Turbocharger with a meridianally divided turbine housing and a variable turbine nozzle

Abstract

The present invention relates to a turbocharger having a meridionally divided turbine housing and a variable turbine nozzle. The turbocharger has a meridionally divided turbine housing defining a first vortex and a first nozzle and a second vortex and a second nozzle. The first and second nozzles are separated from each other by a shroud plate installed in the nozzles, which is used to isolate the exhaust gas flows flowing through the two nozzles from each other. A plurality of first blades are provided in the first nozzle, and a plurality of second blades are provided in the second nozzle. The nozzle ring rotatably supports a plurality of blade shafts extending across the first and second nozzles to pass through an opening in the shroud plate. The first blade and the second blade are fixed to each blade shaft. The rotation of the blade shaft causes the first blade and the second blade to pivot, which is used to adjust the two exhaust gas flows flowing through the first and second nozzles.

Description

Technical Field

[0001] The present invention relates to turbochargers in which a turbine of the turbocharger is driven by exhaust gases from a reciprocating engine. The invention more particularly relates to a turbine housing which is divided into a plurality of substantially separate sections each fed by a separate exhaust system. Background Art

[0002] An exhaust-driven turbocharger is a device used in conjunction with an internal combustion engine to increase the power output of the engine by compressing the air intake delivered to the engine to mix with fuel and burn in the engine. A turbocharger includes a compressor wheel at one end of a shaft mounted in a compressor housing and a turbine wheel at the other end of the shaft mounted in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and there is also another center housing between the turbine housing and the compressor housing for containing bearings for the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle that leads from the chamber to the turbine wheel. Exhaust gas flows from the chamber through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. The turbine thus extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through the inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

[0003] In multi-piston reciprocating engines, it is known to design the exhaust system in such a way as to exploit the pressure pulsations that occur in the exhaust gas flow. In particular, it is known to employ so-called "pulse separation", in which the cylinders of the engine are divided into a plurality of groups, and the pulses from each group of cylinders are substantially isolated from the pulses from the other groups by having a separate exhaust passage for each group. In order to best exploit pulse separation, it is desirable to minimize the communication or "crosstalk" between the separate groups of cylinders. Thus, in the case of a turbocharged engine, it is advantageous to always maintain separate exhaust passages into the turbine of the turbocharger. Thus, the turbine housing into which the exhaust gas is fed is typically divided into a plurality of substantially separate sections.

[0004] There are two basic ways to divide a turbine housing: (1) meridian division and (2) sector division. In a meridian-divided turbine housing, the vortex or chamber surrounding the turbine wheel and into which the exhaust gas is fed is divided into a plurality of passages in the meridian plane, such as that of U.S. Pat. No. 4,027,994. Figure 4 As shown in , each channel occupies approximately the entire circumference and the channels succeed each other in the axial direction.

[0005] In a sectored turbine casing, a generally annular chamber is divided into angular sectors, each of which occupies only a portion of the circumference, so that a turbine casing such as that of U.S. Pat. No. 6,260,358 Figure 2 As shown in , the channels succeed each other in the circumferential direction. The '358 patent also discloses fixed guide vanes located just radially inward from the chamber and directing the flow into the turbine wheel.

[0006] The present disclosure relates to a turbocharger having a meridianally divided turbine housing. The present disclosure also relates to a turbocharger having a variable turbine nozzle. Summary of the invention

[0007] The present disclosure describes an embodiment of a turbocharger having a variable nozzle turbine and also having a meridian-divided turbine housing. According to an embodiment of the present invention, the turbocharger comprises:

[0008] a turbine including a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing defining a vortex extending circumferentially and meridianally divided about the turbine wheel, the meridianally divided vortex defining a first vortex extending substantially completely about the turbine wheel and a separate second vortex extending substantially completely about the turbine wheel;

[0009] a turbine housing defining separate inlets for each of the first and second scrolls, receiving separate first and second exhaust gas flows through the separate inlets;

[0010] a nozzle that leads generally radially inwardly from the meridianally divided vortex to the turbine wheel;

