Patent Description:
This invention relates to electrical heaters, and more particularly to exhaust aftertreatment systems and assemblies that comprise electrical heaters having serpentine designs.

Temperature control can be useful during the treatment of fluid streams. For example, catalytic materials can be used in the treatment of fluid flows, such as in the aftertreatment of engine exhaust. Catalytic activity of such materials may not initiate until the catalytic material reaches some minimum threshold temperature, which may be referred to as the light-off temperature. Overall emissions can be reduced by minimizing the amount of time the catalyst is below its light-off temperature while the engine is in operation. Electrical heaters provide one manner for assisting in control of temperature during treatment of a fluid stream, such as to increase the temperature of a catalyst material.

<CIT> discloses an electrical heater according to the preamble of claim <NUM>.

<CIT> and <CIT> disclose other prior art.

Disclosed herein are various embodiments for electrical heaters, particularly for use in vehicle exhaust aftertreatment systems.

The invention provides an electrical heater for treatment of a fluid flow according to claim <NUM> is provided.

In embodiments, the end segment is wider than another segment of the resistive portion bounded between two adjacent slots of the plurality of slots in a direction transverse to that of current flow along the serpentine path.

In embodiments, the at least one auxiliary slot creates a dead zone of reduced current flow that extends from the outer periphery approximately a length of the at least one auxiliary slot into the end segment.

In embodiments, the heater comprises a plurality of the auxiliary slots in each of the end segments.

In embodiments, the heater comprises a single auxiliary slot in each of the end segments.

In embodiments, each of the single auxiliary slots splits into two terminal ends that terminate within the resistive portion.

In embodiments, each of the single auxiliary slots has a T-, Y-, or W-shape.

In embodiments, one or more of the slots, the at least one auxiliary slot, or both, comprises a receptacle for receiving a slot separator.

In embodiments, the heater further comprises an electrode attached to each of the electrode attachment portions.

In embodiments, the electrodes extend axially or radially from the electrode attachment portions.

In embodiments, the heater further comprises excess conductive material disposed at terminal ends of the slots.

In embodiments, the excess conductive material comprises one or more of the channels at least partially filled with the excess conductive material.

The invention further provides an exhaust treatment assembly according to claim <NUM>.

In embodiments, the aftertreatment component comprises a catalyst substrate, a particular filter, or a combination thereof.

In embodiments, the electrical heater is secured within the tubular housing by one or more retaining rings.

In embodiments, the concentrated region of the end segment is substantially not covered by the retaining ring, but a dead zone of reduced current flow outside of the concentrated region adjacent to the outer periphery is covered by the retaining ring.

The invention further provides a method of manufacturing an electrical heater according claim <NUM>.

In embodiments, forming the plurality of slots, forming the at least one auxiliary slot, or both, comprises three dimensionally printing the plurality of slots, the at least one auxiliary slot, or both, simultaneously with the heater body.

In embodiments, forming the plurality of slots, forming the at least one auxiliary slot, or both, comprises removing material from the heater body.

It is to be understood that both the description herein is directed to exemplary aspects and examples, and thus are intended to provide an overview or framework to understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description, serve to explain principles and operation of the various embodiments.

Reference will now be made in detail to exemplary embodiments which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the exemplary embodiments.

Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described herein are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims.

As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term "about" is used in describing a value or an end-point of a range, the invention should be understood to also include the specific value or end-point referred to.

Directional terms as used herein-for example up, down, right, left, front, back, top, bottom-are made only with reference to the figures as drawn and are not intended to imply absolute orientation. As used herein, the term "radial" refers to directions perpendicular to the indicated axial direction that extend from the center point (center axis) of a shape to or toward the outer perimeter of the shape, regardless of the shape of the component or feature with respect to which the radial direction is used. Similarly, the term "diameter" as used herein is not limited to circular shapes, but instead refers to the longest dimension of a component that passes through the center point (center axis) of the shape of that component. For example, a radial distance of a square-shaped component can be measured as the straight-line distance from the center point (center axis) to an intersection with one of the walls of the square, while the diameter of a square refers to the longest dimension diagonally across the square. The terms "cross-sectional width" or "cross-sectional dimension" may also be used to refer to these directions perpendicular to the axial direction.

