JP7301356B2 - Catalytic converter manufacturing method - Google Patents

Description

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

A conventional catalytic converter has a circular cross-section, in which a cylindrical catalyst with elastic mats wrapped around its sides is press-fitted into a cylindrical case with a similar cross-section. Catalysts include diesel oxidation catalyst (DOC), selective catalytic reduction (SCR), diesel particulate filter (DPF) and gasoline particulate filter (GPF). It is configured by adhering. The elastic mat is made of heat-resistant fibers, protects the catalyst, closes the gap between the case and the catalyst, and elastically supports the catalyst on the case. When the catalyst is pressed into the case, the elastic mat swells and tries to be elastically deformed. rice field.

However, in recent years, there has been a demand for a catalytic converter with an elliptical cross section, and it has become necessary to consider elastic deformation of the case due to swelling of the elastic mat. The method for manufacturing a catalytic converter disclosed in Patent Document 1 is to form an elliptical cylindrical case (elliptic tube) in which a round tube is elastically deformed within an elastic limit by a compressing operation, while maintaining the compressing operation to form an elliptical cross-sectional shape of the case. After inserting an elliptical columnar catalyst with an elastic mat wound on the side surface while maintaining the above, the case is reduced in diameter to a plastic region to manufacture a catalytic converter (Patent Document 1 [Claim 1]). The diameter of the case is reduced by pressing together with a large number of pressing pieces divided in the circumferential direction.

Japanese Patent Application Laid-Open No. 2010-131484

In the method of manufacturing a catalytic converter disclosed in Patent Document 1, after inserting the catalyst into an elliptical cylindrical case larger than the catalyst with an elastic mat wrapped around the side surface, the diameter of the case is reduced and the elastic mat is tightened, The catalyst is press-fitted into an elliptical cylindrical case. Since the case in which the catalyst with the elastic mat wound around the side surface is contracted 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, it is believed that according to the method for manufacturing a catalytic converter disclosed in Patent Document 1, a catalytic converter having an outer shape as required by specifications and in which the catalyst is stably held by the elastic mat can be obtained.

However, in the manufacturing method of the catalytic converter disclosed in Patent Document 1, since the diameter of the case is reduced while the catalyst is inserted, 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 (the number of divisions and individual sizes) and control of the pressing pieces that reduce the diameter of the case with the catalyst inserted. As a result, the method of manufacturing a catalytic converter in which the diameter of the case is reduced while the catalyst is inserted may increase the manufacturing cost of the catalytic converter compared to the case where the case is merely plastically deformed with a simple mold.

When press-fitting a catalyst with an elastic mat wrapped around the sides into an elliptical cylindrical case that has been molded according to specification requirements, the bulge of the elastic mat strongly affects the large curvature of the side surface where the minor axis intersects. This causes elastic deformation that causes the center of the side portion to protrude. From now on, it is conceivable to mold the case into an elliptical cylindrical shape assuming the swelling of the elastic mat, but since the elastic deformation of the side surface with a large curvature where the minor axis intersects is not uniform, it is impossible to mold the case according to the specification requirements. was difficult. Therefore, we investigated a method of manufacturing a catalytic converter that can form an elliptical cylindrical case that satisfies specification requirements even if the case is elastically deformed due to swelling of the elastic mat.

What was developed as a result of the study was a manufacturing method for a catalytic converter in which an elliptical cylinder-shaped catalyst with elastic mats wrapped around the sides was press-fitted into an elliptical cylinder-shaped case with a similar cross section. A molding process of plastically deforming an elliptical cylinder with a shorter minor diameter and recessing the large curvature side surface where the minor diameters of the elliptical tubular case intersect by plastic deformation, and the large curvature side surface where the minor diameters intersect. and a press-fitting step of press-fitting an elliptical cylinder-shaped catalyst wrapped with an elastic mat into an elliptical cylindrical case having a recessed portion, in the order described above. An elliptical cylindrical case with a short diameter shorter than the specification requires no change in the circumference, resulting in a longer diameter than the specification requirement.

The cylindrical case is made of metal that can be plastically deformed, and an electric resistance welded pipe formed by rolling a flat plate or a round pipe with a circular cross section from the beginning is used. As in the conventional case, the catalyst has a structure in which a catalyst material such as a noble metal is adhered to a catalyst carrier such as ceramics. The elastic mat is also composed of heat-resistant fibers, as in the conventional case, and functions to protect the catalyst, close the gap between the case and the catalyst, and elastically support the catalyst on the case. In the molding process, for example, a cylindrical case is sandwiched between a pair of upper and lower molds and plastically deformed into an elliptical cylinder, and a core is inserted into the elliptical cylindrical case to form a side portion with a large curvature where the minor axis intersects. is plastically deformed and dented.

