JP2012117443A - Catalyst converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst converter in which gastightness of a welding part of a sensor mounting boss to a sensor mounting wall is easily secured by allowing a reduced-diameter cylindrical part to be shaped by press working without generating wrinkles on the flat sensor mounting wall.SOLUTION: In the catalyst converter including: a casing 1 having a pair of holding cylindrical parts 7a, 7a aligned in an axial direction and a reduced-diameter cylindrical part 8 having a flat sensor mounting wall 11 on one side and integrally connecting the holding cylindrical parts 7a, 7a; catalyst carriers 2a, 2b accommodated and held in the holding cylindrical parts 7a, 7a; and a sensor mounting boss 21 penetrating through the sensor mounting wall 11 and welded to the outer surface thereof, the reduced-diameter cylindrical part 8 comprises the sensor mounting wall 11 and a major arc part 10 integrally connecting both side ends of the sensor mounting wall 11. The major arc part 10 is formed so that the circumferential length of the inner circumferential side of the reduced-diameter cylindrical part 8 is larger than the circumference of an inscribed circle 12 of the major arc part 10.

Description

The present invention includes a casing having a pair of holding cylinders arranged in the axial direction, a reduced diameter cylinder having a flat sensor mounting wall on one side and integrally connecting the two holding cylinders, A pair of catalyst carriers accommodated and held in the holding cylinder part via a holding material, a sensor mounting boss that is welded to the outer surface of the catalyst carrier while penetrating the sensor mounting wall part, and attached to the sensor mounting boss for sensing parts become more and O ₂ sensor to face between the two catalyst carrier, the reduced diameter cylindrical portion, an improvement in the catalytic converter which is press-formed from a material portion extending between the holding tube portion.

  Such a catalytic converter is already known as disclosed in Patent Document 1 below.

JP 2004-92461 A

In such a catalytic converter casing, disposing the reduced-diameter cylindrical portion between a pair of holding cylindrical portions for accommodating and holding a pair of catalyst carriers means that both ends of the reduced-diameter cylindrical portion and the catalyst carrier adjacent to them. This is effective in ensuring the durability of the holding material by suppressing the intrusion of exhaust gas into the holding material. Also, by attaching an O ₂ sensor to the flat sensor mounting wall on one side of the reduced diameter cylindrical portion via a sensor mounting boss, the sensing portion of the O ₂ sensor is brought closer to the center of the flow path between the two catalyst carriers. And the sensing performance can be improved.

  By the way, the diameter-reduced cylindrical portion of the casing of the conventional catalytic converter is composed of a flat sensor mounting wall and a dominant-arc wall portion having a constant radius that integrally connects both ends thereof. When the material part with the same diameter as the holding cylinder part is reduced in diameter by press working, wrinkles are generated on the sensor mounting wall that should be particularly flat due to the difference in circumference before and after the reduced diameter cylinder part is processed. easy. When wrinkles occur on the sensor mounting wall, it is difficult to stably ensure the airtightness of the welded part, particularly when the sensor mounting boss is projection welded to the outer surface.

  The present invention has been made in view of such circumstances, so that the reduced diameter cylindrical portion can be formed by press working without generating wrinkles on the flat sensor mounting wall, and the sensor is mounted on the sensor mounting wall. It is an object of the present invention to provide a catalytic converter that facilitates ensuring airtightness of a welded portion of a boss.

To achieve the above object, the present invention provides a pair of holding cylinders arranged in the axial direction and a reduced diameter cylinder having a flat sensor mounting wall on one side and integrally connecting the two holding cylinders. A casing provided with a portion, a pair of catalyst carriers accommodated and held in the holding cylinder portions via holding materials, a sensor mounting boss that is welded to the outer surface of the sensor mounting wall portion while penetrating the sensor mounting wall portion, A catalytic converter comprising an O ₂ sensor mounted on a sensor mounting boss and facing a sensing portion between the two catalyst carriers, wherein the reduced diameter cylindrical portion is press-molded from a material portion extending between the holding cylindrical portions. The reduced diameter cylindrical portion is composed of the sensor mounting wall portion and a dominant arc-shaped portion that integrally connects both side ends of the sensor mounting wall portion, and the circumferential length of the inner diameter side of the reduced diameter cylindrical portion. Is larger than the circumference of the inscribed circle of the arcuate part So as to be the first, characterized in that the formation of the 該優 arcuate portion.

