration signal by the A / D converter 752 (see FIG. 2), and the toner corresponding to the toner concentration signal is not shown. Replenish the developer from the hopper.

On the other hand, the black toner has a wavelength of about 96.
Since the near-infrared light of 0 nm is absorbed, the toner density is not detected in the black developing device 4Bk, and the photosensitive drum 1 is not detected.
Wavelength of about 960 for black toner image developed on
The developed black toner density is detected from the ratio of the reflection component on the surface of the photosensitive drum 1 and the absorption component by the black toner by irradiating the near infrared light of nm, and the toner density in the developing device is calculated from this.

The on-drum light amount detection sensor 13 is arranged between the black developing device 4Bk and the transfer charging device 5b, and has a structure capable of detecting the black toner image developed by the black developing device 4Bk before the transfer. It can be detected in a state where there is no toner density fluctuation due to the operation.

Next, the heat roller fixing device 9 will be described in detail. The heat roller fixing device 9 has an upper fixing roller 9a, a lower fixing roller 9b, a fixing web 9c, and a fixing oil coating 9d.

The heat roller fixing device 9 includes fixing rollers 9a and 9a.
The toner on the recording material is melted by the heat energy of b,
The toner melted by the pressure between the fixing rollers 9a and 9b is fixed to the recording material. The surfaces of the upper fixing roller 9a and the lower fixing roller 9b are the upper fixing heater 9e and the lower fixing heater 9f which are built into the substantially central portions thereof, and the upper fixing thermistor 781 and the lower fixing thermistor which detect the respective roller surface temperatures. And 782 independently control the surface temperature.

The fixing web 9c contacts the upper fixing roller 9a when necessary in order to remove dirt on the upper fixing roller 9a or offset toner. At this time, the take-up device incorporated in the fixing web 9c can bring the new surface of the fixing web 9c into contact with the upper fixing roller 9a to improve the cleaning performance. Further, a fixing oil application roller 9 for supplying silicone oil to the surface of the cleaned upper fixing roller 9a.
d is prepared, and silicone oil is applied to the upper fixing roller 9a when necessary so that the toner on the recording material does not adhere to the upper fixing roller 9a.

Further, the heat roller fixing device 9 drives the fixing rollers 9a and 9b and the recording material conveying portion 9g by a fixing drive motor (not shown in FIG. 1). The fixing drive motor is driven by a fixing drive motor driver 761 (see FIG. 2). In this embodiment, in order to eliminate the difference in fixing property depending on the type of recording material, the fixing speed corresponding to four types of recording materials can be realized.

Assuming that a specific peripheral speed of the photosensitive drum 1 during image formation is VP (hereinafter referred to as "process speed"), the plain paper fixing speed VFN = VP, and the fixing speed VFD for the second side of the both surfaces is VFN. It is smaller, the fixing speed VFT for thick paper is smaller than VFD, and the fixing speed VFO for OHP is smaller than VFT. Therefore, VP
= VFN>VFD>VFT> VFO, and the fixing drive motor driver 761 (see FIG. 2) is configured to realize these four types of fixing speeds. The conveying speed of the recording material conveying portion 9g is set to the fixing roller 9
The peripheral speeds of a and 9b are set to be the same. Further, the fixing speed VFD for two-sided and two-sided is used for the two-sided and two-sided fixing of the toner of two or more colors, and is not used in the single-color mode in which only the one-colored toner is fixed even for the two-sided second side. The fixing operation is performed at the fixing speed VFN.

Next, the curl correction unit 500 as the curl correction unit and the paper discharge post-processing unit 600 as the post-processing unit will be described.

It is known that when a toner image formed by an electrophotographic method is fixed on a sheet, the sheet as a recording material curls. It is also well known that the curl adversely affects the alignment quality when performing post-discharge processing. For this reason, in this embodiment, the curl correction unit 500 corrects the curl so that the paper output post-processing unit 600 is not adversely affected and the paper is post-processed.

(Regarding curl correction unit 500) FIG.
Shows the main part of the curl correction unit 500 shown in FIGS. 1 and 22. In FIG. 23, the curling portion 501 is composed of a soft large-diameter upper roller 502 made of an elastic material such as silicon sponge and a metal hard small-diameter lower roller 503. Then, by pressing the metal lower roller 503 against the elastic upper roller 503 against the elastic upper roller 502, a convex nip portion is formed along the outer diameter of the metal lower roller 503, and the sheet P passing through the nip portion is formed. Correct the regular curl (convex downward curl).

The curl correction capability of the curl correction unit 500 is
This can be adjusted by changing the intrusion amount x of the metal lower roller 503 with respect to the elastic upper roller 502. The change of the intrusion amount x is centered on the pressure arm 504 supporting the metal lower roller 503 with respect to the support shaft 505. In addition, the eccentric cam 506 is swung by the rotation of the eccentric cam 506. To rotate the eccentric cam 506, an eccentric cam motor 507 including a stepping motor or the like is driven.

(Post-Discharge Processing Unit 600) Next, the post-discharge processing unit 600 will be described (hereinafter abbreviated as "sorter"). The sorter unit 600 is roughly composed of two parts as shown in FIG. One is a non-sort bin 601, which is used when ejecting sheets for which collating operation is unnecessary. The other is the sort bin 602, which has 20 bins during the collating operation.
By using and to output to the sort bins 602 in order, a collated sheet bundle can be obtained. 603 is
This is a sort flapper that switches the discharge power destination for the non-sort bin 601 and the sort bin 602. The flapper 603 sorts the paper into a non-sort path 604 and a sort path 605, and the non-sort bin 6
01 and the sort bin 602. The non-sort bin 601 has a configuration capable of discharging a larger capacity sheet than the sort bin 602.

Next, referring to FIG. 24, a sorter unit 600
A brief description of the aligning operation and the stapling operation will be given.
FIG. 24 is a perspective view of the sorter 600, and only one bin of the sort bin 602 having 20 bins is shown in this figure for easy understanding. The sheets accumulated in the sort bin 602 are aligned by the alignment rod 606 and the alignment auxiliary rod 607. Since the alignment operation differs depending on the paper size, the alignment sensor 608 and alignment motor 609
This is executed while controlling the operation position of the alignment rod 606 according to the paper size. Therefore, notches 602a and 602b are formed in the sort bin 602, and the rod 6 within a certain range.
It is configured to allow movement of 06 and 607. The sort bin 602 has a staple notch 602c.
And 602d are formed, and the stapling portion (not shown) is configured to staple the paper.

25 to 27, the automatic document feeder 400 (hereinafter abbreviated as "RDF") and the sorter 6 will be described.
A known collating operation in combination with 00 will be briefly described. In FIGS. 25A and 25B, the non-sort bin 601 which is unnecessary for description is not shown. Further, the numbers attached to the output sheets accumulated in the sort bin 602 indicate the order of the originals set in the RDF 400.

In this embodiment, in addition to the non-sort mode in which the collating operation is not performed, two kinds of collating modes, that is, a sort mode and a group mode, are prepared. Therefore, the sorter 600 is configured so that a total of three types of stacking modes can be selected and executed.

FIG. 25 (a) shows the stacking mode in the sort mode. The numbers beside the output sheets stacked in the sort bin 602 indicate corresponding document numbers. Since the RDF 400 is configured to feed the set original document from below, the sort bin 602 is loaded with the paper indicated by the numeral 4 at the bottom. This operation is repeated for 3 bins in FIG. 25 (a), and the next original sheet, which is number 3, is stacked thereon.

FIG. 25 (b) shows a loading mode in the group mode. The numbers beside the output sheets stacked in the sword bin 602 indicate the corresponding document numbers. In the group mode, output sheets corresponding to originals are stacked in each sort bin 602.

In addition to this, the sorter 60 in this embodiment
0 has a stapling function, and the stapling function is controlled so that it can be executed only in the stacking mode of the sort mode.

FIGS. 26A, 26B, and 26C schematically show the stapling position on the original 30 placed on the original table glass 31. In the corner stapling (stapling) in FIG. 26A, the output sheet is output upside down, so the front side of the sorter 600 is stapled. 27A, 27B, and 27C show the RDF 400.
FIG. 3 is a schematic diagram showing the stapling position on the original when the original set on the document is viewed from above.

In both cases of FIG. 26 and FIG. 27, the staple portions (not shown) are staple notches 602c and 602.
2d is used for stapling. To give a specific example, both corners in FIG. 26A and FIG. 27A are controlled so as to staple using the notch 602d.

FIG. 2 is a block diagram of a control system in the color image forming apparatus of one embodiment of the present invention. The color image forming apparatus is roughly divided into two blocks for control purposes. One is mainly the reader unit 201 and the image processing unit 2.
03 is a reader controller 700, and the other one is a printer controller 701 that controls the printer unit 202.

Reference numeral 702 denotes scanning mirrors 32a, 32b, 3
2c and an optical motor driver for driving an optical motor (not shown) for moving the exposure lamp 32, 703 is an RDF controller for controlling an automatic document feeder RDF400 that automatically exchanges documents, and 704 is a color image formation An operation unit for setting the operation mode of the device, 705
Is a ROM in which a control program for the reader controller 700 is stored, 706 is a RAM for storing data such as control values, and 707 is an I / O for driving a load such as the exposure lamp 32. The RAM 706 is backed up by a battery so that the data can be retained even when the power is turned off.

