JP2011093110A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which can reduce eccentricity unevenness even when the eccentricity correction of a transfer roller is not carried out properly, and which can prevent the generation of black streaks and white streaks caused at joining of recording heads without affecting a transfer amount. <P>SOLUTION: A first correction amount calculating means is provided which calculates a correction value according to a transfer error factor brought about from at least either of a recording medium and a transfer means. A second correction amount calculating means is provided which calculates a correction value to change the transfer amount for every sub-scan with no relation to the transfer error factor of the recording medium and the transfer means. A transfer correcting means is provided which corrects the transfer amount using at least either of the first correction amount calculating means and the second correction amount calculating means. The correction value for every sub-scan calculated by the second correction amount calculating means is in such a relationship that an accumulative correction amount when the recording medium is transferred by the same number of times as the number of recording passes for forming an image in the same recording region is offset. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink from a recording head to a recording medium based on image information, and more particularly to a recording medium conveyance correction unit in the ink jet recording apparatus.

  Image forming apparatuses such as printers, facsimiles, and copiers are configured to record an image on a recording medium by a recording head based on image information. After the recording medium is fed from the paper feeding unit, the recording medium is conveyed by the conveying unit through the recording unit and recorded in between. The recorded recording medium is further conveyed and discharged from the apparatus main body. Image forming apparatuses can be classified according to the recording method of the recording head, and one of them is an ink jet recording apparatus that records an image by ejecting ink from a discharge port of the recording head to a recording medium.

  In the image forming apparatus, when the recording medium is transported, the actual transport amount differs from the target transport amount due to the frictional force between the transport roller and the recording medium or the friction that the recording medium receives from the transport path. May occur. In order to prevent the deterioration of the image quality of the recorded image due to such an error in the conveyance amount, for example, Patent Document 1 proposes to correct the conveyance amount for each scan of the recording head. On the other hand, the carry amount is controlled by an encoder that detects the rotation amount of the carry roller. Therefore, if the conveyance roller is eccentric, the conveyance amount varies depending on the angle (phase) of the roller, and an error occurs in the conveyance amount. For example, Patent Document 2 proposes correcting a conveyance error caused by eccentricity of a roller by correcting a conveyance amount according to the angle of the conveyance roller. By performing the two corrections as described above, recording is performed while adjusting the conveyance amount in each scan of the recording head to a target value, thereby preventing image quality deterioration.

Japanese Patent Laid-Open No. 06-238969 Japanese Patent Laid-Open No. 08-101618

  However, in the correction of the eccentric amount of the transport roller, if the eccentric phase is shifted in the roller axial direction, it is difficult to perform appropriate correction simultaneously in all areas in the axial direction. In particular, ink jet recording apparatuses have recently been required to have finer recording droplets and higher image quality, and to improve recording accuracy. Therefore, even when a slight error occurs in the transport amount, the image quality of the recorded image may be adversely affected. Specifically, there is a case where unevenness in density (roller eccentricity unevenness) occurs in the image at the circumferential length pitch of the conveying roller.

  The present invention has been made in view of such technical problems. The object of the present invention is to reduce the uneven eccentricity even when the eccentricity correction of the conveying roller is not properly performed, and it is possible to reduce black and white lines by connecting the recording head without affecting the conveying amount. It is an object of the present invention to provide an ink jet recording apparatus that can prevent the occurrence.

  The present invention relates to a transport for transporting a recording medium in a sub-scanning direction in an ink jet recording apparatus that forms an image of the same recording area by causing a recording head for ejecting ink to scan the same recording area of the recording medium a plurality of times. Means, a first correction amount calculating means for calculating a correction value according to a transport error factor generated from at least one of the recording medium and the transport means when transporting the recording medium, a recording medium when transporting the recording medium, and A second correction amount calculating means for calculating a correction value so as to give a change to the transport amount for each sub-scan without relating to a transport error factor of the transport means; and the first correction amount when transporting a recording medium. And a conveyance correction unit that corrects the conveyance amount using at least one of the calculation unit and the second correction amount calculation unit, and each of the sub-scans calculated by the second correction amount calculation unit. The correction value, characterized in that a relationship of cumulative correction amount when transporting the same number of recording medium and the recording number of passes for forming an image on the same recording area is canceled.

