When the time period is night, processing advances to step S13 to set the initialization speed of a line feed motor to the first speed (v1), and to step S15 to execute initialization operation of the line feed motor at the first speed (v1). When the time period is morning or daytime, the processing advances to step S12 to detect a cover open/closed state. When the cover is open, the processing advances to step S13 to set the initialization speed of the line feed motor to the first speed (v1). When the cover is closed, the processing advances to step S14 to set the initialization speed of the line feed motor to the second speed (v2) which is higher than the first speed (v1). The processing advances to step S15 to execute initialization operation of the line feed motor at the second speed (v2).