Next, the peripheral control section of the printer controller 701 will be described. Reference numeral 750 is a ROM that stores a control program for the printer controller 701, 751 is a RAM that stores data such as control values, and 752 is a digital signal that converts analog signals from the potential sensor 12, the drum light amount detection sensor 13, and the like. An A / D converter, 753 is a D / A converter that outputs an analog set value to the high voltage controller 770 and the like, and 754 is an I / O that drives a load such as a motor and a clutch.

Reference numeral 708 denotes a sorter controller, which communicates with the printer controller 701 and controls stacking in accordance with stacking mode instructions in the non-sort mode, sort mode, or group mode set by the operation unit 704, and staples in accordance with stapling instructions. Take control.

A curl motor driver 763 drives a curl motor which is a drive source of a curl correction unit 500 (not shown) and an eccentric cam motor 507 shown in FIG.

FIG. 3 shows the image processing unit 20 in this embodiment.
3 is a block diagram illustrating a configuration example of FIG. 10 in FIG.
Reference numeral 1 denotes a CCD reading unit, which is an amplifier for amplifying each analog RGB signal input from the above-mentioned full-color sensor 34 (see FIG. 1), and an A / A for converting the analog RGB signal into, for example, an 8-bit digital signal. D
It is composed of a converter, a known shading correction circuit for performing shading correction, and the like, and outputs a digital RGB image signal of an original image.

Reference numeral 102 denotes a shift memory, which responds to a shift amount control signal from the reader controller 700 to CC
The RGB image signals input from the D reading unit 101, for example, are corrected for deviations between colors and pixels. Reference numeral 103 denotes a complementary color conversion circuit, which is an RGB input from the shift memory 102.
The image signal is converted into an MCY image signal. A black extraction circuit 104 extracts a black region of the image from the MCY (magenta, cyan, yellow) image signal input from the complementary color conversion circuit 103 according to the black extraction signal input from the reader controller 700, and extracts the black region. B for the black area
Outputs a k (black) image signal.

Reference numeral 105 denotes a UCR circuit, which is a black extraction circuit 1
Undercolor removal (UCR) processing is performed on the MCY image signal input from the complementary color conversion circuit 103 according to the Bk image signal input from 04 and the UCR amount control signal input from the reader controller 700. That is, the black extraction circuit 10
4 and the UCR circuit 105 set the extracted black area to MCY3.
It is intended to improve color reproducibility by forming an image by replacing Bk toner instead of overlapping color toners.

The Bk image signal output from the black extraction circuit 104 is determined by the following equation (1).

[0052]

BK = A · min (C2, Y2, M2) (1) In the equation (1), A is a black extraction coefficient and C2, Y
2 and M2 are MCY image signals output from the complementary color conversion circuit 103. The black extraction coefficient A is determined by the reader controller 7
00 to determine the black extraction amount control signal.

Further, M output from the UCR circuit 105
The CY image signal is determined by the following equation (2).

[0054]

## EQU00002 ## M1 = B1. (M2-D1.Bk) C1 = B2. (C2-D2.Bk) (2) Y1 = B3. (Y2-D3.Bk) M2 in the equation (2) C2, Y2 are MCY image signals output from the complementary color conversion circuit 103, M1, C1,
Y1 is the MCY image signal output from the UCR circuit 105, and the coefficients B1, B2, B3, D1, D2, D3 are determined by the reader controller 700 according to the UCR amount control signal.

Next, a masking circuit 106 is provided for the reader controller 700 to remove the turbid component of the toner used and to correct the RGB filter characteristics of the CCD.
In response to the masking coefficient control signal input from
Masking processing is performed on the MCY image signal input from the R circuit 105. M output from the masking circuit 106
The CY image signal is expressed by the following equation (3).

[0056]

(Equation 3)

In the equation (3), a11 to a33 are masking coefficients, and M1, C1 and Y1 are UCR circuits 105.
M0, C0, Y0 are MCY image signals output from the masking circuit 106, and the masking coefficients a11 to a33 are determined by a masking coefficient control signal designated by the reader controller 700.

Reference numeral 107 denotes a selector, which responds to the color selection signal input from the reader controller 700 to the selection terminal S, of the M, C, Y, and Bk image signals input from the masking circuit 106 and the black extraction circuit 104. The image signal of one color is selected from the inside and the image signal V1 is output.

Reference numeral 108 denotes a reader gradation correction circuit, which performs gradation correction as shown in FIG. 4 on the image signal V1 input from the selector 107 and outputs an image signal V2. For example, the reader gradation correction circuit 108 performs density correction on the image signal according to any of the conversion characteristics a to e of FIG. 4 selected based on the gradation correction selection signal designated by the reader controller 700. The setting in the reader gradation correction circuit 108 is determined by the image density setting of the operation unit described later.

Reference numeral 109 denotes a printer gradation correction circuit, which gammas an example of which is shown in FIG. 5 according to the printer color selection signal input from the printer controller 701 in order to make the output characteristic of the printer unit 202 linear for each color. Any of the conversion characteristics M, C, Y, and bk is selected to correct the image signal.

A laser driver 110 is included in the laser exposure optical system 3 (see FIG. 1) described above. The laser driver 110 forms a latent image on the photosensitive drum 1 by modulating and driving the semiconductor laser based on the image signal V3 input from the printer gradation correction circuit 109.

FIG. 6 shows the operating section of the color image forming apparatus of the present invention. In FIG. 6, reference numeral 351 is a ten-key pad, which is used for setting the number of image formations and inputting numerical values for mode setting. A clear / stop key 352 is used to stop the set number of image formations and the set image formation operation. Reference numeral 353 denotes a reset key for returning the set number of images to be formed, the operation mode, the selected paper feed stage, and the like to the specified values. Reference numeral 354 denotes a start key. Pressing the start key 354 starts the image forming operation.

Reference numeral 369 is a display panel composed of a liquid crystal or the like, and the display contents are changed according to the setting mode in order to facilitate detailed mode setting. In this embodiment, the cursor keys 366 to 368 move the cursor on the display panel 369, and the OK key 364 determines the setting. Such a setting method can also be configured with a touch panel.

A paper type setting key 371 is set when an image is formed on a recording material thicker than the standard. When the thick paper mode is set by the paper type setting key 371, the LED 3
70 is controlled to light up. In this embodiment, only the thick paper mode can be set, but if necessary, the OHP
The functions can be extended to allow setting of modes for special paper and other types of paper.

A double-sided mode setting key 375 includes, for example, a "single-sided mode" for single-sided output from a single-sided original, a "single-sided mode" for double-sided output for a single-sided original, and a "double-sided output for double-sided original". Both-both mode ", 2 from two-sided original
It is possible to set four types of two-sided mode, that is, a "two-sided mode" for outputting one side of a sheet. The LEDs 372 to 374 are turned on according to the set double-sided mode, and "single-sided mode".
Then, all the LEDs 372 to 374 are turned off, and in the "single-both mode", only the LED 372 is turned on, "both-both mode"
Only LED 373 lights up in L, and L in "double-sided mode"
Only the ED 374 is controlled to light up.

(Specific Example of Image Formation) In the following, as a specific example, the "single-sided image processing" which does not use the automatic document feeder RDF400 is described.
The four-color image forming operation for plain paper for which the thick paper mode is not set in the "single mode" will be described.

In this case, since the recording material on which the image is formed is plain paper, the speed setting for the fixing drive motor driver 761 is set to the same VFN as the image forming speed (process speed) VP of the photosensitive drum 1. Set.

After the operator sets the number of images to be formed with the ten keys 351 and selects the paper feed stage with the paper selection key 303 and instructs the operation start with the start key 354, the printer controller 701 displays the drive motor required for image formation. For example, it instructs each driver of the photosensitive drum drive motor, the fixing drive motor, the paper feed drive motor, and the main drive motor to drive. Next, after the driving states of these drive motors are stabilized, the feeding operation of the recording material P is started from the designated paper feed stage (recording material cassette 7a, 7b, etc.). At this time, at substantially the same time, the reader unit 201 generates the image signal for magenta, which is the first developing color in the four-color mode, so that the above-described shift amount, black extraction amount, and UC
The R amount, the leader color selection signal, and the like are set in each block of the image processing unit 203. In addition, the reader gradation correction circuit 10
8 selects any of the conversion characteristics a to e shown in FIG. 4 corresponding to the contents designated by the density keys 304 and 306 of the operation unit 704. Further, the printer gradation correction circuit 109 is shown in FIG.
The conversion characteristic of m shown in is selected.

The recording material P fed from the designated paper feed stage is sent by the registration roller 50 at the same timing as the optical scanning operation of the reader section 201, and the attraction charger 5c and the attraction roller which is the counter electrode. 5 g is adsorbed on the transfer sheet 5 f.

