JP2001324839A - Double-side printing system for continuous paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a double-side printing system capable of printing on both sides of continuous paper by using two printers. SOLUTION: In the double-side printing system for continuous paper, a 1st counter 56a counts the feed amount of the continuous paper on a 1st printer side by setting a position where the continuous paper is loaded in the 1st printer 11 as reference, and a 2nd counter 56b counts the feed amount of the continuous paper on a 2nd printer side by setting a position where the continuous paper is loaded in the 2nd printer 12 as reference. After setting the continuous paper in the 1st and the 2nd printers, the printing control part 11a of the 1st printer informs the printing control part 12a of the 2nd printer of the counted value N of the 1st counter at the time of starting printing, so that printing on the 1st side is started, and the printing control part of the 2nd printer starts printing on the 2nd side when the counted value by the 2nd counter becomes equal to the counted value N of which the control part informs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous paper double-sided printing system, and more particularly to a continuous paper double-sided printing system for performing printing on both sides of a continuous paper by interlocking two printers. The present invention relates to a two-sided printing apparatus that performs two-sided printing on continuous paper by interlocking the two printing units.

[0002]

2. Description of the Related Art A printing apparatus that uses continuous paper as a printing medium feeds paper while hooking a tractor pin into holes provided on both sides of the continuous paper, so that paper jam does not occur during paper transport. There is an advantage that paper can be easily stored. If printing can be performed on both sides of such continuous paper, the paper can be effectively used, which is extremely useful. For this reason, a printing apparatus for printing on both sides of continuous paper has been conventionally proposed (for example, JP-A-56-99585).

FIG. 39 is a block diagram of the above-mentioned conventional double-sided printing apparatus, wherein 1 is a printing control unit, and 2 is a printing unit. In the print control unit 1, an interface unit 1 a receives print data (front side print data and back side print data) such as a character code to be printed on both sides of the continuous paper CF from a host device.
b is a developing unit for developing front side print data and back side print data into dot image print image data for each page, 1c is a changeover switch, and 1d and 1e are prints for one page to be printed on the front and back sides of continuous paper, respectively. First and second memories 1f and 1g for storing image data read out the print image data from the first and second memories and output the read image data to the first and second image forming units 3a and 3b of the printing unit 2. It is a reading unit.

In the printing unit 2, 3a and 3b are electrophotographic image forming units, 4 is a hopper for supplying continuous paper, 5 is a stacker for storing printed continuous paper CF while folding it,
Reference numerals 6a and 6b denote tractors, which are used to transport continuous paper in the illustrated path by hooking holes provided on both sides of continuous paper with pins on the outer periphery thereof, 7a and 7b are heat fixing rollers, and 8 is a paper feed roller. is there. Image forming portions 3a, in 3b, 3 ₁ denotes a photosensitive drum having a photoconductor (photosensitive member) to the surface, respectively rotate at a constant speed in the arrow A direction. Photosensitive drum 3 ₁ of radius in the image forming portion 3b is considerably larger structure than the radius of the photosensitive drum 3 ₁ of the image forming portion 3a. this is,
This is to enable the second image forming unit 3b to print on the back of the portion printed by the first image forming unit 3a. That is, when the continuous paper is fed after the printing by the first image forming unit 3a and the back surface of the printed portion reaches the printing position of the second image forming unit 3b, the photosensitive drum 3 of the second image forming unit 3b is _The diameter is determined so that the toner image generated in Step ₁ just reaches the printing position.

[0005] 3 ₂ charger before for uniformly charging the photosensitive drum surface, 3 ₃ is the electrostatic latent image forming unit that forms an electrostatic latent image on the photosensitive drum, the pin electrode drive circuit 3 ₃₁ and the pin Electrode 3
_{Has 32} . In addition, a large number of pin electrodes (corresponding to the paper width) are provided in the longitudinal direction of the photosensitive drum. 3 ₄ developing unit for developing the electrostatic latent image into a toner image, ₃₅ the continuous paper CF toner image
Transfer charger for transferring the 3 ₆ is a cleaner for removing and cleaning the toner remaining on the photosensitive drum, a transfer charger 3
The position of ₅ is the printing position. Electrifier 3 ₂ by applying a negative voltage at pin electrodes uniformly example positively charged photosensitive drum 3 ₁ surface when charge of that portion escapes. Therefore,
First on the basis of the image data of dot image, the pin electrodes 3 ₃₂ of the second image forming unit applies a negative voltage, and, according to the image to be printed on the photosensitive drum surface rotates the photosensitive drum 3 ₁ An electrostatic latent image is formed. Then, the developing unit 3 _4, when rubbed the toner positively charged on the photosensitive drum surface the toner - toner image is formed by moving onto the electrostatic latent image. Thereafter, the transfer charger ₃₅ in the continuous paper the toner image by performing a corona discharge from the back surface of the continuous paper CF at a potential of the charging potential of the toner image polarity reverse (negative) CF
Is transferred to Continuous forms CF having the toner image transferred by the transfer charger ₃₅ is a fixing roller 7a is conveyed, is thermally fixed by 7b.

The continuous paper CF is folded in the hopper 4.
Yes, continuous paper is produced by rotating the tractors 6a and 6b.
Move the CF from the hopper 4 in the direction of arrow B
It is stored while being folded in the stacker. First and second images
The print control unit 1 simultaneously sends the front and back sides to the forming units 3a and 3b.
Print image data is input to each photosensitive drum 3₁Same as
Sometimes an electrostatic latent image is formed. First and second image forming units 3
a, 3b photosensitive drum 3 ₁Have different radii, so first
Transfer charger 3 of the electrophotographic image forming unit 3a_FiveAt
Printing is performed on the back side of the continuous paper CF, and then the continuous paper is
The printed portion is sent to the transfer charger 3 of the second image forming portion 3b.
_FiveIs performed on the continuous paper CF surface at the timing of arrival
It is. Thereafter, printing is performed on both sides of the continuous paper CF in the same manner.
Is

[0007]

By the way, even if the conventional apparatus has a plurality of single-sided printing apparatuses, a new expensive double-sided printing apparatus must be purchased if two-sided printing is desired. There's a problem. Therefore, if a double-sided printing system can be constructed using two existing single-sided printing devices, it is convenient in terms of cost and space, and can be conveniently used as a single-sided printing device and a double-sided printing device.

As described above, a first object of the present invention is to provide a continuous paper duplex printing system capable of printing on both sides of continuous paper by interlocking two printers. Second embodiment of the present invention
SUMMARY OF THE INVENTION It is an object of the present invention to provide a double-sided printing system in which a second printer can accurately print on the back surface of a portion printed by a first printer. The third object of the present invention is to
An object of the present invention is to provide a double-sided printing system capable of performing double-sided printing and single-sided printing.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a first printer for printing on one side (first side) of continuous paper, and a first printer for printing on the continuous paper in a conveying direction. And a continuous paper double-sided printing system that prints on both sides of the continuous paper in conjunction with a second printer that prints on the other side (second side) of the continuous paper. A first counter for counting the amount of continuous paper fed on the first printer side based on the position where the continuous paper is loaded; and (2) a continuous counter on the second printer side based on the position where the continuous paper is loaded on the second printer. A second counter for counting the paper feed amount, and (3) a first and a second communicable each other.
This is achieved by a two-sided printing system including a print control unit of a printer.

[0010]

After the continuous paper is set in the first and second printers, the print controller of the first printer sends the count value N of the first counter at the start of printing on the first side to the print controller of the second printer. Then, the printing of the first side is started, and the printing control unit of the second printer starts printing of the second side when the count value of the second counter becomes equal to the notified count value N. In this case, until the count value of the second counter becomes equal to the notified count value N, the print control unit of the second printer sets an amount corresponding to the count n each time the count value of the first counter increases by n. While feeding the continuous paper, the count value of the second counter is increased by n. In this way, printing can be accurately performed on the front and back surfaces of continuous paper.

The higher-level device issues a double-sided printing designation command indicating that the subsequent data is double-sided printing data, or a double-sided printing canceling command indicating that double-sided printing is to be canceled and the subsequent data is single-sided printing data. (1) During double-sided printing, the printing control unit of the first printer notifies the printing control unit of the second printer of the count value N of the first counter when executing the double-sided printing designation command. Until the count value of the second counter increases by n until the count value of the second counter becomes equal to the notified count value N. While feeding the paper, the count value of the second counter is increased by n, and printing of the second side is started when the count value of the second counter becomes equal to N. (2) Printing of the second printer during single-sided printing The control unit counts the first counter The count value of the second counter n with but sends the amount continuous paper in accordance with the count n in every increase n
Perform increasing control. In this way, even a two-sided printing system can perform one-sided printing.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) Outline of duplex printing system FIGS. 1, 2 and 3 are schematic explanatory diagrams of a duplex printing system. In FIG. 1, reference numeral 11 denotes one surface of the continuous paper CF (first
A first printer that prints on the second side of the continuous paper, and a second printer that prints on the other side (second side) of the continuous paper.
Reference numeral 13 denotes a higher-level device that transfers print data to be printed on the first and second pages to the first and second printers. Reference numeral 15 is provided between the first and second page printers. An absorbing intermediate buffer device 16 is provided in the intermediate buffer device, and a detecting unit (e.g., a light emitting / receiving element) 11 that detects the amount of continuous paper CF retained in the intermediate buffer device.
a is the first value when the staying amount becomes equal to or more than the second set value L2.
A printer control unit for stopping paper feeding and printing by the page printer, a printer control unit for stopping printing and paper feeding by the second page printer when the staying amount becomes equal to or less than the first set value L1; 11b is a printing mechanism of the first printer, and 12b is a printing mechanism of the second printer.

In FIG. 2, 56a (first printer side)
Is a counter (PC _A ) for counting the continuous paper feed amount on the first printer side based on the position where the continuous paper is loaded on the first printer 11, and 56a (second printer side) is a second counter.
A counter (PC _B ) for counting the continuous paper feed amount on the second printer side based on the position where the continuous paper is loaded on the printer 12, and 29 is a sensor for detecting the continuous paper feed amount in the first and second printers. is there.

In FIG. 3, reference numeral 60 denotes a double-sided printing apparatus;
Is a higher-level device (host computer) that transfers print data to a duplex printer. In the duplex printing apparatus 60,
Reference numeral 61 denotes a first printing unit that prints on the first surface (front surface) of the continuous paper CF, 62 denotes a second printing unit that prints on the second surface (back surface) of the continuous paper, and 63 denotes a first printing unit that is received from a higher-level device. A print control unit that distributes print data to be printed on the first side and the second side to the first and second printing units; The first and second printing units 61 and 62 have exactly the same configuration, and an image forming unit (recording process unit) 61.
a, 62a, a process control unit 61 for controlling the image forming unit
b, 62b. The image forming units 61a and 62a
The toner images formed on the photosensitive drums 61a-1 and 62a-1 are transferred to the continuous paper C.
Printing is performed by transferring the image to F and fixing it. Each of the process control units 61b and 62b has a bitmap memory BMM that stores N pages of image data expanded into dot image data in page units.

(1) Operation of the two-sided printing system of FIG. 1 An intermediate buffer device 15 between the first printer 11 and the second printer 12 for absorbing the difference in paper feed speed between the two printers
The first printer performs printing on the first side of the continuous paper based on the front side print data input from the higher-level device 13, and the second printer based on the back side print data input from the higher-level device 13 Printing is performed on the second side of the continuous paper. The staying amount detection unit 16 detects the staying amount of the continuous paper CF in the intermediate buffer device 15, and the printer control unit 12a performs printing and paper feeding by the second printer when the staying amount falls below the first set value L1. At the same time, the printer control unit 11a stops paper feeding and printing by the first printer when the staying amount becomes equal to or more than the second set value L2. or,
The printer control unit 12a determines that the staying amount is a predetermined value (for example, L1
2) When it becomes equal to or more than the above, printing and paper feeding of the second printer are resumed, and when the staying amount becomes equal to or less than a predetermined value (for example, L2R), printing and paper feeding of the first printer are resumed.

