JPH06194969A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing color mixture in forming the image of respective colors when the image of plural colors is formed. CONSTITUTION:This device is provided with a latent image means for forming the image with developer on image carriers 9a to 9d, plural image forming stations consisting of a developing means and a cleaning means, a transfer means superposing and transferring a developed image formed by each image forming station on a recording medium 5, and a temporary fixing means temporarily fixing the image transferred on the recording medium 5 by each image forming station for every image forming station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a plurality of image forming stations, and more particularly to an image forming apparatus capable of preventing color mixture between the image forming stations.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic recording type image forming apparatus such as a copying machine, a toner image formed on an image bearing member such as a photosensitive drum is transferred to a recording medium and remains on the image bearing member after the transfer. The collected toner is removed and collected by the cleaning means, but most of the collected toner is discarded as waste toner.

Since the waste toner can be reused for development, it has been proposed in recent years to reuse the toner collected by the cleaning means in a monochrome color copying machine or the like.

[0004]

However, in a monochrome color copying machine, since the toner is one color, it is easy to reuse the collected toner for development. However, in a full-color copying machine or the like. However, since toners of a plurality of colors are used, it is necessary to prevent the toners from being mixed with each other. In this respect, conventionally, there is no specific proposal for preventing color mixture of toners, and reuse of the toner collected by the cleaning means has not been realized in the color image forming apparatus.

The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to prevent color mixture of the developer collected by the cleaning means in the image formation of each color when forming an image of a plurality of colors. It is intended to provide a possible image forming apparatus.

[0006]

A typical constitution according to the present invention for achieving the above object is a latent image means, a developing means and a cleaning means for forming an image on the image carrier with a developer. A plurality of image forming stations, transfer means for superposing and transferring the developed images formed by the respective image forming stations on the recording medium, and the images transferred to the recording medium by the respective image forming stations for each image. An image forming apparatus is configured by providing a hypothetical attaching means for hypothetically attaching between forming stations.

[0007]

In the above construction, the image transferred onto the recording medium at each of the image forming stations is presumed by the presumed fixing means. For this reason, the developer transferred to the recording medium at each image forming station has an increased adsorptivity, so that color mixing does not occur at other image forming stations.

[0008]

【Example】

[First Embodiment] Next, an image forming apparatus according to an embodiment of the present invention will be described. The present embodiment will be described using a color laser printer equipped with a plurality of image forming stations. FIG. 1 is a cross-sectional explanatory diagram showing the overall configuration of a laser printer, and FIG. 2 is a structural explanatory diagram of an image forming station.

First, the schematic structure of the color laser printer will be described with reference to FIG. 1. In the four-drum type color laser printer shown in this embodiment, an exposure means is provided around an image carrier and its periphery in order to speed up the apparatus. , Four image forming stations in which process means such as developing means are arranged, and an image formed on each image forming station on the image carrier is carried and carried by a carrying means which moves adjacent to the image carrier. The recording medium is sequentially transferred onto the recording medium.

Specifically, inside the apparatus main body 1, image forming stations P _a , P _b , P containing process means are built.
_c, P _d are arranged four laterally respective image forming stations _{P a, P b, P c} , P d of the lower belt driving roller 2a, 2b, the endless transfer belt 3 to 2c Has been hung up. The transfer belt 3 is rotated in the arrow C direction by driving and rotating the belt drive roller 2a in the arrow B direction by a drive motor (not shown).

A cassette 4 stores a large number of recording media 5 such as papers and plastic sheets. The recording media 5 housed in the cassette 4 is fed by a pickup roller 6 from the uppermost side. It The pair of registration rollers 7 with skew is corrected, to convey the image forming station _{P a, P b, P c} , on the transfer belt 3 performs and by P _d and synchronization. Reference numeral 8 denotes a conveyance guide for guiding the recording medium 5 from the registration roller pair 7 to the transfer belt 3.

