JPH11160919A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device whose printing processing speed is high even in the case of double-sided printing. SOLUTION: Operation for performing printing processing on the one surface of a second paper when the printing processing is performed on the one surface of a first paper and the first paper is reversed by a reversing mechanism 2, and reversing the second paper by the mechanism 2 when the printing processing is performed again on the reversed first paper at an image printing part (photoreceptor drum 9, transfer roller 19, etc.), are repeated.

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 for printing image data, and more particularly to an image forming apparatus having a reversing mechanism and capable of printing on both sides of a sheet.

[0002]

2. Description of the Related Art Conventional image forming apparatuses capable of double-sided printing are:
As shown in FIG. 5A, a configuration in which a sheet feeding device 7 is provided at a lower stage of the main body device 1 is performed, and the operation is performed as follows. First, the paper P is fed from the paper feeding device 7 by the conveying roller pair A to the main body device 1.
(See FIG. 5A). Next, the sheet P is sent out by the pair of conveying rollers B and the pair of registration rollers 18, the image of the second page is transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and conveyed. It is sent out to the roller pair 21 (see FIG. 5B). The paper P is sent from the pair of transport rollers 21 to the reversing mechanism 2,
The image of the second page sent out and printed by the pair of conveying rollers C, D, and E is positioned on the upper surface (FIGS. 5C to 5C).
(E)). The sheet P is sent out to the registration roller pair 18 by the conveyance roller pair F, and at that time, the printed image of the second page is the lower surface (see FIG. 5F). Next, the sheet P is sent out by the pair of registration rollers 18, the image of the first page is transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and 21 (see FIG. 5 (g)). Then, the sheet P is sent out from the pair of conveying rollers 21 to the pair of conveying rollers G and H (see FIG. 5H), and is discharged to the paper feed tray 6 (see FIG. 5I).

The conventional image forming apparatus capable of double-sided printing repeats the above-described operation, so that page 2, page 1 (the first page has been completed), page 4, page 3 (the second page has been completed), page 6, and page 5. Page (3rd page end), 8 pages, 7 page (4th page end), 10 pages, 9 pages (5 pages)
Printing is performed in the order of the end of the sheet).

[0004]

However, in the conventional image forming apparatus, after printing the back side (even number pages), the sheet is reversed using the reversing mechanism 2 to print the front side (odd number pages). There is a problem that the processing time is about twice as long as the processing time and the printing speed is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made to convey a sheet fed from a sheet feeding cassette to a reversing mechanism after printing is completed in an image printing section. In an image forming apparatus capable of printing on both sides of a sheet by reversing the sheet and transporting it to the image printing unit again, the second sheet is printed when the sheet is printed on one side of the first sheet and then turned over by the reversing mechanism. An image forming apparatus which performs a printing process on one side of the image forming apparatus, and repeats an operation of inverting a second sheet by an inverting mechanism when the inverted first sheet is again printed by an image printing unit. It is.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external view showing an image forming apparatus, in which a main body device 1 is mounted on the uppermost stage in which three sheet feeding devices 7 each having two sheet feeding cassettes 12 and 13 are stacked.

FIG. 2 is a cross-sectional view showing an embodiment of the image forming apparatus in which the reversing mechanism is stored. In the apparatus main body 1, a developing device is provided around the photosensitive drum 9 along the rotation direction. A unit 10, a transfer roller 19, a cleaner 11 for the photosensitive drum 9, and a charging unit (not shown) are provided. The developing unit 10 is configured to be able to appropriately supply a predetermined amount of toner from the toner container 31. An optical scanning unit 5 that forms dots of an image on the surface of the photoconductor drum 9 is provided above the photoconductor drum 9. Registration roller pair 18, transfer roller 19, fixing roller 23,
The reversing mechanism 2 is located below the transport path 36 where the 24 and the like are arranged and formed.
Is detachably mounted on the apparatus main body 1, and the reversing mechanism 2
Below the paper feeder, paper feeders 7 for storing sheets are stacked in three stages, and paper feed cassettes 12 to 17 are provided detachably from the outside. On the right side of the paper feeding device 7, a transport path 37 that communicates with the transport path 34 for transporting the paper of the main body device 1 is provided, and the transport path 37 is provided with a pair of transport rollers A and A '. Further, pickup rollers 74 to 79 for taking out the sheets stored in the sheet cassettes 12 to 17 are provided.
Are arranged. With such a configuration, the sheets stored in the sheet cassettes 12 to 17 are transported to the transport path 37 by the pickup rollers 74 to 79 and can be transported to the registration roller pair 18 by the transport roller pair B.

