JP3913062B2 - Inkjet recording apparatus and inkjet recording method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly to temperature control of a recording head related to discharge recovery processing of a recording head that discharges ink.
[0002]
[Prior art]
Paper, cloth, plastic sheets, OHP as recording devices in printers, copiers, facsimiles, etc., or as recording devices used as composite electronic devices including computers and word processors, and devices that output information processed by workstations, etc. 2. Description of the Related Art Inkjet recording apparatuses that can record with a relatively simple configuration on various recording media such as printing sheets have become widespread. In addition, since this method is basically a non-contact recording method and the type of the recording medium is not limited, in addition to the recording media normally used as described above, cloth, leather, non-woven fabric, metal, etc. are used as the recording medium. A recording apparatus 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) intersecting the conveyance direction (sub-scanning direction) of the recording medium, is mainstream. The recording apparatus of the system has an advantage that it is possible to record an image or the like with relatively simple reproducibility and uniformity with a simple configuration. In particular, the so-called Bubble Jet (registered trademark) system, in which bubbles are generated in ink using the thermal energy generated by the electrothermal conversion element and ink is discharged by the pressure of the bubbles, has a relatively high density of discharge ports. This is a system that has various advantages such as being arranged and having a small noise generated in association with a recording operation, and has been widely used in recent years.
[0003]
By the way, in an ink jet recording apparatus, it is known to perform a recovery process for maintaining a good discharge state of the recording head. For example, ink mist may be generated as ink is ejected from the recording head, or splash may be generated by impact when the ejected ink lands on the recording medium. These mists or the like may adhere to the discharge port surface on which the ink discharge ports are arranged and block the discharge ports, thereby causing a discharge failure. Therefore, as one of the recovery processes, by moving the recording head in a state where a blade made of an elastic material such as rubber is in contact with the discharge port surface, the ink etc. adhering to the periphery of the discharge port is wiped off and removed. So-called wiping is performed.
[0004]
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, when looking at the individual discharge ports, there are discharge ports that do not discharge ink for a certain period of time, and the ink in the vicinity of the discharge ports continues to be exposed to the outside air. There may be a case where an increase in the amount and speed of ink discharged and a discharge defect such as a deflection in the discharge direction occur. Therefore, in order to remove these thickened inks, preliminary ejection is known in which ink ejection irrelevant to recording is performed at a predetermined portion of the apparatus.
[0005]
As another form of the recovery process, suction recovery is known. For example, bubbles may be mixed or generated in the liquid path of the recording head or in the common liquid chamber due to continuous ink discharge or the long-term non-use of the apparatus. Discharging operation may be hindered to cause discharge failure. In order to prevent such discharge failure, a suction that removes by ejecting ink in the vicinity of the discharge port through a cap made of rubber or other material in contact with the surface of the discharge port Recovery takes place.
[0006]
The various recovery processes as described above are performed before image formation (recording), after image formation is completed, or until the next scan starts during image formation. As a result, it is possible to always maintain the ink ejection state of the recording head appropriately, prevent deterioration in image quality, and perform good quality recording. In particular, when recording a relatively large area continuously, such as in banner printing, it is important to perform a recovery operation during each scan in the middle of the recording.
[0007]
Incidentally, the temperature of the ink in the recording head during the recording operation (in this specification, also referred to as “the temperature of the recording head” or simply “the temperature of the head”) is compared with that immediately after the start of recording due to the energy generated for ejection. It is common to get higher. In this case, if the recovery process described above is performed between the next scans, the head temperature falls during this process, and as a result, the discharge amount decreases and an image whose density has changed from the middle is recorded. There is.
[0008]
Such a decrease in head temperature causes a relatively long heat dissipation time by providing a time for recovery processing between scans, and each scan in the case of simply performing a scan continuously. In the case of suction recovery, the ink whose temperature has increased is discharged, and at the same time, the ink having a relatively low temperature is discharged from the common liquid chamber to each liquid path. It is because it is supplied to.
