JP2001158561A - Image forming device and controlling method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of meeting a variety of recording materials without adding a special variable mechanism to a curling function in an image forming device. SOLUTION: This image forming device, having a recording material designating means setting or detecting the types of recording materials, is provided with a recording material supporting means of supporting the recording material, a conveyance means of conveying the recording material to the recording material supporting means, a curling means which is included in the conveyance means and gives prescribed curling to the recording material, and a controlling means of changing the time required for the recording material to pass through the curling means according to the detected results of the recording material designating means.

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 capable of forming an image on various types of recording materials having different materials and thicknesses, and a control method therefor.

[0002]

2. Description of the Related Art For example, in an example of a color image forming apparatus using an electrophotographic system, a toner image formed on a photosensitive drum is transferred for each color to a transfer drum supporting a sheet, and a heat roller is used. Thus, a method of fixing toner to a recording material such as paper is adopted. In order to form an image on this image forming apparatus using various recording materials, before the recording material is supported on the transfer drum, the curling function of the recording material, the variable control of the fixing speed, and the high voltage output value and timing required for image formation For each recording material to control image formation.

[0003]

However, when the type of recording material is increased, particularly when electrostatic attraction is employed as the recording material supporting means of the transfer drum, the suction force, that is, the quality of the recording material conveyance is high. In such a case, it is necessary to vary the curling amount or capacity of the recording material as an auxiliary means of electrostatic attraction to the recording material, and in order to realize this, a variable mechanism must be added, which increases costs. I was

If the curl mechanism as the suction assisting means is not used, it is necessary to realize both the electrostatic suction and the means for physically supporting the recording material by a mechanism called a gripper as the recording material supporting means. However, the size of the apparatus and the cost were also increased.

An object of the present invention is to provide an image forming apparatus capable of coping with various types of recording materials without adding a special variable mechanism to a curling function in the image forming apparatus.

Another object of the present invention is to provide a control method of an image forming apparatus capable of applying curl corresponding to various kinds of recording materials by simple control.

[0007]

The image forming apparatus of the present invention achieves the above object by adjusting the speed of a curling mechanism. That is, the gist of the present invention is to provide a recording material supporting means for supporting a recording material and a conveyance for conveying the recording material to the recording material supporting means in an image forming apparatus having a recording material designating means for setting or detecting the type of the recording material. Means,
In accordance with the detection result of the curling unit included in the conveying unit and for imparting a predetermined curl to the recording material and the recording material designating unit,
An image forming apparatus comprising: a control unit that varies a time required for the recording material to pass through the curling unit.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

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

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

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

In the printer section 202, a photosensitive drum 1 serving as an image carrier is rotatably supported in the direction of an arrow. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3 , A potential sensor 12, a developing device 4 (developing units 4y, 4c, 4m, and 4Bk), a drum light amount detection sensor 13, a transfer device 5, and a cleaning device 6.

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 unit (not shown), and the converted laser light is reflected by a polygon mirror 3a, passes through a lens 3b and a mirror 3c,
The image is projected on the surface of the photosensitive drum 1.

At the time of image formation by the printer unit 202,
The photosensitive drum 1 is rotated in the direction of the arrow, and the pre-exposure lamp 11 is rotated.
After the photosensitive drum 1 is neutralized by the charging unit 2, the latent image is formed by irradiating a light image E for each separation color.

Next, a predetermined developing unit is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developer is an eccentric cam 2
The operation of 4y, 24c, 24m, and 24Bk causes the photosensitive drum 1 to be brought closer to the photosensitive drum 1 in accordance with each separation color.

The developed toner image on the photosensitive drum 1 is stored in a recording material cassette 7a, 7b, 7c, an intermediate tray 22.
Alternatively, the image is transferred from the recording material tray 7m to a recording material supplied to a position facing the photosensitive drum 1 via the transfer system and the transfer device 5. The transfer device 5 of the present embodiment includes a transfer drum 5a as a recording material holding unit, a transfer charger 5b, and a suction roller 5 opposed to a suction charger 5c for electrostatically attracting a recording material.
g, an inner power cutout 5d for removing electricity from the transfer drum 5a, and an outer charger 5e for removing electricity from the transfer drum 5a. A recording material carrying sheet 5f formed of a body is integrally stretched in a cylindrical shape. As the recording material carrying sheet 5f,
A dielectric sheet such as a polycarbonate film is used (hereinafter, referred to as “transfer sheet 5f”).

Various kinds of recording materials can be conveyed from the recording material tray 7m. To assist in attracting these recording materials to the transfer drum 5a, conveyance rollers 71, 72, 43, Of the transfer rollers 74 and 75,
Has a configuration capable of generating a curl such that the recording material is easily attracted (hereinafter, the periphery of the transport roller 74 is referred to as a curling unit 300).

In this embodiment, since the electrostatic attraction is used as the recording material holding means, the recording sheet 5f is 1 / one of the entire circumference of the transfer sheet 5f.
In the case of two or less recording materials (250 mm), an image can be similarly formed on two recording materials. The case where the two sheets are simultaneously image-formed is hereinafter referred to as "two-sheet sticking control", and the case where one sheet of recording material is electrostatically attracted to the transfer sheet 5f to form an image is referred to as "one sheet sticking control". "

FIG. 2A shows a state in which one recording material is adsorbed when one sheet is adhered to the transfer drum 5a. FIG. 2B shows a state in which two recording media are adhered to each other when the two recording media are adhered to the transfer drum 5a. The recording material when one sheet is stuck is adsorbed at the fixed point PTA on the transfer drum 5a at the top, and even if the size of the recording material in the rotation direction of the transfer drum is changed, the fixed point PTA is controlled so as to be adsorbed at the front end (recording). Form of adsorption of material A). On the other hand, in the case of sticking two sheets, similarly, the fixed point PTA is adsorbed so as to be the leading end and the recording material B is adsorbed.) The second sheet has the fixed point PTB which is a point 180 ° opposite to the transfer drum of the fixed point PTA. (The recording material C is adsorbed). Even when two sheets are adhered, even if the recording material size changes as in the case of one sheet adhered, the suction is performed so that the fixed points PTA and PTB become the leading ends.

Although not shown in FIG. 1, a connecting portion 5z for realizing the connection of the transfer sheets 5f in any case.
Adsorb so as to avoid.

Hereinafter, control for adsorbing the recording material so that the leading end of the recording material is at the head of the fixed point PTA will be referred to as A-side adsorption or A-side sticking control
The control of sucking the fixed point PTB so as to be the first will be expressed as B-side suction or B-side sticking control. As the transfer device in the form of a drum, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum 1 is transferred onto a recording material carried on a transfer sheet 5f by a transfer charger 5b. Thus, the desired number of color images are transferred to the recording material sucked and conveyed to the transfer sheet 5f, and a full-color image is formed. In the case of full-color image formation, the recording material on which the transfer of the toner images of four colors has been completed in this manner is separated from the transfer sheet 5f by the separation claw 8a, the separation push-up roller 8b, and the separation charger 5h from the transfer drum 5a. Then, the sheet is discharged to a sheet discharge curl correction unit 500 described later via the heat roller fixing device 9. Then, the recording material is subjected to curl correction control by a curl correction unit 500 as a curl correction unit, and then sent to a post-discharge post-processing unit 600 shown in FIG. Done. The curl correction unit 500 and the post-discharge processing unit 600 will be described later.

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

When images are formed on both sides of a recording material,
Immediately after the recording material having an image formed on one surface thereof is discharged from the fixing device 9, the conveyance path switching guide 19 is driven, and the recording material is once guided to the reversing path 21 a via the conveyance path 20. Due to the reverse rotation of the reversing roller 21 b, the sheet is retracted in a direction opposite to the direction in which the sheet is fed, with the rear end of the sheet being fed, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step. When an image is formed on both the front and back surfaces of the recording material in this manner, the first surface of the recording material on which the image is formed first is “the first surface of both surfaces”, and the second surface on which the image is formed is “the second surface”. Second side of both sides. "

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

In this embodiment, the gap between the recording material carrying sheet 5f and the photosensitive drum 1 is reduced by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5a. It 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, control of toner density in the developing device 4 will be described. Each of the toners in the magenta developing device 4m, the cyan developing device 4c, and the yellow developing device 4y has a wavelength of about 9
Since the light is reflected with respect to near-infrared light of 60 nm, the reflected light is detected by a developer concentration detecting section 780 (see FIG. 9) disposed in each developing device at the time of development by utilizing its characteristic. Then, the toner is converted into a toner density signal by an A / D converter 752 (see FIG. 9), and the toner corresponding to the toner density signal is supplied from a hopper (not shown) to a developing device.

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 concentration is not detected in the black developing device 4Bk, and the photosensitive drum 1 is not detected.
Wavelength of about 960 for the black toner image developed above
nm near-infrared light, the ratio of the reflection component on the surface of the photosensitive drum 1 and the absorption component by the black toner is detected by the on-drum light amount detection sensor 13 and converted by the A / D converter 752 (see FIG. 9). Then, the density of the black toner is detected from the density of the developed toner image, and the toner density in the developing device is calculated based on the detected density.

The on-drum light amount detection sensor 13 is disposed between the black developing device 4Bk and the transfer charger 5b, and is configured to detect a toner image developed by the developing device before transfer.

