JP2011058374A - Method for detecting collection distribution of particulate matter and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the collection distribution of particulate matter for absorbing electromagnetic waves such as PM. <P>SOLUTION: Multiple kinds of electromagnetic waves of different frequencies with their transmittances in passing through a filter different to each other are radiated at two or more radiation angles for detecting the intensities of the electromagnetic waves having passed through the filter. Coefficients α, β are set for the multiple kind of electromagnetic waves each for the two or more radiation angles so that the transmittances of the electromagnetic waves having passed through the filter before collection of the PM are the same between the two or more radiation angles. The intensity of an electromagnetic wave with a higher filter transmittance before collection of the PM is selected out of the intensities of the detected multiple electromagnetic waves. The PM collection amount is calculated each for the two or more radiation angles by multiplying the difference between the intensity of the selected electromagnetic wave and the intensities of the electromagnetic waves having passed through the filter before collection of the PM by the coefficients α, β. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a particulate matter collection distribution detection method and apparatus, and an exhaust gas purification apparatus using the same, and particularly to detect PM deposition distribution of a filter disposed in an exhaust system of a diesel engine. Used for.

  An exhaust system of an internal combustion engine such as a diesel engine is equipped with a collecting device such as a filter that collects PM (soot mainly composed of carbon fine particles, high-molecular-weight hydrocarbon fine particles, sulfur-based fine particles such as sulfate). As a method for detecting the amount of PM collected by the collection device, there is a method disclosed in Patent Document 1 conventionally. In this method, the collection distribution of particulate matter that absorbs electromagnetic waves such as PM is irradiated with electromagnetic waves of several tens of GHz to several THz from the outside, and the intensity of the electromagnetic waves transmitted through the collecting device is detected and determined in advance. In this method, the collection distribution is detected by substituting the intensity into the relational expression between the electromagnetic wave intensity and the collection amount. Since this method can detect the PM collection distribution in a non-destructive manner, it has a dramatic effect on the PM collection distribution detection.

JP 2009-57948 A

  By the way, in order to obtain a CT (computer tomography) image using the non-destructive method of the above-mentioned Patent Document 1, there is a demand that a data signal from the entire circumference (360 °) of the collection device must be acquired. is there.

  The method disclosed in Patent Document 1 irradiates an inspection object with an electromagnetic wave of several tens GHz to several THz. However, depending on the structure of the DPF, if the frequency is 80 GHz or more, the received signal strength is increased or decreased due to an interference phenomenon caused by refraction or reflection of the electromagnetic wave depending on the angle between the wall structure of the collection device and the irradiation direction of the electromagnetic wave. For this reason, it is difficult to obtain a sufficiently strong data signal from the entire circumference necessary for CT.

  It has been confirmed by the inventors' experiments that the frequency of the electromagnetic wave to be irradiated can be less than 80 GHz. However, in order to obtain a sufficiently strong data signal from the entire circumference, the spatial resolution of electromagnetic waves cannot theoretically be 4 mm or less depending on the type and structure of the DPF. For this reason, an upper limit arises in the space resolution capability of the collection distribution of the particulate matter deposited on the collection device.

  This invention is made | formed in view of this situation, and makes it a subject to detect the collection distribution of the particulate matter which absorbs electromagnetic waves, such as PM, with sufficient precision.

  The inventor conducted an experiment of irradiating the collection device with electromagnetic waves of several tens GHz to several THz. Since the wall structure of the collecting device differs in the direction and amount of refracting / reflecting the electromagnetic wave depending on the irradiation angle of the electromagnetic wave, the transmittance of the electromagnetic wave is different. It has been found that the refraction and reflection characteristics of this wall structure change depending on the frequency of the electromagnetic wave to be irradiated.

  Therefore, attention was paid to the fact that the magnitude of the transmittance of the electromagnetic wave for each of two or more irradiation angles can be complemented by appropriately selecting the frequency of the plurality of electromagnetic waves.

(1) The method for detecting the collection and distribution of particulate matter according to the present invention is a method of irradiating an electromagnetic wave from the outside to a collection device in which the particulate matter is collected. In the method of detecting the collection distribution in the collection device,
Intensities of the electromagnetic waves transmitted through the collection device by irradiating the collection device with a plurality of electromagnetic waves having different frequencies and different transmittances when irradiated to the collection device. A detection step for detecting
The two or more irradiation angles so that the transmittance of the electromagnetic wave transmitted through the collection device before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. A setting step for setting a coefficient for each of the plurality of electromagnetic waves,
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, A complementing step of complementing with the intensity of the electromagnetic wave detected in the angular region of
For each of the two or more irradiation angles, the difference between the intensity of the electromagnetic wave supplemented in the complementing process and the intensity of the electromagnetic wave transmitted through the collection device before collecting the particulate matter is determined in the setting process. A calculation step of calculating the trapped amount of the particulate matter for each of the two or more irradiation angles by multiplying by a set coefficient;
(Claim 1).

