JP2013215659A - Catalytic converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalytic converter which can effectively solve such problems that a temperature distribution is generated by a flow of an exhaust gas from a gas inflow end toward a gas outflow end in a substrate constituting a catalytic converter, the temperature distribution causes differences among temperature stresses generated in respective parts of the substrate, and a crack is more likely to be generated in the substrate due to the differences among the temperature stresses.SOLUTION: A catalytic converter 10 includes at least: a substrate 1 including a hollow space 1a through which a gas flows, and having a length L between a gas inflow end from which the gas flows into the hollow space 1a, and a gas outflow end through which the gas flows out from the hollow space; and a catalyst 4 stored inside the substrate 1. In the catalytic converter, a surface pressure of 0.8-1.2 MPa is exerted on an inflow side range between 0.04 L and 0.06 L from the gas inflow end in the substrate 1, and a surface pressure of 0.3-0.6 MPa is exerted on a center range between 0.2 L and 0.25 L toward both a gas inflow end side and a gas outflow end side from 0.5 L that is the center of the substrate.

Description

  The present invention relates to a catalytic converter that is housed and fixed in a pipe constituting an exhaust gas exhaust system.

  Various industries are making various efforts to reduce environmental impact on a global scale. Among them, in the automobile industry, not only gasoline engine cars with excellent fuel efficiency, but also hybrid cars and electric cars. The development of the so-called eco-cars such as the above and the further improvement of its performance is being promoted every day.

  Incidentally, a catalytic converter for purifying exhaust gas is generally disposed in an exhaust system for exhaust gas that connects the vehicle engine and the muffler.

Engines may emit environmentally harmful substances such as CO, NOx, unburned HC, and VOCs, and are coated with a metal catalyst such as palladium or platinum to convert these harmful substances into acceptable substances. By passing exhaust gas through a catalytic converter in which a ceramic structure is placed in a hollow substrate, CO is converted to CO ₂ , NOx is converted to N ₂ and O ₂ , and VOC is burned CO ₂ and H ₂ O will be produced.

  By the way, in the base material which comprises a catalytic converter, it is common that temperature distribution arises by the waste gas flow which goes to the gas outflow end from the gas inflow end. For example, the temperature distribution in the base material is not constant during an actual durability test or when mounted on an actual vehicle, and the front side (Fr side, exhaust gas inflow side) of the base material is more than the rear side (Rr side, exhaust gas outflow side). There is a bias (distribution) in temperature, for example, the temperature is high, and the temperature outside the center of the substrate is low.

  As described above, the temperature distribution (thermal stress) generated in the base material due to the temperature distribution in the base material varies from site to site, and the temperature stress varies from time to time. Thus, if the temperature stress generated for each part of the substrate is different, cracks are likely to occur in the substrate due to the difference in temperature stress.

  Here, Patent Document 1 discloses a cell structure storage container and its assembly in which the variation of the compression surface pressure with respect to the cell structure in the metal container is small and the surface pressure distribution is made uniform to prevent the cell structure from being damaged. Is disclosed. Specifically, it is a cell structure storage container in which the cell structure is stored in a metal container, and a compression elastic material having heat resistance and cushioning properties is arranged in a compressed state between the outer periphery of the cell structure and the metal container. The compression elastic material is a heat resistant low thermal expansion material containing ceramic fibers or ceramic fibers and heat resistant metal fibers, and greatly increases or decreases within the practical temperature range. Therefore, the compressive force acting on the outer peripheral portion of the cell structure does not fluctuate greatly and acts substantially uniformly on the entire outer peripheral portion of the cell structure.

  Even if a configuration in which a compressive force (or surface pressure) is applied substantially uniformly to the entire outer periphery of the base material constituting the catalytic converter based on the technical idea disclosed in Patent Document 1, as described above, In the base material constituting the catalytic converter, a temperature distribution is generated by the exhaust gas flow from the gas inflow end to the gas outflow end, and therefore, the temperature stress generated for each part of the base material is different. Even if uniform surface pressure is applied, the temperature stress cannot be effectively reduced, and it is difficult to suppress the occurrence of cracks.

JP 2001-280124 A

  The present invention has been made in view of the above-described problems, and a temperature distribution is generated by the exhaust gas flow from the gas inflow end toward the gas outflow end in the base material constituting the catalytic converter. It is an object of the present invention to provide a catalytic converter capable of effectively solving the problem that the temperature stress generated in the substrate is different and cracks are likely to occur in the substrate due to the difference in the temperature stress.

