JP4497492B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus that performs recording on a recording material by ejecting ink from a recording head, and more particularly to print control thereof.
[0002]
[Prior art]
Recording devices such as copiers and facsimiles, or printers and plotters used as output devices such as computers, word processors, and workstations use paper, plastic thin plates (OHP paper, etc.) based on image information. An image (including characters and symbols) is recorded on a recording material (recording medium). Such a recording apparatus may be an ink jet type, a wire dot type, a thermal type, a thermal transfer type, a laser beam type, etc., depending on the recording method of the recording means used.
[0003]
In a serial type recording apparatus employing a recording method in which main scanning is performed in a direction crossing the recording material conveyance direction (sub-scanning direction), the recording material is set at a predetermined recording position, and then along the recording material. An image is recorded by a recording means (recording head) mounted on a moving (main scanning) carriage, and after a line of recording is completed, a predetermined amount of paper is fed (sub-scanning), and then the next line is recorded. By repeating the operation of recording (main scanning) the image, the image is recorded in a desired range of the recording material.
[0004]
On the other hand, in a non-serial type recording apparatus, a recording material is set at a predetermined recording position, and a predetermined amount of paper feeding (pitch feeding) is performed while continuously recording one line at a time. An image is recorded on the entire recording material.
[0005]
Of the various recording methods described above, the ink jet type (ink jet recording apparatus) performs recording by ejecting ink from a recording means (recording head) onto a recording material, and the recording means can be easily made compact and has high definition. High-speed images can be recorded without requiring special processing on plain paper, the running cost is low, the non-impact method is low noise, and multi-color ink is used. It has advantages such as being easy to use and recording color images.
[0006]
In particular, an ink jet recording means (recording head) that discharges ink using thermal energy is an electrothermal transducer or electrode formed on a substrate through a semiconductor manufacturing process such as etching, vapor deposition, or sputtering. By forming the liquid channel wall, the top plate, etc., it is possible to easily manufacture a device having a high-density liquid channel arrangement (nozzle arrangement), and to further reduce the size. In addition, by utilizing the advantages of IC technology and micromachining technology, it is easy to make the recording means longer and planar (two-dimensional), and it is also easy to make the recording means full-multiple and high-density mounting. is there.
[0007]
In an ink jet recording apparatus, since recording is performed by directly ejecting ink (recording liquid) from a recording head, it is necessary to keep the head (nozzle) in a state where ink can be ejected at all times. A discharge recovery operation is used.
[0008]
"Suction operation"
Gas is mixed as bubbles in the supply path for supplying ink to the nozzles, which are ejection holes, and in the ink reservoir (common liquid chamber) in the vicinity of the nozzles. When the bubbles reach a certain size, the ink is prevented from being supplied to the nozzles. It may not be discharged. As a countermeasure, a suction operation for sucking ink and bubbles up to the common liquid chamber by applying a negative pressure to the nozzle surface is widely adopted.
[0009]
"Wiper operation"
Ink may not be ejected normally due to things (paper dust, ink, etc.) that interfere with ink ejection that adhere to the surface (face surface) where the nozzles are placed. Wiper operation to wipe the surface is adopted.
[0010]
"Preliminary discharge operation"
Not all nozzles eject ink during image recording. Therefore, there is a case where ink that has not been ejected becomes dried and ink cannot be ejected. In addition, the ink ejected onto the paper surface may bounce off the paper surface and adhere to the vicinity of the nozzles, preventing normal ink ejection. As a result, the landing position changes. In order to improve this image defect, according to a predetermined condition, for example, every nozzle is ejected to a part other than the recording material every predetermined time to prevent drying, and the ink adhering to the vicinity of the nozzle is ejected. An operation of removing with ink is performed.
[0011]
Operations performed by such operations are collectively referred to as head ejection recovery operations. The “head ejection recovery operation” is performed in a timely manner because the head normally ejects ink. In general, the head ejection recovery operation is performed at a predetermined time or when the integrated value of recording pixels exceeds a predetermined value.
