JP2010115784A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which can improve an image formation accuracy. <P>SOLUTION: The image forming apparatus is comprised of an EEPROM 17 which stores both a specified count number I between detection positions A and C of first and second paper detection sensors 6A and 6B and a specified count number J between the detection position A of the first paper detection sensor 6A and a reference position D of a second head module 4B, a conveyance amount measuring part 13b which counts a measured count number i between the detection positions A and C, an estimating part 13c which estimates a second reference value S2 presumed to be measured as a distance from the detection position A to the reference position D on the basis of the specified count number I, measured count number i and specified count number J, and a printing control part 13d which starts the driving control of a head 5 by the second head module 4B on the basis of the fact that the measured count number of paper M from the detection position A reaches the second reference value S2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image by ejecting an image forming material onto an image forming medium, and in particular, has a head on which a plurality of nozzles that eject image forming material are formed, and conveys the image forming medium. The present invention relates to an image forming apparatus having a plurality of head modules arranged at different positions in a direction.

  2. Description of the Related Art Conventionally, an ink jet printer that forms an image by ejecting ink, which is an example of an image forming material, is known. In such an ink jet printer, printing is performed in the paper width direction by moving a carriage on which a head having a plurality of nozzles for ejecting ink is mounted in a direction (paper width direction) perpendicular to the paper transport direction. Things are generally known.

  In the ink jet printer that prints by moving the head, the process of printing by moving the head and the process of transporting the paper are alternately executed, and there is a problem that the image forming speed is slow.

  Therefore, in recent years, a line ink jet printer that has a head module capable of ejecting ink over an entire row in the paper width direction and that can print in the paper width direction without moving the head has appeared. In such a line ink jet printer, for example, in order to realize high image quality and multiple colors, a plurality of head modules are arranged in the paper transport direction.

  For example, in such a line inkjet printer, after a paper detection sensor detects that the paper has been conveyed to a predetermined position by a single paper detection sensor provided upstream in the paper conveyance direction, When the paper is transported to the respective positions for starting the drive control by each head module (when a predetermined amount corresponding to the head module is transported), the head drive control of each head module is started. Thus, the ejection of ink is controlled. Here, the transport amount of the paper can be grasped by, for example, the count value of the pulse of the signal obtained by detecting the encoder scale provided on the belt for transporting the paper by the encoder.

  For example, in a printer, as a technique for improving the conveyance accuracy of a printing medium, the conveyance correction amount due to product variation is stored in the printer body, and the conveyance correction amount according to the paper type / printing speed is stored in the printer driver of the computer body. A technique for controlling the conveyance based on these conveyance correction amounts is known (see, for example, Patent Document 1).

JP 2004-114618 A

  In the above-described line ink jet printer, the paper conveyance amount after that is detected on the basis of the detection time point of the paper by one paper detection sensor provided on the upstream side in the paper conveyance direction, and according to the conveyance amount, The head drive control of each head module is started.

  For example, when a sheet is conveyed by a belt, a paper slip on the belt may occur. In addition, when the paper conveyance amount is detected by the encoder, there may be an error in the conveyance amount detected by the encoder. The closer the head module is to the downstream side of the paper transport direction from the paper detection sensor, the greater the effect of paper slip and the detection error by the encoder, and the larger the print position error on the paper during image formation. There is a risk that the image forming accuracy is lowered.

  The technique of Patent Document 2 described above is a printer that intermittently conveys paper for printing and controls the amount of paper conveyance based on the correction amount, and is a printer other than a printer that intermittently conveys paper for printing. For example, it cannot be applied to a printer that prints while conveying paper at a constant speed.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique capable of improving image forming accuracy.

  To achieve the above object, the image forming apparatus according to the first aspect of the present invention includes a plurality of medium detection sensors that detect whether or not an image forming medium exists at a plurality of different detection positions in the conveyance direction of the image forming medium. An image forming apparatus having a head on which a plurality of nozzles for ejecting an image forming material are formed, and a plurality of head modules arranged at different positions in the transport direction. A set distance value between sensors based on a setting between a position and a detection position of another medium detection sensor downstream from the one medium detection sensor, a detection position of one medium detection sensor, and one or more head modules A distance for storing a reference position setting distance value related to a distance based on a setting with respect to a reference position on which an image forming medium to be positioned as a reference for starting drive control of the head is stored The image forming medium is transported from when it is detected that the image forming medium is present at the detection position of the storage means and one of the medium detecting sensors until it is detected that the image forming medium is present at the detecting position of the other medium detecting sensor. Based on the measurement means for measuring the measured distance value as the measured distance value between the sensors, and the detection position of a certain medium detection sensor based on the set distance value between sensors, the measured distance value between sensors, and the reference position setting distance value An estimation unit that estimates a reference distance value that is expected to be measured as a distance to a position, and a measured conveyance distance value related to a distance by which an image forming medium is conveyed from a detection position of a certain medium detection sensor Drive start means for starting drive control of the head by the head module corresponding to the reference position based on reaching the distance value.

  According to the image forming apparatus, the correspondence between the set value and the actually measured value can be grasped based on the measured actual distance value between the sensors and the set distance value between the sensors. Based on this, it is possible to appropriately estimate the reference distance value expected to be measured as the distance from the detection position of a certain medium detection sensor to the reference position. Accordingly, it is possible to estimate the reference distance value in consideration of the influence of errors and the like included in the measurement. Therefore, by starting the head drive control by the head module based on the reference distance value, an image can be formed at an appropriate position on the image forming medium.

