JP4363134B2 - Inkjet recording device - Google Patents

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).

  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, as a conventional image recording method in which an image is filled with nozzle passes with n passes, banding is performed by performing so-called block printing in which n-1 times are moved by a minute distance and the remaining time is moved by a large distance. Although a method for obtaining a high-quality image free from the occurrence of image generation has been studied, such a recording method has to move the recording medium a large distance at a time in the sub-scanning direction, and dramatically improves the feeding accuracy. Since improvement is required, the actual situation is that printing by this method is not actually performed.

  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.

  Therefore, the present inventors record a predetermined mark on the recording medium by ejecting ink droplets from at least one of the nozzles in the process of moving the recording head in the main scanning direction, and move the mark together with the recording head. By detecting by the mark detecting means, the amount of movement of the recording medium is determined with reference to the position where the mark detecting means detects the detection signal, so that the recording medium can be moved with high accuracy even when the recording medium is moved a large distance. An ink jet recording apparatus that can be used has been proposed (Japanese Patent Application No. 2002-304279).

  In such an ink jet recording apparatus, the mark detection means for detecting the mark recorded on the recording medium is disposed in the vicinity of the recording head, moves along the main scanning direction together with the recording head, and is on the width direction side of the recording medium. It reverses and moves back and forth. Inversion on the side of the width direction of the recording medium requires that the recording head be moved at a constant speed on the printing area of the recording medium, and a constant acceleration from the state where the speed is zero to the constant speed is required. This is because a moving distance is required.

  On the other hand, a mark recorded by a recording head that performs image recording is basically recorded in the vicinity of the side edge of the recording medium that is off the print area on the recording medium. Therefore, in order to detect the mark, it is necessary to temporarily stop the movement of the recording head at the position of the mark recorded on the recording medium.

However, the stop position of the recording head for detecting the mark by the mark detection means is a position where the mark detection means is located above the recording medium and the carriage on which the recording head is mounted is reversed for reciprocal movement. Therefore, the carriage needs to start the reversing operation after resuming the movement from the position where the mark detecting means detects the mark and moving to the reversing position. For this reason, since the carriage repeats starting and stopping by mark detection in addition to the reversing operation for reciprocating movement, the movement is useless, and there is a problem that print productivity is lowered accordingly.
Japanese Patent Laid-Open No. 11-334160 JP 59-171664 A Japanese Patent Laid-Open No. 4-19149

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus capable of moving a recording medium with high accuracy without reducing print productivity.

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

  According to a first aspect of the present invention, there is provided a recording head for ejecting ink droplets from a plurality of nozzles toward a recording medium, recording head moving means for moving the recording head along a main scanning direction, and sub-scanning the recording medium. Recording medium moving means for moving along a direction, and recording the predetermined mark on the recording medium by ejecting ink droplets from at least one nozzle in the process of moving the recording head by the recording head moving means A mark recording unit, and a mark detection unit that is disposed at a certain distance from the recording medium and that is moved together with the recording head by the recording head moving unit and detects a mark recorded by the mark recording unit. The amount of movement of the recording medium by the recording medium moving means is based on the position where the mark detecting means detects the detection signal. In the inkjet recording apparatus to be determined, the mark detection unit is configured such that an interval along the main scanning direction with respect to the recording head is equal to or longer than an acceleration moving distance of the recording head by the recording head moving unit. The inkjet recording apparatus is characterized by being arranged.

  A second aspect of the present invention is the ink jet recording apparatus according to the first aspect, wherein the mark detecting means is provided at both ends of the recording head in the main scanning direction.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording device which can move a recording medium accurately can be provided, without reducing print productivity.

  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. It is preferable to record the mark M in a non-printing area that is out of the printing area of the recording medium P when the “image with border” is recorded. 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 disposed at at least 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. 4, 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.

  FIG. 5 is a schematic diagram showing the positional relationship between the optical sensor 16 and the recording head H. The optical sensor 16 as the mark detection unit is arranged such that the distance along the main scanning direction with respect to the recording head H is equal to or greater than the acceleration moving distance of the recording head H by the recording head moving unit.

  Here, the interval along the main scanning direction of the optical sensor 16 with respect to the recording head H specifically includes a line connecting the centers of the nozzles on the nozzle surface of the recording head H and the image recording surface of the recording medium P. Is the shortest distance between the plane perpendicular to the optical sensor 16 and the optical sensor 16. The position of the optical sensor 16 is the center position of the spot-like detection light when the detection light emitted from the light emitting element 163 is irradiated onto the recording medium P.

  When the recording head H is composed of a plurality of heads as shown in this embodiment, the nozzle surface is a nozzle surface of a head that records the mark M. For example, FIG. 5 shows a state in which a recording head H having a plurality of heads h1 to h4 is stopped on the left side of the recording medium P. Here, the head h4 is a head that records the mark M. An interval along the main scanning direction of the optical sensor 16 with respect to the recording head H (head h4) is shown as an interval d4 in FIG. 5 when the recording head H and the recording medium P are viewed in plan view.