[0012]
[Problems to be solved by the invention]
By the way, if the ejection recovery operation of the head is performed during image recording, the printing interval becomes longer by the time required for the head ejection recovery operation, and the recording is continued after a certain time. This is a problem particularly when performing so-called multi-pass printing in which one band area is recorded by a plurality of head scans. In other words, when the head ejection recovery operation is performed during multi-pass printing, the time for the ink recorded before the head ejection recovery operation to permeate the paper (recording material) will be given extra time. A difference appears in the ink absorption state on the paper between the normal recording operation and the normal recording operation. For this reason, the color of ink between scans changes or the density changes, resulting in uneven printing (main scanning unevenness) along the main scanning direction, resulting in a decrease in print quality. Become.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus capable of preventing deterioration in print quality due to the head recovery operation being inserted during image recording by improving the control of the discharge recovery means. .
[0014]
[Means for Solving the Problems]
An ink jet recording apparatus according to the present invention, the ink image recording by one scanning operation by discharging while moving a plurality of recording heads, that a predetermined amount convey the recording medium after completing the recording of the one scan In an inkjet recording apparatus that records an image repeatedly, a recovery unit that recovers the ejection state of the recording head, and an integration unit that integrates the number of recording pixels of each recording head after the recovery process of the recording head by the recovery unit , in either of the following one scan or previous one scan recording pixels is Exceeding it to become one scan a predetermined value of the recording head of the integrated by said plurality of recording heads by said integrating means, each recording head The ratio of the number of pixels actually recorded to the number of pixels that can be recorded in one scan is obtained, and the ratio of the number of pixels of a plurality of recording heads A calculating means for calculating, anda judging means the sum of the percentage of the number of pixels to determine whether less than a predetermined value calculated by said calculation means, by said determining means, said number of pixels When it is determined that the sum of the ratios is equal to or greater than the predetermined value , the recording is continued without performing the recovery operation by the recovery means, and the determination means determines that the total ratio of the number of pixels is less than the predetermined value. If it is, a recovery operation by the recovery means is performed .
[0015]
With such a configuration, depending on the image portion that is actually intended to be recorded (or recorded) by the recording head, that is, by suppressing the ejection recovery operation when recording a portion with a relatively large ink ejection amount, It is possible to reduce main scanning unevenness such as ink color change and density change due to the ejection recovery operation.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a schematic perspective view showing an example of a serial type ink jet recording apparatus to which the present invention is applied. The recording material 6 inserted into the paper feeding position of the recording apparatus is conveyed to the recordable area of the recording head by the paper feed roller 9 and discharged along the direction of the arrow 19. A platen 8 is provided below the recording material in the recordable area. The carriage 1 is supported by the two guide shafts 4 and 5 so as to be movable, whereby the recording area can be reciprocally scanned by driving means (not shown) while being guided by the guide shafts 4 and 5. Mounted on the carriage 1 is a recording head unit 3 that includes respective recording heads that eject ink of a plurality of colors, which will be described later, and a tank that stores ink supplied to the recording heads. The inks of a plurality of colors provided in the ink jet recording apparatus of this example are four colors of black (K), cyan (C), magenta (M), and yellow (Y).
[0022]
In the present embodiment, each recording head has a plurality of nozzles arranged along the recording material conveyance direction, and a portion (band region) of an image corresponding to the plurality of nozzles is recorded by a plurality of carriage scans. Multi-pass printing is performed.
[0023]
In FIG. 1, a recovery unit 10 that performs an ink suction operation, a wiper operation, and a preliminary discharge operation of the recording head is provided at a position immediately below the recording head unit 3 at the left end of the area where the carriage can move. The recovery unit 10 includes a wiper blade (not shown), a cap, and negative pressure generating means for suction operation. At the time of non-recording or the like, the discharge port portion of the recording head is covered with a cap. This position of the left end is called the home position of the recording head. Note that the recording head used in the present embodiment ejects ink by generating bubbles in the ink using the thermal energy by an electrothermal conversion element that generates thermal energy.
[0024]
The control unit 15 controls the scanning of the carriage 1, the conveyance of the recording material, and the operation of each unit such as the recovery unit 10.
