DRIVE APPARATUS FOR A VEHICLE

Abstract

A drive apparatus for a vehicle having an electric machine whose rotor shaft is constructed as a hollow shaft having an internal tooth arrangement. A gear mechanism drive shaft, which has an external tooth arrangement, is inserted coaxially relative to the hollow shaft into the hollow shaft, to form a torque-transmitting spline. The rotor shaft with a rotor shaft rotary bearing being interposed is guided outward through a bearing opening of an electric machine housing, and the gear mechanism drive shaft has a centering seat which is in abutment with the internal circumference of the rotor shaft with a tight clearance fit. The gear mechanism drive shaft is subjected to bending (D) during travel operation as a result of radially active operating forces (F.sub.R). To reduce the bending stress (D), the centering seat of the gear mechanism drive shaft is arranged without an axial offset with respect to the rotor shaft rotary bearing, in axial alignment relative to the rotor shaft rotary bearing.

Claims

1-10. (canceled)

11. A drive apparatus for a vehicle having an electric machine whose rotor shaft is constructed as a hollow shaft having an internal tooth arrangement, the drive apparatus comprising: a gear mechanism drive shaft, which has an external tooth arrangement, is inserted coaxially relative to the hollow shaft into the hollow shaft, to form a torque-transmitting spline, the rotor shaft with a rotor shaft rotary bearing being interposed is guided outward through a bearing opening of a housing for the electric machine, the gear mechanism drive shaft has a centering seat which is in abutment with an internal circumference of the rotor shaft with a tight clearance fit, the gear mechanism drive shaft subjected to a bending (D) stress during travel operation as a result of radially active operating forces (FR), the centering seat of the gear mechanism drive shaft arranged without an axial offset with respect to the rotor shaft rotary bearing and in axial alignment relative to the rotor shaft rotary bearing, resulting in reducing the bending stress of the gear mechanism drive shaft.

12. The drive apparatus according to claim 11, wherein the rotor shaft rotary bearing is a pretensioned floating bearing to be axially displaceable, resulting in further reducing the bending stress of the gear mechanism drive shaft.

13. The drive apparatus according to claim 11, wherein the external tooth arrangement formed on the gear mechanism drive shaft is arranged offset with respect to the rotor shaft rotary bearing by the axial offset.

14. The drive apparatus according to claim 1, wherein the gear mechanism drive shaft protrudes with the electric machine-side shaft end face thereof into the rotor shaft and the centering seat terminates directly without the external tooth arrangement being interposed, at the electric machine-side shaft end face, and/or that the centering seat merges in a direction towards a gear-side shaft end face into a shaft portion of the gear mechanism drive shaft which has a reduced diameter and in a further axial path into the external tooth arrangement which has a larger diameter.

15. The drive apparatus according to claim 11 wherein the gear mechanism drive shaft is rotatably supported in a gear mechanism housing with a gear mechanism rotary bearing being interposed, in a fixed bearing, and a bearing seat of the gear mechanism drive shaft which is associated with the gear mechanism rotary bearing terminates directly without a tooth arrangement or another functional portion being interposed, at the gear-side shaft end face.

16. The drive apparatus according to claim 11, wherein a tubular oil lance protrudes into a hollow space of the rotor shaft, the tubular oil lance being a component of a rotor inner cooling and delimits an annular gap together with the rotor shaft internal circumference, so that a lubricant and/or coolant volume flow can be guided through the oil lance via an overflow opening into the annular gap.

17. The drive apparatus according to claim 16, wherein the centering seat of the gear mechanism drive shaft includes an axial flow passage and the shaft portion of the gear mechanism drive shaft, which has a reduced diameter, together with the rotor shaft internal circumference delimits an axial flow groove so that the annular gap is connected in terms of flow to the a torque-transmitting spline through the axial flow passage which is formed in the centering seat and through the axial flow groove.

18. A method of producing a gear mechanism drive shaft for a drive apparatus according to claim 11, in which: a shaft blank made from a hardenable steel is provided; both the centering seat and the bearing seat are formed; the shaft blank is hardened in a thermal processing, with component distortion, with shaft deflection and in a following orientation; the hardened shaft blank is clamped by clamping tools at two axially spaced-apart clamping locations and is plastically deformed with a process force (F) to reduce the component distortion, the two clamping locations correspond to the bearing seat and the centering seat formed on the electric machine-side shaft end faces.

19. The drive apparatus according to claim 11, wherein the gear mechanism drive shaft and the rotor shaft form a shaft assembly which is rotatably supported in a three-point bearing in the drive apparatus at the shaft assembly end faces, by a fixed bearing on the electric machine housing and on the gear mechanism housing and at the shaft assembly center by a central floating bearing, respectively.

20. The drive apparatus according to claim 12, wherein the external tooth arrangement formed on the gear mechanism drive shaft is arranged offset with respect to the rotor shaft rotary bearing by the axial offset.

