JP7118664B2 - Inkjet recording device and control method - Google Patents

Description

The present invention relates to an inkjet recording apparatus and its control method.

Japanese Patent Application Laid-Open No. 2002-200003 discloses an inkjet recording apparatus that includes a long line head in which ejection openings are arranged along the width direction of a recording medium, and performs recording by conveying paper in a direction perpendicular to the arrangement direction of the ejection openings. disclosed. Further, in order to reduce image deterioration, a configuration is described in which printing is completed by performing a plurality of ejection operations on a predetermined area of the printing medium while reciprocating the printing medium with respect to the line head. .

However, in such a long line head, since the ejection openings are arranged at high density, it is difficult to dissipate the heat generated when ejecting the ink. As a result, when heat builds up inside the head, ink discharge failure may occur. In order to suppress ejection defects caused by such heat, Patent Document 2 discloses a method of lowering the temperature of the head by setting a standby time based on the temperature of the head and the image data to be printed next. ing.

JP-A-2006-96022 JP-A-2001-113678

However, in the method disclosed in Japanese Patent Laid-Open No. 2002-200013, the setting of the standby time causes a time difference between the previously recorded image and the next image to be recorded, which may cause ink color unevenness and density unevenness between the images. there were.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an inkjet recording apparatus capable of performing excellent recording while suppressing temperature rise of a line head having ejection ports arranged along the width direction of a recording medium. and

In order to achieve the above object, the present invention includes a conveying means for conveying a recording medium, and a plurality of ejection openings for ejecting ink onto the recording medium conveyed by the conveying means, arranged in the width direction of the recording medium. a recording head, wherein the recording head performs a first ejection operation on a predetermined area of the recording medium while transporting the recording medium in a first direction by the transporting means, and the first ejection operation is performed by the transporting means; An inkjet recording apparatus that forms an image in the predetermined area by performing a second ejection operation with the recording head on the predetermined area while conveying the recording medium in a second direction opposite to the direction of the detecting means for detecting the temperature of the recording head; and, when the temperature detected by the detecting means is lower than a threshold value, causing the conveying means to perform a first operation of conveying the recording medium by a first distance for the ejection operation. and performing a first control operation of causing the conveying means to perform a second operation of conveying the recording medium by a second distance shorter than the first distance for the discharge operation when the temperature is higher than the threshold value. and means.

According to the present invention, there is provided an inkjet printing apparatus capable of performing good printing while suppressing temperature rise of a line head having ejection openings arranged along the width direction of a printing medium.

1 is a schematic diagram of a recording section in an inkjet recording apparatus; FIG. 4 is a detailed diagram of the print head; FIG. FIG. 3 is a block diagram showing the configuration of control in the inkjet printing apparatus; FIG. 10 is a diagram for explaining multi-feed printing with a full-line print head; 4 is a flowchart for explaining processing of the first embodiment; It is a figure for demonstrating a 1st control action. FIG. 11 is a diagram for explaining a control selection method in the second embodiment; FIG. FIG. 11 is a schematic diagram for explaining dot count of print data according to the third embodiment; FIG. 11 is a flowchart for explaining processing of the third embodiment; FIG. FIG. 14 is a flowchart for explaining processing of the fourth embodiment; FIG. It is a table|surface which shows the control action selected by control of 4th Embodiment.

An embodiment of an inkjet recording apparatus according to the present invention will be described. However, the constituent elements described in the embodiment are merely examples, and are not intended to limit the scope of the present invention. In this specification, the term “ink” is used as a general term for liquids such as recording liquids. Furthermore, in this specification, the term "recording" includes not only recording two-dimensional objects but also three-dimensional objects. In this specification, the term "recording medium" is used as a general term for recording media such as paper, cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc., onto which liquid is ejected. Further, the recording medium is not limited to roll-shaped continuous paper, and includes cut paper.

