JPH06123222A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device excellent in reliability by heating the emission control device and thereby raising its temperature efficiently within an extremely short time utilizing microwave energy, in order to purify exhaust emission of a gasoline engine, and purifing harmful materials generated in a large amount at the time of cold start of an engine. CONSTITUTION:A heating chamber 9, which feeds power through a waveguide 14 and a coaxial antenna, is fixed between an exhaust manifold 2 and a muffler 8 using a microwave generating high frequency oscillator 12, a purifing means, which is a substance to be heated and supports a heating unit and also a catalyst when required, is fitted to a ceramics carrier, microwave is applied to the purifing means, the substance to be heated, and heat is applied to the purifing means, the substance to be heated, uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purifying means for removing harmful substances such as hydrocarbons and carbon monoxide in exhaust gas discharged from an internal combustion engine at cold start of an automobile (hereinafter referred to as cold start). The present invention relates to a device for purifying exhaust gas by arranging the exhaust gas in the middle of the exhaust pipe to heat and raise the temperature by utilizing microwave energy and exhaust gas temperature discharged from the internal combustion engine.

[0002]

2. Description of the Related Art Pollutants emitted from automobiles are regarded as a problem as one of the sources of air pollution, and automobile exhaust gas regulations have been gradually implemented since the beginning of 1965. In recent years, regulations on the emission of such air pollutants have been tightened in various countries around the world, and in particular, the regulations on automobile exhaust gas have been changed from the conventional concentration regulations to the total amount regulations, and the regulation values themselves have also been significantly reduced. ing.

Among automobiles, gasoline cars are subject to stricter emission restrictions on hydrocarbons, carbon monoxide, and nitrogen oxides contained in exhaust gas. As methods for cleaning these pollutants, there are engine combustion methods such as complex eddy current combustion and lean combustion, and post-treatment methods with catalysts. Currently, post-treatment methods with catalysts, which are technically and economically superior, are put into practical use. Has been done. The catalyst used in this post-treatment system includes hydrocarbons, oxidation catalysts that oxidize carbon monoxide and convert them into harmless carbon dioxide gas and water vapor, and hydrocarbons by controlling the air-fuel ratio near the theoretical air-fuel ratio. There is a three-way catalyst that simultaneously oxidizes carbon oxides and reduces nitrites and converts them into harmless carbon dioxide, water vapor, and nitrogen, and these three-way catalysts are mainly installed in passenger cars.

FIG. 9 shows a conventional exhaust gas purifying apparatus mounted on an automobile. In the figure, 1 is an engine, 2 is an exhaust manifold, 3 is an exhaust pipe, 4 is an oxygen sensor, 5 is a three-way catalyst, 6 is a container for accommodating the catalyst, 7 is an exhaust temperature sensor, and 8 is a muffler. The conventional exhaust gas purifying apparatus comprises a three-way catalyst body 5 and a container 6, and the three-way catalyst 5 is arranged in the middle of an exhaust pipe 3 connected to an exhaust manifold 2. As disclosed in Japanese Examined Patent Publication No. 52-3358, the three-way catalyst body 5 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. A coating layer made of is provided, and fine particles of precious metal such as platinum, palladium, and rhodium are supported on the coating layer.

In the above structure, when the engine 1 is started, the exhaust gas due to combustion is guided through the exhaust manifold 2 to the three-way catalyst body 5 which is an exhaust gas purifying device provided in the middle of the exhaust pipe 3. This exhaust gas passes through each cell forming the honeycomb structure of the three-way catalyst body 5 and is exhausted to the atmosphere from the exhaust pipe 3. At this time, the air-fuel ratio is controlled near the stoichiometric air-fuel ratio by the oxygen sensor 4, and hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas oxidize the three-way catalyst body 5,
It is converted into harmless carbon dioxide, water vapor, and nitrogen by the reduction reaction. However, in order for the above reaction to occur, the three-way catalyst body 5
Needs to be heated to a temperature at which it functions as a catalyst. This three-way catalyst 5 is heated by the heat of the exhaust gas, but it takes about 1 minute to reach the temperature that functions as a catalyst at the cold start, and harmful exhaust gas is discharged to the atmosphere until then. Become.

