JPH03288172A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To form an image by urgently using a developing means even in the case that the fault in an irradiation device on a downstream side occurs by allowing an exposing means on an upstream side to act for an exposing means of the downstream side of a photosensitive body which the fault occurs and using any of plural developing means with the exposing means on the upstream side. CONSTITUTION:This device is provided with fault detection means 1011 and 1012 for detecting the fault of the exposing means 61 and 62 and a means for controlling so that the image may be formed by using the exposing means 61 for exposing the exposing the upstream side in the rotating direction of the photosensitive body and any of the plural developing means when the fault of the exposing means 62 for exposing the downstream side of the rotating direction of the photosensitive body is detected by the means 1012. When the means 1012 detects the fault of the exposing means 62, the image is formed by the exposing means 61 on the upstream side in the rotating direction and any of the plural developing means. Thus, the image is formed by using the developing means even in the case that the fault in the exposing means 62 on the downstream side occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simultaneous multicolor image forming apparatus using multibeams such as a digital copying machine and a laser printer.

[Prior Art] A multicolor image forming apparatus modulates a plurality of laser beams according to image data, irradiates the photoconductor at different positions in the circumferential direction, and repeatedly charges and develops the photoconductor by sandwiching each position. A multicolor image is formed in one rotation. In such an image forming apparatus, a developing device containing toner of a color other than black, such as blue, is usually disposed upstream in the rotational direction of the photoreceptor from a developing device containing black toner. This is because when black toner is mixed with color toner, color stains become noticeable. In addition, in such an image forming apparatus, in order to align the multiple color images formed on the photoreceptor, the laser beam irradiated on the downstream side is output in consideration of the rotation time of the photoreceptor to each irradiation position. The output of image data was delayed compared to the upstream side.

In such an image forming apparatus, if the laser beam irradiation device breaks down, image formation cannot be performed, so a specialized engineer is called to repair the irradiation device. - Image formation using black toner alone for boat fishing is more frequent than other types of image formation, so if the laser beam irradiation device for black toner breaks down, specialized technology is required. It was necessary to call someone to repair the problem immediately.

[Problem to be solved by the invention]

However, when calling a specialized engineer, it is impossible to form an image using black toner from the time the engineer is called until the engineer arrives and starts the repair. There is a problem in that when failures occur frequently, the efficiency of image formation is significantly reduced.

The present invention has been made in view of the above circumstances, and when the irradiation device fails when performing image formation using the irradiation device on the downstream side in the circumferential direction of the photoreceptor, the irradiation of laser light is transferred to the upstream side. By using the irradiation device on the upstream side to perform image formation, even if the downstream irradiation device fails, it is possible to perform image formation on an emergency basis, improving the efficiency of image formation. An object of the present invention is to provide a multicolor image forming apparatus.

[Means to solve the problem]

A multicolor image forming apparatus according to the present invention includes a plurality of exposure means for exposing different exposure positions in the circumferential direction of a rotatable photoreceptor with a plurality of beams according to image data of a plurality of colors, and a multicolor image forming apparatus formed by each exposure means. A multi-color image forming apparatus that forms a multi-color or single-color image at one time and includes a plurality of developing means for developing latent images separately, a failure detection means for detecting a failure of the exposure means; When the detection means detects a failure in the exposure means that exposes the downstream side of the photoreceptor in the rotational direction,
6 [Operation] In the present invention, the failure detection means is characterized by comprising an exposure means for exposing the upstream side thereof and a means for controlling to form an image using any one of the plurality of developing means. When a failure of the exposure means is detected, an image is formed by the exposure means on the upstream side in the rotational direction and one of the plurality of developing means. Therefore, even if the exposure means on the downstream side fails, image formation using the developing means is performed.

[Examples] The present invention will be described in detail below based on drawings showing examples thereof. FIG. 1 shows a multicolor image forming apparatus according to the present invention.
FIG. 1 is a schematic side sectional view showing the configuration of a color copying machine. The copying machine of the present invention develops an image by reversal development, and includes a scanning system 10 that scans an original, an image signal processing section 20 that processes image signals sent from the scanning system, and based on the processed image signals, A print processing unit 4o that outputs image data to two first semiconductor lasers 6L and a second semiconductor laser 62, which will be described later.
, two modulated lights based on image data are sent to the photosensitive drum 71.
an optical system 60 that irradiates the image, and an image forming system 70 that develops the latent image formed by the irradiation and transfers and fixes it onto a sheet of paper, which is a transfer body.
It consists of

The scanning system 10 exposes and scans an original placed on an original platen glass 18, and converts the reflected light from the exposure into an electronic signal by photoelectric conversion elements 16 and 17 using, for example, a CCD array. The photoelectric conversion elements 16 and 17 convert images of a specific color such as red and images of other colors such as black into electrical signals, respectively.

