Honeycomb structure

Abstract

To provide a honeycomb structure which can reduce stress applied by heating and cooling, causes no contact failure, has an electrode part capable of stably energizing and heating and a fixed part in contact with the electrode part and can be heated to a catalyst activation temperature in a short time.SOLUTION: There is provided a honeycomb structure which comprises a honeycomb substrate having cell partition walls for partitioning and forming a large number of cells and an outer peripheral wall and electrode parts provided on the outer peripheral wall and an energizing terminal connected to the electrode parts via a fixed part, wherein the energizing terminal is fixed on the outer peripheral wall by the fixed part in contact with the electrode parts and a part adjacent to at least the outer peripheral wall of the fixed part is composed of a material of the same quality as that of the honeycomb substrate.SELECTED DRAWING: Figure 1B

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 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] However, in a vehicle not equipped with a means for directly heating the honeycomb substrate constituting the exhaust gas purification device, immediately after the vehicle starts driving, since the temperature of the exhaust gas is low, the temperature inside the exhaust gas purification device does not reach the catalyst activation temperature, and it has been difficult to effectively prevent the emission of harmful substances. Also, in a hybrid vehicle not equipped with a means for directly heating the honeycomb substrate, when the motor is operating and the engine is stopped, the temperature inside the exhaust gas purification device may decrease and become lower than the catalyst activation temperature, and again, it has been difficult to effectively prevent the emission of harmful substances.

[0004] In order to solve such problems, an invention in which the honeycomb substrate itself is used as a heating element that generates heat by energization and, if necessary, the temperature inside the exhaust gas purification device is set to a temperature equal to or higher than the catalyst activation temperature is disclosed in Patent Document 1. That is, Patent Document 1 discloses an electrically heated catalyst including a ceramic carrier, an electrode, an underlayer interposed between the ceramic carrier and the electrode, and a fixing layer that fixes the electrode by joining with the underlayer, wherein the fixing layer is formed so as to linearly extend at least at two locations respectively, and the electrode is fixed by joining with the underlayer at each location. In this electric heating type catalyst, the base layer that is interposed between the ceramic carrier and the electrode, and electrically connects and fixes the electrode and the ceramic carrier is formed by spraying.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the fixing by spraying, during long-term use of the electric heating type catalyst mounted on a vehicle, the sprayed portion is likely to peel off or have poor contact, and the resistance of that portion increases, making it difficult to raise the temperature to the set temperature of the ceramic carrier.

[0007] The present invention has been made in view of such problems, and aims to provide a honeycomb structure that can reduce the stress caused by heating and cooling, does not have poor contact even after long-term use, can stably conduct current for heating, and has an electrode portion and a fixing portion in contact with the electrode portion, and can raise the temperature to the catalyst activation temperature in a short time.

Means for Solving the Problems

[0008] The honeycomb structure of the present invention is a honeycomb structure including a honeycomb base material having cell partitions that partition and form a large number of cells and an outer peripheral wall, an electrode portion provided on the outer peripheral wall, and a power supply terminal connected to the electrode portion via a fixing portion, wherein the power supply terminal is fixed to the outer peripheral wall by the fixing portion that contacts the electrode portion, and at least a portion of the fixing portion close to the outer peripheral wall is made of a material of the same quality as the honeycomb base material.

[0009] According to the honeycomb structure of the present invention, at least the portion of the fixing part close to the outer peripheral wall is made of the same material as the honeycomb base material, so that the stress applied to the fixing part can be reduced by heating and cooling, and even after long-term use, there will be no poor contact between the fixing part and the honeycomb base material, and it is possible to stably energize and heat the honeycomb base material through the fixing part, and it can be supplied to a honeycomb structure that can raise the temperature to the catalyst activation temperature in a short time.

[0010] In the honeycomb structure of the present invention, the fixing part is composed of a bolt having a flat part in contact with the outer peripheral wall and a nut screwed onto the bolt, and it is desirable that the through hole of the energizing terminal is inserted into the bolt and the electrode part and the energizing terminal are connected by screwing the nut.

[0011] In the honeycomb structure of the present invention, when the fixing part is composed of a bolt having a flat part in contact with the outer peripheral wall and a nut screwed onto the bolt, and the through hole of the energizing terminal is inserted into the bolt and the electrode part and the energizing terminal are connected by screwing the nut, the flat part of the bolt can be firmly fixed to the outer peripheral wall of the honeycomb base material, and even after long-term use, there will be no poor contact between the fixing part and the honeycomb base material, and it is possible to stably energize and heat the honeycomb base material through the fixing part.

