Electric machine and motor vehicle with an electric machine

Abstract

The invention relates to an electric machine (100) as traction motor of a motor vehicle (200). It comprises a housing (10), a stator (11) and a rotor (12), which extend along a common longitudinal axis (L). Said longitudinal axis (L) forms a cylindrical coordinate system and is oriented parallel to the x-y plane of a vehicle coordinate system (FKS). The stator (11) is delimited in the longitudinal axial direction by two end faces (131, 132), between which a cylindrical inner lateral surface (14) for receiving the rotor (12) extends. The stator (11) contains a plurality of hairpins (15), a subset of which forms an outermost row (161). Said hairpins (15) are interconnected in order to generate a rotating magnetic field and protrude from the stator (11) on at least one end face (131, 132). Outside the stator (11), the hairpins (15) are bent tangentially at least in portions and have at least one uppermost point (20) in relation to the vehicle coordinate system (FKS). The housing (10) has a cooling medium guide (17) with cooling medium outlet openings (18) which are arranged in such a way that, in the intended installation position, the emerging cooling medium (23) acts on the uppermost points (20) of at least 30%, 40% or 50% of the hairpins (15) of the first subset.

Description

[0001] Description

[0002] Electric machine and motor vehicle with an electric machine

[0003] The invention relates to an electrical machine according to the preamble of claim 1.

[0004] Furthermore, the invention relates to a motor vehicle with an electric machine designed as the traction motor of the motor vehicle.

[0005] An electric machine of this type is typically designed as a traction motor for a motor vehicle and comprises a housing, a stator, and a rotor. In the assembled state of the electric machine, the housing, stator, and rotor extend along a common longitudinal axis, which spans a cylindrical coordinate system and, when the electric machine is installed in its intended position, is aligned parallel to the x-y plane of a vehicle coordinate system.

[0006] Within the scope of this application, the directional and spatial references longitudinally, radially, tangentially, externally, and internally refer to the cylindrical coordinate system. In contrast, the directional references above and below refer to the vehicle coordinate system, which is a right-handed Cartesian coordinate system whose x-axis is aligned in the direction of travel of the vehicle and whose z-axis is perpendicular to the vehicle's ground plane.

[0007] The stator is bounded longitudinally by a first end face and a second end face, between which extends a cylindrical inner surface designed to accommodate the rotor. The stator accommodates a multitude of plug-in coils (hairpins) that rest in slots running along the cylindrical surface. The hairpins consist of bent, enameled copper flat wires, typically differentiated into U-shaped hairpins and I-shaped hairpins. U-hairpins are windings twisted and welded on one side, with the winding head on the opposite side formed by end turns of the hairpins. In contrast, I-hairpins consist of straight copper flat wire elements that are inserted into the stator slots, twisted (bent) on both sides, and finally welded (connected).In this configuration, a first subset of the hairpins forms an outermost row with respect to the cylindrical coordinate system. Regardless of the specific design of the hairpins, these are interconnected to generate a rotating magnetic field.

[0008] Furthermore, regardless of their specific design, the hairpins protrude from the stator at at least one of their end faces and are bent tangentially, at least partially, outside the stator, so that each hairpin has at least one highest point outside the stator and with respect to the vehicle coordinate system. With respect to the cylindrical coordinate system, the hairpins are generally bent tangentially such that an angle of 90° to 180° is formed between a longitudinally extending section of a hairpin and a bent section of the hairpin. Due to the tangential bending of the hairpins, the highest points of different hairpins can be spaced apart along their longitudinal axis.

[0009] During normal operation of the electric motor, the hairpins are supplied with three-phase alternating current, inducing a rotating magnetic field. This magnetic field induces a current within the rotor, which in turn induces another magnetic field. The magnetic fields of the stator and rotor interact in such a way that a torque is exerted on the rotor, which can be used via a gearbox to drive the vehicle.

