JP2009508049A - Exhaust gas purification components for purifying exhaust gas of internal combustion engines - Google Patents

Abstract

  1 is an exhaust gas purification component proposed for purifying exhaust gas in an internal combustion engine having a carrier through which a plurality of flow ducts (2) for exhaust gas penetrate. At least a part of the wall (3) of the flow duct is provided with a coating having an oxygen storage capacity. According to the invention, the first compartment region (5, 5 ′, 5 ″) of the carrier is coated with an oxygen storage capacity and the second compartment region (6, 6 ′, 6 ″) is made without a coating having an oxygen storage capacity or a coating having a considerably lower oxygen storage capacity compared to the first region (5, 5 ′, 5 ″). Yes.

Description

  The present invention relates to an exhaust gas purification component for purifying exhaust gas of an internal combustion engine, having the features described in the first part of claim 1.

  In order to purify the exhaust gas of an internal combustion engine, it is common to provide a cylindrical carrier in the exhaust portion through which a plurality of exhaust gas flow ducts pass. For catalyst-assisted exhaust gas purification, the duct is usually provided with a catalytically active coating, whereby the exhaust gas flowing in the duct comes into contact with the coating and is catalyzed by the coating. A component conversion process may occur. The coating often has oxygen storage capacity. This makes it possible in particular to catalyze redox reactions.

  In particular, the stress caused by the temperature rise causes the exhaust gas purification component to age, and accordingly, the function of the exhaust gas purification component decreases. In exhaust gas purification components with a coating having oxygen storage capability, aging can be accompanied by a decrease in oxygen storage capability. When such undesirable aging occurs, the reliability of the corresponding exhaust gas purification component decreases.

  It is an object of the present invention to provide an exhaust gas purification component with improved operational reliability.

  The object is achieved by an exhaust gas purification component having the features of claim 1.

  According to the invention, the first compartment region of the carrier is provided with a coating with oxygen storage capacity and the second compartment region of the support is made without a coating with oxygen storage capacity or the second compartment region. A coating with a considerably lower oxygen storage capacity compared to the region 1 is applied.

  As the coating, it is preferable to use a coating embodied in a method called a thin coating film. Depending on the desired function, the coating may contain finely dispersed catalytically active noble metals (particularly of the platinum group). If the coating has oxygen storage capacity, the coating includes materials capable of storing oxygen, such as rare earth oxides. In this case, the material is evenly dispersed in the coating or dilute coating so that the coating has an overall oxygen storage capacity. Oxygen storage materials that are uniformly dispersed in the coating so that the coating is fully oxygen storage can include oxides based on cerium oxide and / or oxides based on praseodymium oxide, or mixed. Oxides are particularly preferred. For the first region, it is preferred that the material with oxygen storage capacity is included in the coating at a rate of approximately 20% to 70%. On the other hand, the content of the second region is preferably less than 10%. However, in the second region, the coating may not contain any such material or may have no coating applied. For simplicity, in the following, the embodiments of the first region and the second region will be referred to as a high OSC region and a low OSC or no OSC region (OSC = oxygen storage capacity).

  In embodiments according to the present invention in which only a defined area of the carrier is provided with a high OSC coating, the chemical transformation generated by the material with oxygen storage capacity is mainly or completely of the exhaust gas purification component. Limited to this area. Thereby, the heat release associated with the conversion is also limited to this region, with the result that the temperature load of the exhaust gas purification component is reduced, at least in the remaining region. Since the oxygen storage capacity can be reduced by aging, it is also possible to record or evaluate the degree of aging of the exhaust gas purification component by recording the oxygen storage capacity in the high OSC region. If excessive aging or rapid aging is detected, it is possible to intervene in the operation of the internal combustion engine and stop it. This also improves the service life and operational reliability of the exhaust gas purification component.

  Depending on the application, various shaped regions can be implemented as the first and second regions of the exhaust gas purification component. For example, it is possible to realize a first and / or second region that extends over the entire length of the carrier, but not over its entire cross-sectional area. On the other hand, it is also possible to realize first and / or second regions that extend over the entire cross-sectional area of the carrier, but not over the entire length of the carrier.

  In one embodiment of the invention, the first region and / or the second region extend over the entire cross section of the carrier, but are limited in terms of the extent of the carrier in the axial direction. This embodiment is particularly simple to manufacture by dip / adsorption coating.

