JP2013152343A - Image forming device - Google Patents

Abstract

The present invention realizes a configuration in which the alignment of sheets is not easily disturbed even when thin sheets are discharged to a discharge tray without adding structural elements.
When a print job having a setting using two or more thin papers P is generated, a thick paper P is first fed and discharged to a paper discharge tray 140. The airflow X in the direction along the passage path of the paper P is generated. Thereafter, after the thin paper P is fed to form an image by the print job, the thin paper P is discharged onto the paper discharge tray 140 by being placed on the airflow X. The thin paper P riding on the airflow X is discharged to the paper discharge tray 140 without causing deformation such as the leading edge being lifted, and is stacked on the paper discharge tray 140 without disturbing the paper alignment. When the number of images to be printed on the thin paper P by the print job exceeds 10, the thick paper P is interrupted and discharged one by one every time 10 thin paper P is fed and discharged. .
[Selection] Figure 4

Description

  The present invention relates to an image forming apparatus that discharges and stacks sheets on which an image is formed on a discharge tray.

  For example, in response to the need to reduce the thickness when used for the contents of sealed letters, thin paper is provided as a kind of paper used in the image forming apparatus. Since thin paper is weak, the leading edge of the paper floats or turns up due to the air resistance received from the surrounding air when paper is discharged to the paper discharge tray. Such a phenomenon is particularly prominent during high-speed printing in which the paper is conveyed at high speed, and adversely affects the alignment of the discharged paper on the paper discharge tray.

  Therefore, in the case of thin paper, the paper discharge path on the paper output tray is switched to a different path from that for thick paper. It has been proposed that the front end abuts the paper discharge tray at an appropriate angle. According to this proposal, it is possible to prevent the paper alignment from being disturbed when a thin sheet is discharged to the discharge tray (for example, Patent Document 1).

JP 2010-143728 A

  However, since the above-described conventional configuration is premised on providing a plurality of paper discharge paths for the paper discharge tray, it is necessary to secure a space for the paper discharge, resulting in an increase in the size of the apparatus. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a configuration in which paper alignment is not disturbed even when thin paper is discharged to a discharge tray without adding structural elements. An object of the present invention is to provide an image forming apparatus capable of performing the above.

In order to achieve the above object, an image forming apparatus of the present invention described in claim 1 includes:
Based on the input print job, a plurality of types of sheets having different basis weights are selectively fed from the respective sheet feeding units to the sheet conveying unit, and the sheet after forming the image is discharged by the sheet conveying unit. In an image forming apparatus that discharges and stacks on a paper tray,
When the first sheet of paper on which an image is formed by the print job is a sheet whose basis weight is less than a predetermined threshold, the sheet whose basis weight exceeds the predetermined threshold prior to the first sheet. At least one sheet is fed to the sheet conveying means by a corresponding sheet feeding means, and is provided with an interrupt control means for discharging the sheet onto the sheet discharge tray by the sheet conveying means,
Feeding and discharging the first sheet continuously with the paper feeding and discharging by the interrupt control means;
It is characterized by that.

  According to the image forming apparatus of the present invention described in claim 1, when the first sheet of paper on which an image is formed by a print job is so-called thin paper whose basis weight is lower than a predetermined threshold, the paper is discharged. When the paper is discharged to the paper tray, deformation such as lifting of the front end of the paper occurs due to the resistance of air staying in the paper discharge tray. Such deformation of the front end of the sheet becomes a factor that disturbs the sheet alignment when a thin sheet is stacked on the sheet discharge tray.

  On the other hand, when so-called thick paper whose basis weight exceeds a predetermined threshold is discharged to the discharge tray, the thick paper is discharged without being deformed against the resistance of air staying in the discharge tray. Paper is ejected to the tray. At this time, an airflow is generated in the paper discharge tray along the passage path of the thick paper that has been discharged.

  Therefore, if thick paper is discharged to the paper discharge tray prior to thin paper, the subsequent thin paper rides on the airflow generated by the thick paper and does not deform, such as lifting the tip. The paper is discharged. For this reason, the paper alignment of the thin paper is prevented from being disturbed when being stacked on the paper discharge tray. Therefore, it is possible to realize a configuration in which even when thin paper is discharged to the paper discharge tray, the paper alignment is not easily disturbed without adding structural elements.

  According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect of the present invention, wherein the paper fed and discharged by the interrupt control means and the subsequent paper supply and discharge are the same. The first sheet is fed and discharged at a time interval equal to or less than a time interval when the first and subsequent sheets are fed and discharged based on the print job.

