MXPA00001761A - Paired interlocks for stacking of non-rotated lamination cores - Google Patents

Abstract

A rotor core is formed from a stack of laminations. The core includes a plurality of generally circular laminations in a stacked formation one on top of each other. Each lamination defines an axis collinear with an axis of each other lamination in the stacked formation. The laminations each have first and second surfaces and the stack is configured to define at least one inner lamination having laminations adjacent to both its first and second sides and outer laminations having laminations adjacent to only one of its first and second sides. Each lamination has a predetermined number of circumferencially equally spaced slots that define conductor receiving regions. Each inner lamination includes at least one interlocking projection extending from one of the first and second surfaces thereof, at a predetermined radial distance from the lamination axis. Each lamination further defines at least one projection receiving region formed therein for receiving a projection from an adjacent lamination. When viewing the laminations stacks parallel to the axis, the projections are engaged in their respective projection receiving regions so as to define a staggered path of projection and receiving region engagements through the lamination stack. This staggered path configuration defines an elongated, tortuous path having a length greater than a height of the stack for eddy currents through the lamination stack, to increase impedance of an eddy current path therethrough.

Description

BLOCKED INTERLOCKS TO STACK NON-RIGATED LAMINATION NUCLEUS Field of the Invention The present invention relates generally to electric motors and more particularly to matched interlocks for the stacking of non-rotated rolling cores, and to a method for making said cores. BACKGROUND OF THE INVENTION Electric motors have a wide use and impact in every aspect of industrial, commercial and residential life. These motors can vary from small, fractional motors that can be found, for example, in washing machines and refrigerators, to large industrial applications to activate manufacturing equipment, fans and similar. Motors are commonly used to convert electrical energy into rotary energy or rotational force. Commonly, an engine includes a rotating central portion called a rotor, and a stationary outer portion called a stator. The stator and the rotor are housed in a housing containing the motor. The rotor and the stator contain electrical conductive elements. The stator and rotor cores can be formed with a varied number of slots, which are the openings that receive the electrical conductive elements. A rotor core is the central portion of the rotor that contains the conductive elements. The number of bars in the cores of the rotors can vary considerably. In smaller fractionated squirrel-cage motors, for example, those having rotor diameters of approximately 5.08 cm, the number of bars is generally between 8 and 52. The core structure is commonly formed as a plurality of stacked plates or laminations . The laminations, which can be made of metal, can be punched in a press and subsequently piled on top of each other to form the core. In some cores, the laminations are rotated in relation to each other to consider possible asymmetries in the rolling material. In other non-rotated cores, the laminations can simply be stacked one on top of the other and interlocked therebetween to form a rigid core structure, and to prevent the laminations from moving relative to one another. In a known interlocking configuration, each lamination has a recess or depression punched in the surface, which forms a corresponding projection on the opposite side of the lamination. Then, the laminations are stacked one on top of the other with the projections of one lamination engaging and resting on the recess in the next adjacent lamination. In this nested configuration, the laminations are maintained in alignment between them by coupling the projections and recesses. This is a common and accepted method for interlocking laminations. Although such known methods are a common practice, they have their disadvantages. First, this direct embedded configuration provides a relatively short path and therefore, a low impedance current path for eddy currents. This, as will be recognized by those skilled in the art, can cause an increase in magnetic losses through the core. This configuration reduces the efficiency of the motor from which the stator core is built. Accordingly, it remains a need to have a rotor core lamination interlock configuration that facilitates the fabrication of laminations and rotor cores thereof whose interlocking configuration produces a high impedance current path * to reduce electromagnetic losses through the rotor. Brief Description of the Invention A rotor core for use in a dynamo-electric rotary machine is formed from a stack of laminations. The core includes a plurality of generally circular laminations in a formation stacked one on top of the other. Each lamination defines an axis that is collinear with one axis of each other lamination in the stack. Each lamination includes first and second surfaces, and the stack is configured to define at least one internal lamination having laminations adjacent to the first and second sides and external laminations having laminations adjacent to only one of the first and second sides. Each lamination is formed with a predetermined number of equidistantly spaced circular grooves formed therein. The slots are separated from the adjacent slots to define regions that receive conductors. Each internal lamination includes at least one interlock projection formed on one of the first and second sides, the projection of which is formed at a predetermined radial distance from the rolling axis. Each projection is formed to extend out of a plane of one of the first and second sides. Each lamination additionally includes at least one shadow or projection receipt region formed therein to receive