JPH05231139A - Exhaust emission control device for internal combustion engine and exhaust purifying method - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device for controlling exhaust gas emission from the engine start to the ordinary traveling state, as for a device for control the emission of exhaust gas of a gasoline engine which utilizes the high frequency wave energy. CONSTITUTION:An exhaust emission control device is equipped with a first purifying means 3 which is high-frequency-wave-heated by an oscillator for transmitting high frequency waves, second purifying means 4 which is heated by the heat of exhaust gas, and the third purifying means 9. With this constitution, the high purification performance for the harmful substance contained in the exhaust gas can be realized from the engine start to the ordinary traveling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purifying apparatus for decomposing harmful substances such as hydrocarbons and carbon monoxide contained in exhaust gas discharged from an internal combustion engine of an automobile and a method for purifying the same.

[0002]

2. Description of the Related Art In automobiles using gasoline as a fuel, emission regulations of hydrocarbons, carbon monoxide, and nitrogen oxides contained in exhaust gas are being tightened. As one of the purification methods for these pollutants, there is a post-treatment method using a catalyst, which is currently in practical use. As a typical catalyst used in this post-treatment method, by controlling the air-fuel ratio near the stoichiometric air-fuel ratio, oxidation of hydrocarbons and carbon monoxide and reduction of nitrogen oxides are simultaneously performed, and harmless carbon dioxide and steam , There is a three-way catalyst that converts to nitrogen, and this three-way catalyst is mainly installed in passenger cars.

FIG. 5 schematically shows the structure of a conventional exhaust gas purifying unit mounted on a passenger car. In the figure, reference numeral 51 denotes an engine, which has an exhaust manifold 52 and communicates with an exhaust pipe 53. An oxygen sensor 54 is an exhaust pipe 53.
It is attached to. A three-way catalyst 55 is housed in a container 56 and has a function of converting harmful substances in the exhaust gas flow into harmless substances. Reference numeral 57 is an exhaust temperature sensor, and 58 is a muffler. As described above, the conventional exhaust gas purifying apparatus includes the three-way catalyst body 55 and the container 56, and the three-way catalyst body 55 is arranged in the middle of the exhaust pipe 53 connected to the exhaust manifold 52. As disclosed in Japanese Examined Patent Publication No. 52-3358, the three-way catalyst 55 is a carrier made of a cordierite ceramic honeycomb structure containing silica, alumina, and magnesia as main components, and fine particles such as alumina having a large surface area. Is provided, and the fine particles of noble metal such as platinum, palladium, and rhodium are supported on the coating layer.

When the engine 51 is started, the exhaust gas generated by combustion passes through the exhaust manifold 52 and is guided to the exhaust gas purifying device provided in the middle of the exhaust pipe 53. The exhaust gas passes through each cell constituting the honeycomb structure of the three-way catalyst 55 and is discharged to the atmosphere through the exhaust pipe 53 at the right end of the drawing. At this time, the air-fuel ratio is controlled near the stoichiometric air-fuel ratio by the oxygen sensor 54, and hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas are harmless carbon dioxide gas due to the oxidation and reduction reactions of the three-way catalyst body 55. , Converted to steam and nitrogen. However, in order for the above reaction to occur, it is necessary to raise the temperature of the three-way catalyst body 55 to a temperature at which it functions as a catalyst. The three-way catalyst 55 is heated by the heat of the exhaust gas, but it takes about one minute to reach the temperature that functions as a catalyst when the automobile engine starts, and until then, harmful exhaust gas is discharged to the atmosphere. Will be done.

In order to reduce the emission of the harmful exhaust gas, a honeycomb structure made of metal having a smaller volume than the three-way catalyst body 55 and carrying a catalyst is arranged on the front surface of the three-way catalyst body 55. Although a method of rapidly heating the catalyst using a heating means such as an electric heater or a burner to shorten the time required to reach the temperature at which it functions as a catalyst has not been put into practical use yet.

