JP2987927B2 - Two-color image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color image forming apparatus using two beams, such as a digital copying machine and a laser beam printer, and more particularly to a two-color image forming apparatus when a semiconductor laser or a developing device fails. The present invention relates to a technology for printing color image data.

[Conventional technology]

For example, a two-color image forming apparatus modulates two laser beams in accordance with image data, irradiates the laser beams to different positions in the circumferential direction of the photoconductor, repeats charging and development with each position interposed therebetween, and performs one time of the photoconductor. A two-color image is formed by rotation. In this type of image forming apparatus, a developing device containing a color toner other than black, such as red and blue, is usually disposed upstream of the developing device containing the black toner in the rotation direction of the photoconductor. This is because when the black toner is mixed with the color toner, the color stain becomes conspicuous. In addition, in this type of image forming apparatus, in order to align a plurality of colors of images formed on the photoconductor, a laser beam irradiated on the downstream side is output in consideration of a rotation time of the photoconductor to each irradiation position. Output of the image data is delayed as compared with the upstream side.

In such an image forming apparatus, if a laser beam irradiating device as an exposing means for exposing a photoreceptor or a developing device for attaching toner to a latent image becomes defective, it becomes impossible to form an image. The caller had to repair the defective irradiation device or developing device.

[Problems to be solved by the invention]

However, when calling a specialized technician, it is possible to perform image formation using the failed irradiation device or developing device from when the technician is called until the technician arrives and completes the repair. It was impossible, and the image forming apparatus had to be stopped. Therefore, when the above-mentioned inconvenience occurs frequently, there has been a problem that the efficiency of image formation including two simultaneous colors is significantly reduced.

As a prior art for solving this, Japanese Patent Publication No. 61-6158
There is an invention disclosed in Japanese Patent Application Publication No. 5 (1994). When image formation is impossible, an image is formed by using a normal irradiation device and developing device of another color, and expresses a two-color image in mono color. As a result, it is possible to form an image as soon as possible, and it is possible to prevent a decrease in the efficiency of image formation.

However, in the prior art disclosed in the above publication, only two colors are expressed in a mono color, so that there is a problem that the two colors cannot be identified and visibility is low.

The present invention has been made in view of such circumstances, and when forming a two-color image, when one of the color exposure means or the developing device becomes defective, one color is expressed by changing the density of the other color. By doing so, even if one of the color exposure means or the developing device becomes defective, it is possible to form an image immediately without stopping the device, and it is possible to improve the efficiency of image formation. Another object of the present invention is to provide a two-color image forming apparatus capable of distinguishing two colors by a density difference and obtaining an image with high visibility.

[Means for Solving the Problems] A two-color image forming apparatus according to the present invention creates a latent image on a photoreceptor based on first image data, and develops the latent image with a first color. Detecting defects of the image forming means, the second image forming means for forming a latent image on the photosensitive member based on the second image data, and developing the latent image with a second color, and the first image forming means Detecting means, and correcting means for correcting the first or second image data so as to cause a difference in visual image density when a defect of the first image forming means is detected; and corrected image data and uncorrected image data. Control means for supplying the image data together to the second image forming means and forming an image in the second color.

[Action]

In the present invention, when the failure detecting means detects a failure in the exposure means or when the failure detecting means detects a failure in the developing means, one of the colors corresponding to the exposure means or the failure detection means in which the failure or the failure has been detected. The density of the image data is changed to, for example, half the density, the changed image data of one color and the image data of the other color are combined, and the combined image data is used to expose the exposure means or Using the developing means, an image in which a monochromatic image is shaded is formed. Therefore, even if at least one of the two exposure means and the development means becomes faulty or defective, the two-color image can be expressed as a monochromatic gray-scale image in an emergency, and the two colors can be identified.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic side sectional view showing the configuration of a simultaneous two-color copying machine which is a simultaneous two-color image forming apparatus according to the present invention. The copier of the present invention develops an image by reversal development, a scanning system 10 for scanning a document, an image signal processing unit 20 for processing an image signal sent from the scanning system, based on the processed image signal, A print processing unit 40 that outputs image data to two first semiconductor lasers 61 and a second semiconductor laser 62, which will be described later, and an optical system 60 that irradiates the photosensitive drum 71 with two modulated lights based on the image data, and is formed by irradiation. Develops the latent image
The image forming system 70 includes an image forming system 70 for transferring and fixing a sheet on a transfer sheet.

