JPH10157136A - Ink jet recorder and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder in which difference of density on a printed image due to variation of driving conditions is made inconspicuous. SOLUTION: A control section 11 detects the temperature of a recording head 14 through a thermistor 15 and acquires a temperature data through an A/D converter 16 and a temperature detecting section 17. Corresponding driving conditions PA are then determined based on the temperature data thus acquired with reference to a lookup table 18 and employed as temporary driving conditions. A decision is then made whether the driving conditions PA are identical to the driving conditions PB at the time of printing an immediately preceding band. When they are different from each other, a drive circuit 13 is controlled to perform printing while mixing the driving conditions PB for an immediately preceding band with the temporary driving conditions PA. Since the printing can be carried out with the intermediate density of the driving conditions PA, PB, difference of density between the driving conditions PA, PB can be made inconspicuous.

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 which performs recording by causing a heating element provided in a recording head to generate heat to generate bubbles in the ink and ejecting the ink by the pressure at the time of growth. It relates to a recording method.

[0002]

2. Description of the Related Art As one of ink jet recording apparatuses,
2. Description of the Related Art There is a thermal type ink jet recording apparatus that generates bubbles by heating ink and ejects the ink by a pressure at which the bubbles grow to perform recording. In this thermal type ink jet recording apparatus, since the ink is heated by heating the heating element, if printing is performed continuously, heat is accumulated in the recording head and the temperature of the recording head rises. In general, the viscosity of ink changes depending on the temperature, and thus the viscosity of the ink changes due to the temperature rise of the recording head and the change in the environmental temperature, the amount of ejected ink droplets changes, and the print density changes. I will.

Therefore, in the conventional ink jet recording apparatus, the temperature of the recording head is detected by using a temperature detecting element such as a thermistor, and the density is adjusted by changing the driving condition of the heating element based on the detected temperature. . For example, JP-A-3-121852 and JP-A-7-125260
In this publication, the temperature of a recording head is predicted from image information to be printed, and the shape of a pulse to be applied when the heating element is heated is determined from the result. Also, Japanese Patent Application Laid-Open No. 3-28495
In Japanese Patent Application Laid-Open No. 1 (1999) -1995, the temperature of a printhead is detected, and a drive pulse is controlled based on the detected temperature of the printhead.
Further, in Japanese Patent Application Laid-Open No. Hei 5-31906, the temperature of the ink is estimated from the print head temperature and print data detected by the temperature detecting means on the print head, and the driving conditions are controlled based on the estimated ink temperature. .

FIG. 8 is a graph showing an example of the relationship between the recording head temperature and the recording density in a conventional ink jet recording apparatus. In a conventional inkjet recording apparatus,
As shown in FIG. 8, since the driving condition of the heating element changes discretely, the density changes stepwise. For example, the temperature T in the figure, when the temperature of the recording head is upward trend, the temperature of the driving condition P _B in the recording head is too high,
The driving condition is changed to the driving condition P _A with a small amount of heat generation. Conversely, when the temperature of the recording head is decreasing, the temperature of the recording head is too low under the driving condition P _A , so that the driving condition P _B is changed to the driving condition P _B having a large amount of heat generation. Usually, at the same temperature,
Since the amount of ejected ink droplets is larger under the driving condition where the heat generation amount is larger, at the temperature T, the amount of ejected ink droplets changes due to the change of the driving condition, and the printing density changes.

FIG. 9 is an enlarged schematic view showing an example of a printed image when driving conditions are changed in a conventional ink jet recording apparatus. In a serial printer, when the above-described change in the driving conditions occurs in a continuous print image, the density difference becomes conspicuous. For example, in FIG. 9, when performing printing by dividing one page into a plurality of bands, printed by driving the heating element by a large driving condition P _B of the upper half for example calorific, before printing the next band result of detection of the temperature conditions and the like, by driving the heating element with a small driving condition P _a heating value indicates the case of performing the printing. in this way,
The upper and lower two bands shown in FIG. 9 are driven under different driving conditions. In this case, the portion in which printing is performed with a large driving condition P _B of the calorific value of the upper half, because often the amount of ink droplets than the portion in which printing is performed with a small driving condition P _A calorific value of the lower half, the recorded dots Are relatively large in the upper half and smaller in the lower half. Therefore, a density difference appears between the two bands.

