Honeycomb structure

Abstract

To provide a honeycomb structure capable of improving exhaust gas purification performance, and suppressing breakage of a honeycomb segment.SOLUTION: There is provided a honeycomb structure which is formed by combining honeycomb segments which have a partition wall for partitioning and forming many cells through an adhesive layer, the honeycomb structure is configured so that a heating wire is arranged in the adhesive layer, and an end part of the heating wire has an electrode terminal connected thereto for electrification from an outside. The electrode terminal and the heating wire are joined in the adhesive layer. A thickness of a junction where the heating wire and the electrode terminal are joined, is thinner than a total sum of thicknesses of the heating wire and the electrode terminal on a non junction part where the electrode terminal and the heating wire are not joined.SELECTED DRAWING: Figure 5B

Description

Technical Field

[0001] The present invention relates to a honeycomb structure.

Background Art

[0002] In order to purify harmful substances contained in the exhaust gas discharged from an engine, an exhaust gas purification device including a honeycomb substrate carrying a catalyst capable of purifying the exhaust gas is provided in the exhaust pipe path. In order to improve the purification efficiency of harmful substances by the exhaust gas purification device, it is necessary to maintain the temperature inside the exhaust gas purification device at a temperature suitable for catalyst activation (hereinafter also referred to as the catalyst activation temperature).

[0003] Patent Document 1 discloses an exhaust gas purification device that collects soot contained in the exhaust gas of a diesel engine and purifies the exhaust gas. In the exhaust gas purification device described in Patent Document 1, a plurality of filters (also referred to as honeycomb segments) are arranged adjacent to each other. Between the honeycomb segments, a heating wire as a heating element for burning the soot deposited inside the filter is arranged.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The heating wire disposed between the honeycomb segments is joined to the electrode terminal by means such as welding, and then connected to an external power source via the electrode terminal. In order to efficiently transfer the heat energy of the heating wire to the honeycomb segment, it is necessary to arrange the end portion of the heating wire between the filters. That is, it is necessary to arrange the joint portion between the heating wire and the electrode terminal between the honeycomb segments.

[0006] However, when the joint between the heating element and the electrode terminal was placed between honeycomb segments, the joint could come into contact with the honeycomb segments, potentially damaging them. The above problems can be avoided by increasing the gaps between honeycomb segments, but in this case, the volume proportion occupied by the honeycomb segments decreases, which leads to a problem of reduced exhaust gas purification performance.

[0007] This invention was made to solve the above problems, and the object of this invention is to provide a honeycomb filter that can achieve both improved exhaust gas purification performance and suppression of damage to the honeycomb segments. [Means for solving the problem]

[0008] In other words, the honeycomb structure of the present invention is a honeycomb structure formed by combining a plurality of honeycomb segments having partitions that divide a large number of cells via an adhesive layer, wherein a heating wire is arranged inside the adhesive layer, an electrode terminal for supplying power from the outside is connected to the end of the heating wire, the heating wire and the electrode terminal are joined inside the adhesive layer, and the thickness of the joint where the heating wire and the electrode terminal are joined is thinner than the sum of the thickness of the heating wire and the thickness of the electrode terminal in the non-jointed portion where the heating wire and the electrode terminal are not joined.

[0009] The thickness of the joint where the heating element and the electrode terminal are joined is usually equal to or greater than the sum of the thicknesses of the heating element and the electrode terminal. Therefore, if the joint is placed inside the adhesive layer, it is not possible to simultaneously reduce the gaps between honeycomb segments to improve exhaust gas purification efficiency and suppress damage to the honeycomb segments caused by the joint.

[0010] In contrast, in the honeycomb structure of the present invention, the thickness of the joint is thinner than the sum of the thickness of the heating wire and the electrode terminal in the non-jointed areas. Therefore, it is possible to improve exhaust gas purification performance by reducing the thickness of the adhesive layer placed between the honeycomb segments, while suppressing contact between the joint and the honeycomb segments and damage to them.

[0011] In the honeycomb structure of the present invention, it is preferable that the thickness of the joint portion is 1 mm or less. If the thickness of the joint is 1 mm or less, damage to the honeycomb segment can be further suppressed. Furthermore, the thickness of the adhesive layer can be reduced.

[0012] In the honeycomb structure of the present invention, the thickness of the adhesive layer is preferably 1 to 3 mm. When the adhesive layer is 1 to 3 mm thick, the volume of honeycomb segments within the honeycomb structure can be increased, thereby improving exhaust gas purification performance.

[0013] In the honeycomb structure of the present invention, it is preferable that the heating element and the electrode terminals overlap at the joint when viewed from the thickness direction of the adhesive layer. With the above configuration, the contact area between the heating element and the electrode terminal can be increased, thereby improving the bonding strength.

