JPH07259534A - Exhaust particulate control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent such a possibility that additional fuel to be supplied might be discharged out without being oxidized in the case where an exhaust particulate collecting filter of an internal combustion engine carried with a catalyst is regenerated. CONSTITUTION:A catalyst being low in an activating temperature is carried on a circumferential part 23 of a catalyst-operated filter 21, while another catalyst being high in this activating temperature is carried on a central part 22. In this case, even if this circumferential part 23 is cooled by a running wind or the like and its temperature goes down therefore, there is no case that the catalyst will not be less than the activating temperature at all. When fuel additionally sprayed is supplied in an expansion stroke or the like of an internal combustion engine, heat due to an oxidic reaction is produced in the whole area of the filter 21, and since those of particulates accumulated are ignited and the filter is therefore regenerated, the added fuel is not oxidized, namely, it is discharged in the air as it is, so there is no fear of polluting the atmosphere at all. In addition, as the activating temperature of the catalyst carried on the central part 22 is high enough, a degraded temperature is also heightened according to the activating temperature, so that there is no fear of being deteriorated even if the central part 22 is made into high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly provided in an exhaust pipe line of an internal combustion engine, such as a diesel engine, which discharges exhaust gas containing fine particles (particulates) mainly containing carbon particles. The present invention relates to an exhaust particulate purifying apparatus for an internal combustion engine, which has a function of collecting the particulates by the filter and incinerating the particulates collected and deposited on the filter to regenerate the trapping ability of the filter.

[0002]

2. Description of the Related Art Diesel engine exhaust gas contains fine particles consisting mainly of carbon particles called "diesel particulates" and is also the causative substance of "diesel black smoke". In order to purify the exhaust gas, a filter made of a heat-resistant material that is porous and has good air permeability in a honeycomb structure for filtering the exhaust gas and collecting fine particles is provided in the exhaust pipe line. Is being done. Generally, porous ceramics are often used as a material for a filter for collecting fine particles.

When the exhaust gas is filtered by such a filter and the collection of the fine particles is continued, the collected fine particles are gradually deposited on the filter to lower the air permeability of the filter.
Exhaust gas passage resistance increases, which increases the back pressure of the internal combustion engine and lowers performance. Therefore, particulates trapped and accumulated on the filter are sometimes removed by some means (this is called filter regeneration). )Must.

As a means for removing the accumulated fine particles and regenerating the filter, the fine particle collecting filter is made of a porous and heat-resistant inorganic material like the catalyst carrier of a normal catalytic converter. , Because it is placed in the exhaust pipe, it not only functions as a filter for particulates but also as a carrier for the catalyst so that the filter itself is coated with the catalyst and carried, and at the end of the expansion stroke. By injecting additional fuel into the exhaust gas and oxidizing the additional fuel by the catalyst carried on the filter, the temperature of the particulates collected by the filter by the heat of oxidation reaction generated at that time is set to the ignition temperature. A method is known in which the particles are burned by incinerating them by increasing the above.
(See JP-A-58-38311.)

An example of the entire structure of an exhaust gas purification apparatus for an internal combustion engine including this conventional technique will be described with reference to FIG. The diesel engine 1 is a four-cylinder engine having four cylinders # 1 to # 4, and each cylinder includes a fuel (injection) pump 2 to a fuel line 3 (# 1 and # 3 cylinders 3a and 3a, respectively). 3c only) and injector 4 (only injectors 4a, 4c are shown) supplied with fuel pressurized. Exhaust gas discharged from each cylinder flows into a catalytic particulate matter filter (filter with catalyst) 6 through a common exhaust pipe line 5,
It is filtered and discharged from the exhaust pipe 7 into the atmosphere.

In the case of the prior art disclosed in Japanese Patent Laid-Open No. 58-38311, for example, only the flow of fuel from the fuel line 3a of the cylinder # 1 to the fuel line 3c of the cylinder # 3 is allowed. An electromagnetically operable check valve 8 is provided between the fuel lines 3a, 3c so that when the control device 9 issues a control signal, the check valve 8 allows the fuel flow in such a direction. The valve is opened and the valve is kept closed at other times.

