JP3237081B2 - Image forming device - Google Patents

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 capable of forming a multiplex image on a transfer material, such as a color electrophotographic copying machine or a color laser beam printer.

[0002]

2. Description of the Related Art In an image forming apparatus capable of forming a multicolor image, a plurality of developing units and an electrophotographic photosensitive drum (image carrier) are used.
There are many proposals in which a process device such as the above is integrally configured as a process cartridge, and the device is detachably provided to an apparatus main body of the image forming apparatus.

In such a process cartridge, when the photosensitive drum reaches the end of its life or when the toner in the developing device is used up, the entire process cartridge is removed from the apparatus main body, thereby facilitating maintenance. This is intended to improve the maintainability and serviceability of the apparatus by allowing the user to replace the equipment without relying on a service person having specialized knowledge. Further, when a clogging of a transfer material or the like occurs in the apparatus main body, the process cartridge can be easily removed by attaching and detaching the process cartridge.

[0004]

However, due to the shock when the process cartridge is attached and detached, the toner (developer) in the developing device leaks toward the photosensitive drum, and
The leaked toner adheres to the transfer drum (transfer material supporting means, which is a drum that holds and rotates the transfer material to transfer the toner image on the photosensitive drum onto the transfer material) as the photosensitive drum rotates, There has been a problem that the back surface of the transfer material is stained and a bias electric field for uniform transfer cannot be applied, resulting in transfer unevenness.

The problem described above is not limited to the process cartridge. The cartridge includes only one developing device in which one or a plurality of developing devices are detachably disposed in the apparatus main body, and which facilitates maintenance of the developing device itself. Can occur in exactly the same way.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to form an image forming apparatus capable of removing toner adhering to a transfer material support to prevent transfer material from being contaminated by toner. It is to provide a device.

[0007]

In order to achieve the above-mentioned object, the present invention provides a unit detachably mountable to an apparatus main body, the unit comprising at least developing means for developing a latent image on an image carrier with toner. , the transfer material supporting to transfer to the transfer material and the support, has a transfer material which is supported the toner image on the front Kizo bearing member onto the transfer material supporting member for supporting the transfer material
Apply a voltage of the opposite polarity to the charged polarity of the toner to the back of the carrier
In the image forming apparatus, even after the said unit is mounted on the apparatus main body, before the image formation is started, the toner adhering onto the transfer material support for transfer to said image bearing member Toner band electrode on the back of the transfer material support
And a voltage having the same polarity as the voltage .

[0008]

According to the present invention, after the unit is mounted on the apparatus main body, and before the image formation is started, the toner attached to the transfer material support is transferred to the image carrier in order to transfer the toner.
A charge having the same polarity as the charge polarity of the toner is placed on the back surface of the transfer material support.
Since the pressure is applied, the toner on the transfer material support is transferred to the image carrier by the electric field even when the toner leaks from the developing means when the unit is mounted and the toner adheres to the transfer material support. The transfer material can be removed from the transfer material support, and the transfer material supported by the transfer material support can be prevented from being contaminated by toner.

[0009]

[0010]

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

FIG. 1 shows a cross section of an image forming apparatus (laser beam printer) capable of forming a multicolor image by multiple transfer. In FIG. 1, reference numeral 10 denotes an electrophotographic photosensitive drum which is an image carrier which rotates in the direction of an arrow. is there. Around the photosensitive drum 10, a corona charger 11 for charging the photosensitive drum 10 to a negative polarity, a yellow developing device 12A having yellow toner,
Magenta developing device 12B having magenta toner, cyan developing device 12C having cyan toner, black developing device 12D having black toner, cleaning device 13, pre-exposure lamp 14 for removing residual charges on photosensitive drum 10
In addition to the process equipment described above, a transfer drum 15 as a transfer material support member is provided.

