Patent Application
20090112351
Manufacturing a three dimensional core mass with channels, slots, or holes of any shape or dimension that extend in a radial direction from the reference center of the core mass is accomplished by a three dimensional machining process of the entire raw core mass, which in essence, cuts minute layers of material from the entire raw core until the desire shape is obtained. This has the advantage of a very fast manufacturing process to final core mass shape but can distort or change the structural, physical, electrical, magnetic, and so-on performance of the bulk material of the raw core mass due to excessive mechanical or heat stress as a result of the fast cutting. In some cases, the final product must be annealed to re-establish acceptable performance of the core material. Further, the machine tool experiences similar stress, which reduces the performance and life of the machine tool.
One object of the present invention is to provide a machine tool means to manufacture a three dimensional core mass with slots, channels, or holes of any shape or dimension by machining a ribbon or tape of any raw material with the slots, channels, or holes of any shape one layer at a time before the ribbon or tape is spooled (or layered) onto a layering template or spooler. The machining is adjusted so the slots, channels, or holes of any shape extend in a radial or stacked direction perpendicular to the axis of spooling rotation or the plane of layering but following any curve or straight line and with any stacked depth. For example, core masses that are manufactured as described are suitable for axial air-gap magnetic cores for high frequency rotating transformers or for rotor cores and for stator cores of axial-flux rotating electric machines when an appropriate magnetic material, such as magnetic metal or amorphous metal ribbon or tape is used as the raw ribbon material. Furthermore, the core masses that are manufactured as described with the appropriate layering template are suitable for linear transformers and electric machines. This method is different from existing methods because after machining, a portion of the outline of the original raw ribbon shape is obviously distinguishable along the length or circumference of the layering plane. Further, the machining is performed as the ribbon is continuously layered for at least one layer. This method may not be suitable for radial flux machines.
Still another object of the invention is to provide an alternative means to manufacture axial air-gap magnetic cores for rotating electric machines or transformers or for linear electric machines or transformers. This method hydraulically pumps a powdered metal slurry (i.e., with bonding and lubricating agent) into a mold with a negative image of the desired shape of the core while using a wicking method that purges excess bonding agent from the powdered slurry while adding a composite material of strength.
A further object of the invention is to provide a core design for an axial flux air-gap rotating electric machine or transformer. An axial flux air-gap electric machine has a hockey puck or pancake core and is sometimes referred to as a pancake form-factor electric machine.
In some cases, a better approach for certain final three dimensional core shapes and the subject of this patent is to produce the core mass by wrapping, layering, or spooling thin ribbon or tape onto the layering plane of a layering template or spooler of the ribbon. It should be understood that a round core mass could similarly be laid out flat with the core mass still being build up one layer at a time into a flat or linear core shape. As an example in the case of a flat or linear core shape, the ribbon could be wrapped around a rotating layering template, which is a thin rectangle shape, or layered on one side of a flat layering template with each layer being held in place for the layering effect.
Before the ribbon is spooled, it is machined with a two-dimensional (i.e., 2-D) shape that is parallel with the layering plane of spooling. The depth of the plane or the third dimension of a layer of the expected three-dimensional (i.e., 3-D) shape depends on the thickness of the ribbon, which is one resolution of machining dimension, and the stacking depth of the layers onto the spooler. Essentially, the final three-dimensional shape is built-up one layer or step at a time, whereby one example a step or layer is one complete rotation of the spooler. It is conceivable to see actual microscopic steps in the final shape, with the step depth based on the thickness of the ribbon. How the 3-D shape evolves in a radial or stacked direction from the layering plane of the spooler depends on how or when every next layer is machined. For instance, a channel could extend in a radial or stacked direction from the layering plane of the spooler along a straight line, a squiggly line, or a curved line. Consequently, any means to acquire the angular position of the spooler (or perimeter dimension) is required to determine or calculate the machining position of the 2-D plane of the ribbon, because as the spooled core extends in the radial direction, the perimeter dimensions of the stacked layers change at least on an angular basis. The template of the spooler assembly can be any shape, such as flat, round, square, triangular, and so-on, but the axis of rotation is in the desired plane of the template while the spooled ribbon is confined by some means in the plane of rotation.
Machining a core mass one thin layer at a time is a slower process with the following advantages. Mechanical or heat stress is reduced because machining is performed on a single thin layer of material, which mitigate collateral damage or performance degradation of the material in the final product. Heat and mechanical stress can be further reduced by localizing an active cooling process, such as forced cooling air, gas, or liquid, directly to the machining process on the thin layer of ribbon rather then the heat mass of the entire core mass. By mitigating the stress, the expensive and time consuming process of annealing may be avoided and the slower process of machining one layer at a time may in fact be more economical and faster. In any case, some core masses, such as magnetic cores of AC transformers or electric machines, require a layered or ribbon structure (i.e., laminated structure) to improve the magnetic and electrical performance of the core and the machining method described causes less collateral damage to the delicate magnetic material for reasons just describe.
