JPH08137171A - Multicolor image forming device - Google Patents

Abstract

PURPOSE: To provide a multicolor image forming device where an image without density difference between colors is formed in the case of the monocolor image and the image stable in color balance is formed in the case of the image of two colors, three colors or four colors, and whose productivity is not sacrificed. CONSTITUTION: In this multicolor image forming device, one or plural toner images are formed on an image carrier 1 and then transferred altogether to an image receptive body 6. The device is provided with a color designation means 8 optionally selecting a desired color, an image forming stage decision means 9 deciding one or plural image forming stages corresponding to the designated color information by the designation means 8, and an electrifying and developing bias adjusting means 10 adjusting the values of electrifying potential and developing bias in the image forming stage of each color decided by the decision means 9 considering the potential of a toner layer on the image carrier 1 and always keeping a potential difference between latent image potential and the developing bias and between the electrifying potential and the developing bias constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus for forming a multicolor image on an image carrier, and is used for electrophotography, electrostatic recording, facsimile, transmission apparatus, laser printer and the like.

[0002]

2. Description of the Related Art As a multicolor image forming apparatus using electrophotography, a charger, an exposure unit,
A plurality of yellow, magenta, cyan, and black developing devices, transfer devices, and cleaning devices corresponding to the respective colors are arranged, and toner images of the respective colors are sequentially formed on the photoconductor for each rotation, and the toner images are formed on the photoconductor. It is known to collectively transfer the toner images of the respective colors formed on the recording paper onto the recording paper in one transfer process.

In this type of multicolor image forming apparatus, the latent image potential of each color uses the same value, and the number of times of image formation is four times for full color and once for black single color. It is common to do. Further, when an image such as a single color cyan is to be formed, it is general that the image is formed four times in the full color mode and the latent image potential of cyan is used to form the image.

[0004]

In the above-described multicolor image forming apparatus, when a full color image is to be formed, the toner layer is already present on the photoconductor at the time of exposure for the second and subsequent colors, so that the toner layer is formed. There is an electric potential. Therefore, FIG.
As shown in (a), each color (yellow, magenta, cyan, black) has a constant charging potential (VHY = VHM = VHC).
= VHK) and the amount of exposure light, an latent image potential (VLM, VLC, VLK) varies with each latent image formation due to the toner layer potential (VTY, VTYM, VTYMC). Therefore, there is a technical problem that the potential contrast of the image portion changes. In addition, in FIG. 8 (a), VLM ',
VLC 'and VLK' indicate latent image potentials of respective colors when there is no existing toner layer on the photoconductor.

Therefore, as shown in FIG. 8 (b), the charging potentials (VHY, VHM, VHC, VHK) and the developing bias are simultaneously changed to change the potential contrast (| VHY-VLY1 |, | VH).
It has been proposed to keep M-VLM1 |, | VHC-VLC1 |, | VHK-VLK1 |) constant or to keep the potential contrast constant by changing the exposure light amount. Incidentally, FIG. 8 (b)
Among them, VLY1, VLM1, VLC1, and VLK1 represent latent image potentials (image portion potentials) of respective colors, and VLM1 ′, VLC1 ′, and VLK1 ′ represent latent image potentials of respective colors when there is no existing toner layer on the photoconductor. However, when such means is used, as shown in FIG. 8B, a difference occurs in the potential contrast between the image portion and the non-image portion of each color. In this state, when a cyan image is formed in a single color, for example, the potential contrast of the non-image portion between the colors is different, so the density is changed between the colors, or a two-color image such as green is formed. A technical problem arises in that the color shade changes when it is formed. Further, when an image of a single color or two colors is to be formed, the full-color mode is always performed, and thus there is a technical problem that productivity is deteriorated.

On the other hand, the technique disclosed in Japanese Patent Laid-Open No. 3-253873 discloses a method of controlling the charging potential and the amount of exposure light by using a potential detecting means. However, this is merely the description of means for compensating for the color balance of full color, and nothing is mentioned about the latent image forming means for single color or two colors.

The present invention has been made in order to solve the above technical problems. In the case where an image is a single color, there is no difference in density between the colors and there are two colors, three colors and four colors. The present invention provides a multicolor image forming apparatus capable of forming an image having a stable color balance and not sacrificing productivity.