[0014] In the honeycomb structure of the present invention, it is preferable that in a cross section perpendicular to the longitudinal direction of the heating wire, the cross-sectional area of ​​the heating wire at the joint portion and the cross-sectional area of ​​the heating wire at the non-joint portion are substantially the same, the cross-sectional shape of the heating wire at the joint portion is substantially flattened, and the cross-sectional shape of the heating wire at the non-joint portion is substantially circular. With the above configuration, it is possible to prevent abnormal heat generation in the heating element and to increase the contact area between the heating element and the electrode terminal at the joint, thereby increasing the joint strength.

[0015] In the honeycomb structure of the present invention, it is preferable that the thickness of the electrode terminal at the joint portion is thinner than the thickness of the electrode terminal at the non-joint portion. With the above configuration, the thickness of the joint portion can be reduced without deforming the heating wire.

[0016] In the honeycomb structure of the present invention, it is preferable that the heating wire and the electrode terminal overlap at the joint portion when viewed from a direction perpendicular to the thickness direction of the adhesive layer. With the above configuration, the thickness of the joint portion can be further reduced.

[0017] In the honeycomb structure of the present invention, it is preferable that a plurality of heating wires are connected in parallel. When a plurality of heating wires are connected in parallel, even if a part of the heating wire is disconnected, the entire circuit constituted by the heating wires provided in the honeycomb structure will not be disconnected, so that the reduction in heating performance can be minimized.

[0018] [[ID=IS]]In a plan view of the honeycomb structure of the present invention, the honeycomb segments are combined in a lattice pattern vertically and horizontally, and it is preferable that all the heating wires are arranged in the same direction along a first direction which is one of the vertical and horizontal directions of the lattice pattern. With such a configuration, local heat generation can be suppressed. In addition, since no heating wire is arranged in the direction perpendicular to the first direction, the adhesive force between the honeycomb segments by the adhesive layer can be increased.

Brief Description of Drawings

[0019] [Figure 1] FIG. 1 is a perspective view schematically showing an example of the honeycomb structure of the present invention. <00L0089> [Figure 2] FIG. 2 is a cross-sectional view in a direction perpendicular to the longitudinal direction of the honeycomb segment. [Figure 3] [[ID=SS]]FIG. 3 is a partial cross-sectional view of the honeycomb structure shown in FIG. 1. [Figure 4]FIG. 4 is an end view of the honeycomb structure shown in FIG. 1 as viewed from the first end face side. [Figure 5A] FIG. 5A is a schematic diagram showing an example of a joint portion between a heating wire and an electrode terminal in the honeycomb structure of the present invention. [Figure 5B] FIG. 5B is a side view of FIG. 5A as viewed from the side of the heating wire. [Figure 5C] FIG. 5C is a side view of FIG. 5A as viewed from the electrode terminal side. [Figure 5D] FIG. 5D is a cross-sectional view taken along line B-B in FIG. 5B. [Figure 6A] FIG. 6A is a schematic diagram showing another example of a joint portion between a heating wire and an electrode terminal in the honeycomb structure of the present invention. [Figure 6B] FIG. 6B is a side view of FIG. 6A as viewed from the side of the heating wire. [Figure 6C] FIG. 6C is a side view of FIG. 6A as viewed from the electrode terminal side. [Figure 7A] FIG. 7A is a schematic diagram showing yet another example of a joint portion between a heating wire and an electrode terminal in the honeycomb structure of the present invention. [Figure 7B] FIG. 7B is a side view of FIG. 7A as viewed from the side of the heating wire. [Figure 7C] FIG. 7C is a side view of FIG. 7A as viewed from the electrode terminal side. [Figure 8A] FIG. 8A is a schematic diagram showing yet another example of a joint portion between a heating wire and an electrode terminal in the honeycomb structure of the present invention. [Figure 8B] FIG. 8B is a side view of FIG. 8A as viewed from the side of the heating wire. [Figure 8C] FIG. 8C is a side view of FIG. 8A as viewed from the electrode terminal side.

[0020] (Detailed Description of the Invention) [Honeycomb Structure] Hereinafter, the honeycomb structure of the present invention will be described. The honeycomb structure of the present invention is a honeycomb structure formed by combining a plurality of honeycomb segments having partitions that divide a large number of cells via an adhesive layer, wherein a heating wire is arranged inside the adhesive layer, an electrode terminal for supplying power from the outside is connected to the end of the heating wire, the heating wire and the electrode terminal are joined inside the adhesive layer, and the thickness of the joint where the heating wire and the electrode terminal are joined is thinner than the sum of the thickness of the heating wire and the thickness of the electrode terminal in the non-jointed portion where the heating wire and the electrode terminal are not joined.

[0021] Figure 1 is a schematic perspective view showing an example of the honeycomb structure of the present invention. The honeycomb structure 1 shown in Figure 1 is made up of multiple honeycomb segments 20, each having a partition wall 22 that divides a large number of cells 21, and has a first end face 11 through which gas flows in and a second end face 12 through which gas flows out. The direction in which the cells 21 of the honeycomb segment 20 extend is defined as the longitudinal direction (the direction indicated by the double-headed arrow L in Figure 1). Multiple honeycomb segments are joined together via an adhesive layer 30. Furthermore, the electrode terminal 40 protrudes from the first end face 11.

