JP2003162115A - Image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form the image of a test patch for controlling density at the trailing edge of an image to be formed in the midst of forming the image on recording paper even when the peripheral length of an intermediate transfer body is shortened in an image forming apparatus equipped with a rotary developing device. <P>SOLUTION: This image forming apparatus is equipped with a density control means performing processing to form the image of the test patch in the same developing color at the trailing edge of the image to be formed in each printing color in the midst of forming the image for printing on the intermediate transfer body, detecting the toner density of the test patch transferred to the intermediate transfer body by using a sensor, and setting the density of the image to be developed to the fixed density based on the detected result. In the case of starting operation for rotating and controlling the rotary developing device to the developing color to be developed next after forming the image of the test patch when performing processing to form the image of the test patch in the midst of 1/2 surface sticking control, the formed image in the developing color of the rotary developing device which has been rotated and controlled is transferred to the intermediate transfer body so that it is superposed on the already formed image on the intermediate transfer body in the next image pickup cycle by skipping a succeeding image pickup cycle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having an intermediate transfer member and a rotary developing device, and an image forming method,
More specifically, in an image forming apparatus including a rotary developing device and an intermediate transfer member that are configured to face one photoconductor,
The present invention relates to an image forming apparatus and an image forming method for forming a test patch and executing density control processing.

[0002]

2. Description of the Related Art In an image forming apparatus using one conventional photosensitive drum (photoreceptor), a rotary developing device, and an intermediate transfer member, the peripheral length of the photosensitive drum (photoreceptor) is set to 60.phi. In many cases, the circumference is three times the circumference of the photosensitive drum (photoconductor). This is because in order to improve the printing speed in the image forming apparatus, it is possible to wind two sheets of recording paper around the intermediate transfer member for printing (which is called double-sheet image formation). is there. In the case of this two-sheet pasting image formation, the rotary developing device must be rotated by a necessary angle while moving from the rear end of the B surface to the front end of the A surface. Therefore, the positions of the A and B surfaces are changed. Rather than making the intermediate transfer member face each other, by performing uneven bonding by making the distance from the rear end of the B surface to the front end of the A surface longer than the distance from the rear end of the A surface to the front end of the B surface, This is because the time (interval) is extended from after image formation to the start of the next A-side image formation to obtain a margin of the rotation control time allowed by the rotation developing device.

However, since the intermediate transfer member is a component having a high manufacturing cost, there is a problem that the manufacturing cost and the running cost increase as the peripheral length increases. There was a demand to make the circumference of the intermediate transfer member as short as possible. Considering the ease of control, the peripheral length of the intermediate transfer member is preferably an integral multiple of the peripheral length of the photosensitive member. It is configured to be twice the circumference of the body.

However, when such a configuration is adopted,
Due to the shortening of the circumference of the intermediate transfer member, for example, when image formation is performed in A3 size and a test patch is to be formed outside the image formation area, from the rear end of the image of the test patch, The time to the leading edge of the image is shortened, which causes a problem that the rotation of the rotary developing device cannot be performed in time. In order to deal with this, it is necessary to improve the performance of the stepping motor for driving the rotary developing device, and as a result, the manufacturing cost of the intermediate transfer member and the running cost can be reduced by the manufacturing of the rotary developing device. It caused a problem of causing an increase in cost and running cost.

In the case of a color image forming apparatus using a rotary developing device, when one sheet is stuck, one rotation of the intermediate transfer member is performed once.
The color is developed, and the next rotation is performed in the next rotation. The case of attaching two sheets is basically the same as the case of attaching one sheet.

As a conventional technique, there is a development timing skip control disclosed in Japanese Patent Application Laid-Open No. 5-241420. This is because the sub-scan length of the intermediate transfer body is short,
In addition, the relationship between the image formation when two sheets are stuck and the rotation control of the rotary developing device is improved when the process speed is increased to increase the processing capacity. A technique is disclosed in which, when two sheets are pasted so that the rotation control of the rotary developing device cannot be performed in time, a period corresponding to 1/2 rotation of the intermediate transfer member is allocated as a period for controlling the rotation of the rotary developing device. If the rotation control of the rotary developing device is high and the rotation control to the next development color is possible at the interval of image formation of each color when two sheets are pasted, YMCK printing for two pages can be performed by four rotations. When the rotation control of the rotary developing device is not high speed, 1/2 rotation time is allocated to each of the two development color changes in one YMCK printing, that is, one page of YMCK printing is planned. This is a technology that is completed in five rotations, and enables two-sheet sticking printing without speeding up the rotation control of the rotary developing device.

[0007]

However, when considering the control timing of the rotary developing device, it is necessary to consider the process for stabilizing the density of the image formed on the recording paper. The process for stabilizing the image density here is to form a test patch on the intermediate transfer member, measure the toner density, and feed back the measured result to the toner supply amount to the developing device. , Means a density control process of maintaining the toner density of the developing device constant.
Therefore, as a result, the density control process can be said to be a process of maintaining the density quality of the image formed on the recording material.

This density control process needs to be performed during image formation, and there is a demand for performing it without deteriorating the processing capability of the image forming apparatus, that is, the productivity. Normally, test patch image formation is performed on a recording material. It is formed in an area different from the image area to be printed. When considering the rotation control timing of the rotary developing device, if you try to execute the processing including the image formation of this test patch without lowering the processing capacity, the performance of the stepping motor that drives the rotation of the rotary developing device will be improved. There is a problem in that it is improved or is very complicated and critical control is required in terms of timing or accuracy.

The present invention has been made in view of the above problems. An object of the present invention is to provide an image forming apparatus capable of simultaneously performing test patch image formation for two-sheet attachment control and density control. To provide. In particular, in an image forming apparatus in which the peripheral length of an intermediate transfer member is shortened, an image forming apparatus capable of simultaneously executing test patch image formation for two-sheet attachment control and density control while suppressing reduction in processing capacity is provided. Especially.

A further object is to control the density in the one-sheet sticking control when the length of the recording material is long even in the image forming apparatus in which the circumference of the intermediate transfer member is shortened to the circumference of the photosensitive drum (photosensitive member). It is an object of the present invention to provide an image forming apparatus capable of executing a test patch image formation for the above, while suppressing a decrease in processing capability.

[0011]

In order to achieve such an object, the present invention provides a test / control method for controlling image data to be printed on a recording material or density control. A latent image is formed on the photoconductor by exposing the photoconductor on the basis of patch data, the latent image is visualized by using a developing device including a rotary developing device, and the visualized toner image is formed. In an image forming apparatus configured to transfer the toner image to the intermediate transfer body, and further transfer the toner image from the intermediate transfer body to the recording material, an image for printing based on the image data is transferred onto the intermediate transfer body. An image forming unit for forming an image and a test patch with the developing color of the image at the image trailing end of each print color formed while the image forming unit forms an image on the intermediate transfer member. A test patch image forming means for forming an image, and the test patch image forming means. A toner density of the test patch formed by the means, and a density control means for performing density control so that the density of the image developed based on the detection result becomes a predetermined density. The image forming means, during the formation of an image on the intermediate transfer member, during the test
In the case where the operation for controlling the rotation of the rotary developing device to the development color to be developed next is started after the patch image forming means executes the processing for forming the test patch, after the intermediate transfer member is rotated once, In order to superimpose it on the image already formed on the intermediate transfer body, the development color is image-formed on the intermediate transfer body by the rotary developing device after the rotation control.