In order to reduce the emission of the harmful exhaust gas, a metal honeycomb having a volume smaller than that of the three-way catalyst body 5 (one carrying a catalyst or one carrying no catalyst-- In this case, the rear side three-way catalyst body is rapidly heated), and this is rapidly heated using a heating means such as an electric heater or a burner to shorten the time to reach the temperature that functions as a catalyst. It is being examined, but it has not reached the practical level yet.

[0007]

However, in the above-mentioned conventional structure, it takes about 1 to 2 minutes to reach the temperature at which the catalyst functions as a catalyst because the catalyst is heated by the exhaust gas as described above. Although this situation has cleared the current exhaust gas regulations, the emission amount of harmful substances in the exhaust gas at the cold start (especially hydrocarbons that deplete the ozone layer) will be ) Became a problem, and it was difficult to meet the exhaust gas regulations with the current exhaust gas purification device.

In the conventional method of heating the metal honeycomb arranged on the front surface of the three-way catalyst body with the burner, the heating range is narrow, and it is difficult to bring the entire metal honeycomb to a temperature at which it functions as a catalyst in a short time. There is a problem that hydrocarbons are also generated from the heating means of the burner.

Further, the method of using an electric heater instead of the burner requires a large amount of electric power (a large amount of electric current), it is practically difficult to supply a driving power source from an automobile power source, and it is not durable or reliable. There were challenges.

The present invention solves the above-mentioned problems, and efficiently and rapidly heats a purification means for decomposing harmful substances contained in exhaust gas by microwaves to reduce harmful substances in exhaust gas at cold start. At the same time, it is an object of the present invention to provide a device capable of sufficiently supplying drive power for generating microwaves with a battery power source of an automobile.

[0011]

In order to achieve the above object, the present invention has a heating chamber provided in the middle of an exhaust pipe for discharging exhaust gas of an internal combustion engine and a waveguide mounted orthogonal to the heating chamber. A dipole antenna mounted orthogonally to the inside of the waveguide and the waveguide protrudes symmetrically toward the heating chamber, and the purifying means that is the object to be heated is installed substantially at the center of the heating chamber, and is attached to the dipole antenna. It is arranged symmetrically and apart.

The heating chamber provided in the middle of the exhaust pipe for discharging the exhaust gas of the internal combustion engine, and the purifying means, which is the object to be heated, having a diameter of 75 ± 5 mm and a volume of 80 ± 20 cc, are substantially the center of the heating chamber. It is configured to be installed in.

Further, a heating chamber provided in the middle of an exhaust pipe for discharging exhaust gas of an internal combustion engine, a waveguide mounted orthogonal to the heating chamber, and a microwave mounted orthogonal to the inside of the waveguide. The radiating portion of the dipole antenna, which is composed of the orthogonal portion for extracting energy and the portion for radiating microwave energy, has a configuration asymmetrical with respect to the object to be heated before and after the traveling of the microwave in the waveguide. .

Further, the tip diameters of the heating chamber provided in the middle of the exhaust pipe for discharging the exhaust gas of the internal combustion engine and the portion of the dipole antenna that feeds the heating chamber for radiating radio waves are at least approximately the same as the diameter of the object to be heated. Or, it has a smaller structure. Further, the diameter provided in the middle of the exhaust pipe for discharging the exhaust gas of the internal combustion engine is 85 to 100 mm, the length is a distance between the radiating portion of the dipole antenna and the purifying means is about 5 mm, and the end face distance between the purifying means and the heating chamber is substantially. The heating chamber having a diameter of 5 mm and the radiating portion of the antenna having a diameter of 65 ± 5 mm, and the cleaning means as the object to be heated are installed in the approximate center of the heating chamber.

[0015]

According to the present invention, when the engine of a gasoline car is started, high-temperature exhaust gas is discharged, and microwave energy is heated through the waveguide at substantially the same time (including about 10 seconds before engine start). Power is supplied to the heating chamber via a dipole antenna symmetrically arranged with respect to the chamber, and the purification means (heating element) and the catalyst for decomposing harmful substances in the exhaust gas stored in the heating chamber and the catalyst are in a short time. Is heated in.
That is, since the purification means uses a radio wave absorber that efficiently absorbs microwaves, the temperature is raised to a temperature at which hydrocarbons and carbon monoxide that are harmful substances contained in exhaust gas are removed in an extremely short time, A decomposition reaction occurs due to oxidation, and it is converted into harmless water vapor and carbon dioxide, which are released from the exhaust pipe to the atmosphere. Further, if the purifying means is made smaller, the temperature raising efficiency is improved, but the capacity is decreased due to poisoning and the space velocity value (Sp
sce Velocity value (SV value for short) becomes large and the decomposition and removal capacity decreases, so 70-120cc is SV
It is a limit of value and effective.

