Compressor wheel

Abstract

A compressor wheel for an internal combustion engine may include a plurality of blades which in a circumferential direction of the wheel are spaced from one another. The plurality of blades may respectively include an inflow edge which during operation are subject to an inflow of a compressible fluid substantially axially to the wheel axis. The plurality of blades may include a surface layer of locally distinct materials to adapt to locally distinct loads during operation.

Claims

1. A compressor wheel for an internal combustion engine, comprising: a body rotatable about a rotation axis and a plurality of blades disposed on the body and spaced from one another in a circumferential direction of the rotation axis, the plurality of blades respectively including an inflow edge which during operation are subjected to an inflow of a compressible fluid substantially axially to the rotation axis, wherein the plurality of blades respectively include a surface of locally distinct materials resistant to locally distinct loads during operation; and wherein the surface of at least one blade of the plurality of blades includes an armour material disposed locally along the inflow edge and an anti-corrosive coating disposed in a region of the surface spaced away from the inflow edge.

2. The compressor wheel according to claim 1, wherein the anti-corrosive coating includes an anodised layer.

3. The compressor wheel according to claim 1, wherein the armour material and the anti-corrosive coating are disposed adjacently in an axial direction of the rotation axis.

4. A compressor wheel according to claim 3, wherein the armour material in the axial direction of the compressor wheel extends over a length of approximately 10 to 40% of an axial blade length.

5. The compressor wheel according to claim 1, wherein the armour material includes a plasma electrolytic oxidation (PEO) layer.

6. The compressor wheel according to claim 1, wherein the plurality of blades includes a main blade and an auxiliary blade alternating in the circumferential direction, wherein the inflow edges of the main blades are arranged in a plane positioned upstream relative to a plane of the inflow edges of the auxiliary blades with respect to a flow direction of the fluid to be compressed.

7. The compressor wheel according to claim 1, wherein the armour material is substantially provided only directly on the inflow edge.

8. The compressor wheel according to claim 1, wherein the surface of the at least one blade has the armour material only on the inflow edge, and wherein the surface of the at least one blade outside of the inflow edge is without the armour material.

9. The compressor wheel according to claim 1, wherein the plurality of blades includes main blades having inflow edges extending in a radial plane of the compressor wheel.

10. The compressor wheel according to claim 1, wherein the body is a radial compressor wheel.

11. The compressor wheel according to claim 1, wherein the body is composed of a material including at least one of aluminium, magnesium and titanium.

12. The compressor wheel according to claim 1, wherein the at least one blade defines an axial blade length and the armour material extends over 10 to 40% of the axial blade length.

13. The compressor wheel according to claim 1, wherein the anti-corrosive coating includes at least one of a thermally sprayed layer, a physical vapor deposition layer, and a chemical vapor deposition layer.

14. The compressor wheel according to claim 1, wherein the armour material includes at least one of a steel alloy, a nickel-based alloy, a cobalt alloy and a titanium alloy.

15. An exhaust gas turbocharger for an internal combustion engine, comprising: a compressor wheel including a central axial bore for receiving a rotor shaft; a plurality of circumferentially spaced blades disposed on the compressor wheel each including an inflow edge, the plurality of blades further including a plurality of main blades alternating in a circumferential direction with a plurality of auxiliary blades, wherein the inflow edge of the main blades are arranged in a plane positioned upstream relative to a plane of the inflow edge of the auxiliary blades with respect to a flow direction; and wherein at least one main blade has a surface of locally distinct materials, the surface of locally distinct materials including an armour material disposed on the inflow edge and an anti-corrosive coating disposed in a region spaced axially away from the inflow edge with respect to the central axial bore.

16. The exhaust gas turbocharger according to claim 15, wherein the armour material includes a plasma electrolytic oxidation layer.

17. The exhaust gas turbocharger according to claim 15, wherein the armour material and the anti-corrosive coating adjoin one another in an axial direction of the central axial bore.

18. The exhaust gas turbocharger according to claim 15, wherein the anti-corrosive coating is disposed to butt-join the armour material on the inflow edge.

19. The exhaust gas turbocharger according to claim 18, wherein the armour material is provided only on the inflow edge, and wherein the surface of the at least one main blade outside of the inflow edge is without the armour material.

20. The exhaust gas turbocharger according to claim 15, wherein the anti-corrosive coating at least partially overlaps the armour material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawing it shows,

(2) FIG. 1 a top view of the inflow side of a radial compressor wheel according to the invention,

(3) FIG. 2 a perspective lateral view of a blank serving for the production of a radial compressor wheel according to the invention,

(4) FIG. 3 a representation corresponding to FIG. 2, with the help of which the coating of the face end of the blank on the inflow side with armour material is shown, and

(5) FIG. 4 a perspective front view of a radial compressor wheel created through material removal from the blank shown in FIG. 3.

