DE102012218522A1 - Bearing arrangement for electric drive e.g. for driving wheels of vehicle, has supporting portions, socket elements and bearing rings arranged in rotation axis to overlap in radial direction, where bearing rings are formed as inner races - Google Patents

Abstract

The arrangement (10a) has socket elements (14a, 14b) carried with supporting portions (15a, 15b). The supporting portions, the socket elements and bearing rings (13a, 13b) are arranged in rotation axis to overlap in radial direction, where the bearing rings are formed as inner races. The supporting portions are made of aluminum alloy and the socket elements made of steel alloy. The material of the supporting portions has thermal expansion coefficient greater than that of the material of the socket element. An independent claim is also included for an electric drive.

Description

The invention relates to a bearing assembly having a support portion, with a bushing part, which is supported by the support portion, with a bearing ring, wherein the bearing ring is supported by the bushing part and defines a rotation axis and wherein the support portion, the female part and the bearing ring in the radial direction the axis of rotation are arranged overlapping. The invention also relates to an electric drive with this bearing arrangement.

Bearings form the basis for long-lasting and energy-efficient drives. To achieve this goal, the bearings must be installed in the drives according to their installation conditions. In some installation situations, this leads to the fact that complex surroundings constructions have to be created for the bearings in order to meet their installation conditions.

The publication WO2010 / 063567 , which probably forms the closest prior art, relates to a bearing assembly for supporting a shaft of an electric machine, which has a bearing arranged in a bearing plate. The outer ring of the bearing is fixed in the bearing plate, wherein between the bearing plate and the outer bearing ring, a steel ring is provided which forms a positive connection with the bearing plate.

Field of the invention

The invention has for its object to provide a bearing assembly, for example, for an electric drive, which allows to meet the installation conditions for a bearing, in particular a rolling bearing, even in complex installation situations.

This object is achieved by a bearing arrangement with the features of claim 1 and by an electric drive with the features of claim 9. Preferred or advantageous embodiments of the invention will become apparent from the dependent claims, the following description and the accompanying drawings.

The invention thus relates to a bearing arrangement which is suitable and / or designed for an electric drive. In particular, the bearing assembly for supporting a rotor of the electric drive is suitable and / or formed.

The bearing assembly comprises a support portion, a bushing part and a bearing ring. The female part is arranged on the support portion and is supported by this. Preferably, the support portion provides a cylindrical support outer surface and the sleeve portion provides a cylindrical sleeve inner surface, wherein the sleeve inner surface and the support outer surface are in face-to-face contact with each other.

The bearing assembly further includes a bearing ring, wherein the bearing ring is supported by the socket part. In particular, the bearing ring has a cylindrical inner bearing surface and the bushing section has a cylindrical bushing outer surface, wherein bushing outer surface and inner bearing surface contact each other flatly. The support portion, the sleeve part and the bearing ring are arranged coaxially and / or concentrically with respect to the rotation axis, so that these three components are arranged overlapping in the radial direction to the rotation axis. In particular, the support outer surface, bush outer surface, bush inner surface, bush outer surface and bearing outer surface are arranged concentrically and / or coaxially with the axis of rotation.

In the context of the invention, it is proposed that the bearing ring is designed as a bearing inner ring. Preferably, the bearing inner ring is designed as a Wälzkörperlagerinnenring, in particular for rollers or balls, and realized in particular as a ball bearing inner ring. Optionally, the bearing arrangement comprises rolling elements which roll on the bearing inner ring, as well as a bearing outer ring operatively connected to the rolling elements and the bearing inner ring.

The advantage of the invention is that any changes in diameter of the support portion can be limited by temperature changes in the bushing part, so that the diameter variation of the bush outer surface is kept low even with a change in temperature. The sleeve portion acts as a rigid armor around the support portion so that any expansion effects of the support portion are partially compensated for in the compression between the support portion and the sleeve portion and in the deflection of the support portion in other directions. In a preferred embodiment of the invention, the support section is made of a material, in particular a metal, with a first coefficient of thermal expansion, in particular length expansion coefficient and / or expansion coefficient, and the socket part of a material, in particular metal, with a second coefficient of thermal expansion, in the special coefficient of linear expansion and / or space expansion coefficient, wherein the first thermal expansion coefficient is greater than the second coefficient of thermal expansion. For example, the material of the support portion is made of an aluminum alloy and the material of the female part is formed of a steel alloy. The aluminum alloy, or more generally, the material with the larger one Thermal expansion coefficient, will perform a larger diameter change with a temperature increase than the steel alloy, or more generally, the material with the lower coefficient of thermal expansion, so that the invention is particularly advantageous in this material mixture.

