JP5838766B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

For example, those disclosed in Patent Documents 1 and 2 are already known as conventional image forming apparatuses.
Japanese Patent Application Laid-Open No. H10-228688 includes an embodiment provided with a cleaning blade that presses against an image carrier, and externally adds toner to the toner by frictional charging with the image carrier at a position after a cleaning portion by the cleaning blade and before a primary charging portion. A cleaning device for an image forming apparatus is disclosed in which an adsorbing member (scraper or brush roller) charged to a polarity opposite to that of the silica particles is disposed.
In Patent Document 2, a cleaning member that is positively charged and a cleaning member that is negatively charged are placed in contact with a charging roller that is disposed in contact with a photosensitive member, and electrostatic foreign matter recovery is performed together with mechanical recovery. A cleaning device is disclosed.

Japanese Unexamined Patent Publication No. 3-45779 (Description of Examples, FIG. 2) Japanese Patent Laid-Open No. 6-230657 (Example, FIG. 1)

  The technical problem to be solved by the present invention is an image that can effectively eliminate the afterimage quality defect due to the phenomenon of transition of the external additive to the image carrier caused by continuously producing the surface image. It is to provide a forming apparatus.

According to a first aspect of the present invention, there is provided a rotatable image holding member for holding an electrostatic latent image, a latent image forming means for forming an electrostatic latent image based on an image signal on the image holding member, toner, A developer holding body that holds and conveys a developer containing an external additive of the same polarity as the carrier and toner is rubbed against the image holding body by the developer held and conveyed by the developer holding body. A developing unit that develops the electrostatic latent image formed on the image holding member by the latent image forming unit, and a transfer that transfers the toner image on the image holding member developed by the developing unit to a transfer medium. And a cleaning member provided on the downstream side in the rotation direction of the image carrier from the transfer portion by the transfer unit and cleaning the post-transfer residue on the image carrier with a cleaning member that contacts the image carrier. And the rotation direction of the image carrier rather than the cleaning part by the cleaning means And an external additive recovery means for recovering the external additive on the image carrier that has passed through the cleaning site, the external additive recovery means facing the image carrier and An electrified collection member that is disposed so as to extend in a direction that intersects with the rotation direction of the image carrier, and that at least a facing portion that faces the image carrier is made of a material in which a charged column is located on the plus side of the external additive. When having a frictional charging member, wherein the object to be charged collecting member is caused to frictionally charged so as to electrostatically adsorb the external additive, the object to be charged collecting member via the frictional charging member when the image carrier rotational friction The friction charging mechanism for charging and the image holding member provided between the opposite portion of the charged collecting member and the image holding member and the image holding member, and when the charged collecting member is frictionally charged by the friction charging mechanism, the friction The electric field based on the charge generated by charging is , A gap which is allowed to act on the extent possible electrostatic attraction the external additive on the carrier is an image forming apparatus comprising: a.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the external additive collecting unit is such that at least a facing portion facing the image holding member has a charged column located on the plus side of the image holding member. A triboelectric charging member made of a material and a triboelectric charging member that uses the image carrier as a triboelectric charging member, and that forms a protrusion that contacts the triboelectric charging member, which is a triboelectric charging member. And an image forming apparatus.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the frictional charging mechanism includes a protrusion having a tip formed in a curved shape on the charge collection member. Device.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the to-be-charged recovery member has an opposing surface having a shape along the surface shape of the image carrier. The image forming apparatus.
According to a fifth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the frictional charging mechanism forms a protrusion on the downstream side in the rotational movement direction of the image holding member of the charge collection member. In the image forming apparatus, the protrusion of the member to be charged is brought into contact with an image forming region on the surface of the image holding member.
According to a sixth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the triboelectric charging mechanism is configured to collect the charged object with respect to a non-image forming area other than the image forming area on the surface of the image carrier. An image forming apparatus, wherein a protrusion of a member is brought into contact.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the second, third, fifth, and sixth aspects, the frictional charging mechanism is configured to wire the protruding portion of the member to be charged with respect to the surface of the image carrier. The image forming apparatus is characterized in that contact is made at a point-like portion or a plurality of point-like portions.
According to an eighth aspect of the present invention, in the image forming apparatus according to the first aspect, the external additive recovery means includes a charged recovery member that is disposed to face the image carrier via the gap, and the image. An image forming apparatus comprising: a frictional charging mechanism that causes the frictional charging member to rotate relative to the member to be charged when the holder rotates, so that the frictional charging member is slidably contacted.
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the charged collection member is rotatably provided, and the friction charging mechanism rotates the charged collection member when the image holding member rotates. The image forming apparatus is characterized in that, while being driven, the frictional charging member fixedly disposed in advance to the member to be charged is slidably contacted.
According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the external additive collecting means includes a cleaning member for cleaning the external additive electrostatically adsorbed on the charged collection member. The image forming apparatus.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the external additive collecting means serves as the friction charging member and the cleaning member.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the first aspect, the external additive collecting unit is provided on the upstream side in the rotational direction of the image holding member with respect to the latent image forming part by the latent image forming unit. An image forming apparatus characterized by the above.

According to the first aspect of the present invention, it is possible to effectively eliminate afterimage quality defects associated with the phenomenon of transfer of the external additive to the image carrier caused by continuously producing the surface image.
According to the second aspect of the present invention, it is possible to easily triboelectrically charge the member to be charged using the image carrier.
According to the third aspect of the present invention, it is possible to easily triboelectrically charge the member to be charged using the image carrier while suppressing the sliding resistance between the member to be charged and the image carrier.
According to the invention which concerns on Claim 4, compared with the aspect which does not have this structure, the collection | recovery performance of the external additive by a to-be-charged collection member can be kept favorable.
According to the fifth aspect of the present invention, the external additive recovery performance on the image holding member is kept good while ensuring a wide frictional charging area with respect to the charged recovery member as compared with the aspect without this configuration. be able to.
According to the invention of claim 6, compared to the aspect without this configuration, it is possible to keep the friction chargeability with respect to the member to be charged and the recovery performance of the external additive on the image carrier better. .
According to the seventh aspect of the present invention, the gap dimension of the gap portion between the charged collection member and the image holding member can be stabilized as compared with the aspect not having this configuration, and accordingly, An electric field for recovering the external additive acting between the recovery member and the image carrier can be stably formed.
According to the eighth aspect of the present invention, the recovery performance of the external additive on the image holding member can be kept good while reducing the driving load on the image holding member as compared with the aspect without this configuration. .
According to the ninth aspect of the invention, compared to the aspect without this configuration, the electric field for collecting the external additive is concentrated on the gap between the charged collection member and the image carrier, and the external addition is performed. The recovery performance of the agent can be kept better.
According to the tenth aspect of the present invention, compared to the aspect without this configuration, the charged collection member can always be kept in a clean state, and accordingly, the collection performance of the external additive on the image carrier can be improved. Can keep good.
According to the eleventh aspect of the present invention, it is possible to always keep the charged collection member in a clean state without using a dedicated cleaning member, and accordingly, the collection performance of the external additive on the image carrier is improved. Can keep.
According to the twelfth aspect of the present invention, afterimage quality defects associated with the phenomenon of transition of the external additive to the image carrier caused by continuously producing a surface image before forming the latent image by the latent image forming means are eliminated. It can be effectively resolved.

(A) is explanatory drawing which shows the outline | summary of embodiment of the image forming apparatus to which this invention was applied, (b) is explanatory drawing which shows the principal part of the external additive collection | recovery means in (a). (A) is explanatory drawing which shows an example of the initial image which produces a surface image continuously, (b) is the ghost generation | occurrence | production image produced when producing a surface image continuously using the initial image of (a). It is explanatory drawing which shows an example. It is explanatory drawing which shows typically the factor which the ghost generation | occurrence | production image of FIG.2 (b) produces. FIG. 2 is an explanatory diagram schematically showing an image forming process by the image forming apparatus shown in FIG. 1. 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. 3 is an explanatory diagram illustrating a configuration of a peripheral portion of the cleaning device of the image forming apparatus used in Embodiment 1. FIG. FIG. 3 is an explanatory diagram showing a main part of an external additive recovery device used in Embodiment 1. (A) is explanatory drawing which shows the structural example of the external additive collection | recovery apparatus of FIG. 7, (b) is the arrow line view seen from the VIII direction in FIG. FIG. 3 is an explanatory view schematically showing the operating principle of the external additive recovery apparatus used in Embodiment 1. (A) (b) is explanatory drawing which shows the deformation | transformation form of the external additive collection | recovery apparatus used in Embodiment 1. FIG. FIG. 4 is an explanatory diagram illustrating a main part of an image forming apparatus according to a second embodiment. (A) is explanatory drawing which shows the principal part of the external additive collection | recovery apparatus used in Embodiment 2, (b) is the arrow line view seen from B direction in (a). FIG. 10 is an explanatory diagram illustrating a main part of an image forming apparatus according to a third embodiment. (A) is explanatory drawing which shows the principal part of the external additive collection | recovery apparatus used in Embodiment 3, (b) is explanatory drawing which shows an example of the drive system of the external additive collection | recovery apparatus shown to (a). It is explanatory drawing which shows the modification 3-1 of the external additive collection | recovery apparatus used in Embodiment 3. FIG. It is explanatory drawing which shows the modification 3-2 of the external additive collection | recovery apparatus used in Embodiment 3. FIG. It is explanatory drawing which shows the ghost level in Example 1 and Comparative Example 1. It is explanatory drawing which shows the relationship between the ghost level in Example 1, and the number of running cycles.