Other dimensions could be cut into the ribbon for winding placement, for cooling, or for structural reasons. For instance, slots in a radial direction could be machined for winding placement or for increase cooling surfaces. Channels could be cut to fill with other material for structural support, such as material with high shear or compressive strength for structural rigidity.
Other enhancing means or components may complement or enhance the machining means described. An adhesive application means may be incorporated to apply an adhesive on all or specific layers of the ribbon to bond or add structural support to the final core mass. A drier means may be incorporated to dry any cooling fluid applied to the ribbon before applying any adhesive to the ribbon or to modify the properties of the adhesive. A cleaning means may be incorporated, such as a high pressure blower. A ribbon friction, pulling, braking, or squeezing means may be applied to bring the ribbon layers closer together on the spooler. An automatic spooler (or winder) means may be incorporated to automatically spool the ribbon onto the spooler, such as comparable mechanisms found on film projectors or tape recorders. Additional machine tools that function simultaneously or sequentially may be incorporated to improve machining speed or shape complexity. An annealing means may be incorporated. A means to apply several bobbins of ribbon material could be incorporated to spool layers of ribbon with different dimensions or materials. A means to stop or to brake the ribbon during the process of machining each layer of ribbon. A means to idle the ribbon, such as with an idler arm, during machining of a layer of ribbon may be incorporated. A means to hold the raw ribbon material, such as a bobbin, may be incorporated. A means to guide the ribbon through any of the process means described.
Another embodiment of this invention will incorporate a core mass of powdered metal. Powdered metal with a bonding compound (i.e., powdered metal slurry) can be molded into various shapes, such as shapes with winding slots that are ideal for a magnetic core. The method employed is to manufacture a reusable mold to the negative shape of the desired core mass. The mold will have a separable bulk chamber and a face plate, which covers the mouth of the bulk chamber. The bulk chamber and face plate attach together by any clamping means. Together, the bulk chamber and face plate show the negative shape of the desire core mass. The mold and clamping mechanism will be sufficiently strong to tolerate very high hydraulic pressures. First, a protector material, such as a piece of cellophane, plastic, etc., would be inserted into the bulk chamber to protect the mold from the bonding agent. Second, a piece composite cloth, such as a fiberglass cloth, would be inserted in the bulk chamber. Third, another piece of composite cloth would be laid over the mouth of the bulk chamber followed by another piece of protector material. Both the composite cloth and protector material are allowed to extend outside of the junction between the bulk chamber and face plate junction for wicking purposes. The face plate is attached to the bulk chamber by a clamping means, which can sufficiently hold the hydraulic pressure and allow the composite cloth to act as a wick between the bonding agent and the powdered metal. Powdered metal slurry (i.e., powdered metal and bonding agent) is pumped into the chamber between the composite cloth and the protector material under high pressure. When all cavities of the mold are filled, supplemental pressure will squeeze the excess bonding agent through the wicking junction while leaving the actual powdered metal in the mold cavity with a minimum but sufficient amount of bonding agent. The bonding agent is allowed to set before it is removed from the mold. Various bonding agents require different methods of curing. Powdered Metal core masses for electric machines or rotating transformers can be axial (pancake) or radial flux (cylindrical) design.
It is possible that additional assemblies, which are an integral component of the core mass, may be inserted into the bulk chamber before filling with powdered slurry. For instance, a pre-formed winding assembly may be inserted for rotating transformer. In this case, the winding assembly could be energized or excited to more densely pack the powdered slurry. Likewise, an axle, bearing assembly, and so-on may be inserted.
This invention provides a method to manufacture electric machine or high frequency rotating transformer cores of various air-gap area (and power rating) without resorting to customized tooling for each area or power rating. It also allows manufacturing cores with thin magnetic steel laminations or amorphous metal ribbon laminations or powdered metal, which are derivatives of nanocrystalline material. The electric machines or high frequency rotating transformers of particular focus are the Power Generator Motor (PGM) incorporating a Rotor Excitation Generator (REG) of the Electric Rotating Apparatus and Electric Machine patents of this inventor, U.S. Pat. Nos. 4,459,530, 4,634,950, 5,237,255, and 5,243,268. Like any electric machine, the form-factor of the PGM and REG can be a pancake form-factor (or axial flux). Like any electric machine or rotating transformer, the pancake form-factor incorporates slots for the placement of windings. However, this pancake form-factor with slots is now disclosed for the electric machines and related inventions incorporating Brushless Multiphase Self Commutation Control (or BMSCC).