Fluid treatment systems, such as automobile exhaust aftertreatment systems, can comprise a supplemental source of heat to facilitate faster catalyst light-off, particularly in comparison to catalyst-containing aftertreatment systems that do not have any supplemental heat (e.g., instead relying on the heat of the engine exhaust). For example, heat can be supplied by an electric heater (e.g., arranged to transfer heat to the catalyst material) or an electrically heated catalyst substrate (e.g., an electrically conductive substrate that is carrying a catalytic material). For example, a heater can be arranged upstream of a catalyst substrate and heat the catalyst by providing heat to the flow of exhaust (or supplemental air), which in turn heats the catalyst. Aftertreatment systems employing supplemental heat can be provided to reduce emissions in gasoline, diesel, and/or hybrid vehicles to assist in ensuring fast and consistent light-off of the catalyst during operation of the corresponding engine, particularly after cold-start of the engine.

Referring now to <FIG>, a fluid treatment assembly <NUM> is illustrated, e.g., which can be arranged as part of an exhaust system of automobile. The fluid treatment assembly <NUM> comprises an outer housing <NUM> (which may be alternatively referred to as a "can"), such as formed in a generally tubular shape (hollow tube) from metal or suitable material. The tubular housing <NUM> has an inlet <NUM>, e.g., which can be connected in fluid communication with the exhaust manifold of an internal combustion engine, and an outlet <NUM>, e.g., which can be connected in fluid communication with a tail pipe of an automobile.

A flow of fluid, such as exhaust from an engine can be treated (e.g., one or more pollutants removed or abated) as the exhaust is flowed from the inlet <NUM> to the outlet <NUM> through the assembly <NUM>. To this end, the assembly <NUM> further comprises a heater assembly <NUM> and an aftertreatment component <NUM> located between the inlet <NUM> and outlet <NUM>. For example, the aftertreatment component <NUM> can be a catalyst-loaded substrate, a particulate filter, or combination thereof, e.g., a catalyst-loaded particulate filter. For example, catalyst substrates and particulate filters can comprise a porous ceramic honeycomb body having an array of walls that form a plurality of fluid flow paths or channels extending axially (in the direction of exhaust flow and/or perpendicular to the end faces of the body) through the body.

A vehicle exhaust system can be created by connecting additional lengths of piping (not shown) to the assembly <NUM> at the inlet <NUM> (e.g., extending between the inlet <NUM> and the engine exhaust manifold) and outlet <NUM> (e.g., extending from the outlet <NUM> to the tail pipe). Depending on the design or configuration of the exhaust system, which may vary vehicle to vehicle, the various components and/or lengths of piping can have different diameters at different positions along the flow path through the exhaust system. For example, the housing <NUM> can comprise a first transitional portion <NUM>, e.g., at an upstream end and a second transitional portion <NUM>, e.g., at a downstream end. The transitional portions <NUM>, <NUM> are portions of the housing <NUM> that enable or provide a change of dimension in the housing <NUM>. For example, both of the transitional portions <NUM>, <NUM> are tapered in <FIG>. However, the transitional portions <NUM>, <NUM> can be stepped, conical, tapered, radiused, parabolic, or other shape that transitions from a first dimension to a second dimension. For example, the transitional portion <NUM> transitions the housing <NUM> from a first diameter at a first portion <NUM> of the housing <NUM> (at which the heater assembly <NUM> is positioned) to a second diameter of the housing at the end <NUM>.

