Abstract:
The invention relates to an electric machine ( 5 ), in particular for a motor vehicle, comprising a housing ( 9 ), at least one shaft ( 8 ), a stator ( 6 ), a rotor ( 7 ), a cooling circuit for cooling the electric machine ( 5 ) using a liquid, in particular oil, wherein the liquid can be conveyed from at least one at least partially radially aligned channel ( 11 ) into at least one rotating part ( 12 ) of the electric machine ( 5 ) due to a rotational movement of the at least one channel ( 11 ), at least one outlet opening ( 13 ) for draining the liquid from the at least one channel ( 11 ), wherein the electric machine ( 5 ) is provided with at least one agent ( 14 ) for reducing the conveyed amount per unit time of liquid that can be conveyed from the at least one channel ( 11 ) due to the rotational movement of the at least one channel ( 11 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an electric machine and a drive unit. 
         [0002]    Drive units, preferentially hybrid drive units, in particular with a combustion engine and an electric machine are employed for example for driving motor vehicles. The electric machine acting as motor and generator in the motor vehicle comprises an axle or shaft with a stator or rotor arranged thereon. 
         [0003]    The stator and the rotor of the electric machine are cooled by a cooling circuit by means of oil for example. The shaft is generally in two parts and consists of a rotor shaft with an axial bore and an inner shaft. In the axial bore of the rotor shaft, the inner shaft is arranged, wherein between the inner shaft and the rotor shaft a gap that is circular in cross section forms. The oil for cooling is conducted through this gap. On the rotor shaft, a balancing disk is arranged. The rotor shaft and the balancing disk are provided with radial channels through which the oil for cooling is conducted outwardly from the gap in radial direction. Because of the rotational movement of the rotor shaft and the balancing disk the channel acts as a pump. The oil exits at the end of the channels from outlet openings and because of this cools the stator and the rotor of the electric machine. Furthermore, the oil is conducted from an oil sump as coolant circuit into the gap by an additional pump. This pump, which conveys the oil from the pump sump, additionally pumps the oil to other components of the drive unit, which have to be cooled and/or lubricated, for example a differential gear, a transmission and/or the combustion engine. 
         [0004]    Because of the rotary movement of the channels these have a pumping effect and consequently also deliver the oil. At relatively high rotational speeds of the rotor shaft and the balancing disk a great pumping action of the channels occurs. Because of this, there is the risk that for cooling and/or for lubricating the other components of the drive unit insufficient oil is available, because this is sucked in by the channels to an increased extent. Because of this, under certain conditions, these other components of the drive unit cannot be adequately cooled and/or lubricated. 
         [0005]    DE 10 2006 008 049 A1 shows a drive unit, having the following: an engine compartment in which a stator and a rotor are accommodated; a transmission compartment, which is provided adjoining the engine compartment in the direction of the rotary axis of the rotor and in which a transmission is accommodated, wherein the rotation of the rotor is transmitted to the transmission; a bearing for supporting the rotation, both of the rotor and of the transmission; and a wall, which is arranged between the engine compartment and the transmission compartment in order to support the bearing, wherein the wall is provided with an opening so that lubricating oil sprayed by the transmission can be sprayed onto an upper section of the stator. 
         [0006]    DE 102 38 023 B4 shows a combustion engine containing a generator or motor, whose stator comprises a core and coils attached to the core and this stator is located opposite permanent magnets, which are attached to a crankshaft of the combustion engine, wherein the combustion engine furthermore comprises a stator cooling means for cooling the stator with oil, wherein the permanent magnets are attached to the outer circumference of a crank web of the crankshaft and that the stator surrounds the crank web supporting the permanent magnets in the shape of an arc on the side facing away from the cylinder block. 