A fixing roller 23,
A fixing unit is constituted by 24, and the sheet passing between the photosensitive drum 9 and the transfer roller 19 is fixed by fixing rollers 23 and 24. After fixing, the sheet is transferred from the pair of conveying rollers 21 to the reversing mechanism 2 or the conveying path 27. It is configured to pass through and be stacked on the paper discharge tray 6. The paper conveyed to the reversing mechanism 2 is conveyed in a substantially S-shape, and then sent out to the registration rollers 18 through the conveyance path 38, so that the paper is reversed.

According to the present invention, a printing process is performed on one side of a first sheet and a printing process is performed on one side of a second sheet when the sheet is reversed by the reversing mechanism 2. It is characterized in that the operation of reversing the second sheet by the reversing mechanism 2 is repeated when the printing process is performed again by the image printing unit (the photosensitive drum 9, the transfer roller 19, etc.).

FIG. 3 is a diagram for explaining the operation of the present invention. First, the first sheet is fed from the sheet feeding device 7 to the main body device 1 by the conveying roller pair A, is sent out by the conveying roller pair B and the registration roller pair 18, and is sent between the photosensitive drum 9 and the transfer roller 19. The image of the second page is transferred, fixed by the fixing rollers 23 and 24, and conveyed to the conveying roller pair 21 (see FIG. 3A). The first sheet is sent out from the conveying roller pair 21 to the reversing mechanism 2, and the conveying roller pair C,
The image is sent out by D and E, and is inverted so that the image of the second page printed is the upper surface. Further, during the operation, the second sheet is fed, the image of the fourth page is transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and Sent out (Fig. 3
(B)). The image of the first page of the first sheet is again transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and sent out to the transport roller pair 21. During the operation, the second sheet is sent to the reversing mechanism 2 (see FIG. 3C). The first sheet is sent out by the pair of conveying rollers G and H, and is discharged to the discharge toner 6. During the operation, the second sheet is transported by the pair of transport rollers C, D,
E, and the image of the fourth page printed is inverted so that it is on the top side, and a third sheet is fed,
The image of the sixth page is transferred between the photosensitive drum 9 and the transfer roller 19, is fixed by the fixing rollers 23 and 24, and is sent to the transport roller pair 21 (see FIG. 3D). The second sheet is again moved between the photosensitive drum 9 and the transfer roller 19 by 3.
The image of the page is transferred, fixed by the fixing rollers 23 and 24, and sent out to the conveying roller pair 21. Further, during the operation, the third sheet is sent to the reversing mechanism 2 (see FIG. 3).
(E)). The second sheet is sent out by the pair of conveying rollers G and H, and is discharged to the discharge toner 6. During the operation, the third sheet is sent out by the pair of conveying rollers C, D, and E, and the printed image of the sixth page is turned over so that the upper side is turned on. Then, the fourth sheet is fed. The image of the eighth page is transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and sent out to the transport roller pair 21 (see FIG. 3F). The image of the fifth page is transferred again between the photosensitive drum 9 and the transfer roller 19 on the third sheet, is fixed by the fixing rollers 23 and 24, and is sent to the transport roller pair 21. During the operation, the third sheet is sent out to the reversing mechanism 2 (see FIG. 3G). The third sheet is sent out by the pair of conveying rollers G and H, and is discharged to the discharge toner 6. During the operation, the fourth sheet is sent out by the pair of conveying rollers C, D, and E, and the printed image of the eighth page is turned over so as to be on the upper side, and further, the fifth sheet is fed. The image of the tenth page is transferred between the photosensitive drum 9 and the transfer roller 19, fixed by the fixing rollers 23 and 24, and sent out to the transport roller pair 21 (FIG. 3).
(H)).

