JPH07242370A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus capable of improving the reliability of sheet conveyance in the automatic double-sided mode. An image forming apparatus including a double-sided unit 600 that temporarily stores a transfer sheet P on which an image has been formed on one side and sends the transfer sheet P toward the image forming unit again so as to form an image on the non-image forming side. In the double-sided unit 600
In addition, a plurality of stages of relay rollers 611 are provided, and the linear velocity of the downstream relay rollers is made higher than the linear velocity of the upstream relay rollers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an automatic double-sided mode capable of automatically forming images on both sides of transfer paper.
The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a printer.

[0002]

2. Description of the Related Art Image forming apparatuses having an automatic duplex mode have been widely proposed.

In the automatic double-sided mode, the transfer paper on which a single-sided image has been formed, which has passed through the fixing device, is temporarily stored in the double-sided tray of the double-sided unit, and an image is formed on the other side where no image is formed. This transfer paper is sent again toward the transfer portion of the image forming process unit.

By the way, the transfer paper which has passed through the fixing device is
There is a problem that curling may occur due to heat, and the curling easily causes a jam in the re-feeding process.

In order to solve this, JP-A-61-98
No. 367, Japanese Patent Laid-Open No. 2-27368, and Japanese Utility Model Publication No. 5
No. 24924 discloses a technique for blowing curling air onto a transfer sheet to correct the curl.

[0006]

However, as in the above-mentioned prior art, it is not possible to sufficiently suppress the curl by simply blowing air on the transfer paper. Therefore, in the automatic double-sided mode, the countermeasure against the jam caused by the curl is taken. There was a problem of lack of reliability.

An object of the present invention is to provide an image forming apparatus capable of improving the reliability of sheet feeding and conveyance in the automatic double-sided mode.

[0008]

SUMMARY OF THE INVENTION The above-mentioned purpose is to temporarily store a transfer sheet on which an image has been formed on one side and send the transfer sheet toward the image forming section again so as to form an image on the non-image forming side. In an image forming apparatus equipped with a unit, the double-sided unit is provided with a plurality of stages of relay rollers, and the linear velocity of the downstream relay roller is set to be higher than that of the upstream relay roller so as to pull the transfer paper. This is achieved by the first means in which a cooling means for blowing air to the pulled transfer paper to cool it is provided near the duplex unit.

Further, in an image forming apparatus equipped with a double-sided unit that temporarily stores a transfer sheet on which an image has been formed on one side and sends the transfer sheet toward the image forming unit again in order to form an image on the non-image forming side. This is achieved by the second means in which a cooling means for blowing air to the transfer paper to cool it is provided above the transfer paper storage space of the duplex unit.

Further, in the second means, the third means is provided in which a curl pressing member is provided on the inlet side of the double-sided unit.

[0011]

According to the first means, when the transfer paper is re-fed, the transfer paper is pulled, the curl is corrected by this, and the transfer paper in the pulled state is
Since the cooling air is blown as described above, the curl can be removed more efficiently.

In the second means, the cooling air is blown when the transfer paper is re-fed, so that the curl is efficiently removed.

In the third means, since the cooling air is blown onto the transfer paper while the curl pressing member is forcibly suppressing the curl, the curl can be removed more efficiently.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an image forming apparatus according to an embodiment, FIG. 2 is a schematic diagram showing a flow of transfer paper in front side copying in an automatic double-sided mode with a thick black line, and FIG. 3 is a back side in the automatic double-sided mode. FIG. 4 is a schematic diagram showing the flow of transfer paper in copying with a thick black line, FIG. 4 is a schematic diagram showing the flow of transfer paper in a double-sided unit with a thick black line, and FIG. 5 is a perspective view showing the arrangement of relay rollers of the double-sided unit.

As shown in FIG. 1, this apparatus reads an original on a contact glass and forms an latent image on an optical unit 100, and a photosensitive drum 210 is subjected to an image forming process of charging, exposing, cleaning, and discharging. Body unit 200,
A developing unit 300 for developing the latent image formed on the photosensitive drum 210, and a transfer unit 40 for transferring the image formed on the photosensitive drum 210 onto the transfer paper P.
0, a fixing unit 5 for fixing the image on the transfer paper P
00, a double-sided unit 6 for temporarily stacking the transfer paper P to form a double-sided image on the transfer paper P and sending it again to the image forming process section.
00 and a paper feed unit 700 for sending the transfer paper P to the image forming process section.

Next, the flow of the transfer paper P in the automatic double-sided mode will be described with reference to FIGS. 2 and 3, the flow of the transfer paper P is shown by a thick black line, FIG. 2 shows the operation at the time of front side copying, and FIG. 3 shows the operation at the time of back side copying.

First, the transfer sheet P is fed and conveyed from the sheet feeding unit 700 toward the transfer unit 400. At approximately the same time, the original is read by the optical unit 100, a latent image is formed on the photosensitive drum 210 of the photosensitive unit 200, and the latent image is visualized by the developing unit 300. Then, the image is transferred to the transfer paper P by the transfer unit 400 and fixed by the fixing unit 500, and then the transfer paper P is stacked in the duplex unit 600 (see FIG. 2).

When the originals are replaced, the duplex unit 6
00, the transfer sheet P having an image formed on one side is fed and conveyed, an image is formed in the same process as that for the one side, and the sheet is discharged from the main body (see FIG. 3). In this embodiment, the transfer paper P on both sides of which images have been formed is discharged to the sorter 800.

