JP2005266419A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus of high usability, capable of forming a color image in a state near to a normal output. <P>SOLUTION: The color image forming apparatus provided with a dark color image forming part for developing with dark color developer (yellow, magenta, cyan and black) and a light color image forming part for developing with light color developer (light magenta and light cyan) supplementing the dark color image formation, is provided with a 1st image forming mode of forming a color image with dark color and light color (six-color image forming mode: 6C image forming mode), and a 2nd image forming mode of forming a color image with colors other than at least one dark color (light color toner four-color image forming mode: light color toner 4C image forming mode of forming a color image with yellow, light magenta, light cyan and black). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus having a plurality of color image forming units and switching an operation mode according to the availability of the image forming unit.

  Conventionally, in a color image an image forming apparatus capable of forming yellow (Y), magenta (M), a cyan (C), 4-color developing device for black (Bk), a digital color copying can output colors independently there is a machine. In addition, due to the recent demand for higher image quality for image forming apparatuses, in addition to the four colors Y, M, C, and Bk, a digital having a developer of six colors including light magenta (LM) and light cyan (LC). even color copying machines have been proposed. There has also been proposed a digital color copying machine having a six-color developing device to which special colors such as gold and silver, which are difficult to reproduce by the conventional superposition of four colors, are added.

  There are various types of image forming apparatuses in which the number of developer colors is increased. For example, when considering an image forming apparatus using six types of color developer (toner), generally shown in FIG. Image formation using a tandem type image forming apparatus 1 that forms an image using the number of image carriers (photosensitive members) corresponding to the kind of toner, or one photosensitive member as shown in FIG. An image forming apparatus 102 of the type described above, or an image forming apparatus 103 of the type described in Patent Document 1 as shown in FIG.

  The tandem type image forming apparatus 1 shown in FIG. 1 will be described in detail later, but a developing device 14a in which developers having different spectral characteristics are loaded on six image carriers 11a, 11b, 11c, 11d, 11e, and 11f, respectively. , 14b, 14c, 14d, 14e, 14f, and one by one per one respective image carriers in correspondence, the image forming unit a include those of the image bearing member 1 and the developing device 1 combining the, b, c , D, e, f are arranged in series. With this method, even when the image forming apparatus of six colors is considered as a base, the output speed of the image can be made the same.

  On the other hand, in the image forming apparatus 102 shown in FIG. 17, six developing devices 41, 42, 43, 44, 45, 46 correspond to one image carrier 1, and these developing devices. By rotating the rotary 4 loaded with 41 to 46, any one developing device is selectively positioned at the developing unit 40 which is the portion facing the image carrier 1 to perform development sequentially. Accordingly, a configuration is adopted in which the primary transfer is performed on the intermediate transfer member 5 for each color, the multiple transfer is performed, and the secondary transfer is performed on the recording material when all six colors have been transferred. In this way, it is possible to output a six-color image while minimizing space.

  An image forming apparatus 103 shown in FIG. 18 is in the form of a compromise of the image forming apparatuses 1 and 102 shown in FIGS. The image forming apparatus 103 includes two image forming units, that is, a first image forming unit Sa including the first photosensitive drum 1a and a second image forming unit Sb including the second photosensitive drum 1b. Developers 44 to 46 are provided. This is an image forming apparatus that combines the features of both in a well-balanced manner, and was developed to meet the needs for small size, low cost, and high speed.

  In any type of image forming apparatus, the remaining amount of toner of each color is detected by a known algorithm. Flow as in FIG. 19 are known for example Bk toner remaining amount detection. There is a toner bottle (not shown) for each color, and toner is replenished to each color developer by driving a hopper by a motor such as a stepping motor. When the number of rotations of the stepping motor is counted and exceeds the predetermined value Th (S8000), it is determined that there is no toner (S8001), otherwise there is toner (S8002). Such remaining amount detecting means is provided not only for Bk but also for each color.