The yellow, magenta, and black developing units 12A, 12B, 12C, and 12D contain yellow, magenta, cyan, and black toners, respectively, which are selected according to the latent image on the photosensitive drum 10. The developing sleeve 12a of the developing device 12 is rotated, and a developing bias voltage having the same polarity as the toner is applied to the developing sleeve 12a. The image is visualized.
It is assumed that the toner in the developing device 12 is charged to a negative polarity to perform reversal development, and thereafter, the charging polarity of each device is determined to be compatible with the polarity of the toner.

The transfer drum 15 is placed on the surface of the metal cylinder,
An elastic layer made of resin, a conductive layer for applying a transfer bias voltage, and a dielectric layer are laminated in this order, and the transfer material (plain paper) is electrostatically attracted and held, and is brought into contact with the photosensitive drum 10. By rotating, the toner image on the photosensitive drum 10 is electrostatically transferred onto the transfer paper.

A paper feed cassette 16, a paper feed roller 17 and the like are provided below the transfer drum 15 on the paper feed side, and operate when the transfer material is separated from the transfer drum 15 on the upper paper discharge side. A separation corona charger 18, a separation claw 19, a heating roller fixing device 20, a paper discharge tray 21, and the like are provided.
Reference numeral 22 denotes a conventional scanning optical system that scans image light L (laser beam) for a predetermined color image, and reference numeral 23 denotes a reflection mirror for guiding the scanned image light L to the photosensitive drum 10.

The process of forming a multicolor image by the above-described apparatus will be described. The image corresponds to a yellow image which has been color-separated on a photosensitive drum 10 uniformly charged to a negative polarity by a charger 11 via a scanning optical system 22 or the like. When the image light L is exposed, an electrostatic latent image based on the yellow image is formed on the photosensitive drum 10. The electrostatic latent image is supplied with yellow negative polarity toner by the yellow developing unit 12A as the photosensitive drum 10 rotates, and is visualized as a toner image. In this case, the developing sleeves 12a of the magenta, cyan, and black developing units 12B, 12C, and 12D are used to adsorb the toner onto the developing sleeve 12a so that the developing operation is not performed by these developing units 12. A bias voltage having a polarity (plus) opposite to that of the toner is applied.

The yellow toner image is transferred to the transfer drum 15 which rotates in synchronization with the toner image.
Is transferred onto the transfer material. In this case, the transfer material is transferred from the paper feed cassette 16 to the transfer drum 1 via a paper feed roller 17 or the like.
5, immediately before the leading end of the transfer material reaches the transfer start position of the photosensitive drum 10, a transfer bias of the opposite polarity (plus) (for example, +1.8 KV) to the toner is applied to the conductive layer of the transfer drum 15. The toner image of the yellow toner is transferred to the transfer material, and the transfer material is electrostatically attracted to the transfer drum 15. Then, the photosensitive drum 1 having completed the yellow toner transfer process
In the case of 0, the residual toner is cleaned by the cleaning device 13 and the remaining charge is removed by the pre-exposure lamp 14, and then uniformly charged again by the corona charger 11 for the next transfer step.

Next, when image light L corresponding to the magenta image is exposed on the photosensitive drum 10, an electrostatic latent image based on the magenta image is formed on the photosensitive drum 10, and the electrostatic latent image is Magenta toner is supplied by the developing device 12B and is developed as a toner image. The toner image is transferred onto the transfer material on the transfer drum 15 in a superimposed manner. In this case, a transfer bias of, for example, +2.1 KV is applied to the transfer drum 15 in accordance with the magenta toner.

Similarly, when electrostatic latent images corresponding to cyan and black images are formed on the photosensitive drum 10, these electrostatic latent images are sequentially developed as toner images by the cyan and black developing units 12C and 12D. The toner images are further superimposedly transferred onto the transfer material on the transfer drum 15 respectively. Also in this case, the transfer drum 15 is applied with a transfer bias of, for example, +2.5 KV for a cyan toner image and, for example, +3.0 KV for a black toner image, for each transfer. In the transfer efficiency is prevented.