[0006]

In the above conventional structure, the catalyst body is heated by the exhaust gas, and therefore it takes about 1 minute to reach the temperature at which it functions as a catalyst.
Although this situation meets current emission regulations,
Regarding exhaust gas regulations that will be further tightened in the future, the emission amount of harmful substances, especially hydrocarbons, in the exhaust gas at the time of starting the automobile engine becomes a problem, and it is difficult to solve this with the current exhaust gas purification unit. There was a problem that there was.

Further, the conventional method for heating a honeycomb structure made of metal arranged in front of a three-way catalyst body with a burner is as follows.
There have been problems such as the generation of hydrocarbons when the burner is ignited or misfired, and the reliability of the combustion components including the burner is poor.

Further, the method of using an electric heater instead of the burner requires a large amount of electric power, so that the electric wire becomes large and the wiring becomes difficult, and a separate drive power source is required, and sufficient electric power is supplied from the vehicle power source. There was a problem that it was practically difficult.

It is an object of the present invention to solve the above-mentioned problems, and to rapidly heat a purifying means for decomposing harmful substances contained in exhaust gas by high frequency, and to remove harmful substances in exhaust gas at the time of starting an automobile engine. Can be reduced and
It is an object of the present invention to provide an exhaust gas purification device and a purification method thereof, which can sufficiently supply a driving power source of a high frequency generation source from an automobile power source.

[0010]

In order to achieve the above object, a purifying apparatus and a purifying method of the present invention include a high-frequency oscillator for supplying high-frequency energy to a heating chamber in which exhaust gas of an internal combustion engine flows, and a high-frequency oscillator housed in the heating chamber. First purification means that decomposes harmful substances contained in the exhaust gas by being heated by high-frequency energy, and is disposed behind the first purification means with respect to the flow of the exhaust gas while being housed in the heating chamber. ,
Second purification means for decomposing harmful substances contained in the exhaust gas by being heated by the heat of the exhaust gas and heat generated by the first purification means; and the first purification means for the flow of the exhaust gas. The third purification means is disposed behind the heating chamber containing the second purification means, and is heated by the heat of the exhaust gas to decompose the harmful substances contained in the exhaust gas. ..

In addition to the above-mentioned structure, the present invention can also be configured to have a supply means for supplying a gas containing oxygen to the heating chamber.

The present invention also provides, as a first purification means for decomposing harmful substances, a carrier made of ceramics, a high-frequency absorbing material which absorbs high frequencies and generates heat by being carried on the carrier made of ceramics, and the high-frequency absorbing material. It is also possible to use a catalyst that promotes the decomposition of harmful substances carried on the surface and voids of the above, a carrier made of the ceramic, the high frequency absorbing material, and an inorganic binder that adheres the catalyst.

Further, according to the present invention, as a second purifying means and a third purifying means for decomposing harmful substances, a carrier made of metal or ceramic and a catalyst for promoting decomposition of the harmful substances carried on the carrier are provided. It is also possible to adopt the configuration used.

[0014]

According to the present invention, the high-frequency energy is supplied to the heating chamber accommodating the first purifying means at the same time when the engine of the gasoline vehicle is started. At this time, since the first purification means carries a high-frequency absorbing material that efficiently absorbs high-frequency waves and generates heat, and a catalyst that decomposes harmful substances at low temperatures, hydrocarbons that are harmful substances contained in exhaust gas and The temperature can be raised to a temperature at which carbon monoxide is decomposed in a short time, and the harmful substances can be decomposed into harmless water vapor and carbon dioxide gas.

Further, the second purifying means disposed behind the first purifying means is heat generated by the first purifying means heated by high frequency, heat of the exhaust gas itself, and harmful substances in the exhaust gas. The catalyst is heated by the reaction heat generated by the decomposition of the catalyst and rises to a temperature at which the catalyst carried by the second purifying means functions, so that the purification performance of exhaust gas is further improved.

