ELECTRIC MOTOR WITH OPTIMIZED STATOR COATING

Abstract

An electric motor includes a stator having a stator core made of a ferromagnetic material and an outer stator surface. The stator core includes a stator core body and a plurality of stator teeth extending therefrom. The plurality of stator teeth define conductor slots therebetween. The stator further includes a plurality of stator conductors disposed in the conductor slots. The stator additionally includes a slot liner disposed in each conductor slot and surrounding the corresponding stator conductors. A first slot is formed between each stator conductor and the corresponding slot liner, and a second slot is formed between each slot liner and the adjacent stator teeth.A predetermined amount of varnish disposed in each of the first and second slots to limit the size of the open space within the first and second slots that is free of varnish and to regulate the viscous damping of the electric motor.

Description

INTRODUCTION

[0001] The present invention relates to an electric motor according to the preamble of claim 1, as is essentially known from JP 2020 - 28 153 A.

[0002] Further state of the art can also be found in the documents DE 10 2022 111 954 A1, US 6 499 209 B1 and US 2011 / 0 181 146 A1 as well as in the article “Backlackspule” in Wikipedia (edited on 08.03.2020, 12:13 UTC, URL: https: / / de.wikipedia.org / w / index.php?title=Backlackspule&odid-=197562710).

[0003] An electric motor is a machine that converts electrical energy into mechanical energy. Electric motors can be configured as alternating current (AC) or direct current (DC) motors. The operation of an electric motor is based on the electromagnetic interaction between permanent magnets and the magnetic field generated by the machine's selectively charged coils. Electric motors are divided into two categories based on the direction of the magnetic field: axial flux motors and radial flux motors. Generally, axial flux motors contain rotors within their corresponding stators, while radial flux motors contain rotors arranged adjacent to the stators.

[0004] As a byproduct of the torque generated, electric motors generate thermal energy, which can adversely affect motor performance and reliability. Cooling an electric motor can therefore eliminate thermal stress on the motor poles or windings, ensuring longer motor life at or near peak load. Cooling an electric motor can also improve the motor's operation at higher speeds, as well as enable lower motor inertia and encapsulation. Motor cooling is generally accomplished by circulating oil, which can also be used to reduce friction between internal motor components. SUMMARY

[0005] According to the invention, an electric motor is presented which is characterized by the features of claim 1.

[0006] The paint can fill up to 80% of the first and second slots.

[0007] The varnish, which is arranged away from the angular positions with relatively high vibration, can fill more than 90% of the first and second slots.

[0008] The varnish located near the angular positions with relatively high vibration can fill 50% of the first and second slots.

[0009] In side view, the stator core may comprise several adjacent stator laminations arranged along the rotation axis. The amount of coating can be varied axially, i.e., along the rotation axis.

[0010] In plan view, the stator core may include a plurality of circularly arranged mounting bosses that define motor anchoring positions. The angular positions with relatively high vibration may be located between the mounting bosses, and the predetermined amount of paint may be applied within the first and second slots between the mounting bosses.

[0011] In side view, the stator core may have a first stator end and an opposite second stator end. The mounting bosses may be located at the first stator end, and the paint may fill more than 90% of each of the first and second slots axially proximate the mounting bosses.

[0012] Each slot liner may include a first slot liner portion and a second slot liner portion. In such an embodiment, the first slot liner portion may be configured to partially enclose the respective stator conductors, and the second slot liner portion may be configured to partially enclose the respective stator conductors and overlap the first slot liner portion.

[0013] The electric motor can have either a radial flux design or an axial flux design.

[0014] Furthermore, a motor vehicle is disclosed which has an electric motor as described above.

[0015] The above-described features and advantages and other features and advantages of the present invention will become apparent from the following detailed description of the one or more embodiments and the one or more best modes for carrying out the described invention when taken in conjunction with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a motor vehicle having a powertrain that uses an electric motor generator for propulsion. Fig. 2 is a schematic, partially cutaway perspective close-up view of a radial flow embodiment of the Fig. 1, showing a stator defining stator teeth, conductors disposed in conductor slots, and slot liners surrounding the conductors, according to the invention. Fig. 3 is a schematic partial plan or front view of an embodiment of the Fig. 2, illustrating representative adjacent stator teeth, two-piece slot liners surrounding the conductors, first and second slots formed over the slot liners, and a variable amount of varnish disposed in the slots in accordance with the invention. Fig. 4 is a schematic plan or front view of the Fig. 2, showing high resonance locations arranged between stator mounting lugs according to an embodiment of the invention. Fig. 5 is a schematic close-up view in cross-section from the side of the Fig. 2 and shows a fluid circulation system configured according to the invention for supplying oil to the first and second slots between the stator teeth. DETAILED DESCRIPTION

