Electric motor with a support device between a stator and a housing

Abstract

The present subject matter relates to a rotary electrical machine (100) that includes a rotor, a stator (104), a housing (110) and a support device (112). The rotor is rotatable about a rotational axis (116). The stator (104) is in coaxial arrangement to the rotor. The stator (104) includes a stator core (106) and winding (108a; 108b). The housing (110) includes a chamber defined by a closed end (120) at one end and an open end (118) at another end. The chamber at least substantially receives the rotor and the stator (104). A housing inner surface and a stator core outer surface forms an annular space (114) that extends axially there-between. The support device (112) is at least in part disposed between the stator core (106) and the housing (110). The support device (112) at least in part spans the annular space (114). The support device (112) is adapted to at least restrict radial shifting of the stator core (106) with respect to the rotational axis (116).

Description

DESCRIPTIONELECTRIC MOTOR WITH A SUPPORT DEVICE BETWEEN A STATOR AND A HOUSINGFIELD OF INVENTION

[0001] The present subject matter relates to a support device for a stator in a housing of a rotary electrical machine.BACKGROUND

[0002] Rotary electrical machines are widely used in automotive applications and very much so as traction motor. Rotary electrical machines typically include a stator and a rotor that are arranged coaxial to each other, the rotor being configured to rotate about a rotational axis. The stator and the rotor are disposed to face each other along the rotational axis in a housing. The rotor is mounted on a rotor shaft that extends out of the housing to mechanically interact with a pulley or a gear so that a transfer of torque is facilitated. In a known arrangement, the stator is supported by a bracket provided in the housing. In such an arrangement, the rotor is disposed within a cavity of the stator. Further, a gap is maintained between the outer periphery of the stator and the inner periphery of the bracket. Such a gap is particularly required in liquid cooled rotary electrical machine where a cooling medium is made to circulate through said gap. This gap functions as a channel to permit distribution of a cooling medium, such as oil, to cool the stator.

[0003] In the conventional rotary electrical machine having the above-described configuration, it is important to keep the gap uniform along the length of the stator. Meaning, a gap width, or a distance between the outer periphery of the stator and the inner periphery of the bracket In such an arrangement, is preferably to be kept uniform for the life of the rotary electrical machine. The stator is supported at one end and cantilevered, oroverhangs, at the other end. A cantilever effect is induced at the unsupported end of the stator causing a deflection by virtue of the stator’s weight. Such a deflection may also occur during an exposure to vibrations. This adversely affect the gap maintained between the stator and the bracket. Any such deflection occurs particularly in the radial direction from the rotational axis of the rotor, thus causing the structural integrity of the channels to be comprised. More particularly, a circulation of the cooling medium, via the channels, is hindered. The stator windings are accordingly not cooled in the intended manner. Particularly, an adequate circulation of the cooling medium is not achieved, thereby reducing the performance of the rotary electrical machine. It can broadly said that, by virtue of the stator’s cantilever effect and the deflection caused by the stator’s weight, the structural integrity and operational integrity of the rotary electrical machine is compromised. Moreover, the deflection of the stator can lead to an inefficient magnetic field interference between the stator and rotor. Rotary electrical machine of such configuration therefore tends to perform poorly and in an inefficient manner.

[0004] Therefore, the technical problem to be solved by the present subject matter is how to ensure that the gap between the housing and the stator is uniform and maintained irrespective of factors such as, exposure to vibrations and weight of the stator.SUMMARY OF THE INVENTION

[0005] The present subject matter seeks to solve the above- mentioned technical problem in conventional rotary electrical machines. The present subject matter has a particularly advantageous application in rotary electrical machines such as alternators, alternator-starters, or also reversible machines or electric motors. A reversible machine is a rotary electrical machine that can work reversibly, firstly as an electric generator in alternator function, and secondly as an electric motor, for instance, tostart a thermal engine of a motor vehicle. The rotary electrical machine disclosed herein may also be applied as a traction motor for hybrid or electric vehicles.

