Patent Publication Number: US-9890699-B2

Title: Turbocharger turbine wastegate mechanism

Description:
RELATED APPLICATION 
     This application is a continuation of a U.S. application Ser. No. 14/194,909, filed 3 Mar. 2014, issued as U.S. Pat. No. 9,249,721 on 2 Feb. 2016, both of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Subject matter disclosed herein relates generally to turbomachinery for internal combustion engines and, in particular, to turbine wastegates. 
     BACKGROUND 
     A turbine wastegate is typically a valve that can be controlled to selectively allow at least some exhaust to bypass a turbine. Where an exhaust turbine drives a compressor for boosting inlet pressure to an internal combustion engine (e.g., as in a turbocharger), a wastegate provides a means to control the boost pressure. 
     A so-called internal wastegate is integrated at least partially into a turbine housing. An internal wastegate typically includes a flapper valve (e.g., a plug), a crank arm, a shaft or rod, and an actuator. A plug of a wastegate often includes a flat disk shaped surface that seats against a flat seat (e.g., a valve seat or wastegate seat) disposed about an exhaust bypass opening, though various plugs may include a protruding portion that extends into an exhaust bypass opening (e.g., past a plane of a wastegate seat). 
     In a closed position, a wastegate plug should be seated against a wastegate seat (e.g., seating surface) with sufficient force to effectively seal an exhaust bypass opening (e.g., to prevent leaking of exhaust from a high pressure exhaust supply to a lower pressure region). Often, an internal wastegate is configured to transmit force from an arm to a plug (e.g., as two separate, yet connected components). During engine operation, load requirements for a wastegate vary with pressure differential. High load requirements can generate high mechanical stresses in a wastegate&#39;s kinematics components, a fact which has led in some instances to significantly oversized component design to meet reliability levels (e.g., as demanded by engine manufacturers). Reliability of wastegate components for gasoline engine applications is particularly important where operational temperatures and exhaust pulsation levels can be quite high. 
     Various examples of wastegates and wastegate components are described herein, which can optionally provide for improved kinematics, reduced exhaust leakage, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the various methods, devices, assemblies, systems, arrangements, etc., described herein, and equivalents thereof, may be had by reference to the following detailed description when taken in conjunction with examples shown in the accompanying drawings where: 
         FIG. 1  is a diagram of a turbocharger and an internal combustion engine along with a controller; 
         FIG. 2  is a series of view of an example of an assembly that includes a wastegate; 
         FIG. 3  is a cutaway view of an example of an assembly that includes a wastegate; 
         FIG. 4  is a series of views of an example of a biasing member; 
         FIG. 5  is a series of views of examples of assemblies that include a biasing member; 
         FIG. 6  is a series of views of an example of an assembly with respect to disengaged and engaged orientations of a biasing member; 
         FIG. 7  is a series of views of an example of an assembly with respect to disengaged and engaged orientations of a biasing member; 
         FIG. 8  is a perspective view of an example of an assembly that includes an example of a biasing mechanism; 
         FIG. 9  is a diagram that illustrates examples of various degrees of freedom of a control rod with respect to examples of various forces; 
         FIG. 10  is a series of views of an example of an assembly that illustrates examples of deflections; and 
         FIG. 11  is a series of views of portions of the assembly of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Turbochargers are frequently utilized to increase output of an internal combustion engine. Referring to  FIG. 1 , as an example, a system  100  can include an internal combustion engine  110  and a turbocharger  120 . As shown in  FIG. 1 , the system  100  may be part of a vehicle  101  where the system  100  is disposed in an engine compartment and connected to an exhaust conduit  103  that directs exhaust to an exhaust outlet  109 , for example, located behind a passenger compartment  105 . In the example of  FIG. 1 , a treatment unit  107  may be provided to treat exhaust (e.g., to reduce emissions via catalytic conversion of molecules, etc.). 
     As shown in  FIG. 1 , the internal combustion engine  110  includes an engine block  118  housing one or more combustion chambers that operatively drive a shaft  112  (e.g., via pistons) as well as an intake port  114  that provides a flow path for air to the engine block  118  and an exhaust port  116  that provides a flow path for exhaust from the engine block  118 . 
     The turbocharger  120  can act to extract energy from the exhaust and to provide energy to intake air, which may be combined with fuel to form combustion gas. As shown in  FIG. 1 , the turbocharger  120  includes an air inlet  134 , a shaft  122 , a compressor housing assembly  124  for a compressor wheel  125 , a turbine housing assembly  126  for a turbine wheel  127 , another housing assembly  128  and an exhaust outlet  136 . The housing  128  may be referred to as a center housing assembly as it is disposed between the compressor housing assembly  124  and the turbine housing assembly  126 . The shaft  122  may be a shaft assembly that includes a variety of components. The shaft  122  may be rotatably supported by a bearing system (e.g., journal bearing(s), rolling element bearing(s), etc.) disposed in the housing assembly  128  (e.g., in a bore defined by one or more bore walls) such that rotation of the turbine wheel  127  causes rotation of the compressor wheel  125  (e.g., as rotatably coupled by the shaft  122 ). As an example a center housing rotating assembly (CHRA) can include the compressor wheel  125 , the turbine wheel  127 , the shaft  122 , the housing assembly  128  and various other components (e.g., a compressor side plate disposed at an axial location between the compressor wheel  125  and the housing assembly  128 ). 
     In the example of  FIG. 1 , a variable geometry assembly  129  is shown as being, in part, disposed between the housing assembly  128  and the housing assembly  126 . Such a variable geometry assembly may include vanes or other components to vary geometry of passages that lead to a turbine wheel space in the turbine housing assembly  126 . As an example, a variable geometry compressor assembly may be provided. 
     In the example of  FIG. 1 , a wastegate valve (or simply wastegate)  135  is positioned proximate to an exhaust inlet of the turbine housing assembly  126 . The wastegate valve  135  can be controlled to allow at least some exhaust from the exhaust port  116  to bypass the turbine wheel  127 . Various wastegates, wastegate components, etc., may be applied to a conventional fixed nozzle turbine, a fixed-vaned nozzle turbine, a variable nozzle turbine, a twin scroll turbocharger, etc. 
