Patent Description:
Solenoid devices are electromechanical devices that convert electrical energy into linear mechanical movement. Solenoid devices are used in myriad environments and for many applications, and typically include at least a coil, a bobbin, a housing, and a movable armature. When the coil is energized, a magnetic field is generated that exerts a force on the movable armature, moving it to a desired position.

Existing solenoid devices have limited operating temperatures, due to the use of organic insulation materials, and thus may exhibit premature failure due to material degradation (i.e., oxidation, corrosion, etc.) of various components that may occur at relatively high temperatures (e.g., approximately <NUM> (<NUM>°F), depending on atmospheric conditions). These relatively high temperatures can be caused by the ambient conditions of the environment in which the solenoid device is installed, or the heat generated while the coil is being energized during a hold period, or a mixture of both. Such high temperatures can adversely impact lifetime, accuracy, and reliability. Thus, in some instances cooling systems may be used to cool the devices.

Hence, there is a need to provide solenoid devices that can operate at relatively high temperatures (e.g. ><NUM> (><NUM>°F), specifically ≥ <NUM> (≥ <NUM>°F)) by, among other things, prohibiting oxidation and corrosion of the metallic components of solenoid device, prohibiting degradation of the coil materials, and improving the reliability of the magnetic components in the whole assembly level. The present disclosure addresses at least this need. Documents cited during prosecution include <CIT>; <CIT>; and <CIT>.

Aspects and preferred embodiments of the invention are defined in the appended claims.

Disclosed herein is a method of fabricating a high-temperature bobbin for a solenoid assembly includes the step of providing a bobbin configured for use in the solenoid assembly. The bobbin is coated with an anti-oxidation composition and an anti-corrosion composition to produce an oxidation/corrosion resistant bobbin. The oxidation/corrosion resistant bobbin is coated with an electrical insulating composition that is resistant to corona discharge at or below a predetermined voltage threshold to produce an insulated and oxidation/corrosion resistant bobbin. The anti-oxidation composition, the anti-corrosion composition, and the electrical insulating composition can withstand temperatures of subzero up to temperature greater than <NUM>°F.

Also disclosed herein is a method of fabricating a high-temperature bobbin for electrical device includes providing a bobbin configured for use in the electrical device. The bobbin is coated with an anti-oxidation composition and an anti-corrosion composition to produce an oxidation/corrosion resistant bobbin. The oxidation/corrosion resistant bobbin is coated with an electrical insulating composition that is resistant to corona discharge at or below a predetermined voltage threshold to produce an insulated and oxidation/corrosion resistant bobbin. The anti-oxidation composition, the anti-corrosion composition, and the electrical insulating composition can withstand temperatures of subzero up to temperature greater than <NUM>°F.

Furthermore, other desirable features and characteristics of the bobbin and electrical device and method will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.

The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:.

Referring to <FIG> , a simplified cross section view of one exemplary embodiment of a solenoid device <NUM> is depicted. The solenoid device <NUM> includes at least a housing assembly <NUM>, a bobbin <NUM>, a coil <NUM>, and an armature <NUM>. The housing assembly <NUM> includes a housing <NUM>, a front cover plate <NUM>, and a back cover plate <NUM>. The housing <NUM> is configured to include a housing first end <NUM>, a housing second end <NUM>, and an inner surface <NUM> that defines a housing cavity <NUM>. The housing <NUM> may comprise any one of numerous materials having a relatively high magnetic permeability such as, for example, magnetic steel. The housing <NUM>, in addition to having a plurality of components disposed therein, provides a flux path, together with the bobbin assembly <NUM>, for magnetic flux that the coil <NUM> generates when it is electrically energized. The front cover plate <NUM> is coupled to the housing first end <NUM> and the back cover plate <NUM> is coupled to the housing second end <NUM>. The front and back covers <NUM>, <NUM> may also preferably comprise any one of numerous materials having a relatively high magnetic permeability.

The bobbin <NUM> is disposed within the housing cavity <NUM> and fixedly coupled to the housing <NUM>. The bobbin <NUM> preferably comprises a material having a relatively high magnetic permeability and, as will be described in more detail below, is coated with an anti-oxidation and anti-corrosion composition, and an electrical insulating composition. The bobbin <NUM>, together with the housing <NUM> and the armature <NUM>, provides a magnetic flux path for the magnetic flux that is generated when the coil <NUM> is energized.

