Impeller for an exhaust gas turbocharger, exhaust gas turbocharger and method for balancing an impeller for an exhaust gas turbocharger

Abstract

Impeller for an exhaust gas turbocharger, wherein the impeller (1) is rotatably mounted in a housing of the exhaust gas turbocharger (3) about an axis of rotation (4), and wherein the impeller (1) has a wheel hub (6) with a wheel back (7) and a wheel end facing away from the wheel back (7), and wherein a plurality of impeller blades (5) are formed on the wheel hub (6) extending between the wheel back (7) and the wheel end, and wherein a balancing mark (12) is arranged in a blade channel (10) formed between a first blade (8) of the plurality of impeller blades (5) and a second blade (9) of the plurality of impeller blades (5) arranged adjacent to the first blade (8), wherein a width (B) of the balancing mark (12) is less than a length (L) of the balancing mark (12), characterized in that the balancing mark (12) extends in the circumferential direction of the impeller (1). extendswherein the length (L) is formed in the circumferential direction and the width (B) in the radial direction of the wheel (1), and wherein the balancing mark (12) is curved, and wherein the width (B) is substantially constant over the length (L).

Description

[0001] The invention relates to an impeller for an exhaust gas turbocharger of the type specified in the preamble of patent claim 1, an exhaust gas turbocharger according to patent claim 2 and a method for balancing an impeller for an exhaust gas turbocharger of the type specified in the preamble of patent claim 3.

[0002] German Patent Application DE 10 2010 048 099 A1 discloses a rotor assembly with an impeller for an exhaust-gas turbocharger. The impeller has impeller blades arranged on a wheel hub with a wheel back and a wheel face facing away from the wheel back. An arcuate balancing mark is incorporated into the impeller at the wheel back.

[0003] From published patent application DE 10 2015 219 374 A1, a compressor wheel of an exhaust gas turbocharger is known which has a pear-shaped balancing mark. Furthermore, a method is specified for creating the pear-shaped balancing mark, which is created by moving a milling tool in a first direction to create a recess in a flow side of the compressor wheel and subsequently moving the milling tool located in the recess outward in a second direction to convert the recess into the pear-shaped balancing mark.

[0004] The published patent application WO 2015 / 132 896 A1 discloses an impeller of an exhaust gas turbocharger which has a curved balancing mark, but the curvature of the balancing mark is formed along a curvature of the impeller blades.

[0005] It is also known to insert balancing marks into the hub between the wheel back and the wheel face. In this case, the balancing mark is placed in a blade channel formed between two impeller blades, with the balancing mark positioned in the channel floor. However, under certain circumstances, there may not be sufficient mass available for removal in this area, as the balancing mark is preferentially placed near the largest diameter of the impeller. In the worst case, this leads to an increased scrap rate.

[0006] In balancing marks created by milling, high material stresses occur at the base of the balancing mark, i.e., in the area of ​​the smallest thickness of the impeller. This means that sufficient material is removed by material removal across the thickness of the impeller to reduce or eliminate the imbalance.

[0007] It is an object of the present invention to provide an improved impeller for an exhaust gas turbocharger, such an exhaust gas turbocharger and a method for balancing a rotor of such an exhaust gas turbocharger, whereby improved balancing is made possible.

[0008] This object is achieved by an impeller for an exhaust gas turbocharger having the features of patent claim 1, by an exhaust gas turbocharger having the features of patent claim 2, and by a method for balancing an impeller for an exhaust gas turbocharger having the features of patent claim 3. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the dependent claims.

[0009] The first aspect of the invention relates to an impeller for an exhaust gas turbocharger, which impeller is mounted in a housing of the exhaust gas turbocharger so as to be rotatable about a rotational axis. The impeller has a wheel hub with a wheel back and a wheel end facing away from the wheel back. A plurality of impeller blades are formed extending between the wheel hub and the wheel back, wherein a balancing mark is arranged in a blade channel formed between a first blade of the plurality of impeller blades and a second blade of the plurality of impeller blades arranged adjacent to the first blade, wherein a width of the balancing mark is smaller than a length of the balancing mark.According to the invention, the balancing mark extends in the circumferential direction of the impeller, with the length being formed in the circumferential direction and the width in the radial direction of the impeller, and the balancing mark is curved, and the width is substantially constant over the length. In other words, this means that, unlike in the prior art, it is not a point-shaped balancing mark whose width essentially corresponds to its length, but rather a balancing mark extending in the circumferential direction of the impeller.

[0010] The advantage is an enlargement of the balance mark, which shifts the maximum stress occurring in the balance mark to one edge of the balance mark, which is located in a region of greater thickness of the impeller compared to the state of the art. This leads to an increase in the durability and long-term load capacity of the impeller.

