Serpentine heater with features to reduce hot spots at slot ends

Abstract

To provide a serpentine heater having features for reducing hot spots at slot ends.SOLUTION: The heater body includes an outer peripheral surface. A plurality of slots extend from the outer peripheral surface and terminate within the heater body. A plurality of core segments are defined between adjacent pairs of slots. A plurality of bend regions are disposed about each trailer of slots. Each pair of adjacent core segments is connected by a corresponding one of the bend regions. An auxiliary conductive feature is located in each of the bend regions. The plurality of slots electrically isolate each pair of adjacent core segments from each other to form a serpentine current carrying path extending across the heater body through the conductive material of the core segments and the bend regions. Each of the auxiliary conductive features locally reduces the electrical resistance of the heater body in the bend region as compared to the conductive material alone.SELECTED DRAWING: Figure 7A

Description

Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. Section 119 of U.S. Provisional Patent Application No. 63 / 183573, filed May 3, 2021, which claims the benefit of priority under 35 U.S.C. Section 119 of Indian Patent Application No. 202111055328, filed November 30, 2021, which claims the benefit of priority under 35 U.S.C. Section 119 of U.S. Provisional Patent Application No. 63 / 319374, filed March 13, 2022, the contents of which are relied upon and incorporated herein by reference in their entirety. [Technical Field]

[0002] The present disclosure relates to a heater assembly comprising a honeycomb body, particularly a honeycomb body having a serpentine current carrying path defined by slots extending within the honeycomb body, and to an exhaust aftertreatment system including such a heater assembly. [Background technology]

[0003] A pollution abatement system, such as an exhaust aftertreatment system, coupled to an internal combustion engine, e.g., an internal combustion engine of an automobile or other vehicle, may include a heater assembly that provides supplemental heat to assist in the operation of the system. For example, catalytic materials used in catalytic converters or other catalyst-containing aftertreatment components may require a minimum temperature to initiate a catalytic reaction, also known as catalyst light-off.

[0004] In the case of an internal combustion engine, heat can be provided from the exhaust stream itself, but each time the engine is first started, it can take some time for the exhaust temperature to rise sufficiently, also known as a cold start of the engine. Even if the system is arranged to heat the catalyst to light-off temperature within a few seconds with respect to the exhaust stream, these first few seconds after a cold start can contribute significantly to the overall engine emissions, and may even constitute a large portion of the engine's emissions. Therefore, the supplemental heat provided by the heater assembly can significantly reduce the time it takes for the catalyst light-off temperature to be achieved, thereby reducing emissions, especially after a cold start event. Summary of the Invention

[0005] Disclosed herein, for example, is a heater body for an exhaust aftertreatment assembly. In an embodiment, the heater body has an outer circumferential surface; a plurality of slots each extending from the outer circumferential surface and terminating at a termination within the heater body; a plurality of core segments comprised of a conductive material, each core segment defined between a different pair of adjacent slots; a plurality of bend regions comprised of a conductive material, each bend region disposed around a respective one of the slot terminations, each pair of adjacent core segments being connected by a corresponding one of the bend regions; and an auxiliary conductive feature disposed in each bend region adjacent a respective one of the terminations, wherein the plurality of slots electrically separate each pair of adjacent core segments from each other to form a serpentine current carrying path extending through the heater body through the core segments and the conductive material of the bend regions, and each auxiliary conductive feature locally reduces the electrical resistance of the heater body at the bend region compared to the conductive material alone.

[0006] In an embodiment, each auxiliary conductive feature has filleted or rounded corners at the end of the slot.

[0007] In embodiments, the conductive material comprises a foam, molded as a lattice, or interwoven fibers, filaments, or wires that form a plurality of channels axially through the heater body.

[0008] In an embodiment, the conductive material is shaped as an intersecting array of walls that define a plurality of cells in a honeycomb design.

[0009] In an embodiment, each auxiliary conductive feature includes one or more cells in the bend region that are completely filled with a supplemental conductive material.

[0010] In an embodiment, each auxiliary conductive feature includes one or more cells in the bend region that are at least partially filled with a supplemental conductive material.

[0011] In an embodiment, each auxiliary conductive feature comprises a continuous strip of complementary conductive material.

[0012] In an embodiment, the strip includes a plurality of wedges, each wedge partially filling a corresponding one of the cells.

[0013] In an embodiment, the wedge has a linear sloped surface.

[0014] In an embodiment, the wedge is corrugated with a non-linear slope.

[0015] In an embodiment, the wedge increases in width across each cell from a minimum dimension of 0% to 25% of the cell width to a maximum dimension of 25% to 100% of the cell width.

[0016] In an embodiment, each auxiliary conductive feature comprises a continuous strip of thickened wall that is thicker than the wall it intersects.

[0017] In an embodiment, the thickened wall includes a plurality of arms extending from the bend region toward each core segment.

[0018] In an embodiment, each auxiliary conductive feature includes a thickened boundary wall that bounds the end of the slot.

[0019] In an embodiment, each auxiliary conductive feature extends at least partially along the length of the slot.

[0020] In an embodiment, each auxiliary conductive feature extends at least partially along the length of the slot, on opposite sides of the slot.

[0021] In an embodiment, at least a portion of each auxiliary conductive feature that extends at least partially along the length of the slot is also spaced apart from the slot.

[0022] In an embodiment, the conductive material is shaped as an intersecting array of walls that define a plurality of cells in a honeycomb design, with a portion of each auxiliary conductive feature spaced from the slot by at least one cell width.

[0023] In an embodiment, the auxiliary conductive feature extends continuously from a first core segment of the plurality of core segments, through the bend region, to a second core segment of the plurality of core segments.

