JP2019159030A - Recovery device and image forming apparatus - Google Patents

Abstract

To provide a recovery device that has an improved ability to recover an attachment from a recording material, and an image forming apparatus including the recovery device.SOLUTION: A recovery device 9 has a recovery roller 92 that rotates in contact with a surface of a recording material P and recovers an attachment from the recording material P. The recovery roller 92 has a conductive substrate 92a and an insulating surface layer 92b provided at an outside of the substrate 92a to form a surface of the recovery roller 92, and the surface layer 92b has a thickness of 5 μm or more and 250 μm or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a collection device that collects deposits from a recording material, and an image forming device such as a copying machine, a printer, and a facsimile machine, which are used in an image forming apparatus that forms an image on a recording material including paper. Is.

  Conventionally, in an image forming apparatus using an electrophotographic method for forming an image on a recording material including paper, paper dust which is attached to the recording material or generated from the paper is removed from the paper. In some cases, a paper dust collecting device (paper dust removing means) for collecting the dust is provided (Patent Document 1). This image forming apparatus includes a paper dust collecting apparatus including a roller pair including a paper dust removing roller on the upstream side in the recording material conveyance direction from the image forming unit. The paper dust collecting device is configured to collect paper dust from the recording material when the recording material passes through the roller pair.

JP 2014-46996 A

  However, according to the study of the present inventor, the conventional paper dust collecting device may not have sufficient paper dust collecting ability (removing ability), and further improvement of the paper dust collecting ability is desired.

  Paper dust generally contains fibers and fillers that are raw materials for paper. In particular, the components of the filler are likely to adhere to and adhere to an image forming portion (developing roller or the like). Paper dust adheres at a level where there is no problem with a small amount, but depending on the type of paper and the number of sheets passed (feeding paper to the image forming unit), the amount of adhesion increases, causing problems such as image defects. There is a case to let you. Image defects caused by paper dust include, for example, a fogging image in which toner is thinly adhered to a white background due to a decrease in the charge amount of toner due to paper dust adhering to the developing roller. Can be mentioned. In order to extend the life of the image forming apparatus, it is desired to further improve the recovery capability of the recovery device that recovers deposits from the recording material.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a collection device with improved collection ability of deposits from a recording material, and an image forming apparatus equipped with the collection device.

  The above object is achieved by the recovery device and the image forming apparatus according to the present invention. In summary, the present invention relates to a recovery apparatus having a recovery roller that rotates in contact with the surface of a recording material and recovers deposits from the recording material. The recovery roller includes a conductive base material and the base material. And an insulating surface layer that forms the surface of the recovery roller, and the thickness of the surface layer is not less than 5 μm and not more than 250 μm.

  According to another aspect of the present invention, an image forming unit that forms an image on a recording material, a supply unit that supplies the recording material to the image forming unit, and a recording material that is supplied to the image forming unit by the supply unit There is provided an image forming apparatus comprising the collection device of the present invention for collecting deposits.

  According to the present invention, it is possible to provide a recovery device with improved recovery capability of deposits from a recording material, and an image forming apparatus including the recovery device.

1 is a longitudinal sectional view of an image forming apparatus. It is a longitudinal cross-sectional view of a collection | recovery apparatus. It is a graph for demonstrating the relationship between the surface potential and surface charge amount for every film thickness of the surface layer of a collection | recovery roller. It is a longitudinal cross-sectional view of the collection | recovery apparatus of another example. It is a longitudinal cross-sectional view of the collection | recovery apparatus of another example. It is a longitudinal cross-sectional view of the collection | recovery apparatus of another example.

  Hereinafter, the collection device and the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 of this embodiment is a laser beam printer using an electrophotographic system.

  The image forming apparatus 100 includes a photosensitive drum 1 that is a drum-type photosensitive member (electrophotographic photosensitive member) as an image carrier that carries a toner image. The photosensitive drum 1 is configured by providing a photosensitive material such as OPC (organic optical semiconductor), amorphous selenium, and amorphous silicon on a cylindrical drum base formed of aluminum, nickel, or the like. The photosensitive drum 1 is rotatably supported by the apparatus main body 110 of the image forming apparatus 100, and is driven to rotate at a predetermined peripheral speed (process speed) in the direction of arrow R1 in the figure by a drive source (not shown).

  The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential having a predetermined polarity (negative polarity in this embodiment) by a charging roller 2 which is a roller-type charging member as a charging unit. During the charging process, a predetermined charging voltage (charging bias) including a negative DC component is applied to the charging roller 2 from a charging power source (not shown). The surface of the charged photosensitive drum 1 is scanned and exposed with a laser beam L modulated based on image information by an exposure device (laser scanner) 3 as an exposure unit, and an electrostatic image (static) is formed on the photosensitive drum 1. An electrostatic latent image) is formed. The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer by a developing device 4 as developing means, and a toner image (developer image) is formed on the photosensitive drum 1. It is formed. The developing device 4 includes a developing roller 4a as a developer carrying member that carries toner and conveys the toner to a portion facing the photosensitive drum 1. During the development process, a predetermined development voltage (development bias) including a negative DC component is applied to the development roller 4a from a development power source (not shown). In this embodiment, an image portion (exposure portion) in which the absolute value of the potential is reduced by exposure after being uniformly charged is the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment). The charged toner adheres to the toner (reversal development). That is, in this embodiment, the normal charging polarity of the toner, which is the charging polarity of the toner at the time of development, is negative.

