JPS63149665A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce the degree of deterioration such as color darkening in the quality of an image even if developers are mixed with each other, by vertically arraying developing devices storing plural developers oppositely to an image carrier in the other of saturation so that the saturation is gradually reduced from the uppermost developing device. CONSTITUTION:In a device for successively forming a color separation toner images of an original image on a photosensitive belt face by electrophotographic method, an original 0 is set up-side down and covered with an original pressing plate 3. An image carrier 4 is moved at a prescribed speed in an arrow direction from a rotation driving roll 51 to a roll 54. 1st-4th developing devices 15-18 storing respective developers are successively and vertically arranged in accordance with the differences of saturation values in the developers. Since the saturation level of a developer to be mixed and arrayed on the upper side is higher than that of a developer on the lower receiving side, the saturation is not practically reduced even if different colors are mixed with each other. Thereby, the deterioration of color quality such as color darkening and color balance reduction can be reduced.

Description

[Detailed description of the invention] B. Purpose of the invention [Industrial application field] The present invention relates to an image forming apparatus.

More specifically, color developers (toners) that have different colors
It is equipped with a plurality of developing devices containing a plurality of developing devices, and these developing devices are selectively applied to the image carrier to produce mono-color (single-color) printing in a desired color or multi-color printing by combining two or more desired colors. The present invention relates to an image forming apparatus that outputs prints or full-color (natural color) prints.

[Conventional technology]

The above-mentioned image forming devices include electrophotographic color copying machines,
It is used in electrostatic recording color copying machines, etc.

The developing devices are arranged in multiple stages above and below each other so as to face an image bearing member, that is, an electrophotographic photoreceptor such as a rotating drum type or a rotating belt type, or an electrostatic Qa electric body. Develop them according to the image creation sequence specified in the control system! The J position is selectively controlled to move forward and backward relative to the image carrier between a working position 11 (developing working position) and a non-working position, so that the above-mentioned monochrome color or three multicolor color can be obtained.
A full color image print is output.

[Problem that the invention seeks to solve]

In the above-mentioned image forming apparatus, there is a developing device that contains developers of different colors. It is necessary to prevent the developer from getting mixed in between the printers. This is because the mixing of different color developers between developing devices causes deterioration of image quality, such as dulling of colors in the output image due to illegal color mixing and loss of the overall color balance of a full-color image.

Mixing of different color developers between developing devices occurs mainly due to the following reasons. That is, the developing sleeve, developing roller, etc. of the developing device may be damaged due to vibration or developing operation when the developing device is moved forward from a non-working position to a working position for developing a latent image or when the developing device is moved forward from a non-working position to a working position with respect to the image carrier. This is caused when the scattered developer mainly generated on the lower side of the developing device sprinkles onto the developing means such as the developing sleeve and the developing roller of the developing device located lower than the developing device.

Although various efforts have been made to prevent the above-mentioned scattering of developer and scattering of developer from being sprinkled onto the developing means of other developing devices, etc., it is impossible to completely prevent this. It has not yet reached the point where it can be done.

In view of the above, the present invention has been devised to minimize the degree of deterioration in image quality as described above even if different color developers are mixed between developing devices.

1. Structure of the invention [Means for solving problems] The present invention is.

In an image forming apparatus including a plurality of developing devices containing developers of different colors arranged one above the other with the developing means side facing the image carrier, the topmost developing device The developing devices are arranged vertically in such a manner that the layers of the developer contained in each of the developing devices are arranged in order of saturation gradient from high to low as one goes from the device to the lowest stage developing device. The gist of the present invention is an image forming apparatus characterized by the following.

[For production]

In other words, by providing the developing devices in the image forming apparatus main body side in the above-mentioned vertical order arrangement in relation to the saturation of the developer contained therein, Even if a different color developer is mixed into the developing device side of the equipment, mainly due to developer scattering, the chroma of the mixed developer must be higher than the saturation of the developer in the developing device on the side receiving the mixing. Since the difference in saturation gradient between the two is smaller than the difference in saturation with the developer in other developing devices, the saturation of the main developed color in the developing device mixed with the different color developer is substantially reduced. In other words, it is possible to minimize the degree of deterioration of image quality such as dull colors and loss of color balance.

(Example〕 FIG. 1 is a longitudinal sectional front view of an image forming apparatus according to an embodiment.

The apparatus of this example uses an endless rotating belt-type electrophotographic photoreceptor as an image carrier, and sequentially forms color-separated toner images of the original image on the surface of the photoreceptor belt by electrophotography, and the formed color-separated toner images. This is a color copying device that outputs a full-color or multicolor print corresponding to the original image by superimposing and transferring the image onto a transfer material. Of course 11F + 1: I 10 small pictures π-'1-)
It is also possible to output monochrome prints using the R pump.

The principles and processes for forming color-separated full-color or multi-color prints or mono-color prints by electrophotography are well known, and since the present invention itself is out of the point, the structure of the apparatus in this embodiment will be described below. Only a brief description of the installed process equipment will be provided.

1 is an external case of the device, 2 is a fixed document table made of a transparent plate such as glass, which is fitted into a large window hole formed on the upper surface of the case, and the document O is placed with the image side to be copied facing downward. The document is placed a2t at a predetermined position on the upper surface of the document table, and is set by covering the document pressure plate 3 thereon.

4 is an electrophotographic endless photosensitive belt as an image carrier;
Four belt-suspending rollers 5I including a drive roller 5K rotatably driven by a motor (not shown) provided with an encoder
54 and is supported and rotated at a predetermined speed in the direction of the arrow.

6 is a charge corotron that uniformly charges the outer surface of the photosensitive belt positively or negatively.

