JP2013105072A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which resolves accumulation of toner attachment to a position regulation member of a transfer member without increasing a size and a cost of the apparatus.SOLUTION: An image forming apparatus comprises: a toner image carrier 21; a transfer member 27 which contacts with the toner image carrier 21 with a prescribed pressure, and transfers a toner image formed on the toner image carrier 21 to a transferred material; a position regulation member 30 which contacts with the toner image carrier 21, and regulates a biting pressure-contact amount of the transfer member 27; and application means 40 which applies a bias voltage at a prescribed potential on the transfer member 27 and the position regulation member 30. The position regulation member 30 is rotatably attached to a support shaft 27a of the transfer member 27, and comprises a semiconductive material whose resistance value is set larger than a resistance value of the transfer member 27.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that transfers a toner image formed based on image data onto a transfer material.

  Generally, in an image forming apparatus using an electrophotographic process, toner images formed on a plurality of photoconductors are primarily transferred and synthesized on an intermediate transfer belt, and the synthesized toner image is secondarily transferred onto a sheet. doing. The secondary transfer roller is in contact with the intermediate transfer belt at a predetermined pressure, and position control members (rollers) mounted on both ends of the secondary transfer roller are in pressure contact with the intermediate transfer belt, so that the secondary transfer roller is in contact with the intermediate transfer belt. The amount of pressure contact between the transfer roller and the intermediate transfer belt is regulated.

  The position restricting member is in contact with the outside of the image forming area of the intermediate transfer belt, but the toner adheres to the position restricting member because the fog toner adheres to the intermediate transfer belt even outside the image forming area. . If the image forming operation is continued in this state, the toner adheres in a layered manner to the surface of the position regulating member, and problems such as transfer failure of the toner image and damage to the intermediate transfer belt due to fluctuation (decrease) in the biting pressure contact amount occur. In addition, when a paper having a size larger than usual is passed, the back side of the paper on which the toner adheres to the back side of the paper occurs.

  Therefore, conventionally, as described in Patent Document 1, it has been proposed to contact a member for cleaning the toner adhering to the position regulating member and mechanically remove the toner from the position regulating member. Yes. However, mechanical cleaning has a problem that the cleaning ability is lowered when toner is accumulated in the cleaning member, and not only the cleaning member but also a means for collecting the cleaned toner is required. , Leading to increased costs.

Japanese Patent No. 3944432

  The object of the present invention is to eliminate the accumulation of toner adhesion to the position regulating member of the transfer member without causing an increase in size and cost of the apparatus, and transfer failure due to fluctuation (decrease) in the amount of biting pressure contact of the transfer member. An object of the present invention is to provide an image forming apparatus capable of preventing damage to a toner image carrier.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes:
A toner image carrier;
A transfer member for contacting the toner image carrier at a predetermined pressure and transferring the toner image formed on the toner image carrier to a transfer material;
A position regulating member that contacts the toner image carrier and regulates the amount of biting pressure contact of the transfer member;
Means for applying a bias voltage of a predetermined potential to the transfer member and the position regulating member;
With
The position regulating member is rotatably installed on a support shaft of the transfer member, and is made of a semiconductive material and has a resistance value larger than a resistance value of the transfer member.
It is characterized by.

  In the image forming apparatus, by applying a bias voltage also to the position regulating member, the toner attached to the position regulating member is retransferred to the toner image carrier, and the toner is electrostatically removed from the position regulating member. . Therefore, it is possible to prevent toner adhesion from accumulating on the position restricting member, fluctuation (decrease) of the biting pressure contact amount of the transfer member, and damage to the toner image carrier. In addition, since the resistance value of the position regulating member is larger than the resistance value of the transfer member, a current higher than the transfer current is not supplied to the transfer material, and toner transfer is not hindered. In addition, since the position regulating member is not mechanically cleaned, the apparatus is not increased in size and cost. The toner removed from the position regulating member and re-transferred to the toner image carrier is collected as waste toner by a toner collecting means usually installed on the toner image carrier.

  According to the present invention, accumulation of toner adhesion to the position regulating member of the transfer member is eliminated without causing an increase in size and cost of the apparatus, and transfer failure due to fluctuation (reduction) in the amount of biting pressure contact of the transfer member. Damage to the toner image carrier can be prevented.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. FIG. 6 is a perspective view showing a state in which a secondary transfer roller and a position regulating member are pressed against an intermediate transfer belt. It is a perspective view which shows a secondary transfer roller. It is a perspective view which shows a position control member. It is a chart figure which shows a transfer bias voltage.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

  As shown in FIG. 1, an image forming apparatus according to an embodiment is a tandem type electrophotographic printer, and generally includes an image forming unit 10 (for forming toner images of Y, M, C, and K colors). 10Y, 10M, 10C, 10K), an intermediate transfer unit 20, and a fixing unit 29.

  Each of the image forming units 10 is provided with a charging charger, a developing device, and the like (not shown) around the photosensitive drum 11, and a cleaning blade 12 for removing residual toner is provided. A laser scanning device (not shown) for exposing each photosensitive drum 11 to form an electrostatic latent image is disposed. The electrostatic latent images drawn on the respective photosensitive drums 11 are developed by a developing device by a laser beam emitted from the laser scanning device, and toner images of respective colors are formed. Image data is transferred from a scanner (not shown) or from a computer to the printer.

