JP3026051B2 - Image forming device - Google Patents

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-mentioned known image forming apparatus will be briefly described with reference to FIG.

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

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

When the latent image reaches a developing site where the developing device 5 is arranged by rotating the image carrier, the developing device 5
Is supplied from the transfer roller 7 to form a toner image, and this toner image is transferred to the transfer roller 7 by the rotation of the image carrier.
Reaches the arranged transcription site.

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

The transfer material after the transfer is separated from the image carrier, and reaches a fixing portion (not shown) via the transport path 16. On the other hand, at the time of transfer, residual toner remaining on the image carrier without contributing to the transfer is transferred to the cleaner 8 by rotation of the image carrier.
Is reached, and is removed from the image carrier at this position, and the next image forming operation is enabled.

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

In recent years, so-called polymerized toner has been gradually used. This type of toner is
From the manufacturing process, the particle shape becomes substantially spherical, the triboelectric potential is also increased, and a substance having a lower fixing temperature than a known toner obtained by pulverizing and classifying a resin can be used. However, there is a problem that the conventional cleaning method cannot clean the toner well due to the shape of the toner, high potential, etc., and the toner passes through the cleaning blade to easily cause a cleaning failure. .

In the case where a charging roller is used to form the above-described charged surface and the above-described polymerized toner is used to form a toner image, the toner passes through a cleaning portion and reaches the position of the charging roller. There was a high risk of contamination.

When the charging roller is contaminated with toner as described above, there is no danger when a DC is superimposed on an AC as a charging bias. However, when only a DC voltage is applied, poor charging is likely to occur. It is inevitable that the image quality will deteriorate. For this reason, it is necessary to consider providing a cleaning means to the charging roller.

The present invention has been made in order to cope with such a situation. In order to remove residual toner by using a cleaning roller as a means for cleaning an image carrier, the cleaning roller is also used as a charging roller. The charging roller can also be cleaned by contacting it, thereby avoiding poor charging and deteriorating image quality due to this,
Further, it is another object of the present invention to provide an image forming apparatus capable of greatly reducing the size of the cleaning device.

[0013]

Configuration of the Invention

In order to achieve the above object, the present invention provides a charging roller for contacting a running image carrier and charging the same, and a cleaning device for contacting the image carrier and removing residual toner. In an image forming apparatus having a roller and the cleaning roller also in contact with the charging roller, the peripheral speed difference between the surface of the image carrier and the surface of the cleaning roller, and the surface of the cleaning roller and the surface of the charging roller, respectively. An image forming apparatus (1), or a charging roller for contacting and charging a running image carrier, and a cleaning roller for contacting the image carrier and removing residual toner. In an image forming apparatus in which the cleaning roller is in contact with the charging roller, the surface of the charging roller is smooth, and An image forming apparatus (2) characterized in that the surface of the cleaning roller is sponge-like, or a charging roller that contacts and charges a running image carrier, and removes residual toner by contacting the image carrier. An image forming apparatus having a cleaning roller for cleaning, wherein the cleaning roller is also in contact with the charging roller, wherein toner adhered to the cleaning roller is recovered to a developing device via an image carrier during non-image formation. Image forming apparatus (3).

With this configuration, the configuration of the image forming apparatus can be reduced in size and cost can be reduced, and the contamination of the charging roller can be prevented to prevent poor charging and deterioration of image quality due to the charging. Can be.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view of a main part of an image forming apparatus according to an embodiment of the present invention.
The transfer means, the transfer material transporting system, and the like are not particularly different from those of the known image forming apparatus shown in FIG. 6, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. I do.

In the illustrated apparatus, a cleaner 8 is provided with a cleaning roller 20 which contacts the image carrier 3 and also contacts the charging roller 4.

FIG. 2 is a side view showing the structure around the image carrier of the above-described apparatus. As described above, the transfer roller 7 abuts on the image carrier 3 via the registration roller 15. After the transfer is performed on the transfer material (not shown) conveyed to the portion, the transfer material is conveyed to a fixing portion (not shown) through the conveyance path 16, and the transfer material remains on the image carrier after the transfer. It is assumed that the residual toner that has reached the position of the cleaner 8 is rubbed and removed by the cleaning roller 20 that is also in contact with the charging roller 4. Here, 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 configurations of the charging roller 4 and the cleaning roller 20 will be described with reference to FIGS. 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 10 mm core metal 30 in order to make it closely adhere to the image carrier and to prevent generation of noise when an AC bias is applied. A conductive layer 32 having a thickness of 50 to 300 μm is formed to smooth the surface of the roller, and a semiconductive layer 33 having a thickness of about 5 to 50 μm is provided on the surface to prevent leakage.

