Drive device for vehicle

Abstract

The present invention relates to a drive device for a vehicle, which comprises an electric motor (1), a rotor shaft (5) of the electric motor being constructed as a hollow shaft with an internal toothing, a transmission drive shaft (17) having an external toothing (16) and coaxial with the hollow shaft being inserted into the hollow shaft, in particular a mating toothing (15) for forming a torque-transmitting torque, the rotor shaft (5) being guided outward through a bearing opening (11) of a motor housing (13) with a rotor shaft rotating bearing (9) being connected in between, the transmission drive shaft (17) having a centering seat (27) which abuts against the inner circumference of the rotor shaft (5) in a close clearance fit, and during driving operation, due to radially acting operating forces (F R ) causes the transmission drive shaft (17) to bend (D). According to the present invention, in order to reduce the bending stress (D), the centering seat (27) of the transmission drive shaft (17) is arranged to be axially aligned with the rotor shaft rotating bearing (9) without axial misalignment relative to the rotor shaft rotating bearing (9).

Description

Technical Field

[0001] The invention relates to a drive device for a vehicle and a method for producing a transmission drive shaft in such a drive device. Background Art

[0002] In electrically driven dual-track vehicles, for example, the electrically driven front axle can have an electric motor. Optionally, the electric motor can be arranged parallel to the flange shaft leading to the vehicle wheels. In this case, the electric motor can be driven via a single-acting or double-acting spur gear transmission stage to the front axle differential and further to the vehicle's front axle flange shaft leading to the vehicle wheels.

[0003] In this type of drive, the motor's rotor shaft is designed as a hollow shaft with internal toothing. A transmission drive shaft, coaxial with the hollow shaft and having external toothing, is inserted into the hollow shaft, particularly to form a mating toothing for torque transmission. The rotor shaft is guided outward through a bearing opening in the motor housing, with a rotor shaft rotation bearing interposed. Furthermore, to prevent tilting between the transmission drive shaft and the rotor shaft, a centering seat is provided for the external toothing of the transmission drive shaft. This centering seat is a smooth, cylindrical surface extending around the outer circumference of the transmission drive shaft and resting against the inner circumference of the rotor shaft with a close clearance fit.

[0004] In the prior art, the centering seat formed on the transmission drive shaft is spaced axially apart from the rotor shaft bearing by a lever length. It has been shown that when the transmission drive shaft rotates and is subjected to radial loads during driving, shaft deflection occurs, particularly due to the aforementioned lever length. This shaft deflection can lead to excessive loads on the rotor shaft bearing, generate noise, and reduce the service life of the rotor shaft bearing.

[0005] Patent document DE 23 54 301 A1 discloses a drive device for an electrically driven rail vehicle. Patent document EP 1 433 975 B1 discloses a power transmission device. Patent document DE 10 2010 050 217 A1 discloses an electric axle for a motor vehicle. Patent document US 2007 / 0131375 A1 discloses an electric steering device. Summary of the Invention

[0006] The object of the present invention is to provide a drive device for a vehicle in which, compared to the prior art, a transmission drive shaft rotates in a structurally simple manner during driving operation with improved running smoothness.

[0007] This object is achieved by the features described below.

[0008] The present invention is based on the fact that, in the prior art, deflection of the transmission drive shaft occurs primarily due to the lever length between the rotor shaft pivot bearing and the centering seat formed on the transmission drive shaft. Against this background, in order to reduce bending stresses in the transmission drive shaft, the centering seat of the transmission drive shaft is arranged axially aligned with the rotor shaft pivot bearing, without axial offset relative to the rotor shaft pivot bearing (i.e., without lever length). In other words, according to the present invention, the lever length between the centering seat of the transmission drive shaft and the rotor shaft pivot bearing is reduced to zero, thereby enabling radial forces to be transferred from the transmission drive shaft via its centering seat to the rotor shaft pivot bearing in a direct force transfer manner (i.e., without bending stresses). In particular, according to the present invention, deflection of the rotor shaft is limited to the overlapping region of the two shafts.