  The acceleration moving distance of the recording head H generally requires a minimum moving distance and a moving time for acceleration and deceleration when the carriage carrying the recording head H is reciprocated. As shown in FIG. 6, the movement of the carriage reaches the traveling speed (constant speed) after a certain acceleration time from the state where the speed is stopped (reverse position) (outward), and then again reaches the speed 0 after a certain deceleration time. In this state, the travel speed (constant speed) is reached after a certain acceleration time (return path), but from this stop state at speed 0, the print area is reached. This is the minimum travel distance required for acceleration until reaching a constant traveling speed at which image recording can be started. This acceleration moving distance is determined by the weight and moment of inertia of the carriage and the motor torque. Note that since this acceleration movement distance affects the vibration and noise of the recording apparatus, an optimum value is selected for each recording apparatus.

  Therefore, for example, as shown in FIG. 6, the traveling speed of the carriage at a constant speed at the time of image recording in the forward path and the backward path is 500 mm / sec, and the acceleration time until the traveling speed at the constant speed is reached from the stop state. Is 200 msec, the acceleration travel distance required for acceleration during this period (this is d) is 50 mm.

  Therefore, as shown in FIG. 5, with the recording head H having the heads h1 to h4 stopped on the left side of the recording medium P, the head h4 positioned at the head in the moving direction for the next image recording operation When the distance d4 from the optical sensor 16 is set to 50 mm, which is the same as the acceleration movement distance d, the recording head H that has moved to the left side of the recording medium P optically marks the mark M recorded on the recording medium P. After being detected by the sensor 16, it is immediately reversed at that position so that the next image recording operation can be started immediately after passing the recording position of the mark M at the side edge of the recording medium P and reaching the printing area. become. Accordingly, the carriage does not perform any useless operation for detecting the mark M, and there is no possibility of causing a decrease in print productivity.

  Thus, if the distance along the main scanning direction of the optical sensor 16 with respect to the recording head H is the same as the acceleration movement distance, the position where the mark M can be detected by the optical sensor 16 on the side of the recording medium P and the carriage This is preferable in that it can match the reversal position and can minimize the waste of the operation of the carriage. Of the heads h1 to h4, for example, when the head for recording the mark M is the head h3, the optical sensor 16 is in a state where the recording head H is stopped on the left side of the recording medium P as shown in FIG. The distance d3 along the main scanning direction with respect to the head h3 is larger than the acceleration moving distance d (= d4) for enabling image recording by the head h4 at the head in the movement direction when moving toward the recording medium P. Similarly, when the head for recording the mark M is the head h2, the distance d2 between the optical sensor 16 and the head h2 is d2 = d + 2r, and the mark M is recorded. When the head to be operated is the head h1, the distance d1 between the optical sensor 16 and the head h1 is d1 = d + 3r, but the head h4 at the head in the moving direction and the optical sensor 1 The distance d4 between for the same as the acceleration travel distance d, matching the detectable position and the reverse position of the carriage of the mark M by the optical sensor 16 at the side of the recording medium P.

  Even if the distance d4 between the head h4 at the head in the moving direction and the optical sensor 16 is slightly larger than the acceleration moving distance d, the optical sensor 16 detects the mark M at the reverse position during the reciprocating movement of the carriage. If the position is adjusted to a possible position, the carriage does not repeat the start / stop operation for detecting the mark M in addition to the reversing operation for reciprocal movement, so that the useless operation of the carriage can be suppressed.

  In the case where the mark M is recorded in the non-printing area near the both ends of the recording medium P, the optical sensors as the mark detecting means may be arranged at both ends of the recording head H in the main scanning direction. Good. FIG. 7 is a schematic view in plan view of the state in which the optical sensors 16a and 16b are disposed at both ends in the main scanning direction of the recording head H having the heads h1 to h4, respectively. In addition, the recording head H in each of the return path and the return path is stopped at the reverse position.

  As shown in FIG. 7A, when the recording head H is stopped to the left side of the recording medium P, the distance d4 between the head h4 and the optical sensor 16a is the same as the acceleration movement distance d, and FIG. ), When the recording head H is stopped to the right side of the recording medium P, the distance d1 ′ between the head h1 and the optical sensor 16b is the same as the acceleration movement distance d. That is, d1 '= d4 (= d), and the others are d2' = d3, d3 '= d2, d4' = d1.

  As described above, in the aspect in which the optical sensors 16a and 16b are arranged at both ends of the recording head H in the main scanning direction, the mark M can be detected in both the forward and backward passes of the recording head H. For example, when the recording medium P needs to be moved with high accuracy in the sub-scanning direction each time one scan (either the forward path or the backward path) along the main scanning direction of the recording head H is performed, either the forward path or the backward path Even if the mark M is detected in the direction, the carriage does not perform a useless operation, and after the optical sensor 16 detects the mark M, it can be immediately reversed to start the next image recording operation. become.

