HK1136385B

HK1136385B - An inductive device, a constructing method and producing process for bulk amorphous metal magnetic component

Info

Publication number: HK1136385B
Application number: HK10103296.3A
Authority: HK
Inventors: J. Decristofaro Nicholas; E. Fish Gordon; M. Lindquist Scott; E. Kroger Carl
Original assignee: Metglas, Inc.
Priority date: 2003-04-25
Filing date: 2010-03-30
Publication date: 2013-06-21

Description

Inductance device, method for constructing amorphous metal magnetic element and production process

Background

1. Field of the invention

The present invention relates to a process for producing cut shapes of amorphous metal, and more particularly to a selective etching process for producing cut laminations which are bonded to one another to form generally polyhedrally shaped low core loss bulk amorphous metal magnetic components useful in electric drive motors and induction magnetic devices.

2. Description of the Prior Art

Magnetic components made of a plurality of laminations of sheet magnetic material are widely used in electric motors and inductive devices such as transformers, ballasts, inductors, saturable reactors, and the like. The magnetic material is selected taking into account, among other things, the desired device performance and economic considerations.

The most common material for electric drive motor components is non-oriented electrical steel. In various variable reluctance motors and eddy current motors, the stator is made of laminations. The stator and rotor in squirrel cage motors, reluctance synchronous motors and switched reluctance motors are all made of laminations. The laminations are formed, inter alia, by stamping, punching or cutting mechanically soft, non-oriented electrical steel to the desired shape. The formed laminations are then overlapped and bonded together to form a rotor or stator having a desired geometry and sufficient mechanical integrity to maintain their configuration during the manufacture and operation of the motor.

In a rotating electric drive machine, the stator and rotor are separated by a small gap, which may be: (i) radial, i.e. substantially perpendicular to the axis of rotation of the rotor, or (ii) axial, i.e. substantially parallel to the axis of rotation and at a distance from each other. In an electric motor, magnetic flux lines traverse these gaps to connect the rotor and stator. Thus, electromagnetic machines can be broadly classified as either radial flux designs or axial flux designs. The corresponding terms, radial gap design and axial gap design, are also used in the field of electric motors. By far the most common are radial flux machines. The above punching and lamination methods are widely used to construct rotors and stators for radial flux motors.

Although amorphous metals have good magnetic properties relative to non-oriented electrical steels, they have for a long time been considered unsuitable for use in bulk magnetic components such as rotors and stators for electric drive motors due to certain physical properties and subsequent impediments to manufacturing, for example, amorphous metals are thinner and harder than non-oriented steels, thereby causing the manufacturing tools and dies to wear faster. The use of conventional techniques such as punching and stamping to fabricate bulk amorphous metal magnetic components is economically impractical due to the increased tooling and manufacturing costs. The thinner amorphous metal increases the number of laminations in the assembled components, further increasing the overall cost of the amorphous metal rotor or stator assembly.

Amorphous metals are supplied in particular as continuous thin strips with a uniform bandwidth. However, amorphous metals are very hard materials and therefore are not easily cut or shaped. Once annealed to obtain peak magnetic properties, amorphous metal ribbon becomes very brittle. This makes it difficult and expensive to construct bulk amorphous metal magnetic components using conventional methods. The brittleness of amorphous metal ribbon also presents durability problems when applied to bulk magnetic components such as electric motors.

The magnetic stator is subjected to extremely high magnetic force, which rapidly changes according to the high speed of rotation. These magnetic forces can place considerable stress on the stator material, thereby damaging the amorphous metal magnetic stator. Furthermore, the rotor is subjected to mechanical forces both by normal rotation and also by accelerated rotation when the machine is started, switched off and when the load changes, in particular sudden changes, occur.

A limited number of non-conventional methods have been used to construct amorphous metal components, for example, U.S. patent 4,197,146 to Frischmann discloses a stator made by molding and compacting amorphous metal sheets. Although this method can form complex stator shapes, in this configuration there are a large number of air gaps between the dispersed thin sheet particles of amorphous metal. This structure greatly increases the reluctance of the magnetic circuit and the current used to operate the motor.

German patent documents DE 2805435 and DE 2805438 teach the division of the stator into wire-wound pieces and pole shoes. A non-magnetic material is inserted into the joint between the wire members and the pole pieces to increase the effective gap, thereby increasing the reluctance of the magnetic circuit and increasing the current used to operate the motor. The layer of material comprising the pole shoe is oriented such that its plane is perpendicular to the plane of the layer of wound iron protector. This configuration also increases the reluctance of the stator because the adjacent layers of the wire wrap pieces and pole pieces only intersect at the junctions, not along solid line segments at the junctions of their respective faces. In addition, this method teaches that the stacks of wound elements are joined to each other by welding. The amorphous metal laminations are joined using a heat-concentrating process, such as welding, which causes the amorphous metal to recrystallize at or near the joint. Even small portions of recrystallized amorphous metal can increase the magnetic loss in the stator to unacceptable levels.

Another difficulty with ferromagnetic amorphous metals is due to the phenomenon of magnetostriction. Some of the magnetic changes of any magnetostrictive material are responsive to mechanical stress applied to it. For example, when a component comprising an amorphous material is stressed, its magnetic permeability is significantly reduced, while the core loss increases. Degradation of amorphous metal devices due to magnetostriction phenomena may also be caused by stress generated by any combination of the following factors, including: (i) magnetic and mechanical forces during operation of an electrically driven motor; (ii) mechanical stresses generated by mechanically holding or securing the bulk amorphous metal magnetic component in place; or (iii) internal stresses resulting from thermal expansion and/or expansion resulting from magnetic saturation of the amorphous metal material. Since the amorphous metal magnetic stator is stressed, the stator's efficiency in directing or focusing the magnetic flux is reduced, resulting in increased magnetic losses, reduced efficiency, increased heat generation, and reduced power. The degree of such degradation can be considerable, depending on the particular amorphous metal material and the actual stress intensity, as described in U.S. patent 5731649 (' 649 patent). The degradation in core loss is often expressed as a failure factor, i.e., the ratio of the actual core loss of the finished device to the inherent core loss of the constituent material measured under stress-free conditions.

Furthermore, amorphous metals have significantly lower anisotropy energy than conventional soft magnetic materials, including common electrical steels. Thus, stress levels that do not adversely affect the magnetic properties of these conventional metals can have a significant impact on the magnetic properties, such as magnetic permeability and core loss, that are critical to motor components. For example, the' 649 patent further discloses that forming an amorphous metal core by winding amorphous metal into a coil and stacking with epoxy disadvantageously limits the thermal and magnetic saturation expansion of the coil material, resulting in high internal stresses and magnetostriction that can reduce the efficiency of a motor or generator incorporating the core. To avoid stress-induced magnetic degradation, the' 649 patent discloses a magnetic component that includes multiple stacked or coiled portions of amorphous metal carefully mounted or contained in a dielectric package without adhesive bonding.

In many applications of the current art, including those in remote areas such as high speed machine tools, aerospace motors and actuators, and spindle drive motors in magnetic and optical disk drives for storing data in computers and other microelectronic devices, it is desirable that the electric drive motors be operable at high speeds, in most cases in excess of 15,000 and 20,000 revolutions per minute, and sometimes even as much as 100,000 revolutions per minute. The limitations of using existing materials for magnetic components result in a number of design compromises that are both substantial and undesirable. In many applications, the core loss of electrical steels, in particular for motor components, is strictly prohibitive. In which case the designer is only forced to use permalloy instead. However, the attendant reduction in saturation induction (e.g., 0.6-0.9T or less for various permalloys and 1.8-2.0T for common electrical steels) necessitates an increase in the size of the magnetic elements constructed from permalloys or variants thereof. Furthermore, the desired soft magnetic properties of permalloys are affected by adverse and irreversible plastic deformation, which can occur at relatively low stress levels. Such stresses may occur during the manufacture or operation of the permalloy element.

Inductive devices are essential components of many modern electrical and electronic devices, most commonly transformers and inductors. These non-rotating devices most often employ a core comprising a soft ferromagnetic material and one or more electrical windings surrounding the core. Inductors typically employ a single winding with two terminals and function as filters and energy storage devices. Transformers typically have two or more windings and change the voltage from one level to at least one other desired level and electrically isolate different parts of the overall circuit from each other. Inductive devices come in a variety of different sizes and thus have correspondingly different power capabilities. Different types of inductive devices are best operated over a very wide range of frequencies from DC to GHz. Virtually every known type of soft magnetic material can be used to construct the inductive device. The choice of a particular soft magnetic material depends on a combination of desired properties and availability that ensures efficient manufacture and meets the volume and cost requirements of a particular market. In general, the ideal soft ferromagnetic core material has a high saturation induction B_satTo minimize the core size and to maximize efficiency with low coercivity Hc, high permeability μ, and low core loss.

Small to medium sized inductors and transformers for electrical or electronic equipment are also often made from laminations stamped from magnetic steel of different grades of sheet material down to 100 microns in thickness. The laminations are typically stacked and secured and then wound together with the desired electrical winding or windings, which typically comprise high conductivity copper or aluminum wire. These laminations are commonly used for cores having a variety of known shapes.

Various shapes for inductors and transformer cores are assembled from constituent elements having the common form of some typographic letters, such as "C", "U", "E", "I", by which the elements can be identified. The assembled shape may further be represented by letters representing the constituent elements, e.g., an "E-I" shape is assembled from an "E" element and an "I" element. Other widely used mounting shapes include "E-E", "C-I", "C-C". The constituent elements used in prior art cores having these shapes have been constructed from laminated sheets of conventional crystalline ferromagnetic metal and machined bulk soft ferrite blocks.

One important trend in recent electronics is the design of power supplies, converters, and related circuits using switched-mode topology circuits. The current performance improvements of power semiconductor switching devices allow the switched mode devices to operate at higher frequencies. Many devices that were designed in the past to perform linear regulation and operation at linear frequencies (typically 50-60Hz for power grids, or 400Hz in military applications) typically have frequencies of 5-200kHz, sometimes up to 1MHz, under switch mode based management. One of the major drivers of frequency increase is the concomitant reduction in size of the required magnetic components such as transformers and inductors. However, the increase in frequency also significantly increases the magnetic losses of these components. Therefore, it is highly necessary to reduce these losses.

