JP3057961B2 - Double-sided printer and control method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of transferring an image onto a first side of a sheet and then returning the sheet to a transfer section without once discharging the sheet to the outside of the apparatus to transfer the image to the second side. More particularly, the present invention relates to a double-sided printer having a characteristic in timing of conveying a sheet to a transfer unit and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, after a print text is transferred to a first side of a sheet, an image can be transferred to a second side of the sheet returned to a transfer section via a sheet return path in the apparatus. 2. Description of the Related Art A printer is known and has, for example, a configuration as shown in FIG. The two-sided printer includes a photosensitive drum 51 having a surface on which an electrostatic latent image is formed by irradiating image light after being uniformly charged, a charger 52 for uniformly charging the surface of the photosensitive drum 51, An exposure device 53 for irradiating the photosensitive drum 51 with image light based on the digitized image data, a developing device 54 for visualizing an electrostatic latent image on the photosensitive drum 51, and taking out a sheet from a sheet tray 55 A sheet feeding device 56, a transfer device 57 that transfers a toner image formed on the surface of the photosensitive drum 51 to a sheet supplied by the sheet feeding device 56, and a sheet to which the toner image has been transferred is conveyed to a fixing roller 59. The transport belt 58 and a paper return path 60 for returning the paper passing through the fixing roller 59 to the transfer unit without discharging the paper to the outside of the apparatus constitute a main part.

The paper return path 60 is provided with switching means 61 for switching between discharging the paper passing through the fixing roller 59 to the paper discharge tray 64 and leading the paper to the paper return path for returning to the transfer section 57 again, A sheet reversing unit 62 that reversely feeds the sheet to reverse the first side and the second side, and a standby unit 63 that can temporarily suspend the sheet to adjust the timing of feeding the sheet to the transfer unit are provided. ing. By the paper return path 60, the paper on which the image has been transferred to the first surface is returned to the transfer unit without being discharged to the paper discharge tray 64, and the paper on which the image has been transferred to the second surface is discharged as it is. The paper can be discharged to the paper tray 64.

[0004] Such a duplex printer is controlled as follows. When the image forming operation is started, the photosensitive drum 5
1 rotates and the surface is uniformly charged by the charger 52, and then the exposure device 53 irradiates image light based on the image data obtained by dot development, and an electrostatic latent image is formed. The electrostatic latent image is visualized by the toner attached by the developing device 54. On the other hand, the sheet is pulled out from the sheet tray 55 and supplied to the transfer unit 57, where the toner image on the photosensitive drum 51 is transferred to the first surface of the sheet. After the sheet on which the toner image has been transferred passes through the fixing roller 59, the sheet is guided to the sheet return path 60, and the sheet reversing unit 62 reverses the transport direction. Thereafter, the sheet is fed again to the transfer section 57 via the sheet standby section 63, and another image is transferred to the second surface. Such a process is repeated for a plurality of sheets. However, in order to form and transfer an image at a high speed, it is necessary to transfer an image on the first surface and then transfer the image to the second surface of the same sheet. An image is formed and transferred to another sheet.

FIG. 6 is a diagram showing timings for transferring an image based on predetermined page data to both sides of a plurality of sheets. As shown in this figure, first, the image of the first page is transferred to the first surface of the first sheet, and the first sheet is transferred to the sheet return path 6.
It is sent to 0. Subsequently, the image of the third page is transferred to the first surface of the second sheet, and guided to the sheet return path 60. afterwards,
The image is transferred to the second surface of the first sheet which has been reversed and returned in the sheet return path 60, and the first sheet is
It is discharged to 4. Subsequently, an image is formed and transferred sequentially on the first side of the third sheet, the second side of the second sheet, and the first side of the fourth sheet.

In order to form and transfer an image at a high speed in such an order, the timing of sheet transport detects the position of the sheet on which the image is to be transferred first, and then transfers the image based on this. The operation of feeding the paper to be transferred to the transfer unit is started. In other words, the first sheet transferred to the first side reaches the sheet standby section (Ci), temporarily waits, and the sheet tray for the second sheet to be transferred before the transfer on the second side. Is detected, and after that, the first sheet is carried out from the sheet waiting section to the transfer section at a predetermined timing (C).
o). Further, the first sheet discharged from the sheet standby unit is detected, and the third sheet is discharged at a predetermined timing.
In this way, the transfer of the paper supplied from the paper tray to the first surface and the transfer of the paper returned through the paper return path to the second surface are performed alternately.

