JP2006207425A - Exhaust gas treating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treating device capable of shortening a distance between a discharge electrode device and a high voltage generating device and reducing electric power loss occurring in wiring. <P>SOLUTION: This exhaust gas treating device is provided with an exhaust pipe of an internal combustion engine; the discharge electrode device fixed to inside of the exhaust pipe with a discharge electrode protruded; a power supply device arranged in an automobile; and the high voltage generating device boosting voltage supplied from the power supply device and supplying high voltage to the discharge electrode device. Boosting of the voltage by the high voltage generating device is performed by a piezoelectric element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a device for treating exhaust gas from automobiles, particularly exhaust gas from diesel engines.

  Diesel engines and lean-burn fuel systems (lean burn) gasoline engines are operated at lean air-fuel ratios, so they have low fuel consumption and the advantage of being able to suppress emissions of carbon dioxide (CO2), a global warming substance. . However, particulate matter (PM) contained in the exhaust gas is a problem.

Therefore, a method for electrostatically aggregating PM using corona discharge has been devised as a method for treating PM contained in exhaust gas. For example, Patent Document 1 proposes a device that includes a plurality of linear discharge electrode devices that generate corona discharge in a cylindrical body into which a gas containing smoke or PM flows, and that uses a cylindrical body wall as a ground electrode. Has been. In the apparatus described in Patent Document 1, corona discharge is generated by applying a high voltage between the discharge electrode and the ground electrode. The PM in the exhaust gas is charged by this corona discharge, and moves to the ground electrode side by an electrostatic force and aggregates.
JP 2003-144979 A

  However, in the prior art of Patent Document 1, the high voltage generator that applies a high voltage to the discharge electrode device is large and difficult to install in the lower part of the chassis near the exhaust pipe of an automobile. I had to install the voltage generator at a remote location. Since a voltage of several tens of KV (for example, 20 KV) is applied to the discharge electrode device, the high voltage wiring is thick. For this reason, installation of the wiring between the discharge electrode device and the high voltage generator is difficult, and the volume of the wiring is large, which hinders installation in an automobile. Moreover, there is a problem that the power loss generated in the wiring increases as the wiring becomes longer.

  The present invention has been made in consideration of such conventional problems, and the object thereof is to reduce the distance between the discharge electrode device and the high voltage generator and to generate power generated in the wiring. It is an object of the present invention to provide an exhaust gas treatment device with reduced loss.

  In the present invention, an exhaust pipe of an internal combustion engine, a discharge electrode device fixed with a discharge electrode protruding into the exhaust pipe, a power supply device installed in an automobile, and a voltage supplied by the power supply device are boosted. And an exhaust gas treatment device comprising a high voltage generator for supplying a high voltage to the discharge electrode device, wherein the voltage in the high voltage generator is boosted by a piezoelectric element. A gas processing apparatus is provided.

  According to this, since the physique of a high voltage generator can be made small, installation near the exhaust pipe of an automobile becomes easy.

  According to a second aspect of the present invention, the piezoelectric element comprises a long plate-shaped piezoelectric ceramic plate, is accommodated in a substantially cylindrical container, is fixed by a plurality of support portions, One end is in contact with a portion serving as a piezoelectric displacement node of the piezoelectric ceramic plate or in the vicinity thereof, and the other end of the support portion is preferably in contact with the container.

  According to this, it becomes a structure which can prevent the position shift and drop-off | omission of a piezoelectric element by the vibration of a motor vehicle, and does not inhibit the mechanical vibration of a piezoelectric element.

  Further, as in a third aspect of the invention, when the high voltage generator includes an AC-DC conversion circuit, the high voltage generator can convert the alternating voltage boosted by the piezoelectric element into a direct voltage.

  Further, when the high voltage generating device is configured integrally with the discharge electrode device as in the invention described in claim 4, the high voltage generating device is particularly configured as in the invention described in claim 5. A connecting means is provided in the axial direction and in the vicinity of the discharge electrode device, and electrically connecting the output electrode of the high voltage generator and the input electrode of the discharge electrode device, and a housing covering the connecting portion is provided. In this case, since the high voltage wiring connecting the discharge electrode device and the high voltage generator can be shortened, power loss between the discharge electrode device and the high voltage generator can be reduced.

