Compressor assembly for operating a compressed air supply system, compressed air supply system, and vehicle

A compressor arrangement for operating a compressed air supply installation includes a pneumatic compressor and an electric motor arranged inside a drive housing, the electric motor having an internal stator and an external outer rotor. The external outer rotor is arranged in a rotatable manner about the internal stator. The external outer rotor is supported in a rotatable manner about a center axis with respect to the drive housing via a bearing arrangement. The bearing arrangement has at least one bearing. The external outer rotor is supported by the bearing arrangement on an outer circumference of the outer rotor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/EP2018/073809, filed on Sep. 5, 2018, and claims benefit to German Patent Application No. DE 10 2017 009 842.5, filed on Oct. 23, 2017. The International Application was published in German on May 2, 2019 as WO 2019/081106 under PCT Article 21(2).

FIELD

The invention relates to a compressor arrangement including an external rotor electric motor arranged inside a drive housing and further including a pneumatic compressor.

BACKGROUND

Such a compressor arrangement for operating a compressed air supply installation has: an electric motor which is arranged inside a drive housing and which has an internal stator and an external outer rotor, wherein the outer rotor is arranged in a rotatable manner about the internal stator, and a pneumatic compressor. Air supply installations, in particular compressed air supply installations, for pneumatic suspensions, level adjustment systems or other applications are generally known. Such air supply installations produce compressed air in order to supply compressed air consumers therewith, such as the pneumatic suspension mentioned by way of example. The compressed air is produced by means of a compressor which is driven in particular via an electric motor.

WO 2009/033556 A1 discloses a compact dry-running piston compressor having at least one cylinder for compressing air by means of an associated piston which can be moved by electric motor by a crank mechanism which comprises a crankshaft and connecting rod and which is rotatably supported in an oil-bath-free compressor housing via permanently lubricated roller bearings and which produces a housing-internal cooling air flow as a result of the movement cycle, wherein the compressor housing comprises two housing halves which are separated via a partition wall in order to receive the crank mechanism within the first housing half and to receive the electric motor within the second housing half, wherein a roller bearing which is common to the crank mechanism and the electric motor and which is located in the cooling air flow which passes the first housing half is inserted in the partition wall.

DE 10 2013 003 513 A1 discloses a compressor arrangement which is mentioned in the introduction for operating a compressed air supply installation of a vehicle, having a compressor with an electric motor which is formed as an electronically commutated, brushless direct-current motor having a control circuit comprising an electronic power unit (BL-DC motor) and a pneumatic compressor. There is further provision for the electric motor to be formed in the form of an external rotor motor.

SUMMARY

In an embodiment, the present invention provides a compressor arrangement for operating a compressed air supply installation. The compressor arrangement includes a pneumatic compressor and an electric motor arranged inside a drive housing, the electric motor having an internal stator and an external outer rotor. The external outer rotor is arranged in a rotatable manner about the internal stator. The external outer rotor is supported in a rotatable manner about a center axis with respect to the drive housing via a bearing arrangement. The bearing arrangement has at least one bearing. The external outer rotor is supported by the bearing arrangement on an outer circumference of the outer rotor.

DETAILED DESCRIPTION

Approaches utilizing brushless direct-current motors and external rotor motors are in need of further improvement.

It is desirable to improve the function of a compressed air supply installation, with particular regard to compactness, service-life, noise development, assembly and maintenance-friendliness, and efficiency.

The present disclosure describes improved compressed air supply installations which partially or completely achieve such improved function. In particular, the compressed air supply installations reduce the structural space and weight of a compressor arrangement, in particular a drive for a compressor, and improve the operating properties of a compressor.

The present disclosure describes a compressor arrangement for operating a compressed air supply installation having an electric motor which is arranged inside a drive housing and which has an internal stator and an external outer rotor, wherein the outer rotor is arranged in a rotatable manner about the internal stator, and a pneumatic compressor.

On the basis of this compressor arrangement, there is provision for the outer rotor to be supported in a rotatable manner about a center axis with respect to the drive housing via a bearing arrangement which has at least one bearing, and for the outer rotor to be supported, in particular exclusively, by the bearing arrangement on the outer circumference of the outer rotor.

The disclosure takes as a basis the consideration that an external rotor motor acting as a drive motor for a compressor generally leads to advantages. These advantages include in particular the additional property of the outer rotor as a flywheel for storing energy and the moment of inertia which can be achieved in connection with a brushless direct-current motor and the consequently higher dynamic requirements which can be achieved. It is also possible by means of a constructional configuration of the electric motor in the form of an external rotor motor to achieve a considerable reduction of the installation space and consequently the spatial requirements and weight requirements of the entire compressed air supply installation.

