WO2004025088A1

WO2004025088A1 - Slide vane turbocharger

Info

Publication number: WO2004025088A1
Application number: PCT/GB2003/003980
Authority: WO
Inventors: Edwin Richard Deacon
Original assignee: Honeywell Uk Limited
Priority date: 2002-09-12
Filing date: 2003-09-12
Publication date: 2004-03-25
Also published as: GB2392956A; AU2003264764A1; GB0221199D0

Abstract

A turbocharger comprising: a turbine housing having an inlet passage for receiving exhaust gas from an exhaust manifold of an internal combustion engine and an exhaust outlet for the gas: a turbine wheel mounted in the turbine housing, the turbine wheel being connected to a shaft extending from the turbine housing through a shaft bore via a bearing to a compressor impeller; a piston, arranged coaxial with the turbine wheel and movable parallel to the shaft of the turbine wheel; a plurality of vanes extending substantially parallel to the shaft from a first end of the piston across the inlet passage and moveable to control the flow of exhaust gas to the turbine wheel; and an actuator connected to the piston, the actuator comprising a pivotally mounted lever having a lever end engaging in a cut-out in the piston, wherein the lever end has at least one curved edge. Such a turbocharger is relatively efficient, reliable and cost effective.

Description

SLIDE NANE TURBOCHARGER

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to variable geometry turbochargers and particularly to turbochargers having variable nozzle inlets controlled by vanes.

Description of the Related Art:

Nariable geometry nozzle inlets are employed in turbochargers to increase performance and aerodynamic efficiency.

A variable geometry turbocharger may be of the piston (also known as sliding vane) type described in US 5214920 and US 5231831 and US 5441383. In these systems vanes are mounted on a cylindrical piston, or to an opposing nozzle wall, and the piston moves concentric with the axis of rotation of the turbine so that the vanes progressively close the gap between the piston and the wall and reduce the area of the nozzle inlet. Nariable geometry devices are advantageous in that they are potentially fully modulating, being infinitely adjustable throughout their operating ranges. Full flow passes through the turbine at all times and so the engine back pressure is greatly reduced or eliminated.

An actuator is used to control movement of the piston. This may take the form of a pivoted lever connected to the piston.

It is an object of the invention to provide a sliding vane turbocharger with a more efficient, reliable, and relatively cost effective actuator.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a turbocharger comprising a turbine housing having an inlet passage, for receiving exhaust gas from an internal combustion engine, and an exhaust outlet for the gas, a turbine wheel, mounted on a shaft for rotation in the turbine housing, a piston movable parallel to the shaft of the turbine wheel for controlling the flow of exhaust gas to the turbine wheel and an actuator for moving the piston, the actuator comprising a lever pivotally mounted and having a lever end which engages the piston at a surface which curves toward the lever.

Preferably the lever end has curved edges around its circumference which engages a side surface of a cut-out in the piston. These edges may curve with a radius of curvature such as to trace or subtend an imaginery ball or sphere in three dimensions. The line of curvature is cross- section lies in a plane with the lever and the side surface of the cut-out is substantially tangential to the curved surface of the lever end.

The lever may be bifurcated with a curved lever end on each tine.

A plurality of vanes may extend parallel to the shaft from an end of the piston across the inlet passage to control the gas flow and the piston may be coaxial with the shaft and concentrically surround the turbine wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a cross sectional view of a turbocharger showing one embodiment of the invention, with the piston in the open position in the upper part of the figure and with the piston in the closed position in the lower part of the figure.

Figure 2 is an enlarged view of a part of the turbocharger of figure 1. Figures 3 and 4 are cross sections of part of the turbocharger of figure 1 taken generally along the line 111-111.

Figure 5 is a more detailed view of the part of figure 2, shown as a cross-section of figure 4, along line N-N.

Figure 6 is a further enlarged view of figure 2.

Figure 7 is a further enlarged view of part of figure 2 taken orthogonally to figure 6.