[0012] In the honeycomb structure of the present invention, the fixing part is composed of a flat part in contact with the outer peripheral wall, a columnar part extending from the flat part, a tip part having a larger cross-sectional area than the columnar part, and a C-shaped metal member attached around the columnar part, and it is desirable that the energizing terminal and the C-shaped metal member are attached to the columnar part so that the electrode part and the energizing terminal are connected.

[0013] In the honeycomb structure of the present invention, the fixing portion includes a flat portion that contacts the outer peripheral wall, a columnar portion that extends from the flat portion, a tip portion having a larger cross-sectional area than the columnar portion, and a C-shaped metal member attached around the columnar portion. When the energization terminal and the C-shaped metal member are attached to the columnar portion, and the electrode portion and the energization terminal are connected, the flat portion can be firmly fixed to the outer peripheral wall of the honeycomb base material, and even after long-term use, there will be no poor contact between the fixing portion and the honeycomb base material, and stable energization heating can be performed on the honeycomb base material through the fixing portion.

[0014] In the honeycomb structure of the present invention, the fixing portion has a terminal opening for inserting the energization terminal and a wedge opening for pushing in the wedge. It consists of a member (hereinafter referred to as a wedge insertion member) that contacts the outer peripheral wall on one side and the wedge. It is desirable that the energization terminal is inserted into the terminal opening of the wedge insertion member and the wedge is pushed into the wedge opening, whereby the electrode portion and the energization terminal are connected.

[0015] In the honeycomb structure of the present invention, the fixing portion has a terminal opening for inserting the energization terminal and a wedge opening for pushing in the wedge. It consists of a wedge insertion member that contacts the outer peripheral wall on one side and the wedge. When the energization terminal is inserted into the terminal opening of the wedge insertion member and the wedge is pushed into the wedge opening, and the electrode portion and the energization terminal are connected, the wedge insertion member can be firmly fixed to the outer peripheral wall of the honeycomb base material, and even after long-term use, there will be no poor contact between the fixing portion and the honeycomb base material, and stable energization heating can be performed on the honeycomb base material through the fixing portion.

[0016] In the honeycomb structure of the present invention, it is desirable that the portion made of the same material as the honeycomb base material constituting the fixing portion has a coefficient of thermal expansion smaller than that of the honeycomb base material.

[0017] When the coefficient of thermal expansion of the portion made of the same material as the honeycomb base material constituting the fixing portion is larger than the coefficient of thermal expansion of the honeycomb base material, when the temperature rises, the portion made of the same material as the honeycomb base material of the fixing portion expands more and tends to expand outward. Therefore, it is easy to cause damage to the outer peripheral wall and peeling is likely to occur. However, when the coefficient of thermal expansion of the portion made of the same material as the honeycomb base material constituting the fixing portion is smaller than the coefficient of thermal expansion of the honeycomb base material, when the temperature rises, the portion made of the same material as the honeycomb base material does not expand more than the outer peripheral wall, so peeling and the like are less likely to occur.

[0018] In the honeycomb structure of the present invention, it is desirable that the fixing portion is adhered and fixed to the outer peripheral wall with an inorganic conductive adhesive. In the honeycomb structure of the present invention, when the fixing portion is adhered and fixed to the outer peripheral wall with an inorganic conductive adhesive, it is firmly fixed to the outer peripheral wall.

[0019] In the honeycomb structure of the present invention, it is desirable that the fixing portion and the energization terminal are connected in a state where there is play. In the honeycomb structure of the present invention, when the fixing portion and the energization terminal are connected in a state where there is play, it is difficult for the energization terminal or the fixing portion to break or be damaged due to heating and cooling, and the connection between the fixing portion and the energization terminal can be maintained well. Note that the above-mentioned "play" means that there is a slight gap between the members constituting the fixing portion, for example, between a bolt and a nut, between a C-shaped metal member and a columnar portion to which the C-shaped metal member is attached, and between a wedge and a member for pushing the wedge, so that contact can be maintained. As a result, it is difficult for the energization terminal or the fixing portion to break or be damaged even during temperature rise or fall.