  In a further refinement of the invention, the first region is adjacent to the second region. In particular, the high OSC region extends across the entire cross-section of the carrier and is axially adjacent to the low OSC region or the non-OSC region that also extends over the entire cross-section. Thus, the joint is clearly formed and localized in the axial direction of the carrier.

  In a further refinement of the invention, the first high OSC region extends over a larger part of the length of the carrier. This embodiment is particularly advantageous in the case of exhaust gas purification components that require a high oxygen storage capacity in terms of absolute values for the function of the exhaust gas purification component. This is the case, for example, with a three-way catalytic converter.

  In a further refinement of the invention, the first high OSC region extends axially from the distance from the inlet end of the carrier to the outlet end of the carrier. Thus, the input end of the carrier, preferably the disc-shaped region, has a low OSC or no OSC. This prevents the material storing oxygen from undergoing aging in the inlet region of the exhaust gas purification component, which is usually particularly susceptible to thermal stress. Further, the heat supply reaction caused by the oxygen storage material is generated from the inlet region toward the rear in the axial direction. On the other hand, there is sufficient oxygen storage capacity available for the function of the exhaust gas purification component downstream of the inlet region where the OSC is low or has no OSC.

  In a further refinement of the invention, the exhaust gas purification component is provided with at least two first (high OSC) regions spaced from each other. When the disk-shaped low OSC or non-OSC region and the high OSC region are alternately and repeatedly arranged in the axial direction, it is particularly advantageous for the function of the exhaust gas catalytic converter as the exhaust gas purification component.

  In a further refinement of the invention, the exhaust gas purification component is embodied as an exhaust gas catalytic converter. The catalytic converter can be of the type referred to herein as a non-supported catalytic converter or of the type referred to as a supported catalytic converter. One embodiment of the exhaust gas purification component according to the invention is particularly advantageous when it is a three-way catalytic converter.

  In a further refinement of the invention, the exhaust gas purification component is embodied as an exhaust gas particle filter. This is preferably a so-called wall flow type particle filter. The duct of the particle filter can here be coated so as to catalyze along its gas inlet side and / or gas outlet side, or it can be substantially uncoated.

  In a further refinement of the invention, a temperature recording means is provided for recording the temperature of the coating with oxygen storage capacity in the first region. In this way, it is possible to record the temperature change due to the redox reaction caused by the high OSC coating. If the function of the coating is reduced due to aging, the condition can be detected by referring to a record of the temperature of the coating. In particular, the change in the process of modifying the material that stores oxygen occurs when oxygen is stored and usually involves a real amount of heat, so the change can be detected by recording the temperature of the coating. Is possible. The oxygen storage capacity of a coating having oxygen storage capacity can be recorded by recording the temperature of the coating. Thereby, the exhaust gas purification component can be diagnosed. This is because the deterioration of the function of the oxygen storing coating caused by aging can be detected by recording the temperature.

  Advantageous embodiments of the invention are illustrated in the drawings and are described below. It should be noted that the above-described features and the features described below can be used not only in the combination of the specified features, but also in other combinations or alone without departing from the scope of the present invention.

  FIG. 1 is a schematic diagram of an exhaust gas purification component 1 embodied as an exhaust gas catalytic converter with a honeycomb structure. The exhaust gas catalytic converter 1 can be embodied as being referred to as an unsupported catalytic converter in which the honeycomb body itself is made of a catalytically active material, but in the following, it is supported with a metal or ceramic carrier. It is assumed that there is an exhaust gas catalytic converter of the type. A plurality of flow ducts 2 pass through the carrier, and at least a part of the wall 3 of the flow duct 2 is coated (details are not shown). Here, the coating is preferably a catalytically active coating. With respect to the flow direction of the exhaust gas indicated by the arrow 4, the rear part 5 of the exhaust gas catalytic converter 1 is provided with a high OSC coating, that is, a coating having a relatively high oxygen storage capacity. On the other hand, in the inlet end region 6 that is considerably shorter than the rear portion 5, the exhaust gas catalytic converter 1 has no OSC or low OSC. Here, the inlet end region 6 may not be coated, or may be coated with a coating having no oxygen storage capability or a relatively low oxygen storage capability. For reasons of manufacturing technology, it is preferable that the coating is applied almost uniformly on the wall 3 of the flow duct 2 in each of the regions 5 and 6 and includes the entire cross section of the exhaust gas catalytic converter 1 as its range.