[First embodiment]
FIG. 1 is a schematic diagram centering on a recording section of an ink jet recording apparatus (hereinafter referred to as a recording apparatus) of this embodiment. FIG. 1(a) is a schematic cross-sectional view of a main part centering on the recording section, and FIG. 1(b) is a schematic cross-sectional view of the recording section viewed from the upstream side in the conveying direction of the recording medium. The recording unit mainly includes a recording head 101 and a guide shaft 107 that supports the recording head 101 . The recording medium S is conveyed in the x direction by two sets of conveying roller pairs 104 as conveying means driven by a conveying motor (not shown). The conveying roller pair 104 moves in both the +x direction (right direction in FIG. 1A) and the −x direction (left direction in FIG. 1A) opposite to the x direction while nipping the recording medium S. Transportable. The recording head 101 is arranged between two sets of conveying roller pairs 104 in the x direction, and has a plurality of ejection openings 30 (see FIG. 2) in a range corresponding to the width of the recording medium S along the y direction intersecting the x direction. ) are arranged. In this embodiment, the y direction is the width direction of the recording medium S and is orthogonal to the x direction. The guide shaft 107 extends in the y direction as shown in FIG. 1(b).

Although not shown in FIG. 1, the printing apparatus also includes a maintenance unit for performing maintenance on the ejection port surface 201 of the printing head 101 . As maintenance
A preliminary ejection operation for ejecting ink that does not contribute to the printing operation from the print head 101, a purge operation for forcibly ejecting ink from the print head 101, a wiping operation for wiping off ink adhering to the ejection port surface 201, and the like. .

FIG. 2 is a detailed view showing the ejection port surface 201 of the print head 101. As shown in FIG. In the print head 101, a plurality of chips 200 of the same type are arranged along the y direction, and the chips 200 adjacent to each other in the y direction are arranged while being alternately shifted in the x direction. In this embodiment, chips 200A, 200B, 200C, and 200D are arranged from the left side in FIG. Each chip 200 has a plurality of ejection openings 30 arranged in the y direction at a constant pitch d, and the chips 200 are arranged so that the pitch d of the ejection openings 30 in the y direction is maintained between the chips. . Therefore, for example, adjacent chips 200A and 200B are arranged so as to overlap in the y direction. Note that the form of the print head 101 is not limited to this, and may be a form composed of one chip in which a plurality of ejection ports are arranged and which extends in the y direction.

An electrothermal converter that generates heat by receiving an electric signal generated according to image data is provided in the ink flow path that communicates with each ejection port 30 . The heat generated by the electrothermal converter locally heats the ink to cause film boiling, and the pressure generated at that time causes the ink to be ejected from the ejection port 30 . A diode sensor 50 as a head temperature detecting means for detecting the temperature of the recording head 101 is provided on the substrate provided with the heat converter of each chip 200 of the recording head 101 . Two diode sensors 50 are arranged at both ends of the chip 200 in the y direction.

As an inkjet method for ejecting ink from the ejection port 30 of the print head 101, various methods using an ejection energy generating element such as an electrothermal conversion element (heater), a piezo element, an electrostatic element, or a MEMS element are available. can be adopted.

FIG. 3 is a block diagram showing the control configuration in the printing apparatus. Each block (mechanism) is connected to each other via a main bus line 405 , and the CPU 400 controls the entire printing apparatus according to the programs and parameters stored in the ROM 401 while using the RAM 402 as a work area.

For example, the image processing unit 404 performs predetermined image processing on image data received from the image input unit 403 under instructions from the CPU 400 to generate ejection data that can be ejected by the print head 101 . The head drive control unit 414 drives the print head 101 according to the ejection data generated by the image processing unit 404 to eject ink from the individual ejection openings 30 . In parallel with the ejection operation, the transport control unit 417 drives the transport motor under the instruction of the CPU 400, and the two pairs of transport rollers 104 move the recording medium S at a predetermined speed in the +x direction or the −x direction. transport with The transport control unit 417 can arbitrarily change the transport speed and transport amount of the recording medium S by controlling the rotation speed and drive time of the transport motor.

Output data (temperature value) from the diode sensor 50 for detecting the temperature of the printhead 101 is sent to the CPU 400 . The recovery system control unit 407 drives the maintenance unit under instructions from the CPU 400 to perform maintenance processing on the print head 101 . An operation unit 406 receives commands from the user and displays the status of the printing apparatus under instructions from the CPU 400 .

FIG. 4 is a diagram for explaining multi-pass printing (hereinafter referred to as multi-feed printing) by the line-type print head 101, which prints an image by reciprocating the print medium a plurality of times in the transport direction (x direction). . In multi-feed printing, a step of causing the print head 101 to perform the ejection operation while conveying the print medium S in the +x direction and a step of causing the print head 101 to perform the ejection operation while conveying the print medium S in the −x direction are performed. Repeat alternately. At this time, the CPU 400 causes the ejection operation to be performed according to some of the dot data printable by the print head 101 in any transport operation. As a result, an image is formed step by step in a unit area (predetermined area) of the recording medium S by a plurality of conveying operations in the +x direction and the -x direction. Note that the unit area is determined based on the length in which the ejection openings 30 of the print head 101 are arranged in the x direction.

