JP2007155832A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for forming color images while achieving remarkable miniaturization. <P>SOLUTION: A tandem system color digital printer 1 comprises an imaging unit 2M having a developing device 6M storing a developer including a magenta-based toner, an imaging unit 2C having a developing device 6C storing a developer including cyan-based toner, and an imaging unit 2K having a developing device 6K storing a developer including a black-based toner as an imaging unit. The printer forms color images by toner images of three colors of magenta, cyan and black. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for forming a color image.

In the field of color image forming apparatuses, copying machines and printers that form color images using toners of at least four colors of C (cyan), M (magenta), Y (yellow), and K (black) have been developed. Has been done.
In such a copying machine, for example, image forming units for each color of C, M, Y, and K are arranged along the transfer belt, and each color toner image formed by each image forming unit is placed on the intermediate transfer belt. There is a so-called tandem type in which the toner images are sequentially superimposed and transferred, and the transferred toner images are collectively transferred onto a recording sheet. In the tandem system, color images can be formed with a single sheet passing, and therefore, the copying process can be speeded up.
Editor Electrophotographic Society "Continued Fundamentals and Applications of Electrophotographic Technology" Published by Corona Co., Ltd. November 15, 1996 55

In general, a copying machine or the like is often installed in a limited space such as in a company office, and it is desired to make it as small as possible. However, in the configuration in which the four color image forming units are arranged as in the tandem method, the size cannot be significantly reduced.
Such a problem is not limited to the tandem system, and can also occur in a device that forms a color image with toner images of at least four colors of C, M, Y, and K, such as a so-called transfer drum system and an intermediate transfer body system.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method capable of forming a color image while realizing a significant reduction in size as compared with the related art. Yes.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image forming unit having developing units for magenta, cyan, and black except yellow, and magenta, cyan, and black developed by each developing unit. A color toner image is transferred onto a transfer medium to form a color image.

In this way, it is possible to form a color image, and the apparatus main body is significantly larger than an image forming apparatus having a yellow color developing unit in addition to a magenta, cyan and black color developing unit. Miniaturization and cost reduction can be achieved.
The transfer body is a transfer material that is transported on an intermediate transfer body or a transfer material transport body, and the image forming means is arranged in a line along the moving direction of the intermediate transfer body or the transfer material transport body. A magenta toner image is formed on the first image carrier using a magenta color developing unit, and a cyan color developer is formed. Forming a cyan toner image on the second image carrier using the black portion, and forming a black toner image on the third image carrier using the black developing portion. The toner images thus formed are sequentially transferred and superimposed on the intermediate transfer member or the transfer material.

In this way, a so-called tandem image forming apparatus can be configured, and effects such as an increase in the speed of image formation by the tandem method can be obtained.
Here, when the transfer target is an intermediate transfer member, the black toner image is finally transferred onto the intermediate transfer member, and each toner image superimposed on the intermediate transfer member by transfer is used. Is transferred to another transfer material at a time, and when the transfer target is a transfer material, a black toner image is first transferred onto the transfer material. It is characterized by becoming.

In this way, the black toner image is positioned in the lowest layer on the transfer material such as a recording sheet, and the black color reproducibility can be improved.
The transfer target is an intermediate transfer member or a transfer material transported on a transfer material transport member, and the image forming means has one image carrier, and switches each developing unit to change the color. In each case, a toner image is sequentially formed on the image carrier, and the formed toner image is transferred onto the intermediate transfer member or a transfer material and superimposed.

In this way, a so-called intermediate transfer type or transfer drum type image forming apparatus can be configured, and an effect such as cost reduction can be obtained such that only one image carrier is required by the intermediate transfer type or the like. .
Here, when the transfer target is an intermediate transfer member, a black toner image is finally formed on the image carrier, and each toner image superimposed on the intermediate transfer member by transfer is used. Is transferred to another transfer material in a lump, and when the transfer target is a transfer material, a black toner image is first formed on the image carrier. It is characterized by being configured.

In this way, the black toner image is positioned in the lowermost layer on the transfer material such as a recording sheet, and the black color reproducibility can be improved.
Further, the magenta color developing unit has chromaticity points on the chromaticity diagram as compared with full-color magenta toner used when forming a color image with four colors of magenta, cyan, yellow, and black. Full color used when toner shifted in a direction approaching the yellow hue is stored and / or the cyan development unit forms a color image with four colors of magenta, cyan, yellow, and black It is characterized in that it contains toner in which the chromaticity point on the chromaticity diagram is shifted in the direction approaching the yellow hue than the cyan toner for use.

In this way, the reproducibility of the yellow color of the image finally formed on the transfer material such as a recording sheet can be further improved.
Furthermore, the image forming apparatus includes a control unit, and each of the developing units is mounted at any one of the first, second, and third positions, and is configured to be detachable from the apparatus main body. Determination means for determining at which position a developing unit for which color is mounted, and conversion means for converting input data into reproduction color data of magenta, cyan, and black. The content of the conversion process is changed according to the determination result by the means.

In this way, regardless of the position where the developing unit is mounted, the optimum conversion process according to the combination can be executed, and the color reproducibility can be improved.
In addition, the image forming apparatus includes a control unit, and each of the developing units is mounted at any one of the first, second, and third positions, and is configured to be detachable from the apparatus main body. Determining means for determining which color developing unit is mounted at which position, and determining the suitability of the set state of each developing unit according to the determination result by the determining unit, and the determined result is determined by the user. And a notification means for notifying to.