     In the example of  FIG. 1 , an exhaust gas recirculation (EGR) conduit  115  is also shown, which may be provided, optionally with one or more valves  117 , for example, to allow exhaust to flow to a position upstream the compressor wheel  125 . 
       FIG. 1  also shows an example arrangement  150  for flow of exhaust to an exhaust turbine housing assembly  152  and another example arrangement  170  for flow of exhaust to an exhaust turbine housing assembly  172 . In the arrangement  150 , a cylinder head  154  includes passages  156  within to direct exhaust from cylinders to the turbine housing assembly  152  while in the arrangement  170 , a manifold  176  provides for mounting of the turbine housing assembly  172 , for example, without any separate, intermediate length of exhaust piping. In the example arrangements  150  and  170 , the turbine housing assemblies  152  and  172  may be configured for use with a wastegate, variable geometry assembly, etc. 
     In  FIG. 1 , an example of a controller  190  is shown as including one or more processors  192 , memory  194  and one or more interfaces  196 . Such a controller may include circuitry such as circuitry of an engine control unit (ECU). As described herein, various methods or techniques may optionally be implemented in conjunction with a controller, for example, through control logic. Control logic may depend on one or more engine operating conditions (e.g., turbo rpm, engine rpm, temperature, load, lubricant, cooling, etc.). For example, sensors may transmit information to the controller  190  via the one or more interfaces  196 . Control logic may rely on such information and, in turn, the controller  190  may output control signals to control engine operation. The controller  190  may be configured to control lubricant flow, temperature, a variable geometry assembly (e.g., variable geometry compressor or turbine), a wastegate (e.g., via an actuator), an electric motor, or one or more other components associated with an engine, a turbocharger (or turbochargers), etc. As an example, the turbocharger  120  may include one or more actuators and/or one or more sensors  198  that may be, for example, coupled to an interface or interfaces  196  of the controller  190 . As an example, the wastegate  135  may be controlled by a controller that includes an actuator responsive to an electrical signal, a pressure signal, etc. As an example, an actuator for a wastegate may be a mechanical actuator, for example, that may operate without a need for electrical power (e.g., consider a mechanical actuator configured to respond to a pressure signal supplied via a conduit). 
       FIG. 2  shows an example of an assembly  200  that includes an actuator  201 , an actuation rod  202 , an actuator linkage  203 , a center housing  207  (e.g., to house a bearing, bearings, etc. for a turbocharger shaft, etc.), a compressor housing  209 , a turbine housing  210  that includes a bore  212 , a spiral wall  215  (e.g., that defines, in part, a volute), an exhaust outlet opening  216 , a wastegate wall  223  that extends to a wastegate seat  226 , and an exhaust chamber  230 . 
     In the example of  FIG. 2 , the turbine housing  210  may be a single piece or multi-piece housing. As an example, the turbine housing  210  may be a cast component (e.g., formed via sand casting or other casting process). As shown, the turbine housing  210  includes various walls, which can define features such as the bore  212 , a turbine wheel opening, an exhaust outlet opening, the chamber  230 , etc. In particular, the wastegate wall  223  defines a wastegate passage in fluid communication with an inlet conduit where a wastegate control linkage  240  and a wastegate arm and plug  250  are configured for opening and closing the wastegate passage (e.g., for wastegating exhaust). 
     In the example of  FIG. 2 , the wastegate control linkage  240  includes a bushing  242  configured for receipt by the bore  212  of the turbine housing  210 , a control arm  244  and a peg  246  and the wastegate arm and plug  250  includes a shaft  252 , a shaft end  253 , an arm  254  and a plug  256 . As shown, the bushing  242  is disposed between the bore  212  and the shaft  252 , for example, to support rotation of the shaft  252 , to seal the chamber  230  from an exterior space, etc. The bore  212 , the bushing  242  and the shaft  252  may each be defined by a diameter or diameters as well as one or more lengths. 
     As an example, the assembly  200  may be fitted to an exhaust conduit or other component of an internal combustion engine (see, e.g., examples of  FIG. 1 ), for example, via a flange such that exhaust is received via an inlet conduit that may direct exhaust to a volute (e.g., or volutes) that may be defined at least in part by the spiral wall  215 . As an example, a volute (e.g., or volutes) may direct exhaust (e.g., via a nozzle or nozzles) to a turbine wheel disposed in the turbine housing  210  where the exhaust may flow and expand in a turbine wheel space defined in part by the turbine housing  210 . Exhaust may then exit the turbine wheel space by flowing to the chamber  230  and then out of the turbine housing  210  via the exhaust outlet opening  216 . 
     As to wastegating, upon actuation of the control linkage  240  (e.g., by the actuator linkage  203  being operatively coupled to the peg  246 ), the wastegate arm and plug  250  may be rotated such that at least a portion of the received exhaust can flow in the wastegate passage defined by the wastegate wall  223 , past the wastegate seat  226  and into the chamber  230 , rather than through a nozzle to a turbine wheel space. The wastegated portion of the exhaust may then exit the turbine housing  210  via the exhaust outlet opening  216  (e.g., and pass to an exhaust system of a vehicle, be recirculated in part, etc.). 
     As an example, the control linkage  240  may exert a force that acts to force the plug  256  in a direction toward the wastegate seat  226 . For example, the actuator  201  may include a biasing mechanism (e.g., a spring, etc.) that exerts force, which may be controllably overcome, at least in part, for rotating the plug  256  away from the wastegate seat  226  (e.g., for wastegating). As an example, the actuator  201  may be mounted to the assembly  200 . As an example, the actuator  201  may be a linear actuator, for example, for moving the rod  202  along an axis. Depending on orientation of a plug, a shaft, a control linkage and such a rod, to maintain the plug in a closed position, the rod may exert a downward force (e.g., away from the control linkage as in the example of  FIG. 2 ) or the rod may exert an upward force (e.g., toward the control linkage). For example, where the control arm  244  (e.g., and the peg  246 ) of the control linkage  240  are oriented on the same “side” as the plug  256  with respect to the shaft  252 , a downward force applied to the control arm  244  (e.g., via the peg  246 ) may act to maintain the plug  256  in a closed position with respect to the wastegate seat  226 ; whereas, where, for example, an approximately 180 degree span exists between a plug and a control arm, an upward force applied to the control arm may act to maintain the plug in a closed position with respect to a wastegate seat. 
