JP4349035B2 - 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 transport 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 an image has been studied, such a recording method has to move the recording medium at a large distance at a time in the sub-scanning direction. Since improvement in feeding accuracy is required, the actual situation is that printing is not actually performed 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.

For this reason, a technique has been proposed in which a predetermined mark is recorded on the recording medium, and the moving amount of the recording medium is determined with reference to the position where the mark is detected, thereby improving the feeding accuracy of the recording medium. (Patent Documents 4 and 5).
Japanese Patent Laid-Open No. 11-334160 JP 59-171664 A Japanese Patent Laid-Open No. 4-19149 JP-A-3-42264 Japanese Patent Laid-Open No. 2000-218891

  In order to detect the mark recorded on the recording medium, the mark is sensored and the detection output is compared with a constant potential. Since a reflection type photosensor is generally used as such a sensor, its detection output depends on the distance from the recording medium. However, the surface height of the recording medium is not always constant due to the influence of cockling and the fluctuation of the adsorption state on the platen. In addition, there are many factors that cause output fluctuations in terms of circuitry due to the influence of ambient light, element variations, temperature characteristics, and the like. In particular, when the mark is in the form of a thin line, the received light signal is greatly amplified at the time of detection, so that some influence greatly affects the reference level.

  However, when the output values are compared at a constant potential as in the prior art, there is a problem of lack of reliability, for example, when the reference potential is different, an error increases or a portion that is not a mark is detected.

  Accordingly, an object of the present invention is to improve the reliability of mark detection in an ink jet recording apparatus in which a recording medium is moved with high accuracy by detecting a mark recorded on the recording medium.

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

  According to the first aspect of the present invention, there is provided a recording medium moving means for moving the recording medium along the conveying direction, and position information detection for detecting position information of the recording medium moving means in synchronization with the movement of the recording medium moving means. Means, mark recording means for recording a predetermined mark on the recording medium, mark detection means for detecting the mark recorded by the mark recording means and arranged at a certain distance from the recording medium Detecting the position of the mark on the basis of an output signal when the mark is detected by the mark detecting means and the position information from the position information detecting means, and determining the amount of movement of the recording medium by the recording medium moving means. An ink jet recording apparatus having a control means for determining a position of the mark based on an A / D conversion of an output signal from the mark detection means A / D conversion means, and the control means performs A / D conversion of the output signal of the mark detection means at the timing of position information output by the position information detection means, and from the sampling data, An ink jet recording apparatus that calculates a reference detection position.

  According to a second aspect of the present invention, the A / D conversion means, when the control means obtains a sampling value sufficient to calculate the peak position of the detection output by the mark detection means, the mark detection means. 2. The ink jet recording apparatus according to claim 1, wherein the A / D conversion of the output signal from is stopped.

  The invention according to claim 3 is characterized in that the A / D conversion means starts A / D conversion immediately before the control means is predicted to detect the mark by the mark detection means. Or it is the inkjet recording device of 2.

  A fourth aspect of the present invention is the ink jet recording apparatus according to the first, second or third aspect, further comprising filtering means for filtering an output value from the A / D conversion means.

  A fifth aspect of the present invention is the ink jet recording apparatus according to the first, second, third or fourth aspect, wherein a plurality of marks are recorded simultaneously by the mark recording means.

  According to the present invention, it is possible to provide an ink jet recording apparatus capable of moving a recording medium with high accuracy by detecting a mark recorded on the recording medium and improving the reliability of the mark detection. it can.

  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, and FIG. 2 is a configuration block diagram thereof. 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.

  On the lower surface of each head h1 to h4, a large number of nozzles (not shown) are arranged in a line along a direction orthogonal to the main scanning direction of the recording head H, and from each nozzle of each head h1 to h4, respectively. A desired image based on the image data is recorded on the recording medium P disposed opposite to the nozzle surface by controlling the ejection of the ink as a fine droplet at a predetermined timing in the downward direction in FIG. .