[0009]
Specifically, when wiping is performed as a recovery operation, a certain amount of time is required for the wiping operation, and during this time, discharge heat such as thermal energy is not supplied to the recording head, and only heat radiation is performed. Therefore, the head temperature when recording is resumed is often lower than before the recovery operation.
[0010]
Similarly, if preliminary ejection is performed in the middle of recording, ejection energy such as thermal energy for preliminary ejection is provided to the ink, but is smaller than the ejection energy provided to the ink during recording, and during preliminary ejection. Since the effect of heat dissipation is greater, the temperature may drop so that the change in recording density is noticeable.
[0011]
In the case of the suction recovery operation, similar to the above-described wiping and preliminary discharge, the amount of heat dissipated in the time for the operation is large, and as described above, the ink whose temperature has been increased without causing thermal energy or the like. Due to the fact that ink having a relatively low temperature is supplied at the same time as being discharged, a relatively significant head temperature drop occurs.
[0012]
The above-described ejection recovery process that causes a drop in head temperature is performed in the middle of recording. In particular, when the difference between the recording density lowered thereby and the recording density so far occurs in an adjacent area in a recorded image or the like. Even a slight difference in density will noticeably reduce the recording quality.
[0013]
On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 6-328723, the applicant of the present invention applied to the discharge port surface in order to eliminate contamination caused by ink droplets adhering to the discharge port surface of the recording head during recording. A technique for recovering the head temperature to the temperature before the recovery operation after performing a recovery operation for cleaning the surface of the discharge port by overflowing ink in the discharge port is proposed. This publication also proposes performing suction recovery as a recovery process.
[0014]
[Problems to be solved by the invention]
However, in the technique described in the above Japanese Patent Laid-Open No. 6-328723, the head temperature control may be relatively complicated.
[0015]
That is, the technology described in the above publication includes a temperature sensor and a heater for each of a plurality of recording heads, detects the head temperature before recovery processing for each recording head, and based on this, detects each heating heater. To control the head temperature before the recovery process. In such a configuration, the control becomes more complicated as the number of recording heads increases. For example, in addition to the commonly used yellow (Y), magenta (M), cyan (C), and black (K) inks, these inks also have different color material concentrations such as dyes or special color inks. In a recording apparatus including a recording head, the above-described control is necessary for each of the many recording heads.
[0016]
On the other hand, as described above, a decrease in the temperature of each ink appears as a decrease in the amount of each ejected ink, and thus a decrease in the size of the formed dots. However, the recorded image is formed by a set of ink dots. Therefore, the density change corresponding to the temperature drop of each ink appears as an average. Therefore, even if relatively complicated control is performed as in the above-described prior art, an effect corresponding to the control may not be obtained.
[0017]
The present invention has been made based on the above viewpoint, and its object is to control the head temperature lowered by the recovery process during recording by the relatively simple head temperature control to the temperature before the recovery process, An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of preventing a remarkable difference in density and color of a recorded image before and after the discharge recovery process.
[0018]
[Means for Solving the Problems]
Therefore, in the present invention, in an ink jet recording apparatus that uses a plurality of recording heads that eject ink and performs recording by ejecting ink onto a recording medium, the recording operation is performed using the plurality of recording heads. A recording control means for performing an ejection recovery operation of the plurality of recording heads in the middle of the recording medium; a temperature detection means for detecting temperatures of the plurality of recording heads; and a temperature of the recording head after the ejection recovery operation before the ejection recovery operation. The temperature before the discharge recovery operation is a temperature that is detected by the temperature detection unit before the discharge recovery operation for a plurality of recording heads. Of which, the print head temperature is higher than the predetermined threshold temperature. And a head temperature control means using an average.
