JP3688161B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that performs multicolor printing by applying an electrophotographic method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a color image forming apparatus, each color image developing device that stores toner for each color is provided in series in the paper transport direction, and the corresponding color image is the same in each color image developing device as the paper is transported. After the toner image is superimposed on the paper surface and passed through the entire color image developing device, the toner image is superimposed on the paper by passing the heated toner roller of the fixing device through the heat roller of the fixing device. Image formation is performed.
[0003]
[Problems to be solved by the invention]
However, the order in which the color image developing devices are inserted and arranged in the main body determines the order of superposition transfer, and the color toner of the color developing device arranged at the most downstream in the superposition transfer process is the most on the transfer paper. It adheres to the surface and is most susceptible to the heat of the heating heat roller surface of the fixing device. As a result, there has been a problem that a change in the color tone of the color print image is caused by a change in the order in which the developing devices are inserted, that is, the order in which the color toners are superimposed.
[0004]
The present invention has been made to solve the above-described problems, and provides a color image developing device that minimizes a change in color tone of a final color print image regardless of the insertion order of each color developing device. The purpose is to provide.
Also, it is possible to provide a color image developing device that maintains better color image quality even when the development function of each color developing device is insufficient and it is difficult to control the amount of color toner adhering by adjusting the developing bias voltage. Also aimed.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
According to the first aspect of the present invention, there is an electrostatic latent image carrier, an exposure unit that forms an electrostatic latent image on the electrostatic latent image carrier, and a development that holds the formed electrostatic latent image therein. A plurality of image forming units each having a developer that visualizes with an agent are arranged in accordance with each color, and a plurality of developers in each of the image forming units are provided detachably with respect to the apparatus main body. An image forming apparatus having a developing device storage section capable of storing and arranging developing devices in an arbitrary storage site, wherein the developing device array detection means detects a sequence of the developing devices stored in the storage site, and the developing device detection means The developer amount developed by each developing device is set to a predetermined developer amount for each developing device or a developer amount based on a predetermined rule based on the arrangement order of the developing devices, which is the detection result of An image characterized by comprising development amount control means for performing change control In the adult system.
[0006]
The structure of the second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the developing amount control means is a developing bias control device that controls a developing bias voltage of each developing device.
[0007]
According to the configuration of the present invention , the fixing device for fixing the developer image formed on the transfer material to the transfer material by heating is provided, and based on the arrangement order of the developing devices detected by the developing device arrangement detecting means. The image forming apparatus according to the first or second aspect is characterized in that the fixing temperature of the fixing device is changed and controlled.
[0008]
According to the configuration of the present invention, by adjusting the amount of developer at the time of overlay transfer of the color developer, for example, the adhesion amount of the color developer on the outermost surface is controlled low, so that the color developer at the time of fixing The color reproducibility is improved while suppressing the increase in the burden on the fixing device.
[0009]
In addition, if there is a problem such as environmental changes in each developer or a decrease in development density due to a temporary delay in replenishing the color developer by the operator, color developer adhesion control by adjusting the development bias voltage will cause the target color There is a limit to the possibility of following the reproduction.
Therefore, by changing the fixing temperature of the fixing device, it is possible to perform color printing while maintaining the color reproducibility of the developing amount control means, for example, the color developer adhesion amount control by adjusting the developing bias voltage.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view showing a schematic configuration of the color image forming apparatus 1 in cross section. FIG. 2 is a block diagram of a control system of the color image forming apparatus.
The color image forming apparatus 1 includes a central processing unit CPU that controls the entire main body, an image sensor CCD that reads an image (not shown), and photoelectrically converts the read data, and image data of each color for each color. The first to fourth laser scanner units LSU, which are the exposure means of the image forming unit, which will be described later, the image forming units F1 to F4 corresponding to the colors, and the information on the developing devices in the image forming units F1 to F4. Color for detecting a storage device 2 for storing, a conveying belt 3 for conveying a sheet below the image forming portions F1 to F4, and an identification mark 5c which is information of the developing device 5 in the image forming portions F1 to F4. It has information detection means 4 a to 4 d and a fixing roller 8 that is a heating heat roller facing the downstream side of the conveyor belt 3.
[0011]
The image forming portions F1 to F4 for the respective colors include a developing device 5, a guide member 6, and a photosensitive member 7 that store the developer for each color and can be extracted from the apparatus main body 1.
The image forming units F1 to F4 have the same configuration except for the configuration relating to the color of the developer (sometimes referred to as toner). In this embodiment, negatively charged toner is used as the developer, but positively charged toner may be used.
[0012]
The developing unit 5 is provided with a developing tank 5a for containing the developer, a developing roller 5b that is disposed below the developing tank 5a, adheres the developer to the periphery, and conveys the developer to the photosensitive member 7, and a developing tank 5a. And an identification mark 5c for distinguishing the color of the developer contained in the container.