[0006] The present subject matter relates to a rotary electrical machine comprising: a rotor rotatable about a rotational axis; a stator, in coaxial arrangement to the rotor, comprising a stator core and winding; a housing comprising a chamber defined by a closed end at one end and an open end at another end, the chamber at least substantially receiving the rotor and the stator, wherein a housing inner surface and a stator core outer surface forms a annular space extending axially there-between; a support device at least in part disposed between the stator core and the housing, said support device at least in part spanning the annular space and adapted to at least restrict radial shifting of the stator core within respect to the rotational axis. Accordingly, radial shifting, or deflection of the stator is restricted. The integrity of the annular space is maintained. In other words, the annular space defines a radial width between the stator core outer surface and the housing inner diameter, and this radial width is kept uniform along the stator’s length.

[0007] According to an aspect of the present subject matter, the support device includes a bottom surface facing the closed end of the housing and seated on a first recess formed on the housing inner surface, wherein the first recess is an undercut formed radially outward from the rotational axis. The support device is restricted from movement axially, particularly towards the closed end. The support device is thus assembled. The support device may be assembled in an interference fit between the housing inner surface and stator core outer surface. Alternatively, the support device may be fixed by means of fasteners.

[0008] According to an example of the present subject matter, the support device includes at least one channel that is at least partially formedand extending in a an axial direction parallel to the rotational axis. The at least one channel is aligned to the annular space so that adequate and uninterrupted flow of cooling medium in the annular space is achieved. The support device therefore has an additional function of maintaining flow of cooling medium whilst ensuring radial shifting of the stator is eliminated.

[0009] According to an example of the present subject matter, the support device defines at least one flange that extend axially from the bottom surface of the support device. The at least one flange mechanically enhances the structural integrity of the support device. The aforementioned advantage is particularly applicable for when a width of the support device is small, the width being defined by distance between the top surface and bottom surface of the support device is small.

[0010] According to an aspect of the present subject matter, each of the at least one flange is disposed into a second recess formed on the housing inner surface, the second recess being an undercut formed radially outward from the rotational axis. Accordingly, the at least one flange may facilitate indexing during assembly of the support device to the housing of rotary electrical machine.

[0011] According to an aspect of the present subject matter, the first recess is formed further away in the radial direction, from the rotational axis, than the second recess. Therefore, once assembled, the bottom surface is seated on the first recess whilst the at least one flange is inside of the second recess.

[0012] According to an example of the present subject matter, the at least one channel is at least partially formed on an inner side of the support device. An outer side of the support device abuts the housing inner surface and the inner side abuts the stator core outer surface to arrest radial shifting of the stator.

[0013] According to another example of the present subject matter, the at least one flange is formed in close proximity to the inner side and each of the at least one channel is formed along one of the at least one flange, wherein the at least one channel extends in the axial direction. This orientation of the at least one channel aligns it to the annular space, thereby facilitating flow of cooling medium through the support device.

[0014] According to another example, the stator core comprises corresponding partial channels that correspond to the at least one channel formed on the support device, said at least one channel and the corresponding partial channels form a duct configured for flow of the cooling medium. That is, the duct for circulation of cooling medium is partially formed on the support device and partially formed on the stator core. Thus, upon assembling the support device to the rotary electrical machine, the at least one channel and the corresponding partial channels are aligned together to form the duct through which the cooling medium may flow.

[0015] According to yet another example, the at least one channel forms a duct in the support device and the duct is oriented in the axial direction. That is, the duct is fully formed in the support device to permit cooling medium to flow through.

[0016] In an example of the present subject matter, the support device is formed from electrically insulating material.BRIEF DESCRIPTION OF DRAWINGS

[0017] The features, aspects, and advantages of the present invention will be better understood with regard to the following description and accompanying figures. The description refers to the annexed drawings, wherein:

[0018] FIG. 1 illustrates a sectional view of a rotary electrical machine, configured in accordance with the present subject matter; and

[0019] FIG. 2 illustrates a perspective zoomed in view of the rotary electrical machine, depicted in FIG. 1 , configured in accordance with the present subject matter;

[0020] FIG. 3 illustrates an exploded view of the rotary electrical machine, configured in accordance with the present subject matter;

