JP2010201851A - Method of detecting ink discharge condition and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately decide about an influence of auxiliary droplets and automatically restrain the influence of the auxiliary droplets in ink recording. <P>SOLUTION: The method of detecting an ink discharge condition is intended to record a first pattern 15 having a high-density distribution of dots in the direction x/y intersecting the row Ny/17y of nozzles at right angles but a low-density distribution of dots in the direction y/x parallel with the row of nozzles and less susceptible to the influence of the auxiliary droplets, and a second pattern 16/16a/16b having a high-density distribution of dots in the direction y/x parallel with the row of nozzles and a low-density distribution of dots in the direction x/y intersecting the row of nozzles at right angles, having the same recording density as the first pattern and susceptible to the influence of the auxiliary droplets on the recording paper, measure the densities, compute a parameter showing the relative relationship between both pattern densities, and decide about presence of an influence of the auxiliary droplets in a second pattern image by the control means 19 of an inkjet recording device having a recording head 5/17 having the row Ny/17y of nozzles and the control means 19 to relatively scan and drive at least one 5/17 of recording paper 7 in the direction x (Fig.1)/y(Fig.13) intersecting the row of nozzles at right angles, and urge the recording head and discharge ink droplets to the recording paper. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to ink jet recording, and more particularly to a method and apparatus for detecting the occurrence of subdroplets from ink droplets ejected from a recording head.

  2. Description of the Related Art Conventionally, an image recording apparatus has an inkjet head (ink ejection head) in which a large number of nozzles are arranged. By ejecting ink from the nozzles while relatively moving the inkjet head and the recording paper, 2. Related Art Inkjet recording apparatuses (inkjet printers) that record images are known. Conventionally, various methods are known as ink ejection methods in such an ink jet recording apparatus. For example, the diaphragm constituting a part of the pressure chamber (ink chamber) is deformed by deformation of the piezoelectric element (piezoelectric ceramic) to change the volume of the pressure chamber, and when the volume of the pressure chamber is increased, Ink is introduced into the pressure chamber, and when the volume of the pressure chamber is reduced, the ink is ejected from the nozzle as ink droplets, or the ink is heated to generate bubbles and the expansion energy when the bubbles grow. A thermal ink jet method for discharging is known. When ink droplets are widely ejected in ink jet recording, the tail at the time of ejecting main droplets becomes ink droplets due to the surface tension of the ink itself, and sub-droplets are generated separately from the main droplets that are originally required for printing. It has been observed that this sub-droplet is formed by tearing the tail extending from the main drop, so that the flight speed is slower than that of the main drop.

  FIG. 18 shows how ink droplets ejected from the recording head 5 are recorded on the recording paper 7. FIG. 19A shows an ink droplet that has just been ejected, but when the ink droplet has a tail and is interrupted in the air, the large main droplet that flies ahead and the rear shown in FIG. It breaks up into small side drops that follow. At this time, since the subdrop is formed by tearing the tail extending from the main drop, the flying speed is also slower than that of the main drop.

FIG. 20A shows a state in which a plurality of ink droplets are ejected continuously from one nozzle. There is a recording method in which multiple ink droplets are ejected continuously from one nozzle, merged in the air, and landed on the recording paper as one large-volume ink droplet. In some cases, the ink drops on the recording paper as main drops and sub-drops.
For example, FIG. 20B shows that when a plurality of ink droplets are ejected continuously from one nozzle, the droplets merge in the air and land on the recording paper as a single droplet. FIG. 20C shows a state in which a plurality of droplets are not merged in the air and landed on the recording paper as main droplets and sub-droplets.

  When ink droplets land on the recording paper in such a way that they are divided into main droplets and sub-droplets, the main droplet of one ink droplet discharged from the nozzle as the relative speed (recording speed) between the recording head and the recording paper increases. The difference between the position where the ink reaches the recording paper (landing position) and the position where the sub-droplet lands on the recording paper gradually increases.

  Such sub-drop generation can be detected as the density of the recorded image. FIG. 21 (a) shows a case where there is no sub-drop, and FIG. 21 (b) shows a case where a sub-drop occurs. The density value increases as the landing position of the sub-drop drops away from the main drop. Tend to be.

  In this way, when ink droplets land on the recording paper divided into main droplets and sub-droplets, as the relative movement speed (recording speed) between the recording head and the recording paper increases, the main droplet of one ink droplet ejected from the nozzle increases. The difference between the position where the droplet landed on the recording paper (landing position) and the position where the sub-droplet landed on the recording paper gradually increased, and the recording density (surface recording density) increased, affecting the image quality. Adverse effects on character quality, ruled line quality, graininess, color reproducibility, and the like. For example, the line in the orthogonal direction y is thicker than the line in the main scanning direction x of the ruled line.

  In Patent Document 1, the displacement of the landing position of the sub-droplet with respect to the landing position of the main droplet increases as the distance of the nozzle to the paper (gap between papers) increases, and the displacement increases as the conveyance speed of the paper increases. Therefore, a method is described in which a test pattern as shown in FIG. 21A is recorded, the recording density is measured, and the quality of ink ejection is determined based on whether or not the density measurement value exceeds a specified threshold value. ing. Japanese Patent Application Laid-Open No. 2004-228561 describes a method of observing the vicinity of an ink discharge nozzle of an ink recording head with a light emitting element and a light receiving element, and detecting the generation of a sub-drop by changing the amount of received light. In Patent Document 3, the ejection angle of the sub-droplet ejected from the nozzle is offset with respect to the ejection angle of the main droplet, so that the sub-dropping position relative to the landing position of the main droplet is determined during forward scanning and sub-scanning. Assuming that the droplet landing position is different and the recording density is different, a density difference correction signal between forward scanning and sub-scanning is stored in a LUT (Look Up Table: RAM), read out from the LUT, An image recording method is described in which density correction is performed on image data during forward scanning and sub-scanning.

