JP2673457B2 - Cleaning device for image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and the same printer, and particularly to a cleaning apparatus for the image forming apparatus. It is.

(Problems to be solved with the related art) In a well-known image forming apparatus that repeats the process of transferring a toner image electrostatically formed on the surface of an image bearing member to a transfer material mainly composed of paper, transfer is performed at each transfer. The residual toner that does not contribute to the image carrier and remains, the paper dust generated from the paper that is the transfer material, the deposited rosin and talc deposits, and the corona products caused by the presence of high-pressure members in the device Sufficient removal of foreign matter adhering to the carrier is an essential condition for obtaining good quality images.

Conventionally, a cleaning blade made of an elastic material such as rubber is used as a cleaning means for removing residual toner, and an elastic cleaning material such as urethane rubber is used for removing various foreign substances as described above. A configuration in which a roller is rubbed against an image carrier has already been proposed.

FIG. 8 shows a typical example of such a cleaning device, in which the cleaning device 6 is arranged in parallel in proximity to the image carrier 1 which extends in the direction perpendicular to the plane of the drawing and rotates in the direction of the arrow. The other free edge of the cleaning blade 11 having one edge attached to the cleaning device is pressed against the surface of the image carrier so that it does not transfer to the transfer material and remains on the image carrier at the transfer site (not shown). Residual toner shall be removed.

Cleaning blade as viewed in the running direction of image carrier 1
An elastic cleaning roller 9 is disposed on the upstream side of 11, which is in pressure contact with the surface of the image carrier, and during operation, the roller is rotated and run at an appropriate relative speed with respect to the image carrier. Is configured.

A scraper 10 made of a stainless steel plate, a phosphor bronze plate, or the like is brought into contact with the cleaning roller 9 to remove the collected toner and convey the toner in the direction of a conveying screw 12, and at the same time, a part of the toner of the roller 9 is removed. It is assumed that the toner layer is formed by adhering to the surface and is again supplied to the contact portion with the image carrier 1 to remove the toner, foreign matter and the like on the surface of the image carrier 1.

In the cleaning device having such a configuration, the surface potential of the cleaning roller 9 is appropriately maintained by frictional charging by the cleaning roller 9 and the scraper 10, and this electrostatic action is effective for removing various foreign matters. It has been known.

However, if the cleaning roller is maintained at a high potential in this way, after continuous operation, the apparatus is restarted for several tens of minutes, and then the apparatus is restarted, the image corresponding to the portion where the cleaning roller is pressed against the image carrier during suspension. At the position of 1
There was a problem that the width was about 6 mm and the density was low, and in extreme cases white spots (called roller marks) occurred.

The reason why the white spots described above occur is not always clear, but the triboelectric charge generated during the operation of the cleaning roller maintains the surface potential of the roller at a relatively high potential even after the cleaning roller stops, and as a result, the image bearing is performed. A potential close to this is also applied to the body photosensitive layer, and a positive charge is injected from the image bearing member substrate to induce a trap, and therefore, the potential of that portion cannot be sufficiently increased during operation after a pause. Conceivable.

As a means for solving such a problem, it is easy to prevent the cleaning roller from being charged, and therefore it is easy to ground the scraper in contact with the cleaning roller. As a result of an experiment, the generation of roller marks can be prevented, but image deterioration such as filming and image deletion occurs after passing about 10,000 sheets. It is considered that this is because the charging of the cleaning roller is blocked, which causes the cleaning function to deteriorate due to an electrostatic action.

The present invention has been made in order to cope with such a situation. In a cleaning device having an elastic cleaning roller, while maintaining the function of charging the cleaning roller during operation, the cleaning device described above at the time of suspension is maintained. It is an object of the present invention to provide a cleaning device that solves problems such as image deterioration, maintains a stable cleaning function, and contributes to obtaining a high-quality image.

(2) Configuration of the Invention (Technical Means for Solving the Problem and Its Action) In order to achieve the above-mentioned object, the present invention is an elastic cleaning roller that is in pressure contact with an image carrier to rub the surface of the image carrier. In a cleaning device of an image forming apparatus having a conductive scraper that is in contact with the cleaning roller, the scraper is kept in a floating state while an image forming process is in progress by driving the image carrier and the cleaning roller. A cleaning device (1) comprising means for grounding the scraper before and after the time when the image carrier and the cleaning roller are stopped after the image forming process is completed, or the image carrier. An elastic cleaning roller that presses against the body and rubs the surface of the image carrier, and a conductive roller that contacts the cleaning roller. In a cleaning device of an image forming apparatus having a scraper, when the image carrier and the cleaning roller are driven and the image forming process is in progress, the scraper is grounded via a high impedance element and the image forming process is performed. The cleaning device (2) or the above-mentioned (2) characterized in that it comprises means for directly grounding the scraper after an appropriate time before the image carrier and the cleaning roller are stopped and stopped. The cleaning device (3) is characterized in that the high impedance element is a variable resistance element.