Outline of Embodiment FIG. 1A is a schematic diagram showing an outline of an embodiment of an image forming apparatus to which the present invention is applied.
In the figure, an image forming apparatus includes a rotatable image carrier 1 on which an electrostatic latent image is held, and a latent image forming unit 2 that forms an electrostatic latent image on the image carrier 1 based on an image signal. A developer holding body 3b that holds and conveys the toner, the carrier, and the developer G containing the external additive having the same polarity as the toner, and the developer G held and conveyed by the developer holding body 3b A developing means 3 for developing the electrostatic latent image formed on the image holding body 1 by the latent image forming means 2 by rubbing against the image holding body 1 and the image developed by the developing means 3 A transfer unit 4 that transfers the toner image on the holding body 1 to the transfer medium 5, and is provided on the downstream side in the rotation direction of the image holding body 1 with respect to a transfer portion by the transfer means 4, and contacts the image holding body 1. A cleaning unit 6a for cleaning the post-transfer residue on the image carrier 1 with a cleaning member 6a; In the downstream side in the rotational direction of the image carrier 1 than cleaning site by the cleaning means 6, and, provided on the upstream side in the rotational direction of the image carrier 1 than the latent image formed portion by said latent image forming means 2, And an external additive recovery means 10 for recovering the external additive W on the image carrier 1 that has passed through the cleaning portion.
In the present embodiment, the external additive recovery means 10 extends in a direction opposite to the image carrier 1 and intersecting the rotation direction of the image carrier 1 as shown in FIG. It is arranged such, and the charged collecting member 11 made of a material facing portions of the triboelectric series than the external additive W facing at least the image carrier 1 is located on the plus side, the object to be charged collecting member 11 Friction charging member 12a that is frictionally charged so that the external additive W is electrostatically adsorbed, and frictionally charging the charge collection member 11 via the friction charging member 12a during one rotation of the image carrier. When the charging collection member 11 is frictionally charged by the friction charging mechanism 12 provided between the charging mechanism 12 and the portion of the charging collection member 11 facing the image holding body 1 and the image holding body 1. The electricity generated by the frictional charging Electric field E has a gap 13 which is allowed to act on the extent possible electrostatic attraction external additive W on the image carrier 1, a-based.

In such technical means, the image carrier 1 is not limited to a mode in which an electrostatic latent image can be formed by light or ions, such as a photoconductor or a dielectric, but also a latent image corresponding to an electrostatic latent image for each pixel unit. Examples include an image electrode that provides an image potential.
The latent image forming unit 2 may be appropriately selected according to the type of the image carrier. For example, if the image carrier 1 is a photoconductor or a dielectric, it may be anything that forms a latent image by light or ions. In an embodiment using pixel electrodes, a latent image potential corresponding to the electrostatic latent image is supplied. Any device that generates a signal may be used. Here, as a representative aspect of the latent image forming means 2 of the former aspect, a charging means 2a for charging the image holding body 1, and light or ions on the image holding body 1 charged by the charging means 2a. And a latent image writing means 2b for writing a latent image.
Further, the developing unit 3 uses a two-component developer to which an external additive (typically silica) having the same polarity as the toner is added as the developer G, and the developer with respect to the image carrier 1. Any developer holding member 3b for rubbing G may be used. However, the developer holder 3b itself may be disposed in contact with the image carrier or may be disposed in a non-contact manner.
Here, as a typical mode of this type of developing means 3, a developing container 3a is provided that contains developer G and opens to face the image carrier 1, and faces the opening of the developing container 3a. The developer holding body 3b is disposed, and the developer container 3a is provided with an agitating and conveying member 3e (for example, a spiral blade member around a rotatable shaft member) in which the developer G can be agitated and conveyed. ) Is provided. The developer holder 3b is typically a rotatable hollow developing rotator 3c, and a magnet member fixedly included in the developing rotator 3c and having a plurality of magnetic poles arranged around it. 3d is used.
Further, the transfer means 4 includes a wide variety of transfer means for transferring the toner image on the image holding member 1 to the transfer medium 5. The transfer system is typically an electrostatic transfer system, but other systems may be used. . The transfer medium 5 here includes not only the recording material which is the final transfer medium, but also includes an intermediate transfer body that holds the toner image intermediately before the recording material.
Further, the cleaning means 6 may be any means that cleans the post-transfer residue on the image carrier 1 with a cleaning member 6a that contacts the surface of the image carrier 1, and as a typical aspect of the cleaning member 6a. Is a plate-like member or brush-like member that scrapes off the residue.

Further, as shown in FIG. 1B, the external additive collecting means 10 may be any component that includes the member to be charged 11, the friction charging mechanism 12, and the gap portion 13 as constituent elements.
In this example, as the electrified recovery member 11, at least the portion facing the image carrier 1 may be made of a material whose charged column is located on the plus side of the external additive W. For this reason, not only the aspect which comprises the to-be-charged collection | recovery member 11 whole with the material located in a desired charge row | line | column but of course, it comprises with the material located in a desired charge row | line | column only in the surface layer and coating layer corresponding to the said opposing part. Embodiments are also included.
The friction charging mechanism 12 includes a friction charging member 12a that charges the charged collection member 11 to a desired polarity (polarity to which the external additive can be electrostatically attracted). Any mechanism may be selected as long as it is a mechanism that frictionally charges the member to be charged by contact.
Thus, in this aspect, since the frictional charging mechanism 12 is employed, a method of applying a bias for forming an electric field for collecting the external additive is not included.
Further, the gap 13 may be selected as follows. That is, the electric field E generated in the gap 13 includes the distance d between the charged collection member 11 and the image carrier 1 that are frictionally charged, and the charge generated in the charged collection member 11 due to frictional charging. Therefore, the electric field strength may be selected so that the external additive W on the image carrier 1 is electrostatically attracted to the charged collection member 11 side.

Here, before describing the operation of the image forming apparatus according to the embodiment shown in FIGS. 1A and 1B, the image forming apparatus according to the comparative embodiment (the aspect without the external additive collecting means 10) will be described. The operation will be described.
-Outline of operation of image forming apparatus according to comparative mode-
For example, in an image forming apparatus according to a comparative embodiment, for example, a continuous surface image (typically, a so-called solid image with an image density of 100% is mentioned, but the present invention is not limited to this, and the image density is determined in advance. When a high image density (for example, 80% or more) is formed for each turn of the image carrier 1 for a predetermined number of times or more, the image including the area where the surface image is formed is formed. For example, when a halftone image is formed in an image region, a phenomenon in which a continuous surface image appears as an afterimage (ghost) can occur with a relatively high probability. Such an afterimage phenomenon appears remarkably in a halftone image, but may also appear in the background (non-image portion).
For example, as shown in FIG. 2 (a), as the initial images, it is deleted portion of the continuous surface image IM ₁ region, and the example of halftone image IM ₂ is present Alternatively, continuous When the plane image IM ₁ is repeated more than a predetermined number of times, as shown in FIG. 2 (b), in the area overlapping the continuous plane image IM _{1 in the} halftone image IM ₂ , the original image of high continuous residual image (ghost image) of the surface image IM ₁ possibly IMg appears.
Such a situation is, for example, when the circumference of the image carrier 1 is shorter than the length along the moving direction of the image carrier 1 of the initial image (see FIG. 2A) or vice versa. When the initial image (IM ₁ + IM ₂ ) is continuously formed through a predetermined inter-image area instead of the circulation unit of the body 1, the continuous surface image IM ₁ during one rotation of the image carrier _1. situation in which the imaged region of overlap with the imaged region of the halftone image IM ₂ is likely to occur remarkably.