In this way, the user can check the set state of the developing unit. For example, if the magenta developing unit should be mounted in the first position, the developing unit for black color is erroneously mounted. Even if it does, it becomes possible to correct the error immediately.
Here, the notification means is a display means for displaying the determined result.

In this way, the user can visually confirm the suitability of the set state.
The image forming method of the present invention forms a color image by transferring a magenta, cyan, and black color toner image developed by a developing unit for magenta, cyan, and black colors except yellow to a transfer target. It is characterized by that.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing the overall configuration of a tandem color digital printer (hereinafter simply referred to as “printer”) 1.
As shown in the figure, the printer 1 includes an image forming unit 2M, 2C, 2K corresponding to each of magenta (M), cyan (C), and black (K), and an intermediate transfer that rotates in the direction of arrow A. An intermediate transfer unit 10 including a belt 11, a feeding unit 30, a fixing unit 40, and a control unit 100 are provided, connected to a network, here a LAN, from an external terminal device (not shown). When an execution instruction for a print (print) job is received, color image formation of magenta, cyan, and black is executed based on the instruction. Hereinafter, the reproduction colors of magenta, cyan, and black are represented as M, C, and K, and the M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.

  The image forming units 2M to 2K face the intermediate transfer belt 11 at a predetermined interval from the upstream side in the rotational direction (hereinafter simply referred to as “upstream side”) to the downstream side in the rotational direction (hereinafter simply referred to as “downstream side”). Are arranged in series, and are photosensitive drums 3M, 3C, and 3K as image carriers, chargers 4M, 4C, and 4K disposed around the photosensitive drums, exposure units 5M, 5C, and 5K, and M colors. A developer 6M containing a developer containing a toner of type C, a developer 6C containing a developer containing a toner of C color, and a developer containing a developer containing a toner of K color 6K and cleaners 8M, 8C, 8K and the like.

  The intermediate transfer unit 10 includes a driving roller 12, a driven roller 13, a tension roller 14, primary transfer rollers 7M, 7C, and 7K that face the photosensitive drums 3M to 3K, and an intermediate transfer member that is stretched between the rollers. An intermediate transfer belt 11, a drive motor (not shown) that rotates the drive roller 12, and a cleaner 15 that cleans residual toner on the intermediate transfer belt 11.

The feeding unit 30 includes a paper feed cassette 31 that stores the paper S, a feed roller 32 that feeds the paper S in the paper feed cassette 31 one by one, a transport roller pair 33 that transports the fed paper S, and two A timing roller pair 34 for taking the timing of feeding the paper S to the next transfer position 21 and a secondary transfer roller 35 are provided.
When the control unit 100 receives a print instruction from an external terminal device, the control unit 100 receives a transmitted image signal, converts the received image signal into a digital image signal for M, C, and K colors, and sets the exposure units 5M to 5K. A drive signal for driving is generated. The exposure unit 5M receives a drive signal from the control unit 100, emits a laser beam for forming an M-color image, and performs exposure scanning on the photosensitive drum 3M in the main scanning direction. Similarly, the exposure units 5C and 5K emit laser beams for forming images of C and K colors to expose and scan the photosensitive drums 3C and 3K.

The photosensitive drums 3M to 3K are cleaned by the cleaners 8M to 8K before the exposure, and the surface of the photosensitive drums 3M to 3K is uniformly discharged by the chargers 4M to 4K. When being exposed to the laser beam in the state of being charged uniformly in this way, electrostatic latent images are formed on the surfaces of the photosensitive drums 3M to 3K.
The electrostatic latent images are developed by the developing devices 6M to 6K for the respective colors, whereby toner images as M, C, and K developer images are formed on the surfaces of the photosensitive drums 3M to 3K, respectively. At positions 9M, 9C, and 9K, the images are sequentially transferred onto the rotating intermediate transfer belt 11 by the electrostatic force generated by the voltage applied to the primary transfer rollers 7M, 7C, and 7K disposed on the back side of the intermediate transfer belt 11. Go.

  At this time, the image forming operation for each color is executed while shifting the timing from the upstream side toward the downstream side so that the toner image is primarily transferred to the same position on the intermediate transfer belt 11. As a result, the toner images are superimposed on the intermediate transfer belt 11 in the order of M, C, and K. In this sense, it can be said that the image forming units 2M to 2K and the intermediate transfer unit 10 function as image forming means.

The color toner images superimposed on the intermediate transfer belt 11 are moved to the secondary transfer position 21 by the rotation of the intermediate transfer belt 11.
On the other hand, the sheet S is fed from the feeding unit 30 via the timing roller pair 34 in accordance with the movement timing of the intermediate transfer belt 11, and the sheet S is connected to the rotating intermediate transfer belt 11. The toner images on the intermediate transfer belt 11 are collectively conveyed by the electrostatic force generated by the voltage applied to the secondary transfer roller 35 at the secondary transfer position 21 while being sandwiched between the secondary transfer rollers 35 and conveyed. Transferred onto S (secondary transfer).

