ELECTRIC MACHINE FOR A VEHICLE

Description

[0001] The invention relates to an electric machine for a vehicle.

[0002] US 9,755,463 B2 discloses an electric machine with a first carrier containing electromagnetic elements and a second carrier containing electromagnetic elements, wherein the second carrier can move relative to the first carrier. The electric machine has a high current density but has a complex structure.

[0003] DE 10 2018 112 347 A1 discloses an electric machine with a stator and a stator core, wherein conductor elements are arranged in the stator core and cooled by coolant channels. This promotes high current densities, but there is also potential for optimization here.

[0004] DE 10 2015 212 127 A1 discloses an electrical machine according to the preamble of claim 1.

[0005] STJEPAN STIPETIC ET AL: "Optimized design of permanent magnet assisted synchronous reluctance motor series using combined analytical-finite element analysis bass approach", IET ELECTRONIC APLLICATIONS, IET, UK, 2016, Vol. 10, Iss. 5, pages 330-338, XP006100982, ISSN: 1751-8660, DO: 10.1049 / IET-EPA.2015.0245 discloses another electrical machine.

[0006] CN 213 879 402 U and EP 1 873 887 A2 disclose further prior art.

[0007] The object of the invention is to provide an improved electrical machine. It is desirable to provide an electrical machine with a comparatively high current density and increased efficiency using simple construction.

[0008] This object is achieved by an electrical machine according to claim 1.

[0009] The electric machine is used for a vehicle. The electric machine has a stator comprising a stator body (stator core), wherein the stator body has (along a circumferential direction) alternating stator teeth and stator slots, wherein one or more conductor elements are arranged in each of the stator slots. A yoke section with a radially extending yoke height is formed on the stator body radially outside the stator slots and the stator teeth. The stator body has a stator outer radius. The ratio v 1 of the yoke height based on the stator outer radius is between 0.18 and 0.26 (0.18 ≤ ratio v 1 ≤ 0.26).

[0010] The comparatively large yoke height promotes high efficiency of the electric machine, which is achieved through a higher lamination content in the stator and thus a comparatively high current density. This leads to a reduction in iron losses and thus increased efficiency of the electric machine.

[0011] The stator body has two or three stator slots per pole and per phase (one stator winding). Several conductor elements can form one or the phase (one stator winding). In other words, the number of holes (number of stator slots per pole and phase) is q = 2 or q = 3. This leads to efficiency advantages and a compact installation space. The ratio v 3 of the stator tooth width to the stator slot width is between 0.50 and 0.75 with two stator slots per pole and per phase (0.50 ≤ ratio v 3 ≤ 0.75). The ratio v 3 of the stator tooth width to the stator slot width is between 1.05 and 1.50 with three stator slots per pole and per phase (1.05 ≤ ratio v 3 ≤ 1.50). The specified ratios v 3 allow a large stator tooth width to be achieved, while the stator slot width is comparatively small. This allows for a higher lamination ratio, which reduces iron losses. This results in a high current density.

[0012] In particular, the ratio v 1 of the yoke height relative to the stator outer radius can be between 0.20 and 0.24 (0.20 ≤ ratio v 1 ≤ 0.24), more preferably between 0.21 and 0.23 (0.21 ≤ ratio v 1 ≤ 0.23). In a specific example, the ratio v 1 of the yoke height relative to the stator outer radius can be 0.22 (ratio v 1 = 0.22). By designing the stator body with these ratios, the efficiency of the machine can be further optimized.

[0013] The electric machine is, in particular, a traction motor for a vehicle. The electric machine is configured and / or intended to be able to drive a vehicle, preferably solely (traction drive). The vehicle is, in particular, a partially or fully electrically powered motor vehicle (electric vehicle), in particular a passenger car such as a sports car. The conductor elements are, in particular, stator windings.

[0014] The yoke section forms a closed annular section of the stator body along the circumferential direction. The stator body extends along an axial direction. The stator teeth and stator slots also extend along or parallel to the axial direction.

[0015] The stator body can preferably have a stator inner radius, with the ratio v 2 of the stator inner radius relative to the stator outer radius being between 0.61 and 0.69 (0.61 ≤ ratio v 2 ≤ 0.69). This results in a comparatively small stator inner radius. This, in turn, leads to a higher lamination content in the stator, which increases efficiency. The small stator inner radius allows the rotor outer radius to be kept small, which leads to reduced friction losses and thus increased efficiency. The stator outer radius can also be kept comparatively small.

