JPH05222915A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain the exhaust emission control device for an internal combustion engine by which the drop of emission control caused by a leakage between electrodes can be evaded. CONSTITUTION:An electric particulate cohering device 1 has a cycle structure and can introduce the exhaust gas of an internal conbustion engine from the tangential direction of an outer cylinder 5 and discharge it from an inner cylinder 9 and also a minute particle in the exhaust gas is cohered by a corona discharge between the electrodes 11 and the inner cylinder 9 in the inner cylinder 9. A cyclone type particle separator 2 can introduce the gas coming from the particulate cohering device 1 from the tangential direction of an outer cylinder 20 and exhaust it from the inner cylinder 24 and an exhaust pipe 33 and also the particle is discharged from the bottom part of a tapered part 21 and sent to a particle collector 3. The exhaust pipe 33 of the cyclone type particle separator 2 is connected with the housing 10 for supporting electrodes of the electric particulate cohering device 1 by an air purge pipe 31 and an emission-controled gas is blown against the small diameter part 12a an insulator 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for purifying exhaust gas by collecting fine particles such as carbon contained in exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art Carbon particles are contained in the exhaust gas of an internal combustion engine, and it is considered to collect the carbon particles to purify the gas. A cyclone may be used to collect the carbon particles, but the particle size is too small to be collected by the cyclone. Therefore, it is considered that an electric particle agglomerator is provided in the preceding stage of the cyclone to agglomerate the carbon fine particles by using corona discharge to form a large particle diameter and send it to the cyclone.

[0003]

However, the electrode of the particle agglomerator is supported by the insulator, and when carbon adheres to the insulator for supporting the electrode, the applied voltage decreases due to the leakage between the electrodes and the particle aggregating ability is increased. And the dust collection efficiency decreases.

Therefore, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine which can avoid a reduction in purification efficiency due to a leak between electrodes.

[0005]

The present invention has a cyclone structure, has electrodes extending from the bottom of the cyclone into the inner cylinder, and introduces exhaust gas of an internal combustion engine from the tangential direction of the outer cylinder of the cyclone. A particle aggregator that discharges from the cylinder and agglomerates the particles in the exhaust gas by corona discharge between the electrode and the inner cylinder in the inner cylinder, and introduces the gas from the particle aggregator to centrifuge the particles. And a cyclone type particle separator for discharging clean gas from the discharge pipe, a collector for collecting particles from the cyclone type particle separator, and one end of which is connected to the discharge pipe of the cyclone type particle separator The other end is connected to the cyclone bottom of the fine particle agglomerator, and a communication pipe for spraying the clean gas of the discharge pipe of the cyclone type particle separator to the electrode supporting insulator in the cyclone of the fine particle agglomerator. The exhaust gas purifying apparatus for an internal combustion engine having at which its gist.

[0006]

In the particulate agglomerator, the exhaust gas of the internal combustion engine is introduced from the tangential direction of the outer cylinder of the cyclone and discharged from the inner cylinder, and the exhaust gas is generated by corona discharge between the electrode and the inner cylinder in the inner cylinder. The fine particles therein are aggregated to increase the particle size. Then, the gas from the fine particle agglomerator is introduced into the cyclone type particle separator, the particles are centrifugally separated, the clean gas is discharged from the discharge pipe, and the particles are collected by the collector. On the other hand, the clean gas in the discharge pipe of the cyclone type particle separator is sprayed through the communication pipe to the electrode supporting insulator in the cyclone of the particle agglomerator to prevent the carbon particles from adhering to the electrode supporting insulator. As a result, the applied voltage is prevented from lowering due to the leakage between the electrodes, the particle aggregating ability is not lowered, and the exhaust gas purification efficiency is prevented from being lowered.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an exhaust gas purifying apparatus for an internal combustion engine of this embodiment. This apparatus is composed of an electric particle agglomerator 1, a cyclone particle separator 2 and a particle collector 3.

The electric particle agglomerator 1 has a cyclone structure. That is, the cyclone structure 4 includes the outer cylinder 5,
A taper portion 6 extending from one end of the outer cylinder 5, a flat surface portion 7 at the other end of the outer cylinder 5, an exhaust gas inflow portion 8, and an inner cylinder 9,
An exhaust gas inflow portion 8 opens tangentially on the side surface of the outer cylinder 5. An inner cylinder 9 is arranged at the center of the flat portion 7, and the inner cylinder 9 projects into the outer cylinder 5 to form a gas outflow passage. The cyclone structure 4 is made of stainless steel, which is a conductive material, and is electrically grounded.

An electrode supporting housing 10 is screwed to the tip of the tapered portion 6. The electrode-supporting housing 10 has a bottomed cylindrical shape, and an insulator 12 having a round-bar electrode 11 press-fitted therein is wound and fixed to the center thereof. A small-diameter portion 12a is formed on the insulator 12, and the small-diameter portion 1 of the insulator 12 is formed in the electrode supporting housing 10.
An annular space 13 is formed between 2a and the inner peripheral surface of the electrode supporting housing 10. Also, the round bar electrode 11 is the inner cylinder 9
The rod electrode 11 and the inner cylinder 9 form a pair of electrode structures. On the outer peripheral surface of the round bar electrode 11, a projection 11a having a sharp tip (abacus ball shape) over the entire circumference is provided.
Are formed in plural. The round bar electrode 11 is connected to a high voltage generator 14.

