JP5379656B2 - Exhaust purification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device improved in durability. <P>SOLUTION: First conductive materials (31a) of a flat plate shape and second conductive materials (31b) of a flat plate shape each held between a first dielectric material (32a) and a second dielectric material (32b) are laminated alternately. Exhaust passages (36) are formed between the first conductive materials (31a) and the first dielectric materials (32a), and between the first conductive materials (31a) and the second dielectric materials (32b). In the first dielectric materials (32a) and the second dielectric materials (32b), on the surfaces facing the first conductive materials (31a), projections (34) of a hemispherical shape supporting the first conductive materials (31a) while keeping a predetermined distance from them are arranged dispersedly. Electric current is applied between the first conductive materials (31a) and the second conductive materials (31b) to generate plasma fields in the exhaust passages. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an exhaust gas purification device for purifying exhaust gas from an engine or the like, and more particularly to an exhaust gas purification device that improves exhaust gas purification efficiency and durability.

  Conventionally, an exhaust emission control device for purifying harmful substances (nitrogen oxide, carbon monoxide, particulate matter, etc.) contained in exhaust gas discharged from an internal combustion engine such as an engine mounted on a vehicle is provided. At present, exhaust purification apparatuses using precious metals as catalysts are widely used.

  On the other hand, it is known that a pair of electrodes is provided in the exhaust passage, and an silent current is generated by applying an alternating current or a pulse current between the electrodes, and the exhaust is purified from plasma generated by the discharge. ing.

  The plasma field in silent discharge generates active species, radicals, and ions, and is heated by Joule heat. Thereby, reaction and decomposition | disassembly of gas are accelerated | stimulated and the harmful component contained in exhaust_gas | exhaustion can be removed.

  As described above, by generating a plasma for exhaust purification, by laminating a structure having a flat conductor between a dielectric material formed in a comb shape and a flat dielectric, What constitutes a plasma generating electrode (see Patent Documents 1 to 4) is known.

International Publication No. 2004/072445 International Publication 2005/001250 JP 2005-177644 A JP 2006-185715 A

  The conventional plasma generating electrodes as described above can generate plasma at a lower voltage by reducing the distance between the electrodes, and the efficiency is increased. Therefore, a plurality of long rectangular passages are formed in the same direction as the exhaust passage by providing a plurality of dielectrics having a comb-shaped cross section, and exhaust is purified by discharging in the rectangular passage.

  However, in this dielectric having a comb-shaped cross section, the angle of the base portion of the projecting portion is a substantially right angle and an acute angle, so stress due to heat and vibration is concentrated. Since ceramic is generally used as the dielectric, there is a possibility that durability is lowered due to cracks and breakage.

  In addition, the electrodes provided in the long rectangular passage may be deformed by thermal expansion and the distance between the electrodes may be changed, so that the plasma field may not be generated uniformly.

  Moreover, since the cross-sectional area of each passage is reduced by dividing the exhaust passage into a large number, the ventilation resistance increases and the flow velocity of the exhaust increases, thereby shortening the time for the exhaust to pass through the plasma field. The purification efficiency may decrease.

  The present invention has been made in view of such problems, and improves exhaust gas purification efficiency by suppressing an increase in exhaust gas flow velocity, and also improves durability by preventing deformation and breakage due to stress concentration. An object is to provide an improved exhaust purification device.

  In the first aspect of the invention, the flat first conductors and the flat second conductors sandwiched between the first dielectric and the second dielectric are alternately laminated. In addition, an exhaust passage is formed between the first conductor, and the first dielectric and the second dielectric, and the first dielectric and the second dielectric are connected to the first conductor and the first conductor. A plurality of hemispherical protrusions supporting the first conductor at a predetermined distance are arranged on the facing surface, and a current is applied between the first conductor and the second conductor. By doing so, a plasma field is generated in the exhaust passage.

  According to a second aspect of the present invention, in the exhaust emission control device according to the first aspect, the protrusion includes a rib extending in a direction orthogonal to the exhaust flow direction of the exhaust passage.

  According to a third aspect of the present invention, in the exhaust emission control device according to the first or second aspect, the first conductor is a flexible and stretchable material, and a material through which exhaust can pass. It is characterized by comprising.