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

The heat roller fixing device 9 includes fixing rollers 9a and 9
melting the toner on the recording material 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 have a fixing upper heater 9e and a lower fixing heater 9f which are incorporated at substantially the center thereof, a fixing upper thermistor 781 for detecting the respective roller surface temperatures, and a fixing lower thermistor. 782, the temperature is independently controlled so as to be an optimum surface temperature.

The fixing web 9c comes into contact with the upper roller 9a to be fixed when necessary in order to remove dirt on the upper fixing roller 9a or offset toner. At that time, a new surface of the fixing web 9c is brought into contact with the upper fixing roller 9a by a winding device incorporated in the fixing web 9c to improve the cleaning performance.
Further, a fixing oil application roller 9d for supplying silicone oil to the surface of the cleaned upper fixing roller 9a is prepared, and a silicone oil is provided when necessary so that toner on the recording material does not adhere to the upper fixing roller 9a. Oil is applied to the upper fixing roller 9a.

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

Assuming that the peripheral speed of the photosensitive drum 1 at the time of image formation is VP (hereinafter referred to as "process speed"), the fixing speed VFN of plain paper is VPN, and the fixing speed VFD for the second side of both sides is VFN. 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. 9) is configured to realize these four types of fixing speeds. The conveyance speed of the recording material conveyance unit 9g is the same as that of the fixing roller 9.
The peripheral speeds are set to be the same as the peripheral speeds a and 9b. Further, the fixing speed VFD for two sides of two sides is used for the second side of both sides for fixing toner of two or more colors, and is not used in the single color mode in which only one color toner is fixed on the second side of both sides. The fixing operation is performed at the fixing speed VFN.

Next, the curl correcting section 500 as the curl correcting means and the post-discharge processing section 600 as the processing means will be described. These constitute a recording material post-processing device for processing paper as a recording material on which an image is formed.

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

(Regarding the curl correction unit 500) FIG.
FIG. 4 shows a main part of the curl correction unit 500 shown in FIGS. 1 and 3. In FIG. 4, the curling unit 50
1 is a soft large-diameter upper roller 502 made of an elastic body such as a silicon sponge, and a metal hard small-diameter lower roller 503.
It is composed of And the metal lower roller 503
Is pressed against the elastic upper roller 502 to form an upwardly convex nip along the outer shape of the metal lower roller 503, and the paper P passing through the nip is formed.
Correct the normal curl (curl downward convex).

The curl correcting capability of the curl correction unit 500 is as follows.
It can be adjusted by changing the amount x of penetration of the lower metal roller 503 into the upper elastic roller 502. The change in the amount x of penetration can be adjusted by moving the pressing arm 504 supporting the lower metal roller 503 around the support shaft 505. The eccentric cam 506 swings by rotation. To rotate the eccentric cam 506, an eccentric cam motor 507 including a stepping motor or the like is driven.

(Regarding Post-Discharge Processing Unit 600) Next, the post-discharge processing unit 600 will be described (hereinafter, abbreviated as "sorter"). The sorter section 600 is roughly composed of two parts as shown in FIG. One is a non-sort bin 601 which is used when discharging sheets that do not require collating operation. The other is a sort bin 602. During collation operation, the sort bin 602 having 20 bins is used and sequentially output to each sort bin 602.
A collated bundle of paper can be obtained. Reference numeral 603 denotes a sort flapper that switches the discharge power destination for the non-sort bin 601 and the sort bin 602. This flapper 6
03, the paper is sorted into a non-sort path 604 and a sort path 605,
Is discharged to the sort bin 602. Non-sort bin 60
Numeral 1 has a configuration capable of discharging a larger amount of paper than the sort bin 602.

Next, a brief description will be given of the alignment operation and the stapling operation by the sorter unit 600 with reference to FIG. FIG. 5 is a perspective view of the sorter 600, and only 20 bins 602 are shown in the figure for easy understanding of the description. The paper stored in the sort bin 602 is subjected to the alignment operation 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 the alignment motor 609 execute the alignment while controlling the operation position of the alignment bar 606 according to the paper size. Therefore, notch 6 is provided in the sort bin 602.
02a and 602b are formed, and the rod 60 within a certain range is formed.
6,607 is allowed to move. In the sort bin 602, stapling notches 602c and 602d are formed, and a stapling portion (not shown) is configured to be capable of stapling a sheet.

Next, referring to FIGS. 6, 7 and 8, an automatic document feeder 400 (hereinafter abbreviated as "RDF") and a sorter 6 will be described.
A well-known collating operation in combination with 00 will be briefly described. 6A and 6B, the non-sort bin 601 which does not need to be described is not shown.
The numbers on the output sheets stored in the sort bin 602 indicate the order of the documents set on the RDF 400. The RDF in the present embodiment is configured to feed a document from below, and the following description will be made in this embodiment. In order to make the explanation easier to understand, the first sort bin
It is set to output in order from the bin, and 602-
1, numbers are added to the second bins such as 602-2.
Also, the order of the originals is to be numbered in the order in which the originals are set in the RDF. Since the originals are fed from below, images are formed in descending order of the order of the originals.

In this embodiment, in addition to the non-sort mode in which no collation operation is performed, two collation modes, a sort mode and a group mode, are provided. Therefore, the sorter 600 has a configuration in which a total of three types of loading forms can be selected and executed.

FIG. 6A shows a loading mode in the sort mode. The subscript beside the output paper loaded in the sort bin 602 indicates the corresponding document number. . Since the RDF 400 is configured to send the set original from below, the sheets indicated by the subscript ORG4 are stacked at the bottom in the sort bin 602. This operation is illustrated in FIG.
In FIG. 6, the next document (subscript ORG3) is stacked thereon, and the operation is repeated up to ORG1 as the second document (final document feed document). Output in the form of a).

FIG. 6B shows a loading mode in the group mode. The subscript beside the output paper loaded in the sort bin 602 indicates the corresponding document number. In the group mode, output sheets corresponding to the originals are stacked in the respective sort bins 602, and the output form when the number of originals is four is as shown in FIG.
2 for the same document. That is, ORG4 as the fourth document (first document feed document) is output to the first bin 602-1 of the sort bin, and the second bin 602
ORG3, which is the third original, is output to -2.

In addition to this, sort 6 in the present embodiment
00 has a staple function, and the staple function is controlled so that it can be executed only in the stacking mode in the sort mode.

FIGS. 7A, 7B and 7C schematically show staple positions on the original 30 placed on the original platen glass 31. FIG. In the corner stapling (staple) in FIG. 7A, the output sheet is output upside down, so that the front side of the sorter 600 is stapled. FIGS. 8A, 8B, and 8C schematically show staple positions on a document when the document is set on the RDF 400 when viewed from above.

In both cases of FIGS. 7 and 8, staple portions (not shown) are provided with staple notches 602c and 602d.
Is used for stapling. As a specific example, the corner binding in both FIG. 7A and FIG. 8A is controlled to be stapled using the notch 602d.

FIG. 9 is a block diagram of a control system in the color image forming apparatus according to one embodiment of the present invention. The color image forming apparatus is roughly divided into two blocks for control. One is mainly composed of a reader unit 201 and an image processing unit 2.
03 is a reader controller 700 that controls the printer unit 202, and the other 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, an RDF controller for controlling an automatic document feeder RDF400 for automatically exchanging documents; 704, a color image forming apparatus 705 is a ROM in which a control program for the reader controller 700 is stored, and 706 is an R for storing data such as control values.
AM and 707 are I / Os for driving the addition of the exposure lamp 32 and the like. The RAM 706 is backed up by a battery so that data can be retained even when the power is turned off.

Next, the peripheral control unit of the printer controller 701 will be described. 750, a ROM for storing a control program of the printer controller 701; 751, a RAM for storing data such as control values; 752, an analog signal from the potential sensor 12, the on-drum exposure detection sensor 13, etc., is converted into digital data 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 loads such as a motor and a clutch.

Reference numeral 708 denotes a sorter controller, which communicates with the printer controller 701, controls the stacking according to the stacking mode instruction set in the non-sort mode, sort mode, or group mode set by the operation unit 704, or stapling according to the stapling instruction. Perform control.

Reference numeral 763 denotes a curl motor driver which 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. 10 is a block diagram showing a configuration example of the image processing unit 203 in the present embodiment. In FIG. 10, reference numeral 101 denotes a reading unit, which is an amplifier for amplifying each of the analog RGB signals input from the full-color sensor 34 (see FIG. 1), and for converting the analog RGB signals into, for example, 8-bit digital signals. A /
A D converter, a known shading correction circuit for performing shading correction, and the like output a digital RGB image signal of a document image.

Reference numeral 102 denotes a shift memory which corrects, for example, a color difference or a pixel difference of an RGB image signal input from the reading unit 101 in accordance with a shift amount control signal from the reader controller 700. A complementary color conversion circuit 103 converts an RGB image signal input from the shift memory 102 into an MCY image signal. Reference numeral 104 denotes a black extraction circuit, which receives an MC input from the complementary color conversion circuit 103 in accordance with a black extraction signal input from the reader controller 700.
A black region of the image is extracted from the Y (magenta, cyan, yellow) image signal, and a Bk (black) image signal for the extracted black region is output.

Reference numeral 105 denotes a UCR circuit, which is a black extraction circuit 1
The MCY image signal input from the complementary color conversion circuit 103 is subjected to under color removal (UCR) processing according to the Bk image signal input from the input device 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 convert the extracted black area into MCY3
The color reproducibility is improved by forming an image by replacing the color toner with the Bk toner instead of superimposing the color toner.

