Patent Publication Number: US-2004051067-A1

Title: Pressurized valve actuator

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to pintle valves; more particularly, to exhaust gas recirculation (EGR) pintle valves for internal combustion engines; and most particularly, to apparatus and method for preventing entry of exhaust gas components and external contaminants into a valve&#39;s shaft bushing and solenoid actuator.  
       BACKGROUND OF THE INVENTION  
       [0002] Pintle valves are well known for use in controlling flow of fluids, and especially gases. Some applications can expose a valve&#39;s internal surfaces and moving parts to fouling materials; for example, a pintle-type exhaust gas recirculation valve is exposed to corrosive and carbon-bearing materials which can seep into the clearance between the valve pintle shaft and the pintle bushing. Such materials can deposit as undesirable coking on the shaft, but can also pass through the bushing and enter the solenoid actuator where they can cause impairment or failure of the actuator. Typically, a space exists between the valve body and the actuator, which space may be vented to permit escape of gases leaking along the bushing. However, such vents may also permit ingress of external contaminants, especially water when a valve is subjected to intense spray or temporary immersion. These contaminants may then be drawn into the actuator and also cause mechanical and/or electrical failure of the device. In addition, traces of gases escaping through the vents, laden with coke deposits and other sootlike contaminants, are exhausted into the engine compartment leaving undesireable carbon tracks on surfaces near the vents.  
       [0003] What is needed in the art is a means for keeping gas-borne contaminants from reaching bearing surfaces of a valve pintle shaft and its support bushing, from reaching entry points on an associated solenoid actuator, and from being exhausted into the engine compartment and deposited outside the valve. Also needed in the art is a means for preventing contaminants in the outside environment, such as dirt and water, from entering the actuator.  
       [0004] It is a principal object of the present invention to increase the reliability of an exhaust gas recirculation valve by preventing contaminating materials from passing through the valve bushing, from entering the solenoid actuator, and from being exhausted into the engine compartment and deposited outside the valve. Another object is to inhibit the entry of other outside contaminants into the solenoid actuator.  
       SUMMARY OF THE INVENTION  
       [0005] Briefly described, in a solenoid-actuated pintle valve, the solenoid assembly is shrouded by a substantially air-tight jacket connected to a source of air at a pressure higher than the working gas pressure within the valve chamber. During operation of the valve and solenoid assembly, a low mass flow of air is forced continuously throughout the solenoid assembly and exits through any leaks in the jacket and along the bushing bore into the valve chamber. Thus, the bushing bore and solenoid assembly are actively protected against entry of contaminants such as dirt and water from the outside environment and contaminated gases from the engine. Further, since it is no longer necessary to vent the valve to permit the escape of gases leaking along the bushing bore, contaminant-laden gases are kept from being exhausted into the engine compartment and from leaving a carbon track residue.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0006] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
     [0007]FIG. 1 is an elevational cross-sectional view of a pintle-type valve in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0008] Referring to FIG. 1, a pintle-type valve assembly  10  in accordance with the invention includes a valve body  12  comprising a first annular chamber  14  and a second annular chamber  16  separated by a first annular valve seat  18 . Chamber  14  is separated from the exterior  20  by a second annular valve seat  22 . A pintle shaft  24  having a surface  23  is slidably disposed in first axial bore  25  in bushing  26  which is mounted in a second axial bore  28  in valve body  12 . First valve head  30  is fixedly attached to shaft  24  for axial movement therewith and is matable with first valve seat  18  to regulate flow across seat  18  in known fashion. Second valve head  32  is integral with shaft  24  and is matable with second valve seat  22  for regulating flow across seat  22  in known fashion, in concert with first head  30  and first seat  18 . For purposes of discussion of the invention, second seat  22  and second head  32  need not be considered further hereinafter.  
     [0009] Pintle shaft  24  extends from bushing  26  into solenoid actuator assembly  36  attached to valve body  12 , which assembly comprises an armature  38 , first pole piece  40 , second pole piece  42 , spool  44 , windings  46 , and connector cap  48 . A housing  50  surrounds the electromechanical elements.  
     [0010] A pintle valve assembly such as valve assembly  10  may be mounted on an internal combustion engine  34  for use as an exhaust gas recirculation valve in known fashion. In such use, chambers  14  and  16  are fully exposed to engine exhaust gases. The object of the invention is to provide apparatus and method for preventing exhaust gas from leaking from chamber  16  along bores  25  and  28  and thence into actuator assembly  36 , and for preventing dirt and water and other contaminants from the outside environment from entering the actuator assembly as well. This object is achieved by pressurizing the internal reaches of the actuator assembly to a pressure level exceeding the operating pressure in chamber  16 , to forestall passage of exhaust gas along bores  25  and  28 . Of course, pressurized gas may be introduced to equal effect anywhere within assembly  10  above the outer end of bushing  26 .  
     [0011] Housing  50  defines a manifold jacket for assembly  36  and is formed having an opening  52 , preferably provided with hose-attachment means such as nipple  54 , which is connected to any suitable source  56  of pressurized gas, preferably air. Such sources may include, among others, a mechanical air pump, a supercharger, and an engine intake turbocharger. Exhaust pressure in chamber  16  is typically about 140 kPa or less, so the source must deliver gas at a pressure higher than 140 kPa. Gas entering the solenoid assembly via opening  52  flows through all the internal clearances between components, helping to cool the assembly, and has access to bores  25  and  28  along which it flows into chamber  16 . Thus, exhaust gas is prevented from flowing along those bores and entering solenoid assembly  36 . Further, pressurized gas flows continuously from any tiny leaks in housing  50  or its connection to first pole piece  40  and connector cap  48 , thus preventing entrance of external contaminants such as dirt or water to which the valve assembly may be exposed during use.  
     [0012] While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.