GB2425073A

GB2425073A - Catalytic converter and method

Info

Publication number: GB2425073A
Application number: GB0605329A
Authority: GB
Inventors: Said Zidat
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2005-04-12
Filing date: 2006-03-17
Publication date: 2006-10-18
Also published as: GB0605329D0; GB0507326D0

Abstract

The invention relates to catalytic converter apparatus having a catalytic substrate core and a first sleeve 20 which surrounds the substrate core 10. An intermediate member 22 surrounds the first sleeve and substrate core. A second sleeve 24 surrounds the intermediate shell member, the first sleeve and the substrate core. The apparatus allows assembly of the catalytic substrate core within a catalytic converter with minimal risk of damage whilst ensuring that the substrate core is held securely within the can of the converter. A method of installing the substrate core in the catalytic converter is also provided. The first sleeve (inner mat) and a second sleeve (outer mat) are arranged to expand on heating to securely retain the substrate. The inner mat is relatively thin to allow rapid heating and is compressed around the substrate such that the gap bulk density will secure the substrate within the intermediate shell member. The outer sleeve is thicker and has a higher gap bulk density so that arrangement is firmly secured in a outer shell 14.

Description

1 "Catalytic Converter Apparatus and Method" 3 The present invention

relates to catalytic converter 4 apparatus and a method, and particularly, but not exclusively, relates to catalytic converter 6 apparatus and a method which aids manufacture of 7 catalytic converter units used in the automobile 8 industry.

During assembly of conventional catalytic 11 converters, a ceramic fibre or mat is wrapped around 12 a substrate core (containing the catalyst). This 13 forms a "brick" which is subsequently inserted into 14 a metallic casing (or can) that forms the outer body of the converter. The assembled converter may then 16 be integrated into the exhaust system of the 17 automobile.

19 Such mats generally comprise ceramic fibers bound together using a very specific binder (which 21 generally makes up around 10% of the total mat 22 mass). The bound fibers form a mat having a desired 1 thickness and density usually expressed in glcm3.

2 Other components may also be added to the mat such 3 as vermjculate, to assist mat expansion at high 4 temperatures The resulting mat can then be easily wrapped around the substrate core (comprising 6 cordierite or, especially in particulate filters, 7 SIC).

9 The substrate and mat (the brick) is then inserted into a shell using a "stuffing technique" or any 11 other canning technique such as a "clamshell" or 12 "tourniquet" technique as is commonly known in the 13 art. When inserted into the can, the mat is 14 compressed. This aims to ensure that a sufficient holding force is provided between the brick and the 16 can in order to maintain the brick in its 17 operational position when subjected to the high 18 vibration levels experienced during typical 19 automobile operations.

21 The level of the initial holding force will depend 22 on the mat Gap Bulk Density (GED) where GBD is the 23 ratio: Mat Layer density at the free stage/Gap 24 substrate-shell 26 The holding force will change from the initial 27 holding force during vehicle operation after being 28 subjected to a thermal cycle randomly generated 29 depending on the driving cycle of the vehicle as subsequently discussed.

1 Typically, the mat heat up will first result in the 2 burnout of the binder which will decrease the 3 compression force wrapping the mat around the 4 substrate. With multiple heat up cycles, where temperatures exceed around 400C, the binder will 6 tend to burn completely and the mat will tend to 7 expand, particularly when it contains vermiculate.

8 This causes the outer dimensions of the mat to push 9 against the inner dimensions of the can in order to provide the holding force required to hold the 11 ceramic substrate securely within the converter.

13 In certain situations, such as when used in diesel 14 engines, the exhaust gas temperature is low and may never exceed 250 C for any signifjcan length of 16 time. Indeed, in the case of particulate filters, 17 such low temperatures are an even greater issue 18 since the substrate in such filters must be heavily 19 insulated in order to conserve heat and minimize the time required for filter regeneration. The high 21 thickness of mat required for such a level of 22 insulation makes heating even more difficult and the 23 external portion of the mat therefore often never 24 experiences temperatures higher than 200c. In this scenario the binder will only partially burn, 26 thereby significantly reducing the resultant holding 27 force on the brick. This may result in the 28 undesirable situation where a brick is not held 29 properly within the metallic casing even after many cycles of converter operation.