  The image data is temporarily stored in the image memory 13 from the external PC (personal computer) via the I / F unit 11 and the image development unit 12, and the control unit 10 controls the image development unit 12 to control the image memory. 13, and after being developed again in a predetermined arrangement order in the image developing unit 12, it is sent to the head driving unit 14. The head driving unit 14 records an image by ejecting ink droplets according to the image data developed by the image developing unit 12 from the heads h1 to h4.

  The recording head H is mounted on a carriage (not shown), and the main scanning motor 16 is driven by a main scanning driving unit 15 that is driven and controlled by the control unit 10 together with the heads h1 to h4. It can be reciprocated along the main scanning direction shown. In the present embodiment, the control unit 10, the main scanning drive unit 15, and the main scanning motor 16 constitute a recording head moving unit.

  The recording medium P is sandwiched between a pair of feed rollers R1 and R2 composed of a driving roller that is rotationally driven by the sub-scanning motor 18 and a driven roller that is disposed opposite to the driving roller, and is driven by the control unit 10. By driving the sub-scanning motor 18 by the controlled sub-scanning driving unit 17, the sub-scanning motor 18 is intermittently conveyed by a predetermined amount along the sub-scanning direction (left direction in FIG. 1) orthogonal to the scanning direction of the recording head H. It has become so. In the present embodiment, the control unit 10, the sub-scanning drive unit 17, the sub-scanning motor 18, and the feed rollers R1 and R2 constitute the recording medium moving unit of the present invention.

  Here, in the ink jet recording apparatus according to the present embodiment, the head driving unit 14 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. Thus, control is performed such that ink droplets are ejected from at least one of the nozzles and a predetermined mark M is recorded on the recording medium P. In the present embodiment, the control unit 10, the head driving unit 14, and the recording head H constitute the mark recording means of the present invention.

  The mark M recorded on the recording medium P can be recorded by the mark recording means and can be of any form as long as it can be detected by the mark detection means described later. In this case, a straight line (line) having a certain length (for example, 1.0 mm) is recorded along the main scanning direction. If the mark M is such a line-shaped mark, the recording head H can be easily recorded in the course of one scanning along the main scanning direction, and the detection by the mark detection means described later can be performed accurately. As a result, the recording medium P can be moved more accurately.

  Further, in order to prevent the image from being affected in the area where the mark M is recorded on the recording medium P, printing is performed on both sides along the sub-scanning direction of the recording medium P as shown in FIG. When recording an “image with a border” having no non-printing area, 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.

  When recording a mark using a 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). Moreover, the nozzle which discharges an ink drop should just be from at least any one nozzle of several nozzles of one head.

  There are various ways of recording the mark M. For example, as shown in FIG. 4A, only one mark M is recorded from one nozzle of one head, as shown in FIG. A mode in which the mark M is recorded at a time from every other nozzle (two nozzles in this case) among a plurality of adjacent nozzles in one head, as shown in (c), a plurality of adjacent ones in one head A mode in which a plurality of marks M are recorded at a time from these nozzles (here, four nozzles) is mentioned. The black circles in the figure are detection light emitted from the mark detector 19 onto the recording medium P. These show the recording mode of the mark M in the case of recording an image with a border.

  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.

  As shown in FIGS. 1 and 2, a mark detector 19 as a mark detection means of the present invention is provided at one end of the recording head H along the main scanning direction. As shown in FIG. 5A, the mark detector 19 includes a light emitting element 193 that emits detection light approximately perpendicularly toward the surface of the recording medium P through an opening 192 in a housing 191 and the detection light. A condensing lens 194 that condenses and converges on the surface of the recording medium P, a condensing lens 196 that condenses and converges the reflected light reflected by the surface of the recording medium P through the opening 195, and the condensing lens 196. A reflection type optical sensor including a light receiving element 197 that receives the detection light collected by the detection light, and the detection light irradiated on the recording medium P indicates the mark M on the moving recording medium P. The mark M is detected by detecting a change in the amount of light when it passes. An output signal from the mark detector 19 is input to the control unit 10 via an amplification unit 21 and an A / D conversion unit 22 which will be described later.

