JP2009128749A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent contact of a casing with a photoreceptor drum even when the casing is turned, by making a distance from the discharge wire of a charger to the surface of the photoreceptor drum shorter than the distance from the discharge wire to the internal face of the casing. <P>SOLUTION: When the distance from the turning axial center C2 of the casing 102 of the charger 100 to the surface P1 of the photoreceptor drum 10, located on a straight line from the C2 to the rotation center C1 of the drum 10, is L1, and a straight distance from the turning axial center C2 to the leading end P2, located the furthest from the turning axial center C2 of the open end of the casing 102, which is located at one rear edge in a rotating direction A, is L2; and the turning axial center C2 is disposed at a position that satisfies the relation L2<L1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention includes a photosensitive drum and a charger including a casing in which a discharge wire is incorporated and extends in the axial direction of the photosensitive drum, and the casing is charged so that the surface of the photosensitive drum can be charged by the discharge wire. The present invention relates to an image forming apparatus (for example, an image forming apparatus such as an electrostatic copying machine, a printer, a facsimile machine, or a multi-function machine of these) having an opening facing the surface in a state of being positioned.

A charger that uniformly charges the surface of the photosensitive drum by corona discharge generates corona products such as ozone and nitrogen oxides. When the generated corona product adheres to the surface of the photosensitive drum, the surface resistance of the photosensitive drum is lowered under high humidity, and so-called image flow is generated. An image forming apparatus for solving such a problem is disclosed in Patent Document 1, for example. The image forming apparatus disclosed in Patent Document 1 includes a photosensitive drum and a charger including a cylindrical casing that includes a discharge wire and extends in the axial direction of the photosensitive drum. The charger casing has an opening facing the surface in a state where the surface of the photosensitive drum can be charged by the discharge wire, and is configured to be rotatable around the axis of the discharge wire. . According to this image forming apparatus, since the casing of the charger is rotated by 180 ° around the axis of the discharge wire and the opening of the casing is directed in the opposite direction to the surface of the photosensitive drum, the corona product adhered to the casing Is not attracted to the photosensitive drum.
Japanese Patent Laid-Open No. 03-059684

In general, in order to uniformly charge the surface of the photosensitive drum as required by the discharge from the charger, the distance from the discharge wire to the inner surface of the casing (radially outward from the surface of the photosensitive drum) is set. In this case, it is necessary to make the distance from the discharge wire to the surface of the photosensitive drum shorter than the distance to the opposing inner surface). However, in the image forming apparatus, since the casing is configured to be rotatable about the axis of the discharge wire, the distance from the discharge wire to the surface of the photosensitive drum is larger than the distance from the discharge wire to the inner surface of the casing. When the casing is shortened, there is a problem that when the casing is rotated, the open end of the casing collides with the surface of the photosensitive drum.

The object of the present invention is to make the opening end of the casing the photosensitive member even if the casing is rotated by making the distance from the discharging wire to the surface of the photosensitive drum shorter than the distance from the discharging wire to the inner surface of the casing in the charger. To provide a novel image forming apparatus that does not contact the surface of a drum.

According to the present invention,
A photosensitive drum and a charger including a casing with a built-in discharge wire and extending in the axial direction of the photosensitive drum. The casing is positioned at a charging position where the surface of the photosensitive drum can be charged by the discharge wire. In an image forming apparatus having an opening facing the surface in the
The casing is a rotation axis parallel to the rotation axis of the photosensitive drum, and is rotated from the charging position around the rotation axis positioned radially outward from the discharge wire with respect to the surface of the photosensitive drum. Supported in the direction of rotation,
The distance from the rotating shaft center of the casing to the surface of the photosensitive drum positioned on a straight line from the rotational axis of the photosensitive drum when viewed in the axial direction of the photosensitive drum with the casing positioned at the charging position. L1, the linear distance from the pivot axis to the tip of the opening side end of the casing located at the rear end in the one pivot direction is the farthest from the pivot axis is L2. The pivot axis is arranged at a position where L2 <L1.
An image forming apparatus,
Is provided.
When the casing is rotated 90 ° in the one rotation direction from the charging position, it is preferable that the opening end of the casing is closed by the shutter plate urged by the urging means.
The casing is formed in a channel shape having a pair of side walls facing each other at a distance in the tangential direction of the photosensitive drum while being positioned at the charging position, and one of the side walls is at the front end in the one rotation direction. The shutter plate is disposed so as to extend along one of the side walls and is urged toward one of the side walls by the urging means, and the casing is rotated 90 ° from the charging position in the one rotation direction. When the shutter plate is rotated, the shutter plate urges the opening end of the casing positioned so as to face the shutter plate after being retracted against the urging means by the rotation of the one opening side end portion of the side wall. It is preferable to close by pressing by means.
With the casing positioned at the charging position, the casing has a width that matches the tangential direction of the photosensitive drum and extends in the axial direction of the photosensitive drum, and the photosensitive drum from both sides of the ceiling wall in the width direction. And a pair of side walls that extend in parallel toward the surface of the photosensitive drum and face each other at a distance in the tangential direction of the photosensitive drum, and the casing is positioned at the charging position. When viewed in the axial direction, the rotation axis of the casing is preferably disposed at a corner where the side wall of the casing and the top wall intersect at the rear end in the one rotation direction.

