DE102023126956A1 - ROTOR SHAFT FOR AN ELECTRIC MACHINE - Google Patents

Abstract

A rotor shaft (10) for an electrical machine is provided, wherein the rotor shaft (10) comprises a main shaft (1), a sun element (4) which is designed as a sun gear and/or sun shaft (4), and a coupling element (2) for the rotationally fixed and radial offset-compensating coupling of the main shaft (1) and the sun element (4).

Description

The present disclosure relates to a rotor shaft for an electric machine, an electric machine, and/or a motor vehicle with the electric machine.

Electric machines can be used in motor vehicles, for example, as traction machines. The torque from a rotor or rotor shaft of the respective electric machine is transmitted via one or more gears to other components of the respective motor vehicle, e.g., to the motor vehicle's drivetrain. Various types of gears are known for this purpose, including planetary gears.

In a combination of an electric machine and a planetary gear, a separate sun gear is usually connected to the rigid rotor shaft as a shaft-hub connection, or the sun gear and the rigid rotor shaft are formed as a single piece.

However, with a rigid rotor shaft, manufacturing tolerances can cause the sun gear to be imperfectly concentric with the center of the planet gears. This results in an uneven load distribution from the sun gear to the planet gears, which leads to unfavorable stress on the planet gears.

DE 10 2018 209 834 A1 describes a planetary gear comprising a sun gear, a ring gear, and a carrier as elements. The planetary gear has at least one cross-slide element, each of which is assigned to an element of the planetary gear, connects it to a shaft in a rotationally fixed manner, and serves as a radial offset compensation element.

DE 10 2014 203 948 A1 describes a planetary gear with at least one sun gear having a toothed region with external teeth, with at least one planet carrier arranged coaxially and rotatably to the sun gear, wherein a sliding sleeve is arranged between the planet carrier and the sun gear, which sliding sleeve has, on the one hand, an axial stop surface for limiting an axial displacement of the sun gear and, on the other hand, a hollow cylindrical radial stop surface for limiting a radial displacement of the sun gear.

Against the background of this prior art, the object of the present disclosure is to provide a device and/or a method which are each suitable for enriching the prior art.

The problem is solved by the features of the independent claims. The subordinate claims and the dependent claims each contain optional developments of the disclosure.

The task is then solved by a rotor shaft for an electric machine.

The rotor shaft comprises a main shaft and a sun element, which is designed as a sun gear and/or sun shaft.

The rotor shaft comprises a coupling element (e.g. annular and/or annular disc-shaped) for the rotationally fixed and radial offset-compensating coupling of the main shaft and the sun element.

A radial misalignment-compensating coupling can be understood as a connection between the main shaft and the sun element in a rotationally fixed and simultaneously radially displaceable manner, with the central axes (or axes of rotation) of the main shaft and the sun element being identical or running parallel to one another. The radial misalignment-compensating coupling can be expediently designed so that axial forces occurring, viewed along the longitudinal axis of the rotor shaft or the machine axis of the electric machine, can be absorbed and introduced into the rotor shaft or bearing points. Reasons for axial forces occurring include possible helical gearing of the planetary or sun gears or sun shaft and thermal linear expansion of the main shaft, coupling elements and/or the sun gear or sun shaft.

The sun element can be part of a planetary gear system, which is also known in the art as an epicyclic gear system. The sun element is a central driving gear or a central driving shaft surrounded by at least one planetary gear (also known as an epicyclic gear) and configured to transmit torque (e.g., according to a gear ratio) to the at least one planetary gear.

The permanent magnet rotor described above offers a number of advantages. For example, in the development of the present disclosure, a split or assembled rotor shaft with a "floating" sun element was used, ie the sun element can float as optimally as possible into the center of the planetary gears surrounding the sun element due to the radial offset compensating coupling. This ensures that, regardless of Depending on possible manufacturing tolerances, an even load distribution from the sun element to the planetary gears is possible, thus ensuring an even load on the planetary gears.

Possible further developments of the permanent magnet rotor described above are explained in detail below.

The main shaft, the coupling element, and the sun element can each be axially symmetric, e.g., rotationally symmetric. The coupling element and the sun element can be arranged coaxially to one another. The main shaft can be arranged coaxially (through the coupling element) or radially offset (or radially offsettable) to the coupling element and the sun element.

The coupling element can be designed as a cross-disk coupling element (also: cross-slide coupling element) and/or to create a cross-disk coupling (also: cross-slide coupling) between the main shaft and the sun element. Alternatively, other types of radial misalignment-compensating coupling elements are also conceivable.