  The intermediate transfer unit 20 includes an intermediate transfer belt 21 that is rotationally driven in the direction of arrow Z, and is formed on each photoconductive drum 11 by an electric field applied from a primary transfer charger 25 facing each photoconductive drum 11. The transferred toner image is primarily transferred onto the intermediate transfer belt 21 and synthesized. The intermediate transfer belt 21 is stretched endlessly around the support rollers 22 and 23 and is given a certain tension by a spring 24. Further, a cleaning blade 26 for removing residual toner is installed at a position facing the support roller 23, and a secondary transfer roller 27 is installed at a position facing the support roller 22.

  The sheet S as the transfer material is fed one by one from below and conveyed to the nip portion between the intermediate transfer belt 21 and the secondary transfer roller 27, where the toner image (synthesized color image) is secondarily transferred. . Thereafter, the sheet S is conveyed to the fixing unit 29 where the toner is heated and fixed, and is discharged to a tray portion disposed on the upper surface of the printer main body.

  The toner used as the developer is a polymerized toner having a particle size of 7 μm or less, preferably 4.5 to 6.5 μm. The developing method may be either a one-component developing method using only toner or a two-component developing method using a mixture of toner and carrier.

The intermediate transfer belt 21 is obtained by dispersing carbon in polyphenylene sulfide resin, having a surface resistivity per unit area of 1 × 10 ⁷ to 1 × 10 ¹² Ω and a volume resistivity of 1 × 10 ⁶ to 1 × 10 ¹² Ω · cm. It is preferable to use what was adjusted to. As the intermediate transfer belt 21, a resistance value adjusted by dispersing a conductive filler such as carbon or an ionic conductive material in polycarbonate resin, polyimide resin, urethane resin, fluorine resin, or the like. Can be used. The intermediate transfer belt 21 is formed by cutting a cylindrical base material obtained by injection molding or centrifugal molding of the material to a desired peripheral length with a desired width and processing an end for reinforcing the end.

As shown in FIG. 3, the secondary transfer roller 27 is formed by covering a core metal 28 with a foam 29, and the core metal 28 is rotatably mounted on a support shaft 27a. As the foam 29, a foamed sponge made of ion-conductive NBR and hydrin rubber whose resistance value is adjusted to 1 × 10 ⁶ to 1 × 10 ⁸ Ω is used. Further, the foam 29 may have a skin layer whose surface layer is modified in order to improve releasability from the toner.

  The secondary transfer roller 27 is in contact with the intermediate transfer belt 21 by a coil spring (not shown) at a predetermined pressure. In order to form a predetermined nip width with the intermediate transfer belt 21, the secondary transfer roller 27 is in contact with the intermediate transfer belt 21. Position restricting rollers 30 are rotatably mounted on the support shaft 27a on both ends of the roller 27 so that the amount of biting pressure contact is 0.20 mm (see FIG. 2). The position regulating roller 30 is in contact with both end portions (non-image areas) of the intermediate transfer belt 21. In addition, coil springs (not shown) that elastically bias the secondary transfer roller 27 together with the position regulating roller 30 against the intermediate transfer belt 21 are disposed at both ends of the support shaft 27a, and the spring force is applied to each side. And 25N respectively.

  Further, the secondary transfer roller 27 is connected to a high-voltage power supply 40 via a support shaft 27a, and a transfer bias voltage having a polarity opposite to the toner charging polarity is applied from the high-voltage power supply 40 during a transfer operation. The toner is transferred from the intermediate transfer belt 21 onto the paper S by the electric field formed by this bias voltage. Further, since the fog toner adhering to the intermediate transfer belt 21 adheres to the secondary transfer roller 27, positive and negative bias voltages are applied from the high voltage power source 40, and the adhering fog toner is retransferred to the intermediate transfer belt 21. This process is executed during non-printing as a cleaning process of the secondary transfer roller 27, and the fog toner retransferred to the intermediate transfer belt 21 is scraped off by the cleaning blade 26 and collected as waste toner.

  On the other hand, the fog toner adhering to the intermediate transfer belt 21 also adheres to the position restricting roller 30, causing problems such as a decrease in the amount of biting in the secondary transfer roller 27. Therefore, in this embodiment, the position regulating roller 30 is formed of a semiconductive material, and the bias toner applied to the position regulating roller 30 is applied by applying a bias voltage from the high voltage power source 40 via the support shaft 27a. The cleaning is performed electrostatically (retransferred to the intermediate transfer belt 21). The toner reattached to the intermediate transfer belt 21 is also scraped off by the cleaning blade 26 as described above.

