Patent Publication Number: US-8984742-B2

Title: Method of making soft magnetic amorphous metal electromechanical component

Description:
This application is a continuation-in part of U.S. application Ser. No. 10/763,728, filed Jan. 23, 2004, which is a continuation-in-part of U.S. application Ser. No. 10/458,944, filed Jun. 11, 2003 (now U.S. Pat. No. 7,018,498). 
    
    
     BACKGROUND OF THE INVENTION 
     Multi-pole rotating electro-mechanical devices, such as motors, generators, re-gen motors, alternators, brakes and magnetic bearings are comprised of rotors and electro-mechanical components. AC motors rotate by producing a rotating magnetic field pattern in the electro-mechanical component that causes the rotor to follow the rotation of this field pattern. As the frequency varies, the speed of the rotor varies. To increase the speed of the motor, the frequency of the input source must be increased. 
     High frequency motors manufactured with the proper materials can be very efficient. For certain applications, like electric or hybrid cars, highly efficient electric motors are desirable. 
     The construction of electro-mechanical components for high frequency electric motors and generators is problematic. Iron or steel components are quite common in electric motors and generators. However, at high frequencies, such as those greater than 400 Hz, conventional iron or steel components are no longer practical. The high frequency of the AC source increases the core losses of the iron or steel components, reducing the overall efficiency of the motor. Additionally, at very high frequencies, the component may become extremely hot, cannot be cooled by any reasonably acceptable means and may cause motor failure. 
     For construction of electro-mechanical components used in high frequency electric motors, ribbon made from soft magnetic material provides distinct advantages. defined as 0.008″ and thicker, non grain oriented with a typical Si content of 3%+/−12% or 2) alternate soft materials that are 0.007″ or thinner with Si content of 3% to 7%, amorphous, or nanocrystalline alloys and other grain oriented or non grain oriented alloys. Some soft magnetic ribbon materials exhibit inherent characteristics that make their use in high frequency electro-mechanical rotating devices highly desirable. Some soft magnetic ribbons are easy to magnetize and demagnetize, which means an electromechanical component made with these metals would have low power loss, low temperature rise at high frequency, extremely fast magnetization and easy conversion of electrical to mechanical energy. An electro-mechanical component made of such an metal would generate less core losses and be able to operate at much higher frequencies, resulting in motors and generators of exceptional efficiency and power density. 
     Soft magnetic materials are commercially produced as ribbon or strip. A preferred example of a soft magnetic metal ribbon is Metglas®, which is an amorphous material, manufactured by Honeywell, Inc. Soft magnetic metal ribbons are very thin and of varying width. Manufacturing components of soft magnetic metal ribbon requires winding the soft magnetic ribbon into a shape and then heat processing the shape. Simple three dimensional shapes, such as toroids, can currently be constructed from soft magnetic metal ribbon. 
     However electromechanical components are often not simple three dimensional shapes. The electromechanical component can have numerous slots for accommodating motor coils in a generally toroidal structure. 
     Attempts to create complex three dimensional configurations from soft magnetic metal ribbon have heretofore been commercially unsuccessful. Various manufacturing techniques have been attempted by industry such as but not limited to: wire electrical discharge machining, electrochemical creep grinding, conventional electrical discharge machining, cutting, stamping, acid etching and fine blanking. None have proven satisfactory for reasons such as cost-effectiveness, manufacturing repeatability, or process cycle time. 
     This inability to fabricate complex three dimensional shapes from soft magnetic ribbon has been the significant impediment to producing high efficiency axial flux motors and generators. A method to produce electromechanical components from soft magnetic ribbon in a cost effective, end use functional, high volume capable method that will also provide substantial design flexibility for end use requirements is highly desirable. 
     SUMMARY OF THE INVENTION 
     A method for forming a three dimensional soft magnetic metal mass suitable for milling consists of wrapping soft magnetic metal ribbon into a three dimensional shape, then applying adhesive to the three dimensional shape. The adhesive is then cured and the cured form is mechanically constrained in three dimensions. The method results in an soft magnetic metal mass which can withstand the mechanical stresses of machining. The three dimensional soft magnetic metal form can be milled using a horizontal mill, a vertical mill, a computer numeric control (CNC) machine, or any other common milling equipment. Thus, complex three dimensional soft magnetic metal shapes can be created. 