[0024] In an embodiment, the heater assembly comprises a heater body according to any one of the preceding paragraphs coupled to electrode pairs at opposite ends of the serpentine path.

[0025] In an embodiment, an exhaust aftertreatment assembly includes the heater assembly of the immediately preceding paragraph and aftertreatment components connected to a common housing or piping.

[0026] In an embodiment, the after-treatment component comprises a porous ceramic honeycomb body.

[0027] In an embodiment, the heater body, the after-treatment component, or both, include a catalytic material.

[0028] It is to be understood that both the foregoing general description and the following detailed description are exemplary only and are intended to provide an overview or framework for 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 embodiments and, together with the description, serve to explain the principles and operation of the various embodiments. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a cross-sectional view of an exhaust after-treatment assembly according to an embodiment disclosed herein. [Figure 2] FIG. 1 is a front view illustrating an electric heater assembly having a serpentine design formed by a plurality of electrically insulating slots, a plurality of core segments between each pair of adjacent slots, and a bend region near the end of each slot connecting adjacent core segments to each other, according to embodiments disclosed herein. [Figure 3] FIG. 10 illustrates a portion of a heater body with auxiliary conductive features in the bend region of the heater body, with filleted or rounded corners at the intersections between the walls, according to embodiments disclosed herein. [Figure 4] FIG. 1 illustrates a portion of a heater body with auxiliary conductive features in a bend region of the heater body having multiple honeycomb cells completely filled with conductive material according to embodiments disclosed herein. [Figure 5] FIG. 1 illustrates a portion of a heater body with auxiliary conductive features in a bend region of the heater body having multiple honeycomb cells partially filled with a conductive material according to embodiments disclosed herein. [Figure 6A] FIG. 10 is a diagram illustrating a schematic of current paths for a heater body without auxiliary conductive features according to embodiments disclosed herein. [Figure 6B]FIG. 10 is a diagram illustrating a schematic of current paths for a heater body having auxiliary conductive features according to embodiments disclosed herein. [Figure 7A] FIG. 1 illustrates a portion of a heater body with auxiliary conductive features in the bend region of the heater body having strips of conductive material according to embodiments disclosed herein. [Figure 7B] FIG. 7B is an enlarged view of a portion of the strip of FIG. 7A in the form of a wedge that partially fills a honeycomb cell. [Figure 8] FIG. 1 illustrates a portion of a heater body with an auxiliary conductive feature in a bend region of the heater body having a strip of conductive material with a plurality of undulating wedges according to embodiments disclosed herein. [Figure 9A] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 9B] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 9C] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 9D] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 9E] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 9F] 1A and 1B illustrate a portion of a heater body with auxiliary conductive features having thickened wall strips in the bend region of the heater body according to embodiments disclosed herein. [Figure 10]FIG. 10 illustrates a portion of a heater body with auxiliary conductive features in the bend region of the heater body having supplemental walls extending across the honeycomb cells according to embodiments disclosed herein. [Figure 11] FIG. 10 illustrates a portion of a heater body with auxiliary conductive features in the bend region of the heater body, with thickened boundary walls around the ends of the slots, according to embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0030] Reference will now be made in detail to exemplary embodiments illustrated in the accompanying drawings. Wherever possible, the same reference numbers 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.

[0031] Numerical values, including the endpoints of a range, may be expressed herein as approximations, using terms such as "about," "approximately," etc. In such cases, another embodiment includes the particular numerical value. Whether a numerical value is expressed as an approximation, two embodiments are included in the present disclosure: one expressed as an approximation and another not expressed as an approximation. Moreover, it is understood that the endpoints of each range are significant both in relation to the other endpoint and independently of the other endpoint.

[0032] Modifications of the present disclosure will occur to those skilled in the art and to those who make or use the present disclosure. Accordingly, it is understood that the embodiments illustrated in the drawings and described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure, which is defined by the following claims, as interpreted in accordance with patent law principles, including the doctrine of equivalents.

[0033] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not exact and need not be exact, but may be approximate and / or larger or smaller, if desired, to reflect tolerances, conversion factors, rounding, measurement error, etc., and other factors known to those of ordinary skill in the art. When the term "about" is used in describing a value or an endpoint of a range, it is to be understood that the disclosure also includes the specific value or endpoint referred to.

[0034] Directional terms used herein, such as up, down, right, left, front, back, upper, and lower, are described solely with reference to the illustrated figures and are not intended to imply absolute directions. The term "radial" as used herein refers to a direction perpendicular to the indicated axial direction, extending from the center point of the shape (e.g., see central axis C in FIG. 2 ) to or toward the outer periphery of the shape, regardless of the shape of the component or feature to which the term is used. Similarly, the term "diameter" as used herein is not limited to circular shapes but instead refers to the longest dimension of the component passing through the center point (central axis) of the component's shape. For example, the radial distance of a square component can be measured as the linear distance from the center point (central axis) to the intersection with one of the square's walls, and 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.

[0035] Fluid treatment systems, such as automotive exhaust aftertreatment systems or other pollution reduction systems, can be equipped with an auxiliary heat source to facilitate operation, such as, for example, in the case of catalyst-containing systems, to provide faster catalyst light-off. For example, heat can be provided by an electric heater (e.g., positioned to transfer heat to the catalyst material) or an electrically heated catalyst substrate (e.g., a conductive substrate supporting the catalyst material). For example, a heater can be positioned upstream of the catalyst substrate and heat the exhaust stream (or an auxiliary air stream), which then heats the catalyst. To reduce emissions in gasoline, diesel, and / or hybrid vehicles, aftertreatment systems that use auxiliary heat can be provided to help ensure rapid and consistent catalyst light-off during operation of the corresponding engine, especially after a cold start of the engine.

