JP4123750B2 - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

Info

Publication number
JP4123750B2
JP4123750B2 JP2001284396A JP2001284396A JP4123750B2 JP 4123750 B2 JP4123750 B2 JP 4123750B2 JP 2001284396 A JP2001284396 A JP 2001284396A JP 2001284396 A JP2001284396 A JP 2001284396A JP 4123750 B2 JP4123750 B2 JP 4123750B2
Authority
JP
Japan
Prior art keywords
toner
polarity
brush roll
image
image forming
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP2001284396A
Other languages
Japanese (ja)
Other versions
JP2002372878A (en
Inventor
正 小笠原
尚稔 石川
琢 青島
Original Assignee
富士ゼロックス株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP2001110346 priority Critical
Priority to JP2001-110346 priority
Application filed by 富士ゼロックス株式会社 filed Critical 富士ゼロックス株式会社
Priority to JP2001284396A priority patent/JP4123750B2/en
Publication of JP2002372878A publication Critical patent/JP2002372878A/en
Application granted granted Critical
Publication of JP4123750B2 publication Critical patent/JP4123750B2/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer that forms an image by a method such as electrophotographic recording or electrostatic recording, and in particular, a scratch or filming is caused on a latent image carrier such as a photosensitive member. The present invention relates to a long-life image forming apparatus that can prevent the occurrence of defects and suppress the occurrence of defects on an image over a long period of time.
[0002]
[Prior art]
Conventionally, in this type of image forming apparatus such as an electrophotographic copying machine or a laser printer, a toner image corresponding to an image is formed on a latent image carrier such as a photosensitive drum, and the latent image such as the photosensitive drum is formed. An image is formed by transferring and fixing a toner image formed on a carrier onto a recording medium such as paper. As such an image forming apparatus, various so-called “cleaner-less” apparatuses that do not require a cleaner and do not generate waste toner have been already proposed in order to cope with ecology from the viewpoint of global environmental conservation. In the image forming apparatus described above, a cleaner that cleans the latent image carrier in order to prevent scratches and filming on the latent image carrier such as a photosensitive drum and to reduce the size of the apparatus. So-called “cleaner-less” devices that do not use a slab have already been proposed.
[0003]
For example, in Japanese Patent Application Laid-Open Nos. 59-133573 and 59-157661, a toner image is transferred from a latent image carrier such as a photosensitive drum onto a recording medium such as paper without using a cleaning device. An image forming apparatus configured to recover toner remaining in the developing device by transferring toner remaining in the background portion or the like of the latent image carrier to the developing roll of the developing device after being transferred to the developing device is disclosed. Yes.
[0004]
In the image forming apparatuses according to these proposals, unlike the cleaning blade of the cleaning device, there is no member that strongly rubs the latent image carrier, so that the latent image carrier is not damaged and the latent image carrier is not damaged. Filming components such as toner and external additives on the body can also be avoided. Further, since the image forming apparatus according to the above proposal does not require a special cleaning member unlike the cleaning apparatus, the apparatus can be reduced in size and the toner collected by the developing apparatus can be reused. Have.
[0005]
However, in the case of such an image forming apparatus of the simultaneous development cleaning method, the transfer efficiency is poor in a high humidity environment or the like, and the transfer performance is deteriorated due to moisture absorption of the transfer material, etc. If there is a large amount of toner remaining after transfer, there is a problem that image defects such as positive ghosts and negative ghosts are likely to occur. That is, in this type of image forming apparatus, in a high humidity environment or the like, the transfer material or the like absorbs moisture and the transfer charge escapes through the transfer material. In many cases, the transfer device cannot collect all the transfer residual toner, and the nodular transfer residual toner may be left in the image portion or the like. Therefore, at the time of the next image formation, the transfer residual toner left on the latent image carrier is transferred to the white background portion or highlight portion of the recording medium, and the transfer residual toner portion is imaged more than the other portions. A so-called positive ghost in which the concentration increases is generated.
[0006]
In addition, if the amount of transfer residual toner remaining on the surface of the latent image carrier is large as described above, the nodular transfer residual toner inhibits exposure in the exposure portion, and the surface potential VH on the latent image carrier is sufficiently increased. Can not be lowered. In this case, in the case of the reversal development method, when the transfer residual toner inhibits exposure, the density of the transfer residual toner portion appears as a so-called negative ghost in which the density is lower than the surrounding density. In other words, if there is a large amount of residual toner, the residual toner blocks the exposure beam in the exposure process, so that the latent image carrier charge potential VH is insufficiently attenuated and becomes an intermediate potential from the potential VL that attenuates due to the original exposure. As a result, the developing electric field becomes a small value as compared with the surrounding exposed portion, so that the toner is not sufficiently developed, and the transfer residual toner appears as a negative ghost (white-out image).
[0007]
In general, in an image forming apparatus that directly transfers a toner image onto a recording medium such as paper, when the paper or the like is peeled off from a latent image carrier such as a photosensitive drum in the transfer unit, It is known that toner charged to a polarity opposite to the charged polarity is generated. In the case of the reversal development method, the toner charged to the opposite polarity is opposite in polarity to the charged polarity of the latent image carrier, so that it easily reattaches to the latent image carrier and becomes a transfer residual toner on the latent image carrier. Remains.
[0008]
By the way, as described above, in the image forming apparatus of the simultaneous development cleaning method, the toner that can be collected by the developing apparatus has the same polarity as the developing toner, that is, the normal charging polarity, and is charged to the opposite polarity. It is difficult for the developed toner to be collected by the developing device. In this regard, in the image forming apparatus of the simultaneous development cleaning method according to the above proposal, such a reverse polarity toner is assumed to have a normal polarity by being recharged in a charging unit preceding the developing unit. However, as described above, when the transfer performance is deteriorated due to moisture absorption of the transfer material or the like, the residual toner after transfer contains a large amount of toner having a polarity opposite to that of the developing toner. However, it is impossible to charge all the reverse polarity toners to the normal polarity. For this reason, the toner with the reverse polarity cannot be collected by the developing device and remains and accumulates on the latent image carrier, resulting in a positive ghost or a negative ghost, resulting in image defects such as dirt or fog on the white paper portion. There was a problem of becoming.
[0009]
In order to solve the technical problem of such a simultaneous development cleaning method, for example, in an image forming apparatus described in Japanese Patent Laid-Open No. 3-127086, a latent image is formed using a plurality of electrodes (brushes) as a residual toner uniformizing means. It is comprised so that a support body may be contacted. In addition, the recording apparatus described in Japanese Patent Laid-Open No. 4-34566 is configured such that a charging unit made of a conductive contact also serves as a residual toner image equalizing unit.
[0010]
In the image forming apparatus according to these proposals, the residual toner image is rubbed and flattened with a brush or the like that is a uniformizing unit, and at the same time, a reverse polarity toner is charged to a normal polarity by a voltage applying unit, thereby developing Since it can be reliably collected by the apparatus, no ghost is generated. Further, in these image forming apparatuses, when there is toner charged to a polarity opposite to that of the developing toner, the toner charged to the opposite polarity is once collected by the residual toner uniformizing means, and a part of the opposite polarity toner is recovered. It is said that the remaining amount can be reduced by returning the charged polarity to the normal charged polarity by friction, charge injection, or discharging, and collecting a part of the normally charged toner. Further, the toner having the normally charged polarity that has passed through the residual toner uniformizing means is collected by the developing device. As a result, even when there is toner remaining in a nodule shape with a wide charge distribution, the residual toner can be stably sucked and discharged by the residual toner uniformizing means, and the amount of residual toner can be reduced to a low level. It can be suppressed to.
[0011]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. That is, as described in JP-A-3-12786 and JP-A-4-34566, even if the residual toner equalizing means is used, if there is a large amount of residual toner, all the toner is properly Therefore, the toner that is not collected by the developing device is still not positively or negatively ghosted or fogged.
[0012]
Further, since the residual toner is adhered and contaminated over time with the brush as the residual toner uniformizing means, and the ability to uniformize the residual toner is reduced, the residual toner that is not collected by the developing device increases. It also has problems.
[0013]
More specifically, when the residual toner equalizing means as described above is employed, the collected toner is accumulated in the residual toner equalizing means, which hinders the toner recovery and the uniform charge.
[0014]
Part of the toner charged to the opposite polarity to the collected developing toner is returned to the normal charging polarity, but it is difficult to return all the transfer residual toner to the normal charging polarity. The toner cannot be discharged from the toner and gradually accumulates in the residual toner uniformizing means. In such a case, the residual toner uniformizing means is clogged, and not only the performance of the residual toner uniformizing means is lowered, but also the resistance of the residual toner uniformizing means is increased, and the reverse of the residual toner is eventually observed. It becomes difficult to collect the polar toner, and a phenomenon occurs in which the reverse polarity toner passes through the residual toner uniformizing means without being collected. Here, when the residual toner uniformizing means is composed of a monopolar brush, it is difficult to disturb the distribution of the residual toner. Since it cannot be recovered, there still remains a problem of becoming a positive ghost. When the residual toner equalizing means is constituted by a brush roll, an effect of mechanically disturbing the residual toner image can be obtained, so that the occurrence of ghost is surely suppressed. However, in the case of the image forming apparatus according to the above proposal, since there is no means for collecting the reverse polarity toner existing on the latent image carrier, the toner charged to the reverse polarity with respect to the normal charge polarity remains as it is. The problem of remaining on the carrier and causing exposure inhibition, dirt on the white paper portion, and uneven density in the highlight portion has not yet been solved.
[0015]
As described above, in the case of the image forming apparatus according to the above-described conventional proposal, in particular, there is no means for recovering the reverse polarity toner present on the latent image carrier, so that it remains on the latent image carrier. However, problems such as exposure inhibition, white paper stains and highlight density unevenness remained unresolved.
[0016]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to reliably collect the transfer residual toner having a reverse polarity, and to detect positive ghosts, negative ghosts, and An object of the present invention is to provide an image forming apparatus capable of forming a good image over a long period of time without causing fogging or the like.
[0017]
Another object of the present invention is to avoid the problems associated with the accumulation of the collected toner in the residual toner uniformizing means comprising a brush, a brush roll, etc., and to transfer residual toner (particularly reverse polarity toner). Another object of the present invention is to provide an image forming apparatus capable of effectively avoiding image defects due to the passage of the image.
[0018]
[Means for Solving the Problems]
[0023]
According to the first aspect of the present invention, a toner image is formed on a latent image carrier by a developing means to which a predetermined development bias voltage is applied, and the toner image formed on the latent image carrier is converted into the latent image. In an image forming apparatus for forming an image on a recording medium by transferring the image onto a recording medium by a transfer unit arranged so as to come into contact with the carrier, and fixing the recording medium.
  A bias voltage is applied so that an electric field that contacts the latent image carrier and separates the toner charged to a polarity opposite to the charged polarity of the toner image in the non-image forming area is applied, and then the orientation similar to that in the image forming area Charging means for switching the bias voltage so that an electric field of
  Brush roll cleaning means in contact with the latent image carrierAndHave
  A bias voltage is applied to the brush roll cleaning means so that an electric field attracting toner charged to a polarity opposite to the charging polarity of the toner image acts in the image forming area, and the charging polarity of the toner image in the non-image forming area. Applying a bias voltage and a bias voltage so that an electric field attracting the toner charged in the opposite polarity to the charging polarity of the toner image acts so that an electric field that separates the toner charged in the opposite polarity acts, and
  A bias voltage is applied to the transfer means so that an electric field that separates the toner charged in the opposite polarity to the charged polarity of the toner image in the image forming area acts, and the charged polarity of the toner image is reversed in the non-image forming area. A bias voltage is applied so that an electric field that attracts the toner charged to the polarity acts.And
  The bias of the charging unit is not switched until the position on the latent image carrier where the applied bias of the brush roll cleaning unit is switched in the non-image forming area reaches the charging unit.An image forming apparatus characterized by the above.
[0024]
Furthermore,Claim 2The non-image forming area of the latent image carrier is an inter-image portion.Claim 1The image forming apparatus described in the above.
[0025]
That is, the invention described in claim 6 has a brush roll cleaning means 6 that contacts the latent image carrier 1 between the transfer means 5 and the charging means 2 as shown in FIG. Further, the transfer unit 5 includes a transfer member 51 that comes into contact with the latent image carrier 1 or the recording medium 8, and a cleaning member 52 that removes toner attached to the transfer member.
[0026]
With such a configuration, the following voltage is applied to the brush roll 61 of the brush roll cleaning means 6. When facing the area corresponding to the next image forming position on the latent image carrier 1, i.e., the image forming area, an electric field in a direction that attracts the toner having the opposite polarity to the developing toner (toner of the normal charging polarity) to the brush roll 61 is generated. When it is opposed to an area that does not correspond to the image forming position, that is, a non-image forming area, such as between the recording media 8, the toner has a polarity that attracts the toner having the opposite polarity to the developing toner to the latent image carrier 1. The voltage generates an electric field.
[0027]
Thereafter, in the non-image forming area, the toner is attracted to the brush roll 61 in the same direction as when facing the image forming area, that is, the developing toner (toner having normal charging polarity), and the toner having normal charging polarity is attracted. A voltage is applied so as to generate an electric field directed to the latent image carrier 1.
[0028]
here,Claim 3In the invention described in, the length of the non-image forming area is Lint (mm), the process speed is Vp (mm / sec), and an electric field is applied to the brush roll 61 to separate the toner charged to a polarity opposite to the charged polarity of the toner image. The time for applying the bias voltage is Tp (sec), the time for applying the bias voltage for applying an electric field in the same direction as the image forming area to the brush roll 61 is Tm (sec), the rotation center of the brush roll 61 and the latent When the distance of the surface of the image carrier 1 is rb (mm) and the rotational speed of the brush roll 61 at the closest position of the latent image carrier is Vb (mm / sec), the brush roll cleaning means 6 is Lint / Vp ≧ The conditions of Tp + TmTp ≧ 2π · rb / Vb and Tm ≧ 2π · rb / Vb were satisfied.
[0029]
That is, within the time that the brush roll 61 passes through the non-image forming area, the separation of the reversely charged toner from the brush roll 61 and the separation of the regular charged toner adhered between the Tp from the brush roll 61 are completed. Is set to
[0030]
In addition, the following voltage is applied to the transfer member 51. In the image forming area and the non-image forming area, an area of the latent image carrying rest 1 in which an electric field is applied between the brush roll 61 and the latent image carrying body 1 so as to attract toner having a polarity opposite to that of the developing toner to the brush roll 61. Is a voltage that generates an electric field in a direction that attracts the developing toner (normally charged toner) to the transfer member 51, that is, transfers the developing toner to the recording medium 8. Further, in the non-image forming region, when facing the region where an electric field is applied between the brush roll 61 and the latent image carrier 1 so as to attract toner having a polarity opposite to that of the developing toner to the latent image carrier 1, The voltage is such that an electric field is generated in a direction that attracts toner having a polarity opposite to that of the developing toner to the transfer member 51.
[0031]
When a contact-type charger was used as the charging means 2, the following voltage was applied. When facing the next image forming area on the latent image carrier 1, a voltage for obtaining a desired surface potential of the latent image carrier 1 was applied. When facing the non-image forming area, a voltage was applied so as to generate an electric field in a direction that attracted the toner of the reverse charge polarity discharged from the brush roll cleaning means 6 to the latent image carrier 1. Thereafter, when facing the region where the voltage applied to the brush roll 61 is switched, a voltage was applied so that an electric field directed to attract the normally charged polarity toner passing through the brush roll 61 to the latent image carrier 1 was generated.
[0032]
Here, switching of the voltage applied to the charging unit 2 in the non-image forming region is performed after the position on the latent image carrier 1 where the applied bias of the brush roll 61 is switched reaches the charging unit 2.
[0035]
Furthermore,The invention according to claim 4The developing unit is applied with a DC voltage and an AC voltage in the image forming area, and is stopped in the non-image forming area.Claims 1 to 3The image forming apparatus according to any one of the above.
[0036]
[Action]
In the present invention, as shown in FIG. 1, a brush roll cleaning unit 6 is arranged between the transfer unit 5 and the charging unit 2. In addition, the transfer unit 5 includes, for example, a transfer member 51 that comes into contact with the latent image carrier 1 or the recording medium 8, and a transfer member cleaning member 52 that cleans the transfer member 51.
