JP2000242138A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely perform the control of input/output in the case of changing the image forming speed in accordance with the kind of recording material and the timing control of applying high voltage by predicting a recording material position and controlling the control input/output necessary for carrying the recording material based on a prediction signal. SOLUTION: A sensor is arranged in a transfer drum 5a so as to adjust a formed image to recording material attracted to a ransfer drum 5a with a fixed point PTA as a top. A transfer drum reference signal falls before a specified time with respect to latent image forming start timing. A transfer drum reference signal being a timing reference signal for transfer operation executed after a distance LLT from the latent image start timing is prepared. The transfer drum reference signal rises before a specified time with respect to the transfer operation, that is, the passing section (time) of the transfer position of the recording material. Transfer high voltage necessary for the transfer operation rises at the margin of the leading edge of recording material paper and falls at a part passing all the area of the paper.

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 using an electrophotographic system or an electrostatic recording system such as a copying machine or a printer, and more particularly, to various types of recording materials having different materials and thicknesses. The present invention relates to an image forming apparatus capable of forming an image on a recording material.

[0002]

2. Description of the Related Art For example, in an image forming apparatus using an electrophotographic method, generally, a toner image formed on a photosensitive drum is transferred to a sheet as a recording material, and the toner is fixed on the sheet using a heat roller. Has been adopted. In this image forming apparatus, in order to form an image on various recording materials, the image forming control is performed by varying the fixing speed and controlling the output value and timing of the high voltage necessary for the image formation for each recording material. .

[0003]

However, when the fixing speed is changed according to the type of recording material, various I / Os, that is, control of signal input / output and timing of high voltage application are changed in accordance with this control. However, at this time, the individual differences of the apparatuses cannot be sufficiently absorbed, and as a result, the conveyance of the recording material and the image formation are adversely affected.

In order to deal with these problems, it is necessary to add an individual timing adjustment function, and there has been a problem of an increase in cost due to this adjustment.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of reliably performing input / output control and timing control of high voltage application when changing the image forming speed in accordance with the type of recording material, and achieving a desired object. It is to provide a device.

[0006]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
In an image forming apparatus that changes an image forming speed according to a type of a recording material, a control position for the recording material is detected, a position of the recording material is predicted according to the detection signal, and necessary for transporting the recording material based on the predicted signal. An image forming apparatus characterized by controlling various control inputs and outputs.

According to one embodiment of the present invention, the control I
/ O is a high pressure control. Further, the high voltage generating means is a high voltage generating means for transfer or static elimination. Further, according to one embodiment of the present invention, the image forming apparatus is a color image forming apparatus that performs multiple transfer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 shows a configuration diagram of a color image forming apparatus as a first embodiment of the present invention.

In this embodiment, a digital color image reader unit (hereinafter simply referred to as a "leader unit") 2 is provided on the upper part.
01, a digital color image printer unit (hereinafter, referred to as
Simply referred to as "printer section". ) 202, and an image processing unit 203 therebetween.

In the reader unit 201, a document 30 is placed on a document table glass 31, and a reflected light image from the document 30 obtained by exposing and scanning with an exposure lamp 32 is
Reflecting mirrors 32a, 32b, 32c and lens 33
The light is condensed on the full-color sensor 34 integrally formed with the RGB three-color separation filter to obtain a color-separated image analog signal. The analog signal of color separation image 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 as an image carrier is carried rotatably in the direction of the arrow shown in the figure. Around the photosensitive drum 1, a pre-exposure lamp 11 for initializing the surface of the photosensitive drum 1, a photosensitive drum 1
A charger (corona charger in this embodiment) 2 for uniformly charging the surface, a laser exposure optical system 3 for forming an electrostatic latent image on the photosensitive drum 1 according to image information, and a potential on the surface of the photosensitive drum 1 A potential sensor 12 to be detected, and four developing devices 4c, 4m, 4y, and 4B that store developers (toners) of different colors for developing an electrostatic latent image formed on the photosensitive drum 1 into a visible image
k, a fixedly arranged developing device 4, an on-drum light amount detection sensor 13 for detecting the amount of toner on the photosensitive drum 1, a transfer device 5 including a transfer drum 5a as a recording material carrier, and a development remaining on the photosensitive drum 1. A cleaning device 6 for removing the agent is provided.

In this embodiment, the laser exposure optical system 3 comprises a polygon mirror 3a, a lens 3b, a mirror 3c, etc., and an image signal from the reader unit 201 is converted into an optical signal by a laser output unit (not shown). The converted laser light E is reflected by the polygon mirror 3a, projected on the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c, and an electrostatic latent image corresponding to an image signal is formed.

When an image is formed by the printer unit 202, the photosensitive drum 1 is rotated in the direction indicated by an arrow in FIG.
After the surface of the photosensitive drum 1 is neutralized by the charger 1, the charger 2 uniformly charges the surface, and then irradiates a light image E for each separation color to form an electrostatic latent image.

Next, by operating a predetermined developing device, the latent image on the photosensitive drum 1 is developed, and a toner image based on resin is formed on the photosensitive drum 1 sequentially. Each of the developing devices 4c, 4m, 4y, and 4Bk of the developing device 4 has an eccentric cam 24c,
By the operations of 4m, 24y, and 24Bk, a required developing unit is configured to selectively approach the photosensitive drum 1 to perform a developing operation according to the color of the formed latent image.

The developed toner image on the photosensitive drum 1 is transferred from a recording material cassette 7a, 7b or 7c, an intermediate tray 22 or a recording material tray 7m to a transport system including a pickup roller, a paper feed guide, a paper feed roller, and the like. , And is transferred to a recording material supplied to a position facing the photosensitive drum 1 via the transfer device 5.

The transfer device 5 of this embodiment includes a transfer drum 5
a, a transfer charger 5b for transferring a toner image on the photosensitive drum 1 to a recording material, a suction charger 5c for attracting the recording material to the transfer drum 5a, and a suction roller as a counter electrode of the suction charger 5c 5g, an inner charger 5d and an outer charger 5 for removing electricity from the transfer drum 5a for the suction operation.
The recording material carrying sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 5a which is rotatably driven and has a rotational axis. As the recording material supporting sheet 5f, a dielectric sheet such as a polycarbonate film (hereinafter, referred to as "transfer sheet 5f") is used.

In this embodiment, since electrostatic attraction is used as the attraction means, in the case of a recording material (250 mm) which is less than half of the entire circumference of the transfer sheet 5f, two recording materials are used. Simultaneous image formation is possible. The case where the two sheets of recording paper are simultaneously image-formed is hereinafter referred to as “two-sheet sticking control”
The case where one recording material is adsorbed on the transfer sheet 5f to form an image is referred to as "single-sheet application control".

FIG. 26A shows a state in which one recording material is adsorbed when one sheet is adhered to the transfer drum 5a. FIG. 26B shows a state in which the recording material is attracted when two sheets are adhered to the transfer drum 5a. Recording materials for the paste was one is attracted to the head fixed point P _TA on the transfer drum 5a,
Even if the size of the recording material in the rotation direction of the transfer drum changes, control is performed so that the fixed point _PTA is located at the _{front end} (adsorption form of the recording material A). On the other hand, when two sheets are attached, similarly, the fixed point P _TA
(Adsorbing form of recording material B)
The second sheet is attracted such that the fixed point P _TB which is a point 180 ° opposite to the fixed point P _TA of the transfer drum is located at the front end (adsorption form of the recording material C). 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 P _TA and P _TB become the leading _ends .

