JP4949976B2 - Particulate matter collection distribution detection method, collection distribution detection device and exhaust gas purification device - Google Patents

Description

  The present invention relates to a collection distribution detection method and a collection distribution detection apparatus for particulate matter. The present invention can be used for detecting the PM accumulation distribution of a filter arranged in an exhaust system of a diesel engine.

  As for gasoline engines, harmful components in exhaust gas have been steadily reduced due to strict regulations on exhaust gas and advances in technology that can cope with it. However, for diesel engines, harmful components are emitted as PM (primarily carbon particulate soot, high molecular weight hydrocarbon particulates, sulfur particulates such as sulfate, etc.), and exhaust gas purification compared to gasoline engines. Is difficult.

  As exhaust gas purification devices for diesel engines that have been developed so far, a trap type exhaust gas purification device (wall flow) and an open type exhaust gas purification device (straight flow) are known. Among these, as a trap-type exhaust gas purification device, a ceramic plug-type honeycomb body (diesel PM filter) is known. This filter is formed by alternately sealing both ends of the openings of the cells of the ceramic honeycomb structure, for example, in a checkered pattern, adjacent to the inflow side cells clogged on the exhaust gas downstream side and the inflow side cells. It consists of an outflow side cell clogged upstream of the exhaust gas and a cell partition partitioning the inflow side cell and the outflow side cell. The exhaust gas is filtered through the pores of the cell partition wall to collect PM, thereby suppressing emissions. To do.

  However, in the filter, exhaust pressure loss increases due to the accumulation of PM, so it is necessary to periodically remove and regenerate PM accumulated by some means. Therefore, conventionally, a regenerating process is performed in which a reducing agent such as fuel is added to exhaust gas, and the PM collected by the combustion heat is ignited by a high-temperature filter and burned. In addition, an oxidation catalyst is disposed upstream of the filter, and the exhaust gas is heated by burning with the oxidation catalyst, and the high-temperature exhaust gas is supplied to the filter to forcibly regenerate the filter.

  However, when the amount of PM collected in the filter is locally large, there is a problem that the filter is locally melted due to heat generated by combustion. If a large amount of PM is collected on the upstream side of the filter, the exhaust gas is excessively heated by the heat of combustion at that site, which is transmitted to the downstream side of the filter, resulting in thermal runaway and melting. There is also. On the other hand, if the regeneration process is performed while the amount of collected PM is small, the probability of melting damage is reduced, but the fuel consumption deteriorates due to the increase in added fuel.

  For this reason, it is conceivable to forcibly raise the exhaust gas temperature when it is determined that the amount of collected PM exceeds a predetermined value. For example, the PM emission data for the driving situation is stored in the ECU as map data, the PM emission is estimated from the integrated value of the operation time, and this is cumulatively calculated to estimate the PM collection amount. There is a method to regenerate the filter by forcibly increasing the exhaust gas temperature when it is determined that the amount of PM collected exceeds a predetermined amount.

  However, there is a problem that the error is large when the PM emission data for the driving situation is used as map data. In addition, the differential pressure before and after the filter is also used as an index of the amount of PM collected. However, in this method, the value of the limit differential pressure, which is a criterion for determination, varies greatly depending on the operating condition of the engine. Therefore, it is necessary to store the data of the limit differential pressure for each operating condition as map data, Becomes enormous. Furthermore, the relationship between the amount of collected PM and the differential pressure is not a linear relationship, and there is a problem that the detection sensitivity is low in a range where the amount of collected PM is small.

  Therefore, Japanese Patent Application Laid-Open No. 2005-327771 detects the current or voltage generated in the secondary coil wound around the collection container when an alternating current is passed through the primary coil wound around the collection container. In addition, a method for calculating the amount of collected PM from the value is described. Since an induced electromotive force corresponding to the PM trapping amount is generated in the secondary coil, the PM trapping amount can be calculated by detecting the current or voltage generated in the secondary coil.

  Japanese Patent Application Laid-Open No. 10-220219 proposes an exhaust gas purification device that detects the amount of PM by measuring electromagnetic wave intensity with a microwave sensor. This technology uses the fact that when PM is attached to the filter, the dielectric constant and dielectric loss of the filter change, the phase of the microwave in the filter shifts, and the microwave intensity changes, and the microwave detection position is fixed. The microwave intensity at that location is measured, and the amount of PM attached is detected by the change in the microwave intensity.