[0037]
With such a configuration, for example, the following voltage is applied to the brush roll cleaning means 6. When facing the area corresponding to the next image forming area on the latent image carrier 1, an electric field is generated in such a direction that attracts toner having a polarity opposite to that of the developing toner (normally charged toner) to the brush roll cleaning means 6. When the voltage is opposed to an image non-formation region that does not correspond to the image creation position, such as between the recording media 8, an electric field is generated that attracts the toner having a polarity opposite to that of the developing toner to the latent image carrier 1. Voltage.
[0038]
Further, for example, the following voltage is applied to the transfer member 51. When facing the area of the latent image carrier 1 to which the electric field in the direction of attracting the toner having the opposite polarity to the developing toner is applied by the brush roll cleaning means 6, the developing toner is attracted to the transfer member 51, that is, to the recording medium 8. When the voltage is such that an electric field is generated in the direction in which the toner is transferred and the electric field in the direction in which the toner of the polarity opposite to that of the developing toner is attracted to the latent image carrier 1 by the brush roll cleaning unit 6 is opposed to the region. The voltage is such that an electric field is generated in a direction that attracts toner having a polarity opposite to that of the developing toner to the transfer member 51.
[0039]
According to such means, it is possible to avoid problems related to accumulation of collected toner of the brush roll cleaning means 6 and to effectively prevent image defects due to passage of transfer residual toner (particularly reverse polarity toner).
[0040]
Here, the operation and action will be described using an example in which a non-contact DC charging device is used as the charging unit 2 and reversal development is performed.
[0041]
FIG. 9 shows the timing of the bias applied to the charging means, developing means, transfer means, and brush roll cleaning means in the image forming apparatus shown in FIG. 1, and FIG. 10 shows the relationship between the potentials at the respective positions. This is a schematic representation of toner movement.
[0042]
Here, for example, the toner of normal charge polarity is negatively charged, and the surface of the photoreceptor is also negatively charged.
[0043]
As shown in FIGS. 10A to 10A, at the time of image formation, the surface of the latent image carrier 1 after passing through the transfer means is opposite to the reversely charged polarity toner (represented by white circles in the figure) that has not been transferred. There is toner (indicated by black circles in the figure). Here, the potential of the brush roll cleaning means 6 is set larger in the negative direction than the surface potential of the latent image carrier 1 after transfer. As a result, the reverse polarity toner is attracted to the brush roll cleaning means 6 by the Coulomb force and is collected by the brush roll cleaning means 6. Further, even if the regular charged polarity toner is in the form of a nodule, it is mechanically disturbed by the rotation of the brush roll cleaning means 6 and a part thereof is recovered by the brush roll cleaning means 6. However, the collected normally charged polarity toner moves to the latent image carrier 1 by Coulomb force when it comes into contact with the latent image carrier 1 again.
[0044]
By this operation, the reverse polarity toner is collected in the brush roll cleaning means 6, and the normally charged polarity toner is dispersed on the latent image carrier 1.
[0045]
Next, the latent image carrier 1 passes through the charging unit and the exposure unit. As described above, since the normally charged polarity toner on the latent image carrier 1 is dispersed, charging and exposure are not hindered. Further, in the developing unit, the exposed portion on the surface of the latent image carrier 1 is developed with toner. Further, the normally charged polarity toner remaining in the background portion is collected in the developing means 4 by mechanical force and Coulomb force due to contact with the developer.
[0046]
Thereafter, transfer is performed on the recording medium 8 at the transfer position (FIGS. 10a-C). As shown in FIGS. 10a to 10D, the subsequent surface potential and toner state on the latent image carrier 1 are the same as those shown in FIG. 10a-A. Therefore, when the image formation continues, the above flow is repeated. become.
[0047]
As an example of changing from the image creation state to the image non-formation state, a case where the area on the latent image carrier 1 after transfer becomes an inter image in the next cycle will be taken up.
[0048]
The state on the latent image carrier 1 after the transfer is as shown in FIGS. 10a-D. The bias voltage applied to the brush roll cleaning means 6 and the transfer means 5 is switched as shown in FIG. 9 in accordance with the timing when this area reaches the brush roll cleaning area and the transfer area.
[0049]
In the brush roll cleaning region, as shown in FIG. 10b-A, for example, the bias of the brush roll cleaning means 6 is set to the positive side with respect to the surface potential of the latent image carrier 1. For this reason, the reverse polarity toner in the brush roll cleaning means 6 is moved onto the latent image carrier 1 by the Coulomb force, and the regular charged toner remaining after transfer is collected by the brush roll cleaning means 6. As described above, a part of the reverse polarity toner is mechanically collected in the brush roll cleaning unit 6 by the rotation of the brush roll cleaning unit 6, but is discharged when contacting again.
[0050]
Next, as shown in FIG. 10B-B, the area on the latent image carrier 1 where a large amount of reverse polarity toner is present is opposed to the developing means 4. Here, since the charging potential is not changed and exposure is not performed in the inter image portion, the surface potential of the latent image carrier 1 is set to the negative side with respect to the developing bias. Therefore, the developing unit 4 hardly collects the reverse polarity toner due to the Coulomb force.
[0051]
Furthermore, this area moves to the transfer area. Here, a negative bias with respect to the surface potential of the latent image carrier 1 is applied to the transfer unit 5, and the reverse polarity toner moves to the transfer unit 5 by Coulomb force. The toner on the transfer unit 5 is scraped off by the transfer member cleaning member 52.
[0052]
As described above, for example, the normally charged polarity toner dispersed mainly at the time of image creation is collected by the developing unit 4, and the reverse polarity toner can be collected by the transfer unit 5 in an image non-formation region such as an inter image portion. Therefore, it is possible to effectively prevent image defects such as ghost and dirt depending on the polarity of the toner.
[0053]
Further, in the present invention, the above-described operation when the image is not created is frequently performed in the inter-image area. For this reason, it is possible to prevent the amount of reverse polarity toner present in the brush roll cleaning means 6 from increasing and the recovery performance from deteriorating. Furthermore, it can be avoided that the presence of the collected toner for a long time causes charge injection and the like, and the discharge control of the toner by the electric field cannot be performed. That is, the performance of the brush roll cleaning means 6 can be obtained over a long period of time.
[0054]
Since the reverse polarity toner is not collected in the developing unit 4, it can be expected that there is little adverse effect on the developer charging in the developing unit 4.
[0055]
On the other hand, according to the invention described in claims 6 and 9 of the present invention, the problem that the collected toner accumulates in the brush roll cleaning means 6 can be avoided and the transfer residual toner (especially reverse polarity toner) can be passed. Image defects can be effectively prevented.
[0056]
Here, the operation and action will be described using an example in which a contact type DC charging device is used as the charging unit 2 and reversal development is performed.
[0057]
12 shows the timing of the bias voltage applied to the charging means 2, the developing means 4, the transfer means 5 and the brush roll cleaning means 6 in the image forming apparatus shown in FIG. 11, and FIG. 3 shows the image forming area. FIG. 4 schematically shows the relationship between the potential at each position in the non-image forming region and the movement of the toner.
[0058]
Here, the right-charged toner Right Sign Toner (hereinafter abbreviated as “RST”) is negatively charged, and the surface of the latent image carrier 1 is also negatively charged.
[0059]
First, the image forming area will be described.
[0060]
As shown in FIG. 13A, at the time of image formation, the surface of the latent image carrier 1 after passing through the transfer means 5 is inverted in polarity by receiving the transfer remaining normal charged polarity toner RST and the transfer electric field. There is a reverse polarity toner Wron Sign Toner (hereinafter abbreviated as “WST”) charged to a reverse polarity to the charged polarity. In FIG. 13, the normally charged polarity toner RST is represented by a white circle, and the reverse polarity toner WST is represented by a black circle. Here, the potential of the brush roll 61 is set larger in the negative direction than the surface potential of the latent image carrier 1 after transfer. As a result, the reverse polarity (positive polarity) toner WST is attracted to the brush roll 61 by the coulomb and collected. Further, the regular charged polarity toner RST is mechanically disturbed by the rotation of the brush roll 61 even if it is in the form of a nodule. Further, a part of the normally charged polarity toner RST is collected in the brush roll cleaning means 6 by mechanical scraping. In addition, the normal charge polarity toner RST collected on the brush roll 61 may move to the latent image carrier 1 by the coulomber when it comes into contact with the latent image carrier 1 again.
[0061]
By this operation, out of the toner remaining on the surface of the latent image carrier 1 after passing through the transfer unit 5, the reverse polarity toner WST is mainly collected in the brush roll cleaning unit 6, and the normally charged polarity toner RST is It is dispersed on the latent image carrier 1.
[0062]
Next, the latent image carrier 1 passes through the position of the charging unit 2 and the position of the exposure unit 3 as shown in FIG. At that time, as described above, the normally charged polarity toner RST on the latent image carrier 1 is in an electric field that is difficult to adhere to the charging means 2 and dispersed as shown in FIG. 13B. Does not interfere with exposure. Further, at the position of the developing means 4, as shown in FIG. 13C, the exposed portion on the surface of the latent image carrier 1 is developed with the normally charged polarity toner RST. Further, the normally charged polarity toner RST remaining in the background portion of the latent image carrier 1 is collected in the developing unit 4 by mechanical force and Coulomb force due to contact with the developer. The reverse polarity toner WST mixed in the developing unit 4 is electrostatically attached to the non-image portion of the latent image carrier 1 as shown in FIG. 13C.
[0063]
Thereafter, the toner image developed on the latent image carrier 1 is transferred onto the recording medium 8 at the transfer position, as shown in FIG. 13D. As shown in FIG. 13E, the surface potential and the toner state on the latent image carrier 1 after passing through the transfer means 5 are the same as those in FIG. 13A. Will be repeated.
[0064]
Next, as an example of changing from the image creation state to the image non-formation state, a case where the area on the latent image carrier 1 after transfer becomes an inter image in the next cycle will be taken up.
[0065]
The state on the latent image carrier 1 after the transfer is as shown in FIG. 13E. In accordance with the timing when this region reaches the position where the brush roll cleaning means 6, the charging means 2, the developing means 4 and the transfer means 5 act, the bias applied to each means is switched as shown in FIG.
[0066]
At the brush roll cleaning position, the bias of the brush roll 61 is set to be more positive than the surface potential of the latent image carrier 1 as shown in FIGS. For this reason, the reverse polarity toner WST in the brush roll 61 is moved onto the latent image carrier 1 by the Coulomb force. On the contrary, the regular charged toner RST remaining after the transfer is collected by the brush roll cleaning means 6.
[0067]
As described above, when the surface of the latent image carrier 1 passes the position of the brush roll cleaning means 6, the reverse polarity toner WST adheres to the latent image carrier 1, and the latent image carrier to which the reverse polarity toner WST adheres. When the surface of the body 1 passes through the charging unit 2, as shown in FIGS. 14a-B, a voltage that generates an electric field in a direction in which the reverse polarity toner WST is difficult to adhere is applied to the charging unit 2. However, at that time, the bias voltage applied to the charging means 2 is set to a voltage that does not charge the surface of the latent image carrier 1.
[0068]
In this way, the surface of the latent image carrier 1 to which the reverse polarity toner WST is attached passes through the position where the charging unit 2 acts as it is.
[0069]
Next, as shown in FIGS. 14A to 14C, the latent image carrier 1 is opposed to the developing unit 4 in a region where a large amount of the reverse polarity toner WST is present. Here, in the inter image, since charging by the charging unit 2 is not performed, the developing bias is set to be on the positive side with respect to the surface potential of the latent image carrier 1 as shown in FIG. At this time, no AC bias component is applied to the developing means 4. This is because when the AC bias component is applied to the developing unit 4, the reverse polarity toner WST may be mixed into the developing unit 4, or the reverse polarity toner on the latent image carrier 1 may increase extremely due to fogging. This is to prevent this. The developing unit 4 hardly collects the reverse polarity toner WST due to the Coulomb force, and the reverse polarity toner WST existing in the developing unit 4 is slightly fogged depending on the surface potential condition of the latent image carrier 1. Degree.
[0070]
Furthermore, this area moves to the transfer area as shown in FIGS. 14a-D. Here, as shown in FIG. 12, the transfer roll 51 is applied with a bias on the negative polarity side relative to the surface potential of the latent image carrier 1, and includes fog toner slightly generated at the position of the developing means 4. All of the reverse polarity toner WST moves to the transfer roll 51 by the Coulomb force. The toner on the transfer roll 51 is scraped off by a transfer member cleaning member (cleaning member) 52.
[0071]
Next, as shown in FIG. 14B, the voltage setting is switched to the same voltage setting as in the image formation in the non-image forming area as in FIG. 14A. At this time, the regular charged toner RST collected during image formation and non-image formation Tp (see FIG. 14B) is attached to the brush roll 61. The normally charged toner RST adhering to the brush roll 61 is attracted onto the latent image carrier 1 by switching the voltage applied to the brush roll 61 and discharged from the brush roll 61 as shown in FIG. . As in the image formation, the normally charged toner RST passes while being attracted to the latent image carrier 1 at the position where the charging means 2 acts, as shown in FIG. 14B-B. Next, the normally charged toner RST is attracted to the developing unit 4 at a position where the developing unit 4 acts. However, at this time, since the potential difference between the surface of the latent image carrier 1 and the developing means 4 is small and no AC bias is applied, a lot of regular charged toner RST passes as it is, as shown in FIGS. 14b-C. Thereafter, the normally charged toner RST adhering to the surface of the latent image carrier 1 is attracted to the transfer roll 51 whose polarity has been switched by the Coulomb force and scraped off by the transfer member cleaning member 52 as shown in FIGS. All collected.
[0072]
As described above, the reversely charged polarity toner WST is collected by the brush roll cleaning unit 6 during image formation. The normally charged polarity toner RST is mechanically collected by the brush roll cleaning unit 6, dispersed and transferred to an extent that does not cause image defects, or collected by the developing unit 4. On the other hand, the reversely charged polarity toner WST is discharged from the brush roll cleaning unit 6 onto the latent image carrier 1 and collected by the transfer unit 5 during non-image formation such as an inter image.
[0073]
Further, in the latter half of the non-image formation such as an inter-image, the normally charged polarity toner RST collected by the brush roll cleaning unit 6 is switched by switching the voltage, and this is also collected by the transfer unit 5. As described above, it is possible to effectively prevent image defects such as ghosts and dirt depending on the polarity of the toner and accumulation of the collected toner in the brush roll cleaning means 6.
[0074]
Further, since the voltage is switched in the non-image forming area, the normal charge polarity toner RST is discharged from the brush roll cleaning unit 6 when changing from the non-image forming area to the image forming area, and appears as a toner band in the image. Can be prevented.
[0075]
According to the sixth and eighth aspects of the present invention, the above-described operation during non-image formation is frequently performed in the inter-image area. The operation during non-image formation may always be performed in the inter image area, but it is not always necessary to perform the operation, and may be performed about once in several times in the inter image area. For this reason, it is possible to prevent the amount of reverse polarity toner WST present in the brush roll cleaning means 6 from increasing and the recovery performance from being lowered. Further, it can be avoided that the presence of the collected toner for a long time causes charge injection and the like, and the discharge control of the toner by the electric field cannot be performed. That is, the performance of the brush roll cleaning means 6 can be maintained and exhibited over a long period of time.
[0076]
Here, it is confirmed that the discharge of the normally charged polarity toner RST and the reversely charged polarity toner WST is performed around the brush roll 61. Since the rotation speed of the brush roll 61 and the distance between the rotation center and the surface of the latent image carrier 1 are appropriately set, each of the brush rolls 61 makes one or more rounds for discharging the normally charged polarity toner RST and the reversely charged polarity toner WST. I was able to rotate. For this reason, the interimage length is unnecessarily extended, and the productivity of the image forming apparatus is not lowered.
[0077]
In addition, since the reverse polarity toner WST is not collected in the developing unit 4, it can be expected that there is little adverse effect on the developer charging in the developing unit 4.
[0078]
Here, when the switching of the bias when the image was not created was confirmed, the following was found.
[0079]
In the non-image forming area, when the bias of the brush roll cleaning means 6 is switched from the reverse charge polarity toner WST discharge (Tp) bias to the normal charge polarity toner RST discharge (Tm) bias, the discharged toner is the reverse charge polarity toner. The WST is changed to the regular charged polarity toner RST.
[0080]