  In addition to the first feature, the second feature of the present invention is that the sensor mounting wall is disposed inside the inscribed circle.

  Furthermore, in addition to the first feature, the third aspect of the present invention is that the dominant arc-shaped portion is formed by integrally connecting a plurality of wall portions having a radius of curvature larger than the radius of the inscribed circle in the circumferential direction. Features.

  Furthermore, in addition to the first feature of the present invention, the dominant arc-shaped portion includes a concave curved wall portion that is concave radially inward and a convex curved wall portion that is convex radially outward in the circumferential direction. A fourth feature is that a plurality of them are alternately connected together.

  Furthermore, in addition to the first feature, the present invention has a fifth feature that a plurality of ribs extending in the axial direction are formed on the dominant arc-shaped portion.

  According to the first feature of the present invention, since the circumferential length of the inner diameter side of the reduced diameter cylindrical portion is larger than the circumference of the inscribed circle of the dominant arc-shaped portion, Thus, the difference in circumference after molding can be reduced to zero or as small as possible, so that the outer surface of the flat sensor mounting wall can be formed into a high-precision flat surface without wrinkles. Therefore, the airtight joining of the sensor mounting boss to the outer surface of the sensor mounting wall can always be easily and reliably performed by projection welding.

According to the second feature of the present invention, the sensor mounting wall portion is disposed inside the inscribed circle of the arcuate portion of the connecting tube portion, so that the sensor mounting wall portion is attached via the sensor mounting boss. is the O ₂ sensing portion of the sensor can minimize close to meeting channel center between the two catalyst carrier, it is possible to improve the sensing performance of the O ₂ sensor.

  According to the third feature of the present invention, even when the difference between the circumferential lengths before and after molding the reduced diameter cylindrical portion is not zero, wrinkles generated in each wall portion and the sensor mounting wall portion during pressing are As a result, the outer surface of the flat sensor mounting wall is formed into a flat surface with high accuracy without wrinkles. it can.

  Also according to the fourth and fifth features of the present invention, the circumference of the inner diameter side of the reduced diameter cylindrical portion can be made larger than the circumference of the inscribed circle of the dominant arc-shaped portion. The difference between the circumferential length before molding and after molding can be reduced to zero or as small as possible. Therefore, the outer surface of the flat sensor mounting wall can be formed into a high-precision flat surface without wrinkles.

The longitudinal cross-sectional view of the catalytic converter which concerns on 1st Embodiment of this invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. The enlarged view around the sensor mounting wall in FIG. 2 shows the procedure for projection welding of the sensor mounting boss. The state explanatory drawing before the press work of the diameter-reduced cylinder part of FIG. The state explanatory view after press processing of the diameter-reduced cylinder part of FIG. FIG. 3 is a view corresponding to FIG. 2 showing a second embodiment of the present invention. FIG. 4 is a view corresponding to FIG. 2 showing a third embodiment of the present invention. FIG. 5 is a view corresponding to FIG. 2 showing a fourth embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, the description starts with the description of the first embodiment of the present invention shown in FIGS.

In FIG. 1, a catalytic converter C for an automobile includes a cylindrical casing 1, a pair of catalyst carriers 2a and 2b that are accommodated and held in series in the casing 1 with a certain distance from each other, and both the catalysts. It comprises an O ₂ sensor 3 attached to the casing 1 so as to intervene between the carriers 2a and 2b. One end of the casing 1 along the axial direction is connected to the upstream exhaust pipe 4 connected to the intake port of the automobile engine, and the other end is connected to the downstream exhaust pipe 5 connected to the exhaust muffler.

Thus, the exhaust gas discharged from the engine flows into the casing 1 from the upstream exhaust pipe 4 and sequentially passes through the pair of catalyst carriers 2a and 2b, so that harmful substances in the exhaust gas are purified by oxidation and reduction. The exhaust gas thus discharged is discharged into the atmosphere through the downstream exhaust pipe 5. Meanwhile, the O ₂ sensor 3 detects the O ₂ concentration in the exhaust gas between the pair of catalyst carriers 2a and 2b, and outputs the detection signal to an electronic control unit (not shown). Based on the signal, the fuel injection amount and the like are controlled to appropriately control the air-fuel ratio of the intake mixture of the engine.