The coupling element can be arranged radially fixed (or motion-proof) on or in the main shaft. The coupling element and the sun element can be connected (motion-proof).

The main shaft can be designed as a hollow shaft. The coupling element can be housed in the main shaft. The main shaft and the coupling element can be coupled via a spline.

The main shaft may have internal gearing (on an inner side of the main shaft). The coupling element may have external gearing (on an outer surface of the coupling element). The internal gearing of the main shaft and the external gearing of the coupling element may be engaged to produce the spline. The main shaft and the coupling element may be rotationally fixedly coupled via the spline.

The sun element can be designed as a sun shaft. The sun element can have one end facing the coupling element and is at least partially received in the main shaft.

The rotor shaft may include a bearing support. The bearing support may have a first section, wherein the first section may be received in the main shaft and/or may circumferentially surround the end of the sun element. The first section and the main shaft may be coupled via a spline. The bearing support may advantageously serve to ensure that the structure, i.e., the assembled rotor shaft, is axially free of play.

The first section of the bearing support can have external toothing (on an outer surface of the first section). The internal toothing of the main shaft and the external toothing of the first section (of the bearing support) can be engaged to create the spline. The main shaft and the bearing support can be rotationally fixedly coupled via the spline.

The end of the sun element (or sun shaft) may have a (first) outer diameter that is larger than a (second) outer diameter of a remaining part of the sun element.

The remaining part of the sun element may have external gearing (on an outer surface of the remaining part), e.g., helical gearing. The external gearing may be engageable or engageable with one or more planetary gears to create a planetary gear.

The sun element can be designed as part of a planetary gear system. The sun element, e.g., the sun shaft, can be surrounded by one or more planetary gears and/or can mesh with the planetary gears, e.g., via gearing.

The bearing support may have a second section, wherein the second section circumferentially surrounds the remaining part of the sun element in sections. The first section of the bearing support may have a (first) inner diameter that is larger than a (second) inner diameter of the second section.

The first portion of the bearing support can be arranged radially between the end of the sun element and the main shaft. The inner diameter of the first portion of the bearing support can be larger than the outer diameter of the end of the sun element. An outer diameter of the first portion of the bearing support can be smaller than an inner diameter of the main shaft.

An end edge of the first section of the bearing neck may rest against the coupling element.

The bearing support may have a centering seat for radial positioning around the sun element and/or on the main shaft.

The rotor shaft may include an annular, e.g., annular disk-shaped, center piece for establishing a rotationally fixed connection (and/or arrangement) of the coupling element and the sun element. The center piece may be arranged between the coupling element and the sun element.

The middle piece can rest against the same side surface of the coupling element as the end edge of the first section of the bearing socket.

The center piece can have elevations on opposite side surfaces, each facing the coupling element or the sun element. The coupling element and the sun element can each have at least one recess corresponding in shape (each with one of the elevations). The elevations can each be received in one of the corresponding recesses. The elevations can be formed with an undercut geometry, e.g., a circular cross-section (instead of a rectangular cross-section).

The bearing support and/or the center piece can be arranged coaxially to the coupling element and the sun element.

The above description can be summarized in other words and in a possible more concrete embodiment of the disclosure as described below, whereby the following description is not to be interpreted as limiting the disclosure.

The present disclosure may relate to a rotor shaft of an electric motor or an electric machine with a planetary gear, which enables a "radial floating" of the sun gear or sun shaft into the planet gears. This may be achieved by integrating a type of cross-disk coupling into the rotor shaft.

In other words, a type of integrated cross-disk coupling allows the sun gear or sun shaft to be connected to the main shaft in a radially movable manner. This allows the sun gear to optimally align with the center of the planetary gears. The design can be designed to be axially backlash-free.

The torque flow can be initiated via the main shaft and transmitted via a spline to the drive part of the cross-disk coupling. This can be connected to a center piece, which can transmit the torque to the sun shaft. This flexible connection allows for radial misalignment to be compensated while still absorbing the axial force generated by the helical gearing.

A bearing support can then be inserted into the spline of the main shaft, which can be radially positioned using a centering seat. It can axially engage the drive part of the cross-disk coupling. This allows the entire assembly to be axially backlash-free.

The rotor shaft can be used, for example, in a permanently excited synchronous machine with a planetary gear. Radial compensation can be achieved via a cross-disk, although other types of radially compensating couplings are also conceivable.

Furthermore, an electric machine for a motor vehicle is provided, which comprises the rotor shaft described above.

The electric machine may comprise a rotor, wherein the rotor shaft forms part of the rotor.

