Electric machine

Abstract

Electrical machine (10, 10.4, 10.6) - with a cylindrical stator (12), - with a first winding head (14) and a second winding head (16) arranged at the two axial ends of the stator (12), - with a housing (36, 36.4) for the stator (12), - characterized in that - the first winding head (14) and / or the second winding head (16) are at least partially covered by an annular cooling disc (20, 20.6, 22, 22.6), - an electrically insulating heat-conducting element (30) is arranged between the winding head (14, 16) and the cooling disk (20, 20.6, 22, 22.6).

Description

TECHNICAL FIELDThe invention relates to an electric machine having a stator and at least one winding head. Such electric machines can be used in particular as electric motors.PRIOR ARTThe power density and the efficiency and service life of electric machines are critically dependent on the temperature of the components of the electric machine. For cooling the components and for removing the resulting current heat losses, an actively coolable housing is frequently used, as is known, for example, from DE 10 2004 013 133 A1. For cooling and for heat removal, a fluid is generally used, which can be, in particular, air, oil or a water-glycol mixture. The soft magnetic parts of the electric machine are generally directly connected to the heat-dissipating fluid via the metallic housing, so that a high heat dissipation can be achieved in this region of the electric machine. As a rule, a housing enclosing the stator is used, around which the cooling fluid flows. For this purpose, the housing usually has helical notches through which the fluid is conducted. In this case, the fluid absorbs the thermal energy which occurs and removes the latter.The region of the winding head is generally not cooled in this case. Although the exposed winding head can be slightly cooled by the ambient air, an air cushion is formed which has only a low thermal conductivity. Heat dissipation to the actual cooling fluid is thus not provided.In the case of direct oil cooling of the winding head, the fluid is guided around the winding head. In this case, the thermal energy of the winding head can be emitted directly to the fluid. However, oil has a lower heat capacity compared to a water-glycol mixture, so that only a lower heat dissipation can take place.Due to the poorer cooling possibilities for the winding head, the highest temperature is formed there. For this reason, the temperature sensor, which can cause the electric machine to be shut down, is also arranged in the region of the winding head. The temperature of the winding head thus represents a shutdown criterion for the maximum temperature of the winding. In addition, the winding head temperature limits the continuous power of the electric machine.SUMMARY OF THE INVENTIONProceeding from this prior art, the object of the invention is to specify an improved electric machine in which cooling of the winding head as efficiently as possible is possible.The electric machine according to the invention is provided by the features of the main claim 1. Meaningful further developments of the invention are the subject matter of further claims that follow this claim.The electric machine according to the invention has a cylindrical stator with a first and a second winding head, which are arranged at the two axial ends of the stator. The stator is positioned in a housing. According to the invention, an annular cooling disk is present, by means of which the first winding head and / or the second winding head are at least partially covered. Between the winding head and the cooling disc, an electrically insulating heat conducting element with good thermal conductivity is arranged.By positioning a cooling disk in direct connection to the winding head, effective heat dissipation can take place in the region of the winding head, so that the temperature of the winding head can be significantly reduced. The annular cooling disk can have different outer contours. The cooling disk therefore does not have to have a circular outer contour; any desired polygonal outer contours are also possible in principle.Between the winding head and the cooling disc, a heat-conducting element is present which is electrically insulating and heat-conducting. In order to optimize the thermal conductivity of the entire heat path coming from the winding head, the heat-conducting element should be designed with the smallest possible material thickness. The heat-conducting element is therefore preferably made of a material that adapts to the shape of the winding head. This material can be, for example, potting compound, heat-conducting paste or a film such as, in particular, a heat-conducting pad.The annular cooling disc should consist of a heat-conducting material or at least contain such a heat-conducting material. As a result, the heat arising in the region of the winding head can be effectively dissipated to the cooling disk via the heat-conducting element. Preferably, the cooling disc can consist of aluminum or copper.The cooling disk can preferably be in direct contact with the housing. In this way, the cooling disk can serve as a heat bridge between the winding head and the actively or passively cooled housing. In this case, active cooling of the cooling disk does not necessarily have to take place. Rather, the cooling of the housing in combination with the heat bridge by the cooling disk may be sufficient to reduce the temperature of the winding head.In order to enable particularly effective cooling of the winding head, at least one cooling channel can be present in the annular cooling disc, through which a liquid or gaseous cooling medium can be conducted. This allows active dissipation of the generated heat in the region of the winding head, so that the temperature of the winding head can be effectively reduced depending on the cooling fluid used. The cooling fluid can be freely selected in this case, since no direct contact of the cooling fluid with the winding head takes place. The at least one cooling channel can preferably be arranged on the radial outer side of the cooling disk.In a particularly preferred embodiment, the at least one cooling channel of the cooling disk can be connected to at least one cooling channel of the housing. As a result, only one cooling fluid connection is required, so that a compact design is still possible.At