Patent Application
20220255374
The present disclosure relates to a stator, and to a brushless DC motor.
Brushless DC motors include a rotor which is connected to a motor shaft and rotatably mounted in a housing. The rotor is provided with permanent magnets. A stator is arranged around the motor, which carries a number of windings on an iron core. When suitably driven, the windings generate a magnetic field which drives the rotor to rotate. The stator core is formed from at least one stack of laminations including a plurality of stator laminations.
Electric motors with high specific power are limited in power output by their self-heating. The heat loss in the stator arises specifically from the ohmic resistance of the winding. The heat loss is dissipated through the iron core. However, the maximum heat dissipation is limited by the limited thermal conchannelivity of the stator laminations and the partially large distance between the place of heat generation and the iron core.
From the prior art, cooling systems integrated in the stator lamination package are known, in which tubes are inserted into bores in the stator lamination, through which coolant then flows and which form a closed cooling system. Such a cooling system is disclosed, for example, in DE 197 57 605 A1. In order to establish a connection to the metal sheets, the tubes are usually press-fitted or glued. In any case, joints remain which represent an increased thermal resistance due to the low conchannelance. In addition, an increased sheet cross-section is required for the integration of the tubes.
Example embodiments of the present disclosure provide stators, each of which can be cooled efficiently and with little effort.
For the purpose of the geometrical description of electric motors according to example embodiments of the present disclosure, an axis of rotation of the motor is assumed to be the central axis and the axis of symmetry. The stator is concentric with the axis of rotation and the rotor. The axis of rotation simultaneously defines a longitudinal axis of the stator and the stator core. Moreover, with respect to the longitudinal axis, it is spoken of a radial direction, which indicates the distance from the longitudinal axis, and a circumferential direction, which is defined tangentially to a certain radius extending in the radial direction.
A stator of a brushless DC motor includes a stator core with stacked stator laminations each including an annular surface and multiple stator teeth, the stator teeth being evenly spaced in a circumferential direction about a longitudinal axis of the stator and each including a tooth root and a tooth tip. Energizable windings defining coils are provided on the tooth roots of the stator core. The stator core includes three different types of stator laminations including partially corresponding openings cooperating to define cooling channels. Each of the cooling channels extends substantially parallel to the longitudinal axis from one end of the stator core to another end of the stator core.
The cooling channels allow efficient cooling of the stator with a simple structure of the stator package. A liquid coolant can preferably flow through the cooling channels. The cooling channels are preferably designed in such a way that they allow a sufficient cooling volume flow to pass at a pressure of about 2 bar, for example.
Preferably, two types of stator laminations include openings in an area of the tooth root. The coolant can thus be guided particularly close to the point of heat generation.
Preferably, the annular surfaces of the stator laminations define a stator base body. The cooling channels are each branched off several times into a side channel from a main channel extending parallel to the longitudinal axis in the stator base body, the side channel in each case projecting perpendicularly from the main channel into an individual tooth root and structured to lead back to the main channel via a deflection. The coolant is guided in a targeted manner via the side channels.
In this case, it is advantageous if sub-regions of a side channel connected via the inversion are spaced apart from one another in the longitudinal direction and extend parallel to one another, the sub-regions each including at least two stator laminations which are of the same type. Since both sub-regions are defined by the same type of stator lamination, the number of types of stator lamination can be kept to a minimum.
Preferably, another type of stator lamination provides the deflection. Preferably, each deflection is defined by a single stator lamination. The last type of stator lamination preferably defines the main channel. Preferably, the stator laminations defining the sub-portions also have an opening in the region of the main channel, so that they also define a portion of the main channel.
In an example embodiment, each stator tooth includes a single cooling channel. The cooling guide is thus symmetrical, and each stator tooth has the same cooling conditions.
It is advantageous if each cooling channel includes a mirror plane in which the longitudinal axis of the stator core lies and which is identical to a mirror plane of the corresponding stator tooth. This example embodiment achieves a uniform cooling of each tooth.