[0036] 1, there is shown a fluid treatment assembly 10 that may be disposed, for example, as part of an exhaust system of an automobile. Fluid treatment assembly 10 includes an outer housing 12 (alternatively referred to as a "can") that may be generally tubular (e.g., hollow tube) formed from metal or a suitable material. Outer housing 12 has an inlet 14 that may be connected in fluid communication with, for example, an exhaust manifold of an internal combustion engine, and an outlet 16 that may be connected in fluid communication with, for example, a tailpipe of the automobile.

[0037] Exhaust or other fluid stream from an engine (the fluid stream to be treated, generally referred to herein as "exhaust") can be treated (e.g., one or more pollutants removed or reduced) as the exhaust flows through assembly 10 from inlet 14 to outlet 16. To this end, assembly 10 further includes a heater assembly 18 and an aftertreatment component 20 disposed between inlet 14 and outlet 16. For example, aftertreatment component 20 may be a catalyst-loaded substrate, a particulate filter, or a catalyst-loaded particulate filter. For example, catalyst substrates and particulate filters may include a porous ceramic honeycomb body having an array of walls forming a plurality of fluid flow paths or channels extending axially (perpendicular to the direction of exhaust flow and / or the end face of the body) through the body.

[0038] As described in detail herein, the heater assembly 18 may be a resistive heater that provides supplemental heat to facilitate the function of the aftertreatment component 20, for example, by rapidly initiating light-off of catalytic material disposed in or on the walls of the heater assembly 18 and / or the aftertreatment component 20. For example, the heater assembly 18 may include or be otherwise connected to electrodes 22. The electrodes 22 may be positioned to extend through the housing 12 for connecting the heater assembly 18 to a power source, such as a vehicle battery. As shown in FIG. 1 , the electrodes 22 may extend radially through the housing 12. However, the electrodes 22 may alternatively extend axially through the housing 12, and / or one electrode may extend radially and the other electrode may extend axially. In this manner, the heater assembly 18 may be configured to generate heat through Joule heating by connecting the heater assembly 18 to a power source and applying a corresponding voltage to cause current to flow through the walls of the heater assembly 18. Although the electrodes 22 are shown in FIG. 1 as being positioned on opposite sides of the heater assembly 18 (e.g., 180° apart with respect to the exterior of the heater assembly 18), they may be positioned at other locations or angles.

[0039] In embodiments disclosed herein, such as that shown in FIG. 1 , heater assembly 18 is positioned upstream (relative to the direction of exhaust flow) of after-treatment component 20 to increase the temperature of the exhaust stream and / or provide direct heating to after-treatment component 20. This, in turn, increases the temperature of after-treatment component 20, such as the temperature of a catalytic material carried by after-treatment component 20, as the exhaust stream flows through after-treatment component 20. In some embodiments, heater assembly 18 and after-treatment component 20 can be effectively combined into a single device by carrying a catalyst directly on the body of heater assembly 18. Such a configuration, useful for heating catalytic materials, can be referred to as an electrically heated catalyst, or EHC.

[0040] A vehicle exhaust system may be formed by connecting additional lengths of piping (not shown) to the assembly 10 at the inlet 14 (e.g., extending between the inlet 14 and the engine exhaust manifold) and at the outlet 16 (e.g., extending from the outlet 16 to a tailpipe). Depending on the design or configuration of the exhaust system, which may vary from vehicle to vehicle, various components and / or lengths of piping may have different diameters at different locations along the flow path through the exhaust system.

[0041] Heater assembly 18 and after-processing component 20 may be held in place, supported, and / or contained within housing 12 in any suitable manner. For example, the body of heater assembly 18 may be held in place and supported via one or more retention devices 24, such as retaining rings. After-processing component 20 may be supported by a similar retention device and / or by a mat 26, such as an inorganic fiber mat, which helps protect after-processing component 20 from forces such as vibration or thermal expansion exerted on after-processing component 20 during operation.

[0042] 2-3, there is shown one embodiment of heater assembly 18. Consistent with the disclosure herein, any embodiment shown and / or described herein may be used as or incorporated into heater assembly 18 in assembly 10, and combinations of features of the embodiments shown or described herein may be used together for heater assembly 18 in assembly 10.

[0043] As described further herein, heater assembly 18 includes a heater body 30 made of a conductive material that extends in a serpentine current-carrying path (or simply, a "serpentine path") between a pair of electrodes (e.g., electrode 22, not shown in FIGS. 2-3). A portion of the serpentine path for heater body 30 is identified in FIG. 2 by dashed lines and reference numeral 32. As described further herein, serpentine path 32 for body 30 is created by a plurality of slots 34 that extend into body 30 from an outer circumferential surface 36 of body 30.

[0044] The flow of electrical current along the serpentine paths 32 of the heater body 30 can be achieved via electrodes, such as electrodes 22 (not shown in FIG. 2 ), at both ends of the serpentine paths 32. The electrodes, or portions of electrodes, can be integrally formed with the heater body 30 or can be separately attached, for example, by mechanical fastening or welding, to corresponding electrode attachment sites 38. In this manner, electrical connection can be established along the serpentine paths 32 through the body 30 via electrodes secured at both ends. For example, the properties of the honeycomb body 30, such as the dimensions of the honeycomb body 30, the length of the serpentine paths 32, the area of ​​conductive material of the heater body 30 available for current flow per unit length along the serpentine paths, and / or the resistivity of the material of the honeycomb body 30, can be set in relation to a target or selected voltage to be applied to the electrodes 22 to generate heat by resistive heating as electrical current passes through the material of the heater body 30.

