JPH1124354A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of almost evenly consuming the developer of respective color, and increasing output frequency of the monocromatic image without deteriorating the image quality. SOLUTION: In this, a color copying machine is provided with image forming units 15Y, 50M, 50C and 50B outputting respective images in yellow, magenta, cyan and black. By irradiating photoreceptor drum 51Y, 51M, 51C and 51B of respective units with laser beam 41Y, 41M, 41C and 41B whose beam diameter and exposure strength is respectively adjusted, respective latent images are formed. In the case of outputting the monocromatic image, at the time point when a near empty sensor 532b for black toner detects the near empty, by reducing density of the black toner by adjusting the exposure strength of the laser beam for the black 41B, and while forming the toner image in respective color by reducing the beam diameter of other colors, the monoclomatic image is outputted by laminating the toner image in respective colors on the black toner image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms an image with a developer for each color based on a color-separated image signal, and outputs a color image by superimposing the developer images of each color on a transfer-receiving medium. The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that outputs a monochrome image by using a device that outputs a color image.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus for outputting a color image, a color (Y), a magenta (M), a cyan (C), and a black (B) for each color based on color-separated image signals. 2. Description of the Related Art A color copier including four image forming units for forming a toner image is known. The toner image of each color formed by each image forming unit is sequentially superimposed and transferred onto a transfer medium, and is output as a color image on the transfer medium. The toner images of each color transferred onto the transfer medium are pressed against the transfer medium by the fixing device, melted by heating, and fixed on the transfer medium.

When a monochrome image is output using this type of color copying machine, a black toner image is formed using only the black image forming section, and the black toner image is transferred onto a transfer medium. Output a monochrome image.

As described above, when a single copying machine outputs a color image and a monochrome image, three colors other than black (Y,
As compared with the toners of M and C), the consumption amount of the black toner increases, and the number of times of replacement of the black toner increases. In particular, in a system in which the toner of each color is simultaneously replaced as one unit, all other toners must be replaced in time with the replacement of the black toner. For this reason, conventionally, a method has been devised in which the consumption of black toner is suppressed and the toner consumption of each color is made uniform by the following method.

As a first method, a yellow toner image, a magenta toner image, and a cyan toner image are respectively formed by using toners of three colors (Y, M, and C) other than black, and the three color toner images are superimposed. In addition, there is a method of outputting a monochrome image. As a second method, during monochrome printing, the printing density is increased only at the outer edge of the character or symbol to be printed and the printing density at the inner side is reduced, so that the consumption of black toner is reduced. As a third method, there is a method in which the print density of a monochrome image is reduced as a whole to suppress the consumption of black toner. By these methods, the consumption of the black toner is suppressed, and the consumption of the toner of each color is made uniform.

[0006]

However, when a monochrome image is output by the above-described first method, the consumption of yellow toner, cyan toner, and magenta toner other than black is significantly increased, and the cost is increased. is there. Further, according to the first method, since a toner image of each color (Y, M, C) is superimposed on a transfer medium to output a monochrome image, image defects such as color misregistration are likely to occur, and the image quality is degraded. Problem.

In the above-described second and third methods, since the image density is reduced as a result, a complete image cannot be output, and there is a problem that image quality defects such as blurred characters occur. . In particular, when the resolution is increased, poor image quality such as blurred characters becomes noticeable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to form an image by which the developer of each color can be consumed substantially uniformly and the number of times of outputting a monochrome image can be increased without deteriorating the image quality. It is to provide a device.

[0009]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention forms a latent image for each color on an image carrier based on color-separated image signals. Developing means for supplying a yellow, magenta, cyan, and black developer respectively to the latent image for each color formed by the image forming means to develop the latent image for each color; and Transfer means for sequentially superimposing and transferring the developer image of each color developed by the means on the transfer medium, and fixing the developer image of each color transferred by the transfer means on the transfer medium And a detecting unit for detecting near-empty of the black developer supplied by the developing unit. When outputting a monochrome image, the black latent image based on the monochrome image signal is converted to the black latent image. Image carrier The latent image is developed by supplying a black developer to the latent image, and the developed black developer image is transferred and fixed on a transfer-receiving medium, and the near-empty state of the black developer is detected by the detection unit. From the point in time, a developer image of a color other than black is formed based on the monochrome image signal, and the developer images of the other colors are superimposed on the black developer image and output.

