JP5765221B2 - Electric heating catalyst device and method for manufacturing the same - Google Patents

Description

  The present invention relates to an electrically heated catalyst device and a manufacturing method thereof.

  In recent years, an electrically heated catalyst (EHC) attracts attention as an exhaust gas purification device that purifies exhaust gas discharged from an engine such as an automobile. In EHC, even if the exhaust gas temperature is low, such as immediately after the engine is started, and the catalyst is difficult to activate, the catalyst is forcibly activated by energization heating to increase the exhaust gas purification efficiency. Can do.

  The EHC disclosed in Patent Document 1 is a cylindrical carrier having a honeycomb structure on which a catalyst such as platinum or palladium is supported, and is electrically connected to the carrier and arranged opposite to the outer peripheral surface of the carrier. A pair of surface electrodes. In this EHC, the support is energized and heated between the pair of surface electrodes to activate the catalyst supported on the support. Thereby, unburned HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen oxide) and the like in the exhaust gas passing through the carrier are purified by the catalytic reaction.

  Since EHC is provided on the exhaust path of automobiles, etc., the surface electrode material is required not only to have electrical conductivity, but also to have heat resistance, oxidation resistance at high temperatures, and corrosion resistance in an exhaust gas atmosphere. The Therefore, as disclosed in Patent Document 1, a metal material such as a Ni—Cr alloy or a MCrAlY alloy (where M is at least one of Fe, Co, and Ni) is used. The surface electrode is formed on the carrier by thermal spraying. On the other hand, a ceramic material such as SiC (silicon carbide) is used as the material of the carrier. For this reason, during energization heating, thermal stress is generated due to a difference in linear expansion coefficient between the metal material constituting the surface electrode and the ceramic material constituting the carrier.

JP 2011-106308 A

The inventor has found the following problems.
The surface electrode of the EHC extends in the axial direction of the cylindrical carrier. Further, a metal wiring is connected to the center portion of the surface electrode in the carrier axial direction, and current is supplied. When this current spreads in the direction of the carrier axis in the surface electrode, the entire carrier is energized and heated between the pair of surface electrodes.
When energization heating is repeated, cracks in the circumferential direction of the carrier are generated in the surface electrode due to the above-described thermal stress, and current spreading in the direction of the carrier axis is inhibited. As a result, the vicinity of the connection portion between the surface electrode and the metal wiring ( There was a problem that the central part in the axial direction of the carrier was heated intensively.

  The present invention has been made in view of the above, and it is an object of the present invention to provide an electrically heated catalyst device in which the direction of cracks generated in a surface electrode is controlled and the spread of current in the carrier axis direction is maintained. To do.

The electrically heated catalyst device according to one aspect of the present invention is
A carrier made of ceramics carrying a catalyst;
A pair of surface electrodes extending in the axial direction of the carrier while facing each other on the outer peripheral surface of the carrier;
Wiring for supplying electric power to the surface electrode from the outside, and an electrically heated catalyst device for electrically heating the carrier through the surface electrode,
Grooves for controlling the extending direction of cracks generated in the surface electrode are formed on the surface of the surface electrode.
It is possible to provide an electrically heated catalyst device in which the direction of cracks generated in the surface electrode is controlled and the spread of current in the carrier axis direction is maintained.

It is preferable that the wiring is connected to the central portion in the axial direction of the carrier in the surface electrode, and the groove extends in the axial direction of the carrier.
Moreover, it is preferable that the depth of the groove is 1/10 to 2/3 of the surface electrode. Thereby, the direction of the crack which generate | occur | produces in a surface electrode can be controlled reliably.
Furthermore, it is preferable that the cross-sectional shape of the groove is a wedge shape. Thereby, the direction of the crack which generate | occur | produces in a surface electrode can be controlled more reliably.

The surface electrode may be a thermal spray coating made of a Ni—Cr alloy (provided that the Cr content is 20 to 60% by mass) or a MCrAlY alloy (where M is at least one of Fe, Co, and Ni). preferable.
Furthermore, it is preferable that the ceramic contains SiC.

