Image forming apparatus with separately housed cleaning blade and cleaning roller

An image forming apparatus which transfers, onto paper, a toner image formed on a belt-shaped image carrier including an elastic layer on a surface thereof, and forms an image includes a rigid blade which cleans the surface of the image carrier in contact with the image carrier which has transferred the toner image onto the paper; a roller which is upstream of the rigid blade in a rotation direction of the image carrier, and cleans the surface of the image carrier upstream of the rigid blade by coming in contact with the image carrier which has transferred the toner image onto the paper; a rigid blade holder which holds the rigid blade; and a roller holder which holds the roller. The rigid blade holder and the roller holder are installed with a gap therebetween.

BACKGROUND

1. Technological Field

2. Description of the Related Art

The image forming apparatus is now widespread which forms a toner image on a photoconductor, transfers the toner image onto an intermediate transfer belt (image carrier), and transfers the toner image on the intermediate transfer belt onto paper.

A configuration called a blade cleaning method is known in which a blade which scrapes the toner remaining on the intermediate transfer belt after the transfer onto paper. The blade is in contact with the intermediate transfer belt and is provided downstream of a position where the toner is transferred onto paper, in the rotation direction of the intermediate transfer belt in the image forming apparatus. The blade removes the remaining toner (refer to, for example, JP 2012-155253 A).

Moreover, in recent years, a configuration has been proposed which adopts an intermediate transfer belt including an elastic layer made of, for example, a rubber material on a base layer made of a resin material, to prevent a reduction in transfer performance, and uses a blade formed of a metal thin piece (a rigid blade) to reduce a belt drive torque.

In the blade cleaning method using such a rigid blade, the use of a roller upstream of the rigid blade, with respect to the rotation direction of the intermediate transfer belt, is being studied to ensure the cleaning performance and durability of the rigid blade. The roller is installed in such a manner as to counter-rotate with respect to the intermediate transfer belt. The roller has a function of removing paper dust on the intermediate transfer belt, before the paper dust reaches the rigid blade.

However, if such a roller is provided, there may be a case in which a housing of a holder of the rigid blade is deformed by the drive torque of the roller and the posture of the rigid blade is changed. Accordingly it becomes impossible to maintain uniformity of the edge angle of the blade.

The edge angle of the rigid blade is an important factor for maintaining the cleaning function. When the edge angle cannot be uniformly maintained, it is difficult to ensure cleaning performance over a long period of time.

SUMMARY

An issue of the present invention is to provide an image forming apparatus which can maintain cleaning performance over a long period of time.

To achieve at least one of the abovementioned objects, according to an aspect of the present invention, there is provided an image forming apparatus which transfers, onto paper, a toner image formed on a belt-shaped image carrier including an elastic layer on a surface thereof, and forms an image, the image forming apparatus including:

a rigid blade which cleans the surface of the image carrier in contact with the image carrier which has transferred the toner image onto the paper;

a roller which is upstream of the rigid blade in a rotation direction of the image carrier, and cleans the surface of the image carrier upstream of the rigid blade by coming in contact with the image carrier which has transferred the toner image onto the paper;

a rigid blade holder which holds the rigid blade; and

a roller holder which holds the roller, wherein

the rigid blade holder and the roller holder are installed with a gap therebetween.

DETAILED DESCRIPTION OF EMBODIMENTS

Firstly, the configuration of an image forming apparatus in the embodiment is described.

FIG. 1is a schematic configuration diagram of an image forming apparatus100.FIG. 2is a block diagram illustrating the functional configuration of the image forming apparatus100.

As illustrated inFIGS. 1 and 2, the image forming apparatus100is configured to include an image former10, a belt cleaner20, a paper feeder30, a hardware processor41, an operation interface42, a display43, a storage44, and a communicator45, which are connected to each other via a bus.

The image former10includes photosensitive drums11Y,11M,11C, and11K, chargers12Y,12M,12C, and12K, exposers13Y,13M,13C, and13K, developers14Y,14M,14C, and14K, primary transfer rollers15Y,15M,15C, and15K, photoconductor cleaner16Y,16M,16C, and16K, which correspond respectively to colors of yellow (Y), magenta (M), cyan (C), and black (K), an intermediate transfer belt17as an image carrier, a secondary transfer roller18, and a fixer19.