The limitations of using existing materials for magnetic components have resulted in a number of and undesirable design compromises. In many applications, the core loss of common electrical steels is prohibitive. In which case the designer is forced to use permalloy or ferrite instead. However, the concomitant reduction in saturation induction (e.g., 0.6-0.9T for various permalloys or less, 0.3-0.4T for ferrites, and 1.8-2.0T for common electrical steels) makes it necessary to increase the size of the magnetic elements produced. Furthermore, the desired soft magnetic properties of permalloys are adversely and irreversibly affected by plastic deformation, which can occur at relatively low stress levels. Such stresses may occur during the manufacture or operation of the permalloy element. Although soft ferrites generally have desirably low losses, their lower inductance values can cause the devices to become impractically large for many applications where space considerations are important. In addition, an increase in the core size requires longer electrical windings, and thus ohmic losses increase.

For electronic applications such as saturable reactors and some chokes, amorphous metals take the form of toroidal cores with spiral windings. Devices of this form, typically in the range of a few millimetres to a few centimetres in diameter, are commercially available and are commonly used to provide switched mode power supplies of up to a few hundred volt-amperes (VA). Such a core construction may provide a fully closed magnetic circuit in which the demagnetization factor is negligible. However, to achieve the required energy storage capacity, many inductors include magnetic circuits with dispersed air gaps. The presence of such air gaps results in non-negligible demagnetization factors and associated shape anisotropy, which are manifested as shear magnetization (B-H) loops. This shape anisotropy may be much higher than the possible induced magnetic anisotropy, thereby proportionally increasing the energy storage capacity.

Toroidal cores made using dispersed air gaps and conventional materials have been proposed for use in these energy storage applications. However, the gapped annular geometry has little design flexibility. It may be difficult or impossible for the device user to adjust the gap to select the desired shear and stored energy. In addition, the equipment required to apply windings to toroidal cores is more complex, expensive and difficult to operate than the winding equipment required for equivalent laminated cores. Many times, the toroidal geometry core cannot be used for high current applications because the high range wire specified by the rated current cannot be bent to the extent required by the toroidal winding. In addition, the ring design has only one magnetic circuit. As a result, the toroidal designs are not perfectly matched and are difficult to adapt to multi-phase transformers and inductors, including the three-phase devices that are particularly common. Accordingly, there is a need to find other configurations that are easier to manufacture and apply.

Moreover, the stresses inherent in the bar-winding toroidal core cause certain problems. The windings inherently place the outer side of the strip in tension and the inner side in compression. The additional stress is provided by the linear tension required to ensure the windings are smooth. Due to magnetostriction, the toroid windings exhibit significantly less magnetic properties than do the same bars of the flat bar construction. In general, annealing can relieve only a portion of the stress and thus remove only a portion of the degradation. In addition, the provision of gaps in the toroid winding often causes other problems. By means of the air gap, the residual hoop stress in the winding structure is at least partially removed. In practical applications, the net hoop stress is unpredictable and may be either compressive or tensile. The actual gap is therefore often closed or opened, respectively, by a certain unpredictable amount in the respective case, depending on the need to maintain the stress balance. Therefore, the final gap is usually different from the target gap due to the lack of corrective measures. Since the magnetic resistance of the core is largely determined by the gap, it is generally difficult to constantly reproduce the magnetic properties of the completed core in mass production.

Amorphous metals are also used in transformers for higher power devices, such as distribution transformers labeled as power grids rated at 10kVA to 1MVA or higher. The cores of these transformers often form stepped overlapping windings, which are generally rectangular in configuration. In one common construction method, a rectangular core is first formed and annealed. The core is then unwound, allowing the preformed winding to pass through the long prongs of the core. After incorporation of the preformed winding, the stack is rebound and fixed. One exemplary process for manufacturing transformers in this manner is disclosed in U.S. patent No. 4,734,975 to Ballard et al. This process requires a large amount of labor and handling steps, which involve very brittle annealed amorphous metal ribbon. These steps are particularly tedious and difficult to achieve with core powers of less than 10 kVA. Also, cores of this construction are not easy to controllably introduce air gaps, which are essential in many inductor applications.

While the above-described disclosures represent certain advances, there is a need in the art for a more advanced amorphous metal magnetic component that has a combination of superior magnetic and physical properties that meets the needs of high-speed, high-efficiency rotating electrical machines and other non-rotating inductive devices. There is also a need for a construction method that efficiently uses amorphous metals that can be used to mass produce various types of electric motors and magnetic components.

Summary of The Invention

The present invention provides a low loss bulk amorphous metal magnetic component in the shape of a polyhedron comprising a plurality of substantially uniformly shaped layers of amorphous metal strips laminated together by an adhesive. In one aspect of the invention, one or more of these components may be used to form high efficiency electric motors and induction magnetic devices.

The present invention also provides a method of selectively etching amorphous metal strip feedstock to form shapes useful in forming low core loss amorphous metal bulk magnetic components. The term "amorphous metal strip" refers in this application to an elongated amorphous metal ribbon material, i.e., a ribbon having a length and width that are much greater than its thickness. The length and width directions define the top and bottom surfaces of the strip.

More specifically, a magnetic component constructed in accordance with an embodiment of the present invention is excited to a peak induction level "B" at an excitation frequency "f_max"will have an iron loss at room temperature of less than" L ", where L is represented by the formula L ═ 0.005f (B)_max)^1.5+0.000012f^1.5(B_max)^1.6The core loss, excitation frequency and peak induction level are given in units of watts/kg, hertz and tesla, respectively, at the time of measurement. Preferably, the magnetic element has: (i) the amorphous metallic material has a core loss less than or approximately equal to 2.8 watts/kilogram when operated at a frequency of approximately 400Hz and a flux density of approximately 1.3T; (ii) when at a frequency of about 800Hz and a flux density of about 1.3T, the amorphous metallic material has a core loss less than or substantially equal to 5.7 watts/kg; or (iii) the amorphous metallic material has a core loss less than or approximately equal to 9.5 watts/kilogram when operated at a frequency of approximately 2000Hz and a flux density of approximately 1.0T.

Due to the low core losses under periodic magnetic excitation, the magnetic element of the present invention can operate at DC frequencies up to 20000Hz or even higher. Such elements can have higher performance than conventional silicon-steel magnetic elements operating in the same frequency range. The high frequency operability of such components makes them useful, for example, in the manufacture of motors capable of operating at higher speeds and with greater efficiency than components constructed from conventional components.

The bulk amorphous metal magnetic component of the present invention is particularly suited for use as an amorphous metal stator or stator component in high efficiency variable reluctance motors and eddy current motors. Similarly, the amorphous metal bulk element may be used as at least one of a rotor and a stator in a squirrel cage motor, a reluctance synchronous motor and a switched reluctance motor. Those skilled in the art will appreciate that the motor may include one or more rotors or one or more stators. Thus, the terms "rotor" and "stator" in this application with respect to an electric motor refer to a plurality of rotors or stators, from 1 to 3 or more. Those skilled in the art of rotating electrical machines will appreciate that radial flux motors may be constructed as follows: (i) the rotor is located inside and its diameter is generally smaller than that of the stator; or (ii) a structure having an inside-out (inside-out) or a cup-shaped structure, wherein the relative positions and dimensions of the rotor and stator are interchangeable. The rotor or stator of the present invention may be a unitary structure or an assembly of a plurality of substructures connected together by known components, which substructures are disclosed herein.

It will also be appreciated by those skilled in the art that "electric drive motor" as used herein is a generic concept referring to a variety of rotary electric motors, including electric generators and optionally regenerative motors as electric generators. The magnetic component of the present invention may be used to form any of the devices described above. There are many advantages in the application of the present invention. These advantages include ease of manufacture, short manufacturing time, reduced stress (i.e., magnetostriction) experienced during the manufacture of the bulk amorphous metal magnetic component, optimal performance of the finished amorphous metal magnetic component, and improved efficiency of an electric motor that includes the rotor or stator.

One or more of the bulk magnetic components of the present invention may also be usefully incorporated into an inductive device, comprising: (i) a magnetic core having a magnetic circuit with at least one air gap and comprising at least one low-loss ferromagnetic amorphous metal bulk magnetic component; (ii) at least one electrical winding surrounding at least a portion of the magnetic core; and (iii) an element comprising a plurality of planar layers of substantially similarly shaped amorphous metal strips stacked upon one another, aligned and bonded together by an adhesive to form a polyhedrally shaped part. Exciting to a peak induction level B at an excitation frequency "f" of 5kHz_maxThe core loss of such an inductive device is less than about 12W/kg when operated at "0.3T. Such inductive devices can be used in a variety of circuit applications, for example as transformers, auto-transformers, saturable reactors or inductors. The elements of the present invention are particularly useful in the construction of power-regulated electronic devices employing various switch-mode circuit topologies. The devices of the present invention are useful in single phase and multiphase applications, particularly in three phase applications.

Advantageously, bulk amorphous metal magnetic components can be easily assembled to form one or more magnetic circuits of a completed inductive device. In certain aspects, the mating faces of the elements are in intimate contact with each other to form a device having low magnetoresistance and a substantially square B-H loop. However, by assembling the device with an air gap between the mating faces, the magnetic reluctance is increased, thereby providing the device with improved energy storage capabilities that are advantageous for many inductor applications. The air gap is optionally filled with non-magnetic spacers.

The flexibility in the size and shape of the elements of the present invention allows the designer a wide degree of freedom in properly optimizing the inductive element, including the ability to select the size and configuration of the overall core and the winding windows within one or more cores. Selective etching is particularly advantageous when fabricating elements of any desired size and shape. Thus, the overall size of the device is easily reduced, and the volume of the core and the required winding material are reduced. The flexibility of device design and the high saturation induction capability of the core material are advantageous for designing electronic circuit devices that are compact in size and efficient. Transformers and inductors of a given power and energy storage level are generally smaller and more efficient than conventional inductive devices using lower saturation induction core materials. Due to the low core losses upon periodic magnetic excitation, the magnetic element of the present invention can operate in a frequency range of DC frequencies up to 20000Hz or even higher. Such elements can have higher operating performance than conventional silicon-steel magnetic elements operating in the same frequency range. These and other desirable characteristics make the device of the present invention easily customizable to suit specific magnetic applications, for example, transformers or inductors for power-regulated electronic circuits employing switch-mode circuit topologies and switching frequencies of 1kHz to 200kHz or higher.

The present invention also provides a method of forming an amorphous metal bulk magnetic component. The method comprises the following steps: (i) selectively etching the amorphous metal strip material to form a plurality of laminations, each lamination being substantially the same predetermined shape; (ii) stacking the laminations in alignment with each other to form a lamination stack; and (iii) bonding the laminate stack together with an adhesive. The method may further comprise an optional heat treatment or annealing step to improve the magnetic properties of the component, or an optional coating step wherein an insulating coating is applied to at least a portion of the surface of the component. These steps may be accomplished in a variety of sequences using a variety of techniques, including those described below. For example, the adhesive bonding step may be performed before or after the annealing step. The amorphous metal material preferably used to carry out the method has a composition substantially represented by the formula Fe₈₀B₁₁Si₉The components of the composition.