[0010] When the stator is energized, heat is generated, which must be effectively dissipated to maintain the uninterrupted functionality of the electric machine. In conventional electric machines, the housing features a cooling medium guide with cooling medium outlet openings designed to supply at least a subset of the hairpins with a cooling medium when the electric machine is installed in its intended position. The cooling medium is circulated within a cooling medium circuit and absorbs heat from the hairpins, which is then transferred to the environment via a heat exchanger further along the cooling medium circuit. US 202310081217 A1 discloses a structure for injecting cooling oil, wherein the

[0011] Structure includes:

[0012] • a motor comprising a stator core and coils wound on the stator core, the coils protruding from the stator core and running obliquely in an axial direction of the stator core;

[0013] • a first cooling tube, which is attached to a first side of the motor at a distance from the coils and has a first injection hole through which oil is injected onto the coils; and

[0014] • a second cooling pipe, which is attached to a second side of the motor at a distance from the coils and has a second injection hole through which oil is injected onto the coils, wherein

[0015] • the first injection hole is designed to inject oil onto sections of the coils that extend obliquely outwards from the stator core in a direction away from the first injection hole, wherein

[0016] • the second injection hole is configured to inject oil onto parts of the coils that run obliquely towards the stator core, in a direction moving away from the second injection hole, and

[0017] • wherein the second injection hole has a larger diameter than the diameter of the first injection hole.

[0018] The US 2019 / 0305639 A1 reveals a rotating electric machine, comprising:

[0019] • a rotor;

[0020] • a stator comprising a stator core and a stator coil attached to the stator core, the stator being arranged so that it faces the rotor; and

[0021] • a housing that accommodates the rotor and stator, wherein

[0022] • in the stator coil, coils of several phases are connected by a star point busbar, wherein

[0023] • the neutral busbar is provided at a coil end that protrudes axially from an end face of the stator core, wherein

[0024] • a cooling tube is provided inside the housing for cooling the stator coil, and wherein

[0025] • The cooling tube includes a first cooling medium supply opening for draining a cooling medium toward the coil end and a second cooling medium supply opening for draining the cooling medium toward the neutral busbar. US 2011 10156508 A1 describes an electric rotary machine comprising:

[0026] • a rotor;

[0027] • a rotating shaft that is to be turned by the rotor;

[0028] • a stator facing a circumference of the rotor, wherein a plurality of slots are formed in the stator through which a coil is wound such that a coil end projects beyond an end of the stator in an axial direction of the stator;

[0029] • a cooling medium channel in which a flow path is defined through which the cooling medium flows;

[0030] • a cooling medium supply mechanism that feeds the cooling medium into the cooling medium channel;

[0031] • a flow separator arranged in the flow path, wherein the flow separator serves to separate a cooling medium flow into at least two flows; and

[0032] • a first and a second outlet, wherein the first outlet is connected to a first cooling medium flow which is one of the two flows generated by the flow separator, wherein the second outlet is connected to a second cooling medium flow which is the other of the two flows, wherein the first and second outlets discharge the cooling medium to different sections of the coil end.

[0033] US Patent 2021 / 0050764 A1 discloses a motor with a cooling system configured to cool a stator with a coil wound around a core, wherein the cooling system includes oil reservoirs installed laterally under the stator in an interior of a motor housing and which allow the collection of oil to a level that permits the immersion of at least part of a lower end section of the stator for cooling.

[0034] Current electrical machines require improvement with regard to the efficiency of heat dissipation.

[0035] It is therefore the object of the invention to improve, and in particular increase, the efficiency of heat dissipation in an electric machine and in a motor vehicle with such an electric machine. This object is achieved by the electric machine according to claim 1. The electric machine is designed as a traction motor for a motor vehicle and comprises a housing, a stator, and a rotor, which, in the assembled state, extend along a common longitudinal axis, wherein the longitudinal axis spans a cylindrical coordinate system and, in the intended installation position of the electric machine, is aligned parallel to the xy-plane of a vehicle coordinate system.

[0036] • the stator is bounded in the longitudinal axial direction by a first end face and a second end face, between which a cylindrical inner surface extends, designed to receive the rotor, and

[0037] • the stator accommodates a plurality of hairpins, wherein a) a first subset of the hairpins form an outermost row with respect to the cylindrical coordinate system, and b) the hairpins are interconnected to generate a rotating magnetic field, and c) the hairpins project from the stator at at least one of the end faces, and d) the hairpins outside the stator are bent tangentially at least section by section, such that each hairpin outside the stator and with respect to the vehicle coordinate system has at least one topmost position, and

[0038] • the housing has a cooling medium guide with cooling medium outlet openings which are designed to supply at least a subset of the hairpins with a cooling medium when the electric machine is installed in its intended position.

[0039] Based on this, the invention provides that the cooling medium outlet openings are arranged and aligned in such a way that, when the electric machine is in its intended installation position, the cooling medium exiting from the cooling medium outlet openings acts on the uppermost points of at least 30% or at least 40% or at least 50% of the hairpins of the first subset.