On the other hand, about 1 minute after the engine is started, the temperature of the exhaust gas itself becomes high, so that the first purifying means is kept at a temperature above which the harmful substances can be decomposed, and heating by high frequency energy is unnecessary. 1st and 2nd
The third purifying means arranged behind the purifying means is also heated by the heat of the exhaust gas and the heat emitted from the first purifying means, and rises to a temperature at which the harmful substance can be decomposed or higher. Therefore, even if the amount of exhaust gas increases due to the vehicle entering a running state and the engine speed increasing, the third purifying means maintains a high purifying performance because it has a function of decomposing harmful substances in the exhaust gas. You can

Further, by providing the heating chamber with a supply means for supplying a gas containing oxygen, oxygen necessary for decomposing hydrocarbons and carbon monoxide which are harmful substances in the exhaust gas is sufficiently supplied. can do. Therefore, a gas containing oxygen can be supplied from the supply means to the first purification means heated by high-frequency energy, and in this case, the progress of decomposition reaction of harmful substances can be promoted, resulting in higher purification performance. Can be obtained.

Further, by using a catalyst for decomposing harmful substances at a low temperature in the first purifying means, the decomposing reaction of the above-mentioned harmful substances can be caused at a lower temperature, the purifying performance is further improved, and the high frequency energy is increased. It is possible to further reduce the power consumption required for the occurrence of.

Further, since the carrier used for the first, second and third purifying means can be a honeycomb structure of ceramic fibers, in that case, the heat capacity can be further reduced, so that the purifying means can be used. The rate of temperature rise becomes faster,
While being advantageous for improving the purification performance of the harmful substances,
Since the temperature difference of the cleaning means can be reduced, it is possible to prevent the occurrence of cracks due to thermal factors.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) In FIG. 1, 1a and 1b are exhaust pipes for exhausting exhaust gas of an internal combustion engine, and a heating chamber 2 is provided in the middle thereof, and a first purifying means 3 is housed in the heating chamber 2. Has been done. The first purification means 3 has a function of decomposing harmful substances such as hydrocarbons and carbon monoxide contained in the exhaust gas. Reference numeral 4 denotes a second purifying unit which is housed in the heating chamber 2 and which is arranged behind the first purifying unit 3 with respect to the flow of the exhaust gas and has a function of decomposing harmful substances contained in the exhaust gas. .. Reference numeral 5 is a heat insulating material for supporting and insulating the first and second purifying means 3 and 4, respectively. Reference numeral 6 is a high-frequency oscillator that generates high-frequency energy to be supplied to the heating chamber 2, and is connected to a waveguide 7 that transmits the high-frequency generated from the high-frequency oscillator 6 to the heating chamber 2. The exhaust gas inflow side of the heating chamber 2 of the waveguide 7 has a blocking structure 7a that blocks a high frequency and has a large number of punching holes so that the exhaust gas can be introduced into the first purifying means 3. The exhaust gas outflow side has a structure in which the exhaust gas is allowed to pass and an opening is provided for supplying high frequency power to the first purifying means 3. Further, around the opening, there is a blocking structure 7b provided with a large number of punching holes capable of blocking high frequency in order to reduce pressure loss of exhaust gas. Reference numeral 8 is a high-frequency shielding means for preventing high-frequency leakage to the second purification means 4, and is composed of a metal plate having a large number of punching holes or a metal honeycomb structure having a large number of through holes. Reference numeral 9 is a third purifying means for decomposing harmful substances contained in the exhaust gas heated by the heat of the exhaust gas. The third purifying means 9 is a first and second purifying means for the flow of the exhaust gas. It is arranged behind the heating chamber 2 that houses the means 3 and 4.

The exhaust gas discharged from the engine flows through the exhaust pipe 1a in the direction shown by the arrow in FIG. 1 and flows into the first purifying means 3. The harmful substances such as hydrocarbons and carbon monoxide contained in the inflowing exhaust gas are decomposed by the first, second and third purifying means 3, 4, 9 and the purified exhaust gas is discharged to the atmosphere through the exhaust pipe 1b. To be done.