  However, since the ink ejection quality determination method described in Patent Document 1 uses only the measurement value of the recording density of one test pattern, the density variation due to individual differences in the ejection performance of the recording head (variation in ink droplet size). In addition, the recording density variation that appears due to the influence of external factors such as the outside air temperature and the head temperature may be determined to be defective, and the defect determination accuracy is considered to be low. In the satellite detection method described in Patent Document 2, even if the occurrence of a satellite is detected, it cannot be determined whether the satellite has an adverse effect on image quality. Since the recording density varies due to the variation in density due to individual differences in the ejection performance of the recording head and the influence of external factors such as the outside air temperature and the head temperature, the recording density varies even in the image recording method disclosed in Patent Document 3. there is a possibility. By generating a LUT for each print head solid and correlating the LUT density difference correction signal with other parameters such as outside air temperature, head temperature, ink density, etc., it may be possible to improve variations in print density. However, parameter collection for improving LUT generation and variation is complicated.

  The first object of the present invention is to determine whether or not there is an influence of a sub-droplet with a simple and high accuracy for each recording head. A second object is to automatically suppress the influence of sub-drops in ink jet recording.

(1) A recording head (5 / 17y) having a nozzle row (Ny / 17y) in which a plurality of ink ejection nozzles are arranged; at least one of the recording head and recording paper (5 in FIG. 1 and 7 in FIG. 13) The scanning means (2-4 / 25) for scanning and driving relative to the other, in the direction orthogonal to the nozzle row (x in FIG. 1 / y in FIG. 13); and the scanning driving An inkjet recording apparatus comprising: control means (19) for controlling and energizing the recording head to eject ink droplets by the recording head to the recording paper;
A first test pattern (15) having a high density of dot distribution in the direction (x / y) perpendicular to the nozzle row (Ny / 17y) and less affected by sub-drops by the control means (19). The second test pattern (16 / 16a / 16b), which has a low density dot distribution in the direction (x / y) perpendicular to the nozzle row (Ny / 17y) and is likely to be affected by subdrops, is recorded on the recording paper. And
Measuring the density of the first and second test pattern images formed on the recording paper;
A relative parameter representing a relative relationship between the first and second test pattern image densities is calculated, and it is determined based on the relative parameter whether the second test pattern image is affected by a secondary droplet; a method for detecting an ink ejection state .

  In addition, in order to make an understanding easy, the symbol of the corresponding element or the corresponding matter of the Example which is shown in drawing and mentioned later in parentheses is attached for reference as an example. The same applies to the following.

  Since the first test pattern image that is easily affected by the generation of sub-drops and the second test pattern image that is not easily received are simultaneously recorded and the density is compared, the effect of sub-drops can be detected with an inexpensive configuration. Since the relative parameter of the concentration is calculated and it is determined whether there is an influence of the secondary droplet based on the relative parameter, the influence of the secondary droplet can be grasped quantitatively. The image density of the first and second test patterns is affected by dots other than the main droplet, such as a secondary droplet, by using an image density measuring device such as an inexpensive photo sensor or a scanner mounted on an MFP (multifunction printer). Automatic detection is possible. In addition, it is possible to automatically generate a maintenance request according to this and to automatically adjust the influence of the sub-droplet, so that a good image can be provided.

1 is a perspective view illustrating an appearance of an ink jet printer according to a first embodiment of the present invention. FIG. 2 is a perspective view showing an arrangement of nozzle rows Ny to Nk facing the recording paper of the recording head 5 shown in FIG. 1. FIG. 2 is a plan view showing a first test pattern image 15 and a second test pattern image formed on a recording paper 7 by the recording head 5 shown in FIG. 1. It is a block diagram which shows the structure of printer controller PCR to which the inkjet printer 100 shown in FIG. 1 was connected. FIG. 2 is a block diagram illustrating a configuration of a print controller 19 in the inkjet printer 100 illustrated in FIG. 1. 6 is a flowchart showing an outline of a discharge inspection executed by the printer controller PCR shown in FIG. 4 using the print controller 19 shown in FIG. 10 is a flowchart illustrating an outline of a discharge inspection executed by a printer controller PCR of a second embodiment using a print controller 19; It is a top view which expands and shows the 1st test pattern image 15 and the 2nd test pattern image 16 which are recorded on a recording paper in discharge inspection. FIG. 3 is an enlarged plan view showing a first test pattern image 15 and a second test pattern image 16 recorded on a recording paper in two ejections in a discharge inspection. It is a top view which expands and shows the dot recording position of the 2nd test pattern images 16a and 16b formed on a recording paper in discharge inspection. FIG. 9 is a plan view showing one example of each of a first test pattern image and a second test pattern image on a recording sheet on which the first test pattern image 15 and the second test pattern image 16 shown in FIG. 8 are recorded. It is a block diagram which shows the system configuration | structure of the multifunction printer of 3rd Example of this invention. It is a block diagram which shows the mechanism outline | summary of the inkjet printer 100 shown in FIG. FIG. 2 is a block diagram illustrating a configuration of a print controller 19 in the inkjet printer 100 illustrated in FIG. 1. FIG. 15 is a flowchart showing an outline of a discharge inspection executed by the printer controller PCR shown in FIG. 12 using the print controller 19 shown in FIG. 14. 10 is a flowchart illustrating an outline of a discharge inspection performed by a printer controller PCR according to a fourth embodiment using a print controller 19; It is a top view which expands and shows the 1st test pattern image 15 and the 2nd test pattern image 16 which are used by 3rd and 4th Example. FIG. 6 is a perspective view showing the shape of ink ejected from a recording head on a recording paper. FIG. 6 is a longitudinal sectional view illustrating separation of ink ejected from a recording head into main droplets and sub-droplets. 3 is a perspective view of a recording paper showing an image formed on recording paper by ink ejected from the recording head. FIG. FIG. 6 is an enlarged plan view showing two modes of an image obtained by scanning a recording paper with a recording head in the main scanning direction x and recording dots in a zigzag pattern.

  (2) The first test pattern (15) is a plurality of parallel lines parallel to the direction (x / y) orthogonal to the nozzle row (Ny); the ink ejection state according to (1) above Detection method.

  (3) The second test pattern (16) is a plurality of parallel lines parallel to the nozzle row (Ny); The method for detecting an ink ejection state according to (1) or (2) above.