  According to the first aspect of the present invention, since the hemispherical protrusions for maintaining the distance between the first conductor and the first dielectric and the second dielectric are distributed, the exhaust Since the passage is not narrowed more than necessary, the exhaust resistance can be reduced. In addition, since the discharge gap can be kept uniform, a uniform and stable discharge can be obtained throughout the exhaust passage. In addition, since the protruding portion is hemispherical, there is no acute angle and stress is not concentrated. Therefore, cracks can be prevented from occurring in the dielectric, and durability can be improved.

  According to the second aspect of the present invention, since the rectangular parallelepiped-shaped rib extends in the direction perpendicular to the exhaust flow direction of the exhaust passage, the exhaust flow direction is changed and the entire exhaust gas flow is diffused. By being able to be disturbed, the residence time of the exhaust gas in the plasma discharge atmosphere can be lengthened, and the purification efficiency of harmful components can be improved.

  According to the third aspect of the present invention, the exhaust can pass through the first conductor, and the ventilation resistance can be reduced. Further, since the exhaust can be communicated between the upper surface and the lower surface of the first conductor, the exhaust pulsation in the discharge space can be absorbed. Thereby, exhaust loss can be reduced, purification efficiency of harmful components can be improved, and fuel consumption can be improved.

It is explanatory drawing of the exhaust gas purification system centering on the engine of embodiment of this invention. It is explanatory drawing of the exhaust gas purification apparatus of embodiment of this invention. It is an exploded view showing the composition of the exhaust emission control device of the embodiment of the present invention. It is explanatory drawing of the projection part of embodiment of this invention.

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

  FIG. 1 is an explanatory diagram of an exhaust purification system centering on an engine 10 according to an embodiment of the present invention.

  In the exhaust purification system of the present embodiment, the vehicle is driven by the engine 10 mounted on the vehicle. Further, the exhaust of the engine 10 is purified by an exhaust purification device 30 described later.

  The engine 10 as an internal combustion engine obtains a rotational driving force by explosively burning a fuel mixture of air and vaporized fossil fuel. The exhaust gas after the explosion combustion is discharged to the atmosphere through the exhaust pipe 20.

  The exhaust pipe 20 includes a manifold 21, an upstream pipe 22, an exhaust purification device 30, a downstream pipe 23, a silencer 24, and a tail pipe 25.

  Exhaust gas discharged from each cylinder of the engine 10 is collected by the manifold 21 and flows to the upstream pipe 22. The harmful substances contained in the exhaust gas are purified by the exhaust gas purification device 30.

  Exhaust gas that has passed through the exhaust purification device 30 passes through the downstream pipe 23, is silenced by the silencer 24, and is then discharged from the tail pipe 25.

  The exhaust gas purification device 30 generates a plasma field by an alternating current or a pulse current applied from the control device 40. The exhaust purification device 30 purifies the exhaust with active materials, radicals, ions, etc. generated in this plasma field.

  The control device 40 operates using the in-vehicle battery 50 as a power source, and applies an alternating current or a pulse current to the exhaust purification device 30. For example, an alternating current of 8 kV and 24 kHz is applied to the exhaust purification device 30.

  With this configuration, the drive system according to the present embodiment is capable of toxic substances (for example, nitrogen oxide (NOx), carbon monoxide (CO), and raw gas (HC) contained in the exhaust discharged from the engine 10. ) Suspended matter (PM) etc.) is reduced and decomposed into harmless nitrogen, carbon dioxide, etc. in the exhaust purification device 30 and discharged to the atmosphere.

  Next, the exhaust purification device 30 will be described.

  The exhaust purification device 30 of the embodiment of the present invention is provided in the middle of the exhaust pipe 20 and is a relatively harmless substance by reducing and oxidizing NOx, CO, HC, PM, etc. contained in the exhaust passing therethrough. Nitrogen (N2), carbon dioxide (CO2), water (H2O), etc. are changed.

  FIG. 2 is an explanatory diagram of the exhaust purification device 30 of the present embodiment. 2A is a top sectional view of the exhaust purification device 30, and FIG. 2B is a side sectional view of the exhaust purification device 30, respectively. The arrows indicate the flow of exhaust.