According to a second aspect of the invention, the photosensitive member is exposed on the basis of image data to be printed on a recording material or test patch data for density control, and the photosensitive member is exposed on the photosensitive member. A latent image is formed, the latent image is visualized by using a developing device including a rotary developing device, the visualized toner image is transferred to an intermediate transfer member, and the intermediate transfer member further transfers the latent image to the recording material. In an image forming apparatus configured to transfer a toner image, image forming means for forming an image for printing on the basis of the image data on the intermediate transfer body, wherein the image forming means is provided around the intermediate transfer body. An image forming unit including a two-sheet sticking control for executing a two-sheet sticking control for simultaneously forming and printing images for two surfaces of the recording material; and, while the image forming unit is forming an image on the intermediate transfer member, The developed color of the image at the rear end of the image of each print color to be imaged Test for imaging the test patch
The toner density of the patch image forming means and the test patch formed by the test patch image forming means is detected by a sensor so that the density of the image developed based on the detection result becomes a predetermined density. Density control means for performing density control, wherein the image forming means is performing the double-sheet attachment control, and the test / patch image forming means is provided at a rear end of an image of a surface formed lastly out of two surfaces. Does the operation of controlling the rotation of the rotary developing device to the developing color to be developed next after executing the test patch image formation, the subsequent image formation is performed on the last imaged surface and the remaining surface. An image of a development color of a rotation developing device after rotation control is formed on the intermediate transfer body so as to be superposed on an image on the intermediate transfer body already formed in the order of images. Is.

According to a third aspect of the invention, the photosensitive member is exposed on the basis of image data to be printed on a recording material or test patch data for density control, and the photosensitive member is exposed on the photosensitive member. A latent image is formed, the latent image is visualized by using a developing device including a rotary developing device, the visualized toner image is transferred to an intermediate transfer member, and the intermediate transfer member further transfers the latent image to the recording material. An image forming method for transferring a toner image, comprising: an image forming step of forming an image for printing on the basis of the image data on the intermediate transfer member; and an image forming step on the intermediate transfer member by the image forming step. During image formation, a test patch image forming step of forming a test patch on the rear end of the image of each print color to be formed with the development color of the image, and the test pad image forming step. Of the test patch imaged in And a density control step of performing density control so that the density of the image developed based on the detection result is a predetermined density based on the detection result. In the case where the operation of controlling the rotation of the rotary developing device to the development color to be developed next is started after the processing of forming the test patch by the test patch image forming step is executed during the image formation to Then, after the intermediate transfer member is rotated once, an image of the development color of the rotary developing device after the rotation control is formed on the intermediate transfer member so as to superimpose it on the already formed image on the intermediate transfer member. It is characterized by performing.

According to a fourth aspect of the present invention, the photosensitive member is exposed on the basis of image data to be printed on a recording material or test patch data for density control, and the photosensitive member is exposed on the photosensitive member. A latent image is formed, the latent image is visualized by using a developing device including a rotary developing device, the visualized toner image is transferred to an intermediate transfer member, and the intermediate transfer member further transfers the latent image to the recording material. An image forming method for transferring a toner image, comprising: an image forming step of forming an image for printing on the basis of the image data on the intermediate transfer member, wherein the image is formed around the intermediate transfer member. An image forming step including a two-sheet pasting control for simultaneously forming and printing images for two surfaces of the recording material, and an image forming step on the intermediate transfer member by the image forming step, At the rear end of the image of each print color to be imaged, And test patch image formation step of imaging the test patch developed color image, the pre-test
A density control step of detecting the toner density of the test patch formed in the patch image formation step with a sensor and performing density control so that the density of the image developed based on the detection result becomes a predetermined density. In the image forming step, during the execution of the two-sheet pasting control, the test patch image forming step rotates after the test patch image forming step is performed at the rear end of the last image formed surface of the two surfaces. When the operation of controlling the rotation of the developing device to the developing color to be developed next is started, the subsequent images are formed in the order of the image on the last imaged surface and the image on the remaining surface. An image of the development color of the rotation developing device after the rotation control is performed on the intermediate transfer body so as to be superposed on the image on the body.

[0015]

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

FIG. 1 is a schematic sectional view of a color image forming apparatus to which the present invention can be applied.

The present color image forming apparatus includes a digital color image reader section 201 (hereinafter abbreviated as "reader section") arranged at an upper part and a digital color image printer section 202 (hereinafter referred to as "printer") arranged at a lower part. Abbreviated as "part"),
The image processing unit (not shown) is arranged between the reader unit 201 and the printer unit 202.

In the reader unit 201, the original 30 is placed on the original table glass 31 and is exposed and scanned by the exposure lamp 32, whereby the reflected light image from the original 30 is transferred to the lens 3.
3 collects the light on the full color sensor 34 integrally formed with the RGB three color separation filters, and obtains color color separation image analog signals. The color-color-separated image analog signal is digitized through an amplifier circuit (not shown), separated into print colors by the image processing unit 203, subjected to various kinds of processing, and then sent to the printer unit 202.

In the printer unit 202, a photosensitive drum (photosensitive member) 1 which is an image bearing member is rotatably supported in the direction of an arrow, and a pre-exposure lamp 11 and corona charging are provided around the photosensitive drum (photosensitive member) 1. Device 2, laser exposure optical system 3,
Potential sensor 12, rotary developing device 4 (developing devices 4y, 4c,
4m), the developing device 4Bk, the intermediate transfer member 5a, the intermediate transfer member light amount detection sensor 13, and the cleaning device 6 are arranged.

In the laser exposure optical system 3, the image signal from the reader unit 201 is converted into an optical signal by a laser output unit (not shown), the converted laser light is reflected by the polygon mirror 3a, and the lens 3b. And mirror 3c
And is projected onto the surface of the photosensitive drum (photoconductor) 1.

During image formation by the printer unit 202,
Printing generated from each separated color after rotating the photosensitive drum (photoreceptor) 1 in the direction of the arrow and uniformly charging the photosensitive drum (photoreceptor) 1 after the charge is removed by the pre-exposure lamp 11 by the charger 2. Colors (magenta, yellow, cyan, and black)
The laser exposure optical system 3 irradiates the photosensitive drum (photosensitive body) with an optical image for each time to form a latent image on the photosensitive drum (photosensitive body).

Next, when a latent image for a predetermined printing color is formed, a predetermined developing device is operated to develop the latent image on the photosensitive drum (photoreceptor) 1, and the photosensitive drum (photoreceptor) 1 is developed. A toner image based on resin is formed thereon. The developing device is adapted to selectively approach the photosensitive drum (photoreceptor) 1 in accordance with the sequential formation of latent images for each printing color generated from each separation color by rotation of the developing rotary motor.

The developed toner images of each printing color on the photosensitive drum (photoreceptor) 1 are sequentially transferred to the intermediate transfer belt by the high voltage applied by the primary transfer charger.
In the present color image forming apparatus, in the case of a recording material (250 mm) having a length equal to or less than 1/2 of the entire circumference of the intermediate transfer belt,
For the area on the intermediate transfer body corresponding to two recording materials,
Images can be continuously formed while the rotation of the intermediate transfer body is maintained. The case where the images corresponding to these two recording sheets are continuously formed on the intermediate transfer body is referred to as "two-sheet attachment control" hereinafter, and the image corresponding to one recording material is formed on the intermediate transfer belt. The case of forming and forming an image is referred to as "single-sheet pasting control".

FIG. 7A shows a form in which an image is formed by sticking one sheet on the intermediate transfer belt 5a. Also,
FIG. 7B shows a mode in which two sheets of images are formed on the intermediate transfer belt 5a.