  According to a sixth aspect of the present invention, there is provided an electrode made of a conductive film disposed downstream of the discharge electrode device and having a large number of vent holes, and the exhaust pipe and the electrode are substantially installed. If this is the case, an exhaust gas treatment device with less power loss between the discharge electrode device and the high voltage generator can be provided.

  The configuration of the embodiment of the first invention will be described with reference to the drawings. FIG. 1 is a configuration diagram when a discharge electrode device 2 according to the present invention configured integrally with a high voltage generator is applied to an aggregator 1 as an exhaust gas treatment device of a diesel engine.

  The aggregator 1 includes a corona discharge electrode device (hereinafter referred to as a discharge electrode device) 2, a first ground electrode 5 composed of an inner peripheral wall of the exhaust tube at an outer peripheral position of the discharge electrode device 2, A second ground electrode 4 made of a conductive net is provided. The first ground electrode 5 and the second ground electrode 4 are electrically grounded.

  In the aggregator 1 configured as described above, by applying a DC high voltage to the discharge electrode device 2, the discharge electrode 21 of the discharge electrode device 2 is interposed between the first ground electrode 5 and the second ground electrode 4. Generate corona discharge.

  The discharge electrode device 2 includes a cylindrical insulator 22, a discharge electrode 21 provided at an end portion of the insulator 22, and an input electrode 23 provided at the other end portion of the insulator 22. The discharge electrode device 2 is fixed to the wall surface of the exhaust pipe, with the end on the discharge electrode 21 side protruding into the exhaust pipe, and the end on the input electrode side protruding outside the exhaust pipe. The tip of the discharge electrode 21 faces the second ground electrode 4 located downstream with a predetermined interval. Moreover, the discharge electrode 21 is located in the center part of the radial direction of the exhaust passage of an exhaust pipe. The distal end portion of the discharge electrode 21 has a number of acute angle distal end portions, and the distal end portions are radially positioned. Specifically, as shown in FIG. 2, it has a star shape having a plurality of protrusions 62a. As a result, the discharge rate can be increased, and corona discharge can be evenly generated in the exhaust pipe to enhance the agglomeration effect.

  The conductive net serving as the second ground electrode 4 has a disc shape, is disposed across the passage so as to be orthogonal to the exhaust flow, and has an outer peripheral edge fixed to the inner peripheral wall of the exhaust pipe. The large number of air holes formed by the mesh of the conductive net are sized so as not to prevent the passage of the aggregated fine particles. The exhaust fine particles usually have a particle size of 0.1 μm to several μm, and the agglomerated fine particles are usually coarse particles having a particle size of 1 μm to 10 μm. It may be about 1 mm or more. In general, the larger the vent hole, the higher the effect of reducing the pressure loss. However, the smaller the vent hole and the larger the surface area, the greater the coagulation effect due to corona discharge. Therefore, the size of the air holes may be appropriately adjusted so that a desired agglomeration effect is obtained within a range in which the pressure loss is not deteriorated.

  The installation position of the second ground electrode 4 is preferably such that the distance (axial distance) between the discharge electrode 21 and the conductive net to be the second ground electrode 4 is within the exhaust pipe to be the discharge electrode 21 and the first ground electrode 5. It should be longer than the distance to the peripheral wall (distance in the radial direction). In this way, when the exhaust gas flow rate is small, the fine particles are mainly aggregated at the first ground electrode 5, and when the exhaust gas flow rate is large, the fine particles that cannot move to the first ground electrode 5 due to the gas flow The second ground electrode 4 positioned in the direction can be sufficiently agglomerated to form coarse particles that are easy to collect.

  In the aggregator 1 configured as described above, a negative DC high voltage, for example, −20 KV is applied to the discharge electrode device 2 to generate a corona discharge in the vicinity of the discharge electrode 21. As a result, electrons are emitted, oxygen having high electron affinity is negatively ionized, and adheres to nearby PM to be negatively charged. PM is aggregated and coarsened mainly at the second ground electrode 4.

  The coarse PM passes through the vent hole of the second ground electrode 4 and moves downstream.

  FIG. 3 is an enlarged view of the discharge electrode device 2 of FIG. The discharge electrode device 2 includes a housing 202, an insulator 22, a discharge electrode 21, an input electrode 23, a support member 206, a high voltage generator 207, and a high voltage wiring 205.

