JPH061514A - Sheet transport device - Google Patents

Abstract

PURPOSE:To reduce sheet carrying resistance in an image forming device by forming a guiding means to guide a sheet after fixing process through a curved passage of a contacting section to come into partial contact with the sheet for guiding it and a control section to control the position of the sheet. CONSTITUTION:In a laser beam printer, a blank where an image on an image carry-supporting body is transcribed is guided to a fixing apparatus 10 by a guide 111, and passed through between a fixing roller 112 heated to a fixed temperature by a heater 113 and a pressing rubber roller 114 to be followingly rotated, and the image is fixed on the blank at that time. The fixed blank is separated by a separating claw 116, and guided through a curved passage formed of a blank delivering guide 115, and delivered through a blank delivering roller 100. In this case, both the carrying sides of the blank delivering guide 115 are provided with a pair of guide ribs 21 to come into partial contact with the blank for guiding it and plurality of guide ribs 22 which are lower than the ribs 21 and control the position of the blank, and the blank is thereby smoothly guided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer, an LED printer, and a copying machine, and more particularly to a paper discharge apparatus.

[0002]

2. Description of the Related Art Image forming apparatuses such as laser beam printers, LED printers and copying machines for recording images by an electrophotographic process have recently been required to save space and improve user operability.

FIG. 6, FIG. 7 and FIG. 8 show an example of a printer which answers the request. In the figure, a cassette 60
The sheets p stacked on the sheet are conveyed to the image carrier 8 of the image forming unit by the sheet feeding roller 2 and the conveying rollers 116a and 116b.

The image carrier 8 has a scanner unit 1
The latent image formed by exposure from 17 is developed by a developing device (not shown) to form a toner image. This image is formed of a conductive rubber roller, is brought into contact with the image carrier 8 by a light pressure, and is transferred onto the sheet p by the transfer charger 9 to which a predetermined voltage is applied.

The sheet p on which the toner image is formed by the electrophotographic process is guided to the fixing device by the guide 111 which is integrally held by the fixing frame.

The guided paper p is made of aluminum which is kept at a predetermined temperature by a heater 113 and a temperature sensor (not shown), is rotatably held by a bearing (not shown) on the fixing frame 110, and is rotating at a predetermined rotation speed. The fixing roller 112 and a rubber pressure roller 114, which is arranged so as to face the fixing roller 112 and abuts at a predetermined pressure by a pressure spring (not shown) and is driven to rotate, are bitten by the heat and pressure to melt the toner. Fix the image.

[0007]

The paper p discharged while being heated by the fixing means has a paper guide shape curved by the paper discharge guide 115 and the paper discharge guide 11 in order to make the height of the apparatus as small as possible. Is formed, and the paper is discharged and stacked by being guided to the paper discharge roller 100 and the paper discharge roller 101 which are in a position curved with respect to the conveyance direction of the fixing device.

[0008] A thin sheet cannot be fed because the sheet has a weak stiffness, and the sheet is jammed at the conveying guide portion or remains in the conveying portion to cause a wavy undulation mark on the sheet. Further, for thick paper (postcard) and paper having a large transport resistance such as OHP, there is a problem that the printed surface immediately after fixing is rubbed by the rib at the curved portion of the guide to stain the image.

Therefore, conventionally, in order to pass such a sheet having poor carrying performance, a paper carrying roller is provided in the vicinity of the fixing paper discharging section to improve the carrying performance, or another carrying path is provided immediately after fixing. It is arranged to discharge such a sheet to another sheet discharge section by switching the switch provided by the flapper 12.

At this time, an actuator of a paper sensor is arranged in the carrying path in order to detect a carrying failure such as a paper jam between fixing and discharging.

This actuator is provided in each of the two paper discharge paths, or in the portion of the transport path immediately before the paper discharge path is separated so as to detect the paper.

However, with such a configuration,
Due to an increase in the number of constituent parts in the paper discharge section and a complicated transport path, the cost is inevitably increased and the failure rate is also increased.

Further, if a paper sensor is provided in each of the conveying paths, an extra space for that is required, which is a great obstacle to downsizing of the apparatus.

If a sheet sensor is provided in the conveying path immediately before branching and detection is performed by a single actuator, the curved portion that is most likely to cause conveyance failure cannot be detected, and the detection of a jam or the like is delayed. The device will be damaged due to jamming of jammed paper, and jammed paper processing will become difficult.

Further, since there are two transport paths, there is a problem that the installation projected area of the apparatus becomes large.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable sheet conveying apparatus which reduces sheet conveying resistance in a curved path.