[0011] a compressor including a compressor housing and a compressor impeller mounted in the compressor housing and connected to a rotatable shaft for rotation therewith;

[0012] a center housing connected between the compressor housing and the turbine housing and containing bearings for the shaft;

[0013] a generally annular nozzle ring having a first face including one wall of the nozzle and axially spaced from an opposing wall of the nozzle;

[0014] a shield plate installed in the nozzle, the shield plate dividing the nozzle into a first nozzle and a second nozzle along a meridian, the first nozzle receiving a first exhaust flow from the first vortex and the second nozzle receiving a second exhaust flow from the second vortex; and

[0015] A plurality of circumferentially spaced first vanes are provided in the first nozzle and a plurality of circumferentially spaced second vanes are provided in the second nozzle, the first and second vanes being rotatably mounted to the nozzle ring so that the setting angle is variable for adjusting the exhaust gas flow to the turbine wheel.

[0016] In one embodiment, a meridianally divided vortex of the turbine housing defines a partition wall that provides separation between a first exhaust flow in the first vortex and a second exhaust flow in the second vortex. A radially innermost edge of the partition wall is proximate to a radially outer edge of a shroud plate such that the shroud plate continues the separation between the first and second exhaust flows through the nozzle.

[0017] According to one embodiment, the nozzle ring defines a plurality of circumferentially spaced bearing holes, and the variable nozzle includes a plurality of vane shafts, which are respectively disposed in the bearing holes and are rotatable within the bearing holes about respective axes of the vane shafts. Each vane shaft has a first shaft portion fixed to one of the first vanes in the first nozzle, and has a second shaft portion extending through an opening in the shroud plate and fixed to one of the second vanes in the second nozzle. Thus, rotation of the vane shafts about their respective axes causes the first vane to pivot within the first nozzle and the second vane to pivot within the second nozzle. Thus, a single actuator can be used to pivot both sets of vanes in a simultaneous / synchronous manner.

[0018] The second shaft portion of the blade shaft may optionally protrude axially beyond the second blade and extend into a blind shaft receptacle defined in an opposing wall of the nozzle. In this way, the blade shaft can be supported at both ends. In one embodiment, the blind shaft receptacle is defined in an annular insert that is formed separately from the turbine housing and is disposed in an annular groove defined in the turbine housing.

[0019] A plurality of first spacers may be disposed between the nozzle ring and the shroud plate to control a first axial spacing between the first face of the nozzle ring and the shroud plate, and a plurality of second spacers may be disposed between the shroud plate and an opposing wall of the nozzle to control a second axial spacing between the shroud plate and the opposing wall of the nozzle.

[0020] In one embodiment, each of the first spacers includes a pin having a smaller diameter than the first spacer, the pin having a first portion protruding axially from one side of the first spacer toward the nozzle ring, and the nozzle ring defines a plurality of first receiving holes that respectively receive the first portions of the pins of the first spacers.

[0021] Each pin may also include a second portion protruding axially from an opposite side of the first spacer toward an opposite wall of the nozzle, the second portion of the pin passing through a pin receiving hole in the shield plate, and the opposite wall of the nozzle may define a plurality of second receiving holes that respectively receive ends of the second portions of the pins of the first spacer.

[0022] In one embodiment, the second spacer comprises sleeves having a larger diameter than the pins of the first spacer, each sleeve defining a central hole through which a respective one of the pins of the first spacer passes.

[0023] The opposing wall of the nozzle may be defined by an annular insert, and the turbine housing may define an annular recess in which the annular insert is disposed. The annular insert may define a second receiving aperture for the pin.

[0024] In one embodiment, the second receiving bore extends completely through the axial thickness of the annular insert, and the turbine housing defines a plurality of blind holes aligned with the second receiving bores and receiving the ends of the second portions of the pins. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Having generally described the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0026] Figure 1 is an axial cross-sectional view of a turbocharger according to one embodiment of the present invention;

[0027] Figure 2 yes Figure 1 A portion of a turbocharger, enlarged to illustrate a variable nozzle of the turbocharger;

[0028] Figure 3 It is along Figure 2 A cross-sectional view taken along line 3-3 in FIG.