Here, as shown in FIG. 15 (1), the bias applied to the charging means 2 is applied to the reverse charging polarity toner before the region where the normal charging polarity toner RST is discharged onto the latent image carrier 1 reaches the charging position. When switching from the bias where WST is difficult to adhere to the bias where normal charge polarity toner RST is difficult to adhere, reverse polarity toner WST adheres to charging means 2 as shown in FIG. This adhering toner is not discharged from the charging means 2 until the next non-image forming area, as shown in FIGS. This causes a charging failure in the image forming area and causes an image defect. Therefore, as shown in FIG. 15 (2), the application bias switching of the charging means 2 is performed in the non-image forming area after the area where the normal charging polarity toner RST is discharged onto the latent image carrier 1 reaches the charging position. I did it. In this case, the normally charged toner RST on the latent image carrier 1 adheres to the charging means 2 to which a bias to which the reversely charged polarity toner WST is unlikely to adhere is applied as shown in FIG. However, when the bias of the charging unit 2 is switched to a bias to which the regular charging polarity toner RST is difficult to adhere, these toners are discharged as shown in FIG. For this reason, it is possible to prevent image defects caused by toner adhesion or long-term retention of the charging unit 2.
[0081]
That is, the application bias switching of the charging unit 2 in the non-image forming region is performed after the region where the normal charging polarity toner RST is discharged onto the latent image carrier 1 reaches the charging position, thereby further generating image defects. Can be prevented.
[0082]
Further, according to the technical means described in claim 11, while avoiding the problems related to the accumulation of the collected toner in the brush and the brush roll, the transfer residual toner (which could not be collected by the developing means alone) ( In particular, reverse polarity toner) can be reliably collected, and image defects due to passage of transfer residual toner can be effectively avoided.
[0083]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0084]
First embodiment
FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the present invention.
[0085]
As shown in FIG. 1, this image forming apparatus has a photosensitive drum 1 as a latent image carrier having a photosensitive layer on the surface, and charging as a charging means for uniformly charging the surface of the photosensitive drum 1. 2, an image writing device 3 as an exposure unit for irradiating the surface of the photosensitive drum 1 uniformly charged by the charger 2 with image light to form an electrostatic latent image, and a developer. The developing device 4 as the developing means and the transfer for transferring the toner image formed on the photosensitive drum 1 onto the recording paper 8 as the recording medium conveyed by the conveying roll 11 along the paper guide 10. A transfer roll 51 as a transfer member of the means 5; a cleaner 52 as a cleaning means for removing toner adhering to the surface of the transfer roll 51; and after the toner image is transferred from the photosensitive drum 1, A fixing device 7 as a fixing means for fixing the toner image on the recording paper 8 separated from the photosensitive drum 1, a cleaning member 61 as a brush roll cleaning means 6 for temporarily collecting the transfer residual toner, And a casing 62 that covers the periphery of the cleaning member 61.
[0086]
The photosensitive drum 1 is a photosensitive material using a function-separated organic photoconductor (OPC) in which a charge generation layer and a charge transport layer are sequentially laminated on the surface of a drum-shaped metal support made of aluminum or the like. The outer diameter of the photosensitive drum 1 is set to a diameter of 30 mm, for example.
[0087]
The charger 2 is formed by coating an elastic layer made of SBR or the like containing carbon on a metal core, and forming ECO containing an ionic conductive agent as a resistance layer on the elastic layer, On top of that, carbon and SnO2P. containing (conductive filler). A surface layer made of A is formed. The elastic layer has a thickness of 2.8 mm, the resistance layer has a thickness of 150 μm, and the surface layer has a thickness of 10 μm, for example. The resistance value of the entire layer including the surface layer is, for example, 10 μm.7-108It is prepared to Ω. The charger 2 applies a DC voltage to the cored bar to uniformly charge the surface of the photosensitive drum 1 to a predetermined potential. In this embodiment, a contact type charger is used, but a non-contact type charger such as a scorotron or a solid discharge device may be used.
[0088]
Further, the image writing device 3 repeatedly scans the laser beam emitted from the light emitting element (LD) substantially perpendicular to the rotation direction of the photosensitive drum 1, and turns this light emitting element on / off based on the image signal. Image exposure is performed on the photosensitive drum 1 that is rotationally driven.
[0089]
The developing device 4 transfers a toner to the electrostatic latent image formed on the photosensitive drum 1 to form a visible image (toner image). The developing device 4 may be any one using a one-component developer or one using a two-component developer.
[0090]
Further, as the transfer roll 51, for example, a metal foam core having a silicone foam layer having a skin layer and a PTFE film formed on the skin layer is used. . Here, the thickness of the coating layer is 10 μm, and the resistance value of the entire layer including the coating layer is 10 μm.7-108It is prepared to Ω. The transfer roll 51 is disposed so as to be in contact with the surface of the photosensitive drum 1, and is in contact with the surface of the photosensitive drum 1 through the recording paper 8 at the time of transfer. Further, a predetermined transfer bias is applied to the core metal of the transfer roll 51 at a predetermined timing.
[0091]
The cleaner 52 is a plate-like scraper or brush-like cleaning means. In this embodiment, a spring material made of a SUS plate having a plate thickness of 100 μm is used, and the tip is manufactured by etching. .
[0092]
Further, the cleaning member 61 of the brush roll cleaning means 6 is composed of a brush roll in which a conductive brush is wound around a metal core, and the volume resistivity of the brush roll is 102-109The thing of Ωcm is good. In addition, the thickness of the brush fiber can be about 3 to 15 denier, and the flocking density is 5000 to 300000 f / inch.2A degree is preferred. In this embodiment, trade name SA-7 (volume resistivity: 10 manufactured by Toray Industries, Inc.)Three-10FiveΩcm, thickness: 3 denier, density: 300000 f / inch2) Is wound around a cored bar having a diameter of 6 mm to form a brush roll having an outer diameter of 12 mm.
[0093]
Further, the casing 62 is a plate-like member having conductivity, and is formed in a shape that covers the periphery of the cleaning member 61 using metal, conductive resin, or the like. In this embodiment, a SUS plate having a thickness of 0.3 mm is used which is produced by curving into an arch shape. The casing 62 is configured such that a wide gap is formed between the casing 62 and the cleaning member 61 on the downstream side in the rotation direction of the photosensitive drum 1.
[0094]
Further, the fixing device 7 fixes the toner image transferred onto the recording paper 8 to obtain a recorded image, and a device for fixing the toner image by a known heat and pressure is used.
[0095]
Next, the developer used in the developing device 4 will be described.
[0096]
The toner used in the developing device 4 is, for example, one produced by an emulsion polymerization method, and has a spherical shape with an average particle diameter of 6.5 μm and a shape factor of 130 or less. Here, the shape factor is a value obtained by image analysis of an enlarged image of an optical microscope using an image analyzer Luzex III manufactured by Nireco Corporation, and is represented by the following equation.
Shape factor = (absolute maximum diameter of toner)2/ (Projection area of toner) × π / 4 × 100
[0097]
The particle size of the toner greatly affects the image quality, and the larger the particle size, the rougher the image. Even if the toner has an average particle diameter of about 20 μm, there is no practical problem, but in order to increase the resolution of fine lines, it is desirable to use a toner having an average particle diameter of 10 μm or less. However, when the toner diameter is reduced, the physical adhesive force acting between the toner and the carrier becomes dominant, and the developability is lowered. In addition, when the toner diameter is reduced, toner aggregation is likely to occur, resulting in handling problems. From such a viewpoint, the toner used in the present invention preferably has an average particle size of 5 μm or more and 10 μm or less.
[0098]
Further, an appropriate amount of fine particles (external additive) such as silica and titania having an average particle diameter of about 10 to 150 nm is externally added to the toner as a charge control agent and a transfer aid.
[0099]
The toner is not limited to the above production method, and may be produced by, for example, suspension polymerization, suspension granulation, dissolution suspension, kneading and pulverization.
[0100]
As the developer used in the developing device 4, for example, a two-component developer in which the toner and the carrier configured as described above are mixed is used. As this carrier, for example, a resin-coated carrier having a resin coating layer in which a conductive material such as carbon black is dispersed on the surface of a core made of ferrite is used, and the average particle size is set to 45 μm, for example. The
[0101]
As the developer in which the toner and the carrier are mixed, for example, a toner concentration (TC: Toner Concentration) of 8 wt% and a toner charge amount in the developer of 20 to 30 μC / g is used. Here, the toner density (TC) is expressed by the following equation.
TC (wt%) = (weight of toner contained in developer (g)) / (total weight of developer (g)) × 100
[0102]
Furthermore, if the toner charge amount when the toner and the carrier are mixed to form a developer is too high, the adhesion force of the toner to the carrier becomes too high and the toner is not developed. On the other hand, if the charge amount is too low, the adhesion force of the toner to the carrier is weakened, and toner cladding due to free toner occurs, causing fogging during printing. From the viewpoint of transferring the toner to the electrostatic latent image formed on the photosensitive drum 1 and performing good development, the toner charge amount in the developer is 5 to 50 μC / g in absolute value, preferably It is desirable to be in the range of 10-40 μC / g.
[0103]
Next, the operation of the brush roll cleaning member 6 composed of a cleaning member (brush roll) 61, which is an important part of the present invention, and a casing 62 covering the periphery thereof will be described in detail.
[0104]
FIG. 2 is an enlarged view of the cleaning unit of FIG. In the figure, 13 is a voltage applying means for the charger 2, and 14 is a voltage applying means for the cleaning member 6. The voltage applying means 14 applies the same voltage to the casing 62 as the cleaning member 61.
[0105]
By the way, in this embodiment, the amount of biting of the brush roll 61 with respect to the photosensitive drum 1 is set to be 1 mm. The brush roll 61 rotates in the same direction as the photosensitive drum 1 (the movement direction of both surfaces), and its peripheral speed is set to be twice the peripheral speed of the photosensitive drum 1. It is.
[0106]
FIG. 2 shows a state of the cleaning unit in the image forming area. The toner remaining on the photosensitive drum 1 after the transfer is a mixture of negatively charged toner having a normal charging polarity and positively charged toner having a reverse polarity due to peeling discharge or the like. In the image forming area, a negative voltage is applied to the brush roll 61 and the casing 62 (at least, the surface of the brush roll 61 is at a lower potential than the surface of the photosensitive drum 1), and the toner of reverse polarity is , Electrostatically adheres to the brush roll 61 by the Coulomb force. Further, in the casing 62 in the downstream area of the brush roll 61, a part of the normally charged minus toner that has passed through the brush roll 61 is temporarily wound up by the rotation of the brush roll 61. Since it receives an electrostatic repulsive force (Coulomb force) from the surface, it finally falls due to gravity and reattaches to the surface of the photosensitive drum 1. In this process, of the transfer residual toner, the transfer residual toner charged to the regular charge polarity is diffused and dispersed by the brush roll 61, and then passes through the charger 2 and is collected in the developing device 4. The Since a negative voltage having the same polarity as the normal charging polarity is applied to the charger 2, transfer residual toner attached to the surface of the photosensitive drum 1 does not adhere to the charger 2.
[0107]
As described above, in the image forming area, out of the toner remaining on the surface of the photosensitive drum 1, the reverse polarity toner is collected by the brush roll 61, and the normal polarity toner is collected by the brush roll 61 and the charger 2. And is collected in the developing device 4.
[0108]
In this embodiment, as shown in FIG. 2, the casing 62 has a slightly swollen shape on the downstream side of the brush roll 61, and the toner in a cloud shape is the photosensitive drum 1. It is configured so as to be easily reattached to the surface. Further, by making the transfer residual toner into a cloud shape by the brush roll 61, it is possible to disperse even if there is a toner remaining in a lump after the transfer, so that it can be easily collected in the developing device 4 thereafter. It becomes possible.
[0109]
FIG. 3 shows a state of the cleaning unit in the non-image forming area. At this time, a positive voltage is applied to the brush roll 61 and the casing 62 (at least the surface of the brush roll 61 is at a higher potential than the surface of the photosensitive drum 1), and the reverse of the adhesion to the brush roll 61. The polar toner moves to the surface of the photosensitive drum 1 due to the Coulomb force (repulsive force), and the normally charged transfer residual toner adhering to the photosensitive drum 1 is collected by the brush roll 61. At this time, the charger 2 is set to 0 V (at least, the surface of the charger 2 is at a higher potential than the surface of the photosensitive drum 1), so that the reverse of the transition to the surface of the photosensitive drum 1 occurs. The polar toner passes through the charger 2 while adhering to the surface of the photosensitive drum 1.
[0110]
Further, since the developing bias applied to the developing device 4 located on the downstream side of the charger 2 is set to a potential higher than the surface potential of the photosensitive drum 1, the reverse polarity toner is developed by the Coulomb force. It moves to the transfer part without being collected. The transfer roll 51 is set to a potential lower than the surface potential of the photosensitive drum 1, and the reverse polarity toner moves to the transfer roll 51 side by the Coulomb force, and the transfer roll 51 is moved by the cleaner 52 attached to the transfer roll 51. Scraped from the surface.
[0111]
The non-image forming area here is an area corresponding to an area between the recording paper 8 and the recording paper 8 (inter-image portion), or a paper jam has occurred when the power is turned on or at the start / end of the job. This means an area other than the image area in the return mode.
[0112]
FIG. 4 shows a series of operations from discharging the reversely charged toner from the brush roll 61 in the inter-image portion to collecting it by the transfer unit 5, and is applied to the charging unit 2, the developing unit 4, the transfer unit 5, and the cleaning unit 6. Bias timing is shown. Here, the toner of normal charge polarity is negative, and the surface of the photosensitive drum 1 is also negatively charged.
[0113]
With the above configuration, in the image forming apparatus according to the first embodiment, the transfer residual toner having the reverse polarity is reliably collected as follows without causing positive ghost, negative ghost, and fog. Therefore, it is possible to form a good image over a long period of time.
[0114]
That is, in the first embodiment, as shown in FIG. 1, the photosensitive drum 1 is rotationally driven, and the surface of the photosensitive drum 1 is set to −350 V by the charger 2 as shown in FIG. It is charged like this. The photosensitive drum 1 is irradiated with image light at a position facing the image writing device 3, and the potential of the photosensitive layer of the photosensitive drum 1 is reduced to approximately 0 V by exposure, resulting in a difference in electrostatic potential. A latent image is formed. This electrostatic latent image moves to a position facing the developing device 4. A developing bias in which an alternating current component having an amplitude (Peak to Peak) of 1.0 kV, a frequency of 4.0 kHz, and a duty of 0.6 is applied to a developing roller of the developing device 4 is applied to a direct current component of −200V. As a result, the negatively charged toner transferred from the developing roll adheres (reverse development), and the electrostatic latent image is visualized.
[0115]
The toner image thus formed is transferred onto the recording paper 8 by the transfer roll 51 to which a voltage of +450 V is applied. Finally, the image is fixed by the fixing device 7 to obtain a recorded image.
[0116]
On the other hand, after the transfer, the surface potential of the photosensitive drum 1 was 0V in the image portion and −100V in the background portion. Further, a slight amount of toner was observed on the surface of the photosensitive drum 1 after the transfer. Residual toner is sent to a cleaning unit including a cleaning member (brush roll) 61 and a casing 62 covering the periphery thereof.
[0117]
As shown in FIG. 2, when a bias voltage of −250 V is applied to the brush roll 61 and the surface of the photosensitive drum 1 after passing through the brush roll 61 is examined, a slight amount of toner is seen before passing. I couldn't see it. This means that the residual toner having the normal charging polarity is collected by the developing device 4, and all the residual toner having the reverse polarity is collected by the brush roll 61.
[0118]
Next, the potential at the inter-image portion (non-image area) was set as follows.
[0119]
First, when the region of the surface of the photosensitive drum 1 serving as an inter-image portion reaches the brush roll 61, the bias voltage of the brush roll 61 is set to + 150V as shown in FIG. At this time, a slight amount of toner (reverse polarity toner) was adhered on the surface of the photosensitive drum 1 after passing through the brush roll 61.
[0120]
When the region corresponding to the inter-image portion passes through the charger 2 and the developing device 4, as shown in FIG. 4, the voltage applied to the charger 2 is 0V, and the DC bias voltage (DC2) applied to the developing roll is set. The AC bias of the developing roll was not applied.
[0121]
At this time, most of the toner transferred from the brush roll 61 to the surface of the photosensitive drum 1 is the toner of reverse polarity collected in the image area. In the above setting, the surface potential of the photosensitive drum 1 is 0 to −100 V, so that the toner hardly adheres to the charger 2. Further, the developing roll passes almost without being collected.
[0122]
The voltage applied to the charger 2 can be determined from the surface potential of the photosensitive drum 1 and the polarity of the toner, and need not be the same as in the present embodiment as long as toner adhesion can be suppressed / prevented. The bias voltage of the developing device 4 is also determined from the surface potential of the photosensitive drum 1 and the polarity of the toner, and it is sufficient that there is no toner movement between the surface of the photosensitive drum 1 and the developing device 4.
[0123]
The toner that has passed through the developing roll reaches the transfer portion. The applied potential of the transfer roll 51 is set to −300 V, for example. As a result, it was confirmed that the toner charged to the opposite polarity moves to the transfer roll 51 and is scraped off by the scraper 52 on the surface of the transfer roll 51. Further, the back surface of the recording paper 8 was not stained.
[0124]
A running test of 100 kPV (A4 paper) was performed under the above configuration and conditions. As a result, it was confirmed that generation of positive ghost, negative ghost and fog caused by the transfer residual toner was not observed.
[0125]
Second embodiment
6 and 7 show a second embodiment of the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. In the second embodiment, The operation of the cleaning unit is configured to be slightly different from that of the first embodiment. That is, in the first embodiment, in addition to the operation of the cleaning unit in the non-image forming region shown in FIG. 3, an operation as shown in FIG. 6 is further added.
[0126]