  In the image forming apparatus, at least one medium detection sensor of the plurality of medium detection sensors may be disposed at a substantially middle point between two head modules arranged continuously in the conveyance direction. According to such an image forming apparatus, since the distance of the medium detection sensor from the nozzle that ejects the image forming material can be as far as possible, it is possible to appropriately reduce the contamination of the medium detection sensor by the image forming material ejected from the nozzle. it can.

  In the image forming apparatus, the estimation unit calculates a reference distance value by (actually measured distance value between sensors−set distance value between sensors) / set distance value between sensors × reference position set distance value + reference position set distance value. You may do it. According to such an image forming apparatus, the reference distance value can be calculated easily and appropriately.

  Further, in the image forming apparatus, the estimation unit estimates a reference distance value that is expected to be measured as a distance to a reference position corresponding to the head module downstream of the other medium detection sensors, and starts control unit May start drive control of the head module head using the estimated reference distance value. According to such an image forming apparatus, it is possible to start drive control based on an appropriate reference distance value for a head module that will subsequently perform image formation on the image forming medium being conveyed.

  Further, in the image forming apparatus, the estimating means estimates a reference distance value that is expected to be measured as a distance to a reference position corresponding to the head module upstream of the other medium detection sensors, and starts control means. May use the estimated reference distance value to start drive control of the head of the head module with respect to the image forming medium conveyed next. According to such an image forming apparatus, it is possible to start driving control of the upstream head module based on an appropriate reference distance value for an image forming medium conveyed next. Therefore, the image forming accuracy can be improved.

  In the image forming apparatus, the measuring unit measures the measured distance value between the sensors every time the next image forming medium is conveyed, and the estimating unit measures the measured distance value between the sensors by the measuring unit. In addition, the reference distance value may be estimated. According to such an image forming apparatus, it is possible to sequentially estimate the reference distance value according to the situation in image formation, and to appropriately control the start of the head module drive control according to the situation.

  To achieve the above object, the image forming method according to the second aspect of the present invention includes a plurality of medium detection sensors that detect whether or not an image forming medium exists at a plurality of different detection positions in the conveyance direction of the image forming medium. And an image forming method comprising: a head having a plurality of nozzles for ejecting an image forming material; and a plurality of head modules arranged at different positions in the transport direction, wherein one medium An inter-sensor set distance value related to a distance based on a setting between a detection position of the detection sensor and a detection position of another medium detection sensor downstream of the one medium detection sensor, a detection position of a certain medium detection sensor, and 1 The reference position setting distance related to the distance based on the setting with the reference position where the image forming medium as the reference for starting the drive control of the head of the head module is to be located And a distance storage step for storing the information, and from the detection of the image forming medium at the detection position of one medium detection sensor to the detection of the presence of the image forming medium at the detection position of another medium detection sensor. A certain medium detection sensor based on a measurement step for measuring a value related to a distance to which the image forming medium is conveyed as an actually measured distance value between sensors, a set distance value between sensors, an actually measured distance value between sensors, and a reference position set distance value An estimation step for estimating a reference distance value that is expected to be measured as a distance from the detection position to the reference position, and a conveyance measurement relating to a distance by which the image forming medium is conveyed from the detection position of a certain medium detection sensor Based on the fact that the distance value has reached the reference distance value, the drive opening that starts the head drive control by the head module corresponding to the reference position is started. And a step.

  According to the image forming method, it is possible to grasp the correspondence between the set value and the actually measured value based on the measured actual distance value between the sensors and the set distance value between the sensors. Based on this, it is possible to appropriately estimate the reference distance value expected to be measured as the distance from the detection position of a certain medium detection sensor to the reference position. Accordingly, it is possible to estimate the reference distance value in consideration of the influence of errors and the like included in the measurement. Therefore, by starting the head drive control by the head module based on the reference distance value, an image can be formed at an appropriate position on the image forming medium.

  In the image forming method, in the measurement step, the image forming medium is conveyed without starting the head drive control by the head module, and the measured distance value between the sensors is measured. Based on the fact that the printable range of the forming medium is positioned upstream of the head module on the most upstream side, the image forming medium is transported again, and then the actually measured transport distance value reaches the reference distance value. You may make it start the drive control of the head by the head module corresponding to a reference position. According to such an image forming method, it is possible to estimate the reference distance value without forming an image on the image forming medium, that is, without wasting the image forming medium, and then form an image on the image forming medium. For this reason, it is possible to improve the image forming accuracy for more image forming media.

  Embodiments of the present invention will be described with reference to the drawings. The embodiments described below do not limit the invention according to the claims, and all the elements and combinations described in the embodiments are essential for the solution of the invention. Is not limited.

  First, a line inkjet printer as an example of an image forming apparatus according to an embodiment of the present invention will be described.

  FIG. 1 is a partial side view of a line inkjet printer according to an embodiment of the present invention, and FIG. 2 is a partial top view of the line inkjet printer according to an embodiment of the present invention.

  The line inkjet printer 1 (also referred to as printer 1) includes a belt 2 that conveys an image forming medium (referred to as paper M) such as paper, an OHP sheet, and cloth supplied from a paper feed tray (not shown). . The belt 2 is stretched over rollers 3a, 3b, and 3c of the paper transport unit 3, and is driven by a motor (not shown). When printing on the sheet M, the belt 2 conveys the sheet M from the sheet conveyance direction X, that is, from the upstream side (left side in FIG. 1) to the downstream side (right side in FIG. 1) at a substantially constant speed.

