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DE-102024133057-A1 - shaft and electric motor with such a shaft

DE102024133057A1DE 102024133057 A1DE102024133057 A1DE 102024133057A1DE-102024133057-A1

Abstract

The present invention relates to a shaft (1) with a first shaft part (2) and a second shaft part (4) welded to it, - wherein the two shaft parts (2, 3) have an outer diameter d a , - wherein the first shaft part (2) transitions via a step (5) into an axial extension (6) with an outer diameter d f , where d f < d a , and where the outer diameter d f corresponds to an inner diameter d w of the second shaft part (4), - wherein at a transition (7) from the step (5) to the axial extension (6) an annular groove (10) is provided which is oriented obliquely to the axial direction (8), the outer groove wall (11) and the inner groove wall (12) of which have an acute angle α to the axial direction (8), - wherein one radial thickness s a of a step end face (14) corresponds at least approximately to a radial thickness s b of a wave end face (15) of the second wave part (4), - wherein the first shaft part (2) is welded over the entire radial thickness s a of the step end face (14) to the shaft end face (15) of the second shaft part (4).

Inventors

  • Mario Mohler
  • Patrick Altherr
  • Cedric Dobua
  • Christoph Steinmetz

Assignees

  • MAHLE INTERNATIONAL GMBH

Dates

Publication Date
20260513
Application Date
20241112

Claims (13)

  1. Shaft (1) with a first shaft part (2) and a second shaft part (4) welded to it via a weld (3), - wherein the first shaft part (2) and the second shaft part (4) have an outer diameter d a , - wherein the first shaft part (2) transitions via a step (5) into an axial extension (6) with an outer diameter d f such that d f < d a , - wherein the outer diameter d f corresponds at least approximately to an inner diameter of the second shaft part (4), - wherein an annular groove (10) is provided at a transition (7) from the step (5) to the axial extension (6), the annular groove (10) being inclined to the axial direction (8), the outer groove wall (11) and the inner groove wall (12) of which have an acute angle α to the axial direction (8), - wherein a radial thickness s a of a step end face (14) of the first shaft part (2) corresponds at least approximately to a radial thickness s b of a The shaft end face (15) of the second shaft part (4) corresponds, - wherein the first shaft part (2) is welded over the entire radial thickness s a of the step end face (14) to the shaft end face (15) of the second shaft part (4).
  2. Wave (1) after Claim 1 , characterized in that the following relationship applies to the angle α: 15° ≤ α ≤ 35°.
  3. Wave (1) after Claim 1 or 2 , characterized in that the outer groove wall (11) the ring groove (10) transitions over an unbroken edge (17) into the stepped end face (14).
  4. Wave (1) after Claim 1 or 2 , characterized in that the outer groove wall (11) of the annular groove (10) transitions into the step end face (14) via a chamfer of a maximum length of 0.2 mm.
  5. Shaft (1) according to one of the preceding claims, characterized in that the inner groove wall (12) of the annular groove (10) transitions via an unbroken edge (18) into an outer surface (19) of the axial extension (6).
  6. wave (1) after one of the Claims 1 until 4 , characterized in that the inner groove wall (12) of the annular groove (10) transitions via a chamfer of a maximum length of 0.2 mm into an outer surface (19) of the axial extension (6).
  7. Shaft (1) according to one of the preceding claims, characterized in that an axial distance a between the step end face (14) and a deepest point (20) in the axial direction (8) of the annular groove (10) is preferably 1.0 mm.
  8. Shaft (1) according to one of the preceding claims, characterized in that a radial depth b of the annular groove (10) is preferably 1.5 mm.
  9. Shaft (1) according to one of the preceding claims, characterized in that a residual wall thickness r w between an inner diameter di of the first shaft part (2) and a radially deepest point (21) of the annular groove (10) is preferably 1.5 mm.
  10. Shaft (1) according to one of the preceding claims, characterized in that a distance e between the two groove walls (11, 12) is preferably 1.5 mm.
  11. Shaft (1) according to one of the preceding claims, characterized in that the shaft (1) is designed as a rotor shaft of an electric motor (22).
  12. Shaft (1) according to one of the preceding claims, characterized in that the weld seam (3) is produced by means of laser welding.
  13. Electric motor (22) with a shaft (1) according to one of the preceding claims.