[0045] In embodiments, the heater body 30 is configured with a selected voltage (e.g., the voltage available to the heater assembly 18 from a vehicle battery) to reach a temperature suitable for catalyst light-off, e.g., approximately 700°C to 1000°C, although other temperatures may be targeted based on the application of the heater assembly 18 and / or the thermomechanical properties of the material selected for the heater body 30. In embodiments, the heater body material comprises a metal or metal alloy. For example, various metal alloys are particularly advantageous for use in resistive heating elements due to their thermomechanical, environmental resistance, and electrical properties. In embodiments, the metal comprises an alloy containing one or more of nickel, chromium, iron, and / or aluminum, such as a nickel-chromium alloy or an iron-chromium-aluminum alloy, although other materials suitable for use in or as a resistive heater may also be used. However, because these materials comprise metals, they generally have fairly high electrical conductivity. Advantageously, the back-and-forth serpentine design described herein allows the current carrying path length for the heater body to be many times longer than the diameter of the heater body, thereby allowing the overall resistance of the heater body 30 between the electrodes to be high enough to reach sufficient temperatures while maintaining a compact size for the heater body.

[0046] In the illustrated embodiment, the body 30 includes an array or matrix of intersecting walls 40 (see, e.g., FIGS. 3A-3B ) that form a plurality of channels (fluid flow paths) extending axially through the body 30; thus, the body 30 is of a type that may be referred to as a honeycomb body. The channels provide a flow path that allows fluid (e.g., exhaust fluid flow) to flow through the body 30, while the intersecting walls 40 function as resistive elements that generate heat when a voltage is applied to the body 30 and also provide surface area for heat exchange with the fluid flow. Each section of wall that is enclosed together to define a flow channel may be referred to herein as a cell 42. Thus, in FIGS. 2 and 3 , the array of walls 40 defines a corresponding array of square cells 42, which together create the honeycomb design for the body 30. However, the walls 40 may be arranged in other patterns to form cells 42 having any other desired cross-sectional shape (perpendicular to the axial direction), such as a hexagon, triangle, or other polygon.

[0047] Furthermore, instead of cells and channels having regular and / or repeating geometries, the body 30 can have irregularly shaped and sized openings and / or tortuous flow paths, e.g., an irregularly interconnected porous structure. For example, in embodiments, the body 30 comprises a lattice, foam, or interwoven fibers, wires, or filaments (or other elongated fibrous or wire-like elements) of conductive material, where the flow paths through the body 30 are irregularly formed by holes, voids, openings, or gaps in the lattice, foam-like structure, and / or between the interwoven fibers or fibrous elements of the conductive material. Thus, honeycomb, lattice, foam, and interwoven fiber or wire designs are all similar in that they have flow paths that allow fluid to flow axially through the body, while the conductive material functions as a resistive heating element to generate heat while providing a surface area for heat transfer by the flow of fluid (e.g., exhaust gas) through the heater. In embodiments, the body 30 may be formed by additive manufacturing, stamping or perforating a sheet of conductive material, weaving wires, fibers, or filaments into a mesh, mat, or screen, foaming a conductive material, or other suitable process. Thus, whether the heater body 30 comprises a honeycomb, lattice, foam, porous, or interwoven structure, the honeycomb body 30 includes a plurality of flow channels axially therethrough that allow for heat transfer between a fluid flow and the conductive material that forms the flow channels.

[0048] As described above, the body 30 has slots 34 that form separations, e.g., gaps, in the heater body 30 to block electrical conductivity at predetermined locations in the body 30. For example, the slots 34 positively block, separate, or otherwise electrically insulate portions of the body 30 from one another, thereby forcing electrical current to flow in a designated serpentine path 32 around these separated portions. For example, the slots 34 may be air gaps or may be filled with an electrically insulating material. Each slot 34 has an open end 44 where the slot 34 intersects the outer periphery 36 of the body 30 and a terminal end 46 where the slot 34 terminates within the heater body 30.

[0049] As shown in FIG. 2, the slots 34 extend across the body 30 in alternating fashion from opposite sides of the body 30, causing the material of the body 30 (e.g., the intersecting walls 40) to fold back on itself and connect to each other in a serpentine pattern that traverses the body 30 multiple times.

[0050] Further, as shown in FIG. 3 , the slots 34 have a width W and a length L extending from the open end 44 to the terminal end 46 (only a portion of the length L is shown). Because the slots 34 intersect the outer circumferential surface 36 over a small distance due to the curved outer circumferential surface 36, the length L of each slot 34 can be defined, if desired, as the longest dimension of each slot 34 between the terminal end 46 and the open end 44, as in the illustrated embodiment. The length L and / or width W can vary for different slots 34. As a result, current transmitted between the electrodes 22 and through the material of the body 30 is forced to flow along the serpentine path 32. The number, length, angle, width, and other dimensions of the slots 34 can be set to define the shape and / or dimensions of the serpentine path, and the shape and design of the serpentine path are not limited to those shown.

[0051] In embodiments in which the heater body 30 is formed as a honeycomb design, such as the illustrated embodiment including an intersecting array of walls 40, the width W may be equal to the combined width of one or more complete cells 42 formed by the intersecting walls 40. For example, the width W is equal to the width of one complete cell 42 in FIG.

[0052] Thus, the electrical isolation provided by the slots 34 can increase the current path length between the electrodes 22, as the current is forced to traverse back and forth across the body 30 multiple times rather than flowing in a direct line between the electrodes 22. Because the total resistance of the heater body 30 depends (in part) on the total current transmission path length between the electrodes 22, the electrical resistance of the heater assembly 18 can be set, at least in part, by selecting the size, location, and number of slots 34 (thereby setting the parameters of the serpentine current transmission path). For example, as described herein, the serpentine design allows the heater body 30 to be formed as a relatively small, thin disk of a desired metal alloy or other material, while still allowing temperatures of typically several hundred degrees Celsius.

