Abstract
A wastegate assembly for a turbocharger having a turbine casing has a wastegate flap, a wastegate flap lever, a wastegate spindle and a bearing bush for the wastegate spindle. In addition, the wastegate assembly has a sealing unit formed from a soft-material volume sealing ring and a diaphragm spring that contacts the volume sealing ring.
Claims
1-9. (canceled)
10. The wastegate assembly (5) for an exhaust gas turbocharger having a turbine housing, comprising: a wastegate flap (5a); a wastegate flap lever (5c); a wastegate spindle (5b); a bearing bush (7) for the wastegate spindle; and a seal (11, 17) which is formed by a volumetric sealing ring (11) and a plate spring (17) in contact with the volumetric sealing ring (11), wherein the bearing bush (7) has a widening section (7a) arranged in the end region, which faces the wastegate flap lever (5c), of the bearing bush (7), wherein the volumetric sealing ring comprises soft material and is pressed into the widening section (7a) of the bearing bush (7a); a radial bias is present between the wastegate spindle (5b) and the bearing bush (7); and the plate spring (17) is positioned between the volumetric sealing ring (11) and the wastegate flap lever (5c).
11. The wastegate assembly according to claim 10, wherein the volumetric sealing ring (11) comprises soft material in which one or more support layers are layered.
12. The wastegate assembly according to claim 10, wherein the plate spring (17) consists of a material with high temperature resistance.
13. The wastegate assembly according to claim 10, wherein the turbine housing (1) has a receiving step (1b) into which the widening section (7a) of the bearing bush (7) is inserted.
14. The wastegate assembly according to claim 10, further comprising a volumetric sealing ring (11) in the end region, which is remote from the wastegate flap lever (5c), of the bearing bush (7).
Description
[0017] The invention is explained in the following by way of example with reference to the figures, in which:
[0018] FIG. 1 shows a perspective diagram for illustration of the construction of an exhaust gas turbocharger equipped with a wastegate assembly,
[0019] FIG. 2 shows a sectional view for illustration of a wastegate assembly,
[0020] FIG. 3 shows a sectional view for illustration of the leakage path between the wastegate spindle and the bearing bush thereof,
[0021] FIG. 4 shows a sectional view for illustration of a first embodiment of the invention,
[0022] FIG. 5 shows an enlarged illustration of a sub-region of the sectional view shown in FIG. 4 and
[0023] FIG. 6 shows a sectional view for illustration of a second embodiment of the invention.
[0024] FIG. 1 shows a perspective sketch for illustration of the construction of an exhaust gas turbocharger equipped with a wastegate assembly. This exhaust gas turbocharger comprises a turbine housing 1, a compressor housing 2 and a bearing housing 3 arranged between the turbine housing and the compressor housing. The turbine housing 1 is connected with the exhaust gas manifold 1 a of an internal combustion engine, by way of which a hot exhaust gas mass flow of the internal combustion engine is fed to the turbine wheel arranged in the turbine housing. The turbine wheel is driven or set into rotation by this hot exhaust gas mass flow. As a result, the shaft (not illustrated) of the exhaust gas turbocharger, on which the turbine wheel is arranged, is also set into rotation. This rotation of the shaft of the exhaust gas turbocharger is transferred to the compressor impeller arranged in the compressor housing 2 and similarly secured on the shaft of the exhaust gas turbocharger. Fresh air fed to the compressor is compressed through this rotation of the compressor impeller. This compressed fresh air is fed to the internal combustion engine so as to increase the power thereof. The shaft of the exhaust gas turbocharger is rotatably mounted in the bearing housing 3.
[0025] In addition, a wastegate assembly 5 is shown in FIG. 1. This is arranged in the turbine housing 1 and comprises a wastegate flap 5a which is actuable by way of a wastegate flap lever 5c and a wastegate spindle 5b and which is constructed for opening and closing a wastegate channel. The actuation or control of the wastegate flap takes place with use of an actuator 6 which is connected with the wastegate flap lever 5c by way of a setting element 6a.
[0026] As was already mentioned above, the wastegate spindle 5b is mounted in the turbine housing with use of a bearing bush, wherein this bearing bush is, for example, pressed into the turbine housing. This is illustrated in the following by way of FIG. 2, which shows a sectional view for depiction of a wastegate assembly. The wastegate assembly illustrated in FIG. 2 comprises a wastegate flap 5a which is connected with the wastegate flap lever 5c of a linkage system 14 by way of a wastegate spindle 5b. Moreover, a wastegate regulating rod, which is not illustrated in detail and by way of which the wastegate flap lever 5c is connected with an actuator (similarly not illustrated in detail), is part of this linkage system. The wastegate spindle 5b is, in FIG. 2, connected in its lower end region with the wastegate flap 5a and in its upper end region with the wastegate flap lever 5c. The wastegate spindle 5b is guided in the bearing bush 7, which is pressed into the turbine housing 1.
[0027] Sinceas similarly already mentioned abovedue to the heating up of the wastegate spindle 5b, which in operation of the exhaust gas turbocharger occurs more rapidly by comparison with the bearing bush 7, the diameter of the bearing bush is selected to be larger by comparison with the diameter of the wastegate spindle there is a leakage path 9 between the wastegate spindle 5b and the bearing bush 7 in most operating states of the exhaust gas turbocharger.
