JP5201348B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  As an image forming apparatus, a toner image of each color component is sequentially primary transferred onto an intermediate transfer belt, and the toner image superimposed on the intermediate transfer belt is secondarily transferred onto a printing paper as an image recording medium. Yes.

  Here, as the secondary transfer device for performing the secondary transfer, for example, a secondary transfer roller disposed in contact with the toner image holding surface of the intermediate transfer belt and a secondary transfer roller disposed so as to sandwich the intermediate transfer belt Such a backup roller and a bias applying device that applies a secondary transfer bias via the secondary transfer roller and the backup roller are widely used.

  In the image forming apparatus having the above-described configuration, there has been proposed an image forming apparatus that suppresses the occurrence of a fish scale-like image quality defect (a scale defect) in an image transferred to a printing paper.

For example, Japanese Patent Application Laid-Open No. 2004-333521 discloses an image forming apparatus in which a back-up roller is used as one of support rollers inside a transfer belt, and the back surface of the transfer belt in the secondary transfer pre-nip portion is discharged by a charge eliminating belt. .
JP 2004-333521 A

  It is an object of the present invention to provide an image forming apparatus that can more effectively suppress the occurrence of scaly defects.

  In order to solve the above problems, an image forming apparatus according to a first aspect of the present invention includes an image holding member that holds a toner image, an intermediate transfer belt provided to face the image holding member, and an image on the image holding member. A primary transfer unit that primarily transfers a toner image to the intermediate transfer belt, and a secondary transfer unit that secondarily transfers the toner image on the intermediate transfer belt to a recording medium, with respect to the toner image holding surface of the intermediate transfer belt. A transfer roller arranged in contact; a counter roller provided in contact with the intermediate transfer belt so as to face the transfer roller; and provided in contact with the intermediate transfer belt on the upstream side in the rotation direction of the intermediate transfer belt. An endless belt-like conductive film stretched between a tension roller and the opposite roller, and provided so that the conductive film contacts the intermediate transfer belt. And a pressing means that is provided in contact with the inner surface of the endless belt-like conductive film forming the static elimination means and presses a partial region of the conductive film toward the intermediate transfer belt. It is characterized by.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the pressing means is constituted by a plate-like member.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the upstream and downstream ends of the plate-like member are bent or curved.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the contact portion of the plate-like member with the inner surface of the conductive film is curved. It is characterized by that.

  According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the pressing means is composed of a roller member that is rotatable in contact with the inner surface of the conductive film. To do.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the pressing means is a position where the leading end of the recording medium enters the intermediate transfer belt. It is provided in the area | region containing at least.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the pressing means is a position where the leading end of the recording medium enters the intermediate transfer belt. It is characterized in that it is provided in the upstream region.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any of the first to fifth aspects, the tension roller includes a biasing unit that biases the tension roller in a direction away from the facing roller. It is characterized by.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the volume resistivity of the endless belt-like conductive film forming the charge eliminating means is 10 ⁸ to 10 ⁸ . 10 ¹³ Ω · cm.

  An image forming apparatus according to a tenth aspect of the present invention is the image forming apparatus according to any one of the first to ninth aspects, wherein the charge eliminating means is electrically grounded.

  According to the present invention, the following effects can be obtained.

  That is, according to the first aspect of the present invention, the adhesion between the endless belt-like conductive film forming the static elimination means and the intermediate transfer belt is improved as compared with the case where the present configuration is not provided. There is an effect that generation of scaly defects can be more effectively suppressed.

  According to the second aspect of the present invention, it is possible to more effectively suppress the occurrence of scaly defects with a simple structure as compared with the case where the present structure is not provided.

  According to the third aspect of the present invention, the sliding load can be reduced and the contact state between the conductive film and the intermediate transfer belt can be stabilized as compared with the case where this configuration is not provided. The occurrence of scaly defects can be more effectively suppressed.

  According to the invention described in claim 4, the sliding load can be further reduced as compared with the case where the present configuration is not provided, and the contact state between the conductive film and the intermediate transfer belt is stabilized. Thus, the occurrence of scaly defects can be more effectively suppressed.