FIG. 6 shows the state of the cleaning unit in the non-image forming area following the operation of the cleaning unit in the non-image forming area shown in FIG. An operation similar to the operation of the cleaning unit in the non-image forming area shown in FIG. 3 is executed for a predetermined discharge time T1, and the toner of reverse polarity attached to the brush roll 61 is discharged. Subsequently, as shown in FIG. 6, a negative voltage is applied to the brush roll 61 and the casing 62 in the same manner as in the image area (at least, the surface of the brush roll 61 has a lower potential than the surface of the photosensitive drum 1). The toner of reverse polarity remaining after transfer is electrostatically attached to the brush roll 61 by the Coulomb force, and at the same time, the normally charged toner attached to the brush roll 61 is photosensitive by the Coulomb force. Reattaches to the surface of the body drum 1. Similarly to FIG. 2, at this time, the charger 2 is set to 0 V (at least the surface of the charger 2 is at a lower potential than the surface of the photosensitive drum 1). The normal polarity toner transferred to the surface passes through the charger 2. Subsequently, in the development area, the developer 4 is recovered by the mechanical force and the Coulomb force due to contact with the developer. Even when the developing device 4 cannot collect all the normal polarity toners, the transfer roll 51 is set to a potential higher than the surface potential of the photosensitive drum 1 in the next transfer region, and the normal polarity toners are set by the Coulomb force. Moves to the transfer roll 51 side and is scraped off from the surface of the transfer roll 51 by a cleaner 52 attached to the transfer roll 51. Therefore, the normal polarity toner that could not be collected by the developing device 4 is also reliably collected by the transfer roll 51.
[0127]
FIG. 7 shows a series of operations from the time when the reversely charged toner and the toner of normal polarity are discharged from the cleaning means (brush roll) 61 and collected by the transfer means 5 and the developing means 4 in the inter-image part. The timing of the bias applied to the means 4, the transfer means 5 and the cleaning means 6 is shown. Here, the toner of normal charging polarity is negative, and the surface of the photosensitive drum 1 is also negatively charged.
[0128]
In the above configuration, the image forming apparatus according to the present embodiment reliably collects the transfer residual toner having the reverse polarity as follows, and does not generate positive ghost, negative ghost, and fog. It is possible to form a long image.
[0129]
That is, in the second embodiment, a series of operations from the charging process of the photosensitive drum 1 to the fixing process through the exposure / development process and the transfer process are the same as those in the first embodiment.
[0130]
On the other hand, after the transfer, the surface potential of the photosensitive drum 1 is 0 V in the image portion and −100 V in the background portion, and the toner remaining on the surface of the photosensitive drum 1 is sent to the cleaning portion. When a bias voltage of −250 V was applied to the brush roll 61 and the surface of the photosensitive drum 1 after passing through the brush roll 61 was examined, the toner that was slightly seen before the passage was not seen after the passage.
[0131]
Next, the potential in the inter image part was set as follows.
[0132]
First, when the area on the surface of the photosensitive drum 1 that is the first half of the inter-image portion reaches the brush roll 61, the bias voltage (discharge bias voltage) B2 of the brush roll 61 is set to + 150V as shown in FIG. At this time, a slight amount of toner adhered to the surface of the photosensitive drum 1 after passing through the brush roll 61.
[0133]
When the area corresponding to the first half of the inter-image portion passes through the charger 2 and the developing device 4, the voltage applied to the charger 2 is 0V, the DC bias voltage (DC2) applied to the developing roll is + 70V, and the developing roll No AC bias was applied.
[0134]
At this time, most of the toner transferred from the brush roll 61 to the surface of the photosensitive drum 1 is toner having a reverse polarity as shown in FIG. In the above setting, the surface potential of the photosensitive drum 1 is 0 to −100 V, so that the toner hardly adheres to the charger 2. Further, the developing roll passes almost without being collected.
[0135]
The voltage applied to the charger 2 can be determined from the surface potential of the photosensitive drum 1 and the polarity of the toner, and need not be the same as in the present embodiment as long as toner adhesion can be suppressed / prevented. The bias voltage of the developing device 4 is also determined from the surface potential of the photosensitive drum 1 and the polarity of the toner, and it is sufficient that there is no toner movement between the surface of the photosensitive drum 1 and the developing device 4.
[0136]
The toner that has passed through the developing roll reaches the transfer portion. The applied potential of the transfer roll 51 was set to −300V. As a result, it was confirmed that the toner moved to the transfer roll 51 and was scraped off by the scraper 52 on the surface of the transfer roll 51. Further, the back surface of the recording medium 8 was not stained.
[0137]
Next, in the second embodiment, when the region of the surface of the photosensitive drum 1 that is the second half of the inter-image portion reaches the brush roll 61, as shown in FIG. (Discharge bias voltage) B1 was set to -250V. At this time, a slight amount of toner adhered to the surface of the photosensitive drum 1 after passing through the brush roll 61.
[0138]
When the area corresponding to the latter half of the inter-image portion passes through the charger 2 and the developing device 4, the voltage applied to the charger 2 and the DC bias voltage applied to the developing roll are returned to the same conditions as the image forming area. It was.
[0139]
Most of the toner transferred from the brush roll 61 to the surface of the photosensitive drum 1 in the second half of the inter-image portion is normal polarity toner as shown in FIG. Therefore, the toner hardly adheres to the charger 2, and conversely, it is collected by the developing device 4 by Coulomb force or the like. Further, as shown in FIG. 7, the toner of normal polarity that could not be collected by the developing device 4 is all collected by the transfer roll 51 to which a positive transfer bias is applied.
[0140]
A running test of 100 kPV (A4 paper) was performed with the above configuration and conditions. As a result, it was confirmed that generation of positive ghost, negative ghost and fog caused by the transfer residual toner was not observed.
[0141]
In the second embodiment, even when a large amount of regular polarity toner adheres to the brush roll 61 in the first half of the inter-image part, such as when transfer efficiency is reduced at high humidity, all can be collected by the transfer roll 51. Highly effective in preventing positive and negative ghosts.
[0142]
Further, if the same operation is performed when the power is turned on, the effect of preventing the brush roll 61 from being contaminated is further improved.
[0143]
In the above-described embodiments, the black-and-white image recording method has been described, but the same effect can be obtained even in the color image recording method. The above embodiments have been described with the electrophotographic recording system based on the Carlson process. However, any indirect recording system that transfers to recording paper, such as a chargeless system or a back exposure system, can be applied.
[0144]
Third embodiment
FIG. 8 shows a third embodiment of the present invention. The same reference numerals are given to the same parts as those of the above embodiment, and in this third embodiment, the brush roll cleaning means is described. The configuration is different from that of the first embodiment. In the third embodiment, a non-contact charging unit is used instead of a contact charging unit as the charging unit.
[0145]
FIG. 8 is a schematic configuration diagram showing an electrophotographic printer using a brush roll cleaning member to which the present invention is applied.
[0146]
In this embodiment, a non-contact type DC charging device is used as the charging means 2. This applies a DC voltage to amorphous silicon deposited on a glass plane to charge the surface of the photosensitive drum 1. Here, the closest distance between the surface of the charging unit 2 and the surface of the photosensitive drum 1 is set to 0.1 to 0.15 mm. However, the charging means 2 is not limited to this, and a scorotron or the like may be used.
[0147]
In this embodiment, the brush roll cleaning means 6 has a density of 300,000 / square inch at 3 denier and a resistance of 10Three-10FiveA cm brush roll 61 is used. Further, the length of the bristle of the brush was 3 mm, and the closest distance between the surface of the photosensitive drum 1 and the root of the brush was 2 mm. The brush roll 61 is rotated in the same direction as the photosensitive drum 1 at the contact position with the photosensitive drum 1 (that is, the rotation direction is opposite), and the speed is twice that of the surface of the photosensitive drum 1. Although the above-described brush roll 61 is used here, this is not necessarily the case. Regarding the rotation direction, the rotation directions of the photosensitive drum 1 and the brush roll 61 may be the same.
[0148]
Unlike the first embodiment, the brush roll cleaning means 6 does not include a conductive casing, and the brush roll 61 is covered with a housing 63 made of an insulating material such as synthetic resin.
[0149]
Other toner compositions and the like are the same as those in the first embodiment.
[0150]
A specific embodiment of the present invention will be described with the above-described configuration and toner.
[0151]
At the time of image formation, the Φ30 photosensitive drum 1 is charged to −500V, and the potential of the image portion exposed by the light beam is set to −150V. The developing roller of the developing unit 4 is applied with a developing bias in which a direct current component is superimposed on an alternating current component of −350 V with an amplitude (Peak to Peak) of 1.0 kV, a frequency of 4.0 kHz, and a duty of 0.6. As a result, the negatively charged toner is developed on the photosensitive drum 1 to form a toner image.
[0152]
A voltage of +300 V was applied to the transfer roll 51 to transfer the toner image to the transfer paper 10. This voltage may be set such that the transfer efficiency is good and the transfer toner image does not scatter.
[0153]
After the transfer, the surface potential of the photosensitive drum 1 was -100V in the image portion and -300V in the background portion. Here, a slight residual toner was observed.
[0154]
As shown in FIG. 9, a voltage of −450 V was applied to the brush of the brush roll cleaning unit 6. When the residual toner was examined before and after this position, the toner slightly recognized before passing through the brush roll cleaning means 6 was hardly recognized after passing.
[0155]
Next, the potential in the inter image part was set as follows.
[0156]
First, when the region on the photosensitive drum 1 serving as the inter-image portion reaches the brush cleaning means 6, the voltage of the brush 61 of the brush roll cleaning means 6 is set to 0V. At this time, slight toner adhesion was observed on the surface of the photosensitive drum 1 after passing through the brush roll cleaning means 6.
[0157]
In this embodiment, the charging potential and the development DC bias are the same as those at the time of image formation. That is, in this embodiment, since a non-contact type charging device is used, it is not necessary to switch the voltage applied to the charging unit 2 as compared with the time of image formation.
[0158]
The voltage of the transfer roll 51 was set to -600V. As a result, the toner moved from the brush roll 61 onto the photosensitive drum 1 moves to the transfer roll 51. It was confirmed that this toner was scraped off by the metal scraper 52. Further, the back surface of the recording medium 7 was not stained.
[0159]
Here, the interimage portion is set to the recovery potential of the reverse polarity toner to the transfer roll 51. However, not only in the inter-image unit, but a similar cycle may be inserted when the power is turned on or when the job starts / ends.
[0160]
A running test of 100 kPV (A4) was performed with the above configuration and conditions. As a result, it was confirmed that background stains, halftone unevenness, positive or negative ghosting due to the transfer residual toner did not occur.
[0161]
The temperature and humidity at this time were 28 ° C. and 80% RH.
[0162]
Fourth embodiment
FIG. 11 shows a fourth embodiment of the present invention. The same reference numerals are given to the same portions as those of the above-described embodiment, and the description of the overlapping portions is omitted. In the embodiment, the brush roll cleaning unit charges the length of the non-image forming area to Lint (mm), the process speed to Vp (mm / sec), and the brush roll cleaning unit charges to the polarity opposite to the charging polarity of the toner image. Tp (sec) is a time for applying a bias voltage so that an electric field for separating the toner is applied, and Tm (sec) is a time for applying a bias voltage for applying an electric field in the same direction as the image forming area to the brush roll cleaning unit. The distance between the rotation center of the brush roll cleaning means and the surface of the latent image carrier is rb (mm), and the rotation speed of the brush roll cleaning means at the closest position of the latent image carrier is Vb (mm / sec). When,
Lint / Vp ≧ Tp + Tm
Tp ≧ 2π · rb / Vb, Tm ≧ 2π · rb / Vb
It is configured to satisfy.
[0163]
Further, in this embodiment, the non-image forming area of the latent image carrier is configured to be a so-called inter-image part that is at least between the recording medium when it reaches the transfer part next time. Yes.
[0164]
In this embodiment, after a bias voltage is applied so that an electric field that contacts the latent image carrier and separates the toner charged in the non-image forming area with a polarity opposite to the charged polarity of the toner image acts. In an image forming apparatus having a charging unit that switches a bias voltage so that an electric field having a direction similar to that of the image forming region acts,
It is desirable that the bias of the charging unit is not switched until the position on the latent image carrier where the applied bias of the brush roll cleaning unit is switched in the non-image forming region reaches the charging unit.
[0165]
FIG. 11 shows a schematic configuration of an electrophotographic printer using a brush roll cleaning member 6 according to a fourth embodiment to which the inventions according to claims 6 and 8 are applied.
[0166]
In FIG. 11, reference numeral 1 denotes a photosensitive drum as a latent image carrier. The surface of the photosensitive drum 1 is subjected to a known electrophotographic process as it rotates in the direction of arrow A. An electrostatic latent image corresponding to the image image information is formed. That is, when a print operation command is issued from a user interface (not shown) or a client such as a personal computer and the print operation is started, the photosensitive drum 1 is set at a predetermined potential by a contact-type charger 2 as a charging unit. After being uniformly charged (for example, negative polarity), the light beam emitted from the laser beam scanner 3 is subjected to exposure (for example, image portion exposure) according to the image signal, and the surface of the photosensitive drum 1 is exposed. An electrostatic latent image corresponding to the image signal is formed. Further, on the outer periphery of the photosensitive drum 1, a developing device 4 as a developing unit is disposed adjacent to the downstream side in the rotation direction of the photosensitive drum 1, and the developing device 4 includes the photosensitive drum. The electrostatic latent image formed on the surface of 1 is developed (for example, reverse development) to form a toner image. In the image forming apparatus used here, the process speed, which is the rotational speed in the circumferential direction of the photosensitive drum 1, is set to 170 mm / sec, and as shown in FIG. The inter-image length, which is the length between image forming areas formed on the surface of 1, is set to 79 mm (79 (mm) / 170 (mm / sec) = 465 (msec)).
[0167]
In the fourth embodiment, the configuration of the charging means 2 is different from that of the third embodiment (see FIG. 8), and a charger similar to that of the first embodiment is used. That is, the charging means 2 is configured to apply a DC voltage to the cored bar and uniformly charge the surface of the photosensitive drum 1 to a predetermined potential, as in the first embodiment. However, the charging unit 2 is not limited to this, and a scorotron or the like may be used. If the potential of the surface of the photosensitive drum 1 can be set without any trouble in consideration of toner adhesion, the DC bias is used. A charging roll in which an AC bias is superimposed may be used, or a non-contact type charging device such as a scorotron or a solid discharge device may be used.
[0168]
In the fourth embodiment, the other transfer means 5, the fixing device 7, the brush roll cleaning means 6 and the like are configured in the same manner as in the third embodiment.
[0169]
Incidentally, the brush roll 61 rotates in the same direction as the photosensitive drum 1 at the contact position with the photosensitive drum 1 (that is, the rotation direction is opposite), and the speed at the brush tip is twice that of the photosensitive drum surface. That is, it is set to 340 mm / sec. At this time, the rotational speed of the brush roll 61 at the closest position to the surface of the photosensitive drum 1 was 283 mm / sec.
[0170]
Although the above-described brush roll 61 is used here, this is not necessarily the case. Further, the rotation direction of the photosensitive drum 1 and the brush roll 61 may be set to be the same as the rotation direction.
[0171]
In addition, the toner composition, carrier, and the like are the same as those in the third embodiment.
[0172]
Next, a specific example of the fourth embodiment will be described with the above configuration and toner.
[0173]
The surface of the photosensitive drum 1 having a diameter of 30 mm is uniformly charged to −450 V during image formation, and the potential of the image portion exposed by the light beam is set to be −100 V. At this time, the bias voltage applied to the charging means 2 was -1000V. The developing roll of the developing device 4 is applied with a developing bias in which an alternating current component having a direct current component of −350 V and an amplitude (peak to peak) of 1.0 kV, a frequency of 4.0 KHz, and a duty of 0.6 is superimposed. Thus, the toner charged to the same negative polarity as the charging polarity of the photosensitive drum 1 is reversely developed on the exposed portion on the photosensitive drum 1 to form a toner image.
[0174]
Further, a voltage of +350 V is applied to the transfer roll 51, and the toner image is transferred to the recording paper 8. The voltage applied to the transfer roll 51 may be set so as to satisfy the condition that the transfer efficiency is good and the transfer toner image is not scattered.
[0175]
After the toner image formed on the photosensitive drum 1 was transferred to the recording paper 8, the surface potential of the photosensitive drum 1 was -50V for the image portion and -200V for the background portion. Here, a slight amount of toner remained on the surface of the photosensitive drum 1. This residual toner remains negatively charged, which is the original charging polarity, and remains without being transferred to the recording paper 8, and the toner whose charging polarity is reversed by the transfer electric field generated by the transfer roll 51 and charged positively. It consists of.
[0176]
Thereafter, the surface of the photosensitive drum 1 that has passed through the transfer portion moves to the position of the brush roll cleaning means 6 as the photosensitive drum 1 rotates. A voltage of −400 V is applied to the brush roll 61 of the brush roll cleaning means 6 as shown in FIG. When the toner remaining on the surface of the photosensitive drum 1 before and after the brush roll cleaning means 6 is examined, the residual toner slightly recognized before passing through the brush roll cleaning means 6 is removed by the brush roll cleaning means. Almost no longer recognized after passing 6. In FIG. 12, A is a time corresponding to the distance between the brush roll cleaning means 6 and the charging means 2, B is a time corresponding to the distance between the charging means 2 and the developing means 4, and C is a developing means. The time corresponding to the distance between 4 and the transfer means 5 is shown.
