ELECTRIC ENGINE COOLING SYSTEM

Abstract

Electric motor system (10) comprising the following: a stator (12) having windings attached to an end periphery (24) of the stator (12); and a cover (26) which is secured to the stator (12) and defines the following: a channel (30) extending along the end periphery (24) and configured to guide cooling fluid around the windings, and characterized by a collector (32, 54) extending over at least twenty percent of an outer circumference (36) of the cover (26) and configured to direct cooling fluid into the channel (30).

Description

TECHNICAL AREA

[0001] The present disclosure relates to electric motors that can be used as a power source for a hybrid or electric vehicle. BACKGROUND

[0002] Electric motors consist of stators made from an iron core and copper winding heads. The copper winding heads conduct electric current and can generate heat during operation of the electric motor.

[0003] From JP 2012-244 659 A, an electric motor system according to the preamble of claim 1, a cover according to the preamble of claim 9 and a method according to the preamble of claim 16 are known.

[0004] The object of the present invention is to provide optimized cooling of the electric motor system and the cover. According to the invention, an electric motor system according to claim 1, a cover according to claim 9, and a method according to claim 16 are proposed. Advantageous embodiments of the invention are specified in the dependent claims and the following description. SUMMARY

[0005] The problem is solved by an electric motor system with the features of independent claim 1, a cover for winding heads with the features of independent claim 9, and a method for cooling winding heads with the features of independent claim 16. Advantageous embodiments can be found in the dependent claims.

[0006] An electric motor system comprises a stator and a cover. The stator has windings attached to an end periphery of the stator. The cover is secured to the stator and defines a channel and a collector. The channel extends along the end periphery and is configured to direct coolant around the windings. The collector extends over at least twenty percent of the outer circumference of the cover and is configured to direct coolant into the channel.

[0007] A cover for winding heads mounted on the end periphery of an electric motor stator comprises a housing that defines a channel and a collector. The channel is configured to extend along the end periphery and direct coolant around the winding heads. The collector is in flow communication with the channel and is configured to direct coolant into the channel through at least two openings. The collector includes a pressure equalization chamber, which is in flow communication with the at least two openings, and an inlet opening that establishes a flow connection between the pressure equalization chamber and a coolant supply source.

[0008] A method for cooling winding heads attached to an end periphery of an electric motor stator comprises directing cooling fluid into a collector and directing cooling fluid from the collector through at least two openings into a channel extending along the end periphery, such that the cooling fluid is distributed to the winding heads. The collector includes a pressure equalization chamber in flow communication with the at least two openings, and the cooling fluid is directed from the pressure equalization chamber through the at least two openings and into the channel. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an expanded view of an electric motor system; Fig. 2 is a reverse side of a stator winding head cover; Fig. Figure 3 is an enlarged cross-sectional view along line AA and bounded by area BB in Fig. 3; Fig. Figure 4 is an enlarged cross-sectional view along line AA and bounded by area CC in Fig. 3; Fig. 5 is an alternative configuration for a collector defined on an inlet side of the stator winding head cover; and Fig. 6 is a method for cooling the stator winding heads of an electric motor. DETAILED DESCRIPTION

[0009] Embodiments of the present disclosure are described here. It is understood, however, that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be enlarged or minimized to show details of particular components. The specific structural and functional details disclosed here should therefore not be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art how the embodiments can be used in various ways.It is obvious to a person skilled in the art that various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to create embodiments not explicitly illustrated or described. The combinations of illustrated features provide exemplary embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for specific applications or implementations.

[0010] With reference to Fig. Figure 1 shows an exploded view of an electric motor system 10. The electric motor system 10 can consist of an electric machine that operates as a motor, a generator, or a motor-generator combination. The electric motor system 10 comprises a stator 12 and a rotor 14. The stator 12 comprises an iron core 16, which may be made of magnetic steel laminations, and winding heads 18, which may be made of copper. The stator 12 comprises an outer periphery 20, an inner periphery 22, and an end periphery 24. The inner periphery 22 defines an open central space. The copper winding heads 18 may be attached to or extend from the end periphery 24. The rotor 14 is arranged in the open central space of the stator 12. The rotor can be supported in the open central space of the stator 12 by at least two bearings (not shown) arranged on each side of the rotor 14.The rotor 14 can be mechanically connected to a mechanical system, such as a hybrid or electric vehicle powertrain, for the transmission of power generated by the electric motor system 10 to the mechanical system. The rotor 14 can be connected to the mechanical system by a shaft, a gear assembly, a coupling, or any other mechanical linkage. The rotor 14 is configured to rotate when the stator 12 is energized with an electric current.

[0011] The winding heads 18 conduct current and generate heat when the stator 12 is excited. It may be desirable to dissipate some of the heat generated by the winding heads 18 if excess heat is produced. Excess heat generated by the winding heads 18 can either cause damage or reduce the performance of the electric motor system 10. A cooling fluid can be passed over the copper winding heads 18 to dissipate excess heat. A cover 26 can be secured to the stator 12. The front of the cover 26 is in Fig. Figure 1 shows the cover 26. The cover 26 can include various openings, passages, or channels configured for supplying cooling fluid to the winding heads 18. The cover 26 can be secured to the stator 12 by at least one fastening element 27 engaging through holes and threaded holes in the cover 26 or the stator 12. The cover 26 can be configured to cover the winding heads 18.