  According to the said structure, the several electromagnetic wave from which frequency differs is irradiated to the collection apparatus which collected the particulate matter. The plurality of electromagnetic waves have different transmittances through the collection device for each irradiation angle. For this reason, the coefficient is set in advance so that the transmittances between two or more irradiation angles are equal to each other, and the blank intensity between two or more irradiation angles is made equal. Then, the difference between the intensity of the electromagnetic wave transmitted through the post-use collecting device that collected the particulate matter and the intensity of the electromagnetic wave transmitted through the pre-use collecting device that did not collect the particulate matter was determined. By multiplying the above by the above coefficient, data indicating the distribution of the collected amount of the particulate matter collected by the collection device can be obtained.

  Further, the electromagnetic waves to be irradiated have different transmittance at each irradiation angle. In the angle region where the transmittance is small, the detection accuracy of the signal related to the collection amount is low. Therefore, an electromagnetic wave having a higher transmittance is selected from a plurality of electromagnetic waves for each irradiation angle. Electromagnetic waves detected in an angular region where the transmittance is reduced after irradiating a post-use collector that collects particulate matter at an irradiation angle of 2 or more and detecting the intensity of the electromagnetic waves. Is supplemented by the intensity of the electromagnetic wave detected by the electromagnetic wave having the highest transmittance. For this reason, the amount of collection can be detected with high accuracy for each irradiation angle.

  (2) It is preferable that two or more of the plurality of electromagnetic waves are selected from frequency regions having different transmittances that pass through the collection device for each irradiation angle.

  In this case, the collected amount detected by the electromagnetic wave having a low transmittance can be supplemented by the collected amount detected by the electromagnetic wave having a high transmittance.

  (3) In the complementing step, selection data for selecting the electromagnetic wave having the highest transmittance among the plurality of electromagnetic waves is prepared in advance for each irradiation angle, and the plurality of the plurality of electromagnetic waves are selected based on the selection data. It is preferable to select the intensity of the electromagnetic wave having the highest transmittance from the intensity of the electromagnetic wave.

  In this case, the intensity of the electromagnetic wave having the highest transmittance among the plurality of electromagnetic waves is selected for each irradiation angle. The amount of collected particulate matter is calculated in the calculation step using the intensity of the selected electromagnetic wave. For this reason, a highly accurate detection result can be obtained at all of the two or more irradiation angles. In addition, when a particulate matter is detected by irradiating a collection device with a plurality of electromagnetic waves at irradiation intervals at predetermined intervals from 360 ° in all directions, irradiation data from 360 ° in all directions is obtained. ° Accurate detection results can be obtained in all directions.

(4) The particulate matter collection amount distribution detection device of the present invention has a different frequency and irradiates the collection device from the outside of the collection device in which the particulate matter is collected. Irradiating means for irradiating the collection device with a plurality of electromagnetic waves having different transmittances at two or more irradiation angles;
Receiving means for detecting the intensity of electromagnetic waves transmitted through the collecting device;
The two or more irradiation angles so that the transmittance of the electromagnetic wave transmitted through the collection device before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. Setting means for setting a coefficient for each of the plurality of electromagnetic waves for each;
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, Complementing means for complementing with the intensity of the electromagnetic wave detected in the angle region,
For each of the two or more irradiation angles, the difference between the intensity of the electromagnetic wave supplemented by the complementing means and the intensity of the electromagnetic wave transmitted through the collection device before collecting the particulate matter is determined in the setting step. A calculation means for calculating the trapped amount of the particulate matter at the irradiation angle of 2 or more by multiplying a set coefficient;
(Claim 4).

  According to the said structure, the collection distribution of the particulate matter in a collection apparatus can be detected with sufficient accuracy similarly to said (1).

  (5) The irradiation means irradiates the collection device with electromagnetic waves at an equal pitch from all directions of 360 °, and the calculation means calculates the collection amount of the particulate matter in all directions of 360 °. (Claim 5).

  In this case, by using the data on the collected amount of the particulate matter from all directions of 360 °, by reconstructing the computer tomographic image of the collection device, the particulate matter in the collection device is reconstructed. The collection distribution can be built into 2D or 3D information.