FIG. 4 shows the case of 3-pass printing in which the image of the unit area P is formed by three ejection operations. Hereinafter, the process of forming an image will be described step by step, focusing on a unit area P having a distance of 1F in the x direction.

In the first conveying operation indicated by the arrow (1) in FIG. 4, the CPU 400 conveys the recording medium S in the +x direction by a distance corresponding to 2F. In parallel with the first transport operation, the CPU 400 causes the print head 101 to perform the first ejection operation according to dot data of ⅓ of the dot data corresponding to the unit area P. FIG. As a result, the unit area P is in a state where an image corresponding to about 33% of the image data is recorded.

Subsequently, in the second conveying operation indicated by the arrow (2) in FIG. 4, the CPU 400 conveys the recording medium S by a distance corresponding to 1F in the -x direction. In parallel with the second conveying operation, the CPU 400 controls half of the dot data corresponding to the unit area P that were not printed in the first ejection operation (i.e., one half of the dot data). /3) to cause the print head 101 to perform the second ejection operation. As a result, the unit area P is in a state where an image corresponding to about 66% of the image data is recorded.

Next, in the third conveying operation indicated by the arrow (3) in FIG. 4, the CPU 400 conveys the recording medium S in the +x direction by a distance corresponding to 2F. In parallel with the third conveying operation, the CPU 400 causes the print head 101 to print according to the remaining 1/3 of the dot data corresponding to the unit area P, which has not been printed in the first and second ejection operations. A third ejection operation is performed. As a result, an image corresponding to 100% of the image data is recorded in the unit area P, and the image of the unit area P is completed.

By repeating the first to third ejection operations corresponding to the first to third conveying operations in this way, images are printed on a plurality of unit areas P. FIG. By performing multi-feed recording as described above, it is possible to record an image step by step while promoting the fixation of ink in the unit area P, thereby suppressing bleeding of the image and improving color development and density.

FIG. 5 is a flowchart for determining whether or not to execute temperature rise suppression control for the print head 101 before starting the conveying operation. First, in step S100, the CPU 400 acquires the temperature of the printhead 101 detected by the diode sensor 50 (hereinafter referred to as head temperature Tn). Two diode sensors 50 are arranged for each chip, and the highest temperature among all the diode sensors 50 is acquired as the head temperature Tn.

Next, in step S101, the CPU 400 compares the head temperature Tn obtained in step S100 with a predetermined threshold temperature of 70° C. stored in the ROM 401 in advance. If the head temperature Tn is lower than the threshold temperature of 70° C., the CPU 400 turns off the temperature rise suppression control in step S102, and the process ends.

On the other hand, if the head temperature Tn is higher than 70.degree. Note that the threshold temperature of 70° C. is a temperature that is preset based on experimental values and the like according to individual printheads, and is not limited to 70° C. A control operation when it is determined that the temperature rise suppression control of the print head 101 is ON will be described below.

<First control operation>
Similar to FIG. 4, FIG. 6 shows multi-feed printing (three-pass printing) in which an image is completed by three conveying operations and corresponding ejection operations. In FIG. 6, the head temperature Tn detected before the first transport operation indicated by the arrow (1) and the second transport operation indicated by the arrow (2) is less than 70.degree. The head temperature Tn detected before the third to sixth transport operations indicated by arrows (3) to (6) is 70° C. or higher. Furthermore, the head temperature Tn detected before the seventh to ninth transport operations indicated by arrows (7) to (9) is less than 70.degree.

In the first control operation, when the head temperature Tn is detected to be 70° C. or higher, the temperature rise of the print head 101 is suppressed by shortening the transport distance in the transport operation to less than 1F. In this case, the image of the unit area is formed by three conveying operations and ejection operations in the same manner as in the case of FIG. Become.

