Serpentine honeycomb heater design to protect against deformation and shorting

Abstract

An electrical heater assembly including a heater body. The heater body includes a resistive portion that includes a plurality of cells and a plurality of slots that define a serpentine path. A slot end region corresponds to each of the slots as a subset of cells that are located adjacent to terminal ends the slots with respect to a first lateral direction and bounded with respect to a second lateral direction between opposing slot walls of the slots. A first lateral dimension of the cells in the slot end region is greater than a second lateral dimension of the cells. The slot end region includes a plurality of the cells that are adjacent to each other with respect to the second lateral direction and / or where a slot width of the slots is at least two times the second lateral dimension of the cells in the slot end region.

Description

SERPENTINE HONEYCOMB HEATER DESIGN TO PROTECT AGAINST DEFORMATION AND SHORTINGCross Reference to Related Application

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63 / 603,716 filed on November 29, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.FIELD

[0002] This disclosure relates to exhaust aftertreatment systems, and more specifically heater assemblies for use in exhaust aftertreatment systems, and in particular heater assemblies having heater bodies having a serpentine electrical path and a honeycomb wall configuration.BACKGROUND

[0003] 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 vehicle 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 in order to reduce exhaust emissions in automotive or other applications.S MMARY

[0004] Disclosed herein are an electrical heater assemblies. The heater assembly can comprise a heater body comprising a resistive portion comprising a plurality of cells formed by an array of intersecting walls that define a plurality of channels extending in an axial direction through the heater body, wherein the walls comprise first walls extending in a first lateral direction and second walls extending transversely with respect to the first lateraldirection to connect between adjacent ones of the first walls, wherein each cell is formed by a set of the walls enclosing a corresponding one of the channels and each cell is defined by a first lateral dimension extending in the first lateral direction and a second lateral dimension extending in a second lateral dimension perpendicular to the first lateral direction, wherein both of the first lateral direction and the second lateral direction are perpendicular to the axial direction; and a plurality of slots, each slot extending in the first lateral direction from an open end that intersects through an outer periphery of the heater body to a terminal end within the heater body, the plurality of slots defining a serpentine electrical current-carrying path through the resistive portion by electrically disconnecting sections of the resistive portion on opposite sides of each slot from each other, each slot defined by a slot width between an opposing pair of slot walls, wherein the opposing pair of slot walls are portions of the first walls; wherein the resistive portion comprises a slot end region corresponding to each of the slots as a subset of the cells that are located adjacent to the terminal end of a corresponding one of the slots with respect to the first lateral direction and bounded with respect to the second lateral direction between the opposing pair of slot walls, wherein the slot end region comprises a plurality of the cells that are adjacent to each other with respect to the second lateral direction, and wherein the first lateral dimension of the cells in the slot end region is greater than the second lateral dimension of the cells in the slot end region.

[0005] In embodiments, a geometry of the heater body satisfies the equation: W = n*L2 + (n-l)*tl, where W is the slot width, L2 is the second lateral dimension of the cells in the slot end region, n is a number of cells adjacent to each other with respect to the second lateral direction in the slot end region, and tl is a thickness of the first walls.

[0006] In embodiments, a geometry of the heater body satisfies the equation: W = 2*L2 + tl, where W is the slot width, L2 is the second lateral dimension of the cells in the slot end region, and tl is a thickness of the first walls.

[0007] In embodiments, substantially all non-peripheral cells in the heater body have the same first lateral dimension and the same second lateral dimension.

[0008] In embodiments, the second walls extend in the second lateral direction and the cells are rectangular.

[0009] In embodiments, the second lateral dimension of the cells in the slot end region is 0.55 to 0.95 times that of the first lateral dimension of the cells.

[0010] In embodiments, the second lateral dimension of the cells in the slot end region is 0.7 to 0.95 times that of the first lateral dimension.

[0011] In embodiments, the first lateral dimension of the cells in the slot end region is at least 1.1 to 1.8 times the second lateral dimension.

[0012] In embodiments, the first lateral dimension of the cells in the slot end region is at least 1.1 to 1.6 times the second lateral dimension.

[0013] In embodiments, the slot width is 1.2 to 1.95 times the first lateral dimension of the cells in the slot end region.

[0014] In embodiments, the slot width is 1.4 to 1.95 times the first lateral dimension of the cells in the slot end region.

[0015] In embodiments, the thickness of the first walls is equal to that of the second walls.

[0016] In embodiments, the heater body further comprises fillets at the terminal ends of the slots.

[0017] In embodiments, the fillets are integrally formed with the first and second walls.

[0018] In embodiments, each of the fillets occupies a cross-sectional area equal to at least 20% of an area of one of the cells in the slot end region.

[0019] In embodiments, the heater assembly further comprises a pair of electrodes connected to the heater body at opposing locations along the serpentine electrical current-carrying path.

[0020] In embodiments, the heater assembly further comprises a catalytic material deposited on the walls.

[0021] Disclosed herein are exhaust aftertreatment systems. The exhaust aftertreatment system can comprise the heater assembly of any one of the preceding paragraphs and an exhaust aftertreatment component located downstream of the heater assembly.