1 According to the present invention there is provided 2 catalytic converter apparatus comprising:- 3 a substrate member; 4 a first sleeve adapted to at least partially surround said substrate member; 6 an intermediate member adapted to at least 7 partially surround said first sleeve and substrate 8 member; and 9 a second sleeve or adapted to at least partially surround said intermediate shell member, 11 said first sleeve and said substrate member.

13 Preferably, said first sleeve is adapted to change 14 configuration between a first compressed configuration and a second decompressed 16 configuration.

18 Preferably, when in the compressed configuration, 19 said first sleeve is adapted to allow said substrate member and said first sleeve member to be inserted 21 into said intermediate shell member. More 22 preferably, when in the compressed configuration 23 said first sleeve is adapted to frictionally abut 24 against the inner dimensions of said intermediate shell member with a compressed frictional force.

27 Preferably, when in the decompressed configuration 28 said first sleeve is adapted to frictionally abut 29 against the inner dimensions of said intermediate shell member with a decompressed frictional force.

31 More preferably, said decompressed frictional force 32 is greater than said compressed frictional force.

2 Preferably, said first sleeve comprises a mat having 3 heat sensitive binding provided by said first 4 sleeve, wherein said binding is adapted to change between a first configuration, whereby compression 6 of said first sleeve is maintained, and a second 7 configuration whereby compression of said first 8 sleeve is relieved. Typically, said binding is in 9 the first configuration after manufacture of said first sleeve and may change into said second 11 configuration by heating said first sleeve in order 12 to burn said binding.

14 Preferably, said second sleeve is adapted to frictionally abut against the outer dimensions of 16 said intermediate shell member.

18 Preferably, said catalytic converter apparatus 19 further comprises an outer case capable of housing said second sleeve, said shell, said first sleeve 21 and said substrate member.

23 Preferably, said second sleeve is adapted to 24 frictionally abut against the inner dimensions of said outer case.

27 Preferably, said second sleeve is provided with a 28 high gap bulk density relative to the gap bulk 29 density of said first sleeve.

31. Preferably, said apparatus is adapted to be provided 32 between an exhaust gas inlet and an exhaust gas 1 outlet. Preferably, said inlets and outlets are 2 cone shaped.

4 Preferably, locating means, such as stop members, may be provided on said intermediate shell member 6 such that translation of said intermediate shell 7 results in said locating means on said intermediate 8 shell abutting against said outlet and being held 9 thereby.

11 Preferably, said stop members comprise bent over 12 portions of said shell, which are preferably 13 provided at one end of said shell.

Preferably, said inner shell comprises an additional 16 portion having substantially the same size, shape 17 and position as said stop members.

19 Preferably, said intermediate member comprises material having heat retaining properties.

21 Typically, said material comprises stainless steel.

23 According to the present invention, there is also 24 provided a method of manufacturing catalytic converter apparatus comprising:- 26 a) inserting a substrate member into a first 27 sleeve; 28 b) inserting said substrate member and said first 29 sleeve into an intermediate shell; and c) inserting said substrate member, said first 31 sleeve and said intermediate shell into a second 32 sleeve.

2 Preferably, step a) of the method of manufacturing 3 further comprises the step of compressing said first 4 sleeve around said substrate member.

6 Preferably, step c) of the method of manufacturing 7 further comprises the step of pushing said shell in 8 order to insert said substrate member, said first 9 sleeve and said shell into said second sleeve.