The toner image when one sheet is pasted is formed with the fixed point PTA on the intermediate transfer belt 5a at the head, and even if the size of the recording material in the rotating direction of the intermediate transfer body changes, the fixed point PTA is formed.
Is controlled so as to form an image at the leading edge (in the figure, the portion shown in "Form of toner image corresponding to recording material A"). On the other hand, in the case of attaching two sheets, the toner image corresponding to the first transfer material is adsorbed so that the fixed point PTA is located at the front end in the same manner as in the case of attaching one sheet, and the second sheet is the middle of the fixed point PTA. An image is formed so that a fixed point PTB, which is a 180-degree opposite point of the transfer body, is the tip (a portion shown in "Form of toner image corresponding to recording material B" in the figure). Even when two sheets are stuck, the fixed points PTA and PTB are imaged such that the fixed points PTA and PTB are at the leading ends even when the recording material size is changed, as in the case of one sheet.

Hereinafter, the control for forming the image so that the front end of the toner image is at the fixed point PTA is the A-side image formation or the A-side sticking control, and the control for adsorbing the fixed point PTB is the front end is the B-side image formation or B It will be referred to as surface pasting control.

As the belt-shaped transfer device, that is, the intermediate transfer member 5a is rotated, the toner image on the photosensitive drum (photosensitive member) 1 is transferred to the intermediate transfer member 5a by the primary transfer charger. In this way, a desired number of print color images are overlaid on the intermediate transfer member to form a full color image. In the case of full-color image formation, after the transfer of the four color toner images to the intermediate transfer body is completed in this way, the recording material conveyed from the paper feed cassette is conveyed to the position of the secondary transfer roller 5c. Then, the secondary transfer to the recording material is performed. The recording material on which the secondary transfer of the four-color superposed toner images is completed by passing through the secondary transfer roller 5c is ejected to the paper ejection unit 500 via the heat roller fixing device 9.

Photosensitive drum (photoreceptor) 1 after completion of primary transfer
After the residual toner on the surface is cleaned by the drum cleaning device 7, the toner is subjected to the image forming process again. On the other hand, the intermediate transfer body 5a after the secondary transfer 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 the recording material,
After the recording material having an image formed on one surface is discharged from the fixing device 9, the conveyance path switching guide 19 is immediately driven,
The recording material is once guided to the reversing path 21a via the conveying vertical path 20, and then is reversed by the reversing roller 2b to be ejected in the opposite direction to the direction in which the trailing end when fed is the leading end. Store in pass 22. After that, an image is formed on the other surface by the above-described image forming process. When images are formed on both the front and back sides of the recording material in this way, the first side of the recording material on which the image is first formed is the “first side of both sides”, and the second surface on which the image is formed is the “second side”. Both sides are second side. "

Further, in this color image forming apparatus,
By operating the eccentric cam 25 at a desired timing and operating the cam follower integrated with the secondary transfer roller 5c, the gap between the intermediate transfer body 5 and the secondary transfer roller can be set arbitrarily. Has become. For example,
During standby or when the power is off, the intermediate transfer member 5 and
The secondary transfer roller 5c is separated.

Next, the intermediate transfer member reference signal for controlling the image forming operation will be described. In forming an image on the intermediate transfer body 5 so that the fixed point PTA is at the front, a sensor (not shown) and a sensor detection flag are arranged on the intermediate transfer body 5 in order to match the formed images of the toner images of the respective colors. Specifically, FIG. 8 shows the state of the photosensitive drum (photoreceptor) 1 and the intermediate transfer body 5a immediately after the start of latent image formation, and shows that the leading edge of the latent image overlaps the position corresponding to the leading edge of the recording material during transfer. . In contrast,
FIG. 9 shows the relationship between the latent image (laser) and the intermediate transfer member reference signal A.
The intermediate transfer member reference signal A falls before Tprei time. This similar signal is also prepared for the B side control, and this is used as the intermediate transfer member reference signal B (hereinafter referred to as I
TOP-B). These intermediate transfer member reference signals are
It occurs when the intermediate transfer member 5a is rotating.

As will be described later, the photosensitive drum (photoreceptor) motor can also be driven at a plurality of speeds in a manner corresponding to the fixing speed.

Next, the toner density control in the developing device 4 will be described. The respective toners in the magenta developing device 4m, the cyan developing device 4c, and the yellow developing device 4y reflect near infrared light having a wavelength of about 960 nm, so that the characteristics are utilized to develop on the intermediate transfer member 5. The toner image is irradiated with near-infrared light, the reflected component on the intermediate transfer member 5 and the direct light from the irradiation light source are compared by the light amount sensor 13 on the intermediate transfer member, and the A / D converter 752 is used. Is converted, and the toner density is detected from the developed toner image density,
From this, the toner concentration in the developing device is calculated. Regarding the black toner, the toner corresponding to the toner density signal is supplied to the developing device from a hopper (not shown). For yellow, magenta, and cyan toners, the toners corresponding to the toner density signals are supplied to the developing device from a toner cartridge (not shown).

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

The heat roller fixing device 9 includes fixing rollers 9a and 9a.
The toner on the recording material is melted by the heat energy of b,
The toner melted by the pressure between the fixing rollers 9a and 9b is fixed to the recording material. The surfaces of the upper fixing roller 9a and the lower fixing roller 9b are an upper fixing heater 9e and a lower fixing heater 9f which are installed substantially in the center thereof, and an upper fixing thermistor and a lower fixing thermistor which detect the respective roller surface temperatures. Are independently controlled so that the optimum surface temperature is obtained.

The fixing web 9c contacts the upper fixing roller 9a when necessary to remove dirt on the upper fixing roller 9a or offset toner. At this time, the take-up device incorporated in the fixing web 9c can bring the new surface of the fixing web 9c into contact with the upper fixing roller 9a to improve the cleaning performance.

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

Assuming that a specific peripheral speed at the time of image formation on the photosensitive drum (photoreceptor) 1 is VP (hereinafter referred to as "process speed"), the plain paper fixing speed VFN = VP, which is for both sides of the second surface. The fixing speed VFD is smaller than VFN, the fixing speed VFT for thick paper is smaller than VFD,
The fixing speed VFO for OHP is smaller than VFT. Therefore, the relationship of VP = VFN>VFD>VFT> VFO is established, and the fixing drive motor driver 761 (see FIG. 2) is configured to realize these four types of fixing speeds. The conveying speed of the recording material conveying unit 9g is set to be the same as the peripheral speed of the fixing rollers 9a and 9b. The fixing speed VFD for both sides is 2
It is used for the second side of both sides to fix toner of more than color,
Do not use in monochrome mode where only one color of toner is fixed even on both sides of the second side. In this case, plain paper fixing speed VFN
To perform the fixing operation.

FIG. 2 is a block diagram of a control system in the color image forming apparatus to which the present invention is applied. The color image forming apparatus is roughly divided into two blocks for control purposes.
One is mainly a reader unit 201 and an image processing unit 203.
The reader controller 700 controls the printer section 202 and the other is a printer controller 701 that controls the printer unit 202.

Reference numeral 702 is the scanning mirrors 32a, 32.
b and 32c, an optical motor driver for driving an optical motor (not shown) for moving the exposure lamp 32, reference numeral 7
03 is an automatic document feeder RD for automatically replacing documents
RDF controller for controlling F400, code 7
Reference numeral 04 is a CCD for controlling the CCD for image reading
A driver, a reference numeral 705 is a ROM in which a control program of the reader controller 700 is stored, a reference numeral 706 is a RAM for storing data such as control values, and a reference numeral 707 is an I / O for driving a load such as the exposure lamp 32. Is. Further, the RAM 706 is backed up by a battery so that the data can be retained even when the power is turned off.