If the temperature of the print head 101 rises too much, air bubbles generated inside the head may expand due to the heat, causing ink ejection failure at the ejection ports 30 . Therefore, in the first control operation, the conveying distance in the conveying operation is shortened, and the frequency of reversing the conveying direction is increased. Since the temperature of the printhead 101 rises due to the heat generated by the ejection operation, the ejection operation by the printhead 101 is not performed while the reversal operation is being performed, so it is time to radiate heat. In other words, frequent reversal of the transport direction causes frequent heat dissipation from the print head 101, and as a result, the temperature of the print head 101 can be lowered. A specific method thereof will be described below.

First, since the head temperature Tn detected before the first transport operation is less than 70° C., temperature rise suppression control is turned off. In the first conveying operation, the CPU 400 conveys the recording medium S in the +x direction by a distance corresponding to 2F. In parallel with the first transport operation, the CPU 400 causes the print head 101 to perform the first ejection operation with respect to the unit area P1. Since the head temperature Tn detected before the second conveying operation is also less than 70° C., temperature rise suppression control is OFF, and the CPU 400 moves the recording medium S by a distance corresponding to a normal 1F in the −x direction. transport to In parallel with the second transport operation, the CPU 400 causes the print head 101 to perform the second ejection operation with respect to the unit area P1.

Since the head temperature Tn detected before the third transport operation is 70° C. or higher, the temperature rise suppression control is turned ON. In order to suppress the temperature rise, the CPU 400 performs a third transport operation of transporting the recording medium S in the +x direction by a distance corresponding to 1.5F, which is shorter than 2F. That is, in the third conveying operation, the unit area P1 having the length in the x direction of 1F and the unit area P2 having the length in the x direction set to 0.5F, which is shorter than 1F, are printed. A medium S is transported. A third ejection operation is performed on the unit area P1 in parallel with the third transport operation, and the image recording of the unit area P1 is completed. After the third ejection operation for the unit area P1 is finished, the first ejection operation for the unit area P2 is subsequently performed. In other words, the printing on the unit area P1 is completed by the third conveying operation, and the printing on the unit area P2 is started.

Since the head temperature Tn detected before the subsequent fourth conveying operation is also 70° C. or higher, temperature rise suppression control is turned ON, and the CPU 400 moves the recording medium S by a distance corresponding to 0.5 F, which is shorter than normal, −x. A fourth transport operation of transporting in the direction is performed. In parallel with the fourth transport operation, the print head 101 performs the second ejection operation on the unit area P2.

Since the head temperature Tn detected before the fifth transport operation is also 70° C. or higher, the temperature rise suppression control is turned ON. The CPU 400 performs a fifth conveying operation of conveying the recording medium S in the +x direction by a distance corresponding to 1F, which is shorter than usual. Since the head temperature Tn is 70° C. or higher, the length in the x direction of the unit area P3 to be printed next is also set to 0.5F, which is shorter than the usual 1F. In parallel with the fifth transport operation, the print head 101 performs the third ejection operation on the unit area P2, and the image printing of the unit area P2 is completed. After the third ejection operation for the unit area P2 is finished, the first ejection operation for the unit area P3 is subsequently performed.

Since the head temperature Tn detected before the sixth transport operation is also 70° C. or higher, the temperature rise suppression control is turned ON. The CPU 400 performs a sixth transport operation of transporting the recording medium S in the -x direction by a distance corresponding to 0.5F, which is shorter than usual. In parallel with the sixth transport operation, the print head 101 performs the second ejection operation on the unit area P3.

Since the head temperature Tn detected before the seventh transport operation is less than 70° C., temperature rise suppression control is turned off. The CPU 400 performs a seventh transport operation of transporting the recording medium S in the +x direction by a distance corresponding to 1.5F. Since the head temperature Tn has dropped below 70° C., the CPU 400 sets the length in the x direction of the unit area P4 to be printed next to the usual 1F. Therefore, in the seventh conveying operation, the recording medium S is conveyed by the unit area P3 having the length in the x direction of 0.5F and the unit area P4 having the length in the x direction set to 1F. In parallel with the seventh transport operation, the print head 101 performs the third ejection operation on the unit area P3, and the printing on the unit area P3 is completed. Subsequently, the print head 101 performs the first ejection operation on the unit area P4.

Since the head temperature Tn detected before the eighth transport operation is also less than 70° C., the temperature rise suppression control is turned off. The CPU 400 performs an eighth conveying operation of conveying the print medium S in the -x direction by a distance corresponding to a normal 1F, and concurrently the print head 101 performs a second ejection operation on the unit area P4.

