JPH05336331A - Color image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] Improving the image forming speed of the monochrome image forming mode,
Effective use of fixing energy, reduction of waiting time when switching modes, etc. In a color image forming apparatus that controls a laser light emitting element according to an image signal to form an electrostatic latent image on a photoconductor and forms an image on a transfer paper by developing, transferring and fixing, a single color image is formed. The image forming process speed is switched higher than that in full color image formation, and the number of scanning lines of laser light is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention scans a photoconductor with laser light modulated with a recording color component image signal to form an electrostatic latent image, and the latent image is formed into a yellow, magenta, Regarding a color image forming apparatus for developing with a toner such as cyan or black,
In particular, the present invention relates to a color image forming apparatus for selectively performing a full color image forming mode of three colors or four colors and a single color image forming mode.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 60-229041 discloses an analog color electrophotographic copying machine for projecting an original image on a photoconductor, in which a process speed is different between full color copying and single color copying. Switches. Japanese Unexamined Patent Publication No. 1-224780 discloses a monochromatic (black and white) printer that switches the image forming process speed in conjunction with switching the scanning density of laser light. A technique for forming an image using a plurality of laser beams is disclosed in Japanese Patent Publication No.
7-49941, Japanese Patent Publication No. 60-33019, Japanese Patent Publication No. 1-45065, Japanese Patent Publication No. 1-4329.
No. 4, for example.

FIG. 2 shows an example of a color image forming apparatus which controls a laser emitting element in accordance with an image signal to form an electrostatic latent image on a photosensitive member and forms an image on a transfer paper by developing, transferring and fixing. Indicates the format. The image information on the original 100 is stored in the color CCD 2 provided in the reading unit 200.
At 01, it is converted into an electric signal (image data) corresponding to the original image. After that, the image processing unit 400 performs optimum image processing and conversion into a recording color image signal, and then the image data is sent to the writing unit 300 and used for forming an image on the photosensitive drum 5. An image forming member based on the well-known electrophotographic method (color xerography) is installed around the photosensitive drum 5. The photoconductor drum 5 at the charging unit 510
After the surface of the recording medium is uniformly charged, the laser beam 8 emitted by the semiconductor laser 2 provided in the writing section 300 is modulated with the recording color image signal, and the laser beam 8 is photosensitive drum. An electrostatic latent image is formed on the surface of the photoconductor drum 5 by scanning and projecting onto the photosensitive drum 5. The laser beam 8 is incident on a rotary polygon mirror (polygon mirror) 3 which is rotationally driven by a scanner motor 1, and is deflected and scanned by the rotation of the rotary polygon mirror 3. The laser beam reflected by the rotary polygon mirror 3 is imaged in a spot shape on the photosensitive drum 5 by the well-known imaging lens of the fθ lens group 4.

The electrostatic latent image is visualized with toner in the developing section 500. The developing section 500 includes a yellow developing device 500.
Y, magenta developing unit 500M, cyan developing unit 500C,
A black developing device 500Bk is provided. This developing unit 50
Details of 0 are disclosed, for example, in US Pat. No. 4,928,144. The cleaner unit 520 cleans the toner remaining on the photosensitive drum 5 after the transfer.

On the other hand, the transfer papers 601 placed on the paper feeding section 600 are transferred one by one by a paper feeding roller 602 and relayed by a paper feeding roller 602.
It is transferred to the transfer unit 700 via the la roller 604 and the resist roller 603. For details of the transfer unit 700, see, for example, Japanese Patent Publication No. 6
3-34467, JP-B-63-34468, JP-B-63-55068, US Pat. No. 4,8
35,582, U.S. Pat. No. 4,862,214.
No. 4,864,358, US Pat. No. 4,872,037, and the like.

