A BEARING ASSEMBLY

Abstract

The present subject matter relates to a bearing (102a), and more particularly to a rotating machine (100) that includes the bearings (102a). The bearing 102a includes a housing, a shaft (108), and a bearing (102a). The bearing (102a) includes an inner ring (104), an outer ring (106), and a plurality of rolling elements (105). The shaft (108) includes an undercut formed on an outer circumferential surface (110) of the shaft (108). The undercut is defined by a bottom surface and a sidewall on either side of the bottom surface. According to the present subject matter, the electrically insulating material 210 is positioned in a gap between the bore surface of the inner ring and the undercut of the shaft. The gap defines a distance between the surface of the bore and the undercut. As a result, the flow of electric current between the bearing (102a) and the shaft (108) is stopped. Figure for the abstract: Fig. 2

Description

Title of the invention: A BEARING ASSEMBLY FIELD OF THE INVENTION

[0001] The present subject generally relates to a bearing, and in particular to a bearing for automotive applications, for example in rotating machines used for the traction of a motor vehicle.

[0002] CONTEXT

[0003] Conventional bearings used in electrical machines, such as rotating machines, generators or the like, are at high risk of being damaged if an electrical current or charge passes through the bearing. Exposure to a circulating electrical current or charge is detrimental to the raceways of the bearing assembly. In particular, electrical stresses are formed and cause localized heating and erosion of the bearing surfaces. Devices such as grounding rings have been developed to provide an alternative path for the electrical current and thus prevent it from passing through the bearing. However, these devices have complicated structures, for example a solid ring of fibers that facilitates the passage of the electrical current between the shaft and the housing.Additionally, the inclusion of an additional device, such as the one mentioned above, adds complexity to the bearing assembly configuration, resulting in more complex assembly of the bearing assembly and additional costs associated with that complexity. In addition, an additional device increases the bill of materials, which increases the cost of the bearing assembly.

[0004] Therefore, the technical problem to be solved by the present subject is how to provide a bearing, for a rotating machine, which stops the electric current or charge passing through said bearing. Summary of the invention

[0005] The present subject aims to solve the above-mentioned technical problem of the power cut-off mechanism in a conventional rotating machine.

[0006] The present subject matter relates to a rotating machine comprising: a housing comprising an inner circumferential surface; a shaft rotatable about a central axis and comprising an undercut formed on an outer circumferential surface of said shaft, the undercut being defined by a bottom surface and a sidewall on either side of the bottom surface; a bearing, disposed between the outer circumferential surface and the inner circumferential surface, comprising: an inner ring having a first load-bearing surface and a bore surface defining a bore through which the shaft is inserted; an outer ring disposed spaced from the inner ring, said outer ring having a second load-bearing surface; and a plurality of rolling elements disposed in contact with the inner ring and the outer ring, and dimensioned for rolling movement between the first load-bearing surface and the second load-bearing surface, characterized in that an electrically insulating material is positioned in a space between the bore surface of the inner ring and the undercut, wherein the space defines a distance between the bore surface and the undercut.

[0007] As a result, due to the electrically insulating material in the space between the bore surface and the undercut, the traditionally required grounding ring is eliminated. As a result, failure of the bearing due to electrical stresses is eliminated, thereby preserving the structural integrity of the bearing during operation. In addition, the bill of materials is reduced, simplifying assembly of the bearing into the rotating machine. In addition, costs associated with the bill of materials are significantly reduced.

[0008] According to one aspect of the present subject matter, the gap comprises a first gap defined by a first distance between the surface of the bore and the lower surface of the undercut, and wherein the first gap extends parallel to the central axis. The gap is filled with electrically insulating material, which prevents electrical current from flowing between the surface of the bore and the undercut of the shaft. The foregoing is suitable for examples where the inner ring of the bearing is in an interference fit with the undercut of the shaft.

[0009] According to another aspect of the present subject matter, the gap comprises a second gap defined by a second distance between a wall of the inner ring and the side wall of the undercut, said side wall being adjacent to said ring wall, and wherein the second gap extends radially from the central axis. In this aspect, the inner ring is a clearance fit with the undercut. In such an example, the gap between the bore surface and the bottom surface, and the gap between the side wall and the ring wall are filled with electrically insulating material, thereby preventing electrical current from flowing between the inner ring and the shaft.

[0010] According to an example of the present subject, the electrically insulating material disposed in the first space has a first thickness equal to the first distance. The first thickness is therefore uniform in the first space. The service life of the bearing is thus improved.

[0011] According to another example of the present subject, the electrically insulating material disposed in the second space has a second thickness equal to the second distance. The second thickness is uniform in the second space. The life of the bearing is thus improved.