21. The drive apparatus according to claim 12, wherein the gear mechanism drive shaft protrudes with the electric machine-side shaft end face thereof into the rotor shaft and the centering seat terminates directly without the external tooth arrangement being interposed, at the electric machine-side shaft end face, and/or that the centering seat merges in a direction towards a gear-side shaft end face into a shaft portion of the gear mechanism drive shaft which has a reduced diameter and in a further axial path into the external tooth arrangement which has a larger diameter.

22. The drive apparatus according to claim 13, wherein the gear mechanism drive shaft protrudes with the electric machine-side shaft end face thereof into the rotor shaft and the centering seat terminates directly without the external tooth arrangement being interposed, at the electric machine-side shaft end face, and/or that the centering seat merges in a direction towards a gear-side shaft end face into a shaft portion of the gear mechanism drive shaft which has a reduced diameter and in a further axial path into the external tooth arrangement which has a larger diameter.

23. The drive apparatus according to claim 12 wherein the gear mechanism drive shaft is rotatably supported in a gear mechanism housing with a gear mechanism rotary bearing being interposed, in a fixed bearing, and a bearing seat of the gear mechanism drive shaft which is associated with the gear mechanism rotary bearing terminates directly without a tooth arrangement or another functional portion being interposed, at the gear-side shaft end face.

24. The drive apparatus according to claim 13, wherein a tubular oil lance protrudes into a hollow space of the rotor shaft, the tubular oil lance being a component of a rotor inner cooling and delimits an annular gap together with the rotor shaft internal circumference, so that a lubricant and/or coolant volume flow can be guided through the oil lance via an overflow opening into the annular gap.

25. A method of producing a gear mechanism drive shaft for a drive apparatus according to claim 12, in which: a shaft blank made from a hardenable steel is provided; both the centering seat and the bearing seat are formed; the shaft blank is hardened in a thermal processing, with component distortion, with shaft deflection and in a following orientation; the hardened shaft blank is clamped by clamping tools at two axially spaced-apart clamping locations and is plastically deformed with a process force (F) to reduce the component distortion, the two clamping locations correspond to the bearing seat and the centering seat formed on the electric machine-side shaft end faces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other aspects and advantages will become more apparent and more readily appreciated from the following description of the example embodiments, taken in conjunction with the accompanying drawings of which:

[0017] FIG. 1 shows a gear mechanism structure of a drive apparatus;

[0018] FIG. 2 is a half-sectioned partial view of a shaft assembly including the gear mechanism drive shaft and rotor shaft according to a comparative form in the related art;

[0019] FIG. 3 is a view according to FIG. 1 according to an example;

[0020] FIG. 4 shows an orientation station in which a gear mechanism drive shaft is clamped according to a comparative form in the related; and

[0021] FIG. 5 is a view according to FIG. 4 according to an example.

DETAILED DESCRIPTION

[0022] FIG. 1 shows a drive apparatus in which the front axle VA of a two-track vehicle can be driven. The front axle VA has an electric machine 1 which is arranged axially parallel with the flanged shafts 3 which are guided relative to the vehicle wheels. The rotor shaft 5 of the electric machine 1 is drivingly connected to the two flanged shafts 3 by a gear mechanism 7 (FIG. 3). With a rotor shaft rotary bearing 9 (FIG. 1 or 3) being interposed, the rotor shaft 5 is guided outward out of a bearing opening 11 of an electric machine housing 13 and connected by a torque-transmitting spline 15 to a coaxially arranged gear mechanism drive shaft 17. On the gear mechanism drive shaft 17 there is arranged a fixed gear 19 of a gear stage St1 of the gear mechanism 7 which meshes with an input-side gear 21 of an axle differential 23. The axle differential 23 drives at both sides on the flanged shafts 3 which are guided with respect to the vehicle wheels.

[0023] A known shaft assembly according to FIG. 2 will first be described. Consequently, the rotor shaft 5 is constructed as a hollow shaft with an internal tooth arrangement, in which the gear mechanism drive shaft 17 which is coaxial relative thereto and which has an external tooth arrangement 16 (FIG. 4) is inserted, whereby the spline 19 is produced. According to FIG. 2, the gear mechanism drive shaft 17 with the electric machine-side shaft end face 25 thereof protrudes into the rotor shaft 5. There terminates directly at the electric machine-side shaft end face 25, a centering seat 27 which has a circumferential smooth-cylindrical surface which is in a tight clearance fit with the rotor shaft internal circumference which is also smooth-cylindrical.

[0024] The centering seat 27 merges in the direction toward a gear-side shaft end face 29 (FIG. 5) into a shaft portion 31 of the gear mechanism drive shaft 17 of reduced diameter which is adjoined in the further axial path by the external tooth arrangement 16 which has a larger diameter. In the related art FIG. 2, the centering seat 27 formed on the gear mechanism drive shaft 17 is spaced apart from the rotor shaft rotary bearing 9 by a lever arm length h. It has been found that, during travel operation, with a rotating gear mechanism drive shaft 17 and when a radial force F.sub.R acts on the gear mechanism drive shaft 17 as a result of the lever arm length h a shaft deflection D (FIG. 2) which leads to an excessively large loading of the rotor shaft rotary bearing 9 and to noise generation is produced.