(6) The exhaust gas purification apparatus of the present invention includes a filter that is disposed in the exhaust gas passage and collects PM mainly composed of carbon;
A storage container for storing the filter;
A plurality of electromagnetic waves having different frequencies and different transmittances when irradiated to the filter are irradiated to the filter from an incident window formed in the storage container at two or more irradiation angles. Irradiation means;
Receiving means for detecting the intensity of the electromagnetic wave transmitted through the filter;
For each of the two or more irradiation angles, the transmittance of the electromagnetic wave transmitted through the filter before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. Setting means for setting a coefficient for each of the plurality of electromagnetic waves;
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, Complementing means for complementing with the intensity of the electromagnetic wave detected in the angle region,
The difference between the intensity of the electromagnetic wave supplemented by the complementing means and the intensity of the electromagnetic wave transmitted through the filter before collecting the particulate matter is set in the setting step for each of the two or more irradiation angles. Calculating means for calculating the amount of the particulate matter collected at the irradiation angle of 2 or more,
(Claim 6).

  According to the said structure, the collection distribution of the particulate matter in a filter can be detected with sufficient accuracy similarly to said (1). Therefore, based on the collection distribution in the filter, it is possible to take steps to locally heat the part with a large amount of PM collection, shortening the filter regeneration process time, and reducing the time until the filter regeneration process. It can be long. Therefore, the filter regeneration process can be performed efficiently, leading to an improvement in fuel consumption.

  According to the present invention, a plurality of electromagnetic waves having different frequencies and different transmittances with respect to a collecting device are irradiated at two or more irradiation angles with respect to the collecting device that collects the particulate material. For this reason, the collection distribution of the particulate matter can be detected with high accuracy.

It is explanatory drawing which shows the structure of the collection distribution detection apparatus which concerns on one Example of this invention. It is explanatory drawing which shows the collection distribution detection method which concerns on an Example. It is explanatory drawing which shows the transmittance | permeability when the frequency of the millimeter wave irradiated to a filter is changed. It is explanatory drawing of the irradiation angle of the millimeter wave irradiated to a filter. Explanatory drawing (a) which shows the transmittance of 90 GHz millimeter wave, and explanatory drawing (b) which shows the transmittance of 110 GHz millimeter wave. It is explanatory drawing which shows the correction | amendment transmittance | permeability (correction intensity | strength) when the standard transmittance | permeability (blank intensity | strength) for every irradiation angle is made constant.

  The particulate material referred to in the present invention is preferably a material that absorbs millimeter-wave electromagnetic waves having a frequency of several tens of GHz to several THz, and finally converts the energy into thermal energy, mainly carbon. Examples thereof include magnetic powder such as PM and ferrite powder.

  As the frequency of the electromagnetic wave, a millimeter wave level microwave of several tens of GHz to several THz may be used. When the frequency is lower than this range, it becomes easy to transmit the collected particulate matter, but the wavelength becomes longer and the spatial resolution 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. In particular, an inexpensive general-purpose product with stable quality can be used for the electromagnetic wave receiving means for detecting microwaves of 100 to 200 GHz.

  The frequency of the electromagnetic wave is selected to be 2 or more within a range in which the particulate matter can be detected. In addition, there are various types of collection devices such as cell wall thickness, cell shape, cell pitch, collection device shape and material. Therefore, the characteristic of refracting / reflecting electromagnetic waves varies depending on the angle at which the collecting device irradiates the electromagnetic waves. For this reason, in at least a certain range of the electromagnetic wave frequency, the transmittance varies depending on the irradiation angle. Therefore, a frequency region in which the transmittance that passes through the collection device differs depending on the irradiation angle is obtained by measurement, etc., and two or more frequencies differ in magnitude from each other in each irradiation angle from the frequency region. Select.

  The collection device is arranged in a flow path through which a gas containing particulate matter flows and collects the particulate matter, and various filters can be used. As this collection device, a device that transmits a millimeter-wave level microwave having a frequency of several tens of 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, alumina, titania 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 irradiation means is means for irradiating the collection device with electromagnetic waves having a frequency of several tens of GHz to several THz from the outside of the collection device, and a magnetron or the like can be used. It is desirable to irradiate the collector directly with electromagnetic waves, but in the case of a collector that is housed in a metal container such as an exhaust gas purification filter, an electromagnetic wave of several tens of GHz to several THz is formed in the container. The electromagnetic wave is irradiated through an incident window that can pass through the light. As the material of the entrance window, cordierite, silicon nitride, ceramics such as alumina, glass, or the like can be used.

  The receiving means detects the intensity of the electromagnetic wave that has passed through the collection device, and a known device such as a microwave sensor can be used. It is desirable that the receiving means is disposed on the opposite side of the irradiation device with respect to the collecting device and is disposed in the vicinity of the collecting device. However, in the case of the exhaust gas purifying apparatus, since the receiving means may be deteriorated by heat, the receiving means is configured to be received through a radiation window formed in the storage container and capable of transmitting electromagnetic waves of several tens GHz to several THz. The radiation window can be formed of a material having heat resistance similar to the entrance window.

