DE102022209742A1 - Rotor assembly with hollow shaft for an electric loader with electric motor drive and electric charger - Google Patents

Abstract

The invention relates to a rotor assembly (10) of an electric charger (100) with a hollow rotor shaft (40) with an electric motor drive (150) and an electric charger (100) with such a rotor assembly (10). The rotor assembly (10) according to the invention has a hollow rotor shaft (40) having an inner cavity (43), a compressor wheel (30) which is arranged on a first shaft end (41) of the hollow rotor shaft (40), and a rotor permanent magnet arrangement (50), which is arranged in the inner cavity (43) of the hollow rotor shaft (40) and is mechanically firmly connected to the hollow rotor shaft (40). The compressor wheel (30) is plugged onto the first shaft end (41) of the hollow rotor shaft (40) by means of a mounting connection piece (32) and is mechanically firmly connected to it, with the mounting connection piece (32) being an integral part of the compressor wheel (30). or is an integral part of a separate compressor wheel carrier component (32) on which the compressor wheel (30) is mechanically fixed.

Description

The invention relates to a rotor assembly for an electric charger with an electric motor drive, which has a hollow shaft with a rotor-permanent magnet arrangement arranged therein, and an electric charger with such a rotor assembly.

The term electric charger here means a compressor driven by an electric motor, in particular a radial compressor, which is used to charge internal combustion engines. Such electric chargers have long been used as so-called e-chargers or e-boosters to increase the performance of motor vehicle internal combustion engines. This is done with the aim of reducing the size and weight of the internal combustion engine while maintaining the same or even increased performance and at the same time reducing consumption and thus CO ₂ emissions in view of increasingly strict legal requirements in this regard. E-chargers or e-boosters are also used in addition to exhaust gas turbochargers in order to compensate for the exhaust gas turbochargers' performance weaknesses in transient operating ranges, which are also known as so-called turbo lag. The working principle is to increase the pressure in the intake tract of the internal combustion engine and thus ensure a better filling of the combustion chamber with air-oxygen and thus be able to convert more fuel, petrol or diesel, per combustion process, i.e. increasing the performance of the internal combustion engine.

In fuel cells, which can be a component of electromobility, the electrodes are supplied with fuel in the form of gaseous media, e.g. B. Air and hydrogen, supplied under pressure, which react with the release of electrical current to form water, which is released in the form of water vapor, virtually as exhaust gas. Electric chargers, electric chargers or electric boosters can also be used here, which can be used to build up pressure in the supply of gaseous fuels.

For this purpose, the electric charger is arranged in the intake tract or the fuel supply and has a radial compressor in a compressor housing, as well as an electric motor, a rotor assembly and a bearing unit, which are arranged in a bearing housing connected to the compressor housing. In addition to its compressor housing, the radial compressor has a compressor wheel arranged therein that builds up a boost pressure and is part of the rotor assembly. The compressor wheel is arranged in a rotationally fixed manner on one end of a rotor shaft that is also part of the rotor assembly, the so-called rotor shaft, and thus forms the rotor assembly of the electric charger, also known as the compressor rotor. The rotor shaft extends axially through the rotor bearing arranged in the bearing housing and is rotatably mounted radially and axially in relation to the rotor shaft axis. According to this structure, an electric motor, which is also arranged on the rotor shaft, drives the compressor wheel via the rotor shaft, which increases the pressure in the intake tract or in the fuel supply of the combustion unit, based on the gas mass flow behind the radial compressor, and thereby improves the filling of the combustion chamber or reaction unit with air-oxygen or fuel.

A central structural unit of the electric charger is the rotor assembly, which is also referred to as the compressor rotor, which has the rotor shaft, which is also referred to as the rotor shaft, the rotor of the electric motor and the compressor wheel arranged at the end of the rotor shaft. The compressor wheel and the rotor of the electric motor are connected to the rotor shaft in a rotationally fixed manner. In the assembled state, the rotor shaft extends axially through the bearing housing along the electric charger axis and is rotatably mounted therein by means of a bearing arrangement axially and radially about its longitudinal axis, the rotor rotation axis. In an exemplary embodiment of an electric charger, for example, a rotor-permanent magnet arrangement is provided on the rotor shaft, which interacts with a stator arranged in a rotationally fixed manner in the bearing housing and thus forms the electric machine or the electric motor.