Description

The present invention relates to a shaft. The invention also relates to an electric motor with such a shaft. Welded shafts are already used in a variety of ways, often welding together two shaft parts or a shaft part with a functional component, such as a turbine wheel. Laser welding processes are often used for this purpose, achieving optimal results in terms of both weld thickness and weld position. Multi-part shafts can be welded either by through-welding, where the weld penetrates the entire component wall thickness, or by inset welding, where the weld is shorter than the entire component wall thickness. Inset welding is advantageous because it prevents contamination and avoids affecting the shaft's internal geometry. However, inset welding can lead to problems with difficult-to-weld materials, such as cracking or undefined geometry in the weld root area. The risk of cracking is caused by rapid and inhomogeneous cooling, which is more pronounced in inset welding than in through-welding. The higher the carbon equivalent of the material, the greater this risk. Carbon equivalent is a value used to assess the weldability of unalloyed and low-alloy steels. A carbon equivalent value of less than 0.45% indicates good weldability, while higher values, depending on the material thickness, necessitate preheating. Above 0.65%, the workpiece is only weldable with increased effort, as martensite formation can lead to cold cracking and hardening cracks, which can impair load-bearing capacity and/or service life. To improve welding results and reduce the formation of hardening cracks, the parts must be preheated, a process step that increases manufacturing costs. The present invention therefore deals with the problem of providing an improved or at least alternative embodiment for a shaft, by means of which in particular the disadvantages known from the prior art can be overcome. This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims. The present invention is based on the general concept of positively influencing weld quality, and thus the connection between two shaft sections, through a specially designed geometry. This results in homogeneous cooling behavior, pronounced weld root formation, and consequently, reduced susceptibility to cracking in the weld root and the weld seam. The shaft according to the invention comprises a first shaft section and a second shaft section welded to it, the first and second shaft sections each having an at least approximately identical outer diameter d<sub>a</sub> . The first shaft section transitions via a step into an axial extension with a reduced outer diameter, the outer diameter d<sub>f</sub> of the axial extension being smaller than the outer diameter d<sub> a </sub> of the first shaft section. Simultaneously, the outer diameter d <sub>f </sub> of the axial extension corresponds at least approximately to an inner diameter d <sub>w</sub> of the second shaft section, allowing the first shaft section, with its axial extension, to be inserted into the second shaft section until a stepped end face abuts an end face of the second shaft section. This allows for geometrically precise centering. At the transition from the step to the axial extension, an annular groove is arranged, oriented obliquely to the axial direction. The outer and inner groove walls of this groove are each aligned at an acute angle α to a shaft axis and the axial direction, respectively. The outer and inner groove walls preferably run parallel to each other. Because an outer diameter df on the axial extension essentially corresponds to an inner diameter dw of the second shaft section, and both shaft sections simultaneously have an identical outer diameter da , the radial thickness of the step end face sa of the first shaft section corresponds at least approximately to the radial thickness sb of the shaft end face of the second shaft section. The first shaft section is welded to the shaft end face of the second shaft section over the entire radial thickness sa of its step end face. The weld seam extends over the entire thickness sa , sb . This geometry, and in particular the provision of the annular groove oriented obliquely to the axial direction, allows for significantly improved cooling of the weld in the annular groove and thus in the area of the weld root, thereby reducing the susceptibility to cracking in the weld root and the weld seam. This can be significantly reduced. Due to the inventive geometry of the shaft with the inclined annular groove, virtually the same advantages can be achieved when welding the two shaft parts together by means of inset welding as with through-welding. The annular groove creates a space that enables a near-through-welding process. In an advantageous embodiment of the shaft according to the invention, the following relationship applies to the angle α: 15° ≤ α ≤ 35°. T