[0020] In the honeycomb structure of the present invention, at least the portion of the fixing portion close to the outer peripheral wall is desirably made of a material containing SiC, Si, SiO2, carbon, or borosilicate. In the honeycomb structure of the present invention, when at least a portion of the fixing portion close to the outer peripheral wall is made of a material containing SiC, Si, SiO2, carbon, or silicate, the fixing portion has an appropriate electrical resistance, so that a sufficient current can be supplied to the honeycomb substrate.

Brief Description of the Drawings

[0021]

Figure 1A

Figure 1B

Figure 1C

Figure 2A

Figure 2B

Figure 2C

Figure 3A

Figure 3B

Figure 3C

[0022] (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 includes a honeycomb substrate having cell partitions that partition a large number of cells and an outer peripheral wall, an electrode portion provided on the outer peripheral wall, and an energization terminal connected to the electrode portion via a fixing portion, and is a honeycomb structure comprising: The energization terminal is fixed to the outer peripheral wall by the fixing portion that contacts the electrode portion, and at least a portion of the fixing portion that is close to the outer peripheral wall is made of the same material as the honeycomb substrate.

[0023] According to the honeycomb structure of the present invention, since at least a portion of the fixing portion that is close to the outer peripheral wall is made of the same material as the honeycomb substrate, the stress applied to the fixing portion by heating and cooling can be reduced, and even after long-term use, there will be no poor contact between the fixing portion and the honeycomb substrate, and it is possible to stably energize and heat the honeycomb substrate through the fixing portion, and it can be supplied to a honeycomb structure that can raise the temperature to the catalyst activation temperature in a short time.

[0024] The material of the honeycomb substrate constituting the honeycomb structure of the present invention is not particularly limited, but it is preferably a material containing SiC, Si-impregnated SiC, SiO2, or borosilicate. The material containing borosilicate is a ceramic composed of borosilicate particles and Si-containing particles. In the case of SiC, the honeycomb substrate can be made conductive by doping the SiC constituting the honeycomb substrate with a dopant, and the honeycomb substrate can be heated by energization. Furthermore, it is desirable that the material contains Ni or Cr at a ratio of 5% by weight or less based on the whole.

[0025] The shape of the honeycomb substrate is not particularly limited, but a cylindrical shape is desirable. Its structure preferably has a plurality of through-holes arranged side by side in the longitudinal direction with partition walls therebetween, and an outer peripheral wall provided on the outermost periphery. Further, it is desirable that a catalyst for purifying exhaust gas is supported on the partition walls constituting the honeycomb substrate. Examples of the catalyst to be supported include a three-way catalyst composed of noble metals such as platinum, palladium, and rhodium. These catalysts may be used alone or in combination of two or more.

[0026] When a three-way catalyst composed of noble metals is supported, the amount of noble metals supported on the entire honeycomb substrate is preferably 0.1 to 15 g / L, and more preferably 0.5 to 10 g / L. In this specification, the amount of noble metals supported refers to the weight of noble metals per apparent volume of the honeycomb substrate. The apparent volume of the honeycomb substrate is a volume including the volume of voids, and when an adhesive layer is included, it includes the volume of the adhesive layer.

[0027] The exhaust gas discharged from the internal combustion engine passes through the through-holes of the honeycomb substrate heated to a predetermined temperature, contacts the catalyst, and is purified.

[0028] Examples of the material constituting the electrode portion include the same material as the honeycomb substrate, conductive metals, carbon, etc. As the electrode portion, for example, in the case of an electrode portion using SiC, Si powder is interposed between the two, and by heating to the temperature at which Si melts, the honeycomb substrate and the electrode portion can be adhered. Further, an electrode portion may be formed by applying a paste containing a heat-resistant metal having conductivity to the outer peripheral wall of the honeycomb substrate and firing it.

[0029] In the honeycomb structure of the present invention, the energization terminal is fixed to the outer peripheral wall by a fixing portion that contacts the electrode portion, and at least a portion of the fixing portion close to the outer peripheral wall is made of the same material as the honeycomb substrate.

[0030] The structures of the fixing part and the energizing terminal are not particularly limited, but three embodiments described below are assumed. Hereinafter, the three embodiments will be sequentially described.

