JPH06149111A - Sheet carrying device - Google Patents

Abstract

PURPOSE:To prevent irregularities in an image by making the frictional resistance of a form to an entering guide low and smoothly carrying the paper sheet. CONSTITUTION:This sheet carrying device is carrys a sheet whose surface is formed with the image by magnetic toner in an image forming part to a fixing/carrying device. The device is provided with a carrying means and the entering guide 68. The carrying means includes a carrying guide 45 having prescribed electric resistance and guiding the sheet from the image forming part to the side of the fixing/carrying device. The entering guide 68 guids the sheet carried by the carrying means between the thermal roller 50 and pressure roller 51 of the fixing/carrying device and has the surface resistivity higer compared with that of the carrying guide 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a sheet conveying device that conveys a sheet having an image formed by magnetic toner on its surface in an image forming apparatus to a fixing device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a facsimile machine, a toner image is transferred onto a sheet in an image forming section,
The toner image on the paper is fixed in the fixing unit. Therefore, a sheet conveying device for conveying the sheet on which the unfixed toner image is formed is provided between the image forming unit and the fixing device. As this sheet conveying device, there is known a sheet conveying device including a conveying unit including a conveying belt and a conveying guide member, and an entrance guide for guiding the sheet conveyed by the conveying unit onto the fixing unit. In this type of sheet conveying device, a sheet carrying an unfixed toner image is conveyed by a conveying unit to reach an entrance guide, and is guided to the fixing unit by the entrance guide. The entrance guide is a flat member, and the paper is guided to the fixing unit while sliding on the entrance guide.

[0003]

As described above, since the paper on which the unfixed toner image is formed is conveyed between the image forming section and the fixing section, in order to prevent the image from being disturbed, It is necessary to carry out stable transportation. However, in the above-mentioned conventional configuration, since the paper slides on the entrance guide when the paper is guided by the entrance guide, the paper may vibrate due to friction or the like and the image may be disturbed.

An object of the present invention is to reduce the frictional resistance between the paper and the entrance guide and prevent the unfixed toner image from being disturbed.

[0005]

A sheet conveying apparatus according to the present invention is an apparatus for conveying a sheet having an image formed by magnetic toner on the surface thereof to a fixing device in an image forming apparatus. This device includes a conveying means and an entrance guide member. The transport unit includes a transport guide member that has a predetermined electric resistance and that guides the sheet from the image forming unit to the fixing device. The entrance guide member is for guiding the sheet conveyed by the conveying means to the fixing portion of the fixing device, and has a surface resistivity higher than that of the conveying guide member.

[0006]

In the sheet transporting apparatus according to the present invention, the sheet guided by the transport guide member is gradually removed from the sheet having the same polarity as the transfer voltage on the transport guide member. When reaching the entrance guide member, the entrance guide member has a higher surface resistivity than the conveyance guide member, so that the electric charge of the sheet is not further removed, and the electric charge of the sheet is charged on the entrance guide member. Therefore, the sheet and the approach guide member are charged with the same polarity, and the approach guide member and the sheet electrically repel each other.
Therefore, the frictional resistance between the approach guide member and the sheet is reduced, and the sheet is smoothly transported. Therefore,
It is possible to suppress vibration when the paper is conveyed, and to prevent the unfixed toner image from being disturbed.

[0007]

1 is an external perspective view of a facsimile apparatus to which an embodiment of the present invention is applied, and FIG. 2 is a schematic vertical sectional view showing the structure thereof. As shown in these drawings, the present apparatus is provided with a reading unit 1 arranged at an upper portion for reading image information of a document.
And an output unit 2 which is arranged substantially in the center of the apparatus and forms received image information on the front surface of the paper, and a paper feeding unit 3 which is arranged at the bottom of the apparatus and supplies the paper to the output unit 2. Has been done.

The reading section 1 has a document table 5 on which a document is placed.
And a document transport section 6 for transporting the document, and a document discharge tray 7 for storing the document discharged from the document transport section 6. An image information reading sensor 8 for reading the image information of the original is arranged in the original conveying section 6. An operation panel 9 having various keys and a display unit is arranged on the upper surface of the device. Furthermore, a handset 10 is arranged on top of the device. The output unit 2 includes an imaging unit 11 including a photosensitive drum and a developing unit 14 including a developing roller 12 and a toner cartridge 13.
And an image according to the received information
Laser device 15 for forming on the photosensitive drum surface of
And a fixing and conveying device 16 for fixing the toner image formed on the surface of the paper by the imaging unit 11. A paper discharge tray 17 is provided on the downstream side of the fixing and conveying device 16. The paper feeding unit 3 is a paper feeding cassette 21 that is detachable from an opening 20 provided at the bottom of the apparatus body, and a paper feeding device that feeds paper from the paper feeding cassette 21 and supplies the paper to the output unit 2. 22 and 22.