[0012] Then the image forming station P _a,
The structure of P _b , P _c , and P _d will be described. The image forming stations P _a , P _b , P _c , and P _d have the same configuration, and the photosensitive drums 9a, 9b, 9c, which are image bearing members, respectively.
9d, primary chargers 10a, 10b, 10c, 10d, and developing devices 11a, 11b, 11 that form a process means around them.
c, 11d, transfer chargers 12a, 12b, 12c, 12d, and cleaning devices 13a, 13b, 13c, 13d, respectively. Above the photoconductor drums 9a, 9b, 9c and 9d, a laser beam scanner 14 as an exposing means is provided.
a, 14b, 14c and 14d are provided.

The primary chargers 10a, 10b, 10c, 10d
Constitutes a charging means for uniformly charging the surface of the photosensitive drums 9a, 9b, 9c and 9d prior to exposure. Further, the developing devices 11a, 11b, 11c, 11d
Are laser beam scanners 14a, 14b, 14c, 14
The developing means forms a visible image by adhering a developer (toner) corresponding to the electrostatic latent image formed on the drum surface by being exposed from d. In this embodiment, the developing device 11
a is for magenta development, developing unit 11b is for cyan development, developing unit 11c is for yellow development, and developing unit 11d is for black development.

Transfer chargers 12a, 12b, 12c, 12d
Is to transfer the toner images formed on the photoconductor drums 9a, 9b, 9c and 9d onto the recording medium 5, and to superimpose the toner images developed by the developing devices 11a, 11b, 11c and 11d of the respective colors. Then, a full-color image is formed by transferring it to the recording medium 5.

Cleaning devices 13a, 13b, 13c, 13d
Is a cleaning means for removing the residual toner adhering to the drum surface after the image transfer. Further, the laser beam scanners 14a, 14b, 14c, 14d
Is a semiconductor laser (not shown), polygon mirror, fθ
It has a lens and the like, receives an electric digital image signal, and irradiates a laser beam modulated corresponding to the signal in the generatrix direction of the photoconductor drums 9a, 9b, 9c, 9d for exposure.

Reference numeral 15 is a separating charger for separating the recording medium 5 conveyed on the transfer belt 3, and 16 is a fixing device for fixing the transferred image transferred to the recording medium 5. A fixing roller 16a having a heating means such as a heater therein and a pressure roller 16b in pressure contact therewith are provided.
Reference numeral 17 is a discharge tray for stacking the recording media 5 discharged outside the apparatus.

Further, each of the image forming stations P _a and P
_b, P _c, flash fixing lamp 18a as a temporary fixing means between P _d, 18b, 18c are provided. The fixing lamp 18a tentatively attaches the magenta image transferred onto the recording medium 5 by the image forming station P _a , and the fixing lamp 18b
Tentatively attaches the cyan image transferred at the image forming station P _b , and further, the fixing lamp 18 c is at the image forming station P _c.
It is assumed that the yellow image transferred in step 1 will be worn.

FIG. 2 shows an enlarged view of the image forming station P _a for forming a magenta image. The cleaning device 13a includes a cleaning blade 13a1 and a photosensitive drum 9a.
The waste toner above is scraped off and collected in the waste toner reservoir 13a2, and this waste toner reservoir 13a2 is connected to the toner hopper 11a1 of the developing device 11a via the recycle pipe 19. Then, the toner collected in the waste toner reservoir 13a2 is returned to the toner hopper 11a1 through the recycling pipe 19.

The other image forming stations P _b ,
P _c and P _d have the same configuration as this, and the toner collected in the toner reservoir of the cleaning device is returned to the toner hopper of the developing device as described above.

Next, the image forming operation will be described. When an image forming operation start signal is input to the apparatus main body 1, the photosensitive drum 9a starts to rotate in the direction of arrow A and the primary charger 10 is started.
When a voltage of -4 to -9 kV is applied to a, -300 to -900
The photoconductor drum 9a is uniformly charged by the charging current of μA. Then, the laser beam scanner 14a irradiates the drum surface with laser light modulated by an image signal corresponding to the magenta component of the original image to form an electrostatic latent image (exposure).

