Abstract:
A self-regulating wastegate valve actuator for dynamically regulating a wastegate valve in a turbocharged internal combustion engine. The wastegate valve actuator regulates and maintains a desired pressure differential across a throttle valve with minimal controlling elements by controlling a wastegate valve in response to the pressure differential generated across the throttle valve.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to turbocharger regulating systems and in particular to the regulation of turbocharger performance through the mechanical control of a wastegate. 
       BACKGROUND OF THE INVENTION 
       [0002]    A turbocharger is a well known means of providing pressurized air to an internal combustion engine. A typical turbocharger features a turbine wheel driven by engine exhaust gases. The turbine drives a compressor that provides pressured air to the combustion engine&#39;s intake to increase engine performance. In general, as the speed of the combustion engine increases exhaust gas pressure increases. The turbocharger translates increased exhaust gas pressure into increased intake air pressure (boost pressure) and performance improves within practical limits. However, the uncontrolled pressurization of intake air can lead to problems with engine operation and can result in damage to the engine and turbocharger. 
         [0003]    A typical turbocharged engine features a device known as a wastegate that allows exhaust gases to bypass the turbocharger when it is not desirable to increase intake air pressure. One such circumstance is when an increase in boost pressure would result in engine damage. When exhaust gases are diverted away from the exhaust turbine wheel, the turbocharger slows and boost pressure is reduced. A wastegate may divert variable amounts of the exhaust gases in response to a variety of control mechanisms known in the art. 
         [0004]    Various devices have been disclosed in the prior art which operate a wastegate valve in response to many parameters. A common control parameter used to regulate the operation of a wastegate is the pressure difference that develops across a throttle valve placed between the turbocharger and an intake manifold of a combustion engine. Many of these systems are directed to particular applications requiring complex control systems such as aircraft engines operating in variable air pressure and temperature environments or high performance automobile engines which typically experience rapid changes in throttle application. Such systems often incorporate complex electronics and arrangements of mechanical elements and require specialized equipment and expertise to maintain. 
         [0005]    Alternatively, simpler engines or engines designed to be operated primarily in slowly varying load conditions often use a simplified wastegate design which features a valve controlled by a diaphragm and held shut by a spring. The spring rests on the diaphragm in contact with a pressure space which is maintained at the pre-throttle boost pressure. When boost pressure applied to the diaphragm is sufficient to overcome the spring force, the valve is opened and exhaust gases bypass the turbocharger. This pressure set point may be reached while the throttle is closed or open with the wastegate actuator responding to both engine load conditions in the same manner. The adjustment of the chosen pressure set point is accomplished by adjusting the spring tension of the wastegate actuator. It is often not practical or even possible to adjust the spring tension of the wastegate actuator to account for varying conditions during the operation of the engine using these simplified designs. 
         [0006]    Control of the wastegate using a diaphragm does not maintain a pressure differential across the throttle valve of the engine. Engines could benefit from maintaining a pressure differential across the throttle valve; however, the systems used to control the wastegate to maintain the pressure differential are typically too complex to make their use suitable in many engine applications. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with the present disclosure there is provided a wastegate valve actuator for controlling the position of a wastegate valve for a turbocharger of an internal combustion engine. The waste gate valve actuator compresses a first housing defining a first closed chamber sealed at one end with a first diaphragm, the first housing having a boost pressure inlet in fluid communication with the first closed chamber, the first diaphragm adapted to be coupled to the wastegate valve to control the position of the wastegate valve in reaction to movement of the first diaphragm. The wastegate valve actuator further comprises a second housing defining a second closed chamber sealed at one end with a second diaphragm, the second housing having an intake manifold pressure inlet in communication with the second closed chamber. The wastegate valve actuator further comprises an intake manifold pressure communicator located between the first and second housing, the intake manifold pressure communicator coupled to the second diaphragm and communicating a force to the first diaphragm in reaction to movement of the second diaphragm. 
