This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2013-130894 filed on Jun. 21, 2013, the contents of which are incorporated herein by reference in its entirety.
The present disclosure relates to an image forming apparatus having a sheet guide.
An image forming apparatus has been known which has a sheet guide having an electrically grounded metal plate and a plurality of ribs protruding from the metal plate towards a sheet between a transfer unit and a fixing unit. According to this technology, a sheet that passes through the transfer unit and is thus charged is attracted towards the sheet guide by the metal plate, so that conveyance of the sheet is stabilized, and the sheet is not contacted to the metal plate by the ribs, so that an electric discharge, which is caused when the sheet is contacted to the metal plate, is suppressed.
In an environmental situation where the charging of the sheet having passed through the transfer unit is weakened, the sheet may not be appropriately attracted towards the sheet guide. Therefore, it is necessary to increase an attraction force of the metal plate by bringing the metal plate close to the sheet. However, when the sheet and the metal plate come too close to each other in a printing area, an electric discharge may occur by the attraction force of the meal plate.
Therefore, an object of an aspect of the present disclosure is to provide an image forming apparatus having a sheet guide capable of easily attracting a sheet while suppressing an electric discharge.
The aspect of the present disclosure provides the following arrangements.
An image forming apparatus comprising:
a photosensitive drum;
a transfer roller configured to form a nip portion together with the photosensitive drum to transfer an image formed on the photosensitive drum onto a recording sheet; and
a sheet guide that is configured to guide the recording sheet having passed through the nip portion along a guide path in a conveyance direction,
wherein the sheet guide comprises:
wherein the conductor comprises:
wherein protrusion amounts of the end portions with respect to the central portion are smaller than a protrusion amount of each rib from the central portion of the conductor.
An image forming apparatus comprising:
a photosensitive drum;
a transfer roller configured to form a nip portion together with the photosensitive drum to transfer an image formed on the photosensitive drum onto a recording sheet; and
a sheet guide that is configured to guide the recording sheet having passed through the nip portion along a guide path in a conveyance direction,
wherein the sheet guide comprises:
wherein the conductor comprises:
wherein a protrusion amount of the second portion with respect to the first portion is smaller than a protrusion amount of each rib from the first portion of the conductor.
Hereinafter, an illustrative embodiment of the present disclosure will be specifically described with reference to the drawings.
Meanwhile, in the below descriptions, a direction is described based on a user who uses a laser printer 1 that is an example of the image forming apparatus. That is, the left side in
<Schematic Configuration of Laser Printer>
As shown in
The sheet feeding device 3 mainly has a sheet feeding tray 31 that is provided at a lower part in the main body housing 2 and accommodates therein the sheet P, a sheet pressing plate 32, a feeder roller 33, a separation roller 34, a separation pad 35 and conveyance rollers 36. The sheet P in the sheet feeding tray 31 is brought close to the feeder roller 33 by the sheet pressing plate 32 and is delivered towards the separation roller 34 by the feeder roller 33. The delivered sheet P is separated one by one by the separation roller 34 and the separation pad 35 and is fed to the image forming unit 4 by the conveyance rollers 36 and register rollers 37.
The image forming unit 4 mainly has an exposure device 40, a process cartridge 50, a fixing device 60 and a sheet guide 100. The sheet guide 100 will be described later.
The exposure device 40 is provided at an upper part in the main body housing 2 and mainly has a laser light emitting unit (not shown), a polygon mirror 41 that is to rotate, lenses 42, 43 and a reflector 44. A laser light (refer to a dotted and dashed line) that is emitted from the laser light emitting unit and is based on image data is reflected or passes through the polygon mirror 41, the lens 42, the reflector 44 and the lens 43 in corresponding order and is scanned on a surface of a photosensitive drum 51 at high speed.
The process cartridge 50 is arranged below the exposure device 40 and is attached and detached to and from the main body housing 2 through an opening, which is formed when a front cover (a reference numeral thereof is omitted) provided for the main body housing 2 is opened, so as to replace the same. The process cartridge 50 mainly has the photosensitive drum 51, a charger 52, a transfer roller 53, a developing roller 54, a supply roller 55 and a toner accommodation unit 56 that accommodates therein toner.
The fixing device 60 is provided at the rear of the process cartridge 50, and has a heating roller 61 and a pressing roller 62 that is arranged to face the heating roller 61 and presses the heating roller 61. A port of the fixing device 60 for carrying the sheet P therein is positioned at an oblique rear-upper part of a nip portion N formed by the photosensitive drum 51 and the transfer roller 53.
In the image forming unit 4, a surface of the photosensitive drum 51 is uniformly charged by the charger 52 and is then exposed by the high-speed scanning of the laser light from the exposure device 40, so that an electrostatic latent image is formed on the photosensitive drum 51. The toner in the toner accommodation unit 56 is supplied to the developing roller 54 through the supply roller 55 and is carried on the developing roller 54.
