JP2010120339A - Printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer capable of stably obtaining a high-quality print by reducing an effect of a kick-off phenomenon more than heretofore. <P>SOLUTION: The printer includes: a conveyance roller for conveying media on the upper stream side than a print position; a discharge roller for conveying the media on the lower stream side; and a means for printing a test pattern onto the media before and after the state transition when the state is switched from a first state in which the same media are conveyed by the conveyance roller and the discharge roller to a second state in which the media separated from the conveyance roller are conveyed by the discharge roller. Further, the printer repeats the state transition several times and prints the test pattern several times onto the same media. Furthermore, the printer reads the test pattern with a sensor and obtains a correction value for controlling the conveyance of the media. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of an ink jet printer that prints an image on a medium.

  When printing is performed while transporting print media such as cut sheets (hereinafter referred to as media), if the transport accuracy is low, density unevenness of the halftone image or magnification error may occur, resulting in a printed image. The quality of the product deteriorates. For this reason, high-precision parts are used and a precise transport mechanism is installed, but the demand for print quality is severe and further improvement in accuracy is desired. On the other hand, the demand for cost is strict, and both high accuracy and low cost are required.

  Many printers include a conveyance roller and a discharge roller with a printing unit interposed in the conveyance direction. In this configuration, at the moment of switching from a state where the medium is transported by both rollers to a state where the medium is transported only by the discharge roller, the rear end of the medium is ejected from the nip of the transport roller, and the force reaches the media transport direction. A so-called kicking phenomenon can occur. The kicking impedes stable conveyance, and as a result, causes white and black streaks in the printed image.

Patent Document 1 pays attention to a problem in which a conveyance error occurs when the medium is switched from a state where the medium is conveyed by both rollers to a state where the medium is conveyed only by the discharge roller. In order to solve this, a method is disclosed in which a test pattern is printed on a medium before and after switching, and the test pattern is read by a sensor and input to the apparatus as a correction value to correct the transport amount.
JP 2005-7817 A

  In Patent Document 1, a test pattern is printed once and the correction value is acquired when the trailing edge of the medium comes off the transport roller. However, in response to a request for further high accuracy, an optimal correction value for correcting the carry amount may not be obtained by detection only once. Therefore, there still remains a wrinkle that causes quality degradation such as white stripes and black stripes in the printed image.

  The present invention has been made based on recognition of the above problems. An object of the present invention is to provide a printer that can reduce the influence of the kicking phenomenon more than ever and can stably obtain high-quality prints.

  The printer of the present invention that solves the above problems includes a carriage that holds a print head for printing on a medium at a print position, a first rotating body that conveys the medium upstream of the print position, and the print The second rotating body that conveys media downstream from the position, and the first state in which the same medium is conveyed by the first rotating body and the second rotating body are separated from the first rotating body. The test pattern is printed on the medium before and after the state transition to which the state is switched to the second state in which the medium is transported by the second rotating body, and the test pattern is applied to the same medium by repeating the state transition a plurality of times. The means for controlling to print a plurality of times, and the test pattern printed a plurality of times are read by a sensor, It is characterized in that it has a means for obtaining a correction value for controlling the transport of.

  According to the present invention, the test pattern is printed and detected before and after the state transition from the first state to the second state a plurality of times, thereby reducing the influence of the kicking phenomenon more than before and producing a high quality print. A printer that can be obtained stably can be provided.

  Exemplary embodiments of the present invention will be described below with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

  Hereinafter, an ink jet printer will be described as an example. However, the printer of the present invention can also be applied to a multifunction machine having a copying function and a scanning function, a so-called multi-function printer. As the inkjet method, various methods such as a method using a heating element, a method using a piezo element, a method using an electrostatic element, and a method using a MEMS element can be used. Further, the present invention is not limited to the inkjet method, and can be applied to printers of other methods such as an electrophotographic method and a thermal method. The present invention is also applicable to various manufacturing apparatuses that print or process media such as color filter substrates and circuit boards. In this specification, these manufacturing apparatuses are also referred to as a printer.