[0021] FIG. 4A illustrates a support device of the rotary electrical machine, in accordance with the present subject matter;

[0022] FIG. 4B illustrates another perspective view of the support device, in accordance with the present subject matter; and

[0023] FIG. 5 illustrates a zoomed in perspective of the support device disposed between a stator and a housing of the rotary electrical machine, configured in accordance with present subject matter

[0024] The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and / or examples consistent with the description, however, the description is not limited to the examples and / or examples provide in the drawings.DETAILED DESCRIPTION

[0025] In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration specific implementations in which the invention maybe practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limitingsense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0026] FIG. 1 illustrates cross-sectional view of a rotary electrical machine 100, configured in accordance with the present subject matter. The present subject matter relates to a rotary electrical machine 100 that includes a rotor (not shown), a stator 104, a housing 110 and a support device 112. The rotor is rotatable about a rotational axis 116. The stator 104 is in coaxial arrangement to the rotor. The stator 104 includes a stator core 106 and winding 108a, 108b. The housing 110 includes a chamber 122 defined by a closed end 120 at one end and an open end 118 at another end. The chamber 122 at least substantially receives the rotor and the stator 104. A housing inner diameter and a stator outer surface forms a annular space 114 that extends axially there-between. The support device 112 is at least in part disposed between the stator core 106 and the housing 110. Further, the support device 112 at least in part spans the annular space 114 and is adapted to at least restrict radial shifting of the stator core 106. The radial shifting refers to a shifting of the stator core 106 with respect to the rotational axis 116.

[0027] Within the meaning of the present subject matter:

[0028] “axially” or “axial direction” refers to “a direction parallel to the rotational axis 116 of the rotor”,

[0029] “radial” or “radially” means “in a plane perpendicular to the rotational axis 116 of the rotor and along a straight line intersecting this rotational axis 116”,

[0030] “annular space” of the annular space 114 refers to “a space that at least partially circumvents the stator core outer surface or at least partially the housing inner surface”.

[0031] The stator core 106 extends in length along the axial direction. One end of the stator core 106, along the axial direction, is mounted (hence, supported) to the housing 110 by fasteners, and the other end is supported by virtue of the support device 112. Thus, the stator core 104 is supported at both ends. The annular space 114 is therefore uniformly maintained in the axial direction.

[0032] According to an example of the present subject matter, the stator core 106 is a laminated stator core 106 that includes a plurality of stacked laminations (not shown), although it is permissible for the stator core 106 to be non-laminated. The stator core 106, in said example, includes a ferromagnetic material such as steel, although use of any one or more electrically conductive materials is permissible without departing from the scope of the present subject matter. Preferably, the stator core 106 includes a plurality of arcuately spaced apart, generally radially extending teeth. More particularly, each of the teeth includes a generally circumferentially extending yoke, a generally radial arm extending from the yoke, and a crown extending generally circumferentially from the arm. The winding 108a, 108b is electrically conductive wiring wound multiple times about each tooth to form a plurality of turns or loops. The electrically conductive wiring is preferably formed of copper or aluminum, although any one or more of a variety of electrical conductive materials or a combination thereof may be used within the ambit of the present subject matter. Further, the wiring may be coated or uncoated. The wiring is wound around the teeth in a particular manner according to the configuration and desired performance characteristics of the rotary electrical machine 100. Alternatively, the windings 108, 108b may be formed from isolated copper rods (or aluminum, or a combination thereof) in the form of what are referred to as pins, or ll-pins, or hairpin.

[0033] In an example where the rotary electrical machine 100 is applied for propulsion of a motor vehicle, the rotary electrical machine 100may operate in a motor mode in which an electrical current passes across the winding 108a, 108b, and allows the creation of a magnetic field that causes a rotation of the rotor. When the rotary electrical machine 100 is operating in a generator mode, the rotational movement of the rotor allows the creation of a magnetic field into the stator 104, such magnetic field being turned into electrical current which passes across the winding 108a, 108b of the stator 104 to ensure the power supply of various equipment in the motor vehicle.

