JPH07139330A - Diesel particulate filter - Google Patents

Abstract

PURPOSE:To purify exhaust gas by leading exhaust gas in an electric field of static electricity generated by application of voltage and capturing particulates by utilizing their trend to become large particles by aggregation. CONSTITUTION:A pair of staged filters 3 arranged downstream from a flat filter 1 composed of a pair of flat filter elements 21, 22 paced at an prescribed interval between them, a pair of flat filters 4 arranged downstream therefrom, and a pair of staged filters 5 arranged downstream therefrom are arranged in the inside of a filter case in order at some intervals. In capturing particulates, voltage is applied between respective pairs of filter elements 21, 22 so as to generate the electric filed of static electricity so that passing particles are electrically charged so as to be aggregated into large particles, which are captured by holes of the following filter element.

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 particulate matter contained in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art In a diesel engine, light oil as a fuel is injected into high temperature air by adiabatic compression, and the combustion is carried out. Therefore, the diesel engine produces carbon monoxide and hydrocarbons as compared with gasoline engines. Emissions are low, but emissions of particulate matter (particulates) are high.

In such a particulate matter, liquid droplets to be burned are contained in the exhaust gas and floated in the combustion chamber of the engine in an unburned state.
The size is a few μm, but they are 30 to 30
It develops into particles of about 40 μm.

In order to prevent the particulate matter of this kind from being released into the atmosphere, a honeycomb filter made of a material having pores of, for example, about 30 to 40 μm is used as the particulate filter, and exhaust gas is discharged. Guided to collect the particulates.

[0005]

The particulate filter as described above cannot be collected because the particulates having finer particles than the pores of the filter to be collected by filtration pass, and the pores of the filter cannot be collected. If it is set to a small value, there is a problem that the particulates that are collected and accumulated cause clogging in a short time and the exhaust resistance increases.

The present invention is intended to solve such a conventional problem, and an object thereof is to take advantage of the property that particulates grow by charging, and to collect the particulates by a coarse filter. It is to provide a diesel particulate filter.

[0007]

To achieve the above object, according to the present invention, exhaust gas of a diesel engine is passed through a filter element having a large number of through holes, and particulates contained in the exhaust gas are passed through. -In a diesel particulate filter that collects heat and incinerates it by heating, a plurality of sets of facing filter elements that generate an electric field of static electricity by applying a voltage are arranged in the exhaust flow path with a predetermined space. A diesel particulate filter is provided.

[0008]

A turbulent flow generation field exists in the flow path of exhaust gas, and in this flow field, fine particulates have a property of being charged while colliding. In the present invention, a plurality of pairs of filter plates to which a voltage is applied are provided. Since the set and the space are arranged apart from each other, the fine particulates that have passed through the through holes of the filter plate are easily collected because they grow into large particles by the mutual aggregation due to charging.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the construction of an embodiment of a diesel particulate filter according to the present invention.

Reference numeral 1 in FIG. 1 is a filter case, which is made of a metal plate having corrosion resistance, is narrowed in its upstream and downstream directions, and has an upstream port 11 into which exhaust gas is introduced and a downstream port 12 from which exhaust gas is discharged. Is connected to each,
A filter element holding plate 13 made of a heat-resistant electric insulator is arranged on the inner wall of the central portion of the filter case 1.

Reference numeral 2 denotes a flat filter, and a pair of flat filter elements 21 and 22 made of a metal plate having a large number of through holes of, for example, about 100 μm are attached to the holding plate 13 at a predetermined interval. The outer surfaces of the filter elements 21 and 22 are thinly coated with insulative barium titanate, lead titanate, alumina, zirconia, etc., and lead wires for energization are drawn out to the outside of the filter case 1. There is.

Reference numeral 3 denotes a stepped filter, which is disposed in the downstream of the flat filter 2 with a predetermined space therebetween and has a corrugated stepped continuous metal plate of ceramic coating having the same porosity as the flat filter element. The attached filter elements 31 and 32 are formed as shown in the figure, and a pair of them are attached at a predetermined interval, and their lead wires are drawn outward similarly to the above.

Reference numeral 4 is a flat filter which is the same kind as the above-mentioned flat filter 2 and has flat filter elements 41 and 42, and 5 is the same kind as the stepped filter 3 which is stepped filter elements 51 and 52. The stepped filters 3 are sequentially arranged in the space downstream of the stepped filter 3, and lead wires are drawn from the respective filter elements.