[0016] In particular, the ratio v 2 of the stator inner radius relative to the stator outer radius can be between 0.63 and 0.67 (0.63 ≤ ratio v 2 ≤ 0.67), more preferably between 0.64 and 0.66 (0.64 ≤ ratio v 2 ≤ 0.66). In a specific example, the ratio v 2 of the stator inner radius relative to the stator outer radius can be 0.65 (ratio v 2 = 0.65). By designing the stator body with these ratios, efficiency can be further optimized. The stator outer radius can preferably be between 105 mm and 142.5 mm (millimeters). This contributes to comparatively low friction losses and increased efficiency. In particular, the stator outer radius can be between 115 mm and 132.5 mm, more preferably between 120 mm and 127.5 mm. In a specific example, the stator outer radius can be 122.5 mm.

[0017] The ratio v 3 for two stator slots per pole and per phase should be between 0.55 and 0.70 (0.55 ≤ ratio v 3 ≤ 0.70), preferably between 0.60 and 0.65 (0.60 ≤ ratio v 3 ≤ 0.65).

[0018] The ratio v 3 for three stator slots per pole and per phase is between 1.15 and 1.40 (1.15 ≤ ratio v 3 ≤ 1.40), preferably between 1.20 and 1.35 (1.20 ≤ ratio v 3 ≤ 1.35), and more preferably between 1.25 and 1.30 (1.25 ≤ ratio v 3 ≤ 1.30). In a specific example, the ratio v 3 can be 1.27.

[0019] The electrical machine can, for example by adjusting the ratio v 3 , be designed in particular such that at maximum current a maximum current density of greater than 40 A / mm 2< (amperes / square millimeter), preferably of greater than 45 A / mm 2< , more preferably between 45 and 60 A / mm 2< , in particular between 50 and 60 A / mm 2< , is achieved.

[0020] Preferably, the electric machine can have a pole pair number p of p = 3 (3 pole pairs, i.e., a total of 6 poles). This allows a sufficiently high number of pole pairs to be achieved in a relatively compact installation space. The comparatively low frequency of the pole pair number p = 3 offers efficiency advantages, especially in conjunction with the geometric relationships specified above.

[0021] Preferably, at the radially inner end of each stator tooth, a tooth tip can be provided with a cross-section that is larger than the stator teeth (or the stator tooth cross-section outside the tooth tip). This generally promotes higher efficiency and high current density. The tooth tips can each extend radially along a defined tooth tip height.

[0022] Preferably, a can can be arranged radially inwardly adjacent to the stator body, wherein the can covers the stator slots viewed in the radial direction or radially inward. This can seal the stator chamber relative to the rotor chamber. The stator slots can be open radially inward and covered by the can. The can can, for example, rest against the stator teeth or their tooth tips. The can is manufactured, for example, as a preferably fiber-reinforced plastic tube. However, the can can also be made of an elastic and / or flexible material attached to the stator body. For example, the can can be designed as a radially inner lining ("liner") of the stator.

[0023] The electric machine has a rotor that interacts electromagnetically with the stator, in particular a dry-running rotor. The rotor has an outer radius that is smaller than the stator inner radius by a radially oriented air gap height (air gap). The gap tube can also be arranged in the air gap. A clearance fit can be formed, in particular, between the gap tube and a rotor that can be electromagnetically driven radially within the stator.

[0024] The can can seal the rotor from the stator, preventing the rotor from being wetted by any cooling medium present in the stator. Fluid friction with the cooling medium can be prevented by the rotor, especially when running dry. An air gap can be formed between the can and the rotor, preventing the rotor, which rotates relative to the stator, from rubbing against the can. The rotor can, in particular, be coupled to a drive train of the motor vehicle, allowing the motor vehicle to be driven purely electrically using the electric motor.

[0025] Preferably, the stator body can be formed from a laminated core in which several stator laminations are arranged one behind the other along an axial direction, each of the stator laminations having a sheet thickness of 0.25 mm or less. This contributes to efficient operation of the electrical machine with high power ratings. In particular, the stator laminations can have a sheet thickness of 0.10 mm to 0.25 mm.