[0034] According to an aspect of the present subject matter, the stator core 106 is disposed into the chamber 122 via the open end 118 of the housing 110. The stator core 106 is rigidly mounted within the housing 110. The rotor is disposed within a central cavity of the stator core 106. The rotor is capable of rotating in relation to the stator 104, and more particularly rotating about the rotational axis 116. The rotor is carried by a shaft (not shown) and can rotate about the rotational axis 116 in motor mode and / or generator mode of the rotary electrical machine 100. Further, the support device 112 is disposed axially towards the open end 118 of the housing 110, in a direction along the rotational axis 116 so that it is at least in part disposed axially between the stator core 104 and the housing 110. The support device 112 is disposed such that it is at least in part spans the annular space 114. Meaning, the support device 112 at least in part extends axially into the annular space 114. Accordingly, during operation of the rotary electrical machine 100, the stator 104 does not shift radially. Moreover, the rotational axis 116 does not deviate from its originally intended position, thereby ensuring that the stator 104 does not shift radially and adversely impact the rotation of the rotor. The structural and operational integrity is therefore maintained.

[0035] FIG. 2 illustrates a zoomed in view of the rotary electrical machine 100 shown also in FIG. 1 . According to the present subject matter, the support device 112 is arranged so that it is at least in part disposedbetween the stator core 106 and the housing 110. More particularly, the support device 112 is arranged so that at least in part extends axially into the annular space 114. The annular space 114 extends substantially along the length of the stator core 106. By virtue of the support device 112, the annular space 114 is uniformly maintained along the length of the stator core 106.

[0036] According to an aspect of the present subject matter, the support device 112 includes a bottom surface. The bottom surface faces the closed end 120 of the housing 110. Upon disposing the support device 112 between the stator core 106 and the housing 110, the bottom surface is seated on a first recess 204 formed on the housing inner surface. The first recess 204 is an undercut formed on the housing inner. The aforementioned undercut is formed radially outward from the rotational axis 116. In the example shown in figures, the first recess 204 is formed continuously on the housing inner surface.

[0037] According to an example of the present subject matter, the support device 112 includes at least one channel 202, each being at least partially formed. The at least one channel 202 extends axially, specifically, extending towards the closed end 120 of the housing 110. The at least one channel 202 is formed as duct for uninterrupted flow of cooling medium in the annular space 114. Accordingly, the cooling medium may enter or exit the annular space 114. The aforementioned configuration is particularly advantageous for liquid cooled rotary electrical machines 100. In such rotary electrical machines 100, the annular space 114 permits flow of cooling medium and directs said cooling medium to the windings 108a, 108b of the stator 104. In a non-limiting example, the cooling medium is allowed to radially enter the housing 110 via an orifice (not shown), formed on the housing 110, and flow into the annular space 114. The cooling medium, for instance, cooling oil, water, etc., is then dispersed to cool the windings 108a, 108b of the stator 104. The annular space 114 has a radialwidth between the stator core outer surface and the housing inner diameter. The aforementioned radial width of the annular space 114 is uniform along the length of the stator 104 by virtue of the support device 112. A constant flow of the cooling medium is accordingly maintained during operation of the rotary electrical machine 100. Thus, the support device 112 therefore has a dual function - firstly to maintain the radial width of the annular space 114 along the length of the stator core 106; and secondly to maintain uninterrupted flow of cooling medium within the annular space 114 during operation of the rotary electrical machine 100.

[0038] FIG. 3 illustrates an exploded view of the rotary electrical machine 100, in accordance with an example of the present subject matter. FIG. 4A illustrates the support device 112 in accordance with an example of the present subject matter. FIG. 4B illustrates another perspective view of the support device 112 depicted in FIG. 4A. For the sake of brevity, the description that follows pertain to FIG.s 3, 4A and 4B in tandem.