  The embodiment of the catalytic converter shown in FIG. 1 used in the vicinity of the engine as the first catalytic exhaust gas purification component in the exhaust part of the internal combustion engine is preferred. Such exhaust gas purification components are particularly susceptible to thermal stresses in the inlet region since the inflowing exhaust gas can be hot. Reaction of the reactive exhaust gas components with oxygen stored in the catalytic converter and / or changes in the reforming process of the oxygen storage material itself can further increase the thermal stress in the catalytic converter. To protect the inlet end region, which is important for obtaining exhaust gas purification performance, from excessively high temperatures, it may be advantageous to have a low or no OSC catalytic converter inlet region. The inlet end region 6 of the exhaust gas catalytic converter 1 covers approximately 5 to 50 mm (or approximately 5 to 50%) of the entire length of the exhaust gas catalytic converter 1 and is low OSC or non-OSC. It is advantageous. Adjacent downstream regions 5 are preferably uniformly high OSC.

  FIG. 2 shows a second advantageous embodiment of an exhaust gas purification component 1 embodied according to the invention. Here, in contrast to the embodiment of FIG. 1, the inlet end region 5 is high OSC and the adjacent downstream region 6 is low OSC or no OSC. This embodiment is recommended when it is not necessary to increase the oxygen storage capacity in order for the exhaust gas purification component 1 to function. This embodiment can be implemented, for example, in an exhaust gas purification component 1 embodied as an oxidation catalytic converter or a soot filter. The high OSC region 5 at the inlet end can serve as a diagnostic region, particularly in this case, and the aging of the exhaust gas purification component 1 is determined by repeatedly determining the oxygen storage capacity of the high OSC region 5. . The inlet end region 5 of the exhaust gas purification component 1 is advantageously high OSC over approximately 5 to 50 mm (or approximately 5 to 50%) of the total length of the exhaust gas purification component 1.

  FIG. 3 shows a third advantageous embodiment of an exhaust gas catalytic converter 1 embodied according to the invention. In contrast to the embodiment of FIG. 1, the inlet end region 5 ′ has a high OSC as does the rear region 5. That is, the region is embodied by a coating having a relatively high oxygen storage capacity. The central region 6 to be made low OSC or no OSC is disposed between the high OSC regions 5 ′ and 5. The central region 6 that is made low or no OSC preferably occupies approximately 20-30% of the total length of the exhaust gas catalytic converter 1. Therefore, the exhaust gas catalytic converter 1 has a high OSC coating on a considerable part of the entire length so that the most important functions can be fully exhibited.

  FIG. 4 shows a further advantageous embodiment of the exhaust gas catalytic converter 1. In this embodiment, only the central region 5 has a high OSC. On the other hand, the adjacent front region 6 and the adjacent rear region 6 'are low OSC or no OSC. Such an embodiment is particularly advantageous in catalytic exhaust gas purification components where the oxygen storage capacity needs to be relatively low. Compared to a coating embodied by uniformly reducing the oxygen storage capacity over the entire length, this embodiment has the advantage that the heat resistance is reduced only in one region. The central region 5 preferably occupies approximately 20 to 60% of the total length of the exhaust gas catalytic converter 1.

  In a further advantageous embodiment shown in FIG. 5, the high OSC regions 5, 5 ′, 5 ″, 5 ′ ″ are replaced with low OSC or no OSC regions 6, 6 ′, 6 ″, 6 ′ ″. Alternatingly arranged. Here, as illustrated, the inlet end region 6 can be low OSC or no OSC. However, it may also be advantageous if the inlet region has a coating with a high oxygen storage capacity. In particular, cerium-containing coatings can catalyze the water vapor shift reaction by the formation of hydrogen, so in such cases, the region has a high oxygen storage capacity and has a low oxygen storage capacity or an oxygen storage capacity. It is possible to use hydrogen formed in no subsequent regions. In this way, the catalytic function of the exhaust gas catalytic converter 1 can be expanded. Each region preferably occupies approximately 20% of the total length of the exhaust gas catalytic converter 1. Individual regions can be approximately the same length or different lengths.

