Printhead temperature controller that uses nonprinting pulses

A method for real-time, closed-loop control of a printhead temperature, comprising the steps of:

• a. sensing the printhead temperature;
• b. producing a real-time printhead temperature signal;
• c. comparing the printhead temperature signal to a reference temperature signal;
• d. generating a real-time error output signal that is a function of a difference between the reference temperature signal and the printhead temperature signal;
• e. generating a real-time, closed-loop nonprinting pulse having a timing and having an energy;
• and
• f. using the error output signal to control the timing of the closed-loop nonprinted pulse and the energy transferred by the closed-loop nonprinting pulse to the printhead to achieve real-time, closed-loop control of the printhead temperature.

A method for calculating energy carried by a drop ejected from a thermal ink jet printhead, comprising the steps of:

• a. driving the printhead to thermal equilibrium by driving a firing resistor each printing interval with one printing pulse that has a printing pulse amount of energy;
• b. measuring the printing pulse amount of energy;
• c. measuring a printhead thermal equilibrium temperature after the printhead has reached thermal equilibrium;
• d. driving the firing resistor with one or more nonprinting pulses each printing interval that have a nonprinting pulse amount of energy each printing interval, instead of driving the firing resistor with one printing pulse;
• e. adjusting the nonprinting pulse amount of energy until the printhead temperature equals the printhead thermal equilibrium temperature;
• f. measuring the nonprinting pulse amount of energy;
• and
• g. calculating the energy carried by the drop by subtracting the nonprinting pulse amount of energy from the printing pulse amount of energy.

An apparatus for real-time, open-loop control of a temperature of a thermal ink jet printhead, comprising:

• a. a data interpreter that interprets a plurality of print data to determine whether a print command exists;
• b. a means for generating, in response to a print command, a printing pulse that drives a firing resistor with a firing engine, having an ejecting component and a heating component;
• c. a means for ejecting a drop having the ejecting component of said firing engine and for heating the printhead with the heating component of said firing energy when the firing resistor is driven with the printing pulse;
• and
• d. a means for generating, in response to an absence of the print command, one or more open-loop nonprinting pulses that heat the printhead with the heating component of said firing energy.

A method for real-time open-loop control of a temperature of a thermal ink jet printhead, comprising the steps of:

• a. interpreting a plurality of print data to determine whether a print command exists;
• b. generating, in response to the print command, a printing pulse that drives a firing resistor with a firing energy having an ejecting component and a heating component;
• c. ejecting a drop having the ejecting component of said firing energy when the firing resistor is driven with a printing pulse;
• d. heating the printhead with the heating component of said firing energy when the firing resistor is driven with the printing pulse;
• e. generating, in response to an absence of the print command, one or more nonprinting pulses that have a total energy of the heating component of said firing energy for heating the printhead.

An apparatus for real-time control of a temperature of a thermal ink jet printhead, comprising:

• an open-loop system having:
• a. a data interpreter that interprets a plurality of print data to determine whether a print command exists;
• b. a means for generating, in response to a print command, a printing pulse that drives a firing resistor with a firing energy having an ejecting component and a heating component;
• c. a means for ejecting a drop having the ejecting component of said firing energy and for heating the printhead with the heating component of said firing energy when the firing resistor is driven with the printing pulse;
• d. a means for generating, in response to an absence of the print command, one or more open-loop nonprinting pulses that heat the printhead with the heating component of said firing energy;
• and a closed-loop system, having:
• e. a temperature sensor that:
• i. sense the printhead temperature;
• and
• ii. produces a real-time printhead temperature signal;
• f. an error detection amplifier, that:
• i. has an input connected to a reference temperature signal;
• ii. has an input connected to the printhead temperature signal;
• and
• iii. generates a real-time error output signal that is a function of a difference between the reference temperature signal and the printhead temperature signal;
• g. a means for generating a number of closed-loop nonprinting pulses having a width, a voltage, an energy, and a timing;
• and
• h. a means for using the error output signal to control the timing of the number of closed-loop nonprinting pulses and the energy delivered by the number of closed-loop nonprinting pulses to the printhead to achieve real-time, closed-loop control of the printhead temperature.