[0031] [First Embodiment] The honeycomb structure according to the first embodiment of the present invention includes a honeycomb substrate having cell partitions that partition and form a large number of cells and an outer peripheral wall, an electrode portion provided on the outer peripheral wall, and an energizing terminal connected to the electrode portion via a fixing portion. It is a honeycomb structure provided with. In this honeycomb structure, the fixing portion includes a bolt having a flat portion that contacts the outer peripheral wall and a nut screwed onto the bolt. The through hole of the energizing terminal is inserted into the bolt, and the nut is screwed. Thus, a structure in which the electrode portion and the energizing terminal are connected can be mentioned.

[0032] FIG. 1A is a perspective view schematically showing a fixing portion and an energizing terminal in the honeycomb structure according to the first embodiment of the present invention, FIG. 1B is a front partial cross-sectional view showing the fixing portion and the energizing terminal disposed on the outer peripheral wall, and FIG. 1C is a side partial cross-sectional view showing the fixing portion and the energizing terminal disposed on the outer peripheral wall shown in FIG. 1B. In FIGS. 1B and 1C, the inside of the outer peripheral wall and the portion of the electrode provided on the outer peripheral wall are shown in cross section, and the other portions are shown in front and side views.

[0033] As shown in FIGS. 1A, 1B, and 1C, the fixing portion constituting the honeycomb structure 10 of the present invention includes a bolt 12 having a flat portion 12a and a screw portion 12b whose portion in contact with the outer peripheral wall 11a (electrode portion 15) of the honeycomb substrate 11 is flat, and a nut 13 screwed onto the bolt 12. The energizing terminal 14 is a bent plate-like body made of metal having a through hole 14a for inserting into the bolt 12 and a through hole 14b for connecting an electric wire from a power source.

[0034] Then, as shown in FIGS. 1B and 1C, the flat portion 12a of the bolt 12 is adhered and connected to the electrode portion 15 provided on the surface of the outer peripheral wall 11a of the honeycomb substrate 11 via an inorganic conductive adhesive (not shown). The through hole 14a of the energization terminal 14 is inserted into the threaded portion 12b of the bolt 12, and the electrode portion 15 and the energization terminal 14 are connected by screwing the nut 13.

[0035] In the first embodiment, it is desirable that the bolt 12 including the flat portion 12a, which is at least a portion close to the outer peripheral wall, be made of the same material as the honeycomb substrate 11. Therefore, the bolt 12 may be made of the same material as the honeycomb substrate 11 only for the flat portion 12a, or the entire bolt 12 including the threaded portion 12b may be made of the same material as the honeycomb substrate 11. That is, it is desirable that the flat portion 12a of the bolt 12 or the bolt 12 be made of a material containing SiC, Si-impregnated SiC, SiO2, or borosilicate.

[0036] When the flat portion 12a of the bolt 12 is made of the same material as the honeycomb substrate 11 and the threaded portion 12b on which the threads of the bolt are formed is made of a heat-resistant alloy such as Inconel (registered trademark), austenitic SUS, or molybdenum disilicide, when adhering the flat portion 12a to the electrode portion 15 with an inorganic conductive adhesive, insert the through hole 14a of the energization terminal 14 into the threaded portion 12b, screw on the nut 13, and fix the flat portion 12a and the threaded portion 12b to the electrode portion 15 with an inorganic conductive adhesive. In this case, the tip of the threaded portion 12b on the flat portion 12a side needs to be inserted into and fixed in the recess or through hole formed in the flat portion 12a. The entire bolt 12 may be made of a heat-resistant metal or heat-resistant alloy such as tungsten, molybdenum, tantalum, niobium, Inconel (registered trademark), austenitic SUS, or molybdenum disilicide.

[0037] Examples of the material of the energization terminal 14 include heat-resistant metals such as tungsten, molybdenum, tantalum, niobium, Inconel (registered trademark), austenitic SUS, and molybdenum disilicide, or heat-resistant alloys. Examples of the inorganic conductive adhesive include those using an inorganic binder such as silica sol or alumina sol and silver as a filler, which have heat resistance of 900°C or higher. A method of using a conductive heat-resistant metal and heating and bonding it above the melting temperature may also be employed.

[0038] In the honeycomb structure of the present invention, it is desirable that a portion made of the same material as the honeycomb substrate constituting the fixing portion has a coefficient of thermal expansion smaller than that of the honeycomb substrate.

