Electric machine comprising a stator with tooth profile reducing parasitic voltage

Abstract

An electric machine includes a housing, a rotor rotatably mounted to the housing, and a stator mounted to the housing about the rotor. The stator includes a stator body formed from a plurality of laminations. The plurality of laminations includes an outer annular surface defining a radius, an inner annular surface spaced apart from the rotor, and a plurality of radially inwardly extending stator teeth spaced apart from one another by a plurality of gaps. Each of the plurality of gaps extends along the radius and includes an opening exposed at the inner annular surface. The opening has a first side and a second side each extending at an angle relative to the radius.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to electric machines, and more particularly to a stator for an electric machine that includes a tooth profile that reduces parasitic voltage. BACKGROUND

[0002] Electric motors generally include a shaft that supports a rotor. A voltage is applied to the electric machine, causing the shaft to be driven, resulting in the rotor rotating relative to a stator, thereby generating an electromotive force (EMF). In addition to the EMF, an electric motor can also generate a counter electromotive force (CEMF) that is opposite to the voltage applied across the electric motor. When connected to a load, the voltage drop across the electric machine includes the EMF, the CEMF, the voltage drop across the applied load, and a parasitic voltage drop from the shaft into the stator caused by the internal impedance of the rotor. The parasitic voltage travels from the shaft through the rotor into the stator.

[0003] The parasitic voltage results in a reduction in the energy production efficiency of the electric motor. In current systems that typically operate to produce 12 volts, the parasitic voltage is not a concern. However, as operating voltages increase with new faster switching devices, the parasitic voltage can have a more significant negative impact. Accordingly, it is desirable to provide an electric machine that is designed to reduce the parasitic voltage effect. SUMMARY

[0004] An electric machine is disclosed that includes a housing, a rotor rotatably mounted to the housing, and a stator mounted to the housing about the rotor. The stator includes a stator body formed from a plurality of laminations. The plurality of laminations includes an outer annular surface defining a radius, an inner annular surface spaced apart from the rotor, and a plurality of radially inwardly extending stator teeth spaced apart from one another by a plurality of gaps. Each of the plurality of gaps extends along the radius and includes an opening exposed at the inner annular surface. The opening has a first side and a second side each extending at an angle relative to the radius.

[0005] Each of the plurality of radially inwardly extending stator teeth includes, in addition to one or more features described herein, a first end extending from the stator body and a terminal portion defining a portion of the inner annular surface.

[0006] The terminal portion of each of the plurality of radially inwardly extending stator teeth includes, in addition to one or more features described herein, a first end portion defining a first side and a second end portion defining a second side of an adjacent opening.

[0007] The first side includes, in addition to one or more features described herein, a first angle, and the second side of an adjacent one of the plurality of radially inwardly extending stator teeth includes a second angle defining the opening, the first angle and the second angle being one of an acute angle and an obtuse angle.

[0008] In addition to one or more features described herein, the plurality of laminations includes a first plurality of laminations and a second plurality of laminations, wherein the first plurality of laminations includes a first side portion having a first angle and a second side portion having a second angle, and wherein the second plurality of laminations includes a first side portion having a third angle and a second side portion having a fourth angle.

[0009] In addition to one or more features described herein, the second plurality of laminations is located atop the second plurality of laminations.

[0010] In addition to one or more features described herein, the first angle and the second angle combine to define a surface having a first end element, a second end element, and a recess disposed between the first end element and the second end element.

[0011] In addition to one or more features described herein, the plurality of radially inwardly extending stator teeth includes a first plurality of radially inwardly extending stator teeth spaced apart from one another by a first plurality of gaps, each of the first plurality of gaps including a first opening extending at a first angle, and a second plurality of radially inwardly extending stator teeth spaced apart from one another by a second plurality of gaps, the second plurality of gaps including a second opening extending at a second angle different from the first angle.

[0012] In addition to one or more features described herein, the plurality of radially inwardly extending stator teeth includes a third plurality of radially inwardly extending stator teeth spaced apart from one another by a third plurality of gaps, each of the third plurality of gaps being free of an interruption in the inner annular surface.

[0013] In addition to one or more features described herein, each of the third plurality of radially inwardly extending stator teeth includes a terminal portion including a first bridge segment and a second bridge segment, the first bridge segment and the second bridge segment extending across the third plurality of gaps to an adjacent one of the plurality of radially inwardly extending stator teeth.

[0014] A stator for an electric machine is also disclosed that includes a stator body formed from a plurality of laminations. The plurality of laminations includes an outer annular surface defining a radius, an inner annular surface. A plurality of radially inwardly extending stator teeth are spaced apart from one another by a plurality of gaps. Each of the plurality of gaps extends along the radius and includes an opening exposed at the inner annular surface. The opening includes a first side portion and a second side portion each extending at an angle relative to the radius.

