Metal honeycomb and production method thereof

Abstract: This invention relates to a production method for a metal carrier for carrying a catalyst for cleaning exhaust gas of an automobile by forming a core part having a honeycomb cross section, and inserting the resulting core part into an outer cylinder having a diameter nearly equal to that of the outer diameter of the core part, wherein at least one end of the outer cylinder is expanded and a chip of the core part into the outer cylinder, an end face of the core part is pressed to drive the core part into the outer cylinder, and the assembly is heat treated to contract and restore the expanded end; or, a foil solder material is wound around the outer periphery to form a core part having a foil solder wound part, and inserting the resulting core part into an outer cylinder having an inner diameter nearly equal to the outer diameter of the core part, characterized in that the core part is contracted by a split die having a stepped part to a diameter smaller than an inner diameter of the outer cylinder, and the core part is pressed into the outer cylinder to engage the core part with the outer cylinder; or, for a non-circular metal honeycomb carrier, placing two rod-formed or plate-formed winding members having splits, placed at a predetermined interval, as a center part, inserting ends of a flat plate and a corrugated plate to be wound into the splits, winding the flat plate and the corrugated plate around the outer periphery of the center part to form a core part, and encasing the core part into an outer cylinder to form a non-circular metal honeycomb carrier.

Description: This invention relates to a metal honeycomb for carrying a catalyst for cleaning automobile exhaust gas and a production method thereof. A metal honeycomb carrier for carrying a catalyst for cleaning automobile exhaust gas comprises a core part having a honeycomb cross section obtained by stacking flat steel plates and corrugated steel plates and winding round the stacked plates, and a metallic outer cylinder for containing the core part. Since a high-temperature exhaust gas of the automobile recirculates in the metal honeycomb carrier, it is necessary that the outer diameter of the core part and the inner diameter of the outer cylinder are nearly equal to each other so that a clearance between both is as small as possible. For this purpose, various methods are used in inserting the core part into the outer cylinder. For example, Japanese Patent Publication 57-55886 discloses a method in which the core part is pressed into the outer cylinder, the diameter of the outer cylinder is reduced by a contracting tool capable of press-fitting the outer cylinder, and the core part and the outer cylinder are welded or soldered to an extent of press-fitting to link one another. However, with this method, since the core part is difficult to adapt to the outer cylinder, a space tends to be left between the core part and the outer cylinder. On the other hand, to clean an exhaust gas emitted from an internal combustion engine of automobiles, motorcycles, and the like, a core part comprising a honeycomb structure carrying a catalyst is pressed into an outer cylinder to form a metal honeycomb carrier, which is mounted in a gas cleaning apparatus, and the exhaust gas is passed through the carrier to clean the gas. However, a gas pipe for mounting the honeycomb carrier in the exhaust gas cleaning apparatus is not always circular, but often have elliptical or other specific shapes, and the cross section of the metal honeycomb carrier must be in line with the cross sectional shape of the gas pipe mounting the honeycomb carrier. For this purpose, there has heretofore been known a method for producing a non-circular metal honeycomb carrier, in which after a circular honeycomb structure is pressed into an outer cylinder, a die is used to press the carrier to an oval or elliptical cross section (Japanese Patent Publication 57-55886). However, this method has problems in that a deformation occurs in the cell shape between the longer diameter side and the shorter diameter side, and the joining strength is reduced or the cell density is varied, affecting the gas flow distribution. As another method, a center part having a similar shape to a non-circular outer cylinder and having smaller cross sectional dimensions than the outer cylinder by predetermined values is formed, a flat plate and a corrugated plate are wound around the center part to form a core body, and the core body is pressed into the non-circular outer cylinder (Japanese Patent Laid-open Publication 3-196844). However, this method has disadvantages in that since the center part is first fabricated, and the corrugated plate and the flat plate are wound round using the center part as a