JPH04361285A - Image forming device - Google Patents

Abstract

PURPOSE:To easily remove toner adhering to a transfer roller at low cost without necessitating special space in which a cleaner is set in an image forming device where a toner image formed on an electrostatic latent image carrier is transferred on the transfer paper by the transfer roller in a transfer part. CONSTITUTION:This is the image forming device where the toner image formed on a photosensitive drum 1 is transferred on the transfer paper S by the transfer roller 5 in the transfer part A, and it is provided with a transfer roller rotation control part 10 which drives the transfer roller 5 so that its circumferential speed may be higher than a transfer paper feeding speed as the transfer paper S is fed to the transfer part A by a timing roller pair 7 on an upper-stream side than the transfer part A, and thereafter releases the driving of the roller 5 so that the circumferential speed of the roller 5 may be the same or nearly the same as the transfer paper feeding speed before the transfer paper S finishes passing through the timing roller pair 7.

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 printer, in which a toner image formed on an electrostatic latent image carrier is transferred onto a transfer sheet by a transfer roller in a transfer section.

0002

2. Description of the Related Art In this type of image forming apparatus, when transferring a toner image onto a transfer paper, a transfer bias having a polarity substantially opposite to that of the toner is applied to a transfer roller. Therefore, some toner electrically adheres to the transfer roller and contaminates the roller. If this phenomenon is left unaddressed, toner will gradually adhere to and accumulate on the transfer roller, and a non-negligible amount of toner will adhere to the back surface of the transfer paper, making it difficult to form an image on the back surface again.

[0003] Conventionally, therefore, it has been proposed to apply a cleaning bias voltage to the transfer roller during non-transfer or to remove and clean the transfer roller with a cleaner using a blade or brush.

0004

However, in order to apply a cleaning bias voltage, there is a problem that the power supply for this purpose is complicated and expensive, and in addition, providing a cleaner increases the cost accordingly. There is a problem in that a space is required for the installation, and a container for collecting the removed toner and a space for installing the container are also required.

Accordingly, the present invention provides an image forming apparatus in which a toner image formed on an electrostatic latent image carrier is transferred onto a transfer paper by a transfer roller in a transfer section, in which the toner adhering to the transfer roller can be easily and inexpensively removed. The purpose is to enable cleaning without requiring special space.

[0006]

[Means for Solving the Problems] According to the above-mentioned object, the present invention provides an image forming apparatus for transferring a toner image formed on an electrostatic latent image carrier onto a transfer paper by a transfer roller in a transfer section. As the transfer paper is fed to the transfer section by the transfer paper conveying means upstream from the transfer section, the transfer roller is driven such that its circumferential speed is faster than the transfer paper conveyance speed, and then the transfer paper is transported to the transfer section. A transfer roller rotation control means is provided for canceling the drive of the roller so that the peripheral speed of the transfer roller becomes the same or substantially the same as the transfer paper transport speed before the transfer paper finishes passing through the transfer paper transport means. The present invention provides an image forming apparatus that does the following.

[0007] The phrase "as the transfer paper is fed into the transfer section by the transfer paper conveying means upstream of the transfer section" means "before the transfer paper enters the transfer section" or "after the transfer paper begins to enter the transfer section". ” may be used.

[0008]

[Operation] According to the device of the present invention, as the transfer paper is sent to the transfer section by the transfer paper conveyance means upstream from the transfer section, the transfer roller is driven at a higher speed than the transfer paper conveyance speed. The adhering toner is rubbed onto the back side of the transfer paper, and the transfer roller is cleaned.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an electrophotographic laser beam printer that is an embodiment of the present invention. This printer has a photosensitive drum 1 which is an electrostatic latent image carrier in the center.
A charging roller 2, a developing device 4, a transfer roller 5, and a cleaner 6 are sequentially arranged around the charging roller 2. A guide plate 70 and a pair of timing rollers 7 are arranged on the upstream side of the transfer section A where the drum 1 and the transfer roller 5 come into contact, and further upstream there are a paper feed cassette (not shown), a paper feed roller facing the cassette, and a transfer roller. Pairs of paper conveying rollers are arranged. Further, on the downstream side of the transfer section A, a conveyance guide plate 8, a fixing device 9, and further downstream thereof, a paper ejection roller and a paper ejection tray (not shown) are arranged. Above the photoreceptor drum 1, a laser beam modulated according to an image signal is applied to the drum 1.
An optical system (not shown) for image exposure 3 is arranged.

The drum 1, timing roller pair 7, fixing device 9, etc. are driven by a driving means. However, the timing roller pair 7 is driven via a clutch (not shown) so as to send the transfer paper to the transfer section A in synchronization with the toner image on the drum 1. Further, a charging voltage is applied to the charging roller 2 by an unillustrated power source, a developing bias voltage is applied to the developing device 4 by an unillustrated power source, and a transfer bias voltage is applied to the transfer roller 5 by an unillustrated power source. It looks like this.

