JP4147156B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device that removes particulates from exhaust gas of an internal combustion engine such as a diesel engine.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot composed of carbonaceous matter and SOF content (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this kind of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, and are spontaneously combusted and removed when the exhaust gas moves to an operating region. For example, in a vehicle that travels only on a congested road such as a route bus in Tokyo, the accumulated amount is higher than the processing amount of particulates because the operation above the required predetermined temperature does not continue for a long time. There is a possibility that the particulate filter may be clogged.

For this reason, plasma-assisted exhaust purification devices are being developed so that particulates can be burned and removed well even in the operating region where the exhaust temperature is low, and this type of exhaust purification device discharges into the exhaust gas to generate plasma. The exhaust gas is excited to generate an active radical, oxygen becomes ozone, NO becomes NO ₂ , and these exhaust gas excitation components are in an activated state, so the exhaust temperature Thus, it is possible to burn and remove the particulates satisfactorily even in an operation region where the temperature is low.

For example, in Patent Document 1 and Patent Document 2 below, ceramic pellets forming a dielectric material are filled between an outer electrode and an inner electrode made of cylindrical stainless steel that has been perforated, and a packed layer of the pellet is formed. A plasma-assisted exhaust purification system is proposed in which exhaust gas is allowed to flow and particulates in the exhaust gas are collected, while plasma is generated by discharging between the outer electrode and the inner electrode. Has been.
Japanese translation of PCT publication No. 2002-501813 Japanese translation of PCT publication No. 2002-511332

  However, in such a conventional plasma-assisted exhaust emission control device, an outer electrode and an inner electrode made of a metal material such as stainless steel, and ceramics supporting both ends in the axial direction of the outer electrode and the inner electrode are made. Since the thermal expansion difference between the insulating support and the insulating support and the metal filter case is large, a gap due to a dimensional change accompanying a temperature change is formed between these, When mounted on an automobile, there is a risk that rattling may occur due to running vibration and the outer electrode and the inner electrode may be damaged in a short period of time, or the particulates may leak from the gap.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly durable exhaust purification device that can favorably support the outer electrode and the inner electrode within the filter case without rattling. .

  In the present invention, a cylindrical outer electrode having an air hole and an inner electrode are concentrically arranged, and a ceramic pellet forming a dielectric is filled between them to form a discharge collecting portion. A plasma-assist type in which exhaust gas is stored in a filter case in the middle of the exhaust pipe so that the exhaust gas always flows through the packed bed of pellets, and a voltage necessary for discharge can be applied to each of the outer electrode and the inner electrode. The exhaust gas purification device is configured to support both ends in the axial center direction of the discharge collecting portion with an insulating support material, and an insulating buffer material that can be expanded and contracted between at least one of the insulating support materials and the filter case. The filter case is detachably divided at an appropriate position in the axial direction of the discharge collecting portion, and the discharge collecting portion is pushed in the axial direction together with the insulating support material when the divided portion is fastened. Retained It is characterized in that it has constructed so that.

Thus, when exhaust gas passes through the packed bed of pellets, particulates are collected, so that when necessary, a voltage is applied to each of the outer electrode and the inner electrode to exhaust gas. When the exhaust gas is discharged and the exhaust gas is excited by this, active radicals are generated in the packed bed of pellets, oxygen becomes ozone, NO becomes NO ₂ , and is supported by these exhaust gas excitation components. Thus, the particulates are effectively burned off.

  In addition, when assembling the discharge collecting part in the filter case, if the discharge collecting part is installed in the divided filter case and the divided parts of the filter case are fastened, the discharge collecting part is pivoted together with the insulating support material. It will be pushed in the center direction and will be held under pressure while compressing the insulating buffer material, between the outer electrode and the inner electrode and the insulating support material after the assembly, between the insulating support material and the filter case The difference in thermal expansion is satisfactorily absorbed by the expansion and contraction of the insulating cushioning material to prevent the occurrence of backlash, and the damage and particulate leakage due to the backlash of the outer electrode and the inner electrode are avoided.

  Further, in the present invention, it is preferable that a part of each of the outer electrode and the inner electrode is led out of the filter case to serve as an external connection terminal. In this way, connection inside the filter case becomes unnecessary, and the filter The ease of assembling the discharge collecting portion into the case is improved, and the disconnection portion is eliminated, so that the disconnection hardly occurs and the reliability is improved.

  In addition, it is preferable to provide a drain at the lowest position of the filter case, and in this way, condensed water of moisture contained in the exhaust gas can be discharged out of the filter case from the drain.

  According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the first aspect of the present invention, the outer electrode and the inner electrode can be satisfactorily supported in the filter case without rattling, so that the outer electrode and the inner electrode are damaged in a short period of time. And the possibility of particulates leaking from the gap can be surely avoided, and the durability and performance when mounted on an automobile or the like can be greatly improved as compared with the prior art.

