JPH06175453A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which can maintain the cleaning function of a cleaning means in an image forming part which does not contribute to image formation, for a long time. CONSTITUTION:In an image forming device comprising image bearing media 9a, 9b, and a plurality of image forming parts Pa, Pb acting the image carriers 9a, 9b so as to form images, the plurality of image forming parts Pa, Pb have developing means 11a, 11b for developing latent images formed on the image carriers 9a, 9b, and cleaning means 13a, 13b for removing developer remaining on the image carriers 9a, 9b, the developer is allowed to stick to the image carrier from he developing means in at least one of the image forming parts which does not contribute to image formation during an image forming process carried out in the other one of the image forming parts.

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 an image bearing member and a plurality of image forming portions which act on the image bearing member to form an image on a recording material.

[0002]

2. Description of the Related Art Conventionally, as an example of an image forming apparatus having an image bearing member and a plurality of image forming portions which act on the image bearing member to form an image on a recording material, a 4-drum type color image forming apparatus is provided. Is shown in FIG. The four-drum type color image forming apparatus is provided with four image forming units each having an image carrier and process means arranged around the image carrier in order to increase the speed of the apparatus.
The image on the image carrier formed by each image forming unit is sequentially transferred onto the recording material carried and carried by the carrying means moving adjacent to the image carrier.

In FIG. 4, the image forming apparatus includes image forming units P _a , P _b , which are necessary for forming a full-color image.
Photosensitive drums 51a and 51 that are image bearing _members for P _c and P _d
b, 51c and 51d, and chargers 52a, 52b, 52c and 52d, which are charging means, scanning optical devices (not shown), which are optical scanning means, and developing devices 53a, which are developing means.
53b, 53c, 53d, cleaner as a cleaning means
Process means such as 54a, 54b, 54c and 54d are arranged. Further, the transfer means includes an endless belt-shaped transfer belt 55 common to each image forming unit, and transfer chargers 56a, 56b, 56.
c and 56d, and the photosensitive drums 51a and 51d at the respective image forming portions on the transfer material 57 carried and conveyed on the transfer belt 55.
Each color image formed on b, 51c and 51d is transferred. The transfer material 57 is supplied from the feeding cassette 58,
After the transfer process, the transfer image is separated from the transfer belt 55, the transferred image is fixed by the fixing device 59, and the transferred image is discharged onto the discharge tray 60.

In the above arrangement, especially in an office or the like which requires a large amount of processing, the amount of black monochromatic originals is still overwhelmingly larger than that of color originals due to running costs and document preparation, and therefore images of monochromatic black are used. The forming operation is frequently performed. This is because it is difficult to perform high-speed continuous image forming operation in the conventional 1-drum type color image forming apparatus.
Even in the black monochromatic mode in which the image formation on the drum is performed only once, there is a drawback that the image formation can be performed only at a lower speed than that of the monochrome image forming apparatus. On the other hand, the 4-drum type image forming apparatus shown in FIG. 4 can perform high-speed continuous image forming operations similar to the high-speed black-and-white image forming apparatus, and it is considered that the use opportunities in the black monochromatic mode increase. It is also considered that the use of other colors in the single color mode will increase.

[0005]

However, in the color image forming apparatus shown in the above-mentioned prior art, even when the single color mode is continuously performed, the photosensitive drums of other image forming sections are also provided unless special stop means is provided. Rotate together. Since the image (toner image) formed on the photosensitive drum is a single color, no toner is placed on the drum other than the image forming operation, and the toner is not conveyed to the cleaner. Therefore, since there is no substance that acts as a lubricant between the cleaning blade and the photosensitive drum, the friction coefficient μ between the two becomes extremely high, shortening the life due to blade chipping and abrasion, and further causing blade blister. Could result in poor cleaning.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an image forming apparatus capable of maintaining the cleaning performance of the cleaning means of the image forming portion which does not contribute to image formation for a long period of time. is there.

[0007]

A typical means for solving the above-mentioned problems of the prior art and applied to the embodiments described below is an image carrier and an image carrier acting on the image carrier. In an image forming apparatus having a plurality of image forming units for forming an image, the plurality of image forming units include a developing unit that develops a latent image formed on the image carrier, and a developing unit that remains on the image carrier. A cleaning unit for removing the agent, and a cleaning unit on the image carrier from the developing unit in at least one image forming unit that does not contribute to image formation during the image forming process in the one image forming unit. It is characterized in that a developer is attached.