Since the socket part is arranged overlapping with the support section in the radial direction to the rotation axis, the socket part restricts the diameter change of the support section so that the outside diameter of the socket part remains constant or nearly constant in the area of the socket outer face. In this context, it should be noted that the sleeve portion will also change its outer diameter, however, the diameter change due to the lower coefficient of thermal expansion is less than the diameter change of the support portion, so that the resulting diameter change of the bush outer surface for the bearing inner ring is smaller than without the use of the socket part.

Considering the tolerances of the components to each other a little closer, so the bearing assembly is designed in a preferred embodiment so that at a working temperature of the bearing assembly, the socket part on the support portion is fixed against displacement and / or arranged with an interference fit. This design ensures that in the operation of the bearing assembly, the bushing part can not move and / or is frictionally or by the interference fit even preferably fixed in a form-fitting manner in the axial direction to the axis of rotation. In the case of an interference fit, it is stipulated that, at the working temperature, the free inside diameter of the bushing part is chosen to be smaller than the outside diameter of the support section in the region in which the support section and bushing part overlap in the radial direction to the rotation axis. This condition is called coverage.

In addition, the bearing assembly is designed in the preferred embodiment so that at the same operating temperature of the bearing inner ring is arranged on the socket part in a sliding seat and / or with a clearance fit. In particular, it is provided that the bearing inner ring at the working temperature with a certain force in the axial direction of, for example, less than 50 N, preferably less than 30 N and in particular less than 10 N in the axial direction is displaceable. Constructively, this is achieved by the free inner diameter of the bearing inner ring is equal to or greater than the outer diameter of the bushing part in the region which overlaps in the radial direction to the axis of rotation formed.

By this tolerance determination is achieved functionally that the female part is permanently arranged securely on the support portion and at the same time the bearing inner ring is slidable on the socket part, for example, to form a movable bearing in the axial direction.

Really, the bearing assembly is operated not only in a working temperature, but in a working temperature range. For this reason, it is preferred that the bearing assembly in a temperature range between minus 20 degrees Celsius and plus 100 degrees Celsius, and preferably between 0 degrees Celsius and 80 degrees Celsius reached the said tolerance requirements, so that the securing of the socket part and the displaceability of the bearing inner ring of the bearing assembly is independent of the working temperature in the temperature ranges mentioned.

In a constructive embodiment, the female part is pressed onto the support section, so that at a lowest expected temperature, preferably less than minus 20 degrees Celsius, especially less than minus 40 degrees Celsius, there is still an overlap to secure the bushing part displacement, so the socket part can not move out.

As the temperature increases, the pressure between the support portion and the sleeve portion increases to preclude outflow of the sleeve portion. When designing, care must be taken to ensure that the pressure remains within a permissible range for both the support section and the socket part for the highest expected temperatures.

In a preferred embodiment of the invention it is provided that the socket part has at least one, preferably on both axial sides with respect to the axis of rotation a radial section. The radial section projects in the radial direction outwards or inwards, in particular via the bush outer surface or bushing inner surface. The radial section may in particular be formed as a material section in a radial plane to the axis of rotation. The one or more radial sections have the advantage that they act as a gain region for the socket part. Thus, the tensile stresses occurring at an increase in the pressure on the or the radial sections are removed. The one or more radial sections make it possible to form the female part of a thinner material with the same load capacity.

Consequently, it is particularly preferred that the female part as a sleeve, in particular as a thin-walled sleeve with a material thickness of less than 3 millimeters, preferably is formed of less than 2 millimeters and in particular less than 1.5 millimeters. Due to the fact that the sleeve as a socket part only has to derive tensile forces and is optionally reinforced by the radial section (s), the thin-walled material can be used so that the cost of materials and in particular the weight of the bearing arrangement can be reduced.

In a preferred embodiment variant, at least the at least one radial section is produced by forming technology. Particularly preferably, the sleeve or the radial sections is made by a cold forming of a sleeve. It is preferred that the female part is formed in its entirety as a forming part, in particular as a cold-forming part and in particular as a drawn bushing with a deformed radial section or radial sections. In this embodiment, the socket part is characterized by its low weight, its low production costs and its already described functional advantages.

In a preferred embodiment of the invention, the support portion is formed as a stationary portion. In this embodiment can thus be generated by the bearing assembly of the invention, a surrounding structure for the bearing assembly with a low weight. More preferably, the support portion is formed as an insertion portion through which e.g. a wave can be performed. This ensures that the extension of the support portion can be deflected by a thermal deformation radially inward.