The exposers13Y,13M,13C, and13K are each configured to include a laser light source, a polygon mirror, and a lens, and scan and expose surfaces of the photosensitive drums11Y,11M,11C, and11K with laser beams on the basis of image data of the colors, and form latent images.

The developers14Y,14M,14C, and14K apply their respective color toners to the latent images on the photosensitive drums11Y,11M,11C, and11K to develop the images.

The primary transfer rollers15Y,15M,15C, and15K sequentially transfer the toner images of the colors formed on the photosensitive drums11Y,11M,11C, and11K onto the intermediate transfer belt17(primary transfer). In other words, a color toner image being the four-color superimposed toner images is formed on the intermediate transfer belt17.

The photoconductor cleaners16Y,16M,16C, and16K remove the toner remaining on the peripheral surfaces of the photosensitive drums11Y,11M,11C, and11K after the transfer.

The intermediate transfer belt17is an endless belt including an elastic layer, is laid across a plurality of rollers (a drive roller, a tension roller, and a driven roller), and is driven to rotate in a direction indicated by an arrow A ofFIG. 1. The details of the configuration of the intermediate transfer belt17are described below.

The secondary transfer roller18collectively transfers the color toner image formed on the intermediate transfer belt17onto one side of paper (a transferred body) P as the transferred body supplied from the paper feeder30(secondary transfer).

The fixer19fixes the toner transferred onto the paper P on the paper P by heating and pressing.

The belt cleaner20removes residues such as the remaining toner which was not transferred onto the paper P and remains, and paper dust from the intermediate transfer belt17after the color toner image was transferred by the secondary transfer roller18onto the paper P to clean the intermediate transfer belt17. The details of the configuration of the belt cleaner20are described below.

The paper feeder30is provided to a lower part of the image forming apparatus100, and includes a detachable paper feed cassette31. It is configured in such a manner that the paper P stored in the paper feed cassette31is fed into a feed path by a paper feed roller32, one by one from the top sheet.

The hardware processor41is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and integrally controls the processing operation of components of the image forming apparatus100. The CPU reads various processing programs stored in the ROM, develops them in the RAM, and executes various processes in accordance with the developed programs.

The operation interface42includes a touchscreen formed in such a manner as to cover over a display screen of the display43, and various operating buttons such as numeric buttons and a start button. The operation interface42outputs an operation signal based on the operation of a user to the hardware processor41.

The display43is configured to include an LCD (Liquid Crystal Display), and displays various screens in accordance with instructions of display signals input from the hardware processor41.

The storage44includes storage devices such as a nonvolatile semiconductor memory and a hard disk, and stores, for example, data related to various processes.

The communicator45transmits and receives data to and from an external device connected to a network such as a LAN (Local Area Network).

[Configuration of Intermediate Transfer Belt]

Next, the configuration of the intermediate transfer belt17is described.

FIG. 3is a cross-sectional view of the intermediate transfer belt17. InFIG. 3, the upper side is the outer peripheral side of the intermediate transfer belt17.

As illustrated inFIG. 3, for example, an elastic belt where an elastic layer17bmade of rubber such as acrylnitril-butadien copolymer rubber (NBR) or chloroprene rubber (CR) is formed on a base layer17acan be used for the intermediate transfer belt17.

At this point in time, it is preferable to set the thickness of the base layer17ato approximately 50 to 100 μm to make the transportability of the intermediate transfer belt17excellent, and set the thickness of the elastic layer17bto approximately 100 to 500 μm to increase transfer performance for the uneven paper P.

Moreover, it is also preferable to provide an oxidation layer of approximately 3 to 20 μm, or a coat layer of approximately 3 to 50 μm, on a surface of the elastic layer17bto reduce tackiness.

The intermediate transfer belt17is simply required to have desired transfer performance, and its material and thickness are not limited to those described above.