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

Hereinafter, the control for adsorbing the recording material such that the leading end of the recording material is at the fixed point _PTA will be referred to as A-side adsorption or A-side adhering control.
The control for sucking the fixed point P _{TB so} as to be the tip is referred to as B-side suction or B-side sticking control.

As the transfer drum 5a rotates,
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, 4
The recording material on which the transfer of the color toner image has been completed is transferred to the transfer drum 5.
a from the transfer sheet 5f by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h,
The sheet is discharged via a heat roller fixing device 9 to a sheet discharge curl correction unit 500 shown in FIG. Then, after the recording material is subjected to curl correction control by the curl correction unit 500, the recording material is sent to the post-discharge processing unit 600 shown in FIG. 18 and then subjected to desired post-processing such as collation and stapling. Curl correction unit 500 and 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,
After the recording material having an image formed on one side is discharged from the fixing unit 9, the conveyance path switching guide 19 is immediately driven to
After the recording material is once guided to the reversing path 21a via the transport vertical path 20, then the reversing of the reversing roller 21b causes the trailing end of the recording material at the time of feeding to be in the opposite direction to the feeding direction. The recording material is withdrawn and stored in the intermediate tray 22. Thereafter, the recording material is again conveyed from the intermediate tray 22 to the transfer device 5, and an image is formed on the other surface by the above-described image forming process.

When an image is formed on both the front and back surfaces of the recording material, the first surface of the recording material on which the image is formed first is referred to as the "first surface of both surfaces", and the second surface on which the image is formed is subsequently formed. The surface is referred to as the “second surface of both surfaces”.

Further, in order to prevent scattering of powder on the transfer sheet 5f of the transfer drum 5a and adhesion of oil on the recording material, the fur brush 14 is opposed to the fur brush 14 via the transfer sheet 5f. Backup brush 15, an oil cleaning roller 16, an oil cleaning backup brush 17 facing the oil cleaning roller 16 via the transfer sheet 5f, a polishing roller 18 and a polishing roller backup brush facing the recording material carrying sheet 5f. Using 19, cleaning is performed. Such cleaning is performed before or after image formation, and is performed as needed when a jam (paper jam) occurs.

In this embodiment, the eccentric cam 25 is operated at a desired timing, and the cam follower 5p integrated with the transfer drum 5a is operated.
The gap between the transfer sheet 5f and the photosensitive drum 1 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.

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 in the transfer drum 5a in order to match the formed image to the recording material adsorbed on the transfer drum 5a such that the fixed point _PTA is at the head. Specifically, FIG. 27 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 where the leading end of the latent image overlaps the leading end of the recording material at the transfer position.

FIG. 28 shows the relationship between the latent image (laser), the reading operation of the reader unit 201, and the transfer drum reference signal A. The transfer is started Tprei time before the start timing of the latent image formation. The drum reference signal A is configured to fall.

The reader unit 201 controls the transfer drum reference signal A (hereinafter referred to as "ITOP-A") within the achievable reading magnification.
That. ) The scanning mirror 32 can be raised up to a speed required by a predetermined magnification within the time Tprei from the fall, and the required running time or distance for absorbing vibration can be secured. This similar signal is also prepared for B-side sticking control, and this signal is used as a transfer drum reference signal B (hereinafter referred to as “ITOP”).
-B ". ).

These transfer drum reference signals A and B are used when the transfer drum 5a is rotating, that is, the eccentric cam 25 is operated and the photosensitive drum 1 is operated by the photosensitive drum motor driver 760 (see FIG. 2). It is supposed to happen when. 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 driven at a plurality of different speeds in a manner corresponding to the fixing speed.

Next, control of toner density in the developing device 4 will be described. Since each toner in the magenta developing device 4m, the cyan developing device 4c, and the yellow developing device 4y reflects near-infrared light having a wavelength of about 960 nm,
Utilizing the characteristics, a developer density detecting section 780 (see FIG. 2) disposed in each developing device at the time of development detects this reflected light, and converts the reflected light into a toner density signal by an A / D converter 752. The toner corresponding to the toner density signal is supplied from a hopper (not shown) to the developing device.

On the other hand, 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.
The ratio of the reflection component on the surface to the absorption component by the black toner is detected by the on-drum light amount detection sensor 13, converted by the A / D converter 752, and the book toner density is detected from the developed toner image density. The inside toner density is calculated.

The upper black light amount detection sensor 13 is arranged between the black developing device 4Bk and the transfer charger 5b, and is configured to detect a black toner image developed by the black developing device 4Bk before transfer. The detection can be performed in a state where the toner density does not change due to the operation.

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, a fixing oil applying unit 9
d.

The heat roller fixing device 9 includes fixing rollers 9a, 9
The toner on the recording material is melted by the thermal energy between b and the toner melted by the pressure between the fixing rollers 9a and 9b is fixed on the recording material. The upper fixing roller 9a,
The surface of the lower fixing roller 9b has an upper fixing heater 9e and a lower fixing heater 9f which are incorporated at substantially the center thereof, and an upper fixing thermistor 781 and a lower fixing thermistor 782 (see FIG. 2) for detecting the respective roller surface temperatures. Thus, the temperature is independently controlled to be an optimum surface temperature.

The fixing web 9c comes into contact with the upper fixing roller 9a when necessary in order to remove dirt or offset toner on the upper fixing roller 9a. At this 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, so that the cleaning performance can be improved. Further, the fixing oil applying roller 9 for supplying silicone oil to the surface of the cleaned upper fixing roller 9a.
d is prepared, and silicone oil is applied to the upper fixing roller 9a when necessary so that the toner on the recording material does not adhere to the upper fixing roller 9a.

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 drive motor is driven by a fixing drive motor driver 761 (see FIG. 2). 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 (hereinafter, referred to as “process speed”) of the photosensitive drum 1 at the time of image formation is VP, the fixing speed of plain paper VFN = VP, and the fixing speed VFD for the second side of both sides is VFN. Smaller fixing speed VFT for thick paper
Is smaller than VFD, and the fixing speed VFO for OHP is VF.
Less than T. Therefore, VP = VFN>VFD> V
The relationship of FT> VFO is established, and the fixing drive motor driver 761 is configured to realize these four types of fixing speeds. The transport speed of the recording material transport unit 9g is set to be equal to the peripheral speed of the fixing rollers 9a and 9b. Further, the fixing speed VFD for two sides of two sides is used for two sides of two sides for fixing toner of two or more colors, and is not used in the single color mode in which only one color of 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 apparatus for processing a sheet as a recording material on which an image is formed.

It is known that when a toner image formed by electrophotography 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-processing after discharge. Therefore, in this embodiment, the sheet is post-processed after the curl is corrected by the curl correction failure 500 so that the post-discharge processing unit 600 has no adverse effect.

[Regarding Curl Correction Unit 500] FIG.
Shows a main part of the curl correction unit 500 shown in FIG. 1 and FIG. In FIG. 19, the curling portion 501 includes a soft large-diameter upper roller 502 made of an elastic body such as a silicon sponge and a hard small-diameter lower roller 503 made of metal. Then, the metal lower roller 503 is pressed against the elastic upper roller 502 to form an upwardly convex nip portion along the outer diameter of the metal lower roller 503, and the normal curl (downward) of the paper P passing through the nip portion is formed. Correction of convex curl).