11 Preferably, the method of manufacturing further 12 comprises the step of inserting said substrate 13 member, said first sleeve, said shell and said 14 second sleeve into an outer case. More preferably, the method of manufacturing further comprises the 16 step of pushing said shell in order to insert said 17 substrate member, said first sleeve, said shell and 18 said second sleeve into said outer case.

Optionally, the method of manufacturing catalytic 21 converter apparatus further comprises the step of 22 heating up said apparatus in order to burn binding 23 means provided in said first sleeve.

Embodiments of the present invention will now be 26 described, by way of example only, with reference to 27 the accompanying figures, in which:- 29 Fig. 1 is a schematic cross-sectional view of components of a prior art catalytic converter not in 31 accordance with the present invention; 1 Fig. 2 is a schematic cross-sectional view of 2 components of a catalytic converter apparatus in 3 accordance with the present invention showing an 4 intermediate she1l and Fig. 3 is a schematic cross-sectional view of a 6 modified version of the catalytic converter shown in 7 Fig. 2 where physical end stops are provided.

9 Referring to Fig. 1, a conventional prior-art catalytic converter 8P comprises a ceramic substrate 11 core lOP surrounded by a ceramic mat 12P and an 12 outer metallic can l4P. The converter 8P is 13 positioned between opposite connection sockets 16P, 14 16P' of an exhaust pipe 18P, 18P' connected to an automobile engine (not shown).

17 Prior to assernbling the prior art converter 8?, the 18 mat 12P is typically compressed around the substrate 19 core lop such that the combined outer dimension of the substrate core lop and the mat l2P is less than 21 the inner dimension of the can l4P. The mat 12P and 22 substrate core lop may then be easily inserted into 23 the can 14? without damaging the mat 12? or 24 substrate core lOP in so doing. When the converter 8P is fitted between sockets 16P it is ready for 26 use.

28 When the converter sp is sufficiently heated, by the 29 exhaust gas flowing from the engine (not shown) through the exhaust pipe 18P, 18P' (typically above 31 400 C) the binding (not shown) will burn off and 32 the mat 12? starts to expand (decompress) after a 1. number of heat up cycles. The binding may therefore 2 be regarded as being heat sensitive. The expansion 3 increases the frictional force between the mat 12P, 4 substrate core lOP and can 14?, thereby ensuring that the mat 12P and substrate core 10? are secured 6 within the can 14?. However, as previously 7 described, the exhaust gas does not always reach 8 sufficient temperatures to provide the heat required 9 to burn of f the binding and to expand the mat 12?.

This would result in the mat 12? and substrate core 11 lop remaining within the can 14P in a compressed 12 state (i.e. it remains compressed by the binding 13 into relatively small dimensions) which does not 14 provide the necessary support. In other words, there may be a degree of "play" between the mat 12P, 16 substrate core 10? and the can 14?.

18 Referring to Fig. 2, the apparatus according to the 19 present invention contains a number of components

common to the previously described prior art

21 apparatus. Where this applies similar reference 22 numerals will used.

24 The catalytic converter apparatus 8 comprises a substrate core 10 (comprising any suitable material, 26 f or example, a ceramic or SIC substrate) surrounded 27 by an inner mat 20 (or sleeve), intermediate shell 28 22, outer mat 24 (or sleeve) and can 14. The 29 apparatus 8 IS Positioned between Opposite sockets 16, 16' of an exhaust pipe 18, 18' 1 The inner mat 20 is relatively thin (when compared 2 to prior art mats and outer mat 24) and is formed of 3 a ceramic material compressed around the substrate 4 10. The thickness of mat 20 is chosen to allow fast heating of the mat 20 during the operation cycle as 6 discussed subsequently. The inner mat 20 is formed 7 of a material having a nominal gap bulk density 8 which is chosen during manufacture depending upon 9 the application of the converter, as will be described subsequently. 1].

12 The outer mat 24 is relatively thick (compared to 13 the mat 20) and is formed of a ceramic material 14 having a relatively high gap bulk density.

