Methods for estimating the heat distribution of honeycomb structures, methods for manufacturing honeycomb structures, and methods for manufacturing electrically heated carriers.

Abstract

This invention provides a method for estimating the heat distribution of a honeycomb structure, a method for manufacturing a honeycomb structure, and a method for manufacturing an electrically heated carrier. The method for estimating the heat distribution includes: a first step of energizing a columnar honeycomb structure by flowing a predetermined minute current between electrode layers A1 and B1, and measuring the surface potential at multiple locations from electrode layer A1 to B1 on the outer peripheral wall and the surface of the electrode layers; a second step of energizing the columnar honeycomb structure by flowing a predetermined minute current between electrode layers A2 and B2, and measuring the surface potential at multiple locations from electrode layer A2 to B2 on the outer peripheral wall and the surface of the electrode layers; a third step of quantifying at least one of the following based on the measured surface potential at multiple locations: resistance at multiple points within the honeycomb structure, resistance ratio of the current-carrying path, voltage sharing rate, and surface potential of electrode layers A1, A2, B1, and B2; and a step of estimating the heat distribution within the honeycomb structure based on the quantified value in the third step.

Description

Technical Field

[0001] This invention relates to a method for estimating the heat distribution of a honeycomb structure, a method for manufacturing a honeycomb structure, and a method for manufacturing an electrically heated carrier. Background Technology

[0002] In recent years, in order to improve the reduced exhaust gas purification performance after engine startup, electrically heated catalytic converters (EHC) have been proposed. For EHC, the goal is to reduce temperature unevenness within the honeycomb structure and achieve a uniform temperature distribution in order to fully obtain the catalytic effect.

[0003] Previously, the performance evaluation of honeycomb structures involved checking the temperature distribution within the honeycomb structure when it was heated by electricity. Patent Document 1 discloses a method that involves energizing the honeycomb structure, measuring the resistance values ​​at multiple points, estimating the current value at the measured points, and calculating the heat generation based on the estimated value, thereby estimating the heat distribution of the honeycomb structure.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-153325 Summary of the Invention

[0007] The inventors of this invention studied the inspection method described in Patent Document 1 and found that the estimated heat distribution could not reproduce the actual heat distribution when the honeycomb structure was electrically heated, indicating room for improvement. Therefore, the method for inspecting the heat performance of honeycomb structures and electrically heated carriers needs further improvement.

[0008] This invention was created in view of the above circumstances, and its object is to provide a method for estimating the heat distribution of a honeycomb structure simply and inexpensively, and for estimating the heat distribution of a honeycomb structure more accurately. Furthermore, this invention aims to provide a method for manufacturing the aforementioned honeycomb structure and a method for manufacturing an electrically heated carrier.

[0009] The aforementioned problem is solved by the following invention. The invention is defined as follows.

[0010] (1) A method for estimating the heat distribution of a honeycomb structure, wherein the honeycomb structure comprises:

[0011] A columnar honeycomb structure having an outer peripheral wall and a partition wall, the partition wall being disposed on the inner side of the outer peripheral wall and dividing it into multiple compartments, the multiple compartments extending from one end face to the other end face to form a flow path; and,

[0012] A pair of electrode layers, namely electrode layer A and electrode layer B, are disposed on the surface of the outer peripheral wall of the columnar honeycomb structure portion in an opposing manner, sandwiching the central axis of the columnar honeycomb structure portion.

[0013] The electrode layer A and electrode layer B are electrically separated into electrode layer A1 and electrode layer A2, and electrode layer B1 and electrode layer B2, respectively.

[0014] Electrode layers A1 and B1, and electrode layers A2 and B2, are located on the side of the outer peripheral surface of the honeycomb structure that are closer to each other.

[0015] The method for estimating the heat distribution of the honeycomb structure is characterized by including the following steps:

[0016] In the first step, a predetermined minute current is passed between electrode layer A1 and electrode layer B1 to energize the columnar honeycomb structure. The surface potentials at multiple locations separated along the circumferential direction are measured on the outer peripheral wall and the surface of the electrode layers, from electrode layer A1 to electrode layer B1.

[0017] In the second step, a predetermined minute current is passed between electrode layer A2 and electrode layer B2 to energize the columnar honeycomb structure. The surface potentials at multiple locations separated along the circumferential direction are measured on the outer peripheral wall and the surface of the electrode layers, from electrode layer A2 to electrode layer B2.

[0018] The third step involves quantifying, based on the measured surface potentials at the multiple locations, at least one of the following: resistance at multiple points within the honeycomb structure, resistance ratio of the current-carrying path, voltage sharing rate, and surface potentials of electrode layers A1, A2, B1, and B2; and

[0019] The process of estimating the heat distribution within the honeycomb structure based on the quantitative values ​​obtained in the third process.

[0020] (2) A method for manufacturing a honeycomb structure, characterized by comprising the following steps:

[0021] The process of calculating the quantitative value in the third process of the honeycomb structure before inspection using the estimation method of heat distribution of the honeycomb structure described in (1); and

[0022] In the inspection process, based on the threshold obtained in the process of estimating the heat distribution within the honeycomb structure, the quantitative value in the third process is evaluated, and qualified products are selected.

[0023] (3) A method for manufacturing an electrically heated carrier, characterized in that it includes the following steps:

[0024] The process of calculating the quantitative value in the third process of the honeycomb structure before inspection using the estimation method of heat distribution of the honeycomb structure described in (1); and

[0025] In the inspection process, based on the threshold obtained in the process of estimating the heat distribution within the honeycomb structure, the quantitative value in the third process is evaluated, and qualified products are selected.

[0026] Invention Effects

[0027] According to the present invention, a method for estimating the heat distribution of a honeycomb structure can be provided that is simple and inexpensive, and can more accurately estimate the heat distribution of the honeycomb structure. Furthermore, according to the present invention, a method for manufacturing the aforementioned honeycomb structure and a method for manufacturing an electrically heated carrier can be provided. Attached Figure Description

[0028] Figure 1 This is a simplified cross-sectional view of the honeycomb structure in an embodiment of the present invention, perpendicular to the extension direction of the compartments.