The curl correcting capability of the curl correction unit 500 is as follows.
It can be adjusted by changing the amount of penetration X of the lower metal roller 503 into the upper elastic roller 502. The change in the amount of penetration X 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 is driven.

[Regarding Post-Discharge Processing Unit 600]
The post-discharge processing unit (hereinafter, referred to as “sorter”) 600 will be described.

As shown in FIG. 18, the sorter 600 is roughly composed of two parts. 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,
At the time of the collating operation, the collated bundle of papers can be obtained by using the 20 bins 602 and sequentially outputting them to the respective sort bins 602. The sorter 600 has a sort flapper 603 for switching the discharge destination to the non-sort bin 601 and the sort bin 602. By the flapper 603, the paper is sorted into the non-sort path 604 and the sort path 605, and is discharged to the non-sort bin 601 and the sort bin 602, respectively. The non-sort bin 601 has a configuration capable of discharging a larger amount of paper than the sort bin 602.

Next, referring to FIG.
A brief description of the matching operation and the stapling operation will now be given.
FIG. 20 is a perspective view of the sorter 600, and only one bin is shown in FIG. 20 for the sake of easy understanding of the sort bin 602 having 20 bins. The paper accumulated in the sort bin 602 is moved by the alignment rod 606 and the alignment auxiliary rod 607.
A matching operation is performed. 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. For this reason, cutouts 602a and 602b are formed in the sort bin 602 so that the bars 606 and 607 can move within a certain range. Further, staple cutouts 602c and 602d are formed in the sort bin 602, and a staple portion (not shown) is configured to be capable of stapling a sheet.

Next, a well-known collating operation by a combination of an automatic document feeder (hereinafter, referred to as "RDF") 400 and a sorter 600 will be briefly described with reference to FIGS. In FIGS. 21A and 21B, the non-sort bin 601 that 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 this embodiment is configured to feed a document from below, and the following description will be made in this embodiment. Hereinafter, for the sake of simplicity, it is assumed that the sort bin is set to output in order from the first bin,
2-1 and the second bin are numbered like 602-2. In addition, the order of the originals is numbered in the order in which the originals are set in the RDF. Since the originals are fed from below, the images are formed in the descending order of the originals.

In this embodiment, two sort modes, a sort mode and a group mode, are provided in addition to the non-sort mode in which no sort operation is performed. The form can be selectively executed.

FIG. 21A shows a stacking 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. 21 (a), the operation is repeated for three bins, and a sheet with the subscript ORG3 as the next document is stacked thereon, and this operation is repeated up to ORG1 as the second document (final document). Output in form.

FIG. 21B 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 each sort bin 602, and the output form for four originals is as shown in FIG. 21B. Done. That is, ORG4 as the fourth document (first document feed document) is output to the first bin 602-1 in the sort bin, and ORG3 as the third document is output to the second bin 602-2.

In addition, the sorter 60 in this embodiment
0 has a staple function, and the staple function is controlled so as to be executable only in the stacking mode in the sort mode.

FIGS. 22A, 22B and 22C schematically show staple positions on the original 30 placed on the original platen glass 31. FIGS. FIG. 22A shows corner binding, FIG. 22B shows double binding, and FIG. 22C shows single binding. At the corner stapling (staple) in FIG. 22A, the output sheet is output upside down, so that the front side is stapled in the sorter 600.
FIGS. 22A, 22B, and 22C schematically show stapling positions on a document when the document is set on the RDF 400 when viewed from above.

In both cases shown in FIGS. 22 and 23, a staple portion (not shown) has staple cutouts 602c and 602c.
Stapling is performed using 2d. As a specific example, both corner stapling in FIGS. 22A and 23A are controlled to be stapled using the notch 602d.

FIG. 2 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.

The reader controller 700 includes an optical motor driver 702 for driving an optical motor (not shown) for moving the scanning mirrors 32a, 32b, and 32c and the exposure lamp 32, and an RDF 400 for automatically exchanging originals (FIG. 1). Controller 703 for controlling an operation mode, and an operation unit 7 for setting an operation mode of the color image forming apparatus
04, a ROM 705 storing a control program of the reader controller 700, a RAM 706 storing data such as control values, and an I / O 707 for driving a load such as the exposure lamp 32 are connected as peripheral control units. . 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. An RO that stores a control program for the printer controller 701 is
RAM 7 for storing data such as M750 and control values
51, potential sensor 12 and on-drum light amount detection sensor 1
A / D converter 752 for converting an analog signal from digital camera 3 or the like into digital data, D / A converter 753 for outputting an analog set value to high-voltage controller 770 or the like, and I / O 75 for driving loads such as a motor and clutch.
4 are connected.

The sorter controller 708 communicates with the printer controller 701 to control loading according to the loading mode support in the non-sort mode, sort mode, or group mode set by the operation unit 704, or to perform stapling according to the stapling support. Perform control.

Further, a curl motor driver 763 connected to the I / O 754 includes a curl correction unit 50 (not shown).
The eccentric cam motor 507 shown in FIG.

The printer controller 752 includes a fixing upper and lower thermistors 781 and 782, and a temperature sensor 78.
3, a humidity sensor 784 and a temperature detection sensor 785 on the photosensitive drum surface are connected via an A / D converter 752.

FIG. 3 shows an image processing unit 20 according to this embodiment.
3 is a block diagram illustrating a configuration example of FIG. 3, an image processing unit 203 includes a CCD reading unit 101, a shift memory 102, a complementary color conversion circuit 103, a black extraction circuit 104,
UCR circuit 105, masking circuit 106, selector 1
07, a reader gradation correction circuit 108, a printer gradation correction circuit 109, and the like.

The CCD reading unit 101 receives the analog R signal input from the above-described full-color sensor 34 (see FIG. 1).
Amplifier for amplifying each of the GB signals, analog R
It is composed of an A / D converter for converting a GB signal into, for example, an 8-bit digital signal, a known shading correction circuit for performing shading correction, and the like, and outputs a digital RGB image signal of a document image.

The shift memory 102 corrects, for example, a color-to-color or pixel-to-pixel shift of the RGB image signal input from the CCD 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. The black extraction circuit 104
According to a black extraction signal input from the reader controller 700, a black area of an image is extracted from an MCY (magenta, cyan, yellow) image signal input from the complementary color conversion circuit 103, and Bk (black) for the extracted black area is extracted. Outputs an image signal.

The UCR circuit 105 receives the Bk image signal input from the black extraction circuit 104 and the reader controller 700
The under color removal (UCR) process is performed on the MCY image signal input from the complementary color conversion circuit 103 in accordance with the UCR amount control signal input from. In other words, the black extraction circuit 104 and the UCR circuit 105 improve the color reproducibility by forming an image by replacing the extracted black area with Bk toner instead of superimposing the three colors of MCY.

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

[0066]

(Equation 1) In the equation (1), A is a black extraction coefficient, C2, Y
2 and M2 are MCY image signals output from the complementary color conversion circuit 103. The black extraction coefficient A is determined by the reader controller 7
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).

