Exhaust flow control valve

In an exhaust flow control valve comprising a cylindrical flow housing having a cylinder axis and defining a flow passage and a valve plate pivotably mounted within the cylindrical flow housing, also comprising a sealed pivotable mount for pivotably mounting the valve plate, the improvement wherein the sealed pivotable mount comprises:

• a cylindrical extension of the cylindrical flow housing extending in a radial direction exterior of the flow passage, wherein the cylindrical extension defines a cavity with a first cavity portion closest to the flow passage having a first constant diameter and a second cavity portion extending from the first cavity portion away from the flow passage and having a second constant diameter greater than the first constant diameter;
• a first bushing fixedly mounted to an inner peripheral wall of the first cavity portion;
• a second bushing fixedly mounted at an end of the second cavity portion spaced apart from the first cavity portion;
• a shaft attached to the plate and extending through the first bushing, the first and second cavity portions and the second bushing;
• a metal washer rigidly affixed to the shaft within the second cavity portion, wherein the metal washer has one end forming an annular convex surface, wherein the one end faces away from the flow passage;
• a ceramic washer having an opening through which the shaft extends and forming on one end an annular concave surface engageable with the annular convex surface of the metal washer, wherein the ceramic washer is located within the second cavity portion between the metal washer and a face of the second bushing facing the first bushing;
• a retainer rigidly affixed to the shaft exterior of the first bushing with respect to the flow passage;
• and
• a spring located between the retainer and the second bushing, wherein the spring biases the shaft in a direction forcing engagement of the metal washer to the ceramic washer, wherein the metal washer seals against the ceramic washer and the ceramic washer seals against the second bushing, thereby providing a high sealing performance over a wide operating temperature range for preventing exhaust gas from escaping through the pivotable mount to an exterior of the flow passage.