| 摘要 |
PURPOSE:To reduce the number of sensors, contrive a reduction in cost and stopping printing immediately on detecting the stoppage of a recording sheet, by detecting a sheet breakage of the recording sheet based on a sheet-feeding signal and a detection output concerning a continuous mark on the recording sheet. CONSTITUTION:A period of time during which a TOF sensor 205 is detecting a TOF mark indicating the top of a page is L1, and a period of time L2 during which the TOF mark is not detected is the period of time from one TOF mark to the next TOF mark. Assuming that the numbers of pulses of a sheet-feeding signal during the periods of time are constant and are respectively N1 and N2, when the TOF mark is detected by the TOF sensor 205 even after feeding the paper by an amount corresponding to at least N1+alpha pulses, it can be judged that a sheet jam or breakage is generated. Similarly, when the TOF mark is not detected by th sensor 205 even after feeding the sheet by an amount corresponding to at least N2+alpha pulses in the period L2, it can be judged that a sheet jam or breakage is generated. Accordingly, the TOF sensor 205 can be used also as a sheet jamming sensor on the same side.
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