JP2007326235A - Inkjet printer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict contamination of devices and useless consumption of ink by preventing the ink from being ejected to positions without papers if there is no paper at a predetermined printing position because of malfunction such as idle rotation of a feed roller, an error in setting of papers, etc. in an image forming apparatus such as an inkjet printer. <P>SOLUTION: In the inkjet printer 1 with an alignment sensor 11 at either one of two side faces of a main scanning direction side of a carrier 2, a sensor 12 for detecting the same paper as that of the alignment sensor 11 is set at the other side face of the carrier 2. Whether the paper P is present or not at a position where the ink is ejected is correctly detected at all times by using either one of the alignment sensor 11 and the paper detecting sensor 12 which is located ahead of an advancement direction of the carrier 2 that moves back and forth in the main scanning direction. When the paper P is not present, it is determined as the error, and printing processing is terminated by stopping the ejection of ink. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an ink jet printer that performs printing on a sheet by reciprocating a carrier carrying a print head left and right.

  In an image forming apparatus such as a printer or a copying machine, in general, paper is fed one by one from a bundle of paper loaded in a paper feed tray and sent to a printing unit that prints images, characters, and the like. Then, the image is formed and discharged to a paper discharge tray.

  A printing unit such as an ink jet printer is composed of a carrier mounted with a print head that reciprocates in a direction (main scanning direction) orthogonal to the paper conveyance direction (sub-scanning direction), and performs reciprocal movement of the carrier and paper feeding. Images are sequentially formed on the paper by performing the operation synchronously and ejecting ink from the print head onto the paper.

  By the way, in the pick-up processing process for feeding out the paper from the paper feed tray of the printer and the feed processing process for feeding the paper, the paper is skewed or the paper is not fed by a predetermined amount due to a feed error. The print head reciprocates and ejects ink because the paper is not sent to the specified position during printing due to the user forgetting to set the paper or tray to match the paper size used. There may be no paper in the predetermined print area.

  Conventionally, in such a case, since no means for detecting the presence or absence of paper at the position of the print head has been provided, even if there is no paper in a predetermined print area, based on the preset print settings, Since ink is ejected to the area, the platen is soiled with ink or the ink is consumed wastefully.

  In order to remedy these problems, before starting printing, the paper sensor is used to detect the position where the paper is set or to detect the skew of the paper so that ink is applied to the area where there is no paper. There are some which are not discharged, and the following are known.

  For example, in the invention of Patent Document 1, a sheet sensor is provided in a carriage (carrier), and before printing, the carriage is operated from the left end to the right end to detect the left and right ends of the sheet. Then, the print position data scheduled to be printed is compared with the detected paper edge position, and the print data of the portion protruding from the paper is deleted, thereby improving the above problem.

  In the invention of Patent Document 2, a paper width detection sensor is provided in the carriage, the paper width is detected when the paper is taken into the printer, and the degree of inclination of the paper is calculated in advance before printing. The printing range is determined, and printing is performed so that it is within the paper range.

Furthermore, the invention of Patent Document 3 obtains the sheet width and the skew amount of the sheet by an optical sensor provided on the carriage, sets the printable area and optimizes the print area, and also performs this optical operation during the carriage scan. A sensor is used to detect whether or not there is a sheet under the optical sensor, and to avoid ink ejection outside the sheet due to sheet misalignment during printing due to slippage of the conveyance roller or the like.
JP-A-6-31984 JP-A-4-21482 JP 2001-1617 A

  However, as in the inventions of Patent Document 1 and Patent Document 2, in the method of calculating the deviation amount and skew amount of the paper in advance based on the acquired information from the sensor before the start of printing, for example, the feed roller If paper fails to be conveyed due to idling, ink is ejected from the print head even though the paper has not reached the print head position. There is a risk of causing.