  In order to achieve the above object, a catalytic converter according to the present invention has a hollow in which a gas flows, and a base having a length L from a gas inflow end where gas flows into the hollow to a gas outflow end where gas flows out from the hollow And a catalyst housed in the base material, and a surface of 0.8 to 1.2 MPa in the inflow side range from 0.04 L to 0.06 L from the gas inflow end in the base material. Pressure is applied, and a surface pressure of 0.3 to 0.6 MPa is applied in the central range between 0.5 L to 0.25 L from 0.5 L, which is the center of the base material, to the gas inflow end side and the gas outflow end side, respectively. Is.

  The present inventors specify the temperature distribution generated in the hollow base material constituting the catalytic converter through CAE analysis, specify the temperature stress resulting from this temperature distribution, and the threshold value of the temperature stress that can be generated on the surface of the base material And a desired surface pressure is applied to an appropriate position of the base material so that the temperature stress that differs depending on the part of the base material is smaller than this threshold value.

  As a result of the analysis, in the base material having a length L from the gas inflow end to the gas outflow end, a surface pressure of 0.8 to 1.2 MPa is applied in the inflow side range from 0.04 L to 0.06 L from the gas inflow end. By using a catalytic converter to which a surface pressure of 0.3 to 0.6 MPa is applied in the center range between 0.2 L to 0.25 L from the center 0.5 L to the gas inflow end side and the gas outflow end side, respectively. The temperature stress that can occur in the entire range of the substrate can be made less than the specified threshold value, and the occurrence of cracks that can occur in the substrate can be effectively suppressed. For example, in a base material having a length L of 100 mm, a surface pressure in the range of 0.8 to 1.2 MPa is applied in a range between 4 mm and 6 mm from the inflow end, and 20 mm to the gas inflow side from the center 50 mm of the base material. In the range of 25 mm and the range of 20 mm to 25 mm to the gas outflow side (that is, the range of 25 mm to 75 mm from the gas inflow end), a surface pressure of 0.3 to 0.6 MPa is applied.

  Further, in the outflow side range in the vicinity of the gas outflow end in the base material, the same surface pressure may be applied in the same range as the inflow side range, or a range different from the inflow side range (for example, Further, a relatively low surface pressure of about 0.5 MPa may be applied in an extremely short range of about 0.02 L from the outflow end. The reason is that in the outflow side range of the base material, the temperature of the circulating gas is relatively lower than that of the inflow side range, and therefore the surface pressure and the surface pressure application range that can be applied can be made smaller than the inflow side range.

  Here, the base material used is preferably a ceramic material base material capable of supporting a high-power battery, but excludes the use of materials other than ceramic materials such as metal materials. is not. In addition, even when a ceramic material base material is applied, the occurrence of cracks due to the concerned temperature stress is suppressed by applying this to the catalytic converter of the present invention.

  In addition, a honeycomb catalyst or the like can be applied to the catalyst used, and this catalyst has a large number of square or hexagonal lattice contours made of conductive metal such as silicon carbide or stainless steel metal, and alumina or zirconia is contained in each lattice. In addition, catalytic metals such as platinum, palladium, and rhodium are dispersed and supported in a matrix carrier containing ceria as a main component, and a vent hole through which exhaust gas passes is formed in the center of the lattice.

  As a form for applying a desired surface pressure to an appropriate position of the base material, an annular body is disposed at least on the outer periphery of the inflow side range and the outer periphery of the central range of the base material, and between the annular body and the base material. There is a form in which a spacer is fitted (canned) to generate the surface pressure.

  Here, the spacer has rigidity and elasticity capable of imparting a surface pressure enough to reduce the temperature stress on the ceramic base material during canning, for example, than the base material. The thing of a ceramic material with low rigidity and the thing of a metal material whose rigidity is lower than a base material are mentioned. In this manner, by arranging the spacers at appropriate positions, a desired surface pressure can be applied to the appropriate positions of the base material, and in addition, the temperature decrease of the base material can be suppressed by this heat retention effect.

  By adjusting the thickness of the spacer or changing the material of the spacer, the surface pressure generated when the spacer is canned between the annular body and the substrate can be changed as desired. Moreover, changing the material and thickness of the spacer also leads to changing the weight of the spacer, and it can be said that the change in the weight of the spacer contributes to the change in the surface pressure.