When four full-color toner images are formed on the transfer material as described above, the charge acting on the transfer material for electrostatic attraction is removed by the separation corona charger 18 using an AC corona. After that, the sheet is forcibly separated from the transfer drum 15 by the separation claw 19 and sent to the fixing device 20. Then, the transfer material on which the toner image is fixed as a permanent image by the fixing device 20 is stacked on a paper discharge tray 21.

Here, the photosensitive drum 10, the corona charger 1
1. Process devices such as a yellow developing device 12A, a magenta developing device 12B, a cyan developing device 12C, a black developing device 12D, a cleaning device 13, and a pre-exposure lamp 14 are cartridge containers 30a as process cartridges 30.
The apparatus main body 1 of the image forming apparatus is integrally assembled in the inside.
It is arranged detachably inside. When the internal device reaches the end of its life or the like, the process cartridge 30 is replaced with a new process cartridge 30 to facilitate maintenance, or to transfer the transfer material from paper supply to paper discharge. When the transfer material is jammed in the road and a jam occurs, the process cartridge 30 is attached and detached to perform the jam processing.

On the other hand, when the process cartridge 30 is attached to and detached from the apparatus main body 1, the impact force of the developing cartridge 12A
(In the case of a two-component developer, it may include a carrier) leaks from the developing sleeve 12a toward the photosensitive drum 10, and the photosensitive drum 10 may be contaminated with the toner. The leakage toner on the photosensitive drum 10 is rubbed and cleaned by the cleaning device 13 with the rotation of the photosensitive drum 10, so that there is no problem in image formation by the photosensitive drum 10. If the leaked toner adheres to the transfer drum 15, the back surface of the transfer material is stained or a transfer failure occurs.

Therefore, in the present invention, the outer surface of the transfer drum 15 is always cleaned by the cleaning means when the process cartridge 30 is mounted on the apparatus main body 1. A fur brush, an elastic blade, or the like may act on the transfer drum 15 as the cleaning means, but in this embodiment, the photosensitive drum 10 has a function as a cleaning means.

That is, when there is no transfer material on the transfer drum 15, the surface of the photosensitive drum 10 is neutralized by the pre-exposure lamp 14, and its potential is brought close to zero (0) V. Then, the charging of the photosensitive drum 10 by the corona charger 11 is not performed, and the photosensitive drum 10 is kept in a state where the toner easily adheres to the surface thereof. On the other hand, the bias voltage applied to the transfer drum 15 is changed by a transfer high voltage control unit (not shown).
For example, -2.5 KV of the same polarity (minus polarity) as the toner
Switch to

Thus, if the photosensitive drum 10 and the transfer drum 15 rotate under the above conditions, even if the toner spilled from the developing unit 12 or the scattered and leaked toner is on the photosensitive drum 10, the toner is transferred to the transfer drum 15. It is cleaned by the cleaning device 13 without adhering. Further, the toner leaking from the developing device 12 directly adheres to the transfer drum 15 or the toner leaking from the photosensitive drum 10
Even if it adheres to the photosensitive drum 10 or the transfer drum 15
Is rotated several times, the toner on the transfer drum 15 is transferred to the photosensitive drum 10, and the transfer drum 15 is cleaned well.

Next, the operation of the cleaning processing determining circuit for determining the timing of cleaning the transfer drum 15 when the process cartridge 30 is mounted on the apparatus main body 1 will be specifically described with reference to FIG. The attachment / detachment of the process cartridge 30 to / from the apparatus main body 1 is detected by the memory circuit of the apparatus main body 1 regardless of whether the main switch of the apparatus main body 1 is ON or OFF.