         [0007]    DE 199 28 247 B4 shows a motor, comprising a motor housing, a stator of cylindrical shape, which is fastened to the engine housing, an inner rotor, which is rotatably arranged within the stator, an outer rotor being rotatably arranged about the stator, wherein the inner rotor, the stator and the outer rotor are arranged concentrically and comprises a plurality of bolts for fastening the stator to the motor housing, wherein a cooling system is provided, 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 draining coolant from the cooling channels, wherein the coolant inlet opening and the coolant outlet opening are provided at an axial end of the inner rotor and are connected to the cooling channels, a coolant return flow section for connecting each cooling channel pair, wherein the coolant return flow section is provided in another axial end of the inner rotor, and wherein the cooling channels are formed from the stator and the plurality of the bolts. 
       SUMMARY OF THE INVENTION 
       [0008]    Electric machines according to the invention, particularly for a motor vehicle, comprising a housing, at least one shaft, a stator and a rotor, a cooling circuit for cooling the electric machine with a liquid, particularly oil, wherein the liquid can be conveyed from at least one channel aligned radially at least partially in at least one rotating part of the electric machine because of a rotational movement of the at least one channel, at least one outlet opening for draining the liquid from the at least one channel, wherein the electric machine is provided with at least one means for reducing the rate of delivery per unit time of liquid which can be conveyed by the at least one channel because of the rotational movement of the at least one channel. 
         [0009]    The at least one means reduces the rate of delivery per unit time of liquid, which is conveyed by the at least one channel. Because of this, an even cooling independently of the rotational speed of the rotating part is advantageously possible and furthermore can also be utilized upon an integration of the electric machine in a drive unit of the cooling circuit in order to evenly cool and/or lubricate other components of the drive unit. A high rotational speed of the rotating part thus does not result in relatively large quantities of oil being sucked in by the cooling circuit so that for cooling and/or for lubricating other components of the drive unit insufficient oil is available. 
         [0010]    Particularly, the at least one rotating part is the at least one shaft and/or a balancing disk. 
         [0011]    In a further configuration, the at least one shaft comprises a rotor shaft with an axial bore and an inner shaft, wherein the inner shaft is arranged in the axial bore of the rotor shaft. Preferentially, the rotor shafts and the inner shaft are positively interconnected, for example by means of a toothing, so that the rotor shafts and the inner shaft have the same rotational speed and torques can be transmitted between the rotor shaft and the inner shaft. 
         [0012]    In a complementary embodiment, between the inner shaft and the rotor shaft a gap that is circular in cross section is present for conducting the liquid. 
         [0013]    Preferentially, the cooling circuit is provided with a pump for the additional delivery of the liquid, preferentially from a pump sump. The pump, which does not constitute the at least one radially aligned channel, conveys the oil to the at least one channel and preferentially to other components to be cooled and/or to be lubricated, for example a differential gear and/or a transmission and/or the combustion engine. 
         [0014]    In a version, the at least one means comprises at least one air intake opening, wherein the at least one air intake opening is connected in a fluidically conductive manner to the at least one channel for reducing the rate of delivery per unit time of liquid. 
         [0015]    Practically, the at least one air intake opening is designed radially within the at least one outlet opening and/or the at least one air intake opening is designed in the rotating part. The at least one air intake opening thus has a smaller spacing from an axis of the shaft than the at least one outlet opening. Through the at least one air intake opening, which can be connected to the atmospheric pressure of the surroundings, air can be introduced into the at least one channel so that, because of this, the vacuum that can be made available by the at least one channel is reduced at an inlet opening of the at least one channel and the rate of delivery per unit time of liquid, that can be conveyed by the at least one channel because of the rotational movement of the at least one channel, is thus reduced. 
         [0016]    In a further embodiment, the at least one means is designed such that the reduction of the rate of delivery per unit time of liquid takes place because of the rotational movement of the at least one channel as a function of the rotational speed of the rotating part, particularly of the at least one shaft, particularly in that a flow cross-sectional area of the at least one channel is variable. Particularly, the reduction of the rate of delivery per unit time of liquid is indirectly proportional to the rotational speed of the rotating part, i.e. the higher the rotational speed of the rotating part, the greater the reduction of the rate of delivery per unit time of liquid because of the rotational movement of the at least one channel. The reduction is caused by the at least one means. The reduction is the differential from the rate of delivery per unit time of liquid in the electric machine with and without the at least one means. 