[0040] The problem is further solved by a motor vehicle with an electric machine designed as the traction motor of the motor vehicle, wherein the electric machine is designed as described above.

[0041] Due to the special arrangement and orientation of the coolant outlet openings, the hairpins are not supplied with coolant regardless of their geometric position relative to the vehicle's coordinate system during normal operation of the electric motor. Instead, the coolant is directed specifically to the uppermost or highest points of the hairpins. The coolant, which—due to its surface tension—wets the surface of the hairpins and flows downwards along them under the force of gravity, is thus guided over a significantly larger surface area, allowing the coolant to absorb comparatively more heat. This results in a surprisingly high increase in the efficiency of heat dissipation.

[0042] Advantageous embodiments of the invention are specified below and in the dependent claims.

[0043] According to an advantageous embodiment of the invention, the uppermost points of at least 30%, at least 40%, or at least 50% of the hairpins of the first subset, and at least one cooling medium outlet opening in each case, are arranged along a common axis that is aligned parallel to the z-axis of the vehicle coordinate system. This ensures that the uppermost points of the hairpins are supplied with cooling medium regardless of whether the cooling medium is applied to the hairpins under pressure or drips onto them by gravity.

[0044] Preferably, the hairpins are bent radially, and in particular radially outwards, at least partially outside the stator. Because the hairpins are thus bent radially and tangentially, their spatial orientation results in a complex geometry, which means that the highest point, with respect to the vehicle coordinate system, can be located outside the stator along the entire length of the hairpins.

[0045] In an advantageous further development, a second subset of the hairpins forms an inner row with respect to the cylindrical coordinate system. Each hairpin of the first subset is preferably connected to a hairpin of the second subset, in particular by welding. Preferably, a third subset of the hairpins is connected to terminals configured for supplying the hairpins with three-phase current. This allows a rotating magnetic field to be induced within the stator in a manner known per se. Preferably, the cooling medium guide comprises a multi-stage cooling medium channel with an upper channel section and at least one lower channel section. This ensures a constant supply of cooling medium even in the event of inclination. The cooling medium channel can be configured in various ways.

[0046] According to a first embodiment, cooling medium outlet openings are formed within at least one of the lower channel sections, each preferably spaced tangentially apart with respect to the cylindrical coordinate system. This results in cooling medium openings arranged along a row.

[0047] Alternatively and / or additionally, it is preferably provided that cooling medium outlet openings are formed within at least one of the lower channel sections, each spaced longitudinally apart from the others with respect to the cylindrical coordinate system. With an equally distributed number of cooling medium outlet openings, this results in two rows of cooling medium outlet openings, which are configured to supply the hairpins with cooling medium.

[0048] The cooling medium is preferably oil.

[0049] Specific embodiments of the electric machine and the motor vehicle are explained below with reference to the figures. They show:

[0050] Fig. 1 shows a perspective view of an electric machine;

[0051] Fig. 2a shows a first perspective partial view of a stator;

[0052] Fig. 2b shows a front view of the stator;

[0053] Fig. 2c shows a second perspective partial view of the stator;

[0054] Fig. 3a shows a third perspective partial view of the stator;

[0055] Fig. 3b a top view of the stator;

[0056] Fig. 3c shows a fourth perspective partial view of the stator;

[0057] Fig. 4a, b sectional side views of a refrigerant line;

[0058] Fig. 5a-c Top views of a cooling medium channel; and

[0059] Fig. 6 shows a motor vehicle. Fig. 1 shows a perspective view of an electric machine 100, which is designed as a traction motor for a motor vehicle 200. The electric machine 100 has a housing 10, a stator 11, and a rotor 12, which, in their assembled state, extend along a common longitudinal axis L. The longitudinal axis L spans a cylindrical coordinate system and, when the electric machine 100 is installed in its intended position, is aligned parallel to the xy-plane of a vehicle coordinate system FKS. Figs. 2a-c each show a detailed view of the stator 11. The stator 11 is bounded in the longitudinal axial direction by a first end face 131 and a second end face 132. A cylindrical inner surface 14, designed to receive the rotor 12, extends between the end faces 131 and 132.The stator 12 accommodates a plurality of hairpins 15, with a first subset of the hairpins 15 forming an outermost row 161 with respect to the cylindrical coordinate system. The hairpins 15 are interconnected to generate a rotating magnetic field and project from both end faces 131, 132 of the stator 11. Outside the stator 11, the hairpins 15 are bent tangentially and radially, at least in sections. The housing 10 has a cooling medium guide 17 with cooling medium outlet openings 18, which are designed to supply at least a subset of the hairpins 15 with a cooling medium when the electric machine 100 is installed in its intended position. For this purpose, the cooling medium drips from the cooling medium outlet openings 18 following gravity in the direction of arrow P onto the hairpins 15. There, the cooling medium wets the surface of the hairpins 15, at least partially, and absorbs heat.Due to gravity, the cooling medium flows off the surfaces of the hairpins 15, drips into a (not shown) conduit and carries away the heat via a (not shown) heat exchanger.