[0068]

(Equation 2) In the equation (2), M2, C2, and Y2 are MCY image signals output from the complementary color conversion circuit 103, and M1 and C2.
1, Y1 are MCY image signals output from the UCR circuit 105, and coefficients B1, B2, B3, D1, D2, D3
Is determined by the UCR amount control signal from the reader controller 700.

Next, the masking circuit 106 is used to remove the turbid component of the toner used and to correct the RGB filter characteristics of the CCD 33 by the reader controller 700.
UC according to the masking coefficient control signal input from
A masking process is performed on the MCY image signal input from the R circuit 105. M output from masking circuit 106
The CY image signal is expressed by the following equation (3).

[0070]

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

The selector 107 is connected to the reader controller 7
From 00, one color image signal is selected from the M, C, Y, and Bk image signals input from the masking circuit 106 and the black extraction circuit 104 according to the color selection signal input to the color selection terminal S1. The image signal V1 is subjected to gradation correction as shown in FIG. 4 to output an image signal V2. For example, the reader gradation correction circuit 108 selects the signal shown in FIG. 4 selected based on the gradation correction selection signal designated by the reader controller 700.
The density correction is performed on the image signal by any one of the conversion characteristics a to e.

The setting in the reader gradation correction circuit 108 is determined by the image density setting of the operation unit described later. This is set to the terminal S3 of the reader gradation correction circuit 108. Since these density corrections may be different for each color, the same setting as the above-mentioned color selection terminal S1 is set to the color selection terminal S2 of the reader gradation correction circuit 108, and the selected density for the selected color is set. The corrected signal is output as V2.

The printer gradation correction circuit 109 responds to the printer color selection signal input from the printer controller 701 in order to make the output characteristic of the printer unit 202 linear for each color. , M, C, Y, and Bk are selected and set to the color selection terminal S4 for performing image signal correction.

The laser driver 110 is included in the laser exposure optical system 3 (see FIG. 1). Laser driver 1
The reference numeral 10 forms a latent image on the photosensitive drum 1 by modulating and driving the semiconductor laser based on the image signal V3 input from the printer gradation correction circuit 109.

FIG. 6 shows the operation unit 704 of the color image forming apparatus of the present invention. Each element arranged in the operation unit 704 will be described. The ten keys 351 are used to set the number of images to be formed and to input numerical values for mode setting. The clear / stop key 352 is used to stop the set number of images to be formed and the image forming operation. The reset key 353 is used to return the set mode such as the number of formed images, the operation mode, and the selected paper feed stage to a specified value. When the start key 354 is pressed, an image forming operation is started.

The display panel 3 composed of a liquid crystal or the like
Reference numeral 69 changes display contents according to the setting mode in order to facilitate detailed mode setting. In this 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.

The paper type setting key 371 is set when an image is formed on a recording material thicker than the standard. Paper type setting key 37
When the thick paper mode is set by 1, the LED 370 is controlled to light up. In the present embodiment, only the thick paper mode can be set. However, the function can be extended as necessary so that the OHP or other special paper mode can be set.

The two-sided mode setting key 375 is, for example, a "single-sided mode" for performing one-sided output from a one-sided original, a "one-sided-sided mode" for performing double-sided output from a one-sided original, and a "two-sided mode" for performing two-sided output from a two-sided original It is possible to set four types of double-sided modes, that is, a "both-sided mode" and a "both-sided mode" for outputting two single-sided images from a double-sided document. The LEDs 372 to 374 are turned on in accordance with the set double-sided mode, all the LEDs 372 to 374 are turned off in the “one-sided mode”, only the LED 372 is turned on in the “one-sided mode”, and in the “two-sided mode” Only LED 373 lights up, LE in "both-single mode"
Control is performed so that only D374 is turned on.

As a reduction / enlargement key, a reduction key 30
0, an equal-size key 301, and an enlargement key 302. The paper selection key 303 selects the type of paper on which an image is formed. As the key for density, a key for large density 30
5. There is a density key 306 and a density LED 307 indicating the degree of density.

[Specific Example of Image Formation] Hereinafter, as a specific example, a four-color image forming operation on plain paper in which the RDF 400 is not used and the thick paper mode is not set in the "single-single mode" will be mainly described. A description will be given with reference to FIGS.

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 using the numeric keys 351, selects a paper feed stage with the paper selection key 303, and instructs the operation start with the start key 354, the printer controller 701 operates the drive motor required for image formation. For example, it instructs the drivers 760, 761, 762 of the photosensitive drum drive motor, the fixing drive motor, the sheet feed drive motor, and the main drive motor to drive.

Next, after the driving states of the driving motors are stabilized, the designated paper feed stage (recording material cassette 7
a, 7b, etc.), the feeding operation of the recording material P is started. At this time, at substantially the same time, the reader 201
The shift amount, the black extraction amount, the UCR amount, the reader color selection signal, and the like are set in each block of the image processing unit 203 so that an image signal for magenta, which is a developed color of the color, can be generated. The reader gradation correction circuit 108 selects one of the conversion characteristics a to e shown in FIG. 4 corresponding to the contents specified by the density keys 304 and 306 of the operation unit 704.
The conversion characteristic of M shown in FIG. 5 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 charging device 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, the transfer sheet 5f is neutralized by using the inner charger 5d and the outer charger 5e to eliminate the charge. 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.

FIG. 27 shows the positional relationship between the photosensitive drum 1, the transfer drum 5a, and the attracted recording material P at the timing of starting the latent image writing. The recording material P is moved from the fixed point PTA on the transfer drum 5a. This is a state in which the single-sided sticking A-side is being sucked. In the present embodiment, since the full-color image is formed in the order of magenta, cyan, yellow, and black, for example, when the transfer of magenta is completed, when the writing of the cyan latent image onto the photosensitive drum 1 is started, After the time LLT from the laser writing position to the transfer position elapses at the process speed VP,
The cyan transfer operation is started.

FIG. 28 is a timing chart showing the state of FIG. 27, showing 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.

From the fall of the transfer drum reference signal A to T
The optical motor driver 702 is set so that a latent image can be formed after the prei time, and a transfer drum reference signal C, which is a timing reference signal for a transfer operation performed after a distance LLT from the start timing of the latent image, is prepared. ing.
The transfer drum reference signal C is configured to rise before the time Tpret with respect to the transfer operation, that is, the transfer position passage section (time) of the recording material, and is a conventional transfer drum reference signal A for image formation (this embodiment). In this case, more accurate timing control can be performed, particularly when the image forming speed is changed, as compared with the case where the operation timing is generated from the signal B).

Next, in order to make it easier to understand the detailed timing explanation, the distance relationship of each element of the image forming operation in this embodiment will be described with reference to FIG.

As described above, the distance LLT from the laser writing position to the transfer position, the distance LAT from the suction position to the transfer position, the LTS from the transfer position to the separation position, and the distance LTC from the transfer position to the leading end of the recording material conveying section 9g are LTC. = 250
mm, the distance LTD from the transfer position to the outer charger 5e,
The distance LTCLN from the transfer position to the transfer drum cleaning fur brush 14 is 250 mm. The distance from the transfer position to the fixing device 9 is indicated by LTF.