[0022] In embodiments, the exhaust aftertreatment component is a catalyst-carrying substrate, a particulate filter, or both.

[0023] Disclosed herein are electrical heater assemblies. The heater assembly can comprise a heater body comprising: a resistive portion comprising a plurality of cells formed by an array of intersecting walls that define a plurality of channels extending in an axial direction through the heater body, wherein the walls comprise first walls extending in a first lateral direction and second walls extending transversely with respect to the first lateral direction to connect between adjacent ones of the first walls, wherein each cell is formed by a set of the walls enclosing acorresponding one of the channels and each cell is defined by a first lateral dimension extending in the first lateral direction and a second lateral dimension extending in a second lateral dimension perpendicular to the first lateral direction, wherein both of the first lateral direction and the second lateral direction are perpendicular to the axial direction; and a plurality of slots, each slot extending in the first lateral direction from an open end that intersects through an outer periphery of the heater body to a terminal end within the heater body, the plurality of slots defining a serpentine electrical current-carrying path through the resistive portion by electrically disconnecting sections of the resistive portion on opposite sides of each slot from each other, each slot defined by a slot width between an opposing pair of slot walls, wherein the opposing pair of slot walls are portions of the first walls; wherein the resistive portion comprises a slot end region corresponding to each of the slots as a subset of the cells that are located adjacent to the terminal end of a corresponding one of the slots with respect to the first lateral direction and bounded with respect to the second lateral direction between the opposing pair of slot walls, wherein the first lateral dimension of the cells is greater than the second lateral dimension of the cells, and wherein the slot width is greater than two times the second lateral dimension of the cells.

[0024] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and 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.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is cross-sectional side view of an exhaust aftertreatment assembly according to one embodiment disclosed herein.

[0026] FIG. 2 is a front view of a heater body according to one embodiment disclosed herein having a serpentine pattern formed by a plurality of slots extending laterally across the heater body.

[0027] FIG. 3 is an enlarged view of the area identified in FIG. 2 showing a honeycomb configuration of the heater body 30, as well as the terminal ends of two slots and an open end of another slot intersecting at the outer periphery of the heater body.

[0028] FIG. 4 is an enlarged view of the area identified in FIG. 3 showing a cell of the honeycomb configuration of the illustrated heater body.

[0029] FIG. 5 is an enlarged view of the area identified in FIG. 3 showing a portion of a slot end region proximate to the terminal end of the slot in which the slot has a width that spans a distance equal to that of two adjacent cells plus a thickness of a wall in between the adjacent cells.DETAILED DESCRIPTION

[0030] 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.

[0031] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term “about,” “approximately,” or the like. In such cases, other embodiments include the particular numerical values. Regardless of whether a numerical value is expressed as an approximation, two embodiments are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0032] Fluid treatment systems, such as automobile exhaust aftertreatment systems, can comprise a supplemental source of heat, such as to facilitate faster catalyst light-off or filter regeneration, particularly in comparison to aftertreatment systems that do not have any supplemental heat (e.g., instead of 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 exhaust flow to heat downstream aftertreatment components) or an electrically heated substrate (e.g., an electrically conductive substrate that undergoes Joule heating when connected to an electrical power source). For example, a heater can be arranged upstream of a catalyst-carrying substrate and / orparticulate filter and heat the downstream component by providing heat to the flow of exhaust (and / or a supplemental air flow), which in turn heats the downstream aftertreatment component. Aftertreatment systems employing supplemental heat can be provided to reduce emissions in gasoline, diesel, and / or hybrid vehicles, for example by assisting in ensuring fast and consistent light-off of the catalyst during operation of the corresponding engine, particularly after cold-start of the engine.

[0033] To maximize the emission benefits, it is generally desirable that the heater element has a low thermal mass (e.g., for faster heat up), high surface area (e.g., for increased heat exchange with the air flow through the heater), and uniform Joule heating across the face of the heater (e.g., to avoid downstream cold spots) to quickly deliver sufficient heat to the downstream emission control components. One type ofheater that provides the aforementioned features is a heater having a honeycomb configuration formed by an array of intersecting walls arranged into cells, where heater has slots that create a serpentine current-carrying path between opposite sides of the heater, an example of which is described with respect to the embodiment of FIG. 2 herein. To create the high surface area, these heater elements having honeycomb configurations may utilize cell densities in the range of at least 300-400 cells per square inch (CSPI), with a wall thickness of at least about 5 mils (0.127 mm) to provide sufficient thermomechanical strength and / or prevent buckling or deformation of the walls of the honeycomb structure when the maximum temperature of several hundred degrees Celsius is achieved. For example, if a heater were to be exposed to temperatures beyond the high temperature yield strength of the material of the heater, the walls could begin to deform in such a way that the slots forming the serpentine pattern close (e.g., walls on opposite sides of the slots touch together), which could lead to premature failure and / or electrical shorting across the slots. This issue may be exacerbated when the heater is implemented in an automotive application, where the heater is not only subjected to repeated temperature cycling, but is also subjected to a high level of vibration during operation.