  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 193 used in the mark detector 19 so that the mark M can be detected satisfactorily. In addition, the light receiving element 197 is preferably a light receiving element having sensitivity to light having a wavelength of blue, that is, the wavelength emitted by the blue LED. As such a light receiving element 197, a photosensor is generally used.

  The mark detector 19 also serves as a sensor as a recording medium detecting 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 preferred embodiment, and by using the sensor as the recording medium detection means, the number of parts can be reduced and the cost can be reduced.

  In addition, as shown in the present embodiment, in the case of the mark detector 19 configured to reciprocate along the main scanning direction together with the recording head H, bidirectional alignment of the recording head H with respect to the recording medium P is performed. It is also a preferable aspect to use a sensor as a bidirectional position detecting means for this purpose. That is, when the recording head H moves along the main scanning direction, the mark detector 19 detects the positions of both side edges of the recording medium P, whereby the recording head H can be aligned in both directions. In addition, by using the mark detector 19 as a sensor for this purpose, the number of parts can be reduced and the cost can be reduced as described above.

  Of course, it is preferable that the mark detector 19 be used as both the sensor as the recording medium detection unit and the sensor as the bidirectional position detection unit because the number of parts can be further reduced.

  In the mark detector 19 shown in FIG. 5A, the optical axes L1 and L2 of the detection light emitted from the light emitting element 193 and received by the light receiving element 197 have an angle θ along the sub-scanning direction. However, the present invention is not limited to this, and as shown in FIG. 5B, it is arranged so as to be inclined along the main scanning direction with respect to the surface of the recording medium P. Also good. That is, the light emitting element 193 and the light receiving element 197 are arranged so that the optical axes L1 and L2 face 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 mark M has a long line shape in the main scanning direction. In this case, it is difficult to be affected by the line width in the sub-scanning direction of the mark M that is long in the main scanning direction, and the light receiving element 197 enables detection with little error.

  The output signal output when the mark M on the recording medium P is detected by the mark detector 19 is amplified to a predetermined signal level in the amplifier 21 shown in FIG. 2 and then sent to the A / D converter 22. It is done. The A / D conversion unit 22 performs a digital conversion process on the analog output signal amplified by the amplification unit 21 and outputs the converted signal to the control unit 10.

  On the other hand, in this embodiment, a rotary encoder (not shown) is provided as position information detection means for detecting position information of the recording medium P. As shown in FIG. The number of pulses of the rotary encoder output in synchronization with the movement of the pair of feed rollers R1 and R2 that are rotationally driven by the drive of 18 is detected. The number of pulses detected by the encoder sensor 20 is output to the control unit 10 as position information 20a of the recording medium P corresponding to the amount of movement of the pair of feed rollers R1 and R2. This rotary encoder only needs to be provided so as to be synchronized with the rotation of any one of the feed rollers R1 and R2 and the sub-scanning motor 18.

  Here, the control unit 10 outputs an instruction to perform A / D conversion to the A / D converter 22 at the output timing of the position information 20a output from the encoder sensor 20, whereby the analog output signal is output. The A / D converter 22 performs A / D conversion, and control is performed so that a digital output value is input as a sampling input value.

  FIG. 6 is a time chart showing the state of this sampling. In FIG. 2, a is an analog output signal from the mark detector 19 output from the amplifier 21 to the A / D converter 22 in FIG. 2, and b is from the controller 10 to the A / D converter 22. The sampling timing is output, and c is a pulse signal of the position information 20 a output from the encoder sensor 20 to the control unit 10. Here, as shown in FIG. 4C, a case is shown in which each mark M is detected when four marks M are recorded at once from four adjacent nozzles in one head. In particular, as shown in FIG. 4C, if a plurality of marks M are recorded at a time from a plurality of nozzles, the accuracy of detection accuracy of the marks M can be further increased, which is preferable in the present invention. It is an aspect.