The document information read by the reader unit 201 is processed by the image processing unit 203, and the charger 2
The photosensitive drum 1 uniformly charged by the laser is irradiated as a laser beam to form a latent image. First, the magenta developing device 4m
Is developed. The developed image information is transferred by the transfer charger 5b onto the previously adsorbed recording material P.
The image forming operations of M (magenta) document reading, latent image formation, development, and transfer are executed while the photosensitive drum 1 and the transfer drum 5a make one rotation, and similarly, the remaining three colors of C (cyan), The process is also performed for each of Y (yellow) and Bk (black). In addition, at this time, the setting for the image processing unit 203 is performed for each image formation.

The recording material P on which the four color images have been transferred in this manner is separated from the transfer sheet 5f. At that time, the separation charger 5h weakens the attraction force between the transfer sheet 5f and the recording material P, the separation push-up roller 8b deforms the transfer sheet 5f to perform curvature separation, and the separation claw 8a performs the transfer sheet 5 transfer.
The recording material P is separated from f.

The recording material P separated in this way is conveyed to the heat roller fixing device 9 by the recording material conveying section 9g which conveys at the same speed (VP) as the transfer drum 5a, and the fixing speed VFN = VP. After the paper is fixed by, the paper is curled by the discharged paper curl correction unit 500, and then the sorter 60
It is discharged to 0.

Next, the control for the oil cleaning member will be described in detail. Since the control method of the oil cleaning control differs depending on the fixing speed, the oil cleaning control on plain paper will be described first.

First, the control when the oil cleaning member is not operating in the plain paper mode (control when oil cleaning is not performed) will be described, and then the control when the oil cleaning member is operating in the plain paper mode (oil Control during cleaning) will be described.

(Control for not performing oil cleaning in plain paper mode) FIG. 7 shows the transfer operation of the final color from the start of the final color (the final one of a plurality of sheets on which an image of the same original is formed). It is a flowchart showing the control until the image forming operation is stopped, and such control is usually “post-rotation control”.
It is said that. By this post-rotation control, "normal cleaning control" of the transfer drum 5a which is the recording material gripping means is executed.
The normal cleaning control is performed by the fur brush 14 as described later.
It is a normal cleaning control using the fur backup brush 15.

FIG. 8 is a flowchart showing the flow chart of FIG.
When the transfer drum 5a is of a size capable of controlling the sticking of two sheets, a timing chart when the sticking of one sheet is performed by the "fixing (N) rotation control" described later, and FIG. 9 will be described later in the flowchart of FIG. 5 is a timing chart when one-sheet attachment control or two-sheet attachment control is performed by "fixing (N + 1) rotation control".

In the flowchart of the post-rotation control in FIG. 7, when the transfer of the final color of the image forming color determined by the color mode is started (step S1000), first, it is determined whether it is the final paper for the same original, that is, the final paper. It is determined whether or not (step S1001). Thus, it is determined whether or not the post-rotation control is performed after the transfer is completed. If the image is not formed on the final sheet (hereinafter referred to as "final image formation"), the image forming operation is continued (step S100).
2) This control ends (step S1003).

In the case of the final image formation, the size of the recording material in the conveying direction is compared with the distance LTCLN from the transfer position to the transfer sheet cleaning position (step S100).
4). This is because when the recording material is present at both the transfer position and the transfer sheet cleaning position (in this embodiment, the distance LTCLN from the transfer position to the transfer sheet cleaning position is 250 mm), the transfer drum 5a is cleaned during the transfer to the recording material. This is to prevent the occurrence of image disturbance when the operation or the recording material separating operation is performed, and when the recording material is applied to both the transfer position and the transfer sheet cleaning position, the transfer drum 5a is used to end the transfer operation. After idling only one rotation (step S1005), the separating operation (step S1006) and the cleaning operation (step S1008) are performed.

In the normal cleaning control in step S1007, the fur brush 14 is rotated by a motor (not shown), the fur backup brush 15 facing the fur brush 14 is enabled, and the fur brush 14 is applied to the transfer sheet 5f. Just touch them. At this time, the transfer sheet 5f for one round of the transfer drum 5a is cleaned regardless of whether the one-sheet attachment control or the two-sheet attachment control is performed.
The cleaning operation of is finished (step S1009). After that, the load and the high voltage of the operating motor are stopped (step S1009), and the image forming operation is ended (step S1).
010).

(Control during execution of oil cleaning in plain paper mode) When forming a single-color image on both surfaces of plain paper, at the time of image formation on the second surface of both surfaces (hereinafter referred to as "plain paper single color on both surfaces").
(Also referred to as), the oil cleaning operation of the transfer sheet 5f is executed as follows.

The recording material on which the image is formed on the first side, which is fed from one of the cassettes, is once stored in the intermediate tray 22 and then re-fed. The number of re-fed recording materials is 2
It is carried on the transfer drum 5a for image formation on the first side.
At this time, the surface of the transfer sheet 5f of the recording material is 1
The oil which is in contact with the image forming surface of the first surface and adheres in the fixing device 9 at the time of forming the image of the first surface is the transfer sheet 5f.
Will be reattached to the surface of. It is necessary to avoid this oil from adhering to the photosensitive drum 1. To this end, when the transfer sheet 5f during image formation on both sides of the second surface passes the transfer position, the transfer sheet 5f that passes the transfer position. Must be cleaned in advance with oil or controlled so that the recording material is present between the transfer sheet 5f and the photosensitive drum 1. When the fixing speed is the same as the process speed on both sides of plain paper single color both sides, the recording material is always placed between the transfer sheet 5f and the photosensitive drum 1 at the transfer position when images are continuously formed on a plurality of recording materials. Since it exists, it suffices to perform oil cleaning only during the above-described post-rotation control.

By the way, it can be considered that the recording material for image formation on the second surface of both sides is fed from the intermediate tray 22 and is fed from the recording material tray 7m. The recording material tray 7m may be reset by the user in order to output a double-sided image on the recording material that has been subjected to image formation. In this case, in the same manner as the paper feeding from the intermediate tray 22, the first surface is printed. Control is performed assuming that there is a recording material for the second side of both sides on which an image is formed.

Next, a specific oil cleaning control will be described with reference to the flowchart of FIG. This FIG. 10 shows both sides 2
An example will be shown in which the oil cleaning and the normal cleaning are performed on the surface, and only the normal cleaning is performed at other times.

Cleaning of the transfer drum is started (step S150
0) If the paper feed position is the intermediate tray 22 or the recording material tray 7m, it is determined in step S1501 that image formation is for the second side of both surfaces, and the oil cleaning backup brush 17 is used to perform the oil cleaning operation. It is validated (step S1502), the oil cleaning roller 16 is driven and brought into contact with the transfer sheet 5f (step S15).
03). Since the oil cleaning roller 16 is made of a material that absorbs oil, the oil cleaning roller 16 comes into contact with the transfer sheet 5f to remove the oil adhering to the transfer sheet 5f. Next, in order to perform normal cleaning, the fur backup brush 15 is enabled (step S1504), the fur brush 14 is driven to abut against the transfer sheet 5f (step S1505), and the cleaning operation is completed (step S1505). Step S1506). In step S1501, the paper feeding position is the intermediate tray 22 or the recording material tray 7.
If it is not m, oil cleaning is not necessary and only the fur brush 14 is driven for normal cleaning control (steps S1504 and S1505).

By the way, steps S1500 to S1500 in FIG.
S1506 is the transfer drum cleaning control in FIG. 7 (step S
When it is executed in 1007), oil cleaning can be performed as necessary in the post-rotation control.
Further, steps S1500 to S1506 of FIG.
When it is executed between the step S1001 and the step S1002, the oil cleaning or the normal cleaning can be carried out as necessary each time the recording material is separated from the transfer drum 5a. Furthermore, step S1500 to S1500 in FIG.
When step S1503 is executed between step S1001 and step S1002 in FIG. 7, only oil cleaning can be performed as necessary each time the recording material is separated from the transfer drum 5a.

(Peculiarity of fixing speed in thick paper mode)
Since more energy is required to fix toner on thick paper compared to plain paper, the fixing speed is slower than plain paper and the energy per unit area / hour is increased to increase the thickness of thick paper. It secures the fixability of.
In that case, conventionally, by setting the distance from the separation claw 8a to the contact position of the upper and lower fixing rollers 9a and 9b to be larger than the maximum image formation size of thick paper, the transfer drum 5a having the image forming speed (process speed) VP. While the peripheral speed of the recording medium is kept constant, the recording material conveying section 9g fixes the recording material at a fixing speed VF different from that of the transfer drum 5a.
The recording material conveying section 9g was used as a speed conversion area. For this purpose, it is necessary to secure the recording material conveying section 9g having a size corresponding to the maximum size of thick paper on which an image can be formed, and there is a drawback that the apparatus becomes large.

Therefore, in the present embodiment, the speed of the transfer drum 5a is made variable like the fixing speed,
When the fixing speed VF has to be slower than the image forming speed VP, the speed of the transfer drum 5a is reduced to the fixing speed after the transfer of the final color is completed.
This eliminates the need to secure a size as a speed conversion area in the recording material conveying unit 9g, and avoids an increase in size of the apparatus.