FIG. 30 shows each timing required at the time of image formation in terms of the timing with respect to the recording material so that the arrangement of the control parts can be ignored. The image is output with the leading end and the trailing end missing by 6 mm and 4 mm, respectively, with respect to the recording material, and is represented as an effective image 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 DC output area of the inner charger, which operates only before suction, is secured outside the effective area of the transfer high voltage. This is because the potential of the transfer sheet 5f is set to a predetermined value before transfer in order to ensure transferability. Out of the DC area of the charger,
An adsorption high-pressure area used for adsorbing paper is secured, and outside the area, there are AC effective areas of an inner charger and an outer charger, which perform an operation of neutralizing the transfer sheet 5f. If these timing relationships are not achieved, it has been confirmed that a desired transfer performance defect and a recording material conveyance defect (peeling) occur, and the following configuration is used to generate the timing so as to guarantee the respective relationships. Signal is secured.

In the present embodiment, the rising edge of the transfer drum reference signal A is used as the suction operation timing reference (the falling edge of the transfer drum reference signal B is used during B-side suction), and the AC of the inner charger and the outer charger is used. Alternatively, the fall of the transfer drum reference signal A or B is used for DC high voltage control, and the sensor and the sensor are shielded such that the reference signal is generated a predetermined time before each operation. Flag is positioned. The transfer reference signal C is used exclusively for the transfer high voltage requiring the highest control accuracy. With this configuration, even when an image forming speed described later is changed, control can be performed with accurate timing.

The document information read by the reader unit 201 is processed by the image processing unit 203,
The photosensitive drum 1 uniformly charged 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 unit 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 in the above-described manner, the sheet is subjected to curl correction by the sheet discharge curl correction unit 500 and then discharged to the sorter 600.

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 for plain paper will be described first.

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

[Control for Implementing No Oil Cleaning in Plain Paper Mode] FIG. 7 is a diagram showing the operation from the start of the transfer operation of the final color to the final sheet (the last one of a plurality of sheets on which an image of the same document is formed). 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 gripping 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.

FIG. 8 is a flow chart of FIG.
FIG. 9 is a timing chart when one-sheet sticking control is performed by “fixing (N) rotation control” to be described later when the transfer drum 5a is a two-sheet sticking controllable size.
In the flowchart of FIG.
7 is a timing chart when one-sheet sticking control or two-sheet sticking control is performed by “rotation control”.

In the post-rotation control flowchart of FIG. 7, when the transfer of the final color of the image forming color determined by the color mode is started (S1000), first, whether the final sheet for the same original, that is, the final sheet is determined. It is determined whether or not it is (S1001). Thus, after the transfer is completed, it is determined whether to perform the post-rotation control. If image formation is not performed on the last sheet (hereinafter, referred to as “final image formation”), the image forming operation is continued (S1002), and this control ends (S100).
1003).

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 (S1004). This is because when 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 mm), the transfer drum 5a moves during the transfer to the recording material. This is to prevent the image from being disturbed when the cleaning operation or the separation operation of the recording material is performed.When the recording material is applied to both the transfer position and the transfer sheet cleaning position, the transfer drum is required to end the transfer operation. After idle rotation of 5a by one rotation (S1005), separation operation (S1006) and cleaning operation (S1008)
I do.

In the normal cleaning control in S1007, the fur brush 14 is rotated by a motor (not shown), and the fur backup brush 15 opposed to the fur brush 14 is rotated.
And the fur brush 14 may be brought into contact with the transfer sheet 5f. At this time, regardless of the single-sheet sticking control or the two-sheet sticking control, the transfer sheet 5f for one round of the transfer drum 5a is cleaned, and the cleaning operation of the transfer sheet 5f is completed (S1009). Thereafter, the load and high pressure of the motor and the like during operation are stopped (S1009), and the image forming operation is terminated (S1009). [Control when performing oil cleaning in plain paper mode] A single-color image is formed on both sides of plain paper. At the time of image formation on the second side of both sides (hereinafter, also referred to as “at the time of single-sided two-sided single-color plain paper”)
Then, the oil cleaning operation of the transfer sheet 5f is executed as follows.

The 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. For this purpose, when the transfer sheet 5f during image formation on the second side of both sides 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. When the fixing speed is the same as the process speed at the time of two sides of plain paper single color, the recording material is always 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. 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, a specific oil cleaning control is shown in FIG.
This will be described with reference to the flowchart of FIG. FIG. 10 shows an example in which oil cleaning and normal cleaning are performed at the time of the second side of both surfaces, and only normal cleaning is performed at other times.

The transfer drum cleaning is started (S1500).
If the paper feed position is the intermediate tray 22 or the recording material tray 7m, it is determined in S1501 that the both sides are the second side, and the oil cleaning backup brush 17 is enabled to perform the oil cleaning operation (S1502). The cleaning roller 16 is driven to make contact with the transfer sheet 5f (S1503). 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, and the fur brush 14
Is driven to contact the transfer sheet 5f (S1).
505), the cleaning operation ends (S1506). Also,
In step S1501, the feeding position is set to the intermediate tray 2
2 or the recording material tray 7m, the oil cleaning is not necessary, so that only the fur brush 14 is driven to perform the normal cleaning control (S1504, S1505).

Incidentally, steps S1500 to S1500 in FIG.
S1506 is the transfer drum cleaning control (S100) in FIG.
When executed in 7), in post-rotation control, cleaning can be performed as needed. Also, steps S1500 to S1506 in FIG.
When the process is executed between step 1001 and step S1002, oil cleaning or normal cleaning can be performed as needed each time the recording material is separated from the transfer drum 5a. Further, steps S1500 to S1503 in FIG.
When the process is executed between the middle steps S1001 and S1002, only the oil cleaning can be performed as needed every time the recording material is separated from the transfer drum 5a.

[Speciality of Fixing Speed in Thick Paper Mode] Since fixing toner on thick paper requires more energy than plain paper, the fixing speed is set lower than that of plain paper. Thus, the fixing property of the thick paper is secured by increasing the energy per unit area / hour. In that case, in the related art, the upper and lower fixing rollers 9a, 9b
The recording material transport unit 9g keeps the peripheral speed of the transfer drum 5a, which is the image forming speed (process speed) VP, constant by making the distance to the contact position larger than the maximum size of the thick paper capable of forming an image. The recording material is decelerated to a fixing speed VF different from the speed of the transfer drum 5a, and the recording material transport section 9g is 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.

Therefore, in this embodiment, the speed of the transfer drum 5a can be changed in the same manner as the fixing speed. When the fixing speed VF must be lower than the image forming speed VP, the transfer after the transfer of the final color is completed. Then, the speed of the transfer drum 5a is reduced to the fixing speed. Accordingly, it is not necessary to secure a size as a speed conversion area in the recording material conveyance unit 9g, and it is possible to avoid an increase in the size of the apparatus.

When the size of the recording material in the conveyance direction is larger than the distance LTC from the transfer position in FIGS. 1 and 9 to the leading end position of the recording material conveyance section 9g, the speed of the transfer drum 5a is reduced to the fixing speed. It is not in time for the next recording 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 separating operation. in this way,
After the transfer of the final color in the thick paper mode is completed, the control to rotate the transfer drum 5a one more rotation, perform the separating operation, and further perform the fixing is hereinafter referred to as “fixed thick paper (N + 1) rotation control”. In addition, the control is performed when the distance LTC from the transfer position to the leading end position of the recording material transport unit 9g or when the recording material transport unit 9g can be used as a speed conversion area, that is, when it is not necessary to rotate the transfer drum 5a one extra rotation. Hereinafter, it is referred to as “fixing thick paper (N) rotation control”.

