JP3330474B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device that visualizes an electrostatic latent image formed on a rotatable image carrier as a toner image, and transfers the toner image to a recording medium at a transfer unit. The present invention also relates to an image forming apparatus for collecting toner remaining on an image carrier after transferring a toner image to a cleaning member and cleaning the surface of the image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus of the above-mentioned type configured as a copying machine, a printer, a facsimile, or a multifunction peripheral thereof, an image carrier is used repeatedly. It is necessary to remove and collect the residual toner by a cleaning member. For this reason, various cleaning devices for cleaning the image carrier have been conventionally proposed and put into practical use, but the conventional cleaning device generally stores toner collected from the image carrier in a waste toner tank or the like, It is configured to discard this.

In recent years, in this type of image forming apparatus employing an electrophotographic process, it has been attempted to further reduce the cost and further reduce the amount of discarded toner as part of environmental measures. Requested.

In view of the above, for example, when the transfer rate of a toner image from an image carrier to a recording medium is set to 100% to eliminate residual toner after transfer, a so-called cleanerless method is adopted. be able to. As a result, not only can the toner to be discarded be eliminated, but also the cleaning device can be omitted, and the image forming system can be simplified and the cost of the image forming device can be reduced. However, at present, it is difficult to make the transfer rate of the toner image 100%, and there is a problem from the viewpoint of reliability.

Therefore, as a next best measure, the toner remaining on the surface of the image carrier after the transfer of the toner image is adhered to the cleaning member and collected, and the collected toner is re-adhered to the image carrier to form a developing device. (See, for example, Japanese Patent Publication No. 61-30274). This eliminates the need for a means for transferring the scraped toner to a waste toner tank or the like, so that the cost of the image forming apparatus can be reduced, and the toner can be recycled, so that waste toner can be eliminated. .

However, in such a technique, when the input toner amount per unit area to the cleaning member exceeds a certain level, cleaning failure to the image carrier tends to occur. For example, if a recording medium such as transfer paper that should be fed to the transfer unit is not fed due to some abnormality, the toner of the untransferred toner image on the image carrier is
By being directly sent to the cleaning member, the amount of toner input to the cleaning member becomes equal to or higher than a certain level, and the cleaning member cannot collect all the toner, thereby causing poor cleaning of the image carrier.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to collect and collect toner remaining on the surface of an image carrier after transfer of a toner image by attaching the toner to a cleaning member and re-adhering the collected toner to the image carrier. Then, in the image forming apparatus in which the toner is collected by the developing device, by preventing the input toner amount per unit area to the cleaning member from becoming excessively large, it is possible to prevent the occurrence of poor cleaning of the image carrier. An object of the present invention is to provide an image forming apparatus as described above.

[0008]

According to the present invention, in order to achieve the above object, an electrostatic latent image formed on a rotatably driven image carrier is visualized as a toner image by a developing device.
The toner image is transferred to a recording medium by a transfer unit, and the toner remaining on the image carrier after the transfer of the toner image is temporarily collected by a cleaning member. In the image forming apparatus in which the toner is re-attached to the surface portion which does not affect the formation of the latent image, and the re-adhered toner is collected by the developing device, the image forming apparatus contacts the image carrier between the transfer unit and the cleaning member, An abnormality occurs in at least one of a feeding device that feeds a recording medium to the image carrier and a transport device that transports the recording medium to the image carrier, while providing a toner adhesion amount limiting unit that limits the amount of toner passing therethrough,
When the occurrence of the abnormality is detected, the operation of collecting the toner from the image carrier and reattaching the toner to the image carrier before the next toner image is formed is performed more than when the occurrence of the abnormality is not detected. An image forming apparatus is provided that includes a drive control unit that drives a cleaning member and an image carrier so that the image forming apparatus can be executed for a long time.

In this case, in the above configuration, it is advantageous to use a conductive member to which a bias voltage having the same polarity as the charge polarity of the toner during development is applied as the toner adhesion amount limiting means.

[0010]

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, a drum-shaped photosensitive member 1 as an example of a configuration of an image carrier is rotationally driven clockwise in FIG. 1 by a driving unit (not shown). During this rotation, first, a scorotron charger as an example of a charging device is used. 2, the surface of the photoconductor 1 is uniformly charged. In this example, it is assumed that the surface of the photoconductor 1 is uniformly charged to a negative polarity by the operation of the scorotron charger 2. That is, when the switch indicated by the symbol S ₁ is closed, a negative voltage is applied to the scorotron charger 2 by the power supply E ₁ ,
Accordingly, the scorotron charger 2 performs corona discharge, and the surface of the photoconductor 1 is charged to, for example, -850V.