[0029] Figure 4 It is along Figure 3 A cross-sectional view taken along line 4-4;

[0030] Figure 5 yes Figure 1 An isometric view of the turbine of a turbocharger in which the turbine housing and its annular insert are removed so that the variable nozzle is visible;

[0031] Figure 6 is an isometric view of the variable nozzle with the nozzle ring and annular turbine casing insert removed to illustrate details of the variable nozzle; and

[0032] Figure 7 is an isometric view of a variable nozzle with the nozzle ring, annular insert and shroud plate removed to show details of the variable nozzle. DETAILED DESCRIPTION

[0033] The present disclosure will now be described in more detail with reference to the above-mentioned figures, which depict some but not all embodiments of the inventions to which the present disclosure relates. These inventions may be implemented in various forms that may not be explicitly described herein, and should not be construed as being limited to the specific exemplary embodiments described herein. In the following description, the same reference numerals always refer to the same elements.

[0034] The present invention relates to a turbocharger comprising a variable nozzle turbine (VNT) wherein the variable nozzle comprises a row of pivotable vanes whose setting angle can be varied in order to adjust the flow of exhaust gas entering the turbine wheel. Figure 1 A VNT turbocharger 10 according to one embodiment of the invention is illustrated. The turbocharger includes a compressor wheel or impeller 14 disposed in a compressor housing 16 and mounted on one end of a rotatable shaft 18. The shaft is supported in a bearing 19 mounted in a center housing 20 of the turbocharger. The shaft 18 is rotated by a turbine wheel 22 mounted on the other end of the shaft 18 from the compressor wheel, thereby rotatably driving the compressor wheel, which compresses air drawn in through the compressor inlet and delivers the compressed air to a volute 17, which collects the compressed air for supply to the intake of an internal combustion engine (not shown) for improving the performance of the engine.

[0035] The turbocharger also includes a turbine housing 24 that houses the turbine wheel 22. As previously noted, in a reciprocating internal combustion engine having a plurality of cylinders, it is advantageous to design the exhaust system in such a way as to exploit the pressure pulsations that occur in the exhaust stream discharged from the cylinders. In particular, it is advantageous to employ so-called "pulse separation," in which the cylinders of the engine are divided into a plurality of groups, and the pulses from each group of cylinders are substantially isolated from the pulses from the other groups by having separate exhaust passages for each group. In order to best exploit pulse separation, it is desirable to minimize the communication or "crosstalk" between the separated cylinder groups. Thus, in the case of a turbocharged engine, it is advantageous to always maintain separate exhaust passages that enter the turbine of the turbocharger. Thus, the turbine housing 24 according to this embodiment of the invention defines a meridian-divided vortex 26 that surrounds the turbine wheel and receives exhaust gas from the internal combustion engine for driving the turbine wheel. In particular, the turbine housing defines the vortex into two completely separate first and second vortices 26a and 26b, each of which extends approximately 360 degrees around the turbine wheel 22. The turbine housing includes a dividing wall 24d that divides the vortex into two separate vortices. The turbine housing also includes two separate exhaust gas inlets for the meridian-divided vortex, one inlet directing a first exhaust gas flow from a first internal combustion engine cylinder group (not shown) into the first vortex 26a, and the other inlet directing a second exhaust gas flow from a second cylinder group (not shown) into the second vortex 26b. The two separate exhaust gas flows are directed generally radially inwardly from their respective vortices 26a and 26b through a turbine nozzle 28 to the turbine wheel 22. As the exhaust gas flows through the passages between the blades of the turbine wheel, the gas expands to a lower pressure, and the gas discharged from the wheel leaves the turbine housing through a generally axial hole 32 therein.

[0036] According to this embodiment of the invention, the turbine nozzle 28 is a variable nozzle for changing the cross-sectional flow area and flow direction through the nozzle to adjust the flow entering the turbine wheel. The variable nozzle according to the invention advantageously generally maintains the separation between the two exhaust gas flows until the exhaust gas flows impinge on the turbine wheel 22.

