JP2007511699A - Exhaust converter for internal combustion engine - Google Patents

Abstract

  A housing (13) comprising at least one inlet opening (14) for the exhaust to be converted and at least one outlet opening (15) for the converted gas and comprising the conversion system (11) In an internal combustion engine exhaust converter (10), the conversion system comprises a plurality of panels (12) made of fibers (30), the fibers being oxide layers carrying catalytically active metal (33). (32) having a metal core (31) covered by the plurality of panels, wherein the plurality of panels have one of their substantially parallel edges facing the inlet opening and the other facing the outlet opening. And is held at intervals by metal spacers (41, 41 ′; 51, 51 ′; 62; 70).

Description

  The present invention relates to an internal combustion engine converter, and more particularly to an apparatus that can be used to oxidize the exhaust of an internal combustion engine.

  The exhaust of internal combustion engines contains gases that are not completely oxidized, such as carbon monoxide and unburned hydrocarbons, and these gases are a source of environmental pollution. At present, it is required to adopt such a system for reducing exhaust gas such as a converter provided downstream of an internal combustion engine for completely oxidizing the unburned gas.

US Pat. No. 5,294,411 International Patent Publication No. WO97 / 02092

  U.S. Pat. No. 5,294,411 discloses an exhaust treatment apparatus having a honeycomb structure wound spirally. The structure has a continuous surface activated by a catalyst on a ceramic or metal support. Exhaust gas flows along a straight path in a number of passages formed in parallel by the structure and parallel to the flow direction. There are essentially two problems with this type of device. First, the total surface area corresponding to the unfolded state of the spiral in contact with the gas is not very large, and the ratio of the geometric surface area to apply the catalyst to the volume of the device is not advantageous. Second, due to the straight shape of the passage, the gas flow through the structure is mainly laminar and the catalyst cannot be utilized optimally.

  An exhaust treatment device disclosed in International Patent Publication No. WO 97/02092 comprises a perforated metal plate or metal mesh coated with a porous ceramic layer, preferably made of aluminum or zirconia, which is a catalyst precursor solution or suspension. It is formed by immersing in. However, even in this example, the catalyst surface that can be used is not so wide, and therefore the conversion efficiency is limited. Accordingly, an object of the present invention is to provide an exhaust converter that does not have the above-mentioned drawbacks.

  The object is in an exhaust gas converter of an internal combustion engine comprising at least one inlet opening for the exhaust to be converted and at least one outlet opening for the converted gas and comprising a housing containing the conversion system The conversion system comprises a plurality of panels of fibers, the fibers comprising a metal core coated with an oxide layer carrying a catalytically active metal, wherein the plurality of panels are substantially each other. By a converter characterized in that one of the parallel edges is arranged to face the inlet opening and the other is faced to the outlet opening and is held at a distance by a metal spacer Achieved.

  The metal panel of the present invention functions by a catalyst, and has a contact area much higher than a known perforated metal plate or metal net. Furthermore, in the configuration of the present invention comprising a plurality of panels and a plurality of spacers, turbulence occurs in the converter and the gas passes at least partially through the panels while flowing from the inlet to the outlet. . This feature significantly improves the contact between the gas flow and the catalyst and significantly improves the conversion efficiency, in particular the oxidation efficiency, of the converter according to the invention.

  The advantages and features of the converter according to the invention will become apparent to the person skilled in the art from several non-limiting embodiments described below with reference to the accompanying drawings.

  FIG. 1 is an exploded view of a converter 10 of the present invention having a conversion system 11 having a plurality of panels 12. The converter 10, as is well known, includes a housing 13 having at least one inlet opening 14 for the exhaust to be processed from the internal combustion engine and an outlet opening 15 for the gas processed by the system 11. It has. The panel is preferably surrounded by a metal member 16 (not shown in FIG. 1). The metal member forms a frame that is secured to the edge of the panel by suitable means, such as by mechanical crimping. This frame holds the panel 12 flat during thermal cycling (heat treatment to oxidize and functionalize the panel and thermal cycling downstream of the internal combustion engine) and fiber loss at the panel side edges. To prevent. The converter 10 may include a flange (not shown) at the peripheral edge of the outlet 15.

