Drive arrangement, in particular for a motor vehicle

Abstract

Drive arrangement (10), in particular for a motor vehicle, comprising a drive housing (12) in which an electric machine (14) is arranged with a housing-fixed stator (141) and a rotor (142) arranged radially rotatably within the stator (141), the rotor shaft (143) being mounted on at least one end face (121, 122) of the drive housing (12), wherein at least an upper region of the drive housing (12) acts as an air space filled with air surrounding at least an upper region of the electric machine (14), and wherein a dirt trap structure (20) formed integrally with an inner wall of the drive housing (12) and comprising an arrangement of pins (201) projecting from it is arranged, which is suitable for mechanically binding particles contained in the air surrounding the electric machine (14) upon contact, characterized in thatthat the dirt-trapping structure (20) is arranged in the aforementioned upper area and is designed as an embossed or deep-drawn structure.

Description

Field of the invention

[0001] The invention relates to a drive arrangement, in particular for a motor vehicle, comprising a drive housing in which an electrical machine is arranged with a stator fixed to the housing and a rotor which is arranged radially inside the stator and can rotate, the rotor shaft of which is mounted on at least one end face of the drive housing, wherein at least one upper region of the drive housing acts as an air space which is filled with air surrounding at least one upper region of the electrical machine, and wherein a dirt trap structure which is formed in one piece with the drive housing and which comprises an arrangement of pins projecting from it is arranged on an inner wall of the drive housing and which is suitable for mechanically binding particles contained in the air surrounding the electrical machine upon contact. State of the art

[0002] Such a drive arrangement is known from CN 2 04 669 170 U, without any specific mention of its suitability as a traction drive for a motor vehicle.

[0003] Electric machines, such as those suitable as traction drives for electrified vehicles, must operate with high efficiency to deliver the required power in an energy-saving manner. This requires extreme precision in design and operation. In particular, it is desirable to design the air gaps between the rotor and stator as small as possible to avoid unwanted power losses. However, this makes the machines susceptible to contamination in the form of particles suspended or contained in the air surrounding the electric machine, which acts as a supporting fluid film between the rotor and stator. Such particles can be created during manufacturing, assembly, and / or operation and enter the air space of the drive housing.The term “airspace” is to be understood broadly here and includes not only the air-filled space in the immediate vicinity of the electrical machine, but also, for example, the air-filled space above an oil sump that may be located below the electrical machine.

[0004] The penetration of dirt particles into the air gap between the rotor and stator can disrupt the supporting fluid film and damage the counter-rotating surfaces. Furthermore, dirt particles that adhere to the motor winding or power electronics, for example, can lead to performance-reducing short circuits or leakage currents. It is therefore desirable to keep the airspace of an electric vehicle traction drive as free of dirt particles as possible at all times. Extreme care and, if necessary, cleaning during production and assembly are necessary for this, but not sufficient in all cases. On the one hand, residual contamination can remain in the drive housing due to manufacturing and assembly errors. On the other hand, as already mentioned above, new contamination can also arise during operation.

[0005] From US 3 004 180 A it is known to provide one of the counter-rotating surfaces of the rotor and stator with axially extending dirt trap grooves. Particles that have already penetrated the air gap are intended to collect in these dirt trap grooves. However, this concept has two significant disadvantages. Firstly, in order to be trapped in the dirt trap grooves, the particles must already have penetrated the air gap, meaning they may have already caused damage there. Secondly, cleaning the dirt trap grooves, which have filled with particles over time, is extremely complex because the electrical machine must be completely disassembled due to the poor accessibility of the dirt trap grooves.

[0006] The aforementioned, generic publication discloses a complex dirt trap structure on one of the housing end walls below the rotor shaft. A gearwheel fixed to the rotor shaft is surrounded by a funnel-shaped guide plate extending downwards and protruding from the end wall, by means of which dirt accumulating in the gearing area is directed into a chamber located at the lowest point of the guide plate. From the bottom of this chamber rise rows of dirt trap louvers, the main surfaces of which are reinforced with protruding, cube- or trapezoid-shaped pins. Such complex structures, if they are to be formed integrally with the housing end wall, as illustrated in the publication, can only be created by electroerosion or another similarly complex process. This is expensive and time-consuming. A multi-part construction, however, results in an assembly effort that is hardly economically justifiable.

[0007] DE 311 775 A discloses an air cooling system for machines with upstream air cleaning and cooling. For this purpose, the air is passed through a series of impact bars before entering the machine area to be cooled, each of which has a film of water running down its surface. Upon contact with the impact bars or the film of water, the air is purified of dirt particles and simultaneously cooled. This type of air cleaning system is clearly unsuitable for use inside motor housings, particularly for wet-running electrical machines.