The disclosure has recognized that support of the outer rotor, in particular the external rotor, on the outer circumference leads to advantages. These advantages include the additional shielding from electromagnetic radiation as a result of the bearing which is located outside the rotor bell-like member. Radiation emitted by the electric motor is thus shielded in an improved manner and the electromagnetic compatibility of the compressor arrangement is increased in a positive manner.

Furthermore, it may advantageously be possible, as a result of the support on the outer circumference of the outer rotor, for the magnetic flux in the stator to be improved because, in comparison with other known active principles, no opening in the stator is required to introduce the motor shaft.

Furthermore, as a result of the smaller extent of the rotor bell-like member in an axial direction, as a result of the omitted bearing at the ends of the rotor bell-like member, the active diameter of the rotor bell-like member is influenced to a lesser extent as a result of external forces, in particular connecting rod forces. Therefore, the air gap of the motor can be advantageously reduced as a result of a constructional configuration.

The outer rotor can have a flywheel mass weight. In specific terms, this means that there are arranged on the circumference of the external rotor or rotor, in addition to the inherent mass of the outer rotor, in particular the rotor bell-like member, mass-encumbered elements, in particular arranged uniformly over the circumference, or as an integral mass-encumbered element which extends uniformly over the circumference. This results in the advantage that energy which has been produced by the drive or electric motor by the rotating movement can be stored in the form of kinetic energy. As a result of the moment of inertia of the outer rotor which is increased in this manner, in particular brushless direct-current motors can comply in an improved manner with the dynamic requirements which exist in the automotive sector during compressed air production.

There is advantageously provision for the outer rotor to have a practically cylindrical eccentric journal which is arranged about an eccentric axis E, wherein the eccentric axis E is arranged parallel, but with a lifting spacing H relative to the center axis M, in particular the eccentric journal is formed in the form of a formation on a rotor end portion for receiving a connecting rod via a connecting rod bearing. In specific terms, this means that the eccentric journal which is used to rotatably connect the outer rotor to the connecting rod is arranged directly on the outer rotor, in particular on the rotor end portion. In this manner, as a result of this development an even more compact structural form of the compressor arrangement is achieved, particularly because a transmission of the drive energy from the motor to the connecting rod is carried out without any crank pins, or the like, arranged additionally on a drive shaft.

In the context of a preferred development, there is provision for the drive housing to have a drive housing body and a drive housing cover, wherein the stator is retained on the drive housing cover and the outer rotor is supported at an inner side of a housing wall of the drive housing body. In specific terms, this may mean in particular that the stator is arranged on the drive housing cover and consequently the assembly of the electric motor is carried out practically by the insertion of the drive housing cover in the drive housing. As a result of this development, in an advantageous manner an additional contribution to the compactness is achieved since it is possible to dispense with additional, housing-side fixing elements. Furthermore, the accessibility to the drive and consequently the maintenance-friendliness are improved because the stator is already disassembled by the removal of the cover. It is also possible to achieve a desired pretensioning of the bearing by a defined, predetermined spacing of the stator from the outer rotor in an axial direction, which pretensioning is produced by the magnetic forces which act between the stator and the outer rotor of the electric motor. By selecting this spacing in accordance with operating requirements, a positive, negative or neutral pretensioning can be achieved.

There is advantageously provision for the drive housing body to integrally form a motor housing and a crankcase of the compressor. In specific terms, this means that the drive and crank mechanism are located in a common space which is surrounded by the drive housing. This is particularly enabled by the bearing of the outer rotor on the outer circumference and the associated, omitted bearing of a motor shaft which would require an intermediate wall for receiving a crank-mechanism-side motor shaft bearing. As a result of this development, the compactness of the compressor arrangement is advantageously further increased.

There is in particular provision for the drive housing cover to be positioned on a front opening of the drive housing body in a closing manner at the front side. In specific terms, this means that the drive housing cover, similarly to a pot-cover connection, can be placed and fixed in a suitable manner on a face of the drive housing body for assembly. In particular, the drive housing cover and the drive housing body can be constructed by mutually conformed fitting faces in an axial and radial direction in a self-centering manner in order to form a common stator and rotor axis. This means that, during the assembly of the drive housing cover as a result of the contact of the corresponding fitting faces relative to each other, the drive housing cover is orientated relative to the drive housing body and consequently in particular the stator is orientated relative to the outer rotor. As a result of such a development, the assembly and maintenance-friendliness of the drive of the compressor arrangement can advantageously be improved because the orientation of the stator relative to the outer rotor no longer has to be provided by corresponding fixing elements or adjustment steps during the assembly.