         [0017]    In particular, the at least one means comprises at least one radial throttling element that can be at least partially moved in radial direction, wherein the at least one radial throttling element can be moved into the at least one channel by means of a centrifugal force, so that the greater the centrifugal force, the smaller the flow cross-sectional area of the at least one channel becomes. 
         [0018]    In a further configuration, the at least one means comprises at least one elastic element, e.g. a spring, in order to move the at least one radial throttling element in the event of a diminishing centrifugal force so that in the event of a diminishing centrifugal force the flow cross-sectional area of the at least one channel is enlarged. 
         [0019]    In a complementary version, the at least one radial throttling element and/or the at least one elastic element are arranged in the rotating part, e.g. the balancing disk. 
         [0020]    In a further version, the at least one means comprises at least one tangential throttling element at least partially moveable in tangential direction, wherein the tangential throttling element can be moved into the at least one channel by means of an inertial force or tangential force, so that the greater the rotational speed of the at least one tangential throttling element, the smaller the flow cross-sectional area of the at least one channel becomes and vice versa. 
         [0021]    In a further configuration, the at least one means comprises at least one elastic element, e.g. a spring, in order to move the at least one tangential throttling element out of the at least one channel in the event of a diminishing inertial force or tangentially, so that the flow cross-sectional area of the at least one channel is enlarged. 
         [0022]    In particular, the at least one tangential throttling element and/or the at least one elastic element is arranged in the rotating part, for example the balancing disk. 
         [0023]    A drive unit according to the invention, preferentially hybrid drive unit, particularly for a motor vehicle, preferentially comprises a combustion engine, particularly for driving the motor vehicle, preferentially at least one housing, at least one electric machine with a stator and a rotor preferentially arranged in the at least one housing, wherein the at least one electric machine is designed in accordance with an electric machine described in this patent application. 
         [0024]    In a further configuration, the at least one housing is of multiple parts. 
         [0025]    In an additional configuration, the housing is of one part. 
         [0026]    In a further configuration, the at least one electric machine acts as motor and/or as generator. 
         [0027]    A motor vehicle according to the invention comprises at least one electric machine described in this application and/or at least one drive unit described in this application. 
         [0028]    In a further configuration, the motor vehicle comprises rechargeable batteries. The batteries supply the electric machine with electric current and upon deceleration of the motor vehicle the batteries can be charged by means of the electric machine by the electric current generated by the electric machine. In addition, the batteries can also be charged during a stoppage of the vehicle, for example from a public power network. In particular, the batteries are designed as lithium ion batteries. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Two exemplary embodiments of the invention are described in more detail in the following making reference to the enclosed drawings. It shows: 
           [0030]      FIG. 1  a highly schematic representation of a hybrid drive unit, 
           [0031]      FIG. 2  a longitudinal section of an electric machine in a first embodiment, 
           [0032]      FIG. 3  a perspective view of a balancing disk of the electric machine according to  FIG. 2 , 
           [0033]      FIG. 4  a longitudinal section of the electric machine in a second embodiment, 
           [0034]      FIG. 5  an exploded representation of the electric machine in a third embodiment, 
           [0035]      FIG. 6  a longitudinal section of the electric machine according to  FIG. 5  and 
           [0036]      FIG. 7  a view of a motor vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      FIG. 1  shows a drive unit  1  for a motor vehicle  3  designed as a hybrid drive unit  2 . The hybrid drive unit  2  for a motor vehicle  3  comprises a combustion engine  4  and an electric machine  5 , which acts as motor  32  and generator  33 , in each case for driving or decelerating the motor vehicle  3 . The combustion engine  4  and the electric machine  5  are interconnected by means of a driveshaft  20 . The mechanical coupling between the combustion engine  4  and the electric machine  5  can be established and cancelled by means of a clutch  19 . Furthermore, an elasticity  21  is arranged in the driveshaft  20 , which couples the combustion engine  4  and the electric machine  5  together. The electric machine  5  is mechanically coupled to a differential gear  23 . In the driveshaft  20 , which interconnects the electric machine  5  and the differential gear  23 , a converter  22  and a transmission  28  are arranged. By means of the differential gear  23 , the drive wheels  25  are driven via the wheel axles  24 . 