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

FIG. 5 is an explanatory view showing such an image forming apparatus, in particular, a portion of the image bearing member, the charging roller 4 and the cleaning roller 20 in contact with the image bearing member. In the case shown in the figure, reversal development is performed. For this reason, a voltage in which an AC voltage is superimposed on a DC voltage of a negative polarity is applied to the charging roller 4 by a power supply 26, and the polarity of the toner is negative and a developing bias is applied. A voltage obtained by superimposing an AC voltage on a negative DC voltage is applied to perform jumping development. Therefore, the transfer bias applied to the transfer roller at the transfer portion (not shown) has a positive polarity. The developing method is jumping development as described above, and the interval between the toner carrier such as a developing roller and the image carrier is 100 to 300 μm.
m. The toner may be magnetic or non-magnetic.

A positive bias is applied to the cleaning roller 20 by a power supply 25 during image formation,
Most of the residual toner not transferred to the transfer material is sucked and removed by the cleaning roller 20, and a very small portion of the toner is leveled on the surface of the image carrier. The toner adsorbed on the cleaning roller is set in a sequence such that the power supply 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 during non-image formation reaches the position of the developing device as the image carrier rotates, and is shaken off the image carrier by the oscillating electric field and collected by the developing device. In this case, in order to smoothly move the toner to the developing device, it is preferable that the developing bias has a polarity opposite to that of the toner.

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, the surface thereof is not contaminated. Further, if a substantially spherical polymerized toner is used, the toner is mainly adhered to the image carrier only by electrostatic force due to its shape, and the physical adhesion is relatively weak. It can be separated from the image carrier.

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

On the other hand, if the two members run at a constant speed, there is no cleaning function in the charging roller, and there is a possibility that the toner is gradually accumulated and a charging failure may occur. 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 rub off toner adhering to the charging roller to prevent contamination of the charging roller 4. It is configured as follows.

Although the above-described apparatus has been described with respect to the case where jumping development is performed, it is needless to say that the invention can be applied to the case of contact development using a 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-print portion is collected in the developing device. Is easy.

As another embodiment, when there is almost no residual toner remaining on the image carrier after transfer, as in the case of using a polymerized toner, the cleaning roller 20 acts to disperse the residual toner on the image carrier. Just play it. Since the residual toner is largely present in the text portion of the image, if the toner is rubbed with a cleaning roller from above, the toner is scattered around and the charging roller does not cause poor charging. In addition, the operation of the cleaning roller smoothly recovers the residual toner at the developing position.

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

In the above embodiment, the charging roller
Although the case where a voltage obtained by superimposing an alternating current on a direct current is applied has been described, it is of course possible to apply only a direct current to a voltage applied to the charging roller.

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

When such a charging method is used, the negative-polarity toner hardly adheres to the charging roller. In this case, when the polymerized toner is used, there is almost no generation of residual toner, and the cleaning roller uses the toner on the image carrier. Only needs to be dispersed, and the amount of toner adhering to the charging roller is greatly reduced.

Next, an experimental example will be described. "Experimental Example-1" An OPC photoreceptor having a diameter of 30φ was used as an image carrier, and a roller having a diameter of 12φ and a cleaning roller having a diameter of 12 were used as a charging roller, as shown in FIG.
A sponge roller of φ was used. Most of the toner used was a polymerized toner having a substantially spherical shape and an average particle size of about 8 μm.

At the time of image formation, the charging roller 4
A charging bias in which an alternating current of 2 Kv and 2000 Hz is superimposed on a direct current of 0 V is applied to the cleaning roller 20 at +600 V.
1600 to a DC of -500 V as a developing bias.
V and a developing bias on which an alternating current of 2000 Hz was superimposed 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. The vehicle was run at a peripheral speed of 50 mm / sec in a direction opposite to the direction of contact with the body.

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

When a sheet was passed under the above conditions using an image forming apparatus of a cartridge type as shown in FIG. 1, the structure of the cleaning device was greatly reduced, and the cartridge could be downsized. In addition, good images could be output on up to 1000 sheets without cleaning failure, charging failure, toner fusion to the image carrier, and the like.

