Abstract:
The invention relates to an electric motor, in particular for a motor vehicle, comprising a housing ( 9 ), a shaft ( 8 ) having an axle ( 30 ), a stator and a rotor, at least one channel ( 11 ) for conducting a coolant for cooling the electric motor ( 5 ), wherein the geometry of the alignment of at least one section ( 12 ) of the at least one channel ( 11 ) is designed such that the coolant flows in the direction of the axle ( 30 ) of the shaft ( 8 ) through the at least one channel ( 11 ), having a deviation of less than 40°.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electrical machine and to a drive device. 
     Drive devices, preferably hybrid drive devices, in particular comprising an internal combustion engine and an electrical machine, are used, for example, in order to drive motor vehicles. The electrical machine in the motor vehicle, which electrical machine operates as a motor and a generator, has an axle or shaft on which the stator or rotor is arranged. 
     Waste heat is produced in the electrical machine, in particular in the stator and/or rotor, and therefore it is necessary to cool the electrical machine. The stator and rotor are arranged within a housing of the electrical machine. A spiral or helical channel for conducting a cooling fluid for cooling the electrical machine is incorporated in the housing. The axle around which the spiral cooling channel is wound corresponds to the axis of the shaft of the electrical machine in this case. After the cooling fluid is introduced into the channel, the cooling fluid absorbs heat and thus is at a higher temperature. This leads to non-uniform temperature distribution over the axial length of the electrical machine. Therefore, the absorption of heat by the cooling fluid is disadvantageously reduced. 
     DE 199 28 247 B4 describes a motor having a motor housing, a stator of cylindrical shape which is mounted on the motor housing, an internal rotor which is arranged in a rotatable manner within the stator, an external rotor which is arranged in a rotatable manner about the stator, with the internal rotor, the stator and the external rotor being arranged in a concentric manner and having a plurality of pins for mounting the stator on the motor housing, with a cooling system being provided which has a plurality of pairs of cooling channels which are formed in the stator, a coolant inlet opening for introducing coolant into the cooling channels, a coolant outlet opening for diverting coolant from the cooling channels, with the coolant inlet opening and the coolant outlet opening being provided at an axial end of the internal rotor and being connected to the cooling channels, a coolant return section for connecting each pair of cooling channels, with the coolant return section being provided at another axial end of the internal rotor, and with the cooling channels being formed from the stator and the plurality of pins. 
     SUMMARY OF THE INVENTION 
     An electrical machine, in particular for a motor vehicle, comprising a housing, a shaft having an axis, a stator and a rotor, at least one channel for conducting a cooling fluid for cooling the electrical machine, with the geometry or the orientation of at least one section of the at least one channel being designed to the effect that the cooling fluid flows through the at least one channel with a deviation of less than 40°, in particular exclusively, in the direction of the axis of the shaft. 
     The axial flow of cooling fluid in the at least one channel produces a substantially constant temperature distribution in the axial direction of the electrical machine. As a result, the heat absorption by the cooling fluid can be improved, in particular on account of the greatest quantity of heat being given off by the stator and/or the rotor in the region of the central plane of the electrical machine. 
     In particular, the geometry or the orientation of the at least one channel is designed to the effect that, in at least a first pair of two sections of the at least one channel, the cooling fluid in an A section flows in the opposite direction to a B section. When the cooling fluid flows in the opposite and axial direction with a deviation of less than 40 degrees in the A section and in the B section, the heat can be particularly effectively absorbed and uniformly distributed by the cooling fluid because distribution takes place in the axial direction on account of the opposite direction. 
     In a further refinement, a component stream of cooling fluid can in each case be conducted though the A section and through the B section of the at least one channel. Splitting the cooling fluid into two component streams which are each conducted through the A section and the B section has the advantage that, after the two component streams are combined, it is possible to thoroughly mix these separated streams. 
     In a supplementary embodiment, the two component streams are substantially identical, for example with a deviation of less than 30%. 
     The geometry or the orientation of the at least one channel is designed to the effect that the cooling fluid in the A section and in the B section flows to an axial end face of the electrical machine or of a component of the electrical machine. The cooling fluid flowing in the A section and the B section is therefore conducted from a central plane of the electrical machine in each case to the two axial end faces of the electrical machine. The greatest amount of waste heat is released in the region of the central plane, that is to say in the center of the electrical machine, and therefore said waste heat is conducted to the axial end faces and there heat can be given off by the cooling fluid to the surrounding area. 