  (II) According to the invention described in claim 2 of the present invention, it is possible to improve the assembling property of the discharge collecting part in the filter case without the need for the connection in the filter case, and the connection part is Since disconnection is less likely to occur, reliability on electrical wiring can be improved.

  (III) According to the invention described in claim 3 of the present invention, since the drain is provided at the lowest position of the filter case, the condensed water of the moisture contained in the exhaust gas can be quickly discharged from the drain to the outside of the filter case. It can discharge | emit and generation | occurrence | production of the electric current leak etc. by condensed water can be prevented beforehand.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 3 show an example of an embodiment of the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine (internal combustion engine) equipped with a turbocharger 2, and intake air introduced from an air cleaner 3. 4 is introduced into the compressor 2a of the turbocharger 2 through the intake pipe 5 and pressurized, and the pressurized intake air 4 is distributed and introduced to each cylinder of the diesel engine 1 via the intercooler 6.

  Further, exhaust gas 8 discharged from each cylinder of the diesel engine 1 through the exhaust manifold 7 is sent to the turbine 2b of the turbocharger 2, and the exhaust gas 8 driving the turbine 2b is supplied to the plasma assist in the middle of the exhaust pipe 9. Particulates are collected through the exhaust gas purification device 10 and then discharged.

  The details of the exhaust gas purification device 10 are as shown in FIG. 2. A cylindrical outer electrode 12 and an inner electrode 13 each having a vent hole 11 are arranged concentrically, and a ceramic pellet 14 forming a dielectric is filled between them. Thus, a discharge collecting portion 15 is formed, and the discharge collecting portion 15 is accommodated in a filter case 16 in the middle of the exhaust pipe 9 so that the exhaust gas 8 always flows through the packed bed of the pellets 14. It is.

  That is, both end portions in the axial center direction of the discharge collecting portion 15 are supported by the ceramic insulating support members 17 and 18 and accommodated in the filter case 16, and are insulated on the entry side (left side in FIG. 2). Exhaust gas 8 is introduced into the inner side of the inner electrode 13 from the gas introduction port 19 opened in the central portion of the support member 17, while only the exhaust gas 8 that has flowed out of the outer electrode 12 through the packed layer of the pellet 14. Is extracted to the downstream side from the gas discharge port 20 opened at the outer edge portion of the insulating support member 18 on the outlet side (right side in FIG. 2).

  Here, each of the outer electrode 12 and the inner electrode 13 may be made of a punching metal such as stainless steel, but may be made of a metal mesh knitted with a metal wire.

  A part of each of the outer electrode 12 and the inner electrode 13 passes through the insulating support members 17 and 18 and is led out of the filter case 16 and used as it is as the external connection terminals 21 and 22. ing.

  That is, a power source 24 is connected to each of these external connection terminals 21 and 22 via a discharge control unit 23. In particular, in this embodiment, a vehicle-mounted battery is assumed as the power source 24. The voltage is applied to the outer electrode 12 and the inner electrode 13 through the external connection terminals 21 and 22 after the control unit 23 raises the voltage of the power supply 24 to an appropriate voltage that can be discharged.

  When the outer electrode 12 is a negative electrode and the inner electrode 13 is an anode, the external connection terminal 22 on the anode side needs to be insulated from the filter case 16 side by covering with an insulating material 22A.

  In the exhaust purification apparatus 10 having such a structure, in this embodiment, the front end surface and the outer peripheral surface of the insulating support material 17 on the entry side are made of ceramic fibers or the like at locations where the inner surface of the filter case 16 faces the inner surface. The insulating buffer material 31 which can be expanded and contracted is interposed, so that the insulating buffer material 31 can cope with the pressing from the outlet side described later by being compressed.

  On the other hand, the filter case 16 cleans the discharge collecting portion 15 in view of the fact that the ash produced by in-cylinder combustion originating from the lubricating oil gradually accumulates inside and the pellets 14 wear over time. However, in the example shown here, the filter case 16 is divided into three parts, a front part 25, an intermediate part 26 and a rear part 27. They are structured to be detachably fastened with bolts 28 and nuts 29 via flanges 25a, 26a, 27a.

  Here, in particular, the boundary between the intermediate portion 26 and the rear portion 27 of the filter case 16 is formed in accordance with the position of the rear end surface of the insulating support material 18 on the outlet side, and the front end inner peripheral surface of the rear portion 27 is A bracket 30 (see FIG. 3) that abuts on the rear end surface of the insulating support 18 on the outlet side and pushes into the inlet side is provided, and the intermediate portion 26 and the rear portion 27 of the filter case 16 are connected via flanges 26a and 27a. When the bolt 28 and the nut 29 are fastened, the discharge collecting portion 15 is pushed in the axial direction together with the insulating support members 17 and 18 by the bracket 30 of the rear portion 27 so as to be held under pressure.

