Apparatus for preventing coking in a gas management valve

Abstract

An integral pintle shield and annular scraper for protecting and cleaning the pintle shaft of a pintle valve, such as an exhaust gas recirculation valve for an internal combustion engine, to prevent coking and failure of the valve. The scraper surrounds the shaft, making contact with the shaft surface with sufficient force to dislodge incipient coke deposits but with insufficient force to inhibit the axial motion of the pintle shaft in actuation. The scraper is mounted within a radial shield surrounding the pintle shaft and pintle bushing for preventing exposure of the shaft and bushing to combustion products. The scraper is disposed in such a way that the shaft is scraped in both directions during each actuative cycle of the valve.

What is claimed is:  
     
         1 . An anti-coking apparatus for a valve pintle disposed for axial reciprocation in a linear bearing in a valve body of an exhaust gas recirculation valve, comprising: 
 a) shield means surrounding said bearing and extending between said valve pintle and said valve body; and    b) scraper means disposed within said shield means and surrounding said valve pintle for removing deposits therefrom and preventing particulates from reaching said bearing.    
     
     
         2 . An apparatus in accordance with  claim 1  wherein said shield means is a formed element having an inwardly extending flange for closely surrounding said pintle and an outwardly extending flange for retention against said valve body.  
     
     
         3 . An apparatus in accordance with  claim 2  wherein a portion of said element is captured between said bearing and said valve body.  
     
     
         4 . An apparatus in accordance with  claim 1  wherein said scraper means is a cylindrical, annular element.  
     
     
         5 . An apparatus in accordance with  claim 4  wherein said scraper means is attached to said shield.  
     
     
         6 . An apparatus in accordance with  claim 4  wherein said element is formed of a material selected from the group consisting of woven metal mesh, stainless steel “wool”, polymer fiber such as Teflon, ceramic fiber, glass fiber, sintered ceramics, and combinations thereof.  
     
     
         7 . An apparatus in accordance with  claim 4  wherein shield containing said scraper extend into a region of said valve containing exhaust gas.  
     
     
         8 . An exhaust gas recirculation valve for an internal combustion engine, comprising: 
 a) a valve body;    b) a valve pintle disposed for axial reciprocation in a linear bearing in said valve body;    c) shield means surrounding said bearing and extending between said valve pintle and said valve body; and    d) scraper means disposed within said shield means and surrounding said valve pintle for removing deposits therefrom and preventing particulates from reaching said bearing.    
     
     
         9 . An internal combustion engine, comprising an exhaust gas recirculation valve, including 
 a valve body,    a valve pintle disposed for axial reciprocation in a linear bearing in said valve body,    shield means surrounding said bearing and extending between said valve pintle and said valve body, and    scraper means disposed within said shield means and surrounding said valve pintle for removing deposits therefrom and preventing particulates from reaching said bearing.