Exhaust-gas turbocharger having heat throttle cavity

Abstract

An exhaust-gas turbocharger (1) having a shaft (2), a turbine wheel (5), which is fastened to the shaft (2), and a heat throttle (8) between the shaft (2) and the turbine wheel. An end face (3) of the shaft (2) is provided with a protrusion (4), with an outside diameter (A.sub.4) which is smaller than the outside diameter (A.sub.2) of the shaft (2). The turbine wheel (5) has a hollow receiving portion (7), which is formed integrally on the wheel rear side (6) and the inside diameter (I.sub.7) corresponds to the outside diameter (A.sub.4) of the protrusion (4) and the outside diameter (A.sub.7) corresponds to the outside diameter (A.sub.2) of the shaft (2). The protrusion (4) engages into the receiving portion (7). The heat throttle (8) is formed by a cavity (8A, 8B), which has an outside diameter (A.sub.8) which is smaller than the outside diameter (A.sub.4) of the protrusion (4) and extends from the protrusion (4) into the receiving portion (7).

Claims

1. An exhaust-gas turbocharger (1), having a shaft (2), which has an outside diameter (A.sub.2); and a turbine wheel (5), which is fastened to the shaft (2); wherein an end face (3) of the shaft (2) is provided with a hollow protrusion (4), which comprises an outside diameter (A.sub.4) which is smaller than the outside diameter (A.sub.2) of the shaft (2), the turbine wheel (5) has a hollow receiving portion (7), which is formed integrally on the wheel rear side (6) thereof and the inside diameter (I.sub.7) of which corresponds to the outside diameter (A.sub.4) of the protrusion (4) and the outside diameter (A.sub.7) of which corresponds to the outside diameter (A.sub.2) of the shaft (2), wherein the protrusion (4) engages into the receiving portion (7), and the hollow protrusion (4) has an inside diameter (I.sub.8) which is smaller than the outside diameter (A.sub.4) of the protrusion (4), whereby a cavity (8) is defined between the hollow protrusion (4) of the shaft (2) and the hollow receiving portion (7) of the turbine wheel.

2. The exhaust-gas turbocharger as claimed in claim 1, wherein the shaft (2) has a groove (13) for a piston ring adjacent to the end face (3).

3. The exhaust-gas turbocharger as claimed in claim 1, wherein the protrusion (4) has at least one groove (14, 15) for inserting a form-fitting means.

4. The exhaust-gas turbocharger as claimed in claim 3, wherein the form-fitting means is a soldering wire or an adhesive.

5. The exhaust-gas turbocharger as claimed in claim 1, further comprising a ventilation bore (16), which leads from the cavity (8) to a joining surface region (17) between the protrusion (4) and the receiving portion (7).

6. The exhaust-gas turbocharger as claimed in claim 1, further comprising a fitting surface portion (18) between the protrusion (4) and the receiving portion (7), wherein the fitting surface portion (18) is provided on the hollow protrusion (4) of the shaft (2) in the form of a step or bevel, and the hollow receiving portion (7) of the turbine wheel is provided with a complementary mating feature for centering the shaft protrusion (4) in the receiving portion (7).

7. The exhaust-gas turbocharger as claimed in claim 1, wherein the shaft (2) and the turbine wheel (5) are finish-machined before they are assembled.

8. A rotor (12) of an exhaust-gas turbocharger (1), having a shaft (2), which has an outside diameter (A.sub.2); and a turbine wheel (5), which is fastened to the shaft (2); wherein an end face (3) of the shaft (2) is provided with a hollow protrusion (4), which comprises an outside diameter (A.sub.4) which is smaller than the outside diameter (A.sub.2) of the shaft (2), the turbine wheel (5) has a hollow receiving portion (7), which is formed integrally on the wheel rear side (6) thereof and the inside diameter (I.sub.7) of which corresponds to the outside diameter (A.sub.4) of the protrusion (4) and the outside diameter (A.sub.7) of which corresponds to the outside diameter (A.sub.2) of the shaft (2), wherein the protrusion (4) engages into the receiving portion (7), and the hollow protrusion (4) has an inside diameter (I.sub.8) which is smaller than the outside diameter (A.sub.4) of the protrusion (4), whereby a cavity (8) is defined between the hollow protrusion (4) of the shaft (2) and the hollow receiving portion (7) of the turbine wheel.

9. The rotor as claimed in claim 8, wherein the shaft (2) has a groove (13) for a piston ring adjacent to the end face (3).

10. The rotor as claimed in claim 9, wherein the form-fitting means is a soldering wire or an adhesive.

11. The rotor as claimed in claim 8, wherein the protrusion (4) has at least one groove (14, 15) for inserting a form-fitting means.

12. The rotor as claimed in claim 8, further comprising a ventilation bore (16), which leads from the cavity (8A, 8B) to a joining surface region (17) between the protrusion (4) and the receiving portion (7).