With this configuration, it is possible to prevent deterioration of the image quality due to the generation of roller marks even when the roller is stopped, while maintaining good cleaning performance.

(Description of Embodiments) FIG. 1 is a side view of a cleaning device according to an embodiment of the present invention, which has an axis line in the direction perpendicular to the paper surface and rotates in the direction of arrow A (referred to as a photoconductor). The first surface photosensitive layer is uniformly charged by the charger 2, and the charged surface is irradiated with a light image 7 such as a laser beam having an image modulated thereon to form an electrostatic latent image.

Then, toner is supplied to the latent image by the developing device 3, and the latent image is visualized into a toner image.

When the toner image arrives at the transfer site where the photoconductor 1 and the transfer charger 5 face each other, by this time, the transfer material 4 has
It arrives at the transfer site in time with the toner image,
At this time, the toner image is transferred to the transfer material by the action of the transfer bias by the transfer charger 5.

Thereafter, the transfer material is conveyed to a fixing portion (not shown), while the toner not transferred to the transfer material at the time of transfer and the above-mentioned foreign matter adhering to the photoreceptor are accompanied by the rotation of the photoreceptor 1 and the cleaning device. Reach position 6.

The cleaning device is provided with a cleaning blade 11 and an elastic cleaning roller 9, and the basic construction and operation thereof are the same as those shown in FIGS. 8A and 8B, and corresponding parts are designated by the same reference numerals. It is shown, and the description thereof will be omitted unless otherwise necessary.

FIG. 2 is an enlarged side view of the cleaning device. In this device, the cleaning roller 9 comprises an inner layer 9b made of silicon rubber sponge on a core metal, and an outer layer 9a of urethane rubber formed on the inner layer 9b. The scraper 10 made of Sus is pressed against the roller 9 to remove excess toner, form a toner layer on the surface of the roller 9, and further charge the surface of the roller.

Further, the scraper 10 is connected to the changeover switch 14 by a conductor 13, as shown in the figure.

The switch 14 is provided with a terminal a in a floating state and a terminal b grounded, and by a sequence control means (not shown), the switch 14 is set to the float side during operation of the image forming apparatus, and when the apparatus is stopped. , Shall be connected to the ground side a few seconds before stopping (normally 4 to 5 seconds are allowed). After stopping, ground for about 10 seconds.

With this configuration, when the image forming apparatus is in operation, the surface potential of the cleaning roller is maintained at a high potential, and the toner and various foreign substances as described above are effectively removed by rubbing and electrostatic action. When the apparatus is stopped, the electric charge of the cleaning roller escapes to the ground through the conductor 13 and the terminal b, and the surface potential of the roller 9 is quickly attenuated.

Therefore, when the image forming apparatus is in operation, the cleaning device effectively removes the toner and other foreign substances, and when the image forming apparatus is not in operation, the cleaning roller 9 is in a non-charged state, thus preventing a decrease in image density and white spots. can do.

 Next, an experimental example will be described.

Using a copying machine as shown in FIG. 1, as a photoconductor,
Process speed of 330m using OPC photoconductor with 100mm diameter
It was driven at m / sec.

As an elastic cleaning roller, hardness of about 45 ° (Asker C, load 30
A roller having a diameter of 20 mm and having a urethane rubber layer of 0 gr) was run at a peripheral speed of 200 mm / sec and rubbed against the photoreceptor.

The changeover switch used has a configuration that can be switched to the float side while the device is operating and to the ground side when the device is stopped.

As the known cleaning device, the cleaning device shown in FIGS. 8A and 8B was used, and the others were the same as those used in the experimental example.

Evaluation was performed by the following method using the above cleaning means.

Evaluation mode Mode I: Continuous copy of 999 sheets, 〃 II: Leave for 60 minutes, 〃 III: Copy of 10,000 sheets after halftone copying, that is, without limiting the copy material, after continuous copying of 999 sheets, operation is stopped. And left for 60 minutes, and several initial halftone images of Mode III were copied to evaluate the roller marks.

After that, 10,000 sheets were copied to evaluate the cleaning effect. Specifically, it was evaluated by the presence or absence of filming or flow.

 The results are shown in the table below (Table 1).

Next, FIG. 3 shows the change with time of the surface potential of the cleaning roller at this time.

According to the experimental results, the conventional example has the cleaning effect, but the roller mark is generated.

On the other hand, in the apparatus of the example, a good cleaning effect was obtained, and no roller marks were generated, and both functions could be achieved at the same time.

FIG. 3 is a graph showing a temporal change in the surface potential of the cleaning roller in the above-mentioned embodiment and the conventional example,
As can be seen from this graph, in the conventional example, the mode
Although the potential of the cleaning roller is gradually attenuated at the time point II, the surface potential of the roller is rapidly attenuated at this time in the apparatus of the example, and due to such a difference, the low-density image, the image It is considered that white spots are generated.

FIG. 4 is a side view of a main part mainly showing a cleaning device according to another embodiment of the present invention, in which the cleaning device itself and the changeover switch are not particularly different from the device of the above embodiment.
Corresponding parts are designated with similar reference numerals.