  Further, as another form of applying a desired surface pressure to an appropriate position of the base material, the base material is accommodated in a pipe line constituting an exhaust system for exhaust gas, and at least an outer periphery of the inflow side range of the base material and the pipe line The surface pressure may be generated by inserting a spacer between the outer periphery of the central region and between the outer periphery of the central region and the pipe line.

  In this embodiment, a base material is arranged in a pipe line constituting an exhaust gas exhaust system, and a surface pressure is generated when a spacer is canned between the pipe line and the base material.

  Moreover, the form with which the cyclic | annular heat insulating material is arrange | positioned in the range in which a spacer does not exist among the outer periphery of a base material is preferable.

  Unlike the spacer that applies a surface pressure to the base material, this heat insulating material is intended only to suppress a temperature drop in a region where there is no spacer on the surface of the base material. By arranging the heat insulating material in the region without the spacer, it is possible to suppress the temperature decrease of the entire range of the base material together with the spacer, and the temperature decrease region is partially generated in the surface of the base material. This can also be suppressed.

  Furthermore, in another embodiment of the catalytic converter according to the present invention, the base material has conductivity, and an electrode for energizing the base material is arranged in a range where the spacer does not exist in the outer periphery of the base material. It is provided and constitutes an electrically heated catalyst.

  In addition to purifying the exhaust gas at normal temperature, the exhaust system that connects the vehicle engine and the muffler is equipped with an electrically heated catalytic converter that activates the catalyst by electric heating in the cold to purify the exhaust gas. Sometimes. This electric heating type catalytic converter, for example, attaches a pair of electrodes to a honeycomb catalyst and heats the honeycomb catalyst by energizing the electrodes, thereby increasing the activity of the honeycomb catalyst and detoxifying the exhaust gas passing therethrough. It can be referred to as an electrically heated catalytic converter (EHC).

  Since the electrically heated catalytic converter (EHC) has a current heating function, the flow of electricity (heat generation distribution) changes when a crack occurs during an endurance test or when mounted on an actual vehicle. Therefore, by applying the catalytic converter of the present invention as an electric heating type catalytic converter, it is possible to control the temperature stress that is different for each part of the base material to a temperature stress that does not cause cracks, and guarantees the initial heat generation distribution. can do.

  As can be understood from the above description, according to the catalytic converter of the present invention, in the base material having a length L from the gas inflow end to the gas outflow end, the inflow side between 0.04L and 0.06L from the gas inflow end. A surface pressure of 0.8 to 1.2 MPa is applied in the range, and a surface of 0.3 to 0.6 MPa in the central range between 0.5 L, which is the center of the base material, and 0.2 L to 0.25 L from the gas inflow end side to the gas outflow end side, respectively. By using a catalytic converter to which pressure is applied, the temperature stress that can occur in the entire range of the base material can be made less than the specified threshold value, thereby effectively suppressing the occurrence of cracks that can occur in the base material. Can do.