The electric machine may comprise a stator that surrounds at least a portion of the rotor and/or the rotor shaft, e.g., the main shaft, at least circumferentially or in the circumferential direction.

The stator can have several electrical coils which can be supplied with alternating current and/or three-phase current, for example.

The electrical machine can be a synchronous machine, e.g., a permanently excited or separately excited synchronous machine. The electrical machine can comprise a laminated core that surrounds the main shaft of the rotor shaft on the periphery or is arranged on the periphery of the main shaft. Permanent magnets, for example, can be arranged in and/or on the laminated core.

A torque (or torque flow) can be introduced via the main shaft and transmitted via the coupling element to the sun element (and thus, for example, to a sun gear). The main shaft can be moved by means of a magnetic field generated by the stator or by an interaction between the stator and the rotor.

A planetary gear can be provided on the electrical machine, whereby the sun element can be designed as part of the planetary gear.

What was described above with reference to the rotor shaft also applies analogously to the electric machine and vice versa.

Furthermore, a motor vehicle is provided which comprises the electric machine described above and/or the rotor shaft described above.

The motor vehicle can be an electrically driven, e.g., drivable, motor vehicle. The electric machine can be designed as a traction motor or traction machine of the motor vehicle. The motor vehicle can include a traction battery, e.g., for supplying the stator with electrical energy, e.g., via at least one inverter with an alternating current.

The motor vehicle may be a passenger car, in particular an automobile, or a commercial vehicle, such as a truck.

What has been described above with reference to the electric machine and the rotor shaft also applies analogously to the motor vehicle and vice versa.

• 1 zeigt schematisch eine Explosionsansicht einer offenbarungsgemäßen Rotorwelle, und
• 2 zeigt schematisch die Rotorwelle in einem zusammengebauten bzw. eingebauten Zustand.

Below is an optional embodiment with reference to 1 and 2 described.

• 1 shows schematically an exploded view of a rotor shaft according to the disclosure, and
• 2 shows schematically the rotor shaft in an assembled or installed state.

1 shows only schematically the rotor shaft 10 in an exploded view.

The rotor shaft 10 comprises a main shaft 1, which is designed as a hollow shaft and has an internal toothing 1.1 on its inside.

The rotor shaft 10 comprises a sun element 4, which in the illustrated embodiment is designed as a sun shaft. Alternatively, or additionally, the sun element 4 can also be designed as a sun gear.

The sun element 4 comprises an end 4.1 which has an outer diameter which is larger than an outer diameter of a remaining part 4.2 of the sun element 4. On the outer shell of the remaining part 4.2, an external toothing 4.3, e.g. a helical toothing, is formed, which can be brought into engagement with one or more planet gears to produce a planetary gear.

The rotor shaft 10 comprises a coupling element 2 for the rotationally fixed and radial offset-compensating coupling of the main shaft 1 and the sun element 4. The coupling element 2 can be designed as a cross-disk coupling element 2 and/or for producing a cross-disk coupling between the main shaft 1 and the sun element 4. An external toothing 2.1 is formed on the outer surface of the coupling element 2.

To establish a rotationally fixed connection between the coupling element 2 and the sun element 4, the rotor shaft 10 can comprise, for example, an annular center piece 3. The center piece 3 can have elevations 3.1, 3.2 on its side surfaces, which can be configured to correspond in shape to recesses 2.2, 4.4 on the coupling element 2 and the sun element 4 (or the end 4.1).

The rotor shaft 10 may further comprise a bearing support 5. The bearing support 5 comprises a first section 5.1, which has an inner diameter that is larger than an inner diameter of a second section 5.2 of the bearing support 5. An external toothing 5.4 is formed on the outer surface of the first section 5.1.

Furthermore, a circumferential edge 5.3 can be formed on the outer shell of the bearing support 5, e.g. between the first section 5.1 and the second section 5.2.

2 shows only schematically the rotor shaft 10 from 1 in the assembled or installed state.

The coupling element 2, the sun element 4, the center piece 3, and the bearing support 5 are arranged coaxially with each other. The main shaft 1 can be arranged radially displaceable relative to the coupling element 2, the sun element 4, the center piece 3, and the bearing support 5.

The internal gearing 1.1 of the main shaft 1 and the external gearing 2.1 of the coupling element 2 are engaged to create a spline, whereby the main shaft 1 and the coupling element 2 are coupled via the spline. The coupling element 2 is accordingly radially fixedly received in the main shaft 1.

The end 4.1 of the sun element 4 (or the sun shaft) is arranged facing the coupling element 2 and, together with the coupling element 2, is received at least in sections in the main shaft 1.