[0008]

According to the above means, among the plurality of image forming units,
While the image forming process is being performed in the first image forming section, the developer is attached to the image bearing member from the developing means in the at least one image forming section that does not contribute to image formation.

[0009]

【Example】

[First Embodiment] Next, an image forming apparatus according to an embodiment of the present invention to which the above means is applied will be described. In this example,
A color electrophotographic copying machine having a plurality of image carriers and equipped with a plurality of image forming units will be described. FIG. 1 is an explanatory diagram showing the operation of an image forming unit that does not contribute to image formation, FIG. 2 is an explanatory diagram of a cleaning device, and FIG. 3 is a sectional explanatory diagram showing the overall configuration of a copying device.

First, the schematic structure of the color copying apparatus will be described with reference to FIG. 3. In the four-drum type color copying apparatus shown in this embodiment, in order to increase the speed of the apparatus, a process means is provided around the image carrier and its surroundings. Four image forming sections are arranged, and the image on the image carrier formed by each of the image forming sections is carried by the transporting means that moves adjacent to the image carrier.
It is configured to be sequentially transferred onto the conveyed recording material.

Specifically, inside the apparatus main body 1, image forming portions P _a , P _b , P _c , and P _d containing process means are laterally arranged, and each image forming portion P _a , P _b , P
_{Below the c} and P _d , an endless transfer belt 3 is stretched around belt drive rollers 2 a and 2 b. The transfer belt 3 is rotated in the arrow C direction by rotating the belt drive rollers 2a and 2b in the arrow B direction by a drive motor (not shown). A cassette 4 stores a recording sheet 5 which is a recording material, and the recording sheet 5 stored in the cassette 4 is fed by a pickup roller 6 from the uppermost side. And registration roller pair 7
By with skew is corrected, to convey the image forming portion _{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 sheet 5 from the registration roller pair 7 to the transfer belt 3.

Next, the image forming portions P _a , P _b , P _c , P
Explaining the structure of _d , the photosensitive drum 9 which is an image carrier.
a primary chargers 10a, 10b, 10c and 10d having a, 9b, 9c and 9d and constituting process means around them, and a developing device
11a, 11b, 11c, 11d, transfer chargers 12a, 12b, 12
c, 12d and cleaning devices 13a, 13b, 13c, 13d, respectively. The photosensitive drums 9a, 9b,
Above the 9c and 9d, a laser beam scanner (not shown) as an exposing means, the primary chargers 10a and 10b,
10c, 10d and cleaning devices 13a, 13b, 13c, 13d
A pre-exposure light source (not shown) is provided between and.

The primary chargers 10a, 10b, 10c, 10d
Is for uniformly charging the surface of the photosensitive drums 9a, 9b, 9c, 9d prior to exposing the photosensitive drums 9a, 9b, 9c, 9d. Black, magenta, yellow on the latent image
The toner of each color of cyan is adhered to form a visible image. The transfer chargers 12a, 12b, 12c, 12d are for transferring the toner images formed on the photosensitive drums 9a, 9b, 9c, 9d to the recording sheet 5, and are cleaning devices.
Reference numerals 13a, 13b, 13c and 13d are for removing the residual toner adhering to the drum surface after the image transfer. Further, the laser beam scanner has a semiconductor laser, a polygon mirror, an fθ lens, etc., and receives an electric digital image signal input and modulates the laser beam corresponding to the signal to the photosensitive drums 9a, 9b, 9c, 9d. Exposure is performed by irradiating in the direction of the generatrix.

Reference numeral 14 is a separating charger for separating the recording sheet 5 conveyed on the transfer belt 3, and 15 is a fixing device for fixing the transferred image transferred to the recording sheet 5. A fixing roller 15a having a heating means such as a heater therein and a pressure roller 15b in pressure contact with the fixing roller 15a are provided. Reference numeral 16 is a discharge tray for stacking the recording sheets 5 discharged outside the apparatus.