[0039] The support device 112, as explained in the preceding description, is disposed at least in part between the stator core 106 and the housing 110. The support device 112 circumvents the stator’s 104 stator core outer surface 304 and is disposed at least in part to the annular space 114 formed between a housing inner surface 300 and the stator core outer surface 304. In the example shown in FIG. 3, the stator core 106 has a substantially star shaped profile. Accordingly, in said example, the housing inner surface 300 is formed with a complimenting star profile to accommodate the stator core 106. Further, upon disposing the stator 104 into a chamber 122 of the housing 110, the annular space 114 is formed with a star shaped profile. Therefore, in the example shown, the support device 112 is also formed in a substantially star shaped profile so as to circumvent the stator core 106 and at least in part be disposed in the annular space 114. The aforementioned example is a non-limiting configuration of the rotary electrical machine 100. The stator core 106,specifically the stator core outer surface 304, and accordingly the housing inner surface 300, may alternatively be at least substantially circular in profile. Further, in the foregoing example, the annular space 114 is formed with at least a substantial circular profile. Accordingly, the support device 112 is of substantially circular profile.

[0040] FIG. 4A shows a top surface 400, inner side 404 and outer side 406 of the support device 112, FIG. 4B illustrates a bottom surface 402. The bottom surface 402 is seated on a first recess 204 formed on the housing inner surface 300 (shown in FIG. 2). The support device 112 is oriented so that the bottom surface 402 faces the closed end 120 of the housing 110. Upon disposing the support device 112 into the annular space 114, the inner side 404 abuts the stator core outer surface 304; and the outer side 406 abuts the housing inner surface 300. The outer side 404 is specifically configured to abut the first recess 204. In one example, the support device 112 is disposed in the annular space 114 in an interference fit between the stator core outer surface 304 and the housing inner surface 300. In yet another example (not shown), the support device 112 is fastened to the housing 110, specifically to the first recess 204, by means of fasteners, such as, screws, rivets, etc., inserted through holes formed axially on the support device 112. Accordingly, the support device 112 does not loosen over the course of its use in the rotary electrical machine 100.

[0041] According to the examples depicted, particularly in FIGs. 4A and 4B, there are four channels 202, each being adapted to permit circulation of cooling medium in the annular space 114. The four channels 202 are aligned axially towards the closed end 120. Each of the four channels 202 are partially formed and adapted to permit flow of cooling medium.

[0042]

[0043] Accordingly, the stator core 106 includes a corresponding partial channels 500, referred from FIG. 5 illustrating a zoomed in view of the support device 112 disposed between the stator core 106 and the housing 110, which upon assembly aligns with the channels 202 of the support device 112 to form a duct through which cooling medium is permitted to flow. In other words, the duct is partially formed on the support device 112 and partially formed on the stator core 106. “Assembly” within the present disclosure means “disposing the support device 112 into the annular space 114 and the bottom surface 402 abutting the first recess 204”. Alternatively, the at least one channel 202 is formed as a duct through the support device 112, thereby, permitting cooling medium to flow through said device 112. Such a duct of the alternate example aforementioned is oriented in an axial direction to align with the annular space 114.

[0044] According to an example of the present subject matter, the support device 112 defines at least one flange 200 (shown also in FIG. 2) formed from the bottom surface 402. The at least one flange 200 extend in an axial direction in a direction towards the closed end 120 of the housing 110. The at least one flange 200 is formed at least in part circumferentially on the bottom surface 402. The at least one flange 200 is formed in close proximity to the inner side 404 of the support device 112. Each of the at least one channels 202 is formed along one of the at least one flange 200, each channel 202 thus extending in the axial direction. Moreover, such an orientation also ensured that the duct formed by virtue at least one channel 202 is aligned to the annular space 114 so that flow of cooling medium is facilitated. Further, upon assembling the support device 112, the at least one flange 200 is disposed into a second recess 206 (shown in FIG. 2 and 3) formed on the housing inner surface 300. The second recess 206 is an undercut formed on the housing surface 300. The undercut is formed radially outwards from the rotational axis 116. The first recess 204 is formed further away in the radial direction from the rotational axis 116 than thesecond recess 206. In other words, the first recess 204 has an undercut with a depth larger than the second recess 206. The first recess 204 of the examples depicted in FIGs. 2 and 3 is formed continuously in a loop on the housing inner surface 300.

