JP2003162116A - 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 an image forming means for switching and performing two-sheet sticking control and one-sheet sticking control, a test patch image forming means for performing processing to form the image of the test patch in the developing color of the image to be formed at the trailing edge of the image to be formed in each printing color in the midst of forming the image on the intermediate transfer body by the image forming means, and a density control means for controlling density so that the density of the developed image may be previously set density based on the detected result by detecting the toner density of the formed image of the test patch by using a sensor. Then, the processing of the test patch image forming means is performed when the image forming means performs the one-sheet sticking control to recording material having size that the two-sheet sticking control is possible. In the midst of the two-sheet sticking control, the image of the test patch is formed after switching to the one-sheet sticking control. <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, the present invention relates to an image forming apparatus and an image forming method for forming a test patch and performing a density control process in an image forming apparatus having an intermediate transfer member and a rotary developing device.

[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 two-sheet image formation, the rotation developing device must be rotated while moving from the rear end of the B side of the intermediate transfer member to the front end of the A side. By setting the distance from the rear end of the B surface to the front end of the A surface to be longer than the distance from the rear end of the A surface to the front end of the B surface, instead of setting the B surface to the opposite position of the intermediate transfer member. This is because the time (interval) from the image formation to the start of the next A-side image formation is extended to obtain a margin of the rotation control time required by the rotary 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 had returned to the problem of causing an increase in costs and running costs.

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, a process of forming a test patch and measuring the toner density of the test patch is considered in order to stabilize the image density. There is a need to. In this process, a test patch is imaged on the intermediate transfer member, the toner density is measured, and the measured result is fed back to the toner supply amount to the developing device to maintain the toner density at the developing device constant. Density control, which must be performed during image formation. There is a demand for performing this series of density control processing without reducing the productivity of the image forming apparatus.
Usually, the test patch image formation is formed in an area different from the image area printed on the recording material. When considering the control timing of the rotary developing device, if the timing is adjusted to include the image formation of this test patch, the performance of the stepping motor will be further improved, or very complicated control will be required. It was. In the image forming apparatus in which the peripheral length of the intermediate transfer member is shortened, an area is secured for forming the test patch, and the rotation control of the rotary developing device is controlled within the time corresponding to the remaining non-image forming area. It was particularly problematic because it was difficult to secure the time to do it.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus equipped with a rotary developing device, which is an intermediate transfer member having a shortened peripheral length, but having a density. An object of the present invention is to provide an image forming apparatus capable of forming a test patch image for control.

[0009]

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 means for forming an image,
Switching between two-sheet sticking control for simultaneously forming and printing images for two surfaces of the recording material around the intermediate transfer member and one-sheet sticking control for forming and printing images for only one surface of the recording material. Image forming means to be executed by the image forming means, and during the formation of the image on the intermediate transfer member by the image forming means, a test patch is formed at the trailing edge of the image of each print color formed with the development color of the image. A test patch image forming means for performing an image forming process and a toner density of the test patch formed by the test patch image forming means are detected by a sensor, and based on the detection result, the density of an image to be developed is previously determined. A density control means for controlling the density so as to obtain a predetermined density, wherein when the image forming means performs one-sheet sticking control on a recording material of a size capable of controlling two-sheet sticking, The process of the test patch image forming means is executed. It is characterized in.

According to a second 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. 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 that switches and executes two-sheet sticking control for simultaneously forming and printing images for two surfaces of the recording material and one-sheet sticking control for forming and printing images for only one surface of the recording material, Image on the intermediate transfer member by the image forming unit During the formation, a test patch image forming unit that forms a test patch with the development color of the image is formed at the rear end of the image of each print color to be formed, and the test patch image forming unit forms an image. Density control means for detecting the toner density of the imaged test patch by a sensor and performing density control so that the density of the image developed based on the detection result becomes a predetermined density, and the test patch image formation. A density test starting means for controlling the start of the processing of forming the test patch with respect to the means, wherein the density test starting means is configured such that the image forming means before the processing of the test patch image forming means is started. It is determined whether or not the two-sheet pasting control is being executed, and when the two-sheet pasting control is being executed, the above-mentioned steps are performed so as to switch to the one-sheet pasting control after completion of image formation for four colors of the image being formed. Controlling the image means, Determines that the image unit began one stick control, is characterized in that the start control to start the process on the test patch image forming means.