[0020]
Further, in an ink jet recording method in which recording is performed by ejecting ink onto a recording medium using a plurality of recording heads that eject ink, a recording operation is performed using the plurality of recording heads, and the recording operation is performed during the recording operation. Providing a recording control means for performing an ejection recovery operation of a plurality of recording heads, and a temperature detecting means for detecting the temperatures of the plurality of recording heads; A step of controlling to a previous temperature, wherein the temperature before the discharge recovery operation is a temperature detected by the temperature detecting means before the discharge recovery operation for a plurality of recording heads. Of which, the print head temperature is higher than the predetermined threshold temperature. And a head temperature control step using an average.
[0022]
According to the above configuration, when controlling the temperature of the print head after the discharge recovery operation to the temperature before the discharge recovery operation, the temperature before the discharge recovery operation is set as the temperature before the discharge recovery operation before the discharge recovery operation. Since the average of the detected temperatures is used, one control target temperature can be obtained, thereby simplifying the control.
[0023]
In addition to the above action Since the average of the detected temperatures is the average temperature only for the print head whose detected temperature is higher than the predetermined threshold temperature, even if it is a print head that does not discharge ink at all or is discharged depending on the print data When there is a recording head with a low frequency, it can be considered that the temperature of such a recording head does not rise so much, and after the recovery operation, it is not discharged at all or the discharge frequency remains low. When the average temperature for all the recording heads is obtained uniformly and the head temperature control is performed based on the average temperature, it is possible to prevent the temperature difference before and after the recovery process, and hence the change in density due to the recording head from becoming large.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0025]
(Embodiment 1)
FIG. 1 is a top view showing an ink jet recording apparatus according to an embodiment of the present invention.
[0026]
In FIG. 1, reference numeral 2 denotes an apparatus main body including a paper transport system unit. This apparatus performs recording on a relatively large recording sheet (recording medium). Reference numeral 1 denotes a carriage which is mounted and moved with twelve recording heads 5, whereby the recording head 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, the ink used is a total of six colors that add light cyan and light magenta for the purpose of reducing graininess, and improve recording speed. For this purpose, two recording heads are used for one color ink.
[0027]
Reference numerals 30A, 30B, 30C, and 30D denote recovery mechanisms that are provided with caps and perform a suction operation using a pump (not shown) of each recording head 5 as a driving source, and protect the recording head when the recording head is not used. Reference numeral 31 denotes a preliminary ejection ink receiving box that receives ink ejected by the preliminary ejection operation of each recording head 5, and 32 denotes a wiping mechanism for performing a wiping operation of the ejection port surface of each recording head 5.
[0028]
In the above-described apparatus configuration, when receiving the recording data from the host apparatus, the carriage 1 moves in a direction (main scanning direction) along the guide shaft 11 so as to record on a recording sheet sent by a paper transport unit (not shown). Thus, each recording head 5 is scanned, and an image for one band is recorded on the recording paper. Then, the recording paper is conveyed by the paper conveyance unit for one band in a direction (sub-scanning direction) perpendicular to the carriage 1. An encoder film 12 for detecting the movement position of the carriage 1 is arranged along the movement 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, based on the position detection of the encoder, the movement of the carriage 1 to the home position (a position facing the recovery mechanism in the present embodiment) is controlled.
[0029]
Each recording head 5 has 256 ejection openings arranged at a density of 600 dpi (dots / inch) in the sub-scanning direction, and ink is supplied into the ink liquid path communicating with each ejection opening. There is provided an electrothermal converter for locally heating to cause film boiling and ejecting ink by the pressure. Each recording head 5 is provided with a temperature detection sensor 50 (see FIG. 2) on the same substrate as the substrate on which the electrothermal transducer is provided.
[0030]
FIG. 2 is a block diagram showing a configuration of a control system in the ink jet recording apparatus shown in FIG.
[0031]
In the figure, reference numeral 800 denotes a controller that constitutes the main control unit of the recording apparatus. For example, a CPU 801 in the form of a microcomputer for executing a sequence described later in FIG. It has a ROM 802 storing voltage values, pulse widths, and other fixed data, and a RAM 803 provided with an area for developing recording data, an area for work, and the like.