As described herein, the heater assembly <NUM> can be a resistance heater that provides supplemental heat in order to facilitate functionality of the aftertreatment component <NUM>, e.g., by quickly initiating light-off of catalytic material disposed in or on the walls of the heater assembly <NUM> and/or the aftertreatment component <NUM>. For example, the heater assembly <NUM> can comprise, or otherwise be connected to, electrodes <NUM>. The electrodes <NUM> can be arranged extending through the housing <NUM> in order to connect the heater assembly <NUM> to a power source, such as a vehicle battery. As shown in <FIG>, the electrodes <NUM> can extend radially through the through the first portion <NUM> of the housing <NUM>. However, the electrodes <NUM> can alternatively extend through the housing <NUM> at some other location or angle, such as axially through the transitional portion <NUM> of the housing <NUM>. In this way, the heater assembly <NUM> can be arranged to generate heat via Joule heating when the heater assembly <NUM> is connected via the electrodes <NUM> to a power source and a corresponding voltage is applied to create a flow of current through the material of the heater assembly <NUM>. The electrodes <NUM> are shown in <FIG> as being arranged on opposite sides of the heater assembly <NUM> (e.g., spaced <NUM>° apart with respect to the exterior of the heater assembly <NUM>), but can be arranged at other locations or angles, such as positioned at an angle of <NUM> degrees relative to each other, <NUM> degrees relative to each other, <NUM> degrees relative to each other, <NUM> degrees relative to each other, or even closer.

In embodiments, such as shown in <FIG>, the heater assembly <NUM> is positioned upstream of the aftertreatment component <NUM> in order to increase the temperature of the exhaust flow and/or provide direct heating to the aftertreatment component <NUM>, which in turn increases the temperature aftertreatment component <NUM>, such as the temperature of the catalytic material carried by the aftertreatment component <NUM>, as the exhaust flows through the aftertreatment component <NUM>. In embodiments, the heater assembly <NUM> and the aftertreatment component <NUM> can be effectively combined into a single device by directly loading the heater body of the heater assembly <NUM> with a catalyst material. Such arrangements useful for heating a catalyst material may be referred to as an electrically heated catalyst, or EHC.

In this way, the inlet and outlet ends <NUM>, <NUM> can be used to facilitate connection of the assembly <NUM> between exhaust piping of different diameters. In other embodiments, one or both of the upstream and downstream ends <NUM>, <NUM> can have substantially the same diameter as the lengths of piping to which they are connected. Instead of tapers, the exhaust system can alternatively or additionally transition between different dimensions at abrupt steps. In some embodiments, such as shown in <FIG>, the housing <NUM> transitions between different diameters at the heater assembly <NUM> and the aftertreatment component <NUM>. However, in other embodiments, the housing <NUM> can be substantially the same dimension at both the heater assembly <NUM> and the aftertreatment component <NUM>, e.g., such as in embodiments in which the heater assembly <NUM> and the aftertreatment component <NUM> have the same diameter.

The heater assembly <NUM> and the aftertreatment component <NUM> can be held in place, supported, and/or contained within the housing <NUM> in any suitable manner. For example, the body of the heater assembly <NUM> can be held in place and supported via one or more retainers <NUM>, e.g., retaining rings. The aftertreatment component <NUM> can be supported by similar retainers and/or supported by a mat <NUM>, such as an inorganic fiber mat, which assists in protecting the aftertreatment component, such as from vibrations or thermal expansion forces exerted on or experienced by the aftertreatment component <NUM>.

Referring now to <FIG>, embodiments for the heater assembly <NUM> are illustrated. Consistent with the disclosure herein, the embodiments illustrated and/or described herein can be used as, or incorporated in, the heater assembly <NUM> of the assembly <NUM>, and combinations of the features of the embodiments illustrated or described herein can be used together for the heater assembly <NUM> in the aftertreatment assembly <NUM> (e.g., features shown in <FIG> can be used in combination with compatible features shown in <FIG>).

