JP2010042678A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus which can feed a recording medium extremely precisely even if the feeding distance of the recording medium is increased greatly. <P>SOLUTION: Regarding the inkjet recording apparatus having: a recording head H; a recording head moving means to move the recording head H in the main scanning direction; a recording medium feeding means to feed a recording medium P in the sub-scanning direction; and a feeding amount detecting means to detect the driving amount of the recording medium feeding means in the process of moving the recording head H, a mark detected by a mark recording means recording a predetermined mark on the recording medium P by ejecting ink droplets at predetermined timing from at least one of nozzles and moved together with the recording head H is detected, and the feeding amount of the recording medium is determined by a driving amount detected by the feeding amount detecting means on the basis of a position where the mark detecting means detects detection signals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus with improved feeding accuracy when a recording medium is moved in the sub-scanning direction.

  In an ink jet recording apparatus that records a desired image by ejecting ink droplets onto a recording medium, the recording head that ejects ink droplets is moved in the main scanning direction on the recording medium, and the recording medium is The operation of moving in the sub-scanning direction orthogonal to the scanning direction is repeated.

  Conventionally, the movement of the recording medium in the sub-scanning direction is generally performed by an intermittent feeding operation by a stepping motor or using a DC motor equipped with a rotary encoder. In the former case, every time the recording head records one line along the main scanning direction, a predetermined number of pulses is added to the stepping motor, and the number of steps at that time is used as the feed distance to place the recording medium in the sub-scanning direction. A fixed amount is moved (Patent Document 1). In the latter case, the amount of movement when the recording medium is fed and moved in the sub-scanning direction is read as the number of pulses of the rotary encoder, and the number of pulses for obtaining a predetermined feed amount is counted and controlled (patent). Reference 2).

  Further, there is a type in which a rotary encoder is arranged on the rotation shaft of a feed roller for moving the recording medium in the sub-scanning direction, and the feed amount is controlled by counting the number of pulses (Patent Document 3).

Japanese Patent Laid-Open No. 11-334160 JP 59-171664 A Japanese Patent Laid-Open No. 4-19149

  In recent years, in order to record high-quality images at high speed, the number of nozzles of the recording head increases, and as the length along the nozzle row of the recording head increases, the feed amount of the recording medium in the sub-scanning direction also increases. Along with this, improvement in feed accuracy has become essential. For example, conventionally, as a method for recording an image, a method for obtaining a high-quality image free from banding by printing the image for each block has been studied. In such a recording method, the recording medium is moved in the sub-scanning direction. It is necessary to move at a large feed distance at a time, and because the feed accuracy is drastically improved, it is actually not printed in this way. .

  In an ink jet recording apparatus, as described above, the recording medium feed amount is indirectly grasped by counting the number of pulses of the stepping motor that rotates the recording medium feed roller and the number of pulses of the rotary encoder. For this reason, an error occurs with the actual recording medium feed amount, and the image quality is deteriorated due to the occurrence of white stripes between the blocks due to this error.

  That is, the feed amount of the recording medium ascertained by counting the number of pulses, whether it is a stepping motor or a DC servo motor using a rotary encoder, is an error in the diameter of the feed roller, the axial position of the feed roller, Due to many factors such as the difference in thickness of the recording medium and slippage between the feeding roller and the recording medium, it does not represent the true feeding amount of the recording medium, and this is an error between the actual feeding amount of the recording medium. This causes white streaks and the like. Such a problem tends to be improved when a rotary encoder is mounted on the rotation shaft of the feed roller, but a sufficient improvement effect is not obtained with respect to an increase in the feed amount.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus that can move a recording medium with high accuracy even when the feeding distance of the recording medium in the sub-scanning direction is large.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

The invention according to claim 1 is a recording head that ejects ink droplets from a plurality of nozzles toward a recording medium;
Recording head moving means for moving the recording head along the main scanning direction;
Recording medium moving means for moving the recording medium along the sub-scanning direction;
A moving amount detecting means for detecting a driving amount of the recording medium moving means,
In the ink jet recording apparatus, the amount of movement when the recording medium is moved by a predetermined distance by the recording medium moving means is indirectly detected from the driving amount of the recording medium moving means detected by the movement amount detecting means. ,
In the process of moving the recording head along the main scanning direction by the recording head moving means, ink droplets are ejected at a specific timing from at least one specified nozzle to record a predetermined mark on the recording medium. Mark recording means to perform,
A mark detection unit that is arranged at a certain distance from the recording medium and is moved together with the recording head by the recording head moving unit and detects a mark recorded by the mark recording unit;
The recording medium moving means uses the position at which the mark detection means detects the detection signal of the mark in the moving process of the recording medium as a reference position, and the reference position as the movement amount when moving the recording medium by a predetermined distance. The inkjet recording apparatus is characterized in that it is determined by a driving amount detected by the movement amount detecting means.

Invention of Claim 2 has a memory | storage means to memorize | store the movement amount of a recording medium,
2. The recording medium moving unit according to claim 1, wherein when the mark is not normally detected by the mark detecting unit, the recording medium moving unit moves the recording medium based on a previous moving amount stored in the storage unit. It is an inkjet recording device of description.