The Bk image signal output from the black extraction circuit 104 is determined by the following equation (1). Bk = A · min (C2, Y2, M2) (1) In the equation (1), A is a black extraction coefficient, C2, Y
2, 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
It is determined by a black extraction amount control signal designated from 00.

Further, M output from UCR circuit 105
The CY image signal is determined by the following equation (2). M1 = B1 · (M2-D1 · Bk) C1 = B2 · (C2-D2 · Bk) (2) Y1 = B3 · (Y2-D3 · Bk)

In the equation (2), M2, C2, Y2
Is the MCY image signal output from the complementary color conversion circuit 103,
M1, C1, and Y1 are M output from the UCR circuit 105.
CY image signal, coefficients B1, B2, B3, D1, D
2 and D3 are determined by the UCR amount control signal from the reader controller 700.

Next, reference numeral 106 denotes a masking circuit which removes turbid components of the toner to be used and the R of the full-color sensor.
In order to correct the GB filter characteristics, a masking process is performed on the MCY image signal input from the UCR circuit 105 according to the masking coefficient control signal input from the reader controller 700. The MCY image signal output from the masking circuit 106 is expressed by the following equation (3).

[0059]

(Equation 1)

In the equation (3), a11 to a33 are masking coefficients, and M1, C1 and Y1 are UCR circuits 105.
, M0, C0, and 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 specified by the reader controller 700.

Reference numeral 107 denotes a selector, which outputs M, C, Y, and Bk image signals input from the masking circuit 106 and the black extraction circuit 104 in accordance with the color selection signal input from the reader controller 700 to the color selection terminal S1. And selects an image signal of one color to output an image signal V1.

Reference numeral 108 denotes a reader gradation correction circuit which performs gradation correction as shown in FIG. 11 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 one of the conversion characteristics a to e in FIG. 11 selected based on the gradation correction selection signal specified by the reader controller 700. This reader gradation correction circuit 10
The setting at 8 is determined by the image density setting of the operation unit described later. This is connected to the terminal S of the reader gradation correction circuit 108.
Set to 3. Since these density corrections may be different for each color, the same setting as the above-described color selection terminal S1 is set to the color selection terminal S2 of the circuit 108, and the selected density-corrected signal is output as V2. You.

Reference numeral 109 denotes a printer gradation correction circuit. In order to make the output characteristic of the printer unit 202 linear for each color, a gamma, an example of which is shown in FIG. 12, according to a printer color selection signal input from the printer controller 701. One of the characteristics M, C, Y, and Bk is selected and set to the color selection terminal S4 to correct the image signal.

A laser driver 110 is included in the laser exposure optical system 3 (see FIG. 1). 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. 13 shows an example of the configuration of the operation unit 704 of the reader unit in the color image forming apparatus of the present invention. In FIG. 13, reference numeral 351 denotes a numeric keypad;
Used to set the number of images to be formed and to input numerical values for mode setting. Reference numeral 352 denotes a clear / stop key, which is used to stop the set number of images to be formed and to stop the image forming operation. Reference numeral 353 denotes a reset key for resetting the set number of images to be formed, the operation mode, the selected paper feed cutoff mode, and the like to the specified values. Reference numeral 354 denotes a start key. Pressing the start key 354 starts an image forming operation.

Reference numeral 369 denotes a display panel composed of a liquid crystal or the like, and the display content changes according to the setting mode in order to facilitate detailed mode setting. In the present embodiment, the cursor on the display panel 369 is moved with the cursor keys 366 to 368, and the setting is determined with the OK key 364. Such a setting method can be configured by a touch panel.

A paper type setting key 371 is set when an image is formed on a recording material thicker than the standard or various recording materials such as OHP. A paper type selection screen is displayed on the display panel 369 by the paper type setting key 371, and the cursor key 36
Although the paper type is selected in 6 to 369, the setting screen is omitted from the description. When the thick paper mode, which is frequently set, is set, the LED 370 is controlled to light. In other settings, the LED 370 is controlled so as not to light. In the present embodiment, only the thick paper mode can be set. However, the function can be extended as necessary so that the OHP and other special paper modes can be set.

Reference numeral 375 denotes a double-sided mode setting key. For example, a "single-sided mode" for performing single-sided output from a single-sided original, a "single-sided mode" for performing double-sided output from a single-sided original, and a "double-sided output for performing double-sided output from a double-sided original" Two-sided mode, two-sided original to 2
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 the “single-single mode”
, All the LEDs 372 to 374 are turned off, and only the LED 372 is turned on in the “single-both mode”, and the “both-both mode”
, Only the LED 373 is turned on, and in the “both-single mode”, L
Control is performed so that only the ED 374 is turned on. A density display unit 307 displays the density specified by the density keys 304 and 306.

(Specific Example of Image Forming) Hereinafter, as a specific example, "one-sided printing" which does not use the automatic document feeder RDF400 will be described.
The four-color image forming operation on plain paper in 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 to be 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, selects a paper feed stage with the paper selection key 303, and instructs an operation start with the start key 354, the printer controller 701 operates a drive motor necessary for image formation. For example, it instructs each driver of a photosensitive drum drive motor, a fixing drive motor, a sheet feed drive motor, and a main drive motor to drive. Next, after the driving states of the drive motors are stabilized, the feeding operation of the recording material P is started from the designated paper feeding stage (the recording material cassettes 7a and 7b). At this time, the reader unit 201 almost simultaneously generates the above-described shift amount, black extraction amount, and UC so as to generate an image signal for magenta, which is the development color of the first color in the four-color mode.
An R amount, a reader color selection signal, and the like are set in each block of the image processing unit 203. The reader gradation correction circuit 10
An item 8 selects one of the conversion characteristics a to e shown in FIG. 11 corresponding to the contents specified by the density keys 304 and 306 of the operation unit 704. The conversion characteristic m shown in FIG. 12 is selected for the printer gradation correction circuit 109.

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 unit 201, and the suction roller 5c and the suction roller serving as a counter electrode are fed. The transfer sheet 5f is attracted by 5g. As a pre-process of the suction operation, an inner charger 5d for removing electricity from the transfer sheet 5f,
The charge is removed using the outer charger 5e. A for the inner charger
Only AC can be output to C + DC and the outer charger,
Each AC is configured to be out of phase.

The detailed timing of each control will be described below with reference to FIGS. 14, 22 and 23. FIG. 14 shows the positional relationship between the photosensitive drum 1, the transfer drum 5a, and the attracted recording material at the timing of starting the latent image writing. The recording material is attracted from a fixed point PTA on the transfer drum 5a. This is a state of sheet sticking A side adsorption. In the present embodiment, since a full-color image is formed in the order of magenta, cyan, yellow, and black, this is a state when, for example, transfer of magenta is completed, and then writing of a cyan latent image on the photosensitive drum 1 is started. After a lapse of the distance LLT from the laser writing position to the transfer position at the process speed VP, the cyan transfer operation is started.

Next, FIG. 22 is a timing chart showing the state of FIG. 14, and shows the relation between the transfer drum reference signal, which is the basis of the timing control in this embodiment, and each image forming operation. It is.

The transfer drum reference signal for controlling the image forming operation will be described with reference to FIG. A sensor (not shown) and a sensor detection flag are arranged without the transfer drum 5a in order to match the formed image with the recording material adsorbed on the transfer drum 5a such that the fixed point PTA is at the top. More specifically, FIG. 14 shows a state of the photosensitive drum 1 and the transfer drum 5a immediately after the start of the latent image formation, and shows a state in which the leading end of the latent image overlaps the leading end of the recording material at the transfer position.

On the other hand, in FIG. 22, the reading operation of the latent image (laser) and the reader unit 201 and the transfer drum reference signal A
And the transfer drum reference signal A falls before the time Tprei before the latent image formation start timing. The reader unit 201 controls the transfer drum reference signal A (hereinafter, referred to as the transfer drum reference signal A) within the feasible reading magnification.
ITOP-A) Pre-speed scanning mirrors 32a, 32b, 32c required for a predetermined magnification within Tprei time from the fall
It is possible to secure a running time or a distance required for starting up and absorbing vibration.

A similar signal is also prepared for the B-side control, and this signal is used as the transfer drum reference signal B (hereinafter referred to as ITOP-
B). These transfer drum reference signals are output when the transfer drum 5a is rotating, that is, the eccentric cam 25 is operated, and the photosensitive drum 1 is driven by the photosensitive drum motor driver 76.
This is generated when operating at 0.
As a result, during the operation of the eccentric cam 25, the transfer drum 5a rotates at the same speed as the photosensitive drum 1.

As will be described later, the photosensitive drum motor is also configured to be able to be driven at a plurality of speeds corresponding to the fixing speed. The optical motor driver 702 is set so that a latent image can be formed Tprei time after the fall of the transfer drum reference signal A, and a timing reference signal for a transfer operation executed after a distance LLT from the start timing of the main latent image. A certain transfer drum reference signal C is prepared. The transfer drum reference signal C is Tp for the transfer operation, that is, the section (time) of the recording material at the transfer position.
The transfer drum reference signal A (the signal B in the present example) is configured to rise before the ret time, and to be a conventional transfer drum reference signal for image formation.
The same applies to the case where the operation timing is generated, and more accurate timing control can be performed particularly when the image forming speed is changed.

Next, in order to make it easier to understand the timing in more detail, the distance relationship between the respective elements of the image forming operation in this embodiment will be described with reference to FIG.

