CLOSING SYSTEM BETWEEN A CAP AND A STATOR IN AN ELECTRIC MACHINE, PROCESS FOR CLOSING BETWEEN A CAP AND A STATOR IN AN ELECTRIC MACHINE AND STATOR FOR AN ELECTRIC MACHINE

Abstract

A closure system between the cap and the stator in an electric rotating machine, wherein the stator (1) comprises at least one closure hole (1a) defining an inner wall (1b). The cap (2) comprises at least one contact portion (2a), the end of the contact portion comprising at least one through-hole (2c); the through-hole (2c) being substantially aligned with the closure hole (1a) when the end of the contact portion (2a) contacts the stator (1); and wherein a polymer (P) is injected through the through-hole (2c) in the inner wall (1b) of the closure hole. In the closing process of the present invention, the concentricity between the rolling bearing and the stator rotor accommodating bore is ensured by the fact that the geometry of the rolling bearing receiving portion (2e) allows the alignment to be made on the basis of the outer race (E) of the rolling bearing when it is already accommodated in the receiving portion (2e).

Claims

1. A closure system between a cap and a stator in a rotating electric machine, characterized in that: the stator (1) comprises at least one closure hole (1a) defining an inner wall (1b); the cap (2) comprises at least one contact portion (2a), the end of the contact portion comprising at least one through-hole (2c); the through-hole (2c) being substantially aligned with the closure hole (1a) when the end of the contact portion (2a) contacts the stator (1); in which a polymer (P) is injected through the through-hole (2c) into the inner wall (1b) of the closure hole.

2. The closure system according to claim 1, characterized in that the inner wall (1b) of the closure hole (1a) has at least one recess (1c).

3. The closure system according to claim 2, characterized in that the contact portion (2a) is a leg whose end (2b) comprises a flat wall with the through-hole (2c).

4. The closure system according to claim 3, characterized in that the end (2b) comprises a polymer receiving portion (2d) surrounding an edge of the through-hole (2c).

5. The closure system according to claim 3, characterized in that the cap comprises a rolling bearing receiving portion (2d) comprising a radially resilient central portion (20) configured to exert pressure on an outer race of a rolling bearing, the radially resilient central portion (20) comprising a plurality of wall segments (20a) arranged to form a circular central portion, a circular perimetric portion (21) and a plurality of connecting segments (22) extending between the circular perimetric portion (21) and the radially resilient central portion (20).

6. A process for closing between a cap and a stator in a rotating electric machine, characterized by comprising: providing a stator (1) comprising at least one closure hole (1a) and a rotor accommodating bore (1e), the closure hole (1a) defining an inner wall (1b); providing a cap (2) comprising at least one contact portion (2a) and a rolling bearing receiving portion (2e) which receives a rolling bearing having an outer race (E), the end of the contact portion comprising at least one through-hole (2c); aligning the cap (2) with the stator (1) so that the outer race (E) is aligned and concentric with the rotor accommodating bore (1d) and the through-hole (2c) is aligned with the closure hole (1a); and injecting a polymer (P) through the through-hole (2c) into the inner wall (1b) of the closure hole.

7. The process according to claim 6, characterized in that the step of aligning the cap (2) with the stator (1) is carried out with the aid of an alignment device (3).

8. The process according to claim 6, characterized in that it comprises providing two caps (2) at axially opposite ends of the stator, wherein the two caps (2) are aligned with the stator (1), so that the outer race of the respective bearing of each cap is aligned and concentric with the rotor accommodating bore (1d).

9. A stator for an electric rotating machine, the stator (1) comprising a plurality of stacked and pressed blades and being characterized in that it comprises at least one closure hole (1a) defining an inner wall (1b), the wall (1b) having at least one recess (1c).

10. The stator according to claim 9, characterized in that the ate least one recess is formed by machining the inner wall (1b).

11. The stator according to claim 9, characterized in that the inner wall (1b) has a plurality of recesses (1c) and the recesses (1c) are formed automatically in the stamping process by means of punches with two different diameters and with the stacking carried out through turns of the stator blades.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1is a perspective view of the caps and stator assembly of the machine according to an embodiment of the present invention; the assembly being positioned for closing;

[0028] FIG. 2is a cross sectional view of caps and stator assembly of the machine according to an embodiment of the present invention; the assembly being positioned for closing;

[0029] FIG. 3is a top view of the cap according to an embodiment of the present invention;

[0030] FIG. 4is a top perspective view of the cap according to an embodiment of the present invention;

[0031] FIG. 5is a bottom perspective view of the cap according to an embodiment of the present invention;

[0032] FIG. 6is a schematic view of the polymer used by the closing system of the present invention, the polymer being illustrated as it would be after solidifying; and

[0033] FIG. 7is a schematic illustration of the closing between the upper cap and a stator, an alignment device being also shown.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described hereinafter based on examples of preferred embodiments shown in FIGS. 1 to 7.

