JP2004246040A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide two fixing units and perform two-time fixing in a single pass, thereby achieving fixing at relatively low temperatures, to reduce adverse effects of flicker, to perform two-time fixing in a color copy mode which requires large amount of heat for fixing and perform single-time fixing in a monochrome mode, and to allow both-sided copying in a single pass. <P>SOLUTION: The image forming apparatus having the full-color mode and the monochrome mode includes: two fixing means; a two single-time fixing conveyance means which passes through either one of the fixing means; a two-time fixing conveyance means which passes through both the fixing means; a means for selecting one of the conveyance means; and a means for exerting control such that switching between the conveyance means takes place depending on whether the mode is the color or monochrome one. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic copying machine and a printer, and more particularly to a full-color mode in which an image is formed with a plurality of color toners and a single-color mode in which an image is formed with a single color toner. The present invention relates to an image forming apparatus capable of reducing flicker.
[0002]
[Prior art]
In the electrophotographic image forming apparatus, the use ratio of color documents has been increasing in offices and the like in recent years. Therefore, demand for a small and low-price office color image forming apparatus has been increasing.
[0003]
In this office color image forming apparatus, it is important to realize a color copy function at low cost in addition to the performance of a conventional monochrome copying machine such as high productivity, high stability, and low running cost. Further, the rate of double-sided printing of documents handled in offices is increasing from the viewpoint of resource saving, and high productivity in double-sided printing is also required.
[0004]
Therefore, in order to ensure the high speed of both sides, a machine that realizes both sides in one pass has been devised.
[0005]
On the other hand, the importance of energy saving is regarded as a problem from the viewpoints of environmental impact and low running cost, and reduction of power consumption is also required. In particular, the power consumption in the fixing unit is high, and the influence on the entire power consumption is large.
[0006]
However, in color copying, since an image is usually formed using four color toners of yellow, magenta, cyan, and black, the amount of heat required for fixing the toner is smaller than when an image is formed using a conventional single color toner. Is increased. Furthermore, if the temperature of the fixing temperature is increased in order to secure this heat amount, the influence of flicker and the like generated from the fixing device becomes a problem.
[0007]
[Problems to be solved by the invention]
Therefore, the present invention makes it possible to control the fixing at a low temperature adjustment equivalent to that of a monochrome copy even in a color copy while securing high-speed productivity on both sides, and achieves low power consumption, the influence of flicker generated by a fixing device, and the like. It is an object of the present invention to provide a color image forming apparatus capable of reducing the number of colors.
[0008]
[Means for Solving the Problems]
The present invention is an image forming apparatus including a multi-color toner mode for forming an image by sequentially superimposing a plurality of color toner images and a single-color toner mode for forming a single-color image using one specific color toner image,
First and second two fixing means for fixing the toner image transferred onto the recording sheet;
A first conveying unit that conveys the recording sheet so as to pass only the first fixing unit,
A second conveying unit that conveys the recording sheet so as to pass only the second fixing unit,
A third transport unit that transports the recording sheet so as to pass through both the first and second fixing units,
Selecting means for selecting the first, second, and third transport means,
An image forming apparatus, comprising: a control unit that controls the selection by the selection unit between the multi-color toner mode and the single-color toner mode to perform fixing.
[0009]
The image forming apparatus according to claim 1, wherein in the case of the multi-color toner mode, the control unit controls the third conveying unit to pass through two fixing units.
[0010]
Further, in the case where the single-color toner mode is continuously performed, the control unit controls the first fixing unit and the second conveying unit so as to alternately pass through the two fixing units. The image forming apparatus according to claim 1, wherein:
[0011]
In the case where the single-color toner mode is continuously performed, the control unit continuously uses one of the first and second conveyance units, and when the fixing unit cannot be used due to a temperature drop, the other conveyance unit. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to switch to an image forming unit.
[0012]
In addition, the image forming apparatus further includes an abnormality detecting unit that detects an abnormal state of the fixing unit. When the abnormality detecting unit detects an abnormal state of one of the fixing units, and in the case of the single-color toner mode, the control unit controls 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to switch to the transport unit.