The scanning system 10 exposes and scans a document placed on a document table glass 18, and converts reflected light from the document to electric signals by photoelectric conversion elements 16, 17 using, for example, a CCD array.
The photoelectric conversion elements 16 and 17 convert an image of a specific color such as red and an image of another color such as black into electric signals, respectively.

The scanning system 10 is controlled by the scan motor M2 to hold the platen glass 18
Is attached to the scanner 19 which moves in parallel with. The scanning system
10 is an exposure lamp 11 for irradiating the original and a reflecting mirror 12 for changing the direction of the reflected light from the original, two mirrors 13a and 13b for changing the optical path from the reflecting mirror 12, and a lens 14 for condensing the reflected light, A half mirror 15 that determines a color based on the wavelength of the reflected light and reflects or transmits the reflected light to guide the reflected light to the two photoelectric conversion elements 16 and 17, and a photoelectric conversion element 16 that generates an electric signal according to the received light , 17. When the scanning system 10 moves leftward as indicated by an arrow,
The original is exposed and scanned.

The image signal processing unit 20 receives image signals output from the two photoelectric conversion elements 16 and 17 and performs
In addition to normal image processing such as scaling, dither processing, etc., a specific color (red) and other colors are identified and sent to the print processing unit 40.
It is output as image data with color information of the color and density information of 8 bits (256 gradations).

The print processing unit 40 converts the received image data with color information and density information into two first semiconductor lasers 6.
1, while being distributed to the second semiconductor laser 62,
Photoconductor drum 71 of semiconductor laser 61 and second semiconductor laser 62
The image data to be given to the second semiconductor laser 62 is delayed according to the difference in the exposure position.

The optical system 60 includes a first semiconductor laser 61 and a second semiconductor laser 62.
An electrostatic latent image corresponding to a specific color of red and a black image of other colors is formed on the photosensitive drum 71 by the laser light from the photoconductor drum 71.

FIG. 2 is an enlarged perspective view showing a part of the optical system 60. The optical system 60 includes a first semiconductor laser 61 for emitting a laser beam having a wavelength of 750 nm, a second semiconductor laser 62 for emitting a laser beam having a wavelength of 810 nm, a first semiconductor laser 61 and a second semiconductor laser 62.
Using a collimator lens 61a, 62a that converts the laser light emitted from the lens into parallel light, and a dichroic mirror that transmits or reflects the two laser lights according to their wavelengths, thereby combining the two laser lights. 63, a polygon mirror 65 for deflecting the combined laser light in the main scanning direction, and a condenser lens 69 for condensing the deflected laser light,
A mirror 67a that reflects the condensed laser light, and a separation mirror 68 that has the same characteristics as the combining mirror 63 and reflects or transmits the combined laser light and separates the combined laser light into two laser lights,
Reflection mirrors 67b and 67 that reflect the separated laser beams
and c.

The combined laser light reflected by the polygon mirror 65 is directly incident on the reflection mirror 25, and the reflected light is separated by a dichroic mirror having the same characteristics as the combined mirror 63.
It is incident on 22. The incident laser light is separated or transmitted, and the transmitted light, that is, the laser light from the second semiconductor laser 62 enters the beam detector 21 and is detected. The beam detector 21 determines the timing of starting modulation of each laser beam by image data at the timing of receiving the laser beam. The separation mirror 22 can move forward and backward with respect to the optical axis of the laser light. That is, the separation mirror 22 is supported by a support shaft 26 provided on one side thereof.
A lever that can rotate around and is fitted to the support shaft 26
By rotating the tip of 23 by the advance and retreat of the solenoid 24, the separation mirror 22 is advanced and retracted with respect to the optical axis. This retreat operation is performed to determine the modulation timing of the laser light by the laser light from the first semiconductor laser 61 when the second semiconductor laser 62 is in a trouble state.