In the context of a preferred development, there is provision for the stator to be arranged in such a manner that the axis of symmetry of the stator is orientated coaxially with the center axis, in particular the axis of symmetry of the stator is located on the center axis.

This may particularly specifically involve the fact that, as a result of the bearing of the outer rotor on the external circumference of the rotor bell-like member, a drive shaft as used in conventional compressor drives can be dispensed with. There is provision for construction of the outer rotor as a self-carrying unit, that is to say, a unit which transmits drive forces or torques directly and without any drive shaft. Thus, it is advantageously possible for the region of the stator surrounding the center axis to be constructed in a materially filling manner, in particular without any opening for a rotor shaft. Thus, the region around the rotation axis of the outer rotor which would normally be provided for an opening for introducing a motor shaft can be constructed in a materially filling manner. Thus, the magnetic flux in the stator is advantageously improved. Furthermore, it is nevertheless possible for the plate assembly of the stator to be at least partially constructed in a non-materially filling manner and therefore at least partially in a hollow manner. This may be advantageous, for example, in order to achieve weight savings. In particular, it is possible to avoid guiding a shaft through the region inside the region surrounded by the windings. There are thereby afforded advantages with regard to the magnetic flux which can then be guided in a shaft with smaller losses and without rotational fields.

There is advantageously provision for the bearing arrangement to have a bearing without an inner ring or a bearing without an outer ring. A bearing without an inner ring means that the bearing does not have any inner ring. In particular, the outer rotor of the electric motor, in particular the rotor bell-like member, performs the function of the inner bearing ring, of at least one bearing of the bearing arrangement. This includes the fact that the outer rotor, without a bearing inner ring being positioned, is in direct contact with the roller bearings or, in the case of a sliding bearing, in direct contact with the bearing outer ring. Similarly, a bearing without an outer ring means that the bearing does not have an outer ring. In particular, portions of the inner side of the housing wall which form a running face for the roller members perform the function of the bearing outer ring of at least one bearing of the bearing arrangement.

In particular in both developments, the surfaces which perform the function of the respective bearing rings can be produced in such a manner that they have, for example, as a result of suitable processing, surface and shape properties which qualify the outer rotor for use as a bearing inner ring or bearing outer ring. Such processing may particularly have pretreatment steps in order to adjust, in particular to increase, hardness and strength parameters of the surface which is in contact with the roller members, in particular the outer surface of the rotor bell-like member or the inner side of the housing wall, in particular in order to bring about operation of the drive with little noise and wear.

There is in particular provision for the electric motor to be formed as an electronically commutated, brushless direct-current motor having a control circuit comprising an electronic power unit. In specific terms, this means that the electric motor can be constructed according to these two structural forms, in accordance with constructive requirements. These requirements include in particular the price, dynamic properties during operation, such as acceleration, torque, speed and furthermore electromagnetic compatibility, service-life and freedom from maintenance.

In the context of a preferred development, there is provision for the bearing to be selected from a group of bearings comprising: sliding bearings, needle bearings, ball bearings, spherical roller bearings and cylindrical roller bearings. In specific terms, this means that a bearing type is selected in accordance with the constructive requirements. Needle and cylindrical roller bearings and generally roller bearings with cylindrical roller members have, as a result of the linear contact with the running face, a generally high radial load-bearing capacity. In the case of a needle bearing, in addition it is relatively compact as a result of the small roller member diameter and consequently in an advantageous manner it further reduces the installation space of the drive. As a result of the osculation in the roller contacts, ball bearings have a relatively high axial and radial load-bearing capacity. Spherical roller bearings further allow, as a result of the spherical configuration of the roller members and a hollow-sphere-like outer ring ball race, a specific oscillating movement between the inner ring and outer ring. Consequently, non-sensitivity with respect to oblique positioning and alignment errors of the rotor with respect to the stator are achieved.

There is advantageously provision for the bearing arrangement to have at least one single-rowed bearing or at least one multi-rowed bearing. This may involve in specific terms the outer rotor being formed by means of a two-rowed deep-groove ball bearing or two-rowed oblique ball bearing. A multi-rowed arrangement advantageously leads to an increase of the load-bearing capacity and allows, particularly with the oblique ball bearing, the adjustment of different pressure angles. Furthermore, as a result of the arrangement of the oblique bearing rows, freedom from play, support width, axial load-bearing capacity and axial force transmission can be influenced in order to comply with constructive requirements.

