JP2021013886A - Manufacturing method of catalytic converter - Google Patents

Abstract

To provide a manufacturing method of a catalytic converter, for preventing deformation of a case due to swelling of an elastic mat while press-fitting a catalyst having a lateral face wound with an elastic mat into an elliptic cylindrical case molded as a specification request.SOLUTION: A manufacturing method of a catalytic converter includes press-fitting an elliptic cylindrical catalyst having a lateral face wound with an elastic mat into an elliptic cylindrical case having cross sections similar to each other. The manufacturing method includes passing respectively in the described order steps of: a molding step of plastically deforming a cylindrical case to an elliptic cylindrical shape with a diameter shorter than that of a specification request, and recessing by plastic deformation a lateral face portion which has a large curvature and where the short diameters of an elliptic cylindrical case 11 are crossed; and a press-fitting step of press-fitting an elliptic cylindrical catalyst wound with an elastic mat into the elliptic cylindrical case 11 having the lateral face portion which has a large curvature and where the short diameters are crossed.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for manufacturing a catalytic converter having an elliptical cross section.

The conventional catalyst converter has a circular cross section in which a cylindrical catalyst with an elastic mat wrapped around the side surface is press-fitted into a cylindrical case having a similar cross section. The catalyst includes a diesel oxidation catalyst (DOC), selective catalytic reduction (SCR), diesel particulate filter (DPF) and gasoline particulate filter (GPF). For example, a catalytic substance such as a noble metal can be used as a catalyst carrier such as ceramics. It is composed by adhering. The elastic mat is composed of heat-resistant fibers, protects the catalyst, closes the gap between the case and the catalyst, and elastically supports the catalyst in the case. In the case where the catalyst is press-fitted, the elastic mat swells and tries to be elastically deformed. However, since the elastic mat bulges in the circumferential direction without bias and the rigidity of the case is uniform in the circumferential direction, the elastic mat is not elastically deformed. It was.

However, in recent years, a catalytic converter having an elliptical cross section has been required, and it has become necessary to consider the elastic deformation of the case due to the swelling of the elastic mat. The method for manufacturing a catalytic converter disclosed in Patent Document 1 is an elliptical tubular case (elliptical tube) in which a round tube is elastically deformed by an elastic limit by a compression operation, and the compression operation is maintained to form an elliptical cross section of the case. After inserting an elliptical columnar catalyst with an elastic mat wrapped around the side surface, the case is reduced in diameter to the plastic region to manufacture a catalytic converter (Patent Document 1 · [Claim 1]). The diameter of the case is reduced by pushing it all at once with a large number of pressing pieces divided in the circumferential direction.

JP-A-2010-131484

The method for manufacturing a catalyst converter disclosed in Patent Document 1 is to insert the catalyst into an elliptical tubular case larger than the catalyst having an elastic mat wrapped around the side surface, and then reduce the diameter of the case and tighten the elastic mat. A state in which the catalyst is press-fitted into an elliptical tubular case is realized. Since the case in which the catalyst around which the elastic mat is wound is inserted is reduced in diameter by suppressing the bulge of the elastic mat, the problem of elastic deformation of the case due to the elastic mat does not occur. From this, according to the method for manufacturing a catalytic converter disclosed in Patent Document 1, it is considered that a catalytic converter having an outer shape as required by specifications and in which a catalyst is stably held by an elastic mat can be obtained.

However, in the method for manufacturing a catalytic converter disclosed in Patent Document 1, the diameter of the case is reduced with the catalyst inserted, so that the catalyst and the elastic mat may be damaged. In order to avoid damage to the catalyst and elastic mat, it is necessary to finely set and manage the configuration (number of divisions and individual size) and control of the pressing pieces that reduce the diameter of the case with the catalyst inserted. As a result, the method for manufacturing a catalytic converter in which the diameter of the case is reduced with the catalyst inserted may increase the manufacturing cost of the catalytic converter as compared with the case where the case is plastically deformed with a simple mold.

