Patent Application
20170044925
1. Field of the Invention
The present invention relates to a turbocharger in which the turbine stage includes a variable nozzle.
2. Description of Related Art
A turbocharger is a type of forced induction system used with internal combustion engines. Turbochargers deliver compressed air to an engine intake, allowing more fuel to be combusted, thus boosting an engine's horsepower without significantly increasing engine weight. Thus, turbochargers permit the use of smaller engines that develop the same amount of horsepower as larger, normally aspirated engines. Using a smaller engine in a vehicle has the desired effect of decreasing the mass of the vehicle, increasing performance, and enhancing fuel economy. Moreover, the use of turbochargers permits more complete combustion of the fuel delivered to the engine, which contributes to the highly desirable goal of a cleaner environment.
Turbochargers typically include a turbine housing connected to the engine's exhaust manifold, a center bearing housing, and a compressor housing connected to the engine's intake manifold. A turbine wheel in the turbine housing is rotatably driven by an inflow of exhaust gas supplied from the exhaust manifold. A shaft rotatably supported in the center bearing housing connects the turbine wheel to a compressor impeller in the compressor housing so that rotation of the turbine wheel causes rotation of the compressor impeller. As the compressor impeller rotates, it increases the air mass flow rate, airflow density and air pressure delivered to the engine's cylinders via the engine's intake manifold. It is often advantageous to regulate the exhaust gas flowing to the turbine wheel to improve efficiency, responsiveness or the operating range of the turbocharger.
In some aspects, a variable geometry turbine includes a turbine housing that defines a fluid inlet, a fluid outlet, and a volute that receives fluid from the fluid inlet. The turbine includes a turbine wheel disposed in the turbine housing between the volute and the fluid outlet and configured to rotate about an axis, and a radially-extending nozzle that directs fluid from the volute to the turbine wheel. The nozzle is defined between a working surface of an adjustable nozzle ring and a facing surface of the turbine housing. An inner peripheral edge of the nozzle ring is movable in an axial direction relative to an outer peripheral edge of the nozzle ring, whereby the nozzle dimensions can be varied.
The variable geometry turbine includes one or more of the following features: The nozzle ring is movable between a first configuration in which the working surface is parallel to the facing surface, and a second position in which the working surface is angled relative to the facing surface. An angle of the working surface relative to the facing surface is variable. When the working surface is angled relative to the facing surface, the nozzle axial dimension decreases from the volute to the turbine wheel. The nozzle ring is configured to be elastically deformable in a direction parallel to the axis such that the nozzle dimensions can be varied. The outer peripheral edge of the nozzle ring engages the turbine housing. The nozzle ring includes radially extending slots that extend outward from the inner peripheral edge. The nozzle ring is an annular plate and includes a body and a rim formed about the outer periphery of the body, and wherein the rim is connected to the body via a step, whereby the rim is offset relative to the body, and the slots extend from the inner peripheral edge to the step. The working surface is free of surface features. The working surface includes surface features configured to affect fluid flow paths through the nozzle. The turbine includes an actuating ring disposed on a side of the nozzle ring opposed to the working surface, and the actuating ring is configured to change the configuration of the nozzle ring. The nozzle ring includes an actuating surface that is opposed to the working surface, and the actuating surface includes nozzle ring protrusions that are configured to engage corresponding actuating ring protrusions provided on the actuating ring. The actuating ring is rotatable relative to the nozzle ring, and the nozzle ring is configured such that rotation of the actuating ring causes the actuating ring protrusions to engage with the nozzle ring protrusions in a manner such that the working surface is deflected. The nozzle ring includes an annular frame and radially-extending segments that are connected to the frame via a hinge. The segments are shaped and dimensioned so that a first side edge of one segment overlaps a second side edge of an adjacent segment.
In some aspects, an exhaust gas turbocharger includes a compressor section including a compressor wheel; a turbine section including a turbine housing and a turbine wheel disposed in the turbine housing; and a shaft that connects the compressor wheel to the turbine wheel and defines an axis. The turbine housing defines a fluid inlet, a fluid outlet, and a volute that receives fluid from the fluid inlet. The turbine wheel is disposed in the turbine housing between the volute and the fluid outlet. In addition, a radially-extending nozzle is defined between a working surface of an adjustable nozzle ring and a facing surface of the turbine housing, and the nozzle directs fluid from the volute to the turbine wheel. An inner peripheral edge of the nozzle ring is movable in an axial direction relative to an outer peripheral edge of the nozzle ring, whereby the nozzle dimensions can be varied.
