JP2011133449A - Particle concentration measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the resistance, when high-temperature exhaust gas flows into a particle concentration measuring device. <P>SOLUTION: A device for measuring particle concentration in exhaust gas flowing through an exhaust line of a diesel engine includes an exhaust gas collection line branched from the exhaust line, and having a smaller channel sectional area than a channel sectional area of the exhaust line; a particle detection filter installed on the exhaust gas collection line; and a differential-pressure detecting unit for detecting the differential pressure generated between an inlet and an outlet of the particle detection filter. The differential-pressure detecting unit is provided separated from the end on the exhaust gas flow downstream side of the particle detection filter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification technology for an internal combustion engine, and more particularly, to a particulate concentration measuring apparatus that measures the concentration of particulates (PM) contained in exhaust gas from a diesel engine.

  Conventionally, as a device for detecting the concentration of particulate matter (PM) mainly containing C (carbon) in exhaust gas of a diesel engine, a conventional particulate concentration measuring device 20PM (PM sensor) of Patent Document 1 shown in FIG. It has been known. This conventional fine particle concentration measuring device 20PM has a sub-exhaust line 21A branched from the exhaust line 21, a fine particle detection filter 22A installed in the sub-exhaust line 21A, and a difference generated between the inlet and the outlet of the fine particle detection filter 22A. A flow rate measuring unit 24 and a temperature measuring unit T1 are provided in the auxiliary exhaust line 21A, and a heater 22H is provided in the particulate detection filter 22A. The flow rate of the auxiliary exhaust line 21 </ b> A is controlled by the flow rate adjustment valve 23.

In the conventional fine particle concentration measuring device 20PM according to Patent Document 1, the differential pressure ΔP before and after the fine particle detection filter 22A, the exhaust gas temperature T in the auxiliary exhaust line 21A, and the exhaust gas flow rate Q2 in the auxiliary exhaust line 21A are measured. . From the measured differential pressure ΔP, exhaust gas temperature T, and exhaust gas flow rate Q2, the mass PM [g / h] of fine particles trapped by the fine particle detection filter per unit time is calculated. From the mass PM [g / h] of the fine particles, the concentration PM _conc [g / m ³ ] of the fine particles in the exhaust gas is calculated. At this time, if a large amount of fine particles accumulates in the fine particle detection filter 22A, the accuracy of detecting the differential pressure decreases. In the fine particle measurement of Patent Document 1, when a certain amount of fine particles accumulate in the fine particle detection filter, the accumulated fine particles are burned and removed by the heater 22H.

Patent Document 1 discloses a particulate particulate filter (DPF) 22 that is provided in an exhaust line 21 and is made of porous ceramics as a conventional exhaust gas purification device 20PM. The auxiliary exhaust line 21A of the conventional particulate concentration measuring device 20PM is connected to the upstream side of the exhaust gas flow of the particulate trapping filter (DPF) 22, and the obtained particulate concentration PM _conc [g / m ³ ] in the exhaust gas is obtained. The mass PM _{enter full filter} [g / h] of the particulates flowing into the particulate trapping filter (DPF) 22 is calculated from the engine operating state or the gas flow rate Q1 flowing into the particulate capturing filter (DPF) 22 in the exhaust line 21. Yes.

  Incidentally, in the particulate trapping filter (DPF) 22, the trapped particulates gradually accumulate with continuous use, as in the particulate detection filter 22A described above. If the deposition of particulates in the particulate trapping filter (DPF) 22 is left unattended, the pressure generated by the exhaust gas becomes excessive, which may lead to deterioration of fuel consumption and engine damage. For this reason, in the exhaust gas purification apparatus using the particulate trapping filter (DPF) 22, accumulated particulates are periodically burned and removed in the particulate trapping filter (DPF) 22 to regenerate the particulate trapping filter 22. Has been done.

  Such regeneration of the particulate trapping filter (DPF) 22 is performed by flowing high-temperature exhaust gas into the particulate trapping filter (DPF) 22. As a result, the accumulated particulates are removed by combustion.