When a catalyst with an elastic mat wrapped around the side surface is press-fitted into an elliptical tubular case molded according to the specifications, the bulge of the elastic mat strongly affects the side surface portion having a large curvature where the minor diameters intersect, especially. It caused elastic deformation to project the center of the side surface portion. From now on, it is conceivable to mold the case into an elliptical cylinder assuming the swelling of the elastic mat, but since the elastic deformation of the side surface part with a large curvature where the minor diameters intersect is not uniform, the case can be molded as specified. was difficult. Therefore, we investigated a method for manufacturing a catalytic converter that can form an elliptical tubular case as required by the specifications even if the case is elastically deformed due to the swelling of the elastic mat.

As a result of the examination, we developed a method for manufacturing a catalytic converter in which an elliptical columnar catalyst with an elastic mat wrapped around the side surface was press-fitted into an elliptical tubular case with a similar cross section. A molding process in which the elliptical cylinder with a shorter diameter is plastically deformed and the side surface of the elliptical case with a large curvature where the minor diameters intersect is recessed by plastic deformation, and the side portion with a large curvature where the minor diameters intersect. This is a method for manufacturing a catalytic converter, which comprises a press-fitting step of press-fitting an elliptical columnar catalyst on which an elastic mat is wound into an elliptical tubular case having a recessed shape in the order described above. Since the circumference of the elliptical tubular case having a shorter diameter than the specification requirement does not change, the major axis becomes longer than the specification requirement as a result.

The cylindrical case is made of plastically deformable metal, and an electric sewing pipe formed by rolling a flat plate or a round pipe having a circular cross section from the beginning is used. The catalyst has a configuration in which a catalyst substance such as a noble metal is attached to a catalyst carrier such as ceramics as in the conventional case. The elastic mat is also composed of heat-resistant fibers as in the conventional case, and has a function of protecting the catalyst, closing the gap between the case and the catalyst, and elastically supporting the catalyst in the case. In the molding process, for example, a cylindrical case is plastically deformed into an elliptical cylinder by sandwiching it between a pair of upper and lower molds, a core is inserted into the elliptical cylinder case, and a side portion having a large curvature at which minor diameters intersect. Is plastically deformed and dented.

In the present invention, in the molding process, the cylindrical case is plastically deformed into an elliptical cylinder having a shorter diameter than the specification requirement, and the side surface portion having a large curvature where the minor diameters of the elliptical tubular case intersect is concave by plastic deformation. No. The side surface portion having a large curvature where the minor diameters intersect is elastically deformed so as to lengthen the minor diameter by pressing a dent on the elastic mat. At this time, the side surface portion having a large curvature at which the minor diameters intersect has high rigidity due to the dent, and the dent pressed by the elastic mat is made small and elastically deformed as a whole. In this way, the minor axis returns to the specifications required, and a catalyst converter in which an elliptical columnar catalyst wound with an elastic mat is press-fitted into the case according to the specifications can be obtained.

For the elliptical tubular case obtained by plastically deforming the cylindrical case, a target value for a short diameter that is shorter than the specification requirement may be set. However, the portion elastically deformed according to the bulge of the elastic mat is exclusively a side portion having a large curvature where the minor diameters intersect. For this reason, the minor axis may be shortened by the amount of deformation corresponding to the swelling of the elastic mat. In this case, since the elastic mat elastically deforms the side surface portion while reducing the dent formed in the side surface portion having a large curvature at which the minor axis intersects, the length for shortening the minor axis also considers the depth of the dent. To decide.

The dent on the side surface having a large curvature where the minor diameters intersect depends on the material and cross-sectional shape of the case regardless of the range, plan view shape, depth and cross-sectional shape of the dent as long as it enhances the rigidity of the side surface portion. Can be set as appropriate. However, since the elliptical tubular case has an axisymmetric cross-sectional shape with the minor axis in between, the molding process involves sandwiching the minor axis on the side surface portion having a large curvature where the minor axis of the elliptical tubular case intersects. It is preferable to dent a curved surface that is line-symmetrical and to improve the rigidity of the side surface portion evenly by line-symmetry by denting the cross-sectional shape that is line-symmetrical across the minor diameter. The dent may be line-symmetrical with a minor axis in between, and may have the same cross-sectional shape in the extending direction of the case (press-fitting direction of the catalyst).