[0012] According to one aspect of the present subject matter, the first thickness has a value between 3 and 50 microns, and the second thickness has a value between 3 and 50 microns. Accordingly, the first thickness and the first distance are of equal value. Furthermore, the second thickness and the second distance are of the same value.

[0013] According to an example of the present subject, the value of the thickness of the first thickness differs from the value of the thickness of the second thickness.

[0014] According to another example of the present subject, the value of the thickness of the first thickness is equal to the value of the thickness of the second thickness.

[0015] According to an example of the present subject matter, the electrically insulating material is aluminum oxide. Aluminum oxide is an electrically insulating material that stops any flow of electric current. In addition, due to the inherent low friction coefficient property of aluminum oxide, the overall efficiency of the bearing is improved while reducing the risk of overheating of the bearing during operation. Aluminum oxide is stable at high temperatures, which allows the bearing to operate even at high temperatures without structural damage. The electrically insulating material may also be an aluminum alloy having electrically insulating properties.

[0016] According to one aspect of the present subject matter, the undercut is an annular groove formed circumferentially around the shaft. Accordingly, the annular groove may have a cross-section to snugly seat the inner ring of the bearing. The width of the inner ring (defined by the distance between the sides of the width) is snugly seated in the annular groove, such that the inner ring and the shaft rotate together during operation. Brief description of the drawings

[0017] The features, aspects and advantages of the present invention will be better understood in light of the following description and the accompanying figures. The description refers to the accompanying drawings, in which:

[0018] [Fig.l] illustrates a schematic cross-sectional view of a rotating machine, configured in accordance with one aspect of the present subject matter;

[0019] [Fig.2A] illustrates an enlarged view of area A shown in [Fig.1], configured in accordance with the present subject matter;

[0020] [Fig.2B] illustrates another perspective view at A with electrical insulation material removed, and further showing a gap between an inner ring of the bearing and an undercut formed on a shaft, configured in accordance with the present subject matter;

[0021] [Fig. 3] illustrates a sectional view of the shaft with other rotating machine components removed, configured in accordance with one aspect of the present subject matter;

[0022] The figures are not necessarily to scale and the size of certain parts may be exaggerated to more clearly illustrate the example shown. In addition, the drawings provide examples and / or examples consistent with the description, but the description is not limited to the examples and / or examples provided in the drawings. DETAILED DESCRIPTION

[0023] In the following description, reference is made to the accompanying drawings, which are an integral part of the invention, and in which are illustrated specific embodiments in which the invention may be embodied. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that the embodiments may be combined, or that other embodiments may be used, and that structural and logical modifications may be made without departing from the scope of the present invention. The detailed description which follows is therefore not to be construed in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0024] [Fig.l] illustrates a schematic view of a rotating assembly 100 configured in accordance with the present subject matter. The rotating assembly 100 includes a housing 112, a shaft 108, and a bearing 102. The bearing 102 is disposed between an inner circumferential surface 114 of the housing 112 and an outer circumferential surface 110 of the shaft 108. The shaft is rotatable about a central axis 116 and includes an undercut formed on the outer circumferential surface 110. The undercut is defined by a bottom surface and a sidewall on either side of the bottom surface. The bearing includes an inner ring 104, an outer ring 106 disposed relative to the outer ring 104, and a plurality of rolling elements 105 disposed in contact with the inner ring 104 and the outer ring 106. The inner ring 104 includes a first load-bearing surface and a bore surface.The bore surface defines a bore through which the shaft 108 is inserted. The outer ring 106 includes a second load bearing surface. The plurality of rolling elements 105 are sized for rolling movement between the first load bearing surface and the second load bearing surface. Further, an electrically insulating material is positioned in a gap between the bore surface of the inner ring and the undercut. The gap defines a distance between the bore surface and the undercut.

[0025] In the rotating machine 100 illustrated in [Fig.l], the set of bearings 120a, 120b is two in number, a first set of bearings 102a and a second set of bearings 102b. The shaft 108 is supported at one end by the first bearing 102a and at another end by the second bearing 102b. For the sake of simplicity, the The preceding and following descriptions, when read with the accompanying figures, focus on the first bearing assembly 102a. It will be understood from the description that the configuration of the first bearing assembly 102a, described herein, also applies to the second bearing assembly 102b.