  In such a configuration, the control of the image forming apparatus when the toner remaining amount is detected by the toner remaining amount detection has been conventionally performed as shown in FIG. First, the starting process described below (S8), waits until the start signal of the image forming is ON (S80), performs the toner replenishment by the foregoing toner replenishing means in the stage became ON (S81). Performing toner remaining amount detection shown in FIG. 21 for each was replenished color. First, the Bk toner detection is performed by the above-described means (S800). If the Bk toner is not used (S801), a toner-free error status is set (S802). Toners for other colors, that is, Y, M, C, LM, and LC remaining amount detection are performed in the same manner as for Bk described above (S803), and if any color is toner-free (S804), a toner-less warning is issued. to set a (S805).

  In the flow of the remaining toner amount detection, no toner error status (i.e., no Bk toner) If is set (S83), the image forming operation is stopped at the stop processing described later (S84), similarly to the message A will be described later The information is displayed on an operation panel described later (S85). If it is determined in S83 that no toner error is set (that is, no Bk toner is present) and the Bk copy mode is selected by means described later (S86), Bk image formation described later is performed. (S87), the process proceeds to D.

  In S86 a determination, rather than the Bk copy mode (i.e., color copy mode), no toner warning (i.e., no color toner) If is set, is stopped in the stop process (S89), the operation message B below It is displayed on the panel (S90). If it is determined in step S88 that no toner warning has been set (that is, none of the toner is present), and the standard color copy mode (4C copy mode) has been selected by means described later (S91). 4C image formation is performed (S92), and the process proceeds to D. If it is determined in S91 that the high-quality color copy mode (6C copy mode) is selected instead of the 4C copy mode by means described later, 6C image formation described later is performed (S93), and the process proceeds to D. In D, it is determined whether the previous image formation is the last (S94). If it is the last, stop processing is performed (S95), and if not, the process returns to E. As described above, there is conventionally known a control for permitting the use of the Bk copy mode as long as there is Bk toner even if the color toner is used up.

JP-4-204871 discloses

  In the color image forming apparatus having the dark and light toner as described above, the image forming operation of the image forming apparatus is used when the dark cyan toner and the light magenta toner are used but the light cyan toner and the light magenta toner are used. it becomes impossible. When a color image can be sufficiently formed even if light toner is used, such a right of choice is not given to a user who wants to continue the image formation, which is inconvenient. However, if the use of the dark toner is simply stopped, the toner does not appear on the dark color portion of the output image and the color appearance changes greatly. Therefore, some measure has to be devised.

  The present invention has been made based on the above circumstances, and an object thereof is to provide an image forming apparatus that has high usability and can form a color image in a state close to normal output.

  In order to achieve the above object, in the present invention, a dark color image forming unit that performs development with a dark color developer (yellow, magenta, cyan, black), and a light color developer that supplements dark color image formation (light magenta, in the color image forming apparatus having a light color image forming unit that performs development by light cyan), the first image forming mode (the six-color image forming mode for color image formation by dark and light color: 6C image forming mode) and Second image formation mode in which color image formation is performed except at least one dark color (light color toner four color image formation mode in which color image formation is performed using yellow, light magenta, light cyan, and black: light color toner 4C to provide a color image forming apparatus characterized by having an image forming mode) and.

  In the color image forming apparatus according to the present invention, there is a toner remaining amount detecting unit as shown in FIG. 8 for determining whether or not the remaining amount of toner is below a predetermined level in each color image forming unit. And a determination unit (corresponding to the CPU 101) that determines that the use of the image forming unit that uses the toner is not permitted. Then, if at least one dark image forming unit is determined not permitted use in accordance with the flow shown in FIG 7 (S21), performs color image formed by light color toner 4C image forming mode serving the second image forming mode An image forming mode processing unit determination unit (corresponding to the CPU 101) is further included.

  Switching between the 6C image forming mode and the light toner 4C image forming mode is performed by switching the gamma table by means as shown in the block diagram of FIG.

  According to the present invention, light may cyan toner and light magenta toner, since the image forming operation of the image forming apparatus can be continued even if the dark cyan toner and deep magenta toner is used up, it is possible to provide a usability high image forming apparatus . Since the gamma table is switched between the 6C image forming mode and the light toner 4C image forming mode, a color image can be formed in a state close to normal output.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  Figure 1 is a cross-sectional view of a color image forming apparatus embodying the present invention. The color image forming apparatus of this embodiment is an electrophotographic system.