As described above, LLT is from the laser writing position to the transfer position, LAT is the distance from the suction position to the transfer position, LTS is the distance from the transfer position to the separation position, and LTC is the distance from the transfer position to the tip of the recording material transport section 9g. = 250
mm, the distance LTD from the transfer position to the outer charger, and the distance LTCLN from the transfer position to the fur brush 14 for cleaning the transfer drum = 250 mm.

FIG. 24 shows timings required for image formation by timings with respect to the recording material so that the arrangement of the control parts can be ignored. The image is output from the recording material with the leading end and the trailing end missing 6 mm and 4 mm, respectively, and is represented as an effective image area in the figure. This is necessary to prevent the inside of the apparatus from being stained due to toner dropping from transfer to fixing.

The transfer high voltage required for the transfer operation rises at the leading end margin of 6 mm at the leading end of the sheet, and falls at the rear end side over the entire area of the sheet. A CD output area is secured outside the effective area of the transfer high voltage by the inner charger which operates only before suction. This is because the potential of the transfer sheet 5f is set to a predetermined value before transfer in order to ensure transferability. An adsorption high-pressure area used for adsorbing paper is secured outside of the DC area of the charging device, and a charge removing operation for the transfer sheet 5f is performed outside the area. There is an AC effective area for the inner charger and the outer charger. If these timing relationships are not achieved, desired transfer performance and recording material transportability cannot be achieved. Therefore, a timing generation signal is ensured so as to guarantee the respective relationships in the following configuration.

FIG. 25 shows a main configuration of the high voltage control unit 770 for realizing such timing. As an example, a transfer high voltage at which control timing is strict will be described.

Reference numeral 801 denotes an operation amplifier for controlling the current flowing to the secondary side by controlling the current flowing to the primary side of the high voltage transformer 801 for generating the transfer current, and 805 denotes a current detecting resistor.

Next, the high voltage control signal CTL-V, which is a feature of this embodiment, will be described with reference to FIG. Since the transfer sheet 5f is a high-resistance material, the current required for the transfer is very small. At the same time, the transfer sheet 5f is a dielectric material and therefore has some capacitance. Since a very small current flows through the high-resistance transfer sheet 5f having this capacitance, most of the flowing current becomes a charging current for the capacitance at the initial rise of the transfer current, and is necessary for actual transfer. There is a slight delay before the start of the flow of the effective transfer current.

In order to prevent this, as shown in FIG. 26, an accelerating current is superimposed on the charging current at the time of the rise of the transfer current. FIG. 26 shows a case where the conventional acceleration current control is not performed and a case where the present invention is performed. When the acceleration current control is not performed, the effective transfer current It required for the transfer is shown.
May be realized in the middle of the image area. On the other hand, in this embodiment, the high-voltage control signal CTL-V is initially set to the acceleration current set value VctlA, and the required effective transfer current It is set in the middle of the leading edge margin. By setting the value to the set value Vctl, control is performed so as to guarantee the necessary effective transfer current It for the effective image area.

In this embodiment, the rising edge of the transfer drum reference signal A is used as the timing reference for the suction operation (B
The fall of the transfer drum reference signal B is used at the time of surface adsorption), and the fall of the transfer drum reference signal C is used for high voltage control of AC or DC of the inner charger and the outer charger. The sensor and the sensor light shielding flag are positioned so that the reference signal is generated a predetermined time before each operation. With this configuration, it is possible to control at an accurate timing even when an image forming speed described later is changed.

This timing control will be described with reference to FIG. FIG. 27 shows FIG. 22 in more detail.
In the present embodiment, the rise of the transfer drum reference signal C is used for the transfer control as described above. The transfer drum reference signal C rises before the transfer operation, that is, Tpret before the passage time of the transfer position of the leading end of the recording material. In this control, the drum motor clock which is an encoder pulse output from the photosensitive drum motor driver 761 from this rise is used. Lt1 is counted from Tt1, that is, from the transfer drum reference signal projection position on the transfer drum to the acceleration current setting position in the middle of the leading edge margin, and the acceleration current setting value VctlA is output.

As a result, even when the speed of the motor is changing, the acceleration control can be started at a desired position in the middle of the leading edge margin on the recording material. Next, the acceleration setting end time Tt2 is counted by the system clock counting function, which is a built-in function of the printer controller 701, from the acceleration control start setting. This is because the acceleration setting effective period mainly depends on the environmental characteristics of the transfer sheet 5f and the environmental characteristics of the recording material, and does not depend on the image forming speed. By this control, a desired effective transfer current can be secured for the image area.

The acceleration current setting value VctlA
And the acceleration setting end time Tt2 are determined by the type of the recording material and the temperature sensor 7.
83, the humidity sensor 784, the number of transfers, that is, the transfer color, and the operation mode of one side, the first side of both sides, and the second side of both sides are appropriately controlled.

Further, as compared with the case where the measurement of the acceleration control start time Tt1 and the acceleration setting end time Tt2 is counted by using only the drum motor clock or the system clock, the control when the image forming speed is changed becomes more accurate. Needless to say, no adjusting means is required.

The document information read by the reader unit 201 is processed by the image processing unit 203,
The photosensitive drum 1 charged uniformly by the laser beam is irradiated as a laser beam to form a latent image, and is first developed by a magenta developing device 4m. The developed image information is transferred by the transfer charger 5b onto the recording material P adsorbed earlier. The image forming operations of M (magenta) document reading, latent image formation, development, and transfer are performed while the photosensitive drum 1 and the transfer drum 5a make one rotation, and similarly, C (cyan), The process is also performed for each color of Y (yellow) and Bk (black). 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 are transferred is separated from the transfer sheet 5f. At this time, the adsorbing force between the transfer sheet 5f and the recording material P is weakened by the separation charger 5h, the transfer sheet 5f is deformed by the separation push-up roller 8b to perform the curvature separation, and the transfer claw 8a is separated by the separation claw 8a.
The recording material P is separated from f.

The recording material P thus separated 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 sheet is fixed by the above-mentioned method, the sheet is subjected to the curl correction by the sheet discharge curl correction unit 500,
Discharged to zero.

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, control when the oil cleaning member is not operated in the plain paper mode (control when oil cleaning is not performed) will be described, and then control when the oil cleaning member is operated in the plain paper mode (oil cleaning). Control at the time of execution) will be described.

(Control for Implementing No Oil Cleaning in Plain Paper Mode) FIG. 15 is a diagram showing a state in which the transfer operation of the final color to the final sheet (the last one of a plurality of sheets on which the same original image is formed) is started. 5 is a flowchart showing control up to the stop of the image forming operation, and such control is generally called “post-rotation control”. Thereafter, by the rotation control, "normal cleaning control" of the transfer drum 5a as the recording material supporting means is executed. The normal cleaning control is a normal cleaning control using the fur brush 14 and the fur backup brush 15 as described later.

FIGS. 16 and 17 are diagrams showing the timing of the post-rotation control shown in FIG. 15 and the transfer operation of the final color. FIG. 17 shows a timing chart when “N) rotation control” is performed, and FIG. 17 shows a timing chart when “fixing (N + 1) rotation control” is performed.

In FIG. 16, when the final development processing is completed and the transfer is executed, the separation of the recording material is started when the transfer operation has progressed to some extent. At the time when the separation is almost completed, the cleaning operation of the transfer drum starts. After the end of the cleaning, the drum motor is stopped at a predetermined time, and the post-rotation process ends. On the other hand, when there are two recording materials on the transfer drum or when handling a long recording material, the cleaning is not performed during the separation process, and the transfer drum is idled once after the separation process. A cleaning operation is performed (FIG. 17).

In FIG. 15, when the transfer of the final color of the image forming color determined by the color mode is started (step S1000), it is first determined whether or not the last sheet for the same document, that is, the last sheet. (Step S100
1). Thus, after the transfer is completed, it is determined whether to perform the post-rotation control. Image formation on final paper (hereinafter referred to as
If it is not “final image formation”), the image forming operation is continued (step S1002), and this control ends (step S1003).

If it is the final image formation, the size of the recording material in the transport direction is compared with the distance LTCLN from the transfer position to the transfer sheet cleaning position (step S100).
4). This is because the recording material is applied to 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 m).
m), in order to prevent the image disturbance from occurring when the cleaning operation of the transfer drum 5a or the separating operation of the recording material is performed during the transfer to the recording material, the recording material is provided at both the transfer position and the transfer sheet cleaning position. In this case, the transfer drum 5a is idled by one rotation to end the transfer operation (step S1005), and then the separating operation (step S1).
006) and the cleaning operation (step S1007).

In the normal cleaning control in step S1007, the fur brush 14 is rotated by a motor (not shown), and the fur backup brush 15 facing the fur brush 14 is made effective, so that the fur brush 14 contacts the transfer sheet 5f. You only need to make contact. At this time, the transfer sheet 5f for one round of the transfer drum 5a is cleaned and the transfer sheet 5f
End the cleaning operation (step S1009). Thereafter, the load and high pressure of the operating motor and the like are stopped (step S1009), and the image forming operation is terminated (step S1).
010).

(Control for Performing Oil Cleaning in Plain Paper Mode) When forming a single-color image on both sides of plain paper, when forming an image on the second side of both sides (hereinafter, “plain paper single-color double-sided two sides”)
), An oil cleaning operation of the transfer paper and the oil 5f is performed as follows.

