Turbocharger with variable vane turbine nozzle

Abstract

A variable nozzle turbocharger includes: a variable vane mechanism having an annular nozzle ring supporting an array of rotatable vanes; an insert having a nozzle portion axially spaced from the nozzle ring; and a plurality of spacers connected between the nozzle portion of the insert and the nozzle ring to maintain an axial spacing between the nozzle portion of the insert and the nozzle ring. The spacers are structured and arranged to mechanically prevent the vanes from rotating in one direction beyond a maximum open position and to mechanically prevent the vanes from rotating in an opposite direction beyond a minimum open position of the vanes.

Description

Technical Field

[0001] The present invention relates to a turbocharger having a variable nozzle turbine in which a movable vane array is arranged in the nozzle of the turbine for regulating the exhaust gas flow into the turbine. Background Art

[0002] An exhaust-driven turbocharger is a device that is used in conjunction with an internal combustion engine to increase the power output of the engine by compressing air delivered to the air intake of the engine for mixing with fuel and burning in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and there is also another center housing connected between the turbine housing and the compressor housing for accommodating the bearings of 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 leading 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. Thus, the turbine 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] One challenge in improving engine performance with the aid of a turbocharger is achieving a desired amount of engine power output throughout the engine's operating range. It has been found that this is often not easily achieved with a fixed geometry turbocharger, and therefore variable geometry turbochargers have been employed with the goal of providing a greater degree of control over the amount of boost provided by the turbocharger.

[0004] One type of variable geometry turbocharger is a variable nozzle turbocharger (VNT), which includes a variable vane array in the turbine nozzle. The vanes are rotatably mounted to a nozzle ring that forms one wall of the nozzle. The opposing wall of the nozzle is formed by an insert that fits into a space defined in the turbine housing. The axial spacing between the nozzle ring and the insert is maintained by several spacers connected between these parts. The vanes are connected to a mechanism that enables the setting angle of the vanes to be changed. Changing the setting angle of the vanes has the effect of changing the effective flow area in the turbine nozzle, and thus the flow of exhaust gas to the turbine wheel can be adjusted by controlling the vane position. In this way, the power output of the turbine can be adjusted, which allows the engine power output to be controlled to a greater extent than is usually possible with a fixed geometry turbocharger.

[0005] The present disclosure relates to improvements in variable nozzle turbines of the type described above. Summary of the invention

[0006] The present disclosure describes a variable nozzle turbocharger with a variable nozzle turbine in which a plurality of spacers are employed to space the nozzle ring from the insert. According to the present invention, the spacers act as an additional role of hard stops that limit the rotatable travel of the vanes in the opening and closing directions, thereby eliminating the need for separate hard stop components (e.g., pins, etc.). In one embodiment described herein, the turbocharger includes:

[0007] a turbine assembly 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 chamber surrounding the turbine wheel for receiving exhaust gas and supplying the exhaust gas to the turbine wheel, the turbine assembly defining a nozzle opening generally radially inwardly from the chamber toward the turbine wheel;

[0008] a compressor assembly including a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith;

[0009] a center housing connected between the compressor housing and the turbine housing;

[0010] a variable vane assembly including a generally annular nozzle ring and an array of vanes spaced circumferentially about the nozzle ring and disposed in a nozzle such that exhaust gas flows between the vanes to the turbine wheel, each vane rotatably mounted to the nozzle ring and connected to a rotatable actuator ring such that rotation of the actuator ring rotates the vane to adjust exhaust gas flow to the turbine wheel;

[0011] an insert disposed in the turbine housing, the insert defining a nozzle portion axially spaced from the nozzle ring such that the vanes extend between the nozzle ring and the nozzle portion; and

[0012] a plurality of spacers connected between the nozzle portion of the insert and the nozzle ring to maintain an axial spacing between the nozzle portion of the insert and the nozzle ring;

[0013] Wherein the spacer is structured and arranged to mechanically prevent the vane from rotating in one direction beyond a maximum open position and to mechanically prevent the vane from rotating in an opposite direction beyond a minimum open position.