  The housing 202 is made of stainless steel or the like, and includes an insulator support portion 202A formed in a substantially cylindrical shape and a bellows cylindrical portion 202B formed in a cylindrical and bellows shape. A step part 202C formed in a substantially annular shape is provided on the outer periphery of the insulator support part 202A, and a screw part 202D for fixing to the exhaust pipe wall is provided on the exhaust pipe side from the step part 202C. . The material used for the housing 202 may be a material other than stainless steel, and the discharge electrode device 2 is provided in the vicinity of the exhaust pipe, and the temperature of the exhaust pipe is about 600 degrees at the maximum. Since it is exposed outside the vehicle, it should be a material with high corrosion resistance.

The insulator 22 is made of alumina ceramic (Al ₂ O ₃ ) or the like, and is formed in a substantially cylindrical shape. The insulator 22 is fixed to the housing 202 at an intermediate position in the axial direction, and the input electrode 23 side of the insulator 22 is covered with a bellows cylindrical portion 202B of the housing 202.

  The discharge electrode 21 is composed of a metal material having excellent heat conductivity such as Cu as an inner material, and a metal material having excellent heat resistance and corrosion resistance such as a Ni-based alloy as an outer material. It is formed in a shape. The discharge electrode 21 is fixed to a shaft hole (not shown) provided at the end of the insulator 22 on the exhaust pipe side, and is insulated and held by the housing 202 via the insulator 22.

  The input electrode 23 is formed in a substantially cylindrical shape, and is provided at an upper end of the insulator 22 in the figure.

  The support member 206 is formed in a substantially cylindrical shape, and is fixed to the inner periphery of the housing 202. Further, it extends from the upper part of the bellows cylindrical part 202B of the housing 202 toward the step part 202C and covers the upper part of the insulator 22.

  The high voltage generator 207 is formed in a substantially cylindrical shape, and is arranged and fixed in the axial direction on the inner periphery of the support member 206 so as to face the insulator 22. The configuration of the high voltage generator 207 will be described later.

  The high voltage wiring 205 is provided at the end of the high voltage generator 207 on the side of the insulator 22 and is connected to the input electrode 23 provided on the insulator 22.

  In the discharge electrode device 2 configured as described above, the high voltage generator 207 includes a high voltage internally based on power input from a power supply device (not shown) via a power supply input wiring (not shown). Is generated. When the high voltage generated by the high voltage generator 207 is applied to the insulator 22 via the high voltage wiring 205 and the input electrode 23, the insulator 22 causes corona discharge near the tip of the discharge electrode 21. generate.

  At this time, since the high voltage wiring 205 that connects the discharge electrode device 2 and the high voltage generation unit 207 is short, power loss between the discharge electrode device 2 and the high voltage generation unit 207 can be reduced.

  4 is a cross-sectional view of the high voltage generator 207 of FIG. The high voltage generation unit 207 includes a container 300, a piezoelectric element 301, a support unit 304, a feedback resistor 308, and an AC-DC conversion circuit 309. By using the piezoelectric element 301 for the boosting means, the physique of the high voltage generator 207 can be reduced, so that it can be easily installed near the exhaust pipe of an automobile.

  The piezoelectric element 301 is made of a piezoelectric ceramic body and is formed in an elongated and flat plate shape.

  A pair of input electrodes 302 are provided on one half of the piezoelectric element 301 in the width direction so as to face each other with the piezoelectric element 301 sandwiched between upper and lower surfaces. On the other hand, an output electrode 303 is provided on the other half of the piezoelectric element 301 in the width direction.

  The piezoelectric element 301 is fixed to the container 300 via a plurality of support portions 304.

  The container 300 is made of stainless steel or the like and has a substantially rectangular parallelepiped shape.

  The support portion 304 is made of a resin material or the like, is formed in a substantially conical shape, has one end fixed to the piezoelectric element 301 and the other end fixed to the housing portion 300. The position where the piezoelectric element 301 is fixed may be a point where the displacement (distortion) of the piezoelectric element 301 is small when a voltage is applied to the input electrode 302 of the piezoelectric element 301. The portion with less displacement differs depending on the resonance frequency of the piezoelectric element 301. When the resonance frequency is expressed by the following equation, the portion with less displacement is 1/3 and 2/3 when the length is divided into three equal parts. It becomes the point. For example, when the length is 50 mm, it is around 16.7 mm and 33.3 mm.