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

First, an embodiment of a laser printer which is an image forming apparatus configured according to the present invention will be described with reference to FIG.

The laser printer 2 (hereinafter, abbreviated as “printer 2”) includes a printer main body 4 that is a substantially rectangular parallelepiped image forming apparatus main body. On the upper surface of the printer main body 4, a step portion 6 that extends vertically downward from the left end portion in FIG. 6 and a paper discharge tray 8 are formed. The paper discharge tray 8 is formed so as to rise from the lower end of the step portion 6 toward the upper right side in FIG. 6 with a gentle curve and then to extend horizontally at the right end portion in FIG. A discharge port 9 is formed in the stepped portion 6.

In a substantially central region within the printer main body 4, a photosensitive drum 10 as an image carrier is disposed so as to be driven to rotate clockwise in FIG. Around the photosensitive drum 10, a charger 100, a developing sleeve 12A of the developing device 12, a transfer roller 14, a cleaning roller 16A of the cleaning device 16, a static eliminator 18, and the like, which will be described later, are provided. A laser scanning unit LSU that converts input image information into laser light and irradiates the surface of the photosensitive drum 10 is disposed at an upper position in the printer body 4.

A transport path 20 for transporting paper is disposed at a substantially central portion of the printer main body 4 in the vertical direction, and a paper feed cassette 22 is mounted at the lower end. The conveyance path 20 passes between the photosensitive drum 10 and the transfer roller 14 and extends substantially horizontally in the tangential direction thereof. The upstream end region of the transport path 20 is inverted downward and connected to the paper feed cassette 22. On the upstream side of the photosensitive drum 10 in the conveyance path 20, a separation roller pair 24, a conveyance roller pair 26, and a registration roller pair 28 are disposed along the conveyance path 20 in that order from upstream to downstream. Yes. In the paper feed cassette 22, there are disposed a bottom plate 32 which is a paper placement plate supported at one end so as to be rotatable about a shaft 30, a compression coil spring 34 which pushes up the other end of the bottom plate 32, and the like. ing. The upper surface of the leading end of the paper P stacked and accommodated on the bottom plate 32 is pressed against a pickup roller 36 disposed in the printer main body 4.

A fixing device 37 is disposed on the downstream side of the photosensitive drum 10 in the conveyance path 20. The fixing device 37 includes a heat roller 37A and a pressure roller 37B pressed against the heat roller 37A from below. On the downstream side of the fixing device 37 in the conveyance path 20, a conveyance roller pair 38 is disposed. A discharge conveyance path 40 is disposed on the downstream side of the conveyance roller pair 38. The discharge conveyance path 40 extends upward along the inside of the rear wall of the printer main body 4 (the wall located on the left side in FIG. 6), and curves to the front side of the printer main body 4 at the upper end portion to discharge the discharge port 9. It is connected to the. A pair of conveyance rollers 42 is disposed at a substantially central position in the vertical direction of the discharge conveyance path 40, and a pair of discharge rollers 44 is disposed at the upper end (downstream end).