  A color image forming apparatus 1 is roughly divided into an image forming unit (four stations a, b, c, d, e, and f are arranged in parallel, and the configuration is the same), a paper feeding unit, and an intermediate unit. The image forming apparatus includes a transfer unit, a conveyance unit, a fixing unit, an operation unit, and a control unit (not shown).

  Next, each unit will be described in detail.

  The image forming unit is configured as described below.

  That is, the photosensitive drums 11a, 11b, 11c, 11d, 11e, and 11f as image carriers are pivotally supported at the centers and are rotationally driven by a drive motor (not shown) in the arrow direction. Roller chargers 12a, 12b, 12c, 12d, 12e, 12f, scanners 13a, 13b, 13c, 13d, 13e, 13f, developing devices 14a, 14b, in the rotational direction facing the outer peripheral surfaces of the photosensitive drums 11a to 11f, 14c, 14d, 14e, and 14f are arranged.

  The roller chargers 12a to 12f apply a uniform charge amount to the surfaces of the photosensitive drums 11a to 11f. Next, the photosensitive drums 11a to 11f are exposed to light beams such as laser beams modulated by the scanners 13a to 13f according to the recording image signal, thereby forming electrostatic latent images thereon. Further, yellow, visualizes cyan, magenta, black, light magenta, pale six colors of the developer, such as cyan electrostatic latent image by the developing device 14a~14f accommodating (toner), respectively. The visualized visible image is transferred to the intermediate transfer member 30. By the process described above, image formation with each toner is sequentially performed.

  Next, the paper feeding unit includes a portion for storing the recording material P, a roller for conveying the recording material P, a sensor for detecting the passage of the recording material P, and a sensor for detecting the presence or absence of the recording material P. And a guide (not shown) for transporting the recording material P along the transport path.

  21a, 21b, 21c, and 21d are cassettes, 27 is a manual feed tray, and 28 is a deck. 22a, 22b, 22c and 22d are pickup rollers for feeding the recording material P from the cassettes 21a to 21d one by one. In the pickup rollers 22a to 22d, a plurality of recording materials P may be sent out, but only one sheet is reliably separated by the BC rollers 23a, 23b, 23c, and 23d. The recording material P separated by only one sheet by the BC rollers 23 a to 23 d is further transported by the drawing rollers 24 a to 24 d and the pre-registration roller 26, and is transported to the registration roller 25.

  The recording material P stored in the manual feed tray 27 is separated by a BC roller 29 and conveyed to a registration roller 25 by a pre-registration roller 26. Further, a plurality of recording materials P stored in the deck 28 are conveyed to the paper feeding roller 61 by the pickup roller 60, and only one sheet is reliably separated by the paper feeding roller 61 and conveyed to the drawing roller 62. Further, the recording material P is conveyed to the registration rollers 25 by the upstream roller 26.

  The intermediate transfer unit will be described in detail.

  An intermediate transfer belt 30 is made of, for example, PET [polyethylene terephthalate] or PVdF [polyvinylidene fluoride]. A drive roller 32 transmits driving force to the intermediate transfer belt 30, and includes a tension roller 33 that applies an appropriate tension to the intermediate transfer belt 30 by urging a spring (not shown), and a secondary transfer region across the intermediate transfer belt. It is supported by the driven roller 34 to be formed. The driving roller 32 is coated with rubber (urethane or chloroprene) having a thickness of several millimeters on the surface of the metal roller to prevent slippage with the belt. The drive roller 32 is rotationally driven by a stepping motor (not shown). Positions the photosensitive drum 11a~11f and the intermediate transfer belt 30 are opposed to the intermediate transfer Behind the belt 30, primary transfer roller high voltage for transferring the toner image on the intermediate transfer belt 30 is applied 35a~35f There has been placed.

  A secondary transfer roller 36 is disposed so as to face the driven roller 34, and a secondary transfer region is formed by a nip with the intermediate transfer belt 30. The secondary transfer roller 36 is pressed with an appropriate pressure against the intermediate transfer member. Further, on the intermediate transfer belt 30 on the downstream of the secondary transfer region disposed intermediate transfer belt 30 the image forming surface cleaning apparatus 50 for cleaning of the cleaning device 50, as a cleaner blade 51 (made of, Polyurethane rubber or the like is used) and a waste toner box 52 for storing waste toner.

