Rotorhohlwelle

Abstract

Hollow rotor shaft (1) for a rotor of an electric machine rotating about a longitudinal axis, comprising a cylindrical shell (2) surrounding a shaft cavity (3), and end flanges (4) arranged on both sides of the cylindrical shell (2), wherein at least one end flange (4) transitions into a hollow shaft journal (5), wherein the outer circumferential surface of the shaft journal (5) is partially designed as a bearing seat (7), wherein rotor windings connected to current supply lines (10) are arranged on the outer circumference of the cylindrical shell (2), wherein the current supply lines (10) terminate at the end opposite the rotor windings in sliding contacts (11) arranged at the free end of the shaft journal (5), characterized in that these are formed in one piece by forming from a tubular or disc-shaped starting body by means of stretch forming.wherein the power supply lines (10) are arranged at least in the region of the bearing seat (7) in the cavity (6) of the shaft journal (5) and are embedded in a tubular shell (12) made of plastic, which is integrally injection-molded onto the inner circumferential surface of the shaft journal (5), wherein the tubular shell (12) made of plastic with the embedded power supply lines (10) extends axially outwards over the free end of the shaft journal (5) into a free end region (12a) and the sliding contacts (11) are embedded in the tubular shell (12) and arranged on the outer circumference of the free end region (12a).

Description

[0001] The invention relates to a hollow rotor shaft for a rotor of an electric machine rotating about a longitudinal axis, comprising a cylindrical shell surrounding a shaft cavity and end flanges arranged on both sides of the cylindrical shell, wherein at least one end flange transitions into a hollow shaft journal, wherein the outer circumferential surface of the shaft journal is partially designed as a bearing seat, wherein rotor windings connected to current supply lines are arranged on the outer circumference of the cylindrical shell, wherein the current supply lines terminate at the end facing away from the rotor windings in sliding contacts arranged at the free end of the shaft journal.

[0002] In separately excited synchronous machines, magnetic coils are mounted on both the stator and the rotor shaft, through which current flows during operation. While the current supply to the windings of the stationary stator is straightforward, the current supply to the rotor windings is achieved via slip rings on the rotor shaft and stationary brushes. Therefore, current leads running along the rotor shaft are required from the slip rings to the rotor windings.

[0003] In a known hollow rotor shaft with the features of the preamble of claim 1, which is used, for example, in the separately excited synchronous motor of the "Renault Zoe" vehicle type, the sliding contacts are arranged at the free end of a shaft journal of the hollow rotor shaft, and the current leads run along the outer circumferential surface of the shaft journal. Longitudinal grooves are machined into the outer circumference of the shaft journal in the area of ​​the bearing seat, through which the current leads are guided. In the installed state, these leads are radially surrounded on the outside by the associated bearing ring in the area of ​​the bearing seat. Due to these longitudinal grooves, the bearing ring does not have full circumferential contact with the shaft journal. This complicates the mounting of the bearing and also leads to a weakening of the hollow rotor shaft in this area, necessitating an increase in the wall thickness of the shaft journal.

[0004] From DE 10 2019 109 183 A1, a method for manufacturing a hollow shaft by flow forming is known. From DE 10 2016 200 766 A1, an electric machine with a hollow rotor shaft is known. From JP 2014-017 890 A, a hollow rotor shaft is known in which the sliding contacts are arranged at the free end. From DE 10 2018 130 471 A1, a rotor with a rotor shaft designed as a solid shaft is known. From US 2017 / 0 163 134 A1, another rotor with a rotor shaft is known.

[0005] The object of the invention is to create a cost-effective, weight-reduced hollow rotor shaft in which the area of ​​the bearing seat is not affected by the power supply lines.

[0006] This problem is solved according to the invention in a hollow rotor shaft of the type described above by forming it in one piece from a tubular or disc-shaped starting body by means of stretch forming, wherein the current supply lines are arranged at least in the area of ​​the bearing seat in the cavity of the shaft journal and are embedded in a tubular plastic jacket which is injection-molded in one piece onto the inner circumferential surface of the shaft journal, wherein the tubular plastic jacket with the embedded current supply lines extends axially outwards over the free end of the shaft journal into a free end region and the sliding contacts are embedded in the tubular jacket and arranged on the outer circumference of the free end region.

[0007] According to the invention, a hybrid rotor hollow shaft is provided that can be manufactured simply and cost-effectively by stretch forming and subsequent molding of the plastic shell. Since the power supply lines are embedded in the shell inside the shaft journal, at least in the area of ​​the bearing seat, no material-weakening longitudinal grooves are required on the outer surface in the bearing seat area, allowing the shaft journal wall thickness to be reduced, thus saving weight. Furthermore, the bearing ring makes full contact. Additional insulation of the sliding contacts from the shaft journal is not required. Moreover, the power supply lines do not need to be routed through radial openings in the shaft journal in the area of ​​the sliding contacts.

[0008] Preferably, radial openings are provided between the end flange and the bearing seat of the shaft journal, through which the power supply lines are guided radially outwards, embedded in extensions of the plastic jacket that extend outwards through the openings.

[0009] Furthermore, it is advantageously provided that the power supply lines are guided in spacers arranged within the cavity of the shaft journal. This facilitates the positioning of the power supply lines before the plastic sheath is molded. After molding, the spacers are embedded in the sheath.

[0010] Furthermore, a stop ring is provided adjacent to the end flange in the cavity of the shaft journal as a injection edge for the tubular plastic jacket.

[0011] This stop ring can preferably be molded in one piece during the stretch forming process. Alternatively, the stop ring can also be a separate component that is inserted into the hollow rotor shaft.

[0012] The tubular casing can be formed by injection molding or transfer molding. A thermoset plastic is preferably used.