By the way, when the distance LTC from the transfer position in FIG. 1 to the leading end position of the recording material conveying portion 9g is larger than the size in the recording material conveying direction, the transfer drum 5a.
The deceleration up to the fixing speed is not in time for the next recording material separation operation. In such a case, the transfer drum 5a is rotated one extra rotation, and the recording material separation operation is performed at the timing of the subsequent separation operation. In this way, after the transfer of the final color in the thick paper mode is completed, the transfer drum 5a is restarted.
Hereinafter, the control of performing the separating operation after the rotation and the fixing will be referred to as “fixed thick paper (N + 1) rotation control”. Further, when the distance LTC from the transfer position to the leading end position of the recording material conveying unit 9g or the recording material conveying unit 9g can be used as a speed conversion area, that is, the transfer drum 5a is set to 1 extra.
The control when there is no need to rotate is referred to as "fixed thick paper (N) rotation control" below.

Here, in order to make the explanation easy to understand,
Assuming that the distance LTC from the transfer position in FIG. 1 to the leading end position of the recording material conveying unit 9g is 250 mm, the control is performed as follows in the thick paper mode with a typical recording material size.

A4 lateral feed size (feed direction 210 mm)
Sticking 1 sheet: fixing thick paper (N) rotation control A4 vertical feed size (feeding direction 297 mm) 1 piece sticking: fixing thick paper (N + 1) rotation control A3 vertical feeding size (feeding direction 420 mm) 1 sticking: fixing thick paper (N + 1) rotation Control A4 lateral feed size (feeding direction 210 mm) 2 sheets pasted: fixing thick paper (N + 1) rotation control (speciality of oil cleaning in thick paper mode) Next, in thick paper mode in which it is necessary to slow the fixing speed in this way The oil cleaning control will be described.

As described above, in the case of the oil cleaning control of the plain paper, since the speed of the transfer drum 5a is not changed after the image formation of the transfer drum 5a is completed, the image forming operation can be continuously executed, and the oil cleaning can be performed. The control need only be performed at the end of the image forming operation for the final sheet of the document.

On the other hand, in the thick paper mode, the speeds of the transfer drum 5a and the photosensitive drum 1 are set to be the same as the fixing speed VFT for fixing control. The photosensitive drum 1 must be returned to the original speed VP again, and if the recording material is different, continuous image forming operation cannot be performed. Therefore, when an image is formed on the second side of thick paper, the oil adhered on the transfer sheet 5f adheres to the photosensitive drum 1 at the transfer position, and the transfer operation of the final color to each recording material ends. Oil cleaning control is required for each. Therefore, at the time of forming an image in the thick paper mode, the oil cleaning control is performed every time when the transfer operation of the final color onto each recording material is completed, as described below.

(Image Formation Control in Thick Paper Mode) The color image formation control in the thick paper mode will be described below with reference to the flowchart of FIG. The flowchart of FIG. 11 corresponds to all recording materials in the thick paper mode, the plain paper mode, and the OHP mode. So Figure 1
In 1, the control corresponding to the fixing thick paper (N + 1) rotation control and the fixing thick paper (N) rotation control is expressed as the fixing (N + 1) rotation control and the fixing (N) rotation control as common to all recording materials. ing.

As described above, sheet feeding, latent image including suction,
The development and transfer operations (step S2000) are repeated until the final color is transferred (step S2001). After the transfer of the final color, the fixing speed VF is compared with the image forming speed VP (step S2002). Here, in the thick paper mode, the fixing speed VF is a slow fixing speed VFT for thick paper, and since the fixing speed VF is different from the image forming speed VP, the process proceeds from step S2002 to step S2003.

In step S2003, the transfer sheet 5f
It is determined whether or not the mode is for holding a plurality of recording materials. In this embodiment, since electrostatic attraction is used as the recording material carrying means, in the case of a recording material of 1/2 or less of the entire circumference of the transfer sheet 5f, image formation can be performed on two recording materials at the same time. It is possible. In this example, when images are formed on two recording materials at the same time (two sheets are attached), the two recording materials are
Since it is handled as one sheet of recording material that includes the paper distances,
The distance LTC from the transfer position to the leading end position of the recording material conveying section 9g becomes smaller than the size of the recording material conveying direction treated as one sheet of recording material, and the recording material conveying section 9g from the transfer position.
It is assumed that the distance LTC to the tip position of g cannot be used as the speed conversion area. So in this case,
Perform "fixing (N + 1) rotation control" (step S200)
6).

Next, when only one recording material is carried on the transfer sheet 5f and an image forming operation is performed (one sheet is stuck), the distance LTC from the transfer position to the leading end position of the recording material conveying portion 9g is LTC.
And the size PX of the recording material in the recording material conveyance direction are compared (step S2004). When the size PX is larger than the distance LTC, the distance from the transfer position to the leading end position of the recording material conveying unit 9g cannot be used as a conversion area of the fixing speed, so that “fixing (N + 1) rotation control” is performed. (Step S2006). On the contrary, when the size PX is smaller than the distance LTC (step S2004),
Perform "fixing (N) rotation control" (step S200)
5).

In this example, the distance LTC and the size of the recording material in the conveying direction are compared. However, when it takes time to change the speed due to the performance of the drum motor, the time required for the speed change is taken into consideration. Judgment step (step S20
03, step S2004) can be improved. In the fixing (N) rotation control, when the transfer sheet 5f is cleaned at substantially the same time as the recording material separating operation,
Since the cleaning operation of the transfer sheet 5f may adversely affect the recording material being transferred, it is necessary to change the control depending on the size in the recording material conveyance direction and the distance from the transfer position to the transfer sheet cleaning position. In this embodiment, the distance LTC
And the distance LTC from the transfer position to the transfer sheet cleaning position
The LNs are set to 250 mm and are equal to each other.

(Fixing (N) Rotation Control in Thick Paper Mode) The fixing (N) rotation control in the thick paper mode will be described below with reference to the timing chart of FIG. In FIG. 12, C corresponds to the image of cyan, Y corresponds to the image of yellow, and K corresponds to the image of black, and the reference signal of the transfer drum is the transfer drum 5a.
The photosensitive drum speed changes similarly to the transfer drum speed.

Fixing (N) rotation control (step S200
In 5), the operation is started after the start of the final color transfer (step S2001). The separating operation is the same as in the plain paper mode that is not the thick paper mode. That is, until the separation operation start timing t1 is reached, when the separation start timing t1 is reached, the separation claw 8a and the separation push-up roller 8b are operated to start the separation operation.

Next, the process waits until the transfer end timing t2 determined from the size PX of the recording material in the conveying direction. When the transfer end timing t2 is reached, the output of the transfer charger is set to OFF, and the photosensitive drum motor driver 760 is set.
On the other hand, the peripheral speed of the transfer drum 5a is set to be the same as the fixing speed VFT for thick paper. After that, it waits until the separation operation end timing t3, and the separation claw 8a is turned off to end the separation operation.

By the way, when such transfer is performed on the second surface of both sides in the thick paper mode, as described above, the fixing oil on the first surface of the recording material adheres to the surface of the transfer sheet 5f after separation. Therefore, step S200 in FIG.
8, it is determined that oil cleaning is necessary, and oil cleaning control is performed before the area of the transfer sheet 5f to which the fixing oil adheres reaches the transfer position again (step S200).
9). The oil cleaning is performed in step S of FIG. 10 described above.
Similar to 1502 and S1503, the oil cleaning backup brush 17 is enabled and the oil cleaning roller 16 is driven to contact the transfer sheet 5f. After all,
When the second side is the second side in the thick paper mode, the oil cleaning control is performed every time the recording material is separated.

Before the leading edge of the recording material reaches the recording material conveying portion 9g driven at the fixing speed VFT for thick paper, the peripheral speed of the transfer drum 5a becomes the same as the fixing speed VFT, Are normally separated and conveyed, and are fixed at the fixing speed VFT for thick paper. Then, after waiting until the discharge of the recording material is completed (step S2010), the speed of the transfer drum 5a, which is determined by the speed of the drum motor, is set to the speed VP for image formation in order to form an image on the next recording material. Set (Step S201
1).

After performing such an operation for the set number of sheets (step S2012), the image forming operation is ended.

(Fixing (N + 1) Rotation Control in Thick Paper Mode) The fixing (N + 1) rotation control in the thick paper mode will be described below with reference to the timing chart of FIG. FIG.
3 is an example when two sheets are pasted. In the figure, K1 is 1
Corresponding to the black image on the second recording material, Y2 and K2 correspond to the yellow and black images on the second recording material.

In this fixing (N + 1) rotation control, as described above, the size of the recording material in the conveying direction is larger than the distance LTC (= 250 mm) from the transfer position to the leading end of the recording material conveying portion, and the distance between them is set as the fixing speed. When it cannot be used as a speed conversion area, after the transfer operation is completed, the transfer drum 5a is rotated once and then the separation operation is performed.