[0007]

However, the above two-sided printer has the following problems. To visualize printed text input from other devices, such as a computer or word processor, and transfer it to paper, the printed text must be dot-developed into image data, and the exposure device must be operated based on this data. Must. This image data has a large amount of data, especially image data, graphic data, outline characters,
If many bitmap characters and the like are included, it takes time to develop dots, and data cannot be supplied in time for sequential image formation at high speed. If the supply of data to the exposure device cannot be made in time, if the page is to be transferred on the first side of the sheet, the sheet is discharged from the sheet tray, and the page is transferred. Second
Surface, the paper is made to wait in a paper standby unit or the like,
The transfer to the transfer unit is delayed.

However, when the image is transferred to the second side of the sheet in the sheet standby section for a long time to transfer the image, the image is transferred to the first side of the subsequent sheet first. Then, the succeeding sheet approaches the waiting sheet via the sheet return path. For example, in FIG. 7, it takes time to develop dots of the data of the fourth page (the second surface of the second sheet), and a time longer than the standard time which is the maximum time allowed in the standard paper feed timing is required. In this case, after the second sheet reaches the sheet standby unit 63 (Ci), the second sheet stays in the sheet standby unit 63 for a predetermined time or more, that is, for a time indicated by Ta in the drawing. On the other hand, the third sheet on which the image has been transferred onto the first surface has already been guided to the sheet return path 60 and is sent to the sheet standby section 63 at a predetermined timing. At this time, since the waiting time of the second sheet in the sheet standby unit 63 is long,
The paper will collide in the paper standby section 63.

Conventionally, as a method of coping with such a case, it has been practiced to control the transfer of the image as a paper jam so as to interrupt the transfer of the image, or to add a paper standby unit for preventing a rear collision in the paper return path. Have been done. However, when the transfer of the image is interrupted due to a paper jam, the operator needs to perform an operation for recovery each time, which is troublesome for the operator, and it takes a long time to transfer the image. In addition, the addition of a standby unit in the paper return path requires a separate standby mechanism and complicated control, resulting in the production and production of equipment.
There is a problem that the maintenance cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to easily return a sheet even if it may take a long time to develop print text into dots in image data. An object of the present invention is to provide a double-sided printer capable of controlling the conveyance of a sheet on a path and sequentially transferring dot-developed images to both sides of the sheet.

[0011]

According to a fifth aspect of the present invention, an electrostatic latent image is formed on a photoreceptor by an exposure device which is turned on based on a digital signal, and an image visualized by toner adhesion is printed on a sheet. An image forming unit for transferring and fixing;
A printer controller that converts the page data of the print text input from the host device into dot data into image data and outputs the image data to the exposure device; and a first surface of a sheet carried out from a sheet tray provided in the image forming unit. And a sheet return path for transferring an image corresponding to the print text to the second side of the sheet and then returning the sheet to transfer another image to the second side of the sheet. after the transfer, subsequent until performing image transfer to the second surface, and transferring the image on the second surface of the sheet preceding the said sheet, on the paper
Printer for transferring an image to the first side of paper to be printed
A is, the printer controller, an arithmetic unit of the page data can be calculated the time required for dot deployed for each sheet to be transferred to the second surface of the sheet, the sheet return path is returned Wait for paper once
The image forming unit outputs a timing at which an image is transferred to a first surface of a sheet carried out of the sheet tray, and outputs data of a time required for dot development output from the arithmetic unit. controls on the basis of,
The timing at which the paper in the paper standby section is sent out
When dot development of the image transferred to the second side of the paper is completed
It is assumed that a control device for controlling according to is provided.

According to a second aspect of the present invention, there is provided the method for controlling a double-sided printer according to the first aspect, wherein the sheet is carried out from a sheet standby section provided in the sheet return path to a transfer section. A new double-sided printer control method for unloading new paper from a paper tray after detecting paper, detecting paper discharged from the paper tray, and then discharging paper in the paper standby unit toward a transfer unit. Prior to dot development of the page data of the print text, a time required for dot development of the page data to be transferred to the second side of the paper is calculated, and the calculated time is compared with a preset standard value. When the time exceeds the standard value, the carry-out of the succeeding sheet of the sheet to which the page data is transferred from the paper tray is delayed by more than the time exceeding the standard value. .

[0013] In the double-sided printer according to the first aspect, the higher-level device is a device that can output a print text, such as a word processor or a computer. Further, a CPU included in a printer controller can be used as the arithmetic device. As the control device for controlling the timing at which the image is transferred to the paper carried out of the paper tray, a control device (CPU) for controlling the operations of the photoreceptor, the developing device, and the paper return path in the image forming unit may be used. it can.