[0025]
FIG. 2 is a block diagram showing a control configuration of the ink jet recording apparatus described above. The image data transferred from the host computer is temporarily held in the reception buffer 21 of the recording apparatus. Conversely, data for confirming whether or not the data has been correctly transferred and data indicating the operating state of the recording apparatus are transferred from the recording apparatus to the host computer. The data held in the reception buffer 21 is transferred to the memory unit 23 and temporarily stored under the control of the control unit 22 having a CPU or the like. The control unit 22 is stored in the control unit 15 of FIG.
[0026]
The drive control unit 24 controls the driving of the main scanning motor for moving the carriage, the sub-scanning motor for transporting the recording material, and the like according to a command from the control unit 22, and a driving unit for recovery operations such as suction and wiping 25 drive is controlled. The sensor control unit 26 sends signals output from the sensor unit 27 including various sensors and switches (SW) for detecting environmental temperature, humidity, and the like to the CPU in the control unit 22.
[0027]
The head control unit 30 controls driving of the recording heads 31K, 31C, 31M, and 31Y according to a command from the image processing unit 221 of the control unit 22. In addition, temperature information indicating the state of each recording head is transmitted to the control unit 22.
[0028]
Control of the processing operation of each embodiment described below is performed by the configuration of FIG. 2, but the application of the present invention is not limited to such a configuration, and the processing shown in each embodiment Etc. may be performed by the host device, and the ink jet recording apparatus may be operated in accordance with this processing. In this case, the ink jet recording apparatus is provided with a receiving unit that receives control data based on processing by the host device and the like.
[0029]
FIG. 3 is a flowchart showing the procedure of the recording operation of the present embodiment based on the configuration described above. Here, control for performing a suction operation based on the number of recorded pixels will be described.
[0030]
First, in step S1, the integrated value (dot count value) of the recording pixels of each head is checked. As will be described later, this integration starts from 0 when the suction operation is completed for each head. If the integrated value of the recording pixels of any of the heads exceeds the predetermined value C1, each head in one scan to be performed for all the inks of K, C, M, and Y in step S2. Duty DK, DC, DM, and DY are counted. Here, the “duty” corresponds to the ratio of the number of pixels actually recorded to the number of pixels that can be recorded in a unit area (for example, one scanning area) that moves with the recording operation for each color. Since the duty between adjacent scans generally does not change much, the duty may be calculated for the last scan performed instead of “one scan performed from now on”.
[0031]
Next, in step S3, a total duty D corresponding to the total duty of each color ink is calculated from the counted duty, and whether or not the counted total duty D is smaller than a predetermined value D1. Judging. If the total duty D is equal to or greater than the predetermined value D1, the process returns to step S2, and each color duty is counted for the next scan. If the total duty D is less than the predetermined value D1, the process proceeds to step S4, and the suction operation of the head (that is, the head whose dot count is C1 or more) is performed. After this suction operation, the integrated value of the recording pixels of the head is cleared in step S5, and recording pixel counting is started again. If the total duty D is equal to or greater than a predetermined value D1, the current suction operation of the head is suppressed. The determination based on the total duty D of all the heads is that if the duty of the head that has reached the dot count at which the ejection recovery operation should be performed is small but the duty of the other head is large, the ink ejection amount is large in that region. This is because the recording interruption for the discharge recovery operation is considered to affect the image quality.
[0032]
Note that, although an example of the suction operation that takes a relatively long time has been described as an example of the recovery operation, another recovery operation may be used.
[0033]
FIG. 4 is a flowchart showing a modification of the procedure of FIG. In the procedure of FIG. 3, the dot count is simply compared with the predetermined value C1, but in the procedure of FIG. 4, the dot count is compared with C1 and C2 step by step. In FIG. 3, regardless of the dot count, the transition to the suction operation was not performed until the total duty D became D1 or less. However, in FIG. 4, even if the total duty D was D1 or more, the dot count was not changed. When a predetermined value C2 greater than C1 is reached, the head moves to a suction operation. This is based on the idea that if the dot count becomes excessive, the print quality deterioration caused by postponing the recovery operation will be greater than the print quality deterioration caused by the recording interruption for the recovery operation. is there.
