System and method for heating honeycomb bodies

Abstract

An electrical heater and method for heating a catalyst. The electrical heater includes a honeycomb body having a central axis extending longitudinally therethrough. The honeycomb body includes a matrix of intersecting walls forming a plurality of cells extending axially through the honeycomb body. A plurality of electrodes are positioned around an outer periphery of the honeycomb body. The plurality of electrodes are arranged in a plurality of electrode pairs including at least a first electrode pair and a second electrode pair. Each electrode pair includes a first electrode and a second electrode. An electrode length of an electrode along the outer periphery is directly proportional to a center current path length between a center point of the electrode and the electrode of the electrode pair. The electrode lengths of the electrodes of the first and second electrode pairs are different.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Application Serial No. 62 / 927460, filed October 29, 2019, pursuant to 35 USC § 120, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to systems and methods for heating honeycomb structures. Background Technology

[0004] This application generally relates to an electric heater for heating a catalyst (e.g., a catalyst on a substrate of a catalytic converter assembly), and more specifically, to an electric heater comprising a honeycomb and electrodes configured to produce a desired heat distribution on the end faces of the honeycomb. Summary of the Invention

[0005] All the instances and features mentioned below can be combined in any technically feasible manner.

[0006] In one aspect, an electric heater is provided. The electric heater includes: a honeycomb having a central axis extending longitudinally therethrough, the honeycomb comprising a cross-wall matrix forming a plurality of channels extending axially through the honeycomb; a plurality of electrodes disposed around the outer periphery of the honeycomb, the plurality of electrodes being arranged in multiple pairs of electrodes, each pair of electrodes comprising at least a first pair of electrodes and a second pair of electrodes, wherein a current generated by each pair of electrodes flows through at least some of the cross-walls between the electrodes of each pair of electrodes; wherein the electrode length along the outer periphery of the electrodes of each pair of electrodes is proportional to the length of the central current path, the central current length being defined as the shortest distance between the center points of the electrodes of the pair of electrodes through the cross-walls; and wherein the electrode length of the first pair of electrodes is different from the electrode length of the second pair of electrodes.

[0007] In some embodiments, the electric heater further includes a controller configured to apply voltages between the plurality of electrodes according to a heating sequence, wherein the heating sequence includes sequentially applying a first voltage to a first pair of electrodes and applying a second voltage between a second pair of electrodes.

[0008] In some embodiments, an average of the second voltage over the heating sequence is different than an average of the first voltage over the heating sequence. In some embodiments, the heating sequence is configured to produce a substantially uniform heating profile of the honeycomb body. In some embodiments, the heating sequence is configured to produce a substantially uniform heating profile of the honeycomb body when receiving a non-uniform gas flow in a cross-section of the honeycomb body taken transverse to the central axis. In some embodiments, the heating sequence includes a cooling interval disposed between applying the voltage between the first pair of electrodes and applying the voltage between the second pair of electrodes.

[0009] In some embodiments, the electric heater further includes an internal electrode embedded in the honeycomb body, wherein the heating sequence further includes applying a voltage between the internal electrode and at least one of the plurality of electrodes. In some embodiments, the internal electrode is disposed at the central axis.

[0010] In some embodiments, the electric heater further includes a plurality of insulating layers, each extending from an outer periphery of the honeycomb body into an interior of the honeycomb body such that the electrical current is concentrated into an interior region of the honeycomb body.

[0011] In some embodiments, the insulating layers are slits, respectively. In some embodiments, the insulating layers comprise an insulating material, respectively. In some embodiments, each insulating layer extends radially from the outer periphery toward the central axis from a location between each circumferentially adjacent pair of electrodes. In some embodiments, the region is centered at the central axis. In some embodiments, the interior region is centered at a location where the honeycomb body is offset from the central axis.

[0012] In some embodiments, the outer periphery of the honeycomb body is cylindrical and the cell cross-section is rectangular.

[0013] In another aspect, an electric heater is provided. The electric heater includes: a honeycomb body that is substantially cylindrical and has a central axis extending longitudinally therethrough, the honeycomb body including a matrix of intersecting walls; a plurality of electrodes operably positioned around an outer periphery of the honeycomb body, the plurality of electrodes arranged in a plurality of oppositely arranged electrode pairs such that at least a portion of an electric current induced between each oppositely arranged electrode pair flows through the central axis; and a controller configured to apply a voltage between each oppositely arranged electrode pair according to a heating sequence, wherein the heating sequence includes sequentially applying a first voltage between a first pair of oppositely arranged electrode pairs and a second voltage between a second pair of oppositely arranged electrode pairs, wherein a first average of the first voltage is directly proportional to a first current length of a first center current path between centers of the first pair of oppositely arranged electrodes during the heating sequence, wherein a second average of the second voltage is directly proportional to a second current length of a second center current path between centers of the second pair of oppositely arranged electrodes during the heating sequence, and wherein the first current path is longer than the second current path.

[0014] In some embodiments, the first voltage has a magnitude that is greater than a magnitude of the second voltage. In some embodiments, the first voltage is a first pulse width modulation signal, wherein the second voltage is a second pulse width modulation signal, wherein a duty cycle of the first pulse width modulation signal is greater than a duty cycle of the second pulse width modulation signal. In some embodiments, wherein a time period during which the first voltage is applied is longer than a time period during which the second voltage is applied.

[0015] In some embodiments, the electric heater further includes an internal electrode embedded in the honeycomb body, wherein the heating sequence further includes applying a voltage between the internal electrode and at least one of the plurality of electrodes.

[0016] In one aspect, a method of heating a catalyst is provided. The method includes applying a first voltage between a first pair of electrodes and a second voltage between a second pair of electrodes, wherein the electrodes of the first and second pairs of electrodes are arranged around an outer periphery of a honeycomb body, the honeycomb body having a central axis extending longitudinally therethrough and the honeycomb body including a matrix of intersecting walls forming a plurality of channels extending axially through the honeycomb body; wherein an electrode length of each electrode in each pair of electrodes along the outer periphery is directly proportional to a center current path length defined as a shortest distance through the walls between center points of the electrodes of the pair of electrodes, and wherein the electrode length of the electrodes of the first pair of electrodes is different than the electrode length of the electrodes of the second pair of electrodes.

[0017] In some embodiments, applying the first and second voltages comprises applying the first voltage to the first pair of electrodes and applying the second voltage between the second pair of electrodes in sequence according to a heating sequence.

[0018] In some embodiments, the average of the second voltage over the heating sequence is different than the average of the first voltage over the heating sequence.

[0019] In some embodiments, the method further comprises producing a substantially uniform heating profile on the end face of the honeycomb body by the heating sequence.

[0020] In some embodiments, the heating sequence comprises a cooling interval disposed between applying the first voltage between the first pair of electrodes and applying the second voltage between the second pair of electrodes.

[0021] In some embodiments, the method further comprises concentrating current in an inner region that is spaced apart from an outer periphery of the honeycomb body. In some embodiments, the honeycomb body comprises a plurality of electrically insulating layers that prevent current from flowing through wall segments that are cut off by the insulating layers to concentrate current in the inner region. In some embodiments, the honeycomb body comprises an inner electrode located proximate to the inner region, and the method further comprises applying a voltage between the inner electrode and one of the first or second pairs of electrodes.