The scanning system 10 is attached to a scanner 19 that moves parallel to the document table glass 18 by a scan motor M2.

The scanning system 10 includes an exposure lamp 11 that irradiates the original, a reflection mirror 12 that changes the direction of light reflected from the original, and two mirrors 13a13 that change the optical path from the reflection mirror 12.
b, a lens 14 that condenses the reflected light, a half mirror 15 that determines the color based on the wavelength of the reflected light, reflects or transmits it, and guides the reflected light to two photoelectric conversion elements 16 and 17, and a half mirror 15 that receives the light. It has photoelectric conversion elements 16 and 17 that generate electrical signals in response to light. This scanning system 10 exposes and scans the original when the scanner 19 moves to the left as indicated by the arrow.

The image signal processing unit 20 inputs the image signals output from the two photoelectric conversion elements 16 and 17, and in addition to normal image processing such as shading correction, variable magnification, and dither processing,
The print processing unit 4 distinguishes between a specific color (red) and other colors.
0 as image data with a two-color color palette.

The print processing unit 40 distributes the sent image data with erotic binding to the two first semiconductor lasers 61 and the second semiconductor laser 62, and also divides the image data into the two first semiconductor lasers 61. The image data provided to the second semiconductor laser 62 is delayed depending on the difference in the exposure position of the second semiconductor laser 62 on the photoreceptor drum 71.

The optical system 60 includes a first semiconductor laser 6L and a second semiconductor laser 6.
Electrostatic latent images corresponding to images of red, which is a specific color, and black, which is other colors, are formed on the photoreceptor drum 71 by laser light from 2.
It is formed on top. The optical system 60 includes a first semiconductor laser 61. The second semiconductor laser 62 and the first semiconductor laser 6
1. It uses collimator lenses 61a and 62a that convert the laser beam irradiated from the second semiconductor laser 62 into parallel beams, and a dichroic mirror that transmits or reflects the two laser beams depending on their wavelengths. a polygon mirror 65 that deflects the combined laser beam in the main scanning direction, a condensing lens 69 that condenses the deflected laser beam, and a mirror 67a that reflects the condensed laser beam. , a separation mirror 68 that has the same characteristics as the combining mirror 63 and separates the combined laser beam into two laser beams by reflecting or transmitting the combined laser beam, and a reflecting mirror 67b that reflects each of the separated laser beams. 67c
It is composed of

First semiconductor laser 61. The second semiconductor laser 62 independently generates laser beams modulated by the image data output from the print processing section 40 corresponding to red and black images, and the respective laser beams are combined by a combining mirror 63. The direction of the combined laser beams is changed by a polygon mirror 65 rotationally driven by a polygon motor 64 so as to scan the photosensitive drum 71 in the main scanning direction (line direction). The deflected laser beam is focused by a condenser lens 69 so as to form an image on the photoreceptor drum 71, and then the mirror 6
7a, the laser beam is further separated into two laser beams by a separation mirror 68, reflected by mirrors 67b and 67c provided in the respective optical paths, and reaches each exposure position on the photoconductor drum 71, and is then separated into two laser beams by a separation mirror 68. The drum 71 is exposed.

The image forming system 70 develops the electrostatic latent image formed on the photoreceptor drum 71 and transfers and fixes it onto a sheet of paper.
It is composed of C.

The developing/transfer system 70A includes a photoreceptor drum 71 that is rotationally driven in the counterclockwise direction of the arrow, and a grid that uniformly charges the surface of the photoreceptor drum 71 arranged around the photoreceptor drum 71 in order from upstream in the rotational direction. 72aI, a first developer 73a that stores red toner, and a grid 72b that charges the photoreceptor drum 71 again in preparation for second exposure.
A charging charger 72b, a second developing device 73b that stores black toner, a transfer charger 74 that transfers the developed toner image onto the paper, a separation charger 75 that separates the paper from the photoreceptor drum 71, and toner remaining on the surface of the photoreceptor. It is composed of peripheral equipment such as a cleaning section 76 that removes .

