JPH06344640A - Printer - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Automatically return the ejected blank paper to the paper feed mechanism for reuse. [Structure] The CPU II 39 of the control unit 7 is a reset switch 2
When 9a is operated and the mode is the double-sided mode and the front side of the sheet is being printed, if the detection signal from the video signal detection circuit 53 is "L", it is determined that printing without print data has been performed. Then, the guide claw 25 rotates to the position of the broken line and guides the sheet 2 discharged from the fixing unit 4 to the return path 22.
The return rolls 24 a, 24 b, 24 c return the paper 2 to the paper feed cassette 13. The slip roll 15 stores the return paper 2 in the paper feed cassette 13. The CPUII 39 sets the print flag to front side printing. On the other hand, the detection signal is "H".
If so, it is determined that the error data at the time of reset is printed, the guide claw 25 is positioned at the solid line position, and the printed paper is discharged onto the paper discharge tray 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for automatically returning a blank paper (print processing without print data) printed during printing to a paper feeding mechanism for reuse.

[0002]

2. Description of the Related Art Conventionally, when printing is performed by using a page printer, the size of the paper to be used by the operator is different after the printing start instruction is output from the host device such as a personal computer to the printer. If you notice that you specified the size incorrectly, or if you accidentally specified that you want to send data that is different from the data to be printed, operate the reset switch on the printer to print. The process is interrupted.

Normally, such a reset switch resets only the microcomputer on the interface controller side and does not reset the microcomputer on the engine controller side. This is because the printer engine starts the paper transport operation after the interface controller starts the engine controller, so if the engine controller is reset at such a time, the printer engine will remain with paper remaining on the transport path. Is stopped, and it interferes with the next printing process. Therefore, even if the above-mentioned reset operation is performed, the sheet that has started to be conveyed is printed and discharged. If the above reset is performed while only the processing of the side is being performed, the interface controller will stop before starting the engine controller.
The printer engine does not start. Therefore, the printing process is interrupted without starting the conveyance of the printing paper.

However, after the engine controller has been activated, the transfer of the print data from the interface controller to the print head is stopped from the beginning when the engine controller is reset immediately after the engine is activated. The plain paper is ejected. On the other hand, in the case of a reset after the start-up or some time has elapsed, the interface controller stops in the middle of outputting the print data, and thus the partially printed paper is ejected.

After such a reset, the operator corrects the parameters for instructing the print processing, transmits correct print data to the printer, and restarts the print processing.

[0006]

However, even if the paper discharged as described above at this time is not a defective product during printing but a plain white paper, it is often discarded as it is. This is because when you try to return the discharged blank paper to the paper feed cassette, you pull out the paper feed cassette, remove the paper feed cassette lid, set a blank paper in the paper feed cassette, reset the paper feed cassette lid, and feed the paper. This is not only troublesome because it requires an extremely large number of steps such as inserting a cassette, but also the printing operation does not progress.

A large number of printers are now in widespread use, and the number of blank sheets discarded as described above at the site of use of each of these printers is not negligible. In recent years, when resource depletion is regarded as a problem and there is a demand for effective use of these resources, it can be said that the above-mentioned waste is a serious problem.

SUMMARY OF THE INVENTION In view of the above conventional circumstances, it is an object of the present invention to provide a printing apparatus which automatically returns discharged white paper to a paper feed mechanism for reuse.

[0009]

The structure of the printing apparatus according to the present invention will be described below. The present invention includes an image data generation unit that generates image data based on print information input from a host device, and an image formation processing unit that performs print processing according to the image data transferred from the image data generation unit. The following printing device is assumed.

First, in the printing apparatus according to the first aspect of the invention, the input means inputs an instruction to stop the image forming process to the image forming processing section. The means includes, for example, a reset switch.

The sheet conveying mechanism returns the sheet after the image forming processing by the image forming processing section to the sheet feeding start position. The mechanism is, for example, a paper reversing / transporting mechanism of a double-sided printer.
The conveyance path switching means, when the instruction input from the input means is after the start of the paper feed operation of the image forming processing section and before the image data transfer from the image data generating section, the sheet after the image forming processing is the sheet. Carry it into the transport mechanism. The means is, for example, a guide claw or the like.

