Inkjet head cleaning device and cleaning method, and inkjet printing device

An inkjet head cleaning device for an inkjet head having a nozzle surface on which nozzles configured to eject ink are arranged, comprising:

• a wiping member traveling unit allowing a wiping member of elongated shape having absorbency to travel along a conveying path in a longitudinal direction;
• a cleaning liquid supply unit configured to supply a cleaning liquid to the wiping member;
• a pressing unit configured to press and bring the wiping member supplied with the cleaning liquid to and into contact with the nozzle surface;
• a sliding unit configured to relatively slide the wiping member pressed on to the nozzle surface by the pressing unit and the nozzle surface;
• a storage configured to store a relationship represented by a surface tension and viscosity of a mixed liquid of the ink and the cleaning liquid, wherein the relationship represents a border between presence and absence of residue after cleaning the nozzle surface, the border depending on liquid repellent performance of the nozzle surface;
• a unit configured to calculate a mixing ratio of the mixed liquid by which a condition of the absence of the residue is satisfied, from the relationship of the border;
• and
• a controller configured to control at least one of Vweb, L, Vbar and a cleaning frequency of the inkjet head so that R satisfies the calculated mixing ratio, wherein M mg/mm2 is an amount of the ink adhered to the nozzle surface, Vweb mm/s is a traveling speed of the wiping member by the wiping member traveling unit, L mg/mm2 is an amount of the cleaning liquid supplied to the wiping member by the cleaning liquid supply unit, Vbar mm/s is a relative movement speed between the wiping member and the nozzle surface which are relatively slid by the sliding unit, R is a mixing ratio of the mixed liquid of the cleaning liquid and the ink at a contacting portion between the nozzle surface and the wiping member upon cleaning the nozzle surface, and R is expressed by R=M*Vbar/(L*Vweb);
• wherein the relationship represented by the surface tension and viscosity of the mixed liquid is a relationship calculated by experimentally finding the presence or absence of the residue on the nozzle surface upon cleaning the nozzle surface regarding a plurality of mixed liquids different in the surface tension and the viscosity;
• and
• the relationship representing the border between the presence and absence of the residue is a border line between a presence and absence of a residue calculated from a graph plotting a result obtained from the presence or absence of the residue regarding the plurality of mixed liquids with an abscissa axis of surface tensions of various mixed liquids and an ordinate axis of viscosities of the mixed liquid.