The apparatus main body is divided into an upper case 25 and a lower case 26, and the upper case 25 has a hinge portion 27.
It can be freely opened and closed with respect to the lower case 26. In the upper case 25, the reading unit 1 and the imaging unit 11, the developing unit 14, and the laser device 15 of the output unit 2 are included.
Are mounted, and the lower case 26 is provided with the fixing / conveying device 16 of the output unit 2 and the paper feeding unit 3.

FIG. 3 is an enlarged view of the imaging unit 11 and the fixing / conveying device 16 of the output section 2. The imaging unit 11 has a unit case 30. A mounting flange portion 31 protruding upward is formed on the upper portion of the unit case 30. A long hole 31a that is long in the vertical direction is formed in the mounting flange portion 31, and the hole 31a is locked to a pin 32 provided on the body frame side. With such a configuration, the imaging unit 11 can move in the vertical direction within a predetermined range. On the other hand, the lower portion of the unit case 30 is formed with a locking portion 33 protruding downward. The locking portion 33 locks a pin 34 provided on the main body frame side to position the imaging unit 30 in the vertical direction. A photosensitive drum 35 is rotatably attached to the end of the imaging unit 11 on the developing roller side. Further, a cleaning blade 36 for removing the toner remaining on the surface of the photosensitive drum 35 is provided on the side of the photosensitive drum 35. The toner removed from the surface of the photoconductor drum 35 by the cleaning blade 36 is stored in the storage portion 37 in the unit case 30.

Below the photoconductor drum 35, a transfer roller 40 for transferring the toner image formed on the photoconductor drum 35 to a sheet is arranged. The transfer roller 40 is
It is rotatably supported by the frame on the lower case 26 side. A main charging device 41 for charging the surface of the photoconductor drum 35 is arranged above the photoconductor drum 35. As described above, the imaging unit 11, the developing unit 14, the transfer roller 40, and the main charging device 41 constitute an image forming unit that forms a toner image on the surface of the paper. In this embodiment, the photosensitive drum 35 is negatively charged, the toner has a positive charge, and the sheet is negatively charged by the transfer roller 40.

A transport guide 45 for guiding the sheet having a toner image formed on its surface to the fixing transport device 16 is disposed downstream of the image forming portion in the sheet transport direction. The transport guide 45 is made of antistatic resin. This antistatic resin has a surface resistivity of 10 ⁷ Ω or more and 10
Resins of ¹⁴ Ω or less are used. For example, an ABS antistatic resin having a surface resistivity of 1 × 10 ¹⁰ is desirable. Also,
The imaging unit 11 is located above the transport guide 45.
The intermediate frame 46 is disposed in close proximity to. The intermediate frame 46 is made of, for example, an iron plate material and serves as a conductor. The intermediate frame 46 is in contact with the imaging unit 11 via the flange portion 46b, and is grounded via another frame. In this intermediate frame, notches 46a are formed at two end portions in the width direction of the conveyed sheet.

As shown in FIGS. 3 and 4, the fixing / conveying device 16 includes a heat roller 50 having a heater 50a therein,
It has a pressure roller 51 which can be pressed against the heat roller 50. The heat roller 50 is a member whose surface is coated with a conductive polytetrafluoroethylene (PTFE) resin. The surface resistivity of the heat roller 50 is preferably 10 ⁸ Ω, for example.

A fixing upper housing 52 is arranged on the side and above the heat roller 50 so as to cover the heat roller 50. The upper fixing housing 52 extends in the axial direction of the heat roller 50 and is detachable from a lower fixing housing (not shown). In addition, the lower fixing housing is provided for each roller 5
It is fixed to a pair of fixing frames 53 provided on both axial ends of 0 and 51. An entrance guide 68 having an inverted L-shaped cross section is provided on the upstream side of the fixing base 59 provided in the lower fixing housing in the sheet conveying direction. The entrance guide 68 is a member for guiding the sheet guided by the conveyance guide 45 to the heat roller 50. Approach guide 68
Is formed of a non-conductive resin. As this resin, for example, an ABS resin having a surface resistivity of 10 ¹⁶ Ω is used.