[0011] Due to this design of the balancing mark, a rotor to which the impeller is assigned and which comprises a shaft to which the impeller is connected in a rotationally fixed manner can be balanced particularly well, so that the rotor can perform a particularly good and at least almost unbalance-free rotational movement during operation of the exhaust gas turbocharger.

[0012] The balancing mark is curved. It is preferably adapted to a balancing radius. The balancing radius corresponds to a radius extending from the impeller's axis of rotation to the intended position of the balancing mark. Since the balancing mark is intended to reduce or eliminate imbalance during rotating operation of the impeller, a balancing mark shape adapted to the rotating movement is preferable.

[0013] The second aspect of the invention relates to an exhaust gas turbocharger, in particular for an internal combustion engine, comprising a rotor rotatably mounted in a housing, which comprises a shaft and at least one impeller according to the invention that is rotationally fixedly connected to the shaft. Advantageous embodiments of the first aspect of the invention are to be regarded as advantageous embodiments of the second aspect of the invention, and vice versa.

[0014] As a result of the advantageous balancing of the impeller and in particular of the impeller, the rotor of the exhaust gas turbocharger has a particularly smooth rotational movement, which is beneficial for efficient operation of the exhaust gas turbocharger and its long service life.

[0015] The third aspect of the invention relates to a method for balancing a rotor to be rotatably mounted in a housing of an exhaust gas turbocharger, in particular an impeller of the rotor, which has a plurality of impeller blades on a wheel hub of the impeller.Between at least one first blade of the plurality of impeller blades and a second blade of the plurality of impeller blades adjacent to the first blade, a blade channel is formed with a channel bottom, in which a balancing mark is formed, the length of which is greater than the width. According to the invention, it is provided that in order to bring about the balancing mark, the balancing mark extends in the circumferential direction of the impeller, the length being formed in the circumferential direction and the width in the radial direction of the impeller, and the balancing mark is curved, and the width is substantially constant over the length, the impeller is moved in the circumferential direction of the impeller.The advantage is that the balancing mark, which differs from a point-like balancing mark whose length essentially corresponds to its width, is created by a pivoting movement of the tool or the impeller at a predetermined, set xy position of the tool. In other words, only one additional movement—the pivoting movement—of the tool or the impeller or the moving gear is required to create the balancing mark. A change to the set xy position of the tool is not necessary.

[0016] A cost-effective production of the balancing mark is achieved by a material-removing process, in other words by material removal, whereby a milling process is preferably used.

[0017] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Identical or functionally equivalent elements are assigned identical reference numerals. They show: Fig. 1 shows a perspective view of a section of a wheel according to the state of the art, and Fig. 2 shows a perspective view of a section of an impeller according to the invention.

[0018] An impeller 1 of a rotor 2 for an exhaust gas turbocharger 3 according to the prior art is according to Fig. 1. The impeller 1 is designed in the form of a compressor wheel. The rotor assembly 2 comprises the compressor wheel 1 and a turbine wheel (not shown in detail), which is rotationally fixedly connected to the compressor wheel 1 via a shaft (not shown in detail).

[0019] The rotor assembly 2 is rotatably mounted in a bearing section of the exhaust gas turbocharger 3 (not shown in detail) about a rotational axis 4 of the rotor assembly 2. The turbine wheel is rotatably received in a flow-through exhaust gas guide section of the exhaust gas turbocharger 3 (not shown in detail). Exhaust gas from an internal combustion engine (not shown in detail) connected to the exhaust gas turbocharger 3 (not shown in detail) is applied to the turbine wheel via an inlet channel of the exhaust gas guide section (not shown in detail) and is set in rotation.

[0020] Due to the rotationally fixed connection to the compressor wheel 1 formed by the shaft, the compressor wheel 1, which is rotatably mounted in an air guide section (not shown in detail), is also set in rotation, thereby drawing in and compressing air. The compressed air is fed to the internal combustion engine via an outlet duct (not shown in detail) of the air guide section.

[0021] The compressor wheel 1 comprises a plurality of impeller blades 5, with the aid of which it draws in the air, which are arranged on a wheel hub 6 of the compressor wheel 1. The wheel hub 6 has a wheel back 7 and a wheel face of the wheel hub 6 (not shown in detail) facing away from the wheel back 7. The plurality of impeller blades 5 are arranged on the wheel hub 6, extending from the wheel face to the wheel back 7. Between each two blades of the plurality of impeller blades 5, a first blade 8 and a second blade 9, a blade channel 10 with a channel base 11 is formed, along which the air flows.

