CATALYTIC CONVERTER AND METHOD FOR MANUFACTURING CASING

Abstract

A catalytic converter includes: a tubular casing including at least a pair of holding tubular parts and a reduced diameter tubular part that integrally connects the holding tubular parts to each other; and a monolithic catalyst carrier accommodated in each of the holding tubular parts, the reduced diameter tubular part being obtained by press-forming a portion, between the holding tubular parts, of a casing material of a tubular shape that corresponds to that of the holding tubular parts. Flat parts are formed respectively in a plurality of places at intervals in a peripheral direction of the reduced diameter tubular part, a sensor being attached to at least one of the flat parts. Accordingly, a press load when press-forming the reduced diameter tubular part is suppressed from becoming large and unequal in the peripheral direction of the reduced diameter tubular part.

Claims

1. A catalytic converter comprising: a tubular casing including at least a pair of holding tubular parts and a reduced diameter tubular part that integrally connects the holding tubular parts to each other; and a monolithic catalyst carrier accommodated in each of the holding tubular parts, the reduced diameter tubular part being obtained by press-forming a portion, between the holding tubular parts, of a casing material of a tubular shape that corresponds to that of the holding tubular parts, wherein flat parts are formed respectively in a plurality of places at intervals in a peripheral direction of the reduced diameter tubular part, a sensor being attached to at least one of the flat parts.

2. The catalytic converter according to claim 1, wherein a pair of the flat parts are formed in the reduced diameter tubular part so as to extend along a pair of imaginary planes orthogonal to each other.

3. The catalytic converter according to claim 1, wherein the flat parts are formed respectively in a plurality of places at equal intervals in the peripheral direction of the reduced diameter tubular part.

4. The catalytic converter according to claim 1, wherein first protrusions are respectively formed on opposite end portions, along the peripheral direction of the reduced diameter tubular part, of each of the flat parts, the first protrusions protruding outward of the reduced diameter tubular part and extending in an axial direction of the reduced diameter tubular part.

5. The catalytic converter according to claim 2, wherein first protrusions are respectively formed on opposite end portions, along the peripheral direction of the reduced diameter tubular part, of each of the flat parts, the first protrusions protruding outward of the reduced diameter tubular part and extending in an axial direction of the reduced diameter tubular part.

6. The catalytic converter according to claim 3, wherein first protrusions are respectively formed on opposite end portions, along the peripheral direction of the reduced diameter tubular part, of each of the flat parts, the first protrusions protruding outward of the reduced diameter tubular part and extending in an axial direction of the reduced diameter tubular part.

7. The catalytic converter according to claim 4, wherein second protrusions are each formed on an outer surface of the reduced diameter tubular part at a central portion in the peripheral direction between each adjacent ones of the plurality of flat parts, the second protrusions protruding outward of the reduced diameter tubular part and extending in the axial direction of the reduced diameter tubular part.

8. The catalytic converter according to claim 1, wherein the casing material is an electric resistance welded tube which has an electric resistance welded part disposed in one of the plurality of flat parts.

9. The catalytic converter according to claim 2, wherein the casing material is an electric resistance welded tube which has an electric resistance welded part disposed in one of the plurality of flat parts.

10. The catalytic converter according to claim 3, wherein the casing material is an electric resistance welded tube which has an electric resistance welded part disposed in one of the plurality of flat parts.

11. The catalytic converter according to claim 7, wherein the casing material is an electric resistance welded tube which has an electric resistance welded part disposed in one of the plurality of second protrusions.

12. A method for manufacturing the casing in the catalytic converter according to claim 1, comprising obtaining the reduced diameter tubular part by press-forming a portion, between the holding tubular parts, of the tubular casing material by using a plurality of split molds that are divided in a peripheral direction of the casing material and include split molds each having a flat surface for forming the flat part.

13. A method for manufacturing the casing in the catalytic converter according to claim 2, comprising obtaining the reduced diameter tubular part by press-forming a portion, between the holding tubular parts, of the tubular casing material by using a plurality of split molds that are divided in a peripheral direction of the casing material and include split molds each having a flat surface for forming the flat part.