  Further, as in the invention of Patent Document 3, by providing one optical sensor in the carriage and detecting the presence or absence of paper at the time of printing, there is a problem of ink ejection to a paper non-reaching portion due to occurrence of idling of the feed roller, etc. However, since the optical sensor is only on one side of the carriage, detection of the paper may be delayed depending on the scanning direction of the print head, and ink may be ejected to the unreachable portion of the paper. there were. Further, since it is necessary to move the sensor unit to the left and right edges of the paper in order to detect the left and right edges of the paper with one sensor, it is necessary to make the scanning width of the carriage moving mechanism wider than the paper width.

  The present invention has been made in view of the above points, and when a sheet is not fed to a predetermined printing position due to a malfunction such as a feed error such as idling of a feed roller, or the size or setting of a sheet to be used is incorrect. Even in such a case, it is possible to provide a high-speed ink jet printer and an image forming apparatus capable of preventing the ink from being ejected to a position where there is no paper and suppressing the contamination of the apparatus and the wasteful consumption of the ink. Objective.

  In order to achieve the above object, the invention of claim 1 is characterized in that a sheet is loaded and a sheet feeding unit that feeds the sheet one by one, a sheet conveying unit that conveys the sheet in the sub-scanning direction, and ink ejected from the nozzles. A print head that forms an image on the paper is mounted and reciprocally moved in the main scanning direction, a paper sensor that detects the presence or absence of paper in the paper transport unit, and alignment correction information in the main scanning direction of the carrier is detected. An alignment sensor composed of a reflective optical sensor, a ROM that stores firmware for controlling the entire apparatus, and an ASIC that includes a CPU that executes the firmware, and the paper sensor includes a paper transport unit The alignment sensor is provided near one of the two side surfaces on the main scanning direction side of the carrier. In the ink jet printer provided on the side surface, a sheet detection sensor composed of the same reflective optical sensor as the alignment sensor is provided on the side surface portion opposite to the side surface portion of the carrier on which the alignment sensor is provided. The CPU continuously acquires sensor information from a sensor positioned forward in the scanning direction of the carrier among the alignment sensor and the sheet detection sensor when the printing process is executed. Detection of the presence or absence of paper at each position in the moving main scanning direction is performed immediately before the carrier arrives, and when it is detected that there is paper in a predetermined printing area as a result of the detection, printing processing is continued, As a result of the detection, when it is detected that there is no paper in the predetermined print area, the ink ejection from the print head is stopped. Te, in which the printing process is terminated.

  According to the second aspect of the present invention, a sheet conveying unit that conveys a sheet in the sub-scanning direction, a print head that forms an image on the sheet, a carrier that reciprocates in the main scanning direction, and the entire device are controlled. An image forming apparatus comprising: a control unit; and a first sheet detection unit and a second sheet detection unit on each side surface of the carrier in the main scanning direction side, and the control unit includes an image forming process. At the time of execution, the sheet detection information is continuously obtained from the sheet detection means located on the front of the carrier in the scanning direction of the first sheet detection means and the second sheet detection means. Detecting the presence / absence of a sheet at each position, and if it is detected that there is a sheet in a predetermined image forming area, the image forming process is continued. Paper When it is detected that there is to end the image formation process.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, at least one of the first paper detection means and the second paper detection means is used for calibration of the carrier in the main scanning direction. It is used to detect correction information.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the first paper detection means and the second paper detection means have the same configuration.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the first paper detection unit and the second paper detection unit are configured by a reflective optical sensor. It is what.