[0022] The materials used to make up the honeycomb segments (partitions) should preferably have high thermal conductivity, such as SiC or Si-impregnated SiC.

[0023] The thickness of the partition walls is preferably uniform. Specifically, the thickness of the partition walls is preferably less than 0.30 mm, and preferably 0.05 mm or more.

[0024] The shape of the cell is not limited to a rectangular prism; examples include triangular prisms, hexagonal prisms, and so on. The shapes of the cells may differ, but it is preferable that they are all the same. That is, it is preferable that the size of the cells surrounded by partitions is the same in a cross section perpendicular to the longitudinal direction of the honeycomb segment.

[0025] The porosity of the septum should preferably be 50% or less. If the porosity of the bulkhead is 50% or less, it is possible to achieve both high mechanical strength and exhaust gas purification performance.

[0026] If the porosity of the partition wall exceeds 50%, the porosity becomes too high, which reduces the mechanical properties of the honeycomb segment, making the honeycomb structure more susceptible to cracks and fractures during use.

[0027] The shape of the honeycomb structure is not particularly limited and is not limited to a cylindrical shape; examples include prismatic, elliptical, oblong, and chamfered prismatic shapes (for example, chamfered triangular prismatic shapes).

[0028] When the shape of the honeycomb structure is cylindrical, it is preferable that the ratio of the length of the honeycomb structure in the longitudinal direction to the diameter of the end face of the honeycomb structure (length / diameter) is 0.8 or less.

[0029] The length of the honeycomb structure in the longitudinal direction is preferably 150 mm or less, and preferably 50 mm or more.

[0030] Figure 2 is a cross-sectional view of the honeycomb segment perpendicular to the longitudinal direction. When exhaust gas emitted from the internal combustion engine (shown by arrow G in Figure 2, indicating the flow of exhaust gas) reaches the honeycomb segment 20, the exhaust gas flows into the cell 21 from the first end face 11 of the honeycomb segment 20. Furthermore, the exhaust gas passes through the cell 21 while in contact with the catalyst 23 supported on the partition wall 22. At this time, CO, HC, NO in the exhaust gas X These harmful gas components are purified by the catalyst 23 supported on the partition wall 22. The exhaust gas then flows out of the cell 21 at the second end face 12 of the honeycomb segment 20.

[0031] The catalyst 23 is not particularly limited as long as it can treat the exhaust gas, but examples include catalysts made of precious metals such as platinum, palladium, and rhodium, as well as zeolites, titania, and vanadium oxide. The zeolite may be a CHA-type zeolite, and the zeolite may be ion-exchanged with Cu or the like. These catalysts may be used individually or in combination of two or more types. When these catalysts are supported, CO, HC, NO X It can effectively purify toxic exhaust gases such as those mentioned above. In particular, it is preferable to use a honeycomb structure as an SCR catalyst that reduces NOx using zeolite as a catalyst.

[0032] Figure 3 is a partial cross-sectional view of the honeycomb structure shown in Figure 1. A heating element 50 is placed between adjacent honeycomb segments 20. Electrode terminals 40 are provided at both ends of the heating element 50, and the electrode terminals 40 protrude from the first end face 11. The heating element 50 is positioned inside the adhesive layer 30.

[0033] Nickel-chromium alloy, nickel-chromium-iron alloy, chromium-iron-aluminum alloy, etc., can be used as materials for the heating element. Furthermore, the heating element can be used in either a wire or plate form. When the heating element is linear, its diameter is not particularly limited, but is preferably 0.1 to 1 mm. When the heating element is plate-shaped, its thickness is not limited, but is preferably 0.1 to 0.5 mm, and its width is preferably 1 to 10 mm.

[0034] The adhesive layer is formed by applying and drying an adhesive paste containing an inorganic binder and inorganic particles. The adhesive layer may further contain inorganic fibers and / or whiskers. Furthermore, the thickness of the adhesive layer is preferably 1 to 3 mm, more preferably 1 to 2 mm, and even more preferably 1 to 1.5 mm.

[0035] Electrode terminals 40 are connected to both ends of the heating element 50, and the electrode terminals 40 protrude from the first end face 11. Power can be supplied from the electrode terminals 40 to the heating element 50 to generate heat. The electrode terminals 40 are plate-shaped and are joined to the heating element 50. The electrode terminals 40 are connected to each other by wiring that connects the electrode terminals.

[0036] The heating element 50 shown in Figure 3 is a composite heating element in which multiple heating elements (50A, 50B, 50C) are connected in parallel. Electrode terminals 40 are connected to both ends of each heating element. If the heating elements are in a bundled configuration, even if one of the multiple heating elements breaks, the entire bundle will not break, thus minimizing the reduction in heating performance.