Here, in order to make the explanation easy to understand,
1g and 9g from the transfer position
Assuming that the distance LTC to the leading edge position is 250 mm, the following control is performed in the thick paper mode with a typical recording material size.

A4 horizontal feed size (feed direction 210 mm)
One-sheet application: Fixing thick paper (N) rotation control A4 vertical feed size (297 mm in feed direction) One-sheet application: Fixing thick paper (N + 1) rotation control A3-longitudinal feed size (420 mm in feed direction) One-sheet application: Fixing thick paper (N + 1) rotation Control A4 horizontal feed size (feed direction 210 mm) 2 sheets: Fixing thick paper (N + 1) rotation control [Speciality of oil cleaning in thick paper mode] Then, in thick paper mode in which the fixing speed needs to be slowed down as described above. The oil cleaning control will be described.

As described above, in the case of the oil cleaning control of plain paper, since the speed of the transfer drum 5a is not changed after the completion of the image formation on the transfer drum 5a, the image forming operation can be continuously performed, and the oil cleaning is performed. 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. Oil cleaning control is required every time. 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 formation control in thick paper mode]
The color image forming control in the thick paper mode will be described with reference to the flowchart of FIG. The flowchart in FIG. 11 corresponds to all recording materials in the thick paper mode, plain paper mode, and OHP mode. In FIG. 11, 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. It is expressed as

As described above, the latent image including paper feeding and suction,
The development and transfer operations (S2000) are repeated until the final color is transferred (S2001). After the transfer of the final color, the fixing speed VF and the image forming speed VP are compared (S200).
2). Here, in the case of the thick paper mode, the fixing speed VF is a low fixing speed VFT for thick paper, and the fixing speed VF
Is different from the image forming speed VP,
Then, control goes from step 2 to step S2003.

In step S2003, the transfer sheet 5f
It is determined whether or not the mode is for holding a plurality of recording materials. In this embodiment, since the electrostatic attraction is used as the recording material holding means, when the recording material is less than half the entire circumference of the transfer sheet 5f, image formation is performed on two recording materials simultaneously. Is possible. In the present embodiment, when images are simultaneously formed on two recording materials (two sheets are adhered), the two recording materials are handled as one recording material including the distance between them. The distance LTC from the transfer position to the leading end position of the recording material conveying unit 9g is smaller than the size of the recording material conveying direction treated as one sheet of recording material, and the distance LTC from the transfer position to the leading end position of the recording material conveying unit 9g is smaller. It cannot be used as a speed conversion area. Therefore, in this case, “fixing (N + 1) rotation control” is performed (S200).
6).

Next, when an image forming operation is performed with only one recording material carried on the transfer sheet 5f (single-sheet attachment),
Distance L from the transfer position to the leading end position of the recording material conveying unit 9g
A comparison is made between TC and the size PX of the recording material in the recording material conveyance direction (S2004). If the size PX is larger than the distance LTC, the “fixing (N + 1) rotation control” is performed because the distance from the transfer position to the leading end position of the recording material conveyance unit 9g cannot be used as the fixing speed conversion area. (S
2006). Conversely, if the size PX is smaller than the distance LTC (S2004), “fixing (N) rotation control” is performed (S2005).

In this embodiment, the distance LTC and the size of the recording material in the transport direction are compared. 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. The judgment step (S200
3, S2004) can be improved. Also,
In the fixing (N) rotation control, when the transfer sheet 5f is cleaned substantially simultaneously with the separation operation of the recording material, 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 material conveying direction and the distance from the transfer position to the transfer sheet cleaning position. In this embodiment, the distance LTC and the distance LTCLN from the transfer position to the transfer sheet cleaning position are each set to be equal to 250 mm.

[Fixing (N) Rotation Control in Thick Paper Mode] Hereinafter, the fixing (N) rotation control in the thick paper mode will be described with reference to the timing chart of FIG. In FIG. 12, K means 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 the present embodiment, a single A-side A-side A4-size paper sheet is used, and the latent image formation start timing T1200 is generated from the fall timing T1201 of the transfer drum reference signal A before Tprei time, and the timing T12
After a predetermined timing from 01, 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 (T120).
4). At the end of the transfer operation for the recording material size (T1203)
The VFT for the fixing speed is set for the photosensitive drum motor driver 760 in FIG. Before or after this, when the leading end of the recording material reaches the separation position (T1205), the separation operation is started, and the recording material is separated to the fixing device 9 side. The drum clock, which is the encoder output of the photosensitive drum motor, is counted from the separation start timing T1205 for the separated transfer sheet 5f on which the recording material is not adsorbed, and the transfer sheet including the speed change area of the drum motor is counted. The cleaning operation is performed by detecting the cleaning start timing T1206 of 5f.

The operation of the fixing (N) rotation control (S2005) is started after the start of the final color transfer (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, the separation operation start timing T120
5 and when the separation start timing comes, the separation claw 8a and the separation push-up roller 8b are operated,
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. Thereafter, the apparatus waits until the separation operation end timing T1207 is reached, turns off the separation claw 8a, and ends 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 so that the area of the transfer sheet 5f to which the fixing oil has adhered reaches the transfer position again (S2009). The oil cleaning is performed in step S1502 in FIG.
Oil cleaning backup brush 1 as in S1503
7, the control is such that the oil cleaning roller 16 is driven to contact the transfer sheet 5f. As a result, 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.

The peripheral speed of the transfer drum 5a becomes equal to the fixing speed VFT before the leading end of the recording material reaches the recording material transport section 9g driven at the fixing speed VFT for thick paper. Are normally separated and conveyed, and are fixed at a fixing speed VFT for thick paper. Then, after waiting for the end of the discharge of the recording material (S2010), the speed of the transfer drum 5a determined by the speed of the drum motor is set to the speed VP for image formation in order to form an image on the next recording material. (S2011).

After such an operation is performed for the set number (S
2012), the image forming operation ends.

[Fixing (N + 1) rotation control in thick paper mode] The fixing (N + 1) rotation control in thick paper mode will be described below with reference to the timing chart of FIG. FIG.
Reference numeral 3 denotes an example in which two sheets are adhered. 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 attracted from the fixed point P _TA, the recording material for K2 is controlled to be adsorbed from a fixed point P _TB.

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. When the transfer operation cannot be used 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.
At the time of the two-sheet sticking control, since the two sheets are separated at the same time, the sheet size of the two sheets together including the sheet interval becomes larger than LTC, and the actual fixing (N + 1) rotation control is executed.

Therefore, the transfer of the final color (K2) on the second sheet of the two sheets of recording material waits until T1300, and when the transfer end timing T1300 comes, the high voltage of the transfer charger is turned off. Then, the transfer operation ends.
Next, the peripheral speed of the transfer drum 5a is changed to the fixing speed VF for thick paper.
It is set to be the same as T, and waits until the separation start timing T1301 in the next rotation with this fixing speed VFT. At the separation start timing T1301, the separation operation is performed. After the separation operation is completed, the separation claw 8a is turned off, and the operation ends.

During this time, the recording material passes the transfer position. At this time, 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. Controlling. At this time, since the speed of the transfer drum is changing, the transfer reference signal C (T
1302, T1303), the output timing control of the transfer high voltage is performed. According to this control method, the timing is remarkably improved as compared with the direction in which the transfer high voltage is controlled based on the transfer drum reference signals A and B conventionally 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 (S2009).
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.