     As an example, the rod  202  of the actuator  201  may be biased to exert a force on the control linkage  240  that causes the control linkage  240  to exert a force on the plug  256  such that the plug  256  seats against the wastegate seat  226 . In such an example, the actuator  201  may at least in part overcome the force that biases the rod  202  such that the shaft  252  rotates the plug  256  away from the wastegate seat. For example, in  FIG. 2 , to initiate wastegating, the entire plug  256  rotates about an axis of the shaft  252  and moves away from the wastegate seat  226  (e.g., without any portion of the plug  256  moving in a direction into a wastegate opening defined by the wastegate seat  226 ). As an example, the moving away of the plug  256  may be facilitated by exhaust pressure. For example, in a closed position, the plug  256  experiences a pressure differential where pressure is higher below the plug  256  and less above the plug  256 . In such an example, the pressure below the plug  256  acts in a direction that is countered by the closing force applied to the plug  256  via the control linkage  240  (e.g., the pressure differential acts to bias the plug  256  toward an open position). Accordingly, the closing force applied to the plug  256  should overcome pressure force from below the plug  256 . Further, where the shaft  252  may include some play (e.g., axial play, etc.), the closing force applied to the plug  256  may cause the plug  256  to move with respect to the wastegate seat  226 . 
     In the example of  FIG. 2 , the axes of the bore  212 , the bushing  242  and the shaft  252  may be aligned (e.g., defining a common axis), however, during assembly, operation, etc., some misalignment may occur. For example, over time, clearances between the various components (e.g., plug, arm, shaft, bore, bushing, etc.) can change. Forces that can cause such change include aerodynamic excitation, high temperatures, temperature cycling (e.g., temperatures &lt;−20 degrees C. to &gt;1000 degrees C.), chemical attack, friction, deterioration of materials, etc. For at least the foregoing reasons, it may be difficult to maintain effective sealing of a wastegate opening over the lifetime of an exhaust turbine assembly. As to temperature, problems at high temperatures generally include wear and loss of function and consequently leakage, lack of controllability or a combination of leakage and uncontrollability. 
       FIG. 3  shows an example of an assembly  300  that includes a wastegate arm and plug  350  that differs from the wastegate arm and plug  250  of the assembly  200  of  FIG. 2 . In particular, the wastegate arm and plug  350  includes a plug  356  that includes a substantially hemispherical shell portion. As an example, the wastegate arm and plug  350  may be a unitary component (e.g., optionally unitary with the shaft  352 ). 
     In the example of  FIG. 3  the assembly  300  includes a turbine housing  310  that includes a mounting flange  311 , a bore  312 , an inlet conduit  313 , a turbine wheel opening  314 , a spiral wall  315 , an exhaust outlet opening  316 , a shroud wall  320 , a nozzle  321 , a volute  322  formed in part by the spiral wall  315 , a wastegate wall  323  that defines (e.g., at least in part) a wastegate passage  325  where the wastegate wall  323  extends to a wastegate seat  326  that may be an interface between the wastegate passage  325  and an exhaust chamber  330 . 
     In the example of  FIG. 3 , the turbine housing  310  may be a single piece or multi-piece housing. As an example, the turbine housing  310  may be a cast component (e.g., formed via sand casting or other casting process). The turbine housing  310  includes various walls, which can define features such as the bore  312 , the turbine wheel opening  314 , the exhaust outlet opening  316 , the chamber  330 , etc. In particular, the wastegate wall  323  defines at least in part the wastegate passage  325 , which is in fluid communication with the inlet conduit  313  where a wastegate control linkage  340  and the wastegate arm and plug  350  are configured for opening and closing the wastegate passage (e.g., for wastegating exhaust and for not wastegating exhaust). 
     In the example of  FIG. 3 , the wastegate control linkage  340  includes a bushing  342  configured for receipt by the bore  312  of the turbine housing  310 , a control arm  344  and a peg  346  and the wastegate arm and plug  350  includes a shaft  352 , a shaft end  353 , an arm  354  and the plug  356 . As shown, the bushing  342  is disposed between the bore  312  and the shaft  352 , for example, to support rotation of the shaft  352 , to act to seal the chamber  330  from an exterior space, etc. The bore  312 , the bushing  342  and the shaft  352  may each be defined by a diameter or diameters as well as one or more lengths. For example, the shaft  352  includes a diameter D s , the bore  312  includes a diameter D B  while the bushing  342  includes an inner diameter D bi  and an outer diameter D bo . In the example of  FIG. 3 , when the various components are assembled, as to such diameters: D B &gt;D bo &gt;D bi &gt;D s . As to lengths, a length of the shaft  352  exceeds a length of the bushing  342 , which exceeds a length of the bore  312 . Such lengths may be defined with respect to a shaft axis z s , a bushing axis z b  and a bore axis z B . As shown, the bushing  342  is disposed axially between a shoulder of the shaft  352  (e.g., a face of the arm  354  where the arm  354  and the shaft  352  meet) and the control arm  344  of the control linkage  340 . 
     In the example of  FIG. 3 , a gap Δz is shown between a surface of the bushing  342  and a surface of the control arm  344 , which allows for axial movement of the shaft  352 , for example, to facilitate self-centering of the plug  356  with respect to the wastegate seat  326 . For example, the plug  356  may include shape that acts to self-center with respect to a shape of the wastegate seat  326 . As an example, the plug  356  may include a toroidal portion and the wastegate seat  326  may include a conical surface such that the plug  356  may self-center with respect to the wastegate seat  326 . Self-centering may be facilitated by application of force that acts to maintain the plug  356  in a closed position with respect to the wastegate seat  326 . 
