JPH0719027A - Diesel particulate filter - Google Patents

Abstract

PURPOSE:To give electric conductivity to a filter formed by using porous ceramics and increase the electric resistance of a filter in the upstream direction so as to incinerate sediments efficiently. CONSTITUTION:A plurality of electric conductive filter layers 3 and nonelectric conductive filter layers 4 made of porous ceramics laminated and the electric conductive filter layers 3 of less thickness are positioned upstream in exhaust flow and connected serially and a filter block 2 is stored in a filter case 1. If the serially connected electric conductive filter layers 3 are electrified when sediments collected by the filter block 2 are incinerated, the incineration may be started rapidly as the electric resistance is larger on the upstream side and heating value is large. Heating value on the downstream side is small but the upstream side incinerating heat is added thereto and temperature becomes high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter for collecting particulates in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art In a diesel engine, fuel is injected into high-temperature air by adiabatic compression, and the combustion is carried out. Since it is a heterogeneous combustion, the emission of carbon monoxide and hydrocarbons is small, but Nitrogen oxides and particulates
There is a problem that a large amount of waste is emitted.

In order to prevent the release of such particulates to the atmosphere, a particulate filter has been developed which is equipped with a filter in the exhaust passage to filter the exhaust gas and purify it.

[0004]

When a porous ceramic is used as a filter of this kind, and its porous passage is bent to have a large pore size to have a filter function, the gas passage resistance is reduced and the filter is efficient. Is obtained.

However, in this type of filter, since the carbon particles of the particulates penetrate into the filter tissue and are filtered, it is necessary to uniformly heat and incinerate the filter to remove it. Therefore, it suffices to embed the heating wire in the filter itself and energize it, but burying such a heating wire is troublesome and difficult.

The present invention has been made in view of the above problems, and an object thereof is to make a filter itself for filtering carbon particles conductive and to divide a conductive portion to efficiently heat. -It is intended to provide a zelparticulate filter.

[0007]

To achieve the above object, according to the present invention, particulates contained in the exhaust gas of a diesel engine are collected by a porous heat-resistant filter which is laminated. In a diesel particulate filter that is heated and incinerated, the filter is a non-conductive filter and a conductive filter that are alternately laminated by providing gaps to electrically connect the conductive filters in series. Provided is a diesel particulate filter having a small layer thickness of a conductive filter disposed upstream of an exhaust flow passing in a direction perpendicular to the layer.

[0008]

The conductive filter layers and the non-conductive filter layers are alternately laminated to electrically connect the conductive filter layers in series to reduce the thickness of the conductive filter layers arranged in the upstream direction. Since the electric resistance was increased by heating, the amount of heat generated in the upstream portion was large during energization to incinerate the deposits, and the carbon was incinerated early, and the amount of heat generated in the downstream was at least the heat of the incinerated carbon. In addition, it becomes a high temperature and reaches the temperature for incineration sufficiently.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a structural explanatory view showing an embodiment of a diesel particulate filter according to the present invention. In FIG. 1, reference numeral 1 is a filter case, which is formed in a cylindrical shape in which the upstream and downstream directions are gradually narrowed. A flange 11 connected to the exhaust pipe of the engine is provided at the upstream end, and a mounting plate 13 connected to the exhaust tail pipe is provided at the downstream end.

Reference numeral 2 denotes a filter block, which is housed in the central portion 12 of the filter case 1 and filters exhaust gas introduced from the flange 11, and is a conductive filter layer 3
And a plurality of non-conductive filter layers 4 are alternately laminated.

The conductive filter layer 3 is made of conductive SiC as a porous body such as pumice or urethane foam, and is formed in a thick and thin layer. The non-conductive filter layer 4 is made of Al2 O3. A thick body and a thin body are made as the same porous body as described above, and a plurality of sets are alternately stacked, with the exhaust stream upstream being thin and the downstream stream being thick as illustrated.

Reference numeral 5 is a current-carrying connection, which is used to connect the conductive filter layers 3 alternately stacked in series, and mixes powdered Cu with powder having a small coefficient of linear expansion, for example, Al2TiO5 powder, Is sealed together with the melted material at the SiC end of the conductive filter layer, heated, melted, and brought into close contact.

In such a case, the coefficient of linear expansion of Cu is 18
× 10 -6 / K, the coefficient of linear expansion of Al2 TiO5 is 1 × 10
Since it is −6 / K, the linear expansion coefficient of the composite material can be set to about 4 to 5, and therefore electrical connection with SiC or Cu can be sufficiently performed.

Reference numeral 21 shown in the figure is a heat-resistant heat shield material for covering the outer periphery of the filter block 2 constructed as described above and storing it in the central portion 11 of the filter case 21.

Reference numeral 6 denotes a control device for controlling the energization of the filter block 2, which is a generator 61 or a battery 6 as a power source.
The electric power from 2 is supplied to the conductive filter layers 3 connected in series to heat them.

Next, the operation of this embodiment thus constructed will be explained.
1 is introduced into the filter case 1 through the filter case 1 and is filtered by the porous conductive filter layer 3 and the non-conductive filter layer 4 forming the filter block 2. At this time, the gas component of the exhaust gas is discharged from the mounting plate 13 on the downstream side through the porous passage, but the particulate cannot pass through and is collected and deposited on each filter element.

When the control device 6 energizes the conductive filter layer 3 connected in series with the electric power from the generator 61 or the battery 62 in removing such deposits, the SU
The filter layer made of SiC having an electric resistance value similar to that of S402 (Ni8, Cr18) generates heat. And
The thickness of the conductive filter layer 3 in the upstream direction is thin, and since the resistance value is larger than that in the thick portion, the calorific value is large and the incineration of the deposit is started, and in the downstream direction, the heat flow from the upstream and the deposit Even if the calorific value is small due to the heat of incineration, the temperature will be sufficiently high and the incineration of the deposit will be carried out well. Also,
For the conductive filter layer 3, SiC material and SUS402 material are alternately arranged, or the SiC material is arranged on the upstream side and the SUS402 material is arranged on the downstream side so that they are connected in series. Various filter configurations may be adopted.

Although the present invention has been described with reference to the above embodiments, various modifications are possible within the scope of the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

[0019]

According to the present invention as in the above embodiments,
When incinerating filter deposits with good particulate collection efficiency using porous ceramics, conductive filter layers and non-conductive filter layers are alternately laminated and conductivity in the upstream direction of the exhaust flow is obtained. Since the filter layer was thinned and connected in series, the amount of heat generated in the upstream direction was large during energization and the incineration of the deposits started early. In addition, a high temperature is reached, and the effect of efficiently incinerating the deposit is obtained.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of a diesel particulate filter according to the present invention.

[Explanation of symbols]

 2 ... Filter block 3 ... Conductive filter layer 4 ... Non-conductive filter layer 5 ... Conductive connection part 6 ... Control device

Claims (3)

[Claims] 1. A diesel particulate filter in which particulates contained in exhaust gas of a diesel engine are collected by a porous heat-resistant filter and heated and incinerated, wherein the filter is non-conductive. Of electrically conductive and electrically conductive filters are alternately laminated with a space provided therebetween to electrically connect the electrically conductive filters in series, and the electrically conductive filter disposed upstream of the exhaust flow passing in the direction perpendicular to the filter layer. A diesel particulate filter having a small layer thickness. 2. The diesel particulate filter according to claim 1, wherein the conductive filter is made of SiC and the non-conductive filter is made of Al2 O3. 3. The diesel particulate filter according to claim 1, wherein the conductive filter comprises a filter made of SiC material and a filter made of Ni—Cr material connected in series.