[0029] Figure 2 This is a schematic diagram illustrating the method for measuring the surface potential of a honeycomb structure in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram illustrating the method for measuring the surface potential of a honeycomb structure in an embodiment of the present invention.

[0031] Figure 4 This is a simplified cross-sectional view of the electrically heated carrier according to an embodiment of the present invention, perpendicular to the extension direction of the compartment.

[0032] Figure 5 It is a graph showing the relationship between the ratio of the upper resistance to the lower resistance and the temperature difference (°C) of the heat distribution at the ends of the upper and lower electrode layers.

[0033] Figure 6 It is a graph showing the relationship between the distance measured from a specified position on the outer perimeter wall and the overall standardized voltage.

[0034] Figure 7 It is a graph showing the relationship between the voltage sharing rate of the power path of the cellular structure and the temperature difference (°C) of the heat distribution at the ends of the left and right electrode layers.

[0035] Figure 8 It is a graph showing the relationship between the total voltage sharing of the electrode layer relative to the overall standardized voltage and the temperature difference (°C) of the heat distribution between the end and center of the electrode layer.

[0036] Figure 9 It is a graph showing the relationship between the measurement location of the surface potential and the surface potential involved in specific example 1.

[0037] Symbol Explanation

[0038] 10…Honeycomb structure, 11…Columnar honeycomb structure, 12…Outer peripheral wall, 13…Partition wall, 15…Combine, 16…Slit, 20…Electrically heated carrier, 21a, 21b…Metal terminals, 31…Power supply, 32…Current terminal, 33…Measurement location, A1, A2, B1, B2…Electrode layers. Detailed Implementation

[0039] Next, with reference to the accompanying drawings, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes and modifications can be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0040] <Method for estimating the heat distribution of honeycomb structures>

[0041] (1. Honeycomb structure)

[0042] Figure 1 This is a simplified cross-sectional view of the honeycomb structure 10, which is the object of heat distribution measurement in the method for estimating the heat distribution of the honeycomb structure in the embodiments of the present invention, perpendicular to the extension direction of the compartment 15.

[0043] The honeycomb structure 10 has a columnar honeycomb structure portion 11, which has an outer peripheral wall 12 and a partition wall 13. The partition wall 13 is disposed on the inner side of the outer peripheral wall 12 and divides into multiple compartments 15. The multiple compartments 15 pass through from one end face to the other end face to form a flow path.

[0044] The columnar honeycomb structure 11 can be columnar in shape, without particular limitation. For example, it can be a columnar shape with a round end face (cylindrical shape), a columnar shape with an elliptical end face, or a columnar shape with a polygonal end face (quadrilateral, pentagon, hexagon, heptagon, octagon, etc.). Furthermore, the size of the columnar honeycomb structure 11 is not particularly limited; for example, the area of ​​the end face can be 2000–20000 mm². 2 .

[0045] The columnar honeycomb structure 11 is made of conductive ceramic. The honeycomb structure 10 can be heated by Joule heating when energized; the resistivity of the ceramic is not particularly limited and can range from 0.1 to 200 Ωcm. In this invention, the resistivity of the columnar honeycomb structure 11 is set to a value measured using a four-terminal method at 25°C.

[0046] The ceramic used to constitute the columnar honeycomb structure 11 is not limited, and examples include oxide ceramics such as alumina, andalusite, zirconia, and cordierite; and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. Alternatively, silicon carbide-silicon composite materials and silicon carbide / graphite composite materials may also be used. From the viewpoint of combining heat resistance and electrical conductivity, the material of the outer peripheral wall and partition walls is preferably a silicon-silicon carbide composite material or silicon carbide as the main component, and more preferably a silicon-silicon carbide composite material or silicon carbide. When the material of the outer peripheral wall and partition walls is a silicon-silicon carbide composite material as the main component, it means that the outer peripheral wall and partition walls each contain more than 90% by mass of silicon-silicon carbide composite material (total mass). Here, the silicon-silicon carbide composite material contains silicon carbide particles as aggregate and silicon as a binder material for bonding the silicon carbide particles. Preferably, multiple silicon carbide particles are bonded together by silicon through which fine pores are formed between the silicon carbide particles. When the material of the outer peripheral wall and partition wall is mainly composed of silicon carbide, it means that the outer peripheral wall and partition wall each contain more than 90% silicon carbide (total mass) of the whole.

[0047] The shape of the compartments in the columnar honeycomb structure 11 is not particularly limited. In a cross-section orthogonal to the central axis of the columnar honeycomb structure 11, it is preferably a polygon such as a triangle, quadrilateral, pentagon, hexagon, or octagon, a circle, or an ellipse, or it may be other irregular shapes. A polygon is preferred.

[0048] The thickness of the partition wall 13 is not particularly limited, but is preferably 0.05 to 0.50 mm, and more preferably 0.10 to 0.45 mm from the perspective of ease of manufacturing. For example, if the thickness of the partition wall 13 is 0.05 mm or more, the strength of the columnar honeycomb structure portion 11 is further improved; if the thickness of the partition wall 13 is 0.50 mm or less, pressure loss can be reduced. It should be noted that the thickness of the partition wall 13 is defined as the length of the portion passing through the partition wall 13 in a cross section perpendicular to the extending direction of the compartment 15, in which the centroids of adjacent compartments 15 are connected to each other.

[0049] The cell density of the columnar honeycomb structure 11 is not particularly limited, but is preferably 5 to 150 cells / cm². 2 The range is more preferably 5 to 100 compartments / cm². 2 The range is further preferably 31–80 compartments / cm. 2 The range.

[0050] The thickness of the outer peripheral wall 12 is not particularly limited and can be 0.1 mm to 1.0 mm. Here, the thickness of the outer peripheral wall 12 is defined as the thickness in the normal direction of the tangent to the outer peripheral wall 12 at the measurement location when the portion of the outer peripheral wall 12 to be measured is observed at a section perpendicular to the extension direction of the compartment.

[0051] The partition wall 13 can be dense, but is preferably porous. There is no particular limitation on the porosity of the partition wall 13, which can be 35% to 60%. The porosity is the value measured using a mercury porosimeter. It should be noted that dense material refers to material with a porosity of 5% or less.

