JP2000081802A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute operation such as cleaning by an optimum amount and to prevent a harmful influence caused by too much or too little operation by separating an image carrier from a transfer material carrier, executing the cleaning operation for the respective carriers in a temporally overlapped state, and controlling so that at least either the time for starting the cleaning operation or the time for stopping it may be different between them. SOLUTION: By lowering a driven roller 21, a transfer belt 12 on the paper supply side is lowered. At such a time, the roller 21 is opposed to a conductive roller which is grounded. By applying a DC current having the same polarity as a transfer applied current to the roller 21, sucking force enough to carry paper is generated. At the time of a preparation operation and recovering operation after processing for a faulty carrying of transfer material, the belt 12 is lowered after paper ejection so as to be separated from all the photoreceptor drums 1a to 1d, and the operation is executed by the optimum amount. Namely, the drums 1a to 1d are separated from the belt 12, and the cleaning operation for them is executed to be temporally overlapped, and the control is executed so that the time for starting the cleaning operation or the time for stopping it may be different between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer material which is supported on a moving transfer material carrier, and which is formed on an image carrier made of a photoreceptor or an insulator by applying a transfer electric field to the transfer material. The present invention relates to a transfer device for transferring a transferred toner image by superimposing the toner image on the transfer material, and can be suitably used as an image forming apparatus such as a color electrophotographic copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus having a plurality of image forming units, forming toner images of different colors in each image forming unit, and sequentially transferring the toner images to the same transfer material, a so-called color image. Various forming apparatuses have been proposed, and among them, a color recording apparatus based on a multicolor electrophotographic system is frequently used.

An example of such a color electrophotographic recording apparatus will be briefly described with reference to FIG. 3. First, second, third and fourth image forming units Pa, Pb, Pc, and Pd are provided in parallel, and images of different colors are formed through processes of latent image, development, and transfer.

[0004] The structure of the main body will be described. Image forming unit Pa,
Pb, Pc, and Pd each include a dedicated image carrier, in this example, electrophotographic photosensitive drums 1a, 1b, 1c, and 1d, and electrophotographic images formed by the image forming units Pa, Pb, Pc, and Pd. The images on the photosensitive drums 1a, 1b, 1c and 1d are transferred onto a transfer material P that is carried and conveyed on a transfer belt 12 of a transfer material carrier that moves adjacent to each image forming unit. Further, the transfer material P heated and pressed by the fixing device 9 and discharged is discharged.

Hereinafter, the latent image forming section will be described. Exposure lamps (not shown), corona chargers 2a, 2b, 2c, 2d, light source devices (not shown), and polygons for scanning light emitted from the light source devices are provided on the outer periphery of the photosensitive drums 1a, 1b, 1c, and 1d. A mirror and a potential sensor are provided. Laser light emitted from a light source device (not shown) is scanned by rotating a polygon mirror, and scanning light obtained by deflecting a light beam by a reflection mirror is applied to the photosensitive drums 1a and 1a.
A latent image corresponding to an image signal is formed via an fθ lens that converges on the generatrix of 1b, 1c and 1d.

Hereinafter, the developing section will be described. Developing device 4
A, 4b, 4c, and 4d are supplied with respective color developers (not shown) of cyan (hereinafter abbreviated as C), magenta (hereinafter abbreviated as M), yellow (hereinafter abbreviated as Y), and black (hereinafter abbreviated as BK). A predetermined amount is filled by the device. The developing devices 4a, 4b, 4c, 4d apply the developer to the photosensitive drums 1a, 1b, 1c, 1d in accordance with the latent image formed by the scanning light.
Form a visible image on top.

The transfer section will be described below. The transfer material P that has been in the transfer material cassette 7 is sent through a registration roller 13 onto a transfer belt 12 of a transfer material carrier.