[0034] According to embodiments disclosed herein, the width of the slots is wider than a single cell to counteract the possibility of electrical shorting due to temperature-induced deformation. Advantageously, it has additionally been identified that embodiments disclosed herein may also reduce the formation of hot spots at the terminal ends of the slots, by more uniformly distributing current flow through the bends in the serpentine pattern around theterminal ends of the slots. Furthermore, as described herein, the aforementioned benefits have been achieved without sacrificing manufacturability of the heater bodies, particularly via additive manufacturing (e.g., laser powder bed fusion) or extrusion.

[0035] Referring now to FIG. 1, a fluid treatment assembly 10 is illustrated, e.g., which can be arranged as part of an exhaust system of automobile. The fluid treatment assembly 10 comprises an outer housing 12 (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 12 has an inlet 14, e.g., which can be connected in fluid communication with the exhaust manifold of an internal combustion engine, and an outlet 16, e.g., which can be connected in fluid communication with a tail pipe of an automobile.

[0036] Exhaust from an engine can be treated (e.g., one or more pollutants removed or abated) as the exhaust is flowed from the inlet 14 to the outlet 16 through the assembly 10. To this end, the assembly 10 further comprises a heater assembly 18 and an aftertreatment component 20 located between the inlet 14 and outlet 16. For example, the aftertreatment component 20 can be any emissions control component, such as a catalyst-loaded substrate, a particulate filter, or 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.

[0037] A set of Cartesian coordinates is illustrated in FIG. 1, in which the Z-axis corresponds to the axial direction. Additionally, X- and Y-axes can be any combination of directions that are perpendicular to each other and also perpendicular to the axial direction (Z-axis). Correspondingly, the heater body 30 has a central axis 31 in FIG. 1 that is orientated with respect to the axial direction (Z-axis). The X- and Y-axes are discussed in more detail with respect to FIGS. 2-5 below.

[0038] The heater assembly 18 can be arranged as a Joule or resistance heater that provides supplemental heat in order to facilitate functionality of the aftertreatment component 20, e.g., by quickly 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 can comprise, or otherwise be connected to, electrodes 22. The electrodes 22 can be arranged extending through the housing 12 in order to connect the heater assembly 18 to a power source,such as a batery, for example, the batery of the vehicle in which the assembly 10 is installed. The electrodes 22 can extend radially through the housing 12 as shown in FIG. 1 and / or the electrodes 22 can extend through the housing 12 in some other direction, such as axially. In this way, the heater assembly 18 can be arranged to generate heat via Joule heating when the heater assembly 18 is connected to a power source and a corresponding voltage is applied to flow current through the electrically conductive material of the walls of the heater assembly 18. The electrodes 22 are shown in FIG. 1 as being arranged on opposite sides of the heater assembly 18 (e.g., spaced 180° apart with respect to the exterior of the heater assembly 18), but can be arranged at other locations or angles.

[0039] In some embodiments, such as shown in FIG. 1, the heater assembly 18 is positioned upstream of the aftertreatment component 20 such that it generates heat when subjected to an electrical voltage in order to increase the temperature of the exhaust flow and / or provide direct heating to the aftertreatment component 20, which in turn increases the temperature of the aftertreatment component 20, such as the temperature of the catalytic material carried by the aftertreatment component 20 as the exhaust flows through the aftertreatment component 20. In some embodiments, the heater assembly 18 and the aftertreatment component 20 can be effectively combined into a single device by directly loading the body of the heater assembly 18 with a catalyst. Such arrangements useful for heating a catalyst material may be referred to as an electrically heated catalyst, or EHC.

[0040] The heater assembly 18 and the aftertreatment component 20 can be held in place, supported, and / or contained within the housing 12 in any suitable manner. For example, the body of the heater assembly 18 can be held in place and supported via one or more retainers 24, e.g., retaining rings. The aftertreatment component 20 can be supported by similar retainers and / or supported by a mat 26, such as an inorganic fiber mat, which assists in protecting the aftertreatment component 20, such as from compression by the housing 12, vibrations during use, and / or thermal expansion forces exerted on the aftertreatment component 20.

[0041] Referring now to FIG. 2, an embodiment for a heater body 30 for a heater assembly is illustrated. Consistent with the disclosure herein, the embodiments illustrated and / or described with respect to the heater body 30 can be used as, or incorporated in, the heater assembly 18 in the assembly 10 of FIG. 1 , and combinations of the features of the embodimentsillustrated or described herein with respect to the heater body 30 can be used together for the heater assembly 18 in the assembly 10.

[0042] The heater body 30 comprises an electrically resistive (heat-generating) portion 32 that comprises electrically conductive material of a suitable resistivity (e.g., a metal) to enable the heater body 30 to reach a desired temperature and / or output a desired amount of heat when a selected voltage is applied across opposing locations of the resistive portion 32 to cause electrical current to flow across the heater body 30. For example, the resistive portion 32 can comprise a high temperature metal alloy, such as a nickel -chromium alloy or an iron-chromium alloy. As discussed in more detail below, the heater body 30 may be referred to as having a serpentine configuration due to a plurality of slots 34 that are non-conductive and force electrical current flow along a serpentine path. For example, the slots 34 can be arranged as gaps or sections of non-conductive material. The opposing locations of the resistive portion 32 where the voltage is applied can be the very ends of the serpentine pattern, as shown in and discussed herein with respect to FIG. 2, or somewhere else along the serpentine path 44, e.g., depending on where electrodes (e.g., the electrodes 22) are to be positioned and / or at what angle or orientation the electrodes will be positioned with respect to each other.