According to a second aspect of the present invention, there is provided an image forming apparatus, comprising: an image forming means for forming a latent image for each color based on a color-separated image signal on an image carrier; The latent image for each color formed by yellow, magenta,
Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for transferring the developer images for the respective colors developed by the developing means in such a manner that the developer images are sequentially superimposed on the transfer medium. Means, fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, and detecting means for detecting near empty of the black developer supplied by the developing means. When a monochrome image is output, a black latent image based on the monochrome image signal is formed on the image carrier, a black developer is supplied to the latent image, and the latent image is developed. The developer image is transferred onto the medium to be transferred and fixed. From the time when the above-described detection means detects the near empty of the black developer, the density of the black developer supplied to the black latent image is reduced. With, based on the monochrome image signal to form a developer image of another color other than black, a developer image of other colors output by superimposing the black developer image lower the density.

According to another aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member; charging means for applying a charge to the photosensitive member to charge the photosensitive member to a predetermined potential; and a photosensitive member charged by the charging means. Image forming means for irradiating a laser beam for each color emitted on the basis of a color-separated image signal to form an electrostatic latent image for each color on the photoreceptor; Developing means for supplying charged yellow, magenta, cyan, and black developers to the electrostatic latent image for each color formed by the forming means to develop the electrostatic latent image for each color; Transfer means for sequentially superimposing and transferring the developer image of each color developed by the developing means on the transfer medium; and transferring the developer image of each color transferred by the transfer means on the transfer medium. Fixing means for fixing, supplied by the developing means Detection means for detecting near-empty black developer, and when outputting a monochrome image, irradiates a black laser beam based on the monochrome image signal onto the photoconductor to form an electrostatic latent image. Formed and developed by supplying a black developer to this electrostatic latent image,
The developed black developer image is transferred and fixed on a transfer-receiving medium, and from the time when the near-empty state of the black developer is detected by the detection unit, the exposure intensity by the black laser light based on the monochrome image signal is reduced. In addition to lowering the density of the black developer image, a developer image of a color other than black is formed based on the monochrome image signal, and the developer images of these other colors are reduced in density. The output is superimposed on the developer image.

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: a photoreceptor; charging means for applying a charge to the photoreceptor to charge the photoreceptor to a predetermined potential; Image forming means for irradiating a laser beam for each color emitted on the basis of a color-separated image signal to form an electrostatic latent image for each color on the photoreceptor; Developing means for supplying charged yellow, magenta, cyan, and black developers to the electrostatic latent image for each color formed by the forming means to develop the electrostatic latent image for each color; Transfer means for sequentially superimposing and transferring the developer image of each color developed by the developing means on the transfer medium; and transferring the developer image of each color transferred by the transfer means on the transfer medium. Fixing means for fixing, supplied by the developing means Detection means for detecting near-empty black developer, and when outputting a monochrome image, irradiates a black laser beam based on the monochrome image signal onto the photoconductor to form an electrostatic latent image. Formed and developed by supplying a black developer to this electrostatic latent image,
The developed black developer image is transferred and fixed on a transfer-receiving medium, and from the time when the near-empty state of the black developer is detected by the detection unit, the exposure intensity by the black laser light based on the monochrome image signal is reduced. While lowering the density of the black developer image, the laser beam of a color other than black is made smaller than the beam diameter of the laser beam for black based on the monochrome image signal and irradiated onto the photoconductor. Forming electrostatic latent images of other colors, supplying a developer of another color to these electrostatic latent images to form a developer image,
The developer images of these other colors are output by being superimposed on the black developer image having the reduced density.

According to a fifth aspect of the present invention, there is provided an image forming apparatus, comprising: an image forming means for forming a latent image for each color based on a color-separated image signal on an image carrier; The latent image for each color formed by yellow, magenta,
Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for transferring the developer images for the respective colors developed by the developing means in such a manner that the developer images are sequentially superimposed on the transfer medium. Means, and a fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, when outputting a monochrome image, for black based on the monochrome image signal A latent image is formed on the image carrier, a black developer is supplied to the latent image for development, and a latent image of a color other than black is formed on the image carrier based on the monochrome image signal. Each of the latent images is formed, and a developer of another color is supplied to these latent images and developed, and the developed developer images of the respective colors are superimposed and output.

