Electric machine

An electric machine having a stator and a rotor, the rotor having a rotor body and magnets distributed around the outer radial circumference and the stator having a stator body and windings distributed around the inner radial circumference. The stator body has ribs protruding radially outward and heat pipes running from the radially inner windings. The heat pipes extend radially outward into the ribs.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. national stage application pursuant to 35 U.S.C. § 371 of International Application No. PCT/DE2014/200267, filed Jun. 18, 2014, which application claims priority from German Patent Application No. DE 10 2013 213 661.7, filed Jul. 12, 2013, which applications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

Disclosed herein is an electric machine having a rotor and a stator, in particular, for the drivetrain of motor vehicles.

BACKGROUND

Electric machines having a rotor and a stator according to the prior art serve to drive aggregate units or vehicles. In such cases, the stator is situated in an enclosing jacket, which also serves to hold and stabilize the stator. Dissipation heat develops, due in part to induced electric circular currents in the electrically conductive elements of the electric machine. This causes the rotor and stator of the electric machine to heat up, which results in a reduction of the performance of the electric machine. However, the aforementioned jacket has the disadvantage here that the dissipation of heat from the stator is impeded by the jacket.

Cooling systems for electric machines have therefore been developed, such as for example a liquid cooling system in which a liquid coolant flows through a cooling jacket and thereby cools the rotor and the stator. The delivery of liquid to the rotor normally takes place through the axle of the rotor, while the delivery of liquid to the stator normally takes place through a pipe or hose line fed in axially or radially. The liquid coolant is thereby conveyed through the stator and through the rotor, where it is warmed, and is then cooled down again outside the electric machine by means of a cooling radiator cooled, for example, by air. The liquid cooling system thus requires significant construction effort and expense, and not inconsiderable operating costs for the liquid cooling system.

Air cooling systems have also become known in which cooling ribs are provided on the outer jacket so as to enlarge the surface, enabling cooling air to be conveyed along the jacket in order to cool the jacket by the cooling air. The jacket represents a significant heat resistance in this case; however, such that the temperature of the electric machine still leaves something to be desired.

An electric machine has become known through EP 1 432 102 A2 in which so-called heat pipes are used to carry heat away from the gap between rotor and stator and to a cooling radiator. This configuration requires substantial construction space.

SUMMARY

Disclosed herein is an electric machine having a stator and a rotor, the rotor having a rotor body and magnets distributed around the outer radial circumference and the stator having a stator body and windings distributed around the inner radial circumference. The stator body has ribs protruding radially outward. Along with the cooling surface of the stator body, these ribs make an additional “flat” surface available which is effective for cooling.

In an exemplary embodiment, the stator has heat pipes emerging from the windings which are radially to the inside and which extend radially outward into the ribs. This enables air cooling, which is improved by the fact that heat pipes are used for the internal transporting of heat to the ribs.

Advantageously, in an exemplary embodiment, the windings extend in the axial direction of the stator, and at least individual heat pipes are at least partially surrounded by a winding. The result of this is that the heat can be removed directly from the windings.

In an exemplary embodiment, the stator body is made up of a plurality of plates, which are arranged in a stack when regarded in the axial direction of the stator, the plates having cutouts to accommodate the windings. This makes it possible to achieve a stator body that can be constructed simply and yet has good electrical properties with regard to avoiding current leakage.

Advantageously, in an exemplary embodiment, the plates have cutouts to receive a partial section of the heat pipes. This enables a heat pipe to be accommodated partly by a winding and partly by a heat pipe, achieving an improved removal of heat directly from the winding.

Advantageously, in an exemplary embodiment, the plates are made from different types of sheet metal. For example, the plates are made from at least two different types of sheet metal, where the larger plates, i.e., the plates having a greater diameter, form the ribs. In an exemplary, the plates are made from at least two different materials, so that plates of a more heat-conductive material may be provided between the plates of a less heat-conductive material. For example, only a small part, i.e., only every third or only every 10th plate is made of a more heat-conductive material. In this case, in an exemplary embodiment, the plates having the better heat conductivity are all spaced at essentially the same intervals. For example, material for the more heat-conductive plates may also be used here which has a lower magnetic conductivity, i.e., which worsens the magnetic flux and therefore reduces the efficiency of the electric machine.