The conveyance system 70B supplies paper and conveys it to the fixing system 70C, and includes cassettes 80a and 8 for storing the paper.
0b, a paper guide 81 that guides the paper taken out from the cassettes 80a and 80b, a timing roller 82 that adjusts the timing of conveyance of the guided paper to the transfer section between the transfer charger 74 and the photosensitive drum 71, and a fixing system. 70C
It is composed of a conveyor belt 83 and the like that conveys the paper onto which the toner image has been transferred.

The fixing system 70C thermocompresses the toner image transferred onto the paper between a pair of fixing rollers 84, 84.
The paper to which the toner has been fixed is discharged from the copying machine by a discharge roller 85.

Further, on the top of the copying machine, there are operations such as a print button 101 for starting the copying operation, a simultaneous two-color selection button 102 for selecting simultaneous two-color mode, and a color selection button 103 for selecting black or red single-color mode. In addition to buttons, a display device using an LED (not shown) for displaying selection results is also provided.

FIG. 2 is a block diagram showing the configuration of the main parts of the control system of the copying machine of the present invention, and the control system 200 uses a microcomputer (hereinafter referred to as CPU) 201. CPU201
analyzes or displays various switches such as the print button 101 and the simultaneous two-color selection button 102 and various signals, and also controls the image signal processing section 20 and the print processing section 40.

FIG. 3 is a block diagram showing the configuration of the print processing section 40. Image data given from the image signal processing section 20 is given to a color separation section 1001 that switches according to color information, and is switched by a control signal described later, and is sent to a color buffer section 100.
2 or is given to the black buffer section 1003. Further, color information provided from the image signal processing section 20 in synchronization with the image data is provided to the color separation section 1001 via an AND gate 1004 and an OR gate 1010. 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 there is used by a color laser control unit that outputs a modulation signal according to the image data. 1007. Then, the first semiconductor laser 61 is turned on and off by the modulation signal. Further, the black buffer section 1003 performs similar processing on black image data, and the image data output therefrom is given to a delay memory 1005 and a selector 1006. The selector 1006 is also given the output of the delayed memo January 005, and selects the image data from the black buffer section 1003 or the image data from the delayed memo January 005. Delay memo January 005 is for correcting the deviation due to the difference in the exposure position of the two laser beams, and in the simultaneous two-color mode, the photosensitive drum 71 moves between the two exposure positions (the difference in FIG. 11, which will be described later). Black image data is delayed by the rotation time. The selector 1006 selects image data from the black buffer section 1003 in the high speed mode, and selects the output of the delayed memo January 005 in the normal mode. The selected image data is similarly given to the second semiconductor laser 62 via the black laser control section 1008.

In addition, the first semiconductor laser 61 and the second semiconductor laser 62
A first current detector 1011 and a second current detector 101 each detect the output current of a photodiode (not shown) that is built into these and outputs an output current according to the amount of light emitted by each photodiode.
2 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 section 1007, and the detection result of the output current of the second semiconductor laser 62 is given from the second current detector 1012 to the black laser control section 1007. 1008. In the color laser control section 1007 and the black laser control section 1008, when the detection result exceeds a predetermined value, the respective first semiconductor lasers 61. Information indicating that the second semiconductor laser 62 has failed is provided to the CPU 201.

In the color information, for example, "1" indicates color, and "0" indicates black. Further, the CPU 201 is given high speed mote information and black laser failure mode information.

The high speed mode information is applied to the AND gate 1004 via the inverter 1009 and also to the selector 1006 mentioned above. When the single color mode black is selected with the color selection button 103, the high speed mode information is set to "1" and becomes the high speed mode, and is reset when red is selected or when the simultaneous multicolor mode is selected. It becomes "0" and becomes the normal mode.

The black laser failure mode information is given to the OR gate 1o1° and also to a black laser control section 1008, which will be described later. Black laser failure mode information is provided by black laser control unit 1.
When 008 detects a failure in the semiconductor laser 62, black laser failure mode information is set and becomes “1”.
In other cases, it is reset to "0" and enters the normal mode.