[0037] Reference now Figure 2, this separation of the exhaust flow in the nozzle 28 is achieved by providing a shroud plate SP, which includes an annular plate disposed within the turbine nozzle 28, wherein the central axis of the shroud plate is coaxial with the rotation axis of the turbine impeller 22. According to the illustrated embodiment of the present invention, the variable nozzle 28 is defined between an annular nozzle ring 38 mounted within the turbine housing 24 and an opposing wall formed by an annular insert 24i disposed in an annular groove 24r defined in the turbine housing. The shroud plate SP divides the turbine nozzle into a first nozzle 28a and a second nozzle 28b. The first nozzle 28a receives a first exhaust gas flow from the first vortex 26a and guides the gas into the turbine impeller; similarly, the second nozzle 28b receives a second exhaust gas flow from the second vortex 26b and guides the gas into the turbine impeller. The radial outer periphery of the shroud plate SP is as close as possible to the radial inner edge of the vortex partition wall 24d. The radial inner periphery of the shroud plate is as close as possible to the turbine impeller 22 so as to maintain the separation between the two exhaust gas flows substantially all the way to the turbine impeller.

[0038] The variable nozzle includes a plurality of first blades 34a positioned adjacent to a first face of a nozzle ring 38 and spaced circumferentially around a first nozzle 28a. The variable nozzle also includes a plurality of second blades 34b spaced circumferentially around a second nozzle 28b. Each first blade 34a is fixed to a first portion of a blade shaft 36 passing through a bearing hole 39 in a substantially annular nozzle ring 38. Each blade shaft 36 is rotatable about its axis in its bearing hole for rotating the attached blade. The first portion of each of the blade shafts 36 has a blade arm 40 fixed to the end of the blade shaft protruding from the second face of the nozzle ring 38, and is engaged by a substantially annular unison ring 42 (also referred to as an actuator ring) rotatable about its axis and coaxial with the nozzle ring 38. An actuator (not shown) is connected to the unison ring 42 for rotating it about its axis. When the unison ring rotates, the blade arms 40 rotate to rotate the blade shafts 36 about their axes, thereby rotating the first blades 34a, so as to change the cross-sectional flow area and flow direction through the first nozzle 28a.

[0039] like Figure 2 As shown, the second nozzle 28b includes a second vane 34b. In the illustrated embodiment, each vane shaft 36 has a second shaft portion that extends through an opening in the shroud plate SP and is fixed to one of the second vanes 34b in the second nozzle. Thus, rotation of the vane shaft 36 about its respective axis causes the first vane 34a to pivot within the first nozzle 28a and the second vane 34b to pivot within the second nozzle 28b in a simultaneous or synchronized manner. A single actuator (not shown) is capable of pivoting both sets of vanes.

[0040] In the illustrated embodiment of the present invention, the second shaft portion of the blade shaft 36 protrudes axially beyond the second blade 34b and extends into a blind shaft receptacle 44 defined in the opposite wall of the nozzle. In this way, the blade shaft is supported at both ends. As shown, the blind shaft receptacle may be defined in an annular insert 24i, which is formed separately from the turbine housing and is disposed in an annular groove 24r defined in the turbine housing. Alternatively, in another embodiment (not shown), the nozzle wall formed by the annular insert 24i may alternatively be formed by an integral portion of the turbine housing 24, in which case the shaft receptacle 44 may be defined in the turbine housing.

[0041] refer to Figures 4 to 6 , the variable nozzle according to the illustrated embodiment of the present invention includes a plurality of first spacers 50a disposed between the nozzle ring 38 and the shroud plate SP to control a first axial spacing between a first face of the nozzle ring and the shroud plate. Each of the first spacers 50a includes a pin 52 with a smaller diameter than the first spacer. The pin has a first portion that protrudes axially from one side of the first spacer toward the nozzle ring 38. The nozzle ring defines a plurality of first receiving holes 53 that respectively receive the first portions of the pins 52 of the first spacers.