[0016] With reference to Fig. 1, a motor vehicle 10 is shown having a drive train 12. The motor vehicle 10 may include a commercial vehicle, an industrial vehicle, a passenger car, an aircraft, a watercraft, a train, or the like. It is also contemplated that the motor vehicle 10 may be a mobile platform, such as an airplane, a quad (ATV), a boat, a personal mobility device, a robot, and the like, to achieve the purposes of this invention. The drive train 12 includes a first drive source 14, shown as an electric motor generator and configured to produce a first drive source torque T1 (in Fig. 1) for propelling the motor vehicle 10 via driven wheels 16 relative to a road surface. The motor generator 14 may be a radial flux electric motor (e.g., shown in the Fig. 2 and Fig. 4), wherein the magnetic flux is generated perpendicular to the motor's rotational axis, and the air gap between the rotor and the machine's stator is arranged concentrically with the rotational axis. Alternatively, the motor-generator 14 may be configured as an axial-flux electric motor (not shown, but understood by those skilled in the art), wherein the magnetic flux is generated coaxially with the motor's rotational axis, and the air gap between the rotor and the machine's stator is arranged perpendicular to the rotational axis. For the sake of conciseness, the remainder of the present description will focus primarily on the radial-flux design of the motor-generator 14.

[0017] As in Fig. 1, the powertrain 12 may also include a second power source 20, such as an internal combustion engine, configured to produce a second power source torque T2. The power sources 14 and 20 may cooperate to propel the motor vehicle 10 and may be operatively connected to a transmission assembly 22. The transmission assembly 22 may be configured to transmit first and / or second power source torques T1, T2 to a final drive unit 24, which in turn may be connected to the driven wheels 16. The first power source 14, referred to as a motor generator or electric motor throughout the present invention, may, for example, be attached to the second power source 20, attached to (or integrated with) the transmission assembly 22, attached to the final drive unit 24, or be a stand-alone assembly attached to the structure of the vehicle 10.As shown, the motor vehicle 10 additionally includes a programmable electronic controller 26 configured to communicate via a high-voltage bus 27 and control the powertrain 12 to produce a predetermined amount of power source torque (such as the sum of T1 and T2), and various other vehicle systems. The motor vehicle 10 additionally includes an energy storage system 28, such as one or more batteries, configured to generate and store electrical energy to operate the power sources 14 and 20.

[0018] Fig. Figure 2 illustrates a general cross-section of the radial flux embodiment of the motor generator 14. As shown, the motor generator 14 includes a non-rotating stator assembly or stator 30 having a generally cylindrical stator core 32 defining a stator core body or back iron 33 and a plurality of stator teeth 34 extending therefrom. The stator core 32 is made of a ferromagnetic material and has a stator inner diameter (ID) defining a radially inner stator surface 32A and a stator outer diameter (OD) defining a radially outer stator surface 32B, such as shown in Fig. 2. The stator teeth 34 define a plurality of conductor slots 36 therebetween. The stator core 32 may include or be constructed from a plurality of adjacent, e.g., connected, stator laminations 38 arranged along the rotational axis X.

[0019] As in Fig. 2, the stator 30 also includes a plurality of conductors or wire windings 40 disposed within the conductor slots 36. In particular, a plurality of conductors 40 may be disposed within each of the conductor slots 36. Although the stator conductors 40 are generally contained within the conductor slots 36, the end turns of the conductors typically extend beyond the boundaries of the cylindrical core 32 at axially opposite stator ends—a first end 32-1 and a second end 32-2. The motor generator 14 also includes at least one rotor 42 disposed on a shaft defining a rotational axis X and thus mounted for rotation within the stator 30. In particular, the axial flux motor generator 14 may include two rotors 42, each disposed on one side of the stator 30, while the radial flux motor generator 14 may include a single rotor 42 mounted within the respective stator 30.

