Shaft device and motor vehicle comprising a shaft device
Patent Information
- Application Number
- EP2024703305
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-16
- Filing Date
- 2024-01-31
- Publication Date
- 2025-12-24
AI Technical Summary
Existing shaft devices for motor vehicle electric machines lack fail-safe and fuel-efficient operation, particularly in ensuring fluid exchange and current diversion during rotor shaft operation.
A shaft device with a hollow shaft featuring a through opening for fluid exchange and a shaft grounding surface, incorporating a pipe insert with a smaller inner diameter to prevent backflow and a support area with webs for fluid drainage, made from a combination of metallic and plastic materials for weight reduction and improved assembly.
Ensures reliable fluid exchange and current diversion, contributing to fail-safe and fuel-efficient motor vehicle operation by preventing fluid backflow and effectively dissipating leakage, while reducing weight and assembly complexity.
Smart Images
Figure EP2024052309_22082024_PF_FP
Abstract
Description
[0001] Shaft device and motor vehicle with a shaft device
[0002] The invention relates to a shaft device designed for coupling to a rotor shaft of an electric motor of a motor vehicle. Another aspect of the invention relates to a motor vehicle with a shaft device.
[0003] Such shaft devices can be designed, on the one hand, to guide a fluid, for example for cooling and / or lubrication, and, on the other hand, to divert currents via a shaft grounding, as mentioned by way of example in DE 10 2021 204 098 A1. This published patent application discloses a device for electrically coupling a rotatably mounted shaft to a component of a drive system, in which the shaft is part of an at least partially electric drive system. The device comprises a first coupling unit formed from an electrically conductive material and is or can be fastened to the shaft in a rotationally co-rotating manner. Furthermore, the device comprises a second coupling unit formed from an electrically conductive material and can be fastened to the component in the drive system in a fixed manner with respect to the shaft.In an assembled state of the device, in which the first coupling unit is fastened to the shaft and the second coupling unit is fixedly fastened to the component in the drive system with respect to the shaft, a capacitive coupling can be generated between the first coupling unit and the second coupling unit across a gap between them.
[0004] The object of the present invention is to provide a shaft device of the type mentioned above, which contributes to a fail-safe and fuel-efficient operation of a motor vehicle.
[0005] This object is achieved by a shaft device having the features of patent claim 1 and by a motor vehicle having the features of patent claim 8. Advantageous embodiments with expedient further developments of the invention are specified in the subclaims.
[0006] A first aspect of the invention relates to a shaft device designed for coupling to a rotor shaft of an electric machine of a motor vehicle, comprising a hollow shaft, along the axial extent of which a through-opening extends for conducting a fluid for fluid exchange with the rotor shaft, and comprising a shaft grounding surface arranged on the hollow shaft, which is designed for contact with a grounding element in order to divert currents generated during operation of the electric machine via the hollow shaft toward a housing. The housing can, in particular, be assigned to the electric machine.
[0007] According to the invention, the shaft device comprises a tubular insert received in the through-opening, which tubular insert has a through-opening with a smaller inner diameter than a first inner diameter of the through-opening and is designed to form a step, together with a hollow shaft wall of the hollow shaft, within the through-opening that prevents the fluid from flowing back. The advantage here is that the step, which prevents the fluid from flowing back, can ensure that a sufficient quantity of fluid is maintained even when the hollow shaft is rotating during operation of the electric machine, which is particularly the case when the step is designed to be rotationally symmetrical with respect to a rotational axis of the hollow shaft oriented along the axial extension direction.The earthing element can advantageously be designed as a wave earthing pin, which, in contrast to disc-shaped or ring-shaped earthing elements, for example, provides a particularly high degree of flexibility in the arrangement of the earthing element.
[0008] In an advantageous development of the invention, the tube insert has a hollow tube region through which the passage opening extends, as well as a support region over which the hollow tube region is supported on the hollow shaft wall and spaced from the hollow shaft wall. This is advantageous because the hollow tube region and the support region enable a particularly needs-based, and above all, weight-reduced, design of the tube insert. For example, linear or point-shaped support on the hollow shaft wall can be achieved via the support region, with the support region being able to take on the function of a spacer. An air gap can extend in the axial direction of extent between the hollow tube region and the hollow shaft wall along the support region, through which air gap any fluid leakage that occurs, for example, during operation of the electrical machine can be dissipated.
[0009] In a further advantageous development of the invention, the support region has at least two webs, which are oriented at least predominantly in the axial direction. This is advantageous because the at least two webs ensure sufficient positional stability while keeping the weight of the support region low. Furthermore, the at least two webs can easily ensure that the air gap remains the same size even when the shaft device is rotating. Depending on the number of webs, the air gap can be divided circumferentially into several air gap segments, yet the air gap remains sufficiently large to reliably dissipate leakage.