The process optionally includes a step of finishing the component to at least one of: optionally, the component is finished to at least one of the following: (i) removing excess adhesive from the component; (ii) subjecting the element to a suitable surface finish; and (iii) removing material to determine the final dimensions of the element. The process may also include annealing the laminations to improve the magnetic properties of the element.

Advantageously, in the manufacturing method of individually shaped laminations, there are no compressive and tensile stresses inherent in bending the bars at winding. Any stresses caused by the formation of the laminations may be limited to a small area or near its periphery. The lamination stack is then optionally finished and any excess adhesive is removed, and the stack is subjected to appropriate surface polishing and final component sizing.

The desired lamination shape to form the elements of the present invention may be carried out according to a variety of methods including, in non-exclusive manner, mechanical abrasive cutting methods, diamond wire methods, high speed milling performed in either horizontal or vertical orientation, abrasive water jet milling, electrical discharge machining by wire or plunger, electrochemical grinding, electrochemical machining, stamping, laser cutting, or by other methods known to those of ordinary skill in the art.

The bulk magnetic component of the present invention preferably incorporates laminations that are cut by a selective etching process. In general, the process comprises the following steps: (i) providing an amorphous metal sheet having a first surface and a second surface; (ii) printing a chemically stable material on the first surface, the printed pattern defining a preselected shape; (iii) covering a protective layer on the second surface; (iv) exposing the amorphous metal sheet to a corrosive agent to selectively etch amorphous metal from the first surface region outside of the preselected shape; and (v) separating the shape from the amorphous metal sheet. Although the selective etching process of the present invention is preferably used to cut individual layers of amorphous metal components of an assembly for assembly into an amorphous metal bulk magnetic component, the process may be used to fabricate other shapes for other applications, such as braze metal preforms.

The selective etching process of the present invention is advantageous in that it is easier to select or change the size and shape of the laminations relative to the stamping process, which requires expensive redesign or remanufacturing of a precise die set. Moreover, the process of the present invention is easy to implement for complex shapes.

Brief description of the drawings

The present invention will be more fully understood and its advantages more fully apparent from the following detailed description of the preferred embodiments of the invention taken together with the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to similar parts, in which:

fig. 1A is a plan view of a layer of amorphous metal feedstock that has been selectively etched to form amorphous metal toroid elements that are used to form an amorphous metal bulk magnetic component in accordance with the present invention;

fig. 1B is a cross-sectional view at IB-IB of the amorphous metal feedstock layer of fig. 1A that has been selectively etched to form an amorphous metal toroid for use in forming an amorphous metal bulk magnetic component in accordance with the present invention;

fig. 2A is a plan view of a layer of amorphous metal feedstock that has been selectively etched to form amorphous metal toroid elements that are used to form the amorphous metal bulk magnetic component of the present invention;

fig. 2B is a cross-sectional view, at IIB-IIB, of the amorphous metal starting material layer of fig. 2A that has been selectively etched to form an amorphous metal ring member useful in forming the amorphous metal magnetic component of the present invention;

fig. 3 is a perspective view of a three-dimensional rectangular bulk amorphous metal magnetic component constructed in accordance with the present invention;

fig. 4A is a perspective view of a magnetic component formed in accordance with the present invention and having a prismatic shape;

FIG. 4B is a perspective view of an amorphous metal bulk magnetic component having oppositely disposed arcuate surfaces constructed in accordance with the invention;

FIG. 4C is a top view of the stator of the electric motor constructed from the hexagonal prism-shaped element of FIG. 4A and the six-segment arc-shaped element of FIG. 4B;

FIG. 5A is a perspective view of an amorphous metal bulk magnetic stator of an electric drive motor constructed in accordance with the present invention;

FIG. 5B is a perspective view of an amorphous metal bulk magnetic rotor of an electric drive motor constructed in accordance with the present invention;

FIG. 5C is a top view of the stator and rotor of an electric drive motor formed from the stator of FIG. 5A and the rotor of FIG. 5B;

FIG. 5D is a top view of an amorphous metal bulk magnetic stator constructed in accordance with the present invention for use in an inside-out radial gap electric drive motor;

FIG. 6 is a perspective view of an assembly for testing bulk amorphous metal magnetic components, including four components, each having the shape of a polyhedron with oppositely disposed arcuate surfaces, assembled to form a generally right circular annular cylinder;

fig. 7A is a perspective view of a bulk magnetic component having a gapped toroidal core for use in forming an inductive device of the present invention;

FIG. 7B is a plan view of a laminate selectively etched from amorphous metal strip material for incorporation into the component shown in FIG. 7A;

fig. 8 is a perspective view of an inductive device of the present invention in the shape of a "C-I" assembled from bulk amorphous metal magnetic components having the shapes "C" and "I";

fig. 9 is a perspective view of an inductive device of the present invention in the shape of an "E-I" assembled from bulk amorphous metal magnetic components in the shapes of an "E" and an "I" and windings on each prong of the "E";

FIG. 10 is a cross-sectional view of a portion of the device shown in FIG. 9; and

fig. 11 is a plan view of an inductive device of the present invention in the shape of an "E-I", which includes bulk amorphous metal magnetic components in the shapes of an "E" and an "I", with air gaps and spacers mounted between mating faces of the respective components.

Detailed description of the invention

The present invention relates in one aspect to a process for cutting a workpiece from an amorphous metal ribbon or sheet, and to low-loss amorphous metal bulk components incorporating such workpieces. Such components, in turn, can be used to construct a variety of devices, including high efficiency inductive devices and electrically driven motors.

The substantially polyhedral shaped amorphous metal body elements of the present invention can be formed in a variety of geometries including, but not limited to, rectangular and prismatic shapes. Moreover, any of the above geometries may comprise at least one arcuate surface, preferably two oppositely disposed arcuate surfaces to form a generally curved or arcuate bulk amorphous metal component. The present invention also provides an element wherein the polyhedron is generally cylindrical in shape and may include a plurality of teeth extending radially inwardly or outwardly from a generally annular portion. In accordance with the present invention, the entire stator and rotor of certain types of electric motors preferably employ such castellated amorphous metal body elements. These stators and rotors may have an integral construction or may be composed of multiple components and together constitute a complete element. Alternatively, the stator and/or rotor may be a composite structure, including the entire amorphous metal part or a combination of amorphous metal parts and other magnetic materials. The bulk magnetic component of the present invention may be incorporated into an electric drive motor, preferably of the radial flux type.

The present invention also provides an inductive device comprising a bulk magnetic component assembled from one or more amorphous metal layers cut according to the method of the present invention. The inductive device has at least one air gap, but may also have a plurality of more complex shaped air gaps and a plurality of magnetic circuits in which the reluctance of the circuit can be adjusted by varying the air gap in a selected core configuration.

Referring to fig. 1A-1B, one embodiment of a selective etching process for producing a cut-form amorphous metal material in accordance with the present invention is shown. The amorphous metal feedstock in the form of an extended strip 350 has a free side 351. A chemical stabilizing material 358 is applied on the opposite side 353 of the strip in a pattern forming loops 352. A protective material 358 is typically applied over the surface 353, except for a narrow concentric outer circular boundary region 354 and an inner circular boundary region 356. The free side 351 is covered with a protective layer and the tape is then exposed to the etchant for a desired period of time. In one embodiment, the protective layer is comprised of the same chemically stable material used to define the shape of side 353. Alternatively, the free side 351 is bonded to a carrier layer (not shown) of a material that is not significantly attacked by the etchant. The carrier strip is preferably composed of a corrosion-resistant metal, for example stainless steel, a nickel-based alloy, such as inconel, titanium, tantalum, aluminum or a polymeric material. The carrier strip is preferably lightly adhered to the amorphous metal strip with an adhesive. The carrier strip may also be adhered by magnetic or electrostatic forces. In some embodiments, the carrier strip is used to transport the tape through the apparatus in a semi-continuous or continuous roll-to-roll process to complete at least some of the necessary manufacturing steps. Advantageously, the carrier strip may be reused in some embodiments. The protective layer substantially protects free side 351 from erosion, but the amorphous metal on side 353 unprotected by material 358 is chemically etched, creating trenches at regions 354 and 356 that optionally partially penetrate the thickness of strip 350. The grooves weaken the strip, allowing the ring 352 to easily separate from the remainder of the strip 350 sheet. In some embodiments, longer exposure to the etchant completely etches the trench, completely separating the rings 352. Too short an exposure time may not sufficiently weaken the tape and may not allow separation with reasonable force.

A related embodiment of the selective etching process of the present invention is illustrated in fig. 2A-2B. In this embodiment, the outer boundary region 354' is an arc subtending slightly less than 360. The chemical resistant material 358 covers the remainder of the circle. Thus, the etching process leaves a tab 361 by which the ring 352 ' remains attached to the tape tab after etching, regardless of whether the tape 350 is exposed to the etchant for a time sufficient to completely erode and penetrate the thickness of the tape in the grooves at regions 354 ' and 356 '. In other embodiments, a plurality of such tabs may be provided around the workpiece.

Preferably, the method of fig. 1-2 is repeated to form a series of features, such as rings 352, arranged at regular intervals along the length of the amorphous metal strip feedstock. After selective etching, the part remains on top of the stock and can be further processed. More preferably, the feedstock is wound on a spool for an extended length of tape after etching, and a plurality of etched parts are attached to the tape. Alternatively, the carrier layer may remain attached to the tape, but the carrier may also be removed after the etching operation but before the material is again wound. In addition, the process as described in fig. 1-2 can be readily applied in a semi-continuous or continuous roll-to-roll process. The portions of the embodiment of fig. 1-2 have been chosen for ease of illustration, to make the ring shape relatively simple, and the process of the present invention can be readily adapted to manufacture other complex shapes as well. Advantageously, the process of the present invention can be used to form shapes having a plurality of features, such as multi-tooth motor laminations, without the expense of preparing and maintaining complex stamping dies as is required in conventional stamping processes. The process of the present invention is therefore particularly suitable for rapid prototyping or efficient mass production of such parts.

A number of processes are suitable for applying a chemically stable material to a portion of one of the strip surfaces to form a preselected shape of the inventive workpiece in preparation for an etching operation. Preferably, some areas of the surface of the stock material corresponding to the desired shape are coated with the protective material and areas outside the desired shape are uncoated. The chemically stable material protects the coated areas from the etchant and the unprotected areas from corrosion.