[0053] In embodiments, the heater body 30 is axially up to 1 inch (25.4 mm) thick, up to 0.75 inches (19.05 mm) thick, up to 0.5 inches (12.7 mm) thick, for example, 0.1 inch (2.54 mm) to 1 inch (25.4 mm), 0.1 inch (2.54 mm) to 0.75 inches (19.05 mm), 0.1 inch (2.54 mm) to 0.5 inches (12.7 mm), or 0.25 inches (6.35 mm) to 0.5 inches (12.7 mm). In embodiments, the diameter (or widest dimension perpendicular to the axial direction) is up to 10 inches (254 mm), up to 9 inches (228.6 mm), up to 8 inches (203.2 mm), up to 7 inches (177.8 mm), up to 6 inches (152.4 mm), up to 5 inches (127 mm), up to 4 inches (101.6 mm), for example, between 4 inches (101.6 mm) and 10 inches (254 mm), although the size of the heater body can be arranged based on the particular application, for example, to generally correspond to the cross-sectional size of the catalyst substrate or filter to be used with the heater.

[0054] Because the slots 34 provide electrical insulation, the terminations 46 of the slots 34 correspond to locations where the serpentine path 32 bends around the slots 34, and therefore represent locations where the current flow changes direction. It has been found that these bends in the serpentine path can result in more heat being generated, and therefore, the concentration of current flow at the terminations 46 can result in the formation of high temperature "hot spots." That is, current flow tends to concentrate along the shortest path through the bends, which corresponds to the material of the heater body 30 immediately adjacent and / or bounding the terminations 46 of the slots 34. Such hot spots can make these regions of the heater body 30 particularly susceptible to premature failure, fracture, cracking, bending, warping, or other degradation of mechanical or thermomechanical properties or performance, especially as the heater assembly 18 undergoes an increasing number of heating and cooling cycles during use.

[0055] Furthermore, due in part to the concentrated current flow through the material of the heater body 30 directly toward the terminal end 46, the material of the heater body 30 beyond the terminal end 46 (in the direction that the slot 34 extends into the heater body 30) cools more rapidly than both the hot spot and the rest of the heater body 30. This rapid temperature drop occurs because less current flows in the material of the heater body 30 with increasing distance from the terminal end 46 toward the outer periphery 36.

[0056] 2-3, the serpentine path 32 can be defined along a plurality of core segments 48 and a plurality of bend regions 50 of the heater body 30. More specifically, each core segment 48 is defined as the conductive material of the heater body 30 extending between and along each adjacent pair of slots 34, while the bend region 50 includes the conductive material of the heater body 30 in a region proximate the terminal end 46 where the serpentine path 32 bends.

[0057] Examples of general regions corresponding to core segments 48 and bending regions 50 are shown in the drawings. However, because core segments 48 and bending regions 50 are each formed from the conductive material of heater body 30 (e.g., core segments 48 and bending regions 50 may be integrally formed from conductive material as part of the same structure, such as both being formed from or as part of the illustrated array of intersecting walls 40), there may not be a distinct physical separation or boundary between these two regions. Instead, core segments 48 and bending regions 50 may overlap to some extent and / or there may be a transition between them.

[0058] While it may be difficult to physically see the transition between the core segments 48 and the bend regions 50, a temperature profile of the heater body 30 can be useful to more specifically identify where the core segments 48 and bend regions 50 are located. For example, when an appropriate voltage is applied across the heater body 30 to raise the heater body temperature to at least several hundred degrees (e.g., in the range of 700°C to 1000°C), the heater body 30 material within the core segments 48 reaches a substantially uniform or uniform temperature throughout the core segment 48, while the temperature within the bend regions 50 varies significantly from that of the core segment 48. For example, as noted above, bends in the serpentine path 32 located within the bend regions 50 of the heater body 30 tend to undesirably promote both the aforementioned hot spots and rapidly cooling regions within the heater body 30 beyond the terminal ends 46 toward the outer circumferential surface 36 in the direction in which each slot extends into the heater body 30.

[0059] 3-11 , the heater body 30 also includes auxiliary conductive features 52 disposed in at least some of the bend regions 50. As described further herein, the auxiliary conductive features 52 include additional or excess conductive material disposed in various patterns, areas, structures, and / or regions of the heater body 30. As described further herein, it has been discovered that including auxiliary conductive features 52 in the bend regions 50, where the serpentine path 32 bends around the terminations 46 of the slots 34, can advantageously be useful for locally reducing the resistance of the heater body 30 in the bend regions 50. In this manner, reducing the resistance of the heater body 30 locally within the bend regions 50 helps to more significantly distribute the current over a larger area in the bend regions 50. By distributing the current flow over a larger area (through the more conductive material), the auxiliary conductive features 52 help mitigate the formation of hot spots in the material immediately adjacent to or bordering the termination 46 of the slot 34 and the rapid temperature drop in the heater body 30 with increasing distance from the termination 46 towards the periphery.

[0060] The auxiliary conductive features 52 may be the same or different from the conductive material that forms the base structure of the heater body 30. For example, the material of the auxiliary conductive features 52 may be the same or different from the material of the walls 40 if a honeycomb design is used for the heater body 30, or the same or different from the material of the foam, lattice, or interwoven fibers or wires of the embodiments described herein.