  The irradiating means and the receiving means are arranged so as to be positioned on opposite sides of the collecting device. For example, in the case of a cylindrical collecting device 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 device of the present invention, the collection distribution is detected in a state where the collection device in which the particulate matter is collected is disposed 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 the collection distribution detection method and the collection distribution detection device of the present invention, the electromagnetic waves are irradiated toward the collection device at two or more irradiation angles, and the intensity of the electromagnetic waves transmitted at each angle is detected by the receiving unit. .

  Here, the collection device is arranged on a straight line connecting the irradiation means and the reception means. The irradiation angle of electromagnetic waves refers to the angle with respect to this straight line collecting device. The two or more irradiation angles are such that the irradiation unit and the reception unit are arranged at a plurality of different positions in the circumferential direction with respect to the collection device, and the collection device is irradiated with electromagnetic waves from a plurality of directions. The angle to the device.

  In the present invention, the “irradiation angle” refers to an irradiation angle with respect to the reference direction with a certain irradiation direction with respect to the collection device as a reference direction. The two or more irradiation angles may be irradiation angles at the same pitch when the collection device is irradiated at an equal pitch from all directions of 360 °. In this case, the collection distribution of the particulate matter in the collection device can be detected two-dimensionally.

  Detection may be performed at two or more irradiation angles while moving along the circumferential direction of the collection device in a state where the irradiation unit and the reception unit are opposed to each other. Alternatively, it is also preferable to detect at a plurality of locations by moving the irradiation means and the reception means in the axial direction while relatively rotating the circumference of the collection device as in a CT scan. In this way, the collection distribution of the particulate matter in the collection device can be detected three-dimensionally, and two-dimensional or three-dimensional information can be obtained.

  The irradiating means and the receiving means can be arranged at a plurality of locations so as to face each other along the surface of the collection device. For example, in the case of a cylindrical collecting device such as a honeycomb filter, it is preferable to have a plurality of locations in the axial direction, and it is also preferable to have a plurality of locations along the diameter of the end face.

  When the collection device is irradiated with electromagnetic waves while changing the irradiation angle, the irradiation angle of the electromagnetic waves changes with respect to the wall structure of the collection device. For this reason, the refraction and reflection characteristics of the electromagnetic wave by the collecting device change, and the intensity of the electromagnetic wave received by the receiving means increases or decreases.

  Therefore, the setting means and the setting step are such that the transmittance of the electromagnetic wave transmitted through the collection device before collecting the particulate matter for two or more irradiation angles is equal between the two or more irradiation angles. Coefficients are set for a plurality of electromagnetic waves every two or more irradiation angles. That is, the coefficient is determined so that the intensity of the received signal is equal between two or more irradiation angles transmitted only by the collection device.

  The transmittance of the electromagnetic wave that has passed through the collection device varies depending on the material of the collection device, the wall structure, the wall thickness, the size of the cell, and the like. For this reason, it is preferable to irradiate a plurality of electromagnetic waves at two or more irradiation angles for each individual collecting device, measure the transmittance of the transmitted electromagnetic waves, and set the coefficients of the plurality of electromagnetic waves for each irradiation angle. .

  In the angle region where the transmittance of the electromagnetic wave transmitted through the collection device is small, the intensity of the received electromagnetic wave is small and the information is scarce, so the amount of collected particulate matter cannot be detected accurately. Therefore, in the complementing means and the complementing process, the transmittance that has transmitted through at least one electromagnetic wave collecting device among the plurality of electromagnetic waves having different frequencies is transmitted through the other electromagnetic wave collecting device among the plurality of electromagnetic waves. The intensity of the electromagnetic wave detected in the angle region smaller than the rate is complemented by the strength of the electromagnetic wave detected in the angle region of other electromagnetic waves. Specifically, for example, a method of employing a value equal to or higher than the intermediate value between the maximum value and the minimum value of the transmittance at two or more irradiation angles of each electromagnetic wave, or the one having the larger transmittance for each irradiation angle There are methods that employ the intensity of electromagnetic waves. In the latter case, selection data for selecting the electromagnetic wave having the highest transmittance among a plurality of electromagnetic waves is prepared in advance for each irradiation angle. Based on the selection data, the intensity of the electromagnetic wave having the highest transmittance is selected from the intensity of the plurality of electromagnetic waves.