  A transfer roller 5, which is a roller-type transfer member serving as transfer means, is disposed facing the photosensitive drum 1. The transfer roller 5 is pressed against and brought into contact with the photosensitive drum 1 by a transfer pressure spring (not shown) which is an urging member as an urging means, and the transfer portion where the photosensitive drum 1 and the transfer roller 5 come into contact with each other. (Transfer nip) N is formed. The toner image formed on the photosensitive drum 1 is transferred to a recording material P such as paper (paper) conveyed between the photosensitive drum 1 and the transfer roller 5 by the action of the transfer roller 5 in the transfer portion N. Is done. Here, a case where paper (paper) is used as the recording material P will be described as an example, but the image forming apparatus 100 forms an image on the recording material P other than paper (paper) such as a plastic sheet or cloth. It is something that can be done. The paper P is stored in the cassette 7 and is sent out from the cassette 7 one by one by the feeding roller 8. The paper P is conveyed to the transfer unit N at a predetermined timing after passing through a collecting device 9 that collects paper dust as adhering matter from the recording material P, which will be described in detail later. During the transfer process, a transfer voltage (transfer bias) that is a DC voltage having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the transfer roller 5 by a transfer power source (not shown). Is done. As a result, the toner image on the photosensitive drum 1 is transferred to a predetermined position on the paper P.

  The paper P on which the toner image is transferred and carries an unfixed toner image on the surface is conveyed to a fixing device 12 as a fixing unit. The fixing device 12 heats and pressurizes the paper P carrying an unfixed toner image, thereby fixing (melting, fixing) the toner image on the surface of the paper P. The paper P after the toner image is fixed is discharged (output) to the outside of the apparatus main body 110 of the image forming apparatus 100 by the discharge roller 15.

  In addition, toner (transfer residual toner) that is not transferred onto the sheet P and remains on the surface of the photosensitive drum 1 during the transfer process is simultaneously collected from the surface of the photosensitive drum 1 by the developing device 4 that also serves as a cleaning unit.

  In this embodiment, the photosensitive drum 1, the charging roller 2, the exposure device 3, the developing device 4, the transfer roller 5, and the like constitute an image forming unit 10 that forms an image on the recording material P. In this embodiment, the cassette 7, the feed roller 8, and the like constitute a supply unit 11 that supplies the recording material P to the image forming unit 10.

2. Recovery Device FIG. 2 is a longitudinal sectional view showing a schematic configuration of the recovery device 9 in the present embodiment. In the present embodiment, the collection device 9 includes a conveyance roller 91, a collection roller 92 as a collection member, a scraping member 93, and a collection container 96 as a storage unit. The transport roller 91 is a back surface (first surface) opposite to the front surface (first surface) that is the surface (printing surface) of the paper P that contacts the photosensitive drum 1 in the transfer unit N immediately after passing through the collecting device 9. 2 side). The collection roller 92 contacts the surface (first surface) which is the surface (printing surface) of the paper P that contacts the photosensitive drum 1 in the transfer unit N immediately after passing through the collection device 9. The conveyance roller 91 and the collection roller 92 constitute a collection roller pair. The scraping member 93 scrapes off the paper dust adhering to the collection roller 92 and stores it in the collection container 96.

  The transport roller 91 extends in the width direction of the paper P (direction substantially perpendicular to the transport direction), and is substantially the same as the width of the largest paper P used in the image forming apparatus 100 of this embodiment (or It is a cylindrical roller having a long length. In the present embodiment, the transport roller 91 includes a cored bar and a surface layer provided on the outer periphery of the cored bar. The surface layer is made of a material having a sufficient grip force for transporting the paper P, such as urethane resin.

  The collection roller 92 extends in the width direction of the paper P, and has a cylindrical shape having a length substantially the same (or long) as the width of the largest paper P used in the image forming apparatus 100 of the present embodiment. Laura. In this embodiment, the collection roller 92 includes a conductive base material (core metal) 92a and an insulating surface layer 92b provided on the outer periphery of the base material 92a. The conductive substrate 92a is made of a metal such as aluminum or SUS (stainless steel) as a conductive material. In the present embodiment, as the base material 92a, an aluminum columnar member (core metal) was used. The insulating surface layer 92b is made of resin, glass, or the like as an insulating material. Examples of the resin include fluororesins such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (hereinafter referred to as “PFA”), polyimide, polyamide, polycarbonate, nylon, and the like. Examples of the glass include alumina glass. In this embodiment, as the insulating material, a material that is easily charged by rubbing, in particular, PFA, which is a resin that is easily negatively charged in this embodiment, was used. As will be described in detail later, the thickness of the surface layer 92b is set to 5 μm or more and 250 μm or less. With such a configuration, the collection roller 92 can hold a larger amount of charge on the surface thereof, as will be described in detail later.

Note that typically, conductive substrate 92a has a volume resistivity (23 ℃, 50% RH) is 1 × 10 ⁹ Ωcm or less, insulating surface layer 92b, the volume resistivity (23 ° C., 50% RH) is 1 × 10 ¹⁰ Ωcm or more (mostly 1 × 10 ¹⁷ Ωcm or less).

  The scraping member 93 is a member for scraping off paper dust that is a deposit attached to the collection roller 92. In this embodiment, the scraping member 93 is made of urethane sponge, which is a foamed elastic body. In this embodiment, the scraping member 93 is pressed against and brought into contact with the collection roller 92 by a biasing member (not shown) as a biasing means.

  The collection container 96 accommodates paper dust that is a deposit scraped off from the collection roller 92 by the scraping member 93.

  The conveyance roller 91 and the collection roller 92 are disposed to face each other. In this embodiment, the conveyance roller 91 and the collection roller 92 are pressed against and brought into contact with each other by an urging member (not shown) as an urging unit, and the conveyance roller 91 and the collection roller 92 are in contact with each other. A recovery portion (recovery nip) M to be formed is formed. In the present embodiment, the transport roller 91 and the collection roller 92 are rotationally driven in the directions of arrows R2 and R3 in the drawing by a motor or the like (not shown) as a driving unit, respectively. As a result, the transport roller 91 and the collection roller 92 transport the paper P sandwiched between them.