  (4) The relative parameter is a difference or ratio between first and second test pattern image densities; the ink ejection state detection method according to any one of (1) to (3) above.

  (5) When the relative parameter exceeds a predetermined threshold, it is determined that there is an influence of a secondary droplet; the method for detecting an ink discharge state according to (4) above.

  (6) If it is determined that there is an influence of the sub-droplet, the recording condition of the ink jet recording in which the recording head is urged by the control means (19) to eject the ink droplet by the recording head to the recording paper is set as the sub-recording condition. The ink discharge state detection method according to the above (5), wherein the ink discharge state is changed in a direction in which the influence of the droplet is reduced.

  (7) The recording condition includes the speed of the scanning drive by the scanning means (2 to 4/25); The method for detecting the ink ejection state according to (6) above.

  (8) If it is determined that there is an influence of a secondary droplet, recording of the first and second test pattern images, measurement of the density of each pattern image, calculation of relative parameters, and determination of whether there is an influence of the secondary droplet Is repeated, and an alarm is generated when the number of repetitions reaches the set value (nmax); the method of detecting an ink discharge state according to (6) or (7) above.

(9) A recording head (5 / 17y) having a nozzle row (Ny / 17y) in which a plurality of ink discharge nozzles are arranged;
At least one of the recording head and recording paper (5 in FIG. 1/7 in FIG. 13) is relative to the other in a direction orthogonal to the nozzle row (x in FIG. 1 / y in FIG. 13). And scanning means for scanning driving (2 to 4/25);
A recording control means (19) for controlling the scanning drive and for energizing the recording head to discharge ink droplets by the recording head to the recording paper;
In response to the discharge state detection instruction, the recording control means (19) is used to create a high-density dot distribution in the direction (x / y) perpendicular to the nozzle row (Ny / 17y). The first test pattern (15), which is less likely to have an effect, and the second test pattern, which has a low density of dot distribution in the direction (x / y) perpendicular to the nozzle row (Ny / 17y) Discharge test control means (PCR) for recording 16 / 16a / 16b) on recording paper;
Density detecting means (14/110) for measuring the density of the first test pattern image density and the second test pattern image density formed on the recording paper; and
A sub-drop determining means (PCR) that calculates a relative parameter representing a relative relationship between the first and second test pattern image densities and determines whether the second test pattern image is affected by the sub-drop based on the relative parameter. );
An inkjet recording apparatus comprising:

  (10) The density detecting means includes an optical sensor (14) for detecting reflected light by projecting light onto the first and second test pattern images on the recording paper before being discharged out of the apparatus; 2. An ink jet recording apparatus according to 1.

  (11) The density detecting means is a reading device that reads a document image and outputs image data; the sub-drop determining means (PCR) is image data of first and second test pattern images read by the reading device. The ink jet recording apparatus according to (8), wherein a density value of each image is calculated based on the image, and a relative parameter representing a relative relationship between the calculated density values is calculated.

  (12) Any one of the above (9) to (11), further comprising means (PC1 / 120) for notifying the subdroplet determining means (PCR) of information indicating that the subdroplet has an influence. The ink jet recording apparatus described in 1.

  (13) In response to the determination that the sub-drop determining means (PCR) has an influence of the sub-drop, the discharge test control means (PCR) is configured to record the recording head by the recording control means (19). The recording conditions of ink jet recording in which ink droplets are ejected by the recording head onto the recording paper are changed in a direction in which the influence of sub-droplets is reduced; any one of (9) to (12) above Inkjet recording apparatus.

  (14) When the sub-drop determining means (PCR) determines that there is an effect of the sub-drop, the discharge test control means (PCR), the concentration detecting means (14/110) and the sub-drop determining means (PCR) The recording of the first and second test pattern images, the measurement of the density of each pattern image, the calculation of the relative parameters, and the determination of whether there is an influence of the secondary droplets are repeated again. When the number of repetitions reaches the set value (nmax) The discharge test control means (PCR) generates alarm information; the ink jet recording apparatus according to (13) above.

  (15) The ink jet recording apparatus according to (13) or (14), wherein the recording condition includes a speed of the scanning drive by the scanning unit (2 to 4/25).

  (16) The first test pattern (15) is a plurality of parallel lines parallel to a direction (x / y) orthogonal to the nozzle row (Ny); any one of (9) to (15) above The ink jet recording apparatus according to one.

  (17) The second test pattern (16) is a plurality of parallel lines parallel to the nozzle row (Ny); the ink jet recording apparatus according to (9) to (16) above.

  (18) The ink jet recording apparatus according to any one of (9) to (17), wherein the relative parameter is a difference or ratio between first and second test pattern image densities.

  (19) The sub-drop determining means (PCR) determines that there is an effect of a sub-drop when the relative parameter exceeds a predetermined threshold; the ink jet recording apparatus according to (18) above.

  (20) The discharge test control means (PCR) includes a memory (103) for storing the first and second test pattern image data for forming the first and second test pattern images, and outputs a discharge state detection instruction. In response, the first and second test pattern image data is provided to the recording control means (19); the ink jet recording apparatus according to any one of (9) to (19) above.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows an ink jet printer according to a first embodiment of the present invention. In FIG. 1, 100 is an ink jet recording apparatus, and PC1 is a host computer such as a personal computer. The ink jet recording apparatus 100 is of a serial type, and a carriage 4 is movably mounted on guide rails 2 and 3 laid horizontally on the frame 1. A recording head 5 is mounted on the carriage 4, and a motor or the like (not shown) is used. The carriage 4 is driven in the arrow A direction (x direction) by the drive source. The recording paper 7 set on the guide plate 6 is taken in by rotating the platen 10 through a drive gear 8 and a sprocket gear 9 by a drive source (not shown), and the peripheral surface of the platen 10 and a pressure roller 11 pressed against the platen 10 Is conveyed in the arrow B direction (y direction). The platen 10 can also be manually rotated by the feed knob 10a. Then, while the recording head 5 (carriage 4) is moved and scanned in the main scanning direction x (arrow A direction), the paper 7 is conveyed in the sub-scanning direction y (arrow B direction), and ink droplets are discharged from the recording head 5. Is ejected to print an image on the paper 7. Printing is synonymous with printing, printing, recording, and imaging. Discharge is synonymous with injection. Both the head drive and the recording paper conveyance in the main scanning direction x and the sub-scanning direction y can perform forward and backward driving, and printing can be performed by both forward and backward driving.