[0008] DE 345 809 A discloses an air purification system in which an airflow carrying dirt particles is guided along a baffle element equipped with angled deflectors positioned opposite to the flow direction. Heavy particles are intended to settle on the windward side of the deflectors, while light particles, by virtue of vortex formation, are deposited on the leeward side. Firstly, this does not permanently bind the dirt particles. Secondly, there is no constant, unidirectional, near-wall airflow in the housing of an electrical machine. The device is therefore unsuitable for use in the context of the present application.

[0009] JP 2014-225 957 A discloses an electrical machine in which a magnet is arranged on the housing base next to the stator, which is intended to bind metallic abrasion falling downwards. Task

[0010] It is the object of the present invention to further develop a generic drive arrangement in such a way that easier maintenance is possible and costs and assembly effort during production are reduced. Description of the invention

[0011] This object is achieved in conjunction with the features of the preamble of claim 1 in that the dirt trap structure is arranged in said upper region and is designed as an embossed or deep-drawn structure.

[0012] Preferred embodiments of the invention are the subject of the dependent claims.

[0013] The invention initially provides for relocating the dirt trap structure from a position that is difficult to access to a position that is easily accessible for maintenance work, in particular for cleaning the dirt trap structure of bound dirt particles. The inventors have recognized that it is ultimately at least not disadvantageous if the dirt particles are filtered out of the air surrounding the electric machine instead of being bound (only) at the location of their potential damaging effect, namely in the air gap between the rotor and stator, or in the immediate vicinity thereof. The variant according to the invention even has the advantage that not only the air gap remains free of harmful contaminants, but also other areas sensitive to contamination, such as the motor windings and / or the power electronics components.

[0014] According to the invention, the dirt trap structure is formed as a stamped or deep-drawn structure. Corresponding manufacturing processes for the individual parts of the drive housing are generally known to those skilled in the art. The advantages of such a one-piece design of the dirt trap structure with the corresponding housing components, compared to a similarly conceivable design as a separate component, are obvious in terms of cost and assembly effort.

[0015] The end faces of the drive housing have proven to be a particularly advantageous position for the formation of the dirt trap structure. These are often designed as removable covers and are therefore relatively easy to disassemble for maintenance work. In cases in which the rotor shaft is only supported on one side in the drive housing, the end face that does not act as a bearing shield is particularly suitable. In cases where the rotor shaft is supported on both sides, the end face that serves as the bearing shield for the free end of the rotor shaft on the motor side is particularly suitable. The opposite end wall, which in these cases is penetrated by the rotor shaft and usually forms a boundary to an adjacent gearbox or electronics housing, is more difficult to access and therefore less suitable for the arrangement of dirt trap structures that require maintenance. Nevertheless, it is readily possible within the scope of the invention to arrange a dirt trap structure here (as well).This is particularly the case if a completely maintenance-free concept is pursued and / or the dirt trap structure provided here is merely intended as an additional dirt trap structure to another, more easily maintainable dirt trap structure.

[0016] As is generally known from the prior art, the dirt trap structure comprises an arrangement of pins protruding from a surface, namely the inner wall of the drive housing, in particular in the area of ​​an end wall. The specific arrangement, shape, and dimensioning of the pins can be tailored to the expected shape and size of the contamination particles. The better such coordination, which must be carried out in each individual case for a specific drive type and a specific operating concept, the more effectively and completely the drive can be kept free of harmful contamination. It has proven advantageous if at least some of the pins are aligned parallel to one another. Irrespective of this, the pins can be designed to be of different lengths. They can be spaced from one another by a distance that is less than their diameter.Conversely, however, it is also conceivable that they are spaced apart by a distance greater than their diameter. In particular, the pins may have a round or polygonal profile.

[0017] In addition to such a pin structure, the dirt trap structure can comprise an arrangement of ribs protruding from a surface. These ribs can be arranged in a honeycomb pattern, for example. Alternatively or additionally, the dirt trap structure can comprise an arrangement of pipe sockets protruding from a surface. Such a design combines the advantages of the aforementioned pin structure with the ability to bind dirt particles in the cavity of said pipe sockets. Such pipe sockets can be considered annular ribs with a particularly high rib height.

[0018] Further features and advantages of the invention will become apparent from the following specific description and drawings. Short description of the drawings

[0019] They show: Fig. 1: a highly schematic sectional view of a drive arrangement according to the invention and Fig. 2: a highly schematic, enlarged view of the dirt trap structure of the drive assembly of Fig. 1. Detailed description of preferred embodiments

[0020] The same reference numerals in the figures indicate the same or analogous elements.

