Honeycomb structure

Abstract

To provide a honeycomb structure which consists of a plurality of honeycomb segments combined, and which is excellent in emission control efficiency.SOLUTION: The honeycomb structure consists of a plurality of honeycomb segments combined and having partition walls to section and form a number of cells. Catalysts are supported on the respective honeycomb segments, and heating wires are arranged between the adjacent honeycomb segments. To the heating wires, electrode terminals are connected. The electrode terminals are protruded from the end face of the honeycomb structure. On the end face of the honeycomb structure, the electrode terminals are installed only on the outer periphery of the honeycomb structure.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In order to purify harmful substances contained in exhaust gas emitted from an engine, an exhaust gas purification device equipped with a honeycomb substrate carrying a catalyst capable of purifying exhaust gas is installed in the exhaust pipe route. In order to improve the efficiency of purifying harmful substances by an 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 catalyst activation temperature).

[0003] Patent Document 1 discloses a filter that collects soot contained in the exhaust gas of a diesel engine to purify the exhaust gas. In this filter, an electric heating wire is disposed as a heating element between adjacent filters to burn the soot accumulated inside the filter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-54643 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration disclosed in Patent Document 1, heating wires are arranged between adjacent filters, but the heating wires are arranged over the entire outer periphery of each filter (see Figure 1 of Patent Document 1). The filters with heating wires arranged thereon are combined with an adhesive to form an exhaust gas purification device consisting of multiple filters. The heating wires protrude directly from the end faces of the filters. When a plurality of such filters are combined, an exhaust gas purification device made up of a plurality of filters has an electric heating wire protruding from the end face of the exhaust gas purification device for each filter. In addition, gas flow (gas inflow into the cells or gas outflow from the cells) is obstructed in the vicinity of the heating wire protruding from the end face of the exhaust gas purification device. If the flow of gas is obstructed at the end face of the exhaust gas purification device, the purification efficiency will be reduced.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a honeycomb structure formed by combining a plurality of honeycomb segments, which has excellent purification efficiency. [Means for solving the problem]

[0007] The honeycomb structure of the present invention is a honeycomb structure formed by combining a plurality of honeycomb segments each having partition walls that define a large number of cells, characterized in that a catalyst is supported on the honeycomb segments, heating wires are arranged between adjacent honeycomb segments, electrode terminals are connected to the heating wires, the electrode terminals protrude from the end face of the honeycomb structure, and the electrode terminals are installed only on the outer periphery of the honeycomb structure at the end face of the honeycomb structure.

[0008] In the configuration described in Patent Document 1, an electrode terminal is provided for each filter, so that the heating wire and electrode terminals protrude from the end face of the exhaust gas purification device over the entire end face of the exhaust gas purification device. In contrast, in the honeycomb structure of the present invention, when viewed from the end face of the honeycomb structure, the electrode terminals are installed only on the outer periphery of the end face of the honeycomb structure, i.e., the heating wires and the electrode terminals do not protrude from the center of the end face of the honeycomb structure. At the end face of a honeycomb structure, gas naturally flows easily through the center and poorly through the peripheral area. Therefore, if an electrode terminal protrudes from the end face of the honeycomb structure and obstructs gas flow, the obstruction of gas flow by the electrode terminal in the center will have a significant effect. Therefore, it is important to avoid obstructing gas flow in the center of the end face of the honeycomb structure. Therefore, in the honeycomb structure of the present invention, electrode terminals are not provided in the center of the end face of the honeycomb structure (electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure), thereby minimizing the effect of electrode terminals protruding from the end face of the honeycomb structure on obstructing gas flow. Therefore, with the configuration of the present invention, a honeycomb structure having excellent purification efficiency can be obtained.

[0009] In the honeycomb structure of the present invention, it is preferable that the honeycomb segments are combined with each other via an adhesive layer, and the heating wire is disposed inside the adhesive layer.

[0010] In the honeycomb structure of the present invention, the electrode terminals are preferably provided only within a range of 20% of the outer periphery of the honeycomb structure from the center to the outer periphery.

[0011] When the electrode terminals are installed only within the above range, the influence of the electrode terminals protruding from the end faces of the honeycomb structure on obstructing gas flow is further suppressed, resulting in a honeycomb structure with superior purification efficiency. If the electrode terminals are installed beyond the range of 20% on the outer periphery of the honeycomb structure from the center to the periphery, depending on the gas flow velocity, the influence of obstructing gas flow may become greater, resulting in a decrease in purification efficiency.