7 is the lower surface of the document table 2, and the third and fortieth-ra 53 and 54.
The reciprocating motion between the photosensitive belt portion in between is controlled by a tension wire or rotating belt mechanism 8/91Φ92, and the image of the original O set on the original platen 2 with the image surface facing downward is color-separated. Or 3rd and 40th-ra 53"5 without color separation
This is a moving optical device that performs exposure processing on a partial surface of a photoreceptor belt between devices, and includes an optical housing 10. Short focus lens array (trade name SELFOC) 11, document illumination lamp l 2. Reflector 13, dichroic filter for three color separation (red, green,
Consists of 14 magnolia (blue and colorless ones arranged side by side). Then, by exposure by the moving optical device N10, the 3rd and 40th-
An electrostatic latent image is formed on the outer surface of the photoreceptor belt portion between the edges 53 and 51.

15Φ16/17 fist 18 is the 40th-ra 54 and the 10th-
A developing sleeve (or developing roller) 15a@16a*17a@ which is a developing means is placed on the outer surface of the photosensitive belt portion between R5 and R5.
This is a four developing device including a first, second diameter, third and fourth developing device which are arranged vertically in multiple stages with their 18a sides facing each other. In this example, the first to fourth developing devices 15 to 18 contain toners (developers) of different colors, yellow, magenta, cyan, and black, respectively. That is, the chroma of these developers is in the order of yellow, magenta, cyan, and black from highest to lowest. Therefore, in this example, according to the present invention, from the first developing device at the top stage to the fourth developing device at the lowest stage, The developing devices are arranged vertically in such a manner that the saturation of the developer contained in each developing device is in the order of saturation gradient from high to low as one goes toward the device.

The first to fourth developing devices 15 to 18 have their developing sleeves selectively contacted with the surface of the photosensitive belt 4 according to an image forming sequence specified in advance by a control system in an apparatus console (not shown). A switching mechanism (not shown) controls the position switching between a very close developing position and a predetermined non-developing position, and the developing device switched to the developing position forms the four surfaces of the photoreceptor belt W! Six images are color developed by the developing device.

19 is a transfer material cassette (cartridge) loaded with transfer materials P; 20 is a paper feed roller that feeds the transfer material P one sheet at a time from the cassette; 21 is a first and second roller 51; The lower side of the photoreceptor belt between 52 and 52 is moved up and down by an elevating mechanism 23 using cams and links between a position close to the lower surface of the photoreceptor belt and a position separated from the lower surface of the photoreceptor belt. It is an endless rotating belt that conveys transfer material freely.

It is suspended between a drive roller 211 and a turn roller 212, which are rotationally driven by a motor (not shown) provided with an encoder, and is controlled to rotate in the direction of the arrow.

The transfer material P fed out one sheet from the cassette 19 is transferred to the photosensitive belt portion between the first and second rollers 51 and 52 and the conveyor belt)
20, the suction fan 24 and the suction housing 25
It is conveyed while being suctioned and held on the conveyor belt 20 by the air suction force of the suction device consisting of the following.

Reference numeral 26 denotes a transfer Nirotron that transfers the toner image on the outer surface of the photosensitive belt 4 to the E side of the transfer material P transported by the transport belt 2G, and the Nirotron 26 is connected to a tension wire 27φ drive pulley 281 and a driven pulley. 282 controls the reciprocating movement within the suction housing 25 in the left and right directions in the drawing.

29 is a cleaning device fi for removing transfer residual toner from the outer surface of the photosensitive belt, and 30 is a pre-exposure lamp for removing charges from the surface of the photosensitive belt.

Sl is the tip position of the document table provided inside the photosensitive belt 4;
A position sensor for detecting two types of position marks (not shown) indicating the leading edge position of the transfer material, S2 is a conveyor belt 20
This is a leading edge detection sensor for detecting the leading edge of the transfer material P being conveyed.

Reference numeral 31 denotes a toner image fixing device, in which the transfer material P on the conveyor belt 20, on which the toner image has been transferred once or multiple times, is introduced and passes through to fix the toner image. 32 outputs the desired monochrome, multicolor, or full color print.

33 is a door for opening the developing bag mounting section.

It is opened and closed centering around the hinge part 34. It is opened as shown by the two-dot chain line when replenishing developer to the developing device.

Thus, the first to fourth developing devices 15 to 18 are provided in the main body of the image forming apparatus in the above-mentioned vertical order in relation to the saturation of the developer contained therein. , from the developing device side of the upper level equipment (for example, the second developing device 1116) to the developing device side of the lower stage side (for example, v43
Even if a different color developer is mixed into the developing device 17) mainly due to developer scattering, the saturation of the mixed developer is higher than the saturation of the developer in the developing device receiving the mixing. Since the difference in saturation gradient between the two is smaller than the difference in saturation with the developer in other developing devices, the saturation of the main developed color in the developing device mixed with the different color developer is substantially reduced. In other words, it is possible to minimize the degree of deterioration of image quality such as dull colors and loss of color balance.

C1 Effects of the Invention As described above, according to the present invention, even if developer mixes between developing devices of different colors, it is possible to reduce the degree of deterioration of image quality such as dullness of color and loss of color balance. It can be made smaller and achieves the intended purpose better.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of an image forming apparatus according to an embodiment. 2 is a fixed document table; 4 is a rotating belt type electrophotographic photoreceptor;
7 is a moving exposure optical device, 15 to 18 are 1st-:jS4
developing device.

Claims (1)

[Claims] (1) In an image forming apparatus equipped with a plurality of developing devices containing developers of different colors, arranged one above the other with the developing means side facing the image carrier, the topmost one. The developing devices are moved up and down so that the saturation of the developer stored in each developing device is in the order of saturation gradient from high to low as you go from the developing device of the first stage to the lowest developing device. An image forming apparatus characterized in that the image forming apparatus is arranged in order.