Since the head temperature Tn detected before the ninth transport operation is also less than 70° C., the temperature rise suppression control is turned off. The CPU 400 performs a ninth transport operation of transporting the print medium S in the +x direction by a distance corresponding to a normal 2F, and concurrently the print head 101 performs a third ejection operation on the unit area P4.

When the head temperature Tn rises in this manner, the transport direction is reversed at a higher frequency than usual by controlling the transport distance to be shorter than usual. The temperature of the printhead 101 rises during the ejection operation, and the temperature of the printhead 101 decreases during the reversal operation of the transport roller pair 104 in the transport direction because the ejection operation is interrupted. That is, it is possible to prevent the print head 101 from being overheated by controlling the reversing operation in the transport direction to be performed more frequently than usual. Further, when the head temperature Tn drops to a predetermined temperature, the normal transport amount can be restored, so that printing can be performed without lowering the printing speed.

By controlling the transport distance and suppressing excessive temperature rise of the print head 101 in this way, there is no time difference between the unit areas as compared with the case where a standby time is provided between transport operations. As a result, it is possible to suppress the occurrence of ink color unevenness and density unevenness between unit areas.

In FIG. 6, if the head temperature Tn exceeds the threshold temperature of 70° C. before the start of the second transport operation indicated by the arrow (2), the image of the unit area P1 is completed by three transport operations. Therefore, the conveying distance in the -x direction cannot be changed from 1F. Therefore, in 3-pass printing, in which printing is performed by three conveying operations and an accompanying ejection operation as in the present embodiment, the timings at which the conveying distance can be changed are the first, third, and third timings at which the print medium S is conveyed in the +x direction. This is the case where the 5th, 7th, and 9th transport operations are performed.

In the case of three-pass printing as shown in FIG. 6, the head temperature Tn detected before the second, fourth, sixth, and eighth conveying operations for conveying the print medium S in the -x direction exceeds the threshold temperature. Even if it exceeds, the recording is performed without changing the conveying distance. In the case of multi-feed printing in which printing is completed with an odd number of passes such as 3-pass printing, the determination process shown in FIG. 5 may be performed only before the start of the odd-numbered conveying operation in the +x direction.

In the case of the example shown in FIG. 6, even if the head temperature Tn exceeds the threshold temperature of 70.degree. , the transport distance cannot be changed to 1F. In this way, when changing the conveying distance to be shorter, it is necessary to change it step by step as shown in FIG. Similarly, when changing the transport distance to be longer after the seventh transport operation, it is necessary to change in stages.

Although the example of 3-pass printing has been described with reference to FIG. 6, if the head temperature Tn rises in a similar manner with other numbers of passes, the temperature rise may be suppressed by changing the transport amount.

[Second embodiment]
In this embodiment, the control operation when it is determined that control is ON in FIG. 5 will be described for each of the number of printing passes, printing medium, and printing mode.

<Second control operation>
In the second control operation, when the head temperature Tn exceeds the threshold temperature, the temperature rise of the print head 101 is suppressed by reducing the conveying speed of the print medium S. FIG. The 3-pass printing shown in FIG. 4 will be described as an example. A normal transport speed in this embodiment is 15 inches/second. If it is determined that the control is ON in the determination before each transport operation shown in FIG. Then, the ink ejection operation by the print head 101 is performed. As a result, since the conveying speed is reduced to half of the normal speed, the ejection frequency is also reduced by half in the corresponding ejection operation. Therefore, compared with the ejection operation at the normal ejection frequency, the head temperature Tn is less likely to rise. When the head temperature Tn rises in this manner, the print head 101 can be prevented from being overheated by reducing the transport speed for printing.

<Third control operation>
In the third control operation, when the head temperature Tn exceeds the threshold temperature, a standby time is set before the next conveying operation of the print medium S is started, thereby suppressing the temperature rise of the print head 101 . The 3-pass printing shown in FIG. 4 will be described as an example. When it is determined that the control is ON in the determination before each transport operation shown in FIG. take action. By providing the standby time, the time during which the print head 101 does not perform an ejection operation increases, so the head temperature Tn can be lowered. When the head temperature Tn rises in this manner, the print head 101 can be prevented from becoming overheated by providing a standby time to lower the head temperature Tn before printing.

The advantage of the first control operation is that since the drive frequency (ejection frequency) of the printhead 101 is not changed, the relative speed of the printhead 101 with respect to the print medium S is not changed, and the displacement of the landing positions of print dots can be suppressed. . In addition, compared to the third control operation, the printing time difference between the unit areas is short, so image defects such as density unevenness and hue unevenness are less likely to occur.