According to the above, a two-sided printing system capable of printing on both sides of continuous paper using two continuous paper printers can be easily constructed, and the difference between the printing speed of the two printers, that is, the paper feed speed. , And an appropriate amount of paper slack can be always provided between the two printers, thereby eliminating paper jams, running out of paper, and the like. If a reversing mechanism for reversing the front and back of the sheet is provided between the first and second printers, the second printer 12 can easily print on the second side. Further, the continuous paper CF is transferred to the first and second printers 11 and 1.
Assuming that the number of pages between the printing positions of the first and second printers when set to 2 is N, the upper level device 13 adds N pages of blank data after all print data to be printed on the first side. The print data is sent to the first printer 11 and blank data for N pages is added before all the print data to be printed on the second side, and the print data is sent to the second printer 12. If you do this,
The second printer 12 can accurately print on the back surface of the portion printed by the first printer 11. Furthermore, the first and second
Printers 11 and 12 notify the other printer when the start switch is operated so that both printers can print simultaneously. Also, the first and second
When the stop switch is operated during printing, the printers 11 and 12 notify the other printer to that effect so that both printers stop printing at the same time. Further, when the first and second printers 11 and 12 are in a printing disabled state due to running out of toner or the like, the other printers are notified of the fact and the printing is disabled at the same time. In this way, printing can be performed simultaneously by the first and second printers,
Alternatively, printing can be stopped.

(2) Operation of the Duplex Printing System of FIG. 2 The counter 56a (PC _A ) of the first printer sets the first printer 11 based on the position where the continuous paper CF is loaded on the first printer 11.
The continuous paper feed amount on the printer side is counted, and the counter 56a (PC _B ) of the second printer counts the continuous paper feed amount on the second printer side based on the position where the continuous paper is loaded on the second printer 12. . At the start of printing on the first side, the printer controller 11a of the first printer
Notifies the count value N of the _A to the print control unit 12a of the second printer, the print control unit 12a of the second printer counter PC _B
When the counted value of the second side becomes equal to the notified counted value N, printing of the second side is started. In this case, until the count value of the counter PC _B becomes equal to the notified count value N, the printer control unit 12a of the second printer increases the count value of the counter PC _A by n each time the count value of the counter PC _A increases by n. , The continuous paper is fed, and the count value of the second counter is increased by n. In this way, printing can be accurately performed on the front and back surfaces of continuous paper. Further, when a two-sided printing release command is issued from the host device and a one-sided printing is instructed, the print control unit 12a of the second printer every time the count value of the counter PC _A notified from the first printer 11 increases by n. The continuous paper is fed by an amount corresponding to the count value n. In this way, even a two-sided printing system can perform one-sided printing.

Furthermore, the paper between the first and second printers 11 and 12 is slackened, and a virtual intermediate buffer device 15 'for absorbing the difference in the paper feed speed between the two printers is provided therein (actually, there is no such device). Introduced for explanation).
The difference count value [PC _B] of the count value of the counter PC _A [PC _A] a counter PC _B [PC _A] - second printer 12 when the [PC _B] is below the first set value N1 Stop printing and paper feed by. The difference is equal to a second set value N.
When it becomes two or more, paper feeding and printing by the first printer 11 are stopped. Then, the difference [PC _A ] − [P
C _B ] becomes equal to or less than the first set value N1, and the second printer 1
2 stops printing and paper feeding, the difference [PC _A ] −
When [PC _B ] becomes equal to or larger than the set value N1R larger than the first set value N1, the printing and paper feeding of the second printer 12 are restarted. Further, the difference [PC _A] - If [PC _B] stops the second set value N2 or more since the print and paper feed first printer 11, the difference _{[PC A] - [PC B} ] is When the value becomes equal to or smaller than the set value N2R smaller than the second set value N2, the printing and paper feeding of the first printer 11 are restarted. In this way, it is possible to absorb the difference between the printing speeds of the two printers, that is, the paper feeding speed, to always have an appropriate amount of paper slack between the two printers, and to eliminate paper jams and running out of paper. it can. Also, no special intermediate buffer device is required,
The amount of stay can be recognized based on the signal output from the detection sensor 29 used at the time of loading the existing paper, which is advantageous in terms of installation space and cost.

The printer controller 12 of the second printer
In the case of a, the difference between the count values [PC _A ]-[PC _B ] becomes equal to or less than the first set value N1 and printing and paper feeding are stopped. In this case, if the second printer is in the middle of printing, the first printer 1
1 sends a feed request. After receiving the command indicating the end of the print data, the printer control unit 11a of the first printer determines whether a predetermined time has elapsed without receiving the next print data, or a switch (first or second switch) for requesting printing to the end. The printer is provided on one or both of the two printers and communicates the on / off state of the switch).
When either of the conditions is satisfied, the continuous paper is sent. The first difference sheet feeding by a printer [PC _A] - if the [PC _B] is the third set value or more N1R second printer printing resumes paper feeding. In this way, the second printer can resume printing even when printing by the first printer is completed when printing by the second printer is stopped.
After the printing and paper feeding by the second printer 12 are resumed, the first printer 11 sends the continuous paper by an amount corresponding to the count value n each time the count value of the counter PC _B increases by n, and counts the count value of the counter PC _A. Increment the value by n. By doing so, the difference [PC _A ]-[PC _B ] between the count values is changed to the first set value N
It does not become 1 or less, and stop and restart of printing and paper feeding are not repeated.

The printer controller 11a of the first printer
Is the difference between the count values [PC _A ] − [PC _B ] is the second set value N
When the number becomes two or more, printing and paper feeding are stopped. In this case, when the first printer 11 is in the middle of printing, the second printer 1
2 sends a feed request. The printer control unit 12a of the second printer monitors whether a predetermined time has elapsed without receiving the next print data after receiving the command indicating the end of the print data, or whether a switch for requesting printing to the end has been operated. Then, when any of the above conditions is satisfied when the feed is requested, the continuous paper is fed. Difference in paper feed by the second printer [PC _A ]-
When [PC _B ] becomes equal to or less than the set value N2R, the first printer 11 resumes printing and paper feeding. If you do this,
Even when the printing by the second printer 12 is completed, the first printer 11 can resume printing.
After printing and paper feeding by the first printer 11 are resumed, the second printer 12 sends continuous paper by an amount corresponding to the count value n each time the count value of the counter PC _A increases by n, and counts up the counter PC _B each time. Increment the value by n. By doing so, the difference [PC _A ]-[PC _B ] between the count values is then changed to the second set value N
There is no more than two, and stop and restart of printing and paper feeding are not repeated.

Further, the first printer 11 is provided with mark printing means, and the second printer 12 is provided with mark detection means. Then, the mark printing means of the first printer prints the mark on the first side of the continuous paper, and the print control unit of the second printer starts printing on the second side of the continuous paper when the mark detection means detects the mark. I do. By doing so, it is possible to print correctly on the front and back surfaces of continuous paper with a simple configuration. (3) Operation of the duplex printing system in FIG. 3 The duplex printing system in FIGS. 1 and 2 performs two-side printing by cascade-connecting two printers. In FIG. 3, two printings are installed inside the duplex printing apparatus. Section and perform double-sided printing. The first printing unit 61 performs printing on the front side of the continuous paper CF based on the front side print data input from the print control unit 63. On the other hand, the second printing unit 62 develops the print data on the back surface into print image data of a dot image and sequentially stores the print data in the bitmap memory BMM. First and second printing units 6
N is the number of continuous paper pages existing between
When the first printing unit 61 completes the front side printing of page N, the printing control unit 63 instructs the second printing unit 62 to start back side printing. Accordingly, the second printing unit 62 reads the image data on the back side stored in the bitmap memory BMM and starts printing on the back side of the continuous paper. Thereafter, printing on the front and back sides is performed simultaneously. As described above, the bit map memory BMM for storing the image data for N pages is provided in the second printing unit, and the back side printing is started N pages later after the printing by the first printing unit 61 is started. Photosensitive drums 61a-1, 62a-1 of forming sections 61a, 62a
Even if the diameters of the continuous paper are the same, printing can be performed accurately on the front and back surfaces of the continuous paper without any positional deviation.

When instructing the first printing section 61 to start printing the first page on the front side, the printing control section 63 instructs the second printing section 62 to warm up. First printing unit 61
After the warm-up of the image forming unit 61a is performed, printing of the front page is sequentially started, and the second printing unit 62 warms up the image forming unit 62a and waits for a print instruction. The print control unit 63 instructs the second printing unit 62 to start back side printing when the first printing unit 61 completes the front side printing of page N. As a result, the second printing unit 62 immediately starts the bitmap memory BM without warming up.
The back side image data is read from M and printing is started on the back side of the continuous paper. As described above, since the second printing unit 62 warms up at the same time as the first printing unit, it is not necessary to warm up when there is a print instruction.
Printing can be performed immediately and printing efficiency can be improved.

If the page size (length from perforation) of the continuous paper is different, the number of pages of the continuous paper existing between the printing positions of the first and second printing units does not become an integer, and There are fractions like 2.3 pages. In such a case, the printing positions of the first and second printing units 61 and 62 on the continuous paper are not the same. In such a case, the control for accurately performing printing on the front and back surfaces of the continuous paper without displacement is complicated.
Therefore, even if the length per page of continuous paper changes, the first
A paper intermediate buffer including an adjusting unit that adjusts the number of continuous papers existing between the printing positions of the printing unit 61 and the second printing unit 62 so that the number of pages is exactly an integer number of pages is provided. In this way, it is possible to print accurately on the front and back surfaces of the continuous paper without any positional deviation by a simple control.

(B) First Embodiment (a) Overall Configuration of a Duplex Printing System FIG. 4 is an overall configuration diagram of a duplex printing system of a first embodiment. Reference numeral 11 denotes a first printer (page printer) that prints on the front surface of the continuous paper CF, and reference numeral 12 denotes a second printer that is provided behind the first printer in the transport direction of the continuous paper CF and prints on the back of the continuous paper CF. A printer (page printer) 13 is a higher-level device that transfers print data to be printed on the front and back sides to the first and second printers, respectively.
A reversing mechanism (turn bar) 15, which is disposed behind the page printer 11 and reverses the front and back of the sheet, is provided behind the turn bar, and includes first and second page printers 11, 1.
Reference numeral 16 denotes an intermediate buffer device that absorbs the printing speed difference (paper feeding speed difference). Reference numeral 16 denotes a retention amount detection unit that is provided in the intermediate buffer device and detects the retention amount (slack amount) of the continuous paper CF in the intermediate buffer device. For example, it is composed of a light emitting / receiving element.