[0032]
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 recording data supply source, and recording data, other commands, status signals, and the like from the host device are transmitted to and received from the controller 800 via an interface (I / F) 804.
[0033]
Reference numeral 806 denotes a head driver for driving the electrothermal transducer (ejection heater) of the recording head 5 in accordance with recording data or the like during recording or preliminary ejection. 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 described later with reference to FIG. 6 and the like can be controlled.
[0034]
Reference numeral 809 denotes a main scanning motor serving as a driving 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 serving as a driving source for conveying (sub-scanning) the recording paper, and 808 denotes a driver thereof.
[0035]
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.
[0036]
Before explaining the head temperature control of this embodiment, as an example of comparison, FIG. 3 shows an example of the transition of the head temperature when the ink temperature control is not performed after the suction operation is performed as the ejection recovery process in the middle of the recording operation. Shown in In FIG. 3, the recording temperature (printing position) on the recording paper is taken on the horizontal axis, and the head temperature (ink temperature) is taken on the vertical axis, so that the head temperature changes as recording is performed on the recording paper. It shows the situation.
[0037]
In FIG. 3, point A is a point where the suction recovery operation has been performed, and the ink temperature during recording prior to point A is supplied with thermal energy for relatively continuous ink ejection according to the recording data. It gradually increases immediately after the start of recording. On the other hand, after point A, the ink temperature of the recording head immediately after resuming recording is significantly lower than before the ejection recovery operation. This is because the heat energy is not supplied to the ink during the suction recovery operation, but the heat is exclusively dissipated, and new ink having a relatively low temperature flows into the ink liquid path of the recording head.
[0038]
The ink temperature and the ink discharge amount have a certain relationship as shown in FIG. 4, that is, the discharge amount increases as the ink temperature increases. . 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 an adjacent region in a recorded image or the like, even a very small density change (for example, about 0.02 in terms of OD difference) is conspicuous and lowers the recording quality.
[0039]
Even when a wiping operation other than a suction operation or a preliminary discharge operation is performed in the middle of a recording operation as a discharge recovery operation, a density change similar to the density change shown in FIG. To do.
[0040]
On the other hand, in the present embodiment, after performing a suction operation as a discharge recovery process, head temperature control is performed to raise the head temperature lowered thereby to the head temperature before the suction operation. The average of the head temperatures before the suction operation of each head is used.
[0041]
FIG. 6 is a flowchart showing the head temperature control of this embodiment.
[0042]
This process is executed during the recording operation. As shown in FIG. 5, when the suction recovery process 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 the 12 recording heads 5 are stored in the RAM 803 of the controller 800 (S101). This storage timing is a waiting time from the end of one scan of the print head to the start of the next scan, and it is determined whether or not a suction operation has been performed during this waiting time (S102). When the suction operation is not performed, the ink temperatures Ta1 to Ta12 of the plurality of recording heads 5 during the next scan are stored by overwriting the values stored in the previous scan.
[0043]
If it is determined that the suction operation has been activated during the standby time (S102), the RAM 803 is determined as the ink temperatures Tb1 to Tb12 of each recording head 5 before the suction recovery operation (S103). Then, the average value Tave of the determined ink temperatures Tb1 to Tb12 is calculated and stored in the RAM 803 (S104).
[0044]
FIG. 7 is a diagram illustrating an example of the ink temperatures Tb1 to Tb12 determined for each recording head. In the example shown in this figure, the average value Tave is Tave = 43 ° C. In this way, by averaging the detected head temperatures (ink temperatures) for each of the 12 print heads and using that as the head temperature before the recovery process, the same control target temperature is used for all print heads. Accordingly, the parameters used for the head temperature control can be reduced, and the control itself can be simplified. In this case, the head temperature of each recording head when the recording is resumed after the head temperature control is different from the head temperature before the recovery process in terms of individual recording heads, but 12 images are recorded. Therefore, the variation in dot size for each ink is averaged depending on the recorded image. In this case, the head temperature of the above degree is used. It can be said that the effect of the difference on the recorded image is small.