  As shown in FIG. 2, the recording head 5 includes ejection units 12 and 13. The injection unit 12 has two nozzle rows Nk and Nc in which a plurality of nozzles are arranged. The injection unit 13 also has two nozzle rows Nm and Ny in which a plurality of nozzles are arranged. These nozzle rows Nk to Ny are arranged in the scanning drive direction (main scanning direction) x of the recording head 5, and each nozzle row extends in a direction (sub-scanning direction) y orthogonal to the x direction. That is, the main scanning drive direction x is a direction orthogonal to the nozzle row. These four nozzle rows Nk, Nc, Nm and Ny are supplied with black k, cyan c, magenta m and yellow y ink, respectively, in the ejection unit. In the ejection unit, there are drive elements that drive to discharge ink from the nozzles. In this embodiment, each driving element is a heat generating element that generates heat when energized, and the injection units 12 and 13 are so-called film boiling types. However, each driving element uses a piezoelectric element, or each driving element. As an electrostatic type that uses an oscillating plate and an electrode opposite to the oscillating plate and displaces the oscillating plate with electrostatic force between the two to pressurize the ink liquid chamber.

  FIG. 3 shows the relative positions of the recording head 5 and the recording paper 7. Usually, the recording head 5 is reciprocated in the main scanning direction x, and ink droplets are ejected from the nozzles of the ejection units 12 and 13 both when moving in the forward direction and when moving in the backward direction. Make a record. However, there is a case where printing is performed only in one of the movement in the forward direction and the movement in the backward direction.

  In “ejection inspection” NETa (FIG. 6), which will be described later, the first test pattern image 15 and the second test pattern image 16 are printed on the recording paper 7, and the density (area density) of these test image patterns is individually measured. An optical sensor 14 for mounting is mounted on the carriage 4. The optical sensor 14 includes a light source that illuminates one test pattern region, and a photosensor that receives reflected light from the test pattern only in the test pattern region and generates a pattern density signal. . The pattern density signal of the photosensor is digitally converted into pattern density data by the process controller 34 via an interface 36 (FIG. 5), which will be described later, and transferred to the CPU 101 of the printer controller PCR (FIG. 4).

  FIG. 4 shows a system configuration of an image processing system of a full-color printer equipped with the printer 100 shown in FIG. A printer controller PCR, which is a printer control board, includes a main CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, and the like. Are stored, as well as various data and system data necessary for executing these programs. The main CPU 101 controls each unit of the printer 100 using the RAM 104 as a work memory based on a program in the ROM 103. When there is a print command from the host computer PC1, the document provided by the host computer PC1 is printed on the recording paper. An information processing apparatus such as a host computer PC1 and a PC (Personal Computer) is connected to the network interface (network I / F) 109 via a LAN (Local Area Network), and the network I / F 109 is connected from a PC or the like. When there is a print command, the document information of the PC is printed. The ASIC 102 is a DMA that receives print data (document information) from PC1, PC, etc., a data decompressor that decodes (decompresses) the received data, and converts the decompressed image information into image data to convert the image expression characteristics of the printer 100. And an image data processor for converting into recorded image data.

  FIG. 5 shows a part of the configuration of the print controller 19 in the printer 100. Image data for image formation is sent from the printer controller PCR (FIG. 4) to the image memory & memory controller 35 in the print controller 19 and stored in the image memory there. When the process controller 34 in the print controller 19 starts printing, the image memory & memory controller 35 controls each color of the output control 41 via the interface 36 in accordance with a synchronization signal (timing signal) and a control signal given by the process controller 34. The image data of the recording allocation area addressed to each color nozzle row Nk, Nc, Nm and Ny is cut out and output to output control (two-dot chain line blocks) 321 to 324. Each color output control includes an image memory (buffer memory) 38, an output latch 39, and an ink droplet ejection driver 40.

  In each color output control, the image data in the recording allocation area is written in the image memory 38, and the image data is output from the image memory 38 to the output latch 39 and output to the driver 40. The image data of the width in the y direction assigned to one nozzle row is output from the image memory 38 to the output latch 39 at a period of time for ejecting one drop of ink from the nozzles.

  In FIG. 6, in response to a “discharge inspection” instruction from the host computer PC 1, the printer controller PCR (the CPU 101) reads out the “discharge inspection” program stored in the ROM 103 to the RAM 104 and executes it. The contents of NETa are shown.

  When the process proceeds to “Discharge inspection” NETa in response to the “Discharge inspection” instruction, the printer controller PCR waits for the print controller 19 (the process controller 34) to notify that the recording paper 7 is inserted (s1). When the notification is made, the process proceeds to “Test Pattern Measurement” DMT. Therefore, the printer controller PCR reads the first test pattern stored in the “ejection inspection” program, converts it into recorded image data, and outputs it to the print controller 19 to instruct printing (s2). Next, with a predetermined blank space, the second test pattern stored in the “ejection inspection” program is read, converted into recorded image data, and output to the print controller 19 to instruct printing (s3). . As a result, the first and second test pattern images 15 and 16 (FIG. 3) are formed on the recording paper 7.

  The printer controller PCR instructs the process controller 34 to read the image densities of the second and third test pattern images 15 and 16, and in response to this, the process controller 34 reads the second test pattern image 16 printed last. The carriage 4 is returned so that the optical sensor 14 is aligned with the position, and the pattern density signal of the optical sensor 14 is digitally converted into pattern density data D2 (s4), and then the optical sensor 14 is positioned at the position of the first test pattern image 15. The recording paper 7 is returned so as to match, and the pattern density signal of the optical sensor 14 is digitally converted into pattern density data D1 (s5). Then, a difference dD = D2−D1 between the pattern density data D2 and D1 is calculated as a relative parameter (s6).