(B) First Page Printer The first page printer 11 includes a printer control section 11a and a printing mechanism 11b as shown in FIG. In the printing mechanism 11b, 21 is an image forming unit, 22 is a hopper for supplying continuous paper, 23 and 24 are tractors for transporting continuous paper CF, 25 is a fixing unit, 26 is a stacker for single-sided printing, and 27 and 28 are paper. The feed roller 29 is a paper feed detection sensor. The image forming unit 21 is a continuous paper CF based on the principle of electrophotography.
A photosensitive drum 21a having a photoconductor (photoreceptor) on its surface, 21b a pre-charger for uniformly charging the photosensitive drum surface, and 21c irradiating an optical image on the photosensitive drum An exposure optical unit for forming an electrostatic latent image by developing the electrostatic latent image into a toner image;
21e is a transfer charger for transferring the toner image to the continuous paper CF,
Reference numeral 21f denotes a light eliminator for irradiating light to remove charged charges on the photosensitive drum. Reference numeral 21g denotes a cleaner for removing and cleaning toner remaining on the photosensitive drum, and includes a brush 21g-1 and a cleaning fleece 21g-2. I have. The position of the transfer charger 21e is the printing position.

When an optical image is applied to the surface of the photosensitive drum 21a uniformly charged by the pre-charger 21b, for example, the surface of the photosensitive drum 21a is exposed to light, the potential of the light-irradiated portion is reduced, and an electrostatic latent image is formed. Then, in the developing unit portion 21d, a predetermined development voltage V _B at the biased magnet roll when rubs the toner by rotating a (not shown) and positively charged surface of the photosensitive drum the toner - is on an electrostatic latent image It moves to form a toner image. Thereafter, if a corona discharge is generated in the transfer charger 21e from the back surface of the paper CF at a potential having a polarity (minus) opposite to that of the toner image, the paper is negatively charged, whereby the toner image is attracted to the paper CF. Is transcribed. The paper CF on which the toner image has been transferred by the transfer charger 21e is conveyed to the fixing unit 25, where it is thermally fixed, drawn out of the printer housing, and
Is conveyed in the direction of the page printer. When the page printer is used alone for single-sided printing, continuous paper is stored in the stacker 26 as shown by a dotted line.

After the toner image is transferred to the sheet, the photosensitive drum 21a further rotates, and the charge is removed by the light remover 21f.
The residual toner is removed by the cleaner 21g to prepare for the formation of the next electrostatic latent image. FIG. 6 shows an optical unit 21 for exposure.
21c-1 is a laser diode, 21c-2 is a collimator lens, 21c-3 is a laser beam on the photosensitive drum 21.
Reference numeral 21c-4 denotes an F-θ lens (imaging lens), and 21c-5 denotes a spindle motor that rotates the polygon mirror at a constant speed. On / off control of the laser diode 21c-1 is performed based on the print image data of the dot image to modulate the laser light on / off. The laser light on / off modulated by the print image data reaches the polygon mirror 21c-3 via the collimator lens 21c-2. Since the polygon mirror 21c-3 is rotated at a constant speed by the spindle motor 21c-5, the incident laser light is transmitted through the F-θ lens 21c-4 to the photosensitive drum 21c-3.
It is repeatedly moved in the longitudinal direction of a (in the direction of arrow C). Therefore, while rotating the photosensitive drum 21a in the direction of arrow A,
By scanning the laser beam on / off modulated by the print information in the longitudinal direction of the drum, an optical image of a dot image is irradiated, and an electrostatic latent image of the dot image is formed on the surface of the photosensitive drum.

(C) Sheet Reversing Mechanism FIG. 7 is a structural view of a reversing mechanism 14 for reversing the front and back of a sheet, 14a is a rotatable cylindrical turn bar, and 14b is a pair of supporting portions for rotatably supporting the turn bar. , 14c
Is a base member. Continuous forms CF fed from the first page printer 11 is wound with an inclination of approximately 45 ⁰ with respect to its axis in turn bar 14a, it is sent to the intermediate buffer device direction and upside down. (d) Intermediate Buffer Device FIG. 8 is a configuration diagram of the intermediate buffer device 15. The intermediate buffer device 15 includes first and second page printers 11 and 12
An appropriate amount of paper slack is provided between the two printers to absorb a printing speed difference (paper feeding speed difference) between the two printers.
a, first and second fixed rollers 15b provided at the entrance and exit of the continuous paper, a movable roller 15c that moves up and down in accordance with the slack amount (residence amount) L of the continuous paper, and the amount of paper retained in the intermediate buffer device Is provided. Retention amount detection unit 16 is four pairs of sensors (light emitting element LEE, the light receiving element LRE) 16a ₁ and ～16A _4, retention amount notification unit 16b for inputting the sensor outputs to the printer control unit of the first, second page printer It has.

The continuous paper CF is routed as shown in FIG. 8 (b).
c is lifted upward, and lowered when the amount of stay is large. Therefore, the amount of staying paper is reduced and the movable roller 15
When c is moved above the arrangement position of the first sensor 16a _1, the first light receiving element of the sensor 16a ₁ LRE detects the light from the light emitting element LEE, thereby, the amount of retention first set value L1 It is detected that: Further, when the movable roller 15c becomes much paper retention amount is moved downward from the arrangement position of the fourth sensor 16a _4, the light receiving element LRE of the fourth sensor 16a ₄ ceases to detect light from the light emitting element LEE, As a result, it is detected that the stay amount has become equal to or more than the second set value L2. Similarly, the second and third sensors 16a ₂ and 16a ₃ detect that the staying amount has become equal to or higher than the intermediate level L1R and equal to or lower than the intermediate level L2R.

(E) Second page printer FIG. 9 is a block diagram of the second page printer 12, and FIG.
Has the same configuration as the first page printer 11 shown in FIG. 1, 12a is a printer control unit, and 12b is a printing mechanism. The difference from the first page printer 11 is the continuous paper transport path. The continuous paper CF sent out from the intermediate buffer device 15 is guided to the paper transport path via the rollers 30, and is thereafter routed to the stacker 26 along the illustrated path. In the case of single-sided printing alone, continuous paper is supplied from the hopper 22 as shown by a dotted line.

(F) Configuration of Control System in Double-sided Printing System FIG. 10 is a configuration diagram of a control system in the double-sided printing system. Second printer to print to
Reference numeral 3 denotes a higher-level device that transfers print data to be printed on the first and second pages to the first and second page printers respectively. This is a staying amount detection unit that detects the staying amount of continuous paper in the apparatus. In the first and second page printers 11 and 12, reference numerals 11a and 12a denote printer control units for controlling the entire page printer, and 11b and 12b.
Is a printing mechanism.

The staying amount detector 16 includes sensors 16a ₁ to 16a ₁
6a ₄ (see FIG. 8) are output to the printer control unit 1 respectively.
Input to 1a and 12a. Printer control units 11a, 12
a monitors the amount of paper staying from the sensor output, and performs stop and restart control of printing, which will be described later, based on the amount of staying paper. The printer control unit 11a and the printer control unit 12a are configured to be able to communicate with each other.
A printer status signal is communicated to the other party, so that the first and second page printers can start printing simultaneously or stop printing at the same time. Printer control unit 11a,
Reference numeral 12a controls on / off control of various motors in the printing mechanisms 11b, 12b, on / off control of various chargers, control of printing image input, and the like.
The printer receives signals from various sensors provided in the printer and controls the printing mechanism based on the sensor signals.

(G) Printer Control Unit FIG. 11 is a block diagram of the printer control units 11a and 12a. Reference numeral 51 denotes an interface for exchanging data with a higher-level device;
First and second buffers 53 for alternately storing print data (character codes and the like) for pages; 53, an image generator for generating print image data of a dot image from the print data;
54b is a first and second bitmap memory (VRAM) for alternately storing one page of print image data output from the image generator 53, and 55 is one screen alternately from the first and second bitmap memories. The readout circuit reads the image data of each minute by the raster scan method and inputs the data to the optical unit 21c of the image forming unit 21 (FIGS. 5 and 9). Reference numeral 56 denotes a control unit for controlling the entire printer, and reference numeral 57 denotes a control signal (motor on / off signal, charging on / off signal, etc.) to the printing mechanism, and an I / I which receives various sensor signals and other signals from the printing mechanism. An O port 58 is an I / O port for taking in a sensor signal from the stagnant amount detector 16,
9 is a communication interface for performing data communication with the other printer control unit, and 60 is an operation panel.

On the operation panel, a start key STK for setting the page printer in a printable state (READY state), a stop key SPK for setting a page unprintable state (NOT READY state),
Eject key EJK to instruct paper ejection, printable /
It has a display lamp LMP for displaying an impossible state.
The press of the start key STK, the press of the stop key SPK, the press of the eject key EJK, and the READY / NOT READY state are notified to the other printer control unit via the communication interface 59 under the control of the control unit 56. . The interface 51 stores the print data of the i-th page transferred from the host device 13 in the first buffer 52a. The image generator 53 generates image data based on the print data and stores the image data in the first bitmap memory 54a.
The image is read from the image forming unit and input to the image forming unit 21 to generate an electrostatic latent image of the i-th page on the photosensitive drum.

In parallel with the generation of the print image by the image generation unit 53, the interface 51 transmits the (i +
1) The print data of the page is received and stored in the second buffer 52b. In addition, the image generation unit 53 performs the reading of the print image data from the first bitmap memory 54a in parallel with the second bitmap memory 54a.
The second bitmap memory 54 generates print image data based on the print data stored in the buffer 52b.
b. Thereafter, the readout circuit 55 sets the control unit 5
The print image data is read out from the second video map memory 54b under the control of No.
1) Generate an electrostatic latent image of a page on a photosensitive drum. Thereafter, the above operation is repeated alternately, and the first page printer 11 sequentially prints the first and second pages on the front surface of the continuous paper.
.. is printed and the first page on the back side is sequentially printed on the back side
The second page is printed.

(H) Print data from the host device Between the transfer chargers 21e of the first and second printers (between printing positions) when continuous paper is set in the paper transport path of the first and second printers 11 and 12. If the number of pages is N, the higher-level device 13 sends blank page data for N pages to the first printer 11 after all print data to be printed on the first side,
Blank data for N pages is added to the front of all print data to be printed on the second side and sent to the second printer 12. FIG.
= 3, first and second page printers 1
FIG. 3 is an explanatory diagram of print data Nos. 1 and 12; The number of pages N between the printing positions in the two-sided printing system is determined when the printing position of the paper is adjusted.
Reports the page number N to the host device 13 when the power is turned on or when the start key is pressed. Thereby, the host device 1
Numeral 3 recognizes the number N of blank pages and adds blank data for N pages to the print data. As described above, if the print data to which the blank data of N pages are added is input to the first and second page printers 11 and 12, and the first and second page printers 11 and 12 start printing at the same time, The second page printer 12 can accurately print on the back surface of the page portion printed by the first printer 11. For example, the first page printer 11 prints an odd-numbered page ((2n + 1) th page, n = 0, 1, 2,...) On the front side of continuous paper, and the second page printer 12 prints on the back side. Even pages (2nd (n + 1) th page) can be printed.

(I) Setting of Continuous Paper To set the continuous paper CF, the first page printer 11
The continuous paper is set in the paper transport path from the hopper 22, and a paper load key (not shown) is operated. As a result, the printer control unit 11a controls the paper transport system to count the continuous paper CF from the position of the transfer charger 21e and feed it out by M1 pages. Next, the continuous paper fed out of the housing of the first page printer 11 is set in the paper transport path of the second page printer 12 through the reversing mechanism 14 and the intermediate buffer device 15, and the paper load key of the second page printer is operated. I do. The printer control unit 12a controls the paper transport system to count the continuous paper CF from the position of the transfer charger 21e and to feed out M2 pages. As described above, continuous paper is set, and the number of pages between the transfer chargers 21e (between printing positions) in the first and second printers is (M1−M2) = N.