There is in particular provision for the outer rotor to be constructed in order to be fixed by the magnetic forces acting in the electric motor in an axial direction. This involves in specific terms no forces being transmitted via the bearing arrangement in an axial direction, such as, for example, in the case of a fixed/movable bearing or a support bearing, and the outer rotor being retained centrally relative to the stator in an axial direction simply by the magnetic forces acting between the outer rotor and stator. This development leads to the advantage that the bearings are not mechanically tensioned in an axial direction and the collar or the piston ring in the compressor which was otherwise fixed by the bearings consequently cannot be tensioned in a radial direction any more. The radial centering of the collar or the piston ring in the cylinder and the axial centering of the rotor relative to the stator complement each other in the ideal case at a low force level. In this manner, wear and electrical current during operation of the motor are advantageously reduced. Furthermore, forces which act in the crank mechanism act on the deformation of the rotor to a lesser extent as a result of the axial movability which can be achieved according to this development; consequently, a shaft flexion, as may occur in a conventional bearing of a compressor drive, is substantially prevented. By preventing flexion of the rotor or the shaft, in particular a smaller air gap of the electric motor and consequently correspondingly high forces and in particular a high torque of the electric motor are enabled. As a result of such a development, the structure-borne noise transmission from the outer rotor to the stator and therefore to the drive housing is also reduced, which has an advantageous effect on vibrations and noise development. This particularly applies to the reduction of structure-borne noise which would be produced as a result of axial movements of the motor armature during conventional rigid guiding of the rotor including the crankshaft and connecting rod. Furthermore, the risk of damage to the bearing or bearing fixing is reduced by axial forces from the crank mechanism which act in an axial direction and which in particular pulse in an abrupt manner, not being transmitted directly into the bearing and therefore into the entire unit.

In the context of a preferred development, there is provision for the outer rotor to be fixed via a bearing in an axial direction. This may involve in specific terms the fact that the bearing for supporting the rotor on the outer circumference is constructed to receive axial forces. Alternatively or additionally, this may mean that the fixing is carried out in an axial direction via a second bearing which is arranged with an axial spacing from the first bearing. This bearing can be constructed as a radial bearing which receives axial forces or as an exclusively axial bearing. This development leads to the advantage that the outer rotor is fixed in an axial direction, in particular without fixing by a connecting rod or magnetic forces of the electric motor being necessary.

There is advantageously provision for at least one weight, in particular a flywheel mass weight and/or a compensating weight for compensating for imbalance, to be arranged on the circumference of the rotor, in particular on the circumference of the rotor bell-like member. This involves in specific terms there being arranged on the outer rotor at least one weight which is positioned in accordance with the actual mass distribution of the rotor in such a manner on the outer rotor that the total of the forces which act on the rotating outer rotor as a result of the rotation is minimized. This particularly relates to forces which are directed into the outer rotor as a result of the eccentric journal and components fixed thereto. In this manner, a low-vibration and low-noise operation of the drive and consequently of the compressor is advantageously achieved. In particular, a complete rotational mass compensation is achieved.

There is in particular provision for the outer rotor to be rotatably supported on the drive housing by means of two bearings which are arranged with spacing in an axial direction. In specific terms, this means that the outer rotor is supported in the drive housing by means of two bearings which are arranged in particular at sides of the rotor bell-like member which are opposite in an axial direction. In this manner, it is advantageously possible to increase the load-bearing capacity of the bearings. Furthermore, the support width of the bearing can be increased by the two-fold bearing arrangement, in particular for receiving bending moments in an improved manner. This further particularly relates to the use of two single-rowed oblique ball bearings which are arranged in accordance with this development.

In the context of a preferred development, there is provision for the stator to be arranged in an axial direction so as to be adjustable on the drive housing cover. This adjustability can be achieved in constructive terms, for example, by an adjustment thread in the stator or a drive housing cover which is adjustable in an axial direction. In order to achieve this feature, that is to say, adjustability of the drive housing cover in an axial direction, slots can be provided in the drive housing body in an axial direction. As a result of such slots, the drive housing cover can be fixed, for example, by means of screws after adjustment of the desired axial position. Furthermore, the drive housing body can be constructed in such a manner that it has at least one groove which extends helically on a cylindrical inner surface of the opening for the drive housing cover. As a result of corresponding journals which widen radially at the side of the drive housing cover, it can be adjusted in an axial direction by rotating and guiding the journals of the drive housing cover in the grooves of the drive housing body. After the axial position which is intended to be adjusted is reached, the cover can be fixed via screws or similar fixing means and secured to prevent rotation.

As a result of adjustability of the stator in an axial direction, an adaptability of the axial pretensioning of the rotor and in particular of the rotor bell-like member in the assembled state is advantageously achieved. In this manner, a desired operating behavior can be achieved in accordance with the pretensioning, in particular by adjusting a positive, negative or neutral pretensioning.