In some aspects, a turbocharger turbine includes a variable nozzle. In particular, the turbine includes a nozzle that extends radially relative to a rotational axis of the turbine wheel and is defined between a nozzle assembly and a facing surface of the turbine housing. The nozzle assembly includes an annular nozzle ring, and the shape of the nozzle ring is adjustable, whereby the nozzle width can be varied. This feature permits regulation the exhaust gas flowing to the turbine wheel to improve efficiency, responsiveness or the operating range of the turbocharger independently of the engine exhaust flow rate. By varying the shape of the nozzle ring, the shape and size of the nozzle are also varied in such a way that fluid flow into the turbine wheel is uninterrupted and includes a mixed-flow component (i.e., includes an axially-directed component). The mixed flow component aids the transition of fluid flow from circumferentially-directed flow within the volute to the axially-directed flow at the exit of the turbine wheel. This nozzle configuration is advantageous relative to some conventional devices that regulate the exhaust gas flowing to the turbine wheel such as Variable Geometry Turbines (VGT).
VGT turbochargers include a plurality of adjustable guide vanes pivotally supported by a vane support ring within a wheel inlet leading to the turbine wheel. The space between adjacent guide vanes constitutes flow channels for the exhaust gas flowing to the turbine wheel and the geometry of the flow channels is adjustable by adjusting the guide vanes within a pre-determined range of angular positions between an open position and a closed position. In order to provide a high boost pressure at low engine speeds, the guide vanes are adjusted to constrict the flow channels between adjacent guide vanes. This results in the exhaust gas moving through the flow channels at a high speed. The increased kinetic energy of the exhaust gas is transferred to the turbine wheel, increasing the turbine wheel rotational speed and thus the boost pressure. At high engine speeds, the guide vanes are adjusted to open up the flow channels between adjacent guide vanes. This results in the exhaust gas impacting the turbine wheel at a lower speed, thus decreasing the turbine wheel rotational speed and thus the boost pressure.
Typical VGT guide vanes pivot or slide between a pair of vane rings which must be precisely machined and controlled to limit exhaust gas leakage. Efficiency losses in VGT systems are characterized by leakage between the guide vanes and the vane rings, boundary layer effects along the vane rings, boundary layer effects along the guide vane surfaces, and fluid flow blockage by spacers disposed between the vane rings. In addition, it can be difficult to control the clearance to the guide vanes at turbocharger operating temperatures due to thermal expansion of the materials used to form the guide vanes, vane rings, and spacers. For this reason, clearances, and therefore losses, are relatively large to ensure proper function of the VGT system, and relatively expensive materials and processes are used to form these components.
The variable nozzle including the nozzle ring advantageously creates a pressure/velocity gradient by varying the shape of the nozzle ring, and thus varying the shape and size of the diffuser nozzle, with no components permanently protruding into the fluid flow. As the variable nozzle is moved from an open position to a closed position, the nozzle not only imparts a pressure gradient, and also influences the fluid flow direction with an axial vector directed towards the turbine exit.
The variable nozzle has reduced complexity and mass as compared to some conventional VGT systems that include movable vanes. The relative reduction in complexity results in a turbocharger that is less expensive and more reliable than some conventional VGT systems. In addition, the relative reduction in mass results in improved fuel economy and a reduced thermal mass. The reduced thermal mass permits the turbocharger to come to operating temperatures in less time, which can in turn reduce engine emissions in cold start situations.
Advantages of the variable geometry turbine will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to
The compressor section 3 includes a compressor housing 12 that defines the air inlet 16, an air outlet 18, and a compressor volute 14. A compressor wheel 5 is disposed in the compressor housing 12 between the air inlet 16 and the compressor volute 14. The compressor wheel 5 is connected to a shaft 6. The shaft 6 connects the turbine wheel 4 to the compressor wheel 5. The shaft 6 is supported for rotation about a rotational axis R within the bearing housing 8 via bearings (not shown).