The structure of the present invention for attaining the above object has a conveying means for conveying a sheet, and a guiding means for guiding the sheet conveyed by the conveying means along a curved path. The means includes a contact portion that extends along the curved path and guides the sheet by partially contacting the surface of the sheet, and a restricting portion that retracts from the contact portion and restricts the position of the surface of the sheet. It is a characteristic sheet conveying device.

[0018]

According to the present invention, in the image forming apparatus having the curved sheet conveying path from the fixing to the sheet discharging portion, the first rib which positively guides the curved shape of the curved sheet discharging guide after fixing is provided. By using the second rib that guides the paper as an auxiliary, the paper discharge conveyance roller and the thin paper or the OHP paper that has been ejected by the second conveyance path in the related art are provided. Alternatively, it is possible to discharge and stack thick paper such as postcards even immediately after fixing in the curved discharge conveyance path.

Further, by disposing the actuator of the paper discharge sensor in the vicinity of the first rib for positively guiding the paper, the curved shape of the rib of the paper discharge guide is positively guided to the paper. It has become possible to accurately monitor the sheet conveyance state in the sheet discharge conveyance section configured by the first ribs and the second ribs that supplementally guide the sheets.

[0020]

1 to 4 show an embodiment of the present invention. After that,
The present invention will be described based on this.

FIG. 4 is a sectional view of the main body of the embodiment of the laser beam printer according to the present invention, in which 60 is a paper cassette for stacking a plurality of paper sheets, and the paper p stored in the paper cassette 60 is The timing rollers 7a and 7b are separated by the sheet guide 4 provided on the paper cassette and the sheet guides 5 and 6 of the apparatus main body, which are separated one by one by the two sheet feeding rollers at a predetermined timing.
Will be guided to. Also, the timing rollers 7a, 7b
A sheet detection sensor S is provided immediately before, and controls the rotation of the timing rollers 7a and 7b, the laser emission timing, and the like.

The paper p sent out by the timing rollers 7a and 7b and the image carrier 8 rotatably housed in a process cartridge C which houses a plurality of process units for image formation in a single housing. The image carrier 8 is arranged so as to face the image carrier 8 and is applied with a predetermined voltage for transferring the image on the image carrier 8 to the sheet p.
The image is transferred by the transfer roller 9 that rotates in contact with.

The paper p on which the image is formed is a fixing device 10 which is arranged approximately above the image carrier 8 and the transfer roller 9.
And is guided by a guide 111 integrally attached to the fixing frame 110.

The fixing device 10 includes a fixing roller 1 made of aluminum which is heated to a predetermined temperature by a guide 111 for guiding the paper, a heater 113 and a temperature sensor (not shown).
12 and the fixing roller 112, which are arranged so as to face the fixing roller 112, and are fixed at a constant pressure by a spring (not shown).
A pressure roller 1 made of rubber attached so as to rotate freely.
It consists of 14.

The pressure roller 114 is elastically deformed by the spring pressure and is in contact with the fixing roller 112.

Therefore, the paper p on which the image is formed by the image carrier 8 and the transfer roller 9 is fixed on the fixing roller 11.
2 and the fixing nip formed by the pressure roller 114 and the heat from the fixing roller 112, the image is printed on the sheet p.
Settles in.

The sheet p on which the image is fixed by this fixing process is then separated from the fixing roller 112 by a separating claw 116 provided on the downstream side of the fixing roller 112 and above the fixing roller in the figure.

The fixed paper p is curved by the paper discharge guide 115 and the paper discharge upper guide 11 from a vertical direction to a horizontal direction in the paper discharge roller 100.
It is guided to and discharged.

As shown in FIG. 1, a plurality of guide ribs 21 and 22 are provided on the conveying surface side of the paper discharge guide 115. In addition, this rib is a guide rib 21 for positively guiding the paper at the largest curved portion.
Further, two kinds of ribs, which are lower in height than the ribs and which guide the paper in an auxiliary manner, are provided. In the first embodiment, as shown in FIG. 2, the guide rib 2
1 is a space slightly narrower than the shortest width l of the paper to be conveyed, totaling 2
The guide ribs 22 are provided in about 5 to 5
It is provided at intervals of 22 mm. Further, all of these ribs are provided in the same direction as the transport direction. The sheet having the shortest width l passes through the position indicated by l in FIG.

In the first embodiment, this guide rib 21
The difference Δx in rib height between the guide rib 22 and the guide rib 22 is set to about 1.5 to 2 mm at the largest point.

Therefore, in the curved portion having the largest conveyance resistance, the sheet is mainly in contact only with the leading end of the guide 21. The leading end of the guide 22 comes into contact with and guides the paper only when the paper is bent, so that the conveyance resistance in this portion is lower than in the conventional case. Further, in the portion of the guide 22, the gap between the transport guides is apparently wide.