  In accordance with the present invention, the system 11 comprises a plurality of panels 12 spaced apart by a metal spacer with a desired distance. Good results have been obtained when this distance is in the range of about 1 to about 4 mm. If this distance is less than 1 mm, the panel fills too much and the pressure drop becomes too high. On the other hand, if the distance is too large, the number of the assembly panels 12 and the catalyst surface involved in gas treatment are reduced, and if the distance between the panels is too large, the effect of generating turbulence in the airflow is reduced. However, there is a drawback that at least a part of the gas traversing the system 11 passes without contacting the catalyst provided in the panel 12. The optimum value of the distance between adjacent panels is about 2 mm to 3 mm.

  FIG. 2 shows a preferred embodiment of the panel 12 for use in the system of the present invention. The panel includes a metal member 16 surrounding the periphery and a metal fiber mat formed by bonding to each other by sintering. The metal fibers are made of steel, preferably an alloy known as heat-resistant stainless steel (fecralloy, a trademark registered by the British Atomic Energy Agency, Didcot, UK) which contains iron, chromium and aluminum in addition to trace amounts of other components. This alloy is particularly suitable for long-term use at high temperatures, such as use for catalytic converters or filters in internal combustion engines. Panels formed from heat-resistant stainless steel (fecralloy) fibers are manufactured by N.E., Zevegem, Belgium. V. Commercially available from N.V. Bekaert SA under the trade name Bekipor, these panels can be formed in different shapes and can be adapted for different uses.

  FIG. 3 shows a cross-section of the fibers used to form panel 12 (fiber portions are not shown in the correct proportions). The drawing shows a fiber with a rectangular cross-section, like the most typical heat-resistant stainless steel (fecralloy) fiber, but it will be appreciated that the fiber may have other cross-sectional shapes, such as a circular cross-section. . The fiber 30 includes a heat-resistant stainless steel core 31 covered with an oxide layer 32, and a catalyst 33 is supported on the oxide layer. The oxide layer generally comprises a multilayer structure of two or three layers that differ in terms of chemical composition or physical properties. The first oxide layer 32 'is grown and formed on the surface of heat-resistant stainless steel (fecralloy) fiber by high-temperature treatment in an oxidizing atmosphere. The oxide layer formed by this treatment comprises aluminum oxide whiskers with a length of about 0.5-5 μm, preferably less than 3 μm, depending on the treatment time and treatment temperature. The oxides forming the whiskers are generally very dense and uniform. The next step is to form a second oxide layer 32 ″ on the first oxide layer. Unlike the first oxide layer, the second oxide layer 32 ″ is porous and has a high specific surface area. This oxide layer consists of aluminum oxide or other oxides. The second oxide layer can be formed by spraying a solution of the precursor component of the oxide onto the sintered and matted metal fibers, or by immersing the mat in the same solution and then pyrolyzing the precursor. Can be formed. Alternatively, the second oxide layer can be obtained by immersing the mat in a suspension of precursor particles and then firing. If necessary, a third oxide layer 32 ′ ″ is formed on the second oxide layer. This layer also has a high specific surface area. The optionally provided layer 32 '' 'is generally composed of a mixed oxide of cerium and zirconium (lanthanum may be added if necessary) and thus has the property of limiting the sintering of the catalytic metal. This ensures long-term catalytic metal dispersion and maintains high converter efficiency and oxygen storage efficiency for oxidizing unburned gas from the internal combustion engine.