[0022] One or more implementations are described in detail in the drawings and the following description. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 shows a cross-section of a heater for heating a catalyst according to an example, characterized by a plurality of oppositely arranged outer electrodes.

[0024] Figure 2 is an enlarged view of a partial cross-section of a honeycomb structure according to an example.

[0025] Figure 3 shows a perspective view of an exhaust gas treatment system comprising a heater for heating a catalyst and an exhaust gas treatment device according to an example.

[0026] Figure 4A shows a cross-section of a heater for heating a catalyst according to an example, characterized by a plurality of oppositely arranged outer electrodes.

[0027] Figure 4B shows a cross-section of a heater for heating a catalyst according to an example, characterized by a plurality of oppositely arranged outer electrodes.

[0028] Figure 4C A cross-section of a heater for heating a catalyst according to an example is shown, featuring a plurality of oppositely arranged outer electrodes.

[0029] Figure 4D An exemplary heat map showing temperatures of a heater according to an example is shown.

[0030] Figure 4E An exemplary heat map showing temperatures of a heater according to an example is shown.

[0031] Figure 5 A cross-section of a heater for heating a catalyst according to an example is shown, featuring a plurality of oppositely arranged outer electrodes and inner electrodes.

[0032] Figure 6A A cross-section of a heater for heating a catalyst, a voltage source, and a controller according to an example are shown.

[0033] Figure 6B A cross-section of a heater for heating a catalyst, a voltage source, and a controller according to an example are shown.

[0034] Figure 6C A cross-section of a heater for heating a catalyst, a voltage source, and a controller according to an example are shown.

[0035] Figure 7A A cross-section of a heater for heating a catalyst according to an example is shown, featuring a plurality of outer electrodes with varying arc length.

[0036] Figure 7B A cross-section of a heater for heating a catalyst according to an example is shown, featuring a plurality of outer electrodes with varying arc length.

[0037] Figure 8A A heat distribution of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring a plurality of outer electrodes and inner electrodes.

[0038] Figure 8B A heat distribution of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring a plurality of outer electrodes and inner electrodes.

[0039] Figure 8C A heat distribution of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring a plurality of outer electrodes and inner electrodes.

[0040] Figure 8DA thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes and an inner electrode.

[0041] Figure 8E A thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes and an inner electrode.

[0042] Figure 8F A thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes and an inner electrode.

[0043] Figure 8G A thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes and an inner electrode.

[0044] Figure 8H A thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes and an inner electrode.

[0045] Figure 8I A thermal profile of a heater for heating a catalyst during a heating sequence according to an example is shown, featuring multiple outer electrodes (no inner electrode).

[0046] Figure 9 A cross-section of a heater for heating a catalyst according to an example is shown, featuring multiple relatively arranged outer electrodes and multiple insulation layers.

[0047] Figure 10 A cross-section of a heater for heating a catalyst according to an example is shown, featuring multiple relatively arranged outer electrodes and multiple insulation layers.

[0048] Figure 11 A cross-section of a heater for heating a catalyst according to an example is shown, featuring multiple relatively arranged outer electrodes and multiple insulation layers.

[0049] Figure 12 A thermal profile of a heater for heating a catalyst according to an example is shown, featuring multiple relatively arranged outer electrodes and multiple insulation layers.

[0050] Figure 13 A thermal profile of a heater for heating a catalyst according to an example is shown, featuring multiple relatively arranged outer electrodes and multiple insulation layers. DETAILED DESCRIPTION

[0051] Some catalytic converters rely on the heat of engine exhaust gases to activate the catalyst and initiate vehicle emissions treatment. As a result, a significant portion of total emissions in some vehicles may occur immediately after vehicle start-up, while the catalyst is still cold. The embodiments disclosed herein pertain to active heating systems and methods that supplement existing engine exhaust gas heating with electric heating elements, thereby achieving faster heating of the catalyst to an effective temperature and thus further reducing vehicle emissions (especially after a cold start).

[0052] One such method for active exhaust gas heating is electrothermal catalytic converter (EHC), which increases the catalyst temperature by supplying electrical energy from a battery (e.g., an onboard battery) to provide additional heat to the catalytic converter. However, the design of electrothermal catalytic converters is affected by issues such as heating distribution with hot and / or cold spots, which may reduce the performance and efficiency of electrical energy utilization.

[0053] like Figure 1 The diagram shows a cross-sectional view of an electric heater 100a for heating a catalyst, comprising a honeycomb structure 102 around which a plurality of external electrodes 104 are arranged. Two or more of the electrodes 104 can be interconnected and connected to a power source, such as a battery, for example, the battery of a vehicle in which the heater 100a is installed. The honeycomb structure 102 includes a honeycomb structure 106 and a skin 110. Figure 2 As shown more clearly, the honeycomb structure 106 includes a matrix of intersecting walls 112 defining a plurality of adjacent channels 113. The honeycomb cell 102 includes a central axis C extending longitudinally through it. The walls 112 comprise a conductive material such that (e.g., via a battery) a potential applied to the electrodes 104 generates a current flowing through at least a portion of the walls 112 connecting the charged electrodes. Figure 1 As shown, the shape of the honeycomb 102 can be basically cylindrical, but the honeycomb can also have other shapes, such as elliptical, rectangular, triangular, etc.

[0054] According to this disclosure, heater 100a is provided as a specific example of heater 100. Other specific examples of heater 100 are described herein with different letter suffixes (e.g., a, b, etc.). Any description of heater 100 should generally apply to other heaters that share the same reference numeral 100 but have these different letter suffixes appended. Similarly, the general description of other articles, assemblies, or systems herein should apply to other articles, assemblies, or systems that share the same basic reference numerals and have additional letter suffixes (e.g., the description of electrode 104 should generally apply to electrodes 104a, 104b, 104c, 104d, etc.). Furthermore, unless specifically indicated or preemptively used by further description of any particular example, the description of any instance of an article, assembly, or system should generally apply to other articles, assemblies, or systems that share the same basic numerals, regardless of letter suffixes.

[0055] Figure 2 A portion of the honeycomb structure 106 is shown in more detail. It can be formed into any suitable cross-sectional shape (i.e., the cross-section is located at...). Figure 1 in the plane and / or parallel to Figure 1 The channel 113 (of a plane) includes, for example, a square, rectangular, triangular, or hexagonal shape. The wall 112 may contain a conductive material, such as a metal, conductive ceramic, metal-doped ceramic, or a combination thereof. The cross walls 112 are configured to carry current flow between the plurality of external electrodes 104. The cross walls 112 may have resistivity, thereby causing them to generate heat in response to the current as a result of the applied current.

[0056] The honeycomb structure 102 can be formed, for example, by extruding the ceramic material through an extrusion die as a green body, then cutting, drying, and firing it to form the final ceramic honeycomb structure. Alternatively, the honeycomb structure 102 can be formed by additive machining operations (e.g., 3D printing) or subtractive machining operations (e.g., electrical discharge machining, electrochemical machining, etc.). If the selected ceramic material has too high a resistance for providing effective resistance heating, the ceramic material can be doped with a conductor (e.g., a metal) to increase the electrical conductivity of the ceramic.

