JP3000494B2 - Double-sided 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 a double-sided image forming apparatus, such as a laser printer or a facsimile, capable of forming an image on both sides of a recording sheet. The present invention relates to a double-sided image forming apparatus capable of efficiently processing image data.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing a schematic structure of a laser printer which is an example of a double-sided image forming apparatus. In the figure, a mechanism related to a known electrophotographic system is omitted.

The recording paper stored in the paper feed tray 1a or the paper feed tray 1b is separated and fed one by one by a paper feed roller 2, and a conveying path constituted by rollers, guide plates, etc., not shown. The leading edge of the recording paper reaches the pair of registration rollers 3 along. Further, a toner image is formed on the photosensitive drum 4 based on the image information. The recording paper is fed to the photosensitive drum 4 by the registration roller pair 3 in synchronization with the leading end position of the toner image on the photosensitive drum 4,
At the transfer position, the toner image on the photosensitive drum 4 is electrostatically transferred by a transfer charger (not shown). The recording paper to which the toner image has been transferred is heated or pressed by the fixing unit 5 to fix the toner image.

A recording sheet on which an image is formed on one surface by transferring and fixing a toner image is formed by a path changing guide 6 depending on whether an image is formed on the other surface or the image formation is completed. Is determined. The recording paper on which image formation has been completed is routed so as to be discharged, discharged to the paper discharge tray 7, and the recording paper on which an image is formed on another surface is sent to the reverse paper feed unit 8. A route is set to be transported.

The reversing sheet feeding unit 8 includes a roller pair 8a, a recording sheet detecting sensor 8b, a stack tray 8c, a reversing guide 8d, and the like.

[0006] The recording paper having an image formed on one side and having a route to the reversing paper feed unit 8 is conveyed to a pair of rollers 8a and detected by a recording paper detection sensor 8b at a predetermined position. The recording paper detection sensor 8b detects the recording paper, and the roller pair 8a reversely rotates at the timing when the roller pair 8a carries the paper for a predetermined time. At this time, the reversing guide 8 d determines the path of the recording paper so that the recording paper is conveyed to the registration roller pair 3 in a state where the recording paper is reversed so that the surface on which the image is not formed faces the photosensitive drum 4.

[0007] The recording paper conveyed again in a state in which the image was first formed on the registration roller pair 3 is reversed, and the image is formed in the same manner as the image was formed first. The paper is discharged to the paper discharge tray 7.

FIG. 7 is an example of a timing chart when images are continuously formed on both sides of a plurality of recording papers using a conventional laser printer.

The operation of forming an image continuously on a plurality of recording sheets will be described with reference to FIGS. 2 and 7.

First, a toner image on the photosensitive drum 4 is transferred to the surface of the recording paper D1 from the recording paper D1 fed from the paper feeding tray 1a or the paper feeding tray 1b. The image is fixed, and the image of the first page is formed. Next, the recording paper D1 is fed to the reverse paper feeding unit 8.
And the second page image is formed on the back surface. The second recording paper D2 is started to be fed from the paper feed trays 1a and 1b at a predetermined timing, and at the timing when the image formation on the back surface is completed and the recording paper D1 is discharged, the photosensitive drum 4 is discharged. Is transferred to the transfer position, and the image of the third page is formed on the front surface. The image is reverse-fed by the reverse sheet feeding unit to form the image of the fourth page on the rear surface.

Thereafter, the laser printer forms an image on the front and back surfaces of the recording paper based on the image data in accordance with the page order.

Here, the front surface of the recording paper is the surface on which an image is formed first, and the rear surface is the surface on which an image is formed by reverse feeding.

[0013]

In the conventional laser printer, when forming a continuous image on both sides of a plurality of recording sheets, an image is formed on the front side of the recording sheet and an image is formed on the back side. Therefore, the time until the paper is reversed is
The transfer and fixing of the toner image are not performed, and this is the waiting time until the image formation is started. Therefore, when an image is formed on both sides of a recording sheet, there is a problem that the processing time of image data is longer than when an image is formed only on one side.

An object of the present invention is to solve the above-mentioned problem by changing the order of forming images on a page basis so as to reduce the waiting time until the start of image formation on each page. An object of the present invention is to provide a double-sided image forming apparatus.

[0015]

In order to achieve the above object, the present invention provides an image forming means for forming an image on recording paper, a recording paper storage means for storing recording paper, and a recording paper storage means. Paper feed means for feeding recording paper to the image forming position, and reversing paper feeding for reversing the recording paper having an image formed on one side and then re-feeding it to the image forming position to form an image on the other side Means, a recording paper detecting means for detecting a position of the recording paper in the reversing paper feeding means, and a control means for causing the image forming means to form an image, wherein the control means comprises an image data input from the outside. Is stored in correspondence with the order of the pages, and a paper feed time from the recording paper storage unit to the image forming position and a re-feed time calculated based on a detection signal from the recording paper detection unit. The time comparison unit that compares When images are continuously formed on both sides of the recording paper, the waiting time until image formation starts is determined by the image data that has been written to the storage unit and the comparison signal output by the time comparison unit. In order to reduce the time, the image formation is performed in the order of the pages, and the image is formed on the other side of the recording paper on which the image is formed on one side, or the image formation is switched to the order of the pages. And a determination unit for determining whether an image is to be formed on the next recording sheet.