Here, the transfer belt 12 is wound around a driving roller 20 and a driven roller 21, and an upper extending portion is in contact with the photosensitive drums 1a to 1d. The transfer belt 12 includes a polyethylene terephthalate resin film sheet (PET sheet), a polyvinylidene fluoride resin film sheet,
It is a dielectric resin film such as a polyurethane resin film sheet, and its both ends are overlapped and joined to form an endless shape, or a seamless (seamless) belt is used. In the case of a belt having no seams, not only is it difficult to produce a belt having uniform physical properties, but it is not suitable in terms of cost, etc., for mass production such as a belt having a stable circumference and production time. On the other hand, in the case of a belt having a seam, when forming an image on the seam position, changes in physical properties such as unevenness and resistance value of the seam portion are inevitable, and forming an image on the seam disturbs the image. In general, in order to obtain high image quality, means for detecting a seam position (not shown) is provided, and an image is not formed on the seam. Therefore, as a means for detecting this seam, a reflection type optical sensor is used in the case of the opaque transfer belt 12, a detection mark having a light reflection characteristic different from that of the transfer belt is provided, and a transmission type optical sensor is provided in the case of transparent. Or, a mechanical sensor such as a displacement sensor having a shape (for example, a cutout or a projection) is often used. For this reason, it has been proposed to make the peripheral length of the transfer belt 12 an integral multiple of the length obtained by adding the interval between the transfer materials.

When the transfer belt 12 rotates and can be confirmed to be at a predetermined position, the transfer material P is conveyed from the registration roller 13 onto the transfer belt 12. At this time, the image writing signal is turned ON, and an image is formed on the first photosensitive drum 1a at a certain timing. Then, the visible image on the photosensitive drum 1a is transferred by the transfer charger 14a applying an electric field or charge under the first photosensitive drum 1a. At this time, the transfer material P is held on the transfer belt 12 by an electrostatic attraction force, and is conveyed and transferred to the second image forming portion Pb and thereafter. Hereinafter, the transfer material P on which an image has been formed by the fourth image forming unit Pd in the same manner as described above is discharged by a separation charger (not shown) and a peeling charger (not shown). The sheet is separated from the transfer belt 12 and transported to the fixing device 9. Hereinafter, the fixing device 9 will be described. The fixing device 9 includes a fixing roller 91, a pressure roller 92, and a heat-resistant cleaning member (not shown) for cleaning each of them, a heater for heating each roller, and a release agent oil such as dimethyl silicone applied to the fixing roller. An oil application roller, an oil reservoir for supplying the oil, and a thermistor for controlling the fixing temperature.
Hereinafter, the cleaning unit will be described. After the transfer, the developer remaining on the photosensitive drums 1a, 1b, 1c, 1d is
They are removed by the cleaning devices 6a, 6b, 6c, 6d, and are ready for the subsequent latent image formation. Further, the developer remaining on the transfer belt 12 is discharged by the belt discharger 16 of the transfer belt cleaning device 18 to remove the electrostatic attraction force, and the rotated fur brush 17.
Is scraped off. In addition, as a cleaning means of the transfer belt 12, a blade, a nonwoven fabric, a combination thereof, or the like is used.

In the image forming apparatus embodied as the color printer of FIG. 3, each photosensitive drum and the transfer belt are usually in contact with each other, and in this state, cleaning of the photosensitive drum and the transfer belt or control of the potential of the photosensitive drum is performed. In the case of the single-color image forming mode, as shown in FIG. 3, the driven roller 21 is lowered to separate the transfer belt 12 and the three photosensitive drums 1a, 1b, 1c on the upstream side of the transfer material conveying portion of the transfer belt 12, and the transfer belt 1
2 and the downstream photosensitive drum 1d are brought into contact with each other to drive the apparatus to form an image. Further, when a paper jam of the transfer material P or when the transfer belt 12 is replaced, the transfer belt 12 and all the photosensitive drums 1a to 1d are separated as shown in FIG.

[0011]

However, in the above-mentioned conventional example, the photosensitive drum always rotates while being in contact with the transfer belt more than necessary at the time of cleaning or at the time of preparatory rotation for controlling the potential on the photosensitive drum. In such a configuration, the life of the photosensitive drum, the cleaning means for the photosensitive drum, and the transfer belt is shortened.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems by improving the operation of a cleaning means for an image carrier and a transfer material carrier.

[0013]

According to a first aspect of the present invention, there are provided a plurality of image carriers, an image is formed on each image carrier, and the images are transferred onto a transfer material to form an image. Therefore, in the image forming apparatus, the transfer material carrier for transporting the transfer material has a unit for separating the image carrier from the image carrier, and includes an image carrier and a cleaning unit for the transfer material carrier. An image characterized in that the transfer material carrier is separated, the cleaning operations of the respective cleaning means are performed in a timed manner, and at least one of the time for starting or stopping the cleaning operation is controlled to be different. It is a forming device.