  Such an optical sensor 16 (16a, 16b) can be mounted on the carriage on which the recording head H is mounted together with the recording head H so that the detection light can be emitted toward the recording medium P. However, it is not necessarily mounted on the carriage together with the recording head H, as long as the recording head H can be moved along the main scanning direction. Therefore, for example, it can be attached to a support member such as a stay extending from the carriage along the main scanning direction with a length corresponding to the acceleration movement distance, and as shown in FIG. Arranged on the side of the fixing member (sliding bearing) SL to the carriage rail CR that guides the movement of the carriage CA on which the head H is mounted along the main scanning direction so that the detection light can be emitted toward the recording medium P. You may make it do.

  Moreover, it is preferable that these optical sensors 16 (16a, 16b) are provided so that the position along the main scanning direction of the recording head H can be adjusted. Thereby, even when the acceleration movement distance varies depending on the size of the recording medium P, it can be adjusted to an appropriate position. In this case, if visible light is used as the light emitting element 163, there is an advantage that the optical sensor 16 (16a, 16b) can be easily adjusted to the position of the mark M.

  Next, the feeding operation of the recording medium P will be further described with reference to an explanatory diagram of the block printing method shown in FIG. 9 which is an example of the image recording method. 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. 9), 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. 9, 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, image quality degradation such as white streaks occurring between blocks due to feed errors has been observed, but here, during printing, the mark M is applied from any one nozzle as described above. Recording is performed on a 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. 8, at the time of the first scan during one block printing, No. 1 located at the most rear end side in the sub-scanning direction in the head h. 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. 10 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). At this time, the recording head H is stopped at the reverse position in the reciprocating operation, and the optical sensor 16 is at a position where the mark M can be detected.

  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 from a specific nozzle at a specific timing (in FIG. 9, at the first scan of one block from the No. m nozzle of the head h), 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. 9) when 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. As a result, the speed can be improved.

  Further, the mark M recorded on the recording medium P may be recorded on the recording medium P at a time by ejecting ink droplets from a plurality of different nozzles in one head. preferable. 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 in one head at a time, it is possible to suppress the occurrence of errors due to deviation generated for each nozzle, and to further improve the feeding accuracy. Can be improved.

  This aspect will be further described with reference to FIG. FIG. 11 shows a case where five line-shaped marks M1 to M5 are recorded by ejecting ink droplets from five adjacent nozzles in one head at a time. The marks M1 to M5 recorded thereby should be originally designed values of the five adjacent nozzle pitches. In FIG. 11, 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. 11, 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. 11, 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.

  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. 12, 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. 13 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.

FIG. 14A uses a condensing lens 164B common to 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 164 B ₁ that converges and converges incident light on the surface of the recording medium P and a region 164 B ₂ that condenses and converges reflected light from the recording medium P toward the light receiving element 166 are formed. FIG. 14B is a plan view of the condenser lens 164B.

Therefore, the detection light emitted from the light emitting element 163 is condensed and converged substantially perpendicularly on the surface of the recording medium P by the region 164B ₁ of the condenser lens 164B. Then, the reflected light reflected in the substantially vertical direction from the surface of the recording medium P is condensed and converged toward the light receiving element 166 arranged in parallel with the light emitting element 163 by the region 164B ₂ of the condensing lens 164B.

  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. 12 to 14), 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.

  In the embodiment described above, the encoder (rotary encoder) 17 is used as the movement amount detecting means for detecting the movement amount of the recording medium P. However, the present invention is not limited to this, and for example, the feed rollers R1 and R2 are rotated. Alternatively, a stepping motor may be used as the driving means for this, and the movement amount detection means may be configured by the stepping motor, and the movement amount of the recording medium P may be detected by counting the number of pulses applied to the stepping motor.

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 Diagram showing the structure of an optical sensor The figure which shows the arrangement configuration of the optical axis of the optical sensor seen from the sub scanning direction Schematic showing the positional relationship between the optical sensor and the recording head The figure explaining the relationship between the moving speed of carriage reciprocation and time (A) and (b) are schematic views in plan view showing a state in which optical sensors are arranged at both ends in the main scanning direction of the recording head. Schematic configuration diagram showing another arrangement of the optical sensor 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 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

Explanation of symbols

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 (2)

A recording head that ejects ink droplets from a plurality of nozzles toward a recording medium, a recording head moving unit that moves the recording head along a main scanning direction, and a recording medium that moves the recording medium along a sub-scanning direction A moving unit; a mark recording unit that discharges ink droplets from at least one of the nozzles in a process of moving the recording head by the recording head moving unit; and a recording medium that records a predetermined mark on the recording medium; And a mark detecting means for detecting a mark recorded by the mark recording means, which is moved together with the recording head by the recording head moving means, and is recorded by the recording medium moving means. The amount of movement of the medium is determined based on the position where the mark detection means detects the detection signal. A Kujetto recording device,
The ink jet recording characterized in that the mark detecting means is arranged such that an interval along the main scanning direction with respect to the recording head is at least equal to an acceleration moving distance of the recording head by the recording head moving means. apparatus.   2. The ink jet recording apparatus according to claim 1, wherein the mark detecting means is provided on each of both ends of the recording head in the main scanning direction.

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