[0037] The area in the longitudinal direction of the honeycomb structure in which the heating wires are placed is not limited; heating wires may be provided only in a part of the longitudinal direction of the honeycomb structure, or they may be provided along the entire longitudinal direction.

[0038] Figure 4 is an end view of the honeycomb structure shown in Figure 1, viewed from the first end face side. In the end view of the honeycomb structure 1 shown in Figure 4, the honeycomb segments 20 are arranged in a grid pattern both vertically and horizontally. One direction of this grid pattern is designated as the first direction, and the direction perpendicular to the first direction is designated as the second direction. In Figure 4, the horizontal direction is considered the first direction, and the vertical direction is considered the second direction.

[0039] All heating elements 50 are arranged in the same direction along the first direction. In Figure 4, the adhesive layer 30a along the first direction where the heating wire is located is shown with dark hatching, and the adhesive layer 30b along the second direction where the heating wire is not located is shown with light hatching. This configuration helps to suppress localized heat generation. Furthermore, since no heating wires are positioned in the second direction perpendicular to the first direction, the adhesive strength between the honeycomb segments by the adhesive layer can be increased.

[0040] As shown in Figure 4, the heating wires arranged in the adhesive layer 30a along the first direction are each in the form of a heating wire assembly. These heating wire assemblies are connected to each other in parallel. I will explain this in detail. The heating element arranged in the adhesive layer 30a1 along the first direction between the honeycomb segments is referred to as the first heating element 50a1. Between adjacent honeycomb segments at a position different from the position where the first heating element 50a1 is placed, there is another adhesive layer 30a2 aligned with the first direction. The heating element placed in the adhesive layer 30a2 is referred to as the second heating element 50a2. The first heating element 50a1 and the second heating element 50a2 are connected in parallel by wiring that connects the electrode terminals. Figure 4 shows six adhesive layers 30a aligned in the first direction, with a heating element arranged in each adhesive layer 30a. The six heating elements are connected in parallel by wiring.

[0041] When the heating elements are connected in parallel, even if some of the heating elements break, the entire circuit formed by the heating elements in the honeycomb structure will not break, thus minimizing the reduction in heating performance.

[0042] Both ends of the heating element are connected to electrode terminals. The part of the heating element that is joined to the electrode terminal is called the joint, and the rest is called the non-joint. Similarly, the part of the electrode terminal that is joined to the heating element is called the joint, and the rest is called the non-joint.

[0043] In a heating element, the cross-sectional shape of the joint and the non-jointed parts may be the same or different. Furthermore, in the heating element, the thickness of the joint may be the same as or different from the thickness of the non-jointed portion.

[0044] The thickness of the joint where the heating element and the electrode terminal are joined is thinner than the sum of the thickness of the heating element and the electrode terminal in the non-jointed areas where they are not joined.

[0045] If the thickness of the joint is thinner than the sum of the thickness of the heating element and the electrode terminals in the non-jointed areas, the thickness of the adhesive layer placed between the honeycomb segments can be reduced, improving exhaust gas purification performance while suppressing contact between the joint and the honeycomb segments, thereby preventing damage to the honeycomb segments.

[0046] The thickness of the joint is preferably 1 mm or less. If the thickness of the joint is 1 mm or less, damage to the honeycomb segment can be further suppressed. Furthermore, the thickness of the adhesive layer can be reduced.

[0047] When the adhesive layer is viewed from the thickness direction, it is preferable that the heating element and the electrode terminals overlap at the joint.

[0048] The thickness of the joint is preferably 90% or less of the sum of the thickness of the heating element and the electrode terminal in the non-jointed portion, more preferably 85% or less, and even more preferably 80% or less.

[0049] The joint strength of the joint is preferably 50N or more, more preferably 170N or more, even more preferably 210N or more, and most preferably greater than or equal to the tensile strength of the heating element. The joint strength can be measured using a tensile testing machine with a sample (measurement sample) consisting of a heating wire and an electrode terminal joined together.

[0050] The following describes an example of a joint in the honeycomb structure of the present invention.

[0051] Figure 5A is a schematic diagram showing an example of a joint between a heating wire and an electrode terminal in the honeycomb structure of the present invention. Figure 5B is a side view of Figure 5A, seen from the side of the heating wire. Figure 5C is a side view of Figure 5A, seen from the electrode terminal side. Figure 5D is a cross-sectional view of Figure 5B along line BB.

[0052] In the joint shown in Figure 5A, the heating element 50 and the electrode terminal 40 overlap when viewed from the thickness direction. Note that the thickness direction refers to the thickness direction of the adhesive layer.

[0053] As shown in Figures 5A, 5B, and 5C, the end portion 50a of the heating element 50 has a flattened cross-sectional shape. Also, as shown in Figure 5D, the cross-sectional shape of the portion of the heating element 50 other than the end portion 50a is approximately circular.

[0054] As shown in Figures 5B and 5C, the electrode terminal 40 has a flat plate shape with a constant thickness.