Next, the toner replenishing pipe of the developing device 11a shown in FIG.
The toner supplied from the toner hopper 11a1 via 11a2 based on a predetermined signal is mixed and stirred by a stirring member 11a3 as a developer, and a predetermined bias voltage is applied to the developing sleeve 11a4 to develop magenta on the photosensitive drum 9a. To do. The developing method at this time is reversal development, and toner of negative polarity is used.

On the other hand, the recording medium 5 stored in the cassette 4
Is fed by the pick-up roller 6 and the skew is corrected by the registration roller pair 7 which is temporarily stopped, and then the transfer belt is timed with the toner image formed on the photosensitive drum 9a. 3 is conveyed to above.
The recording medium 5 sent to the transfer belt 3 is transfer-charged by the transfer charger 12a at the transfer portion of the image forming station P _a , and the toner image is transferred to the recording medium 5.

When the magenta toner image is transferred to the recording medium 5 as described above, the fixing lamp 18 is attached to the recording medium 5.
The transfer light is assumed to be attached by irradiating flash light from a.
Unlike the fixing by the fixing device 16, this hypothetical fixing does not completely fix the toner image, but the surface of the toner image is melted and the toner particles are brought into close contact with each other, and the close contact with the recording medium 5 is increased.
The degree of hypothetical wear can be adjusted by the amount of flash light.

[0024] Thus, the recording medium 5 has been transferred to the magenta image even in contact with the photosensitive drum 9b in the next image forming station P _b, never magenta toner is re-transferred to the photosensitive drum 9b.

The same image forming process as described above is performed with a cyan image,
The yellow image and the black image are recorded in this order, and the recording medium 5
After the last black image is transferred to the fixing belt 16, it is separated from the transfer belt 3 while being subjected to AC static elimination by the separation charging device 15, and is conveyed to the fixing device 16. Then, after the image is completely fixed by the fixing device 16, the image is discharged to a discharge tray 17 outside the apparatus.

As described above, after the transfer of each color image to the recording medium 5, the hypothetical adhesion is performed, so that the other toner does not adhere to the photosensitive drums 9a, 9b, 9c and 9d of each color. Each cleaning device 13a, 13b, 13c,
The waste toner collected in 13d does not mix colors. Therefore, it is possible to return the toner collected by the cleaning device to the developing device for recycling.

For example, if the transfer efficiency of the toner developed on the photosensitive drum to the recording medium 5 is 80%, the remaining 20% of the toner is recovered as waste toner, and this toner is returned to the toner hopper through the recycling pipe. Therefore, the use efficiency of the toner is remarkably improved.

[Other Embodiments] In the above-described first embodiment, the flash fixing lamps 18a, 18b, 18c are used as hypothetical fixing means.
Although provided, as shown in FIG. 3, instead of the flash fixing lamp, each image forming station P _a, P _b,
Heat generating means 20a, 20b, 20c such as a thermal head is provided on the back surface of the transfer belt 3 between P _c and P _d , and the recording medium 5 on which the toner image is transferred is heated from the back surface and is assumed to be attached. It may be configured to do so.

In the case of providing the presumed fixing means by the heating, as shown in FIG. 4, the preheating means 21 is provided in front of the first image forming station P _a and the recording medium 5 before the toner image is transferred. It is better to preheat. By this preheating, the shrinkage of the paper due to the heating at the time of hypothetical wearing can be eliminated, and the occurrence of a situation in which the size of the image differs for each color can be prevented.

Further, when the hypothetical fixing is performed by the flash fixing lamps 18a, 18b and 18c as in the first embodiment described above, it is more preferable to use the toner having photoconductivity with respect to the flash light. When such a toner is used, the toner image is assumedly attached by the flash light, and at the same time, the electric charge disappears. Retransfer is completely prevented without being affected by the electric field. Further, if the light having the same wavelength as the flash light is exposed in front of the cleaning device, the toner can be cleaned with a light load, and the toner to be recycled is not fused or aggregated.

