JPH07129055A - Image forming device - Google Patents

Abstract

PURPOSE:To evade a deterioration in the quality of an image caused by a failure in electrification by removing residual toner through the use of a cleaning roller as the cleaning means of an image carrier and abutting the cleaning roller on an electrifying roller as well to perform cleaning. CONSTITUTION:A bias having a positive polarity is applied to the cleaning roller 20 by a power source 25 at the time of forming the image, most of the toner left without being transferred onto a transfer material is attracted/removed by the cleaning roller 20 and a very little toner is leveled on the surface of the image carrier. When a sequence is set so that the power source 25 has a negative polarity at the time of nonimage formation, the toner attracted to the cleaning roller is removed therefrom to be transferred onto the image carrier. Moreover, the cleaning roller 20 is arranged in contact with the electrifying roller 4 and simultaneously peripheral speeds are made different between the electrifying roller 4 and the cleaning roller 20, to rub/remove the toner of the electrifying roller 4 and preventing its contamination.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art A typical example of the above known image forming apparatus will be briefly described with reference to FIG.

FIG. 1 is a side view of the main part of the image forming apparatus of this type mainly in the vicinity of the image carrier. The illustrated apparatus is of a cartridge type, and the cartridge 10 includes
A rotating cylindrical image carrier 3 extending in a direction perpendicular to the plane of the drawing,
The charging roller 4 made of an elastic material such as rubber and adjusted to an appropriate volume resistance value, the developing device 5 containing the toner 6, and the cleaner 8 for removing the residual toner remaining after transfer are integrally formed to form an image. It is arranged to be detachable from the main body of the device.

The surface of the image carrier 3 is uniformly charged by the charging roller 4, and an image signal such as an image-modulated laser beam projected from the scanner unit 1 reaches this charging surface to form an electrostatic latent image. Formed.

When the latent image reaches the developing portion where the developing device 5 is arranged by the rotational movement of the image carrier, the developing device 5 is moved.
Toner is supplied from the transfer roller 7 to form a toner image, and the toner image is further transferred with the rotation of the image carrier.
Reach the transcription site where

When the toner image reaches the transfer portion, the transfer material 14 taken out from the cassette 12 by the paper feed roller 13 reaches the position of the registration roller 15 by this time, and the transfer material 14 is transferred in time with the toner image. To the part. At this time, a transfer bias is applied to the transfer roller 7, so that the toner image on the image carrier side is transferred to the transfer material by the action of the electric field formed.

It is assumed that the transfer material, which has completed the transfer, is separated from the image carrier and reaches the fixing portion (not shown) via the conveying path 16. On the other hand, at the time of transfer, the residual toner that does not contribute to the transfer and remains on the image carrier is cleaned by the cleaner 8 as the image carrier rotates.
Is reached and is removed from the image carrier at this position, and the next image forming operation becomes possible.

As described above, in the conventional image forming apparatus, the charging unit and the cleaning unit usually have independent structures and functions.

By the way, in recent years, so-called polymerized toner has been gradually used. This kind of toner is
From the manufacturing process, the particle shape becomes almost spherical, the triboelectric charge potential also increases, and it is possible to use a substance having a lower fixing temperature than a known toner obtained by pulverizing and classifying a resin. However, due to the shape of the toner, the high potential, etc., the conventional cleaning method cannot clean the toner well, and there is a problem that the toner easily passes through the cleaning blade to cause cleaning failure. .

When the charging roller is used for forming the charging surface and the polymerized toner as described above is used for forming the toner image, the toner passes through the cleaning portion and reaches the position of the charging roller. There was a great risk of contaminating it.

When the charging roller is contaminated with the toner as described above, it is negligible when a direct current is superimposed on an alternating current as a charging bias, but a defective charging is apt to occur when only a direct current voltage is applied. There is a risk that image quality will deteriorate. Therefore, it is necessary to consider adding a cleaning means to the charging roller.

The present invention has been made to cope with such a situation, and a cleaning roller is used as a cleaning means for an image bearing member to remove residual toner, and the cleaning roller and the charging roller are also equipped with the cleaning roller. An object of the present invention is to provide an image forming apparatus capable of avoiding charging failure and deterioration of image quality caused by charging failure by contacting the charging roller and cleaning the charging roller.