14. A method for manufacturing the casing in the catalytic converter according to claim 3, comprising obtaining the reduced diameter tubular part by press-forming a portion, between the holding tubular parts, of the tubular casing material by using a plurality of split molds that are divided in a peripheral direction of the casing material and include split molds each having a flat surface for forming the flat part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a longitudinal sectional view of a catalytic converter according to a first embodiment.

[0024] FIG. 2 is a sectional view along line 2-2 in FIG. 1.

[0025] FIG. 3 is a cross sectional view of a press-forming device before press-forming.

[0026] FIG. 4 is a cross sectional view of the press-forming device after completing press-forming.

[0027] FIG. 5 is a cross sectional view of a catalytic converter according to a second embodiment.

[0028] FIG. 6 is a cross sectional view of a catalytic converter according to a third embodiment.

[0029] FIG. 7 is a sectional view according to a fourth embodiment, corresponding to FIG. 2.

[0030] FIG. 8 is a sectional view according to a fifth embodiment, corresponding to FIG. 5.

[0031] FIG. 9 is a sectional view according to a sixth embodiment, corresponding to FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Embodiments of the present invention are explained below referring to the attached drawings.

[0033] A first embodiment of the present invention is now explained referring to FIGS. 1 to 4. First, in FIG. 1, a catalytic converter includes a tubular, for example, cylindrical casing 11A and a plurality of, for example, two monolithic catalyst carriers 12 and 13 that are accommodated in series inside the casing 11A so as to be separated from each other in a direction along an axis of the casing 11A, elastic mats 14 and 15 as holding materials being respectively wound around outer peripheries of the monolithic catalyst carriers 12 and 13.

[0034] The casing 11A is formed so as to integrally include at least one pair of (a pair of, in this embodiment) holding tubular parts 16 and 17, a reduced diameter tubular part 18 integrally connecting the holding tubular parts 16 and 17 to each other, and a pair of funnel-shaped connecting tubular parts 19 and 20 respectively connected to end portions, on sides opposite to the reduced diameter tubular part 18, of the pair of holding tubular parts 16 and 17.

[0035] The monolithic catalyst carriers 12 and 13 are respectively fitted into and held in the holding tubular parts 16 and 17 via the elastic mats 14 and 15. An upstream exhaust pipe 21 continuous to an exhaust port (not illustrated) of an internal combustion engine for a vehicle is connected to the connecting tubular part 19 that is one of the connecting tubular parts 19 and 20, and the other connecting tubular part 20 is connected to an exhaust muffler (not illustrated) via a downstream exhaust pipe 22.

[0036] Exhaust gas discharged from the internal combustion engine is guided from the upstream exhaust pipe 21 into the casing 11A, and then passes through the pair of monolithic catalyst carriers 12 and 13 sequentially so that harmful substances in the exhaust gas are purified by an oxidation reduction effect. The purified exhaust gas passes through the downstream exhaust pipe 22 and the exhaust muffler and is thereafter released into an atmosphere.

[0037] At least one sensor, one O.sub.2 sensor 23 in this embodiment is attached to the reduced diameter tubular part 18 of the casing 11A. The O.sub.2 sensor 23 detects an O.sub.2 concentration in the exhaust gas between the pair of the monolithic catalyst carriers 12 and 13 and inputs the detected signal into an electronic control unit that is not illustrated. Based on the O.sub.2 concentration obtained in the O.sub.2 sensor 23, the electronic control unit controls an amount of fuel that is to be supplied to the internal combustion engine, and thereby an air-fuel ratio of an intake air-fuel mixture of the internal combustion engine is appropriately controlled.

[0038] The reduced diameter tubular part 18 of the casing 11A is obtained by press-forming a portion, between the holding tubular parts 16 and 17, of a casing material 24 of a tubular shape that corresponds to that of the holding tubular parts 16 and 17. Flat parts 18a are formed respectively in a plurality of places at intervals in a peripheral direction of the reduced diameter tubular part 18, the O.sub.2 sensor 23 being attached to at least one (one in this embodiment) of the flat parts 18a.

[0039] The flat parts 18a are formed respectively in a plurality of, preferably three to six places at equal intervals in the peripheral direction of the reduced diameter tubular part 18. In this embodiment, the flat parts 18a are formed in four places at equal intervals in the peripheral direction of the reduced diameter tubular part 18.