winding shaft into a honeycomb form, the production takes a long time and the productivity is low. The inventors have conducted intensive studies to improve these problems so that the core part is easily engaged with the outer cylinder to link them securely, achieving the present invention. A primary object of the present invention is to provide a method for producing a metal honeycomb carrier having a good workability. A further object of the present invention is to provide a method for producing a metal honeycomb carrier in which a flat plate and a corrugated plate regularly contact with each other to form a type of cell structure, without deforming the honeycomb structure. EP-A-0609449, from which the present application is divided, is directed to a method for producing a metal honeycomb carrier for carrying an exhaust gas cleaning catalyst comprising the steps of: stacking corrugated plates and flat plates in alternation; winding round the stacked plates to form a core part having a honeycomb cross section; and inserting said resulting core part into an outer cylinder having an inner diameter nearly equal to an outer diameter of said core part by contracting said core part with a core die and pressing said core part into said outer cylinder to engage said core part with said outer cylinder; characterised in that: the core part is contracted by the core die to a diameter smaller than the inner diameter of said outer cylinder. Thus, there may be provided a method for producing a metal honeycomb carrier for carrying an exhaust gas cleaning catalyst comprising the steps of stacking corrugated plates and flat plates in alternation, winding round the stacked plates to form a core part having a honeycomb cross section, and inserting the resulting core part into an outer cylinder having an inner diameter nearly equal to an outer diameter of the core part, wherein at least one end of the outer cylinder is expanded and a chip of the core part into the outer cylinder, an end face of the core part is pressed to drive the core part into the outer cylinder, and the assembly is heat treated to contract and restore the expanded end. That is the inner diameter of at least one end of the outer cylinder is expanded, at least one end of the core part is inserted into the expanded outer cylinder, the other end of the core part is pressed, and the assembly is then heat treated to shrink the expanded portion for restoration. This cylinder expansion means that the end of the outer cylinder is expanded to an extent that a chip of the core part can be just inserted into the outer cylinder, and typically an expansion of approximately 0.1 to 0.5 mm from the inner diameter of the outer cylinder is sufficient, for example, using a cylinder expansion die having a trapezoidal cross section as cylinder expansion means, which is inserted into the outer cylinder until a predetermined expansion size is achieved. After that, the other end of the core part is pressed by an hydraulic cylinder, or by gripping the core part by a robot hand, to press the entire core part into the outer cylinder. When the hydraulic cylinder is used, it is preferable to use a holder plate on the upper portion of the core part in order to prevent the core from being damaged or flawed due to a load concentration. Furthermore, when the robot hand is used, the core part is gripped by the robot hand and pressed in up to a predetermined position, then the hand is loosened, and the core part is gripped again at a position upper than the inserted portion to be pressed in again by the hand. This procedure is repeated until the entire core part is pressed in. After the pressing, heat treatment is made to restore the expanded cylinder, at a temperature of 800 to 1,200°C for 5 hours to 20 minutes. When the core part and the outer cylinder are soldered, heat treatment may be made at about 1,200°C for 20 minutes under vacuum to achieve restoration and soldering heat treatment. According to the present invention, there is provided a non-circular metal honeycomb carrier comprising a centre part including two rod-formed or plate-formed winding members having splits opposing with a predetermined interval, a core part present on an outer periphery of said centre part formed by inserting in opposite respective directions ends of a flat plate and a corrugated plate into the splits of said winding members and winding round the plates, and an outer cylinder containing said core part. According to the present invention, there is also provided a method for producing a non-circular metal honeycomb carrier comprising the steps of placing two rod-formed or plate-formed winding members having splits, inserting in opposite respective directions ends of a flat plate and a corrugated plate to be wound into said splits, winding the