Preferably, the openings of the stator laminations have the same width tangential to the longitudinal axis.
The stator teeth of the stator can be provided on the outside or inside of the stator base body, depending on the application.
In an example embodiment, all stator laminations have the same thickness (i.e., a length in the longitudinal direction).
Further provided is a brushless DC motor including a rotor mounted to rotate about the longitudinal axis and a stator as previously described. The cooling system may include an external pump. The pump generates a volume flow which is used to cool the stator teeth. Preferably, the coolant is first passed through the cooling channels in the stator and then sprayed onto the outside of the stator teeth. However, the cooling system may also include an internal pump in the DC motor. Preferably, the required pressure is generated by a centrifugal pump on the rotor shaft.
The cooling fluid is preferably an oil or an inert fluid to prevent corrosion, and can be, for example, nitrogen, argon, helium or carbon dioxide in the fluid state, which is preferably designed for direct cooling of electronic components.
The brushless DC motor can be used in pumps, for example, provided that the pumping medium does not have a corrosive effect on the stator. Gear oils or other hydrocarbon-based fluids would be suitable, for example. An application in traction motors is also advantageous.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Example embodiments of the present disclosure are explained in more detail below with reference to the drawings. Similar or similarly acting components are designated in the figures with the same reference signs.
As shown in
A first type of stator lamination 12 has a first rectangular, approximately square opening 13 located in the annular surface 3. The first opening 13 has a mirror plane, which is preferably identical to a mirror plane 50 of the tooth 5. The first type of stator lamination 12 forms the main channel 9.
A second type of stator lamination 14 has a second, rectangular, radially aligned longitudinal opening 15. The second opening 15 extends from the annular surface 3 along the tooth root 6. The mirror plane of the second opening 15 is preferably identical to the mirror plane 50 of the tooth 5. The second opening 15 is formed such that, when the stator laminations are assembled to form a stator pack, the first opening 13 is aligned with the second opening 15 at its end near the annular surface and the openings thus partially correspond. The second type of stator laminations 14 forms the side channel 10.
The third type of stator lamination 16 has a third, rectangular, approximately square opening 17 in the region of the tooth root 6. The third opening 17 has a mirror plane, which is preferably identical to the mirror plane 50 of the tooth 5. The third type of stator lamination 16 forms the deflection of the side channel 10. The third opening 17 is formed such that when the stator laminations 2 are assembled to form a stator pack, the third opening 17 is aligned with the second opening 15 at its end near the tooth tip.
In the assembled state of the stator pack, only a single stator lamination of the first type 12 is used as initial and final lamination for each section. In between, a plurality of stator laminations of the second kind 14 are arranged, in the middle of which a single stator lamination of the third kind 16 is received. The assembled stator pack has a plurality of sections. The sequence or arrangement of the stator laminations is then repeated accordingly. The openings in the stator laminations 13,15,17 form coolant channels 8. Since only three different types of stator laminations 12,14,16 are used, the stator core is inexpensive to manufacture.
The cooling channels 8 have a large surface area for efficient heat dissipation. In addition, they have been shown to ensure a uniform distribution of the magnetic flux. In addition, the channel geometry allows a high flow velocity, with acceptable flow losses in terms of volume flow and pressure loss.
The cooling medium is a liquid, which is preferably an oil or an inert fluid to prevent corrosion, wherein the inert fluid can be, for example, nitrogen, argon, helium or carbon dioxide in the fluid state, which is preferably designed for direct cooling of electronic components.
The stator shown in the figures is part of an internal rotor electric motor. However, it may also be envisaged that the stator is an internal stator circumferentially surrounded by an external rotor. In such an example embodiment, the teeth of the stator core project radially outwardly, away from the longitudinal axis of the stator.
While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 114 264.4 | May 2019 | DE | national |
This is a U.S. national stage of PCT Application No. PCT/EP2020/064660, filed on May 27, 2020, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from German Application No. 10 2019 114 264.4, filed May 28, 2019, the entire disclosures of which are hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/064660 | 5/27/2020 | WO |
