Hollow-Shaft Assembly for a Motor Vehicle

Abstract

A hollow-shaft arrangement for a motor vehicle includes an inner hollow shaft and an outer hollow shaft. An inner shaft shoulder of the outer hollow shaft is arranged behind the inner toothing in an axial direction as viewed from the inflow end of the inner hollow shaft, the inner diameter (D.sub.1) of which shaft shoulder is smaller than a root-circle diameter (D.sub.2) of the inner toothing, so that, when the hollow shafts rotate, the fluid exiting from the outflow end of the inner hollow shaft at least partially is backed up by the shaft shoulder in a tooth root region of the inner toothing and flows back in the direction of the inflow end of the inner hollow shaft within the splice toothing.

Claims

1-9. (canceled)

10. A hollow-shaft arrangement for a motor vehicle, comprising: an inner hollow shaft; and an outer hollow shaft, the inner hollow shaft and the outer hollow shaft being connected to one another with spline toothing, wherein an outer toothing of the inner hollow shaft engages with an inner toothing of the outer hollow shaft in a rotationally conjoint manner, the inner hollow shaft has an inflow end configured to feed a fluid into the interior of the inner hollow shaft and has an outflow end which opens out, within the inner toothing, into the outer hollow shaft, and an inner shaft shoulder of the outer hollow shaft is arranged behind the inner toothing in an axial direction as viewed from the inflow end of the inner hollow shaft, the inner diameter (D.sub.1) of which shaft shoulder is smaller than a root-circle diameter (D.sub.2) of the inner toothing, so that, when the hollow shafts rotate, the fluid exiting from the outflow end of the inner hollow shaft at least partially is backed up by the shaft shoulder in a tooth root region of the inner toothing and flows back in the direction of the inflow end of the inner hollow shaft within the splice toothing.

11. The hollow-shaft arrangement according to claim 10, wherein the inner toothing of the outer hollow shaft axially projects beyond the outer toothing of the inner hollow shaft to such an extent in the direction of the shaft shoulder that, when the two hollow shafts rotate, at least a part of the fluid exiting from the outflow end of the inner hollow shaft passes, due to centrifugal-force action, to the inner toothing of the outer hollow shaft that is not in engagement with the outer toothing.

12. The hollow-shaft arrangement according to claim 11, wherein behind the spline toothing as viewed from the shaft shoulder, the outer hollow shaft has at least one radially extending passage opening through which that portion of the fluid which flows back through the spline toothing can exit the outer hollow shaft.

13. The hollow-shaft arrangement according to claim 12, wherein the inner hollow shaft has at least one radially extending passage opening through which a part of the fluid fed through the inflow end can exit the inner hollow shaft.

14. The hollow-shaft arrangement according to claim 13, wherein the passage openings of the hollow shafts are connected to one another via an intermediate space formed between the hollow shafts.

15. The hollow-shaft arrangement according to claim 14, wherein a fluid feed arranged in the region of the inflow end of the inner hollow shaft introduces the fluid obliquely to the longitudinal direction of the inner hollow shaft.

16. The hollow-shaft arrangement according to claim 15, wherein the fluid feed has at least one nozzle which is oriented obliquely to the longitudinal direction of the inner hollow shaft.

17. The hollow-shaft arrangement according to claim 16, wherein the inner hollow shaft is a transmission input shaft, and the outer hollow shaft is a rotor shaft of an electric drive machine.

18. A motor vehicle comprising: at least one hollow-shaft arrangement according to claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 shows a perspective view of a hollow-shaft arrangement for a motor vehicle, which has an inner hollow shaft in the form of a transmission input shaft and has an outer hollow shaft in the form of a rotor shaft of an electric machine, wherein the outer hollow shaft is illustrated partially in section;

[0020] FIG. 2 shows a perspective view, partially in section, of the hollow-shaft arrangement, wherein both the inner hollow shaft and the outer hollow shaft are illustrated partially in section;

[0021] FIG. 3 shows a sectional side view of a part of the hollow-shaft arrangement; and

[0022] FIG. 4 shows a greatly enlarged sectional side view of the hollow-shaft arrangement in the region of a spline toothing, by way of which the two hollow shafts are connected to one another in a rotationally conjoint manner.

