JP2003200596A - Ink jet recorder and ink jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ink jet recorder in which a significant difference is prevented from occurring in the density or color tone of a recorded image before and after restore processing by controlling the head temperature, lowered through the restore processing in the way of recording, to the level before the restore processing by a relatively simple head temperature control. <P>SOLUTION: Temperatures Ta1-Ta12 of twelve recording heads are detected (S101), average temperature Tave of respective head temperatures Tb1-Tb12 at the time of suction restore processing (S102, S103) is determine (S104). Following to the suction restore processing (S105), respective recording heads are heated until the average temperature is reached (S106, S107) and imaging is resumed when each head has reached the average temperature (S108). Since the target temperature of temperature control can be limited only to the average temperature Tave, temperature control is simplified. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus and an ink jet recording method.
The present invention relates to temperature control of a recording head related to ejection recovery processing of a recording head that ejects ink.

[0002]

2. Description of the Related Art Paper, cloth, etc. are used as a recording device in printers, copying machines, facsimiles, etc., or as a recording device used for outputting information processed by a composite electronic device including a computer, a word processor, etc. and a workstation. , Plastic sheet, OHP
2. Description of the Related Art Inkjet recording apparatuses that can perform recording on various recording media such as a printing sheet with a relatively simple structure are in widespread use. Further, since this system is basically a non-contact recording system and the type of the recording medium is not limited, cloth, leather, non-woven fabric, metal or the like is used as the recording medium in addition to the recording medium which is usually used as described above. A recording device to be used has also been proposed. Further, in this type of ink jet recording apparatus, a so-called serial method in which an image is recorded while a recording head is scanned in a direction (main scanning direction) that intersects a conveyance direction (sub scanning direction) of a recording medium is mainstream. The recording apparatus of the system has an advantage that it can record an image or the like having a relatively simple structure and relatively excellent reproducibility and uniformity. In particular, the so-called bubble jet (registered trademark) method, in which bubbles are generated in the ink by using the thermal energy generated by the electrothermal conversion element and the ink is ejected by the pressure of the bubbles, the ejection ports are relatively densely formed. It is a system that has been widely used in recent years because it has various advantages such as the arrangement, and the noise generated during the recording operation is small.

By the way, in the ink jet recording apparatus,
It is known to perform a recovery process for keeping the ejection state of the recording head good. For example, ink mist may be generated along with ink ejection from the recording head, or splash may occur due to impact when ejected ink lands on a recording medium. Then, these mists adhere to the ejection port surface where the ink ejection ports are arranged and block the ejection ports, which may cause ejection failure. Therefore, as one of the recovery processes, by moving the recording head in a state in which a blade made of an elastic material such as rubber is in contact with the ejection port surface, the ink and the like adhering around the ejection port is wiped off. So-called wiping is performed.

As another recovery process, so-called preliminary ejection is performed. For example, at the time of recording, ink is selectively ejected from a plurality of ejection ports of the recording head according to the recording data. In this case, looking at the individual ejection ports, there are ejection ports that do not eject ink for a certain period of time, and the ink in the vicinity continues to be exposed to the outside air at that ejection port, which causes the viscosity of the ink to increase. In some cases, ejection failure such as an increase in the amount and speed of ejected ink or a decrease in the ejection direction or deflection of the ejection direction may occur. Therefore, in order to remove these thickened inks, preliminary ejection is known, in which ink irrelevant to recording is ejected at a predetermined portion of the apparatus.

Suction recovery is known as another form of the recovery process. For example, bubbles are mixed in or generated in the liquid passage of the print head, the common liquid chamber, or the like due to continuous ink ejection or long-term non-use of the device, and the air bubbles cause ink supply to the liquid passage. The ejection operation may be hindered and ejection failure may occur. In order to prevent such ejection failure, a cap made of a material such as rubber is brought into contact with the ejection port surface and ink near the ejection port is sucked through the cap to remove it. Recovery is performed.

The various recovery processes described above are performed before image formation (recording), after image formation is completed, or before the next scan is started during image formation. This allows
It is possible to always maintain an appropriate ink ejection state of the recording head, prevent deterioration of image quality, and perform good-quality recording. In particular, in the case of continuously printing a relatively large area such as banner printing, it is important to perform the recovery operation during each scan in the middle of the printing.

By the way, the temperature of the ink in the recording head during the recording operation (in this specification, "temperature of recording head")
Alternatively, the "head temperature" is generally higher than that immediately after the start of recording due to energy generated by ejection. In this case, if the above-described recovery process is performed between the next scans, the head temperature drops during this process, and as a result, an image in which the discharge amount decreases and the density changes from the middle is recorded. There is.