[0055] The heating element 50 and the electrode terminal 40 are joined to each other. Specifically, the end portion 50a of the heating element 50 is joined to the electrode terminal 40. Therefore, the end portion 50a of the heating element 50 is also called the joint portion of the heating element 50. The portion 40a where the electrode terminal 40 is joined to the end portion 50a of the heating element is also called the joint portion of the electrode terminal 40. The joint where the heating element 50 and the electrode terminal 40 are joined is indicated by the double-headed arrow J1 in Figure 5B. The non-jointed portion where the heating element 50 and the electrode terminal 40 are not joined is indicated by the double-headed arrow N1 in Figure 5B. The cross-sectional area of ​​the heating element 50 is approximately the same at the joint J1 and the non-joint N1. The cross-sectional shape of the heating element 50 at the joint J1 is approximately flattened, while the cross-sectional shape of the heating element 50 at the non-joint N1 is approximately circular.

[0056] The thickness T50a of the heating element 50 at the joint J1 is thinner than the thickness T50 of the heating element 50 at the non-joint N1. Also, the thickness T40a of the electrode terminal 40 at the joint J1 is the same as the thickness T40 of the electrode terminal 40 at the non-joint N1. The thickness T1 of the joint J1 where the heating element 50 and the electrode terminal 40 are joined is represented by the sum of the thickness T40a of the electrode terminal 40 and the thickness T50a of the heating element 50 at the joint J1. Therefore, the thickness T1 of the joint J1 is thinner than the sum of the thickness T50 of the heating element 50 and the thickness T40 of the electrode terminal 40 at the non-jointed section N1.

[0057] As shown in Figures 5A, 5B, and 5C, by deforming the tip of the heating wire into a flattened shape and joining the deformed portion to the electrode terminal, the thickness of the joint can be made thinner than the sum of the thickness of the heating wire and the electrode terminal in the non-jointed portion.

[0058] The thickness of the tip of the deformed heating element is preferably 50-80% of the thickness (wire diameter) of the undeformed heating element.

[0059] The configurations shown in Figures 5A, 5B, and 5C demonstrate that, in a cross-section perpendicular to the longitudinal direction of the heating wire, the cross-sectional area of ​​the heating wire at the joint and the cross-sectional area of ​​the heating wire at the non-jointed portion are approximately the same, the cross-sectional shape of the heating wire at the joint is approximately flattened, and the cross-sectional shape of the heating wire at the non-jointed portion is approximately circular.

[0060] Figure 6A is a schematic diagram showing another example of the joint between the heating wire and the electrode terminal in the honeycomb structure of the present invention. Figure 6B is a side view of Figure 6A as seen from the side of the heating wire. Figure 6C is a side view of Figure 6A as seen from the electrode terminal side.

[0061] In the joint shown in Figure 6A, the heating element 51 and the electrode terminal 41 overlap when viewed from the thickness direction.

[0062] The heating element 51 is linear in shape, with a uniformly approximately circular cross-sectional shape.

[0063] The electrode terminal 41 is a flat plate shape with a groove 60. When viewed from the thickness direction, the heating element 51 is positioned to overlap the groove 60.

[0064] The heating element 51 and the electrode terminal 41 are joined to each other. Specifically, the end portion 51a of the heating element 51 is joined to the electrode terminal 41. Therefore, the end portion 51a of the heating element 51 is also called the joint portion of the heating element 51. The portion 41a where the electrode terminal 41 is joined to the end portion 51a of the heating element is also called the joint portion of the electrode terminal 41. The joint where the heating element 51 and the electrode terminal 41 are joined is indicated by the double arrow J2 in Figure 6B. The non-jointed portion where the heating element 51 and the electrode terminal 41 are not joined is indicated by the double arrow N2 in Figure 6B. Furthermore, the cross-sectional area of ​​the heating element 51 is the same at both the joint J2 and the non-joint N2, and the cross-sectional shape of the heating element 51 at both the joint J2 and the non-joint N2 is approximately circular.

[0065] As shown in Figures 6B and 6C, the heating element 51 and the electrode terminal 41 overlap when viewed from a direction perpendicular to the thickness direction. In other words, a portion of the heating element 51 is embedded in the groove 60. The thickness of the electrode terminal 41 at the joint J2 where the groove 60 is formed is indicated by T41a, which is thinner than the thickness T41 of the electrode terminal 41 at the non-joint N2 where the groove 60 is not formed.

[0066] The thickness T2 of the joint J2 where the heating element 51 and the electrode terminal 41 are joined is represented by the sum of the thickness T41a of the electrode terminal 41a and the thickness T51a of the heating element 51 at the joint J2. Therefore, the thickness T2 of the joint J2 is thinner than the sum of the thickness T51 of the heating element 51 and the thickness T41 of the electrode terminal 41 at the non-jointed portion.

[0067] As shown in Figures 6A, 6B, and 6C, a groove is formed in the electrode terminal into which at least a portion of the heating wire can be embedded. By joining the heating wire and the electrode terminal with at least a portion of the heating wire embedded in the groove, the thickness of the joint can be made thinner than the sum of the thickness of the heating wire and the electrode terminal in the non-jointed portion.