[0057] Figure 3A perspective view of a heater 100a is shown. The structure, features, functions, and other descriptions of the heater 100a are common to other examples of heaters that share the same reference number 100 but with different letter suffixes added (e.g., heaters 100a-100j). At least a subset of the cells 113 extend in an axial manner between opposite end faces 118, 120 of the honeycomb body 102, defining a set of passages through which a gas (e.g., exhaust gas from a vehicle engine) can flow. Thus, the inlet face 118 can be in fluid communication with the outlet face 120 via the passages, such that gas impinging on the inlet end face 118 can flow through the passages formed by the cells 113 and out the outlet face 120. The outer electrode 104 can extend along the entire axial length of the heater 100a (as shown), or can extend along an axial length of a portion of the heater. Figure 3 The heater 100a can be used in an exhaust gas treatment system 101, as shown. The exhaust gas treatment system 101 includes the heater 100 disposed upstream of an exhaust gas treatment device 121 (e.g., a substrate for catalytic material, a particulate filter, or a portion of a filter). Similar to the heater 100, the exhaust gas treatment device 121 can include a honeycomb body comprising an outer skin 123 and a honeycomb structure 125. The honeycomb structure 125 can be impregnated or coated with a catalyst that activates to react with exhaust gas components when heated by the heater 100 and / or by exhaust gas (which in turn is heated by the heater 100). The honeycomb structure 125 of the exhaust gas treatment device 121 can include a matrix of intersecting walls forming a plurality of adjacent cells. The cells of the exhaust gas treatment device 121 can have any suitable shape cross-section, including, for example: square, rectangular, triangular, or hexagonal. The cells of the exhaust gas treatment device 121 need not have the same shape or dimensions as the cells 113 of the heater 100. In fact, the cells of the exhaust gas treatment device 121 can be larger or smaller than the cells 113 of the heater 100, and / or can have a different cross-sectional shape.

[0058] As shown, the exhaust gas treatment system 101 includes the heater 100 disposed upstream of an exhaust gas treatment device 121 (e.g., a substrate for catalytic material, a particulate filter, or a portion of a filter). Similar to the heater 100, the exhaust gas treatment device 121 can include a honeycomb body comprising an outer skin 123 and a honeycomb structure 125. The honeycomb structure 125 can be impregnated or coated with a catalyst that activates to react with exhaust gas components when heated by the heater 100 and / or by exhaust gas (which in turn is heated by the heater 100). The honeycomb structure 125 of the exhaust gas treatment device 121 can include a matrix of intersecting walls forming a plurality of adjacent cells. The cells of the exhaust gas treatment device 121 can have any suitable shape cross-section, including, for example: square, rectangular, triangular, or hexagonal. The cells of the exhaust gas treatment device 121 need not have the same shape or dimensions as the cells 113 of the heater 100. In fact, the cells of the exhaust gas treatment device 121 can be larger or smaller than the cells 113 of the heater 100, and / or can have a different cross-sectional shape. Figure 3 At least a subset of the cells of the exhaust gas treatment device 121 extend in an axial manner between opposite end faces 127, 129 of the exhaust gas treatment device 121, defining a set of passages through which a gas can flow. If the exhaust gas treatment device 121 is disposed as a filter, at least some of the passages can be plugged, for example, in an alternating manner between the opposite end faces 127, 129. Thus, the inlet face 127 can be in fluid communication with the outlet face 129 via the passages, such that gas impinging on the inlet end face 127 can flow directly through the un-plugged passages (e.g., in the case of a catalytic substrate), or can be forced to flow through the porous walls of the plugged honeycomb body separating adjacent passages (e.g., in the case of a particulate filter) to the end face 129.

[0059] At least a subset of the cells of the exhaust gas treatment device 121 extend in an axial manner between opposite end faces 127, 129 of the exhaust gas treatment device 121, defining a set of passages through which a gas can flow. If the exhaust gas treatment device 121 is disposed as a filter, at least some of the passages can be plugged, for example, in an alternating manner between the opposite end faces 127, 129. Thus, the inlet face 127 can be in fluid communication with the outlet face 129 via the passages, such that gas impinging on the inlet end face 127 can flow directly through the un-plugged passages (e.g., in the case of a catalytic substrate), or can be forced to flow through the porous walls of the plugged honeycomb body separating adjacent passages (e.g., in the case of a particulate filter) to the end face 129.

[0060] The exhaust treatment device 121 can be formed by, for example, extruding a ceramic-forming material through an extrusion die as a green body, which is then cut, dried, and fired to a final ceramic honeycomb body (which includes the outer skin 123 and the honeycomb structure 125). The ceramic-forming material can include inorganics (e.g., alumina, silica, etc.), a binder (e.g., methylcellulose), a pore former (e.g., starch, graphite, resin), a liquid vehicle (e.g., water), a sintering aid, or any other additives that facilitate the manufacture of the final ceramic honeycomb body. The final ceramic honeycomb body of the exhaust treatment device 121 can include cordierite, aluminum titanate, alumina, mullite, silicon carbide, and / or other ceramic materials, or combinations thereof.

[0061] The electrical current flowing through the heater 100 acts to generate heat in the walls 112 to heat the exhaust gas or other gas stream flowing therethrough. The heater 100 can also be positioned adjacent to (e.g., tightly coupled with) the exhaust treatment device 121 to provide radiant heat to the exhaust treatment device 121. Thus, the heater 100 heats the catalyst of the exhaust treatment device 121 both by direct radiant heating and by heating the exhaust gas flowing through the exhaust treatment device 121. In some embodiments, the heater 100 is shorter in the axial direction than the exhaust treatment device 121, such that the heater 100 heats up more quickly, for example, at least in part due to the smaller thermal mass of the heater 100. For example, when the axial length of the exhaust treatment device 121 is about 6 inches, the axial length of the heater 100 can be about 0.25 inches to 0.5 inches, although the length of the heater 100 can be set to other lengths suitable to provide sufficient heat to achieve the desired temperature in the heater 100 and / or in the exhaust treatment device 121. Moreover, the heater 100 and the exhaust treatment device 121 can be extruded as separate bodies, particularly when different material compositions, mesh thicknesses, channel sizes, and / or channel scales are employed between the heater 100 and the exhaust treatment device 121. In some embodiments, the heater 100 can be arranged as a catalyzed substrate (i.e., the walls of the heater 100 are loaded with catalytic material) and / or a particulate filter (i.e., the channels are alternately plugged at opposite end faces), without including the exhaust treatment device 121 as a separate honeycomb body.

[0062] Returning to Figure 1 The outer electrodes 104 of the heater 100 can be arranged in electrically connected pairs of electrodes, such as the pair of electrodes shown in the heater 100a. Each pair of electrodes in the heater 100a includes two outer electrodes 104 that are spaced apart around the perimeter of the honeycomb body 102, such that electrical current flows in one or more current paths defined as the portions of the walls 112 extending between the electrodes spaced apart around the perimeter. For example, Figure 1The outer electrodes 104 are arranged in two pairs of opposing electrodes: the first pair includes electrodes 104a and 104b, and the second pair includes electrodes 104c and 104d. Each of electrodes 104a-104d includes a length L that engages with the honeycomb body 102, due to... Figure 1 In this embodiment, the honeycomb 102 has a circular shape, and its length L is arc-shaped. Each pair of outer electrodes 104 is spaced apart at its center point 108 along its length L by a distance D, which in this embodiment is equal to the diameter of the honeycomb 102. In other words, the center point 108 of outer electrode 104a is spaced apart by a distance D (the diameter of the honeycomb 102) with the center point 108 of outer electrode 104b, and the center point 108 of outer electrode 104c is also spaced apart by a distance D (the diameter of the honeycomb 102) with the center point 108 of outer electrode 104d.