It is the schematic diagram explaining the exhaust system of the exhaust gas which the catalytic converter of this invention interposes. It is the schematic diagram explaining Embodiment 1 of the catalytic converter of this invention. It is the III-III arrow line view of FIG. It is the schematic diagram explaining Embodiment 2 of the catalytic converter of this invention. It is the schematic diagram explaining Embodiment 3 of the catalytic converter of this invention. It is the schematic diagram explaining Embodiment 4 of the catalytic converter of this invention. It is a VII-VII arrow line view of FIG. It is a figure which shows the engine pattern (time history graph of engine speed) of a real machine engine. It is a figure which shows the time history graph of the temperature in the center level of the base material of a catalytic converter. It is a schematic diagram which shows that the base material analysis model (1/4 model of a cylindrical base material) and surface pressure are given to the catalytic converter. FIG. 10 shows the time history of the temperature at each temperature measurement point shown in FIG. 10 and the time history of the temperature difference between the outer peripheral surface and the inner peripheral surface of the base material in defining the threshold value of the temperature stress generated in the base material. It is. It is a figure which shows a temperature stress analysis result, Comprising: It is the figure which specified the stress (threshold of a temperature stress) from which the temperature stress becomes the minimum in the base-material surface. It is a figure which shows the temperature stress analysis result at the time of changing the surface pressure provided to the base-material surface. It is a figure which shows the temperature stress analysis result at the time of fixing a surface pressure to 0.2 MPa and changing the width | variety (width from the center to the gas inflow end side) of the center range to 15 mm, 20 mm, and 25 mm. It is a figure which shows the temperature stress analysis result at the time of fixing a surface pressure to 0.3 MPa and changing the width | variety (width | variety from a center to the gas inflow end side) of a center range to 15 mm, 20 mm, and 25 mm. It is a figure which shows the temperature stress analysis result at the time of fixing a surface pressure to 0.4 MPa and changing the width | variety of the center range (width from the center to the gas inflow end side) to 15 mm, 20 mm, and 25 mm. It is a figure which shows the temperature stress analysis result at the time of changing surface pressure to 0.5MPa and changing the width | variety of the center range (width | variety to the gas inflow end side) from 15mm, 20mm, and 25mm. It is a figure which shows the temperature stress analysis result when fixing a surface pressure to 0.6 MPa and changing the width | variety of the center range (width | variety from the center to the gas inflow end side) to 15 mm, 20 mm, and 25 mm. It is a figure which shows the temperature stress analysis result at the time of fixing the width | variety of the spacer from a gas inflow end to 2 mm, and changing surface pressure into 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 MPa. It is a figure which shows the temperature stress analysis result at the time of fixing the width | variety of the spacer from a gas inflow end to 4 mm, and changing surface pressure into 0.6, 0.8, 1.0, and 1.2 MPa. It is a figure which shows the temperature stress analysis result at the time of fixing the width | variety of the spacer from a gas inflow end to 6 mm, and changing surface pressure into 0.6, 0.8, 1.0, and 1.2 MPa. When the width of the center range (width from the center to the gas inflow end side) is 25 mm and the surface pressure of the center range is 0.4 MPa, the surface pressure applied to the inflow side range with the spacer width of 6 mm from the gas inflow end is It is a figure which shows the temperature stress analysis result at the time of changing to 0.4, 0.6, and 0.8 MPa. When the width of the center range (width from the center to the gas inflow end side) is 25 mm and the surface pressure of the center range is 0.6 MPa, the surface pressure applied to the inflow side range with the spacer width of 6 mm from the gas inflow end It is a figure which shows the temperature stress analysis result at the time of changing to 0.4, 0.6, and 0.8 MPa. It is the figure which showed the time history of the temperature on the base-material surface with and without a spacer.

  Hereinafter, embodiments of the catalytic converter of the present invention will be described with reference to the drawings.

(Exhaust gas exhaust system)
FIG. 1 is a schematic view illustrating an exhaust gas exhaust system in which the catalytic converter of the present invention is interposed.

The exhaust gas exhaust system shown in the figure includes an engine 20, a catalytic converter 10, a three-way catalytic converter 30, a sub muffler 40, and a main muffler 50, which are connected to each other through a system pipe 60. The exhaust gas generated by the engine 20 is the same as that shown in FIG. Exhaust in the X1 direction in the figure. In the exhaust system shown in the figure, when the catalytic converter 10 is an electrically heated catalytic converter (EHC) according to the fourth embodiment, for example, when the engine 20 is started, the electrically heated catalytic converter is quickly turned on. The honeycomb catalyst is heated to a predetermined temperature and the exhaust gas flowing from the engine is purified by the honeycomb catalyst, and the exhaust gas that could not be purified by the electrically heated catalytic converter is located downstream of the three-way catalyst. It will be purified by the purification device 30.
Next, an embodiment of the catalytic converter will be described below with reference to FIGS.

(Embodiment 1 of catalytic converter)
FIG. 2 is a schematic diagram illustrating Embodiment 1 of the catalytic converter of the present invention, and FIG. 3 is a view taken along the line III-III in FIG.

  The catalytic converter 10 accommodated in the pipe 60 is mounted on the cylindrical base material 1 having a length L in the gas flow direction from the gas inflow end to the gas outflow end and the hollow 1a of the base material 1. On the outer periphery of the honeycomb catalyst 4 and the substrate 1, an annular spacer 3a in the range of the length t1 (inflow side range) from the gas inflow end, and an annular in the range of the length t3 (outflow side range) from the gas outflow end A spacer 3c, an annular spacer 3b in the range of t2 on the left and right of the center position (center range of length 2 × t2), and annular bodies 2a, 2b sandwiching the spacers 3a, 3b, 3c together with the base material 1, 2c is roughly constituted. Then, the spacers 3a, 3b, and 3c are canned around the base material 1 by these annular bodies 2a, 2b, and 2c, and pressure is generated in the spacers 3a, 3b, and 3c by this canning, and this causes the spacers 3a, 3b, and 3c to move. Thus, a desired surface pressure is applied to the inflow side range, the center range, and the outflow side range of the substrate 1.