  The printer 1 can perform printing on a plurality of sizes of paper M. In the present embodiment, the printer 1 can print on paper M of various sizes up to a width W2 (maximum printable width) as shown in FIG. The printer 1 of the present embodiment is configured such that the approximate center of the sheet M in the sheet width direction Y is conveyed along the approximate center of the belt 2 in the sheet width direction Y regardless of the size of the sheet. If it is the paper M, it is conveyed so as to pass through the approximate center of the belt 2 as shown in FIG.

  Above the belt 2, an encoder 8 is provided to detect the amount of movement of the belt 2 (corresponding to the amount of paper M transported by the belt 2) so as to face the belt 2. In an area where the paper M of the belt 2 is not conveyed (near the lower end side in FIG. 2), an encoder pattern (not shown) is formed at regular intervals in the paper conveyance direction X. The encoder 8 irradiates the belt 2 with light, receives the reflected light from the belt 2, and outputs a signal corresponding to the light receiving state. When the belt 2 is driven, a pulse signal is output from the encoder 8 due to the difference in reflected light between the encoder pattern and a portion other than the pattern. According to this pulse signal, since the number of patterns that have passed can be grasped as the number of pulses, the amount of movement of the belt 2 can be grasped.

  In the printer 1, a plurality of head modules 4 (4A, 4B) are arranged in the paper transport direction X. The head module 4 has a plurality of heads 5. The head module 4 can be removed from the printer 1 and replaced with a similar head module, so that the printer 1 can be easily repaired.

  In the head 5, a plurality of nozzles 5 a that eject ink as an example of an image forming material are provided toward the side where the paper M is conveyed (lower side in FIG. 1). In the present embodiment, the head 5 is formed with a nozzle row in which a plurality of (for example, 180) nozzles 5a are arranged in the paper width direction Y (the depth direction in FIG. 1) perpendicular to the paper transport direction X, for example. The nozzle rows are formed in a plurality of rows (for example, 8 rows) in the paper transport direction X. For example, if the printer 1 performs printing with four colors of ink, two nozzle rows are assigned to each of yellow, magenta, cyan, and black, and the same color nozzle row is defined in the sheet width direction Y. The nozzles are arranged so that the positions of the nozzles are shifted by a predetermined amount (for example, half the nozzle pitch in the nozzle row).

  As shown in FIG. 2, the head module 4 (4A, 4B) includes a head row in which a plurality of heads 5 are arranged in the paper width direction Y, and the head row is arranged in a plurality of rows (for example, The plurality of heads 5 are arranged in a staggered manner (alternately) in the paper width direction Y. The plurality of heads 5 in the first row (shown in order from the upstream side, hereinafter the same) are arranged along the paper width direction Y at a predetermined interval. Each of the plurality of heads 5 in the second row is arranged so as to supplement printing of a portion that cannot be printed by the head 5 in the first row in the maximum printable width (for example, between the heads 5 in the first row). Has been. With the heads 5 in the first and second rows, ink can be ejected at a predetermined resolution (for example, 360 dpi) over the entire maximum printable width in the paper width direction Y.

  The first head module 4A (upstream head module) and the second head module 4B (downstream head module) have the same configuration, but the first head module 4A and the second head module 4B. Are arranged such that the positions of the corresponding nozzles are shifted in the paper width direction Y by a predetermined amount (for example, ¼ of the nozzle pitch in the nozzle row). As described above, since the positions of the corresponding nozzles of the first head module 4A and the second head module 4B are shifted by a predetermined amount, the maximum printable range in the paper width direction Y (maximum printing The resolution over the entire possible width) can be doubled (for example, 720 dpi) that can be realized by one head module 4.

  The printer 1 also has a plurality of paper detection sensors 6 as examples of medium detection sensors. The upstream paper detection sensor 6 (first paper detection sensor 6A) is provided on the upstream side of the first head module 4A, and the paper M is present at a position (first detection position A) immediately below the belt 2. Whether or not to do so is detected. In the present embodiment, the first detection position A is the position of the approximate center of the belt 2 in the sheet width direction Y, that is, the position where the approximate center of the sheet M in the sheet width direction Y passes regardless of the size. Therefore, it is possible to appropriately detect whether or not the sheet M exists regardless of the size.

  The downstream paper detection sensor 6 (second paper detection sensor 6B) is provided approximately in the middle of the first head module 4A and the second head module 4B in the paper transport direction X, and is positioned on the belt 2 immediately below it ( In the second detection position C), it is detected whether or not the sheet M exists. In the present embodiment, the second detection position C is a substantially center position of the belt 2 in the sheet width direction Y, that is, a position through which the approximately center of the sheet M in the sheet width direction passes regardless of the size. Whether or not the sheet M exists can be appropriately detected regardless of the size. Further, since the second paper detection sensor 6B is provided at a substantially intermediate point in the paper transport direction X between the first head module 4A and the second head module 4B, the second paper detection sensor 6B and each head module 4A. 4B can be secured relatively long, and the influence of contamination by ink mist ejected from the head 5 of each head module 4A, 4B can be reduced.

  Next, the functional configuration of the printer 1 will be described.

  FIG. 3 is a functional configuration diagram of a line inkjet printer according to an embodiment of the present invention.

