JPH05107955A - Image forming device - Google Patents

Abstract

PURPOSE:To miniaturize this device and to stably separate a transfer sheet from a photosensitive body by permitting a cleaning means for a transfer roller to serve also as a destaticizing means for the transfer sheet. CONSTITUTION:A fur brush 72 as the cleaning means for the transfer roller 71 is moved to a second position where it is brought into contact with a photosensitive drum 31 by a moving means, and grounded by the changeover of a switching means 73. Thus, the fur brush 72 is constituted as the destaticizing means and the destaticizing means for the transfer sheet is also used by the fur brush 72. Since the destaticizing means is brought into contact with the photosensitive body 31, it securely performs destaticization by the secure contact with the transfer sheet Q after transfer. After the passing of the transfer sheet Q, the fur brush 72 is returned to a first position where it is brought into contact with the transfer roller 71 by the moving means, and subjected to the application of the prescribed voltage by the changeover of the switching means 73. Toner on the transfer roller 71 is cleared up by the fur brush 72.

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 such as a copying machine or a laser beam printer, and more particularly to an image forming apparatus using a transfer roller.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, an electric charge having a first polarity is applied to a photosensitive drum and an optical image as image information is projected onto the photosensitive drum to form an electrostatic latent image. After formation, a toner image having a second polarity (first polarity when reversal development is performed) different from the first polarity forms a visible image and is introduced between the photosensitive drum and the transfer roller. There is also a so-called transfer roller system in which a visible image is transferred onto a transfer paper. A voltage having a polarity different from that of the toner (including ground) is usually applied to the transfer roller, and the transfer roller applies a so-called back surface charge to the surface of the transfer sheet that is not in contact with the photosensitive drum.

In this transfer roller system, since it is not necessary to give an excessive back surface charge to the transfer paper as in the case of transfer by corona discharge, the toner on the photosensitive drum is transferred before or after the transfer. Attracted to the paper,
There is an advantage that it is possible to suppress the generation of an image scattered around characters. Further, since the transfer paper is introduced between the photoconductor drum and the transfer roller and comes into contact with the photoconductor drum side with a predetermined pressing force, the transfer paper can be reliably conveyed and the misalignment between the photoconductor drum and the transfer paper is caused. There is an advantage that the transfer deviation due to is not generated.

However, when an image having a relatively low printing rate (a large amount of white paper is formed) is formed mainly when reversal development is performed, after the transfer paper passes between the photosensitive drum and the transfer roller, the transfer paper There is a problem that the transfer sheet is attracted to the photosensitive drum side by the electrostatic attraction force of the back surface charge and the surface charge of the photosensitive drum, and the separation of the transfer sheet from the photosensitive drum becomes unstable.

Therefore, in order to stably separate the transfer sheet, there is provided an image forming apparatus in which a charge eliminating needle for removing charge from the transfer sheet is provided at a position near the downstream side of the transfer roller in the transfer sheet conveying direction ( See, for example, JP-A 1-2696969).

[0006]

By the way, in the transfer roller method, when toner adheres to the transfer roller and stains it, the rear surface of the transfer sheet is stained. Therefore, in order to prevent this, a cleaning means for cleaning the transfer roller is required, and there is a problem in that the image forming section becomes large in size in combination with the provision of the charge elimination needle, and thus the image forming apparatus becomes large in size.

Further, since the above-mentioned charge elimination needle is made of a conductive rigid body such as SUS, it must be separated from the photoconductor drum by a predetermined distance so as not to damage the photoconductor drum. Therefore, the charge removal needle of the transfer sheet cannot be surely contacted with the back surface of the transfer sheet, so that the charge removal of the transfer sheet becomes insufficient and the transfer sheet may be wound around the photosensitive drum. Therefore, there remains a problem that the separation of the transfer paper is unstable.

An object of the present invention is to solve the above technical problems and to provide a small-sized image forming apparatus capable of stably separating transfer sheets.

[0009]

As an image forming apparatus of the present invention for achieving the above object, a developing device for visualizing an electrostatic latent image formed on a photoconductor and a transfer of this visual image In an image forming apparatus including a transfer roller for transferring to a sheet and a cleaning unit disposed on the downstream side of the transfer roller in the transfer sheet conveying direction to scrape off the toner adhering to the transfer roller, the cleaning unit is a transfer roller. And a second position where the cleaning member is contacted with the photosensitive member. The cleaning device is provided with a flexible brush-like member that is movable between the first position and the second position where the cleaning member is brought into contact with the photosensitive member. A moving means for moving and returning the transfer paper to the first position after passing the transfer paper is provided, and a state for applying a voltage to the cleaning means in accordance with the first position and the second position of the cleaning means and a clear state. Those characterized by providing a switching means for switching between a state grounding the training means.

