VNT flow calibration adjustment

An exemplary variable geometry turbine includes a turbine wheel; a variable geometry assembly that includes a rotatable control ring that has a slot and a plurality of vanes where each vane has a post pivotably controlled by rotation of the control ring and where adjacent vanes define nozzles to direct exhaust gas to the turbine wheel; a crankshaft that has a pin for receipt by the slot of the control ring where rotation of the crankshaft rotates the control ring; and a center housing that includes a rotatable stop fixed to the crankshaft and having a close stop surface, a secure component and a translatable shaft where the translatable shaft comprises an engagement mechanism to engage the rotatable stop; where translation of the shaft causes rotation of the crankshaft and where the close stop surface establishes a contact with the secure component to limit rotation of the crankshaft and to establish a closed limit for the vanes. Various other exemplary methods, devices, systems, etc., are also disclosed.

FIELD OF THE INVENTION

Subject matter disclosed herein relates generally to turbochargers with variable geometry mechanisms, for example, to adjust flow of exhaust to a turbine.

BACKGROUND

Exhaust gas driven turbochargers include a rotating shaft carrying a turbine wheel and a compressor wheel, which is rotatably supported within a center housing by one or more bearings. During operation, exhaust gas from an internal combustion engine drives a turbocharger's turbine wheel, which, in turn, drives the compressor wheel to boost charge air to the internal combustion engine.

For increased performance (e.g., power, emissions, etc.), some turbochargers include a variable geometry mechanism positioned in an exhaust flow path to a turbine wheel. The terms variable nozzle turbine (VNT) and variable geometry turbine (VGT) are often used to refer to such a mechanism. A VNT typically includes pivotable vanes where each vane has a pair of surfaces extending from a leading edge to a trailing edge where a surface of one vane and a surface of an adjacent vane form a nozzle. As the vanes pivot, the nozzles change shape. In other words, as the vanes pivot, the geometry of the nozzles varies.

A VNT operates in a harsh and changing environment. Exhaust temperatures cycle with operating conditions (e.g., acceleration, deceleration, demand, etc.) and may exceed 500° C. A variable geometry mechanism should be robust and capable of handling environmental and operational conditions. A robust mechanism should be capable of controlling geometry precisely; in a manner that does not vary significantly from unit to unit. Various exemplary methods, devices, systems, etc., described herein pertain to variable geometry mechanisms with improved control and durability.

DETAILED DESCRIPTION

Various exemplary methods, devices, systems, arrangements, etc., disclosed herein address issues related to technology associated with turbochargers. Turbochargers are frequently utilized to increase the output of an internal combustion engine. A turbocharger generally acts to extract energy from the exhaust gas and to provide energy to intake air, which may be combined with fuel to form combustion gas.

Referring toFIG. 1, a prior art system100, including an internal combustion engine110and a turbocharger120is shown. The internal combustion engine110includes an engine block118housing one or more combustion chambers that operatively drive a shaft112. As shown inFIG. 1, an intake port114provides a flow path for air to the engine block118while an exhaust port116provides a flow path for exhaust from the engine block118. A heat exchanger or cooler119may be positioned to cool air prior to entering the engine110.

The turbocharger120acts 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 inFIG. 1, the turbocharger120includes an air inlet134, a shaft122, a compressor124, a turbine126, a housing128and an exhaust outlet136. The housing128may be referred to as a center housing as it is disposed between the compressor124and the turbine126. The shaft122may be a shaft assembly that includes a variety of components.

A variable geometry unit130and a variable geometry controller140allow for control of vanes, nozzles, etc., as explained in the Background section. The variable geometry unit130and the variable geometry controller140optionally include features such as those associated with commercially available variable geometry turbochargers (VGTs). Commercially available VGTs include, for example, the GARRETT® VNT™ and AVNT™ turbochargers, which use multiple adjustable vanes to control the flow of exhaust across a turbine. An exemplary turbocharger may employ wastegate technology as an alternative or in addition to variable geometry technology.