Embodiments of the invention will now be described below with reference to the drawings. These drawings are not necessarily intended to depict the embodiments in a manner true to scale, but instead the drawings are carried out in a schematic and/or slightly distorted form where advantageous for explanation. With regard to supplements to the aspects of teaching which can be directly recognized from the drawings, reference may be made to the relevant prior art. In this case, it should be taken into account that various modifications and changes in relation to the form and detail of an embodiment can be carried out without departing from the general notion of the invention. The features which are disclosed in the description, drawings and claims may be significant both individually and in any combination. Furthermore, all combinations comprising at least two of the features disclosed in the description, drawings and/or claims are included within the scope of the invention. The general notion of the invention is not limited to the precise form or the detail of the preferred embodiments which are shown and described below or limited to subject-matter which would be limited in comparison with the subject-matter claimed in the claims. In the case of measurement ranges set out, values which also lie within the mentioned limits are intended to be disclosed as limit values and are intended to be able to be freely used and claimed. For the sake of simplicity, the same reference numerals are used below for identical or similar components or components with an identical or similar function.

FIG. 1shows a constructive configuration of a compressed air supply installation1000in the context of a first variant of a particularly preferred embodiment. The compressed air supply installation1000has a housing120which in turn has a dryer and valve housing122, a compressor housing124and a drive housing126.

In the constructive illustration of the compressed air supply installation1000ofFIG. 1, the housing120thereof can be seen with a drive housing126for carrying out the compressor arrangement100comprising the compressor400and the drive, wherein the drive in the form of an electric motor300and the crank mechanism350are received in the drive housing126. The drive housing can equally well be configured as a motor housing or a similar housing.

The housing arrangement120further comprises a compressor housing124for the compressor400. A dryer and valve housing122adjoins the compressor housing124and comprises the dryer housing and electric and/or electronic and pneumatic interfaces together with a mechatronic system and an arrangement of valves—substantially to illustrate the valve arrangement142.

A piston402which can be moved back and forth and which has a collar or a piston ring406is retained on a connecting rod404of a crank mechanism350in the compressor housing124. The connecting rod404which is itself configured as a piston rod is supported on an eccentric journal342.

The drive formed with the electric motor300for the crank mechanism350and the crank mechanism350are substantially received in the drive housing126. The drive itself has a stator304with a stator winding306in order to form the electric motor300. Furthermore, the drive has a rotor or outer rotor340having a rotor bell-like member348and an arrangement of permanent magnets308fitted thereto.

In order to construct the motor300in the form of an external rotor motor for the drive, the outer rotor340is retained separately by an air gap312around the stator304. The stator304is consequently surrounded by the outer rotor340in a rotatable manner about a center axis M which coincides with the axis of symmetry S of the stator304by the stator304being arranged accordingly. In this instance, the outer rotor340is rotatably retained on a bearing arrangement320in the drive housing126, that is to say, in an inner side132of a housing wall129of the drive housing126, while the stator304is formed as part of a drive housing cover130. The drive housing126can be closed by means of the drive housing cover130by inserting the drive housing cover130into a front opening134of the drive housing body128. Alternatively, the stator304can also be releasably fixed on the drive housing cover130via suitable fixing means, in particular screws. It is also possible, not illustrated here, for the outer rotor340to be fixed via the magnetic forces MK which act in the electric motor300and which are schematically indicated here in an axial direction A. Furthermore, it is possible according to a development to adjust the stator304relative to the outer rotor340in an axial direction A. This can be achieved, for example, via an adjustment means, for example, one or more threads or one or more fitting faces which allow an axial displaceability of the drive housing cover130relative to the drive housing body128. Additionally or alternatively, adjustment screws can also be used to adjust and fix the drive housing cover or the stator.

The outer rotor340does not have any central rotor shaft in the conventional sense but instead forms with the rotor bell-like member348a self-supporting, in particular integral, unit, on which the eccentric journal342which is particularly formed by an integral formation341is also fixed.

The outer rotor340and the eccentric journal342and the connecting rod404form the significant force-transmitting elements of the crank mechanism350which is driven by the electric motor300, wherein the connecting rod404is connected to the eccentric journal342in a rotationally movable manner by means of a connecting rod bearing344. The connecting rod bearing344is constructed to carry out a rotating movement of the rotor340and, in an additional configuration, also a back and forth movement of the connecting rod404. As a result of a rotating movement of the rotor340, consequently, the connecting rod404and accordingly the piston402is caused to carry out a mainly translational lifting movement for driving the compressor. Furthermore, the outer rotor may have a compensation weight for compensating for the imbalance brought about by the eccentric journal342and components fixed thereto, which is not illustrated in greater detail here.