[0016]

According to the above means, a control means for causing the image forming means to form an image, a storage section in which image data inputted from the outside is written in a corresponding order of pages, and A time comparison unit that compares the paper feeding time of the recording paper with the refeeding time calculated based on the detection signal of the recording paper detection unit, and image data that has been written to the recording unit and the time comparison unit output According to the comparison signal, in order to reduce the waiting time until the start of image formation, the image formation is performed in the order of the pages, and the image is formed on the other side of the recording paper on which the image is formed on one side, or the image is formed. A determination unit that determines whether to form an image on the next recording sheet by performing the formation in the order of the pages, so that the image data that has been written to the storage unit and the one side Image is formed on Based on a comparison signal from a time comparison unit that compares the reversal sheet feeding time of the recording sheet and the sheet feeding time of the next recording sheet, the determination unit that determines that the order in which the images are formed is to be changed is started. Can be controlled to shorten the waiting time until

[0017]

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

FIG. 1 is a block diagram showing a configuration of a control unit of a laser printer according to one embodiment of the present invention.

The control unit shown in FIG. 1 is applied to the laser printer described with reference to FIG.

The control unit comprises a host device 20, a controller 3
0, a panel device 40, a printer engine 50, and the like.

The host device 20 outputs image data and commands to the controller 30, and the image data is output in the order of pages on which images are to be formed. The operator can set the mode setting, the number of copies to be printed, and the like using the panel device 40.

The controller 30 includes a CPU (central processing unit) 31 for controlling the whole controller 30, a program ROM 32 storing a control program, a RAM 33 used as a work memory of the CPU 31, a page buffer memory for image data, and a host device. A host interface 34 for communicating with the panel 20, a panel interface 35 for communicating with the panel device 40, an engine interface 36 for communicating commands and status with the printer engine 50, and a font R storing font pattern data and the like.
It comprises an OM 37, a bit map memory 38 for storing image data obtained by developing image data into images, a CPU bus 39 comprising a data bus, an address bus and a control bus.

The CPU 31 includes a time comparing section 31a for outputting a comparison signal and a page order determining section 31b for changing the order of forming images.

The image forming operation of this embodiment will be described with reference to FIGS.

When image data is sent from the host device 20 to the controller 30 in which the double-sided print mode is set via the panel device 40, the controller 30 converts the image data into an internal code, and It is stored in the page memory area in units of pages. When the image data for one page is stored in the RAM 33, the CPU 31 sends the image data to the printer engine 50 via the engine interface 36.
Output a print command. The printer engine 50 starts the image forming operation according to the print command, and feeds the first recording paper from the paper feed trays 1a and 1b. In the controller 30, the CPU 31 reads out the image data of the first page from the RAM 33, develops the image data into image data, and stores the image data in the bitmap memory 38. The bitmap memory 38 transmits the stored image data to the printer engine 50 in synchronization with the video synchronization signal of the printer engine 50.

The printer engine 50 drives a laser diode (not shown) based on the image data to form a toner image corresponding to the image data on the photosensitive drum 4 by an electrophotographic method.

The toner image on the photosensitive drum 4 is transferred to a recording sheet timed by the pair of registration rollers 3, and the toner image is fixed by the fixing unit 5, and is applied to the surface of the first recording sheet. On the other hand, the image formation for the first page is completed.

The recording paper having an image formed on its surface is conveyed to the reverse sheet feeding unit 8. At this time, the page order determination unit 31b of the CPU 31 next causes the image to be formed on the back surface of the first recording sheet in accordance with the page order, or changes the order and outputs the third page on the front surface of the second recording sheet. It is determined whether or not an image is to be formed.

FIGS. 3, 4 and 5 are timing charts when an image is formed on both sides of a plurality of recording papers according to the present embodiment.

The page order determining section 31b of the CPU 31 checks whether the writing of the image data of the third page to the RAM 33 has been completed since the completion of the image formation of the first page. The time comparison unit 31a of the CPU 31 counts the time from when the reverse feeding of the recording sheet is started by the clock signal of the CPU 31 and is calculated at a constant cycle by the detection signal of the recording sheet detection sensor 8b. The re-feeding time TD until the recording sheet is reversed and reaches the registration roller pair 3 again is compared with a constant paper feeding time TR from the sheet feeding trays 1a and 1b to the registration roller pair 3. The comparison signal is output to the page order determination unit 31b.

As shown in FIG. 3, the page order determining section 31b
When the writing of the image data of the third page is completed when the image formation of the first page is completed, the feeding of the second recording paper D2 is started, and Control is performed to form an image on the page.