[0045]
As described above, the average ink temperature Tave is obtained (S104), and when the suction operation is finished (S105), the control is performed with the average ink temperature as a control target. That is, for each recording head, the temperature detected by the temperature sensor 50 is compared with the ink temperature Tave stored in the controller 800 (S106). If the detected ink temperature is lower than Tave, Tave is reached. Until this is done, the pulses shown in FIG. 8 are supplied to each electrothermal transducer to heat the ink. That is, this pulse gives the ink thermal energy that does not lead to ink ejection, and the ink head temperature is controlled using this pulse (S107), and the ink temperature reaches the average temperature Tave. Image formation is resumed later (S108).
[0046]
FIG. 9 is a diagram showing a change 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 diagram as FIG.
[0047]
As shown in the figure, the ink temperature during recording before point A is the same as the example shown in FIG. On the other hand, the ink temperature immediately after the end of the suction operation at the point A is as described above, and the temperature control of the ink by the pulse heating described above is performed before the image formation is restarted immediately after the end of the suction operation. The ink temperature increases to the average ink temperature Tave.
[0048]
FIG. 10 is a diagram illustrating a change in image formation density when the ink temperature is controlled according to the present embodiment. As shown in this figure, no significant density change occurs before and after the point A where the suction recovery operation is performed.
[0049]
Note that it is clear from the above description that the same head temperature control can be performed in the case of performing the wiping operation and the preliminary discharge operation in addition to the above-described suction operation as the discharge recovery process, and as a result, FIG. In the same manner as shown in FIG. 4, the density change can be reduced before and after the recovery operation.
[0050]
As described above, according to this embodiment, it is possible to reduce the density change caused by the recovery operation being performed during the recording, particularly with simple head temperature control.
[0051]
(Embodiment 2)
FIG. 11 is a flowchart showing head temperature control according to the second embodiment of the present invention. In the present embodiment, an average ink temperature is obtained only for a temperature higher than a predetermined threshold temperature among the ink temperatures of the 12 print heads.
[0052]
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 compared with the temperature control threshold Ts. (S204). Here, if at least one of the temperatures Tb1 to Tb12 is larger than the threshold temperature Ts, an average value Tave only for temperatures higher than the threshold temperature Ts is calculated and stored in the controller 800 (S205).
[0053]
For example, FIG. 12 is a diagram showing the temperatures Tb1 to Tb12 of each head. When the threshold temperature Ts = 35 ° C., the temperatures higher than this temperature Ts are Tb2, Tb5, Tb6, Tb7, Tb8, and Tb11. Their average value Tave is Tave = 47 ° C. In this way, by setting a predetermined threshold temperature, averaging the temperatures detected for only those print heads having a temperature higher than this, and performing temperature control for all the print heads using this as the average ink temperature, It is possible to prevent the average ink temperature calculated based on the temperature of the print head that is not so high from becoming low and the overall density before the recovery operation from being reflected in the head temperature control. For example, if there is a print head that does not discharge ink at all or a print head that does not discharge frequently depending on print data, the temperature of such a print head does not increase so much, and the recovery operation Similarly, no discharge is performed or the discharge frequency remains low. In this case, if the average temperature for all the recording heads is uniformly obtained and the head temperature control is performed based on the average temperature, the temperature difference before and after the recovery process, and hence the change in density due to the recording head increases. May stand out in recorded images. This embodiment makes it possible to prevent such adverse effects.
[0054]
As described above, when the calculation of the average temperature Tave (S205) and the recovery operation (S206) are completed, the average temperature Tave stored in the controller 800 is compared with the ink temperature detected by the temperature sensor of each recording head. (S207), if the detected ink temperature is lower than the average temperature Tave, the ink temperature is obtained by heating with a pulse that does not lead to ink ejection until the average temperature Tave is reached, as in the first embodiment. Is controlled (S208). When the ink temperature reaches the average temperature Tave, the image formation is resumed (S209).