[0013]

[Constitution of the invention]

In order to achieve the above object, the present invention provides a charging roller for contacting a running image carrier to charge it, and a residual toner for contacting the image carrier. In an image forming apparatus equipped with a cleaning roller for removing the cleaning roller, the cleaning roller is arranged in contact with the charging roller in order to clean the charging roller, or in the above, cleaning with the image carrier is performed. The roller and the cleaning roller and the charging roller are run at different speeds respectively, or in the above, the charging roller surface is smooth and the cleaning roller surface is sponge-like, or adheres to the cleaning roller. A means for collecting the formed toner to a developing device through the surface of the image bearing member during non-image formation, or The means for collecting the toner adhering to the cleaning roller to the developing device, the means for applying a bias having the same polarity as the toner to the cleaning roller and the means for applying the bias having the same polarity as the toner to the charging roller during non-image formation. Or in the above, the means for collecting the toner in the developing device has a means for making the developing bias have a polarity opposite to that of the toner during non-image formation, or in all of the above, the toner is As the image forming apparatus, a substantially spherical toner manufactured by a polymerization method is used, or in all of the above, only a DC voltage is applied to the charging roller.

With this structure, the structure of the image forming apparatus can be downsized and the cost can be reduced, and the charging roller can be prevented from being contaminated to avoid the charging failure and the deterioration of the image quality due to the charging failure. You can

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIG. 1" is a side view of a main part of an image forming apparatus showing an embodiment of the present invention.
The transfer means, the transfer material transport system, etc. are not different from those of the known image forming apparatus shown in FIG. 6, and corresponding parts are designated by the same reference numerals, and the description thereof is omitted. To do.

In the illustrated apparatus, the cleaner 8 is provided with the cleaning roller 20, which is arranged so as to be in contact with the image carrier 3 and also with the charging roller 4.

FIG. 2 is a side view showing the structure around the image carrier of the above-mentioned apparatus. As described above, the transfer roller 7 comes in contact with the image carrier 3 via the registration roller 15. After the transfer material (not shown) transferred to the part is transferred, the transfer material is transferred to the fixing part (not shown) through the transfer path 16, and the transfer material remains on the image carrier after the transfer. It is assumed that the remaining toner reaches the position of the cleaner 8 and is scraped off by the cleaning roller 20 that is also in contact with the charging roller 4. Here, it is assumed that the transfer roller 7 is made of a semiconductive elastic material, and a DC voltage is applied so that a current of 2 to 10 μA flows.

Next, the structures of the charging roller 4 and the cleaning roller 20 will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the charging roller 4 has a diameter of 6 to
A conductive sponge rubber layer 31 having a thickness of 2 to 10 mm is formed on a core metal 30 having a thickness of 2 to 10 mm on a core metal 30 having a thickness of 10 mm to prevent noise from being generated when an AC bias is applied to the core metal 30. In order to make the roller surface smooth, a conductive layer 32 having a thickness of 50 to 300 μm is formed, and a semiconductive layer 33 having a thickness of about 5 to 50 μm is provided on the surface for preventing leakage.

FIG. 4 is a perspective view of the cleaning roller 20. A sponge layer of urethane rubber, silicon rubber or the like is formed around a cored bar 21 so that the cells are exposed on the surface.

FIG. 6 is an explanatory view showing such an apparatus, in particular, the image carrier and the charging roller 4 and the cleaning roller 20 which are in contact with the image carrier. In the case shown in the figure, reversal development is performed. Therefore, it is assumed that a voltage obtained by superimposing an AC voltage on a DC voltage having a negative polarity is applied to the charging roller 4 by the power source 26, the polarity of the toner is a negative polarity, and the developing bias is As a negative voltage, a voltage obtained by superimposing an AC voltage on a DC voltage is applied and jumping development is performed. Therefore, the transfer bias applied to the transfer roller at the transfer site (not shown) has a positive polarity. Here, the developing method is a method in which the toner is held on the toner carrier and the toner carrier and the image carrier are maintained at a distance of 100 to 300 μm for development, and the toner may be magnetic or non-magnetic.

A positive bias is applied to the cleaning roller 20 by a power source 25 during image formation,
Most of the residual toner that has not transferred to the transfer material is adsorbed and removed by the cleaning roller 20, and a very small part of the toner is leveled on the surface of the image carrier. The toner adsorbed on the cleaning roller is set by setting the sequence so that the power source 25 has a negative polarity during non-image formation.
It is removed from the cleaning roller and transferred to the image carrier.

The toner transferred to the image carrier at the time of non-image formation reaches the position of the developing device as the image carrier rotates and is shaken off from the image carrier by the oscillating electric field and collected by the developing device. In this case, it is preferable that the developing bias has a polarity opposite to that of the toner in order to facilitate the movement of the toner to the developing device.

In the above process, the toner naturally comes to the portion where the charging roller 4 is in contact with the image carrier, but since the roller is negatively charged, its surface is not contaminated. In addition, if a substantially spherical polymerized toner is used, the shape of the toner adheres to the image carrier mainly only by electrostatic force, and the physical adhesive force is comparatively weak. It can be separated from the image carrier.