In this way, the speed conversion 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 end of the separation of the recording material (2010), the speed of the transfer drum 5a is set to the image forming speed VP for forming an image on the next recording material (S2011). This is because, in the present embodiment, the recording material conveying section 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. It returns to the VP which is the usage speed (T1304).

After such operation setting is performed for the set number of sheets (S1212), the image forming operation is terminated.

[Fixing Normal Rotation Control in Plain Paper Mode] In the case of the plain paper mode with respect to the above-described thick paper mode, since the image forming speed VP is equal to the fixing speed, the flow shifts from step S2002 to S2007 in FIG. Then, "fixing normal rotation control" is performed (S2007). 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,
Even in the case of image formation on the front side, the oil cleaning control is executed after the formation of the set number of images is completed (S2013 to S201).
5).

For plain paper, if it is determined in step S2014 that oil cleaning is necessary after the set number of images has been formed, oil cleaning control (S2015) is performed, and 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.

In the recording mode (OHP mode) for an OHP sheet having a different fixing speed from the thick paper mode, if the fixing speed is set to VFO, the present invention can be applied to an OHP sheet as in the case of thick paper. Further, when the second side of the 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 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 control can be performed regardless of the plain paper mode, the thick paper mode, or the OHP mode.

[Recovery Control] Next, recovery control after detection of a paper jam (hereinafter referred to as “jam detection”) in such an image forming apparatus will be described with reference to the flowchart of FIG. When a jam occurs as is well known (S3000), the conveyance of the recording material is stopped, and the occurrence of the jam is displayed on the operation unit (S3001).

Thereafter, if the door opened to remove the jammed recording material is opened and closed (S3002, S30
03), 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) (S3004). When the removed recording material includes the second sheet of both sides, the transfer sheet 5f at the time of stop
The fixing oil on the image formed on the first surface of the recording material adheres to the surface of the recording material. Therefore, in this case, the process proceeds from step S3005 to S3006, where the oil cleaning control is performed and the cleaning operation of the transfer sheet 5f is performed. Meanwhile, both sides 2
If the paper on the front side is not included, the oil cleaning control is not performed, and the fur brush 14 and the fur backup brush 15
The transfer sheet 5f is cleaned only with the cleaning (S300).
7) Then, control is performed to perform a recovery operation (S3).
008 to 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. Polishing roller 18
Is used to scrape off toner and attached matter 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. With this member, it is possible to scrape off the 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 realized by driving the polishing roller 18 and the polishing roller backup brush 19 and rotating the transfer drum 5a by 20 rotations. Therefore, an execution time of about several minutes is required, and the image forming operation cannot be performed during this time. Therefore, in order not to increase the image forming operation prohibition time that restrains the user, the control is performed so that the polishing control is performed when the fixing rollers 9a and 9b are cooled immediately after the power is turned on (S4000). 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 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 (S4001, S400).
2). 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 (S4003).
The above-described image forming operation is started (S4004). Paper 1
At the end of the image forming operation for each sheet, the polishing control counter is decremented (S4005). This operation is repeated for the set number of sheets (S4006).
If the DF is used, the image forming operation for the set number of sheets for the final document is repeated (S4007, 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 (S4006). If this counter is 0, it means that a predetermined number of images have been formed since the previous polishing operation, and that a polishing operation is necessary. Therefore, when the counter is set to 0, polishing control for performing the polishing operation is performed (S4009, 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 (S4100),
The fur brush 14 alone cleans the transfer drum 5a for one rotation to clean the toner on the transfer sheet 5f (S4).
101). Thereafter, the polishing roller 18 and the polishing backup brush 19 are driven (S4102), and a polishing operation is performed each time the transfer sheet 5f rotates a predetermined number of times (20 rotations in this embodiment) (S4103). After the polishing operation for each predetermined rotation is completed, the driving of the polishing brush 18 and the polishing backup brush 19 is stopped (S4104), and the cleaning is performed again only by the fur brush 14 for one rotation of the transfer drum 5a (S4104). S4105), the shavings generated by the polishing operation are cleaned. Thereafter, an initial number (2000 in this embodiment) is set in the polishing control counter for controlling the number of sheets (S4106), and the polishing control is terminated (S410).
7).

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 the 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 this embodiment. First, an outline of the curl correction control in the curl correction unit 500 will be described, and the detailed description will be made using a flowchart.

As shown in FIG. 19, the single-sided paper as a recording material has a regular curl (curl having a downward convex shape).
Is discharged from the heat roller fixing device 9 in many cases.
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
It depends on the image density (toner amount), paper type (material, stiffness, thickness, size, gap direction, etc.), and the surrounding temperature and humidity environment. ing. In the present embodiment, the toner amount is detected as the processing amount of the image forming apparatus that causes the curl,
The 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. 19, the curl grows in parallel with the area perpendicular to the paper transport direction, whereas the curl grows in the A4 vertical feed size (the feed direction 29 mm).
7 mm), the curl grows around the direction parallel to the paper transport direction. This is considered to be the effect of the above-described paper gap.

In this embodiment, in addition to such factors of the curl growth, the operation mode of the sorter 600, the presence or absence of stapling, and the partial image density (toner amount) are comprehensively determined, and the optimum curl correction is performed. By performing the control, the quality of the output paper in the final form is improved as a result.
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 this embodiment will be described. In order to simplify the explanation, the partial image density (toner amount) will be described as an example in which the partial image density (toner amount) is calculated by dividing it into two in the paper transport direction, and the intrusion amount X in FIG. Explanation will be made as possible.

Hereinafter, description will be made with reference to the flowchart of FIG. 24 and FIG. FIG. 24 is a flowchart of the curl correction control, and the control is started when the image formation of the final color is completed (S6000).

In calculating the image density (toner amount),
First, a potential at the time of image formation is sampled by the potential sensor 12 and averaged, and then converted into a toner amount from the relationship between the potential amount and the toner amount obtained from an experiment. The toner amount here is the toner amount per unit area, and if the density is uniform, the same numerical value is shown even if the paper size changes. When a color image (four colors) is formed, the toner amount includes a magenta toner amount, a cyan toner amount,
It is expressed by the sum of the yellow toner amount and the black toner amount. The operation of calculating the toner amount is performed after the image formation of the final color black is completed, and the first half average toner amount (TNRtop) in the first half of the paper transport direction, the second half average toner amount (TNRbottom) in the second half of the paper transport direction, and the entire area in the paper transport direction. The three toner amounts of the total average toner amount (TNRtotal) are calculated in advance (S6001).

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 intrusion amount X (S6004).

In the staple sort mode in which the stapling is performed at the end of the job in the sort mode, (S60
03) Since the portion to be stapled is the latter half of the sheet, the latter half average toner amount is used as the toner amount for determining the penetration amount X (S6005).

When the mode is neither the non-sort mode nor the staple sort mode, that is, the sort bin 6
In the case of the sort mode or the group mode in which the discharge is performed at 02, 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 intrusion 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 selected. 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 between the small intrusion amount and the intrusion amount
And the switching point data 2 of medium and medium intrusion amount. 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. I do.

[0163]

[Table 1] From this Table 1, the intrusion amount switching slice data 1 and 2 for each paper size are determined, and the intrusion amount X is determined from the intrusion amount determination toner amount described above (S6007). The determined penetration amount X is set every time a sheet passes through the curl correction unit 500, and curl correction control is performed on each sheet (S6006).