  The printer 1 includes a paper transport unit 3, a plurality of head modules 4 (4A, 4B), an encoder 8, a plurality of paper detection sensors 6 (6A, 6B), and a printer controller 11.

  The printer controller 11 includes a communication interface unit (communication I / F unit) 12, a control unit 13, an interface unit (I / F unit) 14, a RAM (Random Access Memory) 15, a head driving circuit 16, and a distance. It has an EEPROM 17 as an example of a storage means.

  The communication I / F unit 12 mediates exchange of print data and the like between a host device (not shown) and the control unit 13. The I / F unit 14 mediates exchange of data and signals between the control unit 13 and the encoder 8, the paper transport unit 3, and the plurality of paper detection sensors 6 (6A, 6B). In the present embodiment, the I / F unit 14 transmits a signal for controlling the sheet conveyance from the control unit 13 to the sheet conveyance unit 3. Further, the I / F unit 14 transmits a signal from the encoder 8 to the control unit 13. Further, the I / F unit 14 transmits signals from the plurality of paper detection sensors 6 to the control unit 13.

  The RAM 15 is used as an area for storing programs and data, or as a work area for storing data used for processing by the control unit 13. In the present embodiment, the RAM 15 stores print data received from a host device (not shown). The print data includes dot data to be printed on the paper M by each head 5. In this embodiment, since the printer 1 can print on the entire surface of the paper M (so-called borderless printing is possible), the dot data for the entire surface of the paper M for each of the heads 5. It is included. In the present embodiment, each head module 4 includes a head 5 having a different position in the paper transport direction. Therefore, the data of the downstream head 5 has a positional deviation from the most upstream head 5. Considered data, that is, data that prevents ink from being ejected while the paper M is transported a distance corresponding to the deviation is included. The RAM 15 stores a first reference value S1 and a second reference value S2 described later.

  The head driving circuit 16 is configured by, for example, an FPGA (Field Programmable Gate Array), and supplies various signals for driving the head 5 to each head 5 of each head module 4. Further, the head driving circuit 16 appropriately transfers necessary print data from the RAM 15 to its own buffer.

  The EEPROM 17 stores various values used for processing.

  FIG. 4 is a diagram for explaining various values used for processing of the line inkjet printer according to the embodiment of the present invention.

  In the printer 1, as shown in FIG. 4, in order from the upstream side in the paper transport direction X, a detection position A for detecting whether or not the paper M is present by the first paper detection sensor 6A, the first head module 4A. The reference position B that is used as a reference for starting the drive control of the head 5, the detection position C where the presence or absence of the sheet M is detected by the second paper detection sensor 6 B, and the drive control of the head 5 of the second head module 4 B The reference positions D that serve as the reference for starting are arranged.

  Here, each reference position (B, D) refers to the sheet M by starting predetermined drive control in each head module 4 (4A, 4B) with reference to the time when the sheet M is transported to this position. In this position, the ink droplets by the nozzle 5a on the most upstream side of each head module 4 can be ejected to the position (most downstream) in the printable range. In the present embodiment, the reference position is, for example, the earliest position in the range in which the printer 1 can print on the paper M until the ink from the nozzles 5a reaches the paper M after starting predetermined drive control. When the ink is discharged from the upstream nozzle 5a by an amount corresponding to the distance that the sheet M is transported in the time required for the sheet M, the downstream end of the sheet M is moved to the upstream side. It is set as the position where it exists, or the position of the vicinity.

  The EEPROM 17 is a printer 1 between a detection position A where the paper M is detected by the first paper detection sensor 6A and a reference position B of the paper M which is a reference for starting drive control of the head 5 of the first head module 4A. The reference position setting distance value (prescribed count number H) relating to the distance based on the setting, the detection position A where the paper M is detected by the first paper detection sensor 6A, and the paper M is detected by the second paper detection sensor 6B. A sensor-to-sensor set distance value (specified count number I) with respect to the distance from the detection position C based on the setting of the printer 1, a detection position A where the paper M is detected by the first paper detection sensor 6A, and a second head module Reference position setting distance value (specified count number J) related to the distance based on the setting of the printer 1 with respect to the reference position D of the paper M as a reference for starting the drive control of the head 5 of 4B. For storing. In the present embodiment, as the distance values, the number of signal pulses counted by the encoder 8 assumed to correspond to the distance is used.

  Returning to the description of FIG. 3, the control unit 13 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and the like, and controls operations of the units 12, 14, 15, 16, and 17. The control unit 13 reads out and executes a program stored in the ROM, whereby a paper detection determination unit 13a, a conveyance amount measurement unit 13b as an example of a measurement unit, an estimation unit 13c as an example of an estimation unit, and drive start A print control unit 13d and a paper transport control unit 13e are configured as an example of the unit.

  The paper detection determination unit 13a receives a signal indicating the presence / absence of the paper M at the detection position A from the first paper detection sensor 6A, and whether or not the paper M has been conveyed to the detection position A of the first paper detection sensor 6A. If it is determined that the sheet M has been transported, the transport amount measuring unit 13b is notified of the fact. Further, the paper detection determination unit 13a receives a signal indicating the presence / absence of the paper M at the detection position C from the second paper detection sensor 6B, and the paper M is conveyed to the detection position C of the second paper detection sensor 6B. If it is detected that the sheet M has been conveyed, the estimator 13c is notified of the fact.