     As an example, the assembly  300  may be fitted to an exhaust conduit or other component of an internal combustion engine (see, e.g., examples of  FIG. 1 ), for example, via a flange (see, e.g., the flange  211  of  FIG. 2 ) such that exhaust is received via the inlet conduit  313 , directed to the volute  322 . From the volute  322 , exhaust is directed via the nozzle  321  to a turbine wheel disposed in the turbine housing  310  via the opening  314  to flow and expand in a turbine wheel space defined in part by the shroud wall  320 . Exhaust can then exit the turbine wheel space by flowing to the chamber  330  and then out of the turbine housing  310  via the exhaust outlet opening  316 . As to wastegating, upon actuation of the control linkage  340  (e.g., by an actuator coupled to the peg  346 ), the wastegate arm and plug  350  may be rotated such that at least a portion of the received exhaust can flow in the wastegate passage  325  (e.g., as defined at least in part by the wastegate wall  323 ), past the wastegate seat  326  and into the chamber  330 , rather than through the nozzle  321  to the turbine wheel space. The wastegated portion of the exhaust may then exit the turbine housing  310  via the exhaust outlet opening  316  (e.g., and pass to an exhaust system of a vehicle, be recirculated in part, etc.). 
     In the example of  FIG. 3 , the axes of the bore  312 , the bushing  342  and the shaft  352  may be aligned (e.g., defining a common axis), however, during assembly, operation, etc., some misalignment may occur. For example, over time, clearances between the various components (e.g., plug, arm, shaft, bore, bushing, etc.) can change. Forces that can cause such change include aerodynamic excitation, high temperatures, temperature cycling (e.g., temperatures &lt;−20 degrees C. to &gt;1000 degrees C.), chemical attack, friction, deterioration of materials, etc. For at least the foregoing reasons, it can be difficult to maintain effective sealing of a wastegate opening over the lifetime of an exhaust turbine assembly. As to temperature, problems at high temperatures generally include wear and loss of function and consequently leakage, lack of controllability or a combination of leakage and uncontrollability. 
     As mentioned, the wastegate arm and plug  350  differs from the wastegate arm and plug  250 . In particular, the plug  356  differs from the plug  256 . Further, the shape of the arm  354  differs from the shape of the arm  254 . In an assembly such as the assembly  200  or the assembly  300 , due to one or more factors, the wastegate arm and plug  350  may enhance performance, controllability, longevity, etc. when compared to the wastegate arm and plug  250 . 
     As mentioned, as an example, the wastegate arm and plug  350  may be a unitary wastegate arm and plug (e.g., a monoblock wastegate arm and plug) or a wastegate arm and plug assembly. 
     As an example, the wastegate arm and plug  350  may have a lesser mass than the wastegate arm and plug  250  and, for example, a center of mass for the wastegate arm and plug  350  may differ compared to a center of mass for the wastegate arm and plug  250 . As an example, due to the shape of the plug  356 , it may perform aerodynamically in a more beneficial manner than the plug  256 . For example, the plug  356  may, due to its shape, act to maintain its center more effectively than the plug  256 . As an example, the wastegate arm and plug  350  may provide benefits as to controllability, for example, due to centering, reduced chatter, aerodynamics, etc. As an example, such benefits may improve performance, longevity, etc. of an actuator that is operatively coupled to the wastegate arm and plug  350  (e.g., for transitioning states, maintaining a state, etc.). As an example, such benefits may improve performance, longevity, etc. of a seal mechanism (e.g., bushing, bushings, etc.) for the shaft  352  of the wastegate arm and plug  350  (e.g., with respect to a bore). 
     As mentioned, an assembly may include a gap such as the axial gap Δz that may facilitate, for example, self-centering of a plug with respect to a wastegate seat. However, where the plug is in an open position, the gap may possibly allow for movement of the plug, for example, due to forces from exhaust flowing past the plug. Where exhaust is pulsating, such forces may possibly cause rattling and noise. For example, forces may cause a shaft to move axially with respect to a bore, a bushing, etc. (e.g., separate components), optionally in a back and forth manner (e.g., consider vibration) that may cause periodic contacting between components that may be detrimental. 
       FIG. 4  shows an example of a biasing cam  400  that may be operatively coupled to a portion of a control linkage for a wastegate plug. For example, the biasing cam  400  may be operatively coupled to the control arm  344  of the control linkage  340  of  FIG. 3 . In such an example, the biasing cam  400  may act to reduce risk of rattling and associated noise, for example, by applying a biasing force that biases the shaft  352  (e.g., axially biasing the shaft) when the plug  356  is in an open position. The biasing cam  400  may also, for example, allow for an amount of axial play when the plug  356  is in a closed position, for example, to allow for movement of the plug  356  (e.g., at least axially) with respect to the wastegate seat  326  (e.g., for self-centering, etc.). 
     In the example of  FIG. 4 , the biasing cam  400  may include a base  410  with an opening  420  defined in part by a surface  422 , biasing members  430 - 1  and  430 - 2  and coupling members  440 - 1 ,  440 - 2 ,  440 - 3  and  440 - 4 . As an example, the base  410  may be planar (e.g., see x and y dimensions) and include sides  412 ,  414 ,  416  and  418 . As an example, the opening  420  may be defined in part by a dimension such as a radius (r) with respect to an axis (z s ). As an example, the base  410  may be defined in part by a thickness or thickness (e.g., see z dimension). 
     As an example, the biasing cam  400  may be formed from a unitary piece of material. For example, a piece of sheet metal may be stamped and formed to a shape of a biasing cam, for example, such as the biasing cam  400  shown in the example of  FIG. 4 . As an example, a biasing cam may be a multi-piece component that may include, for example, a base and one or more biasing components or members such as one or more springs, prongs, extensions, etc. that may be operatively coupled to the base. 