[0028] This is shown in FIG. 3, the subject of which is a sectional view for illustration of the leakage path 9 between the wastegate spindle 5b and the bearing bush 7. It is apparent from this sectional view this that leakage path 9 extends over the entire length of the bearing bush 7. It is connected in its lower end region with an exhaust gas chamber arranged behind the turbine wheel in flow direction. From this exhaust gas chamber 10 exhaust gas enters the leakage path 9, runs through this and is delivered in the upper end region of the bearing bush 7 in undesired manner to the environment 8 via an intermediate space between the bearing bush 7 and the wastegate flap lever 5c.
[0029] In order to prevent this, according to the present invention use is made of a seal which is formed by a volumetric sealing ring and a plate spring contacted by the volumetric sealing ring. By volumetric sealing ring there is understood a seal for high-temperature applications, which comprises a pressed sealing ring encircling a ring axis to be closed in an encircling direction and which is constructed to be resistant to high temperatures, for example temperatures above 300 C., preferably temperatures above 500 C. This volumetric sealing ring consists of soft material, preferably of graphite or mica, in which preferably one or more thin support layers, for example fabric layers, preferably steel strips or steel foils, are layered, which when the volumetric sealing ring is inserted are pressed together with the graphite or the mica at the sealing point of the ring.
[0030] FIG. 4 shows a sectional view for illustration of a first embodiment of the invention. In the case of this embodiment the wastegate spindle 5b is also guided in a bearing bush 7 pressed into the turbine housing 1. This bearing bush 7 has in its upper end region in FIG. 4 a widening section 7a surrounding the wastegate spindle 5b. A volumetric sealing ring of soft material 11, which preferably consists of graphite or mica, in which one or more support layers, for example thin steel strips, are layered, is inserted into this widening section 7a. This volumetric sealing ring 11 is inserted in FIG. 4 from above in axial direction into the widening section 7a of the bearing bush 7 when the wastegate assembly is assembled. Press-fitting of the volumetric sealing ring 11 into the widening section 7a of the bearing bush 7 takes place subsequently. After this press-fitting, a plate spring 17 is placed from above in axial direction on the volumetric sealing ring 11 and is used for biasing the volumetric sealing ring 11 in axial and radial directions. In that case, through the compacting of the volumetric sealing ring 11 in axial direction there is exerted, due to a high degree of plastification of the material of the volumetric sealing ring 11, a high level of force in radial direction 16 not only on the bearing bush 7, but also on the wastegate spindle 5b. A radial biasing between the bearing bush 7 and the wastegate spindle 5b, which is maintained over the operating service life of the wastegate assembly, thereby arises. By virtue of the press-fitting, which takes place in axial direction, of the volumetric sealing ring 11 in the widening region 7a of the bearing bush 7 and the thus-formed radial biasing between the bearing bush 7 and the wastegate spindle 5b the sealing action of the volumetric sealing ring 11 is increased in such a way that in operation of the exhaust gas turbocharger an undesired issue of exhaust gas, which is conducted through the leakage path 9, to the environment is effectively prevented.
[0031] FIG. 5 shows an illustration to enlarged scale of a sub-region of the sectional view shown in FIG. 4. The turbine housing 1, the widening section 7a of the bearing bush 7, the wastegate spindle 5b, the plate spring 17, the volumetric sealing ring 11 and the wastegate flap lever 5c are illustrated in this enlarged illustration. Moreover, the paths 12 of force and the sealing surfaces 13, which result during or through the insertion and compacting of the volumetric sealing ring 11 into and in the widening section 7a of the bearing bush, are illustrated in FIG. 5. Moreover, it is apparent from FIG. 5 that the turbine housing 1 has a receiving step 1 b for reception of the widening section 7a of the bearing bush.
[0032] FIG. 6 shows a sectional view for illustration of a second embodiment of the invention. This differs from the first embodiment shown in FIG. 4 merely in that a volumetric sealing ring 11 is also provided in the lower end region of the bearing bush 7. This further volumetric sealing ring increases the security that exhaust gas cannot be delivered from the exhaust gas chamber 10 via the leakage path 9 to the environment 8.
REFERENCE NUMERAL LIST
[0033] 1 turbine housing
[0034] 1a exhaust gas manifold
[0035] 1b receiving step
[0036] 2 compressor housing
[0037] 3 bearing housing
[0038] 4 turbocharger impeller
[0039] 5 wastegate assembly
[0040] 5a wastegate flap
[0041] 5b wastegate spindle
[0042] 5c wastegate flap lever
[0043] 6 actuator
[0044] 6a setting element
[0045] 7 bearing bush
[0046] 7a widening section
[0047] 8 environment
[0048] 9 leakage path
[0049] 10 exhaust gas chamber
[0050] 11 volumetric sealing ring
[0051] 12 paths of force
[0052] 13 sealing surfaces
[0053] 14 linkage system
[0054] 15 axial direction
[0055] 16 radial direction
[0056] 17 plate spring
