FR2878898A1 - Exhaust gas purification filter for vehicle, has catalyst supported by partitions of body, where body`s heat capacity, which is product of body`s apparent density and ratio related to body`s specific heat capacity, is set to certain value - Google Patents

Abstract

The filter has a body (20) with cells (10) having partitions (2) with porous structure, and sealing units (3) at upstream and downstream ends of respective exhaust and introduction passages. An exhaust gas purifying catalyst is supported by the partitions, where body`s heat capacity, which is a product of body`s apparent density and a ratio related to body`s specific heat capacity, is set to a value lower than 400 kilojoules per Kelvin. An independent claim is also included for a method of manufacturing an exhaust gas purification filter.

Description

EXHAUST GAS PURIFICATION FILTER AND METHOD OF MANUFACTURING THE SAME

THIS 5

  The present invention relates to an exhaust gas purification filter for intercepting and retaining particulate matter such as fine carbon particles contained in exhaust gases emitted as a result of internal combustion, for example in a diesel engine.

  There are exhaust gas cleaning systems for retaining particulate matter such as fine carbon particles contained in exhaust gases from a diesel engine due to internal combustion. In a typical system, a diesel oxide catalyst (DOC) and a diesel particulate filter (DPF) are combined in an exhaust gas system in the form of a two-stage system. The DOC is generally mounted in the immediate vicinity of a diesel engine and the FPD is mounted in a position after the DOC at the downstream end of the exhaust system.

  In such a two stage exhaust gas purification system, the catalyst present in the COD purifies, that is to say oxide or reduces the main substances such as hydrocarbons (HC) and carbon monoxide ( CO) contained in the diesel engine exhaust gas, then the FPD intercepts the particulate matter contained in the exhaust gas. The particulate matter intercepted is burned and disposed of.

  Japanese Patent Publication No. JP-2001-961,213, open to public inspection, has presented one of the FPD systems according to the prior art.

  Since the prior art scrubbing system consists of a combination of DOC and FPD, the system according to the prior art has certain disadvantages, namely that it requires a complex structure, that its manufacturing cost It is accentuated and the complication of the structure limits the degree of freedom for the arrangement of the exhaust gas cleaning system mounted in vehicles.

  There is a strong demand to develop an improved and excellent exhaust cleaning system with a simple configuration in which only a diesel particulate filter (DPF) is present, with a low manufacturing cost. To achieve this goal, it was also necessary to make an exhaust gas purification filter constituting the heart of the exhaust gas purification system.

  The present invention has been developed in view of these disadvantages of the prior art described above. The object of the present invention is to provide a simple configuration exhaust gas purification filter comprising only a diesel particulate filter (DPF) with improved and excellent cleaning function.

  According to one aspect of the present invention, an exhaust gas purifying filter purifies exhaust gases containing particulate matter discharged as a result of internal combustion. The exhaust gas purification filter has a body composed of a plurality of cells or cells disposed in a networked structure and shutter elements. Each cell has a rectangular shape constituted by peripheral partitions with a porous structure and extending along an axis of the body. The cells are divided into introduction passages for the introduction of the exhaust gas and exhaust passages discharging the exhaust gas. The closure members are formed at an upstream end of each exhaust passage and at a downstream end of each introducing passage. A catalyst for purifying the exhaust gas is supported by the cell partitions. In the exhaust gas purification filter according to the present invention, the heat capacity Q of the body is set at a value of not more than 400 (kJ / m3 E K), where Q = Cp X p, Cp (kJ / kg É K) is a ratio corresponding to the specific heat of the body, and p is the apparent density of the body.

  Advantageously, the filter according to the invention has one or more of the following characteristics: the thermal capacity of the body is established at a value no greater than 325 (kJ / m 3 K); the thermal conductivity K of the body is established at a value of not greater than 1.0 (W / m, K); the catalyst consists of an oxidation catalyst or a nitrogen oxides (NOx) catalyst, or both by the oxidation catalyst and the nitrogen oxide (NOx) catalyst; the density of the catalyst supported in a front portion of the body to a desired length measured from an upstream end surface of the body on the axis of the body is greater than the density of the supported catalyst in the rest of the body; the length of the front part of the body is not more than 40 mm; the catalyst is supported by surfaces of the structural partitions; - porous surrounding and facing only introductory passages: the catalyst is ceramic mainly composed of cordierite; - the exhaust gas cleaning filter is a single, tight-coupled system intended to be mounted at a location very close to the location of internal combustion; the exhaust gas cleaning filter is disposed at a distance of not more than 1000 mm measured from a position of a turbocharger to an upstream end surface of the exhaust gas cleaning filter when the turbocharger is associated with internal combustion; one or more exhaust gas and differential pressure temperature sensors are mounted in the exhaust gas cleaning filter.

  The invention also relates to a method of manufacturing an exhaust gas purification filter having a plurality of cells composed of introduction passages and exhaust passages adjacent to each other, through structural bulkheads. porous.

  Alternatively, the method may be characterized by comprising the steps of: - extrusion molding with raw materials to form a honeycomb structural body; dry and cook the body with honeycomb structure; inserting closure members into a first end surface of the body in a checker pattern to seal the exhaust passages in the body entry portion; pouring a slurry of alumina containing alumina on a first end surface of the body comprising the closure elements; - to dry and cook the body; - immerse the body in a slurry to apply a catalyst on the porous structure partitions; dipping a first end surface of the body, wherein the sealing members are formed, in a highly concentrated slurry, to a predetermined depth L to form a thick catalyst layer on the partitions; - to dry and cook the body; and - inserting the closure members into the other end surface of the body in a checker pattern to seal the introducer passages in the exit portion of the body.