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: an image forming means for forming a latent image for each color based on a color-separated image signal on an image carrier; The latent image for each color formed by yellow, magenta,
Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for transferring the developer images for the respective colors developed by the developing means in such a manner that the developer images are sequentially superimposed on the transfer medium. Means, and a fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, when outputting a monochrome image, for black based on the monochrome image signal A latent image is formed on the image carrier, and a black developer is supplied to the latent image at a low density to form a black developer image having a low density, and a black developer image other than black based on the monochrome image signal is formed. The latent images of other colors are formed on the image carrier, and the latent images are developed by supplying the developers of other colors, respectively, and superimposed with the black developer image having the reduced density. output That.

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: a photosensitive member; charging means for applying a charge to the photosensitive member to charge the photosensitive member to a predetermined potential; and a photosensitive member charged by the charging means. Image forming means for irradiating a laser beam for each color emitted on the basis of a color-separated image signal to form an electrostatic latent image for each color on the photoreceptor; Developing means for supplying charged yellow, magenta, cyan, and black developers to the electrostatic latent image for each color formed by the forming means to develop the electrostatic latent image for each color; Transfer means for sequentially superimposing and transferring the developer image of each color developed by the developing means on the transfer medium; and transferring the developer image of each color transferred by the transfer means on the transfer medium. Fixing means for fixing, and a monochrome image When power is applied, a black laser beam based on the monochrome image signal is irradiated onto the photoreceptor at a reduced exposure intensity to form an electrostatic latent image, and a black developer is supplied to the electrostatic latent image. To form a black developer image having a reduced density, and irradiating the photoconductor with laser light of a color other than black on the basis of the monochrome image signal to thereby obtain a static image of another color. An electrostatic latent image is formed, each of these electrostatic latent images is developed by supplying a developer of another color, and the developer images of the other colors are superimposed on the black developer image having the reduced density. Output.

Further, in the image forming apparatus according to the present invention, there is provided an image forming apparatus comprising: a photosensitive member; charging means for applying a charge to the photosensitive member to charge the photosensitive member to a predetermined potential; and a photosensitive member charged by the charging means. Image forming means for irradiating a laser beam for each color emitted on the basis of a color-separated image signal to form an electrostatic latent image for each color on the photoreceptor; Developing means for supplying charged yellow, magenta, cyan, and black developers to the electrostatic latent image for each color formed by the forming means to develop the electrostatic latent image for each color; Transfer means for sequentially superimposing and transferring the developer image of each color developed by the developing means on the transfer medium; and transferring the developer image of each color transferred by the transfer means on the transfer medium. Fixing means for fixing, and a monochrome image When power is applied, a black laser beam based on the monochrome image signal is irradiated onto the photoreceptor at a reduced exposure intensity to form an electrostatic latent image, and a black developer is supplied to the electrostatic latent image. Forming a black developer image having a low density by developing the laser beam, and making the laser beam of a color other than black thinner than the beam diameter of the black laser beam based on the monochrome image signal to thereby form the photosensitive layer. Irradiation is performed on the body to form electrostatic latent images of other colors, respectively, and a developer of another color is supplied to these electrostatic latent images for development. The output is superimposed on the lowered black developer image.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a color copying machine 1 (hereinafter, referred to as an image forming apparatus) according to the present invention.
FIG. 2 is a perspective view of the copying machine 1 as viewed obliquely from the rear left side. FIG. 2 is a perspective view of the copying machine 1 viewed obliquely from the rear left side. First, the overall configuration of the copying machine 1 will be described with reference to FIGS.

As shown in FIG. 1, at the top of the copying machine 1,
A document table 2 on which a document is placed is provided. A document holder 3 for preventing the document from moving is provided on the document table 2 so as to be openable and closable in the direction of arrow a.

An operator panel 4 for setting and executing various instructions to the copying machine 1, such as a copy start switch, is provided at the upper front side of the copying machine 1. At the lower portion of the copying machine 1, paper cassettes 5a and 5b for mounting recording paper as a transfer medium are provided so as to be drawn out in the directions of arrows b and c with respect to the copying machine 1.

On the right side of the copying machine 1, there are provided an access cover 6 for jam clearance and a paper guide 7 for manual paper feeding which can be stored in the direction of arrow d with respect to the copying machine 1. .