  Here, although the base material 1 which comprises the hollow 1a is suitably formed from ceramics such as silicon carbide, it may be formed from a conductive metal such as a stainless steel metal.

  The honeycomb catalyst 4 accommodated in the hollow of the substrate 1 has a large number of quadrangular or hexagonal lattice contours made of a conductive metal such as silicon carbide or stainless steel metal, and alumina, zirconia, A catalytic metal such as platinum, palladium, and rhodium is dispersed and supported in a matrix carrier mainly composed of ceria and the like, and has a structure in which a vent hole through which exhaust gas passes is formed in the center of the lattice.

  Furthermore, the spacers 3a, 3b, and 3c are made of a material having rigidity and elasticity capable of imparting a surface pressure that can reduce the temperature stress to the base material 1 of the ceramic material, for example, during canning, As an example, a ceramic material having a lower rigidity than the base material 1 and a metal material having a lower rigidity than the base material 1 can be given.

  In the base material 1 having a length L from the gas inflow end to the gas outflow end, the length t1 from the gas inflow end shown in the figure is in the range between 0.04L and 0.06L (referred to as the inflow side range). In the side range, a surface pressure of 0.8 to 1.2 MPa is applied.

  Regarding the application of this surface pressure, the thickness of the spacers 3a, 3b, 3c is adjusted, or the material of the spacers 3a, 3b, 3c is changed, so that this is applied between the annular bodies 2a, 2b, 2c and the base material 1. The surface pressure generated when canned can be changed as desired. Moreover, changing the material and thickness of the spacers 3a, 3b, and 3c leads to changing the weight of the spacers 3a, 3b, and 3c, and the change in the weight also changes the surface pressure.

  The left and right lengths t2 from the center of the base material 1 shown in the figure are 0.2L to 0.25L from the gas inflow end side to the gas inflow end side and the gas outflow end side from the gas inflow end that is the center of the base material 1, respectively. In the middle range, a surface pressure of 0.3 to 0.6 MPa is applied.

  Furthermore, the length t3 from the outflow end of the illustrated gas is not particularly limited (this range is referred to as the outflow side range), and may be set to the same length as the length t1 of the inflow side range, The length may be set shorter than the length t1, and the surface pressure applied to the outflow side range is not particularly limited, and may be set to the same surface pressure as the inflow side range. A surface pressure smaller than the side range may be set.

  The length range of the inflow side range and the surface pressure range given here, and the length range of the central range and the surface pressure range given here are all based on the analysis results by the present inventors. This is the range in which the base material 1 is not cracked or hardly caused. The contents of analysis and the results will be described later.

  According to the catalytic converter 10 shown in the figure, in the base material 1 having a length L from the gas inflow end to the gas outflow end, the surface is 0.8 to 1.2 MPa in the inflow side range from 0.04 L to 0.06 L from the gas inflow end. Pressure is applied, and a surface pressure of 0.3 to 0.6 MPa is applied to the gas inflow end side and the gas outflow end side from the position of 0.5 L, which is the center of the substrate 1, in a central range between 0.2 L and 0.25 L, respectively. Therefore, the temperature stress that can occur in the entire range of the substrate 1 can be made less than a predetermined threshold value, and the occurrence of cracks that can occur in the substrate 1 can be effectively suppressed.

(Embodiment 2 of catalytic converter)
FIG. 4 is a schematic diagram illustrating Embodiment 2 of the catalytic converter of the present invention. In the catalytic converter 10A shown in the figure, the annular heat insulating material 5 is disposed in the region where the spacers 3a, 3b, 3c are not present on the outer peripheral surface of the base material 1 constituting the catalytic converter 10 shown in FIGS. Is.