[0035] FIGS. 1, 2 and 7 the stator and caps assembly of a rotating electric machine. FIGS. 1 and 2 show the assembly in the closed position, and FIG. 7 schematically shows the upper cap being engaged for closure.

[0036] FIG. 1 shows a stator core 1 formed mainly by a plurality of stator blades. The detailed construction of this kind of stator is known to those skilled in the art and will not be discussed here.

[0037] The stator is preferably manufactured of steel, but other materials could be used. As better shown in FIGS. 2 and 7, the stator has at least one region with a closure hole 1a. The closure hole 1a defines a substantially tubular inner wall 1b. Preferably, the stator has four closure holes 1a, and each hole is disposed spaced from one another, for example, at the corners of the stator 1.

[0038] Naturally, when the stator has non-rectangular blades, the holes are arranged in a spaced configuration in the vicinity of the edges of the plates.

[0039] As known to those skilled in the art, the stator also has a central bore 1d which accommodates the rotor.

[0040] An end cap 2 is fixed to each end of the stator core. The construction of an end cap is known to those skilled in the art, so that the cap features which will be detailed are those relevant to the understanding of the inventive solution described herein.

[0041] Other components of the moving core of the electric machinefor example, rotor and shaftare fully known to those skilled in the art and therefore will not be described in detail herein.

[0042] As better shown in FIGS. 3 to 5, each end cap has at least one contact portion 2a formed to contact the stator core 1 for closing (attachment) between the parts.

[0043] As known to those skilled in the art, the end cap has a central portion 2d which receives rolling bearings, such as ball bearings. For correct assembly of the electric machine, it is necessary to ensure concentricity between the cap's rolling bearing and the region (central bore 1d) that accommodates the rotor in the stator.

[0044] In the closure system of the present invention, the end 2b of the contact portion 2a comprises at least one through-hole 2c. As shown in the figures, the contact portion 2a may comprise a leg 2a and the end 2b may comprise, for example, a flat wall 2b with the through-hole 2c. It should be emphasized, however, that the contact portion could be a continuous wall or even spaced wall segments.

[0045] In the embodiment shown in the figures, each end cap has four contact legs. However, the number of legs could be greater or lesser depending on the design of the contact portion. Naturally, the number of closure holes of the stator may also vary, so that each contact leg corresponds to a closure hole of the stator.

[0046] Additionally, in the embodiment shown in the figures, the four contact legs 2a are arranged spaced apart such that each leg is close to each of the stator core corners when mounting the assembly. In this case, the stator core has a corresponding closure hole in each corner,

[0047] Naturally, when the stator is formed by circular or non-rectangular blades, the contact legs 2a will be arranged in spaced locations so that they can match the stator holes.

[0048] During assembly for the closing between the stator 1 and the cap 2, the through-hole 2c is substantially aligned with the closure hole 1a. Thus, for the closure, i.e., for the attachment of the cap 2 to the stator 1, a polymer P is injected through the through-hole 2c into the closure hole.

[0049] The polymer used may be any suitable polymer such as, for example, the Technyl A 216 polymer. The polymer may be injected by any means known in the art, such as with an injector arranged in the closing positioning structure or with an independent injection device.

[0050] As best shown in FIGS. 3 to 5, the contact legs 2a may have a polymer receiving portion 2d proximate to the through-hole 2c. The receiving portion 2d may take the form of a recess at the end 2b, the recess surrounding the edge of the through-hole 2c.

[0051] Thus, for the locking, the polymer P fills the through-hole 2c and the polymer receiving portion 2d, locking together the cap and the stator.

[0052] The injected polymer secures the cap to its position, so that the polymer absorbs all variations in the positioning. In addition, with the use of the polymer as a fastener, there is no need for riveting of the parts nor for the use of an additional fastening element (such as a screw or the like).

[0053] As best shown in FIG. 2, in the preferred embodiment of the present invention, the inner wall 1b of the closure hole 1a has at least one recess 1c, Preferably, the inner wall 1b of the closure hole 1a has a plurality of recesses 1c.

[0054] The recesses 1c function as regions for anchoring the injected polymer, so that the differences in the coefficient of thermal expansion of the stator metallic material (steel) and plastic do not affect the dimension of the assembly, avoiding relative displacements between the different materials when heated due to the motor operating temperature.