The transfer sheet is held and conveyed by the transfer drum 701, and the toner image on the photosensitive drum 5 is transferred to the transfer sheet by the transfer charger 702. During black-and-white copying, which is a typical example of single-color recording, a black toner image is formed on the photosensitive drum 5 by black development, and this is transferred onto a transfer paper. The latent image formation, development and transfer are each performed only once. In the case of full color copying (printing), the image forming step (latent image formation, latent image formation, latent image formation, three times, once for each of Y, M, and C, or once for each of Y, M, C, and BK) (Development and transfer) are repeated (transfer is performed 3 or 4 times).
After the transfer of the toner image is completed, the transfer paper is separated from the transfer drum 701 by the transfer paper separating unit 703. After that, the fixing unit 8
At 00, the toner image is fixed on the transfer paper and is discharged to the outside of the machine.

FIG. 3 shows another color image forming apparatus which controls a laser emitting element in accordance with an image signal to form an electrostatic latent image on a photosensitive member and forms an image on a transfer paper by developing, transferring and fixing. One form is shown. Manuscript 100
The image above is a color CC provided in the reading unit 200.
Electrical signal (image data) corresponding to the original image at D201
Is converted to. After that, the image processing unit 400 performs optimum image processing and conversion into recording color signals, and then the recording color signals are sent to the writing unit 300 and used for image formation on the photosensitive drum 5. An image forming member based on the well-known electrophotographic method (color xerography) is installed around the photosensitive drum 5. The surface of the photosensitive drum 5 is uniformly charged by the charging unit 510. Writing unit 30
The semiconductor laser 2 provided at 0 emits the laser beam 8 modulated by the recording color signal, and the scanner motor 1
Rotating polygon mirror (polygon mirror) 3 driven by
Apply to. The laser beam reflected by the rotary polygon mirror 3 is imaged in a spot shape on the photosensitive drum 5 by a well-known fθ lens. The laser beam 8 is deflected and scanned by the rotation of the rotary polygon mirror 3. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 5.

The electrostatic latent image is visualized with toner in the developing section 500. The developing section 500 includes a yellow developing device 500.
Y, magenta developing unit 500M, cyan developing unit 500C,
A black developing device 500Bk is provided. This developing unit 50
Details of 0 are disclosed, for example, in US Pat. No. 4,928,144. The cleaner unit 520 cleans the toner remaining on the photosensitive drum 5 after the transfer.
The toner image on the surface of the photosensitive drum 5 is transferred to the intermediate transfer member 701.

On the other hand, the transfer papers 601 placed on the paper supply unit 600 are fed one by one by a paper feed roller 602, and are passed through a relay roller 604, a registration roller 603, and a secondary transfer roll.
It is transferred to Le 704. The secondary transfer roll 704 is disclosed in detail in Japanese Patent Application Laid-Open No. 62-182766, Japanese Patent Application Laid-Open No. 2-187070 and the like.

At the time of black-and-white copying (printing), the black toner that has undergone black development is transferred to the intermediate transfer member 701 and the black toner is transferred.
Is transferred to a transfer paper by a secondary transfer roll 704. That is, the transfer is performed once. In the case of full-color copying (printing), the image forming steps (latent image formation, development and transfer to the intermediate transfer member 701) of Y, M, C and Bk are repeated 3 to 4 times. Do). The toner image (for three colors or four colors) on the intermediate transfer member 701 is the second
It is collectively transferred onto the transfer paper 601 by the secondary transfer roll 704 of the next transfer section. After the transfer is completed, the toner image on the transfer paper is fixed by the fixing unit 800, and the transfer paper is ejected outside the machine.

FIG. 4 shows a color image forming apparatus for controlling a laser emitting element in accordance with an image signal to form an electrostatic latent image on a photosensitive member and performing image formation on a transfer sheet by developing, transferring and fixing. Yet another form is shown. Image signals from a personal computer, workstation, etc. (mainly image data read by a separate scanner) are subjected to optimum image processing and conversion into recording color signals by the image processing unit 400. The recording color signal is sent to the writing unit 300 and used for forming an image on the photosensitive drum 5. Around the photoconductor drum 5, elements for forming an image by a well-known electrophotographic method (color xerography) are installed. The surface of the photoconductor drum 5 is uniformly charged by the charging unit 510. A laser beam 8 oscillated by the semiconductor laser 2 provided in the writing unit 300 is modulated by a recording color signal and is incident on a rotary polygon mirror (polygon mirror) 3 which is rotationally driven by a scanner motor 1. The rotary polygonal mirror 3 is rotated to deflect and scan, and a spot image is formed on the photosensitive drum 5 by the well-known image forming lens of the fθ lens group 4. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 5.

