Exhaust throttle valve

Abstract

An exhaust pressure control valve comprises a casing including a bore and a pair of first and second shaft support parts, and a valve shaft placed across the bore and rotatably supported by the shaft support parts. A first end portion of the valve shaft is arranged protruding outside the casing. A throttle valve is secured to the valve shaft inside the bore. An actuator is coupled to the first end portion to open and close the throttle valve. The second shaft support part is located in a bypass passage downstream from a bypass valve and has an opening in which a cap formed with a through hole is fitted. The inside of the second shaft support part is allowed to communicate with atmosphere through the through hole, the bypass passage, and others so that an end face of a second end portion can be subjected to atmospheric pressure.

1 . An exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising:
 a casing including a bore and a pair of first shaft support part and second shaft support part;   a valve shaft that has a first end portion and a second end portion and is placed across the bore, the first end portion being rotatably supported by the first shaft support part and the second end portion being rotatably supported by the second shaft support part,   the first end portion having one end passing through the first shaft support part to protrude outside the casing; and   a butterfly-type valve element attached to the valve shaft inside the bore;   wherein an inside of the second shaft support part supporting the second end portion is allowed to communicate with atmosphere so that an end face of the second end portion can be subjected to atmospheric pressure.   
   
   
       2 . An exhaust throttle valve which can be mounted in an exhaust system of an engine to restrict a flow of exhaust gas, comprising:
 a casing including a bore and a pair of first shaft support part and second shaft support part;   a valve shaft that has a first end portion and a second end portion and is placed across the bore, the first end portion being rotatably supported by the first shaft support part and the second end portion being rotatably supported by the second shaft support part,   the first end portion having one end passing through the first shaft support part to protrude outside the casing; and   a butterfly-type valve element attached to the valve shaft inside the bore; and   an actuator coupled with the end of the first end portion protruding outside the casing and arranged to drive the valve element to open and close,   wherein an inside of the second shaft support part supporting the second end portion is allowed to communicate with atmosphere so that an end face of the second end portion can be subjected to atmospheric pressure.   
   
   
       3 . The exhaust throttle valve according to  claim 1  further comprising:
 a bypass passage formed in the casing to detour the valve element to provide communication between the bore upstream from the valve element and the bore downstream from the valve; and   a bypass valve element for opening and closing the bypass passage.   
   
   
       4 . The exhaust throttle valve according to  claim 2  further comprising:
 a bypass passage formed in the casing to detour the valve element to provide communication between the bore upstream from the valve element and the bore downstream from the valve; and   a bypass valve element for opening and closing the bypass passage.   
   
   
       5 . The exhaust throttle valve according to  claim 3 , wherein
 the inside of the second shaft support part supporting the second end portion is placed to communicate with the bypass passage downstream from the bypass valve element.   
   
   
       6 . The exhaust throttle valve according to  claim 4 , wherein
 the inside of the second shaft support part supporting the second end portion is placed to communicate with the bypass passage downstream from the bypass valve element.   
   
   
       7 . The exhaust throttle valve according to  claim 1 , wherein
 the second end portion is fitted in the second shaft support part and placed inside thereof,   the first and second end portions are rotatably supported by the first and second shaft support parts through bearings respectively.   
   
   
       8 . The exhaust throttle valve according to  claim 2 , wherein
 the second end portion is fitted in the second shaft support part and placed inside thereof,   the first and second end portions are rotatably supported by the first and second shaft support parts through bearings respectively.   
   
   
       9 . The exhaust throttle valve according to  claim 5 , wherein
 the second end portion is fitted in the second shaft support part and placed inside thereof,   the first and second end portions are rotatably supported by the first and second shaft support parts through bearings respectively.   
   
   
       10 . The exhaust throttle valve according to  claim 6 , wherein
 the second end portion is fitted in the second shaft support part and placed inside thereof,   the first and second end portions are rotatably supported by the first and second shaft support parts through bearings respectively.   
   
   
       11 . The exhaust throttle valve according to  claim 7 , wherein
 at least one of the first and second shaft support parts includes a seal ring adjoining to the bearing.   
   
   
       12 . The exhaust throttle valve according to  claim 8 , wherein
 at least one of the first and second shaft support parts includes a seal ring adjoining to the bearing.   
   
   
       13 . The exhaust throttle valve according to  claim 9 , wherein
 at least one of the first and second shaft support parts includes a seal ring adjoining to the bearing.   
   
   
       14 . The exhaust throttle valve according to  claim 10 , wherein
 at least one of the first and second shaft support parts includes a seal ring adjoining to the bearing.   
   
   
       15 . The exhaust throttle valve according to  claim 7 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.   
   
   
       16 . The exhaust throttle valve according to  claim 9 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.   
   
   
       17 . The exhaust throttle valve according to  claim 10 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.   
   
   
       18 . The exhaust throttle valve according to  claim 11 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.   
   
   
       19 . The exhaust throttle valve according to  claim 13 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.   
   
   
       20 . The exhaust throttle valve according to  claim 14 , wherein
 the second shaft support part has an opening which can be subjected to the atmospheric pressure, and   the exhaust throttle valve further includes a cap fitted in the opening of the second shaft support part, the cap being formed with a through hole for providing communication between the inside and an outside of the second shaft support part so that the atmospheric pressure can act on an end face of the second end portion through the through hole.