[0034]
First, in step S11, the integrated value (dot count value) of the recording pixels of each head is checked. If the integrated value of the recording pixels of any of the heads exceeds the predetermined value C1, each head in one scan to be performed for all the inks of K, C, M, and Y in step S12. Duty DK, DC, DM, and DY are obtained. Next, in step S13, a total duty D corresponding to the total duty of each color ink is calculated from the counted duty, and whether or not the counted total duty D is smaller than a predetermined value D1. Judging.
[0035]
Up to this point, the procedure is the same as in FIG.
[0036]
If the total duty D is less than the predetermined value D1, the process proceeds to step S14 and the head is sucked. On the other hand, if the total duty D is equal to or greater than the predetermined value D1, the process proceeds to step S15, and it is further determined whether or not the integrated value (dot count value) of the recording pixels for each head to be recorded is equal to or greater than the predetermined value C2. If the integrated value is less than C2, the process returns to step S13. If the integrated value is equal to or greater than C2, the process proceeds to step S14, and the corresponding head is suctioned. After the suction operation, the integrated value of the recording pixels is cleared in step S16, and counting of the recording pixels is started again.
[0037]
The calculation of the total duty D in steps S3 and S13 described above is a simple sum of the duties DK, DC, DM, and DY of each color in the present embodiment, but is not limited thereto. It may be the sum of the results of weighting each duty depending on the physical properties such as lightness and saturation of the ink. Further, it may be a difference in ejection amount due to head characteristics.
[0038]
In steps S2 and S12, the duty of each color is determined by counting the number of recording pixels for one scan. However, there are cases where the pixels are evenly distributed over the entire row and there are cases where the duty is locally high. However, these cannot be distinguished and processed. When printing is locally performed at a high duty, there is a possibility that density unevenness occurs when the area is printed after the discharge recovery operation. Therefore, one scanning area may be divided into a plurality of areas, and a high-duty area in the divided area may be detected and determined.
[0039]
Alternatively, the number of recording pixels that become a connecting portion (area) between each scan may be counted for determination. It is desirable that the predetermined value D1 of the total duty is variably set to an optimum value depending on characteristics such as paper ink absorbability.
[0040]
In the first embodiment described above, control is performed by obtaining the duty of each color, but in the second embodiment described below, the ejection recovery operation is controlled by measuring the head temperature of each head. . The head temperature rises by ejecting ink. Also, the more recorded data, the higher the temperature rise. Therefore, an image having a high duty can be determined by head temperature measurement.
[0041]
FIG. 5 is a flowchart showing the procedure of the recording operation of the second embodiment based on the configuration described in the first embodiment. Here, control for performing a suction operation based on the number of recorded pixels will be described. First, in step S21, it is determined whether or not the integrated value (dot count value) of recording pixels for each head exceeds a predetermined value C1. Next, in step S22, the temperature TK, TC, TM, TY of each head in a single scan to be performed is measured for all the heads of K, C, M, Y, and the minimum of the measured values is measured. The control unit determines the value and the maximum value. Normally, the minimum value of the head temperature is observed at each scanning start time of the head, and the maximum value is observed at a portion where ink ejection of the head is continuous.
[0042]
Next, in step S23, a difference ΔT between the minimum and maximum values of each color head is calculated from the minimum value and the maximum value, and it is determined whether or not the temperature difference ΔT is smaller than a predetermined value T1. If the temperature difference ΔT is used, the influence of the environmental temperature and the like can be offset. However, in a general use situation, it is sufficient to use only the maximum value.
[0043]
If ΔT is less than the predetermined value T1 for any of the heads, the process proceeds to step S24, and the head is suctioned. On the other hand, if even one head temperature difference ΔT is greater than or equal to the predetermined value T1, the process returns to step S22. That is, the suction operation is suppressed. “If at least one temperature difference ΔT is greater than or equal to the predetermined value T1”, the reason is that if the temperature difference of the head that has reached the dot count for performing the ejection recovery operation is small but the temperature difference of the other heads is large, This is because the ink discharge amount is large in that region, and it is considered that the recording interruption for the discharge recovery operation affects the image quality. After the suction operation, in step S25, the integrated value of the recording pixels of the head is cleared, and counting of the recording pixels is started again.