According to Patent Literature 1, the amount of fine particles actually captured by the fine particle capture filter (DPF) 22 is obtained by _obtaining the mass PM _{enter full filter} [g / h] of the fine particles captured by the fine particle capture filter (DPF) 22. However, it is possible to accurately determine whether or not a predetermined threshold value that requires reproduction is exceeded.

EP1916394A1 publication

  However, in the conventional fine particle concentration measuring apparatus 20PM, when the fine particles of the fine particle detection filter 22A are burned, high-temperature gas flows into the differential pressure measuring unit, and in the worst case, the differential pressure cannot be measured. There is a possibility.

  In addition, high-temperature exhaust gas from the diesel engine toward the particulate trapping filter (DPF) 22 may flow into the sub exhaust line 21A and flow into the differential pressure measurement unit 22B.

  An object of the present invention is to improve resistance when a high-temperature exhaust gas flows into a fine particle concentration measuring apparatus.

  According to one aspect, the present invention is an apparatus for measuring the concentration of fine particles in exhaust gas flowing through an exhaust line of a diesel engine, wherein the flow path is branched from the exhaust line and is smaller than the cross-sectional area of the exhaust line. An exhaust gas collection line having a cross-sectional area; a particulate detection filter installed in the exhaust gas collection line; and a differential pressure detection unit that detects a differential pressure generated between an inlet and an outlet of the particulate detection filter. The pressure detection unit provides a fine particle concentration measurement device that is provided apart from an end of the fine particle detection filter on the downstream side of the exhaust gas flow.

  According to the present invention, the differential pressure detector is provided apart from the downstream end of the exhaust gas flow in the particulate detection filter, for example, when particulate accumulated in the particulate detection filter is removed by combustion, or the particulate Even when a high-temperature exhaust gas having a temperature of 600 ° C. or higher flows through the exhaust line during regeneration of the trapping filter, it is possible to reduce the damage of the differential pressure detection unit or being heated to a temperature higher than the heat resistant temperature. Therefore, the fine particle concentration measuring apparatus of the present invention can maintain normal operation.

  In the present invention, the end on the downstream side of the exhaust gas flow in the particulate detection filter refers to the most downstream position of the particulate detection filter where particulates accumulate (see FIGS. 3 and 4).

  According to a preferred embodiment, the differential pressure detector is provided at a distance of 10 cm or more, more preferably 30 cm or more from the branch point. With this configuration, the differential pressure detection unit is not exposed to high-temperature gas, and normal operation can be maintained.

It is a figure which shows the structure of the conventional exhaust gas purification apparatus. It is a figure which shows the exhaust gas purification apparatus containing the fine particle concentration measuring apparatus by 1st Embodiment. It is a figure explaining the effect | action of the particulate detection filter in the particulate concentration measuring apparatus by 1st Embodiment. It is a figure which shows the modification of the microparticle detection filter in the microparticle density | concentration measuring apparatus by 1st Embodiment. It is a figure which shows the structure of the fine particle concentration measuring apparatus by 1st Embodiment in detail. It is a graph which shows the relationship between the distance D from a particulate detection filter downstream end, and exhaust gas temperature in the particulate concentration measuring device by a 1st embodiment. 6 is a graph showing the relationship between the distance D from the downstream end of the particle detection filter and the measurement error in the particle concentration measuring apparatus according to the first embodiment. It is a figure which shows the structure for measuring the true value of the amount of fine particles in the measurement of FIG. It is a figure showing the whole particulate concentration measuring device by a 1st embodiment. It is a figure which shows the modification of the fine particle concentration measuring apparatus by 1st Embodiment. It is a figure which shows the structure of the exhaust gas purification apparatus using the fine particle concentration measuring apparatus by 2nd Embodiment. It is a figure which shows the structure of the modification of the particulate detection filter by 1st Embodiment.