[0009] To further reduce shaft bending stresses, it is particularly preferred to implement the rotor shaft's rotating bearing not as a fixed bearing, but rather as an axially displaceable, in particular spring-preloaded, floating bearing. Even when a fixed bearing is provided instead of a floating bearing, deflection reduction is achieved. The spring preload serves to limit the load on the rolling elements at all times, thereby preventing a no-load state that could impair running smoothness.

[0010] In one technical implementation, the external toothing formed on the transmission drive shaft can be arranged offset relative to the rotary bearing by axial offset. The transmission drive shaft can extend into the rotor shaft with its motor-side shaft end. Preferably, the motor-side shaft end directly terminates in a centering seat. In this way, the greatest possible axial distance is achieved between the centering seat and the bearing seat of the transmission drive shaft, which will be described later. This limits the deflection of the rotor shaft, especially in the overlapping area of ​​the two shafts. The centering seat arranged directly on the motor-side shaft end can first transition into a shaft section with reduced diameter in the direction of the transmission-side shaft end. As the shaft extends further, the external toothing with a larger diameter is connected to the shaft section with reduced diameter.

[0011] In one technical implementation, the transmission drive shaft is rotatably supported in the transmission housing with an interposed transmission rotary bearing (in particular, a fixed bearing). The transmission housing rotary bearing is mounted on a corresponding bearing seat of the transmission drive shaft. Preferably, the bearing seat of the transmission drive shaft is arranged directly on the transmission-side shaft end, thereby providing the greatest possible axial bearing distance between the bearing seat and the centering seat of the transmission drive shaft.

[0012] Preferably, the transmission drive shaft and the rotor shaft form a shaft assembly that is integrally rotatably supported in the drive unit using a three-point bearing arrangement. The three-point bearing arrangement preferably includes bearing points on each end face of the shaft assembly, where the shaft assembly is rotatably supported on the motor housing and the transmission housing via fixed bearings, while the rotor shaft rotation bearing serves as a central floating bearing located in the center of the shaft assembly. Compared to conventional four-point bearing arrangements, this three-point bearing arrangement offers significantly lower costs and reduced manufacturing complexity.

[0013] In a particularly preferred embodiment, the rotor shaft is part of the rotor internal cooling system, wherein a tubular oil nozzle extends into the rotor shaft cavity. The oil nozzle can define an annular gap together with the rotor shaft inner circumference. During driving operation, a volume flow of lubricating and / or cooling medium can be directed into the annular gap via a pressure pump through the oil nozzle at the overflow opening. From this annular gap, the volume flow of lubricating and / or cooling medium can be directed further in the direction of the centering seat of the transmission drive shaft. In this case, the centering seat of the transmission drive shaft can have an axial flow passage. The reduced diameter shaft section of the transmission drive shaft can define an axial flow groove together with the rotor shaft inner circumference. In this way, the annular gap can be fluidically connected / flow-connected to the mating toothing via the centering seat flow passage and the axial flow groove. To ensure the removal of fretting corrosion particles, a small volume flow of lubricating and / or cooling medium can flow through the mating toothing due to the tooth clearance.

[0014] Preferably, the transmission drive shaft can be implemented as a hollow shaft. In order to produce the transmission drive shaft, a shaft blank made of hardenable steel can first be provided. In the shaft blank, the centering seat and the bearing seat are already constructed. Subsequently, a heat treatment step is carried out, in which the shaft blank is hardened, in particular in the case of component deformation with corresponding shaft deflection. In order to minimize component deformation, a straightening process step is carried out, in which the hardened shaft blank is clamped at two clamping points axially spaced apart from each other by means of a clamping tool. In the clamped state, the shaft blank is plastically deformed by a process force in order to reduce the component deformation. The process force acts between the two clamping points axially spaced apart from each other.