However, since the dielectric constant and dielectric loss of the filter are affected by temperature, it is necessary to correct the temperature, and the electromagnetic field intensity is detected by a microwave sensor using a standing wave rather than direct phase difference measurement. Therefore, there is a problem that it is difficult to separate the influence of the attenuation of the microwave in one point measurement and it cannot be accurately detected. Therefore, it is necessary to make a comprehensive evaluation by measuring at a plurality of locations, or to perform a troublesome evaluation using map data. The 2.45 GHz microwave, which is normally used as a microwave, has a wavelength of about 12 cm and has a low resolution, so it cannot detect the local concentration of PM collection.
JP 2005-327771 A JP-A-10-220219

  Although the method described in each of the above publications can detect the average amount of PM collected as a whole filter or the physical quantity related to the total amount of PM collected, it can detect the PM collection distribution in the filter. It is difficult. In a filter mounted on a vehicle, for example, the PM accumulation amount may be greater on the exhaust gas upstream side than on the downstream side. Also, the amount of accumulated PM is larger in the outer peripheral part where heat is easily removed than in the inner peripheral part. Therefore, even if the average amount of PM collected or the total amount of PM collected is detected, the amount of information is insufficient to accurately determine whether or not the regeneration process should be performed.

  On the other hand, if the filter in which PM is collected is cut, the PM collection distribution can be measured. However, it is desirable that the PM collection distribution can be detected by nondestructive inspection.

The present invention has been made in view of the above circumstances, and the problem to be solved is to detect the collection distribution of particulate matter that absorbs microwaves such as PM, nondestructively, easily and with high accuracy. To do.

The feature of the collection distribution detection method of the particulate matter of the present invention that solves the above problems is that the ceramic collection container in which the particulate matter is collected is irradiated with millimeter-wave level microwaves from the outside, Detecting the intensity of the microwave that has passed through the collection container, and substituting the intensity into a predetermined relation between the microwave intensity and the collection amount to calculate the collection amount of the particulate matter. For each of multiple locations,
The purpose is to detect the collection distribution of the collected particulate matter in the collection container.

In addition, the particulate matter collection and distribution detection device of the present invention is characterized by millimeter-wave level microwaves from the outside of a ceramic collection container in which particulate matter is collected toward multiple locations of the collection container. Microwave irradiation means for irradiating ;
Microwave receiving means for respectively detecting the intensity of the microwaves transmitted through a plurality of locations of the collection container;
And calculating means for calculating the collection amount of the particulate matter from the intensity detected by the microwave receiving means and calculating the collection distribution of the particulate matter in the collection container.

And the feature of the exhaust gas purifying apparatus of the present invention is a ceramic filter that is arranged in the exhaust gas flow path and collects PM mainly composed of carbon,
A storage container for storing the filter;
A microwave irradiation means for irradiating a plurality of locations of the filter with millimeter-wave level microwaves from an incident window formed in the storage container;
Microwave receiving means for respectively detecting the intensity of the microwave transmitted through the filter and radiated from the radiation window formed in the storage container;
And calculating means for calculating the PM collection distribution from the respective intensities detected by the microwave receiving means .

According to the collection distribution detection method and collection distribution detection apparatus for particulate matter of the present invention, microwaves having a frequency of several tens of GHz to several THz (wavelength is in mm level) are used to absorb microwaves by particulate matter. Since the collection amount of particulate matter is detected by detecting the collection amount of particulate matter at the irradiated location and detecting the collection amount at multiple locations, the particulate matter in the collection container Can be detected with high accuracy.

  According to the exhaust gas purifying apparatus of the present invention, since the concentration of the local PM collection amount can be detected with high accuracy, a filter due to thermal runaway can be performed by performing a regeneration process in a state where the collection amount does not increase excessively locally. It is possible to prevent melting damage. Further, since the amount of reducing agent supplied to the exhaust gas during the regeneration process can be minimized, fuel efficiency is also improved.

Collecting distribution detection device of the present invention comprises a collection vessel, a microwave irradiating means for irradiating a microwave to the collection vessel, the microwave receiver for detecting the intensity of microwaves transmitted through the plurality of portions of the collecting container, respectively And means for calculating the collection amount of the particulate matter from the intensity detected by the microwave receiving means and calculating the collection distribution of the particulate matter in the collection container.