The image forming operation will now be described. When an image forming operation start signal is input to the apparatus main body 1, the photosensitive drum 9a starts rotating in the direction of arrow A, and the primary charger 10a.
Are uniformly charged by a laser beam scanner (not shown), and a laser beam modulated by an image signal corresponding to the black component of the original image is applied to the drum surface to form an electrostatic latent image (exposure). . Next developing device
The yellow toner is supplied by 11a to form a toner image by visualizing the latent image.

On the other hand, the recording sheet 5 accommodated in the cassette 4 is fed by the pickup roller 6 and is formed on the photosensitive drum 9a after the skew feeding is corrected by the registration roller pair 7 which is temporarily stopped. The toner image is conveyed onto the transfer belt 3 at the timing of the toner image thus formed.
Recording sheet 5 sent into the transfer belt 3, the transfer charging by the transfer charger 12a at the transfer portion of the image forming portion P _a is performed, the toner image is transferred onto the recording sheet 5. The above steps are similarly performed in the image forming units P _b , P _c , and P _d , and the magenta toner image, the cyan toner image, and the black toner image are sequentially transferred to the recording sheet 5.

The recording sheet 5 on which the image transfer has been completed is separated from the transfer belt 3 while being subjected to AC static elimination by the separation charging device 14 at the left end portion of the transfer belt 3, and is conveyed to the fixing device 15. Then, the recording sheet 5 on which the image is fixed by the fixing device 15 is discharged to the discharge tray 16 outside the apparatus.

A fur brush 17 as a belt cleaning means is in contact with a part of the transfer belt 3,
By rotating the fur brush 17 at a high speed, the toner accumulated on the transfer belt 3 is removed from the belt.

The cleaning devices 13a, 13b, 13c,
13d (hereinafter, simply referred to as "cleaning device 13") is a photosensitive drum 9a, 9b, 9c, 9d after the image transfer process is completed.
To remove the toner remaining in the image (hereinafter abbreviated as "photosensitive drum 9"), as shown in FIG. 2, the cleaning blades 18 that come into contact with the drum surface from the direction opposite to the drum rotation direction shown by arrow A are respectively attached. Have The cleaning blades 18 are fixed to the blade holders 20 provided on the downstream side of the cleaning container 19 in the drum rotation direction by screwing or the like. The cleaning blade 18 is provided on the downstream side of the cleaning container 19 in the drum rotation direction.
A squeeze sheet 21 is provided for storing the toner scraped off by the inside of the container. Further, inside the cleaning container 19, a conveying screw 22 for collecting and conveying the waste toner is provided.

Next, an image forming operation in the image forming portion P _b which does not contribute to image formation will be described with reference to FIG. In the single-color mode, that is, when the image forming operation is performed only in the image forming unit P _a , the developing device 11 _b in the image forming unit P _b is used.
Developing sleeve 11b ₁ of the rotating while in pressure contact with the photosensitive drum 9b. Then, when the charging, the exposure amount, and the developing bias control are set so as to adhere to the extent of toner fog, the toner adhering to the developing sleeve 11b ₁ is conveyed to the cleaning device 13b, and between the cleaning blade 18b and the photosensitive drum 9b. Be transported.

[0021] Thus, the photosensitive cleaning blade 18b of the image forming portion P _b which does not contribute to the image formation drum 9
Since the toner that acts as a lubricant intervenes between b, the friction coefficient μ between the two is kept low, and the life of the blade is shortened due to chipping or wear, and it is possible to prevent the blade from curling and causing cleaning failure. Therefore, the performance of the cleaning device 13b can be maintained for a long period of time.

[0022] Incidentally, the invention is not limited to the image forming portion P _b is to convey the toner to the cleaning means during the non-image forming, the image forming unit P _c which does not contribute to other image forming, also in P _d It is also possible to
It is also possible to perform it in at least one of the image forming units.

[Second Embodiment] Next, another example of the image forming apparatus shown in the first embodiment will be described. Since the schematic structure of the copying apparatus is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted.