  The porous structure of the outer oxide layer (32 ″ or 32 ′ ″) optimally supports the catalyst metal, ensures dispersion of the catalyst metal, and adheres well to the fiber surface. In order to use the fiber panel, it is necessary to functionalize the oxide layer with the catalyst 33. The catalyst is preferably one or more noble metals or compounds thereof selected from group 8 of the periodic table, preferably using platinum.

  FIG. 4 is a partially exploded view of a first optimal embodiment of the system 11. In this embodiment, the system 11 is a stack in which panels 12 and metal plates 40 are alternately stacked (only two panels and one metal plate are shown. Metal member 16 is not shown). The plate has a plurality of bulging portions 41, 41 ′,... Protruding from both surfaces of the metal plate. These bulges are all formed at the same height, and provide a plurality of contact points on which two panels 12 (one on one side of the metal plate 40) are placed. ing. The metal plate 40 is also formed of a high heat resistant metal, preferably the same heat resistant stainless steel used to manufacture the fibers of the panel 12. The metal plate is generally formed as thin as is compatible with the required mechanical resistance at high temperature, and the optimum thickness is 0.15 to 0.45 mm.

  FIG. 5 is a view similar to FIG. 4 showing a slightly different embodiment of the system 11. In this example, the metal plate 50 (similar to the metal plate 40) has a plurality of holes 52, 52 ′,. This configuration enhances gas turbulence as the gas flows across the system 11. Although a circular hole is shown in FIG. 5, other shapes may be used as necessary. In the system 11 comprising the metal plate 50, the plurality of holes are preferably less than 50% of the surface area of the metal plate so that structural problems do not occur in the metal plate when the system 11 operates at high temperatures. .

  More preferably, the bulging portion and the hole are provided at the same position. FIG. 6 is an example of this embodiment. In this example, the metal plate 60 has a plurality of openings 61. The opening is formed by partially cutting the metal plate, forming a “wing portion” 62 connected to the metal plate along the side edge, and bending the wing portion along the side edge. The The distance between the surface of the metal plate 60 and the adjacent panel 12 is determined by the dimensions of the wing portion and the bending angle with respect to the plane of the metal plate, and these wing portions constitute spacers. Although a rectangular wing (and opening) is shown in FIG. 6, it will be appreciated that other suitable shapes may be used. Cutting for forming the wing portion can be performed by mechanical shearing, laser cutting, or other known methods.

  A system 11 of the kind described above is preferably inserted into a metal casing that surrounds all sides except the inlet and outlet sides of the system, which casing is then inserted into the housing 13. A plate member made of ceramic fibers is preferably disposed between the metal casing and the housing 13 for heat insulation.

  FIG. 7 shows a panel 12 that can be used for yet another embodiment of the system 11 of the present invention. For purposes of clarity, this figure shows the panel assembly with a reduced number of spacers. In this example, the spacer 70 (unlike the metal plates 40, 50, 60) has a geometric area that is much smaller than the geometric area of the panel 12, and the contact points for adjacent panels are curved. It is a metal plate wound in a roll shape so as to be smooth. The spacer 70 is held in a correct position by being fixed to the metal tape 71 (for example, by spot welding). The metal tape 71 has a necessary and sufficient mechanical strength and is formed as thin as possible to provide an area where the spacer 70 can be fixed. Next, the metal tape 71 is held in a correct position by being fixed to a member such as the two metal members 16 (for example, by spot welding). The metal member 16 is fixed to two side edges of the panel 12 parallel to each other (shown by arrows, in the direction of gas flow in the converter 10) by caulking. The other two metal members 16 (one facing the inlet 14 of the converter 10 and the other facing the outlet 15) can be joined to the panel prior to the thermal oxidation treatment of the fibers. The two metal members 16 provided on the side edges are preferably attached to the panel 12 at the final stage of manufacture in order to prevent oxidation and ensure good welding properties to the metal tape 71. The other spacer 70 is provided on the other side surface of the panel 12 although not shown. The spacer is preferably placed in the same position on all panels of the conversion system. Thereby, when a plurality of panels are stacked, the spacer forms a kind of support column that increases the strength of the entire structure.