  The particulate matter referred to in the present invention is not particularly limited as long as it is a substance that absorbs a millimeter-wave level microwave having a frequency of several tens of GHz to several THz and ultimately converts the energy into heat energy. Examples thereof include magnetic powder such as main PM and ferrite powder.

In the present invention, a microwave of millimeter wave level having a frequency of several tens of GHz to several THz is used. When the frequency is lower than this range, the collected particulate matter is easily transmitted, and the detection accuracy of the collected amount is lowered. Further, if the frequency is higher than this range, it becomes difficult for the collected particulate matter to pass through, and the detection accuracy also decreases. It is preferable to use a microwave having a frequency of about 100 to 600 GHz. In particular, an inexpensive general-purpose product with stable quality can be used as the microwave receiving means for detecting microwaves of 100 to 200 GHz.

  A collection container is arrange | positioned in the flow path through which the gas containing particulate matter distribute | circulates, and collects particulate matter, Various filters can be used. As this collection container, a container that transmits a microwave of millimeter wave level with a frequency of several tens GHz to several THz is used. A part of the microwave may be absorbed. In the case of an exhaust gas purification device, a filter made of ceramics such as cordierite, silicon carbide, silicon nitride, and alumina is typically used. These ceramics have a high transmittance of millimeter wave level microwaves having a frequency of several tens of GHz to several THz.

  It is also preferable to use a filter with a catalyst in which an oxidation catalyst layer is formed on the cell partition wall surface of the filter and the pore surface in the cell partition wall. Microwaves are also absorbed by noble metals such as Pt as a catalyst. However, if the loading and distribution of the noble metal are constant, the collection distribution of the particulate matter can be detected with high accuracy.

The microwave irradiation means is means for irradiating the collection container with microwaves having a millimeter wave level of several tens of GHz to several THz from the outside of the collection container, and a magnetron or the like can be used. It is desirable to directly irradiate the collection container with microwaves. However, in the case of a collection container stored in a metal storage container such as an exhaust gas purification filter, it is formed on the storage container and has a frequency of several tens of GHz to several THz. It irradiates through the incident window which can transmit the microwave of millimeter wave level . As the material of the entrance window, cordierite, silicon nitride, ceramics such as alumina, glass, or the like can be used.

The microwave receiving means detects the intensity of the microwave transmitted through the collection container, and a known one such as a microwave sensor can be used. The microwave receiving means is preferably arranged on the side opposite to the microwave irradiating means with respect to the collection container, and is arranged close to the collection container. However, in the case of an exhaust gas purification device, the microwave receiving means may be deteriorated by heat, so it is received through a radiation window that is formed in the storage container and can transmit millimeter wave level microwaves of several tens of GHz to several THz. To be configured. The radiation window can be formed of a material having heat resistance similar to the entrance window.

The microwave irradiating means and the microwave receiving means are arranged so as to be located on opposite sides of the collection container. For example, in the case of a cylindrical collection container such as a honeycomb filter, it can be arranged on both sides in the diameter direction. Alternatively, it is also preferable that the exhaust gas inflow side and the exhaust gas outflow side are disposed so as to be opposite to each other on the plane including the axis. In this way, it is possible to detect the amount of PM collected over the entire length in the exhaust gas flow direction.

  In the collection distribution detection method and the collection distribution detection apparatus of the present invention, the collection distribution is detected in a state where the collection container in which the particulate matter is collected is placed in a constant humidity chamber having at least a constant humidity. Is desirable. This is because a millimeter wave level microwave with a frequency of several tens of GHz to several THz is absorbed by moisture, so that when the humidity of the measurement atmosphere varies, the detection value also varies and the accuracy decreases.

In collecting distribution detecting method and collecting distribution detection device of the present invention, the microwave is irradiated at a plurality of locations toward the collection container, the intensity of microwave transmitted through the respective points are detected respectively by the microwave receiving means The A plurality of microwave transmitting means and microwave receiving means can be arranged so as to face each other along the surface of the collection container. In addition, detection may be performed at a plurality of locations while moving along the axial direction of the collection container or the diameter direction of both end faces in a state where the pair of microwave irradiation means and microwave reception means are opposed to each other. Alternatively, it is also preferable to detect at a plurality of locations by moving the microwave irradiating means and the microwave receiving means in the axial direction while rotating along the periphery of the collection container, as in a CT scan. In this way, the collection distribution of the particulate matter in the collection container can be detected three-dimensionally and can be displayed as a two-dimensional or three-dimensional image.