Since the toner images are in the order of M, C, K from the bottom on the intermediate transfer belt 11, they are in the order of K, C, M from the bottom on the paper S, and the K-color toner image is positioned at the lowest layer. Will do. In this way, the color reproducibility can be further improved by placing the K-color toner image on the paper S in the state of being positioned at the lowest layer.
The sheet S that has passed through the secondary transfer position 21 is conveyed to the fixing unit 40, where the toner image is heated and pressed to be fixed on the sheet S, and then onto the discharge tray 41 via the discharge roller pair 36. Discharged.

As a result, a color image is formed by toner images of three colors of M, C, and K. However, in the case of monochrome, for example, K color image formation, only the image forming unit 2K is used and the above transfer is performed. Through these steps, a K-color image is formed on the sheet.
As described above, in this embodiment, a configuration in which a yellow (Y) color is not used is employed. This is because the Y color is the toner that has the least influence on the reproduced image and the deterioration of the color reproducibility can be minimized, but the Y color is reproduced only by not using the Y color toner. In this embodiment, the toner of M and C colors is devised. Specifically, the chromaticity point is changed from that of the conventional configuration using Y color.

FIG. 2 is a chromaticity diagram showing chromaticity points of M and C color toners in the L ^* a ^* b ^* color system. Here, for the M and C colors, the white circle plots indicate the chromaticity points of the toner of the conventional configuration (a configuration in which a color image is formed using the Y, M, and C colors), and the square marks are the present implementations. The chromaticity point of the toner in the configuration of the form (configuration of forming a color image without using Y color) is shown.
As shown in the figure, for example, regarding the M-color toner, the toner of this embodiment has a chromaticity point at a position shifted in the red (R) direction as compared with the conventional toner, and the C color. Looking at the system toner, it can be seen that the toner of this embodiment has a chromaticity point at a position shifted in the green (G) direction as compared with the conventional toner.

Here, the red direction means the hue direction of the R (red) color resulting from the mixture of the M color and the Y color. Having a chromaticity point at a position shifted in the red direction means that the hue of the M color is the color of the R color. It means getting close to hue.
Similarly, the green direction means the hue direction of G (green) color by the mixed color of C color and Y color, and having a chromaticity point at a position shifted in the green direction means that the hue of C color is changed to that of G color. It means getting close to hue.
As described above, as the M and C color toners, toners whose chromaticity points are shifted in the direction of R and G colors as compared with the conventional configuration are used. Therefore, the R color (R = M + Y) and G (G = C + Y) color reproducibility can be secured to some extent without Y toner, and reproducibility of frequently used colors such as R and G colors can be improved.

  The shift amount and the shift direction of the chromaticity points of the M-color and C-color toners can be obtained in advance by experiments or the like, and are not limited to the above. The chromaticity point M and C colors shifted in a direction having a directional component approaching the hue of the Y color on the chromaticity diagram with respect to the chromaticity points of the M and C color toners in the conventional configuration. This is because the color reproducibility can be improved by using the system toner.

For example, when JapanColor is used as a reference, the chromaticity point of the M color toner is set to R color (a ^* : 68.5, b ^* : 48.0) under the observation condition of the 2-degree visual field D50. ) Around or very close to the chromaticity point of the C-color toner may be set around or very close to the G color (a ^* : −73.5, b ^* : 25.0). .
Further, even when another color standard such as SWOP (Specifications for Web Offset Publications) or Euro Color is used, the chromaticity point of M-color or C-color toner is made close to the hue of R, G color or Y color. The same effect can be obtained.

In addition, as a manufacturing method of the above-described toner, a method in which a coloring material having the above chromaticity point is contained in a binder resin or the like in a conventional toner manufacturing method is used.
Returning to FIG. 1, each of the image forming units 2M to 2K is configured to be detachable from the apparatus main body. If necessary, for example, when the toner of a certain unit runs out, the user takes out the unit and adds a new one. Can be easily replaced with a new unit. Here, for each unit, a slot (not shown) for storing the unit is provided in the apparatus main body, and a user opens an exterior cover (not shown) on the front side of the apparatus and is stored in each slot. The unit can be attached and detached by pulling the unit toward the front side of the apparatus or by pushing the unit toward the back side of the apparatus. Of course, this configuration is not limited as long as it is detachable.

Further, in this embodiment, as an image forming unit for M and C colors, a developer containing toner of M and C colors having the same chromaticity point as that of a conventional one is accommodated in a developing device. Image forming units 2M ′ and 2C ′ (not shown) are prepared as options, for example, and can be mounted on the apparatus main body instead of the image forming units 2M and 2C.
The other image forming units 2M ′ and 2C ′ have basically the same configuration and size as the image forming units 2M and 2C, but differ only in the chromaticity point of the toner.

  The user can select 2M or 2M ′, 2C or 2C ′ as the image forming unit and attach it to the apparatus main body. Here, each image forming unit has an unillustrated signal output means for outputting an identification signal indicating which color corresponds, for example, a 3-bit signal from an output terminal (not shown). For example, the image forming unit 2M is “001”, 2M ′ is “010”... 2K is “101”, and the like.