DETAILED DESCRIPTION

[0023] In the figures, identical and functionally identical elements are denoted by the same reference signs. A hollow-shaft arrangement 10 for a motor vehicle is shown in a perspective view in FIG. 1. The hollow-shaft arrangement 10 comprises an inner hollow shaft in the form of a transmission input shaft 12 and an outer hollow shaft in the form of a rotor shaft 14, which are connected to one another by means of a spline toothing 16. The spline toothing 16 is formed by an outer toothing 18 of the transmission input shaft 12 and by an inner toothing 20 of the rotor shaft 14, which engage with one another in a rotationally conjoint manner.

[0024] The transmission input shaft 12 has an inflow end 22 for feeding of a fluid into the interior of the transmission input shaft 12 and has an outflow end 24 which opens out, within the inner toothing 20 of the rotor shaft 14, into the latter. As viewed from the inflow end 22 of the transmission input shaft 12, an inner shaft shoulder 26 of the rotor shaft 14 is arranged behind the inner toothing 20 in an axial direction. Here, an inner diameter of said shaft shoulder 26 is smaller than a root-circle diameter of the inner toothing 20. In other words, the inner shaft shoulder 26 projects radially inward further than a root circle of the inner toothing 20.

[0025] The hollow-shaft arrangement 10 is shown in a further perspective view in FIG. 2, wherein both hollow shafts 12, 14 are illustrated partially in section. In the present illustration, two radially extending passage openings 28 of the transmission input shaft 12 can be seen. A part of the fluid introduced at the inflow end 22 can exit the transmission input shaft 12 radially outward through said passage openings 28. The remaining part of the fluid flows onward axially to the outflow end 24.

[0026] From there, the fluid passes, due to centrifugal-force action, since the hollow-shaft arrangement 10 rotates during intended operation, radially to to the inner toothing 20, specifically to that part of the inner toothing 20 which is not in engagement with the outer toothing 18 of the transmission input shaft 12. From there, the fluid flows axially as far as the shaft shoulder 26 and is backed up by the latter. The fluid is thus backed up by the shaft shoulder 26, which projects radially inward further than a root circle of the inner toothing 20, in the root region of the inner toothing 20 and is consequently directed back in the direction of the inflow end 22, specifically such that at least a part of the fluid flows through the spline toothing 16 and in this way lubricates the latter.

[0027] A part of the hollow-shaft arrangement 10 is shown in a sectional side view in FIG. 3. In the region of the inflow end 22 of the transmission input shaft 12, there is arranged a fluid feed 30, which transports the fluid into the interior of the transmission input shaft 12 obliquely to the longitudinal direction or axial direction of the transmission input shaft 12. The fluid feed 30 may have for example one or else multiple nozzles, which may be oriented obliquely to the longitudinal direction or to the axial direction of the transmission input shaft 12.

[0028] A fluid flow 32 is schematically indicated in the present case so as to show how the fluid introduced flows through the interior of the transmission input shaft 12, partially exits radially outward through the passage openings 28, and then flows onward as far as the outflow end 24. During the operation of the hollow-shaft arrangement 10, the transmission input shaft 12 and the rotor shaft 14 rotate. By way of this rotational movement, the fluid passes, due to centrifugal-force action, radially outward after it has passed the outflow end 24 of the transmission input shaft 12.

[0029] The inner toothing 20 of the rotor shaft 14 axially projects beyond the outer toothing 18 (not visible here) of the transmission input shaft 12 to such an extent in the direction of the shaft shoulder 26 that, when the two hollow shafts 12, 14 rotate, at least a part of the fluid exiting from the outflow end 24 of the transmission input shaft 12 passes, due to centrifugal-force action, to the inner toothing 20 of the rotor shaft 14 that is not in engagement with the outer toothing 18. The fluid thus flows internally within the rotor shaft 14 firstly along the outer toothing 18 at least substantially in an axial direction, specifically until the fluid has flowed as far as the shaft shoulder 26.