  According to the image forming apparatus of the present invention described in claim 2, in the image forming apparatus of the present invention described in claim 1, the air flow generated in the discharge tray by discharging thick paper to the discharge tray is Over time, it fades away and disappears. Therefore, in order to discharge thin paper onto the paper discharge tray in the airflow generated by the discharge of thick paper, it is important to continuously discharge the thin paper within the period in which the airflow remains. Become.

  Here, at least at a time interval that is less than or equal to the paper supply and discharge interval of the paper on which an image is formed by the print job, that is, at a time interval that is less than or equal to the paper conveyance interval during image formation based on the print job, If the paper is discharged to the paper discharge tray, it is possible to expect the remaining airflow generated in the paper discharge tray due to the discharge of the thick paper even when the thin paper is discharged to the paper discharge tray.

  Therefore, by discharging the thin paper following the thick paper to the paper output tray at a time interval that is less than the paper supply / discharge interval for the first and subsequent sheets of the print job, the thick paper is discharged. Paper discharge that does not involve deformation of thin paper using the generated airflow can be more reliably realized.

  Further, the image forming apparatus of the present invention described in claim 3 is the image forming apparatus of the present invention described in claim 1 or 2, wherein the sheet fed and discharged by the interrupt control unit is the sheet conveying unit. The size in the transport direction is larger than that of the first sheet.

  According to the image forming apparatus of the present invention described in claim 3, in the image forming apparatus of the present invention described in claim 1 or 2, the thick paper having a size larger than that of the thin paper in the transport direction of the paper transport means. Passes through the air staying in the paper discharge tray over a longer time than the thin paper when paper is discharged to the paper discharge tray. Therefore, the air flow generated in the paper discharge tray due to the discharge of the thick paper is more stable than the case where the size of the thick paper in the transport direction is the same as that of the thin paper, and the remaining period becomes longer.

  For this reason, it is possible to continue the state in which the thin paper discharged following the thick paper is discharged without deformation in the airflow of the paper discharge tray for a longer time.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second or third aspect of the present invention, the interrupt control means is a sheet on which an image is formed by the print job. Only when there are a plurality of sheets, a sheet whose basis weight exceeds the predetermined threshold is fed and discharged prior to the first sheet.

  According to the image forming apparatus of the present invention described in claim 4, in the image forming apparatus of the present invention described in claim 1, 2 or 3, when there is one sheet on which an image is formed by a print job, Since other sheets and paper are not stacked on the paper discharge tray, there is no problem of paper alignment. Therefore, even if the paper on which the image is formed is a thin paper, it is not necessary to discharge the thick paper prior to that and generate an airflow in the paper discharge tray. Therefore, it is possible to prevent the thick paper from being consumed more than necessary in order to improve the paper alignment on the paper discharge tray.

  Further, the image forming apparatus of the present invention described in claim 5 is the image forming apparatus of the present invention described in claim 1, 2, 3 or 4, wherein the interrupt control means forms an image by the print job. When the sheet to be printed is a sheet that exceeds the predetermined number of sheets continuously from the first sheet and the basis weight is below a predetermined threshold value, the basis weight is set to the predetermined amount each time the predetermined number of sheets are fed and discharged. It is characterized in that at least one sheet exceeding the threshold value is fed and discharged by interruption.

  According to the image forming apparatus of the present invention described in claim 5, in the image forming apparatus of the present invention described in claim 1, 2, 3, or 4, the thick sheet is discharged by discharging it to the discharge tray. The airflow generated in the paper tray weakens with time and disappears.

  Therefore, if the thick paper is interrupted again and discharged to the paper output tray before the air current generated in the paper output tray by the continuous paper discharge of the thin paper weakens and disappears, the air current in the paper output tray Can be maintained without disappearing, and a thin sheet can be placed on the airflow again and discharged without deformation.

  Therefore, a predetermined number of sheets is determined based on the number of thin sheets discharged to the discharge tray just before the air flow generated in the discharge tray is weakened and disappears by discharging thick sheets. Each time a number of sheets are ejected continuously, a thick sheet of paper is interrupted and ejected, so that the airflow in the ejection tray can be maintained without disappearing. Thus, thin paper on which an image is formed by a print job can be discharged continuously without disturbing paper alignment.

