JP2006104975A - Method of manufacturing silencer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide superior high temperature oxidation resistance and corrosion resistance, by inexpensively and easily coating a sound absorbing material, an inner pipe or a welding part particularly exposed to the high temperature among a silencer, with a uniform ceramic coating film of a submicron. <P>SOLUTION: After integrally winding stainless fiber 3 having an average fiber diameter of 30 to 150 μm as sound absorbing material fiber in bulk density of 50 to 500 kg/m<SP>3</SP>on the inner pipe 2, these integrated inner pipe 2 and stainless fiber 3 are coated in the film thickness of 0.05 to 1 μm with the ceramic coating film by a chemical solution method for simultaneously soaking and drying these in precursor solutions A and B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a silencer provided in an exhaust system of an internal combustion engine for automobiles or the like.

  The exhaust gas temperature of automobiles tends to gradually increase due to engine combustion improvement for the purpose of cold start countermeasures and fuel efficiency improvement. Further, the silencer tends to be a moist environment due to internal corrosion due to exhaust gas condensate and external corrosion due to snowmelt salt sprayed on highways and the like in winter. When the temperature in the silencer is in a higher temperature environment, excellent high-temperature oxidation resistance and corrosion resistance are required for the sound-absorbing material (stainless fiber or the like), inner pipe, or welded part exposed to the high temperature side.

In response to this demand, the following prior art has been proposed.
(1) Technology for improving heat resistance by adding rare earth elements to high Al-containing ferritic stainless steel fibers for severe applications where the exhaust gas temperature is high and general-purpose stainless steel fibers cause oxidative degradation. It is disclosed in Patent Documents 1-3.
(2) Furthermore, what improved high temperature tensile strength is disclosed by patent document 4 etc.
(3) Moreover, the prior art of the ceramic coating | cover for the heat resistance modification | reformation of stainless steel and catalyst function consideration is disclosed by patent documents 5-10. Patent Literature 5 is immersion in an alumina sol containing colloidal alumina, Patent Literature 6 is immersion in a slurry such as alumina, Patent Literature 7 is application of a ceramic mixed turbid liquid, and Patent Literature 8 is a CVD method. Yes, Patent Document 9 is melt coating from particles or foil, and Patent Document 10 is immersion in silica slurry / alumina slurry.
(4) There is another method of coating a heat-resistant paint.
JP-A-4-354850 JP-A-6-172932 JP-A-6-172933 JP 2000-273588 A JP 55-94646 A JP 7-178343 A Japanese Patent Laid-Open No. 8-225956 JP-A-9-67672 Japanese Patent Laid-Open No. 10-251862 Japanese Patent Laid-Open No. 10-5603

  However, each material of the above (1) to (3) or each coated processed product of (5) to (10) is expensive and unsuitable as a part of an automobile silencer that requires low cost. Moreover, in the coating of the heat-resistant paint of (4) above, the film thickness greatly exceeds 1 μm and is usually 10 to 50 μm. Therefore, when the sound absorbing material is coated, the sound absorbing performance is remarkably deteriorated. Moreover, although the brand name Tyranno Coat manufactured by Ube Industries Co., Ltd. is commercially available as a heat resistant paint, it is expensive.

  An object of the present invention is to provide a submicron uniform ceramic coating on a sound absorbing material, an inner pipe or a welded part that is exposed to a high temperature in a silencer, easily and inexpensively, and has excellent high temperature oxidation resistance. And to get corrosion resistance. Furthermore, when the sound absorbing material is a stainless fiber, the high temperature oxidation resistance and the corrosion resistance are improved without impairing the sound absorbing performance.

  The present invention is characterized in that, in a method of manufacturing a silencer provided in an exhaust system of an internal combustion engine, a sound absorbing material fiber, an inner pipe or a welded portion of the silencer is coated with a ceramic film by a chemical solution method. The use of the internal combustion engine is not particularly limited, and examples thereof include automobiles, railway vehicles, and ships.