[0063] Because the walls 112 are arranged in a cross matrix of conductive elements and because of the length L of the electrodes spanning a distance across the perimeter of the cell 102, multiple current paths can be formed through the walls 112 between any given pair of electrodes (that is, multiple different combinations of walls 112 and / or portions of walls 112). In general, the current through each possible current-carrying path is proportional to the resistance of the path, and the sum of the resistances of all possible paths between each pair of electrodes can be expressed as an equivalent resistance. For the sake of discussion herein, since the length of each possible current path cannot always be conveniently determined, the center current path of each pair of electrodes can be defined relative to the shortest distance between the center points 108 on the walls 112 between the paired electrodes. For example, Figure 4A Electrodes 104a and 104b are aligned with respect to wall 112, such that one of the electrodes in wall 112 extends in a straight line between the center points 108 of the electrodes. That is, as Figure 4A As shown, one of the walls 112 at the center point 108 of electrodes 104a and 104b meets the outer skin 110 perpendicularly (at a 90° angle) to the tangent of the honeycomb 102 at the center point 108. In this way, a central current path 114 is formed by this wall 112 extending directly between the center points 108 of electrodes 104a and 104b (perpendicular to the tangent of the honeycomb 102 at the outer periphery where the honeycomb 102 engages with the electrodes 104a and 104b at their respective center points 108). In this embodiment, the length between electrodes 104a and 104b of the central current path 114 is equal to... Figure 1 The distance D represents the diameter of the honeycomb cell 102. Similarly, as... Figure 4BAs shown, when a voltage is applied to it, a central current path 115 is formed between electrodes 104c and 104d. This central current path 115 is formed through a wall in wall 112 that extends directly between the center point 108 of electrodes 104c and 104d, and thus also has a length equal to the diameter of the honeycomb 102.

[0064] If the electrodes are aligned with respect to the wall 112 such that no wall 112 extends in a single straight line between the center points 108, the current path length will be longer than the diameter of the honeycomb (longer than the distance D between the center points of the opposing electrodes). For example, in Figure 4C In the case of electrodes 104x and 104y of heater 100z, a central current path 116 is formed along a generally serrated path on the partial wall 112 connecting electrodes 104x and 104y. That is, as Figure 4C As shown, wall 112 at the center point 108 of electrodes 104x and 104y meets the outer skin 110 at an angle of approximately 45° relative to the tangent of the honeycomb 102 at the center point 108. Therefore, the current path length of the central current path 116 is defined as the sum of the lengths of the portions of wall 112 through which the current travels along the central current path 116. Due to its serrated characteristics, Figure 4C The length of the central circuit path 116 will be significantly longer than the diameter of the honeycomb 102 (unlike...). Figure 4A and 4B The lengths of the central current paths 114 and 115 are equal to the diameter of the honeycomb structure 102 (as described above). For example, in Figure 4C In the middle, the diameter of the honeycomb is approximately equal to the width of about twelve to thirteen channels 113 (eleven complete channels 113, and two partial channels 113 at each end), while the length of the central current path 116 is approximately equal to the width of about eighteen channels 113.

[0065] Although Figure 1 The diagram shows four outer electrodes 104 forming two pairs of electrodes, but any suitable number of outer electrodes 104 can be arranged around the outer periphery of the honeycomb 102. Furthermore, each electrode can be paired with more than one other electrode spaced apart at the periphery. For example, a single positive electrode can be electrically paired with two or more corresponding negative electrodes, thereby generating a current flow relative to each of the paired negative electrodes.

[0066] Back Figure 4A Applying a voltage between the outer electrodes 104a and 104b generates a current that flows through one of the walls 112 extending between the center point 108 of electrodes 104a and 104b, approximately centered along the central current path 114 (shown as a dashed line). As mentioned above... Figure 1 and4A The path length of the central current path 114 is approximately equal to the distance D between the electrodes 104a and 104b (which is also approximately equal to the diameter of the honeycomb 102). According to Ohm's law, the current density J is inversely proportional to the path length of the current path. Thus, the current density J is highest near the electrodes 104a and 104b and decreases as the distance from the electrodes 104a and 104b increases. Figure 4A The heat generated by the heater 100a is concentrated and centered symmetrically in the central current path 114. Similarly, as shown in Figure 4B applying a voltage between the electrodes 104c and 104d results in a current and thus heat being generated in the region concentrated and / or centered symmetrically in the central current path 114 along the central current path 115. Similarly, applying a voltage between Figure 5 the electrodes 104x and 104y of the heater 100z results in the central current path 116, in respect to which the heat is concentrated.

[0067] However, Figure 4A , 4B and 4C, the central current paths 114, 115, 116 represent only one possible current-carrying path between the center points 108 of a given pair of outer electrodes 104. That is, some of the current between each pair of electrodes will be carried on portions of the walls 112 not defined by the central current paths 114, 115, 116, and the total number of current paths formed between a particular pair of electrodes will include a large number of intersecting walls 112 connected between each particular pair of electrodes. For example, Figure 4D an exemplary thermal map showing the temperature of the walls 112 of the heater 100a resulting from applying a voltage between the electrodes 104a and 104b is shown. In Figure 4D and 4E the walls 112 shown in black or darker colors are relatively cooler, while the walls 112 shown in white or lighter / brighter colors are relatively hotter. In the example shown in Figure 4D the temperature is highest near and along the length L of the electrodes 104a and 104b, where the current density is highest. The hotter temperature regions extend from each electrode 104a, 104b in a generally wedge-shaped pattern from the electrodes 104 along their respective lengths, and partially along the central current path 114. The temperature distribution corresponding to the electrodes 104c and 104d of Figure 4B will be similar to that shown in Figure 4D , but rotated appropriately according to the positions of these electrodes on their respective heaters and centered along their corresponding central current paths 115. Similarly, Figure 4E an exemplary temperature map is shown that would result from applying a voltage between the electrodes 104x and 104y of the heater 100z of Figure 4C Due to the small size of the channels 113 in Figure 4E , the central current path 116 of the heater 100z is not shown in Figure 4E , but fromFigure 4C It can be appreciated that the wall 112 extends in a zigzag pattern between the center points 108 of the electrodes 104x and 104y.

[0068] To generate current across the entire cross-section of the honeycomb body 102, and thus a more uniform current, in some embodiments, voltage is applied to pairs of electrodes 104 according to a predetermined heating sequence. For example, in the example of FIGS. 1A-1C, voltage can be first applied between the electrodes 104a and 104b (as shown in FIG. 1A) for a first time period, and then applied between the electrodes 104c and 104d (as shown in FIG. 1B) for a second time period. The first and second time periods can be any length of time suitable to generate a desired amount of heat in the walls 112 of the heater. For example, the first and second time frames can each last 1 second or more, or fractions of a second, during which the corresponding pair of electrodes is cycled on and off. Figure 4A and 4B Figure 4A and 4D Figure 4B

[0069] Applying voltage to pairs of electrodes 104 in sequence (rather than simultaneously) can be useful to prevent current flow between outer electrodes 104 that are not oppositely arranged. In other words, applying voltage in sequence between oppositely arranged pairs of electrodes 104 creates a current path through the diameter of the honeycomb (e.g., through the center axis C or adjacent to the center axis C) rather than through the skin 110 or any other manner along a shorter path between adjacent electrodes.