The electrostatic latent image is visualized with toner in the developing section 500. The developing section 500 includes a yellow developing device 500.
Y, magenta developing unit 500M, cyan developing unit 500C,
A black developing device 500Bk is provided. Cleaner part 52
At 0, the toner remaining on the surface of the photosensitive drum 5 after the transfer is cleaned.

On the other hand, the transfer papers 601 placed on the paper feed unit 600 are transferred one by one by a paper feed roller 602 to a transfer unit via a registration roller 603.

At the time of black-and-white printing, one transfer is performed to transfer a black toner image by black development onto a transfer paper. In the case of full-color printing, a toner image is formed on the photosensitive drum 5 by repeating Y, M, C, and Bk three to four times. The toner image on the photoconductor is collectively transferred onto the transfer paper 601 by the transfer roller 702 at the transfer unit. After the transfer is completed, the transfer paper is discharged to the outside of the machine through the fixing unit 800.

In the conventional various systems described above and other color electrophotographic copiers (or printers), exposure, development,
Since the image forming process speed such as transfer is set to a constant value, a black and white copy (or print) can be made on a machine equipped with a black developing device, or a copier (or printer) equipped with a three-color or black and developing device. To make a single color copy (or print) of yellow, magenta, and cyan,
Since exposure, development, and transfer are only required once, the time required for copying (or printing) is one-third or one-fourth that of full-color copying (or printing) when three or four colors are overlaid. It will be.

[0016]

By the way, the amount of toner adhered on the transfer paper is 3 to 4 times as much as that in monochrome copying (single color copying) in full color copying when copying from the same original. Further, a color original has many pictures, and the image occupying area thereof is about three times that of a black-and-white original (many documents). Therefore, in full-color copying and black-and-white copying (or single-color copying), the fixing energy is much more required in full-color copying. For this reason, the fixing speed and the fixing temperature are set so that the full-color copy can be fixed. Therefore, the fixing energy becomes a large surplus for fixing the black and white (or single color) copy, and the electric power is wasted. In addition, as a normal usage of a color copying machine, it is common to copy a plurality of full-color and black-and-white (or single-color) mixed originals, and under these conditions of use, to meet the fixing conditions of full-color and black-and-white (or single-color). The fixing temperature range became very narrow, and high-precision temperature control was required. The thermal characteristics of the toner also need to have a wide range of fixing temperature range, which limits the selection range of toner resin materials.
It was very difficult to satisfy the optimum toner color characteristics and charging characteristics at the same time from the viewpoints of durability, environmental stability, and economical efficiency.

The present invention relates to a color image forming apparatus for controlling a laser light emitting element in accordance with an image signal to form an electrostatic latent image on a photosensitive member and performing image formation on a transfer paper by developing, transferring and fixing. 1) Improving the image forming speed in the monochromatic image forming mode, 2) Effective utilization of fixing energy, 3) Ensuring image quality, 4) Reduction of waiting time when switching image forming modes, 5) Efficiency of image signal processing The purpose is to enable

[0018]

In order to achieve the above-mentioned object, in the present invention, a laser light emitting element is controlled according to an image signal to form an electrostatic latent image on a photosensitive member, and development is performed. ，
In a color image forming apparatus that forms an image on a transfer paper by transfer and fixing, the image forming process speed is switched between full color image formation and single color image formation, and at the same time full color image formation and single color image formation are performed. -The number of scanning lines of the light is switched.