[First Embodiment]
FIG. 2 shows a configuration of an exhaust gas purification apparatus for a diesel engine having a particulate concentration measuring apparatus 40PM (PM sensor) according to the first embodiment of the present invention. However, in FIG. 2, the same reference numerals are given to the parts described above, and the description thereof is omitted. In the particulate concentration measuring apparatus 40PM according to the embodiment of the present invention shown in FIG. 2, an abnormality occurs in the particulate trapping filter (DPF) 22, and the particulates exceed the threshold in the exhaust gas line 21 downstream of the particulate trapping filter (DPF) 22. If it leaks out, it can be used to detect this and give an alarm, such as an alarm, lamp lighting or flashing.

  Referring to the first embodiment of the present invention shown in FIG. 2, an exhaust line 21 of a diesel engine in which a particulate trapping filter (DPF) 22 is arranged has exhaust gas at one end on the downstream side of the particulate trapping filter (DPF) 22. An exhaust gas collection line 41A having a collection unit 41a is connected via the exhaust gas collection unit 41a. The exhaust gas collection line 41A measures the particulate detection filter 42A shown in FIG. 3 and the flow rate Q2 of the exhaust gas collection line. A flow meter 44 is connected in series. The exhaust gas collection line 41A is connected at its downstream end to a portion where the pressure is lower than the inlet of the particulate detection filter 42A, such as a negative pressure tank or an air intake (not shown), for example. The exhaust gas is sucked into the particulate detection filter 42A. This is the same as connecting a suction pump to the downstream side of the exhaust gas collection line 41A, and the exhaust gas can be reliably supplied to the particulate detection filter 42A of the exhaust line 21.

  In addition, the particle detection filter 42A is provided with a temperature measurement unit T1 that measures the temperature of the particle detection filter 42A, and is also provided with a differential pressure measurement unit 42B. The differential pressure measurement unit 42B is provided before and after the particle detection filter 42A. The differential pressure ΔP is measured. The exhaust gas sampling part 41 a has a flow path cross-sectional area smaller than the flow path cross-sectional area of the exhaust gas line 21.

  As the differential pressure measuring section 42B described above, a diaphragm pressure gauge or a known pressure gauge such as a gauge type, bellows type, or thermal type can be used, and the flow rate measuring section 44 can be a hot wire flow meter, A known flow meter such as a venturi flow meter can be used.

  FIG. 3 shows an example of the particulate detection filter 42A in the first embodiment of the present invention. However, in the example of FIG. 3, only a single cell 42b is formed in the particle detection filter 42A. However, as shown in FIG. 12, the particle detection filter 42A has a plurality of cells 42b. Also good. Moreover, a plate-shaped filter may be sufficient. Each cell 42b made of porous ceramic forms a gas passage 42a having one end opened and the other end closed.

In the present embodiment, the particle detection filter 42A as a whole is 5% or less, for example 0.05 to 5%, or 65 ml or less, for example 0.05 to 65 ml, of the total volume of the exhaust gas passage in the particle capturing filter 22 (DPF). state volume or 0.1~1000cm that one or more gas passages 42a having a ^second filter area (preferably filtration area of 1 to 10 cm ^2), is, for example, a rectangular cross-sectional shape, one end is closed (In FIG. 3, the rear is closed).

  Referring to the first embodiment of the present invention shown in FIG. 3, the exhaust gas introduced into the gas passage 42a moves to the adjacent gas passage through the cell wall made of porous ceramic. At that time, fine particles are trapped on the inner wall surface of the cell 42b, and a fine particle layer 42c is formed.

  FIG. 4 shows a modification of the first embodiment of the present invention of the cell 42b of FIG. In the cell shown in FIG. 4, the exhaust gas passes from the outside of the cell through the cell wall and flows into the gas passage 42a inside the cell, and at this time, the particulate layer 42c is deposited on the outer surface of the cell 42b. In the filter of FIG. 12, the cells of FIG. 3 and the cells of FIG. 4 are formed adjacent to each other alternately.