[0014] In some embodiments of the invention, each vane is coupled to a shaft that passes through a bearing hole in the nozzle ring, wherein an end of each shaft protrudes from the bearing hole at a second face of the nozzle ring opposite the first face and is coupled to a vane arm. The vane arm engages the actuator ring such that rotation of the actuator ring causes the vane arm to pivot about the shaft and thereby rotate the vane. According to the embodiment, at least one of the spacers has an extension that protrudes from the second face of the nozzle ring and is structured and arranged to be abutted by one of the vane arms to mechanically prevent the vane from rotating in the one direction beyond the maximum open position.

[0015] Optionally, a plurality of the spacers may have extensions that protrude from the second face of the nozzle ring and are structured and arranged to be respectively abutted by a plurality of the vane arms to mechanically prevent rotation of the vanes in the one direction beyond the maximum open position.

[0016] In an embodiment of the invention, at least one of the spacers is structured and arranged to be abutted by one of the blades to mechanically prevent the blade from rotating in the opposite direction beyond the minimum open position. Alternatively, a plurality of the spacers may be structured and arranged to be abutted by a plurality of the blades, respectively, to mechanically prevent the blade from rotating in the opposite direction beyond the minimum open position. In such embodiments, one of the spacers may be structured and arranged to be abutted by another of the blades to mechanically prevent the blade from rotating in the one direction beyond the maximum open position. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Having thus generally described the invention, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0018] Figure 1 is a cross-sectional view of a turbocharger according to one embodiment of the present invention;

[0019] Figure 2 is an isometric view of a variable vane assembly for a turbocharger according to one embodiment of the present invention, viewed from the vane side of the assembly, the variable vane assembly being shown with the vanes in a minimum open position;

[0020] Figure 3 yes Figure 2 an isometric view of a variable vane assembly viewed from an opposite side of the assembly;

[0021] Figure 4 is similar to Figure 2 Isometric view of , but with the blades in the maximum open position;

[0022] Figure 5 is similar to Figure 3 Isometric view of , but with the blades in the maximum open position;

[0023] Figure 6 is a plan view of a variable vane assembly according to another embodiment of the present invention as viewed from the vane side of the assembly, wherein the vanes are shown in a minimum open position; and

[0024] Figure 7 yes Figure 6 A plan view of the component viewed from opposite sides of the component;

[0025] Figure 8 Show Figure 6 a variable vane assembly, but the vanes are in a maximum open position when viewed from the vane side of the assembly; and

[0026] Fig. 9 Show Figure 6 The variable vane assembly of the present invention is shown with the vanes in a maximum open position when viewed from the opposite side of the assembly. DETAILED DESCRIPTION

[0027] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the invention are shown. Indeed, these inventions may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Throughout the text, like reference numerals refer to like elements.

[0028] A turbocharger 10 according to one embodiment of the present invention is shown in cross-sectional view. Figure 1 The turbocharger includes a compressor 12 having a compressor wheel or impeller 14 mounted in a compressor housing 16 on one end of a rotatable shaft 18. The shaft is supported in bearings 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 a compressor inlet and delivers the compressed air to the intake of an internal combustion engine (not shown) for enhancing the performance of the engine.

[0029] The turbocharger also includes a turbine housing 24 that houses a turbine wheel 22. The turbine housing defines a generally annular chamber 26 that surrounds the turbine wheel and receives exhaust gas from the internal combustion engine for driving the turbine wheel. The exhaust gas is directed generally radially inward from the chamber 26 through a turbine nozzle 28 to the turbine wheel 22. As the exhaust gas flows through passages between blades 30 of the turbine wheel, the gas expands to a lower pressure, and the gas discharged from the wheel exits the turbine housing through a generally axial hole 32 therein.