         [0008]    In accordance with the present disclosure there is also provided a turbocharger system for an internal combustion engine. The turbocharger system comprises a turbocharger driven by exhaust gases of the internal combustion engine, the turbocharger generating boost pressure provided to an intake manifold of the internal combustion engine through an intake pipe comprising a throttle valve located between the turbocharger and the intake manifold; and a wastegate valve moveable between an open position that diverts exhaust of the internal combustion engine away from the turbocharger and a closed position which directs exhaust of the internal combustion engine to the turbocharger. The turbocharger system further comprises a wastegate valve actuator for controlling the position of the wastegate valve, the waste gate valve actuator comprising a first housing defining a first closed chamber sealed at one end with a first diaphragm, the first housing having a boost pressure inlet coupled to the intake pipe between the turbocharger and the throttle valve, the boost pressure inlet in fluid communication with the first closed chamber, the first diaphragm adapted to be coupled to the wastegate valve to control the position of the wastegate valve in reaction to movement of the first diaphragm; a second housing defining a second closed chamber sealed at one end with a second diaphragm, the second housing having an intake manifold pressure inlet coupled to the intake pipe between the throttle valve and the intake manifold, the intake manifold pressure inlet in fluid communication with the second closed chamber; and an intake manifold pressure communicator located between the first and second housing, the intake manifold pressure communicator coupled to the second diaphragm and communicating a force to the first diaphragm in reaction to movement of the second diaphragm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawing wherein: 
           [0010]      FIG. 1  shows a schematic diagram of an intake and an exhaust of a turbocharged internal combustion engine featuring a partially exploded profile of a wastegate control system in accordance with an embodiment of the present invention. 
           [0011]      FIG. 2  shows multiple views of the piston housing component of the wastegate control system of the present invention.  FIG. 2(   a ) is a view of the piston housing from the boost pressure diaphragm side.  FIG. 2(   b ) is a view of the piston housing from the intake manifold pressure diaphragm side.  FIG. 2(   c ) is a side view of the piston housing. 
           [0012]      FIG. 3  shows a partially disassembled adjustable contact post with a threaded connector rod removed. 
           [0013]      FIG. 4  shows a cross section of an intake manifold pressure reaction piston. 
           [0014]      FIG. 5  shows a cross section of an intake manifold pressure housing. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In a typical turbocharged engine, it is often desirable to control the operation of a wastegate actuator in response to the pressure differential that develops across a throttle valve in the path of the engine&#39;s air intake. Changes in the pressure differential across the throttle valve may cause the engine to surge violently. An engine that surges violently causes erratic movement of its throttle valve which may lead to extreme stress on the turbocharger and contribute to turbocharger and engine failure. A typical wastegate may be adjusted to prevent this effect at a given engine load but changes in conditions such as engine load or temperature necessitate readjustment for optimal performance. By controlling the wastegate to maintain a pressure differential across the throttle valve, surging of the engine may be reduced. 
         [0016]    Turbocharged engines may be used in various applications. Stationary natural gas burning internal combustion engines are an example of turbocharged engines that operate in slowly varying load and environmental conditions. Turbocharged engines that operate in these conditions are well suited to the wastegate control described herein; however, the wastegate control may be used advantageously in other turbocharged engine applications. 
         [0017]    An illustrative application of an engine operating in slowly varying load and environmental conditions is in the compression of natural gas from well heads to reach typical pipeline distribution pressures. These natural gas compressing engines operate continuously and have typically required frequent manual adjustment of their wastegates due in part to local temperature variation. In many cases multiple compressor stages are used and where one compressor fails, the remaining compressors are subject to a sudden sharp increase in load. A sudden reduction in load, which may place the engine into a surging state, is also difficult to manage with conventional simplified wastegate designs. 
         [0018]    A schematically represented turbocharging system is shown in  FIG. 1 . A turbocharger  100  is used to compress air from an internal combustion engine air intake  106 . When the intake turbine wheel  104  spins, compressed air is provided to the intake pipe  108 . The air provided is pressurized to a boost pressure dependant on the rate at which the intake turbine wheel  104  is rotating. A throttle valve  110  is then used to adjust the air flow to the engine air intake manifold  112 . 