The high voltage generator 14 is shown in FIG. The high voltage generator 14 has a structure similar to that of a high voltage generator of an ignition device for a general spark ignition type internal combustion engine, and includes a coil section 15, a transistor 16 and a signal generator 17. The coil portion 15 is a primary coil 15a having a small number of turns.
And a secondary side coil 15b having a large number of turns, one end of the primary side coil 15a is connected to a battery 19 via an ignition switch 18, and the other end is grounded via a transistor 16. On the other hand, the secondary coil 15
One end of b is electrically connected to the ignition switch 18 side of the primary coil 15a, and the other end is electrically connected to the round bar electrode 11. The base terminal of the transistor 16 is connected to the signal generator 17, and the transistor 16 is repeatedly turned on and off by a pulse signal from the signal generator 17.
By the on / off operation of the transistor 16, a pulsed negative high voltage is generated in the secondary coil 15b and sent to the round bar electrode 11.

In FIG. 1, a cyclone type particle separator 2 is provided.
Is an outer cylinder 20 and a tapered portion 2 extending from the lower end of the outer cylinder 20.
1, a flat portion 22 at the upper end of the outer cylinder 20, and a gas inflow portion 23
And an inner tube 24 and a discharge pipe 33. A gas inflow portion 23 is opened in the tangential direction on the side surface of the outer cylinder 20, and the gas inflow portion 23 and the inner cylinder 9 of the electric fine particle agglomerator 1 communicate with each other. An inner cylinder 24 is provided at the center of the flat surface portion 22 so as to project into the outer cylinder 20, and
A discharge pipe 33 extending outward from is provided. The other end of the discharge pipe 33 is open to the atmosphere. Taper part 21
A relief passage 25 opens at the lower end of the relief passage 25, and the relief passage 25 is open to the atmosphere via the particle collector 3.

FIG. 3 shows the structure of the particle collector 3. The metal housing 26 of the particle collector 3 has a central cylindrical portion 26a.
And the conical portions 26 formed at both ends of the cylindrical portion 26a.
b and 26c. A collection filter 27 is housed in the cylindrical portion 26a. The collecting filter 27 is made of a material having a high melting point and a large heat insulating property, for example, alumina, and has a columnar core portion 27a having a capillary void.
And a jacket portion 27b surrounding the core portion 27a and concentric with the core portion 27a and having no void. In FIG. 3, exhaust gas flows in the direction of the arrow, that is, from left to right in the figure. A hot-wire regenerative heater 28 is arranged near the left end of the collection filter 27. As shown in FIG. 4, the regeneration heater 28 is formed in a wavy shape and is arranged over substantially the entire cross section of the core portion 27a. The heater 28 is drawn out through an insulating material 29.

The heater 28 is connected to the control circuit 30 shown in FIG. 1, and an engine speed detection signal is input to the control circuit 30. Then, the control circuit 30 is
After turning on, when the rotation speed is integrated and reaches a predetermined value, the heater 28 is energized for a predetermined time, and then the integrated rotation speed is reset and this is repeated. That is, the heater 28 is energized for a predetermined time each time the integrated rotation speed reaches a predetermined value.

In FIG. 1, a cyclone type particle separator 2 is provided.
An air purge pipe 31 as a communication pipe is connected to the discharge pipe 33 of. The other end of the air purge pipe 31 is connected to the electrode supporting housing 10 of the electric particle agglomerator 1 and opens at the left end of the annular space 13. Further, the opening direction is configured to be the same tangential direction as the swirling direction of the exhaust gas in the cyclone structure 4.

Next, the operation of the exhaust gas purifying apparatus for an internal combustion engine configured as above will be described. Electric type particle agglomerator 1
The exhaust gas flowing into the cylinder reaches the taper portion 6 while swirling the outer cylinder 5 of the cyclone structure 4. After that, the direction of the gas flow reverses from the leftward flow to the rightward in FIG. 1, and flows into the inner cylinder 9 while swirling around the round bar electrode 11. A pulsed negative high voltage is applied from the high voltage generator 14 to the round bar electrode 11, and the protrusion 1 of the round bar electrode 11 is applied.
The gas near 1a is locally ionized, and negative ions and free electrons travel toward the inner wall of the inner cylinder 9 (so-called corona discharge). The fine particles in the exhaust gas are negatively charged by the collision with the negative ions and free electrons, and are aggregated and deposited on the inner wall of the inner cylinder 9 by the Coulomb force. As the deposition progresses, it is separated by the flow of gas, but the carbon fine particles once agglomerated do not easily separate, and therefore have a larger particle diameter than before the agglomeration and flow into the cyclone type particle separator 2. The exhaust gas that has flowed in turns toward the taper portion 21 below while swirling the outer cylinder 20.
In this process, the particles are separated from the gas by the centrifugal force, and only clean gas is discharged to the atmosphere through the inner cylinder 24 and the exhaust pipe 33.