  The conveyance amount measurement unit 13b starts measuring the conveyance amount of the paper M after the paper detection determination unit 13a detects that the paper M has been conveyed to the detection position A of the first paper detection sensor 6A. In the present embodiment, the transport amount measurement unit 13b detects the pulse of the signal of the encoder 8 after the paper detection determination unit 13a detects that the paper M has been transported to the detection position A of the first paper detection sensor 6A. A count number (amount of movement of the belt 2, that is, a conveyance amount of the paper M) is measured. Here, the count number measured until the transport amount measuring unit 13b detects that the paper M is transported by the second paper detection sensor 6B is related to the distance between the detection position A and the detection position C. The measured distance value between sensors (measurement count number i).

  When the estimation unit 13c receives a notification from the paper detection determination unit 13a that the paper M has been transported to the detection position C, the estimation unit 13c determines the count number (measurement count number i) of the encoder 8 from the transport amount measurement unit 13b. get. In addition, the estimation unit 13c acquires the prescribed count number H, the prescribed count number I, and the prescribed count number J of the EEPROM 17.

  Further, the estimation unit 13c is measured as a distance from the detection position A of the first paper detection sensor 6A to the reference position D based on the measurement count number i, the specified count number I, and the specified count number J. The estimated reference distance value (second reference value S2) is estimated. In this embodiment, the estimation part 13c calculates 2nd reference value S2 according to Formula (1).

  Second reference value S2 = specified count number J + (measured count number i−specified count number I) / specified count number I × measured count number J (1).

  Here, (measurement count number i−specified count number I) / specified count number I is the error count number at the time of actual measurement with respect to the specified one count between the first paper detection sensor 6A and the second paper detection sensor 6B. When this value is multiplied by the measurement count number J, it is assumed that the count number is an error from the specified count number at the reference position D. Therefore, when the specified count J is added to the error count, the second reference value S2 assumed as the measurement count at the reference position D is obtained.

  Further, the estimation unit 13c is measured as a distance from the detection position A of the first paper detection sensor 6A to the reference position B based on the measurement count number i, the specified count number I, and the specified count number H. The estimated reference distance value (first reference value S1) is estimated. In this embodiment, the estimation part 13c calculates 1st reference value S1 according to Formula (2).

  First reference value S1 = specified count number H + (measured count number i−specified count number I) / specified count number I × measured count number H (2).

  Here, (measured count number i−prescribed count number I) / prescribed count number I represents the count number of errors at the time of actual measurement with respect to a predetermined one count between the first detection sensor 6A and the second paper detection sensor 6B. When this value is multiplied by the measurement count number H, it is assumed that the count number is an error from the specified count number at the reference position B. Accordingly, when the specified count H is added to the error count number at the reference position B, the first reference value S1 assumed as the measurement count number at the reference position B is obtained.

  When the print control unit 13d receives print data from a host device (not shown), the print control unit 13d stores the print data in the RAM 15. In addition, the print control unit 13d determines that the pulse count number (measured conveyance distance value) measured by the conveyance amount measurement unit 13b after the paper M is detected by the first paper detection sensor 6A is the first reference value S1. It is determined whether or not it has been reached, and if it is determined that it has been reached, an instruction is given to cause the head drive circuit 16 to start driving control of the head 5 of the first head module 4A. In addition, the print control unit 13d determines that the pulse count number (measured conveyance distance value) measured by the conveyance amount measurement unit 13b after the paper M is detected by the first paper detection sensor 6A is the second reference value S2. It is determined whether or not it has been reached, and if it is determined that it has been reached, an instruction is given to cause the head drive circuit 16 to start drive control of the head 5 of the second head module 4B.

  The paper transport control unit 13e controls the paper transport unit 3 to take out the paper M from the paper feed tray, transport it onto the belt 2, drive the belt 2, and transport the paper M from above the belt 2. The paper M is conveyed to a paper discharge tray (not shown). In the present embodiment, the paper transport control unit 13e can drive the belt 2 in the opposite direction to transport the paper M upstream in the paper transport direction, that is, in the returning direction.

  Next, a printing process according to an embodiment of the present invention will be described.

  FIG. 5 is a flowchart of print processing according to an embodiment of the present invention.

  For example, the printing process is started when the control unit 13 receives print data from a host device (not shown) via the communication I / F unit 12.

  The paper transport control unit 13e takes out the paper M of the size and type specified in the print data from a paper feed tray (not shown) by the paper transport unit 3, transports the paper M onto the belt 2, drives the belt 2, and drives the paper M Is started (step S1). In the following, the number of sheets M required for printing are sequentially conveyed at intervals.

  Next, the paper detection determination unit 13a acquires a signal from the first paper detection sensor 6A via the I / F unit 14, and whether or not the paper M is newly detected based on the signal, that is, the paper M is conveyed. It is determined whether it has been received (step S2).

  As a result, if a new sheet M is not detected, step S2 is repeatedly executed. On the other hand, if a new sheet M is detected, a printing process for each sheet (see FIG. 6) is started (step S3). ).

  Next, it is determined whether or not the printing control unit 13d has completed the printing of the necessary number of sheets M (step S4), and the printing of the number of sheets M necessary for the printing has not been completed. In step S5, on the other hand, if the execution of printing the required number of sheets M has been completed, it is determined whether or not the discharge of the last sheet M has been completed (step S5).