In such a situation, the cause of the above-mentioned afterimage phenomenon is estimated as follows.
That is, as shown in FIG. 3, if an external additive W of the toner T adheres to the image carrier 1 when producing a continuous surface image, the normal image carrier 1 has a cleaning means. 6 is often provided. Here, although the cleaning member 6a (for example, a plate-like cleaning member) of the cleaning means 6 is excellent in the ability to clean the toner T, it can be said that it is not necessarily excellent in the ability to remove the external additive W of the toner T. Absent. Since the external additive W added to the T surface of the toner has a small particle size, the cleaning member 6a may slip through the cleaning member 6a when the scraping force of the cleaning member 6a is low.
Silica is often used as a representative of this type of external additive W, and almost all toners currently used in products because of its excellent functions as an external additive such as chargeability and transferability. Externally attached to T. However, the silica released from the toner T while being agitated and conveyed by the agitating and conveying member 3e in the developing container 3a of the developing means 3 and the silica originally released from the toner migrate to the surface of the image carrier 1 and adhere to it. Easy to do.
Since the silica as the external additive W transferred to the image carrier 1 has a small particle size and is relatively firmly attached, it cannot be scraped off by the scraping force of the cleaning member 6a, and the cleaning member 6a. Passes through the cleaning area due to the above, and as the image carrier 1 circulates, it again reaches the developing area of the developing means 3.
At this time, the image carrier 1 is charged to a predetermined charging potential Vh by the latent image forming means 2 (in this example, charging means 2a + latent image writing means 2b) (e in the figure is a negative charged charge). ), An electrostatic latent image Z is formed, so that the silica as the external additive W that has passed through the cleaning member 6a is given a negative charge e when passing through the charging means 2a of the latent image forming means 2. However, since the silica charged by the charge application is removed by the rubbing force (scavenging force) by the developer in the developing area of the developing unit 3, the surface potential of the image carrier 1 changes. Happens. Specifically, the latent image potential Vz relating to the site where the silica has been scraped is likely to be in a state where the absolute value of the latent image potential Vz is further lowered by ΔV.
In this state, when a developing operation is performed by applying a developing voltage Vbias (| Vh |> | Vbias |> | Vz |) to the developer holding body 3b of the developing unit 3, the electrostatic latent image Z More toner T than the surroundings is developed in the portion where the silica has been scraped off, resulting in a ghost image IMg (FIG. 2B) which is an afterimage having a different density from the other portions.
In particular, in the case where the surface images are continuously formed, since the images are repeatedly formed on the same portion of the image carrier 1, the charged silica accumulates, and the generation of the ghost image IMg is remarkable. .
Further, in a mode in which a charging member that is in contact with the image carrier 1 is used as the charging unit 2a, the silica that has passed through the cleaning member 6a adheres to the charging member of the charging unit 2a and causes a charging failure. There is also a concern that image quality is likely to deteriorate.
The afterimage (ghost) phenomenon described above is mainly caused by an increase in the amount of silica transferred to the image carrier 1 with a large development amount when a high-density image is continuously formed. However, if the total amount of charges of the slipped silica is large, an afterimage (ghost) phenomenon may appear even if it is not a high-density image.

-Outline of operation of image forming apparatus according to embodiment-
On the other hand, in the image forming apparatus according to the embodiment shown in FIGS. 1A and 1B, as shown in FIG. 4, the external additive W (for example, silica) adhering to the image carrier 1 is cleaned. 6, the external additive W that has passed through the cleaning member 6 b passes through the external additive collecting means 10 before passing through the latent image forming means 2.
At this time, the external additive recovery means 10 disposes the charged recovery member 11 with respect to the image carrier 1 through the gap 13 and frictionally charges the charged recovery member 11 with the frictional charging mechanism 12. A charge having a predetermined polarity is generated on the charge collection member 11, and an electric field E that can electrostatically attract the external additive W on the image carrier 1 is applied to the gap 13 by the generated charge. .
For this reason, the external additive W adhering to the image carrier 1 is electrostatically attracted toward the charged collection member 11 by the action of the electric field E while passing through the gap 13 and is collected by the charged collection member 11. Is done.
As a result, the external additive W that has passed through the cleaning member 6a hardly passes through the charging unit 2a of the latent image forming unit 2, and a negative charge e is applied to the external additive W, so that the developing region of the developing unit 3 is exposed. Never reach. For this reason, there is almost no phenomenon in which the external additive W charged by the charge application is removed by the rubbing force (scavenging force) by the developer in the developing region of the developing means 3, and the image accompanying the removal of the charged external additive W. The phenomenon that the surface potential of the holder 1 changes hardly occurs. Therefore, for example, the latent image potential Vz of the electrostatic latent image Z corresponding to the halftone image is hardly lowered, and the electrostatic latent image Z is developed as a substantially uniform halftone image.
In the present embodiment, even when the charging member 2a uses a charging member that contacts the image carrier 1, the external additive W attached to the image carrier 1 adheres to the charging member. Hardly occurs.

Next, a typical aspect or a preferable aspect in the present embodiment will be described.
First, as a typical aspect of the external additive recovery means 10, there is an aspect in which the image carrier 1 is used as the friction charging member 12a. Specifically, at least a portion facing the image carrier 1 has a charged collection member 11 made of a material in which a charged column is located on the plus side of the image carrier 1 and the image carrier 1 is a friction charging member. And a friction charging mechanism 12 that is used as a charging recovery member 11 and has a protrusion (not shown) that contacts the image carrier 1 as the friction charging member 12a.
As the frictional charging mechanism 12 in this aspect, from the viewpoint of suppressing the sliding resistance with the image carrier 1, an aspect in which the tip of the charge collection member 11 is a protrusion having a curved surface is preferable.
Furthermore, as a preferable aspect of the to-be-charged recovery member 11, an aspect having an opposing surface having a shape along the surface shape of the image carrier 1 can be mentioned.
In this embodiment, when the image carrier 1 is, for example, a drum-like rotator, the charge collection member 11 only needs to have a facing surface along a shape that matches the curvature of the rotator. In the portion corresponding to the linear portion in the shape of the rotating body, the to-be-charged recovery member 11 only needs to have a linear opposing surface along the linear portion of the rotating body.
In such an aspect, since the gap 13 between the charged collection member 11 and the image carrier 1 is substantially the same dimension d, the electric field strength between the charged collection member 11 and the image carrier 1 is low. It is kept substantially equal over the entire area of the opposing surface. For this reason, the external additive W on the image carrier 1 is hardly electrostatically attracted locally to a part of the charged collection member 11, and the external additive W of the charged collection member 11 is static. Since the electric field is weakened by the electrostatic shielding effect at the portion where the external additive W is collected toward the portion where the external additive W is not electrostatically adsorbed, it is transferred to another location where the external additive W is not electrostatically adsorbed. It is collected over a wide area.

Furthermore, the following aspects are mentioned as a preferable aspect of the protrusion of the to-be-charged recovery member 11.
As a first aspect, a protrusion is formed on the downstream side in the rotational movement direction of the image carrier 1 in the charged collection member 11, and the charged collection member on the image forming area on the surface of the image carrier 1. There is an aspect in which 11 protrusions are brought into contact.
In this aspect, the protrusion is a functional part that frictionally charges the member to be charged 11, and in the aspect provided on the downstream side in the rotational movement direction of the image carrier 1 in the member to be charged 11, the protrusion is more than this protrusion. The gap 13 is secured on the upstream side in the rotational movement direction of the image carrier 1. For this reason, most of the external additive W on the image carrier 1 remains in the image forming area, but before passing through the contact portion between the protrusion of the charged member 11 and the image carrier 1, the image carrier 1. The upper external additive W is recovered on the charged recovery member 11 side by the electric field E in the gap 13.
As a 2nd aspect, the aspect which makes the protrusion part of the to-be-charged collection | recovery member 11 contact the non-image formation area other than an image formation area among the surfaces of the image carrier 1 is mentioned.
In this aspect, the protrusion of the member to be charged 11 is in contact with the portion of the surface of the image carrier 1 corresponding to the non-image formation region, so that the external additive remaining in the image formation region of the image carrier 1 W does not pass through the contact portion between the protrusion and the image carrier 1, and the external additive W does not adhere to the contact portion and the frictional charging performance to the member to be charged 11 is not impaired.
As a 3rd aspect, the aspect which makes the protrusion part of the to-be-charged collection | recovery member 11 contact with the surface of the image carrier 1 in multiple places is mentioned.
In this embodiment, the protrusion may be a single spot for the function of frictionally charging the charged member 11, but the gap dimension d of the gap 13 between the charged member 11 and the image carrier 1 is stabilized. From the viewpoint of making it, it is preferable to provide a linear portion or a plurality of dotted portions.