DETAILED DESCRIPTION OF THE INVENTION

The figures are various cross-sectional views of a turbine forming part of a turbocharger of the variable geometry piston type, such as is described in detail in WO 01/53679. A turbine housing 1 is shown with an integral discharge outlet 2. Exhaust gas from an exhaust manifold of an internal combustion engine (not shown) is provided to an inlet volute passage 3 in the turbine housing 1, passes through an inlet nozzle 17, expands in the turbine and exits via the outlet 2. The energy from the exhaust gas drives a turbine wheel 4 connected through a shaft 5 to a compressor (not shown) in known manner.

A variable geometry mechanism to control the exhaust gas flow is provided by a substantially cylindrical piston 6 received within the turbine housing 1 coaxially aligned with the rotational axis 30 of the turbine wheel 4. Vanes or blades 7 extend axially from a radial projection 8 at one end of the piston 6 concentric with the turbine wheel 4. These vanes 7 determine the area of the inlet nozzle 17 to the turbine wheel 4 from the inlet volute 3 and thus control the flow of exhaust gas from the engine into the turbine. The combination of the piston 6 and the vanes 7 form a vaned stator.

At the top of figure 1 the piston 6 is shown in a fully open position with maximum flow. At the bottom of figure 1 the piston 6 is in a closed position with minimum or zero flow. When the piston is in the closed position as shown in figure 2 then the vanes 7 slide into a recessed portion 10 in the housing 1, the depth of which provides a mechanical limit stop to prevent complete closure of the inlet nozzle 17.

A heat screen 12 is interposed between the turbine housing 1 and a central housing 13 (only a part of which is shown) connecting the turbine to the compressor (not shown). The screen 12 is of a suitable shape to extend into the cavity of the turbine housing from the interface between the central housing 13 and the turbine housing 1 and to provide a wall inside the intake nozzle of the turbine.

An oxidation resistant liner 11 reduces the friction surrounding the piston 6 to make it slide more easily.

In operation the turbine exhaust gases pass from the turbine housing scroll through the inlet volute 3 and a connecting passage into the turbine wheel 4 in known manner. The exhaust gas has a relatively high axial loading force which exerts pressure on the vanes 7 in the inlet nozzle 17 tending to push the vanes 7 into a more open position for the nozzle 17. The pressure exerted on the vanes 7 increases with engine load and speed and urges the vaned piston 6 to move in a direction to open the nozzle 17 (to the right in the figures).

This movement is resisted and controlled as necessary by an actuator 20 connected to the piston 6 by means of a lever 21, the end 23 of which fits into a cut-out or recess 22 on the piston.

The lever end 24 of the actuator 20 has its edges curved as shown most clearly in figures 2, 3, 6 and 7. The radius of curvature is indicated in these figures by the broken line forming a circle 23 (which forms a sphere in 3D). The curving is toward the lever (21). The curved surface traces an arc which is effectively tangential to the surface of the piston which it engages, ie. the side wall of the cut-out 22. In this way the lever end only engages the piston over a small surface area at any time. This can reduce friction and wear.

The lever 21 is connected to a spindle and bush arrangement passing through the side wall of the turbine housing 1 as shown particularly in figure 5. A crank assembly is welded to the exterior of the spindle.

The crank assembly length is chosen relative to the effective length of the ball ended lever (21). The arrangement is therefore flexible inasmuch as the angular position of the crank assembly can be chosen to suit the predetermined location of the actuator. Also the degree of mechanical advantage of the system may be varied depending on the selected crank assembly length. The lever 21 is provided with sufficient space to be rotated to a position allowing installation and/or removal of the piston 6 without dismantling the turbine housing assembly. This is particularly useful for development testing and also for field service requirements. Assembly consists of inserting the piston 6 from the end of the central housing 13. The lever 21 is rotated to engage the socket of piston 6 in the process of insertion. The structure so formed does not impede exhaust gas leaving the turbine wheel, and also allows an integral discharge bend to be combined with the turbine housing casting. The arrangement is neat and axially short.

The interface contact plane between the ball end of lever 21 and the socket (cut-out) in the piston 6 is always normal to the turbocharger shaft axis. The forces imposed by the actuator on the vaned stator are therefore parallel to the shaft axis. When a bending couple is introduced tending to "cock" the vaned stator, the choice of an adequate length/diameter ratio to the vaned stator within the turbine housing bore ensures that "cocking" is minimal and jamming is not a consideration.