  The calculation means or the calculation process is a coefficient set in the setting process to the difference between the intensity of the electromagnetic wave supplemented in the complementing process and the electromagnetic wave blank intensity in the case of only a collecting device in which particulate matter is not collected. To calculate the amount of particulate matter collected. Since the collection device itself often absorbs electromagnetic waves with a frequency of several tens of GHz to several THz to some extent, first measure the reception intensity of only the collection device in the state where particulate matter is not collected as a blank. deep. 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.

  The “electromagnetic wave intensity” may be a transmittance or a reception intensity transmitted through the collection device and received by the receiving means. The transmittance means the ratio of the irradiation intensity irradiated from the irradiation means to the collection device with respect to the reception intensity transmitted through the collection device and received by the reception means.

  Data relating to the calculated amount of collected particulate matter can be reconstructed by computer tomographic images to create two-dimensional and three-dimensional collection distribution information.

  In the exhaust gas purifying apparatus of the present invention, the filter regeneration process can be performed according to the detected PM collection distribution while detecting the PM collection distribution. The exhaust gas purifying apparatus includes means for controlling the temperature of exhaust gas flowing into the filter to be different between the outer periphery and the inner periphery, means for controlling the relationship between the inflow side end face of the filter and the amount of exhaust gas flowing into the filter, and the shaft of the filter It is preferable to further use a means for heating a specific part in the direction. By using these means, it is possible to locally heat a portion with a large collection amount according to the PM collection distribution.

  Water is also an electromagnetic wave 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 practically without any problem. can do.

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

  The collection distribution detection apparatus of this example is a CT apparatus, and a schematic diagram thereof is shown in FIG. As shown in FIG. 1, this device includes a filter 1 used in an exhaust system of a diesel engine, a millimeter wave transmitter 2, a millimeter wave receiver 3, and a calculation device 4.

  The filter 1 corresponds to the collection device according to the present invention, and 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, an inflow side cell, It has a honeycomb-shaped wall flow structure having a porous cell partition wall that partitions outflow side cells and has a large number of pores, and is formed of cordierite. The cell partition of the filter 1 has a thickness of 0.3 mm and forms a square section cell having a side of 1.4 mm. The outer shape of the filter 1 is a cylindrical shape having a diameter of 130 mm. The filter 1 is placed so that the outflow side end surface is in contact with a rotatable sample stage 10.

  The millimeter wave transmitter 2 includes a transmission unit 20, which is disposed on the outer peripheral surface of the filter 1. The transmission unit 20 irradiates millimeter waves toward the peripheral surface of the filter 1.

  The millimeter wave receiver 3 includes a receiving unit 30. The receiving unit 30 is arranged at a position symmetrical to the transmitting unit 20 with respect to the central axis of the filter 1 and receives the microwave transmitted through the filter 1. The transmitter 20 and the receiver 30 can move up and down in the axial direction of the filter 1 while maintaining a horizontal positional relationship in which electromagnetic waves are appropriately transmitted and received. The transmitting unit 20 and the receiving unit 30 are fixed in the vertical direction in the axial direction of the filter 1 while maintaining a positional relationship that is an appropriate receiving position in the horizontal direction. It can be moved up and down.

  A plurality of transmitters 20 and receivers 30 may be provided. In this case, the plurality of transmitters 20 and the plurality of receivers 30 are preferably opposed to each other on a straight line passing through the center of the filter 1 and arranged at equal intervals in the axial direction of the filter. In this case, the movement and detection time of each transmitter and receiver can be shortened, and the three-dimensional information of the collection distribution can be created quickly.

  The collection distribution of PM collected by the collection device is detected using the collection distribution detection device described above.

<Pre-process>
First, as shown in FIGS. 1 and 2, a new filter 1 was placed on the sample stage 10, and a 10 to 260 GHz millimeter wave was irradiated from the transmitter 20 at an input intensity IB. While rotating the sample stage 10, the filter 1 is rotated in the circumferential direction, and the millimeter wave is irradiated from the transmission unit 20 at an equal pitch (for example, every 0.5 °) in the entire circumference (360 °) direction of the filter 1. Then, the receiving unit 30 measures the output intensity IA of the millimeter wave that has passed through the filter 1 in the diameter direction. The ratio of the output intensity IA to the input intensity IB (IA / IB) is obtained, and this is the millimeter wave transmittance.

  The millimeter wave transmittance is shown in FIG. The X axis in FIG. 3 indicates the irradiation angle of the millimeter wave with respect to the filter 1, and the Y axis indicates the frequency of the millimeter wave. On the coordinates, the millimeter wave transmittance is shown. As shown in FIG. 4, the irradiation angle of the millimeter wave with respect to the filter 1 is a reference angle (θ0) (θ = 0 °) when parallel to the cell wall of the filter 1, and clockwise on the paper surface of FIG. This is the angle θ with respect to the reference angle when the irradiation direction is rotated.