  FIG. 8 is an exploded view of the preferred assembly of the system 11 when using the spacer 70. For purposes of clarity, the spacer 70 is not shown. In this example, in order to ensure the mechanical stability of the system, it is preferable to insert two side retaining members 80, 80 'in the form of a light fret in the panel. The panel 12 can be fixed to the members 80 and 80 ′ by mechanically caulking the lightning-shaped portion to the metal member 16 on the side edge that supports the metal tape 71. The assembly consisting of the panel and the holding member is then inserted into the metal casing 81. The metal casing surrounds four sides parallel to the gas flow in the assembly, but the inlet and outlet sides are open. In this configuration, a passage 82 is formed, and the gas passes through the passage to bypass the system 11 and reaches the outlet 15 untreated. In order to avoid this, the passage 82 is filled with a high temperature heat resistant adhesive (not shown). This adhesive usually contains metal powder (for example, steel powder) mixed in an inorganic binder. A suitable adhesive is Duraco 954, commercially available from Cotronics, Brooklyn, New York. The assembly is completed by joining two frames 83, 83 ′ to the rear surface and the front surface. This ensures that there is no passage for the gas from the internal combustion engine to bypass the system 11. The frames 83, 83 ′ are bonded to the front and rear metal members 16, the holding members 80, 80 ′, and, if necessary, the casing 81 by bonding.

  The converter according to the invention is arranged by providing a panel made of metal fibers, in particular in a position as close as possible to the internal combustion engine, ie ensuring that the converter operates at the highest temperature and obtains a high conversion efficiency. It is particularly suitable for configurations that are known in the art as “CC (Close-Coupled) Catalysts or CCCs. Because of the metal structure, the converter of the present invention is a near-reducing contaminant that flows from an internal combustion engine. The drastic temperature changes that can occur in the system of time are allowed, especially in the case of diesel engines, the so-called “post-injection” phase, in which fuel is injected into the cylinder during the exhaust stroke (the exhaust valve is open), is important. Does not explode in the cylinder, reaches the CCC converter without burning, and is catalytically oxidized by the high temperature of the converter. Thus, the gas becomes hot and is exhausted from C.C.C, allowing the particles stored in a suitable filter (known in the art as a “diesel particulate filter or DPF”) to burn. As a result, the DPF can be regenerated. An example of a DPF is described in Italian Patent Application No. MI2003A002211 by the same applicant as the present application.

Another important advantage of the conversion system of the present invention is that compared to prior art hydrocarbon conversion systems of the same volume (and having approximately the same amount of catalytic metal and essentially the same conversion efficiency): The carrier weight is small. The inventors prepared different types of converters of the present invention and measured their weight and volume, resulting in a system weight of 0.28 g / cm ³ , and in prior art systems 1 cm ³ It was found that the weight per hit was 0.62 g. In addition to the low total weight (although already an advantage), the thermal inertia is low and the system of the present invention reaches the high temperature at which the catalyst works optimally more quickly, reducing the problem of "cold start". And has an important advantage.

It is an exploded view of the converter of this invention. It is a perspective view of the panel which consists of metal fiber used by this invention. It is sectional drawing of the fiber which forms the panel of FIG. It is a detailed view of the conversion system of the present invention. It is a detailed view of the conversion system of the present invention. It is a detailed view of the conversion system of the present invention. It is a detailed view of the conversion system of the present invention. FIG. 2 shows a preferred conversion system according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Converter 11 Conversion system 12 Panel 13 Housing 14 Inlet opening 15 Outlet opening 16 Metal member 30 Fiber 31 Metal core 32 Oxide layer 32 '1st layer 32''2nd layer 32''' 3rd layer 33 Catalyst 41 Metal spacer 41 'Metal spacer 51 Metal spacer 51' Metal spacer 62 Metal spacer 70 Metal spacer