DETAILED DESCRIPTION

(6) The radial compressor wheel 1 shown in FIG. 1 has a central axial bore 2, with which the radial compressor wheel 1 can be arranged on a corresponding section of a rotor shaft, which in the case of a turbocharger connects the compressor wheel 1 to a turbine wheel in a rotationally fixed manner. During the operation of the turbocharger, the turbine wheel is driven within a turbine housing by an exhaust gas flow of an internal combustion engine and then in turn drives the radial compressor wheel 1. In the shown example, the latter has six main blades 3, between auxiliary blades 4 are arranged in each case. All blades 3 and 4 have contoured edges 5, the shape of which is matched to the profile of the inside of a compressor housing which is not shown, which receives the radial compressor wheel 1. Accordingly, the contours of the edges 5 and the inner surface of the inner housing are matched to one another so that as close as possible a “sealing gap” is formed.

(7) The compressor housing has an inlet that is axial with respect to the access of the compressor wheel, which directs air to be compressed by the compressor wheel 1 or other gases to the inflow edges 6 of the main blades 3 of the compressor wheel 1. The inflow edges 6 as a rule lie in a radial plane of the compressor wheel 1 that is common to all inflow edges 6. The inflow edges of the auxiliary blades 4 as a rule are axially offset to the back relative to the inflow edges 6 of the main blades 3 and are therefore not visible in the representation of FIG. 1.

(8) The inflow edges 6 of the main blades 3 are subjected to extraordinarily high mechanical loading during the compressor operation in the case of low-pressure exhaust gas recirculation, be it through abrasive particles or condensate particles and cavitation of water or oil mists.

(9) In order to be able to ensure a long lifespan of the compressor wheel 1 despite this, the inflow edges 6 of the main blades 3 are provided with armour 7, which can extend to a greater or lesser degree over the blade surfaces adjoining the inflow edges 6. For producing the armour 7, any coating methods can be employed in principle, as has already been explained further up.

(10) The inflow edges of the auxiliary blades 4 which are offset towards the back in axial direction of the compressor wheel 1 in the drawing are subjected to only comparatively low loading so that armour is not required there. However, all surfaces of the compressor wheel 1, which are subjected to the fluid to be compressed, are exposed to the corrosive influence of chemically aggressive components of the fluid to be compressed, in particular sulphuric acid and sulphurous acid. It is therefore provided according to the invention to anti-corrosively coat these surfaces. Accordingly, the anti-corrosive coating can butt-join the armour 7. Instead, it is also possible to let the anti-corrosive coating overlap the armour 7 at least in regions.

(11) In the following, a first preferred method for producing a compressor wheel 1 is explained in more detail. Initially, a blank 8, see FIG. 2, is produced, for example by casting. This blank 8 has an outer surface having the form of an enveloping surface of the compressor wheel 1 to be produced, see for example FIG. 1. This blank 8 has a small face end 9 in the region of the inflow edges 6 of the main blades 3 still to be produced and a large face end 10 on the opposite side of the blank 8.

(12) In a following method step at least one radially outer annular zone of the small face end 9 is cleaned through material removal, which in the case of a blank 8 formed as a cast body means removing the casting skin.

(13) The cleaned annular zone is subsequently coated with a material provided for armouring the inflow edges 6 of the main blades 3, so that a coated or armoured annular zone 11 that is more or less wide is formed.

(14) Now, the main and auxiliary blades 3, 4 of the desired compressor wheel are produced through material removal, for example by means of chip-removing tools. This is synonymous to producing the free spaces intended between the desired blades. In the region of these free spaces, the coating with the armour material is also cleared on the small face end in the process.

(15) As a result, merely the inflow edges 6 of the main blades 3 on the face end of the small face end 9 remain with face end armour. Since the coating with the armour material was initially applied onto the comparatively large and non-stepped small face end 9 and the close bond between the armour material and the material of the blank 8 thus formed is not subjected to any impairment during its subsequent chip-removing machining for forming the blades 3 and 4, excellent adhesion of the armoured inflow edges 6 on the main blades 3 is ensured. Through material-removing finishing the armoured inflow edges can be provided with an aerodynamically optimal profile. This material removal can be performed in the sense of precision balancing in such a manner that any unbalances on the compressor wheel 1 to be produced are avoided.