[0040] In one of the flat parts 18a, to which the O.sub.2 sensor 23 is attached, an attaching hole 25 is formed. A sensor attaching boss 26 is fitted into the attaching hole 25 and fixed by welding to the one flat part 18a. The sensor attaching boss 26 has a screw hole 27, and the O.sub.2 sensor 23 is screwed into the screw hole 27. A sensing part 23a provided at a tip end portion of the O.sub.2 sensor 23 is disposed in an intermediate portion between the pair of the monolithic catalyst carriers 12 and 13.

[0041] Moreover, first protrusions or ribs 18b are respectively formed on opposite end portions, along the peripheral direction of the reduced diameter tubular part 18, of each of the flat parts 18a, the first protrusions 18b protruding outward of the reduced diameter tubular part 18 and extending in an axial direction of the reduced diameter tubular part 18. In addition, second protrusions or ribs 18c are each formed on an outer surface of the reduced diameter tubular part 18 at a central portion in the peripheral direction between each adjacent ones of the plurality of flat parts 18a, the second protrusions 18c protruding outward of the reduced diameter tubular part 18 and extending in the axial direction thereof.

[0042] In FIG. 3, the casing material 24 is formed from an electric resistance welded tube including an electric resistance welded part 28. The reduced diameter tubular part 18 is obtained by press-forming the portion, between the holding tubular parts 16 and 17, of the casing material 24 by using a plurality of split molds 29 and 30 that are divided in a peripheral direction of the casing material 24, the split molds 29 each having a flat surface 29a for forming the flat part 18a. In this embodiment, four split molds 29 each having the flat surface 29a and four split molds 30 are disposed outside the casing material 24, the split molds 30 corresponding to portions, other than the flat parts 18a, of the reduced diameter tubular part 18. A core mold 31 is fixedly disposed inside the casing material 24, a shape of an outer periphery of the core mold 31 corresponding to a shape of an inner periphery of the reduced diameter tubular part 18.

[0043] The casing material 24 is press-formed radially inward toward the core mold 31 by using the eight split molds 29 and 30 as described above, so that the reduced diameter tubular part 18 having the four flat parts 18a as shown in FIG. 4 is obtained. Moreover, the electric resistance welded part 28 of the casing material 24 is disposed in one of the plurality of second protrusions 18c.

[0044] An operation of the first embodiment is now explained. The casing 11A includes the pair of holding tubular parts 16 and 17 in which the monolithic catalyst carriers 12 and 13 are respectively accommodated, and the reduced diameter tubular part 18 integrally connecting the holding tubular parts 16 and 17 to each other. The reduced diameter tubular part 18 is obtained by press-forming the portion, between the holding tubular parts 16 and 17, of the casing material 24 of a tubular shape that corresponds to that of the holding tubular parts 16 and 17. The flat parts 18a are respectively formed in the plurality of, for example, four places at intervals in the peripheral direction of the reduced diameter tubular part 18. The O.sub.2 sensor 23 is attached to at least one (one in this embodiment) of these flat parts 18a. Accordingly, in order to form the flat parts 18a, press loads act on the casing material 24 from a plurality of (four in this embodiment) directions so as to prevent the press loads from becoming large and unequal in the peripheral direction of the reduced diameter tubular part 18, thereby enabling an amount of deformation per one place of the reduced diameter tubular part 18 to be minimized.

[0045] In addition, since the flat parts 18a are formed respectively in the plurality of (four in this embodiment) places at equal intervals in the peripheral direction of the reduced diameter tubular part 18, the flat parts 18a are disposed with a proper balance in the reduced diameter tubular part 18. Moreover, since adjacent ones of the flat parts 18a extend along planes orthogonal to each other, one and the other of the adjacent flat parts 18a reinforce each other such that one flat part 18a suppresses deformation of the other flat part 18a, thereby enabling strength of the reduced diameter tubular part 18 to be enhanced, and it is possible to reduce a thickness of the casing material 24 so as to reduce a weight of the casing 11A.