Therefore, the process waits until the transfer end time t11 of the final color of the second sheet of the recording material stuck to two sheets is reached, and when the transfer end timing t11 is reached, the high voltage of the transfer charger is turned off and the transfer operation is performed. To finish. Next, the transfer drum 5
The peripheral speed of a is set to be the same as the fixing speed VFT for thick paper, and the fixing speed VFT is kept as it is until the separation start timing t12 in the next rotation. The separation operation is performed at the separation start timing t12,
After the separation operation is completed, the separation claw 8a is turned off and the operation is completed.

By the way, when such transfer is performed on the second surface of both sides in the thick paper mode, as described above, the fixing oil on the first surface of the recording material adheres to the surface of the transfer sheet 5f after separation. Therefore, step S200 in FIG.
8, it is determined that the oil cleaning is necessary, and the oil cleaning control is performed before the area of the transfer sheet 5f to which the fixing oil adheres reaches the transfer position again (step S20).
09). After all, when the fixing (N + 1) rotation control in the thick paper mode is the second surface of both sides, the oil cleaning control is performed every time the recording material is separated.

In this way, the transfer drum 5a makes one extra rotation to form a speed conversion area, and the fixing operation in the thick paper mode for the recording material up to the maximum image forming size in the normal operation is performed. Is possible. Also, 2
It is possible to realize the thick paper mode even in the operation of sticking sheets.

Then, after waiting for the discharge of the recording material (step S2010), the speed of the transfer drum 5a is set to the image forming speed VP for forming an image on the next recording material (step S2011).

After performing such an operation for the set number of sheets (step S2012), the image forming operation is ended.

(Fixing Normal Rotation Control in Plain Paper Mode) In the plain paper mode as compared with the thick paper mode described above, the image forming speed VP and the fixing speed are equal, and therefore, FIG.
1 from step S2002 to step S2007, and "fixing normal rotation control" is performed (step S200
7). In this fixing normal rotation control, the fixing speed is equal to the image forming speed VP, so images are continuously formed on the transfer sheet 5f, and the oil cleaning control is performed for the set number of sheets even in the image formation of the second surface of both sides. Is executed after the image formation is completed (steps S2013 to S2015).

FIG. 14 shows such control in comparison with FIGS. 12 and 13 in the case of the thick paper mode described above.
16 is a timing chart of FIG. 15. 14 is the same as the case of the thick paper mode shown in FIG.
FIG. 14 is a timing chart when two sheets are stuck, similar to the case of the thick paper mode of FIG. 13 described above.

For plain paper, when it is determined that oil cleaning is necessary in step S2014 after forming a set number of images, oil cleaning control (step S2015).
And then control ends. It is judged that the oil cleaning is necessary when the second side of the sheet is fed from the intermediate tray 22 or the recording material tray 7m as described above.

By the way, in the recording mode (OHP mode) for an OHP sheet having a fixing speed different from that of the thick paper mode, if the fixing speed is set to VFO, it can be applied to the OHP paper as in the case of the thick paper. .
When the second surface of the both surfaces is not in the single color mode, the fixing speed VFD is different from the process speed VP, and therefore the same oil cleaning control as that of the second surface of the thick paper mode may be performed.

Further, in consideration of the influence of the toner or the like attached to the first surface of the recording material on the fixing of the second surface, the fixing speed may be controlled to be slower on the second surface of both sides than on the first surface of both sides. This kind of control can be done in plain paper mode,
It can be executed regardless of the thick paper mode or the OHP mode.

(Recovery Control) Next, recovery control after paper jam detection (hereinafter, abbreviated as “jam detection”) in the image forming apparatus thus realized will be described with reference to the flowchart of FIG. As is well known, when a jam has occurred (step S3000), the conveyance of the recording material is stopped, and the occurrence of the jam is displayed on the operation unit (step S3000).
3001).

Thereafter, if the door that is opened to remove the jammed recording material is opened or closed (step S300)
2, S3003), it is confirmed by a sheet conveyance sensor (not shown) whether or not the recording material is removed from the sheet conveyance path or the transfer drum (step S3004). When the removed recording material includes the second-sided sheet of paper, the fixing oil on the image formed on the first side of the recording material adheres to the surface of the transfer sheet 5f when stopped. Therefore, in this case, steps S3005 to S3006
Then, the process proceeds to step 5 to perform the oil cleaning control and the transfer sheet 5f cleaning operation. On the other hand, when the second-sided sheet is not included, the oil cleaning control is not performed, and the transfer sheet 5 is formed only by the fur brush 14 and the fur backup brush 15.
After cleaning f (step S3007), the recovery operation is controlled (step S3008,
Steps S3009 and S3010).

Further, the judgment in step S3005 may be a judgment as to whether or not the oil cleaning control is necessary. When a paper jam detection requiring the oil cleaning control is detected, the oil cleaning control is performed before the recovery control. It is possible to prevent the fixing oil from adhering to the photosensitive drum 1 during the recovery control. In the present embodiment, since the presence or absence of oil cleaning control is determined according to the fixing speed and the paper feeding place, by expanding these judgment conditions, it is possible to perform oil cleaning control before recovery control in all cases. Become.

(Control of Polishing Roller 18) Next, control of the polishing roller 18 will be described with reference to the flowchart of FIG.

The polishing roller 18 operates together with the polishing roller backup brush 19 which faces the polishing roller 18. Polishing roller 18
Is used to scrape off toner and adhering substances from the paper that cannot be removed even by cleaning with the fur brush 14. Therefore, a member having the same effect as sandpaper is wound around the outer periphery of the polishing roller 18, and by this member, it becomes possible to scrape off the adhered matter that cannot be cleaned by the fur brush 14. The operation of the polishing roller 18 is the transfer sheet 5a.
Therefore, for example, the polishing control is performed every 2000 image forming operations.

The polishing control in this embodiment is realized by driving the polishing roller 18 and the polishing roller backup brush 19 and rotating the transfer drum 5a by 20 rotations. Therefore, it takes about several minutes to execute the image forming operation during that time. Therefore, in order not to increase the image forming operation inhibition time for restraining the user, the polishing control is performed when the fixing roller is cold immediately after the power is turned on (step S4000). As a result, the polishing control is performed while the temperature of the fixing roller reaches the temperature required for image formation, and the image formation operation inhibition time is shortened.

More specifically, when the detection temperatures of the fixing rollers (9a, 9b) detected by the upper fixing thermistor 781 and the lower fixing thermistor 782 are both 100 degrees or less, the above-described polishing control is performed (step S4001,
S4002). The determination as to whether or not to execute the polishing control when the power is turned on is not limited to this.
Whether or not the polishing control is performed may be determined based on the detection temperature of the fixing roller and the number of sheets after the polishing is performed.

When the fixing roller is heated, the image forming operation becomes possible, the desired mode is set by the operation section, and the start key 354 is pressed (step S40).
03), the above-mentioned image forming operation is started (step S4).
004). At the end of the image forming operation for each sheet, the polishing control counter is decremented (step S
4005). This operation is repeated for the set number of sheets (step S4006). When the automatic document feeder RDF is used, the image forming operation for the set number of sheets for the final original document is repeated (steps S4007, S400).
8). At this point in time, all the image forming operations have been completed, so the polishing control counter decremented according to the image forming operation is checked (step S400).
6). When this counter is 0, it means that a predetermined number of images have been formed since the last polishing operation, and the polishing operation is necessary. Therefore, when the counter is 0, the polishing control for performing the polishing operation is performed (steps S4009 and S401).
0). Since an image forming operation cannot be performed during polishing control, a message to that effect is displayed on the operation unit. By doing so, polishing control can be provided to the user as a series of image forming operations.

Next, the content of the polishing control in step S4010 will be described with reference to the flowchart of FIG. If the polishing control is started (step S410)
0), the fur brush 14 alone cleans the transfer drum 5a for one rotation to clean the toner on the transfer sheet 5f (step S4101). After that, the polishing roller 18 and the polishing backup brush 19 are driven (step S410).
2) The polishing operation is performed every time the transfer sheet 5f rotates by a predetermined rotation (20 rotations in this example) (step S41).
03). After the completion of the polishing operation for each predetermined number of rotations, the driving of the polishing brush 18 and the polishing backup brush 19 is stopped (step S4104), and the transfer drum 5 is restarted.
Cleaning is performed only by the fur brush 14 for one rotation of a (step S4105), and the shavings generated by the polishing operation are cleaned. After that, the initial number (2000 in this example) is set to the polishing control counter for controlling the number of sheets (step S4106), and the polishing control is ended (step S).
4107).

By the way, in this example, the number of recording materials is controlled from the time of the polishing control from the previous time, but in the case of the fur brush cleaning and the oil cleaning described above, the counter for such number management is independently set. With the provision, it is possible to prevent adverse effects on the apparatus due to a user's setting error when setting the type of paper and an operation error such as oil adhesion due to addition of output paper to the cassette.

(Cleaning Operation for Transfer Drum) Next, the execution of the cleaning operation for the transfer drum from the operating portion will be described. In this embodiment, an environment that can be executed only by a service person, not by the user is provided, but it may be executed by the user as necessary.

