| 摘要 |
PROBLEM TO BE SOLVED: To suppress generation of noise without having to reduce the moving speed of a valve element during a closing stroke. SOLUTION: Upper and lower throttle parts 32 and 33 are protruded from a first cylinder chamber 18, to reciprocate a valve stem 7 coupled to a valve element 6 to open and close the valve port 4 of an EGR valve 1 and a first piston 21, and a second cylinder chamber 24 and a second piston 28. The upper throttle part 32 is formed in a manner to be inserted in the opening part 15a of a first port 15, to feed air to the upper side of the first piston 21 of the first cylinder chamber 18, and the lower throttle part 33 is formed in a manner to be inserted in the opening part 31a of the communication passage 29 of the second piston 28. Thus, the throttle part reduces the speed of a piston, by throttling a flow of fluid in the vicinity of the terminal point of a closing stroke by the valve spring of the piston and prevents the generation of strike noise as a result of the piston colliding with a cylinder chamber. Since the stroke speed of the piston is set to a high value, the generation of black smoke during pedaling of an accelerator is prevented from occurring through prevention of the increase of a closing stroke.
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