The invention according to claim 3 has a movement amount detecting means for detecting the movement amount of the recording medium,
The recording medium moving means is based on the case where the moving amount of the recording medium by the recording medium moving means is determined based on the position where the mark detecting means detects the detection signal, and only the detection signal from the moving amount detecting means. 3. An ink jet recording apparatus according to claim 1, further comprising switching means for switching between the case where the amount of movement of the recording medium by the recording medium moving means is determined.

  According to a fourth aspect of the present invention, the mark detection unit also serves as a recording medium detection unit that detects the presence or absence of a recording medium and / or a bidirectional position detection unit that performs bidirectional alignment of the recording head with respect to the recording medium. The inkjet recording apparatus according to claim 1, wherein:

The invention according to claim 5 is characterized in that the mark recording means records a plurality of marks on the recording medium at a time by ejecting ink droplets from a plurality of different nozzles.
The mark detection means detects each of the plurality of marks,
The recording medium moving means calculates and estimates a position at which a detection error from a distance interval calculated from the nozzle pitch of the recording head is minimized from the position of each mark detected by the mark detecting means, and the calculation estimation The inkjet recording apparatus according to claim 1, wherein the movement amount is determined using the determined position as a reference position.

  A sixth aspect of the present invention is the ink jet recording apparatus according to any one of the first to fifth aspects, wherein the mark is recorded in a portion deviated from a print area on the recording medium.

  The invention according to claim 7 is characterized in that the mark is recorded on the upstream side in the conveyance direction of the recording medium from the area recorded by the main scanning of the recording head. It is an inkjet recording device of description.

  According to an eighth aspect of the present invention, the recording head includes a plurality of heads, and a head having a nozzle for recording a predetermined mark on the recording medium by ejecting ink droplets among the plurality of heads. 8. The ink jet recording apparatus according to claim 7, wherein the ink jet recording apparatus is provided on the upstream side in the conveyance direction of the recording medium with respect to another head by being shifted by one nozzle interval or more.

According to a ninth aspect of the present invention, the mark detection means includes a light emitting element that emits detection light toward the recording medium, a condensing lens that condenses and converges the detection light from the light emitting element, and the light collecting element. The detection light condensed and converged by the optical lens comprises a reflective sensor having at least a light receiving element for detecting reflected light reflected by the surface of the recording medium,
The inkjet according to any one of claims 1 to 8, wherein the light axes of the light emitting element and the condensing lens are arranged so as to be inclined along a main scanning direction with respect to a surface of the recording medium. It is a recording device.

According to a tenth aspect of the present invention, the mark detection means includes a light emitting element that emits detection light toward the recording medium, a condensing lens that condenses and converges the detection light from the light emitting element, and the light collecting element. The detection light condensed and converged by the optical lens comprises a reflective sensor having at least a light receiving element for detecting reflected light reflected by the surface of the recording medium,
9. The inkjet recording apparatus according to claim 1, wherein optical axes of the light emitting element and the condenser lens are disposed so as to be substantially perpendicular to a surface of the recording medium.

  The invention according to claim 11 is the ink jet recording apparatus according to any one of claims 1 to 10, wherein the color of the mark is yellow.

  The invention according to claim 12 is the ink jet recording apparatus according to claim 11, wherein the light emitting element is a blue LED, and the light receiving element is a light receiving element having sensitivity to blue.

  The invention according to claim 13 is the ink jet recording apparatus according to any one of claims 1 to 12, wherein the mark is a straight line along the main scanning direction.

  According to the present invention, it is possible to provide an ink jet recording apparatus that can move a recording medium with high accuracy even when the feeding distance of the recording medium in the sub-scanning direction is large.

1 is a configuration diagram showing an outline of an ink jet recording apparatus according to the present invention. The figure which shows the recording position of the mark on the recording medium The figure which shows the structure of the mark detection means Explanatory drawing explaining an example of block printing Flow chart showing control operation during movement of recording medium Explanatory drawing explaining operation when recording a plurality of marks The figure which shows the arrangement configuration of the optical axis of the optical sensor seen from the sub scanning direction The block diagram which shows other embodiment of the inkjet recording device which concerns on this invention. The figure which shows the other aspect of an optical sensor The figure which shows the other aspect of an optical sensor (A) is a figure which shows the other aspect of an optical sensor, (b) is a top view which shows the condensing lens

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing an outline of an ink jet recording apparatus according to the present invention. In the figure, H is a recording head. Here, for example, four heads h1 to h4 corresponding to four colors of YMCK are shown, but the number of heads constituting the recording head H is not particularly limited.

  A large number of nozzles (not shown) are arranged in a line along the direction orthogonal to the main scanning direction of the recording head H on the lower surface of each of the heads h1 to h4, and are provided in the ink jet recording apparatus main body. The head driver 11 driven and controlled by the unit 10 controls the ejection of ink from the nozzles of the heads h1 to h4 as fine droplets at predetermined timings in the downward direction in FIG. A desired image is recorded and formed on a recording medium P arranged to face the surface.

  The recording head H is mounted on a carriage (not shown). The heads h1 to h4 are integrated with each other, and the main scanning motor 13 is driven by the motor driver 12 that is driven and controlled by the control unit 10 along the main scanning direction. Can be moved in both directions. In the present embodiment, the control unit 10, the motor driver 12, and the main scanning motor 13 constitute the recording head moving means of the present invention.

