JP2012246778A - Pm sensor - Google Patents

Abstract

There is provided a PM sensor capable of detecting an average PM deposition amount of the entire DPF and ensuring a sufficiently large capacitance for detection.
A first electrode 6 made of an electrode plate covering the DPF 3 along the outer periphery of the DPF 3 and a plurality of cells 2 along a closed curve that is located on the inner periphery of the first electrode 6 and surrounds the center of the DPF 3. A second electrode 7 composed of a plurality of inserted electric wires, and a second electrode composed of a plurality of electric wires inserted into the plurality of cells 2 along a closed curve located on the inner periphery of the second electrode 7 and surrounding the center of the DPF 3. The third electrode 8 is provided, the first electrode 6 and the third electrode 8 are the one-side electrode 4 of the capacitor, and the second electrode 7 is the opposite-side electrode 5 of the capacitor.
[Selection] Figure 1

Description

  The present invention relates to a PM sensor that can detect an average amount of PM deposited in the entire DPF, and can secure a sufficient capacitance for detection.

  In a vehicle equipped with an internal combustion engine such as a diesel engine, a diesel particulate filter (hereinafter referred to as DPF) is installed in an exhaust gas exhaust flow path from the internal combustion engine to the atmosphere, and particulate matter ( Particulate Matter (hereinafter referred to as PM) is collected. The DPF is a member that temporarily collects PM in a honeycomb pore filter made of porous ceramic.

  When the amount of PM collected in the DPF (hereinafter referred to as PM accumulation amount) increases, the exhaust pressure of the internal combustion engine rises and the characteristics of the internal combustion engine deteriorate, so the process of burning the collected PM is performed. Is called. This process is called DPF regeneration. During the DPF regeneration, fuel injection for increasing the exhaust temperature is performed. When the exhaust gas temperature rises, the DPF is heated up and the PM collected in the DPF burns.

  At this time, if the amount of accumulated PM is too large, the DPF is damaged by the heat during DPF regeneration. In order to regenerate the DPF before the PM accumulation amount becomes too large, it is necessary to accurately detect the PM accumulation amount.

  As a PM sensor for detecting the PM deposition amount, there is known a sensor in which two electrodes are installed in the DPF and the PM deposition amount is detected from the capacitance of a capacitor formed by the two electrodes. In this type of PM sensor, PM, which is a mixture of a dielectric and a conductor, is deposited between the electrodes, so that the capacitance increases linearly with respect to the amount of PM deposited.

  The conventional PM sensor 91 shown in FIG. 9 has two electrodes 93 and 94 formed in a half-cylindrical shape on the outer periphery of a columnar DPF 92. When the two electrodes 93 and 94 face each other with the DPF 92 interposed therebetween, the capacitance of the capacitor formed by the two electrodes 93 and 94 changes according to the total amount of PM deposited on the DPF 92 (Patent Document 1).

  In the conventional PM sensor 101 shown in FIG. 10, one electrode 103 is installed on the outer periphery of a cylindrical DPF 102, and the other electrode 104 is installed concentrically on the inner side. The capacitance of the capacitor formed by the two electrodes 103 and 104 changes according to the amount of PM deposited on a part of the DPF 102 sandwiched between the two electrodes 103 and 104 (Patent Document 2).

JP 2010-144630 A JP 2011-012577 A

  In the PM sensor 91 of FIG. 9, two electrodes 93 and 94 are installed on the outer periphery of the DPF 92 and face each other. However, since the diameter of the DPF 92 is about 200 mm, the capacitor using the two electrodes 93 and 94 has a large distance between the electrodes and a very small capacitance, which is practical for accurately detecting the PM deposition amount. Not.

  In the PM sensor 101 of FIG. 10, one electrode 103 is installed on the outer periphery of the DPF 102, and the other electrode 104 is installed on the inner side. Also in this case, if the inner electrode 104 is too far from the outer electrode 103, the capacitance of the capacitor becomes very small, which is not practical for accurately detecting the PM deposition amount.

  The PM sensor 91 of FIG. 9 cannot shorten the distance between the electrodes, but the PM sensor 101 of FIG. 10 can shorten the distance between the electrodes by bringing the inner electrode 104 closer to the outer periphery.

  However, when the exhaust gas temperature rises during DPF regeneration, the temperature rise of the DPF is not uniform in the radial direction, and even if the central portion of the DPF becomes high temperature, the peripheral portion is deprived of heat and remains at a low temperature. The combustion temperature of PM is not reached.

  For this reason, PM is burned well in the central portion of the DPF during DPF regeneration, but PM hardly burns in the peripheral portion, and the PM that has once accumulated remains without being burned even by DPF regeneration.