And only when the color information is color (="1") and the high-speed mode information is normal mode (-"0") is the anime game h 10
The color information output from 04 becomes “1”, and color separation unit 1
001 switches to the color buffer section 1002 side. In other cases, the color information from the ant gate 1004 is "0", and the color separation unit 1001 is transferred to the black buffer unit 100.
Switch to side 3. Furthermore, when the black laser failure mode information is a failure mode (="l"), the color information of "1" is forcibly given from the OR gate 1010 to the color separation unit 1001, and the color information given from the antgame 004 is The color separation section 1001 switches to the color buffer section 1003 side without any problem.

Next, the operation of the control system will be explained. FIG. 4 is a flowchart showing the main routine of the CPU.

Before explaining the flowchart, the terms on-edge and off-edge used therein will be defined. On-edge is defined as when the state of a switch, sensor, signal, etc. changes from an off state to an on state. Off-edge is defined as an off-edge when the state of a switch, sensor, signal, etc. changes from an on state to an off state.

First, when the power is turned on, in step #1, the states of various timers, flags, counters, etc. used in subsequent subroutines are set to their initial states, and then the internal timer value, which is the reference time for the following processing, is set. to start the internal timer (Step #2). Input processing (step #3) for performing input processing for various input switches, first semiconductor laser 61
and printing processing by the second semiconductor laser 62 (step #
4), development/transfer system processing to develop the electrostatic latent image formed on the photosensitive drum 71 and transfer it onto the paper (step #5), and conveyance system processing to transport the paper to the transfer section (step #5). 6) Fixing system processing to heat and press the paper to which the toner image has been transferred (step +17) and other processing (step #8)
are executed sequentially, wait for the internal timer to end, and then
9), return to step #2.

FIG. 5 is a flowchart showing the processing contents of the input processing subroutine in step #3. In step #301, it is determined whether the color selection button 103 is on-edge or not, and if it is on-edge, whether the black copy LED data is "0" or not. When the black copy LED data is “0”, that is, when the current world copy is selected, the black copy LED data is set to “1” and the red copy LED data is set to “02”.
Reset to .

In addition, when the black copy LED data is "1", the black copy LED data is reset to "02", and the red copy LED data is reset to "02".
Set D data to "12. Next, step #305
determines whether the simultaneous two-color selection button 102 is on-edge, and when it is on-edge, the simultaneous two-color LED data is inverted, if the simultaneous two-color mode has already been selected, it is set to single-color mode, and when the single-color mode is selected, is set to two-color mode at the same time. Also, in step #301, color selection button 10
If 3 is not on-edge, the process proceeds to step #305, and if the simultaneous two-color selection button 102 is not on-edge in step #305, step #306 is skipped.

Next, in step #307, the simultaneous two-color LED data is “0”
, that is, whether or not the single color mode is selected. If it is the single color mode (step +1307 YES), it is determined whether the black copy LED data is "1", that is, whether black is selected in the single color mode. (Step #308).

When black is selected (step #308 YES)
sets the high-speed mode information to "1" to enter the high-speed mode (step #309). This causes delay memory 1
005, the black image data is sent to the black laser control unit 1008.
The first copy can be made without delay. If red is selected in step #308 (step #308 NO), the high speed mode information is reset to "0" and the normal mode is set (step #310). In addition, when it is determined in step #307 that the mode is not the single color mode but the simultaneous two color mode (step #307 No), the high speed mode information is reset, the black image data is output via the delay memo 005, and the black image data is output. Perform alignment with the red image. At this time, both the black copy LED data and the red copy LED data are set to "1" to indicate that the simultaneous two-color mode has been set (step 11311).
. When these processes are completed, other input processes are performed in step #312, and then the process returns to the main routine.

FIG. 6 is a flowchart showing the processing contents of the print processing subroutine of step #4. In step #401, it is determined whether the print button 101 is on-edge, and if it is on-edge (step #401 YES), a laser emission check mode is set (step #402).

Next, it is determined whether the laser emission check mode is set (step #403), and the laser emission check subroutine is processed (step #404).

FIG. 7 is a flowchart showing the processing contents of the laser emission check subroutine. In step #40401, the first semiconductor laser 61 and the second semiconductor laser 62 are forced to emit light, and a predetermined period of time is allowed to elapse until the light emission becomes stable.