Since the # 1 cylinder and the # 3 cylinder are in a phase-shifted relationship such that the latter piston is at the bottom dead center when the former piston is at the top dead center, the former is in the compression stroke. The latter is at the end of the expansion stroke. Therefore, when the check valve 8 is opened by the control device 9 at that time, the normal fuel injection is performed from the injector 4a to the cylinder # 1 and the # 3 cylinder is injected.
No additional fuel is normally supplied to the cylinder at the end of the expansion stroke, so that additional fuel is injected from the injector 4c, and the fuel additionally injected from the injector 4c mixes with the exhaust gas and the catalyst from the exhaust pipe 5 Formulation Particulate matter is supplied to the filter 6, is oxidized by the catalyst carried on the filter 6 to generate heat, and heats the particulates deposited on the filter 6 to an ignition temperature (about 650 ° C) or higher for ignition.
To burn.

[0008]

The above-mentioned prior art has the advantage that it enables a simple and compact system configuration of an exhaust gas purification apparatus, but since it utilizes a catalyst supported on a filter, If a low temperature part below the activation temperature of the catalyst (about 250 ° C. for a normal catalyst) occurs even in a part of the filter, the additional fuel passing through that part is not oxidized by the catalyst, so that the exhaust pipe 7 is directly exposed to the atmosphere. It will be released into the interior and worsen the emissions.

In order to collect the particulates in the exhaust gas of an internal combustion engine such as the diesel engine 1, the container of the exhaust particulate purifying apparatus 10 which contains a filter for collection usually has a cross section as shown in FIG. Have a shape. That is, this container
It is composed of a central tubular body 11 having a circular or elliptical cross section, a conical introduction portion 12 connected to the front portion of the tubular body 11, and a conical delivery portion 13 also connected to the rear portion. The exhaust pipe line 5 as shown in FIG. 3 is connected to the introduction part 12, and the exhaust pipe 7 is connected to the extraction part 13. Exhaust particulate purification device 1 housed in a container having such a shape
0 is generally attached to a well-ventilated place such as under the floor of an automobile.

According to the experiment, when the catalytic particulate matter filter 6 in the above-mentioned prior art is housed in the cylindrical body 11 of the container of the exhaust particulate purifying apparatus 10 as shown in FIG. Diesel engine 1 which is the subject
In the normal running state of the car equipped with
The temperature of the central portion of the filter 6 is about 380 ° C, whereas the temperature of the outer peripheral portion of the filter 6 is about 230 ° C, and a temperature difference of 150 ° C occurs between them. this is,
This is because, in the outer peripheral portion of the filter, heat escapes to a low temperature because it is cooled by the traveling wind of the vehicle through the container, whereas the central portion is hardly cooled and heat is retained and becomes a high temperature.

Therefore, when a platinum-based catalyst generally used in gasoline engines and the like is used as the catalyst supported on the filter 6, the temperature at which the platinum-based catalyst is activated is approximately 300 ° C. The activation temperature is lower than the activation temperature in the outer peripheral portion of the filter 6, and the additional fuel (unburned) supplied to the filter 6 has an activation temperature of 300 ° C. as indicated by a hatched arrow in FIG. Only those passing through the central part of the filter 6 that have passed are purified by being subjected to the oxidation reaction and discharged as shown by the white arrow, but those passing through the outer peripheral part of the filter 6 are shown as indicated by the broken arrow. Instead of being purified, it is released from the exhaust pipe 7 into the atmosphere as it is, and the emission is deteriorated.

Therefore, it is conceivable to use a catalyst having a low activation temperature as the catalyst to be carried on the filter 6, but in general, a catalyst activated at a low temperature has a low deterioration temperature, so that fine particles are burned in the outer peripheral portion of the filter 6. When reaching a temperature (about 650 ° C.), the temperature of the central part of the filter 6 becomes higher by about 150 ° C., so that the catalyst having a low activation temperature carried on that part is deteriorated. It becomes a problem. Therefore, the problem of the prior art cannot be solved by the method of supporting the catalyst having a low activation temperature on the entire filter 6.