[0068] In Figures 6A, 6B, and 6C, grooves 60 are formed on the electrode terminals 41 even at positions that do not come into contact with the heating element 51. However, grooves 60 may be provided only at positions that come into contact with the heating element 51.

[0069] In the configurations shown in Figures 6A, 6B, and 6C, the thickness of the electrode terminals at the joint is thinner than the thickness of the electrode terminals at the non-jointed areas.

[0070] When grooves are provided in the electrode terminals, the depth of the grooves is preferably 20 to 60% of the thickness of the electrode terminals.

[0071] Figure 7A is a schematic diagram showing yet another example of the joint between the heating wire and the electrode terminal in the honeycomb structure of the present invention. Figure 7B is a side view of Figure 7A as seen from the side of the heating wire. Figure 7C is a side view of Figure 7A as seen from the electrode terminal side.

[0072] As shown in Figure 7A, the heating element 52 and the electrode terminal 42 do not overlap when viewed from the thickness direction. On the other hand, as shown in Figure 7C, the heating element 52 and the electrode terminal 42 overlap when viewed from a direction perpendicular to the thickness direction.

[0073] As shown in Figure 7A, the tip 52a of the heating element 52 is bent at a 90° angle to form an L-shape. The heating element 52 is a linear shape with a uniformly approximately circular cross-section.

[0074] As shown in Figures 7B and 7C, the electrode terminal 42 has a flat plate shape with a constant thickness.

[0075] As shown in Figure 7A, the side surface of the tip 52a of the heating element 52 is joined to the electrode terminal 42. The joint where the heating element 52 and the electrode terminal 42 are joined is indicated by the double arrow J3 in Figure 7C. The non-jointed portion where the heating element 52 and the electrode terminal 42 are not joined is indicated by the double arrow N3 in Figure 7C. Furthermore, the tip 52a of the heating element 52 is also called the joint of the heating element 52. The part 42a where the electrode terminal 42 is joined to the tip 52a of the heating element is also called the joint of the electrode terminal 42.

[0076] As shown in Figure 7C, the thickness of the joint J3 between the heating element 52 and the electrode terminal 42 is equal to the thicker of the two thicknesses, T52 of the heating element 52 and T42 of the electrode terminal 42. Therefore, the thickness T3 of the joint J3 is thinner than the sum of the thickness T52 of the heating element 52 and the thickness T42 of the electrode terminal 42 in the non-jointed section N3.

[0077] As shown in Figures 7A, 7B, and 7C, by bending the tip of the heating wire into an L-shape and joining the tip to the side of the electrode terminal, the thickness of the joint can be made thinner than the sum of the thickness of the heating wire and the electrode terminal in the non-jointed area.

[0078] Figure 8A is a schematic diagram showing yet another example of the joint between the heating wire and the electrode terminal in the honeycomb structure of the present invention. Figure 8B is a side view of Figure 8A as seen from the side of the heating wire. Figure 8C is a side view of Figure 8A as seen from the electrode terminal side.

[0079] As shown in Figure 8A, the heating element 53 and the electrode terminal 43 do not overlap when viewed from the thickness direction. On the other hand, as shown in Figures 8B and 8C, the heating element 53 and the electrode terminal 43 overlap when viewed from a direction perpendicular to the thickness direction.

[0080] The heating element 53 is a linear shape with a uniformly approximately circular cross-section.

[0081] The electrode terminal 43 has a rectangular notch 65 when viewed from the thickness direction. The notch 65 has sides 65a and 65b parallel to the direction in which the heating element 53 extends, and a side 65c connecting sides 65a and 65b. The width W1 of the notch 65 is wider than the width W2 of the heating element 53. Therefore, the tip of the heating element 53 can be fitted into the notch 65.

[0082] As shown in Figure 8A, the end 53a of the heating element 53 is joined to the notch 65 of the electrode terminal 43 by fitting it into it. The joint where the heating element 53 and the electrode terminal 43 are joined is indicated by the double arrow J4 in Figure 8B. The unjointed portion where the heating element 53 and the electrode terminal 43 are not joined is indicated by the double arrow N4 in Figure 8B. Furthermore, the end portion 53a of the heating element 53 is also called the joint portion of the heating element 53. The portion 43a where the electrode terminal 43 is joined to the end portion 53a of the heating element is also called the joint portion of the electrode terminal 43.

[0083] As shown in Figure 8B, the thickness T4 of the joint J4 between the heating element 53 and the electrode terminal 43 is equal to the thicker of the two thicknesses, T53 of the heating element 53 and T43 of the electrode terminal 43. Therefore, the thickness T4 of the joint J4 is thinner than the sum of the thickness T53 of the heating element 53 in the non-jointed section N4 and the thickness T43 of the electrode terminal 43.