Next, in the printing apparatus according to the second aspect of the present invention, the input means, the paper transport mechanism, and the transport path switching means, and further, the image data generating section after the paper feeding operation of the image forming processing section is started. In addition to the blank data detection means for recognizing that the image data for one page of paper transferred from the paper is blank, the conveyance path switching means is such that the instruction input from the input means and the blank data detection means are one page of paper. In response to the detection of the blank data for the minutes, the paper after the image forming processing is carried into the paper transport mechanism.

The blank data detecting means comprises, for example, an AND gate, a flip-flop and the like.

[0014]

Therefore, according to the first aspect of the invention, when the input means inputs an instruction to stop the image forming processing to the image forming processing section, the conveying path switching means receives the instruction input from the input means as the image forming processing section. After the start of the sheet feeding operation and before the transfer of the image data from the image data generating unit, the sheet after the image forming processing is carried into the sheet conveying mechanism, and the sheet conveying mechanism causes the sheet after the image forming processing by the image forming processing section. Is returned to the paper feed start position. As a result, the blank-printed paper is automatically returned to the paper feed start position by inputting an instruction to stop the image forming process before transferring the image data.

Next, in the invention described in claim 2, in addition to the operation of the invention described in claim 1, the blank data detecting means is transferred from the image data generating portion after the paper feeding operation of the image forming processing portion is started. It is recognized that the image data for one page of incoming paper is blank, and the conveyance path switching means inputs an instruction from the input means and the blank data detection means detects blank data for one page of paper. The sheet after the forming process is carried into the sheet transport mechanism. As a result, when there is an instruction input from the input unit and the image data for forming an image on the sheet is blank, the sheet subjected to the blank sheet print processing is automatically returned to the paper feed start position.

[0016]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an entire image forming apparatus according to an embodiment. This figure shows L as an example.
The case of an ED double-sided printer is shown.

In the figure, the LED double-sided printer 1 is
An image forming processing section including a recording section 3 for recording the image data on the sheet 2 and a fixing section 4 for fixing the image data recorded on the sheet 2, and the like, which is arranged below the apparatus in accordance with the recording timing of the image data. Paper feed unit 5 that feeds paper 2 in sequence
And a conveyance mechanism section including a conveyance section 6 and the like that reverses the sheet 2 discharged from the image forming processing section and conveys it to a predetermined position,
The circuit board 7 is provided at the bottom of the apparatus and has an interface controller for generating the image data, an engine controller for controlling the image forming processing section, the transport mechanism section and the like.

The recording unit 3 of the image forming processing unit is indicated by an arrow A.
Photoconductor drum 7 that rotates in the direction, and this photoconductor drum 7
It is composed of a charger 8, an LED head 9, a developing device 10, a transfer device 11, a cleaner 12 and the like which are sequentially arranged in the vicinity of the peripheral surface. The charger 8 applies a uniform charge to the photosensitive surface of the photosensitive drum 7. In the LED head 9, the LED element group selectively emits light to form an electrostatic latent image by exposure on the photosensitive surface of the photoconductor drum 7 to which the above-mentioned charge is applied. The developing device 10 visualizes the electrostatic latent image formed on the photosensitive surface of the photosensitive drum 7 as a toner image. The transfer device 11 transfers the toner image onto the sheet 2. The cleaner 12 removes the toner remaining on the photosensitive surface of the photosensitive drum 7 after the transfer.
Then, the fixing unit 4 receives the paper 2 conveyed from the recording unit 3.
The upper toner image is heat-fixed by heating and pressure.

On the other hand, the sheet feeding section 5 of the transport mechanism section is disposed close to and above the sheets 2 stored in the sheet feeding cassette 13 and carries out the sheets 2 one by one from the top to the feeding path 17. The paper feed roller 14, the slip roll 15 disposed adjacent to the paper feed roller 14 and lightly contacting the uppermost paper 2 and the unloading end of the paper 2 are urged toward the unloading surface of the paper feed roller 14. Biasing member 16 and feeding path 17 for guiding the discharged sheet 2 in the conveying direction
Guide plate 17a, a standby roll 18 that conveys the paper 2 fed along the guide plate 17a to the recording unit 3, and the paper 2 is temporarily stopped and then sent to the transfer device 11 in synchronization with the conveyance timing. It is composed of a stopper 18a and the like.