As shown in FIG. 2, on the left side of the copying machine 1, a paper discharge port 8 for discharging the recording paper on which the image formation is completed, and a paper discharge tray for receiving the discharged recording paper. 9 are provided. The paper discharge tray 9 is detachably attached to the copying machine 1.

On the back of the copier 1, the copier 1
Power cord 10 for supplying power to the computer, I / F connector 1 for connecting to a computer device such as a personal computer
1. An I / F connector 12 for connecting to a facsimile is provided.

FIG. 3 is a sectional view showing the internal structure of the copying machine 1. Here, a schematic configuration of the entire copying machine 1 will be described first, and a detailed configuration will be described later.

The copying machine 1 can be broadly classified into: 1) a document reading unit 20 for digitally reading an image held in a document to be copied and converting the image into an image signal 2) an image forming unit using an electrophotographic method 3) It can be classified into a paper feeder 80 including paper cassettes 5a and 5b and a manual paper feeder (described later).

An original reading section 20 includes an illumination lamp 2 for illuminating an original (not shown) placed on the original placing table 2.
1. The light reflected from the original is reflected by a reflection mirror 22a, 2
2b, 22c, light receiving element 24 using imaging lens 23, etc.
25, a light receiving element 24 such as a CCD for converting light from an original into an electric signal, and color-separating the electric signal obtained by the photoelectric conversion into an image for each color of yellow, magenta, cyan, and black. It has an image processing device 26 for creating a signal.

The image forming section 30 is an application of a known electrophotographic system, and is an exposure device 40 (image forming means) for exposing a photosensitive drum provided for each color (Y, M, C, B). An image forming mechanism 50 including a photosensitive drum for each color;
Transfer mechanism 60 (transfer unit), fixing device 70 (fixing unit)
And so on.

The details of the image forming section 30 will be described below. The transfer mechanism 60 has an endless belt-shaped conveyor belt 61 that conveys recording paper. On the upper surface side of the conveyor belt 61, an image forming unit that forms images of yellow, magenta, cyan, and black from the right, respectively. Unit 50
Y, 50M, 50C, and 50B are arranged at equal intervals.

Further, above these, an exposure apparatus 40
Is provided. The exposure device 40 has laser light sources 42Y, 42M, 42C, and 42B that are driven according to image signals for each color created by the image processing device 26. Each of the laser light sources 42Y, 42M, 42C, and 42B emits laser light 41Y, 41M, 41M according to the color-separated image signal.
C and 41B are emitted, and each image forming unit 50
The electrostatic latent images are formed on the photosensitive drums 51Y, 51M, 51C, 51B provided in Y, 50M, 50C, 50B.

The transfer mechanism 60 includes a transfer device 62.
Y, 62M, 62C, and 62B are the respective photosensitive drums 51Y,
It is provided facing 51M, 51C, 51B. The drive roller 63 is rotated in a direction indicated by an arrow by a motor (not shown) so that the transport belt 61 runs at a predetermined speed in a direction indicated by an arrow. A predetermined tension is applied to the driven roller 64 in a direction away from the driving roller 63 by a pressing mechanism (not shown).
1 is not sagging.

On the conveyor belt 61, there are provided a paper feed guide device 65 for feeding the recording paper onto the conveyor belt 61 so as not to shift, and a cleaning device 66 for cleaning the surface of the conveyor belt 61. I have.

Each image forming unit 50Y, 50M, 50
C and 50B have the same configuration, and form an image corresponding to each color by a known electrophotographic process.

As shown in detail in FIG.
1Y, 51M, 51C, and 51B, the charging devices 52Y, 52M, 52C, and 52B
(Charging means), developing devices 53Y, 53M, 53C, 53
B (developing means), transfer devices 62Y, 62M, 62C, 6
2B (see FIG. 3), cleaning devices 54Y and 54M,
54C, 54B, and static eliminators 55Y, 55M, 55
C, 55B, respectively, and a laser beam 41 emitted from the exposure device 40 according to an image signal separated for each color.
Color images corresponding to Y, 41M, 41C and 41B are formed.

The developing device 53 of each image forming unit
Y, 53M, 53C, and 53B are toner hoppers 531Y, 531M, and 531 containing toners of the respective colors.
C, 531B, and near-empty sensors 532Y, 532M, 532C, 532B (detection means) for detecting near-empty toner are provided in each toner hopper. The developing devices 53Y, 53M, 53C, and 53B of each unit can adjust the toner density by changing the amount of toner supplied to the surface of the photosensitive drum.