  Unit connection terminals 71, 72, 73 are disposed at positions corresponding to the mounting positions of the image forming units 2 </ b> M to 2 </ b> K of the printer 1. The unit connection terminals 71 to 73 are electrically connected to output terminals provided in the image forming unit when the image forming unit is attached to the apparatus main body. The identification signal output from each image forming unit is sent to the control unit 100 via the unit connection terminals 71 to 73.

  When the set state determination unit 109 (FIG. 3) of the control unit 100 receives the identification signal from each imaging unit, which imaging unit is mounted at which position from the 3-bit information indicated by the identification signal. Judge whether there is. Specifically, for example, when the identification signal received through the unit connection terminal 71 is “001”, the image forming unit 2M is mounted at the position corresponding to the unit connection terminal 71 (the left end of the apparatus). Suppose that Hereinafter, the position corresponding to the unit connection terminal 72 is referred to as “device center”, and the position corresponding to the unit connection terminal 73 is referred to as “device right end”.

Each image forming unit has a label (not shown) indicating information (name, etc.) for the user to identify which color the unit corresponds to and which chromaticity point is filled with toner. ) Is affixed so that the user can identify each unit without making a mistake by looking at the label.
FIG. 3 is a block diagram illustrating a configuration of the control unit 100.

As shown in the figure, the control unit 100 includes, as main components, a CPU 101, a communication interface (I / F) unit 102, an image processing unit 103, an image memory 104, an LD driving unit 105, and a RAM 106. A ROM 107, a proper information storage unit 108, and a set state determination unit 109, and can exchange data via the bus 110.
The communication I / F unit 102 is an interface for connecting to a network such as a LAN such as a LAN card or a LAN board.

The set state determination unit 109 receives an identification signal from each image forming unit currently mounted via the unit connection terminals 71 to 73, and determines which image forming unit is mounted at which position. To do.
The appropriate information storage unit 108 includes a nonvolatile memory, and stores appropriate information indicating which combination is appropriate as a combination of image forming units when performing image formation.

FIG. 4 is a schematic diagram illustrating an example of the content of appropriate information.
As shown in the drawing, the appropriate information indicates an example of an appropriate combination of image forming units mounted at positions on the left end of the apparatus, the center of the apparatus, and the right end of the apparatus. Specifically, pattern 1 shows an example in which M, C, and K image forming units are mounted in the order of the left end, the center, and the right end of the apparatus.
The pattern 2 is a combination of M ′, C ′, and K. Needless to say, M and C are the most suitable combinations of toners from the viewpoint of reproducibility. For example, charts such as graphs in company offices can be expressed in color even if they cannot be reproduced accurately. For a user who thinks it is good, convenience may be improved by using M ′ and C ′ as a combination of image forming units, and pattern 2 is within the proper range. Depending on the adjustment of the chromaticity point of the toner, it is possible to consider the case of a combination of M ′ and C or M and C ′.

  Returning to FIG. 3, the image processing unit 103 is a known image signal such as shading for image signals received via the communication I / F unit 102, for example, red (R), green (G), and blue (B) data. A correction process is performed. Each pixel is converted into a digital image signal (image data) for reproduction colors of M, C, and K, and the converted image data is stored in the image memory 104. This conversion is performed by the MCK color conversion unit 1031.

FIG. 5 is a block diagram illustrating a configuration of the MCK color conversion unit 1031.
As shown in the figure, the MCK color conversion unit 1031 includes a selection unit 1130 and conversion processing units 1131 and 1132.
The selection unit 1130 converts the conversion from the R, G, and B colors to the M, C, and K colors according to the combination of the image forming units (patterns 1 and 2). Select whether to use the processing unit.

The conversion processing units 1131 and 1132 perform conversion from R, G, B to M, C, K using a predetermined conversion formula.
This conversion formula is based on those used in image processing such as conventional UCR (under color removal), BP (black generation), γ correction, etc., and the coefficients for Y, M, C, K color data are In consideration of the combination of the chromaticity point of the toner and the image forming unit, etc., an optimum value is determined for each combination by experiments.

Here, the data of the conversion formula corresponding to the case of pattern 1 is stored in advance in the conversion processing unit 1131, read at the time of conversion, and used for the processing. For pattern 2, the conversion processing unit 1132 stores the data of the conversion formula in advance. The contents of the conversion process by the MCK color conversion unit 1031 will be described later.
In addition, it is not restricted to the method of devising the value of a coefficient using the conventional conversion formula, For example, the new conversion formula corresponding to the structure of this invention which forms a color image using only M, C color is experimentally etc. You may ask. In addition, as long as data can be converted based on a predetermined condition, various methods such as a conversion table can be used without being limited to equations.

Returning to FIG. 3, under the control of the CPU 101, the LD driving unit 105 reads M, C, and K color image data for each scanning line from the image memory 104, and drives the exposure units 5M to 5K.
The ROM 107 is a program related to the image forming units 2M to 2K, the image forming operation in the intermediate transfer unit 10 and the sheet S feeding operation by the feeding unit 30, and the program related to the set state notifying process for notifying the user of the image forming unit set state. Is stored.

The RAM 106 serves as a work area when the CPU 101 executes a program.
The CPU 101 reads out a necessary program from the ROM 107 and controls the image formation, feeding operation, etc. in a unified manner while taking timing to execute a smooth printing operation. Also, a set state notification process is executed.
FIG. 6 is a flowchart showing the contents of the set state notification process. This process is executed when at least one image forming unit is replaced.