Further, the transport section 6 of the transport mechanism section branches downward from a normal paper discharge transport path 21 formed between the transport roll 19 and the paper discharge roll 20, and a rising portion of the paper discharge transport path 21. And a return transport path 22 that passes under the paper feed cassette 13 and is connected to the paper feed unit 5. These two
The two conveying directions are switched by rotating the guide claw 25.

The above-mentioned paper discharge conveying path 21 carries out the image-formed paper 2 discharged from the fixing section 4 onto the paper discharge tray 23. On the other hand, the return conveyance path 22 includes three pairs of return conveyance rolls 24a, 24b, and 24c that eject the white paper 2 discharged from the fixing unit 4 without any image data by resetting which will be described later.
The sheet is conveyed to the sheet feeding cassette 13 via. The path of the sheet 2 to be fed to the feeding path 17 and the path of the blank sheet 2 returned to the sheet feeding cassette 13 from the return path are switched by the rotation of the actuator 26.

FIG. 2 is a side sectional view showing the main parts of the normal paper discharge / transport path 21 and the return transport path 22 and the guide claws 25.
The guide claw 25 shown in the figure is composed of two straight lines and a curved line whose cross-sectional shape is substantially orthogonal, and the concave curved surface 2 corresponding to the curved line.
5a, and the concave curved surface 25a is disposed so as to face the inside of the apparatus. The guide claws 25 are provided on the outer guide plate 21 a of the discharge conveyance path 21 and the outer guide plate 2 of the return conveyance path 22.
A sheet 25 discharged between the two sheets is normally rotatably supported by a shaft 25b provided between the two 2a along the vicinity of a corner formed by the above-described two orthogonal straight lines and is indicated by a solid line in FIG. The position S1 for guiding the sheet to the paper discharging and conveying path 21 and the position S2 for guiding to the returning and conveying path 22 are selectively switched.

FIG. 3 is a side sectional view showing the main parts of the return conveying path 22 and the feeding path 17, the actuator 26 and the like. The actuator 26 shown in the same figure has a cross-section having a shape mainly composed of two curved lines forming a tip and connecting and a straight line forming a bottom with respect to the tip, and the tip is directed to the inside of the apparatus. Two concave curved surfaces 26a, 26 corresponding to the above two curves
They are arranged with b facing upward and downward, respectively.
The actuator 26 is rotatably supported by a shaft 26c provided between the outer guide plate 17a of the feed path 17 and the outer guide plate 22b of the return conveyance path 22 along the vicinity of the bottom formed by the straight line. Normally, the bottom plate 13 of the paper feed cassette 13 is
It is located at a position T1 for feeding and guiding the paper 2 on a. And
When the leading edge of the blank sheet 2 passes from the return conveyance path 22 toward the sheet feeding cassette 13, the blank sheet 2 is switched to the position T2 shown by the broken line to guide the blank sheet 2 to the sheet feeding cassette 13 and the passage of the leading edge of the blank sheet 2 is detected. Notify the department. Based on this notification, the slip roll 15 rotates in the direction shown by the arrow in FIG. 3 and reliably stores the paper returned via the return conveyance path 22 in the uppermost part of the paper feed cassette 13.

FIG. 4 is a block diagram of a control circuit for controlling the LED double-sided printer 1. These circuits are shown in FIG.
Mounted on the circuit board 7. The host device 27 shown in FIG. 4 is a word processor, a personal computer, an office computer, or the like that sends information to be printed out to the LED double-sided printer 1, and the control code, character code, etc. sent from the host device 27. Image information of the interface controller 2 through the interface circuit 28 of the LED double-sided printer 1.
9 is input.

The interface controller 29 is a CP
The UI 31 is provided. The CPUI31 has a ROM (Rea
d Only Memory) I32 and RAM (Random Access Memory)
I33 is connected, and further, via the input / output bus line 31a, the interface circuit 28, the buffer 30, the pattern data generator 34, the frame memory 3
6, an address control unit 35, and a read / write (R / W) control unit 37 are connected to each other. CPUI31 is R
By executing a program stored in advance in the OMI 32, each of the circuits described above is controlled to generate image data of a dot image to be output to the engine controller 38 described later.

