Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-12-12
2001-08-21
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06276776
ABSTRACT:
This application is based on Patent Application Nos. 08-336,506 filed Dec. 17, 1996 in Japan, the content of which is incorporated fereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet printer in which a plurality of recording heads are temperature controlled at an optimum recording temperature to obtain a good image quality in a low-temperature environment, and to a temperature control method of the plurality of recording heads.
2. Description of the Related Art
Heretofore, a recording head has a sub-heater, a driving signal applied to the sub-heater is pulse width modulated (PWM) in accordance with a detected present temperature of the recording head to increase the recording head temperature to an optimum temperature for printing.
For example, when making recording using four recording heads in a low-temperature environment, sub-heaters of all the recording heads are necessary to be applied with voltages by the PWM control.
For example, when a sub-heater of each recording head is applied with a voltage at a 25% duty with respect to the driving period, since the heating power supply voltage VH is applied simultaneously to all the recording heads (only area A of FIG.
8
), the heating power supply voltage VH for increasing the temperature of the recording heads in area A is dropped, so that the temperature does not reach the target or desired temperature resulting in a degraded recording or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink-jet printer (print apparatus) which can solve the above prior art problems and prevent occurrence of degraded image quality due to temperatures of a plurality of recording heads in a low-temperature environment.
Another object of the present invention is to provide a temperature control method of recording head which can solve the above prior art problems and prevent degradation of image quality due to temperatures of a plurality of recording heads in a low-temperature environment.
In a first aspect of the present invention, there is provided an ink-jet printer including:
a plurality of recording heads:
heating means for respectively heating the plurality of recording heads according to a repetition of a predetermined driving period; and
temperature detection means for detecting respective temperatures of the plurality of recording heads; the ink-jet printer comprising:
pulse width control means for driving the heating means in a dispersed manner in a divided driving period determined by dividing the predetermined time period in accordance with the number of the recording heads;
pulse width ratio change means for ratio changing pulse widths of pulses to be applied to the recording heads in accordance with results detected by the temperature detection means in the divided driving period.
Here, the pulse with ratio change means may make ratio change in such a way that the pulse widths are equal to each other.
In a second aspect of the present invention, there is provided an ink-jet printer including:
n (≧2) units of recording heads:
1st to n'th heating means for respectively heating the n units of recording heads;
1st to n'th temperature detection means for detecting respective temperatures of the n units of recording heads; and
1st to n'th pulse width control means for making pulse width control over the 1st to n'th heating means respectively at predetermined periods in accordance with temperatures detected respectively by the 1st to n'th temperature detection means;
the ink-jet printer comprising:
judgment means for judging which recording head is to be heating controlled in accordance with temperatures detected by the 1st to n'th temperature detection means;
unit number counting means for counting the number of units of recording heads to be heating controlled in accordance with a judgment result of the judgment means;
maximum pulse width determination means for determining a maximum pulse width of pulse train generated by pulse width control means corresponding to the recording head to be heating controlled in accordance with the number of recording heads counted by the unit number counting means;
pulse width ratio change means for respectively ratio changing the pulse width of a pulse train generated by pulse width control means corresponding to the recording head to be heating controlled in accordance with the maximum pulse width determined by the maximum pulse width determination means; and
timing shift means for successively shifting timings at which the pulse trains having a pulse width ratio changed by the pulse width ratio change means are supplied respectively to the heating means corresponding to the recording head to be controlled by the maximum pulse width.
Here, the maximum pulse width may be a pulse width obtained by equally dividing the predetermined period by the number of units of recording heads counted by the unit number counting means.
In a third aspect of the present invention, there is provided an ink-jet printer comprising:
n (≧2) units of recording heads:
1st to n'th heating means for respectively heating the n units of recording heads;
1st to n'th temperature detection means for detecting respective temperatures of the n units of recording heads; and
1st to n'th pulse width control means for making pulse width control over the 1st to n'th heating means respectively at predetermined periods in accordance with temperatures detected respectively by the 1st to n'th temperature detection means;
the ink-jet printer comprising:
judgment means for judging which recording head is to be heat controlled in accordance with temperatures detected by the 1st to n'th temperature detection means;
unit number counting means for counting the number of units of recording heads to be heating controlled in accordance with a judgment result of the judgment means;
maximum duty ratio determination means for determining a maximum duty ratio of pulse train generated by pulse width control means corresponding to the recording head to be heating controlled in accordance with the number of recording heads counted by the unit number counting means;
duty ratio change means for changing a maximum duty ratio of a pulse train generated by pulse width control means corresponding to the recording head to be heating controlled in accordance with the maximum duty ratio determined by the maximum duty ratio determination means; and
timing shift means for successively shifting timings at which the pulse trains having a duty ratio changed by the duty ratio change means are supplied respectively to the heating means corresponding to the recording head to be heating controlled by a time in accordance with a maximum duty ratio determined by the maximum duty ratio determination means;
The maximum duty ratio may be obtained by equally dividing the predetermined period by the number of recording heads counted by the unit number counting means and by dividing the resulting time by the predetermined period.
In the second and third aspects of the present invention, the determination means may determine a recording head having a temperature detected by the 1st to n'th temperature detection means being lower than a predetermined temperature as a recording head to be heating controlled.
The determination means may judge a recording head to be temperature controlled when recording is started.
The predetermined temperature may be an optimum recording temperature.
The ink-jet printer may further comprise recording start control means for immediately starting recording when the number of units of recording heads to be heating controlled is zero as a result of counting by the unit number counting means, and starting recording when the temperature control of recording head to be heating controlled is completed when the number is 1 or more.
In a fourth aspect of the present invention, there is provided a temperature control method for recording heads comprising the steps of:
detecting respective tem
Kuronuma Akira
Murata Takayuki
Omo Shinichi
Umezawa Masahiko
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stewart Jr. Charles W.
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