[0045] According to an example of the present subject matter, each of the at least one flange 200 is provided to have one channel 202. These channels 202 may be partially formed so as to form a duct with the corresponding partial channels 500 of the stator core 106. Alternatively, these channels 202 form a duct through the support device 112 through which cooling medium may flow.

[0046] In the example where the support device 112 is of substantially circular shape, these flanges 200 by virtue of their extension axially, facilitates indexing during assembly. Further, “Indexing” within the present disclosure refers to “error free alignment of the support device 112 whilst disposing into the annular space 114”, a concept otherwise known as “poka-yoke”. Upon assembling the support device 112 to the rotary electrical machine 100, the flanges 200 are disposed into the second recess 206 and an uninterrupted means for flow of cooling medium is provided by virtue of the channels 202.

[0047] In a non-limiting manner, the support device 112, in accordance with the present subject matter, may be formed from an electrically insulating material.

[0048] The present subject matter speaks of applying the rotary electrical machine in automobile applications, however, it can be understood that the application can extend to various other industries and may be used in fans, blowers, machine tools, turbines, pumps, compressors, rolling mills, movers, paper mills, etc.

[0049] Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the scope of the present subject matter is defined.

Claims

Claims1 . Rotary electrical machine (100) comprising: a rotor rotatable about a rotational axis (116); a stator (104), in coaxial arrangement to the rotor, comprising a stator core (106) and winding (108a; 108b); a housing (110) comprising a chamber (122) defined by a closed end (120) at one end and an open end (118) at another end, the chamber (122) at least substantially receiving the rotor and the stator (104), wherein a housing inner surface (300) and a stator core outer surface (304) forms an annular space (114) extending axially there-between; a support device (112) at least in part disposed between the stator core (106) and the housing (110), said support device (112) at least in part spanning the annular space (114) and adapted to at least restrict radial shifting of the stator core (106) with respect to the rotational axis (116) wherein the stator core (106) extends in length along an axial direction, one end of the stator core (106), along the axial direction, is mounted to the housing (110) by fasteners, and the other end is supported by virtue of the support device (112).

2. Rotary electrical machine (100) as claimed in claim 1 , wherein the support device (112) comprises a bottom surface (402) facing the closed end (120) of the housing (110) and seated on a first recess (204) formed on the housing inner surface (300), wherein the first recess (204) is an undercut formed radially outward from the rotational axis (116).

3. Rotary electrical machine (100) as claimed in claim 2, wherein the support device (112) comprises at least one channel (202) that is at least partially formed and extending in an axial direction parallel to the rotational axis (116).

4. Rotary electrical machine (100) as claimed in claim 3, wherein the support device (112) defines at least one flange (200) that extend axially from the bottom surface (402) of the support device (112).

5. Rotary electrical machine (100) as claimed in claim 4, wherein each of the at least one flange (200) is disposed into a second recess (206) formed on the housing inner surface (300), the second recess (206) being an undercut formed radially outward from the rotational axis (116).

6. Rotary electrical machine (100) as claimed in claim 5, wherein the first recess (204) is formed further away in the radial direction, from the rotational axis (116), than the second recess (206).

7. Rotary electrical machine (100) as claimed in claim 3, wherein the at least one channel (202) is at least partially formed on an inner side (404) of the support device (112).

8. Rotary electrical machine (100) as claimed in any one of claims 3 to 6, wherein the at least one flange (200) is formed in close proximity to the inner side (404) and each of the at least one channel (202) is formed along one of the at least one flange (200), wherein the at least one channel (202) extends in the axial direction.

9. Rotary electrical machine (100) as claimed in claim 8, wherein the stator core (106) comprises corresponding partial channels (500) that correspond to the at least one channel (202) formed on the support device (112), said at least one channel (202) and the corresponding partial channels (500) form a duct configured for flow of the cooling medium.

10. Rotary electrical machine (100) as claimed in any one of claims 2 to 8, wherein the at least one channel (202) forms a duct in the support device (112) and the duct is oriented in the axial direction.

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