[0013] The invention is explained in more detail below with reference to the drawing. This shows in Fig. 1 a longitudinal section through a partially depicted hollow rotor shaft.

[0014] A hollow rotor shaft for a rotor of an electrical machine, in particular a separately excited synchronous machine, rotating about a longitudinal axis L, is generally designated by 1 and is only partially shown with the components essential for the invention.

[0015] The hollow rotor shaft 1 has a cylindrical shell 2, shown only partially, on which rotor windings (not shown in the finished rotor) are arranged. The cylindrical shell 2 surrounds a shaft cavity 3, shown only partially, and is bounded on both sides by an end flange 4, of which only one end flange 4 is shown. The end flange 4 transitions into a hollow shaft journal 5, the cavity of which is designated 6.

[0016] The rotor hollow shaft 1 described in this respect is manufactured in one piece according to the invention by forming it by means of stretch pressing from a tubular or disc-shaped starting body not shown.

[0017] The outer circumferential surface of the shaft journal 5 is partially designed as a bearing seat 7. An inner bearing ring (not shown) of a ball bearing or the like is arranged on this bearing seat 7, wherein circumferential grooves 8, 9 for snap rings or the like are provided on both sides of the bearing seat 7.

[0018] Power supply lines 10 are provided for the rotor windings (not shown), each terminating at the end furthest from the rotor windings in circumferential ring-shaped sliding contacts 11. These sliding contacts 11 cooperate with stationary brushes (not shown) of the electric machine for current transmission.

[0019] According to the invention, the power supply lines 10 are arranged at least in the region of the bearing seat 7 in the cavity 6 of the shaft journal 5 and embedded in a tubular shell 12 made of plastic. This tubular shell 12 is formed on the inner circumferential surface of the shaft journal 5 (by injection molding or compression molding). Radial passage openings 13 are provided between the end flange 4 and the bearing seat 7 of the shaft journal 5, through which the power supply lines 10 are guided radially outwards, embedded in extensions 14 of the plastic shell 12 that project outwards through the passage openings 13. From there, the power supply lines 10 extend further to the rotor windings (not shown). The power supply lines 10 are also not shown in the area outside the radial passage through the passage openings 13.

[0020] The tubular plastic sheath 12 with the embedded power leads 10 extends axially outwards beyond the free end of the shaft journal 5. In this free end region 12a, which extends beyond the shaft journal 5, the annular sliding contacts 11 are embedded in the tubular sheath 12 or the end region 12a.

[0021] To position the power supply lines 10 within the cavity 6 of the shaft journal 5 before the injection molding or compression molding of the shell 12, spacers (not shown) can be arranged within the cavity 6, in which the power supply lines 10 are guided. These spacers are then embedded in the shell 12 during injection molding or compression molding.

[0022] To enable flawless injection molding or injection molding of the jacket 12, a stop ring 15 is provided as a gate edge adjacent to the end flange 4 in the cavity 6 of the shaft journal 5. This stop ring 15 can be integrally formed into the hollow rotor shaft 1, i.e., produced by stretch forming. In the illustrated embodiment, only an annular stop edge 16 is formed by stretch forming, against which a separate stop ring 15 rests. Reference symbol list: 1 Rotor hollow shaft 2 cylinder shell 3 wave cavity 4 Front flange 5 hollow shaft pin 6 Cavity 7 bearing seat 8 grooves 9 grooves 10 Power supply 11 Sliding contact 12 tubular jacket 12a free end area 13 Passage opening 14 Approach 15 Stop ring 16 Stop edge L Longitudinal axis

Claims

[1] Hollow rotor shaft (1) for a rotor of an electrical machine rotating about a longitudinal axis, having a cylinder jacket (2) surrounding a shaft cavity (3), and end flanges (4) arranged on both sides of the cylinder jacket (2), at least one end flange (4) merging into a hollow shaft journal (5), the outer circumferential surface of the shaft journal (5) being designed in some areas as a bearing seat (7), rotor windings connected to power supply lines (10) being arranged on the outer circumference of the cylinder jacket (2), the power supply lines (10) opening into sliding contacts (11) at the end facing away from the rotor windings, which sliding contacts are arranged at the free end of the shaft journal (5), characterized bythat it is formed in one piece by forming by means of stretch forming from a tubular or round blank-shaped starting body, wherein the power supply lines (10) are arranged at least in the region of the bearing seat (7) in the cavity (6) of the shaft journal (5) and are embedded in a tubular casing (12) made of plastic which is injection-molded in one piece onto the inner circumferential surface of the shaft journal (5), wherein the tubular casing (12) made of plastic with the embedded power supply lines (10) extends axially outwards over the free end of the shaft journal (5) into a free end region (12a) and the sliding contacts (11) are embedded in the tubular casing (12) and are arranged on the outer circumference of the free end region (12a). [2] Hollow rotor shaft (1) according to claim 1, characterized bythat radial through-openings (13) are provided between the end flange (4) and the bearing seat (7) of the shaft journal (5), through which the power supply lines (10) are guided radially outwards, embedded in projections (14) of the plastic casing (12) which extend outwards through the through-openings (13). [3] Hollow rotor shaft (1) according to claim 1 or 2, characterized by that the power supply lines (10) are guided in spacers arranged within the cavity (6) of the shaft journal (5). [4] Hollow rotor shaft (1) according to claim 1, 2 or 3, characterized by that adjacent to the end flange (4) in the cavity (6) of the shaft journal (5) a stop ring (15) is provided as a molding edge for the tubular casing (12) made of plastic. [5] Hollow rotor shaft (1) according to claim 4, characterized by that the stop ring (15) is formed in one piece. [6] Hollow rotor shaft (1) according to one of claims 1 to 5, characterized bythat the tubular jacket (12) is formed by injection molding or transfer molding.

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