[0039] When the coefficient of thermal expansion of the portion made of the same material as the honeycomb substrate constituting the fixing portion is smaller than that of the honeycomb substrate, when the temperature rises, the portion made of the same material as the honeycomb substrate does not expand more than the outer peripheral wall, so peeling or the like is less likely to occur. Naturally, the coefficient of thermal expansion of the portion made of the same material as the honeycomb substrate constituting the fixing portion may be the same as that of the honeycomb substrate.

[0040] [Second Embodiment] The honeycomb structure according to the second embodiment of the present invention is a honeycomb structure including a honeycomb substrate having cell partitions that partition and form a large number of cells and an outer peripheral wall, an electrode portion provided on the outer peripheral wall, and a power supply terminal connected to the electrode portion via a fixing portion. In this honeycomb structure, the fixing portion includes a flat portion that contacts the outer peripheral wall, a columnar portion that extends from the flat portion, a tip portion having a larger cross-sectional area than the columnar portion, and a C-shaped metal member attached around the columnar portion. A structure in which the power supply terminal and the C-shaped metal member are attached to the columnar portion, whereby the electrode portion and the power supply terminal are connected, may be mentioned.

[0041] FIG. 2A is a perspective view schematically showing a fixing portion and a power supply terminal in the honeycomb structure according to the second embodiment of the present invention, FIG. 2B is a front partial cross-sectional view showing the fixing portion and the power supply terminal disposed on the outer peripheral wall, and FIG. 2C is a side partial cross-sectional view showing the fixing portion and the power supply terminal disposed on the outer peripheral wall shown in FIG. 2B. In FIGS. 2B and 2C, the cross-section of the portion of the electrode provided inside and on the outer peripheral wall is shown, and the other portions show the front and side views.

[0042] As shown in FIGS. 2A, 2B, and 2C, the fixing portion constituting the honeycomb structure 20 of the present invention includes a connection fixing member 22 composed of a flat portion 22a whose portion in contact with the outer peripheral wall 11a is flat, a columnar portion 22b extending from the flat portion 22a, and a tip portion 22c having a larger cross-sectional area than the columnar portion 22b, and a substantially C-shaped C-type metal member 23 attached around the columnar portion 22b of the connection fixing member 22. The energization terminal 24 is a bent plate-like body made of metal having a through-hole 24a for inserting into the connection fixing member 22 and a through-hole 24b for connecting an electric wire from a power source.

[0043] And as shown in FIGS. 2B and 2C, the flat portion 22a of the connection fixing member 22 is adhered and connected to the electrode portion 15 provided on the surface of the outer peripheral wall 11a of the honeycomb base material 11 via an inorganic conductive adhesive (not shown). The energization terminal 24 is attached to the columnar portion 22b through the through-hole 24a, and further, the C-type metal member 23 is inserted and attached to the columnar portion 22b of the connection fixing member 22, whereby the electrode portion 15 and the energization terminal 24 are connected.

[0044] In the second embodiment, it is desirable that the connection fixing member 22 including the flat portion 22a, which is at least a portion close to the outer peripheral wall, be made of the same material as the honeycomb base material 11. Therefore, the connection fixing member 22 may be made of the same material as the honeycomb base material 11 only for the flat portion 22a, or the entire connection fixing member 22 may be composed of the same material as the honeycomb base material 11. That is, it is desirable that the flat portion 22a of the connection fixing member 22 or the connection fixing member 22 be made of a material containing SiC, Si-impregnated SiC, SiO2, or borosilicate. As the inorganic conductive adhesive, those described in the first embodiment can be used.

[0045] The columnar portion 22b and the tip portion 22c of the connection fixing member 22 may be made of a heat-resistant alloy such as Inconel (registered trademark), austenitic SUS, or molybdenum disilicide. The entire connection fixing member may be made of a heat-resistant metal or a heat-resistant alloy such as tungsten, molybdenum, tantalum, niobium, Inconel (registered trademark), austenitic SUS, or molybdenum disilicide.

[0046] Examples of the material of the energization terminal 24 include heat-resistant metals such as tungsten, molybdenum, tantalum, niobium, Inconel (registered trademark), austenitic SUS, and molybdenum disilicide, or alloys.

[0047] In the honeycomb structure of the present invention, it is desirable that the portion made of the same material as the honeycomb base material constituting the fixing portion has a coefficient of thermal expansion smaller than that of the honeycomb base material.