In use, the turbine wheel 4 in the turbine housing 11 is rotatably driven by an inflow of exhaust gas supplied from the exhaust manifold 15a of an engine 15. Since the shaft 6 connects the turbine wheel 4 to the compressor wheel 5 in the compressor housing 12, the rotation of the turbine wheel 4 causes rotation of the compressor wheel 5. As the compressor wheel 5 rotates, it increases the air mass flow rate, airflow density and air pressure delivered to the engine's cylinders via an outflow from the compressor air outlet 18, which is connected to the engine's air intake manifold 15b.
Referring to
The nozzle assembly 30 includes an annular nozzle ring 32 and an annular actuating ring 82 that is disposed parallel to, and nested with, the nozzle ring 32. The shape of the nozzle ring 32 is adjustable via the actuating ring 82, whereby the shape and axial width of the nozzle 20 can be varied, as discussed further below.
Referring also to
The nozzle ring 32 includes an axially outward-facing working surface 34, and an opposed, axially inward-facing actuating surface 36. The working surface 34 faces, and is axially spaced apart from, the facing surface 11b of the turbine housing 11. In addition, the working surface 34 is generally free of surface features. The nozzle ring 32 includes radially extending slots 48 that extend axially between the working surface 34 and the actuating surface 36 such that the slots 48 pass through the thickness of the body 42. In addition, the slots 48 extend radially between the inner peripheral edge 40 and the step 44. The slots 48 segregate the body 42 into discrete segments 50. The width of the slots 48 (e.g., the spacing between the segments 50) is minimized to minimize exhaust gas leakage therethrough.
The nozzle ring actuating surface 36 faces the actuating ring 82, and includes axially-extending protrusions 54 that protrude toward the actuating ring 82 (
The nozzle ring 32 may be formed, for example, by stamping, and may be formed of a spring steel or high temperature alloy such as Inconel 718. The protrusions 54 may be formed integrally with the body 42, or alternatively may be formed separately and connected to the actuating surface 36 by conventional methods such as brazing or welding.
The actuating ring 82 includes an outer peripheral edge 88, an inner peripheral edge 90 that is concentric with the outer peripheral edge 88, and an axially-extending flange 94 that is formed integrally with the inner peripheral edge 90. The actuating ring 82 also includes radially-inward protruding drive pins 98 arranged equidistantly apart about the radially-inward facing surface 96 of the flange 94. In particular, when the nozzle ring 32 is in an open position, each drive pin 98 is arranged adjacent a minimum height portion 62 of a corresponding ramp 58 of the nozzle ring 32.
Referring again to
Referring to
Referring to
In order to move the nozzle ring 32 toward the closed position, the actuating ring 82 is rotated, which in turn moves the drive pins 98 across the surface of the corresponding ramp 58 in a direction from the minimum height portion 62 toward the maximum height portion 60. As the drive pins 98 move across the surface of the corresponding ramp 58 in a direction from the minimum height portion 62 toward the maximum height portion 60, each individual nozzle ring segment 50 is urged axially toward the turbine housing facing surface 11b. Since the position of the nozzle ring outer peripheral edge 38 is fixed, movement of the drive pins 98 across the surfaces of the corresponding ramps 58 causes the nozzle ring body 42 and inner peripheral edge 40 to elastically deform, and thus deflect axially relative to the nozzle ring outer peripheral edge 38 toward the turbine housing facing surface 11b. In particular, the nozzle ring body 42 and inner peripheral edge 40 are axially displaced into the nozzle 20. The amount of axial displacement of the segments 50 is determined by the amount of rotation of the actuating ring 82.
Displacement of the segments 50 into the nozzle 20 results in a change in the shape of the nozzle 20. In particular, the axial width of the nozzle 20 is made to radially vary such that in some configurations, the nozzle width can be made greater adjacent the nozzle ring step 44 than the nozzle width adjacent the nozzle ring inner peripheral edge 40. For example, when the nozzle ring 32 is moved toward the closed position, the axial width of the nozzle 20 radially varies such that the nozzle width w1 is greater adjacent the nozzle ring step 44 than the nozzle width w2 adjacent the nozzle ring inner peripheral edge 40 (
The shape of the working surface 34 will depend on the stiffness properties of the material used to form the nozzle ring 32. For example, use of a relatively stiff material will result in a substantially linear radial variation in nozzle width and the working surface 34 being angled relative to the turbine housing facing surface 11b when viewed in cross-section (
In addition, when the nozzle ring 32 is moved toward the closed position, the direction of the exhaust gas flow through the nozzle 20 is changed by the shape of the nozzle ring 32 from a solely radial flow direction to a flow direction that includes both a radial component and an axial component. This mixed-direction exhaust gas flow aids the transition of the exhaust gas flow from radial flow to axial flow as it passes over the turbine wheel 4.