  FIG. 1 is a perspective view showing a configuration of a main part of an ink jet printer according to an embodiment of the present invention. The medium M is sandwiched between the conveyance roller 1 (first rotating body) and a plurality of pinch rollers 2 that are energized and driven by the conveyance roller 1, and is guided by the platen 3 by the rotation of the conveyance roller 1. The medium M is conveyed in the direction of arrow A in the figure. The conveyance roller 1 is made of a metal roller that has been processed so that a large frictional force can be generated by forming fine irregularities on the surface. Thereafter, the medium M is also sandwiched between the discharge roller 12 (second rotating body) and the plurality of spurs 13 that are energized and driven by the medium, transported in the transport direction A, and discharged to the discharge tray 15. The discharge roller 12 is a rubber roller having a large coefficient of friction. The discharge roller 12 is set to have a roller diameter that is increased by about 1% in order to prevent sagging when the medium M is transported with respect to the transport roller 1. Therefore, when the medium M is sandwiched and transported by both the transport roller 1 and the discharge roller 12, the transport is performed in a state in which the discharge roller 12 is slightly slipped due to the difference in the sandwiching force.

  Printing is performed at a printing position between the conveyance roller 1 and the discharge roller 12. That is, the conveyance roller 1 is in a positional relationship such that the medium M is conveyed upstream from the printing position, and the discharge roller 12 is conveyed in the downstream side from the printing position. In order to perform printing, the carriage 7 mounts and holds the ink jet print head 4 and reciprocates along the two guide rails 5 and 6 in the main scanning direction orthogonal to the sub-scanning direction. The carriage 7 is equipped with a reflective optical sensor 16. The optical sensor 16 includes a light source and a light receiving unit, and optically reads a test pattern printed on a medium and an edge of the medium.

  The print head 4 includes a plurality of nozzle rows for discharging inks of different colors (here, four colors) formed along the main scanning direction. Close to the surface. Each nozzle row is composed of 1280 nozzles arranged at an interval of 1200 dpi along the sub-scanning direction. A plurality of inks of each color are supplied to the print head 4 from an independent cartridge type ink tank 8 through a flexible tube 10. The ink tank 8 is detachably mounted on a tank mounting unit 9 provided at a location independent of the carriage 7.

  A recovery unit 11 is provided next to the platen 3 in the main scanning direction. The recovery unit 11 is a cap for preventing ink evaporation on the ejection surface of the print head 4, a suction mechanism for forcibly sucking ink while the ejection surface is capped, and wiping dirt on the ejection surface. A cleaning blade or the like. The media pressing portion 14 is a regulating member that regulates that the edge of the media M in the main scanning direction is lifted upward (from the print head 4 side) from the platen 3. The control unit 20 includes a CPU 21, a memory 22, and various I / O interfaces, and is a controller that controls various controls of the entire printer, and is built in the apparatus main body.

  Next, the transport control procedure for the medium M will be described. During the printing operation, printing is performed with multi-pass (8 passes in this embodiment). In addition, by dividing the entire surface of the medium M into three regions and changing the conveyance / printing operation for each region, it is possible to stably obtain a good image with high throughput.

  FIG. 2 is a diagram showing that the medium M is divided into three areas along the transport direction. The medium is divided into three areas A, B, and C. FIG. 3 is a cross-sectional view of the state of each process of the medium M transported along the transport path as viewed from the side.