As described herein, an exemplary mechanism allows for precise control of a variable geometry unit. Precise flow control or adjustment is desirable to reduce unit to unit variation and to provide a more repeatable product. In the context ofFIG. 1, a repeatable product facilitates an engine manufacturer's ability to achieve an emissions target.

More specifically, an exemplary mechanism includes an arrangement of components that limits travel of a crankshaft that actuates a variable geometry mechanism. In a particular example, the mechanism includes a stop and setscrew that limit travel of a crankshaft. Such components can be optionally implemented in conjunction with a conventional cam/gear arrangement of a conventional variable geometry unit.

The aforementioned AVNT mechanism typically does not have an adjustable flow setting. Instead, such an AVNT relies on vane tabs bottoming in unison ring slots, an arrangement that stacks-up a series of components. According to an exemplary stop and setscrew arrangement, by stopping rotation at the cam/gear, the number of components in the stack-up is reduced. This can reduce unit to unit variation. Another benefit of stopping travel at the cam/gear is that the components downstream of the stop do not have to withstand full actuator torque, which can reduce component wear.

FIG. 2shows an exemplary mechanism200in conjunction with various conventional variable geometry components. An exemplary center housing280houses various components for actuating a variable geometry assembly300that includes a plurality of vanes302oriented with respect to a turbine wheel260.

The center housing280includes a shaft bore282configured to receive a turbocharger shaft (e.g., shaft122of the turbocharger120ofFIG. 1), a crankshaft bore284configured to receive a crankshaft342for actuating a variable geometry assembly300, and a piston cylinder286to receive a piston shaft362and a piston head364.

The center housing280also includes fluid ports288and a fluid port controller290that includes a connector292for receiving power and control signals. A control signal can cause the fluid port controller290to allow fluid to flow in the center housing280. For example, such an arrangement can cause fluid to flow to the piston cylinder286where pressure causes movement of the piston head364and the attached piston shaft362. In turn, translation of the piston shaft362causes the crankshaft342, via an engagement mechanism, to rotate and actuate the variable geometry assembly300. In the example ofFIG. 2, rotation of the crankshaft342causes a lever arm and pin344to actuate the variable geometry assembly300. With respect to position feedback, a sensor (see, e.g.,FIG. 3) may be positioned in the opening294of the center housing280.

While not shown inFIG. 2, a turbine housing is typically connected to the center housing280, for example, using multiple clamps secured by bolts. The turbine housing houses, at least in part, the turbine wheel260. Exhaust gas or other high energy gas supplying the turbocharger enters the turbine housing through an inlet and is distributed through the volume in the turbine housing for substantially radial entry into the turbine wheel through a circumferential nozzle array, as determined by the variable geometry assembly300.

With respect to the variable geometry assembly300, the vanes302reside between an upper ring304and a lower ring306. A post303extends from each of the vanes302to engage a lobed component310set in a control ring312. The control ring312further includes a slot314to receive the lever arm and pin344. Rotation of the crankshaft342causes movement of the lever arm and pin344in the slot314, which, in turn, causes rotation of the control ring312and pivoting of the vanes302about their respective posts303.

InFIG. 2, a subassembly340includes the crankshaft342, the lever arm and pin344, a setscrew346(or bolt), a nut347and a cam/gear/stop component350, which may be an integral component or an assembly of components. The subassembly340meshes with the piston shaft362via an engagement mechanism (e.g., a rack gear on the piston shaft362and gear teeth on the cam/gear/stop component350).

FIG. 3shows various components of the exemplary mechanism200ofFIG. 2in a cross-sectional view and in a perspective view. The perspective view shows the subassembly340, identifying a stop352, a cam354and gear teeth356of the component350. As explained, translational movement of the shaft362causes, via an engagement mechanism, rotation of the crankshaft342. The engagement mechanism may include gear teeth356that engage a rack gear363of the piston shaft362. In the example ofFIG. 3, rotation of the crankshaft342stops once a contact is established between the setscrew346and the stop352. In other words, the stop352may operate to stop clockwise and/or counter-clockwise rotation of the crankshaft342.