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

Reference numeral 708 is a sorter controller, which communicates with the printer controller 701 and which is set in the operation unit 704 in the non-sort mode or the sort mode.
The stacking control is performed according to the stacking mode instruction in the mode or the group mode, and the stapling control is also performed according to the stapling instruction.

FIG. 3 is a block diagram showing an example of the arrangement of the image processing unit 203 in this color image forming apparatus. Figure 3
In the figure, reference numeral 101 is a CCD reading unit, which is an amplifier for amplifying the analog RGB signals input from the above-mentioned full color sensor 34 (see FIG. 1),
It is composed of an A / D converter for converting an analog RGB signal into 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.

Reference numeral 102 is a shift memory, which responds to a shift amount control signal from the image processing control unit.
For example, the RGB image signals input from the CCD reading unit 101 are corrected for deviations between colors and pixels. Reference numeral 103
Is a complementary color conversion circuit, which converts the RGB image signal input from the shift memory 102 into an MCY image signal. Reference numeral 104 is a black extraction circuit, which responds to the black extraction signal input from the image processing control unit according to the complementary color conversion circuit 10
The black area of the image is extracted from the MCY (magenta, cyan, yellow) image signal input from the circuit 3, and the Bk (black) image signal for the extracted black area is output.

Reference numeral 105 is a UCR circuit, which responds to the Bk image signal input from the black extraction circuit 104 and the UCR amount control signal input from the image processing control unit.
Undercolor removal (UCR) processing is performed on the MCY image signal input from the complementary color conversion circuit 103. That is, the black extraction circuit 1
04 and the UCR circuit 105 make the extracted black area MCY
It is intended to improve the color reproducibility by forming an image by replacing the three color toners with each other and by replacing the toners with Bk toners.

The Bk image signal output from the black extraction circuit 104 is determined by the following equation (1). Bk = A · min (C2, Y2, M2) (1)

In the equation (1), A is a black extraction coefficient, and C2, Y2 and M2 are MCY image signals output from the complementary color conversion circuit 103. The black extraction coefficient A is determined by the black extraction amount control signal designated by the image processing control unit.

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

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

Next, reference numeral 106 is a masking circuit, which removes the turbid component of the toner used and the RGB of the CCD.
In order to correct the filter characteristics, according to the masking coefficient control signal input from the image processing control unit,
Masking processing is performed on the MCY image signal input from the UCR circuit 105. The MCY image signal output from the masking circuit 106 is expressed by the following equation (3). | M0 | | a11 a12 a13 || M1 | | Y0 | = | a21 a22 a23 || Y1 | (3) | C0 | | a31 a32 a33 || C1 |

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

Reference numeral 107 is an image memory unit, which has a high-speed page memory and a large-capacity memory (hard disk) capable of accumulating a plurality of page image data. The plurality of image data stored in the hard disk are output in the order according to the edit mode designated by the operation unit.
For example, in the case of sorting, the images of the document bundle read by the reader unit 201 are sequentially output. The image data of the document once stored is read from the hard disk, and this is repeated a plurality of times for output. This allows it to play the same role as a sorter with multiple bins. The image data from the computer, which is input from the external I / F processing unit 4, has been processed as image data by the external I / F processing unit, and like the image signal from the reader unit, once in the image memory unit. , Page memory, or hard disk.

Reference numeral 108 denotes a selector, which corresponds to the masking circuit 106 and the black extraction circuit 104 according to the color selection signal input from the image processing control section to the color selection terminal S1.
1 out of M, C, Y, Bk image signals input from
The color image signal is selected and the image signal V1 is output.

Reference numeral 109 is a printer gradation correction circuit, and one example is shown in FIG. 5 according to the printer color selection signal input from the printer controller 701 in order to make the output characteristic of the printer unit 202 linear for each color. Any of M, C, Y, and Bk of the gamma conversion characteristics shown is selected and set to the color selection terminal S4 in order to correct the image signal.

Reference numeral 110 is a laser driver,
It is included in the laser exposure optical system 3 (see FIG. 1) described above.
The laser driver 110 is the printer gradation correction circuit 1.
09, the semiconductor laser is modulated and driven based on the image signal V3 input from the photosensitive drum (photoreceptor).
1 to form a latent image.

Next, details of the image memory unit 107 will be described with reference to FIG. In the image memory unit 107, the external I / F processing unit 7 is added to the page memory unit 731 composed of a memory such as DRAM via the memory controller unit 732.
20, writing image data from the image processing unit 203, reading an image to the external I / F processing unit 720, the printer unit 701, and a hard disk 734 that is a large-capacity storage device.
Access the input and output of the image. The memory controller unit 732 generates a DRAM refresh signal for the page memory 730, and also controls the image I / F processing unit 7
20, arbitration of access to the page memory 731 from the image processing unit 203 and the hard disk 734. Further, a write address to the page memory unit 731,
It controls the read address and the read direction from the page memory unit 731. As a result, the image processing unit 2
Reference numeral 03 denotes a function for arranging and laying out a plurality of original images in the page / memory unit 731 and outputting them to the printer unit.
It controls the function to cut out and output only part of the image and the image rotation function.

Next, the configuration of the external I / F processing unit 702 will be described with reference to FIG. As described above, the external I / F processing unit 702 uses the image memory unit 730 to connect the reader unit 7 with the image memory unit 730.
The image data of 00 is taken into the external I / F processing unit, and the image data from the external I / F is output to the printer unit 701 via the image memory unit 730 to form an image. The external I / F processing unit 702 has a core unit 406, a facsimile unit 401, a hard disk 402 for storing communication image data of the facsimile unit, an external computer 11
Computer interface section 403 to connect with
Formatter unit 404 and image memory unit 405
have.

The facsimile unit 401 is a modem (not shown)
It is connected to a public line via a public line and receives facsimile communication data from the public line and transmits facsimile communication data to the public line. The facsimile unit 401 has a facsimile function, such as performing fax transmission at a designated time and transmitting image data when the other party inquires for a designated password.
The image for fax is stored in 02 and processed. Thus, once the image is transferred from the reader unit 201 to the facsimile unit 401 and the facsimile hard disk 402 via the image memory unit 730, the reader unit 20
1. The fax transmission can be performed without using the image memory unit 730 for the facsimile function.

Computer interface section 403
Is an interface unit for performing data communication with an external computer, and has a local area network (hereinafter, LAN), a serial I / F, an SCSII / F, a Centro I / F for data input of a printer, and the like. Via this I / F, the state of the printer unit and the reader unit is notified to the external computer, and the image read by the reader unit 201 is transferred to the external computer according to the instruction of the computer. Also, it receives print image data from an external computer.

Since the print data notified from the external computer via the computer interface section 403 is described by a dedicated printer code,
The formatter unit 404 stores the code in the image memory unit 7.
Raster that forms an image in the printer unit 2 via 30
Convert to image data. The formatter unit 404 expands raster image data in the image memory unit 405. The image memory unit 405 is thus used by the formatter unit 404 as a memory for expanding raster image data, or the image of the reader unit is sent to an external computer via the computer interface unit 403. In the case of (image scanner function), the image data sent from the image memory unit 730 is once expanded in the image memory unit 405, converted into the format of the data to be sent to the external computer, and the data is sent from the computer interface unit 403. It is also used in all cases.

The core section 406 includes a facsimile section 401,
It controls and manages data transfer among the computer interface unit 403, the formatter unit 404, the image memory unit 405, and the image memory unit 730. As a result, even if the external I / F processing unit 702 has a plurality of image output units and even if the image memory unit 730 has only one image transfer path, exclusive control and priority control are performed under the control of the core unit 406. Control is performed and image output is performed.