  According to the first aspect of the present invention, in the ink jet printer in which the alignment sensor is provided on one of the two side surfaces on the main scanning direction side of the carrier, the same side as the alignment sensor is provided on the opposite side surface of the carrier. By providing the paper detection sensor, the CPU uses the sensor located on the front side in the traveling direction of the print head mounted on the carrier that reciprocates in the main scanning direction among the alignment sensor and the paper detection sensor. It is always possible to accurately detect whether there is a sheet at a position immediately before the print head ejects ink. If the result of detection is that there is no paper, the CPU stops ink ejection. Therefore, even when the paper is not sent to a predetermined printing position due to a malfunction such as a feed error, it is detected that there is no paper at the expected ink ejection position immediately before ink ejection, so ink ejection to that position is stopped. As a result, the device is prevented from being soiled and wasteful ink consumption. In addition, even if the user uses the wrong paper size, paper feed position, device or device driver settings, ink is not ejected at a position where no paper is detected at the expected ink ejection position. , Equipment pollution and wasteful consumption of ink are prevented.

  In addition, since the reflection type optical sensors are provided on both surfaces in the reciprocating direction of the carrier, the presence / absence of a sheet in front of the carrier traveling direction is always detected immediately before the arrival of the carrier. Accordingly, it is possible to more reliably detect the sheet, and it is possible to improve the printing speed by minimizing the amount of carrier movement necessary to detect the left and right edges of the sheet.

  According to the second aspect of the present invention, in the image forming apparatus provided with the first sheet detecting unit and the second sheet detecting unit on each side surface of the carrier in the main scanning direction side, the control unit is configured to execute the image forming process. Of the first paper detection means and the second paper detection means, the position immediately before the print head forms an image on the paper by using the paper detection means that is positioned forward in the traveling direction of the carrier. In addition, it is possible to accurately detect whether or not a sheet is present. As a result of the detection, if there is no sheet, the control unit stops forming an image on the sheet. Accordingly, even when the paper is not sent to a predetermined printing position due to a malfunction such as a feed error, it is detected that there is no paper at the planned image forming position immediately before the image formation. Stopped, the waste of equipment and wasteful consumption of ink and the like are prevented. In addition, even if the paper size used by the user, the paper feed position, the device or device driver settings are incorrect, an image is not formed at the detected position when there is no paper at the planned image formation position. Equipment contamination and wasteful consumption of ink and the like are prevented.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, at least one of the first paper detection means and the second paper detection means is used for calibration in the main scanning direction of the carrier. Therefore, it is not necessary to provide a separate sensor for calibration. Therefore, the function can be improved at a low cost without increasing the number of parts. Further, since no extra installation space is required, the device can be miniaturized.

  According to the invention of claim 4, in the image forming apparatus according to claim 2 or claim 3, since the first sheet detecting means and the second sheet detecting means have the same configuration, the same parts are used. Cost can be reduced.

  According to the invention of claim 5, in the image forming apparatus according to claims 2 to 4, since the first paper detection means and the second paper detection means are constituted by the reflection type optical sensor, the paper It is possible to detect the presence / absence of a sheet in a non-contact manner without touching the sheet and bending the sheet or making a line.

  Hereinafter, the configuration of an ink jet printer according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. First, a schematic configuration of the entire inkjet printer will be described with reference to FIG. FIG. 1 shows the structure of the main part of the inkjet printer.

  An ink jet printer 1 (image forming apparatus) reciprocates a carrier 2 on which an ink cartridge 3 having a print head 3a (image forming means) for ejecting ink is mounted in a main scanning direction (indicated by an arrow A in the figure). Thus, an image is formed on the paper P that is conveyed in the sub-scanning direction (indicated by an arrow B in the figure) orthogonal to the main scanning direction. The inkjet printer 1 is connected to, for example, an external personal computer (not shown), and forms an image on the paper P based on data and commands transmitted from the personal computer.

  The ink jet printer 1 has a paper feed tray 20 as a paper feed unit for holding the paper P to be printed on the upper rear side of the chassis 10, and printed paper below the front surface of the chassis 10. A paper discharge tray 30 for discharging P is provided.