  When the “test pattern measurement” DMT is completed, the printer controller PCR informs the PC 1 that maintenance is necessary if the difference value dD is equal to or greater than the threshold value (set value in the program) dDs. Guidance for prompting maintenance of the recording head is displayed on the display (s7, s8). When the difference value dD is less than the threshold value dDs, ready (printing is possible) is notified to the PC 1, and in response to this, the PC 1 displays on the display of the PC 1 that ink jet recording can be started (s7, s9).

  In this embodiment, the first test pattern is for printing the pattern image shown in FIG. 8A on the recording paper, and the second test pattern is the pattern image shown in FIG. 8B. It is printed on recording paper. In the nozzle distribution shown in FIG. 2, the first test pattern image (FIG. 8A) can be printed by one x-direction scan (x-direction head drive), but the second test pattern image (FIG. 8 ( In b)), in order to fill the gap between dots in the y direction, it is necessary to perform printing by scanning twice in the x direction, and printing the second time by shifting the position in the y direction. Therefore, in this embodiment, both the first and second test patterns are printed by two x scans as shown in FIG.

  FIG. 10 shows the first test pattern image 15 and the second test pattern image 16 that are formed under the discharge conditions in which the sub-drop is generated and the recording appears on the recording paper 7. In the first test pattern image 15 shown in FIG. 10 (a), the sub-drop of the ink droplet ejected from the nozzle subsequent to the nozzle is recorded in the main droplet region of the ink droplet ejected in advance. There is almost no increase in image density (area density) due to subdrops. However, in the second test pattern image 16 shown in FIG. 10 (b), there is a space between the main droplets of the ink droplets ejected from the nozzle before and after, so that it was ejected from the nozzle behind. Ink droplets tend to appear in the blank portion. When a sub-drop appears in the blank portion, an increase in image density (area density) due to the sub-drop is observed. In this state, the second test pattern image density D2 is greater than the first test pattern image density D1, and the difference value dD = D2−D1 is equal to or greater than the threshold value dDs, and the maintenance of the recording head is urged on the PC1 display. Guidance is displayed.

  Note that the droplet ejection position of the second test pattern 16 shown in FIG. 8B on the recording paper is that of 16b shown in FIG. 11B, but the mosaic pattern shown in FIG. It may be distributed 16a. In addition, in the first test pattern, dots are densely distributed in the x direction and sparsely distributed in the y direction. In the second test pattern, dots are sparsely distributed in the x direction and densely distributed in the y direction. Any other pattern can be used. Note that the printing densities of the first and second patterns that are not affected by the sub-drops need not be the same. This is because the threshold value dDs may be set to a value obtained by adding or subtracting the density difference between the first and second test patterns in printing without the influence of the subdrop.

  In this embodiment, the difference dD = D2−D1 between the pattern density data D2 and D1 is used as the relative parameter. However, an embodiment in which the relative parameter is the ratio rD = D2 / D1 of the pattern density data D2 and D1 is also possible. is there. In this embodiment, the printer controller PCR notifies that maintenance is necessary when rD = D2 / D1 is equal to or greater than the threshold value rDs, and notifies ready when it is less than the threshold value rDs.

  The hardware of the second embodiment is the same as that of the first embodiment described above, but the contents of “ejection inspection” are different. FIG. 7 shows the contents of the “ejection inspection” NETb executed by the printer controller PCR of the second embodiment. In this “ejection inspection” NETb, the printer controller PCR sets the three stages of printing speed set in the printer 100, low speed (high quality printing), medium speed (standard speed: standard quality printing) and high speed (low quality printing). Are automatically adjusted using a “test pattern measurement” DMT.

  When the printer controller PCR proceeds to “discharge inspection” NETb in response to an instruction of “discharge inspection” from the host computer PC1, the printer controller PCR waits for the print controller 19 to notify that the recording paper 7 is inserted (s11). If there is a notification, the process proceeds to “Low-speed recording ejection inspection” LvET. Therefore, the printer controller PCR sets the low-speed reference speed V1s, which is a fixed value, to the main scanning speed V (the x-direction driving speed of the carriage 4), and initializes the measurement count value n to 0 (s12). Next, the printer controller PCR performs “test pattern measurement” DMT. This content is the same as that shown in FIG.

  “Measurement of Test Pattern” When the first test pattern image density D1 and the second test pattern image density D2 are measured by the DMT and the difference value dD1 as a relative parameter is calculated, the printer controller PCR determines that the difference value dD1 is the threshold value dDs1. If it is equal to or greater than the threshold value dDs1 (if the influence of the secondary droplet is predicted), the measurement number n is incremented by 1 (s14), and the main scanning speed Vx1 is the previous value. A value obtained by subtracting the adjustment step value dVx1 (fixed value) from Vx1 is updated (s16), that is, the speed is changed to a low speed by dVx1, and the “test pattern measurement” DMT is executed. “Measurement of test pattern” DMT to s16 are repeated while the difference value dD1 which is a relative parameter obtained by DMT is equal to or greater than the threshold value dDs1, but when the number n of measurement reaches the set value nmax, the maintenance of low-speed recording is required. The PC 1 is notified (s15, s18), and the process proceeds to the next “medium-speed recording ejection inspection” MvET.

  However, if the difference value dD1 becomes less than the threshold value dDs1 before the number of measurements n reaches the set value nmax, the currently set main scanning speed Vx1 is set as the main scanning speed V1 for low-speed recording (s13, s17). That is, the main scanning speed V1 for low-speed recording is set to the currently set main scanning speed Vx1. Then, the process proceeds to the next “medium-speed recording ejection inspection” MvET.

  The contents of “medium-speed recording ejection inspection” MvET and “high-speed recording ejection inspection” HvET are the same as the above-described “low-speed recording ejection inspection” LvET. The main scanning speed V3 for recording is set.

  In printing in response to a normal print command from the host computer PC1, the printer controller PCR corresponds to the designated speed corresponding to the recording speed designation (low speed / medium speed / high speed) included in the print command. The process controller 34 is instructed for the main scanning speed set by the discharge inspection LvET, MvET, and HvET.