Such a drop in the head temperature means that there is a relatively long heat radiation time because the time for the recovery process is provided between the scans, and when the scans are simply performed continuously. More heat is dissipated than the amount dissipated during each scan of, and ink with a higher temperature is discharged during suction recovery, and at the same time ink with a relatively lower temperature is discharged from the common liquid chamber. This is because the liquid is supplied to each liquid path.

Specifically, when wiping is performed as a recovery operation, a certain time is required for the wiping operation, and during this time, ejection energy such as heat energy is not supplied to the recording head and heat is exclusively radiated. Therefore, the head temperature when recording is restarted is often lower than that before the recovery operation.

Similarly, if preliminary ejection is performed during recording,
Ejection energy such as heat energy for preliminary ejection is supplied to the ink, but it is smaller than the ejection energy supplied to the ink during recording, and the effect of heat dissipation during preliminary ejection is large, so the recording density changes. May cause a noticeable temperature drop.

In the suction recovery operation, as in the case of the above wiping or preliminary ejection, the amount of heat released is large during the operation, and as described above, the temperature rises without the heat energy being introduced. The ink is ejected exclusively, and at the same time, the ink having a relatively low temperature is supplied, causing a relatively remarkable decrease in the head temperature.

The above-described ejection recovery process that causes a drop in the head temperature is performed in the middle of recording, and in particular, the difference between the recording density lowered by this and the recording density up to that time is adjacent to each other in the recorded image. Occurs, the recording quality is conspicuously deteriorated even with a slight density difference.

On the other hand, the applicant of the present invention has filed Japanese Patent Application Laid-Open No. 6-32
As disclosed in Japanese Patent No. 8723, in order to eliminate contamination due to ink droplets adhering to the ejection port surface of the recording head during recording, ink in the ejection port overflows to the ejection port surface and After the recovery operation for cleaning, the head temperature is restored to the temperature before the recovery operation. This publication also proposes performing suction recovery as a recovery process.

[0014]

However, in the technique described in Japanese Patent Laid-Open No. 6-328723, the head temperature control may be relatively complicated.

That is, the technique described in the above publication is equipped with a temperature sensor and a heater for each of a plurality of recording heads, detects the head temperature before the recovery process for each recording head, and based on this, detects the head temperature. The heater is driven to control the head temperature before the recovery process. With such a configuration, the control becomes more complicated as the number of recording heads increases. For example, in addition to commonly used yellow (Y), magenta (M), cyan (C), and black (K) inks, inks having different concentrations of color materials such as dyes or inks of special colors may be used. In a printing apparatus including a printhead, the above control is required for each of the many printheads.

On the other hand, as described above, the decrease in the temperature of each ink appears as a decrease in the amount of ejected ink, and thus a decrease in the size of the dots formed, but the recorded image is a collection of ink dots. Since the ink is formed by, the density change corresponding to the temperature decrease of each ink appears as an average. Therefore, even if relatively complicated control is performed as in the above-described conventional technique, the effect commensurate with the control may not be obtained.

The present invention has been made based on the above viewpoint, and an object of the present invention is to change the head temperature lowered by the recovery process during recording to a temperature before the recovery process by a relatively simple head temperature control. It is an object of the present invention to provide an inkjet recording apparatus and an inkjet recording method that can be controlled to prevent a significant difference in the density and color tone of a recorded image before and after the ejection recovery process.

[0018]

Therefore, according to the present invention, an ink jet recording apparatus which uses a plurality of recording heads for ejecting ink and ejects the ink onto a recording medium for recording, uses the plurality of recording heads. The recording operation, the recording control means for performing the ejection recovery operation of the plurality of recording heads during the recording operation, the temperature detecting means for detecting the temperature of the plurality of recording heads, and the recording after the ejection recovery operation. Means for controlling the temperature of the head to a temperature before the ejection recovery operation, wherein the temperature before the ejection recovery operation is detected by the temperature detection means for a plurality of recording heads before the ejection recovery operation. And a head temperature control means that uses an average of the temperatures.

In another form, the average of the temperatures of the plurality of recording heads is the average of the temperatures detected among the plurality of recording heads used in the recording apparatus whose detected temperature is higher than a predetermined threshold temperature. Is characterized in that.