     In one variant, the geometry or the orientation of the at least one channel is designed to the effect that, in at least a second pair of two sections of the at least one channel, the cooling fluid in a C section flows in the opposite direction to a D section. 
     Expediently, a component stream of cooling fluid can in each case be conducted through the C section and through the D section of the at least one channel. 
     In a further embodiment, the two component streams are substantially identical, for example with a deviation of less than 30%. 
     In particular, the geometry or the orientation of the at least one channel is designed to the effect that the cooling fluid in the C section and in the D section flows to a central plane of the electrical machine or of a component of the electrical machine, said central plane being perpendicular to an axis of the shaft. The central plane is expediently at the same distance from both axial end faces of the electrical machine or a component of the electrical machine. 
     In a further refinement, the cooling fluid can be conducted though two curve sections of the at least one channel from the at least one first pair comprising the A section and the B section to the at least one second pair comprising the C section and the D section, and/or vice versa. In the two curve sections, the cooling fluid is conducted from the first pair to the second pair, and vice versa. In the two curve sections, the cooling fluid flows at least partially in the radial direction, and therefore the cooling fluid can also be conducted through the housing and/or the stator in the radial direction as a result. 
     In a supplementary variant, the at least one first pair comprising the A section and the B section and the at least one second pair comprising the C section and the D section are fluidically separated from one another by means of a separating crosspiece. The separating crosspiece permits structurally simple fluidic separation of the first pair comprising the A section and the B section from the second pair comprising the C section and the D section. 
     In a further variant, the cooling fluid can be conducted through the electrical machine in the radial direction, for example by it being possible to conduct the cooling fluid through at least two curve sections of the at least one channel and/or through at least one connecting section of the at least one channel. 
     In a further refinement, the cooling fluid can be conducted through at least one connecting section of the at least one channel from the at least one first pair comprising the A section and the B section to the at least one second pair comprising the C section and the D section, and/or the cooling fluid can be conducted through at least one connecting section of the at least one channel from the at least one second pair comprising the C section and the D section to the at least one first pair comprising the A section and the B section. 
     The cooling fluid flows at least partially in the radial direction in the at least one connecting section, and therefore the cooling fluid can also be conducted through the electrical machine in the radial direction as a result. Furthermore, the component streams of the cooling fluid, which component streams are conducted through the C section and the D section, are combined in the at least one connecting section, and therefore possible temperature differences in the region between the C section and the D section can be substantially compensated for by through mixing in the at least one connecting section. In addition, the at least one connecting section is preferably arranged in the region of a central plane of the electrical machine, the greatest quantity of heat being released in the region of said connecting section. The connection section, in particular the flow cross section of the connecting section, is, in this case, preferably designed to the effect that the cooling fluid is conducted through the connection section in a turbulent stream. This results firstly in good admixing of the cooling fluid and secondly heat can be absorbed particularly effectively in the case of a turbulent stream, this having the advantage that a particularly effective cooling action of the cooling fluid is also possible in the at least one connecting section on account of the turbulent stream in the region of the electrical machine with the greatest need for cooling because the greatest quantity of heat is produced in said region. 
     In particular, the at least one channel is formed in the housing and/or in the stator, and/or the cooling fluid is a liquid, in particular an oil or a water/glycol mixture, and/or the cooling fluid can be conducted through the at least one channel in the radial and axial direction of the electrical machine, and can preferably be conducted in a meandering manner, in particular with opposing axial flow. 
     A drive device according to the invention, preferably a hybrid drive device, in particular for a motor vehicle, comprises preferably an internal combustion engine, in particular for driving the motor vehicle, preferably at least one housing, at least one electrical machine, which is preferably arranged in the at least one housing and has a stator and a rotor, with the at least one electrical machine being designed in accordance with an electrical machine as described in this property right application. 
     In a further refinement, the at least one housing has two or more parts. 
     In an additional refinement, the housing has one part. 
     In a further refinement, the at least one electrical machine operates as a motor and/or as a generator. 
     A motor vehicle according to the invention comprises an electrical machine which describes this property right application and/or a drive device as described in this property right application. 