According to a third 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. 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 method for transferring a toner image, an image forming step of forming an image for printing on the basis of the image data on the intermediate transfer body, wherein the recording material is formed around the intermediate transfer body. An image forming step of switching and executing two-sheet pasting control for simultaneously forming and printing images for two sides and one-sheet pasting control for forming and printing images for only one side of the recording material; Onto the intermediate transfer member by the image step A test patch image forming step of forming a test patch with the development color of the image on the rear end of the image of each print color to be formed during image formation; and the test patch image forming step. A density control step of detecting the toner density of the test patch formed in step 1 by a sensor and setting the density of the image to be developed to a predetermined density based on the detection result. The step is characterized in that the processing of the test / patch image forming means is executed when the one-sheet pasting control is performed on the recording material having a size capable of controlling the two-sheet pasting.

According to a fourth 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 method for transferring a toner image, an image forming step of forming an image for printing on the basis of the image data on the intermediate transfer body, wherein the recording material is formed around the intermediate transfer body. An image forming step of switching and executing two-sheet pasting control for simultaneously forming and printing images for two sides and one-sheet pasting control for forming and printing images for only one side of the recording material; Onto the intermediate transfer member by the image step A test patch image forming step of forming a test patch with the development color of the image on the rear end of the image of each print color to be formed during image formation; and the test patch image forming step. A density control step of detecting the toner density of the test patch formed by the above-mentioned method with a sensor and performing density control so that the density of the image developed based on the detection result becomes a predetermined density. A density test starting step for starting the processing of the patch image forming step is provided, wherein the density testing starting step executes the two-sheet pasting control before the processing of the test patch image forming step is started. It is determined whether or not there is a two-sheet pasting control, and when the two-sheet pasting control is being executed, the image forming step is controlled so as to switch to the one-sheet pasting control after the image formation for four colors of the image being completed , It is determined that the image forming step is started one stick control, characterized in that to start the processing of the test patch image formation step.

[0013]

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

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

This color image forming apparatus includes a digital color image reader unit 201 (hereinafter abbreviated as "reader unit") arranged at an upper portion and a digital color image printer unit 202 (hereinafter referred to as a "printer") arranged at a lower portion. 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.
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 as 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 rotational 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 an 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-surface attachment 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 (photosensitive member) 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 drive 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 (photoconductor) 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, reference numeral 705 is a reader / controller 700
Is a ROM storing the control program, reference numeral 706 is a RAM storing data such as control values, and reference numeral 707 is an I / O for driving a load such as the exposure lamp 32.
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 section 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, 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 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 formula (2), M2, C2, and Y2 are The MCY image signal output from the complementary color conversion circuit 103, M1, C1,
Y1 is an MCY image signal output from the UCR circuit 105, and the coefficients B1, B2, B3, D1, D2 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 | Coefficients M1, C1, and Y1 are MCY image signals output from the UCR circuit 105, M0, C0, and Y0 are MCY image signals output from the masking circuit 106, and masking coefficients a11 to a33 are designated by the image processing control unit. Determined by the masking coefficient control signal.

Reference numeral 107 denotes 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 a 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 saves a fax image on the hard disk 402, which is a facsimile function, such as performing fax transmission at a designated time or transmitting image data when a partner inquires for a designated password. Perform processing.
As a result, once the reader unit 201 to the image memory unit 73
After the image is transferred to the facsimile unit 401 and the facsimile hard disk 402 via 0, the facsimile transmission can be performed without using the reader unit 201 and 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. The status of the printer unit and the reader unit is notified to the external computer via this I / F, and the image read by the reader unit 201 is transferred to the external computer according to an instruction from 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, and the image of the reader unit is sent to the external computer via the computer interface unit 403 ( 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 stored in the computer.
It is also used when data is transmitted from the interface unit 403.

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, which are "single-both mode" for outputting both sides from a single-sided original, "double-both mode" for outputting both sides from a double-sided original, and two for the double-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 on which the image is formed 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 tray with the paper selection key 303 and gives an instruction to start the operation with the start key 354, the printer controller 701 performs 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 carried out by sequentially sending to the printer unit the image data decomposed into each printing color from the image processing unit so as to match the reference signal of the intermediate transfer member. Be seen.