[0013]
The developing tank 5a contains a developer of each color of yellow, magenta, cyan, or black, and supports a developing roller 5b rotatably at the lower part.
[0014]
The developing roller 5b is a conductive elastic roller made of conductive urethane rubber. The developing roller 5b rotates in contact with the photoconductor 7 through a developer layer. For example, a developing bias voltage is supplied from a developing bias power source (not shown) through a stainless steel shaft. -450 (v) is applied.
[0015]
The identification mark 5c, which is color information presenting means, is formed by bar code information of color information formed at a predetermined position, or a mark directly representing each color. Note that the color information presenting means may be a transparent window portion through which the developer in the developing device 5 can be seen.
The identification mark 5c is attached to the guide member 6 in which the developing device 5 is accommodated, and in a set state, the identification mark 5c is read, and the positions facing the color information detection units 4a to 4d that detect and identify color information, respectively. Is provided.
[0016]
When the bar code is used as the identification mark 5c, the color information detecting means 4a to 4d use a bar code reader or the like that reads bar code information, and the color information presenting means displays a window portion or color mark where the developer color is visible. In this case, it can be constituted by a photosensor that identifies a color from the amount of reflected light.
[0017]
The guide member 6 is a housing member that accommodates the developing device 5 in the main body of the apparatus 1 so as to be freely inserted and removed.
Therefore, when replacing the developing device 5, the operator can remove all the developing devices 5 of the respective colors by the same operation, and can attach new developing devices 5 of the respective colors by the same operation.
[0018]
The negatively charged photoconductor 7 is provided with a conductive base material and has a surface potential of, for example, −550 (v). At the time of image formation, the photoconductor 7 is exposed by the laser scanner unit LSU, and image data is formed as an electrostatic latent image. Then, the electrostatic latent image is developed by the toner of the developing roller 5 b due to the potential difference between the developing roller 5 b and the photosensitive member 7, and the toner image is transferred to the sheet conveyed by the transfer conveyance belt 3.
[0019]
Next, the operation of the color image developing device 1 will be described.
When each developing device 5 is set on each guide member 6, the color information of the identification mark 5 c that is the color information presentation means is detected by the color information detection means 4 a to 4 d provided at the corresponding positions, respectively. The information is output to the CPU.
Based on the color information, the CPU recognizes which color developing device 5 is mounted on the guide member 6 of the image forming unit F1 to F4 at which position, and stores the image forming unit F1 to F4 in the storage device 2. The color information of the developing device 5 provided is stored.
[0020]
When an image forming operation is instructed by an operation means such as an operation panel (not shown) or a keyboard, the CPU performs predetermined image processing in an image processing unit (not shown) output from a document reading unit such as a CCD. The image data of each color generated in this way is output to the first to fourth laser scanner units LSU of the image forming units F1 to F4 corresponding to each color.
[0021]
The laser light output from each scanner unit LSU exposes each photoconductor 7 in the drawing, and proceeds to the developing process.
In the development process, development and transfer are executed in order from the upstream side in the traveling direction of the transfer conveyance belt 3.
Here, as described above, the order in which the developing devices 5 are inserted and arranged in the main body 1 determines the order of the superposition transfer, and the color toner of the development device 5 arranged at the most downstream in the superposition transfer step. Adheres to the outermost surface of the paper and becomes most susceptible to the heat of the heating heat roller surface of the fixing device 8. As a result, a change in the color tone of the color print image is caused by a change in the order in which the developing devices 5 are inserted, that is, the order in which the color toners are superimposed.
Therefore, in the present embodiment, the toner adhesion amount control is performed based on the arrangement pattern of the developing devices 5 of the respective colors arranged in the image forming units F1 to F4.
[0022]
FIG. 3 shows red (R), green (G), and blue for the mounting order 1 to 6 of the developing tanks 5a for yellow (Y), magenta (M), cyan (C), and black (K). (B) shows the overlapping order of each color toner when expressing the color and the overlapping amount per unit area of the color toner in consideration of the arrangement relationship of the developing tank 5a.
[0023]
FIG. 4 shows the color toner superposition amount in three stages for the yellow (Y), magenta (M), cyan (C), and black (K) developing tanks 5a in the order of installation 1 to 6. The normal adhesion amount is shown as No. 1, the next smallest adhesion amount as No. 2, and the smallest amount as No. 3.