Further, when the dent of the side surface portion having a large curvature at which the minor diameters intersect extends to the opening peripheral edge of the case, it becomes difficult to improve the rigidity of the side surface portion. Therefore, in the molding step, it is preferable that the side surface portion having a large curvature where the minor diameters of the case intersect is recessed by plastic deformation within a range that does not reach the opening peripheral edge of the elliptical tubular case. As a result, it is possible to prevent a situation in which the dent extends to the peripheral edge of the opening of the case and it becomes difficult to improve the rigidity. The dent has a cross-sectional shape that is axisymmetric with the minor axis in between, and when it is formed in a range that does not reach the opening periphery of the case, the dent is centered on the plan view center of the side surface having a large curvature where the minor axis intersects, and the plan view center is The deepest planar circular or elliptical spherical curved surface long in the major axis direction is preferable.

According to the manufacturing method of the present invention, it is possible to obtain a catalytic converter in which an elliptical columnar catalyst in which an elastic mat is wound on a side surface is press-fitted into an elliptical tubular case as specified in the specifications. This is because in the molding process, a dent is formed on the side surface portion having a large curvature that intersects the minor axis shorter than the specification requirement, thereby suppressing the influence of elastic deformation of the case due to the swelling of the elastic mat, and the curvature that the minor axis intersects. This is the effect of elastically deforming the large side surface of the. In addition, the manufacturing method of the present invention has an effect of not increasing the manufacturing procedure and the manufacturing cost because the manufacturing procedure and the required mold are almost the same as those in the prior art.

The molding process of denting the side surface part with a large curvature where the minor axis of the elliptical tubular case intersects into a line-symmetric curved surface with the minor axis in between improves the rigidity of the side surface portion evenly in line symmetry, and the bulge of the elastic mat It is possible to prevent the influence of the above from being biased in the circumferential direction. In addition, in the molding process in which the side surface portion having a large curvature where the minor diameters of the case intersect is recessed by plastic deformation within the range not reaching the opening peripheral edge of the elliptical tubular case, the recess extends to the opening peripheral edge of the case to improve the rigidity. It is possible to prevent the situation where it becomes difficult to do so and prevent the influence of the swelling of the elastic mat from being biased in the circumferential direction. Since there is no change in the manufacturing procedure and no special mold is required in any of the molding steps, there is an effect that the manufacturing procedure and the manufacturing cost are not increased.

It is a perspective view which shows the execution state of the first stage of a molding process in an example of the manufacturing method to which this invention is applied. It is a front view which shows the case which finished the first stage of the molding process of this example. It is a central sectional view in FIG. 2 which shows the case which completed the first stage of the molding process of this example. It is a perspective view which shows the carrying-out state of the latter stage of a molding process of this example. It is a perspective view which shows the case which finished the latter stage of the molding process of this example. It is a front view which shows the case which finished the latter stage of the molding process of this example. It is a central sectional view in FIG. 6 which shows the case which finished the latter stage of the molding process of this example. It is a perspective view which shows the press-fitting process of this example. It is a front view which shows the case which completed the press-fitting process of this example. It is a central sectional view in FIG. 9 which shows the case which completed the press-fitting process of this example.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The method for manufacturing the catalytic converter in this example is the first stage of the molding process (see FIG. 1) in which the cylindrical case 14 is plastically deformed into the elliptical tubular case 11 as specified, and the elliptical tubular case 11 as specified. The latter stage of the molding process (see FIG. 4) to obtain an elliptical tubular case 12 in which the side surface portion 121 having a large curvature at which the minor axes intersect is recessed by plastic deformation. A press-fitting step (FIG. 8) is provided in which an elliptical columnar catalyst 13 around which an elastic mat 131 is wound is press-fitted into an elliptical tubular case 12 in which a large side surface portion 121 is recessed.