  In this way, PM continues to remain even when DPF regeneration is performed in the peripheral portion. Therefore, when the inner electrode 104 is brought closer to the outer periphery in the PM sensor 101 of FIG. 10, the remaining PM is mainly detected. As a result, the PM in the central portion deposited or removed is not detected. That is, the PM sensor 101 cannot detect the average PM deposition amount of the entire DPF.

  Accordingly, an object of the present invention is to provide a PM sensor that solves the above-described problems, can detect the average amount of PM deposited in the entire DPF, and can secure a sufficiently large capacitance for detection. .

  In order to achieve the above object, the PM sensor of the present invention is formed by a plurality of electrodes provided in a diesel particulate filter (hereinafter referred to as DPF) in which a plurality of cells are stacked vertically and horizontally. In a PM sensor in which the amount of particulate matter (hereinafter referred to as PM) deposited on the DPF is detected by the capacitance of a capacitor, a first electrode made of an electrode plate covering the DPF along the outer periphery of the DPF; A second electrode composed of a plurality of electric wires inserted in a plurality of cells along a closed curve located on the inner circumference from the first electrode and surrounding the center of the DPF; and located on the inner circumference from the second electrode And a third electrode composed of a plurality of electric wires inserted into a plurality of cells along a closed curve surrounding the center of the DPF, and the first electrode and the third electrode are the capacitors One-sided electrode, but the second number electrodes are opposite electrodes of the capacitor.

  A fourth electrode composed of a plurality of electric wires inserted into a plurality of cells along a closed curve located on the inner periphery of the third electrode and surrounding the center of the DPF, and the fourth electrode of the capacitor The opposite electrode may be used.

  The odd-numbered electrode and the even-numbered electrode are alternately provided with a plurality of electric wires inserted into a plurality of cells along a closed curve sequentially located on the inner circumference from the fourth electrode, and the odd-numbered electrode is one side electrode of the capacitor The even-numbered electrode may be the opposite electrode of the capacitor.

  The present invention exhibits the following excellent effects.

  (1) The average PM deposition amount of the entire DPF can be detected.

  (2) A sufficient capacitance can be secured for detection.

It is an end view of DPF to which PM sensor showing one embodiment of the present invention was attached. It is a perspective view of DPF of FIG. It is a partial end elevation of DPF to which the present invention is applied. It is a partial sectional side view of DPF to which the present invention is applied. FIG. 2 is a partial end view of the DPF in FIG. 1. FIG. 2 is a partial end view of the DPF in FIG. 1. It is an end view of DPF with which PM sensor showing other embodiments of the present invention was attached. It is an end view of DPF with which PM sensor showing other embodiments of the present invention was attached. It is a perspective view of the conventional PM sensor. It is a perspective view of the conventional PM sensor.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIGS. 1 and 2, the PM sensor 1 according to the present invention is provided with a plurality of electrodes 4 and 5 on a DPF 3 in which a plurality of cells 2 (see FIGS. 5 and 6) are stacked vertically and horizontally. In the PM sensor in which the PM deposition amount of the DPF 3 is detected by the capacitance of the capacitor formed by the plurality of electrodes 4 and 5, the first electrode 6 made of an electrode plate covering the DPF 3 along the outer periphery of the DPF 3, A second electrode 7 consisting of a plurality of electric wires inserted into a plurality of cells 2 along a closed curve that is located on the inner circumference from the first electrode 6 and surrounds the center of the DPF 3, and on the inner circumference from the second electrode 7 And a third electrode 8 composed of a plurality of electric wires inserted into the plurality of cells 2 along a closed curve surrounding the center of the DPF 3, and the first electrode 6 and the third electrode 8 are provided on the capacitor. One side electrode 4 and the second electrode 7 Those which are opposite electrode 5 of the capacitor.

  The one side electrode 4 composed of the first electrode 6 and the third electrode 8 and the opposite side electrode 5 composed of the second electrode 7 are respectively connected to a detection circuit (not shown). Since the detection circuit is the same as the conventional one, the description thereof is omitted.

  Here, the structure and function of the DPF will be described as the basis of the present invention.

  As shown in FIG. 3, the DPF 3 is formed by stacking a plurality of cells 2 vertically and horizontally surrounded by walls 9 made of a porous material vertically and horizontally, and sealing the end surfaces of the cells 2 vertically and horizontally. In the figure, the sealing is indicated by hatching. The sealed cell 2 is referred to as a sealed cell 2a, and the unsealed cell is referred to as an open cell 2b. As shown in the drawing, both vertical and horizontal neighbors of the sealed cell 2a are open cells 2b, and both vertical and horizontal neighbors of the open cell 2b are sealed cells 2a. The end face shape of the cell 2 is a square here, but may be any shape that can be continuously arranged, such as a rectangle or a parallelogram.