[0052] The average pore size of partition 13 is not particularly limited and can be 2–15 μm. The average pore size is the value obtained by measuring using a mercury porosity meter.

[0053] A pair of electrode layers A and B (electrode layers A and B form a pair) are disposed on the surface of the outer peripheral wall 12 of the columnar honeycomb structure portion 11, facing each other with respect to the central axis of the columnar honeycomb structure portion 11. Electrode layer A is electrically separated into electrode layer A1 and electrode layer A2, and electrode layer B is electrically separated into electrode layer B1 and electrode layer B2. Electrode layers A1 and B1, and electrode layers A2 and B2 are located on the side of the outer peripheral surface of the honeycomb structure 10 that is closer to each other. That is, electrode layers A1, B1, B2, and A2 are arranged sequentially along the outer peripheral surface of the honeycomb structure 10.

[0054] Figure 1 In the illustrated embodiment, electrode layers A1 and A2, and electrode layers B1 and B2 are electrically separated by slits 16 extending along the columnar honeycomb structure portion 11. Electrical separation means that no current flows through the electrode layers themselves. The electrical separation of electrode layers A1 and A2, and electrode layers B1 and B2, is not limited to using slits; it can also be achieved by pre-printing the electrode layers separately, or by providing insulating components to achieve electrical separation. When electrical separation is performed using slits 16, the slit width can be, for example, 0.5 to 5 mm.

[0055] From the viewpoint of improving the uniformity of heating of the columnar honeycomb structure 11, the electrode layers A1, A2, B1, and B2 can be provided in a strip shape extending along the circumferential direction of the outer peripheral wall 12 and the extension direction of the compartment on the outer surface of the outer peripheral wall 12. Specifically, the electrode layers A1, A2, B1, and B2 can be provided to extend for more than 80% of the length between the two end faces of the columnar honeycomb structure 11.

[0056] The thickness of electrode layers A1, A2, B1, and B2 is not particularly limited and can be 0.01 to 5 mm. The thickness of electrode layers A1, A2, B1, and B2 is defined as the thickness of the outer surface of electrode layers A1, A2, B1, and B2 in the normal direction to the tangent at the measurement location when the measurement site is observed in a cross section perpendicular to the extension direction of the compartment.

[0057] By making the resistivity of electrode layers A1, A2, B1, and B2 lower than that of the columnar honeycomb structure 11, electricity can preferentially flow through the electrode layers, and when energized, the electricity can easily spread along the flow path direction and circumferentially within the compartment. The resistivity of electrode layers A1, A2, B1, and B2 is not limited and can be less than 1 / 10 of the resistivity of the columnar honeycomb structure 11. The lower limit of the resistivity of electrode layers A1, A2, B1, and B2 is not particularly limited, but is preferably 1 / 200 or higher. The resistivity of electrode layers A1, A2, B1, and B2 is a value measured using a four-terminal method at 25°C.

[0058] Metals and conductive ceramics can be used as materials for electrode layers A1, A2, B1, and B2. Examples of metals include elemental metals such as Cr, Fe, Co, Ni, Si, or Ti, or alloys containing at least one metal selected from the group consisting of these metals. The conductive ceramics are not limited; examples include silicon carbide (SiC), tantalum silicide (TaSi2), and chromium silicide (CrSi2), as well as metal compounds such as metal silicides. Furthermore, composite materials (cermets) formed by combining one or more of the aforementioned conductive ceramics with one or more of the aforementioned metals can be used. Specific examples of cermets include composites of silicon metal and silicon carbide, and composites of metal silicides such as tantalum silicide and chromium silicide with silicon metal and silicon carbide. Furthermore, from the viewpoint of reducing thermal expansion, composite materials obtained by adding one or more of insulating ceramics such as alumina, andalusite, zirconium oxide, cordierite, silicon nitride, and aluminum nitride to one or more of the aforementioned metals can be used. As the materials for electrode layers A1, A2, B1, and B2, among the various metals and conductive ceramics mentioned above, a combination of metal silicides such as tantalum silicide and chromium silicide with composite materials of metal silicon and silicon carbide can be used.

[0059] On the outer peripheral wall 12 of the columnar honeycomb structure section 11, slits may be provided between the surface where electrode layer A1 is provided and the surface where electrode layer B1 is provided, and / or between the surface where electrode layer A2 is provided and the surface where electrode layer B2 is provided, respectively, along the extending direction of the compartment 15. With this configuration, the thermal stress mitigation characteristics of the honeycomb structure 10 are improved. The length and width of these slits (thermal stress mitigation slits) are not particularly limited and can be appropriately designed according to the desired thermal stress mitigation characteristics.

[0060] (2. Method for estimating the heat distribution of honeycomb structures)

[0061] Next, the method for estimating the heat distribution of the honeycomb structure according to the embodiments of the present invention will be described in detail. First, as Figure 2As shown, a predetermined minute current flows between electrode layer A1 and electrode layer B1, thereby energizing the columnar honeycomb structure. At this time, two current terminals 32 electrically connected from the power supply unit 31 are pressed against electrode layers A1 and B1 of the honeycomb structure 10, respectively, maintaining the energized state. The minute current flowing between electrode layers A1 and B1 is a current of such magnitude that the honeycomb structure 10 does not heat up. The minute current, which is such that the honeycomb structure 10 does not heat up, depends on the material and resistivity of the honeycomb structure 10 and can be 1 to 1000 mA. Within this range, a constant current flows between electrode layers A1 and B1. Furthermore, if the honeycomb structure is a low-resistivity dense material, a range of 10 to 1000 mA is preferred; if the honeycomb structure is a porous material, its resistance is relatively high compared to a low-resistivity dense material, therefore, a range of 10 to 100 mA is preferred.

[0062] Next, with a specified minute current flowing between electrode layer A1 and electrode layer B1 to energize the columnar honeycomb structure, the surface potential of multiple locations separated along the circumferential direction on the outer peripheral wall 12 and the surfaces of electrode layers A1 and B1, from electrode layer A1 to electrode layer B1, is measured. Figure 2 In this example, three measurement sites 33 are provided on electrode layer A1, four measurement sites 33 are provided on the outer peripheral wall 12 between electrode layer A1 and electrode layer B1, and three measurement sites 33 are provided on electrode layer B1. The number of surface potential measurement sites on electrode layer A1, on the outer peripheral wall 12 between electrode layer A1 and electrode layer B1, and on electrode layer B1 are not limited to... Figure 2 The example shown can be appropriately set, preferably measuring the surface potential at at least two locations. The more locations measured, the more detailed and accurate the heat distribution of the honeycomb structure 10 can be estimated.