[0010]

According to the image forming apparatus having the above construction, the cleaning means is moved to the second position where it is brought into contact with the photosensitive member by the moving means, and is grounded by switching the switching means. Thus, the cleaning unit is configured as a charge eliminating unit, and the cleaning unit also serves as a charge eliminating unit for the transfer sheet. Since the charge removing unit is brought into contact with the photoconductor, it can surely contact the transfer sheet after the transfer, so that the charge of the transfer sheet can be surely removed.

After passing the transfer paper, the cleaning means
It is returned to the first position where it is brought into contact with the transfer roller by the moving means, and a predetermined voltage is applied by switching the switching means. The cleaning unit located at the first position cleans the toner on the transfer roller.

[0012]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 3 is a schematic configuration diagram of a copying machine as an image forming apparatus showing an embodiment of the present invention. 1 and 2 are schematic configuration diagrams of the transfer device. Referring to FIG. 3, the copying machine A includes a contact glass 11 inside the apparatus main body 1.
An optical system 2 for illuminating and scanning a document placed on the document and guiding reflected light from the document P to a photoconductor drum 31 as a photoconductor, and an electrostatic latent image formed on the photoconductor drum 31 as a developing device. After being visualized by 33, it has an image forming section 3 for transferring it onto a transfer sheet by a transfer roller 71, and a fixing section 41 for fixing a toner image in the middle thereof. From the inside of the device body 1,
Paper transport unit 4 that discharges from the paper discharge unit 44 through the image forming unit 3
Is equipped with.

As the image forming unit 3, the photosensitive drum 31 is used.
A charging charger 32, a developing device 33, a transfer roller 71, and a cleaner 34 are arranged in this order along the rotation direction of the photoconductor drum 31 in the order around. The operation of the image forming unit 3 will be described. The charging charger 32 imparts a uniform negative charge to the surface of the photosensitive drum 31. On the photosensitive drum 31 thus charged,
The optical system 3 irradiates light according to the original image. As a result, the photosensitive drum 31 is divided into a portion where light irradiation is performed and the potential is lowered and a portion where light irradiation is not performed and the potential is high. Then, so-called reversal development, in which the electrostatic latent image is developed by using the toner of negative polarity supplied from the developing device 33, is performed on the portion where the potential is lowered by the light irradiation. The visible image thus formed on the photoconductor drum 31 is taken out from the paper feed cassette 42, and introduced into the transfer position (between the photoconductor drum 31 and the transfer roller 71) at the same timing by the registration roller 45. The image is transferred onto a transfer sheet (not shown). Photoconductor drum 3
In No. 1, the residual toner is removed by the cleaner 34 after the transfer process is completed.

The transfer roller 71 is connected to a power supply 74 which applies a voltage for applying a back surface charge to the transfer sheet. Further, the transfer roller 7 is provided on the downstream side of the transfer roller 71 in the transfer sheet conveying direction.
A fur brush 72 is provided as a cleaning unit that removes the toner attached to No. 1. The fur brush 72 has a first position (see FIG. 2) in contact with the transfer roller 71 and a second position (see FIG. 1) in contact with the photoconductor drum 31 by moving means (not shown). And moved to. Further, the fur brush 72 is connected to an output side terminal 73a of a switch device 73 as a switching means. This switch device 73 has a contact 73d.
Is switched to the ground side terminal 73a or the power source input side terminal 73b connected to the power source 75 and brought into contact therewith. As the moving means for moving the fur brush 72, a solenoid or the like for vertically moving an arm that rotatably supports the fur brush 72 can be exemplified.

Next, the operation of this copying machine will be described with reference to the time chart shown in FIG. Timing a
At the same time when the print key indicated by is turned on, the power supply of the main drive motor is turned on. As a result, the photosensitive drum 31, which is connected to the drive motor via the driving force transmission means such as a chain and the clutch means,
The registration roller 45 and the transfer roller 71 are in a drivable state. Then, an electrostatic latent image is formed and visualized as the photosensitive drum 31 rotates. On the other hand, at the same time as the timing a, by switching the switch device 73, the voltage (cleaning voltage) is applied to the fur brush 72 that is in contact with the transfer roller 71 at the first position. The brush 72 attracts the toner attracted to the transfer roller 71 by an electrostatic attraction force and separates the toner from the transfer roller 71. In addition,
The toner attracted to the fur brush 72 is scraped off by a blade (not shown).

After that, the registration roller 45 is moved at the timing b corresponding to the photosensitive drum 31 side so that the transfer sheet reaches the transfer position at the timing when the visible image on the photosensitive drum 31 reaches the transfer position. Turned on. At the same time as this timing b, the switching tap for switching the power supply to the moving means such as the solenoid is turned on, whereby the fur brush 72 is moved to the second position where it is brought into contact with the photosensitive drum 31. At the same time as this timing b, the fur brush 7 is switched by the switch device 73.
The application of the cleaning voltage to 2 is released and the fur brush 72 is grounded. In this way, the fur brush 72 is grounded and brought into contact with the photosensitive drum 31,
It is configured as a charge eliminating means.