In the molding process of the present invention, the cylindrical case is plastically deformed into an elliptical cylinder with a shorter minor axis than the specification requirements, and the side surface portion of the elliptical tubular case with a large curvature where the minor axis intersects is concaved by plastic deformation. Let The large-curvature side portions where the short diameters intersect are elastically deformed so as to lengthen the short diameters by pressing the depressions against the elastic mat. At this time, the side surface portion with a large curvature where the minor axis intersects has high rigidity due to the dent, and the dent pressed by the elastic mat is reduced while the whole is elastically deformed uniformly. In this way, a catalytic converter is obtained in which the short diameter is returned to the required specification, and the cylindrical catalyst wrapped with the elastic mat is press-fitted into the case meeting the required specification.

For an elliptical cylindrical case obtained by plastically deforming a cylindrical case, a target value for the minor axis to be shorter than the specification requirements may be determined. However, the portion that elastically deforms according to the expansion of the elastic mat is exclusively the side surface portion with a large curvature where the minor axes intersect. For this reason, the short diameter should be shortened by the amount of deformation corresponding to the expansion of the elastic mat. In this case, the elastic mat elastically deforms the side surface portion while reducing the dent formed in the side surface portion having a large curvature where the minor axis intersects. to decide.

The dents on the sides with a large curvature where the minor axis intersects can be made according to the material and cross-sectional shape of the case, regardless of the range of the dents, shape in plan view, depth and cross-sectional shape, as long as they increase the rigidity of the side portions. can be set as appropriate. However, since the elliptical cylindrical case has a line-symmetrical cross-sectional shape across the minor axis, the molding process is performed by aligning the side surface with a large curvature where the minor axis of the elliptical cylindrical case intersects with the minor axis. It is preferable that the rigidity of the side portion is improved evenly in line symmetry by denting in a line-symmetrical curved surface and by denting in a line-symmetrical cross-sectional shape with respect to the minor axis. The recess may be line-symmetrical with respect to the minor axis, and may have the same cross-sectional shape in the extending direction of the case (in the direction of press-fitting of the catalyst).

In addition, if the concave portion of the side portion having a large curvature where the minor axis intersects extends to the periphery of the opening of the case, it becomes difficult to improve the rigidity of the side portion. Therefore, in the forming process, it is preferable to dent the large curvature side surface portion where the minor axis of the case intersects by plastic deformation within a range not reaching the opening peripheral edge of the elliptical cylindrical case. As a result, it is possible to prevent a situation in which the dent extends to the periphery of the opening of the case and makes it difficult to improve the rigidity. The recess has a line-symmetrical cross-sectional shape across the minor axis, and when formed in a range that does not reach the periphery of the opening of the case, the center in plan view is the center of the side surface with large curvature where the minor axis intersects, and the center in plan view is the center. The deepest circular surface in plan view or an elliptical spherical curved surface elongated in the major axis direction is preferred.

According to the production method of the present invention, it is possible to obtain a catalytic converter in which an elliptical cylinder-shaped catalyst having elastic mats wrapped around its side surfaces is press-fitted into an elliptical cylindrical case that satisfies specification requirements. In the molding process, by forming a dent in the side surface with a large curvature that intersects the short diameter shorter than the specification requirement, the effect of elastic deformation of the case due to the swelling of the elastic mat is suppressed, and the curvature where the short diameter intersects is suppressed. This is the effect obtained by elastically deforming the large side portion of the whole. Moreover, the manufacturing method of the present invention has the effect of not increasing the manufacturing procedure and the manufacturing cost because the manufacturing procedure and necessary molds are almost the same as the conventional ones.

The molding process in which the large curvature of the side surface where the minor axis of the elliptical cylindrical case intersects is recessed into an axisymmetric curved surface across the minor axis improves the rigidity of the side surface evenly and symmetrically, allowing the elastic mat to swell. It is possible to prevent the influence from being biased in the circumferential direction. In addition, the molding process uses plastic deformation to dent the large-curvature side surface where the minor axis of the case intersects, within a range that does not extend to the rim of the elliptical cylindrical case opening. It is possible to prevent the situation in which it is difficult to perform the operation, and to prevent the influence of swelling of the elastic mat from being biased in the circumferential direction. In either molding process, there is no change in the manufacturing procedure and no special mold is required, so there is an effect of not increasing the manufacturing procedure and the manufacturing cost.