  According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the present invention, wherein the sheet is fed and discharged by the interrupt control means in the first, second, third, fourth or fifth aspect of the present invention. Selecting means for selecting whether or not image formation is performed, and when the image forming validity is selected by the selection means, image formation is performed on the paper to be fed and discharged by the interrupt control means, When invalidity of image formation is selected by the selection unit, image formation on a sheet to be fed / discharged by the interrupt control unit is not executed.

  According to the image forming apparatus of the present invention described in claim 6, in the image forming apparatus of the present invention described in claim 1, 2, 3, 4 or 5, thin paper on which an image by a print job is formed is discharged. Select whether or not to form an image on thick paper that is ejected prior to thin paper in order to generate an airflow in the paper tray that disturbs paper alignment and prevents paper from being ejected. It can be selected by means.

  For this reason, it is possible to arbitrarily determine whether or not to form an image on the thick paper according to the contents of the print job, and to make effective use of the thick paper.

  According to the present invention, it is possible to realize a configuration in which even if thin paper is discharged to a paper discharge tray, the paper alignment is hardly disturbed without adding structural elements.

It is explanatory drawing which shows typically the internal structure of the printing apparatus which concerns on embodiment. It is a functional block diagram showing a print control system module according to the embodiment. FIG. 6 is an explanatory diagram illustrating a state where a thin sheet is discharged from the first sheet to a discharge tray of the printing apparatus according to the embodiment. FIG. 10 is an explanatory diagram illustrating a state in which thick paper is discharged from the first sheet to a paper discharge tray of the printing apparatus according to the embodiment. 6 is a flowchart showing the contents of scheduling performed by a scheduling unit of the printing apparatus according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating an internal configuration of a printing apparatus 100 according to an embodiment of the present invention.

(Overall configuration of printing device)
A printing apparatus 100 according to the present embodiment illustrated in FIG. 1 is an inkjet line color printer. Therefore, the printing apparatus 100 includes a plurality of head units 110 in which a large number of nozzles are formed. Each head unit 110 ejects black or color ink to perform printing in line units, and forms a plurality of images on the paper P on the transport belt so as to overlap each other.

  Then, the printing apparatus 100 uses the plurality of head units 110 to form an image on the paper P conveyed on the annular conveyance path. This transport path has a normal transport path CR and a reverse path SR.

  The normal transport path CR transports the paper P fed to the registration unit R from the paper feed path FR to the head unit 110, and transports the paper P on which an image is formed by the head unit 110 to the paper discharge path DR1. The paper discharge path DR1 is a path through which the paper P on the transport path is conveyed (discharged) to the paper discharge tray 140 on the paper discharge tray 150. The normal transport path CR is also a path for transporting (discharging) a part of the paper P to be discharged to the face-up paper discharge port 141 to the straight paper discharge path DR2.

  The normal conveyance path CR is endlessly connected to a registration driving unit 240 that guides the sheet P fed from the sheet feeding path FR to the registration unit R, and a conveyance belt 160 provided on the opposite surface of the head unit 110 by a driving roller 162. And a belt driving unit 250 to be moved. Is wound around a driven roller 161 and a driving roller 162 disposed on the front end and the rear end of the surface facing the head unit 110, and moves around in the clockwise direction in the drawing.

  The paper feed path FR is a path for transporting (feeding) the paper P from the paper feed trays 130a to 130d and the side paper feed tray 120 to the registration unit R. The paper feed path FR includes a paper feed path for feeding the paper P from the paper feed trays 130 a to 130 d to the normal transport path CR by the tray driving units 230 a to 230 d, and a paper from the side paper feed tray 120 by the side paper feed driving unit 220. A paper feed path for feeding P.

  The reversing path SR transports the paper P from the connection point of the normal transport path CR and the paper discharge path DR1 to the switchback space in the paper discharge tray 150, and the paper P whose front and back are reversed by the switchback is the normal transport path. It is conveyed to the resist portion R of the CR. The transport destination of the paper P from the normal transport path CR is switched by the switching mechanism 170 to either the paper discharge path DR1 or the reverse path SR. Further, the transport path of the paper P is switched by the switching mechanism 172 between when the paper P is transported to the switchback space and when the paper P is transported from the switchback space to the registration unit R.

  Note that the part of the reversing path SR from the paper discharge tray 150 to the registration unit R also constitutes a part of the paper feeding path FR.