A recording material fed from one of the cassettes and having an image formed on the first side is once stored in the intermediate tray 22 and then fed again. The re-supplied recording material is 2
It is carried on the transfer drum 5a for image formation on the surface.
At this time, the surface of the transfer sheet 5f of the recording material is
The oil adhering to the fixing unit 9 during the image formation of the first side is transferred to the transfer sheet 5f.
Will re-adhere to the surface. This oil must be prevented from adhering to the photosensitive drum 1, and for that purpose, when the transfer sheet 5f during image formation on the second side of both surfaces passes through the transfer position, the transfer sheet 5f passing through the transfer position Must be controlled in advance so that the recording material is present between the transfer sheet 5 f and the photosensitive drum 1. At the time of image formation on a plurality of recording materials, the recording material is always located 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 when the fixing speed is the same as the process speed when the plain paper is a single-color two-sided surface. For this reason, for example, it is sufficient to perform oil cleaning only during the post-rotation control described above.

By the way, the recording material for forming the image on the second side of both sides may be supplied from the intermediate tray 22 or supplied from the recording material tray 7M. In some cases, the recording material on which the image has been formed is reset on the recording material tray 7m in order to output a double-sided image. The control is performed assuming that the recording material for the second surface on both sides on which an image is formed exists.

Next, specific oil cleaning control will be described with reference to the flowchart of FIG. This FIG.
An example is shown in which oil cleaning and normal cleaning are performed at the time of face-up, and only normal cleaning is performed at other times.

The transfer drum cleaning is started (step S15).
If the sheet feeding position is the intermediate tray 22 or the recording material tray 7m, it is determined in step S1501 that image formation is to be performed on the second side of both sides, and the oil cleaning backup brush 17 is used to perform an oil cleaning operation. Enable (step S1502), and drive the oil cleaning roller 16 to contact the transfer sheet 5f (step S1).
503). Since the oil cleaning roller 16 is made of a material that absorbs the oil, the oil cleaning roller 16 contacts the transfer sheet 5f to remove the oil attached to the transfer sheet 5f. Next, in order to perform normal cleaning, the fur backup brush 15 is enabled (step S1504), and the fur brush 14 is driven to contact the transfer sheet 5f (step S1505), and the cleaning operation ends. (Step S1506). If the paper feed position is not the intermediate tray 22 or the recording material tray 7m in step S1501, oil cleaning is unnecessary, and only the fur brush 14 is driven to perform normal cleaning control (steps S1504 and S1505). .

Incidentally, steps S1500 to S1500 in FIG.
When S1506 is performed in the transfer drum cleaning control (step S1007) in FIG. 15, oil cleaning can be performed as necessary in post-rotation control.
Also, steps S1500 to S1506 in FIG.
5, the oil cleaning and the normal cleaning can be performed as needed each time the recording material is separated from the transfer drum 5a. Further, step S1500 in FIG.
To step S1503 in step S1001 in FIG.
If the processing is performed between step S1002 and step S1002, only oil cleaning can be performed as needed each time the recording material is separated from the transfer drum 5a.

(Curling Control) Next, curling control which is a feature of the present invention will be described. In the present invention, the control of the sheet feeding / conveying section 70 is changed according to the type and thickness of the recording material, thereby controlling the curl amount without using an additional mechanism.

FIG. 20 shows the curling section 30 in FIG.
FIG. 3 is a diagram illustrating a configuration of a zero and its surroundings. Of the transport rollers, 74 and 75 have a configuration in which the drive speed can be varied, and details thereof will be described with reference to FIG. The transport roller 74 is composed of three transport rollers 74a, 74b, and 74c (hereinafter, the transport roller 74 is a 74
a, 74b, and 74c), the recording material is configured to have a downward curl when passing through the main transport roller.

In order to generate the drive timing of this roller and to detect OHP, which will be described later, O
An HP detection second sensor 52 is provided. Downstream of the transport roller 74, a transport roller 75 (a generic name of 75a and 75b) that can be driven at the same speed as the transport roller 74 is provided assuming that the transport of the sheet is performed simultaneously with the transport roller 74. Since the passage of thick paper or the image formation is limited from the recording material tray 7m to the apparatus configuration, there is no transport roller capable of curling when feeding from the recording material cassette 7a.

When the paper is fed from the recording material tray 7m, the transport rollers 75, 74, and 76 (76a
And 76b), and the recording material may be conveyed across the transport roller 77 (general term for 77a and 77b).
Since the conveying roller 74 has the conveying force, in this case, the driving of the conveying rollers 76 and 77 does not need to be performed, and as a result, when the leading end of the recording material reaches the conveying roller 74, the conveying roller 7
By stopping the driving of the transfer rollers 76, 7
7 eliminates the need for the drive speed switching function, thereby preventing an increase in cost.

Next, the control of the transport roller 74 during the transport of thick paper will be described with reference to the timing chart of FIG. The function of varying the drive speed of the transport roller 74 includes, for example, a stepping motor capable of varying the speed.
The drive start timing of 4 is generated from the upstream OHP detection second sensor 52, and the recording material is driven at a speed Vct0 <VP (image forming speed) before the leading end of the recording material reaches the conveyance roller 74. On the other hand, in the case of plain paper, it is driven at the same timing at the speed Vcn = VP (image forming speed).

As a result, the curling amount of the recording material per unit time can be varied depending on the type of paper, and as a result, the same curling amount can be secured before the suction operation, so that the recording material can be stably conveyed. Was. In this embodiment, one type of thick paper can be set from the operation unit 704. However, the operation unit setting can be extended to set several types of thick paper, specifically, based on the basis weight of the recording material. Needless to say, it is possible to cope with such a case by making the speed of the transport roller 74 variable.

(Speciality of fixing speed in thick paper mode)
To fix toner on thick paper requires more energy than plain paper, so the fixing speed is slower than plain paper, and the energy per unit area / hour is increased. Secures fixability. In that case, conventionally, the upper and lower fixing rollers 9 are separated from the separation claw 8a.
By setting the distance between the a and 9b to the contact position larger than the maximum size of the thick paper capable of forming an image, the recording material transport unit is maintained at a constant peripheral speed of the transfer drum 5a, which is the image forming speed (process speed) VP. At 9 g, the recording material was reduced to a fixing speed VF different from the speed of the transfer drum 5 a, and the recording material transporting portion 9 g was used as a speed conversion area. For this purpose, it is necessary to secure a recording material conveyance section 9g having a size corresponding to the maximum size of a thick paper on which an image can be formed.

Thus, in the present embodiment, the transfer drum 5a
When the fixing speed VF must be lower than the image forming speed VP, the transfer of the final color is completed.
The speed of the transfer drum 5a is reduced to the fixing speed. This eliminates the need to secure a size as a speed conversion area in the recording material conveyance section 9g, thereby avoiding an increase in the size of the apparatus.

When the size of the recording material in the conveying direction is larger than the distance LTC from the transfer position in FIG. 1 to the leading end position of the recording material conveying portion 9g, the deceleration to the fixing speed of the transfer drum 5a is performed next. It is not in time for the material separating operation. In such a case, the transfer drum 5a is rotated one extra turn, and the recording material is separated at the timing of the subsequent separation operation. In this manner, the control for performing the separation operation after the transfer drum 5a is rotated once more after the transfer of the final color in the thick paper mode is completed, and further performing the fixing is hereinafter referred to as “fixed thick paper (N + 1) rotation control”. In addition, the distance LTC from the transfer position to the leading end position of the recording material transport unit 9g, or the case where the recording material transport unit 9g can be used as a speed conversion area, that is, the transfer drum 5a needs
The control when the rotation is not necessary is hereinafter referred to as “fixing thick paper (N) rotation control”.

Here, in order to make the explanation easy to understand,
Assuming that the distance LTC from the transfer position in FIG. 1 to the top position of the recording material transport unit 9g is 250 mm, the following control is performed in the thick paper mode using a typical recording material size. A4 horizontal feed size (210 mm in feed direction) applied: fixing thick paper (N) rotation control A4 vertical feed size (297 mm in feed direction) applied: Fixed thick paper (N + 1) rotation control A3 vertical feed size (420 mm in feed direction) 1 Sheet sticking: Fixing thick paper (N + 1) rotation control A4 horizontal feed size (feeding direction 210 mm) Sticking two sheets: Fixing thick paper (N + 1) rotation control

(Specialty of Oil Cleaning in Thick Paper Mode) Next, oil cleaning control in the thick paper mode in which the fixing speed needs to be slowed down will be described.

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

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

(Image Forming Control in Thick Paper Mode) The control of forming a color image in the thick paper mode will be described below with reference to the flowchart of FIG. The flowchart of FIG. 28 corresponds to all recording materials in the thick paper mode, the plain paper mode, and the OHP mode. So Figure 2
In No. 8, the control corresponding to the fixing thick paper (N + 1) rotation control and the control corresponding to the fixing thick paper (N) rotation control are defined as fixing (N + 1) rotation control and fixing (N) rotation control, which are common to all recording materials. .

As described above, the latent image including sheet feeding and 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 and the image forming speed VP are compared (step S2002). Here, in the case of the thick paper mode, since the fixing speed VF is the slow fixing speed VFT for the thick paper and 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 the present embodiment, since the electrostatic attraction is used as the recording material holding means, if the recording material is less than half of the entire circumference of the transfer sheet 5f, image formation is simultaneously performed on the two recording materials. It is possible. In this example, when images are simultaneously formed on two sheets of recording material (two sheets are adhered), the two sheets are treated as one sheet including the distance between the sheets. The distance LTC from the transfer position to the top position of the recording material conveyance unit 9g is smaller than the size of the recording material conveyance direction handled as the recording material of the above, and the distance LTC from the transfer position to the top position of the recording material conveyance unit 9g is smaller. It cannot be used as a speed conversion area. Therefore, in this case, "fixing (N + 1) rotation control" is performed (step S2).
006).