Embodiments of the exhaust gas purification component having a first compartment region with a high OSC coating and a second compartment region that is low or no OSC results in the catalytic function of the exhaust gas purification component. Improve. In addition, embodiments according to the present invention can be used to monitor the aging of exhaust gas purification components. For this purpose, the temperature of the coating with oxygen storage capacity is in the high OSC region so that the reaction heat of the change in the process of reforming the material with oxygen storage capacity that occurs during storage of oxygen can be recorded. To be recorded. When oxygen is stored in a material having oxygen storage capacity, the material changes from low oxygen reforming to high oxygen reforming. For example, in the case of a material based on cerium oxide having oxygen storage capacity, cerium oxide changes from a ternary form (Ce ₂ O ₃ ) to a quaternary form (CeO ₂ ). Since the corresponding oxygen absorption reaction occurs rapidly in the form of exotherm, the temperature of the coating with oxygen storage capacity increases during oxygen storage. Thus, depending on the nature of the temperature rise, it can be determined whether and how much a change has occurred in the reforming process. That is, it is possible to determine whether and how effective a material having oxidation storage ability is. Catalytic converter aging (eg, as a result of temperature rise or contamination) is manifested through a reduction in oxygen storage capacity, so assessing the temperature rise during oxygen storage assesses the aging status of the exhaust gas purification component. It is possible to make a diagnosis. For this purpose, for example, the magnitude of the temperature rise is detected and compared with a reference value.

  The nature and result of the temperature increase that occurs when oxygen is stored in a material having oxygen storage capacity must here clearly differ from the temperature increase that can occur due to the occurrence of a catalytic gas reaction. In the first case, the exothermic change in the reforming process of the material having oxygen storage ability causes the temperature rise. In the second case, the exothermic reaction of the exhaust gas component causes the temperature rise. . The reaction heat released with the storage of oxygen acts directly in the coating itself, resulting in rapid heating of the coating, resulting in a temperature rise even when no exothermic gas reaction occurs. On the other hand, the gas reaction catalyzed by the coating heats the coating indirectly and occurs late, especially in the area of the exhaust gas purification component, which is a little away from the gas inlet. Thus, if the temperature is recorded at some distance from the exhaust gas inlet, it is possible to distinguish between a temperature increase as a result of gas oxidation and a temperature increase as a result of changes in the reforming process within the coating. . That is, if the temperature is recorded at a position slightly away from the exhaust gas inlet, the exhaust gas purification component can be particularly reliably monitored by determining the oxygen storage capacity at that location. It is preferable to evaluate the temperature rise that occurs immediately when the operation mode of the internal combustion engine changes to shift from an exhaust gas reduction state in which oxygen is insufficient to an exhaust gas oxidation state in which oxygen is excessive. In this way, the temperature effect caused by gas oxidation can be effectively eliminated.

  The reaction heat of the change in the reforming process that occurs when oxygen is stored in a material with oxygen storage capability is primarily provided with a high OSC coating from the beginning, corresponding to the embodiment shown in FIGS. It can be advantageously recorded using an exhaust gas purification component. The temperature recording can here be performed at only one point in the high OSC coating or at a plurality of points offset relative to each other in the axial and / or radial direction.

  To monitor an exhaust gas purification component that does not have a coating with oxygen storage capability from the outset, a coating with oxygen storage capability can be applied locally to a relatively small compartment of the exhaust gas purification component. . By assessing the temperature rise associated with oxygen storage that occurs in this region, monitoring and diagnostics can be performed on components that have few coatings with oxygen storage capability. In this respect, it is advantageous to embody the exhaust gas purification component according to the variants shown in FIGS. 2, 4 and 5.

  In order to record the reaction heat of the change in the reforming process that occurs when oxygen is stored in a material with oxygen storage capacity, it is necessary to place a temperature sensor in the heat conduction connection with the corresponding coating. preferable. The temperature sensor is preferably introduced radially or axially into the exhaust gas purification component with its temperature sensitive region in heat transfer contact with the high OSC coating.

  FIG. 6 is a schematic diagram showing the installation of the temperature sensor 7 in the radial direction of the exhaust gas purification component 1. Here, the temperature sensitive region of the temperature sensor 7 can be shifted from the center. Of course, it is also possible to arrange the temperature sensor 7 substantially at the height of the central axis in the longitudinal direction.

  FIG. 7 is a schematic diagram showing the installation of the temperature sensor 7 in the axial direction of the exhaust gas purification component 1. It is not necessary to position the temperature sensor 7 at the height of the central axis in the longitudinal direction as shown. The axis of the sensor can be arranged parallel to or intersecting with the central axis in the longitudinal direction, or can be arranged at an angle with respect to the central axis in the longitudinal direction.