a projection of an adjacent lamination. When the lamination stack is observed parallel to the axis, the projections are coupled in corresponding shadows to define an alternate path of shadow and projection couplings through the lamination stack. This alternate trajectory of shadow and projection couplings defines a tortuous path having a length greater than a stack height, so that eddy currents through the lamination stack increase the impedance of a parasitic path therethrough. In a preferred core, each lamination includes a plurality of projection receiving regions and a plurality of projections. Preferably, the laminations are configured so that each receiving region can receive any of the projections from an adjacent lamination. In one configuration, the projection has an elongated arched shape, and the projection receiving region has an arcuate, elongated and complementary shape to fully receive a projection of an adjacent lamination. The receiving region may have a length that is greater than a length of the corresponding projection. Other aspects, benefits and advantages of the present invention will be apparent from the following figures, detailed description and appended claims. Description of the Drawings Figure 1 is an exploded perspective view of an exemplary engine, illustrating a rotor and having a core formed in accordance with the principles of the present invention; Figure 2 is a perspective view of a rotor core formed of a stacked plurality of laminations including a mode of a matched interlocking system; Figure 3 is a top perspective view of one of the laminations of the core of Figure 2; Figure 4 is a bottom perspective view of the lamination of Figure 3; Figure 5 is an enlarged view of the lam ination of the Figure 4, illustrating an interlocking projection; Figure 6 is a partial sectional view of the rolling stack taken along line 6-6 of Figure 2; Figure 7 is a partial sectional view taken along line 7-7 of Figure 5; Figure 8 is a partial perspective view of a lamination including an alternative embodiment of the matched interlocking system; and Figures 9A-9E illustrate various alternative projection forms for the interlock system of the present invention. Detailed Description of the Invention Although the present invention is susceptible to modality in various forms, currently preferred embodiments and methods are shown and described in the drawings with the understanding that the present disclosure should be considered an exemplification of the invention and not it is intended to limit the invention to the specific embodiments illustrated and the methods described. Referring now to the Figures and in particular to Figure 1, there is shown an engine generally illustrated at 10. The engine 10 is housed in a housing 12 and includes a rotor 14 and a stator 16. The stator 16 is the stationary portion of the motor 10 which is mounted to, and inside the housing 12. The stator 16 defines a longitudinal axis indicated at 18, through it. The rotor 14 is the rotating portion of the motor 10 which is placed in the stator 16. The rotor 14 also defines a longitudinal axis, indicated at 20, which is aligned with the stator 16 so that the axes 18, 20 of the rotor 14 and Stator 16 are collinear. The rotor 14 is placed in the stator 16 to define a clearance, called the air space, indicated 22. The space 22 allows the rotor 14 to rotate freely in the stator 16 without the rotor 14 and the stator 16 making contact among them inadvertently. In a typical, small fractional motor, for example, less than one horsepower, space 22 may be approximately 0.0254 cm. The rotor 14 is formed of a plurality of plates or laminations 24 that are stacked one on top of the other. The laminations 24 are secured in place in relation to each other by an interlock system indicated generally at 26. The interlocking system 26 prevents the laminations 24 from rotating and moving relative to each other and separating therefrom, and thus, maintains the core 28 as a unitary member during manufacture. As illustrated in Figures 2 and 3, the core 28 includes a predetermined number of slots 30 formed therein at one edge or periphery 32 of each lamination 24. The slots 30 are defined by teeth 34 that separate the slots 30 therebetween. . In a typical rotor lamination 24, the teeth 34 are integral with the central rolling portion 36. The spaces between the teeth, i.e. the slots 30, are configured to receive and secure conductive elements, an example of which is indicated at 38 in Figure 2. In an exemplary fraction engine, the conductors 38 are each formed as a single mass of, for example, aluminum that has been injected into the slots 30 in molten form. This type of rotor manufacturing is commonly called a squirrel-cage engine. The plates or laminations 24 are generally formed of sheet material, such as lamellar steel, which has been stamped in the shape of the laminations 24. Then, the individual laminations 24 are stacked, one on top of the other, to form the core. Although some cores 28 are formed using a rotation process wherein each lamination 24 is rotated a predetermined number of degrees relative to the next adjacent lamination 24, certain cores 28 do not require such rotation. Commonly, these non-rotated cores 28 can be formed of materials in which the material thickness tolerance is controlled or the cores 28 themselves can be subject to a post-manufacturing turning operation to ensure that the core 28 is formed of a symmetrical way. In some cases, the core mass 28 may be too large to rotate the laminations 24 or there may simply be no need to control the dimensions of the core 28. However, said cores 28 nevertheless require an interlock configuration 26 to ensure that the laminations 24 remain fixed among them. The present invention utilizes an interlock system 26 which includes a raised tab 44 which is formed on a surface 46 of the lamination 24 and a corresponding projection receiving region, aperture or shadow 48 in the next adjacent lamination 24 in which resides the lug or projection 44.