  As a result, when the discharge of the last sheet M has not been completed, the process waits until the discharge of the sheet M is completed. On the other hand, when the discharge of the sheet has been completed (step S5: YES), the sheet is conveyed. The control unit 13e stops the conveyance by the paper conveyance unit 3 (step S6) and ends the process.

  FIG. 5 is a flowchart of the print processing for each sheet according to the embodiment of the present invention.

  When the printing process for each sheet is started, the carry amount measuring unit 13b starts counting pulses based on the signal received from the encoder 8 via the I / F unit 14 (step S11).

  Next, the print control unit 13d acquires the pulse count number (conveyance amount) from the conveyance amount measurement unit 13b (step S12), and determines whether or not it matches the first reference value S1 (the count number is the first reference value S1). Is determined) (step S13). Here, in the present embodiment, the first reference value S1 is the specified count number H as an initial value. If the result of this determination is that they do not match (step S13: NO), it means that the paper M has not been transported to the reference position B for driving the first head module 4A, so the print control unit 13d. Advances the process to step S12.

  On the other hand, if the pulse count matches the first reference value S1 (step S13: YES), it means that the paper M is being transported to the reference position B, so that the print control unit 13d The head drive circuit 16 starts drive control of the head 5 of the first head module 4A (step S14). Thereby, printing according to the print data by each head 5 of the first head module 4A is started on the paper M.

  Next, the paper detection determination unit 13a acquires a signal from the second paper detection sensor 6B via the I / F unit 14, and the paper M is newly detected at the detection position C of the second paper detection sensor 6B based on the signal. Whether or not the paper M has been conveyed to the detection position C of the second paper detection sensor 6B is determined (step S15).

  As a result, when the paper M is not detected, step S15 is repeatedly executed. When the paper M is newly detected, the paper detection determination unit 13a conveys the paper M to the detection position C. The estimation unit 13c, which has received the notification, acquires the count number (measurement count number i) of the encoder 8 from the transport amount measurement unit 13b (step S16).

  Next, the estimation unit 13c acquires the specified count number H, the specified count number I, and the specified count number J from the EEPROM 17, and based on the measured count number i, the specified count number I, and the specified count number J. Then, a second reference value S2 that is expected to be measured as a distance between the detection position A of the first paper detection sensor 6A and the reference position D is calculated and stored in the RAM 15 (step S17). Thereby, the actual measurement result can be appropriately reflected on the second reference value S2, and the subsequent printing by the second head module 4B can be performed with high accuracy. Next, the estimation unit 13c is measured as a distance from the detection position A of the first paper detection sensor 6A to the reference position B based on the measurement count number i, the specified count number I, and the specified count number H. The first reference value S1 expected to be calculated is calculated and stored in the RAM 15 (step S18). As a result, the actual measurement result can be appropriately reflected on the first reference value S1, and the subsequent printing by the first head module 4A, that is, the printing on the paper M that is subsequently conveyed is highly accurate. To be able to do that.

  Next, the print control unit 13d acquires the measurement count number from the carry amount measurement unit 13b (step S19), determines whether or not it matches the second reference value S2 stored in the RAM 15 (step S20). If not (NO in step S20), it means that the sheet M has not been conveyed to the reference position D for driving the second head module 4B, and the process proceeds to step S19.

  On the other hand, when the measured count number and the second reference value S2 match (step S20: YES), it means that the sheet M is being conveyed to the reference position D of the second head module 4B. The print control unit 13d causes the head drive circuit 16 to start drive control of the head 5 of the second head module 4B (step S21), and the process ends. As a result, printing by the heads 5 of the second head module 4B on the paper M is started.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be applied to various other modes.

  For example, before starting the printing process shown in FIG. 5 of the above embodiment, a process for determining at least one of the first reference value S1 and the second reference value S2 may be performed. For example, as shown in FIG. You may make it perform a preliminary conveyance process.

  FIG. 7 is a flowchart of the preliminary transport process according to a modification of the present invention.

  In the preliminary transport process, first, the paper transport control unit 13e takes out the paper M of the size and type specified in the print data from a paper feed tray (not shown) by the paper transport unit 3, and transports the paper M onto the belt 2. Is driven to start the conveyance of the sheet M (step S31).

  Next, the paper detection determination unit 13a acquires a signal from the first paper detection sensor 6A via the I / F unit 14, and whether or not the paper M is newly detected based on the signal, that is, the paper M is conveyed. It is determined whether it has been received (step S32). As a result, if the paper M is not newly detected, step S32 is repeatedly executed. On the other hand, if the paper M is newly detected, the carry amount measuring unit 13b starts the I / F unit 14 from the encoder 8. On the basis of the signal received via the counter, the pulse counting is started (step S33).

  Next, the paper detection determination unit 13a acquires a signal from the second paper detection sensor 6B via the I / F unit 14, and the paper M is newly detected at the detection position C of the second paper detection sensor 6B based on the signal. Whether or not the paper M has been conveyed to the detection position C of the second paper detection sensor 6B is determined (step S34).

  As a result, when the sheet M is not detected, step S34 is repeatedly executed. On the other hand, when the sheet M is newly detected, the sheet detection determination unit 13a conveys the sheet M to the detection position C. The estimation unit 13c, which has received the notification, acquires the count number (measurement count number i) of the encoder 8 from the transport amount measurement unit 13b (step S35).