  For functional reasons, exhaust gas purification components that have little or no oxygen storage capacity coating have high temperature only in the immediate vicinity of the temperature sensor or its thermal area. It is possible to provide an OSC coating. An exemplary embodiment for the radial installation type of the temperature sensor is shown in cross-sectional views (corresponding to lines A and B in FIG. 6) in FIGS. In FIGS. 8 a and 8 c, the region 5 extends over the entire length of the exhaust gas purification component 1, but only occupies a part of the cross section, in which the temperature sensor 7 is inserted, and the high OSC Coating is applied. In FIG. 8 a, the region 5 surrounds the temperature sensing part (here, the tip part) of the temperature sensor 7 and extends to the outer surface of the exhaust gas purification component 1. In FIG. 8 c, the high OSC region 5 only surrounds the warm region of the temperature sensor 7 in the radial direction. However, according to FIGS. 8 b and 8 d, the high OSC region 5 is preferably relatively short in the axial direction and only exists around the temperature sensor 7. In FIG. 8 b, the high OSC region 5 surrounds the entire sensor 7 contained in the exhaust gas purification component 1. In FIG. 8 d, the high OSC region 5 surrounds only the temperature sensitive tip of the temperature sensor 7. Using the embodiment shown in FIGS. 8a-8d, it is possible to monitor aging of an exhaust gas purification component with a coating that has a fairly low oxygen storage capacity or a coating that does not have oxygen storage capacity. .

  As shown in FIGS. 9a to 9c, for example, it is also possible to introduce the temperature sensor 7 embodied as a thermocouple in the axial direction into the exhaust gas purification component 1 to be monitored. The temperature sensor 7 can be in heat transfer contact with a high OSC coating (ie, axial region) that is uniformly formed over the entire length of the component. Alternatively, as shown, the temperature sensor 7 can be in heat transfer contact with a high OSC coating that exists only in the immediate vicinity of the temperature sensitive region.

1 shows a first advantageous embodiment of an exhaust gas purification component according to the invention. 2 shows a second advantageous embodiment of an exhaust gas purification component according to the invention. 3 shows a third advantageous embodiment of an exhaust gas purification component according to the invention. 4 shows a fourth advantageous embodiment of an exhaust gas purification component according to the invention. 5 shows a fifth advantageous embodiment of an exhaust gas purification component according to the invention. A first arrangement of a temperature sensor for an exhaust gas purification component according to the present invention is shown in a side view (left side) and a front view (right side). 2 shows a second arrangement of a temperature sensor for an exhaust gas purification component according to the invention in a side view. FIG. 7 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to FIG. 7 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to FIG. 7 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to FIG. 7 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to FIG. Fig. 8 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to Fig. 7; Fig. 8 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to Fig. 7; Fig. 8 shows a further advantageous embodiment of the exhaust gas purification component according to the invention and a temperature sensor arranged according to Fig. 7;

Claims (9)

An exhaust gas purification component for purifying exhaust gas in an internal combustion engine, having a carrier through which a plurality of flow ducts (2) for exhaust gas pass, comprising at least a part of a wall (3) of the flow duct A coating with oxygen storage capacity is applied,
The first compartment region (5, 5 ′, 5 ″) of the carrier is coated with the oxygen storage capacity, and the second compartment region (6, 6 ′, 6 ″) of the carrier is It is made without a coating having an oxygen storage capacity, or a coating having an extremely low oxygen storage capacity compared to the first region (5, 5 ′, 5 ″) is applied. Features exhaust gas purification components.   The first region (5, 5 ′, 5 ″) and / or the second region (6, 6 ′, 6 ″) extend over the entire cross section of the carrier, The exhaust gas purification component according to claim 1, wherein the exhaust gas purification component is limited to a range constituting the carrier.   The first region (5, 5 ', 5 ") is adjacent to the second region (6, 6', 6"). Exhaust gas purification component.   4. The exhaust gas according to claim 1, wherein the first region (5, 5 ′, 5 ″) extends over a larger part of the length of the carrier. Purification component.   The first region (5, 5 ', 5' ') extends from a location spaced from the inlet end of the carrier in an axial direction to the outlet end of the carrier. Item 5. The exhaust gas purification component according to any one of Items 1 to 4.   5. Exhaust gas purification component according to any one of the preceding claims, characterized in that at least two first regions (5, 5 ', 5 ") spaced from each other are provided.   The exhaust gas purification component according to any one of claims 1 to 6, wherein the exhaust gas purification component (1) is embodied as an exhaust gas catalytic converter.   The exhaust gas purification component according to any one of claims 1 to 7, wherein the exhaust gas purification component (1) is embodied as an exhaust gas particle filter.   A temperature recording means (7) is provided for recording the temperature of the coating having oxygen storage capacity in the first region (5, 5 ', 5' '). The exhaust gas purification component according to any one of the above.

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