Next, when an image forming operation is performed with only one recording material being carried on the transfer sheet 5f (single-sheet attachment), the distance LT from the transfer position to the leading end position of the recording material transport section 9g is set.
C is compared with the size PX of the recording material in the recording material conveyance direction (step S2004). The size PX is the distance LTC
If it is larger, the distance from the transfer position to the leading position of the recording material transporting unit 9g cannot be used as the conversion area of the fixing speed, so that “fixing (N + 1) rotation control” is performed (step S2006). Conversely, size PX
Is smaller than the distance LTC (step S200).
4) Perform “fixing (N) rotation control” (step S20)
05).

In this example, the distance LTC is compared with the size of the recording material in the conveying direction. If the speed change takes time 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 almost simultaneously with the separation operation of the recording material,
Since the cleaning operation of the transfer sheet 5f may have an adverse effect on the recording material during transfer, 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 the present embodiment, the distance LT
C and distance LT from the transfer position to the transfer sheet cleaning position
CLN is set equally at 250 mm.

(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. 29, K indicates a black image, and indicates a period from the time of forming the black image, which is the final color of the four-color operation, to the time of the transfer drum cleaning operation.

In this example, a single A-side A4-size paper sheet is attached, and the latent image formation start timing T1200 is set at Tp.
The timing T1201 is generated from the falling timing T1201 of the transfer drum reference signal A before the rei time.
After a predetermined timing, the driving of the optical system is started. At timing T1200, control is performed so that the original can be read.

After a developing operation (not shown), a transfer start timing T1202 is reached after a lapse of the distance LLT at the process speed VP from the latent image start timing T1200, and the transfer operation is started. At this time, in order to achieve the accuracy of the transfer high voltage control, the transfer high voltage is controlled from the rising edge of the transfer reference position signal C output a predetermined distance before the transfer position (T12).
04). At the end of the transfer operation for the recording material size (T120
In 3), a VFT for the fixing speed is set for the photosensitive drum motor driver 760. Before or after this, when the leading end of the recording material reaches the separation position (T1205), the separating operation is started, and the recording material is separated to the fixing device 9 side. For the transfer sheet 5 side that has been separated and the recording material is not adsorbed,
By counting the drum clock, which is the encoder of the photosensitive drum motor, from the separation start timing T1205, the cleaning start timing T1206 of the transfer sheet 5f including the speed change region of the drum motor is detected, and the cleaning operation is performed.

Fixing (N) rotation control (step S200)
The operation 5) starts after the start of the final color transfer (step S2001). The separating operation is the same as in the case of the plain paper mode which is not the thick paper mode. That is, it waits until the separation operation start timing T1205, and when the separation start timing comes, 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 T1208, which is determined from the size PX of the recording material in the conveying direction, is reached. When the transfer end timing comes, the output of the transfer charger is set to OFF, and the photosensitive drum motor driver 7 is turned off.
For 60, the peripheral speed of the transfer drum 5a is set to be the same as the fixing speed VFT for thick paper. afterwards,
Wait until the separation operation end timing T1207, and turn off the separation claw 8a to end the separation operation.

When such transfer is performed on the second side of both sides in the thick paper mode, as described above, the fixing oil of the first side 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 has adhered reaches the transfer position again (step S200).
9). The oil cleaning is performed in step S in FIG.
Similar to steps 1502 and S1503, the control is such that the oil cleaning backup brush 17 is activated and the oil cleaning roller 16 is driven to abut the transfer sheet 5f. After all,
At the time of the second side of both sides in the thick paper mode, the oil cleaning control is performed every time the recording material is separated.

Before the leading end of the recording material reaches the recording material conveying section 9g driven at the fixing speed VFT for thick paper, the peripheral speed of the transfer drum 5a becomes equal to the fixing speed VFT, and Is normally separated and conveyed, and is fixed at a fixing speed VFT for thick paper. Then, after waiting for the end of the discharge of the recording material (step S2010), the speed of the transfer drum 5a determined by the speed of the drum motor is changed 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 ends.

(Fixing (N + 1) rotation control in thick paper mode) Hereinafter, the fixing (N + 1) rotation control in the thick paper mode will be described with reference to the timing chart of FIG. FIG.
0 is an example when two sheets are adhered, and in the same figure, K1 corresponds to a black image for the first recording material with two sheets attached, and K2 is a black image for the second recording material with two sheets attached. Corresponding to The recording material for K1 is controlled to be attracted from the fixed point PTB, and the recording material for K2 is controlled to be attracted from the fixed point PTA.

In the fixing (N + 1) rotation control, as described above, the size of the recording material in the conveyance direction is larger than the distance LTC (= 250 mm) from the transfer position to the leading end of the recording material conveyance section, and the distance between these is determined by the fixing speed. When the transfer operation cannot be performed as the speed conversion area, after the transfer operation is completed, the transfer drum 5a is rotated once, and then the separation operation is performed. The size of the sheet including the two sheets is larger than the LTC, and the actual fixing (N + 1) rotation control is executed.

Therefore, the transfer of the final color on the second sheet of the two sheets of recording material is waited until T1300 is reached, and when the transfer end timing T1300 is reached, the high voltage of the transfer charger is turned off to perform the transfer operation. To end. Next, the peripheral speed of the transfer drum 5a is set to be equal to the fixing speed VFT for thick paper, and the fixing speed VFT is waited until the separation start timing T1301 in the next rotation is reached. At the separation start timing T1301, the separation operation is performed, and after the separation operation is completed, the separation claw 8a is turned off.
F, and the operation ends.

During this time, the recording material passes through the transfer position. At this time, control is performed so that a transfer high voltage for preventing retransfer is output so that the toner transferred to the recording material is not retransferred to the photosensitive drum 1 again. are doing. At this time, since the speed of the transfer drum is changing, the transfer reference signal C
Based on (T1302, T1303), the output timing of the transfer high voltage is controlled. In this control method, the timing controllability is remarkably improved as compared with the conventional method of controlling the transfer high voltage based on the transfer drum reference signals A and B configured for image formation.

When such transfer is performed on the second side of both sides in the thick paper mode, as described above, the fixing oil of the first side 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 has adhered reaches the transfer position again (step S20).
09). After all, at the time of the second side of both sides in the fixing (N + 1) rotation control in the thick paper mode, the oil cleaning control is performed every time the recording material is separated.

As described above, the speed change area is formed by the extra rotation of the transfer drum 5a, and the fixing operation in the thick paper mode for the recording material up to the maximum size of the image formation in the normal operation is performed. Becomes possible. Also, 2
The cardboard mode can be realized even with the sheet sticking operation.

After waiting for the completion of the separation 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). This is because, in the present embodiment, the recording material conveying unit 9g is driven by the fixing motor, and the effective area of the transfer drum speed for the recording material is the end of the separation operation. V for speed
It returns to P (T1304). After such an operation is performed for the set number of sheets (step S2012), the image forming operation is terminated.

(Fixing Normal Rotation Control in Plain Paper Mode) In the case of the thick paper mode in the plain paper mode, since the image forming speed VP is equal to the fixing speed, FIG.
8 to step S2007 to perform “fixing normal rotation control” (step S200).
7). In the fixing normal rotation control, since the fixing speed is equal to the image forming speed VP, the image is continuously formed on the transfer sheet 5f. (Steps S2013 to S2015).

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 is performed (step S2015).
Is performed, and then the control is terminated. As described above, it is determined that the oil cleaning is necessary for the second side of both sides fed from the intermediate tray 22 or the recording material tray 7m.

By the way, in the recording mode (OHP mode) for an OHP sheet having a different fixing speed from that of the thick paper mode, if the fixing speed is set to VFO, application to OHP sheets is possible as in the case of thick paper. .
If the second side of both sides is not in the single color mode, the fixing speed VFD is different from the process speed VP, so that the same oil cleaning control as that of the second side of both sides of the thick paper mode may be performed.

In consideration of the effect of the toner or the like adhering to the first side of the recording material upon fixing the second side, the fixing speed may be controlled to be slower for the second side than for the first side. Such controls include plain paper mode,
It can be executed regardless of the thick paper mode or the OHP mode.

(Recovery Control) Next, recovery control after detecting a paper jam (hereinafter abbreviated as “jam detection”) in the image forming apparatus realized as described above will be described with reference to the flowchart in FIG. When a jam occurs as is well known (step S3000), the conveyance of the recording material is stopped, and the occurrence of the jam is displayed on the operation unit (step S3).
001).

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

The determination in step S3005 may be a determination as to whether oil cleaning control is necessary. If a paper jam requiring oil cleaning control is detected, oil cleaning control is performed before 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 the oil cleaning control is determined according to the fixing speed and the paper feeding location, it is possible to perform the oil cleaning control before the recovery control in all cases by extending these determination conditions. 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 opposing polishing roller backup brush 19. The polishing roller 18 is used to scrape off toner and deposits from paper that cannot be removed even by cleaning with the fur brush 14.
Therefore, a member having the same effect as sandpaper is wrapped around the outer periphery of the polishing roller 18, and with this member, it is possible to scrape off deposits that cannot be cleaned by the fur brush 14. Since the operation of the polishing roller 18 is related to the life of the transfer sheet 5a, it is controlled so that the polishing control is performed every 2000 image forming operations, for example.