Then, it is determined whether or not this predetermined time has elapsed (step #40402), and if the predetermined time has elapsed (step #40402 YES), the output current of the first current detector 1011 of the first semiconductor laser 61 as described above is changed. It is determined whether the detection result is greater than or equal to a predetermined value (step #40403).

If the detection result of the output current is greater than or equal to the predetermined value (step #40403 YES), the first semiconductor laser 6
1 is determined to be normal (step #40404).

On the other hand, if the detection result of the output current is smaller than the predetermined value (step #40403 NO), it is determined that the first semiconductor laser 61 is in a failure state (step $140405).

Next, it is determined whether the detection result of the output current by the second current detector 1012 of the second semiconductor laser 62 as described above is greater than or equal to a predetermined value (step #40406).

If the detection result of the output current is greater than or equal to the predetermined value (step #40406 YES), the second semiconductor laser 6
Step #40407) is considered normal.
- On the other hand, if the detection result of the output current is smaller than the predetermined value (step 140406 NO), it is determined that the second semiconductor laser 62 is in a failure state (step 140408).

Then, when such a laser emission check is completed, a laser emission check completion flag is set in step #4.
0409), the first semiconductor laser 61 and the second semiconductor laser 62 are turned off, and the process returns to step #40410), the print processing subroutine.

When the laser emission check subroutine ends, it is determined whether the laser emission check completion flag is set (step #405). If the laser emission check end flag is not set (step #405 No.
), the process advances to step #414 to perform other processing. On the other hand, if the laser emission check end flag is set (step #405 YES), the second semiconductor laser 6
2 is out of order (step #406
).

If it is determined that the second semiconductor laser 62 is out of order (step #406 YES), it is determined whether or not the first semiconductor laser 61 is out of order (step #4).
07). If the first semiconductor laser 61 is out of order (step #407 YES), it is determined that both the first semiconductor laser 61 and the second semiconductor laser 62 are out of order (step #408). On the other hand, if the first semiconductor laser 61 is not out of order (step #407 No.
) determines that only the second semiconductor laser 62 is in a failed state, sets the black laser failure mode information to "l" to set it as failure mode, and resets the high speed mote information to "0" (step # 409) Also, step #40
Even if it is determined in step #6 that the second semiconductor laser 62 is not malfunctioning, it is determined whether the first semiconductor laser 61 is malfunctioning (step #410). First semiconductor laser 6
1 is out of order (step #410 YES), it is determined that only the first semiconductor laser 61 is out of order, and the color laser failure mode information is set and the high speed mode information is set to "1". (Step #41
1). - On the other hand, if the first semiconductor laser 61 is not broken (step 1410 NO), the first semiconductor laser 6
It is determined that both the first and second semiconductor lasers 62 are operating normally, and the black laser failure mode information and the color laser failure mode information are each reset to "0" (step #41'2).

And step #408. #409. #411. #4
When the processing in step #12 is completed, the laser emission check flag and the laser emission check end flag are reset, and a copy flag indicating that the copy operation is in progress is set (step #4).
13). When these processes are completed, print subroutine processing is performed (step #414).

FIG. 8 is a flowchart showing the processing contents of the print subroutine. In step #41401, it is determined whether the high-speed mode information is set to "1". When the black single color mode is selected by the color selection button 103 and the high speed mode is set, the color information forcibly input to the color separation unit 1001 becomes “O” regardless of the color information input to the print processing unit 40. , the color separation unit 1001 switches to the black side, and all input red and black image data are temporarily stored in the black color separation unit 1003 (Step #4
1402). Then selector 1006 indicates high speed mode="
1” is given, and the selector 1006 selects the black buffer section 10.
Step #4 Select the image data output from 03.
Step #41404) Give the black modulation signal to the black laser control unit 1008, generate a black modulation signal, and output it to the second semiconductor laser 62.
emits light (step #41405) and returns to the main routine. As a result, in the high-speed mode, image data is output without going through the delay memory 1005, and when the image data is given from the image processing section 20 to the print processing section 40,
The data is written on the photosensitive drum 71 without any delay, and the first copy can be output quickly in conjunction with the above-described transport system processing.

