JP3320166B2 - Image forming device - Google Patents

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 having a sheet conveying means, and more particularly to an image forming apparatus for forming an image on both sides.

[0002]

2. Description of the Related Art Many conveyance apparatuses for printing double-sided images in an image forming apparatus, or sheet feeding apparatuses related thereto, have been commercialized. The double-sided image printing transport device prints the opposite side by switching back the sheet material printed on one side, but the sheet material that is transferred by the image forming unit and fixed by the heat roller is completely printed. The resistance value, the curl amount, and the like are different from those of a sheet material that is not used. Therefore, it is difficult to obtain a stable sheet material conveyance and a high-quality image as compared with single-sided printing.
Furthermore, due to various needs in the market, such as miniaturization and cost reduction of the image forming apparatus main body, the conveying device for double-sided image printing and the sheet material feeding device related thereto are often treated as options rather than the standard equipment, so that general As a result, the sheet material conveyance distance becomes longer.

[0003]

In the case of double-sided image printing, the order of each page becomes important when continuously outputting printed images, but the image forming apparatus main body side discharges a plurality of sheets at once. When you send it, a new one
It must be output from the first sheet, which is very uneconomical.

[0004]

An image forming apparatus according to the present invention comprises an image forming means for forming an image on a sheet, a sheet on which an image is formed on one side by the image forming means, and an image on the other side. Conveying means for re-conveying to the image forming means in order to form an image, and when a plurality of overlapping sheets have been conveyed to the conveying means by the image forming means, the sheet on which the image is formed and another Separating means for separating the sheet from the sheet, the separating means having a pair of rollers for switching back the sheet while holding the sheet, and a first side on the side which comes into contact with the image-formed surface of the sheet. A second roller that contacts the surface of the sheet opposite to the surface on which the image is formed when the roller is driven to rotate in the reverse direction for switchback and to convey the sheet to the image forming unit; roller , The direction for conveying the sheet to said image forming means is an image forming apparatus, characterized in that for discharging the other sheet is driven to rotate in the opposite direction from the roller pair.

[0005]

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, 1 is an image forming apparatus, 2 is a scanner unit in an image forming section, 3 is an image forming section,
Reference numeral 4 denotes a sheet material cassette, 5 denotes rollers for conveying the sheet material stacked in the sheet material cassette, 6 denotes a fixing device for fixing the transferred and printed sheet material, and 20 denotes a conveying device for double-sided image printing according to the present embodiment. , 21 is a switching flapper for switching between single-sided and double-sided printing, 22 is a reverse flapper for performing switchback, 23-1, 23-2, 23-3,
23-4, 23-5 are rollers for transporting the sheet material in the transport device for double-sided image printing, 24-1 and 24-2 are guide rollers for transporting the sheet material smoothly through the sheet material transport unit, and 25. Is a sensor lever for detecting the jam and timing for re-feeding the sheet material.

The operation of this embodiment will be described based on the above configuration.

The sheet material stacked on the sheet material cassette 4 is carried into the image forming section by the pickup roller 5-1 and the conveying rollers 5-2, 5-3, and 5-4 together with a sheet feed signal. The image information is scanned by the scanner 2 to the image forming unit, and the image is transferred to the sheet material in synchronization with the sheet material. Then, the image is fixed by the fixing device 6 and discharged onto the discharge tray 27 by the transport rollers 5-5 and 5-6. This is a so-called face-down discharge. When the double-sided mode is set, when the switching flapper 21 connected to the solenoid rotates near the exit of the fixing device 6, the switching flapper 21 is conveyed into the double-sided image printing conveyance device 20 instead of face-down. A reversing flapper 22 having a sensor such as a photo interrupter is provided in the vicinity of the conveying roller 23-1 in the conveying device 20 for double-sided image printing.
The driving of the reversing roller 23-1 is reversed at the same time when the trailing end of the sheet material being discharged to the sheet is detected. This is a so-called switchback operation. The reversing flapper 22 will be described later with reference to FIG. Accordingly, the sheet material is guided by the guide members 26-1, 26-2, 26-3, 26-4, and is conveyed by the conveying rollers 23-2, 23-3, 23.
-4, 23-5, and the reverse of the surface printed earlier
At the same time, the image is re-conveyed from the rear end to the image forming section 3 and both sides of the image are printed. Thereafter, the image is output via the fixing device 6 and the transport rollers 5-5 and 5-6 in the same manner as in the single-sided printing process.

From the roller nips of the fixing device 6 to the nip of the transport roller 23-1 on the double-sided image printing apparatus, a transport system (A dimension in the drawing) having a straight shape is used as much as possible.
The conveying speed of 3-1 is increased by 7% compared to the fixing roller, and the shape of the reversing tray 24-a for performing switchback is made into an R shape, and the sheet material is hung downward.

In this configuration, the fixing roller 6-1 and the conveying roller 23-1 are pulled against the sheet material, and the curl and waving are corrected where the sheet material is as hot as possible.
Furthermore, the curl correction of the entire sheet material is further performed by making the reversing portion 28 into an R shape and hanging the sheet material backward.

In this configuration, there is also an effect that the sheet material to be switched back by hanging the sheet material vertically downward is prevented from hanging on the upper surface of the image forming apparatus 1 and obstructing the user.