  According to the present invention, even when the eccentricity correction of the conveying roller is not properly performed, the eccentricity unevenness can be reduced, and black lines and white lines caused by connecting the recording heads are not affected without affecting the conveying amount. An ink jet recording apparatus capable of preventing the occurrence is provided.

1 is a longitudinal sectional view of an ink jet recording apparatus according to an embodiment. FIG. 2A is a cross-sectional view illustrating an example of an eccentric transport roller, and FIG. 2B is a graph illustrating an example of the transition of the transport start point of the transport roller and the cumulative transport error. Sectional drawing which shows the structure of the part of the conveyance roller of a conveyance means Explanatory drawing of a 2nd correction amount calculation means Explanatory drawing showing the movement transition of the recording area of the recording head when recording the same recording area with multiple recording passes

  Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 1 is a longitudinal sectional view of an ink jet recording apparatus 1 according to an embodiment. The sheet-like recording medium fed from the sheet feeding unit is conveyed through the recording unit by the conveying unit. In the present embodiment, a paper feed unit 21 that feeds the cut paper P having a certain size and a paper feed unit 22 that feeds the roll paper R wound in a roll shape are provided. The fed recording medium is first conveyed to a recording start position on the platen 24 by a conveying roller pair 23 including a conveying roller 2 and a pinch roller 3 constituting a conveying unit. A carriage 4 capable of reciprocating in the main scanning direction intersecting the transport direction (a plurality of scanning directions) is disposed at a position facing the platen 24, and a recording head 13 is mounted on the carriage 4.

  When the recording medium is transported to the recording start position, ink is ejected from the ejection port (nozzle) of the recording head to the recording medium based on image information while main scanning is performed by a carriage (not shown) by a carriage (not shown). Discharge to record an image. An image is formed on the recording medium by alternately repeating recording for one recording pass (one main scanning) by the recording head and sub-scanning (pitch conveyance) of the recording medium. The recorded recording medium is discharged through a discharge roller pair 27 including a discharge roller 25 and a spur 26. In the case of roll paper R, the vicinity of the rear end of the recorded image is cut and discharged. As the recording medium, various materials capable of image recording such as paper, plastic sheet, photographic paper, and cloth can be used as long as they are in sheet form.

  The inkjet recording apparatus 1 is provided with a control unit 50 including a controller having a CPU, a memory, an I / O circuit, and the like. The control means 50 controls the operation of the drive motor and various devices according to a control program stored in advance in the internal memory. As a result, the feeding and conveying operations of the recording medium are controlled, and an image is formed on the recording medium by controlling the recording head 13 based on image information (recording signal, recording data, etc.). The control unit 50 controls the correction value output of the first correction amount calculation unit and the second correction amount calculation unit, which will be described later, and corrects the conveyance amount based on the output from the correction amount calculation unit. Control the correction means. Furthermore, it controls the operation of the entire device and its timing.

  Here, the eccentric unevenness of the transport roller 2 will be described. FIG. 2A is a cross-sectional view illustrating an example of an eccentric transport roller, and FIG. 2B is a graph illustrating the transition of the recording start angle and the cumulative transport error of the transport roller in FIG. The roller shown in FIG. 2A is a cross section of a conveying roller having a large eccentricity, and the radius OB is the largest radius and the radius OD is the smallest radius among the rollers. Here, for simplification, it is assumed that the roller circumference is 2 inches (50.8 mm), the radius OA and the radius OC are ideal radii, and the lengths of the arc DAB and the arc BCD are equal. In FIG. 2B, the horizontal axis indicates the angular position (conveyance start point) at the start of recording of the conveyance roller 2, and the vertical axis indicates the recording by repeating the conveyance for the same number of times as the recording path by rotating the conveyance roller 180 degrees. The transition of the cumulative conveyance error when recording for the length of the head is completed is shown. That is, the change in the accumulated conveyance error amount due to the conveyance start point of the conveyance roller is shown.