On the other hand, if the high speed mode information is "0" in step #41401 and the normal mode is selected, it is determined whether the color information input to the print processing section 40 is "1" or not.Step #4
1406), when it is "0", the output of the AND gate 1004 becomes "0", color information "0" is input to the color separation section 1001, and the color separation section 1001 selects the black sofa section 1003.
(Step #41407). Then, the selector 1006 selects the output of the delay memory 1005, and the image data whose color information is "0" is delayed in the delay memory 1005 (step #41408), and step #414
Proceed to 04. Further, if the color information is "1" in step #606 and it is color, the color information "1" is sent to the color separation unit 1001.
is input, and the color separation unit 1001 transfers the color buffer unit 10 to the color separation unit 1001.
02 side (step #41409), image data with color information "1" is given to the color laser control section 1007, and a color modulation signal is outputted.Step #414
10) and cause the first semiconductor laser 61 to emit light (step #
41411), returns to the print subroutine, and then returns to the main routine. However, when the black laser failure mode information is a failure mode (="l"), the output of the OR gate 1014, that is, the color information, is forcibly set to "1", and the color separation unit 1001 switches to the color buffer unit 1002 side. It looks like this.

FIG. 9 is a flowchart showing the processing contents of the processing subroutine for the development/transfer processing in step #5. simultaneous 2
After selecting the type of developing device used for image formation using the color button 102 and color selection button 103, a process is performed to correct the selection according to the operating states of the first semiconductor laser 61 and the second semiconductor laser 62. .

First, in step #501, it is determined whether or not the copy flag is set, that is, whether or not a copy operation is in progress. If the copy operation is not in progress (step #501 No), it is determined that the developing device to be used has been reset. After resetting the re-input completion flag representing step #519) and performing other processing (step #511), the process returns to the main routine.

Also, when copying is in progress (step #501 YES)
In step #502, it is determined whether or not all lasers have failed as set in step #408 (step #502).
502). When all lasers fail (step #502
If YES), other processing such as failure display is performed (step #511) and the process returns to the main routine.

If all the lasers are not in failure (step #502 No), it is determined whether the black laser failure mode is present (step #503), and if the second semiconductor laser 62 is in failure (step #503 YES), the upstream side Since the first semiconductor laser 61 is used, it is possible to use either the first developing device 73a or the second developing device 73b, and it is necessary to reset which developing device 73a or 73b is used.

Specifically, in step #504, it is determined whether the re-input completion flag has been set, that is, whether the developing units 73a and 73b have already been reset, and if the re-input completion flag has not been set yet, then ( Step 1504 No), when the on-edge of the color selection button 103 is detected (Step #
505 YES), it is determined whether the black copy LED data is "1", that is, whether black has been selected (step #506). When black is selected (step #506 YES), the black copy LED data is
0", the red copy LED data is set to "1", the use of the first developing device 73a is permitted, the use of the second developing device 73b is prohibited, and the single color mode is set to red (step #
507). Further, when black is not selected (NO in step 1506), the black copy LED data is set to 1' and the red copy LED data is set to 0', the use of the first developer 73a is prohibited, and the second developer 73b and select black in monochrome mode (step #508)
, and repeats the processing of steps #503 to j1508 until the on-edge of the print key 101 is detected (step #509 No), and when the on-edge of the print key 101 is detected (step #509 YES)
Set the re-input completion flag (step #510),
The resetting of the developing units 73a and 73b is completed.

Also, when it is determined in step #503 that the second semiconductor laser 62 is not out of order (step 1503 No)
, determine whether the color laser failure mode is “1” (
Step #512). When the first semiconductor laser 61 is out of order (step #512 YES), only the second semiconductor laser 62 and second developing device 73b on the downstream side can be used, so there is no choice but to change the black copy LED data to 1 and the red copy LED data to 1. The data is set to O, the use of the first developer 73a is prohibited, the use of the second developer 73b is permitted, and the monochrome mode black is set.

Next, in step #512, it is determined that the color laser is not in failure mode, that is, the first semiconductor laser 61 and the second semiconductor laser 6
2 are not malfunctioning (step #512)
Step #514) If the simultaneous two-color mode is selected, the first developer 73a and the second developer 73
b. Permit use of both (step $1515).

On the other hand, when monochrome mode is selected (step #5
14 No) is whether the black copy LED data is 1” or not.
That is, it is determined whether black is selected in the single color mode (step #516). When black is selected (step $1516 YES), use of the first developing device 73a is prohibited and use of the second developing device 73b is permitted (step #517). If red is selected (NO in step 1516), use of the first developing device 73a is permitted and use of the second developing device 73b is prohibited (step 1518). After performing other processing (step #511), the process returns to the main routine.