[Coating part: sound absorbing material fiber, inner pipe or welded part]
The material of the sound-absorbing material fiber is not particularly limited, but stainless material (stainless fiber) such as stainless steel and stainless alloy is preferable, and ferritic stainless steel (for example, SUS434) is particularly preferable. Although it does not specifically limit as a manufacturing method of a fiber, A single wire drawing method, a focused wire drawing method, a wire cutting method, a vibration vibration cutting method, a coil material cutting method etc. can be illustrated. Moreover, in the case of a stainless fiber, an average fiber diameter can illustrate 30-150 micrometers, and 80-120 micrometers is preferable. The thinner the average fiber diameter, the better the sound absorption performance, but the specific surface area increases and the high temperature oxidation resistance decreases. The bulk density is preferably 50 to 500 kg / m ^{3 in} the case of stainless steel fibers. If it is less than 50 kg / m ³ , there is almost no sound absorption performance, and if it exceeds 500 kg / m ³ , it becomes heavy.

  The inner pipe is used as an inner pipe of a sub muffler or a main muffler. The material of the inner pipe is not particularly limited, but a stainless material such as stainless steel or stainless alloy is preferable.

  Examples of the welded part include a joint part of the inner pipe itself, a welded part at a joint part between the inner pipe and the outer cylinder or the separator, and the like. Although it does not specifically limit as a weld metal of a welding part, Stainless steel, such as stainless steel and a stainless alloy, is preferable. Although it does not specifically limit as a welding method, MIG (metal-inert gas), TIG (tungsten-inert gas), MAG welding, electron beam welding, laser welding, covering arc welding, submerged arc welding, plasma arc welding, Examples thereof include resistance welding and brazing with a filler metal.

[Ceramic coating]
The film thickness of the ceramic coating (total film thickness in the case of multiple layers) is not particularly limited, but is preferably 0.05 to 1 μm, and particularly preferably 0.1 to 0.3 μm. If it exceeds 1 μm, cracks are likely to occur in the coating, and particularly when the sound absorbing material fibers are coated, the sound absorbing performance starts to deteriorate. On the other hand, when it is less than 0.05 μm, it is difficult to obtain sufficient high-temperature oxidation resistance. Therefore, it is preferable to coat a ceramic film with a film thickness of 0.05 to 1 μm on a stainless fiber as a sound absorbing material fiber having an average fiber diameter of 30 to 150 μm among the sound absorbing material fiber, the inner pipe or the welded portion.

  Although it does not specifically limit as ceramics of a ceramic film, A silica, an alumina, a zirconia, a titania etc. can be illustrated. In addition, a single layer or a plurality of layers of ceramics alone or a mixture thereof, or a plurality of layers of different ceramic materials can be used. However, silica is preferable from the viewpoint of adhesion to metal and cost, and therefore, the ceramic coating is preferably composed mainly of silica. Specifically, a single layer or a plurality of layers of a silica film by a single substance of silica or a mixture mainly containing silica, or a plurality of layers of different materials including a silica film are preferable.

  Ceramic coating using the chemical solution method is mainly performed by applying a precursor solution obtained by mixing and dissolving a metal organic compound, which is a starting material, together with an acid or water in a solution to the object to be processed, followed by heating. This is a method of forming a film by processing. This method is relatively inexpensive, and it is easy to obtain a uniform submicron coating even for complicated shapes (such as sound absorbing material fibers).

(A) In the case of a silica coating, tetraethoxysilane is preferably used as a starting material, and as a precursor solution therefor, tetraethoxysilane, acetic acid and water are mixed and dissolved in ethanol at an appropriate molar ratio and concentrated by heating. Can be exemplified.
(A) In the case of an alumina coating, it is preferable to use aluminum butoxide dissolved in ethyl acetate as a starting material. As a precursor solution therefor, aluminum butoxide, acetic acid and water are mixed and dissolved in ethanol at an appropriate molar ratio. Examples thereof are those produced by heating and concentration.
(C) In the case of a zirconia coating, it is preferable to use zirconium tetra-n-propoxide as a starting material, and as a precursor solution therefor, ethanol in an appropriate molar ratio of zirconium tetra-n-propoxide, acetylacetone and acetic acid is used. Examples thereof include those produced by mixing and dissolving in the solution and concentrating by heating.
(D) In the case of a titania coating, it is preferable to use titanium tetra-n-butoxide as a starting material, and as a precursor solution therefor, titanium tetra-n-butoxide and acetic acid are mixed and dissolved in ethanol at an appropriate molar ratio. And can be produced by heating and concentrating.