Next, in the exposing section 3, a predetermined electrostatic latent image is formed on the surface of the photoreceptor 1 by performing optical writing scanning using the color-modulated laser light 11.
In this manner, the photosensitive member 1 that is driven to rotate during image formation
An electrostatic latent image is formed thereon. The potential of the portion A irradiated with the laser beam for forming the electrostatic latent image is, for example, about -150 V, and the potential of the portion B not irradiated with the laser beam is about -150 V.
Is maintained at approximately -850V.

[0014] The developing device 4 comprises a developing roller 5 disposed opposite to the photosensitive member 1, the bias voltage source E ₂ in the developing roller 5, for example, a bias voltage of about -600V is applied. The developing roller 5 is an example of a developer carrying member. In the developing device 4 shown here, a two-component developer D having a toner and a carrier is used, and the toner is negatively charged by friction with the carrier.

The developing roller 5 is driven to rotate in a counterclockwise direction in the drawing. The thickness of the developer D carried on the peripheral surface of the developing roller 5 is regulated by a regulating blade 10. The toner in the developer is electrostatically attracted to the electrostatic latent image on the photoconductor 1 and adheres to that portion. That is, the toner charged to the same negative polarity as the charging polarity of the photoconductor adheres to the portion A irradiated with the laser light, and the electrostatic latent image is visualized as a toner image. As described above, the electrostatic latent image is visualized as a toner image by the developing device 4, but in this example, a reversal developing method (negative / positive developing method) is employed. In addition, for the developing unit 6,
The toner T in the downstream region in the rotation direction of the photoconductor 1 is schematically shown largely.

A transfer charging roller 7, which is an example of a transfer device, is provided below the photosensitive member 1. A recording medium 9 made of, for example, transfer paper is sent toward a transfer section 8 between the transfer charging roller 7 and the photoconductor 1 in contact with the transfer charging roller 7.
The toner image formed thereon is transferred to the recording medium 9. That is, in a state where the switch indicated by the symbol S ₃ is closed, the bias voltage source E _4, a transfer charging roller 7
A positive bias voltage, for example, a voltage of +950 V is applied to the photosensitive drum 1 at this time.
Is electrostatically attracted to the recording medium 9 side, adheres to the recording medium 9, and the toner image on the photoconductor 1 is transferred to the recording medium 9.

As described above, the toner image on the photoreceptor 1 is transferred to the recording medium 9 by the transfer unit 8, and after the transfer of the toner image, the toner not contributing to the transfer is transferred to the surface of the photoreceptor 1. There is residual adhesion. When the residual toner reaches the cleaning unit 14, it is temporarily collected by the cleaning roller 12, which is an example of a cleaning member.

The cleaning roller 12 is made of, for example, a foam having a medium specific resistivity having a medium resistance value, and is driven to rotate clockwise in the drawing, and has a positive bias opposite to the charging polarity of the toner. Voltage, for example + 300V
Bias voltage is applied by the bias voltage source E _5. Here, assuming that the toner T shown between the transfer unit 8 and the cleaning roller 12 is the residual toner after the transfer, the toner T is electrostatically applied to the cleaning roller 12 to which the positive bias voltage is applied. It is attracted, adheres to the roller 12, and is temporarily collected by this roller. As a result, the surface of the photoconductor 1 is cleaned. The bias as described above is applied to the cleaning roller 12 such that an electric field is formed between the photoreceptor and the residual toner on the photoreceptor so as to be electrostatically attracted toward the cleaning roller 12. The voltage is applied. The cleaning roller 12 also performs a function of frictionally charging the toner with the photoreceptor 1 and frictionally charging the toner such that the toner has the same negative polarity as the original polarity.

The surface of the photosensitive member 1 has a cleaning roller 12
After the cleaning, the surface is neutralized by a neutralization lamp 13 which is an example of a neutralization device, and the above-described image forming operation is continued. In this manner, one toner image is formed on the photoconductor 1 and is transferred to the recording medium 9. The area on the photoconductor 1 where the toner image is formed is an image forming area. , And the subsequent areas are non-image forming areas. When the rear end of the image forming area in the photoconductor rotation direction passes through the scorotron charger 2, the charger 2 is turned off at this time.