  The fixing unit 40 includes an internal (sometimes with a heat source to the roller) fixing roller 41a and pressure roller 41b is pressurized to the roller having a heat source such as a halogen heater, it has been discharged from the roller pair And an inner discharge roller 44 for conveying the recording material P.

  On the other hand, the recording material P conveyed to the registration roller stops and temporarily stops the rotation of the roller upstream of the registration roller, and the upstream roller including the registration roller 25 rotates in accordance with the image formation timing of the image forming unit. Driving resumes. The recording material P is sent out to a secondary transfer area described later. The recording material P to which the image has been transferred in the secondary transfer area and the image has been fixed in the fixing unit 40 passes through the inner paper discharge roller 44 and is then switched by the switching flapper 73. When the switching flapper 73 is on the face-up discharge side, the recording material P is discharged to the face-up discharge tray 2 by the outer discharge roller 45.

  On the other hand, when the switching flapper 73 is on the face-down paper discharge side, the recording material P is conveyed in the direction of the reverse rollers 72 a, 72 b, 72 c and discharged to the face-down paper discharge tray 3. A plurality of sensors are arranged on the conveyance path of the recording material P to detect the passage of the recording material P. The paper feeding retry sensors 64a, 64b, 64c and 64d, the deck paper feeding sensor 65, the deck pulling out. There are a sensor 66, a registration sensor 67, an internal paper discharge sensor 68, a face-down paper discharge sensor 69, a double-sided pre-registration sensor 70, a double-sided paper re-feed sensor 71, and the like. The cassettes 21a to 21d that store the recording material P are provided with cassette paper presence / absence sensors 63a, 63b, 63c, and 63d that detect the presence or absence of the recording material P, and the manual tray 27 has a recording on the manual tray 27. manual feed tray paper Arinashi sensor 74 for detecting the presence or absence of the timber P is placed, a deck paper Arinashi sensor 75 for detecting the presence or absence of the recording material P in the deck 28 is arranged on the deck 28.

  The control unit includes a control board (not shown) for controlling the operation of the mechanism in each unit, a motor drive board (not shown), and the like.

  3 is disposed on the upper surface of the image forming apparatus 1, and includes a touch panel 400 that serves as both a display device and an input device, a reset key 401, a numeric key 402, a start key 403, a stop key 404, and a user mode key. consisting of 4008. The number of copies to be output can be input from the numeric keypad 402, and a value from 1 to 999 can be set. The set copy output number is displayed on the output number display 4001 in the touch panel 400. When the paper selection key is touched, the display on the touch panel 400 changes to a screen as shown in FIG. Touching the key 40022 selects the cassette 21a, touching the key 40023 selects the cassette 21b, touching the key 40024 selects the cassette 21c, and touching the key 40025 selects the cassette 21d. When the manual selection key 40026 is touched, the feeding of the recording material P from the manual tray 27 is selected. When the automatic determination key 40021 is touched, the size of the original read by the reader unit 104 is determined from a known mechanism, and the paper feed stage is automatically selected. The selection result is displayed on the paper feed stage display 4006. In this example, automatic selection is set.

  When the magnification change key 4003 is touched, the size of the original image read by the reader unit 104 can be changed at a designated magnification. The set magnification is displayed on the magnification display 4007. In this example, the same magnification (100%) is set. Regardless of what magnification is set, it is possible to immediately return to the same magnification setting by touching the equal magnification key 4004 key.

  When the color mode designation key 4005 is touched, the display on the touch panel 400 transitions as shown in FIG. When the high-quality color key 40052 is touched, image formation is performed in the 6-color mode. Image forming Touching standard color key 40053 is carried out in four-color mode. Image forming Touching the black-and-white key 40054 is carried out in Bk mode. When an automatic color selection key 40051 is touched, the type of the image read by the reader unit is color-determined according to a known algorithm, and the Bk and 6-color modes can be automatically switched for each document image. Even in the same color original, the color mode may be automatically changed from the original contents such as a six-color mode if the contents are photographic images and a four-color mode if the contents are presentation materials. Viewing by conducting selective touch panel 400 is changed as in FIG. In this example, the high image quality color mode is selected.