[0030] Reference now Figures 2 to 5 , which depicts a subassembly of a turbocharger including a variable vane assembly for a turbine nozzle 28 for varying the cross-sectional flow area through the nozzle, thereby regulating the flow into the turbine wheel. The assembly includes a plurality of vanes 34 spaced circumferentially around the nozzle. Each vane is attached to a shaft 36 that passes through a hole in a generally annular nozzle ring 38, which is mounted coaxially relative to the turbine wheel 22. Each shaft 36 is rotatable about its axis to rotate the attached vane. The nozzle ring 38 forms one wall of the flow passage of the nozzle 28. Each of the shafts 36 has a vane arm 40 attached to the end of the shaft that protrudes from the nozzle ring 38. The vane arm 40 is engaged by a generally annular unison ring 42 (also referred to herein as an actuator ring), which is rotatable about its axis and coaxial with the nozzle ring 38. A guide 39 mounted on the nozzle ring 38 engages the inner periphery of the unison ring for guiding its rotational movement so that it remains substantially concentric with the nozzle ring and prevents the unison ring from moving in an axial direction away from the nozzle ring. An actuator (not shown) is connected to the unison ring 42 to rotate it about its axis. When the unison ring rotates, the vane arms 40 rotate to cause the shaft 36 to rotate about its axis, thereby rotating the vanes 34 to change the cross-sectional flow area through the nozzle 28.

[0031] In the illustrated embodiment, the variable vane mechanism is provided in the form of a unit 50 that can be installed in and removed from the turbocharger. The unit 50 includes the nozzle ring 38, the vanes 34, the shaft 36, the vane arms 40, and the unison ring 42. The unit is connected to an insert 52 ( Figure 1 The insert defines a nozzle portion 56 that is axially spaced from the nozzle ring 38 such that the vanes 34 extend between the nozzle ring 38 and the nozzle portion 56.

[0032] The turbocharger includes a heat shield 80 ( Figure 1), when the variable vane unit 50 is installed in the turbocharger, the heat shield 80 is securely held between the nozzle ring 38 and the center housing 20. The heat shield 80 provides a seal between the nozzle ring and the center housing to prevent hot exhaust gas from migrating between these components into the cavity in which the vane arms 40 and the unison ring 42 are located. The heat shield 80 is advantageously a resilient elastic material, such as spring steel or the like, and the shield is configured so that it is compressed in the axial direction between the nozzle ring 38 and the center housing 20 so that the restoring force of the shield axially pushes the nozzle ring 38 toward the turbine wheel 22 (at Figure 1 center, right).

[0033] A plurality of spacers 60 are mounted to the nozzle ring 38 and project toward the nozzle portion 56 of the insert 52. The ends of the spacers 60 abut the nozzle portion 56 (urged by the resilient heat shield 80 described in the previous paragraph) in order to maintain the desired axial spacing between the nozzle portion 56 of the insert and the nozzle ring 38. Thus, the spacers help ensure that a small axial gap exists between the ends of the blades 34 and the nozzle ring 38 (on one end) and the nozzle portion 56 (on the other end). The axial spacing set by the spacers 60 is designed to ensure that those gaps do not become too small (which could result in binding of the blades) or too large (which could compromise turbine efficiency).

[0034] refer to Figure 2 and Figure 3 According to an embodiment of the present invention, the spacer 60 not only serves to set the axial spacing between the nozzle ring 38 and the insert nozzle portion 56, but also acts as a hard stop for the vane assembly to limit how far the closure vane 34 can move. Figure 2 and Figure 3 The vanes 34 are shown in a minimum open position, which is set by certain vanes 34 of adjacent spacers 60. More particularly, the spacers are constructed and positioned relative to the vanes so that the desired minimum open position is achieved when the vanes of each of the adjacent three spacers 60 are rotated by the unison ring 42 until the vanes abut against the adjacent spacer.

[0035] refer to Figure 4 and Figure 5 , the spacers 60 are also used to set the maximum open position of the vanes 34. Each spacer includes an extension 60E that projects from the face of the nozzle ring 38 adjacent to the vane arms 40. The spacers are constructed and positioned so that the extension 60E sets the maximum open position of the vanes when the vane arm 40 adjacent each extension 60E is rotated by the unison ring until it abuts against the extension.

[0036] Thus, the spacer 60 is a multi-tasking component that allows the variable vane unit 50 to be simplified in terms of the number of parts and the number of manufacturing and assembly steps. Since the spacer acts not only as a spacer, but also as a hard stop for the vane mechanism, the hard stop pins typically required to limit the travel of the vanes, and the manufacturing and assembly steps associated with their use, are eliminated.