[0012] In the honeycomb structure of the present invention, when viewed from an end face of the honeycomb structure, the honeycomb segments are combined vertically and horizontally in a lattice pattern, and it is preferable that all of the heating wires are arranged in the same direction along a first direction, which is either the vertical or horizontal direction of the lattice pattern. This configuration can suppress localized heat generation. In addition, since no heating wires are arranged in the direction perpendicular to the first direction, the adhesive layer can increase the adhesive strength between the honeycomb segments.

[0013] In the honeycomb structure of the present invention, it is preferable that the electrode terminal is plate-shaped, and the heating wire and the electrode terminal are welded to each other. With this configuration, disconnection between the electrode terminal and the heating wire can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a honeycomb structure of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a honeycomb segment in a direction perpendicular to the longitudinal direction. [Figure 3] FIG. 3 is a partial cross-sectional view of the honeycomb structure shown in FIG. [Figure 4] FIG. 4 is an end view of the honeycomb structure shown in FIG. [Figure 5] FIG. 5 is an end view of the honeycomb structure shown in FIG.

[0015] (Detailed Description of the Invention) [Honeycomb structure] The honeycomb structure of the present invention will be described below. The honeycomb structure of the present invention is a honeycomb structure formed by combining a plurality of honeycomb segments each having partition walls that define a large number of cells, characterized in that a catalyst is supported on the honeycomb segments, heating wires are arranged between adjacent honeycomb segments, electrode terminals are connected to the heating wires, the electrode terminals protrude from the end face of the honeycomb structure, and the electrode terminals are installed only on the outer periphery of the honeycomb structure at the end face of the honeycomb structure.

[0016] FIG. 1 is a perspective view schematically showing an example of a honeycomb structure of the present invention. The honeycomb structure 1 shown in Figure 1 is made up of a combination of multiple honeycomb segments 20 each having partition walls 22 that define 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 FIG. 1). The honeycomb segments are joined together via an adhesive layer 30 . In addition, an electrode terminal 40 protrudes from the first end face 11 .

[0017] The material for forming the honeycomb segments (partition walls) is preferably one with high thermal conductivity, such as SiC or Si-impregnated SiC.

[0018] The thickness of the partition walls is preferably uniform. Specifically, the thickness of the partition walls is preferably less than 0.30 mm. Also, the thickness is preferably 0.05 mm or more.

[0019] The shape of the cells is not limited to a quadrangular prism, but may be a triangular prism, a hexagonal prism, or the like. The cells may have different shapes, but are preferably all the same, i.e., in a cross section perpendicular to the longitudinal direction of the honeycomb segment, the size of the cells surrounded by the partition walls is preferably the same.

[0020] The porosity of the partition walls is preferably 50% or less. When the porosity of the partition walls is 50% or less, it is possible to achieve both high mechanical strength and exhaust gas purification performance.

[0021] If the porosity of the partition walls exceeds 50%, the porosity becomes too high, which reduces the mechanical properties of the honeycomb segments, making the honeycomb structure more susceptible to cracks, breakage, and the like during use.

[0022] The shape of the honeycomb structure is not particularly limited, and is not limited to a cylindrical shape, but may be a rectangular pillar, an elliptical pillar, an oblong pillar, a rectangular pillar with rounded edges (for example, a triangular pillar with rounded edges), etc.

[0023] When the honeycomb structure has a cylindrical shape, the ratio of the length in the longitudinal direction of the honeycomb structure to the diameter of the end face of the honeycomb structure (length / diameter) is preferably 0.8 or less.

[0024] The length of the honeycomb structure in the longitudinal direction is preferably 150 mm or less, and more preferably 50 mm or more.

[0025] FIG. 2 is a cross-sectional view of a honeycomb segment in a direction perpendicular to the longitudinal direction. When exhaust gas (the flow of exhaust gas is indicated by arrow G in FIG. 2) emitted from an internal combustion engine reaches the honeycomb segment 20, the exhaust gas flows into the cells 21 from the first end face 11 of the honeycomb segment 20. Furthermore, the exhaust gas passes through the cells 21 while coming into contact with the catalyst 23 supported on the partition walls 22. At this time, CO, HC, NO in the exhaust gas are X Harmful gas components such as these are purified by the catalyst 23 carried on the partition walls 22. Then, the exhaust gas flows out of the cells 21 at the second end face 12 of the honeycomb segment 20.