The coil <NUM> is disposed within the housing <NUM> and is adapted to be electrically energized from a non-illustrated electrical power source. As noted above, when energized, the coil <NUM> generates magnetic flux. As depicted, the coil <NUM> is wound around a portion of the bobbin <NUM>, and comprises a high-temperature insulated magnet wire. Although one coil <NUM> is depicted in <FIG>, it will be appreciated that the solenoid device <NUM> could be configured with more than this number of coils, if needed or desired. It will be appreciated that the high-temperature insulated magnet wire may be any one of numerous known types of high-temperature insulated magnet wire. Some non-limiting examples include, but are not limited to, the high-temperature insulated magnet wire disclosed in <CIT>, the high-temperature insulated magnet wire disclosed in <CIT>, the high-temperature insulated magnet wire disclosed in <CIT>, or the high-temperature insulated magnet wire disclosed in <CIT>, all of which are assigned to the Assignee of the instant application.

The armature <NUM> is disposed (at least partially) within the housing assembly <NUM>. More specifically, the bobbin <NUM> has an inner surface <NUM> that defines an armature cavity <NUM>. The armature <NUM> is disposed (at least partially) within the armature cavity <NUM> and is axially movable relative to the bobbin <NUM>. The armature <NUM> preferably comprises a material having a relatively high magnetic permeability. As noted previously, the armature <NUM>, together with the housing <NUM>, and the bobbin <NUM>, provides a magnetic flux path for the magnetic flux that is generated by the coil <NUM> when it is energized. This results in axial movement of the armature <NUM> within the housing <NUM> between a first position (depicted in <FIG>) and a second position (not depicted).

The solenoid device <NUM> depicted in <FIG> additionally includes a bias spring <NUM> and a plurality of feedthroughs <NUM> (<NUM>-<NUM>, <NUM>-<NUM>). The bias spring <NUM>, which may be variously implemented, is disposed within the armature cavity <NUM> and engages the housing <NUM> (more specifically, the back cover <NUM>) and the armature <NUM>. The bias spring <NUM>, at least in the depicted embodiment, is configured to supply a bias force that urges the armature <NUM> toward the first position. It will be appreciated, however, that in other embodiments, the spring <NUM> could be disposed such that it supplies a bias force that urges the armature <NUM> toward the second position.

The feedthroughs <NUM> are preferably formed of a ceramic material and are bonded to the bobbin <NUM>. More specifically, each feedthrough <NUM> extends through, and are bonded in, a separate opening <NUM> formed in the bobbin <NUM>. A portion of the high-temperature insulated magnet wire extends through each of the feedthroughs <NUM> for connection to a non-illustrated external power source. In some embodiments, a joint can be made between the high-temperature magnet wire and lead wires (not separately depicted) inside the housing <NUM> before being passed through the feedthroughs <NUM>. Moreover, in some alternative embodiments, the feedthroughs <NUM> may be configured to allow the high-temperature magnet wire-to-lead wire joint to be made inside the feedthroughs <NUM>.

The depicted solenoid device <NUM> is able to withstand temperatures of subzero up to temperatures that exceed <NUM>°F. This, in part, is due to the process that is used to fabricate the bobbin <NUM> and then assemble the solenoid device <NUM>. With reference now to <FIG>, this process will now be described in more detail.

As depicted in flowchart form in <FIG>, the process <NUM> begins by obtaining a suitable bobbin (<NUM>). An oxidation/corrosion resistant bobbin <NUM> (see <FIG>) is then produced by coating the bobbin <NUM> with an anti-oxidation and anti-corrosion composition <NUM> (<NUM>). The specific anti-oxidation and anti-corrosion composition <NUM> may vary, and may be implemented using a single composition or plural compositions, but in each case the selected composition(s) can withstand temperatures of subzero up to temperature greater than <NUM>°F and may also impart electrical insulation properties. Some non-limiting examples of suitable anti-oxidation and anti-corrosion compositions <NUM> include Bismuth Oxide, Boron Oxide, Zinc Oxide, ternary glass, silicate, or borate glasses, just to name a few.