When the main switch of the apparatus main body 1 is turned on, it is determined whether or not the initialization has been completed (step 1). It is determined whether the cartridge 30 is unused (new) (step 2). Whether the process cartridge 30 is used or unused is determined by, for example, as shown in FIG.
When a new process cartridge 30 is inserted into the apparatus main body 1 and the claw 30b is broken, the switch 24 on the apparatus main body 1 is operated to determine that the cartridge new / old flag is new. And the nail 30
When the used process cartridge 30 having the broken b is mounted in the apparatus main body 1, the switch 24 does not operate this time, and only another switch 25 on the apparatus main body 1 operates.
The old and new cartridge flags remain in the old state. still,
The determination as to whether the process cartridge 30 has been used or not has been made to clarify a criterion for starting measurement of the amount of toner used in the developing device 12.

If the answer is NO in step 2 and it is determined that the process cartridge 30 has been used, it is determined whether or not the process cartridge 30 has been attached to or detached from the apparatus main body 1 (step 3). This is determined by considering whether the main body flag changes when the process cartridge 30 is attached to or detached from the apparatus main body 1 and whether the main body flag has changed from the initial state. For example, consider a first flag that changes only by an operation of attaching the process cartridge 30 to the apparatus main body 1 and a second flag that changes only by an operation of removing the process cartridge 30 from the apparatus main body 1. In other words, if the first and second flags after the process cartridge 30 is mounted in the apparatus main body 1 are [1, 0], the first and second flags after the process cartridge 30 is removed are described. The flag becomes [1,1], and when the process cartridge 30 is subsequently mounted in the apparatus main body 1, the first and second flags change to [0,1], and the first and second flags are changed. From the initial value [1, 0].
Therefore, by comparing the changes in the first and second flags, it is possible to confirm whether the process cartridge 30 has been remounted or removed.

Then, if the main body flag changes and the process cartridge 30 is attached or detached, the answer is YES in step 3 and the main body flag is once set to the initial value (step 4), and then the transfer drum 15 is cleaned. The processing is performed (step 6). When the cleaning is completed, the cleaning is completed (step 7) and the initial is completed (step 8).

If it is determined in step 3 that the process cartridge 30 has not been attached or detached, the process proceeds to step 8 and the initialization is completed. Furthermore,
If YES in step 2 and it is determined that the cartridge is an unused cartridge, the cartridge new / old flag is also set to old (step 5), the cleaning process of the transfer drum 15 is performed (step 6), and the cleaning is completed. If the cleaning is completed (step 7), the cleaning is initialized (step 8).

Hereinafter, as long as the main switch is ON,
Further, it is determined whether or not the initialization has been completed (step 1). However, since the initialization has been performed for the second time or later, the determination is YES, the process is terminated, the process returns to the start, and the loop is repeated. Note that once the main switch is turned off and then turned on, step 1 and step 2 are performed again as described above.
Proceed to.

When the main switch is ON, 100
If the image formation (printing) has been performed once or 500 times, as shown in FIG. 3, it is determined whether or not a predetermined number of prints have been reached (step 9). Alternatively, the transfer drum 15 may be cleaned (step 6). In this case, although the process cartridge 30 is not attached or detached, the toner scattered from the developing device 12 during the development is
5 and the transfer drum 15 can be prevented from being contaminated. This cleaning process is performed at the start of printing or immediately after the process cartridge 30 is mounted on the apparatus main body 1.

Incidentally, even if the process cartridge 30 is removed for some reason during image formation and toner leaks from the developing device 12, the transfer material is present on the transfer drum 15, so that the transfer drum 15 is not contaminated. . Accordingly, in such a case, the cleaning process determination circuit may determine that the image is being formed, and may not perform the cleaning operation of the transfer drum 15 as described above.

Further, as shown in FIG. 4, a yellow developing unit 12A, a magenta developing unit 12B, and a cyan developing unit 12
C, only the black developing device 12D has the cartridge container 31
a, the same problem as in the above-described process cartridge 30 occurs in the developing cartridge 31 which is integrally mounted in the apparatus main body 1 and which is detachably disposed in the apparatus main body 1. Alternatively, the transfer drum 15 may be cleaned in exactly the same manner. In this case, it is a matter of course that only the black developing device 12D may be a separate cartridge, and the transfer drum 15 may be cleaned in conjunction with the attachment / detachment of the black developing device 12D.