[0055]
If it is determined in step S204 that all the ink temperatures Tb1 to Tb12 of each recording head are lower than the threshold temperature Ts, the average temperature Tave is set to an extremely low temperature, 20 ° C. in this embodiment (S210). . That is, the fact that all the head temperatures are lower than the threshold temperature Ts indicates that ink is not ejected or the ejection frequency is low, and the density of the recorded image is very low. For this reason, even if there is a drop in the head temperature during the recovery operation, it is assumed that the resulting decrease in density is indistinguishable in the recording result. Therefore, the ink temperature must not be controlled after the discharge recovery operation. Is not a problem. Therefore, in order to prevent an increase in the overall recording time due to the ink temperature control, the average temperature Tave is extremely lower than the temperature during recording (for example, regardless of the values of the temperatures Tb1 to Tb12 of each recording head) , About 20 ° C.), immediately after the end of the suction operation (S206), the comparison between the average temperature Tave and each ink temperature (S207) can be immediately exited and image formation can be resumed (S209).
[0056]
As described above, according to this embodiment, it is possible to prevent the density change before and after the recovery operation, and it is unnecessary to perform unnecessary head temperature control for the recording head which is unlikely to cause the density change. On the other hand, it is possible to prevent the density change from occurring by controlling the head. In addition, since the recording operation is resumed immediately when the density change is unlikely to occur due to the recovery operation as a whole of the plurality of recording heads, it is possible to prevent a decrease in throughput due to unnecessary head temperature control.
[0057]
FIG. 13 is a diagram showing a temperature change when the ink temperatures Tb1 to Tb12 of each recording head 5 before the ejection recovery operation are all lower than the temperature control threshold Ts, that is, when temperature control is not performed. The ink temperature changes slightly before and after the point A where the suction operation is performed. However, since the ink temperature is very low, the ink discharge amount is similarly small, and the density change is slight as shown in FIG. 14 even in the recording after performing the recovery operation during the recording. Become. 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 color for humans.
[0058]
(Embodiment 3)
In the present embodiment, the ink temperature control threshold Ts in the second embodiment is determined according to the environmental temperature and the transport length (paper feed amount) per sub-scan.
[0059]
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 indicates the number of ejection openings in each recording head, and indicates that the paper feed amount is N (or N / k) × ejection opening pitch.
[0060]
As shown in the figure, the threshold temperature Ts is set higher as the conveyance length per sub-scan increases. This is because as the transport length per sub-scan increases, the width of the band to be recorded in one main scan increases, so the amount of ink ejected from the print head increases, and the ink is continuously supplied to the ink. This is because more heat energy is generated. This is shown in FIG. That is, in the formation of images having the same density, the ink temperature immediately before the discharge recovery operation increases as the transport length per sub-scan increases. In other words, the ink temperature immediately before the ejection recovery operation is such that the density of the recorded image is very low and there is no problem even if the ink temperature control is not performed. Get higher. Accordingly, by increasing the threshold value Ts as the transport length per sub-scan increases, it is possible to efficiently prevent an increase in overall recording time due to unnecessary head temperature control.
[0061]
Further, the higher the environmental temperature, the higher the threshold temperature. This is because when the environmental temperature is high, the ink temperature rise during recording becomes large. This is shown in FIG. That is, in the formation of images 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 the increase in recording time can be efficiently prevented, as in the case of the paper feed amount.
[0062]
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 Ts is optimized by the environmental temperature and the transport length per sub-scan. An increase can be prevented more efficiently.
[0063]
As is clear from the description of Embodiments 1 to 3 above, a color recording apparatus that records using the same or different color ink as long as it is an inkjet recording apparatus having a recording head having a plurality of ink ejection openings, Alternatively, the present invention can be similarly applied to a gradation recording apparatus that records at the same color and at different densities, and also a recording apparatus that combines these, and the same effect can be achieved. Furthermore, the present invention provides a recording means including 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 separated and connected between them by a tube for supplying ink, etc. The present invention can be similarly applied to any arrangement of the ink tanks, and the same effect can be obtained.