At a timing c after a lapse of a predetermined time from the timing b when the registration roller 45 is turned on, the transfer voltage is applied to the transfer roller 71 and the transfer is performed. The application of the transfer voltage to the transfer roller 71 is turned off at a timing e when a predetermined time has elapsed from the timing d when the registration roller 45 is turned off. Further, at the above timing e, the fur brush 72 is moved to the first position where it is brought into contact with the transfer roller 71 by switching the switching tap, and the cleaning voltage is applied to the fur brush 72 by switching the switch device 73. When turned on, the fur brush 72 again cleans the transfer roller 71.

Then, at the same time as the timing f when the driving motor is turned off after the copying operation is completed, the switch device 73 is turned on.
The application of the cleaning voltage is canceled and the fur brush 72 is grounded by switching to the standby state for the next copying process. The timing c of applying the transfer voltage to the transfer roller 71 is preferably a predetermined time before the leading edge of the transfer sheet Q reaches the transfer position, and the application of the transfer voltage of the transfer roller 71 is released. It is desirable that the timing e of is a predetermined time after the trailing edge of the transfer sheet Q reaches the transfer position. This is for the following reason. Adsorption to the surface of the photoconductor drum 31 on the downstream side in the rotational direction from the portion where the leading edge of the transfer sheet Q contacts, and on the upstream side in the rotational direction from the portion where the rear end of the transfer sheet Q contacts. The applied toner is attracted to the transfer roller 71 side before reaching the fur brush 72 in contact with the photoconductor drum 31, and the toner is not adsorbed to the fur brush 72 side. Therefore, even if the fur brush 72 is brought into contact with the photoconductor drum 31 as described above, the toner is not adsorbed to the fur brush 72 side, and the fur brush 72 can be prevented from being soiled.

As described above, according to this embodiment, the fur brush 72 is used in the pre-process and the post-process of the transfer.
Acts as a cleaning unit for the transfer roller 71, and as a charge removing unit for the transfer sheet Q during the transfer process (or including a predetermined time before and after the transfer process). That is, the fur brush 72 as a cleaning unit for the transfer roller 71 also serves as a charge removing unit for the transfer sheet Q, so that the image forming unit 3 can be downsized as compared with the case where a charge removing unit is separately provided, and thus an image forming operation is performed. The overall size of the device can be reduced.

Further, the fur brush 7 constituting the charge eliminating means.
Since the sheet 2 is brought into contact with the photosensitive drum 31, the sheet 2 is surely brought into contact with the transfer sheet Q after the transfer, and the charge of the transfer sheet Q can be surely removed. Therefore, the transfer paper Q does not wind around the photoconductor drum 31 due to insufficient charge removal, and the transfer paper Q can be reliably separated from the photoconductor drum 31. Moreover, since the fur brush 72, which constitutes the charge eliminating means, can contact the entire length of the photosensitive drum 31 in the longitudinal direction, uniform charge attenuation can be achieved over the entire width.

The present invention is not limited to the above embodiment, but can be applied to the case of regular development. In addition, various design changes can be made within the scope of the present invention without changing the gist of the present invention, such as a belt-shaped photoreceptor.

[0022]

【The invention's effect】 . As described above, according to the image forming apparatus of the present invention, the cleaning unit can also serve as the charge eliminating unit for the transfer sheet, so that the image forming unit can be downsized as compared with the case where the charge eliminating unit is separately provided, and thus the image forming unit can be improved. The entire forming apparatus can be downsized. In addition, the static elimination means,
Since the photoconductor is brought into contact with the photoconductor, the photoconductor can be surely brought into contact with the transfer paper after the transfer, the charge of the transfer paper can be surely removed, and the transfer paper can be stably separated from the photoconductor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a transfer device of a copying machine according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of the transfer device.

FIG. 3 is a schematic configuration diagram of the copying machine.

FIG. 4 is a diagram showing a timing chart.

[Explanation of symbols]

 31 photoconductor drum 33 developing device 71 transfer roller 72 fur brush (cleaning means) 73 switch device (switching means) Q transfer paper

Claims (1)

[Claims] 1. A developing device that visualizes an electrostatic latent image formed on a photoconductor, a transfer roller that transfers the visualized image to a transfer sheet, and a transfer roller downstream of the transfer roller in the transfer sheet conveying direction. In the image forming apparatus including a cleaning device for scraping off the toner adhered to the transfer roller, the cleaning device is configured to contact the transfer roller with the first cleaning device.
And a second position which is in contact with the photosensitive member by a flexible brush-like member, and the cleaning means is moved to the second position before the transfer sheet passes and A moving means for returning to the first position after passing is provided, and a switching means for switching between a state in which a voltage is applied to the cleaning means and a state in which the cleaning means is grounded according to the first position and the second position of the cleaning means. An image forming apparatus characterized by being provided.