(J) Print control based on the amount of paper staying FIG. 13 is a processing flow based on the amount of paper staying in the first page printer 11, and FIG. 14 is a processing flow based on the amount of paper staying in the second page printer 11. (j-1) Control of paper staying amount of first page printer When printing is being performed by the first and second page printers 11 and 12, the controller 56 of the first page printer operates the sensor of the staying amount detector 16 With reference to the signal, it is monitored whether or not the sheet retention amount L in the intermediate buffer device 15 has exceeded L2. Position of the movable roller 15c is lowered when the sheet retention amount increases, the light receiving element LRE of the fourth sensor 16a ₄ does not detect the light becomes more than L2. Therefore, the control unit 5
6 monitors whether the paper retention amount is equal to or greater than L2 the sensor signal of the fourth sensor 16a ₄ (Step 10
1). If the paper staying amount L is not equal to or more than L2, printing is continued (step 102), and it is checked whether printing of all pages is completed (step 103). If completed, printing is ended. However, if printing of all pages has not been completed, the process returns to step 101.

On the other hand, if the amount of staying paper exceeds L2 in step 101, the page currently being printed is printed (step 104), and then printing and paper feeding are stopped (step 105). It should be noted that the paper staying amount L being equal to or larger than L2 means that the second page printer 12 has stopped printing for some reason. Thereafter, when the cause of the stop is removed and the printing by the second page printer 12 is restarted, the amount of accumulated paper is reduced. The control unit 56 monitors whether the amount L of retained paper has fallen below L2R. It raised the position of the movable roller 15c when the sheet retention amount decreases, the light receiving element LRE of the third sensor 16a ₃ is to detect light and becomes equal to or less than the L2R. Therefore, the control unit 56 the paper retention amount is monitored whether drops below L2R by the sensor signal of the third sensor 16a ₃ (step 106). When the amount of staying paper becomes equal to or less than L2R, the control unit 56 restarts the printing and paper feed control by the first page printer 11 (step 10).
7). As described above, the second page printer 1
If 2 stops printing, the first page printer 11 also stops printing. Further, when the cause of the stop is removed and the printing of the second page printer 12 is resumed, and the amount of staying paper becomes an appropriate amount, the printing of the first page printer 11 is resumed. As a result, simultaneous printing can be performed by the first and second page printers 11 and 12 while an appropriate amount of paper is retained in the intermediate buffer device 15.

(J-2) Control of paper staying amount of second page printer When printing is performed by the first and second page printers 11 and 12, the controller 56 of the second page printer 12
With reference to the sensor signal of the staying amount detecting unit 16, it is monitored whether the sheet staying amount in the intermediate buffer device 15 has become L1 or less. Position of the movable roller 15c is increased when the sheet retention amount decreases and becomes less than L1 first light receiving element LRE of the sensor 16a ₁ comes to detect light. Therefore, the control unit 56 monitors whether the paper retention amount becomes L1 below the first sensor signal of the sensor 16a ₁ (Step 2
01). If the paper staying amount is not less than L1, printing is continued (step 202), and it is checked whether printing of all pages is completed (step 203). If completed, printing is ended. However, if printing of all pages is not completed, the process returns to step 201.

On the other hand, if the amount of staying paper is less than L1 in step 201, the page currently being printed is printed (step 204), and then printing and paper feeding are stopped (step 205). It should be noted that the fact that the sheet retention amount L has become equal to or less than L1 means that the first page printer 11 has stopped printing for some reason. Thereafter, when the cause of the stop is eliminated and the printing by the first page printer 11 is restarted, the amount of retained paper increases. The control unit 56 monitors whether the amount of retained paper has reached L1R or more. Position is lowered movable rollers 15c when the sheet retention amount increases, the light receiving element LRE of the second sensor 16a ₂ does not detect the light becomes more than L1R. Therefore, the control unit 56 controls the second sensor 16
monitors whether the paper retention amount becomes L12 Thus the sensor signal of a ₂ (step 206). Paper staying amount is L1
When it becomes R or more, the control unit 56 restarts the printing and paper feed control by the second page printer 12 (step 207).

As described above, if the first page printer 11 stops printing for some reason, the second page printer 12
Also stop printing. Further, when the cause of the stop is removed and the printing of the first page printer 11 is resumed, and the amount of staying paper becomes an appropriate amount, the printing of the second page printer 12 is resumed.
As a result, simultaneous printing can be performed by the first and second page printers 11 and 12 while an appropriate amount of paper is retained in the intermediate buffer device 15.

(K) Printing start / stop control FIG. 15 shows printing start / stop in the first and second page printers.
It is a flowchart of a process of stop control. The control unit 56 monitors whether or not the start key STK of its own device is operated (start switch ON) (step 301). At the same time, the lamp LMP is turned on (step 302). On the other hand, if the own start switch is not on, it is monitored whether a start switch on signal has been received from the other party (step 303).
Similarly, the state is changed to the READY state, and the lamp LMP is turned on (step 304).

In this state, when print data is transferred from the host device, the first and second page printers 11 and 12
Starts printing based on the print data (step 3
05). If the printing has not been completed (step 306),
Whether the stop switch has been turned on or the stop switch has been received from the other page printer,
Alternatively, it is determined whether or not the printer itself is in a print impossible state (NOT READY state) due to a lack of toner, or has received a print impossible state signal (NOT READY state signal) from the other page printer (step 307). To 310), printing is continued if all are “NO”. Thereafter, if there is nothing, all pages are printed and the process is terminated (step 30).
6).

However, when the stop key SPK of the own device is operated and the stop switch is turned on, the stop switch ON signal is transmitted to the partner page printer, and both page printers 11 and 12 are simultaneously placed in the NOT READY state (printing state). Stop), and turns off the lamp LMP (step 31).
1). On the other hand, when the stop switch ON signal is received from the other party, the state is similarly set to the NOT READY state (printing stop), and the lamp LMP is turned off (step 313). or,
If there is no toner remaining in the machine or printing becomes impossible (NOT READY) due to other hardware failure,
The printing is stopped and a NOT READY signal is sent to the other party (step 312). Furthermore, NOT RE from the partner page printer
If the ADY signal is received, printing is stopped and the state is changed to the NOT READY state (step 314).

In this way, the first and second page printers can start printing at the same time and stop printing at the same time, eliminating the problem that occurs when only one of the printers prints. In the above description, the two-sided printer is used to construct the two-sided printing system. However, it goes without saying that the two-sided printing system can be constructed using a printer other than the page printer. Furthermore, the example of the duplex printing system using a separate page printer has been described, but it goes without saying that the duplex printing device may include two printing units and an intermediate buffer device in one housing.

(C) Second Embodiment (a) Overall Configuration of a Duplex Printing System FIG. 16 is an overall configuration diagram of a duplex printing system according to a second embodiment. The same reference numerals are given. 11 is a first printer (page printer), 12 is a second printer (page printer),
Reference numeral 13 denotes a host device, and reference numeral 14 denotes a reversing mechanism (turn bar) for reversing the front and back of a sheet. The second embodiment differs from the first embodiment in that the intermediate buffer device 15 is not provided.
In the second embodiment, a continuous paper feed amount detection sensor, which will be described later, and feed amount counters PC _A , P
Using C _B. The first and second printers 11 and 12 have the configuration shown in FIGS. 5 and 9 similarly to the first embodiment.
4 has the configuration shown in FIG. Note that the sheet reversing mechanism is not always necessary. This means that one printer is
80 ⁰ rotation, be arranged face-to-face surfaces of the sheet stack side of both printers together, because both sides of the paper can be reversed without reversing mechanism. In this way, the installation space can be reduced.

(B) Configuration of Control System in Double-sided Printing System FIG. 17 is a configuration diagram of a control system in the double-sided printing system. Reference numeral 11 denotes a first page printer for printing on the first side (front side) of continuous paper. Is a second printer that prints on the second side (back side) of the continuous paper, and 13 is a higher-level device that transfers print data to be printed on the first and second sides to the first and second page printers, respectively. First and second page printers 1
In 1 and 12, 11a and 12a are printer control units for controlling the entire page printer, and 11b and 12b are printing mechanisms. In the printing mechanisms 11b and 12b, a sensor 29 detects a continuous paper feed amount in each printer;
56a is a first, first on the basis of the position Rodengu the continuous paper to the second printer, the counter for counting the feed amount of the continuous paper in the second printer (PC _A, PC _B).

The printer control unit (print control unit) 11a and the printer control unit 12a can communicate with each other.
Various switches (start switch, stop switch,
A push signal of a ready switch, an all-page print instruction switch, a paper discharge switch, etc.), a printer status signal, and counter values of the counters PC _A and PC _B are communicated to the other party. The printer control units 11a and 12a are the printing mechanism 1
1b and 12b, on / off control of various motors, on / off control of various chargers, control of printing image input, etc., and also receives signals from various sensors provided in the printing mechanisms 11b and 12b, The printing mechanism is controlled based on the signal.

(C) Printer Control Unit FIG. 18 is a block diagram of the printer control units 11a and 12a, and the same parts as those in FIG. 11 are denoted by the same reference numerals. FIG.
8 is different from the configuration of FIG. 11 in that the control unit 56 is provided with PC _A and PC _B for counting the continuous paper feed amount (for example, in page units). A paper feed switch (feed switch) FEED, a ready switch RDY for putting the printer in a ready state, and an all-page print designation switch APP for instructing printing of all pages are provided. The point that the count value of the PC _A or the counter PC _B is communicated to the control unit 56 of another printer, and the point that the control unit 56 controls printing based on the count values of the counters PC _A and PC _B.

(D) Print data from the host device The print data for each print job (see FIG. 19A) is shown in FIG.
(b), as shown in FIG. 19 (c), are separated and input to the first and second printers 11, 12 (FIG. 17). SPH is separation data, which is printed at the beginning of the job in order to sort printed materials for each job, BSP is a double-sided print designation command for instructing double-sided printing, PDT is print data (user program data) for each page, SSP Is a double-sided print release command for instructing single-sided printing, and SPT is separation data to be printed at the end of a job in order to sort printed materials for each job. The first separation data is printed on the front side, the next print data is printed alternately on the front side and the back side, and the last separation data is printed on the front side. For example, even if the print data ends on the front side, the last separation data is generally printed on the front side. A two-sided printing designation command or a similar command is sent to start two-sided printing, and a two-sided printing release command or a similar command such as EOT (Endof Transmission) or Mark Form (End of
Job) is sent. The separation data may be omitted.

The interface 51 (FIG. 18) of the printer controller 11a in the first printer 11 is shown in FIG.
Is input, and is appropriately input to the first and second buffers 52a and 52b. The printer control unit 12a of the second printer 12 receives the print information shown in FIG. 19C and inputs the print information to the first and second buffers 52a and 52b as appropriate.

(E) Print Control FIGS. 20 and 21 show a first processing flow of the print control of the present invention. The continuous paper is set in the first printer 11, and the continuous paper is fed to a default print position (preset print position) by operating a paper loading switch (not shown) (paper loading, step 401). . The sheet loading is an operation of feeding a sheet in advance for the purpose of adjusting the printing position of the sheet as desired. Next, the page counter 56a of the first printer 11 (hereinafter, PC _A
Is set to the initial value (1 page) (1 → [PC _A ], step 402). After initializing the page counter PC _A , turn the paper feed knob (fine adjustment) to change the print position of the paper to another location, or
Press the feed switch FEED to feed the continuous paper, and adjust the paper to the position where printing is desired (step 40).
3). A mark is engraved on the side of the tractor on the printer, and printing is performed at a desired position by adjusting the position where printing is to be started.