That is, the CPUI 31 reads image information input from the host device 27 via the interface circuit 28, and stores image data such as character codes and graphic data in the buffer 30.

The pattern data generating section 34 has a storage section for storing pattern data corresponding to a character code and an arithmetic section for generating a graphic image based on coordinate data and the like. When the CPUI 31 reads the control information for instructing the print output in the image information, it reads the image data from the buffer 30 and transfers it to the pattern data generator 34. If the image data is a character code, the pattern data generation unit 34 generates pattern data corresponding to the character code. On the other hand, if the image data is graphic data, the pattern data generation unit 34 generates graphic image data by calculation to generate the bus line 31a. Send to.

The CPUI 31 controls the R / W controller 37 to switch the frame memory 36 to a data write state, and while controlling the address controller 35, the pattern data or graphic image data sent to the bus line 31a. Are sequentially stored in a predetermined area of the frame memory 36 to develop image data of a print image for one page (hereinafter referred to as print image data) in a bitmap format.

The RAMI 33 is used as a work area for temporarily storing the intermediate result of the above processing. When the development of the print image data for one page is completed, then,
The CPUI 31 outputs a start signal to the engine controller 38. When the image data transfer permission signal is received from the engine controller 38, the R / W control unit 37 is controlled to switch the frame memory 36 to the data reading state, and the address control unit 35 is controlled to be expanded in the frame memory 36. The print image data for one page described above is sequentially line-by-line for each engine controller 3
Output to 8.

The interface controller 29 is provided with a reset switch 29a, which is connected to the CPU 31.
When the reset switch 29a is operated to be input, the CPUI 31 immediately interrupts each processing described above and returns to the initial state. At this time, all the print image data expanded in the frame memory 36 are also cleared, and only a blank signal (a signal without data) is sent to the engine controller 38.

The engine controller 38 is a CPUII3.
9 and the CPUII39 is the CPUI31 described above.
It is started by the start signal input from. CPU
A ROMII 40 and a RAMII 41 are connected to the II 39, and the CPUII 39 controls each unit described below that is connected to the CPUII 39 while using the work area of the RAMII 41 based on the program stored in the ROMII 40. Interface controller 29
All the image forming processing based on the print image data transferred from is executed.

That is, each part state detection sensor 42 is an LED
The sensors are provided in each part of the double-sided printer 1, and are provided, for example, in the vicinity of the paper feed cassette 13 to detect the presence or absence of print paper, or are provided in the feed path 17, the discharge conveyance path 21, or the like. Detects the paper passage timing. CPUII3
When the sheet state detection sensor 42 detects that the sheet 2 has reached the standby section in the transport path 17 where the standby roll 18 is present, the sheet 9 temporarily stops the sheet 2 and allows the interface controller 29 to transfer the print image data. Send a signal.

The operation input section 43 is provided with an operation panel section (not shown) in which various switch groups are arranged, and inputs a switching instruction of a printing mode or the like, an instruction to switch between single-sided printing and double-sided printing of paper, and the like. Note that these instructions can also be directly issued from the host device 27 by a command. CP
When the UII 39 recognizes that the double-sided printing is instructed, the UII 39 stores the double-sided mode in the RAM II 41 and sets the back surface flag. And, for each one-sided printing of one sheet of paper,
The contents of the back side flag are first inverted to "0" and then to "1" to recognize the front and back sides of the paper. That is, the CPUII 39 checks the back surface flag each time the image forming process on one side of the paper is completed, and if the back surface flag is "0", the guide claw 25 is indicated by a broken line S2.
Is switched to, the sheet 2 is introduced into the return conveyance path 22 and returned to the sheet feeding cassette 13, and then the back surface flag is inverted to "1". On the other hand, if the back surface flag is "1" after the image forming process on one side of the sheet, the guide claw 25 is switched to the position S1 shown by the solid line, and the sheet 2 is discharged from the sheet discharge conveying path 21 onto the sheet discharge tray 23.

The display unit 44 is provided with various indicators, and depending on these indicators, the state of the return transport path 22 and the currently performed image forming process is one side (front side) or the other side of double-sided printing. It is displayed and informed whether it is the front side (back side) or the like.