In an exemplary embodiment, in the outer areas, i.e., outside of the stator surface formed by the rib-free area, the ribs also have a form or configuration that further enlarges the surface of the ribs. This means, for example, that the ribs are modified in at least one of the following ways: with jagged edges, with notching, provided with holes, incised and pulled apart like expanded metal, or generally made non-round. These methods enlarge the surface and/or enable an improved flow through the ribs, any of which beneficially supports convection.

In an exemplary embodiment, the ribs have additional functional features, which serve to facilitate assembly, for example, involving assembly or orientation features. In an exemplary embodiment, the ribs are attaching holes or hooks or empty spaces, or a plurality of various ones of these features together. Each of these additional features increases the usefulness of the ribs as such. The functionality of the ribs is also increased by the described heat pipes, in that they set up a thermal cooling path to the ribs which begins already in the interior of the winding, instead of only at the surface of the copper winding.

In an exemplary embodiment, the stator body is made up of plates that have cutouts for the heat pipes and those that do not have cutouts for the heat pipes. This makes it possible to achieve the spaced arrangement of heat pipes in a modular design.

Advantageously, in an exemplary embodiment, the ribs run in the axial direction, and are formed of plates which receive the heat pipes in the area of the ribs.

The axial direction is defined in reference to the rotor and the stator, the axis in terms of the axial direction being the axis of rotation of the rotor.

Advantageously, in an exemplary embodiment, the ribs run in the circumferential direction, and are formed of plates which also receive the heat pipes in the area of the ribs. Depending on the configuration of the electric machine and of the air flow, this can make it possible to achieve good cooling.

Advantageously, in an exemplary embodiment, the plates have the cutouts for the windings distributed at their inner circumference, extending radially outward. This enables easy installation from radially inside, and the gap between the windings and the magnets of the rotor can be reduced.

Advantageously, in an exemplary embodiment, the plates have cutouts for the heat pipes which extend radially outward starting from the cutouts for the windings. The result of this is that starting from the windings the heat pipes can be routed radially outward to the ribs, so as to achieve good air cooling.

Advantageously, in an example embodiment, the plates have projections extending radially outward which form the ribs.

DETAILED DESCRIPTION

FIG. 1is a perspective cross-sectional view of an exemplary embodiment of electric machine1with ribs. Machine1includes rotor2and stator3. Stator3is positioned radially outside of rotor2, with rotor2being able to rotate radially inside stator3.

Rotor2includes rotor body4, which has magnets6on radially outer circumference5, which are distributed around circumference5. Gap7is provided between rotor2and stator3, so that rotor2is able to rotate freely radially inside stator3.

Stator3includes stator body8, which extends in a ring shape around rotor2. Stator body8has receptacles9to receive windings10. Windings10extend in the axial direction of stator body8, there being a plurality of windings10distributed around stator body8. In an exemplary embodiment, windings10extend in the axial direction. Radially on the outside, stator body8has ribs11projecting radially outward, and extending in the axial direction.

Starting from winding10, heat pipes12are provided, which extend outward in the radial direction, and which along part of extension13are situated in winding10and along another part of their extension14extend inside stator body8in the area of ribs11. To this end, recesses and cutouts15are provided within winding10and stator body8or rib11, which receive heat pipes13.

In an exemplary embodiment, heat pipes13in the radially internal region can also be joined in the area of winding10by means of connecting element16, so that connecting element16, which is connected to a plurality of heat pipes, is located in winding10.

Ribs11, which extend in the axial direction, are distributed protruding radially outward beyond the circumference of stator body8. In an exemplary embodiment, ribs11have an essentially trapezoidal cross-sectional area. According to other exemplary embodiments, the cross-sectional area of rib11are, essentially rectangular or triangular or the like.

FIG. 2is a front view of an exemplary embodiment of a plate for the stator body shown inFIG. 1.