In a preferred embodiment, the projection 44 has a main portion 50 and a rear portion 52. The main portion 50 can be staggered as shown in Figure 5. Essentially, the main portion 50 is the uppermost portion raised from the surface 46. of the lamination 24. The rear portion 52 can taper or form a downward ramp from the main portion 50, forming the slope toward the surface 46 of the lamination 24. As best seen in Figure 5, the projection 44 can define an arcuate shape along its circumferential length as indicated by Lp so that the center line, as indicated at 54, remains at a fixed radial distance dp from the rolling axis, i.e. the axis of the rotor 20. A Unlike the known interlocks using a series of projections that are fixed or nested between them in a fixed relationship and at a fixed position, the projections 44 of the present invention they are received in the shadows or openings 48 that are also formed in the lamination 24. The shadows 48 may be elongated to receive the projections 44 along the length of the open region and to thereby allow the projection 44 to reside fully in the shadow 48. Similar to projection 44, shadow 48 is preferably arcuate so that a central line of the shadow indicated at 56 is at a fixed radial distance d from the axis (rotor axis 20) equal to the radial distance dp of the projection 44 of axis 20. Preferably, projections 44 and shadows 48 are matched therebetween and each shadow 48 has a circumferential length Ls that is longer than the length Lp of its corresponding projection 44. The present invention provides a number of advantages over the nested depression projection configuration. Particularly, the present invention provides a higher impedance current path for eddy currents through the core 28. Those skilled in the art will recognize that this results in a reduction of electromagnetic losses in the core 28, which in turn produces a more efficient motor . More specifically, as illustrated in Figure 6, each interlocking location 26 in a series of laminations 24 alternates between its shadow position 48 and its projection position 44. As such, the path for eddy currents is no longer a straight path through the core 28 as in the nested depression projection configuration, but is a tortuous path resembling a zigzag configuration rather than a straight line path through the core 28. This path length increased and the resulting increased resistance to eddy currents reduces the electromagnetic losses through the core. As is evident from Figure 6, the trajectory thus created is longer than the height of the rolling stack 24 or core 28. A wide variety of corresponding projections and shadow shapes can be used to carry out the present invention. For example, as illustrated in Figures 9A-9E, the projections may take the form of raised, circular or oval solid elements 144, rectangular raised elements 244, raised square elements 344, as well as elongated, curved raised elements 444 and elements in the form of a "tie bow" 544. As will be apparent from the Figures, the shadow configurations 148, 248, 348, 448 and 548 are complementary to the projection configurations 144, 244, 344, 444 and 544, respectively . In a contemplated configuration, two or more projections 144-544 may be placed in a single shadow 148-548. A preferred method for manufacturing a rotor core 28 of said laminations 24 includes drilling a first lamination 24 with a predetermined number of interlocking torque locations (corresponding to the projection 44 and shadow 48). Each interlocking pair has a projection 44 and a corresponding shadow 48 positioned equidistant from the axis of the lamination 20 (i.e., rotor). The projection 44 and its corresponding shadow 48 are placed at a predetermined radial distance therebetween or at a predetermined angle a relative to the lamination 24a on the axis 20 (Figure 2). A second lamination, for example, the lamination 24b is perforated and has a predetermined number of projection pairs 44 and shadow 48. The projections 44 and the shadows 48 are in opposite relationship to those formed in the first lamination 24a. Then, the second lamination 24b is stacked on the first lamination 24a, so that the projection 44 of the first lamination 24a resides in the shadow 48 of the second lamination 24b, or the projection 44 of the second lamination 24b resides in the first lamination 24a of shade 48. Preferably, a last lamination 24z in core 28 is formed having only shadows 48 therein and does not include any projection in lamination 24z. Since the core 28 is of the "non-rotated" type, there is no limitation or restriction as to the number of interlocking pairs or the spacing of the corresponding projections 44 and the shadows 48. In this way, the laminations 24 can be formed with any number of corresponding projections 44 and shadows 48 and the only limitation is in terms of the consistency of the radial distance dp, ds of the projections 44 and the shadows 48 of the rolling axis 20 and the consistency in the circumferential distance, i.e. the angle a between projections 44 and corresponding shades 48. Since the core 28 is formed of non-rotated laminations 24, the projections 44 can be used, to a certain degree, to consider possible asymmetries in the core 28. That is, the projections 44 can be used to "wedge" the laminations 24 in relation to between them to adjust minor and similar inconsistencies in the rolling stock. From the above it will be noted that numerous modifications and variations can be made without departing from the true spirit and scope of the novel concepts of the present invention. It should be understood that no limitation is intended or inferred with respect to the specific modalities illustrated or the methods presented. The description is intended to cover, by means of the appended claims, all modifications that are within the scope of the claims.