If the feed amount exceeds one page length in the sheet feed by the feed switch FEED, the page counter PC _A counts up by one each time the page advances.
Even if 1.1 or 1.2 pages are fed by feed switch operation, fractions 0.1 and 0.2 are discarded and 1
Only pages are added to the page counter PC _A. When the paper setting operation is completed, the first printer 11
The ready switch RDY is pressed to inform the host device (host computer or the like) 13 that the device has come online. As a result, the host device 13 sends the printer control units 11a and 12a of the first printer 11 and the second printer 12 as shown in FIG.
The print information (assuming that there is no separation data) shown in 9 (a) is transmitted. The printer control unit 11a of the first printer 11 executes the duplex printing designation command transmitted first from the host device, and sends the count value of the page counter PC _A (= N) to the printer control unit 12a of the second printer 12 at that time. Is notified (step 404). The second printer 12 recognizes the print start page from the count value N.

Next, the interface 5 of the first printer
1 receives the print data (FIG. 19B) from the host device 13, develops the print data of each page into dot image image data, and prints it on the surface of continuous paper (step 40).
5). The printer control unit 11a of the first printer 11 counts the value of the counter PC _A [PC _A ] in response to the continuous paper feed.
And notifies the second printer 12 of the count value [PC _A ] (step 406). Next, it is checked whether the continuous paper has been printed in an appropriate amount for loading on the first printer 12, and if "NO", the flow returns to step 405 to repeat the subsequent processing. However, after printing the appropriate amount of continuous paper on the second printer 12, the stop switch SPK of the first printer 11 is operated to put the first printer 11 offline and stop printing (step 40).
8). The determination of the appropriate amount for loading the continuous paper into the second printer 12 is based on the number of continuous papers to be output from the external discharge unit of the first printer 11 when two printers are installed. And make a judgment by comparing with the amount. This amount is not required to be strict, for example, when the paper output from the external discharge unit of the first printer 11 is folded at the floor 5 to 8 times, so that the operation is easy. Therefore, even if the printing is performed manually by the operator, there is no problem in the normal printing operation. Of course, the first printer 11
It is also possible to configure so that when the output is performed within the set amount, the printer automatically goes offline and stops printing.

Next, the continuous paper is loaded to the printing position of the second printer 12 (step 409), and the count value of the counter 56a (PC _B ) of the second printer 12 is set to the initial value (1).
(1 → [PC _B ], step 41)
0). Turn the paper feed knob if necessary, finely adjusted in a range that does not affect the count value of the page counter PC _B of the printing position (step 411). When the fine adjustment is completed as described above, the ready switches RDY of the first printer 11 and the second printer 12 are operated, and the host device 13 is notified that both printers 11 and 12 are online. Thereby, the first and second printers 11 and 12 are connected to the host device 1.
The print data is received from No. 3 (step 412). still,
When one of the ready switches RDY of the first and second printers is operated, both of the printers 11 and 12 can be made online. The first printer 11 resumes printing of odd-numbered pages based on the received data, increments the count value [PC _A ] of the counter PC _A according to paper feed, and sends the [PC _A ] to the second printer 12. Notification is made (step 413).

The print controller 12a of the second printer 12 checks whether the count value [PC _B ] of the counter PC _B is equal to N (the page on which the first printer started printing) (step 414). If they are not equal, the second printer 12 executes the paper feeding operation in the “sheet front-back mode” until the count value [PC _B ] of the counter PC _B becomes N. The “sheet front-to-back mode” means that each time the count value of the counter PC _A of the first printer 11 increases by n (an integer of 1 or more, for example, one page), an amount corresponding to the count value n or the counter PC
The amount of the count value of _B [PC _B] up when more than N exceeds N, and sends a continuous sheet, which is the count value of the counter PC _B a mode for increasing n (step 415). Then
It is checked whether the print job of the first printer 11 has been completed (step 416).
The subsequent operation is repeated. The printing by the first printer proceeds, and the counter PC is set in the "sheet front-back mode".
If equal count value to N of _B, the print control unit 12a of the second printer 12 is incremented the count value of the counter PC _B with printing the print data based on the received data on the back side (step 417). Next, it is checked whether or not the print job of the first printer 11 has been completed (step 416), and if not completed, the operation from step 412 onward is repeated.
If the print job of the first printer 11 has been completed, the first
The printer executes an operation according to the processing mode after the completion of the print job described later (step 417). Next, it is checked whether the print job of the second printer 12 has been completed (step 418), and if not completed, the processing of step 412 and thereafter is repeated. As described above, even pages can be correctly printed on the back of odd pages.

(F) Another print control FIG. 22 is a second processing flow of the print control of the present invention.
According to the first print control, printing can be started from the place where the continuous paper is loaded in the first printer 11, and the waste of the continuous paper is eliminated, which is effective. However, when the continuous paper can be loaded on the second printer 12, printing by the first printer must be stopped and the continuous paper must be set on the second printer 12. For this reason, there is a problem that the operator cannot leave the printer position until the continuous paper is loaded on the second printer, and the operation is troublesome because the operation is performed twice. In the second print control, continuous paper is loaded and printed on the first and second printers at a time. The continuous paper is set in the first printer 11, and the paper loading switch is operated to feed the continuous paper to the print start position (paper loading, step 501). Then, the counter P of the first printer 11
The count value [PC _A ] of C _A is set to an initial value (= 1 page) (1 → [PC _A ], step 502). After initializing the page counter PC _A , the feed switch FEED of the first printer 11 is pressed to feed the continuous paper for several pages so as to be loaded into the second printer 12, and the count value of the counter PC _A [PC _A ] is advanced in page units according to the feed amount (step 503).

[0059] Then, Rodengu continuous paper to the printing position of the second printer 12 (step 504), the count value [PC _B] the initial value of the counter PC _B of the second printer 12 (= 1
Page) (1 → [PC _B ], step 50)
5). Thereafter, the first printer 11 and the second printer 1
By operating the ready switch RDY No. 2 to notify the host device 13 that both printers 11 and 12 are online, the first and second printers 11 and 12 receive print data from the host device 13 ( Step 50
6). The first printer 11 resumes printing of the odd-numbered pages based on the received data, increments the count value [PC _A ] of the counter PC _A according to the paper feed, and changes the [PC _A ] to the second value.
The printer 12 is notified (step 507).

The printer controller 12a of the second printer 12
Checks whether the count value [PC _B ] of the counter PC _B is equal to N (the page on which the first printer started printing) (step 508). If not equal, the second printer 12 is the count value of the counter PC _B is until N, executes the paper feed operation by "sheet sides registration mode". That is,
Every time the count value of the counter PC _A of the first printer 11 increases by n (for example, one page), the second printer 12
Or the count value of the counter PC _B [PC _B ]
If is greater than the N amounts of up to more than N, and sends a continuous sheet, the count value of the counter PC _B increases n (step 509). Next, it is checked whether the print job of the first printer 11 has been completed (step 510), and if not completed, the operation from step 506 onward is repeated.

[0061] Printing proceeds of the first printer 11, and, if equal the count value of the counter PC _B is in N by "sheet sides adjusting mode", the print control unit of the second printer 12 12
a is incremented the count value of the counter PC _B while printing the print data of the second page on the back side (step 511). Next, it is checked whether the print job has been completed (step 51).
0), if not finished, repeat the operation from step 506. If the print job of the first printer 11 has been completed, the first printer executes an operation according to a processing mode after the completion of the print job described later (step 512). Next, it is checked whether or not the print job of the second printer 12 has been completed (step 513).
The processing after 06 is repeated. In this way, double-sided printing can be executed by one loading operation and without stopping printing of the first printer. In addition, even pages can be correctly printed on the back of odd pages.

(G) Double-sided, single-sided printing control Not all pages are printed on both sides. Some pages print only the front side, and some pages print only the back side. If such a page is one to several pages, the data on the opposite side from the host may be used as a skip page command and sent to a blank page. However, when the number of pages reaches several tens or hundreds, it is advantageous to cancel the double-sided printing designation and set the single-sided printing designation, and not send the print data to the other printer, because the data from the host can be reduced. In general, it is rare to print a large amount only on the back surface, and in most cases, print only a large amount on the front surface. Therefore, in the present invention, a duplex printing designation command and a duplex printing cancel command are provided as commands sent from the host. In the case of a double-sided print job, the print data is sent to the first and second printers with a double-sided print designation command and a double-sided print release command interposed therebetween (see FIG. 19). On the other hand, in the case of single-sided printing, a double-sided printing cancel command is issued first,
The sheet is sent to the second printer to be in the front side printing state.

FIG. 23 is a flowchart showing the operation of single-sided and double-sided printing control. Each of the first and second printers 11 and 12 checks that a double-sided printing designation command has been instructed by the host device 13 (step 601), and if "YES", performs the double-sided printing control described in FIG. 22 (step 601). 602). In brief, the printer control unit 11a of the first printer 11 calculates the count value N of the counter PC _A when executing the duplex printing designation command.
To the printer control unit 12a of the second printer 12,
Thereafter, printing of odd pages is performed. Until the count value of the counter PC _B becomes equal to the notified count value N, the printer control unit 12a of the second printer 12 sets an amount corresponding to the count n every time the count value of the counter PC _A increases by n. Send paper and counter PC _B
Is increased by n. Then, the count value of the counter PC _B to start printing the even page to the second surface when it becomes equal to N.

On the other hand, when the double-sided printing cancel command is instructed (step 603), the first and second printers 1
1 and 12 are in a single-sided printing state. At the time of such single-sided printing, the first printer 11 prints the input print data of all pages on the front side and also sets a counter P in page units in accordance with the paper feed amount.
The count value of C _A is incremented. Further, the second printer 12 is set to the "sheet front-back mode", and performs an operation according to the mode. That is, the counter PC of the first printer 11
The amount the count of _A corresponding to the regimen value n in every increase n, and sends a continuous sheet, the count value of the counter PC _B increases n (step 604). The second printer 12 performs this operation until the one-side printing by the first printer is completed (steps 605 and 604).

(H) Printing control based on the amount of paper staying In double-sided printing, the first printer and the second printers 11 and 12 respectively have their own counters PC _A and PC _B count values [P
C _A ] and [PC _B ] are notified to the other printer. The counter PC _A counts up the feed amount of the continuous paper of the first printer 11 in page units, and the counter PC _B counts up the feed amount of the continuous paper of the second printer 12 in page units. At the initial stage, there are N pages of continuous paper between them. However, due to the difference in printing speed between the two printers, the amount of continuous paper existing between the two printers changes and becomes too small or too large. The amount of the paper web existing between the two printers, counter PC _A, the count value of the PC _B [PC _A], the difference between the _{[PC B] ([PC A} ] - [P
C _B ]). Therefore, the difference corresponding to the level L1 in FIG. 1 is N1, the difference corresponding to the level L2 is N2, the difference corresponding to the level L1R is N1R, and the level L2.
If the difference corresponding to R is N2R, [PC _A ]-[P
C _B] and N1, N2, N1R, it is possible to perform printing control based on the same sheet holdup in the first embodiment based on the magnitude of the N2R.

(H-1) Printing when the amount of staying paper is low
Control FIGS. 24 and 25 show the first and second modes when the amount of retained paper is reduced.
7 is a processing flow of print control of a second printer. 2nd pre
The printing speed of the printer 12 is lower than the printing speed of the first printer.
If it is early, the amount of paper staying between the first and second printers
The counter PC decreases in proportion to this _A, PC_BCount value
[PC_A], [PC_B] Decreases. Therefore, the second
The control unit 56 of the linter 12 determines the difference [PC_A]-[PC_B]But
It is monitored whether it has become equal to or less than the first set value N1 (step 7).
01). If the difference is not less than N1, printing is continued (step
702) Next, check whether printing of all pages is completed.
Check (step 703), and if completed, end printing
I do. However, if all pages have not been printed,
Return to step 701.