  In the case of a cylindrical collection container such as a honeycomb filter, the plurality of locations are preferably a plurality of locations in the axial direction, and more preferably a plurality of locations along the diameter of the end face.

The computing means computes the collection amount of the particulate matter from the microwave intensity detected by the microwave receiving means at a plurality of locations, and computes the collection distribution of the particulate matter in the collection container from the computation result. . For example, the amount of collected particulate matter at each irradiation position is calculated by substituting the microwave intensity detected by the microwave receiving means into a relational expression between a predetermined intensity and the collected amount. The collection distribution can be calculated by calculating the collection amount at a plurality of irradiation positions.

Since the collection container itself often absorbs microwaves with a frequency of several tens of GHz to several THz to a certain extent, reception is first performed only with a collection container in which no particulate matter is collected as a blank. Measure the strength. If it does so, the amount of collection of particulate matter can be computed from the difference with the receiving intensity in the state where particulate matter was collected.

In the case of the exhaust gas purification device, the calculation means calculates the absorption coefficient of the microwave in the filter in which PM is collected from the detection value by the microwave reception means, and only the filter in which the PM measured in advance is not collected. It is desirable to calculate the amount of PM trapped from the ratio to the absorption coefficient of microwaves at . By using the microwave absorption coefficient as an index, the relationship between the amount of PM collected and the absorption coefficient is a primary expression regardless of various factors such as temperature, so calculation of the amount of PM collected is easy and accurate. be able to. The absorption coefficient is expressed by the logarithm of the transmittance, and the transmittance is a ratio of the radiation output to the incident output.

  According to the exhaust gas purification apparatus of the present invention, the PM collection distribution can be detected with high accuracy. Therefore, it is possible to detect that a large amount of PM has been collected locally, so the regeneration process is performed in a state where the amount of PM collected at that part does not exceed a predetermined value, thereby minimizing deterioration in fuel consumption and filtering. It is possible to reliably prevent melting during regeneration.

  The exhaust gas purifying apparatus of the present invention includes means for controlling the temperature of the exhaust gas flowing into the filter to be different between the outer periphery and the inner periphery, and means for controlling the relationship between the inflow end face of the filter and the flow path flowing into the filter. It is preferable to further use a means for heating a specific position in the axial direction of the filter. By using these means, it is possible to locally heat a part with a large amount of PM collection according to the PM collection distribution, shortening the time for filter regeneration processing or extending the time until filter regeneration processing. can do. Therefore, the fuel consumption can be further reduced.

As described above, water is also a microwave absorber, and the amount of water in the filter affects the detection value. Therefore, it is desirable to detect the amount of water detected using a moisture sensor or the like. However, if the temperature of the filter is controlled to a constant value and detected, the saturated water vapor pressure is constant, so the moisture contained in the exhaust gas can be regarded as constant, and the PM collection distribution can be detected without any problem in practice. Can do.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
In FIG. 1, the collection distribution detection apparatus of a present Example is shown typically. This device is composed of a filter 1 used in an exhaust system of a diesel engine, a microwave transmitter 2, a microwave receiver 3, and an arithmetic device 4.

  The filter 1 includes an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and an inflow side cell and an outflow side cell. And a porous cell partition wall having a honeycomb-shaped wall flow structure having cordierite.

  The filter 1 is placed so that the outflow side end surface is in contact with the sample stage 10. The sample table 10 is provided with a weight sensor 11 for detecting the weight of the filter 1.

  The microwave transmitter 2 includes three systems of transmitters 20, 21, and 22. The transmitters 20, 21, and 22 are arranged on a straight line along the outer peripheral surface of the filter 1 and parallel to the central axis of the filter 1. The transmitting part 20 is directed toward the inflow side end of the filter 1, the transmitting part 22 is directed toward the outflow side end, and the transmitting part 21 is located between the transmitting part 20 and the transmitting part 22 in the axial center of the filter 1. Irradiate each part with 600GHz millimeter waves.

  The microwave receiver 3 is provided with three systems of receivers 30, 31, and 32. The receivers 30, 31, and 32 are arranged symmetrically with the transmitters 20, 21, and 22, respectively, with respect to the central axis of the filter 1. Then, the microwave transmitted through the filter 1 is received.

With collecting distribution detection device described above, is first brand-new filter 1 is placed on the sample base 3, while measuring the weight W _B by the weight sensor 11, the millimeter wave 600GHz from the transmission section 20, 21, 22 irradiation with input intensity I _B. Then, the receiving units 30, 31, and 32 measure the output intensities I ₀ , I ₁ , and I ₂ of the millimeter waves that have passed through the filter 1 in the diameter direction.