[0046] Moreover, since the first protrusions 18b protruding outward of the reduced diameter tubular part 18 and extending in the axial direction thereof are respectively formed on the opposite end portions, along the peripheral direction of the reduced diameter tubular part 18, of each of the flat parts 18a, radially inward contraction of portions of the reduced diameter tubular part 18 due to formation of the flat parts 18a can be absorbed by the first protrusions 18b and it is also possible to contribute to enhancement of strength of the flat parts 18a.

[0047] Also, since the second protrusions 18c are each formed on the outer surface of the reduced diameter tubular part 18 at the central portion in the peripheral direction between each adjacent ones of the plurality of flat parts 18a, it is possible to minimize a difference in peripheral length between the reduced diameter tubular part 18 and the holding tubular parts 16 and 17, prevent wrinkles and the like from occurring on the reduced diameter tubular part 18, and further enhance the strength of the reduced diameter tubular part 18.

[0048] Further, since the casing material 24 is an electric resistance welded tube with its electric resistance welded part 28 being disposed in one of the plurality of second protrusions 18c, an amount of deformation of the electric resistance welded part 28 can be minimized so as to reduce a burden applied to the electric resistance welded part 28.

[0049] Furthermore, since the reduced diameter tubular part 18 is obtained by press-forming the portion, between the holding tubular parts 16 and 17, of the tubular casing material 24 by using the plurality of split molds 29 and 30 that are divided in the peripheral direction of the casing material 24 and the split molds 29 each have the flat surface 29a for forming the flat part 18a, a press load by one split mold 29 or 30 can be reduced so as to minimize an amount of deformation of the reduced diameter tubular part 18, and thus it is possible to form the casing 11A while suppressing the deformation of the reduced diameter tubular part 18.

[0050] A second embodiment of the present invention is now explained referring to FIG. 5. Parts corresponding to those of the first embodiment are denoted by the same reference numerals and symbols and only illustrated in the drawing, and detailed explanation thereof is omitted.

[0051] A reduced diameter tubular part 32 of a casing 11B is obtained by press-forming a portion, between holding tubular parts 16 and 17, of a casing material 24 of a tubular shape that corresponds to that of the holding tubular parts 16 and 17. Flat parts 32a are formed respectively in a plurality of, three in this second embodiment, places at equal intervals in the peripheral direction of the reduced diameter tubular part 32. An O.sub.2 sensor 23 is attached to one of these flat parts 32a.

[0052] First protrusions or ribs 32b are respectively formed on opposite end portions, along a peripheral direction of the reduced diameter tubular part 32, of each of the flat parts 32a, the first protrusions 32b protruding outward of the reduced diameter tubular part 32 and extending in an axial direction thereof. Moreover, second protrusions or ribs 32c are each formed on an outer surface of the reduced diameter tubular part 32 at a central portion in the peripheral direction between each adjacent ones of the plurality of (three in this second embodiment) flat parts 32a, the second protrusions 32c protruding outward of the reduced diameter tubular part 32 and extending in the axial direction thereof.

[0053] Also in this second embodiment, an effect similar to that of the first embodiment can be achieved.

[0054] A third embodiment of the present invention is now explained referring to FIG. 6. Parts corresponding to those of the first and second embodiments are denoted by the same reference numerals and symbols and only illustrated in the drawing, and detailed explanation thereof is omitted.

[0055] A reduced diameter tubular part 33 of a casing 11C is obtained by press-forming a portion, between holding tubular parts 16 and 17, of a casing material 24 of a tubular shape that corresponds to that of the holding tubular parts 16 and 17. Flat parts 33a are formed respectively in a plurality of, two in this third embodiment, places at intervals in a peripheral direction of the reduced diameter tubular part 33.

[0056] These flat parts 33a are formed in the reduced diameter tubular part 33 so as to extend along a pair of imaginary planes 34 and 35 orthogonal to each other. An O.sub.2 sensor 23 is attached to one of these flat parts 33a.

[0057] First protrusions or ribs 33b protruding outward of the reduced diameter tubular part 33 and extending in an axial direction thereof are respectively formed on opposite end portions, along the peripheral direction of the reduced diameter tubular part 33, of each of the flat parts 33a. Second protrusions or ribs 33c protruding outward of the reduced diameter tubular part 33 and extending in the axial direction thereof are each formed on an outer surface of the reduced diameter tubular part 33 at a central portion in the peripheral direction between each adjacent ones of the plurality of (two in this third embodiment) flat parts 33a.