[0048] [Third Embodiment] The honeycomb structure according to the third embodiment of the present invention includes a honeycomb base material having cell partitions and an outer peripheral wall that partition and form a large number of cells, an electrode portion provided on the outer peripheral wall, and an energization terminal connected to the electrode portion via a fixing portion. In this honeycomb structure, the fixing portion has a terminal opening for inserting the energization terminal and a wedge opening for pressing the wedge, and includes a wedge insertion member that contacts the outer peripheral wall on one side and the wedge. The energization terminal is inserted into the terminal opening of the wedge insertion member, and the wedge is pushed into the wedge opening, whereby the electrode portion and the energization terminal are connected.

[0049] FIG. 3A is a perspective view schematically showing the fixing portion and the energization terminal in the honeycomb structure according to the third embodiment of the present invention, FIG. 3B is a front partial cross-sectional view showing the fixing portion and the energization terminal disposed on the outer peripheral wall, and FIG. 3C is a side partial cross-sectional view showing the fixing portion and the energization terminal disposed on the outer peripheral wall shown in FIG. 3B. In FIGS. 3B and 3C, the inside of the outer peripheral wall and the portions of the electrodes provided on the outer peripheral wall show cross-sections, and the other portions show the front and side views.

[0050] As shown in FIGS. 3A, 3B, and 3C, the fixing portion constituting the honeycomb structure 30 of the present invention has a terminal opening 32a for inserting the energizing terminal 34 and a wedge opening 32b for pressing the wedge 33, and is composed of a box-shaped wedge insertion member 32 that contacts the outer peripheral wall 11a (electrode portion 15) at the bottom surface 32c and the wedge 33. The energizing terminal 34 is a bent plate-like body made of metal having a through-hole 34a for connecting an electric wire from a power source.

[0051] Then, as shown in FIGS. 3B and 3C, the bottom surface 32c and its peripheral portion of the wedge insertion member 32 are adhered and connected to the electrode portion 15 provided on the surface of the outer peripheral wall 11a of the honeycomb base material 11 via an inorganic conductive adhesive (not shown). The energizing terminal 34 is inserted into the terminal opening 32a of the wedge insertion member 32, and the wedge 33 is inserted into the wedge opening 32b, whereby the electrode portion 15 and the energizing terminal 24 are connected. Note that the inside of the wedge insertion member 32 is also filled with an inorganic conductive adhesive, and the energizing terminal 34 and the wedge 33 are also fixed by the inorganic conductive adhesive.

[0052] In the third embodiment, at least the wedge insertion member 32 close to the outer peripheral wall is made of the same material as the honeycomb base material 11. Therefore, it is desirable that the wedge insertion member 32 be made of a material containing SiC, Si-impregnated SiC, SiO2, or borosilicate. The entire wedge insertion member may be composed of a heat-resistant metal or heat-resistant alloy such as tungsten, molybdenum, tantalum, niobium, Inconel (registered trademark), austenitic SUS, or molybdenum disilicide. As the inorganic conductive adhesive, those described in the first embodiment can be used.

[0053] In the honeycomb structure of the present invention, the honeycomb substrate is made conductive, and by passing an electric current through the honeycomb substrate via the energization terminal and the electrode portion, the honeycomb substrate generates heat. Therefore, even immediately after starting an internal combustion engine such as an engine, or even when the internal combustion engine is not operating, if necessary, the honeycomb substrate can reach a temperature at which it functions as a catalyst, and the catalyst supported on the honeycomb substrate can fully exhibit its performance.

[0054] The shape of the honeycomb substrate used in the honeycomb structure of the present invention is not limited to a cylindrical shape, and examples include a prismatic shape, an elliptical prismatic shape, an oblong prismatic shape, a prismatic shape with rounded edges (for example, a triangular prismatic shape with rounded edges).

[0055] The thickness of the partition walls of the honeycomb substrate is preferably uniform. Specifically, the thickness of the partition walls of the honeycomb fired body is preferably less than 0.30 mm. Also, it is preferably 0.05 mm or more. The thickness of the outer peripheral wall of the honeycomb substrate is preferably 0.10 to 0.50 mm.

[0056] The shape of the through-holes constituting the honeycomb substrate is not limited to a quadrangular prism shape, and examples include a triangular prism shape and a hexagonal prism shape. The shapes of the through-holes may be different from each other, but it is preferable that they are all the same. That is, in a cross-section perpendicular to the longitudinal direction of the honeycomb substrate, it is preferable that the sizes of the through-holes surrounded by the partition walls are the same.