[0021] Fig. Figure 1 shows a highly schematic representation of a drive assembly 10 according to the invention. The drive assembly 10 comprises a drive housing 12, inside which an electric machine 14 is arranged. The electric machine 14 comprises a stator 141 fixed to the housing and a rotor 142 arranged for rotation radially within the stator 141. The rotor 142 is fixed to a rotor shaft 143, which in turn is mounted in rotor shaft bearings 16 on the end faces 121, 122 of the housing 12.

[0022] The Fig. 1 left-hand end wall 121 is designed as a cover, by means of which the remaining, pot-shaped drive housing 12, comprising essentially the Fig. 1, shown on the right, is closed by an end wall 122 and a hollow cylindrical shell wall 123. The free end of the rotor shaft 143 is mounted in the corresponding rotor shaft bearing 16. The opposite end wall 122, however, is penetrated by the rotor shaft 143. This continues into an adjacent gearbox or electronics housing in a manner not shown.

[0023] In the illustrated embodiment, an oil sump 18 is provided below the electric motor 14. This sump can be separated by an intermediate wall. Embodiments without such an oil sump at all, or with an oil sump provided in another way, are also conceivable.

[0024] The two end walls 121, 122 are reinforced on their respective insides with a dirt trap structure 20. This consists, for example, in Fig.2, in the form of an arrangement of pins 201 preferably protruding perpendicularly from the respective wall, or at least comprises such pins. The pins can differ in their length I, their diameter d and / or their distance a from one another. The overall configuration of the dirt trap structure 20 is preferably optimized such that dirt particles suspended in the air space, i.e. in this case above the oil sump 18, are effectively mechanically bound upon contact with the dirt trap structure. This process is promoted by the fact that the rotation of the rotor 142 during operation of the drive arrangement 10 creates a strong air flow within the drive housing 12, which drives any dirt particles present through the dirt trap structure or into it.

[0025] In the illustrated embodiment, the dirt trap structure 20 extends into the oil sump 18. This also allows for the filtering of dirt particles from the oil there. However, this is not crucial for the primary effect of the invention.

[0026] If cleaning of the dirt trap structure 20 is necessary during maintenance work, the dirt trap structure 20 arranged on the end wall 121 designed as a cover is particularly easily accessible. Therefore, in an alternative embodiment, only this end wall 121 can be reinforced with a dirt trap structure 20.

[0027] Of course, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. In light of the disclosure herein, a broad spectrum of possible variations is available to those skilled in the art. In particular, other forms of dirt trap structures than those shown, such as ribs or pipe sockets, can also be used. It is also conceivable for the individual elements of the dirt trap structure 20 to have a sticky surface and / or be magnetized, so that in addition to the mechanical bond, adhesive and / or magnetic interactions can also be used to filter out dirt particles from the air in the drive housing 20. List of reference symbols 10 Drive arrangement 12 drive housing 121 first front wall 122 second end wall 123 shell wall 14 electric machine 141 Stator 142 Rotor 143 Rotor shaft 16 rotor shaft bearings 18 Oil sump 20 dirt trap structure 201 pen a distance between 201 d diameter of 201 I Length of 201

Claims

[1] Drive arrangement (10), in particular for a motor vehicle, comprising a drive housing (12) in which an electric machine (14) is arranged with a stator (141) fixed to the housing and a rotor (142) arranged radially within the stator (141) for rotation, the rotor shaft (143) of which is mounted on at least one end face (121, 122) of the drive housing (12), wherein at least one upper region of the drive housing (12) acts as an air space filled with air surrounding at least one upper region of the electric machine (14), and wherein a dirt trap structure (20) is arranged on an inner wall of the drive housing (12), which dirt trap structure is formed in one piece therewith and comprises an arrangement of pins (201) projecting therefrom, which dirt trap structure is suitable for mechanically binding particles contained in the air surrounding the electric machine (14) upon contact, characterized bythat the dirt trap structure (20) is arranged in said upper region and is designed as an embossed or deep-drawn structure. [2] Drive arrangement (10) according to claim 1, characterized by that the dirt trap structure (20) is formed on an end face (121, 122) of the drive housing (12). [3] Drive arrangement (10) according to one of the preceding claims, characterized by that at least some of the pins (201) - are aligned parallel to each other, - are of different lengths, - are spaced apart by a distance (a) which is less than their diameter (d), - have a round profile and / or - have a polygonal profile. [4] Drive arrangement (10) according to one of the preceding claims, characterized by that the dirt trap structure (20) comprises an arrangement of ribs projecting from a surface. [5] Drive arrangement (10) according to claim 4, characterized by that the ribs are arranged in a honeycomb shape. [6] Drive arrangement (10) according to one of the preceding claims, characterized by that the dirt trap structure (20) comprises an arrangement of pipe sockets projecting from a surface.

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