Drive mechanism, in particular wheel hub motor, for a motor vehicle

Abstract

The invention relates to a drive mechanism (10) for a motor vehicle, comprising: a housing (12); a planetary gearing (14) having a ring gear (16); and a ring gear carrier (21) which is fixedly connected to the ring gear (16), is in the form of an annular body, and is mounted, via one bearing (24) each, on two cylindrical pins (22) which are opposite one another along a pivot axis (SA) which runs perpendicularly to an axis of rotation of the planetary gearing (14) and are fixedly connected to the housing (12), so that the ring gear carrier is pivotable relative to the housing (12) about the pivot axis (SA).

Description

[0001] Mercedes-Benz Group AG

[0002] Drive unit, in particular wheel hub drive, for a motor vehicle

[0003] The invention relates to a drive device, in particular a wheel hub drive, for a motor vehicle, especially for a car.

[0004] DE 102014202494 A1 discloses a planetary gear comprising a planetary stage which includes a ring gear operatively connected to a housing, on the inner circumferential surface of which at least three planet gears are arranged.

[0005] The object of the present invention is to create a particularly advantageous drive device, in particular designed as a wheel hub drive, for a motor vehicle, especially for a car.

[0006] This problem is solved by a drive device with the features of claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0007] The invention relates to a drive device for a motor vehicle, also referred to simply as a vehicle, preferably a motor car, in particular a passenger car. This means that the motor vehicle, in its fully manufactured state, has the drive device and can be driven by means of the drive device. Preferably, the drive device is a wheel hub drive. In particular, the wheel hub drive, especially in the fully manufactured state of the motor vehicle, is arranged in a wheel of the motor vehicle, the wheel of which can be driven by means of the wheel hub drive, in particular purely electrically. The drive device comprises a housing and a planetary gear set, which, for example, can be arranged at least partially in the housing. The planetary gear set has a ring gear.For example, the planetary gear set comprises a sun gear and a planet carrier, as well as at least one planet gear rotatably mounted on the planet carrier, which meshes, in particular simultaneously, with the sun gear and the ring gear. In particular, the sun gear is rotatable about an axis of rotation of the planetary gear set relative to the housing and preferably also relative to the ring gear. Preferably, the planet carrier is rotatable about the axis of rotation relative to the housing and preferably also relative to the ring gear. Preferably, the ring gear, which is designed separately from the housing, is fixedly, i.e., rotationally fixed, to the housing for rotations about the axis of rotation, so that relative rotations about the axis of rotation between the ring gear and the housing are prevented. The drive unit, in particular the planetary gear set, has a ring gear carrier, which is designed as a ring body and is fixedly connected to the ring gear.This means that relative movement between the ring gear and the ring gear carrier is prevented. In principle, it would be conceivable for the ring gear and the ring gear carrier to be formed as a single unit, i.e., from a single piece, so that preferably the ring gear carrier and the ring gear are formed by a single, integral body, thus forming a single ring gear. Furthermore, it would be conceivable for the ring gear and the ring gear carrier to be formed separately and rigidly connected to each other, so that relative movement between the ring gear and the ring gear carrier is prevented.The ring gear carrier, and thus the ring gear itself, is pivotally mounted relative to the housing about a pivot axis perpendicular to the axis of rotation of the planetary gear. It is supported by two cylindrical pins, also referred to as pins, located opposite each other along this pivot axis and rigidly connected to the housing. The characteristic that each pin is cylindrical means that, at least along its length, the pin has a cylindrical shape on its outer circumference. The bearing can be, for example, a rolling bearing or a plain bearing. For instance, the bearing can be a cylindrical roller bearing. In particular, the two cylindrical pins are arranged in the same plane.The respective pin is formed separately from the housing and, in particular, directly, is firmly connected to the housing, so that relative movements between the respective pin and the housing are prevented. In an advantageous embodiment of the invention, it is provided that a respective outer ring of the respective bearing is firmly connected to the ring gear carrier, wherein a respective inner ring of the respective bearing is firmly connected to the respective cylindrical pin.

[0008] In an advantageous embodiment of the invention, it is provided that the respective pin is connected to the housing via a respective screw connection.

[0009] In an advantageous embodiment of the invention, a radially circumferential gap is provided between the housing and the hollow gear carrier.

[0010] In an advantageous embodiment of the invention, it is provided that an axial gap is provided on both sides of the hollow gear carrier to the components surrounding the hollow gear carrier.

[0011] The respective screw connection has, for example, a thread arranged on a respective outer surface of the respective pin, in particular designed as an external thread, which is screwed, for example, in particular directly, into a corresponding further thread of the respective screw connection, in particular designed as an internal thread and formed on a corresponding inner surface of the housing.

[0012] An advantage of the invention is that the ring gear carrier, and thus the ring gear itself, is supported on the housing only by the two bearings. Apart from the bearings, neither the ring gear nor the ring gear carrier has contact with other components and is therefore at least almost freely movable, particularly for slight pivoting movements around the pivot axis and relative to the housing.

[0013] The invention is based in particular on the following findings and considerations: In drive systems designed especially as wheel hub motors, high chassis forces can occur, acting on a wheel carrier that can simultaneously serve as a housing for an electric motor and the transmission, also simply referred to as a gearbox. The resulting twisting, if no countermeasures are taken, leads to detrimental gear contact patterns. Furthermore, unfavorable gear meshing can lead to increased noise. The aforementioned problems and disadvantages can now be avoided by the invention. Because the ring gear carrier, and thus the ring gear itself, is pivotably mounted on the pins via bearings, and therefore on the housing, an adaptive connection of the ring gear to the housing is possible.The bearings, designed for example as rolling bearings, plain bearings, or elastomer bearings, define the pivot axis for the ring gear carrier and thus the ring gear itself. The ring gear carrier and the ring gear can tilt around this pivot axis relative to the housing, thereby aligning themselves with the position of the planet carrier and the planet gear. Advantageous structure-borne noise decoupling can be achieved by connecting the respective bearing to the housing, particularly to the housing's bearing block, especially with the aid of elastomer inserts. This also ensures favorable noise characteristics.