  FIG. 3A shows a state in which the medium is transported only by the transport roller 1. FIG. 3A shows a state in which the medium is conveyed only by the conveyance roller 1, and FIG. 3B shows a state in which the medium is conveyed by the conveyance roller 1 and the discharge roller 12. FIG. 3C shows a state immediately before the medium is switched from the state where the medium is transported by the transport roller 1 and the discharge roller 12 to the state where the medium is transported only by the discharge roller 12. FIG. 3D shows a state immediately after the medium is separated from the transport roller 1 and switched to a state where the medium is transported only by the discharge roller 12. FIG. 3E shows a state where the medium is conveyed only by the discharge roller 12. In this specification, the states of FIGS. 3 (b) and 3 (c) are referred to as “first state”, and the states of FIGS. 3 (d) and 3 (e) are referred to as “second state”. The switching between the first state and the second state is referred to as “state transition”.

  In FIG. 2, in the area A, the medium M is transported only by the transport roller 1 (see FIG. 3A), or is transported by the two rollers of the transport roller 1 and the discharge roller 12 at the time of printing in this region. (See FIG. 3B). The clamping force between the conveying roller 1 and the pinch roller 2 is sufficiently larger than the clamping force between the discharge roller 12 and the spur 13. Therefore, even if the state is switched from the state shown in FIG. 3A to the state shown in FIG.

  The area B of the medium is conveyed only by the discharge roller 12 from the first state (see FIG. 3C) in which the medium is conveyed by the two rollers of the conveyance roller 1 and the discharge roller 12 when printing in this area. This is a region including the moment of state transition that switches to the second state (see FIG. 3D). In this region, a so-called kicking phenomenon occurs. The kicking phenomenon is that at the moment when the rear end of the medium to be conveyed comes out of the conveying roller 1 and the pinch roller 2, the roller is kicked in the conveying direction, and the urging force momentarily acts to change the conveying amount. It is a phenomenon. In this embodiment, in order to ensure the correction of the conveyance amount before and after the state transition, the trailing end of the medium M is stopped in the range of 3 mm before and after the nip position between the conveyance roller 1 and the pinch roller 2 during the printing operation. Do not carry.

  The area C of the medium is an area in which the medium is transported only by the discharge roller 12 when the area is printed (see FIGS. 3D and 3E). Since the discharge roller 12 is a rubber roller, an eccentric error of the roller diameter tends to occur. In addition, the clamping force between the discharge roller 12 and the spur 13 is small, and slip is likely to occur. In this embodiment, in order to reduce this influence, the step feed amount (64 nozzles) by the discharge roller 12 in the region C is made smaller than the step feed amount (160 nozzles) by the transport roller 1.

  FIG. 4 is a diagram for explaining the operation of normal printing of 8 passes in the area A. In the figure, one of the small horizontally long squares has 16 nozzles in the transport direction (A direction). 80 of these gather in the transport direction to form a 1280 nozzle. N1 indicates the first nozzle on the most downstream side (discharge roller 12 side) of the transport path, and N1280 indicates the 1280th nozzle on the most upstream side (transport roller 1 side) of the transport path. The numbers [1] to [8] indicate the number of print passes (main scanning of the print head 4). In the figure, for convenience of explanation, the nozzle row is drawn so as to move relative to the print location of the medium M from top to bottom, but the medium M actually moves in the direction A in the figure.

  In the area A, printing is performed using all 1280 nozzles provided in the print head 4 up to immediately before the area B. Subsequent to the first pass printing, the medium M is stepped by 160 nozzles in the sub-scanning direction to perform the second pass printing. Similarly, step feed for 160 nozzles and printing for the third to eighth passes are repeated. A print is completed in eight print passes [1] to [8] in the same area. The shaded area in FIG. 4 indicates a print completion area in which an area for 160 nozzles is completed in 8 passes in the transport direction.

  FIG. 5 is a diagram for explaining the printing operation when the print area is shifted from the area A to the area B and further to the area C. The numbers [0] to [20] indicate the number of print passes. Further, gray squares indicate nozzles to be used, and white squares indicate non-use nozzles that restrict use.