  For example, a switch (not shown) for detecting the image forming unit is determined to be exchanged. Specifically, the switch is turned on when the image forming unit is attached and turned off when the image forming unit is not attached. Is provided in the apparatus main body, and a method may be considered in which replacement is performed when the signal from the switch changes from off to on. Of course, any method may be used as long as it can detect attachment / detachment of the image forming unit.

As shown in the figure, the control unit 100 receives identification information from each mounted image forming unit (step S11), and from the received identification information, the set state of the mounted image forming unit, that is, which It is determined which color image forming unit is attached to the position (step S12). This determination is performed by the set state determination unit 109.
Then, the determined setting state of the image forming unit is displayed on the operation panel 50 (step S13).

FIG. 7 is a diagram showing an example in which the setting state of the image forming unit is displayed by a message.
FIG. 7A is a diagram illustrating an example of a screen 201 on which a message indicating that the image forming units are attached in order of M, K, and C in order from the left end of the apparatus. FIG. 7B is a diagram illustrating an example of a screen 202 on which messages indicating that the devices are mounted in the order of M ′, C ′, and K from the left end of the apparatus are displayed.

  Returning to FIG. 6, the control unit 100 determines whether or not the set state is appropriate (step S14). Here, the determination as to whether or not the image is appropriate is made based on whether or not the combination of the mounted image forming units matches one of the patterns 1 and 2 indicated by the aptitude information. Specifically, as the set state, for example, when the image forming units M, C, and K are mounted in the order of the left end, the center, and the right end of the apparatus, it corresponds to the pattern 1 and is thus determined to be appropriate. If the order is M, K, and C as in the example of FIG. 7A, it is determined that the pattern is not appropriate because there is no corresponding pattern. On the other hand, the example of FIG. 7B corresponds to the pattern 2 and is appropriate.

If it is determined that it is not appropriate ("NO" in step S14), a message indicating that and a guide for setting the appropriate state is displayed on the operation panel 50 (steps S15 and S16).
FIG. 7C is a diagram illustrating an example of a screen 203 displayed when the setting is not appropriate. This figure is a display example corresponding to the case of FIG. 7A, indicating that the set state is not appropriate, and that the positions of the image forming units K and C may be exchanged as a guide for making it appropriate. This is an example in which a message is displayed. In addition, although the message indicating that it is not appropriate and the message of the guide for making it appropriate are displayed on one screen, separate screens may be provided and switched to be displayed.

When the control unit 100 determines that the image forming unit has been set properly by the user or the like ("YES" in step S14), the control unit 100 displays the screen 201 displayed on the operation panel 50. Etc. are turned off (step S17), and the process is terminated.
In the above description, it is determined whether or not it is appropriate. However, the present invention is not limited to this. For example, it may be determined whether or not it is optimal. In this case, in step S14, it is possible to adopt a configuration in which it is determined that the pattern 1 is optimum and the other cases are not optimum. When it is determined that the pattern 2 is not optimal, for example, the screen 204 in FIG. 7D may be displayed on the operation panel 50. The screen 204 shows a message indicating that an optimal state can be obtained by replacing the M ′ and C ′ image forming units with the M and C image forming units.

In addition, it is only necessary to be able to notify the user, so it is not limited to message display, for example, voice, lighting of a lamp indicating that, or display means such as a display for an external terminal device such as a personal computer as a job issuer Notification processing such as giving an instruction to display that may be performed. This can also be applied to a second embodiment described later.
FIG. 8 is a flowchart showing the contents of conversion processing in the MCK conversion unit 1031.

  As shown in the figure, when R, G, B color data after correction processing such as shading is received (step S101), a pattern indicating the set state of the image forming unit is determined (step S102). This determination is performed by executing the same processing as the processing in steps S11, S12, and S14. Specifically, the determination result by the set state determination unit 109 and appropriate information are referred to, and from the determination result, it is determined which image forming unit is mounted at which position. It is determined which pattern corresponds to.

If it is determined that it is pattern 1 (“YES” in step S103), the conversion processing unit 1131 is selected as a processing unit to be used for conversion (step S104).
Then, the received R, G, B color data is transmitted to the selected conversion processing unit, here 1131 (step S105).
The conversion processing unit that has received the R, G, B color data, here, 1131 reads out the data of the conversion formula stored in itself, and uses the conversion formula to convert the R, G, B color data into M. , C, K color image data (step S106). Then, the converted image data is output to the image memory 104 (step S107), and the process ends.

If it is determined that the pattern is 2 (“NO” in step S103), the conversion processing unit 1132 is selected as a processing unit to be used for conversion (step S108), the process proceeds to step S105, and the conversion is performed in steps S105 to S107. Data transmission to the processing unit 1132, conversion to M, C, K, and data output are performed.
In the above description, it is determined that one of the patterns 1 and 2 is determined as the combination of the image forming units. However, for example, when the image forming unit is set in a combination other than this, the set state described above follows step S102. A configuration may be adopted in which the notification processing is executed and the processing after step S103 is executed after the setting state is determined to be appropriate by the user's resetting operation.

