Liquid ejection head

A liquid ejection apparatus comprising:

• a liquid ejection head,
• an electric control unit that transmits electrical power and an ejection control signal to the liquid ejection head;
• the liquid ejection head comprising:
• a nozzle including an ejection port for ejecting a liquid, and a pressure chamber in which an energy generating element that generates energy used for discharging the liquid from the ejection port is disposed;
• and
• a heating unit that heats the liquid,
• wherein during an operation period in which a recording on a recording medium is performed, the liquid in the pressure chamber is circulated to and from an outside of the pressure chamber, and
• wherein an average number of preliminary ejections per nozzle of all the nozzles during the operation period is controlled to be equal to or greater than 0 and equal to or less than 20 by means of the electric control unit,
• wherein the operation period is from when the liquid ejection head is in a standby state until when the liquid ejection head again enters the standby state after the recording is performed, in the standby state, the ejection port is covered with a cap,
• wherein the nozzle includes the ejection port part to communicate the ejection port with the pressure chamber, when the upstream-side height of the supply-side flow passage at communication part between the ejection port part and the pressure chamber is indicated as H [μm], the length of the ejection port part in the direction of ejecting a liquid from the ejection port is indicated as P [μm], and the length of the ejection port part in the flow direction of the liquid in the pressure chamber is indicated as W [μm], the height H, the length P and the length W have a relationship satisfying the following Expression (1)
• H−0.34×P−0.66×W>1.5 (1).