Semi-active muffler
A semi-active muffler has a casing, an inlet pipe for exhaust gas, at least one outlet pipe for the exhaust gas, a valve element controlling flow of exhaust gas, a spring cooperating with the valve element and biasing the valve element into a first position. Cooling means are provided for reducing the amount of heat transferred from the exhaust gas to the spring.
1 . Semi-active muffler having a casing, an inlet pipe for exhaust gas, at least one outlet pipe for said exhaust gas, a valve element controlling flow of exhaust gas, a spring cooperating with said valve element and biasing said valve element into a first position, and cooling means for reducing the amount of heat transferred from said exhaust gas to said spring.
2 . The muffler of claim 1 wherein said cooling means is an isolating body circumscribing said spring.
3 . The muffler of claim 2 wherein said isolating body is made from a ceramic material.
4 . The muffler of claim 2 wherein said isolating body is made from a sintered body consisting of hollow metal spheres.
5 . The muffler of claim 2 wherein said isolating body consists of two shells separated by a space filled with air.
6 . The muffler of claim 1 wherein said cooling means is an admission system for admitting a cooling fluid.
7 . The muffler of claim 6 wherein said admission system has an admission opening which is arranged in said inlet pipe upstream of said muffler for admitting said cooling fluid to said exhaust gas prior to entering said muffler.
8 . The muffler of claim 6 wherein said admission system has an admission opening which is arranged within said muffler for introducing said cooling fluid in a vicinity of said spring.
9 . The muffler of claim 6 wherein said cooling fluid is ambient air.
10 . The muffler of claim 6 wherein said cooling fluid is a liquid.
11 . The muffler of claim 10 wherein said cooling fluid is water.
12 . The muffler of claim 1 wherein said cooling means is a heat exchanger arranged so as to reduce the temperature of said exhaust gas.
13 . The muffler of claim 12 wherein said heat exchanger comprises at least one rib extending from a point in a vicinity of said spring to a point outside said muffler so as to reduce the temperature of said exhaust gas in a vicinity of said spring.
14 . The muffler of claim 13 wherein said rib has a longitudinal axis which is parallel to a main flow direction of said exhaust gas in said muffler.
15 . The muffler of claim 12 wherein said heat exchanger is at least one cooling rib on an outside of said inlet pipe.
16 . The muffler of claim 1 wherein said cooling means is a shield arranged inside said muffler for preventing said spring from being directly exposed to said exhaust gas.
17 . The muffler of claim 16 wherein said shield is arranged upstream of said spring.
18 . The muffler of claim 16 wherein said shield is arranged downstream of said spring.
19 . The muffler of claim 16 wherein an actuator is provided for actuating said valve element, said actuator being formed so as to direct said exhaust gas away from said spring.
20 . The muffler of claim 1 wherein said spring consists of Inconel.