Another object of the invention relates to an electric drive, which is preferably suitable and / or designed for driving a vehicle. For example, the electric drive is formed as part of an electrical axis, which provides two outputs for driving wheels of a vehicle. The electric drive comprises a motor, which has at least one rotor, and a housing in which the motor and thus the rotor are arranged.

The housing has at least one housing section, wherein the housing section forms the support section, in particular the stationary support section, and the rotor is mounted via at least one, preferably two bearing arrangement, as described above.

The housing preferably comprises a base housing and a bearing plate, wherein the housing portion may form part of the base housing and / or a part of the bearing plate. In both variants, it is preferred that the housing is made of an aluminum alloy in order to reduce the weight of the electric drive, so that the invention can be advantageously carried out in this technical context, as has already been described. In particular, it is achieved by the inventive design of the electric drive and / or the bearing assembly that the electric drive can be operated reliably at different operating temperatures than the working temperature and at the same time the rotor can be stored in a complex installation situation with a minimum and at the same time neutral weight adjustment of the surrounding construction.

In a preferred embodiment of the invention, the bearing inner ring of the bearing assembly is biased in the axial direction to the axis of rotation by a spring means. The spring means may e.g. be realized as a plate spring, a coil spring, etc. This bias may prove necessary with respect to the bearing of the rotor. The design of the bearing assembly, it is possible to implement an axial bias of the rotor, since the bearing ring on the socket part, in particular independently of the working temperature, is slidably disposed.

Particularly preferably, the spring device is arranged between the bearing ring and the radial section of the socket part, so that the spring device is supported on one side on the bearing inner ring and on the other side on the radial section and thus on the socket part. Since the socket part is preferably designed as a steel component, this can support the spring device permanently without closure or at least wear. Thus, the socket part, despite its simple design assumes a double function, namely on the one hand as diameter limiting element for the bearing surface of the bearing ring and the other as a support of the spring device. The spring device can be used in the bearing assembly in other environmental constructions or application examples and is thus independent of the electric drive.

In a preferred embodiment of the invention, the bearing arrangement is arranged in the radial direction to the axis of rotation congruent to the rotor. In this embodiment, the advantages of the invention come particularly well, since it is advantageous in this embodiment to couple the rotor with the outer rings of the bearing assembly and the housing with the bearing inner rings of the bearing assembly.

Further features, advantages and effects of the invention will become apparent from the following description of a preferred Embodiment of the invention and the accompanying figures. Showing:

1 a schematic cross-sectional view of an electric drive with a bearing assembly as a first embodiment of the invention;

2 a detailed view in the 1 ;

3 the support section with the female part of the preceding figures in an enlarged view.

The 1 shows an electric drive 1 in a schematic cross-sectional view through an axis of rotation 2 of the electric drive 1 , The electric drive 1 serves to drive a vehicle and has an electric motor 3 with a stator 4 and a rotor 5 on, with the electric motor 3 in a housing 6 is arranged.

The housing 6 comprises a housing base 7 and a bearing plate 8th , The housing body 7 has a cylindrical receiving space in which the electric motor 3 is arranged, the bearing plate 8th closes the housing body 7 in an axial direction to the rotation axis 2 from. The coaxial and concentric with the stator 4 internal rotor 5 has an interface in exemplary form of internal teeth 9 for coupling to an output shaft (not shown) which controls the drive torque of the electric motor 3 for example, to a transmission or differential passes. The electric motor 3 is designed to produce a power greater than ten kilowatts.

For storage of the rotor 5 opposite the housing 6 are two bearing arrangements 10a b, whose construction is related to the 2 which explains the bearing arrangements 10a , b show in an enlarged detail. Each of the bearing arrangements 10a , b has a rolling bearing 11a , b on, which is in each case designed as a single-row deep groove ball bearing. Every rolling bearing 11a , b has an outer ring 12a or b and a bearing inner ring 13a or b on, with the outer ring 12a , b in each case in a bearing seat of the rotor 5 non-slip pressed.