[0026] Specifically, the stator body can be manufactured from a laminated core in which a plurality of stator laminated disks, in particular produced by stamping from a metal sheet, are arranged one behind the other in the axial direction and pressed against one another, preferably in a fluid-tight manner. In particular, the stator body can be manufactured cost-effectively by stamping and stacking. Preferably, the electrical machine can have a cooling device, wherein the cooling device has a plurality of cooling channels, each extending from an inlet (cooling channel inlet) axially or along the axial direction through the stator body to an outlet (cooling channel outlet), wherein the cooling channels are each filled with a dielectric serving as the cooling medium or carry the dielectric serving as the cooling medium. As a result, heat generated at the stator during operation of the electrical machine can be reliably dissipated.

[0027] The electric machine may optionally have a housing which may have a first sub-housing and a second sub-housing.

[0028] The first sub-housing can be arranged at a first axial end of the stator and, together with the can and the end face of the stator, define a first end volume, which can be configured, for example, as an annular space. The first end volume is fluidly connected to the cooling channels (cooling channel inlet) in the stator and is filled with a dielectric serving as the cooling medium. Winding heads formed on the conductor elements can optionally be arranged in the first end volume. Independently of this, an inlet for supplying cooling medium can be formed on the first sub-housing.

[0029] The second sub-housing can be arranged at a second, in particular at the other, axial end of the stator and, together with the can and the end face of the stator, define a second end volume, which can be designed, for example, as an annular space. The second end volume is fluidly connected to the cooling channels (cooling channel outlet) in the stator and is filled with a dielectric serving as the cooling medium. Winding heads formed on the conductor elements can optionally be arranged in the second end volume. Independently of this, an outlet for discharging the cooling medium can be formed on the second sub-housing.

[0030] The outlet on the second sub-housing can be fluidly connected to the inlet on the first sub-housing. A fluid pump for conveying the cooling medium, one or more heat exchangers for cooling the cooling medium, and / or a cooling medium reservoir can be integrated into this flow connection.

[0031] The cooling channels provided in the stator body can be designed separately from the stator slots. This minimizes flow resistance, as the cooling medium can flow freely in the cooling channel and does not have to pass through or around the conductor elements (flow obstructions). The cooling channels can extend axially or along the axial direction through the stator body. The central longitudinal axes of the cooling channels can be arranged parallel to the central longitudinal axes of the stator slots.

[0032] Alternatively, the cooling channels can each be arranged in one of the stator slots, so that the conductor elements are cooled over the entire axial length of the stator body with the dielectric serving as the cooling medium, in particular (relative to the conductor element(s)) the cooling medium flows around them "from the outside." In other words, the cooling channels coincide with the stator slots (the stator slot also simultaneously serves as a cooling channel). This allows the conductor elements arranged in the stator slot, each of which is provided with an insulating layer, to be directly cooled by the cooling medium (direct contact of the cooling medium or dielectric with the conductor elements). This allows sufficient cooling even at comparatively high current densities. The flow direction of the cooling medium is oriented, in particular, along or parallel to the central longitudinal axis of the conductor elements.

[0033] A flow around the conductor elements with the cooling medium, in particular with oil, can thus take place within the stator slot and, if the first partial housing (first end volume) and / or the second partial housing (second end volume) are present, also at the winding head(s) (sections of the conductor elements projecting axially from the stator body).

[0034] Preferably, the dielectric can have a maximum density of 0.75 kg / l at 15°C and / or a maximum viscosity of 6 mm² / s at 40°C and / or a minimum heat capacity of 2.3 kJ / (kg*K) at 80°C and / or a minimum thermal conductivity of 0.12 W / (m / K) at 80°C and / or a maximum electrical conductivity of 1000 nS / m at 25°C. This allows advantageous cooling properties to be achieved.

[0035] Preferably, the electrical machine can be designed as a permanent magnet synchronous machine or as a separately excited synchronous machine.

[0036] Further advantageous embodiments will become apparent from the following description and the drawing. The drawing shows: Fig.1 a schematic longitudinal section of an electrical machine and Fig.2 a partial section of the electrical machine from Fig.1 (segment) along a Figur 1 drawn section axis AA.

[0037] In Fig.1 A longitudinal section through an electrical machine 100 is shown schematically.

[0038] The electric machine 100 has a stator 101 with a stator body 102 and a rotor 104 with a permanent magnet 104'. The axial direction is designated by reference numeral 105. The stator body 102 surrounds the rotor 104 radially outward, wherein the stator body 102 and the rotor 104 are separated from one another by an air gap 106. A gap tube 107 is arranged in the air gap 106, which separates the space in which the rotor 104 is arranged (rotor space) from the space in which the stator 101 is arranged (stator space). In the example, several magnets 108 are arranged in the rotor 104, which are optionally equipped with air pockets 110 (see Fig.2 ).