It is a perspective view showing the implementation state of the former stage of the formation process in an example of the manufacturing method to which the present invention is applied. It is a front view showing the case which finished the former stage of the molding process of this example. FIG. 3 is a cross-sectional view at the center of FIG. 2 showing the case that has undergone the first stage of the molding process of this example. It is a perspective view showing the implementation state of the molding process latter stage of this example. It is a perspective view showing the case which finished the molding process latter stage of this example. It is a front view showing the case which finished the molding process latter stage of this example. FIG. 7 is a cross-sectional view at the center of FIG. 6 showing the case that has undergone the latter stage of the molding process of this example. It is a perspective view showing the press-fitting process of this example. It is a front view showing the case which finished the press-fitting process of this example. FIG. 10 is a cross-sectional view at the center of FIG. 9 showing the case after the press-fitting process of this example.

EMBODIMENT OF THE INVENTION Hereafter, it demonstrates, referring a figure for the form for implementing this invention. The manufacturing method of the catalytic converter of this example consists of the former stage of the molding process (see FIG. 1) in which the cylindrical case 14 is plastically deformed into the elliptical tubular case 11 as required by the specifications, and the elliptical tubular case 11 as required by the specifications. , and the elliptical cylindrical case 12 is obtained by plastically deforming the side portion 121 with a large curvature where the minor axis intersects. and a press-fitting step (FIG. 8) of press-fitting an elliptical cylinder-shaped catalyst 13 wrapped with an elastic mat 131 into an elliptical cylindrical case 12 having a large side portion 121 recessed.

The molding process of this example consists of the former stage of the molding process for obtaining the elliptical cylindrical case 11 that satisfies the specification requirements, and the latter stage of the molding process for obtaining the elliptical cylindrical case 12 that shortens the minor axis of the case 11 and forms a recess. divided into In this way, the multi-step forming process simplifies the device structure for each step, and allows more accurate setting of how much the minor diameter is to be shortened compared to the specification requirements. In addition, since the molding process is divided into two parts, the molding work can be carried out separately, so that there is an advantage that the productivity is improved.

In the first stage of the molding process, as shown in FIG. 1, a cylindrical case 11 is plastically deformed by sandwiching it vertically between an upper mold 21 and a lower mold 22 having vertically symmetrical concave surfaces. Thus, an elliptical cylindrical case 12 meeting the specification requirements is obtained. The mold used in the former stage of the molding process may be divided into a number of pieces. However, the molding die consisting of the pair of upper and lower dies 21 and lower dies 22 is preferable because it can be easily press-molded into the elliptical cylindrical case 12 simply by attaching it to a pressing device and sandwiching the cylindrical case 11 from above and below. .

The elliptical cylindrical case 11, which has undergone 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, and the curvature at which the short axis intersects. A large side surface portion (=upper surface or lower surface) 111 and a small curvature side surface portion (=right side surface or left side surface) 112 where the major axis intersects are continuous. The large-curvature side portion 111 intersected by the minor axis is a side surface extending in the direction in which the major axis extends, and the small-curvature side portion 112 intersected by the major axis is a side surface extending in the direction in which the minor axis extends. The side portions 111 and 112 in this example are divided by the arc-shaped midpoints of the upper, lower, left, and right corners.

As can be seen in FIG. 4, the latter stage of the molding process is the pre-process of flattening the elliptical tubular case 11 obtained in the previous stage of the molding process, and the large curvature side portion where the minor axis of the flattened case 12 intersects. (In FIG. 4, for convenience, the upper die 31, lower die 32 and core 33 necessary for the pre-process and the post-process are all shown). Molds used in the latter stage of the molding process in this example are an upper mold 31 and a lower mold 32 having convex molding portions 311 and 321 provided so as to be retractable from vertically symmetrical concave surfaces. The convex molded portions 311 and 321 may be configured to protrude by being pushed by a ram of a press device, or may be configured to protrude electrically.

In the pre-process, the case 11 is sandwiched between the upper mold 31 and the lower mold 32 from above and below with the convex molded parts 311 and 321 retracted, and is flattened by plastic deformation. Since the case 12 is formed into an elliptical cylindrical shape according to specification requirements in the former stage of the forming process, it can be easily flattened. In the post-process, a core 33 having a pair of upper and lower concave molding portions 331, 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 and 321 are extruded and recesses 123 are formed by plastic deformation in the large curvature side portions where the minor axes intersect (see FIGS. 5-7).