  The surface of the collection roller 92 is charged by the rubbing caused by the rotational drive. The paper dust that is attached to the paper P or generated from the paper P adheres to the surface of the collection roller 92 when the paper P is nipped and conveyed by the conveyance roller 91 and the collection roller 92. Then, it is removed from the paper P and collected. At this time, the paper dust adheres to the surface of the collection roller 92 due to the contact with the surface of the collection roller 92 and the action of the electric field due to the charged surface charge of the collection roller 92. The paper dust adhering to the surface of the collection roller 92 is scraped off from the surface of the collection roller 92 by the scraping member 93 and stored in the collection container 96.

  Paper is generally made of pulp fibers such as cellulose as a raw material and added with filler components such as calcium carbonate and talc. In the image forming apparatus 100, the fibers and fillers fall out of the paper and become paper dust by rubbing between the papers, rubbing by contact with various members during conveyance, or the like. In addition, paper dust generated at the time of cutting the paper may adhere to the paper. In paper dust, the fiber is often in the form of a fiber having a size of 10 μm to 2 mm, and the filler is often in the form of a powder having an average particle size of several tens of μm. Depending on the type of paper, some papers are prone to slipping off and becoming paper dust. For example, from paper having a fiber to filler weight ratio of fiber: filler = 7: 3, a paper powder having a fiber to filler weight ratio of fiber: filler = 3: 7, ie, a paper powder having a high proportion of filler components. May occur.

3. Principle of Paper Dust Collection As described above, the paper dust of the paper P is not physically contacted with the surface of the collection roller 92 when the paper P is nipped between the conveyance roller 91 and the collection roller 92 and conveyed. The surface of the collecting roller 92 adheres due to the electric field generated by the charged electric charge on the surface.

  The surface of the paper P has minute irregularities. Therefore, even when the paper P is nipped and transported between the transport roller 91 and the recovery roller 91, the contact area between the paper P and the surface of the recovery roller 92 is limited, and the surface of the paper P is substantially the recovery roller. It will have a part which does not contact the surface of 92. That is, because of the unevenness of the surface of the paper P, not all of the surface of the paper P contacts the surface of the collection roller 92. The portion of the paper powder on the surface of the paper P that is not in direct contact with the collection roller 92 is attracted to the collection roller 92 by the action of an electric field due to the surface charge of the collection roller 92 and adheres to the surface of the collection roller 92. Therefore, increasing the surface charge amount of the collection roller 92 is effective as means for increasing the amount of paper powder adhering to the surface of the collection roller 92 and improving the paper powder collection capability of the collection roller 92. In particular, a filler having a relatively small particle size is more easily collected by the action of an electric field than by physical contact, and it is effective to increase the surface charge amount of the collecting roller 92 to improve the paper dust collecting ability. It is. For example, as described above, a paper powder having a fiber to filler weight ratio of fiber: filler = 7: 3 and a fiber to filler weight ratio of fiber: filler = 3: 7, ie, a filler component This is effective when collecting paper powder with a high ratio.

  Actually, the paper dust collecting capacity (paper dust adhesion amount) of the collecting roller 92 depends on the surface charge amount of the charged collecting roller 92. That is, as the surface charge amount of the collection roller 92 increases, the amount of paper powder adhering to the surface increases, and the paper powder collection capability increases.

  Therefore, in this embodiment, the collection roller 92 is configured such that a relatively thin insulating surface layer 92b is provided on the conductive base material 92a. Thereby, the electrostatic capacity of the collection roller 92 can be increased and the surface charge amount can be increased, so that the paper dust collection capability can be improved.

4). FIG. 3 shows the relationship between the surface potential and the surface charge amount for each film thickness (thickness) of the surface layer 92b of the collecting roller 92 using PFA which is an insulating material. It is a graph which shows the result of having confirmed the relationship. The results in FIG. 3 were obtained by charging the surface of the PFA sheet and measuring its surface potential, then contacting the surface of the charged PFA sheet with the SUS plate and measuring the amount of charge transferred to the SUS plate. It is. Specifically, the surface potential and the surface charge amount of the measurement sample were measured by the following measurement procedures (1) and (2), respectively.
(1) Prepare a measurement sample with a PFA sheet (area 20 mm x 20 mm) fixed on a metal fixing base (weight: 114 g), and charge the surface of the measurement sample (PFA sheet side) by friction or the like And measure the surface potential of the PFA sheet.
(2) The surface of the charged PFA sheet of the measurement sample is brought into contact with an SUS plate having an area of 100 mm × 100 mm (pressed by the weight of the metal fixing base), and the surface of the PFA sheet is brought into contact with a coulometer. The charge amount of the SUS plate made is measured.

  As the PFA sheet of the measurement sample, commercially available PFA sheets having a film thickness of 25 μm, 50 μm, 100 μm, 250 μm, and 500 μm were used. The surface potential was measured using a Trek surface potential meter (model 347). Moreover, the measurement of an electric charge used Kasuga Denki Co., Ltd. Coulomb meter (NK-1001A).

  Here, for convenience, not the surface charge amount of the PFA sheet but the charge amount of the SUS plate is measured. In other words, strictly speaking, the amount of the surface charge of the charged PFA sheet that contacts the SUS plate and moves to the SUS plate side is measured. However, since the measurement is performed by bringing the PFA sheet and the SUS plate into contact with each other with a constant pressure (self-weight of the metal fixing base), the contact state between the PFA sheet and the SUS plate is constant. Therefore, the difference in the relationship between the surface potential and the surface charge amount due to the difference in the film thickness of the PFA sheet can be confirmed by the measurement method used here. Here, for the sake of convenience, the magnitude (increase / decrease) relationship between the surface potential and the surface charge amount is expressed as a relationship when compared in terms of absolute values.