[0043] The heater body 30 may also comprise one or more electrode attachment portions 36 (two attachment portions 36 illustrated in FIG. 2) or be otherwise configured for attachment to a pair of electrodes (e.g., the electrodes 22). In this way, an electrical connection can be established through the resistive portion 32 via one or more electrodes 22, e.g., secured at the one or more electrode attachment portions 36 for carrying current to, from, and / or between the electrodes 22. For example, the properties of the resistive portion 32 and conductive material from which the resistive portion 32 is made, can be set with respect to the voltage applied across the electrodes 22 in order to generate a desired amount of heat and / or reach a desired temperature as electrical current passes through the material of the resistive portion 32 of the body 30. In embodiments, the voltage is selected with respect to the resistance of the heater 30 such that the desired temperature achieved by the heater is at least 400°C, at least 500°C, or even at least 600°C, such as up to 1000°C.

[0044] The slots 34 can be formed as cutouts, slits, or otherwise as sections of non- conductive material that create electrical disconnections and break electrical conductivity at certain locations in the body 30, for example, by severing, breaking, or disconnecting sectionsof the resistive portion 32 of the body 30 from each other electrically, thereby forcing electrical current to flow in a designated path around the slots 34. For example, the slots 34 can be air gaps, or formed from, or fdled with, an electrically insulating material, e.g., a glass and / or ceramic material.

[0045] In the embodiment of FIG. 2, a pair of electrodes (e.g., the electrodes 22) is intended to be attached to the heater body 30 at one of the electrode attachment portions 36, which are shown enlarged in FIG. 3. Unlike the resistive portion 32 of the body 30 (e.g., intersecting walls), the attachment portions 36 can be formed as a densified or solidified block or section of conductive material without the channels 48. The additional material at the attachment portions 36 not only provides additional strength and material to support attachment of electrodes, but also increases conductivity of the body 30 at the attachment portions 36 to inhibit the generation of an undue amount of heat at the electrodes, where the concentration of electrical current will be particularly high. In contrast, the smaller thickness of the walls 46 of the heater body 30 at the resistive portion 32 (e.g., provided by the honeycomb configuration) corresponds to a reduced conductivity, and thus increased resistivity, which enables the resistive portion 32 to generate heat. Accordingly, the geometry and cross-sectional area of the walls 46 can be set to generate a desired amount of heat (e.g., to reach a target temperature) when a selected voltage is applied to the heater body 30.

[0046] The electrode attachment portions 36 and the resistive portion 32 can be formed from the same material. The attachment portions 36 can be integrally (monolithically) formed with the resistive portion 32, or connected via welding, mechanical fasteners, or other attachment means. With reference to FIG. 3, it can be seen that the electrode attachment portions 36 provide sufficient surface area, e.g., at least as large as, or larger than, the cross-sectional size of the face of each electrode that is to be attached to the heater body 30.

[0047] As shown in FIG. 2, the slots 34 extend across the body 30 altematingly from opposite sides of the body 30, such that the resistive portion 32 of the body 30 bends around the slots to traverse back and forth across the body 30 between the opposing ends. That is, each of the slots 34 extends from an open end 38 at an intersection through an outer periphery 40 of the heater body 30 and terminates within the heater body 30 at a terminal end 42. Accordingly, the slots 34 define a serpentine pattern for the resistive portion 32 that doubles back on itself across the body 30 multiple times. Electrical current correspondingly flows in a serpentine path44, a portion of which is shown by an arrow in FIG. 2. Thus, the open ends 38 caused by the slots 34 create a corresponding disconnection, break, or gap in the outer periphery 40 of the resistive portion 32 and between sections of the resistive portion 32 located on opposite sides of each slot 34. As a result, electrical current carried through the material of the body 30 (e.g., between the electrodes 22 and / or electrode attachment portions 36) is forced along the serpentine path 44. The serpentine path 44 is not limited to that shown in FIG. 2, as the slots 34 can be included at different lengths, angles, widths, or other dimensions in order to set other shapes for the serpentine path 44.

[0048] The electrical disconnections caused by the slots 34 enables the current-carrying path length to be increased between opposite sides of the resistive portion 32 (e.g., between the pair of the electrode attachment portions 36 and / or the electrodes 22 attached thereto), as the electrical current is forced to traverse back and forth across the body 30 multiple times instead of directly flowing in a straight line directly across the body 30. Since the overall resistivity of the heater body 30 is dependent on the current-carrying path length between the electrodes 22, the resistivity of the heater body 30 and / or heater assembly 18 can be set, at least in part, by selecting the dimensions, locations, and number of slots 34 (thereby setting the dimensions of the resistive portion 32 and the serpentine current-carrying path 44).