     In a cross-sectional view along a line A-A, the biasing members  430 - 1  and  430 - 2  are shown extending downward from the base  410  to respective ends  432 - 1  and  432 - 1 , which may be disposed at approximately a radius of a radius of the opening  420 . In such a configuration, the opening  420  may receive a shaft where the surface  422  of the opening  420  may contact a surface of the shaft and where the ends  432 - 1  and  432 - 2  may be moveable at least axially with respect to the surface of the shaft (e.g., for movement upward and downward to exert an appropriate biasing force). Also shown in the cross-sectional view are portions of the coupling members  440 - 1  and  440 - 3 . For example, the coupling members  440 - 1  and  440 - 3  may include riser portions  442 - 1  and  442 - 3  and inwardly facing clip portions  444 - 1  and  444 - 3 . In such an example, the clip portions  444 - 1  and  444 - 3  may act to operatively couple the biasing cam  400  to a control arm, etc. 
     As an example, a method may include operatively coupling a biasing cam to a control arm and then operatively coupling a shaft thereto (e.g., as received by an opening of the biasing cam). 
     As an example, as to cam functionality, locations of the biasing members  430 - 1  and  430 - 2  may determine an orientation or orientations where biasing may occur (e.g., consider angles about a central axis that define such locations). For example, if an assembly includes an orientation where the biasing members  430 - 1  and  430 - 2  do not contact or exert biasing force against another component, the biasing members  430 - 1  and  430 - 2  may be considered to be non-biasing (e.g., a non-biasing position). However, if an assembly includes an orientation where the biasing members  430 - 1  and  430 - 2  contact and exert a biasing force against another component, the biasing members  430 - 1  and  430 - 2  may be considered to be biasing (e.g., in a biasing position). 
     As an example, a biasing member may include a disengaged orientation and an engaged orientation. As an example, a disengaged orientation may include a clearance between a portion of a biasing cam and another component. As an example, an engaged orientation may include contact between a portion of a biasing cam and another component, for example, where a biasing force is applied via the contact. As an example, an engaged orientation may include a transitional orientation, for example, where rotation of a biasing cam results in increased biasing force, increased axial displacement of a shaft, etc. 
     As an example, a biasing cam may include at least one biasing member that may be in a disengaged or non-biasing position or an engaged or biasing position, for example, depending on orientation of an assembly. As an example, an orientation of an assembly may be determined by orientation of a plug with respect to a wastegate seat, for example, that may correspond to orientation of a shaft operatively coupled to the plug (e.g., degrees of rotation of the shaft with respect to a bore, etc.). 
       FIG. 5  shows an example of the biasing cam  400  operatively coupled to the control arm  344  where the opening  420  receives the shaft  352 . Also shown in the example of  FIG. 5  is a bushing  500  that includes recesses  510 - 1  and  510 - 2  that cooperate with the biasing members  430 - 1  and  430 - 2  of the biasing cam  400 . As an example, the recesses  510 - 1  and  510 - 2  may, for example, receive portions of the biasing members  430 - 1  and  430 - 2  while providing axial clearance. In such an example, the biasing members  430 - 1  and  430 - 2  may be capable of axial movement within the recesses  510 - 1  and  510 - 2  for purposes of axial movement of the shaft  352  and self-centering of a plug, operatively coupled to the shaft  352 , with respect to a wastegate seat. 
     As an example, contact may occur between the biasing members  430 - 1  and  430 - 2  and recess surfaces of the bushing  500  that may allow for some amount of biasing force to be applied therebetween. However, such an amount of biasing force may be less than that achieved when the biasing members  430 - 1  and  430 - 2  of the biasing cam  400  are moved to not align with the recesses  510 - 1  and  510 - 2 . As an example, the recesses  510 - 1  and  510 - 2  may include at least one cambered (e.g., sloping) side such that the biasing members  430 - 1  and  430 - 2  may ride the cambered side, for example, in a manner that riding higher may exert a higher biasing force (e.g., consider a Hookean biasing force where force increases with compression). 
     As an example, an assembly may include a biasing cam that includes at least one biasing member and a component with at least one feature that can determine whether the at least one biasing member applies a biasing force. For example, the at least one feature may be a recess of a bushing that can, in a particular orientation, receive the at least one biasing member optionally with an axial clearance and that can, in a different orientation (e.g., or orientations), not receive the at least one biasing member or receive the at least one biasing member in a manner by which a biasing force is exerted between the biasing cam and the bushing (e.g., to take up, reduce, etc. axial play). 
     As an example, an assembly may include a biasing cam that can provide “zero clearance” between a bushing and a control arm for one or more orientations of the control arm with respect to the bushing and that can provide for clearance between the bushing and the control arm in a manner that can allow for centering of a plug with respect to a wastegate seat (e.g., where the plug is operatively coupled to the control arm, for example, via a shaft). In such an example, the biasing cam may be a spring that exerts force at certain plug opening angles (e.g., cam functionality). In such a manner, the biasing cam may reduce risk of rattling and associated noise while still allowing for self-centering of a plug with respect to a wastegate seat. In other words, as an example, a biasing cam may act selectively as a spring that can be loaded to remove clearance between a control arm and a bushing if a plug is open but may not be loaded if the plug is closed. As an example, a biasing cam may include a linear coil spring (e.g., positioned between a control arm and a housing, etc.). As an example, a spring may be a metal spring. 
     As an example, a biasing cam may assist with opening of a plug with respect to a wastegate seat. For example, where an actuator exerts a downward force to maintain a plug in a closed position, the biasing cam may have a clearance such that it does not exert an opposing force. Whereas, upon opening of the plug, the actuator must overcome the downward force by applying an upward force; noting that, upon rotation of the biasing cam, it too may apply an upward force. Thus, in such an example, the biasing cam may reduce an amount of upward force to be exerted by such an actuator (e.g., once the biasing cam engages and exerts its biasing force). 