FIG. 2 shows the appearance of the first purifying means 3 used in the exhaust gas purifying apparatus of the present invention. As the carrier 3a of the first purifying means 3, a honeycomb structure having a large number of communication holes 3c formed by ceramic partition walls 3b as shown in FIG. 2 is applied. The carrier 3a made of this honeycomb structure is made by corrugating a porous sheet made of ceramic fibers such as alumina, silica, zirconia, or by extruding a cordierite ceramic powder mainly containing alumina, silica, magnesia. Be done. The carrier 3a made of the honeycomb structure described above carries a high-frequency absorbing material that efficiently absorbs high-frequency waves and generates heat, and a catalyst that decomposes harmful substances in exhaust gas at low temperatures.

In FIG. 3, the high frequency absorbing material and the catalyst are carriers 3
It is a partial cross section figure of the 1st purification | cleaning means 3 which shows the state supported by a. FIG. 3A shows a carrier 3a having a honeycomb structure.
Is composed of ceramic powder, and 3b is a ceramic partition wall of the carrier 3a, so that most of the high frequency absorbing material 10 and the catalyst 11 are ceramic partition walls 3b.
In the state of being carried on the surface of the above, the above-mentioned respective materials are adhered by the inorganic binder 12. On the other hand, the same figure (b)
Shows the case where the carrier 3a having the honeycomb structure is made of ceramic fibers, and 13 shows the ceramic fibers. Since the carrier 3a composed of the ceramic fibers 13 is porous, the high-frequency absorbing material 10 and the catalyst 11 are supported not only on the surface of the carrier 3a but also inside the carrier 3a. Are glued together.

A conventional three-way catalyst can be applied to the second and third purification means 4 and 9, and a coating layer made of fine particles such as alumina having a large surface area is provided on a ceramic carrier having a honeycomb structure. It is obtained by supporting fine metal particles of platinum, palladium, rhodium or the like on (not shown). Further, a metal carrier having an oxide film formed thereon instead of the ceramic carrier and the oxide film carrying the catalyst can also be applied. Further, the second and third purifying means 4 and 9 may have the same composition as that of the first purifying means 3. However, in that case, the high frequency absorbing material 10
You don't have to.

Next, a purification process by decomposing harmful substances contained in the exhaust gas in the exhaust gas purifying apparatus of the present invention will be described.

When the engine of a gasoline vehicle is started, the exhaust gas containing harmful substances such as carbon monoxide and hydrocarbons discharged from the engine passes through the exhaust pipe 1a and passes through the first purification means 3
Flow into. At the same time when the engine is started, the high frequency oscillator 6 generates a high frequency according to a command from a control unit (not shown),
This high-frequency energy is transmitted through the waveguide 7 and supplied to the heating chamber 2 that houses the first purifying means 3. The high-frequency absorbing material 10 forming the first purifying means 3 absorbs the supplied high-frequency energy and is converted into heat energy, whereby the first purifying means 3 is heated. At this time the first
A catalyst 11 is carried on the purifying means 3 of the above, and when the catalyst 11 rises to a temperature capable of decomposing harmful substances in the exhaust gas, it reacts with oxygen contained in the exhaust gas and is harmless with water vapor and carbon dioxide. It decomposes into gas and the exhaust gas is purified.

On the other hand, the second purifying means 4 arranged behind the first purifying means 3 generates heat from the first purifying means 3 heated by high-frequency energy, heat of the exhaust gas itself, and in the exhaust gas. It is heated by the heat of reaction generated by the decomposition of harmful substances. When this heating causes the catalyst carried by the second purification means 4 to rise to a temperature at which harmful substances in the exhaust gas can be decomposed, it reacts with oxygen contained in the exhaust gas and decomposes into harmless water vapor and carbon dioxide gas. The exhaust gas is further purified. Due to the function of the second purification means 4, the exhaust gas purification performance is further improved. The purified exhaust gas passes through the muffler and is discharged to the atmosphere through the exhaust pipe 1b.