[0070] In some embodiments, all of the electrodes are energized simultaneously. For example, rather than heating in sequence, if positive voltage is applied to the electrodes 104a and 104c, and the electrodes 104b and 104d are grounded, current can flow between the electrodes 104a and 104d and between the electrodes 104b and 104c, rather than between the oppositely arranged electrodes 104c and 104d. If the majority of the current is carried between adjacent electrodes (e.g., between electrodes 104a and 104d, between electrodes 104a and 104c, between electrodes 104b and 104c, and / or between electrodes 104b and 104d) rather than between oppositely arranged electrodes (e.g., between electrodes 104a and 104b, or between electrodes 104c and 104d), this can create hot spots in the walls between adjacent electrodes, and thus fail to heat other portions (e.g., near the center of the honeycomb 102). In this manner, applying voltage in sequence between designated pairs of electrodes (e.g., oppositely arranged pairs of electrodes) facilitates current flow through the entire cross-section of the honeycomb, and thus more uniform heating of the heater 100.

[0071] ​​​In addition to the outer electrode 104, the heater 100 may include electrodes disposed within the honeycomb structure 102. Such internal electrodes may be positioned, for example, to introduce additional current into areas requiring additional heating, such as areas expected to receive a larger volume of exhaust gas flow compared to other areas of the heater 100. For example, as... Figure 5 As shown, placing the internal electrode 126 at the central axis C of the heater 100b facilitates current flow in the region 128 arranged around and surrounding the central axis C, and consequently contributes to heat generation. The internal electrode 126, arranged in this way at the central axis C, can receive a voltage between itself and any or all of the other external electrodes 104. However, the internal electrode 126 does not necessarily have to be placed at the central axis C; instead, it can be placed anywhere within the honeycomb structure 106 where a larger current is required. Furthermore, multiple internal electrodes 126 can be placed inside the honeycomb 102. Voltages can be applied between any or all of the internal electrodes 126 and any or all of the external electrodes 104, or between the internal electrodes 126 themselves, either simultaneously with or as part of a heating sequence.

[0072] Figure 6A-6C An example of the heating sequence of heater 100b is shown, characterized by four external electrodes 104 (two opposing electrode pairs) and an internal electrode 126 arranged at the central axis C. In the sequence shown, as... Figure 6A As shown, a voltage is first applied to the external electrodes 104a and 104b. Then, in the sequence, as... Figure 6B As shown, a voltage is applied to the external electrodes 104c and 104d. And finally, as... Figure 6C As shown, a voltage is applied between the internal electrode 126 and the external electrode 104. Figure 6A-6C The heating sequence shown is merely an example, and any sequence that can be used to heat the cell 102 appropriately can be executed.

[0073] like Figure 6A-6C As shown, the controller 130 is connected to electrodes 104 and 126, thereby controlling the voltage application between various configurations of the outer electrode 104 and / or the internal electrode 126. Figure 6A-6C In this example, controller 130 can apply voltage to different electrodes 104 by setting a series of switches 132, which are arranged to interrupt or establish electrical connections between one or more electrodes 104 and power terminals (shown as automotive battery 134). For example, as Figure 6AAs shown, depending on the position of the switch 132 (open or closed), the switch 132a is arranged to interrupt or establish an electrical connection between the electrode 104a and the positive terminal of the automotive battery 134. Thus, by setting the position of the switch 132, the controller 130 determines whether the electrode 104 is in electrical communication with the positive terminal of the automotive battery 134. Extending this to the remaining electrodes 104, by setting the position of the switch 132, the controller 130 can configure the voltage applied to the honeycomb body during any given point in the sequence.

[0074] Although each electrode is shown as having a switch 132 arranged to interrupt or establish an electrical connection with one terminal of the automotive battery 134, in alternative examples, each electrode can be configured to be connectable to either terminal (e.g. by more than one switch). Furthermore, each switch 132 can interrupt or establish an electrical connection between a terminal and more than one electrode 104. For example, a switch 132 can be connected to a terminal on one side and to a plurality of electrodes 104, 126 on the other side. However, this can hinder the sequential activation of the electrodes 104, 126 connected to the switch 132 relative to each other.

[0075] The heater 100 disclosed herein can include any additional intervening circuitry such that each electrode 104, 126 is not directly connected to a terminal of the battery, but has intervening circuitry to regulate the battery voltage applied to the electrode. Such circuitry is widely known in the art and therefore does not warrant additional discussion herein. Furthermore, voltage sources other than an automotive battery can be used.

[0076] The controller 130 can include a processor and a data storage medium (e.g. a non-transitory storage medium) such as a hard disk drive or solid state drive for storing program code which, when executed by the processor, runs instructions to perform a heating sequence (e.g. as described in relation to Figure 6A-6C Alternatively or additionally, the controller 130 can include hardware, firmware or software components configured to perform such a heating sequence.

[0077] The switches 132 can each include any solid state switch (e.g. MOSFET or BJT) or mechanical switch suitable for being controlled by the controller 130 and suitable for interrupting or establishing an electrical connection between one or more electrodes 104, 126 and one or more voltage sources.

[0078] In any given heating sequence, a cooling period (i.e. a period in which no voltage is applied to selected ones of the electrodes 104 or 126) can be inserted between heating periods (i.e. periods in which a voltage is applied to at least two of the electrodes 104, 126) to allow local hot spots to dissipate via conduction through the adjacent walls. For example, in the sequence described above, a cooling period can be inserted between the first and second heating periods. Figure 6A-6CIn the example, it can be found Figure 6A heating section and Figure 6B A cooling section is applied between the heating sections to dissipate any hot spots formed (e.g., near the electrodes) to the adjacent wall. The length of the cooling section can be predetermined to produce the desired temperature uniformity (e.g., all temperatures on the surface of heater 100 fall within preset maximum and minimum temperature thresholds). In some embodiments, the heating section is a fraction of a second, e.g., about 10 ms to 500 ms, less than 500 ms, or less than 250 ms, less than 150 ms, less than 100 ms, or less than 50 ms, while the cooling section is shorter than the heating section, e.g., half or one-third the length of the heating section. For example, a cooling section of about 50 ms can be performed between heating sections of 100 ms. Although controller 130, on-board battery 134, and switcher 132 are shown as being connected to heater 100b, such a configuration can be applied to any example of heater 100, including heaters 100a-j.

[0079] The current path through the wall 112, with its varying resistance between the electrode pairs of electrode 104, depends on the shape of the channel 113 and its orientation relative to the electrode 104. For example, variations in the length of the current path between the electrodes 104, resulting from the shape of the channel 113 and the orientation of the wall 112 relative to the electrode 104, will produce such different resistances. For example, using... Figure 7A In the square cross-section of the channel 113 of the heater 100d shown, the current path between the outer electrodes 104e and 104f will be direct because the intersecting wall 112 forms a straight line between the outer electrodes 104e and 104f. That is, similar to the heater 100a discussed above, the angle at which one of the walls 112 intersects the center point 108 of the electrodes 104e and 104f is perpendicular to the tangent of the honeycomb 102 at the center point 108. In this way, the central current path between the electrodes 104e and 104f will be similar to the current paths 114 and 115 discussed above, extending in a straight line through the honeycomb 102 and having a length equal to the diameter of the honeycomb.