As shown in FIG. 4A, the position restricting roller 30 has a semiconductive resin layer 31 rotatably attached to a support shaft 27a, and the semiconductive resin layer 31 has a resistance value of 1 × 10 ⁸ to. Those adjusted to 1 × 10 ¹⁰ Ω are used. The semiconductive resin layer 31 may be made of a material in which carbon is dispersed in a polyimide resin, a polyphenylene sulfide resin, a polycarbonate resin, or the like in addition to the polyacetal resin. Further, as shown in FIG. 4B, a metal core bar 32 rotatably attached to the support shaft 27a may be coated with a semi-conductive hard rubber layer 33. Furthermore, as shown in FIG. 4C, the surface of the hard rubber layer 34 having semiconductivity may be covered with a metal layer 35. Here, the hard rubber is obtained by adjusting the resistance value by dispersing carbon in EPDM, for example.

Although the above-mentioned various types of rollers can be used as the position regulating roller 30, the resistance value needs to be larger than the resistance value of the secondary transfer roller 27. This is because during the secondary transfer operation, a transfer current is supplied from the secondary transfer roller 27 to the intermediate transfer belt 21 via the paper S, and in this embodiment, a leakage current is also generated from the position regulating roller 30 at the same time. . In order to reduce this leakage current, the resistance value of the position regulating roller 30 is set larger than the resistance value of the secondary transfer roller 27. The resistance value of the position regulating roller 30 is preferably about 10 to 100 times the resistance value of the secondary transfer roller 27 in order to remove toner. For example, when the resistance value of the secondary transfer roller 27 is 1 × 10 ⁷ Ω, the resistance value of the position regulating roller 30 is set to 1 × 10 ⁸ to 1 × 10 ⁹ Ω.

  The resistance value R of the position regulating roller 30 is obtained by R = V / I based on the current value I that flows when the voltage V is applied to the support shaft 27a. The resistance value of the secondary transfer roller 27 is obtained in the same manner.

  By the way, the cleaning process (executed during non-printing) of the secondary transfer roller 27 and the position regulating roller 30 is performed by outputting a predetermined bias voltage from the high-voltage power supply 40 to the support shaft 27a. In this embodiment, since the toner is negatively charged, in order to remove the toner from the rollers 27 and 30, a negative bias voltage may be applied to the rollers 27 and 30. However, since the fog toner includes toner that is improperly charged with positive polarity, it is preferable to apply positive and negative voltages alternately as the bias voltage applied in the cleaning process. Specifically, as shown in FIG. 5, voltages of +500 V and −500 V are alternately applied with a period A. The period A corresponds to one rotation of the secondary transfer roller 27 (also one rotation of the position regulating roller 30).

Using the apparatus of the above-described embodiment, an experiment was performed by combining the resistance values of the secondary transfer roller 27 and the position regulating roller 30 with predetermined values, and evaluated. As the position regulating roller 30, the one shown in FIG. As shown in Table 1 below, the resistance value of the secondary transfer roller 27 varies in the range of 1 × 10 ⁶ to 1 × 10 ⁸ Ω, and the resistance value of the position regulating roller 30 is 1 × 10 ⁶ to 1 × 10. Variable in the range of ¹⁰ Ω. As is clear from Table 1, it is preferable that the resistance value of the position regulating roller 30 is larger than the resistance value of the secondary transfer roller 27. In particular, the resistance value of the position regulating roller 30 is 1 × 10 ⁷ to 1 ×. No secondary transfer failure or toner removal failure occurred in the range of 10 ¹⁰ Ω.

  Note that the image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  In particular, the basic mode of the image forming apparatus (monochrome machine, color machine, copying machine, printer, multifunction machine) is arbitrary. In the above embodiment, the position restricting member is shown as a position restricting member for the secondary transfer roller that is in pressure contact with the intermediate transfer belt. The position regulating member may be used.

  As described above, the present invention is useful for an image forming apparatus, and is particularly excellent in that accumulation of toner adhesion on a position regulating member can be eliminated.

DESCRIPTION OF SYMBOLS 10 ... Image forming unit 11 ... Photosensitive drum 21 ... Intermediate transfer belt 27 ... Secondary transfer roller 27a ... Support shaft 30 ... Position control roller 40 ... High voltage power supply

Claims (5)

A toner image carrier;
A transfer member for contacting the toner image carrier at a predetermined pressure and transferring the toner image formed on the toner image carrier to a transfer material;
A position regulating member that contacts the toner image carrier and regulates the amount of biting pressure contact of the transfer member;
Means for applying a bias voltage of a predetermined potential to the transfer member and the position regulating member;
With
The position regulating member is rotatably installed on a support shaft of the transfer member, and is made of a semiconductive material and has a resistance value larger than a resistance value of the transfer member.
An image forming apparatus. The image forming apparatus according to claim 1, wherein a resistance value of the position regulating member is 1 × 10 ⁷ to 1 × 10 ¹⁰ Ω.   The image forming apparatus according to claim 1, wherein the bias voltage applying unit applies a positive or negative bias voltage to a support shaft of the transfer member.   The image forming apparatus according to claim 3, wherein the cycle of the positive and negative bias voltages corresponds to one rotation of the transfer member. The toner image carrier is an intermediate transfer belt on which a toner image formed on a photoreceptor is primarily transferred and the toner image is secondarily transferred onto paper.
The transfer member is a secondary transfer roller;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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