  The recording medium P is sandwiched between a pair of feed rollers R1 and R2 that are rotationally driven by the sub-scanning motor 15, and the sub-scanning motor 15 is driven by the motor driver 14 that is driven and controlled by the control unit 10. Thus, the sheet is intermittently conveyed by a predetermined amount along the sub-scanning direction (left direction in the figure) orthogonal to the scanning direction of the recording head H. In the present embodiment, the control unit 10, the motor driver 14, the sub-scanning motor 13, and the feed rollers R1 and R2 constitute the recording medium moving means of the present invention.

  In the ink jet recording apparatus according to the present invention, the head driver 11 is driven and controlled by the control unit 10 in the process of moving the recording head H along the main scanning direction by the recording head moving unit. Control is performed so that a predetermined mark M is recorded on the recording medium P by ejecting ink droplets from at least one of the nozzles. In the present embodiment, the control unit 10, the head driver 11, and the recording head H constitute a mark recording unit of the present invention.

  The mark M recorded on the recording medium P can be recorded by ejecting ink droplets in the process of moving the recording head H in the main scanning direction, and can be detected by a mark detection means described later. In this case, it is recorded as a straight line (line) having a certain length (for example, 1.0 mm) along the main scanning direction. If the mark M is such a line-shaped mark, recording can be easily performed by only scanning the recording head H, and detection by a mark detection means described later can be performed accurately. Can be moved more accurately.

  In the case of the recording head H composed of a plurality of heads h1 to h4 as shown in the present embodiment, the head for recording the mark M may be any one of the heads (for example, the head h4), and the ink droplets. The nozzle which discharges should just be from any one nozzle of the one head.

  When the mark M is recorded using a plurality of heads to record an image of a plurality of colors of ink, if the recording is performed using Y (yellow) ink, the mark M is conspicuous on the recording medium P. It is preferable because it becomes difficult. In addition, in the case where light and dark inks can be ejected from a plurality of heads, it is preferable to use light Y ink because it is less noticeable.

  Further, in order to prevent the image from being affected by the area where the mark M is recorded, as shown in FIG. 2, non-printing areas where printing is not performed on both sides along the sub-scanning direction of the recording medium P are provided. When recording the “image with borders”, it is preferable to record the mark M in a non-printing area outside the printing area of the recording medium P. In this case, the mark M may be recorded in each of the non-printing areas on both sides, but only if only one of the non-printing areas is recorded, specifically on the side where the mark detection means described later is provided. Good.

  As shown in FIG. 1, an optical sensor 16 serving as a mark detection unit of the present invention is provided at one end of the recording head H along the main scanning direction. As shown in FIG. 3, the optical sensor 16 includes a light emitting element 163 that irradiates detection light obliquely toward the surface of the recording medium P through an opening 162 in the housing 161, and the detection light on the recording medium P. A condensing lens 164 that condenses and converges on the surface, a condensing lens 165 that condenses and converges reflected light reflected by the surface of the recording medium P, and detection light that is condensed by the condensing lens 165 is received. By detecting a change in the amount of light when the detection light irradiated on the recording medium P passes through the mark M on the moving recording medium P. The mark M is detected. An output signal from the optical sensor 16 is input to the control unit 10, and the control unit 10 determines whether or not the mark M is detected.

  When the mark M is recorded with Y ink, a blue LED (wavelength: 460 nm to 500 nm) is used as the light emitting element 163 used in the optical sensor 16 so that the mark M can be detected satisfactorily. The light receiving element 166 is preferably a light receiving element that is sensitive to light of a wavelength emitted by blue, that is, the blue LED. As such a light receiving element 166, a photosensor is generally used.

  The optical sensor 16 serving as the mark detection means also serves as a sensor serving as a recording medium detection means for detecting the presence or absence of the recording medium P, that is, whether or not the recording medium P is conveyed to the recording position by the recording head H. This is a preferable mode, and by using the sensor as the recording medium detection means, the number of parts can be reduced and the cost can be reduced.

  It is also a preferred aspect that the optical sensor 16 also serves as a sensor as bidirectional position detecting means for performing bidirectional alignment of the recording head H with respect to the recording medium P. That is, when the recording head H moves along the main scanning direction, the optical sensor 16 detects the positions of both side edges of the recording medium P, thereby performing bidirectional alignment of the recording head H. By using the optical sensor 16 as a sensor for this purpose, the number of parts can be reduced and the cost can be reduced as described above.

  Of course, the optical sensor 16 is preferably used as both the sensor as the recording medium detection means and the sensor as the bidirectional position detection means because the number of parts can be further reduced.

  In the optical sensor 16 shown in FIG. 3, the optical axes L1 and L2 of the detection light emitted from the light emitting element 163 and received by the light receiving element 166 are opposed to each other with an angle θ along the sub-scanning direction. However, the present invention is not limited to this, and as shown in FIG. 7, the recording medium P may be arranged so as to be inclined along the main scanning direction. That is, the light emitting element 163 and the light receiving element 166 are arranged so that the optical axes L1 and L2 are opposed to each other along the main scanning direction with an angle θ. As described above, the optical axes L1 and L2 of the detection light are inclined along the main scanning direction orthogonal to the conveyance direction (sub scanning direction) of the recording medium P, so that the height of the surface of the recording medium P along the sub scanning direction. The light receiving element 166 is less susceptible to the influence of position fluctuations, and can be detected with less error.