[0080] Conversely, the current path between the outer electrodes 104i and 104j is not a straight line because the current is forced to flow along the intersecting or zigzag path portion of the crosswall 112. As a result, the central current path between the center points of electrodes 104i and 104j is longer and therefore more resistant than the current path between electrodes 104e and 104f (similar to how the length of the central current path 116 is longer than the diameter of the heater 100z, as discussed in...). Figure 4CThe length difference of such different current paths is generated irrespective of the fact that the diameter of the honeycomb body 102 (i.e., the distance D) separates both cases of electrodes 104 and 104f and electrodes 104i and 104j, because the current between each pair of electrodes must pass through the walls 112.

[0081] In some embodiments, for example as shown in Figure 7A-7B each outer electrode 104 of the honeycomb body 102 in each electrode pair is proportional to the length of the central current path between the respective center points of the electrodes 104 forming the electrode pair. That is, all other variables being equal, a longer current path will have a higher resistance than a shorter current path. In this way, by varying the length of the electrodes 104 in each pair that is proportional to the length of the current path in each pair, a more uniform heating profile can be achieved. The length of each possible current path between each pair of electrodes cannot be readily found, and thus the central current path described herein will be a representatively useful for this purpose.

[0082] For example, as shown in Figure 7A-7B the arc length of the outer electrodes 104e and 104f (and 104g and 104h) is shorter than the arc length of the outer electrodes 104i and 104j (and 104k and 1041), compensating for the longer current path between electrodes 104i and 104j. This is shown in Figure 7A as the difference between a first angle θ1 (having the end point of electrode 104i and the center axis C as vertices) and a second central angle θ2 (having the end point of electrode 104e and the center axis C as vertices). In other words, angles θ1 and θ2 correspond to the length of the respective electrodes engaged with the honeycomb body 102. Because Figure 7A the honeycomb body of FIG. 1 has a circular cross-section, the difference between central angles θ1 and θ2 will be proportional to the difference in arc length of electrodes 104i and 104e. Thus, as shown in Figure 7B the first length L1 of electrode 104i (and electrodes 104j, 104k, and 1041) is longer than the second length L2 of electrode 104e (and electrodes 104f, 104g, and 104h).

[0083] By increasing the arc length of a given pair of outer electrodes 104, the current resulting from the applied voltage will be provided directly by the electrodes to a greater number of intersecting walls 112. In other words, if the electrodes 104 of a given pair of outer electrodes 104 have a longer length (arc angle), the total number of current paths between these electrodes should be greater than the total number of current paths between a pair of outer electrodes 104 having a shorter length (arc angle). An example of this can be seen inFigure 7A The length (LI) of the pair of electrodes 104i and 104j is longer than the length (L2) of the pair of electrodes 104e and 104f. As a result, the number of walls 112 that end at electrode 104i and / or intersect the portion of the skin 110 that engages electrode 104i is greater than the number of walls 112 that end at electrode 104e and / or intersect the portion of the skin 110 that engages electrode 104e. In this way, although the length of the current path between electrodes 104i and 104j (e.g., as represented by the central current path) is longer than the length of the current path between electrodes 104e and 104f, the equivalent resistance of the current path between electrodes 104i and 104j is thus more uniform or even the same as the equivalent resistance of the current path between electrodes 104e, 104f. Therefore, by varying the length of the electrodes in proportion to the length of the current path (e.g., the central current path), the equivalent resistance between different pairs of oppositely disposed electrodes can be made substantially similar. By making each pair of electrodes 104 have a more uniform equivalent resistance, a more uniform temperature can be achieved across the face of the heater 100.

[0084] Alternatively or in addition to varying the length of the electrodes 104, the average voltage applied to a given pair of electrodes 104 can be varied, e.g., in proportion to the length of the current path that runs between pairs of oppositely disposed electrodes. For example, the average voltage between different pairs of electrodes can be varied by varying the magnitude of the voltage applied to each pair of electrodes, by varying the duty cycle of a pulse width modulated voltage waveform applied to each pair of electrodes, by varying the duration of the applied voltage, or by some combination of these methods. For example, during a heating sequence, a first magnitude of voltage can be applied to one pair of outer electrodes 104 and a second magnitude of voltage can be applied to another pair of outer electrodes 104, the first magnitude of voltage being higher than the second magnitude of voltage. (This results in an increase in the average voltage applied to the first pair of oppositely disposed outer electrodes 104 if the voltage is applied for the same period of time.

[0085] The variation in the magnitude of the applied voltage can be achieved in various ways. Generally, however, the magnitude can be varied by applying different voltages at the voltage source (e.g., at the circuit that regulates the voltage from the vehicle battery 134) or by placing some resistance in series with a given pair of outer electrodes 104. For example, if a first resistance is placed in series with a first pair of outer electrodes 104 and a second, lower resistance is placed in series with a second pair of outer electrodes 104, the magnitude of the voltage across the first pair of outer electrodes 104 will be less than the magnitude of the voltage across the second pair of outer electrodes 104. The resistance that is implemented can be a discrete element (i.e., a resistor). Alternatively, instead of placing a resistance in series with the outer electrodes 104, the composition or thickness of the outer electrodes 104 can be varied to vary the inherent resistance of the outer electrodes 104 themselves.

[0086] As described above, the duty cycle of the pulse width modulation (PWM) waveform can be adjusted individually for each pair of oppositely arranged electrodes 104. The PWM waveform can be executed by rapidly switching the switching state of the voltage applied to each electrode pair. By changing the duration the switch is in the on state (i.e., the duty cycle), the average voltage applied to a given electrode pair can be changed. For example, a PWM waveform with a 70% duty cycle can be applied to one pair of oppositely placed external electrodes 104; while a PWM waveform with a 30% duty cycle can be applied to a pair of oppositely placed external electrodes 104. As a result, the average voltage applied to the first pair will be 40% higher than that of the second pair.

[0087] Similarly, the total duration of the voltage applied to the electrode pairs of the external electrodes 104 can be varied. For example, the voltage applied to the first pair of oppositely arranged external electrodes 104 can last for a first time period (e.g., 12 ms), while the voltage applied to the second pair of oppositely arranged external electrodes 104 can last for a second time period (e.g., 100 ms). All other things being equal, this alters the average voltage applied to the electrode pairs of the external electrodes 104, similar to changing the voltage magnitude and duty cycle.

[0088] Furthermore, there are examples where combinations of the methods described above can be used to change the average voltage. For instance, a heater can vary the magnitude of the applied voltage between the individual electrode pairs as well as the application time.

[0089] Furthermore, although the example of changing the average voltage was described above in conjunction with the outer electrode 104, the same method of changing the average voltage can be used for electrode pairs that include an inner electrode and an outer electrode.

[0090] Furthermore, the length of electrode 104, the average voltage applied between electrodes 104, and which electrode 104 applies the voltage can be changed to compensate for the situation where a given region receives additional exhaust gas flow. Additionally, for a given region (e.g., Figure 4C The mesh thickness in zone 128 (shown) or the mesh composition in a given region can be varied (e.g., by selectively coating or impregnating the mesh with a conductive material) to change the resistance of that region, thereby supplementing the additional exhaust gas flow.