  Inside the chassis 10 of the ink jet printer 1 are a carrier 2, an ink cartridge 3 mounted on the carrier 2, a shaft 4 disposed on the back side of the carrier 2 so that the main scanning direction is the longitudinal direction, and paper A paper transport mechanism 5 serving as a paper transport unit for transporting P, a carrier drive mechanism 6 that applies a driving force to the carrier 2 to reciprocate, and a chassis 10 that is used to detect the position of the carrier 2 in the main scanning direction. In addition, an encoder scale 7 arranged along the main scanning direction and a circuit board 8 on which a control circuit for controlling various operations of the ink jet printer 1 is mounted.

  The carrier 2 supports the ink cartridge 3 so that it can be inserted and removed. In the present embodiment, two ink cartridges 3 are mounted on the carrier 2, one filled with black ink and one filled with color inks of, for example, three colors of cyan, magenta, and yellow. That is, the inkjet printer 1 is configured to be able to form a color image on the paper P. The configuration of the ink cartridge 3 mounted on the carrier 2 is not limited to this. For example, the black ink and the color ink are combined into one, or the color ink is separately sealed for each color. It may be. In addition, the ink jet printer 1 may be one in which only the ink cartridge 3 in which black ink is sealed in the carrier 2 is mounted, and an image such as a gray scale is formed.

  The carrier 2 is slidably fitted to the shaft 4 and is connected to a part of the belt 6a of the carrier driving mechanism 6 as will be described later, and is arranged to be movable in the main scanning direction while sliding with the shaft 4. ing. The carrier 2 is equipped with a photocoupler (not shown), and the photocoupler scans the encoder scale 7 having a predetermined resolution so that the position of the carrier 2 in the main scanning direction can be detected. It is configured.

  In addition, on the left and right side surfaces of the carrier 2, that is, the front and back portions in the main scanning direction, one surface (the left side as viewed from the paper discharge tray 30) is formed with a reflective optical sensor. The sensor 11 is provided, and on the other surface (right side as viewed from the paper discharge tray 30 side), the same reflective optical as the alignment sensor 11 (first paper detection means or second paper detection means). A sheet detection sensor 12 (a first sheet detection unit or a second sheet detection unit) configured by a sensor is provided so that the detection surface faces the lower side where the sheet P exists.

  The alignment sensor 11 is a sensor for performing calibration in the main scanning direction of the carrier 2 when the ink cartridge 3 is replaced. For example, the alignment sensor 11 prints a line pattern or the like at a predetermined interval on the paper P and prints this print image. By detecting with the alignment sensor 11, it is determined whether the control of the carrier 2 in the main scanning direction is accurately performed, and the position of the carrier 2 and control parameters are corrected as necessary.

  The alignment sensor 11 and the paper detection sensor 12 are sensors for detecting the presence or absence of the paper P during the printing process, that is, when the carrier 2 reciprocates in the main scanning direction while ejecting ink from the print head 3a. It has come to be used. The presence / absence of the paper P by the alignment sensor 11 and the paper detection sensor 12 is determined by using the difference in light reflectance between the surfaces of the paper P and other parts (black platen or the like). A high sensor output voltage is obtained, and when there is no paper P, the output voltage is low.

  Since the sheet detection sensor 12 has the same configuration as the alignment sensor 11, it can also be used for the calibration similar to the alignment sensor 11. The paper detection sensor 12 is not necessarily limited to the same sensor as the alignment sensor 11 as long as it can detect the presence or absence of the paper P.

  The carrier drive mechanism 6 includes, for example, an annular belt 6a disposed along the main scanning direction on the chassis 10 of the inkjet printer 1, and a DC motor 6b for rotating the belt 6a. is there. A part of the belt 6 a is connected to the rear of the carrier 2. The carrier driving mechanism 6 rotates the belt 6a by the DC motor 6b to apply a driving force to the carrier 2 to reciprocate in the main scanning direction. The carrier driving mechanism 6 is not limited to this configuration.