The molding process of this example includes the first stage of the molding process for obtaining the elliptical tubular case 11 as required by the specifications, and the second stage of the molding process for obtaining the elliptical tubular case 12 which shortens the minor axis of the case 11 and forms a dent. It is divided into. In this way, if the molding process is configured in multiple stages, the device configuration in each stage can be simplified, and how much the minor axis can be shortened as compared with the specification requirements can be set more accurately. Further, since the molding process is divided into two, the molding work can be carried out in each of them, which has an advantage of improving productivity.

As seen in FIG. 1, the first stage of the molding process is plastically deformed by sandwiching the cylindrical case 11 up and down between the upper mold 21 and the lower mold 22 having vertically symmetrical concave surfaces, and is seen in FIGS. 2 and 3. Obtain an elliptical tubular case 12 as required by the specifications. The molding die used in the first stage of the molding step may be divided into a large number. However, a molding die consisting of a pair of upper and lower dies 21 and a lower die 22 is preferable because it can be easily press-molded into an elliptical tubular case 12 simply by attaching it to a pressing device and sandwiching the cylindrical case 11 from above and below. ..

The elliptical tubular case 11 which has been subjected to the first stage of the molding process has a substantially rectangular cross section in which the side surfaces bulge outward in an arc shape and the corners where the side surfaces intersect are chamfered in an arc shape. The large side surface portion (= upper surface or lower surface) 111 and the side surface portion (= right side surface or left side surface) 112 having a small curvature where the major axis intersects are continuous. The side surface portion 111 having a large curvature at which the minor axis intersects is a side surface extending in the extending direction of the major axis, and the side surface portion 112 having a small curvature at which the major axis intersects is a side surface extending in the extending direction of the minor axis. The side surface portions 111 and 112 in this example are divided by arcuate midpoints at the top, bottom, left and right corners.

As seen in FIG. 4, the latter stage of the molding process is a side surface portion having a large curvature at which the minor axis of the flattened case 12 intersects with the pre-process of flattening the elliptical tubular case 11 obtained in the first stage of the molding process. (In FIG. 4, for convenience, the upper die 31, the lower die 32, and the core 33 required for the pre-process and the post-process are all shown). The molding dies used in the latter stage of the molding process of this example are the upper dies 31 and the lower dies 32 in which the convex molding portions 311, 321 are provided so as to be able to appear and disappear from the vertically symmetrical concave surface. The convex molded portions 311, 321 may be configured to be pushed by the ram of the press device to project, or may be electrically projecting.

In the previous step, the case 11 is sandwiched between the upper die 31 and the lower die 32 from above and below with the convex molded portions 311, 321 retracted, and flattened by plastic deformation. Since the case 12 is molded into an elliptical cylinder as required by the specifications in the first stage of the molding process, it can be easily flattened. In the post-process, the core 33 having a pair of upper and lower concave molding portions 331 and 331 is inserted into the flattened case 12 while being sandwiched between the upper mold 31 and the lower mold 32, and convex molding is performed from the upper mold 31 and the lower mold 32, respectively. The portions 311, 321 are extruded to form a recess 123 by plastic deformation in a side portion having a large curvature where the minor diameters intersect (see FIGS. 5 to 7).

The elliptical tubular case 12 that has completed the latter stage of the molding process is flattened with a shorter minor diameter than specified, and the side surface portion 121 having a large curvature at which the minor diameters intersect is brought closer to flat, and as a result, the major diameters intersect. The side surface portion 122 having a small curvature is rounded (see FIG. 6). Further, the side surface portion 121 having a large curvature at which the minor axis intersects forms a recess 123 over a wide range up to the boundary with the side surface portion 122 having a small curvature at which the major axis intersects. The dent 123 is actually only a little deep and difficult to see with the naked eye, but in the illustration of this example, the outline that is the outer circumference of the dent 123 is represented by a solid line so that its existence can be understood (see FIG. 5). ).