  In the present embodiment, the length in the conveyance direction (recording head length) of the ejection port array of the recording head 13 is 1 inch (25.4 mm), and an area corresponding to the length of the recording head (also referred to as the same recording area) is recorded. It is assumed that the number of recording passes (number of main scans) required for this is eight. FIG. 2B shows how far the accumulated conveyance amount is from the ideal conveyance amount (1 inch) after the conveyance of 1/8 inch (for one recording pass) is repeated eight times. A cumulative transport error of + indicates that the transport amount is large, and a negative value indicates that the transport amount is small. Further, the conveyance roller 2 conveys the recording medium by one recording pass by rotating from the point A in the direction of B → C → D.

  In order to complete recording for the length of the recording head, it is necessary to convey 1 inch, and therefore it is necessary to rotate the conveying roller 2 180 degrees. For example, when transport is started from point A, it is necessary to rotate to point C via point B. From point A to point C is a portion where the roller diameter is large, an accumulated conveyance error occurs in the direction of excessive feeding. On the other hand, when the conveyance is started from the point C, since the conveyance is performed at a portion where the roller diameter is small, an accumulated conveyance error occurs in a direction where the feeding is insufficient. Therefore, when the error transition of the accumulated conveyance error with respect to the angle of the conveyance start point when the recording in the same recording area is completed is plotted as shown in FIG. When transport is started from the points B and D, the transport is performed using both the large and small portions of the roller diameter, so an error occurs in the transport amount every 1/8 inch, but the cumulative transport amount Is offset.

  In this way, when the transport roller is eccentric, the cumulative transport error amount changes in a cycle with the roller circumferential length (center angle 360 degrees) as a pitch, and the cumulative transport amount is too much for each recording pass. By offsetting the shortage of feed, a certain amount corresponding to the length of the recording head is obtained. On the other hand, the amplitude H in that case is determined by the amount of eccentricity of the conveying roller. If the amplitude H is large, the density difference between the large and small portions of the roller circumferential length is conspicuous, and the conveying roller deviates in the same recording area. Recognized as uneven core.

  FIG. 3 is a cross-sectional view showing a configuration of a portion of the conveyance roller 2 of the conveyance means. A pulley 9 is fixed to one end of the conveying roller 2, and the conveying roller 2 is rotationally driven by a motor 8 via a belt 7 and a pulley 9. In addition, a rotary encoder 5 is fixed to one end of the transport roller 2, and the rotation amount (transport length) and angular position of the transport roller 2 are detected by detecting the rotation of the rotary encoder 5 with the encoder sensor 11. Can do. The conveyance operation by the conveyance roller 2 can be controlled based on the detection result of the encoder sensor 11.

  In the present embodiment, slits or cords 10 are formed in the rotary encoder 5 at intervals of 1/360 inch in the circumferential direction, and this is detected by the encoder sensor 11. Based on the detection result, processing is performed by the calculation unit of the control unit 50, whereby the transport length can be controlled in units of 1/9600 inch (9600 dpi). The rotary encoder 5 is provided with a home position mark 12 for confirming the reference position in the rotation direction of the transport roller 2, and the angular position of the transport roller 2 is detected by detecting the mark 12 with the home position sensor 6. Can be confirmed.

  Next, a method for transporting the recording medium by the transport unit will be described. In this embodiment, the circumferential length of the transport roller 2 is 2 inches, the length of the recording head 13 in the transport direction (the length of the same recording area) is 1 inch, and the same by performing eight main scans (8 recording passes). Image recording in the recording area is completed. That is, the recording roller is rotated by 22.5 degrees, the recording medium is conveyed 1/8 inch, and the recording of 1/8 inch is repeated 8 times to form an image for the length of the recording head. In the present embodiment, the first correction amount calculation means aiming at conveying the required amount (ideal amount) regardless of the eccentricity state of the conveying roller or the condition difference of the recording medium, and the scanning (recording pass) Second correction amount calculation means for changing the transport amount is also provided. And it is comprised so that each conveyance amount of the same recording area may be controlled using at least one of these correction amount calculation means.