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

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

FIG. 8 shows the positional relationship between the photosensitive drum (photosensitive member) 1 and the intermediate transfer member 5a at the start timing of the latent image writing, and recording is performed with the fixed point PTA on the intermediate transfer member 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 fall 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 controls a current flowing to the primary side of the high voltage transformer 801 using a high voltage control signal (voltage) set in the D / A section 753 as a reference. Thus, an operation amplification unit for controlling the current flowing to the secondary side, reference numeral 805 is a current detection resistor.

Further, the document information sent from the reader unit is processed by the image processing unit 203, and irradiated on the photosensitive drum (photoreceptor) 1 uniformly charged by the charger 2 as a laser beam. 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 way, the four-color images are sequentially primary-transferred, and the superimposed toner images on the intermediate transfer member are at the position of the secondary transfer roller 5c and the timing suitable for the secondary transfer by the registration roller 5c. The secondary transfer is performed on the recording material conveyed in. At this time, a secondary transfer high voltage is applied between the intermediate transfer body 5a and the recording material P by the secondary transfer roller 5c to form a secondary transfer current, so that the superposed toner images are transferred to the recording material 2 Next transfer.

The recording material P, which has thus passed through the secondary transfer roller 5c and has the toner image, is conveyed by the recording material conveying section 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 is made variable like 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. 12 is a diagram for explaining the control timing of the rotary developing device when two sheets are stuck. 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. About A side and B side of pasting two pieces 1
After the magenta of the color is developed, the next cyan development is A
From the surface to the start, rotate the rotary developing device,
The cyan developing device moves to a position facing the photoconductor.
In the figure, when the time corresponding to the amount of movement from the rear end of the B side to the front end of the A side is equal to the time required for the rotary developing device to rotate from magenta to cyan in relation to the length of two sheets of paper stuck together. Is 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 Bk developing device 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 replenishment 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 rear end 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.

(Image formation of test patch at rear end of image) FIG. 14 is a flow chart of test patch execution control for forming a test patch. When it becomes necessary to adjust the image density, or when the toner consumption amount from the previous density adjustment exceeds the specified value, control is performed so that the test patch forming module forms the test patch image. In that case, it is determined according to this flowchart whether or not to execute the patch image formation processing by the test patch formation module.

In this test / patch execution control, first, in step S1401, it is determined whether the current image forming control is the two-sheet pasting control or the one-sheet pasting control. When the two-sheet attachment control is performed, the interval between the images on the two surfaces formed on the intermediate transfer body becomes short, and when patch formation is performed at the image trailing edge, the trailing edge of the test patch Since the rotation processing of the rotary developing device cannot be completed within the time corresponding to the time from the next time to the image leading edge, the test patch is not formed and the process is ended. That is, the test
Postpone patch imaging.

If it is determined in step S1401 that the one-sheet sticking control is performed, the process proceeds to step S1402, in which the image size is being formed (related to the size of the recording material to be recorded). to decide. When a large size image such as A3 or LDR that cannot be pasted with two sheets is being formed, the distance from the trailing edge of one image to the leading edge of the next image is short even though the one sheet is controlled. Corresponding time is getting shorter. In this case, if the test patch is imaged at the trailing edge of the imaged image, the rotation control of the rotary developing device can be completed within the movement period from the trailing edge of the imaged image to the leading edge of the next imaged image. It's gone. Therefore, in step S1402, the size of the image currently being formed is determined, and if the size is such that two sheets cannot be pasted, the patch image forming process is not performed and the process ends. That is, the test patch image is postponed.

The delayed test patch image is
It is executed at the time when the state becomes executable, including the cases described below.

If it is determined in step S1402 that the image size currently being formed is an image size capable of adhering two images such as A4 and LTR, the size capable of adhering two images is set to 1.
Since it is controlled to paste sheets, there is enough space at the trailing edge of the image-formed image for the test patch image formation and space for the rotation processing of the rotary developing device after the test patch image formation. There will be space. That is, there is sufficient time for rotation control. Therefore, the process advances to step S1403 to execute the test patch image forming process.