The rotation direction and relative speed relationship of the image carrier 3, the charging roller 4 and the cleaning roller 20 will be briefly described. The charging roller 4 runs in the same direction and at substantially the same speed at the contact portion with the image carrier 3, and rubs the toner on the image carrier due to the difference in speed so as to prevent the occurrence of fusion. Has become.

On the other hand, if both of them run at the same speed, there is a possibility that the charging roller does not have the cleaning function and the toner is gradually accumulated to cause the charging failure. The cleaning roller 20 is disposed in contact with the charging roller 4, and a peripheral speed difference is provided between the charging roller 4 and the cleaning roller 20 to remove the toner adhering to the charging roller by rubbing and removing it, thereby preventing the charging roller 4 from being contaminated. It is configured as follows.

In the above-mentioned apparatus, the case of performing jumping development has been described, but it is needless to say that it can be applied to the case of contact development method using non-magnetic one-component toner. In this developing method, since the toner carrier such as the developing sleeve of the developing device is in contact with the image carrier and the electric field strength between the image carrier and the toner carrier is large, the unnecessary toner in the non-printing portion is collected in the developing device. Is easy.

As another embodiment, when there is almost no residual toner remaining on the image bearing member after transfer as in the case of using polymerized toner, the cleaning roller 20 has a function of dispersing the residual toner on the image bearing member. Just play. Since a large amount of residual toner is present in the character portion of the image, if the cleaning roller is rubbed over the residual toner, the toner will be scattered around and the charging roller will not be defectively charged. Further, by the action of the cleaning roller, the residual toner is smoothly collected at the developing position.

In this example, since a large amount of toner does not accumulate on the surface of the cleaning roller, the sequence for cleaning the surface of the cleaning roller for each print as described above is not always necessary, and simplification of the apparatus and improvement of usability are not achieved. Get rid of.

In the above-mentioned actual command, the case where the voltage in which the alternating current is superimposed on the direct current is superimposed is applied to the charging roller, but it is possible to apply only the direct current to the charging roller.

In this case, the charging characteristics of the charging roller are:
When the applied voltage is 0 to -700V, it is hardly charged and is almost-
It is linearly charged at 700V or higher. For example, by applying -1500V to the charging roller, the surface potential of the image carrier becomes about -700V to -1500V.

When such a charging method is used, the toner having a negative polarity hardly adheres to the charging roller. In this case, when the polymerized toner is used, the residual toner is hardly generated, and the cleaning roller is the toner on the image carrier. The toner attached to the charging roller is greatly reduced.

Next, an experimental example will be described. [Experimental Example 1] An OPC photosensitive member having a diameter of 30φ is used as an image carrier, a roller having a diameter of 12φ and a cleaning roller having a diameter of 12φ are configured as shown in FIG. 3 as a charging roller.
A φ sponge roller was used. As the toner, a polymerized toner having a substantially spherical shape and an average particle diameter of about 8 μm was used.

At the time of image formation, the charging roller 4 is set to -70.
A charging bias in which 2 Kv and 2000 Hz alternating current are superimposed on 0 V direct current is applied to the cleaning roller 20 by +600 V.
The developing bias is 1600 at a DC of -500V.
A developing bias in which an alternating current of V and 2000 Hz was superposed was applied.

The developing method is jumping development, the image carrier is run at a peripheral speed of 100 mm / sec, the charging roller is run in the same direction and at the same speed at the contact portion with the image carrier, and the cleaning roller is the image carrier. At the contact area with the body, the vehicle was run in the opposite direction at a peripheral speed of 50 mm / sec.

During non-image formation, the charging bias and the developing bias were not changed, and the voltage applied to the cleaning roller was set to -500 V to clean the roller.

Using a cartridge type image forming apparatus as shown in FIG. 1 and passing the paper under the above conditions, the construction of the cleaning device portion was greatly reduced and the cartridge could be miniaturized. In addition, good images could be obtained up to 1000 sheets without any cleaning failure, charging failure, or toner fusion to the image carrier.

[Experimental Example 2] The same image carrier, charging roller, cleaning roller, and toner as those in Experimental Example 1 were used, and at the time of image formation, the charging roller was -700V.
The charging bias in which the alternating current of 2 Kv and 1000 Hz is superposed on the direct current of +600 V for the cleaning roller and the direct current of -500 V for the developing bias is 1600 V,
A developing bias in which an alternating current of 2000 Hz was superposed was applied. Jumping development was used as the development method.

