PURPOSE:To automatically obtain an engine warming operational condition, by placing an exhaust brake valve of an engine to a closed position at inoperative time of an actuator and preventing the running under a condition with insufficient pressure of actuator fluid. CONSTITUTION:An exhaust gas passage 2 is formed to an exhaust valve body 1 provided to the half way of an exhaust pipe, and a valve 3 and an actuator 5 slided in the direction at a right angle with the passage 2 are provided. A piston 9 slidably fitted in a cylinder 6 of the actuator to divide the inside of the cylinder 6 into a pressure chamber 7 and an atmospheric pressure chamber 8 is provided and connected to the valve 3 through a piston rod 10. At inoperation, the piston 9 is urged rightward by a compression spring to place the valve 3 in a closed position and an exhaust brake in an operative condition, while at operation, the valve 3 is opened to enable the start of an engine only when pressure of fluid supplied to the chamber 7 from an introducing port 14 reaches a sufficient value.
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