         [0038]    Instead of the arrangement of the combustion engine  4  and the electric machine for the motor vehicle  3  shown in the arrangement in  FIG. 1 , other possibilities are also conceivable (not shown). For example, the electric machine  5  can be arranged laterally on the combustion engine  4  and mechanically connected to the combustion engine  4  by means of a belt or a chain or of gear wheels instead of the driveshaft  20  (not shown) depicted in  FIG. 1 . In addition, the electric machine  5  could be arranged on a transmission, e.g. a differential gear, or the electric machine  5  can act as wheel hub motor and/or as wheel hub generator, i.e. be arranged in the region of a wheel hub (not shown). 
         [0039]      FIG. 2  shows the electric machine  5  for the hybrid drive unit  2  as internal pole machine in a first embodiment with a fixed stator  6  and a rotating rotor  7  of the hybrid drive unit  1  in a highly simplified representation, so that for example electrical lines, the windings of the stator  6  and of the rotor  7 , and fixing means for the stator  6  are not shown or only shown highly simplified form. A shaft  8  consists of metal, e.g. steel, on which the rotor  7  is concentrically arranged, wherein the shaft  8  and the rotor  7  are mounted on a fixed housing  9  by means of a bearing  39 . The stator  6  is arranged on the housing  9 , concentrically around the rotor  7 , and is attached thereto by means of fixing means (not shown). The stator  6  can also be fastened to the housing  9  without additional fixing means, e.g. by means of a press connection and/or shrink connection. The shaft  8 , in this case, is connected to the driveshaft  20  of the hybrid drive unit  2  within the hybrid drive unit  2  or constitutes a part of the driveshaft  20 . 
         [0040]      FIG. 2  shows the electric machine  5  only above an axis  37  of the shaft  8 . The shaft  8  of the electric machine  5  consists of an inner shaft  17  and a rotor shaft  16 . The rotor shaft  16  is provided with an axial bore  18 , in which the inner shaft  17  is arranged. Between the inner shaft  17  and the rotor shaft  16  a gap  26  that is circular in cross section is created because of the geometry of the axial bore  18  and of the diameter of the inner shaft  17 . The rotor shaft  16  and the inner shaft  17  are rotating parts  12  of the electric machine  5 , which rotate about the axis  37  of the shaft  8  or of the rotor shaft  16  and the inner shaft  17 . The rotor shaft  16  is provided with radial channels  11  (in  FIG. 2 , only one channel  11  is shown). On the rotor shaft  16 , a balancing disk  15  is additionally arranged. The balancing disk  15  has the objective of preventing unbalances on the rotor  7  and additionally delivering and distributing oil for the cooling. The balancing disk  15  ( FIGS. 2 and 3 ) likewise comprises radially aligned channels  11 , which at the radially viewed inner end has inlet openings  38  and outlet openings  13  at the radially viewed outer end. 
         [0041]    From a cooling circuit  10  with a pump  27  and a pump sump  29  which is not shown in  FIGS. 2 and 3  a liquid, particularly oil, is conducted into the gap  26  for cooling the stator  6  and the rotor  7 . The oil in this case flows out of the gap  26  through the channels  11  worked into the rotor shaft  16  and subsequently through the channels  11  worked into the balancing disk  15 . The oil thus flows out of the channels  11  of the rotor shaft  16  through the inlet openings  38  into the channels  11  of the balancing disk  15  and exits again at the outlet openings  13  of the balancing disk  15  and is sprayed onto the stator  6  and onto the rotor  7  for cooling the stator  6  and the rotor  7 . Following this, the sprayed-out oil again collects in the collection region which is not shown and is additionally conducted in the pump sump  29  not shown in  FIG. 2 . The rotor shaft  16  and the balancing disk  15  as rotating parts  12  with the channels  11  also co-rotating have a suction effect because of the centrifugal forces that are active in the channels  11  so that these centrifugal forces can generate a vacuum in the cooling circuit  10 . 