13. The rotor as claimed in claim 8, further comprising a fitting surface portion (18) between the protrusion (4) and the receiving portion (7), wherein the fitting surface portion (18) is provided on the hollow protrusion (4) of the shaft (2) in the form of a step or bevel, and the hollow receiving portion (7) of the turbine wheel is provided with a complementary mating feature for centering the shaft protrusion (4) in the receiving portion (7).

14. The rotor as claimed in claim 8, wherein the shaft (2) and the turbine wheel (5) are finish-machined before they are assembled.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Further details, advantages and features of the present invention will become apparent from the following description of an exemplary embodiment with reference to the drawing, in which:

(2) FIG. 1 shows a schematically greatly simplified basic illustration of an exhaust-gas turbocharger according to the invention, and

(3) FIG. 2 shows a schematically slightly simplified illustration of the joining region between the shaft and the turbine wheel of the exhaust-gas turbocharger shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows, in a schematically greatly simplified basic illustration, an exhaust-gas turbocharger 1 according to the invention. The exhaust-gas turbocharger 1 has a shaft 2, which is mounted in a bearing housing 12. A turbine wheel 5 of a turbine 4 is mounted at one end of the shaft 2. At the opposite end, a compressor wheel 10 of a compressor 11 is fixed to the shaft 2.

(5) FIG. 2 shows the joining or connecting region between the shaft 2 and the turbine wheel 5 in enlarged form. FIG. 2 shows that an end face 3 of the shaft 2 is provided with a protrusion 4, which has an outside diameter A.sub.4 which is smaller than the outside diameter A.sub.2 of the shaft 2.

(6) The turbine wheel 5 has a hollow receiving portion 7 of complementary form which is formed integrally on the wheel rear side 6 thereof. The inside diameter I.sub.7 of the receiving portion 7 corresponds to the outside diameter A.sub.4 of the protrusion 4, i.e. it is either of the same size or slightly smaller, in order to preferably make a transition fit possible. FIG. 2 shows the assembled state of the rotor of the exhaust-gas turbocharger 1, which is formed by the shaft 2 and the turbine wheel 5. In this assembled state, the protrusion 4 is inserted into the hollow receiving portion 7. For centering purposes, a fitting surface portion 18 is provided in this respect and is formed either as a bevel or, as shown in FIG. 2, as a step and comprises surface regions of the protrusion 4 and of the receiving portion 7.

(7) As FIG. 2 further shows, provision is made of a heat throttle 8 in the form of a cavity 8A, 8B, which has a diameter I.sub.8 which is smaller than the outside diameter A.sub.4 of the protrusion 4. The aforementioned inside and outside diameter dimensions are each symbolized by arrows proceeding from the longitudinal center line L outward.

(8) The selection of the inside diameter I.sub.8 makes it possible to arrange the heat throttle 8 both in the protrusion 4 and in a region of the turbine wheel 5. In the particularly preferred embodiment shown in FIG. 2, the cavity splits into two subspaces 8A and 8B, the subspace 8A being arranged in the protrusion 4 and the subspace 8B being arranged in the turbine wheel 5. This represents a particularly preferred embodiment, but it would also be possible in principle to provide such a cavity only in the protrusion 4 or only in the turbine wheel. Furthermore, it is of course also possible to adapt the cavity or the heat throttle 8 in terms of inside diameter I.sub.8 and in terms of length to different mounting situations.

(9) FIG. 2 furthermore shows that the shaft 2 has a groove 13, into which a piston ring (not shown) can be inserted, adjacent to the end face 3.

(10) Furthermore, in the particularly preferred embodiment shown, the protrusion 4 has two grooves 14 and 15, which serve for the insertion of a form-fitting means, such as for example a soldering wire or an adhesive. In this respect, it is of course possible to provide either only one groove or else a greater number of grooves, depending on the length of a resultant joining surface region 17, between the protrusion 4 and the receiving portion 7. A ventilation bore 16 is provided in the protrusion 4, extending from the cavity 8A, 8B to the joining surface portion 17, such that air can escape during the insertion, and particularly during the joining process, of the protrusion 4 into the hollow receiving portion 7.

(11) In addition to the above written disclosure of the invention, reference is hereby explicitly made, to supplement the disclosure thereof, to the illustrative representation in FIGS. 1 and 2.

LIST OF REFERENCE SIGNS

(12) 1 Exhaust-gas turbocharger 2 Shaft 3 End face 4 Protrusion 5 Turbine wheel 6 Wheel rear side 7 Receiving portion 8 Heat throttle 8A, 8B Cavity, consisting of subspaces 8A, 8B 9 Bearing housing 10 Compressor wheel 11 Compressor 12 Rotor 13 Groove 14, 15 Grooves 16 Ventilation bore 17 Joining surface region 18 Fitting surface portion L Longitudinal center line of the exhaust-gas turbocharger or rotor 12 A.sub.2 Outside diameter of the shaft 2 A.sub.4 Outside diameter of the protrusion 4 I.sub.7 Inside diameter of the receiving portion 7 I.sub.8 Inside diameter of the cavity 8A, 8B