As may be appreciated, at least in some embodiments, some additional processing steps, such as drying and/or firing in a furnace, may be implemented to produce the oxidation/corrosion resistant bobbin <NUM>. The specific number and type of additional processing steps may depend, for example, on the specific anti-oxidation and anti-corrosion composition <NUM> that is used. In one particular example, the additional processing steps drying the coated bobbin in an oven at a temperature around <NUM>. In some embodiments, heating to an intermediate temperature of <NUM> may be required. After drying, the bobbin is then heated to about <NUM> to eliminate organics and the vehicle (depending on the composition), and then heating the bobbin to the desired processing condition of the coating (approximately <NUM>-<NUM>). This latter step may require a specialized atmosphere (e.g., nitrogen, argon, etc).

No matter the particular additional processing steps, thereafter an insulated and oxidation/corrosion resistant bobbin <NUM> is produced by coating the oxidation/corrosion resistant bobbin <NUM> with an electrical insulating composition <NUM> (<NUM>). The specific electrical insulating composition <NUM> may vary, but the selected composition is resistant to corona discharge at or below a predetermined breakdown voltage threshold (VB). Some non-limiting examples of suitable electrical insulating compositions <NUM> include Bismuth Oxide, Boron Oxide, Zinc Oxide, ternary glass, silicate, or borate glasses, just to name a few. Additionally, the predetermined voltage threshold may vary, but it is preferably based on the equation VB=<NUM>*Va+<NUM>, where Va is the expected applied voltage in the system. It is noted that the value of 1500V is generally added since it is the minimum for lightning strike resistance. The electrical insulation thickness can vary depending on the breakdown voltage requirements of the device. Moreover, just like the anti-oxidation composition and the anti-corrosion composition, the electrical insulating composition can also withstand temperatures of subzero up to temperature greater than <NUM>°F.

As may be appreciated, at least in some embodiments, some additional processing steps, may be implemented to produce the insulated and oxidation/corrosion resistant bobbin <NUM>. The specific number and type of additional processing steps may depend, for example, on the specific electrical insulating composition <NUM> that is used. In one particular example, the additional processing steps heating the bobbin to approximately <NUM>-<NUM>, depending on the specific composition. This step may require a specialized atmospheres (e.g., nitrogen, argon, etc).

After the insulated and oxidation/corrosion resistant bobbin <NUM> is produced, the feedthroughs <NUM> are disposed within a separate one of the openings <NUM> formed in the bobbin <NUM> and are bonded thereto (<NUM>). As noted above, the feedthroughs <NUM> are preferably formed of a ceramic material such as, for example, alumina, Macor®, Zirconia, quartz, glasses, and glass-metal, just to name a few. The feedthroughs <NUM> are preferably bonded via a metal bonding using the same materials as the anti-oxidation and anti-corrosion composition <NUM>, the electrical insulating composition <NUM>, various cements, and/or various geopolymers.

As <FIG> also depicts, after the feedthroughs <NUM> are bonded to the bobbin <NUM>, the insulated and oxidation/corrosion resistant bobbin <NUM> preferably undergoes a voltage breakdown test (<NUM>). The voltage breakdown test ensures that the insulated and oxidation/corrosion resistant bobbin <NUM> can withstand the above-described breakdown voltage (VB), which may or may not include the 1500V lightning strike margin, depending on the end-use environment. If the insulated and oxidation/corrosion resistant bobbin <NUM> does not pass the voltage breakdown test (<NUM>), additional electrical insulating composition <NUM> is applied (<NUM>) and the voltage breakdown test (<NUM>) is run again. These steps are repeated until the insulated and oxidation/corrosion resistant bobbin <NUM> passes the voltage breakdown test (<NUM>).

After passing the voltage breakdown test, and as depicted in <FIG>, the high-temperature insulated wire <NUM> is wound onto the insulated and oxidation/corrosion resistant bobbin <NUM> and a portion of the high-temperature insulated wire is passed through each of the ceramic feedthroughs <NUM> to thereby produce the high-temperature bobbin <NUM> (<NUM>). The high-temperature bobbin <NUM> is then disposed within housing <NUM> (<NUM>), and a potting material <NUM> (see <FIG>), such as a high-temperature geopolymer potting material, is then injected into the housing <NUM> (<NUM>) such that the potting material <NUM> surrounds at least a portion of the high-temperature bobbin <NUM>. The potting material <NUM> may then be processed, either before or after the armature <NUM> are bias spring <NUM> installed, and the front and back cover plates <NUM>, <NUM> are coupled to the housing first and second ends <NUM>, <NUM>. It will be appreciated that if, as noted above, the magnet wire-to-lead wire joint is inside the housing <NUM>, then the injected potting material <NUM> also surrounds the joint.