As can be seen from FIG. 3, the amount of surface charge increases as the surface potential increases. Further, as can be seen from FIG. 3, the ratio of the change in the surface charge amount with respect to the change in the surface potential varies depending on the film thickness of the PFA sheet, and the surface potential when the film thickness is smaller than when the film thickness is thicker. The rate of change of the surface charge amount with respect to the change of is large. This relationship is expressed by the following (formula-1) showing the relationship between the electric charge and the potential of the plate capacitor.
Q = C · V (Formula-1)
However, C = ε · S / d
Q: Charge V: Potential C: Capacitance ε: Dielectric constant S: Area d: Film thickness

  When the film thickness is thick, the capacitance is smaller and the amount of charge with respect to the potential is smaller than when the film thickness is thin. In FIG. 3, for example, when the film thickness is 50 μm and the film thickness is 500 μm, the surface charge amounts when the surface potential is −1 kV are about −80 nC and about −8 nC, respectively. That is, even with the same surface potential, the surface charge amount is 10 times greater in the case of the film thickness of 50 μm than in the case of the film thickness of 500 μm (1/10 times the film thickness and 10 times the charge amount).

5). Range of surface layer thickness From the results of our experiments and the like, as a measure for improving the paper dust collection capability of the collection roller 92, the surface charge amount of −40 nC or more in the measurement shown in FIG. Is desirable. As the film thickness of the surface layer 92b of the collection roller 92 is reduced, the capacitance of the collection roller 92 can be increased and the amount of charge that can be held on the surface of the collection roller 92 can be increased. It is preferable for improving the powder recovery capability.

  However, when the film thickness of the surface layer 92b of the collection roller 92 is less than 5 μm, it may be difficult to form a uniform film thickness as a roller due to the manufacturing method. In addition, when the film thickness is less than 5 μm, when the life of the image forming apparatus 100 is to be extended, the dielectric breakdown does not occur due to the abrasion of the surface layer 92b due to rubbing or the like. There is a possibility that a leak will occur. If a hole or the like occurs in the surface layer 92b of the collecting roller 92 due to the leak, there is a possibility that a desired paper dust collecting ability cannot be obtained.

  On the other hand, when the film thickness of the surface layer 92b of the collecting roller 92 is thicker than 250 μm, the surface charge amount is reduced with respect to the magnitude of the surface potential, and a desired paper dust collecting ability may not be obtained. When this film thickness is large, the surface potential tends to increase due to rubbing. Then, a discharge or the like is generated to affect a sheet metal in the image forming apparatus 100, and electrical noise is generated, which may cause a malfunction such as a malfunction of the image forming apparatus 100. Although depending on the configuration of the image forming apparatus 100 and the like, in general, charging exceeding 3 kV (−3 kV in the present embodiment) on the surface of the collection roller 92 is not preferable from the viewpoint of the generation of electrical noise as described above.

  As can be seen from FIG. 3, when the film thickness is 25 μm or when the film thickness is 100 μm, the surface potential is −1 kV to −2 kV and the surface charge amount is higher than −40 nC. A sufficient amount can be secured. In the case of a film thickness of 250 μm, the surface potential is about −2.5 kV and the surface charge amount is about −40 nC, which indicates that a desired paper dust collecting ability can be obtained. On the other hand, when the film thickness is larger than 250 μm, for example, when the film thickness is 500 μm, even if the surface potential is set to −4 kV, the surface charge amount is less than −40 nC, which is insufficient for improving the paper dust collecting ability. Further, if the surface potential is larger than −3 kV, there is a possibility that problems such as malfunction of the image forming apparatus 100 may occur due to the generation of electrical noise as described above, which is not preferable. For this reason, making the film thickness thicker than 250 μm is not substantially suitable for improving the paper dust collecting ability.

  Therefore, the thickness of the surface layer 92b of the collection roller 92 is set to 5 μm or more and 250 μm or less.

6). Effect Confirmation In order to confirm the paper dust collecting ability of the collecting roller 92, the amount of paper dust collected when 1K sheets (1000 sheets) of paper are actually passed using the image forming apparatus 100 of this embodiment, and 2K A test for confirming the image after passing the sheet and the image after passing the 10K sheet was performed.

  In this embodiment, the collecting roller 92 is a surface layer 92b formed by coating a 25 μm thick PFA on an aluminum base material 92a having an outer diameter of 16 mm. Further, as a comparative example, a test similar to the present example was performed using a recovery roller 92 in which the surface layer 92b was formed of PFA having a thickness of 500 μm. The configuration and operation of the image forming apparatus 100 according to the comparative example are substantially the same as those of the image forming apparatus 100 according to the present embodiment except for the above point (the thickness of the surface layer 92b of the collecting roller 92). Table 1 shows the results of confirming the recovered amount of paper dust when 1K sheets were passed and the images after passing 2K sheets and after passing 10K sheets.

  As can be seen from Table 1, in the comparative example, the amount of recovered paper dust is 6 mg / 1K sheets, and there is no problem with the image after passing 2K sheets, but the image after passing 10K sheets has an image defect (on the white background). A fogged image with a light toner adhering occurred. This is because the paper dust that could not be sufficiently collected by the collecting unit M is sent to the developing roller 4a via the photosensitive drum 1, and the paper dust adheres to the developing roller 4a as the number of sheets passed increases, This is thought to be due to a decrease in the amount of charged electric charge.

  On the other hand, in this example, the paper dust collection amount was 20 mg / 1K, which was three times or more the paper dust collection amount of the comparative example. The images after passing 2K sheets and after passing 10K sheets were also good.

  In the comparative example, when continuous paper feeding is repeated in a low humidity environment (for example, 15% RH), the surface potential of the collection roller 92 may be −5 kV, and malfunctions such as malfunction due to electrical noise occur. There was a possibility. On the other hand, in the present embodiment, even when continuous paper feeding is repeated in a low humidity environment, the surface potential of the collection roller 92 is smaller than -3 kV, and there is no concern that a problem due to electrical noise occurs.