Then, the toner carried on the developing roller 54 is supplied to the electrostatic latent image on the photosensitive drum 51, so that the electrostatic latent image becomes visible and a toner image is thus formed on the photosensitive drum 51. After that, the sheet P fed from the sheet feeding device 3 is conveyed between the photosensitive drum 51 and the transfer roller 53, so that the toner image on the photosensitive drum 51 is transferred onto the sheet P.
The sheet P having the toner image transferred thereon is conveyed between the heating roller 61 and the pressing roller 62, so that the toner image is heat-fixed. The sheet P having the toner image heat-fixed thereon is conveyed through a conveyance path 23 by conveyance rollers 63 and is discharged onto a sheet discharge tray 22 from the conveyance path 23 by discharge rollers 64.
<Detailed Configuration of Sheet Guide>
Subsequently, the sheet guide 100 is specifically described.
The sheet guide 100 is a member that is configured to guide, along a guide path, a non-printing surface of the sheet P having passed through the nip portion N formed by the photosensitive drum 51 and the transfer roller 53, i.e., a surface of the sheet P facing the transfer roller 53, and has a conductor 120 and ribs 110 protruding upwards from the conductor 120, as shown in
The conductor 120 is configured by bending a flat plate-shaped metal plate and is arranged at a position facing the sheet P from the lower. The conductor 120 is electrically grounded and an electric potential thereof is zero upon the using. That is, the conductor 120 has an electric potential that attracts the sheet P, which has passed through the nip portion N and is thus charged, towards the conductor 120.
As shown in
The central portion 121 has a left-right width wider than a printing area W and is positioned within a range corresponding to the printing area W in the left-right direction. As shown in
The facing surface 121A is configured so that an upstream part thereof in a conveyance direction of the sheet P substantially horizontally extends from the front towards the rear and a downstream part thereof is gradually upwardly inclined from the front towards the rear. In the meantime, the configuration of the central portion 121 is not limited thereto and may be arbitrarily set, such as a configuration where the central portion is not inclined.
As shown in
The slits 121B are provided side by side in the left-right direction at positions at which the ribs 110 are arranged, and have a size within which the rib 110 can pass therethrough in the upper-lower direction.
The pair of end portions 122 is located at an area corresponding to the outer sides of the printing area W in the left-right direction and is formed by bending left and right ends of the facing surface 121A so that the end portions more protrude upwardly toward the guide path than the central portion 121. The pair of end portions 122 has protrusion parts 122A that extend upwardly from the left and right ends of the facing surface 121A and extension parts 122B that extend outwardly from upper ends of the protrusion parts 122A in the left-right direction. In the below descriptions, since the pair of end portions 122 have a bilaterally symmetric configuration, only the one is described and the description of the other is omitted.
The extension part 122B is a part that faces the sheet P, and a facing surface thereof protrudes towards the sheet P from a virtual plane A extending outwardly from the facing surface 121A of the central portion 121 in the left-right direction. The extension part 122B is configured so that an upstream part of the facing surface thereof in the conveyance direction of the sheet P substantially horizontally extends from the front towards the rear and a downstream part thereof is gradually upwardly inclined from the front towards the rear. In other words, the extension part 122B is configured so that the downstream side thereof in the conveyance direction of the sheet P is located at a position closer to the photosensitive drum 51 than the upstream side thereof in the facing direction of the transfer roller 53 and the photosensitive drum 51, i.e., in the upper-lower direction.
As shown in
The rib 110 is configured to protrude from the slit 121B of the conductor 120 towards the upper, i.e., the sheet P. More specifically, a protrusion amount H1 of the rib 110 from the conductor 120 is set so that when the sheet P, which has passed through the nip portion N and is thus charged, is attracted onto the upper surface of the rib 110, an electric discharge is not caused between the sheet and the conductor 120. The protrusion amount H1 of the rib 110 from the central portion 121 is set to be substantially the same in the front-rear direction. In the meantime, the protrusion amount H1 is not limited thereto and may be arbitrarily set.
The upper surface of the rib 110 is a contact surface 111 that can contact the sheet P and guides the sheet P.
As shown in
As shown in
In the meantime, the end portion 122 is not limited to the above and may be appropriately changed depending on the using modes. For example, the extension part 122B may not be provided, and the protrusion part 122A and the extension part 122B may be separately provided and integrally combined.
Operational effects of the laser printer 1 having the sheet guide 100 configured as described above are described.
As shown in
Here, the protrusion amount H1 of the rib 110 is set so that an electric discharge is not caused between the charged sheet P and the conductor 120. Therefore, there is a possibility that the sheet P will not be sufficiently attracted in an environmental situation where the charging of the sheet P having passed through the nip portion N is weakened.