       FIG. 6  shows examples of the assembly of  FIG. 5  in two orientations, a so-called 0 degrees orientation (e.g., a disengaged orientation) and a Φ degrees orientation (e.g., an engaged orientation) where the biasing member  430 - 1  of the biasing cam  400  is engaged by a surface of the busing  500 . Various dimensions are shown in  FIG. 6  including, for example, a biasing cam and bushing clearance Δz cb , which may be altered in a manner dependent on orientation of the control arm  344  with respect to the bushing  500 . For example, a method may include orienting the biasing member  430 - 1  of the biasing cam  400  with respect to the recess  510 - 1  of the bushing  500  for altering a biasing cam to bushing axial clearance. As shown in the example of  FIG. 6 , altering may include moving the shaft  352  axially outwardly away from the turbine housing  310 . 
       FIG. 7  shows examples of the assembly of  FIG. 5  in the two orientations of  FIG. 6 . As shown, one orientation is associated with a closed orientation (e.g., or position) of the plug  356  with respect to the wastegate seat  326  and the other orientation is associated with an open orientation (e.g., or position) of the plug  356  with respect to the wastegate seat  326  (e.g., where the shaft  352  is translated axially outwardly by a biasing force exerted by the biasing cam  400 ). 
     As shown in the examples of  FIG. 7 , a clearance may be reduced between a face  505  at the end of the bushing  500  and a face  355  at the end of the arm  354  when the plug  356  transitions from a closed orientation to an open orientation with respect to the wastegate seat  326 . As an example, a reduction in clearance may act to impede gas flow (e.g., exhaust leakage) at an interface or interfaces, for example, as bias exerted by a biasing cam may act to pull the  355  against the face  505  of bushing  500 . 
     As an example, during operation, a chamber space of a turbine assembly may have a pressure that exceeds an ambient pressure. In such an example, a pressure differential may act as a driving force for flow of exhaust from the chamber space to an ambient space. As such a flow of exhaust may occur prior to an exhaust treatment unit (see, e.g., the unit  107  of  FIG. 1 ), it may be detrimental as to a goal of achieving an environmental standard or standards. As an example, wastegating may occur to avoid excessive boost to an internal combustion engine. As an example, wastegating may act to increase a pressure differential between a chamber space and an ambient space. In the example of  FIG. 7 , an axially outward shift of the shaft  352  responsive to action of the biasing cam  400  being rotated to a biasing position as an actuator acts to effectuate wastegating, such a shift may act to reduce a clearance or clearances that act to impede flow of exhaust from the chamber  330  to an ambient space via the bore  312 . Such an approach may act to reduce rattling, vibration, etc., which, in turn, may act to reduce flow of exhaust from the chamber  330  to an ambient space via the bore  312 . 
       FIG. 8  shows an example of an assembly  800  that includes an actuator  801  operatively coupled to a control rod  803  that includes a notch  804 . In the example of  FIG. 8 , the actuator  801  is coupled to a compressor housing  807  that is coupled to a center housing  809  that is coupled to a turbine housing  810  that includes a wastegate valve controllable via a control arm  844  (e.g., via rotation of the control arm  844 ). 
     As shown in the example of  FIG. 8 , a peg  846  extends from the control arm  844  where the peg  846  is coupled to the control rod  803 , for example, via a coupler  805  that may be adjustable (e.g., as to axial position along with respect to the control rod  803  via threads, etc.). As shown, a spring  910  may be provided as a biasing mechanism. In the example of  FIG. 8 , the spring  910  may be a coil spring that includes a fixed end  912  that operatively couples to the compressor housing  807  via a clamp  920  (see, e.g., an opening  922  in the clamp  920 ) and that includes a movable end  914  that operatively couples to the control rod  803  via the notch  804  (e.g., or other feature such as an opening, etc.). 
     In the example of  FIG. 8 , various components may be arranged such that the spring  910  exerts a biasing force on the control rod  803  in a manner that depends on position of the control rod  803  as controlled by the actuator  801 . For example, the spring  910  may not exert a load (or exert a partial load) when the plug coupled to the control arm  844  is about to close (e.g., or in a closed position) and the spring  910  may exert an increased load with respect to increased stroke of the control rod  803 , for example, for opening the plug (e.g., opening a wastegate for wastegating). In such an example, the direction of force exerted by the spring  910  on the control rod  803  may act to pull a shaft coupled to the control arm  844  in an outward direction, for example, to minimize a gap or clearance. As an example, the spring  910  may, in a first state, allow for axial movement of a shaft coupled to the control arm  844  where such movement may facilitate centering of a plug, coupled to (e.g., optionally integrally) to the shaft, with respect to a wastegate seat of the turbine housing  810 . In such an example, the spring  910  may, in a second state, cause axial movement of the shaft outwardly, for example, to reduce a clearance (e.g., between a face of a bushing and a face of the shaft). 
       FIG. 9  shows an example of the control rod  803  of  FIG. 8  with respect to the spring  910 , which is an off-axis biasing mechanism in that its axis does not align with that of the control rod  803 . As an example, the spring  910  may be characterized at least in part by a spring constant k, for example, as in an equation F BM =−kx where x may be a length dimension or position of the spring  910 . As shown in the example of  FIG. 9 , an actuator force F A  may be applied to the control rod  803 , for example, as including a component along the axis of the control rod  803  (e.g., a primary component of actuator force). Also shown in the example of  FIG. 9  is a control arm force F CA  as associated with a control arm being operatively coupled to the coupler  805 . 
     As shown in the example of  FIG. 9 , one or more biasing mechanisms  910 ,  911  and  913  may be operatively coupled to the control rod  803  or a component operatively coupled to the control rod  803 . In such an example, the one or more biasing mechanisms  910 ,  911  and  913  may be off-axis and change in length responsive to movement of the control rod  803 . One or more off-axis biasing mechanisms (e.g., springs, etc.) may act to apply force to a control rod or a control linkage in a manner that depends on position of the control rod or the control linkage, for example, as controlled by an actuator that may control opening and/or closing of a wastegate valve (e.g., position of a wastegate plug with respect to a wastegate seat). 
       FIG. 10  shows an example of an assembly  1000  that includes an actuator  1001  operatively coupled to a control linkage  1003 . In the example of  FIG. 10 , the actuator  1001  is coupled to a compressor housing  1007  that is coupled to a center housing  1009  that is coupled to a turbine housing  1010  that includes a wastegate valve controllable via a control arm  1044  (e.g., via rotation of the control arm  1044 ). 