On the other hand, in step 701, the difference is N1
In the following cases, the controller 56 of the second printer 12 prints the page currently being printed (step 704), and then stops printing and paper feeding (step 705). Control unit 56
Sends a feed request to the control unit 56 of the first printer 11 if the printing is in the middle of the back side printing (step 706). Since then
The difference [PC _A] - waits until [PC _B] is more than the third set value N1R (step 707). And the first
The continuous paper is fed out by the printer 11 and [PC _A ] −
If [PC _B ]> N1R, the control unit 56 resumes the printing and paper feed control by the second printer 12 (step 70).
8), cancel the feed request (step 709). Thereafter, printing is continued by returning to the beginning.

On the other hand, the control unit 56 of the first printer 11 monitors whether there is a feed request from the second printer 11 (step 711), and if there is no feed request, continues printing (step 712). On the other hand, [PC _A ]-[P
C _B ] <N1, and when a feed request is issued from the second printer, it is checked whether a command corresponding to the end of the print job has been received (step 713). All page print switch A
Check that PP has been turned on (step 714).
If it is not turned on, printing is continued (step 71).
5) Then, it is checked whether the feed release request has been output from the second printer (step 716). If the request has been output, the process returns to the beginning and repeats the subsequent processing. The fact that the feed release request is output from the second printer 12 means that [PC _A ] − [PC _B ]> N1R naturally due to the feeding of the continuous paper accompanying the printing by the first printer 11 or This means that the second printer 12 has completed printing all the print jobs.

On the other hand, if a command corresponding to the end of the print job is received in step 713, the continuous paper is not fed out by the first printer 11 unless the next print data is received thereafter. In such cases,
[PC _A ]-[PC _B ]> N1R is not reached forever, and the back side printing by the second printer 12 is not completed. Therefore, when a print job end command or the like is received, the processing mode changes to a processing mode after the print job is completed. In the processing mode after the completion of the print job, the counting of the elapsed time after reception is started (step 717), and it is monitored whether the next print data has been received (step 718). It is checked whether or not the time has exceeded the set time Ts (step 719).

If T <Ts, the flow returns to step 717 to repeat the subsequent processing. If the next print data is received before T ≧ Ts, the continuous paper is fed out in the printing operation of the first printer 11 and [PC _A ] − [PC _B ]> N1R. Is repeated. On the other hand, in step 719, without receiving the next print data, T ≧ T
If s, the control unit 56 determines that [PC _A ]-[PC _B ]> N1
Continuous paper is automatically fed until the number reaches 2. Thus, the second printer 12 starts printing (step 72).
0). Thereafter, the process returns to the beginning and executes the subsequent processes. Also, if the all-page print switch APP is turned on in step 714, the operation of step 720 is executed.
Go back to the beginning.

By the way, in the operation of only step 720, after several pages have been printed, [PC _A ] −
[PC _B ] <N1, printing stops, the above operation is repeated, and high-speed printing cannot be performed. Therefore, step 72
1 is provided. That is, by the paper feed of the first printer 11,
[PC _A ]-[PC _B ]> N1R and the second printer 1
When the printer 2 resumes printing, the second printer 12 periodically notifies the first printer 11 of the count value of the count PC _B. The first printer 11 increments the count value [PC _B ] by one each time it advances by one step.
The paper is fed by the number of pages, and the count value of the counter PC _A is incremented by one. Thereafter, this operation is performed until the second printer completes printing (step 721). If you do this,
After resuming printing, printing can be performed to the end without stopping. In step 720, the first printer 11 sets [P
When the continuous paper is fed until C _A ]-[PC _B ]> N1R, the second printer 12 needs to skip printing the back side of the fed portion. Therefore, step 72
At 0, the control unit 56 of the first printer 11 stores the count value before and after the counter PC _A to feed the continuous paper, and notifies them counts the second printer 12, skip back side printing of the moiety To do it.

(H-2) Printing control when the amount of retained paper increases
FIGS. 26 and 27 show the first and second charts when the amount of retained paper increases.
5 is a processing flow of print control of two printers. 1st pudding
The printing speed of the second printer 12
Is too fast, the amount of paper staying in the intermediate buffer 15 increases.
And the counter PC _A, PC_BCount value
[PC_A], [PC_B] Increases. Therefore, the first
The controller 56 of the linter 11 determines the difference [PC_A]-[PC_B]But
It is monitored whether or not the second set value N2 has been exceeded (step 8).
01). If the difference is not greater than N2, printing is continued (step
802) Next, check whether printing of all pages is completed.
Check (step 803), and if completed, end printing
I do. However, if all pages have not been printed,
Return to step 801.

On the other hand, at step 801, the difference is N2
Then, the control unit 56 of the first printer 11 prints the page currently being printed (step 804), and then stops printing and paper feeding (step 805). Control unit 56
Sends a feed request to the control unit 56 of the second printer 11 if printing is being performed on the front side (step 806). Since then
The difference continuous paper is fed by the second printer 12 [PC _A] - waits until [PC _B] is less than the fourth set value N2R (step 807). And [PC _A ]
If [PC _B ] <N2R, the control unit 56 resumes the printing and paper feed control by the first printer 11 (step 8).
08), and cancels the feed request (step 809).
Thereafter, printing is continued by returning to the beginning.

On the other hand, the control section 56 of the second printer 12 monitors whether there is a feed request from the first printer 11 (step 811), and if there is no feed request, continues printing (step 812). On the other hand, [PC _A ]-[P
When C _B ]> N 2 and a feed request is issued from the first printer, printing of the unexecuted data is executed (steps 813, 812, 811). It is checked whether a corresponding command has been received (step 814). If not, it is checked that the all-page print switch APP of the first printer 11 or the second printer 12 has been turned on (step 815). If it is not turned on, counting of the elapsed time is started (step 816), and it is monitored whether the next print data is received (step 81).
7) If it has not been received, it is checked whether the elapsed time T has exceeded the set time Ts (step 818).

If T <Ts, the flow returns to step 816 to repeat the subsequent processing. If the next print data is received before T ≧ Ts, printing is continued (step 81).
2) Then, the process returns to step 811 to repeat the subsequent processing. On the other hand, if there is data that has not been processed in step 813, printing is continued (step 812).
Returning to step 811, the subsequent processing is repeated. In step 814, if a double-sided print release command or a command corresponding to the end of the print job has been received, or
If T ≧ Ts in step 818, the control unit 56 sets [P
Continuous paper is automatically fed until C _A ]-[PC _B ] <N2R. Thus, the first printer 11 starts printing (steps 819 and 812). Thereafter, printing is continued, and then the process returns to the beginning and repeats the processing in step 811 and thereafter. Also, if the all-page print switch APP is turned on in step 815, the operation of step 819 is executed, then printing is continued, and then the process returns to the beginning and repeats the processing from step 811.

By the way, in the operation of only step 819, after several pages have been printed, [PC _A ] −
[PC _B ]> N2, printing stops, the above operation is repeated, and high-speed printing cannot be performed. Therefore, step 82
0,821. That is, in the paper feed of the second printer 12, [PC _A] - When the first printer 11 becomes [PC _B] <N2R resumes printing, the first printer 11 is periodically notified to the second printer 12 Each time the count value [PC _A ] of the counter PC _A advances by one, paper is fed by one page, and the count value of the counter PC _B is incremented by one. Thereafter, this operation is executed until the second printer receives the print data (steps 820 and 821). The above operation is executed until the first printer completes printing, and after printing is resumed, printing can be performed to the end without stopping.

(I) Printing Control Using Marks The above is a case where printing start control is performed using the count values of the two counters PC _A and PC _B.
Thus, the mark may be printed so that the first page can be identified, and the mark may be detected by the second printer and printed on the back side. This may cause a situation in which the sheet is torn before loading the sheet to the second printer 12, and it may be necessary to cut out a few sheets of the sheet before loading. Even in such a case, it is possible to correctly print the front and back sides. Mark printing is performed as follows. The control unit 56 of the first printer 11 controls the image generating unit 53 based on the double-sided print designation command input from the higher-level device 13 to generate a mark image, and converts the mark image to the first page (front page) of the front surface. The image is superimposed on the image and stored in the first bitmap memory 54a. Thereafter, the image is read out from the bitmap memory 54a and mark printing is performed. The mark detector 31 (see FIG. 9) has a structure for irradiating light to the continuous paper and detecting a mark from the reflected light, and is arranged on the paper transport path. When the image is formed on the photosensitive drum 21a after the detection of the mark, the mark detector 31 is disposed at a position where the toner image can be correctly transferred to the back surface of the first page at the transfer position.

The mark may be an OMR mark, a bar code, a numeral, a symbol, or the like. If a simple OMR mark or a simple symbol such as a solid black square is used as the mark, the configuration of the mark detector can be simplified. If a bar code or OCR numeral is used as a mark, erroneous detection can be prevented. The mark is recorded outside the user print area. For example, printing is performed at positions indicated by oblique lines in FIGS. 28 (a), (b), and (c). FIG. 28 (a) shows an example of a mark recording area when two cut sheets of letter size (11 ″ × 8.5 ″) are cut out from continuous paper of the illustrated size. ER is the mark recording area. FIG.
(b) and (c) are examples of mark recording areas when two A4 size (297 mm × 210 mm) cut sheets are cut out from continuous paper of the illustrated size.

The mark is generally recorded on the first page. However, if the printing of the back side is started after detecting the mark recorded on the first page, printing on the back side cannot be performed properly due to the physical dimensions, arrangement and structure of the recording unit. There are cases. In such a case, the mark is recorded on the page one before the head image. FIG. 29 and FIG. 30 are processing flows of print control using marks. The continuous paper is set in the first printer 11, and the paper loading switch is operated to feed the continuous paper to the printing start position (paper loading, step 901). Next, the counter PC of the first printer 11
The count value [PC _A] of _A is set to an initial value (= 1 _{page) (1 → [PC A]} , step 902). After the page counter PC _A is initialized, the feed switch FEED of the first printer 11 is pressed to feed the continuous paper for several pages, and the count value [PC _A ] of the counter PC _A is incremented in page units according to the feed amount. (Step 903).

[0080] Then, Rodengu continuous paper to the printing position of the second printer 12 (step 904), the count value [PC _B] the initial value of the counter PC _B of the second printer 12 (= 1
Page (1 → [PC _B ], step 90)
5). Thereafter, the first printer 11 and the second printer 1
By operating the ready switch RDY No. 2 to notify the host device 13 that both printers 11 and 12 are online. As a result, the first and second printers 11 and 12 receive the double-sided print designation command from the host device 13 (Step 906). Upon receiving the duplex printing designation command, the first printer 11 prints a mark on the first page,
The count value [PC _A ] (= N) of the counter PC _A is notified to the second printer 12. The second printer 12 starts the mark detection operation in response to receiving the double-sided print designation command (Step 907). Thereafter, the first printer 11 starts printing odd-numbered pages based on the received data, increments the count value [PC _A ] of the counter PC _A according to the paper feed, and transfers the [PC _A ] to the second printer. 12 (step 9
08).

The print controller 12a of the second printer 12 checks whether the mark recorded on the first page has been detected (step 909a), and if not, checks whether the mark has been detected (step 909b). If no mark is detected, the second printer 12 executes an operation according to the “sheet front-back mode”. That is, the count value of the counter PC _A of the first printer 11 is n (for example, 1
The amount corresponding to the regimen numeric n (= 1) each time the page) increases, and sends a continuous sheet, the count value of the counter PC _B increases n (step 910). Next, it is checked whether the print job has been completed (step 911). If the print job has not been completed, the print data is received and printing is continued (steps 912 and 9).
08).