The bearing inner rings 13a , b on the other hand sit on a socket 14a or b, where the book parts 14a , b each on a support section 15a , b are attached. At the left bearing arrangement 10a is the support section 15a as a part of the housing main body 7 educated. In particular, the support section 15a is formed as a collar or a free, tubular end portion and has a central passage opening for a shaft, in particular for a plug-in shaft. The free diameter D of the support section 15a is greater than 30 mm in this embodiment, the wall thickness of the support portion 15a is smaller than 10 mm. In the right bearing arrangement 10b is the support section 15b as an end portion of the endshield 8th educated. In particular, the support section 15b formed as a collar or a free tubular end portion of the bearing plate 8th protruding in the direction of the engine compartment. The free diameter D 'and the wall thickness is at the support portion 15b in the same area as the support section 15a , especially the same.

The housing body 7 and the bearing plate 8th are each made of an aluminum alloy, so that the two support sections 15a , b consist of aluminum alloy. The support sections 15a , b each provide a cylindrical support outer surface 16a , b ( 3 ), which are concentric and coaxial with the axis of rotation 2 are arranged. Laterally are the support sections 15a , b or the support outer surface 16a , b by a radially outwardly extending shoulder 17a , b limited.

The book parts 14a , b, however, are designed as an example drawn sleeve and made of a steel material. The book parts 14a , b each have a central socket section 18a or b on and two each arranged on the axial edge side radial sections 19a , b, 20a , b. The radial section 19a , b is at the level 17a or b on, the radial section 20a , B is located on the free end face of the support portion 15a , or b on. The radial section 19a , B extends in a radial plane perpendicular to the longitudinal extent of the axis of rotation 2 for example disc-shaped to the outside, the radial section 20a On the other hand, b is, for example, directed disc-shaped inwards. Both radial sections 19a or b, 20a or b are in a radial plane to the axis of rotation 2 ,

Exemplary shows the 3 in a cross-sectional view of the installation situation of the support areas 15a , b and the female part 14a , b in an enlargement.

At the radial inside, the socket part 14a , b each have a female inner surface 21a , B and on the radially outer side of a bush outer surface 22a , b on. Bushing inner surface 21a , b and bush outer surface 22a , b are each coaxial and concentric with the axis of rotation 2 aligned. The female part 14a , b is on the support section 15a or b arranged shift-fixed. In particular, the female part 14a , b with an interference fit on the support section 15a or b pressed on. The bush inner surface 21a , b stands in a two-dimensional contact with the support outer surface 16a , b.

On the bush outer surface 22a , b is the bearing inner ring 13a or b rolling bearings 11a b, so that the cylindrical bush outer surface 22a , b in surface contact with a bearing outer surface 23a or b stands. In particular, the bearing inner ring is supported 13a , b exclusively on the female part 14a or b. The bearing inner ring 13a , b is on the socket 14a or b slidably mounted or with a clearance fit.

The electric drive 1 can assume different operating temperatures during operation. So it is possible that the electric drive 1 during a cold start in winter has an initial temperature of eg -20 ° C as the working temperature. In contrast, it is also possible that the electric drive 1 reached in summer a temperature of 100 ° C as the working temperature. At these temperature differences, the components of the electric drive expand 1 depending on their thermal expansion coefficient different. In particular, the aluminum alloy of the housing 6 and the steel material of the bearing inner ring 13a , b have different coefficients of thermal expansion. In the event that the bearing inner ring 13a , b directly on the support section 15a , b, the different thermal expansion coefficient could cause the bearing ring 13a , b "rattle" at low temperatures and "pinch" at high temperatures. Through the between the bearing ring 13a , b and support section 15a , b intermediary socket parts 14a , b made of steel material, this effect is avoided.

This is due to the fact that the socket section 14a , b due to its material does not expand otherwise than the bearing inner ring 13a , b, so that these components behave approximately the same with temperature changes. In contrast, the diameter change of the support section 15a , b significantly more pronounced due to a change in temperature than in the socket part 14a , b, so that a pressure between the support section 15a , b and the female part 14a , b constantly increasing with increasing temperature. This pressure leads to tensile stresses in the socket part 14a , b in the circumferential direction, which, however, due to the closed contour of the female section 18a , B in the direction of rotation and acting as reinforcing rings radial sections 19a , b, 20a , b only a small change in diameter of the socket part 14a , b, in particular in the area of the bush outer surface 22a , b leads.

To achieve this is the bearing assembly 10a , B designed so that in the working temperature range of -40 ° C to + 130 ° C, the outer diameter of the support portion 15a , b, in particular the diameter of the support outer surface 16a , b, larger to the free inner diameter of the female part 14a , b, in particular the female inner surface 21a , b, is at the same working temperature. In this way it is ensured that the socket part 14a , b on the support section 15a or b can not move. In addition, the bearing assembly 10a , b designed so that in the working temperature range from -20 ° C to + 100 ° C, the outer diameter of the socket part 14a , b. in particular the bush outer surface 22a , b, less than or equal to the outer diameter of the bearing inner ring 13a , b, in particular the bearing outer surface 23a , B is to a shift, in particular a clearance of the bearing inner ring 13a , b on the socket section 14a to reach b.