  The casing 1 is formed by connecting cylindrical holding cylinder portions 7a and 7b arranged in series with the opposing end portions of the holding cylinder portions 7a and 7b. The diameter of the casing 1 is smaller than those of the holding cylinder portions 7a and 7b. It is comprised by the cylinder part 8 and a pair of funnel-shaped guide cylinder parts 9a and 9b connected to the outer end of both holding cylinder parts 7a and 7b, respectively. The pair of catalyst carriers 2a and 2b are press-fitted into the inner peripheral surfaces of the holding cylinder portions 7a and 7b via elastic holding members 6 arranged on the outer peripheral surfaces. Alternatively, after the catalyst carriers 2a and 2b are inserted into the holding cylinder portions 7a and 7b together with the holding material 6, the holding cylinder portions 7a and 7b are subjected to diameter reduction processing to give the holding material 6 holding force. Thus, the catalyst carriers 2a and 2b are accommodated and held in the holding cylinder portions 7a and 7b.

  The reduced diameter cylindrical portion 8 is formed before the holding carrier portions 7a and 7b receive and hold the catalyst carriers 2a and 2b, and the guide cylinder portions 9a and 9b are formed on the holding carrier portions 7a and 7b. , 2b is molded and held.

Next, the structure of the reduced diameter cylindrical portion 8, its molding method, and the mounting structure of the O ₂ sensor 3 will be described.

  As shown in FIGS. 1 and 2, the diameter-reduced cylindrical portion 8 is originally formed by subjecting the material portion 8 ', which is continuous to the holding cylinder portions 7a and 7b, to the same diameter as that of the holding cylinder portions 7a and 7b, by pressing. , A plurality of wall portions 10a, 10a,... Are integrally connected in the circumferential direction, and a flat sensor mounting wall portion 11 that integrally connects the opposite ends of the dominant arc portion 10 to each other. The wall portions 10a, 10a,... Are formed such that the radius of curvature R2 is larger than the radius R1 of the inscribed circle 12 of the arcuate portion 10. Also, the arcuate portion 10 is formed such that its inscribed circle 12 is substantially equal to the outer diameter of the catalyst carriers 2a and 2b.

  Thus, with the above-described structure of the reduced diameter cylindrical portion 8, when the circumference of the inner peripheral side of the reduced diameter cylindrical portion 8 is S1, and the circumference of the inscribed circle 12 of the dominant arc-shaped portion 10 is S2, S1> S2 It becomes.

  As shown in FIGS. 4 and 5, the press device 15 for forming such a reduced diameter cylindrical portion 8 includes a core die 16 having an outer peripheral surface corresponding to the inner peripheral surface of the reduced diameter cylindrical portion 8 to be formed, .. And a plurality of divided outer dies 17, 17... Each having an inner peripheral surface corresponding to the outer peripheral surface of the sensor mounting wall portion 11.

  In forming the reduced diameter cylindrical portion 8, the core die 16 is disposed in the raw material portion 8 'before forming the reduced diameter cylindrical portion 8, and a plurality of divided outer dies 17, 17,. Deploy. Then, the split outer dies 17, 17... Are simultaneously moved radially inward by a hollow taper cylindrical cam (not shown), and the material portion 8 'is clamped between the split outer dies 17, 17. By reducing the diameter, a dominant arc-shaped portion 10 composed of a plurality of wall portions 10a, 10a... And a flat sensor mounting wall portion 11 are formed. That is, the reduced diameter cylindrical portion 8 is formed.

  By the way, S1> S2, that is, the circumferential length S1 on the inner peripheral side of the reduced diameter cylindrical portion 8 is larger than the circumference S2 of the inscribed circle 12 of the dominant arc-shaped portion 10, so that the reduced diameter cylindrical portion 8 is formed. The difference between the circumferential lengths before and after molding can be reduced to zero or as small as possible, so that the outer surface 11a of the flat sensor mounting wall 11 can be formed into a high-precision flat surface without wrinkles. .