[0026] The catalyst 23 is not particularly limited as long as it can treat exhaust gas, but examples thereof include catalysts made of precious metals such as platinum, palladium, and rhodium, zeolites, etc. The zeolite may be CHA zeolite, and the zeolite may be ion-exchanged with Cu or the like. These catalysts may be used alone or in combination of two or more. When these catalysts are supported, CO, HC, NO X The present invention can effectively purify toxic exhaust gases such as toluene, ... In particular, it is preferable to use the honeycomb structure as an SCR catalyst that reduces NOx using zeolite as a catalyst.

[0027] Fig. 3 is a partial cross-sectional view of the honeycomb structure shown in Fig. 1. Fig. 3 schematically shows an area in which an electric heating wire is arranged in the honeycomb structure. A heating wire 50 is disposed between adjacent honeycomb segments 20. Electrode terminals 40 are provided on both ends of the heating wire 50, and the electrode terminals 40 protrude from the first end face 11.

[0028] The heating wires may be provided over the entire space between the adjacent honeycomb segments, or may be provided only in a portion thereof.

[0029] In the honeycomb structure 1 shown in Fig. 3, the heating wires 50 are arranged in a predetermined range from the first end face 11 of the honeycomb structure 1 in the longitudinal direction of the honeycomb segment 20. The region where the heating wires are arranged is referred to as the heating wire arrangement region. In Fig. 3, this is the region indicated by the double-headed arrow B. The heating wires 50 are not arranged in a predetermined range from the second end face 12 of the honeycomb structure 1 in the longitudinal direction of the honeycomb segment 20. The region where the heating wires are not arranged is referred to as the heating wire non-arrangement region. In Fig. 3, this is the region indicated by the double-headed arrow C. The region where no heating wire is arranged occupies a range of at least 20% of the length of the honeycomb structure in the longitudinal direction from the second end face of the honeycomb structure.

[0030] That is, a heating wire area is provided within a predetermined range from the first end face through which the gas flows in, and a heating wire non-area is provided within a predetermined range from the second end face through which the gas flows out. The heat generated in the region where the heating wire is located near the first end face moves along with the gas flow toward the second end face of the honeycomb structure, so that the entire honeycomb structure can be heated even if no heating wire is located in the region near the second end face.

[0031] The material of the heating wire may be a nickel-chromium alloy, a nickel-chromium-iron alloy, a chromium-iron-aluminum alloy, etc. The heating wire may be in the form of either a wire or a plate. When the heating wire is linear, its diameter is not particularly limited, but is preferably 0.1 to 1 mm. When the heating wire is plate-shaped, its thickness is not particularly limited, but is preferably 0.1 to 0.5 mm, and its width is preferably 1 to 10 mm.

[0032] The heating wire 50 is disposed inside the adhesive layer 30 . The adhesive layer is formed by applying and drying an adhesive paste containing an inorganic binder and inorganic particles, and may further contain inorganic fibers and / or whiskers. The thickness of the adhesive layer is preferably 0.5 to 3 mm.

[0033] Electrode terminals 40 are connected to both ends of the heating wire 50, and the electrode terminals 40 protrude from the end faces of the honeycomb structure, and electricity can be supplied from the electrode terminals 40 to the heating wire 50 to cause the heating wire to generate heat. The electrode terminal 40 is plate-shaped and is welded to the heating wire 50 . If the electrode terminal is plate-shaped and welded to the heating wire, disconnection between the electrode terminal and the heating wire can be prevented. The electrode terminals 40 are connected to each other by wiring 60 that connects the electrode terminals together.

[0034] When the electrode terminal is in the form of a plate, its dimensions are preferably 5 mm x 50 mm to 20 mm x 150 mm, and its thickness is preferably 0.1 to 1 mm. Moreover, the length of the electrode terminal protruding from the end face of the honeycomb structure is preferably 5 to 30 mm. The material of the electrode terminals is preferably stainless steel, an alloy similar to that of the heater, or the like.

[0035] 3 is a set of heating wires in which a plurality of heating wires (51, 52, 53) are connected in parallel. Electrode terminals 40 are connected to both ends of each heating wire. If the heating wire is a set of heating wires, even if one of the heating wires breaks, the set of heating wires will not break as a whole, so the deterioration of heating performance can be minimized.

[0036] In the honeycomb structure of the present invention, the electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure. This will be explained with reference to the drawings.