[0039] The stator body 102, the structure of which is explained in more detail below, has alternating stator teeth 112 and stator slots 114 along a circumferential direction with conductor elements 116 arranged therein (cf. Fig.2 ). The conductor elements 116 each have sections projecting axially from the stator body 102, which form winding heads 117 (cf. Fig.1 ).

[0040] The electric machine 100 has a cooling device that has a plurality of cooling channels 115, each extending from an inlet 119 through the stator body 102 to an outlet 121. The cooling channels 115 are each filled with a dielectric 131 serving as a cooling medium (see Fig.2 ). In the example, the cooling channels 115 coincide with the stator slots 114. The cooling medium or dielectric is thus guided directly along the conductor elements 116, which, in the example, are flowed around "from the outside." The dielectric 131 can have the properties explained above.

[0041] The electric machine 100 has a housing 123, which has a first sub-housing 123' and a second sub-housing 123" (cf. Fig.1 ). The first sub-housing 123' is arranged at a first axial end of the stator body 102 and, together with the can 107 and the end face 103' of the stator body 102, defines a first end volume 125', which in the example is designed as an annular space. The first end volume 125' is fluidly connected to the cooling channels 115 (cooling channel inlet) in the stator body 102 and is filled with dielectric 131 serving as the cooling medium. The winding overhangs 117 formed on the conductor elements 116 are arranged in the first end volume 125'. An inlet 127 for supplying cooling medium is formed on the first sub-housing 123'.

[0042] The second sub-housing 123" is arranged at the other axial end of the stator body 102 and, together with the can 107 and the end face 103" of the stator body 102, defines a second end volume 125", which in the example is designed as an annular space. The second end volume 125" is fluidly connected to the cooling channels 115 (cooling channel outlet) in the stator body 102 and is filled with dielectric 131 serving as the cooling medium. The winding heads 117 formed on the conductor elements 116 are arranged in the second end volume 125". An outlet 129 for discharging cooling medium is formed on the second sub-housing 123". The outlet 129 can be fluidly connected to the inlet 127, as explained above.

[0043] In Fig.2 is schematically a segment S or a partial section (cross section) through an electrical machine 100 according to the section axis AA in Fig.1 shown.

[0044] As already explained above, the stator body 102 has alternating stator teeth 112 and stator slots 114 with conductor elements 116 arranged therein along a circumferential direction. A yoke section 118 with a radially extending yoke height 120 is formed on the stator body 102 radially outside the stator slots 114 and the stator teeth 112, wherein the stator body 102 has a stator outer radius 122. The ratio v 1 of the yoke height 120 relative to the stator outer radius 122 is between 0.18 and 0.26 in the example (0.18 ≤ v 1 ≤ 0.26).

[0045] The stator body 102 has a stator inner radius 124. The ratio v 2 of the stator inner radius 124 relative to the stator outer radius 122 is between 0.61 and 0.69 (0.61 ≤ v 2 ≤ 0.69) in the example. The stator outer radius 122 is between 105 mm and 142.5 mm in the example.

[0046] In the example, the electrical machine 100 has a pole pair number p of p = 3 (a total of 6 poles). On the stator body 102, three stator slots 114 are provided per pole and the conductor elements 116, which form a phase or conductor winding, in the example (in Fig.2 Three identically depicted stator slots 114 correspond to one strand. In other words, the number of holes (number of stator slots 114 per pole and strand) is q = 3.

[0047] The stator teeth 112 each have a stator tooth width of 126. The stator slots 114 each have a stator slot width of 128. In the example, the ratio v 3 of the stator tooth width 126 to the stator slot width 128 is between 1.05 and 1.50 (1.05 ≤ v 3 ≤ 1.50).

[0048] At the radially inner end of each stator tooth 112, a tooth tip 130 is formed with a cross-section that is enlarged relative to the stator teeth 112. The tooth tips 130 each extend along a defined tooth tip height 132.

[0049] The rotor 104 has a rotor outer radius 134, wherein the rotor outer radius 134 is smaller than the stator inner radius 124 by a radially oriented height 136 of the air gap 106 (air gap height 136). The gap tube 107 is also arranged in the air gap 106.