The image forming apparatus of the present invention performs printing processing of the next sheet while the sheet is inverted by the reversing mechanism 2, specifically, when performing double-sided printing of 10 pages, 2 pages, 4 pages, One page (1
Page 6), page 3 (page 2), page 8, page 5 (page 3), page 10, page 7 (page 4), page 9 (page 5) By performing printing in order, the printing processing speed can be increased.

In this embodiment, the order of printed pages in the case of face-down discharge is shown. However, in the case of face-up discharge, the same processing can be performed by changing the order of even-numbered pages and odd-numbered pages. Specifically, when performing 10-sided double-sided printing, page 1, page 3, page 2, page 5, page 4, page 7, page 6, page 6
Printing may be performed in the order of page 9, page 8, page 8, and page 10.

Further, in the sheet supply order according to the present invention, if the sheet in the sheet cassette currently fed is out of paper, etc., one of the following operations must be performed. (1) The paper supply is interrupted, and the paper being processed by the reversing mechanism 2 is printed and discharged. For example, in a case where double-sided printing of 10 pages is performed, if the current paper feed cassette of the paper feeding device 7 runs out of paper when the third paper is fed, the second page, 4 The third sheet (the sheet on which the sixth page is printed) remaining in the reversing mechanism 2 after printing in the order of page, 1 page, 6 pages, and 3 pages is again transferred to the photosensitive drum 9 and the transfer roller 19. The control is performed so that the image of the fifth page is transferred in between, discharged, and replenished, and then printed again in the order of pages 8, 10, 7, and 9. (2) Supply paper from another paper cassette. In any operation, it is necessary to feed the paper at a constant interval, appropriately detect the out of paper in the paper feed cassette, and appropriately perform the subsequent processing.

The present invention is characterized in that control is performed as follows in order to realize the above-mentioned operation (1) or (2). (A) A first signal instructing a paper feed timing so that paper feed from the paper feed cassette to the image printing unit is at a constant interval, and a first signal indicating that the paper feed cassette being fed is out of paper. When the second signal detects that the paper has run out, control is performed so as to change the order of pages processed by the image printing unit. For example, when double-sided printing of 10 pages is performed, printing is normally performed in the order of 6, 3, 8, and 5 pages.
Is detected, the control is performed to change the order of page 6, page 3, and page 5. (B) When it is detected from the second signal that the paper has run out, control is performed so that the paper in the reversing mechanism is printed. For example, when performing double-sided printing of 10 pages, usually 6
When printing is performed in the order of page 3, page 8, page 5, and page 5, when the second signal is detected when the sheet for printing page 6 is fed, the sheet in the reversing mechanism 2 is sent out to the print processing unit. The control is performed so as to print the fifth page. This operation means that when the second signal is detected, control is performed so as to perform the same operation as the conventional operation as shown in FIG. (C) When the second signal detects that the paper has run out, control is performed so that the paper is fed from another paper feed cassette. For example, in the case of performing double-sided printing of 10 pages, if a second signal is detected when paper for printing 6 pages is fed,
Control is performed so that subsequent paper feeding is performed from another paper feeding cassette. Note that the first signal in (a) to (c) is used to determine the timing of the longest distance between the image printing unit and the paper feed position 7, that is, the timing of feeding paper at regular intervals from the paper feed cassette 17 in FIG. By doing so, the other sheet cassettes 12 to 16
Since the paper is fed faster than that, it is possible to reliably maintain a constant interval. Further, by using two signals as the first signal and the second signal, the fed sheet is the last sheet in the sheet cassette while the printing speed is high and the sheet feeding interval is constant. The image forming apparatus can determine whether or not the image forming apparatus can process the sheet when the sheet runs out.

FIG. 4 is a flowchart showing the operation of the above (b) when performing double-sided printing by the face-down method.
Will be described. First, after the back side printing (even pages) is performed (step 1), a second signal is waited for (step 2), and it is determined whether or not there is a sheet in the sheet cassette (step 3). If there is no paper, the front side printing of the paper in the reversing mechanism 2 is performed and the paper is discharged (step 4), and then the apparatus enters a standby state (step 5). If there is a sheet, the next sheet is fed at the instruction timing of the first signal to print the back side (even pages) (step 6), and then wait for the first signal (step 7).
At the instruction timing of the first signal, the front side printing of the sheet in the reversing mechanism 2 is performed, the sheet is discharged, and the process returns to step S1.