[0013]
2. The image forming apparatus according to claim 1, wherein when the single color toner mode is executed when the state of the image forming apparatus is in a low power state or a sleep state, only one of the fixing units is activated. It is.
[0014]
An image forming apparatus including a multi-color toner mode for forming an image by sequentially superimposing a plurality of color toner images and a single-color toner mode for forming a single-color image using one specific color toner image,
First and second two fixing means for fixing the toner image transferred onto the recording sheet;
First and second paper feeding paths, which are paths connecting the recording sheet storage and the first and second fixing units,
A transport path that is a path connecting the first fixing unit and the second fixing unit,
First and second discharge paths, which are paths extending from the first and second fixing units to the outside of the apparatus,
A first paper feed path, a first fixing means, a first transport means for transporting the recording sheet so as to pass in the order of the first paper discharge path,
A second paper feed path, a second fixing means, a second transport means for transporting the recording sheet so as to pass in the order of the second discharge path,
A first feeding path, a first fixing unit, a conveying path, a second fixing unit, a third conveying unit that conveys the recording sheet so as to pass in the order of the second discharging path,
Selecting means for selecting the first, second, and third transport means,
In the case of the multi-color toner mode, the third transport unit is selected, and when the single-color toner mode is continuously performed, the first transport unit and the second transport unit are alternately selected. And a control unit for controlling the unit.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
First, as an example of the embodiment, a configuration of a basic image forming apparatus will be described with reference to FIGS.
[0016]
[Configuration of color reader unit]
First, the configuration of the color reader will be described.
[0017]
FIG. 2 shows the overall configuration of the image forming apparatus.
[0018]
Here, 101 is a CCD, 211 is a substrate on which the CCD 101 is mounted, 200 is a control unit that controls the entire image forming apparatus, 212 is a printer processing unit including the image processing unit of FIG. A document table glass (platen) 202 is a document feeder (DF) (a mirror pressure plate (not shown) may be mounted in place of the document feeder 202), and 203 and 204 are light sources for illuminating the document. (Halogen lamps or fluorescent lamps), 205 and 206 are reflectors for condensing the light of the light sources 203 and 204 on the original, 207 to 209 are mirrors, and 210 is the condensed light or projection light from the original on the CCD 101. A lens 214 is a carriage that houses the halogen lamps 203 and 204, the reflectors 205 and 206, and the mirror 207. Yarijji, 213 denotes an external interface (I / F) with other devices. The entire surface of the document is scanned (sub-scanning) by mechanically moving the carriage 214 at a speed V and the carriage 215 at a speed V / 2 in a direction perpendicular to the electrical scanning (main scanning) direction of the CCD 101. ).
[0019]
Also, as shown in FIG. 3, the control unit 200 includes a CPU 301 having an I / F for exchanging information for controlling the digital image processing unit 212, the external I / F 213, and the printer control I / F 280, respectively. 302 and a memory 303. The operation unit 302 is configured by a liquid crystal with a touch panel for inputting processing execution content by the operator, information on processing for the operator, and notification of a warning or the like.
[0020]
The external I / F 213 is an interface for exchanging image information, code information, and the like with the outside of the image forming apparatus. Specifically, the external I / F 213 can be connected to a personal computer terminal device, a LAN interface device, or the like. The control of the exchange procedure of the image information and the code information with the personal computer terminal device and the LAN interface device is performed by mutual communication between each connection device and the CPU 301 of the control unit 200.
[0021]
Next, the digital image processing unit 212 will be described in detail.
[0022]
FIG. 1 is a block diagram showing a detailed configuration of the digital image processing unit 212.