A similar cell is also formed in the conventional particulate trapping filter (DPF) 22 described in FIG. 1, but the outer shape of the gas passage 42a and the cell 42b is not necessarily the gas passage in the particulate trapping filter (DPF) 22. Need not be formed in the same size or the same cross-sectional shape, and may be any shape such as a circle, a quadrangle, an octagon, an ellipse, or the like. Note that the material of the porous ceramic constituting the particulate detection filter 42A (cell 42b) need not be the same as the porous ceramic constituting the particulate capturing filter (DPF) 22, and may not be ceramic. Should. The total volume of the gas passage 42a, 5% of the total volume of the exhaust gas passage in the diesel particulate filter (DPF) in 22 or less, or 65ml or less in volume, or the filtration area (preferably 0.1 - ² 1 to 10 cm ² In the cell 42b, uniform deposition of the particulate layer occurs. Therefore, as will be described below, the particulate deposition amount in the particulate trapping filter (DPF) 22 can be reduced easily and easily. It becomes possible to measure accurately.

  In the fine particle concentration measurement apparatus 40PM according to the first embodiment of the present invention shown in FIG. 2, the accumulated amount of fine particles captured by the fine particle detection filter 42A is calculated by an expression of the following form.

（式１）
ただしΔＰは［Ｐａ］単位で表した差圧を、μは［Ｐａ・ｓ］単位で表した動粘性係数を、Ｑは［m³／ｓ］単位で表した排ガス流量を、αは［ｍ］単位で表したセルの一辺の長さを、ρ［ｇ／ｍ^３］単位で表した排ガス密度を、Ｖtrapは［ｍ³］単位で表したフィルタ体積を、Ｗsは［ｍ］単位で表した壁厚を、Ｋｗは［ｍ^−１］単位で表した壁のガス透過率（パーマビリティ）を、Ｋsootは［ｍ^−１］単位で表した捕捉微粒子層のガス透過率（パーマビリティ）を、Ｗは［ｍ］単位で表した捕捉微粒子層の厚さを、Ｆは係数（＝２８．４５４）を、Ｌは［ｍ］単位で表した有効フィルタ長さを、βは［ｍ^−１］単位で表した多孔質壁のフォルヒハイマー係数を、ζは［Ｐａ］単位で表したフィルタ通過による差圧を表す。

(Formula 1)
Where ΔP is the differential pressure in [Pa] units, μ is the kinematic viscosity coefficient in [Pa · s] units, Q is the exhaust gas flow rate in [m ³ / s] units, and α is [m ] The length of one side of the cell in units, the exhaust gas density in units of ρ [g / m ³ ], Vtrap the filter volume in units of [m ³ ], and Ws in units of [m]. the wall thickness, Kw is [m ^-1] gas permeability expressed wall in units (perm capability), Ksoot the [m ^-1] gas permeability of trapping particulate layer expressed in units of (permanent capability) , W is the thickness of the trapped particulate layer in [m] units, F is the coefficient (= 28.454), L is the effective filter length in [m] units, and β is [m ^−1. ] Represents the Forchheimer coefficient of the porous wall expressed in units, and ζ represents the differential pressure due to passage through the filter expressed in [Pa] units.

Next, the mass m _{soot of} the fine particles captured by the fine particle detection filter 42A (cell 42b) is _expressed by the equation

（式２）
により求められる。ただしｍ_sootは、捕捉された微粒子の質量［ｇ］、Ｎcellsは、入口側セルの開口数、ρ_sootは、捕捉された微粒子の密度である。

(Formula 2)
Is required. Where m _soot is the mass [g] of the captured fine particles, Ncells is the numerical aperture of the inlet side cell, and ρ _soot is the density of the captured fine particles.

Then, by _dividing m _soot by the elapsed time [s] from the previous regeneration of the fine particle detection filter 42A, the trap amount PM [g / s] per unit time can be obtained.