Further, in an ink jet recording method in which a plurality of recording heads ejecting ink are used to perform recording by ejecting ink onto a recording medium, a recording operation using the plurality of recording heads is performed and the recording operation is performed. A step of preparing recording control means for performing ejection recovery operation of the plurality of recording heads on the way and a temperature detection means for detecting temperatures of the plurality of recording heads, and the temperature of the recording heads after the ejection recovery operation is ejected. In the step of controlling the temperature before the recovery operation, the head using the average of the temperatures detected by the temperature detection means before the recovery recovery operation for a plurality of recording heads as the temperature before the recovery recovery operation And a temperature control step.

In another embodiment, the average of the temperatures of the plurality of recording heads is the average of the temperatures detected among the plurality of recording heads used in the recording apparatus whose detected temperature is higher than a predetermined threshold temperature. Is characterized in that.

According to the above construction, when the temperature of the recording head is controlled to the temperature before the ejection recovery operation after the ejection recovery operation, the ejection recovery operation is performed for a plurality of recording heads as the temperature before the ejection recovery operation. Since the average of the temperatures detected before is used, the control target temperature can be one, which simplifies the control.

According to another aspect, in addition to the above-mentioned action, the average of the detected temperatures is set to the above-mentioned average temperature only for the print head whose detected temperature is higher than a predetermined threshold temperature. Therefore, if there is a print head that does not eject ink at all, or if there is a print head that does not eject ink frequently, the temperature of such a print head does not rise so much and even after recovery operation, there is no ejection. It is possible to consider whether or not the ejection frequency remains low, and if the head temperature control is performed on the basis of the average temperature for all recording heads uniformly, the temperature difference before and after the recovery process, It is possible to prevent the density change due to the recording head from increasing.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 is a top view showing an ink jet recording apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 2 denotes an apparatus main body including a paper carrying system unit, and this apparatus records on a relatively large-sized recording sheet (recording medium). Reference numeral 1 denotes a carriage, which has 12 recording heads 5 mounted thereon and moves, whereby the recording heads 5 can scan the recording paper. That is, the carriage 1 is guided and supported by the guide shaft 11 so as to be movable along the guide shaft 11, and can be reciprocated by the driving force transmitted through the belt 13. In addition to cyan, magenta, yellow and black, a total of 6 colors were used, including light cyan and light magenta for the purpose of reducing the granularity, and improved recording speed. For the purpose of
Two recording heads are used for one color ink.

30A, 30B, 30C and 30D are
The recovery mechanism is provided with a cap for performing a suction operation using a pump (not shown) of each recording head 5 as a drive source, and for protecting the recording head when the recording head is not used. Reference numeral 31 is a preliminary ejection ink receiving box for receiving ink ejected by the preliminary ejection operation of each recording head 5, and 32 is a wiping mechanism for performing a wiping operation of the ejection port surface of each recording head 5.

In the above device configuration, the carriage 1
When the print data is received from the host device, is controlled so as to move in the direction along the guide shaft 11 (main scanning direction) so as to print on the print paper sent by the paper transport unit (not shown). The recording head 5 is scanned to record an image for one band on the recording paper. Then, the recording paper is carried by the paper carrying unit in the direction orthogonal to the carriage 1 (sub-scanning direction) by one band. An encoder film 12 for detecting the moving position of the carriage 1 is arranged along the moving path of the carriage 1, and an encoder sensor mounted on the carriage 1 knows the position of the carriage based on a signal for detecting this. be able to. Further, the movement of the carriage 1 to the home position (the position facing the recovery mechanism in this embodiment) is controlled based on the position detection of the encoder.

Each recording head 5 has a density of 600 dpi (dots / inch) in the sub-scanning direction.
56 ejection ports are arranged, and in the ink liquid path communicating with each ejection port, the ink is locally heated to cause film boiling, and electrothermal conversion for ejecting the ink by the pressure. The body is provided. In addition, each recording head 5
In the above, a temperature detecting sensor 50 (see FIG. 2) is provided on the same substrate as the substrate on which the electrothermal converter is provided.

FIG. 2 is a block diagram showing the configuration of a control system in the ink jet recording apparatus shown in FIG.

In the figure, reference numeral 800 denotes a controller which constitutes a main control unit of the present recording apparatus, and is, for example, a CPU 801 in the form of a microcomputer that executes a sequence described later with reference to FIG. 6 and the like, programs and tables corresponding to the procedure, It has a ROM 802 which stores fixed values such as a voltage value of a heat pulse, a pulse width, and the like, and a RAM 803 which is provided with an area for expanding recording data, an area for work, and the like.

The environmental temperature detected by the environmental temperature sensor 811 is input to the controller 800. Reference numeral 805 denotes a host device serving as a supply source of print data, and print data, other commands, status signals, etc. from the host device are transmitted / received to / from the controller 800 via an interface (I / F) 804.