[0049] FIGS. 2-5 each include a set of coordinates showing representative X- and Y-axes corresponding generally to the coordinates of FIG. 1, such that the X- and Y-directions extend perpendicularly to the Z-axis, with the Z-axis corresponding to the axial direction, which is understood to be into and out of the plane in which these figures are drawn. For example, FIG. 2 illustrates the central axis 31 of the heater body 30, which extends parallel to the axial direction (Z-axis), and is therefore perpendicular to the X and Y directions. For the ease of discussion herein, the X direction may be interchangeably referred to as a first lateral direction, while the Y direction may be interchangeably referred to as a second lateral direction.

[0050] FIG. 3 shows an enlarged view of the indicated portion of heater body 30 enclosed by dashed-line rectangle in FIG. 2. As shown in FIGS. 2-3, the resistive portion 32 of the heater body 30 has a honeycomb or cellular configuration, in that it comprises an array of intersecting walls 46 that form a plurality of channels 48 extending in an axial direction through the body 30. In this way, the channels 48 enable a fluid to flow through the body 30 (e.g., a flow ofexhaust) and the intersecting walls 46 provide surface area for heat exchange with the fluid flow.

[0051] As described in more detail below, the walls 46 comprises a plurality of first walls 46P (parallel walls) that extend parallelly with respect to the first lateral direction and a plurality of second walls 46T (transverse walls) that extend transversely (non-parallel) with respect to the first walls 46P to connect between adjacent ones of the first walls 46P. For example, in the illustrated embodiments, the second walls 46T extend in the second lateral direction, perpendicular to the first walls 46P.

[0052] For ease of reference, the portion of the first walls 46P that form the opposing pair of walls of the slots 34 are also identified in FIG. 3, and may be referred to herein, as slot walls 46S. That is, the slot walls 46S may be formed integrally with and / or as part of the first walls 46P in the array of intersecting walls 46. Accordingly, the slots 34 can be effectively formed by exclusion, absence, or removal of the transverse walls 46T between the slot walls 46S along the length of the slots 34.

[0053] It is to be understood that the use of the alphabetic suffixes (e.g., “P” for the first walls 46P, “T” for the second walls 46T, and “S” for the slot walls 46S) is intended to facilitate ease of discussion with respect to specific subsets of the walls 46, and that general reference to “the walls 46” is thus intended to refer to all of the walls that share the base reference numeral 46 regardless of alphabetic suffix.

[0054] As labelled in FIG. 4, the first walls 46P have a first thickness tl (the thickness tl extending in the second lateral direction, perpendicular to the direction of the first walls 46P) and the second walls 46T have a second thickness t2 (the thickness t2 extending in the first lateral direction, perpendicular to the direction of the second walls 46T). In the illustrated embodiments, the first thickness tl and the second thickness t2 are the same, which may be advantageous to simplify manufacturing processes in accordance with the manufacturing discussions herein, although different thicknesses can be used. The wall thicknesses tl and t2 can be selected to provide sufficient mechanical strength to the heater body 30, while providing a suitable cross-sectional area to provide a targeted resistivity / conductivity for the heater body 30 based on the voltage applied and the axial width of the heater body 30. In embodiments, the thicknesses tl and t2 are in the range of about 3 mils (0.0762 mm) to 8 mils (0.2032 mm), such as from 5 mils (0.127 mm) to 7 mils (0. 1778 mm).

[0055] As shown further with respect also to FIG. 4, which is an enlarged view of the area indicated in FIG. 3, each set of the walls 46 that encloses together to define one of the channels 48 can be referred to as a cell 50, such that the body 30 comprises a repeating array of the cells 50 formed by the walls 46. For example, in FIGS. 3-4, each of the cells 50 is rectangular, and is formed by a total four wall segments in the form of two segments of the first walls 46P and two segments of the second walls 46T. Accordingly, in the illustrated figures, the array of walls 46 define a corresponding array of rectangle-shaped cells 50, which together form a honeycomb (or cellular) design for the body 30. However, the cells 50 can have any other desired cross-sectional shape (the shape in the plane perpendicular to the axial direction), such as triangular, trapezoidal, or some other non-rectangular polygon. Regardless of shape of the cells 50, the first walls 46P are aligned extending in the first lateral direction, parallel to slots 34, while the second walls 46T extend transversely thereto, as described herein. In embodiments, the body 30 can be formed by any suitable manufacturing process, such as in particular, additive manufacturing (e.g., laser powder bed fusion) or extrusion.

[0056] As shown in FIG. 4, the cells 50 extend a first lateral dimension LI (e.g., a first length) in the first lateral direction, and a second lateral dimension L2 (e.g., a second length) in the second lateral direction. It is noted that due to the circular shape of the heater body 30 and the rectangular shape of the cells 50 in the illustrated embodiments, there are some cells directly adjacent to the outer periphery 40 that are truncated in shape due to intersection with the outer periphery 40, and thereby do not share the same shape as the cells 50 that do not intersect with the periphery 40. Accordingly, reference to the cells 50 generally refers to the non-peripheral cells that have the first lateral dimension LI and the second lateral dimension L2, while the peripheral cells directly adjacent to the outer periphery are referred to herein as peripheral cells 51.