  Next, the configuration of the present invention will be further described with reference to an explanatory diagram of a block printing system shown in FIG. 4 which is an example of an image recording system. Here, for convenience of explanation, attention is paid only to the operation of one of the recording heads H having a plurality of heads h1 to h4 (referred to as h in FIG. 4), and the recording medium is not shown. explain.

  The block printing method shown in FIG. No. 1 nozzle An example of a printing method in the case where one block is printed by filling a gap between the nozzles with four passes using a head h of m nozzles up to m nozzles is illustrated. Here, it is assumed that printing is performed by ejecting ink droplets when the head h is moved (scanned) in the right direction in the figure along the main scanning direction. One nozzle is indicated by ● (black circle), and the other nozzles are indicated by ○ (white circle).

  In the n-th scan of the head h (this is expressed as n-scan), after recording m lines by ejecting ink droplets from each nozzle, a recording medium is then used to perform n + 1 scan by the same head h. The recording medium is moved by a predetermined amount in the sub-scanning direction by the operation of the moving means. In FIG. 4, for the convenience of explanation, the movement of the recording medium is represented by the movement of the head h from the n-th scan position to the n + 1-th scan position in the lower right direction in the figure.

  In this printing method, at the n + 1th scan, the head h. The line printed by one nozzle is No. in the nth scan. The recording medium is moved so as to be adjacent to the line printed by the two nozzles. The line printed by one nozzle is No. in the (n + 1) th scan. The recording medium is moved so as to be adjacent to the line printed by the two nozzles. The line printed by one nozzle is No. in the (n + 2) th scan. The recording medium is moved so as to be adjacent to the line printed by the two nozzles. The line printed by one nozzle is the No. of the n + 3 scan. The recording medium is moved so as to be adjacent to the line printed by the two nozzles. Here, for example, when moving from the n scan to the n + 1 scan, no. The line printed by 1 nozzle is the No. of n scan. Adjacent to the line printed by the two nozzles is that the four adjacent lines printed by the four passes are not printed by the ink droplets ejected from the same nozzle, and the nozzle of the head h This is to vary the error due to the landing deviation of the ink droplets ejected from the ink.

  Through the above four operations (four passes), all the gaps between the lines printed at the n-th scan are filled, thereby completing one block printing. The movement of the recording medium during the four-pass operation is a relatively short movement, but when printing of one block is completed by four passes, the second block is printed by the same operation as described above. The recording medium is moved to the position of the (n + 4) th scan by the head h as shown in the figure. The movement at this time is a relatively long and long distance movement.

  For example, assuming that the number of nozzles of the head h is 128 and the nozzle interval is 140 μm, when the four-pass operation is performed as described above, the movement of the recording medium three times is a small distance of 140 + 140/4 = 175 μm. The movement becomes a large distance movement of (128−4) × 140 + 140/4 = 17395 μm every fourth time.

  Conventionally, during this large distance movement, degradation in image quality such as white streaks occurring between blocks due to a feed error has been observed. However, in the present invention, as described above, any one of the nozzles can be used to print the mark M during printing. Is recorded on the recording medium, and the recording medium is moved with high accuracy by the following operation. Note that at least one mark M may be recorded before moving a large distance, for example, in the case of the block printing described above, in one block printing, and at a specific timing from a specific nozzle. By doing so, it may be performed at any timing during printing. In FIG. 4, No. 1 positioned at the most rear end side in the sub-scanning direction in the head h at the time of the first scan in one block printing. A case where a line-shaped mark M having a certain length along the main scanning direction from the m nozzle is recorded in the non-printing area is shown.

  FIG. 5 is a flowchart showing a control operation from the last n + 3 scan at the time of one block printing by the head h to the first n + 4 scan at the next block printing when the recording medium is moved over a long distance. The control operation will be described with reference to this flowchart and FIGS.

  When the printing of one block by four passes is completed, the control unit 10 drives and controls the motor driver 14 to drive the sub-scanning motor 15 at a high speed, and the position where the mark M is recorded is provided in the recording head H. The recording medium P is moved at high speed along the sub-scanning direction so as to reach the vicinity of the type sensor 16 (S1).

  In the present embodiment, as shown in FIG. 1, the feed roller R1 or R2 is provided with an encoder 17 as a movement amount detecting means for detecting the movement amount of the recording medium P. If the mark M is recorded at a specific timing from a specific nozzle, the approximate position is known in advance, so that the mark M is counted by counting the number of pulses of the encoder 17 when moving the recording medium P. It is possible to detect whether M has approached the vicinity detected by the optical sensor 16.

  When the control unit 10 detects that the recording medium P has moved to the vicinity where the mark M is detected by the optical sensor 16 by counting the number of pulses of the encoder 17 (S2), the optical sensor 16 accurately determines the mark M. In this case, the driving of the sub-scanning motor 15 is switched to a low speed and the recording medium P is moved at a low speed (S3). In this way, the recording medium P is moved at a high speed to the vicinity where the mark M is detected, and is moved at a low speed when it reaches the vicinity of the detection. This is a preferable mode because the recording time can be shortened.