The first semiconductor laser 61 and the second semiconductor laser 62 independently generate laser light modulated with image data output from the print processing unit 40 in correspondence with red and black images, respectively. Synthesized by 63. The direction of the synthesized laser beam is changed by a polygon mirror 65 rotated and driven by a polygon motor 64 so as to scan in the main scanning direction (line direction) on the photosensitive drum 71. The deflected laser light is condensed by a condensing lens 69 so as to form an image on the photosensitive drum 71, the direction is changed by a mirror 67a, and further separated by a separation mirror 68 into two laser lights. The light is reflected by mirrors 67b and 67c provided therein, reaches respective exposure positions on the photosensitive drum 71, and exposes the photosensitive drum 71.

The image forming system 70 develops the electrostatic latent image formed on the photosensitive drum 71 and transfers and fixes it on paper.
Is composed of a development / transfer system 70A, a transport system 70B, and a fixing system 70C.

The development / transfer system 70A has a photosensitive drum 71 that is driven to rotate in the direction of the arrow that is a counterclockwise direction, and a grid that uniformly charges the surface of the photosensitive drum 71 that is disposed around the photosensitive drum 71 in order from the upstream in the rotation direction. grid 72 to charge the first electric charger 72a of the scorotron, the first developing unit 73a for storing red toner, the photosensitive drum 71 again in preparation for the second exposure having 72a ₁
a scorotron-type second charging charger 72b having b ₁
A second developing unit 73b for storing the black toner, a transfer charger 74 for transferring the developed toner image onto the paper, a separation charger 75 for separating the paper from the photosensitive drum 71, and a cleaning for removing the toner remaining on the photosensitive body surface And peripheral devices such as the unit 76.

Toner is supplied to the first and second developing units 73a and 73b by a toner bottle (not shown). The first and second toner empty sensors 27a and 27a detect the empty state of the toner supplied from the toner bottle. 27b is provided. The first and second toner empty sensors 27a and 27b use reflection type photodetectors, and detect the presence or absence of toner supplied from the toner bottle. In this embodiment, the malfunction of the developing units 73a and 73b is detected.

In FIG. 1, a transport system 70B is provided with a paper supply and fixing system 7.
The cassette 80a, 80b for storing sheets, a sheet guide 81 for guiding sheets taken out of the cassettes 80a, 80b, and a transfer charger 74 for the guided sheets and the photosensitive drum 71. It comprises a timing roller 82 for adjusting the timing of transport to the transfer section between them, a transport belt 83 for transporting the sheet on which the toner image has been transferred to the fixing system 70C, and the like.

The fixing system 70C is for thermocompression-bonding the toner image transferred onto the sheet to the sheet between a pair of fixing rollers 84, 84, and the sheet on which the toner is fixed is discharged to the outside of the copying machine by a discharge roller 85. .

A print key 101 for starting a copying operation, a simultaneous two-color selection key 102 for selecting a simultaneous two-color mode, and a color selection key 103 for selecting a black or red single-color mode are provided on the upper surface of the copying machine. An operation key is provided, and a display device using an LED (not shown) for displaying a selection result is provided.

FIG. 3 is a block diagram showing a configuration of a main part of a control system of the copying machine according to the present invention. The control system 200 uses a microcomputer (hereinafter, CPU) 201. Print key for CPU201
Various keys such as 101, a simultaneous two-color selection key 102, a switch, and various signals are input and analyzed, and display and load signals are output according to the various signals. Further, input and output data with the image signal processing unit 20 and the print processing unit 40,
Perform those controls.