Further, as another representative aspect of the external additive recovery means 10, there is an aspect in which a charged recovery member 11 that is not in contact with the image carrier 1 is charged using a dedicated friction charging member. Specifically, the charged collection member 11 disposed opposite to the image holding body 1 via the gap 13 and the friction charging member 12a relatively to the charged collection member 11 when the image holding body 1 rotates. And a frictional charging mechanism 12 that is slidably contacted by being driven to rotate.
In this aspect, it is sufficient that at least one of the frictional charging member 12a and the charged collection member 11 is rotationally driven. Further, since the charge collection member 11 is arranged in non-contact with the image carrier 1, the rotational movement operation of the image carrier 1 is stabilized, and the degree of freedom in selecting the material of the friction charge member 12 a and the charge collection member 11 is stable. Is preferable from the viewpoint of high.
As a preferred aspect of this aspect, the charged member 11 is rotatably provided, and the frictional charging mechanism 12 rotates the charged member 11 when the image carrier 1 rotates, and the charged member 11 is also charged. For example, the friction charging member 12a fixedly arranged in advance may be slidably contacted.
In this embodiment, as a method for rotationally driving the charge collection member 11, a dedicated drive source may be used, but a method for transmitting a driving force via the drive transmission system of the image carrier 1 is preferable. Further, the to-be-charged recovery member 11 is frictionally charged at the contact portion with the fixedly arranged friction charging member. Further, there is a closest part between the charged collection member 11 to be rotationally driven and the image carrier 1, and a high-intensity electric field is concentrated on the closest part, so that the image carrier is formed. The external additive W on 1 is efficiently recovered by the charged recovery member 11.
Moreover, in the aspect which rotationally drives the to-be-charged collection member 11, the aspect which has the cleaning member (not shown) in which the external additive W electrostatically adsorbed to the to-be-charged collection member 11 is cleaned is preferable.
In this embodiment, from the viewpoint of reducing the number of parts, an embodiment in which the friction charging member 12a and the cleaning member are combined is preferable.

Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings.
Embodiment 1
―Overall configuration of image forming device―
FIG. 5 is an overall configuration diagram of Embodiment 1 of the image forming apparatus to which the present invention is applied.
In this figure, this image forming apparatus 20 is a quadruple tandem full-color image forming apparatus, and has a plurality of color components (in this example, yellow (Y), magenta (M), cyan (C), black (K)). The image forming units 30 (specifically, 30Y, 30M, 30C, and 30K) as image forming units capable of outputting the images are arranged side by side at predetermined intervals in the order of image formation, and face each image forming unit 30. An intermediate transfer body 40 capable of temporarily holding an image formed by each image forming unit 30 is disposed at the site, and the image held on the intermediate transfer body 40 is recorded by a batch transfer device 50. After batch transfer to P, the fixing device 60 fixes the image transferred onto the recording material P. Reference numeral 70 denotes a recording material conveyance system for conveying the recording material P to the batch transfer portion.

<Image forming unit>
Each of the image forming units 30 (30Y to 30K) includes a drum-shaped photoreceptor 31 as an image carrier having a photoreceptor layer on the surface, a charging device 32 that uniformly charges the photoreceptor 31, and a uniform An exposure device 33 that forms an electrostatic latent image by irradiating the charged photoreceptor 31 with image light, and a toner image (image) by transferring toner to the electrostatic latent image formed on the photoreceptor 31. A developing device 34, a cleaning device 36 for cleaning toner remaining on the photoconductor 31 after primary transfer of the toner image on the photoconductor 31 to the intermediate transfer body 40, and a rotation direction of the photoconductor 31 relative to the cleaning device 36. An external additive collecting device 37 that is provided on the downstream side and collects the external additive remaining on the photosensitive member 31 that has passed through the cleaning device 36.
In this example, in the image forming unit 30, the photosensitive member 31, the charging device 32, the developing device 34, the cleaning device 36, and the external additive collecting device 37 are configured as a process cartridge integrated together in advance. The process cartridge is detachably attached to the housing of the image forming apparatus in order to be exchangeable for each color component.
Here, the photoreceptor 31 is obtained by laminating and forming a photosensitive layer on a conductive metal base having a diameter of about 20 to 100 mm, for example. This photosensitive layer is a function-separated type in which a charge generation layer and a charge transport layer are sequentially laminated. Usually, it has a high resistance, but its specific resistance is changed by light irradiation (specifically, it has a low resistance by light irradiation). And has the property of becoming conductive).
As the charging device 32, for example, a scorotron is used, but is not limited to this, and a device using contact or non-contact type charging members such as corotron, various other dischargers, roll shape / blade shape, etc. You can select as appropriate.
As the exposure device 33, a laser scanning device, an LED array, or the like is used.
The developing device 34 has a developing container 34a that opens opposite to the photoreceptor 31 and accommodates a two-component developer, and faces the opening of the developing container 34a, and a developing roll that can hold and convey the developer 34b is disposed. In the developing container 34a, an agitating / conveying member (not shown) capable of agitating and conveying the two-component developer and a layer regulating member (not shown) in which the layer thickness of the developer held on the developing roll 34b is regulated. )) And other functional members are incorporated.
As the developer toner used in this example, for example, toner produced by an emulsion polymerization method can be used, but not limited to this production method, for example, suspension polymerization method, suspension granulation method, It may be produced by a dissolution suspension method, a kneading pulverization method, or the like. Here, the particle size of the toner has a large influence on the image quality, and the smaller the particle size, the better the image quality. However, if the particle size is small, the developability deteriorates and the handling becomes difficult, so the average particle size is 3 μm or more and 10 μm or less. Is desirable. Further, an appropriate amount of silica or titania having an average particle diameter of about 10 to 150 nm is externally added to the toner as a charge control agent or a transfer aid. In this example, silica having a relatively large particle diameter is externally added in order to ensure particularly cleanability and transfer maintenance. Specifically, silica having a number average particle diameter of about 100 to 150 nm is externally added. The “number average particle diameter” referred to here is determined by the equivalent circle diameter (Heywood diameter) by a microscope method based on JIS Z 8901, and a scanning electron microscope (SEM) was used as the microscope.
The details of the cleaning device 36 and its peripheral configuration will be described later.

<Intermediate transfer member and its peripheral configuration>
The intermediate transfer member 40 is composed of an endless belt member that is circulated and rotated by a plurality of (three in this example) stretching rolls 41 to 43. For example, the intermediate transfer body 40 is a driving roll that can be driven to rotate. Driven, a predetermined tension is applied using the tension roll 42 as a tension adjustment roll.
In this example, the intermediate transfer member 40 has a surface resistivity of 10 by dispersing a substance for imparting conductivity such as carbon or an ion conductive substance in a resin material such as polyimide, polyamideimide, polycarbonate, or fluorine resin. It is formed by adjusting to about ¹⁰ to 10 ¹² Ω / □ (measurement voltage: 100 V).
Also, a primary transfer device 45 is disposed on the back surface of the intermediate transfer body 40 facing the photoconductor 31 of each image forming unit 30. The primary transfer device 45 applies, for example, a predetermined primary transfer voltage. The toner image on each photoconductor 31 is primarily transferred to the intermediate transfer body 40.
Further, an intermediate transfer body cleaning device 46 is disposed in a portion of the intermediate transfer body 40 that faces the stretching roll 41. The intermediate transfer body cleaning device 46 is, for example, a plate-like shape that contacts the surface of the intermediate transfer body 40. The residual toner on the intermediate transfer body 40 is cleaned.