[0020] When the image forming area rear end passes the developing roller 5 of the developing device 4, the switch S ₂ is switched, the developing roller 5 is connected towards the bias voltage source E _3, in its developing roller 5 In order to prevent the toner from adhering to the photoconductor 1, a positive bias voltage opposite to the charging polarity of the toner, for example, a voltage of +150 V is applied.

The rear end of the image forming area is located at the transfer section 8.
When passing through the open switch S _3, the voltage applied to the transfer charging roller 7 is interrupted.

Furthermore, when the image forming region trailing after the toner image is transferred onto the recording medium 9 has passed the cleaning roller 12, the switch S ₄ is switched, the cleaning roller 12 toward the bias voltage source E ₆ Connected
A bias voltage of, for example, -500 V, having the same negative polarity as the charged polarity of the toner, is applied to the cleaning roller 12. That is, the cleaning roller 12 and the photoconductor 1
Between the cleaning roller 12 and the non-image forming area.
An electric field is generated in a direction in which the upper toner is emitted toward the photoconductor 1.

With this electric field, the toner temporarily collected on the cleaning roller 12 is reattached to the non-image forming area on the photosensitive member 1 and returned. The toner re-adhering to the photoconductor 1 passes below the charge removing lamp 13 and the scorotron charger 2 by the subsequent rotation of the photoconductor 1, and reaches the developing device 4. At this time, a positive voltage having a polarity opposite to the charging polarity of the toner is applied to the developing roller 5 as described above. , And is collected in the developer D.

When the image forming operation is performed continuously,
The above operation is repeated a predetermined number of times.

As described above, the residual toner is collected on the cleaning roller 12, the collected toner is re-adhered to the photosensitive member 1, and the re-adhered toner is collected by the developing device 4. is there. The toner collected in the developing device 4 is reused in the developing device 4.
In this way, waste toner can be eliminated. Further, there is no need to provide a toner conveying pipe or the like for returning the toner collected by the cleaning roller to the developing device.

In this embodiment, the cleaning roller 12
Collected on the photoreceptor 1 re-adheres to the non-image forming area near the rear end of the image forming area. The next formed electrostatic latent image is not affected. The toner is re-attached to the surface of the photoreceptor 1 which does not affect the formation of the next latent image. That is, in any of the electrostatic latent images, the toner from the cleaning roller 12 is re-attached to the surface of the photoreceptor which is formed on the photoreceptor without being disturbed by the re-adhesion toner.
It is also possible to adopt a configuration in which the toner from the cleaning roller 12 is re-attached to the rear part in the image forming area.

Here, as described at the beginning, if the input toner amount per unit area to the cleaning roller 12 exceeds a certain level, there has been a problem that cleaning failure is likely to occur.

For example, if the recording medium 9 to be sent to the transfer section 8 is not fed due to some abnormality such as a feeding error of the recording medium 9, the untransferred toner image on the photosensitive member is The toner may be sent to the cleaning roller 12 as it is, so that the toner amount per unit area input to the cleaning roller 12 becomes a certain level or more. In such a case, it is difficult to collect all the toner by the cleaning roller 12, and the toner remains on the photoconductor 1, so that cleaning failure of the photoconductor 1 occurs.

Therefore, in the image forming apparatus of this embodiment,
Between the transfer unit 8 and the cleaning member including the cleaning roller 12, there is provided a toner adhering amount limiting unit that abuts on the image carrier including the photosensitive member 1 and limits the amount of toner passing therethrough. When viewed in the rotation direction of the photoconductor 1, the transfer unit 8, the toner adhesion amount limiting unit, and the cleaning roller 1
2 are arranged in this order. In FIG. 1, reference numeral 15 denotes a toner adhesion amount regulating blade which is an example of a configuration of the toner adhesion amount limiting unit. The blade 15 is made of, for example, a polyethylene terephthalate sheet having a thickness of about 0.1 mm and a free length of about 10 mm, and is in contact with the surface of the photoconductor 1 in a belly state.

Here, when the normal proper transfer is performed, a relatively small amount of residual toner is carried to the contact portion of the blade 15, but at this time, the blade 15 Has almost no effect on toner. That is, the residual toner in an amount smaller than a certain level passes through the blade 15 and moves to the cleaning roller 12 as it is, and is collected without any trouble.