The lever 21 acts as an effective anti-rotation device for the vaned stator. Gas forces passing through the vaned stator blade passages tend to rotate the vaned stator if no anti-rotation device is incorporated. The vaned stator is designed such that the volute tail aligns (blends) with one of the vanes. Since the anti-rotation feature is an integral part of the turbine housing and vaned stator assembly, the turbine housing may be rotated relative to the centre housing for orientation reasons, with total certainty that the vane/volute tail alignment blend is always maintained. Previous designs featured an anti-rotation device comprising loosely pinning the wheel shroud to the centre housing which requires precise orientation of the turbine to the central housing 13 for a good volute tail to vane blend. Furthermore, the previous design has the disadvantage that the vaned stator is prevented from rotation by the wheel shroud slots acting against the vaned stator blades which opens the possibility of wear between the sliding vane flanks and the wheel shroud slots. For optimum performance the nominal gap between the vanes and the slots should not exceed 0.005" because performance degradation ensues beyond that clearance.

The design of the present invention featuring the spherical configuration of the ball ended lever 21 is also tolerant of manufacturing tolerance misalignment, and permits operation even when the lever and vaned stator may not be perfectly aligned due to manufacturing tolerances. This is shown in Figure 3 where a 2° misalignment of the lever 21 as shown.

The lever 21 may be a single lever arm as shown with a spherical end feature or may be bifurcated in a form such as a forked device with each tine end featuring an individual curved, or spherical end engaging an appropriate respective cut-out, ie a geometrical feature, hole or cavity, in the piston 6.

The vaned stator (piston 6) may also feature a reduced diameter main body which reduces the gas load forces on the device and results in a reduction in the actuator forces which are needed.

The minimum and maximum opening limit stops for the vaned stator may be built in to the structural assembly so that no adjustment is necessary. This produces a further cost saving by elimination of a further production variable. '

Claims

1. A turbocharger comprising: a turbine housing (1) having an inlet passage (17), for receiving exhaust gas from an internal combustion engine, and an exhaust outlet (2) for the gas; a turbine wheel (4), mounted on a shaft for rotation in the turbine housing (1) a piston (6) movable parallel to the shaft (5) of the turbine wheel (4) for controlling the flow of exhaust gas to the turbine wheel (4); and an actuator for moving the piston (6), the actuator comprising a lever (21) pivotally mounted and having a lever end (23) which engages the piston (6) at a surface which curves toward the lever.

2. A turbocharger according to Claim 1 wherein the lever end surface has a line of curvature, which, in cross-section, lies in a plane with the lever (21).

3. A turbocharger according to Claim 1 or 2, wherein the piston (6) comprises a plurality of vanes (7) extending substantially parallel to the shaft (5) from a first end of the piston (6) across the inlet passage (17) to control the gas flow.

4. A turbocharger according to any one of the preceding claims, wherein the lever end (23) surface is an arc with a radius of curvature which traces a sphere in three dimensions.

5. A turbocharger according to any one of the preceding claims, wherein the lever end (23) engages in a cut-out in the piston (6).

6. A turbocharger according to Claim 5, wherein at least one side of the cut-out in the piston (6) lies generally tangential to the curved surface of the lever end (23).

7. A turbocharger according to any one of the preceding claims wherein the lever (21) is bifurctuated with a first tine supporting the lever end (23) and a second tine supporting a second lever end which has a curved edge surface which curves towards the second tine.

8. A turbocharger according to Claim 7, wherein each lever end engages a respective cut-out in the piston (6) and wherein the edges of each lever end are curved at the circumferential surface which engages the cut-out in the piston (6).

9. A turbocharger according to Claim 8, wherein each lever end (23) has edge surfaces comprising an arc with a radius of curvature which traces a sphere in three dimensions. '

10. A turbocharger according .to any one of the preceding claims, wherein the piston (6) is arranged coaxial with the turbine wheel shaft.

11. A turbocharger according to any one of the preceding claims, wherein the piston (6) concentrically surrounds the turbine wheel.