  The invention will be better understood on studying the detailed description of an embodiment taken by way of nonlimiting example and illustrated by the appended drawings, in which: FIG. 1 is a schematic view of an end surface of an exhaust gas cleaning filter according to a first embodiment of the present invention; FIG. 2 is a longitudinal sectional view of the exhaust gas purification filter taken along the line A-A of FIG. 1; FIG. 3 is a schematic view showing a catalyst applied to a septum with a porous structure in cells of the exhaust purification filter according to the first embodiment; FIG. 4 is a schematic view of a single closely coupled or close coupling exhaust gas purification system having an exhaust gas cleaning filter according to the first embodiment; FIG. 5 is a flowchart illustrating a manufacturing process of the exhaust gas cleaning filter according to the first embodiment; FIG. 6A is a perspective view showing an arrangement of closure elements at one end of a body of the exhaust gas cleaning filter according to the first embodiment; FIG. 6B is a bottom view of the exhaust purification filter according to the first embodiment; FIG. 7 is a perspective view showing a supply of a slurry of alumina for the exhaust gas purification filter body according to the first embodiment; FIG. 8 is a view showing an alumina layer formed on a porous structure wall surface in each cell of the exhaust gas cleaning filter according to the first embodiment; FIG. 9 is a view illustrating an immersion operation of the body in a slurry to support a catalyst of the exhaust gas cleaning filter according to the first embodiment; FIG. 10 is a view showing the catalyst supported on the surface of the porous structure partition in cells of the exhaust purification filter according to the first embodiment; FIG. 11 is a flowchart showing a process for manufacturing the exhaust gas cleaning filter according to the second embodiment; FIG. 12 is a view showing a body dip operation in a slurry to support a catalyst during the manufacturing process of the exhaust gas purification filter according to the second embodiment; FIG. 13 is a perspective view showing a front end of the exhaust gas cleaning filter according to the second embodiment; FIG. 14 illustrates a relationship between a catalyst support rate at a front end portion in a body and an HC emission rate according to a first experimental result; FIG. 15 illustrates a relationship between a heat capacity and a different body scrubbing rate according to a second experimental result; FIG. 16 is a schematic view showing the structure of a single close coupled exhaust gas purification system comprising the exhaust gas cleaning filter according to a third embodiment of the present invention; FIG. 17 shows an experimental result indicating a relationship between the temperature in an electrically heated furnace and the heat capacity of each individual body when a crack occurs in each individual body; and FIG. 18 shows an experimental result indicating a relationship between a pressure loss and a length L of a catalyst layer with a high concentration in each individual body.

  In the following description of various embodiments of the present invention, the same characters or numerals refer to all the different views of identical or equivalent elements.

  First Embodiment Referring to FIGS. 1 to 10, a feature of an exhaust gas purifying filter according to the first embodiment of the present invention will now be described.

  Fig. 1 is a schematic view of an end surface of the exhaust gas cleaning filter according to the first embodiment of the present invention. Fig. 2 is a longitudinal sectional view of the exhaust gas purification filter taken along the line A-A of FIG. 1.

  As shown in FIGS. 1 and 2, the exhaust gas purification filter 1 has a body 20 in which a plurality of cells 10 are formed in the axial direction of the body 20. The cells 10 are surrounded and formed by partitions 2 with a porous structure. The cells are divided into introduction passages 11 through which the exhaust gases 9 are introduced into the filter 1 and into the exhaust passages 12 through which the exhaust gases 9 passing through the partitions 2 of the porous structure are rejected to the outside of the filter 1. In the body 20, closure elements 3 are formed at the downstream end of the introduction passages 11 and are also formed at the upstream end of the exhaust passages 12 for sealing first ends of the cells 10.

  Fig. 3 is a schematic view showing a catalyst 5 applied to the partitions 2 of the cells 10. As shown in FIG. 3, the catalyst 5 is applied to the surface of the partitions 2. The catalyst 5 purifies the exhaust gases 9.

  In the first embodiment, the heat capacity Q (kJ / m3 K) of the body 20, defined by the equation Cp X p is set to a value of about 400 or less, Cp (kJ / kg K) being a ratio corresponding to the specific heat of the body 20, and p being the apparent density of the body 20, K being Kelvin.

  As shown in FIG. 1 and FIG. 2, the body 20 in the exhaust gas cleaning filter 1 according to the first embodiment comprises a plurality of cells, each of which has a rectangular shape, to form a honeycomb shaped honeycomb structural body. cylindrical outer. The body 20 with a honeycomb structure is made of ceramic mainly composed of cordierite. The introduction passages 11 and the exhaust passages 12 forming the cells 10 are arranged alternately in the body 20 in a patterned network structure or a honeycomb structure, so that the introduction passages 11 and the passageways exhaust 12 are adjacent to each other. The closure elements 3 are formed at the downstream end of the introduction passages 11 and at the upstream end of the exhaust passages 12. If both the upstream end and the downstream end of the body 20 are observed, it can be seen that the sealing elements 3 are arranged in a checker pattern.