On the other hand, if the toner of the toner image which is not transferred on the photosensitive member, that is, the multi-layered toner, is carried to the contact portion of the blade 15 due to a mistake in feeding the recording medium or the like. The contact pressure of the blade 15 exerts a force for shifting the toner, and the blade 15 passes the toner through the contact portion, for example, with a smaller amount of adhesion. As a result, the toner having an amount less than a certain level per unit area is conveyed to the cleaning unit 14, so that the toner can be collected without hindering the cleaning roller 12, and cleaning failure is less likely to occur. Can be.

The amount of toner adhered per unit area after passing through the contact portion of the blade 15 is determined by variously selecting the thickness of the blade, its free length, and material.
It can be controlled freely by changing the contact pressure.

Further, by using a toner adhering amount limiting means such as a toner adhering amount regulating blade 15 which comes into contact with the photoreceptor 1, the toner and the photoreceptor and the toner and toner adhering amount restricting means are provided at the abutting portion. The toner whose charge polarity has been reversed in the transfer unit 8 due to frictional charging between the toner and the toner can be recovered to the original charge polarity, in this example, the negative polarity, and the occurrence of cleaning failure is more reliably prevented. And cleaning performance can be improved. Although a positive bias voltage is applied to the transfer charging roller 7, the negatively charged toner T may be positively charged with this application. The positively charged toner is charged to the negative polarity at the blade contact portion, and is adjusted to this polarity.

By using a material capable of charging the toner to the negative polarity as the toner adhesion amount regulating blade 15, as described above, the toner charged to the positive polarity by the influence of the transfer is changed to the negative polarity. However, if the following means is used as the toner adhesion amount limiting means, the charging polarity of the toner can be more effectively made uniform, and the occurrence of cleaning failure can be more reliably prevented.

As shown in FIG. 2, a conductive member 25 is provided between the transfer charging roller 7 and the cleaning roller 12 as a toner adhesion amount limiting unit. Photoconductor 1
When viewed in the rotation direction, the cleaning member including the transfer unit 8, the conductive member 25, and the cleaning roller 12 is arranged in this order. The conductive member 25 is made of, for example, a conductive urethane blade having a thickness of about 1.0 mm and a free length of about 10 mm, and is used in contact with the surface of the photoreceptor as shown in FIG. It is desirable to use an elastic member as such a conductive member.

The conductive member 25 functions to regulate the amount of toner adhering and feed the toner to the cleaning unit 14 as in the previous example. The conductive member 25 having such a function includes:
The power supply E _4, the photosensitive member and the toner after the toner image transfer, the toner having the same polarity as the charging polarity of the charge, a bias voltage such as a negative charge in this embodiment can be injected is applied during development . The other configuration in FIG. 2 is the same as the image forming apparatus shown in FIG.

By the contact of the conductive member 25 described above,
Since the toner amount of the photoconductor 1 toward the cleaning unit 14 is regulated, it is no different from the configuration shown in FIG. 1 that sufficient cleaning performance can be obtained. Further, the cleaning performance of the photoconductor 1 depends on the charge amount of the toner. The positive polarity charge of the toner by the conductive member 25 causes the toner to have a predetermined polarity, and at the same time, the charge amount also decreases. Since the cleaning roller 12 is set at a certain level, the cleaning performance of the cleaning roller 12 can be further improved. In the transfer unit 8, even if the toner on the photoreceptor 1 receives a transfer charge and is charged to a positive polarity,
This can be made negative by the conductive member 25, so that such residual toner can be efficiently collected by the cleaning roller 12 to which a positive voltage has been applied.

FIG. 1 shows the process from when the toner on the photoreceptor after passing through the conductive member 25 is temporarily collected by the cleaning roller 12 to when it is collected by the developing unit. Since this is the same as the case of the above-described embodiment, the description is omitted here.

In the embodiments shown in FIGS. 1 and 2, in order to prevent an excessive amount of toner from being input to the cleaning unit 14, each of the toner adhering amount limiting means 15, 25 causes an excessive amount of toner. It is possible to regulate the maximum amount of toner adhering in the image forming area while smoothing an appropriate amount of toner.

However, for example, when the untransferred black solid toner enters the portion of the toner adhering amount restricting means, the toner adhering amount remains even after both the toner recovery and toner reattaching modes are completed. There is a possibility that the toner may stay at the restricting portion. In such a case, in the next image forming cycle, stains on the background are likely to occur. If a feeding device (not shown) for sending the recording medium 9 to the photoconductor 1 is in an abnormal state, or the feeding device reaches the transfer unit,
The above-described situation occurs when the recording medium is jammed in the recording medium conveyance unit, the recording medium conveyance becomes abnormal, or the recording medium is not sent to the transfer unit.