The present invention solves the above-mentioned problems in the prior art very easily, there is no fear of deterioration of the catalyst carried on the filter, and the unburned fuel additionally supplied does not filter the filter. An improved catalyst filter and improved use of the filter, in which fine particles deposited on the filter are incinerated uniformly without passing through to the atmosphere and good filter regeneration is performed. An object is to provide an exhaust particulate purification device.

[0014]

As a means for solving the above-mentioned problems, the present invention is provided in an exhaust pipe line from an internal combustion engine to collect fine particles in exhaust gas and at the same time to provide a catalyst on itself. A catalyst-carrying filter that is carried, and a control means that determines the regeneration time of the catalyst-equipped filter according to the amount of particulates deposited on the catalyst-equipped filter, and outputs a control signal for regeneration at the regeneration time; And a fuel injection unit which receives a control signal output from the control unit and injects and supplies, to the upstream side of the filter with the catalyst, a fuel to be oxidized by the catalyst carried by the filter with the catalyst. The catalyst-carried filter carries at least two types of catalysts, a catalyst having a high activation temperature and a catalyst having a low activation temperature, and the activation temperature is relatively high in the central portion. An exhaust gas purification apparatus for an internal combustion engine, which is characterized in that a catalyst having a relatively low activation temperature is disposed on the outer peripheral portion together with a medium, and a filter with a catalyst having a novel configuration used for the same. provide.

The present invention is basically characterized by arranging catalysts having different activation temperatures in a specific manner in a catalyst-equipped filter used in an exhaust gas purification apparatus for an internal combustion engine. However, the idea of the present invention is not limited to a filter with a catalyst, but can be applied to a three-way catalyst used for purification of exhaust gas of a normal gasoline engine, a catalyst for nitrogen oxide used for a diesel engine, etc. Is.

[0016]

When the amount of fine particles collected and accumulated by the filter with the catalyst increases and it becomes necessary to regenerate the catalyst, the control means issues a control signal to the fuel injection means, and the expansion stroke of the internal combustion engine and / or Alternatively, in the exhaust stroke, additional fuel is injected to the upstream side of the filter with catalyst. The additionally injected fuel is oxidized by the catalyst carried by the catalyst-equipped filter to generate reaction heat, and the heat is given to the fine particles deposited on the catalyst-equipped filter, and the fine particles are about 650.
It reaches the combustion temperature of ° C and is incinerated.

Since the outer peripheral portion of the catalyst-equipped filter is cooled from the outside by running wind or the like, the temperature is lower than that of the central portion, but in the catalyst-equipped filter of the present invention, the catalyst having a high activation temperature and the activation temperature are used. The temperature of the outer peripheral portion of the filter with catalyst is lowered by cooling because the outer peripheral portion carries at least two kinds of catalysts and the catalyst whose activation temperature is relatively low. However, it does not fall below the activation temperature of the catalyst in that portion. Therefore, regeneration is achieved by reaching the combustion temperature of the particulates in the entire area of the filter, and there is no fear that the additional fuel is not oxidized but is released into the atmosphere as it is and deteriorates the emission. Further, since the center of the filter is not cooled from the surroundings, the temperature becomes high. However, since the catalyst having a relatively high activation temperature is carried in the center, there is no fear of deterioration of the catalyst in the center.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows an exhaust particulate purifying apparatus 20 as a first embodiment of the present invention. FIG. 2 shows a partially cut-away perspective view of the catalyst-equipped filter 21 housed inside as a main part of the apparatus 20. Cylindrical body 11, introduction section 12, and derivation section 1 which constitute the container of the exhaust gas purification apparatus 20.
3 and the like may be the same as those that constitute the exhaust particulate purifying apparatus 10 according to the prior art shown in FIG. 4, and are therefore denoted by the same reference numerals.

