The present disclosure relates to a permanent magnet motor.
Electric motors, such as those typically used in hybrid electromechanical powertrains for automotive vehicles, have a rotor and a stator surrounding the rotor. The rotor can rotate relative to the stator, and the stator is fixed to a stationary member, such as a transmission housing or casing. An air gap is established by the radial clearance between the rotor and the stator.
It is useful to minimize the torque ripple and the radial force in a permanent magnet (PM) motor in order to maximize its efficiency and minimize the noise, vibration, and harshness (NVH) during operation. In the present disclosure, “torque ripple” refers to a periodic increase or decrease in output torque in electric motors. The design of the presently disclosed PM motor minimizes the torque ripple and the radial force during operation, thereby maximizing efficiency.
In an embodiment, the presently disclosed PM motor includes a stator defining an inner stator opening. The inner stator opening extends along a stator axis. The PM motor further includes a rotor disposed inside the stator. The rotor can rotate about the stator axis relative to the stator. The stator includes a plurality of lamination segments stacked together along the stator axis. Each lamination segment includes an annular stator body and teeth extending from the annular stator body toward the stator axis. The annular stator body is commonly referred to as the back iron. The teeth are spaced apart from one another so as to define a plurality of slots annularly arranged about the stator axis. Each slot is defined between two teeth. The stator defines slot openings annularly arranged about the stator axis. At least one of the lamination segments is rotationally offset relative to another lamination segments so that at least one of the slot openings is circumferentially offset from another slot openings in the other lamination segment.
The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the teachings when taken in connection with the accompanying drawings.
Referring to the drawings, wherein like reference numbers correspond to like or similar components throughout the several figures, and beginning with
In the depicted embodiment, the PM motor 10 includes a stator 12 and a rotor 14 disposed within the stator 12 and can be configured as an interior permanent magnet motor. When the PM motor 10 receives electrical energy from a power supply, the rotor 14 can rotate relative to the stator 12 in order to propel the vehicle 8. An air gap 16 is defined between the stator 12 and the rotor 14. The rotor 14 may have a substantially annular shape and includes a plurality of permanent magnets 18. The stator 12 may also have a substantially annular shape and defines an inner stator opening 21 configured, shaped, and sized to receive the rotor 14. The inner stator opening 21 extends along a stator axis Z (see also
With reference to
With reference to
The stator 12 further defines a plurality of slot openings 30 arranged annularly about the stator axis Z (
In addition, each slot opening 30 has a center C2 in the middle of the slot opening width W. An opening central axis O extends along the slot opening 30 in the radial direction and intersects the center C2 of the slot opening 30. All or some of the slot openings 30 may be circumferentially offset from the slot central axis S in order to minimize torque ripple. In other words, the center C2 of the slot opening 30 may be circumferentially offset from the center C1 of the slot 28 by an opening offset distance D. The circumferential opening offset distance D is defined from the opening central axis O to the slot central axis S. Each of the slot 28 and slot opening 30 combinations (i.e., the slot/opening combination) may have a different opening offset distance D. The slot 28 and slot opening 30 combination refers to the slot 28 and the slot opening 30 that are in communication with each other. Some slots 28 and slot openings 30 combinations may have the same offset distances D. It is also contemplated that all the slots 28 and slot openings 30 may not be circumferentially offset relative to one another. At least two of the slot/opening combinations have different circumferential offset distances B.
With reference to
With reference to
The PM motor 10 can be manufactured by first stacking and aligning all the lamination segments 22 so that the stator openings 30 of each lamination segment 22 are substantially aligned with one another along the axial direction A. Then, at least one of the lamination segments 22 is rotated relative to another lamination segment 22 about the stator axis Z in order to misalign at least some of the slot openings 30 along the axial direction A. At this juncture, one of the lamination segments 22 is rotationally offset from at least one other lamination segment 22 such that at least one of the slot openings 30 of one lamination segment 22 is axially misaligned relative to the slot opening 30 of another lamination segment 22. Next, the stacked lamination segments 22 are coupled to one another. For instance, the lamination segments 22 may be glued together.
While the best modes for carrying out the teachings have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the teachings within the scope of the appended claims.