| 摘要 |
PROBLEM TO BE SOLVED: To prevent a switching element of a motor drive circuit from being damaged due to the lowering of a power voltage in an internal combustion engine in which a valve timing is varied by using a motor as the drive source. SOLUTION: An ECU 30 outputs the signal of a target motor speed calculated according to the deviation between a target cam stem phase and an actual cam stem phase to an EDU 31 (motor drive circuit). The EDU 31 so controls, by feedback, the output current (motor current) of the EDU 31 that the deviation between the target motor rotational speed and an actual motor rotational speed can be reduced to control, by feedback, the actual cam stem phase to the target cam stem phase. The ECU 30 limits the varied amount of the target motor rotational speed (corrected amount of rotational speed F/B) output to the EDU 31 to limit the output current of the EDU 31. The ECU 30 also cuts off the output current of the EDU 31 by limiting the varied amount of the target motor rotational speed (corrected amount of rotational speed F/B) output to the EDU 31 when the power voltage of the EDU 31 lowers an operation limiting voltage set higher than a minimum operationally guaranteed voltage to limit the output current of the EDU 31. The ECU 30 also cut off the output current of the EDU 31 when the power voltage lowers the minimum operationally guaranteed voltage. COPYRIGHT: (C)2008,JPO&INPIT
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