  When the start key 403 is pressed while these modes are set, the copy operation is started in the set mode. If the stop key 404 is pressed during the copying operation, the copying operation is interrupted. When the reset key 401 is pressed, all the modes set above return to the default state. That is, in the case of the color image forming apparatus 1 according to the present embodiment, the process returns to the settings of automatic color selection, magnification 100%, paper feed stage automatic selection, and number of output copies 1. A user mode key 4008 is a key for the user to change device settings.

  Next, a description will be added in accordance with the operation of the apparatus. As an example, the case of conveying the recording material P from the cassette 21a.

  After a predetermined time has elapsed since the image forming operation start signal was issued, first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the transfer material P is conveyed by the paper feed roller 23 to the registration roller 25 via the drawing roller 24 a and the pre-registration roller 26. At that time, the registration roller 25 is stopped and the leading edge of the paper hits the nip portion. Thereafter, the registration roller starts rotating in accordance with the timing at which the image forming unit starts image formation. The rotation timing is set so that the transfer material P and the toner image primarily transferred from the image forming unit onto the intermediate transfer belt exactly coincide with each other in the secondary transfer region.

  On the other hand, in the image forming unit, when an image forming operation start signal is issued, a high voltage is applied to the toner image formed on the photosensitive drum 11f that is the most upstream in the rotation direction of the intermediate transfer belt 30 by the process described above. By the transferred transfer roller 35f, primary transfer is performed on the intermediate transfer belt 30 in the primary transfer region. The primarily transferred toner image is conveyed to the next primary transfer area. In this case, image formation is performed with a delay of the time during which the toner image is conveyed between the image forming units, and the next toner image is transferred with the leading edge of the image aligned on the previous image. The same process is repeated thereafter, and eventually, the six color toner images are primarily transferred onto the intermediate transfer belt 31.

Thereafter, when the recording material P enters the secondary transfer region and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the recording material P. Then, 6-color toner image formed on the intermediate transfer belt is transferred onto the surface of the recording material P by the process described above. Thereafter, the recording material P is guided to the fixing roller nip portion. Then, the roller pair 41a, a toner image by the pressure of the heat and nip 41b is fixed on the paper surface. Then, according to the switching direction of the switching flapper, it is discharged to the face-up paper tray 2 or the face down tray 3.

  FIG. 2 is a control block diagram of the color image forming apparatus 1 according to the present embodiment.

  The CPU 101 performs basic control of the image forming apparatus. A ROM 102 in which a control program is written and a work RAM 103 for processing are connected to the CPU 101 via an address bus or a data bus. The printer unit 100 is connected to loads such as a motor, a clutch, and a sensor (not shown) for performing an image forming operation. The CPU 101 executes an image forming operation according to the contents of the control program. An operation unit 4 is connected to the CPU 101. Further, a reader unit 104 that converts a document image into digital data, an image processing unit 105 that performs image processing on the digital data, and an HDD 106 that stores image data, an operation mode setting of the image forming apparatus, and the like are connected to the CPU 101. It is. Network I / F107 is the interface for data input and output to an external host PC108 connected via a network, for example, stores the image data sent through the network from the host PC108 the HDD 106, printer unit 100 Or the image data read by the reader unit 104 can be stored in the HDD 106 and output to the host PC 108 via the network.

  Next, the operation of the color image forming apparatus 1 according to the present embodiment when there is no toner will be described.

  FIG. 7 is a flowchart for determining the operation when there is no toner.

  When the start key 403 is pressed in a state where the copy mode is set by the method described above, a start process as shown in FIG. 9 is performed (S1). (A) explains the operation of only the Bk station. First, the Bk drum 11a, starts driving the scanner 13a. However, it takes time until the scanner 13a is driven stably, and in the case of the color image forming apparatus 1 according to the present embodiment, it takes about 3.5 seconds. Life of the photosensitive drum 11a is also depends on the cumulative time during which a high voltage is applied, by aligning the rising completion of the high voltage to rise completion of the scanner 13a, thereby achieving a long life.