  Next, the estimation unit 13c acquires the specified count number H, the specified count number I, and the specified count number J from the EEPROM 17, and based on the measured count number i, the specified count number I, and the specified count number J. Then, a second reference value S2 that is expected to be measured as a distance from the detection position A of the first paper detection sensor 6A to the reference position D is calculated and stored in the RAM 15 (step S36). Thus, the actual measurement result can be appropriately reflected on the second reference value S2, and printing by the second head module 4B can be performed with high accuracy. Next, the estimation unit 13c is measured as a distance from the detection position A of the first paper detection sensor 6A to the reference position B based on the measurement count number i, the specified count number I, and the specified count number H. The first reference value S1 expected to be calculated is calculated and stored in the RAM 15 (step S37). Thereby, the actual measurement result can be appropriately reflected on the first reference value S1, and the printing by the first head module 4A can be performed with high accuracy.

  Thereafter, the paper transport control unit 13e causes the paper transport unit 3 to feed the paper M on the belt 2 at least upstream of the reference position B of the first head module 4 (for example, from the detection position A of the first paper detection sensor 6A). Is also transported back to the upstream side (step S38). Thereafter, the printing process shown in FIG. 5 is executed. As a result, it is possible to print on the first sheet M to be printed by the head 5 of the first head module 4A using the first reference value S1 reflecting the measurement result, and the printing accuracy can be improved. .

  Further, in the above modification, after the preliminary conveyance process is performed, the printing process for each sheet shown in FIG. 6 is executed so that the first reference value S1 and the second reference value S2 are sequentially updated and used. However, the present invention is not limited to this. For example, after the preliminary conveyance process, the first reference value S1 and the second reference value S2 calculated by the preliminary conveyance process are used without being updated. May be.

  In the above-described embodiment, the second reference value S2 and the first reference value S1 are calculated every time the second sheet detection sensor 6B detects that a new sheet M is conveyed in the sheet-by-sheet printing process. However, the present invention is not limited to this. For example, when the second paper detection sensor 6B detects that a new sheet M is conveyed a plurality of times, the second reference value S2 and the first reference value are detected. The value S1 may be calculated, and when the second paper detection sensor 6B detects that a new sheet M is conveyed after a predetermined time has elapsed, the second reference value S2 and the first reference value S1 are calculated. The reference value S1 may be calculated.

  In the above embodiment, when the type or size of the paper M to be printed is changed, the preliminary conveyance process may be performed, or the preliminary conveyance process is performed every predetermined time. Also good.

  Further, the second reference value S2 in the above embodiment is not limited to the one calculated by the above-described formula, and for example, the detection position A of the first paper detection sensor 6A and the detection position C of the second paper detection sensor 6B. The specified count number I is subtracted from the measured count number i corresponding to the distance between them, and the specified count number J from the detection position A of the first paper detection sensor 6A to the reference position D of the second head module 4B is subtracted from that number. Can be added. In this way, it is possible to appropriately remove the influence of the deviation between the measured count value generated up to the detection position C of the second paper detection sensor 6B and the set count value.

  In the above embodiment, the number of pulses counted by the encoder is used as each distance value. However, the present invention is not limited to this. For example, a distance value in units of μm, mm, or the like may be used. Any value may be used as long as it is a value related to the distance.

  In the above embodiment, the start of drive control of the head 5 of each head module 4 is determined based on the transport amount (measurement pulse number) of the paper M from the detection position A of the first paper detection sensor 6A. However, the present invention is not limited to this. For example, the start of the drive control of the head 5 of each head module 4 is performed by conveying the paper M from the position detected by the nearest paper detection sensor on the upstream side of each head module 4. You may make it determine based on quantity.

  In the above embodiment, each paper detection sensor 6 (6A, 6B) is provided substantially at the center of the belt 2 in the paper width direction. However, the present invention is not limited to this. For example, in the printer 1, the paper M Regardless of the size of the sheet M, when the sheet M is transported on the basis of one end of the sheet M in the width direction (for example, the lower end of the sheet M) (so that one end side of the sheet M passes on the same line) Regardless, the paper detection sensor 6 (6A, 6B) may be provided so as to face the region (the end region in the paper width direction of the belt 2) through which the paper M passes.

  In the above embodiment, the head module 4 (4A, 4B) performs maximum printing in order to enable printing of the entire width (maximum printable width) in the paper width direction of the maximum print range (maximum image formation range). A plurality of heads capable of printing only a part of the possible width are provided, and these heads are arranged so as to enable printing of the entire maximum printable width. However, the present invention is not limited to this, and maximum printing is possible. One head capable of printing the entire width, that is, one head having a plurality of nozzles arranged so as to print the entire maximum printable width may be provided.

  In the above embodiment, the two head modules 4A and 4B are provided in the paper conveyance direction. However, the present invention is not limited to this, and three or more head modules 4 may be provided in the paper conveyance direction. Good. In the above embodiment, a single head module 4 ejects a plurality of colors of ink. However, the present invention is not limited to this. For example, one head module ejects a predetermined color of ink. In this case, a plurality of head modules having different ink colors may be provided.

  In the above embodiment, a line inkjet printer has been described as an example of the image forming apparatus. However, the present invention is not limited to this, and an image forming apparatus that ejects a liquid other than ink or a powdery substance such as toner is used. The present invention can also be applied to an image forming apparatus that flies.