  Paper P is set on each of the side paper feed tray 120 and the paper feed trays 130a to 130d. The paper feed trays 130a to 130d are so-called paper feed cassettes, each of which has different sizes (A4, A3, B4, B5, etc.), orientations (vertical, horizontal), and paper quality (for example, thick paper having a large basis weight). , Thin paper with a small basis weight, etc.) can be set. The side paper feed tray 120 is a so-called manual feed tray, and can set paper P having an arbitrary specification that can be transported along the transport path.

  In the printing apparatus 100 of the present embodiment, the conveyance path having the normal conveyance path CR and the reversal path SR, the paper feed path FR and the paper discharge path DR1, the conveyance belt 160, the registration driving unit 240, and the belt driving unit. 250, tray drive units 230a to 230d, and side paper feed drive unit 220 are included in the sheet conveying means in the claims.

  Furthermore, the printing apparatus 100 includes an arithmetic processing unit 330 (corresponding to an interrupt control unit in claims). The arithmetic processing unit 330 is configured by a processor such as a CPU or DSP (Digital Signal Processor), memory, hardware such as other electronic circuits, software such as a program having the function, or a combination thereof. It is an arithmetic module.

  Then, the arithmetic processing unit 330 virtually constructs various functional modules by appropriately reading and executing the program, and the constructed functional modules perform processing related to image data, operation control of each unit, and user operations. Various processes are performed. In addition, an operation panel 340 is connected to the arithmetic processing unit 330, and an instruction and a setting operation by a user can be received through the operation panel 340.

(Configuration of print control system module)
The conveyance control in the conveyance path of the paper P described above is performed by the print control system module of the arithmetic processing unit 330. FIG. 2 is a block diagram illustrating modules related to printing control in the arithmetic processing unit 330. The “module” used in the description refers to a functional unit that is configured by hardware such as an apparatus or a device, software having the function, or a combination thereof, and achieves a predetermined operation. .

  In the present embodiment, the printing apparatus 100 includes a scanner 300, a printing condition setting unit 341, a conveyance state detection unit 342, a display unit 343, and a communication processing unit 344.

  The scanner 300 reads an image of a document as image data. The print condition setting unit 341 receives settings such as duplex / single-sided printing, paper size, and resolution. In other words, the print condition setting unit 341 is an interface that accepts print condition settings based on, for example, print job data sent from a PC connected to the printing apparatus 100 or a user instruction via the operation panel 340.

  The transport state detection unit 342 detects the transport state of the paper P in the transport path based on a signal from the transport sensor. The display unit 343 displays information regarding the printing apparatus. The communication processing unit 344 communicates with a computer or the like (hereinafter referred to as “PC”) serving as a host of the printing apparatus 100 and receives print data.

  In the printing process, the arithmetic processing unit 330 generates image data according to the printing conditions received by the printing condition setting unit 341, and controls the printing process in the printing execution unit 350 including a printing mechanism such as a print head. To do. Specifically, the arithmetic processing unit 330 includes an image data generation unit 331, a memory control unit 332, a scheduling unit 333, and a drive control unit 334. The memory control unit 332 includes a page memory 335 and an image data transfer unit. 336.

  The image data generation unit 331 is a module that generates image data in a format that can be processed by the print execution unit 350 based on the print data received by the communication processing unit 344. Specifically, the image data generation unit 331 develops print job data (including a group of image data read by the scanner 300) acquired through the scanner 300 or the communication processing unit 344 as image data on the page memory 335. Perform the process. The expanded image data is stored in the page memory 335 through the memory control unit 332.

  The memory control unit 332 is a module that acquires a set of a plurality of image data belonging to a series of print processes as print job data, and controls writing and reading of image data to and from the page memory 335. In the present embodiment, the memory control unit 332 manages a plurality of data acquisition paths for acquiring each print job data from the communication processing unit 344 and the scanner 300, and processes a plurality of print job data acquired from different data acquisition paths in parallel. It has a function to process. Specifically, the memory control unit 332 includes a page memory 335 and an image data transfer unit 336.

  The page memory 335 is a memory device that temporarily stores a plurality of image data related to image formation, has a storage area of a predetermined capacity, and is based on control by the memory control unit 332. Access addresses and write and read data. On the other hand, the image data transfer unit 336 performs processing to transfer the image data stored in the page memory 335 to the print execution unit 350 while adjusting the timing in units of pages.

  In this embodiment, the page memory 335 and the image data transfer unit 336 are connected by a PCI bus or the like, and correspond to burst transfer in which a plurality of data is transferred continuously based on one address information. Yes. In burst transfer, image data to be transferred is continuously stored on the page memory 335 in page units (front and back sides in double-sided printing). Then, the image data transfer unit 336 transfers the image data to the print execution unit 350 in order to start image printing when the image data to be formed on each sheet P is stored and held in the page memory 335.