[0022] To ensure a particularly smooth rotation of the rotor assembly 2, a balancing mark 12 is formed on the channel bottom 11 of the compressor wheel 1. The balancing mark 12, which is produced by a milling process, is point-shaped, with a width B of the balancing mark 12 essentially corresponding to a length L of the balancing mark 12.

[0023] In Fig. Figure 2 shows an impeller 1 according to the invention, which is also designed in the form of a compressor wheel. The impeller 1 could also be designed in the form of a turbine wheel.

[0024] The balancing mark 12 extends along its circumferential direction U in the circumferential direction of the impeller 1 and is essentially circular segment-shaped. It is notched, meaning it was produced by removing material. Likewise, the balancing mark 12 could also be linear. The balancing mark 12 of the impeller 1 according to the invention has a length L that is greater than the width B.

[0025] To create the balancing mark 12 in so-called high-speed balancing, either the material-removing tool or the impeller 1 or the rotor 2 itself can be moved. The linear balancing mark 12 is preferably created with a moving tool, whereas the curved balancing mark 12 is preferably produced with a moving impeller 1 or the rotor 2.

[0026] In order to achieve sufficient material removal to reduce the imbalance, a depth of the balancing mark 12 can also be increased, whereby care must be taken that the depth does not exceed a thickness D of the impeller 1 required for the strength of the impeller 1.

[0027] The advantage of the curved balancing mark 12 is that it ensures a maximum compensation radius, and thus a maximum unbalance effect, of the impeller mass to be removed. With the straight balancing mark 12, however, a chord of a circular segment in the circular impeller 1 is removed, whereby the maximum compensation radius is usually only achieved at the end points of the balancing mark 12.

[0028] To create the balancing mark 12, any material-removing process, in other words, any material removal method, can be used. In particular, if the impeller 1 is designed in the shape of a turbine wheel, grinding is conceivable. Material removal could also be achieved using a laser process. The balancing mark 12 could also be created on an outer edge of the impeller 1 using a cutting process. The advantage of milling lies in the possibility of surface finishing and in its cost advantage over other processes, as milling is cost-effective and flexible.

[0029] In an embodiment not shown in detail, the balancing mark 12 is designed to extend at least partially in the radial direction over its length L. A complete radial extension of the balancing mark 12 over its length L is also possible.

Claims

[1] Impeller for an exhaust gas turbocharger, wherein the impeller (1) is rotatably mounted in a housing of the exhaust gas turbocharger (3) about a rotational axis (4), and wherein the impeller (1) has a wheel hub (6) with a wheel back (7) and a wheel end facing away from the wheel back (7), and wherein a plurality of impeller blades (5) are formed on the wheel hub (6) extending between the wheel back (7) and the wheel end, and wherein a balancing mark (12) is arranged in a blade channel (10) formed between a first blade (8) of the plurality of impeller blades (5) and a second blade (9) of the plurality of impeller blades (5) arranged adjacent to the first blade (8), wherein a width (B) of the balancing mark (12) is smaller than a length (L) of the balancing mark (12), characterized bythat the balancing mark (12) extends in the circumferential direction of the impeller (1), wherein the length (L) is formed in the circumferential direction and the width (B) in the radial direction of the impeller (1), and wherein the balancing mark (12) is curved, and wherein the width (B) is substantially constant over the length (L). [2] Exhaust gas turbocharger, in particular for an internal combustion engine, with a rotor (2) rotatably mounted in a housing of the exhaust gas turbocharger (3), which rotor comprises a shaft and at least one impeller (1) according to claim 1 which is connected in a rotationally fixed manner to the shaft. [3] Method for balancing a rotor assembly (2) rotatably mounted in a housing of an exhaust gas turbocharger (3), wherein the rotor assembly (2) comprises an impeller (1) having a plurality of impeller blades (5) on a wheel hub (6) of the impeller (1), and wherein a blade channel (10) with a channel bottom (11) is formed between at least one first blade (8) of the plurality of impeller blades (5) and a second blade (9) of the plurality of impeller blades (5) adjacent to the first blade (8), and wherein a balancing mark (12) is formed in the channel bottom (11), the length (L) of which is greater than the width (B), characterized byin that to bring about the balancing mark (12), wherein the balancing mark (12) extends in the circumferential direction of the impeller (1), wherein the length (L) is formed in the circumferential direction and the width (B) in the radial direction of the impeller (1), and wherein the balancing mark (12) is curved, and wherein the width (B) is substantially constant over the length (L), the impeller (1) is moved in the circumferential direction of the impeller (1). [4] Method according to claim 3, characterized by that the balancing mark (12) is produced by material removal.

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