In the control method of the double-sided printer according to the second aspect, the detection of the sheet conveyed from the sheet standby section to the transfer section is performed, for example, by returning the sheet from the sheet standby section or the sheet standby section to the transfer section. This can be done by providing a sensor on the road. Further, the detection of the sheet carried out from the sheet tray can be performed, for example, by providing a sensor in the sheet tray or a sheet conveyance path from the sheet tray to the transfer unit.

The calculation of the time required for the dot development is completed in a very short time as compared with the time for dot development of the page data of the print text. It is sufficient that the operation is completed before being carried out of the tray. The preset standard value is a time required for developing the page data in dots, and is a time allowed for the double-sided printer to sequentially perform image transfer without delaying the image transfer timing. Can be set as the maximum value of

[0016]

In the double-sided printer according to the first aspect of the present invention, before the dot development of the print text is completed, the computing device calculates the time required for dot development. As a result, if the time required for dot development of the page data to be printed on the second side is long, the control device determines whether or not the control device should take out the sheet following the sheet onto which the image of the page data is transferred from the sheet tray. Delay. The transfer of the image to the first side of the subsequent sheet is performed before transferring the page requiring a long time for dot development to the second side of the sheet, and the subsequent sheet is transferred to the first side. Is transferred to the paper return path.

Therefore, if the subsequent sheet is carried out from the sheet tray and the transfer of the image to the first surface is performed at a normal timing without delay, the dot is returned when the sheet is returned through the sheet return path. If the preceding sheet remains in the sheet standby section because it takes a long time to unfold, both sheets approach or collide, but the timing is delayed in advance from the stage where the subsequent sheet is carried out from the sheet tray. When the image is transferred back to the first side after being transferred to the first side, the sheet is transported to the paper standby section while maintaining an appropriate distance from the delayed sheet, and is transferred to the second side. Is performed. For this reason, it is possible to appropriately control the paper feed without controlling the timing of unloading the paper from the paper tray without providing a complicated standby mechanism in the paper return path, and without causing the inconvenience such as the paper colliding. It becomes possible.

Further, in the control method of the double-sided printer according to the present invention, the time required for dot development of the page data to be transferred to the second side of the sheet is calculated before the dot development of the page data of the print text, When the calculated time is compared with the standard value and exceeds the standard value, control is performed such that the carry-out of the subsequent sheet of the sheet to which the page data is transferred from the paper tray is delayed for a time exceeding the standard value or more. Therefore, when the image is transferred to the first surface of the subsequent sheet and then returned via the sheet return path, the sheet is conveyed while maintaining an appropriate interval with the sheet whose transfer to the second side is delayed. Thus, transfer to the second surface can be performed. Therefore, it is not necessary to control the standby of the paper in the paper return path in a complicated manner only by controlling the timing of carrying out the paper from the paper tray, and it is possible to easily perform appropriate paper feeding.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a duplex printer according to an embodiment of the present invention. This double-sided printer is a printer controller 1 that temporarily stores a print text input from an external device such as a personal computer or a word processor, and develops dots in image data.
And an image forming unit 2 that forms an image corresponding to the dot-expanded image data and transfers the image onto paper.

The print controller 1 includes a CPU 11 capable of performing dot development of print text and calculating the time required for dot development, a hard disk 12 for temporarily storing print text input from an external device,
A page buffer 13 for temporarily storing the dot-expanded image data and then outputting it to the exposure device. The image forming unit 2 includes a photosensitive drum 21 having a surface on which an electrostatic latent image is formed by irradiating uniformly charged image light, and a charging unit for uniformly charging the photosensitive drum 21. Device 22, an exposure device 23 for irradiating the photosensitive drum 21 with image light based on the dot-developed data, a developing device 24 for visualizing an electrostatic latent image on the photosensitive drum by attaching toner, and a photosensitive drum A transfer device 27 for transferring the upper toner image onto the paper, a paper feeding device 26 for feeding the paper stored in the paper tray 25 to a transfer unit where the transfer device 27 faces the photosensitive drum 21, and a transfer device on the paper. A fixing device 29 for heating and pressurizing the toner image, a sheet return path 30 for reversing the sheet on which the image is formed on the first surface and sending the sheet back to the transfer unit, and a CPU 31 for controlling these operations are provided. ing.