  The exhaust emission control device 30 is configured by laminating a conductor 31a and a conductor 31b sandwiched between a pair of dielectrics 32a and 32b.

  The conductor 31a has a rectangular flat plate shape, and a spacer 35 for holding the conductor 31a is provided on each short side. The spacer 35 holds the conductor so that the distance between the conductor 31a and the dielectrics 32a and 32b is kept constant.

  The conductor 31a is formed of a flexible and elastic conductive metal material (for example, a metal fiber sheet with a porosity of 80%). This allows a slight displacement in the thickness direction and a slight displacement in the plate direction.

  The conductor 31a is also made of a material through which exhaust can pass. Thus, the exhaust gas is configured to pass through the conductor 31a and pass from one surface of the conductor 31a to the other surface.

  Each of the dielectric bodies 32a and 32b has a rectangular flat plate shape, and a recess 33 for holding the conductor 31b is formed on one surface, and a plurality of protrusions 34 are formed on the other surface.

  The dielectrics 32a and 32b are made of dielectric ceramic such as cordierite, alumina, mullite, zirconia.

  The concave portion 35 has a concave shape that is substantially the same area as the conductor 31b and has a depth that is approximately half the thickness of the conductor 31b. In addition, the conductor 31b is comprised with the metal plate which has electroconductivity.

  As a result, the dielectrics 32a and 32b face each other on the concave portion 35 side, and the conductor 31b is sandwiched between the dielectrics 32a and 32b so that the conductor 31b is held between the dielectrics 32a and 32b. The

  A space formed between the conductor 31a and the dielectric 32a constitutes the exhaust passage 36a, and a space formed between the conductor 31a and the dielectric 32b constitutes the exhaust passage 36b. Exhaust gas passes through the exhaust passages 36a and 36b.

  The dielectric bodies 32a and 32b have the same structure and differ only in that the vertical direction is reversed. Henceforth, unless otherwise distinguished, “dielectric body 32” and “exhaust passage 36”. Is written.

  FIG. 3 is an exploded view showing the configuration of the exhaust emission control device 30 according to the embodiment of the present invention.

  A cable 310 is connected to the conductor 31a. A cable 311 is connected to the conductor 31b. These are connected to the control device 40. The conductor 31 a and the conductor 31 b are kept at a distance from each other by the spacer 33, and a space having a predetermined interval is formed by the dielectric 32.

  The control device 40 applies an alternating current (or pulse current) with the cable 310 as the ground side and the cable 311 as the high voltage side. Thereby, a silent discharge is generated between the conductor 31a and the dielectric 32 holding the conductor 31b. A plasma field is generated in the exhaust passage 36 by this silent discharge.

In this plasma field, oxygen and water contained in the passing exhaust gas are generated into active states such as radicals, ozone (O ₃ ) and ions (O ⁻ , OH ⁻ ). At this time, Joule heat is generated by the micro discharge current in the silent discharge flowing between the conductor 31a and the conductor 31b, and the PM mainly composed of carbon is burned.

  Thereby, NOx is reduced and converted into nitrogen and water. Further, CO, HC, PM and the like are oxidized and converted into carbon dioxide and water.

  The exhaust gas is purified by such an action.

  Here, the purification of the exhaust gas by the plasma field is more uniformly generated in the exhaust gas purification device 30 to increase the efficiency. In order not to increase the power consumption more excessively, it is desirable to make the distance between the electrodes, that is, the distance of the discharge gap between the conductor 31a and the dielectric 32 uniform.

  Efficiency also increases when the passing exhaust remains in the plasma field longer. For this purpose, it is desirable that the flow rate of the exhaust gas is suppressed and the flow of the exhaust gas is not linear inside the exhaust gas purification device 30 but becomes turbulent.

  On the other hand, the exhaust purification device 30 is placed in a place where a lot of vibrations are generated, such as an automobile, and receives thermal stress due to a rise and fall in temperature. For this reason, the positional relationship between the conductor 31 and the dielectric 32 may change due to vibration, or the distance between the conductor 31a and the conductor 31b may change due to thermal expansion of the conductor 31a. This prevents the generation of a uniform plasma field.

