JPH03107982A - Cleaning device for image forming device - Google Patents

Abstract

PURPOSE:To obtain good-quality images without generating the trace of a cleaning roller even if an operation is restarted after the operation is temporarily stopped by impressing the bias voltage of the polarity reverse from the polarity of the charge accumulated by friction of the roller and a scraper on the cleaning roller at the time of stopping the roller. CONSTITUTION:The elastic cleaning roller 4 which rubs the surface of an image carrying member 1 by coming into pressurized contact therewith and the scraper 5 which comes into contact with the cleaning roller 4 are provided. Means 7, 8 for impressing the voltage of the polarity reverse from the polarity of the charge accumulated by friction of the roller 4 and the scraper 5 at the time of stopping the cleaning roller 4 are provided. The surface potential of the cleaning roller 4 is maintained at a certain value to effectively remove the toner, etc., on the image carrying member side during the operation of the device. The potential of the roller 4 is attenuated to prohibit the generation of the trace of the roller in the next and ensuing images during the stoppage. The good-quality images are thus obtd..

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer, and a cleaning apparatus thereof. It is something.

(Prior art and issues to be solved) In a well-known image forming apparatus, the process of transferring the transferable toner image formed on the surface of the image carrier to a transfer material mainly made of paper is It is necessary to sufficiently remove residual toner that does not contribute to transfer and remains on the image carrier.

As a means of cleaning such residual toner, a cleaning blade made of an elastic material such as rubber has a simple structure, is small in size, is cost-effective, and has an excellent toner removal function, so it is widely used (in practical use). However, on the other hand, cleaning blades can remove fine paper dust, rosin, talc, and other precipitates generated from the paper used as the transfer material.
It is not always effective in removing foreign substances that adhere to the image carrier, such as corona products caused by the presence of high-pressure members in the device, that absorb moisture and cause deterioration of image quality. Ta.

Therefore, as a means for removing the above-mentioned foreign substances, a cleaning roller made of an elastic material such as silicone rubber, urethane rubber, fluorocarbon rubber, or polyethylene rubber is pressed against the surface of the image carrier, and the cleaning roller is moved at an appropriate relative speed to the cleaning roller. A cleaning means has been proposed in which the roller is rubbed and a scraper is brought into contact with the roller.

Such a method is effective in removing the above-mentioned foreign matter that cannot be removed by a cleaning blade. This is because the scraper comes into contact with the cleaning roller and is frictionally charged, thereby raising the surface potential of the roller to a certain value. It is known that toner and other foreign substances are removed by the electrostatic action of the toner.

However, if the cleaning roller is configured to be charged in this way, when the operation of the image forming apparatus is temporarily stopped and then restarted, the portion of the cleaning roller that corresponds to the portion that was in contact with the image carrier while the image forming apparatus was stopped is removed. A defect called so-called roller trace occurs, in which the image deteriorates.

Although the cause of roller marks is not necessarily clear, in such devices, even when the cleaning roller is stopped, the surface potential of the cleaning roller is relatively high (this induces traps in the photosensitive layer of the image carrier, and This is thought to be caused by the charging potential of the relevant portion of the image carrier becoming insufficient when the apparatus is next operated.

In order to prevent such a situation from occurring, a possible method is to apply a bias to the core metal of the cleaning roller with a polarity opposite to the polarity of the potential due to frictional charging to prevent the surface potential of the cleaning roller from increasing. However, by doing this, it is possible to prevent the occurrence of roller marks caused by stopping the device, but if the device is stopped for a certain period of time after the image forming process is completed and then restarted, the filter will be Occurrence of printing, image blurring, etc. was observed, and deterioration of the cleaning effect was observed.

This is considered to be because the surface potential of the cleaning roller is maintained low during operation, resulting in a decline in the ability to remove toner and other foreign matter due to electrostatic attraction.

The present invention has been made to deal with such a situation, and in an image forming apparatus equipped with a cleaning device using a leaning roller as described above, the cleaning roller is placed at a high potential during operation of the image forming apparatus. At the same time, near the time of stopping, a bias with the opposite polarity to the charge generated on the cleaning roller during operation is applied to neutralize and eliminate the charge, thereby achieving a good cleaning function and temporarily stopping the work. The purpose is to provide a leaning device that can obtain high-quality images even if it is stopped and restarted immediately.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an elastic cleaning roller that presses against and slides against the surface of an image carrier, and a scraper that comes into contact with the cleaning roller. In a cleaning device equipped with
The present invention is characterized by comprising means for applying a bias voltage to the cleaning roller when the cleaning roller is stopped, the polarity of which is opposite to the charge accumulated by friction between the cleaning roller and the scraper.