The fixing device 70 comprises two upper and lower heating rollers 71a, 71b, etc., is pressurized at a predetermined temperature and pressure, and is transferred onto the recording paper by passing the recording paper between the rollers. The melted toner is melted and fixed on the recording paper.

Next, the paper feeding / conveying section 80 will be described.
Below the transfer mechanism 60, sheet cassettes 5a and 5b for stacking and storing a plurality of sheets of recording paper, and recording sheets taken out of each of the sheet cassettes 5a and 5b are stored in the image forming unit 30.
Is provided with a paper feeding unit 82 for feeding and transporting the paper.

The paper feed unit 82 has a paper feed roller 83 for picking up recording paper from each of the paper cassettes 5a and 5b.
a and 83b, a pair of transport rollers 84a and 84b for guiding the recording paper onto the transport belt 61, and a pair of aligning rollers 85 for adjusting the timing of feeding the recording paper.

On the upstream side of the aligning roller 85, there is provided a manual paper feeder 86 for guiding the recording paper manually fed via the paper guide 7 (see FIG. 1) onto the transport belt 61. ing. When the recording paper is placed on the upper surface of the paper guide 7 with the paper guide 7 opened, the pickup roller 87
Is rotated, and the leading end of the recording paper is aligned with the aligning roller pair 85.
It is to be sent to.

Next, the operation of the copying machine 1 configured as described above will be described. First, when a signal for performing copying is input via the operator panel 4, the document reading unit 20 starts operating, the illumination lamp 21 is turned on, and the optical system 25 is moved. The light reflected from the document passes through the optical system 25, is taken into the light receiving element 24, is converted into an electric signal, and is sent to the image processing device 26.

The image signal sent in this way is decomposed by the image processing device 26 into image signals for respective colors of yellow, magenta, cyan, and black, and sent to a writing image processing device (not shown).

A signal from the writing image processing control device is sent to the exposure device 40, and at the same time, the photosensitive drums 51Y and 51
M, 51C, 51B, the conveyance belt 61, the fixing device 70, etc. start to rotate.

The recording paper stored in the paper cassette 5a or 5b is picked up by paper feed rollers 83a and 83b or a pick-up roller 87 of a manual paper feed unit, conveyed by conveying roller pairs 84a and 84b, and aligned by an aligning roller. The timing is adjusted by the pair 85, and the sheet is sent onto the transport belt 61.

On the other hand, the image signal from the image writing control device is sent to the exposure device 40, and the laser light 4 corresponding to each color is transmitted.
Emitted as 1Y, 41M, 41C, 41B. At this time, the laser beams 41Y, 41M, 41C, 41B emitted from the respective laser light sources 42Y, 42M, 42C, 42B.
Is emitted with its beam diameter and exposure intensity adjusted to desired values.

For example, with respect to the yellow signal, the exposure device 40 controls the laser light source 4 according to the image signal for yellow.
2Y is energized to emit a laser beam 41Y. The photosensitive drum 51Y uniformly charged by the charging device 52Y is exposed to the laser light 41Y to form an electrostatic latent image corresponding to a yellow image signal.

The photosensitive drum 51Y is rotating in the direction of arrow e (see FIG. 4), and the electrostatic latent image on the photosensitive drum 51Y is developed by the developing device 53Y to form a yellow toner image. At this time, the density of the yellow toner supplied to the surface of the photosensitive drum 51Y by the developing device 53Y is adjusted to a predetermined value.

This yellow toner image is transferred to the transfer device 62Y
Is transferred to the recording paper on the conveyor belt 61. Thereafter, the yellow toner remaining on the surface of the photosensitive drum 51Y without being transferred is cleaned by the cleaning device 54Y.

Further, the residual potential on the photosensitive drum 51Y is reduced uniformly by the illumination of the charge removing device 55Y, so that the apparatus is ready for the next electrophotographic process. For magenta, cyan, and black, corresponding image signals are sent to the exposure device 40, and a laser beam 41
M, 41C, and 41B are ejected, and each image forming unit forms an image through the same process as the yellow image forming unit 50Y.