The heater assembly <NUM> comprises a heater body <NUM> made of electrically conductive material (e.g., a metal, metal alloy, or metal composite). The heater body <NUM> comprises a resistive (heat-generating) portion <NUM> and one or more electrode attachment portions <NUM> (two attachment portions <NUM> illustrated in <FIG> and <FIG>). As described herein, the resistive portion <NUM> forms or defines a current-carrying path between the electrode attachment portions <NUM> to enable the resistive portion <NUM> to generate heat when a voltage is applied to electrodes attached to the electrode attachment portions <NUM>. The body <NUM> and/or the resistive portion <NUM> thereof can be formed having a shape, e.g., defined by an outer periphery <NUM>, centered axially at a central axis C. The electrode attachment portions <NUM> can extend radially from the resistive portion <NUM>, such as shown in <FIG>, or be radially contained within the footprint or outer periphery of the resistive portion <NUM>, such as shown in <FIG>. The electrodes <NUM> can extend axially or radially from the heater body <NUM> and/or through the housing <NUM>. The electrode attachment portions <NUM> and the resistive portion <NUM> can be formed from the same material. The attachment portions <NUM> can be integrally (monolithically) formed with the resistive portion <NUM> (e.g., extruded or printed together with the resistive portion <NUM>), or connected as separate components via welding, mechanical fasteners, or other attachment means.

In the illustrated embodiments, the resistive portion <NUM> of the body <NUM> is illustrated as comprising an array of intersecting walls <NUM> that define a plurality of channels <NUM> extending in an axial direction through the body <NUM>, and thus is of the type that may be referred to as a honeycomb body (for clarity, the walls <NUM> and channels <NUM> are labeled with reference numerals in the enlarged view of <FIG>, but these features can be seen throughout the drawings). For example, the channels <NUM> enable a fluid to flow through the body <NUM> (e.g., a flow of exhaust fluid) and the intersecting walls <NUM> provide surface area for heat exchange with the fluid flow. Each of the sections of the walls that are enclosed together to define one the flow channels <NUM> may be referred to herein as a cell. Accordingly, the array of intersecting walls <NUM> define a corresponding array of square-shaped cells, which together form a honeycomb design for the body <NUM>. However, the cells can have any other desired cross-sectional shape (the shape perpendicular to the axial direction), such as hexagonal, triangular, or other polygon. Furthermore, in some embodiments, in lieu of geometrically-shaped cells and channels, the resistive portion <NUM> of the body <NUM> comprises irregular flow passages, such as an irregular interconnected porous structure. For example, in embodiments, the resistive portion <NUM> of the body <NUM> can be comprised of a foam-like or interwoven fiber (or other elongated fiber-like or wire-like elements) configuration of conductive material in which the flow paths through the body <NUM> are irregularly formed by the pores, voids, openings, or interstices in the foam-like structure and/or between interwoven fibers or fiber-like elements of conductive material. In embodiments, the body <NUM> can be formed by additive manufacturing, perforation of a sheet of conductive material, extrusion, casting, sintering, weaving of wires or fibers into a mesh, mat, or screen, foaming an electrically conductive material, or other suitable process or combination thereof.

An electrical connection can be established through the resistive portion <NUM> via the electrodes <NUM> secured at the one or more electrode attachment portions <NUM> for carrying current to, from, and/or between the electrodes <NUM> at the electrode attachment portions <NUM>. For example, the properties of the resistive portion <NUM> (e.g., resistivity/conductivity and dimensions) can be set with respect to the voltage applied across the electrodes <NUM> in order to generate heat as electrical current passes through the material of the resistive portion <NUM> of the body <NUM>. In other words, the material properties and dimensions of the structure of the heater body <NUM> that defines the current-carrying path between the electrodes <NUM> can be set such that the electrical heater assembly <NUM> generates a targeted amount of heat and/or reaches a targeted temperature when a selected voltage is applied across the electrodes <NUM>. Applied voltages can range from relatively low voltages capable by traditional vehicle batteries to relatively high voltages capable by higher capacity batteries included on hybrid or electrical vehicles, such as over a range of 12V to 600V, or even more. Target temperatures can range, for example, from about <NUM> to <NUM>, such as a temperature of up to about <NUM>.