  Moreover, as shown in FIG. 3, the catalyst 5 is applied to the surface of the partitions 2 in the body 20. The catalyst 5 is supported by an alumina coating layer 29 on the surface of the partitions 2. In the first embodiment, the uniform catalyst layer 5 is applied approximately to all the surfaces of porous structure partitions 2, and platinum (Pt) is used as the oxidation catalyst. According to the description of the first to third embodiments according to the present invention, although the catalyst consists of both the oxidation catalyst and the nitrogen oxides (NOx) catalyst, it is possible, of course, to design the catalyst using a single catalyst, namely the oxidation catalyst or the nitrogen oxide (NOx) catalyst.

  The thermal capacity Q of the body 20 is set to a low value, namely of the order of 400 (kJ / m 3 / K) or less, depending on the requirements formulated, and the thermal conductivity K of the body 20 is set to a value of of the order of 1.0 (W / m K) or less. The heat capacity Q and the thermal conductivity K of the body 20 are controlled by adjusting the dimensions of the body 20 and adopting an optimal porosity of the body 20. The optimum porosity can be obtained by adjusting the quantities of raw materials for forming the body 20 .

  The heat capacity Q of the body is globally modified according to the apparent density, namely the mass of the body. Thanks to the present invention, the mass of the body is proportional to the porosity of the body. If the body has a low porosity value, the body mass is large. On the other hand, if the porosity of the body is strong, the mass of the body becomes weak. Cordierite, which is the main constituent of a ceramic is composed of raw materials such as kaolin, talc, aluminum hydroxide, fused silica and alumina. However, the porosity of the body is controlled only in percentages of 30 to 50% by modifying the proportions of the raw materials combined above. To further increase the porosity of the body, it is necessary to add organic materials such as graphite and a resin. Thanks to the present invention, the porosity of the body is adjusted according to the proportions of the combined raw materials which are the cordierite forming the ceramic and the organic materials, for example graphite and resin. The dimensions of the body are constant, each body having for example 300 cells, and the thickness of the wall being 0.3 mm (12 mils).

  Porosity is defined as the proportion of bubbles in the volume of the partitions 2. The increase in porosity implies an increase in the number of bubbles in the partitions 2, it is illustrated by the white circles (see Fig. 3).

  The porosity of the body is known according to the following equation: Porosity (%) = A / (A + B) X 100, where A denotes the total volume of the bubbles in the partitions 2, and B denotes the total volume of the partitions 2.

  Fig. 4 is a schematic view showing a single, tightly coupled exhaust gas purification system which is integrated in the exhaust gas cleaning filter 1 according to the first embodiment. As shown in FIG. 4, the exhaust gas cleaning filter 1 according to the first embodiment is used as the only tight coupling system mounted somewhere in the exhaust gas circuit in the immediate vicinity of a diesel engine 7. In a Concrete example, the exhaust gas cleaning filter 1 according to the first embodiment is mounted at a location close to a turbocharger (T / C) 75 in the exhaust gas circuit 70 for the diesel engine 7 .

  The manufacturing process of the exhaust gas cleaning filter 1 according to the first embodiment will now be described.

  Fig. 5 is a flowchart illustrating the manufacturing process of the exhaust gas cleaning filter 1 according to the first embodiment. Fig. 6A is a perspective view showing an arrangement of the shutter members 3 at one end of the body 20 of the exhaust gas cleaning filter 1 according to the first embodiment. Fig. 6B is a bottom view of the exhaust gas cleaning filter 1.

  To begin, extrusion molding is performed with raw materials to form a honeycomb structural body 20 (S100). Drying and baking are then performed to form the honeycomb structural body (S110).

  Then, the shutter members 3 are sunk into a first end surface 201 of the body 20 (S120). As shown in FIG. 6A and FIG. 6B, the closure members are arranged in a checker pattern on a first end surface 201, and another end surface 202 of the body is opened, i.e. all the cells other end surface 202 of the body 20 are open.

  Then, as shown in FIG. 7, the other end surface 202 of the body 20 where no shutter member 3 is formed is placed at the bottom. A slurry 290 of alumina containing alumina is poured onto the end surface 201 of the body 20 (S130). The slurry of alumina 290 penetrates the cells 10 through the end surface 201 of the body 20 where the closure members 3 are formed. In this way, the slurry of alumina 290 is applied to the surface of the slats. partitions 2 with a porous structure.

  The body 20 whose partitions 2 are coated with the slurry of alumina 290 is then dried and cooked (S140). The slurry of alumina 290 is thus transformed into a layer of alumina coating the surface of the partitions 20.

  Following the above operation, as illustrated in FIG. 9, the body 20 is immersed in a slurry 50 from the end surface 201 of the body 20 to which the closure members 3 are formed. The body 20 is thereby immersed in the slurry 50 to apply the catalyst (S150). The body is then dried and cooked (S160). This results in the body 20 in which the catalyst 5 supported by the alumina layer 29 is applied to the surface of the partitions 2 in the body 20.

  Finally, as shown in FIG. 10, the closure members 3 are formed on the end surface 202, i.e., the end surface opposite the end surface 201 of the body 20 (S170).

  The above operations lead to the exhaust gas purification filter 1 in which the catalyst 5 is applied to or supported by the surface of the porous structure partitions 2 only opposite the introduction passages 11.