It is a partial side view of the line inkjet printer which concerns on one Embodiment of this invention. It is a partial top view of the line inkjet printer which concerns on one Embodiment of this invention. It is a functional lineblock diagram of a line ink jet printer concerning one embodiment of the present invention. It is a figure explaining the various values utilized for the process of the line inkjet printer which concerns on one Embodiment of this invention. 6 is a flowchart of print processing according to an embodiment of the present invention. It is a flowchart of a printing process for each sheet according to an embodiment of the present invention. It is a flowchart of the preliminary conveyance process which concerns on the modification of this invention.

Explanation of symbols

1 line inkjet printer, 2 belt, 3 paper transport unit, 3a, 3b, 3c roller, 4 head module, 4A first head module, 4B second head module, 5 head, 5a nozzle, 6 paper detection sensor, 6A 1st Paper detection sensor, 6B second paper detection sensor, 8 encoder, 11 printer controller, 12 communication I / F unit, 13 control unit, 13a paper detection determination unit, 13b carry amount measurement unit, 13c estimation unit, 13d print control unit, 13e Paper transport control unit, 14 I / F unit, 15 RAM, 16 head drive circuit, 17 EEPROM, M paper.

Claims (8)

A plurality of medium detection sensors for detecting whether or not the image forming medium exists at a plurality of different detection positions in the conveyance direction of the image forming medium; and a head on which a plurality of nozzles for ejecting the image forming material are formed. A plurality of head modules arranged at different positions in the transport direction, and ejecting the image forming material onto the image forming medium to form an image,
An inter-sensor set distance value relating to a distance based on a setting between the detection position of the one medium detection sensor and the detection position of the other medium detection sensor downstream of the one medium detection sensor; A reference position setting distance value related to a distance based on a setting between the detection position of the medium detection sensor and the reference position where the image forming medium should be positioned as a reference for starting drive control of the head of one or more head modules. Distance storage means for storing
The image formation from when it is detected that the image forming medium exists at the detection position of the one medium detection sensor to when it is detected that the image forming medium exists at the detection position of the other medium detection sensor. Measuring means for measuring a value related to the distance that the medium is transported as an actually measured distance value between sensors;
Expected to be measured as a distance from the detection position of the certain medium detection sensor to the reference position based on the set distance value between sensors, the measured distance value between sensors, and the reference position setting distance value. Estimating means for estimating a reference distance value to be performed;
By the head module corresponding to the reference position based on the fact that the actually measured transport distance value related to the transport distance of the image forming medium from the detection position of the certain medium detection sensor has reached the reference distance value. An image forming apparatus having drive start means for starting drive control of the head. 2. The image forming apparatus according to claim 1, wherein at least one medium detection sensor of the plurality of medium detection sensors is disposed at a substantially middle point between the two head modules continuously arranged in the transport direction. The said estimation means calculates the said reference distance value by (actually measured distance value between sensors-set distance value between sensors) / set distance value between sensors x reference position set distance value + reference position set distance value. The image forming apparatus according to 2. The estimation means estimates the reference distance value expected to be measured as a distance to a reference position corresponding to the head module downstream of the other medium detection sensor;
4. The image forming apparatus according to claim 1, wherein the start control unit starts driving control of the head module using the estimated reference distance value. 5. The estimation means estimates the reference distance value expected to be measured as a distance to a reference position corresponding to the head module upstream of the other medium detection sensor;
5. The start control unit starts driving control of the head of the head module with respect to the image forming medium to be transported next, using the estimated reference distance value. 6. The image forming apparatus described in 1. The measuring means measures the measured distance value between the sensors every time the next image forming medium is conveyed,
The image forming apparatus according to claim 1, wherein the estimation unit estimates the reference distance value every time the measurement distance value between the sensors is measured by the measurement unit. A plurality of medium detection sensors for detecting whether or not the image forming medium exists at a plurality of different detection positions in the conveyance direction of the image forming medium; and a head on which a plurality of nozzles for ejecting the image forming material are formed. And an image forming method by an image forming apparatus comprising a plurality of head modules arranged at different positions in the transport direction,
An inter-sensor set distance value relating to a distance based on a setting between the detection position of the one medium detection sensor and the detection position of the other medium detection sensor downstream of the one medium detection sensor; A reference position setting distance value related to a distance based on a setting between the detection position of the medium detection sensor and the reference position where the image forming medium should be positioned as a reference for starting drive control of the head of one or more head modules. A distance storing step for storing
The image formation from when it is detected that the image forming medium is present at the detection position of the one medium detection sensor to when it is detected that the image forming medium is present at the detection position of the other medium detection sensor. A measurement step for measuring a value related to the distance that the medium is transported as an actually measured distance value between sensors;
Expected to be measured as a distance from the detection position of the certain medium detection sensor to the reference position based on the set distance value between sensors, the measured distance value between sensors, and the reference position setting distance value. An estimation step for estimating a reference distance value to be performed;
By the head module corresponding to the reference position based on the fact that the actually measured transport distance value related to the transport distance of the image forming medium from the detection position of the certain medium detection sensor has reached the reference distance value. An image forming method comprising: a drive start step of starting drive control of the head; In the measurement step, the image forming medium is transported without starting the drive control of the head by the head module, and the measured distance value between the sensors is measured,
In the driving start step, the printable range of the image forming medium is returned to the upstream side of the head module on the most upstream side, the image forming medium is transported again, and then the actually measured transport distance value is The image forming method according to claim 7, wherein drive control of the head by the head module corresponding to the reference position is started based on reaching the reference distance value.

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