         [0042]    The balancing disk  15  comprises a ring-shaped air intake opening  30 , so that at the transition of the oil flowing through the channels  11  from the rotor shaft  16  to the balancing disk  15  a reduction of the vacuum in the channels  11  occurs, because the air intake opening  30  is connected to the atmospheric pressure and because of this air can flow into the channels  11  in the region between the balancing disk  15  and the rotor shaft  16 . Because of this, the suction effect of the channels  11  in the balancing disk  15  can be substantially reduced, so that even at very high rotational speeds of the rotating parts  12  of the electric machine  5  only a small vacuum is generated by the channels  11 . Because of this, an intensive vacuum can be avoided within the cooling circuit  10  that is not shown. Furthermore, at high rotational speeds of the rotating parts  12  quantities of oil which are not too large are sucked out of the cooling circuit  10  by the channels  11  so that upon an integration of the electric machine  5  into the drive unit  1  even additional components of the drive unit  1 , which are to be cooled and/or lubricated by the oil, have sufficient oil for cooling at their disposal. Here, the oil continues to be conducted to the desired surfaces, i.e. the end face of the rotor  7  and the winding heads of the stator  6 , which are to be cooled by the oil, because the outlet openings  13  are unchanged. Thus, the air intake opening  13  is a means  14  for reducing the rate of delivery per unit time of oil. Because of the integration of the air intake opening  13  into the balancing disk  15 , advantageously no additional installation space for the means  14  for reducing the rate of delivery of oil is required. 
         [0043]    In  FIG. 4 , a second exemplary embodiment of the electric machine  5  is shown. The electric machine  5 , similar to the first exemplary embodiment according to  FIGS. 2 and 3 , comprises a shaft  8  consisting of the inner shaft  17  and the rotor shaft  16 , wherein between the inner shaft  17  and the rotor shaft  16  the gap  26  for passing through oil as cooling liquid is provided. The oil is conducted into the gap  26  by means of the pump  27  from the pump sump  29  through oil lines  41  in the gap  26 . From a collecting region that is not shown the oil is again conducted back to the pump sump  29  by means of collecting lines which are not shown, so that the cooling circuit  10  is designed for the cooling by means of oil.  FIG. 4  does not depict the stator  6 , the rotor  7  and the housing  9  of the electric machine  5 . Tangential recesses  40  are worked into the rotor shaft  16  on the inside in the region of the axial bore  18 . In the tangential recesses  40  are located tangential throttling elements  36 . The tangential throttling elements  36  are guided in the tangential recess  40  by means of guidance devices (not shown), e.g. a plain bearing by means of a tongue and groove connection (not shown) of the tangential throttling elements  36 , and can thus be moved in tangential direction in the tangential recesses  40 . Radial channels  11 , which are represented by interrupted lines in  FIG. 4 , are worked into the rotor shaft  16  and in the balancing disk  15  arranged above said rotor shaft. Thus, the oil flows through the gap  26  and through the channels  11  and exits the outlet openings  13  on the balancing disk  15  for the cooling of the stator  6  and of the rotor  7  which are not shown in the Figure. Upon an increase of the rotational speed of the rotating parts  12  with the worked-in channels  11 , i.e. of the rotor shaft  16  and the balancing disk  15 , an inertial force or mass inertial force or a tangential force occurs, which acts on the tangential throttling element  36 . Because of this, the tangential throttling elements  36  move in tangential direction in the tangential recesses  40 . The tangential throttling elements  36  in this case are arranged relative to the channels  11  so that upon an increase of the rotational speed the flow cross-sectional area of the channels  11  is reduced. Because of the reduction of the flow cross-sectional area of the channels  11  the quantity of oil conveyed from the channels  11  per unit time is reduced. 
