JP2007090255A - Exhaust gas purifying apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a exhaust gas purifying apparatus capable of detecting PM deposition using plasma discharge. <P>SOLUTION: This exhaust gas purifying apparatus is provided with: insulating honeycomb structure; a casing disposed in the outer periphery of the honeycomb structure and functioning as an outer peripheral electrode; a rod-like discharge electrode held on a central axis of the casing; and a particulate matter detecting electrode. The particulate matter detecting electrode forms a circuit together with the casing or other electrode, and deposition of the particulate matter on the electrode causes the formation of an electric conduction between the electrode and the casing or other electrode. By detecting the electric conduction, deposition of the particulate matter can be confirmed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purifying apparatus that purifies harmful components in exhaust gas from an internal combustion engine or the like using plasma discharge, and more specifically, exhaust gas capable of grasping the accumulation state of particulate matter (hereinafter referred to as PM). The present invention relates to a purification device.

  Various harmful components are contained in exhaust gas discharged from internal combustion engines and incineration facilities used in automobiles and the like. Of these harmful components, it is desired to reduce NOx, SOx, and PM emissions. For diesel engines. In recent years, in particular, it has been strongly desired to reduce the emission of PM, and a particulate filter is used to remove this PM.

  This type of particulate filter has a porous honeycomb structure made of ceramics such as cordierite, and the inlets of each flow path partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. The outlets are sealed in the flow paths, and only the exhaust gas that has permeated through the porous walls that define each flow path is discharged downstream. Since PM in the exhaust gas cannot pass through the porous wall, PM is collected on the inner surface of the porous wall.

  In such a filter, the collected PM causes the filter to be clogged, resulting in an increase in ventilation resistance and a burden on the engine. Therefore, before the ventilation resistance due to this clogging increases, the PM is appropriately adjusted. It is necessary to burn off and regenerate the filter. However, in the normal operation state of a diesel engine, an exhaust temperature that is high enough to cause PM to self-combust is not obtained.

  Therefore, recently, it has been proposed that plasma is generated by discharge, PM is burned and removed by the oxidizing action of the plasma, and NOx and the like are purified by the oxidizing action of the plasma and the reducing action of the catalyst.

  For example, a particulate filter is disposed in the engine exhaust system, and a plasma generator is disposed on the upstream side of the particulate filter, and it is determined that PM is deposited on the particulate filter. There has been proposed an exhaust purification device that operates a plasma generator during spikes to improve PM oxidation removal capability in a particulate filter (see Patent Document 1).

JP 2002-349240 A

  However, the above exhaust purification apparatus merely estimates that PM accumulates depending on the engine state, and does not directly detect the PM accumulation state. Therefore, for example, there is a case where it is not necessary to generate plasma even at the time of rich spike, and there is a case where it is necessary to generate plasma even at the time of lean, and the plasma generation time is not truly optimally controlled. .

  An object of the present invention is to provide an exhaust gas purifying apparatus using plasma discharge, which can solve such problems and can detect PM accumulation on a particulate filter.

In order to solve the above problems, according to the present invention,
Insulating honeycomb structure,
A case for housing the honeycomb structure, which is disposed on the outer peripheral portion of the honeycomb structure and functions as an outer peripheral electrode;
In an exhaust gas purification apparatus having a rod-like discharge electrode held on the central axis of the case and a particulate matter detection electrode, the particulate matter detection electrode forms a circuit with the case or another electrode. It is confirmed that the particulate matter is deposited on the electrode to form an electrical continuity with the case or another electrode, and the particulate matter is deposited by detecting the electrical continuity. It is possible to grasp.

  According to the present invention, it is possible to grasp PM deposition by detecting that a current flows through a circuit including a PM deposition detection electrode disposed in an exhaust gas purification apparatus, and plasma for burning and removing PM. Can be optimally controlled.

  Hereinafter, an exhaust gas purification apparatus of the present invention will be described with reference to the drawings. As shown in FIG. 1, an embodiment of the exhaust gas purifying apparatus includes an insulating honeycomb structure 1, a case 2 that accommodates the honeycomb structure and is disposed on the outer peripheral portion of the honeycomb structure 1 and functions as an outer peripheral electrode. And a rod-shaped discharge electrode 3 held on the central axis of the case 2. The discharge electrode 3 is inserted into the case from above the case 2 so as not to contact the insulating honeycomb structure 1 and is held by an insulating alumina tube or insulator 4.

  The discharge electrode 3 is electrically connected to a power source 5, and the case 2, which is an outer peripheral electrode, is grounded. By causing the power source 5 to act based on a control signal from a control unit (not shown), the discharge electrode A corona discharge is caused between 3 and the case 2 to generate plasma.

  As the insulating honeycomb structure 1, a porous particulate filter made of ceramic such as cordierite or an exhaust gas purification catalyst in which a catalyst metal such as a noble metal is supported on a ceramic honeycomb can be used.