[0042] The variable nozzle also includes a plurality of second spacers 50b disposed between the shroud plate SP and the opposing wall of the nozzle to control a second axial spacing between the shroud plate and the opposing wall of the nozzle. In the illustrated embodiment, the opposing wall of the nozzle is formed by the insert 24i. Each pin 52 also includes a second portion that protrudes axially from the opposite side of the first spacer 50a toward the insert 24i. The second portion of the pin 52 passes through the pin receiving hole in the shroud plate, and the insert 24i defines a plurality of second receiving holes 54 that respectively receive the ends of the second portion of the pin of the first spacer. In the illustrated embodiment, the second spacer 50b includes a sleeve with a larger diameter than the pin 52 of the first spacer, each sleeve defining a central hole through which a corresponding one of the pins 52 of the first spacer passes.

[0043] In the illustrated embodiment, the second receiving bore 54 extends completely through the axial thickness of the annular insert 24 i , and the turbine housing 24 defines a plurality of blind holes 56 that align with the second receiving bore 54 and receive the distal ends of the second portions of the pins 52 .

[0044] In the illustrated embodiment, Figure 3 As shown, the opening in the shroud plate for the blade shaft 36 comprises a slot 37 extending all the way to the radially inner periphery of the shroud plate SP. Advantageously, each blade shaft 36 and its associated first blade 34a and second blade 34b comprise an integral, one-piece structure, and the axial spacing between the first and second blades is slightly greater than the thickness of the shroud plate. Figure 3 and 4The slot 37 then facilitates assembly of the variable nozzle by allowing a portion of the vane shaft 36 between the first and second vanes to be inserted into the open end of the slot 37 and to slide radially outward to the closed end of the slot, wherein the first and second vanes 34a, b are disposed on opposite sides of the shroud plate. The pin 52 for the first spacer 50a is inserted through the pin receiving opening in the shroud plate, and the second spacer 50b is sleeved on the pin. The first portion of the vane shaft 36 can then be inserted into the bearing hole 39 in the nozzle ring 38 ( Figure 2 ), and the spacer pin 52 can be inserted into the first receiving hole 53 in the nozzle ring ( Figure 4 ). The second portion of the blade shaft 36 can be inserted into the blind shaft receptacle 44 in the insert 24i while simultaneously inserting the spacer pin 52 through the second receiving hole 54 in the insert 24i. The subassembly can then be assembled with the turbine housing 24 by installing the insert 24i into the recess 24r in the turbine housing to ensure that the ends of the spacer pin 52 protruding from the opposite side of the insert 24i fit into the blind holes 56 in the turbine housing 24 ( Figure 4 The ends of the vane shafts 36 that protrude from the opposite sides of the nozzle ring 38 can then be secured to the vane arms 40 ( Figure 7 ), and the unison ring 42 can engage with the vane arm to complete the assembly of the variable nozzle.

[0045] It will be appreciated by those skilled in the art based on the present disclosure that variations and other embodiments of the invention described herein can be made without departing from the inventive concepts described herein. For example, although the illustrated embodiment has first and second nozzles 28a and 28b of equal axial width, alternatively, the two nozzles may have different widths. Additionally or alternatively, although the first blade 34a is illustrated as having the same configuration as the second blade 34b, alternatively, the first blade may be different from the second blade in configuration, such as having different airfoil shapes and / or different setting angles. Other variations are possible in the practice of the present invention. The specific terms used herein are for illustrative purposes rather than restrictive purposes. Therefore, the present invention should not be limited to the specific embodiments disclosed, and variations and other embodiments should be included within the scope of the appended claims.