Thereafter, it is checked whether or not the staple sort is performed (S6009). In the case of the staple sort mode and not the A4 vertical feed size (297 mm in the feed direction) or the B5 vertical feed size (257 mm in the feed direction) (S6010), the staple is set on condition that the document is the last document and the last sheet (S6015). Execute (S6016).

On the other hand, in the staple sort mode and A4
If the size is the vertical feed size or the B5 vertical feed size (S6010), the entire average toner amount is stored for stapling prohibition determination (S6011). In the mechanism for performing the curl correction in the paper transport direction as in the present embodiment, the curl correction control may not be sufficiently applied to the paper when the total toner amount is large and the A4 vertical size or the B5 vertical size is used. Here, the total average toner amount is stored as data for staple prohibition 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 average toner amounts exceeds a predetermined value. Is checked (S6013). If it exceeds the specified value,
The fact that stapling is not to be performed is displayed on the display panel 369 (S6014), and the operation ends without executing stapling.

In the present embodiment, it is determined whether 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. Of the number of sheets whose toner amount exceeds a predetermined value is determined based on whether or not the number of sheets exceeding the predetermined value occupies the width of the stapled paper. The same effect can be obtained by the method.

Embodiment 2 In the first embodiment, the oil cleaning control is performed even in the OHP mode. However, it is also possible not to perform the oil cleaning on OHP paper on which it is difficult to form images on both sides.

Embodiment 3 In the first embodiment, the conveying speed of the recording material conveying unit 9g is the same as the fixing speed, but the conveying speed of the recording material conveying unit 9g is the same as the peripheral speed of the transfer drum 5a. Even if you configure
The object of the present invention can be achieved.

[0170] In this case, it can be realized by a distance L _TC to be compared with the recording material conveyance direction size PX in the recording material in the first embodiment are replaced by a distance L _TF to the fixing roller from the transfer position.

Embodiment 4 In the first 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, even when the thermal energy supplied to the recording material per unit time is relatively small, in the one-color mode and the thick paper mode, it is possible to output an image whose fixing property is guaranteed without lowering the fixing speed. In some cases, the operation can be performed 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.

Embodiment 5 A known gripper means may be used as the suction means.

Embodiment 6 In the first embodiment, the type of recording material is set by using a setting key or the like. By using the OHP detection sensors 51 and 52 in FIG. 1, whether or not the recording material is OHP is determined. Can also be detected. These two OHP detection sensors 5
Both 1 and 52 have a light emitting unit and a light receiving unit,
OHP is configured to detect the passage of the recording material by shielding the light between the light emitting portion and the light receiving portion by the recording material. Since this is not the case, it is possible to detect whether or not an OHP is used by utilizing such characteristics.

OH used in the image forming apparatus of this embodiment
As for P, as shown in FIGS. 17A and 17B, a light shielding body S is arranged at the leading end of the recording material in the sheet feeding direction.

As described above, by utilizing the characteristics of the OHP, the oil removal control and the image formation control by the OHP detection can be automatically executed.

[0177]

As is apparent from the above description, according to the image forming apparatus of the present invention, the control position for the recording material is detected, the position of the recording material is predicted according to the detection signal, and the prediction signal is obtained. By controlling the input and output required to convey the recording material based on the control, the input and output control when changing the image forming speed in accordance with the type of the recording material and the timing control of the high voltage application can be performed reliably. Since the object can be achieved and the control is performed including the individual difference of the apparatus, it is possible to stably feed the recording material and output a high quality image.

Further, it is not necessary to add an individual timing adjusting function, and cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a color image forming apparatus according to a first embodiment of the present invention.

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

FIG. 3 is a detailed control block diagram of an image processing unit shown in FIG. 2;

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

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

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

FIG. 7 is a flowchart for explaining the operation from the start of the final color transfer operation on the final paper to the stop of the image formation operation in the color image forming apparatus shown in FIG. 1;

8 is a timing chart when one-sheet sticking control is performed by fixing (N) rotation control in the flowchart of FIG. 7;

FIG. 9 is a flow chart of FIG.
1 is a timing chart when one-sheet sticking control or two-sheet sticking control is performed by rotation control.

FIG. 10 is a flowchart for explaining an applicable transfer drum cleaning operation in the flowchart of FIG. 7;

FIG. 11 is a flowchart illustrating fixing control in the color image forming apparatus of FIG. 1;

FIG. 12 is a timing chart for explaining a fixing (N) rotation operation in a thick paper mode in the flowchart of FIG. 11;

FIG. 13 is a timing chart for explaining a fixing (N + 1) rotation operation in a thick paper mode in the flowchart of FIG. 11;

FIG. 14 is a flowchart for explaining processing when a jam occurs in the color image forming apparatus of FIG. 1;

FIG. 15 is a flowchart showing a polishing control process in the color image forming apparatus of FIG. 1;

FIG. 16 is a flowchart for explaining polishing control in the polishing control process of FIG. 15 in further detail;

FIG. 17 is a plan view showing OHP sheets usable in the color image forming apparatus of FIG. 1 in a horizontal feed (a) and a vertical feed (b).

18 is a schematic sectional view illustrating a curl correction unit and a post-discharge processing unit connected to the color image forming apparatus of FIG. 1;

FIG. 19 is a perspective view showing a main part of the curl correction unit in FIG. 18;

20 is a perspective view illustrating a main part of a post-discharge processing unit in FIG. 18;

FIG. 21 is an explanatory diagram of an operation mode of the post-discharge processing unit in FIG. 18;

FIG. 22 is an explanatory diagram showing a relationship between a document set on the document table glass of FIG. 18 and a staple position.

FIG. 23 is an explanatory diagram showing a relationship between a document set in the automatic document feeder of FIG. 18 and a staple position;

FIG. 24 is a flowchart illustrating control of a curl correction unit and a post-discharge processing unit of FIG. 18;

25 is an explanatory diagram illustrating a relationship between a control amount of the curl correction unit in FIG. 18 and a toner detection amount.

FIG. 26 shows one-sheet sticking control (a) and 2 for the transfer drum.
It is explanatory drawing of sheet sticking control (b).

FIG. 27 is an explanatory diagram illustrating a positional relationship between a transfer drum and a photosensitive drum.

FIG. 28 is a timing chart for explaining a transfer reference signal.

FIG. 29 is an explanatory diagram illustrating a distance relationship related to each component of the image forming apparatus illustrated in FIG. 1;

FIG. 30 is a high-pressure control timing chart for a recording material.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 4 developing device 5 transfer device 9 heat roller fixing device 202 printer unit 203 image processing unit 701 printer controller 754 I / O 760 photosensitive drum motor driver 761 fixing device driving motor driver 762 main motor driver

Claims (4)

[Claims] An image forming apparatus that changes an image forming speed according to a type of a recording material, detects a control position of the recording material, predicts a recording material position according to the detection signal, and, based on the prediction signal, An image forming apparatus for controlling a control input / output required for conveying a recording material. 2. The image forming apparatus according to claim 1, wherein a high voltage generating unit is controlled by the detection signal. 3. The image forming apparatus according to claim 2, wherein said high voltage generating means is a high voltage generating means for transfer or static elimination. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus that performs multiple transfer.