Exhaust brake variable bypass circuit

An exhaust brake comprising:

• a main exhaust passage;
• a main butterfly valve in said main exhaust passage for selectively blocking the flow of exhaust gas through the main exhaust passage;
• means for selectively opening and closing the main butterfly valve;
• a bypass exhaust passage communicating with said main exhaust passage at upstream and downstream locations relative to the main butterfly valve, said bypass providing for the flow of exhaust gas past the main butterfly valve;
• a bypass valve in said bypass exhaust passage for selectively closing the bypass exhaust passage;
• a spring assisted means for biasing the bypass valve in a closed position;
• and
• means for varying a biasing force provided by the biasing means responsive to an engine condition selected from the group consisting of:
• engine speed, exhaust gas pressure, engine temperature, exhaust gas recirculation activation, compression release braking activation, intake manifold pressure, fuel rate, throttle position, percent of engine load, ambient temperature, air fuel ratio, vehicle start up, and head rejection to coolant Btu/min;
• wherein the bypass valve comprises a conical shaped stopper.

An exhaust brake comprising:

• a main exhaust passage;
• a main butterfly valve in said main exhaust passage;
• a bypass exhaust passage through the main butterfly valve;
• a bypass valve for opening and closing the bypass exhaust passage;
• an actuator connected to the main butterfly valve through a first lever arm;
• a second lever arm linked to the bypass valve at an axle end;
• and
• a tension spring connecting the first and second lever arms such that the bypass valve linked to the second lever arm is biased in a closed position.

An exhaust brake comprising:

• a main exhaust passage;
• a main valve in said main exhaust passage for selectively blocking the flow of exhaust gas through the main exhaust passage;
• means for selectively opening and closing the main valve;
• a bypass exhaust passage communicating with said main exhaust passage at upstream and downstream locations relative to the main valve, said bypass providing for the flow of exhaust gas past the main valve;
• a conical shaped stopper in said bypass exhaust passage for selectively closing the bypass exhaust passage;
• a spring assisted means for biasing the stopper in a closed position;
• a rod linking the stopper and the spring assisted biasing means;
• a bushing providing a seal along the rod between the stopper and the spring assisted biasing means;
• and
• means for varying a biasing force provided by the biasing means responsive to exhaust gas pressure in the bypass exhaust passage.

A method of operating an exhaust brake having a bypass system comprising the steps of:

• providing an exhaust brake with a main valve and a conical shaped bypass valve for restricting the flow of exhaust gas;
• selectively biasing the bypass valve into a closed position;
• selectively closing the main valve;
• increasing exhaust back pressure in the bypass system as a result of closing the main valve;
• mechanically pulling the bypass valve open responsive to the level of exhaust back pressure in (1) the bypass system and (2) an upstream side of the main valve;
• and
• closing the bypass valve responsive to the level of exhaust back pressure in the bypass system.