[0008]

That is, the present invention provides:
As shown in FIG. 1, a charging means 2 for uniformly charging the surface of the photoconductive image carrier 1 and an electrostatic latent image on the surface of the charged image carrier 1 by exposure scanning corresponding to each color image. The image carrier comprises an exposure unit 3 for forming an image and a multicolor developing unit 4 for selectively developing an electrostatic latent image formed on the image carrier 1 by applying a developing bias with each color toner. 1, a plurality of color toner images are sequentially formed on the image carrier 1 by repeating each color image forming process of charging, exposing and developing, and then the plurality of color toner images are collectively transferred to the image receptor 6. In the multi-color image forming apparatus in which the means 5 collectively transfers the toner and the residual toner on the image carrier 1 is cleaned by the cleaning means 7, a color designation means 8 for arbitrarily selecting a desired color, and Youthful corresponding to the color information specified by the color specifying means 8. The image forming process determining means 9 for determining a plurality of image forming processes, and the charging potential and the developing bias value during the image forming process of each color determined by the image forming process determining means 9 are used as the toner on the image carrier 1. A charging / developing bias adjusting means 10 is provided which is adjusted in consideration of the layer potential and keeps the potential difference between the latent image potential and the developing bias and the charging potential and the developing bias constant.

In such a technical means, the image forming step determining means 9 determines the image forming step of a required color by the color specifying means 8 and the number of cycles of the image carrier 1, and the color specifying means. If 8 specifies a single color,
When the number of cycles of the image carrier 1 is set to 1 and the image formation is completed only in the first image forming step, and the color designating means 8 designates a color formed by a plurality of colors, the image carrier 1 The number of cycles may be set to the required number, and the image formation may be ended when the required number of image forming steps are sequentially repeated from the first image forming step. Further, the image forming process determining means 9 performs the transfer process and the process of cleaning the residual toner on the image carrier 1 immediately after the number of cycles of the image carrier 1 (the image forming process of the required color) is completed. Has become.

Further, in the present invention, the charging / developing bias adjusting means 10 may be one which adjusts the charging potential and the developing bias in consideration of the potential of the toner layer on the image carrier 1, and the image forming step The relationship between the number and the toner layer potential may be held in advance as data, and the charging potential and the developing bias may be adjusted appropriately based on this data, but from the viewpoint of more accurate adjustment, For example, while detecting the potential of the toner layer on the image bearing member 1 by a potential detecting sensor or the like at a predetermined timing (for each image forming step, once for every several image receiving members, once at the start of the job of the day, etc.). It is preferable to adjust the charging potential and the developing bias.

Further, in the present invention, since the thickness of the toner layer formed on the image carrier 1 varies depending on the number of image forming steps, from the viewpoint of maintaining the transfer performance by the batch transfer means 5 better. It is preferable that the transfer output adjusting unit 11 adjusts the transfer output value according to the number of image forming steps.

[0012]

According to the above technical means, when the desired color is arbitrarily selected by the color designating means 8, the image forming process determining means 9 causes the image forming step determining means 9 to select one or a plurality of images corresponding to the designated color information. The forming / deciding process is decided, and the charging / developing bias adjusting means 10 adjusts the values of the electrifying potential and the developing bias in the decided image forming process of each color in consideration of the toner layer potential on the image carrier 1 to form a latent image. The potential difference between the potential and the developing bias and the potential difference between the charging potential and the developing bias are always kept constant. In such an image forming process, since the electric potential contrasts of the image portion and the non-image portion are the same in each image forming step of each color, in the case of a single color, there is no density difference between the colors, and the two-color image and the three-color image In the case of images and 4-color images, stable color balance can be obtained.

Further, since only the necessary image forming process is determined according to the color information designated by the color designating means 8, for example, in forming a single color image or a two color image, the image formation of each color of the full color image is performed. There is no need to carry out all the steps.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 2 shows an embodiment of a multicolor image forming apparatus to which the present invention is applied. In the figure, reference numeral 21 is a photosensitive member such as a cylindrical photosensitive drum, and 22 is a photosensitive member 2.
A charger for charging 1 such as a scorotron, 23
Is a laser light generator that incorporates a semiconductor laser (not shown), a polygon mirror 231, etc., and writes an electrostatic latent image on the photoconductor 21 charged by a light beam 232 according to each color component image data. Developing devices for yellow, magenta, cyan, and black, 28 is a potential detecting sensor for detecting the toner layer potential on the photoconductor 21, 29 is a toner image for each color component, and then each toner image and photosensitive Body 21
Is a pre-transfer charger that charges or removes the toner in an optimal state for transfer, 30 is a transfer charger that collectively transfers the toner images of respective color components onto the recording paper 32 carried along the paper guide 31,
33 is a peeling charger for peeling off the recording paper 32 adhering to the photoconductor 21 after transfer, 34 is a cleaning device for removing the residual toner on the photoconductor 21, and 35 is a destaticizing exposure device for removing the residual charge on the photoconductor 21. Reference numerals 36 denote transport belts for transporting the recording paper 32 after transfer to a fixing device (not shown). In this embodiment, the photoconductor 21 will be described as an organic photoconductor that is negatively charged. Therefore, the toner of the developer is negatively charged.