[0024]
In the graph of FIG. 5, the horizontal axis is the reflected image density information defining the image density, the vertical axis is the control developing bias (−v) applied to the developing roller 5b, and the adhesion amount No. 1 shown in FIG. Development bias control curves No. 1 to No. 3 for each of the developing tanks 5a for yellow (Y), magenta (M), cyan (C), and black (K) for realizing .about.3. . Therefore, the developing bias voltage is determined according to the developing bias control curves No. 1 to No. 3, and the developing bias driving device 10 (FIG. 2) controls the developing bias voltage of the developing roller 5b for each color under the control of the CPU.
The reflected image density information can be obtained by detecting the color toner image reflection density on the surface of each photoconductor 7 or the surface of the paper (transfer material) and the surface of the transfer conveyance belt 3 after development or transfer.
[0025]
FIG. 6 shows changes in vividness for each color of red (R), green (G), and blue (B) when the control developing bias is applied to the mounting order 1 to 6 of each developing tank 5a and when it is not performed. It is a graph to show.
[0026]
The developing bias voltage control curve is selected by recognizing the arrangement of the developing devices 5 from the signals of the developing device color information detecting means a to 4d shown in FIG. A developing bias voltage control curve is selected based on the array storage information of the developing device 5.
[0027]
The development bias voltage at the time of developing each color toner is determined in advance by the reflection density information means 11 (FIG. 2) based on the reflected image density of the color toner image after development or transfer, which is executed in advance when the machine body is started up. The developing bias voltage at the time of developing each color toner is determined by using the reflection density information obtained by the detection result and the control curve selected earlier.
[0028]
If the development bias driving device 10 controls the development bias voltage thus determined to be output to the developing device 5 in accordance with each process timing, the toner adhesion amount control shown in FIG. 3 is performed, and a vivid color is obtained as shown in FIG. Reproducibility is realized without significant changes in the current apparatus main body 1 and each image forming process.
[0029]
Specifically, in the case where YMCK is arranged from the upstream side as the mounting order 1 of the developing tank 5a, the adhesion amounts of magenta (M) and cyan (C) are made smaller than the adhesion amount of yellow (Y). In this case, cyan (C) and magenta (M) are No. 2, yellow (Y) and black (K) are No. 1, and the controlled development bias is controlled by the CPU and the development bias driving device 10. It is applied to each developing roller 5b and executes development of each color.
[0030]
Similarly, when YCMK is arranged from the upstream side as the mounting order 2 of the developing tank 5a, the adhesion amount is increased in the order of magenta (M), cyan (C), and yellow (Y). In this case, cyan (C) is No. 2, magenta (M) is No. 3, yellow (Y) and black (K) are No. 1, and a control developing bias is applied to each developing roller 5b. Then, development of each color is executed.
[0031]
Further, when the MYCK is arranged from the upstream side as the order 3 of installing the developing tank 5a, the amount of cyan (C) attached is made smaller than the amounts of magenta (M) and yellow (Y) attached. In this case, cyan (C) is No. 2, magenta (M), yellow (Y), and black (K) are No. 1, and similarly, a control developing bias is applied to each developing roller 5b, and each color is changed. Execute development.
[0032]
Further, when the mounting order 4 of the developing tank 5a is MCYK arrangement from the upstream side, the attached amounts of cyan (C), magenta (M), and yellow (Y) are the same. In this case, all colors are No. 1, and similarly, a control development bias is applied to each development roller 5b, and development of each color is executed.
[0033]
Further, when the mounting order 5 of the developing tank 5a is CMYK arrangement from the upstream side, the magenta (M) adhesion amount is made smaller than the cyan (C) and yellow (Y) adhesion amounts. In this case, magenta (M) is No. 2, cyan (C), yellow (Y), and black (K) are No. 1. Similarly, a control developing bias is applied to each developing roller 5b, and each color is changed. Execute development.
[0034]
Finally, also in the case where CYMK is arranged from the upstream side as the mounting order 6 of the developing tank 5a, the magenta (M) adhesion amount is made smaller than the cyan (C) and yellow (Y) adhesion amounts. Also in this case, magenta (M) is No. 2, cyan (C), yellow (Y), and black (K) are No. 1. Similarly, the control developing bias is supplied from the developing bias driving device 10 to each developing roller 5b. To develop each color.
[0035]
2, 7, and 8, even when the developing function of each color developing device 5 is insufficient and it is difficult to appropriately control the amount of color toner attached by adjusting the developing bias voltage, the fixing device 8 A case where better color image quality is provided by changing the heating heat roller set temperature will be described.
[0036]
In FIG. 7, the horizontal axis represents image input data, the vertical axis represents print image density (ID), and the development bias voltage is set to −400 (v) and −300 (v). The reproduction density curve of a halftone image is shown.
In general, in the two-component development method, the development bias voltage is changed to control the developability, but only the saturation density changes as shown in FIG. 7, and the balance of the entire halftone reproduction characteristic changes. There is a bug. This is not preferable in terms of color image quality because it is not the originally intended halftone reproduction characteristic.