16 During assembly of the converter 8, the substrate 17 core 10 is surrounded by inner mat 20. Inner mat 20 18 is compressed around substrate core 10 in such a way 19 that the resultant gap bulk density of the inner mat 20 will sufficiently secure the substrate core 10 21 within intermediate shell 22 once inserted therein.

22 In this regard, it should be noted that the combined 23 outer dimensions of the inner mat 20 and substrate 24 core 10 are such that a small amount of resistance exists when inserting the substrate core 10 and 26 inner mat 20 into the intermediate shell 22; however 27 this resistance is not sufficient to risk damaging 28 the substrate core 10 itself (which is typically 29 very fragile).

31 The assembly comprising the substrate core 10, inner 32 mat 20, and intermediate shell 22 may now be 1 inserted into the outer mat 24. The gap bulk 2 density of the outer mat 24 will be chosen during 3 manufacture to ensure that resistance exists when 4 inserting the assembly comprising the substrate 10, S inner mat 20, and intermediate shell 22 therein.

6 However, being inserted between two steel shells and 7 without any pressure on the substrate, the gap bulk 8 density of the outer mat 24 can be high which will 9 ensure a high holding force of the inner sub assembly (comprising substrate core 10, inner mat 11 20, shell 22) even if the inner mat 20 does not 12 fully expand and the binder does not completely 13 burn.

The assembly comprising the substrate core 10, inner 16 mat 20, intermediate shell 22, and outer mat 24 may 17 now be inserted into can 14. The presence of outer 18 mat 24 and intermediate shell 22 protects the inner 19 substrate core 10 from any risk of damage caused by inserting the assembly into the can 14.

22 It should be noted that at this stage, the inner 23 substrate core 10 is frictionally held by the inner 24 mat 20 which is in turn frictionally held by intermediate shell 22 due to the chosen gap bulk 26 density of inner mat 20. In this regard the 27 frictional force between the inner mat 20 and 28 substrate core 10 and the inner mat 20 and the 29 intermediate shell 22 is relatively weak in order to ensure that the substrate core 10 is not damaged 31 during the assembly process.

1 In addition, the intermediate shell 22 (and hence 2 the inner mat 20 and substrate 10) is held by 3 frictional force provided by the outer mat 24. This 4 frictional force may be stronger than the frictional force acting between the inner substrate 10 and the 6 inner mat without the risk of damaging the inner 7 substrate due to the presence of intermediate shell 8 22 there between.

Assembly of the apparatus 8 therefore involves the 11 following steps:-.

13 a) inserting substrate core 10 into inner mat 20, 14 wherein the inner mat is bound such that it is compressed against the substrate core 10; 16 b) inserting substrate core 10 and inner mat 20 17 into intermediate shell 22; 18 C) inserting substrate 10, inner mat 20 and 19 intermediate shell 22 into the outer mat 24 by pushing the shell 22 (using, for example, a press 21 (not shown)) into the outer mat 24; 22 d) inserting substrate 10, inner mat 20, 23 intermediate shell 22 and outer mat 24 into the can 24 14 by pushing the shell 22.

26 In use, when the converter 8 is heated sufficiently, 27 the binding (not shown) of the inner mat 20 will 28 burn thereby allowing the inner mat 20 to expand and 29 provide a much greater frictional force between the substrate core 10 and the intermediate shell 22. In 31 this regard, the thin dimensions (relative to prior 32 art systems) of the inner mat 20 efficiently allows 1 heat in the exhaust system to cause the bindings 2 (not shown) of the inner mat 20 to burn whilst the 3 thicker outer mat 24 provides insulation that 4 further assists in this process. In addition, the outer mat 24 (which is relatively thick) provides 6 added insulation against external cooling effects 7 such as ventilation or sprays of water. This is 8 necessary in certain situations, such as in a diesel 9 engine where gas temperatures may never exceed 250 C for any significant period of time. In addition, 11 where particulate filters are used, it is necessary 12 to heavily insulate the substrate core 10 in order 13 to conserve heat and minimize the required time for 14 filter regeneration.