[0044]
In FIG. 5, instead of determining the temperature for each head, the sum of the temperature differences ΔT of all the heads can be obtained and compared with a predetermined value.
[0045]
Further, the dot count is compared only with C1, but as shown in FIG. 4, in the present embodiment, it may be further determined whether or not the ejection recovery operation can be inhibited by comparing with C2.
[0046]
The temperature difference of each head may be weighted according to physical properties such as lightness and saturation of ink.
[0047]
In step S22, a method of determining the temperature difference ΔT between the minimum value and the maximum value of each head for one scan is used. However, the duty is locally higher than the maximum temperature value in a low-duty image. In the case of recording, the maximum temperature value may become low, and the temperature difference ΔT becomes small. In that case, the ejection recovery operation is performed, and after that operation, there is a possibility that density unevenness occurs when recording the area. Therefore, a temperature increase rate (temperature increase per unit time) within one scan may be obtained, and a portion having a high duty may be detected and determined.
[0048]
In any of the above embodiments, each predetermined value is variably set and controlled depending on the state in which the ink permeates the recording material, that is, the characteristics of the recording material, the characteristics of the ink, the environment, and the like. Thus, a more stable image can be output.
[0049]
【The invention's effect】
According to the present invention, the ratio of the number of pixels actually recorded to the number of pixels that can be recorded by each recording head related to the ink ejection amount in a predetermined area of the image being recorded is obtained, and the case where necessary In addition, since the ejection recovery process of the recording head is suppressed, main scanning unevenness such as a change in ink color and density due to the ejection recovery operation is reduced, and deterioration in print quality is prevented. can do.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example of an ink jet recording apparatus to which the present invention is applied.
2 is a block diagram showing a control configuration of the ink jet recording apparatus of FIG. 1. FIG.
FIG. 3 is a flowchart showing a recording operation procedure based on the configuration of FIG. 2;
FIG. 4 is a flowchart showing a modification of the procedure of FIG.
FIG. 5 is a flowchart showing a procedure of a recording operation in a second embodiment according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Carriage 3 Recording head unit 4, 5 Guide shaft 6 Recording material 8 Platen 9 Paper feed roller 10 Recovery unit 21 Reception buffer 22 Control part 23 Memory part 24 Drive control part 25 Drive part 26 Sensor control part 27 Sensor part 30 Head control Part

Claims (4)

Ink images recorded one scan by ejecting while moving a plurality of recording heads, ink jet recording for recording an image by repeating by a predetermined transport amount of the recording material after completion of recording of the one scan In the device
And recovery means for recovering the discharge state of said recording head,
Integration means for integrating the number of recording pixels of each recording head after the recovery processing of the recording head by the recovery means;
In either of the following one scan or previous one scan recording pixels is Exceeding it to become one scan a predetermined value of the recording head of the integrated by said plurality of recording heads by said integrating means, the respective recording heads A calculation means for calculating a ratio of the number of pixels actually recorded with respect to the number of pixels that can be recorded in one scanning, and further calculating a total of the ratio of the number of pixels of a plurality of recording heads ;
Determining means for determining whether or not the sum of the ratios of the number of pixels calculated by the calculating means is smaller than a predetermined value;
When the determination means determines that the total ratio of the number of pixels is equal to or greater than the predetermined value , the recording is continued without performing the recovery operation by the recovery means ,
An ink jet recording apparatus , wherein when the determination unit determines that the total ratio of the number of pixels is less than a predetermined value, a recovery operation is performed by the recovery unit. The inkjet recording apparatus according to claim 1, wherein the recovery unit performs suction recovery of the recording head that causes the number of recording pixels to exceed a predetermined value. Has a second predetermined value which is rather large set than the predetermined value for the number of the recording pixels are integrated by the integration means, recording the number of pixels of one of the recording heads of the plurality of recording heads the first If you exceed second predetermined value, the inkjet recording according to claim 1, 2 the total percentage of the number of pixels that the calculated is to this and wherein performing a recovery operation be determined to a predetermined value or more apparatus. Type of the recording medium, ink jet recording apparatus according to any one of claims 1 to 3, characterized in that variably sets the predetermined value in response to at least one of ambient temperature, and humidity.

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