FIG. 3 is a block diagram showing the control system of the multicolor image forming apparatus. In the figure, reference numeral 41 is a console panel which is an operation unit of the multicolor image forming apparatus,
A print switch 42, a print number setting section 43, and a color designating section 44 for designating a color to be printed are provided.
In this embodiment, the color designating section 44 includes selection switches 441 to 444 for single color mode (black, yellow, magenta, cyan) and selection switches 445 to 447 for two color mode (green, red, blue). And 3
Select switch 448 for color mode and full color (4
A selection switch 449 for the (color) mode is provided.

Further, reference numeral 50 is an image forming process determining device which determines the image forming process and the number of cycles of the photoconductor 21 based on the color information from the color designating section 44 of the console panel 41. This image forming process determining device Reference numeral 50 is configured by using, for example, a microcomputer system, and supplies a control signal regarding the determined image forming process and the number of cycles of the photoconductor 21 to the process controller 51.

Furthermore, the image forming process determining device 50.
Detects the toner layer potential on the photoconductor 21 by the potential detection sensor 28 at every predetermined timing (in this embodiment, when the power is turned on), and outputs the control signal relating to the detected toner layer potential to the charging voltage controller 52. And developing bias controller 53, and the charging voltage controller 52 controls the charging voltage of the charger 22, and the developing bias controller 53 develops each developing device for yellow, magenta, cyan, and black. Two
The developing bias of 4 to 27 is controlled.

Further, the image forming process determining device 50 is
A control signal relating to the number of cycles of the photoconductor 21 is sent to the transfer voltage controller 54, and this transfer voltage controller 54 controls the transfer output voltage to the transfer charger 30.

Next, the image forming process in the full color mode of the multicolor image forming apparatus according to this embodiment will be described with reference to FIG. First, the cylindrical photoreceptor 21 is charged by the charger 22 (a). Then, a latent image corresponding to yellow is formed at a predetermined position on the photoconductor 21 by the laser light 232 from the laser light generator 23 (b). At this time, the laser light 232 writes the image portion, and the toner having the same polarity charge as the surface potential polarity of the photoconductor 21 charged by the charger 22 has the potential of the laser light irradiation portion of the photoconductor 21. The well portion is subjected to reversal development by the yellow developing device 24 (c).
The yellow developing device 24 is configured to be in non-contact with the photoconductor 21 at least after the completion of development, so that the toner image once developed is prevented from being scraped before the development process of another color is started. There is.

In the second image forming step of the next step, the photoconductor 21 is irradiated by the charger 22 with the non-image portion potential lowered by the dark decay in the previous step and the laser beam 232, and the potential after the yellow development is completed. The portion of the photoconductor 21 whose temperature has dropped is recharged so as to return to the original potential state (d). After that, a latent image corresponding to magenta is again irradiated onto a predetermined position of the photoconductor 21 by the laser light 232 from the laser light generator 23 (e), and the surface potential polarity of the photoconductor 21 charged by the charger 22 is changed. Magenta toner having the same polarity charge is developed on the laser irradiation portion of the photoconductor 21 by the magenta developing device 25 (f).

Thereafter, similarly, as the third image forming step, recharging (g) by the charger 22 and the laser beam generator 2 are performed.
Irradiation with a cyan image by a laser beam 232 from 3 (h), development of a magenta image by a developing device 26 for cyan (i), recharging (j) by a charger 22 and generation of a laser beam as a fourth image forming step. Laser light 2 from the container 23
Irradiation of a black image by 32 (k) and development of a black image by the developing device 27 for black (1) are performed.