In the first embodiment, the developing sleeve 11b ₁ in the image forming portion P _b that does not contribute to image formation during non-image formation is rotated while being pressed against the photosensitive drum 9b. The toner consumption in the developing device 11b increases. In this embodiment, in order to prevent this, the developing device 11
The developing sleeve 11b ₁ of b is abutted against the photosensitive drum 9b and is not rotated. In other words, the primary charging in the image forming unit P _b, exposing the to 0, the pre-exposure light source (not shown) to erase the potential of completely photosensitive drum 9b, while a developing bias to 0, the developing sleeve 11b _By bringing the toner on ₁ into contact with the photosensitive drum 9b, it becomes possible to convey the toner by a smaller amount than in the first embodiment. With the above configuration, the performance of the cleaning device 13b can be maintained for a long period of time, and the amount of toner used can be reduced, so that the running cost can be reduced.

[Third Embodiment] Next, another example of the image forming apparatus shown in the first embodiment will be described. Since the schematic structure of the copying apparatus is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted.

[0026] The first, in the second embodiment, the image forming unit P _b which does not contribute to the image formed on the non-image-forming, albeit in trace amounts maintains the performance of the cleaning device 13b by continuing feeding toner However, since the friction coefficient μ between the photosensitive drum 9b and the cleaning blade 18b becomes high under environmental conditions such as high temperature and high humidity, a large amount of toner is supplied from the developing device 11b to the photosensitive drum 9b in advance to reduce the temperature and humidity. Occasionally, values of primary charge amount, exposure amount, developing bias, etc. are stored in a ROM table so that a small amount of toner is supplied, and a variable value is stored in the RAM each time depending on a temperature and humidity value detected by a detection unit (not shown). And developing device
It is also possible to control the amount of toner supplied in 13b.

[0027]

As described above, according to the present invention, among a plurality of image forming sections, development is performed in at least one image forming section that does not contribute to image formation while the image forming step is being performed in one image forming section. By attaching the developer onto the image carrier from the means, the cleaning performance of the cleaning means can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an operation of an image forming unit that does not contribute to image formation.

FIG. 2 is an explanatory diagram of a cleaning device.

FIG. 3 is a cross-sectional explanatory diagram showing an overall configuration of a copying apparatus.

FIG. 4 is an explanatory diagram of a conventional copying apparatus.

[Explanation of symbols]

P _a , P _b , P _c , P _d ... Image forming unit 1 ... Device body 2a, 2b ... Belt driving roller 3 ... Transfer belt 4 ... Cassette 5 ... Recording sheet 6 ... Pickup roller 7 ... Registration roller pair 8 ... Conveyance guide 9a, 9b, 9c, 9d ... photosensitive drum 10a, 10b, 10c, 10d ... the primary charger 11a, 11b, 11c, 11d ... developing device 11a _1, 11b ₁ ... developing sleeve 12a, 12b, 12c, 12d ... transfer charger 13a, 13b, 13c, 13d ... Cleaning device 14 ... Separating charging device 15 ... Fixing device 15a ... Fixing roller 15b ... Pressure roller 16 ... Discharge tray 17 ... Fur brush 18a, 18b, 18c, 18d ... Cleaning blade 19 ... Cleaning container 20… Blade holder 21… Squisheet 22… Conveyor screw

Claims (5)

[Claims] 1. An image forming apparatus having an image carrier and a plurality of image forming units that act on the image carrier to form an image on a recording material, wherein the plurality of image forming units are the image carrier. 1 has a developing means for developing the latent image formed thereon and a cleaning means for removing the developer remaining on the image carrier.
An image forming apparatus characterized in that a developer is attached onto an image carrier from a developing means in at least one image forming section that does not contribute to image formation during the image forming step in the image forming section. 2. The image forming apparatus according to claim 1, wherein the amount of the developer deposited on the image bearing member in the image forming portion that does not contribute to the image formation is smaller than that during the image formation. 3. The primary charge amount, the exposure amount, the developing bias, etc. are made variable so that a variable amount of the developer adheres to the image carrier in the image forming portion which does not contribute to the image formation. The image forming apparatus according to item 1. 4. The image forming apparatus according to claim 1, wherein the amount of the developer deposited on the image carrier in the image forming portion that does not contribute to the image formation is variable with respect to the environment. 5. The image forming apparatus according to claim 4, wherein the amount of the developer attached to the image bearing member in the image forming unit that does not contribute to the image formation is larger at high temperature and high humidity than at low temperature and low humidity. apparatus.