  FIG. 12 shows the configuration of the image processing system of the multifunction printer according to the third embodiment. This multifunction printer is a full-color digital copier. The printer controller PCR, which is a printer control board, is an extension of the image processing system of the first embodiment shown in FIG. The printer controller PCR includes a main CPU 101, a ROM 103, a RAM 104, and the like. The ROM 103 stores various programs such as a copier system program and an image information management program, and is necessary for executing these programs. Various data and system data are stored. The main CPU 101 uses the RAM 104 as a work memory based on a program in the ROM 103 to control each unit of the copying machine, reads an image by the scanner 110, stores an image, and prints with the host computers PC1 and PC (personal computer). Transmission / reception, facsimile transmission / reception, copying of a document image read by the scanner 110 and printing by the printer 100, printing (printing out by the printer 100), management of stored information, usage management, and the like. One typical aspect of printing is printing in response to a print command from the host computer PC1 or PC.

  The operation board 120 includes various operation keys such as a numeric keypad, a start key, a stop key, and a function key, and also includes a display (liquid crystal display). A user instruction can be input by each operation key and displayed on the display. . The display also displays the status of the copier and notifications from the PC 1, PC and facsimile.

  The facsimile control unit FCU is connected to a telephone line PN, exchanges facsimile control signals with the other facsimile machine, executes a facsimile communication procedure, and includes a network control unit, a modem, and the like. Thus, automatic outgoing / incoming call processing is performed, and transmission / reception signal modulation / demodulation processing is performed by the modem. As described above, the facsimile control unit FCU performs facsimile communication procedures by exchanging facsimile control signals with the other facsimile apparatus during facsimile communication. The fact that the printer 100 is provided with various functions such as encoding and decoding is added to the facsimile control signal to be notified to the (transmission-side facsimile apparatus) and transmitted to the other party. An information processing apparatus such as a PC is connected to the network interface (network I / F) 109 via a LAN, and the network I / F 109 exchanges document information with the PC 1, PC, etc. The document information stored in the HDD 105 is transferred to the PCs 1 and PC so that the image information can be used on the PCs 1 and PC. The ASIC 102 is a DMA that receives print data (document information) from PC1, PC, etc., a data decompressor that decodes (decompresses) the received data, and converts the decompressed image information into image data to convert the image expression characteristics of the printer 100. And an image data processor for converting into recorded image data. The ASIC 102 also reads / writes data from / to the HDD.

  FIG. 13 shows an outline of the printer 100. The printer 100 conveys recording paper by an air suction belt conveyance method. The recording paper is sequentially fed out from the top of the recording paper group 22 on the paper tray 21 by the paper feeding roller 23, temporarily stopped at the position of the registration roller 24, and conveyed by the registration roller 24 at a predetermined timing. It is fed into the belt 25. The transport belt 25 sucks the recording paper by air suction and transports it in the left direction y which is the sub-scanning direction. There are full-line recording heads 17y, 17m, 17c, and 17k that respectively discharge yellow ink, magenta ink, cyan ink, and black ink onto the recording paper at positions facing the recording paper conveyed by the conveyance belt 25. These are all fixed, and each has a nozzle row that can record the entire length of the recording paper. The nozzle rows are parallel to a direction x perpendicular to the paper surface.

  The print controller 19 controls ink ejection by these full line recording heads based on image data provided by the printer controller PCR. The print controller 19 monitors paper detection signals of several types of recording paper sensors (not shown), and stops feeding by the roller 23 when the recording paper fed out by the roller 23 reaches the registration roller 24 and the paper leading edge is slightly curved. Then, the registration roller 24 is rotationally driven at a timing at which the recording paper can be sent to the transport belt 25 to feed the recording paper to the transport belt 25. An electric pulse having a frequency proportional to the moving speed of the belt 25 generated by the rotary encoder 26 in synchronization with the movement of the conveying belt 25 from the start of driving of the registration roller 24 or from the time when the recording paper reaches the conveying belt 25. When the count reaches a count value at which the leading edge of the recording paper reaches each of the heads 17y to 17k, ink ejection by each head, that is, image recording (printing) is started.

  FIG. 14 shows a part of the configuration of the print controller 19. Image data for image formation is sent from the printer controller PCR to the image memory & memory controller 35 and stored in the image memory there. When the process controller 34 starts printing, the image memory & memory controller 35 controls each color output control (two points) of the output control 41 via the interface 36 in accordance with a synchronization signal (timing signal) and a control signal given by the process controller 34. Image data assigned to each recording head (recording color) is output for each line to chain line blocks 321 to 324. Each of the color output controls 321 to 324 includes an image memory (buffer memory) 38, an output latch 39, and an ink droplet ejection driver 40.

  In each color output control 321-324, the line image data provided by the image memory & memory controller 35 is written into the image memory 38, and each color output control outputs the image data from the image memory 38 to the output latch 39 line by line. , Output to the driver 40. One line of image data is output from the image memory 38 to the output latch 39 at a period of time for ejecting one drop of ink from the nozzles.

  FIG. 15 shows the contents of “Discharge inspection” NETc that the printer controller PCR reads out the “Discharge inspection” program stored in the ROM 103 and executes it in response to the “Discharge inspection” instruction from the operation board 120. Show.

  When the process proceeds to “Discharge inspection” NETc in response to the instruction “Discharge inspection”, the printer controller PCR waits for a start instruction from the operation board 120 (s21). Proceed to DMTa. Therefore, the printer controller PCR reads the first test pattern 15 (FIG. 17A) stored in the “ejection inspection” program, converts it into print image data, and prints a single pattern print image. Printed image data of the first test pattern group, in which data is arranged for eight in the main scanning direction x at a predetermined pitch, is output to the print controller 19 to instruct printing (s22). Next, with a predetermined blank space in the sub-scanning direction y, the second test pattern (FIG. 17B) stored in the “ejection inspection” program is read and converted into print image data. The recording image data of the second test pattern group in which the recording image data of one pattern is arranged in a predetermined pitch in the main scanning direction x is output to the print controller 19 to instruct printing (s23). Then, the recording paper is discharged (s24), and a guidance “Please set the paper discharge to the scanner and read” is displayed on the display panel of the operation board 120. When the user sets the recording paper on which the test pattern is recorded in accordance with this and presses the start key, the printer controller PCR responds to the start key being turned on (start instruction: reading instruction here) (s26). The original image is read by 110 (s28), the image data of the first test pattern image group is cut out from the image data read by the scanner and integrated, and 1/8 of the integrated value is set as the first test pattern image density D1, Further, the image data of the second test pattern image group is cut out and integrated, and 1/8 of the integrated value is set as the second test pattern image density D2 (s28 to s30). Then, the difference value dD = D2−D1 is calculated as a relative parameter (s31).

