Exhaust passage control valve

摘要

An exhaust passage control valve has a valve element (21) of a spiral shape mounted on a valve seat portion (20a) of a housing (20) through which exhaust gases from an engine pass. The valve element (21) is urged by a valve spring (22) in a direction of closing the valve. A spring constant of the valve spring (22) is kept low without enlarging the valve spring, and there can be obtained opening and closing characteristics in that the valve opens at a stretch when an exhaust-gas pressure has reached a predetermined value. As the valve spring (22), a helical torsion spring having a coiled cylindrical body portion (22a) is used. Arm portions (22b, 22b) on both ends of a coiled cylindrical body portion (22a) are engaged with a pair of spring receiving members (23, 23). The spring receiving members (23, 23) are disposed in the housing (20) on circumferentially opposite sides of the valve seat portions (20a). The arm portion (22b, 22b) are engaged with the spring receiving members (23, 23) so as to be slidable in a longitudinal direction of the arm portions (22b, 22b). The valve element (21) is thus urged, in a direction of closing the valve, through the coiled cylindrical body portion (22a).