[0037] FIG. 4 is an end view of the honeycomb structure shown in FIG. The electrode terminals 40 are installed only on the outer periphery of the end face of the honeycomb structure 1. That is, the heating wires and electrode terminals do not protrude from the center of the end face of the honeycomb structure.

[0038] At the end face of a honeycomb structure, gas naturally flows easily through the center and poorly through the peripheral area. Therefore, if an electrode terminal protrudes from the end face of the honeycomb structure and obstructs gas flow, the obstruction of gas flow by the electrode terminal in the center will have a significant effect. Therefore, it is important to avoid obstructing gas flow in the center of the end face of the honeycomb structure. Therefore, in the honeycomb structure of the present invention, electrode terminals are not provided in the center of the end face of the honeycomb structure (electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure), thereby minimizing the effect of electrode terminals protruding from the end face of the honeycomb structure on obstructing gas flow. Therefore, with the configuration of the present invention, a honeycomb structure having excellent purification efficiency can be obtained.

[0039] In Fig. 4, the electrode terminals 40 are exposed on the first end face 11 of the honeycomb structure 1, and are installed only on the outer periphery of the first end face 11. Since the electrode terminals do not obstruct the flow of gas into the honeycomb structure at the center of the first end face of the honeycomb structure, the effect of obstructing gas flow caused by the electrode terminals can be reduced.

[0040] In a form in which electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure, the electrode terminals are preferably provided only within a range of 20% of the outer periphery of the distance from the center to the outer periphery of the honeycomb structure.

[0041] In Fig. 4, the center of the honeycomb structure is indicated by point Q, and an arbitrary point on the periphery of the honeycomb structure is indicated by point P. Of the length of the line connecting point Q and point P, a range (region R) of 20% on the side closer to point P is set as the periphery of the honeycomb structure, and it is preferable to provide electrode terminals in this range.

[0042] When the electrode terminals are installed only within the above range, the influence of the electrode terminals protruding from the end faces of the honeycomb structure on obstructing gas flow is further suppressed, resulting in a honeycomb structure with superior purification efficiency. If the electrode terminals are installed beyond the range of 20% on the outer periphery of the honeycomb structure from the center to the periphery, depending on the gas flow velocity, the influence of obstructing gas flow may become greater, resulting in a decrease in purification efficiency.

[0043] In addition, as a form in which electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure, electrode terminals may be provided between adjacent honeycomb segments including the honeycomb segments located at the outermost periphery of the honeycomb structure (hereinafter also referred to as outer periphery honeycomb segments). In this case, an electrode terminal may be provided between two adjacent peripheral honeycomb segments, or an electrode terminal may be provided between a peripheral honeycomb segment and a honeycomb segment that is not a peripheral honeycomb segment. If at least one of the two adjacent honeycomb segments on which the electrode terminal is installed is an outer periphery honeycomb segment, the electrode terminal is installed on the outer periphery of the end face of the honeycomb structure.

[0044] In addition, as a mode in which the electrode terminals are provided only on the outer periphery of the end face of the honeycomb structure, the electrode terminals may be installed only within a range of a distance of 25 mm or less from the outer periphery of the honeycomb structure.

[0045] In the honeycomb structure configurations described so far, the electrode terminals are exposed on the first end face of the honeycomb structure, but the electrode terminals may also be exposed on the second end face of the honeycomb structure. In this case, the electrode terminals are installed only on the outer periphery of the second end face of the honeycomb structure. In this case, too, the electrode terminals do not obstruct the outflow of gas from the honeycomb structure at the center of the second end face of the honeycomb structure, so the effect of the electrode terminals on obstructing gas flow can be reduced.

[0046] FIG. 5 is an end view of the honeycomb structure shown in FIG. 5, the honeycomb segments 20 are combined lengthwise and widthwise in a lattice pattern. One direction of this lattice pattern is defined as a first direction, and the direction perpendicular to the first direction is defined as a second direction. In FIG. 5, the horizontal direction is the first direction and the vertical direction is the second direction.

[0047] All the heating wires 50 are arranged in the same direction along the first direction. In FIG. 5, the adhesive layer 30a along the first direction, in which the heating wire is arranged, is shown with dark hatching, and the adhesive layer 30b along the second direction, in which the heating wire is not arranged, is shown with light hatching. This configuration can suppress localized heat generation. In addition, since no heating wires are arranged in the second direction perpendicular to the first direction, the adhesive layer can increase the adhesive strength between the honeycomb segments.