  As is apparent from FIG. 3, below 80 GHz, the transmittance was almost constant when the irradiation angle was changed. In the case of 80 GHz or more, the transmittance changed when the irradiation angle was changed. The transmittance changed symmetrically around an irradiation angle of 45 °. Further, the transmittance decreased as the frequency increased. In the range of 80 GHz or more, there were a frequency region where the transmittance was relatively large and a frequency region where the transmittance was small at the same irradiation angle. A combination of two or more frequencies can be selected so that the transmittance of one frequency is large and the transmittance of the other frequency is small at all irradiation angles. For example, there are combinations of 90 GHz and 110 GHz, 120 GHz and 190 GHz, 140 GHz and 180 GHz. This combination of millimeter waves can complement the output intensity IA transmitted through the filter 1 for each irradiation angle. That is, for each irradiation angle, the output intensity of the millimeter wave of one frequency having a small output intensity can be supplemented with the output intensity of the millimeter wave of the other frequency having a large output intensity. In this example, 90 GHz and 110 GHz were selected as a combination of millimeter wave frequencies, and the following collection distribution was detected.

<Selection process>
FIG. 5 shows the results of measuring the transmittance of millimeter waves at 90 GHz and 110 GHz. FIG. 5A shows the transmittance of a 90 GHz millimeter wave, and FIG. 5B shows the transmittance of a 110 GHz millimeter wave. In both figures, the X-axis indicates the irradiation angle with respect to the filter 1, and the Y-axis indicates the millimeter wave transmittance. As shown in FIG. 4, the irradiation angle with respect to the filter 1 is a reference angle (θ0) (θ = 0 °) when parallel to the cell wall of the filter. For the X axis in FIG. 5, the direction of clockwise rotation on the paper surface of FIG. 4 from the position where the irradiation angle is 0 ° is indicated by “+”, and the direction of counterclockwise rotation is indicated by “−”. From the figure, it can be seen that the transmittance for each irradiation angle is different between 90 GHz and 110 GHz. For example, in the vicinity of an angle of 0 °, the 90 GHz millimeter wave shows 60%, while the 110 GHz millimeter wave is as small as 5% or less. Near an angle of ± 23 °, it is as small as 5% or less for 90 GHz millimeter waves and as large as 50% or more for 110 GHz millimeter waves. In this way, the 90 GHz millimeter wave and the 110 GHz millimeter wave have the opposite relationship in transmittance.

  For each irradiation angle, the transmittance of 90 GHz millimeter wave and the transmittance of 110 GHz millimeter wave are compared, and the frequency with the larger transmittance is selected. For each irradiation angle, the selected frequency is stored as selection data. For example, as shown in FIG. 5, when the irradiation angle is around 0 °, the transmittance of 90 GHz millimeter wave is 60%, which is larger than 110 GHz millimeter wave, and the signal detected by 90 GHz millimeter wave is sufficient. It contains much more accurate information on the amount of PM collected. On the other hand, the signal detected by the 110 GHz millimeter wave is too small and does not contain accurate information on the amount of PM trapped. In this case, a signal obtained from a 90 GHz millimeter wave having a high transmittance is selected.

  When the irradiation angle is around 23 °, the transmittance of 90 GHz millimeter waves is 5% or less, which is smaller than the transmittance of 110 GHz millimeter waves. In this case, a signal detected with a millimeter wave of 110 GHz having a high transmittance is selected. In this way, a millimeter wave signal having a larger transmittance is selected for each irradiation angle.

<Setting process>
In addition, a coefficient was obtained for each irradiation angle so that the transmittance for each irradiation angle of millimeter waves of 90 GHz and 110 GHz was constant. For example, as shown by the two-dot chain line in FIG. 5, in order to achieve a transmittance of 50%, the coefficient α1 near the 90 ° angle of 0 ° is 0.8 (= 50% / 60%) and the 110 GHz angle is 0. The coefficient β1 near ° is 10 or more (= 50% / 5% or less), and the coefficient α2 near 90 ° at an angle of 23 ° is 10 or more (= 50% / 5% or less), at an angle of around 110 ° at 110 GHz. The coefficient β2 is 1 or less (= 50% / 50% or more). Find the coefficients α and β for each irradiation angle in the 360 ° direction at 90 GHz and 110 GHz.