In the image forming apparatus to which the present invention is applied,
Actually, the case of controlling the sticking of one sheet of the size that allows two sheets occurs when the sheet cassette is switched,
In this case, the difference in the feeding time of the recording paper becomes large and it becomes impossible to form images on two sheets of paper at the same time, the OHP and the middle insert paper are alternately fed, and the number of pages of the image data itself is large. When the number is an odd number, etc. are considered.

(Second Embodiment) This second embodiment is a test patch which is different from the first embodiment in that whether simultaneous image formation surface number control, that is, one-sheet attachment control or two-sheet attachment control is performed. Of the image of
When performing patch image formation, the number of surfaces to be imaged at the same time is controlled.

FIG. 15 is a flow chart of switching of image formation control associated with test patch image formation in the second embodiment, that is, simultaneous image formation surface number control. When the two-sheet sticking control is being performed or is being performed, the switching of the image forming control is determined according to this flowchart.

First, in step S1501, it is determined whether the size is such that two sheets can be attached. Image size is A
In the case of an image size such as 3, LDR, which allows only one-sheet sticking control, there is no room for determination, and the process advances to step S1505 to perform one-sheet sticking control. If it is determined in step S1501 that the image size is such that A4, LTR, or the like can be formed on two sheets, the process advances to step S1502.
Further, the judgment including the patch image formation is performed.

In step S1502, the presence or absence of patch image formation is determined. When it is necessary to adjust the image density and try to perform patch image formation, the image size is such that two sheets can be pasted, but if the patch image is formed at the rear end of the image formation on the B side, it will rotate. In some cases, the rotation control of the developing device is not completed between the trailing edge of the image and the leading edge of the next image. Therefore, even if the image size is such that two sheets can be pasted, when patch image formation is performed, two sheets are not controlled to be controlled, and the process proceeds to step S1503 to perform one sheet control. By doing so, only one image is formed on one surface of a short image in the sub-scanning direction in which two sheets can be controlled. Therefore, the interval between the images is increased and the time margin for controlling the rotation of the rotary developing device is increased. growing. Even if the patch image is formed, the problem that the rotation processing of the rotary developing device is not in time does not occur.

If it is determined in step S1502 that patch image formation is not performed, the image size is such that two sheets can be pasted, and therefore the flow advances to step S1504 to form two images on the intermediate transfer member. Two-sheet sticking control is performed.

In the present embodiment, the processing shown in FIG.
For example, it is executed when a new image of, for example, four colors is formed based on the image data. For example, if 5 originals are copied using the 10-sheet and 2-sheet paste control, the test patch creation is performed while the first and second originals are copied 7 sheets each. When the image request is received, the process shown in FIG. 15 is executed at the start of copying the third document after completing the copying of each of the ten sheets. Then, the third original is copied under the single-sheet attachment control. The next fourth and fifth originals are copied back to the two-sheet pasting control. If a copy of each copy of a plurality of originals is copied under the control of sticking two sheets, the copy on one recording material is copied under the control of sticking one sheet.

In the case of color, the test patch image formation is basically executed for each print color. But,
As described above, since it is necessary to execute the toner currently used, only the print color of black is executed when monochrome printing is being executed, and is executed for each print color during color printing. As a matter of course, when a large amount of copying or the like is executed at one time, the test patch image forming process is performed plural times during the execution, and the printed density is maintained at the specified value.

[0098]

As described above, according to the present invention, in the image forming apparatus having the rotary developing device, the manufacturing cost,
Even if the circumference of the intermediate transfer member is shortened in order to reduce the running cost and both costs, the test patch image formation can be executed without increasing the manufacturing cost and running cost. It has become possible to reduce the size and maximize the efficiency of machine productivity.

Further, according to the first aspect of the invention, the processing of the test patch image forming means is executed when the one-sheet sticking control is performed on the recording material having a size capable of controlling the two-sheet sticking. By doing so, it is possible to execute test patch imaging without affecting productivity.

Further, according to the second aspect of the present invention, when starting the density test, it is judged whether or not the two-sheet pasting control is being executed, and when the two-sheet pasting control is being executed, the image formation is performed. The image forming means is controlled so as to switch to the one-sheet attachment control after the completion of the image formation for four colors of the image, and it is judged that the image forming means has started the one-sheet attachment control, and the test / patch image forming processing is performed. Since it is started, it is possible to execute the test patch image forming process without increasing the cost even when the two-sheet attaching control is being executed.