  If the mark M is recorded from a specific nozzle at a specific timing, the approximate position is known in advance, so the encoder sensor 20 counts the number of pulses of the rotary encoder when moving the recording medium P. By doing so, it is possible to detect whether or not the mark M has approached the vicinity detected by the mark detector 19. Sampling of the output value of the A / D conversion unit 22 by the control unit 10 is a position where the mark M is predicted to be detected by the mark detector 19 by counting the number of pulses of the rotary encoder by the encoder sensor 20. Start immediately before.

  The position information 20 a and sampled output value data (hereinafter also referred to as sampling data) are stored in a predetermined storage area in the control unit 10.

  Then, the control unit 10 calculates the reference detection position of the mark M by searching for the peak position of the output signal from the mark detector 19 from the sampling data. Since this sampling data is synchronized with the position information 20a from the encoder sensor 20, from the position information 20a corresponding to the peak position, the center when the detection light of the mark detector 19 passes through one mark M is obtained. The position, that is, the center position of the mark M along the sub-scanning direction can be detected. The calculated position information is stored in a predetermined storage area in the control unit 10.

  In the present invention, the position of the mark M is detected based on the output signal when the mark M is detected by the mark detector 19 and the position information 20a, and the position of the mark M thus calculated is used as a reference. The amount of movement of the recording medium P by the recording medium moving means is determined. Since the position of the mark M by the mark detector 19 is detected by the peak position of the sampling data A / D converted by the A / D converter 22, the influence of cockling of the recording medium P and the adsorption to the platen The detection reliability can be improved without being affected by the fluctuation of the state.

  Next, a specific operation of the recording medium P according to the present invention will be described with reference to an explanatory diagram of a block printing method shown in FIG. 7 which is an example of an 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. 7), 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. 7, for the convenience of explanation, the movement of the recording medium is expressed 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 of image quality such as white streaks occurring between blocks due to a feed error has been observed, but here, during printing, at least one of the nozzles as described above is marked M 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. 7, No. 1 positioned at the most rear end side in the sub-scanning direction in the head h during the first scan in one block printing. A case is shown in which one line-shaped mark M having a fixed length along the main scanning direction is recorded in the non-printing area from the m nozzle.

  FIGS. 8 and 9 are flowcharts showing the 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 further described with reference to this flowchart and FIG. 1, FIG. 2, and FIG.

  When printing of one block by four passes is completed, the control unit 10 drives and controls the sub-scanning drive unit 17 to drive the sub-scanning motor 18 at 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 come close to the mark detector 19 (S1).

  By counting the number of pulses of the rotary encoder when moving the recording medium P by the encoder sensor 20, it is possible to detect whether or not the mark M has approached the vicinity detected by the mark detector 19. Therefore, when the control unit 10 detects that the recording medium P has moved to the vicinity where the mark M is detected by the mark detector 19 by counting the number of pulses of the rotary encoder (S2), the mark detector 19 detects the mark M. In this case, the driving of the sub-scanning motor 18 is switched to a low speed, the recording medium P is moved at a low speed (S3), and the interruption of the position information of the recording medium P is permitted, as shown in FIG. Interrupt processing is performed (S4).

  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 is moved, the recording head H is positioned so that the detection light emitted from the mark detector 19 passes over the mark M recorded on the recording medium P (here, the non-printing area of the recording medium P). The analog detection signal that is waiting and detected by the mark detector 19 is first amplified by the amplifier 21 and then sent to the A / D converter 22 where it is converted into a digital signal (S41).

  Here, the control unit 10 converts the analog output signal from the mark detector 19 to the A / D conversion unit 22 immediately before the position where the mark M is predicted to be detected, at the output timing of the position information 20a. The position information 20a from the encoder sensor 20 corresponding to the sampling data of each output value is input (S42), and the position information 20a and the output value sampled by the A / D conversion are input. Store (S43). This stored data is stored in a predetermined storage area in the control unit 10.