Further, the CPU 201 receives the detection signal from the beam detector 21, and when detecting the signal, instructs the print processing unit 40 to process the next one line of data. On the other hand, the print processing unit 40 receives a detection signal from the beam detector 21, and upon detecting the detection signal, outputs a modulation signal based on image data at a predetermined timing. Further, the CPU 201 receives a toner empty signal of the first and second toner empty detectors 27a and 27b or a laser trouble signal of the first and second semiconductor lasers 61 and 62, which will be described later, and prints the print processing unit in accordance with predetermined conditions. A monochromatic density conversion signal is output to 40. The CPU 201 also operates the simultaneous two-color selection key 102, the color selection key 103, and the first semiconductor laser 61 and the second semiconductor laser 61 in response to the first and second laser trouble signals.
First and second laser use permission signals for permitting the use of the respective lasers 62 are output to the print processing unit 40.

FIG. 4 is a block diagram showing the configuration of the print processing unit 40. Image data having 8-bit density information provided from the image signal processing unit 20 is provided to a color separation unit 1001 that switches according to color information. For example, when the color information is “1”, the color information is shown, and when the color information is “0”, black is shown. Therefore, when the color information is “0”, the color separation unit 1001 is switched to the direction indicated by the solid line. The switched image data is converted to a color density
1015 or a black density conversion unit 1016 and one input terminal of the color OR circuit 1019 or the black OR circuit 1020. The color / black density converters 1015 and 1016 use, for example, a ROM.
Converts the input 8-bit density information into, for example, half-density information. Half-density information is stored in an address accessed by the 8-bit density information. In the case where the density is converted into half as in the present embodiment, the density converters 1015 and 1016 may be configured by a register which shifts the input density information right by one bit and outputs it. The converted image data output from the color / black density converters 1015 and 1016 are supplied to the other input terminals of the black / color OR circuits 1020 and 1019 via switch circuits 1017 and 1018, respectively. The color / black OR circuits 1019 and 1020 combine two image data by a logical OR of the converted image data of one color and the image data of the other color before conversion.
This makes it possible to express two image data of two colors at the same time in a monochromatic shade. In addition, switch circuits 1017 and 1
Reference numeral 018 turns on / off according to the monochromatic density conversion signal output from the CPU 201, turns on when the monochromatic density conversion signal is "1", and turns off when it is "0". The outputs of the color and black OR circuits 1019 and 1020 are given to a color buffer unit 1002 and a black buffer unit 1003, respectively. The color buffer unit 1002 is used for synchronizing each line of color image data and adjusting the start timing of main scanning, and the image data output from the color buffer unit 1002 outputs a modulation signal corresponding to the image data. Given to 1007. Then, the first semiconductor laser 61 is turned on and off by the modulation signal. Further, the black buffer unit 1003 performs the same processing on the black image data, and the image data output therefrom is transferred to the delay memory 1005 and the selector 10.
Given to 06. The output of the delay memory 1005 is also given to the selector 1006, and selects the image data from the black buffer unit 1003 or the image data from the delay memory 1005. The delay memory 1005 corrects a shift due to the difference between the exposure positions of the two laser beams, and delays the black image data by the time during which the photosensitive drum 71 rotates between the two exposure positions in the simultaneous two-color mode. The selector 1006 selects image data from the black buffer unit 1003 when the first semiconductor laser 61 is unusable, that is, when the first laser use permission signal is “0”, and conversely, when the first laser use permission signal is “1”. When the delay memory 1005
Select the output of This is because the first copy in the black monochrome mode is performed at high speed. The selected image data is similarly transmitted to the second semiconductor laser via the black laser controller 1008.
Given to 62.

Further, the first semiconductor laser 61 and the second semiconductor laser 62 each include a first current detector 1011 for detecting the output current of a photodiode (not shown) which outputs a current corresponding to the amount of light emitted from the photodiode. A second current detector 1012 is provided. The detection result of the output current of the first semiconductor laser 61 is given from the first current detector 1011 to the color laser control unit 1007, and the detection result of the output current of the second semiconductor laser 62 is
The current is supplied from the current detector 1012 to the black laser control unit 1008. When the detection result exceeds a predetermined value in the color laser control unit 1007 and the black laser control unit 1008,
The first and second laser trouble signals indicating that the first semiconductor laser 61 and the second semiconductor laser 62 have failed are supplied to the CPU 201.