16 The intermediate shell 22 typically comprises a 17 metallic shell made of a suitable material, such as 18 stainless steel, and its thickness chosen during 19 manufacture depending upon the particular application. Typically, the shell 22 may have a 21 wall thickness in the region of 0.8mm to 1.5mm 22 although the skilled reader will realise that 23 different thicknesses may be used. The shell 22 24 provides an additional benefit by acting as a heat buffer which further discourages cooling of the 26 inner mat 20. In other words, as the outside of the 27 converter is cooled, the residual heat in shell 22 28 will tend to keep the inner mat 20 warm.

The apparatus 8 described therefore allows assembly 31 with minimal risk of damaging the substrate core 10 32 whilst ensuring that the substrate core 10 will be 1 held securely within the can 14 even at relatively 2 low operational temperatures 4 Modifications and improvements may be made to the foregoing without departing from the scope of the 6 invention, for example:- 8 Referring to Fig. 3 the converter apparatus 8 may be 9 provided with locating means such as stops 26 which provide a further means of ensuring that the inner 11 substrate core 10 and inner mat 20 do not move with 12 respect to the intermediate shell 22 during 13 assembly. This may be particularly useful when 14 installing the outer mat 24 onto the intermediate shell 22 in order to ensure that the inner substrate 16 core 10 and mat 20 are not disturbed.

18 It-i addition, it should be noted that in previous 19 systems, such as that shown in Fig. 1, it can be necessary to provide a physical stop such as a wire 21 rope (not shown) in order to prevent movement if the 22 brick. it is especially important to provide such a 23 stop in Diesel Particulate Filters which can 24 experience excessive soot loading due to engine control malfunction leading to longer periods before 26 regeneration is triggered. The soot build up in 27 such situations creates a high pressure leading to 28 possible movement of the filter. Wire rope is 29 therefore normally provided to prevent the filter from hitting the outlet cone 16 and being damaged.

1 The intermediate shell 22 of the present invention 2 provides an alternative to the wire rope of previous 3 systems in the form of stops 26 which may be placed 4 at the end of the shell 22. In an excessive soot build up situation, the filter will be pushed 6 against end stops 26 which will impact outlet cone 7 16' thereby protecting the filter from damage.

Claims

1 CLAIMS 3 1. Catalytic converter apparatus comprising:- 4 a substrate

member; a first sleeve adapted to at least partially 6 surround said substrate member; 7 an intermediate member adapted to at least 8 partially surround said first sleeve and substrate 9 member; and a second sleeve adapted to at least partially 11 surround said intermediate shell member, said first 12 sleeve and said Substrate member.

14 2. Catalytic converter apparatus according to claim 1, wherein said first sleeve is adapted to change 16 configuration between a first compressed 17 configuration and a second decompressed 18 configuration.

3. Catalytic converter apparatus according to claim 21 1, wherein when in the compressed configuration, 22 said first sleeve is adapted to allow said substrate 23 member and said first sleeve member to be inserted 24 into said intermediate shell member.

26 4. Catalytic converter apparatus according to claim 27 3, wherein when in the compressed configuration said 28 first sleeve is adapted to frictionally abut against 29 the inner dimensions of said intermediate shell member with a compressed frictional force.

1 5. Catalytic converter apparatus according to claim 2 4, wherein when in the decompressed configuration 3 said first sleeve is adapted to frictionally abut 4 against the inner dimensions of said intermediate shell member with a decompressed frictional force.

7 6. Catalytic converter apparatus according to claim 8 6, wherein said decompressed frictional force is 9 greater than said compressed frictional force.