Reference numeral 806 denotes a head driver for driving the electrothermal converter (ejection heater) of the recording head 5 in accordance with recording data or the like during recording or preliminary ejection. Further, each recording head 5 is provided with a temperature sensor 50, and the temperature detection value detected by this sensor is input to the controller 800, whereby the head temperature can be controlled as will be described later with reference to FIG. 6 and the like.

Reference numeral 809 denotes a main scanning motor which is a drive source for moving the carriage 1 in the main scanning direction, and 807 denotes a driver thereof. Reference numeral 810 denotes a sub-scanning motor which is a drive source for conveying (sub-scanning) the recording paper, and 808 denotes a driver thereof.

In the ink jet recording apparatus described above, the control of the head temperature when the ejection recovery process is performed during the recording operation will be described below.

Before describing the head temperature control of this embodiment, as a comparative example, an example of a change in the head temperature when the ink temperature control is not performed after the suction operation is performed as the ejection recovery process during the recording operation is performed. Is shown in FIG. In FIG. 3, the horizontal axis indicates the recording position (printing position) on the recording paper,
By plotting the head temperature (ink temperature) on the vertical axis, the head temperature changes as recording is performed on the recording paper.

In FIG. 3, point A is the point where the suction recovery operation is performed, and the ink temperature during recording before point A is
Since thermal energy is supplied for ink ejection in a relatively continuous manner in accordance with print data, the heat energy gradually increases immediately after the start of printing. On the other hand, after the point A, the ink temperature of the print head immediately after restarting the printing becomes significantly lower than that before the ejection recovery operation. This is because during the suction recovery operation, heat energy is not supplied to the ink and heat is radiated exclusively, and new ink having a relatively low temperature flows into the ink liquid path of the recording head.

The ink temperature and the ink discharge amount have a constant relationship as shown in FIG. 4, that is, the higher the ink temperature, the larger the discharge amount.
At that point, the discharge amount is significantly reduced. As a result, as shown in FIG. 5, when the head temperature control is not performed after the suction recovery process is performed during recording, a relatively large density change occurs before and after the point A. Since this density change occurs in adjacent areas in a recorded image or the like, it is very small (for example, OD difference of 0.
(About 02) A change in density is also noticeable and deteriorates the recording quality.

This is also the case when the wiping operation other than the suction operation or the preliminary ejection operation is performed as the ejection recovery operation during the recording operation, although there is a difference in the degree thereof, but FIG.
A density change similar to the density change shown in FIG.

On the other hand, in this embodiment, after the suction operation is performed as the ejection recovery processing, the head temperature is controlled to raise the head temperature lowered by the suction operation to the head temperature before the suction operation. The average of the head temperatures of the plurality of recording heads before the suction operation is used.

FIG. 6 is a flow chart showing the head temperature control of this embodiment.

This processing is executed during the recording operation, and as shown in the figure, when the suction recovery processing is not performed after the start of image formation (recording), the temperature of the recording head is monitored at a predetermined timing (S101, S102). That is, the ink temperatures Ta1 to Ta12 of each of the 12 recording heads 5 are stored in the RAM 803 of the controller 800 (S10).
1). The storage timing is a waiting time from the end of one scan of the print head until the start of the next scan, and it is determined whether or not the suction operation is performed during this wait time (S102). If the suction operation is not performed,
Each ink temperature Ta1 of the plurality of recording heads 5 during the next scan
~ Ta12 is stored by overwriting the value stored in the previous scan.

When it is determined that the suction operation has been activated during the waiting time (S102), the values stored at that time are set to the ink temperatures Tb1 to Tb of each recording head 5 before the suction recovery operation.
The RAM 803 is determined as 12 (S103). Then, the determined average value Tave of the ink temperatures Tb1 to Tb12 is calculated and stored in the RAM 803 (S10).
4).

FIG. 7 is a diagram showing an example of the ink temperatures Tb1 to Tb12 determined by each recording head. In the example shown in this figure, the average value Tave is Tave = 43 ° C. In this way, the head temperatures (ink temperatures) detected for each of the 12 recording heads are averaged,
By using it as the head temperature before the recovery process, it is possible to make the control target temperature the same for all recording heads. This makes it possible to reduce the parameters used for head temperature control and simplify the control itself. You can In this case, the head temperature of each recording head when recording is restarted after the head temperature control is different from the head temperature before the recovery process for each recording head, but 12 images are recorded. Since it is represented as a set of dots by each ink ejected from the recording head, the variation in dot size for each ink is averaged depending on the recording image. It can be said that the difference has little effect on the recorded image.