FIG. 6 shows the operating section of the color image forming apparatus of the present invention. In FIG. 6, reference numeral 351 is a ten-key pad, which is used for setting the number of image formations and inputting numerical values for mode setting. Reference numeral 352 is a clear / stop key, which is used to stop the set number of images to be formed and the image forming operation. Reference numeral 353 is a reset key, which is used to return the set number of image forming sheets, the operation mode, the selected paper feed stage, and other modes to the specified values. Reference numeral 354 is a start key, and this start key 3
The image forming operation is started by pressing 54.

Reference numeral 369 is a display panel made of liquid crystal or the like, and the display content changes depending on the setting mode in order to facilitate detailed mode setting. In this color image forming apparatus, the cursor keys 365 to 368 are used to display the display panel 369.
The cursor is moved and the setting is determined by the OK key 364. Such a setting method can also be configured with a touch panel.

Reference numeral 371 is a paper type setting key, which is set when an image is formed on a recording material thicker than the standard. When the thick paper mode is set by the paper type setting key 371, LE
The D370 is controlled to light up. In this color image forming apparatus, only the thick paper mode can be set, but the function can be expanded so that the mode for OHP or other special paper can be set if necessary.

Numerals 372 to 374 are double-sided mode setting keys, each of which is a "single-both mode" for outputting both sides from a one-sided original, a "two-sided mode" for outputting both sides from a two-sided original, and two for a two-sided original This is used to set three types of double-sided mode, "double-sided mode", which outputs one side of a sheet. Then, the LEDs 372 to 374 are selectively turned on according to the set double-sided mode, and by pressing the double-sided mode setting key that is being turned on again, the single-sided original output is changed to the “single-sided mode”. LED in "one-to-one mode"
All of 372 to 374 are controlled to be turned off.

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

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

After the operator sets the number of images to be formed with the ten keys 351 and selects the paper feed stage with the paper selection key 303 and gives an instruction to start the operation with the start key 354, the printer controller 701 is ready for image formation. Driving is instructed to each driver of a necessary drive motor, for example, a photosensitive drum (photoconductor) drive motor, a fixing drive motor, a paper feed drive motor, and a main drive motor. next,
After the driving states of those drive motors are stabilized, the feeding operation of the recording material P is started from the designated sheet feeding stage (recording material cassettes 7a, 7b, etc.). At this time, substantially at the same time, the reader unit 201 causes the shift amount, black extraction amount, UCR amount,
And a leader color selection signal and the like are set in each block of the image processing unit 203. Further, the conversion characteristic of m shown in FIG. 5 is selected for the printer gradation correction circuit 109.

Image formation on the intermediate transfer member is performed by sequentially sending the image data decomposed into each print color from the image processing unit to the printer unit so as to match the reference signal of the intermediate transfer member. Be seen.

The recording material P fed from the designated paper feeding stage is conveyed by the registration roller 50 at a timing which can be matched with the reference position on the intermediate transfer member, and then on the secondary transfer roller, on the recording material P. The image is transferred to a predetermined position.

The detailed timing of each control will be described below with reference to FIGS. 8 to 9.

FIG. 8 shows the positional relationship between the photosensitive drum (photoreceptor) 1 and the intermediate transfer body 5a at the start timing of latent image writing, and recording is performed with a fixed point PTA on the intermediate transfer body 5a at the head. It is a state of one-sheet A-side image formation in which an image corresponding to the material A is temporarily transferred. In this color image forming apparatus, since full-color images are formed in the order of magenta, cyan, yellow, and black, for example, magenta primary transfer is completed, and then a cyan latent image is formed on the photosensitive drum (photoreceptor). ) 1, that is, when writing is started on the magenta image. From this point, the distance LLT from the laser writing position and the transfer position from the photosensitive drum (photoconductor) to the intermediate transfer member is set to the process speed VP.
After a lapse of the moving time, the primary transfer operation of the toner image developed with the cyan toner is started.

Next, FIG. 9 is a timing chart showing the situation at the time of FIG. 8, and shows the relation between the intermediate transfer member reference signal and each image forming operation which is the basis of the timing control in this color image forming apparatus. It shows the situation.

From the trailing edge of the intermediate transfer member reference signal A to T
The image processing unit is set so that the latent image can be formed after the prei time. The timing for the primary transfer operation executed after the distance LLT from the main latent image start timing is also determined based on this signal.

FIG. 10 shows each of the required timings at the time of image formation in terms of the timing with respect to the paper as the recording material so that the arrangement of the control parts can be ignored. An image is output on the intermediate transfer member in such a manner that the leading end portion and the trailing end portion are chipped by 6 mm and 4 mm, respectively, and is represented as an effective image area in the figure. This is necessary in order to prevent the inside of the device from being soiled due to toner falling from the secondary transfer to the fixing. The high transfer pressure required for the secondary transfer operation rises while the 6 mm front end margin area of the paper front end is moving in the secondary transfer section, and an image is formed starting from the position 6 mm after the front end margin with the PTA on the intermediate transfer member as the top. The transferred image is transferred, and the trailing edge of the sheet falls at a portion beyond the entire area of the sheet.

FIG. 11 shows a block diagram of a high voltage controller 770 for realizing such timing. As an example, a transfer high voltage whose control timing is severe will be shown. Reference numeral 801 denotes a high voltage transformer for generating a transfer current, and reference numeral 804 denotes a high voltage control signal (voltage) set by the D / A unit 753 as a reference to control a current flowing to the primary side of the high voltage transformer 801. Reference numeral 805 is a current detection resistor for controlling the current flowing to the next side.

Further, the document information sent from the reader unit is processed by the image processing unit 203 and is irradiated as a laser beam on the photosensitive drum (photoconductor) 1 uniformly charged by the charger 2 so as to be latent. An image is formed and is first developed by the magenta developing device 4m. The developed image information is transferred by the primary transfer charger onto P on the intermediate transfer body corresponding to the recording material. The image forming operations of M (magenta) latent image formation, development, and transfer are performed while the photosensitive drum (photoconductor) 1 and the intermediate transfer member 5a make one rotation, and similarly, the remaining three colors of C (cyan) are formed. ), Y (yellow), and Bk (black). At this time, the image processing unit 2
The setting for 03 is performed for each image formation.

In this manner, the four color images are sequentially primary-transferred, and the superimposed toner images on the intermediate transfer body are positioned at the secondary transfer roller 5c at a timing suitable for the secondary transfer by the registration roller. Secondary transfer is performed on the conveyed recording material. At that time, the secondary transfer roller 5c
Thus, a secondary transfer high voltage is applied between the intermediate transfer member 5a and the recording material P to form a secondary transfer current, so that the superimposed toner images are secondarily transferred to the recording material.

The recording material P, which has passed through the secondary transfer roller 5c and has the toner image thereon in this way, is heated by the recording material conveying portion 9g which is conveyed at the same speed (VP) as that of the intermediate transfer member 5a. The sheet is conveyed to the sheet 9, and is fixed at the fixing speed VFN = VP, and then discharged to the sorter 600.

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

Therefore, in this color image forming apparatus, the speed of the intermediate transfer member 5a can be varied similarly to the fixing speed, and the fixing speed VF is set to the image forming speed VP.
When it is necessary to further slow down the speed, after the transfer of the final color is completed, the speed of the intermediate transfer body 5a is reduced to the fixing speed. This eliminates the need to secure a size as a speed conversion area in the recording material conveying unit 9g, and avoids an increase in size of the apparatus.