The transfer roller 5 rotates under the control of its rotation control section 10 in accordance with the movement of the photosensitive drum 1 or the transfer paper passing between the drum and the roller 5, and the timing roller pair. It is possible to switch to a state in which the transfer paper is rotated at a higher speed than the conveyance speed of the transfer paper conveyed at step 7 (this is set to be the same as the circumferential speed of the photosensitive drum 1). That is, the control unit 10 includes a clutch CL that connects the transfer roller 5 to the motor M, and an instruction unit C that switches the clutch CL between “connection” and “disconnection”. The instruction section C operates after the timing roller pair 7 starts rotating to send the transfer paper to the transfer section A until the paper passing sensor D detects the timing just before the transfer paper finishes passing through the roller pair 7. clutch CL
is connected and the transfer roller 5 is rotated at high speed by the motor M.
In other cases, clutch CL is "disconnected".

[0012] Instead of adopting the paper passing sensor D,
The instruction section C or the like may be provided with a function of counting the passage time of the transfer paper, and the time immediately before the transfer paper finishes passing through the pair of timing rollers 7 may be detected by counting the time. According to the printer described above, the photosensitive drum 1 is rotated counterclockwise in the figure at a circumferential speed of 35 mm/sec, and the surface thereof is uniformly charged by the charging roller 2. An image is exposed 3 to the charged area from an optical system (not shown), and an electrostatic latent image is formed. This latent image is developed by a developing device to become a toner image and arrives at the transfer section A. On the other hand, transfer paper is supplied from a paper feed cassette (not shown) and sent to the timing roller pair 7.

The roller pair 7 feeds the transfer paper S to the transfer section A in synchronization with the toner image on the drum 1, as shown in FIG. 2A. Immediately before the transfer paper S reaches the nip portion between the drum 1 and the transfer roller 5, the clutch CL is connected in the control section 10 under the instruction of the instruction section C, and the transfer roller 5 is moved by the motor M, as shown in the figure. Peripheral speed 40-50 in direction
It starts to be rotated at mm/sec.

The transfer paper S sent to the transfer section A is conveyed by the timing roller pair 7 because the conveyance force by the timing roller pair 7 is stronger than the clamping conveyance force between the drum 1 and the roller 5. Transfer roller 5 while moving at circumferential speed
A toner image is transferred thereon by the action of . Further, the toner adhering to the surface of the transfer roller 5 is rubbed against the back surface of the transfer paper S while the roller rotates at a peripheral speed higher than the conveyance speed of the transfer paper S, and is cleaned.

When the sensor D detects just before the rear end of the transfer paper S finishes passing through the timing roller pair 7, the instruction section C in the control section 10 disconnects the clutch CL. Thereafter, the transfer roller 5 follows the movement of the transfer paper S and rotates at approximately the same peripheral speed as the conveyance speed. Therefore, as shown in FIG. 2B, even when the transfer paper S passes through the timing roller pair 7, the toner image is transferred normally without stretching or misalignment.

FIG. 3 shows the state of the transfer paper passing through the timing roller pair 7, the state of the transfer paper passing through the nip between the photosensitive drum 1 and the transfer roller 5, and the switching timing between driving rotation and driven rotation of the transfer roller 5. ing. The transfer paper S onto which the toner image has been transferred is then guided by a guide plate 8 and arrives at a fixing device 9, where the toner image is fixed, and then discharged outside the machine.

Note that the transport speed of the transfer paper S and the transfer roller 5
If the difference in circumferential speed is not made too large as in the above embodiment, the dirt on the transfer roller 5 will be gradually rubbed onto the back surface of the transfer paper S, and the user can ignore this. In other words, in the present invention, the speed difference is desirably set to such an extent that dirt rubbed onto the back surface of the transfer paper can be ignored.

[0018]

According to the present invention, in an image forming device that transfers a toner image formed on an electrostatic latent image carrier onto a transfer paper by a transfer roller in a transfer section, the toner attached to the transfer roller can be easily removed. It can be cleaned at low cost and without requiring a special space for installing a cleaner or the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a part particularly related to the present invention in an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which a transfer sheet passes through a transfer section.

FIG. 3 is a timing chart showing the passing state of the transfer paper and the timing of switching between driving and following the transfer roller.

[Explanation of symbols]

1 Photoreceptor drum 5 Transfer roller 7 Timing roller pair A Transfer section 10 Control section C Instruction part CL Clutch M Motor D　　　　Paper passing sensor S Transfer paper

Claims (1)

[Claims] 1. In an image forming device that transfers a toner image formed on an electrostatic latent image carrier onto a transfer paper using a transfer roller in a transfer section, the transfer paper is provided on a transfer paper conveying means upstream of the transfer section. As the transfer paper is sent to the transfer section by the transfer roller, the transfer roller is driven so that its circumferential speed becomes faster than the transfer paper conveyance speed, and then, before the transfer paper finishes passing through the transfer paper conveyance means, so that the transfer roller circumferential speed is the same or approximately the same as the transfer paper conveyance speed,
An image forming apparatus comprising a transfer roller rotation control means for canceling the driving of the roller.