As a first purifying means 3 of an embodiment of the present invention, a carrier 3a made of ceramic powder having a honeycomb structure.
When using (as shown in FIG. 3 (a)), the high frequency absorbing material 1
0 and the catalyst 11 are carried on the surface of the ceramic carrier. Therefore, the absorption of high frequency energy is the first
Only the surface layer of the purifying means 3 can raise the temperature of the catalyst 11 to a temperature at which the harmful substances can be decomposed in a short time, and the purification performance of the harmful substances contained in the exhaust gas at the time of starting the automobile engine is improved. Can be made

When the ceramic fiber 13 is used as the ceramic carrier (shown in FIG. 3 (b)), the high frequency absorbing material 10 and the catalyst 11 are carried not only on the surface of the first purifying means 3 but also inside thereof. A porous structure can be obtained as the state changes. Therefore, the first purifying means 3 can increase the heat generation surface area and the catalyst surface area and also have a small heat capacity, so that the entire first purifying means 3 can be raised to a temperature at which harmful substances can be decomposed in a short time. The purification performance of exhaust gas can be further enhanced.

Further, the high-frequency absorbing material 10 having high high-frequency absorption characteristics is carried on the ceramic carrier constituting the first purifying means 3, whereby the above-mentioned first purifying means 3 is carried out.
In the case of applying the high frequency heating method as the heating means, the power consumption can be about 1/3 to 1/2 as compared with the case where the same temperature rise is obtained by the electric heater heating method (heating of the metal honeycomb carrier). Therefore, the driving power source of the high frequency generation source can be sufficiently supplied from the vehicle power source.

High frequency absorption material 1 having high high frequency absorption characteristics
Examples of 0 include semiconductor materials, and particularly selected from the group consisting of zinc, copper, manganese, cobalt, iron, tin, titanium, oxides containing silicon as a main component, carbides, and complex oxides containing the metals. At least one type is applied. The mechanism by which the above-mentioned material absorbs a high frequency and converts it into heat is that the semiconductor material absorbs a high frequency due to the large dielectric constant and dielectric loss of the semiconductor material and generates heat.

Examples of the catalyst 11 for decomposing harmful substances in exhaust gas at low temperature include precious metals such as platinum, palladium and rhodium, copper, manganese and cobalt oxides, and perovskite type complex oxides, and at least one of them is used. Are supported on a ceramic carrier having a honeycomb structure together with the high frequency absorbing material 10.

The inorganic binder 12 is not particularly limited, but colloid particles of alumina, silica, zirconia, etc., which are excellent in heat resistance and adhesiveness, are preferable.

Next, concrete experimental examples of the first purifying means 3 of the present invention will be described. As a carrier, the ceramic honeycomb structure (cordierite, volume 2) shown in FIG.
00cc, 200 cells / square inch), high frequency absorbing material 1
Fibrous (preferably whiskers) silicon carbide as 0,
A first purifying means 3 composed of palladium as the catalyst 11 and alumina sol as the inorganic binder 12, and FIG.
Propylene 8 was used as the model gas for the exhaust gas using the exhaust gas purification device (high-frequency power consumption 1.5 kW) shown in
When the propylene purification performance by a hydrocarbon analyzer was evaluated as a concentration of 00 ppm (flow rate 80 liters / minute),
A purification rate of about 70% was obtained in one minute of high frequency power feeding. Further, in place of the fibrous silicon carbide which is the high frequency absorption material 10, oxides of zinc, copper, manganese, cobalt, titanium, tin, iron, a mixture thereof, and a metal thereof are used.
Almost the same purification performance was obtained when the compound oxide containing at least one species and the compound of titanium-silicon-carbon-oxygen were used.
Moreover, when a noble metal such as platinum or rhodium, a perovskite type complex oxide such as lanthanum or cobalt, or an oxide of copper, manganese or cobalt is used instead of palladium which is the catalyst 11, a purification rate of 40 to 70% is obtained. Was given.