least one aperture can be present in the cooling disc, through which the connecting cables of the winding head can be passed.Preferably, the side of the cooling disk directed toward the winding head can have at least one annular curved wall. The cantilever wall does not have to have a circular contour; any desired polygonal contours of the cantilever wall are also possible. The at least one cantilever wall can bear laterally on the winding head, so that the winding head is surrounded as completely as possible by the cooling disk. As a result, a particularly effective heat transfer from the winding head to the cooling disk is achieved.Preferably, the at least one annular cantilevered wall can be arranged on the radial outer wall of the cooling disk. This facilitates the heat transfer from the cooling disk to the housing, since the curved wall of the cooling disk can be in contact with the inner wall of the housing. At the same time, the stator is generally cast somewhat more strongly on its outer side, so that there is a wider air gap to the housing here, which can be bridged by the cooling disk in this way. Each electric machine has a stator back due to the magnetic flux, which increases the heat conducting path between the winding head and the cooling system. At the same time, the cooling disk can be axially abutted against the stator.The electric machine according to the invention makes it possible to achieve a significant temperature reduction with the same power, while maintaining the same overall size. As a result, the efficiency can be increased due to the temperature dependence of the resistance of the winding. Alternatively, a clearly improved performance could be achieved with the temperature of the winding head remaining the same. Alternatively, the overall size of existing electric machines could also be reduced with constant power. This leads to a weight reduction and to a reduction in the material consumption. In particular, the reduction of the material consumption can be economically and environmentally advantageous with regard to the consumption of rare earths and of copper for the windings.Further advantages and features of the invention can be taken from the features further specified in the claims and from the exemplary embodiments below.BRIEF DESCRIPTION OF THE DRAWINGSThe invention is described and explained in more detail below with reference to the exemplary embodiments shown in the drawing. The following are shown: FIG. 1 shows a perspective illustration of a first embodiment of the electric machine according to the invention without a housing, FIG. 2 shows a plan view of the electric machine according to FIG. 1 with housing, FIG. 3 is a longitudinal section along the line H--H in FIG. 2, FIG. 4 shows a plan view of a second embodiment of the electric machine, FIG. 5 is a longitudinal section along the line G--G in FIG. 4, FIG. 6 shows a longitudinal section according to FIG. 5 through a third embodiment of the electric machine.WAYS OF CARRYING OUT THE INVENTIONA first embodiment of the electric machine 10 according to the invention is schematically illustrated in FIGS. 1 to 3. The electric machine 10 has a cylindrical stator 12, in which the individual windings are cast in a suitable casting compound. At the two axial ends of the stator 12, there is a first winding head 14 or a second winding head 16 respectively.In the present example, the two winding heads 14, 16 are each covered by an annular cooling disk 20, 22. The outer contour of the cooling disk 20, 22 corresponds substantially to the outer contour of the stator 12 in this case. a total of three apertures 24 are present in the cooling disk 20 in the present example case. By means of these apertures 24, connecting cables 26 of the stator 12 can be led through the cooling disk 20. In addition, in the present example, a plurality of recesses 28 are arranged in the outer wall of the cooling disk 20. Further connecting cables could also be led through these recesses 28 through the cooling disc 20. In contrast, no apertures 24 or recesses 28 are present in the second cooling disc 22. In contrast to the embodiment shown in the drawing, the two cooling disks 20, 22 could also be formed identically to one another.A heat conducting element 30 is provided between the two cooling disks 20, 22 and the end windings 14, 16. The heat-conducting element 30 is designed to be electrically insulating and heat-conducting.In the present example, the two cooling disks 20, 22 each have an annular curved wall 32 on the side directed toward the end windings 14, 16, which curved wall is arranged on the radial outer side of the cooling disks 20, 22. The cantilever walls 32 thus also bear against the outer side of the winding heads 14, 16, so that optimum heat transfer to the cooling disks 20, 22 is achieved.The outer walls 34 of the two cooling disks 20, 22 bear against the inner wall of a housing 36. The cooling disks 20, 22 thus form a heat bridge from the end windings 14, 16 to the housing 36. Along the cooling ribs 38, air can flow as cooling fluid along the housing 36 and provide active cooling. The two cooling disks 20, 22 are not actively cooled here; in the present example, they serve merely as a heat bridge.A second embodiment of the electric machine 10.4 is shown in FIGS. 4 and 5. The electric machine 10.4 differs from the electric machine 10 according to FIGS. 1 to 3 only by the housing 36.4. the housing 36.4 is designed for water cooling and therefore has a plurality of cooling channels 40. In this example case too, the two cooling disks 20, 22 are not actively cooled; they only serve as a heat bridge.A third embodiment of the electric machine 10.6 is shown in FIG. 6. In the case of the electric machine 10.6, the housing 36.4 of the embodiment according to FIGS. 4 and 5 is inserted, but other cooling disks 20.6, 22.6 are inserted. In contrast to the cooling disks 20, 22 of FIGS. 1 to 5, the cooling disks 20.6, 22.6 each have a continuous cooling channel 42 on their outer wall. The cooling disks 20.6, 22.6 can thus be actively cooled. The cooling channel 42 of the cooling disks 20.6, 22.6 is connected to the cooling channel 40 of the housing 36.4, so that the selected cooling medium can be conducted both through the two cooling disks 20.6, 22.6 and through the housing 36.4.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2004 013 133 A1