In the above-described image formation, while the recording paper is conveyed by the conveyance belt 61, the images of each color are successively transferred, and thereafter are conveyed by separation by the curvature of the driving roller 63 or forced separation by separation claw (not shown). Belt 61
From the fixing device 70.

The recording paper is subjected to image fixing by heat and pressure in the fixing device 70, and then is discharged through a paper discharge port 8 onto a paper discharge tray 9 provided outside the copying machine 1.

Next, a control operation for outputting a monochrome image on a predetermined number of recording sheets using the copying machine 1 of the present embodiment will be described. When outputting a monochrome image, the black laser light source 42B is output based on the monochrome image signal.
By operating only the black image forming unit 50B, a black toner image is formed on the photosensitive drum 51B, and the black toner image is transferred to a recording sheet, thereby outputting a monochrome image. When the near empty sensor 532B provided in the toner hopper 531B containing the black toner detects the near empty of the black toner, the mode is switched to the near empty mode, and the control of the present invention is performed.

That is, in the near empty mode, the laser light sources 42Y, 42Y
Laser beams 41Y, 41M, 41C, 41 having a predetermined beam diameter and exposure intensity via 42M, 42C, 42B
B are respectively emitted, and the toner images of each color formed on the photosensitive drum are transferred onto the recording paper in a superimposed manner, and a monochrome image is output. At this time, the toner density of each color is adjusted to a predetermined value by the developing devices 53Y, 53M, 53C and 53B of each image forming unit.

In this embodiment, the laser light sources 42Y, 42M, and 42C for yellow, magenta, and cyan are controlled so that the diameter of the laser beam of another color becomes smaller than the diameter of the laser beam 41Y for black. In addition, the exposure intensity by the black laser beam 41B is controlled so that the image density output from the black image forming unit 50B is reduced.

As described above, the consumption of the black toner can be reduced by lowering the black image density, and this reduction in density can be compensated for by superimposing a toner image of another color on the black toner image. It is possible to output a monochrome image with a high density for a long time. At this time, by reducing the diameters of the laser beams of other colors, the problem of color misregistration due to superposition can be reduced, and a high-quality image can be output.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, the exposure intensity of the laser beam 41B is adjusted to reduce the density of the black toner image. However, the density of the black toner image is adjusted by adjusting the supply amount of the black toner by the developing device 53B. You may do it.

In the above-described embodiment, the mode for outputting a monochrome image is switched when the black toner becomes nearly empty. However, the mode may be switched to the mode of the present invention before the near empty is detected. good.

[0055]

As described above, since the image forming apparatus of the present invention has the above-described configuration and operation, the developers of each color can be consumed substantially uniformly, without deteriorating the image quality. The number of times of outputting a monochrome image can be increased.

[Brief description of the drawings]

FIG. 1 is a front perspective view showing a copying machine according to an embodiment of the present invention.

FIG. 2 is a rear perspective view showing the copying machine shown in FIG. 1;

FIG. 3 is a sectional view showing the internal configuration of the copying machine of FIG. 1 in detail.

FIG. 4 is a schematic diagram showing a main part of the internal configuration of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Color copier, 2 ... Document stand, 3 ... Document holder, 4 ... Operator panel, 5a, 5b ... Paper cassette, 6 ... Access cover, 7 ... Paper guide, 8 ... Discharge port, 9 ... Discharge tray Reference Signs List 10 power supply cord 11 12 I / F connector 20 document reading section 21 illumination lamp 22a, 22b, 22c reflection mirror 23 imaging lens 24 light receiving element 25 optical system 26 image processing apparatus 30 image forming unit 40 exposure apparatus 41Y, 41M, 41C, 41B laser light, 42Y, 42M, 42C, 42B laser light source, 50Y, 50M, 50C, 50B image formation Means, 51Y, 51M, 51C, 51B: photoconductor drum, 52Y, 52M, 52C, 52B: charging device, 53Y, 53M, 53C, 53B: developing device, 4Y, 54M, 54C, 54B: Cleaning device, 55Y, 55M, 55C, 55B: Static elimination device, 60: Transfer means, 61: Conveying belt, 62Y, 62M, 62C, 62B: Transfer device, 63: Drive roller, 64: Driven roller, 65: paper feeding guide device, 66: cleaning device, 70: fixing device, 71a, 71b: heating roller, 80: paper feeding / conveying unit, 82: paper feeding unit, 83a, 83b: paper feeding roller, 84a, 84b: transport roller pair, 85: aligning roller pair, 86: manual paper feeder, 87: pickup roller.