A method for producing an electrically heated catalyst device according to an aspect of the present invention includes:
A method for producing an electrically heated catalyst device in which the carrier is energized and heated via a surface electrode formed on the surface of a carrier made of ceramics on which a catalyst is supported,
Forming a pair of surface electrodes extending in the axial direction of the carrier so as to face each other on the outer peripheral surface of the carrier; and
Forming a groove on the surface of the surface electrode for controlling an extension direction of a crack generated in the surface electrode;
Connecting wiring for supplying electric power from the outside to the surface electrode.

In the step of forming the groove, the groove extends in the axial direction of the carrier, and in the step of connecting the wiring, the wiring is connected to the central portion in the axial direction of the carrier in the surface electrode. preferable.
Moreover, it is preferable that the depth of the groove is 1/10 to 2/3 of the surface electrode.
Furthermore, the cross-sectional shape of the groove is preferably a wedge shape.

  According to the present invention, it is possible to provide an electrically heated catalyst device in which the direction of cracks generated in the surface electrode is controlled and the spread of current in the carrier axis direction is maintained.

1 is a perspective view of an electrically heated catalyst device 100 according to Embodiment 1. FIG. FIG. 3 is a plan view seen from directly above the surface electrode 31 of the electrically heated catalyst device 100 according to the first embodiment. It is sectional drawing by the III-III cutting line in FIG. It is sectional drawing by the IV-IV cutting line in FIG. It is sectional drawing by the IV-IV cutting line in FIG. 2, Comprising: It is a figure which shows the modification of the cross-sectional shape of the groove | channel 31a. It is sectional drawing by the IV-IV cutting line in FIG. 2, Comprising: It is a figure which shows the modification of the cross-sectional shape of the groove | channel 31a. It is a top view of the surface electrode 31 of the electric heating type catalyst apparatus 100 which concerns on Embodiment 1, Comprising: It is a figure which shows the modification of the pattern of the groove | channel 31a. It is a top view of the surface electrode 31 of the electric heating type catalyst apparatus 100 which concerns on Embodiment 1, Comprising: It is a figure which shows the modification of the pattern of the groove | channel 31a. It is a top view of the surface electrode 31 of the electric heating type catalyst apparatus 100 which concerns on Embodiment 1, Comprising: It is a figure which shows the modification of the pattern of the groove | channel 31a. 6 is a plan view seen from directly above a surface electrode 31 of an electrically heated catalyst device 200 according to Embodiment 2. FIG.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

(Embodiment 1)
First, with reference to FIGS. 1-4, the electrically heated catalyst apparatus which concerns on Embodiment 1 is demonstrated. FIG. 1 is a perspective view of an electrically heated catalyst device 100 according to the first embodiment. FIG. 2 is a plan view seen from directly above the surface electrode 31 of the electrically heated catalyst device 100 according to the first embodiment. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2 and is a cross-sectional view at a portion where the fixed layer 33 is formed. 4 is a cross-sectional view taken along the line IV-IV in FIG.

  The electrically heated catalyst device 100 is provided on an exhaust path of an automobile or the like, for example, and purifies exhaust gas discharged from the engine. As shown in FIG. 1, the electrically heated catalyst device 100 includes a carrier 20, a surface electrode 31, a wiring 32, and a fixed layer 33. A groove 31 a is formed in the surface electrode 31. In FIG. 1, the groove 31a formed on the surface of the surface electrode 31 is omitted. 2 shows the positional relationship of the carrier 20, the wiring 32, the fixed layer 33, and the groove 31a for one surface electrode 31, the same applies to the other surface electrode 31.

  The carrier 20 is a porous member that supports a catalyst such as platinum or palladium. Further, since the carrier 20 itself is energized and heated, it is made of a ceramic having conductivity, specifically, for example, SiC (silicon carbide). As shown in FIG. 1, the carrier 20 has a substantially cylindrical outer shape and has a honeycomb structure inside. As indicated by the arrows, the exhaust gas passes through the inside of the carrier 20 in the axial direction of the carrier 20.