FIGS. 2A to 2Fillustrate as a cross-sectional cutout by way of example different embodiments of the bearing320of the rotor340. The cutout shows a cross-section through the bearing ring at the transition between the rotor bell-like member348and the drive housing body128.

FIG. 2Aschematically shows a cutout of the rotor bearing. In this development shown, a bearing arrangement320ahas a bearing313ain the form of a sliding bearing314which allows a rotating relative movement between the rotor bell-like member348of the outer rotor340and the drive housing body128. The advantage of a sliding bearing involves the small constructive complexity by means of which the bearing can be produced. In particular, it is possible in the case of a sliding bearing to dispense with rotating roller members. In the form of the sliding bearing illustrated, an axial movability of the rotor is provided and is limited only by other forces which act on the outer rotor340, for example, of the stator304or the connecting rod404. The sliding bearing can further be produced using different construction methods, for example, by a sliding sleeve which is formed from a low-friction material or in the form of a hydrodynamic sliding bearing. For the last case, however, constructive measures for shielding and storing a lubricant would again have to be carried out and increase the construction complexity.

FIG. 2Bfurther shows a cutout I of an additional embodiment of the rotor bearing. In this development, a bearing arrangement320bhas a bearing313bwithout an inner ring in the form of a needle bearing315without an inner ring, that is to say that the needle bearing315without an inner ring does not have any bearing inner ring but instead the roller members322bare in direct contact with the outer surface of the rotor bell-like member348. An outer ring324bof the needle bearing315further has at the left side and the right side thereof an edge B, which limits the movement of the roller members322bin an axial direction. Furthermore, the surface of the rotor bell-like member348is constructed in such a manner that it can be moved in an axial direction relative to the roller members322band therefore the needle bearing315without an inner ring is formed as a movable bearing. In a manner similar to the embodiment shown inFIG. 2A, this results in an axial movability of the rotor340which is limited only by the already-described additional forces which act on the outer rotor340. The embodiment shown inFIG. 2Bhas a particularly advantageous effect on the necessary structural space as a result of the compact construction type, particularly as a result of the small roller member diameter and the omitted bearing inner ring.

Nevertheless, it is possible in an alternative embodiment of a bearing arrangement320b′ which is shown in an additional view II to provide, with a bearing313b′ which does not have an outer ring, an arrangement which is transposed in a radial direction of the bearing elements described here. In this case, roller members322b′ are in direct contact with the inner side132of the drive housing body128. A bearing inner ring326b′ has, similarly to the above-described outer ring324b, at the left side and right side thereof an edge B′, which limits the movement of the roller members322b′ in an axial direction. Consequently, the above-described advantages are similarly achieved, with particular regard to the structural space.

In both cases, it is possible and even advantageous to accordingly process the surface which as a running face is in direct contact with the roller members322b,322b′, that is to say, the inner side132of the drive housing body128or the outer surface of the rotor bell-like member348, in order to improve the tribological properties. In particular, a hardening or coating of the surface is conceivable here.

FIG. 2Cshows a cutout of an additional preferred development of a rotor bearing. In this development, the rotor bell-like member348is rotatably supported in the drive housing body128via a bearing arrangement320cwhich is constructed with a bearing313cin the form of a needle bearing316with an inner ring. In this embodiment, the bearing316has both a bearing outer ring324cand a bearing inner ring326c. Furthermore, both the bearing outer ring324cand the bearing inner ring326chave at the left side and right side edges B which limit the movement freedom of the rolling members322cin an axial direction and thus allow the transmission of axial forces by the bearing arrangement320c. In this embodiment, consequently, the outer rotor340or the rotor bell-like member348is retained via the bearing arrangement320caxially in the drive housing body128. In this manner, forces which act in an axial direction and which, for example, are directed via the connecting rod into the outer rotor340can be taken up by the bearing arrangement320cand directed into the drive housing body128independently of the magnetic forces which act as a result of the electric motor300.

FIG. 2Dshows an additional preferred embodiment of the rotor bearing. In this development, a bearing arrangement320dhas a bearing313din the form of a multi-rowed rolling bearing317having a bearing outer ring324dand a bearing inner ring326dwhich is formed in this instance as a two-rowed deep-groove ball bearing317′. As a result of the doubled number of roller members322din comparison with a one-rowed configuration, a corresponding increase of the load-bearing capacity of the bearing is produced. The two-rowed construction type also has a positive effect on the prevention of tilting of the rotor as a result of torques, in particular bending torques, which are introduced via connecting rod forces which act on the outer rotor340. It is further possible, instead of the two-rowed deep-groove ball bearing317′, to use a one-rowed ball bearing317″, in particular a deep-groove ball bearing, which has only one row of roller members322dand which is not illustrated here.