As described above, the average ink temperature Tave is obtained (S104), and when the suction operation is completed (S105),
Control is performed with the average ink temperature as a control target. That is, the temperature detected by the temperature sensor 50 of each print head is compared with the ink temperature Tave stored in the controller 800 (S10).
6) Ta when the detected ink temperature is lower than Tave
The pulse shown in FIG. 8 is supplied to each electrothermal converter to heat the ink until reaching ve. That is, this pulse gives thermal energy to the ink to the extent that ink ejection is not possible, and the head temperature of the ink is controlled using this pulse (S107), and the ink temperature reaches the average temperature Tave. After that, image formation is restarted (S108).

FIG. 9 is a diagram showing changes in the head temperature when the head temperature control shown in FIG. 6 is performed after the suction recovery operation is performed during recording, and is the same as FIG.

As shown in the figure, the ink temperature during recording before point A is the same as that in the example shown in FIG. on the other hand,
As described above, the ink temperature immediately after the end of the suction operation at point A is the ink temperature immediately before the restart of the image formation because the temperature control of the ink by the above-mentioned pulse heating is performed before the image formation is restarted immediately after the end of the suction operation. The temperature has risen to the average ink temperature Tave.

FIG. 10 is a diagram showing a change in image forming density when the ink temperature of the present embodiment is controlled. As shown in this figure, no remarkable density change occurs before and after the point A where the suction recovery operation is performed.

It should be noted from the above description that similar head temperature control can be performed when the wiping operation or the preliminary ejection operation is performed as the ejection recovery processing in addition to the above-described suction operation. By Figure 1
As in the case of 0, it is possible to reduce the density change before and after the recovery operation.

As described above, according to this embodiment, in particular,
By simple head temperature control, it is possible to reduce the density change due to the recovery operation being performed during recording.

(Second Embodiment) FIG. 11 is a flow chart showing the head temperature control according to the second embodiment of the present invention. In this embodiment, the average ink temperature is calculated only for the temperatures higher than a predetermined threshold temperature among the ink temperatures of the 12 recording heads.

That is, as in the first embodiment, after the ink temperatures of the recording head 5 before the recovery operation are determined as Tb1 to Tb12 (S201, S202, S203), these temperatures Tb1 to Tb12 are respectively set to the temperature control threshold Ts.
(S204). Here, the temperatures Tb1 to Tb1
If at least one of the two values is higher than the threshold temperature Ts, the average value T of only the temperatures higher than the threshold temperature Ts.
ave is calculated and stored in the controller 800 (S2
05).

For example, FIG. 12 shows the temperatures Tb1 to Tb1 of each head.
It is the figure which showed Tb12, and when the threshold temperature Ts = 35 degreeC, the temperature higher than this temperature Ts is Tb2, Tb5,
They are Tb6, Tb7, Tb8, and Tb11, and their average value Tave is Tave = 47 ° C. In this way, by setting a predetermined threshold temperature, taking the average of the temperatures detected for them only for print heads having a higher temperature, and using this as the average ink temperature to perform temperature control for all print heads, It is possible to prevent in advance that the average ink temperature calculated by the temperature of the print head that is not so high becomes low and the overall density before the recovery operation is not reflected in the head temperature control. For example, depending on the print data, if there is a print head that does not eject ink at all or a print head that does not frequently eject ink, the temperature of such a print head does not rise so much and a recovery operation is performed. Similarly, after that, the ejection is not performed at all or the ejection frequency remains low. In this case, if the average temperature of all the print heads is uniformly obtained and the head temperature control is performed based on this, the temperature difference before and after the recovery process, and accordingly, the density change by the print head becomes large. May be noticeable in recorded images. The present embodiment can prevent such an adverse effect.

As described above, the average temperature Tave is calculated.
When the recovery operation (S206) is completed (S205), this average temperature Tave stored in the controller 800 is stored.
Is compared with the ink temperature detected by the temperature sensor of each recording head (S207), and if the detected ink temperature is lower than the average temperature Tave, the same as in the first embodiment until the average temperature Tave is reached. The ink temperature is controlled by heating with a pulse that does not result in ink ejection (S208). When the ink temperature reaches the average temperature Tave, image formation is restarted (S2).
09).