     The ability to create three dimensional soft magnetic metal shapes allows the use of soft magnetic metal for a variety of applications heretofore foreclosed by the mechanical characteristics of soft magnetic metal ribbon. 
     To manufacture an soft magnetic electromechanical component, soft magnetic metal ribbon is wound into a toroid. The toroid is then placed in a milling assembly. Adhesive is applied to the toroid, and then cured. The toroid is then milled into an electromechanical component shape, and then thermally processed into a electromechanical component. 
     These and other objects, advantages and features of the invention will be more readily understood and appreciated by reference to the detailed description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a soft magnetic metal ribbon being wound on an inner ring. 
         FIG. 2  shows an inner containment hat. 
         FIG. 3  shows an outer containment hat. 
         FIG. 4  shows a milling assembly. 
         FIG. 5  shows a milling assembly being milled. 
         FIG. 6  shows a soft magnetic metal electromechanical component. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows soft magnetic metal ribbon  10  being wound about a winding axis  11  on an inner ring  14 . Winding machine  13  contains soft magnetic metal ribbon roll  12 . Inner ring  14  is placed on winding plate  16 . Soft magnetic metal ribbon  10  is wound on inner ring  14 , forming soft magnetic metal toroid  18 . Soft magnetic metal toroid  18  has an inner side surface  15 , an outer side surface  17 , a top  19 , and a bottom  21 . 
     While  FIG. 1  shows the formation of an soft magnetic metal toroid  18 , it will be appreciated that a three dimensional shape could be created with a geometry distinctly different from the soft magnetic metal toroid  18 . For example, it would be possible by winding around four corners to create a rectangular prism. 
     Soft magnetic metal ribbon  10  can be wound using a variety of machines and methods. Preferably, a consistent, firm toroid will have at least an 85% wind density compared to the inherent ribbon density. Soft magnetic metal toroid  18  is then removed from winding plate  16 . Soft magnetic metal ribbon  10  can be wound around the inner ring  14  while attached to the inner containment hat  20  as a single unit. 
     An adhesive is then applied to the soft magnetic ribbon toroid  18  in a manner to permeate the soft magnetic metal toroid  18 . Inner ring  14  is still contained within the soft magnetic ribbon toroid  18 . A suitable adhesive is Scotch Cast adhesive by 3M, diluted by acetone so as to achieve about a 20% mix by volume. The adhesive is applied to soft magnetic ribbon toroid  18  by an ambient atmospheric soak process. Soft magnetic ribbon toroid  18  is immersed in the adhesive until the adhesive infiltrates the layers. 
     Alternatively, the adhesive could be applied by immersing soft magnetic ribbon toroid  18  into the adhesive inside a vessel that is evacuated of air. The vacuum created would enhance the infiltration of the adhesive into the soft magnetic ribbon toroid  18  layers. Adhesive could also be applied to the soft magnetic ribbon during the winding process utilizing a wet spray or dry electrolytic deposition process. Alternative resins, epoxies or adhesives may be used. Different brands as well as different types of resins, epoxies or adhesives may be used. Heat cured epoxies that require various temperatures as well a two stage epoxies that cure at room temperature would also be suitable. 
     After soft magnetic ribbon toroid  18  is sufficiently infiltrated with adhesive, soft magnetic ribbon toroid  18  is allowed to drain. Once dry, soft magnetic ribbon toroid  18  is placed inside an oven for curing. Importantly, the temperature for heat treating the adhesive be a fraction of the temperature for heat processing soft magnetic metal ribbon  10 . A preferable fraction is ½, although fractions of ¼ and ¾ might also be satisfactory. 
       FIG. 2  shows inner containment hat  20 . Inner containment hat  20  is a cylinder comprised of a number of columns  22  extending upward from the inner containment hat base  24 . Fingers  26  extend outward from columns  22  at approximately a right angle. Fingers  26  increase in width as they extend further from the columns  22 . Fingers  26  are arranged in a circle, forming an annulus  28 . The columns  22  and fingers  26  form a plurality of inner containment hat grooves  29 . Columns  22  of inner containment hat  20  are placed inside inner ring  14 . 