  Returning to the flow of FIG. 8, when the mark detector 19 finishes passing the mark M by transporting the recording medium P in the sub-scanning direction (S5), the position information 20a interrupt processing is disallowed. The interruption of the information 20a is terminated (S6). Next, the control unit 10 calculates position information corresponding to the peak A / D conversion value from the A / D conversion value (sampling data) for each position information 20a (S7). The calculated position information is stored in a predetermined storage area in the control unit 10.

  Since the calculated position information is the center position of the mark M, the control unit 10 sets this position information as a reference position for moving the recording medium P over a large distance. That is, the control unit 10 further drives and controls the sub-scanning driving unit 17 to drive the sub-scanning motor 18 to move the recording medium P in the sub-scanning direction, and newly starts the encoder sensor 20 from the position indicated by the position information. To start counting the number of pulses of the rotary encoder. Since the mark M is recorded at a specific timing from a specific nozzle (at the time of the first scan of one block from the No. m nozzle of the head h in FIG. 7), from the position indicated by the position information where the peak of the mark M is detected It can be seen how many counts the recording medium P is moved to move to an appropriate position to perform the first scan (n + 4 scan in FIG. 7) when printing the next block.

  The control unit 10 stores the number of counts up to the appropriate position (specified count number), and the control unit 10 counts the number of pulses of the rotary encoder by the encoder sensor 20, thereby The recording medium P is moved from the position showing the peak by the designated count number (S8), and the normal movement operation by the detection of the mark M is finished.

  Since the distance from the mark detector 19 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 mark detector 19 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.

  On the other hand, in the step of S5, after the position information interruption process is started, the recording medium P is moved by a predetermined distance (a distance that the detection light of the mark detector 19 is expected to pass through the mark M), and the mark is moved. Even though the recording medium P is moved to the position where M should be detected, the mark M is not recorded on the recording medium P for some reason, or the recorded mark M disappears. If the mark M is not normally detected by the mark detector 19 (S9), the position information interruption process started in step S4 is not permitted (S10), and the recording medium P is based on the previous movement amount. Move.

  That is, as described above, the control unit 10 stores the position information obtained by detecting the peak position of the mark M. Therefore, the stored position information obtained by detecting the peak position of the previous mark M and the specified count number are stored. From the above, the amount of movement of the recording medium P at the time of a large distance movement can be determined. Therefore, even when the mark M is not normally detected, the control unit 10 controls the driving of the sub-scanning driving unit 17 and the sub-scanning motor 18 based on the movement amount up to the previous time without causing a large error. The recording medium P can be moved.

  After such movement, the control unit 10 stops driving (S11) and ends the movement when the mark M is not detected.

  In the present invention, the A / D conversion unit 22 outputs an output signal from the mark detector 19 when the control unit 10 acquires a sampling value sufficient to calculate the peak position of the detection output by the mark detector 19. It is preferable to stop the A / D conversion. As a result, time waste of data processing can be eliminated and the storage capacity for storing sampling data can be reduced.

  In the present invention, it is also preferable to have a filtering means for filtering the output value from the A / D converter 22. This filtering means performs filtering according to the waveform of the normal distribution predicted for the data to be A / D converted, thereby canceling malfunction due to uncertain elements due to spike noise, etc., and reliability and accuracy Can be further improved. Such filtering means can be realized by providing a low-pass filter in software in the control unit 10.

  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. Since the recording medium P is conveyed in the sub-scanning direction, the mark M can be detected when the mark detector 19 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 when the mark M is recorded on the upstream side in the transport direction of the recording medium P from the region 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. 10, 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.

  As described above, 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 interval or more on the upstream side in the conveyance direction of the recording medium P. Therefore, the mark M is recorded in advance by the amount D of the deviation 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 mark detector 19 is conveyed by transporting the recording medium P 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 mark detector 19. In order to record the mark M in such a sufficiently small area, the data corresponding to the nozzle for recording the mark M is ejected by a distance necessary for recording the mark M along the main scanning direction. preferable.