         [0044]    Upon a reduction of the rotational speed of the rotating parts  12  the tangential throttling elements  36  again move back in the opposite direction, so that because of this the flow cross-sectional area of the channels  11  is enlarged and because of this the reduction of the rate of delivery per unit time of oil is reduced because of the reduction of the flow cross-sectional area of the channels by means of the tangential throttling elements  36 . The return movement of the tangential throttling elements  36  upon a falling rotational speed is preferentially supported by an elastic element  34 , e.g. a spring  35 , which is not shown in  FIG. 4 , in order to ensure a return movement. 
         [0045]    The third exemplary embodiment of the electric machine  5  is shown in  FIGS. 5 and 6 . The stator  6 , the housing  9  and the cooling circuit  10  of the electric machine  5  are not shown in  FIGS. 5 and 6 . Radial recesses as channels  11  are worked into the balancing disk  15  ( FIG. 5 ). Because of this, the channels  11  ( FIG. 6 ) develop or form between the rotor  7  and the balancing disk  15 . The electric machine  5  has two crescent-shaped radial throttling elements  31 . On a socket  42  of the crescent-shaped radial throttling elements  31  the elastic element  34  designed as spring  35  is arranged in each case ( FIG. 5 ). The elastic element  34  or the spring  35  are not shown in  FIG. 6 . The socket  42  with the spring  35  are arranged in a recess  43  of the balancing disk  15  (not shown).  FIG. 6  shows the position of the radial throttling element  31  at a very low rotational speed. The oil conveyed by the pump  27  which is not shown in  FIG. 6  of the cooling circuit  10  flows through the gap  26 , the channels  11  in the rotor shaft  16  and the channels  11  in the balancing disk  15  to the outlet openings  13  and sprays onto the stator  6  (not shown) to be cooled and the rotor  7  (not shown in  FIGS. 5 and 6 ) to be cooled. The oil thus flows about the radial throttling element  31  as shown in  FIG. 6 . Upon an increase of the rotational speed of the rotating parts  12  of the electric machine  5  the radial throttling element  31  radially moves outwardly (not shown) because of the higher centrifugal force, which acts on the radial throttling element  31 . Because of this, the flow cross-sectional area of the channel  11  in the balancing disk  15  is reduced in the region of the radial throttling element  31 , so that because of this the rate of delivery of oil per unit time is reduced. The centrifugal force acting on the radial throttling element  31  is counteracted by the spring force of the spring  35 . The higher the rotational speed of the rotating parts  12 , the further from an axis  37  of the shaft  8  not depicted in  FIG. 6  is the radial throttling element  31  and the smaller is the flow cross-sectional area of the channels  11  in the region of the radial throttling elements  31 . Upon a reduction of the rotational speed of the rotating parts  12  the centrifugal force acting on the radial throttling element  31  is reduced so that because of this the radial throttling element  31  radially moves in the direction of the axis  37  because of the spring force of the spring  35 , so that because of this the flow cross-sectional area of the channel  11  is again enlarged in the region of the balancing disk  15 . The greater the rotational speed of the rotating parts  12 , the smaller the flow cross-sectional area of the at least one channel  11  in the region of the balancing disk  15  and vice versa. Because of this, it is advantageously avoided at a high rotational speed of the rotating parts  12  that because of the suction effect of the channels  11  a vacuum is generated in the cooling circuit  10  and because of this leaks can develop. The radial throttling element  31  as means  14  for reducing the rate of delivery of oil per unit time can also be designed such that from a determined rotational speed of the rotating parts  12  no oil flows through the channels  11  any longer, i.e. that the flow cross-sectional area of the channels  11  is zero or substantially equal to zero. 
         [0046]    The details of the different exemplary embodiments can be combined with one another provided nothing to the contrary is mentioned. 
         [0047]    Considered on the whole, substantial advantages are connected with the drive unit  1  according to the invention. The quantity of oil for cooling conveyed by the channels  11  because of the rotational movement of the channels  11  is reduced or limited by means  14 , so that for other components  4 ,  23 ,  28  to be cooled and/or to be lubricated of the drive unit  1 , e.g. the transmission  28  and/or the differential gear  23  and/or the combustion engine  4  sufficient oil for cooling and/or for lubricating remains which is conveyed by the pump  27  to these components  4 ,  23 ,  28 .