  As shown in FIG. 1, the surface electrode 31 is a pair of electrodes that are arranged to face each other on the outer surface of the carrier 20. As shown in FIG. 2, the surface electrode 31 has a rectangular planar shape and extends in the carrier axis direction. The surface electrode 31 is not formed near both ends in the carrier axis direction. The surface electrode 31 is connected to a power source such as a battery via a wiring 32. Then, a current is supplied to the carrier 20 through the surface electrode 31 and heated by energization. One of the pair of surface electrodes 31 is a positive electrode and the other is a negative electrode. However, any surface electrode 31 may be a positive electrode or a negative electrode. That is, the direction of the current flowing through the carrier 20 is not limited.

  Here, as shown in FIG. 2, on the surface of the surface electrode 31, a groove 31a for controlling the direction of a crack generated by a thermal cycle load extends in the carrier axis direction. As shown in FIG. 4, the cross-sectional shape of the groove 31a is a wedge shape. Stress concentrates on the apex of the wedge, and cracks occur along the apex of the wedge. Here, FIGS. 5A and 5B are cross-sectional views taken along the line IV-IV in FIG. 2, and are diagrams showing modifications of the cross-sectional shape of the groove 31 a. As shown in FIGS. 5A and 5B, the cross-sectional shape of the groove 31a is not limited to the wedge shape, and may be a semicircular shape or a rectangular shape. Details of the groove 31a will be described later.

  As shown in FIG. 1, the plurality of wirings 32 are disposed on each of the pair of surface electrodes 31. The plurality of wirings 32 are ribbon-like thin metal plates that are in physical contact with and electrically connected to the surface electrode 31. In order to withstand use at a high temperature of 800 ° C. or higher, the wiring 32 is preferably made of a heat-resistant (oxidation-resistant) alloy such as a stainless alloy, a Ni-based alloy, or a Co-based alloy.

  Further, as shown in FIG. 2, the plurality of wirings 32 are extended over the entire region where the surface electrode 31 is formed in the carrier circumferential direction. Further, all the wirings 32 are extended from one side of the formation region of the surface electrode 31 and are integrated at the protruding end. On the other hand, the plurality of wirings 32 are arranged on the surface electrode 31 at substantially equal intervals along the carrier axis direction. In the electrically heated catalyst device 100 according to the present embodiment, twelve wirings 32 are provided in the central portion in the axial direction of the carrier 20 on each surface electrode 31. As a matter of course, the number of the wirings 32 is not limited to 12, but is determined as appropriate.

  The carrier 20 is fixed and held on the exhaust path by a mat (not shown) made of a heat-resistant material in the vicinity of both ends in the carrier axial direction. When the wiring 32 comes into contact with the mat, friction is generated between the wiring 32 and the mat due to a thermal cycle load, and the wiring 32 may be disconnected. Therefore, in the electrically heated catalyst device 100 according to the first embodiment, the wiring 32 is disposed only in the center portion in the carrier axial direction where no mat is formed.

  As shown in FIGS. 1 and 2, the wiring 32 is fixed to the surface electrode 31 by a fixing layer 33. Here, FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2, and is a cross-sectional view at a portion where the fixed layer 33 is formed. As shown in FIG. 3, the surface electrode 31 is a sprayed coating having a thickness of 50 to 200 μm formed on the outer peripheral surface of the carrier 20. The surface electrode 31 is in physical contact with the carrier 20 and is electrically connected.

  The fixing layer 33 is a button-shaped sprayed coating formed so as to cover the wiring 32 in order to fix the wiring 32 to the surface electrode 31. Here, the fixed layer 33 is button-shaped in order to relieve stress based on the difference in coefficient of linear expansion between the surface electrode 31 and the fixed layer 33 that are metal-based thermal sprayed coatings and the carrier 20 made of ceramics. It is. That is, the stress is relieved by making the fixed layer 33 as small as possible. As shown in FIG. 2, the fixed layer 33 is in physical contact with and electrically connected to the wiring 32 and the surface electrode 31.

  As shown in FIG. 1, the fixing layer 33 is provided at two locations on each wiring 32 so as to fix the wiring 32 to the surface electrode 31 at substantially both ends in the carrier circumferential direction. Further, as shown in FIG. 3, in the wirings 32 adjacent to each other, the fixed layer 33 is arranged so as to be shifted in the carrier circumferential direction. In other words, on each surface electrode 31, along the two long sides of the rectangular surface electrode 31, twelve fixing layers 33 on each side are arranged in a zigzag manner in the carrier axis direction.