  The paper transport mechanism 5 is provided with a feed roller (not shown) for transporting the paper P, and the paper P fed from the paper feed tray 20 by a pick roller (not shown) is placed in the main body of the inkjet printer 1. The paper is fed in synchronization with the reciprocating movement of the carrier 2. The feed rollers are a pair of upper and lower rollers made of a material having a high friction coefficient such as rubber and the like that is rotationally driven by a drive motor 5b such as a stepping motor via a drive force transmission means 5a such as a gear.

  Also, a paper sensor (not shown) is provided in the vicinity of the paper feed mechanism 5 on the side of the paper feed tray 20. When the paper P is supplied from the paper feed tray 20 to the paper feed mechanism 5, the paper sensor It comes to detect. This paper sensor is composed of a mechanical switch such as a micro switch. When the paper P enters the paper transport mechanism 5, the switch comes into contact with a part of the paper surface and is turned on. It can be detected. Note that the paper sensor is not limited to a mechanical switch as long as it can detect the presence or absence of the paper P, and may be, for example, a reflective optical sensor.

  The circuit board 8 is held on the back side of the chassis 10. A control circuit mounted on the circuit board 8 controls operations of the paper transport mechanism 5, the carrier drive mechanism 6, the print head 3a, and the like. Then, print processing is executed based on control commands and data received from software such as a device driver operating on an external computer. The control circuit may be configured to operate a predetermined function in response to an operation button (not shown) provided on the inkjet printer 1 that can be operated by the user operated by the user. .

  Next, the configuration of the control system of the inkjet printer 1 will be described with reference to FIG. FIG. 2 shows the configuration of the control system of the inkjet printer 1 when connected to a computer. An ASIC (Application Specific IC) 13 serving as a control unit is provided on the circuit board 8 and includes a CPU 14 that performs arithmetic processing, a ROM (Read Only) in which initial setting information of the inkjet printer 1 and firmware 15 (program) are stored. Memory 16 (non-volatile storage means), RAM (Random Access Memory) 17 used for a work area, and the like. In addition, the inkjet printer 1 includes an interface unit 18 such as a USB (Universal Serial Bus) or IEEE1394 standard, and is connected to the computer 50 via the interface unit 18.

  The CPU 14 executes the firmware 15 stored in the ROM 16 to perform operation control and status monitoring of the entire inkjet printer 1, and based on control commands and print data from the connected computer 50, the paper transport mechanism 5. And the drive motor of the carrier drive mechanism 6 and various devices such as the print head 3a are integratedly controlled to execute the printing process.

  A device driver 52 for controlling the inkjet printer 1 is installed in the HDD 51 built in the computer 50. For example, when image data stored in the computer 50 is printed by the inkjet printer 1, The computer 50 transmits image data to the inkjet printer 1 via the device driver 52 to print it.

  When transmitting print data of image data to the inkjet printer 1, the device driver 52 transmits print setting information such as paper size, paper type, and resolution set by the computer 50 to the inkjet printer 1 simultaneously with the print data. . The inkjet printer 1 that has received these data executes print data print processing based on the sent print setting information.

  Next, the flow of ink ejection control using the alignment sensor 11 and the paper detection sensor 12 by the inkjet printer 1 according to the above configuration will be described with reference to FIGS. FIG. 3 shows a flow of detecting the presence or absence of the paper P using the alignment sensor 11 and the paper detection sensor 12, and determining whether to continue or end the printing process. 4A shows how the alignment sensor 11 detects the paper P when the carrier 2 scans in the left direction, and FIG. 4B shows how the paper P is detected by the paper detection sensor 12 when the carrier 2 scans in the right direction. (C) shows a state in which no paper is detected by the paper detection sensor 12 (paperless error) when the carrier 2 is scanned in the right direction.

  When print setting information and print data are sent from the computer 50 to the inkjet printer 1 via the device driver 52, the CPU 14 starts a paper feed process and feeds the paper P one by one to the paper transport mechanism 5. Pull out. In the paper transport mechanism 5, when the paper sensor 19 (see FIG. 2) detects the paper P, the drive motor 5b for rotating the feed roller of the paper transport mechanism 5 is driven to start the paper feed process.