<Detection process>
Next, PM is collected by the new filter 1. In steps S51 and S52 in FIG. 2, 90 mm and 110 GHz millimeter waves are applied to the filter 1 that has collected PM to measure transmittance. That is, the filter 1 that has collected PM is placed on the sample stage 10 and 90 GHz and 110 GHz millimeter waves are emitted from the transmitter 20 at the input intensity IB. While rotating the filter 1 in the circumferential direction, the millimeter wave is irradiated from the transmission unit 20 at an equal pitch (for example, every 0.5 °) in the entire circumference (360 °) direction of the filter 1. Then, the millimeter wave transmittance IC transmitted through the filter 1 is measured by the receiving unit 30. The transmittance IC is a ratio of the output intensity output from the filter and received by the receiving unit 30 to the input intensity irradiated from the transmitting unit 20 and input to the filter.

<Complementary process>
For each irradiation angle, a millimeter wave having a high transmittance is adopted among a plurality of millimeter wave transmittances IC (intensity) detected in the detection step. For example, when the irradiation angle is around 0 °, the transmittance of 90 GHz millimeter waves is 60%, the transmittance of 110 GHz millimeter waves is 5% or less, and the transmittance of 90 GHz millimeter waves is 110 GHz millimeter waves. Select the transmittance IC when 90GHz millimeter wave is applied to the filter after PM collection.

  A millimeter wave having a frequency stored as selection data has high transmittance among a plurality of millimeter waves, and thus has high detection accuracy. For this reason, the transmittance IC detected by irradiating the filter after PM collection with millimeter waves having high transmittance is adopted. Moreover, since the thing with a large transmittance | permeability among several millimeter waves differs for every irradiation angle, out of the several millimeter wave transmittance IC (intensity) detected for each irradiation angle, A millimeter wave with a high transmittance is used.

<Calculation process>
In steps S53 and S54, the calculation device 4 uses the millimeter wave transmittance IC adopted in the plurality of millimeter waves and a new filter before PM collection for each irradiation angle. A difference (IC-IA) from the transmittance IA is obtained, and this difference is multiplied by the coefficients α and β for each irradiation angle set in the setting step to obtain a corrected transmittance D. As shown in FIG. 6, when the corrected reference transmittance D0 of the filter 1 where PM is not collected is set to 50%, for example, the corrected transmittance D of the filter 1 where PM is collected is the dotted line in FIG. As shown by, it became smaller than 50%. The difference between the corrected reference transmittance D0 and the corrected transmittance D increased as the amount of PM collected increased. The difference between the corrected reference transmittance D0 and the corrected transmittance D correlates with the amount of collected PM. Thereby, the distribution of the amount of PM collected for each irradiation angle in the 360 ° direction is obtained. Note that it is possible to measure a new DPF filter at a time between DPFs of the same specification.

<Move in Y direction>
FIG. 2 shows a position passing through the center of the radial cross section of the filter 1. The above setting, detection, and interpolation are performed while moving the filter 1 in the Y direction of FIG. 2 from the lower end to the upper end of the DPF in FIG. 2. And each process of calculation is performed, and the amount of PM trapped in the entire circumference (360 °) direction at each position is obtained.

<Reconstruction process>
In step S55, image reconstruction of the computer tomographic image of the filter 1 is performed using the data related to the amount of collected PM calculated in the calculation step. Specifically, image reconstruction of the computer tomographic image of the filter 1 is performed by performing inverse Fourier transform on the position coordinates (X, Y, Z) = (position in the Y direction, irradiation angle, PM collection amount). 2D image information is obtained.

<Three-dimensional process>
While the filter 1 is moved up and down in the axial direction of the filter 1 (Z direction in FIG. 2), the above setting, detection, interpolation, calculation, and reconstruction processes are performed to create a three-dimensional reproduced image.

<Display process>
In step S56, the two-dimensional and three-dimensional images representing the amount of collected PM are displayed on a screen of a display device such as a display.

  In this example, 90 GHz and 110 GHz electromagnetic waves are applied to the filter 1 that collects PM. The transmittances of the electromagnetic waves transmitted through the filter 1 are different from each other for each irradiation angle. For this reason, coefficients α (= α1, α2,...), Β (= β1, β2,...) Are set in advance for each irradiation angle so that the transmittances between two or more irradiation angles are equal to each other. The reference transmittance (blank) between two or more irradiation angles is made equal. The difference (IC-IA) between the transmittance IC of the electromagnetic wave output from the filter 1 collecting PM and the transmittance IA of the electromagnetic wave transmitted through the filter 1 before collecting PM is calculated for each irradiation angle. In addition, by multiplying this difference by the above coefficients α and β, data indicating the distribution of the amount of PM collected collected by the filter 1 can be obtained.