Each of the electrodes <NUM> can be attached to the heater body <NUM> at one of the electrode attachment portions <NUM>. Unlike the resistive portion <NUM> of the body <NUM> (e.g., intersecting walls, foam-like structure, interwoven fibers, etc.), which have channels, openings, holes, or other flow passages therethrough, the attachment portions <NUM> can be formed as a densified or solidified block or section of conductive material. Accordingly, a density of the body <NUM> at the electrode attachment portions can be greater than the density of the body <NUM> at the resistive portion <NUM>. For example, the relatively lower density of the resistive portion <NUM> can be achieved by the inclusion of the fluid flow passages, e.g., channels, pores, openings, or interstices, that enable fluid to flow through the body <NUM>, while the electrode attachment portions <NUM> are relatively solidified and/or densified. The relatively higher density of the body <NUM> at the attachment portions not only provides additional strength and material to support attachment of the electrodes <NUM>, but also increases conductivity of the body <NUM> at the attachment portions <NUM> to inhibit the generation of heat at the electrodes <NUM>. In contrast, the relatively lower density of the body <NUM> at the resistive portion <NUM> (e.g., provided by the channels, voids, openings, pores, interstices, or other flow passages as described herein) corresponds to a reduced conductivity, and thus increased resistivity, which enables the resistive portion <NUM> to generate heat when the selected voltage is applied.

The body <NUM> further comprises cutouts, slits, slots, or other features that create electrical discontinuities or disconnections, which are referred to herein as slots <NUM>. The slots <NUM> are, or otherwise create, electrical disconnections, e.g., gaps, that break electrical conductivity at certain locations in the body <NUM>, for example, by severing, breaking, or otherwise electrically disconnecting portions of the body <NUM> from each other. In this way, electrical current through the body <NUM> is forced to flow in a designated path, which may be referred to herein as a serpentine current-carrying path described further below, around these disconnected portions formed by the slots <NUM>. For example, the slots <NUM> can be air gaps and/or filled with an electrically insulating material. A portion of the serpentine path is indicated by a dashed arrow <NUM> in some of the figures.

As shown in the illustrated embodiments, the slots <NUM> extend across the body <NUM> alternatingly from opposite sides of the body <NUM>, such that the material of the body <NUM> (e.g., intersecting walls <NUM>) is connected together in a serpentine pattern that doubles back on itself across the body <NUM> multiple times. The slots <NUM> intersect the outer periphery of the resistive portion <NUM> of the body <NUM> at intersections <NUM>. In other words, each of the slots <NUM> extends from one of the intersections <NUM> at the outer periphery to a terminal end <NUM> within the heater body <NUM>. Thus, the intersections <NUM> caused by the slots <NUM> create a corresponding disconnection, break, or gap (generally, an electrical disconnection) in the outer periphery of the resistive portion <NUM>, and this electrical disconnection continues along the length of the slots <NUM> into the body <NUM>.

In accordance with the foregoing, the resistive portion <NUM> of the body <NUM> in the illustrated embodiments comprises a plurality of segments <NUM> separated by the slots <NUM>. Adjacent segments <NUM> connect to each other around the terminal ends <NUM> of the slots <NUM>, thereby forming the serpentine path <NUM>. As a result of the electrical disconnections caused by the slots <NUM>, electrical current carried through the material of the body <NUM> between the electrodes <NUM> is forced along the serpentine path <NUM> through the segments <NUM> of the resistive portion <NUM> of the body <NUM>. The serpentine path <NUM> is not limited to that shown in <FIG>, as the slots <NUM> can be included at different lengths, angles, widths, or other dimensions in order to set other shapes for the serpentine path <NUM> and the segments <NUM>.

Accordingly, the electrical disconnections caused by the slots <NUM> enables the current path length between the electrodes <NUM> to be increased, as the electrical current is forced to traverse back and forth across the body <NUM> multiple times instead of directly flowing in a straight line directly between the electrodes <NUM>. Since the overall resistivity of the heater body <NUM> is dependent on the overall current-carrying path length between the electrodes <NUM>, the resistivity of the heater assembly <NUM> can be set, at least in part, by selecting the dimensions, locations, and number of slots <NUM> (thereby setting the dimensions of the serpentine current-carrying path). Accordingly, as described herein, the amount of heat generated by the heater <NUM> and/or the temperature achieved in the resistive portion <NUM> of the heater body <NUM> can be predictably set by setting the dimensions and material properties of the heater body <NUM> with respect to the voltage applied to the electrodes <NUM>.