[0015] In terms of smooth alignment of the shaft blank, it is preferred that the two axially spaced apart clamping locations are spaced apart from each other at the largest possible axial spacing. In this context, it is particularly preferred that the two clamping locations are a bearing seat and a centering seat respectively configured on the shaft end side of the transmission drive shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0017] in:

[0018] Figure 1 The transmission structure of the drive device is shown;

[0019] FIG2 shows a partially half-sectioned view of a shaft composite structure including a transmission drive shaft and a rotor shaft according to a comparative variant not included in the present invention;

[0020] Figure 3 A comparative variation not included in the present invention is shown, corresponding to Figure 1 's view;

[0021] FIG4 shows an alignment station in which a transmission drive shaft according to a comparative variant not included in the present invention is clamped; and

[0022] Figure 5 A view according to the invention corresponding to FIG. 4 is shown. DETAILED DESCRIPTION

[0023] exist Figure 1 1 shows a drive device with which the front axle VA of a double-track vehicle can be driven. The front axle VA has an electric motor 1, which is arranged parallel to the flange shaft 3 leading to the vehicle wheels. The rotor shaft 5 of the electric motor 1 is connected to the transmission 7 ( Figure 3 ) is connected to the two flange shafts 3. Rotor shaft 5 - connected to the rotor shaft rotating bearing 9 in the middle ( Figure 1 or Figure 3 ) - it is guided outwards from the bearing opening 11 of the motor housing 13 and connected to the coaxially arranged transmission drive shaft 17 via a torque-transmitting mating toothing 15. The fixed gear 19 of the gear stage St1 of the transmission 7 is arranged on the transmission drive shaft 17 and meshes with the input-side gear 21 of the axle differential 23. The axle differential 23 is driven on both sides to the flange shaft 3 that leads to the vehicle wheels.

[0024] In order to simplify the understanding of the present invention, the shaft composite structure not included in the present invention will be described first with reference to FIG2. Therefore, the rotor shaft 5 is constructed as a hollow shaft with an internal toothing, and a coaxial shaft with an external toothing 16 (FIG. 4 or FIG. 5 ) is provided. Figure 5 ) is inserted into the hollow shaft, thereby forming the mating toothing 19. According to FIG2 , the transmission drive shaft 17 projects with its motor-side shaft end 25 into the rotor shaft 5. A centering seat 27 terminates directly at the motor-side shaft end 25 and has a circumferential, smooth cylindrical surface that forms a tight clearance fit with the likewise smooth cylindrical inner circumference of the rotor shaft.

[0025] The shaft end side 29 (FIG. 4 or 5) of the centering seat 27 faces the transmission side. Figure 5) direction into a shaft section 31 of reduced diameter, to which the external toothing 16 of larger diameter adjoins in the further axial direction. In the comparative variant shown in FIG. 2 , the centering seat 27 formed on the transmission drive shaft 17 is spaced apart from the rotor shaft rotary bearing 9 by a lever length h. It has been shown that during driving operation, when the transmission drive shaft 17 rotates and the radial force F R When acting on the transmission drive shaft 17 , a shaft deflection D ( FIG. 2 ) occurs due to the lever length h, which leads to excessive loading of the rotor shaft rotary bearing 9 and to noise generation.

[0026] In this context, Figure 3 In order to reduce the shaft deflection D, the following measures are taken: The difference from Figure 2 is that Figure 3 In this embodiment, the centering seat 27 of the transmission drive shaft 17 is no longer spaced apart from the rotor shaft rotary bearing 9 by the lever length h, but is instead arranged without axial offset and in axial alignment with the rotor shaft rotary bearing 9. This reduces the bending stresses in the transmission drive shaft 17. In addition, the rotor shaft rotary bearing 9 is designed as an axially displaceable, spring-prestressed floating bearing.

[0027] The transmission drive shaft 17 and the rotor shaft 5 form a shaft composite structure W ( Figure 1 ), the shaft assembly is rotatably supported in the drive device in a structurally simple three-point bearing manner, in particular, on the end sides of the two shaft assemblies, each supported on the motor housing via a fixed bearing 33 and on the transmission housing 37 via another fixed bearing 35. The rotor shaft rotary bearing 9, which is implemented as a floating bearing, is located in the center of the shaft assembly.