By operating the operation unit 704 in a predetermined manner, the input screen of the service mode used only by the service person is displayed on the display panel 369. FIG. 19 shows a state in which the service mode related to the cleaning operation for the transfer drum is displayed. In this state, press the cursor keys (365, 3
66, 367, 368) and the OK key 364 to select and execute the cleaning mode. Since the oil removal mode is selected in FIG. 19, when the OK key 364 is pressed in this state, the oil removal mode is executed.

The service mode related to cleaning the transfer drum will be described below with reference to the flowchart of FIG. First is the service mode, which is shown in FIG.
It is checked whether or not the transfer drum cleaning related service mode shown in 9 is set (step S5000). When it is affirmed, the input of the OK key 364 is monitored (step S5001), and the cleaning mode is confirmed at the time of the input. Then, the type of the selected cleaning mode is determined (steps S5002 and S5003), and if cleaning is selected, the process proceeds from step S50.
Proceeding to 06, transfer cleaning without oil removal is executed. This is step S30 in FIG. 16 described above.
The control is the same as 07, and the transfer sheet 5f is cleaned only by the fur brush 14 and the fur backup brush 15. On the other hand, when oil removal is selected, the process proceeds from step S5003 to step S5005, and transfer cleaning with oil removal is executed. This is the same control as step S3006 in FIG.
In addition to the fur brush 14 and the fur backup brush 15, the oil cleaning backup brush 17 and the oil cleaning roller 16 are driven to clean the transfer sheet 5f.

If a cleaning mode other than the above two is selected, the polishing control is executed (step S500).
4). This is to execute the oil removal control itself shown in FIG.

As described above, by selectively performing the cleaning operation for the transfer drum in the service mode, the service work can be shortened, the efficiency can be improved, and a high quality image can be formed.

(Operation of Curl Correction Unit 500 and Sorter 600) Next, a detailed description will be given of a control method for the curl correction unit 500 and the sorter 600 in this embodiment. First, an outline of curl correction control in the curl correction unit 500 will be described, and details thereof will be described using a flowchart.

As shown in FIG. 23, the one-sided output sheet of recording material has a positive curl (curl convex downward).
In many cases, it is discharged from the heat roller fixing device 9.
It is known that the positive curl of the paper is caused by the toner heated and melted by the heat roller fixing device 9 contracting due to air cooling after discharging. Also, the curl amount is
It is also known that it varies depending on the image density (toner amount), paper type (material, rigidity, thickness, size, crease direction, etc.) and the surrounding temperature and humidity environment, and that there is a correlation with the above-mentioned factors of change. ing. In this embodiment, the amount of toner is detected as the processing amount of the image forming apparatus that causes the curl, and the curl correction amount is controlled using the detected amount. As the processing amount of the image forming apparatus that causes the curl, various processing amounts that cause the curl can be detected in addition to the amount of toner, and can be used to control the correction amount of the curl.

First, as a specific example of curl generation, the curl growth direction when the feed direction of A4 size paper at the same image density is changed will be described. In the case of the A4 horizontal feed size (feed direction 210 mm), the curl grows in parallel to the side orthogonal to the paper conveyance direction as shown in FIG. 23, whereas the A4 vertical feed size (feed direction 29
In the case of 7 mm), the curl grows on the side parallel to the paper conveyance direction. This is considered to be an effect of the above-mentioned sheet gap.

In this example, in addition to such factors of curl growth, the operation mode of the sorter 600, the presence or absence of stapling, and the partial image density (toner amount) are comprehensively determined.
By performing the optimum curl correction control, the quality of the output paper in the final form is improved as a result. Further, the curl correction control is performed in consideration of the crevices expected from the paper size, and when it is determined that the curl cannot be completely removed, the stapling operation is prohibited to prevent the staple failure.

First, the method of calculating the partial image density (toner amount) in this embodiment will be described. In order to simplify the explanation, the partial image density (toner amount) will be described as an example in which the partial image density (toner amount) is divided into two in the paper conveyance direction, and the intrusion amount X in FIG. It will be described as possible.

The following is the flowchart of FIG. 28 and FIG.
Will be explained. FIG. 28 is a flow chart of the curl correction control, and the control is started when the image formation of the final color is completed (S6000).

When calculating the image density (toner amount),
First, the potential sensor 12 samples the potential at the time of image formation, averages it, and then converts it into a toner amount from the relationship between the potential amount and the toner amount obtained from an experiment. The toner amount here is the toner amount per unit area, and if the density is uniform, the same value is shown even if the paper size is changed. When forming a color image (4 colors),
The toner amount is represented by the sum of the magenta toner amount, the cyan toner amount, the yellow toner amount, and the black toner amount.
This toner amount calculation operation is performed after the image formation of the final color black is completed, and the first half average toner amount (TNRtop) in the first half of the paper transport direction, the second half average toner amount (TNRbottom) in the second half of the paper transport direction, and the entire area in the paper transport direction. Three toner amounts of the total average toner amount (TNRtotal) are calculated (S6001).

Next, the calculated toner amount is selectively used depending on the stacking mode for the sorter 600. That is, in the non-sort mode in which the sheets are discharged to the non-sort bin 601, since there is no matching operation, the loading amount is more important than the loading quality, and the bin shape is also the sorting bin 602.
Is different from Therefore, in the non-sort mode, the total average toner amount is used as the toner amount for determining the penetration amount X. (S6004).

In the staple sort mode in which the stapling is performed in the sort mode and at the end of the job, the portion to be stapled is in the latter half of the sheet, so the latter half average toner amount is used as the toner amount for determining the intrusion amount X (S
6005).

Further, when the mode is neither the non-sort mode nor the staple sort mode, that is, the sort bin 60.
In the case of the sorting mode or the group mode in which the sheet is discharged to 2, the larger one of the first half average toner amount and the second half average toner amount is used as the toner amount for determining the intrusion amount X in order to improve the stacking quality. (S6006). In this case, the curl correction quality particularly when the toner amount has a deviation is significantly improved as compared with the case where the total average toner amount is used.

As described above, the amount of toner used for determining the penetration amount X that determines the curl correction performance is determined. Next, a method of determining the penetration amount X according to the toner amount will be described with reference to FIG.

In this embodiment, the invasion amount X can be switched among three levels, which will be expressed as "small intrusion amount", "medium intrusion amount", and "large intrusion amount". Since the curl amount is proportional to the toner amount as described above, when the total toner amount is taken on the horizontal axis, the switching point data 1 between the small intrusion amount and the intrusion amount is 1
There are switching point data 2 for the intrusion amount medium and the intrusion amount large. Further, since the curl amount also depends on the paper size and the grain size, the data 1 and the data 2 are determined according to each paper size. This is expressed in Table 1 below. Since the curl amount also depends on the paper type, thickness, etc., data corresponding to Table 1 below is prepared for each type of recording material such as plain paper, OHP sheet, or thick paper on which images can be formed. .

[0143]

[Table 1]

From this table 1, the penetration amount switching data 1 and 2 for each paper size are determined, and the penetration amount X is determined from the above-described penetration amount determining toner amount (S6007). The determined penetration amount X is set every time the paper passes through the curl correction unit 500, and curl correction control is performed on each paper (S600).
8).

After that, it is checked whether it is staple sort (S6009). In the staple sort mode and when the size is not A4 vertical feed size (feeding direction 297 mm) or B5 vertical feed size (feeding direction 257 mm), stapling is executed on condition that it is the last original and the last sheet.

On the other hand, in the staple sort mode and A4
If the size is the vertical feed size or the B5 vertical feed size (S6010), the total average toner amount is stored for stapling inhibition determination (S6011). In the mechanism for performing the curl correction in the sheet conveying direction as in the present embodiment, when the total toner amount is large and the A4 vertical size or the B5 vertical size is used, the curl correction control may not be sufficiently applied to the paper. Therefore, here, the total average toner amount is stored as data for stapling inhibition determination.

After that, if the final original and the final sheet, that is, the timing at which stapling can be performed (S6012), whether or not even one of the total average toner amounts stored previously exceeds a predetermined value. Is checked (S6013). If it exceeds a certain value,
Since the quality of stapling cannot be guaranteed, the user is informed that stapling is not performed on the display panel 369 as shown in FIG. 30 (S6014), and the operation is terminated without performing stapling.

In the present embodiment, it is determined whether or not the total average toner amount exceeds the predetermined value even for one sheet in order to determine the A4 portrait size or B5 portrait size stapling prohibition. Of the number of sheets whose toner amount exceeds a predetermined value exceeds the predetermined number, or the ratio of the number of sheets whose toner amount exceeds the predetermined value in the stapling sheet bundle The same effect can be obtained by the method.

(Curl Correction Control During Double Sided Image Formation) Next, the curl correction control including the double sided image forming operation will be described with reference to the flowcharts of FIGS. 31 to 33. Description of the same parts as those in the flowchart of FIG. 28 described above will be omitted.