  When the recording medium P moves, the recording head H waits at a position where the detection light emitted from the optical sensor 16 passes over the mark M recorded on the recording medium P (here, the non-printing area of the recording medium P). Eventually, the mark M is detected by the optical sensor 16, and a detection signal is sent to the control unit 10 (S4).

  When the mark M is detected, the control unit 10 detects the position of the mark M from the count value of the encoder 17 and resets the count number that has been counted for the number of pulses of the encoder 17 until then (S5). . In addition, this count number is memorize | stored in the memory | storage part 18 from the control part 10 as shown in FIG.

  Next, the control unit 10 sets the detection position of the detection signal of the mark M as a reference position for moving the recording medium P over a large distance. That is, the control unit 10 further controls the motor driver 14 to drive the sub-scanning motor 15, thereby moving the recording medium P in the sub-scanning direction, and newly counting the number of pulses of the encoder 17 from the detection position. Start. Since the mark M is recorded at a specific timing from the specific nozzle (at the time of the first scan of one block from the No. m nozzle of the head h in FIG. 4), how many counts the recording medium P is moved from the detection position of the mark M By doing so, it can be seen whether or not the first scan (n + 4 scan in FIG. 4) for printing the next block is moved to an appropriate position.

  The control unit 10 stores the number of counts up to the appropriate position (specified count number). The control unit 10 counts the number of pulses of the encoder 17 so that the recording medium is detected from the detection position of the mark M. P is moved by the designated count number (S6). Since the distance from the optical sensor 16 to the position where the mark M actually recorded on the recording medium P is detected is adjusted once, it is fixed at the recording position of the optical sensor 16 and the mark M. It is constant regardless of the surrounding environment and mechanical errors of the feed rollers R1, R2, etc. Accordingly, even when the recording medium P is moved in the sub-scanning direction by a large distance close to the head length, only a small amount of movement error occurs, and the feeding error can be drastically reduced with respect to the movement over a large distance. become able to. As a result, even when printing of the next block is started by the recording head H, printing can be performed without the occurrence of white stripes or the like with the previously printed block.

  Even though the recording medium P is moved to the position where the mark M should be detected, the mark M is not recorded on the recording medium P for some reason, or the recorded mark disappears. When the mark M is not normally detected by the optical sensor 16 in step S4, the control unit 10 moves the recording medium P based on the previous movement amount. That is, as described above, since the count number of the encoder 17 until the previous mark M is detected is stored in the storage unit 18, the previous recording is performed from the stored count number and the specified count number. The amount of movement when the medium P is moved over a large distance is known. Therefore, even when the mark M is not normally detected, the control unit 10 controls the motor driver 14 and the sub-scanning motor 15 based on the amount of movement up to the previous time, thereby preventing a large error from occurring. P can be moved.

  The movement distance in the sub-scanning direction of the recording medium P until the optical sensor 16 detects the mark M recorded on the recording medium P is the amount of movement that should be moved in the sub-scanning direction, that is, the above-described distance. In the case of block printing, it is preferable that the amount of movement is smaller than that when moving a large distance in order to print the next block. Thereby, when the mark M recorded on the recording medium P is detected by the optical sensor 16, the mark M is performed from one direction along the sub-scanning direction, so that the detection accuracy can be improved. it can.

  In the above description, when the recording medium P is moved by a large distance in the sub-scanning direction, the mark M recorded on the recording medium P is detected by the optical sensor 16 and recorded based on the detection position of the detection signal. The amount of movement of the recording medium P by the medium moving means is determined. This count number is obtained by counting the number of pulses from the encoder 17 shown in FIG. 1 when the recording medium P is moved in the sub-scanning direction. It is also preferable to be able to appropriately switch between the case of determining the amount of movement of the recording medium P by the recording medium moving means based only on the above.

  In this case, the control unit 10 is provided with switching means for switching in any of the above cases as a method for determining the moving amount of the recording medium P by the recording medium moving means, and for example, it is desired to minimize streak in high image quality recording. In this case, the amount of movement is determined based on the detection position of the detection signal for detecting the mark M recorded on the recording medium P, and the pulse from the encoder 17 is used when priority is given to the printing time over the image quality in high-speed recording. If the movement amount is determined based only on the count number, the recording medium P can be moved with high feeding accuracy in the former case, and the movement time of the recording medium P can be shortened in the latter case. Thus, the speed can be improved.

  It is also preferable that the mark M recorded on the recording medium P is recorded on the recording medium P at a time by ejecting ink droplets from a plurality of different nozzles. Normally, the nozzles of the recording head are set so that the nozzle pitch is fixed at the design stage on the assumption that ink droplets are ejected straight from each nozzle. Ink droplets that land on the recording medium may deviate from their normal positions due to variations in shape from nozzle to nozzle, ink ejection speed from nozzle to nozzle, or variations in ejection angle. If the mark M is recorded by the ink droplets ejected from the nozzles causing the deviation and the recording medium is moved by a large distance with reference to the detected position, an error may occur. By recording a plurality of marks M on the recording medium P from a plurality of different nozzles at a time, it is possible to suppress the occurrence of an error due to the deviation generated for each nozzle, and to further improve the feeding accuracy. be able to.

