| 摘要 |
A rotational angle sensor for an EGR valve memorizes a correlated characteristic between hall voltage and output voltage. Hall voltage of the rotational angle sensor at a reference angle is matched to a boundary value for the hall voltage on a valve closing side, wherein the reference angle is set at such an angle, which is shifted by a predetermined angle in the valve closing side from an upper-limit angle of a flow-rate dead zone. A valve full-closing control is carried out in order that the hall voltage will coincide with the boundary value on the valve closing side. An actual value of the rotational angle coincides with a value, which is shifted from the reference angle in a valve closing or opening direction by a changing range decided by changing factors of a sensor side and/or a mechanical-part side.
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