  As a modification of the present embodiment, a PFA tube having a thickness of 50 μm (Modification 1) and a thickness of 250 μm (Modification 2) is respectively coated on an aluminum base material 92a having an outer diameter of 16 mm. A test similar to the above was performed using the collecting roller 92 on which 92b was formed. However, in the second modification, the contact pressure of the scraping member 93 is set to 1.5 times that of the present embodiment in order to increase the amount of charge on the surface of the collection roller 92 by rubbing. As a result, the amount of recovered paper dust was 17 mg / 1K sheets and 12 mg / 1K sheets in Modification 1 and Modification 2, respectively, which was about twice or more that of the comparative example. Further, in Modification 1 and Modification 2, the images after passing 2K sheets and after 10K were also good. Moreover, in the modification 1 and the modification 2, there was no fear that the malfunction by an electrical noise generate | occur | produces.

7). Capacitance per unit area of the collection roller The capacitance C / S per unit area of the collection roller 92 is calculated from the following formula (Formula-2), which is the calculation formula of the capacitance C of the cylindrical body (Formula- It can be calculated as in 3).
C = 2π × ε × l / (log (b / a)) (Formula-2)
C: Capacitance ε: Dielectric constant (= ε ₀ × ε _r )
ε ₀ : Dielectric constant of vacuum 8.85 × 10 ⁻¹² (F / m)
ε _r : relative dielectric constant l: longitudinal length of cylinder a: inner diameter of cylinder b: outer diameter of cylinder C / S = ε / (b × log (b / a)) (formula-3)
S: Surface area of cylindrical body (= l × 2πb)

For example, in this embodiment, the collection roller 92 has a configuration in which a surface layer 92b of PFA having a thickness of 25 μm is formed on an aluminum base material 92a having an outer diameter of 16 mm. Therefore, from the above (Formula-3), the capacitance C / S per unit area is 1.63 × 10 ⁻⁶ (F / m ² ) (the relative permittivity of PFA is calculated as 2.0). .

That is, the inner diameter a of the cylinder is a = ^16/2 × 10 ⁻³ (mm), the outer diameter b of the cylinder is b = (16/2 + 0.025) × 10 ⁻³ (mm), and the relative dielectric constant ε _Assuming that _r is ε _r = 2.0, from (Equation-3), C / S is
C / S = 8.85 × 10 ⁻¹² × 2.0 / (((16/2 + 0.025) × 10 ⁻³ ) × log (((16/2 + 0.025) × 10 ⁻³ ) / (16 / 2 × 10 ⁻³ )))
= 1.63 × 10 ⁻⁶ (F / m ² )
It becomes.

On the other hand, when the thickness of the surface layer 92b is 500 μm (comparative example), the capacitance C / S per unit area is 7.91 × 10 ⁻⁸ (F / m ² ).

That is, the inner diameter a of the cylinder is a = ^16/2 × 10 ⁻³ (mm), the outer diameter b of the cylinder is b = ( ^16/2 + 0.5) × 10 ⁻³ (mm), and the relative dielectric constant ε When the _r and epsilon _r = 2.0, the C / S from the (formula -3),
C / S = 8.85 × 10 ⁻¹² × 2.0 / (((16/2 + 0.5) × 10 ⁻³ ) × log (((16/2 + 0.5) × 10 ⁻³ ) / (16 / 2 × 10 ⁻³ )))
= 7.91 × 10 ⁻⁸ (F / m ² )
It becomes.

As described above, the capacitance per unit area is defined by the film thickness and the relative dielectric constant. It is assumed that the relative dielectric constant of an insulating material such as a general resin is about 1.0 to 8.0. In this case, the capacitance C / S per unit area of the collecting roller 92 having a thickness of the surface layer 92b of 5 μm or more and 250 μm or less is in the following range.
8.03 × 10 ⁻⁸ (F / m ² ) ≦ C / S ≦ 3.26 × 10 ⁻⁵ (F / m ² )

That is, when the film thickness is 5 μm and the relative dielectric constant is 8.0, C / S is
^{C / S = 8.85 × 10 -12} × 8.0 / (((16/2 + 0.005) × 10 -3) × log (((16/2 + 0.005) × 10 -3) / (16 / 2 × 10 ⁻³ )))
= 3.26 × 10 ⁻⁵ (F / m ² )
It becomes. When the film thickness is 250 μm and the relative dielectric constant is 1.0, C / S is
C / S = 8.85 × 10 ⁻¹² × 1.0 / (((16/2 + 0.250) × 10 ⁻³ ) × log (((16/2 + 0.250) × 10 ⁻³ ) / (16 / 2 × 10 ⁻³ )))
= 8.03 × 10 ⁻⁸ (F / m ² )
It becomes.

8). Charge Density of Collection Roller The charge density σ (C / m ² ) of the cylinder can be calculated by the following (Formula-4).
σ = ε × V / d (Formula-4)
σ: charge density ε: dielectric constant (vacuum dielectric constant ε ₀ × relative dielectric constant ε _r )
V: Surface potential (absolute value)
d: thickness

In order to improve the paper dust collection capability, as described with reference to FIG. 3, it is desired that a charge amount larger than “−40 nC” can be obtained with a charge amount smaller than “−3 kV”. Therefore, the collection roller 92 is preferably configured such that the surface charge density is 2.12 × 10 ⁻⁴ (C / m ² ) or more.

For example, when the thickness is 250 μm, the charge amount becomes “40 nC” or more if the potential is 3000 V. Therefore, when the relative permittivity is 2.0,
^{σ = 8.85 × 10 -12 × 2.0} × 3000 / (0.250 / 0.001)
= 2.12 × 10 ⁻⁴ (C / m ² )
It becomes.

Here, in order to obtain a charge amount larger than “−40 nC” with a charge amount smaller than “−3 kV”, assuming that the relative dielectric constant is 1.0 to 8.0 and the film thickness is 5 μm to 250 μm, FIG. The charge density σ is in the following range.
8.85 × 10 ⁻⁵ (C / m ² ) ≦ σ ≦ 4.25 × 10 ⁻² (C / m ² )

  That is, when the relative dielectric constant is 1.0, the film thickness is 250 μm, and the potential is 2500 V, the charge density is the smallest, and when the relative dielectric constant is 8.0, the film thickness is 5 μm, and the potential is 3000 V, the charge density is the largest.