Then, the absorption coefficient α _r (reference) of the new filter 1 in which PM is not collected is calculated from Equation (1).

Since PM is not collected and the filter 1 has the same cross-sectional structure from one end to the other end, the absorption coefficient α _r values at the upstream end portion, the central portion, and the downstream end portion are the same. Further, the transmittance (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ) of each part is also the same.

Next, a plurality of types of filters 1 in which a known amount of PM is uniformly collected from the upstream end to the downstream end in advance are prepared, and only the PM collection amount is different. The output intensities I ₀ , I ₁ and I ₂ of the millimeter wave transmitted in the diameter direction are measured. The transmittance (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ) is the same in the same filter 1, and is different among a plurality of types having different PM collection amounts. FIG. 2 shows the relationship between the amount of PM collected in advance and the measured transmittance (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ).

  As can be seen from FIG. 2, the relationship between the amount of collected PM and the transmittance is not a linear expression. Therefore, complicated calculation is required to estimate the amount of PM trapped from the transmittance.

Therefore, the arithmetic device 4 calculates the absorption coefficient α _w (with PM) when the filter 1 in which PM is uniformly collected is used from Equation (1). And PM ratio ((alpha) _w / (alpha) _r ) which is ratio with respect to the absorption coefficient (alpha) _r of the new filter 1 is calculated, and the relationship between PM collection amount and PM ratio is shown in FIG.

  From FIG. 3, it is clear that the relationship between the PM collection amount and the PM ratio is a linear expression, and it can be seen that the PM collection amount can be easily and accurately detected by measuring the PM ratio.

Therefore, a new filter 1 was mounted on the exhaust system of the diesel engine, and after traveling 100 km under a steady running condition of 60 km / hr, the filter 1 was taken out and used as a sample. The spent filter 1 is placed on the sample stage 3, while measuring the weight W ₀ by weight sensor 11, it is irradiated by the input intensity I _B millimeter wave 600GHz from the transmission unit 20, 21, 22. Then, the receiving units 30, 31, and 32 measure the output intensities I ₀ , I ₁ , and I ₂ of the millimeter waves that have passed through the filter 1 in the diameter direction.

Then, the arithmetic unit 4 calculates the absorption coefficient (α _w0 , α _w1 , α _w2 ) at each of the upstream end portion, the central portion, and the downstream end portion of the used filter 1 from the equation ( ₁ ). The PM ratio, which is the ratio of the filter 1 to the absorption coefficient α _r , is calculated. The picture from the graph of FIG. 3, reads the amount of collected PM corresponding to each PM ratio, PM trapped by weight _{(W 0 -W B, W 1} -W B, W 2 -W B) the result of the correction by 4 shows.

  From FIG. 4, the upstream end of the used filter 1 has the largest amount of PM collected, and the amount of PM collected decreases rapidly toward the center, and the amount of PM collected from the center to the downstream end It can be seen that there is a gradual decrease. That is, according to the collection distribution detection method and the collection distribution detection apparatus of the present embodiment, the PM collection amount distribution in the exhaust gas flow direction can be easily and accurately detected without destroying the used filter 1. Can do.

In this embodiment, the absorption coefficient α _r values at the upstream end portion, the central portion, and the downstream end portion of the filter 1 where PM is not collected are the same, and the transmittance (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ) are also the same. However, even if the transmittance of each part is different, it is possible to calculate the distribution of the PM collection amount from the difference in the PM collection amount in the same part.

(Example 2)
In this example, the same filter 1 as in Example 1 was used, and the filter was placed so that the central axis thereof was parallel to the surface of the sample table 10 as shown in FIG. The transmitters 20, 21, and 22 are arranged in the diametrical direction facing the inflow side end face of the filter 1, the transmitter 20 and the transmitter 22 are directed toward the outer peripheral cell or plug, and the transmitter 21 is an axial core Irradiate a 600 GHz millimeter wave toward the cell or plug at the location. The receiving units 30, 31, and 32 are arranged in a diametrical direction so as to face the outflow side end face of the filter 1, are arranged at positions facing the transmitting units 20, 21, and 22, respectively, and receive microwaves that have passed through the filter 1.