[0063] Next, as Figure 3 As shown, a predetermined minute current flows between electrode layer A2 and electrode layer B2 to energize the columnar honeycomb structure. At this time, two current terminals 32 electrically connected from the power supply unit 31 are pressed against electrode layers A2 and B2 of the honeycomb structure 10, respectively, maintaining the energized state. The minute current flowing between electrode layers A2 and B2 is set to a constant current of the same magnitude as the minute current flowing between electrode layers A1 and B1.

[0064] With a specified minute current flowing between electrode layer A2 and electrode layer B2 to energize the columnar honeycomb structure, the surface potential of multiple locations separated along the circumferential direction on the outer peripheral wall 12 and the surfaces of electrode layers A2 and B2, from electrode layer A2 to electrode layer B2, is measured. Figure 3 In this example, three measurement sites 33 are provided on electrode layer A2, four measurement sites 33 are provided on the outer peripheral wall 12 between electrode layer A2 and electrode layer B2, and three measurement sites 33 are provided on electrode layer B2. The number of surface potential measurement sites on electrode layer A2, on the outer peripheral wall 12 between electrode layer A2 and electrode layer B2, and on electrode layer B2 are not limited to... Figure 3 The example shown can be appropriately set, preferably measuring the surface potential at at least two locations. The more locations measured, the more detailed and accurate the heat distribution of the honeycomb structure 10 can be estimated.

[0065] The surface potentials at multiple locations circumferentially separated from electrode layer A1 to electrode layer B1, as described above, can be measured along the extending direction of the compartments 15 of the columnar honeycomb structure 11, as well as at multiple locations circumferentially separated from electrode layer A2 to electrode layer B2. With this configuration, since measurements are also performed at locations along the extending direction of the compartments 15 of the columnar honeycomb structure 11, the heat distribution of the honeycomb structure 10 can be estimated in greater detail and with higher accuracy.

[0066] Next, based on the measured surface potentials at multiple locations, at least one of the following is quantified: resistance (hereinafter also referred to as energized resistance), resistance ratio of energized paths, voltage sharing rate, and surface potentials of electrode layers A1, A2, B1, and B2 at multiple locations within the cellular structure 10. These quantifications may be performed individually or in combination.

[0067] Regarding the quantification described above, the resistance ratio of the energized resistance can be calculated based on (i) and / or (ii), where (i) in the measurement of surface potential at the multiple locations mentioned above, the difference between the lowest surface potential at the measurement location in electrode layer A1 and the highest surface potential at the measurement location in electrode layer B1 (hereinafter also referred to as the lower resistance); and (ii) in the measurement of surface potential at the multiple locations mentioned above, the difference between the lowest surface potential at the measurement location in electrode layer A2 and the highest surface potential at the measurement location in electrode layer B2 (hereinafter also referred to as the upper resistance). That is, the resistance ratio of the energized resistance can be calculated based on the potential difference between the lowest surface potential of the electrode layer where the surface potential measurement starts and the highest surface potential of the electrode layer where the surface potential measurement ends. In addition, at this time, the resistance at multiple locations within the honeycomb structure can be estimated based on the average of the surface potential differences between the starting and ending points of the multiple locations measured from electrode layer A1 through the outer peripheral wall to electrode layer B1, and the average of the surface potential differences between the starting and ending points of the multiple locations measured from electrode layer A2 through the outer peripheral wall to electrode layer B2.

[0068] In addition, regarding the quantification mentioned above, the surface potentials of electrode layers A1, A2, B1, and B2 are quantified, namely, (iii) the surface potentials are measured at multiple locations in electrode layers A1 and B1 to obtain the surface potentials in electrode layer A1 and B1, and / or (iv) the surface potentials are measured at multiple locations in electrode layers A2 and B2 to obtain the surface potentials in electrode layer A2 and B2. Based on the obtained surface potentials, the total voltage of electrode layers A1, A2, B1, and B2 is calculated, and the total voltage sharing rate of electrode layers A1, A2, B1, and B2 relative to the overall voltage is calculated.

[0069] In addition, regarding the above quantification, for the resistance ratio of the power path of the cellular structure 10, the ratio of the upper resistance (upper resistance / (upper resistance + lower resistance)) is calculated based on the upper resistance and the lower resistance.

[0070] As in the example above, at least one of the resistivity ratio of the current-carrying path, the voltage sharing rate of the current-carrying path, and the surface potential of electrode layers A1, A2, B1, and B2 of the honeycomb structure 10 is quantified. Based on these quantified values, the heat distribution within the honeycomb structure 10 is estimated. For example, to estimate the heat distribution, one can compare the values ​​of the resistivity ratio of the current-carrying path, the voltage sharing rate of the current-carrying path, and the total voltage sharing rate of the electrode layers relative to the overall voltage with the heat distribution at these values, thereby setting the first to third indicators below the desired heat distribution (with less heat deviation, etc.). Regarding the comparison with the heat distribution, one can, for example, perform energizing heating on multiple honeycomb structures (each sample) after quantifying the surface potential under specified energizing conditions (in the specific example described later, power: 1.5 kW, application time: 20 seconds), calculate the temperature difference at the location described later, and compare the relationship with this temperature difference.

[0071] Regarding the resistance ratio of the energized path (upper and lower sides), the following first indicator can be used to determine whether it is the desired heat distribution.

[0072] • First indicator: Calculate the resistance ratio between the upper and lower resistors (upper resistance / (upper resistance + lower resistance)), and set this value as 0.50 ± α (constant value). Regarding α (constant value), as follows... Figure 5As shown, the resistance ratio of the current path (the ratio between the upper resistance and the lower resistance) is plotted on the horizontal axis, and the difference between the maximum and minimum temperatures of the heat distribution at the ends of the upper and lower electrode layers is plotted on the vertical axis. The condition where the desired heat distribution is obtained from this point (the difference between the maximum and minimum temperatures of the heat distribution becomes smaller, and the heat deviation becomes smaller) is set as normal. α is set according to the location of the sample that becomes normal.