[0012] With reference to Fig. Figures 2-4 show the rear side of the cover 26 (which can also be referred to as a stator winding head cover). The cover includes a cover housing 28. The cover housing 28 can define a channel 30. The channel 30 is configured to extend along the end periphery 24 and around the winding heads 18 when the cover 26 is secured to the stator 12. The channel 30 can further be configured to direct coolant around the winding heads 18 when the cover 26 is secured to the stator 12. The cover housing 28 can further define a collector 32, which is in flow communication with the channel 30 and is configured to direct coolant into it. The collector 32 can be defined in a collector housing 34, which is either attached to the cover housing 28 or is an integral part of the cover housing 28.The collector 32 and the collector housing 34 can extend over at least twenty percent of an outer circumference 36 of the cover 26 (or the cover housing 28).

[0013] The collector 32 comprises an inlet opening or inlet 38, several openings or outlets 40, and a pressure equalization chamber 42. In the illustrated embodiment, three outlets 40 are shown; however, it is understood that two or more outlets 40 may be included. The inlet 38 is in flow communication with a cooling fluid supply source and the pressure equalization chamber 42. The several outlets 40 are in flow communication with the pressure equalization chamber 42 and the channel 30. The cooling fluid supply source is configured to supply cooling fluid to the pressure equalization chamber 42 via the inlet 38. The pressure equalization chamber 42 is configured to supply cooling fluid to the channel 30 via the several outlets 40. The multiple outlets 40 can include at least one right outlet 44 and at least one left outlet 46, which extend from an upper central point 48 of the end periphery 24 (see Fig. 1) of the stator 12 are offset to the right or left when the cover 26 is secured to the stator 12. The at least one right outlet 44 and the at least one left outlet 46 can also be offset to the right or left from an upper central point 50 of the cover housing 28.

[0014] The cover housing 28 can further include a channel outlet 52, which is in flow communication with the channel 30. The channel outlet 52 is configured to discharge cooling fluid from the channel 30 at a lower end after the cooling fluid has dissipated the excess heat from the winding heads 18.

[0015] With reference to Fig. Figure 5 shows an alternative configuration for a collector 54, defined by the cover housing 28. The collector 54 functions in the same manner as described above with reference to the collector 32, unless otherwise specified. The collector 54 comprises an inlet or opening 56, multiple openings or outlets 58, and a pressure equalization chamber 60. The inlet or opening 56, the multiple openings or outlets 58, and the pressure equalization chamber 60 function in the same manner as the inlet or opening 38, the multiple openings or outlets 40, and the pressure equalization chamber 42, respectively, unless otherwise specified. The inlet 56 is in flow communication with a cooling fluid supply source and the pressure equalization chamber 60. The multiple outlets 58 are in flow communication with the pressure equalization chamber 60 and the channel 30.The coolant supply source is configured to supply coolant to the pressure equalization chamber 60 via the inlet 56. The pressure equalization chamber 60 is configured to supply coolant to the channel 30 via the multiple outlets 58.

[0016] The pressure equalization chamber 60 can taper in a direction away from the inlet 56. This tapering of the pressure equalization chamber 60 in the direction of coolant flow can prevent the formation of a circulating zone within the chamber. The formation of a circulating zone is undesirable because the coolant would flow in a circular flow profile within the chamber instead of flowing from the inlet 56 to the multiple outlets 58. A perforated plate 62 can also be arranged within the pressure equalization chamber 60. A perforated plate can further assist in equalizing the pressure of the coolant within the chamber.

[0017] With reference to Fig.Figure 6 describes a method 100 for cooling the stator winding heads 18 of the electric motor system 10. Method 100 begins at block 102 by directing cooling fluid into the collector 32 of the cover 26 while the cover is attached to the stator 12. Then, at block 104, the cooling fluid is directed from the collector 32 into the channel 30 through the multiple openings or outlets 40 to distribute it to the winding heads 18. The cooling fluid then flows through the channel 30 and around the winding heads 18 of the stator 12 to dissipate any excess heat from the winding heads 18. The cooling fluid is then discharged from the channel 30 at block 106 through the channel outlet 52.

[0018] The electric motor system 10 can be an electric motor, an electric generator, or an electric motor-generator combination used in an electric or hybrid vehicle to propel the vehicle, recover kinetic energy (e.g., through regenerative braking), or provide a reaction force (e.g., an electric motor mechanically coupled to a first element of a planetary gear assembly, while an internal combustion engine is coupled to a second element of the planetary gear assembly). The electric motor system 10 could be used in any type of electric or hybrid vehicle, including, but not limited to, battery electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), series hybrid vehicles, parallel hybrid vehicles, series-parallel hybrid vehicles, and power-split hybrid vehicles.

[0019] When the electric motor system is used in a vehicle, the cooling fluid used to cool the winding heads 18 of the stator 12 can be transmission fluid pumped into the inlet 38 of the collector 32. The transmission fluid supply source can include transmission fluid that has accumulated in a pan of a vehicle transmission. A transmission pump can be used to direct the transmission fluid from the pan to the inlet 38 of the collector 32. Transmission fluid can exit through the channel outlet 52 from the cooling channel 30 of the cover housing 28. The transmission fluid exiting the cooling channel 30 can be returned to the pan. The transmission fluid can be directed into the pan by gravity or by an additional pump.

[0020] The terms used in the description serve to describe rather than limit the scope, and it is understood that various modifications can be made without departing from the intent and scope of the disclosure. As previously described, the features of different embodiments can be combined to form further embodiments of the invention, which may not be explicitly described or illustrated. Although various embodiments have been described as offering advantages or being preferred over other embodiments or implementations of the prior art with respect to one or more desired properties, it is nevertheless apparent to the person skilled in the art that compromises may be made between one or more features or properties in order to achieve the desired overall system features, which depend on the specific application and implementation.Therefore, embodiments that are described as less desirable than other embodiments or implementations of the prior art with respect to one or more properties are not outside the scope of protection of the disclosure and may be desirable for certain applications.

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