<Batch transfer device>
The batch transfer device 50 has a secondary transfer roll 51 on the surface of the intermediate transfer body 40 facing the stretch roll 43 of the intermediate transfer body 40, and the stretch roll 43 facing the secondary transfer roll 51 is connected to the counter electrode. Also used as a roll, by applying a secondary transfer voltage to the stretching roll 43 or the secondary transfer roll 51, a transfer electric field is generated in the transfer area between both rolls, and the recording material P conveyed by the transfer electric field is applied to the recording material P On the other hand, the toner image on the intermediate transfer body 40 is transferred collectively (secondary transfer).
<Fixing device>
The fixing device 60 may be appropriately selected as long as it can transfer an unfixed toner image on the recording material P. For example, a heating fixing roll 61 including a heating source and the recording material between the heating fixing roll 61 and the fixing device 60 may be selected. An embodiment having a pressure fixing roll 62 that is arranged to press and convey P and rolls together with the heat fixing roll 61 is exemplified.
<Recording material conveyance system>
The recording material conveyance system 70 includes a recording material accommodation device 71 in which the recording material P is accommodated so that it can be sent out for each sheet. The recording material P delivered from the recording material accommodation device 71 is conveyed along the conveyance path 72. In the transport path 72, an alignment roll 73 for aligning the supply timing of the recording material P to the batch transfer site is disposed before the batch transfer site, and from the batch transfer site in the transport path 72. In addition, by disposing a conveyance belt 74 on the downstream side in the conveyance direction of the recording material P, the recording material P after batch transfer is conveyed toward the fixing device 60, and a discharge roll 75 is disposed immediately after the fixing device 60. Thus, the recording material P is discharged toward a recording material discharge receiver (not shown).

-Basic image forming operation of image forming device-
A basic image forming operation of the image forming apparatus according to the present embodiment will be described.
In each image forming unit 30 (30Y to 30K), each color component image is formed on the photoreceptor 31.
Hereinafter, an operation of forming a yellow image in the image forming unit 30Y will be described.
First, prior to the operation, the surface of the photoreceptor 31 is charged to a predetermined potential (for example, a potential of about −600 V to −800 V) by the charging device 32. Thereafter, a light beam such as a laser beam is output from the exposure device 33 to the surface of the charged photoreceptor 31 according to the yellow image data sent from a control unit (not shown). This light beam is applied to the photosensitive layer on the surface of the photoconductor 31, whereby an electrostatic latent image of a yellow print pattern is formed on the surface of the photoconductor 31. The electrostatic latent image here is an image formed on the surface of the charged photoconductor 31, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the light beam, and the charged charge on the surface of the photoconductor 31. On the other hand, it is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the light beam.
The electrostatic latent image formed on the photoconductor 31 in this way is rotated to a predetermined development position by the rotation of the photoconductor 31. At this development position, the electrostatic latent image on the photoconductor 31 is converted into a visible image (toner image) by the developing device 34. In the developing device 34, for example, yellow toner having an average particle diameter of 3 to 8 [mu] m manufactured by an emulsion polymerization method is accommodated. The yellow toner is triboelectrically charged by being stirred inside the developing device 34 and has a charge of the same polarity (−) as the charge on the surface of the photoreceptor 31. As the surface of the photosensitive member 31 passes through the developing device 34, the yellow toner is electrostatically attached only to the latent image portion on the surface of the photosensitive member 31, and the electrostatic latent image is developed by the yellow toner. The The photoconductor 31 continues to rotate, and the yellow toner image developed on the surface of the photoconductor 31 is conveyed to a predetermined primary transfer position. When the yellow toner image on the surface of the photoconductor 31 is conveyed to the primary transfer position, a predetermined primary transfer voltage is applied to the primary transfer device 45 (primary transfer roll in this example), and the photoconductor 31 moves toward the primary transfer device 45. The electrostatic force acts on the toner image, and the toner image on the surface of the photoreceptor 31 is transferred to the surface of the intermediate transfer member 40.
At this time, the applied primary transfer voltage is a (+) polarity opposite to the polarity (−) of the toner. For example, in the image forming unit 30Y, a constant current control is performed to about +20 to 30 μA by a control unit (not shown). Has been. On the other hand, the transfer residual toner on the surface of the photoreceptor 31 is cleaned by the cleaning device 36.

Further, the primary transfer voltage applied to the primary transfer device 45 subsequent to the second image forming unit 30M after the first image forming unit 30Y is controlled in the same manner as described above. Thus, the intermediate transfer body 40 to which the yellow toner image has been transferred by the first image forming unit 30Y is sequentially conveyed through the second to fourth image forming units 30M, 30C, and 30K, and the toner images of the respective colors are similarly formed. Overlaid and multiple transferred. The intermediate transfer member 40 on which the toner images of all colors are transferred in multiple numbers through the first to fourth image forming units 30 (30Y to 30K) is conveyed in the direction of the arrow and is opposed to the inner surface of the intermediate transfer member 40. (Stretching roll) 43 and a secondary transfer roll 51 arranged on the image holding surface side of the intermediate transfer body 40 are reached to a collective transfer site.
On the other hand, the recording material P is supplied at a predetermined timing after the recording material P is aligned to the batch transfer portion by the alignment roller 73 via the recording material conveyance system 70, and a predetermined secondary transfer voltage is applied to the secondary transfer roll, for example. 51 is applied. The secondary transfer voltage applied at this time is the polarity (−) opposite to the polarity (−) of the toner, and the electrostatic force from the intermediate transfer body 40 toward the recording material P acts on the toner image, and the surface of the intermediate transfer body 40 The toner image is transferred onto the surface of the recording material P. In this example, the secondary transfer voltage is determined according to the resistance detected by a resistance detection means (not shown) for detecting the resistance of the batch transfer site, and is controlled by a constant voltage.
Thereafter, the recording material P is fed into the fixing device 60, the toner image is heated and pressurized, and the color-superposed toner image is melted and fixed on the surface of the recording material P. Thus, the recording material P on which the fixing of the color image has been completed is carried out toward a recording material discharge receiver (not shown), and a series of color image forming operations is completed. The residual toner on the intermediate transfer member 40 is cleaned by the intermediate transfer member cleaning device 46.

Next, the cleaning device 36 and its peripheral configuration will be described in detail.
-Cleaning device and its peripheral configuration-
FIG. 6 is an explanatory view showing the cleaning device 36 and its peripheral configuration.
<Cleaning device>
In the figure, the cleaning device 36 has a cleaning container 81 that is disposed in the vicinity of the photoconductor 31 and opens on the side facing the photoconductor 31, and the rotation of the photoconductor 31 out of the opening edge of the cleaning container 81. A cleaning blade 82 is provided at a portion (on the upper edge of the opening in FIG. 6) located on the downstream side in the direction.
Here, the cleaning blade 82 is a cleaning member formed in a plate shape with a predetermined thickness by an elastic material, and the material of the cleaning blade 82 has mechanical properties such as wear resistance, chipping resistance, and creep resistance. For example, excellent thermosetting polyurethane rubber is used, but the invention is not limited thereto, and functional rubber materials such as silicone rubber, fluorine rubber, ethylene / propylene / diene rubber may be widely used. In addition, as a mounting structure of the cleaning blade 82, a support bracket 83 made of a sheet metal having a substantially L-shaped cross section is fixed to the upper edge of the opening of the cleaning container 81 with a stopper 84 such as a screw. The base of the cleaning blade 82 is bonded to the surface facing the body 31, and the protruding portion protruding from the bonded portion of the cleaning blade 82 is extended in a direction against the rotation direction of the photosensitive member 31, and the leading edge of the protruding portion For example, the contact portion may be in contact with the surface of the photoreceptor 31. In this example, the pressing method of the cleaning blade 82 employs a constant displacement method (a method of displacing the tip edge portion of the cleaning blade 82 by a predetermined amount) with a simple structure and low cost. A predetermined pressure is obtained based on the elastic coefficient of the blade 82 and the amount of displacement thereof. However, the pressurization method of the cleaning blade 82 is not limited to the constant displacement method, and for example, a constant load method in which the contact pressure hardly changes with time may be used.
Further, a seal member 85 is fixed to a portion (the lower edge of the opening in FIG. 6) of the opening edge of the cleaning container 81 located on the upstream side in the rotation direction of the photosensitive member 31. The seal member 85 is made of a resin film having flexibility (for example, a thermoplastic polyurethane film having a thickness of 0.1 mm) or the like, and the protruding portion that protrudes from the fixed portion extends along the rotation direction of the photoreceptor 31. In this state, it is brought into contact with the photosensitive member 31 in a state of extending in the direction, and the gap between the photosensitive member 31 and the cleaning container 81 is almost closed, and waste toner or the like accommodated in the cleaning container 81 is prevented from leaking outside. .
Further, inside the cleaning container 81, a conveying member 86 for conveying the waste toner accommodated along the axial direction of the photosensitive member 31 is disposed.