[0073] Regarding the voltage sharing rate of the power supply path, the following second indicator can be used to determine whether it is the desired heat distribution.

[0074] • Second index: Calculate the surface potential difference P between electrode layer A1 or A2 and the outer peripheral wall of the honeycomb structure, and the surface potential difference Q between electrode layer B1 or B2 and the outer peripheral wall of the honeycomb structure. Calculate the voltage sharing rate (P / P+Q) of the current-carrying path of the honeycomb structure, and set this value as 0.50±α (constant value) as the index. At this time, if... Figure 6 As shown, regarding the surface potentials of the upper side (electrode layers A2 and B2) and lower side (electrode layers A1 and B1) of the honeycomb structure, according to... Figure 6 The voltage sharing ratio of the left side (surface potential difference P) and the total surface potential of the left and right sides (surface potential difference P+Q) of the honeycomb structure in the graph is calculated. Figure 6 In the diagram, the horizontal axis represents the distance measured from a specified position on the outer perimeter wall, and the vertical axis represents the surface potential at the measured location when the surface potential difference (overall voltage) between the lowest and highest surface potential points is set to 1 and the overall voltage is normalized. Regarding α (a constant value), as... Figure 7 As shown, the voltage sharing rate of the energized path is plotted on the horizontal axis, and the temperature difference between the high-temperature side and the low-temperature side of the electrode layer in the heat distribution at the ends of the left and right electrode layers is plotted on the vertical axis. The values ​​of each sample are plotted, and the situation where the desired heat distribution is obtained from this point (the temperature difference at the ends of the electrode layers in the heat distribution becomes smaller, and the heat deviation becomes smaller) is set as normal. α is set according to the location of the sample that becomes normal.

[0075] The quantification of the surface potentials of electrode layers A1, A2, B1, and B2 can be achieved by using the following third indicator to determine whether the desired heat distribution is obtained.

[0076] • Third indicator: such as Figure 6As shown, the total voltage R shared by electrode layers A1 (B1) and A2 (B2) was calculated, and the total voltage sharing ratio (R / 1) of the electrode layers relative to the overall voltage (the standardized voltage of the whole) was calculated. As the overall voltage, in the surface potential measurements of the upper or lower half of the honeycomb structure, the surface potential difference between the lowest and highest points was standardized to 1 and set as the standardized voltage of the whole. Furthermore, the total voltage shared by the electrode layers refers to the value obtained by summing the surface potential difference between the lowest and highest points and the end of the electrode layer.

[0077] The third indicator is a threshold value for the total voltage sharing rate of the electrode layer. This threshold sets the upper limit for the voltage sharing rate of electrode layers with a temperature difference of T1°C or higher between the electrode layer's tip and center, and the lower limit for the voltage sharing rate of electrode layers with a temperature difference of T2°C or lower. It should be noted that T1 can be, for example, set to 0°C or higher to facilitate current distribution from the center to the tip of the electrode layer. On the other hand, T2 can be appropriately set based on the diameter, volume, resistivity of the honeycomb structure, and the electrode layers themselves. Figure 8 In the figure, the total voltage sharing rate of the electrode layer is plotted on the horizontal axis, and the temperature difference (°C) of the heat distribution between the end and center of the electrode layer is plotted on the vertical axis. In this case, the situation between the lower and upper thresholds is presumed to have the desired heat distribution (the difference between the maximum and minimum temperatures of the heat distribution becomes smaller, and the heat deviation becomes smaller).

[0078] According to an embodiment of the present invention, a method for estimating the heat distribution of a honeycomb structure involves passing a small current through the honeycomb structure 10 to a degree that prevents it from heating up, measuring the surface potential of the honeycomb structure 10, and quantifying at least one of the following based on the measured surface potentials: resistance at multiple locations within the honeycomb structure, resistance ratio of the current-carrying path, voltage sharing rate, and surface potential of electrode layers A1, A2, B1, and B2. Based on the quantified values, a desired heat distribution can be estimated. Therefore, it eliminates the need to heat and cool the honeycomb structure or electrically heated carrier, enabling energy-saving (low-cost) inspection, and thus, estimation can be performed simply and inexpensively. Furthermore, according to an embodiment of the present invention, since the electrode layers are segmented, the method for estimating the heat distribution of a honeycomb structure can calculate the resistance ratio and voltage sharing rate of the current-carrying path (upper / lower side), and calculate the total voltage sharing rate in the electrode layers. Based on this value, a preferred heat distribution of the honeycomb structure can be estimated.

[0079] <Manufacturing Method of Honeycomb Structures>

[0080] Regarding the method for manufacturing a honeycomb structure according to the embodiments of the present invention, firstly, as described above, by using the method for estimating the heat distribution of the honeycomb structure according to the embodiments of the present invention, at least one of the resistance at multiple locations within the honeycomb structure 10, the resistance ratio of the current path, the voltage sharing rate, and the surface potential of the electrode layers A1, A2, B1, and B2 is quantified, and a quantitative value is calculated.

[0081] Next, based on the threshold obtained in the process of estimating the heat distribution within the honeycomb structure, the quantitative value is evaluated, and qualified products are selected. The selection criteria for qualified products can be appropriately set based on the threshold required for the honeycomb structure 10. For example, a selection criterion could be: quantifying the resistance ratio, voltage sharing ratio, and surface potential of the electrode layers A1, A2, B1, and B2 by passing through the aforementioned specified minute current, estimating the heat distribution of the honeycomb structure, and evaluating it based on the threshold obtained in this process using the aforementioned first to third indicators that represent the desired heat distribution. If the threshold values ​​given by these indicators are met, the product is designated as qualified.

[0082] According to the method for manufacturing a cellular structure according to an embodiment of the present invention, a quantitative value is calculated as described above, a predetermined index is set, and a quantitative value is evaluated based on a threshold in the index, thereby obtaining a cellular structure that is selected as a qualified product. Therefore, it is possible to simply and cheaply produce cellular structures selected based on high-precision evaluation.