  2 indicates a drain provided at the lowermost position in the rear portion of the filter case 16, and the condensed water of moisture contained in the exhaust gas 8 can be discharged out of the filter case 16 by the drain 32. It is like that.

Thus, if the exhaust gas purification device is configured in this way, the particulates are collected when the exhaust gas 8 passes through the packed layer of the pellets 14, so that each of the outer electrode 12 and the inner electrode 13 is required when necessary. When the exhaust gas 8 is discharged by applying a voltage to the exhaust gas 8 to excite the exhaust gas 8, active radicals are generated in the packed layer of the pellets 14, oxygen becomes ozone, and NO becomes NO ₂ . Thus, the particulates are effectively burned and removed with the assistance of these exhaust gas excitation components.

  Moreover, in assembling the discharge collecting portion 15 in the filter case 16, the discharge collecting portion 15 is installed in the front portion 25 and the intermediate portion 26 of the filter case 16, and finally the rear portion 27 is attached to the intermediate portion 26. When fastened, the rear end face of the insulating support member 18 on the outlet side is pushed into the entry side by the bracket 30 of the rear portion 27, whereby the discharge collecting portion 15 is pushed together with the insulating support members 17 and 18 in the axial direction. The insulation buffer material 31 is compressed and held under pressure, and after the assembly, between the outer electrode 12 and the inner electrode 13 and the insulation support materials 17 and 18, or between the insulation support materials 17 and 18 and the filter case 16. The thermal expansion difference between the outer electrode 12 and the inner electrode 13 is satisfactorily absorbed by the expansion / contraction of the insulating cushioning material 31 to prevent the backlash from occurring. So that the leakage of Yureto is avoided.

  Therefore, according to the above embodiment, the outer electrode 12 and the inner electrode 13 can be favorably supported in the filter case 16 without rattling, and thus the outer electrode 12 and the inner electrode 13 may be damaged in a short period of time. In addition, the possibility of the particulates leaking from the gap can be surely avoided, and the durability and performance when mounted on an automobile or the like can be significantly improved as compared with the prior art.

  In addition, since a part of each of the outer electrode 12 and the inner electrode 13 is led out of the filter case 16 and used as an external connection terminal, connection within the filter case 16 is unnecessary, and the discharge collecting portion 15 into the filter case 16 is unnecessary. As a result, it is possible to improve the assembling property of the wiring, and further, since the disconnection is less likely to occur due to the absence of the connection portion, the reliability on the electrical wiring can be improved.

  Further, since the drain 32 is provided at the lowermost position of the rear portion of the filter case 16, the condensed water of the moisture contained in the exhaust gas 8 can be quickly discharged out of the filter case 16 from the drain 32, and the condensed water It is possible to prevent the occurrence of current leakage due to the above.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment. When the discharge collecting portion is pushed together with the insulating support member in the axial direction by fastening the divided portions of the filter case, the filter case In addition to providing a separate push-in bracket on the inner peripheral surface, it is possible to change the shape of the filter case itself to form a stepped portion for push-in, etc. Although the case where it is divided is illustrated, the filter case may be divided into two parts or may be divided into four parts or more, and furthermore, an oxidation catalyst for the purpose of assisting the combustion removal of the collected particulates as necessary for the pellets Of course, various modifications may be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows the detail of the exhaust gas purification apparatus of FIG. FIG. 3 is a detailed explanatory diagram regarding a main part of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Exhaust gas 9 Exhaust pipe 10 Exhaust gas purification apparatus 11 Ventilation hole 12 Outer electrode 13 Inner electrode 14 Pellet 15 Discharge collection part 16 Filter case 17 Insulation support material 18 Insulation support material 21 External connection terminal 22 External connection terminal 30 Bracket 31 Insulation buffer Material 32 Drain

Claims (3)

  A cylindrical outer electrode and an inner electrode having vent holes are arranged concentrically and filled with a ceramic pellet forming a dielectric between them to form a discharge collecting portion. The discharge collecting portion is pelletized by exhaust gas. A plasma-assisted exhaust gas purification device that is accommodated in a filter case in the middle of the exhaust pipe so that it flows through the packed bed of the gas and can apply a voltage required for discharge to each of the outer electrode and the inner electrode. Then, both ends in the axial center direction of the discharge collecting part are supported by the insulating support material, and an insulating buffer material that can be expanded and contracted is interposed between at least one of the insulating support material and the filter case, and The filter case is detachably divided at an appropriate position in the axial direction of the discharge collecting portion, and the discharge collecting portion is pushed in the axial direction together with the insulating support member when the divided portion is fastened so as to be held under pressure. In Exhaust gas purification apparatus being characterized in that form.   2. The exhaust emission control device according to claim 1, wherein a part of each of the outer electrode and the inner electrode is led out of the filter case to be an external connection terminal.   The exhaust emission control device according to claim 1 or 2, wherein a drain is provided at a lowermost position of the filter case.

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