The polishing control in this embodiment is performed by driving the polishing roller 18 and the polishing roller backup brush 19,
This is realized by rotating the transfer drum 5a 20 times.
Therefore, an execution time of about several minutes is required, and the image forming operation cannot be performed during this time. Therefore, the fixing rollers 9a and 9b immediately after the power is turned on (step S4000) so as not to increase the image forming operation inhibition time that restrains the user.
The control is performed so that this polishing control is performed when is cooled. Thus, the polishing control is performed while the temperature of the fixing roller reaches a temperature required for image formation, thereby shortening the image forming operation prohibition time.

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

When the fixing roller is heated, an image forming operation is enabled, a desired mode is set from the operation unit, and the start key 354 is pressed (step S40).
03), the image forming operation described above 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 a predetermined 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 last document is repeated (step S4007, step S400).
8).

At this point, since all image forming operations have been completed, the polishing control counter decremented in accordance with the image forming operation is checked (step S).
4006). If this counter is 0,
A predetermined number of images have been formed since the previous polishing operation, which means that the polishing operation is necessary. Therefore, when the counter is set to 0, the polishing control for performing the polishing operation is performed (Step S4009, Step S4010). Since the image forming operation cannot be performed during the 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 contents of the polishing control in step S4010 will be described with reference to the flowchart of FIG. When the polishing control is started (Step S41)
00), the cleaning for one rotation of the transfer drum 5a is performed only by the fur brush 14, and the toner on the transfer sheet 5f is cleaned (step S4101). Then, the polishing roller 18 and the polishing backup brush 19 are driven (step S41).
02), a polishing operation is performed each time the transfer sheet 5f rotates a predetermined number of times (20 rotations in the present embodiment) (step S1403).

After the completion of the polishing operation for each predetermined rotation, the driving of the polishing brush 18 and the polishing backup brush 19 is stopped (step S4104), and only the fur brush 14 for one rotation of the transfer drum 5a is used again. Cleaning is performed (step S4105), and shavings generated by the polishing operation are cleaned. After that, the initial value (2000 in this embodiment) is set in the polishing control counter for controlling the number of sheets (step S4106), and the polishing control is terminated (step S4107).

In the present embodiment, the number of recording materials is controlled from the previous polishing control. In the case of the fur brush cleaning and oil cleaning, the counter for controlling the number of recording materials is independent. In this way, it is possible to prevent a user from making a mistake in setting the type of paper, or an erroneous operation on the apparatus due to an operation error such as oil adhesion caused by adding output paper to the cassette.

(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 the present embodiment. First, the outline of the curl correction control in the curl correction unit 500 will be described, and the details will be described with reference to a flowchart.

As shown in FIG. 4, the sheet of recording material output on one side is often discharged from the heat roller fixing device 9 in a normal curl (curl having a downward convex shape). It is known that the normal curl of the paper is caused by the toner heated and melted by the heat roller fixing device 9 contracting by air cooling after discharge. The curl amount is determined by the image density (toner amount), the type of paper (material, rigidity, thickness,
It depends on the size, the direction of the gap, etc.) and the surrounding temperature and humidity environment, and it is also known that there is a correlation between the above-mentioned change factors. In the present embodiment, a toner amount is detected as a processing amount of the image forming apparatus that causes a curl, and a curl correction amount is controlled using the detected amount and the like. As the amount of processing of the image forming apparatus that causes the curl, various amounts of processing that cause the curl can be detected in addition to the amount of toner, and can be used to control the amount of curl correction.

First, as a specific example of the occurrence of curl, a description will be given of the direction of growth of curl when the feed direction of A4 size paper at the same image density is changed. In the case of the A4 horizontal feed size (210 mm in the feed direction), as shown in FIG. 4, the curl grows in parallel to the side perpendicular to the paper transport direction, whereas the curl grows in the A4 paper feed size (the feed direction 297).
mm), the curl grows on the side parallel to the paper transport direction. This is considered to be the effect of the above-described paper gap.

In the present invention, in addition to such factors of the curl growth, the operation mode of the sorter 600, the presence / absence of staples, and the partial image density (toner amount) are comprehensively determined, and the optimum curl correction control is performed. As a result, the quality of the output paper in the final form is improved.
Also, curl correction control is performed in consideration of the gap expected from the paper size, and if it is determined that the curl cannot be completely removed, stapling operation is prohibited to prevent stapling failure.

First, a method of calculating the partial image density (toner amount) in the present 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 calculated by dividing it into two in the paper transport direction, and the intrusion amount X in FIG. Description will be made as possible.

The following is a flowchart of FIG. 32 and FIG.
This will be described with reference to FIG. FIG. 32 is a flowchart of the curl correction control. The control is started when the image formation of the final color is completed (S6000).

In calculating the image density (toner amount),
First, the potential sensor 12 samples the potential at the time of image formation, averages the potential, and then converts the potential to the 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 numerical value is shown even if the paper size changes. When forming a color image (four 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 completion of black image formation as the final color, and the first half average toner amount (TNRtop) in the first half of the paper conveyance direction and the second half average toner amount in the second half of the paper conveyance direction
(TNRbottom), the total average toner amount (TNRt
otal) is calculated (S600)
1).

Next, the calculated toner amount is selectively used in the loading mode for the sorter 600. That is, in the non-sort mode for discharging to the non-sort bin 601, there is no alignment operation, so the load amount is more important than the load quality, and the bin shape is also different from the sort bin 602.
Is different. Therefore, in the non-sort mode, the total average toner amount is used as the toner amount for determining the insertion amount X (S6004).

In the staple sort mode in which the stapling is performed at the end of the job in the sort mode, the latter half average toner amount is used as the toner amount for determining the insertion amount X (S
6005).

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 sort mode or the group mode in which the discharge is performed to the second position, the larger of the first half average toner amount and the second half average toner amount is used as the toner amount for determining the penetration amount X in order to improve the stacking quality. (S6006). In such a case, the curl correction quality particularly when the toner amount is uneven is significantly improved as compared with the case where the total average toner amount is used.

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

In the present embodiment, the intrusion amount X can be switched in three stages, which are expressed as “small amount of intrusion”, “medium amount of intrusion”, and “large amount of intrusion”. As described above, the curl amount is proportional to the toner amount. Therefore, when the total toner amount is plotted on the horizontal axis, the switching point data 1 for the small and large penetration amounts and the switching point data for the medium and large penetration amounts There are two. Further, since the curl amount also depends on the paper size and the grain size, data 1 and data 2 corresponding to each paper size are determined. Table 1 below expresses this. 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 an image can be formed. .

[0168]

[Table 1]

Based on Table 1, the intrusion amount switching slice data 1 and 2 are determined for each paper size, and the intrusion amount X is determined from the intrusion amount determination toner amount described above (S6007).
The determined penetration amount X is determined every time a sheet passes through the curl correction unit 500, and the curl correction control is performed on each sheet (S
6008).

Thereafter, it is checked whether the staple sort is performed (S6009). Staple sort mode and A4 vertical feed size (297 mm in feed direction) or B
If it is not 5 vertical feed size (257 mm in feed direction), on condition that it is the last document and the last paper,
Perform stapling.

In the staple sort mode and A4
If the size is the vertical feed size or the B5 vertical feed size (S6010), the entire average toner amount is stored for stapling prohibition determination (S6011). In a mechanism that performs curl correction in the paper transport direction as in the present embodiment,
When the total toner amount is large and the A4 vertical size or the B5 size is used, the curl correction control may not be sufficiently applied to the sheet. Therefore, here, the total average toner amount is stored as data for staple inhibition determination.

Thereafter, if it is the last document and the last sheet, that is, if it is the staple executable timing (S6012), it is determined whether or not even one of the previously stored total average toner amounts exceeds a predetermined value. Is checked (S6013). If it exceeds the specified value,
Since stapling quality cannot be guaranteed, the user is instructed not to execute stapling on the display panel 369 as shown in FIG. 34 (S6014), and the operation ends without executing stapling.

In the present embodiment, it is determined whether or not the total average toner amount of a single sheet exceeds a predetermined value in order to prohibit stapling of A4 portrait size or B5 portrait size. Among them, a method of determining whether or not the number of sheets having a toner amount exceeding a predetermined value exceeds a predetermined number, or a ratio of the number of sheets having a toner amount exceeding a predetermined value in a stapled sheet bundle is used. The same effect can be obtained by the method.

[Second Embodiment] In the first embodiment,
By making the recording material passage speed of the curled portion at the time of thick paper variable, it was disclosed that it corresponds to the thickness of the recording material,
A control method corresponding to a further thickness (basis weight) will be described with reference to a timing chart of FIG.

FIG. 35 is a representation that allows comparison of the control for super-thick paper with the timing for thick paper so that comparison with FIG. 21 is possible. 200g / m2 for super cardboard
(Grams per square meter)
After a while, the leading edge of the recording material passes through the transport roller 74, which is a curling portion, the transporting of the recording material is stopped, a state in which the curling function is maximized is secured for a predetermined time, and the transport speed Vct0 is again set. Restart transport. Accordingly, in the case of a recording material having a large basis weight, curling can be realized more effectively than reducing the conveyance speed, and the types of recording material that can be conveyed can be increased.