  Further, even when the difference between the circumferential lengths of the reduced diameter cylindrical portion 8 before and after the molding is not zero, the divided outer dies 17, 17... 8 ′, since pressing is started from each intermediate portion of the portions corresponding to the wall portions 10a, 10a... And the sensor mounting wall portion 11, the wall portions 10a, 10a. The generated wrinkles are pushed from the intermediate portions of the wall portions 10a, 10a,... And the sensor mounting wall portion 11 toward both ends, that is, the ridges between the wall portions 10a, 10a,. As a result, the outer side surface 11a of the flat sensor mounting wall portion 11 is formed as a highly accurate flat surface without wrinkles.

  As shown in FIGS. 2 and 3, thereafter, a mounting hole 20 is formed in the sensor mounting wall 11, and a sensor mounting boss 21 is fitted into the mounting hole 20, and projection welding is performed. That is, the sensor mounting boss 21 includes a cylindrical portion 21a having a screw hole 22 and fitted into the mounting hole 20, and a flange portion 21b integrally provided on the outer periphery of the outer end portion of the cylindrical portion 21a. The flange portion 21b is formed with an annular protrusion 23 that faces the outer surface 11a of the sensor mounting wall portion 11. The annular mounting 23 is welded to the outer surface 11a of the sensor mounting wall 11 by projection welding, so that the sensor mounting boss 21 is joined to the outer surface of the sensor mounting wall 11. At this time, in particular, the outer surface 11a of the sensor mounting wall 11 can be formed into a flat surface with high accuracy without any wrinkles, as described above, so that the sensor mounting wall 11 of the sensor mounting boss 21 can be obtained by projection welding. Highly airtight joining to the outer surface can always be performed easily and reliably.

The O ₂ sensor 3 is screwed into the screw hole 22 of the sensor mounting boss 21, and the sensing portion 3a at the tip thereof is disposed in the middle portion between the catalyst carriers 2a and 2b.

  Meanwhile, the arcuate portion 10 is formed such that its inscribed circle 12 has substantially the same diameter as the outer diameter of the catalyst carriers 2a and 2b, and the sensor mounting wall 11 has a radius larger than that of the inscribed circle 12. Molded to occupy a position inward in the direction. By doing so, the gap between the reduced diameter cylindrical portion 8 and the catalyst carriers 2a and 2b adjacent thereto is narrowed, the intrusion of the exhaust gas to the holding material 6 side is suppressed as much as possible, and the durability of the holding material 6 is improved. Can do.

Further, the sensor mounting wall portion 11 is disposed inside the inscribed circle 12 of the arcuate portion 10 of the reduced diameter cylindrical portion 8, so that O ₂ attached to the sensor mounting wall portion 11 via the sensor mounting boss 21. The sensing portion 3a of the sensor 3 can be brought as close as possible to the center of the flow path between the two catalyst carriers 2a and 2b, and the sensing performance of the O ₂ sensor 3 can be improved.

  Next, a second embodiment of the present invention shown in FIG. 6 will be described.

  In the second embodiment, the dominant arc-shaped portion 10 of the reduced diameter cylindrical portion 8 includes a concave curved wall portion 25 that is concave inward in the radial direction and a convex curved wall portion 26 that is convex outward in the radial direction in the circumferential direction. Are alternately connected to each other. Since other configurations are the same as those of the previous embodiment, portions corresponding to those of the previous embodiment in FIG. 6 are denoted by the same reference numerals, and redundant description is omitted.

  Also according to the second embodiment, the circumferential length S1 on the inner peripheral side of the reduced diameter cylindrical portion 8 is larger than the circumference S2 of the inscribed circle 12 of the dominant arc-shaped portion 10, and before and after the reduced diameter cylindrical portion 8 is molded. The difference between the peripheral lengths afterward can be reduced to zero or as small as possible. Therefore, the outer surface 11a of the flat sensor mounting wall portion 11 can be formed into a high-precision flat surface free from wrinkles. Also in this case, the sensor mounting wall portion 11 is disposed inside the inscribed circle 12 of the dominant arc-shaped portion 10.

  Next, a third embodiment of the present invention shown in FIG. 7 will be described.

  In the third embodiment, the dominant arc-shaped portion 10 of the reduced diameter cylindrical portion 8 is formed on the dominant arc wall 27 and the dominant arc wall 27 bulges outward in the radial direction at a predetermined interval in the circumferential direction. It comprises a plurality of ribs 28 extending in the axial direction. Since the other configuration is the same as that of the first embodiment, the same reference numerals are assigned to the portions corresponding to those of the previous embodiment in FIG.