[0025] Against this background, in order to reduce a shaft deflection D the following measures are taken in FIG. 3: in contrast to FIG. 2, in FIG. 3 the centering seat 27 of the gear mechanism drive shaft 17 is no longer spaced apart from the rotor shaft rotary bearing 9 by a lever arm length h, but instead arranged without any axial offset and in axial alignment with respect to the rotor shaft rotary bearing 9. The bending stress of the gear mechanism drive shaft 17 is thereby reduced. In addition, the rotor shaft rotary bearing 9 may be in form of an axially displaceable, resiliently pretensioned floating bearing 10.

[0026] The gear mechanism drive shaft 17 and the rotor shaft 5 form a shaft assembly W (FIG. 1) which is rotatably supported in a structurally simplified three-point bearing in the drive apparatus, at both shaft assembly end faces by a fixed bearing 33 on the electric machine housing and by an additional fixed bearing 35 on the gear mechanism housing 37, respectively. The rotor shaft rotary bearing 9 which is in the form of a floating bearing is located at the shaft assembly center.

[0027] As can further be seen in FIG. 3, there protrudes into the hollow space of the rotor shaft 5 a tubular oil lance 39 which is a component of a rotor inner cooling. The oil lance 39 delimits together with the rotor shaft internal circumference an annular gap 41. When the rotor inner cooling is activated, a pressure pump 43 conveys a lubricant and/or coolant volume flow m from a pump sump 45 through the oil lance 39 and via the overflow opening 47 thereof into the annular gap 41. From the annular gap 41, the lubricant and/or coolant volume flow m is conveyed via an outlet opening 49 of the rotor shaft 5 into the electric machine inner space. Furthermore, the lubricant and/or coolant volume flow m is conveyed via a flow passage 51 which is formed in the centering seat 27 and via an axial flow groove 53 as far as the spline 15. The axial flow groove 53 is delimited between the shaft portion 31 which has a reduced diameter and the rotor shaft internal circumference.

[0028] A process sequence for producing the gear mechanism drive shaft 17 will be described below with reference to FIGS. 4 and 5: accordingly, a shaft blank 57 made from a hardenable steel is first provided. The shaft blank 57 has both the centering seat 27 and the bearing seat 30. The bearing seat 30 is arranged in FIGS. 4 and 5 directly on the gear-side shaft end face 29 of the gear mechanism drive shaft 17.

[0029] The shaft blank 57 is subsequently hardened in a thermal processing, with component distortion, whereby a shaft deflection D is produced. The shaft deflection D is depicted in FIGS. 4 and 5 by of the illustrated bending lines. In a subsequent orientation process, the shaft blank 57 is clamped by clamping tools 55 at two clamping locations which are axially spaced apart from each other and plastically deformed with a process force F until the component distortion is reduced. The greater the spacing between the two clamping locations is, the simpler it is to reduce the component distortion (and the shaft deflection involved). Against this background, in FIG. 5 the two clamping locations are the bearing and centering seats 27, 30 formed at the electric machine-side and gear-side shaft end faces 25, 29, respectively. In this manner, in FIG. 5, the two clamping locations are spaced apart from each other by the greatest possible axial spacing.

[0030] In contrast, in the example shown in FIG. 5 the centering seat 27 of the gear mechanism drive shaft 17 is not formed directly on the electric machine-side shaft end face 25, but instead positioned in a manner offset from the electric machine-side shaft end face 25 by an axial offset a. In this manner, the electric machine-side shaft end face 25 protrudes into the rotor shaft 5 with an overhang over the clamping location (on the left in FIG. 5), whereby even after carrying out the orientation process, a component distortion remains in the gear mechanism drive shaft 17.

LIST OF REFERENCE NUMERALS

[0031] 1 Electric machine

[0032] 3 Flanged shafts

[0033] 5 Rotor shaft

[0034] 7 Gear mechanism

[0035] St1 Gear stage

[0036] 9 Rotor shaft rotary bearing

[0037] 10 Pretensionied spring

[0038] 11 Bearing opening

[0039] 13 Electric machine housing

[0040] 15 Spline

[0041] 17 Gear mechanism drive shaft

[0042] 19 Fixed gear

[0043] 21 Input-side gear

[0044] 23 Axle differential

[0045] 25 Electric machine-side shaft end face

[0046] 27 Centering seat

[0047] 29 Gear-side shaft end face

[0048] 30 Bearing seat

[0049] 31 Shaft portion with reduced diameter

[0050] 33 Fixed bearing

[0051] 35 Fixed bearing

[0052] 37 Gear mechanism housing

[0053] 39 Oil lance

[0054] 41 Annular gap

[0055] 43 Pressure pump

[0056] 45 Pump sump

[0057] 47 Overflow opening

[0058] 49 Outlet opening

[0059] 51 Centering seat flow passage

[0060] 53 Axial flow groove

[0061] 55 Clamping tool

[0062] 57 Shaft blank

[0063] D Shaft deflection

[0064] W Shaft assembly

[0065] h Lever arm length

[0066] a Axial offset

[0067] F Process force

[0068] F.sub.R Radial force

[0069] m Coolant volume flow

[0070] A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).