As described above, in the present embodiment, the tandem color digital printer is configured to include only the image forming units for M, C, and K colors, so that deterioration in color reproducibility is minimized. A color image can be formed, and the apparatus can be greatly reduced in size and cost can be realized by not including a Y-color image forming unit.
In addition, since the image forming unit for K color is provided, if only three image forming units of M, C, and Y are provided, a black color can be obtained by simply superimposing the M, C, and Y color toners. This means that black characters such as documents used in business can be reproduced more neatly without the fact that the so-called black color cannot be reproduced.
(Second Embodiment)
In the first embodiment, the configuration example of the tandem color digital printer has been described. However, in this embodiment, a so-called intermediate transfer body color digital printer is used, which is different in this point. Hereinafter, description will be made mainly on parts different in configuration from those of the first embodiment, description of the same parts is omitted, and the same reference numerals are given.

FIG. 9 is a diagram showing an overall configuration of the printer 81 according to the present embodiment.
As shown in the figure, the printer 81 is greatly different from the printer 1 in the first embodiment in an image forming section 82 and an intermediate transfer section 90 as image forming means.
The intermediate transfer unit 90 includes a drive roller 92, a driven roller 93, a tension roller 94, an intermediate transfer belt 91 as an intermediate transfer member stretched around these rollers, and the like.

The image forming unit 82 includes a photosensitive drum 83, a charger 84, an exposure unit 85, a developing unit 86, a primary transfer roller 87, a cleaner 88, and the like.
The exposure unit 85 includes a laser diode, and exposes the surface of the photosensitive drum 83 for each reproduction color based on a drive signal from the control unit 150.
The photosensitive drum 83 is uniformly charged by the charger 84 after the residual toner on the surface of the photosensitive member is removed by the cleaner 88 before receiving the exposure, and the exposure is performed in such a uniformly charged state. In response, an electrostatic latent image is formed on the photoreceptor on the surface of the photoreceptor drum 83.

  The developing unit 86 is configured by inserting three developing units 86M, 86C, and 86K containing a developer containing M, C, and K color toners into a developing rack 98, and a support shaft 99 of the developing rack 98 is provided. At the center, it is rotationally driven in the direction of arrow B by the development switching motor 97, and so that any development unit corresponding to the next reproduction color is located at the development position facing the photosensitive drum 83. The electrostatic latent image on the surface of the photosensitive drum 83 is developed under the rotation control by the control unit 150. This figure shows a state in which the development unit 86M for M color is located at the development position.

  The connection terminals 71 to 73 provided in the developing rack 98 have the same functions as those of the first embodiment, and when the developing unit is attached, output terminals (not shown) provided in the developing unit. And an identification signal for identifying the developing unit output from the output terminal to the control unit 150. Accordingly, the control unit 150 can determine which developing unit is mounted at which position of the developing rack 98.

The apparatus main body is provided with a sensor (not shown) for detecting the rotation angle of the developing rack 98, and the control unit 150 determines which developing unit is located at the developing position based on a detection signal from the sensor. You can determine whether you are doing.
The toner image formed on the photosensitive drum 83 is transferred onto the intermediate transfer belt 91 by the electric field generated between the primary transfer roller 87 and the photosensitive drum 83 at the primary transfer position 96. At this time, the image forming operation on the photosensitive drum 83 is performed by switching between exposure and developing units so that the toner images of M, C, and K colors are transferred to the same position on the intermediate transfer belt 91 in that order. This is executed by controlling the timing. As a result, the color toner images are sequentially superimposed on the intermediate transfer belt 91 to form a color toner image.

When the primary transfer of the toner images of the respective colors onto the intermediate transfer belt 91 is completed, the toner images of the respective colors are collectively transferred onto the paper S at the secondary transfer position 21 and are then transferred onto the paper S at the fixing unit 40. After fixing, the toner is discharged onto the discharge tray 41.
FIG. 10 is a block diagram illustrating a configuration of the control unit 150.
As shown in the figure, the control unit 150 is basically the same as the control unit 100 in the first embodiment, except that the rotation control of the development switching motor 97 is performed, and an image forming operation for one color. In order to perform control for starting the image forming operation for the next color after finishing the process, the LD drive unit 151 reads the image data in the order of M, C, and K colors and sends a drive signal to the exposure unit 85. Is different.

  In the first embodiment, the image forming unit 2M and the like are detachable. However, in the present embodiment, the image forming unit 2M is detachable in units of developing units, and the user is stored in the developing rack 98. The developing units 86M to 86K can be individually detached from the apparatus main body and attached. Similarly to the first embodiment, development units 86M ′ and 86C ′ including toners having chromaticity points corresponding to those of M and C colors are prepared as options. For C color, it is possible to select and use the developing units 86M and 86M ′ and 86C and 86C ′. The control of the MCK conversion unit 1031 in this case is the same as that in the first embodiment. That is, the conversion processing units 1131 and 1132 are selected from the conversion processing units 1131 and 1132 in accordance with the combination and mounting position of the three developing units mounted.