Some examples of suitable high-temperature geopolymer potting materials include, for example, various sodium-silicates, various alumino-silicates, and various magnesia-silicates. The assembly may then undergo additional/final thermal processing to allow the high-temperature geopolymer potting material to dry/cure. This processing may entail, for example, placing the assembly in an oven/furnace and raising the temperature directly to the desired temperature - typically just above the expected maximum operating temperature of the device. For example, if the desired operating temperature of the device is <NUM> °C_(<NUM>°F), the oven/furnace temperature may be set to <NUM> (<NUM>°F), and allowed to soak overnight.

It will be appreciated that although the various compositions mentioned above were described as being applied to the bobbin <NUM>, it will be appreciated that, at least in some embodiments, these compositions may also be applied to one or more of the armature <NUM>, the housing <NUM>, and/or the front and back cover plates <NUM>, <NUM>. It will additionally be appreciated that the processing steps described herein may also be used with other similar devices, such as a linear variable differential transformer (LVDT) sensor.

As used herein, the term "axial" refers to a direction that is generally parallel to or coincident with an axis of rotation, axis of symmetry, or centerline of a component or components. For example, in a cylinder or disc with a centerline and generally circular ends or opposing faces, the "axial" direction may refer to the direction that generally extends in parallel to the centerline between the opposite ends or faces. In certain instances, the term "axial" may be utilized with respect to components that are not cylindrical (or otherwise radially symmetric). For example, the "axial" direction for a rectangular housing containing a rotating shaft may be viewed as a direction that is generally parallel to or coincident with the rotational axis of the shaft. Furthermore, the term "radially" as used herein may refer to a direction or a relationship of components with respect to a line extending outward from a shared centerline, axis, or similar reference, for example in a plane of a cylinder or disc that is perpendicular to the centerline or axis. In certain instances, components may be viewed as "radially" aligned even though one or both of the components may not be cylindrical (or otherwise radially symmetric). Furthermore, the terms "axial" and "radial" (and any derivatives) may encompass directional relationships that are other than precisely aligned with (e.g., oblique to) the true axial and radial dimensions, provided the relationship is predominantly in the respective nominal axial or radial direction. As used herein, the term "substantially" denotes within <NUM>% to account for manufacturing tolerances. Also, as used herein, the term "about" denotes within <NUM>% to account for manufacturing tolerances.

Claim 1:
A method of fabricating a high-temperature bobbin for an electrical device, comprising the steps of:
providing (<NUM>) a bobbin configured for use in an electrical device;
coating (<NUM>) the bobbin with an anti-oxidation composition and an anti-corrosion composition to produce an oxidation/corrosion resistant bobbin;
coating (<NUM>) the oxidation/corrosion resistant bobbin with an electrical insulating composition; and
after coating the oxidation/corrosion resistant bobbin with the electrical insulating composition, performing (<NUM>) a voltage breakdown test on the bobbin to determine if the insulated and oxidation/corrosion resistant bobbin can withstand a predetermined voltage threshold, wherein, if the insulated and oxidation/corrosion resistant bobbin cannot withstand the predetermined voltage threshold during the voltage breakdown test, the method further comprises applying (<NUM>) additional electrical insulating composition to the insulated and oxidation/corrosion resistant bobbin and repeating the steps of performing (<NUM>) the voltage breakdown test and applying (<NUM>) the additional electrical insulating composition until the voltage breakdown test is passed, so as to produce an insulated and oxidation/corrosion resistant bobbin that is resistant to corona discharge at or below the predetermined voltage threshold,
wherein the anti-oxidation composition, the anti-corrosion composition, and the electrical insulating composition can withstand temperatures of lower than -<NUM> (subzero Fahrenheit) up to temperatures greater than <NUM> (<NUM>°F).