[0061] 3, the auxiliary conductive feature 52 comprises a filleted or rounded corner 54 of the wall 40 immediately adjacent the termination 46 of the slot 34, causing the termination 46 to be correspondingly rounded or tapered. In embodiments in which the heater body 30 has a honeycomb design, the termination 46 need not be tapered or pointed, but may have a shape that differs from the shape of the regular pattern of intersecting walls 40, or may otherwise occupy only a portion of one of the cells 42 (e.g., the termination 46 could terminate in one half of the cell 42, with the auxiliary conductive feature 52 comprising the other half filled with a conductive material).

[0062] FIG. 4 illustrates an embodiment in which the heater body 30 has a honeycomb design, in which the auxiliary conductive feature 52 includes a plurality of cells 42 that are fully filled with conductive material immediately adjacent the terminal end 46, designated by the reference numeral 55. FIG. 5 illustrates an embodiment in which the auxiliary conductive feature 52 includes a plurality of partially filled cells 42 that are immediately adjacent the terminal end 46, designated by the reference numeral 56. The partially filled cells 56 thus include flow channels 58 therein to assist in further heat transfer, for example, by fluid flow through the heater. For example, fully filled channels such as those shown in FIG. 4 can be used in combination with partially filled cells 56 such as those shown and described in FIG. 5. Any number of cells (e.g., more or fewer than the illustrated number of fully filled cells 55 and / or partially filled cells 56) or combinations of cells (e.g., different from the illustrated pattern) can also be used.

[0063] A rough schematic comparison of a heater body 30 that does not include an auxiliary conductive feature 52 proximate the termination 46 of the slot 34 in the bend region 50 with a heater body 30 that includes an auxiliary conductive feature 52 can be seen with reference to FIGS. 6A and 6B. More specifically, in FIGS. 6A-6B, a path that approximates the center of current flow, and thus generally represents the serpentine path 32, is shown schematically as a dashed line. As shown in FIG. 6A without the auxiliary conductive feature 52, consistent with the description herein, the current flow tends to concentrate at the termination 46, as indicated by the "pinching" in the dashed lines near the termination 46 in FIG. 6A. This concentration of current flow can result in the aforementioned hot spot at the termination 46. In contrast, the addition of auxiliary conductive feature 52 shown in Figure 6B (feature 52 shown in Figure 6B similar to the fully filled strip of five cells 55 of the embodiment of Figure 4) results in the current spreading out, thereby making a "wider" bend around termination 46 shown in Figure 6B. In this manner, auxiliary conductive feature 52 located at termination 46 may be effective in embodiments for reducing hot spots at termination 46 of slot 34 where serpentine path 32 is bent to fold back on itself.

[0064] It has been found that having the auxiliary conductive features 52 not only extend beyond the terminal ends 46 of the slots 34, but also extend at least partially along the length L of the slots (see FIG. 3 ), can be particularly beneficial in embodiments to further assist in “steering” current away from the terminal ends 46. For example, FIG. 7A illustrates one such embodiment in which the auxiliary conductive features 52 take the form of multiple strips 60 that extend partially along the length L of the slots 34 and also extend beyond the terminal ends 46 in the direction of extension of the slots 34 into the heater body 30, as indicated by arrows 62 in FIG. 7A . More specifically, each strip 60 has multiple wedges 64 that partially fill corresponding ones of the cells 42, and these wedges are designated with alphabetical suffixes “a” through “d” for ease of illustration.

[0065] An auxiliary conductive feature 52 can be determined to be at least partially located along the length L of the slot 34 if at least a portion of the auxiliary conductive feature 52 intersects an imaginary line extending from a side of the slot 34 perpendicular to the direction 62 of the slot 34. That is, in the case of strip 60, both wedge portions 64a and 64b are located along the length L of the slot 34, while wedge portions 64c and 64d are located beyond the end portion 46 in the direction 62.

[0066] It has also been found that it can be further beneficial to have at least a portion of the auxiliary conductive feature 52 spaced from the slot 34 at a location where the auxiliary conductive feature 52 also extends along the length of the slot 34 to assist in "guiding" the current away from the termination 46. For example, as described above, both wedges 64a and 64b are positioned along the length L of the slot 34. In addition, both wedges 64a and 64b are spaced from the slot 34. In particular, wedge 64b is spaced from the slot 34 by one full width of a cell 42, while wedge 64a is spaced about 1.5 cell widths. In this manner, the auxiliary conductive feature 52 in the form of the strip 60 functions to "collect" a higher density of current from the corresponding core segment 48 and "guide" this higher density of current around and away from the termination 46. Auxiliary conductive features 52, such as strips 60, can extend from the bend region 50 into the adjacent core segment 48, if desired.

[0067] FIG. 7B shows an enlarged view of a single cell 42 partially filled by one of the wedges 64 of FIG. 7A. The dashed white line is shown to facilitate distinction between the wedge 64 and the wall 40 (having a wall thickness t), but it should be noted that the wedge 64 can be integrally formed with the wall 40. In effect, the wedge 64 can be positioned as a filled or heavily filleted corner between intersecting walls 40. As shown in FIG. 7B, the wedge 64 can extend at least partially along one or both of the relevant cross-sectional dimensions of the cell 42 partially filled by the wedge. The dimensions of the cell 42 are indicated by X and Y in FIG. 7B. In FIG. 7B, the cell 42 is square, and therefore X and Y are the same, but in other embodiments, these dimensions may be different. In the illustrated embodiment, wedge 64 extends the entire first dimension X (in the direction 62 of slot 34) but only partially along second dimension Y (perpendicular to direction 62). In embodiments, wedge 64 extends only partially along both dimensions X and Y. For example, in some embodiments, wedge 64 does not extend the entire cell distance X, but begins between 25% and 75% of dimension X. Wedge 64 is also shown increasing in width from a minimum width on one side (left side of FIG. 7B) to a maximum width on the opposing side (right side of FIG. 7B). In embodiments, the minimum width range may be from 0% to about 50% of the second dimension Y, such as from 0% to 25%, or even from 0% to 10%, while the maximum width range is from about 20% to about 100% of the second dimension Y, such as from 20% to 80%, from about 30% to about 70%, or from about 40% to about 60%.