[0023]
The original on the platen glass reflects light from the light sources 203 and 204, and the reflected light is guided to the CCD 101 and converted into an electric signal. (When the CCD 101 is a color sensor, an RGB color filter is provided on a one-line CCD. May be in-line in RGB order, or a 3-line CCD with R, G, and B filters arranged for each CCD. The filter may be on-chip, or the filter may be different from the CCD. May be used). Then, the electric signal (analog image signal) is input to the image processing unit 212, and the clamp & Amp. The sample and hold (S / H) is performed by the & S / H & A / D unit 102, the dark level of the analog image signal is clamped to the reference potential, and is amplified to a predetermined amount (the processing order is not limited to the notation order). The signal is D-converted and converted into, for example, a digital signal of 8 bits each of RGB.
[0024]
Subsequently, the RGB signals are subjected to shading correction and black correction in a shading unit 103. The corrected RGB signals are further connected by the connection & MTF correction & document detection unit 104. If the CCD 101 is a 3-line CCD, the connection processing differs in the reading position between lines, so the delay amount for each line is adjusted according to the reading speed. The signal timing is corrected so that the reading positions of the three lines are the same, and the MTF correction corrects the change because the reading MTF changes depending on the reading speed and the magnification, and the document detection detects the document on the platen glass. The document size is recognized by scanning.
[0025]
The input masking unit 105 corrects the spectral characteristics of the CCD 101 and the spectral characteristics of the light sources 203 and 204 and the reflectors 205 and 206 for the digital signal whose read position timing has been corrected. The output of the input masking unit 105 is input to a selector 106 that can be switched with an external I / F signal. The signal output from the selector 106 is input to the color space compression & background removal & LOG conversion unit 107 and background removal unit 115. After the signal input to the background removal unit 115 is removed from the background, the signal is input to a black character determination unit 116 that determines whether or not the document is a black character in the document, and a black character signal is generated from the document. The color space compression & background removal & LOG conversion unit 107, to which the output of the other selector 106 is input, determines whether the read image signal is within the range that can be reproduced by the printer and enters the color space compression. If it does not, the correction is made so that the image signal falls within the range that can be reproduced by the printer. Then, a background removal process is performed, and the RGB signals are converted into CMY signals by LOG conversion. Then, the timing of the output signal of the color space compression & background removal & LOG conversion unit 107 is adjusted by the delay 108 in order to correct the timing and the signal generated by the black character determination unit 116. The two types of signals are subjected to moiré removal by a moiré removal unit 109 and are subjected to scaling processing in 110 in the main scanning direction.
[0026]
Reference numeral 111 denotes a UCR & masking & black character reflecting unit. The CMY signal processed by the scaling unit 110 is generated by a UCR process to generate a CMYK signal. The determination signal generated at 116 is fed back to the CMYK signal. The signal processed by the UCR & masking & black character reflection unit 111 is subjected to density adjustment by the γ correction unit 112 and then subjected to smoothing or edge processing by the filter unit 113.
[0027]
[Configuration of printer unit]
Next, the configuration of the printer unit will be described.
[0028]
FIG. 2 is a main part configuration diagram of a full-color printer as an example of the image forming apparatus according to the present invention.
[0029]
A photoreceptor drum (hereinafter, simply referred to as a “photoreceptor”) 225 as an image carrier is provided to be rotatable in the direction of arrow A by a motor (not shown). Around the photoreceptor 225, a primary charger 221, an exposure device 218, a black developing unit 219, a color developing unit 223, a transfer charger 220, and a cleaner device 222 are arranged.
[0030]
The black developing device 219 is a developing device for monochrome development, and develops the latent image on the photoconductor 225 with K toner. The color developing unit 223 includes three developing devices 223Y, 223M, and 223C for full-color development. The developing devices 223Y, 223M, and 223C develop the latent images on the photoconductor 225 with Y, M, and C toners, respectively. When developing the toner of each color, the developing unit 223 is rotated in the direction of arrow R by a motor (not shown), and the developing device of the color is positioned so as to contact the photoconductor 225.