  That is, the ink jet recording apparatus according to the present embodiment scans a recording head having a plurality of (eight) ejection units that eject ink a plurality of times (eight times) in the main scanning direction with respect to the same recording area of the recording medium. Thus, an image of the same recording area is formed. Then, a transport unit having a transport roller 2 for transporting the recording medium in the sub-scanning direction is provided. Further, when the recording medium is transported, at least one of the first correction amount calculation unit, the second correction amount calculation unit, and the second correction amount calculation unit is used. And a conveyance correction unit for correcting the above.

  Therefore, the first correction amount calculation unit calculates a correction value according to a transport error factor generated from at least one of the recording medium and the transport unit when transporting the recording medium. On the other hand, the second correction amount calculating means calculates the correction value so that the transport amount for each sub-scan is changed without being related to the transport error factor of the recording medium and the transport means when transporting the recording medium. . Then, the correction value for each sub-scan calculated by the second correction amount calculator cancels the cumulative correction amount when the recording medium is conveyed the same number of times as the number of recording passes for forming an image in the same recording area. It is controlled to be in a relationship.

  Here, the first correction amount calculating means will be specifically described. First, in the first correction amount calculation means, a correction value for the conveyance amount is obtained with the aim of performing a necessary amount of conveyance in each conveyance irrespective of the difference in the eccentric state of the roller and the condition of the recording medium. . In this embodiment, since the image is completed by repeating the 1/8 inch conveyance eight times, a correction value is output so that the conveyance amount for each recording pass becomes 1/8 inch. For example, in FIG. 2A, when carrying at an angle close to point B where the carrying roller diameter is large, a correction value that reduces the carry amount is output. It is detected by a home position sensor 6 shown in FIG. In this case, an optimal correction value is stored in advance for each angle coordinate of the transport roller in the control unit 50, and correction is performed using the information. The correction value is output in units of 1/9600 inch (9600 dpi).

  In addition, when a deviation in conveyance with the ideal conveyance length caused by other than the eccentricity of the conveyance roller 2 is assumed, an optimum correction value is stored in the control unit 50 for the deviation as well, depending on each condition. Can be corrected. The environment in which the first correction amount calculation means outputs the correction value includes the state of the conveyance path, the type of the recording medium, the width of the recording medium in the main scanning direction, the type of the paper feeding unit (cut paper / roll paper), and the recording device The individual difference of a main part etc. are mentioned. For example, when a recording medium that is slippery and has a small friction between the conveyance roller and the recording medium is conveyed, the conveyance amount is corrected to be larger than usual. The correction value is output in units of 1/9600 inch (9600 dpi). As a result, regardless of the difference between the eccentric state of the transport roller and the condition of the recording medium, correction is performed aiming to transport the ideal amount as required in each transport.

  Next, the second correction amount calculating means will be specifically described. The second correction amount calculation means performs further correction in addition to the correction of the first correction amount calculation means described above in order to give a change to the carry amount in each scan. FIG. 4 is an explanatory view showing a correction example by the second correction amount calculating means in comparison with the conventional example. FIG. 4A shows the recorded matter recorded using the conventional example and the discharge port arrangement in the recorded matter. FIG. 4B shows the recorded matter recorded in the present embodiment and the discharge port arrangement in the recorded matter. Indicates.

  FIG. 4A shows a state in which appropriate correction has been performed by applying the first correction amount calculation means in the conventional example. FIG. 4B shows a state in which appropriate correction has been performed by applying the first correction amount calculation means in the present embodiment. Here, the width W1 is an ideal conveyance amount obtained by repeating the 1/8 inch conveyance eight times, and this is 1 inch which is the conveyance length in the same recording area. O indicates the ejection part, and the numbers in O indicate the number of recording passes recorded in the same recording area. In the conventional example (A), the conveyance is always performed at regular intervals from the first conveyance to the eighth conveyance. Therefore, if the gap (non-recorded space) between the first recording area and the second recording area is A1, the gap from the first recording area to the third recording area is A2,. When proper correction is performed, A1 to A7 are all zero.