However, in this exemplary embodiment, since the pair of end portions 122 provided outside the area corresponding to the printing area more protrudes upwardly than the central portion 121, it is possible to bring the pair of end portions 122 closer to the sheet P than the central portion 121. For this reason, while suppressing the electric discharge in the printing area W of the sheet P, it is possible to increase an attraction force of the conductor 120, so that it is possible to easily attract the sheet P towards the conductor 120.
Since the heights of the pair of end portions 122 in the upper-lower direction are smaller than the ribs 110 and the end portions are arranged at the positions spaced from the sheet P, the sheet P is guided towards the fixing device 60 with being contacted to the ribs 110. In the meantime, since the ribs 110 are arranged on the central portion 121 of the conductor 120, the sheet P and the central portion 121 are not contacted to each other, so that the electric discharge in the printing area W is suppressed.
When the end portions 122 are contacted to the sheet P, transfer current may be transferred and leaked from the nip portion N through the sheet P and the end portions 122. However, in this exemplary embodiment, since the end portions 122 are spaced from the sheet P, it is possible to suppress the leak of the transfer current.
Since the contact surfaces 111 of the ribs 110 and the extension parts 122B of the end portions 122 are obliquely inclined in the rear-upper direction so that they are directed from the nip portion N towards the fixing device 60, it is possible to smoothly convey the sheet P towards the fixing device 60. Since the extension parts 122B of the end portions 122 are inclined in conformity with the inclination of the contact surfaces 111 of the ribs 110, it is possible to make a distance between the sheet P and the extension parts 122B be substantially constant, so that it is possible to stabilize the conveyance of the sheet P.
Although the exemplary embodiment has been described, the invention is not limited to the above exemplary embodiment. The specific configuration can be appropriately changed without departing from the scope of the invention. In the below descriptions, the substantially same configurations as those of the above exemplary embodiment are denoted with the same reference numerals and the descriptions thereof are omitted.
In the above exemplary embodiment, the protrusion amounts H2 of the pair of end portions 122 with respect to the central portion 121 are the same at the left and right sides. However, the invention is not limited thereto and the respective protrusion amounts may be different.
Here, as shown in
In this case, as shown in
In this configuration, the first end portion 222 and the second end portion 223 configuring the pair of end portions are respectively configured by protrusion parts 222A, 223A and extension parts 222B, 223B, like the above exemplary embodiment. In the meantime, the respective protrusion amounts H3, H4 are smaller than the protrusion amount H1 of the rib 110 from the conductor 120, like the above exemplary embodiment.
According to the above configuration, since the protrusion amount H3 of the first end portion 222 with respect to the central portion 121 is smaller than the protrusion amount H4 of the second end portion 223 with respect to the central portion 121, distances between both ends of the sheet P, which is discharged with being downwardly inclined as it faces the right end side, and the respective end portions 222, 223 can be easily made to be substantially constant. That is, it is possible to easily attract both left and right ends of the sheet P, which is discharged with being inclined, towards the respective end portions 222, 223 by the substantially same attraction force. For this reason, it is possible to easily convey the sheet P, compared to the configuration where the protrusion amounts of the pair of end portions are the same.
Meanwhile, in the configuration of
In the above exemplary embodiment, the contact surface 111 of the rib 110 is obliquely inclined in the rear-upper direction so that it is directed from the nip portion N towards the fixing device 60. However, the invention is not limited thereto and the contact surface may not be inclined. The ribs 110 are preferably provided in two or more rows.
In the above exemplary embodiment, the extension part 122B of the end portion 122 is obliquely inclined in the rear-upper direction so that it is directed from the nip portion N towards the fixing device 60. However, the invention is not limited thereto and the extension part may not be inclined.
In the above exemplary embodiment, the conductor 120 is made of the metal plate. However, the invention is not limited thereto and the conductor may be made of a conductive resin.
In the above exemplary embodiment, the conductor 120 is electrically grounded. However, the invention is not limited thereto and the conductor may be applied with a bias becoming an electric potential that attracts the sheet having passed through the nip portion.
In the above exemplary embodiment, the invention is applied to the laser printer 1. However, the invention is not limited thereto and can be applied to the other image forming apparatus, such as a copier, a complex machine and the like.
In the above exemplary embodiment, the sheet P such as a cardboard, a postcard, a thin sheet and the like has been exemplified as the recording sheet. However, the invention is not limited thereto and an OHP sheet may be also used.
Number | Date | Country | Kind |
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2013-130894 | Jun 2013 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
7680449 | Shimizu | Mar 2010 | B2 |
20060182479 | Miyake | Aug 2006 | A1 |
20060198668 | Tsujita | Sep 2006 | A1 |
20070147920 | Shimizu | Jun 2007 | A1 |
Number | Date | Country |
---|---|---|
S59-151175 | Aug 1984 | JP |
H04-146456 | May 1992 | JP |
H08-110665 | Apr 1996 | JP |
2007-176611 | Jul 2007 | JP |
Number | Date | Country | |
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20140376975 A1 | Dec 2014 | US |