  By disposing the heat insulating material 5 in this way, the outer peripheral surface of the base material 1 is completely surrounded by a separate member together with the spacers 3a, 3b, and 3c, and the temperature decrease of the base material 1 is effectively suppressed. In addition, like the catalytic converter 10, the outer peripheral surface of the substrate 1 is cooled from the outer periphery by mixing a region surrounded by another member (spacers 3 a, 3 b, 3 c) and an unexposed region. This causes a temperature distribution in the base material 1, and the problem that this may cause cracks cannot occur.

(Embodiment 3 of catalytic converter)
FIG. 5 is a schematic view illustrating Embodiment 3 of the catalytic converter of the present invention. The catalytic converter 10B shown in the figure does not include an annular body, and spacers 3a ′, 3b ′, and 3c ′ are fitted between the exhaust gas system pipe line 60 and the base material 1. As with the catalytic converters 10 and 10A, the thicknesses and materials of the spacers 3a ′, 3b ′, and 3c ′ are adjusted, so that specific desired surfaces for the inflow side range, the central range, and the outflow side range of the base material 1 are obtained. Pressure is applied.

(Embodiment 4 of catalytic converter)
FIG. 6 is a schematic diagram illustrating Embodiment 4 of the catalytic converter of the present invention, and FIG. 7 is a view taken along arrows VII-VII in FIG.

  The illustrated catalytic converter 10 </ b> C has a pair of electrodes 6, 6 on the outer periphery of the substrate 1, and these electrodes 6, 6 are electrically heated catalytic converters (EHC) connected to a power supply circuit. In addition, it is preferable that the power supply circuit shown in the figure has a switching element (not shown), and when it is energized and heated, an ON control signal from a control unit (not shown) is received and switched. Good.

  In the electrically heated catalytic converter, as shown in the drawing, the electrode 6 is attached to a region where the spacer does not exist on the outer peripheral surface of the substrate 1.

  In the catalytic converter 10C, among the regions where the spacers 3a, 3b, 3c are not present, a heat insulating material as shown in FIG. In the region, a heat insulating material may be similarly disposed in a region other than the attachment position of the electrode 6.

[Analysis and results to define the range of surface pressure applied to the substrate and the size range of surface pressure]
The present inventors use the engine pattern of the actual engine and the time history data of the temperature in the base material based on this, obtain the temperature stress that can occur in the base material by analysis, and the temperature at which cracks due to the temperature stress do not occur The stress threshold value is defined, and the surface pressure application range and surface pressure are applied so that a desired surface pressure is applied to an appropriate position of the base material so that any temperature stress that can occur in each part of the base material is less than the specified threshold value. An analysis was performed to identify the size range.

  FIG. 8 is a view showing an engine pattern (time history graph of engine speed) of an actual engine, and FIG. 9 is a view showing a time history graph of temperature at the center level of the base material of the catalytic converter. In addition, FIG. 10 shows that a catalytic converter base material analysis model (a model with a length of L / 2 of a cylindrical base material having a length L and a quarter of the model) and surface pressure are applied. It is a schematic diagram which shows. Further, FIG. 11 shows the time history of the temperature at each temperature measurement point shown in FIG. 10 and the time of the temperature difference between the outer peripheral surface and the inner peripheral surface of the base material in defining the threshold value of the temperature stress generated in the base material. FIG. 12 is a diagram showing a result of thermal stress analysis, and is a diagram specifying a stress (temperature stress threshold) at which the thermal stress is minimum on the substrate surface.

  The temperature at the center level in the base material of the catalytic converter in the engine pattern shown in FIG. 8 is about 150 ° C. to 900 ° C. as shown in FIG.

  In this analysis, the specifications of the substrate are 5.3 mil / 600 cpsi, the hollow diameter is 93 mm, and the length is L = 100 mm.

The base material has a single tube structure, and the physical properties of the base material (ceramic material of 72% alumina and 28% silica) and the honeycomb catalyst are shown in Table 1 below.

  In the computer, a 1/4 model of the base material shown in FIG. 10 (1/2 length model with a total length of 100 mm) is created, and surface pressure is applied to the entire surface of the base material and a desired range.

  First, the time history curve of the temperature at each position of No. 2, No. 5, and No. 8 in the analysis model shown in FIG. 10 is obtained by temperature analysis, and this is shown in FIG. Note that No5 is a point on the inner peripheral surface of the substrate at the gas inflow end of the base material model, No8 is a point on the outer peripheral surface of the base material at the gas inflow end of the base material model, and No2 is a gas inflow end of the base material model It is the point of the base material center level.