As described above, in the intermediate transfer body system, the color image is formed with three colors of M, C, and K. Therefore, the developing unit can be made smaller than the case of using four colors including the Y color. Significant downsizing can be realized.
Compared to the four-color configuration, the time required for forming a color image on one sheet can be shortened by the amount that the Y-color image forming process is unnecessary, and productivity can be improved. In addition, since the driving time of the members such as the photosensitive drum and the belt with respect to one sheet is shortened, the consumption of each member by driving can be further reduced, and the replacement cycle of each member can be made longer. Thus, the reliability of the apparatus can be improved.

  The present invention is not limited to an image forming apparatus, and may be a color image forming method. Furthermore, the method may be a program executed by a computer. The program according to the present invention includes, for example, a magnetic disk such as a magnetic tape and a flexible disk, an optical recording medium such as a DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, and PD, and a flash memory recording medium. It can be recorded on various computer-readable recording media, and may be produced, transferred, etc. in the form of the recording medium, wired and wireless various networks including the Internet in the form of programs, In some cases, the data is transmitted and supplied via broadcasting, telecommunication lines, satellite communications, or the like.

  Further, the program according to the present invention does not have to include all modules for causing the computer to execute the processing described above. For example, a separate information process such as a communication program or a program included in an operating system (OS) is performed. You may make it make a computer perform each process of this invention using the various general purpose programs which can be installed in an apparatus. Accordingly, it is not always necessary to record all the modules on the recording medium of the present invention, and it is not always necessary to transmit all the modules. Further, there are cases where predetermined processing can be executed using dedicated hardware.

(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the first embodiment, a message indicating that the image forming unit is inappropriate is displayed until the image forming unit is reset to an appropriate state. However, the user does not replace the image forming unit. In a case where an inappropriate state continues for a predetermined period of time, for example, a method for displaying another message for canceling or discarding a print job to be executed thereafter and giving a warning and executing processing such as cancellation It may be taken.

  (2) Although the arrangement order of the image forming units is defined as patterns 1 and 2, for example, the type of the image forming units used is appropriate but the arrangement order is not appropriate. , C, and M are arranged in this order, the following processing can also be performed. That is, a message indicating that the arrangement order is different is displayed, and a message for accepting selection input as to whether or not to ignore the arrangement order is displayed. When the user selects to ignore, the image is formed in the arrangement order. It is set as the structure which performs operation | movement.

In this configuration, the image forming order is changed from the original order of M, C, K to the order of K, C, M, specifically, the K, C, M color toner images are intermediately transferred in that order. This can be realized by changing the timing of charging, exposure, transfer and the like for each of the image forming units 2M to 2K so that the image is primarily transferred onto the belt 11.
Considering that the color reproducibility may change depending on the order of arrangement of image forming units, for example, as appropriate information, information with a separate pattern number assigned to each order of arrangement is used as new information, and each pattern number is supported. It is possible to adopt a configuration in which a conversion processing unit is prepared and a conversion processing unit to be used is selected (the content of the conversion processing is changed) according to the combination and the arrangement order. Specifically, the first conversion processing unit is in the order of M, C, K, the second conversion processing unit is in the order of K, C, M, and the second conversion processing unit is in the order of M, K, C. 3 conversion processing unit and the like.

  (3) Further, the appropriate information and the conversion processing unit itself determine which pattern the combination of the installed image forming units corresponds to, regardless of the arrangement order of the image forming units, in the above embodiment. The conversion processing unit corresponding to the determined pattern may be selected. For example, in the order of K, C, M from the left end of the apparatus, the conversion processing unit 1131 corresponding to the pattern 1 is selected. The above (1) and (2) can also be applied to the second embodiment.

(4) In addition to the patterns 1 and 2, for example, when the image forming unit 2K is attached, monochrome image formation may be permitted.
(5) As an image forming apparatus, any apparatus that forms a color image on a transfer medium such as a sheet using only three image forming units for M, C, and K colors excluding Y color may be used. The present invention is not limited to this, and can be applied to a copying machine, an MFP (Multiple Function Peripheral), a facsimile machine, and the like.

The tandem method is not limited to the above, and for example, a transfer material conveyance body such as a conveyance belt is provided instead of the intermediate transfer belt 11, and a transfer material such as a recording sheet is adsorbed on the transfer material conveyance body. A configuration may be adopted in which the toner images of the respective colors are sequentially transferred onto the transfer material that is conveyed while being held.
Further, the transfer method is not limited to the tandem method or the intermediate transfer member method. For example, instead of the intermediate transfer belt 91 in the second embodiment, a transfer drum as a transfer material conveyance body is provided, and a recording sheet or the like is transferred onto the transfer drum. A so-called transfer drum in which a color image is obtained by rotating a material while being held by suction or the like, and sequentially transferring and superimposing toner images of respective colors formed on the photosensitive drum 83 onto the transfer material. The present invention can be applied to various image forming apparatuses such as a method. The transfer material transport body may be in the form of a drum or a belt as long as it can transport the transfer material, and is not limited thereto. Further, although the intermediate transfer belts 11 and 91 are used as the intermediate transfer member in the first and second embodiments, the intermediate transfer member is not limited to the belt shape, and may be a drum shape, for example.

  In the second embodiment, the developing rack 98 is rotated to sequentially move the developing units for the respective colors to the developing position. However, the present invention is not limited to this method. For example, the developing units are arranged around the photosensitive drum. A configuration may be employed in which development is performed in order for each color in a fixed arrangement. Further, in the case of adopting a configuration in which the developing unit is moved, the developing unit is not limited to a rotation method, and for example, a sliding method in which each developing unit is moved individually or each developing unit is stored in a rack and moved in a straight line. An elevator system or the like may be used.