  According to the fifth aspect of the present invention, the sliding load can be further reduced and the contact state between the conductive film and the intermediate transfer belt can be stabilized as compared with the case where this configuration is not provided. Thus, the occurrence of scaly defects can be more effectively suppressed.

  According to the sixth aspect of the present invention, compared with the case where the present configuration is not provided, the adhesion between the conductive film and the intermediate transfer belt is moderately increased, and the occurrence of scaly defects is more effective. Can be suppressed.

  According to the seventh aspect of the present invention, compared with the case where the present configuration is not provided, the adhesion between the conductive film and the intermediate transfer belt is moderately enhanced, and the generation of scaly defects is more effective. Can be suppressed.

  According to the eighth aspect of the invention, compared to the case where the present configuration is not provided, the contact state between the conductive film and the intermediate transfer belt is stabilized, and the generation of scaly defects is more effective. Can be suppressed.

  According to the ninth aspect of the present invention, the occurrence of discharge can be effectively prevented and the occurrence of scaly defects can be more effectively suppressed as compared with the case where the present configuration is not provided.

  According to the tenth aspect of the present invention, the occurrence of discharge can be effectively prevented and the occurrence of scaly defects can be more effectively suppressed as compared with the case where this configuration is not provided.

  Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  (First embodiment)

  With reference to FIGS. 1 to 5, an image forming apparatus PR1 according to a first embodiment of the present invention will be described.

  The image forming apparatus PR1 according to the first embodiment uses at least an image carrier that forms an electrostatic latent image according to image information, and the electrostatic latent image formed on the image carrier as a colorant. A developing unit that visualizes the toner image with toner, an intermediate transfer belt on which the toner image formed on the image carrier is primarily transferred, a primary transfer unit that primarily transfers the toner image to the intermediate transfer belt, Secondary transfer means for secondary transfer of the toner image primarily transferred to the transfer belt to a recording medium, and the primary transfer roller provided as the primary transfer means on the inner peripheral surface side of the intermediate transfer belt. Yes.

  The configuration of the image forming apparatus will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a configuration diagram showing a configuration example of a color printer PR1 as an image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic configuration diagram in which the periphery of a primary transfer roller of the color printer PR1 is enlarged.

  The color printer PR1 sequentially includes a plurality of image forming units 100 (100Y, 100M, 100C, 100K) on which each color component toner image is formed by, for example, electrophotography, and each color component toner image formed by each image forming unit 100. Intermediate transfer belt 110 to be transferred (primary transfer) held, secondary transfer device 120 to collectively transfer (secondary transfer) the superimposed image transferred on intermediate transfer belt 110 to printing paper P as a recording medium, and batch transfer And a fixing device 150 that fixes the printed image on the printing paper P.

  In the present exemplary embodiment, the image forming unit 100 for each color component includes a yellow image forming unit 100Y, a magenta image forming unit 100M, a cyan image forming unit 100C, and a black image forming unit 100K from the upstream side in the transport direction B of the intermediate transfer belt 110. In order.

  Each image forming unit 100 includes a uniform charger 102 for charging the photosensitive drum 101 around the photosensitive drum 101 serving as an image holding member rotating in the direction of arrow A, and a static charge on the photosensitive drum 101. A laser exposure device 103 in which an electrostatic latent image is written (an exposure beam is indicated by a symbol Bm), development in which each color component toner is accommodated and the electrostatic latent image on the photosensitive drum 101 is visualized Various electronic devices such as a device 104, a primary transfer roller 105 as a transfer device for transferring each color component toner image on the photosensitive drum 101 to the intermediate transfer belt 110, and a drum cleaner 106 for removing residual toner on the photosensitive drum 101 A photographic device is provided.

  Further, as shown in FIG. 2, a DC bias having a polarity opposite to the toner charging polarity (positive polarity in this embodiment) is applied to each primary transfer roller 105 (105Y, 105M, 105C, 105K). A transfer bias power source 107 (107Y, 107M, 107C, 107K) is provided.

  Each of these transfer bias power sources 107 applies a constant current to each primary transfer roller 105.

  Further, as shown in FIG. 1, the intermediate transfer belt 110 is stretched around a plurality (five in the present embodiment) of support rollers 131 to 135.

  Here, the support roller 131 is a driving roller of the intermediate transfer belt 110, the support rollers 132 and 135 are driven rollers, the support roller 133 is a tension roller that adjusts the tension of the intermediate transfer belt 110, and the support roller 200 is the secondary transfer device 120. A backup roller (opposing roller).

  As shown in FIGS. 1 to 4, the endless belt spanned between a supporting roller 200 and a stretching roller 201 provided in contact with the intermediate transfer belt 110 on the upstream side in the rotation direction of the intermediate transfer belt 110. A static elimination device M1 is provided as a static elimination means constituted by the belt-like conductive film F.

  A part of the conductive film F is configured to contact the intermediate transfer belt 110.

  Further, a plate-like member 300 is provided as a pressing unit that contacts the inner surface of the endless belt-like conductive film F and presses a part of the region E of the conductive film F to the intermediate transfer belt 110 side.

The conductive film F is made of a material having a volume resistivity of 10 ⁸ to 10 ¹³ Ω · cm, such as polyimide.

  Further, the static eliminator M1 is electrically grounded via an earth wire or the like.

  With the static eliminator M1 having such a configuration, the adhesiveness between the conductive film F and the intermediate transfer belt 110 is enhanced, and surplus charges are efficiently released, and the occurrence of scaly defects is suppressed.

  Here, assuming that an image forming apparatus that does not include the static eliminator M1 is used as a comparison target, the occurrence state and the cause of occurrence of a scaly defect will be briefly described.

  When an image is formed using an intermediate transfer belt having ion conductivity in an image forming apparatus as a comparison target that does not include the static eliminator M1, a fish scale-like image quality defect is included in the image transferred to the printing paper. (Referred to as a scaly defect).

  The scaly defect is caused by gap discharge generated between the intermediate transfer belt and the backup roller in the pre-nip region immediately before the printing paper enters the nip region (transfer nip region) between the intermediate transfer belt and the secondary transfer roller. It has been elucidated that it occurs.

  In particular, when a spherical toner having a high transfer efficiency is used as the toner, the toner adheres to the toner, and the toner is easily separated from the intermediate transfer belt even by a weak discharge. It is also known that defects are likely to occur.

  In addition, in the image forming apparatus according to the comparison target, when tension is applied to the belt of the conductive film by the tension mechanism, the backup is performed in order to secure the accommodation space for the tension mechanism and from the viewpoint of the ease of assembly of the belt unit. A certain distance is required between the shafts of the roller and the tension roller, and the belt stretching surface of the secondary transfer pre-nip portion becomes long. For this reason, the tension of the belt of the secondary transfer pre-nip portion is generated between the belt and the transfer belt due to variations in the tension of the belt of the conductive film, or due to rotation of the transfer belt or lateral displacement in the roller axis direction. As a result of unstable contact, an image defect (a scale-like pattern) occurs.

  In the color printer PR <b> 1 according to the present embodiment, surplus charges are removed through the conductive film F that is in close contact with the intermediate transfer belt 110 by providing the neutralization device M <b> 1. As a result, the occurrence of gap discharge between the intermediate transfer belt 110 and the backup roller (supporting roller 200) is suppressed, and as a result, the occurrence of scaly defects is suppressed and a good image is obtained.

  In addition, although not particularly limited, in the configuration example illustrated in FIG. 3, the stretching roller 201 includes a spring 202 as a biasing unit that biases in a direction away from the support roller 200.

  As a result, the contact state between the conductive film F and the intermediate transfer belt 110 is stabilized, and the occurrence of scaly defects is more effectively suppressed.

  As shown in FIG. 4, the plate-like member 300 as the pressing means can be provided in a region (pre-nip region) upstream from the position N where the leading end of the printing paper P enters. Thereby, the adhesiveness of the electroconductive film F and the intermediate transfer belt 110 is moderately improved, and the occurrence of scaly defects is more effectively suppressed.

  The position where the plate-like member 300 is provided may be an area including at least the position N where the leading end of the printing paper P enters.

  In FIG. 4, the static eliminator M <b> 1 is covered with a housing 500, and metal power supply rollers 501 and 502 that stably apply a bias having the same polarity as the charging polarity of the toner to the support roller 200. Note that only one of the power supply rollers 501 and 502 may be provided.

  In addition, the shape of the plate-like member 300 is not particularly limited, but for example, it can be a shape as shown in FIGS.

  In the example shown in FIG. 5A, the upstream and downstream ends 300a and 300b are processed to be bent or curved. Thereby, the sliding load with the conductive film F can be reduced, the contact state between the conductive film and the intermediate transfer belt is stabilized, and the occurrence of scaly defects is more effectively suppressed.

  In the example shown in FIG. 5B, the contact portion 300c with the conductive film F is curved in an arc shape. Thereby, the sliding load with the conductive film F can be reduced, the contact state between the conductive film and the intermediate transfer belt is stabilized, and the occurrence of scaly defects is more effectively suppressed.

  Here, another configuration of the color printer PR1 shown in FIGS. 1 and 2 will be described.

  The intermediate transfer belt 110 is made of a resin such as polyimide or polyamide containing an appropriate amount of an antistatic agent such as carbon black.

  Further, the secondary transfer device 120 includes a secondary transfer roller 113 disposed in pressure contact with the toner holding surface side of the intermediate transfer belt 110 and a counter electrode of the secondary transfer roller 113 disposed on the back surface side of the intermediate transfer belt 110. A backup roller (also used as the support roller 200) is provided. The backup roller 200 is made of a metal to which a bias having the same polarity as the toner charging polarity is stably applied from a bias power source (not shown). The power supply rollers 501 and 502 are arranged in contact with each other (see FIG. 3).

  Note that a roller brush (not shown) is attached to the secondary transfer roller 113 to remove the dirt adhering to the secondary transfer roller 113 to prevent the back surface of the printing paper P from being stained. Reference numeral 136 denotes a belt cleaner that cleans the surface of the intermediate transfer belt 110 after the secondary transfer, and reference numeral 137 denotes an image density sensor that detects the image density of an image formed on the intermediate transfer belt 110.

  The paper transport system feeds the print paper P from the paper tray 116 at a predetermined timing by the pickup roller 117 and feeds it to the secondary transfer position via the transport roller 118 and the paper transport path 119. .

  Then, the printing paper P after the secondary transfer is guided to the transport belt 140 and is transported to the fixing device 150 by the transport belt 140.

  (Second Embodiment)

  With reference to FIG. 6, an image forming apparatus PR2 according to a second embodiment of the present invention will be described.

  The main configuration of the image forming apparatus PR2 is the same as that of the image forming apparatus PR1 according to the first embodiment.

  The difference is that, as shown in FIG. 6, as a pressing means for pressing a part of the region E of the conductive film F toward the intermediate transfer belt 110, it contacts the inner surface of the conductive film F instead of the plate-like member 300. Thus, a rotatable roller member 600 is provided.

  The static eliminator M2 is electrically grounded through an earth wire or the like.

  Further, the roller member 600 as the pressing means can be provided in a region (pre-nip region) upstream from the position N where the leading end of the printing paper P enters (see FIG. 4). Thereby, the adhesiveness of the electroconductive film F and the intermediate transfer belt 110 is moderately improved, and the occurrence of scaly defects is more effectively suppressed.

  The position where the roller member 600 is provided may be in an area including at least the position N where the leading end of the printing paper P enters.

  This can further reduce the sliding load with the conductive film F, stabilize the contact state between the conductive film F and the intermediate transfer belt 110, and more effectively suppress the occurrence of scaly defects. Is done.

  Although the invention made by the present inventor has been specifically described based on the embodiments, the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed technology. Should not be considered. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above embodiment, but should be construed according to the description of the scope of claims. All modifications that fall within the scope of the claims and the equivalent technology are included.

  The image forming apparatus according to the present invention can be applied to a copying machine, a laser printer, a full-color printer, a multifunction machine, a facsimile machine, and the like.

1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus PR1 according to a first embodiment. 2 is a schematic configuration diagram enlarging the periphery of a primary transfer roller of an image forming apparatus PR1 according to a first embodiment. FIG. It is a block diagram which shows the structure of the static elimination apparatus M1. It is explanatory drawing which shows the structure of the static elimination apparatus M1. FIG. 6 is an explanatory diagram showing a configuration example of a plate-like member 300. It is a block diagram which shows the structure of the static elimination apparatus M2.

Explanation of symbols

PR1, PR2 Image forming device (color printer)
100 Image forming unit 100C Cyan image forming unit 100K Black image forming unit 100M Magenta image forming unit 100Y Yellow image forming unit 101 Photosensitive drum (image carrier)
102 Uniform charger 103 Laser exposure device 104 Development device 105 Primary transfer roller (primary transfer means)
106 Drum cleaner 107 Transfer bias power supply 110 Intermediate transfer belt 113 Secondary transfer roller (secondary transfer means)
116 Paper tray 117 Pickup roller 118 Transport roller 119 Paper transport path 120 Secondary transfer devices 131, 132, 133 Support roller 140 Transport belt 150 Fixing device M1, M2 Static elimination device (static elimination means)
F Endless belt-shaped conductive film 200 Opposing roller (support roller, backup roller)
201 Tension roller 202 Spring (biasing means)
300 Plate member (pressing means)
300a, b End portion 300c Contact portion 500 Housing 501 Feed roller 600 Roller member (pressing means)
P Printing paper (recording medium)

Claims (10)

An image carrier for holding a toner image;
An intermediate transfer belt provided to face the image carrier;
Primary transfer means for primarily transferring the toner image on the image carrier to the intermediate transfer belt;
A transfer roller disposed in contact with the toner image holding surface of the intermediate transfer belt as a secondary transfer means for secondary transfer of the toner image on the intermediate transfer belt to a recording medium;
A counter roller provided in contact with the intermediate transfer belt so as to face the transfer roller;
The intermediate transfer belt is formed of an endless belt-like conductive film stretched between a tension roller provided in contact with the intermediate transfer belt on the upstream side in the rotation direction of the intermediate transfer belt and the counter roller, Neutralizing means provided so that the conductive film is in contact with,
A pressing means that is provided in contact with the inner surface of the endless belt-like conductive film forming the static elimination means, and presses a partial region of the conductive film toward the intermediate transfer belt;
An image forming apparatus comprising: The pressing means is
The image forming apparatus according to claim 1, wherein the image forming apparatus is configured by a plate-like member.   The image forming apparatus according to claim 2, wherein the upstream and downstream ends of the plate-like member are bent or curved.   The image forming apparatus according to claim 2, wherein a contact portion of the plate-like member with the inner surface of the conductive film is curved. The pressing means is
The image forming apparatus according to claim 1, wherein the image forming apparatus includes a roller member that is rotatable in contact with an inner surface of the conductive film. The pressing means is
The image forming apparatus according to claim 1, wherein the image forming apparatus is provided in an area including at least a position where a leading end of the recording medium enters the intermediate transfer belt. The pressing means is
The image forming apparatus according to claim 1, wherein the image forming apparatus is provided in a region upstream of a position where a leading end of the recording medium enters the intermediate transfer belt. The tension roller is
The image forming apparatus according to claim 1, further comprising an urging unit that urges the counter roller away from the counter roller. 9. The image forming apparatus according to claim 1, wherein a volume resistivity of the endless belt-like conductive film forming the charge eliminating unit is 10 ⁸ to 10 ¹³ Ω · cm. .   The image forming apparatus according to claim 1, wherein the charge eliminating unit is electrically grounded.

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