  After raising the charging AC bias to be applied to the roller charger 12a, a transfer DC bias is applied to the primary transfer roller 35a. Then, a charging DC bias is applied to the roller charger 12a, and a developing DC bias is applied to a sleeve (not shown) in the developing device 14a. Further, after a sleeve motor for driving the sleeve is rotated, a developing AC bias is applied. (B) is a process for preparing a high voltage start-up necessary for the image forming process in order to form a six-color image. The start-up method for each color is the same as the Bk start process in (a). A high voltage start-up of the member was replaced with an oblique line. The start-up of each color is delayed by an interval (image gap) for each image forming unit cf. In the case of the color image forming apparatus 1 according to the present embodiment, the image forming units a to f are provided at intervals of 100 mm, and the image conveyance speed by the intermediate transfer belt 30 is 130 mm / s. The delay amount is set to 770 ms.

  When an image formation start signal is issued from the CPU 101 in this state (S10), toner supply is performed by a known mechanism in parallel with the image forming operation (S11). The toner remaining amount detection shown in FIG. 8 is performed for each color for which toner is supplied. First, Bk no-toner detection is performed by a known algorithm (S120). If no Bk toner is present (S121), a no-toner error status is set (S122). Y, M, and C remaining amount detection is also performed in the same manner as Bk (S123). If any color is out of toner (S124), a toner-less warning is set (S125).

  Further, LM and LC remaining amount detection is performed in the same manner (S126), and if any of the colors is free of toner (S127), a light toner free warning is set (S128). If no toner error status (that is, no Bk toner) is set in the toner remaining amount detection flow (S13), the image forming operation is stopped by a stop process described later (S14), and message A shown in FIG. Is displayed on the touch panel 400 in the operation unit 4 (S15), and the job is canceled when the OK key 4009 is touched on this screen. As shown in FIG. 10, the stop process is completely opposite to the start process, and each high voltage used in the image forming process is lowered and the motor is stopped. Here, (a) shows only the Bk station, and (b) shows stop processing for each color. In (b), the method of lowering the stations other than Bk is the same as the Bk stop process in (a), so the high voltage rise of each member was substituted with an oblique line.

  If it is determined in S13 that no toner error is set (that is, no Bk toner is present) and the monochrome mode is selected (S16), Bk image formation is performed (S17), and the process proceeds to A. . If it is determined in S16 that the Bk image is not formed (that is, color copy) and the light toner-less warning is set (that is, no LM / LC toner) (S18), the process is stopped by the stop process (S19). the message B shown in FIG. 12 displayed on the touch panel 400 (S20). If an OK key 4010 is touched on this screen, the job is canceled. If it is determined in S18 that no light toner warning is set (that is, LM / LC toner is not used) and no toner warning is set (that is, Y / M / C toner is not used). (S21), it is determined whether or not a later-described light toner 4C image formation mode is set (S22). If so, light toner 4C image formation is performed (S23), and the process proceeds to A.

  On the other hand, if it is not the light toner 4C image formation mode, it is stopped by the stop process (S24), and the message C shown in FIG. 13 is displayed on the touch panel 400 (S25). In this screen, the key input is waited (S26), and when the OK key 4011 is touched (S27), the light toner 4C image forming mode is set (S28), and the process returns to C.

  On the other hand, when the cancel key 4012 is touched in S27, the job is canceled. In S21 in decision no toner warning is not set if (i.e., both some of the toner), it is determined whether high-quality color mode or standard color mode (S29), the 4C imaging if standard color mode performed (S30), the process proceeds to A. On the other hand, if it is determined in S29 that the high quality color mode is selected, 6C image formation is performed (S31), and the process proceeds to A. In A, it is determined whether the previous image formation is the last (S32). If it is the last, stop processing is performed (S33), and if it is not the last, the process returns to B.

  Next, the light toner 4 image forming mode will be described with reference to FIG.

  The image sensor (not shown) in the reader unit 104, the original is photoelectrically converted. Original image by the image sensor is color-separated into RGB (Red, Green, Blue), the reader unit 104 converts the received voltage an image signal with same AD converter (not shown) of the leader portion 104 into a digital value of 0 to 255 , it transferred as image data to the CPU 101. The CPU 101 once buffers the received image data in the HDD 106. In parallel, the CPU 101 reads the status (STS) of the printer unit and determines the image forming mode.