[0028] If you can also Figure 3 As shown in FIG. 1 , a tubular oil nozzle 39 extends into the cavity of the rotor shaft 5 and is part of the rotor internal cooling system. The oil nozzle 39, together with the rotor shaft inner circumference, defines an annular gap 41. When the rotor internal cooling system is activated, the pressure pump 34 delivers a lubricating and / or cooling medium volume flow m from a pump sump 45 through the oil nozzle 39 and through its overflow opening 47 into the annular gap 41. From the annular gap 41, the lubricating and / or cooling medium volume flow m is delivered through an outlet 49 of the rotor shaft 5 into the interior of the motor. Furthermore, the lubricating and / or cooling medium volume flow m is delivered via a flow passage 51 formed in the centering seat 27 and via an axial flow groove 53 to the mating toothing 15. The axial flow groove 53 is defined between the reduced diameter shaft section 31 and the rotor shaft inner circumference.

[0029] Next, according to Figure 4 and Figure 5The process flow for manufacturing the transmission drive shaft 17 is described as follows: First, a shaft blank 57 made of hardenable steel is provided. The shaft blank 57 has both a centering seat 27 and a bearing seat 30. The bearing seat 30 is shown in FIG. Figure 5 It is arranged directly on the transmission-side shaft end 29 of the transmission drive shaft 17 .

[0030] Subsequently, the shaft blank 57 is hardened in a heat treatment step, in particular in the case of component bending, whereby the shaft deflection D is obtained. Figure 5 In FIG, the shaft deflection D is indicated by means of a curve. In the subsequent straightening step, the shaft blank 57 is clamped at two axially spaced-apart clamping locations by means of a clamping tool 55 and plastically deformed with a process force F until the component deflection is reduced. The greater the distance between the two clamping locations, the easier it is to reduce the component deflection (and the shaft deflection associated therewith). In this context, Figure 5 In the embodiment, the two clamping locations are the bearing seat 30 and the centering seat 27 constructed at the shaft end sides 25 and 29. Figure 5 In the embodiment, the two clamping locations are spaced apart from each other by the greatest possible axial distance.

[0031] In contrast, Figure 5 In the comparative variant shown, the centering seat 27 of the transmission drive shaft 17 is not formed directly on the motor-side shaft end 25, but is positioned in a manner offset axially with respect to the shaft end. In this way, the motor-side shaft end 25 is positioned with an axial offset a. Figure 5 The left side in the middle) protrudes beyond the clamping point, so that even after the straightening step, component bending remains in the transmission drive shaft 17.

[0032] List of reference numerals:

[0033] 1 motor

[0034] 3 flange shaft

[0035] 5 Rotor shaft

[0036] 7 Transmission

[0037] St1 gear stage

[0038] 9 Rotor shaft bearing

[0039] 10 Preload spring

[0040] 11 Bearing opening

[0041] 13 Motor housing

[0042] 15 Mating tooth

[0043] 17 Transmission drive shaft

[0044] 18 fixed gear

[0045] 21 Input side gear

[0046] 23-axle differential

[0047] 25 Shaft end side on the motor side

[0048] 27 center seat

[0049] 29 Transmission side shaft end

[0050] 30 bearing seat

[0051] 31 Shaft section with reduced diameter

[0052] 33 Fixed bearing

[0053] 35 fixed bearing

[0054] 37 Transmission housing

[0055] 39 oil nozzle

[0056] 41 Annular gap

[0057] 43 pressure pump

[0058] 45 Pump pit

[0059] 47 Overflow opening

[0060] 49 Exit

[0061] 51 Centering seat flow through part

[0062] 53 Axial flow channel

[0063] 55 Clamping tool

[0064] 57 Shaft blank

[0065] D-axis deflection

[0066] W-axis composite structure

[0067] h Lever length

[0068] a Axial misalignment

[0069] F Process Force

[0070] F R Radial force

[0071] m Cooling medium volume flow

Claims

1. A drive device for a vehicle, comprising an electric motor (1), the rotor shaft (5) of the electric motor being configured as a hollow shaft with an internal toothing, a transmission drive shaft (17) coaxial with the hollow shaft and having an external toothing (16) being inserted into the hollow shaft to form a mating toothing (15) for transmitting torque, wherein: The rotor shaft (5) is guided outward through the bearing opening (11) of the motor housing (13) with the rotor shaft rotating bearing (9) connected in between. The transmission drive shaft (17) has a centering seat (27) which abuts against the inner circumference of the rotor shaft (5) with a tight clearance fit. The transmission drive shaft (17) is subjected to radial operating forces (F R ), characterized in that, in order to reduce the bending stress (D), the centering seat (27) of the transmission drive shaft (17) is arranged axially aligned with the rotor shaft rotating bearing (9) without axial offset relative to the rotor shaft rotating bearing (9), the transmission drive shaft (17) extends into the rotor shaft (5) with its motor-side shaft end side (25), the centering seat (27) ends directly - that is, without an external toothing (16) as an intermediate layer - at the motor-side shaft end side (25), and / or the centering seat (27) transitions into a shaft section (31) with reduced diameter in the direction of the transmission-side shaft end side (29) and transitions into an external toothing (16) with increasing diameter in the further axial direction.

2. The driving device according to claim 1, characterized in that In order to further reduce the shaft bending stress, the rotor shaft rotation bearing (9) is realized as a spring-preloaded floating bearing that can move axially.

3. The driving device according to claim 1, characterized in that An external toothing (16) formed on a transmission drive shaft (17) is arranged offset relative to a rotor shaft rotary bearing (9) by an axial offset (a).

4. The driving device according to any one of claims 1 to 3, characterized in that: The transmission drive shaft (17) is rotatably supported in the transmission housing (37) with a transmission rotary bearing (35) in the form of a fixed bearing connected in between, and the bearing seat (30) of the transmission drive shaft (17) provided for the transmission rotary bearing (35) ends directly - that is, without a toothing or other functional section as an intermediate layer - at the shaft end side (29) on the transmission side.

5. The driving device according to any one of claims 1 to 3, characterized in that: A tubular oil nozzle (39) extends into the cavity of the rotor shaft (5). The oil nozzle is a component of the rotor internal cooling system. The oil nozzle (39) defines an annular gap (41) together with the inner circumference of the rotor shaft. A volume flow (m) of lubricating and / or cooling medium can be guided into the annular gap (41) through the oil nozzle (39) via an overflow opening (47).

6. The driving device according to claim 5, characterized in that An axial flow passage (51) is formed in the centering seat (27) of the transmission drive shaft (17), and the reduced diameter shaft section (31) of the transmission drive shaft (17) defines an axial flow groove (53) together with the inner circumference of the rotor shaft, so that the annular gap (41) is connected to the mating toothing (15) in terms of flow technology via the flow passage (51) formed on the centering seat (27) and via the axial flow groove (53).

7. The driving device according to any one of claims 1 to 3, characterized in that: The transmission drive shaft (17) and the rotor shaft (5) form a shaft composite structure, which is rotatably supported in the drive device in a three-point bearing manner. The end sides of the shaft composite structure are supported on the motor housing (13) and the transmission housing (37) respectively through fixed bearings and are supported in the center of the shaft composite structure through a central floating bearing (9).

8. A method for producing a transmission drive shaft (17) for a drive device according to any one of the preceding claims 1 to 7, wherein: A shaft blank (57) made of hardenable steel is provided, in which both a centering seat (27) and a bearing seat (30) are formed, wherein the shaft blank is hardened in a heat treatment step while deforming the component with shaft deflection, and in a subsequent straightening step, the hardened shaft blank (57) is clamped at two axially spaced clamping locations by means of a clamping tool (55) and plastically deformed with a process force (F) to reduce the component deformation, the two clamping locations being the bearing seat (30) and the centering seat (27) constructed on the shaft end sides (25, 29).

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