Claims (8)

[Claims] 1. An image forming means for forming a latent image for each color on an image carrier based on a color-separated image signal, and a latent image for each color formed by the image forming means, wherein yellow, magenta, Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for superimposing and transferring the developer images for the respective colors, developed by the developing means, onto a transfer-receiving medium sequentially Means, fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, and detecting means for detecting near empty of the black developer supplied by the developing means. When outputting a monochrome image, a black latent image based on the monochrome image signal is formed on the image carrier,
A black developer is supplied to the latent image and developed, and the developed black developer image is transferred and fixed on a transfer-receiving medium.
From the point in time when the near-empty state of the black developer is detected by the detection means, a developer image of a color other than black is formed based on the monochrome image signal, and the developer images of the other colors are formed by the black developer An image forming apparatus characterized in that an image is output by being superimposed on an image. 2. An image forming means for forming a latent image of each color on an image carrier based on a color-separated image signal; and a yellow, magenta, Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for superimposing and transferring the developer images for the respective colors, developed by the developing means, onto a transfer-receiving medium sequentially Means, fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, and detecting means for detecting near empty of the black developer supplied by the developing means. When outputting a monochrome image, a black latent image based on the monochrome image signal is formed on the image carrier,
A black developer is supplied to the latent image and developed, and the developed black developer image is transferred and fixed on a transfer-receiving medium.
From the point in time when the near-empty state of the black developer is detected by the detection means, the density of the black developer supplied to the black latent image is reduced, and the development of other colors than black is performed based on the monochrome image signal. An image forming apparatus which forms a developer image and superimposes the other color developer image on the black developer image having the reduced density to output the resultant image. 3. A photoreceptor, charging means for applying a charge to the photoreceptor to charge the photoreceptor to a predetermined potential, and charging the photoreceptor charged by the charging means based on a color-separated image signal. Image forming means for irradiating a laser beam for each color emitted respectively to form an electrostatic latent image for each color on the photoreceptor; and an electrostatic latent image for each color formed by the image forming means. Developing means for supplying charged yellow, magenta, cyan and black developers, respectively, to develop the electrostatic latent images of the respective colors; and developing the developer images of the respective colors developed by the developing means Transfer means for sequentially superimposing and transferring the image on the transfer medium, fixing means for fixing the developer image of each color transferred by the transfer means on the transfer medium, and supply by the developing means Detecting near empty of black developer When outputting a monochrome image, irradiates a black laser beam based on the monochrome image signal onto the photoreceptor to form an electrostatic latent image. The developer is supplied and developed, and the developed black developer image is transferred and fixed on a transfer-receiving medium. Based on the monochrome image signal, the detection means detects the near empty of the black developer. The exposure intensity of the black laser beam is reduced to lower the density of the black developer image, and a developer image of a color other than black is formed based on the monochrome image signal, and the development of these other colors is performed. An image forming apparatus which outputs a developer image by superimposing the developer image on the black developer image having the reduced density. 4. A photoconductor, charging means for applying a charge to the photoconductor and charging the photoconductor to a predetermined potential, and a photoreceptor charged by the charging means, based on a color-separated image signal. Image forming means for irradiating a laser beam for each color emitted respectively to form an electrostatic latent image for each color on the photoreceptor; and an electrostatic latent image for each color formed by the image forming means. Developing means for supplying charged yellow, magenta, cyan, and black developers, respectively, to develop the electrostatic latent images of the respective colors; and developing the developer images of the respective colors developed by the developing means. Transfer means for sequentially superimposing and transferring the image on the transfer medium, fixing means for fixing the developer image of each color transferred by the transfer means on the transfer medium, and supply by the developing means Detecting near empty of black developer When outputting a monochrome image, irradiates a black laser beam based on the monochrome image signal onto the photoconductor to form an electrostatic latent image, and the black image is formed on the electrostatic latent image. The developer is supplied and developed, and the developed black developer image is transferred and fixed on a transfer-receiving medium, and based on the monochrome image signal from the time when the detection means detects the near empty of the black developer. While lowering the exposure intensity of the black laser beam to lower the density of the black developer image, the laser beam of a color other than black is made thinner than the beam diameter of the black laser beam based on the monochrome image signal. And irradiates the photoreceptor to form an electrostatic latent image of another color, supplies a developer of another color to the electrostatic latent image to form a developer image, and forms a developer image of the other color. The developer image is An image forming apparatus, which outputs a superimposed image with a black developer image having a reduced degree. 