flat plate and the corrugated plate around said winding members by rotating said winding members to form a non-circular metal honeycomb structure, and encasing said non-circular metal honeycomb carrier into a non-circular outer cylinder having the same shape. According to the present invention, there is also provided a method for producing a non-circular metal honeycomb carrier comprising the steps of holding two rod-formed or plate-formed winding members having splits maintaining a predetermined interval, inserting in opposite respective directions ends of a flat plate and a corrugated plate to be wound into said splits, winding the flat plate and the corrugated plate around said winding members to form a non-circular metal honeycomb structure, and encasing said non-circular metal honeycomb carrier into a non-circular outer cylinder having the same shape. The present invention will now be described with reference to the drawings. In the present invention, corrugated plates and flat plates are stacked in alternation to form the core part 1. When the resulting core part 1 is pressed into the outer cylinder 3, 2-part pressing stepped dies 6 and 6 having a stepped part 5 as shown in Fig.2 are used. The outer cylinder 3 is held by a large diameter part of the pressing stepped dies 6 and 6, and the core part 1 is held by a small diameter part, and a pressure is applied by the dies 6 and 6 to the core part 1 to contract it. The pressure applied is about 3 kgf/cm 2 . This reduces the diameter of the core part 1 by about 3%, and the core part and the outer cylinder 3 are shaped to round forms. Then, a pressure is applied uniformly by a hydraulic cylinder from the upper part of the core part 1 to press the core part 1 into the outer cylinder 3. This condition is shown in Fig.2(b). In this case, it is preferable to use a holder plate on the upper portion of the core part 1 in order to prevent the core from being damaged or flawed due to a load concentration, and it is also preferable to provide a taper 9 on the inner surface of the core mounting part of the die to facilitate insertion into the outer cylinder. Referring to Fig.3, the pressing die is 2-part split dies which comprise a core die 7 and an outer cylinder die 8. Corrugated plates and flat plates are stacked in alternation to form the core part 1, and the resulting core part 1 is wound round on the outermost periphery with a foil solder material 2. The core part 1 is held by the core dies 7 and 7, and the outer cylinder is held by a receiving tool, for example, the outer cylinder dies 8 and 8. The core dies may be replaced with a robot hand. The core dies 7 and 7 held with the core part 1 are placed to engage with the outer cylinder 3. The outer diameter of the core part 1 is contracted by the core dies to be smaller than the inner diameter of the outer cylinder, and pressed into the outer cylinder. The pressing means is as described above. Fig.4 is a schematic perspective view of the non-circular metal honeycomb carrier of the present invention. Referring to Fig.4, a flat plate 11 and a corrugated plate 12 are formed by winding in alternation, and then encased in a non-circular outer cylinder 3. Fig.5 is a schematic view for explaining the production method of the non-circular metal honeycomb. First, two split pin-formed winding shafts 13 and 13 as rod-formed winding members are disposed in parallel at an interval X to coincide with the shape of a honeycomb carrier to be formed (a). Then, ends of the flat plate 11 and the corrugated plate 12 are individually inserted into splits of the individual winding shafts 13 and 13 (b). While maintaining the interval between the winding shafts 13 and 13, the winding shafts 13 and 13 are rotated about a winding center axis 14 provided at the center of the winding shafts to stack and wind the flat plate and the corrugated plate (c), (d). In another embodiment of the production method according to the present invention, two rod-formed winding members 13 and 13 having splits as rod-formed winding members are disposed and retained in parallel at an interval X to coincide with the shape of the honeycomb carrier to be formed. The flat plate and the corrugated plate are wound around the winding members while stacking the plates. Fig.6 is a schematic view for explaining a case where plate-formed members are used as the winding members. Referring to Fig.6, the winding members comprising plate-formed members 15 and 15 have a length X according to the shape of a honeycomb body 4, and side edges of the flat plate and the corrugated plate are inserted into the splits of the winding members to be retained (a). Then, the flat plate 11 and the corrugated plate 12, while being stacked, are wound around the winding members to form a core body (b). In the present invention, the