In the cleaning device 36 having such a configuration, as shown in FIG. 6, the transfer residual toner T remaining on the surface of the photoconductor 31 passes through the contact portion between the seal member 85 and the photoconductor 31 as it is, and then is cleaned. Scraped by 82. The toner T scraped off by the cleaning blade 82 is once stored in the cleaning container 81, and is finally transported and discharged to the outside of the cleaning container 81 by the transport member 86.
However, in such a cleaning device 36, when the tip of the cleaning blade 82 is worn by rubbing against the photoreceptor 31, or when the coefficient of friction of the surface of the photoreceptor 31 is high, the tip of the cleaning blade 82 is When the blocking force of the toner T is reduced due to irregular deformation, the external additive W having a small particle size is likely to slip through the cleaning blade 82. In particular, the silica used as the external additive W has a small particle size and is firmly attached to the surface of the photoreceptor 31 by van der Waals force or the like, so that it can be completely cleaned with the scraping force by the cleaning blade 82. Therefore, it is easy to slip through the contact portion between the cleaning blade 82 and the photosensitive member 31.

<External additive recovery device>
Among such slipping-out phenomenon of the external additive W, especially large-diameter silica has a concern that a ghost image is likely to be generated during continuous printing or a factor of image quality deterioration as described above. From the viewpoint of avoidance, an external additive recovery device 37 is provided.
As shown in FIGS. 7 and 8A and 8B, the external additive recovery device 37 is provided with a support base 110 having, for example, a substantially L-shaped cross section along the axial direction of the photoreceptor 31. Then, the support part 111 which is one arm part of the support base material 110 is disposed so as to face the photoconductor 31, and the plate-like charged recovery member 100 is bonded and fixed to the support part 111 of the support base material 110. Is.
In this example, the support base 110 is made of, for example, a leaf spring material, and is attached to the housing (not shown) of the process cartridge via a stopper (not shown) such as a screw on the other arm. It is fixed by fixing 112. The support base 110 is not limited to a leaf spring material, and may be appropriately selected from metal, resin, and the like.
Further, in this example, the charge collection member 100 is made of a long plate-like member extending in the axial direction of the photoconductor 31 and is made of a material having a charged column on the plus side of silica as the external additive W. In particular, a material on the positive side in the charged column is preferable. Furthermore, in this example, the to-be-charged recovery member 100 is required to be made of a material that is on the plus side of the charge train with respect to the surface material of the photoreceptor 31.
That is, as shown in FIG. 9, if the charged column of silica as the external additive W is Cw, the charged column of the photosensitive member 31 is Cp, and the charged column of the charged member 100 is Ck, the following relationship is satisfied.
+ ← Ck> Cw →-
+ ← Ck> Cp →-
For example, if the surface material of the photoconductor 31 is polycarbonate, the charged collection member 100 may be selected from a material having a charged column on the plus side. In particular, Nylon (registered trademark), for example, is selected as a preferable material if a material on the positive side in the charging train is selected, and a material having excellent wear resistance and a low surface friction coefficient is selected. The Of course, any material other than nylon (registered trademark) can be used as long as it is on the plus side of the polycarbonate.

Further, in the present embodiment, as shown in FIGS. 7 and 8A and 8B, the charged collection member 100 is rotated by the charged collection plate 101 and the rotation of the photosensitive member 31 of the charged collection plate 101. And a protrusion 105 that is integrally formed so as to protrude toward the photosensitive member 31 at the downstream end in the moving direction.
In this example, the charged collection plate 101 is set to a length dimension that includes at least the image forming area m of the photoconductor 31, and the surface facing the photoconductor 31 is relative to the radius of curvature Rp of the photoconductor 31. It has a curved portion 102 that is curved with a concentric curvature radius Rk.
Further, the protrusion 105 is provided so as to extend linearly corresponding to the length dimension of the charged collection plate 101, and in this example, the image forming area m of the photoreceptor 31 and the non-image forming areas located on both sides thereof. Are also partly provided.
In particular, in this example, the protrusion 105 has a curved surface portion 106 whose tip is formed in a curved shape, and is arranged in contact with the surface of the photoreceptor 31 via the curved surface portion 106.
Furthermore, in the present embodiment, the charge collection member 100 is supported by the support base 110 and the protrusion 105 is disposed in contact with the surface of the photoreceptor 31, so that the charge collection plate 101 and the surface of the photoreceptor 31 are arranged. A minute gap 120 is formed between the two.
In particular, in the present embodiment, since the opposing surface of the charged collection plate 101 is the curved portion 102 that is curved along the surface shape of the photoreceptor 31, the gap portion 120 has a predetermined substantially uniform spacing dimension d. It is formed with.
The gap dimension d of the gap 120 will be described in detail later. Silica as the external additive W remaining on the photosensitive member 31 when the member to be charged 100 is frictionally charged by the photosensitive member 31 is used. It is necessary to select an electric field E necessary for electrostatic recovery.
Therefore, it is preferable that the gap dimension d of the gap portion 120 is narrow in that the electrostatic force on the silica acts more strongly. Preferably, the upper limit is 1 mm or less, more preferably 0.5 mm or less, and the lower limit is set to be about 0.01 mm in consideration of mechanical accuracy.

The external additive recovery apparatus 37 according to the present embodiment operates on the following operation principle.
First, when each image forming unit 30 performs an image forming operation, the photoreceptor 31 rotates at a predetermined process speed vp as shown in FIGS.
In this state, the protrusion 105 of the member to be charged 100 is frictionally charged to (+) by rubbing against the photoreceptor 31, and the entire member to be charged 100 is frictionally charged to (+). As a result, a charge (positive polarity) is generated in the charged collection member 100 that is frictionally charged, and due to this charge, the gap portion 120 between the curved portion 102 of the charged collection member 100 and the photoconductor 31 is substantially uniform. An electric field E is generated.
On the other hand, the silica as the external additive W has a strong tendency to be negatively charged, and the silica as the external additive W that has passed through the cleaning blade 82 of the cleaning device 36 is charged to (−).
In this state, when the silica on the photosensitive member 31 reaches the gap 120 (for example, the region A in FIG. 7) of the charged member 100 as the photosensitive member 31 rotates, as shown in FIG. The silica on 31 receives electrostatic attraction force due to the electric field E in the gap 120 and flies through the gap 120 in the direction of the arrow indicated by the dotted line in FIG. 9 to curve the charged collection plate 101 of the charged collection member 100. The part 102 is electrostatically attracted. In this state, the to-be-charged recovery member 100 recovers silica as the external additive W.
At this time, since the curved portion 102 of the charged member 100 is opposed to the surface of the photosensitive member 31 through the gap portion 120 having a substantially uniform spacing d, the curved portion of the charged member 100 is charged. A substantially uniform electric field strength acts on the entire region 102, and the entire curved portion 102 functions as a silica recovery surface. For this reason, the silica as the external additive W on the photosensitive member 31 is electrostatically adsorbed over a wide range toward the exposed surface other than the portion where the silica has already been collected in the curved portion 102 of the charged collection member 100. The

Further, since a large amount of untransferred toner T remaining on the surface of the photoconductor 31 is present in the image forming area m of the photoconductor 31, silica as an external additive W that passes through the cleaning device 36 is also an image of the photoconductor 31. Although there are many in the formation region m, as described above, almost all of the silica on the photoconductor 31 is collected in the charged collection member 100 in the region of the gap portion 120 of the charged collection member 100, so that the charged collection is performed. Even if the protrusion 105 of the member 100 is in contact with the image forming area m of the photoconductor 31, the external additive W on the photoconductor 31 is provided at the contact portion between the protrusion 105 and the photoconductor 31. As a result, the silica hardly reaches, and the silica hardly stays at the contact site or passes through the contact site.
For this reason, in the present embodiment, silica as the external additive W hardly reaches the charged portion of the photosensitive member 31 by the charging device 32, so that, for example, along with the discharging action of the scorotron as the charging device 32. There is no concern that the silica on the photoconductor 31 adheres to the discharge wires 321 and the grid 322, etc., causing a charging failure. Even if the charging device 32 is, for example, a charging roll in contact with the photoreceptor 31, the silica on the photoreceptor 31 hardly adheres to the charging roll, so that the silica adheres to the charging roll. There is no concern about poor charging due to this.
Further, since the protrusion 105 of the member to be charged 100 is disposed in contact with the surface of the photoconductor 31 via the curved surface portion 106, the sliding resistance at the contact portion between the protrusion 105 and the photoconductor 31 is reduced. Accordingly, the rotation operation of the photosensitive member 31 is stably maintained, and the wear of the protrusion 105 is also reduced.