On the other hand, the separated particles pass through the relief passage 25 together with a part of the gas, are collected by the collecting filter 27 of the particle collector 3, and are incinerated by the regeneration heater 28.
As a result, only clean gas is released into the atmosphere.

In the treatment of the exhaust gas of the internal combustion engine as described above, the inside of the exhaust pipe 33 of the cyclone type particle separator 2 has a high pressure (for example, +50 mmHg) and the vicinity of the center of the taper portion 6 of the electric type particle agglomerator 1 is used. Has a low pressure (for example, +30 mmHg) due to the swirling flow of gas. Therefore, a part of the clean gas flowing through the exhaust pipe 33 of the cyclone type particle separator 2 is supplied to the annular space 13 inside the electrode supporting housing 10 through the air purge pipe 31 and swirls inside the annular space 13 while being swirled. It flows toward the cylinder 9.
At this time, the air flow is blown to the outer peripheral surface of the small diameter portion 12a of the insulator 12. This air flow prevents carbon particles from adhering to the small diameter portion 12a of the insulator 12. As a result, the leak current from the rod electrode 11 to the cyclone structure 4 is eliminated, and the output voltage is prevented from decreasing.

As described above, in this embodiment, the air purge pipe 3 is used.
One end (communication pipe) is connected to the discharge pipe 33 of the cyclone type particle separator 2 and the other end is an electric type particle agglomerator 1
Is connected to the electrode supporting housing 10 (electrode supporting part) at the bottom of the cyclone, and the clean gas in the discharge pipe 33 of the cyclone type particle separator 2 is supplied to the annular space 13 of the electric particle agglomerator 1.
Introduced into the structure, the outer peripheral portion of the small diameter portion 12a of the insulator 12 is swung to pass. Therefore, the insulator 12
Of carbon particles to the small-diameter portion 12a of the rod is prevented, the applied voltage is prevented from lowering due to the leak between the rod electrode 11 and the cyclone structure 4, and the particle aggregating ability is not lowered, so that the exhaust gas is purified. A decrease in efficiency is avoided. In other words, periodic cleaning for cleaning the small diameter portion 12a of the insulator 12 and air purging with an air pump are unnecessary.

The present invention is not limited to the above embodiment, and for example, the electrode 11 in the electric fine particle agglomerator 1 has a pointed shape so that a stable corona discharge can be obtained, and the corona Any structure may be used as long as the discharge can be formed over the entire cross section of the inner cylinder 9. An example thereof is shown in FIGS. The electrode 32 is composed of a round bar portion 32a and a plurality of needle-like protrusions 32b. The needle-like protrusion 32b is welded in the radial direction of the round rod portion 32a and is also welded at a position symmetrical with the needle-like protrusion 32b. Form a pair of needle-like protrusions. The pair of needle-shaped projections are welded at equal intervals in the lengthwise direction of the round bar portion 32a and at a predetermined angle offset in the radial direction.

In the above embodiment, the cyclone type particle separator 2 is a tangential inflow type cyclone, but an axial flow type cyclone may be used.

[0021]

As described in detail above, according to the present invention,
It exhibits an excellent effect of avoiding a reduction in purification efficiency due to a leak between electrodes.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an exhaust gas purifying apparatus for an internal combustion engine of an embodiment.

FIG. 2 shows a high voltage generator.

FIG. 3 is a diagram showing a structure of a particle collector.

FIG. 4 is a view showing a cross section taken along the line AA of FIG.

FIG. 5 is a diagram showing an electrode of another example.

6 is a diagram showing a cross section taken along the line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric fine particle agglomerator 2 Cyclone type particle separator 3 Particle collector 5 Outer cylinder 9 Inner cylinder 10 Electrode supporting housing 11 Round bar electrode 12 Insulator as an insulator for electrode support 31 Air purge pipe 33 as a communicating pipe 33 Discharge pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Takeyama 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute, Inc.

Claims (1)

[Claims] 1. A cyclone structure, having electrodes extending from the bottom of the cyclone into the inner cylinder, wherein exhaust gas of an internal combustion engine is introduced from the tangential direction of the outer cylinder of the cyclone and discharged from the inner cylinder, and the inner cylinder A particle aggregator that agglomerates the particles in the exhaust gas by corona discharge between the electrode and the inner cylinder, and a gas from the particle aggregator is introduced to centrifuge the particles and discharge the clean gas from the discharge pipe. A cyclone type particle separator, a collector for collecting particles from the cyclone type particle separator, one end of which is connected to the discharge pipe of the cyclone type particle separator and the other end of which is the fine particle agglomerator A communication pipe connected to the bottom of the cyclone, for spraying the clean gas of the discharge pipe of the cyclone type particle separator onto the electrode supporting insulator in the cyclone of the particle agglomerator. Exhaust gas purification device for combustion engine.