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 necessary for image formation, the manufacturing cost, the running cost, and the It is possible to reduce the cost of the. 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.

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 showing a start control process of test patch image formation according to the first embodiment of the present invention.

FIG. 15 is a flowchart showing an image formation control process executed at the start of test patch image formation according to the second embodiment of the present invention.

[Explanation of symbols]

201 Reader section 202 printer section 400 Automatic document feeder 1 photosensitive drum 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 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

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA09 DC19 DE02 DE09 EA06                       EB04 EC03 EC18                 2H030 AB02 AD16 AD17 BB02 BB24                       BB36 BB42                 2H077 AD06 BA10 DA02 DA05 DA63                       DB02 EA01 GA03 GA13                 2H200 FA02 FA17 GA23 GA34 GA44                       GA47 GA50 GB11 GB25 GB41                       HA02 HB12 HB22 JA02 JA30                       JB10 JC03 JC20 LA12 PB17

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. 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 that switches and executes two-sheet sticking control for simultaneously forming and printing images and one-sheet sticking control for forming and printing an image of only one surface of the recording material; During the formation of the image on the intermediate transfer member, a test that performs a process of forming a test patch with the developed color of the image on the trailing edge of the image of each print color to be formed.
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. A density control unit for performing density control, wherein the test is performed when the image forming unit performs one-sheet sticking control on a recording material having a size capable of controlling two-sheet sticking.
An image forming apparatus, wherein processing of a patch image forming unit is executed. 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 that switches and executes two-sheet sticking control for simultaneously forming and printing images and one-sheet sticking control for forming and printing an image of only one surface of the recording material; During the formation of the image on the intermediate transfer member, a test that performs a process of forming a test patch with the developed color of the image on the trailing edge of the image of each print color to be formed.
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. A density control means for controlling the density and a density test starting means for controlling the start of the process of forming the test patch with respect to the test patch image forming means are provided, and the density test starting means includes the test patch. Before starting the processing of the image forming means, it is judged whether or not the image forming means is executing the two-sheet pasting control. After the image formation is completed, the image forming means is controlled so as to switch to the one-sheet attachment control, and it is judged that the image forming means has started the one-sheet attachment control,
An image forming apparatus, wherein start control is performed on the test patch image forming unit so as to start processing. 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. In the image forming method described above, in the image forming step of forming an image for printing on the basis of the image data on the intermediate transfer body, an image for two surfaces of the recording material is formed around the intermediate transfer body. An image forming step of switching and executing two-sheet sticking control for simultaneously forming and printing and one-sheet sticking control for forming and printing an image of only one surface of the recording material; and the intermediate transfer by the image forming step. A test patch image forming step of forming a test patch with the development color of the image on the rear end of the image of each print color to be formed during formation of the image on the body; Imaged in the patch imaging step The toner density of the test patch is detected by a sensor, and a density control step of setting the density of the image to be developed based on the detection result to a predetermined density is provided. An image forming method, wherein the process of the test / patch image forming means is executed when one sheet is attached to a recording material having a size capable of being attached. 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. In the image forming method described above, in the image forming step of forming an image for printing on the basis of the image data on the intermediate transfer body, an image for two surfaces of the recording material is formed around the intermediate transfer body. An image forming step of switching and executing two-sheet sticking control for simultaneously forming and printing and one-sheet sticking control for forming and printing an image of only one surface of the recording material; and the intermediate transfer by the image forming step. A test patch image forming step of forming a test patch with the development color of the image on the rear end of the image of each print color to be formed during formation of the image on the body; Imaged in the patch imaging step A density control step of detecting the toner density of the test 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; and a test patch image forming step. A density test starting step for starting processing is provided, wherein the density test starting step determines whether or not the image forming step is performing a two-sheet pasting control before starting the processing of the test / patch image forming step. However, when the two-sheet pasting control is being executed, the image forming step is controlled so as to switch to the one-sheet pasting control after the completion of the image formation for the four colors of the image being formed, and the one image pasting step is performed. An image forming method, comprising: determining that control has been started, and starting the processing of the test patch image forming step.