     A cutaway view shows the turbine housing  1010  as including a bore  1012 , a wastegate seat  1026 , a chamber  1030 , a bushing  1042  and a wastegate arm and plug  1050  that includes a shaft  1052  with a shaft end  1053 , an arm  1054  and a plug  1056 . 
     As shown in  FIG. 10 , the control linkage  1003  may experience deflections such as end deflection in a direction β 1  and end deflection in a direction β 2 . As indicated in the cutaway view, the shaft  1052  may experience movement along its axis as well as angular movement that, for example, off-sets the axis of the shaft  1052  from an axis of the bore  1012  and/or an axis of the bushing  1042 . For example, tilting of the shaft  1052  may cause the shaft  1052  and/or the bushing  1042  to form points of contact that differ at portions of the shaft  1052  and/or the bushing  1042  with respect to the bushing  1042  and/or the bore  1012 , respectively. 
       FIG. 11  shows cutaway views of portions of the assembly  1000  of  FIG. 10 , including a cutaway view along a line C-C. As shown in  FIG. 11 , a control arm  1044  may be operatively coupled to the control linkage  1003  via a peg  1046  and the peg  1046  may experience deflections such as end deflection in a direction α 1  and end deflection in a direction α 2 . Such deflections may be due to forces. As an example, one or more biasing mechanisms may be included in the assembly  1000  that can apply force to reduce one or more deflections, increase one or more deflections, etc. 
     As an example, one or more biasing mechanisms may act to firm-up a shaft of a wastegate valve, especially where the valve is in an open position. In such an example, the firming-up may act to reduce rattling, noise, exhaust leakage, etc. 
     As an example, an assembly may include clearances between parts in kinematics where, for example, the parts are operatively coupled to an actuator, a control linkage, etc. of a turbocharger. For example, a turbocharger assembly may include an electric actuator that actuates a rigid linkage component that is operatively coupled to one or more other components. As an example, one or more clearances may be provided for purposes of accommodating one or more misalignments that may stem from manufacturing of a component or components, thermal distortion, etc. One or more clearances may allow for movement that may lead to noise, wear, etc. As an example, one or more biasing mechanisms may be included in a turbocharger assembly that act to eliminate and/or damp movement (e.g., vibration damping, etc.). As an example, one or more biasing mechanisms may provide for “zero clearance” kinematics at one or more interfaces between components. 
     As an example, an assembly may include a spring (e.g., a coil spring, etc.) positioned outboard of a kinematics control system. In such an example, the coil spring may reduce axial and/or radial clearances in along a kinematic chain, for example, optionally with little to no effect on actuator calibration or in a manner that may be accounted for in actuator calibration. As an example, a spring may have a relatively constant stiffness (e.g., application of force) over a stroke range of an actuator with respect to a control linkage. 
     As an example, the assembly  800  of  FIG. 8  may include one or more features of an assembly such as the assembly  200  of  FIG. 2 , the assembly  300  of  FIG. 3 , etc. As an example, an assembly may include a biasing cam such as the biasing cam  400  and may include a biasing mechanism such as the spring  910 . For example, an assembly may include multiple mechanisms that may act to exert a biasing force on a shaft of a wastegate where the biasing force may depend on rotational orientation of the shaft about an axis of the shaft where rotational orientation may determine whether a wastegate is in a closed state or an open state. 
     As an example, an assembly may include multiple biasing features. As an example, an assembly may include multiple springs. In such an example, a control rod or a control linkage may include features for coupling one or more springs to the control rod or the control linkage, for example, to exert a biasing force to the control rod or the control linkage that acts to move a shaft operatively coupled to a wastegate plug, optionally in a manner where the biasing force varies depending on the position of the control rod or the control linkage (e.g., consider an axial position, as controlled via an actuator). As an example, in a cylindrical coordinate system with a z-axis defined along a control axis of a control rod or a control linkage, one or more springs may be operatively coupled to the control rod or the control linkage where such one or more springs extend at an angle (e.g., or angles). In such an example, the one or more springs may act to shift the z-axis in space, for example, in a manner that acts to move a shaft (e.g., in at least an axial direction along an axis of the shaft) that is operatively coupled to the control rod or the control linkage (e.g., via a control arm, etc.). In such an example, a shift may depend on position of the control rod or the control linkage as controlled by an actuator (e.g., for opening or closing a wastegate valve). 
     As an example, an actuator may include a linkage operatively coupled to a control arm and a biasing mechanism that is operatively coupled to the linkage and that is operatively coupled to one or more of a compressor assembly, a center housing assembly and a turbine assembly. In such an example, the linkage may be or include a rod. As an example, a linkage may include one or more components that may be configured for movement such as movement along an axis, for example, to control a control arm operatively coupled to a wastegate plug. 
     As an example, an assembly can include a turbine housing that includes a bore, a wastegate seat and a wastegate passage that extends to the wastegate seat; a bushing configured for receipt by the bore; a rotatable wastegate shaft configured for receipt by the bushing; a wastegate plug extending from the wastegate shaft; a control arm operatively coupled to the wastegate shaft; and a biasing cam operatively coupled to the control arm where the biasing cam includes a disengaged orientation associated with a closed position of the wastegate plug with respect to the wastegate seat and an engaged orientation associated with an open position of the wastegate plug with respect to the wastegate seat. In such an example, the disengaged orientation may include an axial clearance for axial movement of the wastegate shaft with respect to the bushing and/or the engaged orientation may include a zero axial clearance for axial movement of the wastegate shaft with respect to the bushing. 
     As an example, an axial clearance of a disengaged orientation may provide for self-centering of a wastegate plug with respect to a wastegate seat. As an example, a zero axial clearance may provide for reduction in noise (e.g., rattling of one or more components). 
     As an example, a biasing cam may include a base and at least one biasing member that extends from the base. As an example, a bushing may include at least one feature where the disengaged orientation of the biasing cam orients at least one biasing member with respect to the at least one feature. 