[0057] The porosity of the honeycomb substrate is desirably 50% or less. When the porosity of the honeycomb fired body is 50% or less, it is possible to achieve both high mechanical strength and exhaust gas purification performance.

[0058] When the porosity of the honeycomb fired body exceeds 50%, since the porosity becomes too high, the mechanical properties of the honeycomb substrate deteriorate, and cracks, breakages, etc. are likely to occur during use of the honeycomb substrate.

[0059] The honeycomb base material constituting the honeycomb structure is, for example, manufactured by producing a honeycomb fired body having a square column shape by a known manufacturing method, and then laminating a plurality of honeycomb fired bodies via a conductive adhesive layer to produce a honeycomb fired body aggregate composed of a plurality of honeycomb fired bodies. Thereafter, the honeycomb fired body aggregate may be cut to have a cylindrical shape, and an outer peripheral wall may be formed on the outer periphery to obtain a honeycomb base material.

[0060] A catalyst is supported on the honeycomb base material. As a method for supporting a noble metal on the honeycomb base material, for example, a method of immersing the honeycomb fired body or the honeycomb base material in a solution containing high specific surface area particles such as alumina to which noble metal particles are attached and then pulling it out and heating it can be mentioned.

[0061] (Example) Hereinafter, examples specifically disclosing the present invention will be shown. Note that the present invention is not limited only to the following examples.

[0062] (Example 1) [Manufacture of honeycomb base material]

[0063] Si powder, boric acid powder, and silica powder were mixed at a mass ratio of 16:6:78, and 6.7% by weight of an organic binder (methyl cellulose), 4.5% by weight of a lubricant (Unirub manufactured by NOF Corporation), and 14.4% by weight of water were added to the obtained mixed powder (74.4% by weight) and kneaded to prepare a raw material composition.

[0064] The obtained raw material composition was molded using an extrusion molding machine to obtain a honeycomb molded body having a cylindrical shape with a square cross-sectional shape for each cell. Thereafter, a part of the outer peripheral surface of the obtained honeycomb molded body was lightly pressed with a member having a rectangular plane to form a recess for a fixing part for installing the fixing part. Next, the honeycomb molded body having the recess formed was dried by heating with high-frequency dielectric, and then dried at 120°C for 2 hours using a hot air dryer, and both end faces were cut by a predetermined amount to obtain a honeycomb dried body. Then, the honeycomb dried body was degreased (pre-fired) at 600°C for 10 hours, and then fired at 1325°C for 3 hours in an inert atmosphere to manufacture a honeycomb base material.

[0065] Next, Si powder, boric acid powder, and silica powder were mixed at a mass ratio of 80:10:10, and methyl cellulose and a lubricant (Uni Lub manufactured by NOF Corporation) were added as binders. Water and ethanol were also added and mixed to prepare an electrode paste. This electrode paste was applied to the outer peripheral surface of the honeycomb substrate so that the thickness after firing would be 0.35 mm.

[0066] Next, the electrode paste applied to the outer peripheral surface of the honeycomb substrate was dried at 80°C, degreased at 600°C for 10 hours, and then fired at 1325°C for 3 hours in an inert gas atmosphere to obtain a honeycomb substrate having an electrode portion. The end face of the obtained honeycomb substrate was circular with a diameter of 130 mm, and the length in the longitudinal direction of the honeycomb substrate was 60 mm. Further, a recess for a fixing portion was formed in the electrode portion.

[0067] Next, a flat portion 12a of a bolt 12 made of Si and borosilicate was adhered to the recess for a fixing portion where the electrode portion of the honeycomb substrate was formed, using an inorganic conductive adhesive. A through-hole 14a of a current-carrying terminal 14 made of austenitic SUS was inserted into a screw portion 12b of the bolt 12, and a nut 13 made of austenitic SUS was screwed thereon (see FIGS. 1A, 1B, and 1C). A wire was connected to the current-carrying terminal 14, and electricity was supplied at a voltage of 200 V to raise the temperature of the honeycomb substrate to 600°C in 20 seconds. In addition, the above-described current-carrying test was conducted 10 times, but no breakage occurred in the inorganic conductive adhesive, bolt, nut, or current-carrying terminal, and the temperature of the honeycomb substrate could be raised satisfactorily by supplying electricity.