The advantage of the second control operation is that the temperature rise can be suppressed by immediately lowering the transport speed in the transport operation at the timing when the head temperature Tn exceeds the threshold temperature. That is, the temperature rise of the print head 101 can be suppressed regardless of the number of print passes. However, when the transport speed is changed, the ejection frequency is also changed, and there is a possibility that the landing positions of the print dots are shifted.

The advantage of the third control operation is that, like the second control operation, it is possible to immediately suppress the temperature rise by providing a standby time in the transport operation at the timing when the head temperature Tn exceeds the threshold temperature. Density unevenness and hue unevenness may occur due to the difference in printing time, but there are cases in which it is possible to reduce the adverse effects on the image depending on the number of printing passes and the type of printing medium. For example, as the number of printing passes increases, the occurrence of density unevenness and hue unevenness is reduced. As for the type of recording medium, compared with coated paper and glossy paper having an ink receiving layer, plain paper having no ink receiving layer is less likely to cause density unevenness and hue unevenness.

In this embodiment, an appropriate control operation is selected from the above-described first to third control operations according to the number of printing passes, the type of printing medium, and the printing mode, thereby suppressing the temperature rise of the printing head 101. . FIG. 7 is a table showing control operations selected according to the number of printing passes, printing medium, and printing mode.

FIG. 7A shows the number of printing passes and control operations selected accordingly. For example, when the number of printing passes is 3, the first control operation is selected. is selected.

FIG. 7(b) shows the type of recording medium and the control operation selected accordingly. For the recording medium A, the first control operation is selected. For the recording medium B, the third control operation, which provides a standby time, is selected because the recording time difference has little effect on the image. Note that the recording medium A is, for example, coated paper or glossy paper, and the recording medium B is, for example, plain paper.

FIG. 7(c) shows recording modes and control operations selected accordingly. When the recording mode is the high-speed mode, the second control operation is selected because the recording speed is more important than the image quality. On the other hand, when the recording mode is the high image quality mode, the first control operation is selected in order to maintain the image quality.

As described above, by selecting the control operation according to the number of printing passes, the printing medium, and the printing mode, it is possible to suppress the temperature rise of the printing head 101 by appropriate control for each application.

[Third embodiment]
In the present embodiment, a configuration for performing control for suppressing temperature rise of the printhead 101 by predicting the amount of head temperature rise based on the dot count of print data will be described. FIG. 8 is a schematic diagram for explaining the dot count of print data in this embodiment, and shows the internal state of the print buffer. In the following, the third transport operation (arrow (3)) for the unit area P shown in FIG. 4 and the corresponding third ejection operation will be described as an example.

In FIG. 8, the area enclosed by the solid line corresponding to the arrow (3) indicates print data printed on the unit area P in the third ejection operation. The print buffer stores print data corresponding to areas printable by each print head 101 . In this embodiment, the print data corresponding to the printable area by one ejection operation of the print head 101 is 64 dots in the nozzle array direction (y direction) x the transport direction (x direction) corresponding to the print area enclosed by the solid line. ) It is assumed that print data corresponding to a 16-dot area is stored. In FIG. 8, A3, B3, C3, and D3 indicate print data corresponding to the printable areas of the four chips 200 (A to D) of the print head 101, and the printable areas are divided for each chip 200. It is. Here, print data refers to binary data indicating ejection "1" or non-ejection "0". Note that the recording area surrounded by solid lines in FIG. 8 indicates the area where the recording is actually performed on the recording medium excluding margins and the like.

In the third conveying operation, the CPU 400 causes the print head 101 to perform the third printing according to the remaining ⅓ of the dot data corresponding to the unit area P that has not been printed in the first and second ejection operations. Cause a discharge operation to be performed. That is, of the dot data corresponding to the print areas indicated by A3, B3, C3, and D3, 1/3 of the print data that was not printed in the first and second ejection operations is the dot of each chip in the third ejection operation. count value.