[0002]

Claims

Electric machine (10, 10.4, 10.6) - with a cylindrical stator (12), - with a first winding head (14) and a second winding head (16), which are arranged at the two axial ends of the stator (12), - with a housing (36, 36.4) for the stator (12), - characterized in that - the first winding head (14) and / or the second winding head (16) are at least partially covered by an annular cooling disc (20, 20.6, 22, 22.6), - an electrically insulating heat-conducting element (30) is arranged between the winding head (14, 16) and the cooling disc (20, 20.6, 22, 22.6).Electric machine according to Claim 1, - characterized in that - the annular cooling disc (20, 20.6, 22, 22.6) consists of a thermally conductive material or contains at least one such material.Electric machine according to Claim 2, - characterized in that - the annular cooling disc (20, 20.6, 22, 22.6) consists of aluminium or copper.Electric machine according to one of Claims 1 to 3, characterized in that - the annular cooling disc (20, 20.6, 22, 22.6) is in direct contact with the housing (36).Electric machine according to one of the preceding claims, characterized in that - in the annular cooling disc (20.6, 22.6) there is at least one cooling duct (42), through which a liquid or gaseous cooling medium can be conducted.Electric machine according to Claim 5, characterized in that - the at least one cooling duct (42) is arranged on the radial outer side of the annular cooling disc (20.6, 22.6).Electric machine according to Claim 5 or 6, characterized - in that the at least one cooling duct (42) of the cooling disc (20.6, 22.6) is connected to at least one cooling duct (40) of the housing (36.4).Electric machine according to one of the preceding claims, - characterized in that - in the annular cooling disc (20, 20.6) there is at least one aperture (24), through which a connecting cable (26) of the winding head (14) can be passed through the cooling disc (20, 20.6).Electric machine according to one of the preceding claims, - characterized in that - the side of the cooling disc (20, 20.6, 22, 22.6) which is directed towards the winding head (14, 16) has at least one annular cantilevered wall (32).Electric machine according to Claim 9, characterized in that - the annular cantilevered wall (32) is arranged on the radial outer wall (34) of the cooling disc (20, 20.6, 22, 22.6), such that - the annular cantilevered wall (32) is in contact with the inner wall (36, 36.4) of the housing (36, 36.4).

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