When the mass PM [g / s] of the fine particles deposited per unit time is obtained in this way, the fine particle concentration PMconc [g / m ³ ] in the exhaust gas passes through the fine particle detection filter 42A and the exhaust gas flow rate Q2 [m]. ³ / s]
PM [g / s] = PMconc [g / m ³ ] × Q2 [m ³ / s] (Formula 3)
Is required.

  As shown in FIG. 2 of the first embodiment of the present invention, by arranging such a particulate concentration measuring device 40PM on the downstream side of the particulate trapping filter (DPF) 22, the particulate trapping filter (DPF) 22 is abnormal. In the present embodiment, when the particulate matter leaks in the exhaust line 21 to the downstream side of the particulate trapping filter (DPF) 22 beyond the threshold value, according to the present embodiment, such an abnormality is immediately detected and an alarm or a lamp is turned on or blinked. Etc. can be issued.

  By the way, in the diesel engine system equipped with the exhaust gas purifying apparatus of the first embodiment of the present invention shown in FIG. 2 as described above, the particulates deposited on the particulate trapping filter (DPF) 22 are heated at a high temperature. Combusted and removed by exhaust gas. As a result of the combustion of the fine particles, a large amount of high-temperature gas of generally 600 ° C. to 700 ° C. is generally generated and may flow into the exhaust gas collection line 41A. Further, even when the particulates accumulated in the particulate detection filter 42A are burned and removed by the heater, the high-temperature exhaust gas flows through the exhaust gas collection line 41A. At this time, the thin film and the strain sensor of the diaphragm pressure gauge used as the differential pressure detector 42B are damaged by the heat of the high-temperature exhaust gas, or the operation becomes inaccurate, and the reliability of the fine particle concentration measurement result is impaired. There is a fear.

  For this reason, in the present embodiment, the differential pressure detection unit 42B is separated by a distance D from the downstream end of the exhaust gas flow in the particulate detection filter 42A as shown in the first embodiment of the present invention in FIG. Are arranged.

  Referring to FIG. 5 which is the first embodiment of the present invention, the particulate detection filter 42A is housed in a housing 42E, one end of which constitutes the exhaust gas collection part 41a and is continuous with the exhaust gas collection line 41A. The diaphragm pressure gauge constituting the detection unit 42B is formed at a position D at a distance measured from the inner wall surface of the downstream end of the particulate detection filter. One end of the differential pressure detection unit 42B is connected to the upstream side of the particulate detection filter 42A, and the other end is connected to the exhaust gas collection line 41A on the downstream side of the particulate detection filter 42A. As a result, the differential pressure detection unit 42B Can measure the differential pressure across the cell 42b constituting the particulate detection filter 42A.

  FIG. 6 shows a graph of the relationship between the distance D from the downstream end of the particulate detection filter of the first embodiment of the present invention and the exhaust gas temperature. In this experiment, 10 g / L of fine particles were deposited on the fine particle detection filter 42A of the fine particle concentration measuring apparatus 40PM of FIG. 2A, and the fine particle detection filter 42A was heated to 650 ° C. by a heater to burn the fine particles. The relationship between the temperature of the differential pressure measuring unit 42B and the distance D at this time is shown in the graph of FIG.

  Referring to the graph of FIG. 6 according to the first embodiment of the present invention, when the distance D is less than 10 cm, the temperature of the differential pressure detector 22B exceeds about 120 ° C. From this, as the differential pressure detector 42B, It can be seen that when a pressure gauge having a heat resistance of about 120 ° C. or lower is used, the distance D needs to be set to 10 cm or more in order to avoid damage to the pressure gauge.

  Thus, the temperature of the exhaust gas tends to decrease as the differential pressure measurement unit is separated from the end. On the other hand, if the differential pressure detection unit 42B is arranged far away from the downstream end of the particulate detection filter 42A, the measurement error tends to increase in the differential pressure measurement. For accurate differential pressure measurement, the differential pressure detector 42B is preferably as close to the particulate detection filter 42A as possible.

  The results of Table 1 below and the graph of FIG. 7 show the results of determining the measurement error of the fine particle concentration measurement apparatus 40PM according to the embodiment of the present invention when the distance D is variously changed.