The nozzle assembly 30 including the nozzle ring 32 and actuating ring 82 thus permits control of the speed of the turbocharger 1 substantially independently of the engine exhaust flow rate. This is accomplished without insertion of flow-directing vanes into the exhaust gas flow path which may be associated with efficiency losses due to exhaust gas leakage, vane boundary layer effects, and gas flow blockage. In addition, due to its relatively simple structure, the nozzle ring 32 can more easily accommodate thermal growth and distortion that can occur at turbocharger operating temperatures than some conventional vanes, which require sufficient clearances to ensure proper vane pivoting function despite thermal growth, and thus introduce additional losses into the system.
When the actuator drives the actuating ring 82 to move the nozzle ring 32 toward the open position, rotation of the actuating ring 82 moves the drive pins 98 across the surface of the corresponding ramp 58 in a direction from the maximum height portion 60 toward the minimum height portion 62. As a result, due to the resilient properties of the material used to form the nozzle ring 32, each individual nozzle ring segment 50 returns to its unloaded configuration. Specifically, the nozzle ring body 42 and inner peripheral edge 40 retract from the nozzle 20 and move axially toward the actuating ring 82. In addition, the reaction force due to material elasticity that urges the segments 50 to return to the unloaded configuration may be aided by the pressure of the exhaust gas flow through the nozzle 20.
Because the nozzle ring 32 can be refracted from the nozzle 20, there are operating conditions in which there are minimal or no obstructions to exhaust gas flow within the nozzle 20. This is advantageous relative to some VGT systems in which the guide vanes remain in the exhaust gas flow path regardless of the operating position of the guide vanes.
Referring to
In this regard, the nozzle ring 132 includes the annular frame 133, the segments 150, and a wire loop 148 that serves as the hinge pin for each segment 150. The frame 133 includes a radially extending portion that defines a rim 136. When assembled in the turbocharger 1, the rim 136 is clamped between the turbine housing portion 11a and the flange 8a of the bearing housing 8, whereby the position of the annular frame 133 is fixed relative to the turbine housing 11.
An inner peripheral edge 142 of the rim 136 includes a step 138 that extends axially and terminates in circumferentially-spaced rim knuckles 140. In some embodiments, the rim knuckles 140 are formed by folding portions of the step 138 back on itself.
Each segment 150 is a flat plate, and when seen in top plan view (
Each segment 150 includes an axially outward-facing segment working surface 154, and an opposed, axially inward-facing segment actuating surface 156. The segment working surface 154 faces, and is axially spaced apart from, the facing surface 11b of the turbine housing 11. In addition, the segment working surface 154 is generally free of surface features. The segment actuating surface 156 faces the actuating ring 82, and includes an axially-extending protrusion 54 that protrudes toward the actuating ring 82. The protrusion 54 is positioned closer to the inner peripheral edge 160 than to the outer peripheral edge 158. As in the previous embodiment, the free end of each protrusion 54 is angled to form a ramp 58 that cooperates with a corresponding pin 98 of the actuating ring 82 to change the configuration of the nozzle ring 32. When the segments 150 are assembled with the frame 133, the protrusions 54 are arranged so that the respective ramps 58 generally lie on a circle (not shown) that is concentric with the segment inner peripheral edge 160, with a maximum height portion 60 of a given ramp 58a facing a minimum height portion 62 of an adjacent ramp 58b.
In the nozzle ring 132, the segments 150 are arranged about the rim inner peripheral edge 142 so that a first side edge 162a of one segment 150a abuts the second side edge 164b of an adjacent segment 150b (
The shape and axial width of the nozzle 20 can be varied by controlling the relative positions of the nozzle ring 132 and the actuating ring 82. The rotational orientation of the nozzle ring 132 is fixed, and rotational orientation of the actuating ring 82 is controlled by the actuator as described above. Thus, rotational movement of the actuating ring 82 causes the nozzle ring 132 to change between an “open” position in which the working surface 134 and the turbine housing facing surface 11b are parallel and the nozzle 20 has a maximum volume, and a “closed” position in which a portion of the nozzle ring working surface 134 adjacent the inner peripheral edge 40 is moved closer to the turbine housing facing surface 11b, as a result of movement of the actuating ring 82.