The plurality of segments <NUM> includes an end segment <NUM>' at each opposite end of the serpentine path <NUM>. Instead of being defined between two adjacent slots <NUM>, as with the other segments <NUM>, the end segments <NUM>' are bounded between a first slot <NUM>' and the outer periphery <NUM> of the heater body <NUM>. The first slots <NUM>' are identified as those of the slots <NUM> that are closest to the electrode attachment portions <NUM> and that causes the current to/from the electrode attachment portions <NUM> to flow along the serpentine path <NUM> (thus there is one of the first slots <NUM>' and one of the end segments <NUM>' at each end of the resistive portion <NUM> of the heater body <NUM>). Accordingly, the electrode attachment portions <NUM> are connected to the resistive portion <NUM> at the end segments <NUM>'.

For various reasons, the end segments <NUM>' may have a different shape or size than the segments <NUM> along the remainder of the serpentine path <NUM>. For example, in the illustrated embodiments, the circular cross-sectional shape of the outer periphery <NUM> for the heater body <NUM> results in the end segments <NUM>' being substantially wider than the rest of the segments <NUM> (e.g., compare the width of the first bracket indicating the size end segment <NUM>' to the width of the bracket indicating the size of one of the other segments <NUM> in <FIG>). As another example, in embodiments, the electrode attachment portions <NUM> may need to be at least a minimize size in order to facilitate attachment to the electrodes <NUM>, and this minimize size may result in the end segments <NUM>' being larger than the remaining segments.

In embodiments in which the end segments <NUM>' are larger than the other segments <NUM>, this larger size may result in a substantially lower temperature achieved by the material of the heater body in the end segments <NUM>'. That is, the larger width of the end segments <NUM>' (e.g., the width measured in a direction generally transverse, e.g., perpendicular to the direction of current flow at any given location) results in a lower concentration of current flow per unit volume along the serpentine path <NUM> through the end segments <NUM>' in comparison to the relatively higher concentration of current flow per unit volume along the serpentine path through the relatively narrower segments <NUM>. To this end, as the segments are made wider (in a direction transverse, e.g., perpendicular, to the direction of the serpentine path <NUM>), the current has more material to spread out through, thereby reducing the temperature achieved throughout these relatively wider segments.

As shown in the embodiments of <FIG>, the heater assembly <NUM> comprises at least one auxiliary slot <NUM> that is used to create a region of reduced current flow, which may be referred to as a "dead zone" <NUM> proximate to the outer periphery <NUM> of the heater body <NUM> in the end segment <NUM>'. For example, the embodiment of <FIG> illustrates a plurality of the auxiliary slots <NUM>, while the embodiment of <FIG> illustrates a single one of the auxiliary slots <NUM> that has a T-shape ending in two terminal ends <NUM>. Similar to the slots <NUM>, the auxiliary slots <NUM> are disconnections, breaks, or gaps that create electrical disconnection between portions of the heater body <NUM> on opposite sides of the auxiliary slots <NUM>.

Unlike the slots <NUM>, the auxiliary slots <NUM> are not included to create a bend in the serpentine current flow path <NUM>. Instead, each of the auxiliary slots <NUM> extends from the outer periphery <NUM> toward the corresponding first slot <NUM>' in a direction generally transverse (e.g., perpendicular) to the direction in which the first slot <NUM>' extends. In this way, the auxiliary slots <NUM> prevent, hinder, or reduce the flow of electrical current in material of the heater body <NUM> that is adjacent to the auxiliary slot(s) <NUM> proximate to the outer perimeter <NUM> within the end segment <NUM>'. As labeled in <FIG>, and shown in a grayed out area in <FIG>, the auxiliary slots <NUM> create the "dead zone" <NUM>, where heat is not significantly generated due to the lack of current flow in this area. As a result, the auxiliary slots <NUM> assist in directing or biasing the electrical current to flow through a concentrated region <NUM> of each of the end segments <NUM>' that is adjacent to and extends along the respective first slot <NUM>'. Since the concentrated region <NUM> has a relatively narrower width (transverse to the direction of current flow through the serpentine path <NUM>) in comparison to that of the end segment <NUM>' as a whole, the temperature achieved for a given applied voltage is effectively increased by addition of the auxiliary slots <NUM>.