[0030] The shaft shoulder 26 projects radially inward further than a root circle of the outer toothing 18. Consequently, the fluid is backed up by the shaft shoulder 26 and flows in reverse, that is to say to the left in the present illustration, through the spline toothing 16. This results in centrifugal-force-driven counterflow lubrication of the spline toothing 16. As soon as the teeth or tooth interspaces of the outer toothing 20 have been completely filled by the fluid, the fluid runs radially inward over the shaft shoulder 26 and in this way passes further into the interior of the rotor shaft 14, that is to say flows away to the right in the present illustration.

[0031] Behind the spline toothing 16 as viewed from the shaft shoulder 26, the rotor shaft 14 has multiple radially extending passage openings 34 through which that portion of the fluid which flows back through the spline toothing 16 can exit the rotor shaft 14 outward, so as, in this way, to lubricate and/or to cool surrounding components. The passage openings 28, 34 of the two hollow shafts 12, 14 are connected to one another via an intermediate space 36 formed between the two hollow shafts 12, 14. The fluid exiting through the passage openings 28 thus passes into the intermediate space 36, as does likewise the flowing-back part of the fluid which has passed the spline toothing 16 beforehand. From the intermediate space 36, both fluid flows then together pass radially outward through the passage openings 34 and thereby exit the rotor shaft 14.

[0032] FIG. 4 shows a region around the shaft shoulder 26 of the hollow-shaft arrangement 10 in a greatly enlarged sectional side view. In the present case, the already mentioned inner diameter Di of the shaft shoulder 26 is shown, wherein moreover the already mentioned root-circle diameter D.sub.2 of the inner toothing 20 is also shown. The shaft shoulder 26 may, in a radial direction, for example project inward to such an extent that the inner diameter D.sub.1 is not only smaller than the root-circle diameter D.sub.2, but for example also may be smaller than a pitch-circle diameter or tip-circle diameter (not illustrated here) of the inner toothing 20.

[0033] Thus, in a radial direction, the shaft shoulder 26 may project inward to such an extent that, as seen in the radial direction, said shaft shoulder for example projects into the interior of the rotor shaft 14 to the same extent as the respective teeth (not denoted in any more detail here) of the inner toothing 20. In this case, the shaft shoulder 26 can make provision for the fluid to be backed up over the entire tooth height of the inner toothing 20 due to the shaft shoulder 26 and to centrifugal-force action. The fluid accumulates in particular in the tooth root region and then flows, in relation to an axial main flow direction, according to which the fluid flows through the transmission input shaft 12, in reverse or in a reactive manner, as a consequence of which the spline toothing 16 is lubricated. As soon as the fluid has been backed up beyond the height of the inner shaft shoulder 26 as viewed in a radial direction, further fluid runs over the shaft shoulder 26 and in this way passes further to the right according to the present illustration, into the interior of the rotor shaft 14.

[0034] The above explanations apply not only to a hollow-shaft arrangement 10 in which the inner hollow shaft is a transmission input shaft 12 and the outer hollow shaft is a rotor shaft 14, but for any types of hollow-shaft arrangements in which a fluid firstly is introduced into the interior of such a hollow shaft 12, from there flows in the direction of the outer hollow shaft 14, and then, by way of a shaft shoulder 26 of said type, is at least partially diverted so as to flow in reverse in such a way that the respective spline toothing 16 undergoes lubrication.

LIST OF REFERENCE SIGNS

[0035] 10 Hollow-shaft arrangement [0036] 12 Inner hollow shaft in the form of a transmission input shaft [0037] 14 Outer hollow shaft in the form of a rotor shaft [0038] 16 Spline toothing [0039] 18 Outer toothing [0040] 20 Inner toothing [0041] 22 Inflow end [0042] 24 Outflow end [0043] 26 Shaft shoulder [0044] 28 Passage openings of the transmission input shaft [0045] 30 Fluid feed [0046] 32 Fluid flow [0047] 34 Passage openings of the rotor shaft [0048] 36 Intermediate space [0049] D.sub.1 Inner diameter of the shaft shoulder [0050] D.sub.2 Root-circle diameter of the inner toothing