  Also according to the third embodiment, the circumferential length S1 on the inner peripheral side of the reduced diameter cylindrical portion 8 is larger than the circumference S2 of the inscribed circle 12 of the dominant arc-shaped portion 10, and before and after the reduction diameter cylindrical portion 8 is molded. The difference between the peripheral lengths afterward can be reduced to zero or as small as possible. Therefore, the outer surface 11a of the flat sensor mounting wall portion 11 can be formed into a high-precision flat surface free from wrinkles. Also in this case, the sensor mounting wall portion 11 is disposed inside the inscribed circle 12 of the dominant arc-shaped portion 10.

  Finally, a fourth embodiment of the present invention shown in FIG. 8 will be described.

  In the fourth embodiment, the casing 1 is divided into a casing main part having holding cylinder parts 7a and 7b and a reduced diameter cylinder part 8, and funnel-shaped guide cylinder parts 9a and 9b, and the guide cylinder part 9a, 9b is fitted to the outer end portions of the holding cylinder portions 7a and 7b and is air-tightly welded. Other configurations are the same as those in the first embodiment, and therefore correspond to the previous embodiment in FIG. Parts are denoted by the same reference numerals, and redundant description is omitted.

  The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention. For example, the catalyst carriers 2a and 2b are not limited to the monolith type, but may be other types, for example, a metal honeycomb type. The casing 1 can also be formed in an elliptical cross section. Further, MIG welding or TIG welding other than projection welding can be used for welding the sensor mounting boss 21 to the outer surface of the sensor mounting wall 11.

C ··· Catalytic converter 1 ··· Casing 2a, 2b ··· Catalyst carrier 3 ··· O ₂ sensor 3a ··· Sensing unit 6 ··· Holding Material 7a, 7b ··· Holding cylinder portion 8 ··· Reduced diameter tube portion 8 '··· Material portion 10 · · · Arc portion 10a ··· Wall portion 11 ···・ Sensor mounting wall 12... Inscribed circle 21 of the superior arc-shaped part .. Sensor mounting boss 25... Concave wall part 26... Convex wall part 28. ···rib

Claims (5)

A reduced diameter having a pair of holding cylinder parts (7a, 7b) arranged in the axial direction and a flat sensor mounting wall part (11) on one side and integrally connecting the two holding cylinder parts (7a, 7b). A casing (1) having a cylindrical portion (8), a pair of catalyst carriers (2a, 2b) accommodated and held in both holding cylindrical portions (7a, 7b) via holding materials (6), and the sensor A sensor mounting boss (21) welded to the outer surface of the mounting wall (11) while passing through the mounting wall (11), and the sensor mounting boss (21) mounted on the sensor (3a) is connected to the two catalyst carriers (2a, 2b). ) O ₂ sensor (3 for exposing between) and becomes more, the reduced diameter cylindrical portion (8) is press-molded from the holding tubular portion (7a, 7b) the material portion extending between (8 ') In catalytic converter,
The reduced diameter cylindrical portion (8) is composed of the sensor mounting wall portion (11) and a dominant arc-shaped portion (10) that integrally connects both side ends of the sensor mounting wall portion (11). The formation of the arcuate part (10) so that the circumference of the inner peripheral side of the diameter cylinder part (8) is larger than the circumference of the inscribed circle (12) of the arcuate part (10). Characteristic catalytic converter. The catalytic converter according to claim 1,
The catalytic converter, wherein the sensor mounting wall (11) is disposed inside the inscribed circle (12). The catalytic converter according to claim 1,
The arcuate portion (10) is formed by integrally connecting a plurality of wall portions (10a) having a radius of curvature (R2) larger than the radius (R1) of the inscribed circle (12) in the circumferential direction. Catalytic converter. The catalytic converter according to claim 1,
A plurality of concave arcuate wall portions (25) that are concave inward in the radial direction and convex curved wall portions (26) that are convex outward in the radial direction are joined together in the circumferential direction. A catalytic converter characterized by comprising. The catalytic converter according to claim 1,
The catalytic converter according to claim 1, wherein a plurality of ribs (28) extending in the axial direction are formed on the arcuate portion (10).

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