[0014] The invention allows at least the following advantages to be realized:

[0015] Compared to conventional solutions, this design offers a better contact pattern of gear flanks in a gearbox under chassis influences, especially under high chassis forces.

[0016] Improved noise behavior (NVH behavior) due to the improved bearing pattern; improved noise behavior due to structure-borne sound decoupling of the ring gear to the housing.

[0017] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0018] The drawing shows in Fig. 1 a partial schematic and cutaway perspective view of a drive device designed as a wheel hub drive for a motor vehicle;

[0019] Fig. 2 shows a schematic perspective view of a planetary gear of the drive unit, and

[0020] Fig. 3 shows another schematic perspective view of the planetary gear.

[0021] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0022] Fig. 1 shows a schematic, cutaway perspective view of a drive unit 10 of a motor vehicle, preferably designed as a wheel hub drive. The wheel hub drive is also referred to as a wheel hub motor. The drive unit 10 comprises a housing 12 and a planetary gear set 14, which is, for example, at least partially arranged in the housing 12. The planetary gear set 14 has a ring gear 16, a planet carrier 18, and planet gears 20, which are rotatably mounted on the planet carrier 18. The planet carrier 18 is rotatable about an axis of rotation of the planetary gear set 14 relative to the housing 12 and, in this case, also relative to the ring gear 16. The respective planet gear 20 meshes with the ring gear 16. For rotations about the axis of rotation, the ring gear 16 is held fixedly to the housing 12, so that relative rotations about the axis of rotation between the ring gear 16 and the housing 12 are prevented.

[0023] The drive unit 10, in particular the planetary gear 14, also includes a ring-shaped ring carrier 21, which is rigidly connected to the ring gear 16. In this case, the ring gear 16 and the ring gear carrier 21 are formed from a single piece, i.e., they are integrally formed. The ring gear carrier 21, and thus the ring gear 16, is pivotally mounted relative to the housing 12 about a pivot axis SA perpendicular to the axis of rotation of the planetary gear 14. The pins are mounted on two cylindrical pins 22, also referred to as pins, which are fixedly connected to the housing 12 and are positioned opposite each other along the pivot axis SA. Each pin 22 is separate from the housing 12, separate from the ring gear 16, and separate from the ring gear carrier 21, and is rigidly connected to the housing 12, so that relative movement between the respective pin 22 and the housing 12 is prevented.In the embodiment shown in the figures, each bearing 24 is a rolling bearing. Each bearing 24 has an outer ring 26 and an inner ring 28. The outer ring 26 of each bearing 24 is rigidly connected to the ring gear carrier 21. The inner ring 28 of each bearing 24 is rigidly connected to the cylindrical pin 22.

[0024] In the embodiment shown in the figures, each pin 22 is connected to the housing 12 via a screw connection. Each screw connection has a first thread and a second thread. The first thread is an external thread located on the outside of the pin 22. The second thread is an internal thread located on the inside of the housing 12. The external thread is screwed, in particular directly, into the internal thread, thereby screwing the pin 22, in particular directly, to the housing 12 and thus firmly connecting it to the housing 12.

[0025] Particularly clearly visible in Fig. 2 are the ring gear 16, the ring gear carrier 21, the pins 22 and the planet carrier 18. It is particularly evident in Fig. 2 that the respective pin 22 is cylindrical on its outer circumference, at least in a certain length range.

[0026] One of the bearings 24 is particularly well shown in Fig. 3. The respective outer ring 26 and the respective inner ring 28 form a raceway. Each bearing 24 has rolling elements that roll on the raceways, in particular directly, when the ring gear carrier 21, and thus the ring gear 16 and the pivot axis SA, pivots relative to the housing 12. This provides an advantageous mounting of the ring gear 16 on the housing 12. Reference numeral list

[0027] 10 Drive unit 12 Housing

[0028] 14 planetary gear sets 16 ring gears

[0029] 18 planet carrier 20 planet gear

[0030] 21 Hollow wheel carrier 22 Pin

[0031] 24 warehouses

[0032] 26 outer ring

[0033] 28 inner ring

[0034] SA swivel axis

Claims

Mercedes-Benz Group AG Patent claims 1. Drive device (10) for a motor vehicle, comprising a housing (12), a planetary gear (14) which has a ring gear (16), and a ring gear carrier (21) which is fixedly connected to the ring gear (16) and designed as a ring body, and which is pivotable relative to the housing (12) about a pivot axis (SA) extending perpendicular to an axis of rotation of the planetary gear (14) on two cylindrical pins (22) fixedly connected to the housing (12) and opposite each other along the pivot axis (SA) via a respective bearing (24).

2. Drive device (10) according to claim 1, characterized by the fact that a respective outer ring (26) of the respective bearing (24) is firmly connected to the hollow gear carrier (21), wherein a respective inner ring (28) of the respective bearing (24) is firmly connected to the respective cylindrical pin (22).

3. Drive device (10) according to claim 1 or 2, characterized by the fact that The respective pin (22) is connected to the housing (12) via a respective screw connection.

4. Drive device (10) according to one of the preceding claims, characterized by the fact that a radially circumferential gap is provided between the housing (12) and the hollow gear carrier (21).

5. Drive device (10) according to one of the preceding claims, characterized in that an axial gap is provided on both sides of the hollow gear carrier (21) to the components surrounding the hollow gear carrier (21).

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