The image carrier is run at a peripheral speed of about 100 mm / sec, the charging roller is run in the same direction and at the same speed at the contact position with the image carrier, and the cleaning roller is in contact with the image carrier. Peripheral speed of 50m in the opposite direction at the part
It was run at m / sec.

During non-image formation, the charging roller is 0.5 to
The voltage becomes 0 V only once, which makes it easier for the toner to adhere to the image carrier. At this time, the DC component of the developing bias is set to 0 V so that the developing image is not performed. After that, the charging roller was
The toner is prevented from adhering even when the surface potential of the image carrier reaches 0V after returning to 700V. When the potential of the image carrier reaches 0V, the potential of the cleaning roller is set to 0V to transfer the toner on the surface of the cleaning roller to the image carrier.

When the image forming apparatus as shown in FIG. 1 was used to carry the paper under the above conditions, no defective cleaning occurred and the cartridge was clean even though the structure of the cleaning device was greatly reduced. It was confirmed that remarkable downsizing can be achieved, and good image output can be achieved up to 6000 sheets without charging failure or fusion of the toner to the image carrier. This embodiment is more preferable than the above-mentioned embodiments from the viewpoint of downsizing of the device and cost reduction without increasing the types of high pressure.

[Experimental Example 3] The same image carrier, charging roller, cleaning roller, and toner as those in Experimental Example 1 were used, and the charging roller was used during image formation.
A charging bias that superimposes 2 Kv and 1000 Hz alternating current on 700 V direct current is +600 V on the cleaning roller.
Is applied, and in developing, a contact developing system is adopted in which a non-magnetic polymerized toner is carried on a developing roller made of a semiconductive and elastic material and brought into contact with an image carrier. Only DC bias was applied.

The image carrier travels at a peripheral speed of 100 mm / sec, the charging roller travels at the same position in the same position as the image carrier, and the cleaning roller contacts the image carrier in the same position. In the same direction as 50 mm / s
It was run at ec.

At the time of non-image formation, the charging bias and the developing bias are not changed, and only the voltage applied to the cleaning roller is set to -500V for cleaning.

In this apparatus, the cleaning roller and the image carrier travel in the same direction, which is effective in preventing the toner from adhering to the image carrier, and the speed difference at the contact portion with the charging roller is large. Therefore, the cleaning function of the roller is also improved.

Under the conditions as described above, the paper was passed through like the image forming apparatus as shown in FIG. 1, but the cleaning device can be greatly reduced and the cartridge can be downsized. It was confirmed that a high-quality image can be output up to 6,000 sheets of paper, without the occurrence of poor charging and toner fusion.

[Experimental Example 4] The same image carrier, charging roller, cleaning roller and toner as those in Experimental Example 1 were used, and a charging bias of DC-1500V was applied to the charging roller during image formation. , A voltage of -500 V is not applied to the cleaning roller, and in developing, a developing roller made of a semi-conductive and elastic material is made to carry a non-magnetic polymerized toner and brought into contact with the image carrier. A DC voltage of -500V was applied to the developing roller.

The image carrier travels at a peripheral speed of 100 mm / sec, the charging roller travels at the same speed in the same direction as the contact position of the image carrier, and the cleaning roller contacts the image carrier. 50mm / in the same direction at the part
It was run in sec.

In this apparatus, since the cleaning roller and the image carrier travel in the same direction and only the DC voltage is applied to the charging roller, the charging roller does not vibrate and the toner on the image carrier does not move. The effect of preventing fusion is great. Further, in this apparatus, the cleaning roller has almost no need to perform the action of removing the toner for the reason of remaining, and since it is sufficient to disperse the toner on the image carrier, the sequence of cleaning the cleaning roller after the printing is completed is unnecessary. ,
Contributes to the simplification of the device.

Further, even if the positively charged particles are attached to the charging roller, there is little possibility that the cleaning roller removes the particles to cause defective charging. In particular, when a DC voltage is applied to the charging roller, uneven charging is more likely to occur due to dirt on the roller surface than when an AC voltage is applied, but such a situation can be avoided in the case of the present invention.

In the case of this experimental example, the charging roller was run at the same speed as the image carrier, but it is possible to reduce charging unevenness by running the image carrier faster. In this case, the fusion of the toner on the image carrier becomes easy to occur,
Since it is a DC voltage, it can be less than that of an AC voltage.

When paper is passed through the image forming apparatus as shown in FIG. 1 under the above conditions, the cleaning device can be greatly reduced in size and the cartridge can be downsized, and the image carrier can be charged. It was confirmed that high-quality images can be produced up to 6,000 sheets of paper without causing defects or toner fusion.