[0068] FIG. 8 illustrates an embodiment of an auxiliary conductive feature 52 that is generally similar to the embodiment of FIGS. 7A-7B but includes two key differences. First, the auxiliary conductive feature 52 of FIG. 8 includes a single, continuous strip 66 that extends at least partially along the slot 34, completely surrounding the termination 46 on either side of the slot 34. By comparison, FIG. 7A illustrates two strips 60, including any additional material, separated by one of the cells 42 beyond the termination. However, each of the two strips 60 is considered continuous in itself because each successive wedge 64 within that strip abuts the same wall 40 as the preceding wedge 64. Second, the auxiliary conductive feature 52 of FIG. 8 includes curved or corrugated wedges 68, as opposed to the linear, sloping surfaces of the wedges 64. Wedge 68 may extend over a percentage range of dimensions X and Y of cell 42 similar to that described with respect to wedge 64, except that wedge 68 follows a non-linear curve rather than the linear slope of wedge 64.

[0069] A curved or corrugated wedge 68 can be particularly advantageous in some embodiments to achieve a similar temperature drop as a linear wedge 64, but using significantly less material. Using less material in the wedge 68 can provide a larger open area for fluid (e.g., exhaust) to flow through the heater body 30 and can also help reduce distortion in the heater body 30 due to differential thermal expansion or other temperature-based dimensional changes.

[0070] 9A-9F illustrate various embodiments in which the heater body 30 has a honeycomb design and the auxiliary conductive features 52 include various strips of thickened walls 70 (designated by corresponding alphabetical suffixes "a"-"f") that have a greater wall thickness than the walls 40 throughout the heater body 30. Similar to the embodiments of FIGS. 7A-8, the auxiliary conductive features 52 in the embodiments of FIGS. 9A-9F include portions that extend at least partially along the length L of the slot 34. In particular, each of the embodiments of FIGS. 9A-9F includes a continuous strip of thickened walls 70 that extends continuously at least partially along the length L, not only around the sides of the slot 34 but also around the termination 46. In embodiments, some or even all of the corners between intersecting thickened walls 70 can be at least partially filled with fillets or wedges, as described with respect to wedges 64 and 68. In some embodiments, the thickened wall 70 is at least 25% thicker than the intersecting wall 40, at least 50% thicker than the intersecting wall 40, at least 75% thicker than the intersecting wall 40, or even at least twice the thickness of the intersecting wall 40.

[0071] More specifically, Figures 9A-9C each show different patterns of strips of thickened walls 70, shown as thickened walls 70a, 70b, and 70c, respectively. As shown, thickened walls 70a and 70b in Figures 9A and 9B can be useful for positioning auxiliary conductive features 52 further away from slot 34 at positions along the length L of slot 34 than the position of thickened wall 70c in Figure 9C, which is relatively closer to the sides of slot 34 (as generally described with respect to the embodiment of Figure 7A above). That is, thickened wall 70c in Figure 9C is spaced approximately two cell widths from the sides of groove 34, while walls 70a and 70b in Figures 9A and 9B increase their distance from the sides of slot 34 in a stepwise manner to a distance of four cell widths. The thickened wall 70d of Figure 9D is generally similar to the thickened wall 70a in Figure 9A, except that the wall 70d additionally has a plurality of arms 72 that extend at least partially along the length of the slot 34. The thickened wall 70e of Figure 9E is also generally similar to the thickened wall 70a, except that the heater body 30 of Figure 9E has portions of the wall 40 removed on either side of the termination 46 to form gaps 74. These gaps 74 can be particularly useful for preventing current flow in the material of the heater body 30 directly adjacent to the termination 46. However, removing the wall portions may reduce the strength of the heater body 30 of Figure 9E. Thus, FIG. 9F shows a design similar to FIG. 9E, except that there are two additional diagonal walls 76 extending diagonally from thickened wall 70f to terminal end 46, which advantageously provides additional strength or support to heater body 30 to offset that lost by forming gap 74.

[0072] 10 illustrates an embodiment in which the auxiliary conductive feature 52 includes a supplemental wall 78 that extends across some of the cells 42. The supplemental wall 78 is arranged, similar to several other embodiments herein, to extend as a continuous strip or path at least partially along the length L of the slot 34, on opposite sides of the slot, and completely surrounding the termination 46. Furthermore, the portion of the supplemental wall 78 that extends at least partially along the length L of the slot 34 is also spaced from the slot 34.

[0073] 11 illustrates an embodiment in which the auxiliary conductive feature 52 includes a thickened boundary wall 80 that extends around the termination 46 and at least partially along the length of the slot 34. Thus, the thickened boundary wall 80 is generally similar to the filleted corner 54 of FIG. 3, but also extends down part of the side of the slot 34 at the thickened portion. For example, the thickened boundary wall 80 may be at least 50% thicker than the wall 40, at least twice the thickness of the wall 40 it intersects, or even at least three times the thickness of the wall 40 it intersects.

[0074] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claimed subject matter, and therefore, the claimed subject matter should not be restricted except in light of the attached claims and their equivalents.

[0075] Preferred embodiments of the present invention will be described below in detail.