[0083] <Manufacturing Method of Electric Heating Carrier>

[0084] (1. Electric heating carrier)

[0085] Figure 4 This is a simplified cross-sectional view of the electrically heated carrier 20 according to an embodiment of the present invention, perpendicular to the extending direction of the compartment. The electrically heated carrier 20 includes: the honeycomb structure 10 described above and metal terminals 21a and 21b.

[0086] (2. Metal terminals)

[0087] Metal terminals 21a and 21b are respectively disposed on electrode layers A1 and A2, and electrode layers B1 and B2 of the honeycomb structure 10, and are electrically connected. Accordingly, if a voltage is applied to the metal terminals 21a and 21b through the electrode layers A1, A2, B1, and B2, electricity can be passed through and the honeycomb structure 10 can be heated by Joule heating.

[0088] The materials used for the metal terminals 21a and 21b can be any metal, with no particular restrictions. Elemental metals and alloys can also be used. However, from the viewpoints of corrosion resistance, resistivity, and linear expansion, alloys containing at least one element selected from the group consisting of Cr, Fe, Co, Ni, and Ti are preferred, and stainless steel and Fe-Ni alloys are more preferred. The shape and size of the metal terminals 21a and 21b are not particularly limited and can be appropriately designed according to the size and electrical performance of the electrically heated carrier 20.

[0089] By supporting the catalyst on the electrically heated carrier 20, the electrically heated carrier 20 can be used as a catalyst. Fluids such as automobile exhaust can flow through the flow path of the multiple compartments 15. Examples of catalysts include noble metal-based catalysts and catalysts other than noble metal-based catalysts. Examples of noble metal-based catalysts include three-way catalysts and oxidation catalysts in which noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are supported on the surface of alumina micropores and co-catalysts such as cerium dioxide and zirconium oxide are included; or NOx absorption and reduction catalysts (LNT catalysts) containing alkaline earth metals and platinum as NOx absorption and storage components are also included. Examples of catalysts that do not use noble metals include NOx selective reduction catalysts (SCR catalysts) containing copper-substituted zeolites or iron-substituted zeolites. Furthermore, two or more catalysts selected from the group consisting of these catalysts can be used. It should be noted that there are no particular limitations on the catalyst support method; conventional methods for supporting catalysts on honeycomb structures can be used.

[0090] (3. Manufacturing method of electrically heated carrier)

[0091] Regarding the manufacturing method of the electrically heated carrier according to the embodiments of the present invention, firstly, a honeycomb structure 10 according to the embodiments of the present invention is prepared, and metal terminals 21a and 21b are provided on the electrode layers A1, A2, B1 and B2 of the honeycomb structure 10 by welding or thermal spraying.

[0092] Next, as described above, the quantitative value in the third process of the honeycomb structure 10 before inspection (specifically, before the inspection process described later) is calculated using the method for estimating the heat distribution of the honeycomb structure according to the embodiments of the present invention.

[0093] Next, an inspection process is performed, namely, evaluating the quantitative values ​​in the third process based on the threshold obtained in the estimation process of heat distribution within the honeycomb structure 10, and screening out qualified products. Through such an inspection process, the electrically heated carrier 20 can be manufactured. It should be noted that the quantitative values ​​in the third process of the honeycomb structure 10 before inspection can also be evaluated using the estimation method of heat distribution within the honeycomb structure 10, and qualified products can be screened out. Then, metal terminals 21a and 21b are provided on the electrode layers A1, A2, B1, and B2 of the qualified honeycomb structure 10.

[0094] The selection criteria for qualified products can be appropriately set based on the threshold required for the honeycomb structure 10 to achieve the desired heat distribution. For example, the selection criteria for qualified products given in the above-described method for manufacturing honeycomb structures can be adopted.

[0095] (4. Specific examples)

[0096] The following examples illustrate specific examples to better understand the invention and its advantages; however, the invention is not limited to these specific examples.

[0097] <Concrete example 1>

[0098] (1. Preparation of the honeycomb structure)

[0099] Prepare Figure 1 The honeycomb structure shown is made of Si-SiC, with circular end faces of 100 mm in diameter and a height (length of the cell in the flow path direction) of 100 mm. The cell density is 93 cells / cm³. 2 The thickness of the partition wall is 101.6 μm, the porosity of the partition wall is 45%, and the average pore size of the partition wall is 8.6 μm.

[0100] The electrode layers A1, A2, B1, and B2 of the honeycomb structure are made of Si-SiC. The width of the slit between electrode layers A1 and A2, and between electrode layers B1 and B2, is 1.5 mm. The thickness of electrode layers A1, A2, B1, and B2 is 0.2 mm.

[0101] In addition, the honeycomb structure has 1.5 mm wide slits (thermal stress relief slits) on its outer peripheral wall, between the surface where electrode layer A1 is provided and the surface where electrode layer B1 is provided, and between the surface where electrode layer A2 is provided and the surface where electrode layer B2 is provided, respectively, along the extension direction of the compartment.

[0102] (2. Power-on test)

[0103] Next, as Figure 2As shown, two current terminals electrically connected to the power supply are pressed onto the electrode layers A1 and B1 of the honeycomb structure, respectively, so that a constant current (microcurrent) of 40mA flows through it, thus energizing it.

[0104] Next, with the cellular structure energized, the surface potential of a total of 36 locations separated along the circumferential direction were measured on the outer peripheral wall and the surfaces of electrode layers A1 and B1, from electrode layer A1 to electrode layer B1.

[0105] Next, as Figure 3 As shown, two current terminals electrically connected to the power supply are pressed onto electrode layers A2 and B2 of the honeycomb structure, respectively, so that a constant current (microcurrent) of 40mA flows through it, thus energizing it.

[0106] Next, with the cellular structure energized, the surface potential of a total of 36 locations separated along the circumferential direction were measured on the outer peripheral wall and the surfaces of electrode layers A2 and B2, from electrode layer A2 to electrode layer B2.

[0107] The graphs showing the relationship between the positions of the 36 locations measured from electrode layer A1 through the outer peripheral wall to electrode layer B1 and their surface potentials, and the relationship between the positions of the 36 locations measured from electrode layer A2 through the outer peripheral wall to electrode layer B2 and their surface potentials are presented in [the figure]. Figure 9 .