A groove 52a is formed in the center of the upper wall of the upper fixing housing 52 along the roller axial direction, and a mounting member 54 is removably inserted into the groove 52a. The mounting member 54 has a recess 54a at the center, and a cleaning member 55 for cleaning the surface of the heat roller 50 is attached to the lower end thereof. Further, notches 52c are formed at two locations in the roller axial direction on a side wall 52b of the upper fixing housing 52 on the paper discharge side. A pin-shaped supporting portion 56 is formed in the notch 52c, and a peeling claw 57 is rotatably supported by the supporting portion 56. The peeling claw 57 has a fulcrum portion 57 supported by the support portion 56.
a, a peeling portion 57b extending from the fulcrum portion 57a toward the heat roller 50, and a lever portion 57c extending from the fulcrum portion 57a to the outside of the side wall 52b. The peeling portion 57b is
It is pressed against the surface of the heat roller 50 by a torsion spring 58. Further, the lever portion 57c extends from the notch 52c so as to be exposed to the outside of the side wall 52b, and when the fixing upper housing 52 is attached or detached, an operator attaches the lever portion 57c to the side wall 52b as shown in FIG. By pushing it to the side, the peeling portion 57b at the tip is separated from the surface of the heat roller 50.

As shown in FIG. 3, the heat roller 50 has a bearing 6
It is rotatably supported by the fixing frame 53 by 0. On the other hand, the shaft 61 of the pressure roller 51 is supported by the fixing frame 53 via a bearing 62 and a spring 63. At the upper portion of the bearing 62, the protrusion 6 protruding upward is provided.
2a is formed. Further, the bearing 62 is the frame 5
3 is movable up and down, and is always urged toward the heat roller 50 by the spring 63. The bearing 62 and the spring 63 are arranged at both ends in the roller axial direction.

On the other hand, pressure contact release levers 65 are concentrically and rotatably mounted on the outer peripheral portions of the pair of bearings 60 that support the heat roller 50. 1
The pair of pressure contact release levers 65 includes a support portion 65a that covers the outer periphery of the bearing 60, and a cam portion 6 formed in a part of the support portion 65a.
5b and an L-shaped lever portion 65c extending from the support portion 65a to the image forming portion side. The pressure contact release lever 65 is urged counterclockwise in FIG. 3 by a spring 66 whose one end is locked to the fixing frame 53. When the imaging unit 11 is attached to the apparatus, the tip of the lever portion 65c is located at the intermediate frame 4
The imaging unit 11 passes through the notch 46a of 6
Is in contact with the bottom surface of the unit case 30, so that the lever portion 65c is rotated clockwise against the urging force of the spring 66. In this state, the cam portion 6
5b is separated from the bearing protrusion 62a of the pressure roller 51. Therefore, the pressure roller 51 is pressed against the heat roller 50 by the spring 63. When the image unit 11 is not attached or when the upper case 25 is opened, the pressure contact release lever 65 rotates counterclockwise,
The pressure roller 51 causes the heat roller 5 to move by pressing the cam portion 65b.
Move away from zero. In this state, the paper jammed by the fixing and conveying device 16 can be easily taken out.

As shown in FIGS. 3 and 4, a pair of discharge rollers 75 and 76 are arranged on the downstream side of the fixing and conveying device 16. The upper roller 75 is fixed to a drive shaft 77 supported by the fixing frame 53. On the other hand, the lower roller 7
6 is rotatably supported by the lower fixing housing.
The lower roller 76 is made of, for example, a resin such as POM (polyacetal), and has a plurality of substantially U-shaped grooves formed on its outer peripheral surface.

Next, an image forming operation on a sheet and a conveying operation will be described. When the facsimile device receives the information, the laser device 15 forms an electrostatic latent image on the surface of the photosensitive drum 35 according to the received content. This electrostatic latent image is visualized as a toner image by the developing unit 14.
The toner image is transferred onto the surface of the paper by the transfer roller 40.