Further, each developing device 12 in the developing cartridge 31 may be a sub-cartridge and may be attached to and detached from the developing cartridge 31, or each developing device 12 may be directly attached to and detached from the apparatus main body 1 as a developing cartridge. It goes without saying that the present invention can be applied to such a case.

In the above embodiment, a laser beam printer has been described as an image forming apparatus. However, an original image is converted into an electric signal by an image pickup device such as a CCD, and the electric signal is input to a scanning unit, or the original image is optically converted. Of course, the present invention can also be applied to a copying apparatus in which the original image is directly exposed to the photosensitive drum using an optical system after color separation. In the above embodiment, the formation of a full-color image is described as an example of forming a multiplex image. However, the present invention is not limited to this, and a multiplex image such as a combination of a single color and black may be used.
Further, the present invention is applicable not only to the process cartridge 30 having the structure according to the present embodiment but also to a combination of an image carrier and a developing unit, or a combination of an image carrier, a charging unit and a developing unit. Of course you can.
The transfer material supporting member may be of a drum type such as a transfer drum, or may be of a type in which an endless sheet member is rotatably moved via a roller or the like.

[0036]

As is apparent from the above description, according to the present invention, there is provided a unit which is detachable from the apparatus main body and has at least a developing means for developing a latent image on an image carrier with toner. , anda transfer member support for supporting the transfer material, before the back of the transfer material supporting member to transfer the toner image on Kizo bearing member supported transfer material to the transfer material supporting member
In an image forming apparatus that applies a voltage having a polarity opposite to the charging polarity of the toner to the surface, after the unit is mounted on the apparatus main body, and before image formation is started, the image is formed on the transfer material support. The transferred toner is transferred to the image carrier .
The same polarity as the charge polarity of the toner on the back surface of the transfer material support
Is configured to apply a neutral voltage,
Even if the toner adheres to the transfer material support, it is possible to prevent the transfer material from being stained by the toner.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus.

FIG. 2 is a flowchart of a transfer drum cleaning processing determination circuit.

FIG. 3 is another flowchart of a transfer drum cleaning process determination circuit.

FIG. 4 is a sectional view of an image forming apparatus according to a modified embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Apparatus main body 10 Photosensitive drum (image carrier, cleaning means) 12 Developing device (developing means) 15 Transfer drum (transfer material support member)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G03G 21/10 G03G 21/00 310 (72) Inventor Fumio Ueno 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-61-99179 (JP, A) JP-A-2-106676 (JP, A) JP-A-56-123577 (JP, A) JP-A-58-102278 (JP, A) JP-A-64-109386 (JP, A) JP-A-63-191169 (JP, A)

Claims (3)

(57) [Claims] 1. A unit detachably mountable to an apparatus main body and including at least a developing unit for developing a latent image on an image carrier with toner, and a transfer material support for supporting a transfer material. , the transfer material supporting the toner image on the front Kizo bearing member for transferring a transfer material supported on the transfer material supporting member
Apply a voltage of the opposite polarity to the charged polarity of the toner to the back of the carrier
In the image forming apparatus, the unit even after mounted in the apparatus main body, an image
Before formation is started, the transfer material supporting the toner adhering to the transfer material material support on to transfer to the image bearing member
Apply a voltage of the same polarity as the charged polarity of the toner to the back of the carrier.
Image forming apparatus characterized by that. 2. An image forming apparatus according to claim 1, further comprising cleaning means for cleaning toner transferred from said transfer material support to said image carrier. 3. The image forming apparatus according to claim 1, wherein a plurality of color toner images are sequentially transferred from the image carrier to a transfer material supported by the transfer material support.