(Control of Rotating Developing Device) In this embodiment, the developing device is composed of a rotating developing device of YMC three colors and a fixed developing device of Bk. FIG. 12A is a diagram for explaining the control timing of the rotary developing device in the case of sticking two sheets. At the start of copying, the magenta developing device is moved in advance to a position facing the photoconductor to prepare for the first magenta development. After developing the first color magenta on the A and B sides of the two sheets stuck together, the rotary developing device is rotated until the next cyan development starts from the A side, and the cyan developing device is exposed to light. Move to a position facing the body. In the figure, B is
The case where the time corresponding to the amount of movement from the rear end of the surface to the front end of the surface A and the time required for the rotary developing device to rotate from magenta to cyan are equal are shown. The control in yellow is the same. After the development of yellow is completed, the development of black is performed, but the rotation of the rotary developing device is unnecessary for the development of black.

The position control of the rotary developing device is performed by stepping
This is performed by counting the number of pulses with a motor, and the stop position when facing the photosensitive drum (photoconductor) of the developing device is accurately controlled. Further, since the distance between the AB planes is short, in the control of the rotary developing device, high speed rotation control using acceleration and deceleration is performed by the stepping motor. Each side of the trapezoid shown in the figure corresponds to an acceleration region, a constant velocity region, and a deceleration region.

The developing device of Bk is an independent fixed device, and it is not necessary to control its rotation.

(Density Control by Test / Patch Image Formation) This color image forming apparatus does not have a sensor for measuring the toner density in the developing device. The toner consumption amount is calculated based on the video count number of the printed image data, and this is used as the toner supply amount from the toner cartridge to the developing device. In the toner cartridge,
It is equipped with a screw (not shown). The supply amount G when the screw is rotated for a certain time is known in advance, and the relationship between the supply amount X and the screw rotation time t is
It is calculated by a linear expression of X = Gt.

At the time of toner replenishment, the replenishing operation must be performed within the time during which the developing unit is operating so that the toner is uniformly replenished to the developing unit. When the rotation time of the screw accompanying replenishment exceeds one development time, the replenishment operation is performed over the two development operations.

The toner replenishing operation based on the video count can maintain an almost correct replenishing amount in a short period of time, but there is an error, and it is not possible to control whether or not the actually developed toner image has the correct density. Therefore, in the embodiment of the present invention, after a predetermined number of prints, the test
By forming an image of the patch and measuring the density of the patch, feedback to the toner supply amount is performed. This allows the video
The error of the replenishment amount that occurs when the replenishment amount is calculated from the count is compensated.

As shown in FIG. 13, the image formation of the test patch is usually performed so that the patch of the immediately preceding image printing color is formed at a position slightly apart from the trailing edge of the image of the image formation. This patch is primarily transferred, and the amount of reflected light is measured by an intermediate transfer member reflected light amount sensor 13 installed at a predetermined position on the intermediate transfer member. The test patch image is not secondarily transferred, and after the transfer of the image to be recorded on the recording material is completed, the toner image is cleaned by the cleaner 6 on the intermediate transfer member.

(Imaging of Test Patch at Rear Edge of Image) FIG. 12B shows the rotary developing device in the present embodiment when the test patch is not imaged and when the test patch is imaged. FIG. 6 is a diagram showing the difference in the control timing of FIG.

In the upper part of FIG. 12B, when the test patch is not imaged, the gap from the rear end of the B surface to the front end of the A surface is
Since the rotation developing device is wider than the gap corresponding to the time required to execute the predetermined rotation control, the state in which the development of two sheets can be continuously executed is shown. When two sheets are printed on a sheet having such a sheet length and a test patch is formed at the trailing edge of the B-side image, rotation is performed after the test patch is formed and before the development of the second color is started. The developing device cannot be completely rotated. That is, the time point when the rotation is completed is the time point when the front end of the magenta image formed on the A side has already passed the developing device. Therefore, by changing the image forming order of the A surface and the B surface on the intermediate transfer material, the second color image is superimposed on the B surface image, and then the second color image of the A surface is superimposed. Extend the time from the test patch formation to the development of the second color,
The rotation control of the rotary developing device is executed within this expanded time.

In this case, the order of reading the image data from the image memory section is changed when the period for executing the rotation control of the rotary developing device is ensured by performing the control as described above. In the normal case where the test patch is not imaged, FIG.
As shown in the upper row, after transferring and developing any color data of MCYK on the N-th surface, the color data of the N + 1-th surface is transferred and developed, and image formation is performed in page order. But,
For example, when considering a skip of development control when a test patch is formed after magenta and a skip occurs when shifting to cyan development, the first color magenta develops in order of the Nth surface and the N + 1th surface. The cyan of the color is
The images must be formed in order of N + 1 plane and N plane.

FIG. 15 is a diagram for explaining a range wider than the range shown in FIG. 12, and FIG. 15 (a) shows that plural sheets of image are formed by two-sheet sticking control and one-sheet sticking control. In this case, the relationship between the image formation including upstream exposure, development, and transfer and the drive of the developing rotary motor is shown from the viewpoint of image formation in the present embodiment, that is, transfer onto the intermediate transfer body. In this figure, the relationship between the rotation of the intermediate transfer member, the image formation on the intermediate transfer member, and the driving of the developing rotary motor (shown by a black trapezoid) is shown in time series.

Further, FIG. 15B shows the case where a test patch is formed at the end of each color image formed by the same expression as in FIG. 15A, and that portion is shown by a black square. . After that shown in this figure, image formation is performed in the form as shown in FIG. The vertical dotted line is
It is intended to support the above-mentioned PTA and PTB.

When the test patch image formation is not performed as shown in FIG.
The development color changes each time the intermediate transfer member makes one rotation, and within one rotation, the A surface and the B surface are imaged in order. Also, 1
In the case of the sheet sticking control, the developing color changes every one rotation, and the image formation is performed in a predetermined order. The development rotary motor is operated when the development color changes from magenta to cyan and when the development color changes from cyan (C) to yellow (Y) both in the single-sheet attachment control and in the double-sheet attachment control. Rotation control is being performed. This development rotary motor rotation control is completed by the time when the development of the next color is started. Further, when the development color is switched from yellow (Y) to black (Bk) and magenta (M), the development is performed after the development of yellow (Y) is completed and then the development of magenta (M) is started. Rotary
Motor rotation control is performed.

In FIG. 15B, when the development rotary motor rotation control is performed in preparation for the development of the next color after the test patch is created, the control completion time is later than the development start time. . Therefore, when the development color is changed from magenta (M) to cyan (C) and from cyan (C) to yellow (Y), the period of time during which an image to be developed or an image of one color should be developed is originally required. Is skipped, and the image appearing next or the image of one color is developed during the period in which it should be developed.

When skipping is performed as described above, in the case of the two-sheet sticking control, the image formation of cyan (C) after the first magenta (M) patch is formed is formed on the surface B of the intermediate transfer member. The second original is printed, and then the first original imaged on the surface A of the intermediate transfer body is printed. Then, the image formation of yellow (Y) is performed on the first original image formed on the A side of the intermediate transfer body, and then the two sheets formed on the B side of the intermediate transfer body. Performed on the eye manuscript

In the case of the one-sheet sticking control, the image forming order is not changed even if the above-mentioned skip is performed.

FIG. 14 is a flow chart for explaining a software module for performing the image forming order control and skip control processing as shown in FIG. This software module determines the image forming order, for example, according to whether or not a patch is formed before the image formation of the M color of the Nth surface is started, and sets the image reading to the image memory means in that order. Thus, the skip control and the order change control of the image forming image data at the time of the skip control are performed.