  As described above, all 1280 nozzles are used until the print pass 0 (eight passes before the end point of the area A). On the other hand, after the print pass [1], the number of nozzles to be used is limited and the transport amount (step feed amount) of the medium is also changed depending on the location. The start position of the print pass [1] is determined according to the distance from the rear end of the medium M. From the print pass [1] to the print pass [7], the number of nozzles to be used is sequentially reduced by 32 nozzles. At the same time, the step feed amount of the medium M between the print buses is reduced from 160 nozzles to 128 nozzles.

  During the print pass [7], the rear end of the medium M is at the position shown in FIG. From the nip position between the conveying roller 1 and the pinch roller 2, the rear end of the medium M remains by 144 nozzles (3 mm) upstream. Between the print pass [7] and the print pass [8], the medium M is moved by 288 nozzles (6 mm). As a result, during the print pass [8], the rear end of the medium M is in the position shown in FIG. 3D, and is 144 nozzles (3 mm) downstream from the nip position between the conveying roller 1 and the pinch roller 2. It becomes the moved position.

  In the area C, the number of unused nozzles that limit use is sequentially increased from the print pass [8] to the print pass [20], and the amount of step movement of the medium M is reduced to 64 nozzles. In the present embodiment, the print end position is a position 3 mm from the rear end of the medium M (rear end margin 3 mm). However, it is not limited to 3 mm and can be an arbitrary margin length.

  In the area B and the area C, media conveyance in the state transition from the first state to the second state is controlled. FIG. 6 shows a test pattern printed on the medium M, which is used to obtain a correction value for this control. The test pattern includes pattern elements 1001 to 1010 having the same shape. Pattern elements 1001 to 1005 are pattern elements for acquiring correction values in the region B, and pattern elements 1006 to 1010 are pattern elements for acquiring correction values in the region C. Each of these pattern elements is formed at a position separated from the rear end of the medium M by a predetermined distance. Each of the pattern elements 1001 to 1010 is composed of seven patch groups C0 to C6 arranged in the main scanning direction, and the size of one patch is 160 nozzles (3.4 mm) in the sub scanning direction, and 472 nozzles in the main scanning direction. Minute (10 mm). The test pattern is formed by two print passes as described below.

  FIG. 7A is a partially enlarged view of ink dots included in three patches (C2, C3, C4) in any one of the pattern elements 1001 to 1010 formed in the first pass. The interval between the lines in the transport direction is equal to 6 nozzles (1200 dpi).

  FIG. 7B is an enlarged view of ink dots of the same patch portion formed in the second pass. The dot row is formed at the same position in C3 with respect to the ink dot row formed in the first pass. However, the patches at other positions are formed by shifting the ink dot rows by a predetermined amount in the media transport direction. Specifically, the C2 pattern 1101b is shifted to the downstream in the transport direction by one nozzle, and conversely, the C4 pattern 1103b is shifted to the upstream in the transport direction by one nozzle. Although not shown in the figure, the C1 pattern is shifted to the downstream side in the transport direction by 2 nozzles, the C0 pattern is shifted by 3 nozzles, and conversely, the C5 pattern is 2 nozzles and the C6 pattern is 3 nozzles. It is formed by shifting to the upstream side in the transport direction by the amount.

  FIG. 7C shows ink dots formed as a result of overlapping the first pass shown in FIG. 7A and the second pass shown in FIG. 7B. Between the first pass and the second pass, the medium M is transported in the forward direction, and the state transitions from the first state to the second state. For convenience of explanation, the pattern printed at the first time is indicated by a white circle, and the pattern printed at the second time is indicated by a black circle, but both are the same color.

  In the ideal state where the conveyance error is zero, the overlapping white circle and black circle are completely overlapped with each other in the pattern 1102 at C3. In the patterns 1101 and 1103, the overlapping ink dots are shifted by one nozzle in the transport direction, and the area factor (ratio of the ink dots covering the print surface) is relatively higher than that of the pattern 1102. For this reason, the print density of the pattern 1101 and the pattern 1103 is higher than that of the pattern 1102. Similarly, since the ink dots are superimposed in a state shifted by two nozzles in the patterns C1 and C5 and by three nozzles in the patterns C0 and C6, the patterns 1101 and 1103 are further overlapped with the pattern 1102. Print density also increases.