[0015] Each of the plurality of radially inwardly extending stator teeth includes a first end extending from the stator body and a terminal end portion defining a portion of the inner annular surface, in addition to one or more features described herein.

[0016] The terminal end portion of each of the plurality of radially inwardly extending stator teeth includes a first end portion defining a first side and a second end portion defining a second side of an adjacent opening, in addition to one or more features described herein.

[0017] The first side includes a first angle and the second side includes a second angle that are complementary angles, in addition to one or more features described herein.

[0018] The plurality of laminations includes a first plurality of laminations and a second plurality of laminations, in addition to one or more features described herein, wherein the first plurality of laminations includes a first side having a first angle and a second side having a second angle, and wherein the second plurality of laminations includes a first side having a third angle and a second side having a fourth angle.

[0019] The second plurality of laminations is positioned atop the second plurality of laminations, in addition to one or more features described herein.

[0020] The first angle and the second angle combine to define a surface having a first end element, a second end element, and a recess disposed between the first end element and the second end element, in addition to one or more features described herein.

[0021] The plurality of radially inwardly extending stator teeth includes a first plurality of radially inwardly extending stator teeth spaced apart from one another by a first plurality of gaps, each of the first plurality of gaps including a first opening extending at a first angle, and a second plurality of radially inwardly extending stator teeth spaced apart from one another by a second plurality of gaps, the second plurality of gaps including a second opening extending at a second angle different from the first angle, in addition to one or more features described herein.

[0022] The plurality of radially inwardly extending stator teeth includes a third plurality of radially inwardly extending stator teeth spaced apart from one another by a third plurality of gaps, each of the third plurality of gaps being free of an interruption in the inner annular surface, in addition to one or more features described herein.

[0023] Each of the third plurality of radially inwardly extending stator teeth includes a terminal end portion including a first bridge segment and a second bridge segment, the first bridge segment and the second bridge segment extending across the third plurality of gaps to an adjacent one of the plurality of radially inwardly extending stator teeth, in addition to one or more features described herein.

[0024] The above-described features and advantages, as well as other features and advantages, of this disclosure will become apparent when taken in conjunction with the accompanying drawings and the following detailed description. Attached Figure Description

[0025] Other features, advantages, and details appear only by way of example in the following detailed description, with reference to the accompanying drawings, wherein:

[0026] Figure 1 This is a schematic diagram of an electric motor including a rotor and a stator, based on a non-limiting example, wherein the stator has a tooth profile that reduces parasitic voltage;

[0027] Figure 2 It is based on the non-restrictive example. Figure 1 Axial end views of the rotor and stator;

[0028] Figure 3 It is based on the non-restrictive example. Figure 2 A partial perspective view of the stator;

[0029] Figure 4 It is based on the non-restrictive example. Figure 1 A partial plan view of multiple stator teeth of the stator;

[0030] Figure 5 It is based on the non-restrictive example. Figure 4 A plan view of the end portion of one of the stator teeth;

[0031] Figure 6 This is a partial axial end view of the rotor and stator based on another non-limiting example;

[0032] Figure 7 It is based on the non-restrictive example. Figure 6 A partial perspective view of the stator;

[0033] Figure 8A It is a partial plan view of a stator lamination including a plurality of stator teeth in a first configuration, according to a non-limiting example;

[0034] Figure 8B It is a partial plan view of a stator lamination including a plurality of stator teeth in a second configuration, according to a non-limiting example;

[0035] Figure 8C It is based on the stacking of non-restrictive examples. Figure 8A The top of the stator laminations Figure 8B A partial plan view of the stator laminations;

[0036] Figure 9A It is a partial plan view of the first plurality of stator teeth of the stator lamination according to a non-limiting example;

[0037] Figure 9B is a plan view of a stator lamination according to a non-limiting example Figure 9A of a second plurality of stator teeth of the stator lamination;

[0038] Figure 9C is a plan view of a stator lamination according to a non-limiting example Figure 9A of a third plurality of stator teeth of the stator lamination; and

[0039] Figure 10 is a plan view of a stator tooth according to another non-limiting example DETAILED DESCRIPTION

[0040] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0041] An electric machine according to a non-limiting example is generally indicated at 10 in Figures 1-3 The electric machine 10 includes a housing 14 that supports a rotor 18 mounted to a shaft 22. The shaft 22 is rotatably supported in the housing 14 by a first bearing 24 and a second bearing 26. The rotor 18 includes an outer annular surface 28 and is disposed radially inward of a stator 30 that supports stator windings 34. The stator 30 includes a stator body 40 formed of a plurality of stacked laminations 44 that define an outer annular surface 46 having a radius R1 and an inner annular surface 48 having a radius R2.