Next, the flow of the transfer paper P in the duplex unit will be described with reference to FIGS. In FIG. 4, the flow of the transfer paper P is shown by a thick black line.

In FIG. 4, 601 is a conveying roller, 602 is a brush roller, 603 is a curl pressing member, 604 is a double-sided tray, 605 is a gathering roller, 606 is a calling roller, 6
Reference numeral 07 is a pressure arm, 608 is a separation belt, 609 is a separation roller, 610 is a conveyance roller, and 611 (611a, 611).
b, 611c) is a relay roller, 612 is a cooling fan as a cooling means, 620 is a double-sided outlet detection unit, 621 is a double-sided pressure solenoid, 622 is a double-sided paper discharge detection unit, 623 is a double-sided paper end detection unit, and 624 is a jogger. Motor, 625
Is a double-sided contact roller solenoid, 626 is a double-sided jogger home detection unit, and 627 is a double-sided entrance detection unit.

Transfer paper P having an image formed and fixed on one side
Is sent to the two transfer rollers 601 and the brush roller 6
02 and the curl pressing member 603 suppress the curl after fixing and stack the sheets on the double-sided tray 604. At that time, both sides of the transfer paper P are aligned while being stacked by a paper alignment mechanism (not shown), and the left end of the transfer paper P is returned by the approach roller 605 so as to face the calling roller 606.

Next, a calling roller 606 is issued by a sheet feeding (hereinafter referred to as sheet re-feeding) signal from a main body control unit (not shown).
And the pressure arm 607, the loaded transfer paper P is sent from below to the paper feed separating unit (shown in FIG. 4),
The separation belt 608 and the separation roller 609 separate and feed the sheets one by one, and the conveyance roller 610 and the relay roller 611 convey the sheet in the transfer process direction.

The cooling fan 612 provided in the lower portion of the conveying portion is operated by the above-mentioned re-feeding signal, and the cooling air is blown to the transfer paper P passing through the conveying portion.

As shown in FIG. 5, the relay rollers 611 are arranged in order from the upstream side in the sheet re-feeding direction 611a, 611b, 611.
It is provided in 3 steps with c, and the relay roller 61
The linear velocity of 1b is more than ten percent higher than that of the relay roller 611a.

In the above-described embodiment, when the transfer paper P is re-fed in the double-sided tray 604, the transfer paper P is pulled, and the curl is corrected. . Since the cooling air is blown onto the transfer paper P in the further pulled state as described above, the curl is removed more efficiently.

FIG. 6 is a perspective view of an essential part showing another example of the cooling fan arrangement.

In another embodiment, brush roller 602
By curling the transfer paper P after the fixing by the curl pressing member 603 and blowing the cooling air sent by the cooling fan 613 onto the transfer paper P through the duct 614, the curl of the transfer paper P is further corrected and suppressed. .

Incidentally, the constitution which is not particularly described in the other embodiments is the same as that of the above-mentioned embodiment.

[0030]

According to the first aspect of the present invention, when the transfer sheet is re-fed from the duplex unit, the transfer sheet is pulled by the front (downstream) relay roller in the traveling direction. As a result, the curl is corrected and the transfer sheet in the pulled state is blown with the cooling air as described above, so that the curl is forcibly removed. As a result, it is possible to suppress the jam of the transfer paper in the automatic double-sided mode and improve the transport reliability.

According to the second aspect of the invention, since the cooling air is blown when the transfer paper is re-fed, the curl is efficiently removed.

According to the third aspect of the present invention, in addition to the function and effect of the second aspect, since the cooling air is blown onto the transfer paper while the curl pressing member is forcibly suppressing the curl, the curl can be more efficiently curled. Removal is done.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram showing a flow of a transfer sheet in an automatic double-sided mode by a thick black line.

FIG. 3 is a schematic diagram showing a flow of a transfer sheet in an automatic double-sided mode with a thick black line.

FIG. 4 is a schematic diagram showing a flow of transfer paper in a duplex unit with a thick black line.

FIG. 5 is a perspective view showing an arrangement of relay rollers of the duplex unit.

FIG. 6 is a perspective view showing another example of a cooling fan arrangement.

[Explanation of symbols]

 100 optical unit 200 photoconductor unit 300 developing unit 400 transfer unit 500 fixing unit 600 double-sided unit 601 transporting roller 602 brush roller 603 curl pressing member 604 double-sided tray 605 pulling roller 606 calling roller 611 relay roller 612, 613 cooling fan 700 paper feeding unit

Claims (3)

[Claims] 1. An image forming apparatus provided with a double-sided unit, which temporarily accommodates a transfer sheet on which an image has been formed on one side, and sends the transfer sheet again toward an image forming section in order to form an image on the non-image forming side. The double-sided unit is provided with a plurality of stages of relay rollers, and the linear velocity of the downstream relay roller is set higher than the linear velocity of the upstream relay roller so that the transfer paper is pulled, and the pulling is performed near the double-sided unit. An image forming apparatus, comprising: a cooling unit for blowing air onto the transferred transfer paper to cool it. 2. An image forming apparatus comprising a double-sided unit for temporarily accommodating a transfer sheet on which an image has been formed on one side, and for sending the transfer sheet toward the image forming section again so as to form an image on the non-image forming side. An image forming apparatus, characterized in that cooling means for blowing air to the transfer paper to cool the transfer paper is provided above the transfer paper storage space of the duplex unit. 3. The image forming apparatus according to claim 2, wherein a curl pressing member is provided on the entrance side of the duplex unit.