At the time when the black image developing process by the black developing device 27 is completed, yellow, magenta, cyan, and black toner images corresponding to the irradiation image are present on the photoconductor 21 (m). The toner image and the photoconductor 21 are irradiated with the pre-transfer charger 29 as necessary,
After being charged or discharged to an optimum state for transfer, the transfer charging device 30 allows the toner images of yellow, magenta, cyan, and black on the photoconductor 21 to be uniformly recorded on the recording paper 32 that has entered from the paper guide 31. Transferred in a single process (n).

After the transfer process is completed, the recording paper 32 is de-charged by the peeling charger 33, peeled off from the photoconductor 21, and conveyed to the fixing device section (not shown) by the conveyor belt 36 for the fixing step (o). .

On the other hand, after the transfer process is completed, the residual toner on the photoconductor 21 is cleaned by the cleaning device 34. In this cleaning step, for example, the cleaning blade 341 comes into contact with the photoconductor 21 and is cleaned by the pressure thereof (p). After receiving the exposure from the static eliminator / exposure device 35, the charging process by the charger 22 is started again, and all the above-mentioned processes are repeated to output a plurality of continuous prints (q).

Next, a method of determining the image forming process of the image forming process determining device 50 of the multicolor image forming apparatus according to this embodiment will be described. In this embodiment, arbitrary selection switches 441 to 44 of the color designating section 44 of the console panel 41 are used.
By selecting any one of 9,
It is possible to specify such as yellow, magenta, cyan), two colors (green, red, blue), three colors, and four full colors. Based on the designated color, the image forming process determination device 50 determines how many images of the designated color should be formed, and determines the image forming process (which color of the charging process, the exposing process, and the developing device). ),
Further, the number of cycles of the photoconductor 21 is also determined according to the content of this determination.

More specifically, as shown in FIG. 5, in the case of forming a monochromatic image, a developing device selected in accordance with a yellow charging step and an exposure step, and a color to be output. The image forming process including the developing process is performed in one cycle of rotation of the photoconductor 21, and the transfer process, the cleaning process and the fixing process are performed (A).

In the case of forming a two-color image, the first step comprises a yellow charging step and an exposure step, and a developing step by a developing device selected corresponding to the first color forming the two-color image. Rotation of the photoconductor 21 includes a second image forming step including an image forming step, a magenta charging step and an exposing step, and a developing step by a developing device selected corresponding to a second color for forming a two-color image. The process is sequentially performed in a cycle, and a transfer process, a cleaning process, and a fixing process are performed (B).

Further, in the case of forming a three-color image, an image forming process including a charging process for each of yellow, magenta, and cyan, an exposing process, and a developing process is sequentially performed in three cycles of rotation of the photoconductor 21, and a transfer process, The cleaning process and the fixing process are reached (C). Furthermore, in the case of forming a four-color image (full-color image), an image forming process including a charging process for each of yellow, magenta, cyan, and black, an exposing process, and a developing process is sequentially performed in four rotation cycles of the photoconductor 21. , A transfer process, a cleaning process, and a fixing process (D).

The charging voltage controller 52 and the developing bias controller 53 receive a control signal from the image forming process determining device 50, and in the image forming process of each color mode, the charging potential in the charging process and the developing bias in the developing process. The charging potential and the developing bias are changed for each color while keeping the difference between the constants.

More specifically, taking the full-color image forming process as an example, as shown in FIG.
For example, the value of the toner layer potential (-80 V) on the photoconductor 21 formed by the yellow image forming process is set to the charging potential (-800 V) of the yellow charging process and the developing bias value (-700 V) of the developing process. Each of them is summed up and the summed value is set to the magenta charging potential (-880 V) and the developing bias (-780 V). Similarly, the value of the toner layer potential (-160 V) on the photoconductor 21 formed by the yellow and magenta image forming process is the charging potential (-800 V) of the yellow charging process and the developing bias (-) of the developing process.
700V), and the total value is added to the cyan charging potential (-960V) and the developing bias (-860V).
V). Similarly, the value of the toner layer potential (-240V) on the photoconductor 21 formed by the image forming process of yellow, magenta, and cyan is set to the charging potential (-800V) of the yellow charging process and the developing bias of the developing process. (-
700V), and the total value is added to the black charging potential (-1040V) and the developing bias (-94V).
0V).