  This aspect will be further described with reference to FIG. FIG. 6 shows a case where five line marks M1 to M5 are recorded by ejecting ink droplets from five adjacent nozzles at a time. The marks M1 to M5 recorded thereby should be originally designed values of the five adjacent nozzle pitches. In FIG. 6, the assumed positions where five marks that are normally calculated from the design value of the nozzle pitch are to be recorded are indicated by solid lines. The assumed positions are arranged at equal intervals with nozzle pitches. However, the actual marks M1 to M5 have different distance intervals from each other as shown in FIG. Note that the assumed position indicated by the solid line is a process within the control unit 10 shown in FIG. 1 and is not actually displayed on the recording medium P.

  As shown in FIG. 1, the optical sensor 16 provided in the recording head H sequentially detects the positions of the marks M1 to M5 recorded on the recording medium P by the movement of the recording medium P in the sub-scanning direction. In FIG. 6, the detection positions where the marks M <b> 1 to M <b> 5 are detected by the optical sensor 16 are indicated by a one-dot chain line.

  Here, the control unit 10 shown in FIG. 1 detects errors G1 to G5 between the assumed position and the detection position. The errors G1 to G5 are detected as a positive or negative error amount depending on the position with respect to the assumed position along the sub-scanning direction. For example, in FIG. 6, it can be seen that the errors G1, G2, and G5 have a positive error amount, and the errors G3 and G4 have a negative error amount.

  Next, the control unit 10 calculates the sum of the errors G1 to G5, and estimates the position of the assumed position where this value is minimum. Thereby, the position where the detection error of the detection position from the assumed position, which is the distance interval calculated from the nozzle pitch, is minimized. Then, the control unit 10 determines the amount of movement of the recording medium P with reference to the calculated estimated position, drives the motor driver 14 to drive the sub-scanning motor 15, and moves the recording medium P. As a result, the error in the detection position of the mark M caused by the variation of the nozzles of the recording head can be minimized, and the recording medium P can be moved with high accuracy.

  In the above description, as shown in FIG. 2, the mark M is recorded in the non-printing area outside the printing area on the recording medium P. However, the image is recorded to the full width of the recording medium P. In the case of forming the “borderless image” to be performed, since the entire surface of the recording medium P becomes a printing area, the above-described mode of recording the mark M in the non-printing area and detecting it cannot be used. For this reason, when forming an “edgeless image”, the mark M is preferably recorded on the upstream side in the transport direction of the recording medium P from the area recorded by the main scanning of the recording head H.

  The upstream side of the recording medium P in the transport direction with respect to the area recorded by the main scanning of the recording head H is an area where recording has not yet been performed by the recording head H. When the recording medium P is conveyed in the sub-scanning direction, the mark M can be detected when the optical sensor 16 passes over the mark M. In addition, after that, the image is recorded by the main scanning of the recording head H, so that the mark M is embedded in the image, and it is difficult to visually recognize the image.

  A configuration of the recording head H that is preferable in the case where the mark M is recorded on the upstream side in the transport direction of the recording medium P from the area recorded by the main scanning of the recording head H will be described with reference to FIG. The same reference numerals as those in FIG. 1 denote the same components, and the description thereof is omitted here.

  As shown in FIG. 8, among the recording heads H composed of four heads h1 to h4, a head having a nozzle for recording the mark M on the recording medium P by ejecting ink droplets (here, referred to as head h4). However, it is provided with a predetermined amount (D) shifted from the other heads h1 to h3 on the upstream side in the conveyance direction (sub-scanning direction) of the recording medium P. When this deviation amount D increases, the overhead at the end of writing and writing increases, and the printing time is adversely affected. Therefore, it is equal to or more than one nozzle interval of the head h1 for recording the mark M, preferably one nozzle interval. This is the N / 5 nozzle interval or less. N is the number of nozzles per head.

  Thus, the head h4 having the nozzles for recording the mark M in the recording head H is provided so as to be shifted from the other heads h1 to h3 by one nozzle or more on the upstream side in the conveyance direction of the recording medium P. As a result, the mark M is recorded in advance by the deviation amount D on the upstream side in the transport direction of the recording medium P by the head h4. Since the area where the mark M is recorded in advance is an area where recording has not yet been performed on the recording medium P, the optical sensor 16 is conveyed when the recording medium P is conveyed in the sub-scanning direction. Can be detected. Then, the mark M recorded on the recording medium P is buried in the image by the main scanning of the recording head H.

  Since the area where the mark M is recorded in this way is in the printing area of the “rimless image”, the influence on the image is minimized as much as possible even though it is buried in the image by the subsequent main scanning of the recording head H. In a lesser sense, the mark M should be recorded in an area small enough to be detected by the optical sensor 16. In order to record the mark M in such a sufficiently small area, data corresponding to the nozzle for recording the mark M is set to 1 (= ink ejection) for a distance necessary to record the mark M along the main scanning direction. on). In particular, the mark M used for recording this “borderless image” can be recorded in a sufficiently small area by being formed by one straight line formed only by ink ejection from one nozzle. Therefore, it becomes more preferable.

  In addition, since the mark M is clearly discriminated from the image and recorded, in order to ensure detection by the optical sensor 16, 0 fill ( = Ink discharge off) is preferably controlled.