     As an example, a bushing may include a recess, a biasing cam may include a biasing member and a disengaged orientation and/or an engaged orientation may be defined with respect to the recess and the biasing member. 
     As an example, a wastegate shaft and a wastegate plug may be a unitary component (e.g., optionally including an arm disposed between the shaft and the plug). 
     As an example, a wastegate seat may include a profile defined in part by a cone. In such an example, a wastegate plug may include a profile defined at least in part by a portion of a torus for contacting the profile of the wastegate seat defined in part by the cone. 
     As an example, a method may include providing an assembly that includes a turbine housing that includes a bore, a wastegate seat and a wastegate passage that extends to the wastegate seat; a bushing configured for receipt by the bore; a rotatable wastegate shaft configured for receipt by the bushing; a wastegate plug extending from the wastegate shaft; a control arm operatively coupled to the wastegate shaft; and a biasing cam operatively coupled to the control arm; rotating the control arm; and, responsive to rotating the control arm, engaging the biasing cam for application of a biasing force to the wastegate shaft that reduces an axial clearance associated with the wastegate shaft. In such an example, the engaging the biasing cam may include rotating a biasing member of the biasing cam with respect to recess of the bushing. 
     As an example, the aforementioned method may include rotating the control arm in an opposite rotational direction and, responsive to the rotating in the opposite rotational direction, disengaging the biasing cam. In such an example, the disengaging the biasing cam may include rotating a biasing member of the biasing cam with respect to a recess of the bushing. In such an example, the method may include receiving the biasing member by the recess to provide an axial clearance between at least a portion of the biasing member and a surface of the recess. 
     As an example, a turbocharger may include a compressor assembly; a center housing assembly; and a turbine assembly that includes a biasing cam operatively coupled to a control arm that controls position of a wastegate plug with respect to a wastegate seat where the biasing cam includes a disengaged orientation associated with a closed position of the wastegate plug with respect to the wastegate seat and an engaged orientation associated with an open position of the wastegate plug with respect to the wastegate seat. Such a turbocharger may include, as an example, a bushing disposed in a bore of a turbine housing and a wastegate shaft disposed at least partially in the bushing where the control arm is operatively coupled to the wastegate shaft. In such an example, the bushing may include a recess and the biasing cam may include a biasing member where disengaged and engaged orientations of the biasing cam may be defined with respect to the recess and the biasing member. 
     As an example, a turbocharger may include an actuator that includes a linkage operatively coupled to the control arm. As an example, a turbocharger may include an actuator that includes a linkage operatively coupled to a control arm and a biasing mechanism that is operatively coupled to the linkage and that is operatively coupled to one or more of a compressor assembly, a center housing assembly and a turbine assembly of the turbocharger. 
     As an example, an assembly can include a turbine housing that includes a bore, a wastegate seat and a wastegate passage that extends to the wastegate seat; a bushing configured for receipt by the bore; a rotatable wastegate shaft configured for receipt by the bushing; a wastegate plug extending from the wastegate shaft; a control arm operatively coupled to the wastegate shaft; a control linkage operatively coupled to the control arm where the control linkage includes a control axis; an actuator operatively coupled to the control linkage for translation of the control linkage in a direction of the control axis; and a biasing mechanism operatively coupled to the control linkage where the biasing mechanism can apply an off-axis force to the control linkage. In such an example, the biasing mechanism may be or include a spring (e.g., a coil spring, etc.). 
     As an example, an assembly may include a compressor housing that includes a bracket where a biasing mechanism is operatively coupled to the bracket. As an example, a control linkage may include a notch, an opening or other feature that may, for example, provide for coupling of a biasing mechanism to the control linkage. As an example, an assembly may include one or more biasing mechanisms that may apply off-axis force(s) to a control linkage. As an example, such an assembly may further include a biasing cam, for example, operatively coupled to a wastegate shaft. 
     As an example, in an assembly, translation of a control linkage in a direction of a control axis may position a wastegate plug in an open state with respect to a wastegate seat and translation of the control linkage in another direction of the control axis may position the wastegate plug in a closed state with respect to the wastegate seat. As an example, a control linkage may be biased to position a wastegate plug in a closed state with respect to a wastegate seat where, for example, an actuator may overcome a biasing force to position the wastegate plug in an open state with respect to the wastegate seat. 
     As an example, an assembly may include a center housing and/or a compressor housing. As an example, an assembly may include a bracket mounted to (e.g., directly and/or indirectly) at least one of a turbine housing, a center housing and a compressor housing where, for example, a biasing mechanism or biasing mechanisms may be operatively coupled to the bracket. As an example, an assembly may include multiple brackets, connection points, etc. for coupling of a biasing mechanism that also couples to a control linkage (e.g., or control linkages). 
     As an example, a control linkage may be or include a control rod. As an example, an assembly may include a peg that extends from a control arm where a control linkage is operatively coupled to the peg. In such an example, the control linkage may include a coupler (e.g., a fitting) that receives the peg (e.g., via an opening, a recess, etc.). 
     As an example, an actuator may be or include an electric actuator. As an example, such an actuator may include an electric motor, an inductor, etc. 
     As an example, a turbocharger can include a compressor assembly; a center housing assembly; a turbine assembly that includes a control arm that controls position of a wastegate plug with respect to a wastegate seat; a control linkage operatively coupled to the control arm; an actuator operatively coupled to the control linkage for translation of the control linkage along a control linkage axis; and a biasing mechanism operatively coupled to the control linkage where the biasing mechanism can apply an off-axis force to the control linkage. In such an example, the biasing mechanism may be or include a spring. As an example, a turbocharger may include a bracket mounted to at least one of a compressor assembly, a center housing assembly and a turbine assembly where a biasing mechanism is operatively coupled to the bracket. In such an example, the biasing mechanism may be or include a coil spring. 
     Although some examples of methods, devices, systems, arrangements, etc., have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the example embodiments disclosed are not limiting, but are capable of numerous rearrangements, modifications and substitutions.