The above-described correction of curling and waving achieves a stable double-sided image printing apparatus having a long conveying distance, a sheet feeding apparatus related thereto, and a stable sheet conveying in the image forming apparatus for printing the second side. This is to achieve high quality image quality in the second side printing.

FIGS. 2A and 2B show reversing rollers 23-1.
(A) shows the detailed structure of 23-1 (b).

The double-sided image printing apparatus side conveyance roller 23-1
Drive transmission means transmits the drive via a torque limiter. The torque limiter is, for example, a roller shaft 23-1.
(E) and the reversing roller 23-1 (b).

In FIG. 2A, the reverse flapper 22
In (a), the light blocking portion 22 (b) of the photo interrupter is urged by a reversing spring 22 (c). The reversing roller 23-1 (a) is on the transport side, and the reversing roller 23-1 (b) is on the so-called reverse roller side. Reverse roller 23-1
(B) The swing arm 23-1 (c) urged by the separation spring 23-1 (d) swings up and down.

The sheet material conveyed out of the fixing device 6 is guided to the double-sided image printing apparatus side by a solenoid (not shown in the figure) which engages with a signal for double-sided image printing from the switching flapper 21 when the signal is received. Then, the switching flapper 22 (a) is pushed down by the conveying force of the sheet material,
The sheet material is carried into the reversing roller nip. When the trailing edge of the sheet material passes through the reversing flapper 22 (a), the light-shielding portion 22 (b) cuts off the photo interrupter 22 (d) by the urging force of the reversing spring 22 (c), and at the same time, drives the reversing roller. The motor (no indication in the figure) reverses,
At the same time, the reversing roller also carries the reverse rotation. This is a so-called switchback operation (see FIG. 2B).

Here, the reverse roller 23-1 (b) via the torque limiter always rotates counterclockwise in the drawing.
Performs the judgment function only at the time of inversion. If a plurality of sheets fed from the image forming apparatus are conveyed to the double-sided image printing apparatus, the unprinted sheet remains on the reversing tray. By doing so, especially for a double-sided image printing apparatus that requires printing in the order of pages, double-feeding and printing on each side of a jam or upper and lower sheet materials must not be caused by fouling or the like.
The present invention has been made in view of the above, and further improves the reliability of the double-sided image printing apparatus.

The separating function of the reversing roller 23-1 (b) will be described in detail. When the sheet material is fed in the discharge direction, the reversing rollers 23-1 (a) and (b) rotate in the directions of the arrows in FIG. Figure 2 during switchback operation
The reversing roller 23-1 (a) as shown in FIG.
Is driven to rotate counterclockwise, but the roller shaft 23-1
(E) is driven to rotate in the direction to rotate the reversing roller 23-1 (b) counterclockwise in the same manner as when discharging. However, if there is nothing between the reversing roller 23-1 (a) and only one sheet material is sandwiched between the roller shaft 23-1 (e) and the reversing roller 23-1 by the action of the torque limiter.
(B) and slippage occurs, and the reversing roller 23-1
(B) rotates clockwise following the reversing roller 23-1 (a) or the sheet material. However, two sheets
When the sheets are nipped, slippage occurs between the sheet materials having a small lashing force, and the reversing roller 23 on which an image is formed on one surface is formed.
-1 (a) contacts the reversing roller 23
-1 (a) is sent to the conveying roller 23-2,
The sheet material that is in contact with the reversing roller 23-1 (b) is discharged onto the switchback tray 28 by the reversing roller 23-1 (b) that has been driven counterclockwise by the drive transmitted by the torque limiter. .

[0019]

As described above, the image forming apparatus of the present invention forms a double-sided image on a multi-fed sheet as it is, and forms a page in order, or forms an image on two sheets one by one. This has the effect of preventing that.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating details of a reversing roller of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image forming part 4 Sheet material cassette 5 Image forming apparatus-side conveying rollers 20 Double-sided image printing apparatus 23 Double-sided image printing apparatus-side conveying rollers 23-1 Reverse roller 24 Reverse tray

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuo Ikuo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Eiichiro Kimizuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Masanobu Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (56) References JP-A-59-182138 (JP, A) JP-A-63-1554539 (JP) JP-A-3-98946 (JP, A) JP-A-51-113637 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 29/58 B65H 29/64

Claims (2)

(57) [Claims] 1. An image forming means for forming an image on a sheet, and a sheet having an image formed on one surface by the image forming means is conveyed to the image forming means again to form an image on the other surface. Conveying means for performing, when a plurality of overlapping sheets have been conveyed to the conveying means from the image forming means, having a separating means for separating the sheet on which the image is formed and other sheets, The separating means has a pair of rollers for switching back while holding the sheet, and the first roller on the side in contact with the surface of the sheet on which the image is formed is rotated in reverse for switchback to remove the sheet. When driven to rotate in the direction of conveyance to the image forming unit, the second roller that contacts the surface of the sheet opposite to the surface on which the image is formed,
The image forming apparatus is driven to rotate in a direction opposite to a direction in which a sheet is conveyed to the image forming unit, and discharges the other sheet from the pair of rollers. 2. The image forming apparatus according to claim 1, wherein the second roller is driven via a torque limiter.