Since the test patch image formation is normally performed once for each color in one time density control, in the present embodiment and under the conditions as described above, a series of image formation processing from magenta is performed. The order of the image forming image data is changed twice when the image is transferred to cyan and then to cyan.

The process for controlling the order of the imaged image data is initialized before the start, but is omitted. When initialized, the process proceeds to step S1401. Here, it is assumed that the process is repeated and the image forming process for the Mth color of the Nth surface is started at present. First, step S
At 1401, it is determined whether or not the two-sheet pasting control is currently being performed. In case of one-sheet sticking control, step S
Proceed to 1422.

(Control of Sticking Two Sheets) When two pages of image data of a size capable of sticking two sheets are stored in the image memory as the image data, the sticking of two sheets is possible and The paste control is being executed. That time,
The process advances to step S1402, and it is determined whether or not the test patch has been imaged for the (M-1) th color, that is, at the trailing edge of the previously developed color. If the test patch has not been imaged, the process advances to step S1410. If the test patch is imaged, the process advances to step S1403, where the distance from the trailing edge of the test patch to the leading edge of the next image on the intermediate transfer member is the time at which the rotation control of the rotary developing device is completed. Whether it is greater than the corresponding distance, that is,
Check whether there is time to control the rotation of the rotary developing device by the time of starting to superimpose the image formation of the next color on the (M-1) color image already formed on the intermediate transfer member. To be done. If the start time comes after the completion of the rotation control of the rotary developing device, the process proceeds to step S1410, and if it is not in time, the process proceeds to step S1404. In step S1404, it is confirmed whether the M color to be imaged at present is cyan or yellow. If the M color to be imaged at present is cyan or yellow, step S
The process advances to step 1405, and if the M color currently to be imaged is magenta or black, step S1410.
Proceed to. In the determination in step S1404, in the present embodiment, images are formed in the order of magenta, cyan, yellow, and black, and the control time of the rotation control of the rotary developing device is a problem from magenta to cyan, and from cyan to yellow.
This is because it is only when the development color is changed to.

In step S1405, even if the test patch formation is performed and then the rotation control of the rotary developing device is started, the control is not completed before the development start timing of the next color, and in the present embodiment, Since this rotation control is required, this image formation cycle (see FIG.
Skip 1 or skip 2 of pasting one sheet) and wait until the next imaging cycle (the period corresponding to 2C or 1Y in FIG. 15B), and then step S1.
Proceed to 406. At the time of executing step S1406, the rotation control of the rotary developing device is completed, and the developing device for the developing color to be developed is present at the position facing the photoconductor.

In step S1406, it is determined whether the current M color to be developed is cyan. If it is yellow, the process proceeds to step S1410, and if it is cyan, steps S1407 and S1408 are executed, the order of reading the images is exchanged, the N + 1th surface is imaged first, and the Nth surface is imaged later.

Steps S1410 and S1411 are for cases where the sub-scan length of the image data is short, and even if a test patch is formed after image formation, the rotation control of the rotary developing device after that is in time or not in time. Even if there is, if the current development color is not cyan, it is executed when the image formation on each surface in the two-sheet attachment control is performed without changing the development order.

Step S1408 or step S1
After executing the processing of 411, image forming setting is executed in preparation for the next image forming in step S1409. That is, the next color is set, or the first color is set on the next page to be imaged. After setting, go back to the first step,
The process for a new image forming cycle is repeated.

(One-Piece Sticking Control) Steps S1412 to S14
The processing of 1424 is step S in the case of the two-sheet sticking control.
Since it is the same as 1402 to S1404, the description is omitted.
In step S1425, as shown in FIG. 15B, the cycle in which an image is to be formed here (see FIG.
The period corresponding to skip 1 and skip 2 in the case of sticking one sheet in (B) is skipped, and the next imaging cycle (FIG. 15) is performed.
Waiting until (1C or 1Y in the one-sheet pasting of (b)), the process proceeds to step S1430. At the time of proceeding to step S1430, the rotation control of the rotary developing device is completed, the developing device of the developing color to be developed is present at the position facing the photoconductor, and the image forming process intended for the image forming process is performed. Run. And step S143
Proceed to step 9 to set the next color, or set the first color on the next page to be imaged. After the setting is completed, the process returns to the first step and the process for a new image forming cycle is repeated.

Step S in the case of the one-sheet sticking control described above
In the processing of 1422 to S1425, it is necessary to adjust the image density when the image size to be formed on the intermediate transfer member is large and two sheets cannot be attached, and the test is performed at the rear end of the image. When the control for forming the image of the patch is required, it is assumed that the development processing including the area of the test patch is required in addition to the sub-scan length of the actual image. In this case, since the rotation of the rotary developing device is started from the timing of the trailing edge of the test patch, the necessary rotation control may not be completed while moving to the leading edge of the next image. Is being processed.

When it is necessary to form a test patch during image formation with one sheet stuck, the skip control is performed to increase the time for allowing rotation control, and While performing the formation, the test patch is formed and the density adjustment and the like can be performed.

[0109]

As described above, according to the present invention, in the image forming apparatus having the rotary developing device and the peripheral length of the intermediate transfer member is short, the test patch for the density control is executed during the two-sheet adhering control. When an image is formed on the rear edge of the B-side image, the distance from the rear edge of the test patch to the image start point of the A-side becomes small, so a rotary developing device for changing the development color in relation to the process speed. Rotation control cannot be performed in time, in other words, in an image forming apparatus in which the peripheral length of the intermediate transfer body is short, test patch image formation is performed for density control during execution of two-sheet attachment control without lowering processing capacity. The problem of being unable to do so is solved. Also, the problem that the test patch image formation cannot be performed for the density control without deteriorating the processing capacity even during the one-sheet sticking control is solved by the configuration of the present invention.

Further, with the structure of the present invention, while improving the quality of the image by the test patch, the peripheral length of the intermediate transfer member is set as the minimum required for image formation, and the manufacturing cost, the running cost, and the It has become possible to reduce the cost of. In addition, it is possible to improve the quality by simplifying the control contents, downsizing the device, and maximizing the efficiency of machine productivity.

[Brief description of drawings]

FIG. 1 is a sectional view of a color image forming apparatus to which the present invention can be applied.

FIG. 2 is a block diagram of the color image forming apparatus shown in FIG.

FIG. 3 is a block diagram of an image processing unit shown in FIG.

FIG. 4 is a block diagram of an external I / F processing unit shown in FIG.

5 is an explanatory diagram of gradation correction of the image processing unit shown in FIG.

FIG. 6 is a diagram illustrating an operation unit of the color image forming apparatus.

FIG. 7 is a diagram illustrating a form in which an image is formed by sticking one sheet on an intermediate transfer belt and an image is formed by sticking two sheets.

FIG. 8 is a diagram illustrating a state of a photosensitive drum (photosensitive member) and an intermediate transfer member immediately after the start of latent image formation, and a diagram for explaining transfer timing.

FIG. 9 is a diagram illustrating a relationship between a latent image (laser) and an intermediate transfer member reference signal A, and is a diagram for explaining transfer timing.

FIG. 10 is a diagram illustrating a transfer high-voltage control timing, and is a diagram expressed as timing for a sheet as a recording material.

FIG. 11 is a block diagram of a high voltage controller.

FIG. 12 is a diagram for explaining the control timing of the rotary developing device in the case of sticking two sheets, and illustrates the relationship between the rotary developing device control and image formation during test patch image formation in the embodiment of the present invention. It is a figure.