  The present invention is not limited to the above manufacturing process, and for example it is possible to change the order in which the shutter element forming operation S170 3 and the step S160 take place. In addition, it is also possible to proceed in a different manner to produce the alumina layer 29 and the catalyst support 5.

  As described above, the exhaust gas cleaning filter 1 according to the first embodiment comprises the body 20 in which the catalyst 5 is supported by the surface of the porous structure partitions 2 and the thermal capacity Q of the body 20 is established at a value of not more than 400 ((kJ / m3 E K), it is therefore possible to build and realize an excellent exhaust gas purification system comprising a single filter 1 for purifying gas from This makes it possible to reduce the structure and the manufacturing cost of the exhaust gas purification system, in particular, as illustrated in FIG 4, it is possible to reduce the total cost of manufacture of the exhaust gas purification system. exhaust gas purification by simple configuration by the use of the exhaust gas cleaning filter 1 in a single, tightly coupled system, and it is possible to have a certain freedom of arrangement of the exhaust gas cleaning system mounted in vehicles.

  The exhaust gas purification filter according to the present invention is in the form of an excellent FPD supporting the catalyst. Therefore, the exhaust gas cleaning filter of the present invention can serve both as a conventional diesel particulate filter (DPF) and a conventional diesel oxide (DOC) catalyst. With the aid of the exhaust gas purification filter according to the present invention, it is possible to design a single structure exhaust gas purification system and to increase the margin of freedom for the arrangement of the exhaust gas system. mounting in vehicles. The present invention is not limited to the above effects, and the exhaust gas purification filter can obviously be combined with another DOC or the like.

  Furthermore, the heat capacity Q of the body 20 in the exhaust gas cleaning filter 1 according to the first embodiment is set to a low value, in this case not greater than 400 ((kJ / m 3 This can cause a rapid rise in body temperature due to the heat of the exhaust gas passing through the body of the exhaust gas cleaning filter 1 and the catalyst supported by the exhaust gas filters. Partitions 2 in the body 20 can be rapidly activated, which can advantageously favor the purification function that the catalyst 5 has.

  According to the present invention, it is preferable to set the thermal capacity Q of the exhaust gas filter body at no more than 325 ((kJ / m3 E K), and it is preferable to use the limit value of 100 ((kJ / m3 K) as the minimum value of the thermal capacity Q of the exhaust gas cleaning filter body taking into account the minimum required quantity of particulate matter accumulated in the body.

  Moreover, the particulate matter contained in the exhaust gas 9 is intercepted in the partitions 2, and then burned to remove them following a regular combustion process.

  In addition, the thermal conductivity K of the body 20 of the exhaust gas cleaning filter 1 according to the first embodiment is set to 1.0 (W / m E K) or less. It is therefore preferable to establish the thermal conductivity K of the body at no more than 1.0 (W / m E K). The body temperature rises in contact with the exhaust gas. In other words, the most heated part of the body is the upstream end surface of the body. If the body has a high thermal conductivity, the heat is rapidly transmitted from the upstream end to the downstream end of the body, so that there is a delay for increasing the temperature of the upstream end portion. from the body. To avoid this problem, it is preferable to set the body's thermal conductivity to no more than 1.0 (W / m K). This configuration makes it possible to obtain a rapid increase in the temperature in the front end portion of the body, and thus the catalyst supported by the front end portion of the body can be quickly activated.

  It is therefore possible to effectively purify the exhaust gas using catalysts supported by the front end portion of the body, in contact with which come the exhaust gases.

  This can promote a rapid increase in the temperature at the upstream end of the body 20. In other words, it is therefore possible to rapidly activate the catalyst 5 supported by the partitions 2 near the upstream end of the body 20, and it is It is possible to effectively purify the exhaust gases 9 with the aid of the catalyst 5 near the upstream end of the body 20 in contact with which the introduced exhaust gases 9 initially come into contact.

  In the embodiment, since the catalyst consists of an oxidation catalyst and a nitrogen oxides (NOx) catalyst, it is therefore possible to purify hydrocarbons (HC), carbon monoxide (CO ) and nitrogen oxides (NOx) using a single filter 1 exhaust gas purification. This makes it possible to construct a single tight coupling system by using the exhaust gas cleaning filter 1 according to the first embodiment.

  In the present invention, the abbreviation "CS system" (tight coupling) means that the exhaust gas discharged by the diesel engine is scrubbed using a type of catalyst that corresponds to the gas scrubbing filter. exhaust system according to the present invention. The term "CS" means disposed in close proximity to the diesel engine.

  In the present invention, only the single exhaust purification filter is mounted in close proximity to the diesel engine. It is therefore possible to provide the exhaust gas filter at a higher temperature compared to an underfloor system (UF) in which an exhaust purification filter is mounted remote from the diesel engine. This can promote the great effect of purifying the exhaust.

  If the oxide catalyst is supported by the body, the purification can be done easily, namely by carrying out the oxidation of hydrocarbons (HC) and carbon monoxide (CO). Platinum (Pt), palladium (Pd) and the like are a concrete example of the oxide catalyst.

  In addition, if the nitric oxide catalyst is supported by the body, it is possible to easily perform the purification, in this case to achieve the reduction of nitrogen oxides (NOx). Platinum (Pt), rhodium (Rh), barium (Ba), potassium (K) and others are a concrete example of a nitrogen oxide (NOx) catalyst.

