JP2652160B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic recording or magnetic recording process.

(Prior Art and Problems to be Solved) In a known image forming apparatus which repeats a process of transferring a transferable toner image formed on the surface of an image carrier running endlessly to a sheet-like transfer material such as paper, It is essential to sufficiently remove the residual toner remaining on the surface of the image carrier without contributing to the transfer every time transfer is performed in order to continuously obtain a high quality image.

As a cleaning means for this purpose, a cleaning blade made of a suitable elastic material such as urethane rubber has been widely used because it is small and compact and has an excellent toner removing function.

However, the cleaning blade is suitable for removing toner.However, fine paper powder generated from paper as a transfer material, deposits such as rosin and talc generated from paper, and corona such as nitride due to the presence of high-pressure members in the apparatus. Various foreign substances such as products that adhere to the image carrier do not function well. To deal with this, an elastic cleaning roller is pressed against the image carrier and a part of the toner collected in the cleaning device is removed. A thin layer is formed on the surface of the roller by a scraper, and the foreign matter is removed by rubbing the image carrier. It is effective.

However, with the recent progress in miniaturization of this type of image forming apparatus, the image carrier formed exclusively in a rotating cylinder has also been miniaturized, and for this purpose, an image forming apparatus arranged around the image carrier has been used. In this situation, it is substantially difficult to dispose the cleaning roller together with the cleaning blade in the cleaning device.

Further, a cartridge in which some of the process means around the image carrier is integrated has come to be awarded, but in such a case, the provision of the cleaning roller makes the configuration of the cartridge. It is not preferable because the advantages of the cartridge system cannot be utilized because the size, complexity and cost are increased.

The present invention has been made in order to cope with such a situation, and it is possible to clean an image carrier without disposing the above-described cleaning roller in the cleaning device and in the same manner as having the cleaning roller. Accordingly, it is an object of the present invention to make it possible to further reduce the size of the image forming apparatus.

(2) Configuration of the Invention (Technical Means for Solving the Problems, Action of the Invention) In order to achieve the above object, the present invention provides an image carrier,
A transfer roller that forms a nip portion with the image carrier, transfers a transfer material between the nip portion and transfers an image from the image carrier to the transfer material, a cleaning member that cleans the transfer roller, And a drive unit for moving the cleaning member toward and away from the transfer roller. It is set so that there is a peripheral speed difference between the image carrier and the transfer roller. The driving unit brings the cleaning member into contact with the transfer roller so that the cleaning surface of the transfer roller cleaned by the cleaning member arrives. When the informing unit detects the leading end of the transfer material, the driving unit controls the uncleaned surface of the transfer roller that has not been cleaned by the cleaning member to reach the nip after the rear end of the transfer material reaches the nip. An image forming apparatus comprising: a control unit that separates the cleaning member from the transfer roller.

With this configuration, there is no need to dispose a cleaning roller in the cleaning device, the size of the device can be reduced by including the peripheral members, and the surface of the image carrier is rubbed by the transfer roller as described above. Various foreign substances can be removed.

(Explanation of the Embodiment) FIG. 1 is a side view of an essential part showing an embodiment in which the present invention is applied to a copying machine having a rotating cylindrical photoconductor, and extends in a direction perpendicular to the paper surface, and is indicated by an arrow A. Photoreceptor 1 that rotates
It is assumed that a transfer roller 3 disposed in parallel with the photoconductor is pressed against the photoconductor and rotates at substantially the same peripheral speed as the photoconductor following the photoconductor during transfer.

The toner image formed on the surface of the photoreceptor 1 travels together with the photoreceptor, reaches a transfer portion where the transfer roller 3 is pressed, and is supplied with the transfer material (not shown) by the transport path 2 at a timing. , And the toner image is transferred to the transfer material by the transfer roller 3 which is biased by the bias power supply 6 in the opposite polarity to the toner.