The sheet feeding SOL 45 is a solenoid that controls the rotation of the sheet feeding roller 14 that carries the sheet 2 out of the sheet feeding cassette 13, and when turned on, transmits the driving force of a drive system (not shown) to the sheet feeding roller 14. To feed the paper 2 to the feeding path 17.

The transport path switching SOL 46 is a solenoid for switching the transport path of the sheet 2, and when it is turned on, the guide claw 25 disposed downstream of the fixing device 4 is moved to the position S in FIG.
The sheet 2 discharged from the fixing device 4 is guided to the return conveyance path 22 by operating the sheet 2 to the fixing device 4.

The electromagnetic clutch 47 is the slip roll 15
To drive the slip roll 15 to rotate in the direction shown by the arrow in FIG. The other movable devices 48 are all other movable devices controlled by the engine controller 38 other than the above, such as the charger 8, the developing device 10, the transfer device 11, and the like.
The cleaner 12, each part of the fixing unit 4, a light source (not shown), and the like.

The image data control unit 49 converts the print image data input from the frame memory 36 of the interface controller 29 into a serial video signal and outputs L as a video signal.
The horizontal / vertical synchronizing signal is supplied to the LED drive control unit 50 while being output to the ED drive control unit 50.

The LED drive control unit 50 generates a drive signal for controlling the light emission of the LED head 9 shown in FIG. 1 based on the supplied video signal, and based on the horizontal / vertical sync signal also supplied. Then, the drive signal is applied to the LED head 9 as described above.

Each element of the LED array of the LED head 9 selectively emits light in accordance with a drive signal supplied from the LED drive controller 50, and the peripheral surface of the rotating photosensitive drum 7 is exposed by this optical information. .

In this embodiment, the CPUII 39 is
As shown in FIG. 5, a video signal detection circuit 53 including an OR gate 51 and a flip-flop 52 is provided,
In this way, it is determined whether blank printing has been performed.

A clock signal bar CLK and a video signal bar VIDEO are input to the input side of the OR gate 51 in synchronization with this clock. The output of the OR gate 51 is the input clock signal bar CLK and video signal bar VI.
It is "L" only when both DEO are "L", and at other times (when the clock signal bar CLK is always "L", in this case, when the video signal bar VIDEO is "H"), H ". The output of the OR gate 51 is inverted and input to the clock terminal bar CK of the flip-flop 52. That is, the video signal bar VIDEO is "L"
When it is (“0”, that is, white data), the output “L” of the OR gate 51 is inverted and input to the flip-flop 52 at “H”. On the other hand, the video signal bar VIDEO is "H".
In the case of "1", that is, black data, the output "H" of the OR gate 51 is inverted and input "L" to the flip-flop 52.

The flip-flop 52 inverts and inputs the signal input to the clock terminal bar CK. That is, when the input signal is "H" (video signal bar VIDEO is "0", that is, white data), "L" is input, and the input signal is "L" (video signal bar VIDEO is "1", that is, black). Input “H” for data). The flip-flop 52 outputs the "H" signal POUT input from the CPUII 39 every time the image forming process is started on one side of the sheet 2.
When the clock terminal bar CK inputs "H", the output of the terminal Q is set to "H". The output of the terminal Q is input to the input port PIN of the CPUII 39.

The CPUII 39 recognizes that the print image data is black data when the output of the flip-flop 52 input to the input port PIN is "H". The processing operation for controlling the conveyance of the transfer paper (paper 2) among the image forming processing operations in the present embodiment having such a configuration will be described with reference to the flowchart shown in FIG. It should be noted that this processing is performed by the CPU II 39 in the ROM at regular intervals during the image forming processing (hereinafter also referred to as printing processing) which is the main processing.
It is read from II40 and executed. In addition, in this process, a timer 1 and a timer 2 (not shown) are used.