[0091] As discussed above, a heating sequence can be used to generate a more uniform temperature on the surface of heater 100, for example, to remove hot spots (e.g., temperatures above a maximum threshold) or cold spots (e.g., temperatures below a minimum threshold). Figure 8A-8H The figure shown is determined by modeling relative to Figure 7A-7B An exemplary heating sequence for heater 100d. In the first step of the heating sequence, such as... Figure 8AAs shown, a voltage is applied between the inner electrode 126 and each outer electrode 104 for a first period of time, e.g., 12 ms. In a second step, as shown in Figure 8B As shown, a positive voltage is applied to outer electrodes 104a and 104d, and a negative voltage is applied to outer electrodes 104b and 104c, for 16 ms. In a third step, as shown in Figure 8C As shown, a voltage is applied between electrodes 104a and 104b for 12 ms. In a fourth step, as shown in Figure 8D As shown, a voltage is applied between electrodes 104e and 104f for 100 ms. In a fifth step of the heating sequence, as shown in Figure 8E As shown, a voltage is again applied between the inner electrode 126 and each outer electrode 104 for 12 ms. In a sixth step, as shown in Figure 8F As shown, a positive voltage is again applied to outer electrodes 104a and 104d, and a negative voltage is applied to outer electrodes 104b and 104c, for 16 ms. In a seventh step, as shown in Figure 8G As shown, a voltage is applied between electrodes 104c and 104d for 12 ms. In an eighth step, as shown in Figure 8H As shown, a voltage is applied between electrodes 104g and 104h. Between the above steps, a cooling period of 50 ms is performed, respectively.

[0092] The above exemplary heating sequence provided is merely to illustrate the type of heating sequence that can be used to heat the honeycomb body 102. Other sequences for the heater 100 can be performed in other examples, e.g., including: different orders of electrode activation, longer or shorter activation and / or cooling time periods, different numbers of electrodes, or simultaneous activation of multiple electrode pairs suitable for heating the honeycomb body 102 and consistent with the description of the present disclosure.

[0093] Figure 8I An exemplary temperature map is shown resulting from the same heating sequence as Figure 8A-8H but without the inner electrode 126 or any steps involving the inner electrode 126. As a result, Figure 8I the example results in cooler regions 139 (relative to the temperatures achieved at other locations) that are not present in the example of Figure 8H which includes the inner electrode 126. Thus, by comparing the example of Figure 8H with the example of Figure 8I it can be seen that the inclusion of the inner electrode is useful for increasing the heat generated at locations in the vicinity of the inner electrode 126, e.g., in the region 128 shown. Figure 5

[0094] ​While several of the systems and methods described herein are directed to improving more uniform heating distribution, in some embodiments, the heater 100 is arranged to produce one or more temperature-increased zones, for example, by additional current flow biasing or directing to certain areas. For example, some examples herein are directed to using the inner electrodes 126 to produce current flow-increased zones, thus resulting in temperature increases. Figure 9 A heater 100f is shown according to another example, in which a plurality of electrically insulating layers 140 are arranged (extending from the outer periphery of the honeycomb body 102 into the interior of the honeycomb structure 106) to direct current flow toward certain areas of the honeycomb structure 106. In other words, current flow from the electrodes is prevented from moving along current paths that are interrupted by the insulating layers 140, thus concentrating the current produced by each electrode into a smaller number of total current paths in a smaller area of the heater 100.

[0095] By directing current flow, the current density in the interior regions or zones 142 near the ends of the insulating layers is increased compared to a similar heater 100 without the insulating layers 140. Moreover, for a given degree of applied potential difference between adjacent electrodes (e.g., electrodes 104a and 104c), the inclusion of the insulating layers 140 (e.g., insulating layer 140a) interrupts the shorter electrical paths between adjacent electrodes 104, thus improving the temperature uniformity of the heater 100f. In examples, the insulating layers can be formed by any suitable structure or gap that introduces an electrical interruption in the honeycomb structure 106. For example, the insulating layers 140 can be slits cut in the honeycomb structure 106 (by, for example, laser ablation, mechanical cutting, or any other suitable technique). In alternative examples, the slits can be filled with an insulating material, such as an electrically non-conductive ceramic (e.g., silicon carbide or cordierite), although other suitable insulating materials (e.g., polymers) can also be used.

[0096] Figure 10 An example is shown having four outer electrodes 1104a, 104b, 104c, and 104d arranged in two pairs of opposing arrangements. However, the insulating layers 140 can be used in connection with heaters 100 having any number of outer electrodes 104. For example, the insulating layers 140 can be used in connection with a heater having eight outer electrodes 104 (e.g., as shown in Figure 10

[0097] As shown in Figure 9 and 10 At locations between adjacent electrodes 104, the outer end 144 (i.e., the end of the insulating layer 140 that is farthest from the central axis C) can extend to or through the outer skin 110. For example, as shown in Figure 9 ​As shown, the outer end 144a of the insulating layer 140a is located between adjacent electrodes 104a and 104c. Alternatively, a given electrode 104 may extend over the outer end 144a of a given insulating layer 140. For example, in some embodiments, the electrode 104a extends over the outer end 144a of the insulating layer 140 such that an axis extending longitudinally along the insulating layer 140a extends through the electrode 104a.

[0098] To what extent is the insulating layer 140 incorporated in the heater 100 having opposingly arranged outer electrodes 104 (and inner electrodes 126) a heating sequence configured as described herein for sequential heating of the electrode pairs. The insulating layer 140, disposed between adjacent electrodes 104, can be used to improve the formation of hot spots by applying a potential difference to the adjacent electrodes 104. Therefore, the heating sequence may include additional or longer sections in which a potential difference is applied between adjacent electrodes without generating undesirable hot spots therebetween.

[0099] The depth of the insulating layer 140 (e.g., the radial distance into the honeycomb 102) and / or the angle (relative to the outer skin 110 and / or the central axis C) can be adjusted to heat specific portions of the honeycomb 102. In other words, the distance between the inner ends 146 of the insulating layer 140 (i.e., those ends closer to the central axis C) can be used to position local regions in the honeycomb 102 that have increased current density (relative to the current density in the region surrounding a given local area). For example, in Figure 11 In this arrangement, the insulating layers 140 are asymmetrically arranged within the honeycomb 102 (two of the insulating layers 140 are longer than the other two), thereby directing current to localized regions located off-center from the central axis C (increasing current density). For example, the off-center localized regions with increased current (and thus increased heat) are useful for exhaust gas treatment systems that are intended to receive non-uniform and asymmetrical flows of exhaust gas concentrated in localized areas.

[0100] For example, such as Figure 11 As shown, for comparison, the distance between the inner ends 146 of insulating layers 140o and 140p (labeled D2) is smaller than the distance between the inner ends 146m and 146n of insulating layers 140m and 140n (labeled D3). As a result, the current density in the first inner region or region 148 between the inner ends 146o and 146p of insulating layers 140o and 140p (centered at point C2) is higher than the current density in the second region 150 between the inner ends 146m and 146n of insulating layers 140m and 140n (centered at point C3). Therefore, the heat generated in the first region 148 is higher than that in the second region 150. This can be seen in, for example... Figure 12 and 13This demonstrates the thermal profile of the example heater 100i (similar to the heater 100f shown in Figure 9 FIG. 16) having symmetrically insulating layers 140, and the thermal profile of the example heater 100j (similar to the heater 100h shown in Figure 11 FIG. 15) having asymmetrically insulating layers 140. As a result, the current density in the region 152 in Figure 13 FIG. 16 is higher than the current density in the comparable region in Figure 13 FIG. 15 as a result of the narrow gap between the insulating layers in Figure 12 FIG. 16.