When a print signal is transmitted to the printer 2, the surface of the photosensitive drum 10 uniformly charged by the charger 100 is exposed by the laser scanning unit LSU, whereby an electrostatic latent image is formed on the surface. This electrostatic latent image is developed by the developing sleeve 12A of the developing device 12 to become a toner image. This toner image is transferred onto one side of the paper P conveyed from the paper feed cassette 22 at a predetermined timing by the transfer roller 14. The sheet P to which the toner image has been transferred is guided by the transport path 20 and transported to the fixing device 37, where it is thermally fixed while passing through the nip portion between the heat roller 37A and the pressure roller 37BA. The sheet P on which the toner image is fixed is discharged face down from the discharge port 9 to the discharge tray 8 through the discharge transfer path 40 by the transfer roller pair 38, the transfer roller pair 42, and the discharge roller pair 44. .

Next, the charger 100 will be described. 1 to 3, the charger 100 includes a casing 102. The casing 102 includes a casing body 103 and a shield case 108 described later. A casing main body 103 formed of a suitable synthetic resin has a ceiling wall 104 extending linearly in the longitudinal direction with a constant width, and extends perpendicularly from both sides of the ceiling wall 104 in the width direction to one side of the ceiling wall 104. A channel shape having a pair of side walls 105F and 105R and having an opening 106 on the opposite side of the top wall 104 is formed. End walls 107 are integrally formed at both ends of the casing body 103 in the longitudinal direction. Each of the end walls 107 is disposed so as to be orthogonal to each of the side walls 105F and 105R. Each of the side walls 105F and 105R and the end surface of the end wall 107 on the opening 106 side are positioned on a substantially common virtual plane (not shown).

A shield case 108 formed in a channel shape from a metal plate such as stainless steel is fitted and attached to an intermediate region excluding both end regions in the longitudinal direction of the casing body 103 so as to cover the three outer sides. In the casing body 103, one discharge wire 110 is provided with tension so as to extend in the longitudinal direction. A grid 112 is disposed at the end of the opening 106 of the casing body 103. The opening 106 is positioned to face the surface in a state where the opening 106 is positioned at a charging position (position shown in FIGS. 1 to 3) where the surface of the photosensitive drum 10 can be charged by the discharge wire 110.

The casing 102 is a rotation axis L parallel to a rotation axis (not shown) passing through the rotation center C <b> 1 of the photosensitive drum 10, and is more radially outward than the discharge wire 110 with respect to the surface of the photosensitive drum 10. One rotation direction A (indicated by arrow A in FIG. 3) from the charging position (FIGS. 1 to 3) around the positioned rotation axis L (rotation axis L passing through the rotation axis C2 of the casing 102). It is supported so that it can be rotated clockwise.

More specifically, in the state where the casing 102 is positioned at the charging position (FIGS. 1 to 3), the top wall 104 of the casing body 103 is tangential to the photosensitive drum 10 (in FIGS. 1 and 3). The pair of side walls 105F and 105R extend in the width direction of the top wall 104 and extend in the axial direction of the photosensitive drum 10 (direction perpendicular to the paper surface in FIGS. 1 and 3). To the surface of the photosensitive drum 10 and are positioned so as to face each other with a gap in the tangential direction of the photosensitive drum 10. One side wall 105F is located at the front end in one rotational direction A, and the other side wall 105R is located at the rear end in one rotational direction A.

When viewed in the axial direction of the photosensitive drum 10 with the casing 102 positioned at the charging position, the rotational axis C2 of the casing 102 is the side wall of the casing main body 103 positioned at the rear end in one rotational direction A. It is arranged at the corner where 105R and the top wall 104 intersect. At the corners, gears 114 are provided so as to extend from the end walls 107 of the casing main body 103 in the longitudinal direction of the casing main body 103 (longitudinal direction parallel to the rotation axis of the photosensitive drum 10). Teeth are formed on the outer peripheral surface of each gear 114, and a supported hole 116 is formed in the center. Each of the supported holes 116 has the rotation axis L that is a common axis. Corresponding to each supported hole 116 of the gear 114, the printer body 4 is provided with a support shaft 118, and each of the supported holes 116 is rotatably supported by the corresponding support shaft 118. The casing 102 is rotatably supported at a predetermined position of the printer body 4. Each axis of the support shaft 118 is also positioned on the rotation axis L.