FIG. 3is a front view of an exemplary embodiment of a plate for the stator body shown inFIG. 1.FIG. 2andFIG. 3show plates20,21respectively, which form stator body8according toFIG. 1through a side-by-side arrangement in the axial direction. Plate20is ring-shaped, and has cutouts22on its radially inner circumference, which serve to receive windings10. Advantageously, in an exemplary embodiment, cutouts22are rectangular, but other shapes of cutout are also possible. Advantageously, cutouts22are open radially toward the inside.

On its radially outer circumference, plate20has projections23which form ribs11. The projections are distributed around the circumference. Fastening holes24are provided for attachment and assembly.

In the arrangement according toFIG. 1, plate20is inserted between heat pipes12, in order to form a corresponding part of stator body8between heat pipes12.

Plate21, according toFIG. 3, has cutouts25on its radially inner circumference, which serve to receive windings10. Starting from cutouts25, cutouts26extending radially outward are provided cutouts26receive heat pipes12. On the radially outer circumference, plate21has projections27which form ribs11. Cutouts26advance clear into projections27, so that heat pipes12located in cutout26extend clear into ribs11.

In the arrangement according toFIG. 1, plate21is used in the area of heat pipes12, in order to form the corresponding part of stator body8.

FIG. 4is a perspective view of an example configuration of the connecting element shown inFIG. 1with heating pipes.FIG. 4shows a configuration of connecting element16having an arrangement of heat pipe12elements. In this case, heat pipes12are embedded in connecting element16for part of their radial extension, and for another part of their radial extension, protrude beyond connecting element16. Connecting element16also serves as a collector for good thermal coupling of heat pipe12elements to corresponding winding10. The collector is designed with good thermal conductivity and at the same time with good electrical insulation, while the collector has high mechanical stability under thermal inflow. The materials of connecting element16are preferably made of ceramic or polymer.

Heat pipes12, which are tube-shaped, are embedded in connecting element16designed as a collector, are preferably received or injected into bore holes; heat pipes12have an internal circuit of evaporating and re-condensing coolant.

FIG. 5is a perspective cross-sectional view of an exemplary embodiment of electric machine51with ribs. Electric machine51includes rotor52and stator53. Rotor52includes rotor body54, with magnets56distributed around circumference55. Rotor52is again able to turn radially within stator53, with stator body58extending in a ring shape around rotor52and gap57being provided between rotor52and stator53.

Stator body58has receptacles59to receive windings60of the stator; receptacles59are arranged openly in the radially inner edge zone of stator body58. In the radially outer edge zone of stator body58, ribs61are provided which extend in the circumferential direction, with individual ribs61being spaced apart from each other. Situated in windings60and in ribs61are heat pipes62, which are positioned within windings60for a part of their extension63and within ribs61for another part of their extension64. In an exemplary embodiment, heat pipes62have their radially inner edge zone embedded in connecting element66.

FIG. 6is a front view of an exemplary embodiment of a plate for the stator body shown inFIG. 5.

FIG. 7is a front view of an exemplary embodiment of a plate for the stator body shown inFIG. 5.

FIG. 8is a front view of an exemplary embodiment of a plate for the stator body shown inFIG. 5.FIGS. 6 through 8show plates70through72, which are used to form stator body58.

Plate70serves to receive windings60and heat pipes62. Plate70has, on its radially inner circumference, cutouts73to receive windings60. Radially outside of cutouts73, adjoining cutouts74are provided to receive heat pipes62. Bore holes75are provided to connect the plates70.

Plate71has only cutout73to receive windings60, cutout73extending radially outward from the radially inner edge zone. Bore holes75for attaching are also provided.

The radial height or extension of plate71corresponds to the radial height of plate70, so that ribs61are formed by plates70and71, plate70being the plate which receives a heat pipe element and plate71being an adjacent element to cover heat pipe elements72laterally.

Plate72is similar in design to plate71, having cutouts73situated radially on the inside, with plate72having a lesser radial extension than plates70and71, so that plate72is used in the exemplary embodiment ofFIG. 5to space ribs61apart from each other. Plates72form stator body58in the region between ribs61.

LIST OF REFERENCE NUMBERS