[0177]
Next, in the fourth embodiment, the potential at the inter-image part is set as follows.
[0178]
First, when the region on the photosensitive drum 1 serving as an inter-image portion (see FIG. 11B) reaches the brush roll cleaning means 6, the applied voltage of the brush roll 61 was set to + 200V. At this time, toner adhesion was observed on the surface of the photosensitive drum 1 after passing through the brush roll cleaning means 6.
[0179]
Here, most of the toner moved from the brush roll 61 onto the photosensitive drum 1 is considered to be the reverse polarity toner WST. When the area from which the toner is discharged from the brush roll 61 passes through a position opposite to the DC charging unit 2 and the developing device 4, the voltage applied to the charger 2 is + 200V, the DC bias applied to the developing roll is 0V, and the development is performed. No roll AC bias was applied.
[0180]
In the above setting, since the surface potential of the photosensitive drum 1 was −200 to −500 V, the reverse polarity toner WST moved to the surface of the photosensitive drum 1 does not adhere to the contact DC charger 2. The reverse polarity toner WST passed through the developing roll almost without being collected.
[0181]
As described above, when the surface of the photosensitive drum 1 corresponding to the inter-image portion passes through the contact DC charging unit 2, the voltage applied to the contact DC charging unit 2 is the surface potential of the photosensitive drum 1 and the toner. If it can be determined from the polarity and toner adhesion can be prevented, it is not necessary to be the same as in this embodiment. Further, the bias of the developing unit 4 is determined based on the relationship with the surface potential of the photosensitive drum 1, and may be appropriately set as long as there is no toner movement between the surface of the photosensitive drum 1 and the developing unit 4. .
[0182]
Here, the amount of toner adhering to the surface of the photosensitive drum 1 is visually compared between the upstream side of the contact DC charging unit 2 and the downstream side of the developing unit 4. Although it was a small amount, it was confirmed that there was almost no difference.
[0183]
Further, the voltage applied to the transfer roll 51 when the surface of the photosensitive drum 1 corresponding to the inter-image portion passes through the transfer roll 51 was set to −500V. As a result, all of the reverse polarity toner WST toner moved from the brush roll 61 onto the photosensitive drum 1 could be moved onto the transfer roll 51. It was confirmed that the reverse polarity toner WST toner moved on the transfer roll 51 was scraped off by the metal scraper 52.
[0184]
Here, as shown in FIG. 12, for example, the time Tp for applying a bias voltage of +200 V to the brush roll 61 of the brush roll cleaning means 6 was set to 230 msec. During this time, the brush roll 61 of the brush roll cleaning means 6 is set to make about 2.1 turns. When the bias setting was made, it was confirmed that the toner was discharged from the brush roll 61 with a length of about 19 mm on the photosensitive drum 1. That is, it is considered that the brush roll 61 has almost completely discharged the reverse polarity toner WST in the first round.
[0185]
Thereafter, the bias voltage applied to the brush roll 61 was set to −400V. As a result, it was confirmed that toner was discharged onto the photosensitive drum 1. After this region reached the position where the charging unit 2 acts, the bias voltage applied to the charging unit 2 was switched to -1000V. From this point, the surface potential of the photosensitive drum 1 became −450V. Here, immediately before the switching of the bias voltage, toner adhesion was observed on the charging means 2. However, after switching the bias voltage, no toner adhered to the charging means 2 was seen. This is presumably because the adhered toner was discharged.
[0186]
Next, at the timing when the area where the bias voltage applied to the brush roll 61 is switched reaches the developing position, the applied bias of the developing unit 4 is set to −350 V, and the AC bias is not applied. As a result, the toner amount on the photosensitive drum 1 hardly changed before and after the development position.
[0187]
When this area reached the transfer position, the bias applied to the transfer roll 51 was set to + 350V. Here, it was confirmed that the toner adhering to the surface of the photosensitive drum 1 moved to the transfer roll 51 and was scraped off by the metal scraper 52.
[0188]
Thereafter, image formation was performed again, but no backside contamination of the recording medium 8 occurred. As shown in FIG. 12, the time Tm from the switching of the bias voltage in the inter-image part to the leading end of the next image forming area is about 235 msec, and the brush roll 61 is about 2.1 in the meantime. Around. Also here, it was confirmed that the toner was discharged from the brush roll 61 almost once after the switching of the bias voltage. Note that the outer diameter of the brush roll 61 is set, for example, to a diameter of about 12 mm up to the brush tip.
[0189]
In this embodiment, Tp + Tm = 465 msec is set, which is equal to the length of the inter-image portion (= 465 msec). As a result, it is not necessary to extend the length of the inter-image portion, and the productivity of the image forming apparatus There was no decline.
[0190]
In the embodiment described above, the inter-image portion is set to the toner recovery potential to the transfer roll 51. However, not only in the inter-image unit, but also in a non-image forming area such as when the power is turned on or when the job is started / finished, a similar cycle may be inserted to collect the toner remaining on the surface of the photosensitive drum 1. Good.
[0191]
In the above-described embodiment, the potential setting at Tm is the same as that in the image forming area. However, as long as the toner can be reliably discharged from the brush roll 61 and the toner can be collected by the transfer unit 5 without adhering to the charging unit 2, this is not necessarily the case.
[0192]
A running test of 100 kpV (1 kpV = 1000 prints, A4 size) was performed with the above configuration and conditions. As a result, it was confirmed that background stains, halftone unevenness, positive or negative ghosting due to the transfer residual toner did not occur.
[0193]
As described above, in the case of the present embodiment, there is no need to extend the inter-image part or a special toner discharge / collection cycle, and dirt or halftone unevenness in the background part due to the transfer residual toner in long-term use, It was confirmed that no positive or negative ghost occurred. The temperature and humidity during the running test were 28 ° C. and 80% RH.
[0194]
Fifth embodiment
Next, a fifth embodiment of the present invention will be described by assigning the same reference numerals to the same portions as those of the above embodiment.
[0195]
In the fifth embodiment, the brush roll 61 is rotated in the opposite direction to the photosensitive drum 1 at the contact position with the photosensitive drum 1 (that is, the rotational direction is the same), and the speed at the brush tip is the same as the process speed. That is, the rotation speed of the brush roll 61 at the closest position to the surface of the photosensitive drum 1 is set to 170 mm / sec, which is 142 mm / sec, which will be described below.
[0196]
Other configurations, potential settings, and the like are the same as in the fourth embodiment.
[0197]
In the fifth embodiment, the rotation speed of the brush roll 61 is set slower than that in the fourth embodiment. However, since the rubbing direction on the surface of the photosensitive drum 1 is reversed, the toner recoverability is as follows. Equivalent performance was obtained.
[0198]
Further, the switching time of the bias voltage in the inter image was set such that Tp was 230 mm / sec and Tm was 235 mm / sec, as in the fourth embodiment. At this time, each of the brush rolls 61 has about 1 to 1.1 rounds, and it was confirmed that the toner was reliably discharged over the entire circumference.
[0199]
Even under these conditions, it is not necessary to extend the inter-image part or special toner discharge / recovery cycle, and in long-term use, background stains, halftone unevenness, positive or negative ghosting caused by residual toner may not occur. It could be confirmed.
[0200]
Sixth embodiment
FIG. 16 shows a sixth embodiment of the present invention. The same reference numerals are given to the same portions as those in the above-described embodiment. In the sixth embodiment, the latent image carrier is shown in FIG. A toner image is formed on the latent image carrier, and the toner image formed on the latent image carrier is transferred onto a recording medium by a transfer unit disposed so as to be in contact with the latent image carrier, and then fixed. In an image forming apparatus for forming an image on the recording medium,
A plurality of brush roll cleaning means that come into contact with the latent image carrier, and the plurality of brush roll cleaning means include a toner charged to a polarity opposite to the charged polarity of the toner image attached on the latent image carrier; A bias voltage is applied to collect toner having the same polarity as the charged polarity of the image, and a bias voltage is applied so that an electric field that separates the toner charged to a polarity opposite to the charged polarity of the toner image acts in the non-image forming area. With
The transfer unit includes a transfer member disposed so as to be in contact with the latent image carrier, and a cleaning member that removes toner attached to the transfer member. The transfer member includes the toner in a non-image forming region. A bias voltage is applied so that an electric field that attracts toner charged to a polarity opposite to the charged polarity of the image acts.
[0201]
In this sixth embodiment, a bias voltage is applied to the plurality of brush roll cleaning means so that an electric field that separates the toner charged to a polarity opposite to the charged polarity of the toner image acts only in the non-image forming area. Is configured to do.
[0202]
FIG. 16 shows a schematic configuration of an electrophotographic printer using brush roll cleaning members 6a and 6b to which the sixth embodiment of the present invention is applied.
[0203]
In this embodiment, a non-contact type DC charging device is used as the charging means 2 as in the third embodiment. However, the charging means 2 is not limited to this, and a scorotron or the like may be used. If the potential can be set without any trouble in consideration of toner adhesion, the charging as in the fifth embodiment is performed. A roll or the like may be used.
[0204]
By the way, in the sixth embodiment, as shown in FIG. 16, two brush roll cleaning means 6a and 6b that come into contact with the photosensitive drum are provided. These two brush roll cleaning means 6a and 6b are respectively configured in the same manner as in the above embodiment. The brush roll cleaning means 6a and 6b are configured to be applied with a voltage having a desired polarity and a desired value by a power source (not shown), and the voltage application timing is also controlled by a control means (not shown). It can be controlled at a desired timing such as an image forming area or a non-image forming area such as an inter-image portion.
[0205]
Each of the brush roll cleaning means 6a and 6b includes a brush roll 61, and each brush roll 61 has the same speed as the surface speed of the photosensitive drum 1, and the rotation direction is a contact position with the photosensitive drum 1. Is set in the opposite direction to the photosensitive drum 1. In addition, although the above-mentioned brush roll 61 was used here, it is not necessarily this limitation. The rotational direction may also be set in the same direction as the photosensitive drum 1 at the contact position with the photosensitive drum 1.
Other toner compositions, carriers, and the like are the same as those in the third embodiment.
[0206]
A specific example of the sixth embodiment will be described with the above configuration and toner.
[0207]
FIG. 17 is an explanatory diagram of switching applied voltages in the image forming unit and the inter image unit, and FIG. 18 is a schematic diagram of potential setting and toner movement.
[0208]
First, the temporary collection means for the transfer residual toner will be described with reference to FIG. The transfer residual toner means the same toner as described in the various embodiments described above.
[0209]
At the time of image formation (image portion), as shown in FIG. 18A, the transfer residual toner composed of the normally charged polarity toner RST and the reversely charged polarity toner WST generated by the transfer unit 5 is applied from above the photosensitive drum 1. These are temporarily collected by the brush roll cleaning means 6a and the brush roll cleaning means 6b, respectively.
[0210]
That is, when the toner image composed of the normally charged polarity toner RST formed on the photosensitive drum 1 is electrostatically transferred onto the recording medium 8 by the charging of the transfer roll 51 as shown in FIG. A part of the toner image composed of the normally charged polarity toner RST remains on the recording medium 8 and is also affected by the positive transfer electric field by the transfer roll 51 to reverse the polarity so that the positively charged reverse polarity toner is positive. WST remains on the surface of the photosensitive drum 1.
[0211]
Therefore, in the sixth embodiment, at the time of image formation, as shown in FIG. 18A, the transfer residual toner composed of the normally charged polarity toner RST and the reversely charged polarity toner WST generated by the transfer unit 5 is used as the photosensitive member. The first brush roll cleaning means 6a and the second brush roll cleaning means 6b are temporarily collected from the drum 1 respectively.
[0212]
At that time, one first brush roll cleaning means 6a has a toner RST of normal charge polarity (negative polarity), and the other second brush roll cleaning means 6b has a toner WST of reverse charge polarity (positive polarity). A bias voltage is applied in a direction to electrostatically collect and hold the. Now, the recovery bias voltage ΔV is
ΔV = (Brush applied bias voltage value)-(Photoconductor surface potential)
Then, for example, a bias voltage such that ΔV = + 300 V for temporarily collecting negatively charged regular charged polarity toner RST and ΔV = −300 V for temporarily collecting positively charged reversely charged polarity toner WST. Is applied to the brush roll cleaning means 6a and the brush roll cleaning means 6b by a power source (not shown). Here, the regular charging polarity toner RST is temporarily collected by the upstream first brush roll cleaning means 6a, and the reverse charging polarity toner WST is temporarily collected by the downstream second brush roll cleaning means 6b.
[0213]
Next, of the regular charge polarity toner RST and the reverse charge polarity toner WST temporarily collected by the brush roll cleaning means 6a and 6b, only the reverse charge polarity toner WST is interimaged as shown in FIG. The operation of discharging on the photosensitive drum 1 in the section (non-image forming section) will be described.
[0214]
At this time, when the applied bias ΔV of the upstream brush roll cleaning means 6 a is switched to −300 V and the applied bias ΔV of the downstream brush roll cleaning means 6 b is switched to +300 V, respectively, the brush roll cleaning means 6 a shows FIG. As shown in b), the regular charged polarity toner RST recovered temporarily is discharged onto the photosensitive drum 1 by the coulomb repulsive force. This regular charged polarity toner RST is immediately cleaned by the downstream brush roll cleaning. Collected by means 6b. At the same time, the transfer residual toner generated on the transfer roll 51 flows from the upstream side of the brush roll cleaning means 6a, and the reversely charged polarity toner WST is temporarily stored in the brush roll cleaning means 6a as shown in FIG. The regular charged polarity toner RST is collected and temporarily collected by the brush roll cleaning means 6b. Then, the reversely charged polarity toner WST is discharged onto the photosensitive drum 1 from the brush roll cleaning unit 6b. That is, in the inter-image portion (non-image forming region), as shown in FIG. 18B, only the reversely charged polarity toner WST is discharged onto the photosensitive drum 1 on the downstream side of the brush roll cleaning units 6a and 6b. Will be.
[0215]
Next, an operation of discharging the regular charged polarity toner RST temporarily collected by the downstream brush roll cleaning means 6b onto the photosensitive drum 1 will be described with reference to FIG.
[0216]
That is, in the next image portion following the inter-image portion (non-image forming region), as shown in FIG. 18C, the applied bias ΔV of the brush roll cleaning means 6a is set to + 300V, and the brush roll cleaning means 6b When the applied bias ΔV is −300 V, the reversely charged toner WST that has been temporarily recovered is discharged from the brush roll cleaning unit 6 a onto the photosensitive drum 1, but is discharged onto the photosensitive drum 1. The reversely charged polarity toner WST is immediately collected by the downstream brush roll cleaning means 6b. At the same time, the transfer residual toner generated on the transfer roll 51 flows from the upstream side of the brush roll cleaning means 6a, of which the normally charged polarity toner RST is recovered by the brush roll cleaning means 6a, and the reversely charged polarity toner WST is It is collected by the roll cleaning means 6b. Then, the regular charge polarity toner RST is discharged onto the photosensitive drum 1 from the brush roll cleaning unit 6b. That is, only the regular charged polarity toner RST is discharged onto the photosensitive drum 1 on the downstream side of the brush roll cleaning member 6.
[0217]
Here, the brush bias voltage applied at the time of ejection is set to the same magnitude as the reverse polarity of the applied bias voltage at the time of recovery. However, the voltage may be changed. At that time, in order to enhance the discharge effect, it is desirable to apply a voltage larger than that at the time of recovery.
[0218]
By the way, the relationship between the bias polarity applied to the two brush roll cleaning means 6a and 6b and the discharged toner polarity appearing on the photosensitive drum 1 downstream from the brush roll cleaning means 6a and 6b is organized based on FIG. This will be described as follows.
[0219]
That is, when the regular charging polarity toner RST and the reverse charging polarity toner WST move from the upstream side of the two brush roll cleaning means 6a and 6b while adhering to the surface of the photosensitive drum 1, the two brush roll cleaning operations are performed. Depending on the combination of the polarities of the bias voltages applied to the means 6a and 6b, negative polarity and positive polarity (FIG. 19 (a)), positive polarity and negative polarity (FIG. 19 (b)), negative polarity and negative polarity (FIG. 19). 19 (c)), and four cases of positive polarity and positive polarity (FIG. 19D) are conceivable.
[0220]
More specifically, of the two brush roll cleaning means 6a and 6b, as shown in FIG. 19A, a negative bias voltage is applied to the upstream brush roll cleaning means 6a, and the downstream brush roll cleaning means 6b. When a positive bias voltage is applied to the toner, only the reversely charged toner WST is ejected, as in FIG. 18B, and the upstream brush roll cleaning is performed as shown in FIG. 19B. When a positive bias voltage is applied to the means 6a and a negative bias voltage is applied to the downstream brush roll cleaning means 6b, as in the case of FIG. 18C, only the normally charged polarity toner RST is ejected. Is done.
[0221]
Further, as shown in FIG. 19C, when a negative bias voltage is applied to both the upstream and downstream brush roll cleaning means 6a and 6b, only the normally charged polarity toner RST is ejected and vice versa. In addition, as shown in FIG. 19 (d), when a positive bias voltage is applied to both the upstream and downstream brush roll cleaning means 6a, 6b, only the reversely charged polarity toner WST is ejected.
[0222]
As described above, when the polarity of the bias voltage applied to the upstream and downstream brush roll cleaning means 6a and 6b is set, the upstream and downstream brush roll cleaning means 6a and 6b include Before that, it is assumed that a reverse polarity voltage has been applied, and that each of the brush roll cleaning means 6a, 6b has temporarily collected toner having a polarity opposite to that at the time of ejection. This is because, if bias voltages having opposite polarities are applied to the upstream and downstream brush roll cleaning means 6a and 6b, both of the toners can be used if the brush roll cleaning means 6a and 6b have no previous temporarily recovered toner. This is because both can be collected and no toner is discharged.