  As described above, when a plurality of marks M are recorded for the purpose of ensuring feeding accuracy, the spot diameter of the detection light from the optical sensor 16 is made smaller than the interval along the sub-scanning direction of each mark M, It is preferable to change and control the data corresponding to the nozzle for recording M to 1 (= ink ejection on) by a distance necessary for recording the mark M along the main scanning direction. Thereby, the mark M is recorded in a sufficiently small area, and each of the plurality of marks M can be reliably detected by the detection light.

  These nozzles are controlled by the control unit 10 (shown in FIG. 1).

  By the way, in the optical sensor 16 composed of a reflective sensor, the detection light emitted from the light emitting element 163 passes through the condenser lens 164 and is incident obliquely on the surface of the recording medium P as shown in FIG. Since the reflected light passes through the condenser lens 165 and is received by the light receiving element 166, the optical axis L1 of the detection light emitted from the light emitting element 163 toward the recording medium P and the recording medium P toward the light receiving element 166. Is opposite to the optical axis L2 of the detection light reflected at an angle θ. In this case, cockling occurs or wrinkles due to ink being placed on the recording medium P, and air enters between the recording medium P and the platen disposed on the back surface thereof, so that the recording medium P becomes the recording head. If the surface of the recording medium P is wavy due to various factors such as floating to the H side, the detection light reflected by the surface of the recording medium P is not properly received by the light receiving element 166 and detected. It causes an error.

  The optical sensor 16 that is more preferable in that the mark M can be detected accurately even when the height of the surface of the recording medium P fluctuates due to such a cause will be described.

  Such an optical sensor 16 is arranged such that the optical axes L1 and L2 of the detection light are substantially perpendicular to the surface of the recording medium P. Since the optical axes L1 and L2 of the detection light are substantially perpendicular to the surface of the recording medium P, the detection light receiving position in the sub-scanning direction is large even if the height of the surface of the recording medium P varies. Since the fluctuation does not occur and the detection accuracy is not greatly affected, the mark M can be detected accurately.

  Here, “substantially perpendicular” refers to the optical axis L1 of the detection light emitted from the light emitting element toward the surface of the recording medium P and the optical axis L2 of the detection light reflected from the surface of the recording medium P toward the light receiving element. The angle θ formed is in the range of ± 10 °.

  The configuration of the optical sensor 16 will be described with reference to FIGS.

  In FIG. 9, the light emitting element 163 and the light receiving element 166 are arranged close to each other so as to be substantially parallel to the surface of the recording medium P. The detection light emitted from the light emitting element 163 is incident on the surface of the recording medium P substantially perpendicularly through the condenser lens 164A. A wedge lens 167 is disposed in front of the condensing lens 164A (on the side where the light emitting element 163 and the light receiving element 166 are disposed). From the light emitting element 163 through the condensing lens 164A toward the surface of the recording medium P. Part of the detection light that is irradiated is regulated. As a result, the reflected light reflected in the substantially vertical direction on the surface of the recording medium P similarly passes through the condenser lens 164A and then passes through the wedge lens 167 to the light receiving element 166 arranged in parallel with the light emitting element 163. Incident light is received.

  FIG. 10 shows an example in which a prism 168 is used instead of the wedge lens 167 in FIG. In this case, the detection light irradiated from the light emitting element 163 through the condenser lens 164A toward the surface of the recording medium P substantially vertically is partly regulated by the prism 168 and is substantially perpendicular to the surface of the recording medium P. The reflected light that has been reflected similarly passes through the condenser lens 164A, then passes through the prism 168, and enters and is received by the light receiving element 166 arranged in parallel with the light emitting element 163.

  Here, the light receiving element 166 and the light emitting element 163 are arranged side by side. However, according to this aspect, there is an advantage that the extraction position of the reflected light can be freely set by the configuration of the prism 168, and the arrangement of the light receiving elements 166 is free. The degree can be improved.

In FIG. 11A, a common condensing lens 164B is used for the light emitting element 163 and the light receiving element 166, and this condensing lens 164B is formed from the light emitting element 163 as shown in FIG. A region 164B ₁ that condenses and converges incident light on the surface of the recording medium P and a region 164B ₂ that condenses and converges reflected light from the recording medium P toward the light receiving element 166 are divided. FIG. 11B is a plan view of the condenser lens 164B.

Therefore, the detection light emitted from the light emitting element 163 is irradiated are substantially vertically convergent light converging on the surface of the recording medium P by the region 164B ₁ of the condenser lens 164B. The reflected light is reflected substantially perpendicularly from the surface of the recording medium P, the area 164B ₂ of the condenser lens 164B, are converged condensing toward the light receiving element 166 provided in parallel to the light emitting element 163.

  According to this aspect, the optical axis of the detection light irradiated from the light emitting element 163 to the recording medium P can be arranged so as to be substantially perpendicular to the recording medium P by using only one condenser lens 164B. Therefore, the configuration of the optical sensor 16 can be simplified.

  As described above, when the optical sensor 16 that is arranged so that the optical axes L1 and L2 of the detection light are substantially perpendicular to the surface of the recording medium P is used as the mark detection unit, a plurality of as described above. When recording a plurality of marks M on the recording medium P by ejecting ink droplets from different nozzles, the arrangement of the light emitting element 163, the condensing lenses 164A and 164B, and the recording medium P is as follows. The chip size of the light emitting element 163 in the sub-scanning direction is k, the distance between the condensing lenses 164A and 164B and the light emitting element 163 is a, and the distance between the condensing lenses 164A and 164B and the surface of the recording medium P is b. When the pitch width of the mark M along the sub-scanning direction is m (see FIGS. 9 to 11), it is preferable that the condition of k × b <a × m is satisfied.