[0048] 5, the heating wires arranged on the adhesive layer 30a along the first direction are grouped together as heating wire sets, and the grouped heating wire sets are connected in parallel. This will be explained in detail. The heating wire set arranged in the adhesive layer 30a1 along the first direction between the honeycomb segments is referred to as a first heating wire set 50a1. Another adhesive layer 30a2 is disposed along the first direction between adjacent honeycomb segments at a position different from the position where the first pair of heating wires 50a1 is disposed. The pair of heating wires disposed on the adhesive layer 30a2 is referred to as the second pair of heating wires 50a2. The first heating wire assembly 50a1 and the second heating wire assembly 50a2 are connected in parallel by wiring 60 that connects the electrode terminals. 5, there are six adhesive layers 30a arranged along the first direction, and a heating wire set is disposed on each adhesive layer 30a. The six heating wire sets are connected in parallel by wiring 60.

[0049] When the heating wires are connected in parallel, even if some of the heating wires are broken, the entire circuit made up of the heating wires provided in the honeycomb structure will not be broken, so the deterioration of heating performance can be minimized.

[0050] An example of a method for manufacturing a honeycomb structure of the present invention will be described. The honeycomb structure can be manufactured, for example, by preparing honeycomb segments made of ceramic by 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 segments, heating wires are arranged between the honeycomb segments, and electrode terminals are connected to the ends of the heating wires so that the electrode terminals protrude from the end faces of the honeycomb structure. At this time, the positions of the ends of the heating wires and the electrode terminals are adjusted so that the electrode terminals protrude from the outer periphery of the honeycomb structure.

[0051] When bonding the honeycomb segments, multiple honeycomb segments are arranged so that the surfaces parallel to the first direction in the honeycomb structure are exposed, an adhesive paste that will become the adhesive layer is applied, and a heating wire is placed on the adhesive paste. Furthermore, a plurality of heating wires are connected in parallel to form a heating wire set, and electrode terminals are exposed from the end faces of the honeycomb structure.

[0052] An adhesive paste is further applied onto the heating wires, and then the honeycomb segments are arranged on the adhesive paste. This process is repeated to combine the honeycomb segments to form a honeycomb assembly. The honeycomb aggregate is heated to heat and solidify the adhesive paste to form an adhesive layer, thereby producing a honeycomb structure. The outer periphery of the honeycomb aggregate may be processed to form a desired shape, and after processing, the outer periphery may be coated with a paste similar to the adhesive paste. The electrode terminals are exposed only at the outer periphery of the end face of the honeycomb structure. The electrode terminals are connected together so that the heating wire pairs are connected in parallel. Through the above steps, the honeycomb structure can be manufactured.

[0053] It is also preferable to immerse the manufactured honeycomb structure in a slurry containing the catalyst and then dry it to support the catalyst on the partition walls of the honeycomb structure. [Explanation of symbols]

[0054] 1 Honeycomb structure 11 first end face 12 Second end face 20 honeycomb segments 21 cells 22 Bulkhead 23 Catalyst 30 Adhesive layer 30a, 30a1, 30a2 adhesive layers along the first direction 30b Adhesive layer along the second direction 40 electrode terminal 50 Heating wire (assembled heating wire) 50a1 First set of heating wire 50a2 Second set of heating wire 51, 52, 53 heating wire 60 Wiring connecting electrode terminals

Claims

1. A honeycomb structure formed by combining a plurality of honeycomb segments each having partition walls that define a large number of cells, A catalyst is supported on the honeycomb segments, A heating wire is disposed between adjacent honeycomb segments, an electrode terminal is connected to the heating wire, and the electrode terminal protrudes from an end face of the honeycomb structure; On the end face of the honeycomb structure, the electrode terminals are installed only on the outer periphery of the honeycomb structure, A honeycomb structure characterized in that, when viewed from the end face of the honeycomb structure, the honeycomb segments are combined vertically and horizontally in a lattice pattern, and all of the heating wires are arranged in the same direction along a first direction, which is either the vertical or horizontal direction of the lattice pattern.

2. 2. The honeycomb structure according to claim 1, wherein the electrode terminals are disposed only within a range of 20% of the outer periphery of the honeycomb structure from the center to the outer periphery.

3. 3. The honeycomb structure according to claim 1, wherein the electrode terminals are plate-shaped, and the heating wires and the electrode terminals are welded to each other.

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