In the two-color mode, the value of the toner layer potential (-80 V) on the photoconductor 21 formed in the yellow image forming process is set to the charging potential (-800 V in the yellow charging process).
V) and the value of the developing bias (-700 V) in the developing process, and the total value is added to the charging potential (-8) of the second color.
80 V) and developing bias (-780 V). Further, in the three-color mode, the charging potential and the developing bias similar to those in the image forming process of yellow, magenta, and cyan in the full-color mode are set.

Further, in this embodiment, it is possible to form an image in each mode according to the number of cycles of the photoconductor 21, but since the toner amount on the photoconductor 21 differs depending on the designated color, the transfer is performed. The voltage controller 54 receives a control signal regarding the number of cycles of the photoconductor 21 from the image forming process determination device 50, and changes the transfer output value during the transfer process according to the number of cycles of the photoconductor 21.

More specifically, as shown in FIG. 7, in the case of a color which requires only one image forming step, the transfer output voltage value (A) is used, and when two image forming steps are required. Is the transfer output voltage value (B), the transfer output voltage value (C) is used when three image forming steps are needed, and the transfer output voltage value (C) is used when four image forming steps are needed. D) is used, and the transfer output voltage value is set larger as the amount of toner on the photoconductor 21 increases, thereby increasing the toner transfer capability.

In the above embodiment, when the image quality of each color in the monochromatic mode was examined, there was no density difference between the colors, and the image quality in the two-color mode, the three-color mode and the full-color mode was examined. It was confirmed that a multicolor image with good color balance can be obtained.

[0035]

As described above, according to the present invention, the necessary image forming process is determined according to the color information designated by the color designating means, and the image portion of each color image forming process is determined. Since the potential contrast of the non-image area is adjusted to the same value, productivity is sacrificed because it is not necessary to perform all the image forming steps for each color of a full-color image to form a single-color image or a two-color image, for example. Further, in the case of a single color, there is no density difference between the colors, and in the case of a two-color image, a three-color image, or a four-color image, it is possible to obtain a multicolor image with stable color balance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a multicolor image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a multicolor image forming apparatus to which the present invention is applied.

FIG. 3 is an explanatory diagram showing a control system of the multicolor image forming apparatus according to the embodiment.

FIG. 4 is an explanatory diagram showing a full-color image forming process of the multicolor image forming apparatus according to the embodiment.

FIG. 5 is an explanatory diagram showing an image forming process corresponding to each color mode of the multicolor image forming apparatus according to the embodiment.

FIG. 6 is a charging potential of the multicolor image forming apparatus according to the embodiment,
It is explanatory drawing which shows the setting method of a developing bias.

FIG. 7 is an explanatory diagram showing the relationship between the number of image forming steps and the transfer output voltage value of the multicolor image forming apparatus according to the embodiment.

FIG. 8A is an explanatory diagram showing a latent image potential change in the conventional multicolor image forming apparatus when the charging potential is constant, and FIG. 8B is a latent image potential when the charging potential in the conventional multicolor image forming apparatus changes. It is explanatory drawing which shows a change.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Charging means, 3 ... Exposure means, 4 ... Multicolor developing means, 5 ... Batch transfer means, 6 ... Image receptor, 7 ... Cleaning means, 8 ... Color designating means, 9 ... Image formation Process determining means, 10 ... Charging / developing bias adjusting means, 11 ... Transfer output adjusting means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nagakazu Okegawa 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A charging means (2) for uniformly charging the surface of a photoconductive image carrier (1), and an exposure scan corresponding to each color image on the surface of the charged image carrier (1). And an exposing means (3) for forming an electrostatic latent image, and a multi-color developing means for selectively developing the electrostatic latent image formed on the image carrier (1) by applying a developing bias with each color toner. (4), a plurality of color toner images are sequentially formed on the image carrier (1) by repeating the image forming steps of charging, exposing and developing for the image carrier (1), Batch transfer means (5) for transferring the plurality of color toner images to the image receptor (6)
In the multi-color image forming apparatus, in which the residual toner on the image carrier (1) is cleaned by the cleaning means (7) while being collectively transferred by the color designation means (8). ), An image forming process determining unit (9) that determines one or a plurality of image forming processes corresponding to the color information designated by the color designating unit (8), and the image forming process determining unit (9). The values of the charging potential and the developing bias during the image forming process of each color determined are adjusted in consideration of the toner layer potential on the image carrier (1), and the potential difference between the latent image potential and the developing bias and the charging potential and the developing bias. A multi-color image forming apparatus comprising: a charging / developing bias adjusting means (10) for keeping the above constant.