Other than that, the absorption coefficient (α _w0 , α _w1 , α _w2 ) is calculated for each part on the outer peripheral part, the inner peripheral part, and the lower peripheral part of the used filter 1 in the same manner as in the first embodiment. Then, the PM ratio, which is the ratio of the new filter 1 to the absorption coefficient α _r , is calculated. Figure from the graph of FIG. 3, reads the amount of collected PM corresponding to each PM ratio, PM trapped by weight _{(W 0 -W B, W 1} -W B, W 2 -W B) the result of the correction by 6 Shown in

  From FIG. 6, it can be seen that the amount of collected PM is large at the upper and lower outer peripheral portions of the used filter 1 and is small at the inner peripheral portion. That is, according to the collection distribution detection method and the collection distribution detection apparatus of the present embodiment, it is possible to easily and accurately detect the PM collection amount distribution in the diameter direction without destroying the used filter 1. it can.

In this embodiment, the absorption coefficient α _r value is the same in each part on the outer peripheral part, the inner peripheral part, and the lower peripheral part of the filter 1 where PM is not collected, and the transmittance (I ₀ / I _{B) of} each part. , I ₁ / I _B , I ₂ / I _B ) are also the same. However, even if the transmittance of each part is different, it is possible to calculate the distribution of the PM collection amount from the difference in the PM collection amount in the same part.

(Example 3)
FIG. 7 shows the exhaust gas purifying apparatus of this embodiment. Connected to the exhaust manifold 50 of the diesel engine 5 is a steel converter 51 that houses a filter 1 ′ having a cylindrical shape with catalyst. Most of the exhaust gas from the exhaust manifold 50 flows through the converter 51 and passes through the filter 1 and is discharged. A part of the exhaust gas is returned to the intake manifold 54 of the diesel engine 5 through the turbocharger 52 and the intercooler 53. It is. An injection nozzle 55 is disposed in the exhaust manifold 50, and is configured so that light oil is intermittently injected into the exhaust gas.

  The filter with a catalyst 1 ′ is divided into an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and an inflow side cell and an outflow side cell. The filter has a honeycomb-shaped wall flow structure having a porous cell partition wall having a plurality of pores, and is formed of cordierite similar to that in Example 1. A catalyst layer in which Pt is supported on alumina is formed on the surface of the cell partition wall and the surface of the pores of the filter 1.

  The converter 51 has three transmitters (20, 21, 22) extending from a microwave transmitter (not shown) and three receivers (30, 30) extending from a microwave receiver (not shown) on the outer side of the center. 31 and 32) are installed. The three transmitters (20, 21, 22) and the three receivers (30, 31, 32) are on both sides of the filter with a catalyst 1 ′ on a plane including the central axis of the filter with a catalyst 1 ′. Are arranged so as to face each other. The driving of the microwave transmitter is controlled by the ECU 6, and a signal received by the microwave receiver is input to the ECU 6. As shown in FIG. 8, the surface of the converter 51 facing the three transmitters (20, 21, 22) and the three receivers (30, 31, 32) is made of alumina and can transmit microwaves. An incident window 56 and a radiation window 57 are formed.

In this exhaust gas purification apparatus, first, a new filter 1 ′ with catalyst is used, and 600 mm millimeter waves are transmitted from the three transmitters (20, 21, 22) with the input intensity IB without driving the engine 5. The output intensity (I ₀ , I ₁ , I ₂ ) received by the three receiving units (30, 31, 32) is measured. The transmitted millimeter-wave energy is absorbed to some extent by the entrance window 56, the filter with catalyst 1 ', and the radiation window 57. However, since PM is not collected, the catalyst-equipped filter 1 ′ has the same cross-sectional structure from one end to the other end, and the Pt carrying distribution is uniform, so the upstream end, the center, and the downstream end The absorption coefficient α _r value in each part is the same. Further, the transmittance (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ) of each part is also the same.

Then, the absorption coefficient α _{r in} the case of only the filter with catalyst 1 ′ is calculated from the equation (1).

  In this embodiment, the three transmitters (20, 21, 22) are always driven while the engine 5 is driven, and the ECU 6 is calculated from the output intensity received by the receivers (30, 31, 32). Always observe each PM ratio. When the PM collection amount is calculated from the relational expression corresponding to FIG. 3 and the PM collection amount on the inflow side detected by the receiving unit 30 exceeds a predetermined value, the ECU 6 To supply a predetermined amount of light oil into the exhaust gas.