[0060] A second subset of the hairpins 15 forms an inner row 162 with respect to the cylindrical coordinate system. Each hairpin 15 of the first subset is connected, in particular welded, to a hairpin 15 of the second subset. Independently of this, the hairpins 15 of a third subset are connected to terminal blocks 19, which are configured to supply the hairpins 15 with three-phase alternating current.

[0061] Because the hairpins 15 are bent tangentially and radially outside the stator 11, at least partially, each hairpin 15 outside the stator 12 has at least one topmost point 20 with respect to the vehicle coordinate system FKS. In Figures 3a-c, the topmost points 20 of the relevant hairpins 15 are marked with circles, with only a selection of these numbered as examples. The cooling medium outlet openings 18 of the cooling medium guide 17 are arranged and oriented such that, in the intended installation position of the electric machine 100, the cooling medium exiting from the cooling medium outlet openings 18 acts on the topmost points 20 of 50% of the hairpins 15 of the first subset. In the illustrated embodiment, these are all hairpins 15 that run at least partially within the upper half of the stator 11.The upper half of the stator 11 is the part of the stator 11 that, in the intended installation position of the electric machine 100, is located above a cross-sectional plane that is parallel to the xy-plane of the vehicle coordinate system FKS and within which the longitudinal axis L of the electric machine 100 runs. In the illustrated embodiment, the uppermost points 20 of the hairpins 15 and each of the cooling medium outlet openings 18 are arranged along a common axis that is aligned parallel to the z-axis of the vehicle coordinate system FKS. With a pressureless cooling medium supply 17, the cooling medium drips directly onto the uppermost points 20 of the hairpins 15 under the force of gravity g. There, the cooling medium wets the surface of the hairpins 15 and absorbs heat. Due to gravity, the cooling medium flows along the surfaces of the hairpins 15 along the lines shown in the figures.3a-c unnumbered arrow directions, drips into a (not shown) conduit and carries away the heat via a (not shown) heat exchanger.

[0062] Fig. 4a shows a sectional side view of a horizontally oriented cooling medium guide 17, which comprises a cooling medium channel 21 with a two-stage cross-section, consisting of an upper channel section 221 and a lower channel section 222. The cooling medium channel 21 holds a cooling medium 23 up to a fill level H. Cooling medium outlet openings 18 are formed at the lower edge of the lower channel section 222, from which the cooling medium 23 flows or drips out (without pressure).

[0063] Fig. 4b shows the cooling medium channel 21 in an inclined orientation. The two-stage design of the cooling medium channel 21 increases the maximum possible angle of inclination at which the cooling medium outlet is maintained through all cooling medium outlet openings 17, because the lower channel section 222 has a comparatively smaller base area than the upper channel section 221, resulting in a comparatively higher fill height H for the same fill quantity. Figs. 5a-c show top views of different embodiments of cooling medium channels 21.

[0064] Fig. 5a shows a top view of a cooling medium channel 21, which has a single lower channel section 222 in which cooling medium outlet openings 18 are formed, spaced apart tangentially and longitudinally with respect to the cylindrical coordinate system. In this respect, the cooling medium outlet openings 18 form a row.

[0065] Fig. 5b shows a top view of a cooling medium channel 21, which has a single lower channel section 221 in which cooling medium outlet openings 18 are formed. Two cooling medium outlet openings 18 are spaced apart longitudinally. Furthermore, the cooling medium outlet openings 18 are spaced apart tangentially in pairs. Thus, the cooling medium outlet openings 18 form two parallel rows.

[0066] Fig. 5c shows a top view of a cooling medium channel 21, which has two lower channel sections 222, each containing cooling medium outlet openings 18 that are spaced apart tangentially and longitudinally with respect to the cylindrical coordinate system. In this respect, the cooling medium outlet openings 18 of each of the two lower channel sections 222 form a row.