The charge density σ when the relative dielectric constant is 1.0, the film thickness is 250 μm, and the potential is 3000 V is
σ = 8.85 × 10 ⁻¹² × 1.0 × 2500 / (0.250 / 0.001)
= 8.85 × 10 ⁻⁵ (C / m ² )
It becomes.

The charge density σ when the relative dielectric constant is 8.0, the film thickness is 5 μm, and the potential is 3000 V is
^{σ = 8.85 × 10 -12 × 8.0} × 3000 / (0.005 / 0.001)
= 4.25 × 10 ⁻² (C / m ² )
It becomes.

  As described above, the image forming apparatus 100 according to the present exemplary embodiment includes the image forming unit 10 that forms an image on the recording material P, the supply unit 11 that supplies the recording material to the image forming unit 10, and the image forming unit using the supply unit 11. And a collection device 9 that collects paper dust from the recording material P supplied to 10. The collection device 9 has a collection roller 92 that rotates in contact with the surface of the recording material P and collects deposits from the recording material. In this embodiment, the collection roller 92 contacts the surface on which an image is formed by the image forming unit 10 immediately after passing through the collection device 9 for the recording material P. The collection roller 92 includes a conductive base material 92 a and an insulating surface layer 92 b that is provided outside the base material 92 a and forms the surface of the collection roller 92. And the thickness of the surface layer 92b is 5 micrometers or more and 250 micrometers or less. In this embodiment, the collection roller 92 is driven to rotate. In the present embodiment, the collection device 9 has another roller (conveyance roller) 91 that contacts the collection roller 92, and the recording material P is sandwiched and conveyed by the collection roller 92 and the other roller 91. . In this embodiment, the other roller 91 is rotationally driven. In this embodiment, both the collection roller 92 and the other roller 91 are rotationally driven. However, either one may be rotationally driven and the other may be driven to rotate. In this embodiment, a surface layer 92b is provided on the base material 92a.

  As described above, according to the present embodiment, the collection capability of the deposits from the recording material P by the collection device 9 can be improved. Therefore, even when the life of the image forming apparatus 100 is to be extended, Occurrence of defects such as image defects can be suppressed.

[Example 2]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the image forming apparatus according to the first exemplary embodiment. Accordingly, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do.

1. FIG. 4 is a longitudinal sectional view showing a schematic configuration of the recovery apparatus 9 in the present embodiment. In the present embodiment, the collection device 9 includes a conductive brush 94 that is a charge application member (conductive member) as a charge application unit that applies a charge to the surface of the collection roller 92. In this embodiment, the conductive brush 94 is disposed in contact with the surface of the collection roller 92. The conductive brush 94 includes a brush portion formed of conductive fibers. The conductive brush 94 is pressed against and brought into contact with the collecting roller 92 with a predetermined pressure by a biasing member (not shown) as a biasing means. Then, a voltage is applied to the conductive brush 94 by a collection power source 95 as a voltage application unit, thereby charging the surface of the collection roller 92 and applying a predetermined charge amount. Similar to the first embodiment, the collecting roller 92 with a predetermined charge on the surface causes paper dust to adhere to the surface of the collecting roller 92 when the paper P is sandwiched and conveyed with the conveying roller 91. The paper dust is removed from the paper P and collected.

  In the present embodiment as well, as with the first embodiment, since the collection roller 92 having a large capacitance is used, the surface charge amount of the collection roller 92 can be increased, and the paper dust collection capability can be improved. Can do. Further, in this embodiment, since the electric charge is applied to the surface of the collection roller 92 by the conductive brush 94, it is possible to stably apply a desired charge to the surface of the collection roller 92.

  The charge applying unit may be any device that can apply a charge to the surface of the collection roller 92. The charge imparting member is not limited to a brush-like member, and may be, for example, a pad-like member or a sheet-like member. Further, the charge applying means may be a charger (such as a corona discharger) that does not contact the surface of the collection roller 92. However, it is preferable to use a contact-type charge imparting member as in this embodiment in terms of simplification of configuration and space saving.

2. As described above, in this embodiment, since the charge is applied to the surface of the collection roller 92 by the conductive brush 94, a desired charge can be stably applied to the surface of the collection roller 92. Is possible.

  That is, generally, in charging by rubbing, as the contact area and contact time (number of times of contact) due to contact between members increases, the charged potential increases. In the case of charging due to the sliding of the roller, the surface potential is determined according to the number of rotations (number of times of contact with the rubbing portion). That is, at the beginning of the rotation of the roller, the surface potential is small because the number of times of contact is small, and the surface potential of the roller increases as the number of times of contact increases during continuous paper passing. Therefore, the collection roller 92 has a smaller amount of charge at the beginning of the rotation than that at the time of continuous paper passage, and has a small paper dust collection capability. In addition, the charging potential of the member also varies depending on the environment such as temperature and humidity. In particular, in a high humidity environment, the charging potential due to rubbing tends to be small, and the paper dust collecting ability tends to be low.

  In contrast, in this embodiment, a predetermined charge is applied to the collection roller 92 by the conductive brush 94. Therefore, a desired charge amount can be applied to the surface of the collection roller 92 from the beginning of the rotation of the collection roller 92, and the paper dust collection capability can be improved. In addition, a desired amount of charge can be imparted to the surface of the collection roller 92 regardless of the environment such as temperature and humidity.

  In this embodiment, the degree of freedom in selecting the material of the surface layer 92b of the collection roller 92 can be increased. In other words, in this embodiment, a charge is applied to the surface of the collection roller 92 by the conductive brush 94. Therefore, it is not necessary to select a material that is particularly easily charged by rubbing as the material of the surface layer 92b of the collection roller 92. For example, an inexpensive material that is easy to process can be selected. The material of the surface layer 92b of the collecting roller 92 is preferably an insulating and wear-resistant material. For example, a material such as polyimide, polyamide, polycarbonate, nylon, or alumina glass can be selected regardless of the charging property (charging column). it can.