Claims

1. A turbocharger having a meridian-split variable nozzle turbine, comprising: a turbine including a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing defining a vortex extending circumferentially and meridianally divided about the turbine wheel, the meridianally divided vortex defining a first vortex extending completely about the turbine wheel and a separate second vortex extending completely about the turbine wheel; The turbine housing defines a separate inlet for each of the first and second scrolls, receiving separate first and second exhaust gas flows through the separate inlets; a nozzle leading radially inwardly from the meridian-divided vortex to the turbine wheel; a compressor including a compressor housing and a compressor impeller mounted in the compressor housing and connected to the rotatable shaft for rotation therewith; a center housing connected between the compressor housing and the turbine housing and containing bearings for the shaft; an annular nozzle ring having a first face including one wall of the nozzle and axially spaced from an opposing wall of the nozzle; a shield plate installed in the nozzle, the shield plate dividing the nozzle into a first nozzle and a second nozzle along a meridian, the first nozzle receiving the first exhaust flow from the first vortex, and the second nozzle receiving the second exhaust flow from the second vortex; and A plurality of circumferentially spaced first vanes are provided in the first nozzle and a plurality of circumferentially spaced second vanes are provided in the second nozzle, the first and second vanes being rotatably mounted to the nozzle ring so that a setting angle is variable for adjusting exhaust gas flow to the turbine wheel.

2. The turbocharger according to claim 1, wherein: The meridianally divided vortex of the turbine housing defines a partition wall that provides separation between the first exhaust flow in the first vortex and the second exhaust flow in the second vortex, and wherein a radially innermost edge of the partition wall is proximate a radially outer edge of the shroud plate such that the shroud plate continues the separation between the first and second exhaust flows through the nozzle.

3. The turbocharger according to claim 1, wherein: The nozzle ring defines a plurality of circumferentially spaced bearing holes and further includes a plurality of vane shafts, each of which is disposed in the bearing holes and is rotatable within the bearing holes about a respective axis of the vane shaft, each vane shaft having a first shaft portion fixed to one of the first vanes in the first nozzle and having a second shaft portion extending through an opening in the shroud plate and fixed to one of the second vanes in the second nozzle, such that rotation of the vane shaft about its respective axis causes the first vane to pivot within the first nozzle and causes the second vane to pivot within the second nozzle.

4. The turbocharger according to claim 3, wherein: The second shaft portion of the vane shaft projects axially out of the second vane and extends into a blind shaft receptacle defined in an opposing wall of the nozzle.

5. The turbocharger according to claim 4, wherein: The blind shaft receptacle is defined in an annular insert formed separately from the turbine housing and disposed in an annular groove defined in the turbine housing.

6. The turbocharger according to claim 1, further comprising: a plurality of first spacers disposed between the nozzle ring and the shroud plate to control a first axial spacing between the first face of the nozzle ring and the shroud plate; and a plurality of second spacers disposed between the shroud plate and the opposing wall of the nozzle to control a second axial spacing between the shroud plate and the opposing wall of the nozzle.

7. The turbocharger according to claim 6, wherein: Each of the first spacers includes a pin having a smaller diameter than the first spacer, the pin having a first portion axially protruding from a side of the first spacer toward the nozzle ring, and wherein the nozzle ring defines a plurality of first receiving holes that respectively receive the first portions of the pins of the first spacers.

8. The turbocharger according to claim 7, wherein: The pin also includes a second portion that protrudes axially from an opposite side of the first spacer toward an opposite wall of the nozzle, the second portion of the pin passes through the pin receiving hole in the guard plate, and wherein the opposite wall of the nozzle defines a plurality of second receiving holes that respectively receive ends of the second portion of the pin of the first spacer.

9. The turbocharger according to claim 8, wherein: The second spacer includes sleeves having a larger diameter than the pins of the first spacer, each sleeve defining a central hole through which a corresponding one of the pins of the first spacer passes.

10. The turbocharger according to claim 8, wherein: The opposing wall of the nozzle is defined by an annular insert, and the turbine housing defines an annular groove in which the annular insert is disposed, and wherein the annular insert defines the second receiving aperture for the pin.

11. The turbocharger according to claim 10, wherein: The second receiving bore extends completely through an axial thickness of the annular insert, and wherein the turbine housing defines a plurality of blind holes aligned with the second receiving bore and receiving a distal end of the second portion of the pin.

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