[0020] The rotor(s) 42 each have an outer rotor surface(s) 42A. Each rotor 42 has a ferromagnetic rotor core 44. The rotor core 44 has axially opposite rotor core ends—a first end 44-1 and a second end 44-2. In the case of the radial flux motor generator 14, the outer rotor surface 42A is a radially outer surface, whereas in the radial flux motor generator, the outer rotor surface 42A is defined by either the first end 44-1 or the second end 44-2. The rotor core 44 may be made of a relatively soft magnetic material such as laminated silicon or iron steel. As shown in Fig. 2, the outer rotor core surface 44A in the radial flux motor generator 14 forms an air gap 46 between the rotor 42 and the stator 30, that is, between the outer rotor surface 42A and the outer stator surface 32A.

[0021] With continued reference to Fig. 2, each rotor 42 includes a plurality of magnetic poles 48, each pole configured to generate a magnetic flux. The stator conductors 40 are configured to interact with the rotor's magnetic poles 48 to generate a rotating magnetic field that exerts a torque on the rotor(s) 42. The stator conductors 40 are supplied with multiphase alternating current from an inverter to generate a rotating magnetic field that exerts a torque on the rotor(s) 42. As shown in Fig. 3, the stator 30 also includes a plurality of slot liners 50, each slot liner being disposed within a respective conductor slot 36 and surrounding the corresponding stator conductors 40. Each slot liner 50 may include a first slot liner portion 50-1 and a second slot liner portion 50-2. The first slot liner portion 50-1 is configured to partially enclose the corresponding stator conductors 40 disposed within a respective conductor slot 36. The second slot liner portion 50-2 is configured to also partially enclose the same stator conductors 40 and to overlap a portion of the first slot liner portion 50-1 such that the respective conductors are encased by the two slot liner portions, as seen in a stator top view (in Fig. 3). Each of the conductor slots 36 may include an enlarged portion 36A for receiving the overlapping first and second slot liner portions 50-1, 50-2.

[0022] As shown in the partial plan view of the stator 30 (in Fig. 3), a first slot 52-1 is formed between each stator conductor 40 and the corresponding slot liner 50. A second slot 52-2 is formed between each slot liner 50 and the adjacent stator teeth 34 on each side of the respective conductor slot 36. The respective first and second slots 52-1, 52-2 are disposed entirely within their corresponding conductor slots 36. A predetermined or controlled amount of varnish 54 is disposed within each of the first and second slots 52-1, 52-2. To produce a required amount of varnish 54 within the first and second slots 52-1, 52-2, the varnish may be applied by capillary action to specific conductors 40 and into strategically identified areas of the conductor slots 36. Such varnish application may occur after the stator wire windings are twisted and welded and before the stator assembly 30 cures.In this way, a specific amount of varnish 54 is arranged to limit the size of the open space 56, which is free of varnish, within the first and second slots 52-1, 52-2 in order to regulate or adjust the viscous damping, including the noise, vibration, and harshness (NVH) characteristics, of the electric motor 14, as described in detail below. The amount of varnish 54 can be varied, for example, in the radial direction between the stator inner diameter and the stator outer diameter.

[0023] As in Fig. 5, the motor generator 14 may also include a lubrication or fluid circulation system 60 configured to supply oil 62 to the stator 30, e.g., via a fluid pump 64. During operation of the motor generator 14, a portion of the oil 62 may fill the open space 56 within the first and second slots 52-1, 52-2, thereby affecting the NVH characteristics of the electric motor. For example, the paint 54 may fill up to 80% of the first and second slots 52-1, 52-2 of the entire stator 30, with the remaining 20% ​​being filled by the oil 62. Referring again to the Fig. 4, the predetermined amount of varnish 54 may be applied in slots 36 located distal to, or away from, relatively high vibration or resonance angular positions 66 on the stator 30. In such an embodiment, during operation of the electric motor 14, the oil 62 would variably fill the open spaces 56 in the remaining slots (indicated by reference numerals 36') near the relatively high resonance positions 66 to dampen stator vibrations.