The dot count value thus counted corresponds to the amount of heat generated in each chip 200 per unit time. Therefore, by calculating the amount of heat generated in each chip 200 from the dot count value, it is possible to calculate the temperature of each chip that rises due to printing in the third ejection operation. For this purpose, the relationship between the dot count value and the amount of increase in chip temperature is measured in advance, and the amount of increase in chip temperature is calculated from the dot count value. Specifically, when the dot count value of chip A is 160 dots, the temperature of the printhead increases by 10.degree. Therefore, if the printhead temperature before the start of the transport operation is 40.degree. C., the predicted temperature of the printhead after transport rises to 50.degree.

As described above, before the start of printing, the predicted temperature that will rise due to printing in the ejection operation corresponding to each transport operation is calculated based on the print data in advance, and whether temperature rise suppression control is performed based on the calculated predicted temperature A determination is made as to whether or not FIG. 9 is a flowchart for explaining the process of calculating the predicted temperature of the print head 101 from print data in advance before starting printing, and determining whether or not to perform temperature rise suppression control based on the calculated predicted temperature. .

First, in step S200, the CPU 400 sets n=1. Here, n is the number of transport operations, and by setting n=1, it is determined whether or not to perform control in the first transport operation. Next, in step S201, the CPU 400 calculates the predicted temperature of the print head 101 (hereinafter referred to as predicted head temperature Tyn) from the print data. The highest predicted temperature of the four chips 200 is assumed to be the predicted head temperature Tyn.

Next, the CPU 400 compares the predicted head temperature Tyn calculated in step S201 with a predetermined threshold temperature of 70° C. stored in advance in the ROM 401 (step S202). If the predicted head temperature Tyn is lower than 70° C., the CPU 400 determines that Sn=0 (control OFF) (step S203). In step S204, the CPU 400 determines whether all print data processing has been completed. If the print data processing has not ended, the process proceeds to step S207. Next, the CPU 400 sets n=n+1 in step S207 and proceeds to determination regarding the next transport operation. In step S208, the CPU 400 calculates the predicted head temperature Tyn when Sn=0 (control OFF), and proceeds to step S202.

If the estimated head temperature Tyn is higher than 70° C., the CPU 400 determines that Sn=1 (control ON) (step S205). In step S206, the CPU 400 determines whether all print data processing has been completed. If the print data processing has not ended, the process advances to step S209, and the CPU 400 sets n=n+1 and shifts to determination regarding the next transport operation. In step S210, the CPU 400 calculates the predicted head temperature Tyn when Sn=1 (control ON), and proceeds to step S202.

By performing the processing as described above, it is possible to determine whether or not to implement the temperature rise suppression control in all the transport operations before the start of printing.

[Fourth embodiment]
In this embodiment, a configuration will be described in which control is performed by combining the first to third control operations according to the head temperature Tn. FIG. 10 is a flowchart for explaining the process of determining whether or not to execute the temperature rise suppression control, and if so, which control operation to execute, depending on the head temperature Tn.

First, in step S300, the CPU 400 acquires the head temperature Tn. Next, the CPU 400 compares the head temperature Tn obtained in step S300 with a predetermined first threshold temperature of 60° C. stored in advance in the ROM 401 (step S301). If the head temperature Tn is lower than 60° C., it is determined that the control is OFF (step S303), and the process ends. If the head temperature Tn is higher than 60° C., the process proceeds to step S302, and the CPU 400 compares the head temperature Tn with a predetermined second threshold temperature of 70° C. previously stored in the ROM 401 (step S302). If the head temperature Tn is lower than 70° C., the CPU 400 selects the third control operation (step S304) and terminates the process. If the head temperature Tn is higher than 70° C., the process proceeds to step S305, the CPU 400 selects the first control operation and the third control operation, and ends the process.

As described above, determination is made based on the head temperature Tn, and an appropriate control operation is performed based on the determination result, thereby preventing the temperature rise of the print head 101 .

FIG. 11 shows control operations selected according to the number of printing passes, printing mode, and head temperature Tn. FIG. 11A shows the number of printing passes, the head temperature Tn, and the control operation selected accordingly. When the number of printing passes is 3 and the head temperature Tn is 60° C.≦Tn<70° C., the first control operation is selected. When the number of printing passes is 3 and the head temperature Tn is 70° C.≦Tn, the first control operation and the third control operation are selected. On the other hand, when the number of printing passes is 7 and the head temperature Tn is 60° C.≦Tn<70° C., the third control operation is selected because the printing time difference has little effect. When the number of printing passes is 7 and the head temperature Tn is 70° C.≦Tn, the first control operation and the third control operation are selected in order to prioritize suppression of temperature rise over the influence of the printing time difference.