For this purpose, the rotor assembly usually has a continuous rotor shaft onto which the other components are, so to speak, threaded. By means of this rotor shaft, which is designed as a tie rod at one end, for example, the individual components, for example the compressor wheel, axial bearing disks, radial bearings, etc., are braced on the rotor shaft using screws or nuts and thereby fixed. Additionally or optionally, individual components, for example magnet arrangements, radial bearings, etc., can also be pressed onto the rotor shaft.

By threading, pressing and clamping the individual components onto the rotor shaft, tolerances can lead to skewing or distortion of the rotor shaft and thus of the entire rotor assembly. This can result in imbalances and shaft deflections or vibrations caused during operation, which have a significant negative influence on the smooth running of the rotor assembly during operation and the overall rotor dynamics and thus, for example, also contribute to shortened service lives of the radial bearings.

Attempts are made to counteract this effect through very small tolerances of the individual components in production, high precision during assembly and, if necessary, multiple high-precision balancing. This significantly increases the manufacturing effort and possibly the reject rate in production, which has a negative impact on the manufacturing costs.

The problem to be solved by the invention is therefore to provide a rotor assembly for an electric charger with an electric motor drive and an electric charger, which have improved smoothness in operation with reasonable manufacturing effort and contribute to improved service life of the radial bearings of the rotor shaft.

This task is solved by a rotor assembly with a hollow shaft for an electric charger with an electric motor drive and an electric charger with such a rotor assembly according to the independent patent claims.

The objects according to the invention have the advantages that there is no tensioning of the rotor assembly via a central, continuous rotor shaft and thereby unbalances of the rotor assembly caused by manufacturing and assembly technology are reduced. In addition, the rotor permanent magnet arrangement inside the hollow rotor shaft is effectively protected from mechanical influences or damage during transport and assembly in the manufacturing process and is secured during operation against the high centrifugal forces that occur at high speeds of rotation of the rotor assembly.

The rotor assembly according to the invention for an electric charger with an electric motor drive has a hollow rotor shaft designed as a hollow shaft, having an inner cavity and rotatable about a rotor axis of rotation, a compressor wheel which is arranged on a first shaft end of the hollow rotor shaft, the opposite free, second shaft end being closed is, and a rotor permanent magnet arrangement, which is arranged in the inner cavity of the hollow rotor shaft and is mechanically firmly connected to the hollow rotor shaft. The compressor wheel is plugged onto the first shaft end of the hollow rotor shaft by means of a mounting connection piece and is mechanically firmly connected to it. The mounting connecting piece is either designed as an integral part of the compressor wheel or the mounting connecting piece is an integral part of a separate compressor wheel carrier component on which the compressor wheel is mechanically fixed.

In this context, a mechanically fixed connection is understood to mean both a positive, a non-positive and a cohesive connection that connects two or more components to one another in such a way that their position relative to one another is fixed in such a way that they meet the expected mechanical, external or internal stresses during operation.

Advantageous embodiments are disclosed in the subclaims and described below and with reference to the figures.

One embodiment of the rotor assembly is characterized in that the mounting connection piece at the first shaft end protrudes precisely into the inner cavity of the hollow rotor shaft by an axial insertion length. This design has the advantage that there is more scope for arranging a radial bearing on the outer circumference of the hollow rotor shaft and the bearing can advantageously be arranged close to the compressor wheel on the hollow rotor shaft.

A further embodiment of the rotor assembly is characterized in that the mounting connection piece encloses an outer circumference of the first shaft end with a precise fit and overlaps by an axial insertion length. The advantage of this design is that more space is gained in the interior of the hollow rotor shaft for the rotor permanent magnet arrangement.

Furthermore, within the scope of the above-mentioned embodiments, a combination can also be implemented on the mounting connection piece in such a way that the mounting connection piece at the first shaft end protrudes into the inner cavity of the hollow rotor shaft with a precise fit by an axial plug-on length and, at the same time, with the first mounting connection piece, an outer circumference of the first Shaft end fits precisely and overlaps by an axial insertion length.

In other words, in such an embodiment, an axial plug-in groove is formed on an end face of the assembly connecting piece of the compressor wheel facing the hollow rotor shaft, which runs concentrically to the rotor axis of rotation, into which the respective end of a cylinder wall surrounding the inner cavity of the hollow rotor shaft and forming the hollow rotor shaft is inserted with a precise fit. The depth of the plug-in groove can correspond to the plug-in length, with the plug-in groove base forming a stop for the respective inserted rotor shaft end. This type of connection is characterized by particular strength and makes it possible to reduce the axial attachment length while maintaining the same strength of the connection.