  In the image forming process, the scheduling unit 333 determines the speed, order, and timing related to the feeding of the paper P to be printed on the front surface, the refeeding of the paper P whose front and back are reversed through the reversing path, and the image formation and conveyance. It is a module to do. Then, based on the schedule determined by the scheduling unit 333, the print execution unit 350 and the drive control unit 334 execute an image forming process and a conveyance operation.

  Note that in the present embodiment, the printing apparatus 100 has a function of interrupting and transporting the thin paper P for dummy paper P (thick paper) for adjusting the paper alignment on the paper discharge tray 140. For this reason, the scheduling unit 333 has a function of performing the following scheduling.

  That is, in response to the interrupt conveyance function of the dummy paper P, the scheduling unit 333 sets the dummy paper P (thick paper) on which an image is not formed by a print job to the paper P on which an image is formed by a print job. By interrupting the feeding of the (thin paper) from the paper feeding path FR, a schedule for feeding the registration unit R from the paper feeding path FR is determined. The reason for performing such scheduling is to prevent the paper alignment of the thin paper P discharged to the paper discharge tray 140 from being disturbed when a print job using the thin paper P is executed.

  That is, when the thin paper P is discharged from the first sheet to the paper discharge tray 140, the leading edge of the thin paper P is lifted as shown in FIG. Cause deformation. When such deformation occurs, the discharge position and direction of the thin paper P are disturbed, and the paper alignment of the thin paper P stacked on the paper discharge tray 140 is disturbed.

  On the other hand, when the thick paper P is discharged to the paper discharge tray 140, the thick paper P is not deformed against the resistance of air staying in the paper discharge tray 140 as shown in FIG. The paper is discharged onto the paper discharge tray 140. At this time, an airflow X is generated in the paper discharge tray 140 in a direction along the passage path of the discharged thick paper P.

  Accordingly, when the thick paper P is discharged to the paper discharge tray 140 prior to the thin paper P, the thin paper P to be subsequently discharged rides on the airflow X generated by the thick paper P and the leading edge is The paper is discharged to the paper discharge tray 140 without causing deformation such as floating. For this reason, it is possible to prevent the paper alignment of the thin paper P stacked on the paper discharge tray 140 from being disturbed.

  Note that the airflow X generated by the thick paper P is weakened and disappears with time. Until the airflow X disappears, the thin paper P rides on the airflow X and is discharged to the paper discharge tray 140 without deformation. Accordingly, it is desirable that the interval between the discharge of the thick paper P and the discharge of the next thin paper P is as short as possible.

  For example, the time between sheets when thin paper P is continuously fed and discharged is usually determined to a length suitable for realizing the processing capability required of the printing apparatus 100. Therefore, it is desirable to discharge the next thin sheet P after discharging the thick sheet P at intervals equal to or less than the sheet interval time within the range of the maximum processing capability of the printing apparatus 100, using the sheet interval time as a guide. .

  As described above, the scheduling unit 333 continuously feeds a thin sheet P after feeding a thick sheet P when a print job using a plurality of thin sheets P continuously occurs. Scheduling to form an image of a paper print job with the head unit 110 is performed.

  The scheduling unit 333 also performs scheduling for restoring the airflow X that weakens with time to the initial momentum. This scheduling is a scheduling for interrupting and feeding one thick sheet P every time the continuous number of thin sheets P reaches a predetermined number. After the interruption of thick paper P, the remaining thin paper P is continuously fed and the remaining image of the print job is formed by the head unit 110.

The thick paper P and the thin paper P can be distinguished from each other by using the basis weight (unit: g / m ² ) of the paper P. As a guide, a paper P of 52 g / m ² or less can be defined as a thin paper P. Further, the thick paper P and the thin paper P may be distinguished by using “pure stiffness” (unit μN · m ² / m) as an alternative parameter proportional to the basis weight. As a guide, a paper P of 75 μN · m ² / m or less can be defined as a thin paper P.

In the present embodiment, the basis weight threshold of the paper P is set to 53 g / m ^2, and whether the paper P is thicker or lighter paper P is distinguished depending on whether the basis weight of the paper P exceeds the threshold.

  Further, the predetermined number of sheets described above can be the same as the number of discharged thin sheets P that are obtained by experiment, for example, before the airflow X is weakened and disappears with the lapse of time. In the present embodiment, the predetermined number is 10.