This is because the electric field is concentrated on the image peripheral portion of the electrostatic latent image generated at the time of reproducing the dot image at the time of laser writing, and the image is developed much during development.
On the other hand, in the saturated density portion, since there is no electric field concentration in the peripheral portion of the image, developability proportional to the development bias voltage can be obtained.
[0037]
In order to solve the problems as described above, the fixing roller is set for each of the developing tanks 5a in order of installation 1 to 6 as shown in FIG. 8 while controlling the developing property by controlling the developing bias voltage. The temperature is also changed and controlled in multiple stages such as Hi / Lo. Specifically, in the case of the mounting order 4, the fixing temperature setting of the fixing heater driving device 12 (FIG. 2) of the fixing device 8 is set to Lo, and the other mounting orders 1, 2, 3, 5, and 6 are used. The fixing temperature setting of the fixing heater driving device 12 is set to Hi.
[0038]
As a result, good color image reproduction characteristics were obtained over the entire halftone reproduction characteristics without lowering the saturation density as shown in FIG.
In addition, since this fixing temperature setting is performed only for a specific developer color combination as shown in FIG. 8, unnecessary energy is not consumed, and if necessary, the operator can change the arrangement to an optimum developer arrangement. This can be displayed on the display device 13 and prompted.
[0039]
In the above embodiment, the preferred example of the present invention has been described, but the present invention is not limited to this.
[0040]
【The invention's effect】
As described above, according to the inventions of the first and second aspects, an image developing apparatus that can minimize a change in color tone of a final multi-color printed image regardless of the arrangement order of the developing devices can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing, in section, a schematic configuration of a color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a control block diagram of the color image forming apparatus according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating the toner of each color when expressing red (R), green (G), and blue (B) colors in the order of installation 1 to 6 of the developing tank 5a for each color according to the embodiment of the present invention; FIG. 6 is an explanatory diagram showing an overlapping amount per unit area of color toner in consideration of an overlapping order and an arrangement relationship of the developing tank 5a.
FIG. 4 is an explanatory diagram in which a color toner superposition amount is indicated by symbols in three stages with respect to mounting orders 1 to 6 for each color according to an embodiment of the present invention.
5 is the reflection image density information defining the image density, the vertical axis is the control developing bias (−v) applied to the developing roller 5b, and the adhesion amounts No. 1 to 3 shown in FIG. FIG. 6 is an explanatory diagram of development bias control curves No. 1 to No. 3 for each development tank 5a for each color for realizing the above.
FIG. 6 shows red (R), green (G), and blue (B) when the control developing bias is applied to the mounting order 1 to 6 of the developing tank 5a for each color according to the embodiment of the present invention and when it is not performed. It is explanatory drawing which shows the vividness change for every color of ().
FIG. 7 is a representation of halftone images of each color when the horizontal axis is image input data, the vertical axis is print image density, and the development bias voltage is set to −400 (v) and −300 (v). It is explanatory drawing which shows a density | concentration curve.
FIG. 8 is an explanatory diagram showing fixing temperature setting of the fixing roller 8 with respect to the mounting order 1 to 6 of the developing tank 5a for each color according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Color image forming apparatus CPU Central processing unit F1-F4 Image formation part LSU Laser scanner unit 2 Memory | storage device 3 Transfer conveyance belt 4a-4d Color information detection means 5 Developer 5b Developing roller 5c Identification mark 6 Guide member 7 Photoconductor 8 Fixing Roller 10 Development bias drive 11 Reflection density information means 12 Fixing heater drive

Claims (2)

Development that visualizes an electrostatic latent image carrier, an exposure unit that forms an electrostatic latent image on the electrostatic latent image carrier, and a developer that holds the formed electrostatic latent image therein A plurality of image forming units each having a container are arranged according to each color,
A plurality of developing devices in each of the image forming units are provided detachably with respect to the apparatus main body, and an image forming apparatus having a developing device storage unit that can store and arrange each developing device in an arbitrary storage site,
Developing device arrangement detecting means for detecting the arrangement order of the developing devices stored in the storage site;
Based on the arrangement order of the developing devices, which is the detection result of the developing device detecting means, the amount of developer to be developed by each developing device is determined based on a predetermined developer amount for each developing device or a predetermined rule. Development amount control means for controlling the change to the developer amount,
The developing amount control means selects a developing bias voltage control curve based on information on the result of detecting the arrangement of the developing devices by the developing device array detecting means, and determines a change control amount from the developing bias voltage control curve. An image forming apparatus. 2. The image forming apparatus according to claim 1 , wherein the developing amount control means is a developing bias control device that controls a developing bias voltage of each developing device.

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