If the driving conditions are set for each page, the density difference between the bands disappears, but the density may differ between the beginning and end of one page. Also,
If the driving conditions are controlled finely, the above-described density difference between the bands is reduced, but a large amount of memory is required to store the driving conditions and data for judging the driving conditions. It will be up. In addition, there is a limit to the minimum time width in which the time of the pulse width for driving the heating element can be adjusted, so that there is a problem that it is difficult to adjust the ink ejection amount in a minute amount.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an ink jet recording apparatus which requires a small amount of memory and makes a density difference on a printed image inconspicuous due to a change in driving conditions. The purpose is to do so.

[0008]

According to a first aspect of the present invention, a heating element provided in a recording head generates heat to generate bubbles in ink, and the ink is ejected by the pressure at the time of growth to perform recording. In the recording method of the ink jet recording apparatus for performing the above, at least the temperature of the recording head is measured, and the provisional driving condition which is a condition for driving the heating element determined by the measured temperature and the current driving used in the past recording. And comparing the conditions with each other, and when the conditions are different, the driving of the heating element under the provisional driving condition and the current driving condition is mixed and performed.

According to a second aspect of the present invention, in the recording method of the ink jet recording apparatus according to the first aspect, the heating element is driven by a pre-pulse that does not eject ink and a main pulse that actually ejects ink. The provisional driving condition and the current driving condition are the pulse width of the pre-pulse.

According to a third aspect of the present invention, there is provided an ink jet recording apparatus which performs recording by causing a heating element provided in a recording head to generate heat to generate bubbles in the ink and ejecting the ink by the pressure at the time of growth. Temperature measuring means for measuring the temperature of the recording head, storage means for storing the temperature of the recording head and driving conditions of the heating element in association with each other, and the storage means based on the temperature measured by the temperature measuring means. A corresponding driving condition is obtained as a tentative driving condition, and the tentative driving condition is compared with the current driving condition used in the past recording. If both are different, the heating element based on the tentative driving condition and the current driving condition is obtained. And control means for controlling the driving of the heating element so that the driving of the heating elements is performed in a mixed manner.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to the third aspect, the control means includes:
The heating element is driven by a pre-pulse that does not eject ink and a main pulse that actually ejects ink, and the driving condition stored in the storage unit is at least a pulse width of the pre-pulse. is there.

[0012]

FIG. 1 is a block diagram showing an embodiment of an ink jet recording apparatus according to the present invention.
In the figure, 1 is an ink jet recording apparatus, 2 is a host computer, 11 is a control unit, 12 is a print data developing unit, 13
Is a drive circuit, 14 is a recording head, 15 is a thermistor, 1
Reference numeral 6 denotes an A / D converter, reference numeral 17 denotes a temperature detector, and reference numeral 18 denotes a lookup table.

A print command sent from the host computer 2 is developed into print data in a print data developing unit 12. The print data developing unit 12 sends print data to the recording head 14 in the order of printing according to an instruction from the control unit 11.

The drive circuit 13 sends a drive pulse to the recording head 1.
4 to generate heat in a heating element (not shown) in accordance with the print data sent from the print data developing unit 12 and eject ink to perform printing. FIG. 2 is an explanatory diagram of an example of the drive pulse. Here, as an example, an example is shown in which one driving of the heating element is performed by two driving pulses. In this example, a pre-pulse P1 for heating the ink without ejecting the ink and a main pulse P3 for actually ejecting the ink are applied to the heating element to eject the ink. Of course, the heating element may be driven by a single pulse.

The recording head 14 is provided with a thermistor 15 for detecting the temperature of the recording head 14.
The number of thermistors 15 is not limited to one, and a plurality may be provided.
Further, a thermistor for detecting the environmental temperature may be provided. The output of the thermistor 15 is converted to digital data by an A / D converter 16 and
Has been entered. In the temperature detector 17, the thermistor 1
5 is converted into a temperature and input to the control unit 11.