11 7. Catalytic converter apparatus according to any 12 preceding claim wherein said first sleeve comprises 13 a mat having heat sensitive binding provided by said 14 first sleeve, wherein said binding is adapted to change between a first configuration, whereby 16 compression of said first sleeve is maintained, and 17 a second configuration whereby compression of said 18 first sleeve is relieved.

8. Catalytic converter apparatus according to claim 21 7, wherein said binding is in the first 22 configuration after manufacture of said first sleeve 23 and may change into said second configuration by 24 heating said first sleeve in order to burn said binding.

27 9. Catalytic converter apparatus according to any 28 preceding claim wherein said second sleeve is 29 adapted to frictionally abut against the outer dimensions of said intermediate shell member.

1 10. Catalytic converter apparatus according to any 2 preceding claim, wherein said catalytic converter 3 apparatus further comprises an outer case capable of 4 housing said second sleeve, said shell, said first sleeve and said substrate member.

7 11. Catalytic converter apparatus according to claim 8 10, wherein said second sleeve is adapted to 9 frictionally abut against the inner dimensions of said outer case.

12 12. Catalytic converter apparatus according to any 13 preceding claim, wherein said second sleeve is 14 provided with a high gap bulk density relative to the gap bulk density of said first sleeve.

17 13. Catalytic converter apparatus according to any 18 preceding claim provided between an exhaust gas 19 inlet and an exhaust gas outlet.

21 14. Catalytic converter apparatus according to claim 22 13, wherein said inlets and outlets are cone shaped.

24 15. Catalytic converter apparatus according to either of claims 13 or 14, wherein locating means, 26 such as stop members, may be provided on said 27 intermediate shell member such that translation of 28 said intermediate shell results in said locating 29 means on said intermediate shell abutting against said outlet and being held thereby.

1 16. Catalytic converter apparatus according to claim 2 15, wherein said stop members comprise bent over 3 portions of said shell.

17. Catalytic converter apparatus according to claim 6 16, wherein said stop members are provided at one 7 end of said shell.

9 18. Catalytic converter apparatus according to any of claims 15 to 17, wherein said inner shell 11 comprises an additional portion having substantially 12 the same size, shape and position as said stop 13 members.

19. Catalytic converter apparatus according to any 16 preceding claim, wherein said intermediate member 17 comprises material having heat retaining properties.

19 20. Catalytic converter apparatus according to claim 19, wherein said material comprises stainless steel.

22 21. A method of manufacturing catalytic converter 23 apparatus comprising:- a) inserting a substrate member into a first 26 sleeve; 27 b) inserting said substrate member and said 28 first sleeve into an intermediate shell; and 29 c) inserting said substrate member, said first sleeve and said intermediate shell into a 31 second sleeve.

1 22. A method of manufacturing catalytic converter 2 apparatus according to claim 21, wherein step a) 3 further comprises the step of compressing said first 4 sleeve around said substrate member.

6 23. A method of manufacturing catalytic converter 7 apparatus according to either of claims 21 and 22, 8 wherein step c) of the method of manufacturing 9 further comprises the step of pushing said shell in order to insert said substrate member, said first 11 sleeve and said shell into said second sleeve.

13 24. A method of manufacturing catalytic converter 14 apparatus according to claims 21 to 23 further comprising the step of inserting said substrate 16 member, said first sleeve, said shell and said 17 second sleeve into an outer case.

19 25. A method of manufacturing catalytic converter apparatus according to claim 24, further comprising 21 the step of pushing said shell in order to insert 22 said substrate member, said first sleeve, said shell 23 and said second sleeve into said outer case.

26. A method of manufacturing catalytic converter 26 apparatus according to claims 21 to 24 further 27 comprising the step of heating up said apparatus in 28 order to burn binding means provided in said first 29 sleeve.

1 27. Catalytic converter apparatus substantially as 2 hereinbefore described with reference to Figures 2 3 and3.

28. A method of manufacturing catalytic converter 6 apparatus substantially as hereinbefore described.