(Equation 1)
Resonance frequency f = speed of sound in piezoelectric transformer / length of piezoelectric transformer
(Sound velocity in piezoelectric transformer: 3250 m / s)
The material used for the support portion 304 may be a material other than a resin material, and the discharge electrode device 2 is provided in the vicinity of the exhaust pipe, and the temperature of the exhaust pipe is about 600 degrees at the maximum. In order to prevent the piezoelectric element 301 from being damaged, it is preferable that the material is flexible, and because it is in contact with the electrode, a material having high insulating properties is preferable. Thus, the piezoelectric element 301 can be prevented from being displaced and dropped due to automobile vibration, and the effective vibration of the piezoelectric element 301 itself is not hindered.

  An input wiring 306 and a ground wiring 305 are provided on the input electrode 302 of the piezoelectric element 301. The input wiring 306 is connected to an AC power supply circuit (not shown). The ground wiring 306 is connected to an automobile body or the like.

  A high voltage wiring 307 is provided on the output electrode 303 of the piezoelectric element 301 and is connected to an AC-DC conversion circuit 309 for converting an AC voltage generated in the piezoelectric element 301 into a DC voltage.

  The AC-DC conversion circuit 309 includes a feedback resistor 308, and the feedback resistor 308 is electrically connected via an input electrode 302 provided at one end of the piezoelectric element 301 in order to measure a voltage output from the piezoelectric element 301. The other end is electrically connected to the high voltage wiring 307 through a wiring pattern (not shown) provided on the substrate of the AC-DC conversion circuit 309. The AC-DC conversion circuit 309 is provided with a high voltage wiring 309 for outputting the converted electric power to the outside.

  The high voltage generator 207 configured as described above amplifies the voltage by the piezoelectric element 301 when an AC voltage is applied from the AC power supply circuit to the piezoelectric element 301 via the input wiring 306 and the input electrode 302. Then, the high voltage generated in the piezoelectric element 301 is sent to the AC-DC conversion circuit 309 via the output electrode 303 of the piezoelectric element 301 and the high-voltage wiring 307, and the AC-DC conversion circuit 309 converts the AC voltage to the DC voltage. Then, a high DC voltage is supplied to the input electrode 23 provided on the top of the insulator 22 in FIG. Further, the voltage across the feedback resistor 308 is measured, the measured voltage value is fed back to an external variable frequency oscillator (not shown), and the frequency of the variable frequency oscillator is set according to the measured voltage value. By making it low or high, it is possible to control the output voltage of the high voltage generator 207 to a predetermined voltage, for example, −20 KV.

  Moreover, since the physique of a high voltage generator can be made small by using the piezoelectric element 301, the installation to the exhaust pipe vicinity of a motor vehicle becomes easy. Here, when using a piezoelectric element in an automobile with a lot of vibrations, vibration countermeasures are also important. In the present invention, the support portion 304 can prevent displacement and dropping of the piezoelectric element 301 due to the vibration of the automobile, and the piezoelectric element 301 can be prevented. It has a configuration that does not inhibit its own effective vibration.

  FIG. 5 is an explanatory diagram for explaining the circuit configuration of the high voltage generator 207. The high voltage generating unit 207 includes a piezoelectric element 301, a feedback resistor 308, and an AC-DC conversion circuit 309. The high voltage generator 207 configured as described above amplifies the voltage by the piezoelectric element 301 when an AC voltage is applied to the piezoelectric element 301 from an AC power supply circuit (not shown). Then, the high voltage generated in the piezoelectric element 301 is sent to the AC-DC conversion circuit 309, and the AC-DC conversion circuit 309 converts the AC voltage to the DC voltage, and the DC high voltage is applied to an external load (not shown). Supply. Also, the voltage across the feedback resistor 308 is measured and fed back to a variable frequency oscillator (not shown) provided outside, and the frequency of the variable frequency oscillator is lowered or raised according to the measured voltage value. Thus, the output voltage of the high voltage generator 207 can be controlled to a predetermined voltage, for example, −20 KV.