  Since the thermal spray coating constituting the surface electrode 31 and the fixed layer 33 is energized in the same manner as the wiring 32, it needs to be a metal base. The metal constituting the matrix of the thermal spray coating is a Ni-Cr alloy having excellent oxidation resistance at high temperatures in order to withstand use at high temperatures of 800 ° C. or higher (however, the Cr content is 20 to 60% by mass) ), MCrAlY alloy (where M is at least one of Fe, Co and Ni). Here, the NiCr alloy and MCrAlY alloy may contain other alloy elements. The thermal spray coating constituting the surface electrode 31 and the fixed layer 33 may be porous. By being porous, the function to relieve stress is enhanced.

  With the above configuration, in the electrically heated catalyst device 100, the carrier 20 is electrically heated between the pair of surface electrodes 31, and the catalyst supported on the carrier 20 is activated. Thereby, unburned HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen oxide) and the like in the exhaust gas passing through the carrier 20 are purified by the catalytic reaction.

  Next, the details of the groove 31a will be described. As shown in FIG. 2, seven grooves 31 a are provided by being divided into both ends of the surface electrode 31 in the carrier axis direction of the surface electrode 31 via the center part in the carrier axis direction of the surface electrode 31. That is, the groove 31a is not provided at the center in the carrier axial direction of the surface electrode 31 to which the wiring 32 is connected. In addition, the groove | channel 31a may be provided over the whole carrier axial direction of the surface electrode 31, without dividing. As a matter of course, the number of the grooves 31a is not limited to seven, and is appropriately determined.

  In the electrically heated catalyst device 100 according to the present embodiment, since the groove 31a extending in the carrier axial direction is formed on the surface of the surface electrode 31, a crack in the carrier axial direction along the groove 31a is likely to occur. Become. That is, it becomes difficult for cracks in the carrier circumferential direction to occur in the surface electrode 31, and the current spread in the carrier axial direction is maintained. Therefore, the vicinity of the central portion in the axial direction of the carrier 20 is not intensively heated, and thermal stress cracking due to this intensive heating can be avoided.

  Here, the groove 31a can be formed by embossing, grinding, cutting, or the like after the surface of the surface electrode 31 that is a thermal spray coating is smoothed by polishing. The depth of the groove 31a is preferably 1/10 to 2/3 of the thickness of the surface electrode 31. If the depth of the groove 31a is less than 1/10 of the thickness of the surface electrode 31, the crack direction cannot be controlled. On the other hand, if the depth of the groove 31a exceeds 2/3 of the thickness of the surface electrode 31, formation of the groove 31a becomes extremely difficult, and the carrier 20 may be damaged due to processing resistance or the like.

  Next, a modified example of the pattern of the groove 31a will be described with reference to FIGS. 6A to 6C are plan views of the surface electrode 31 of the electrically heated catalyst device 100 according to the first embodiment, and are diagrams showing modifications of the pattern of the groove 31a. Even if any of the patterns of the grooves 31a shown in FIGS. 6A to 6C is used, the same effects as those of the electrically heated catalyst device 100 shown in FIG. 2 can be obtained.

  Like the pattern of the groove 31a shown in FIG. 6A, the groove 31a may be divided into a plurality of pieces in the carrier axis direction. Furthermore, as shown to FIG. 6A, each groove | channel 31a may be arrange | positioned at zigzag form.

  Moreover, the groove | channel 31a may have the part formed in the support | carrier circumferential direction like the pattern of the groove | channel 31a shown by FIG. 6B. For example, as shown in FIG. 6B, an H-shaped configuration comprising two grooves extending in the carrier axis direction and one groove extending in the carrier circumferential direction connecting the central portions of the two grooves. The basic pattern may be aligned. In the basic pattern, a ladder shape having two or more grooves extending in the circumferential direction of the carrier may be used.

  Furthermore, like the pattern of the groove 31a shown in FIG. 6C, the groove 31a may be formed obliquely rather than parallel to the carrier axis direction. For example, as shown in FIG. 6C, a configuration in which a plurality of grooves formed obliquely may be formed in a zigzag manner in the carrier axis direction.