"Experimental Example 2" The same image bearing member, charging roller, cleaning roller and toner as in Experimental Example 1 were used.
A DC bias of 2 Kv and an alternating current of 1000 Hz, a cleaning bias of +600 V, and a developing bias of -500 V DC of 1600 V
A developing bias on which an alternating current of 2000 Hz was superimposed was applied. Jumping development was used as a 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 portion with the image carrier, and the cleaning roller is in contact with the image carrier. Circumferential speed of 50m in the opposite direction
The vehicle was run at m / sec.

During non-image formation, the charging roller is set to 0.5 to
The voltage is set to 0 V for one rotation so that the toner is easily attached 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 returns to the original −
It returns to 700 V and prevents the toner from adhering even when the surface potential of the image carrier reaches 0 V. When the potential of the image carrier reaches 0V, the toner on the surface of the cleaning roller is transferred to the image carrier by setting the potential of the cleaning roller to 0V.

When the paper was passed under the above conditions using the image forming apparatus as shown in FIG. 1, no defective cleaning occurred even though the cleaning device portion was greatly reduced in construction. It was confirmed that remarkable miniaturization could be achieved, no defective charging and no fusion of toner to the image carrier, and good image output was possible up to 6000 sheets. This embodiment is more suitable than the above-described embodiments in terms of downsizing of the apparatus and cost reduction without increasing the types of high pressure.

"Experimental Example-3" The same image bearing member, charging roller, cleaning roller and toner as those in Experimental Example-1 were used.
A charging bias in which 2 Kv and 1000 Hz AC are superimposed on 700 V DC, and +600 V is applied to the cleaning roller
In the development, a non-magnetic polymerized toner is carried on a developing roller made of a semiconductive and elastic material, and a contact developing method is adopted in which the developing roller is brought into contact with the image carrier. Only a DC bias was applied.

The image carrier is run at a peripheral speed of 100 mm / sec, the charging roller is run at the same speed in the same direction as the contact portion with the image carrier, and the cleaning roller is run at the same speed with the image carrier. 50 mm / s in the same direction
ec.

At the time of non-image formation, the charging bias and the developing bias were not changed, and the cleaning was performed by setting only the applied voltage to the cleaning roller to -500V.

In this apparatus, since the cleaning roller and the image carrier run in the same direction, it is effective to prevent the toner from fusing 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 above conditions, the paper was passed in the same manner as the image forming apparatus as shown in FIG. 1, but the cleaning device could be reduced in size and the cartridge could be downsized. It was confirmed that high-quality images could be output up to 6,000 sheets of paper without causing charging failure and toner fusing.

"Experimental Example-4" The same image bearing member, charging roller, cleaning roller and toner as those in Experimental Example-1 were used. During image formation, a charging bias of DC-1500 V was applied to the charging roller. A voltage of -500 V is not applied to the cleaning roller, and a non-magnetic polymerized toner is carried on a developing roller made of a semiconductive and elastic material for development, and a contact developing method of contacting the image carrier is adopted. A DC voltage of -500 V was applied to the developing roller.

The image carrier is run at a peripheral speed of 100 mm / sec, the charging roller is run at the same position in the same direction as the contact portion with the image carrier, and the cleaning roller is brought into contact with the image carrier. 50mm /
We ran in sec.

In this apparatus, since the cleaning roller and the image carrier run in the same direction and only the DC voltage is applied to the charging roller, the vibration of the charging roller is small, and the toner Has a large effect of preventing fusing. Further, in this apparatus, the cleaning roller hardly needs to perform the action of removing the residual toner, and only needs to disperse the toner on the image carrier, so that a sequence of cleaning the cleaning roller after printing is completed is unnecessary. This contributes to the simplification of the device.

Further, even if particles charged to the positive polarity may adhere to the charging roller, there is little possibility that the particles are removed by the cleaning roller to cause poor charging. In particular, when a DC voltage is applied to the charging roller, charging unevenness due to dirt on the roller surface is more likely to occur than when an AC voltage is applied. However, in the case of the present invention, such a situation can be avoided.

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, fusing of the toner on the image carrier is likely to occur,
Because it is a DC voltage, it requires less than an AC voltage.