When printing by the first printer 11 proceeds and the mark detector 31 of the second printer 12 detects a mark, the printer controller 12a of the second printer 12
_It is checked whether the count value [PC _B ] of _B is equal to N (step 913). If they are not equal, N → [PC _B ] is corrected (step 914). Then, the second printer 1
The second printing control unit 12a for stepping the count value of the counter PC _B while printing the print data of the second page on the back surface of the continuous sheet (step 915). Thereafter, it is checked whether the print job has been completed (step 911). If the print job has not been completed, the operations after step 912 are repeated. After that, since the mark has been detected, the processing of step 908 → step 909 a → step 915 → step 911 → step 912 is repeated until double-sided printing is completed. In this way, the start of printing by the second printer can be controlled by the mark, and double-sided printing can be executed by a single loading operation without stopping printing by the first printer 11.

The printer controller 12a of the second printer 12
As described above, until the mark is detected when duplex printing is instructed by the duplex printing designation command, the first printer 1
Each time the count value of the counter PC _A increases by n (generally n = 1), the continuous paper is fed by an amount corresponding to the count value n, and the count value of the counter PC _B is increased by n (step 9).
10). Then, at the time of double-sided printing, printing of the second side is started when a mark is detected (step 915). When one-sided printing is instructed by the two-sided printing release command, the second printer 12 sends continuous paper by an amount corresponding to the count value n each time the count value of the counter PC _A of the first printer 11 increases by n. with the count value of the counter PC _B increases n.
This operation is performed until the one-sided printing is completed.
After the mark is detected, the second printer 12 operates the counter PC.
The count value of the _A count value of [PC _A] a counter PC _B [PC _B]
With the difference between the stops printing and paper feeding when it becomes below the first set value N1, the difference _{[PC A] - [PC B} ] becomes the third set value or more N1R greater than the first set value N1 When printing and paper feeding resume. On the other hand, the first printer 11 stops paper feeding and printing when the difference is equal to or larger than the second set value N2, and the difference is smaller than the second set value N2R.
When the following occurs, printing and paper feeding are restarted.

In the above description, the feed amounts of the counters PC _A and PC _B are counted in page units (from perforations to perforations). However, the feed amounts are measured in arbitrary units such as feet, inches, or 1/6 inch. Can be counted.

(D) Third Embodiment (a) Overall Configuration FIG. 31 is a configuration diagram of a duplex printing apparatus according to a third embodiment. The two-sided printing system in the first and second embodiments performs two-sided printing by cascading two printers. In the third embodiment, two-sided printing is provided inside the two-sided printing apparatus to perform two-sided printing. Do. Reference numeral 60 denotes a double-sided printing apparatus, and reference numeral 70 denotes a higher-level device (host computer) that transfers print data to the double-sided printing apparatus. In the double-sided printing apparatus 60, reference numeral 61 denotes a first printing unit for printing on the first side (front side) of the continuous paper CF;
Reference numeral 62 denotes a second printing unit that prints on the second surface (back surface) of the continuous paper, and 63 denotes a first and second printing unit that prints the print data to be printed on the first and second surfaces received from the host device for each page. A print control unit 64 for analyzing print data received from a higher-level device and converting the print data into printable data (eg, page information); a hopper 65 for feeding out continuous paper CF folded at perforations; Reference numeral 66 denotes a stacker for storing printed continuous paper while folding it. The print control unit 63 distinguishes the print data into front surface data and back surface data, expands the image data into dot image image data if it is front surface data, and inputs it to the first printing unit 61; Expand to image data and second
Input to the printing unit 62.

The first and second printing units 61 and 62 have exactly the same configuration, and have image forming units (recording process units) 61 a and 6.
2a, Process control units 61b and 62 for controlling the image forming unit
b. The image forming units 61a and 62a have the same structure as the image forming unit 21 of the first and second printers 11 and 12 (see FIGS. 5 and 9) in the first embodiment, and
a-1, 62a-1 is transferred to continuous paper CF,
Printing is performed by fixing by the fixing units 61a-2 and 62a-2. The process control units 61b and 62b have a bitmap memory BMM for storing image data expanded into dot image data in page units.

(B) Configuration of Control System FIG. 32 is a configuration diagram of a control system of the duplex printing apparatus. 61 is a first printing unit, 62 is a second printing unit, 63 is a printing control unit, and 64 is a data control unit. The analysis unit 67 inputs various data,
Alternatively, it is an operation panel for displaying the status of the printing apparatus.
Reference numerals 61a and 61b denote image forming units, which are photosensitive drums 61a-1 and 62.
a-1, fixing units 61a-2, 62a-2, and optical units (laser units) 61a-3, 62a-3 for irradiating an optical image to form an electrostatic latent image on the photosensitive drum are shown. The optical units (laser units) 61a-3, 62a-3 have the same configuration as in FIG. 61b, 62b are first bitmap memories BMM for storing images corresponding to characters,
1, a second bitmap memory BMM2 for storing an image corresponding to a figure, and instructions from the print control unit 63 (print instructions,
Warming-up instructions, etc.), and
It has a control unit PRC for controlling 62a. It should be noted that the print data may not be developed by the print control unit 63 into a dot image image, but may be developed by the process control units 61b and 62b and stored in the bitmap memories BMM1 and BMM2.

The first printing unit 61 performs printing on the surface of the continuous paper CF based on the odd page print data, and the second printing unit 62 performs the continuous paper CF based on the even page print data.
Is printed on the back side of. The distance between the printing positions (transfer positions) in the first and second printing units 61 and 62 is exactly N pages in terms of the number of continuous paper pages. Therefore, after the first printing unit 61 has printed N pages, the second printing unit starts printing even-numbered pages (second pages) on the back surface. FIG. 33A shows a state where the first printing unit 61 starts printing the first page on the surface of the continuous paper when N = 3.
FIG. 33B shows that the first printing unit 61 has the first page and the third page
When the page and the fifth page are printed, the back surface of the first page has arrived at the second printing unit 62. At this point, the print control unit 63 instructs the first and second printing units 61 and 62 to perform printing, whereby the seventh page is printed on the front side and the second page is printed on the back side.
The page is printed, and thereafter the 2nd page is printed on the front side and the (2n + 1) th page is printed on the back side. By the way, as shown in FIG. 34, the print data continuously arrives from the host device 70 in the order of first page → second page → third page → fourth page → fifth page. For this reason, the bitmap memory BMM of the second printing unit 62
1, BMM2 has an area for storing image data for N pages.

(C) Operation When the continuous paper is set in the double-sided printing apparatus and enters the ready state, print data arrives from the host apparatus 70 in the order shown in FIG. The data analysis unit 64 analyzes the received data, converts the data into printable data, and passes the data to the print control unit 63.
The print control unit 63 distinguishes between print data on the front side and print data on the back side, develops each into a dot image, and processes the process control units 61b and 61b of the first and second printing units 61 and 62.
The data is input to the bit map memories BMM1 and BMM2 of 62b.
The control unit PRC of the first printing unit 61 has a bitmap memory B
Image data is read from MM1 and BMM2 and input to the optical unit 61a-3. The optical unit 61a-3 generates an optical image based on the image data and irradiates the photosensitive drum 61a-1 to form an electrostatic latent image on the photosensitive drum. Thereafter, the first page is formed on a continuous paper surface by an electrophotographic process. Is printed.
Thereafter, the first printing unit 61 prints the third and fifth pages, and the second printing unit 62 prints the second and fourth pages.
The image data of the sixth page is stored in bitmap memories BMM1 and BMM2.
To accumulate.

The print control unit 63 determines that the first print unit 61 has N (=
3) When the front side printing of the page is completed, the image data of the seventh page is input to the first printing unit 61 and the second printing unit 6
Instruct 2 to print the second page. As a result, the first and second printing units 62 read the front-side image data of the seventh page and the back-side image data of the second page stored in the bitmap memories BMM1 and BMM2, and print them on the front and back sides of the continuous paper simultaneously. Perform Thereafter, similarly, printing of the 2nd page on the front side and printing of the (2n + 1) th page on the back side are performed simultaneously. As described above, the bitmap memories BMM1 and BMM2 for storing image data for N pages are provided in the second printing unit 62, and the back side printing is started N pages later after the printing by the first printing unit 61 is started. From the image forming units 61a,
Even if the diameters of the photosensitive drums 61a-1 and 62a-1 are the same, printing can be performed accurately on the front and back surfaces of the continuous paper without displacement.

(D) Physical gap avoidance function at the start of printing When the image forming units 61a and 62a issue a print instruction, they do not start printing immediately. It is necessary to rotate it and warm it. So-called warm-up time is required. For example, FIG.
Considering the front side printing of the print job shown in FIG.
(1) Warm up the image forming unit 61a in accordance with a print instruction of the first page, and (2) start printing the first page. (3) Thereafter, the warm-up is unnecessary, and the third page, the fifth page,. On the other hand, considering backside printing, (1) the second, fourth, and sixth pages are stored in the bitmap memory. (2) When the first printing unit 61 completes the printing of the fifth page in this state, the printing control unit 63
The second printing unit instructs printing of the second page, and the first printing unit instructs printing of the seventh page. (3) At this time, the first printing unit 6
1 can start printing immediately, but the second printing section 62 warms up and then prints the second page. For this reason, the reverse side printing is shifted by the warm-up time.

If the printing by the first printing unit 61 is stopped until the warming is completed in order to prevent the printing deviation due to the warming-up, the printing speed is reduced. Therefore, in the present invention, printing deviation due to warm-up is prevented without stopping printing by the first printing unit 61. That is, the print control unit 63 is the first print unit 61
At the same time, it instructs the second printing unit 62 to warm up. The first printing unit 61 prints the first page after warming up the image forming unit 61a, and the second printing unit 62 warms up the image forming unit 62a and waits for a print instruction.

Thereafter, the first printing unit 61 prints the third and fifth pages based on the print data input from the host device, and the second printing unit 62 prints the second, fourth and sixth pages. Bitmap memory BMM for page image data
Accumulate in 1 and 2. When the first printing unit 61 completes the front side printing of N (= 3) pages, the printing control unit 63 inputs the image data of the seventh page to the first printing unit 61 and sends the second printing unit 62 the second image data. Instruct page printing. Thus, the first printing unit 61 reads the front surface image data of the seventh page stored in the bitmap memories BMM1 and BMM2, and prints the front surface of the continuous paper. Also, since the second printing unit 62 has already completed the warm-up, the second printing unit 62 immediately stored in the bitmap memories BMM1 and BMM2 in response to the print instruction.
The image data of the page is read and printed on the back side of the continuous paper. Thereafter, similarly, printing of the 2nd page on the front side and printing of the (2n + 1) th page on the back side are performed simultaneously.

FIG. 35 is a flow chart of a print misalignment avoiding process due to warm-up. Upon receiving the print data (step 1001), the print control unit 63 checks whether the print data is the print data of the first page (step 1001).
2) If it is the print data of the first page, the print data is developed into image data and input to the first printing unit 61 to instruct printing (step 1003), and the second printing unit 6
2 is instructed to warm up (step 100).
4) Wait for reception of the next print data. Step 1002
In step (2), if the print data is data of the second and subsequent pages, the print data of the second page is expanded into image data and input to the second printing unit 62. Further, the print data of the (2n + 1) th page is developed into image data and input to the first printing unit 61 to instruct printing (step 1005). Next, it is checked whether or not a print instruction has been issued to the second print unit 62 (step 1006).
It is checked whether printing of N pages has been instructed at step 1 (step 1007). If not, the process returns to the beginning and waits for reception of the next print data. On the other hand, in step 1007, if the first print unit 61 is instructed to print N pages, the second print unit 62 is instructed to print the second page (step 1008), and the process returns to the beginning and repeats the subsequent processes. . Since then
In step 1006, “YES” is set, and the first and second printing units 61 and 62 perform double-sided printing.