  Since the difference between the inner and outer surfaces of the base material is directly linked to the temperature stress at that part of the base material, the position at which time No. 3 and No. 8 have the largest difference value in FIG.

  Then, at this time of 3 seconds, the surface pressure is applied to the base material model while changing the surface stress, and the temperature stress generated on the surface of the base material is analyzed. The result is shown in FIG.

  From this analysis result, it is assumed that the temperature stress of the substrate when applying 0.4 MPa to the entire surface of the substrate is 23.9 MPa minimum, and if the entire substrate can clear this value, the substrate will not crack This temperature stress of 23.9 MPa was defined as the target threshold value.

  Note that FIG. 13 shows the temperature stress analysis result when the surface pressure applied to the substrate surface is changed. From this analysis result, the gas of the substrate when 0.4 MPa is applied as the surface pressure is also shown. It is confirmed that the temperature stress is below the threshold value of 23.9 MPa over the entire length of the analysis model 50 mm from the inflow end (Fr).

  Based on this analysis result, it is considered that by changing the surface pressure for each part of the base material, the size of the surface pressure can be expanded to a certain range, and the design variation of the base material can be expanded. In addition, in the case of EHC where it is necessary to attach an electrode to a part of the base material, since the surface pressure cannot be applied to the entire surface of the base material, the base material is divided into a region where no surface pressure is applied and a region where the surface pressure is applied. It is possible to define a surface pressure application range and a surface pressure magnitude range in which the temperature stress as a whole falls below the threshold value.

  Based on this, the present inventors set the surface pressure application range from a gas inflow side to a constant range (inflow side range) and a constant range at the center of the base material (center range), and temperature stress. An analysis was performed to identify the surface pressure application range at these two locations and the size range of the surface pressure at the two locations that can satisfy the threshold.

  The contents of analysis were to change the central range from 15mm to 25mm in width and the surface pressure from 0.2MPa to 0.6MPa in order to identify the central range of the substrate and the range of the surface pressure in that range. . The analysis results are shown in FIGS. More specifically, in FIGS. 14 to 18, the surface pressure is fixed to 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, and 0.6 MPa, respectively, and the width of the central range (width from the center to the gas inflow end) is 15 mm. The results of thermal stress analysis when changed to 20mm and 25mm are shown.

  From FIG. 14, it is proved that in any surface pressure range, when the surface pressure is 0.2 MPa, the temperature stress threshold value cannot be satisfied.

  On the other hand, FIGS. 15 to 18 demonstrate that the surface pressure of 0.3 MPa or more can satisfy both the width of 20 mm and 25 mm and less than the temperature stress threshold.

  From this analysis result, it is desirable that the surface pressure application range in the central range of the base material is a range of at least 20 mm or more from the central position, and the size range of the surface pressure applied to the base material is at least 0.3 MPa or more. I can confirm that. And based on this analysis result, the surface pressure application range in the center range of the base material is in the range of 20mm to 25mm from the center position (because the actual length of the analysis model is 100mm, this length is L The range of 0.2 to 0.25 L from the center), it can be confirmed that the range of surface pressure applied to the substrate is preferably 0.3 to 0.6 MPa, these numerical ranges The surface pressure application range and the surface pressure size range in the central range of the substrate are defined. In addition, it has been found that canning becomes difficult in the range where the surface pressure in the central range of the substrate exceeds 0.6 MPa, and from this, the size of the surface pressure applied to the central range of the substrate is also known. Can be defined as 0.6 MPa.

  On the other hand, in this analysis, in order to specify the inflow side range in the base material and the range of the surface pressure in that range, the inflow side range was changed from 2 mm to 6 mm in width, and the size of the surface pressure was 0.2 MPa to 1.2 MPa. It was changed with. The analysis results are shown in FIGS. More specifically, FIGS. 19 to 21 show results of thermal stress analysis when the surface pressure application range is fixed to 2 mm, 4 mm, and 6 mm, respectively, and the surface pressure applied is changed from 0.2 MPa to 1.2 MPa. Is shown.

  FIG. 19 demonstrates that the width of 2 mm cannot satisfy the temperature stress threshold value less than most of the surface pressure.

  On the other hand, FIG. 20 demonstrates that a width of 4 mm can satisfy a surface pressure of 0.8 MPa or more and less than the temperature stress threshold. Further, FIG. 21 demonstrates that the width of 6 mm can satisfy the surface pressure of 0.6 MPa or more and less than the temperature stress threshold.