  It is especially preferable that the oxidation catalyst and the nitrogen oxides (NOx) catalyst are supported by the partitions present in the body.

  In the first embodiment, the catalyst 5 is supported by the septa 2 with a porous structure only in the introduction passages 11 of the body 20. This means that the catalyst 5 is supported by the partitions 2 of the introduction passages 11 which The first is achieved by the exhaust gas 9. This reduces the amount of catalyst compared to the prior art, and increases the capacity of the catalyst without any increase in the catalyst compared to the prior art. . Thus, the exhaust gas cleaning filter 1 according to the first embodiment can increase the capacity of the catalyst without any increase in the cost of the catalyst.

  Still further, since the body 20 of the exhaust gas cleaning filter 1 according to the embodiment is ceramic mainly composed of cordierite, which has a lower cost than silicon carbide (SiC) as the main constituent of the body in an exhaust gas purification filter according to the prior art, it is possible to lower the cost of the exhaust gas cleaning filter 1 material, and relatively easily achieve excellent cooling characteristics. thermal capacity Q and thermal conductivity K of the body 20.

  Ceramic mainly composed of cordierite is the most suitable material for producing the body of the exhaust gas cleaning filter 1 according to the present invention.

  The exhaust gas cleaning filter 1 according to the first embodiment can easily have excellent action and achieve the excellent effects described above.

  Second Embodiment With reference to Figures 11 to 13, a feature of an exhaust gas purifying filter according to the second embodiment of the present invention will now be described.

  Fig. 11 is a flowchart illustrating a process for manufacturing the exhaust gas cleaning filter according to the second embodiment. Fig. 12 illustrates a body immersion operation, which constitutes the exhaust gas cleaning filter according to the second embodiment, in the slurry which supports a catalyst.

  In the second embodiment, the dimensions of the exhaust gas cleaning filter are the same as those of the first embodiment. The amount of catalyst supported by the partitions is not the same in two stages of the body as compared to that of the first embodiment.

  To begin, as in the first embodiment, the extrusion molding is carried out using raw materials constituting a honeycomb structure body 120 (in the honeycomb) in the exhaust gas purification filter ( S200). The drying and baking are carried out so as to form the body 120 with a cellular structure (S210).

  Then, the shutter members 3 are sunk into a first end surface of the body 120 (S220). The closure elements 3 are arranged in a checkerboard combination on a first end surface and, on the other hand, the other end surface of the body 120 is open, that is to say that all the cells 110 in the other end surface of the body 120 are open.

  Then, the other end surface of the body 120, where the shutter elements 3 are formed, is placed at the bottom. A slurry of alumina containing alumina is poured onto the end surface of the body 120 (S230).

  The slurry of alumina penetrates into the cells 110 through the end surface of the body 120 where the closure members 3 are formed. In this way, the slurry of alumina is applied to the surface of the structural bulkheads. porous.

  The body 120 whose partitions are coated with the slurry of alumina is then dried and cooked (S240). As a result, the slurry of alumina is transformed into a layer of alumina applied to the surface of the partitions.

  The body 120 is then immersed in the slurry 50 to apply the catalyst 5 to the porous structure partitions (S250).

  The second embodiment is such that the amount of catalyst supported by the bulkheads of the body 120 to a depth L is slightly less than that of the first embodiment.

  After the above operation, the body 120 is immersed in a slurry 51 from the front end surface (or upstream end) of the body 120 on which the closure members 3 (S260) are formed. The concentration of the slurry 51 is greater than that of the slurry 50 used in the manufacturing process according to the first embodiment.

  Fig. 13 is a perspective view showing the front end portion of the exhaust gas cleaning filter according to the second embodiment. In FIG. 13, the TL mark denotes the total length of the body 120 and L denotes the front end portion of the body 120. As shown in FIG. 13, the immersion depth L of the upstream end surface in the slurry 51 is set to an approximate value L of 40 mm, measured from the front surface of the body 120.

  The body 120 having the partitions on which the catalyst is supported by the slurry of alumina is then dried and fired (S270).

  Finally, the closure members 3 are formed in the other end surface which constitutes the end surface opposite the first end surface of the body 120 (S280).

  As shown in FIG. 13, the density of the catalyst formed in the L-shaped front portion of 40 mm in the body 120 is larger than that of the remainder of the body 120.

  The present invention is not limited to the above order of operations, it is for example possible to perform the step S280 for fixing the closure elements to the other end surface of the body 120 before the step S270.

  In the exhaust gas purification filter according to the second embodiment, as the high density catalyst is supported by the 40 mm L-front portion in the body 120 where the exhaust gas heat 9 is driven first, most of the catalyst present in the body 120 is reacted or is activated quickly and effectively in the front part at a distance L of 40 mm by the heat of the exhaust gas 9.

  In addition to the above condition, it is also permissible that the total amount of catalyst supported by the body is the same as that on the body not having the above catalyst configuration. This can allow an effective reaction of the catalyst for the exhaust gas 9.

  It is furthermore preferable to set the distance L measured from the front end surface of the body to 40 mm or less.