With this configuration, in a cleaning device that includes a cleaning roller and a scraper that comes into contact with the cleaning roller and removes toner and other foreign matter by frictional charging of both, the cleaning function can be maintained while the scraper is in contact with the cleaning roller. It is possible to effectively prevent the occurrence of image defects called roller marks that occur when the machine is restarted after a while.

(Description of Embodiments) FIG. 1 is a side view showing the configuration of a cleaning device according to the present invention, and has an axis perpendicular to the paper surface and parallel to a cylindrical image carrier 1 rotating in the six directions of arrows. A cleaning device 2 is provided, and one edge of one end of a cleaning blade 3 attached to the cleaning device 2 is attached to the image carrier 1.
The toner is pressed against the surface and placed at a transfer position (not shown) to scrape off residual toner that is not transferred to the transfer material and remains on the image carrier.

An elastic cleaning roller 4 is disposed on the upstream side of the cleaning blade 3 when viewed in the running direction of the image carrier 1, and is brought into pressure contact with the image carrier at a relative speed by an appropriate drive source (not shown). The toner and the foreign substances mentioned above shall be removed by rubbing.

The toner etc. scraped off from the image carrier 1 adheres to the cleaning roller 4 and is conveyed, and is removed by the scraper 5 and reaches the toner storage section. By appropriately setting the charging polarity, the roller 4 electrostatically adsorbs and removes toner and the like from the image bearing system as described above.

It should be noted that, of course, there are a wide charger, an image signal applying means, a developing device, a transfer means, and other members necessary for image formation around the image carrier 1; Since it is not directly related to the invention, it is omitted.

The cleaning roller 4 is formed by forming an inner layer 4b made of silicon sponge around a core metal 4a, and an outer layer 4c made of solid urethane rubber on the outside thereof, and the core metal 4a is connected to a switch 7 as shown in the figure. It is connected to a constant voltage power supply 8.

During the image forming operation, the switch 7 is open as shown in the figure, and as a result, the surface potential of the cleaning roller 4 increases due to friction with the scraper 5 and is maintained at a certain value, as described above. It functions to remove toner and the like from the surface of the image carrier 1.

When the image forming operation is completed and each part stops, the switch 7 is closed in response to this, and the power supply 8 charges the cleaning roller 4 with a polarity opposite to that of the frictional charge accumulated on the roller by that time. A bias of 1 is applied, and as a result, the potential of the cleaning roller is rapidly attenuated, so that it is possible to prevent roller marks from occurring when the image forming operation is restarted thereafter.

As described above, by using the cleaning device according to the present invention, the surface potential of the cleaning roller is maintained at a certain value while the device is in operation to effectively remove toner, etc. from the image bearing system, and while the device is stopped, the surface potential of the cleaning roller is maintained at a certain value. By attenuating the potential of the roller, it is possible to prevent roller marks from occurring in subsequent images.

Next, an experimental example will be explained.

As an image carrier, the diameter is 100+ nm and the peripheral speed is 330 mm/
A sec OPC photoreceptor (-order charge is negative polarity) was used, and a positively chargeable one-component toner was used.

The cleaning device has the configuration shown in the first figure, and the elastic cleaning roller has a stainless steel core 9a with a diameter of 4 μm, an inner layer 4b made of silicone sponge with a diameter of 16 mm, and an inner layer 4b made of silicone sponge with a hardness of 45 mm on the outside. Asker-C load: 300 gr) A urethane rubber layer 4c with a thickness of 2 mm is formed, the overall diameter is 20 mm, and the circumferential speed is 200 mm/
sec.

The constant voltage power supply 8 had a rating of 200±20V, and was connected with the switch side as positive.

For comparison with the above, as a cleaning device,
The switch 7 and power source 8 were removed from the apparatus shown in FIG. 1, and a device having the same configuration as that shown in FIG.

Using the leaning apparatus described above, images were evaluated by the following means.