[0101] While several inventive examples have been described and illustrated, it is understood that modifications will occur to those skilled in the art. Numerous other examples can be devised which fall within the scope of the inventive examples described herein. More generally, any example described herein as comprising, consisting of, consisting essentially of, or consisting of, particular components or steps can include additional components or steps, and any example described herein as excluding certain components or steps can include additional components or steps. Accordingly, the examples are intended to embrace all such alterations, modifications, and variations which fall within the scope of the inventive examples described herein. Further, it is intended that any mechanism of the inventive examples that manages, manipulates, or controls data, information, signals, or commands be interpreted in the broadest possible sense. Moreover, the inventive examples described herein can be implemented in software and / or hardware. The examples can be implemented using a digital electronic circuit, or using a computer software module, firmware, or hardware components. The examples described herein can be implemented using one or more computer programs running on one or more computers or computer systems, or using one or more computer programs running on one or more computers or computer systems and one or more hardware components. The examples described herein can be implemented using one or more computer programs running on one or more computers or computer systems, or using one or more computer programs running on one or more computers or computer systems and one or more hardware components. The examples described herein can be implemented using one or more computer programs running on one or more computers or computer systems, or using one or more computer programs running on one or more computers or computer systems and one or more hardware components.

Claims

1. An electric heater, comprising: A honeycomb having a central axis extending longitudinally through it, the honeycomb comprising a matrix of intersecting walls forming a plurality of channels extending axially through the honeycomb; Multiple electrodes are placed around the outer periphery of the honeycomb, the multiple electrodes being arranged into multiple electrode pairs, each including at least a first electrode pair and a second electrode pair, each electrode pair containing a first electrode and a second electrode, wherein the current generated by each electrode pair flows through at least some cross walls between the electrodes of each electrode pair. Wherein, measured along the outer periphery in a cross-sectional plane perpendicular to the central axis, the electrode length of each pair of electrodes is proportional to the central current path length, which is defined as the shortest distance through the wall between the center points of the electrodes of the pair of electrodes, and wherein the electrode length of the first pair of electrodes is different from the electrode length of the second pair of electrodes.

2. The electric heater of claim 1, further comprising a plurality of insulating layers, each insulating layer extending from the outer periphery of the honeycomb into the interior of the honeycomb, thereby concentrating the current into the interior region of the honeycomb.

3. The electric heater as described in claim 2, wherein, Each insulating layer extends radially from the outer periphery toward the central axis from the position between each circumferentially adjacent electrode pair.

4. An electric heater, comprising: A honeycomb having a central axis extending longitudinally through it, the honeycomb comprising a matrix of intersecting walls forming a plurality of channels extending axially through the honeycomb; A plurality of electrodes are placed around the outer periphery of a honeycomb structure, the plurality of electrodes being arranged in a plurality of electrode pairs, each including at least a first electrode pair and a second electrode pair, each electrode pair comprising a first electrode and a second electrode, wherein current generated by each electrode pair flows through at least some crosswalls between the electrodes of each electrode pair; and A controller configured to apply voltages between the plurality of electrodes according to a heating sequence, wherein the heating sequence includes sequentially applying a first voltage to a first electrode pair and applying a second voltage between the second electrode pairs. The electrode length along the outer periphery of each electrode pair is proportional to the length of the central current path, which is defined as the shortest distance through the wall between the center points of the electrodes of the electrode pair, and wherein the electrode length of the first electrode pair is different from the electrode length of the second electrode pair.

5. The electric heater as claimed in claim 4, wherein, The average value of the second voltage on the heating sequence is different from the average value of the first voltage on the heating sequence.

6. The electric heater of claim 4, further comprising: An internal electrode embedded in a honeycomb, wherein the heating sequence further includes applying a voltage between the internal electrode and at least one of the plurality of electrodes.

7. A system comprising the electric heater as described in claim 1 and an exhaust gas treatment device.

8. The system of claim 7, wherein, The cross walls of the electric heater support the catalytic material.

9. An electric heater comprising: A basic cylindrical honeycomb structure having a central axis extending longitudinally through it, the honeycomb structure comprising a matrix of intersecting walls; Multiple electrodes are operably placed around the outer periphery of the honeycomb, the multiple electrodes being arranged in multiple opposing electrode pairs such that at least a portion of the current induced between each opposing electrode pair flows through the central axis. A controller configured to apply a voltage between each pair of oppositely arranged electrodes according to a heating sequence, wherein the heating sequence includes sequentially applying a first voltage between a first pair of oppositely arranged electrodes and applying a second voltage between a second pair of oppositely arranged electrodes, wherein during the heating sequence, a first average value of the first voltage is proportional to a first current in a first central current path between the centers of the first pair of oppositely arranged electrodes, wherein during the heating sequence, a second average value of the second voltage is proportional to a second current in a second central current path between the centers of the second pair of oppositely arranged electrodes, and wherein the length of the first central current path is longer than the length of the second central current path, wherein the length of the central current path is defined as the shortest distance through a wall between the center points of the electrodes of the pair of electrodes. An internal electrode embedded in a honeycomb, wherein the heating sequence further includes applying a voltage between the internal electrode and at least one of the plurality of electrodes.

10. A method for heating a catalyst, comprising: A first voltage is applied between a first pair of electrodes and a second voltage is applied between a second pair of electrodes, wherein the electrodes in the first and second pairs of electrodes are arranged around the outer periphery of a honeycomb having a central axis extending longitudinally therethrough, and the honeycomb comprising a matrix of cross walls forming a plurality of channels extending axially through the honeycomb. In each electrode pair, the electrode length along the outer periphery is proportional to the central current path length, which is defined as the shortest distance through the wall between the center points of the electrodes in that pair, and wherein the electrode length of the first electrode pair differs from the electrode length of the second electrode pair. Applying the first voltage and the second voltage includes: sequentially applying the first voltage to the first electrode pair according to the heating sequence, and applying the second voltage between the second electrode pairs.

11. The method of claim 10, wherein, The average value of the second voltage on the heating sequence is different from the average value of the first voltage on the heating sequence.

12. The method of claim 10, further comprising generating a substantially uniform heating distribution on the end face of the cell via a heating sequence.

13. The method of claim 10, wherein, The heating sequence includes a cooling interval arranged between applying the first voltage between the first electrode pairs and applying the second voltage between the second electrode pairs.

14. The method of claim 10, further comprising concentrating current in an inner region, said inner region being spaced apart from the outer periphery of the honeycomb.

15. The method of claim 14, wherein, The honeycomb structure includes multiple electrically insulating layers that prevent current from flowing through the wall sections that are cut off by the insulating layers, thereby concentrating the current in the internal region.

16. The method of claim 14, wherein, The cell includes an internal electrode located near an internal region, and the method further includes applying a voltage between the internal electrode and one of the first or second electrode pairs.

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