A printing process is preferred when applying the chemically stable material. Printing refers to any process that rapidly replicates a pre-selected pattern of stabilizing material on the surface of a feedstock material. Many known printing processes can be used with the present invention, including photolithography, raised plate printing, recessed plate printing, and screen printing methods. In addition, electrostatic printing and inkjet deposition methods are also suitable. In many of the processes described, deposition may be accomplished by continuously adding feedstock without the need for an indexing motion in which portions of the feedstock are sequentially brought into position and deposition of material begins in a region. The indexing operations required require starting and stopping of the material, complicating process automation and leading to frequent false material additions, interruptions and other problems requiring manual operations or intervention. Conventional double-sided lithographic processes for metal strip materials often require such indexing steps.

The single-sided selective etching process described above has significant advantages over existing photolithographic etching methods suitable for metal strip materials. The latter method generally requires that the pattern be formed in registration with each other on both sides of the stock, especially when the dimensional requirements of the part being produced are less critical, for example, the precise alignment of the photolithographic dies on both sides of the strip, and incidental dimensional tolerances are controlled to within about 1 micron. However, many components for magnetic components do not require such tight dimensional control, and tolerances within 10 microns are acceptable. Thus, deposition of the shaped single-sided protective layer, as well as other shaping processes, can be performed with greater efficiency and at greater speed without requiring precise alignment of the etched patterns on opposite sides of the tape stock, thus reducing complexity and cost of producing individual parts.

The selective etching of the features of the present invention is accomplished by exposing the feedstock side containing the patterning stabilizer to a corrosive agent, which may be gaseous, but is preferably a liquid, such as a strong acid, for a sufficient period of time to achieve the desired etch depth. In some embodiments, the exposure is for a time sufficient to remove material from the region between the workpiece and the remaining sheet to the full depth of the feedstock, such that the desired portion is broken away from the remaining portion of the feedstock sheet. In other embodiments, the exposure is of a shorter duration so that the etchant does not penetrate the entire depth, leaving a weakened portion defining the boundary between the desired portion and the remaining sheet. Optionally, the chemically stable material may be removed from the surface of the ribbon after the etching step is completed. A variety of techniques may be used, including dissolving the material in a suitable solvent, decomposition, or mechanical scraping, abrasion, and the like.

Advantageously, the process embodiments illustrated in fig. 1-2 facilitate subsequent processing and bonding of selectively etched portions of the bulk magnetic element. Preferably, the boundary between the workpiece of interest and the remaining sheet of amorphous metal strip stock is weakened sufficiently to allow the workpiece to be easily separated during production. As noted above, the etching may remove a substantial portion of the thickness in the boundary region, preferably at least about 50%, and more preferably at least about 80%. Alternatively, a portion of the peripheral boundary layer may be substantially completely penetrated while the other portion is not so penetrated such that the workpiece remains attached to the tape tab through a small number of tabs, such as at least one tab shown in fig. 2A-2B. In any of the methods, mechanical operations, such as manual separation or simple manual or automatic stamping operations, may then be used to remove and collect the desired amount of work pieces to assemble the body element. Such a stamping operation is much easier to operate and less demanding than conventional stamping techniques which must cut the workpiece accurately and which do not form the predetermined weakened zone. An automated in-line process, which sequentially includes the stamping steps of transporting the feedstock from a supply spool, selectively etching the workpieces and sheets as described above, separating the workpieces and collecting the individual workpieces, and collecting the remaining sheets on a take-up spool, is preferred because of the high production efficiency and cost effectiveness.

The above-described process is advantageously used to make amorphous metal laminations and use them in generally polyhedral amorphous metal motor body elements. The term "polyhedron" as used herein refers to polyhedral or sided solids, including, but not limited to, three-dimensional rectangles, squares, trapezoids, and prisms. In addition, any of the above geometries may include at leastOne, and preferably two, mutually opposed arcuate surfaces or sides to form a generally arcuate shaped element. The element of the invention may also have a substantially cylindrical shape. The magnetic component 10 of fig. 3 is comprised of a plurality of generally uniformly shaped amorphous metal strip material layers 20, which material layers 20 are laminated together and annealed. Constructed in accordance with the invention and excited to a peak induction level "B" at an excitation frequency "f_max"the three-dimensional magnetic component 10 has a core loss at room temperature of less than about" L ", where L is 0.005f (B) from the formula L_max)^1.5+0.000012f^1.5(B_max)^1.6The units of measurement for core loss, excitation frequency and peak induction level are given in watts/kilogram, hertz and tesla, respectively. In certain preferred embodiments, the magnetic element has: (i) the amorphous metallic material has a core loss of less than or about equal to 2.8 watts/kilogram when operated at a frequency of about 400Hz and a flux density of about 1.3 tesla (T); (ii) the amorphous metallic material has a core loss of less than or about equal to 5.7 watts/kilogram when operated at a frequency of about 800Hz and a flux density of about 1.3T; or (iii) an amorphous metallic material having a core loss of less than or about equal to 9.5 watts/kilogram when operated at a frequency of about 2000Hz and a flux density of about 1.0T.

An advantage of the element of the present invention is that the element has low core loss when the element or any portion thereof is magnetically excited in any direction generally in the plane of the contained amorphous metal component. The lower core loss of the element of the invention in turn provides the efficiency of the motor or inductive device incorporating the element. The low core loss values make the bulk magnetic component of the present invention particularly useful in motors where high frequency magnetic excitation, e.g., above 100Hz excitation, is required for high pole count or high rotational speed. The inherent high core loss of conventional steels at high frequencies often makes them unsuitable for motors requiring high frequency excitation. These core loss performance values apply to all embodiments of the invention regardless of the particular geometry of the amorphous metal body element.

The magnetic element 100 depicted in fig. 4A is generally prismatic in shape and preferably includes five sides 110 or surfaces. The pentagonal polyhedral element 100 is comprised of a plurality of layers of amorphous metal strip material 20 of substantially identical size and shape, the strip material 20 being laminated, laminated together, and then annealed.

The magnetic element 200 depicted by fig. 4B includes at least one, and preferably two oppositely disposed arcuate surfaces 210. The arcuate shaped member 200 is comprised of a plurality of layers of amorphous metal strip material 20, the layers being substantially the same size and shape, the strip material 20 being laminated, laminated together, and then annealed.

The bulk amorphous metal magnetic component 300 depicted in fig. 4C may be used as a stator for a radial gap electric motor and is comprised of six magnetic components 100 and six magnetic components 200.

The bulk amorphous metal magnetic component 400 depicted in fig. 5A is generally circular and includes a plurality of generally rectangular teeth 410 extending radially inward toward the center of the circular component 400. The component 400 comprises a plurality of layers of amorphous metal strip material 20, the layers being of substantially the same size and shape, the strip material 20 being laminated, laminated together and then annealed. The amorphous metal bulk component constructed in accordance with the embodiment of fig. 5A may be used as a stator for a radial air gap electric drive motor.

The bulk amorphous metal component 500 shown in fig. 5B is generally disk-shaped and includes a plurality of generally rectangular teeth 510 extending radially outward. The element 500 is comprised of a plurality of layers of amorphous metal strip material 20, the layers being substantially the same size and shape, the strip material 20 being laminated, laminated together, and then annealed. The bulk amorphous metal component constructed in accordance with the embodiment of fig. 5B may be used as a rotor for a radial air gap electric drive motor.

Referring next to fig. 5C, stator 400 and rotor 500 are bulk amorphous metal components according to the present invention and are part of a high efficiency radial air gap electric drive motor 600. The motor also includes windings and bearings that rotatably support rotor 500 in alignment with stator 400, as will be appreciated by those skilled in the motor art.

The bulk amorphous element 800 shown in fig. 5D may be used as a stator in a high efficiency inside-out radial air gap electric drive motor. The element 800 comprises a plurality of laminations 20 of substantially identical shape. Each lamination 20 includes a central portion 810 having a generally annular size and shape, and a plurality of toothed portions 820 extending radially outward from the central portion 810. The toothed portion 820 is often referred to simply as a tooth. The laminate 20 may be cut to the desired shape by any suitable process, preferably a selective etching process. The laminations are then stacked in registration with each other and the laminations are bonded together by impregnation of an adhesive to form the element 800. The impregnation serves to disperse and penetrate the adhesive between the laminations so that at least a portion of the surface of each lamination is covered with the adhesive. In operation of the element 800 as a stator for an electric motor, the central portion 810 acts as back iron, i.e., a flux return path for flux lines entering and exiting the stator through the teeth 820. Each tooth 820 has a widened portion 830 at the tooth end near the outer circumference of the element 800. The portion 840 of each tooth 820 proximate the central portion 810 is commonly referred to as the root. Winding slots 850 are formed by the gaps between adjacent pairs of teeth 820. When element 800 is used as a motor stator, electrical windings (not shown) are looped around each tooth 820, passing through winding slots 850 next to the tooth. In operation of the motor, the windings are energized by a flow of current to provide a magnetomotive force. The windings of each tooth may be interconnected and energized by a variety of methods known in the motor art.

The invention also provides a method of constructing a low loss bulk component. In one aspect, individual laminations of the desired shape are prepared using amorphous metal strips, which are then laminated into a three-dimensional lamination stack and bonded together. The laminate may be cut by any suitable method, but selective etching is preferred. The bonding preferably includes the steps of applying and activating an adhesive to bond the laminations to one another such that the lamination stack has sufficient mechanical and structural integrity to allow the component to be handled and manipulated in the finished device. Optionally, the component is finished to at least one of the following: (i) removing excess adhesive; (ii) polishing the appropriate surface of the component; and (iii) removing material to determine the final dimensions of the element. The method also includes an optional annealing step to improve the magnetic properties of the element. The steps of the method may be performed in a variety of sequences and using a variety of techniques, including those set forth herein and others known to those of skill in the art.

It is particularly preferred to form the laminate in a manner that does not create burrs or other edge defects. More specifically, these and other defects protruding from the plane of the lamination may form under certain processes and conditions. These defects often cause electrical shorts between layers, which in turn disadvantageously increase the core loss of the component.

Advantageously, selectively etching a feature generally greatly reduces or avoids such edge defects. Selectively etched features exhibit, inter alia, rounded edges and the thickness of the features tapers proximate the edges, thus reducing the likelihood of layer-to-layer shorts, as described above, in the stack of features. In addition, the impregnation of such adhesive laminate can be improved by improving wicking and capillary action near the tapered edges. The impregnation can be further improved by providing one or more small holes through each lamination. When the individual laminations are stacked in register, the holes may be aligned to form channels through which the impregnating agent flows easily, which ensures a more rational distribution of the impregnating agent over at least a substantial part of the surface of each lamination in combination with the adjacent lamination. Other structures such as surface channels and notches may also be incorporated into each laminate to serve as means for enhancing the flow of the impregnant. In a photo-etched laminate, the above-described holes and flow enhancement means can be easily and efficiently provided. In addition, various spacers may be inserted in the lamination stack to promote improved flow.