Mode: 999-sheet continuous copy evaluation mode Mode: 60-minute standstill mode: After halftone copying, 10,000 sheets of continuous copying For objects to be copied (not limited to, first 999-sheet continuous copying) After that, there was a pause of 60 minutes, and then several halftone images were copied to evaluate the roller marks.After that, 10,000 copies of the original copy were continuously made to evaluate the cleaning effect (filming, image blurring, etc.). (presence/absence) was evaluated.

The results are shown in Table 1. Also, Figure 2 shows the above case.
It shows the temporal change in the surface potential of the cleaning roller.

(The following is a blank space.) FIG. 3 is a side view of a cleaning device showing another embodiment of the present invention, in which parts corresponding to the device shown in FIG. 1 are given the same reference numerals. , the explanation of them will be omitted.

In the illustrated device, the core metal 4 of the cleaning roller 4 is
A is connected to the power supply 8 via the changeover switch 7a.

The switch 7a has a terminal connected to the power source 8 and a grounded terminal a, and is connected to the terminal a when the image forming apparatus is in operation and to the terminal A when the image forming apparatus is not in operation.

With this device, no significant difference was observed in the cleaning effect compared to the previous example, but in terms of prevention of roller marks, the device of this example was better than the previous example. showed more effective results.

This will be discussed using the graph shown in FIG. 4, which shows the change over time in the surface potential of the cleaning port.

In this example device, since the core metal 4a of the cleaning roller 4 is grounded through the terminal a during operation, a part of the charge due to the frictional potential leaks, and the surface potential of the roller 4 changes as described above. It will be maintained at a slightly lower value than when it is in the float state as in the example.

For this reason, when the device is stopped and a reverse bias is applied to the core bar 48, the surface potential of the roller 4 attenuates more quickly than in the embodiment described above, which also prevents the occurrence of roller marks. It is considered to be excellent.

FIG. 5 is a side sectional view of a cleaning device showing still another embodiment of the present invention.

In this device as well, parts corresponding to those in each of the embodiments described above are shown with the same reference numerals, and the core metal 48 of the cleaning roller 4 is connected to the variable constant voltage element 9.

With this configuration, an optimal bias voltage can be applied respectively when the image forming apparatus is in operation and when it is stopped.

Table 2 shows the results of an experiment conducted with the voltages applied during operation and stop of this device as E, , E.

The evaluation method was the same as in the previous example.

(Margins below) According to this, with regard to roller marks, setting the bias voltage E+ applied during operation higher can suppress the roller surface potential to a lower level, and therefore the potential attenuation after stopping is also faster. This is effective, but on the other hand, the cleaning effect may be affected if the bias applied during operation is too high.
It became difficult to maintain the potential required for the cleaning action, and the cleaning function deteriorated.

(3) According to the present invention, as described in detail, in a cleaning device using an elastic cleaning roller, while maintaining its cleaning function, it is possible to effectively remove the roller marks when restarting after stopping the cleaning device. This greatly contributes to preventing such problems and obtaining high-quality images.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a cleaning device according to an embodiment of the present invention, Fig. 2 is a graph showing temporal changes in the surface potential of the cleaning roller same as above, and Fig. 3 is a side sectional view of a cleaning device showing another embodiment. , FIG. 4 is a graph showing temporal changes in the surface potential of the cleaning roller, and FIG. 5 is a side sectional view of a cleaning device showing still another embodiment. 1... Image carrier, 2... Cleaning device, 3...
・Cleaning blade, 4... Elastic cleaning roller, 5... Scraper, 7.7a... Switch,
8... Constant voltage power supply, 9... Variable constant voltage element. Fig. ft review (intermediate) Call volume (current)

Claims (2)

[Claims] (1) In a cleaning device equipped with an elastic cleaning roller that presses against and slides against the surface of the image carrier, and a scraper that comes into contact with the cleaning roller, when the cleaning roller is stopped, the amount of water that is accumulated due to the friction between the roller and the scraper is A cleaning device for an image forming apparatus, comprising means for applying a bias voltage of opposite polarity to the cleaning roller to the cleaning roller. (2) The cleaning device according to claim 1, wherein the means for applying a bias voltage to the cleaning roller includes means for grounding the roller when the roller is in operation.