In this type of image forming apparatus, the supply of the recording medium is performed by a sensor (not shown) provided in the above-described feeding device or a conveying device for conveying the recording medium sent out from the feeding device to the photosensitive member 1. When the occurrence of an abnormality such as feeding or transporting is detected, the machine body stops.

After the machine is stopped, the user re-turns on the machine power after taking measures such as removing jammed paper. At this time, the photoconductor is recovered by collecting the toner on the cleaning roller 12 for a longer time than usual. Cleaning and
If the toner is re-attached to the photoreceptor 1, the toner staying in the toner-adhesion-amount limiting unit can be reliably passed, and cleaning defects can be eliminated, thereby preventing the occurrence of background contamination and the like.

That is, when an abnormality occurs in at least one of the above-described feeding device and the conveying device, and the occurrence of the abnormality is detected, the toner is recovered from the photosensitive member 1 before the next toner image is formed. Then, the cleaning roller 12 and the photoconductor 1 are driven by drive control means (not shown) so that the operation of reattaching the toner to the photoconductor 1 is performed longer than when no abnormality is detected. . As a result, an excessive amount of toner per unit area, such as untransferred toner, captured by the toner adhesion amount limiting means can be reliably processed.

After processing the toner staying in the toner adhering amount limiting means for a long time as described above, the machine is in a standby state, and in the image forming apparatus,
The next image forming cycle mode can be started.

According to the present invention, after charging the image carrier, an electrostatic latent image is formed by a portion not irradiated with light, and development is performed by attaching a toner charged to a polarity opposite to the polarity of the potential. The present invention can also be applied to a positive / positive developing type image forming apparatus. Further, the present invention can be applied to an image forming apparatus using a roller-shaped cleaning member or an endless belt-shaped member as the cleaning member, or an image forming device using an endless belt-shaped one instead of a drum-shaped image carrier. . Further, the present invention can be applied to an image forming apparatus in which an intermediate transfer member is used as a recording medium, a toner image is transferred from the image carrier to the intermediate transfer member, and then the toner image is transferred to a transfer material.

Further, as the toner adhesion amount regulating means,
In addition to the blades 15 and 25 shown in the figure, rollers and the like can be used.

[0047]

According to the image forming apparatus of the present invention, it is possible to prevent an excessive amount of toner per unit area, such as untransferred toner, from being sent to the cleaning member. The occurrence of defects can be suppressed. In addition, an excessive amount of toner per unit area, such as untransferred toner, captured by the toner adhesion amount restricting means, can be reliably processed, and the background stain on the image can be suppressed.

According to the image forming apparatus of the second aspect,
Even if the charge polarity or charge amount of the toner changes due to the influence of the transfer charge, the toner can be sent to the cleaning member with the same charge polarity and charge amount, so that the cleaning failure is further ensured. Can be prevented.

[0049]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 4 Developing device 8 Transfer unit 9 Recording medium T Toner

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 21/10-21/12 G03G 15/08-15/08 507 G03G 21/00 370-540 G03G 21/14

Claims (2)

(57) [Claims] An electrostatic latent image formed on a rotatably driven image carrier is visualized as a toner image by a developing device, and the toner image is transferred to a recording medium by a transfer unit. The toner remaining on the image carrier is temporarily collected by the cleaning member, and then the collected toner is re-attached to a surface portion of the image carrier that does not affect the formation of the next latent image. In an image forming apparatus for recovering the re-adhered toner by a developing device, a toner adhering amount restricting means is provided between a transfer unit and a cleaning member, the toner adhering amount restricting means being in contact with the image carrier and restricting the amount of toner passing therethrough. An abnormality occurs in at least one of the feeding device that sends out the recording medium to the carrier and the transport device that conveys the recording medium to the image carrier, and when the occurrence of the abnormality is detected, the next toner image is formed. Before the image A drive control unit for driving the cleaning member and the image carrier is provided so that the operation of collecting the toner from the body and reattaching the toner to the image carrier is performed longer than when no abnormality is detected. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein a conductive member to which a bias voltage having the same polarity as the charge polarity of the toner at the time of development is applied is used as the toner adhesion amount limiting unit.