| 摘要 |
A printing cam is rotated forward from a print starting position by a motor in a printing operation. Then, a print hammer is driven in association with a cam follower driven by the printing cam, so that a printing operation is executed. An encoder disk is disposed so as to rotate integrally with the printing cam. A plurality of slits are disposed in an equidistantly spaced relationship in an encoder disk. A phase setting portion is provided in the encoder disk as a reference position for providing a rotational position of the encoder disk. The phase setting portion is an interval between two specific slits, the interval being formed by enlarging the interval between two slits. While the encoder disk rotates forward, a slit counter executes an additional operation every time a photosensor detects a slit. While the encoder disk rotates reversely, a slit counter executes an subtractional operation every time the photosensor detects a slit. After the printing operation is ended, the motor rotates reversely. Thus, the printing hammer returns to the print starting position. Meanwhile, until a count value N of the slit counter reaches a count value NS corresponding to the phase setting portion plus 10, the motor is controlled at the speed which is determined by setting a slit interval time to 0.8 mu sec. When the count value N reaches the count value (NS+10), the motor is controlled at a predetermined duty ratio. When the slit interval time T reaches at least 2.4 mu sec. in the passage of the phase setting portion into the photosensor, the count value N is set to be a count value (NS-1).
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