  When the above “test pattern measurement” DMTa is completed, the printer controller PCR gives guidance for prompting maintenance of the recording head to the display panel of the operation board 120 when the difference value dD is equal to or greater than a threshold value (setting value in the program) dDs. Display (s32, s34). When the difference value dD is less than the threshold value dDs, the display panel of the operation board 120 displays that ink jet recording can be started (s32, s33).

  The first and second test patterns 15 and 16 used in the third embodiment are for printing the test pattern image shown in FIG. 17 on the recording paper. These patterns correspond to those obtained by exchanging the x-axis and the y-axis as shown in FIG. 8 used in the first embodiment. In the first embodiment (FIG. 1), the recording head 5 is scanned and driven in the direction x orthogonal to the nozzle rows (Nk to Ny in FIG. 2) with respect to the recording paper. This is because in the third embodiment (FIG. 13), the full line recording heads 17y to 17k are fixed, and the recording paper 7 is driven to scan in the direction y that crosses the direction x in which the nozzle rows extend. That is, the relative scanning direction between the recording head and the recording paper during printing in which ink droplets are ejected from the nozzles is 90 degrees different from that in the first embodiment.

  The hardware of the fourth embodiment is the same as that of the third embodiment, but the contents of “ejection inspection” are different. FIG. 16 shows the contents of the “ejection inspection” NETd executed by the printer controller PCR of the fourth embodiment. In this “ejection inspection” NETd, the printer controller PCR sets the three stages of printing speed set in the printer 100, low speed (high quality printing), medium speed (standard speed: standard quality printing), and high speed (low quality printing). Each of these is automatically adjusted by using “test pattern measurement” DMTa shown in FIG. This outline is the same as that of the second embodiment shown in FIG.

  In printing in response to a print command from the operation board 120 or PC1, PC, the printer controller PCR corresponds to the designated speed corresponding to the recording speed designation (low speed / medium speed / high speed) included in the print command. The process controller 34 is instructed for the sub-scanning speed (recording paper conveyance speed) set in the ejection inspections LvET, MvET, and HvET in FIG.

  Although the first to fourth embodiments have been described above, in any of the embodiments, the first and second test patterns 15 and 16 are moved relative to each other as shown in FIGS. It is desirable that a plurality of lines parallel to the direction x (FIG. 1) or y (FIG. 13) and a plurality of vertical lines are arranged in parallel. However, these are intended to be a recording pattern that is not affected by the generation of sub-droplets and a recording pattern that is received, and may not necessarily be composed of lines.

  Further, regarding the recording method of the recording pattern 16 that is affected by the sub-drop and the recording pattern 15 that is not affected, it is desirable that at least one of the recording frequency, the used droplet configuration, and the used nozzle is the same. This is for measuring only the influence of sub-drop generation when comparing two recording patterns. For example, when one pattern is recorded by two scans as shown in FIG. 9, the recording frequency can be unified.

  Moreover, about the ink droplet which comprises a line, a line may be comprised using the droplet of the same size, and a line may be comprised using a droplet of a different size. This is because when an image is actually recorded using an ink jet recording apparatus, only drops of the same size may be used, or drops of different sizes may be combined, and the frequency and degree of occurrence of sub-drops are different. It is desirable to use a droplet configuration that assumes the case of actually recording an image.

  Further, on the digital data indicating the dot recording position, the line width may always be the same width, or a plurality of lines having various widths may be used. This is because when an image is actually recorded using an ink jet recording apparatus, how many dots form the image differs depending on the recording resolution and image size. For this reason, it is desirable to use a droplet configuration that assumes the case of actually recording an image.

  Also, on the digital data indicating the dot recording position, the intervals between the parallel lines may be always the same, or various intervals may be combined. This is because the distance at which the sub-drop is generated from the main droplet changes depending on the recording conditions. Depending on the line interval, the generated sub-drop overlaps with the adjacent line, making it difficult to detect density changes. This is because there are cases.

  Furthermore, on the digital data indicating the dot recording position, the line width and the interval between the lines may be always the same, or the line width and the interval between the lines may be different. This is because the quality and characteristics of the ink droplets appear remarkably when a recording pattern having the same recording position and recording position interval on the digital data as shown in FIG. 11 is used. However, the same interval is not always good, and the desired image width and interval differ depending on the image and line recording conditions.

  Also, as in the flows shown in FIGS. 6, 7, 15, and 16, when it is determined by the discharge inspection that sub-drops related to image degradation are generated, maintenance or sub-drop reduction effects can be achieved. It is desirable to perform the adjustment automatically or to prompt the user to perform the adjustment. The term “maintenance” as used herein refers to an item that has an effect of stabilizing the ejection of ink droplets, such as head and nozzle cleaning. The adjustment here includes not only the scanning speed but also the change in the drive waveform of the recording head, the change in the recording frequency, the change in the ink discharge speed, and the like. The recording conditions in which multiple ink droplets are likely to merge in the air before landing on the paper, the recording conditions that reduce the distance between the generated secondary droplets and the main droplets, or the arrangement of the droplets are changed. This refers to changes or adjustments to the recording method that makes the occurrence less noticeable.