FIG. 11(b) shows the print mode and head temperature Tn, and the control operation selected accordingly. When the print mode is the high-speed mode and the head temperature Tn is 0° C.≦Tn<70° C., the third control operation is selected. When the print mode is the high-speed mode and the head temperature Tn is 70° C.≦Tn, the second control operation and the third control operation are selected. On the other hand, when the print mode is the high image quality mode and the head temperature Tn is 0° C.≦Tn<70° C., the third control operation is selected. Further, when the print mode is the high image quality mode and the head temperature Tn is 70° C.≦Tn, the first control operation and the third control operation are selected.

As for the combination of the head temperature Tn and the selected control operation, the most appropriate control operation may be selected from the viewpoint of the printing speed, the image deterioration, and the effect of suppressing the head temperature rise. Also, depending on the type of recording medium and the head temperature Tn, a combination of control operations may be selected.

30 Ejection port 101 Recording head 104 Conveying roller pair (conveying means)
P unit area (predetermined area)
S recording medium

Claims (9)

a conveying means for conveying a recording medium;
a recording head in which a plurality of ejection openings for ejecting ink onto the recording medium conveyed by the conveying means are arranged in the width direction of the recording medium;
While the recording medium is being transported in the first direction by the transporting means, the recording head performs a first ejection operation on a predetermined area of the recording medium, and the transporting means performs a second ejection operation opposite to the first direction. An inkjet recording apparatus that forms an image in the predetermined area by performing a second ejection operation with the recording head on the predetermined area while conveying the recording medium in a direction,
detection means for detecting the temperature of the recording head;
When the temperature detected by the detection means is lower than the threshold value, the conveying means is caused to perform a first operation of conveying the recording medium by a first distance for the ejection operation, and when the temperature is higher than the threshold value, the and a control unit that performs a first control operation for causing the conveying unit to perform a second operation of conveying the recording medium by a second distance shorter than the first distance for an ejection operation. recording device. When the second operation is performed, the control means gradually increases the distance by which the recording medium is conveyed by the conveying means so that the number of ejection operations performed for forming the image in the predetermined area is not changed. 2. The ink jet recording apparatus according to claim 1 , wherein the ink jet recording apparatus is changed. The control means causes the conveying means to convey the recording medium at a first conveying speed for the discharging operation in the first operation, and causes the conveying means to convey the recording medium for the discharging operation in the second operation. 3. The inkjet recording apparatus according to claim 1, wherein a second control operation is performed to transport the recording medium at a second transport speed lower than the first transport speed. 4. The inkjet recording method according to any one of claims 1 to 3 , wherein in the second operation , the control means performs a third control operation in which a waiting time is provided before the start of transportation by the transportation means. Device. The control means performs at least one of the first control operation, the second control operation, and the third control operation according to the number of ejection operations performed to form an image in the predetermined area. 5. The ink jet recording apparatus according to claim 4 , wherein: 5. The control means executes at least one of the first control operation, the second control operation and the third control operation according to the type of recording medium. 5. The inkjet recording apparatus according to 5. 7. The method according to any one of claims 4 to 6 , wherein said control means executes at least one of said first control operation, said second control operation and said third control operation according to a recording mode. 1. The inkjet recording apparatus according to item 1 or 1. The control means executes at least one of the first control operation, the second control operation, and the third control operation according to a dot count value in print data corresponding to the ejection operation. The ink jet recording apparatus according to any one of claims 4 to 7 , characterized by: a conveying means for conveying a recording medium;
A control method for an inkjet recording apparatus comprising a recording head in which a plurality of ejection openings for ejecting ink onto a recording medium conveyed by the conveying means are arranged in a width direction of the recording medium,
While the recording medium is being transported in the first direction by the transporting means, the recording head performs a first ejection operation on a predetermined area of the recording medium, and the transporting means performs a second ejection operation opposite to the first direction. a recording step of forming an image in the predetermined area by performing a second ejection operation with the recording head on the predetermined area while conveying the recording medium in a direction;
a detection step of detecting the temperature of the recording head ;
When the temperature detected in the detection step is lower than the threshold , the recording medium is conveyed by the conveying means for a first distance for the ejection operation, and when the temperature detected in the detection step is higher than the threshold , A control method , wherein the conveying means conveys the recording medium by a second distance shorter than the first distance for the ejection operation .

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