[0031]
The toner images of each color developed on the photoconductor 225 are sequentially transferred to a belt 226 as an intermediate transfer body by the transfer charger 220, and the toner images of four colors are superimposed. The belt 226 is stretched around rollers 227, 228, and 229. Among these, the roller 227 is coupled to a driving source (not shown) and functions as a driving roller for driving the belt 226, the roller 228 functions as a tension roller for adjusting the tension of the belt 226, and the roller 229 functions as a secondary transfer device. Function as a backup roller for the transfer roller 231 of FIG. The transfer roller attaching / detaching unit 250 is a drive unit for adhering or detaching the transfer roller 231 to / from the belt 226. A belt cleaner 232 is provided at a position facing the roller 227 with the belt 226 interposed therebetween. The belt cleaner attaching / detaching unit 268 is a drive unit for adhering or detaching the belt cleaner 232 to / from the belt 226. The residual toner on the belt 226 is scraped off by the blade by the operation of the belt cleaner 232 in the attaching direction by the belt cleaner attaching / detaching unit 268.
[0032]
The recording sheet medium stored in the cassettes 240 and 241 and the manual paper feed unit 253 is nipped by a registration roller 255 and a pair of paper feed rollers 235, 236 and 237, that is, a contact portion between the secondary transfer device 231 and the belt 226. Is sent to At this time, the secondary transfer device 231 is in contact with the belt 226 by driving the transfer roller attaching / detaching unit 250 in the contact direction. The toner image formed on the belt 226 is transferred onto a recording sheet medium at the nip portion, is thermally fixed by a fixing device 234, and is discharged out of the device. Note that the cassettes 240 and 241 and the manual paper feed unit 253 have sheet-less detection sensors 243, 244, and 245 for detecting the presence or absence of a recording sheet medium, respectively. The cassettes 240 and 241 and the manual paper feed unit 253 have paper feed sensors 247, 248 and 249 for detecting a pickup failure of the recording sheet medium, respectively.
[0033]
In the color printer having the above configuration, image formation is executed as follows.
[0034]
First, the operation of transporting the recording sheet medium in the paper feeding unit will be described.
[0035]
The recording sheet media stored in the cassettes 240 and 241 and the manual paper feed unit 253 are conveyed one by one onto the paper feed path 266 by the pickup rollers 238, 239 and 254. When the recording sheet medium on the paper supply path 266 is conveyed to the registration rollers 255 by the pair of paper supply rollers 235, 236, and 237, the passage of the recording sheet medium is detected by the registration sensor 256 immediately before. In this embodiment, when the passage of the recording sheet medium is detected by the registration sensor 256, the conveyance operation is temporarily interrupted after an appropriate time has elapsed. As a result, the recording sheet medium collides with the stopped registration roller 255, and the conveyance is stopped. At this time, the position of the recording sheet medium is fixed so that the end of the recording sheet medium in the traveling direction is perpendicular to the conveyance path, and the recording is performed. When the skew occurs due to the shift of the conveyance direction of the sheet medium with respect to the conveyance path, the conveyance direction of the feeding path is corrected. This process is usually referred to as paper feed registration. The paper feed registration is indispensable for minimizing the inclination of the image forming direction with respect to the recording sheet medium thereafter. After the paper feed registration, the registration roller 255 is activated to supply the recording sheet medium to the secondary transfer device 231.
[0036]
Next, a procedure for forming an image on a recording sheet medium supplied to the secondary transfer device 231 will be described.
[0037]
First, a voltage is applied to the charging device 221 to uniformly negatively charge the surface of the photoconductor 225 at a predetermined charging unit potential. Subsequently, exposure is performed by an exposure device 218 including a laser scanner so that the charged image portion on the photoconductor 225 has a predetermined exposure portion potential, thereby forming a latent image. The exposure device 218 forms a latent image corresponding to an image by turning on and off based on the image signal.