The color and black laser control units 1007 and 1008 have the CPU 201
First and second laser use permission signals from
They control its operation.

Next, the operation of the control system 200 will be described. Figure 5 shows the CPU
4 is a flowchart showing the contents of a main routine of 201.

Before describing the flowchart, the terms on-edge and off-edge used therein will be defined. The on-edge is defined as an on-edge when a state of a switch, a sensor, a signal, or the like changes from an off state to an on state. The off edge is defined as an off edge when a state of a switch, a sensor, a signal, or the like changes from an on state to an off state.

First, when the power is turned on, in step # 1, various timers, flags, counters, and the like used in the subsequent subroutines are set to the initial state, and then an internal timer value serving as a reference time for the following processing is set. To start the internal timer (step # 2). An input process for inputting various input switches and sensors (step # 3), and a development / transfer system process for developing the electrostatic latent image formed on the photosensitive drum 71 and transferring the image onto paper (step # 4) ), Paper feed system processing for transporting the paper to the transfer unit (step # 5), checking the states of the first semiconductor laser 61, the second semiconductor laser 62, and the developing units 73a and 73b, selecting printable conditions, and controlling printing. (Step # 6), and other processes such as receiving data from the scanning system 10 (Step # 7), and wait for the end of the internal timer (Step # 8).
Return to 2.

FIG. 6 is a flow chart showing the processing contents of the input processing subroutine of step # 3. In step # 301, the on-edge of the print key 101 is determined, and the print key 101 is determined.
Is on-edge, a print operation mode flag is set (step # 302). If the print key 101 is not on-edge, the print operation mode flag is checked (step # 303), and the flag is set.
If the copying operation is being performed, the process jumps to step # 315 so that the selection input of the developing units 73a and 73b is not accepted. If the print operation is not being performed, the on-edge of the color selection key 103 is determined (step # 304). If the color selection key 103 is on-edge, it is determined whether or not the black copy LED data is "0". Is "0", that is, when color copy is currently selected, the black copy LED data is set to "1" and the color copy LED data is reset to "0" (step # 306). If the black copy LED data is "1", the black copy LED data is reset to "0" and the color copy LED data is set to "1" (step # 307). Next, in step # 308, the on-edge of the simultaneous two-color selection key 102 is determined. If the on-edge is selected, the simultaneous two-color LED data is inverted. If the simultaneous two-color mode is already selected, the single-color mode is set. If it is selected, the simultaneous two-color mode is set (Step # 30)
9). If the color selection key 103 is not on-edge in step # 304, the process proceeds to step # 308, and the process proceeds to step # 3.
If the simultaneous two-color selection key 102 is not on-edge at 08, step # 309 is skipped.

Next, in step # 310, it is determined whether or not the simultaneous two-color LED data is "0", that is, whether or not the single color mode is set. That is, it is determined whether black has been selected in the monochrome mode (step # 311). When black is selected (step # 311 YES), the first laser use permission signal is set to "0".
Then, the second laser use permission signal is set to "1", the use of the black second developer 73b is permitted, and the use of the first color developer 73a is disabled (step # 312). As a result, the black image data is sent to the black laser control unit 1008 without passing through the delay memory 1005, and the first copy can be performed without delay. When the color is selected in step # 311 (step # 311 NO), the first and second laser use permission signals are set to "1" and "0", and the second developing unit 73b is disabled. The use of the one developing unit 73a is permitted (step # 313). If it is determined in step # 310 that the mode is not the single color mode but the simultaneous two-color mode (step # 310 NO), the first and second laser use permission signals are both set to "1", and the first and second developing devices 73a, 73a 73b
Are allowed to be used together, black image data is output via the delay memory 1005, and the black image and the color image are aligned. At this time, both the black copy LED data and the color copy LED data are set to "1" to indicate that the simultaneous two-color mode has been set. When these processes are completed, the end of the copy operation is checked in step # 315. If the copy operation is not completed, other input processes are performed in step # 317, and the process returns to the main routine. Also,
When the copy operation is completed, the print operation mode is reset (step # 316), and the process proceeds to step # 317.