Further, in the device of this embodiment, the terminal a on the float side of the switch 14 of the device of the embodiment is connected to the high impedance element 15.

In such a device, the high impedance element 15 has a rating of 3000V (a), 2400V (b), 1200V (c), 6V.
The evaluation was performed in the same manner as in the above-mentioned example except that the varistor of 00V (d) and 200V (e) was used.

The results are shown in Table 2, and the time change of the surface potential of the cleaning roller is shown in FIG.

The evaluation results can be summarized as follows: It is preferable to use one having a rating of 2400V or less, particularly 1200V or less, and it is preferable to use one having a rating of 600 or more, particularly 1200V or more for the cleaning effect.

In conclusion, the varistor has a rating in the range of 600V to 2400V, preferably 1000V to 1400V.

In the varistor (a) having a rating of 2400 or more, it takes time for the potential to decay after the image forming apparatus is stopped, and a roller mark is generated.

Also, when the rated voltage is 600 V (e) or less, the electrostatic cleaning effect does not work sufficiently, so that the cleaning function is deteriorated.

Although a varistor was used as the high impedance element in this embodiment, it is needless to say that the present invention is not limited to this, and a resistor, a Zener diode or the like can be used as the element. Not again.

As can be seen from the operation of the apparatus of this embodiment, the surface potential of the cleaning roller is set as low as possible within a range that does not adversely affect the cleaning effect, so that the surface potential of the cleaning roller after the image forming apparatus is stopped. Can be rapidly attenuated, and therefore by providing an appropriate high-impedance element, it is possible to perform finer control in order to maintain the cleaning function and the element for generating the roller trace at the same time. Even better results are obtained than with the device shown in FIGS.

FIG. 6 shows still another embodiment of the present invention.

The basic structure of this cleaning device is the same as that of each of the above-described embodiments, and in this case also, the parts corresponding to those of the above-mentioned device are designated by the same reference numerals.

In the illustrated apparatus, one terminal a of the changeover switch 14
The variable resistor 16 is connected to.

The charging of the cleaning roller usually depends on triboelectric charging, but in such a case, the surface potential of the roller depends on the environment,
In particular, since it greatly changes due to humidity, deterioration of the roller, and the like, by making the surface resistance value of the cleaning roller variable in this way, it is possible to always sell a good action in response to changes in the environment and characteristics of the roller.

FIG. 7 shows still another embodiment of the present invention, in which the terminal a of the switch 14 is
A plurality of high impedance elements 17 having different values are connected.

It can be readily understood that this device, like the device of the above-described embodiment, exhibits an action corresponding to environmental changes and the like.

(3) Effects of the Invention As described above, according to the present invention, in a cleaning device including an elastic cleaning roller that rubs an image carrier, a good cleaning function is maintained by including this type of cleaning roller. However, when the image forming apparatus is stopped and then restarted,
It has a remarkable effect in obtaining a high-quality image by preventing the occurrence of a low-density image and white spots in the image.

[Brief description of the drawings]

FIG. 1 is a side view of an essential part of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is an enlarged side sectional view showing the structure of the above-mentioned cleaning device, and FIG. 3 is a temporal view of the surface potential of the above-mentioned cleaning roller. FIG. 4 is a side view of a main part of a cleaning device showing another embodiment of the present invention, FIG. 5 is a graph showing the time change of the surface potential of the cleaning roller, FIG. FIG. 7 is a side view of a cleaning device showing another embodiment of the present invention, and FIG. 8 is a side view of a known cleaning device. 1 ... Photoconductor, 2 ... Primary charger, 3 ... Developer, 4 ...
... transfer material, 5 ... transfer charger, 6 ... cleaning device, 7 ... optical image signal, 9 ... cleaning roller, 10 ...
… Scraper, 11 …… Cleaning blade, 13 …… Conductor wire, 14 …… Changeover switch, 15 …… High impedance element, 16 …… Variable resistance.

Claims (3)

(57) [Claims] 1. A cleaning device of an image forming apparatus, comprising: an elastic cleaning roller that is in pressure contact with an image carrier and rubs the surface of the image carrier; and a conductive scraper that is in contact with the cleaning roller. While the image forming process is in progress by driving the cleaning roller and the cleaning roller, the scraper is kept in a floating state, before the time when the image forming process ends and the image carrier and the cleaning roller stop, after an appropriate time. The cleaning device is provided with means for grounding the scraper. 2. A cleaning device for an image forming apparatus, comprising: an elastic cleaning roller that is in pressure contact with an image carrier and rubs the surface of the image carrier; and a conductive scraper that contacts the cleaning roller. When the image forming process is in progress by driving the cleaning roller and the cleaning roller, the scraper is grounded through the high impedance element, and appropriately before the time when the image forming process is completed and the image carrier and the cleaning roller are stopped. A cleaning device comprising means for directly grounding the scraper after the point of time. 3. The cleaning device according to claim 2, wherein the high impedance element is a variable resistance element.