[0038]
A developing bias preset for each color is applied to the developing rollers of the black developing device 219 and the color developing device 223, and the latent image is developed with toner when passing through the position of the developing roller, and is visualized as a toner image. Is done. The toner image is transferred to the belt 226 by the transfer device 220, further transferred to the recording sheet medium conveyed from the paper feeding unit by the secondary transfer device 231, and then to the fixing device 234 via the fixing conveyance belt 230. Is conveyed. The fixing device 234 is charged by pre-fixing chargers 251 and 252 in order to supplement the toner attraction force and prevent image disturbance, and after the toner image is heat-fixed by the fixing roller 233, the discharge flapper 257. As a result, the transport path is switched to the paper discharge path 258 side, and the paper is directly discharged to the paper discharge tray 242.
[0039]
During full-color printing, four color toners are superimposed on the belt 226 and then transferred to recording paper. The toner remaining on the photoconductor 225 is charged by a preliminary cleaning device (not shown) so that the toner is easily cleaned, and is removed and collected by the cleaner device 222. Finally, the photoconductor 225 is removed from the photoconductor 225 (not shown). The charge is uniformly removed to around 0 volts in preparation for the next image forming cycle.
[0040]
The image forming timing of the color printer is controlled based on a predetermined position on the belt 226. The belt 226 is stretched around rollers including a drive roller 227, a tension roller 228, and a backup roller 229, and a predetermined tension is applied by the tension roller 228.
[0041]
A reflection sensor 224 for detecting a reference position is disposed between the driving roller 227 and the roller 229. The reflection sensor 224 detects a marking on a reflection tape or the like provided at the end of the outer peripheral surface of the belt 226 and outputs an I-top signal.
[0042]
The circumference of the photoconductor 225 and the circumference of the belt 226 are in an integer ratio represented by 1: n (n is an integer). With this setting, the photoconductor 225 rotates an integer while the belt 226 makes one rotation, and returns to the same state as one before the rotation of the belt 226, so that four colors are superimposed on the intermediate transfer belt 226. At the time of matching (the belt makes four revolutions), it is possible to avoid color shift due to uneven rotation of the photoconductor 225.
[0043]
In the image forming apparatus of the intermediate transfer system as described above, after detecting the I-top signal, the exposure is started by the exposure device 218 including a laser scanner after a predetermined time has elapsed. Further, as described above, while the belt 226 makes one rotation, the photoconductor 225 rotates an integer and returns to the same state as one before the rotation of the belt 226, so that a toner image is always formed at the same position on the belt 226. You. Although the toner image size also changes depending on the paper size, there is a range on the belt 226 where the toner image never covers.
[0044]
Further, the belt 226 has a belt length capable of forming a toner image for two images in the case of a short paper size image. In particular, the belt 226 has two belts for forming a color image in which four colors are superimposed. The productivity can be improved by making it possible to form the image in only four rotations of the belt.
[0045]
Subsequently, an operation when an image is formed on the back surface of the recording sheet medium will be described in detail.
[0046]
When forming an image on the back surface of the recording sheet medium, first, image formation on the front surface of the recording sheet medium is performed. The operation of forming an image on the front surface has been described in detail above and will not be described here. However, if the image is formed only on the front surface, after the toner image is heat-fixed by the fixing device 234 after image formation, the discharge flapper 257 Is switched to the paper discharge path 258 side, and the paper is discharged to the paper discharge tray 242 as it is. However, when image formation on the back side is performed subsequently, the paper path is switched to the back side path 259 by the paper discharge flapper 257. The recording sheet medium is once conveyed into the two-sided reversing path 261 by the rotation of the reversing roller 260. Thereafter, the recording sheet medium is conveyed into the two-sided reversing path 261 by the width of the sheet medium in the feeding direction, and then the reversing drive of the reversing roller 260 and the driving of the two-sided path conveying roller 262 change the traveling direction by the two-sided reversing path guide. The sheet is switched to a double-sided path 263 with the image formed on the surface facing down.