FIG. 7 is a flowchart showing the processing contents of the print processing subroutine of step # 6. At step # 601, the on-edge of the print key 101 is determined, and if it is on-edge (step # 401 YES), the laser emission check mode is set (step # 602). Next, it is determined whether or not the laser emission check mode is set (step # 603). If the laser emission check set is set, the process of the laser emission check subroutine is performed (step # 604).

FIG. 8 is a flowchart showing the processing contents of the laser emission check subroutine. First in step # 60401
The semiconductor laser 61 and the second semiconductor laser 62 are forcibly emitted, and a predetermined time elapses until the emission is stabilized. Then, it is determined whether or not the predetermined time has elapsed (step # 60).
402), when the predetermined time has elapsed (step # 60402: YE
In S), it is determined whether or not the detection result of the output current of the first semiconductor laser 61 by the first current detector 1011 is equal to or larger than a predetermined value (step # 60403).

If the detection result of the output current is equal to or more than the predetermined value (step # 60403 YES), the first semiconductor laser 61 is determined to be normal and the first laser trouble signal is reset (step # 60404). On the other hand, when the detection result of the output current is a value smaller than the predetermined value (step # 60403)
In NO, the first laser 61 is determined to be in a failure state, and the first laser trouble signal is set (step # 6040).
Five).

Next, it is determined whether or not the detection result of the output current of the second semiconductor laser 62 by the second current detector 1012 is equal to or more than a predetermined value (step # 60406). When the detection result of the output current is equal to or more than a predetermined value (step # 60406: YE
In S), it is determined that the second semiconductor laser 62 is normal, and the second laser trouble signal is reset (step # 6040).
7) On the other hand, if the detection result of the output current is smaller than the predetermined value (NO in step # 60406), it is determined that the second semiconductor laser 62 is in a failure state and the second laser trouble signal is reset. (Step # 60408).

When such a laser emission check is completed, a laser emission check end flag is set (step #).
60409), first semiconductor laser 61 and second semiconductor laser 62
Is turned off (step # 60410), and the process returns to the print processing subroutine.

In the print processing subroutine of FIG. 7, when the laser emission check subroutine ends, it is determined whether or not the laser emission check end flag is set, and it is checked whether or not the laser emission check is being performed (step # 60).
Five). If the laser emission check end flag has not been set and the laser emission check is still in progress (step # 60)
In 5 NO), the process proceeds to step # 625 to perform other processing. Also, when the laser emission check mode is not set in step # 603, the process proceeds to step # 625. On the other hand, when the laser emission check end flag is set (step # 605 YES), the laser emission check end flag is reset (step # 606), and the troubles of the first and second semiconductor lasers 61 and 62 are determined in the following routine. Each process is performed according to the toner empty of the first and second toner empty detectors 27a and 27b.

When it is determined that the second semiconductor laser 62 is in trouble and the first semiconductor laser 61 is normal (step # 607)
YES, step 608 NO), since the exposure position of the first semiconductor laser 61 is upstream of the first and second developing units 73a, 73b, even if the second semiconductor laser 62 is in trouble and cannot be used,
If the first or second developing device 73a, 73b is usable, image formation is possible, so it is determined by toner empty whether both developing devices 73a, 73b are usable (step # 609, # 610). If the second developing unit 73b cannot be used due to toner empty or the like and the first developing unit 73a can be used (step # 609 YES, step # 610 NO), the usable first semiconductor laser 61 and the first In order to print in the pseudo two-color mode by changing the developing density in combination with the developing unit 73a, the monochromatic density conversion flag is set, the use of the first semiconductor laser 61 is permitted, the use of the second semiconductor laser 62 is prohibited, and the second
The use of the developing device 73b is prohibited, and the use of the first developing device 73a is permitted (step # 611).

Note that if two simultaneous colors are not specified in the input processing subroutine shown in FIG. 6, this density conversion is meaningless, but if not two simultaneous colors, only one laser and developer are used from the beginning. Otherwise, there is no data to be subjected to density conversion, and there is no problem here. When both the second developing device 73b and the first developing device 73a cannot be used due to toner empty or the like and when both the first and second semiconductor lasers 61 and 62 have trouble, printing is impossible. Is displayed (step # 612).