In such a double-sided printer, print text output from an external device such as a word processor or a personal computer and input to the printer controller is temporarily stored on the fixed disk 12. The time required to develop the dot data of the page data to be transferred to the second side of the sheet out of the page data of the print text is determined by the CPU 11.
Is calculated by This calculation is performed according to the procedure shown in FIG. It is determined whether or not the image data amount, the graphic data number, the outline character number, and the bitmap character number are each equal to or less than a predetermined value. If the image data amount, graphic data number, outline character number, and bitmap character number are equal to or more than the predetermined value, the times Ti, Tj, T
k and Tl are calculated. And the sum of these is the time required beyond the standard time for dot development,
The time obtained by adding the sum of these to the standard time is the time required for dot development.

When the size of the paper on which the image corresponding to the print text is to be transferred is selected, as shown in FIG. 3, a standard value Ts corresponding to the normal paper feed timing is determined for each paper size. Also, predetermined values of the image data amount, the figure data number, the outline character number, and the bitmap character number are determined for each paper size. When the amount of image data, the number of graphic data, the number of outline characters, and the number of bitmaps included in a certain page data exceed these predetermined values, the time T required to develop the excess amount into dots is used.
i, Tj, Tk, and Tl are calculated. And the standard value Ts
The value obtained by adding Ti, Tj, Tk and Tl to the page data is the time required for dot development of the page data.

The time required for dot development calculated as described above is input from the CPU 11 of the printer controller 1 to the CPU 31 of the image forming unit 2. On the other hand, in the CPU 11 of the printer controller 1, each page data is dot-developed into image data. The order in which the dot development is performed is not necessarily the order of the page numbers, but is performed in accordance with the order in which the images are transferred. The dot-expanded image data is stored in the page buffer 13 and sequentially output to the exposure device 23. When the image data is output from the page buffer 13 to the exposure device 23, the image forming unit 2 operates in response to the image data formation, feed, transfer of the toner image, and paper return. Image forming unit 2
Is controlled by the CPU 31.

Next, a control method of the double-sided printer according to an embodiment of the present invention will be described, which is an example of the timing of sheet feeding and image transfer in the image forming section of the double-sided printer of the above embodiment. . FIG. 4 is a schematic diagram showing the timing of sheet feeding and image transfer of the duplex printer of the above embodiment. In this control method, an image is transferred to the first surface of one sheet, and the image is transferred to the second surface of the preceding sheet until another image is transferred to the second surface of the same sheet. Transfer of an image to the first surface of one succeeding sheet. In such control, as shown in the figure, the order of image transfer is such that the image of the first page is transferred to the first surface of the first sheet, and then the image of the third page is transferred to the first surface of the second sheet. Then, the image of the second page is placed on the second surface of the first sheet, the image of the fifth page is placed on the first surface of the third sheet, and then the image of the fourth page,
Image on page 7, image on page 6, image on page 9, image 8
The transfer is performed in the order of the images on the page. Therefore, dot development to image data is also performed in this order.

The paper feed control is performed as follows. After the transfer to the first surface is completed, the first sheet sent to the sheet return path 30 is conveyed to the sheet standby section 32 in the sheet return path. This first sheet is detected from the sheet tray that the second sheet has been carried out, and then sent out from the sheet standby section 32 to the transfer section at a predetermined timing. The third sheet is carried out of the sheet tray at a predetermined timing after detecting that the first sheet has been sent from the sheet standby section 32 to the transfer section.

Further, it is detected that the third sheet has been carried out of the sheet tray 25, and thereafter, at a predetermined timing, the second sheet is sent out from the sheet standby section 32, and then the fourth sheet is It is carried out of the tray 25. At this time, the CPU 11 of the printer controller calculates the time required for dot development of the page data of the sixth page (the second surface of the third sheet). As a result, the required time is longer than the standard time. If it is longer by T, the result is sent to the CPU 31 of the image forming unit 2 and the timing of carrying out the fourth sheet from the sheet tray 32 is controlled so as to be delayed by the time T. At the same time, the carry-out of the third sheet from the sheet standby section 32 is controlled to be delayed by the time T. Therefore, the image is transferred to the first surface of the fourth sheet, and the third sheet is carried out of the sheet standby unit at a predetermined interval. It is transported without back collision on the return path. In addition, since the third sheet is carried out of the sheet standby unit with a delay of T time from the predetermined timing, when the third sheet is conveyed to the transfer unit, the data of the sixth page is developed into dots and can be supplied as image data. The formation of the toner image and the transfer of the sheet are performed immediately. Then, the first of the fifth sheet
The transfer is performed by the same control as the second surface of the fourth sheet.