Moreover, the intermediate transfer belt17preferably has a surface microhardness of equal to or greater than 50 to 500 MPa. Here, the surface microhardness is evaluated using a microhardness tester (Fischerscope_H100) under conditions of an indenter at 90° (Cube Corner Top) and a maximum load of 30 μN.

If the surface microhardness of the intermediate transfer belt17is less than 50 MPa, that is, if the elastic layer17bis too soft, the following situation may occur: infinitesimal deformation occurs on the surface of the elastic layer17b, a reaction force acts in a direction of slipping through from the edge of the rigid blade21a, the remaining toner slips by, and cleaning failure occurs.

On the other hand, if the surface microhardness of the intermediate transfer belt17exceeds 500 MPa, that is, if the elastic layer17bis too hard, infinitesimal deformation does not occur on the surface of the elastic layer17b. Accordingly, the following situation may occur: the surface of the elastic layer17bcannot follow uneven contact at the ridge of the rigid blade21a, minute gaps are generated, the remaining toner slips therethrough, and cleaning failure occurs.

Next, the configuration of the belt cleaner20is described.

FIG. 4is a schematic configuration diagram of the belt cleaner20.

The components configuring the belt cleaner20is extra-long along a width direction intersecting the rotation direction of the intermediate transfer belt17.

As illustrated inFIG. 4, the belt cleaner20includes a first casing CA1as a rigid blade holder, and a second casing CA2as a roller holder provided upstream of the first casing CA1in the rotation direction of the intermediate transfer belt17.

A gap H is provided between the first casing CA1and the second casing CA2. The first casing CA1and the second casing CA2are placed in such a manner as to be in a non-contact state where they are not in contact with each other.

The first casing CA1includes, for example, a blade section21and a screw22therein. In other words, the first casing CA1is a housing which covers around the blade section21and the screw22.

Moreover, a blade counter roller23as a first counter roller is provided at a position facing the first casing CA1(the blade section21) across the intermediate transfer belt17.

The second casing CA2includes, for example, a pre-brush24as a roller, a flicker roller25, and a screw26therein. In other words, the second casing CA2is a housing which covers around the pre-brush24, the flicker roller25, and the screw26.

Moreover, a brush counter roller27as a second counter roller is provided at a position facing the second casing CA2(the pre-brush24) across the intermediate transfer belt17.

The blade section21includes, for example, a rigid blade21a, a blade holder21b, and a biasing spring21c.

The rigid blade21ascrapes and removes residues on the intermediate transfer belt17with a distal end of the rigid blade21ain counter contact with the rotating intermediate transfer belt17. The rigid blade21ais held by the blade holder21bin such a manner as to be rotatable about a hinged support G.

It is preferable that the thickness of the rigid blade21abe 70 to 200 μm. If the thickness of the rigid blade21aexceeds 200 μm, the rigid blade21ais too thick to follow unevenness in a longitudinal direction. If the thickness is less than 70 μm, the rigid blade21ais too thin, and the edge floats, and the residue removal effect is reduced.

Moreover, it is also preferable that the rigid blade21ainclude a coat layer of diamond-like carbon. At this point in time, the thickness of the coat layer is preferable to be 1 to 10 μm. If the thickness of the coat layer exceeds 10 μm, the coat layer is too thick relative to the dimension of the rigid blade21a. Accordingly, the edge floats. If the thickness is less than 1 μm, it is too thin, and there is no point in the coat layer.

The blade holder21bis configured in such a manner as to hold the rigid blade21aat one end, and be rotatable about the hinged support G. The biasing spring21cis engaged at the other end of the blade holder21b. It is configured in such a manner that a contact force (contact pressure) of the rigid blade21aagainst the intermediate transfer belt17is obtained by the force of the spring.

The biasing spring21cis, for example, a tension coil spring. The biasing spring21capplies the force of rotating in a counterclockwise direction to the blade holder21band the rigid blade21ato bring the rigid blade21ainto contact with the intermediate transfer belt17with constant pressure.

In such a constant pressure contact method (spring loaded method), the contact pressure can be appropriately maintained irrespective of an environment. As long as the constant pressure contact method can be achieved, other than the tension coil spring, a helical compression spring or the like may also be used.