Further, the second developing device 73b can be used, and the first developing device 7b can be used.
If 3a cannot be used (step # 609 NO, step # 613 YES), printing is performed in the pseudo two-color mode in which the density is changed by the combination of the usable first semiconductor laser 61 and the second developing unit 73b. , A monochromatic density conversion flag is set, the use of the first semiconductor laser 61 is permitted, and the second semiconductor laser
The use of 62 is prohibited, the use of the second developing device 73b is permitted, and the use of the first developing device 7
The use of 3a is prohibited (step # 614). If both the second developing unit 73b and the first developing unit 73a are usable (step # 609 NO, step # 613 NO), it is determined whether the simultaneous two-color mode is designated (step # 615). If the simultaneous two-color mode is specified (step # 615
YES), the second developing unit 73b is selected, and a monochromatic density conversion flag is set, and the use of the first semiconductor laser 61 is permitted, and the use of the second semiconductor laser 62 is prohibited, in order to print in two colors by density conversion. The use of the second developing device 73b is permitted, and the use of the first developing device 73a is prohibited (step # 616). Simultaneously 2
If no color mode is selected (Step # 615 N
O) Here, the first semiconductor laser 61 on the upstream side can be used and can be used in both the black and color developing units 73a and 73b.
Only the use of the second semiconductor laser 62 is prohibited, and the designation of the developing device to be used is not specified, and the developing is performed by the developing device selected in the input processing subroutine of step # 3.

Next, when it is determined that the second semiconductor laser 62 is normal and the first semiconductor laser 61 is in trouble (step # 607 NO, step # 608 YES), the beam is normally emitted only by the second semiconductor laser 62. The detection signal from the detector 21 is generated. If a trouble occurs in the second semiconductor laser 62, the detection signal cannot be generated.
22 is retracted by the solenoid 24, and the first semiconductor laser
Make 61 scan the beam detector 21 (step #
619).

Next, it is determined whether or not the second developing device 73b can be used (step # 620). If it can be used (step # 619 NO), the combination of the usable second semiconductor laser 62 and the second developing device 73b is used. To print in the pseudo two-color mode with different densities, set the monochromatic density conversion flag and set the first semiconductor laser
The use of the second semiconductor laser 62 is permitted, the use of the second developing device 73b is permitted, and the use of the first developing device 73a is prohibited (step # 621). Here, the first semiconductor laser 61
Is located downstream of the first developing device 73a, so that the first developing device 73a cannot be used.

If the second developing unit 73b is unusable (step # 620 YES), printing is not possible, and a message indicating a trouble is displayed (step # 622).

On the other hand, when both the first semiconductor laser 61 and the second semiconductor laser 62 are usable (step # 607 NO, step # 618 N
O), it is determined whether or not each of the developing devices 73a and 73b can be used.
If both the developing unit 73b and the first developing unit 73a cannot be used (step # 623 YES, step # 624 YES), a message indicating trouble is displayed because printing is impossible (step # 622).

When the second developing unit 73b is unusable and the first developing unit 73a is usable (YES in step # 623, step # 624
NO), pseudo 2 using only usable first developing unit 73a
In order to develop the image by changing the density so as to print in color, the monochromaticity conversion flag is set, the use of the first semiconductor laser 61 is permitted, the use of the second semiconductor laser 62 is prohibited, and the second developing device 73b
Is prohibited, and the use of the first developing unit 73a is permitted (step # 625).

If the second developing device 73b is usable and the first developing device 73a is not usable (NO in step # 623, Y in step # 626
ES), pseudo 2 using only usable second developing unit 73b
In order to change the density to print with color and develop,
The monochromatic density conversion flag is set, the use of the first semiconductor laser 61 is prohibited, the use of the second semiconductor laser 62 is permitted, the second developing device
The use of the first developing device 73a is prohibited and the use of the first developing device 73a is prohibited (step # 627).

