Exhaust throttle valve for internal combustion engine

Abstract

An exhaust throttle valve 1 includes a housing 2 formed with a gas passage 2 a, first and second valve shafts 3 and 4 rotatably journaled in the housing 2, a large valve body 5 connected to the first valve shaft, and a small valve body 6 connected the second valve shaft. A communication hole 17 is provided in the large valve body, and urging means that urges the small valve body in a direction of abutting against the large valve body is provided in the second valve shaft. When the large valve body closes the gas passage and pressure of a gas in the gas passage increases from a state where the small valve body closes the communication hole (FIG. 2 ( b )), the small valve body is separated from the large valve body against an urging force of the urging means to open the communication hole (FIG. 2 ( c )). With an easy configuration, exhaust gas pressure can be adjusted without depending on a gas temperature deference.

1 . An exhaust throttle valve for an internal combustion engine comprising:
 a housing formed with a gas passage through which a gas passes;   a valve shaft rotatably journaled in said housing; and   a valve body that is connected to said valve shaft and opens and closes said gas passage,   characterized in that said valve shaft includes a first valve shaft and a second valve shaft that are coaxially provided and are relatively rotatable,   said valve body includes a large valve body that is connected to said first valve shaft and formed to have substantially the same diameter as the gas passage, a communication hole provided in said large valve body, and a small valve body that is connected to said second valve shaft and abuts against the large valve body to close said communication hole,   urging means that urges said second valve shaft in a direction of said small valve body abutting against said large valve body is provided outside the gas passage, and   when pressure of the gas in the gas passage increases with said large valve body closing the gas passage, said small valve body is separated from the large valve body against the urging force by said urging means to open said communication hole.   
     
     
         2 . The exhaust throttle valve for an internal combustion engine according to  claim 1 , characterized in that said urging means is a torsion coil spring surrounding said second valve shaft and elastically fitted between said second valve shaft and the housing. 
     
     
         3 . The exhaust throttle valve for an internal combustion engine according to  claim 1 , characterized in that a first through hole and a second through hole are provided in said housing so as to face each other with the gas passage therebetween, said first valve shaft is provided in the first through hole, and said second valve shaft is provided in the second through hole. 
     
     
         4 . The exhaust throttle valve for an internal combustion engine according to  claim 3 , characterized in that said large valve body includes a first valve shaft holding portion that is formed on the side of the first through hole and to which the first valve shaft is connected, a second valve shaft passing portion that is formed on the side of the second through hole and rotatably holds the second valve shaft, a first flap protruding from the first valve shaft holding portion and the second valve shaft passing portion, and a second flap protruding from the side opposite to the first flap,
 said small valve body includes a second valve shaft holding portion located between the first valve shaft holding portion and the second valve shaft passing portion of said large valve body and to which the second valve shaft passing through said second valve shaft holding portion is connected, and a third flap protruding from said second valve shaft holding portion,   a communication hole having a smaller opening than said third flap is formed in said first flap, and said urging means urges the third flap to abut against the first flap from a downstream side of the gas passage via the second valve shaft.   
     
     
         5 . The exhaust throttle valve for an internal combustion engine according to  claim 1 , characterized in that stopper means is provided that holds the small valve body and the large valve body at predetermined degrees of opening when said small valve body is separated from the large valve body.