  In order to suppress the deformation of the conductor 31a exposed in the exhaust flow path, it is conceivable to project a lot of “support” portions on the dielectric 32 holding the conductor 31a. However, if a large number of support portions are formed in the exhaust flow path, the exhaust flow path is narrowed, the ventilation resistance is increased, and the exhaust flow velocity is increased.

  In addition, when the supporting portion is vertically provided from the dielectric 32, the base portion of the supporting portion is substantially perpendicular, and stress is concentrated. In particular, since the dielectric is made of ceramic, there is a possibility that cracks and breakage occur due to stress.

  Therefore, the exhaust gas purification apparatus 30 according to the embodiment of the present invention has a characteristic configuration as described below, and does not increase the ventilation resistance of the exhaust gas, and the gap between the conductor 31a and the dielectric 32 that generates a plasma field. In addition to minimizing the change in temperature, cracks and breakage due to thermal stress can be prevented.

  As described above, the dielectric 32 includes a plurality of protrusions 34 dispersed on the surface.

  The protrusion 34 includes a hemispherical protrusion 34a that protrudes in a hemispherical shape from the surface of the dielectric 32, and rectangular ribs 34b and 34c that extend in the radial direction of the hemispherical protrusion 34a. The ribs 34b and 34c are arranged in directions that are substantially perpendicular to the flow direction of the exhaust gas.

  The dielectric 32 has the protrusions 34 arranged in a lattice pattern. That is, as shown in FIG. 2A, the protrusions 34 are distributed and arranged in the long side direction and the short side direction of the dielectric 32. These protrusions 34 are arranged in a staggered arrangement in the exhaust passage 36.

  By arranging the projections 34 in this way, the direction of the flow of the exhaust gas passing through the exhaust passage 36 is changed by the projections 34. Thereby, since the exhaust is diffused and disturbed in the entire exhaust passage 36, the residence time of the exhaust in the plasma field can be lengthened and the purification efficiency can be improved.

  Further, by arranging the projections 34 in this way, the exhaust passage 36 as a whole is communicated, so that the pressure change of the exhaust having pulsation exhausted from the engine 10 is reduced, and the exhaust passage 36 Since the uneven pressure is also reduced, the durability of the conductor 31a is improved.

  FIG. 4 is an explanatory diagram showing a more specific configuration of the protrusion 34 according to the embodiment of the present invention. 4A is a top view of the protrusion 34, and FIG. 4B is a side sectional view of the protrusion 34. FIG.

  As shown in FIG. 4, the protrusion 34 includes a hemispherical protrusion 34 a that protrudes in a hemispherical shape, and ribs 34 b and 34 c that extend in the radial direction of the hemispherical protrusion 34 a.

  The height (radius) of the hemispherical protrusion 34a is configured to be slightly higher than the height of the ribs 34b and 34c.

  With this configuration, when the conductor 31a and the dielectric 32 are stacked, the hemispherical protrusion 34a holds the conductor 31a.

  As described above, since the conductor 31a is made of a flexible material, the conductor 31a is allowed to be deformed by the hemispherical protrusion 34a slightly protruding in the height direction from the ribs 34b and 34c.

  As a result, the conductor 31a and the dielectric 32 are positioned and fixed in the plate direction.

  Furthermore, even when the conductor 31a expands due to an increase in temperature, the slip resistance with respect to the conductor 31a is reduced by the hemispherical protrusion 34a, so that accumulation of thermal deformation strain of the conductor 31a can be suppressed. it can.

  With such a configuration, fluctuations in the distance between the conductor 31a and the dielectric 32 can be suppressed, so that the generation of the plasma field becomes more uniform.

  As an example of the shape of the protrusion 34, the height (r) of the hemispherical protrusion 34a is equal to the radius of the hemispherical protrusion 34a and equal to the discharge gap. The height (h) of the ribs 34b and 34c is set to (0.8 × r) so that the spherical portion of the hemispherical protrusion 34a and the conductor 31a are in contact with each other. The total width (w) of the ribs 34b and 34c is preferably about (4 × r) in consideration of an increase in ventilation resistance.

  The portable exhaust purification device 30 according to the present invention configured as described above can keep the discharge gap uniform by supporting the conductor 31a from above and below by the hemispherical protrusion 34a. A uniform and stable discharge can be obtained over the entire exhaust flow path of the device 30.