Finally, when both the first and second semiconductor lasers 61 and 62 and the first and second developing devices 73a and 73b can be used normally, they can be used as set in the input processing subroutine. move on.

In step # 624, the laser emission check mode flag set in step # 602 is reset, and after performing other processing (step # 625), the process returns to the main routine.

FIG. 9 is a diagram summarizing the processing contents for the combinations (16 ways) of the states of the first and second semiconductor lasers 61 and 62 and the first and second developing units 73a and 73b in the print processing subroutine. Of the 8 combinations, half of the 8 combinations cause trouble and printing is impossible, but the remaining 8 combinations except for the normal state
Pseudo-simultaneous two-color printing by single-color density exchange becomes possible in the same combination, and a copy with high visibility can be obtained as soon as possible.

In the embodiment, the malfunction of the developing device is detected by toner empty, but the present invention is not limited to this.
Needless to say, it is also possible to detect other troubles in the drive system of the through roller, such as a trouble of the drive system, which may cause the development to be impossible.

Further, in the present embodiment, two beams are combined and separated by the optical system. However, the present invention is not limited to this, and the photosensitive member may be exposed without combining and separating the two beams. In this case, the failure of the exposure unit includes a failure of the drive system of the polygon mirror and the like.

Further, in the above-described embodiment, an example has been described in which both the failure detection means for individually detecting the failure of the exposure means and the failure detection means for individually detecting the failure of the developing means are provided. However, either one of the detection means is provided. Or just

〔effect〕

As described above, in the present invention, when at least one of the two image forming units becomes defective, one of the image data is corrected so that a difference occurs in the image density by visual recognition, and both of the image data are corrected. Since an image is formed by an image forming unit having no image, it is possible to form a pseudo two-color image based on color density. Therefore, an image can be formed in an emergency, and the efficiency of the image formation is improved, and excellent effects such as formation of an image with high visibility despite forming a two-color image with one color are obtained. Play.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing the structure of a simultaneous two-color copying machine which is a simultaneous two-color image forming apparatus according to the present invention, FIG. 2 is an enlarged perspective view showing a part of the structure of an optical system, and FIG. FIG. 4 is a block diagram showing a configuration of a control system, FIG. 4 is a block diagram showing a configuration of a print processing unit, FIGS. 5 to 8 are flowcharts showing processing procedures of the control system, and FIG. FIG. 6 is a diagram illustrating a relationship between a combination of troubles and processing contents. 27a first toner empty detector, 27b second toner empty detector, 40 print processing unit, 60 optical system, 61 first semiconductor laser, 62 second semiconductor laser, 71 ...... Photoreceptor drum 73a First developing system 73b
2nd developing unit, 102: Simultaneous two-color selection key, 201: CPU, 1
011 first current detector, 1012 second current detector, 101
5 …… Color density converter, 1016 …… Black density converter, 1017,
1018 …… Switch circuit, 1019 …… Color or circuit, 1020
...... Black or circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 21/00 500

Claims (3)

(57) [Claims] A first image forming means for forming a latent image on a photoconductor based on the first image data and developing the latent image in a first color; and a second image data on the photoconductor based on the second image data. A second image forming unit that creates a latent image by developing the latent image with a second color, a detecting unit that detects a defect of the first image forming unit, and a defect of the first image forming unit is detected. In this case, a correction unit that corrects the first or second image data so as to cause a difference in image density due to visual recognition, and both the corrected image data and the uncorrected image data are supplied to the second image forming unit. A two-color image forming apparatus, comprising: control means for forming an image in a second color. 2. The two-color image forming apparatus according to claim 1, wherein the first and second image forming units each include a first and a second exposing unit for forming a latent image on a photoreceptor. A first and a second developing unit for developing the latent image formed by the first and the second exposing unit; and the detecting unit includes a first and a second exposing unit and / or a first and a second developing unit.
A two-color image forming apparatus for detecting a failure of the second developing means. 3. The two-color image forming apparatus according to claim 1, wherein said detecting means detects toner empty of said image forming means.