[0037] Figure 2-5 The embodiment of the invention shown in and described above is only an example of one possible way to practice the invention. The invention is not limited to the details of the embodiment described, but can be practiced in many different ways. As another example, Figures 6 to 9 A second embodiment of a variable blade unit 50' according to the present invention is shown. In the second embodiment, the spacer 60' acts only on the blade 34 and not on the blade arm 40. Therefore, referring to Figure 6 To set the minimum open vane position, one of the three spacers is positioned so that the desired minimum open position is achieved when the vane 34 adjacent to the spacer is rotated by the unison ring 42 until the vane abuts the spacer. The other two spacers do not contribute to setting the minimum open position.

[0038] refer to Figure 8 To set the maximum open position, the other two spacers 60' are positioned so that the desired maximum open position is achieved when the vanes 34 of each of the two adjacent spacers are rotated by the unison ring 42 until the vanes abut the adjacent spacers.

[0039] Other variations of using multi-tasking spacers as hard stops for the blade mechanism are also possible within the scope of the present invention. Any given spacer can act as a hard stop for the blade or blade arm for either the minimum open position or the maximum open position. However, not every spacer can act as a hard stop.

[0040] Therefore, having the benefit of the teachings presented in the foregoing description and the associated drawings, those skilled in the art to which these inventions pertain will think of many modifications and other embodiments of the inventions set forth herein. Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A turbocharger having a variable nozzle turbine, comprising: a turbine assembly 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 chamber surrounding the turbine wheel for receiving and supplying exhaust gas to the turbine wheel, the turbine assembly defining a nozzle opening generally radially inwardly from the chamber toward the turbine wheel; a compressor assembly including a compressor housing and a compressor wheel 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; a variable vane assembly including a generally annular nozzle ring and an array of vanes adjacent a first face of the nozzle ring and spaced circumferentially about the nozzle ring, the vanes disposed in the nozzle such that exhaust gas flows between the vanes to the turbine wheel, each vane rotatably mounted to the nozzle ring and connected to a rotatable actuator ring such that rotation of the actuator ring rotates the vanes to regulate exhaust gas flow to the turbine wheel; an insert disposed in the turbine housing, the insert defining a nozzle portion axially spaced from the first face of the nozzle ring such that the vanes extend between the nozzle ring and the nozzle portion; as well as a plurality of spacers connected between the nozzle portion of the insert and the nozzle ring to maintain axial spacing between the nozzle portion of the insert and the nozzle ring, wherein the spacers are structured and arranged to mechanically inhibit rotation of the vanes in one direction beyond a maximum open position and mechanically inhibit rotation of the vanes in an opposite direction beyond a minimum open position.

2. The turbocharger according to claim 1, wherein: Each vane is coupled to a shaft that passes through a bearing hole in the nozzle ring, wherein an end of each shaft protrudes from the bearing hole at a second face of the nozzle ring opposite the first face and is coupled to a vane arm, wherein the vane arm engages the actuator ring such that rotation of the actuator ring causes the vane arm to pivot about the shaft and thereby rotate the vane, and wherein at least one of the spacers has an extension that protrudes from the second face of the nozzle ring and is structured and arranged to be abutted by one of the vane arms so as to mechanically prevent the vane from rotating in the one direction beyond the maximum open position.

3. The turbocharger according to claim 2, wherein: One or more of the spacers have extensions that project from the second face of the nozzle ring and are structured and arranged to be respectively abutted by one or more of the vane arms to mechanically prevent the vanes from rotating in the one direction beyond the maximum open position.

4. The turbocharger according to claim 1, wherein: At least one of the spacers is structured and arranged to be abutted by one of the vanes so as to mechanically inhibit rotation of the vane in the opposite direction beyond the minimum open position.

5. The turbocharger according to claim 4, wherein: A plurality of the spacers are structured and arranged to be respectively abutted by a plurality of the vanes so as to mechanically prevent the vanes from rotating in the opposite direction beyond the minimum open position.

6. The turbocharger according to claim 4, wherein: One of the spacers is structured and arranged to be abutted by another of the vanes so as to mechanically prevent the vanes from rotating in the one direction beyond the maximum open position.

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