Further, the image forming apparatus according to the present invention is not limited to the case of full color recording having four image forming stations as in the above-described first embodiment, but may be, for example, an image forming apparatus such as a two-color image or a three-color image. Can also be applied to.

As the developing method, various known developing methods such as a two-component magnetic brush developing method, a cascade developing method, a touchdown developing method and a cloud developing method can be used.

As for the constitution of the charging means, as in the first embodiment described above, a metal shield such as aluminum is provided around the three sides of the tungsten wire, and a positive or negative voltage is produced by applying a high voltage to the tungsten wire. In addition to the configuration in which the ions are moved to the surface of the photosensitive drum and the surface of the drum is uniformly charged, it is naturally possible to use a so-called contact charging method in which, for example, a charging roller is brought into contact with a photosensitive drum Is. Further, the charging means may be of a blade type (charging blade), a pad type, a block type, a rod type, a wire type or the like, other than the roller type.

As a method for cleaning the toner remaining on the photosensitive drum, the cleaning means may be constituted by using a blade, a fur brush, a magnetic brush or the like.

Further, although the laser beam printer is illustrated as the image forming apparatus in the above-mentioned embodiments, the present invention is not limited to this, and other image forming apparatuses such as an electrophotographic copying machine, a facsimile machine, a word processor and the like can be used. It is also possible to use for.

[0036]

As described above, according to the present invention, since the developed image is assumedly attached between the image forming stations, it is possible to eliminate the color mixture of the developers between the image forming stations even when forming plural color images. I can. Therefore, the developer collected by the cleaning means can be returned to the developing means and reused.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a configuration in which toner collected by a cleaning device in an image forming station is returned to a developing device.

FIG. 3 is an explanatory diagram of a configuration of an image forming apparatus that performs hypothetical attachment by heating the back surface.

FIG. 4 is a configuration explanatory diagram of an image forming apparatus that preheats a recording medium.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Device body 2a, 2b, 2c ... Belt drive roller 3 ... Transfer belt 4 ... Cassette 5 ... Recording medium 6 ... Pickup roller 7 ... Registration roller 8 ... Conveying guide 9a, 9b, 9c, 9d ... Photosensitive drum 10a, 10b , 10c, 10d ... Primary charger 11a, 11b, 11c, 11d ... Developing device 12a, 12b, 12c, 12d ... Transfer charger 13a, 13b, 13c, 13d ... Cleaning device 14a, 14b, 14c, 14d ... Laser beam scanner 15 ... separation charger 16 ... fixer 16a ... fixing roller 16b ... pressing roller 17 ... discharge tray 18a, 18b, 18c ... flash fixing lamp 19 ... recycling pipe 20a, 20b, 20c ... heat generating means 21 ... preheating means P _a, P _b , P _c , P _d ... Image forming station

Claims (5)

[Claims] 1. A plurality of image forming stations each comprising a latent image means, a developing means and a cleaning means for forming an image with a developer on an image carrier, and a developed image formed by each of the image forming stations. An image forming device comprising: a transfer unit that transfers the image onto the recording medium in an overlapping manner; and a hypothetical attaching unit that hypothetically attaches the image transferred to the recording medium by each image forming station between the image forming stations. apparatus. 2. The image forming apparatus according to claim 1, wherein the hypothetical fixing means is based on flash exposure. 3. The image forming apparatus according to claim 1, wherein the hypothetical fixing means is a device for heating the back surface of the recording medium. 4. The image forming apparatus according to claim 1, further comprising means for preheating before transferring the developed image to the recording medium. 5. The image forming apparatus according to claim 1, wherein each of the image forming stations has means for supplying the developer collected by the cleaning means to the developing means.