[0010] In a further advantageous development of the invention, the at least two webs extend, at least in part, in a helical shape between the hollow tube region and the hollow shaft wall. This is advantageous because the helical configuration of the at least two webs allows for improved drainage of any fluid leakage between the hollow tube region and the hollow shaft wall resulting from rotation of the hollow shaft together with the tube insert during operation of the electric machine. In other words, the at least partially helical shape of the at least two webs can promote the drainage of leakage from an intermediate space between the hollow tube region and the hollow shaft wall.
[0011] In a further advantageous development of the invention, the hollow shaft is made of a metallic material and the tube insert is made of a plastic. This advantageously represents a particularly needs-based material combination, which, in particular, allows for weight savings.
[0012] In a further advantageous development of the invention, the hollow shaft comprises a first hollow shaft region, in which the through-opening has the first inner diameter, and a second hollow shaft region adjoining the first hollow shaft region, in which the through-opening has a second inner diameter that is larger than the first inner diameter, wherein the tubular insert is accommodated in the second hollow shaft region. This is advantageous because the different first and second inner diameters of the respective hollow shaft regions allow a rotationally symmetrical gradation of the through-opening to be realized, which enables particularly simple installation of the tubular insert in the through-opening.
[0013] In a further advantageous development of the invention, the tubular insert has at least one locking element, via which the tubular insert is locked to the hollow shaft and secured against sliding out of the hollow shaft in the axial direction. The locking element advantageously allows for a simple and reliable securing of the tubular insert on the hollow shaft, in particular on the hollow shaft wall.
[0014] A second aspect of the invention relates to a motor vehicle with a shaft device according to the first aspect of the invention, in which the rotor shaft of the electric machine is coupled to the hollow shaft of the shaft device for fluid exchange, and a grounding element is in contact with the shaft grounding surface. This enables fail-safe and fuel-efficient operation of the motor vehicle.
[0015] The preferred embodiments and their advantages presented with respect to one of the aspects apply accordingly to the other aspects of the invention and vice versa.
[0016] The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention.
[0017] Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and from the drawings.
[0018] The invention is explained once again below using a specific embodiment. This shows:
[0019] Fig. 1 is a perspective sectional view of a variant of a shaft device which is designed for coupling to a rotor shaft of a schematically illustrated electrical machine of a likewise schematically illustrated motor vehicle, wherein the shaft device has a hollow shaft, along the axial extent of which a through-opening extends for conducting a fluid for fluid exchange with the rotor shaft, and a shaft earthing surface arranged on the hollow shaft is provided, which is designed for contact with a grounding element in order to divert currents arising during operation of the electrical machine via the hollow shaft in the direction of a housing, wherein the shaft device has a tube insert received in the through-opening, which has a through-opening with a smaller inner diameter than a first inner diameter of the through-opening and is designed toto form a step preventing the backflow of the fluid together with a hollow shaft wall of the hollow shaft within the through opening;,
[0020] Fig. 2 is a perspective view of a first variant of the tube insert, showing several straight webs that are at least predominantly oriented in the axial direction;
[0021] Fig. 3 is a perspective view of a second variant of the tube insert, wherein the webs are at least partially helical; and
[0022] Fig. 4 is a detailed view showing a locking element of the tubular insert, by means of which the tubular insert is locked to the hollow shaft and secured against sliding out of the hollow shaft in the axial direction.
[0023] Fig. 1 shows an abstract representation of a motor vehicle K with a shaft device 10 shown in a perspective sectional view, which is coupled to a rotor shaft 102 of an electric machine 100 of the motor vehicle K. The shaft device 10 has a hollow shaft 20, which can be coupled to the rotor shaft 102, for example, via a spline, such that torque is transmitted, as is indicated by way of example in Fig. 1.
[0024] The hollow shaft can have a toothing shown in Fig. 1, but not provided with a reference number, via which further drive elements of the motor vehicle K, not shown here, can be driven.
[0025] The hollow shaft 20 has a through-opening 22 which extends along an axial extension direction X indicated by an arrow in Fig. 1. The axial extension direction X runs along a rotation axis R shown in dashed lines in Fig. 1, about which axis the shaft device 10 and thus also the hollow shaft 20 can rotate during operation of the electric machine 100, for example as a result of driving the motor vehicle K using the electric machine 100. The through-opening 22 serves to conduct a flow of a fluid, which can also be referred to as fluid flow 12 and is indicated by an arrow in Fig. 1. An arrowhead of this arrow also indicates a flow direction of the fluid flow 12. For reasons of clarity, an illustration of further line elements of the motor vehicle K which carry the fluid flow 12 to the hollow shaft 20 has been omitted.