◎ Deformation form 1-1
In the present embodiment, the protrusion 105 of the member to be charged 100 is formed to extend linearly, but is not limited to this, and for example, as shown in FIG. You may make it form separately in the location (for example, two places near the both ends of a longitudinal direction).
◎ Deformation form 1-2
Further, in the present embodiment, the charged collection member 100 is entirely composed of silica as the external additive W and a material in which the charged column is positioned on the plus side with respect to the photoreceptor 31, but is not limited thereto. A coating layer 103 is provided on a surface other than the surface to be bonded to the support substrate 110 of the member to be charged (charged collecting plate 101 + projection 105), and the external additive W is used as the material of the coating layer 103. A material in which the charged column is positioned on the plus side with respect to the silica and the photoconductor 31 may be used. In this example, it is possible to arbitrarily select a material other than the covering layer 103 in the charged collection member 100.

Embodiment 2
FIG. 11 is an explanatory diagram showing a main part of the image forming apparatus according to the second embodiment.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but includes an external additive collecting device 37 different from that of the first embodiment. Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
In the same figure, the external additive recovery device 37 has a support base 110 similar to that of the eleventh embodiment, but uses a charged recovery member 100 different from the first embodiment.
In this example, as shown in FIGS. 11 and 12A and 12B, the charged collection member 100 corresponds to at least the image forming area m of the photoreceptor 31 and a part of the non-image forming areas on both sides thereof. The charging recovery plate 101 extending in the axial direction of the photosensitive member 31 so as to cover the range, and a single unit are formed so as to protrude toward the photosensitive member 31 at portions corresponding to the corners of the charging recovery plate 101. A plurality of (four in this example) protrusions 130 (specifically, 130a to 130d).
Here, as in the first embodiment, the surface of the charged recovery plate 101 facing the surface of the photoconductor 31 is configured as a curved portion 102.
On the other hand, the protrusion 130 (130a to 130d) includes a protrusion 131 that contacts the surface of the photoconductor 31 corresponding to a non-image forming area other than the image forming area m of the photoconductor 31. The spherical portion 132 is used.

Also in the present embodiment, the to-be-charged recovery member 100 is frictionally charged by the photosensitive member 31 through the protrusion 130 as in the first embodiment. However, in this embodiment, the protrusion 130 is charged. Is in contact with a non-image forming area other than the image forming area m of the photoreceptor 31, and silica as an external additive W and transfer residual toner T are hardly present in the non-image forming area. Silica as the external additive W or the transfer residual toner T hardly adheres to the contact portion between the portion 130 and the photosensitive member 31 and filming, and the frictional charging by the protrusion 130 is maintained well over a long period of time. A stable external additive collecting operation is performed by the charged collection member 100.
In this example, since the tip of the protrusion 130 is configured as a spherical portion 132, the sliding resistance between the protrusion 130 and the photoconductor 31 is small, and the rotation operation of the photoconductor 31 is stable. In addition, the wear of the protrusion 130 is reduced.
In the present embodiment, four protrusions 130 are provided corresponding to the respective corners of the charged collection plate 101. However, the present invention is not limited to this. The protrusions 130 may be provided corresponding to the two corners located on the downstream side in the rotation direction of the photoconductor 31, or non-image formation of the photoconductor 31 instead of each corner of the charged recovery plate 101. Of course, the design may be changed as appropriate, such as providing linear or dot-like protrusions 130 corresponding to both sides corresponding to the region.

Embodiment 3
FIG. 13 is an explanatory diagram showing a main part of the image forming apparatus according to the third embodiment.
In the figure, the basic configuration of the image forming apparatus is substantially the same as in the first and second embodiments, but includes an external additive collecting device 37 that is different from the first and second embodiments. Components similar to those in the first and second embodiments are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
As shown in FIGS. 13 and 14 (a) and 14 (b), the external additive recovery device 37 includes a charged recovery member 140 disposed opposite to the photosensitive member 31, and a rotation of the photosensitive member 31. And a frictional charging mechanism 150 that frictionally charges the member to be charged 140.
In this example, the charged collection member 140 includes a rotatable charged collection roll 141, and this charged collection roll 141 extends along the axial direction of the photosensitive member 31, and the gap 120 ( They are arranged in a non-contact manner via the spacing dimension d).
On the other hand, the frictional charging mechanism 150 rotates and drives the charged collection roll 141 when the photosensitive member 31 rotates, and can rub one side surface of a plate-like frictional charging member 151 fixedly arranged in advance on the charged collection roll 141. It was made to contact.

Here, the frictional charging member 151 is, for example, bonded and fixed to a support base material 152 that is fixed to a housing of a process cartridge (not shown) with a stopper (not shown) such as a screw, and contacts the charged collection roll 141. Has been placed. In order to maintain the contact state between the frictional charging member 151 and the charged collection roll 141, the support base 152 is made of a leaf spring material, and the frictional charging member 151 is pressed against the charged collection roll 141 with a predetermined pressure. It is preferable.
In particular, in this example, the charged collection roll 141 differs from the first and second embodiments in that it is frictionally charged by the dedicated friction charging member 152, so that the selection range of the material of the charged collection roll 141 is the first and second embodiments. It becomes wider than 2.
That is, it is not necessary to consider the charge train with the photoreceptor 31 for the charged collection roll 141, and basically, a material having a charge train on the plus side of silica as the external additive W can be selected. Specifically, synthetic rubber such as urethane rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, nitrile rubber, butylene rubber, polysulfide rubber, acrylic rubber, ethylene propylene rubber, and natural rubber can be used. High hardness and low friction coefficient are good. In addition, plastic materials such as polyethylene, polyethylene terephthalate (PET), polypropylene, polyvinyl chloride, acrylic resin, polystyrene, polyacetal, polyimide, polyamideimide, phenol resin, epoxy resin, polyester resin, melamine resin, and polyurethane can also be used. Furthermore, glass is suitable because it has a strong positive chargeability.
In addition, as the to-be-charged collection roll 141, the whole may be comprised with the material mentioned above, for example, you may make it comprise the coating layer of the surface of a roll main body with the material mentioned above.
Further, the frictional charging member 151 is arbitrarily selected from materials in which the charge train is on the minus side of the charged collection roll 141.
Further, as shown in FIG. 14B, the drive system 160 of the charged collection roll 141 used in this example is provided with a drive transmission gear 161 coaxially with the photoreceptor 31, for example, and coaxial with the charged collection roll 141. A driven transmission gear 162 that meshes with the drive transmission gear 161 is provided to transmit a rotational driving force to the charged collection roll 141 via the drive transmission gear 161 and the driven transmission gear 162 when the photosensitive member 31 rotates. Reference numeral 163 denotes a drive motor as a drive source of the photoconductor 31.
The drive system of the charged collection roll 141 is an embodiment using the drive system of the photoconductor 31, but is not limited to this, and it is needless to say that a dedicated drive system may be used.

According to the present embodiment, the external additive recovery device 37 operates as follows.
First, when the photosensitive member 31 is rotationally driven, as shown in FIG. 14B, the charged collection roll 141 is moved via the drive system 160 (the drive transmission gear 161 and the driven transmission gear 162) of the charged collection roll 141. Start rotating.
In this state, as shown in FIG. 14A, the frictional charging member 151 rubs at the contact portion with the charged collection roll 141 (S region in FIG. 14A), and the charged collection roll 141 is charged to (+) by the frictional charging member 151, and a charge associated with the frictional charging is generated.
Then, an electric field E based on this electric charge is intensively generated in the gap 120 between the charged collection roll 141 and the surface of the photosensitive member 31, and silica as the external additive W on the photosensitive member 31 is collected and charged. It is electrostatically attracted to the roll 141 and collected.
In this example, the charged collection roll 141 is driven to rotate, and the collected silica passes through the contact portion between the charged collection roll 141 and the friction charging member 151, but the silica is placed on the charged collection roll 141 side. Since it is electrostatically adsorbed, there is no concern that it will stay unnecessarily at the contact site.
Needless to say, a cleaning member for removing the silica as the external additive W collected on the charged collection roll 141 may be added as necessary.