  FIG. 4B shows a state recorded by applying the second correction amount calculating means in the present embodiment. In (f), by applying the above-described second correction amount calculation means, control is performed to change each transport amount from the first time to the eighth time. As shown in FIG. 2 (b), the phase of the correction value obtained by the second correction amount calculating means is a period (pitch) of 1 inch, which is a conveyance amount (conveyance length) for completing recording in the same recording area. ) Is a sine wave (FIG. 2B). The maximum amplitude of this sine wave is 10 μm. If the correction amount for the first transport is Δ1, the correction amount for the second transport is Δ2, and the correction amount for the eighth transport is Δ8, the sum (total value) of Δ1 to Δ8 is + -Is offset to zero. For this reason, the total transport amount calculated by applying the second correction amount calculating means of this embodiment is also W1 (1 inch), and this transport amount is the same as W1 in the case of (a) of the conventional example.

  In the case of (F) in the present embodiment, a gap is generated between each recording pass (each main scan) when transporting more than 1/8 inch which is the ideal transport amount at each transport. In the present embodiment, a gap B1 between the first recording pass and the second recording pass, a gap B2 between the second recording pass and the third recording pass, a sixth recording pass, and a seventh recording pass. And a gap B7 between the seventh recording pass and the eighth recording pass are generated. On the other hand, there is no gap between the recording passes conveyed by less than 1/8 inch because the recording passes overlap as shown in B3 to B5. That is, the sum (sum) of the gaps B1 to B7 is not zero. In this case, as the sum of the gaps B1 to B7 between the recording passes increases, the white background of the gaps that are not recorded becomes more conspicuous, and the recorded matter appears thinner. On the other hand, if the sum of the gaps B1 to B7 is small, the white background of the gaps that are not recorded becomes inconspicuous and the recorded matter looks dark. Therefore, when comparing (a) of the conventional example (a) and (f) of the present embodiment (b), the (a) of the conventional example looks darker.

  (A) in FIG. 4A shows a state in which proper conveyance is not performed even when the first correction amount calculating means is applied in the conventional example. Specifically, when the eccentricity correction is not properly performed and the conveyance amount is increased, for example, when the conveyance is performed from the point A to the point C in FIG. 2A, the eccentricity correction amount is not sufficient. Indicates the state of overfeed. This state exemplifies a case where the error is particularly large when the sheet is conveyed for the third to fifth times. In the conventional example of FIG. 4A, the amount of overfeed in the same recording area is W2-W1 as compared with the ideal transport amount of 1 inch. That is, a gap A′1 is generated between the first recording pass and the second recording pass, and gaps A′2 to A′7 are similarly generated between the other recording passes. The sum of the gaps A′1 to A′7 coincides with W2−W1.

  In FIG. 4B, (i), that is, in the case where the second correction amount calculation means is applied in the present embodiment to perform correction that changes the transport amount each time, the first recording pass and the second recording pass are also performed. A gap B′1 is generated between the two recording passes, and a gap is also generated between the other recording passes. However, in this embodiment, since the correction for changing the target transport amount every time is performed, the gap between B′3 and B′5 is smaller than that of A′3 and A′5 of the conventional example, and B ′ In 4, no gap was generated. Here, ΔA is obtained by subtracting the sum of the gaps A1 to A7 of (A) from the sum of the gaps A′1 to A′7 of (A) in the conventional example, and (G) gap B ′ in this embodiment. A value obtained by subtracting the sum of the gaps B1 to B7 from the sum of 1 to B′7 is ΔB. When these are compared, ΔA> ΔB, and the gap ΔA of the conventional example is larger. Therefore, when comparing the difference in density between the recorded materials (A) and (B) in the conventional example and the difference in density between the recorded materials (F) and (G) in the present embodiment, the conventional example is more The difference in shade will be large.

  As described above, compared to the conventional example, when the second correction amount calculating unit according to the present embodiment changes each transport amount, even when the first correction amount calculating unit does not perform appropriate correction, By reducing the density difference of the recorded matter, the density difference can be made invisible. Therefore, according to the present embodiment, a transport amount correction method that is more effective and advantageous in reducing the density difference due to uneven eccentricity of the transport roller as compared with the conventional example can be obtained.