In step S204, the ink temperatures Tb1 to Tb12 of the print heads are all the threshold temperature T.
When it is determined that the temperature is smaller than s, the average temperature Tave is set to an extremely low temperature, 20 ° C. in the present embodiment (S2).
10). That is, if all the head temperatures are lower than the threshold temperature Ts, it means that ink is not ejected,
Alternatively, it indicates that the ejection frequency is low, and the density of the recorded image is very low. Therefore, even if the head temperature decreases during the recovery operation, it is assumed that the density decrease due to the decrease is not recognizable in the recording result. Therefore, it is not necessary to control the ink temperature after the ejection recovery operation. Does not matter. Therefore, in order to prevent an increase in the overall recording time due to the execution of the ink temperature control, the average temperature Tave is set to the temperatures Tb1 to Tb of the recording heads.
Regardless of the value of b12, the temperature is set extremely lower than the temperature during printing (for example, about 20 ° C.) to compare the average temperature Tave with each ink temperature after the suction operation is completed (S206) (S207). ), The image formation can be restarted (S209).

As described above, according to the present embodiment, it is possible to prevent the density change before and after the recovery operation, and to perform the unnecessary head temperature control for the recording head which is unlikely to cause the density change. By controlling the heads, it is possible to prevent the density change from occurring. In addition, as a whole of multiple recording heads,
If the density change is unlikely to occur due to the recovery operation, recording is resumed immediately, so that it is possible to prevent a decrease in throughput due to execution of unnecessary head temperature control.

In FIG. 13, all the ink temperatures Tb1 to Tb12 of each recording head 5 before the ejection recovery operation are the temperature control threshold T.
It is a figure which shows the temperature change when it is smaller than s, ie, when temperature control is not performed. Point A where the suction operation was performed
Before and after, the ink temperature change occurs though it is minute.
However, since the ink temperature is very low,
Similarly, the change in the ink ejection amount is small, and even after the recovery operation is performed in the middle of recording, the density change is small as shown in FIG. It can be said that the density change occurring before and after the point A shown in FIG. 14 is so small that it cannot be recognized as a change in density and tint by a human.

(Embodiment 3) In this embodiment, the ink temperature control threshold Ts in Embodiment 2 is determined according to the environmental temperature and the transport length (paper feed amount) per sub-scanning.

FIG. 15 is a diagram schematically showing the contents of a table in which the threshold temperature Ts is set according to the environmental temperature and the paper feed amount. In the figure, N represents the number of ejection ports in each recording head, and the paper feed amount is N (or N /
k) × ejection port pitch.

As shown in the figure, the threshold temperature Ts is set to be higher as the conveyance length per sub-scan is longer. This is because the width of the band printed in one main scan becomes larger as the conveyance length per sub-scan becomes larger, so that the amount of ink ejected from the recording head increases and the ink is continuously supplied to the ink. This is because the amount of heat energy used is also large. This state is shown in FIG. That is, in forming an image with the same density, the ink temperature immediately before the ejection recovery operation becomes higher as the conveyance length per sub-scan becomes longer. In other words, the ink temperature just before the ejection recovery operation is such that the density of the image to be printed is very low and it does not matter even if the ink temperature control is not performed. Get higher Therefore, by increasing the threshold value Ts as the conveyance length per sub-scanning increases, it is possible to effectively prevent an increase in the overall recording time due to execution of unnecessary head temperature control.

Further, the higher the environmental temperature, the higher the threshold temperature. This is because when the environmental temperature is high, the temperature rise of the ink during recording becomes large. This state is shown in FIG. That is, in forming an image with the same density, the higher the environmental temperature, the higher the ink temperature immediately before the ejection recovery operation. Therefore, as the environmental temperature is higher, the ink temperature control threshold value Ts is also increased, and it is possible to efficiently prevent the increase in recording time, as in the case of the paper feed amount.

As described above, in the case of the present embodiment, in addition to the effects of the first and second embodiments, the ink temperature control threshold T
Since s is optimized according to the environmental temperature and the transport length per sub-scan, it is possible to more efficiently prevent an increase in recording time.

As is clear from the above description of the first to third embodiments, in the case of an ink jet recording apparatus having a recording head having a plurality of ink ejection ports, color recording using ink of the same or different colors is possible. A recording device, or a gradation recording device for recording the same color with different densities,
Furthermore, in the case of a recording device that combines these,
Similarly, the present invention can be applied and the same effect can be achieved. Further, according to the present invention, a recording means such as a configuration using a replaceable ink jet cartridge in which the recording means and the ink tank are integrated, a configuration in which the recording means and the ink tank are provided separately, and the space between them is connected by an ink supply tube or the like. It can be similarly applied to any arrangement of the ink tank and the ink tank, and similar effects can be obtained.