  In the results of Table 1, the measurement error was determined by the formulas (1) to (3) with the actual measurement value (described later) of the fine particles in the exhaust line 21 in the configuration of the first embodiment of the present invention shown in FIG. The deviation of the fine particle concentration from this true value is obtained as a measurement error.

  As shown in the configuration of the fine particle concentration measuring apparatus according to the first embodiment of the present invention in FIG. 8, the exhaust gas discharged from the diesel engine 11 to the exhaust line 21 is guided to the dilution tunnel 111 into which clean air is introduced. Diluted and cooled to a temperature of 52 ° C. or lower, collected on the primary collection filter 115 and the secondary collection filter 116, and measured the mass with a microbalance to directly measure the amount of fine particles in the exhaust gas. This was converted to the concentration in the exhaust line 21 and this was taken as the true value. The measurement error is obtained by comparing the calculated value (PMconc) of the particulate concentration detector 40PM provided in the same exhaust line 21 with the true value. The distance between the diesel engine 11 and the fine particle concentration detection device 40PM is 1.5 to 2.0 m. In the configuration of the particulate concentration detection device 40PM according to the first embodiment of the present invention shown in FIG. 8, after passing through the dilution tunnel 111, the exhaust gas is sucked by the blower 114 through the heat exchanger 112 and the critical flow venturi tube 113. The A blower 117 is also provided on the downstream side of the primary collection filter 115 and the secondary collection filter, and sucks exhaust gas.

表１の結果および図７のグラフを参照するに、距離Ｄを１０ｃｍ〜２００ｃｍの範囲とした実施例１〜実施例５では測定誤差は±１０％以下であるのに対し、距離Ｄを５ｃｍとした比較例１では、差圧検知部４２Ｂを構成するダイヤフラム圧力計が溶損してしまっているのがわかる。一方距離Ｄを、２００ｃｍを超えて延ばしてしまうと、微粒子濃度測定装置４０ＰＭの測定誤差が±１０％を超えてしまうことがわかる。

Referring to the results of Table 1 and the graph of FIG. 7, in Examples 1 to 5 where the distance D is in the range of 10 cm to 200 cm, the measurement error is ± 10% or less, whereas the distance D is 5 cm. In the comparative example 1, it can be seen that the diaphragm pressure gauge constituting the differential pressure detector 42B has melted. On the other hand, if the distance D is extended beyond 200 cm, it can be seen that the measurement error of the fine particle concentration measuring device 40PM exceeds ± 10%.

  From the above knowledge, in the fine particle concentration measurement apparatus 40PM according to the present embodiment, when the one having a heat resistant temperature of 120 ° C. or less is used, the distance D is preferably set to 10 cm or more and 200 cm or less, preferably 50 cm or less.

  9 is inserted into the exhaust line 21 of the exhaust gas purification apparatus of the first embodiment of the present invention shown in FIG. 2 on the downstream side of the particulate trapping filter (DPF) 22. The particle concentration measuring device 40PM includes a pipe-shaped housing 42E, a flexible hose 42F, and a control unit 42G that form a fixed head portion 42e.

  A flexible hose 42F through which exhaust gas passes extends from the housing 42E as shown in the particulate concentration measuring apparatus 40PM of this embodiment in FIG. 9, and a differential pressure measuring unit 42B is provided at the downstream end of the flexible hose 42F. And the control unit 42G which stored the flow measurement part 44 is formed. The exhaust gas that has passed through the control unit 42G is discharged to the exhaust pipe 42g. For example, a particulate detection filter 42A made of a porous ceramic such as SiC (silicon carbide) is disposed in a housing 42E made of a heat-resistant metal such as stainless steel. Here, the head portion 42 e constitutes a part of the exhaust gas collection line inserted into the exhaust line 21.

  According to such a configuration, the desired particle concentration measuring device 40PM can be configured in a small size, and as a result, the particle concentration measuring device can be attached to any part of the vehicle as required.