  The light oil supplied into the exhaust gas flows into the filter with a catalyst 1 ′ and ignites and burns even in a low temperature region due to the catalytic action of Pt supported on the catalyst layer. This combustion heat raises the temperature of the filter with catalyst 1 ′ to about 600 ° C. or more, and the collected PM burns. At this time, the ECU 6 constantly observes each PM ratio. Then, the addition of light oil is continued until at least the inflow side PM trapped amount falls below a predetermined value among the inflow side, central portion, and outflow side PM trapped amount, and at least the inflow side PM trap amount is at the predetermined value. When it becomes below, ECU6 stops the drive of the injection nozzle 55, and prevents the filter 1 'with a catalyst from melting and Pt grain growth.

  That is, according to the exhaust gas purification apparatus of the present embodiment, the PM collection distribution can be easily and accurately detected by measuring the PM ratio. In addition, by using millimeter-wave level microwaves, it is possible to accurately detect the density of the amount of PM trapped locally. Therefore, since the regeneration process of the filter with catalyst 1 ′ can be reliably performed in a state where the amount of PM trapped does not increase excessively, melting damage due to thermal runaway can be prevented in advance. Furthermore, since the driving of the injection nozzle 55 can be minimized, fuel efficiency is improved.

In this embodiment, the absorption coefficient α _r values at the upstream end portion, the central portion, and the downstream end portion of the filter with catalyst 1 ′ where PM is not collected are the same, and the permeation of each portion is the same. The case where the rates (I ₀ / I _B , I ₁ / I _B , I ₂ / I _B ) are also the same is shown. However, even if the transmittance of each part is different, it is possible to calculate the distribution of the PM collection amount from the difference in the PM collection amount in the same part.

It is explanatory drawing which shows the structure of the collection distribution detection apparatus which concerns on one Example of this invention. It is a graph which shows the relationship between PM collection amount and the transmittance | permeability. It is a graph which shows the relationship between PM collection amount and PM ratio. It is a graph which shows PM collection distribution in the flow direction of the filter detected in one Example of this invention. It is explanatory drawing which shows the structure of the collection distribution detection apparatus which concerns on 2nd Example of this invention. It is a graph which shows PM collection distribution in the diameter direction of the filter detected in 2nd Example of this invention. It is a block diagram of the exhaust gas purification apparatus which concerns on the 3rd Example of this invention. It is a principal part expanded sectional view of the exhaust gas purification apparatus which concerns on the 3rd Example of this invention.

Explanation of symbols

1: Filter 2: Microwave transmitter 3: Microwave receiver 4: Computing device 10: Sample stage 11: Temperature sensor
20, 21, 22: Transmitter 30, 31, 32: Receiver

Claims (4)

Microwave irradiation of a millimeter wave level from the outside to the collection container made of ceramics particulate matter trapped, detects the intensity of the microwaves transmitted through the the collecting container, the predetermined micro Substituting the intensity into the relational expression between the wave intensity and the collected amount and calculating the collected amount of the particulate matter for each of a plurality of locations of the collecting container,
A method for detecting a collection distribution of particulate matter, comprising: detecting a collection distribution of the collected particulate matter in the collection container. A microwave irradiation means for irradiating a millimeter-wave level microwave from the outside of a ceramic collection container in which particulate matter is collected toward a plurality of locations of the collection container;
Microwave receiving means for respectively detecting the intensity of the microwave transmitted through the plurality of locations of the collection container;
Calculating means for calculating the amount of collection of the particulate matter from the intensity detected by the microwave receiving means , and calculating the collection distribution of the particulate matter in the collection container. An apparatus for detecting the collection amount distribution of particulate matter. A ceramic filter that collects PM, mainly carbon, arranged in the exhaust gas flow path;
A storage container for storing the filter;
Microwave irradiation means for irradiating a plurality of locations of the filter with millimeter-wave level microwaves from an incident window formed in the storage container;
Microwave receiving means for respectively detecting the intensity of the microwave transmitted through the filter and radiated from a radiation window formed in the storage container;
An exhaust gas purification apparatus comprising: an arithmetic means for calculating a PM collection distribution from each of the intensities detected by the microwave receiving means . Said calculating means, said calculating the absorption coefficient of the microwave in the filter PM is collected from the detection value by the microwave receiving means, said micro the definitive only the filter premeasured PM is not trapped The exhaust gas purification apparatus according to claim 3, wherein the amount of PM trapped is calculated from a ratio to a wave absorption coefficient.

Images