PURPOSE: To carry out soot removing operation in a pressure region having a high soot-removing effect without increasing a capacity of an ejection medium source by detecting the rotation of an ejection tube at every predetermined rotational angle, controlling the rotational motion of the ejection tube on the basis of a signal thus detected, and controlling the ejection of an ejection medium at every predetermined rotational angle. ;CONSTITUTION: Limit switches 24a, 24b, which measure in advance a pressure decrease to be caused by the ejection and discharge of an ejection medium fed through a pipe 26, are also the means for serving to detect pressure and to detect a rotational angle, which are disposed in a rotational angle position within a pressure range effective for removing soot. When an ejection tube 1 is rotated at an angle of 180 degrees and an engaging member 25 is engaged with the limit switch 24a, a cam follower 15 is engaged with a closed cam part 14b to close a head valve 3, and soot removing operation is thereby temporarily suspended. Also, when the engaging member 25 is engaged with the limit switch 24b, for example, the number of rotations of the ejection tube 1 is detected as the predetermined number of rotations. Then, the cam follower 15 is engaged with the closed cam part 14b to change over the head valve to a closed state, thus finishing soot removing operation.;COPYRIGHT: (C)1996,JPO
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