  In this exhaust gas purification apparatus, the PM detection electrode 6 is arranged on the wall surface in the case 2 and forms a circuit with the case. An example of the configuration of this PM detection electrode is shown in FIG. In this PM detection electrode, a conductor 9 is fixed on an inner wall surface of the case 2 via an insulator 8 such as an insulator, and another insulator 10 is further exposed on the conductor 9 so that at least a part of the conductor 9 is exposed. Are arranged so as to sandwich them. A lead wire 11 is wired from the conductor 9 to the outside, and this lead wire is connected to the case 2 to constitute a circuit.

  Further, another example of the configuration of the PM detection electrode is shown in FIGS. In the electrode shown in FIG. 3, the insulator 10 is excluded from the electrode shown in FIG. The electrode shown in FIG. 4 is arranged so that the surface of the conductor 9 faces the upper side, that is, the side on which PM is deposited, so that PM is easily deposited.

  When the exhaust gas discharged from the engine or the like flows into the exhaust gas purification apparatus having such an electrode, PM in the exhaust gas accumulates on the electrode 6 and finally, as shown in FIG. 5, the electrode conductor 9 and the case 2 Electrical continuity is formed between the two. As shown in FIG. 1, since a circuit is formed on the wall surface of the case 1 from the conductor 9 via the current detector 7 as shown in FIG. 1, there is a gap between the conductor 9 and the case 2 before PM is deposited. Although insulated, if the insulation between the conductor 9 and the case 2 is broken by the deposition of PM as described above, a current flows through the circuit, and this current is detected by the current detector 7. That is, by observing the current detector 7, it is possible to detect whether PM has accumulated.

  In FIG. 5, the electrode shown in FIG. 2 is used, and the PM deposition sensitivity can be adjusted by adjusting the area of the exposed portion of the conductor 9, the distance between the conductor 9 and the case, and the like. That is, if the electrode as shown in FIG. 3 is used, the conductor 9 is completely exposed, so that a current flows only by depositing a smaller amount of PM than in the electrode shown in FIG. Furthermore, in the electrode shown in FIG. 4, PM is more easily deposited on the conductor, so that the PM deposition detection sensitivity can be further increased.

  Another embodiment of the exhaust gas purifying apparatus of the present invention is shown in FIG. In this exhaust gas purifying apparatus, two PM detection electrodes 6 are arranged in the case 2 as a pair. The electrodes 6 form a circuit outside the case, but are insulated from each other inside the case. When PM is deposited in this apparatus and conduction is established between the two electrodes 6, a current flows through the circuit, and this current is detected by the current detector 7 to detect that PM has been deposited. The

  When it is detected that PM has accumulated in the exhaust gas purification device in this way, the power source 5 is actuated by a control signal from a control unit (not shown), and corona discharge continues between the discharge electrode 3 and the case 2 over a relatively wide range. Is done. Then, the exhaust gas passing through this portion is excited, PM, NO, etc. contained in the exhaust gas are activated as plasma by corona discharge, and highly active components flow into the honeycomb structure 1.

  In the case where a particulate filter is used as the insulating honeycomb structure 1, the oxidation reaction of PM collected by this particulate filter is promoted by the above-mentioned highly active component. As a result, PM is ignited at a lower temperature than before. Will be burned off. In addition, when an exhaust gas purification catalyst is used as the insulating honeycomb structure 1, since the components in the exhaust gas flow in as highly active components, harmful components in the exhaust gas can be efficiently oxidized or reduced and rendered harmless.

It is sectional drawing which shows the one aspect | mode of the exhaust gas purification apparatus of this invention. It is sectional drawing which shows the structure of the electrode for PM detection. It is sectional drawing which shows the structure of the electrode for PM detection. It is sectional drawing which shows the structure of the electrode for PM detection. 1 is a schematic diagram showing a state where PM is deposited on a PM detection electrode. It is sectional drawing which shows the one aspect | mode of the exhaust gas purification apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Honeycomb structure 2 Case 3 Discharge electrode 4 Alumina tube 5 Power supply 6 PM detection electrode 7 Current detector 8 Insulator 9 Conductor 10 Insulator 11 Lead wire

Claims (3)

Insulating honeycomb structure,
A case for housing the honeycomb structure, which is disposed on the outer peripheral portion of the honeycomb structure and functions as an outer peripheral electrode;
An exhaust gas purification apparatus having a rod-shaped discharge electrode held on the central axis of the case and a particulate matter detection electrode, wherein the particulate matter detection electrode forms a circuit with the case or another electrode The particulate matter is deposited on the electrode to form an electrical continuity with the case or another electrode, and the particulate matter is deposited by detecting the electrical continuity. An exhaust gas purification device that can grasp this.   The particulate matter detection electrode is disposed on the wall surface of the case via an insulator, the particulate matter is deposited on the electrode, and the deposited particulate matter becomes a part of a circuit to form the electrode and the case. The exhaust gas purification device according to claim 1, wherein electrical continuity is formed between the exhaust gas purification device and the exhaust gas purification device.   At least two particulate matter detection electrodes are disposed in the case, the particulate matter is deposited on the electrodes, and the deposited particulate matter becomes a part of a circuit and is electrically connected between the at least two electrodes. The exhaust gas purifying apparatus according to claim 1, wherein automatic conduction is formed.

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