[0064]
In addition, the present invention brings about an excellent effect in an ink jet recording apparatus that uses a recording unit that discharges ink using thermal energy, among other ink jet recording systems.
[0065]
【The invention's effect】
As described above, according to the present invention, when the print head temperature is controlled to the temperature before the discharge recovery operation after the discharge recovery operation, the discharge recovery is performed for a plurality of print heads as the temperature before the discharge recovery operation. Since an average of temperatures detected before operation is used, one control target temperature can be obtained, thereby simplifying the control.
[0066]
In addition to the above action Since the average of the detected temperatures is the average temperature only for the print head whose detected temperature is higher than the predetermined threshold temperature, even if it is a print head that does not discharge ink at all or is discharged depending on the print data When there is a recording head with a low frequency, it can be considered that the temperature of such a recording head does not rise so much, and after the recovery operation, it is not discharged at all or the discharge frequency remains low. When the average temperature for all the recording heads is obtained uniformly and the head temperature control is performed based on the average temperature, it is possible to prevent the temperature difference before and after the recovery process, and hence the change in density due to the recording head from becoming large.
[0067]
As a result, the head temperature lowered by the recovery process during recording is controlled to a temperature before the recovery process by relatively simple head temperature control, and a remarkable difference occurs in the density and color of the recorded image before and after the round process. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a top view showing an ink jet 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 ink jet recording apparatus shown in FIG.
FIG. 3 is a diagram illustrating how the head temperature changes as recording is performed on a recording sheet.
FIG. 4 is a diagram illustrating 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 illustrating a density change of a recorded image in a case where ink temperature control is not performed after performing an ejection recovery operation during recording 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 illustrating an example of the determined ink temperature of each recording head that can be placed in the head temperature control.
FIG. 8 is a diagram schematically showing recording head drive pulses 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 a suction recovery operation is performed during recording.
FIG. 10 is a diagram illustrating a change in image formation density when head temperature control is performed according to the present exemplary embodiment.
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 illustrating a temperature change when the ink temperature of each recording head before the ejection recovery operation is lower than the temperature control threshold value in the head temperature control of the second embodiment.
14 is a diagram showing a change in density according to a temperature change shown in FIG.
FIG. 15 is a diagram schematically showing the contents of a table in which a threshold temperature is set according to an environmental temperature and a paper feed amount, which is used in head temperature control according to the third embodiment of the present invention.
FIG. 16 is a diagram illustrating a change in ink temperature for each transport length per sub-scanning according to the third embodiment.
FIG. 17 is a diagram illustrating a change in ink temperature for each environmental temperature according to the third embodiment.
[Explanation of symbols]
1 Carriage
2 Main unit (including transfer system unit)
5 Recording head
11 Guide shaft
12 Encoder film
13 belt
30A, 30B, 30C, 30D Recovery mechanism
31 Pre-discharge 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

Claims (18)

In an inkjet recording apparatus that uses a plurality of recording heads to eject ink and performs recording by ejecting ink onto a recording medium.