[0027]

As described above, in the double-sided printer according to the first aspect, the printer controller calculates, for each sheet, the time required for developing the dot data of the page data to be transferred to the second side of the sheet. The image forming unit controls a timing at which an image is transferred to a sheet carried out from the sheet tray based on data of a time required for dot development output from the arithmetic unit. The time required for dot development of the page data to be transferred to the second side of the paper is calculated by the time when the subsequent paper is carried out of the paper tray, and is required for a predetermined standard time or more. If
Control can be performed so that the subsequent sheet is carried out of the sheet tray with a delay of the excess time. Therefore, without providing a plurality of paper standby sections in the paper return path, the paper can be transported so as not to collide or cause a paper jam, and a simple structure can smoothly transfer various page data. A two-sided printer capable of the above is obtained.

Further, in the control method of the double-sided printer according to the second aspect, before developing the dot data of the page data of the print text, the time required for the dot development of the page data to be transferred to the second surface of the sheet is calculated. When the calculated time is compared with the standard value and exceeds the standard value, control is performed such that the carry-out of the subsequent sheet of the sheet to which the page data is transferred from the paper tray is delayed for a time exceeding the standard value or more. Therefore, even if a plurality of sheet standby units are not provided in the sheet return path, sheets can be transported without colliding with the sheet return path or causing paper jam.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a double-sided printer according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a process of calculating a time required to develop page data into dots in the duplex printer shown in FIG. 1;

FIG. 3 is a flowchart showing another example of the process of calculating the time required to develop the page data into dots in the double-sided printer shown in FIG. 1;

FIG. 4 is a timing chart showing an example of the operation of the duplex printer shown in FIG. 1 and showing a control method of the duplex printer which is an embodiment of the invention according to claim 2;

FIG. 5 is a schematic configuration diagram showing a conventional duplex printer.

FIG. 6 is a timing chart showing a method of controlling sheet feeding and image transfer in a conventional duplex printer.

FIG. 7 is a timing chart showing a problem of the conventional duplex printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Image forming part 11 CPU 12 Hard disk 13 Page buffer 21 Photoconductor drum 22 Charger 23 Exposure device 24 Developing device 25 Paper tray 26 Paper feed device 27 Transfer device 29 Fixing device 30 Paper return path 31 CPU 32 Paper standby portion

Continuation of the front page (51) Int.Cl. ⁷ identification code FIG06F 3/12 B41J 3/00 S (58) Investigated field (Int.Cl. ⁷ , DB name) B41J 5/30 B41J 3/60 B41J 13 / 00 B41J 29/38 G03G 15/00 106 G06F 3/12

Claims (2)

(57) [Claims] An image forming section for forming an electrostatic latent image on a photosensitive member by an exposure device which is turned on based on a digital signal, and transferring and fixing an image visualized by toner adhesion onto a sheet; A printer controller for expanding the page data of the print text to be formed into image data and outputting the image data to the exposure device; and the print text on a first surface of a sheet carried out from a sheet tray provided in the image forming unit. Having a paper return path for returning a sheet to transfer another image to the second side of the sheet after transferring the image corresponding to the sheet, after transferring the image to the first side of the sheet, until performing image transfer to the second surface, the image of the transfer of the image of the second surface of the sheet preceding the said sheet, the first surface of the sheet following the the paper
And a printer controller , wherein the printer controller is capable of calculating, for each sheet, a time required for developing dot data of page data to be transferred to the second side of the sheet; Return path for temporarily returning the returned paper
A paper standby unit, wherein the image forming unit determines the timing at which an image is transferred to the first surface of the paper carried out of the paper tray, based on the time required for dot development output from the arithmetic unit; based controls and door
Timing of feeding the paper in the paper standby section
Is completed on the image to be transferred to the second surface of the sheet.
A double-sided printer comprising a control device for performing control in accordance with a time period . 2. The method for controlling a two-sided printer according to claim 1, further comprising the step of: detecting a sheet carried out from a sheet standby section provided in the sheet return path to a transfer section; A method of controlling a double-sided printer that unloads a sheet of paper and detects the sheet unloaded from the sheet tray, and then unloads the sheet in the sheet standby unit toward the transfer unit, develops the dot data of the page data of the print text. Before calculating the time required for dot development of page data to be transferred to the second surface of the sheet, comparing the calculated time with a preset standard value, and calculating the calculated time exceeds the standard value. A method of controlling a double-sided printer, wherein the carry-out of a sheet subsequent to the sheet on which the page data is transferred from the sheet tray is delayed for a time exceeding the standard value.