[0047]
Subsequently, when the recording sheet medium is conveyed on the double-sided path 263 toward the re-feed roller 264, the passage of the recording sheet medium is detected by the re-feed sensor 265 immediately before. In this embodiment, when the passage of the recording sheet medium is detected by the re-feed sensor 265, the conveyance operation is suspended once after a suitable time has elapsed. As a result, the recording sheet medium collides with the stopped re-feed roller 264 and the conveyance is temporarily stopped. At this time, the position of the recording sheet medium is fixed so that the end of the recording sheet medium in the traveling direction is perpendicular to the conveyance path. When the skew occurs due to the conveyance direction of the recording sheet medium being deviated from the conveyance path in the re-feed path, the conveyance direction of the re-feed path is corrected. This process is usually referred to as re-feed registration. The re-feed registration is indispensable in order to minimize the inclination of the image forming direction with respect to the back surface of the recording sheet medium thereafter.
[0048]
After the re-feeding registration, the re-feeding roller 264 is activated to convey the recording sheet medium onto the feeding path 266 again with the front and back reversed. Subsequent image forming operations are the same as the above-described front surface image forming operations, and will not be described here.
[0049]
In this way, the recording sheet medium on which the images are formed on both the front and back sides is directly switched to the discharge path 258 by the discharge flapper 257, and is discharged onto the discharge tray 242 as it is. With the above operation, in this embodiment, it is possible to automatically form an image on both sides of the sheet medium without the operator having to set the front and back of the sheet medium again.
[0050]
Next, a description will be given of a control example of selecting a path and performing fixing in performing fixing in the present embodiment.
[0051]
FIG. 4 is a block diagram showing two fixing units and a path for passing through the fixing units.
[0052]
Reference numeral 401 denotes a paper cassette in which a recording sheet medium is stored, 411 and 421 denote image forming units, and 412 and 422 denote fixing units. In addition, the paths for passing through the respective fixing units will be described with arrows in the drawing. The path 1 passing only through the fixing unit 422 is “P11 → P14”, and the path 2 passing only through the fixing unit 412 is “P12 → P15 ”and the path 3 passing through both the fixing units 412 and 422 are“ P12 → P13 → P14 ”.
[0053]
When the duplex mode is executed in the apparatus having such a configuration, the path 3 is selected for both full-color printing and monochrome printing, and both sides of the recording sheet medium are fixed. In the case of the one-sided mode, the path 3 is selected at the time of full-color printing, the image is fixed once by the fixing unit 412, and is also fixed again by the fixing unit 422. In addition, during monochrome printing in the one-sided mode, the path 1 and the path 2 are alternately selected. As a result, since the recording sheet medium passes through the respective fixing units alternately, it is possible to reduce a decrease in the temperature of the fixing units, and it is possible to maintain the respective fixing units at a relatively low temperature.
[0054]
A control example at the time of fixing at this time will be described.
[0055]
FIG. 5 is a flowchart showing a control operation when fixing is performed, and is started each time one sheet of printing is started.
[0056]
First, in step S101, it is determined whether the recording sheet medium is in the duplex mode. If the mode is the double-sided mode, the process proceeds to step S102, and the path 3 is selected. Next, the process proceeds to step S103, where the image forming unit 411 forms an image on the back surface. Next, the process proceeds to step S104, where the fixing unit 412 fixes the toner image. Then, the process proceeds to step S105, where the image forming unit 421 forms an image on the front surface. Then, the process proceeds to step S106, where the fixing unit 422 performs fixing and discharges. Here, the reason why the back side image is formed first is that the surface on which the image is formed first becomes the upper surface and is discharged at the time of discharge. That is, it is for stacking the recording sheets discharged face down.
[0057]
On the other hand, if the mode is not the duplex mode in step S101, the process proceeds to step S107, and it is determined whether the mode is the color print mode. If the mode is the color print mode, the process proceeds to step S108, and path 3 is selected. Next, the process proceeds to step S109, where the image forming unit 411 forms an image of a color image. Next, the process proceeds to step S110, where the fixing unit 412 performs the first fixing of the toner image. Subsequently, the process proceeds to step S111, where the fixing unit 422 performs the second fixing of the toner image.