(16) Following the production of the blades 3 and 4, all surfaces of the compressor wheel 1 subjected to the fluid to be compressed are additionally treated anti-corrosively on and between the blades 3 and 4. Following a renewed precision balancing process if required, the desired compressor wheel is then completed.

(17) In the method described preceding this, the material provided for the armour forms a layer on the small face end of the blank or on the edges of the compressor wheels on the inflow side that is of a substrate-specific material.

(18) According to a second preferred method for producing a compressor wheel, the armour material can also be provided as a substrate-specific deposit or diffusion layer.

(19) With this second method, additionally a blank 8 is again produced from the base material intended for the compressor wheel later on, for example cast. Following this, material is again removed from the small face end 9, i.e. in the case the blank is produced by casting, the casting skin is removed on a radially outer annular zone of the small end face 9.

(20) Following this, a physical-chemical treatment of the cleaned small face end 9 takes place in order to change the material structure of the surface layer of the small face end 9 in terms of “armouring”. In a preferred manner, a PDO layer (plasma electrolytic oxidation) is created, namely with specifiable thickness of the PEO layer.

(21) This is then followed with chip-removing machining of the blank by the production of the compressor wheel blades, wherein the inflow edges of the main blades located in the plane of the small end face 9 have armouring in the form of a PEO layer.

(22) In a third preferred production method, a blank 8 is initially produced again from a base material to be specified, for example cast, which is then cleaned in a chip-removing manner. Following this, the compressor wheel blades are formed through chip-removing machining. The inflow edges of the compressor wheel blades and the blade regions axially following the inflow edges are now physically-chemically processed in order to form a surface layer of armour material on the inflow edges and the following blade regions. Preferentially, a PEO surface layer is again produced which according to a preferred embodiment of the invention can extend over up to 30% of the axial length of the compressor wheel.

(23) The above representations of the production process where based on a radial compressor wheel 1 whose main blades 3 comprise inflow edges 6 which extend in a radial plane of the compressor wheel 1 and accordingly are linear. In principle, compressor wheels shaped differently with differently shaped inflow edges 6 can also be produced from a blank 8 the outside of which forms an enveloping surface of the desired compressor wheel 1. If appropriate, the face end of the blank containing the subsequent onflow edges will then have to have a curved, rotation-symmetrical form. In addition to this, the mentioned face end could also be designed wavy in such a manner that it contains inflow edges which are alternatingly provided in different axial positions of the compressor wheel.

(24) The invention thus utilises the realisation that elaborate design measures in the exhaust path in the case of low-pressure exhaust gas recirculation are superfluous when the compressor wheel arranged in the exhaust gas recirculation path has corrosion-resistant surfaces which are armoured in regions that are subject to high mechanical loads. In the invention, the realisation is used in particular that on the one hand armouring that is limited to the inflow edges 6 of the blades of the compressor wheel and on the other hand anti-corrosive treatment or coating of the remaining blade surfaces in the case of a compressor wheel having a basic body of aluminium or a comparable light metal are adequate. The production of the compressor wheel according to the invention can be effected in a simple manner that initially a blank of aluminium or light metal is created, the outer surface of which substantially has the form of an enveloping surface of the desired compressor wheel. Such a blank comprises an end face containing the inflow edges of the compressor blades of the compressor wheel to be produced on which initially, at least in a radially outer annular region, a surface of armour material is created over the entire area. Since the mentioned end face although arched or curved if appropriate, but is free of steps in the vicinity of the inflow edges of the compressor blades still to be produced, a sound tightly adhesive bond between the armour material and the aluminium or light metal of the blank provided as base material is ensured. In the following, the compressor wheel blades can then be produced in that the blank provided with armour material on the aforementioned end face is machined in a material-removing or chip-removing manner. Following this, anti-corrosive coating of the compressor wheel produced in this manner takes place.

(25) In all embodiments, the end faces of the compressor wheel preferentially remain without armour in its central bore.

(26) With respect to suitable methods, in particular for the anti-corrosive coatings, reference can exemplarily be made to the following methods:

(27) plasma spraying, flame and high-speed flame spraying, cold gas spraying, arc spraying, PVD and CVD methods.

(28) The surface layers of armour material can on the one hand be formed through substrate-extraneous deposit or diffusion layers and in particular consist of steel, nickel, cobalt and/or titanium alloys.

(29) On the other hand, substrate-specific deposit or diffusion layers are possible and under the aspect of cost-effective production are particularly preferred, this applies in particular to PEO layers.

(30) In particular aluminium is provided as base material of the compressor wheel. Other light metals, such as for example magnesium and/or titanium are however likewise suitable.