  As shown in FIGS. 6A to 6C, in the surface electrode 31 according to the first embodiment, a groove pattern in which a crack generated by a thermal cycle load extends in the carrier axial direction and does not extend in the carrier circumferential direction. If it is, it will not specifically limit.

(Embodiment 2)
Next, with reference to FIG. 7, the electrically heated catalyst device according to the second embodiment will be described. FIG. 7 is a plan view seen from directly above the surface electrode 31 of the electrically heated catalyst device 200 according to the second embodiment. In the electrically heated catalyst device 100 according to the first embodiment, the wiring 32 is arranged only in the center portion of the surface electrode 31 in the carrier axial direction. On the other hand, in the electrically heated catalyst device 200 according to the second embodiment, as shown in FIG. 7, the wires 32 are arranged uniformly over the entire carrier axis direction. Furthermore, in the electrically heated catalyst device 100 according to the first embodiment, the groove 31a extends in the carrier axis direction. On the other hand, in the electrically heated catalyst device 200 according to the second embodiment, as shown in FIG. 7, eleven grooves 31a are extended in the carrier circumferential direction between the adjacent wires 32.

  In the electrically heated catalyst device 200 according to the present embodiment, since the groove 31a extending in the carrier circumferential direction is formed on the surface of the surface electrode 31, a crack in the carrier circumferential direction along the groove 31a occurs. It becomes easy to do. Even if the surface electrode 31 is divided into 12 blocks by this crack, the wiring 32 is connected to each block, so that the current spread in the carrier axis direction is maintained. Therefore, the vicinity of the central portion in the axial direction of the carrier 20 is not intensively heated, and thermal stress cracking due to this intensive heating can be avoided.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

20 Carrier 31 Surface electrode 31a Groove 32 Wiring 33 Fixed layer 100, 200 Electric heating catalyst device

Claims (8)

A carrier made of ceramics carrying a catalyst;
A pair of surface electrodes extending in the axial direction of the carrier while facing each other on the outer peripheral surface of the carrier;
Wiring for supplying electric power to the surface electrode from the outside, and an electrically heated catalyst device for electrically heating the carrier through the surface electrode,
On the surface of the surface electrode is formed with a groove for controlling the direction of extension of cracks generated on the surface electrode,
The wiring branches into a plurality of branches and extends in the circumferential direction of the carrier, and is connected to the central portion in the axial direction of the carrier at the surface electrode,
The energization heating type catalyst device is characterized in that the groove extends in the axial direction of the carrier in the surface electrode and is not formed in the central portion . Electrically heating type catalyst device according to claim 1, the depth of the groove, characterized in that it is a 1 / 10-2 / 3 of the surface electrode. Cross-sectional shape of the groove is electrically heating type catalyst device according to claim 1 or 2, characterized in that a wedge-shaped. The surface electrode is a sprayed coating made of a Ni—Cr alloy containing 20 to 60 mass% of Cr , or a MCrAlY alloy containing at least one of Fe, Co, and Ni as M. The electrically heated catalyst device according to any one of to 3 . The electrically heated catalyst device according to any one of claims 1 to 4 , wherein the ceramic contains SiC. A method for producing an electrically heated catalyst device in which the carrier is energized and heated via a surface electrode formed on the surface of a carrier made of ceramics on which a catalyst is supported,
Forming a pair of surface electrodes extending in the axial direction of the carrier so as to face each other on the outer peripheral surface of the carrier; and
Forming a groove on the surface of the surface electrode for controlling an extension direction of a crack generated in the surface electrode;
E Bei and a step of connecting the wiring for supplying power from outside to said surface electrode,
In the step of forming the groove, the groove extends in the axial direction of the carrier, and is not formed in the central portion in the axial direction of the carrier.
In the step of connecting the wires, the method of manufacturing an electrically heated catalyst device is characterized in that the wires branched into a plurality of wires and extending in the circumferential direction of the carrier are connected to the central portion . The depth of the said groove | channel is 1/10-2/3 of the said surface electrode, The manufacturing method of the electrically heated catalyst apparatus of Claim 6 characterized by the above-mentioned. The method of manufacturing an electrically heated catalyst device according to claim 6 or 7 , wherein a cross-sectional shape of the groove is a wedge shape.

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