     In a further refinement, the motor vehicle comprises rechargeable batteries. The batteries supply electrical power to the electrical machine and, when the motor vehicle is decelerated by means of the electrical machine, the batteries can be charged by the electrical power generated by the electrical machine. In addition, the batteries can also be charged when the vehicle is stationary, for example by a public power supply system. In particular, the batteries are in the form of lithium ion batteries. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One exemplary embodiment of the invention will be described in greater detail below with reference to the attached drawings, in which: 
         FIG. 1  shows a highly schematic illustration of a hybrid drive device, 
         FIG. 2  shows a side view of an electrical machine, 
         FIG. 3  shows a section A-A according to  FIG. 2 , 
         FIG. 4  shows a perspective view of the housing of the electrical machine according to  FIG. 1  comprising a channel for conducting a cooling fluid, 
         FIG. 5  shows a plan view of the housing of the electrical machine according to  FIG. 1  comprising the channel for conducting the cooling fluid, and 
         FIG. 6  shows a view of a motor vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     A drive device  1 , in the form of a hybrid drive device  2 , for a motor vehicle  3  is illustrated in  FIG. 1 . The hybrid drive device  2  for a motor vehicle  3  comprises an internal combustion engine  4  and also an electrical machine  5  which operates as a motor  32  and a generator  33 , in each case for driving or decelerating the motor vehicle  3 . The internal combustion engine  4  and the electrical machine  5  are connected to one another by means of a drive shaft  20 . The mechanical coupling between the internal combustion engine  4  and the electrical machine  5  can be established and broken by means of a clutch  19 . Furthermore, an elasticity means  21  is arranged in the drive shaft  20  which couples the internal combustion engine  4  and the electrical machine  5  to one another. The electrical machine  5  is mechanically coupled to a differential transmission  23 . A converter  22  and a transmission  28  are arranged in the drive shaft  20  which connects the electrical machine  5  and the differential transmission  23  to one another. The drive wheels  25  are driven by means of the differential transmission  23  via the wheel axles  24 . 
     Other options (not illustrated) besides the arrangement illustrated in  FIG. 1  of the internal combustion engine  4  and the electrical machine  5  for the motor vehicle  3  are also feasible. For example, the electrical machine  5  can be arranged on the side of the internal combustion engine  4  and can be mechanically connected to the internal combustion engine  4  by means of a belt or a chain or by gear wheels (not illustrated) instead of the drive shaft  20  depicted in  FIG. 1 . In addition, the electrical machine  5  could be arranged on a transmission, for example a differential transmission, or the electrical machine  5  can operate as a wheel hub motor and/or as a wheel hub generator, that is to say it can be arranged in the region of a wheel hub (not illustrated). 
       FIGS. 2 and 3  show the electrical machine  5  for the hybrid device  2  in the form of an internal pole machine in a first embodiment with a stationary stator  6  and a rotating rotor  7  of the hybrid drive device  1  in a highly simplified illustration, and therefore electrical lines, the windings of the stator  6  and of the rotor  7 , and fixing means for the stator  6 , for example, are not illustrated or are illustrated only in a highly simplified manner. A shaft  8  comprises metal, for example steel, on which the rotor  7  is arranged in a concentric manner, with the shaft  8  and the rotor  7  being mounted on the stationary housing  9  by means of a bearing (not illustrated). The shaft  8 , the rotor  7  and the stator  6  are arranged within the housing  9 . The stator  6  is arranged, concentrically around the rotor  7 , on a housing  9 , said stator being mounted on said housing by means of fixing means (not illustrated). The stator  6  can also be mounted on the housing  9  without additional fixing means, for example by means of a compression joint and/or shrink-fit joint. The housing  9  is produced, for example, by means of a lost foam casting process, an investment casting process or a permanent mold casting process. The wall thickness of the housing  9  is, for example, in the range of from 2 to 6 mm. In this case, the shaft  8  is connected to the drive shaft  20  of the hybrid drive device  2  within the hybrid drive device  2  and/or constitutes a part of the drive shaft  20 . 
     The electrical machine  5  has a channel  11  for conducting a cooling fluid for cooling the electrical machine  5 . The channel  11  is integrated in the housing  9  of the electrical machine  5 . An inlet opening  36  for introducing the cooling fluid into the channel  11  and an outlet opening  37  for discharging cooling fluid from the channel  11  are formed in the outer face of the housing  9  of the electrical machine  5  ( FIGS. 2 to 5 ). The inlet opening  36  and the outlet opening  37  are formed in the region of a central plane  29  of the electrical machine  5 . The central plane  29  is perpendicular to an axis  30  of the shaft  8 . The greatest quantity of heat is given off by the stator  6  and/or the rotor  7  in the region of the central plane  29 . On account of the introduction of the cooling fluid into the inlet opening  36  in the region of the central plane  29 , the cooling fluid is therefore fed in in that region in which the greatest amount of heat is released within the electrical machine  5 , and therefore particularly effective cooling is possible in this critical region of the electrical machine  5 . The channel  11  constitutes a part of the cooling circuit  10  (not completely illustrated) of the electrical machine  5  having lines for the cooling fluid and having a heat exchanger or radiator for cooling the cooling fluid. 