[0026] On one end face of the hollow shaft 20, the latter has a shaft grounding surface 21, oriented perpendicular to the axial extension direction X, which is contacted by a grounding element 110. The grounding element 110, also shown abstractly in Fig. 1, can be designed, for example, as a shaft grounding pin. Currents generated during operation of the electrical machine 100 can be diverted from the hollow shaft 20 toward a housing 104 via the shaft grounding surface 21 and the grounding element 110. The housing 104 can, for example, be assigned to the electrical machine 100 and surround the shaft device 10.
[0027] A tubular insert 40 of the shaft device 10, which has a through-opening 42, is received in the through-opening 22. While the hollow shaft 20 is formed from a metallic material, for example, steel, the tubular insert 40 can be formed from a plastic for weight reasons.
[0028] The hollow shaft 20 comprises a first hollow shaft region 24, in which the through-opening 22 has the first inner diameter 11. In addition, the hollow shaft 20 comprises a second hollow shaft region 34 directly adjoining the first hollow shaft region 24, in which second hollow shaft region 34 the through-opening 22 has a second inner diameter 12 that is larger than the first inner diameter 11. The tubular insert 40 is received in the second hollow shaft region 34, as can be seen in Fig. 1. In addition, the toothing not provided with a reference numeral is also assigned to the second hollow shaft region 34, whereas the spline toothing for coupling the hollow shaft 20 to the rotor shaft 102 is assigned to the first hollow shaft region 24.
[0029] The passage opening 42 has an inner diameter I which is smaller than the two inner diameters I1, I2 of the through-opening 22. The tube insert 40 therefore forms a step 70, together with a hollow shaft wall 38 of the hollow shaft 20 within the through-opening 22, which step prevents the fluid flow 12 from flowing back. It can be seen from Fig. 2 and Fig. 3 that the tube insert 40 generally has a hollow tube region 44, in other words a region designed as a hollow tube. The hollow tube can also be referred to as a hollow cylinder. In addition, the tube insert 40 has a support region 50, by means of which the hollow tube region 44 is supported on the hollow shaft wall 38 and is spaced apart from the hollow shaft wall 38.
[0030] In the present case, the support region 50 has three webs 52, 54, 56 arranged uniformly circumferentially of the hollow tube region 44, which, in the variant shown in Fig. 2, are oriented parallel to the axial extension direction X. In the variant shown in Fig. 3, however, the corresponding webs 52, 54, 56 are also predominantly oriented in the axial extension direction X, but are at least partially helically designed and thus partially surround the hollow tube region 44 in a helical manner. In the variant of the tube insert 40 shown in Fig. 3, the webs 52, 54, 56 extend at least partially in a helical shape between the hollow tube region 44 and the hollow shaft wall 38. The expression “at least predominantly” is to be understood in the context of the present disclosure that the webs 52, 54, 56 extend mainly over a major part of their spatial extent in the axial extension direction X, which is the case for both in Fig. 2 and Fig.3 variants shown apply.
[0031] Fig. 4 shows a partial, schematic representation of an optional embodiment of the tubular insert 40, which can be used with all variants of the tubular insert 40. In this embodiment, the tubular insert 40 has a locking element 60, via which the tubular insert 40 is locked to the hollow shaft 20 and secured against sliding out of the hollow shaft 20 in the axial direction X. For this purpose, the locking element 60 engages in a recess 36, which can extend, for example, as an annular groove around the rotation axis R along the hollow shaft wall 38.
[0032] The shaft device 10, on the one hand, enables the fluid flow 12 to be conducted through the hollow shaft 20, wherein the step 70 prevents or at least impedes a backflow of the fluid. The shaft device 10 can be designed to be particularly lightweight due to the tube insert 40, which is preferably made of plastic. While the tube insert 40 is omitted in hollow shaft elements known from the prior art and the different diameters, namely the inner diameter I and the first inner diameter 11, are provided exclusively by metallic tube walls, the tube insert 40 in the present shaft device 10 leads to comparatively high weight savings and thus to the avoidance of additional costs, high weight, and increased use of resources.
[0033] The tubular insert 40 makes it possible to design the through-opening 22 with the first inner diameter 11 and the second inner diameter 12 exclusively taking into account the requirements for the required rigidity, strength, natural frequency, and external interfaces to the hollow shaft 20, so that, for example, rolling bearings, plain bearings, gears, or gear rims connected to the hollow shaft 20 can be used in a fail-safe manner without having to make the hollow shaft 20 unnecessarily heavy. The inner diameter 1 is provided in this case by the tubular insert 40, wherein the tubular insert 40, which can also be referred to as a plastic insert, both enables the fluid to be conducted at least through one area, namely the second hollow shaft area 34 of the hollow shaft 20, and contributes to reducing (obstructing) the fluid backflow by means of the step 70 and is supported on the hollow shaft wall 38.The support region 50, which can also be referred to as the support geometry, enables fluid leakage to be diverted from an air gap 39 formed between the hollow tube region 44 and the hollow shaft wall 38, through which the support region 50 extends. Advantageously, the leakage can be guided to the shaft grounding surface 21, where it can provide lubrication at the sliding contact between the shaft grounding surface 21 and the grounding element 110, thereby achieving improved durability of the grounding element 110 and thus increased reliability.