For example, as shown in <FIG>, when installed in the assembly <NUM>, the retaining ring <NUM> (the inner diameter of which is indicated in dashed lines in <FIG>) may physically cover the outer portion of the heater body <NUM>, thereby blocking or otherwise preventing the exhaust flow from encountering the peripheral-most material of the heater body <NUM> around the outer periphery <NUM>. Therefore, any heat generated in these peripheral areas is largely wasted, as it does not significantly participate in heat transfer with the exhaust flow or the aftertreatment component <NUM>. Accordingly, the creation of the concentrated region <NUM> by the auxiliary slots <NUM> advantageously increases the temperature of the portions of the heater body <NUM> that is not blocked by the retaining ring <NUM>, thereby advantageously increasing heat transfer efficiency with the exhaust flow through the heater assembly <NUM> and increasing electrical efficiency and reducing wasted heat generation.

Referring more particularly to the embodiment of <FIG>, the heater body <NUM> has a single one of the auxiliary slots <NUM> in contrast to the plurality of the auxiliary slots <NUM> in the embodiment of <FIG>. However, the auxiliary slot <NUM> in <FIG> has a T-shape that splits into two of the terminal ends <NUM>, each of which terminal ends <NUM> extends from the auxiliary slot <NUM> in a direction substantially parallel to that of the first slot <NUM>'. Thus, while the two terminal ends <NUM> are illustrated in <FIG> as extending at <NUM> degrees relative to each other (and parallel to the first slot <NUM>'), the two terminal ends <NUM> in other embodiments can extend at different angles, e.g., providing a Y-shape, W-shape, or other shape instead of the illustrated T-shape.

The heater body <NUM>, as well as the slots <NUM> and/or auxiliary slots <NUM> formed in the heater body <NUM>, can be formed in any suitable manner. In embodiments, the heater body <NUM> is manufactured by three-dimensional printing, such as laser powder bed fusion, or other additive manufacturing process. In embodiments, the heater body <NUM> is formed as a single monolithic component (e.g., a sintered metallic or metal-containing body). In embodiments, the resistive portion <NUM> of the heater body <NUM> is formed simultaneously with the slots <NUM> and/or auxiliary slots <NUM>, such as via additive manufacturing processes where the various slot features can be simply printed into the design of the heater body. In embodiments, the slots <NUM> and/or auxiliary slots <NUM> are formed in one or more manufacturing steps by slitting, punching, cutting, into an unslotted body that does not yet contain the slots <NUM>.

With reference to <FIG>, the slots <NUM> and auxiliary slots <NUM> of the heater assembly <NUM> can comprise receptacles <NUM>. When arranged in the assembly <NUM>, the receptacles <NUM> can receive slot separators, e.g., electrically insulating components, such as rods, blocks, or bars, that can be inserted into receptacles <NUM> to ensure the slots <NUM> remain open. For example, during operation, the body <NUM> may experience forces, such as from vibration or thermal expansion, which might cause physical deformation of the body <NUM>. In this way, the slot separators assist in preventing the slots <NUM> "closing", i.e., in which portions of the walls on opposite sides of the slots <NUM> come into electrical contact with each other, which may result in an electrical short. Slot separators can be formed as axially extending portions of the retaining rings <NUM> or discrete axially-extending structural components.

The receptacles <NUM> can be positioned at the outer periphery <NUM>, or spaced away from the outer periphery <NUM> by some distance (as shown in <FIG>). The receptacles <NUM> and slot separators can be added to any of the embodiments described herein, such as the embodiment of <FIG>. The slot separators can be held in the receptacle portions <NUM> such as via a friction fit, via a flange, head, cap, or lip, or otherwise affixed with adhesives, welding, or mechanical fasteners. The slot separators can be at least partially made of a generally nonconductive material (e.g., a ceramic or dielectric material or coating), such that slot separators maintain electrical isolation of the portions of the heater body <NUM> on opposite sides of the slots <NUM> when the selected voltage is applied across the heater body. Slot separators and the receptacle portions <NUM> can take various complementary shapes, e.g., both can have circular cross-sectional shapes. In embodiments, the heater assembly <NUM> can have multiple differently shaped slot separators and/or receptacles, or all of the slot separators and receptacles can be the same shape. Any suitable combination of shapes for the slot separators and receptacle portions can be included.

