METAL HONEYCOMB SUPPORT MANUFACTURING METHOD

Abstract: This invention relates to a method of manufacturing a metal support for holding a catalyst for cleaning an automobile exhaust gas, consisting of the steps of forming a cross-sectionally honeycomb type core, inserting a front end portion of the resultant core into an outer cylinder, the inner diameter of which is substantially equal to the outer diameter of the core, with at least one end portion of the outer cylinder expanded, press-fitting the core into the outer cylinder by pressing an end surface of the former, and then contracting the expanded portion of the outer cylinder to the original dimensions by heat-treating the same; or forming a cross-sectionally honeycomb type core, forming a foil solder-wound portion by winding foil solder around a substantially axially intermediate part of the core, drawing the resultant core to an outer diameter smaller than the inner diameter of an outer cylinder by using a stepped portion-carrying metal mold before press-fitting the core into the outer cylinder the inner diameter of which is substantially equal to the outer diameter of the core, and then press-fitting the core into the outer cylinder. Especially, a non-circular metal honeycomb support consists of an outer cylinder in which a core is housed and fixed, this core being obtained by forming a core member using a take-up member composed of two rod type or plate type materials having regularly spaced opposed rifts, and then winding in layers flat plates and wavy plates around the outer circumferential surface of the core member with the end portions of the flat and wavy plates inserted into the rifts in the take-up member.

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. EP-A-0,218,062, on which the precharacterising portion of appended claim 1 is based, discloses a method of producing a non-circular carrier matrix using a number of deflection pins. The carrier matrix may be fitted into a sheath using a funnel arrangement. In particular, the outlet cross-section of the funnel corresponds to the internal cross-section of the sheath, such that, as the carrier matrix is advanced through the funnel into the sheath, it is automatically deformed into the cross-section of the sheath. The inventors have conducted intensive studies to improve the problems discussed above 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. Therefore, according to the present invention there is provided a method a 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. Preferably, the outer cylinder is held by a receiving tool, the core part is contracted by a die to a diameter smaller than an inner diameter of the output cylinder, and the core part is pressed in an axial direction to drive the core part into the outer cylinder, whereby engaging the cored part with the outer cylinder. Preferably, the outer cylinder is held by a receiving tool, the core part is held by a core die and its chip is contracted to a diameter smaller than an inner diameter of the output cylinder, pressed into the outer cylinder to the vicinity of the foil solder wound part of the core part, and the core part is pressed into the outer cylinder. That is, in the present method, corrugated plates and flat plates are stacked in alternation, the stacked plates are wound round to form a core part having a honeycomb cross section, the chip of the core part or the entire core part is contracted by a small diameter part of a split die having a stepped part to a diameter smaller than an inner diameter of the outer cylinder, the outer cylinder is held by a large diameter portion of the die, the core part is pressed into the outer cylinder, or the outer cylinder is held by a receiving tool, the chip of the core part of the entire core part is pressed by the die to contract the diameter of the core part to a diameter smaller than the inner diameter of the outer cylinder, and then the core part is pressed into the outer cylinder. To retain the core part and the outer cylinder more securely, a wound part of a foil solder material may be present on the outermost periphery of the core part. Furthermore, the die used is preferably a split die. In the above-described method, the foil solder material wound part may be present of absent on the outermost periphery of the core part. However, particularly when the foil solder material wound part is present on the outermost periphery of the core part, the core part is held by the die and its chip is contracted to a diameter smaller than the inner diameter of the outer cylinder, pressed into the outer cylinder to the vicinity of the foil solder wound part of the core part, held by the die in the vicinity of the foil solder wound part and the outer diameter of the core part is contracted to a diameter smaller than the 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, thereby obtaining the metal honeycomb carrier. In the present invention, the pressing means can be a hydraulic cylinder or the like, which presses the upper portion of the core, or can be a robot hand which is also used as a core die. When the upper portion of the core is pressed, 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, and it is also preferable to provide a taper on the inner surface of the core mounting part of the die to facilitate insertion into the outer cylinder. Furthermore, when the robot hand is used, the core part is gripped by the robot hand and pressed in to the vicinity of a position where the core part is held by the hand, 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 successively to the soldered portion of the core part. After that, the die is used again to contract the outer diameter of the soldered portion, and the core part is pressed in by the same method. In these methods, the cross section of the metal honeycomb carrier is not limited to a circular form, but may by a race track form (non-circular) or any other forms as far as a die can be produced. Such non-circular core part may be formed by a method comprising the steps of placing two rod-formed or plate-formed winding members having splits, 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 winding members by rotating the winding members to form a non-circular metal honeycomb structure, and encasing the non-circular metal honeycomb carrier into a non-circular outer cylinder having the same shape, or, holding the winding members, winding the flat plate and the corrugated plate around the winding members to form a non-circular metal honeycomb structure, and encasing the non-circular metal honeycomb carrier into a non-circular outer cylinder having the same shape. After the non-circular metal honeycomb structure is formed, the winding members may be removed. A desired honeycomb cross sectional shape can be obtained by varying the interval of the two rod-formed or plate-formed members used as a winding member, and a honeycomb body having a similar shape to a non-circular outer cylinder can be obtained simply by winding the flat plate and the corrugated plate around two shafts, it is unnecessary to process the once-formed honeycomb body to a non-circular shape as in the prior art, and the flat plate and the corrugated plate will not make an irregular contact. Furthermore, since it is also unnecessary to form a center part previously which is wound by the plates, a core part comprising a regularly-formed honeycomb structure can be obtained. The winding member used preferably has a split pin form so that the ends or side edges of the flat plate and the corrugated plate can be retained, and the ends of the flat plate and the corrugated plate are inserted and retained into the splits of the shaft. The rod-formed or plate-formed winding members may be rotated about their center to wind the flat plate and the corrugated plate, or the winding members may be held and wound round by the flat plate and the corrugate plate while stacking the plates. The present invention will now be described with reference to the drawings. Figs 1(a) and 1(b) are schematic views for explaining an embodiment of the present invention, and Fig. 2 is a schematic view for explaining another embodiment. 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. 1 are used. The outer cylinder 3 is held by a larger 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.1(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.2, 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 10. 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 that the inner diameter of the outer cylinder, and pressed into the outer cylinder. The pressing means is as described above. Fig. 3 is a schematic perspective view of the non-circular metal honeycomb carrier. Referring to Fig.3, 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.4 is a schematic view form 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 production method, 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.5 is a schematic view for explaining a case where plate-formed members are used as the winding members. Referring to Fig. 5, 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 preferably 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. Embodiment 1 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.1(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. 1(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. Embodiment 2 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 25 µm 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. 1(a) as in Embodiment 1. This reduced the core diameter by 0.2 to 0.5 mm, and the core was pressed into an outer cylinder. This condition is shown in Fig. 1(b). Embodiment 3 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 25 µm 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. 1(a) as in Embodiment 1. 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. This condition is shown in Fig.1(b). Embodiment 4 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 25 µm and a width of 15 mm. The resulting core part was set in a die having a taper 9 so that the solder material protrudes by about 1 mm from the end face of the die as shown in Fig.1(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. 1(b). Embodiment 5 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 25 µm and a width of 15 mm. The resulting core part was set in a core die as shown in Fig. 2 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.