In many cases, this embodiment, which may be useful for removing individual workpieces from a ribbon web using stamping or similar operations, with optional, moderate heat treatment prior to stamping, may advantageously alter the mechanical properties of the amorphous metal. In particular, the heat treatment reduces the ductility of the amorphous metal to some extent, thereby limiting the amount of mechanical deformation of the amorphous metal prior to fracture during the stamping process, as well as limiting the mechanical die force required. The reduced ductility of the amorphous metal may reduce direct grinding and abrasion of the stamping and die materials due to deformation of the amorphous metal.

The present invention uses an adhesive to bond together a plurality of pieces or laminations of amorphous metal strip material in proper alignment with one another to form a bulk three-dimensional object. This combination provides sufficient structural integrity to allow the components of the present invention to be handled and used, or incorporated into other larger structures. Suitable adhesives are many and include epoxies, varnishes, anaerobic adhesives, cyanoacrylate adhesives and Room Temperature Vulcanizing (RTV) silicone materials. The adhesive preferably has low tack, low shrinkage, low elastic modulus, high peel strength, high temperature capability, and high dielectric strength. The adhesive may cover any portion of the surface area of each laminate to an extent sufficient to sufficiently bond adjacent laminates to one another to ensure sufficient strength for the completed component to have sufficient mechanical integrity. The adhesive may cover substantially the entire surface area. The epoxy resins may be multi-component cured by chemical activation or may be one-component cured by thermal activation or ultraviolet activation. The adhesive preferably has a viscosity of less than 1000cps with a coefficient of thermal expansion approximately equal to that of the metal, or about 10 ppm. One preferred adhesive is a heat activated epoxy sold by the company p.d. george under the trade designation Epoxylite 8899. The adhesion of the device of the invention is preferably achieved by impregnation with such an epoxy resin, diluted with acetone in a volume ratio of 1: 5, so as to reduce its adhesion and increase the interpass permeability of the tape. Another preferred adhesive is a methyl cyanoacrylate adhesive sold under the trade name Permabond 910FS by National Starch and Chemical Company. The bonding of the device according to the invention is preferably carried out by applying such an adhesive, which penetrates between the layers of the tape by capillary action. Permabond 910FS is a one-part, low viscosity liquid that cures within 5 seconds when exposed to moisture at room temperature.

Suitable methods of applying the adhesive include dipping, spraying, brushing, and electrostatic deposition. In strip or ribbon form, the coating of the amorphous metal may also be accomplished by passing the metal through a rod or roller for delivering the adhesive to the amorphous metal. Rollers or rods having a rough surface, such as gravure or wire-wound rollers, are particularly effective in uniformly applying the adhesive to the amorphous metal. The adhesive is applied to one amorphous metal layer at a time, either before or after cutting, or to the individual layers after cutting. Alternatively, the adhesive may be applied to the entire stack after lamination of the laminations. Preferably, the adhesive is impregnated between the laminations by capillary flow of the adhesive between the laminations. The impregnation can be carried out at room temperature and pressure. Optionally but preferably, the laminate is placed under vacuum or static pressure to allow more thorough impregnation while minimizing the total volume of adhesive added, thereby ensuring a high lamination factor. Preferably, a low tack adhesive is used, such as an epoxy or cyanoacrylate adhesive. Warming may also reduce the tack of the adhesive, thus promoting penetration between the lamination layers. The adhesive may be activated as needed to improve bonding. After any required activation and curing of the adhesive, the component is finished, any excess adhesive is removed, the component is suitably surface polished and the final desired component dimensions are determined. Activation or curing of the binder may also be used to affect magnetic properties if performed at a temperature of at least about 175 ℃, as will be described in more detail below in this application.

Finishing of the inventive component may also include applying a topcoat over at least a portion of its outer surface. Suitable coatings include paints, lacquers, varnishes, or resins. The coating may be applied by various methods including spraying and dipping in a bath or fluidized bed. Simple spray techniques with or without a solvent carrier can be used. Alternatively, electrostatic or electrophoretic deposition techniques may be suitable. The finishing operation may also include removing any excess coating, if desired. This process is particularly advantageous for motor elements having excess material present in the close spaces between the mutually rotating parts. The outer coating advantageously protects the insulating construction of the electrical windings on the components from wear by the metal extreme edge regions and serves to trap any flakes or other material that would fall off the components or be attracted by the permanent magnets, which would otherwise fall improperly into the motor or its nearby structures.

The construction disclosed herein is particularly applicable to magnetic components such as stators and rotors and non-rotating inductive devices for electric motors. The magnetic element is simplified and has reduced manufacturing time, and the stress experienced by the amorphous metal body element is minimized when the element is constructed by other methods. The resulting device has optimal magnetic properties. The various process steps described herein may be performed in the order listed herein or may be performed in other orders known to those of skill in the relevant art.

The bulk amorphous metal magnetic component of the present invention may be fabricated from a wide variety of amorphous metal alloys. In general, the alloys suitable for use in making the elements of the present invention are represented by the formula: m_70-85Y_1-20Z_0-20Defined, the subscripts represent atomic percentages wherein "M" is at least one of Fe, Ni, and Co, "Y" is at least one of B, C and P, "Z" is at least one of Si, Al, and Ge, with the proviso that: (i) up to 10 atomic percent of component M may be replaced by at least one of the metals Ti, V, Cr, Mn, Cu, Zr, Nb, Mo, Ta and W, (ii) up to 10 atomic percent of component (Y + Z) may be replaced by at least one of the non-metals In, Sn, Sb and Pb. As used herein, the term "amorphous metallic alloy" refers to a metallic alloy that is substantially free of any long-range order and that is characterized by an X-ray diffraction intensity peak that is qualitatively similar to that of a liquid or inorganic oxide glass.

Amorphous metal alloys suitable as starting materials for the practice of the present invention are commercially available in generally continuous thin strips or ribbons having widths of up to 20cm or more and thicknesses of about 20-25 microns. These alloys have a substantially fully glassy microstructure (e.g.At least about 80% of the material volume has an amorphous structure). Preferably, approximately 100% of the material in the alloy has an amorphous structure. The volume fraction of the amorphous structure can be determined by methods known in the art, such as X-ray, neutron, electron diffraction, transmission electron microscopy, or differential scanning calorimetry. For alloys in which "M", "Y", and "Z" are at least predominantly iron, boron, and silicon, respectively, the highest induction values of the alloys can be obtained at the lowest cost. Accordingly, the alloy preferably contains at least 70 atomic percent Fe, at least 5 atomic percent B, and at least 5 atomic percent Si, with the proviso that the total content of B and Si is at least 15 atomic percent. Amorphous metal strips composed of an iron-boron-silicon alloy are more preferred. Most preferably, the amorphous metal strip comprises about 11 atomic percent boron and about 9 atomic percent silicon, with the balance being iron and impurities. Alloy strips of this type having a saturation induction of about 1.56T and a resistivity of about 137 μ Ω -cm are sold by Honeywell International Inc. under the trade nameAlloy 2605 SA-1. Another suitable amorphous metal strip has a composition including about 13.5 atomic percent boron, about 4.5 atomic percent silicon, and about 2 atomic percent carbon, with the balance being iron and impurities. Alloy strips of this type having a saturation induction of about 1.56T and a resistivity of about 137 μ Ω -cm are sold by Honeywell International Inc. under the trade nameAlloy 2605 SC. For applications requiring higher saturation induction, bars consisting essentially of iron, about 18 atomic percent Co, about 16 atomic percent boron, about 1 atomic percent silicon, the balance being iron and impurities are suitable. Such alloy strip is sold by Honeywell International Inc. under the trade name ofAlloy 2605 CO. However, the losses of components constructed from such materials are slightly higher than for components constructed from such materialsAlloy 2605 SA-1.

As is known in the art, a ferromagnetic material can be characterized by its saturation induction, or by its saturation flux density or magnetization. Alloys suitable for use in the present invention preferably have a saturation induction of at least about 1.2 tesla (T), more preferably at least about 1.5T. The alloy also has a high electrical resistivity, preferably at least about 100 μ Ω -cm, and most preferably at least about 130 μ Ω -cm.

The mechanical and magnetic properties of the amorphous metal strip designated for use in the component can generally be improved by heat treatment at a temperature and for a time sufficient to ensure the desired improvement, while the substantially fully glassy microstructure of the strip is not altered. The heat treatment includes a heating section, an optional soaking section, and a cooling section. The magnetic field may be applied to the strip selectively during at least one portion, for example at least during a cooling portion of the heat treatment. The preferred application of a magnetic field during operation of a given magnetic element, in a direction substantially along which the flux is located, in some cases further increases the magnetic properties of the element and reduces its core loss. Optionally, the heat treatment comprises more than one such thermal cycle. Furthermore, one or more heat treatment cycles may be performed at different stages of the component fabrication. For example, the discrete laminations or lamination stack may be heat treated before or after adhesive bonding. Preferably, the heat treatment is performed before bonding, as many attractive adhesives do not withstand the temperatures required for heat treatment.

The heat treatment of the amorphous metal may be by any heating means that provides the metal with a desired thermal profile. Suitable heating means include infrared heat sources, ovens, fluidized beds, contact with high temperature heat sinks, resistive heating by passing current through the strip, and inductive (RF) heating. The choice of heating means may depend on the order of the process steps listed above.

The magnetic properties of certain amorphous alloys suitable for use in components can be greatly improved by heat treating the alloy to form a nanocrystalline microstructure. The microstructure is characterized by the presence of a high density of grains having an average size of less than about 100 nm, preferably less than 50 nm, and more preferably about 10-20 nm. The grains preferably constitute at least 50% by volume of the iron-based alloy. These preferred materials have low core loss and low magnetostriction. The low magnetostriction property also makes the material less susceptible to magnetic degradation from stresses induced by the fabrication and/or operation of the motor or inductive device. The heat treatment to form the nanocrystalline structure in a given alloy must be carried out at a higher temperature or for a longer time than the heat treatment carried out to maintain the substantially fully glassy microstructure. Amorphous metals and amorphous alloys, as used herein, also include a material that initially forms a substantially fully glassy microstructure and is subsequently transformed by heat treatment or other processes into a material having a nanocrystalline microstructure. Amorphous alloys that can be heat treated to form nanocrystalline microstructures may be referred to generally simply as nanocrystalline alloys. The method of the present invention allows the use of nanocrystalline alloys to produce bulk magnetic components of desired geometry. Such preparation is further facilitated when the alloy is still in its as-cast, ductile, substantially amorphous form before the alloy is heat treated to form the nanocrystalline structure, since the formation of the nanocrystalline structure by heat treatment generally makes the alloy more brittle and more difficult to handle.