In the printer main body 4, a drive shaft 120 extending parallel to the rotation axis L of the casing 102 is rotatably disposed, and gears 122 are disposed at both ends of the drive shaft 120 so as to be integrally rotatable. . Each of the gears 122 is meshed with the gear 114 of the casing 102. One end of the drive shaft 120 is drivingly connected to the electric motor M.

In order to prevent the casing 102 from rotating in the direction opposite to the one rotation direction A and to be positioned at the charging position, the position of the printer main body 4 facing the other side 105R of the side wall at both longitudinal ends of the casing main body 103. Each is provided with a stopper 124. Each of the stoppers 124 is made of rubber.

As clearly shown in FIG. 3, the distance between the discharge wire 110 and the inner surface of the casing 102, specifically, the inner surface of the top wall 104 of the casing body 103, with the casing 102 positioned at the charging position. The distance from the discharge wire 110 to the surface of the photosensitive drum 10 is set short. This configuration enables the charger 100 to charge the surface of the photosensitive drum 10 as required.

Further, as clearly shown in FIG. 3, when the casing 102 is positioned at the charging position, when viewed in the axial direction of the photosensitive drum 10, the rotation center of the photosensitive drum 10 from the rotation axis C <b> 2 of the casing 102. The distance to the surface P1 of the photosensitive drum 10 located on the straight line up to C1 is L1, and the opening 106 of the casing 102 located at the rear end in one rotational direction A from the rotational axis C2 of the casing 102. When the linear distance from the side end to the tip P2 farthest from the rotational axis C2 is L2, the rotational axis C2 is arranged at a position where L2 <L1. In this embodiment, the front end P2 exists at the front end on the opening 106 side of the side wall located at the rear end in the one rotation direction A of the shield case 108. With this configuration, even when the casing 102 is rotated in one rotation direction A from the charging position (FIG. 1), the casing 102 does not contact the surface of the photosensitive drum 10. Therefore, according to the present invention, even if the casing 102 is rotated by making the distance from the discharge wire 110 to the surface of the photosensitive drum 10 shorter than the distance from the discharge wire 110 to the inner surface of the casing 102 in the charger 100. The open end of the casing 102 does not contact the surface of the photosensitive drum 10. By rotating the casing 102, the opening 106 can be directed to a position not facing the surface of the photosensitive drum 10, so that an image flow due to the adsorption of the corona product can be prevented.

In order to prevent the above problem more reliably, in the present invention, when the casing 102 is rotated 90 ° in the one rotation direction A from the charging position, the opening 106 end of the casing 102 is a plurality of biasing means. It is configured to be closed by a shutter plate 130 biased by a compression coil spring 126.

This will be described more specifically. As described above, in the state where the casing 102 is positioned at the charging position, one side wall 105F is positioned at the front end in one rotation direction A, and the other side wall 105R is the rear end in one rotation direction A. Positioned on. The shutter plate 130 is disposed so as to extend along the one side wall 105 </ b> F, and is urged toward the one side wall 105 </ b> F by the compression coil spring 126.

The shutter plate 130 is made of a suitable synthetic resin and is formed in a rectangular flat plate shape. One end of each of the longitudinal ends of the shutter plate 130 is connected to one end of two compression coil springs 126, and the other end of each compression coil spring 126 is held by a spring holding portion 132 provided in the printer body 4. Has been. In this way, the shutter plate 130 is held by the spring holding portion 132 provided in the printer main body 4 via the four compression coil springs 126. The other surface of the shutter plate 130 is positioned so as to face one side 105 </ b> F of the casing 102. In the embodiment, ribs 134 are formed at both ends in the longitudinal direction of one side 105F of the casing 102 so as to extend from the end of the opening 106 at a right angle in the direction opposite to the other side 105R of the side wall. Since the shield case 108 fitted to the casing 102 protrudes slightly toward the one rotation direction A side than the side wall located on the one rotation direction A side, both end portions in the longitudinal direction of the other surface of the shutter plate 130 Are positioned to abut or press against the tips of the ribs 134 with a relatively weak pressure.