[Experimental Example 5] The same image carrier, charging roller, and cleaning roller toner as those used in Experimental Example 1 were used, and a DC roller was applied to the charging roller during image formation.
A contact developing method is applied in which a charging bias of 1500 V, +600 V is applied to the cleaning roller, and a non-conductive polymerized toner is carried on the developing roller made of a semi-conductive elastic material and brought into contact with the image carrier during development. A developing bias of DC-500V was applied to the developing roller.

The peripheral speed of the image carrier is set to 100 mm / sec, the charging roller is made to run at the same speed as the contact position with the image carrier, and the cleaning roller is moved at the same position as the contact position with the image carrier. Direction was made to travel at 50 mm / sec.

At the time of non-image formation, the charging bias and the developing bias are not changed, and only the voltage applied to the cleaning roller is set to -500V for cleaning.
In this case, some toner remains on the image carrier, and toner is temporarily accumulated on the surface of the cleaning roller. Since a DC voltage is applied to the charging roller, uneven charging is more likely to occur due to dirt on the surface of the charging roller than when an AC voltage is applied. However, in this case, since the cleaning roller cleans the surface of the charging roller,
It is possible to avoid a situation where uneven charging is a problem.

Further, in order to ensure the charging, it is possible to make the charging roller run faster than the image bearing member. In this case, fusion of the toner on the image bearing member is likely to occur, It can be said that it is not so much as in the case of electrification and can be practically used.

Under the above conditions, the image forming apparatus as shown in FIG. 1 was used to pass the paper. However, the cleaning device can be greatly reduced in size, and the cartridge can be downsized. It was confirmed that a good-quality image can be output up to 6,000 sheets of paper without generation of charging failure and fusion of thinner.

The case where the present invention is applied to the cartridge type laser beam printer has been described above. However, the present invention is not limited to this, and may be applied to a well-known copying machine or an image forming apparatus which does not adopt the cartridge type. It can be easily understood that it can be applied.

[0057]

As described above, according to the present invention,
Provide a charging roller that contacts the rotating cylindrical image carrier and a cleaning roller that contacts both the image carrier and the charging roller, and set the peripheral speed and potential of these image carrier, charging roller, and cleaning roller appropriately. The cleaning roller cleans the charging roller and collects the toner adhering to the cleaning roller to the developing device, preventing the occurrence of charging failure, greatly reducing the size of the cleaning mechanism, and reducing the cost of the device. It is possible to down, and particularly when a polymerized toner is used, there is a remarkable effect in improving image quality and fixability.

[Brief description of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is an enlarged side view showing the configuration of the vicinity of the image carrier of the above apparatus.

FIG. 3 is a perspective view of a charging roller of the same apparatus.

FIG. 4 is a perspective view of a cleaning roller of the moving device.

FIG. 5 is an image carrier and a charging roller disposed in contact with the image carrier;
Explanatory drawing showing the action of the cleaning roller

FIG. 6 is a side view of essential parts showing the configuration of a known image forming apparatus.

[Explanation of symbols]

 1 Scanner Unit 3 Image Carrier 4 Charging Roller 5 Developer 7 Transfer Roller 8 Cleaner 14 Transfer Material 15 Registration Roller 20 Cleaning Roller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03G 15/06 101 6605-2H G03G 21/00 326

Claims (8)

[Claims] 1. An image forming apparatus comprising: a charging roller for contacting a running image carrier to charge the image carrier; and a cleaning roller for contacting the image carrier to remove residual toner. An image forming apparatus, which is disposed in contact with the charging roller so as to clean the charging roller. 2. The image forming apparatus according to claim 1, wherein the image carrier and the cleaning roller and the cleaning roller and the charging roller run with a difference in speed. 3. The image forming apparatus according to claim 1, wherein the surface of the charging roller is a smooth surface and the surface of the cleaning roller is sponge-like. 4. The toner adhered to the cleaning roller,
The image forming apparatus according to any one of claims 1 to 3, further comprising means for collecting the image through the surface of the image bearing member to the developing device during non-image formation. 5. A means for collecting the toner adhering to the cleaning roller to a developing device, a means for applying a bias having the same polarity as the toner to the cleaning roller during non-image formation, and a bias for the charging roller having the same polarity as the toner. The image forming apparatus according to claim 4, further comprising: 6. The image forming apparatus according to claim 5, wherein the means for collecting the toner adhering to the cleaning roller to the developing device has a means for making the developing bias have a polarity opposite to that of the toner during non-image formation. 7. The image forming apparatus according to claim 1, wherein a substantially spherical toner manufactured by a polymerization method is used as the toner. 8. The image forming apparatus according to claim 1, wherein only a DC voltage is applied to the charging roller.