When the actuator drives the actuating ring 82 to move the nozzle ring 132 toward the closed position, rotation of the actuating ring 82 moves the drive pins 98 across the surface of the corresponding ramp 58 in a direction from the minimum height portion 62 toward the maximum height portion 60. As the drive pins 98 move across the surface of the corresponding ramp 58 in a direction from the minimum height portion 62 toward the maximum height portion 60, each individual nozzle ring segment 150 is urged axially toward the turbine housing facing surface 11b. Since the position of the nozzle ring frame 133 is fixed, movement of the drive pins 98 across the surfaces of the corresponding ramps 58 causes the segments 150 to pivot about the wire loop 148. In particular, the inner peripheral edge 160 of each segment 150 is axially displaced into the nozzle 20. The amount of axial displacement of the segments inner peripheral edge 160 is determined by the amount of rotation of the actuating ring 82. Displacement of the segments 150 into the nozzle 20 results in a change in the shape of the nozzle 20.
When the actuator drives the actuating ring 82 to move the nozzle ring 132 toward the open position, rotation of the actuating ring 82 moves the drive pins 98 across the surface of the corresponding ramp 58 in a direction from the maximum height portion 60 toward the minimum height portion 62, the pressure of the exhaust gas flow through the nozzle 20 urges the segments 150 to return to the unloaded configuration. In some embodiments, a spring (not shown) may also be provided to the nozzle assembly 30 to urge the segments 150 to return to the unloaded configuration.
Referring to
Although the variable nozzle 20 described above is used to direct fluid to a mixed-flow type turbine wheel 4, other types of turbine wheels can be used with the variable nozzle 20. For example, in some embodiments, the turbine section 2 can include a radial flow turbine wheel. In this regard, by using the nozzle assembly 30, 130 including the elastically deformable nozzle ring 32, 132, 232 a mixed flow of exhaust gas is directed into the turbine wheel 4, whereby a turbocharger that included a radial flow turbine wheel would provide advantages similar to that of one using a mixed-flow turbine wheel.
Although the nozzle ring 32 includes slots 48 that extend between the inner peripheral edge 40 to the step 44, the slots 48 are not limited to this configuration, and may be used to tune the stiffness properties of the nozzle ring 32. For example, the slots 48 are configured to intercept the inner peripheral edge 40 and extend radially outward in a range of 30 to 100 percent of the radial distance between the inner peripheral edge 40 and the step 44.
Although the nozzle ring working surface 34 is described above as being free of surface features, the nozzle ring working surface 34 is not limited to this configuration. For example, in some embodiments, the working surface 34 includes surface features configured to influence rotational movement or to straighten fluid flow through the turbine nozzle. The surface features may include, but are not limited to, grooves or ridges.
Although the actuating ring 82 includes the drive pins 98 that are fixed to the radially-inward facing surface 96 of the flange 94 via welding, brazing, press-fit or other methods, the actuating ring 82 is not limited to using drive pins 98, and other structures may be provided to deflect the nozzle ring protrusions 54. In one example, cam followers may be used instead of the drive pins 98. In another example, the flange 94 could be formed having deflected teeth that are integral with the actuating ring 82 and configured to engage the nozzle ring protrusions 54 during rotation of the actuating ring 82.
The linkage 110 has been described herein as including a particular arrangement of the first pin 112, the block 114, the pivot shaft 118, the pivot arm 120 and the ball joint 122. However, the linkage 110 is not limited to this configuration, and may be of any configuration and/or combination of linking elements and joints that transmit the motion of the actuator to the actuating ring 82.
In the embodiment illustrated above with respect to
The variable nozzle 20 including the nozzle assembly 30 has been described herein with respect to use in the exhaust gas turbocharger 1, but is not limited to this application. For example, the variable nozzle 20 including the nozzle assembly 30 may be used in other types of turbochargers, in other systems that include turbines such as, but not limited to, Rankine Cycle systems, and in non-automotive applications including, but not limited to, those in heavy industry.
Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, may be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.
This application claims priority to and all the benefits of U.S. Provisional Application No. 61/982,484, filed on Apr. 22, 2014, and entitled “Turbocharger Turbine With Variable Nozzle,” which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/024859 | 4/8/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61982484 | Apr 2014 | US |