InFIG. 3, the center housing280includes a bore281configured to receive the setscrew346(or bolt) and the nut347. A cap283may be positioned to seal the bore281. The piston cylinder286is also shown as being sealed by an end cap285, noting that alternative arrangements are possible (e.g., piston ring seal, etc.). The center housing280is also shown as having a sensor297positioned in the opening294. In this example, the sensor297includes a shaft298that seats against a surface of the cam354such that rotation of the cam354causes movement of the shaft298. In turn, a control signal emanates from the sensor297via a control line299.

As an alternative, translational movement of the shaft362may be limited or stopped by contact between the piston head364and the end cap285. Further, the end cap285may be adjustable with respect to the piston cylinder286to thereby allow for adjustment of the stop position of the shaft362and, correspondingly, the crankshaft342. For example, the exemplary mechanism200ofFIG. 3may rely on the component350to stop rotation of the crankshaft342in one direction and rely on the end cap285to stop rotation of the crankshaft342in an opposite direction. As configured in the example ofFIG. 3, such a mechanism can have a close stop defined by a contact between the component350(rotational stop) and the setscrew346(or bolt) and an open stop defined by a contact between the piston head364and the end cap285(translational stop). Hence, an exemplary mechanism may include a rotational stop mechanism and a translational stop mechanism.

FIG. 4shows a perspective view of the exemplary component500in a cylindrical coordinate system with coordinate x, r and θ. The component500rotates plus or minus degrees θ about the x-axis.

The component500includes a stop520, a cam540and an engagement mechanism560. The stop520includes a surface522that is substantially a portion of an outer surface of a cylinder (e.g., disposed at a radius that may vary with respect to θ). The surface522meets a “close stop” surface523that extends toward the x-axis from an outer radius (R2) to an inner radius (R1). In the example ofFIG. 4, the close stop surface523has an axial width Δxs. The close stop surface523then meets another surface that includes an “open stop” surface524. As mentioned with respect toFIG. 3, the piston364can form a contact with the end cap285to act as an “open stop” to stop rotation of the crankshaft342. As described herein, an exemplary assembly may rely on a surface of a rotating component or the surface of a translating component to define an open stop for a variable geometry mechanism (e.g., the vanes302ofFIG. 2).

As shown inFIG. 4, upon clockwise rotation of the component500, the close stop surface523contacts a secured component420(e.g., the setscrew346); whereas upon counter-clockwise rotation, the open stop surface524contacts the secured component420.

The close stop surface523contacts the secured component420at an angle γ (e.g., which may be 0 or some other angle). Similarly, the open stop surface524may contact the secured component420at an angle.

As indicated, the close stop surface523and the open stop surface524are configured to allow for a particular range of motion, expressed as angle θ. The range of motion may be determined in part by the position of the secured component420. For example, as shown inFIG. 3, the setscrew346(or bolt) may be adjusted (e.g., via the nut347). In operation, the secured component420and the stop520bear the force of actuation when the vanes are adjusted to a closed limit (e.g., the end of the secured component420and the surface523) or to an open limit (e.g., a side portion of the secured component420and the surface524).

The secured component420may be a bolt having sufficiently durable material properties. The secured component420may be set firmly in the center housing. The stop520may have sufficiently durable material properties as well.

The exemplary component500shifts torque and corresponding wear away from components of the variable geometry assembly300(downstream) and brings the torque and corresponding wear closer to the source of actuation (e.g., upstream, in a center housing).

FIG. 4also shows various aspects of the cam540. In particular, the cam540includes an outer surface542disposed at a radius that increases to Rmaxat an angle θ about the x-axis. Upon rotation of the cam540, the outer surface542can cause the plunger or shaft of a sensor to translate in a manner related to the rotational position of a crankshaft.

In the example ofFIG. 4, the stop520includes a substantially flat surface526disposed in an r-θ plane an axial distance from a substantially flat surface544of the cam540, also disposed in an r-θ plane. The component500may be an integral component or separate components. For example, the stop520and the cam540may be separate components mounted on a common crankshaft. The stop520and the cam540may be mounted adjacent to each other or they may be separated by some axial distance.