[0084] As shown in Figures 8A, 8B, and 8C, by providing a notch in the electrode terminal and joining the electrode terminal with the tip of the heating wire fitted into the notch, the thickness of the joint can be made thinner than the sum of the thickness of the heating wire and the electrode terminal in the non-jointed area.

[0085] The configurations shown in Figures 8A, 8B, and 8C can be described as examples in which the groove shape is modified in the configurations shown in Figures 6A, 6B, and 6C until the groove depth is equal to the thickness of the electrode terminal.

[0086] In Figures 8A, 8B, and 8C, only the side surface 65a of the notch 65 of the electrode terminal 43 is in contact with the heating element 53, and there is a gap between the side surfaces 65b and 65c of the notch 65 of the electrode terminal 43 and the heating element 53. The position where the heating element 53 and the electrode terminal 43 are joined is not particularly limited. Only the side surface 65a or 65b of the notch 65 of the electrode terminal 43 may be joined to the heating element 53, or both the side surfaces 65a and 65b of the notch 65 of the electrode terminal 43 may be joined to the heating element 53, or both the side surfaces 65a, 65b and 65c of the notch 65 of the electrode terminal 43 may be joined to the heating element 53. It is preferable that the joining area between the side surface of the notch 65 and the heating element 53 is larger, as this increases the joining strength between the heating element 53 and the electrode terminal 43.

[0087] An example of a method for manufacturing the honeycomb structure of the present invention will be described. The above-mentioned honeycomb structure can be manufactured, for example, by fabricating honeycomb segments made of ceramic using a known manufacturing method, and then bonding the honeycomb segments together via an adhesive layer. When forming the adhesive layer on the side surface of the honeycomb segment, a heating wire is placed between the honeycomb segment, and electrode terminals are connected to the ends of the heating wire so that the electrode terminals protrude from the first end face of the honeycomb structure.

[0088] When bonding the honeycomb segments, multiple honeycomb segments are arranged so that a surface parallel to the first direction in the honeycomb structure is exposed, an adhesive paste is applied to form the adhesive layer, and a heating wire is placed on top of the adhesive paste. Furthermore, multiple heating wires are connected in parallel to form a heating wire assembly, and the electrode terminals are exposed from the direction that will become the first end face in the honeycomb structure.

[0089] At this time, the heating element and the electrode terminal are joined together such that the thickness of the joint is less than the sum of the thickness of the heating element and the electrode terminal in the non-jointed area. In this case, for example, methods such as deforming a part of the end of the heating wire into a roughly flattened shape by heat pressing, forming grooves or notches in a part of the electrode terminal, and bending a part of the tip of the heating wire and joining it on the side can be used.

[0090] After applying more adhesive paste to the heating element, arrange the honeycomb segments on top of the adhesive paste. This process is repeated to combine the honeycomb segments and form a honeycomb assembly. By heating the honeycomb assembly, the adhesive paste is heated and solidified to form an adhesive layer, thereby creating a honeycomb structure. The honeycomb aggregate may be processed on its outer surface to achieve the desired shape, or the outer surface may be coated with a paste similar to adhesive paste after processing. Electrode terminals are exposed at the first end face of the honeycomb structure. Connect the electrode terminals so that the heating elements are connected in parallel. Through the above process, a honeycomb structure can be manufactured.

[0091] Furthermore, it is preferable to immerse the manufactured honeycomb structure in a slurry containing the catalyst and dry it to support the catalyst on the partition walls of the honeycomb structure. [Examples]

[0092] (Example 1) The tip of a 0.6mm diameter heating wire was pressed to flatten the top 10mm of the wire into a 0.4mm thick shape. The tip of a flattened heating wire was placed on a 0.5 mm thick stainless steel plate that would serve as an electrode terminal, and joined by spot welding to obtain a sample according to Example 1.

[0093] (Example 2) A groove measuring 0.6 mm in width and 0.3 mm in depth was formed in a 0.5 mm thick stainless steel plate, which would serve as the electrode terminal, by machining. The thickness of the electrode terminal in the grooved portion was 0.2 mm. The tip of a 0.6 mm diameter heating wire was placed in contact with this groove for 10 mm, and the heating wire and the stainless steel plate were joined by spot welding to obtain a sample according to Example 2.

[0094] (Example 3) A 0.5 mm thick stainless steel plate, which would serve as the electrode terminal, had a notch measuring 0.6 mm in width and 10 mm in length formed by machining. The tip of a 0.6 mm diameter heating wire was fitted into this notch, and the heating wire and the stainless steel plate were joined by spot welding to obtain a sample according to Example 3. In Example 3, the electrode terminal was joined to the heating wire at positions corresponding to sides 65a and 65b of the notch 65 shown in Figure 8A.

[0095] (Example 4) The tip of a 0.6 mm diameter heating wire was bent 90° into an L-shape at a 10 mm angle. With the bent portion in contact with the side of a 0.5 mm thick stainless steel plate that would serve as the electrode terminal, the heating wire and the stainless steel plate were joined by spot welding to obtain a sample according to Example 4.