Further, in order to efficiently raise the temperature of the purifying means, microwave energy is supplied from the axial direction of the purifying means through the waveguide, but the temperature of the microwave does not rise completely uniformly, that is, The microwave on the opposite side of the radiating part of the dipole antenna with the high-frequency oscillator is stronger and the temperature becomes higher. To improve this, the shape of the dipole antenna is changed from symmetrical to partially asymmetrical, that is, the length of the radiating part. This can be improved by making the diameter (diameter) longer or shorter than other portions, or changing the length of the T-shaped or L-shaped tip of the radiating portion.

Similarly, in order to efficiently and uniformly raise the temperature of the purifying means, a fine heat generation temperature can be obtained by providing a plurality of portions of the dipole antenna that radiate microwave energy.

Further, it is effective that the tip diameter of the portion of the dipole antenna that radiates microwave energy is substantially the same as or smaller than the outer diameter of the purifying means. The reason seems to be that the microwave radiation is emitted from the tip of the antenna and is directly irradiated, and the portion is exposed to more radio waves due to the superposition effect of reflected waves. However, if the diameter of the radiating part of the antenna becomes small all around, the feeding cannot be matched, resulting in poor efficiency and poor temperature rise.

The shape of the heating chamber has a diameter of 9 from the experimental results.
When the length is 0 mm, the distance between the radiation part of the dipole antenna and the cleaning means is approximately 5 mm, and the distance between the cleaning means and the end face of the heating chamber is 5 m.
m, the diameter of the radiation part of the dipole antenna is approximately 65 ± 5 mm
Was the best to raise the temperature (Fig. 9). As described above, it is possible to raise the temperature of only the radio wave absorber and the catalyst by using the radio wave absorber that efficiently absorbs microwaves in the purification means, and the carrier is made of a material with small dielectric loss. Since the microwaves are not absorbed and the power consumption for generating the microwave energy, that is, for raising the temperature can be reduced, the drive power source of the microwave generation source can be sufficiently supplied from the battery of the vehicle power source.
Further, it goes without saying that by installing the device in front of the three-way catalyst body, the purification means is also effective as a temperature raising means for the three-way catalyst body.

[0020]

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

1 to 8, the same numbers represent the same parts names, 1 is an engine, 2 is an exhaust manifold, 3 is an exhaust pipe for discharging exhaust gas of an internal combustion engine, and 4 is oxygen for controlling an air-fuel ratio. A sensor, 5 is a three-way catalyst body, 6 is a container holding the three-way catalyst body 5, 7 is a temperature sensor for checking that the temperature of the three-way catalyst body 5 is raised, 8 is a muffler, 9 is a heating chamber, Reference numeral 10 is a heating object housed in the heating chamber 9, and purification means for decomposing hydrocarbons and carbon monoxide which are harmful substances contained in the exhaust gas while the exhaust gas passes through. 11 is inside the heating chamber 10. The supporting member for supporting the purifying unit 11 is made of a low dielectric material. The supporting member 11 also has a heat insulating function between the outer periphery of the purifying unit 10 and the inner wall of the heating chamber 9. Reference numeral 12 is a high-frequency oscillator that generates microwave energy to feed the heating chamber 9, 13 is a fan motor that cools the high-frequency oscillator 12, and 14 is a waveguide that transmits the microwave generated from the high-frequency oscillator 12 to the heating chamber 9. .
Reference numerals 15 and 16 denote dipole antennas A and B for irradiating the object to be heated with the transmitted microwave energy, 15 denotes a portion for extracting a radio wave from the waveguide, 16 denotes a portion for emitting the radio wave, and 17 denotes a heating chamber 9 Exhaust gas passage part A
And is composed of a metal plate having a punching hole for passing exhaust gas. Reference numeral 18 denotes an exhaust gas passage portion B that constitutes the heating chamber 9, and is constituted by a metal plate (or metal honeycomb) having a large number of punching holes. The high temperature exhaust gas discharged from the engine 1 flows through the manifold 2 from the direction shown by the arrow in FIG. The harmful substances such as hydrocarbons and carbon monoxide contained in the inflowing exhaust gas are purified by the purifying means 10, and the purified exhaust gas is discharged from the exhaust pipe 3 to the atmosphere through the muffler 8.

FIG. 3 is a second improvement plan, and it is considered that the microwaves emitted from the dipole antenna B16 are symmetrical. However, due to the dimensional structure of the heating chamber 9, it is difficult to achieve perfect symmetry. The other side of becomes stronger (higher temperature). In order to solve it easily, it can be solved by making the shape of the microwave emission dipole antenna B16, which is symmetrical, asymmetric. In the experiment, if the radius on the opposite side of the high-frequency oscillator with respect to the dipole antenna B16 is reduced by 5 to 8 mm, the temperature of the purifying means rises almost uniformly, but it may be reversed depending on the shape (size) of the purifying means. FIG. 4 is a variation plan of the emitting portion of the dipole antenna 16B.

FIG. 5 is a sectional perspective view of the main part of the heating chamber of the present invention. FIG. 6 shows a heating chamber configuration of the present invention having excellent heat generation efficiency, and shows the basic dimensions of essential parts. The diameter of the purification means 10, which is the object to be heated, is 68 mm and the thickness is 28 mm (102 cc)
At that time, the diameter of the heating chamber 9 is 90 mm, the length is 60 mm, the diameter of the radiating portion of the dipole antenna B16 is 70 mm, and the diameter of the purification means 10 which is the object to be heated is 68 mm and the thickness is 20 mm.
When (73cc), the heating chamber 9 has a diameter of 90mm and a length of 55.
mm, the diameter of the radiation part of the dipole antenna B16 is 60 m
m, and the diameter of the purification means 10 which is an object to be heated is 68 mm,
When the thickness is 14 mm (51 cc), the diameter of the heating chamber 9 is 90 mm,
When the length was 50 mm and the diameter of the radiating portion of the dipole antenna B16 was 60 to 65 mm, the best heat was generated. Under the same conditions, if the diameter of the heating chamber is smaller than 90 mm, the efficiency gradually deteriorates, and if the diameter becomes 85 mm, the efficiency deteriorates by about 20% (80 ° C. under a certain condition.
℃). However, the efficiency did not improve even if the diameter of the heating chamber was made larger than 90 mm. Furthermore, the diameter is 90
Increasing the length in mm didn't help.

FIG. 7 is a graph showing the temperature rise in the structure of FIG. FIG. 8A shows the appearance of the purifying means 10 used in the exhaust gas purifying apparatus of the present invention. As the carrier of the purifying means 10, a honeycomb structure having a large number of communication holes formed by ceramic partition walls 19 is applied as shown in FIG. 8B. The carrier made of this honeycomb structure is made by corrugating a porous sheet made of ceramic fibers such as alumina, silica, zirconia or by extrusion of ceramic powder of godierite mainly containing alumina, silica, magnesia. . Then, the carrier composed of the above-mentioned honeycomb structure carries a heating element (radio wave absorber) 20 for absorbing microwaves and a catalyst 21 to promote purification. With the above configuration, the purifying means 10 uniformly heats and raises the temperature by the microwaves, and at the same time, the heat generated by the catalytic reaction is applied to the downstream three-way catalytic body shown in FIGS. 1 and 2 at an early stage. It is possible to provide an exhaust gas purifying device that is extremely efficient in raising the temperature and using the battery of the automobile.

[0025]

As described above, in the exhaust gas purifying apparatus of the present invention, the waveguide is provided and the dipole antenna uniformly irradiates the heating element with microwaves to heat and raise the temperature of the purifying apparatus at the same time. Since it is superposed by temperature, the catalyst reaches the activation temperature very efficiently and in a short time to purify the exhaust gas, and at the same time, the heat of this reaction is further applied, and the temperature of the downstream three-way catalyst is also raised early to reach the activation temperature and the exhaust gas is exhausted. It is effective for purifying hydrocarbons that are often generated when the engine cold starts. Further, the power consumption of microwaves is small, and the present invention is a very useful invention in which the exhaust gas purifying device can be mounted on the existing battery.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the main part.