Thereafter, the transfer material further advances to a fixing portion (not shown), and the residual toner remaining on the photoreceptor without contributing to the transfer is cleaned by the cleaning device 5 and prepared for the next step.

The transfer roller 3 has an inner layer made of a silicon sponge in which a conductive material such as carbon is dispersed in a cored bar 3a.
3b and an outer layer 3c also made of solid silicon rubber in which carbon is dispersed, and is formed to be electrically conductive as a whole.

In the drawing, reference numeral 4 denotes a cleaning device which removes back stains on the transfer material and prevents a reduction in the electrode effect of the roller.

In addition, a primary charger, an image signal applying unit, a developing device, a transfer charger and other members necessary for image formation are of course disposed around the photoreceptor. All are omitted because they have no direct relationship.

The transfer roller 3 is composed of a core metal 3a, an inner layer 3b made of silicon sponge in which carbon is dispersed, and an outer layer 3c also made of solid EPDM or urethane rubber in which carbon is dispersed. It is assumed that it is configured in nature. A direct current or an alternating current is superimposed on the direct current, and a bias having a polarity substantially opposite to that of the toner is applied to the roller by a bias power supply 6.

The transfer roller 3 is pressed against the photoreceptor 1 with an appropriate nip width, and as shown in FIG.
Is connected to the drive unit 8 via the clutch 7.

At the time of the transfer in which the transfer material is present in the nip portion, the clutch 7 disconnects the connection between the roller 3 and the drive unit 8, and the transfer roller 3 follows the photoreceptor and runs at substantially the same speed. When there is no non-transfer, the two are connected to forcibly drive the transfer roller.

Then, the rotation of the transfer roller at this time is such that the transfer roller rubs the photoreceptor at the nip portion of both.
It shall be determined that there is an appropriate peripheral speed difference.

That is, the peripheral speed difference at the nip portion between the image carrier and the transfer roller is set to be larger during non-transfer than during transfer.

FIG. 1 shows a state at the time of non-transfer. At this time, the cleaning blade 4a mounted on the cleaning device 4 is at a position retracted from the transfer roller, and as described above, the transfer roller 3 is Since the photosensitive member 1 is rotated at a predetermined speed difference from the photosensitive member 1, residual toner remaining on the photosensitive member at the time of transfer of the transfer material that has passed therethrough, and part of the toner in the cleaning device 4 adhere to the transfer roller. It is assumed that a thin layer is formed and the foreign matter is removed by rubbing the photosensitive member.

The speed difference between the photoconductor and the transfer roller during non-transfer is
It is appropriate that 0.9 ≧ Vd / Vr ≧ 0.5 and 2.0 ≧ Vd / Vr ≧ 1.1.

3A and 3B show an example of a means for causing the cleaning blade to take a cleaning position and a non-cleaning position retracted from the cleaning position.

A cleaning member having a cleaning blade 4a attached thereto is pivotally attached to a shaft 4b attached to an appropriate position of the cleaning device 4, and a spring 10 and a solenoid 9 are attached to the other leg 4b of the member. is there. At the time of transfer, as shown in FIG. 3A, the blade 4a is pressed against the transfer roller 3 by the action of the spring 10, and at the time of non-transfer, the solenoid is excited to resist the action of the spring 10 as shown in FIG. 3B. As a result, the cleaning member rotates counterclockwise in the drawing, and the cleaning blade 4a separates from the transfer roller 3.

Briefly describing the timing of contact and separation of the cleaning blade 4a, a sensor including the light source 11 and the light receiving element 12,
The sensor is disposed at a distance 1 from the transfer position, and the distance between the transfer position and the position at which the cleaning blade contacts the transfer roller is set in the circumferential direction. L and l> L.

When the transfer material is not at the transfer site, the blade 4a is separated from the transfer roller 3. When the sensor detects the presence of the transfer material, as shown in FIG. 4, the solenoid 9 is urged by the solenoid drive circuit 15 via the detection and determination circuit 13, and the blade 4a is brought to its operating position.