According to a second aspect of the present invention, when a transfer material conveyance failure occurs, the preparatory operation for stopping the transfer operation and returning to the transfer operation is performed in accordance with the transfer material conveyance failure occurrence location. The image forming apparatus according to the first aspect, wherein an image carrier to be performed is selected, and a cleaning time is controlled.

According to the first and second aspects of the present invention, an operation such as cleaning is performed by an optimum amount for each of the image carrier and the transfer material carrier, thereby preventing an adverse effect due to excessive or insufficient operation. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 In the color printer of FIG. 1 according to the present invention, usually, a transfer material P is fed from a registration roller 13 onto a transfer belt 12, and an image is formed on a photosensitive drum 1a of a first image forming unit Pa. Is done. At this time, the transfer material P is electrostatically attracted to the transfer belt 12 by the transfer current applied. In addition, although not shown, there is a method in which the transfer material P is electrostatically adsorbed onto the transfer belt 12 by an adsorption roller or the like before being fed to the photosensitive drum 1a. These transfer materials P
When the suction roller is used, the amount of loops formed during the electrostatic attraction from the registration roller 13 to the transfer belt 12 is limited, and the first image forming unit Pa In order to obtain the same amount as in the transfer charging method, it is necessary to increase the size of the conveying path, for example, by lengthening the conveying path. This loop is necessary to absorb the difference in rotation speed between the registration roller 13 and the transfer belt 12.
When the transfer material P passes through, the transfer material P, whose speed was initially controlled by the registration roller 13, changes to the control of the transfer belt 12, so that a shock due to the change in speed appears in the image. If the amount is too large, it may cause frequent jamming and transfer material contamination. It is very difficult to completely eliminate the difference in rotational speed between the registration roller 13 and the transfer belt 12 in consideration of productivity and the like. Therefore, a method of making the registration roller 13 faster than the transfer belt 12 is generally used. In other words, the conveyance force by the registration roller 13 must be pulled or slipped by the suction force between the transfer belt 12 and the transfer material P. However, the transfer force of the registration roller 13 is limited to the transfer material P unless various transfer materials are stable under various environments.
If the writing position in is unstable and terrible,
The image is transferred onto the transfer belt 12. Therefore, it is necessary to supply the transfer material P by forming a loop as described above. Further, in consideration of the cost, it can be generally said that a system as shown in FIG.

In addition to the configuration shown in FIG. 1, there is a method in which the transfer material P is always sucked before the first image forming portion Pa. However, if the suction step is provided in this manner, if the transfer material P is not suctioned onto the transfer belt 12 in a state where there is almost no stress, poor suction (the transfer material P is sucked while floating from the transfer belt 12 or the like). ) Easily occurs. Therefore, a loop is formed as a method of removing the stress. However, in consideration of securing a space for forming the loop, cost, and the like, an ideal form is established if a method without a dedicated suction means as shown in FIG. 3 can be established.

In the multicolor image forming apparatus, only the fourth image forming section Pd functions so as to output a single color, and the other image forming sections Pa, Pb and Pc do not form an image. Therefore, in order to achieve multi-color and single-color image formation with the apparatus shown in FIG. 3, when a frequently used black BK image is output in a single color, the transfer material P is transported to the fourth image forming unit Pd. Transfer chargers 14a, 14b, 1
4c is at rest, and the transfer material P is not attracted to the transfer belt 12, so that the transportability becomes extremely unstable. Thus, FIG. 2 shows a case where the transfer belt 12 on the paper feed side is separated from the photosensitive drums 1a, 1b, 1c.

FIG. 2 lowers the driven roller 21 of FIG. 3 to slightly lower the transfer belt 12 on the paper supply side. At this time, the driven roller 21 faces a grounded conductive roller (not shown). Then, by applying a direct current having the same polarity as the transfer application current to the driven roller 21, an attraction force that can be conveyed is generated.

In this example, 80 g paper generates an adsorption force of about 500 gf even in a high temperature and high humidity environment at 5 kV and 50 μA.

