| 摘要 |
PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus causing no damage on brake of a rotational driving mechanism of a rotary frame even if a power failure accident happens during rotation of the rotary frame for mounting an X-ray tube and an X-ray detector. SOLUTION: A V-belt 6 is extended between a large diameter pulley 2 integrally rotating with a rotary frame 1 for oppositely installing an X-ray tube 20 and an X-ray detector 21 and a small diameter pulley 5 fixed to a rotary shaft of a servomotor 4. The idler 11 is disposed at such a position that a contact angleθof the small diameter pulley 5 in relation to the V-belt 6 absorbs, by the slide caused between the small diameter pulley 5 and the V-belt 6, a large rotational energy due to an inertial angular moment caused by an inertial rotation of the rotary frame 1, even if the energy is transmitted to the small diameter pulley 5 through the V-belt 6, in a state that the rotational driving force of the small pulley 5 rotationally driven by the servomotor 4 during a normal rotation is effectively, surely transmitted to the large pulley 2 integrated with the rotary frame 1 through the V-belt 6 and a braking force 11 applied to the servomotor 4 during power failure, thereby preventing the breakage of the brake 3 for stopping the rotation of the servomotor 4.
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