As a result, even if the paper is weak, the paper does not buckle due to the conveyance resistance. In the case of thick paper such as postcards, the increase in the gap between the guide portions formed by the guides 22 reduces the bending resistance of the paper caused by the bending of the transport guide against the waist force of the paper. As a result, the transport resistance can be reduced.

In the vicinity of the guide rib 21, there is an actuator 31 which is a sheet detecting means, and the sheet p
When the paper passes through the paper discharge section, the actuator 31 moves the shaft 3
The photo sensor 33 is interrupted by a flag 31a which rotates about 1b and rotates integrally with the actuator, and detects troubles such as passage of paper and jam, and performs predetermined control.

(Other Embodiments) FIGS. 5 to 6 show some other embodiments according to the present invention.

In FIG. 5, a first guide rib 21a that positively guides the sheet and a second guide rib 22a that is lower than the first guide rib that assists the sheet in the second embodiment are provided in the upper conveyance guide. It is an example.

In FIG. 6, the guide ribs 21 that positively guide the paper in the third embodiment are arranged slightly inside the position where the paper having the minimum width indicated by l passes, and the difference in the guide height is Δx.
A guide 22 for guiding the paper sheet is disposed inside thereof, and a guide 22b for guiding the paper sheet having a guide height difference of Δx2 is arranged outside.

By thus providing the guide members having a plurality of heights, for example, the guide 22 is optimally set for conveying a postcard, and the guide 22b is optimal for conveying an OHP or thin paper. It can also be set.

Further, in the embodiment of the present invention, the curved direction of the conveying guide is the fixing roller 112 side (the left side in the drawing), but the present invention is not limited to this, and is curved to the pressure roller side. But it goes without saying that it has the same effect.

Further, the guide ribs do not necessarily have to be in the same direction as the carrying direction, may have an angle with respect to the carrying direction, and the number of guides 21 need not be two.

[0040]

As described above, in the image forming apparatus having the curved conveying path from the fixing to the sheet discharging section, the first sheet is positively guided to the curved conveying path after fixing.
By configuring the guide ribs 21 and the second guide ribs 22 that are lower than the first guide ribs that guide the auxiliary, it is possible to reduce the discharge conveyance resistance at the curved portion,
Conventionally, it is possible to discharge thin paper that cannot be discharged or special paper such as OHP or thick paper even if it has the curved discharge conveyance path described in the embodiment of the present invention. It is no longer necessary to have the paper discharge conveyance roller 13 for discharging these papers, the second paper discharge unit for these special papers, and the flapper 12 as in the prior art.

Further, by arranging an actuator which is a sheet detecting means in the vicinity of the first guide rib, the flap of the sheet also occurs in the conveyance system having the guide ribs having different heights in the curved sheet guide portion as in the present configuration. It is possible to prevent defective actuation due to factors such as the above, and it is possible to accurately detect the state of paper conveyance. Therefore, it is possible to arrange the detecting means in the curved portion where such a conveyance failure is likely to occur, so that it becomes possible to accurately detect the conveyance failure such as a jam and react quickly.

As a result, the apparatus structure can be simplified and downsized while being compatible with a wide range of papers, and productivity can be improved, cost can be reduced, and high versatility and reliability can be realized, resulting in cost performance. It has become possible to provide an excellent device.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a layout explanatory view of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the first embodiment of the present invention.

FIG. 4 is a sectional view of the main body of the printer according to the present invention.

FIG. 5 is a sectional view of the second embodiment of the present invention.

FIG. 6 is a layout explanatory diagram of a third embodiment according to the present invention.

FIG. 7 is a conventional cross-sectional view.

FIG. 8 is a sectional view of a main body of a conventional printer.

[Explanation of symbols]

 112 Fixing Roller 113 Fixing Heater 114 Pressurizing Roller 115 Paper Ejection Guide 21 Guide Ribs for Positively Guide 22 Guide Ribs for Auxiliary Guide 100 Paper Ejection Roller 11 Paper Ejection Guide 31 Actuator 33 Photo Sensor

Claims (5)

[Claims] 1. A conveying means for conveying a sheet, and a guide means for guiding the sheet conveyed by the conveying means along a curved path, the guiding means extending along the curved path, A sheet conveying apparatus, which has a contact portion that partially contacts the surface of the sheet and guides the sheet, and a restricting portion that retracts from the contact portion and restricts the position of the surface of the sheet. 2. The sheet conveying apparatus according to claim 1, wherein the contact portion is formed in a rib shape. 3. The sheet conveying apparatus according to claim 2, wherein the regulation is formed in a rib shape. 4. The sheet conveying apparatus according to claim 1, wherein the contact portions are formed at two positions so as to contact both end portions of the sheet having the smallest width to be conveyed. 5. The sheet conveying apparatus according to claim 1, wherein the guide unit guides the fixed sheet.