Control device and control method for reducing agent injection device, and reducing agent injection device

A microcomputer control device for a reducing agent injection device, the microcomputer control device configured to cause the reducing agent injection device to fill with a reducing agent at a start-up of an internal combustion engine and to control injection of the reducing agent into an exhaust passage of the internal combustion engine by an injector, the microcomputer control device further configured to:

• perform energization control in which, after an exhaust temperature of the internal combustion engine becomes equal to or higher than a specified threshold value, a temperature of the injector is increased by energizing a coil of the injector for a specified time and melting of crystals of the reducing agent precipitated in the injector is promoted;
• calculate an estimated defrosting time required to defrost the frozen reducing agent at the start-up of the internal combustion engine;
• and
• in the case where the estimated defrosting time is not zero, start energizing the coil of the injector before a lapse of the estimated defrosting time after the exhaust temperature of the internal combustion engine becomes equal to or higher than the specified threshold value.