  The acid may be nitric acid, hydrochloric acid or the like in addition to acetic acid, and is not particularly limited. The alcohol may be methanol, toluene, xylene or the like in addition to ethanol, and is not particularly limited. Instead of alcohol, an oil system such as silicone oil may be used, or only water may be used. A plurality of these various alcohols, acids, oils, and water may be appropriately mixed. In addition, commercially available heat-resistant paints may be diluted in these ceramic solutions and used by mixing. The solution is not particularly limited as long as the metal organic compound is mixed and dissolved in the solution.

The following additives can also be added to the precursor solution.
(F) By adding an organic binder, it is possible to stabilize the solution for a long period of time and secure an appropriate film thickness. As the organic binder, PVB (polyvinyl butyral) is preferable because it is directly soluble in ethanol, and the addition amount is most preferably 0.5 to 1% by mass from the viewpoint of workability.
(G) Addition of a small amount of rare earth elements such as hafnium (Hf), scandium (Sc), yttrium (Y), cerium (Ce), and lanthanum (Ln) further improves oxidation resistance and adhesion. .
(H) When at least one of platinum (Pt), palladium (Pd), and rhodium (Rh) is contained, the catalyst carrier is loaded and applied to a higher temperature side to improve exhaust gas purification performance. Can contribute.
(G) By adding fine particles or fibrous materials such as partially stabilized zirconia, alumina, titania, lanthanum (La) -zirconium (Zr) -based oxide, strontium (Sr) -niobium (Nb) -based oxide, The heat shielding effect is increased, and the oxidation resistance can be improved.

  Although it does not specifically limit as a coating method of a precursor solution, The method of immersing in a precursor solution, the method of spraying a precursor solution with a spray etc. can be illustrated. 200-500 degreeC is preferable and, as for the drying temperature after application | coating, 250-350 degreeC is especially preferable. If it is lower than 200 ° C., it is insufficient for proceeding with the polycondensation reaction of hydroxyl groups in the molecules of the precursor solution (silica solution, etc.) attached, and the adhesion is inferior. If it exceeds 350 ° C., energy efficiency and productivity are increased. The cost is significantly increased.

More specifically, in a method of manufacturing a silencer provided in an exhaust system of an internal combustion engine, after stainless steel fibers as sound absorbing material fibers are wound around an inner pipe to a bulk density of 50 to 500 kg / m ³ and integrated, It is preferable that the integrated inner pipe and the stainless fiber are simultaneously coated with a ceramic film by a chemical solution method. This is because scattering, dropping, and cracking of the ceramic coating of the stainless steel fiber can be suppressed, and the inner pipe (and the welded portion (if any)) can be covered at the same time. Moreover, the adhesiveness of the stainless steel fiber wound around an inner pipe can also be improved. In addition, after coating the ceramic coating on the stainless steel fiber by the chemical solution method, it may be wound around the inner pipe, but in that case, the stainless steel fiber ceramic coating is scattered, dropped off, or cracked during winding. There is a fear.

  According to the method for manufacturing a silencer according to the present invention, a uniform submicron ceramic coating can be easily and inexpensively applied to a sound absorbing material fiber, an inner pipe, or a welded portion by a chemical solution method. High temperature oxidation resistance and corrosion resistance can be obtained.

  In addition to the above effects, excellent high temperature oxidation resistance and corrosion resistance can be obtained without impairing the sound absorption performance by coating a stainless steel fiber having an average fiber diameter of 30 to 150 μm with a ceramic film to a film thickness of 0.05 to 1 μm.

  Further, by adopting a silica coating using tetraethoxysilane as a starting material, particularly excellent high temperature oxidation resistance can be obtained.

  In addition, after winding stainless steel fiber with a predetermined bulk density around the inner pipe, the chemical solution method can be used at the same time to prevent the ceramic coating from scattering, falling off and cracking during winding, and simultaneously covering the inner pipe and welded part. In addition, a silencer having excellent high temperature oxidation resistance and corrosion resistance can be manufactured inexpensively and easily.

In a method of manufacturing a silencer provided in an exhaust system of an internal combustion engine, after stainless steel fibers having an average fiber diameter of 30 to 150 μm as sound absorbing material fibers are wound around an inner pipe to a bulk density of 50 to 500 kg / m ³ and integrated. The integrated inner pipe and stainless fiber are simultaneously coated with a ceramic film to a thickness of 0.05 to 1 μm by a chemical solution method.