[0057] In embodiments, the width W of the slots 34 is set so that the width W is wider than one of the cells 50 in the second lateral direction. That is, the width W is larger than the second lateral dimension L2 of the cells 50. In particular, a slot end region 52, identified in FIG. 4, can be defined that comprises a plurality of the cells 50 that are located adjacent to the terminal ends 42 of each slot 34 with respect to the first lateral direction and also within the slot width W with respect to the second lateral direction. That is, since the slot walls 46S extend as a portion of some of the first walls 46P, the cell end region 52 is accordingly defined as thosecells 50 that are bounded in the second lateral direction between the slot walls 46S of the corresponding slot 34. Since the slot walls 46S are portions of the first walls 46P, the cells 50 are bounded in the second lateral direction between the slot walls 46S if the cells 50 are located in between the pair of the first walls 46P from which the slot walls 46S are formed.

[0058] In embodiments, the slot width W is at least as wide as a plurality of the cells 50 adjacent to each other in the second lateral direction. In order to enable the slot walls 46S to be formed as portions of the first walls 46P, the slot width W must be equal to the sum of the second lateral dimensions L2 of the cells 50 adjacent to each other in the second lateral direction that are located within the slot end region 52 and the thickness tl of any of the first walls 46P located between the adjacent cells 50. For example, as shown in FIGS. 2-3 and 5, the slot width W spans the same distance in the second lateral direction as two of the cells 50, including the thickness tl of the segment of the wall 46 located between these two cells 50. In other words, the dimensions for each slot 34 and at least the cells 50 in the slot end region 52, satisfy the equation: W = n*L2 + (n-l)*tl, where n is the number of cells 50 within the slot end region 52 that are adjacent to each other in the second lateral direction. In order to maintain suitable dimensional relationships to facilitate manufacturing processes while preventing undesirably high amounts of “bypass” flow through the slots (described further herein), the value of n may generally be from 2 to 4, with 2 being a preferred value for heater geometries suitable for exhaust aftertreatment applications. For example, in FIG. 3, the dimensions for each slot 34 and at least the cells 50 in the slot end region 52, satisfy the equation: W = 2*L2 + tl. In some embodiments, all non -peripheral cells 50 or substantially all non-peripheral cells 50 (i.e., at least 90% of all non-peripheral cells 50) satisfy one or both of the aforementioned relationships.

[0059] Assuming the aforementioned relationship between the slot width W and the second lateral dimension L2 of the slots 34, the relationship between the first and second lateral dimensions L 1 and L2 of the cells, as well as the relationship between the slot width W and the first lateral dimension LI, can also be set. For example, maintaining a sufficiently large second lateral dimension L2 in comparison to the first lateral dimension LI may be particularly beneficial in embodiments in which the heater body 30 is made by a powder-based additive manufacturing process, as the unsintered powder may become increasingly stuck within the channels or otherwise difficult to remove as the size of the channels decreases. It has beenobserved by the current inventors that depowderization may become particularly difficult when the dimensions of a square-shaped cell becomes less than about 1 mm, and that if any powder particles are left in the part they may agglomerate in future manufacturing steps, such as during a stress relief thermal treatment, making the stuck powder unfeasible if not impossible to remove. Accordingly, in some embodiments, LI > L2 > 1 mm, particularly for powder-based manufacturing processes. However, other dimensions may be possible as depowderization techniques are improved over time. Additionally, for non-square shaped cells, the size of one of the lateral dimensions being greater than about 1 mm may sufficiently address the depowderization issue even if the other lateral dimension is less than about 1 mm.

[0060] In some embodiments that are suitable for use in exhaust aftertreatment applications, the second lateral dimension is in the range of about 0.9 mm to 1.4 mm. In these embodiments, the value of the first lateral dimension LI can range from about 1.1 mm to 1.7 mm. In these embodiments, the value of the slot width W can range from at least about 1.9 mm to at most about 3 mm.

[0061] As another example, if the slot width W is too large relative to the dimensions of the cells 50, an undesirably large amount of the flow through the heater body 30 will “bypass” through the slots 34 as opposed to undergoing heat exchange with the walls 46 of the cells 50. That is, flow through the slots 34 will undergo reduced heat exchange in comparison to flow through the cells 50 due to the lack of the transverse walls 46T within the slots 34.