[0076] Embodiment 1 A heater body comprising: the outer surface and; a plurality of slots each extending from the outer circumferential surface and terminating at a terminal end within the heater body; a plurality of core segments made of a conductive material, each core segment being defined between a different pair of adjacent slots; a plurality of bend regions of the electrically conductive material, each bend region disposed around a respective one of the terminations of the slot, each pair of adjacent core segments being connected by a corresponding one of the bend regions; an auxiliary conductive feature disposed in each of the bend regions adjacent a respective one of the terminations; It has the plurality of slots electrically separate each pair of adjacent core segments from each other to form a serpentine current carrying path that extends through the core segments and the conductive material in the bend region across the heater body; each of the auxiliary conductive features locally reduces the electrical resistance of the heater body in the bending region compared to the conductive material alone; Heater body.

[0077] Embodiment 2 2. The heater body of embodiment 1, wherein each auxiliary conductive feature has a filleted or rounded corner at the end of the slot.

[0078] Embodiment 3 2. A heater body as described in embodiment 1, wherein the conductive material is a foam, molded as a lattice, or made of interwoven fibers, filaments or wires that form a plurality of channels axially penetrating the heater body.

[0079] Embodiment 4 2. The heater body of embodiment 1, wherein the conductive material is shaped as an intersecting array of walls that define a plurality of cells in a honeycomb design.

[0080] Embodiment 5 5. A heater body as recited in embodiment 4, wherein each auxiliary conductive feature includes one or more of the cells in the bending region completely filled with a supplemental conductive material.

[0081] Embodiment 6 5. A heater body as recited in embodiment 4, wherein each auxiliary conductive feature includes one or more of the cells in the bending region at least partially filled with a supplemental conductive material.

[0082] Embodiment 7 5. A heater body as recited in embodiment 4, wherein each auxiliary conductive feature comprises a continuous strip of complementary conductive material.

[0083] Embodiment 8 8. The heater body of embodiment 7, wherein the strip includes a plurality of wedges, each wedge partially filling a corresponding one of the cells.

[0084] Embodiment 9 9. The heater body of embodiment 8, wherein the wedge-shaped portion has a linear inclined surface.

[0085] Embodiment 10 9. The heater body according to embodiment 8, wherein the wedge-shaped portion is formed in a corrugated shape with a non-linear inclined surface.

[0086] Embodiment 11 The heater body according to any one of embodiments 8 to 10, wherein the wedge-shaped portion increases in width across each cell from a minimum dimension of 0% to 25% of the cell width to a maximum dimension of 25% to 100% of the cell width.

[0087] Embodiment 12 5. A heater body as recited in embodiment 4, wherein each auxiliary conductive feature comprises a continuous strip of thickened wall that is thicker than the wall it intersects.

[0088] Embodiment 13 13. The heater body of embodiment 12, wherein the thickened wall includes a plurality of arms extending from the bend region toward each core segment.

[0089] Embodiment 14 5. A heater body as recited in embodiment 4, wherein each auxiliary conductive feature includes a thickened boundary wall that bounds the terminal end of the slot.

[0090] Embodiment 15 15. The heater body of any one of embodiments 1 to 14, wherein each auxiliary conductive feature extends at least partially along the length of the slot.

[0091] Embodiment 16 16. A heater body as recited in embodiment 15, wherein each auxiliary conductive feature extends at least partially along the length of the slot on opposite sides of the slot.

[0092] Embodiment 17 16. A heater body as recited in embodiment 15, wherein at least a portion of each auxiliary conductive feature that extends at least partially along the length of the slot is also spaced apart from the slot.

[0093] Embodiment 18 18. A heater body as described in embodiment 17, wherein the conductive material is shaped as an intersecting array of walls defining a plurality of cells in a honeycomb design, and the portion of each auxiliary conductive feature is spaced from the slot by at least one cell width.

[0094] Embodiment 19 A heater body according to any one of embodiments 1 to 18, wherein the auxiliary conductive feature extends continuously from a first core segment of the plurality of core segments, through the bending region, to a second core segment of the plurality of core segments.

[0095] Embodiment 20 20. A heater assembly comprising the heater body of any one of embodiments 1 to 19 coupled to electrode pairs at both ends of a serpentine path.

[0096] Embodiment 21 An exhaust after-treatment assembly comprising the heater assembly of embodiment 20 and after-treatment components connected to a common housing or piping.

[0097] Embodiment 22 22. An exhaust after-treatment assembly as recited in embodiment 21, wherein the after-treatment component comprises a porous ceramic honeycomb body.

[0098] Embodiment 23 22. An exhaust after-treatment assembly as recited in embodiment 21, wherein the heater body, the after-treatment component, or both, comprise a catalytic material.

Claims

[Claim 1] A heater body comprising: an outer peripheral surface; a plurality of slots each extending from the outer circumferential surface and terminating at a terminal end within the heater body; a plurality of core segments made of a conductive material, each core segment being defined between a different pair of adjacent slots; a plurality of bend regions of the conductive material, each bend region disposed around a respective one of the terminations of the slot, each pair of adjacent core segments being connected by a corresponding one of the bend regions; an auxiliary conductive feature disposed in each of the bend regions adjacent a respective one of the terminations; It has the plurality of slots electrically separate each pair of adjacent core segments from each other to form a serpentine current carrying path that extends through the core segments and the conductive material in the bend region across the heater body; each of the auxiliary conductive features locally reduces the electrical resistance of the heater body in the bending region compared to the conductive material alone; the conductive material is shaped as an intersecting array of walls defining a plurality of cells in a honeycomb design; Each auxiliary conductive feature includes a continuous strip of complementary conductive material; the strip includes a plurality of wedges, each wedge partially filling a corresponding one of the cells; Heater body.

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