FIG. 10 is a flowchart showing the processing contents of the transport system processing subroutine of step #6. First, it is determined whether the copy flag is "1", that is, whether or not a copy operation is in progress (step #601).
601 (YES), it is determined whether conveyance of paper has started (step 1602). When conveyance of paper has not started (step [02No]), the cassette 80a or 8 selected by the cassette selection button (not shown) is selected.
The paper is taken out from 0b and conveyance of the paper is started (step #603). The paper is conveyed to the timing roller 82 (step #604). Next step #60
In step 5, it is determined whether the high speed mode information has been set, that is, whether the first copy has been selected in the black monochrome mode. FIG. 11 is a diagram showing the distance from the exposure position of the two laser beams to the transfer section. 5. The distance from the position exposed by the laser beam from the second half conductor laser 62 for black images to the transfer section is denoted by L2. Their difference is L3 (=L
+ L2). In the high-speed mode in which high-speed mode information is set, the registration timer that determines the rotation start timing of the timing roller 82 is set to a timer value lower A that corresponds to the time it takes for the photosensitive drum 71 to move the distance L2 (step j1606). . On the other hand, when the high speed mode information is the normal mode, the registration timer is set to a timer value T8 corresponding to the time it takes for the photosensitive drum 71 to move the distance L1 (step #607). Next, it is determined whether or not the imprinting of the image onto the photoreceptor drum 71 has started (step #608), and when it has started, the registration timer is started to count (step #609), and the set timer value is set. Wait until TA or Tll ends (step #610). When the registration timer ends, the timing roller 82 is turned on (step #611) and rotated to send the paper to the transfer section and synchronize the leading edge of the toner image formed on the photosensitive drum 71 with the leading edge of the paper.

Then, when the end of the copy operation is detected (step #61
2 YES), reset the copy flag (step #613), and after other transport processing (step #61).
4) Return to the main routine.

As explained above, when the black laser failure mode information becomes the failure mode, the second semiconductor laser 62 becomes unusable, and the first semiconductor laser 61, the first developer 73a, and the second
For example, the first semiconductor laser 61 forms an electrostatic latent image corresponding to a black image on the photoreceptor drum 71, and the second developer 73b is used to form an electrostatic latent image corresponding to a black image. A black image can be formed by development.

In this embodiment, the present invention has been explained using a simultaneous two-color copying machine as an example of a multicolor image forming apparatus, but the present invention is not limited to this, and can be applied to a multicolor image forming apparatus such as a laser printer with three or more colors, a digital copying machine, etc. Needless to say, the invention can also be applied to color image forming apparatuses. In addition, in this embodiment, one polygon mirror 6
5, two types of laser beams are used for scanning, but each laser beam may be scanned by a separate polygon mirror, and it goes without saying that this can also be applied to a failure of the polygon mirror driving means.

〔effect〕

As detailed above, in the present invention, when the exposure means on the downstream side of the photoreceptor fails, the exposure means on the upstream side takes over as the exposure means, and this and any one of the plurality of developing means. By using this method, even if the downstream irradiation device fails, it becomes possible to perform image formation using the developing means on an emergency basis, which brings about excellent effects such as improving the efficiency of image formation.

[Brief explanation of the drawing]

FIG. 1 is a schematic side sectional view showing the configuration of a simultaneous two-color copying machine which is a multicolor image forming apparatus according to the present invention, FIG. 2 is a block diagram showing the configuration of the control system, and FIG. 3 is a print processing unit. 4 to 10 are flowcharts showing the processing procedure of the control system, and FIG. 11 is a diagram showing the distance from the exposure position of the two laser beams to the transfer section.

Claims (1)

[Claims] 1. A plurality of exposure means that expose different exposure positions in the circumferential direction of a rotatable photoreceptor with a plurality of beams according to image data of a plurality of colors, and a latent image formed by each exposure means. In a multi-color image forming apparatus that is provided with a plurality of developing means for developing each image separately and forms a multi-color or single-color image at one time, a failure detection means detects a failure of the exposure means; When a failure of the exposure means that exposes the downstream side in the rotational direction of the photoreceptor is detected, means for controlling the exposure means that exposes the upstream side and one of the plurality of developing means to form an image; A multicolor image forming apparatus comprising: