JP2013195832A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress toner, scattered after a toner image is transferred from an image holding body to a recording medium, from being attached to the recording medium.SOLUTION: Even if discharge (surface discharge) occurs between a secondary transfer roller and a recording medium P and scattered toner TA scatters from a toner image T, a magnetic brush roller 120 electrically adsorbs the scattered toner TA, and thereby the scattered toner TA can be suppressed from being attached to the recording medium P. Accordingly, a reduction in image quality due to the attachment of the scattered toner TA to the recording medium P can be suppressed. The scattered toner TA adsorbed to a magnetic brush 126 of the magnetic brush roller 120 moves to a removing member 110, and thereby a reduction in adsorption performance due to accumulation of the scattered toner TA in the magnetic brush roller 120 is suppressed.

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, a conductive plate is disposed in close proximity to the transfer material on the transfer path on which the toner image is transferred, and a voltage having the same polarity as the frictional charging polarity of the toner is applied to the conductive plate. A technique for preventing scattering of toner from a transfer material is disclosed (see Patent Document 1).

Japanese Patent Laid-Open No. 02-247672 JP 2005-221537 A

  An object of the present invention is to suppress adhesion of toner scattered from a recording medium after the toner image is transferred from the image carrier to the recording medium.

  According to the first aspect of the present invention, an image holding body on which a toner image is formed by toner charged to a predetermined polarity, and a voltage having a polarity opposite to the predetermined polarity is applied to form the image holding body. A transfer member for transferring the toner image to the recording medium, and a surface of the recording medium at a downstream exit portion of the recording medium in the conveyance direction of the recording medium. A first conductive member to which a voltage having a polarity opposite to the predetermined polarity is applied.

  According to a second aspect of the present invention, the first conductive member is a rotating body, is provided in contact with or close to the first conductive member, and has the same polarity as the voltage of the first conductive member and a large absolute value. A second conductive member to which a voltage is applied is included.

  According to a third aspect of the present invention, the first conductive member is a magnetic brush roll having a magnetic brush formed by raising magnetic particles on the roll surface.

  According to the first aspect of the present invention, compared to the case where the first conductive member is not provided at the downstream exit portion in the transport direction of the transfer member with respect to the recording medium, the scattered toner is prevented from adhering to the recording medium. be able to.

  According to the second aspect of the present invention, the toner scattered by the first conductive member is adsorbed as compared with the case where the second conductive member in contact with or close to the first conductive member of the rotating body is not provided. It is possible to suppress a decrease in the adsorption performance.

  According to the third aspect of the present invention, the adsorption performance for adsorbing the scattered toner is improved as compared with the case where the first conductive member is other than the magnetic brush roll.

1 is a schematic configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram schematically illustrating an image forming unit of the image forming apparatus in FIG. 1. It is an enlarged view which shows the principal part of FIG. It is a schematic diagram which shows typically the adsorption | suction apparatus shown by FIG. It is a schematic diagram which shows typically the adsorption | suction apparatus of a 1st modification. It is a schematic diagram which shows typically the adsorption | suction apparatus of a 2nd modification.

  Below, an example of an embodiment concerning the present invention is described based on a drawing. Note that an arrow F in the drawing indicates the conveyance direction of the recording medium P in the vicinity of the downstream side of the secondary transfer unit, which will be described later, in the conveyance direction downstream side exit portion 102. Further, the toner image T finally transferred to the recording medium P shown in FIGS. 3 to 6 is shown to be thicker and larger than the actual size for easy understanding.

<Overall configuration of image forming apparatus>
First, the overall configuration of the image forming apparatus will be described.

  As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment forms a toner image T (see FIG. 3) on a recording medium storage unit 12 that stores a recording medium P such as paper and a recording medium P. The image forming unit 14, the transport unit 16 that transports the recording medium P from the recording medium storage unit 12 to the image forming unit 14, and the toner image T (see FIG. 3) formed by the image forming unit 14 are fixed to the recording medium P. And a recording medium discharge section (not shown) from which the recording medium P on which the toner image T (see FIG. 3) is fixed by the fixing apparatus 18 is discharged.

  The image forming unit 14 includes image forming units 22C, 22M, 22Y, and 22K that form toner images of each color of cyan (C), magenta (M), yellow (Y), and black (K) (see FIG. (See also 3). In the following, when it is necessary to distinguish YMCK, a description will be given by adding any of Y, M, C, and K after the reference. When YMCK does not need to be distinguished, Y, M, C, K is omitted.

  In addition, the image forming unit 14 includes an intermediate transfer belt 24 as an example of an image carrier to which toner images formed by the image forming units 22C, 22M, 22Y, and 22K are transferred, and image forming units 22C, 22M, 22Y, The primary transfer rolls 26C, 26M, 26Y, and 26K that transfer the toner image formed at 22K to the intermediate transfer belt 24, and the toner image T (see FIG. 3) transferred to the intermediate transfer belt 24 are transferred to the recording medium P. And a secondary transfer roll 28 as an example of a transfer member.

  Further, the suction device 100 is provided at the outlet 120 on the downstream side in the transport direction with respect to the recording medium P of the secondary transfer roll 28 (see also FIG. 3). Details of the adsorption device 100 will be described later.

  As shown in FIG. 2, each image forming unit 22 has a photoreceptor 30 that holds a latent image and rotates in one direction (clockwise in FIGS. 1 and 2). Around the photoconductor 30, a charging device 32, an optical head 34, a developing device 36, and a removal device 40 are provided in order from the upstream side in the rotation direction of the photoconductor 30.

  In each image forming unit 22, the surface of the photoreceptor 30 is charged by the charging device 32, and the optical head 34 exposes the charged surface of the photoreceptor 30 to form an electrostatic latent image on the surface of the photoreceptor 30. The electrostatic latent image formed on the surface of the photoreceptor 30 is developed by the developing device 36 to form a toner image. Then, the toner image formed on the photoreceptor 30 is transferred to the intermediate transfer belt 24 by a primary transfer roll 26 described later. Further, the toner remaining on the surface of the photoreceptor 30 without being transferred to the intermediate transfer belt 24 is removed by the removing device 40.

  The developing device 36 charges the internal toner to a predetermined polarity (negative polarity or positive polarity), and develops the electrostatic latent image formed on the surface of the photoreceptor 30 to form a toner image. In this embodiment, the toner and the carrier are agitated to be frictionally charged to a predetermined polarity (negative polarity or positive polarity).

  As shown in FIG. 1, the intermediate transfer belt 24 is supported by a counter roll 42, a drive roll 44, and a support roll 46 facing the secondary transfer roll 28, and is in one direction (in FIG. It moves in a circular manner (clockwise direction).

  As shown in FIGS. 1 and 2, each primary transfer roll 26 faces each photoconductor 30 with the intermediate transfer belt 24 interposed therebetween. A primary transfer position where the toner image on each photoconductor 30 is primarily transferred to the intermediate transfer belt 24 is formed between each primary transfer roll 26 and each photoconductor 30. At the primary transfer position, each primary transfer roll 26 transfers the toner image on the surface of each photoconductor 30 to the intermediate transfer belt 24 by a pressing force and an electrostatic force.

  As shown in FIGS. 1 and 3, the secondary transfer roll 28 faces the opposing roll 42 with the intermediate transfer belt 24 interposed therebetween. A secondary transfer position where the toner image T (see FIG. 3) on the intermediate transfer belt 24 is secondarily transferred to the recording medium P is formed between the secondary transfer roll 28 and the opposing roll 42. At this secondary transfer position, the secondary transfer roll 28 transfers the toner image T (see FIG. 3) on the surface of the intermediate transfer belt 24 to the recording medium P by a pressing force and an electrostatic force.

  The secondary transfer roll 28 is applied with a voltage having a polarity opposite to a predetermined charging polarity (negative polarity or positive polarity) of the toner.

  As shown in FIG. 1, the transport unit 16 transports the recording medium P stored in the recording medium storage unit 12 and transports the recording medium P transported by the transport roll 50 to the secondary transfer position. A roll pair 52. The fixing device 18 is disposed downstream in the transport direction from the secondary transfer position, and fixes the toner image T (see FIG. 3) transferred at the secondary transfer position to the recording medium P.

  A conveyance belt 54 as an example of a conveyance member that conveys the recording medium P to the fixing device 18 is disposed downstream of the secondary transfer position in the conveyance direction and upstream of the fixing device 18 in the conveyance direction.

  With the above configuration, in the image forming apparatus 10 according to the present embodiment, the recording medium P sent out from the recording medium storage unit 12 is first sent to the secondary transfer position by the transport roll pair 52.

  On the other hand, the toner images of the respective colors formed by the image forming units 22C, 22M, 22Y, and 22K are superimposed on the intermediate transfer belt 24 to form a color toner image T (see FIG. 3). The toner image T (see FIG. 3) formed on the intermediate transfer belt 24 is transferred to the recording medium P sent to the secondary transfer position.

  The recording medium P to which the toner image T (see FIG. 3) has been transferred is conveyed to the fixing device 18, and the transferred toner image T (see FIG. 3) is fixed by the fixing device 18. The recording medium P on which the toner image T (see FIG. 3) is fixed is discharged to a recording medium discharge unit (not shown). As described above, a series of image forming operations are performed.

<Adsorption device>
Next, the adsorption device will be described.

  As shown in FIGS. 3 and 4, the adsorption device 100 includes a magnetic brush roll 120 as an example of a first conductive member and a removal member 110 as an example of a second conductive member. Yes.

  The magnetic brush roll 120 is provided at the outlet 102 on the downstream side in the transport direction of the secondary transfer roll 28 with respect to the recording medium P. In other words, the magnetic brush roll 120 is provided near the downstream side in the transport direction of the secondary transfer roll 28. Here, the vicinity in the downstream side is a position where the recording medium P arrives within 0.5 seconds after the recording medium P is discharged from the outlet portion 102, for example. The magnetic brush roll 120 is provided in the vicinity of the surface of the recording medium P to which the toner image has been transferred (for example, a position of 5 mm to 50 mm from the surface to which the toner image is transferred). The magnetic brush roll 120 includes a sleeve 124, a magnet roll 122, and a magnetic brush 126.

  As shown in FIG. 4, the sleeve 124 has a cylindrical shape made of a nonmagnetic material, and a magnet roll 122 is provided therein. The magnet roll 122 has a configuration in which a plurality of fan-shaped permanent magnets 123 are provided around the metal rod 121. The magnetic brush 126 is formed by causing the magnetic particles 128 provided on the surface of the sleeve 124 to rise along the magnetic force lines formed by the magnet roll 122. In FIG. 4 (and FIG. 3), the magnetic brush 126 is shown in an easy-to-understand manner, so that it is different from the actual spike shape (the actual magnetic brush is not shown in the same shape). Further, the tip of the magnetic brush 126 and the toner image (recording medium P) are configured to be spaced from each other (the magnetic brush 126 and the toner image (recording medium P) are not in contact).

  In the magnetic brush roll 120 of the present embodiment, the magnet roll 122 (the metal rod 121) is fixed to the apparatus main body (not shown), and the sleeve 124 is configured to rotate in the direction indicated by the arrow K by a driving apparatus (not shown). . Therefore, the magnetic particles 128 move along the surface of the sleeve 124 in the direction of the arrow K while the surface of the sleeve 124 rises along the lines of magnetic force to form the magnetic brush 126.

  The sleeve 124 may be fixed and the magnet roll 122 may be rotated. In this case, in order to set the moving direction of the magnetic particles 128 to the K direction, the magnet roll 122 is rotated in the arrow K direction.

  The removal member 110 as an example of the second conductive member is a flat plate made of a conductive member such as a metal, and the plate surface is disposed at a distance from the tip of the magnetic brush 126 of the magnetic brush roll 120.

  The magnetic brush roll 120 and the removing member 110 are each applied with a voltage having a polarity opposite to the predetermined charging polarity of the toner. Further, a higher voltage than the magnetic brush roll 120 is applied to the removing member 110. To be precise, in the case of negative polarity, the absolute value is applied so as to be larger than that of the magnetic brush roll 120.

  Further, the axial length of the magnetic brush roll 120, that is, the width of an area where the magnetic brush 126 is formed (an adsorption area where the scattered toner TA described later is adsorbed) is assumed to be recorded by the image forming apparatus 10. The maximum recording medium P is set to have a width substantially equal to or wider than the paper width (width in the direction orthogonal to the conveyance direction F).

<Action and effect>
Next, the operation and effect of this embodiment will be described.

  As shown in FIG. 3, the toner image T is transferred from the intermediate transfer roll 28 to the recording medium P by the secondary transfer roll 28. After the secondary transfer, discharge (creeping discharge) may occur between the secondary transfer roll 28 and the recording medium P, and the toner may be scattered from the toner image T due to this discharge. Hereinafter, the scattered toner is referred to as scattered toner TA.

  The scattered toner TA is electrically adsorbed to the magnetic brush 126 of the magnetic brush roll 120 to which a voltage having a polarity opposite to the charging polarity of the toner is applied. After the suction, the magnetic brush roll 120 rotates, so that the magnetic brush 126 in a state where the scattered toner TA is attracted moves to the side facing the removal member 110.

  A higher voltage than the magnetic brush roll 120 is applied to the removing member 110. Therefore, an electric force is generated in the scattered toner TA in the direction toward the removal member 110 due to the electric field between the removal member 110 and the magnetic brush roll 120. Due to this electric force, the scattered toner TA flies from the magnetic brush roll 120 to the removing member 110 and moves, and the scattered toner TA is adsorbed and removed by the removing member 110.

  Then, after the scattered toner TA flies (moves) from the magnetic brush 126 to the removing member 110, the magnetic brush roll 120 rotates, so that the magnetic brush 126 moves to the side where the scattered toner TA is floating, and is again magnetic. The scattered toner TA is electrically attracted to the brush 126.

  In this way, even if discharge (creeping discharge) occurs between the secondary transfer roll 28 and the recording medium P and the scattered toner TA is scattered from the toner image T, the magnetic brush roll 120 is electrically scattered toner. Since the TA is adsorbed, the adsorption of the scattered toner TA onto the recording medium P can be suppressed. Therefore, a decrease in image quality due to the scattered toner TA adhering to the recording medium P is suppressed.

  Further, since the scattered toner TA adsorbed to the magnetic brush 126 of the magnetic brush roll 120 moves to the removal member 110 and is removed, a decrease in the adsorption performance due to accumulation of the scattered toner TA on the magnetic brush roll 120 is suppressed. .

  Furthermore, since the magnetic brush 126 of the magnetic brush roll 120 is formed by connecting the magnetic particles 128 along the lines of magnetic force, for example, the brush density (toner adsorbs more easily than the configuration in which conductive brush hairs are implanted. Surface area) to be increased. Therefore, compared with other brush hair, adsorption performance is high.

  Here, it is desirable that as much scattered toner TA as possible be attracted to the magnetic brush roll 120 before the scattered toner TA scattered by the discharge adheres to the recording medium P. Therefore, it is desirable that the magnetic brush roll 120 be disposed closer to the secondary transfer roll 28 than the position where the scattered toner TA adheres to the recording medium P. If it demonstrates from another viewpoint, the magnetic brush roll 120 will be arrange | positioned in the position which can reduce the quantity which the scattering toner TA adheres to the recording medium P (it suppresses adhesion).

<Modification>
In the said embodiment, although the 1st electroconductive member was the magnetic brush roll 120 which has the magnetic brush 126 formed by making a magnetic particle stand on the roll surface, it is not limited to this. Therefore, the adsorption | suction apparatus which has another 1st electroconductive member next as a modification is demonstrated. In any of the modifications, the width of the suction region of the first conductive member is substantially the same as the paper width of the maximum recording medium P on which image recording is assumed in the image forming apparatus 10 or the paper width. Is also set to be wide.

(First modification)
As shown in FIG. 5, the suction device 200 of the first modified example includes a conductive brush roll 220 in which conductive brush bristles 226 are planted as an example of a first conductive member, and an example of a second conductive member. And a removing member 110. The conductive brush roll 220 is configured to rotate in a direction indicated by an arrow K while being applied with a voltage having a polarity opposite to the charging polarity of the toner. Further, a higher voltage is applied to the removing member 110 than the conductive brush roll 220 (in the case of negative polarity, the absolute value is applied to be larger than that of the conductive brush roll 220). .

  Similar to the above-described embodiment, the scattered toner TA is electrically adsorbed to the brush bristles 226 of the conductive brush roll 220 of the adsorption device 200 of the first modified example. Further, the scattered toner TA flies from the conductive brush roll 220 to the removal member 110 and moves, and is adsorbed and removed by the removal member 110.

  Therefore, even if a discharge (creeping discharge) occurs between the secondary transfer roll 28 and the recording medium P, and the scattered toner TA is scattered from the toner image T (see FIG. 3), the conductive brush roll 220 is electrically Since the scattered toner TA is adsorbed to the recording medium P, the adhesion of the scattered toner TA to the recording medium P can be suppressed. Therefore, a decrease in image quality due to the scattered toner TA adhering to the recording medium P is suppressed.

  Further, since the scattered toner TA adsorbed to the brush bristles 226 of the conductive brush roll 220 moves to the removal member 110 and is removed, a reduction in adsorption performance due to accumulation of the scattered toner TA on the conductive brush roll 220 is suppressed. Is done. The conductive brush roll 220 has a simple structure as compared with, for example, a magnetic brush roll, and thus is low in cost.

(Second modification)
As shown in FIG. 6, the adsorption device 300 of the second modification is configured to include a metal roll 320 as an example of a first conductive member, and a removal device 324. The metal roll 320 is configured to be applied with a voltage having a polarity opposite to the charging polarity of the toner and to rotate in the direction indicated by the arrow K. The removing device 324 has a scraper 322 whose tip is in contact with the surface of the metal roll 320.

  The scattered toner TA is electrically adsorbed on the metal roll 320 of the adsorption device 300 of the second modification. The scattered toner TA adsorbed on the surface of the metal roll 320 is scraped and removed by the scraper 322 of the removing device 324 and is collected in the housing 326.

  Therefore, even if a discharge (creeping discharge) occurs between the secondary transfer roll 28 and the recording medium P and the scattered toner TA is scattered from the toner image T (see FIG. 3), the metal roll 320 is electrically scattered. Since the toner TA is adsorbed, adhesion of the scattered toner TA to the recording medium P can be suppressed. Therefore, a decrease in image quality due to the scattered toner TA adhering to the recording medium P is suppressed.

  Further, since the scattered toner TA adsorbed on the metal roll 320 is scraped off and removed by the scraper 322, a decrease in adsorption performance due to the accumulation of the scattered toner TA on the metal roll 320 is suppressed. In addition, the metal roll 320 has a simple structure and is low in cost as compared with, for example, a magnetic brush roll or a conductive brush.

(Other variations)
The first conductive member may be other than the above configuration. For example, the first conductive member (magnetic brush roll 120, conductive brush roll 220, metal roll 300) may be rotated in the direction opposite to the K direction. Further, the first conductive member may be configured not to rotate. For example, a flat metal member may be used.

  The second conductive member may have a configuration other than the removing member 110. For example, the second conductive member may be provided so as to be in contact with the magnetic brush 126 and the brush bristles 226. Furthermore, the structure which does not have a 2nd electroconductive member may be sufficient.

<Others>
The present invention is not limited to the above embodiment.

  For example, in the above embodiment, the transfer member is the secondary transfer roll 28, but is not limited thereto. It may be a transfer member having a shape (structure) other than the roll shape. For example, a belt-shaped transfer member (transfer belt) may be used. Further, it may be a corotron.

  In the above embodiment, the image carrier is an intermediate transfer belt, but is not limited thereto. For example, a roll-shaped intermediate transfer member (intermediate transfer roll) may be used. Further, the image may be transferred directly from the photosensitive member to the recording medium P without using an intermediate transfer member. In this case, the photosensitive member serves as an image holding member. Further, the photoconductor may be a belt-like photoconductor (photoconductor belt) other than the drum shape.

  Further, the configuration of the image forming apparatus is not limited to the configuration of the above-described embodiment, and various configurations can be employed. Furthermore, it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.

10 Image forming apparatus 24 Intermediate transfer belt (an example of an image carrier)
28 Secondary transfer roll (an example of a transfer member)
110 Removal member (example of second conductive member)
120 magnetic brush roll (an example of a first conductive member)
220 conductive brush (an example of a first conductive member)
226 Magnetic brush 320 Metal roll (an example of a first conductive member)
P Recording medium PA Toner image-transferred surface T Toner image TA Scatter toner

Claims (3)

An image carrier on which a toner image is formed by toner charged to a predetermined polarity;
A transfer member that applies a voltage having a polarity opposite to the predetermined polarity and transfers the toner image formed on the image carrier to a recording medium;
The recording medium is provided in the vicinity of the surface on which the toner image of the recording medium is transferred at an outlet portion on the downstream side in the conveyance direction of the recording medium with respect to the transfer member. A conductive member;
An image forming apparatus comprising: The first conductive member is a rotating body,
The second conductive member is provided in contact with or close to the first conductive member, and a voltage having the same polarity and a large absolute value as the voltage of the first conductive member is applied.
The image forming apparatus according to claim 1. The first conductive member is a magnetic brush roll having a magnetic brush formed by raising magnetic particles on the roll surface.
The image forming apparatus according to claim 1.

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