JPH06149108A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress irregularities in an unfixed toner image by specifying the relation of each surface resistivity of a thermal roller, a carrying guide and an entering guide. CONSTITUTION:A facsimile device is provided with an image forming part forming a toner image on a sheet by using magnetic toner, a fixing part including the thermal roller 50 having the surface resistivity A and fixing the toner image formed by the image forming part on the sheet, a carrying means including the carrying guide 45 having the surface resistivity C and guiding the sheet on which the toner image is formed to the downstream side and the entering guide 68 having the surface resistivity B and guiding the sheet carried by the carrying means to the fixing part and each surface resistivity of A, B and C is 1X10<7>OMEGA<=1X10<14>OMEGA and satisfies the relation of A<=B<=C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an image forming apparatus, and more particularly to
The present invention relates to an image forming apparatus that forms a toner image on a sheet using magnetic toner and fixes the formed toner image on the sheet.

[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, the sheet on which the unfixed toner image is formed is conveyed by the conveying section between the image forming section and the fixing section.

When a sheet on which an unfixed toner image is formed is conveyed to a fixing unit, it is necessary to prevent the unfixed toner image from being disturbed. Therefore, in Japanese Patent Publication No. 1-59581, the surface resistivity of the guide member is 1 × 10 ⁶ Ω or more and 1 × 1 in the conveying unit including the conveying belt and the guide member.
It is shown to be within the range of ⁰⁹ Ω or less. In this apparatus, since the guide member has a predetermined electric resistance, the electric charge charged on the paper does not suddenly escape, thereby ensuring the carrying force of the unfixed toner image on the paper.

[0004]

SUMMARY OF THE INVENTION In the above conventional configuration,
Disturbance of the unfixed toner image can be suppressed by setting the surface resistivity of the guide member arranged at a short distance between the transport belt and the fixing roller. However, in the case of the transport guide member having a long transport distance corresponding to both the transport belt and the guide member, the electric charge of the paper easily escapes at the surface resistivity. For this reason, the electric carrying force of the unfixed toner becomes small during the conveyance, and the disturbance of the unfixed toner image cannot be sufficiently suppressed.

An object of the present invention is to prevent the unfixed toner image formed on the sheet surface from being disturbed.

[0006]

An image forming apparatus according to the present invention includes an image forming section for forming a toner image on a sheet by using a magnetic toner, and a heat roller having a surface resistivity A.
The image forming unit includes a fixing unit that fixes the toner image formed on the sheet, and a conveyance guide member that has a surface resistivity C and guides the sheet on the surface of which the toner image is formed to the downstream side. It has a conveying means and a surface resistivity B, and an entrance guide member for guiding the sheet conveyed by the conveying means to the fixing portion, and the surface resistivity A, B, C is 1
It is not less than × 10 ⁷ Ω and not more than 1 × 10 ¹⁴ Ω, and satisfies the relationship of A ≦ B ≦ C.

[0007]

In the image forming apparatus according to the present invention, the sheet on which the unfixed toner image is formed in the image forming section is guided from the image forming section to the downstream side by the conveyance guide member and reaches the entrance guide member. Then, the entrance guide member further guides the fixing portion, and the fixing portion fixes the unfixed toner image on the sheet. Here, the surface resistivity of each member is set to a large value to be a semi-conductor, and the value of the surface resistivity is such that the transport guide member ≥ the entrance guide member ≥ the heat roller, so that the sheet is transported. The charge gradually escapes as the temperature rises.

As described above, by gradually releasing the electric charge of the sheet, it is possible to suppress the rapid movement of the electric charge, and the carrying force of the unfixed toner image on the sheet does not suddenly decrease. Therefore, it is possible to prevent the unfixed image on the sheet from being disturbed. In particular, even when the transport distance of the transport guide member is long, the movement of charges is suppressed, so that the carrying force for the unfixed toner image during transport can be maintained.

Further, when the surface resistivities are the same, even if some electric charge escapes first on the transport guide member, the subsequent abrupt movement of electric charge on the entry guide member and the heat roller is eliminated, and In addition, it is possible to maintain the bearing power of the unfixed toner image and prevent image disturbance. Further, since the surface resistivity of the heat roller is made small, the charge accumulated in the heat roller can be reduced, and when the sheet enters the heat roller, the image disturbance of the unfixed toner image due to the charge of the heat roller can be prevented.

[0010]

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 detachably attached to an opening 20 provided at the bottom of the apparatus main 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 ¹² 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 and 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. This surface resistivity may be smaller than or equal to the approach guide 68 described later. For example, the surface resistivity is 10
⁸ Ω is desirable.