  FIG. 10 shows a modification of the fine particle concentration measuring apparatus 40PM of FIG. In the configuration of the particulate concentration measuring device 40PM of the present invention shown in FIG. 9, a pump 42P may be connected to an exhaust pipe 42g that exhausts exhaust gas from the flow rate control unit 42G to exhaust exhaust gas forcibly. In such a configuration, even if the head portion 42e is stationary, that is, provided in an exhaust gas atmosphere without a flow, the exhaust gas is sucked in by the negative pressure generated by the pump 42P, and a desired fine particle concentration measurement can be performed. .

  Further, the exhaust gas collection line 41A is preferably provided with a heat dissipation structure between the downstream end of the exhaust gas flow in the particulate detection filter 42A and the differential pressure detection unit 42B. The reason is that high-temperature exhaust gas does not easily enter the differential pressure detector, and therefore, it is not necessary to use heat-resistant parts. In addition, the distance between the particulate detection filter and the differential pressure detection unit can be shortened.

[Second Embodiment]
FIG. 11 shows the configuration of an exhaust gas purification device 60 for a diesel engine having a particulate concentration measuring device 60PM (PM sensor) according to the second embodiment of the present invention.

  Referring to the particulate concentration measuring device 60PM according to the second embodiment of the present invention shown in FIG. 11, the exhaust gas purification device 60 has a configuration similar to that of the exhaust gas purification device 20 shown in FIG. DPF) 22 has an exhaust gas collection line 41A branched on the upstream side. However, in FIG. 11, the same reference numerals are assigned to the portions corresponding to the portions described above, and the description thereof is omitted.

  In the configuration of the particle concentration measuring device 60PM according to the second embodiment of the present invention shown in FIG. 11, the exhaust gas that has not passed through the particle trapping filter 22 is captured by the particle detection filter 42A, and the particulates captured by the particle detection filter 42A are collected. Based on the amount, the following processing is performed in addition to the above formulas (1) to (3).

The particulate concentration PMconc in the exhaust gas is the same both in the exhaust gas collection line 41A and in the exhaust gas line 21, and therefore the amount of particulate passing through the exhaust gas line 21 (PM enter full filter [g / h]) is
PM enter full filter [g / h] = PMconc [g / m ³ ] × Q1 [m ³ / h]
(Formula 4)
Is required. Here, Q1 represents the exhaust gas flow rate of the exhaust gas line 21.

  Thereby, the amount of fine particles accumulated in the fine particle trapping filter (DPF) 22 can be estimated. Where Q1 is the flow rate of exhaust gas passing through the particulate trapping filter (DPF) 22. Q1 may be obtained by actual measurement or may be estimated from the operating state of the engine.

  In the configuration of the particulate concentration measuring device 60PM according to the second embodiment of the present invention shown in FIG. 11, a valve 43 is further provided in the exhaust gas collection line 41A, and the valve 43 is the same as that of the conventional exhaust gas purification device 20 shown in FIG. Similarly, it is controlled by the flow meter 44, and the exhaust gas flow rate in the exhaust gas sampling line 41A is controlled to a predetermined value Q2.

  On the other hand, in such a configuration, the particulate detection filter 42A is regenerated because particulates accumulate in the particulate detection filter 42A over time.

  Therefore, in the present embodiment, the heater 42h is formed on the particulate detection filter 42A (cell 42b), and the heater 42h is driven as necessary by electric power from a drive line (not shown), whereby the cell 42b. The particulates mainly composed of carbon (C) trapped in are burned to regenerate the particulate detection filter 42A.

  Also in the second embodiment of the present invention, the same effects as in the first embodiment can be exhibited.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope described in the claims. For example, the flow rate measurement unit in the above embodiment can be eliminated if the flow rate flowing through the exhaust gas collection line is known in advance. Further, the temperature measuring unit may be eliminated if the exhaust gas characteristics are considered constant. Furthermore, the heater in the second embodiment may be eliminated if there is no need for regeneration processing. Furthermore, if the flow rate is accurately measured, the valve can be eliminated. Further, the heater described in the second embodiment may be arranged in the fine particle concentration measuring apparatus of the first embodiment.