First, the interface controller 29
It is monitored whether or not the start signal is input from (step S1). Then, when the input of the start signal is recognized (S1 is Y), the sheet feeding SOL 45 is turned on for a predetermined time (ON).
(Step S2). As a result, the stopper of the one-way clutch for transmitting the drive of the drive source to the roller shaft 14a of the paper feed roller 15 is disengaged, and the paper feed roller 15 is rotated once and stopped. By one rotation of the paper feed roller 15, the uppermost sheet 2 of the paper feed cassette 13 is carried out to the feeding path 17.
Then, it is monitored whether or not a standby sensor, which is one of the state detection sensors 42, is turned on (step S3). Although not particularly shown, this standby sensor is arranged immediately before the standby roll 18 and is turned on when the leading edge of the sheet 2 passes. When the CPUII 39 recognizes that the standby sensor is turned on (S3, Y), first, the output of POUT is changed from "L" to "H" to reset the flip-flop 52 (step S4), and then the rotation state is reached. The standby roll 18 is stopped (step S5). As a result, the leading edge of the sheet 2 comes into contact with the stopper 18a and stops.

On the other hand, by turning on the standby sensor,
The CPUII 39 controls the image data control unit 49 to send a video signal based on the print image data to the LED drive control unit 50, and controls the LED drive control unit 50 to drive the LED head 9 based on the video signal. Start printing. In order to match the feeding timing of the leading edge of the print and the paper 2, the value of a timing timer (not shown) that measures a predetermined time from the start of printing is monitored (step S6), and when the time is up (S6, Y), not shown. The drive signal is output to the standby roll clutch (step S7). As a result, the standby roll 18 is re-driven and the stopper 18a rotates to lower the tip thereof. And paper 2
Is re-fed at the same timing as the toner image formed on the rotating photosensitive drum 7, the toner image is transferred by the recording unit 3, and the toner image is fixed by the fixing unit 4.

Subsequent to the above, the CPUII 39 monitors the output of the fixing outlet sensor, which is one of the state detecting sensors 42 (step S8). Although not shown in particular, the fixing outlet sensor is arranged in the vicinity of the outlet of the fixing unit 4, and is turned on by detecting the leading edge of the sheet 2 discharged from the fixing unit 4. When the fixing exit sensor is turned on, the CPUII 39
Determines whether or not the double-sided mode is set by referring to the predetermined area of the RAMII 41 (step S9). Then, if it is not the double-sided mode, the sheet 2 is discharged as it is onto the sheet discharge tray 23 and the processing of the transfer sheet conveyance control ends, but if the double-sided mode is set (S9, Y), the RAMII41 It is determined whether the back surface flag of "1" is "1" (step S10). As a result, when double-sided printing is designated, it is determined whether the paper surface during the image forming process is the front surface or the back surface. Then, if the back surface flag is "0" (S10, N), it is determined that it is the front surface of the paper 2, the back surface flag is set to "1", and the next processing is performed on the back surface of the paper 2. (Step S11), and subsequently, the transport path switching SOL46 is turned on (step S12). As a result, the guide claw 25 pivots to the position S2 shown by the broken line to guide the sheet 2 to the return conveyance path 22, and the sheet 2 is returned to the return conveyance rolls 24a, 24b, 2 and 2.
The sheet 4c is conveyed toward the sheet cassette 13.

The CPUII 39 has a state detection sensor 42 for each part.
The output of an actuator sensor (not shown), which is one of the above, is monitored (step S13), and when it is recognized that the actuator sensor is turned on (S13, Y), the paper 2 conveyed through the return conveyance path 22 is detected. Actuator 2 at the tip
It is determined that 6 has been rotated, the timer 1 in which a predetermined time count T1 is set in advance corresponding to the paper size is started (step S15), and the rotation start timing of the slip roll 15 is measured (step S16).

When it is recognized that the leading edge of the sheet 2 reaches below the slip roll 15 after the lapse of the predetermined time T1 and the timer 1 counts up (S16, Y), the electromagnetic clutch 47 is turned on (step S16). S17). As a result, the slip roll 15 rotates and the paper 2 having only one surface printed thereon is stored in the paper feed cassette 13 with its printing surface facing upward.

Following the above, the counted-up timer 1 is reset (step S18). As a result, the timer 1 returns to the initial state. Next, a predetermined count value is set in the timer 2 (step S19). As a result, the front end of the paper 2 that has been printed on one side is slip roll 1
The time from when the number of sheets reaches 4 to when the sheets are completely stored in the sheet feeding cassette 13 is set according to the size of the sheet.