  Further, by increasing the electrostatic capacity by making the surface layer 92b of the recovery roller 92 thin, it is possible to secure the amount of charge necessary for improving the paper dust recovery capability even when the surface potential is low. In this embodiment, since the surface potential of the collection roller 92 can be set low by the conductive brush 94, charging of the paper P after passing through the collection device 9 can also be suppressed. As a result, it is possible to obtain an effect of suppressing the occurrence of conveyance failure and image failure due to the charging of the paper P.

  Also in this example, a test for confirming the paper dust collecting ability was performed in the same manner as described in Example 1. Specifically, in this embodiment, as the collection roller 92, a surface layer 92b is formed by coating a polyimide resin with a thickness of 20 μm on an aluminum base material 92a having an outer diameter of 10 mm. Using. Then, a negative voltage was applied to the conductive brush 94 so that the surface potential of the collection roller 92 was −1 kV, and a negative charge was applied to the surface of the collection roller 92. As a result, in this example, the paper dust collection amount was 25 mg / 1K, which was four times or more the paper dust collection capacity compared to the comparative example described in Example 1. In addition, the images after passing 2K sheets and after passing 10K sheets were also good. The same effect was obtained even when a material coated with polycarbonate instead of polyimide was used as the material of the surface layer 92b of the collecting roller 92.

3. Next, a modification of the present embodiment will be described. This modification is an example in which a positive voltage is applied to the conductive brush 94 and a positive charge is applied to the collection roller 92. Specifically, in this modification, as the collection roller 92, a surface layer 92b is formed by coating a polyimide resin to a thickness of 20 μm on an aluminum base material 92a having an outer diameter of 10 mm. Using. Then, a positive voltage was applied to the conductive brush 94 so that the surface potential of the collection roller 92 was +1 kV, and a positive charge was applied to the surface of the collection roller 92.

  Even when PFA, which is easily negatively charged, is used as the material of the surface layer 92 b of the recovery roller 92, it is possible to apply a positive charge to the surface of the recovery roller 92 by applying a charge by the conductive brush 94.

  In this modified example, as in the present embodiment, since the collection roller 92 having a large electrostatic capacity is used, the surface charge amount of the collection roller 92 can be increased, and the paper dust collection capability is improved. Can do. Also in the present modification, as in the present embodiment, the charge is applied to the surface of the collection roller 92 by the conductive brush 94, so that a desired charge can be stably applied to the surface of the collection roller 92. Is possible.

  Further, the configuration in which a positive charge is imparted to the collection roller 92 imparts a positive charge to the print surface side of the paper P. As a result, in the configuration of the present embodiment in which toner having a normal charging polarity of negative polarity is used, a charge having a polarity opposite to the normal charging polarity of the toner is applied to the printing surface side, so that the transfer of the toner during transfer is performed. The effect of improving the image quality and the image quality is also obtained.

  Also in this modified example, a test for confirming the paper dust collecting ability was performed in the same manner as described in Example 1. As a result, in this modification, the paper dust collection amount was 25 mg / 1K, which was four times or more the paper dust collection capacity compared to the comparative example described in Example 1. In addition, the images after passing 2K sheets and after passing 10K sheets were also good.

  Since the paper dust is charged to either plus or minus depending on the conditions, the collecting roller 92 can collect the paper dust both when a plus charge is applied and when a minus charge is applied. The charging state of the paper dust can be confirmed using, for example, Q / d-meter manufactured by EPPING. The Q / d-meter manufactured by EPPING Co., Ltd. allows the sample sucked with a predetermined suction force to pass between the slide glasses to which positive and negative predetermined voltages are applied, and the position of the sample attached to each slide glass. The amount of charge of a sample is measured from the size. Actually, when the paper dust generated from the paper P was measured by Q / d-meter, there were almost the same number of positively charged paper dust and negatively charged paper dust.

  In the above, an example in which a negative voltage or a positive voltage is applied by the voltage applying unit to apply a negative charge or a positive charge to the collection roller 92 has been described. On the other hand, it is good also as a structure which selectively applies the voltage of plus polarity and minus polarity by a voltage application means. That is, as shown in FIG. 5, a negative voltage output unit (first output unit) 95a that outputs a negative polarity voltage and a positive voltage output unit (first output) that outputs a positive voltage to a recovery power source 95 as a voltage application unit. 2 output unit) 95b. Then, the polarity of the voltage applied from the recovery power supply 95 to the conductive brush 94 can be selected between the negative polarity and the positive polarity according to the situation by the control unit 120 as the control means. For example, the control unit 120 receives an instruction from an operator such as a user or a service person from an operation unit (not shown) provided in the apparatus main body 110 or an external device such as a personal computer connected to the apparatus main body 110. Accordingly, the above selection can be made. Alternatively, the control unit 120 can perform the above selection according to polarity selection information such as the type of paper P selected to be used for image formation. For example, by setting in advance a type of paper P that is known to have more paper dust of a predetermined polarity than paper dust of the opposite polarity, more paper dust can be collected from the paper P. Can be selected (a polarity opposite to the polarity of the paper dust expected to be larger).

  Thus, in the present embodiment, the collection device 9 includes the conductive member 94 that contacts the surface of the collection roller 9 and the power source 95 that applies a voltage to the conductive member 94. Here, the power source 95 applies only one of a negative voltage and a positive voltage to the conductive member 94, or selectively applies a negative voltage or a positive voltage to the conductive member 94. It may be applied by switching to.

  As described above, in the present embodiment, the charge is applied to the collection roller 92 by the charge application unit, so that the charge having a desired polarity (positive polarity or negative polarity) can be obtained according to the required characteristics of the apparatus. Thus, it can be applied to the collection roller 92. Also, with this configuration, it becomes easy to control the amount of charge applied to the collection roller 92 to a desired value.

[Example 3]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the image forming apparatus according to the first exemplary embodiment. Accordingly, in the image forming apparatus according to the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do.