Claims (15)

In an exhaust converter (10) of an internal combustion engine,
A housing (13) comprising at least one inlet opening (14) for the exhaust to be converted and at least one outlet opening (15) for the converted gas and comprising the conversion system (11) Equipped,
The conversion system comprises a plurality of panels (12) comprising fibers (30), the fibers being covered by an oxide layer (32) carrying a catalytically active metal (33). The plurality of panels are arranged such that one of the substantially parallel edges faces the inlet opening and the other faces the outlet opening, and the metal spacer (41 , 41 ′; 51, 51 ′; 62; 70).   The core (31) of the fiber (30) is made of an alloy containing iron, chrome and aluminum and is covered by a multilayer structure (32) made of oxide, the multilayer structure being in contact with the alloy A first layer (32 ') and a second oxide layer (32' ') made of aluminum oxide, and a third layer (32) made of cerium, zirconium and, optionally, lanthanum oxide The converter according to claim 1, including '' ') as necessary.   The converter according to claim 2, wherein the multilayer structure (32) is coated with one or more catalysts (33) selected from Group 8 noble metals of the periodic table or compounds thereof.   The converter of claim 3, wherein the catalyst is platinum.   The converter according to claim 1, wherein the conversion system (11) is formed from a plurality of panels (12) surrounded by a metal member (16).   The converter according to claim 1, wherein the distance between two adjacent panels (12) of the conversion system (11) is 1 to 4 mm.   The converter according to claim 1, wherein the distance between two adjacent panels (12) of the conversion system (11) is 2 to 3 mm.   The conversion system (11) is formed by alternately stacking panels (12) and metal plates (40), and a plurality of bulging portions (41, 41 ′) are provided on both side surfaces of the metal plates. The converter according to claim 1.   The conversion system (11) is formed by alternately stacking panels (12) and metal plates (50), and a plurality of bulging portions (51, 51 ') are provided on both side surfaces of the metal plate. The converter according to claim 1, wherein a plurality of holes (52, 52 ′) through which gas to be converted can flow from one side surface to the other side surface of the metal plate are formed.   The bulging portion and the hole are arranged at the same position, and are formed by cutting the metal plate (60), whereby the wing portion (62) connected to the metal plate along at least one side edge. The converter according to claim 9, wherein the hole (61) is opened by bending the wing portion along the side edge.   The conversion system (11) comprises a stack comprising a plurality of panels (12) held at a predetermined distance by spacers (70) comprising a metal plate, wherein the metal plate is less than the geometric area of the panel. 6. The converter according to claim 5, wherein the converter has a small geometric area and is wound in a roll shape so that a contact point with respect to an adjacent panel is curved and smooth.   The spacer (70) is held in a correct position by being fixed to a metal tape (71), and the metal tape is fixed in a correct position by being fixed to two of the metal members (16) surrounding the panel. The converter according to claim 11, which is held in   The converter according to claim 12, wherein the two metal members (16) are arranged on a side edge parallel to a flow of gas flowing in the converter at a side edge of the panel. The side edges of the panel parallel to the flow of gas flowing through the converter are held by two side holding members (80, 80 ') of a light fret (Greek fret),
An assembly composed of the panel (12) and the holding member (80, 80 ') is inserted into a metal casing (81), and the metal casing is adapted to flow a gas flowing through the converter in the assembly. Surrounds four parallel sides, but the inlet and outlet sides are open,
The passage (82) between the holding member (80, 80 ') and the casing (81) is filled with a high temperature heat resistant adhesive,
Two frames (83, 83 ′) are joined to the front and rear metal members (16) of the panel (12), the holding members (80, 80 ′), and optionally the casing (81). The converter according to claim 13.   The conversion system (11) is inserted into the casing (81) and then disposed in the housing (13) of the converter (10), and a ceramic plate is inserted between the casing and the housing. The converter according to any one of claims 1 to 14.

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