  If a conveyance error occurs in the conveyance after the first pass printing, the position where the white circle and the black circle overlap with each other at the time of printing in the second pass is not C3 but another patch position. For example, when it is shorter than the original transport distance by one nozzle, white circles and black circles overlap in the C2 pattern 1101 without deviation, and the C2 patch density is the lowest. For example, when the transport distance is long by two nozzles, the white circle and the black circle of the C5 pattern overlap without deviation, and the density of the C5 patch is the lowest. Therefore, by comparing the density of each patch and detecting the position (C0 to C6) of the patch where the density is lowest, a shift in the transport distance of the medium, that is, a transport error can be obtained.

  FIG. 8 shows an example of the reflected light intensity when detecting the density of each patch. The vertical axis represents the intensity of the scattered reflected light. The stronger the reflected light, the lower the patch density. The horizontal axis represents the positions C0 to C6 of the seven patches (left and right direction in FIG. 6). The optical sensor 16 detects the intensity of scattered reflected light from the surface of the medium M at each patch position. As a result, when seven detection values as shown in FIG. 8 are obtained, a function is calculated using the least square method for the seven detection values. Then, by deriving the adjustment value corresponding to the position of the maximum value of the curve, it is possible to acquire the transport error with an accuracy exceeding the nozzle resolution.

  Next, a procedure for printing the test pattern shown in FIG. 6 on the medium before and after the state transition from the first state to the second state will be described with reference to FIG.

  The pass [1] is the first state shown in FIG. 3C, and the rear end of the medium is shifted by 144 nozzles (3 mm) upstream from the nip position between the transport roller 1 and the pinch roller 2. Here, the first patch row constituting the test pattern is printed (first pass of the pattern element 1001). Specifically, a patch group in which seven patches having a size corresponding to 160 nozzles (3.4 mm) in the transport direction and 472 nozzles (10 mm) in the main scanning direction are arranged in the transport direction is formed on the medium.

  Next, the medium is conveyed in the forward direction by a distance of 288 nozzles (6 mm). By this conveyance, the state transitions from the first state to the second state. This carry amount is equal to the carry amount during actual image printing.

  The pass [2] is in the second state shown in FIG. 3D, and the rear end of the medium is shifted by 144 nozzles (3 mm) downstream from the nip position between the transport roller 1 and the pinch roller 2. Here, among 1280 print nozzles, ink is ejected from a nozzle array shifted by 288 nozzles (6 mm) from the nozzle array used in the first pass, and is superimposed on the pattern element 1001 formed in the first pass. Print the second pass. [2] The print pattern in the second pass is shifted by one nozzle according to the position of the patch as described with reference to FIG.

  When the first patch row is formed in this way, the medium is fed back by 288 nozzles (6 mm) in the direction opposite to the transport direction (forward direction) so far. The rear end of the media returns to the position shown in FIG. Then, in the pass [3], the second patch row constituting the test pattern using 160 nozzles shifted by 160 nozzles (3.4 mm) with respect to the print nozzles used in the above pass [1]. Printing (first pass of pattern element 1002) is performed. Then, the medium M is conveyed in the forward direction by 288 nozzles (6 mm), and the state is changed from the first state to the second state. Then, the second pass is printed in pass [4] to complete the second patch row (pattern element 1002).

  Thereafter, the same procedure is repeated to form the third column to the fifth column (pattern elements 1003 to 1005) by the passes [5] to [10]. Thus, the test pattern corresponding to the region B is completed.