The recess 123 in this example is a spherical curved surface that is line-symmetrical across the minor axis (see FIG. 6) and line-symmetrical in the front-rear direction (see FIG. 7), and is left and right on the side surface portion 121 having a large curvature where the minor axis intersects. It is formed in a range that does not reach the opening peripheral edge of the oval tubular case 12, and enhances the rigidity of the side surface portion 121. The depth of the dent 123 (the amount of dent from the original curved surface of the side portion 121 having a large curvature where the minor diameters intersect) is determined by the shape of the dent 123 and the size of the side portion 121 having a large curvature where the minor diameters intersect, as well as the case. Determined in consideration of the strength and rigidity of the materials that make up 12.

In the press-fitting process, as shown in FIG. 8, the elliptical tubular case 12 flattened in the latter stage of the molding process is elastically deformed by sandwiching it between the right mold 41 and the left mold 42 having symmetrical concave surfaces. The cross-sectional shape was corrected according to the specifications, and the elliptical columnar catalyst 13 with the elastic mat 131 wrapped around the side surface was press-fitted through one opening of the case 12, and the specifications were as shown in FIGS. 9 and 10. A catalyst converter 1 is obtained by press-fitting the catalyst 13 into the case 11 having an elliptical cylinder as required. The catalyst 13 is press-fitted into the case 11 from above by a press device, for example, with the case 11 held in the right mold 41 and the left mold 42 and fixed in an upward position.

The elliptical tubular case 12 sandwiched between the right mold 41 and the left mold 42 is corrected to a cross-sectional shape as required by the specifications by pushing the side surface portion 122 having a small curvature where the major axes intersect inward. The elliptical tubular case 12 in the straightened state is in a tense state in which an elastic force is generated in the direction of extending the major axis and contracting the minor axis, and the bulge of the elastic mat 131 wound around the side surface of the press-fitted catalyst 13 is described above. Elastic forces oppose. Then, as a result of the bulge of the elastic mat 131 exceeding the elastic force, the side surface portion 121 having a large curvature where the minor axis intersects is elastically deformed as a whole until it is regulated by the right type 41 and the left type 42, and is an ellipse as specified. A catalyst converter 1 in which the catalyst 13 is press-fitted into the tubular case 11 is obtained.

1 Catalytic converter
11 Elliptical tubular case as required by specifications
111 Large side portion with large curvature where the minor diameters intersect
112 Side part with small curvature where major axes intersect
12 Flattened oval tubular case (second stage of molding process)
121 Side part with large curvature where minor diameters intersect
122 Side part with small curvature where major axes intersect
123 dent
13 Oval columnar catalyst
131 Elastic mat
14 Cylindrical case
21 Upper mold in the first stage of the molding process
22 Lower mold in the first stage of the molding process
31 Upper mold in the latter stage of the molding process
311 Convex molded part
32 Lower mold in the latter stage of the molding process
321 Convex molded part
33 core
331 Concave molded part
41 Right type of press-fitting process
42 Left mold of press-fitting process

Claims (3)

This is a method for manufacturing a catalyst converter in which an elliptical columnar catalyst with an elastic mat wrapped around its side surface is press-fitted into an elliptical tubular case having a similar cross section.
A molding process in which the cylindrical case is plastically deformed into an elliptical cylinder with a shorter diameter than the specification requirement, and the side surface portion having a large curvature where the minor diameters of the elliptical tubular case intersect is recessed by plastic deformation.
A press-fitting process in which an elliptical columnar catalyst wrapped with an elastic mat is press-fitted into an elliptical tubular case in which a side portion having a large curvature at which minor diameters intersect is recessed.
A method for producing a catalytic converter, which comprises the order described above. The method for manufacturing a catalytic converter according to claim 1, wherein the molding step is a method of manufacturing a catalytic converter according to claim 1, wherein a side surface portion having a large curvature at which the minor diameters of an elliptical tubular case intersect is recessed into a line-symmetric curved surface with the minor diameters interposed therebetween. The method for manufacturing a catalytic converter according to claim 1 or 2, wherein in the molding step, a side surface portion having a large curvature where the minor diameters of the case intersect is recessed by plastic deformation within a range not reaching the opening peripheral edge of the elliptical tubular case. ..

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