Patent Application
20180262076
The present invention relates to a closure system between the caps of an electric machine and a stator of an electric machine.
Rotating electrical machines are widely known in the art, and basically comprise a static part (stator) and a rotating part (rotor). In a simplified manner, the stator comprises a plurality of plates stacked and pressed to form a block or package, known as the stator core. These plates are commonly called stator blades,
In some constructions of electric machines, the caps of the electrical machine are attached to the stator block by rivets. This construction requires a careful observation of the concentricity between the cap and the stator, so that the assembly is achieved within a suitable tolerance threshold.
In addition to the matter of concentricity in the assembly, the riveting process itself can cause shifts of the blades of the stator package due to buckling of the rivets and/or reinforcements under the package during the pressing operation needed for the attachment. That is, the buckling of the rivet can cause its lateral displacement towards the blade package, moving the blades towards the rotor and reducing the machine air gap.
Additionally, the efforts needed to deform the rivets compromise the correct positioning of the cap since the absorption of forces exerting lateral efforts may displace the cap from the correct position.
The present invention seeks to provide a closure system between the cap and the stator in an electrical machine which eliminates the need for a component manufacturing process having a high dimensional accuracy.
The present invention also seeks to provide a closure system between the cap and the stator in an electrical machine that allows the attachment of a cap manufactured by an injection process without this cap having to be machined nor manufactured with high dimensional accuracy,
The present invention also seeks to provide a closure system between the cap and the stator in an electric machine which eliminates the need for riveting between the cap and the stator.
The present invention also seeks to provide a closure system between the cap and the stator which allows centralization of the assembly using the outer face of the rolling bearing as a reference.
The present invention also seeks to provide a closure process between the cap and the stator in an electric machine which ensures concentricity between the cap and the stator.
The present invention also seeks to provide a stator for a rotating electric machine which enables the cap to be secured by the injection of a polymer.
The present invention also seeks to provide a closure process between the cap and the stator in an electric machine which eliminates the need for rivets or other fastening elements.
The present invention achieves the above objectives by means of a closure system between the cap and the stator in a rotating electric machine, wherein the stator comprises at least one closure hole defining an inner wall; the cap comprises at least one contact portion, the end of the contact portion comprising at least one through-hole; the through-hole being substantially aligned with the closure hole when the end of the contact portion contacts the stator; wherein a polymer is injected through the through-hole into the inner wall of the closure hole.
Preferably, the inner wall of the closure hole has at least one recess, and the contact portion is a leg whose end comprises a flat wall with the through-hole.
The end of the leg may comprise a polymer receiving portion surrounding an edge of the through-hole.
The cap may further comprise a rolling bearing receiving portion for receiving a rolling bearing having an outer race, with radially resilient central portion configured to exert pressure on the outer race of the rolling bearing, the radially resilient central portion comprising a plurality of wall segments arranged to form a circular central portion, and a plurality of connecting segments extending between the circular perimetric portion and the radially resilient central portion.
The present invention also contemplates a process for closing between the cap and the stator in a rotating electric machine, comprising the steps of:
providing a stator comprising at least one closure hole and a rotor accommodating bore, the closure hole defining an inner wall;
providing a cap comprising at least one contact portion and a rolling bearing receiving portion which receives a rolling bearing having an outer race, the end of the contact portion comprising at least one through-hole;
aligning the cover with the stator so that the outer race of the bearing is aligned and concentric with the rotor accommodating bore and the through-hole is aligned with the closure hole; and
injecting a polymer through the through-hole into the inner wall of the closure hole.
Preferably, the step of aligning the cap with the stator is performed with the aid of an alignment device.
The closing process may comprise simultaneously closing with two caps disposed at axially opposing ends of the stator, wherein the two caps are aligned with the stator do that the outer race of the respective bearing of each cap is aligned and concentric with the rotor accommodating bore.
The present invention also relates to a stator for a rotating electric machine, the stator comprising a plurality of stacked and pressed blades and comprising at least one closure hole defining an inner wall, the inner wall having at least one recess.
In an embodiment, the recesses are formed automatically in the stamping process by punches having two different diameters and with the stacking performed through turns of the stator blades.
Alternatively, the recesses may be machined in the inner wall.
The present invention will be described hereinafter based on examples of preferred embodiments shown in
The stator is preferably manufactured of steel, but other materials could be used. As better shown in
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.
As known to those skilled in the art, the stator also has a central bore 1d which accommodates the rotor.
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.
Other components of the moving core of the electric machine—for example, rotor and shaft—are fully known to those skilled in the art and therefore will not be described in detail herein.
As better shown in
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.
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.
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.
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,
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.
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.
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.
As best shown in
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.
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).
As best shown in
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.
The recesses 1c may be formed in any suitable manner. For example, the recesses may be formed by machining
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.
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.
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.
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,
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
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).
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.
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
To that end, as best seen in
The resilient central portion 20 comprises a plurality of wall segments 20a arranged to form a circular central portion.
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.
As can be seen in
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.
In that sense, as shown in
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.
After alignment, the polymer P is injected through the through-hole 2c into the inner wall 1b of the closure hole.
The cap 2 is formed in one piece from an aluminum injection process, however, any suitable material could be used.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 62469951 | Mar 2017 | US |