  The CPU 14 ejects ink from the print head 3a according to the contents of the print setting information and the print data while reciprocating the carrier 2 in the main scanning direction in synchronization with the paper feed of the paper P, and sequentially prints images on the paper. To form. At this time, as shown in FIG. 3, the CPU 14 determines whether or not the carrier 2 next moves leftward as viewed from the paper discharge tray 30 side (S1), and then the carrier 2 moves leftward. When moving to (YES in S1), the CPU 14 starts detecting the paper P using the alignment sensor 11 on the left side of the carrier 2 (S2), and the carrier 2 as shown in FIG. Is moved leftward (S4). Next, when the carrier 2 does not move in the left direction (when it moves in the right direction) (NO in S1), detection of the paper P by the paper detection sensor 12 on the right side of the carrier 2 is started (S3). As shown in FIG. 4B, the carrier 2 is moved rightward (S5). Then, while moving the carrier 2, it is detected whether there is a sheet P from the sensor information from the sensor located on the front side in the traveling direction of the carrier 2 among the alignment sensor 11 and the sheet detection sensor 12 (S <b> 6). As shown in FIG. 4C, when it is detected that there is no paper P in a predetermined printing area (image forming area) set by paper setting or the like (NO in S6), it is determined as a paperless error (S8). Then, the ejection of ink from the print head 3a is stopped, the paper P is discharged to the paper discharge tray 30, and the printing process is ended. If it is detected that there is a sheet P (YES in S6), a printing process is performed (S7), it is further determined whether the printing process is continued (S9), and if the printing process is continued. (YES in S9), the process returns to S1 again, and the same process as described above is repeated. If it is determined that the printing process is finished (NO in S9), the paper P is discharged to the paper discharge tray 30 and the printing process is finished.

  By configuring the inkjet printer 1 as described above and providing the alignment sensor 11 on one side of the carrier 2 and providing the same sheet detection sensor 12 as the alignment sensor 11 on the other side, the CPU 14 Among the alignment sensor 11 and the paper detection sensor 12, the print head 3a is always used by using the reflective optical sensor located in front of the traveling direction of the print head 3a mounted on the carrier 2 reciprocating in the main scanning direction. It is possible to accurately detect whether or not the paper P is present at a position immediately before ink is ejected.

  If the result of detection is that there is no paper P, the CPU 14 stops ink ejection. Accordingly, even when the paper P is not sent to a predetermined printing position due to a malfunction such as a feed error, it is detected that there is no paper P at the expected ink ejection position immediately before ink ejection. Is stopped, and the device is prevented from being soiled and wasted ink. In addition, even if the user has mistakenly set the size of the paper P to be used, the paper feed position, the device or the device driver, the ink is detected at the position where it is detected that there is no paper P at the expected ink discharge position. Since the ink is not ejected, the device is prevented from being polluted and the ink wasted.

  In addition, since the reflective optical sensors are provided on the two side surfaces of the carrier 2 on the reciprocating direction side, the presence or absence of the paper P in the forward direction of the carrier 2 is always detected immediately before the arrival of the carrier 2. Accordingly, it is possible to detect the paper more reliably, and to improve the printing speed by minimizing the amount of carrier movement necessary to detect the left and right edges of the paper P.

  In addition, the alignment sensor 11 used for detecting correction information for calibration in the main scanning direction of the carrier 2 also has a function as a sheet detection sensor, so that it can function at low cost without increasing the number of parts. Can be improved. Further, since no extra installation space is required, the device can be miniaturized.

  In addition, since the alignment sensor 11 and the paper detection sensor 12 have the same configuration, the cost can be reduced by using the same components. Further, since the alignment sensor 11 and the paper detection sensor 12 are constituted by reflection type optical sensors, the presence or absence of the paper P can be checked without contact with the paper P without bending or scoring the paper P. Can be detected.