[0026] [Fig. 2A] illustrates the rotating machine 100 at A of [Fig. 1], the rotating machine 100 being configured in accordance with the present subject matter. [Fig. 2B] illustrates the rotating machine 100 of [Fig. 2A] without the electrically insulating material therein. [Fig. 2A] illustrates a first load-bearing surface 200 of the inner ring 104 and a second load-bearing surface 206 of the outer ring 106, and the plurality of rolling elements 105 sized for rolling motion therebetween. In the assembled state, the bearing 102 is rotatably connected to the shaft 108. In the assembled state, the electrically insulating material 210 is positioned in a space 212a, 212b as illustrated in [Fig. 2B]. The gap 212a, 212b is located between a bore surface 202 of the inner ring 104 and the undercut formed on the shaft 108. Furthermore, the gap defines a distance D1, D2 between the bore surface 202 and the undercut.The electrically insulating material 212, positioned in the space 212a, 212b, prevents the electric current from passing between the shaft 108 and the bearing 102.

[0027] According to an example of the present subject matter, an electrically insulating material is disposed between the outer ring 106 and the inner circumferential surface 114 of the housing 112. Accordingly, in an example where the housing 112 is electrically conductive, the electrically insulating material, positioned in the aforementioned manner, stops a flow of electrical current between the housing 112 and the bearing 102a, 102b. The aforementioned electrically insulating material may be a coating provided on an outer surface 208 of the outer ring 106.

[0028] [Fig. 3] illustrates a sectional view of the shaft 108 of the rotating machine 100 with the other components of the rotating machine shown. [Fig. 3] illustrates an undercut 300, mentioned in the preceding description, formed on the outer circumferential surface 110 of the shaft 108. surface 302. In [Fig. 3], the undercut 300 includes a bottom surface 302 and a side wall 304a, 304b on either side of the bottom surface 302. In one example, the undercut 300 is an annular groove formed circumferentially around the shaft 108. In the assembled state, the distance D1, D2 between the undercut 300 and the surface of the bore 202, defined by the gap 212a, 212b, is provided with the electrically insulating material 210. According to one aspect of the present subject matter, the gap 212a, 212b is filled with the electrically insulating material 210.

[0029] According to one aspect of the present subject matter, the space 212a, 212b comprises a first space 212a. The first space 212a is defined by a first distance D1 between the surface of the bore 202 and the lower surface 302 of the undercut 300. Further, the first gap 212a is configured to extend parallel to the central axis 116. In one example, when the bearing assembly 102a and the shaft 108 are assembled, the inner ring 104 is in an interference fit between the sidewalls 304a, 304b of the undercut 300. In such a configuration where the interference fit is achieved, the electrically insulating material 210 fills the first gap 212a. Therefore, a thickness value of the electrically insulating material 210 filled in the first gap 212a is equal to the first thickness Tl, the first thickness Tl being equal to the first distance Dl. In one example, the first thickness Tl has a thickness value selected between 3 microns and 50 microns. The first thickness Tl is chosen according to the needs and application of the bearing assembly 102a, 102b.Consequently, the first distance Dl has a value equal to the first thickness Tl.

[0030] According to one aspect of the present subject matter, the inner ring 104 of the bearing 102a, 102b comprises two ring walls 204a, 204b. An axial distance between the two walls 204a, 204b defines a width W of the inner ring 104. In one example, the inner ring 104 is in a loose fit with the undercut 300 of the shaft 108. In such a fit, illustrated in [Fig.l], 2A and 2B, the gap 212a, 212b further comprises a second gap 212b. The second gap 212b is defined by a second distance D2 between the side wall 304a, 304b and the annular wall 204a, 204b. In the example illustrated in [Fig.l], 2A and 2B, the second space 212b is disposed between the side wall 304a (or "first side wall 304a") of the undercut 300 and the annular wall 204a (or "first annular wall 204a") of the inner ring 104. In the assembled state, the first annular wall 204a is adjacent to the first side wall 304a.Therefore, the electrically insulating material 210 fills the second gap 212a with the second thickness T2, the value of the second thickness T2 being equal to the second distance DL. In one example, the second thickness T2 has a thickness value selected between 3 microns and 50 microns. The second thickness T2 is selected according to the needs and application of the bearing assembly 102a, 102b. Accordingly, the first distance D2 has a value equal to the second thickness T2. According to one aspect of the present subject matter, the second gap 212b extends radially from the central axis 116. Therefore, the first gap 212a and the second gap 212b are arranged perpendicular to each other. In the examples illustrated in FIGs.1, 2A and 2B, the arrangement of the first space 212a and the second space 212b (formed between the first side wall 304a and the first annular wall 204a) forms an L-shaped space which is circumferentially formed around the shaft, and the electrically insulating material 210 fills the L-shaped space.

[0031] In one example, the value of the first thickness T1 is equal to the second thickness T2. In this example, the first distance DI is equal to the second distance D2. Therefore, the value of the thickness of the electrically insulating material 210 is uniform in the first space 212a and the second space 212b.

