Patent ID: 7658458

Claim:
An inkjet recording apparatus comprising: a passage unit comprising a common ink chamber and an individual ink passage leading, from an outlet of the common ink chamber via a pressure chamber to an ink ejection port; an actuator that can selectively take a first state in which the volume of the pressure chamber is V 1 and a second state in which the volume of the pressure chamber is V 2 larger than V 1 ; and a controller that controls the actuator to change from the first state into the second state and then change back into the first state to eject ink from the ejection port, the individual ink passage configured to satisfy both of the following conditions: (a) a curved line representing a change in the ejection speed of ink to be ejected from the ejection port, relative to a change in the time period To from a time point at which the actuator starts to change from the first state into the second state, to a time point at which the actuator starts to change from the second state into the first state, when the actuator changes from the first state into the second state and then changes back into the first state to eject ink from the ejection port, has a general shape being convex in the direction of the ejection speed increasing; and (b) the ink ejection speed attains a first maximal value on the curved line in a region in which To is larger than ½ times the period Tc of proper oscillation of ink filling up the individual ink passage and the ink ejection speed attains a second maximal value in a region in which To is less than ½ times the period Tc, and the ink ejection speed attains a minimal value in a region on the curved line between the first maximal value and the second maximal value, wherein the controller controls the actuator such that the value of To/Tc falls within a range from 0.51 to 0.54, and the minimal value on the curved line is in a region in which the value of To/Tc falls within a range from 0.51 to 0.54.