[0223]
In the sixth embodiment, the case of FIG. 19A is used to discharge the reversely charged polarity toner WST, but the bias voltage applied to the upstream and downstream brush roll cleaning means 6a and 6b. Other cases may be used by appropriately setting the polarity.
[0224]
In this way, by appropriately setting the polarity of the bias voltage applied to the upstream and downstream brush roll cleaning means 6a, 6b, the opposite polarity of the two brush roll cleaning means 6a, 6b from the upstream side. Even when the residual toner has moved, after passing through these two brush roll cleaning means 6a and 6b, only the residual toner of one polarity remains attached to the surface of the photosensitive drum 1, that is, two The toner that is temporarily collected by the brush roll cleaning means 6a and 6b and then discharged can be either the regular charge polarity toner RST or the reverse charge polarity toner WST.
[0225]
Next, on the premise of the above, the timing of discharging the reversely charged polarity toner WST and the regular charged polarity toner RST temporarily collected by the two brush roll cleaning means 6a and 6b to the surface of the photosensitive drum 1 will be described ( 17 and 18).
[0226]
That is, here, if the non-image forming area corresponding to the space between the recording media at the time of continuous paper feeding is the inter image part, the image forming cycle becomes the inter image part when facing the transfer roll 51 part in the next cycle. After discharging the reversely charged polarity toner WST onto the photosensitive drum 1, the regular charged polarity toner RST is sequentially discharged onto the photosensitive drum 1 which becomes an image portion when facing the transfer roll 51 portion in the next cycle. Is set. However, the order in which the reversely charged polarity toner WST and the normally charged polarity toner RST are discharged is changed, and the normally charged polarity toner RST is applied to the photosensitive drum 1 which becomes an image portion when facing the transfer roll 51 portion in the next cycle. After discharging, the reversely charged toner WST may be set to be sequentially discharged onto the photosensitive drum 1 serving as an inter-image portion when facing the transfer roll 51 portion in the next cycle.
[0227]
The normally charged polarity toner RST discharged onto the photosensitive drum 1 serving as the image portion can be collected by the developing device 4 simultaneously with the development, while the reversely charged polarity toner WST can be collected by the developing device 4. Can not. Further, as will be described later, in order to collect the reversely charged toner WST by the transfer roll 51, an electric field in the direction opposite to the direction in which the developed toner image is transferred to the recording medium 8 is generated in the nip portion of the transfer roll 51. It is necessary to let Therefore, at least the area on the photosensitive drum 1 where the reversely charged polarity toner WST is discharged needs to be an inter-image portion in the next image forming cycle.
[0228]
In this embodiment, the regular charged polarity toner RST temporarily collected by the brush roll cleaning means 6 is discharged to the image portion in the next image forming cycle. However, the discharged toner is cleaned by the brush roll cleaning. It is rubbed by means 6 and is more uniformly dispersed than ordinary transfer residual toner, and is less likely to cause an exposure hindrance. Further, in order to completely avoid the exposure trouble, the regular charge polarity toner RST may be discharged to the inter image portion instead of the image portion. It should be noted that the same cycle may be inserted not only at the inter-image unit but also at the time of power-on or job start / end.
[0229]
FIG. 20 shows the polarity of the toner discharged from the brush roll cleaning means 6 onto the photosensitive drum 1 and the area to be discharged. In this embodiment, as shown in FIG. 20B, the case where the reversely charged polarity toner WST is discharged at the inter image portion and the normal charged polarity toner RST is discharged at the image forming portion is used. As shown in FIG. 20, the reversely charged polarity toner WST is discharged from the inter-image portion, and the regular charge-polarity toner RST is discharged from the image forming portion before or after the case shown in FIG. As shown in FIG. 20 (d), the reversely charged polarity toner WST and the normally charged polarity toner RST are discharged only in the inter image portion, or as shown in FIG. Of course, other cases for discharging the reversely charged polarity toner WST may be used.
[0230]
Next, a method for collecting the normally charged polarity toner RST discharged on the photosensitive drum 1 in the image forming unit as described above will be described.
[0231]
The normally charged polarity toner RST discharged onto the photosensitive drum 1 passes through the charger 2 and is collected by the developing device 4. At this time, the bias applied to the charger 2 and the developing device 4 is the same as that during normal image formation, the surface potential of the photosensitive drum 1 after passing through the charger 2 is −500 V, and the developing bias voltage is −350 V. As a result, an electric field is generated in such a direction that the regular charged polarity toner RST present on the surface of the photosensitive drum 1 is moved from the photosensitive drum 1 to the developing device 4, and thus the regular charged polarity toner RST is electrostatically developed. It is possible to collect with the container 4.
[0232]
Next, a method of collecting the reversely charged polarity toner WST discharged onto the photosensitive drum 1 in the inter image part (non-image forming part) as described above will be described.
[0233]
Since the electric field generated between the photosensitive drum 1 and the developing device 4 works in a direction to attract the reversely charged polarity toner WST onto the photosensitive drum 1, the reversely charged polarity toner WST discharged onto the photosensitive drum 1 is It passes through the developing device 4 as it is. When the reversely charged polarity toner WST present on the photosensitive drum 1 faces the transfer roll 51, the bias voltage applied to the transfer roll 51 is set to −500V.
[0234]
Then, an electric field is generated between the photosensitive drum 1 and the transfer roll 51 so as to attract the reversely charged polarity toner WST to the transfer roll 51, and the reversely charged polarity toner WST moves from the photosensitive drum 1 to the transfer roll 51. To do. Then, the reversely charged polarity toner WST attached to the transfer roll 51 is removed by the metal scraper 52. Further, the voltage applied to the transfer roll 51 when the toner image is transferred to the recording medium 8 except when the reversely charged polarity toner WST discharged onto the photosensitive drum 1 is opposed to the transfer roll 51 is + 300V. .
[0235]
As described above, according to the sixth embodiment, a problem related to accumulation of collected toner in the brush and the brush roll can be avoided, and the transfer residual toner (particularly conversely) that could not be collected by only the developing device. (Polar toner) can be reliably collected, and image defects due to the passage of transfer residual toner can be effectively avoided.
[0236]
Seventh embodiment
FIG. 21 shows a seventh embodiment of the present invention. The same reference numerals are given to the same portions as those in the above-described embodiment. In the seventh embodiment, the plurality of brush rolls are described. A bias voltage is sequentially applied to the cleaning means so that an electric field that separates toner charged to a polarity opposite to the charged polarity of the toner image in the non-image forming region and toner charged to the same polarity as the charged polarity of the toner image acts. It is configured as follows.
[0237]
FIG. 21 is an explanatory diagram of switching of the applied voltage between the image forming unit and the inter-image, and FIG. 22 is a schematic diagram of potential setting and toner movement.
[0238]
First, a means for temporarily collecting transfer residual toner will be described with reference to FIG. At the time of image creation (image portion), as shown in FIG. 22A, the transfer residual toner composed of the normal charging polarity toner RST and the reverse charging polarity toner WST generated by the transfer unit 5 is applied from above the photosensitive drum 1. The first brush roll cleaning means 6a and the second brush roll cleaning means 6b are respectively temporarily collected. The first brush roll cleaning means 6a is applied with a normally charged polarity toner RST, and the other second brush roll cleaning means 6b is applied with a bias voltage in a direction to electrostatically hold the reversely charged polarity toner WST. To do. Now, the recovery bias voltage
ΔV = (Brush applied bias voltage value)-(Photosensitive rest surface potential)
For example, the bias is such that ΔV = + 300 V for temporarily collecting negatively charged regular charged polarity toner RST and ΔV = −300 V for temporarily collecting positively charged reversely charged polarity toner WST. Apply voltage. Here, reversely charged polarity toner WST is temporarily collected by upstream brush roll cleaning means 6a, and regular charged polarity toner RST is temporarily collected by downstream brush roll cleaning means 6b.
[0239]
Next, the operation of discharging the regular charged polarity toner RST temporarily collected by the brush roll cleaning means 6a and 6b as described above onto the photosensitive drum 1 will be described (FIG. 22B).
[0240]
Assuming that the applied bias ΔV = + 300V of the brush roll cleaning means 6a and the applied bias ΔV = −300V of the brush roll cleaning means 6b, the brush roll cleaning means 6a temporarily collects them as shown in FIG. 22 (b). The reversely charged polarity toner WST that has been discharged is discharged onto the photosensitive drum 1, but is immediately recovered by the brush roll cleaning means 6b on the downstream side. At the same time, the transfer residual toner generated on the transfer roll 51 flows from the upstream side of the brush roll cleaning means 6a. Among them, the normally charged polarity toner RST is temporarily collected by the brush roll cleaning means 6a, and the reversely charged polarity toner WST is used as the brush. It is temporarily collected by the roll cleaning means 6b. Then, the regular charge polarity toner RST is discharged onto the photosensitive drum 1 from the brush roll cleaning unit 6b. That is, only the regular charged polarity toner RST is discharged onto the photosensitive drum 1 on the downstream side of the brush roll cleaning member 6.
[0241]
Next, an operation of discharging the temporarily collected reversely charged polarity toner WST onto the photosensitive drum 1 will be described (FIG. 22C).
[0242]
When the applied bias ΔV of the brush roll cleaning means 6a is −300V and the applied bias ΔV of the brush roll cleaning means 6b is + 300V, the normally charged polarity toner RST temporarily recovered from the brush roll cleaning means 6a is the photoreceptor. Although it is discharged onto the drum 1, it is immediately recovered by the brush roll cleaning means 6b on the downstream side. At the same time, the transfer residual toner generated on the transfer roll 51 flows from the upstream side of the brush roll cleaning unit 6a, of which the reversely charged polarity toner WST is collected by the brush roll cleaning unit 6a, and the regular charged polarity toner RST is It is collected by the brush roll cleaning means 6b. Then, the reversely charged polarity toner WST is discharged onto the photosensitive drum 1 from the brush roll cleaning unit 6b. That is, only the reversely charged polarity toner WST is discharged onto the downstream side photosensitive drum 1 of the brush roll cleaning member 6.
[0243]
Here, the brush bias voltage applied at the time of ejection is set to the same magnitude as the reverse polarity of the applied bias at the time of recovery. However, the magnitude of the voltage may be changed. In order to enhance the discharge effect, it is desirable to apply a voltage larger than that at the time of recovery.
[0244]
In the seventh embodiment, as is apparent from the above description, the case of FIG. 19A is used to discharge the reversely charged polarity toner WST, but the cases of FIGS. 19B to 19C are used. Of course, other cases may be used.
[0245]
Next, the discharge timing of the reversely charged polarity toner WST and the normally charged polarity toner RST temporarily collected by the brush roll cleaning means 6a and 6b as described above onto the photosensitive drum 1 will be described (FIGS. 21 and 22). .
[0246]
Also here, if the non-image portion corresponding to the recording medium 8 at the time of continuous paper feeding is an inter-image portion, a photoreceptor that becomes an inter-image portion when facing the transfer roll 51 portion in the next cycle in the image forming cycle. After discharging the normally charged polarity toner RST onto the drum 1, the reversely charged polarity toner WST is sequentially discharged onto the photosensitive drum 1 serving as the same inter-image portion. However, the normal charging polarity toner RST may be sequentially discharged after the reverse charging polarity toner WST is discharged.
[0247]
The normally charged polarity toner RST can be collected by the developing device 4 simultaneously with the development, but the reversely charged polarity toner WST cannot be collected by the developing device 4. Further, as will be described later, in order to collect the reversely charged polarity toner WST by the transfer roll 51, it is necessary to generate an electric field in the direction opposite to the direction in which the developed toner image is transferred to the recording medium 8 at the time of collection. Therefore, at least the area on the photosensitive drum 1 where the reversely charged toner WST is ejected needs to be an inter-image part in the next image forming cycle.
[0248]
In the present embodiment, the regular charged polarity toner RST temporarily collected by the brush roll cleaning means 6 is also ejected to the inter-image portion in the next image forming cycle, so that the ejected regular charged polarity toner RST passes through the exposure portion. The exposure trouble at the time can be completely avoided. Further, since the normally charged polarity toner RST discharged after being temporarily collected by the brush roll cleaning means 6 is uniformly dispersed, it is unlikely to cause an exposure failure. Therefore, as shown in FIGS. 20 (a) and 20 (b) described above. In addition, the regular charged polarity toner RST may be discharged to the image portion.
[0249]
Further, not only in the inter-image unit, but a similar cycle may be inserted when the power is turned on or when the job starts / ends.
[0250]
Next, a method for collecting the normally charged polarity toner RST discharged onto the photosensitive drum 1 will be described.
[0251]
The normally charged polarity toner RST discharged to the inter image portion on the photosensitive drum 1 is collected by the developing device 4 after passing through the charging device 2. At this time, as shown in FIG. 21, the bias applied between the charger 2 and the developing device 4 is the same as that during normal image formation, the surface potential of the photosensitive drum 1 after passing through the charger 2 is −500 V, and development is performed. When the bias voltage is −350 V, an electric field is generated in such a direction as to move the normally charged polarity toner RST from the photosensitive drum 1 to the developing device 4. Therefore, the normally charged polarity toner RST is electrostatically collected by the developing device 4. be able to. On the other hand, the method of collecting the reversely charged polarity toner WST discharged onto the photosensitive drum 1 is the same as in the sixth embodiment.
[0252]
As described above, according to the seventh embodiment, while avoiding the problems related to the accumulation of collected toner in the brush and the brush roll, the transfer residual toner (particularly the reverse) that could not be collected by only the developing device. (Polar toner) can be reliably collected, and image defects due to the passage of transfer residual toner can be effectively avoided. In addition, since the normal charging polarity toner RST is discharged onto the photosensitive drum 1 in the inter image portion, the normal charging polarity is compared with the case where the normal charging polarity toner RST is discharged onto the image portion on the photosensitive drum 1. It is possible to reliably prevent the toner RST from becoming an obstacle to image exposure.
[0253]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably collect the transfer residual toner having the reverse polarity, and to form a good image over a long period of time without generating positive ghost, negative ghost, and fog. Image forming apparatus can be provided.
[0254]
In addition, according to the present invention, it is possible to avoid problems associated with accumulation of collected toner in a uniformizing means such as a brush or a brush roll, and to effectively prevent image defects caused by passing of transfer residual toner (particularly reverse polarity toner). Therefore, it is possible to provide an image forming apparatus that can be avoided.
[0255]
further,Claim 3According to the invention described in the above, it is possible to avoid the problem related to the accumulation of the collected toner in the brush and the brush roll without reducing the productivity of the image forming apparatus, and to prevent the image defect due to the passage of the transfer residual toner (particularly the reverse polarity toner). It is possible to realize an image forming apparatus that can effectively avoid the above and suppress defects on the image over a long period of time.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a main part of the image forming apparatus according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a main part of the image forming apparatus according to the first embodiment of the present invention.
FIG. 4 is a timing chart showing the operation of the image forming apparatus according to the first embodiment of the present invention.
FIG. 5 is a potential explanatory diagram showing an operation of the image forming apparatus according to the first embodiment of the present invention.
FIG. 6 is a block diagram showing a main part of an image forming apparatus according to a second embodiment of the present invention.
FIG. 7 is a timing chart showing the operation of the image forming apparatus according to the second embodiment of the present invention.
FIG. 8 is a block diagram showing an image forming apparatus according to a third embodiment of the present invention.
FIG. 9 is a timing chart showing the operation of the image forming apparatus according to the third embodiment of the present invention.
FIG. 10 is an explanatory diagram showing the operation of the image forming apparatus according to the present invention.
FIG. 11 is a block diagram showing an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 12 is a timing chart showing the operation of the image forming apparatus according to the fourth embodiment of the present invention.
FIG. 13 is a block diagram showing a main part of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 14 is a block diagram showing a main part of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 15 is a block diagram showing a main part of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 16 is a block diagram showing an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 17 is a timing chart showing the operation of the image forming apparatus according to the sixth embodiment of the present invention.
FIG. 18 is a block diagram showing a main part of an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 19 is a block diagram showing a main part of an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 20 is a block diagram showing a main part of an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 21 is a timing chart showing the operation of the image forming apparatus according to the seventh embodiment of the present invention.
FIG. 22 is a block diagram showing a main part of an image forming apparatus according to a seventh embodiment of the present invention.
[Explanation of symbols]
1: Photosensitive drum (latent image carrier), 5: transfer means, 51: transfer roll, 52: cleaner, 6: brush roll cleaning means, 61: brush roll, 62: casing, 8: recording paper (recording medium) 14: Voltage application means for the cleaning member.

