Method and apparatus for driving an ink jet recording head

An apparatus for generating a driving voltage for driving at least one piezoelectric unit of an ink jet recording head which, when driven, changes the volumetric capacity of an ink chamber of the recording head to jet out ink droplets through a nozzle hole in the recording head, said apparatus comprising:

• a clock which generates a clock signal having a variable frequency;
• a counter which counts the clock signal;
• a controller which outputs an adding signal, a counting stop signal, and a deducting signal in repetition at prescribed time intervals to the counter;
• a digital-analog (D/A) converter for converting the digital output from the counter into an analog voltage;
• and
• an amplifier which amplifies the analog voltage to provide the driving voltage, a rise time and a fall time of the driving voltage being constant regardless of the frequency of the clock signal.

A method for generating a driving voltage for driving at least one piezoelectric unit of an ink jet recording head which, when driven, changes the volumetric capacity of an ink chamber of the recording head to jet out ink droplets through a nozzle hole in the recording head, said method comprising the steps of:

• providing a variable voltage which varies in accordance with a correcting voltage signal;
• generating a first constant current in proportion to the variable voltage;
• charging a capacitor by the first constant current to a voltage approximately equal to the variable voltage within a first constant period of time whose length is unaffected by a variance in a value of the correcting voltage signal;
• generating a second constant current in proportion to the variable voltage to discharge the capacitor in accordance therewith within a second constant period of time whose length is unaffected by the variance in the value of the correcting voltage signal;
• and
• amplifying the voltage of the capacitor to provide said driving voltage, said driving voltage having a constant rise time which corresponds to said first constant period of time and a constant fall time which corresponds to said second constant period of time, said constant rise time and said constant fall time being unaffected by the variance in the value of the correcting voltage signal.

A method for generating a driving voltage for driving at least one piezoelectric unit of an ink jet recording head which, when driven, changes the volumetric capacity of an ink chamber of the recording head to jet out ink droplets through a nozzle hole in the recording head, said method comprising the steps of:

• generating a digital clock signal having a variable frequency;
• counting the clock signal;
• outputting an adding signal, a counting stop signal, and a deducting signal in repetition at prescribed time intervals to the counter;
• converting the digital clock signal into an analog signal;
• and
• amplifying the analog signal to provide the driving voltage, a rise time and a fall time of the driving voltage being constant regardless of the frequency of the clock signal.