Image forming apparatus

An image forming apparatus comprising:

• a recording head including,
• at least one nozzle configured to eject droplets of liquid, and
• at least one corresponding piezoelectric element configured to generate pressure that causes the droplets to be ejected from the at least one nozzle;
• a driving-waveform generating unit configured to generate a driving waveform to be applied to the at least one piezoelectric element of the recording head;
• a first switching device between the driving-waveform generating unit and the at least one corresponding piezoelectric element;
• a second switching device between a voltage and the at least one corresponding piezoelectric element;
• and
• a slight-vibration control unit configured to control the at least one corresponding piezoelectric element to generate slight vibrations that vibrate a meniscus of the liquid in the at least one nozzle to an extent at which no droplet is ejected from the at least one nozzle, wherein
• when the at least one nozzle is a non-ejection nozzle from which a droplet is not to be ejected, the slight-vibration control unit is configured to control the at least one corresponding piezoelectric element by,
• changing a voltage state of the at least one corresponding piezoelectric element by placing the second switching device in a conduction state, and
• when a period of time has elapsed after a switch of the second switching device to the conducting state, changing the voltage state of the at least one corresponding piezoelectric element by placing the second switching device in a non-conduction state and placing the first switching device in a conduction state, and
• wherein when the at least one corresponding piezoelectric element generates the slight vibrations in a first drive period and a droplet is to be ejected from the at least one nozzle in a second drive period that is immediately after the first drive period, timing for state transition of the first switching device and the second switching device in the first drive period is shifted depending on a size of the droplet to be ejected from the at least one nozzle in the second drive period.

A method for controlling a recording head that includes at least one nozzle configured to eject droplets of liquid, at least one corresponding piezoelectric element, a driving-waveform generating unit, a first switching device between the driving-waveform generating unit and the at least one corresponding piezoelectric element and a second switching device between a voltage and the at least one corresponding piezoelectric element, the method comprising:

• generating, in one vibration state, pressure that causes the droplets to be ejected from the at least one nozzle, and
• generating, in another vibration state, slight vibrations for the at least one corresponding piezoelectric element to vibrate a meniscus of the liquid of the at least one nozzle to an extent at which no droplet is ejected from the at least one nozzle;
• in the other vibration state, changing a voltage state of the at least one corresponding piezoelectric element to a first voltage state by applying a voltage to the at least one corresponding piezoelectric element, and
• when a period of time has elapsed after a switch to the first voltage state, changing the voltage state of the at least one corresponding piezoelectric element to a second voltage state by switching off the voltage to the at least one corresponding piezoelectric element, and connecting the driving-waveform generating unit to the at least one corresponding piezoelectric element, wherein
• when a droplet is ejected from the at least one nozzle in a first drive period and the at least one corresponding piezoelectric element generates the slight vibrations in a second drive period that is immediately after the first drive period, timing for state transition of the first switching device and the second switching device in the second drive period is shifted depending on a size of the droplet ejected from the at least one nozzle in the first drive period.