FIG. 2Eshows an additional preferred embodiment of the rotor bearing. In this development, a bearing arrangement320ehas a bearing313ein the form of a cylindrical roller bearing318. Unlike a needle bearing315,316, the roller members322eof a cylindrical roller bearing318have a larger diameter. In spite of the higher structural space requirements, this embodiment is advantageous with regard to speeds of the rotor340which can be reached. Furthermore, in this embodiment both the bearing outer ring324eand the bearing inner ring326ealso have edges B, which limit the axial freedom of movement of the roller members322e. Similarly to the embodiments shown inFIGS. 2C and 2D, the outer rotor340is fixed by the bearing arrangement320ein the embodiment shown inFIG. 2E. It is also possible to use, instead of a cylindrical roller bearing318, a spherical roller bearing319which has sphere-like roller members in place of cylindrical roller members and which is not illustrated here.

FIG. 2Fshows an additional particularly preferred embodiment of the rotor bearing. In this embodiment, a bearing arrangement320fhas two separate roller bearings313, which are constructed in this instance as deep-groove ball bearings317, that is to say, a bearing313.1remote from the connecting rod and a bearing313.2near the connecting rod. The bearing313.1remote from the connecting rod has a bearing outer ring324f.1and a bearing inner ring326f.1. The bearing313.2near the connecting rod has a bearing outer ring324f.2and a bearing inner ring326f.1. In this embodiment, the advantage already afforded in the development illustrated inFIG. 2Dinvolving an increased load-bearing capacity of the bearing is also achieved in particular in a further improved manner. The bearings313.1,313.2are constructed in this development as a one-rowed deep-groove ball bearing317. By selecting a larger bearing spacing L which describes the axial spacing of both bearings313.1,313.2, the capacity of the bearing to receive torques can be further improved. Such torques can be directed into the outer rotor340in particular in the form of connecting rod forces which act on the eccentric journal342.

The bearing types which are illustrated inFIGS. 2B, 2C, 2D and 2E, in particular the bearing arrangements320b,320c,320d,320e, can be fixed in an axial direction in the drive housing in a positive-locking manner. This can be achieved in particular by a step on the fitting face which acts as a bearing seat in the drive housing body128, against which step the bearing outer ring324,324b,324c,324d,324eis pressed during assembly of the drive housing cover130by a suitable annular step in the drive housing cover130.

The bearings313b-e,313.1,313.2illustrated inFIGS. 2B, 2C, 2D, 2E and 2Fin the bearing arrangements320b,320c,320d,320e,320fare all special construction forms of one or more roller bearings. The individual bearing types can be varied depending on requirements and applications. Thus, for example, in place of the arrangement shown inFIG. 2Fof two deep-groove ball bearings, two needle bearings or cylindrical roller bearings can also be used.

In an embodiment shown inFIG. 2Fwith a plurality of bearings being arranged, a spacer sleeve for fixing in an axial direction can further be used between the bearing outer rings of the individual bearings. Alternatively, in this embodiment steps with different diameters can also be used both at the side of the rotor340and at the side of the drive housing body128in order to fix the respective bearing outer rings324f.1,324f.2and bearing inner rings326f.1,326f.2in a positive-locking manner in an axial direction. Furthermore, it is also possible to use bearings having different inner and outer diameters in order to be fixed in a positive-locking manner in an axial direction at different cylindrical steps with similarly different diameters. Finally, it is also possible to achieve the axial fixing of the bearing arrangements320,320a-fby the outer surface of the rotor bell-like member348and/or the inner surface of the drive housing body128being configured conically.

FIG. 3Ais a schematic view of an electric motor300′ in another preferred development. In this view, the stator304is arranged on the drive housing cover130. The rotor bell-like member348′ of the outer rotor340′ is constructed and arranged in such a manner that it radially surrounds the stator304and is supported rotatably about the center axis M. An illustration of details, in particular of the bearings, has been omitted for reasons of clarity and simplification. The outer rotor340′ further has on the rotor end portion346′ an eccentric journal342in the form of an integral formation341, the eccentric axis E of which is arranged with radial lifting spacing H from the center axis M.