5. An image forming means for forming a latent image for each color on an image carrier based on a color-separated image signal; and a yellow, magenta, Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for superimposing and transferring the developer images for the respective colors, developed by the developing means, onto a transfer-receiving medium sequentially Means, and fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, when outputting a monochrome image, a black image based on the monochrome image signal. Forming a latent image on the image carrier,
A black developer is supplied to the latent image to be developed, and latent images of colors other than black are formed on the image carrier based on the monochrome image signal, respectively. An image forming apparatus which supplies and develops the developer, and superimposes and outputs the developed developer images of the respective colors. 6. An image forming means for forming, on an image carrier, a latent image for each color based on a color-separated image signal; and a yellow, magenta, Developing means for supplying cyan and black developers, respectively, to develop the latent images for the respective colors; and transfer for superimposing and transferring the developer images for the respective colors, developed by the developing means, onto a transfer-receiving medium sequentially Means, and fixing means for fixing the developer image of each color transferred by the transfer means on the transfer-receiving medium, when outputting a monochrome image, a black image based on the monochrome image signal. Forming a latent image on the image carrier,
By supplying a black developer with a low density to the latent image, a black developer image having a low density is formed, and a latent image of a color other than black based on the monochrome image signal is formed on the image carrier. Each of these latent images is developed by supplying a developer of another color to these latent images,
An image forming apparatus, which outputs a superimposed image with a black developer image having a reduced density. 7. A photoreceptor, a charging unit for applying a charge to the photoreceptor to charge the photoreceptor to a predetermined potential, and a photoreceptor charged by the charging unit based on a color-separated image signal. Image forming means for irradiating a laser beam for each color emitted respectively to form an electrostatic latent image for each color on the photoreceptor; and an electrostatic latent image for each color formed by the image forming means. Developing means for supplying charged yellow, magenta, cyan, and black developers, respectively, to develop the electrostatic latent images of the respective colors; and developing the developer images of the respective colors developed by the developing means. A transfer unit for sequentially superimposing and transferring the image on the transfer medium; and a fixing unit for fixing the developer image of each color transferred by the transfer unit on the transfer medium, and outputs a monochrome image. Sometimes, based on this monochrome image signal, A laser beam for a rack is irradiated onto the photoreceptor at a reduced exposure intensity to form an electrostatic latent image, and a black developer is supplied to the electrostatic latent image to develop the latent image. A developer image is formed, and a laser beam of a color other than black is irradiated on the photosensitive member based on the monochrome image signal to form an electrostatic latent image of another color. An image forming apparatus for supplying and developing a developer of another color to an electro-latent image, and superimposing the developer image of the other color on the black developer image having the reduced density, and outputting the resultant image. . 8. A photoreceptor, charging means for applying a charge to the photoreceptor to charge the photoreceptor to a predetermined potential, and a photoreceptor charged by the charging means, based on a color-separated image signal. Image forming means for irradiating a laser beam for each color emitted respectively to form an electrostatic latent image for each color on the photoreceptor; and an electrostatic latent image for each color formed by the image forming means. Developing means for supplying charged yellow, magenta, cyan, and black developers, respectively, to develop the electrostatic latent images of the respective colors; and developing the developer images of the respective colors developed by the developing means. A transfer unit for sequentially superimposing and transferring the image on the transfer medium; and a fixing unit for fixing the developer image of each color transferred by the transfer unit on the transfer medium, and outputs a monochrome image. Sometimes, based on this monochrome image signal, A laser beam for a rack is irradiated onto the photoreceptor at a reduced exposure intensity to form an electrostatic latent image, and a black developer is supplied to the electrostatic latent image to develop the latent image. A developer image is formed, and based on the monochrome image signal, a laser beam of a color other than black is made narrower than the beam diameter of the laser beam for black, and is irradiated on the photoreceptor to thereby obtain a static color of another color. An electrostatic latent image is formed, and a developer of another color is supplied to these electrostatic latent images for development. The developer images of the other colors are superimposed on the black developer image having the reduced density and output. An image forming apparatus.