[Third Embodiment] In the first embodiment,
The type of recording material is set using a setting key or the like.
OHP detection first sensor 51 and OHP detection second sensor 5
By using 2, it is also possible to detect whether or not the recording material is OHP. Each of these two OHP detection sensors 51 and 52 has a light-emitting portion and a light-receiving portion, and the space between the light-emitting portion and the light-receiving portion is shielded by the recording material, so that the recording material passes therethrough. OHP is configured such that only its tip portion is shielded from light and does not block light from the middle, so whether or not OHP is OHP is determined by utilizing such characteristics. Can be detected. FIG. 36 shows an OHP used in the image forming apparatus of the present embodiment. In FIG. 36, 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 based on the OHP detection can be automatically executed.

[0177]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, in the embodiment, the acceleration control is used for the transfer high voltage control. However, the present invention may be applied to the control of the suction high voltage and the control of the inner charger and the outer charger. Further, a contact charger such as a conductive brush charger may be used as the transfer charger.

Further, in the embodiment, the oil cleaning control is performed even in the OHP mode. However, it is also possible not to perform the oil cleaning on the OHP paper in which it is difficult to form images on both sides.

Further, in the embodiment, the recording material transporting section 9g has the same transporting speed as the fixing speed, but the transporting speed of the recording material transporting section 9g is the same as the peripheral speed of the transfer drum 5a. However, the object of the present invention can be achieved.

In this case, the distance LTC is compared with the size PX of the recording material in the recording material transport direction in the first embodiment.
Is replaced by the distance LTF from the transfer position to the fixing roller.

Further, in the embodiment, the case of the four-color mode and the cardboard mode has been described. However, the present invention can be realized in any of the one-color, two-color, and three-color modes and the cardboard mode.

Further, in the one-color mode in which the thermal 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 whose fixing property is guaranteed without lowering the fixing speed. , It is also possible to operate without lowering 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.

[0184]

As described above, according to the present invention, the number of curls is controlled by controlling the number of rotations of a conveying roller, which is a curl applying means, in accordance with conditions such as the thickness and material of a recording material. There is an effect that various recording materials can be handled without using a mechanism.

[Brief description of the 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 diagram illustrating one-sheet sticking control for a transfer drum 5 (FIG. 2);
3A is an explanatory diagram of two-sheet sticking control (FIG. 2B). FIG.

3 is a schematic sectional view of a curl correction unit and a post-discharge processing unit in the color image forming apparatus of FIG.

FIG. 4 is a perspective view of a main part of a curl correction unit in FIG. 3;

FIG. 5 is a perspective view of a main part of a post-discharge processing unit in FIG. 3;

FIG. 6 is an explanatory diagram of an operation mode of a post-discharge processing unit in FIG. 3;

FIG. 7 is an explanatory diagram of a relationship between a document set on a document table glass of FIG. 3 and a stapling position;

FIG. 8 is an explanatory diagram of a relationship between a document set in the automatic document feeder of FIG. 3 and a staple position;

FIG. 9 is a block diagram of a control system of the color image forming apparatus of FIG.

FIG. 10 is a detailed control block diagram of the image processing unit shown in FIG. 9;

FIG. 11 shows the input / output in the reader gradation correction circuit of FIG.
FIG. 4 is a gradation correction characteristic diagram showing an example of an output signal.

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

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

FIG. 14 is a diagram illustrating a positional relationship between the transfer drum 5 and the photosensitive drum 1.

FIG. 15 is a flowchart illustrating an operation from the start of the final color transfer operation on the final paper to the stop of the image forming operation in the color image forming apparatus illustrated in FIG. 1;

FIG. 16 is a flowchart showing fixing (N) in the flowchart of FIG.
It is a timing chart at the time of performing one-sheet sticking control by rotation control.

FIG. 17 is a flowchart showing fixing (N +
1 is a control timing chart when one-sheet sticking control or two-sheet sticking control is performed by rotation control.

FIG. 18 is a flowchart illustrating a transfer drum cleaning operation applicable in the flowchart of FIG. 15;

FIG. 19 is a flowchart for describing polishing control in the color image forming apparatus of FIG. 1;

20 is a detailed cross-sectional view around the curling unit 300. FIG.

FIG. 21 is a timing chart for explaining control of the curling unit 300 at the time of transporting thick paper.

FIG. 22 is a timing chart for explaining a transfer reference signal.

FIG. 23 is a diagram illustrating a distance relationship of the image forming apparatus illustrated in FIG. 1;

FIG. 24 is a timing chart illustrating high-pressure control timing for a recording material.

FIG. 25 is a block diagram of a high-pressure control unit 770.

FIG. 26 is a timing chart illustrating transfer control timing.

FIG. 27 is a timing chart illustrating transfer acceleration control.

FIG. 28 is a flowchart illustrating fixing control in the color image forming apparatus of FIG. 1;

FIG. 29 is a timing chart for explaining a fixing (N) rotation operation in a thick paper mode in the flowchart of FIG. 28;

30 is a timing chart for explaining a fixing (N + 1) rotation operation in the thick paper mode in the flowchart of FIG. 28.

FIG. 31 is a flowchart for explaining processing when a jam occurs in the color image forming apparatus of FIG. 1;

FIG. 32 is a flowchart illustrating control of a curl correction unit and a post-discharge processing unit of FIG. 3;

FIG. 33 is an explanatory diagram of a relationship between a control amount of the curl correction unit in FIG. 3 and a toner detection amount.

FIG. 34 is a diagram illustrating an example of a message display when stapling is not performed.

FIG. 35 is a timing chart illustrating control of the curling unit 300 during conveyance of an ultra-thick sheet.

FIG. 36 is a plan view of an OHP sheet usable in the color image forming apparatus of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 4 developing device 5 transfer device 5f recording material carrying sheet (transfer sheet) 7 recording material cassette 8a separation claw 8b separation pushing roller 9 heat roller fixing device 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 Section 203 Image Processing Section 369 Display Panel 500 Curl Correction Section 600 Post-Discharge Processing Section

Claims (18)

[Claims] 1. An image forming apparatus having a recording material designating means for setting or detecting the type of recording material, comprising: a recording material supporting means for supporting the recording material; and a conveying means for conveying the recording material to the recording material supporting means. A curling unit included in the transporting unit for imparting a predetermined curl to the recording material; and a time required for the recording material to pass through the curling unit according to a detection result of the recording material designating unit. An image forming apparatus having variable control means. 2. An image forming apparatus having a recording material designating means for setting or detecting a type of recording material, comprising: a recording material supporting means for supporting the recording material; and a conveying means for conveying the recording material to the recording material supporting means. A curling unit included in the transporting unit for imparting a predetermined curl to the recording material; and a time required for the recording material to pass through the curling unit according to a detection result of the recording material designating unit. Or,
An image forming apparatus comprising: a control unit configured to stop the transport unit for a predetermined time while the leading end of the recording material is damaged by the curling unit. 3. A recording material supporting mechanism for supporting a conveyed recording material, and a curling mechanism for applying a predetermined curl by passing the recording material before the recording material reaches the recording material supporting mechanism. An image forming apparatus having control means for changing a time required for the recording material to pass through the curling means in accordance with a supplied setting signal. 4. The curling device has a curling mechanism that imparts a desired curl by pressing the recording material during conveyance, and the control unit adjusts a conveyance speed of the curling mechanism. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 4, wherein the control unit stops the conveyance by the curling mechanism for a predetermined time while the recording material is present in the curling mechanism. 6. The image forming apparatus according to claim 5, wherein the stopping is performed a plurality of times on the same recording material. 7. The image forming apparatus according to claim 6, wherein the stopping is performed in a state where the leading end of the recording material is present in a curling mechanism. 8. The image according to claim 3, further comprising a determination unit that determines conditions such as a size, a material, and a thickness of the recording material, wherein the setting signal is generated by the determination unit. Forming equipment. 9. An image forming apparatus according to claim 3, wherein said recording material supporting means is a transfer drum. 10. The printing apparatus according to claim 1, wherein said curling means comprises a plurality of roll means for conveying said recording material, and said control means adjusts a rotation speed of said plurality of roll means. The image forming apparatus according to claim 1. 11. An image forming apparatus according to claim 4, wherein said control means stops rotation of said plurality of roll means in a state where said recording material exists between said plurality of roll means. 12. The image forming apparatus according to claim 11, wherein said stopping is performed a plurality of times for the same recording material. 13. The image forming apparatus according to claim 12, wherein the stopping is performed in a state where the leading end of the recording material is present in a curling mechanism. 14. A recording material supporting mechanism for supporting a conveyed recording material, and a curling mechanism for applying a predetermined curl by passing the recording material before the recording material reaches the recording material supporting mechanism. And controlling the time required for the recording material to pass through the curling unit in accordance with a supplied setting signal. 15. The recording device according to claim 1, wherein the curling mechanism presses the recording material during conveyance to impart a desired curl to the recording material, and adjusts the conveyance speed of the curling unit to perform the recording. The method according to claim 14, wherein a time required for the material to pass through the curling unit is changed. 16. The method according to claim 15, wherein adjusting the rotation speed includes stopping conveyance in a state where the recording material is present in the curling mechanism. 17. The method according to claim 16, wherein the conveyance stop is performed a plurality of times on the same recording material in accordance with the setting signal. 18. The method according to claim 16, wherein the conveyance is stopped in a state where the leading end of the recording material is present in the curling mechanism.