[0062] In embodiments, with respect to at least the cells 50 in the slot end region 52, and particularly those embodiments in which the slot end region 52 comprises two of the cells 50 adjacent to each other with respect to the second lateral direction, the second lateral dimension L2 in the second lateral direction is greater than one half of the first lateral dimension LI in the first lateral direction (i.e., L2 > 0.5L1). In embodiments, with respect to at least the cells 50 in the slot end region 52, the second lateral dimension L2 is from 0.55 to 0.95 times the first lateral dimension LI (0.55*Ll < L2 < O.95*L1), and preferably about 0.85 times, such as in the range from 0.6 to 0.95 times (O.6*L1 < L2 < O.95*L1), 0.7 to 0.95 times (O.7*L1 < L2 < O.95*L1), 0.75 to 0.95 times (O.75*L1 < L2 < O.95*L1), or 0.8 to 0.95 times (0.8*Ll < L2 < O.95*L1). In embodiments, with respect to at least the cells 50 in the slot end region 52, the first lateral dimension LI is from 1.1 to 1.8 times the second lateral dimension L2 (1.1*L2 < LI < 1.8*L2), such as in the range from 1.1 to 1.7 (1.1*L2 < LI < 1.7*L2), from 1.1 to 1.6(1.1*L2 < L1 < 1.6*L2), from 1.1 to 1.5 (1.1*L2 < L1 < 1.5*L2), from 1.1 to 1.4 (1.15*L2 < LI < 1.4*L2), from 1.1 to 1.3 (1.15*L2 < LI < 1.3*L2), from 1.1 to 1.25 (1.1*L2 < LI < 1.25*L2). In general, larger L1 / L2 ratios may be more applicable as the value of L2 decreases.

[0063] If the slot width W is made too large, then an undesirable amount of fluid may “bypass” through the slots in comparison to the flow through the channels 48 of the cells 50, as described above, but if the slot width W is not made wide enough then the risk of deformation-based electrical shorting is not significantly reduced. In particular, it has been found by the current inventors that the slot width L2 being greater than about two times the first lateral dimension LI results in an undesirably high amount of bypass flow, and therefore, reduced heat transfer performance. Additionally, the slot width being less than about 1.2 times the first lateral dimension LI does not result in significant reduction to the risk of deformationbased electrical shorting. Accordingly, in embodiments, with respect to at least the cells 50 in the slot end region 52, the slot width W is at least 1.2 times the first lateral dimension LI (W > 1.2*L1), at least 1.3 times (W > 1.3*L1), at least 1.4 times (W > 1.4*L1), at least 1.5 times (W > 1.5*L1), at least 1.6 times (W > 1.6*L1), or even at least 1.7 times (W > 1.7*L1), but at most 1.95 times the first lateral dimension LI (W < 1.95*L1), at most 1.9 times (W < 1.8*L1), at most 1.85 times (W < 1.85*L1), including ranges having these values as endpoints, such as from 1.2 times to 1.95 times (1.2*L1 < W < 1.95*L1), or from 1.4 times to 1.95 times (1.4*L1 < W < 1.95*L1).

[0064] In embodiments, at least the slot end cells 50 in the slot end region 52 have the same size with the first lateral dimension LI and second lateral dimension L2 having a relationship as defined in the preceding paragraph. However, in some embodiments, all non-peripheral cells 50 in the heater body 30, including those outside of the slot end region 52, have the same size with the first lateral dimension LI and second lateral dimension L2 as defined in the preceding paragraph. Arrangements in which all non-peripheral cells have the same configuration may be particularly advantageous to facilitate manufacturing processes. For example, if the body 30 is made by extrusion, the consistent dimensions may reduce velocity variances at different locations across an extrusion die through which the material forming the heater body 30 is being extruded, which facilitates uniform extrusion and thereby improves geometry and minimizes defect formation. If formed via additive manufacturing, all non-peripheral cells 50 having the same size and shape assists in enabling consistent process parameters duringformation of the cells, e.g., a constant laser power and speed for a laser bed powder process. In contrast, a body with inconsistent cell sizes may require the manufacturing process parameters (e.g., input vectors, laser power, etc.) to be changed repeatedly during manufacture, which may increase complexity, increase manufacturing time, and / or increase a rate of defects or nonconformitie s .

[0065] As shown in FIG.5, the slots 34 having the slot width W greater than the dimensions LI and L2 enables a fdlet 54 with a larger radius to be added than prior slots that have a slot width equal to the dimension of a single cell. By occupying a greater area, the fdlets 54 assist in mitigating the formation of hot spots at the terminal ends 42, by distributing current flow through a wider cross-sectional area of conductive material around the terminal ends 42 of the slots 34. For example, using the geometry of shown in FIG. 5, with the fillet 54 formed by drawing a circle having tangents at the terminal end 42 and at both of the slot walls 46S, each fillet 54 occupies an area corresponding to over 20% of the area of the channel 48 through one of the cells 50.

[0066] 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. Accordingly, the claimed subject matter is not to be restricted except in light of the attached claims and their equivalents.