Another version of the rotor assembly is characterized in that the Mon The connecting piece of the compressor wheel is designed as a hollow piece with an axially extending piece wall that runs concentrically around the axis of rotation of the rotor assembly and a piece recess that faces the inner cavity of the hollow rotor shaft and is surrounded by the piece wall. By designing the mounting connection piece as a hollow piece, the weight of the rotor assembly is advantageously reduced and material is saved. This also has a positive influence on the dynamics of the rotor assembly during operation.

In a further development of the embodiment described above, a further embodiment of the rotor assembly is characterized in that the connecting piece recess in the assembly connecting piece of the compressor wheel extends into the compressor wheel. This means that not only is the assembly connection piece designed as a hollow piece, but the compressor wheel is also hollow in the hub area. The inner diameter of the corresponding recess can be adapted to the outer diameter of the mounting connection piece and the hub of the compressor wheel in such a way that the wall thickness of the respective nozzle wall and the hub of the compressor wheel is minimized to a level that results in a maximum weight reduction, but which does not withstand the mechanical loads still holds up safely during operation. This further reduces the overall weight of the rotor assembly and the material requirement, which advantageously significantly reduces its mass inertia.

A further embodiment of the previous embodiments of the rotor assembly is characterized in that the mounting connection piece of the compressor wheel has a stop edge which runs concentrically to the rotor axis of rotation, which is arranged opposite the end face of the first shaft end and limits the axial insertion length. With such a design, the positioning of the individual components, the hollow rotor shaft and the compressor wheel, relative to one another is made possible in a simple manner with a high degree of accuracy. In a further development of the embodiment described above with a mounting connecting piece protruding into the inner cavity of the hollow rotor shaft, the circumferential stop edge can be arranged, for example, on the outer circumference of the mounting connecting piece and have an outer diameter that radially projects beyond the inner diameter of the inner cavity of the hollow rotor shaft at the first shaft end.

In a further embodiment of the rotor assembly according to one of the previously described embodiments, a further embodiment is characterized in that the compressor wheel is mechanically firmly connected via the mounting connection piece to the assigned first shaft end of the hollow rotor shaft by means of a press connection or a welded connection. Both types of connection mentioned have been tried and tested and can be manufactured easily and advantageously with high precision.

In a connection according to the exemplary embodiment, in which the mounting connecting piece protrudes into the inner cavity of the hollow rotor shaft, in a press connection, for example, the outer diameter of the mounting connecting piece has a small excess dimension compared to the inner diameter of the inner cavity at the assigned first shaft end, so that a press fit between the two assembly partners.

According to a further exemplary embodiment, the rotor assembly is characterized in that an axial bearing disk is arranged as an integral part of the mounting connection piece or as a separate component on the mounting connection piece, for axially supporting the rotor assembly in a bearing housing of the electric charger. This advantageously and easily enables the forces acting axially on the rotor assembly to be supported during operation.

In a further exemplary embodiment, the rotor assembly is characterized in that a separate compressor wheel carrier component is provided, which has a shaft journal extending away from the hollow rotor shaft, on which the compressor wheel is arranged in a mechanically fixed manner. This design has the advantage that conventional compressor wheels, which are designed to be mounted on a conventional rotor shaft, can be used, but without sacrificing the advantages of the hollow rotor shaft with an integrated rotor-permanent magnet arrangement and the connection between the compressor wheel and the hollow motor shaft by means of mounting connecting pieces to have to. As an alternative to the integrated version, the compressor wheel and mounting connection piece form a pre-assembled subassembly.

An embodiment of the aforementioned embodiment with compressor wheel carrier component and shaft journal is characterized in that the compressor wheel is mechanically firmly connected to the shaft journal of the compressor wheel carrier component by means of a press connection or a welded connection or a screw connection. The connection methods mentioned have been tried and tested for the connection between compressor wheels and are easily manageable from an assembly point of view.

A further embodiment of the rotor assembly is characterized in that at least one object from a group formed by the hollow rotor shaft, the mounting connection piece, the compressor wheel and a hollow shaft closure cover, have one or more axial or radial openings towards the inner cavity of the hollow rotor shaft, for cooling ventilation of the rotor permanent magnet arrangement in the inner cavity of the rotor hollow shaft. This enables the operating temperature of the rotor-permanent magnet arrangement to be reduced and thus a higher performance level of the electromotive drive. For example, a through hole running centrally through the hub can be provided in the compressor wheel, through which air is guided from the compressor area into the inner cavity of the hollow rotor shaft. On the opposite side of the hollow rotor shaft, through holes can be provided, for example, extending radially through the hollow rotor shaft wall or axially through the hollow shaft closure cover into the inner cavity, through which air can escape from the inner cavity of the hollow rotor shaft into the environment.