[0067] Fig. 6 shows a motor vehicle 200 with an electric machine 100, which is designed as described above and is configured as the traction motor of the motor vehicle 200.

[0068] Reference symbol list

[0069] 100 electric machine 00 motor vehicle

[0070] 10 cases

[0071] 11 Stator

[0072] 12 Rotor

[0073] 131 first front face

[0074] 132 second front face

[0075] 14 Inner surface area

[0076] 15 Hairpin

[0077] 161 outer row

[0078] 162 inner row

[0079] 17 Cooling medium routing

[0080] 18 Cooling medium outlet opening

[0081] 19 Terminal block

[0082] 20 top position

[0083] 21 Cooling medium channel

[0084] 221 upper channel section

[0085] 222 lower channel section

[0086] 23 Cooling medium

[0087] L Longitudinal axis

[0088] FKS vehicle coordinate system

[0089] P Arrow direction

[0090] H Filling height g Gravity

Claims

Patent claims 1. An electric machine (100) designed as a traction motor for a motor vehicle (200), comprising a housing (10), a stator (11) and a rotor (12) which, in the assembled state, extend along a common longitudinal axis (L), wherein the longitudinal axis (L) spans a cylindrical coordinate system and, when the electric machine (100) is installed in its intended position, is aligned parallel to the x-y plane of a vehicle coordinate system (VCS), wherein • the stator (11) is bounded in the longitudinal axial direction by a first end face (131) and a second end face (132), between which a cylindrical inner surface (14) extends, which is designed to receive the rotor (12), and • the stator (11) accommodates a plurality of hairpins (15), wherein a) a first subset of the hairpins (15) form an outermost row (161) with respect to the cylindrical coordinate system, and b) the hairpins (15) are interconnected to generate a rotating magnetic field, and c) the hairpins (15) project from the stator (11) at at least one of the end faces (131, 132), and d) the hairpins (15) are bent tangentially at least section by section outside the stator (11) such that each hairpin (15) has at least one topmost position (20) outside the stator (11) and with respect to the vehicle coordinate system (VCS), and • the housing (10) has a cooling medium guide (17) with cooling medium outlet openings (18) which are arranged to supply at least a subset of the hairpins (15) with a cooling medium (23) when the electric machine (100) is installed in its intended position, characterized in that the cooling medium outlet openings (18) are arranged and oriented such that, when the electric machine (100) is installed in its intended position, the cooling medium (23) exiting from the cooling medium outlet openings (18) reaches the uppermost points (20) affected by at least 30% or at least 40% or at least 50% of the hairpins (15) of the first subset.

2. Electric machine (100) according to claim 1, wherein the uppermost points (20) of at least 30% or at least 40% or at least 50% of the hairpins (15) of the first subset and at least one cooling medium outlet opening (18) are arranged along a common axis which is aligned parallel to the z-axis of the vehicle coordinate system (VCS).

3. Electric machine (100) according to one of the preceding claims, wherein the hairpins (15) are bent radially, in particular radially outwards, at least section by section outside the stator (11).

4. Electric machine (100) according to one of the preceding claims, wherein a second subset of the hairpins (15) form an inner row (162) with respect to the cylindrical coordinate system.

5. Electric machine (100) according to claim 4, wherein each hairpin (15) of the first subset is interconnected, in particular welded, with a hairpin (15) of the second subset.

6. Electric machine (100) according to one of the preceding claims, wherein the cooling medium guide (17) comprises a cooling medium channel (21) with a multi-stage cross-section, having an upper channel section (221) and at least one lower channel section (222).

7. Electric machine (100) according to claim 6, wherein cooling medium outlet openings (18) are formed within at least one of the lower channel sections (222), each being tangentially spaced apart from the other with respect to the cylindrical coordinate system.

8. Electric machine (100) according to claim 6, wherein cooling medium outlet openings (18) are formed within at least one of the lower channel sections (222), which - 14 - each are spaced apart longitudinally in relation to the cylindrical coordinate system.

9. Electric machine (100) according to one of claims 1 to 8, wherein a third subset of the hairpins (15) are connected to terminals (19) which are arranged to supply the hairpins (15) with three-phase current.

10. Motor vehicle (200) with an electric machine (10) designed as a traction motor of the motor vehicle (20), characterized in that the electric machine (100) is designed according to one of claims 1 to 9.

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