  FIG. 5 is an explanatory diagram showing the movement transition of the recording area of the recording head 13 when an image of the same recording area is formed by a plurality of (eight times) recording passes. In the present embodiment, the correction amount pitch (distance for periodically changing the correction amount) obtained by the second correction amount calculation means is a recording path required to complete an image in the same recording area corresponding to the length of the recording head 13. The number is set to a length obtained by integrating the transport amount per time. The reason will be described below with reference to FIG. The length of the recording head 13 (for example, the length in the transport direction of the ink ejection row) is 1 inch. The number of recording passes (the number of main scans by the recording head 13) for recording the same recording area of 1 inch length is 8. The circled numbers in FIG. 5 indicate the number of passes recorded in the eight-pass recording in the recording area indicated by diagonal lines.

  As shown in the figure, in the first pass printing, the discharge section at the most downstream in the transport direction (1/8 discharge section of the fixed recording range) is used. Next, after the recording medium is conveyed by a pitch of about 1/8 inch, the second pass recording is performed. Similarly, as the third to eighth passes are recorded in the same manner, the use area (use discharge unit) of the recording head 13 gradually moves to the upstream side of conveyance. Then, the eighth pass is recorded using the most upstream discharge section, thereby completing image formation (recording) in the same recording area.

  The correction amount calculated by the second correction amount calculation means is canceled by carrying eight recording passes. For this reason, the most upstream side discharge portion coincides with the most upstream portion (the hatched area shown in the circle at the right end of the figure) of the hatched recording area shown in the eighth pass printing. If the correction value calculated by the second correction amount calculation means remains in the feeding direction after the completion of the eighth pass, the recording head 13 (its uppermost discharge portion) moves downstream from the hatched recording area shown in the drawing. It will come out. In that case, there is a portion on the recording medium where the eighth pass recording is not performed, which causes white streaks. On the other hand, when the correction value calculated by the second correction amount calculating means remains less in the feeding direction after the end of the 8th pass, the most upstream discharge portion of the recording head 13 is located upstream of the illustrated hatched recording area. It will remain. In that case, the ninth pass recording (the first pass recording in the next recording range) is performed in the hatched recording area, which causes black streaks between the recording heads.

  In the present embodiment, the correction amount pitch (periodic fluctuation distance) obtained by the second correction amount calculation means is a length obtained by multiplying the number of recording passes necessary to complete an image by the conveyance amount per time (this embodiment). In the form, it is 1 inch). In other words, the correction amount calculated by the second correction amount calculating means is such that the cumulative correction amount in the same recording area is the same as the number of recording passes required to form an image in the same recording area. The relationship is to be offset (some or all are offset). As a result, it is possible to reduce or eliminate the occurrence of streaks caused by the joints of the recording head 13 (its ink ejection portion).

  In the present embodiment, the case where the correction amount pitch of the second correction amount calculating means is obtained by multiplying the conveyance amount of one time by the number of recording passes, but this is obtained by multiplying the divisor of the number of recording passes. But it ’s okay. For example, in the case of the present embodiment, 0.5 inch multiplied by 4 may be used, or a correction means having a correction amount pitch of 0.25 inch multiplied by 2 may be used. The reason is that even if the correction amount pitch is 0.5 inch or 0.25 inch, the correction value (cumulative correction amount) can be canceled by carrying 1 inch.

  In the present embodiment, the correction amount transition for each conveyance by the second correction amount calculation means is represented by a sine wave. However, the correction amount transition may be represented by another waveform such as a rectangular wave or a triangular wave. Furthermore, a histogram of the correction amount for each conveyance by the second correction amount calculation means may be expressed as a normal distribution. Further, the second correction amount calculation means outputs an irregular correction value for each conveyance, but is canceled by accumulating the correction values for the number of recording passes or for the number of times the number of recording passes is divided by an integer. If there is a relationship, the correction amount may be output using another transport error distribution.

  In the above embodiment, the case where the conveyance error is corrected based on the correction values output from both the first correction amount calculation unit and the second correction amount calculation unit has been described. However, in the present embodiment, control may be performed so that the correction by the second correction amount calculation unit is not performed depending on the correction amount calculation result of the second correction amount calculation unit. For example, when the conveyance fluctuation amplitude calculated by the second correction amount calculation unit is larger than the eccentricity amplitude of the conveyance roller, the conveyance variation calculated by the second correction amount calculation unit causes image disturbance. Sometimes. When it is determined that there is no need to use the second correction amount calculation means under such a situation, it is possible to perform recording with higher accuracy by not applying this. The following case can be given as a specific example when it is not necessary to correct the transport error by the second correction amount calculation means. That is, when the eccentric amount of the conveying roller itself is sufficiently small, when the correction amount calculated by the first correction amount calculating means is small, when the number of recording passes is small, the type of recording in which the conveying roller eccentric unevenness is difficult to see. When conveying a medium (for example, plain paper etc.), etc. are mentioned.