Claims

What is claimed is:

1. An electrical heater assembly comprising: a heater body comprising: a resistive portion comprising a plurality of cells formed by an array of intersecting walls that define a plurality of channels extending in an axial direction through the heater body, wherein the walls comprise first walls extending in a first lateral direction and second walls extending transversely with respect to the first lateral direction to connect between adjacent ones of the first walls, wherein each cell is formed by a set of the walls enclosing a corresponding one of the channels and each cell is defined by a first lateral dimension extending in the first lateral direction and a second lateral dimension extending in a second lateral dimension perpendicular to the first lateral direction, wherein both of the first lateral direction and the second lateral direction are perpendicular to the axial direction; and a plurality of slots, each slot extending in the first lateral direction from an open end that intersects through an outer periphery of the heater body to a terminal end within the heater body, the plurality of slots defining a serpentine electrical current-carrying path through the resistive portion by electrically disconnecting sections of the resistive portion on opposite sides of each slot from each other, each slot defined by a slot width between an opposing pair of slot walls, wherein the opposing pair of slot walls are portions of the first walls; wherein the resistive portion comprises a slot end region corresponding to each of the slots as a subset of the cells that are located adjacent to the terminal end of a corresponding one of the slots with respect to the first lateral direction and bounded with respect to the second lateral direction between the opposing pair of slot walls, wherein the slot end region comprises a plurality of the cells that are adjacent to each other with respect to the second lateral direction, and wherein the first lateral dimension of the cells in the slot end region is greater than the second lateral dimension of the cells in the slot end region.

2. The heater assembly of claim 1, wherein a geometry of the heater body satisfies the equation: W = n*L2 + (n-l)*tl, where W is the slot width, L2 is the second lateral dimensionof the cells in the slot end region, n is a number of cells adjacent to each other with respect to the second lateral direction in the slot end region, and tl is a thickness of the first walls.

3. The heater assembly of claim 1, wherein a geometry of the heater body satisfies the equation: W = 2*L2 + tl, where W is the slot width, L2 is the second lateral dimension of the cells in the slot end region, and tl is a thickness of the first walls.

4. The heater assembly of any of claims 1-3, wherein substantially all non-peripheral cells in the heater body have the same first lateral dimension and the same second lateral dimension.

5. The heater assembly of any of claims 1 -4, wherein the second walls extend in the second lateral direction and the cells are rectangular.

6. The heater assembly of any of claims 1-5, wherein the second lateral dimension of the cells in the slot end region is 0.55 to 0.95 times that of the first lateral dimension of the cells.

7. The heater assembly of any of claims 1-6, wherein the second lateral dimension of the cells in the slot end region is 0.7 to 0.95 times that of the first lateral dimension.

8. The heater assembly of any of claims 1-7, wherein the first lateral dimension of the cells in the slot end region is at least 1. 1 to 1.8 times the second lateral dimension.

9. The heater assembly of any of claims 1-8, wherein the first lateral dimension of the cells in the slot end region is at least 1. 1 to 1.6 times the second lateral dimension.

10. The heater assembly of any of claims 1-9, wherein the slot width is 1.2 to 1.95 times the first lateral dimension of the cells in the slot end region.

11. The heater assembly of any of claims 1-10, wherein the slot width is 1.4 to 1.95 times the first lateral dimension of the cells in the slot end region.

12. The heater assembly of any of claims 1-11, wherein the thickness of the first walls is equal to that of the second walls.

13. The heater assembly of any of claims 1-12, wherein the heater body further comprises fillets at the terminal ends of the slots.

14. The heater assembly of claim 13, wherein the fillets are integrally formed with the first and second walls.

15. The heater assembly of claim 13, wherein each of the fillets occupies a cross-sectional area equal to at least 20% of an area of one of the cells in the slot end region.

16. The heater assembly of any one of claims 1-15, further comprising a pair of electrodes connected to the heater body at opposing locations along the serpentine electrical currentcarrying path.

17. The heater assembly of any one of claims 1-16, further comprising a catalytic material deposited on the walls.

18. An exhaust aftertreatment system comprising the heater assembly of any one of claims 1-17 and an exhaust aftertreatment component located downstream of the heater assembly.

19. The exhaust aftertreatment system of claim 18, wherein the exhaust aftertreatment component is a catalyst-carrying substrate, a particulate filter, or both.

20. An electrical heater assembly comprising: a heater body comprising: a resistive portion comprising a plurality of cells formed by an array of intersecting walls that define a plurality of channels extending in an axial direction through the heater body, wherein the walls comprise first walls extending in a first lateral direction and second walls extending transversely with respect to the first lateral direction to connect between adjacent ones of the first walls, wherein each cell is formed by a set of the walls enclosing acorresponding one of the channels and each cell is defined by a first lateral dimension extending in the first lateral direction and a second lateral dimension extending in a second lateral dimension perpendicular to the first lateral direction, wherein both of the first lateral direction and the second lateral direction are perpendicular to the axial direction; and a plurality of slots, each slot extending in the first lateral direction from an open end that intersects through an outer periphery of the heater body to a terminal end within the heater body, the plurality of slots defining a serpentine electrical current-carrying path through the resistive portion by electrically disconnecting sections of the resistive portion on opposite sides of each slot from each other, each slot defined by a slot width between an opposing pair of slot walls, wherein the opposing pair of slot walls are portions of the first walls; wherein the resistive portion comprises a slot end region corresponding to each of the slots as a subset of the cells that are located adjacent to the terminal end of a corresponding one of the slots with respect to the first lateral direction and bounded with respect to the second lateral direction between the opposing pair of slot walls, wherein the first lateral dimension of the cells is greater than the second lateral dimension of the cells, and wherein the slot width is greater than two times the second lateral dimension of the cells.

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