Furthermore, a flywheel mass weight360which is constructed in this development as an annular mass-encumbered member which in this instance constitutes practically an extension of the rotor bell-like member in an axial direction is arranged on the rotor end portion346′. Nevertheless, naturally other construction types and arrangements of a flywheel mass weight360are possible, for example, on the outer circumference343of the rotor bell-like member348′ or on the inner circumference345, with an adequate axial spacing from the stator winding306, permanent magnet arrangement308and a bearing arrangement320,320a-fwhich is not illustrated here, and generally as the structural space of the development allows. It is generally the case that an arrangement of the flywheel mass weight360further outward on the diameter of the rotor increases the moment of inertia of the outer rotor340. In this instance, it can be seen that the radial extent of the flywheel mass weight360above the eccentric journal342is greater than under the eccentric journal342. As a result of a variable configuration of the flywheel mass weight360which differs from an annular shape in a radial direction, a mass compensation can further advantageously be achieved in order to minimize or eliminate imbalances occurring during operation.

The development of an electric motor300″ shown inFIG. 3Bdiffers from the development shown inFIG. 3Ain that it does not have any flywheel mass weight360but instead on the rotor end portion346″ a compensation weight370which is arranged in particular opposite the eccentric journal342in a radial direction in order to achieve a rotational mass compensation. It is thereby particularly intended to be possible for the mass and inertia forces of the eccentric journal342and the components which are connected to the eccentric journal342, in particular the connecting rod404, which is not illustrated here, and piston402to be compensated for by the accelerated compensation weight370. Thus, it may be possible in a constructive manner for occurring imbalances to be able to be minimized and in particular practically completely eliminated. In this case, the compensation weight is fitted as close as possible to the outer circumference343of the rotor bell-like member348″ of the outer rotor340″ because it can thus advantageously be smaller in order to produce a force which compensates for the imbalances, in particular in comparison with an arrangement nearer the axis of symmetry S of the stator or rotor.

FIG. 4is a highly simplified, schematic overview of a compressed air supply installation1000with a compressor arrangement100for supplying a pneumatic installation600. The compressed air supply installation1000has an air intake0for drawing fresh air which is further connected to an inlet of the compressor400in a fluid-conveying, in particular gas-conveying manner. The compressor400is driven as part of the compressor arrangement100by a drive200having an electric motor300which is constructed in this case as a brushless direct-current motor301and which is controlled by a control circuit700with an electronic power unit701, via an outer rotor340. The compressed fresh air is further provided via a compressed air source1, to which a branch510is connected. A ventilation3is connected to this branch510, on the one hand, via a ventilation valve520. On the other hand, an air dryer540which further leads to a compressed air connection2is connected to the branch510. A compressed air store560is connected thereto via a storage line564and a storage valve562and furthermore the pneumatic installation600is connected thereto via a screen570. The pneumatic installation600may be, for example, a pneumatic spring installation or an additional pneumatic installation, in particular of a vehicle. Furthermore, individual valves, throttles and similar adjustment means and individual components, in particular of the pneumatic installation, are not illustrated in this illustration for reasons of clarity and simplification.

FIG. 5is a schematic illustration of a vehicle2000—in this case, in the form of a passenger vehicle—having a compressed air supply installation1000and a pneumatic installation600. In vehicles in the passenger vehicle sector, low-noise and low-vibration operation is highly significant because here, unlike applications in the commercial vehicle sector, the acoustic requirements are higher or more sensitive. The passenger vehicle2000which is illustrated here by way of example for this reason, without limiting the applicability to trucks or other utility vehicles, has four wheels801,802,803and804, of which the two front wheels are shown here as a result of the cross-sectional illustration. Similarly to the number of wheels, the pneumatic installation600has four pneumatic springs601,602,603and604, of which the two front pneumatic springs are shown here as a result of the cross-sectional illustration similarly to the wheels. The pneumatic springs601,602,603and604which are each associated with the wheels801,802,803and804are supplied with compressed air as part of the pneumatic installation600by the compressed air supply installation1000. The compressed air supply installation1000is connected in a fluid-conveying manner via the screen570to the components of the pneumatic installation600, in this case the pneumatic springs601,602,603and604illustrated here.

The compressed air supply installation1000is shown in this illustration in a highly simplified manner so that only the compressed air store560and the compressor400can be seen.

However, the compressor400could be used additionally or alternatively independently of the compressed air supply installation in a modification which is not shown here.

The concept preferably provides the basis for a compressor arrangement which functions in an improved manner, in particular one which is compact and low in noise and vibrations. Furthermore, a reduction of forces and/or moments and in particular a reduction of the dynamic loads and vibrations which are connected with the forces and/or moments lead to a more protective operation which has a positive effect on the efficiency and service-life of the compressor arrangement.

LIST OF REFERENCE NUMERALS