[0024] The varnish 54, which is arranged away from the angular positions 66 with relatively high vibration, can fill more than 90% and up to 100% of the first and second slots 52-1, 52-2. On the other hand, the varnish 54, which is arranged near the relatively high resonance angular positions 66, can fill approximately 50% of the first and second slots 52-1, 52-2, respectively. The amount of varnish 54 can be varied between the adjacent stator laminations 38 axially along the rotational axis X, as can be seen in the side view shown in Fig. 5. The variation of the lacquer quantity 54 can be consistent between the multiple stator laminations 38 or can be adjusted differently along the rotational axis X according to identified resonance regions of the stator 30.

[0025] As in the Fig. 2 and Fig. 4, the stator core 32 may have a plurality of mounting lugs 68. The mounting lugs 68 may be arranged circularly on the radially outer stator surface 32B and may be indexed in structurally advantageous positions. The mounting lugs 68 define anchoring positions of the electric motor 14 relative to the structure of the motor vehicle 10. In such an embodiment, the angular positions 66 may be arranged with relatively high oscillation between the mounting lugs 68 (in Fig. 4). Accordingly, the predetermined amount of the paint filling 54 can then be arranged within the first and second slots 52-1, 52-2 between the fastening projections 68. In the Fig.5, the mounting lugs 68 may be located at or near the first stator end 32-1. In such an embodiment, the paint 54 may be concentrated near the first stator end 32-1 and fill more than 90% of each of the first and second slots 52-1, 52-2 axially near the mounting lugs 68.

Claims

[1] Electric motor (14) comprising: a stator (30) having a stator core (32) constructed of a ferromagnetic material and having an outer stator surface (32B); wherein: the stator core (32) comprises a stator core body (33) and a plurality of stator teeth (34) extending therefrom; and the plurality of stator teeth (34) define conductor slots (36) therebetween; and wherein: the stator (30) additionally comprises: a plurality of stator conductors (40) arranged in the conductor slots (36); and a slot liner (50) disposed in each conductor slot (36) and surrounding the corresponding stator conductors (40); a first slot (52-1) is formed between each stator conductor (40) and the corresponding slot lining (50); and a second slot (52-2) is formed between each slot liner (50) and the adjacent stator teeth (34); and a predetermined amount of varnish (54) disposed in each of the first and second slots (52-1, 52-2) and configured to limit the size of the open space (56) within the first and second slots (52-1, 52-2) that is free of varnish (54) and to regulate the viscous damping of the electric motor (14); characterized by , that the electric motor (14) further comprises a lubrication system configured to supply the stator (30) with oil (62), wherein a portion of the oil (62) fills the open space (56) within the first and second slots (52-1, 52-2) during operation of the electric motor (14) to thereby influence the noise, vibration, and harshness (NVH) characteristics of the electric motor (14); and / or the lacquer (54) is arranged away from angular positions with relatively high vibration; and / or the stator (30) has a stator inner diameter (ID) and a stator outer diameter (OD) and wherein the amount of paint (54) varies in the radial direction between the stator inner diameter (ID) and the stator outer diameter (OD) [2] Electric motor (14) according to claim 1, wherein the paint (54) fills up to 80% of the first and second slots (52-1, 52-2). [3] The electric motor (14) of claim 1, wherein the paint (54) is located away from the angular positions of relatively high vibration and fills more than 90% of the first and second slots (52-1, 52-2). [4] The electric motor (14) according to claim 1, wherein the paint (54) disposed near the angular positions of relatively high vibration fills 50% of the first and second slots (52-1, 52-2). [5] The electric motor (14) of claim 1, wherein the stator core (32) comprises a plurality of adjacent stator laminations (38) arranged along the rotational axis (X), and wherein the amount of lacquer (54) varies along the rotational axis (X). [6] The electric motor (14) of claim 1, wherein the stator core (32) comprises, in plan view, a plurality of circularly arranged mounting lugs (68) defining the motor anchoring positions, wherein the angular positions of relatively high vibration are arranged between the mounting lugs (68), and wherein the predetermined amount of paint (54) is applied within the first and second slots (52-1, 52-2) between the mounting lugs (68). [7] Electric motor (14) according to claim 6, wherein the stator core (32) has a first stator end (32-1) and an opposite second stator end (32-12) in side view, wherein the fastening lugs (68) are arranged on the first stator end (32-1) and wherein the varnish (54) fills more than 90% of each of the first and second slots (52-1, 52-2) axially near the fastening lugs (68).

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