The rotor 5 is in the axial direction by a spring device 24 biased. The spring device 24 is arranged so that these between the support section 15b and the bearing inner ring 13b acts. In this way, the on the socket part 15b slidably arranged bearing inner ring 13b biased in the axial direction. The preload is over the rolling bearing 11b on the rotor 5 and from there via the rolling bearing 11a on the bearing inner ring 13a so that it is also biased in the same axial direction. The described force path is in the 1 with an arrow 25 visualized.

The spring device 24 however, does not support directly on the support section 15b but over the radial section 19b in the axial direction at the shoulder 17b of the support section 15b is applied. This configuration expresses the spring device 24 against a steel area and not against an area of aluminum alloy so that any wear is minimized.

LIST OF REFERENCE NUMBERS

1

 electric drive

2

 axis of rotation

3

 electric motor

4

 stator

5

 rotor

6

 casing

7

 Housing body

8th

 end shield

9

 internal gearing

10a, b

 bearing arrangement

11a, b

 roller bearing

12a, b

 outer ring

13a, b

 Bearing inner ring

14a, b

 female connector

15a, b

 support section

16a, b

 Supporting outer surface

17a, b

 shoulder

18a, b

 bushing section

19a, b

 radial section

20a, b

 radial section

21a, b

 Bushing inner surface

22a, b

 Bush outer surface

23a, b

 Bearing outer surface

24

 spring means

25

 Power off

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/063567 [0003]

Claims (10)

Bearing arrangement ( 10a , b) with a support section ( 15a , b), with a female part ( 14a , b), which of the support section ( 15a , b) is supported, with a bearing ring ( 13a , b), whereby the bearing ring ( 13a , b) of the female part ( 14a , b) is supported and a rotation axis ( 2 ), wherein the support section ( 15a , b), the female part ( 14a , b) and the bearing ring ( 13a , b) are arranged overlapping in the radial direction to the axis of rotation, characterized in that the bearing ring as a bearing inner ring ( 13a , b) is formed. Bearing arrangement ( 10a , b) according to claim 1, characterized in that the support section ( 15a , b) of a material with a first thermal expansion coefficient and the female part ( 14a , b) is formed of a material having a second coefficient of thermal expansion, wherein the first thermal expansion coefficient is greater than the second coefficient of thermal expansion. Bearing arrangement ( 10a , b) according to one of the preceding claims, characterized in that the support section ( 15a , b) an aluminum alloy and the female part ( 14a , b) is formed of a steel alloy as a material. Bearing arrangement ( 10a , b) according to one of the preceding claims, characterized in that the bearing arrangement ( 10a , b) is formed such that at a working temperature of the bearing assembly ( 10a , b) the female part ( 14a , b) on the support section ( 15a , b) is disposed so as to be resistant to displacement and / or with an interference fit and that at the working temperature the bearing inner ring ( 13a , b) on the female part ( 14a , b) is arranged in a sliding seat and / or with a clearance fit. Bearing arrangement ( 10a , b) according to claim 4, characterized in that the working temperature in a range between -20 ° C and + 100 ° C, preferably between 0 ° C and 80 ° C is arranged. Bearing arrangement ( 10a , b) according to one of the preceding claims, characterized in that the socket part ( 14a , b) at least one axial side of a radial section ( 19a , b, 20a , b). Bearing arrangement ( 10a , b) according to claim 6, characterized in that the at least one radial section ( 19a , b, 20a , b) is made by forming technology. Bearing arrangement ( 10a , b) according to one of the preceding claims, characterized in that the support section ( 15a , b) is formed as a stationary portion. Electric drive ( 1 ) with a housing ( 6 ), with at least one rotor ( 5 ) and the bearing assembly ( 10a , b) according to one of the preceding claims, characterized in that the housing ( 6 ) a housing section ( 7 . 8th ), wherein the housing section ( 7 . 8th ) the support section ( 15a , b) and the rotor ( 5 ) via the bearing arrangement ( 10a , b) is stored. Electric drive ( 1 ) according to one of the preceding claims, characterized in that the bearing inner ring ( 13a , b) in the axial direction to the axis of rotation ( 2 ) by a spring device ( 24 ) is biased.

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