  Sealing and opening are reversed between the one end face and the opposite end face. That is, in one cell 2, if one end face is sealed, the opposite end face is always open, and if one end face is open, the opposite end face is always sealed. Therefore, when the same cell 2 is viewed from one side, it becomes a sealed cell 2a, and when viewed from the opposite side, it becomes an open cell 2b.

  As shown in FIG. 4, the DPF 3 is installed in the exhaust gas discharge flow path, and one end face is desired upstream and the opposite end face is desired downstream. On the upstream side, exhaust gas does not flow into the sealing cell 2a, but exhaust gas flows only into the open cell 2b. Since the open cell 2b into which the exhaust gas has flowed is sealed at the opposite end face desired downstream to become a sealed cell 2a, the exhaust gas passes through the wall 9 made of a porous material and is adjacent to the sealed cell 2a. Move to. The adjacent sealing cell 2a has an open cell 2b that is open at the opposite end face desired downstream, so that the exhaust gas flows out from the open cell 2b. In this way, when exhaust gas passes through the wall 9, PM in the exhaust gas is adsorbed on the wall 9 made of the porous material. In FIG. 4, it is shown that the exhaust gas flowing into one open cell 2b moves to two adjacent sealing cells 2a, but actually the exhaust gas flowing into one open cell 2b is adjacent vertically and horizontally. Since it moves to the four sealing cells 2a, PM is adsorbed on the four walls 9 in the vertical and horizontal directions.

  In the PM sensor 1 of the present invention, an electric wire is inserted into the cell 2 at a position along an appropriate closed curve in order to form a concentric electrode inside the DPF 3 having a honeycomb pore structure as shown in FIG. Specifically, as shown in FIG. 5 and FIG. 6, electric wires (indicated by black circles) serving as the second and subsequent electrodes are inserted into a plurality of open cells 2 b belonging to a specific pattern among all the open cells 2 b. Is done. The electric wire inserted into the open cell 2b is, for example, a metal wire.

  The depth at which the electric wire is inserted from the end face is arbitrary, but as the wire is inserted deeper, the electrode length becomes longer, which contributes to an increase in the electrode facing area. Therefore, for example, it is preferable that the electric wire reaches near the place where the opposite end face of the open cell 2b is sealed.

  The end face into which the electric wire is inserted may be the end face desired upstream of the exhaust gas discharge passage or the end face desired downstream, but the electric wire of the second electrode 7 and the electric wire of the third electrode 8 are inserted into the same end face. The

  In the pattern of FIG. 5, an electric wire is inserted into the plurality of open cells 2b arranged in a diagonal line. In the pattern of FIG. 6, an electric wire is inserted into the plurality of open cells 2b arranged in a line in the vertical direction. Although not shown, there is also a pattern in which electric wires are inserted into a plurality of open cells 2b arranged in a line in the horizontal direction, as in the pattern of FIG. There is also a pattern in which electric wires are inserted into a plurality of open cells 2b arranged in a diagonal line orthogonal to the pattern of FIG. These patterns can be combined to form an octagonal closed curve as seen in the second electrode 7 and the third electrode 8 of FIG. The closed curve may be quadrangular or hexagonal like the third electrode 8 in FIG.

  The electric wires inserted into the open cells 2b in one row are short-circuited by the short-circuit wire 10. Similarly, the electric wires inserted into another row of open cells 2 b are short-circuited by another short-circuit line 11. In this way, the plurality of electric wires inserted into the plurality of open cells 2b are short-circuited by the short-circuit wires 10 and 11 for each column, so that the second electrode 7 and the third electrode 8 shown in FIG. Is formed.

  In the pattern of FIG. 5, the distance between one row of open cells 2b into which electric wires are inserted and another row (the interval between short-circuit wire 10 and short-circuit wire 11) is the number of open cells 2b into which no electric wires are inserted as viewed in the diagonal direction. It is assumed that it is pinched. In the illustrated example, three open cells 2b are sandwiched, but may be two or four or more. In the pattern of FIG. 6, the distance between one row of open cells 2b into which electric wires are inserted and another row (the interval between short-circuit wire 10 and short-circuit wire 11) is the number of open cells 2b into which electric wires are not inserted as viewed in the horizontal direction. It is assumed that it is pinched. In the illustrated example, two open cells 2b are sandwiched, but three or more may be used.

  Hereinafter, the operation of the PM sensor 1 of the present invention will be described.

  As shown in FIG. 1, the PM sensor 1 has a first electrode 6 made of an electrode plate covering the DPF 3 along the outer periphery of the DPF 3, and is positioned on the inner periphery of the first electrode 6 and surrounds the center of the DPF 3. A second electrode 7 composed of a plurality of electric wires inserted into the plurality of cells 2 along the closed curve, and a plurality of cells 2 along the closed curve that is located on the inner periphery of the second electrode 7 and surrounds the center of the DPF 3. And a third electrode 8 made of a plurality of inserted electric wires. Therefore, a capacitor having the first electrode 6 and the third electrode 8 as the one-side electrode 4 and the second electrode 7 as the opposite electrode 5 has a concentric triple cylindrical shape having a predetermined inter-electrode distance and an electrode facing area. It can be regarded as a capacitor consisting of the electrode plate.