[0068] (Example 2) In the same manner as in Example 1, after manufacturing a honeycomb substrate, a flat portion 22a of a connection fixing member 22 made of Si and borosilicate was adhered to the recess for a fixing portion where the electrode portion of the honeycomb substrate was formed, using an inorganic conductive adhesive. A through-hole 24a of a current-carrying terminal 24 made of austenitic SUS was inserted into the connection fixing member, and a C-shaped metal member 23 made of austenitic SUS was attached (see FIGS. 2A, 2B, and 2C). An electric wire was connected to the energization terminal 24, and energization was performed at a voltage of 200 V to cause the temperature of the honeycomb substrate to reach 600 °C in 20 seconds. Further, the above-mentioned energization test was performed 10 times, but no damage occurred to the inorganic conductive adhesive, the connection fixing member, or the energization terminal, and the honeycomb substrate could be heated up well by energization.

[0069] (Example 3) In the same manner as in Example 1, after manufacturing the honeycomb substrate, a wedge insertion member 32 made of Si and borosilicate was placed in the recess for the fixing part where the electrode part of the honeycomb substrate was formed. An energization terminal 34 made of austenitic SUS was inserted into the terminal opening 32a of the wedge insertion member 32, and a wedge 33 was inserted into the wedge opening 32b made of austenitic SUS. After that, these members were adhered to the electrode part 15 using an inorganic conductive adhesive (see FIGS. 3A, 3B, and 3C). An electric wire was connected to the energization terminal 34, and energization was performed at a voltage of 200 V to cause the temperature of the honeycomb substrate to reach 600 °C in 20 seconds. Further, the above-mentioned energization test was performed 10 times, but no damage occurred to the inorganic conductive adhesive, the wedge insertion member, the wedge, or the energization terminal, and the honeycomb substrate could be heated up well by energization.

Explanation of reference numerals

[0070] 10, 20, 30 Honeycomb structure 11 Honeycomb substrate 11a Outer peripheral wall 12 Bolt 12a Flat part 12b Threaded part 13 Nut 14, 24, 34 Energization terminal 14a, 14b, 24a, 24b, 34a Through hole 15 Electrode part 22 Connection fixing member 22a Flat part 22b Columnar part 22c Tip part 23 C-shaped metal member 32 Wedge insertion member 32a Terminal opening Opening for Wedge 32b Bottom Surface 32c Wedge 33

Claims

1. A honeycomb structure comprising a honeycomb substrate having cell partitions that form a plurality of cells and an outer peripheral wall, an electrode portion provided on the outer peripheral wall, and an energization terminal connected to the electrode portion via a fixing portion, wherein the energization terminal is fixed to the outer peripheral wall by the fixing portion that contacts the electrode portion, and at least a portion of the fixing portion close to the outer peripheral wall is made of a material containing Si and silicate, wherein the honeycomb substrate is made of a material containing Si, SiO₂, and silicate. The honeycomb structure is characterized by this.

2. The honeycomb structure according to claim 1, wherein the fixing portion comprises a bolt having a flat portion that contacts the outer peripheral wall and a nut screwed onto the bolt, and a through-hole of the energization terminal is inserted into the bolt, and the nut is screwed so that the electrode portion and the energization terminal are connected.

3. The honeycomb structure according to claim 1, wherein the fixing portion comprises a flat portion that contacts the outer peripheral wall, a columnar portion extending from the flat portion, a tip portion having a larger cross-sectional area than the columnar portion, and a C-shaped metal member attached around the columnar portion, and the energization terminal and the C-shaped metal member are attached to the columnar portion so that the electrode portion and the energization terminal are connected.

4. The fixing portion has an opening for the terminal for inserting the energization terminal and an opening for the wedge for pushing in the wedge, and comprises a member that contacts the outer peripheral wall on one side and the wedge. The honeycomb structure according to claim 1, wherein the energization terminal is inserted into the opening for the terminal, and the wedge is pushed into the opening for the wedge so that the electrode portion and the energization terminal are connected.

5. The honeycomb structure according to any one of claims 1 to 4, wherein at least a portion of the fixing portion close to the outer peripheral wall has a coefficient of thermal expansion smaller than that of the honeycomb substrate.

6. The honeycomb structure according to any one of claims 1 to 5, wherein the fixing portion is adhered and fixed to the outer peripheral wall by an inorganic conductive adhesive.

7. The honeycomb structure according to any one of claims 1 to 6, wherein the fixing portion and the energization terminal are connected in a state where there is play.

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