A further embodiment of the rotor assembly is characterized in that the rotor permanent magnet arrangement is fixed axially and rotationally in the inner cavity of the hollow rotor shaft by means of a clamp connection, a press connection or an adhesive connection. For example, individual permanent magnet segments can be arranged and fixed in a carrier component, the outer diameter of the carrier component being dimensioned such that a press fit is formed with the inner diameter of the inner cavity of the hollow rotor shaft. However, separate clamping disks can optionally or additionally be used on both sides of the rotor-permanent magnet arrangement, which establish a clamping connection between the hollow rotor shaft and the rotor-permanent magnet arrangement and thus axially and rotationally fix the rotor-permanent magnet arrangement in the inner cavity of the hollow rotor shaft. The rotor-permanent magnet arrangement can also be fixed using an adhesive connection.

A further embodiment of the rotor assembly is characterized in that the rotor permanent magnet arrangement arranged in the inner cavity of the hollow rotor shaft has a core axis which extends centrally through the rotor permanent magnet arrangement and/or has a magnet sleeve, which includes the rotor permanent magnet arrangement over its entire axial extent. In particular, the core axis can also extend through the aforementioned clamping disks, which for this purpose have a central through hole into which the core axis is inserted, for example by means of a press fit. In this way, the core axis contributes to further stiffening of the rotor assembly and contributes to a rotor assembly that is designed to be durable against bending vibrations. If the material of the core axis is chosen appropriately, for example soft iron, a positive influence can also be had on the magnetic flux of the rotor-permanent magnet arrangement and thus on the performance of the electromotive drive. The magnet sleeve also ensures that the rotor permanent magnet arrangement is protected from damage caused by external influences before and during assembly.

The electric charger according to the invention has a radial compressor with a compressor housing, a bearing unit with a bearing housing in which a bearing arrangement and a stator of an electric motor drive are arranged, and a rotor assembly, with at least the features of the first-mentioned embodiment and possibly further features as above and described using the exemplary embodiments shown below, which is rotatably mounted in the bearing arrangement and which interacts with the stator of the electric motor drive.

A selection of exemplary embodiments of the invention as well as various possible combinations of features of different designs, according to the claims, are explained in more detail below using the illustrations in the drawing.

• 1 bis 3 unterschiedliche Ausführungen der erfindungsgemäßen Rotor-Baugruppe in Ausführung mit Montage-Anschlussstutzen als integraler Bestandteil des Verdichterrades, in schematisch vereinfachter Schnitt-Darstellung;
• 4 bis 6 unterschiedliche Ausführungen der erfindungsgemäßen Rotor-Baugruppe in Ausführung mit Montage-Anschlussstutzen als integraler Bestandteil eines separaten Verdichterradträgerbautels, in schematisch vereinfachter Schnitt-Darstellung;
• 7 eine Ausführung des erfindungsgemäßen Elektroladers in schematisch vereinfachter Schnitt-Darstellung.

Show it:

• 1 to 3 different versions of the rotor assembly according to the invention in a version with a mounting connection piece as an integral part of the compressor wheel, in a schematically simplified sectional representation;
• 4 to 6 different versions of the rotor assembly according to the invention in a version with a mounting connection piece as an integral part of a separate compressor wheel carrier component, in a schematically simplified sectional view;
• 7 an embodiment of the electric charger according to the invention in a schematically simplified sectional view.

Parts with the same function and name are marked with the same reference numerals throughout the figures.

1 shows schematically a rotor assembly 10 according to the invention for an electric charger 100 with an electric motor drive 150. As a central component, this has a rotor assembly. Axis of rotation 11 rotatable hollow rotor shaft 40 designed as a hollow shaft with a first shaft end 41, a second shaft end 42 and an inner cavity 43. A compressor wheel 30 is mechanically firmly connected to the first shaft end 41. For this purpose, a mounting connection piece 32 is formed on the compressor wheel 30, which forms an integral component unit with the compressor wheel 30 and with which the compressor wheel 30 is plugged onto the first shaft end 41 of the hollow rotor shaft 40 and is mechanically firmly connected to it. The second shaft end 42 is free and is only closed with a hollow shaft closure cover 60, which is mechanically firmly connected to the second shaft end 42. For this purpose, as shown in this example, a mounting connection piece 32 can also be formed on the hollow shaft closure cover 60, which is plugged onto the second shaft end 42 of the hollow rotor shaft 40 and is mechanically firmly connected to it.