  The present invention is not limited to the configuration of each of the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in the present embodiment, an ink jet printer is illustrated, but the printing method is not limited to the ink jet method as long as the print head is reciprocated in the main scanning direction to form an image on a sheet. .

The perspective view which shows the structure of the mechanism of the principal part of an inkjet printer. The block diagram of the control system of the inkjet printer at the time of computer connection. 6 is a flowchart of a printing process using an alignment sensor and a paper detection sensor. (A) is a schematic diagram showing how a sheet is detected by the alignment sensor when scanning the carrier in the left direction, (b) is a schematic diagram showing how the sheet is detected by the sheet detection sensor when scanning the carrier in the right direction, and (c). FIG. 4 is a schematic diagram showing a state when a paperless error occurs during scanning of the carrier in the right direction.

Explanation of symbols

1 Inkjet printer (image forming device)
2 Carrier 3 Ink cartridge 3a Print head 5 Paper transport mechanism (paper transport unit)
6 Carrier drive mechanism 8 Circuit board 10 Chassis 11 Alignment sensor (first paper detection means or second paper detection means)
12 Paper detection sensor (first paper detection means or second paper detection means)
13 ASIC (control means)
14 CPU
15 Firmware (Program)
19 Paper sensor 20 Paper feed tray (paper feed unit)
50 Computer 52 Device driver

Claims (5)

A paper feed unit that loads paper and feeds the paper one by one;
A paper transport unit for transporting paper in the sub-scanning direction;
A print head that discharges ink to form an image on the paper and is reciprocated in the main scanning direction;
A paper sensor for detecting the presence or absence of paper in the paper transport unit;
An alignment sensor composed of a reflective optical sensor for detecting alignment correction information in the main scanning direction of the carrier;
A ROM that stores firmware for controlling the entire device, and an ASIC that includes a CPU that executes the firmware;
The paper sensor is provided in the vicinity of the paper feed unit side of the paper transport unit,
In the inkjet printer in which the alignment sensor is provided on one of the two side surfaces on the main scanning direction side of the carrier,
A sheet detection sensor composed of the same reflective optical sensor as the alignment sensor is provided on the side surface portion opposite to the side surface portion of the carrier on which the alignment sensor is provided,
The CPU
During the printing process, the main scanning direction in which the carrier moves by continuously acquiring sensor information from the alignment sensor and the paper detection sensor that are located forward in the traveling direction of the carrier. Immediately before the carrier arrives to detect the presence or absence of paper at each of the positions,
As a result of the detection, when it is detected that there is paper in the predetermined print area, the printing process is continued,
As a result of the detection, when it is detected that there is no paper in a predetermined printing area, the ink ejection from the print head is stopped and the printing process is terminated. A paper transport unit for transporting paper in the sub-scanning direction;
A print head that forms an image on the paper is mounted and reciprocated in the main scanning direction;
In an image forming apparatus comprising a control means for controlling the entire device,
A first paper detection means and a second paper detection means on each side surface of the carrier in the main scanning direction side;
The control means includes
When the image forming process is executed, the sheet detection information from the sheet detection unit located on the front side in the traveling direction of the carrier among the first sheet detection unit and the second sheet detection unit is continuously received. Obtain and detect the presence or absence of paper at each position,
As a result of the detection, when it is detected that there is a sheet in a predetermined image forming area, the image forming process is continued,
As a result of the detection, when it is detected that there is no sheet in the predetermined image forming area, the image forming process is ended.   At least one of the first paper detection unit and the second paper detection unit is used to detect correction information for calibration in the main scanning direction of the carrier. Item 3. The image forming apparatus according to Item 2.   The image forming apparatus according to claim 2, wherein the first paper detection unit and the second paper detection unit have the same configuration.   5. The image forming apparatus according to claim 2, wherein the first paper detection unit and the second paper detection unit are configured by a reflective optical sensor. 6.

Images