In this embodiment, as shown in FIG. 23, only the curl correction in the upward convex direction is possible with respect to the output paper on which the positive curl (convex downward) is predicted. . In double-sided output in which an image is formed on both sides and output, when the toner amount on the first side of both sides is large and the toner amount on the second side of both sides is small, that is, the image on the second side of both sides is fixed.
When a large amount of toner is deposited on the lower side of the sheet (first side image on both sides) and a small amount of toner is deposited on the upper side of the sheet (second side image on both sides) when fixing with, a reverse curl (convex upward) state Sheet is sent to the curl correction unit 500, and the reverse curl adversely affects the stacking of the sheet on the sorter 600.

Therefore, in the case where such reverse curl occurs and the stacking of sheets is adversely affected, for example, in the sort mode, the image forming operation is stopped and the sorter 60 is operated.
The control is performed so that the operation is restarted after the paper in 0 is removed.

31 to 33 are flow charts of the curl correction control including the countermeasure when the reverse curl occurs due to the double-sided image formation, and include the flow chart of FIG. 28 described above. Therefore, as in the case of FIG. 28, the control is started when the image formation of the final color is completed (S7).
000).

First, the first half average toner amount TNRtop and the second half average toner amount TNRbo described with reference to FIG.
Three toner amounts of ttom and total average toner amount TNRtotal are calculated (S7001).

Next, it is judged whether or not it is the first surface of the automatic both sides (S7002). Here, automatic double-sided refers to a case where a double-sided image is formed using the intermediate tray 22 (see FIG. 1). In the image forming apparatus of this embodiment, the intermediate tray 22
In addition to using, the double-sided image can be formed by setting the paper on one side of which the image is formed on the recording material tray 7m (hereinafter, referred to as "manual double-sided").

In S7002, in the case of the first automatic double-sided sheet, the sheet on which the image of the first double-sided sheet is formed is stored in the intermediate tray 22 without passing through the curl correcting section 500, so that the curl correction control is performed. Not performed. But,
After the sheet is fed from the intermediate tray 22 and the image on the second side of both sides is formed, the curl correction control is performed. Therefore, the total average toner amount TNRtotal of the image on the first side of both sides is automatically stored for the control. (S700
3).

Next, the calculated toner amount is selectively used depending on the stacking mode for the sorter 600. That is, in the non-sort mode in which the sheets are discharged to the non-sort bin 601, the loading amount is more important than the loading quality because there is no matching operation, and the bin shape is different from that of the sorting bin 602. Therefore, in the non-sort mode, the total average toner amount T is set as the toner amount for determining the intrusion amount X.
NRtotal is used (S7007).

In the staple sort mode in which the stapling is performed in the sort mode and at the end of the job, since the stapled portion is the latter half of the sheet, the latter half average toner amount TNRbottom is used as the toner amount for determining the intrusion amount X (S7008). .

Further, when the mode is neither the non-sort mode nor the staple sort mode, that is, the sort bin 60.
In the sort mode or the group mode in which the discharge is performed to 2, the toner amount for determining the intrusion amount X is determined to be the larger one of the first half average toner amount TNRtop and the second half average toner amount TNRbottom in order to improve the stacking quality. (S7009).

These S7007, S7008, and S
Since the toner amount used for determining the intrusion amount X in 7009 may be subjected to a correction calculation using the toner amount of the first surface of both sides when the automatic second side of the second surface described later, the provisional intrusion amount X The amount of toner for determination is set.

Next, in S7010, it is determined whether or not it is the second surface of the automatic both sides. First, a case where the automatic second side is not the second side will be described.

If the automatic second side is not the second side, that is, if the single sided output or the manual double side using the recording material tray 7m, the toner for determining the intrusion amount X provisionally determined in steps S7007, S7008, and S7009. Since the automatic second-side correction of the second surface, which will be described later, is unnecessary, the toner amount is used as the official toner amount for determining the intrusion amount X (S
7012), in steps S7013 to S7022 of FIG.
The same control as S6007 to S6016 in the flowchart of FIG. 28 described above is performed. In the case of the manual image formation operation of both sides of the both sides using the recording material tray 7m,
Although it is a double-sided image, there is no method of storing the toner amount of the first side of both sides, and therefore the curl correction control is performed by the same control as that of one side, that is, the toner amount is calculated only by the image of the second side of both sides.

In the case of the automatic double-sided second side in S7010, the double-sided one stored in S7003 from the toner amount tentatively determined in S7007, S7008, or S7009 according to the operation mode of the sorter 600 when the second side is the second side. The toner amount on the surface is subtracted, and this is set as the toner amount for determining the intrusion amount X (S7011).

This is because it has been experimentally confirmed that the curl growth amount when images are formed on both sides is proportional to the difference between the toner amounts on the first and second surfaces of both sides. To give a specific example that is easy to understand, it has been confirmed that curls hardly grow when the toner amounts on the first and second surfaces of both sides are equal. When the amount of toner on the first surface of both sides is large and the amount of toner on the second surface of both sides is small, the curl is discharged to the sorter 600 in a reverse curl state (convex upward) as described above. If such a reverse curl (convex upward) at the time of double-sided output affects the stackability of the sorter 600 and the matching operation,
The processing contents are changed in accordance with the operation mode of No. 1 to continue the image forming operation, and after the sheet in the sort bin 602 is once removed, the image forming operation is restarted.

That is, first, in S7023, it is checked whether or not a misalignment due to reverse curl (convex upward) occurs. FIG. 35 shows the relationship between the misalignment due to the reverse curl and the toner amount for determining the intrusion amount X on the second surface of the automatic both sides. FIG. 35 shows a form in which minus data is added to the above-described FIG. 29, and the toner amount determined in S7011 can take both plus data and minus data depending on the toner amount of the first side of both surfaces. When the toner amount determined in S7011 is negative data and smaller than the data 3 shown in FIG. 35, the reverse curl amount is large and the curl correction control does not function effectively as described above. In this case, in S7023, it is determined that a misalignment may occur. On the other hand, when the data is larger than the data 3, the aligning operation and the stapling operation can be normally performed even when the paper is in the reverse curl state, and thus S7013 in FIG.
From S7022 to S7022, the same control as from S6007 to S6016 in the above-described flowchart of FIG. 28 is performed.

Further, even if the toner amount is smaller than the data 3, in the non-sort mode in which the paper is output to the non-sort bin, there is no aligning operation by the aligning rod, so that the image forming operation is executed from step S7024 as it is ( Steps S7013 to S7022).

Next, it is determined whether the operation mode of the sorter 600 is the group mode (S7025). The same sort bin 60 if it is in group mode
Sheets of the same image (toner amount) are stacked on the sheet 2, and misalignment due to reverse curl is predicted on the sheets to be stacked in the same manner. A message as shown in FIG. 34 (b) is displayed on 369 (see FIG. 6) (S7030), image formation is prohibited for a sheet that has not been fed yet, and the operation ends (S7031).

In S7025, if the operation mode of the sorter 600 is not the group mode, that is, if it is the sort mode or the staple sort mode, the output paper for which misalignment due to reverse curl is predicted is the sort bin 602.
Since one sheet is loaded on each sorting bin, this output is
The image forming operation is continued until the sheets are stacked in 02 (S70).
26). After that, a message as shown in FIG. 34A is displayed on the display panel 369 (S7027) to notify the user to remove the paper from the sort bin 602.

After displaying the message, the sort bin 6 is detected by the sensor in the sort bin (not shown) of the sorter 600.
When it is detected that the paper has been removed from 02 (S7028), the image forming operation is restarted (S7028).
7029). At this time, since there is no sheet in the sort bin 602 where misalignment due to reverse curl is predicted, normal stacking operation is possible.

In this embodiment, the data 3 in FIG. 35 is used to judge the stacking failure due to the reverse curl in S7023. However, by changing the data 3 according to the paper size and the paper type, Accurate judgment is possible.

[Second Embodiment] In the first embodiment, OH
Although the oil cleaning control is performed even in the P mode, it is possible not to perform the oil cleaning on the OHP paper on which it is difficult to form images on both sides.

[Third Embodiment] In the first embodiment, the recording material conveying portion 9g has the same conveying speed as the fixing speed, but the conveying speed of the recording material conveying portion 9g is the peripheral speed of the transfer drum 5a. The object of the present invention can be achieved even if it is configured to be the same.

In this case, the distance LTC to be compared with the size PX of the recording material in the recording material conveyance direction in the first embodiment.
Can be realized by substituting the distance LTF from the transfer position to the fixing roller.

[Fourth Embodiment] In the first embodiment, the case of the four-color mode and the thick paper mode is shown. However, even in the case of any one-color, two-color, three-color mode and the thick paper mode. It is feasible.

Further, in the one-color mode in which the heat energy supplied to the recording material per unit time may be relatively small and in the thick paper mode, it is possible to output an image of which the fixing property is guaranteed without lowering the fixing speed. In this case, it is also possible to operate without decreasing the fixing speed only in the one-color mode. In this case, the oil cleaning control may be realized by the same control as that for plain paper.

[Fifth Embodiment] In the first embodiment, the suction means is used as the recording material carrying means, but a known gripper means may be used.