  When performing such scheduling, the scheduling unit 333 confirms the paper quality (whether it is thin paper) of the paper P used for image formation by referring to the attributes of the print job, and based on the result, the paper P feeding order, timing, etc. are determined as a schedule. Here, the attribute of the print job is an attribute relating to print processing. In this embodiment, the attribute includes the size and quality of the paper P (thick paper, thin paper, etc.).

  Then, the memory control unit 332 sets a storage area of the page memory 335 allocated to the print job using the thin paper P based on the schedule determined by the scheduling unit 333.

  Note that the memory control unit 332 secures a storage area corresponding to the thick paper P in the page memory 335 when the scheduling unit 333 performs scheduling to interrupt the thin paper P and feed the thick paper P. To do. At this time, dummy image data different from the image of the print job may be stored in the storage area corresponding to the thick paper P, or may be blank without storing the image data.

  When the storage area corresponding to the thick paper P in the page memory 335 is blank, the head unit 110 does not form an image on the thick paper P. When the dummy image data is stored in the storage area corresponding to the thick paper P in the page memory 335, a dummy image is formed on the thick paper P in the head unit 110.

  The drive control unit 334 operates the registration driving unit 240, the driving roller 162, the tray driving units 230a to 230d, the side paper feeding driving unit 220, and the like according to the schedule determined by the scheduling unit 333, and transports the paper P. Module to perform.

  For example, when executing a print job using a plurality of thin sheets P, the drive control unit 334 controls the sheet feeding unit to start feeding the sheets P according to the schedule by the scheduling unit 333. At this time, the paper P starts to be fed when the image data of the thin paper P related to the print job is stored in the page memory 335 or the image data of the thin paper P related to the print job. And the dummy image data of the thick paper P not related to the print job is stored and held in the page memory 335.

  The print execution unit 350 is a module that controls the head unit 110, which is an image forming unit, and its peripheral circuits, and the image forming process is executed under the control of the print execution unit 350.

(Printer operation)
Next, the operation of the printing apparatus 100 having the above configuration when executing a print job using a plurality of thin sheets P will be described.

  First, when print job data is received from the PC, the data is input to the arithmetic processing unit 330, and the image data generation unit 331 develops the image data into a format that can be processed by the print execution unit 350. The developed image data is temporarily stored and held in the page memory 335 through the memory control unit 332.

  The image data developed on the page memory 335 is transferred at high speed by burst transfer through PCI by the image data transfer unit 336. In order to perform this burst transfer, it is necessary that image data is continuous on the page memory 335 in the order of printing. Therefore, in the present embodiment, the scheduling unit 333 determines the paper feed order, image formation timing, and the like as a schedule according to the content of the attribute data related to the paper quality of the print job.

  Here, it is assumed that the quality of the paper P used for image formation is thin paper P as attribute data of the print job. Further, it is assumed that the print job is set to, for example, 20 pages (sheets) single-sided printing as attribute data.

  Hereinafter, the contents of scheduling performed by the scheduling unit 333 will be described with reference to the flowchart of FIG. The scheduling unit 333 first checks whether or not the attribute data of the print job is set to use the thin paper P from the first sheet (step S1).

  If the setting is not to use the thin paper P from the first sheet (NO in step S1), normal pattern scheduling is performed (step S5), and the series of scheduling processes is terminated. On the other hand, if the setting is to use thin paper P from the first sheet (YES in step S1), the number of sheets using thin paper P is one (one page for single-sided printing, front and back for double-sided printing). 2 pages) is confirmed (step S3). Even when the number of thin sheets P used is one (YES in step S3), scheduling of the normal pattern in step S5 is performed, and the series of scheduling processes is terminated.

  Here, in the normal pattern scheduling in step S5, the scheduling unit 333 feeds the number of pages (number of sheets) and the paper quality P set in the attribute data of the print job, and the head unit 110 transfers the image to the paper P ( , A schedule of contents to be discharged onto the discharge tray 140 is determined.

  On the other hand, if the number of printed sheets is not one (NO in step S3), it is confirmed based on the attribute data whether or not the number of sheets using the thin paper P exceeds a predetermined number (10 sheets in the present embodiment). (Step S7). If the number of thin paper P does not exceed the predetermined number (NO in step S5), the first pattern is scheduled (step S9). If the number of thin paper P exceeds the predetermined number (step S9) In step S7, the second pattern is scheduled (step S11), and both the series of scheduling processes are terminated.