When the present invention is applied to a printer having this configuration, first, the fourth image forming section Pd is used as an image forming section for outputting a black BK image, and the transfer belt 12 is lowered as shown in FIG. At this time, when outputting a uniform image, the photosensitive drum 1
It is sufficient to perform only the potential control of d. In addition, when the black BK single-color image is output, and when a conveyance failure occurs, only the photosensitive drum 1d need only perform the preparatory rotation for cleaning and potential control. Assuming that the diameter of the photosensitive drum used in the description in this example is 60 mm,
The required number of rotations is 3 and the process speed is 180 mm /
Assuming that s, about 3 seconds are required. On the other hand, in the preparatory rotation for the cleaning operation of the transfer belt 12 and the charge elimination, the number of revolutions is one.
At this time, the circumference of the transfer belt 12 is set to 128
If it is 0 mm, about 7 seconds are required. Conventionally, in such a case, the photosensitive drums 1a to 1d and the transfer belt 12 are always in contact with each other, so that the preparation rotation of the photosensitive drum is also performed for about 7 seconds, which is twice the rotation required for cleaning the photosensitive drum 1d. The above rotation had to be done. Therefore, as shown in FIG. 1, at the time of the preparatory operation and the return operation after the processing for the transfer material conveyance failure, the transfer belt 12 is lowered after being discharged to separate from all the photosensitive drums 1a to 1d, and each operation is performed by an optimal amount. Only do. In particular, after the process at the time of transfer material conveyance failure, if the transfer belt 12 is operated in a state of being lowered or ascending during the process, the entire operation time is not excessively increased.

The reason for separating the photosensitive drums 1a to 1c that do not contribute during image output is to realize a system that does not need to rotate the separated photosensitive drums 1a to 1c. In other words, by stopping this rotation,
Longer life of cleaning device for photosensitive drum, longer life by suppressing wear of photosensitive drum, suppression of wear of transfer material carrier,
Accordingly, the rotation of the developing device can be stopped, so that the consumption of the developer can be reduced and the running cost of the apparatus main body can be reduced.

Therefore, by applying the present invention to the above-described printer, the above-mentioned effect is made more effective.
The life of each image forming unit can also be improved. In particular, when the cleaning member used for the cleaning device of the photosensitive drum is made of a blade of urethane or the like, cleaning by rotating the photosensitive drum in a state where toner is not adhered to the surface of the photosensitive drum is performed by cleaning. This has a significant effect on shortening the life of members. Therefore, this example is very effective in increasing the life of the cleaning device using such a blade.

By separating the photosensitive drum and the transfer belt as described above, each cleaning state can be optimized at a normal recording speed, and a motor corresponding to a high speed such as triple speed is not required. Therefore, a cheaper configuration that changes the speed is also possible.

[Embodiment 2] In the printer having the configuration described in the embodiment 1, even when the output is performed by all the image forming units Pa to Pd, a transfer failure of the transfer material carrier occurs, and the transfer belt as shown in FIG. It is not necessary to always perform the preparatory operation in all the image forming units Pa to Pd even when 12 moves down and returns to the transfer operation again. In the printer in the transfer state shown in FIG. 3, the distance from the developing unit to the transfer unit is １ ／ of the photosensitive drum, that is, 60 rotations.
The photosensitive drum of mmφ has a distance of about 47 mm, and development starts when the transfer material P is transported before the transfer nip. Therefore, assuming that the distance between the transfer nips of the image forming units Pa to Pd is 150 mm, the portions after the transfer nip of the first image forming unit Pa have not yet been developed after the second image forming unit Pb. That is, when a transfer material conveyance failure occurs immediately before the first image forming unit Pa, the cleaning operation of the second image forming unit Pb and thereafter is performed in a state where there is no toner on the surfaces of the photosensitive drums 1b, 1c, and 1d. Will do. Further, as mentioned in the first embodiment, the potential control on the photosensitive drum is not always necessary. Sufficient control can be performed by performing the control periodically, for example, once every five minutes. Therefore, a timer is provided to the apparatus, and after the transfer material conveyance failure processing, the photosensitive drums 1b, 1c, and 1d and the developing devices 4b, 4c, and 4d are not rotated within 5 minutes until the recovery operation is started, and the image forming unit Pa By performing only the cleaning operation, unnecessary rotation can be avoided. At this time, the transfer belt 12 is lowered as shown in FIG. 1 to be separated from all the photosensitive drums 1a to 1d, and is rotated once or half to prevent contamination and wear of the photosensitive drums 1b, 1c and 1d. good. If the transfer material P is originally fed onto the transfer belt 12 and stopped by the transfer charger 14a, the transfer belt 12 moves to the place where the transfer material P has passed the fourth image forming unit Pa. Color mixing with the photosensitive drum 1d can be avoided, and when the transfer belt 12 is rotated to the cleaning device 18, toner fusion on the transfer belt 12 is avoided. However, it is conceivable that the unfixed toner on the transfer material P in which the conveyance failure has occurred may scatter and adhere to somewhere on the transfer belt 12 during the conveyance failure processing.

