Liquid ejection apparatus and determination method capable of determining whether or not liquid filling of pressure chamber has been completed

A liquid ejection apparatus comprising:

• a nozzle configured to eject a liquid;
• a pressure chamber communicating with the nozzle and configured to contain the liquid;
• a piezoelectric element configured to change a pressure in the pressure chamber in response to an input of a drive signal;
• an output processing portion configured to cause the piezoelectric element to output a first electric signal corresponding to vibration generated in the pressure chamber in response to the input of the drive signal to the piezoelectric element;
• a determination processing portion configured to determine whether or not the pressure chamber is in a filled state in which the pressure chamber is filled with the liquid, based on a frequency of the first electric signal output by the output processing portion;
• a band-pass filter configured to output a second electric signal obtained by removing a frequency component not included in a predetermined specific frequency band from the first electric signal in response to an input of the first electric signal;
• and
• a comparator configured to output a pulse signal when the second electric signal exceeds a predetermined threshold value, wherein
• the predetermined specific frequency band is a frequency band including a frequency of the first electric signal when the pressure chamber is in the filled state and not including a frequency of the first electric signal when the pressure chamber is not in the filled state, and
• the comparator outputs the pulse signal to the determination processing portion when the second electric signal changes.