         [0019]    Intake turbine wheel  104  is rotatably driven by the exhaust turbine wheel  102  which is driven by engine exhaust gases in exhaust pipe  114 . Generally, as more air is supplied to the engine intake manifold  112  via control of throttle valve  110 , the internal combustion engine will produce increasing pressures of exhaust gases which in turn increases the boost pressure in the intake pipe  108 . A wastegate valve  120  is provided to allow exhaust gases in the exhaust pipe  114  to bypass the exhaust turbine wheel  102  and allow the turbocharger  100  to slow when it is desirable to reduce the boost pressure in the intake pipe  108 . 
         [0020]    The wastegate valve is opened and closed using a wastegate valve head  122  that is mounted to a shaft  126  connected to the wastegate actuator  132  (shown partially exploded). More particularly, shaft  126  is mounted to the boost pressure reaction diaphragm  130  which seals a chamber within the wastegate housing  128 . The chamber within the wastegate housing  128  is maintained at boost pressure by boost pressure sense line  118 . An increase in boost pressure on the boost pressure reaction diaphragm  130  has the effect of increasing the net forces acting to open the wastegate valve in the overall system. 
         [0021]    A spring  134  is seated against the boost pressure reaction diaphragm  130  and provides a reaction force that resists the opening of the wastegate valve. The spring is housed within a piston housing  142  attached to chamber  128 . The piston housing  142  has an atmospheric pressure air bleed hole  140  which ensures that the pressure on the spring-side of the boost pressure reaction diaphragm  130  is maintained at atmospheric pressure. 
         [0022]    At the far end of the piston housing  142  from the boost pressure reaction diaphragm  130  is the intake manifold pressure reaction diaphragm  148 . The intake manifold pressure reaction diaphragm  148  seals a chamber formed by the intake manifold pressure housing  152  and is fixed to a piston housing  142 . The intake manifold pressure reaction diaphragm  148  is secured in position with a diaphragm hold down plate  150 . The chamber within the intake manifold pressure housing  152  is maintained at the pressure within the air intake manifold  112  by the intake manifold pressure sense line  116 . 
         [0023]    When pressure from the intake air manifold is applied to the intake manifold pressure reaction diaphragm  148 , the diaphragm applies pressure to an intake reaction pressure piston  146  within the piston housing  142  which in turn applies pressure to an adjustable diaphragm contact post  136 . The top portion of the adjustable diaphragm contact post  136  is shaped so as to engage the spring  134  and transfers force generated by the intake manifold pressure reaction diaphragm  148  to the spring  134 . Therefore, an increase in pressure in the air intake manifold results in an increase in the net forces acting to close the wastegate valve  120 . Further, the adjustable diaphragm contact post  136  may extend partially through the spring  134 . The section of the contact post  136  that extends partially through the spring may come into contact with the boost pressure reaction diaphragm  130  to apply pressure to it. 
         [0024]    The maximum pressure that may be exerted on the boost pressure reaction diaphragm  130  by the adjustable diaphragm contact post  136  is limited by the maximum travel of the intake manifold pressure reaction piston  146 . The intake manifold pressure reaction piston  146  engages piston stop  138  to limit the maximum distance that the piston may travel. A rider band  144  stabilizes the intake manifold pressure reaction piston  146  within the piston housing  142 . 
         [0025]    The dimensions of the diaphragms are chosen to tune the response of the wastegate actuator. Generally, the intake manifold pressure reaction diaphragm  148  is selected to have a larger surface area than the boost pressure reaction diaphragm  130  because the intake manifold pressure will always be less than or equal to boost pressure. During engine operation, the boost pressure is invariably higher than the intake manifold pressure. The tension of spring  138  is dynamically regulated by the action of the intake manifold pressure reaction diaphragm  148  in response to the intake manifold pressure. The operation of the wastegate valve is therefore regulated by the pressure difference across the throttle valve  110 . In the preferred embodiment of this invention as used in stationary natural gas burning internal combustion engines, the dimensions of the diaphragms, the spring tension, the position of the adjustable diaphragm post, and other mechanical variables that will be apparent to a person skilled in the art can all be adjusted to achieve the desired result. The preferred embodiment of the invention may be constructed to target and maintain a desirable pressure differential across the throttle valve of 7″ Hg for example. A person skilled in the art will recognize that the invention is applicable to virtually any internal combustion engine using a throttle valve or plate and operating at a relatively constant atmospheric pressure such as a gasoline or propane burning engine. 