(E) Mechanism for preventing print misalignment due to differences in page size If the page size (length from perforation) of the continuous paper is different, the printing position of the first and second printing units 61 and 62 will be different. The number of existing continuous paper pages is not exactly an integer, but is a fraction such as 3.3 pages. In such a case, the printing positions of the first and second printing units 61 and 62 on the continuous paper are not the same. FIG. 36A shows a case where the number of continuous paper pages existing between the printing positions is exactly three pages.
6 (b) shows that the number of continuous paper pages existing between the printing positions is 3.
This is the case of five pages. In such a case, the control for accurately performing printing on the front and back surfaces of the continuous paper without displacement is complicated. Therefore, even if the size of the continuous paper changes, there is a means for adjusting the number of continuous paper existing between the printing positions of the first printing unit 61 and the second printing unit 62 so that the number of pages is exactly an integer number of pages. It is convenient. Therefore, as shown in FIG. 36C, a paper intermediate buffer 68 is provided between the first and second printing units 61 and 62, and a paper size adjustment lever 69 is provided, and the lever is moved up and down according to the paper size. And the first and second printing units 6
An adjustment is made so that the number of pages of continuous paper existing between the printing positions of 1, 62 becomes just an integer.

FIG. 37 is a partially detailed view of a two-sided printing apparatus provided with a sheet intermediate buffer. Reference numerals 61 and 62 denote first and second printing sections, and a sheet size adjusting lever 6 is provided between these.
9 is provided. The paper size adjustment lever 69 is longer than the paper width of the continuous paper CF,
It is attached to the guide portion 69a so as to be movable in the vertical direction. A paper size memory is recorded in the guide portion 69a in the vertical direction. When the lever 69 is fixed at a position corresponding to the size of the continuous paper, the continuous paper existing between the printing positions of the first and second printing portions 61 and 62 is provided. The number of paper pages is just an integer. According to the above, the number of pages of the continuous paper existing between the printing positions of the first and second printing units 61 and 62 can be made just an integer, and there is no displacement between the front and back surfaces of the continuous paper by simple control. Printing can be performed accurately.

(F) Print mode The print mode is roughly classified into two-sided printing and one-sided printing.
In double-sided printing, print data from the host device (1)
When it comes alternately like back → front → back → front → ... and (2) back → back → front → back → like a cut sheet printer.
・ There are cases where the printing surface is specified and arrives. FIG. 38 (a) shows an example of the print command chain of (2), where front side skip → print (back side) → front side skip → print (back side)
A print command with data designating a print surface such as → print (front) → print (back) →...

As shown in FIG. 34, when the print data of the front and back sides alternately arrives, the print control unit 63 alternately prints the print data to the first and second printing units 61 and 62. When print data specifying a skip surface and a print surface arrives as shown in FIG. 38A, the print control unit 63 converts the skip command into a blank page print instruction and outputs it. Therefore, when the print data of FIG. 38A arrives, the print control unit 63 converts the print data into a front print data sequence 91 and a back print data sequence 92 as shown in FIG.
Output to the first and second printing units 61 and 62. This allows
Printing is performed on the front and back surfaces of the continuous paper as shown in FIG. In one-sided printing, printing on the surface of continuous paper,
There is a case where printing is performed on the back side, and when printing is performed on the front side, the print control unit 61 inputs all print data of each page to the first printing unit 61 and performs front side printing. When printing on the back side, the print control unit 61 inputs all the print data of each page to the second printing unit 62 and performs back side printing.

Which mode is to be used for printing is set from the operation panel 67 and stored in the backup memory 63a (memory for retaining the stored contents even when the power is turned off) 63a (FIG. 32). . Then, the contents of the backup memory are stored in the work area by the IMPL (Initial mimi
cro program loading), and thereafter, the above-described double-sided printing, front side printing, and back side printing are controlled in the set mode. The mode can be set by issuing a mode setting command from the host device 70. Upon receiving the mode setting command from the host device, the print control unit 63 prints the print data received so far and stops. After the printing is stopped, the operation environment of the control program of the print control unit 63 is changed to a designated mode (double-sided printing, front-side printing, back-side printing), and print control is performed by receiving subsequent print data in this mode. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0100]

As described above, according to the present invention, the counter for counting the continuous paper feed amount on the first printer side based on the position where the continuous paper has been loaded on the first printer, and the continuous paper loaded on the second printer. A counter for counting the continuous paper feed amount on the second printer side based on the position, and a printer control unit of the first and second printers that can communicate with each other, wherein the printer control unit of the first printer is on the first surface ( The counter value N of the first counter at the start of printing on the front side is notified to the printer control unit of the second printer, and the printer control unit of the second printer makes the count value of the second counter equal to the notified count value N. Since the printing of the second surface (back surface) is started when the printing is completed, the printing can be accurately performed on the front and back surfaces of the continuous paper.

According to the present invention, when a double-sided printing release command is issued from a higher-level device to instruct single-sided printing,
Since the printer control unit of the second printer is configured to feed the continuous paper in an amount corresponding to the count value n each time the count value of the counter notified from the first printer increases by n, the printer control unit is a two-sided printing system. Can also be printed on one side. Also, by using the first and second printers separately,
It can be used as two single-sided printers.

[Brief description of the drawings]

FIG. 1 is a first schematic explanatory diagram of a duplex printing system.

FIG. 2 is a second schematic explanatory diagram of the duplex printing system.

FIG. 3 is a third schematic explanatory diagram of the duplex printing system.

FIG. 4 is an overall configuration diagram of a duplex printing system (first embodiment);
It is.

FIG. 5 is a configuration diagram of a first page printer.

FIG. 6 is a configuration diagram of an optical unit.

FIG. 7 is a configuration diagram of a reversing mechanism.

FIG. 8 is an explanatory diagram of an intermediate buffer device.

FIG. 9 is a configuration diagram of a second page printer.

FIG. 10 is a configuration diagram of a control system in the duplex printing system.

FIG. 11 is a configuration diagram of a printer control unit.

FIG. 12 is an explanatory diagram of print data from a higher-level device.

FIG. 13 is a flowchart of a process performed by the first page printer based on the amount of retained paper.

FIG. 14 is a flowchart of a process performed by the second page printer based on the amount of retained paper.

FIG. 15 is a processing flowchart of print start / stop control.

FIG. 16 is an overall configuration diagram of a duplex printing system (second embodiment).

FIG. 17 is a configuration diagram of a control system in the duplex printing system.

FIG. 18 is a configuration diagram of a printer control unit.

FIG. 19 is an explanatory diagram of print data from a higher-level device.

FIG. 20 is a first processing flow (part 1) of print control.

FIG. 21 is a first process flow (2) of print control.

FIG. 22 is a second processing flow of print control.

FIG. 23 is a flow chart for controlling duplex printing and simplex printing.

FIG. 24 is a processing flow of the second printer when the amount of retained paper is reduced.

FIG. 25 is a processing flow of the first printer when the amount of retained paper is reduced.

FIG. 26 is a processing flow of the first printer when the amount of retained paper increases.

FIG. 27 is a processing flow of the second printer when the amount of retained paper increases.

FIG. 28 is an explanatory diagram of a mark recording position.

FIG. 29 is a process flow (part 1) of print control using marks.

FIG. 30 is a process flow (part 2) of printing control using marks.

FIG. 31 is a configuration diagram of a duplex printing apparatus according to a third embodiment.

FIG. 32 is a configuration diagram of a control system of the duplex printing apparatus.

FIG. 33 is an explanatory diagram of a print page on the front and back sides of continuous paper.

FIG. 34 is an explanatory diagram of print data from a higher-level device.

FIG. 35 is a processing flow of print control including a warming operation.

FIG. 36 is an explanatory diagram of a relationship between a continuous paper size and a printing position, and an explanatory diagram of a mechanism for adjusting the length of the continuous paper existing between the printing positions of the first and second printing units;

FIG. 37 is a partial configuration diagram of a two-sided printing apparatus including a mechanism for adjusting the length of continuous paper existing between printing positions of first and second printing units.

FIG. 38 is an explanatory diagram of print control when print data specifying a print surface is received.

FIG. 39 is a configuration diagram of a conventional duplex printing apparatus.

[Explanation of symbols]

11. First printer 12. Second printer 11a, 12a Printer control unit 11b, 12b Printing mechanism 13. Upper device 29 Paper feed detection sensor 56a (PC _A ) Counter 56a (PC _B ) of the first printer for counting the counter of the second printer for counting the feed amount

Continued on the front page (72) Inventor Banri Nagayama 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Mitsuhiro Ino 2-4-1-19 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Shares Company Fujitsu Program Giken

Claims (4)

[Claims] A first printer that prints on one surface (first surface) of the continuous paper; and a second printer that is provided rearward of the first printer in a direction in which the continuous paper is transported.
In a continuous paper duplex printing system that prints on both sides of continuous paper in conjunction with a second printer that prints on the continuous paper, the continuous paper on the first printer side based on the position where the continuous paper is loaded on the first printer A first counter for counting the feed amount of the continuous paper; a second counter for counting the feed amount of the continuous paper on the second printer side based on the position where the continuous paper is loaded on the second printer; A print control unit of the second printer, wherein the print control unit of the first printer notifies the print control unit of the second printer of the count value N of the first counter at the start of printing on the first side; When the count value of the second counter becomes equal to the notified count value N,
A continuous paper duplex printing system that starts printing on the side. 2. The print control unit of the second printer, until the count value of the second counter becomes equal to the notified count value N,
2. The continuous paper duplex printing system according to claim 1, wherein each time the count value of the first counter increases by n, the continuous paper is fed by an amount corresponding to the count n and the count value of the second counter is increased by n. 3. The continuous paper duplex printing system according to claim 1, wherein the first printer starts printing on the first side after setting the continuous paper in the first and second printers. 4. A first printer for printing on one surface (first surface) of the continuous paper, and a first printer provided behind the first printer in the direction of transport of the continuous paper, and the other surface (second surface) of the continuous paper.
And a higher-level device for transferring print data to the first and second printers. The first and second printers are linked to perform printing on both sides of continuous paper. In the printing system, a first counter for counting the continuous paper feed amount on the first printer side based on the position where the continuous paper is loaded on the first printer, and a second counter based on the position where the continuous paper is loaded on the second printer. (2) The printer has a second counter for counting the amount of continuous paper fed on the printer side, and a print control unit of the first and second printers that can communicate with each other. , Or a double-sided print release command indicating that the data after releasing double-sided printing is single-sided print data, to the first and second printers. A first counter count value N when the print controller of the first printer is to perform a two-sided print designation command second
The print control unit of the second printer notifies the print control unit of the printer every time the count value of the first counter increases by n until the count value of the second counter becomes equal to the notified count value N. While feeding the continuous paper by an amount corresponding to the count n, the count value of the second counter is increased by n,
When the count value of the second counter becomes equal to N, printing on the second side is started. During single-side printing, the print control unit of the second printer increases the count value of the first counter by n every time the count value of the first counter increases by n. A continuous paper duplex printing system that controls the feeding of continuous paper by a corresponding amount and the control to increase the count value of a second counter by n.