Patent Application
20060197388
1. Field
The present teachings generally relates to apparatuses and methods for improving magnetic circuits, and particularly for improving manufacturing yield of such magnetic circuits.
2. Related Art
Magnetic circuits are employed in a wide variety of applications. In electro-mechanical apparatuses, magnetic circuits are often adapted to actuate an associated mechanical part. One example of a magnetic circuit used to actuate a mechanical part is a solenoid.
Production yield is of concern to the manufacturer when designing and manufacturing solenoids. Production testing is performed to ensure quality and compliance with design specifications prior to releasing manufactured solenoids for sale or installation into another machine. One such production test relates to tuning a “magnetic circuit” inside a solenoid.
The magnetic circuit is somewhat analogous to an electrical circuit. For example, the magnetic circuit has several components that are required to complete the circuit so that magnetic flux is harnessed according to specified tolerances. One such component in the magnetic circuit is referred to in the art as a reluctance element (which is analogous to a resistive element in an electrical circuit). One commonly used reluctance element is an “air gap”, through which magnetic flux passes.
As is well known, “permeability” of a material determines the degree to which the material resists magnetic flux flow. “Permeability” (“μ”) is typically measured in units of Tesla (“T”) times Meters (“m”) per Ampere (“Tm/A”). Described in another way, permeability describes the ease of passage of magnetic lines of force through a material. Measurements of permeability are taken with permeability of free space as a reference. The permeability of free space (“μo”) has a fixed value of 4π×10−7 Tm/A. By contrast, permeability of a material, such as iron, has a permeability of several thousand times that of free space.
In one embodiment, the magnetic circuit 200c of
R=MMF/Φ Equation 1
Another calculation for a reluctance element involves a ratio of a permeability (μ) of a material, multiplied by an average length (L) of a selected path in a material, divided by a cross-sectional area (A′) of the material, as shown in Equation 2 below.
R=μL/A′ Equation 2
As is well known, different materials have different magnetic properties. One commonly used material in magnetic apparatuses is iron. As most molecules in iron easily turn under an influence of a magnetizing force, the overall effect of magnetizing iron is quite strong. In other materials, few or none of the molecules turn, due to the rigid structure of the materials. Hence, iron has a very low permeability value (e.g., 6000×4π×10−7 Tm/A).
It is well-known that magnetic flux transmitted through free space, such as, for example, an air gap, loses substantial amounts of force, due primarily to the permeability of free space. That is, the magnetic flux transmitted across an air gap is commonly referred to as “lossy”, due to the fact that much of the magnetic force is lost during transmission across the air gap. By contrast, transmission of magnetic flux through iron is not “lossy”. That is, the magnetic flux lines passing through iron do not lose as much strength as do the magnetic flux lines passing through air. This is due primarily to the difference in permeability of free space (4π×10−7 Tm/A) and the permeability of iron (e.g., 6000×4π×10−7 Tm/A).
Each solenoid produced by a production facility assembly line has slight variations in the air gap. Therefore the air gap requires fine tuning in order to meet desired design tolerance and parameters. Such variances in air gap tolerances are caused by typical manufacturing tolerances of several different parts that are subsequently assembled together. Any variation in the air gap will cause variations in a loss of magnetic flux passing through the air gap, which degrades solenoid performance. In order to calibrate for manufacturing variations, air gaps are measured and calibrations are performed to ensure proper solenoid performance.
Referring now to
A magnetic circuit that requires no calibration subsequent to assembly will allow substantial cost savings in the manufacturing of magnetic circuits generally, and in the manufacturing of solenoid circuits specifically.
Therefore, a need exists for an apparatus and method that addresses the aforementioned issues. The present teachings provide such an apparatus and method.
In one embodiment, an improved magnetic circuit apparatus is disclosed. In one embodiment, the improved magnetic circuit comprises a magnetic circuit assembly and a predetermined quantity of flux-enhancing material. The magnetic circuit assembly comprises, inter alia, an external canister magnetically coupled to a magnetic flux collector member. The magnetic circuit assembly also comprises a first reluctance element, having a first end and a second end, wherein the first end is operatively coupled to the magnetic flux collector member. A pole piece element is operatively coupled to the magnetic flux collector member via the second end of the first reluctance element. A predetermined quantity of flux-enhancing material is disposed between the first and the second end of the first reluctance element. The predetermined quantity of flux-enhancing material is adapted to reduce loss associated with the magnetic flux across the first reluctance element of the magnetic circuit.
In one embodiment, an improved solenoid apparatus having a magnetic circuit is disclosed. The magnetic circuit is adapted to actuate a mechanical part associated with the solenoid. In this embodiment, the solenoid comprises, inter alia, an external canister magnetically connected to a magnetic flux collector member and an air gap. The air gap has a first end and a second end, wherein the first end is associated with the magnetic flux collector member. A pole piece element is operatively coupled to the magnetic flux collector member via the second end of the air gap. In one embodiment, a selected quantity of iron powder is disposed between the first end and the second end of the air gap. The selected quantity of iron powder reduces loss associated with magnetic flux across the air gap.
In one embodiment, a method of improving manufacturing yield of assembled magnetic circuits is disclosed. The method comprises producing a magnetic circuit having an upper assembly and a lower assembly, wherein the upper assembly has an associated and corresponding first reluctance element, and wherein the lower assembly has an associated and corresponding second reluctance element. The method proceeds by setting a dimension for the second reluctance element. Next, the method provides a selected quantity of flux-enhancing material. Next, the selected quantity of flux-enhancing material is coupled to the upper assembly, inside the first reluctance element. Finally, the method couples the upper assembly to the lower assembly.