[0034] When the shaft device 10 rotates due to operation of the electric machine 100, the support region 50 enables the drainage of leakage from the air gap 39. With a helical design of the support region 50 or the webs 52, 54, 56, a favorable, rotation-induced conveyance of the fluid from the air gap 39 can even be achieved. In other words, the removal of the fluid from the air gap 39 can be assisted by the webs 52, 54, 56, particularly if the webs extend at least partially in a helical shape within the air gap 39, i.e., between the hollow tube region 44 and the hollow shaft wall 38. This prevents any dead volume and / or any accumulation of contaminants, such as particles, fibers, or the like, in the air gap 39. List of Reference Symbols
[0035] 10 Shaft device
[0036] 12 Fluid flow
[0037] 20 hollow shaft
[0038] 21 Shaft grounding surface
[0039] 22 passage opening
[0040] 24 first hollow shaft area
[0041] 34 second hollow shaft area
[0042] 36 recess
[0043] 38 Hollow shaft wall
[0044] 39 Air gap
[0045] 40 pipe insert
[0046] 42 Passage opening
[0047] 44 Hollow tube area
[0048] 50 support area
[0049] 52 jetty
[0050] 54 jetty
[0051] 56 bridge
[0052] 60 locking element
[0053] 70 level
[0054] 100 electric machine
[0055] 102 Rotor shaft
[0056] 104 housings
[0057] 110 Earthing element
[0058] I inner diameter
[0059] 11 first inner diameter
[0060] 12 second inner diameter
[0061] K Motor vehicle
[0062] R rotation axis
[0063] X Axial extension direction
Claims
Claims 1. Shaft device (10) which is designed for coupling to a rotor shaft (102) of an electric machine (100) of a motor vehicle (K), having a hollow shaft (20), along the axial extent (X) of which a through-opening (22) extends for passing a fluid for fluid exchange with the rotor shaft (102), and having a shaft grounding surface arranged on the hollow shaft (20) (21) which is designed to make contact with a grounding element (110) in order to divert currents arising during operation of the electrical machine (100) via the hollow shaft (20) in the direction of a housing (104), characterized in that the shaft device (10) has a tubular insert (40) accommodated in the through-opening (22), which has a through-opening (42) with a smaller inner diameter (I) than a first inner diameter (I1) of the through-opening (22) and is designed to form a step (70) preventing a backflow of the fluid together with a hollow shaft wall (38) of the hollow shaft (20) within the through opening (22).
2. Shaft device (10) according to claim 1, characterized in that the tube insert (40) has a hollow tube region (44) through which the passage opening (42) extends and a support region (50) via which the hollow tube region (44) is supported on the hollow shaft wall (38) and is spaced from the hollow shaft wall (38).
3. Shaft device (10) according to claim 2, characterized in that the support region (50) has at least two webs (52, 54, 56) which are oriented at least predominantly in the axial extension direction (X).
4. Shaft device (10) according to claim 3, characterized in that the at least two webs (52, 54, 56) extend at least partially helically between the hollow tube region (44) and the hollow shaft wall (38).
5. Shaft device (10) according to one of the preceding claims, characterized in that the hollow shaft (20) is made of a metallic material and the tube insert (40) is made of a plastic.
6. Shaft device (10) according to one of the preceding claims, characterized in that the hollow shaft (20) comprises a first hollow shaft region (24) in which the through-opening (22) has the first inner diameter (11) and a second hollow shaft region (34) adjoining the first hollow shaft region (24), in which the through-opening (22) has a second inner diameter (12) which is larger than the first inner diameter (11), wherein the tube insert (40) is received in the second hollow shaft region (34).
7. Shaft device (10) according to one of the preceding claims, characterized in that the tubular insert (40) has at least one locking element (60) via which the tubular insert (40) is locked to the hollow shaft (20) and is secured against sliding out of the hollow shaft (20) in the axial direction of extension (X).
8. Motor vehicle (K) with a shaft device (10) according to one of the preceding claims, in which the rotor shaft (102) of the electric machine (100) is coupled to the hollow shaft (20) of the shaft device (10) for fluid exchange and an earthing element (110) is in contact with the shaft earthing surface (21).