Then, the timer 2 starts counting (step S20), waits for the timer 2 to count up (step S21), and when the timer 2 counts up (S21, Y), the actuator sensor continues to operate. It is determined whether it is turned off (step S2).
2). As a result, it is determined whether or not the trailing edge of the single-side printed sheet 2 returned from the return conveyance path 22 passes through the actuator 26 (that is, the single-side printed sheet 2 is normally stored in the paper feed cassette 13). Is determined.

If the actuator sensor is ON (S22, N), it is determined that the sheet 2 is jammed at the actuator 26, and the jam processing is performed (step S25). This process interrupts the printing process,
This is processing such as notifying the occurrence of paper jam and its location on the display panel.

On the other hand, if the actuator sensor is off (S22, Y), it is determined that the paper 2 is normally stored in the paper feed cassette 13, and in this case, the slip roll 1
The electromagnetic clutch 47 that transmits the drive to 4 is turned off (step S23). As a result, the slip roll stops.

Then, the guide path 25 is displaced to the position S2, and the conveying path switching SOL46 is turned off.
5 is localized at position 1 (step S24), and the process returns to the main process.

However, the sheet 2 for which the printing process on one side has been completed is stored in the paper feed cassette 13 with the front side and the rear side reversed from the initial state and the printing side facing upward. Next, when a back side printing start signal is input from the host device 27 through the interface controller 29 to perform the back side printing process, the CPU of the engine controller 38
The II 39 restarts the transfer paper conveyance control process.
Then, steps S1 to S9 are performed, and step S10
Then, it is judged that the back surface flag is "1" (S10, Y), the current processing is judged to be the back surface, the back surface flag is set to "0", and the next processing is the front surface. After indicating that there is (step S14), the process returns to the main process. As a result, the paper 2 for which the back side printing has been completed (that is, double-sided printing has been completed) is guided in the direction of the paper discharge conveyance path 21 due to the guide claw 25 being positioned at the position 1 in the previous step S24, and discharged. It is discharged onto the paper tray 23.

When the reset switch 29a of the interface controller 29 shown in FIG. 4 is operated during the printing process, the interface controller 29
The operation input by the reset switch 29a is notified to the engine controller 38 as an error occurrence signal and the frame memory 36 is cleared.

CPUII 39 of engine controller 38
When receiving the above error occurrence signal, shifts to the error processing shown in FIG. In this case, the CPU II 39 performs the error processing shown in the figure only when it is confirmed that the double-sided mode is set before the error processing is started, and when it is confirmed that the surface processing is being performed now.

First, the CPU II 39 checks the signal input to the input port PIN (step S31). If this signal is "L" (all video signals are "0"), it is determined that there is no image print data. (S31, "L"), a process of returning the discharged sheet 2 that has been subjected to the blank sheet printing processing and discharged to the sheet feeding cassette 13 is performed (step S32). This process is the same as the process of steps S12, S13, S15 to S24 of the process shown in FIG. As a result, the paper 2 that has been blank-printed on one surface (hence both surfaces are blank)
Is automatically returned to the paper feed cassette 13 and used for printing processing with correct data after reset.

Subsequently, the back surface flag indicating the next paper printing processing surface (back surface) is inverted and a flag indicating the current paper printing processing surface (front surface) to be reprocessed is set, and the process returns to the main processing. .

On the other hand, if the signal is "H" in step S31, it is determined that there is a video signal of "1", that is, error data is printed (S31, "H"), and immediately in this case. Return to main processing. As a result, when the image print data has already been started to be transmitted from the interface controller 29 at the time of reset, the printing process for one side is normally continued, and the paper on which the error data is printed is discharged.

In the present embodiment, the case of the double-sided mode (double-sided printing process) in the double-sided printer has been described. However, also in the single-sided mode (printing process on only one side), the blank sheet discharge 2 is similarly supplied. Can be returned to 13. In this case, the confirmation process before entering the error process of FIG. 7 only needs to confirm that the mode is the single-sided mode, and if it is the single-sided mode, the determination process of step S31 may be started immediately. Further, in this case, since the reverse processing of the back surface flag is unnecessary, step S33 may be omitted.