As described above, the effect can be improved by cleaning only the developed photosensitive drum not only in the first image forming section Pa but also in the image forming mode and the position where the conveyance failure occurs.

[Third Embodiment] In the second embodiment, a case has been described in which a timer for regulating the potential control interval is provided in the apparatus. However, in the preparation operation to which the present invention is applied, the most time-consuming operation is to recover the temperature drop of the fixing device 9 in many cases.

Therefore, the second embodiment can be controlled by the temperature of the fixing unit 9. For example, a diameter of 20 mm,
In the case of an RTV silicone rubber roller having a thickness of 2 mm, if the heating is stopped, the temperature falls below the set temperature of about 20 ° C. at 150 ° C. in 4 minutes at room temperature of 25 ° C. Therefore, when the temperature drops further, the all-color potential control is performed in the all-color output mode. At this time, the returning operation is performed by the transfer belt 1 as described above.
Starting from the state shown in FIG. 2 where 2 is lowered, it takes 7 seconds to clean the transfer belt 12 and 3 seconds to control the potential.
The return operation starts with the rotation of the transfer belt 12 and starts the potential control after 4 seconds. The transfer material P is picked up from the transfer material cassette 7 after 5 seconds.
The transfer belt 12 is then transferred to the photosensitive drums 1a, 1b, 1 by a transfer belt lifter (not shown).
If the state shown in FIG. 3 is completely in contact with c and 1d, the loss time of the preparation time is equal to that in the conventional case, or is shortened by the preparation operation while raising the transfer belt 12.

Fourth Embodiment In the second embodiment described above, the returning operation after the occurrence of the conveyance failure has been described. However, the present invention is not limited to such a case. After normal image formation, toner scattering and dirt on the transfer belt 12 are smaller than at the time of conveyance failure. Therefore, it is sufficient to rotate by the distance from the last image forming unit Pd to the transfer material cleaning device 18 and clean the transfer material. . In other words, the distance from the transfer unit of the fourth image forming unit Pd to the transfer material cleaning device 18 is 170 mm. If the transfer belt 12 is rotated (periphery of 180 mm), the transfer belt 12 should be stopped earlier to reduce the wear of the transfer belt 12.

As described above, in the present invention, it is not always better to stop the photosensitive drum earlier.

[0032]

As described above, according to the first aspect of the present invention, the image carrier and the transfer material carrier for carrying the transfer material are separated from each other at the time of cleaning so that each cleaning operation is completed in time. , The wear of the image carrier cleaning means and the image carrier and the transfer material carrier is reduced, the life of the image carrier and the cleaning means and the transfer material carrier is extended, and the consumption of the developer is reduced. Therefore, there is an effect of reducing costs.

According to the second aspect of the present invention, in the first aspect, only the necessary image carrier is cleaned in accordance with the location of the transfer material conveyance failure, so that the effects of the first aspect are further enhanced. Becomes larger.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view when a photosensitive drum and a transfer belt are completely separated.

FIG. 2 is a vertical cross-sectional view of the printer when outputting only a black image forming unit.

FIG. 3 is a longitudinal sectional view of a conventional printer.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 5 transfer device 6 cleaning device 16 belt static eliminator 18 transfer belt cleaning device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhiko Takekoshi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masahiro Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Akihito Hosaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A transfer material carrier having a plurality of image carriers, forming an image on each image carrier, and transferring the transfer material to form an image by transferring the image onto a transfer material. In the image forming apparatus having means for separating the image carrier and the cleaning means for the image carrier and the transfer material carrier, in the image forming apparatus, the image carrier and the transfer material carrier are separated from each other. An image forming apparatus characterized in that the cleaning operation is repeatedly performed temporally, and at least one of the time for starting the cleaning operation and the time for stopping the cleaning operation is controlled to be different. 2. A transfer operation is stopped when a transfer failure of the transfer material occurs, and a preparation operation for returning to the transfer operation is selected according to a transfer failure occurrence location of the transfer material. The image forming apparatus according to claim 1, wherein a cleaning time is controlled.