     The height of columns  22  is approximately equal to the height of the soft magnetic metal toroid  18 . The diameter of the soft magnetic metal toroid  18  is about equal to the diameter of the annulus  28 . 
     Following the placement of inner containment hat within soft magnetic metal toroid  18 , outer containment hat  30  shown in  FIG. 3 , is placed around soft magnetic metal toroid  18 . 
     Outer containment hat  30  is cylindrical, with a base  32 . Bars  34  extend upward from base  32 . At the top of each bar  34  is a lug  36  extending inward. Lug  36  for each bar  34  forms a flange for securing the amorphous metal toroid  18  within outer containment hat  30 . Bars  34  and lugs  36  form a plurality of outer containment hat grooves  38 . 
     Milling assembly  40 , shown in  FIG. 4 , is then formed. Soft magnetic metal toroid  18 , still containing inner ring  14 , along with the inner containment hat  20  is placed within outer containment hat  30 . Lugs  36  and fingers  26  are aligned. Milling assembly  40  contains the soft magnetic metal toroid  18  within a toroidal geometry. Alternatively, soft magnetic metal toroid  18  could be placed within outer containment hat  30  and inner containment hat  20  prior to treatment with the adhesive. 
     After application of the adhesive and placement within the mechanical constraints of the inner ring  14 , inner containment hat  20 , and outer containment hat  30 , the soft magnetic metal toroid  18  has sufficient structural integrity to withstand the stresses of milling. 
     Milling plate  44  is placed on the bottom of the soft magnetic metal toroid  18 . Milling plate  44  could be the same as winding plate  16 . 
     Soft magnetic metal toroid  18 , having been treated with an adhesive, is thus firmly contained within a structure, allowing soft magnetic metal toroid  18  to be milled and formed in three dimensions. Complex shapes can thus be constructed from the metal ribbon toroid  18 , allowing structures such as electromechanical components to be made from the soft magnetic metal toroid  18 . 
     As illustrated by  FIG. 5 , milling assembly  40  is placed in mill  50 . Mill  50  could be a horizontal mill, a vertical mill, a CNC machine, or any other type of mill. However, mill  50  should preferably have the axis of rotation of the mill tools  52  perpendicular to the axis of the soft magnetic metal toroid  18 . By having the axis of rotation of the mill tool  52  perpendicular to the axis of the soft magnetic metal toroid  18 , the depth and width of the slots milled into the soft magnetic metal toroid  18  can be finely controlled. 
     Mill  50  cuts slots or other geometries into the soft magnetic metal toroid  18 . Inner ring  14 , still contained within soft magnetic metal toroid  18 , acts as a positive mechanical stop for the inside edge of soft magnetic metal toroid  18 . Inner ring  14 , in conjunction with the epoxy, does not allow strips of soft magnetic metal ribbon  10  to separate during machining, thereby producing clean and accurate cuts. 
     After the soft magnetic metal toroid  18  is milled into an electromechanical component shape, milling assembly  40  is removed from mill  50 . Milling assembly  50  is then thermally processed in accordance with the recommendations of the manufacturer of soft magnetic metal ribbon  10  as required. If the amorphous metal ribbon  10  is Metglas®, thermal processing consists of placing milling assembly  50  into a vacuum furnace at 695 degrees Fahrenheit for approximately sixty minutes. Some soft magnetic ribbon materials require thermal processing to achieve the desired magnetic properties while others require thermal processing to properly relieve the stresses in the milled electromechanical component shape as a result of the milling process. It is conceivable that, given proper mechanical containment during milling, some materials that do not require thermal processing for magnetic properties could forego the thermal processing. 
     Following thermal processing, the milling assembly  40  is disassembled by removing retainer  42 , outer containment  30 , inner containment hat  20 , and inner ring  14 . Soft magnetic metal toroid  18  has thus been made into an soft magnetic metal electromechanical component  60 , shown in  FIG. 6 . 
     The method as described allows for the creation of three dimensional forms from soft magnetic metal ribbon. The applications for such three dimensional forms could be as electromechanical components for a variety of machines. 
     The above description is of the preferred embodiment. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any references to claim elements in the singular, for example, using the articles “a,” “an”, “the,” or “said,” is not to be construed as limiting the element to the singular.