When the image formation for the first page is completed and the writing of the image data for the third page is not completed when the image formation for the first page is completed, the re-feeding time TD of the recording paper D1 is set to the paper feeding time TR. It is checked at regular intervals whether the writing of the image data of the third page is completed until it becomes equal to.

As shown in FIG. 4, the page order determination section 31b
When the writing of the image data of the third page is completed at the timing of TD> TR, the control is performed so that the image of the third page is formed as in FIG.

Also, as shown in FIG.
31b forms the image of the second page on the back surface of the reverse-fed recording paper D1 according to the page order if the writing of the image data of the third page is not completed before TD = TR. Control to make it.

Thereafter, when the image formation on the front side of the recording sheet is completed, the page order determination section 31b performs the same control as above to form an image on the back side of the recording sheet according to the page order, or On the other hand, the order in which images are formed is exchanged, and it is determined whether or not an image is to be formed on the surface of a recording sheet to be fed next, and the order of pages on which images are formed is controlled.

FIG. 6 is a flowchart of the data processing of the page order judging section of this embodiment.

In step (S) 1, 1 is set to the number D of recording sheets fed, and 1 is set to the number P of pages on which an image is formed. Feeding of the first recording paper starts
(S2) The first sheet of recording paper has an image of the first page formed on the surface thereof (S3). The recording sheet on which the image of the first page has been formed is conveyed to the reversing sheet feeding unit 8 and reversingly fed. Paper is produced (S4). At this time, by the comparison signal of the time comparison unit 31a,
The page order determination unit 31b checks whether TD = TR or TD> TR (S5), and if TD = TR, forms an image on the second page (S6). 1 is added, 2 is added to the number of pages (S7), and the process returns to S2.

If TD> TR, the page order determination unit
31b checks whether writing of the image data of the third page is completed (S8), and if not completed, returns to S5; if completed, feeds the second recording paper Is started (S9), and the image of the third page is
The recording paper is formed on the surface of the first recording paper (S10), and the recording paper is reversed and fed (S11). Then, the second page image is formed (S12), and the fourth page image is formed.
(S13).

When the image formation for the fourth page is completed, 2 is added to the number of recording sheets, 4 is added to the number of pages (S14), and the process returns to S2.

Although not shown in FIG. 6,
The CPU 31 checks the remaining image data at a predetermined timing, and if there is no image data, performs a work stop process.

According to the above laser printer, when the image formation is completed on the front surface of the recording paper, the image is formed on the back surface of the recording paper in accordance with the order of the pages, or the order is changed, and the recording paper is inverted. The time comparison unit determines whether an image is formed first on the surface of the next recording paper while paper is being fed.
The page order determination unit 31b that determines the comparison signal of the page 31a and the image data that has been written to the RAM 33 can reduce the waiting time until the start of image formation on each page. The time required for the operation can be shortened.

[0042]

As described above, according to the present invention, according to the present invention, the control means controls the time comparing section for comparing the re-feeding time with the sheet feeding time, the comparison signal output by the time comparing section and the storage section. A determination unit that determines whether to perform image formation in accordance with the page order with the image data for which writing has been completed or to perform image formation in a reversed order with respect to the page order; Can be shortened, so that the time for processing the image data can be shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control unit of a laser printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a laser printer as an example of a two-sided image forming apparatus.

FIG. 3

FIG. 5 is a timing chart when an image is formed on both sides of a plurality of recording papers according to the embodiment.

FIG. 6 is a flowchart of data processing of a page order determination unit according to the embodiment.

FIG. 7 is a timing chart when an image is formed on both sides of a plurality of recording papers by a conventional laser printer.

[Explanation of symbols]

1a, 1b: paper feed tray, 4: photosensitive drum, 8: reverse paper feed unit, 20: host device, 30: controller, 31: CPU, 31a: time comparison unit, 31b: page order determination unit, 33: RAM , 38 ... bitmap memory,
50… Printer engine.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 3/60 B41J 13/00 B41J 21/00 G03G 15/00 H04N 1/23 G06F 3/12

Claims (1)

(57) [Claims] An image forming means for forming an image on a recording paper; a recording paper storing means for storing the recording paper; a paper feeding means for feeding the recording paper from the recording paper storing means to an image forming position; Reversing sheet feeding means for reversing a recording sheet having an image formed on one surface and then re-feeding the sheet to an image forming position for forming an image on the other side, and detecting the position of the recording sheet in the reversing sheet feeding means A recording sheet detection unit, and a control unit that controls the image forming unit to form an image, wherein the control unit includes a storage unit in which image data input from the outside is written in correspondence with the order of pages, A time comparison unit that compares a paper feeding time from the recording paper storage unit to the image forming position with a re-feeding time calculated based on a detection signal from the recording paper detection unit; To form images continuously According to the image data that has been written to the storage unit and the comparison signal output by the time comparison unit, the image formation is performed in the order of pages in order to reduce the waiting time until image formation starts. Judgment to determine whether to form an image on the other side of recording paper having an image formed on one side, or to perform image formation in the order of pages, and form an image on the next recording paper And a double-sided image forming apparatus.