  Here, the schedule determined by the scheduling unit 333 in the scheduling of the first pattern in step S9 has the following contents. That is, a thick sheet P is fed as a dummy sheet for the first sheet, and a thin sheet P is fed for the number of printed sheets after the second sheet. After the head unit 110 forms an image corresponding to the print job, the thick paper P and the thin paper P are discharged to the paper discharge tray 140 in the paper feeding order.

  Further, the schedule determined by the scheduling unit 333 in the second pattern scheduling in step S11 has the following contents. That is, a thick sheet P is fed as a dummy sheet as the first sheet, and a thin sheet P is fed as many sheets as the number of printed sheets from the second sheet. Each time, the thick paper P is interrupted and fed, and on the thin paper P (one or both sides), the head unit 110 forms an image corresponding to the print job, and then the thick paper P The thin paper P is discharged to the paper discharge tray 140 in the paper feeding order.

  When forming a dummy image unrelated to the print job on the dummy thick paper P, the thick paper is used in the head unit 110 in each scheduling of the first and second patterns in step S9 and step S11. A schedule including forming a dummy image on P (one side or both sides) is determined.

  Incidentally, whether or not to form a dummy image on the thick dummy paper P is determined by, for example, attribute data of a print job sent from a PC connected to the printing apparatus 100 or a user instruction via the operation panel 340. Thus, the print condition setting unit 341 may accept the print condition as one of the print condition settings. In this case, the printing condition setting unit 341 corresponds to the selection unit in the claims.

  In the printing apparatus 100 of the present embodiment configured as described above, when a print job that uses two or more thin papers P is generated, the thick paper P is first fed and discharged. The paper is discharged onto the tray 140, and the airflow X shown in FIG. 4 is generated along the passage path of the discharged thick paper P. Then, after the thin paper P is fed to form an image by a print job, the thin paper P is discharged onto the paper discharge tray 140 by being placed on the airflow X.

  When the number of images to be printed on the thin paper P by the print job exceeds 10, the thick paper P is interrupted and discharged one by one for every 10 thin paper P fed / discharged. Is done. Thus, the airflow X in the paper discharge tray 140 is maintained without weakening and disappearing until all the thin paper P is discharged after the image formation.

  The thin paper P riding on the airflow X is discharged to the paper discharge tray 140 without causing deformation such as the leading edge being lifted. For this reason, the thin paper P can be discharged and stacked on the paper discharge tray 140 without disturbing the paper alignment.

  However, even if a print job is set to use thin paper P, if the number of printed sheets is one, one thin paper P is fed as it is to form an image and then discharged to the paper discharge tray 140. Paper. In this case, as shown in FIG. 3, the thin paper P that is discharged to the paper discharge tray 140 is deformed such that the leading edge of the thin paper P is lifted due to the resistance of air staying in the paper discharge tray 140. The delivery position and direction of P are disturbed. However, since only one sheet is discharged and it is not necessary to align the sheets, there is no problem.

  Regardless of whether the number of prints is one or more, when executing a print job that uses thin paper P, the thick paper P is generally fed and discharged as the first sheet, followed by printing. The thin paper P related to the job may be fed and discharged. In that case, if it is set to use the thin paper P from the first sheet in step S1 in the flowchart of FIG. 5 (YES), the process proceeds to step S7, and the number of sheets using the thin paper P is the predetermined number ( In this embodiment, whether or not the number exceeds 10) is confirmed based on the attribute data.

  However, as in the present embodiment, only when a print job set to use a plurality of thin paper P is executed, if the thick paper P is interrupted and discharged, the thick paper P Consumption can be reduced by refraining from use.

  Further, it is preferable that the time interval from the supply / discharge of the thick paper P to the supply / discharge of the next thin paper P is shorter in consideration of the fact that the airflow X of the discharge tray 140 becomes weaker with time. However, the paper supply / discharge interval between the thick paper P and the next thin paper P may be longer than the time between papers when the thin paper P is continuously supplied and discharged.

  By the way, in the embodiment described above, there is no mention of the paper sizes of the thin paper P and the thick paper P. Commonly speaking, the thick paper P should be the same paper size as the thin paper P, but the thick paper P may be larger than the thin paper P in the paper transport direction. For example, when A4 size portrait paper with the short side along the transport direction is used as the thin paper P, A3 size landscape paper with the long side along the transport direction is used as the thick paper P. It may be used.