Further, the present invention is not limited to a double-sided printer, but can be applied to a single-sided printer. In this case, a paper return mechanism may be attached to the single-sided printer to perform the above-mentioned processing.

When all the video signals input to the detection circuit 53 are "0", the discharged paper 2 is fed to the paper feed cassette 13
However, it is not limited to the case where all the video signals are "0", but the video signals which become "1" are counted, and when the count value is a certain number or less, all , The paper discharge cassette 2
It may be returned to. This is in consideration of the fact that the density of printed dots has become finer with the improvement of technology in recent years, and the field of view of each dot is extremely small, and the printing of a small number of black dots may be ignored.

[0064]

As described above in detail, according to the present invention, when both sides of the printing paper discharged at the time of reset are blank, the paper can be automatically returned to the paper feed cassette. , The problem that waste reusable blank paper is wastefully discarded is eliminated, and thus effective use of resources is realized. Further, since it can be automatically returned to the paper feed cassette, the number of steps can be saved and there is no trouble, so that the printing work progresses and the efficiency is improved. Further, it is economical because it can be realized by simply using a returning mechanism of the double-sided printer and adding a simple detection circuit.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an entire image forming apparatus according to an embodiment.

FIG. 2 is a side sectional view showing main parts and guide claws of a normal paper discharge conveyance path and a return conveyance path.

FIG. 3 is a side sectional view showing a main part of a return conveyance path and a feeding path, an actuator and the like.

FIG. 4 is a control circuit block diagram for controlling an LED double-sided printer.

FIG. 5 is a diagram showing a video signal detection circuit.

FIG. 6 is a flowchart illustrating a processing operation for controlling transfer paper (paper) conveyance in the image forming processing operation according to the present exemplary embodiment.

FIG. 7 is a flowchart illustrating error processing by reset.

[Explanation of symbols]

 1 LED Double-sided Printer 2 Paper 3 Recording Part 4 Fixing Part 5 Paper Feeding Part 6 Conveying Part 7 Circuit Board 8 Charging Device 9 LED Head 10 Developing Device 11 Transfer Device 12 Cleaner 13 Paper Feeding Cassette 13a Bottom Plate 14 Paper Feeding Roll 15 Slip Roll 16 Energizing member 17 Feeding path 117a Guide plate 18 Standby roll 18a Stopper 19 Conveying roll 20 Discharging roll 21 Discharging conveying path 21a, 22a Outer guide plate 22 Conveying path 23 Discharging tray 24a, 24b, 24c Conveying roll 25 Guide claw 25a, 26a, 26b concave curved surface 25b, 26c axis 26 actuator 27 host device 28 interface circuit 29 interface controller 29a reset switch 30 buffer 31 CPUI 31a input / output bus line 32 ROM (Read Only Memory) I 33 RA (Random Access Memory) I 34 Pattern data generator 36 Frame memory 35 Address controller 37 Read / write (R / W) controller 38 Engine controller 39 CPUII 40 ROMII 41 RAMII 42 State detection sensor 43 Operation input unit 44 Display unit 45 Paper feeding SOL 46 Transport path switching SOL 48 Other movable equipment 49 Image data control unit 50 LED drive control unit 51 OR gate 52 Flip-flop 53 Video signal detection circuit

Claims (2)

[Claims] 1. An image data generation unit that generates image data based on print information input from a host device, and an image formation processing unit that performs character printing processing according to the image data transferred from the image data generation unit. In the printing device, an input unit for inputting an instruction to stop the image forming process to the image forming processing unit, a sheet conveying mechanism for returning the sheet after the image forming process by the image forming processing unit to a sheet feeding start position, When the instruction input from the input means is after the start of the paper feed operation of the image forming processing unit and before the image data transfer from the image data generating unit, the paper path after the image forming processing is carried into the paper carrying mechanism. A printing device comprising: a switching unit. 2. A blank data detection unit for recognizing that the image data for one page of the sheet transferred from the image data generation unit after the start of the paper feeding operation of the image formation processing unit is blank. The carrying path switching means carries in the paper after the image forming processing to the paper carrying mechanism in response to an instruction input from the input means and the blank data detecting means detecting blank data for one page of the paper. The printing apparatus according to claim 1, wherein: