| 摘要 |
PURPOSE: A variable volume type resonator is provided to be installed compactly in a narrow engine room, and efficiently reduce intake noise all over operation ranges of an engine. CONSTITUTION: A resonator comprises a neck(7) connected to an air duct(1); a fixed resonance box(3) connected to the neck; a rotary resonance box unit(5) connected to the fixed resonance box by a rotary shaft(9), having connecting state with the fixed resonance box switched as rotated, and having a plurality of resonance boxes(11) with various volume forming a single circular plane centering on the rotary shaft; a step motor(21) rotating the rotary shaft so that the rotary resonance box unit is rotated with respect to the fixed resonance box; and an ECU(19) controlling the step motor depending on working state of an engine. The fixed resonance box is formed to be cylindrical. Protrusive parts are formed on the resonance boxes to be protruded from sides thereof contacting with the fixed resonance box and to cover an outer ring of the fixed resonance box so as to guide rotation of the rotary resonance box unit.
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