Two preferred alloys for improving magnetic properties by forming nanocrystalline microstructures therein are given by the following formula, where the subscripts are atomic percent.

A first preferred nanocrystalline alloy is Fe_{100-u-x-y-z-w}R_uT_xQ_yB_zSi_wWherein R is at least one of Ni and Co, T is at least one of Ti, Zr, Hf, V, Nb, Ta, Mo, and W, Q is at least one of Cu, Ag, Au, Pd, and Pt, u ranges from 0 to about 10, x ranges from about 3 to 12, y ranges from 0 to about 4, z ranges from about 5 to 12, and W ranges from 0 to about less than 8. In which the alloy is heat treated to form nanocrystalline microstructures thereinAfter construction, it has a high saturation induction (e.g., at least about 1.5T), low core loss, and low saturation magnetostriction (e.g., absolute value of magnetostriction less than 4X 10^-6). Such alloys are particularly suitable for use in devices requiring a minimum size to achieve the required power rating.

The second preferred nanocrystalline alloy is Fe_{100-u-x-y-z-w}R_uT_xQ_yB_zSi_wWherein R is at least one of Ni and Co, T is at least one of Ti, Zr, Hf, V, Nb, Ta, Mo, and W, Q is at least one of Cu, Ag, Au, Pd, and Pt, u ranges from 0 to about 10, x ranges from about 1 to 5, y ranges from 0 to about 3, z ranges from about 5 to 12, and W ranges from 8 to 18. After the alloy has been heat treated to form a nanocrystalline microstructure therein, it has a saturation induction of at least about 1.0T, particularly low core loss and low saturation magnetostriction (e.g., absolute values of magnetostriction less than 4X 10)^-6). Such alloys are particularly suitable for use in components requiring operation at high excitation frequencies (e.g. at 1000Hz or higher), such as in very high speed motors or high frequency inductors or transformers.

Amorphous magnetic components are magnetized and demagnetized more efficiently than components made from other iron-based magnetic metals. In operation, an amorphous metal bulk component generates less heat than a component made of another iron-based magnetic metal when both components are magnetized at the same induction and frequency. Therefore, an electric drive motor using an amorphous metal bulk component is designed to operate under the following conditions: (i) lower operating temperatures; (ii) higher inductance to allow for a reduction in size and weight; or (iii) higher frequencies, the size and weight reduction or the motion control is improved when compared to electrically driven motors using components made of other iron-based magnetic metals.

A further advantage is that motors incorporating the amorphous metal bulk elements of the invention can be designed with a high pole count. The speed of the motor is proportional to the ratio of the electrical excitation frequency to the number of poles. The use of low core loss components as disclosed herein allows electrical excitation at much higher frequencies than used for conventional motors made of other known soft magnetic materials, which have higher core losses. Thus, the designer has more freedom to choose the number of poles and excitation frequency for a given speed. A high pole count motor may be selected that operates with acceptable core loss at maximum speed, but at the same time maintains acceptable power and torque performance over a wide range of excitation frequencies (and thus over a wide range of rotational speeds). In some applications, this flexibility means that the load can be driven directly without passing through the gearbox, thus avoiding a reduction in gearbox complexity, maintenance requirements and efficiency.

As known in the art, core loss refers to the dissipation of energy that occurs inside a ferromagnetic material as the magnetization of the ferromagnetic material changes over time. The core loss of a given magnetic element is typically determined by cyclically exciting the element. A time-varying magnetic field is applied to the element to produce a corresponding time-varying magnetic induction or flux density within the element. To standardize the measurement, the excitation is generally chosen such that the magnetic induction within the sample is uniform and the magnetic induction is a function of time at frequency "f" and of peak amplitude B_maxBut varies sinusoidally. The core loss is then determined by known electrical measurement instruments and techniques. Traditionally, losses are recorded in watts per unit mass or unit volume of the excited magnetic material. As known in the art, the loss varies with f and B_maxBut monotonically increases. Most standard protocols for measuring the core loss of soft magnetic materials used for motor components [ e.g. ASTM standards A912-93 and A927(A927M-94)]A sample of material in a substantially closed magnetic circuit, i.e. a configuration in which the closed magnetic flux lines are completely contained within the sample volume, is required. On the other hand, the magnetic material employed by the motor element, such as the rotor or stator, is located in a magnetically open circuit, i.e., a configuration in which lines of magnetic flux traverse an air gap. A given material tested in an open circuit typically exhibits higher core loss, i.e., watts per unit mass or volume, due to fringing field effects and non-uniformity of the magnetic fieldThe value is higher than the corresponding value measured in the closed circuit. Advantageously, the bulk magnetic components of the present invention exhibit low core loss over a wide range of flux densities and frequencies, even in an open circuit configuration.

Without being bound by any theory, it is believed that the total iron loss of the low-loss amorphous metal body component of the present invention consists of values derived from hysteresis loss and eddy current loss. Both values are peak magnetic induction B_maxAnd the excitation frequency f. Prior art analyses of core loss in amorphous metals (e.g., g.e.fish, j.appl.phys.57, 3569(1985) and g.e.fish et al, j.appl.phys.64, 5370(1988)) are generally limited to data obtained from materials in closed magnetic circuits.

Total iron loss per unit mass L (B) of the bulk magnetic component of the present invention_maxF) may be substantially defined by the function L (B)_max，f)＝c₁f(B_max)ⁿ+c₂f^q(B_max)^mIs defined by the coefficient c₁And c₂The indices n, m and q must all be determined empirically, without known theory to accurately determine their values. The use of such equations allows the total core loss of the bulk magnetic component of the present invention to be determined at any desired operating induction and excitation frequency. It is often found that in many magnetic devices of particular geometry, particularly in motor rotors and stators, the magnetic field is not uniform in spatial distribution. Modeling, such as finite element modeling, is a technique known in the art for evaluating the spatial and temporal variation of peak flux density that closely approximates the flux density distribution measured in an actual motor or generator. By introducing an appropriate empirical formula for determining the core loss of a given material at a spatially uniformly distributed flux density, this technique can predict with appropriate accuracy the corresponding actual core loss of a given component in an operating configuration by numerically integrating the component volume.

The core loss of the magnetic component of the present invention can be measured by various methods known in the art. Methods particularly suitable for measuring the components of the invention will be described below. The method includes forming a magnetic circuit using the magnetic component and flux containment structure arrangement of the present invention. Alternatively, the magnetic circuit may comprise a plurality of magnetic elements of the invention and a flux enclosing structure arrangement. The flux enclosing structure arrangement preferably comprises a soft magnetic material having a high magnetic permeability and a saturation flux density at least equal to the flux density at the test element. Preferably, the saturation flux density of the soft magnetic material is at least equal to the saturation flux density of the component. The flux direction along which the component is tested generally forms first and second opposite faces of the component. The flux lines enter the element generally in a direction orthogonal to the plane of the first opposing face. The magnetic flux lines generally pass out of the second opposing face along the plane of the amorphous metal strip. The flux enclosure structure arrangement generally includes flux enclosure magnetic elements that are preferably constructed in accordance with the present invention, but may also be constructed in accordance with methods and materials known in the art. The flux-enclosing magnetic element also has first and second opposing faces into and out of which the lines of magnetic flux enter generally in a direction orthogonal to their respective planes. The opposing faces of the flux blocking element are substantially the same size and shape as the corresponding faces of the magnetic element with which the flux blocking element is mated during actual testing. The flux enclosing magnetic element is disposed in mating relationship with its first and second faces in close proximity and relatively close proximity, respectively, to the first and second faces of the magnetic element of the present invention. Magnetomotive force is applied by passing a current through a first winding that surrounds the magnetic elements of the invention or the flux-enclosing magnetic elements. The resulting flux density is determined by faraday's law from the voltage induced in the second winding surrounding the magnetic element to be tested. The applied magnetic field is determined by the magnetomotive force by ampere's law. The core loss was then calculated by the applied magnetic field and the resulting flux density using conventional methods.

Fig. 6 depicts an assembly 60 for implementing one of the testing methods described above that does not require a flux enclosure arrangement. The assembly 60 includes four of the arc-shaped bulk amorphous metal magnetic components 200 of the present invention. Each element 200 is a substantially identical right circular, annular and cylindrical arcuate segment subtending 90 with an arcuate surface 210 as shown in figure 4B. Each element has a first opposing face 66a and a second opposing face 66 b. The elements 200 are arranged in mating relationship to form an assembly 60 having a generally right circular cylinder. The first opposing face 66a of each element 200 is proximate to and generally parallel to the corresponding first opposing face 66a of an adjacent element 200. The adjacent faces of the four sets of elements 200 thus define four equally spaced gaps around the assembly 60. The elements 200 may be tightly coupled by the band 62. The assembly 60 forms a magnetic circuit having four permeable segments (each segment including an element 200) and four gaps 64. Two copper wire windings (not shown) are helically threaded through the assembly 60. An alternating current of appropriate strength passes through the first winding and provides a magnetomotive force which excites the assembly 60 at the desired frequency and peak flux density. The resulting lines of magnetic flux lie generally in the plane of the strip 20 and along the circumferential direction. In each element 200, a voltage is induced in the second winding that is representative of the flux density over time. The total core loss is determined by conventional electronic means from voltage and current measurements and is equally distributed among the four elements 200.

In another aspect of the present invention, it is advantageous to incorporate a low-loss bulk amorphous metal magnetic component in an inductor device. Turning in detail to fig. 7A, fig. 7A illustrates an inductive device of the present invention comprising a magnetic core 650 comprising a single amorphous metal body element having a circular ring shape with an internal air gap 660. As best shown in fig. 7B, a plurality of substantially similarly shaped planar layers 652 are cut from the amorphous metal strip. The layers are then stacked in registration and bonded together with an adhesive. That is, the layers 652 are positioned such that their respective inner and outer edges 656, 654 and notches 657 are generally aligned to form smooth, generally cylindrical inner and outer surfaces. The alignment may be accomplished by adding each layer 652 in turn to the stack. Alternatively, the layers may be arranged in a set after lamination is complete. The aligned notches together define an air gap 660 with a spacer (not shown) optionally interposed between faces 658 and 658'.