On the other hand, a honeycomb structure (alumina / silica fiber, volume 200 cc, 200 cells / inch 2) made of the ceramic fiber 13 shown in FIG. 3B is used as a carrier, and a fibrous (whisker-shaped) material is used as the high frequency absorbing material 10. Silicon carbide, palladium as catalyst 11, inorganic binder 1
First purification means 3 composed of alumina sol as 2
And the exhaust gas purification device (high frequency power consumption 1.5
When the propylene purification performance was evaluated by a hydrocarbon analyzer using kW as a model gas of the exhaust gas and 800 ppm concentration of propylene (flow rate of 80 liters / minute), a purification rate of about 80% was obtained in 1 minute of high frequency power supply. It was When zirconia fibers were used instead of alumina / silica fibers, the same performance as above was obtained.

The above-mentioned ceramic carrier having a honeycomb structure may be any of those shown in FIGS. 3 (a) and 3 (b), but the ceramic fiber 13 shown in FIG. 3 (b) has a higher heat capacity. Since it can be made small (the weight per unit volume is small), the rate of temperature rise can be increased, and more excellent purification performance of harmful substances can be obtained. Further, since the temperature difference between the carriers can be reduced, it is possible to prevent the occurrence of cracks caused by thermal strain.

Since the oxygen concentration in the exhaust gas is extremely low when the engine is operated near the stoichiometric air-fuel ratio, the catalyst 11 is preferably a three-way catalyst composition of platinum and rhodium or palladium and rhodium. With this catalyst composition, a redox reaction can be caused by nitrogen oxides, hydrocarbons, and carbon monoxide in the exhaust gas, and harmful substances can be purified even in an oxygen-deficient exhaust gas atmosphere.

On the other hand, the exhaust gas temperature gradually rises after the engine is started, and after about 1 minute, the first and second purifying means 3 and 4 rise above the temperature at which the harmful substances can be decomposed only by the exhaust gas temperature. .. Therefore, it is not necessary to heat the first purifying means 3 with the high frequency energy, and the high frequency oscillation from the high frequency oscillator is stopped. Normally, the vehicle is in a running state at this time, the amount of exhaust gas increases as the engine speed increases, and the first and second purifying means 3 and 4 can sufficiently purify harmful substances in the exhaust gas. Disappear.

However, in the exhaust gas purifying apparatus of the present invention, the third purifying means 9 is arranged behind the first and second purifying means 3 and 4, and the third purifying means 9 is the exhaust gas itself. And the heat released by the catalytic reaction of the first and second purifying means 3 and 4 are heated, and the temperature rises above the temperature at which harmful substances in the exhaust gas can be decomposed in a short time. Therefore, even if the vehicle enters a running state and the amount of exhaust gas increases, the third purifying unit 9 in addition to the first and second purifying units 3 and 4 has a function of decomposing harmful substances in the exhaust gas. It is possible to obtain high exhaust gas purification performance.

(Embodiment 2) FIG. 4 shows the structure of an exhaust gas purifying apparatus for an internal combustion engine according to another embodiment of the present invention. In the figure, the same members and the same functional members as in FIG. 1 are indicated by the same numbers. The difference from FIG. 1 is that the exhaust gas purifying apparatus is provided with a supply means for supplying a gas containing oxygen. Reference numeral 14 is a supply means for supplying a gas containing oxygen to the heating chamber 2, and a blower or various pumps are applied to the supply means 14, and the gas is introduced into the heating chamber 2 through the air guide tube 15. Further, a valve 16 for controlling the supply of the gas is provided in the middle of the air guide tube 15. The valve 16 is closed so that the exhaust gas from the engine does not flow into the supply means 14 when the exhaust gas purifying apparatus of the present invention is not used. Reference numeral 17 denotes an antenna that radiates a high frequency, and the high frequency generated from the high frequency oscillator 6 is transmitted through the waveguide 7 and is radially fed from the antenna 17 to the first purifying means 3. In this case, the waveguide 7 inside the heating chamber 2 does not need an opening for feeding high frequency as shown in FIG.
A large number of punching holes that allow exhaust gas to pass therethrough and shield high frequencies are provided. Reference numeral 4 denotes a second purifying means made of a metal molded body having a honeycomb structure, and an oxide film formed on the metal carries a three-way catalyst made of a noble metal such as platinum, palladium or rhodium.
When a metal molded body having a honeycomb structure is used as the second purification means 4, the microwave shielding means 8 shown in FIG. 1 need not be provided because it has a high-frequency shielding function itself. Further, a third purifying means 9 is arranged behind the first and second purifying means.