  Examples in which the present invention is embodied as a sub-muffler will be described below. As shown in FIG. 2 (a), the sub-muffler 1 includes a stainless steel inner pipe 2 through which a large number of air holes are penetrated, and a ferritic stainless steel fiber as a sound absorbing material fiber wound around the outer periphery thereof. 3 and an outer tube 4 which covers the stainless fiber 3 and is welded to the inner pipe 2. The inner pipe 2 is a steel pipe with a seam formed by bending a stainless steel plate and TIG-welding a joint portion, and has a welded portion 5 in itself. The weld metal of the welded part 5 is Y430 defined in JIS Z3321. In addition, this invention can also be actualized in the inner pipe 12 of the main muffler 11, and a sound-absorbing material fiber (not shown) as shown in FIG.2 (b).

[Example 1] As shown in FIG. 1A, a stainless fiber 3 made of SUS434 cut to an average fiber diameter of 80 μm is wound around an inner pipe 2 made of SUS410 at a bulk density of 400 kg / m ³ to be integrated. After that, the integrated inner pipe 2 and stainless fiber 3 are immersed in the precursor solution A as shown in FIG. 1 (b) and shaken lightly, as shown in FIG. 1 (c). 9 and dried at 250 ° C. for 20 minutes. The precursor solution A was prepared by adding a 0.5 mass% PVB ethanol solution to a solution obtained by mixing tetraethoxysilane, acetic acid and water in a molar ratio of 1: 3: 4, and using a hot stirrer to a temperature of 80 ° C. And heated to 0.5 mol / liter. After drying, an appropriate amount of stainless steel fiber was taken out from the inner pipe and used as the test fiber of Example 1. In addition, the stainless steel fiber was pulled out and the inner pipe was processed into a specified size to obtain the test pipe of Example 1.

[Example 2] For the inner pipe and stainless steel fiber integrated in the same manner as in Example 1, the same steps from dipping to drying as in Example 1 were repeated twice, and after the second drying, an appropriate amount of stainless steel was removed from the inner pipe. The fiber was taken out and used as a test fiber of Example 2. Further, the stainless steel fiber was pulled out and the inner pipe was processed into a specified size to obtain a test pipe of Example 2.

[Example 3] The inner pipe and stainless fiber integrated in the same manner as in Example 1 were immersed in the precursor solution B, shaken lightly, and dried at 250 ° C for 20 minutes. The precursor solution B was prepared by adding a 1% by mass PVB ethanol solution to a solution in which tetraethoxysilane, acetic acid and water were mixed at a molar ratio of 1: 3: 2, and using a hot stirrer at a temperature of 80 ° C. It was prepared by heating to 5 mol / liter. After drying, an appropriate amount of stainless steel fiber was taken out from the inner pipe and used as the test fiber of Example 3. In addition, the stainless steel fiber was pulled out and the inner pipe was processed into a specified size to obtain a test pipe of Example 3.

[Example 4] For the same inner pipe and stainless fiber as in Example 1, the same steps from immersion to drying as in Example 3 were repeated twice, and after the second drying, an appropriate amount of stainless fiber was taken out from the inner pipe. Thus, the test fiber of Example 4 was obtained. In addition, the stainless steel fiber was pulled out and the inner pipe was processed into a specified size to obtain a test pipe of Example 4.

[Comparative Example 1] About the inner pipe and stainless steel fiber integrated in the same manner as in Example 1, an appropriate stainless steel fiber was taken out from the inner pipe without coating with ceramics, and used as a test fiber of Comparative Example 1. Moreover, the inner pipe which is not coated with ceramics was processed into a specified size to obtain a test pipe of Comparative Example 1.

[Comparative Example 2] Stainless steel fibers made of SUS434 cut to an average fiber diameter of 120 μm were wound around an inner pipe made of SUS410 at a bulk density of 400 kg / m ³ , and then integrated without being covered with ceramics. Appropriate stainless steel fibers were taken out and used as test fibers of Comparative Example 2.

[Test 1] High-temperature oxidation resistance test 10.00 g of each test fiber of Examples 1 to 4 and Comparative Examples 1 and 2 was placed in a heat-resistant crucible, and the high-temperature oxidation resistance was measured and compared in an electric furnace. The results are shown in Table 1. As heating conditions, heating was performed at 800 ° C. for 20 hours, and then cooling for 4 hours was set as one cycle, and repeated 17 cycles. As is apparent from Table 1, the test fibers of Examples 1 to 4 according to the present invention all have a reduced oxidation gain and exhibit excellent high-temperature oxidation resistance. On the other hand, the test fiber of Comparative Example 1 having the same diameter and not coated with ceramics generates about three times the amount of oxidation. In addition, the test fibers of Examples 1 to 4 are similar to Comparative Example 2 of 120 μm that is not coated with ceramics, although the average fiber diameter is 80 μm, and high temperature oxidation resistance per specific surface area. It is excellent.

