Printing apparatus and control method

A printing apparatus comprising:

• a printing element board comprising a nozzle configured to eject printing material;
• a circulation path comprising the printing element board and configured to circulate printing material, supply the printing element board with printing material, and collect printing material not ejected from the printing element board;
• an acquisition unit configured to acquire information on concentration of printing material circulating through the circulation path;
• and
• a discharge control unit configured to execute discharge control of printing material in which printing material is discharged from the circulation path according to the information on concentration and the circulation path is supplied with an amount of printing material corresponding to a discharge amount,
• wherein in a case where the discharge control is executed, the discharge control unit selectively executes one of (1) first discharge control in which a discharge amount of printing material is a first discharge amount and (2) second discharge control in which the discharge amount is a second discharge amount greater than the first discharge amount, wherein the information on concentration comprises (1) an estimated concentration value which is an estimated value of concentration of the printing material and (2) an estimation error which is an error that may occur in the estimated concentration value,
• wherein the discharge control unit executes first control in which the first discharge control is executed in a case where a sum of the estimated concentration value and the estimation error is equal to or greater than a limit value of printing material concentration which causes at least one of occurrence of density unevenness in a printed image, decrease in ejection characteristic of printing material from the nozzle, and decrease in reliability of a printing material circulating function in the circulation path, and
• wherein the discharge control unit executes second control in which the second discharge control is executed in a case where at least one of (1) a first condition that the sum of the estimated concentration value and the estimation error is equal to or greater than the limit value and (2) a second condition that a ratio between the estimated concentration value and the estimation error is equal to or greater than a ratio between the estimated concentration value and the estimation error in the first discharge control in a latest occurrence of the first control is satisfied, and the first discharge control is executed in a case where neither the first condition nor the second condition is satisfied.

A control method of a printing apparatus configured to execute discharge control of printing material concentration in which, according to concentration of printing material circulating through a circulation path comprising a printing element board comprising a nozzle configured to eject printing material, printing material is discharged from the circulation path and an amount of printing material corresponding to a discharge amount is supplied to the circulation path, the control method comprising:

• acquiring information on concentration of printing material circulating through the circulation path;
• and
• selectively executing, according to the information on concentration, one of (1) first discharge control in which a discharge amount of printing material concentration is a first discharge amount and (2) second discharge control in which the discharge amount is a second discharge amount greater than the first discharge amount,
• wherein the information on concentration comprises (1) an estimated concentration value which is an estimated value of concentration of the printing material and (2) an estimation error which is an error that may occur in the estimated concentration value, and
• wherein the estimation error differs according to a print duty.