Embodiments of the present disclosure will be more readily understood by reference to the following figures, in which like reference numbers and designations indicate like elements.
a shows a cross-sectional view of an improved magnetic circuit shown in a “switched-off” configuration in an assembly having no post-assembly calibration feature.
b shows a cross-sectional view of an embodiment of a magnetic circuit shown in a switched-off configuration, wherein the inventive magnetic circuit includes flux-enhancing material.
c illustrates in cross-section the inventive magnetic circuit of
d shows a cross-sectional view of a lower assembly of an embodiment of the inventive magnetic circuit.
e shows a cross-sectional view of an upper assembly of an embodiment of the magnetic circuit.
f shows a cross-sectional view of an upper assembly of an embodiment of the magnetic circuit including flux-enhancing material.
The present teachings disclose an improved magnetic circuit apparatus and method.
a shows a set of elements associated with a magnetic circuit 200a.
Referring now to
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In one embodiment, when upper assembly and lower assembly portions of a solenoid are fitted together at a production facility, reluctance elements 207 and 209 comprise air gaps. As described above, variations in air gaps can cause variations in an amount of magnetic flux passing through the air gaps, which can substantially change the responsiveness and performance of a magnetic circuit in the solenoid. By adding the flux-enhancing material 210, such variations in assembly is diminished, or eliminated altogether, as the force lines of magnetic flux are “focused”, that is maximized, across the air gaps, such that any loss of flux associated with the magnetic circuit in the assembly process of the upper and lower assemblies is minimized. Hence, the present teachings eliminate the prior art need for a calibration feature.
As described above, the loss of magnetic flux is higher when passed through an air gap as compared to through a material, such as iron. Contrasting magnetic flux loss through different elements of the magnetic circuit 200c is instructive to understanding the present teachings. As noted above, in one embodiment, the flux-enhancing material 210 comprises iron powder. By filling the first set of reluctance elements 207 and 209 with the flux enhancing materials, magnetic flux loss is reduced. The flux-enhancing material 210 enhances and conserves the magnetic flux that passes from the flux collector members 208 and 231, through the reluctance elements 207 and 209, and into the pole piece 211. The flux enhancing property is useful when adapted to reduce manufacturing variations at a production facility. When the upper assembly and the lower assembly are fitted together, the predetermined flux-enhancing material 210 aids in reducing flux variations between the upper assembly and the lower assembly. As described above, the prior art calibration feature 102 of
As described above in more detail in a calibration feature 102 required in the solenoid 100 of
By contrast, the magnetic circuit 200c does not require any mechanical “tuning” during the manufacturing process. Therefore, the need for a calibration feature is removed. Instead of having a single air gap 104 that provides a reluctance element, the present teachings disclose a magnetic circuit 200c having a first set (207 and 209) and a second set of reluctance elements 270 and 271. The magnetic circuit 200c does not require any manufacturing variations “tuning”. The flux-enhancing material (e.g., iron powder) reduces or eliminates any flux loss created during the manufacturing assembly process.
Referring now to
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At a STEP 308, the flux-enhancing material is inserted within the first set of reluctance elements of the magnetic circuit. In one embodiment, the first set of reluctance elements comprises a set of air gaps. In one embodiment, iron powder is inserted within the air gaps in order to “focus” the magnetic flux lines passing through the air gaps. As described above in more detail, less magnetic flux loss occurs in the air gaps that have iron powder inserted therein than occurs in the air gaps not having iron powder.
In a final STEP 310, the upper assembly is joined with the lower assembly. The joining of the upper assembly and the lower assembly completes the magnetic circuit. Although there may be some manufacturing variations created by the joining of the upper and the lower assemblies, such variations will not adversely affect circuit performance, due to the “focusing” effect of the iron powder. No post manufacturing or post-assembly “tuning” is required after the upper assembly is joined to the lower assembly. This reduces the costs associated with manufacturing of the circuit, and improves circuit performance.
The foregoing description illustrates exemplary implementations, and novel features, of aspects of an apparatus for correcting undesired characteristic associated with an incoming electrical signal. Alternative implementations are suggested, but it is impractical to list all alternative implementations of the apparatus. Therefore, the scope of the presented disclosure should be determined only by reference to the appended claims, and should not be limited by features illustrated in the foregoing description except insofar as such limitation is recited in an appended claim.
While the above description has pointed out novel features of the present disclosure as applied to various embodiments, the skilled person will understand that various omissions, substitutions, permutations, and changes in the form and details of the methods and systems illustrated may be made without departing from the scope of the present teachings.
Each practical and novel combination of the elements and alternatives described hereinabove, and each practical combination of equivalents to such elements, is contemplated as an embodiment of the present teachings. Because many more element combinations are contemplated as embodiments of the present teachings than can reasonably be explicitly enumerated herein, the scope of the present teachings is properly defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the various claim elements are embraced within the scope of the corresponding claim. Each claim set forth below is intended to encompass any apparatus or method that differs only insubstantially from the literal language of such claim, as long as such apparatus or method is not, in fact, an embodiment of the prior art. To this end, each described element in each claim should be construed as broadly as possible, and moreover should be understood to encompass any equivalent to such element insofar as possible without also encompassing the prior art. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising.”