On the other hand, the look-up table 18 stores data in which the temperature of the recording head 14 is associated with the driving conditions of the recording head. FIG. 3 is an explanatory diagram of an example of the contents of the lookup table. In this example, an example is shown in which the pulse widths of the pre-pulse P1 and the main pulse P3 shown in FIG. 2 and the interval P2 between the pre-pulse and the main pulse are stored in correspondence with the temperature of the recording head. In this example, the width of the pre-pulse P1 is shortened when the temperature of the recording head is high, and the width of the pre-pulse P1 is increased when the temperature of the recording head is low. Also, P1 + P2 + P3
In addition, the pulse width of the main pulse P3 is fixed, and the interval P2 is adjusted according to the pulse width of the pre-pulse P1. Of course, look-up table 1 shown in FIG.
The content of 8 is an example, and the numerical value and the like are set according to the recording head. Further, in this example, the main pulse P3 is fixed and the pre-pulse P1 is set according to the temperature of the recording head. However, the present invention is not limited to this, and the main pulse P3 can be made variable or both can be made variable. When driving with a single pulse, the pulse width of the driving pulse may be stored according to the temperature.

In the example shown in FIG. 3, the pulse width of the pre-pulse P1 is changed in units of ８ μsec.
Depending on the drive circuit 13, there is a case where the pulse width can be changed only by this degree. Even in such a case, it is possible to reduce the density unevenness when the driving conditions are changed as described later. Further, if the change can be made in units smaller than 1/8 μsec, it is conceivable to increase the entries of the look-up table 18 to reduce the density unevenness when the driving condition is changed. It is large and requires a lot of memory capacity. However, by performing drive control as described later, the density unevenness at the time of changing the drive condition can be reduced even with only a small number of entries in the look-up table 18.

The control unit 11 retrieves the driving conditions corresponding to the temperature of the recording head 14 detected by the temperature detecting unit 17 from the look-up table 18 and instructs the driving circuit 13 to perform driving under the driving conditions. Perform At this time, when the drive condition is changed, the control unit 11 controls the drive circuit 13 so that both the drive condition up to that time and the drive condition to be changed are mixed and printing is performed. By such control, a change in print density due to a change in driving conditions can be reduced.

FIG. 4 is a flowchart showing an example of the processing of the control unit in the embodiment of the ink jet recording apparatus of the present invention. Here, a case of a serial type inkjet recording apparatus that prints an image of one page for each of a plurality of band-shaped areas will be described as an example.

First, in S21, the temperature of the recording head 14 is detected by the thermistor 15 or the like, and the A / D converter 1
6. Acquire temperature data via the temperature detection unit 17. S
At 22, the lookup table 18 is referred to based on the temperature data acquired at S21, and the corresponding driving condition P
_{Get A.} The provisional driving conditions the driving condition P _A obtained at this point.

[0021] In S23, when the driving condition for printing the immediately preceding band was one obtained by mixing the two driving conditions proceeds to S25, it performs printing by provisional driving condition P _A.

[0022] When a not driving conditions printing bands are mixed just before, in addition S24, the provisional driving condition P _A to determine whether the same or not as the driving condition P _B when printing the immediately preceding band . Since it is sufficient to print as it is driving condition if the same, in S25, the continue printing by driving condition P _A. If the driving condition P _B of the immediately preceding band is different from the provisional driving condition P _A , the two bands may be printed at different densities in an image extending over the two bands. In such a case, S
To print the next band by mixing driving condition P _B provisionally driving condition P _A of the immediately preceding band at 26.

In S26, the driving condition P of the immediately preceding band
After performing the printing by mixing provisional driving condition P _A and _B, and when printing the next band, the process proceeds to step S25 by determining S23, will be printed provisional driving condition P _A as the driving condition . Subsequent bands are printed under the same driving conditions until the driving conditions change due to the temperature change of the recording head.

[0024] Note that when printed by mixing two drive condition in S26, by storing the driving condition P _A as before driving condition P _B, it is also possible to omit the determination process in S23.

As a specific example, the heating element is driven by the pre-pulse P1 and the main pulse P3 as shown in FIG. 2, and the contents as shown in FIG.
Consider the case where it is stored in When the temperature of the recording head when printing a certain band is 33 ° C., the pulse width of the pre-pulse P1 = 0.500 μsec and the interval P2 width = from the contents of the look-up table 18 shown in FIG.
5. 250 μsec, pulse width of main pulse P3 =
The heating element is driven in 2.000 μsec. The driving condition is a driving condition P _B.