The screw22discharges the residue scraped by the rigid blade21ato the outside of the first casing CAL

The blade counter roller23is placed at the position facing the blade section21across the intermediate transfer belt17.

The blade counter roller23is preferable to be placed, slightly displaced approximately 1 mm downstream of a distal end portion of the rigid blade21ain the rotation direction of the intermediate transfer belt17.

Such a placement can prevent the rigid blade21afrom being raised by minute projections and depressions on the blade counter roller23, or minute projections and depressions on the intermediate transfer belt17, and slipping by on the left and right of the minute uneven portion, what is called a stapler-like slip.

The pre-brush24is a brush body which rotates in a counter direction to the rotation direction of the intermediate transfer belt17. The pre-brush24removes deposits, such as paper dust, on the intermediate transfer belt17, the deposits reaching the rigid blade21a, and reduces paper dust filming with the rigid blade21a.

A torque of, for example, 0.1 to 0.4 N·m is applied between the pre brush24and the intermediate transfer belt17. If the value of torque is less than 0.1 N·m, the cleaning function of the pre-brush24is not achieved. If the value of torque exceeds 0.4 N·m, the torque may be too large for the intermediate transfer belt17to rotate, and images may be displaced.

As long as a predetermined deposit removal function is provided, the material, physical properties, and settings of the pre-brush24are not particularly limited.

Moreover, it may not be a brush body such as the pre-brush24, and may be, for example, a metal roller which has a suction effect by an electric field, or a foam roller.

The flicker roller25is provided at a position which can be in contact with the pre-brush24, and rotates in a counter direction to the rotation direction of the pre-brush24to remove deposits attached to the pre-brush24.

As long as a predetermined flicking function is provided, the material, physical properties, and settings of the flicker roller25are not particularly limited.

Moreover, a scraper25ais provided to the flicker roller25to scrape deposits off the flicker roller25.

The screw26discharges the deposits removed by the pre-brush24to the outside of the second casing CA2.

The brush counter roller27is placed at a position facing the pre-brush24across the intermediate transfer belt17, and maintains the deposit removal function of the pre-brush24excellently.

Next, the operation of the belt cleaner20in the embodiment is described.

In the belt cleaner20of the embodiment, the pre-brush24counter-rotates with respect to the intermediate transfer belt17first, removes deposits such as paper dust on the intermediate transfer belt17, and reduces deposits reaching the rigid blade21a.

Next, the rigid blade21aof the blade section21scrapes and removes the remaining residues which have not been transferred onto the paper P from the intermediate transfer belt17to clean the intermediate transfer belt17.

In this manner, the pre-brush24is provided upstream of the blade section21to ensure the cleaning performance and durability of the rigid blade21a.

Here, the rigid blade21ais not capable of following the deformation of the intermediate transfer belt17unlike a rubber blade. Accordingly, even with a minute change in contact angle, the distal end of the rigid blade21amay float slightly. The floating of the distal end causes the degradation of the cleaning performance (the slipping through of toner). Accordingly, the edge angle of the rigid blade21ais preferable to be maintained uniformly from the beginning to the end of use.

However, if the blade section21and the pre-brush24are in the same housing, the housing may deform due to the drive torque of the pre-brush24, and the posture (edge angle) of the rigid blade21amay change.

In contrast, in the belt cleaner20of the embodiment, each of the blade section21and the pre-brush24has the separate housings, which are fixed separately. The rigid blade21acan maintain the edge angle uniformly without being influenced by the drive torque of the pre-brush24.

Moreover, each of the blade section21and the pre-brush24have the separate housings. Accordingly, it is possible to make the utmost use of their individual functions (lifespans).

FIG. 5is a table comparing the numbers of pages where an image could be formed by the time image defect occurred in a case where the belt cleaner20of the embodiment illustrated inFIG. 4was used, a case where the blade section21and the pre-brush24were in the same housing (an integral type), and a case where the pre-brush was not provided.

