Patent Publication Number: US-2007119170-A1

Title: Non-rotating turbocharger waste gate valve

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention (Technical Field)  
      The present invention relates to waste gate valves for turbochargers used in internal combustion engines.  
      2. Backqround Art  
      A turbocharger is an exhaust-driven blower that forces air into the engine under pressure. Turbochargers are used on gasoline and diesel engines to increase power output, while often improving engine efficiency (fuel economy and emissions levels).  FIG. 1  shows a typical turbocharger. The maximum amount of boost pressure produced by the turbocharger is controlled by waste gate  200 , which comprises a channel extending between inlet  270  from the engine&#39;s exhaust manifold and turbocharger outlet  210 . When waste gate valve  230  is opened, the exhaust gasses, which enter turbocharger via inlet  270  and are normally routed directly to the exhaust turbine located in turbine housing  240 , at least partially bypass the exhaust turbine, thus reducing the boost pressure. The further the waste gate is opened, the more exhaust bypasses the turbine, thereby further decreasing the boost. Under partial load, the waste gate is typically closed and the system routes all of the exhaust gases directly into turbine housing  240 . Gases introduced into turbine housing  240  exit the housing via opening  220  and then proceed to the exhaust system via turbocharger outlet  210 . Without a waste gate, the boost pressure produced by the turbocharger could exceed the maximum allowable combustion chamber pressure. This could lead to misfiring and engine damage.  
      The waste gate is typically operated by a diaphragm assembly  250 . The actuator diaphragm is typically connected to the intake manifold, typically via a vacuum hose connected to fitting  255 . A spring in the assembly typically keeps the waste gate closed at lower intake manifold pressures. As pressure builds up in the manifold over a preset value, the diaphragm compresses the spring, which is typically connected to waste gate valve  230  via linkage  260 , thus partially or fully opening the waste gate. This redirects the flow of a portion of the exhaust gas from the turbocharger into the waste gate passage and out into the exhaust system via outlet  210 , thereby reducing the boost pressure. The waste gate may alternatively be actuated electronically, or by other mechanical means, in response to one or more desired parameters other than, or in addition to, the intake manifold pressure.  
       FIG. 2  shows a typical prior art waste gate valve assembly  10  of the prior art. Shaft  20  of valve  30  is inserted into opening  40  in arm  50 . Shaft  20  is prevented from sliding out of opening  40  by washer or other fastener  70 . Arm  50  is actuated by the diaphragm assembly as described above in order to seat or unseat valve  30 , thereby closing or opening the waste gate. Valve  30  is preferably not integrated with arm  50  to enable a small freedom of movement, which enables the valve to make a good seal, preventing leakage. Because shaft  20  and opening  40  comprise a circular cross section, valve  30  can rotate while disposed in arm  50 . Because of high exhaust bypass volumes and velocities, and high exhaust temperatures (especially in gasoline engines), this rotation results in valve failure due to excessive wear.  
      This rotation can be limited to less than one rotation by the addition of anti-rotation pin  60  to valve  30 . When valve  30  rotates, pin  60  eventually contacts arm  50 , which prevents further rotation. However, some rotation still exists, which eventually causes valve wear and failure. Even if pin  60  is integrated with valve  30 , and not attached via welding or a similar technique, pin  60  is not robust enough to withstand the turbocharger environment and eventually fails, resulting in unrestrained rotation and faster valve failure. Further, the existence of pin  60  causes thermomechanical distortion of valve  30  in the area of pin  60 , which causes further damage to valve  30 . Thus there is the need for a robust, cost-effective mechanism for preventing any rotation of a waste gate valve.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention is a turbocharger waste gate assembly comprising a waste gate valve comprising an oblong shaft and an arm comprising an opening for receiving said shaft. The opening is preferably oblong. The shape of the opening is preferably substantially the same as the shape of the shaft. The shaft is preferably integrally formed with the valve during manufacture, although it optionally may be attached to the valve. The waste gate assembly preferably further comprises a fastener disposed on the shaft. The fastener, preferably comprising a washer, preferably prevents the shaft from sliding out of the opening.  
      The invention is also a method of preventing rotation of a turbocharger waste gate valve, the method comprising the steps of providing a waste gate valve comprising an oblong shaft, disposing the shaft into an opening of an arm, and disposing a fastener on the shaft. The opening is preferably oblong. The shape of the opening is preferably substantially the same as a shape of the shaft. The providing step preferably comprises integrally forming the shaft with the valve during manufacture. The method preferably further comprises the step of attaching the shaft to the valve. The fastener, preferably a washer, preferably prevents the shaft from sliding out of the opening.  
      A primary object of the present invention is to reduce failure rates of turbocharger waste gate valves.  
      Another object of the present invention is to prevent rotation of waste gate valves.  
      A primary advantage of the present invention is that the anti-rotation mechanism provided is robust enough to withstand the operating environment of a turbocharger.  
      Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings:  
       FIG. 1  is a perspective semi-transparent view of a turbocharger showing a waste gate valve assembly;  
       FIG. 2  depicts a prior art waste gate valve assembly; and  
       FIG. 3  depicts a waste gate valve assembly of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention is a non-rotating turbocharger waste gate valve. As used throughout the specification and claims, “oblong” means having any non-circular shape or cross section, such as oval, elliptical, elongate, square, and the like.  
      As shown in  FIG. 3 , waste gate valve assembly  100  of the present invention comprises valve  130  and arm  150 . Valve  130  comprises shaft  120 , which is inserted into opening  140  of arm  150 . Shaft  120  is prevented from sliding out of opening  140  preferably by washer or other fastener  170 . Rotation of valve  130  is prevented due to the oblong cross section of shaft  120 . Opening  140  is also preferably oblong, further preventing rotation of shaft  120 , especially under high loads. Opening  140  preferably comprises the same shape as shaft  120 , so that shaft  120  fits snugly in opening  140 . However, opening  140  optionally can comprise any shape which allows insertion of shaft  120  but prevents its rotation. The shape chosen for shaft  120  is preferably sufficiently elongated or non-circular to prevent rotation of valve  130  under high load conditions in the turbocharger. Shaft  120  is preferably integrated or formed with valve  130  during manufacture, such as through casting, although it may optionally be attached after manufacture, such as through welding or the like.  
      Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above, and of the corresponding applications, are hereby incorporated by reference.