[0016]

As described above, according to the present invention,
When the printing process is performed on one side of the first sheet and the sheet is reversed by the reversing mechanism, the printing process is performed on one side of the second sheet, and the inverted first sheet is printed again by the image printing unit. By repeatedly performing the operation of reversing the second sheet by the reversing mechanism during the operation, it is possible to provide an image forming apparatus having a high print processing speed even during double-sided printing.

A first signal for instructing a paper feed timing so that paper is fed from the paper feed cassette to the image printing unit at a constant interval, and a signal indicating that paper has run out in the paper feed cassette being fed. When the second signal indicates that the paper has run out, the image printing unit changes the order of the pages to be processed, or prints the paper conveyed into the reversing mechanism. Or by controlling paper to be fed from another paper cassette, it is possible to determine whether or not the fed paper is the last paper in the paper cassette while keeping the paper feed interval constant. It is possible to provide an image forming apparatus that can judge and appropriately process when paper runs out.

Further, by setting the first signal to be the timing of the longest distance between the image printing section and the sheet feeding position, it is possible to provide an image forming apparatus which can reliably maintain a constant sheet feeding interval.

[Brief description of the drawings]

FIG. 1 is an external view showing an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view illustrating the image forming apparatus of the present invention.

FIG. 3 is a diagram illustrating the operation of the image forming apparatus of the present invention.

FIG. 4 is a flowchart illustrating an operation of the image forming apparatus of the present invention.

FIG. 5 is a diagram illustrating an operation of a conventional image forming apparatus.

[Explanation of symbols]

1: main unit 2: reversing mechanism 5: optical scanning unit 6: paper feed tray 7: paper feeder 9: photosensitive drum 10: developing unit 11: cleaner 12, 13, 14, 15, 16, 17: paper feed Cassette 18: registration roller pair 19: transfer roller 23, 24: fixing roller 27, 34, 36, 37, 38: transport path 31: toner container 74, 75, 76, 77, 78, 79: pickup roller A, A ' , B, C, D, E, F, G, H, 21: transport roller pair

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B65H 85/00 B65H 85/00 G03G 21/00 370 G03G 21/00 370

Claims (7)

[Claims] An image printing unit completes printing of a sheet fed from a sheet cassette, and then conveys the sheet to a reversing mechanism to invert the sheet and conveys the sheet to the image printing unit again, thereby enabling printing on both sides of the sheet. In the image forming apparatus, the image printing unit performs a printing process on one side of the first sheet and the image printing unit performs a printing process on one side of the second sheet when the first sheet is inverted by the reversing mechanism. An image forming apparatus that repeats an operation of reversing the second sheet by the reversing mechanism while performing the printing process on the inverted first sheet again in the image printing unit. A first signal for instructing a paper feed timing so that paper is fed from the paper feed cassette to the image printing unit at a constant interval; and that there is no paper in the paper feed cassette being fed. 2. The image forming apparatus according to claim 1, further comprising: changing a page order to be processed by the image printing unit when the second signal indicates that the paper has run out. apparatus. 3. The image forming apparatus according to claim 2, wherein the first signal is a timing of a longest distance between the image printing unit and a sheet feeding position. 4. A first signal for instructing a paper feed timing so that paper feed from the paper feed cassette to the image printing section is at a constant interval, and that there is no paper in the paper feed cassette being fed. And detecting that the paper has run out based on the second signal, the image printing unit prints the paper conveyed into the reversing mechanism. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 4, wherein the first signal is a timing of a longest distance between the image printing unit and a sheet feeding position. 6. A first signal for instructing a paper feed timing so that paper is fed from the paper cassette to the image printing unit at a constant interval, and the paper cassette being fed is out of paper. 2. The image forming apparatus according to claim 1, further comprising: a second signal indicating that the sheet has run out, and when the second signal indicates that the sheet has run out, the sheet is fed from another sheet cassette. 3. . 7. The image forming apparatus according to claim 6, wherein the first signal is a timing of a longest distance between the image printing unit and a sheet feeding position.