  Further, since the conductor 31a and the dielectric 32 have different coefficients of thermal expansion, the conductor 31a having a relatively large coefficient of thermal expansion expands and contracts as the temperature rises and falls.

  On the other hand, the sliding frictional resistance can be reduced by making the contact surface of the protrusion 34 supporting the conductor 31a spherical.

  As a result, since the thermal deformation distortion of the conductor 31a does not accumulate inside, the discharge gap can always be kept uniform, so that a uniform and stable discharge can be performed throughout the exhaust flow path of the exhaust purification device 30 even during operation. Can be maintained.

  Further, the shape of the protrusion 34 supporting the conductor 31a is a hemispherical protrusion 34a, and the ribs 34b and 34c are formed, so that the base of the surface of the dielectric 32 has an acute angle like a ridge shape. Since the portion is eliminated, the stress concentration portion can be eliminated, the occurrence of cracks in the dielectric 32 can be prevented, and the durability can be improved.

  Further, since the conductor 31a is made of a flexible and elastic conductive metal material (for example, a metal fiber sheet), the heat in the vertical direction generated from the difference in the temperature distribution inside the exhaust purification device 30 is obtained. Since the deformation is absorbed by the spring effect of the conductor 31a, the durability can be improved.

  Further, by configuring the conductor 31a with a material having a gap inside, the exhaust can pass through the conductor 31a, and the ventilation resistance can be reduced. Further, since the exhaust can be communicated with the upper surface and the lower surface of the conductor 31a, exhaust pulsation in the discharge space can be absorbed, and exhaust loss can be reduced.

  In addition, since the ribs 34b and 34c provided on the projection 34 are provided facing the exhaust flow direction, the exhaust flow direction can be changed to diffuse and disturb the entire exhaust gas flow. Thereby, the residence time of the exhaust gas in the plasma discharge atmosphere can be lengthened, and the purification efficiency of harmful components can be improved.

  Furthermore, since the purification efficiency of harmful components is improved, the exhaust purification device 30 can be reduced in size, so that power consumption and exhaust loss of the exhaust purification device 30 can be reduced, and fuel consumption can be improved. .

  In the embodiment of the present invention, an example in which only the exhaust purification device 30 is used for exhaust purification of the internal combustion engine as shown in FIG. 1 is shown, but a conventional catalytic converter may be further used in combination.

  For example, since the purification efficiency of the catalytic converter is reduced when the engine 10 is cold-started, the exhaust purification device 30 performs purification, and when the engine 10 is in steady operation, the exhaust purification device 30 uses only the catalytic converter. The function may be stopped.

  And since the catalytic converter increases the catalytic activity when the exhaust gas is at a high temperature, there is a restriction that the catalytic converter must be arranged as close to the engine 10 as possible, but the arrangement position of the exhaust purification device 40 is not limited. Therefore, the exhaust purification device 40 may be installed in the silencer 24 or the tail pipe 25.

  As a result, the amount of catalytic noble metal used by the catalytic converter can be reduced, and the energy efficiency of the vehicle can be increased to improve fuel efficiency.

10 Engine (Internal combustion engine)
20 Exhaust pipe 30 Exhaust purification device 31a, 31b Conductor 32a, 32b Dielectric 33 Recess 34 Protrusion 34a Hemisphere projection 34b, 34c Rib 35 Spacer 36a, 36b Exhaust passage 40 Control device

Claims (3)

The flat first conductor and the flat second conductor sandwiched between the first dielectric and the second dielectric are alternately stacked, and the first conductor An exhaust passage is formed between the first dielectric and the second dielectric,
The first dielectric body and the second dielectric body have a hemispherical protrusion that supports the first conductor at a predetermined distance on a surface facing the first conductor. Place multiple
An exhaust emission control device that generates a plasma field in the exhaust passage by applying a current between the first conductor and the second conductor. The exhaust emission control device according to claim 1,
The exhaust emission control device according to claim 1, wherein the protrusion includes a rib extending in a direction orthogonal to an exhaust flow direction of the exhaust passage. The exhaust emission control device according to claim 1 or 2,
The first electric conductor is a flexible and stretchable material, and is configured by a material through which exhaust can pass.

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