  In a standard exhaust gas cleaning filter, the rapid temperature increase occurs in the front end portion at a distance of 40 mm in the body. Thus, when the front end portion of the body comprises the highly concentrated catalyst, that is, has the greatest density to support the catalyst, it is possible to obtain a rapid effect of the catalyst. Since the total amount of catalyst in the body is the same as in the prior art, i.e., it is substantially unaltered, and since the catalyst generally has a high cost, it is possible to form the exhaust gas cleaning filter without increasing the cost.

  In addition, it is preferable that the catalyst is supported on the surface of the porous structure partitions, which are opposite the introduction passages.

  Thus, the catalyst is supported only by the surface of the partitions situated opposite the introduction passages, which are easily reached by the introduced exhaust gases, and it is not supported by the partitions facing the exhaust passages. . This improves the function of the catalyst without any increase in the cost of the catalyst material. It is also preferable to combine the above configuration of the introduction passages with the catalyst support density characteristic discussed above.

  In the second embodiment, the length of the front end portion of the body having the highly concentrated catalyst is set to an L value of 40 mm.

  Fig. 18 illustrates the relationship between the pressure loss and the length L (mm) of the high concentration catalyst layer in the body. The experimental result presented in FIG. 18 indicates that the length L should be set at 40 mm or less in order to obtain a pressure loss of 1.5 or less from the body, because if the pressure loss is greater than 1.5, the power of the engine becomes low and fuel consumption of the engine is reduced. The length L (mm), shown in FIG. 13, of the highly concentrated catalyst layer in the body is also set to reduce the amount of catalyst since the catalyst is an expensive raw material. Thus, the length L (mm) is determined both from the pressure loss and from the cost of the catalyst material.

  The other effects of the second embodiment are identical to those of the first embodiment.

  First experiment The first experiment was conducted using 4 types of bodies, each having substantially the same configuration as the body 120 of the exhaust gas cleaning filter according to the second embodiment. The first experiment consisted in measuring the purification function of each body having a different rate between the length L of the front part and the length TL - L of the rest of the body.

  The bodies examined have various catalyst carrier A / B levels of 1.0, 1.5, 2.0 and 2.5, the resulting ratio of A / B or A is the catalyst supported density of the catalyst. front end L and B denotes the density of the catalyst supported by the rest (TL-L) of the body. The rate is established in the first experiment so that each body contains the same total amount of catalyst.

  The experiment consisted in measuring a quantity of hydrocarbons (HC) released in the exhaust gases emitted by each body, in accordance with the EU standard of test modality (EU-MODE) for emission controls. Specifically, HC emissions (g / km) were measured under conditions corresponding to a 195-second cycle of ECE or a city driving cycle of NEDC 2000 in EU-MODE.

  Fig. 14 is a result of the first experiment illustrating a relationship between the catalyst support A / B ratio of each body and a quantity of HC rejection. In FIG. 14, the horizontal axis indicates the catalyst support A / B ratio of each body and the vertical axis indicates the HC rejection rate. Each HC release rate is a relative value with respect to the HC emission rate of 1.0 when the catalyst support ratio is 1.0.

  As clearly illustrated in FIG. 14, the higher the catalyst support rate, the lower the HC rejection in the catalyst support rate range of 1.0 to 2.5. This means that the body with the largest catalyst support A / B ratio can increase its purification capacity.

  It is especially preferable to set the catalyst support A / B ratio to not less than 1.5. Thus, supporting the largest amount of catalyst on the front end portion of the body provides the improved cleaning effect.

  Second experiment The second experiment was conducted using ten types of bodies, each of which has a thermal capacity Q different from that of the others, but has substantially the same configuration as that of the body 120 of the exhaust gas cleaning filter according to the second embodiment. The ten bodies used during the second experiment had the same catalyst support A / B ratio, namely 2.0. Table 1 below provided details of the bodies used during the second experiment.

Table 1

  Porosity Heat Capacity Conductivity HC EU Thermal Thermal MODE, ECE / Volume Rate Sample Purification Density N Material (%) p (g / cm3) Cp (kJ / kgEK) (kJ / m3K) K (W / mEk) ( g / km) per cycle (%) 1 Cordierite 60 0.37 0.84 311 0.42 0.041 42.0 2 Cordierite 65 0.32 0.84 272 0.42 0.037 50.0 3 Cordierite 70 0.28 0 , 84 233 0.42 0.034 58.0 4 Cordierite 75 0.23 0.84 194 0.42 0.030 66.0 Cordierite 80 0.18 0.84 155 0, 42 0.027 74.0 6 Cordierite 85 0.14 0 , 84 117 0.42 0.023 82.0 7 SiC 49 0, 53 0.79 422 42 0.057 5.8 8 SiC 48 0.54 0.79 428 42 0.058 4.0 9 SiC 58 0, 44 0, 79 348 42 0.047 28.1 SiC 60 0.42 0.79 334 42 0.045 32.4 In the second embodiment, the purification rate was obtained in the form of the evaluation of the purification function or the Exhaust gas cleaning capacity according to EU-MODE, as for the first experiment.

  Specifically, the rate (%) of HC treatment was obtained under the conditions of a cycle (lasting 195 seconds) of ECE (ie a city driving cycle) in NEDC 2000 of EU -FASHION.

  Fig. 15 shows the result of the experiment, namely the relation between the heat capacity Q and the rate (%) of purification of HC by the exhaust gas purification filter.