[0058] According to this third embodiment, since the pair of flat parts 33a of the reduced diameter tubular part 33 extend along the pair of imaginary planes 34 and 35 orthogonal to each other, the flat parts 33a influence each other so that one of the flat parts 33a suppresses the other flat part 33a from deforming, thereby enabling an amount of deformation per one place of the reduced diameter tubular part 33 to be minimized.

[0059] A fourth embodiment of the present invention is now explained referring to FIG. 7. Parts corresponding to those of the first to third embodiments are denoted by the same reference numerals and symbols and only illustrated in the drawing, and detailed explanation thereof is omitted.

[0060] As in the first embodiment shown in FIGS. 1 to 4, a casing 11D of a catalytic converter of this fourth embodiment integrally includes a pair of holding tubular parts 16 and 17 and a reduced diameter tubular part 18 integrally connecting the holding tubular parts 16 and 17 to each other, the reduced diameter tubular part 18 being obtained by press-forming a portion, between the holding tubular parts 16 and 17, of a casing material 24 (see FIG. 1) that is an electric resistance welded tube including an electric resistance welded part 28.

[0061] Moreover, the casing material 24 is press-formed so as to have the electric resistance welded part 28 disposed in, out of four flat parts 18a of the reduced diameter tubular part 18, one of three flat parts 18a other than a flat part 18a to which an O.sub.2 sensor 23 is attached.

[0062] According to this fourth embodiment, in a cross sectional shape of the casing 11D, that portion of the casing 11D in which the electric resistance welded part 28 is disposed does not change in shape, and compared with an uneven shape, stress applied to the electric resistance welded part 28 can be reduced.

[0063] A fifth embodiment of the present invention is now explained referring to FIG. 8. Parts corresponding to those of the first to fourth embodiments are denoted by the same reference numerals and symbols and only illustrated in the drawing, and detailed explanation thereof is omitted.

[0064] As in the second embodiment shown in FIG. 5, a casing 11E of a catalytic converter of this fifth embodiment integrally includes a pair of holding tubular parts 16 and 17 and a reduced diameter tubular part 32 integrally connecting the holding tubular parts 16 and 17 to each other, the reduced diameter tubular part 32 being obtained by press-forming a portion, between the holding tubular parts 16 and 17, of a casing material 24 (see FIG. 1) that is an electric resistance welded tube including an electric resistance welded part 28.

[0065] Moreover, the casing material 24 is press-formed so that the electric resistance welded part 28 is disposed in, out of three flat parts 32a of the reduced diameter tubular part 32, one of two flat parts 32a other than a flat part 32a to which an O.sub.2 sensor 23 is attached.

[0066] Also in this fifth embodiment, as in the fourth embodiment, stress applied to the electric resistance welded part 28 can be reduced.

[0067] A sixth embodiment of the present invention is now explained referring to FIG. 9. Parts corresponding to those of the first to fifth embodiments are denoted by the same reference numerals and symbols and only illustrated in the drawing, and detailed explanation thereof is omitted.

[0068] As in the third embodiment shown in FIG. 6, a casing 11F of a catalytic converter of this sixth embodiment integrally includes a pair of holding tubular parts 16 and 17 and a reduced diameter tubular part 33 integrally connecting the holding tubular parts 16 and 17 to each other, the reduced diameter tubular part 33 being obtained by press-forming a portion, between the holding tubular parts 16 and 17, of a casing material 24 (see FIG. 1) that is an electric resistance welded tube including an electric resistance welded part 28.

[0069] Moreover, the casing material 24 is press-formed so that the electric resistance welded part 28 is disposed in one of a pair of flat parts 33a of the reduced diameter tubular part 33 other than a flat part 33a to which an O.sub.2 sensor 23 is attached.

[0070] Also in this sixth embodiment, as in the fourth and fifth embodiments, stress applied to the electric resistance welded part 28 can be reduced.

[0071] Embodiments of the present invention are explained above, but the present invention is not limited to the above-mentioned embodiments and may be modified in a variety of ways as long as the modifications do not depart from the gist of the present invention.