[0032] According to another example of the present subject matter, the value of the thickness of the first thickness T1 differs from the value of the thickness of the second thickness T2. In the aforementioned example, the first distance DI differs from the second distance D2, the first distance DI being equal to the first thickness T1 and the second distance D2 being equal to the second thickness T2. The value of the thickness of the electrically insulating material 210 is uniform in the first space 212a and uniform in the second space 212b, although the value of the thickness of the electrically insulating material 210 in the first space 212a differs from the value of the thickness of the electrically insulating material 210 in the second space 212b.

[0033] In another example of the present subject matter, the arrangement of the inner ring 104 with the shaft 108 is such that the second gap is disposed between the side wall 304b (or "second side wall 304b") and the annular wall 204b (or "second annular wall 204b"). In the assembled state, the second annular wall 204b is adjacent the second side wall 304b. Therefore, in this example, the electrically insulating material 210 fills the second space between the second side wall 304b and the second side wall 304. In yet another example of the present subject matter, the arrangement of the inner ring 104 is such that the second space 212b is formed between the first side wall 304a and the first ring wall 204a, and in the space (not shown) between the second side wall 304b and the second ring wall 204b.Therefore, in the above-mentioned example, there are two second spaces 212b, and the electrical insulating material 210 fills the two second spaces 212b (one of the two second spaces 212b being between the first side wall 304a and the first ring wall 204a; and the other of the two second spaces 212b being between the second side wall 304b and the second ring wall 204b). Accordingly, due to the first space 212a and the two second spaces 212b, a U-shaped space formed circumferentially around the shaft is filled with electrical insulating material 210.

[0034] According to an example of the present subject matter, the electrically insulating material 210 is aluminum oxide or a suitable aluminum alloy that has electrically insulating properties.

[0035] Various modifications to the disclosed embodiments, as well as other embodiments of the subject matter, will become apparent to those skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications may be made without departing from the scope of the present subject matter.

Claims

Claims

1. A rotating machine (100) comprising: a housing (112) including an inner circumferential surface (114); a shaft (108) rotatable about a central axis (116) and including an undercut (300) formed on an outer circumferential surface (110) of said shaft (108), the undercut (300) being defined by a bottom surface (302) and a side wall (304a; 304b) on either side of the bottom surface (302); a bearing (102a; 102b), disposed between the outer circumferential surface (110) and the inner circumferential surface (114), comprising: an inner ring (104) having a first load-bearing surface (200) and a bore surface (202) defining a bore through which the shaft (108) is inserted; an outer ring (106) disposed spaced from the inner ring (104), said outer ring (106) having a second load-bearing surface (206);and a plurality of rolling elements (105) arranged in contact with the inner ring (104) and the outer ring (106), and dimensioned to have rolling movement between the first load-bearing surface (200) and the second load-bearing surface (206), characterized in that an electrically insulating material (210) is positioned in a space (212a; 212b) between the bore surface (202) of the inner ring (104) and the undercut (300), wherein the space (212a; 212b) defines a distance (DI; D2) between the bore surface (202) and the undercut (300).;

2. A rotating machine (100) according to the preceding claim, wherein the space (212a; 212b) comprises a first space (212a) defined by a first distance (Dl) between the surface of the bore (202) and the lower surface (302) of the undercut (300), and wherein the first space (212a) extends parallel to the central axis (116).

3. A rotating machine (100) according to any preceding claim, wherein the space (212a; 212b) comprises a second space (212b) defined by a second distance (D2) between an annular wall (204a; 204b) of the inner ring (104) and the side wall (304a; 304b) of the undercut (300), said side wall (304a; 304b) being adjacent to said annular wall (204a; 204b), and in which the second space (212b) extends radially from the central axis (116).

4. A rotating machine (100) according to claim 2, wherein the electrically insulating material (210) disposed in the first space (212a) has a first thickness (Tl) equal to the first distance (Dl).

5. A rotating machine (100) according to claim 3, wherein the electrically insulating material (210) disposed in the second space (212a) has a second thickness (T2) equal to the second distance (Dl).

6. A rotating machine (100) according to claims 4 and 5, wherein the first thickness (T1) has a thickness value of between 3 microns and 50 microns, and the second thickness (T2) has a thickness value of between 3 microns and 50 microns.

7. Rotating machine (100) according to the preceding claim, in which the value of the first thickness (T1) differs from the value of the second thickness (T2).

8. Rotating machine (100) according to the preceding claim, in which the value of the first thickness (T1) is equal to the value of the second thickness (T2).

9. A rotating machine (100) according to any preceding claim, wherein the electrically insulating material (210) is aluminum oxide.

10. A rotating machine (100) according to any preceding claim, wherein the undercut (300) is an annular groove formed circumferentially around the shaft (108).

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