  As is clear from FIG. 15, the lower the heat capacity Q, the greater the rate (%) of purification of HC. In particular, under conditions of thermal capacity Q (kJ / m3K) of not more than 400, it is possible to achieve the excellent improved purification effect. Under conditions of thermal capacity Q (kJ / m3K) no greater than 325, the rate (%) of purification not less than 20 can be obtained.

  In addition, as is clear from Table 1, in particular, the relationship between heat capacity Q and HC indicates that the lower the heat capacity, the better the HC scrubbing rate.

  Fig. 17 shows a thermal shock resistance experiment result of an exhaust gas cleaning filter body. In FIG. 17, the vertical axis indicates a temperature difference between the temperature set in the electric heating oven and the ambient temperature of 20 C, the horizontal axis indicates a thermal capacity Q of each sample body. During the experiment, the individual sample bodies were held for two hours at various temperatures in an electric heating oven, then removed from the electric heating oven and maintained at an ambient temperature of 20% C to verify the appearance of cracks in each individual body tested. Each point appearing in FIG. 17 indicates the difference between the temperature set in the electric furnace and the ambient temperature of 20 C when a crack appears in each body.

  The experimental result illustrated in FIG. 17 clearly indicates that the body has a high resistance to thermal shock if the thermal capacity Q of the body is not greater than 400 (kJ / m3 K), the body having in particular excellent resistance to thermal shock if the thermal capacity Q is not greater than 350 (kJ / m3 E K).

  Moreover, the thermal conductivity K is determined according to the dimensions of each individual body. Thus, the greater the length of the body, the lower the thermal conductivity of the body, since the physical properties of cordierite constituting the main material of the ceramic are the same in all the individual bodies tested. In the experiments according to the present invention, the thermal conductivity of each body becomes 1.0 (W / mk) if the length of each body is set to 50 mm.

  Third Embodiment Referring to FIG. 16, there will now be described a detailed feature of a single CS system utilizing the exhaust purification filter according to the third embodiment of the present invention.

  Fig. 16 is a schematic view showing the structure of a single CS exhaust gas cleaning system according to the third embodiment, comprising the exhaust gas cleaning filter 1 according to the first embodiment.

  In FIG. 16 representing the unique CS system according to the third embodiment, the marker 71 designates a common rail 71 placed in a diesel engine 7, the marker 72 designates an exhaust gas recirculation valve ERG and the marker 73 designates a ERG cooler. The ERG 72 valve and the ERG 73 cooler are used for exhaust gas recirculation. A charge air cooler 61 for cooling the inlet air is mounted on an inlet system 60 at the upstream end of the diesel engine 7.

  As illustrated in FIG. 16, an exhaust pipe 74 is mounted on the exhaust system 70 located at the downstream end of the diesel engine 7. A turbocharger (T / C) 75 is mounted at the junction of the exhaust pipe 74 and the engine 7. A single exhaust gas cleaning filter 1 according to the present invention is mounted on the exhaust pipe 74. The distance from the turbocharger 75 to the upstream end surface 101 of the gas cleaning filter 1 exhaust is 700 mm. This distance indicates the longitudinal distance Ld of the central geometric axis of the exhaust system 70 indicated by a dashed line in FIG. 16.

  Furthermore, exhaust gas temperature sensors 76 and a differential pressure sensor 77 are integrated in the exhaust gas cleaning filter 1. The exhaust gas temperature sensors 76 measure the temperature of the exhaust gases before and after the exhaust gas cleaning filter 1. The differential pressure sensor 77 measures an exhaust gas pressure difference before and after the exhaust gas cleaning filter 1.

  In the single CS system having the above configuration of the embodiment illustrated in FIG. 16, as the filter 1 of exhaust gas purification is mounted in the immediate vicinity of the diesel engine 7, it is possible to introduce the exhaust gas at a higher temperature in the filter 1 gas cleaning exhaust system compared to an underfloor system (UF) in which the exhaust gas cleaning filter is located far from the location of the diesel engine. This effectively achieves oxidation and / or reduction of the particulate matter intercepted by the catalyst, and then the particulate matter is burned for removal. In addition, it is possible to effectively remove various particulates such as hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx).

  In the third embodiment, the distance from the turbocharger (T / C) 75 to the upstream end surface 101 of the exhaust gas cleaning filter 1 is 700 mm, i.e. its distance is set to a value of the order of 1000 mm maximum. This ensures that the higher temperature exhaust gases pass through the exhaust gas cleaning filter.

  Therefore, it is possible to further improve the purification effect of the exhaust gas discharged by the diesel engine 7 compared to the effect of the prior art in which the distance to it is greater than 1000 mm.

  In general, the higher the temperature of the exhaust gas passing through the exhaust gas cleaning filter 1, the greater the resistance of the body of the filter 1 to the heat must be increased. To solve this problem, the exhaust gas cleaning filter 1 comprises means for increasing the heat capacity Q of the body 20.

  In addition, the exhaust gas cleaning filter 1 according to the third embodiment is equipped with both the exhaust gas temperature sensors 76 and the differential pressure sensor 77. These sensors 76 and 77 measure the temperatures of the exhaust gas passing through the filter 1 and the differential pressure between the inlet end and the outlet end of the exhaust gas cleaning filter 1. From the measured values, it is possible to predict the temperature inside the exhaust gas cleaning filter 1 and the amount of particulate matter accumulated in the partitions of the filter 1, and it is therefore possible to regulate the combustion of the accumulated particulates under optimum conditions preventing the occurrence of melting losses and the cracking of the exhaust gas cleaning filter. This regulation can prevent any occurrence of melting losses and any cracking of the exhaust gas cleaning filter.