FIG. 3 is a sectional view of the dipole antenna unit.

FIG. 4 is a cross-sectional view of a microwave energy radiation part of the dipole antenna part.

FIG. 5 is a partial cross-sectional perspective view of a main part of the heating chamber.

[Fig. 6] Detailed dimensional drawing of the heating chamber

FIG. 7 is a diagram showing temperature characteristics of the heating chamber.

FIG. 8 is an enlarged perspective view of the purifying unit B. An enlarged view of a partition wall of the purifying unit.

FIG. 9 is an overall configuration diagram of a conventional example.

[Explanation of symbols]

 3 Exhaust pipe 9 Heating chamber 10 Purifying means (object to be heated) 12 High frequency oscillator 14 Waveguide 15 Dipole antenna A 16 Dipole antenna B

Claims (7)

[Claims] 1. A heating chamber provided in the middle of an exhaust pipe for discharging exhaust gas of an internal combustion engine, a waveguide attached to the heating chamber, and a dipole antenna attached to the waveguide are provided in the heating chamber. A purifying means, which is an object to be heated, is installed substantially at the center of the heating chamber and is arranged apart from the dipole antenna, and at the same time, microwave energy generated by a high-frequency oscillator feeding the heating chamber is used. An exhaust gas purifying apparatus for an internal combustion engine configured to raise the temperature of the purifying means, which is the object to be heated, by heat and exhaust gas temperature to remove harmful substances contained in the exhaust gas. 2. A heating chamber provided in the middle of an exhaust pipe for exhausting exhaust gas from an internal combustion engine and having a diameter of 75 ± 5 mm and a volume of 80.
The purification means, which is an object to be heated of ± 20 cc, is a purification means which is the object to be heated by the heat and the exhaust gas temperature by the microwave energy generated by the high-frequency oscillator that is installed in the approximate center of the heating chamber and supplies power to the heating chamber. An exhaust gas purifying device for an internal combustion engine, which is configured to raise the temperature of the exhaust gas and decompose harmful substances contained in the exhaust gas. 3. A heating chamber provided in the middle of an exhaust pipe for discharging exhaust gas of an internal combustion engine, a waveguide mounted in the heating chamber, and a waveguide mounted in the waveguide along the flow of the exhaust gas. The microwave energy radiating portion of the dipole antenna composed of a portion for extracting microwave energy and a portion for radiating microwave energy is asymmetric with respect to the traveling of microwaves in the waveguide with respect to the object to be heated. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, which has a shape. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein the portion that radiates microwave energy has a plurality of radial arms. 5. The portion for radiating microwave energy has a T-shaped or L-shaped tip of a radial arm.
Alternatively, the exhaust gas purifying apparatus for an internal combustion engine according to claim 4. 6. The diameter of the tip of the heating chamber provided in the middle of the exhaust pipe for discharging the exhaust gas of the internal combustion engine and the portion of the dipole antenna that feeds the heating chamber for radiating radio waves is at least approximately the diameter of the object to be heated. The exhaust gas purifying device for an internal combustion engine according to claim 5, wherein the exhaust gas purifying device is the same or smaller. 7. A diameter provided in the middle of an exhaust pipe for discharging exhaust gas of an internal combustion engine is 85 to 100 mm, a length is a distance between a radiating portion of a dipole antenna and a purifying means is about 5 mm, and the purifying means and a heating chamber are A heating chamber having an end face distance of about 5 mm and a diameter of the radiation portion of the dipole antenna of 65 ± 5 mm, and a dipole antenna attached to the heating chamber are projected toward the heating chamber, and purification means that is an object to be heated is provided. The object to be heated is installed in the heating chamber and is symmetrically arranged with respect to the dipole antenna, and at the same time, at the same time, the object to be heated is purified by the heat of the microwave energy generated by the high frequency oscillator feeding the heating chamber and the exhaust gas temperature. Heating up the means,
An exhaust gas purification device for an internal combustion engine configured to remove harmful substances contained in exhaust gas.