As shown inFIG. 4, the component500includes an aperture to receive a crankshaft. Further, depending on the configuration of the component500, one or more setscrews may be used to secure the component to a crankshaft. For example, the stop520may be welded (or otherwise bonded) to the cam540. In such an example, the cam540may have an aperture configured to receive a setscrew to secure the cam540and the stop520to a crankshaft.

While various examples show gear teeth and a rack gear as an engagement mechanism, other engagement mechanisms may be used. In general, an engagement mechanism provides for rotation of a stop, which may be connected to, or integral to, a cam.

As described herein, a stop for limiting rotation of a crankshaft for adjusting geometry of a variable geometry turbine includes an aperture for receiving the crankshaft where the crankshaft has a rotational axis and wherein the aperture is centered on the rotational axis, and a close stop surface extending from a first radius from the rotational axis to a second radius from the rotational axis, the close stop surface having a width in the axial direction where the close stop surface establishes a contact with a secured component set in a center housing of a turbocharger to limit rotation of the crankshaft and, correspondingly, to establish a close position for the variable geometry turbine. Such a stop optionally includes a cam. For example, the cam can include an aperture for receiving the crankshaft where the aperture is centered on the rotational axis of the crankshaft.

An exemplary stop optionally includes an open stop surface that establishes a contact with a secured component set in a center housing of a turbocharger to limit rotation of a crankshaft and, correspondingly, to establish an open position for a variable geometry turbine.

In an example that includes a close stop surface and an open stop surface, an angle θ exists between the close stop surface and the open stop surface upon establishment of their respective contacts with a secured component. In such an example, adjustment of the secured component alters the angle θ.

As described herein, a variable geometry turbine includes a turbine wheel, a variable geometry assembly that includes a rotatable control ring that has a slot and a plurality of vanes where each vane has a post pivotably controlled by rotation of the control ring and where adjacent vanes define nozzles to direct exhaust gas to the turbine wheel, a crankshaft that has a pin for receipt by the slot of the control ring where rotation of the crankshaft rotates the control ring and a center housing that includes a rotatable stop fixed to the crankshaft and having a close stop surface, a secure component and a translatable shaft where the translatable shaft has an engagement mechanism to engage the rotatable stop, where translation of the shaft causes rotation of the crankshaft and where the close stop surface establishes a contact with the secure component to limit rotation of the crankshaft and to establish a closed limit for the vanes.

The aforementioned variable geometry turbine optionally includes a cam fixed to the crankshaft where the cam cooperates with a vane position sensor.

An exemplary variable geometry turbine optionally includes an open stop surface that establishes a contact with a secured component to limit rotation of a crankshaft and to establish an open limit for vanes. In an example that includes a close stop surface and an open stop surface, an angle θ exists between the close stop surface and the open stop surface upon establishment of their respective contacts with a secured component. In general, adjustment of the secured component alters the angle θ.

An exemplary method includes actuating a variable geometry turbine controller to arrive at a close position, in response to the actuating, rotating a stop fixed to a crankshaft positioned in a center housing of the variable geometry turbine and, in response to the rotating, contacting the stop and a secure component set in the center housing to stop the rotation of the crankshaft and to arrive at the close position of the variable geometry turbine.

An exemplary method may include actuating a variable geometry turbine controller to arrive at an open position, in response to the actuating, rotating a stop fixed to a crankshaft positioned in a center housing of the variable geometry turbine and, in response to the rotating, contacting the stop and a secure component set in the center housing to stop the rotation of the crankshaft and to arrive at the open position of the variable geometry turbine.

In various methods, rotating can include rotating a cam fixed to the crankshaft. Such an example may include sensing the position of the cam.

An exemplary method may include adjusting the position of the secured component to thereby alter the close position. For example, such adjusting may be to target an emission standard.

An exemplary method can include contacting between a stop and a secured component that prevents downstream components of a variable geometry turbine from experiencing torque and associated wear.

An exemplary method can include actuating that occurs in response to an operational condition of an internal combustion engine.