         [0026]      FIG. 2  shows various views of a piston housing  142  of one embodiment of the invention.  FIG. 2(   a ) is a view of the piston housing  142  from the side fixed to the boost pressure diaphragm  130 . The boost side inner dimension  202  shows the diameter of the piston housing  142  exposed to the boost pressure diaphragm of one embodiment of the present invention. The intake side inner dimension  204  shows the diameter of the piston housing  142  exposed to the intake manifold pressure diaphragm of one embodiment of the present invention. The selection of 4.300″ for the intake manifold pressure diaphragm side and 4.100″ for the boost pressure diaphragm side serves to target and maintain a desirable pressure differential across the throttle valve of 7″ Hg for a natural gas burning engine in one embodiment of the invention. 
         [0027]      FIG. 3  shows a schematic cross section of an adjustable contact post  136  of one embodiment of the invention. A threaded connector rod  302  is shown removed from the body of the adjustable contact post  136 . The length of the adjustable contact post  136  may be adjusted by threading the threading connector rod  302  to varying degrees into the upper and lower portions of the adjustable contact post  136 . Nuts  304  are used to secure the threaded connector rod  302 . 
         [0028]      FIG. 4  shows a schematic cross section of an intake reaction pressure piston  146  with intake reaction pressure piston rider band groove  402 .  FIG. 5  shows a schematic cross section of an intake manifold pressure housing  152  of one embodiment of the invention. 
         [0029]      FIGS. 2 ,  3 , 4  and  5  recite various measurements for different components. It is understood that the measurements are given as only one example of an illustrative embodiment of a wastegate valve actuator. It is understood that the dimensions of the components may be changed to adapt the wastegate valve actuator to different sizes of engines and/or turbochargers, as well as to different operating environments such as operating pressures and/or temperatures. The dimensions of the components may also be changed to adapt the wastegate valve actuator to maintain different pressure differentials across the throttle valve. 
         [0030]    In a typical operating scenario an internal combustion engine is started in a low load condition with the throttle valve minimally open. Exhaust gases apply pressure to the exhaust turbine wheel  102  and to the boost pressure reaction diaphragm  130 . As the turbocharger applies increasing boost pressure, minimal pressure is applied to the intake manifold reaction diaphragm  148  as the throttle valve restricts air flow to the intake manifold  112 . As boost pressure builds, the wastegate valve opens, the turbocharger slows, and the pressure differential between intake pipe  108  and intake manifold  112  is reduced. 
         [0031]    As the throttle valve is opened further and the engine load is increased to a mid-range load scenario, increasing pressure is applied to the intake manifold reaction diaphragm  148  relative to the boost pressure applied to the boost pressure reaction diaphragm  130 . The intake pressure reaction diaphragm  148  moves the intake manifold reaction pressure reaction piston  146  and compresses the spring  134  until adjustable diaphragm contact post  136  contacts the boost pressure reaction diaphragm  130  resulting in a force that tends to further close the wastegate valve. 
         [0032]    As the throttle valve is opened still further and the engine approaches a maximum load scenario, the intake pressure reaction diaphragm  148  moves the intake manifold reaction pressure reaction piston  146  further until this motion is restricted by the piston stop  138 . The motion of the intake manifold reaction pressure reaction piston  146  is restricted by the piston stop  138  to prevent the situation where the wastegate valve would be forced closed to prevent an over-pressure situation and engine damage. 
         [0033]    When the throttle valve is closed, the boost pressure rapidly increases in response to the action of the turbo charger while the intake ma pressure is reduced by the restriction of the throttle valve. In this case the system allows more exhaust gases to be diverted around the exhaust turbine wheel until the desired pressure differential is once again attained. 
         [0034]    One or more currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.