Further, the present invention brings excellent effects particularly in an ink jet recording apparatus using a recording means of a method of ejecting ink by utilizing thermal energy among the ink jet recording methods.

[0065]

As described above, according to the present invention, when the temperature of the recording head is controlled to the temperature before the ejection recovery operation after the ejection recovery operation, a plurality of temperatures are set as the temperature before the ejection recovery operation. Since the average of the temperatures detected before the ejection recovery operation is used for the print head, the control target temperature can be set to one, which simplifies the control.

Further, according to another embodiment, in addition to the above-mentioned action, the average of the detected temperatures is set to the above-mentioned average temperature only for the recording head whose detected temperature is higher than a predetermined threshold temperature, and therefore it depends on the recording data. Therefore, if there is a print head that does not eject ink at all, or if there is a print head that does not eject ink frequently, the temperature of such a print head does not rise so much and even after recovery operation, there is no ejection. If you do not do it or you can consider that the ejection frequency remains low, uniformly calculate the average temperature for all recording heads, and when performing head temperature control based on this, the temperature difference before and after the recovery process, Therefore,
It is possible to prevent the density change due to the recording head from increasing.

As a result, the head temperature lowered by the recovery process in the middle of recording is controlled to the temperature before the recovery process by the relatively simple head temperature control, and a remarkable difference in the density and tint of the recorded image etc. is observed before and after the rotation process. It is possible to prevent the occurrence of.

[Brief description of drawings]

FIG. 1 is a top view showing an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system in the inkjet recording apparatus shown in FIG.

FIG. 3 is a diagram showing how the head temperature changes as recording is performed on a recording sheet.

FIG. 4 is a diagram showing a relationship between an ink temperature and an ink discharge amount in a recording head according to a conventional example.

FIG. 5 is a diagram showing a density change of a print image in the case of not performing ink temperature control after performing an ejection recovery operation during printing according to a conventional example.

FIG. 6 is a flowchart showing head temperature control according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an example of an ink temperature determined by each recording head that can be placed in the head temperature control.

FIG. 8 is a diagram schematically showing a recording head drive pulse used for the head temperature control.

FIG. 9 is a diagram showing a change in head temperature when the head temperature control shown in FIG. 6 is performed after the suction recovery operation is performed during recording.

FIG. 10 is a diagram showing a change in image forming density when the head temperature control of the present embodiment is performed.

FIG. 11 is a flowchart showing head temperature control according to the second embodiment of the present invention.

FIG. 12 is a diagram showing the temperature of each recording head detected in the head temperature control of the second embodiment.

FIG. 13 is a diagram showing a temperature change when the ink temperature of each recording head before the ejection recovery operation is less than a temperature control threshold value in the head temperature control of the second embodiment.

FIG. 14 is a diagram showing changes in concentration according to changes in temperature shown in FIG.

FIG. 15 is a diagram schematically showing the contents of a table used for the head temperature control according to the third embodiment of the present invention, in which threshold temperatures are set according to the environmental temperature and the paper feed amount.

FIG. 16 is a diagram showing a change in ink temperature for each transport length per sub-scanning according to the third embodiment.

FIG. 17 is a diagram showing a change in ink temperature for each environmental temperature according to the third embodiment.

[Explanation of symbols]

1 carriage 2 Device body (including transport system unit) 5 recording head 11 Guide shaft 12 encoder film 13 belt 30A, 30B, 30C, 30D Recovery mechanism 31 Preliminary ejection ink receiving box 32 Wiping mechanism 50 temperature sensor 800 controller 801 CPU 802 ROM 803 RAM 804 interface 805 host device 806 head driver 807,808 Motor driver 809 Main scanning motor 810 Sub-scanning motor 811 Environmental temperature sensor

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B41J 2/185

Claims (20)