Each layer is generally annular in shape and has an outer edge 654 and an inner edge 656. Each layer 652 has a notch 65 formed therein extending from an outer edge 654 to an inner edge 656. The width of the notches 657 is selected so that an appropriate demagnetization factor is achieved within the finished core 650. The layers 652 are bonded by an adhesive, preferably impregnated with a low tack epoxy 662. In the aspect depicted, the layers are circular rings, but other non-circular shapes are possible, such as oval, racetrack, and square and rectangular frame shapes of any aspect ratio. The inner or outer top of the layers in any of the embodiments may optionally be radiused. The notches 657 are shown in a radial direction, but may be formed in any orientation extending from the inboard edge 656 to the outboard edge 654. Additionally, notches 657 may be formed in the generally rectangular shape described, or in a tapered shape, or may have a suitable profile to achieve the desired effect on the B-H loop of the core. The construction of the inductive device of the present invention further comprises providing at least one toroid winding (not shown) on the core.

The selective etching process of the present invention is particularly preferred for the manufacture of small parts because it is relatively easier to automate and enables tighter and more reproducible control of the dimensions of the finished layer. This control enables the mass production of cores comprising laminations of uniform size, which thus have excellent and uniform magnetic properties. The manufacturing method according to the invention has an advantage over a core structure with windings, since the compressive and tensile stresses inherent in bending the strip into a helical structure are no longer present in the flat laminations. Any stresses resulting from cutting, punching, etching, etc. may be limited to a small area or to a peripheral area close to each lamination.

In another aspect of the invention, similar manufacturing processes are used to form layers incorporated in bulk amorphous metal magnetic components, which generally have overall shapes resembling printed letters such as "C", "U", "E", and "I", by which the components can be identified. Each element comprises a plurality of planar layers of amorphous metal. The layers are bonded together in alignment with each other at approximately the same height and packing density to form the components for the inductive device of the invention. The elements of the device of the present invention are assembled by securing the elements adjacent to the stationary member to form at least one magnetic circuit. In the assembled configuration, the amorphous metal strip layers within all of the components lie in substantially parallel planes. Each element has at least two mating faces adjacent to each other which are the same number and parallel to complementary mating faces on the other elements. Some shapes, such as C, U and E-shapes terminate in mating faces that are generally substantially coplanar. The I-shape (or rectangular prismatic shape) may have two parallel mating faces at its opposite ends, or one or more mating faces at its long sides, or both. The mating faces are preferably substantially perpendicular to the plane of the constituent tapes within the component to minimize core loss. Some embodiments of the present invention also include a bulk magnetic component having mating faces that are mitered with respect to the elongated direction of the component feature.

In some embodiments of the invention, when forming an inductive device with a single magnetic circuit, two magnetic elements with two mating faces are used. In other aspects, the element has more than two mating faces, or the device has more than two elements; thus, some of these embodiments also provide more than two magnetic circuits. In this application, the term "magnetic circuit" refers to a path through which continuous lines of magnetic flux flow due to an applied magnetomotive force generated by an electrically charged winding encircling at least a part of the magnetic circuit. A closed magnetic circuit refers to a magnetic circuit in which the magnetic flux is exclusively within the core of magnetic material, whereas in an open circuit, part of the magnetic circuit is outside the core of material, e.g. across an air gap or a non-magnetic spacer between core parts. The magnetic circuit of the device of the present invention is preferably relatively closed, with the magnetic circuit being largely located within the magnetic layers of the device elements, but also passing through at least two air gaps between adjacent mating faces of the respective elements. The degree of openness of the circuit can be dictated by the contribution to the total reluctance from the air gap and the permeable core material. Preferably, in the reluctance of the magnetic circuit of the device of the invention, the resistance caused by the gap is at most ten times the resistance caused by the permeable element.

Optionally, the manufacture of the component comprises the step of preparing a mating face on the component, said face being substantially planar and perpendicular to the constituent layers. If desired, the step of fabricating the faces may include finishing the mating faces and removing any rough or uneven flattening operations. The planarization operation preferably includes at least one of milling, surface grinding, cutting, polishing, chemical etching, and electrochemical etching, and the like, to provide planar mating surfaces. The planarization step is particularly preferred for the mating surfaces on one side of the component to counteract any effects due to imperfect alignment of the amorphous metal layer.

Referring specifically to fig. 8, fig. 8 depicts a generally "C-I" shaped inductive device 30 of the present invention that includes a "C" shaped magnetic element 32 and an "I" shaped magnetic element 33. The "C" member 32 further includes a first prong 29 and a second prong 44, each extending perpendicularly from a common side of the back portion 34 and terminating at distal ends of a first rectangular mating surface 43 and a second rectangular mating surface 45. The mating faces are generally substantially coplanar. The prongs 29 and 44 extend out from opposite ends of one side of the spine portion 34. The "I" element 33 is a rectangular prism having a first rectangular mating face 42 and a second rectangular mating face 46, both of which are located on a common side of the element 33. The mating faces 42 and 46 are complementary in size and spacing to the corresponding mating faces 43 and 45 at the ends of the prongs 29 and 44 of the member 32. The prongs 29 and 44, the back portion 34 between the prongs and the I-member 33 all have a generally rectangular geometric cross-section, preferably all having substantially the same height, width and effective magnetic area. The effective magnetic area refers to the area occupied by the magnetic material in the geometric cross-section, which is equal to the total geometric area multiplied by the stacking factor. One or more windings may be applied to the elements of device 30, such as windings 47 and 48 to the corresponding prongs 29 and 44 of C-element 32, as is known in the art. Alternatively, the windings may be applied to the I-element 33 in an embodiment (not shown).

Fig. 9-11 depict an "E-I" device 80 of the present invention that includes "E" and "I" shaped constituent elements. The E-element 82 comprises a plurality of layers made of ferromagnetic metal strips. Each layer has substantially the same E-shape. The layers are joined together to form an E-member 82 of substantially uniform thickness having a back portion 84, a central prong 86E, a first side prong 90, and a second side prong 94. The center prong 86 and the side prongs 90, 94 each extend perpendicularly from a common side of the portion 84 and terminate at distal ends of the rectangular faces 87, 91 and 95, respectively. A central prong 86 extends from the center of the back portion 84, while side prongs 90 and 94 each extend from opposite ends of the same side of the back portion 84. The lengths of the center prong 86 and the side prongs 90, 94 are generally approximately the same such that the respective faces 87, 91 and 95 are substantially coplanar. As shown in FIG. 10, the A-A cross section of the back portion 84 between the center prong 86 and either side prong 90 and 94 is substantially rectangular, with the thickness defined by the height of the stacked layers and the width defined by the width of each layer. The A-A cross section of back portion 84 is preferably at least as wide as any of faces 87, 91 and 95.

The I-element 81 has a rectangular prismatic shape and includes a plurality of layers that employ the same ferromagnetic metal strips as the inner layers of the E-element 82. The layers are bonded together to form an I-piece 81 of substantially uniform thickness. The thickness and width of the I-member 81 is substantially equal to the thickness and width of the back portion 84 at section A-A, and its length is substantially equal to the length of the E-member 82 as measured between the outer side surfaces of the side prongs 90, 94. The mating face 88 is provided centrally on one side of the I-member 81, and the first end mating face 92 and the second end mating face 96 are located at opposite ends of the same side of the member 81. The dimensions of each mating face 87, 91 and 95 are substantially the same as the dimensions of faces 88, 92 and 96, respectively.

As further shown in fig. 9 and 11, assembly of device 80 includes: (i) providing one or more electrical windings, such as windings 77, 78 and 79, surrounding one or more portions of element 82 or 81; (ii) aligning the E-component 82 and the I-component 81 in close proximity with all layers in substantially parallel planes; and (iii) mechanically fixing the elements 81 and 82 in a side-by-side array. The elements 82 and 81 are aligned so that the faces 87 and 88, 91 and 92, 95 and 96, respectively, abut. The spacing between the sets of faces forms three air gaps of substantially equal thickness. Spacers 89, 93 and 97 are optionally placed in these gaps to improve the reluctance and energy storage capability of each magnetic circuit in the device 80. Alternatively, the respective faces may be in close fitting contact to minimize air gaps and improve initial inductance.

The "E-I" device 80 may be incorporated into a single phase transformer having a primary winding and a secondary winding. In one such embodiment, winding 79 serves as the primary winding, while the series-connected auxiliary windings 77 and 78 serve as the secondary windings. In such an embodiment, it is preferred that each of the side prongs 90 and 94 have a width that is at least half the width of the central prong 86.

The embodiment of fig. 9-11 provides three magnetic circuits, the paths of which are shown by dashed lines 51, 52 and 53 in "E-I" device 80. Thus, the device 80 may be used as a three-phase inductor, with three prongs each carrying a winding for one of the three phases. In another embodiment, the "E-I" device 80 may be used as a three-phase transformer, with each prong having primary and secondary windings for one of the three phases. In most embodiments of the E-I device for a three-phase circuit, the prongs 86, 90 and 94 are preferably of the same width to better balance the three phases. In some specialized designs, different prongs may have different cross sections, different gaps, or different numbers of turns. Other forms suitable for various multiphase applications will be apparent to those skilled in the art.

The following examples are provided to provide a more complete understanding of the invention. The particular techniques, conditions, materials, proportions and listed data set forth to illustrate the principles and practice of the invention are exemplary and should be considered as limiting the scope of the invention.

Example 1

Preparation and testing of amorphous metal stators

The laminations of the amorphous metal stator for the inside-out spindle electric drive motor are Fe from about 22 microns thick by a selective etching process₈₀B₁₁Si₉The amorphous metal ribbon is cut. Each lamination includes a central generally annular ring-shaped zone and a plurality of teeth extending radially outwardly from the central ring-shaped zone, as generally shown in fig. 5D. Of annular zonesThe inner and outer diameters are about 9 mm and 11 mm, respectively. The outer diameter of the element measured at the periphery of the tooth was about 25 mm. The laminate is heat treated at 350-. Approximately 120 laminations are then stacked to form a generally cylindrical structure having a height of approximately 4.2 millimeters. The laminate is soaked in a low viscosity heat activated epoxy resin which can impregnate and penetrate the spaces between adjacent laminations. The epoxy resin used is Epoxylite^TM8899, diluted with acetone at a volume ratio of 1: 5 to obtain the appropriate viscosity. The stacks were aligned with each other in the jig and lightly pressed to a height of about 4 mm to increase the compaction density of the stacks. The impregnated stack is then exposed to a temperature of about 177 c for approximately 2.5 hours to activate and cure the epoxy resin solution. After cooling, the stack was removed from the jig and coated with 3M ScotchCast by electrophoresis^TMElectrical resin 5133 to form a stator suitable for use in an inside-out motor.