[0096] (Comparative Example 1) A heating wire with a diameter of 0.6 mm was placed on a stainless steel plate with a thickness of 0.5 mm, which would serve as the electrode terminal, and joined by spot welding to obtain a sample corresponding to Comparative Example 1.

[0097] (Measurement of the thickness of the joint) Ten samples were prepared for each example and comparative example, and the thickness of the joint was measured. The average value was then calculated. If the thickness of the joint was not uniform, the thickness of the thickest part was measured. The results are shown in Table 1.

[0098] (Impact resistance evaluation) Samples for each example and comparative example were placed on the surface of a segment, a 1 mm thick spacer was placed on top, adhesive paste was applied, another segment was placed on top, and the sample was vibrated for 1 minute while pressure was applied. After that, the surface of the segment that had come into contact with the adhesive paste was cleaned and observed to check for damage or indentation. Segments showing damage or indentation on the surface were marked with ×, and those showing no damage or indentation were marked with ○. The results are shown in Table 1.

[0099] (Measurement of joint strength) For each sample, the heating wire was pulled using a tensile testing machine while the stainless steel plate was fixed, and the strength at which the sample broke was defined as the joint strength. Measurements were performed on 10 samples for each example and comparative example, and the average value was calculated. The results are shown in Table 1. Note that a joint strength of 50N or higher indicates that the joint between the heating wire and the electrode terminal has sufficient joint strength.

[0100] [Table 1]

[0101] The results in Table 1 show that, in the samples related to Examples 1 to 4, it was possible to maintain sufficient bonding strength while making the thickness of the joint thinner than the sum of the thickness of the heating element and the electrode terminals in the non-jointed areas. Although the sample in Comparative Example 1 possessed sufficient bonding strength, the thickness at the joint was equal to the sum of the thickness of the heating wire and the electrode terminal at the non-jointed portion, and the joint was in contact with the honeycomb segment. As a result, damage or indentation was observed on the surface of the segment during the impact resistance evaluation. [Explanation of symbols]

[0102] 1. Honeycomb structure 11 First end face of honeycomb structure 12 Second end face of honeycomb structure 20 Honeycomb Segments 21 cells 22 Bulkhead 23 Catalyst 30, 30a, 30a1, 30a2, 30b adhesive layer 40, 41, 42, 43 electrode terminal 40a, 41a, 42a, 43a: The part where the electrode terminal is joined to the heating element (joint). 50, 50A, 50B, 50C, 51, 52, 53, 54 heating wire 50a, 51a, 52a, 53a Ends (joints) of the heating wires 50a1 First set of heating elements 50a2 Second set of heating wires 60 grooves 65 Notches 65a, 65b, 65c Sides of the notches J1, J2, J3, J4 joints N1, N2, N3, N4 Non-joint parts

Claims

1. A honeycomb structure comprising multiple honeycomb segments having partitions that divide a large number of cells, combined via an adhesive layer, The heating element is placed inside the adhesive layer. An electrode terminal for supplying power from the outside is connected to the end of the aforementioned heating element. The heating element and the electrode terminal are joined together inside the adhesive layer. A honeycomb structure characterized in that the thickness of the joint portion where the heating wire and the electrode terminal are joined is thinner than the sum of the thickness of the heating wire and the thickness of the electrode terminal in the non-joint portion where the heating wire and the electrode terminal are not joined.

2. The honeycomb structure according to claim 1, wherein the thickness of the joint portion is 1 mm or less.

3. The honeycomb structure according to claim 1 or 2, wherein the thickness of the adhesive layer is 1 to 3 mm.

4. The honeycomb structure according to any one of claims 1 to 3, wherein, when viewed from the thickness direction of the adhesive layer, the heating element and the electrode terminal overlap at the joint.

5. The honeycomb structure according to claim 4, wherein in a cross section perpendicular to the longitudinal direction of the heating wire, the cross-sectional area of ​​the heating wire at the joint portion and the cross-sectional area of ​​the heating wire at the non-joint portion are substantially the same, the cross-sectional shape of the heating wire at the joint portion is substantially flattened, and the cross-sectional shape of the heating wire at the non-joint portion is substantially circular.

6. The honeycomb structure according to claim 4 or 5, wherein the thickness of the electrode terminal at the joint is thinner than the thickness of the electrode terminal at the non-joint portion.

7. The honeycomb structure according to any one of claims 1 to 4, wherein, when viewed from a direction perpendicular to the thickness direction of the adhesive layer, the heating element and the electrode terminal overlap at the joint.

8. A honeycomb structure according to any one of claims 1 to 7, wherein multiple heating wires are connected in parallel.

9. The honeycomb structure according to any one of claims 1 to 8, wherein, in an end view of the honeycomb structure, the honeycomb segments are arranged in a grid pattern vertically and horizontally, and all of the heating wires are arranged in the same direction along a first direction which is either vertically or horizontally in the grid pattern.

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