  From this analysis result, the surface pressure application range in the inflow side range that is the end of the base material is at least 4 mm from the gas inflow end, and the surface pressure applied range to the base material is at least 0.8 MPa. It can be confirmed that the above is desirable. And based on this analysis result, the surface pressure application range in the inflow side range that is the end of the base material is in the range of 4mm to 6mm (because the actual length of the analysis model is 100mm, this length is L is in the range of 0.04L to 0.06L from the center), it can be confirmed that the range of the surface pressure applied to the base material is preferably 0.8 to 1.2 MPa. Based on these numerical ranges The surface pressure application range and the surface pressure size range in the inflow side range of the material are defined.

  22 and 23 show other temperature stress analysis results. Specifically, in FIGS. 22 and 23, when the width of the center range (width from the center to the gas inflow end side) is 25 mm and the surface pressure of the center range is 0.4 MPa and 0.6 MPa, respectively, It is a figure which shows the temperature stress analysis result at the time of changing the surface pressure provided to the inflow side range in the width of 6 mm of this spacer to 0.4, 0.6, and 0.8 MPa.

  Both results demonstrate that the surface pressure in the inflow range is 0.8 MPa, which is below the temperature stress threshold (satisfying the above-described surface pressure magnitude range of 0.8 to 1.2 MPa).

  Further, FIG. 24 shows the substrate surface at the point (substrate surface 1 in the figure) inside the substrate 30 mm from the gas inflow end (Fr) with and without the spacer in the substrate analysis model. The temperature difference of the substrate surface at the point inside the 50mm substrate from the gas inflow end (Fr) (substrate surface 2 in the figure), the point inside the 70mm substrate from the gas inflow end (Fr) (Fig. The analysis result regarding the temperature of the substrate surface in the substrate surface 3) is shown. Table 2 shows the temperature difference between the inner and outer surfaces of the substrate at each point.

  From FIG. 24 and Table 2, the temperature difference between the inner and outer surfaces of the base material in the base material model having the spacer is more prominent as it is closer to the gas inflow end, compared to the model having no spacer on the base material surface. It has been demonstrated that the temperature difference is reduced by more than 40%. By greatly reducing the temperature difference between the inner and outer peripheral surfaces of the base material, the temperature stress is remarkably reduced, leading to effective suppression of cracks.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Base material, 1a ... Hollow, 2a, 2b, 2c ... Ring body, 3a, 3b, 3c, 3a ', 3b', 3c '... Spacer, 4 ... Honeycomb catalyst, 5 ... Thermal insulation material, 6 ... Electrode, 10 , 10A, 10B ... catalytic converter, 10C ... (electrically heated) catalytic converter, 20 ... engine, 30 ... three-way catalytic converter, 40 ... sub-muffler, 50 ... main muffler, 60 ... piping (system pipe)

Claims (5)

A base material having a length L from a gas inflow end through which gas flows into the hollow to a gas outflow end through which gas flows out from the hollow;
A catalytic converter comprising at least a catalyst housed in the substrate,
In the base material, a surface pressure of 0.8 to 1.2 MPa is applied in the inflow side range between 0.04 L and 0.06 L from the gas inflow end,
A catalytic converter in which a surface pressure of 0.3 to 0.6 MPa is applied in a central range between 0.5 L to 0.25 L from 0.5 L, which is the center of the base material, to a gas inflow end side and a gas outflow end side.   An annular body is disposed at least on the outer circumference of the inflow side range and the outer circumference of the central range of the base material, and a spacer is fitted between the annular body and the base material to generate the surface pressure. 2. The catalytic converter according to 1.   The base material is accommodated in a pipe line that constitutes an exhaust gas exhaust system, and spacers are provided at least between the outer periphery of the inflow side range of the base material and the pipe line, and between the outer periphery of the central range and the pipe line, respectively. The catalytic converter according to claim 1, wherein the catalytic converter is fitted to generate the surface pressure.   The catalytic converter according to any one of claims 1 to 3, wherein an annular heat insulating material is disposed in a range where no spacer exists in the outer periphery of the substrate.   The base material has electrical conductivity, and an electrode for energizing the base material is provided in an outer periphery of the base material in a range where no spacer is present, thereby constituting an electrically heated catalyst. The catalytic converter according to any one of 1 to 4.

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