[0108] (3. Quantification of surface potential and estimation of heat distribution)

[0109] The resistance (current resistance), resistance ratio of the current path, voltage sharing rate, and surface potential of electrode layers A1, A2, B1, and B2 at multiple locations within the honeycomb structure were quantified. Regarding the estimation of heat distribution, the temperature difference (described later) was calculated for each sample (multiple honeycomb structures) when energized with a power of 1.5 kW for an application time of 20 seconds.

[0110] Specifically, the resistance at multiple locations within the honeycomb structure is estimated by averaging the surface potential differences between the start and end points at 36 locations measured from electrode layer A1 through the outer peripheral wall to electrode layer B1, and the surface potential differences between the start and end points at 36 locations measured from electrode layer A2 through the outer peripheral wall to electrode layer B2.

[0111] Based on the surface potential data, determine the electrode layer with the lower surface potential among A1 and B1, or A2 and B2, and calculate the total voltage sharing (R) of electrode layers A1, A2, B1, and B2. Then, calculate the total voltage sharing ratio (R / 1) of the electrode layers relative to the overall voltage (the overall normalized voltage).

[0112] For multiple honeycomb structures (each sample), the total voltage sharing rate of the electrode layers was calculated similarly, such as... Figure 8 As shown, the total voltage sharing rate of the electrode layer relative to the overall standardized voltage is plotted on the horizontal axis, and the temperature difference (°C) of the heat distribution between the electrode layer tip and the center of the electrode layer is plotted on the vertical axis. Regarding the total voltage sharing rate of the electrode layer, a threshold voltage sharing rate is set as the upper limit and a threshold voltage sharing rate is set as the lower limit. The case where the value falls between the lower and upper thresholds is presumed to have the desired heat distribution (the average temperature difference of the heat distribution decreases, and the heat deviation decreases).

[0113] Based on the surface potential difference at the outer peripheral walls between electrode layers A1 and B1 and between electrode layers A2 and B2, the resistance ratio of the current-carrying path of the cellular structure is calculated. Specifically, the difference between the lowest surface potential of electrode layer A1 and the highest surface potential of electrode layer B1 (lower resistance) is calculated at 36 locations measured from electrode layer A1 through the outer peripheral wall to electrode layer B1. Then, the difference between the lowest surface potential of electrode layer A2 and the highest surface potential of electrode layer B2 (upper resistance) is calculated at 36 locations measured from electrode layer A2 through the outer peripheral wall to electrode layer B2. Finally, the ratio between the upper resistance and the lower resistance (upper resistance / (upper resistance + lower resistance)) is calculated, thereby determining the resistance ratio of the current-carrying path of the cellular structure.

[0114] For multiple cellular structures (each sample), the resistivity ratio of the current-carrying path was calculated similarly, such as... Figure 5 As shown, a graph is plotted with the ratio of the resistance between the upper and lower sides of the current-carrying path (the resistance ratio of the current-carrying path in the honeycomb structure) as the horizontal axis and the difference between the maximum and minimum temperatures of the heat distribution at the ends of the upper and lower electrode layers as the vertical axis, for each sample. A threshold value (0.50 ± α) is set for the ratio of the upper and lower resistance of the current-carrying path. Cases within this threshold are considered to have the desired heat distribution (a smaller difference between the maximum and minimum temperatures of the heat distribution, and a smaller heat deviation).

[0115] Based on surface potential data, determine the electrode layer with the lower surface potential (either A1 or B1, or A2 or B2), and calculate the voltage sharing ratio of the current-carrying path in the honeycomb structure. Specifically, calculate the surface potential difference P between a point with a constant surface potential in electrode layer A1 (or A2) and a specified position on the outer peripheral wall, and the surface potential difference Q between a point with a constant surface potential in electrode layer B1 (or B2) and a specified position on the outer peripheral wall. Based on these surface potential differences P and Q, calculate the voltage sharing ratio (P / P+Q) of the current-carrying path. It should be noted that the specified position on the outer peripheral wall is: a position where the distance between electrode layer A1 (or A2) and a certain position on the outer peripheral wall (the left half of the outer peripheral wall) is equal to the distance between electrode layer B1 (or B2) and a certain position on the outer peripheral wall (the right half of the outer peripheral wall).

[0116] For multiple cellular structures (each sample), the voltage sharing rate of the current-carrying path was calculated similarly, such as... Figure 7 As shown, the voltage sharing ratio of the energizing path is plotted on the horizontal axis, and the temperature difference between the high-temperature and low-temperature electrode layer ends at the ends of the left and right electrode layers is plotted on the vertical axis. A threshold value (0.50±α) is set for the voltage sharing ratio of this energizing path, and cases within this threshold are considered to have the desired heat distribution (the difference between the maximum and minimum temperatures of the heat distribution decreases, and the heat deviation decreases).

[0117] As described above, the resistance ratio of the current-carrying paths, the voltage sharing rate of the current-carrying paths, and the surface potential of electrode layers A1, A2, B1, and B2 (total voltage sharing rate of the electrode layers) within multiple honeycomb structures (each sample) are quantified. Based on these quantitative values, the heat distribution within the honeycomb structure is estimated, thereby estimating a scenario with the desired heat distribution. Specifically, the resistance ratio of the current-carrying paths, the voltage sharing rate of the current-carrying paths on the low-resistance side, and the total voltage sharing rate of the electrode layers on the low-resistance side relative to the overall standardized voltage are calculated. These calculated values ​​are compared with the relationship between the heat distribution at these values, and the first to third indicators mentioned above are set as the desired heat distribution, thereby estimating the heat distribution within the honeycomb structure.

[0118] It should be noted that by comparing the difference between the measured surface potential and the designed surface potential, the resistance difference between the measured value and the designed value of the honeycomb structure can be estimated.

[0119] As shown in Example 1, a tiny current is passed through the honeycomb structure to the point that it does not heat up. The change in the surface potential of the honeycomb structure is measured and its distribution is quantified, thereby allowing the estimation of its heating performance. Therefore, the heat distribution of the honeycomb structure can be estimated simply and inexpensively.