In the embodiment shown, the compressor wheel 30 has a mounting connection piece 32, which protrudes at the first shaft end 41 of the hollow rotor shaft 40 into the inner cavity 43 of the hollow rotor shaft 40 by an axial slip-on length 33. The mounting connecting piece 32 is manufactured as an integral component unit, in one piece with the compressor wheel 30 and as a hollow piece with an axially extending piece wall 34 that extends concentrically around the rotor axis of rotation 11 and a piece that faces the inner cavity 43 of the hollow rotor shaft 40 and is enclosed by the piece wall 34 -Recess 36 formed. To connect the compressor wheel 30 to the hollow rotor shaft 40, for example, a press connection or a welded connection can be provided between the mounting connection piece 32 and the first shaft end 41 of the hollow rotor shaft 40. Such a mounting connecting piece 32 has an advantageous effect on the rigidity and stability of the rotor assembly 10, depending on the dimensioning of the axial slip-on length 33 and the material thickness of the nozzle wall 34, and enables a reliable and simple connection between the compressor wheel 30 and the hollow rotor shaft 40 .

Furthermore, the mounting connection piece 32 of the compressor wheel 30 has a stop edge 35 running around its outer circumference, which is arranged opposite the end face of the first shaft end 41 and limits the axial attachment length 33. The outer diameter of the stop edge 35 projects beyond an inner diameter of the inner cavity 43 of the hollow rotor shaft 40 at the associated first shaft end 41 in the radial direction. This enables simple and precise axial positioning of the compressor wheel 30 on the hollow rotor shaft 40.

A rotor permanent magnet arrangement 50 is arranged in the inner cavity 43 of the hollow rotor shaft 40 and is mechanically firmly connected to the hollow rotor shaft 40. This can, for example, consist of a carrier component and several different polarized magnet segments held therein, which are pressed together into the inner cavity 43 of the hollow rotor shaft 40. A mechanically fixed connection between the hollow rotor shaft 40 and the rotor permanent magnet arrangement 50 can, as exemplified and schematically in 1 shown, can also be produced or supplemented using clamping disks 57. An adhesive connection between the rotor permanent magnet arrangement 50 and the rotor hollow shaft 40 can also be used optionally or in addition. The connection technologies mentioned have been tried and tested many times and are easy to use.

2 shows an embodiment of the rotor assembly, which essentially has the same structure as that in 1 version shown. However, a different configuration of the mounting connection piece 32 is shown here. Thus, the compressor wheel 30 is equipped with a mounting connection piece 32, which precisely encompasses an outer circumference of the first shaft end 41 and overlaps by an axial slip-on length 33. Thus, a socket recess 36 is provided here, the inner circumference of which, at least in the area of a slip-on length 33, is adapted to the outer circumference of the first shaft end 41 and the first shaft end 41 of the hollow rotor shaft 40 protrudes over the slip-on length 33 into the mounting connection socket 32. On the inner circumference of this socket recess 36, a circumferential stop edge 35 is provided, which is arranged opposite the end face of the first shaft end 41 and limits the axial insertion length 33.

In the 2 The embodiment shown is further characterized in that an axial bearing disk 55 is arranged as a separate component on the outer circumference of the mounting connection piece 32. This serves to axially mount the rotor assembly 10 in a bearing housing 141 of the electric charger 100. The axial bearing disk 55 is mechanically firmly connected to the mounting connection piece 32. In the example shown, this can be ensured using a welded connection or a press fit.

The mounting connection piece 32 of the in 3 Compressor wheel 30 shown has a further alternative design of the mounting connection piece 32. The embodiment of the mounting connection piece 32 shown represents a combination of which in 1 shown version of the mounting connection piece 32 and in 2 shown version of the mounting connection piece zens 32. Here, the assembly connecting piece 32 of the compressor wheel 30 on the first shaft end 41 protrudes into the inner cavity 43 of the rotor hollow shaft 40 with a precise fit by an axial insertion length 33 and also encompasses the outer circumference of the first shaft end 41 with a precise fit and engages over the first shaft end 41 by an axial Attachment length 33. The part protruding into the inner cavity 43 and the part of the assembly connecting piece 32 encompassing the first shaft end 41 can have different extensions in the axial direction, so that this results in two different attachment lengths 33 on the inside and outside of the first shaft end 41 can.

In this way, in this embodiment, an axial plug-in groove 37 is formed on the end face of the mounting connection piece 32, which faces the hollow rotor shaft 40, concentrically to the rotor axis of rotation 11, into which the first shaft end 41, i.e. the inner cavity 43 of the hollow rotor shaft 40 comprehensive cylinder wall forming the rotor hollow shaft 40 is inserted precisely. The depth of the plug-in groove 37 can correspond to the axial plug-on length 33, with the plug-in groove base 37a forming a stop edge for the inserted first shaft end 41. In addition, a socket recess 36 is also provided here, so that the axial plug-in groove 37 is concentric in the axially extending around the rotor axis of rotation 11 circumferential nozzle wall 34 is formed.

Furthermore, those in the 2 and 3 The compressor wheels 30 shown each have a socket recess 36 in the mounting connection socket 32 of the compressor wheel 30, which extends into the compressor wheel 30 and thus contributes to the advantageous reduction of the weight and the mass moment of inertia of the compressor wheel 30.

Finally, they show in the 2 and 3 shown embodiments a rotor assembly 10, which is characterized in that the rotor hollow shaft 40 in the area of the second shaft end 42 has a plurality of radial openings 45, in the form of radially extending through holes through the rotor hollow shaft 40, towards the inner cavity 43 of the rotor hollow shaft 40. Furthermore, in the example shown, an axial opening 44 is provided in the hub of the compressor wheel 30 and in the hollow shaft closure cover 60 in the form of a central, axial through hole. This enables air circulation in the inner cavity 43 of the hollow rotor shaft 40 for cooling ventilation of the rotor-permanent magnet arrangement 50.

4 shows schematically a rotor assembly 10 according to the invention for an electric charger 100 with an electric motor drive 150. This also has, as a central component, a hollow rotor shaft 40 designed as a hollow shaft with a first shaft end 41, a second shaft end 42 and an inner cavity 43. A compressor wheel carrier component 31 is mechanically firmly connected to the first shaft end 41. The compressor wheel 30 is arranged on the compressor wheel carrier component 31 and is also mechanically firmly connected to it. The second shaft end 42 is free and has a hollow shaft closure cover 60, as already described in FIG 1 to 3 shown, locked.

The compressor wheel carrier component 31 has, as an integral component, a mounting connection piece 32, which protrudes at the first shaft end 41 of the hollow rotor shaft 40 into the inner cavity 43 of the hollow rotor shaft 40 by a first axial insertion length 23. The assembly connecting piece 32 is designed as a hollow piece with an axially extending circumferential piece wall 34 and a piece recess 36 facing the inner cavity 43 of the hollow rotor shaft 40 and enclosed by the piece wall 34. To connect the compressor wheel carrier component 31 to the hollow rotor shaft 40, for example, a press connection or a welded connection can be provided between the mounting connection piece 32 and the first shaft end 41 of the hollow rotor shaft 40. Depending on the dimensioning of the axial insertion length 33 and the material thickness of the nozzle wall 34, such a connecting piece has an advantageous effect on the rigidity and stability of the rotor assembly 10 and enables a connection between the compressor wheel carrier component 31 and the hollow rotor shaft 40 that is as reliable as it is simple.

Furthermore, the compressor wheel carrier component 31 has 4 a shaft journal 38 which extends away from the hollow rotor shaft 40 and on which the compressor wheel 30 is arranged in a mechanically fixed manner. In this exemplary embodiment, the mechanically fixed connection is realized by means of a clamping nut 56, with which the compressor wheel 30 is clamped onto the shaft journal 38. However, other types of connection can also be used here as an alternative or in addition, such as a press connection or a screw connection using a thread in the compressor wheel bore or a welded connection, etc. Such a design of the compressor wheel carrier component 31 has the advantage of simple assembly of the compressor wheel 30 on the Compressor wheel carrier component 31 and at the same time allows the use of conventional compressor wheels that are equipped with a compressor wheel hole for mounting on a conventional rotor shaft.

As in 4 shown has the assembly connecting piece 32 of the compressor wheel carrier partly 31 has a radially circumferential stop edge 35, the outer diameter of which radially projects beyond an inner diameter of the inner cavity 43 of the hollow rotor shaft 40 at the assigned first shaft end 41 and limits the axial insertion length 33 of the connecting piece 32. This enables simple and precise axial positioning of the compressor wheel carrier component 31 on the hollow rotor shaft 40.

Furthermore, the exemplary embodiment is in 4 characterized in that the hollow rotor shaft 40 and the mounting connecting piece 32 have a plurality of radial openings 45 towards the inner cavity 43 of the hollow rotor shaft 40 and that the shaft journal 38 of the compressor wheel carrier component 31 and the hollow shaft closure cover 60 each have one or more axial openings 44 towards the inner cavity 43 of the hollow rotor shaft 40, which serve to provide cooling ventilation for the rotor-permanent magnet arrangement 50.

The ones in the 5 The embodiment shown also has a separate compressor wheel carrier component 31, as already shown in 4 described, but is also characterized in that an axial bearing disk 55 is arranged on the compressor wheel carrier component 31 for axially supporting the rotor assembly 10 in a bearing housing 141 of an electric charger 100. The axial bearing disk 55 is designed as an integral part of the compressor wheel carrier component 31 and at the same time limits the axial insertion length 33 of the first connecting piece 32 by acting as a stop for the first shaft end 41. In this way, the function of the axial bearing is easily integrated into the rotor assembly 10 and enables simple and precise axial positioning of the compressor wheel carrier component 31 on the hollow rotor shaft 40.

In the 5 The embodiment shown also differs from the embodiments in terms of the rotor-permanent magnet arrangement 50 1 to 4 . Here, the rotor permanent magnet arrangement 50 has a core axis 58, which extends centrally through the rotor permanent magnet arrangement 50 and the clamping disks 57 arranged on both sides of it and is pressed therewith. In this way, the core axis 58 contributes to further stiffening the rotor assembly 10. With an appropriate choice of the material of the core axis 58, for example soft iron, a positive influence can also be had on the magnetic flux of the rotor-permanent magnet arrangement 50 and thus on the performance of the electromotive drive 150.

In addition to the core axis 58, this embodiment also has a magnet sleeve 59, which encompasses the rotor permanent magnet arrangement 50 over its entire axial extent. This magnet sleeve 59 causes additional stiffening of the rotor permanent magnet arrangement 50 and protects it from damage caused by external influences before and during assembly.

Core axis 58 and magnet sleeve 59 both advantageously contribute to a design of the rotor assembly that is durable against bending vibrations.

In the 6 The version shown differs from the version shown 4 in that an axial bearing disk 55 is provided, which is designed as a separate component and is fixed to the compressor wheel carrier component 31 for assembly purposes, i.e. is not designed as an integral part of the compressor wheel carrier component 31. In the example shown, the axial bearing disk 55 is arranged on a shoulder of the shaft journal 38 of the compressor wheel carrier component 31 and clamped together with the compressor wheel 30 by means of a clamping nut 56.

In addition, in the exemplary embodiment 6 the compressor wheel carrier component 31 does not have a stop edge. This enables an axial insertion length 33 that is variable within limits and thus a fine adjustment of the overall length of the rotor assembly 10 during assembly.

It should be noted that in the 1 to 6 shown feature combinations of the exemplary embodiments are to be understood as examples and are not intended to exclude further exemplary embodiments having deviating feature combinations. The features named in the dependent patent claims can be combined with the features of their independent patent claims individually, in combinations or completely, provided that they do not form mutually exclusive alternatives.

7 shows an electric charger 100 according to the invention in a simplified schematic representation. The electric charger 100 has a radial compressor 130 with a compressor housing 131 in which the compressor wheel 30 of the rotor assembly 10 is arranged.

A bearing unit 140 with a bearing housing 141 is arranged on the compressor housing 131 of the radial compressor 130. A bearing arrangement 142 and a stator 151 of an electric motor drive 150 are arranged in the bearing housing 141, as well as a rotor assembly 10 according to the invention according to one of the previously described embodiments. The rotor assembly 10 is rotatably mounted in the bearing arrangement 142 and interacts with the stator 151 of the electromotive drive 150 by means of its rotor-permanent magnet arrangement 50.

Reference symbol list

10

Rotor assembly

11

Rotor rotation axis

30

Compressor wheel

31

Compressor wheel carrier component

32

Mounting connection piece

33

axial attachment length

34

nozzle wall

35

Stop edge

36

Nozzle recess

37

Plug-in groove

37a

Slot base

38

shaft journal

40

Rotor hollow shaft

41

first wave end

42

second shaft end

43

Interior cavity

44

axial breakthrough

45

radial breakthrough

50

Rotor permanent magnet arrangement

55

Thrust bearing washer

56

clamping nut

57

Clamping disc

58

Core axis

59

Magnet sleeve

60

Hollow shaft closure cover

100

Electric loader

130

Centrifugal compressor

131

Compressor housing

140

Storage unit

141

bearing housing

142

Storage arrangement

150

electric motor drive

151

stator

Claims (14)

Rotor assembly (10) of an electric charger (100) with an electric motor drive (150), which has - a hollow rotor shaft (40) designed as a hollow shaft, having an inner cavity (43) and rotatable about a rotor axis of rotation (11), - a compressor wheel (30) which is arranged on a first shaft end (41) of the hollow rotor shaft (40), with an opposite free shaft end (42) being closed, - a rotor permanent magnet arrangement (50), which is arranged in the inner cavity (43) of the hollow rotor shaft (40) and is mechanically firmly connected to the hollow rotor shaft (40), - wherein the compressor wheel (30) is plugged onto the first shaft end (41) of the hollow rotor shaft (40) by means of a mounting connection piece (32) and is mechanically firmly connected to it, the mounting connection piece (32) being an integral part of the compressor wheel (30 ) or wherein the mounting connection piece (32) is an integral part of a separate compressor wheel carrier component (31) on which the compressor wheel (30) is mechanically fixed. Rotor assembly (10). Claim 1 , characterized in that the assembly connecting piece (32) at the first shaft end (41) protrudes precisely into the inner cavity (43) of the hollow rotor shaft (40) by an axial insertion length (33). Rotor assembly (10). Claim 1 or 2 , characterized in that the assembly connecting piece (32) encloses an outer circumference of the first shaft end (41) with a precise fit and overlaps by an axial slip-on length (33). Rotor assembly (10) according to one of the preceding claims, characterized in that the assembly connecting piece (32) is designed as a hollow piece with an axially extending piece wall (34) running concentrically around the rotor axis of rotation (11) and an inner cavity (43 ) a nozzle recess (36) is formed facing the hollow rotor shaft (40) and enclosed by the nozzle wall (34). Rotor assembly (10). Claim 4 , characterized in that the connecting piece recess (36) in the mounting connecting piece (32) of the compressor wheel (30) extends into the compressor wheel (30). Rotor assembly (10) according to one of the preceding claims, characterized in that the mounting connection piece (32) of the compressor wheel (30) has a circumferential stop edge (35) which is arranged opposite an end face of the first shaft end (41) and which axial attachment length (33) limited. Rotor assembly (10) according to one of the preceding claims, characterized in that the mounting connection piece (32) of the compressor wheel (30) is mechanically firmly connected to the associated shaft end (41) of the hollow rotor shaft (40) by means of a press connection or a welded connection . Rotor assembly (10) according to one of the preceding claims, characterized in that an axial bearing disk (55) is arranged as an integral part of the mounting connecting piece (32) or as a separate component on the mounting connecting piece (32) for axial storage of the Rotor assembly (10) in a bearing housing (141) of the centrifugal compressor (100). Rotor assembly (10) according to one of the preceding claims, characterized in that the compressor wheel carrier component (31) has a shaft journal (38) which extends away from the hollow rotor shaft (40) and on which the compressor wheel (30) is arranged in a mechanically fixed manner . Rotor assembly (10). Claim 8 , characterized in that the compressor wheel (30) is mechanically firmly connected to the shaft journal (36) of the compressor wheel carrier component (31) by means of a press connection or a welded connection or a screw connection. Rotor assembly (10) according to one of the preceding claims, characterized in that at least one object from a group formed by the hollow rotor shaft (40), the mounting connection piece (32), the compressor wheel (30) and a hollow shaft closure cover ( 60), one or more axial or radial openings (44, 45), towards the inner cavity (43) of the rotor hollow shaft (40), for cooling ventilation of the rotor permanent magnet arrangement (50). Rotor assembly (10) according to one of the preceding claims, characterized in that the rotor permanent magnet arrangement (50) is axially and rotationally fixed in the inner cavity (43) of the hollow rotor shaft (40) by means of a clamp connection, a press connection or an adhesive connection. Rotor assembly (10) according to one of the preceding claims, characterized in that the rotor permanent magnet arrangement (50) arranged in the inner cavity (43) of the rotor hollow shaft (40) has a core axis 58 which extends centrally through the rotor Permanent magnet arrangement 50 extends and / or has a magnet sleeve 59 which includes the rotor permanent magnet arrangement 50 over its entire axial extent. Electric charger (100) which has a radial compressor (130) in a compressor housing (131), a bearing unit (140) with a bearing housing (141) in which a bearing arrangement (142) and a stator (151) of an electric motor drive (150) are arranged, and a rotor assembly (10) according to one of the preceding claims, which is rotatably mounted in the bearing arrangement (142) and whose rotor-permanent magnet arrangement (50) cooperates with the stator (151) of the electric motor drive (150).

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