  When a sheet having a larger size in the sheet conveyance direction than the thin paper P is used as the thick paper P, it takes a longer time than the thin paper P to discharge the paper to the discharge tray 140, and the discharge tray Thick paper P passes through the air staying at 140. Accordingly, the airflow X generated in the paper discharge tray 140 due to the discharge of the thick paper P is more stable and longer than the case where the size of the thick paper P in the paper transport direction is the same as that of the thin paper P. Become.

  For this reason, the state in which the thin paper P discharged after the thick paper P rides on the airflow X of the paper discharge tray 140 and is discharged without deformation can be continued for a longer time.

  Further, in the printing apparatus 100 according to the above-described embodiment, the number of thick sheets P to be interrupted and discharged is set to one sheet at a time, but two or more thick sheets P are interrupted to be discharged and discharged at one time. You may do it.

  Furthermore, in the above-described embodiment, the case where the discharge destination of the paper P is the discharge tray 140 has been described as an example, but the present invention is also applied to the case where the discharge destination is the face-up discharge portion 141. Is possible.

  In the above-described embodiment, the printing apparatus 100 has been described by taking an inkjet line color printer as an example. However, the present invention can be widely applied to various image forming apparatuses that can perform printing using thin paper P and stacked paper discharge, such as an electrophotographic system, a stencil printing system, and a multi-pass inkjet printer.

DESCRIPTION OF SYMBOLS 100 Printing apparatus 110 Head unit 120 Side paper feed stand 130a-130d Paper feed tray 140 Paper discharge tray 141 Face-up paper discharge part 150 Paper discharge stand 160 Conveying belt 161 Driven roller 162 Driving roller 170 Switching mechanism 172 Switching mechanism 220 Side paper feeding Drive unit 230a to 230d Tray drive unit 240 Registration drive unit 300 Scanner 330 Arithmetic processing unit 331 Image data generation unit 332 Memory control unit 333 Scheduling unit 334 Drive control unit 335 Page memory 336 Image data transfer unit 340 Operation panel 341 Print condition setting unit 342 Transport state detection unit 343 Display unit 344 Communication processing unit 350 Print execution unit CR Normal transport path DR1 Paper discharge path DR2 Straight paper discharge path FR Paper feed path P Paper R Registration part SR Reverse path X airflow

Claims (6)

Based on the input print job, a plurality of types of sheets having different basis weights are selectively fed from the respective sheet feeding units to the sheet conveying unit, and the sheet after forming the image is discharged by the sheet conveying unit. In an image forming apparatus that discharges and stacks on a paper tray,
When the first sheet of paper on which an image is formed by the print job is a sheet whose basis weight is less than a predetermined threshold, the sheet whose basis weight exceeds the predetermined threshold prior to the first sheet. At least one sheet is fed to the sheet conveying means by a corresponding sheet feeding means, and is provided with an interrupt control means for discharging the sheet onto the sheet discharge tray by the sheet conveying means,
Feeding and discharging the first sheet continuously with the paper feeding and discharging by the interrupt control means;
An image forming apparatus.   As for the sheet fed and discharged by the interrupt control means and the first sheet fed and discharged subsequently, the first and subsequent sheets are fed and discharged based on the print job. 2. The image forming apparatus according to claim 1, wherein the sheet is fed and discharged at a time interval equal to or less than the time interval.   3. The image forming apparatus according to claim 1, wherein the sheet fed and discharged by the interrupt control unit is larger in size in the transport direction by the sheet transport unit than the first sheet.   The interrupt control means feeds / discharges a sheet having a basis weight exceeding the predetermined threshold preceding the first sheet only when there are a plurality of sheets on which an image is formed by the print job. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is paper.   The interrupt control means is configured to determine whether the paper on which an image is formed by the print job is a paper that exceeds a predetermined number of sheets continuously from the first sheet and whose basis weight is lower than a predetermined threshold value. 5. The image forming apparatus according to claim 1, wherein each time a sheet is fed or discharged, at least one sheet having a basis weight exceeding the predetermined threshold is fed and discharged by interruption. .   The image forming apparatus further comprises selection means for selecting whether or not image formation is performed on the paper fed / discharged by the interrupt control means, and when the image forming validity is selected by the selection means, the interruption control means supplies / discharges the paper. The image formation on the paper to be fed / discharged by the interrupt control means is not executed when the image formation on the paper to be paper is executed and invalidity of the image formation is selected by the selection means. The image forming apparatus according to claim 1, 2, 3, 4, or 5.

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