The middle piece 3 is arranged between the coupling element 2 and the sun element 4, with the elevation 3.1 in the recess 4.4 of the sun element 4 and the elevation 3.2 is received in the recess 2.2 of the coupling element.

The bearing support 5 inverts the sun element 4, with the first section 5.1 of the bearing support 5 being received in the main shaft 1 and circumferentially surrounding the end 4.1 of the sun element 4. The second section 5.2 of the bearing support 5 circumferentially surrounds a section of the remaining part 4.2 of the sun element 4, with the external toothing 4.3 of the sun element not being surrounded by the bearing support 5 (or the second section 5.2) (and thus exposed for planetary gears).

The bearing support 5 is pushed over the sun element 4 (and the center piece 3) as far as it will go, i.e. an end edge of the first section 5.1 of the bearing support 5 can rest on the coupling element 2 and/or the circumferential edge 5.3 can rest on an end edge of the main shaft 1.

The internal toothing 1.1 of the main shaft 1 and the external toothing 5.4 on the first section 5.1 of the bearing support 5 are engaged to produce a spline, wherein the main shaft 1 and the bearing support 5 are coupled via the spline.

The rotor shaft 10, e.g., according to the previously described embodiment, can be part of an electrical machine, e.g., a (permanently excited) synchronous machine, for a motor vehicle, wherein the electrical machine can be designed, e.g., as a traction motor or traction machine of the motor vehicle.

List of reference symbols

1

Main shaft

1.1

Internal gearing of the main shaft

2

coupling element

2.1

External teeth of the coupling element

2.2

recess

3

centerpiece

3.1, 3.2

Surveys

4

solar element, solar wave

4.1

End of the solar element

4.2

remaining part of the solar element

4.3

External gearing of the sun element

4.4

recess

5

bearing support

5.1

first section of the bearing support

5.2

second section of the bearing support

5.3

Circumferential edge of the bearing support

5.4

External toothing of the bearing support

10

rotor shaft

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2018 209 834 A1 [0005]
• DE 10 2014 203 948 A1 [0006]

Claims (9)

Rotor shaft (10) for an electrical machine, wherein the rotor shaft (10) comprises: - a main shaft (1), and - a sun element (4) which is designed as a sun gear and/or sun shaft (4), characterized in that the rotor shaft (10) comprises: - a coupling element (2) for the rotationally fixed and radial offset-compensating coupling of the main shaft (1) and the sun element (4). Rotor shaft (10) after Claim 1 , characterized in that the coupling element (2) is designed as a cross-disk coupling element (2) and/or for producing a cross-disk coupling between the main shaft (1) and the sun element (4). Rotor shaft (10) after Claim 1 or 2 , characterized in that - the main shaft (1) is designed as a hollow shaft, - the coupling element (2) is accommodated in the main shaft (1), and - the main shaft (1) and the coupling element (2) are coupled via a spline (1.1, 2.1). Rotor shaft (10) after Claim 3 , characterized in that the sun element (4) is designed as a sun shaft (4) and has an end (4.1) which faces the coupling element (2) and is at least partially received in the main shaft (1). Rotor shaft (10) after Claim 4 , characterized in that the rotor shaft (10) comprises: - a bearing support (5) which has a first section (5.1), wherein the first section (5.1) is received in the main shaft (1) and circumferentially surrounds the end (4.1) of the sun element (4), and wherein the first section (5.1) and the main shaft (1) are coupled via a spline (1.1, 5.4). Rotor shaft (10) after Claim 5 , characterized in that - the end (4.1) of the sun element (4) has an outer diameter which is larger than an outer diameter of a remaining part (4.2) of the sun element (4), and - the bearing socket (5) has a second section (5.2), wherein the second section (5.2) surrounds the remaining part (4.2) of the sun element (4) in sections on the circumference, and wherein the first section (5.1) of the bearing socket (5) has an inner diameter which is larger than an inner diameter of the second section (5.2). Rotor shaft (10) according to one of the Claims 1 until 6 , characterized in that the rotor shaft (10) comprises: - an annular center piece (3) for establishing a rotationally fixed connection between the coupling element (2) and the sun element (4), the center piece (3) being arranged between the coupling element (2) and the sun element (4). Electrical machine for a motor vehicle, characterized in that the electrical machine has the rotor shaft (10) according to one of the Claims 1 until 7 includes. Motor vehicle, characterized in that the motor vehicle has the electrical machine according to Claim 8 and/or the rotor shaft (10) according to one of the Claims 1 until 7 includes.

Images