  Next, a test pattern for region C is formed. After the pass [10] is printed, the medium M is conveyed in the forward direction by 128 nozzles (2.7 mm). Then, the pass [11] is printed. At this time, among the print nozzles, 320 nozzles are used, the downstream side (upper side in the figure) 160 nozzles (3.4 mm) are used in the second pass, and the upstream side (lower side in the figure) 160 nozzles (3.4 mm). Is used in the first pass. Only the last pass [15] uses only 160 nozzles. By repeating the forward conveyance of 128 nozzles (2.7 mm) and the passes [12] to [15], the sixth to tenth patch rows (pattern elements 1006 to 1010) included in the region C are repeated. ) Is completed.

  Among the test patterns formed as described above, the pattern elements 1001 to 1005 are detected by the optical sensor 16, and the transport error in the region B, that is, the transport error before and after the state transition from the first state to the second state is detected. get. Further, the pattern elements 1006 to 1010 are detected by the optical sensor 16 to acquire a conveyance error in the region C, that is, a conveyance error when the medium is conveyed only by the discharge roller 12 and the spur 13.

  Next, a specific procedure for acquiring a conveyance error and setting a correction value will be described with reference to the flowchart of FIG. The following sequence is realized by the CPU 21 of the control unit 20 controlling and calculating.

  In step S1, the user selects a blank medium to be used for setting a correction value and sets it in the printer body. In step S2, a test print is instructed. In step S3, the test pattern shown in FIG. 6 is printed according to the above-described procedure based on the instruction. In step S4, the printed test pattern is read by the optical sensor 16. This detects the density of seven patches for each column of the pattern elements 1001 to 1005 (region B) and the pattern elements 1006 to 1010 (region C) in FIG. Using this detection result, the transport error in each row is calculated by the method described in FIG.

  In step S5, the average value of the five transport errors calculated by the pattern elements 1001 to 1005 is calculated for the region B, and the average value of the five transport errors calculated by the pattern elements 1006 to 1010 is calculated for the region C. And it memorize | stores in the memory 22 of the control part 20 as a correction value in each of the area | region B and the area | region C. FIG. For region B, the correction value per transport distance for 288 nozzles is stored in units of 9600 dpi. For the area C, a value per conveyance distance for 1280 nozzles is stored in units of 9600 dpi, and a value proportionally calculated according to each conveyance amount is added in units of 9600 dpi. At the time of actual image printing, referring to the correction value stored in the memory 22, the conveyance of the media when the areas B and C pass the printing unit is controlled. Since the control method is well-known, detailed description is abbreviate | omitted.

  As described above, the test pattern is printed on the medium before and after the state transition from the first state to the second state, and the test pattern is printed on the same medium a plurality of times by repeating the state transition a plurality of times. The test pattern printed a plurality of times is read by the optical sensor 16 to obtain a correction value for controlling the conveyance of the medium. Using the correction value obtained in this way, media conveyance control is performed when actual image printing is performed. As a result, the effect of the kicking phenomenon is reduced more than before, and an excellent printer capable of stably obtaining high-quality prints is realized.

(Another embodiment)
Another embodiment of the present invention will be described below. In addition, it demonstrates centering on a different part from previous embodiment, and abbreviate | omits the structure and operation | movement which overlap.

  When a large-sized medium is used, the conveyance direction of the medium is not stable due to the weight of the medium, and skewing may occur. When skewing occurs, the variation in the transport error between the regions B and C becomes larger. Therefore, the number and arrangement of test patterns are varied according to the size of the media. FIG. 11 shows an example of a test pattern when a large size medium is used. Compared to the test pattern of FIG. 6, the number of pattern elements (patches) is increased in the main scanning direction.

  Furthermore, the number and arrangement of pattern elements may be set according to the type of media. Of the media, plain paper has more ink dots applied on the media than glossy paper, so the image quality itself is inferior to glossy paper, but image streaks due to transport errors are less than glossy paper. Therefore, it is possible to reduce the time required for pattern reading and the calculation load by reducing the number of pattern elements for the test pattern on plain paper than on glossy paper. Furthermore, the pattern element of the test pattern may be changed according to the combination of the size and type of media.