[Test 2] Corrosion Resistance Test Corrosion resistance was measured and compared for the test fibers of Examples 1 to 4 and Comparative Example 1 by the JASO (Automobile Technical Society) M611-92 automotive muffler internal corrosion test method. The results are shown in Table 2. The test conditions were full impregnation by Method A (semi-immersion test), the liquid was changed every 24 hours, and the test time was 168 hrs at 80 ° C. As is apparent from Table 2, the test fibers of Examples 1 to 4 according to the present invention all have reduced corrosion weight loss and are excellent in corrosion resistance. On the other hand, the test fibers of Comparative Examples 1 and 2 that are not coated with ceramics are corroded 2 to 5 times.

[Test 3] Sound absorption test Disk-shaped test pieces (bulk density 400 g / m ³ , thickness 10 mm) defined in JIS-A-1405 from the test fibers of Examples 1 to 4 and Comparative Examples 1 and 2 The sound absorption coefficient at each frequency was measured and compared according to the normal incident sound absorption coefficient measurement method by the in-tube method. The results are shown in Table 3. As is apparent from Table 3, all of the test fibers of Examples 1 to 4 according to the present invention have excellent sound absorption performance without being accompanied by a decrease in normal incident sound absorption coefficient. In addition, when the film thickness is sufficiently thick, the fiber diameter of the stainless fiber becomes remarkably large, and the sound absorption performance is deteriorated.

[Test 4] Pipe Corrosion Resistance Test With respect to the test pipes having the welded parts 5 of Examples 1 to 4 and Comparative Example 1, the corrosion resistance was measured and compared by the JASO M611-92 automotive muffler internal corrosion test method. The results are shown in Table 4. The test conditions were a semi-immersion test in a semi-sealed Erlenmeyer flask with a cooling water circulation function, and carried out at 80 ° C. for 500 hours. The size was post-processed with a thickness of 1 mm, an outer diameter of φ50 mm to an arc of 25 mm, and a length of 300 mm to 100 mm. As is clear from Table 4, each of the test pipes of Examples 1 to 4 according to the present invention has a reduced corrosion weight loss and exhibits excellent corrosion resistance. On the other hand, the test pipe of Comparative Example 1 not coated with ceramics has a corrosion weight loss of 5 to 10 times and a corrosion hole depth of 3 times or more.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

The manufacturing method of the sub muffler of the Example which concerns on this invention is shown, (a) is a perspective view at the time of winding of a sound-absorbing material fiber, (b) is the schematic at the time of immersion in a precursor solution, (c) is dry It is the schematic of time. (A) is sectional drawing of the sub-muffler, (b) is a front view of another example main muffler.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sub muffler 2 Inner pipe 3 Stainless steel fiber 4 Outer pipe 5 Welded part 9 Drying furnace 11 Main muffler 12 Inner pipe A Precursor solution B Precursor solution

Claims (4)

  A method for manufacturing a silencer, comprising: a method of manufacturing a silencer provided in an exhaust system of an internal combustion engine, wherein a sound absorbing material fiber, an inner pipe, or a welded portion of the silencer is coated with a ceramic film by a chemical solution method.   The method for producing a silencer according to claim 1, wherein the sound absorbing material fibers are stainless steel fibers having an average fiber diameter of 30 to 150 µm, and at least the sound absorbing material fibers are coated with the ceramic coating to a thickness of 0.05 to 1 µm.   The method for producing a silencer according to claim 1 or 2, wherein the ceramic coating is composed mainly of silica, and a starting material used in the chemical solution method is tetraethoxysilane. In a method of manufacturing a silencer provided in an exhaust system of an internal combustion engine, stainless steel fibers as sound absorbing material fibers are wound around an inner pipe and integrated to a bulk density of 50 to 500 kg / m ³ , and then the integrated inner pipe And a method for producing a silencer, wherein a stainless steel fiber is simultaneously coated with a ceramic film by a chemical solution method.

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