As described above, since l> L, when the leading end of the transfer material reaches the transfer position, the cleaning blade is already in its operating position and performs an effective cleaning action, so that the transfer material is not contaminated. . That is, the cleaning surface of the transfer roller cleaned by the cleaning blade is formed in the nip portion before the leading end of the transfer material reaches the nip portion (transfer portion).

When the sensor detects the trailing end of the transfer material, it outputs a signal indicating that there is no transfer material, and the detection and determination circuit 13 activates the solenoid drive circuit after a predetermined time ΔT via the timer circuit (delay circuit) 14 to transfer the blade. Separate from rollers.

ΔT is, when the peripheral speed of the transfer roller and V _TR, L +
It is determined that (ΔT × V _TR )> l.
That is, the uncleaned surface of the transfer roller that has not been cleaned by the cleaning blade reaches the nip after the rear end of the transfer material reaches the nip.

As described above, by separating the cleaning blade from the transfer roller after the transfer material has passed the transfer position, it is possible to prevent the transfer material from being contaminated by the toner.

As described above, according to the present apparatus, there is no need to dispose an elastic cleaning roller in the cleaning device, and there is no need to separately connect a transfer charger, so that the configuration around the photoconductor is simply and compactly assembled. be able to.

Furthermore, since the transfer material can be brought into close contact with the image carrier, the image quality can be improved by improving the transfer rate, and the transfer material can be sufficiently pressed against the image carrier to give a curved tendency, so that separation after transfer is also effective. That can be accomplished.

In the above-described apparatus, the residual toner is used as the toner for rubbing the photoreceptor. However, the toner is supplied from the developing device even during non-transfer, and the toner is also transferred to the toner layer of the transfer roller. It is also possible to configure so as to contribute to the formation.

With this configuration, it is possible to avoid a situation in which toner is insufficient due to the state of the document and cleaning failure occurs.

It will be easily understood that the present invention is applicable not only to the above-described copying machine but also to other image forming apparatuses.

(3) Effects of the Invention As described above, the present invention is configured such that the transfer is performed using the transfer roller and the image carrier is rubbed and cleaned by the roller during non-transfer.
The structure of the image forming apparatus, especially around the image carrier, can be simplified, and the size and size of the portion can be reduced, the image quality can be improved, and the effect of separating the transfer material can be promoted.

[Brief description of the drawings]

FIG. 1 is a side view of a main part showing an embodiment in which the present invention is applied to a copying machine. FIG. 2 is a partial end view showing the structure of a transfer roller. FIGS. 3A and 3B show the operation of a cleaning blade. FIG. 4 is a block diagram of a circuit for controlling the operation of the solenoid. DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 3 ... Transfer roller, 4 ... Cleaning device, 6 ... Bias power supply, 7 ... Clutch, 9 ... Solenoid, 10 ... Spring.

Claims (1)

(57) [Claims] An image carrier, a nip portion formed with the image carrier, a transfer roller for nipping and transferring a transfer material at the nip portion to transfer an image from the image carrier to the transfer material; An image forming apparatus comprising: a cleaning member that cleans a roller; a detection unit that detects a transfer material upstream of the nip in a transfer material movement direction; and a driving unit that moves the cleaning member toward and away from the transfer roller. In the non-transfer, it is set so that there is a peripheral speed difference between the image carrier and the transfer roller in the nip portion, and when the detecting means detects the leading end of the transfer material, the leading end of the transfer material is placed in the nip portion. The driving means rotates the cleaning member so that the cleaning surface of the transfer roller cleaned by the cleaning member reaches the nip portion before the cleaning member reaches the nip portion. When the detection unit detects the rear end of the transfer material, the uncleaned surface of the transfer roller that has not been cleaned by the cleaning member reaches the nip after the rear end of the transfer material reaches the nip. An image forming apparatus, wherein the driving unit includes a control unit that separates the cleaning member from the transfer roller.