[0058]
If the mode is not the color print mode in step S107, that is, if monochrome printing is to be executed, the process proceeds to step S112, and it is determined whether or not a page on which an image is to be formed is an odd page. If the page is an odd page, the process proceeds to step S113, and path 1 is selected. Next, the process proceeds to step S114, where the image forming unit 421 forms an image. Next, the process proceeds to step S115, where the fixing unit 422 fixes the toner image. On the other hand, if the page is not an odd page in step S112, the process proceeds to step S116, and path 2 is selected. Next, the process proceeds to step S117, where the image forming unit 411 forms an image. Next, the process proceeds to step S118, where the fixing unit 412 fixes the toner image.
[0059]
By performing control as described above, it is possible to perform two fixings in the case of the full color print mode and one fixing in the case of the monochrome print mode when performing the fixing.
[0060]
The above is an example of control when fixing is performed.
[0061]
Next, another embodiment will be described with reference to FIG.
[0062]
FIG. 6 is a block diagram showing two fixing units and a path for passing through the fixing units.
[0063]
Reference numerals 601 and 602 denote paper cassettes containing recording sheet media, 611 and 621 denote image forming units, and 612 and 622 denote fixing units. The path through each fixing unit will be described with an arrow in the drawing. The path 1 passing only through the fixing unit 612 feeds recording sheets from the paper cassette 601 to “P21 → P22”, and The path 2 that passes only the unit 622 is “P23” by feeding recording sheets from the paper cassette 602, and the path 3 that passes both the fixing units 612 and 622 is “P21 → P23”.
[0064]
In the apparatus having such a configuration, when the duplex mode is executed, the path 3 is selected for both full-color printing and monochrome printing, and both sides of the recording sheet medium are fixed. In the case of the one-sided mode, the path 3 is selected at the time of full-color printing, and is fixed once by the fixing unit 612, and is also fixed again by the fixing unit 622. Also, during monochrome printing in the one-sided mode, path 2 whose path length is shorter than path 1 is usually selected. However, if the temperature of the fixing unit falls below a specified value due to continuous paper passing, the path is switched to path 1. In addition, even when there is no recording sheet in the paper cassette 601 or 602, the path is switched to the other path. Thus, the respective fixing units can be effectively used, so that the respective fixing units can be kept at a relatively low temperature.
[0065]
By performing control as described above, it is possible to perform two fixings in the case of the full color print mode and one fixing in the case of the monochrome print mode when performing the fixing.
[0066]
【The invention's effect】
According to the present invention, two fixing units are provided, and a path passing through each fixing unit and a path passing through both fixing units are provided. In the color mode, fixing is performed twice, and in the monochrome mode, fixing is performed once. Is controlled so as to perform the switching. For this reason, it is possible to control the fusing at the same low-temperature control as in monochrome copying, while maintaining high-speed productivity on both sides, and reduce the effects of flicker generated by the fixing unit with low power consumption. This has the effect that it is possible to
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an image digital image processing unit. FIG. 2 is a diagram showing an overall configuration of an image forming apparatus. FIG. 3 is a block diagram showing a configuration of a control unit. FIG. FIG. 5 is a flowchart showing a control operation according to a first embodiment of the present invention. FIG. 6 is a block diagram showing a second embodiment of the present invention.