[0019]

Since the image forming process speed is switched between the full-color image formation and the single-color image formation, and the number of laser light scanning lines is switched between the full-color image formation and the single-color image formation, a polygon mirror is used. A fixed speed that does not require speed change can be used for the rotationally driven scanner motor, and a fixing device that does not require power switching can be used.
Further, it is possible to use an image signal processing circuit which does not require switching of pixel frequencies of a plurality of laser beams.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the main part of one embodiment of the present invention.
This is a full-color copying machine shown in FIGS. 2, 3 and 4 or any other type in which a laser light emitting element is controlled in accordance with an image signal to form an electrostatic latent image on a photoreceptor, and development, transfer and fixing are performed. A control system used in a full-color copying machine for forming an image on a transfer sheet or a printer for forming an image of this kind is shown in FIG. 1. In FIG. 1, 10 is an image signal processing circuit, 11 is a DC controller, and 12 is the number of scanning lines. Means, 13 is a selection switch for designating an image forming mode. By the selection switch 13, full color copy
Mode 1 (4 colors) Full color copy mode 2 (3 colors),
When two-color copy mode (color classification: with color designation) or single color copy mode (color classification: with color designation) is designated, the scanning line number switching means 12 corresponds to the designated mode. Image forming process speed information (rotational speed of the drum driving motor 16, charging device voltage, developing bias voltage, transfer device voltage, etc. is read from a reference table (memory) and given to the DC controller 11. The process speed information is given to the motor driver 15, the developing bias power source 20, and the high-voltage power source 21. That is, the motor driver 15 is supplied with a signal for changing the rotation speed of the photosensitive drum.
Similarly to changing the rotational speed of the photosensitive drum 5, signals are sent from the DC controller 11 to the developing bias power source 20 and the transfer / charging high voltage power source 21 to change their outputs. In FIG. 1, 1 is a scanner motor, 3 is a rotary polygon mirror, 4 is an fθ lens group, 5 is a photosensitive drum, 6 is a horizontal synchronization detection sensor, 18 is a horizontal synchronization signal generation circuit, and 17 is a scanner motor driver. Selection switch 13
Is attached to an operation unit provided on the apparatus body.
In the present invention, the image forming process speed is switched between full color image formation and monochromatic image formation, and the number of scanning lines of laser light is switched between full color image formation and monochromatic image formation. In the case of a copying machine, these changes are output by a selection switch 13 shown in FIG. 1 which outputs a signal designating a copy mode such as full color, black and white or single color. The selection switch 13 may be a touch key operated by a user or a signal from an automatic document identification device known in the industry, which is installed in a normal copying machine main body. In the case of a printer, the scanning line number switching means 12 receives a signal designating a recording mode such as full color, black and white or single color from a personal computer, a workstation or the like. In response to the mode designation signal, the scanning line number switching means 12 instructs the motor driver 15 and the like via the DC controller 11 the speed corresponding to the designated mode. That is, the drum driving motor 16 and the like are controlled so that the image forming process speed becomes a desired speed, and in addition, the image forming process conditions such as the developing bias, transfer, and charging are optimized, and the developing bias power source 20 and the high voltage power source are used. 21 and the like.
In the case of black and white (or other monochrome), semiconductor laser-2a,
One of 2b is driven, and the other control means performs the same optimization process by the control means described above. Modulation of a laser beam spot has been conventionally known as a high quality image processing. In full-color image recording, one-dot multi-value processing and binary processing for black and white or other monochrome are often used. In the present invention, in full-color image recording, modulation means (power modulation, pulse width modulation, combined use of both of them) adapted to one-dot multi-value / binarization (not shown) in the laser driver 14
Is provided for performing laser beam modulation corresponding to multi-value / binarization of one dot. In the case of black and white or other monochrome, laser beam modulation adapted to binarization of one dot is performed. The scanner motor 1 that drives the rotary polygon mirror 3 is driven at a constant speed, and is urged to rotate at the same constant speed in the full-color image forming mode and the single-color image forming mode. The fixing power source 22 of the fixing device does not need to switch the power corresponding to these modes. When the number of scanning lines in the full-color image forming mode and the number of scanning lines in the single-color image forming mode are n and N, respectively, the single-color image forming process speed V is full color.
V = (N / n) v is set for the image forming process speed v. The number n of scanning lines in the full-color image forming mode and the number N of scanning lines in the single-color image forming mode may be arbitrary as long as N> n.

[0021]

[Effect] 1) The copying (printing) speed at the time of single-color copying (printing) is improved. It saves power.

Conventionally, since the image forming process speed was constant, the black-and-white or single-color copy speed was only about 3 to 4 times that of full-color copy, but according to the present invention, it is almost the same. A copy speed of 6 times or more can be obtained with power consumption.

2) The waiting time when switching the copy (print) mode is reduced.

Since the rotary polygon mirror 3 always needs to maintain a constant rotation speed, there is no target speed change at the time of switching from full color to black-and-white or other monochrome color, and vice versa. There is no time to wait until it stabilizes. That is, no waiting time is required.

3) Ensuring image quality-In order to improve the color image quality, it is essential to make one dot multi-valued for the spot of the laser beam. Most of the characters, such as documents and illustrations,
Since it is a number and a line drawing, one dot binary value is often used.
In the case of 1-dot multi-valued, the laser beam is modulated by power modulation, pulse width modulation or a combination of these, so highly accurate control is required and the scanning line of the laser beam is required. Although the control becomes more difficult as the number of lines increases, the one-dot binary value used for monochrome images such as black and white can be controlled with high accuracy even if the number of scanning lines increases, and the number of scanning lines can be increased to improve image quality or Can be maintained.

4) Improvement in efficiency of image signal processing Since the rotation speed of the rotary polygon mirror 3 is constant regardless of whether it is a full color or a single color such as black and white, the pixel frequency in the image signal processing is constant, which is efficient and economical. It is highly reliable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control system of an embodiment of the present invention.

FIG. 2 is a block diagram showing one type of full color copying machine to which the control system shown in FIG. 1 is applied.

FIG. 3 is a block diagram showing another type of full-color copying machine to which the control system shown in FIG. 1 is applied.

4 is a block diagram showing another type of full-color copying machine to which the control system shown in FIG. 1 is applied.

[Explanation of symbols]

1: Scanner motor 2: Semiconductor laser 3: Rotating polygon mirror 4: fθ
Lens group 5: Photosensitive drum 6: Synchronous detection sensor 8: Laser beam 10: Image signal processing circuit 11: DC controller (switching means) 12: Scanning line number switching means (switching means) 13: Selection switch (input means) 14 : Laser driver 100: Original 200:
Reading unit 300: Writing unit 400:
Image processing unit 500: Development unit 600:
Paper feeding unit 701: Intermediate transfer member 800:
Fixing unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 15/00 102 15/01 R 112 A 15/04 116 9122-2H H04N 1/29 G 9186- 5C

Claims (5)

[Claims] 1. A full-color image in a color image forming apparatus that controls a laser emitting element according to an image signal to form an electrostatic latent image on a photoconductor and forms an image on a transfer paper by developing, transferring and fixing. Forming means and input means for specifying an image forming mode including monochromatic image forming, process control means for executing the image forming process of the mode specified by the input means, and mode specified by the input means.
Depending on the mode, the image forming process speed is switched between the full color image forming mode and the single color image forming mode,
A color image forming apparatus comprising: means for switching the number of scanning lines of laser light between a full-color image forming mode and a single-color image forming mode. 2. The color image forming apparatus according to claim 1, wherein the switching means increases the image forming process speed of the single color image forming mode between the full color image forming mode and the single color image forming mode. 3. The color image forming apparatus according to claim 1, wherein the switching means increases the number of scanning lines of laser light in the single color image forming mode between the full color image forming mode and the single color image forming mode. .. 4. The means for switching, when the number of scanning lines in the full-color image forming mode and the number of scanning lines in the single-color image forming mode are n and N, respectively, the monochromatic image forming process speed V is changed to full-color image forming. For process speed v, V =
The color image forming apparatus according to claim 1, wherein (N / n) v. 5. A switching means for switching the modulation of a laser light beam spot of a monochromatic image forming mode to a different one from that of a full color image forming mode. Color image forming apparatus.