[0050] As already indicated above, the conductor elements 116 are directly cooled. For this purpose, in the example, a cooling channel 115 is provided in each stator slot 114 (stator slot 114 and cooling channel 115 coincide), whereby the conductor elements 116 are cooled over the entire axial length of the stator body 102 by the dielectric 131 serving as the cooling medium and are surrounded by this dielectric from the outside (cf. enlarged partial section in Fig.2 ).

[0051] The stator slots 114 are open radially inward and are covered or closed by the gap tube 107. The gap tube 107 rests against the tooth tips 130 of the stator teeth 112.

[0052] As already explained above, the stator body 102 is formed from a laminated core in which a plurality of stator laminated discs are arranged one behind the other along the axial direction 105, wherein the stator laminated discs each have a sheet thickness of 0.25 mm or less (cf. Fig.1 )

[0053] The Fig. 1 and 2 The electric machine 100 shown can be used for the purely electric drive of a motor vehicle. For this purpose, the electric machine 100 can be powered during motor operation from a motor vehicle battery, which is connected to the conductor elements 116 in order to generate an electrically generated magnetic field in the stator 101, which can interact with permanent magnets 104' of the rotor 104, in particular a dry-running rotor.

Claims

1. An electrical machine (100) for a vehicle, having a stator (101) which has a stator body (102), wherein the stator body (102) comprises alternating stator teeth (112) and stator grooves (114) having conductor elements (116) arranged therein, wherein a yoke portion (118) having a radially extending yoke height (120) is formed on the stator body (102) radially outside the stator grooves (114), wherein the stator body (102) comprises a stator outer radius (122), and wherein two or three stator grooves (114) are provided on the stator body (102) per pole and per strand, wherein the ratio (v1) of the yoke height (120) relative to the stator outer radius (122) is between 0.18 and 0.26, characterised in that the ratio (v3) of the stator tooth width (126) to the stator groove width (128) is between 0.50 and 0.75 for two stator grooves (114) per pole and per strand, or that the ratio (v3) of the stator tooth width (126) to the stator groove width (128) is between 1.05 and 1.50 for three stator grooves (114) per pole and per strand.

2. The electrical machine (100) according to claim 1, wherein the stator body (102) comprises a stator inner radius (124), characterised in that the ratio (v2) of the stator inner radius (124) to the stator outer radius (122) is between 0.61 and 0.69.

3. The electrical machine (100) according to claim 1 or 2, characterised in that the stator outer radius (122) is between 105 mm and 142.5 mm.

4. The electrical machine (100) according to any one of the preceding claims, characterised in that the electrical machine (100) comprises a pole pair number (p) of p = 3.

5. The electrical machine (100) according to any one of the preceding claims, characterised in that, at each radially inner end of the stator teeth (112), a respective tooth head (130) is formed with a cross-section respectively enlarged relative to the stator teeth (112).

6. The electrical machine (100) according to any one of the preceding claims, characterised in that a can (107) is arranged radially inside abutting the stator body (102), wherein the can (107) covers the stator grooves (114) when viewed in the radial direction.

7. The electrical machine (100) according to any one of the preceding claims, characterised in that the stator body (102) is formed from a sheet metal package in which several stator sheet metal plates are arranged one behind the other along an axial direction, wherein the stator sheet metal plates each have a sheet metal thickness of 0.25 mm or less.

8. The electrical machine (100) according to any one of the preceding claims, characterised in that a cooling device is provided, wherein the cooling device comprises several cooling channels (115), each extending from an inlet (119) along the axial direction (105) through the stator body (102) to an outlet (121), wherein the cooling channels (115) are each filled with a dielectric material (131) serving as the cooling medium.

9. The electrical machine (100) according to claim 8, characterised in that the cooling channels (115) are each arranged in one of the stator grooves (114), such that the conductor elements (116) are cooled over the entire axial length of the stator body (102) with the dielectric material (131) serving as the cooling medium, in particular surrounded by a flow from the outside.

10. The electrical machine (100) according to claim 8 or 9, characterised in that the dielectric material (131) has a maximum density of 0.75 kg / l at 15°C and / or a maximum viscosity of 6 mm2 / s at 40°C and / or a minimum thermal capacity of 2.3 kJ / (kg*K) at 80°C and / or a minimum thermal conductivity of 0.12 W / (m / K) at 80°C and / or a maximum electrical conductivity of 1000 nS / m at 25°C.

11. The electrical machine (100) according to any one of the preceding claims, characterised in that the electrical machine (100) is configured as a permanently stimulated synchronous machine or as an externally stimulated synchronous machine.