  By satisfying the above conditions, the spot diameter of the detection light becomes smaller than the pitch width of the mark M along the sub-scanning direction, and the signal level of the detection light can be sufficiently lowered between the plurality of marks M to be detected. it can. Therefore, the detection part of the mark M and the non-detection part between the marks M can be clearly identified, and a plurality of marks M can be detected accurately.

H: Recording head h1 to h4: Head P: Recording medium M, M1 to M5: Mark R1, R2: Feed roller 10: Control unit 11: Head driver 12: Motor driver 13: Main scanning motor 14: Motor driver 15: Sub Scanning motor 16: optical sensor 17: encoder 18: storage unit

Claims (13)

A recording head that ejects ink droplets from a plurality of nozzles toward a recording medium;
Recording head moving means for moving the recording head along the main scanning direction;
Recording medium moving means for moving the recording medium along the sub-scanning direction;
A moving amount detecting means for detecting a driving amount of the recording medium moving means,
In the ink jet recording apparatus, the amount of movement when the recording medium is moved by a predetermined distance by the recording medium moving means is indirectly detected from the driving amount of the recording medium moving means detected by the movement amount detecting means. ,
In the process of moving the recording head along the main scanning direction by the recording head moving means, ink droplets are ejected at a specific timing from at least one specified nozzle to record a predetermined mark on the recording medium. Mark recording means to perform,
A mark detection unit that is arranged at a certain distance from the recording medium and is moved together with the recording head by the recording head moving unit and detects a mark recorded by the mark recording unit;
The recording medium moving means uses the position at which the mark detection means detects the detection signal of the mark in the moving process of the recording medium as a reference position, and the reference position as the movement amount when moving the recording medium by a predetermined distance. An ink jet recording apparatus characterized in that it is determined by a driving amount detected by the movement amount detecting means. Storage means for storing the movement amount of the recording medium;
2. The recording medium moving unit according to claim 1, wherein when the mark is not normally detected by the mark detecting unit, the recording medium moving unit moves the recording medium based on a previous moving amount stored in the storage unit. The inkjet recording apparatus described. A movement amount detecting means for detecting the movement amount of the recording medium;
The recording medium moving means is based on the case where the moving amount of the recording medium by the recording medium moving means is determined based on the position where the mark detecting means detects the detection signal, and only the detection signal from the moving amount detecting means. The inkjet recording apparatus according to claim 1, further comprising a switching unit that switches between a case where the amount of movement of the recording medium by the recording medium moving unit is determined.   The mark detection means also serves as a recording medium detection means for detecting presence / absence of a recording medium and / or a bidirectional position detection means for performing bidirectional alignment of the recording head with respect to the recording medium. 4. The ink jet recording apparatus according to any one of 3 above. The mark recording means discharges ink droplets from a plurality of different nozzles to record a plurality of marks on the recording medium at a time,
The mark detection means detects each of the plurality of marks,
The recording medium moving means calculates and estimates a position at which a detection error from a distance interval calculated from the nozzle pitch of the recording head is minimized from the position of each mark detected by the mark detecting means, and the calculation estimation The inkjet recording apparatus according to claim 1, wherein the movement amount is determined with the determined position as a reference position.   The inkjet recording apparatus according to claim 1, wherein the mark is recorded in a portion outside the print area on the recording medium.   The inkjet recording apparatus according to claim 1, wherein the mark is recorded on the upstream side in the conveyance direction of the recording medium from an area recorded by main scanning of the recording head.   The recording head is composed of a plurality of heads, and a head having a nozzle for recording a predetermined mark on the recording medium by ejecting ink droplets out of the plurality of heads is different from the other head. 8. The ink jet recording apparatus according to claim 7, wherein the ink jet recording apparatus is provided on the upstream side in the conveying direction by being shifted by one nozzle interval or more. The mark detection means is a light-emitting element that emits detection light toward the recording medium, a condensing lens that condenses and converges the detection light from the light-emitting element, and is condensed and converged by the condensing lens A detection sensor comprising a reflective sensor having at least a light receiving element for detecting reflected light reflected by the surface of the recording medium;
The inkjet according to any one of claims 1 to 8, wherein optical axes of the light emitting element and the condenser lens are arranged so as to be inclined along a main scanning direction with respect to a surface of the recording medium. Recording device. The mark detection means is a light-emitting element that emits detection light toward the recording medium, a condensing lens that condenses and converges the detection light from the light-emitting element, and is condensed and converged by the condensing lens A detection sensor comprising a reflective sensor having at least a light receiving element for detecting reflected light reflected by the recording medium surface;
9. The ink jet recording apparatus according to claim 1, wherein the light axes of the light emitting element and the condenser lens are arranged so as to be substantially perpendicular to the surface of the recording medium.   The inkjet recording apparatus according to claim 1, wherein a color of the mark is yellow.   12. The ink jet recording apparatus according to claim 11, wherein the light emitting element is a blue LED, and the light receiving element is a light receiving element having sensitivity to blue.   The inkjet recording apparatus according to claim 1, wherein the mark is a linear line along a main scanning direction.

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