Claims

1. A method for estimating the heat distribution of a honeycomb structure, wherein, Honeycomb structures have the following characteristics: The columnar honeycomb structure has an outer peripheral wall and a partition wall. The partition wall is disposed on the inner side of the outer peripheral wall and divides the space into multiple compartments. The multiple compartments are connected from one end face to the other end face to form a flow path. as well as, A pair of electrode layers, namely electrode layer A and electrode layer B, are disposed on the surface of the outer peripheral wall of the columnar honeycomb structure portion in an opposing manner, sandwiching the central axis of the columnar honeycomb structure portion. The electrode layer A and electrode layer B are electrically separated into electrode layer A1 and electrode layer A2, and electrode layer B1 and electrode layer B2, respectively. Electrode layers A1 and B1, and electrode layers A2 and B2, are located on the side of the outer peripheral surface of the honeycomb structure that are closer to each other. The method for estimating the heat distribution of the honeycomb structure is characterized by including the following steps: In the first step, a predetermined minute current is passed between electrode layer A1 and electrode layer B1 to energize the columnar honeycomb structure. The surface potentials at multiple locations separated along the circumferential direction are measured on the outer peripheral wall and the surface of the electrode layers, from electrode layer A1 to electrode layer B1. In the second step, a predetermined minute current is passed between electrode layer A2 and electrode layer B2 to energize the columnar honeycomb structure. The surface potentials at multiple locations separated along the circumferential direction are measured on the outer peripheral wall and the surface of the electrode layers, from electrode layer A2 to electrode layer B2. The third step involves quantifying, based on the measured surface potentials at the multiple locations, at least one of the following: resistance at multiple points within the honeycomb structure, resistance ratio of the current-carrying path, voltage sharing rate, and surface potentials of electrode layers A1, A2, B1, and B2; and The process of estimating the heat distribution within the honeycomb structure based on the quantitative values ​​obtained in the third process. The microcurrent is 1 to 1000 mA.

2. The method for estimating the heat distribution of a honeycomb structure according to claim 1, characterized in that, Along the extension direction of the compartments of the columnar honeycomb structure, the surface potentials at multiple locations separated circumferentially from electrode layer A1 to electrode layer B1, and at multiple locations separated circumferentially from electrode layer A2 to electrode layer B2, are measured.

3. The method for estimating the heat distribution of a honeycomb structure according to claim 1 or 2, characterized in that, The electrode layers A1 and A2, as well as the electrode layers B1 and B2, are electrically separated through slits.

4. The method for estimating the heat distribution of a honeycomb structure according to claim 1 or 2, characterized in that, In the first step, the surface potential measurement at the multiple locations involves measuring the surface potential at at least two locations among electrode layer A1, electrode layer B1, and the outer peripheral wall between electrode layers A1 and B1. In the second step, the surface potential at the multiple locations is measured at at least two locations in the electrode layer A2, electrode layer B2, and the outer peripheral wall between electrode layers A2 and B2.

5. The method for estimating the heat distribution of a honeycomb structure according to claim 1 or 2, characterized in that, The third step includes: calculating the resistance ratio of the energized path based on the surface potential difference described below (i) and / or (ii). (i) In the first step, in the measurement of surface potential at the plurality of locations, the difference between the lowest surface potential at the measurement location in electrode layer A1 and the highest surface potential at the measurement location in electrode layer B1, (ii) In the second step, in the determination of surface potential at the plurality of locations, the difference between the lowest surface potential at the measurement location in electrode layer A2 and the highest surface potential at the measurement location in electrode layer B2.

6. The method for estimating the heat distribution of a honeycomb structure according to claim 1 or 2, characterized in that, The third step includes: calculating the total voltage of the electrode layers A1, A2, B1, and B2 based on the surface potentials described in (iii) and / or (iv) below, and calculating the total voltage sharing rate of the electrode layers A1, A2, B1, and B2 relative to the overall voltage. (iii) In the first step, the surface potential is measured at multiple locations in the electrode layer A1 and the electrode layer B1 to obtain the surface potential in the electrode layer A1 and the surface potential in the electrode layer B1. (iv) In the second step, the surface potential is measured at multiple locations in the electrode layer A2 and the electrode layer B2 to obtain the surface potential in the electrode layer A2 and the surface potential in the electrode layer B2.

7. The method for estimating the heat distribution of a honeycomb structure according to claim 1 or 2, characterized in that, The third step includes: calculating the voltage sharing rate (P / P+Q) of the power path of the cellular structure based on the surface potential differences P and Q as described below (v). (v) The surface potential difference P between the electrode layer A1 or electrode layer B1 and the outer peripheral wall in the first process, and the surface potential difference Q between the electrode layer A2 or electrode layer B2 and the outer peripheral wall in the second process.

8. A method for manufacturing a honeycomb structure, characterized in that, The process includes the following steps: The process of calculating the quantitative value in the third step of the honeycomb structure before inspection using the estimation method of heat distribution of the honeycomb structure according to any one of claims 1 to 7; and In the inspection process, based on the threshold obtained in the process of estimating the heat distribution within the honeycomb structure, the quantitative value in the third process is evaluated, and qualified products are selected.

9. A method for manufacturing an electrically heated carrier, characterized in that, The process includes the following steps: The process of calculating the quantitative value in the third step of the honeycomb structure before inspection using the estimation method of heat distribution of the honeycomb structure according to any one of claims 1 to 7; and In the inspection process, based on the threshold obtained in the process of estimating the heat distribution within the honeycomb structure, the quantitative value in the third process is evaluated, and qualified products are selected.

10. The method for manufacturing an electrically heated carrier according to claim 9, characterized in that, The method for manufacturing the electrically heated carrier includes: Before the step of calculating the quantitative value in the third step of the honeycomb structure, a step of setting metal terminals on the electrode layer A and electrode layer B of the honeycomb structure before inspection.

11. The method for manufacturing an electrically heated carrier according to claim 9, characterized in that, The method for manufacturing the electrically heated carrier includes: Following the inspection process, a process is performed to install metal terminals on electrode layer A and electrode layer B of the honeycomb structure.

Images