     After the cooling fluid is introduced into the inlet opening  36 , the channel  11  splits into an A section  15  and into a B section  16  ( FIGS. 4 and 5 ). The A section  15  and the B section  16  form a first pair  13  of sections  15 ,  16  of the channel  11 . The A section  15  and the B section  16  are both oriented in the axial direction, and therefore the cooling fluid flows in the axial direction of the electrical machine  5  in the A section  15  and in the B section  16 . On account of the cooling fluid being split into the A section  15  and the B section  16 , the cooling fluid in the A section flows in the opposite direction to in the B section  16 . The cooling fluid therefore flows to an axial end face  26  of the electrical machine  5  both in the A section  15  and in the B section  16 . The housing  9 , as a component  27  of the electrical machine  5 , has two axial end faces  26  ( FIGS. 4 and 5 ). 
     After flowing through the A section  15  of the channel  11 , the cooling fluid enters a curve section  31  of the channel  11  and flows further into a C section  17  of the channel  11 . Furthermore, the cooling fluid flowing through the B section  16  flows, in an analogous manner, through a further curve section  31  into a D section  17  of the channel  11  ( FIGS. 4 and 5 ). The C section  17  and the D section  18  together form a second pair  14  of sections  17 ,  18  of the channel  11 . The cooling fluid flows in the axial direction of the electrical machine  5  in the C section  17  and in the D section  18 . The A section  15 , the B section  16 , the C section  17  and the D section  18  constitute sections  12  of the channel  11  in which the cooling fluid flows exclusively in the axial direction. Furthermore, the cooling fluid flows in opposing directions in the C section  17  and the D section  18 , and therefore the cooling fluid flows from the axial end face  26  to the central plane  29  of the electrical machine  5 . The first pair  13  and the second pair  14  are fluidically separated from one another or sealed off from one another by means of a separating crosspiece  34 . The two component streams of cooling fluid flowing through the C section  16  and the D section  17  are combined with one another and thoroughly mixed in a connecting section  35  of the channel  11  and flow to a further first pair  13  comprising an A section  15  and a B section  16  of the channel  11 . After flowing through the connecting section  35 , the cooling fluid is again split into two component streams, into a further first pair  13  comprising the A section  15  and the B section  16 . This flow process is repeated until the cooling fluid has flowed from the inlet opening  36 , around the entire circumference of the housing  9 , to the outlet opening  37 . At the outlet opening  37 , the cooling fluid is again conducted out of the housing  9  and cooled by means of a heat exchanger (not illustrated) of the cooling circuit  10  and then introduced into the inlet opening  36  again. 
     The cooling fluid therefore flows through the channel  11  in the housing  9  both in the axial direction and in the radial direction of the electrical machine  5  in a meandering manner. As a result, particularly effective and uniform cooling of the electrical machine  5 , in particular of the housing  9 , is possible on account of this opposing flow pattern of the cooling fluid in the housing  9 . The greatest quantity of heat is produced in the region of the central plane  29  of the electrical machine  5 . Here, the heat is absorbed by the cooling fluid and enters the first pair  13  comprising the A section  15  and the B section  16  on the two axial end faces  26  of the electrical machine  5 . Significantly less heat is given off by the stator  6  at the two axial end faces  26  than in the region of the central plane  29 . As a result, the temperature of the housing  9  in the region of the axial end faces  26  is lower than in the region of the central plane  29 . The cooling fluid can therefore give off heat to the housing  9  in the region of the axial end face  26 , for example in the region of the curve sections  31  of the channel  11 . This enables uniform temperature distribution in the axial direction of the housing  9 , and therefore the housing  9  can also give off heat to the surrounding area in a uniform manner. The connecting sections  35  of the channel  11  have a small flow cross-sectional area, and therefore the cooling fluid flows through the connecting sections  35  in a turbulent manner. This advantageously firstly permits particularly effective heat absorption by the cooling fluid in the region of the central plane  29  of the electrical machine  5 , and secondly particularly effective through mixing of the component streams from the C section  17  and the D section  18  of the cooling fluid is possible as a result. 
     Overall, the drive device  1  and the electrical machine  5  according to the invention have significant associated advantages. The cooling fluid is conducted through the channel  11  in the radial and axial direction of the electrical machine  5  in a meandering manner, and therefore the housing  9  can be uniformly cooled.