Claims (4)

  1. A toner image is formed on the latent image carrier by a developing means to which a predetermined developing bias voltage is applied, and the toner image formed on the latent image carrier is disposed so as to contact the latent image carrier. In an image forming apparatus for forming an image on the recording medium by transferring the image onto the recording medium after transferring the image on the recording medium.
    A bias voltage is applied so that an electric field that contacts the latent image carrier and separates the toner charged to a polarity opposite to the charged polarity of the toner image in the non-image forming area is applied, and then the orientation similar to that in the image forming area Charging means for switching the bias voltage so that an electric field of
    And a brush roll cleaning means in contact with the latent image carrier,
    A bias voltage is applied to the brush roll cleaning means so that an electric field attracting toner charged to a polarity opposite to the charging polarity of the toner image acts in the image forming area, and the charging polarity of the toner image in the non-image forming area. Applying a bias voltage and a bias voltage so that an electric field attracting the toner charged in the opposite polarity to the charging polarity of the toner image acts so that an electric field that separates the toner charged in the opposite polarity acts, and
    A bias voltage is applied to the transfer means so that an electric field that separates the toner charged in the opposite polarity to the charged polarity of the toner image in the image forming area acts, and the charged polarity of the toner image is reversed in the non-image forming area. A bias voltage is applied so that an electric field that attracts the toner charged to the polarity acts ,
    An image forming apparatus, wherein the bias of the charging unit is not switched until the position on the latent image carrier where the applied bias of the brush roll cleaning unit is switched in the non-image forming region reaches the charging unit .
  2.   The image forming apparatus according to claim 1, wherein the non-image forming area of the latent image carrier is an inter-image portion.
  3. The brush roll cleaning means pulls away the toner charged to a polarity opposite to the charged polarity of the toner image to the brush roll cleaning means, the length of the non-image forming area being Lint (mm), the process speed is Vp (mm / sec). The time for applying the bias voltage so that the electric field acts is Tp (sec), the time for applying the bias voltage for applying the electric field in the same direction as the image forming area to the brush roll cleaning means is Tm (sec), and the brush roll cleaning means Lt / Vp ≧ Tp + TmTp ≧ When the distance between the rotation center of the toner and the surface of the latent image carrier is rb (mm) and the rotational speed of the brush roll cleaning means at the closest position of the latent image carrier is Vb (mm / sec) 3. The image forming apparatus according to claim 1, wherein 2π · rb / Vb and Tm ≧ 2π · rb / Vb are satisfied.
  4. Wherein the developing means, in the image forming area, is applied a DC voltage and an AC voltage is in the non-image forming region, any one of claims 1 to 3, characterized in that the alternating voltage is stopped The image forming apparatus described in the item.
JP2001284396A 2001-04-09 2001-09-19 Image forming apparatus Expired - Fee Related JP4123750B2 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2001110346 2001-04-09
JP2001-110346 2001-04-09
JP2001284396A JP4123750B2 (en) 2001-04-09 2001-09-19 Image forming apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2001284396A JP4123750B2 (en) 2001-04-09 2001-09-19 Image forming apparatus