Claims: A method for producing a metal honeycomb carrier for carrying an exhaust gas cleaning catalyst comprising the steps of: stacking corrugated plates (12) and flat plates (11) in alternation; winding round the stacked plates to form a core part (1) having a honeycomb cross section; and inserting said resulting core part (1) into an outer cylinder (3) having an inner diameter nearly equal to an outer diameter of said core part by contracting said core part (1) with a core die (6,7) and pressing said core part (1) into said outer cylinder (3) to engage said core part with said outer cylinder; characterised in that: the core part (1) is contracted by the core die to a diameter smaller than the inner diameter of said outer cylinder. A method according to claim 1, wherein said core die (6,7) comprises a split die (6) and said core part (1) is contracted by a small diameter part of the split die (6) having a stepped part to a diameter smaller than the inner diameter of the outer cylinder. A method according to claim 1, wherein said outer cylinder (3) is held by a receiving tool (7), said core part (1) is contracted by the die (7) to a diameter smaller than an inner diameter of said outer cylinder (3) and said core part (1) is then pressed in an axial direction to drive said core part (1) into said outer cylinder (3). A method according to claim 1, 2 or 3, further comprising winding a foil solder material (10) around the outer periphery of the wound stacked plates to form a core part (1) having a foil solder wound part. A method according to claim 1 comprising winding a foil solder material (10) around the outer periphery of the wound stacked plates to form a core part (1) having a foil solder wound part, wherein a portion of said core (1) is contracted to a diameter smaller than an inner diameter of said outer cylinder (3) and pressed into said outer cylinder (3) to the vicinity of said foil solder wound part (10) of said core part, and said core part (1) is then pressed into said outer cylinder (3). A method according to any one of claims 1 to 5 wherein the cross section of the carrier is race track-formed (non-circular). A method according to claim 6 wherein said steps of stacking and winding said plates comprise: providing two rod-formed (13) or plate-formed (15) winding members having splits; inserting the ends of a flat plate (11) and a corrugated plate (12) to be wound into said splits; and winding the flat plate (11) and the corrugated plate (12) around said winding members to form a non-circular metal honeycomb core part. A method according to claim 7, wherein the winding members (13) are rod-formed and are a predetermined distance apart. A method according to claim 7, wherein the winding members (15) are plate-formed and have a predetermined length. A method according to claim 7, 8 or 9, wherein the step of winding the flat plate and the corrugated plate around the winding member (13, 15) includes rotating said winding members. The method according to any one of claims 7 to 10 wherein said winding members (13, 15) are removed after the flat plate and the corrugated plate are wound around said winding members.

Inventors: AOKI YUKIO, IMOTO FUJIYA, INAMURA MICHIO, KOSHIBA Y, MINAKATA T, NAKAGAWA JUNITI, YASUNAGA TOMOHIRO, AOKI, YUKIO, IMOTO, FUJIYA, INAMURA, MICHIO, KOSHIBA, Y., MINAKATA, T., NAKAGAWA, JUNITI, YASUNAGA, TOMOHIRO, AOKI, Yukio, Nippon Yakin Kogyo Co Ltd., R&amp;D Div., KOSHIBA, Y., Nippon Yakin Kogyo Co Ltd R&amp;D Div., MINAKATA, T., Nippon Yakin Kogyo Co Ltd., R&amp;D Div., YASUNAGA, TOMOHIRO, NAS ENGINEERING CO., LTD.
Applicants: NIPPON YAKIN KOGYO CO LTD, NIPPON YAKIN KOGYO CO., LTD.
Application year: 1993
Main classification: B01J35
IPC codes: B01J35, F01N3, B23K1