Claims (8)

1. CLAIMS 1.A rotor core formed of a stack of laminations comprising: a plurality of generally circular laminations in a formation stacked on top of each other, each of said laminations defining an axis thereto which is collinear with an axis of each one of said laminations in said stacked formation, each of said laminations has first and second laminations, the stack is configured to define at least one internal lamination having laminations adjacent to both of said first and second sides and the outer laminations have laminations adjacent to one of such first and second sides, each of said laminations has a predetermined number of equally spaced circumferentially spaced apart grooves formed in an edge of said lamination, each of said grooves being separated from the grooves adjacent to the lamination. same to define regions of driver reception, each of such the Internal shims includes at least one interlock projection formed in one of said first and second surfaces at a predetermined radial distance from said axis, said at least one projection being formed to extend out of a plane of one of said first and second surfaces. , each lamination additionally defines at least one projection receipt region formed therein to receive a projection of an adjacent lamination, wherein when said stack of laminations is observed parallel to said axis, said projections are coupled in such regions of projection receipt for defining an alternate projection path and receiver region couplings through said stack of laminations to define a tortuous, elongated path having a length greater than a height of such stack for eddy currents through the stack of laminations to increase the impedance of a trajectory of eddy current through it.
2. 2. The rotor core according to claim 1, wherein each of said laminations includes a plurality of projection receiving regions.
3. 3. The rotor core according to claim 1, wherein each of said laminations includes a plurality of projections.
4. 4. The core of the rotor according to claim 1, wherein at least one projection has an arcuate, elongated shape and wherein at least one projection receiving region has an arched, elongated shape complementary to said at least one a projection 5.
5. The rotor core according to claim 4, wherein said projection receiving region has a length that is longer than a length of its corresponding projection.
6. The rotor core according to claim 1, which includes at least two projections and at least two corresponding projection receipt regions, wherein each of said laminations is configured so that each of said regions Projection receipt is adapted to receive each of the aforementioned projections.
7. The rotor core according to claim 1, wherein the at least one projection provides a wedge between the laminations.
8. 8. The rotor core according to claim 1, wherein the at least one shadow simultaneously accommodates more than one projection.