The sheet on the surface of which the toner image is formed is guided to the fixing and conveying device 16 side by the conveying guide 45.
At this time, the positively charged residual toner is stored in the storage portion 37 of the imaging unit 11. on the other hand,
The sheet that has passed through the transfer roller 40 is charged with the opposite polarity to the toner. The residual toner stored in the storage portion 37 of the unit case 30 is positively charged. Moreover, since the intermediate frame 46 is grounded, the intermediate frame 46 is negatively charged by electrostatic induction. Further, as described above, since the negative charges of the paper on the transport guide 45 gradually escape, the electric attraction of the paper with respect to the residual toner in the accommodating portion 37 becomes small, and the paper is prevented from rolling up. it can. Therefore, stable transportation can be performed.

The sheet conveyed in this manner is guided by the entrance guide 68 of the fixing base 59 and is guided between the heat roller 50 and the pressure roller 51. Then, the toner image on the surface of the paper is fixed by being heated while being sandwiched between these rollers 50 and 51 by a predetermined pressure. Here, if the transport guide 45 is formed of a good conductor,
The electric charge of the paper suddenly escapes via the conveyance guide 45, and the carrying force of the unfixed toner on the paper disappears. Therefore, the image on the surface of the paper is disturbed during the transportation. However, in this embodiment, as shown in FIG.
8 and the heat roller 50 are formed of the antistatic resin, the non-conductive resin, and the PTFE resin having the surface resistivity as described above, the electric charge of the paper gradually escapes during the conveyance. As a result, it is possible to suppress abrupt movement of charges, and it is possible to suppress disturbance of the unfixed toner image. In particular, in this embodiment, since the distance of the transport guide 45 is long, by setting the surface resistivity to the above-mentioned value, it is possible to prevent the image from being disturbed due to the escape of charges even during the transport.

Further, since the entrance guide 68 is made of a non-conductive resin and has a surface resistivity higher than that of the conveyance guide 45, the electric charge of the unfixed paper charged to the same polarity as the transfer voltage is applied to the entrance guide 68. As it passes, it charges the entrance guide 68. Therefore, the forces of electrically repelling the paper and the approach guide 68 act on each other, and the paper is less likely to contact the approach guide 68. Therefore, the frictional resistance between the paper and the entrance guide 68 is reduced, and the paper is conveyed smoothly, so that the unfixed toner image can be prevented from being disturbed by vibration.

The sheet for which the fixing operation has been completed is peeled off from the heat roller 50 by the peeling claw 57, and is further discharged onto the discharge roller 7.
The sheet is discharged onto a sheet discharge tray by 5,76. [Other Embodiments] (a) In the above embodiment, the approach guide 6 is used.
Although the surface resistivity of No. 8 was set to 1 × 10 ¹⁶ Ω, this surface resistivity may be larger than that of the transport guide 45 and 1 × 10 ¹⁴ Ω or more.

(B) The entry guide 68 may be formed of a resin other than the ABS resin.

[0025]

In the sheet conveying apparatus according to the present invention, since the surface resistivity of the entrance guide member is higher than the surface resistivity of the convey guide member, the sheet from which the charge is removed by the convey guide member is conveyed onto the enter guide member. Then, the electric charge of the sheet is not removed any more, and the entrance guide member is charged with the same polarity as the sheet. For this reason, an electrically repulsive force acts between the sheet and the approach guide member, the frictional resistance between the sheet and the approach guide member decreases, the sheet is conveyed smoothly, and image disturbance can be prevented. .

[Brief description of drawings]

FIG. 1 is an external perspective view of a facsimile device to which an embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram of a vertical cross section of FIG.

FIG. 3 is a front view of an image forming unit and a fixing / conveying device of the apparatus.

FIG. 4 is a partial vertical cross-sectional configuration diagram of a fixing and conveying device.

FIG. 5 is a schematic diagram showing a state of charges.

[Explanation of symbols]

 11 Imaging Unit 16 Fixing and Conveying Device 45 Conveying Guide 50 Heat Roller 50a Heater 51 Pressure Roller 68 Entry Guide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daisuke Hayashi 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (1)

[Claims] 1. A sheet conveying device for conveying a sheet having an image formed by magnetic toner formed on a surface thereof to a fixing device in an image forming apparatus, wherein the sheet from the image forming section has a predetermined electric resistance. A conveyance unit including a conveyance guide member that guides to the fixing device side, and a surface resistivity larger than that of the conveyance guide member for guiding the sheet conveyed by the conveyance unit to the fixing unit of the fixing device. A sheet conveying device including an entrance guide member.