[0042] Referring to Figure 4 and with continued reference to Figure 1 and 2 The stator 30 includes a plurality of radially inwardly extending stator teeth, one of which is indicated at 60. The radially inwardly extending stator teeth 60 are spaced apart from one another by gaps, such as 64. Selected ones of the gaps 64 include an opening 70 defined by a local discontinuity in the inner annular surface 48. Each opening 70 is defined by a first side 74 extending from one of the radially inwardly extending stator teeth 60 and a second side 76 extending from another one of the radially inwardly extending stator teeth 60. In the non-limiting example, the first side 74 extends at a first angle with respect to the radius R1 and the second side 76 extends at a second angle with respect to the radius R1. In the non-limiting example, the first and second angles are substantially similar. The first and second angles can take the form of acute or obtuse angles.

[0043] Referring to Figure 5 and with continued reference to Figure 4Each of the plurality of radially inwardly extending stator teeth 60 includes a first end 82 positioned proximate the outer annular surface 46 and a terminal portion 84 defining a portion of the inner annular surface 48. The terminal portion 84 includes a first end portion 91 defining the first side 74 of the first opening 70a and a second end portion 93 defining the second adjacent side 76 of the second opening 70b. With this arrangement, each opening 70 extends at an angle relative to the radius Rl so as to at least partially electrically shield the rotor 18 from the stator winding 34 to reduce magnetic flux transfer and lower parasitic voltages.

[0044] Reference will now be made to Figures 6-7 and with continued reference to Figure 1 wherein the stator body 40 formed in accordance with another non-limiting example is described. In one embodiment, the stator body 40 can be formed from a first plurality of laminations 100 and a second plurality of laminations 102. In the non-limiting example, the first and second pluralities of laminations can be identically formed, but integrated into the stator body 80 in different orientations. For example, one or more of the second plurality of laminations 102 can be flipped or inverted and placed atop one or more of the first plurality of laminations 100 to reduce magnetic impact. In the illustrated non-limiting example, a stack of the second plurality of laminations 102 (not individually labeled) is positioned on and aligned with a stack of the first plurality of laminations 100.

[0045] In Figure 8A the illustrated non-limiting example, each of the first plurality of laminations 100 includes a plurality of radially inwardly extending stator teeth 103 having a terminal portion 104. The terminal portion 104 includes a first side 107 and a second side 110. Each of the first and second sides 107, 110 includes a corresponding surface (not individually labeled) having a first angle. Figure 8B One of the second plurality of laminations 102 including a plurality of radially inwardly extending stator teeth 109 is depicted. Figure 8B The second plurality of laminations 102 depicted in

[0046] In the non-limiting example, the plurality of radially inwardly extending stator teeth 109 of the second plurality of laminations 102 includes a terminal portion 112 having a first side 114 and a second side 116. Each of the first and second sides 114, 116 includes a corresponding surface (not individually labeled) having a second angle. In the non-limiting example, as Figure 8CAs shown, one or more of the second plurality of laminations 102 overlies one or more of the first plurality of laminations 100 forming a composite end portion 118 to reduce magnetic impact. The composite end portion 118 includes a first end element 121 and a second end element 123 separated by a recess 125. Similarly, the composite end portion 118 includes opposite third and fourth end elements 126, 128 separated by a recess 130. Thus, in non-limiting examples, the composite end portion 118 creates differently oriented openings that create barriers to magnetic flux that reduce stray capacitance, disrupt flow paths between the stator 30 and the rotor 18, and reduce parasitic voltages that can degrade the overall efficiency of the electric machine 10.

[0047] Reference will now be made to Figures 9A-9C and continued reference to Figure 1 wherein a stator body 40 formed in accordance with another non-limiting example is described. In one embodiment, the stator body 40 can be formed from a plurality of laminations 138 having a first plurality of radially extending stator teeth 140 and a second plurality of radially extending stator teeth 143 and a third plurality of radially extending stator teeth 146. The first plurality of radially extending stator teeth 140 define a first plurality of gaps 154, the second plurality of radially extending stator teeth 143 define a second plurality of gaps 156, and the third plurality of radially extending stator teeth 146 define a third plurality of gaps 158.