  FIG. 11 shows the recording mode of the mark M when recording a borderless image. The recording mode of the mark M when recording the borderless image is also a mode in which only one mark M is recorded from one nozzle of one head, as shown in (a), and as shown in (b), A mode in which the mark M is recorded at a time from every other nozzle (two nozzles in this case) among a plurality of adjacent nozzles in one head, as shown in (c), a plurality of adjacent nozzles in one head A mode in which a plurality of marks M are recorded at once from the nozzles (here, four nozzles) can be mentioned.

  When a plurality of marks M are recorded for the purpose of ensuring feeding accuracy, the spot diameter of the detection light by the mark detector 19 is made smaller than the interval along the sub-scanning direction of each mark M, and the nozzle for recording the mark M It is preferable that the data corresponding to is ejected by a distance necessary to record 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).

  The detection of the position information of the recording medium P in the ink jet recording apparatus according to the present invention described above is not limited to counting the number of pulses of the rotary encoder, and when a stepping motor is used as the sub-scanning motor 18, This may be performed by counting the number of step pulses applied to the stepping motor.

  In addition, the mark recording means for recording the mark M is not limited to the one that also serves as the recording head H for performing image recording, but has a certain positional relationship with the mark detection means in the direction along the conveyance direction of the recording medium P. As long as the recording head H is arranged so as to be maintained, the recording head H may be a separate and independent configuration. In this case, the position where the mark M is recorded is not limited to the image recording surface of the recording medium P, but may be the back surface side thereof. At this time, it goes without saying that the mark detection means is also arranged on the back side of the image recording surface of the recording medium P.

1 is a configuration diagram showing an outline of an ink jet recording apparatus according to the present invention. Configuration block diagram of ink jet recording apparatus according to the present invention The figure which shows the recording position of the mark on the recording medium (A)-(c) is a figure explaining the recording mode of the mark in the case of recording a framed image (A) (b) is a figure which shows the structure of a mark detection means. Time chart showing sampling Explanatory drawing explaining an example of block printing Flow chart showing control operation during movement of recording medium Flow chart showing control operation during movement of recording medium The block diagram which shows other embodiment of the inkjet recording device which concerns on this invention. (A)-(c) is a figure explaining the recording mode of the mark in the case of recording a borderless image

Explanation of symbols

H: recording heads h1 to h4: head P: recording medium M: marks R1, R2: feed roller 10: control unit 11: I / F unit 12: image developing unit 13: image memory 14: head driving unit 15: main scanning Driving unit 16: main scanning motor 17: sub-scanning driving unit 18: sub-scanning motor 19: mark detector 20: encoder sensor 20a: position information 21: amplification unit 22: A / D conversion unit

Claims (5)

A recording medium moving means for moving the recording medium along the conveying direction;
Position information detecting means for detecting position information of the recording medium moving means in synchronization with movement of the recording medium moving means;
Mark recording means for recording a predetermined mark on the recording medium;
Mark detecting means for detecting a mark which is arranged with a certain distance from the recording medium and which is recorded by the mark recording means;
The position of the mark is detected based on the output signal when the mark is detected by the mark detection means and the position information from the position information detection means, and the amount of movement of the recording medium by the recording medium moving means is An inkjet recording apparatus having control means for determining the position of the mark as a reference,
A / D conversion means for A / D converting the output signal from the mark detection means,
The control means performs A / D conversion of an output signal of the mark detection means at a timing of position information output by the position information detection means, and calculates a reference detection position of the mark from the sampling data. Inkjet recording apparatus.   The A / D conversion means outputs an A / D signal output from the mark detection means when the control means obtains a sampling value sufficient to calculate the peak position of the detection output by the mark detection means. 2. The ink jet recording apparatus according to claim 1, wherein the conversion is stopped.   3. The ink jet recording apparatus according to claim 1, wherein the A / D conversion unit starts A / D conversion immediately before the control unit is predicted to detect the mark by the mark detection unit.   4. An ink jet recording apparatus according to claim 1, further comprising filtering means for filtering an output value from said A / D conversion means.   5. An ink jet recording apparatus according to claim 1, wherein a plurality of marks are simultaneously recorded by said mark recording means.

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