The magnetic properties of the stator are tested by attaching primary and secondary electrical windings around a central annular region. The primary winding is excited by an AC current source of the desired frequency and amplitude; the resulting maximum flux density is calculated from the induced voltage across the secondary winding, assuming that the flux is fully embodied within the central annular region, effectively ignoring any flux near the root of the tooth. The excitation is adjusted to provide a series of test points of specified frequency and flux density. The core loss was determined using a Yokogawa2532 watt meter.

The stator core in this embodiment exhibits advantageously low core loss in frequency amplitudes from DC up to at least 2 kHz. Notably, the loss at 50Hz (0.05kHz) and 1.0T is about 0.21W/kg; losses at 400Hz (0.4kHz) and 1.0T are about 1.6W/kg, 2.8W/kg at the same frequency and 1.3T; the loss at 800Hz (0.8kHz) and 1.0T is about 3.3W/kg, and at the same frequency and 1.3T is 5.7W/kg; the loss at 2000Hz (2kHz) and 1.0T was about 9.5W/kg, and at the same frequency and 1.3T was 14.8W/kg.

It should also be noted thatThe loss behavior of the stator core can be represented by a function L (B)_max，f)＝c₁f(B_max)n+c₂f^q(B_max)^mTo describe. In particular, the loss of the stator is less than 0.005 (B) of the utilization function L_max)^1.5+0.000012f^1.5(B_max)^1.6The estimated value.

The resulting low core loss values make the stator core particularly suitable for use in high speed motors where the electrical frequency can be as high as 1-2kHz or higher.

Example 2

Preparation of nanocrystalline alloy rectangular prism

Lamination pass through for inside-out spindle motor stator about 30 mm wide and 0.018 mm thick Fe_73.5Cu₁Nb₃B₉Si_13.5Amorphous metal ribbon is made by photolithography. Each lamination includes a generally annular central annular region having a plurality of teeth extending radially outwardly therefrom, as generally shown in fig. 5D. The annular region has adjacent inner and outer diameters of about 9 mm and 11 mm, respectively. The outer diameter of the element measured at the periphery of the tooth was about 25 mm. The laminate is subjected to a heat treatment to form a nanocrystalline microstructure within the amorphous metal. Annealing is performed by performing the following steps: 1) heating the part to 580 ℃; 2) holding at a temperature of about 580 ℃ for about 1 hour; and 3) allowing the part to cool to room temperature. Approximately 160 heat treated laminations are then stacked to form a generally cylindrical structure of about 4.2 mm height and immersed in a low viscosity heat activated epoxy resin which is capable of impregnating and infiltrating the spaces between adjacent laminations. The epoxy resin used is Epoxylite^TM8899, diluted with acetone at a volume ratio of 1: 5 to obtain the appropriate viscosity. The stacks were aligned with each other in the jig and lightly pressed to a height of about 4 mm to increase the compaction density of the stacks. The impregnated stack is then exposed to a temperature of about 177 ℃ for approximately 2.5 hours to activate and cure the epoxy resinAnd (3) solution. After cooling, the stack was removed from the jig and coated with 3M ScotchCast by electrophoresis^TMThe resin 5133 is formed to form a stator suitable for an inside-out motor.

The nanocrystalline alloy stator exhibits low core loss. Notably, the loss at 50Hz (0.05kHz) and 1.0T is about 0.21W/kg; losses at 400Hz (0.4kHz) and 1.0T are about 1.6W/kg, 2.8W/kg at the same frequency and 1.3T; the loss at 800Hz (0.8kHz) and 1.0T is about 3.3W/kg, and at the same frequency and 1.3T is 5.7W/kg; the loss at 2000Hz (2kHz) and 1.0T was about 9.5W/kg and at the same frequency and 1.3T was 14.8W/kg. Therefore, the stator is suitable for an electric drive motor with high speed and high efficiency.

Having described the invention in rather full detail, it is to be understood that such detail is not necessarily strictly adhered to, but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

Claims

1. An inductive device, comprising:

a magnetic core having a magnetic circuit with at least one air gap and comprising at least one low-loss ferromagnetic amorphous metal bulk magnetic component;

at least one electrical winding surrounding at least a portion of the magnetic core;

the component comprises a plurality of generally similarly shaped, selectively etched, planar layers of amorphous metal strips stacked and aligned with one another, the planar layers being bonded together by an adhesive to form portions of a polyhedron shape; and

the inductive device is excited to a peak induction level B when excited at an excitation frequency f of 5kHz_maxWhen the operation is carried out at 0.3T, the iron loss is less than 12W/kg;

wherein the selectively etched amorphous metal strip is prepared by a selective etching process comprising:

depositing a chemically stable material on a first side of each of the metal strips in a pattern defining a preselected shape;

mating a second side of each of the metal strips with a carrier strip;

exposing a first side of each of the metal strips to an etchant to selectively etch a desired shape; and

separating the shape from the metal strip.

2. The inductive device of claim 1, wherein said device is selected from the group consisting of a transformer and an inductor.

3. The inductive device of claim 1, wherein said magnetic core comprises a plurality of said low-loss ferromagnetic amorphous metal bulk magnetic components each having at least two mating faces, said components being assembled in juxtaposition such that each of said mating faces is proximate to and substantially parallel to one of the mating faces of the other of said components.

4. The inductive device of claim 1, wherein each of said elements has a shape selected from the group consisting of C, E, I, U, trapezoidal, and arcuate.

5. The inductive device of claim 1, wherein said inductive device has a shape selected from the group consisting of E-I, E-E, C-I, C-C and C-I-C.

6. The inductive device of claim 1, wherein said deviceWhen excited to a peak induction level B at an excitation frequency "f_maxWhen operated at the lower part, the alloy has an iron loss less than "L", wherein L is 0.005f (B) expressed by the formula L_max)^1.5+0.000012f^1.5(B_max)^1.6The core loss, the excitation frequency and the peak induction level are given in watts/kilogram, hertz and tesla, respectively.

7. A method for constructing a low core loss bulk amorphous metal magnetic component, comprising:

selectively etching the amorphous metal strip material to form a plurality of laminations each having substantially the same predetermined shape;

stacking the laminations in alignment with each other to form a lamination stack; and

bonding the lamination stack with an adhesive;

wherein the selectively etching comprises:

mating a second side of each of the metal strips with a carrier strip;

separating the shape from the metal strip.

8. The method of claim 7, further comprising:

finishing the element to achieve at least one of the following objectives: (i) removing excess adhesive from the component; (ii) subjecting the element to a suitable surface finish; and (iii) removing material to determine the final component dimensions of the component.

9. The method of claim 7, further comprising:

annealing the laminations to increase the magnetic properties of the element.

10. The method of claim 9, wherein the annealing is performed after the bonding step.

11. The method of claim 9, wherein the annealing is performed before the bonding step.

12. The method of claim 7, further comprising:

coating at least a portion of the surface of the element with an insulating coating agent.

13. The method of claim 7, further comprising:

at least two mating faces are prepared on the element, the faces being substantially planar and perpendicular to the layers.

14. The method of claim 13, wherein the preparing comprises a planarizing operation comprising at least one of milling, surface grinding, cutting, polishing, and chemically etching the mating face.

15. The method of claim 14, wherein the chemical etching is electrochemical etching.

16. The method of claim 7, wherein said bonding comprises dip treating said lamination stack.

17. The method of claim 7, wherein the adhesive comprises at least one component selected from the group consisting of one-and two-component epoxies, varnishes, anaerobic adhesives, cyanoacrylate adhesives and Room Temperature Vulcanizing (RTV) silicone materials.

18. The method of claim 17, wherein the adhesive comprises a low tack epoxy.

19. The method of claim 18, wherein the adhesive has a tack of less than 1000 cps.

20. The method of claim 18, wherein the adhesive has a coefficient of thermal expansion of less than 10 ppm.

21. The method of claim 19, wherein the adhesive has a coefficient of thermal expansion of less than 10 ppm.

22. A low core loss bulk amorphous metal magnetic component, comprising:

a plurality of laminations of selectively etched amorphous metal strip material, the laminations each having substantially the same predetermined shape; and

a lamination stack of the aligned laminations, wherein the lamination stack is bonded with an adhesive;

wherein the plurality of laminations of selectively etched amorphous metal strip material are prepared by a selective etching process comprising:

mating a second side of each of the metal strips with a carrier strip;

separating the shape from the metal strip.

23. The bulk amorphous metal magnetic component of claim 22 wherein said component is excited to a peak induction level B at an excitation frequency "f_maxWhen operated at the lower part, the alloy has an iron loss less than "L", wherein L is 0.005f (B) expressed by the formula L_max)^1.5+0.000012f^1.5(B_max)^1.6The core loss, the excitation frequency and the peak induction level are given in watts/kilogram, hertz and tesla, respectively.

24. A process for producing a cut amorphous metal part having a preselected shape, comprising:

providing an amorphous metal sheet having a first surface and a second surface;

printing a chemically stable material on the first surface in a pattern defining the preselected shape;

covering the second surface with a protective layer;

exposing the amorphous metal sheet to a corrosive agent to selectively etch amorphous metal from regions of the first surface outside of the preselected shape; and

separating the shape from the exposed amorphous metal sheet;

wherein the selectively etched metal sheet is laminated and bonded with a plurality of similarly shaped metal sheets by an adhesive.

25. The process of claim 24, wherein the printing comprises at least one printing method selected from the group consisting of flat-bed printing, raised-bed printing, recessed-bed printing, screen printing, electrostatic printing, and inkjet deposition printing methods.

26. The process of claim 24, wherein the printing deposits the chemically stable material during continuous motion of the amorphous metal sheet.

27. The process of claim 24 wherein said pattern defining said preselected shapes and said overcoat comprise substantially the same chemically stable material.

28. The process of claim 24, wherein the protective layer comprises a carrier strip.

29. The process of claim 28 wherein the carrier strip comprises at least one metal selected from the group consisting of stainless steel, nickel-based alloys, titanium, tantalum, and aluminum.

30. The process of claim 28 wherein the carrier strip is comprised of a polymeric material.

31. The process of claim 24, wherein the exposing is for a period of time sufficient to substantially weaken the connection of the shape to the sheet.

32. The process of claim 24, wherein the exposing is for a time sufficient to penetrate the sheet to separate the shape from the sheet.

33. The process of claim 24, wherein the shape includes at least one tab connecting the shape to the remainder of the sheet.

34. The process of claim 24, wherein the separating comprises a stamping operation that severs the shape from the amorphous metal sheet.