  When the CPU 101 issues an image formation start signal to the printer unit 100, the RGB image data is sequentially read from the HDD 106 and transferred to the image processing unit 105. The CPU 101 outputs a γLUT (γ-Look Up Table) select signal (SEL) to the image processing unit 105 according to the previously determined image forming mode. If the image formation mode is 6-color image formation, 6CγLUT 1051 is selected, and YMCBk, LM, and LC image data are transmitted to the printer unit 100 via the CPU 101. Concentration output of this time, for example, magenta is as shown in FIG. Image data that produces a light magenta amount in the low density region and a larger magenta amount in the high density region is generated as YMCBk, LM, and LC image data from the RGB data by the 6CγLUT 1051. Incidentally are you light magenta and deposition rate of magenta at 255 level just intermediate level 128 near the extent by 50%, in order to make inconspicuous the switching portion of the used toner.

  On the other hand, if it is the light toner 4C image formation mode, 6C′γLUT 1050 is selected, and YMCBk, LM, and LC image data are transmitted to the printer unit 100 via the CPU 101. For example, magenta output at this time is as shown in FIG. 16, and magenta is not output. At this time, since magenta toner is not consumed, color image formation can be continued using light magenta toner.

  The present invention is applicable to a color image forming apparatus that has a plurality of color image forming units and switches the operation mode according to the availability of the image forming unit.

1 is a cross-sectional view of a main part of a printer unit of a digital color copying machine showing an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram for explaining a printer control unit of the printer unit shown in FIG. 1. It is a figure explaining the structure of the operation part connected to the image control part shown in FIG. It is a figure explaining the display structure of the operation part shown in FIG. It is a figure explaining the display structure of the operation part shown in FIG. It is a figure explaining the display structure of the operation part shown in FIG. 6 is a flowchart illustrating an example of control determination when no toner is detected in the image forming apparatus according to the present invention. Is a flowchart illustrating a status set no toner in the image forming apparatus according to the present invention. Is a timing chart illustrating the starting process. Is a timing chart for explaining the stop processing. It is a figure explaining the display structure of the operation part shown in FIG. It is a figure explaining the display structure of the operation part shown in FIG. It is a figure explaining the display structure of the operation part shown in FIG. It is a block diagram explaining the switching process of a color mode. Is a graph illustrating the output from 6CγLUT shown in FIG. Is a graph illustrating the output from 6C'γLUT shown in FIG. It is a schematic block diagram which shows an example of the conventional image forming apparatus. It is a schematic block diagram which shows an example of the conventional image forming apparatus. It is a flowchart explaining the algorithm of the conventional toner absence detection. 10 is a flowchart for explaining an example of control determination when no toner is detected in a conventional image forming apparatus. 10 is a flowchart for explaining a tonerless status set in a conventional image forming apparatus.

Explanation of symbols

4 operation unit 11 photosensitive drum 35 the primary transfer roller 30 the intermediate transfer belt 36 secondary transfer roller 100 printer unit 101 CPU
104 Reader unit 105 Image processing unit

Claims (4)

In a color image forming apparatus having a dark color image forming unit that performs development with a dark color developer and a light color image forming unit that performs development with a light color developer that supplements dark color image formation,
A color image forming apparatus comprising: a first image forming mode for forming a color image with dark and light colors; and a second image forming mode for forming a color image excluding at least one dark color. .   Dark image forming unit, yellow, magenta, cyan, black, color image forming apparatus according to claim 1, wherein the light color image forming unit is light magenta, light cyan.   A determination unit configured to determine whether or not to permit the use of the image forming unit when the remaining amount of developer in each color image forming unit is equal to or lower than a predetermined level, and the determination unit prohibits the use of at least one dark color image forming unit; The color image forming apparatus according to claim 1, further comprising an image forming mode processing unit configured to form a color image in the second image forming mode when the determination is made.   3. The color image forming apparatus according to claim 1, wherein a gamma different from that in the first image forming mode is used in the second image forming mode.

Images