Oxygen is required to decompose the harmful substances such as hydrocarbons and carbon monoxide in the exhaust gas and convert them into water vapor and carbon dioxide. However, when the engine is operated in the vicinity of the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is extremely low, which causes a problem that the above reaction is not performed smoothly. In the present invention, as shown in the above configuration, the reaction can be smoothly caused by supplying the gas containing oxygen necessary for decomposing the harmful substance from the supply means 14 to the heating chamber 2. This can improve the purification performance of harmful substances such as hydrocarbons and carbon monoxide contained in the exhaust gas. When the amount of oxygen supplied from the supply means 14 exceeds the amount required for the above reaction, the concentration of nitrogen oxides in the exhaust gas tends to increase. Therefore, it is preferable to control the amount of oxygen to be supplied to an amount necessary for causing the above reaction smoothly.

In the present invention, the catalyst applied to the second and third purifying means 3 and 4 is preferably a three-way catalyst composition capable of purifying not only the above-mentioned hydrocarbons and carbon monoxide but also nitrogen oxides.

The first, second and third purifying means 3, 4,
The mounting position of 9 is not particularly limited, and is appropriately selected depending on the engine displacement, exhaust gas temperature, and the like.

[0045]

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention as described in the above embodiments, the following effects can be obtained. (1) Since high-frequency energy is supplied to the first purification means, the temperature rises to a temperature at which hydrocarbons and carbon monoxide, which are harmful substances contained in the exhaust gas, are decomposed in a short time, and the decomposition reaction causes no harm. Can be converted to steam and carbon dioxide. Therefore, it is possible to purify the harmful substances contained in the exhaust gas at the time of starting the automobile engine, and prevent or reduce the emission of the harmful substances to the atmosphere. When a high-frequency absorbing material having excellent high-frequency absorption characteristics is used for the first purifying means, the temperature rise is even faster. (2) Further, the exhaust gas purification performance is improved by arranging the second purification means heated by the heat of the exhaust gas and the heat released from the first purification means behind the first purification means. Therefore, the amount of harmful substances contained in the exhaust gas at the time of starting the automobile engine can be further reduced. (3) When a high frequency absorption material having high high frequency absorption characteristics is carried on the ceramic carrier constituting the first purifying means to oscillate high frequency energy, a heating method using an electric heater (heating of the metal honeycomb carrier) In comparison with the case where the same temperature rise is obtained, the power consumption can be reduced to about 1/3 to 1/2, and the driving power source of the high frequency generation source can be sufficiently supplied from the automobile power source. (4) Further, by disposing the third purifying means behind the first and second purifying means, the vehicle enters a running state, and even if the exhaust gas amount increases due to the engine speed increasing, In addition to the first and second purifying means, the third purifying means can decompose harmful substances in the exhaust gas, so that high exhaust gas purifying performance can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration cross-sectional view of an exhaust gas purifying apparatus for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a first purifying unit of the purifying apparatus.

FIG. 3 is a partially enlarged sectional view of the first purifying means.

FIG. 4 is a sectional view showing the configuration of an exhaust gas purifying apparatus for an internal combustion engine according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a conventional exhaust gas purifying apparatus.