non-circular honeycomb structure 1 is formed of the flat plate 11 and the corrugated plate 12 using the above method to form a core part, which is pressed into the outer cylinder 3 having the same shape as the core part. The present invention will be described further in detail with reference to the embodiments. Referring to Fig.1, a cylinder expansion die 2 is inserted by about 1 to 2 mm into one end face of an outer cylinder 3 (a) to expand the inner diameter of the end portion of the outer cylinder 3 end by 0.1 to 0.2 mm. The expanded cylinder end is shown in b. Then, a core part 1 is inserted into the expanded outer cylinder 3, a pressure is applied from the other end face of the core part to press the core part into the outer cylinder 3 (d), the assembly is heat treated at about 900°C for 60 minutes to restore the expanded portion, thereby obtaining a metal honeycomb carrier 4. Corrugated plates and flat plates comprising 0.05-mm thick stainless steel foils were stacked, and the stacked foils were wound round to form a core part with an outer diameter of 150 mm having a honeycomb cross section. The resulting core part was set in a pressing stepped die shown in Fig.2(a), the die was pressed in the axial direction at a pressure of 3 kgf/cm 2 to contract the core diameter to 149.5mm. The core was then pressed from the upper portion with a uniform pressure of about 5 kgf/cm 2 into an outer cylinder. This condition is shown in Fig.2(b). In this case, it is preferable to use a holder plate in order to prevent the core part from being damaged or flawed due to a concentration of load. Corrugated plates comprising 0.05-mm thick stainless steel foils and flat plates of the same thickness were stacked, the stacked foils were wound round to form a core part with an outer diameter of 150 mm having a honeycomb cross section, and a foil solder material was wound round the core part at its axial center, so that a flat plate comes at the outermost periphery and the solder material is present at an end face of its outermost periphery. The solder material at this moment had a thickness of 25µm and a width of 15 mm. The resulting core part was contracted in the direction of the core part center using the pressing device shown in Fig.2(a) as described above. This reduced the core diameter by 0.2 to 0.5 mm, and the core was pressed into an outer cylinder as described above. This condition is shown in Fig.2(b). Corrugated plates comprising 0.05-mm thick stainless steel foils and flat plates of the same thickness were stacked, the stacked foils were wound round to form a core part with an outer diameter of 150 mm having a honeycomb cross section, and a foil solder material was wound round the core part at its axial center, so that a corrugated plate comes at the outermost periphery and the solder material is present at its outermost periphery. The solder material at this moment had a thickness of 25µm and a width of 15 mm. The resulting core part was contracted in the direction of the core part center using the pressing device shown in Fig.2(a) as described above. This reduced the core diameter by 0.2 to 0.5 mm. A looseness is generated at the core diameter reduction, however, since the looseness goes to the valley side of the corrugated plate and is inserted into the outer cylinder, the solder material present on the outer periphery of the corrugated plate at the outermost periphery will not be damaged or shifted. The resulting core was pressed into the outer cylinder as described above. This condition is shown in Fig.2(b). Corrugated plates comprising 0.05-mm thick stainless steel foils and flat plates of the same thickness were stacked, the stacked foils were wound round to form a core part with an outer diameter of 150 mm having a honeycomb cross section, and a foil solder material was wound round the core part at its axial center, so that a flat plate comes at the outermost periphery and the solder material is present at an end face of its outermost periphery. The solder material at this moment had a thickness of 25µm and a width of 15 mm. The resulting core part was set in a die having a taper so that the solder material protrudes by about 1 mm from the end face of the die as shown in Fig.2(a), the core part was contracted by a pressure of 6 to 10 kgf/cm 2 to contract the outer diameter of the core part to 149.5 mm, 1.5 mm smaller than the diameter of the outer cylinder. On the other hand, the outer cylinder was set in the die and held at a pressure of 3 kgf/cm 2 , the above core part was inserted into the outer cylinder, and a pressure of 6 to 10 kgf/cm 2 was applied to the core die to press the core into the outer cylinder. This condition is shown in Fig.2(b). Corrugated plates comprising 0.05-mm thick stainless steel foils and flat plates of the