[Claims] 1. An ink jet recording apparatus for ejecting ink onto a recording medium for recording by using a plurality of recording heads for ejecting ink, wherein the recording operation is performed by using the plurality of recording heads. A recording control unit that performs an ejection recovery operation of the plurality of recording heads on the way, a temperature detection unit that detects the temperature of the plurality of recording heads, and a temperature of the recording head after the ejection recovery operation before the ejection recovery operation. Head temperature control means for controlling the temperature, wherein the temperature before the ejection recovery operation uses an average of the temperatures detected by the temperature detection means before the ejection recovery operation for a plurality of recording heads, An ink jet recording apparatus comprising: 2. The average of the temperatures of the plurality of recording heads is
The inkjet recording apparatus according to claim 1, wherein, of the plurality of recording heads used in the recording apparatus, a detected temperature is an average of temperatures detected for a recording head having a temperature higher than a predetermined threshold temperature. 3. The head temperature control means performs a process of avoiding a process of controlling the temperature before the ejection recovery operation when all of the plurality of print heads used in the printing device are lower than the threshold temperature. 2. The method according to claim 2, wherein
The inkjet recording device according to item 1. 4. The head temperature control means sets the average temperature to a predetermined temperature lower than the threshold temperature when all of the plurality of recording heads used in the recording apparatus are lower than the threshold temperature. The ink jet recording apparatus according to claim 3, wherein the process of controlling the temperature before the ejection recovery operation is avoided. 5. The ink jet recording apparatus according to claim 2, wherein the predetermined threshold temperature differs depending on the environmental temperature. 6. The apparatus further comprises scanning means for scanning the recording head in the main scanning direction, and paper feeding means for conveying the recording medium in the sub-scanning direction, wherein the predetermined threshold temperature is one for the paper feeding means. 6. The inkjet recording apparatus according to claim 2, wherein the inkjet recording apparatus is different depending on the amount of conveyance of the paper feed recording medium. 7. Each of the plurality of recording heads includes an electrothermal converter, and ejects ink by supplying an electric pulse to the electrothermal converter. The process for controlling the temperature of the head to the temperature before the ejection recovery operation is performed by supplying an electric pulse that does not result in ejection to the electrothermal converter to heat the ink. 7. The inkjet recording device according to any one of 6. 8. The ink jet recording apparatus according to claim 1, wherein the ejection recovery operation ejects ink that is not involved in recording from a recording head. 9. The ejection recovery operation is an operation of wiping at least a surface of the recording head on which the ejection openings are provided with a blade.
The inkjet recording device according to any one of 1. 10. The ink jet recording apparatus according to claim 1, wherein the ejection recovery operation is to cause the ink in the plurality of recording heads to flow and be discharged. 11. An ink jet recording method in which a plurality of recording heads ejecting ink are used to perform recording by ejecting ink onto a recording medium, and a recording operation is performed using the plurality of recording heads, and the recording operation is performed. A step of preparing recording control means for performing ejection recovery operation of the plurality of recording heads on the way and a temperature detection means for detecting temperatures of the plurality of recording heads; In the step of controlling the temperature before the recovery operation, as the temperature before the recovery recovery operation, an average of the temperatures detected by the temperature detecting means before the recovery recovery operation for a plurality of recording heads is used. Temperature control step,
An inkjet recording method comprising: 12. The average of the temperatures of the plurality of recording heads is the average of the temperatures detected for the recording heads whose detected temperature is higher than a predetermined threshold temperature among the plurality of recording heads used in the recording apparatus. The inkjet recording method according to claim 11, wherein 13. The head temperature control step performs a process of avoiding a process of controlling to a temperature before the ejection recovery operation when all of a plurality of print heads used in the printing apparatus are lower than the threshold temperature. The inkjet recording method according to claim 12, wherein 14. The head temperature control step comprises setting the average temperature to a predetermined temperature lower than the threshold temperature when all of the plurality of recording heads used in the recording apparatus are lower than the threshold temperature. The ink jet recording method according to claim 13, wherein the process of controlling the temperature before the ejection recovery operation is avoided. 15. The ink jet recording method according to claim 12, wherein the predetermined threshold temperature differs depending on the environmental temperature. 16. The method further comprises the step of preparing a scanning means for scanning the recording head in the main scanning direction and a paper feeding means for conveying the recording medium in the sub scanning direction, wherein the predetermined threshold temperature is the paper feeding means. 16. The ink jet recording method according to any one of claims 12 to 15, wherein is different according to the amount of conveyance of the paper feed recording medium for one time. 17. Each of the plurality of recording heads comprises:
An electrothermal converter is provided, and ink is ejected by supplying an electric pulse to the electrothermal converter. The head temperature control step controls the temperature of the recording head to a temperature before the ejection recovery operation. 17. The ink jet recording method according to claim 11, wherein the treatment is performed by supplying an electric pulse that does not cause ejection to the electrothermal converter to heat the ink. 18. The ink jet recording method according to claim 11, wherein the ejection recovery operation is to eject ink that is not involved in recording from a recording head. 19. The ink jet recording method according to claim 11, wherein the ejection recovery operation is an operation of wiping at least a surface of the recording head on which the ejection port is provided with a blade. . 20. The ink jet recording method according to claim 11, wherein the ejection recovery operation is to cause the ink in the plurality of recording heads to flow and be discharged.