100: inkjet recording apparatus PC1: host computer 1: frame 2, 3: guide rail 4: carriage 5: recording head 6: guide plate 7: recording paper 8: drive gear 9: sprocket gear 10: platen 10a: feed knob 11: Pressure rollers 12, 13: injection units 12nf, 13nf: nozzle surfaces Nk, Nc, Nm, Ny: nozzle array 14: optical sensor 15: first test patterns 16, 16a, 16b: second test patterns 17y to 17k: full line Recording head 21: Paper tray 22: Stacked paper 23: Paper feed roller 24: Registration roller 25: Conveying belt 26: Rotary encoders 321 to 324: Color output control

JP 2007-245614 A JP 2007-76265 A Japanese Patent Application No. 9-361581

Claims (20)

A recording head having a nozzle row in which a plurality of ink discharge nozzles are arranged; scanning that scans and drives at least one of the recording head and recording paper relative to the other in a direction perpendicular to the nozzle row And a control means for controlling the scanning drive and for energizing the recording head to eject ink droplets by the recording head on the recording paper.
By the control means, a first test pattern having a high density of dot distribution in a direction orthogonal to the nozzle row, and a low density dot distribution in a direction perpendicular to the nozzle row, which is less susceptible to the effects of subdroplets, Record on the recording paper a second test pattern that is susceptible to the effects of secondary droplets;
Measuring the density of the first and second test pattern images formed on the recording paper;
A relative parameter representing a relative relationship between the first and second test pattern image densities is calculated, and it is determined based on the relative parameter whether the second test pattern image is affected by a secondary droplet; a method for detecting an ink ejection state .   The method of detecting an ink ejection state according to claim 1, wherein the first test pattern is a plurality of parallel lines parallel to a direction orthogonal to the nozzle row.   The method for detecting an ink ejection state according to claim 1, wherein the second test pattern is a plurality of parallel lines parallel to the nozzle row.   The ink discharge state detection method according to any one of claims 1 to 3, wherein the relative parameter is a difference or ratio between first and second test pattern image densities.   The ink discharge state detection method according to claim 4, wherein when the relative parameter exceeds a predetermined threshold, it is determined that there is an influence of a sub-droplet.   If it is determined that there is an influence of the sub-droplet, the recording condition of the ink jet recording in which the recording head is urged by the control unit to eject the ink droplet by the recording head to the recording paper is less affected by the sub-droplet. The method for detecting an ink discharge state according to claim 5.   The ink discharge state detection method according to claim 6, wherein the recording condition includes a speed of the scanning drive by the scanning unit.   If it is determined that there is an influence of a secondary droplet, the recording of the first and second test pattern images, the measurement of the density of each pattern image, the calculation of relative parameters, and the determination of whether there is an influence of the secondary droplet are performed again. 8. The method of detecting an ink ejection state according to claim 6 or 7, wherein an alarm is generated when the number of repetitions reaches a set value. A recording head having a nozzle row in which a plurality of ink ejection nozzles are arranged;
Scanning means for scanning and driving at least one of the recording head and the recording paper relative to the other in a direction orthogonal to the nozzle row;
Recording control means for controlling the scanning drive, for recording and energizing the recording head, and discharging ink droplets by the recording head to the recording paper;
In response to a discharge state detection instruction, the recording control unit is used to form a first test pattern having a high-density dot distribution in a direction orthogonal to the nozzle row and in which the influence of sub-drops is less likely to appear, and the nozzle row Discharge test control means for recording on the recording paper a second test pattern having a low-density dot distribution in a direction perpendicular to the surface and which is susceptible to the influence of subdrops;
Density detecting means for measuring the density of the first test pattern image density and the second test pattern image density formed on the recording paper; and
Sub-drop determining means for calculating a relative parameter representing a relative relationship between the first and second test pattern image densities and determining whether the second test pattern image is affected by the sub-drop based on the relative parameter;
An inkjet recording apparatus comprising:   The inkjet recording apparatus according to claim 9, wherein the density detection unit includes an optical sensor that detects reflected light by projecting light onto the first and second test pattern images on the recording paper before being discharged out of the apparatus.   The density detecting unit is a reading device that reads a document image and outputs image data; the sub-drop determining unit is configured to read each image based on the image data of the first and second test pattern images read by the reading device. The inkjet recording apparatus according to claim 8, wherein density values are calculated, and a relative parameter representing a relative relationship between the calculated density values is calculated.   The inkjet recording apparatus according to any one of claims 9 to 11, further comprising: means for notifying information indicating determination that the sub-drop determining unit has an effect of the sub-drop.   In response to the determination that the sub-drop determining unit has an effect of the sub-drop, the discharge test control unit records and urges the recording head by the recording control unit to ink the recording head with respect to the recording paper. The inkjet recording apparatus according to any one of claims 9 to 12, wherein the recording conditions of inkjet recording in which droplets are ejected are changed in a direction in which the influence of subdrops is reduced.   When the sub-drop determining unit determines that there is a sub-drop effect, the discharge test control unit, the density detecting unit, and the sub-drop determining unit record the first and second test pattern images, and determine the density of each pattern image. 14. The measurement according to claim 13, wherein measurement, calculation of relative parameters, and determination of whether there is an influence of a secondary droplet are repeated again, and when the number of repetitions reaches a set value, the discharge test control means generates alarm information; Inkjet recording device.   The inkjet recording apparatus according to claim 13 or 14, wherein the recording condition includes a speed of the scanning drive by the scanning unit.   The inkjet test apparatus according to claim 9, wherein the first test pattern is a plurality of parallel lines parallel to a direction orthogonal to the nozzle row.   The inkjet test apparatus according to claim 9, wherein the second test pattern is a plurality of parallel lines parallel to the nozzle row.   The inkjet recording apparatus according to claim 9, wherein the relative parameter is a difference or ratio between first and second test pattern image densities.   The inkjet recording apparatus according to claim 18, wherein the sub-drop determining unit determines that there is an effect of the sub-drop when the relative parameter exceeds a predetermined threshold value.   The ejection test control means includes a memory for storing first and second test pattern image data for forming the first and second test pattern images, and the first and second tests are performed according to the ejection state detection instruction. 20. The ink jet recording apparatus according to claim 9, wherein pattern image data is read from the memory and supplied to the recording control unit.

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