101 CCD
102 Clamp & Amp. & S / H & A / D unit 103 Shading unit 104 Connecting & MTF correction & Original detection unit 105 Input masking unit 106 Selector 107 Color space compression & background removal & LOG conversion unit 108 Delay 109 Moiré removal unit 110 Magnification processing unit 111 UCR & Masking & Black character reflection Unit 112 gamma correction unit 113 filter unit 115 background removal unit 116 black character determination unit 200 control unit 201 platen glass (platen)
202 Document Feeder (DF)
203, 204 Light source (halogen lamp or fluorescent lamp)
205, 206 Reflectors 207-209 Mirror 210 Lens 211 Substrate 212 Printer processing unit (digital image processing unit)
213 External interface (I / F)
214 Carriage 215 Carriage 218 Exposure device 219 Black developing unit 220 Transfer charger 221 Primary charger 222 Cleaner device 223 Color developing unit 224 Reflective sensor 225 Photoconductor drum 226 Belts 227, 228, 229 Roller 230 Fixing and conveying belt 231 Transfer roller 232 Belt cleaner 233 Fixing roller 234 Fixing devices 235, 236, 237 Feed roller pairs 238, 239, 254 Pickup rollers 240, 241 Cassette 242 Discharge trays 243, 244, 245 No sheet detection sensors 247, 248, 249 Feed sensor 250 Transfer roller attaching / detaching units 251 and 252 Pre-fixing charger 253 Manual feed unit 255 Registration roller 256 Registration sensor 257 Paper ejection flapper 258 Paper ejection path 259 Back path 260 Roller 261 duplex reversing path 262 duplex path conveying rollers 263 duplex path 264 refeed roller 265 re-feed sensor 266 paper feeding path 268 belt cleaner detachable unit 280 a printer control I / F
301 CPU
302 Operation unit 303 Memory 401 Paper cassettes 411, 421 Image forming units 412, 422 Fixing unit

Claims (7)

An image forming apparatus comprising: a multicolor toner mode for forming an image by sequentially superimposing toner images of a plurality of colors; and a single color toner mode for forming a single color image using one specific color toner image,
First and second two fixing means for fixing the toner image transferred onto the recording sheet;
A first conveying unit that conveys the recording sheet so as to pass only the first fixing unit,
A second conveying unit that conveys the recording sheet so as to pass only the second fixing unit,
A third transport unit that transports the recording sheet so as to pass through both the first and second fixing units,
Selecting means for selecting the first, second, and third transport means,
An image forming apparatus comprising: a control unit that controls selection by the selection unit between the multicolor toner mode and the single-color toner mode to perform fixing. 2. The image forming apparatus according to claim 1, wherein in the case of the multicolor toner mode, the control unit controls the third conveying unit to pass through two fixing units. The method according to claim 1, wherein the control unit controls the first fixing unit and the second fixing unit so that the fixing unit passes the two fixing units alternately by using the first conveying unit and the second conveying unit alternately. 2. The image forming apparatus according to 1. When the monochrome toner mode is continuously performed, the control unit continuously uses one of the first and second conveyance units, and when the fixing unit cannot be used due to a temperature drop, the control unit switches to the other conveyance unit. The image forming apparatus according to claim 1, wherein the image forming apparatus controls the switching. An abnormality detecting unit that detects an abnormal state of the fixing unit; and when the abnormality detecting unit detects an abnormal state of one of the fixing units, and in the case of the single-color toner mode, the control unit controls the other conveyance unit. 2. The image forming apparatus according to claim 1, wherein control is performed so as to switch to a unit. 2. The image forming apparatus according to claim 1, wherein when the single color toner mode is executed when the state of the image forming apparatus is in a low power state or a sleep state, only one of the fixing units is activated. An image forming apparatus comprising: a multicolor toner mode for forming an image by sequentially superimposing toner images of a plurality of colors; and a single color toner mode for forming a single color image using one specific color toner image,
First and second two fixing means for fixing the toner image transferred onto the recording sheet;
First and second paper feeding paths, which are paths connecting the recording sheet storage and the first and second fixing units,
A transport path that is a path connecting the first fixing unit and the second fixing unit,
First and second discharge paths, which are paths extending from the first and second fixing units to the outside of the apparatus,
A first paper feed path, a first fixing means, a first transport means for transporting the recording sheet so as to pass in the order of the first paper discharge path,
A second paper feed path, a second fixing means, a second transport means for transporting the recording sheet so as to pass in the order of the second discharge path,
A first feeding path, a first fixing unit, a conveying path, a second fixing unit, a third conveying unit that conveys the recording sheet so as to pass in the order of the second discharging path,
Selecting means for selecting the first, second, and third transport means,
In the case of the multi-color toner mode, the third transport unit is selected, and when the single-color toner mode is continuously performed, the first transport unit and the second transport unit are alternately selected. An image forming apparatus comprising: a control unit that controls a unit.

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