◎ Deformation 3-1
In the present embodiment, one side surface of the plate-shaped frictional charging member 151 is in contact with the charged collection roll 141, but the present invention is not limited to this. For example, as shown in the region S in FIG. The leading edge portion 153 of the frictional charging member 151 may be disposed in contact with the charged collection roll 141.
In this aspect, since the frictional force between the frictional charging member 151 and the charged collection roll 141 can be set high, the frictional charging performance with respect to the charged collection roll 141 can be improved, and the frictional force can be improved. Since the leading edge portion 153 of the charging member 151 also serves to scrape off the silica as the external additive W collected on the charged collection roll 141, the friction charging member 151 also has a cleaning member for cleaning the charged collection roll 141. In other words, the charged collection roll 141 can be always kept in a refreshed state. In this aspect, since the friction charging member 151 can be made of, for example, urethane rubber already used as a cleaning member, versatility can be further enhanced in terms of material selection.
◎ Deformation 3-2
Further, in the present embodiment, the charged collection member 140 is configured to be a charged collection roll 141 that can be rotationally driven and the friction charging member 150 is fixedly arranged. However, the present invention is not limited to this. As shown in FIG. 16, the friction charging member 151 of the friction charging mechanism 150 is a friction charging roll 155 that can be driven to rotate, and the charged collection plate 145 that is disposed in a non-contact manner as the charged collection member 140 facing the photoreceptor 31. The friction charging roll 155 is driven to rotate by using a drive system substantially the same as that of the first embodiment, and the friction charging roll 155 and the charged collection plate 145 are rubbed to each other. 145 may be triboelectrically charged.
In this example, the charge collection plate 145 is disposed in a non-contact manner with respect to the photoconductor 31, but changes in the gap 120 due to vibration caused by contact with the frictional charging roll 155 that is driven to rotate are detected. From the standpoint of suppression, positioning protrusions (not shown) that protrude toward the non-image forming area of the surface of the photoreceptor 31 are provided at the respective corners of the charged recovery plate 145, and the positioning protrusions are used to It is preferable to position the charge collection plate 145.

Next, using the image forming apparatus according to Embodiment 1 as Example 1, an experiment for verifying the effect of the external additive recovery apparatus 37 was performed. A mode in which the external additive recovery device 37 is not provided is referred to as Comparative Example 1.
The experimental conditions are as follows.
In the verification experiment, an on-demand printing machine DocuColor8000 manufactured by Fuji Xerox was used, and an external additive collecting device 37 was incorporated between the cleaning device 36 and the charging device 32.
-Toner used: Toner having an average particle diameter of 5.8 μm produced by an emulsion polymerization method (silica having a number average particle diameter of 100 to 150 nm is externally added)
Cleaning blade: Urethane rubber blade with a pressure of 39.2 N / m Sealing member: Thermoplastic polyurethane film with a thickness of 0.1 mm Further, the evaluation method is a continuous ghost evaluation chart (for example, see FIG. 2A). Fifty sheets were printed, and the ghost level of the 50th sheet was evaluated by ΔL *. ΔL * referred to here means, for example, the brightness difference between the region where the ghost image IMg exists in FIG. 2B and the region of the halftone image IM ₂ other than this region.
The evaluation results are shown in FIG.
According to the figure, the smaller the value of ΔL *, the better the ghost level.
In Comparative Example 1, the value of ΔL * was 2.0 and the occurrence of continuous print ghost was observed, whereas in Example 1, the value of ΔL * was reduced to 0.1 and the continuous print ghost was recognized. It is understood that it will improve to a level that is not done.
Moreover, regarding the improvement effect of the external additive recovery apparatus 37 in Example 1, a running test was performed in order to confirm its maintainability.
The total number of running cycles (total number of rotations of the photoreceptor) is 100,000 cycles. As a result of performing the ghost evaluation in the same manner as described above every 10,000 cycles, the value of ΔL * changes from 0.1 to 0.2 as shown in FIG. 18, and it is determined that it has not changed if the measurement variation is taken into consideration. The sustainability of Example 1 was confirmed.

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 2 ... Latent image formation means, 2a ... Charging means, 2b ... Latent image writing means, 3 ... Development means, 3a ... Developing container, 3b ... Developer holding body, 3c ... Development rotating body, 3d DESCRIPTION OF SYMBOLS ... Magnet member, 3e ... Agitation conveyance member, 4 ... Transfer means, 5 ... Transfer medium, 6 ... Cleaning means, 6a ... Cleaning member, 10 ... External additive collection means, 11 ... Charged collection member, 12 ... Friction charging mechanism , 12a ... frictional charging member, 13 ... gap, E ... electric field, W ... external additive, d ... gap size

Claims (12)

A rotatable image carrier that holds the electrostatic latent image;
A latent image forming means for forming an electrostatic latent image based on an image signal on the image carrier;
A developer holder that holds and conveys the toner, the carrier, and a developer containing an external additive having the same polarity as the toner; and the developer held and conveyed by the developer holder is slid against the image carrier. Developing means for developing the electrostatic latent image formed on the image carrier by the latent image forming means;
Transfer means for transferring the toner image on the image carrier developed by the developing means to a transfer medium;
A cleaning unit that is provided on the downstream side in the rotation direction of the image carrier from the transfer site by the transfer unit, and that cleans the post-transfer residue on the image carrier with a cleaning member that contacts the image carrier;
An external additive collecting means that is provided on the downstream side in the rotation direction of the image holding body with respect to the cleaning portion by the cleaning means, and collects the external additive on the image holding body that has passed through the cleaning portion;
The external additive recovery means includes
It is arranged so as to face the image carrier and extend in a direction intersecting with the rotation direction of the image carrier, and at least the opposite part facing the image carrier has a charged column on the plus side with respect to the external additive. A charged collection member made of a material;
The charged collection member has a friction charging member that is frictionally charged so as to electrostatically attract the external additive, and frictionally charges the charged collection member via the friction charging member when the image carrier rotates. Friction charging mechanism,
The charge collection member is provided between a portion of the charge collection member facing the image carrier and the image carrier, and the charge generated by the frictional charging when the charge collection member is frictionally charged by the friction charging mechanism. A gap in which an electric field based on the external support on the image carrier can act to an extent capable of electrostatic attraction;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The external additive collecting means includes at least a portion to be opposed to the image holding member, a charged collecting member made of a material in which a charged column is positioned on the plus side of the image holding member,
A friction charging mechanism that uses the image holding member as a friction charging member, and has a protruding portion that contacts the image holding member, which is a friction charging member, formed on a part of the member to be charged; Forming equipment. The image forming apparatus according to claim 2.
2. The image forming apparatus according to claim 1, wherein the frictional charging mechanism has a protrusion with a curved end at the charge collection member. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the charge collection member has a facing surface having a shape along a surface shape of the image carrier. The image forming apparatus according to claim 2 or 3,
The frictional charging mechanism forms a protrusion on the downstream side in the rotational movement direction of the image holding member of the charged collection member, and the protrusion of the charged collection member against the image forming region on the surface of the image holding member. An image forming apparatus characterized by bringing a part into contact. The image forming apparatus according to claim 2 or 3,
2. The image forming apparatus according to claim 1, wherein the frictional charging mechanism causes the protrusion of the charged member to be brought into contact with a non-image forming area other than the image forming area on the surface of the image carrier. The image forming apparatus according to claim 2, 3, 5 or 6.
The image forming apparatus according to claim 1, wherein the frictional charging mechanism causes the protrusion of the member to be charged to come into contact with the surface of the image holding member at a linear portion or a plurality of dotted portions. The image forming apparatus according to claim 1.
The external additive recovery means includes
A to-be-charged recovery member disposed opposite to the image carrier via the gap;
An image forming apparatus, comprising: a frictional charging mechanism that causes the frictional charging member to rotate relative to the charged member to be slidably contacted with each other when the image carrier rotates. The image forming apparatus according to claim 8.
The charged collection member is rotatably provided,
The friction charging mechanism rotates the charged collection member when the image carrier rotates, and makes the friction charging member fixedly disposed in advance to the charged collection member slidably contact with the charged collection member. An image forming apparatus. The image forming apparatus according to claim 9.
2. The image forming apparatus according to claim 1, wherein the external additive collecting unit includes a cleaning member for cleaning the external additive electrostatically attracted to the member to be charged. The image forming apparatus according to claim 10.
The image forming apparatus according to claim 1, wherein the external additive collecting means serves as the friction charging member and the cleaning member. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the external additive collecting unit is provided on the upstream side of the rotation direction of the image holding member with respect to a latent image forming part by the latent image forming unit.

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