  FIG. 6 is an explanatory diagram showing a circuit configuration of the AC power supply circuit according to the embodiment of the present invention. The AC power supply circuit includes a battery 501, a DC-AC conversion circuit 502, and a variable frequency oscillator 503. The AC power supply circuit configured as described above sends a DC voltage from the battery 501 to the DC-AC conversion circuit 502, converts the DC voltage into an AC voltage by the DC-AC conversion circuit 502, and converts the AC voltage by the variable frequency oscillator 503. Adjust the frequency and output.

  As described above, according to the present invention, the size of the high-voltage generator can be reduced, so that it can be easily installed near the exhaust pipe of an automobile. Moreover, since the high voltage wiring connecting the discharge electrode device and the high voltage generator can be shortened, it is possible to provide an exhaust gas treatment device with little power loss between the discharge electrode device and the high voltage generator.

  Note that the configuration used in the present invention is not limited to the configuration of the present embodiment as long as the object of the present invention can be achieved. For example, when a corona discharge is generated between the discharge electrode device 2, the first ground electrode 5, and the second ground electrode 4, the voltage drop applied between both electrodes is set in the range of 5 KV to 50 KV. To do. Thereby, it is possible to obtain a suitable exhaust particle aggregation effect while satisfying an appropriate withstand voltage leak characteristic when a voltage is applied between the electrodes. Preferably, the voltage drop applied between the two electrodes is preferably set in the range of 10 KV to 30 KV, and the distal end portion of the discharge electrode 21 is not limited to a shape in which a plurality of distal end portions are positioned radially, but as required The container 300 can be appropriately changed as necessary, such as a cylindrical shape, and the bellows cylindrical portion 202B of the housing 202 can be appropriately changed as necessary, such as a cylindrical shape. The first ground electrode 5 made of the inner peripheral wall of the exhaust pipe and the second ground electrode 4 made of a conductive net are not necessarily at the ground potential, and as shown in FIG. The potential may be adjusted higher by providing a capacitor or the like.

It is sectional drawing which shows the structure of the coagulator of embodiment in this invention. FIG. 7 is a view taken in the direction of arrow X in FIGS. 1 and 6. It is an enlarged view of the discharge electrode apparatus 2 of FIG. It is explanatory drawing which shows the structure of the high voltage generation | occurrence | production part 207 of FIG. It is explanatory drawing explaining the circuit structure of the high voltage generation part 207 of FIG. It is description which shows the circuit structure of the alternating current power supply circuit of embodiment in this invention. It is sectional drawing (2) which shows the structure of the coagulator of embodiment in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aggregator 2 Discharge electrode apparatus 3 1st ground electrode 4 2nd ground electrode 5 Exhaust pipe 207 High voltage generation part

Claims (6)

An exhaust pipe of an internal combustion engine;
A discharge electrode device fixed in a state in which the discharge electrode protrudes into the exhaust pipe;
A power supply installed in the car;
An exhaust gas treatment device comprising a high voltage generator for boosting a voltage supplied by the power supply device and supplying a high voltage to the discharge electrode device,
The exhaust gas treatment apparatus according to claim 1, wherein the voltage boosting in the high voltage generator is performed by a piezoelectric element. The piezoelectric element comprises a long plate-shaped piezoelectric ceramic plate,
Housed in a substantially cylindrical container,
Fixed by a plurality of supports,
One end of the support portion is in contact with or near a portion that becomes a node of piezoelectric displacement of the piezoelectric ceramic plate,
The exhaust gas processing apparatus according to claim 1, wherein the other end of the support portion is in contact with an inner wall of the container. The exhaust gas processing apparatus according to claim 2 or 3, wherein the high voltage generator includes an AC-DC conversion circuit. 4. The exhaust gas processing apparatus according to claim 1, wherein the high voltage generator is integrated with the discharge electrode device. The high voltage generator is installed in the axial direction and in the vicinity of the discharge electrode device,
Connection means for electrically connecting the output electrode of the high voltage generator and the input electrode of the discharge electrode device is provided,
The exhaust gas processing apparatus according to claim 4, further comprising a housing that covers the connection portion. A ground electrode made of a conductive film disposed downstream of the discharge electrode device and having a large number of air holes;
6. The exhaust gas processing apparatus according to claim 1, wherein the exhaust pipe and the ground electrode are substantially grounded.

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