  According to the embodiment described above, since the target conveyance amount for each recording pass is not constant, even when the eccentricity correction of the conveyance roller is not properly performed, uneven eccentricity can be reduced, and the conveyance amount can be reduced. There is provided an ink jet recording apparatus capable of preventing the occurrence of black and white lines due to the connection of recording heads without affecting them. That is, by making the conveyance error for each conveyance an error that is not linked to the eccentric phase of the conveyance roller, it is possible to reduce random irregularities in the conveyance roller by causing random changes in the recorded matter. It becomes possible. In addition, since the cumulative correction amount is canceled when the same number of recording passes as the number of recording passes necessary to record an image in the same recording area is canceled, the transport error in the same recording area is reduced without affecting the transport amount. In addition to being able to reduce effectively, it is possible to prevent the occurrence of black and white stripes due to the joints of the recording head. In addition, the second correction amount calculation unit according to the present embodiment can be applied only when the conveyance roller eccentricity unevenness is likely to be large, thereby reducing the occurrence of image disturbance caused by correction. It becomes.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Conveyance roller 3 Pinch roller 4 Carriage 13 Recording head 23 Conveyance roller pair 50 Control means W1 Ideal conveyance amount with respect to a fixed recording range W2 Conveyance amount with respect to a fixed recording range

Claims (9)

In an inkjet recording apparatus that forms an image of the same recording area by causing a recording head that discharges ink to scan the same recording area of the recording medium a plurality of times.
Conveying means for conveying the recording medium in the sub-scanning direction;
First correction amount calculating means for calculating a correction value according to a transport error factor generated from at least one of the recording medium and the transport means when transporting the recording medium;
Second correction amount calculation means for calculating a correction value so as to give a change to the conveyance amount for each sub-scan without relating to the conveyance error factor of the recording medium and the conveyance means when conveying the recording medium;
A transport correction unit that corrects the transport amount using at least one of the first correction amount calculation unit and the second correction amount calculation unit when transporting the recording medium;
With
The correction value for each sub-scan calculated by the second correction amount calculator cancels the cumulative correction amount when the recording medium is conveyed the same number of times as the number of recording passes for forming an image in the same recording area. An ink jet recording apparatus characterized by having a relationship.   The inkjet recording apparatus according to claim 1, wherein the correction amount transition for each conveyance by the second correction amount calculation unit is expressed by a sine wave.   The inkjet recording apparatus according to claim 1, wherein the correction amount transition for each conveyance by the second correction amount calculation unit is represented by a rectangular wave.   The inkjet recording apparatus according to claim 1, wherein the correction amount transition for each conveyance by the second correction amount calculation unit is represented by a triangular wave.   The inkjet recording apparatus according to claim 1, wherein a histogram of correction amounts for each conveyance by the second correction amount calculation unit is a normal distribution.   Whether to use the transport correction unit that performs correction using both the first correction amount calculation unit and the second correction amount calculation unit is determined according to a correction value of the first correction amount calculation unit. An ink jet recording apparatus according to any one of claims 1 to 5.   Whether to use the conveyance correction unit that performs correction using both the first correction amount calculation unit and the second correction amount calculation unit is determined according to an eccentric amount of a roller of the conveyance unit. An ink jet recording apparatus according to any one of claims 1 to 5.   2. The determination as to whether or not to use the conveyance correction unit that performs correction using both the first correction amount calculation unit and the second correction amount calculation unit is made according to the number of recording passes. The inkjet recording apparatus according to any one of 5.   2. The determination as to whether or not the conveyance correction unit that performs correction using both the first correction amount calculation unit and the second correction amount calculation unit can be used according to a type of a recording medium. The inkjet recording apparatus according to any one of 5.

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