  FIG. 6 is a longitudinal sectional view showing a schematic configuration of the recovery device 9 in the present embodiment. In the present embodiment, the collecting roller 92 includes a conductive elastic layer 92c between a conductive base material (core metal) 92a similar to the collecting roller 92 in the first embodiment and an insulating surface layer 92b. It has the structure provided.

As the conductive elastic layer 92c, for example, a conductive rubber obtained by dispersing and mixing a conductive material such as carbon in silicone rubber can be suitably used. The volume resistivity of the conductive elastic layer 92c is preferably 10 ⁻² Ωm or more and 10 ⁴ Ωm or less. Further, the thickness of the elastic layer 92c increases the nip width (width in the conveyance direction of the paper P) of the collection unit M formed between the conveyance roller 91 and the collection roller 92 with respect to the unevenness of the surface of the paper P. In order to improve the followability of the surface, 50 μm or more and 2 mm or less are preferable. In the present embodiment, the conductive elastic layer 92c is a single layer, but a plurality of conductive elastic layers formed of, for example, a plurality of different materials are provided between the base material 92a and the surface layer 92b. It may be.

  As in this embodiment, by providing the conductive elastic layer 92c on the recovery roller 92, the electrostatic capacity of the recovery roller 92 can be increased and the amount of charge accumulated on the surface can be increased. In addition to this, the width of the contact nip with the paper P can be widened, and the followability of the surface of the collection roller 92 to the unevenness of the surface of the paper P can be improved. As a result, the paper dust collection capability of the collection roller 92 can be improved. That is, by forming the thin insulating surface layer 92b on the base material 92a and the elastic layer 92c, which are conductors, the capacitance of the collection roller 92 can be increased, and a large amount of charge is imparted to the surface layer 92b. It becomes possible. Further, since the elastic layer 92c is provided, the contact nip width with the paper P is widened. As a result, the contact time between the paper P and the collection roller 92 can be increased, and the followability of the surface of the collection roller 92 with respect to the irregularities on the surface of the paper P can be improved. The area can be increased. As a result, the paper dust collecting ability of the collecting roller 92 can be improved.

  Also in this example, a test for confirming the paper dust collecting ability was performed in the same manner as described in Example 1. As a result, it was confirmed that the paper dust collection ability with respect to Example 1 was improved. The images after passing 2K sheets and after passing 10K sheets were also good.

[Others]
As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  In the above-described embodiment, a so-called cleaner-less configuration is adopted in which no special cleaning device is provided to collect the transfer residual toner remaining on the surface of the photosensitive drum after the transfer process. In an image forming apparatus having a cleaner-less configuration, the paper dust attached to the photosensitive drum cannot be removed by the cleaning device. For example, the cleaning device may cause a problem due to paper dust such as an image defect due to the paper dust sticking to the developing roller. It is more likely to occur than the image forming apparatus having the above. Therefore, it can be said that the effect by the improvement of the paper dust collecting capability of the collecting apparatus according to the present invention can be obtained more significantly in the cleaner-less image forming apparatus than in the image forming apparatus having the cleaning device. However, the present invention is also applicable to an image forming apparatus having a cleaning device that removes and collects transfer residual toner from a photosensitive drum. This case is also effective in suppressing problems such as defective cleaning due to paper dust being sandwiched between the cleaning member and the photosensitive drum.

  In the above-described embodiment, a roller that contacts one surface of the sheet (a printing surface on which an image is formed in the image forming unit immediately after passing through the collecting device in the above-described embodiment) of the roller pair included in the collecting device. A collecting roller according to the present invention was obtained. Alternatively, both rollers of the pair of rollers provided in the collecting device, that is, the respective rollers that contact both surfaces of the paper may be used as the collecting roller according to the present invention. By adopting a configuration in which paper dust is removed from the surface opposite to the printing surface of the paper, for example, paper dust attached to or scattered from other paper on the paper adheres to the image forming unit and causes image defects, etc. It is possible to suppress the occurrence of defects.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure apparatus 4 Developing apparatus 4a Developing roller 5 Transfer roller 9 Collection | recovery apparatus 100 Image forming apparatus P Recording material (paper)

Claims (11)

In a collection device having a collection roller that rotates in contact with the surface of the recording material and collects deposits from the recording material,
The collection roller has a conductive substrate and an insulating surface layer that is provided outside the substrate and forms the surface of the collection roller,
The surface layer has a thickness of 5 μm or more and 250 μm or less.   The collection device according to claim 1, wherein the collection roller is rotationally driven.   3. The collecting apparatus according to claim 1, further comprising another roller that contacts the collecting roller, wherein the recording material is sandwiched and conveyed by the collecting roller and the another roller.   The recovery apparatus according to claim 3, wherein the another roller is rotationally driven.   5. The recovery device according to claim 1, further comprising: a conductive member that contacts the surface of the recovery roller; and a power source that applies a voltage to the conductive member.   The power source applies only one of a negative voltage and a positive voltage to the conductive member, or selectively switches a negative voltage or a positive voltage to the conductive member. The recovery device according to claim 5, wherein the recovery device is applied.   The recovery apparatus according to claim 1, wherein the surface layer is provided on the base material.   The recovery apparatus according to claim 1, wherein a conductive elastic layer is provided between the base material and the surface layer. An image forming unit for forming an image on a recording material;
A supply unit for supplying a recording material to the image forming unit;
The collection device according to any one of claims 1 to 8, wherein the depositing material is collected from the recording material supplied to the image forming unit by the supply unit.
An image forming apparatus comprising:   The image forming apparatus according to claim 9, wherein the collection roller is in contact with a surface on which an image is formed in the image forming unit immediately after passing through the collection device for the recording material.   The image forming unit includes an image carrier that carries a toner image, a developing unit that supplies toner to the image carrier to form a toner image, and a transfer unit that transfers the toner image from the image carrier to a recording material. The image forming apparatus according to claim 9, wherein the toner remaining on the surface of the image carrier after the transfer is collected by the developing unit.

Images