When the electric motor M is driven to rotate in one direction and the casing 102 is rotated 90 ° in the one rotation direction A from the charging position, the shutter plate 130 firstly opens the end 106 side end (rib) of one side 105F of the side wall. 134) is retracted against each spring force of the compression coil spring 126 (see FIG. 4). Further rotation of the casing 102 causes the end of the opening 106 of the casing 102 to be positioned so as to face the other surface of the shutter plate 130, and the other surface of the shutter plate 130 causes the end of the opening 106 to move to each spring force of the compression coil spring 126. To close by pressing (see FIG. 5). At the same time, the rotation drive of the electric motor M is stopped, and the casing 102 is positioned in the closed position where the opening 106 is closed by the shutter plate 130. In the printer 2, the opening 106 of the casing 102 is closed by the shutter plate 130 while the printing operation is stopped. During this time, the problem that the corona product generated in the charging device 100 adheres to the surface of the photosensitive drum 10 is prevented, so that the occurrence of image flow is prevented.

When the electric motor M is rotationally driven in the reverse direction and the casing 102 is rotated 90 ° from the closed position to the charging position in the other rotation direction opposite to the one rotation direction A, the casing 102 and the shutter plate The operation opposite to the previous operation is performed between the casing 102 and the casing 102, the casing 102 is rotated to the charging position (FIGS. 1 to 3), and the shutter plate 130 is positioned at the position shown in FIG. . At the same time, the rotational drive of the electric motor M is stopped.

1 is a schematic cross-sectional view showing a configuration of an embodiment of a main part including a charger in a laser printer configured according to the present invention. It is a top view of the charger shown in FIG. FIG. 2 is an enlarged schematic cross-sectional view illustrating a casing and a photosensitive drum of the charger illustrated in FIG. 1. It is a cross-sectional schematic diagram which shows the other operation | movement aspect of the charger shown in FIG. It is a cross-sectional schematic diagram which shows the further another operation | movement aspect of FIG. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a laser printer including the charger illustrated in FIG. 1.

Explanation of symbols

2: Laser printer 4: Printer body 10: Photosensitive drum 100: Charger 102: Casing 103: Casing body 106: Opening 110: Discharge wire 126: Compression coil spring (biasing means)
130: Shutter plate
C1: Rotation center of photosensitive drum
C2: Casing rotation center

Claims (4)

A photosensitive drum and a charger including a casing with a built-in discharge wire and extending in the axial direction of the photosensitive drum. The casing is positioned at a charging position where the surface of the photosensitive drum can be charged by the discharge wire. In an image forming apparatus having an opening facing the surface in the
The casing is a rotation axis parallel to the rotation axis of the photosensitive drum, and is rotated from the charging position around the rotation axis positioned radially outward from the discharge wire with respect to the surface of the photosensitive drum. Supported in the direction of rotation,
The distance from the rotating shaft center of the casing to the surface of the photosensitive drum positioned on a straight line from the rotational axis of the photosensitive drum when viewed in the axial direction of the photosensitive drum with the casing positioned at the charging position. L1, the linear distance from the pivot axis to the tip of the opening side end of the casing located at the rear end in the one pivot direction is the farthest from the pivot axis is L2. The pivot axis is arranged at a position where L2 <L1.
An image forming apparatus. The image forming apparatus according to claim 1, wherein when the casing is rotated 90 ° in the one rotation direction from the charging position, the opening end of the casing is closed by a shutter plate biased by a biasing means. The casing is formed in a channel shape having a pair of side walls opposed to each other at a distance in the tangential direction of the photosensitive drum while being positioned at the charging position, and one of the side walls is at the front end in the one rotation direction. The shutter plate is disposed so as to extend along one of the side walls and is urged toward one of the side walls by the urging means, and the casing is rotated 90 ° from the charging position in the one rotation direction. When rotated, the shutter plate urges the opening end of the casing positioned so as to face the shutter plate after being retracted against the urging means by the rotation of one opening side end portion of the side wall. The image forming apparatus according to claim 1, wherein the image forming apparatus is pressed and closed by means. With the casing positioned at the charging position, the casing has a width that matches the tangential direction of the photosensitive drum and extends in the axial direction of the photosensitive drum, and the photosensitive drum from both sides in the width direction of the ceiling wall. Formed in a channel shape having a pair of side walls extending in parallel toward the surface of the photosensitive drum and facing each other at a distance in the tangential direction of the photosensitive drum,
When viewed in the axial direction of the photosensitive drum in a state where the casing is positioned at the charging position, the rotation axis of the casing intersects the side wall of the casing located at the rear end portion in the one rotation direction and the top wall. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed at a corner.

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