A recording control means for performing a recording operation using the plurality of recording heads, and performing an ejection recovery operation of the plurality of recording heads during the recording operation;
Temperature detecting means for detecting temperatures of the plurality of recording heads;
A means for controlling the temperature of the recording head after the discharge recovery operation to a temperature before the discharge recovery operation, wherein the temperature before the discharge recovery operation is the temperature before the discharge recovery operation for a plurality of recording heads. An ink jet recording apparatus comprising: a head temperature control unit that uses an average of the temperatures of the recording heads higher than a predetermined threshold temperature among the temperatures detected by the detection unit. 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 apparatus are lower than the threshold temperature. The ink jet recording apparatus according to claim 1 . 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, thereby performing the ejection recovery operation. The inkjet recording apparatus according to claim 2 , wherein a process of controlling to a temperature before is avoided. The predetermined threshold temperature, the ink jet recording apparatus according to any one of claims 1 to 3, wherein vary depending on environmental temperature. The apparatus further comprises scanning means for scanning the recording head in the main scanning direction and paper feeding means for transporting the recording medium in the sub-scanning direction, and the predetermined threshold temperature is determined by the paper feeding means for one paper feeding recording medium. The ink jet recording apparatus according to claim 1 , wherein the ink jet recording apparatus is different depending on a transport amount to be transported. Each of the plurality of recording heads includes an electrothermal converter, and discharges ink by supplying an electric pulse to the electrothermal converter, and the head temperature control means controls the temperature of the recording head. a process of controlling the temperature before the ejection recovery operations, in any one of 5 claims 1, characterized in that carried out by heating the ink by supplying an electrical pulse that does not lead to a discharge on the electrothermal transducer The ink jet recording apparatus described. The ejection recovery operation, the ink jet recording apparatus according to any one of claims 1 to, characterized in that for ejecting ink that does not participate in the recording from the recording head 6. The ejection recovery operation, the ink jet recording apparatus according to any one of claims 1, characterized in that an operation for wiping the surface of at least the discharge port is disposed in the recording head by the blade 6. The ejection recovery operation, the ink jet recording apparatus according to any one of claims 1 to 6, characterized in that to discharge by flowing the ink in said plurality of recording heads. In an inkjet recording method in which recording is performed by discharging ink to a recording medium using a plurality of recording heads that discharge ink.
A recording control unit that performs a recording operation using the plurality of recording heads and performs an ejection recovery operation of the plurality of recording heads during the recording operation; and a temperature detection unit that detects temperatures of the plurality of recording heads; Steps to prepare,
The step of controlling the temperature of the recording head after the ejection recovery operation to a temperature before the ejection recovery operation, wherein the temperature before the ejection recovery operation is the temperature before the ejection recovery operation for a plurality of recording heads. A head temperature control step using an average of the temperatures of the print heads higher than a predetermined threshold temperature among the temperatures detected by the detection means;
An inkjet recording method characterized by comprising: In the head temperature control step, when all of the plurality of recording heads used in the recording apparatus are lower than the threshold temperature, a process of avoiding a process of controlling the temperature before the ejection recovery operation is performed. The inkjet recording method according to claim 10 . In the head temperature control step, when all of the plurality of recording heads used in the recording apparatus are lower than the threshold temperature, the discharge recovery operation is performed by setting the average temperature to a predetermined temperature lower than the threshold temperature. The ink jet recording method according to claim 11 , wherein a process of controlling the temperature before is prevented. The ink jet recording method according to claim 10 , wherein the predetermined threshold temperature varies depending on an environmental temperature. A step of preparing a scanning unit that scans the recording head in the main scanning direction and a paper feeding unit that transports the recording medium in the sub-scanning direction; 14. The ink jet recording method according to claim 10, wherein the ink jet recording method is different depending on a transport amount for transporting the feed recording medium. Each of the plurality of recording heads includes an electrothermal transducer, and discharges ink by supplying an electrical pulse to the electrothermal transducer, and the head temperature control step includes controlling the temperature of the recording head. a process of controlling the temperature before the ejection recovery operations, in any one of claims 10, characterized in that carried out by heating the ink by supplying an electrical pulse that does not lead to a discharge on the electrothermal transducer 14 The inkjet recording method as described. 16. The ink jet recording method according to claim 10 , wherein the discharge recovery operation discharges ink that is not involved in recording from a recording head. 16. The ink jet recording method according to claim 10 , wherein the discharge recovery operation is an operation of wiping at least a surface of the recording head on which the discharge port is provided with a blade. 16. The ink jet recording method according to claim 10 , wherein the discharge recovery operation is to discharge ink by flowing the ink in the plurality of recording heads.

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