  Further, although the identification signal is used as a method for discriminating the image forming (developing) unit, it is needless to say that the method is not limited to this as long as it can be discriminated. For example, a code for identification is printed at a predetermined position for each unit, and when each unit is mounted on the main body of the apparatus, the code is read to determine which unit is mounted at which position. Possible ways to do this.

  The above embodiment and the above modification examples may be combined.

  The present invention can be widely applied to image forming apparatuses that form color images.

1 is a diagram illustrating an overall configuration of a printer 1 according to a first embodiment. FIG. 4 is a chromaticity diagram showing chromaticity points of M and C color toners in an L ^* a ^* b ^* color system. 2 is a block diagram illustrating a configuration example of a control unit 100 of the printer 1. FIG. 4 is a schematic diagram illustrating an example of the content of appropriate information stored in an appropriate information storage unit 108 of the control unit 100. FIG. 3 is a block diagram illustrating a configuration of an MCK color conversion unit 1031 of the control unit 100. FIG. 4 is a flowchart showing the contents of a set state notification process executed in the control unit 100. It is a figure which shows the example of the message display explaining the setting state of an image formation unit. 10 is a flowchart showing the contents of conversion processing in the MCK conversion unit 1031; It is a figure which shows the whole structure of the printer 81 concerning 2nd Embodiment. 3 is a block diagram illustrating a configuration example of a control unit 150 of a printer 81. FIG.

Explanation of symbols

1, 81 Printer 2M, 2C, 2K Image forming unit 6M, 6C, 6K Developer 10, 90 Intermediate transfer unit 82 Image forming unit 86M, 86C, 86K Development unit 100, 150 Control unit 109 Set state determination unit 1031 MCK conversion unit

Claims (10)

  It is equipped with image forming means having developing sections for magenta, cyan, and black colors except yellow, and a magenta, cyan, and black color toner image developed by each developing section is transferred onto a transfer medium to form a color image Forming an image forming apparatus. The transfer object is a transfer material conveyed on an intermediate transfer material or a transfer material conveyance body,
The image forming means includes:
Having first, second, and third image carriers arranged along the moving direction of the intermediate transfer member or the transfer material transport member;
Forming a magenta color toner image on the first image carrier using a magenta color developer;
Forming a cyan toner image on the second image carrier using a cyan developing unit;
Forming a black toner image on the third image carrier using a black developing unit;
The image forming apparatus according to claim 1, wherein the formed toner images are sequentially transferred and superimposed on the intermediate transfer member or the transfer material. When the transfer target is an intermediate transfer member,
The black toner image is finally transferred onto the intermediate transfer member, and each toner image superimposed on the intermediate transfer member by transfer is further transferred onto another transfer material at once. And
When the transfer object is a transfer material,
The image forming apparatus according to claim 2, wherein a black color toner image is first transferred onto the transfer material. The transfer object is a transfer material conveyed on an intermediate transfer material or a transfer material conveyance body,
The image forming means includes:
One image carrier is provided, and each developing unit is switched to sequentially form toner images on the image carrier for each color, and the formed toner images are formed on the intermediate transfer member or the transfer material. The image forming apparatus according to claim 1, wherein the image forming apparatus transfers and superimposes. When the transfer target is an intermediate transfer member,
A black toner image is finally formed on the image bearing member, and each toner image superimposed on the intermediate transfer member by transfer is further collectively transferred onto another transfer material. And
When the transfer object is a transfer material,
5. The image forming apparatus according to claim 4, wherein a black toner image is formed on the image carrier first. The magenta color developing unit has a chromaticity point on the chromaticity diagram that is yellower than the full-color magenta toner used when forming a color image with four colors of magenta, cyan, yellow, and black. Contains toner shifted in a direction approaching hue and / or
The cyan development unit has a chromaticity point on the chromaticity diagram that is yellower than the full-color cyan toner used when forming a color image with four colors of magenta, cyan, yellow, and black. The image forming apparatus according to claim 1, wherein toner shifted in a direction approaching a hue is stored. With control means,
Each of the developing units is mounted at any one of the first, second, and third positions, and is configured to be detachable from the apparatus main body.
The control means includes
Determining means for determining which color developing unit is mounted at which position;
Conversion means for converting input data into data of reproduction colors of magenta, cyan, and black, and
The image forming apparatus according to claim 1, wherein the content of the conversion process is changed according to a determination result by the determination unit. With control means,
Each of the developing units is mounted at any one of the first, second, and third positions, and is configured to be detachable from the apparatus main body.
The control means includes
Determining means for determining which color developing unit is mounted at which position;
Notification means for determining the suitability of the set state of each developing unit according to the determination result by the determination means, and notifying the user of the determined result;
The image forming apparatus according to claim 1, further comprising: The notification means includes
The image forming apparatus according to claim 8, wherein the image forming apparatus is a display unit that displays the determined result.   An image forming method comprising forming a color image by transferring a magenta, cyan, and black color toner image developed by a developing unit for magenta, cyan, and black colors excluding yellow to a transfer target .

Images