[Explanation of symbols]

 1a, 1b Exhaust pipe 2 Heating chamber 3 First purification means 4 Second purification means 6 High frequency oscillator 7 Waveguide 8 Microwave shielding means 9 Third purification means 10 High frequency absorption material 11 Catalyst 12 Inorganic binder 13 Ceramic fiber 14 supply means 17 antenna

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location F01N 3/28 301 B 9150-3G

Claims (10)

[Claims] 1. A heating chamber in which exhaust gas of an internal combustion engine flows, a high-frequency oscillator for supplying high-frequency energy to the heating chamber, a high-frequency oscillator housed in the heating chamber, heated by the high-frequency energy, and contained in the exhaust gas. A first purifying means for decomposing harmful substances contained in the heating chamber and a first purifying means which is housed in the heating chamber and arranged behind the first purifying means with respect to the flow of the exhaust gas. Second purification means that is heated by the heat generated and decomposes harmful substances contained in the exhaust gas, and is disposed behind the first purification means and the second purification means with respect to the flow of the exhaust gas, An exhaust gas purifying apparatus for an internal combustion engine, comprising: a third purifying unit that is heated by the heat of the exhaust gas and decomposes harmful substances contained in the exhaust gas. 2. An exhaust gas purifying apparatus for an internal combustion engine, comprising a supply means for supplying a gas containing oxygen to the heating chamber according to claim 1. 3. A carrier in which the first purifying means is made of ceramic, a high-frequency absorbing material that absorbs high-frequency waves carried by the carrier made of ceramic, and a catalyst carried on the surface and in the voids of the high-frequency absorbing material. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 2, further comprising: a carrier made of the ceramic; a high-frequency absorbing material; and an inorganic binder that adheres the catalyst. 4. The internal combustion engine according to claim 1, wherein the second purifying means and the third purifying means have a carrier made of metal or ceramic and a catalyst carried on the surface of the carrier. Exhaust gas purification device for engines. 5. The first purifying means, the second purifying means, and the third purifying means each have a carrier made of ceramic or metal, and the carrier is a molded body having a honeycomb structure. The exhaust gas purification device for an internal combustion engine according to any one of 1 to 4. 6. The first purifying means, the second purifying means, and the third purifying means have a carrier made of ceramics, and the carrier is made of ceramic powder or ceramic fibers. Item 6. An exhaust gas purification device for an internal combustion engine according to any one of items 1 to 5. 7. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the first purifying means includes a high frequency absorbing material that absorbs high frequency, and the high frequency absorbing material is a semiconductor material. .. 8. The first purifying means comprises a high-frequency absorbing material that absorbs high-frequency waves, and the high-frequency absorbing material is zinc,
3. At least one selected from the group consisting of copper, manganese, cobalt, iron, tin, titanium, oxides containing silicon as a main component, carbides, and complex oxides containing the metal. 8. An exhaust gas purification device for an internal combustion engine according to any one of items 1 to 7. 9. The first purifying means, the second purifying means, and the third purifying means are provided with a catalyst, and the catalyst is platinum.
9. The method according to claim 1, further comprising at least one selected from the group consisting of rhodium, palladium metal, copper, manganese, or cobalt oxide, or perovskite complex oxide. An exhaust gas purification device for an internal combustion engine as described. 10. A high-frequency oscillating step of supplying high-frequency energy to a heating chamber in which exhaust gas of an internal combustion engine flows, and decomposing harmful substances contained in the exhaust gas when heated by the high-frequency energy in the heating chamber. A first purifying step, a second purifying step of decomposing harmful substances contained in the exhaust gas that has been heated by the heat generated in the first purifying step and passed through the first purifying step, and A method of purifying exhaust gas for an internal combustion engine, comprising: a third purification step of decomposing harmful substances contained in the exhaust gas that has been heated by the heat of the exhaust gas and passed through the second purification step.