When the temperature of the recording head is detected when printing the next band, it is assumed that the temperature has risen to 35 ° C., for example.
The driving conditions in this case are as follows from the contents of the look-up table 18 shown in FIG.
75 μsec, interval P2 width = 5.375 μsec
c, pulse width of main pulse P3 = 2.000 μsec
Are obtained as driving conditions. The driving conditions and the provisional driving conditions P _A. In this case, since the provisionally driving condition P _A driving condition P _B is not the same, it will be printed by mixing the provisional driving condition P _A and the driving condition P _B.

When printing the next band,
Since it is after printing by mixing two drive conditions, thereby performing printing by the latter drive condition P _A. In this way, when the driving conditions are changed, by mixing and printing the driving conditions before and after the change, the density change due to the change in the driving condition can be reduced and the density change can be made inconspicuous.

FIGS. 5 to 7 are explanatory diagrams of an example of a print pattern in the case of printing by mixing two driving conditions in one embodiment of the ink jet recording apparatus of the present invention. The bandwidth printed by the recording head in one scan is 8 dots here for the sake of simplicity, but is actually larger. The recording head prints eight dots per line arranged in the band width direction at one print timing. While moving the recording head in the left-right direction in the figure, 8 dots in each row are printed at each printing timing. Here, it is shown that each dot is printed independently, but the printed dot may actually be connected to an adjacent dot.

The examples shown in FIGS. 5 to 7 show the case where the temperature of the recording head is rising, and show three bands including the band where the driving condition changes. Bands on among the three bands is driven by the relative generates much heat driving condition P _B, because of the large amount of ink to be ejected, dot diameter to be printed increases, the printing density becomes high I have.

When the temperature of the recording head is detected when printing the middle band of the three bands, the temperature of the recording head has risen. There is a change in P _a. After the transition to conventional manner as drive condition P _A, as shown in FIG. 9, in successive images would appear uneven density. Therefore, in the present invention, the driving condition P _B and the driving condition P _A
Are mixed and printed.

As a method of printing by mixing the driving conditions P _B and P _A , for example, as shown in FIG. 5, dots printed at one printing timing are printed under the same driving conditions, There is a method of printing under different driving conditions at printing timing. By performing such control, a print pattern in which high-density dots and low-density dots alternately appear in the left-right direction is printed, as in the band shown in the middle part of FIG.

As shown in FIG. 6, there is also a method of printing under different driving conditions between dots printed at one printing timing regardless of each printing timing. By such control, a print pattern in which high-density lines and low-density lines appear alternately is printed as in the band shown in the middle part of FIG.

Further, as shown in FIG. 7, both the pattern shown in FIG. 5 and the pattern shown in FIG. 6 are printed under different driving conditions for each dot printed at one printing timing. There is also a method of printing by changing the driving conditions for each timing. By performing such control, a print pattern in which high-density dots and low-density dots are printed alternately, as in the band shown in the middle part of FIG.

[0034] After performing printing of one band by mixing with the driving condition P _A such driving condition P _B, the lower band of the three bands, the printing with the modified drive condition P _A Do. By performing such printing, as shown in each of FIGS. 3, the printing density of the middle band, apparently, the printing density when printing is performed with driving conditions P _B, in which printing is performed with driving conditions P _A Since the print density is intermediate between the print densities in the case, the change in the density when the driving condition is changed becomes gentle, and the influence on the image quality can be reduced.

In the above-described specific example, the case where the driving method using the pre-pulse P1 and the main pulse P2 as shown in FIG. 2 has been described. When the pulse width before and after the change is changed, the pulse width before and after the change can be mixed and driven, thereby printing can be performed in a print pattern as shown in FIGS. 5 to 7, for example. It can be less noticeable.