  As yet another embodiment, the transport distance of the medium M when the state transitions from the first state to the second state may be detected using a so-called media sensor. FIG. 12 shows a configuration in which the carriage 7 is mounted with the media sensor 100 together with the print head 4. The media sensor 100 includes a light source 101 such as an LED or an OLED and a light receiving unit 102, and captures the surface of the medium M illuminated by the light source 101 with the light receiving unit 102 to obtain one-dimensional or two-dimensional image data. The acquired image data is subjected to image processing by the control unit 20 to extract image features, thereby obtaining an image shift amount. For image feature extraction, for example, the image data is subjected to Fourier transform to check for coincidence for each frequency, the peak portion is extracted to acquire the amount of positional deviation, or the acquired print image data is used. There is a method of binarizing and checking pattern matching.

  FIG. 13 shows a test pattern detected by the media sensor. The test pattern 200 is configured by arranging fine lines 201a, 201b,... 205a, 205b at regular intervals in the transport direction. First, the line 201a is printed before the state transition from the first state to the second state, and the line 201b is printed after the state transition. The interval between the pairs of lines 201a and 201b includes transport error information before and after the state transition. Next, the medium M is sent back by the same amount in the reverse direction, the state is changed from the second state to the first state, and the lines 202a to 205a and the lines 202b to 205b are changed in the same procedure using different nozzles. 4 sets are printed in order. Thus, a test pattern consisting of five sets of lines is formed on the medium M. The distance between each set is detected by the media sensor 100, a transport error with respect to the designed transport amount is calculated, and the average of these five erroneous transport errors is used as a correction value to determine the memory of the control unit 20 22 to store.

The perspective view which shows the structure of the principal part of a printer Diagram showing three areas on the media Cross-sectional view showing each process of media transport The figure explaining the operation | movement of the 8-pass normal printing in the area | region A The figure explaining printing operation at the time of shifting to area A, area B, and area C The figure which shows the test pattern printed on the medium M A partially enlarged view of the ink dots forming the patch The figure which shows the example of the reflected signal strength at the time of detecting each patch The figure explaining the printing operation at the time of forming a test pattern The flowchart figure which shows the specific procedure which acquires a conveyance error and sets a correction value Diagram showing test pattern when using large size media The figure which shows the structure of embodiment using a media sensor. Diagram showing test pattern detected by media sensor

Explanation of symbols

1 Conveying roller (corresponding to the first rotating body)
2 Pinch roller 3 Platen 4 Print head 7 Carriage 12 Discharge roller (corresponding to the second rotating body)
13 Spur 16 Optical sensor 20 Control unit

Claims (6)

A carriage for holding a print head for printing on a medium at a print position;
A first rotating body that conveys media upstream of the print position;
A second rotating body that conveys media downstream of the print position;
From the first state in which the same medium is transported by the first rotating body and the second rotating body, to the second state in which the medium separated from the first rotating body is transported by the second rotating body. Means for printing a test pattern on a medium before and after a state transition in which the state is switched, and controlling the state pattern to be printed a plurality of times on the same medium by repeating the state transition a plurality of times;
A printer comprising: means for reading a test pattern printed a plurality of times with a sensor and acquiring a correction value for controlling the conveyance of the medium. The test pattern includes a plurality of pattern elements that are formed for each of the plurality of state transitions and that have different positions in the medium conveyance direction,
The printer according to claim 1, wherein the pattern element is formed by printing before and after the state transition. The test pattern includes a plurality of pattern elements formed for each of the state transitions a plurality of times and having different positions in the main scanning direction of the print head,
3. The printer according to claim 1, wherein the pattern element is formed by printing before and after the state transition.   The printer according to claim 2 or 3, wherein the sensor detects the density or interval of the plurality of pattern elements.   The printer according to claim 1, wherein the test pattern is changed according to the size or type of the medium.   The printer according to claim 1, wherein the print head performs printing by an inkjet method.

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