  Further, the electromagnetic waves to be irradiated have different transmittance at each irradiation angle. The detection accuracy is low in the angle region where the transmittance is small. Therefore, the millimeter wave with the higher transmittance is selected from a plurality of millimeter waves for each irradiation angle. Multiple millimeter waves are irradiated to the collection device after PM collection at two or more irradiation angles, and after detecting the intensity of the multiple millimeter waves, the transmittance of the multiple millimeter waves (IC ) Of the millimeter wave with the higher transmittance selected in advance. For this reason, the amount of collection can be detected with high accuracy for each irradiation angle.

1: Filter, 2: Millimeter wave transmitter, 3: Millimeter wave receiver, 4: Computing device, 10: Sample stage, 20: Transmitter, 30: Receiver.

Claims (6)

In the method of detecting the collection distribution of the collected particulate matter in the collection device by irradiating electromagnetic waves from the outside to the collection device in which the particulate matter is collected,
Intensities of the electromagnetic waves transmitted through the collection device by irradiating the collection device with a plurality of electromagnetic waves having different frequencies and different transmittances when irradiated to the collection device. A detection step for detecting
The two or more irradiation angles so that the transmittance of the electromagnetic wave transmitted through the collection device before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. A setting step for setting a coefficient for each of the plurality of electromagnetic waves,
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, A complementing step of complementing with the intensity of the electromagnetic wave detected in the angular region of
For each of the two or more irradiation angles, the difference between the intensity of the electromagnetic wave supplemented in the complementing process and the intensity of the electromagnetic wave transmitted through the collection device before collecting the particulate matter is determined in the setting process. A calculation step of calculating the trapped amount of the particulate matter for each of the two or more irradiation angles by multiplying by a set coefficient;
And a method for detecting the collection amount distribution of particulate matter.   2. The collection amount distribution detection method according to claim 1, wherein two or more of the plurality of electromagnetic waves are selected from frequency regions having different transmittances that pass through the collection device for each irradiation angle.   The supplementing step creates in advance selection data for selecting the electromagnetic wave having the highest transmittance among the plurality of electromagnetic waves for each irradiation angle, and based on the selection data, the intensity of the plurality of electromagnetic waves The collection amount distribution detection method according to claim 1 or 2, wherein the intensity of the electromagnetic wave having the highest transmittance is selected from the list. A plurality of electromagnetic waves having different frequencies and different transmittances when irradiated to the collecting device from the outside of the collecting device in which the particulate matter is collected are applied to the collecting device. Irradiating means for irradiating at an irradiation angle of 2 or more;
Receiving means for detecting the intensity of electromagnetic waves transmitted through the collecting device;
The two or more irradiation angles so that the transmittance of the electromagnetic wave transmitted through the collection device before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. Setting means for setting a coefficient for each of the plurality of electromagnetic waves for each;
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, Complementing means for complementing with the intensity of the electromagnetic wave detected in the angle region,
For each of the two or more irradiation angles, the difference between the intensity of the electromagnetic wave supplemented by the complementing means and the intensity of the electromagnetic wave transmitted through the collection device before collecting the particulate matter is determined in the setting step. A calculation means for calculating the trapped amount of the particulate matter at the irradiation angle of 2 or more by multiplying a set coefficient;
An apparatus for detecting the collection amount distribution of particulate matter.   The irradiation means irradiates the collection device with electromagnetic waves at an equal pitch from all directions of 360 °, and the calculation means calculates the collection amount of the particulate matter in all directions of 360 °. 4. The collection amount distribution detection device according to 4. A 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 plurality of electromagnetic waves having different frequencies and different transmittances when irradiated to the filter are irradiated to the filter from an incident window formed in the storage container at two or more irradiation angles. Irradiation means;
Receiving means for detecting the intensity of the electromagnetic wave transmitted through the filter;
For each of the two or more irradiation angles, the transmittance of the electromagnetic wave transmitted through the filter before collecting the particulate matter with respect to the two or more irradiation angles is equal between the two or more irradiation angles. Setting means for setting a coefficient for each of the plurality of electromagnetic waves;
The intensity of the electromagnetic wave detected in an angular region in which the transmittance of at least one electromagnetic wave of the plurality of electromagnetic waves is smaller than the transmittance of the other electromagnetic waves of the plurality of electromagnetic waves, Complementing means for complementing with the intensity of the electromagnetic wave detected in the angle region,
The difference between the intensity of the electromagnetic wave supplemented by the complementing means and the intensity of the electromagnetic wave transmitted through the filter before collecting the particulate matter is set in the setting step for each of the two or more irradiation angles. Calculating means for calculating the amount of the particulate matter collected at the irradiation angle of 2 or more,
An exhaust gas purification apparatus comprising:

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