same thickness were stacked, the stacked foils were wound round to form a core part with an outer diameter of 150 mm having a honeycomb cross section, and a foil solder material was wound round the core part at its axial center, so that a flat plate comes at the outermost periphery and the solder material is present at its outer periphery. The solder material at this moment had a thickness of 25µm and a width of 15 mm. The resulting core part was set in a core die as shown in Fig.3 so that the solder material protrudes by about 1 mm from the end face of the die, the core part was contracted by a pressure of 6 to 10 kgf/cm 2 to reduce the outer diameter of the core part to 149.5 mm, 1.5 mm smaller than the diameter of the outer cylinder. On the other hand, the outer cylinder was set in the outer cylinder die and held at a pressure of 3 kgf/cm 2 , the chip of the above core part was inserted into the outer cylinder, a pressure of 6 to 10 kgf/cm 2 was applied to the core die to press the core into the outer cylinder, the core die was then shifted upward, the core part was again held, and a pressure was applied to successively press the core part into the outer cylinder. As a result, the core was pressed into the outer cylinder without peeling or breaking the solder material. As described above, since one end face of the outer cylinder is expanded, for example, using a cylinder expansion die, the core part can be easily inserted, and, when the outer cylinder and the core part are soldered, the restoration step can be carried out simultaneously, thereby producing a uniform, high-quality metal honeycomb carrier. In particular, when the metal honeycomb has a non-circular cross section, the winding members comprising two rod-formed or plate-formed members are used as a center part, which is wound by the flat plate and the corrugated plate while stacking them, the resulting metal honeycomb carrier is integrally structure from its center to the outer periphery. Therefore, since it is unnecessary to form a metal carrier and then process as in the prior art, the joining strength and the gas flow distribution are not affected, and since it is unnecessary to specifically process the center part, processing steps can be reduced providing improved economy.

Claims: A non-circular metal honeycomb carrier comprising a centre part including two rod-formed (13) or plate-formed (15) winding members having splits opposing with a predetermined interval, a core part present on an outer periphery of said centre part formed by inserting in opposite respective directions ends of a flat plate (11) and a corrugated plate (12) into the splits of said winding members and winding round the plates, and an outer cylinder (3) containing said core part. A method for producing a non-circular metal honeycomb carrier comprising the steps of placing two rod-formed (13) or plate-formed (15) winding members having splits, inserting in opposite respective directions ends of a flat plate (11) and a corrugated plate (12) to be wound into said splits, winding the flat plate (11) and the corrugated plate (12) around said winding members (13, 15) by rotating said winding members (13, 15) to form a non-circular metal honeycomb structure (1), and encasing said non-circular metal honeycomb carrier (1) into a non-circular outer cylinder (3) having the same shape. A method for producing a non-circular metal honeycomb carrier comprising the steps of holding two rod-formed (13) or plate-formed (15) winding members having splits maintaining a predetermined interval, inserting in opposite respective directions ends of a flat plate (11) and a corrugated plate (12) to be wound into said splits, winding the flat plate (11) and the corrugated plate (12) around said winding members (13, 15) to form a non-circular metal honeycomb structure (1), and encasing said non-circular metal honeycomb carrier (1) into a non-circular outer cylinder (3) having the same shape. The method for producing a non-circular metal honeycomb carrier of claim 2 or claim 3 wherein said winding members (13, 15) are removed after the flat plate (11) and the corrugated plate (12) are wound around said winding members to form a non-circular metal honeycomb structure. The honeycomb carrier of claim 1 or the method for producing a metal honeycomb carrier of claims 2, 3 or 4 wherein the cross section of the carrier is race track-formed (non-circular).

Inventors: AOKI YUKIO, IMOTO FUJIYA, INAMURA MICHIO, KOSHIBA YOSHIKAZU, MINAKATA TSUYOSHI, NAKAGAWA JUNITI, YASUNAGA TOMOHIRO, AOKI, YUKIO, IMOTO, FUJIYA, INAMURA, MICHIO, KOSHIBA, YOSHIKAZU, MINAKATA, TSUYOSHI, NAKAGAWA, JUNITI, YASUNAGA, TOMOHIRO
Applicants: NIPPON YAKIN KOGYO CO LTD, NIPPON YAKIN KOGYO CO., LTD.
Application year: 1993
Main classification: B01J35
IPC codes: F01N3, B01J35