As described herein, the ends <NUM> of the slots <NUM> that terminate within the body <NUM> are located at the bends in the serpentine path <NUM> defined by the slots <NUM>, and thus represent the locations at which the current flow changes direction. It has been found that these bends in the serpentine path <NUM> can result in hot spots due to concentration of the current flow. Advantageously, the inclusion of additional material at these locations increases local conductivity in this area, thereby alleviating hot spots.

For example, as shown in <FIG>, the slots <NUM> can have a width W. In some embodiments, the width W is equal to the combined width of one or more whole cells or channels <NUM> formed by the intersecting walls. For example, the width W is equal to the width of one whole channel in <FIG>. As also shown in <FIG>, the terminal end <NUM> of the slots <NUM> can be tapered, such as rounded in the illustrated embodiment. In embodiments in which the heater body <NUM> comprises a honeycomb design, the ends <NUM> need not be tapered or pointed, but can have a shape that is different than that of the intersecting walls <NUM> or otherwise occupy only a fraction or portion of a whole one of the channels <NUM>. For example, in <FIG>, the terminal ends <NUM> of the slots <NUM> have excess material <NUM>, e.g., electrically conductive material. For example, the conductive material <NUM> is formed as fillets at the terminal ends <NUM> in the illustrated embodiment of <FIG>.

<FIG> illustrates an embodiment in which one or more of the channels <NUM> directly proximate to the terminated ends <NUM> are completely filled with the excess conductive material <NUM>. Any number (e.g., greater than or fewer than the seven shown) or combination of channels (e.g., different than the ones shown) can be arranged as filled with the material <NUM>. <FIG> illustrates an alternate embodiment in which some of the channels <NUM> at the terminal end <NUM> are partially filled with the material <NUM>, but which contain a flow passage therein, e.g., to assist in further heat transfer with the fluid flow through the heater. Completely filled channels, e.g., as shown in <FIG>, can be used alternatively to, or in combination with, the partially filled areas as shown and described in <FIG> and <FIG>.

Claim 1:
An electrical heater for treatment of an exhaust or supplemental air, flow comprising:
a heater body (<NUM>) having a resistive portion (<NUM>), the resistive portion (<NUM>) being configured to generate heat when electrical current is passed therethrough, wherein the resistive portion (<NUM>) comprises an intersecting array of walls (<NUM>) defining channels (<NUM>) extending axially through the electrical heater, the channels (<NUM>) being configured to enable the exhaust or supplemental air to flow through the heater body (<NUM>);
a pair of electrode attachment portions (<NUM>) at opposite ends of the resistive portion (<NUM>);
a plurality of slots (<NUM>, <NUM>') that extend into the resistive portion (<NUM>) from an outer periphery of the resistive portion (<NUM>) and electrically disconnect segments of the resistive portion (<NUM>) from each other to define a serpentine current-carrying path (<NUM>) extending through the resistive portion (<NUM>) between the pair of electrode attachment portions (<NUM>),
wherein each of the electrode attachment portions (<NUM>) is connected to a respective end segment (<NUM>') of the resistive portion (<NUM>) that is bounded between an outer periphery of the resistive portion (<NUM>) and a respective first slot (<NUM>') of the plurality of slots (<NUM>, <NUM>'),
characterized by
at least one auxiliary slot (<NUM>) in each of the end segments (<NUM>') that extends from the outer periphery toward the first slot (<NUM>') in a direction transverse to the first slot (<NUM>') to bias current flow through a concentrated region adjacent to and extending along the first slot (<NUM>') in each end segment (<NUM>').