When the sheet was passed through the image forming apparatus as shown in FIG. 1 under the above conditions, the cleaning device could be reduced in size, the cartridge could be downsized, and the image carrier could be charged. It was confirmed that high-quality images could be output up to 6,000 sheets without causing defects and toner fusing.

"Experimental Example-5" The toner used for the image carrier, the charging roller, and the cleaning roller was the same as that used in Experimental Example-1.
A contact developing method in which a charging bias of 1500 V is applied, +600 V is applied to a cleaning roller, and a non-magnetic polymerized toner is carried on a developing roller made of a semiconductive and elastic material and is brought into contact with an image carrier during development. A developing bias of DC -500 V was applied to the developing roller.

The peripheral speed of the image carrier is set to 100 mm / sec. The charging roller is driven at a constant speed at the contact portion with the image carrier, and the cleaning roller is moved at the same position at the contact portion with the image carrier. It was run at 50 mm / sec in the direction.

At the time of non-image formation, the charging bias and the developing bias were not changed, and only the voltage applied to the cleaning roller was -500 V to perform the cleaning.
In this case, a small amount of toner remains on the image carrier, and the toner temporarily accumulates on the surface of the cleaning roller. Since a DC voltage is applied to the charging roller, uneven charging due to contamination on the surface of the charging roller is more likely to occur than when an AC voltage is applied. In this case, however, since the cleaning roller cleans the surface of the charging roller,
A situation where the occurrence of charging unevenness becomes a problem can be avoided.

In order to ensure charging, the charging roller can be run faster than the image carrier. In this case, fusion of toner on the image carrier is likely to occur. It can be said that it is not so much as in the case of charging and is of a degree that does not interfere with practical use.

Under the above conditions, the paper was passed by the image forming apparatus as shown in FIG. 1, but the cleaning device could be reduced in size and the size of the cartridge could be reduced. It was confirmed that high-quality images could be output up to 6,000 sheets without occurrence of charging failure and fusion of thinner.

The case where the present invention is applied to a cartridge type laser beam printer has been described above. However, the present invention is not limited to this, and is applicable to a well-known copying machine or an image forming apparatus which does not use a cartridge type. It will be easy to understand what is applicable.

[0057]

As described above, according to the present invention,
Provide a charging roller that comes into contact with the rotating cylindrical image carrier, and a cleaning roller that comes into contact with both the image carrier and the charging roller, and appropriately set the peripheral speeds and potentials of the image carrier, the charging roller, and the cleaning roller. The cleaning roller cleans the charging roller, and the toner adhered to the cleaning roller can be collected in the developing device. This prevents the occurrence of charging failure, reduces the size of the cleaning mechanism, and reduces the cost of the apparatus. This makes it possible to lower the image quality, and particularly when polymerized toner is used, there is a remarkable effect on improving the image quality and the fixability.

[Brief description of the drawings]

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

FIG. 2 is an enlarged side view showing a configuration of a portion near an image carrier of the above device.

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

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

FIG. 5 shows an image carrier and a charging roller arranged in contact with the image carrier;
Explanatory diagram showing the operation of the cleaning roller

FIG. 6 is a side view of a main part showing a configuration of a known image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner unit 3 Image carrier 4 Charging roller 5 Developing device 7 Transfer roller 8 Cleaner 14 Transfer material 15 Registration roller 20 Cleaning roller

Claims (3)

(57) [Claims] A charging roller for contacting and charging the running image carrier; and a cleaning roller for contacting the image carrier to remove residual toner, wherein the cleaning roller also contacts the charging roller. In the image forming apparatus which is in contact with the image forming apparatus, the surface of the image carrier and the surface of the cleaning roller, and the surface of the cleaning roller and the surface of the charging roller run with a peripheral speed difference. 2. The image forming apparatus according to claim 1, further comprising: a charging roller that contacts and charges the moving image carrier; and a cleaning roller that contacts the image carrier and removes residual toner. The cleaning roller also contacts the charging roller. An image forming apparatus in contact with an image forming apparatus, wherein the surface of the charging roller is smooth, and the surface of the cleaning roller is sponge-shaped. 3. A charging roller for contacting and charging a running image carrier, and a cleaning roller for contacting the image carrier and removing residual toner, wherein the cleaning roller also contacts the charging roller. In the image forming apparatus in contact, the toner adhering to the cleaning roller is
An image forming apparatus wherein the toner is collected in a developing device via an image carrier during non-image formation.