  As mentioned above, although this invention was described about preferable embodiment, this invention is not limited to this specific embodiment, A various deformation | transformation and change are possible within the summary described in the claim.

DESCRIPTION OF SYMBOLS 11 Diesel engine 20 Exhaust gas purification apparatus 20PM, 40PM Particulate concentration measuring device 21 Exhaust line 21A Sub exhaust line 22 Particulate capture filter 22A, 42A Particulate detection filter 22B, 42B Differential pressure measurement part 22H Heater 23, 43 Flow control valve 24, 44 Flow rate Measurement part 41A Exhaust gas collection line 41a Exhaust gas collection part 42E Housing 42F Flexible hose 42G Control unit 42P Pump 42a Exhaust gas passage 42b Cell 42c Particulate layer 42e Head part 42g Exhaust pipe 60PM Particulate concentration measuring device 111 Dilution tunnel 112 Heat exchanger 113 Critical Flow venturi 114, 117 Blower 115 Primary collection filter 116 Secondary collection filter T1, T2 Temperature measurement unit

Claims (13)

An apparatus for measuring the concentration of fine particles in exhaust gas flowing through an exhaust line of a diesel engine,
An exhaust gas collection line branched from the exhaust line and having a flow passage cross-sectional area smaller than the flow passage cross-sectional area of the exhaust line;
A particulate detection filter installed in the exhaust gas collection line;
A differential pressure detector that detects a differential pressure generated between an inlet and an outlet of the particulate detection filter,
The said differential pressure | voltage detection part is a fine particle concentration measurement apparatus spaced apart from the edge part of the exhaust gas flow downstream in the said fine particle detection filter. 2. The fine particle concentration measuring apparatus according to claim 1, wherein the differential pressure detector is provided at a distance of 10 cm or more from the end. The fine particle concentration measurement apparatus according to claim 1, wherein the differential pressure detection unit is provided at a distance of 200 cm or less from the end portion. The fine particle concentration measurement apparatus according to claim 3, wherein the differential pressure detection unit is provided at a distance of 50 cm or less from the end. 5. The fine particle concentration measurement apparatus according to claim 1, wherein the differential pressure detection unit uses a material having a heat resistance of 120 ° C. or less as a pressure detection material. The fine particle concentration measuring device according to any one of claims 1 to 4, wherein the exhaust gas collecting line is provided with a heat dissipation structure between the end portion and the differential pressure detecting portion. The fine particle concentration measurement apparatus according to any one of claims 1 to 6, further comprising a flow rate measurement unit that is inserted into the exhaust gas collection line and measures an exhaust gas flow rate in the exhaust gas collection line. A flow control valve that is inserted into the exhaust gas collection line and controls an exhaust gas flow rate in the exhaust gas collection line; and the flow control valve is controlled based on the exhaust gas flow rate measured by the flow measurement unit, and the exhaust gas The fine particle concentration measuring device according to claim 7, further comprising a control device that controls the exhaust gas flow rate in the collection line to a predetermined value. The particulate concentration measuring apparatus according to any one of claims 1 to 8, wherein a downstream side of the exhaust gas flow of the particulate detection filter is connected to a negative pressure portion. The fine particle concentration measuring apparatus according to any one of claims 1 to 7, further comprising a pump disposed downstream of the exhaust gas flow of the fine particle detection filter. The particulate concentration measuring device according to any one of claims 1 to 10, wherein a particulate capturing filter having a filter volume larger than that of the particulate detecting sensor is disposed in the exhaust line. The particulate concentration measuring apparatus according to any one of claims 1 to 11, wherein the exhaust gas collecting line is connected to a downstream side of the particulate trapping filter in the exhaust line. The particulate concentration measuring device according to any one of claims 1 to 11, wherein the exhaust gas collecting line is connected to an upstream side of the particulate trapping filter in the exhaust line.

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