[0055] The recesses 1c may be formed in any suitable manner. For example, the recesses may be formed by machining

[0056] Preferably, the recesses are formed automatically in the stamping process by means of punches with two different diameters and with the stacking performed through turns of the stator blades. The amount of stacked blades with each diameter type is variable as it depends on the programming performed during stamping and stator package formation.

[0057] In one embodiment, the stacking is performed in 90 rotations, but smaller (e.g., 45) or larger (e.g., 135) rotations could also be used.

[0058] While in the embodiment shown in the figures the inner wall 1b of the closure hole 1a comprises a plurality of circular recesses 1c spaced apart in relation to the axis of the inner wall 1b, it should be noticed that the recesses could have any shape and any spatial distribution in the closure hole 1a.

[0059] FIG. 6 shows the polymer P in the configuration in which it would be after being solidified. Thus, upon injection and solidification, the polymer P has a cylindrical wall P1 corresponding to the inner wall 1b of the closure hole 1a, shoulders P2 corresponding to the recesses 1c of the closure hole 1a, an enlarged end portion P3 corresponding to the polymer receiving portion 2d of the contact portion 2a, and a transition portion P4 corresponding to the through hole 2c of the contact portion 2a.

[0060] It will be understood that the closure process of the present invention is that of assembly or closure between the cap (or caps) and the stator. Thus, the closing process comprises locking, attaching or mounting together the cap and the stator,

[0061] In the closing process of the present invention, the stator and the cap, or the caps, are disposed in a positioning structure having an alignment device 3 (see FIG. 7).

[0062] The positioning structure, equipped with the alignment device 3, allows assembly between the cap and the stator (when two caps are used, the assembly can be performed with the two caps simultaneously or separately). The alignment device 3 determines the desired positioning (concentricity).

[0063] One of the main advantages obtained with the present invention is the possibility of significantly improving the concentricity between the bearing and the rotor accommodating bore.

[0064] One of the factor that further improves this concentricity in the closing system of the present invention is the fact that the geometry of the rolling bearing receiving portion 2e allows the alignment to be made with reference to the outer race E of the rolling bearing already accommodated in the receiving portion 2e (see FIG. 7). That is, since the rolling bearing is visible on the cap, it is possible to align the stator bore 1d with the outer race E of the rolling bearing itself, significantly improving concentricity.

[0065] To that end, as best seen in FIGS. 3 to 5, the rolling bearing receiving portion 2e may comprise a radially resilient central portion 20 configured to exert pressure on the outer race of the rolling bearing.

[0066] The resilient central portion 20 comprises a plurality of wall segments 20a arranged to form a circular central portion.

[0067] The elasticity or resiliency of the receiving portion is achieved by the geometry of the cap which comprises a circular perimetric portion 21 and a plurality of connecting segments 22 extending between the circular perimetric portion 21 and the radially resilient central portion 20.

[0068] As can be seen in FIGS. 4 and 5, each connecting segment 22 comprises a first end attached to the circular perimetric portion 21 and a second split end, with a first portion attached to a first of the wall segments 20a of the radially resilient central portion 20 and a second portion attached to one adjacent of the wall segments.

[0069] The closing process comprises aligning, with the aid of the alignment device 3, the cap 2 with the stator 1, so that the outer race E of the rolling bearing is aligned and concentric with the rotor accommodating bore 1d and the through hole 2c is aligned with the closing hole 1a. The reference used for alignment is the outer race of the rolling bearing.

[0070] In that sense, as shown in FIG. 7, the alignment device 3 includes projections 3a, so that, upon alignment, each projection 3a is disposed between the two-part ends of the connecting element 22. In this way, the tool is able to position itself in the vicinity of the bearing receiving portion 2e, so that the alignment is made with the outer race E of the bearing received in the receiving portion 2e.

[0071] It is important to note that although the closing process of the present invention requires the outer race E of the bearing to be aligned and concentric with the rotor accommodating hole 1d, it is sufficient that the through hole 2c is aligned with the closing hole 1a is enough to form a channel for receiving the polymer.

[0072] After alignment, the polymer P is injected through the through-hole 2c into the inner wall 1b of the closure hole.

[0073] The cap 2 is formed in one piece from an aluminum injection process, however, any suitable material could be used.

[0074] Thus, the closure solution proposed by the present invention eliminates the need for rivets or other fastenings between the caps and the stator, while ensuring concentricity between the cap and the stator.

[0075] Having described examples of the preferred embodiments of the closure system of the present invention, it should be understood that the scope of the present invention encompasses other possible variations of the inventive concept described, being limited solely by the wording of the appended claims, including the possible equivalents.