As illustrated inFIG. 5, the occurrence of image defect was not seen even beyond 600000 pages in the belt cleaner20of the embodiment while the occurrence of image defect was seen at 100000 pages in the case of the integral type. Moreover, the occurrence of image defect was seen at 200000 pages in the case where the pre-brush was not provided.

As described above, according to the embodiment, the image forming apparatus100which transfers, onto the paper P, a toner image formed on the intermediate transfer belt17including the elastic layer17bat the surface thereof to form an image includes the metal rigid blade21awhich cleans the surface of the intermediate transfer belt17in contact with the intermediate transfer belt17which has transferred the toner image onto the paper P, the pre-brush24which is provided upstream of the rigid blade21ain the rotation direction of the intermediate transfer belt17to clean the surface of the intermediate transfer belt17in contact with the intermediate transfer belt17upstream of the rigid blade21a, the first casing CA1which holds the rigid blade21a, and the second casing CA2which holds the pre-brush24. The first casing CA1and the second casing CA2are installed with the gap H therebetween.

Hence, each of the rigid blades21aand the pre-brush24have the separate housings. Accordingly, it is possible to prevent the drive torque of the pre-brush24from influencing the rigid blade21a. Accordingly, it is possible to prevent the occurrence of a situation where the first casing CA1which holds the rigid blade21ais deformed due to the influence of the drive torque of the pre-brush24, the posture of the rigid blade21ais changed, and accordingly the edge angle cannot be uniformly maintained.

Hence, the cleaning performance can be ensured over a long period of time.

Moreover, in the embodiment, the flicker roller25is included which is in contact with the pre-brush24while counter-rotating, and scrapes deposits attached to the pre-brush24.

Hence, it is possible to remove the deposits attached to the pre-brush24and promote an increase in the lifespan of the pre-brush24.

Moreover, in the embodiment, the pre-brush24counter-rotates with respect to the intermediate transfer belt17. A torque of equal to or greater than 0.1 N·m and equal to or less than 0.4 N·m is applied between the pre-brush24and the intermediate transfer belt17.

Hence, the cleaning function of the pre-brush24can be appropriately maintained.

Moreover, in the embodiment, the blade counter roller23provided at the position facing the first casing CA1across the intermediate transfer belt17, and the brush counter roller27provided at the position facing the second casing CA2across the intermediate transfer belt17are included. The edge of the rigid blade21ais in contact with the intermediate transfer belt17at the position between the blade counter roller23and the brush counter roller27.

Hence, it is possible to prevent the occurrence of slipping through due to the lifting of the rigid blade21a.

Moreover, in the embodiment, the rigid blade21ais in contact with the intermediate transfer belt17with constant pressure.

Hence, the contact pressure can be appropriately maintained irrespective of an environment.

Moreover, in the embodiment, the rigid blade21ahas a thickness of equal to or greater than 70 μm and equal to or less than 200 μm.

Hence, the bending of the rigid blade21acan be appropriately maintained.

Moreover, in the embodiment, the rigid blade includes the coat layer of diamond-like carbon. The coat layer has a thickness of equal to or greater than 1 μm and equal to or less than 10 μm.

Hence, the wear of the rigid blade21acan be prevented.

An embodiment to which the present invention can be applied is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope which does not depart from the gist of the present invention.

For example, the above embodiment has been described assuming that each of the first casing CA1and the second casing CA2has a shape which covers the components therein. However, as long as it has a configuration in which the drive torque of the pre-brush24does not influence the rigid blade21a, the embodiment is not limited to the above configuration.

For example, as illustrated inFIG. 6, a cut corresponding to the gap H may be provided at a position between the rigid blade21aand the pre-brush24of one casing CA3. A soft member28which fills the cut (the gap H) may be provided.

In other words, the upper side of the casing CA3is a housing whose underside is open. The lower side of the casing CA3is a housing whose top side is open. The gap H is provided with the soft member28which fills the gap H.

For example, sponge, PET, or urethane can be used as the soft member28.

The entire disclosure of Japanese patent application No. 2017-055283, filed on Mar. 22, 2017, is incorporated herein by reference in its entirety.