FIG. 13 is a diagram illustrating test / patch formation timing according to the embodiment of the present invention, showing a state in which a patch of the immediately preceding image printing color is formed at a position slightly apart from the image trailing edge of the image. Is.

FIG. 14 is a flowchart illustrating a software module that performs processing of image formation order control and skip control according to the present invention.

FIG. 15 is a diagram illustrating image formation in the present embodiment, that is, transfer onto an intermediate transfer body as a viewpoint, when performing image formation of a plurality of sheets by two-sheet attachment control and one-sheet attachment control; FIG. 6 is a diagram illustrating a relationship between image formation including transfer and driving of a developing rotary motor.

[Explanation of symbols]

201 Reader section 202 printer section 400 Automatic document feeder 1 Photosensitive drum (photoreceptor) 2 Primary charger 3 Laser exposure part 3a polygon mirror 3b lens 3c mirror 4 rotation developing device 4Bk black developing device 4m magenta developer 4c cyan developing device 4Y yellow developer 5a Intermediate transfer belt 5c Secondary transfer roller 6 Intermediate transfer belt cleaner 7 Photosensitive drum (photoconductor) cleaner 7a Right deck 7b 1-stage cassette 7c two-stage cassette 7d left deck 9 Fixing device 9a Fixing upper roller 9b Lower fixing roller 9c web 9e Fixing heater 9f Lower fixing heater 11 Pre-exposure LED 12 Potential sensor 13 Test patch density sensor 19 flapper 20 Double-sided vertical pass 21a Reverse path 21b Reverse roller 22 double-sided pass 25 Secondary transfer roller cleaner 30 manuscripts 31 Platen 32 exposure lamp 33 lenses 34 Full color sensor 700 Reader / Controller 701 Printer controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 G03G 15/16 21/14 21/00 372 F term (reference) 2H027 DA22 DA23 DA32 DB09 DE02 DE04 DE07 DE09 EA06 EB04 EC04 EC06 EC07 EC18 EC20 ED02 ED06 ED08 ED24 EE01 EE07 FA04 FA16 FA30 FA35 FB14 ZA07 2H030 AA03 AA06 AD08 AD17 BB02 BB16 BB23 GABB13 DA23 DB21 FA17 DB23 DB11 DA21 DB23 GA34 GA40 GA44 GA47 GA50 GA60 GB02 GB22 HA02 HA12 HA28 HB12 HB22 JA02 JA29 JC03 JC09 JC12 JC19 JC20 LA12 LA23 LA40 PA03 PA10 PA12 PA14 PA19 PA20 PA26 PB13 PB17 PB39

Claims (4)

[Claims] 1. A latent image is formed on the photoconductor by exposing the photoconductor on the basis of image data to be printed on a recording material or test patch data for density control.
A developing device including a rotary developing device is used to visualize the latent image, the visualized toner image is transferred to an intermediate transfer body, and further, the toner image is transferred from the intermediate transfer body to the recording material. An image forming device configured to form an image for printing on the intermediate transfer body based on the image data, the image forming means forming an image on the intermediate transfer body. A test patch image forming means for forming a test patch with the development color of the image at the rear end of the image of each print color to be formed, and the test formed by the test patch image forming means. A density control unit that detects the toner density of the patch with a sensor and controls the density of the image to be developed based on the detection result so as to reach a predetermined density. During image formation on the transfer body,
After the test patch image forming means executes the process of forming the test patch, when the operation for controlling the rotation of the rotary developing device to the development color to be developed next is started, the intermediate transfer member is rotated once. Image formation on the intermediate transfer body after the rotation, so as to form an image of the development color of the rotation developing device after the rotation control so as to be superimposed on the image already formed on the intermediate transfer body. apparatus. 2. A latent image is formed on the photoconductor by exposing the photoconductor on the basis of image data to be printed on a recording material or test patch data for density control.
A developing device including a rotary developing device is used to visualize the latent image, the visualized toner image is transferred to an intermediate transfer body, and further, the toner image is transferred from the intermediate transfer body to the recording material. In the image forming apparatus configured as described above, the image forming unit forms an image for printing on the basis of the image data on the intermediate transfer body, and the image forming unit covers two surfaces of the recording material around the intermediate transfer body. An image forming unit including a two-sheet pasting control for performing two-sheet pasting control for simultaneously forming and printing images, and each printing performed while the image forming unit forms an image on the intermediate transfer member. A test patch image forming means for forming a test patch with the developed color of the image at the rear end of the image of a color, and a toner density of the test patch formed by the test patch image forming means is detected by a sensor. The density of the developed image based on the detection results. A density control unit for performing density control so as to obtain a predetermined density, wherein the image forming unit is executing the two-sheet sticking control, and after the image of the last image-formed surface of the two surfaces, When the operation for controlling the rotation of the rotary developing device to the development color to be developed next is started after the test patch image forming means executes the test patch image forming at the end, the subsequent image forming is executed at the end. The imaged surface,
Then, in order of the image on the remaining surface, the development color image is formed on the intermediate transfer body after being rotationally controlled so as to be superimposed on the image on the intermediate transfer body already formed. An image forming apparatus characterized by. 3. A latent image is formed on the photoconductor by exposing the photoconductor on the basis of image data to be printed on a recording material or test patch data for density control.
A developing device including a rotary developing device is used to visualize the latent image, the visualized toner image is transferred to an intermediate transfer body, and further, the toner image is transferred from the intermediate transfer body to the recording material. An image forming method for forming an image for printing on the basis of the image data on the intermediate transfer body, wherein the image forming step is for forming an image on the intermediate transfer body. A test patch image forming step of forming a test patch with the development color of the image at the rear end of the image of each print color to be formed, and the test formed in the test pad image forming step. A density control step of detecting the toner density of the patch with a sensor, and performing density control so that the density of the image developed based on the detection result becomes a predetermined density; To the transfer body When the operation of controlling the rotation of the rotary developing device to the developing color to be developed next is started after executing the process of forming the test patch by the test patch image forming step during the image formation of
Then, after the intermediate transfer member is rotated once, an image of the development color of the rotary developing device after the rotation control is formed on the intermediate transfer member so as to superimpose it on the already formed image on the intermediate transfer member. An image forming method characterized by performing. 4. A latent image is formed on the photoconductor by exposing the photoconductor on the basis of image data to be printed on a recording material or test patch data for density control.
A developing device including a rotary developing device is used to visualize the latent image, the visualized toner image is transferred to an intermediate transfer body, and further, the toner image is transferred from the intermediate transfer body to the recording material. An image forming method for forming an image for printing on the basis of the image data on the intermediate transfer body, the image forming method comprising: An image forming step including a two-sheet pasting control for performing simultaneous two-sheet pasting control for forming and printing images, and each printing performed during the image formation on the intermediate transfer member by the image forming step. A test patch image forming step of forming a test patch with the developed color of the image at the rear end of the image of the color; and a toner density sensor of the test patch formed in the pre-test patch image forming step. Detected based on the detection results A density control step of performing density control so that the density of the image to be developed becomes a predetermined density, wherein the image forming step is the last one of the two surfaces during execution of the two-sheet attachment control. When the test patch image forming step starts the operation of controlling the rotation of the rotary developing device to the development color to be developed next after the test patch image forming step is executed at the rear end of An image of the development color of the rotary developing device after rotation control is formed so as to superimpose it on the image on the intermediate transfer body that has already been formed in the order of the image on the last imaged surface and the image on the remaining surface. An image forming method, which is performed on the intermediate transfer member.