Publications (2)

Publication Number Publication Date
JP2002372878A JP2002372878A (en) 2002-12-26
JP4123750B2 true JP4123750B2 (en) 2008-07-23

Family

ID=26613317

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2001284396A Expired - Fee Related JP4123750B2 (en) 2001-04-09 2001-09-19 Image forming apparatus

Country Status (1)

Country Link
JP (1) JP4123750B2 (en)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4622262B2 (en) * 2004-02-19 2011-02-02 富士ゼロックス株式会社 Image forming apparatus
JP2006072270A (en) * 2004-09-06 2006-03-16 Fuji Xerox Co Ltd Image forming apparatus
JP3994996B2 (en) 2004-10-18 2007-10-24 コニカミノルタビジネステクノロジーズ株式会社 Image forming apparatus
JP4089681B2 (en) 2004-10-20 2008-05-28 コニカミノルタビジネステクノロジーズ株式会社 Image forming apparatus
JP2006337394A (en) * 2005-05-31 2006-12-14 Konica Minolta Business Technologies Inc Image forming apparatus
JP4742812B2 (en) * 2005-10-27 2011-08-10 コニカミノルタビジネステクノロジーズ株式会社 Image forming apparatus
JP2007286392A (en) * 2006-04-18 2007-11-01 Konica Minolta Business Technologies Inc Image forming method and image forming apparatus
JP4984935B2 (en) * 2007-02-06 2012-07-25 コニカミノルタビジネステクノロジーズ株式会社 Image forming apparatus and image forming method
JP5073332B2 (en) * 2007-03-19 2012-11-14 株式会社リコー Image forming apparatus
JP2010032586A (en) * 2008-07-25 2010-02-12 Seiko Epson Corp Cleaning device for image carrier, cleaning method, and image forming apparatus
JP5965887B2 (en) * 2013-10-31 2016-08-10 京セラドキュメントソリューションズ株式会社 Image forming apparatus

Also Published As

Publication number Publication date
JP2002372878A (en) 2002-12-26

Similar Documents

Publication Publication Date Title
DE3706873C2 (en) Imaging device
JP4928972B2 (en) Image forming apparatus
JP4928973B2 (en) Cleaning device, process cartridge, and image forming apparatus
US6950620B2 (en) Image forming apparatus with settable peak to peak voltages applied to image bearing member
US6744994B2 (en) Image forming apparatus with environmentally-controlled first and second charging members
JP3652331B2 (en) Image forming apparatus
JP2619154B2 (en) Image forming device
US7756462B2 (en) Image forming apparatus and cleaning device
JP4065496B2 (en) Image forming apparatus
JP3074037B2 (en) Image forming method
US6480695B2 (en) Cleaning system and image forming method
JP3848097B2 (en) Charging member, charging device, image forming apparatus, and process cartridge
JP4133281B2 (en) Foreign matter removal mechanism, printing apparatus, and foreign matter removal method
US7058335B2 (en) Process cartridge and image forming apparatus with toner fed cleaning mode
JP3768800B2 (en) Image forming apparatus
JP2007163708A (en) Cleaning device and image forming apparatus equipped with same
JP2005173485A (en) Developing device, process cartridge and image forming apparatus
JP4124988B2 (en) Image forming apparatus
JP2008116501A (en) Cleaning device, image carrier unit and image forming apparatus
US6813468B2 (en) Image forming device with a cleaning unit
JPH05210300A (en) Image forming device and method
JP2004117960A (en) Image forming apparatus
CN101154084B (en) Image forming apparatus
JPH0915976A (en) Developing device
JP2007108656A (en) Image forming apparatus

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20040917

RD05 Notification of revocation of power of attorney

Free format text: JAPANESE INTERMEDIATE CODE: A7425

Effective date: 20050509

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20070517

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20070710

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20070907

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20071113

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20080111

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20080415

A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20080428

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110516

Year of fee payment: 3

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110516

Year of fee payment: 3

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120516

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130516

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140516

Year of fee payment: 6

LAPS Cancellation because of no payment of annual fees