Claims (1)

  An exhaust gas cleaning filter (1) that purifies exhaust gases containing particulate matter discharged from internal combustion, the exhaust gas cleaning filter (1) including a body ( 20) composed of several cells (10) arranged in a network structure, and closure elements (3), each cell having a rectangular shape constituted by peripheral partitions (2) with a porous structure, extending along an axis of the body (20), the cells being divided into introduction passages (11) for introducing the exhaust gases and exhaust passages discharging the exhaust gases, the closure elements (3) being formed at an upstream end of each exhaust passage (12) and at a downstream end of each introducing passage (11), and a catalyst (5) for purifying the exhaust gases being supported by the partitions (2) cells (10), characterized in that that the heat capacity Q of the body (20) is set to a value of not more than 400 (kJ / m3 E K), where Q = CpXp, Cp (kJ / kgE K) is a ratio corresponding to the specific heat of the body (20) and p is the apparent density of the body (20).   Exhaust gas cleaning filter (1) according to claim 1, characterized in that the heat capacity of the body (20) is set at no more than 325 (kJ / m3 K).   An exhaust gas cleaning filter (1) according to claim 1 or claim 2, characterized in that the thermal conductivity K of the body (20) is set to no greater than 1.0 (W / m É K).   Exhaust gas cleaning filter (1) according to one of Claims 1, 2 and 3, characterized in that the catalyst (1) consists of an oxidation catalyst or an oxide catalyst. nitrogen (NOx), or both the oxidation catalyst and the nitrogen oxides (NOx) catalyst.   Exhaust gas cleaning filter (1) according to one of Claims 1 to 4, characterized in that the density of the catalyst (5) supported in a front part of the body (20) to a desired length measured from an upstream end surface of the body (20) on the axis of the body (20) is greater than the density of the catalyst (5) supported in the rest of the body (20).   6. Filter (1) for purifying exhaust gas according to claim 5, characterized in that the length of the front portion of the body (20) is set to a value no greater than 40 mm.   Exhaust gas cleaning filter (1) according to one of Claims 1 to 6, characterized in that the catalyst (5) is supported by surfaces of the porous structure surrounding walls (2) and look only at introductory passages (11).   8. Filter (1) for exhaust gas purification   according to any one of claims 1 to 7,   characterized in that the catalyst (5) is ceramic mainly composed of cordierite.   Exhaust gas cleaning filter (1) according to one of Claims 1 to 8, characterized in that the exhaust gas cleaning filter (1) is a single close-coupled system for to be mounted at a location very close to the location of the internal combustion.   Exhaust filter (1) according to Claim 9, characterized in that the exhaust gas cleaning filter (1) is arranged at a distance of not more than 1000 mm measured from a position a turbocharger to an upstream end surface of the exhaust gas cleaning filter (1) when the turbocharger is associated with the internal combustion.   An exhaust gas cleaning filter (1) according to one of claims 1 to 10, characterized in that one or more exhaust gas temperature and differential pressure sensor (76,77) are mounted in the filter (1) of exhaust gas purification.   A method of manufacturing an exhaust gas cleaning filter (1) having a plurality of cells (10) composed of introducing passages (11) and exhaust passages (12) adjacent to one another, through partitions (2) with a porous structure, the method being characterized in that it comprises the steps of: extrusion molding with raw materials to form a honeycomb-shaped body (20); drying and baking the body (20) with honeycomb structure; inserting shutter members (3) into a first end surface of the body (20), in a checkerboard combination, to seal the exhaust passages (12) in the body inlet portion (20) ; pouring a slurry of alumina containing alumina onto a first end surface of the body (20) having the closure members (3); drying and baking the body (20); immersing the body (20) from the first end surface of the body (2) provided with the closure members (3) in a slurry to apply a catalyst (5) to the porous structure partitions (2); drying and baking the body (20); and inserting closure members (3) into the other end surface of the body (20) in a checker pattern to seal the introduction passages (11) in the body exit portion (20) .   13. A method of manufacturing an exhaust gas cleaning filter (1) comprising a plurality of cells (10) composed of introduction passages (11) and exhaust passages (12) adjacent to each other at through partitions (2) of a porous structure, the method characterized by comprising the steps of: extrusion molding with raw materials to form a honeycomb-shaped body (20); drying and baking the body (20) with honeycomb structure; inserting closure members (3) into a first end surface of the body (20) in a checker pattern to seal the exhaust passages (12) in the body inlet portion (20); pouring a slurry of alumina containing alumina onto a first end surface of the body (20) having the closure members (3); drying and baking the body (20); immersing the body (20) in a slurry to apply a catalyst (5) to the porous structure partitions (2); dipping a first end surface of the body (20), in which the closure elements (3) are formed, in a very concentrated thick suspension, to a predetermined depth L to form a thick catalyst layer on the partitions ( 2); drying and baking the body (20); and inserting the closure members (3) into the other end surface of the body (20) in a checker pattern to seal the introduction passages (11) in the body exit portion (20). .