[0048] In non-limiting examples, each of the first plurality of gaps 154 defines a first opening 162 extending through the inner annular surface 48 at a first angle having a first orientation, and each of the second plurality of gaps 156 defines a second opening 164 extending through the inner annular surface 48 at a second angle having a second orientation different from the first orientation. Each of the third plurality of radially extending stator teeth 146 includes an end portion 172 having a first bridge section 177 and an opposite second bridge section 179. The first and second bridge sections 177, 179 eliminate any discontinuities in the inner annular surface 48 at the third plurality of gaps 158. Thus, the plurality of laminations 138 define a hybrid lamination including differently oriented openings and bridge sections that create various barriers to magnetic flux that reduce stray capacitance, disrupt flow paths between the stator 30 and the rotor 18, and reduce parasitic voltages that can degrade the overall efficiency of the electric machine 10.

[0049] Reference will now be made to Figure 10 and continued reference to Figure 1wherein a stator 40 including a plurality of stator teeth 200 according to another non-limiting example is described. Each of the plurality of stator teeth 200 includes a tip portion 204 having a first side 206 and a second side 208. In the non-limiting example, the second side 208 is spaced apart from a first side (not individually labeled) of an adjacent one of the plurality of stator teeth 200. The first side 206 includes a first stepped profile 212 and the second side 208 includes a second stepped profile 214. In the non-limiting example, the second stepped profile 214 is spaced apart from a stepped profile (not individually labeled, forming an interleaved opening 220) on an adjacent stator tooth of the plurality of stator teeth 200.

[0050] At this time, it will be appreciated that the various configurations of the tip portions according to the non-limiting examples shown and described herein establish slot openings of selected dimensions that allow for easy installation of stator windings while disrupting flow paths through parasitic voltages that can reduce the overall efficiency of the electric machine 10.

[0051] While the foregoing disclosure has been described in reference to illustrative embodiments, those skilled in the art will appreciate that various changes can be made and equivalents substituted without departing from the scope of the disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the central scope thereof. Therefore, the disclosure is not intended to be limited to the particular embodiments disclosed, but can include all embodiments falling within the scope of the disclosure.

Claims

1. An electric machine comprising: a housing; a rotor rotatably mounted to the housing; and a stator mounted to the housing about the rotor, the stator comprising a stator body formed from a plurality of laminations, the plurality of laminations comprising an outer annular surface defining a radius, an inner annular surface spaced apart from the rotor, and a plurality of radially inwardly extending stator teeth spaced apart from one another by a plurality of gaps, each of the plurality of gaps extending along the radius and comprising an opening exposed at the inner annular surface, the opening having a first side and a second side, the first side extending at a first angle relative to the radius, the second side extending at a second angle relative to the radius, the first and second angles being complementary angles. Each of the plurality of radially inwardly extending stator teeth comprises a first end extending from the stator body and a terminal portion defining a portion of the inner annular surface.

2. The electric machine of claim 1, wherein, The terminal portion of each of the plurality of radially inwardly extending stator teeth comprises a first end portion defining the first side and a second end portion defining the second side of an adjacent opening.

3. The electric machine of claim 2, wherein, The first side comprises a first angle and the second side of an adjacent one of the plurality of radially inwardly extending stator teeth comprises a second angle defining the opening, the first and second angles being one of an acute angle and an obtuse angle.

4. The electric machine of claim 1, wherein, The plurality of laminations comprises a first plurality of laminations and a second plurality of laminations, wherein the first plurality of laminations comprises a first side having a first angle and a second side having a second angle, and wherein the second plurality of laminations comprises a first side having a third angle and a second side having a fourth angle.

5. The electric machine of claim 1, wherein, The second plurality of laminations is atop the first plurality of laminations.

6. The electric machine of claim 5, wherein, The first and third angles combine to define a surface having a first end element, a second end element, and a recess disposed between the first and second end elements.

7. The electric machine of claim 6, wherein, The plurality of radially inwardly extending stator teeth comprises a first plurality of radially inwardly extending stator teeth spaced apart from one another by a first plurality of gaps, each of the first plurality of gaps comprising a first opening extending at a first angle, and a second plurality of radially inwardly extending stator teeth spaced apart from one another by a second plurality of gaps, the second plurality of gaps comprising a second opening extending at a second angle different from the first angle.

8. The electric machine of claim 1, wherein, The plurality of radially inwardly extending stator teeth comprises a third plurality of radially inwardly extending stator teeth spaced apart from one another by a third plurality of gaps, each of the third plurality of gaps being uninterrupted in the inner annular surface.

9. The electric machine of claim 8, wherein, Each of the third plurality of radially inwardly extending stator teeth comprises a terminal portion comprising a first bridge segment and a second bridge segment, the first and second bridge segments extending across the third plurality of gaps to an adjacent one of the plurality of radially inwardly extending stator teeth.

10. The electric machine of claim 9, wherein, ​

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