The elliptical cylindrical case 12, which has undergone the latter stage of the molding process, is flattened by shortening the minor axis from the specification requirements, flattening the large curvature side portion 121 where the minor axis intersects, and as a result, the major axis intersects. The small curvature side portion 122 is rounded (see FIG. 6). Further, the large-curvature side portion 121 intersected by the minor axis forms a recess 123 in a wide range extending to the boundary with the small-curvature side portion 122 intersected by the major axis. The dent 123 actually has only a slight depth and is difficult to see with the naked eye, but in the illustration of this example, the outer periphery 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 linearly symmetrical with respect to the minor axis (see FIG. 6) and also linearly symmetrical in the front and rear (see FIG. 7). , and is formed in a range that does not extend to the periphery of the opening of the elliptical cylindrical case 12, increasing the rigidity of the side portion 121. As shown in FIG. The depth of the dent 123 (the amount of dent from the original curved surface of the side portion 121 with a large curvature where the minor axis intersects) depends on the shape of the dent 123 and the size of the side portion 121 with a large curvature where the minor axis intersects. Determined by considering the strength and rigidity of the material that composes 12.

In the press-fitting process, as shown in FIG. 8, the elliptical cylindrical case 12 flattened in the latter stage of the molding process is elastically deformed by sandwiching it between right and left molds 41 and 42 having symmetrical concave surfaces. The cylindric catalyst 13, whose cross-sectional shape has been corrected as required by the specifications, and whose side surface is wrapped with an elastic mat 131, is press-fitted through one opening of the case 12, and the catalyst 13 meets the specifications as shown in FIGS. 9 and 10. To obtain a catalytic converter 1 in which a catalyst 13 is press-fitted into an elliptical cylindrical case 11 as required. For example, the catalyst 13 is press-fitted into the case 11 from above by a pressing device while the case 11 is held by the right mold 41 and the left mold 42 and fixed upward.

The elliptical cylindrical case 12 sandwiched between the right die 41 and the left die 42 is corrected to have a cross-sectional shape as required by the specification by pressing inward the small-curvature side portion 122 where the major axis intersects. The elliptical cylindrical case 12 in the corrected state is in a tension 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 wrapped around the side surface of the press-fitted catalyst 13 causes the above-mentioned The elastic force opposes. Then, as a result of the swelling of the elastic mat 131 exceeding the elastic force, the side surface portion 121 with a large curvature where the minor axis intersects is elastically deformed as a whole until it is regulated by the right mold 41 and the left mold 42, resulting in an elliptical shape as required by the specifications. A catalytic converter 1 in which the catalyst 13 is press-fitted into the cylindrical case 11 is obtained.

1 catalytic converter
11 Oval-cylindrical case as required by the specifications
111 Side portion with large curvature where minor axis intersects
112 Side portion with small curvature where major axis intersects
12 Flattened elliptical cylindrical case (after the molding process)
121 Side portion with large curvature where the minor axis intersects
122 Side portion with small curvature where major axis intersects
123 dent
13 Cylindrical catalyst
131 elastic mat
14 cylindrical case
21 Upper die before molding process
22 Lower die before molding process
31 Upper die in the latter stage of the molding process
311 Convex molded part
32 Lower die in the latter stage of the molding process
321 Convex molded part
33 core
331 concave part
41 Right type of press fitting process
42 Left type of press fitting process

Claims (3)

A method for manufacturing a catalytic converter in which an elliptical cylinder-shaped catalyst having elastic mats wrapped around its side surface is press-fitted into an elliptical cylinder-shaped case having a similar cross section,
A forming process in which a cylindrical case is plastically deformed into an elliptical cylinder with a shorter minor axis than the elliptical cylinder required by the specifications, and the side surface portion of the elliptical tubular case with a large curvature where the minor axis intersects is dented by plastic deformation. and,
and a press-fitting step of press-fitting an elliptical cylinder-shaped catalyst wrapped with an elastic mat into an elliptical cylinder-shaped case in which a side portion having a large curvature where the short axis intersects is recessed. . 2. The method of manufacturing a catalytic converter according to claim 1, wherein in the forming step, a side portion of the elliptical cylindrical case having a large curvature where the minor axis intersects is recessed into a line-symmetrical curved surface with respect to the minor axis. 3. The method of manufacturing a catalytic converter according to claim 1, wherein in the forming step, a side surface portion having a large curvature where the minor axis of the case intersects is dented by plastic deformation within a range not reaching the periphery of the opening of the elliptical cylindrical case. .

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