[Sixth Embodiment] In the first embodiment, the type of recording material is set using a setting key or the like.
By using the HP detection sensor 51 and the OHP detection sensor 52, it is possible to detect whether or not the recording material is OHP. These two OHP detection sensors 51, 5
Reference numeral 2 has both a light emitting portion and a light receiving portion, and the passage of the recording material is detected by shielding the space between the light emitting portion and the light receiving portion by the recording material.
Due to the structure of the OHP, only the tip portion of the OHP is shielded from light and the light is not shielded from the middle. Therefore, it is possible to detect whether or not the OHP is an OHP by utilizing such characteristics. The OHP used in the image forming apparatus of this embodiment is shown in FIG.
It is shown in FIG. In FIG. 21, S is a light-shielding band. As described above, by utilizing the characteristics of the OHP, the oil removal control and the image forming control by the OHP detection can be automatically executed.

[Seventh Embodiment] In the first half and the second half of the sheet conveyance direction, the toner amount calculation area is set in accordance with the staple type such as the corner binding, double binding, and single binding shown in the first embodiment. By further increasing two or more of the above, or by making it possible to calculate the toner amount of the portion not only in the paper feeding direction but also in the direction orthogonal to the paper feeding direction,
It is possible to more accurately control the curl correction according to the type of staple.

[Eighth Embodiment] In the first embodiment, the method of calculating the toner amount from the surface potential amount of the potential sensor 12 is shown. However, as the method of calculating the toner amount, the on-drum light amount detection sensor 13 or It is also possible to add the image signals after the printer gradation correction circuit 109 in FIG.

In the above-described embodiment, in step S6013 of FIG. 28, the toner amount of each of the A4 vertical size and the B3 vertical size is compared with a predetermined value. Is compared with the first predetermined value, and the toner amount of the B5 vertical size is compared with the second predetermined value to predict the curl amount according to the characteristics of each size and control whether stapling can be performed. May be.

Further, in the above-described embodiment, the invasion amount X is determined based on Table 1 in any mode, but it corresponds to each characteristic of the non-sort mode, the staple sort mode, the sort mode, and the group mode. Prepare a table (data 1 for each paper size, data 2)
The intrusion amount X may be determined based on these tables.

[0181]

As described above, according to the present invention, it is determined whether or not a curl which cannot be curled is generated on the recording material based on the processing amount in the image forming means such as the amount of toner fixed on the recording material. The recording operation is automatically stopped when a curl that cannot be corrected for curl occurs on the recording material.
It is possible to avoid continuing the discharge of the recording material for which the curl correction is insufficient.

As a result, for example, it is possible to prevent the defective loading of recording materials and the defective alignment in the post-processing means such as a sorter.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a color image forming apparatus as an embodiment of the present invention.

FIG. 2 is a block diagram of a control system of the color image forming apparatus of FIG.

FIG. 3 is a detailed control block diagram of the image processing unit shown in FIG.

4 is a gradation correction characteristic diagram showing an example of input / output signals in the reader gradation correction circuit of FIG.

5 is a gradation correction characteristic diagram showing an example of input / output signals in the printer gradation correction circuit of FIG.

FIG. 6 is a schematic plan view of the operation unit shown in FIG.

7 is a flow chart for explaining the operation from the start of the final color transfer operation of the final paper to the stop of the image forming operation in the color image forming apparatus shown in FIG.

FIG. 8 is a timing chart when one-sheet sticking control is performed by fixing (N) rotation control in the flowchart of FIG.

FIG. 9 is the fixing (N + 1) in the flowchart of FIG.
It is a control timing chart at the time of performing one-sheet sticking control or two-sheet sticking control by rotation control.

FIG. 10 is a flowchart for explaining a transfer drum cleaning operation applicable in the flowchart of FIG.

11 is a flow chart for explaining fixing control in the color image forming apparatus of FIG.

FIG. 12 is a timing chart for explaining the fixing (N) rotation operation in the thick paper mode in the flowchart of FIG.

13 is a timing chart for explaining the fixing (N + 1) rotation operation in the thick paper mode in the flowchart of FIG.

14 is a timing chart for explaining a fixing (N) rotation operation in a plain paper mode in the flowchart of FIG.

FIG. 15 is a timing chart for explaining the fixing (N + 1) rotation operation in the plain paper mode in the flowchart of FIG.

16 is a flowchart for explaining a jam process in the color image forming apparatus of FIG.

17 is a flowchart showing a polishing control process in the color image forming apparatus of FIG.

FIG. 18 is a flowchart for explaining polishing control in the color image forming apparatus of FIG.

19 is a schematic plan view for explaining a display example of the display panel in the service mode in the color image forming apparatus of FIG.

20 is a flow chart for explaining a process of a transfer drum cleaning mode in the color image forming apparatus of FIG.

21 is a plan view of an OHP sheet usable in the color image forming apparatus of FIG.

22 is a schematic cross-sectional view of a curl correction unit and a paper discharge post-processing unit that are connected to the color image forming apparatus of FIG.

23 is a perspective view of an essential part of the curl correction unit in FIG. 22.

24 is a perspective view of a main part of the paper discharge post-processing unit in FIG. 22.

FIG. 25 is an explanatory diagram of an operation mode of the paper ejection post-processing unit in FIG. 22.

FIG. 26 is an explanatory diagram of a relationship between an original set on the original platen glass of FIG. 22 and a staple position.

FIG. 27 is an explanatory diagram of a relationship between a document set on the automatic document feeder of FIG. 22 and a staple position.

FIG. 28 is a flowchart for explaining control of the curl correction unit and the paper discharge post-processing unit in FIG. 22.

FIG. 29 is an explanatory diagram of a relationship between the control amount of the curl correction unit of FIG. 22 and the toner detection amount.

FIG. 30 is an explanatory diagram of a display example when displaying that stapling cannot be performed in the step in FIG. 28.

FIG. 31 is a flowchart for explaining another example of control of the curl correction unit and the paper discharge post-processing unit in FIG. 22.

FIG. 32 is a flowchart for explaining another example of control of the curl correction unit and the paper discharge post-processing unit in FIG. 22.

FIG. 33 is a flowchart illustrating another example of control of the curl correction unit and the paper discharge post-processing unit in FIG. 22.

FIG. 34 is an explanatory diagram of a display example when a message is displayed in the steps of FIGS. 32 and 33.

FIG. 35 is an explanatory diagram of the relationship between the amount of toner for determining the amount of penetration and the curl obtained in the step in FIG. 31.

[Explanation of symbols]

 1 Photosensitive Drum 4 Developing Device 5 Transfer Device 5f Recording Material Support Sheet (Transfer Sheet) 7 Recording Material Cassette 8a Separation Claw 8b Separation Push-up Roller 9 Heat Roller Fixer 14 Fur Brush 15 Fur Backup Brush 16 Oil Cleaning Roller 17 Oil Cleaning Backup Brush 18 polishing roller 19 polishing roller backup brush 202 printer unit 203 image processing unit 369 display panel 500 curl correction unit 600 paper discharge post-processing unit

Claims (12)

[Claims] 1. An image forming unit capable of forming an image on a recording material, a curl correcting unit capable of correcting curl of the recording material on which an image is formed by the image forming unit, and a cause of curl of the recording material. Detecting means for detecting the processing amount of the image forming means, and judging means for judging whether or not the curl generated on the recording material can be corrected by the curl correcting means based on the detection result of the detecting means. And image forming means for stopping the image forming operation by the image forming means when the judging means judges that the curl correcting means cannot correct the image. apparatus. 2. The image forming apparatus according to claim 1, wherein the detection unit detects the processing amount for each predetermined area of the recording material. 3. The image forming means has a heat roller for fixing the toner image transferred to the recording material, and the detecting means is fixed on the recording material by the image forming means as the processing amount. The image forming apparatus according to claim 1, wherein the amount of toner is detected. 4. The image forming apparatus according to claim 3, wherein the detecting unit detects a difference in the amount of toner fixed on each of the front surface and the back surface of the recording material by the image forming unit. 5. The curl correction unit can correct only one of a curl that is convex on the front surface and a curl that is convex on the back surface of the recording material. The image forming apparatus according to any one of 4 above. 6. The curl correcting unit can correct the curl of the recording material by passing the recording material between a soft roller and a hard roller. An image forming apparatus according to claim 2. 7. The image forming apparatus according to claim 1, further comprising a display unit that displays a determination result of the determination unit. 8. The image forming apparatus according to claim 1, further comprising a post-processing unit that processes the recording material whose curl is corrected by the curl correcting unit. 9. The image forming apparatus according to claim 8, wherein the determination unit changes the determination standard based on the operation mode of the post-processing unit. 10. The image according to claim 8, wherein the control unit restarts the image forming operation by the image forming unit when the recording material is removed from the post-processing unit. Forming equipment. 11. The image forming apparatus according to claim 8, wherein the post-processing unit is a sorter capable of sorting the recording material on a plurality of trays. 12. The image forming apparatus according to claim 11, wherein the sorter has a stapler capable of stapling the recording materials accumulated on the tray.