  When PM is deposited on the DPF 3, the amount of PM deposited on the wall of the cell 2 between the one-side electrode 4 and the opposite-side electrode 5 increases. Therefore, the capacitance of the capacitor composed of the one-side electrode 4 and the opposite-side electrode 5 increases.

  At this time, in the PM sensor 1 of the present invention, there are two one-side electrodes 4 for one opposite electrode 5, and therefore only the outer peripheral electrode 103 and the inner electrode 104 are formed as in the PM sensor 101 of FIG. Capacitance is larger than that of the capacitor, and the amount of deposited PM can be accurately detected.

  Further, in the PM sensor 1 of the present invention, unlike the PM sensor 101, the third electrode 8, which is one of the one-side electrodes 4, is different from the arrangement in which the electrodes 103 and 104 are biased near the outer periphery of the DPF 102. 7, the average PM deposition amount of the entire DPF 3 can be detected.

  Next, another embodiment of the present invention will be described.

  As shown in FIG. 7, in addition to the configuration of the PM sensor 1, the PM sensor 71 of the present invention includes a plurality of cells 2 along a closed curve that is located on the inner periphery of the third electrode 8 and surrounds the center of the DPF 3. The 4th electrode 12 which consists of a plurality of electric wires inserted in is provided. Since the fourth electrode 12 becomes the opposite electrode 5, a capacitor formed of a concentric quadruple cylindrical electrode plate is formed, and the capacitance is larger than that of the PM sensor 1, so that the PM deposition amount is accurately detected. In addition, it is possible to detect the average PM deposition amount of the entire DPF 3. In particular, in the illustrated example, since the fourth electrode 12 is positioned substantially at the center of the DPF 3, the PM deposition amount in the entire range from the outer periphery to the center of the DPF 3 can be detected. Note that the electric wire of the fourth electrode 12 is inserted into the cell 2 along a straight line, not a closed curve, because it is not necessary to provide an electrode inside the fourth electrode 12.

  As shown in FIG. 8, in addition to the configuration of the PM sensor 71, the PM sensor 81 according to the present invention includes a plurality of PM sensors 81 inserted into the plurality of cells 2 along a closed curve sequentially located on the inner circumference from the fourth electrode 12. 1 to a plurality of odd-numbered electrodes 13 and one to a plurality of even-numbered electrodes 14 are alternately provided. The odd-numbered electrode 13 becomes the one-side electrode 4 and the even-numbered electrode 14 becomes the opposite-side electrode 5, thereby forming a capacitor composed of concentric multiple cylindrical electrode plates. Since this capacitor has a very large total electrode facing area and a short distance between the electrodes, the capacitance is larger than that of the PM sensor 71.

1 PM Sensor 2 Cell 2a Sealing Cell 2b Open Cell 3 Diesel Particulate Filter (DPF)
4 One side electrode 5 Opposite side electrode 6 1st electrode 7 2nd electrode 8 3rd electrode 12 4th electrode

Claims (3)

A diesel particulate filter (hereinafter referred to as DPF) in which a plurality of cells are stacked vertically and horizontally is provided with a plurality of electrodes, and the particulate matter of the DPF (hereinafter referred to as the DPF) due to the capacitance of a capacitor formed by the plurality of electrodes. PM sensor) in which the accumulated amount of PM is detected,
A first electrode comprising an electrode plate covering the DPF along the outer periphery of the DPF;
A second electrode consisting of a plurality of electric wires inserted into a plurality of cells along a closed curve located on the inner periphery of the first electrode and surrounding the center of the DPF;
A third electrode consisting of a plurality of electric wires inserted into a plurality of cells along a closed curve located on the inner circumference from the second electrode and surrounding the center of the DPF;
The PM sensor, wherein the first electrode and the third electrode are one side electrodes of the capacitor, and the second electrode is an opposite electrode of the capacitor. A fourth electrode composed of a plurality of electric wires inserted in a plurality of cells along a closed curve located on the inner periphery of the third electrode and surrounding the center of the DPF;
The PM sensor according to claim 1, wherein the fourth electrode is an electrode opposite to the capacitor. The odd-numbered electrode and the even-numbered electrode made up of a plurality of electric wires inserted into a plurality of cells along a closed curve sequentially located on the inner circumference from the fourth electrode are alternately provided,
3. The PM sensor according to claim 2, wherein the odd-numbered electrode is one side electrode of the capacitor, and the even-numbered electrode is the opposite side electrode of the capacitor.