An upper fixing 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 attachable to and detachable from a fixing base 59 provided in the lower fixing housing. Also, the fixing base 5
Reference numeral 9 denotes a roller provided at each axial end of each roller 50, 51.
It is fixed to a pair of fixing frames 53. Fixing base 5
An entry guide 68 having an inverted L-shaped cross section is provided on the upstream side of sheet conveyance direction 9 of the sheet. The entrance guide 68 is a member for guiding the sheet guided by the conveyance guide 45 to the heat roller 50. The entry guide 68 is made of antistatic resin. As this antistatic resin, a resin having a surface resistivity of 10 ⁷ Ω or more and 10 ¹⁴ Ω or less is used. For example, an ABS antistatic resin having a surface resistivity of 1 × 10 ¹¹ Ω is desirable. The surface resistivity of the approach guide 68 is
It may be smaller than or equal to the surface resistivity of the transport guide 45.

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, the 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 attached to the outer periphery of each of the pair of bearings 60 supporting 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 the upper case 25 is opened, the pressure contact release lever 65 rotates counterclockwise, and the pressure roller 51 is heated by pressing the cam portion 65b. Move away from the roller 50. In this state, the paper jammed by the fixing and conveying device 16 can be easily taken out. On the downstream side of the fixing and conveying device 16, as shown in FIGS. 3 and 4, a pair of discharge rollers 7 is provided.
5, 76 are arranged. The upper roller 75 is fixed to a drive shaft 77 supported by the fixing frame 53. On the other hand, the lower roller 76 is rotatably supported by the lower fixing housing 59. The lower roller 76 is, for example, POM.
It is made of a resin such as (polyacetal) and has a plurality of substantially U-shaped grooves formed on the 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 which the toner image is transferred 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 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 or the PTFE resin having the surface resistivity as described above, the electric charge of the paper is gradually removed on the transport guide 45, the entrance guide 68, and the heat roller 50. To be done. 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 a conductive PTFE layer is formed on the surface of the heat roller 50, electric charges are less likely to be accumulated, so that the paper is heated by the heat roller 50 and the pressure roller 5.
It is possible to reduce the electric influence of the heat roller 50 on the unfixed toner image on the surface of the paper (disturbance of the image) when entering between the heat roller 50 and the sheet 1.

The sheet on which the fixing operation has been completed is peeled from the heat roller 50 by the peeling claw 57, and is further discharged onto the paper discharge tray by the discharge rollers 75 and 76. [Other Embodiments] (a) In the above embodiment, the surface resistivity is determined by the conveyance guide 4
5, the entrance guide 68 and the heat roller 50 are set to be smaller in this order, but the surface resistivity of the conveyance guide 45 and the surface resistivity of the entrance guide 68 may be equal. In this case, it is desirable that the surface resistivity of the transport guide 45 and the entrance guide 68 are both ABS type electrostatic resin having, for example, 1 × 10 ¹¹ Ω. Further, the surface resistivity of the entry guide 68 and the heat roller 50 may be equal. In this case, it is desirable that each surface resistivity be about 1 × 10 ¹¹ Ω.

(B) Transport guide 45, entry guide 68
The surface resistivities of the heat roller 50 and the heat roller 50 may be equal to each other.
In this case, a value of about 1 × 10 ⁸ Ω is desirable for each. In this embodiment, as shown in FIG. 6, the unfixed sheet charged to the same polarity as the transfer voltage has some electric charge initially discharged on the conveyance guide 45. However, the approach guide 6 after that
8. Since the surface resistivity is the same on the heat roller 50, rapid movement of electric charges is eliminated, and the influence of the electric force of the toner on the paper is reduced. Therefore, similarly, the disturbance of the unfixed toner image can be suppressed.

[0027]

In the image forming apparatus according to the present invention, the conveyance guide member, the entrance guide member, and the heat roller are each formed of a member having a high surface resistivity. Since the relationship of guide member ≧ heat roller is satisfied, the electric charge gradually escapes when an unfixed charged sheet is conveyed, so that the disturbance of the unfixed toner image can be suppressed.

[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 charge removal state.

FIG. 6 is a view corresponding to FIG. 5 of another embodiment.

[Explanation of symbols]

 11 Imaging Unit 16 Fixing / Conveying Device 45 Conveying Guide 50 Heat Roller 68 Entry Guide

Front Page Continuation (72) Inventor Daisuke Hayashi 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (1)

[Claims] 1. A fixing device comprising an image forming unit for forming a toner image on a sheet by using a magnetic toner and a heat roller having a surface resistivity A, and fixing the toner image formed by the image forming unit on the sheet. Section, a conveying means having a surface resistivity C, and a conveying guide member for guiding a sheet having a toner image formed on the surface in the image forming section to the downstream side, and a conveying means having a surface resistivity B, An approach guide member for guiding the sheet conveyed by the means to the fixing unit, and the surface resistivity A, B, C is 1 × 10 ⁷ Ω or more and 1 × 1.
An image forming apparatus of 0 ¹⁴ Ω or less and satisfying the relationship of A ≦ B ≦ C.