In the above description, a case where a continuous image is formed by a plurality of bands has been described.
For example, in the case where images are not continuous in two adjacent bands, or in two bands sandwiching a portion where only a sheet is fed due to the presence of a white line, even if the driving method is different and the image density is different, it is not so noticeable. . Therefore, in such a case, printing may be performed simply by changing the driving method without performing printing in which the two driving methods described above are mixed. In such a control, in the flowchart shown in FIG. 4, after determining the provisional driving condition in S22, it is determined whether or not the images are continuous. If the images are not continuous, the driving condition P in S25 is determined. _What is necessary is just to comprise so that it may shift to the step of printing by _A.

[0037]

As is apparent from the above description, according to the present invention, when the provisional driving conditions and the past driving conditions are different, the two driving conditions are mixed and printed, whereby the two driving conditions are used. Printing can be performed at a density intermediate between the conditions. Therefore, it is possible to reduce the density difference between adjacent print areas caused by discrete changes in driving conditions, and to make the density inconspicuous. This makes it possible to obtain a printed image of good image quality with no noticeable density unevenness.

In addition, since the density difference between adjacent printing areas can be reduced even under such discrete driving conditions, the driving pulse control in the driving circuit does not have to be precise, and the driving conditions and the like can be reduced. According to the present invention, there are various effects, for example, the capacity of the memory storing

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an example of a driving pulse.

FIG. 3 is an explanatory diagram illustrating an example of the content of a look-up table in an embodiment of the inkjet recording apparatus of the present invention.

FIG. 4 is a flowchart illustrating an example of a process performed by a control unit according to the embodiment of the inkjet recording apparatus of the present invention.

FIG. 5 is an explanatory diagram of an example of a print pattern in a case where two driving conditions are mixed and printing is performed in an embodiment of the inkjet recording apparatus of the present invention.

FIG. 6 is an explanatory diagram of another example of a print pattern in a case where printing is performed by mixing two driving conditions in an embodiment of the inkjet recording apparatus of the present invention.

FIG. 7 is an explanatory diagram of still another example of a print pattern in a case where printing is performed by mixing two driving conditions in the embodiment of the inkjet recording apparatus of the present invention.

FIG. 8 is a graph showing an example of a relationship between a printhead temperature and a print density in a conventional inkjet printing apparatus.

FIG. 9 is an enlarged schematic diagram illustrating an example of a printed image when a driving condition is changed in a conventional inkjet recording apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ink jet recording apparatus, 2 ... Host computer, 11 ... Control part, 12 ... Print data development part, 13 ... Drive circuit, 14 ... Recording head, 15 ... Thermistor, 16 ...
A / D converter, 17: temperature detector, 18: lookup table.

Claims (4)

[Claims] In a recording method of an ink jet recording apparatus for performing recording by causing a heating element provided in a recording head to generate heat to generate bubbles in ink and ejecting the ink by a pressure at the time of growth, at least the recording head Is measured, and a comparison is made between the provisional driving conditions, which are the conditions for driving the heating element determined by the measured temperature, and the current driving conditions used in the past recording. A recording method for an ink jet recording apparatus, wherein the driving of the heating element under the provisional driving condition and the current driving condition are mixed and performed. 2. The heating element is driven by a pre-pulse that does not eject ink and a main pulse that actually ejects ink, and the provisional driving condition and the current driving condition are pulse widths of the pre-pulse. The recording method for an ink jet recording apparatus according to claim 1, wherein: 3. An ink jet recording apparatus which performs recording by causing a heating element provided in a recording head to generate heat to generate bubbles in the ink and ejecting the ink by a pressure at the time of the growth to reduce the temperature of the recording head. Temperature measuring means for measuring, storage means for storing the temperature of the recording head and driving conditions of the heating element in association with each other, and obtaining the corresponding driving conditions from the storage means based on the temperature measured by the temperature measuring means. As a tentative driving condition, the tentative driving condition is compared with the current driving condition used in the past recording, and when both are different, the driving of the heating element under the tentative driving condition and the current driving condition is mixed and performed. An ink jet recording apparatus comprising a control means for controlling the driving of the heating element as described above. 4. The control unit drives a heating element by a pre-pulse that does not eject ink and a main pulse that actually ejects ink, and the driving condition stored in the storage unit is at least a pulse of the pre-pulse. The ink jet recording apparatus according to claim 3, wherein the width is a width.