A switching relay 6 is operated by a command from a controller, which will be described later. The lead wires from the above-mentioned filter elements are put together and connected as shown in the drawing. At the time of collecting particulates in exhaust gas, a voltage is applied between each pair of filter elements to form an electric field of static electricity, and the passing particulates are charged to accelerate their assembly and to collect them. When burning the collected deposits, switching control is performed so that electric power for heating is supplied.

Next, a controller 7 is provided with an electronic circuit and a power circuit, and when collecting the particulates, the direct current from the battery 71 is exchanged with a pulse current to lead it to the transformer circuit 72, and the transformer circuit 72 boosts the voltage. The pulsating flow of the generated voltage is applied to the pair of filter elements of the flat filters 2 and 4 and the stepped filters 3 and 5 through the switching relay 6 as a direct current by the rectifying circuit 73, and When the deposit is incinerated, heating power from the battery 71 is supplied to all the filter elements through the contacts of the switching relay 6 that has been switched to generate heat.

Next, the operation of the present embodiment thus constructed will be described. When the upstream port 11 of this embodiment is connected to the exhaust passage of the diesel engine and the exhaust gas is introduced into the passage of the filter case 1, the switching relay 6 is switched as shown in FIG. At the same time, the controller 7 converts the direct current from the battery 71 into a predetermined pulse current. Then, the voltage is boosted to a predetermined pulsating flow through the transformer circuit 72, and is supplied to each filter element of each filter through the rectifier circuit 73 and the switching relay 6.

Therefore, an electrostatic electric field is generated between the pair of filter elements of the flat filters 2 and 4 and the stepped filters 3 and 5, and the particulates that have passed through the through holes of the filter elements are collected. When passing between a pair of filter elements, the static electricity is charged with static electricity due to the effect of an electric field, and the fine particles aggregate in the space behind each filter to grow into large particles.

Therefore, the particles of the greatly grown particulates cannot be passed through the through holes of the next filter and are collected.

As described above, in the present embodiment having a plurality of sets of filter elements and spaces, the particulates in the exhaust gas can be efficiently collected even by the filter having a relatively coarse through hole. become.

Next, when the filter is clogged due to the accumulation of particulates collected over time,
The switching relay 6 is switched as shown by the broken line arrow in the figure, and the controller 7 stops energizing the pulse current and supplies the heating power from the battery 71 to each filter element.

Therefore, each filter element of the metal plate generates heat, the deposit containing carbon as a main component is heated and incinerated, and the filter element is regenerated and cleaned.

FIG. 2 shows a stepped filter in the above-described embodiment in which each step is transformed from a trapezoidal shape to a rectangular shape. Such a pair of filter elements has a porous metal plate made of a ceramic material like the above filter elements. -They are insulated and mutually insulated from each other.

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

[0024]

According to the present invention as in the above embodiments,
A pair of filter elements made of a metal plate having coarse through holes are arranged at intervals in the exhaust gas flow path, and an electrostatic electric field is generated between these filter elements by application of a voltage, so that the electric field is passed through. The particulates that collect are gathered in the next space by charging and grow into large particles, so that they are collected by the filter element in the next stage, and due to such repetition, the particulates can be efficiently used even in a coarse filter element. -There is an advantage in that the electric power for heating can be directly supplied when the deposit is incinerated because the filter material is a metal plate.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a modified example of the stepped filter plate of the present embodiment.

[Explanation of symbols]

 1 ... Filter case 2, 4 ... Flat filter 3, 5 ... Stepped filter 6 ... Switching relay 7 ... Controller

Claims (4)

[Claims] 1. A filter element provided with a large number of through holes.
A diesel engine that allows exhaust gas from a diesel engine to pass through, collects particulate matter contained in the exhaust gas, and incinerates it by heating.
In the zer particulate filter, a plurality of sets of filter elements, which are opposed to each other at a distance using a metal plate coated with ceramics on the filter elements and generate an electric field of static electricity by applying a voltage, are provided in an exhaust passage, and a predetermined number of sets are provided. The diesel particulates are characterized by sequentially arranging them with spaces in between and applying a voltage to the filter element at the time of collecting the particulates, and switching to the heating power after the collection to control the energization. filter. 2. The ceramic is barium titanate,
2. The diesel particulate filter according to claim 1, wherein any one of lead titanate, alumina and zirconia is used. 3. A plurality of sets of the above-mentioned filter elements have a mixed shape of a set of flat filter plates and a set of stepped filter plates, and the set of the stepped filter plates have a trapezoidal or rectangular cross-sectional shape. 2. The diesel particulate filter according to claim 1, wherein a pair of continuous filter plates are combined. 4. The diesel particulate filter according to claim 1, further comprising an energization switching mechanism for switching between application of a voltage for electrostatic electric field to said filter element and heating power.