Although the first embodiment does not show the configuration of the entire system of the internal combustion engine except the exhaust particulate purifying apparatus 20, it may be the same as the system of the prior art shown in FIG. Other systems may be used. In short, the control device (9) determines the regeneration timing of the exhaust particulate purification device 20, and when the control device (9) issues a control signal (fuel injection signal) at the regeneration timing, the injector (4) receives the control signal (fuel injection signal). It suffices that additional fuel is injected into each cylinder during the expansion stroke and / or the exhaust stroke of the diesel engine (1) and the additional fuel is supplied to the exhaust particulate purification device 20 together with the exhaust gas. The timing of regeneration of the filter with catalyst 21 is determined by the control device (9) by measuring the differential pressure across the filter by means such as the differential pressure sensor 14 shown in FIG.

The temperature distribution diagram shown by the solid line curve in FIG. 1 (b) shows that the temperature is higher from the right side to the left side, and the filter 21 is shown in the operating state of the engine connected to the exhaust pipe line 5. 30mm from the left end surface of
Although the temperature distribution in the AA cross-section is shown, as described above, even if the central portion 22 of the catalyst-equipped filter 21 becomes hot, the outer peripheral portion 23 has the outer peripheral portion 23.
The central portion 2 is cooled by the traveling wind or the like through the
It is much colder than 2

Therefore, in the first embodiment of the present invention, as shown in FIG.
As indicated by a broken line in (b), a low temperature activated catalyst having an activation temperature of about 150 ° C. is supported on the outer peripheral portion 23 up to about 10 mm from the outer surface of the filter 21 in the radial direction, and other than that. The central portion 22 of the filter 21 carries a normal catalyst used in gasoline engines and the like having an activation temperature of about 300 ° C.
The catalyst is characterized in that it has a configuration in which a difference in activation temperature is given to the catalyst.

With such a structure, in the catalyst-equipped filter 21 of the first embodiment, even if the outer peripheral portion 23 is cooled to a low temperature of about 230 ° C., the temperature is retained in the outer peripheral portion 23. Since the temperature is higher than the activation temperature of 150 ° C, which is the activation temperature of the low temperature activated catalyst, the low temperature activated catalyst in the outer peripheral portion 23 is sufficiently activated, and therefore the unburned additional fuel passing through this portion is There is no fear that the additional fuel will be oxidized by the low-temperature activation catalyst and will pass through the exhaust particle purification device 20 to deteriorate emission. Further, in the central portion 22 of the filter 21, since it is not cooled from the outside, the temperature is 380 °.
Even if the temperature reaches a high temperature of about C, since the catalyst having an activation temperature of about 300 ° C. and a high deterioration temperature corresponding to the catalyst is supported in the central portion 22, there is no problem of deterioration of the catalyst.

FIG. 5 shows a second embodiment of the present invention. In the above-described first embodiment, as in the prior art shown in FIG. 3, the diesel engine (1) is used as an additional fuel for increasing the temperature of the particulates to the combustion temperature by being oxidized by the catalyst supported on the filter 21. It is premised that the fuel is injected into the cylinder in the expansion stroke and / or the exhaust stroke by the injector (4) for injecting the normal fuel into the cylinder of the second embodiment, but in the second embodiment, the additional fuel is purified by the exhaust particulate purification. It is characterized in that it is supplied from a unique fuel injection nozzle for the device.

Also in the exhaust particulate purifying apparatus 30 of the second embodiment shown in FIG. 5, the filter 21, the catalyst, the tubular body 11, the introducing section 12, the deriving section 13 and the like constituting the container are the exhaust particulate of the first embodiment. The structure may be the same as that of the corresponding portion of the purification device 20, but as a feature of the second embodiment, the filter 2
1 has a dedicated fuel injection nozzle 31 in the exhaust pipe line 5 on the upstream side.
Is provided, and additional fuel for oxidizing the catalyst of the filter 21 to raise the temperature of the fine particles is injected from the fuel injection nozzle 31 and directly supplied to the filter 21. Therefore, according to the second embodiment, there is an advantage that the additional fuel is efficiently used and the fuel loss is reduced.

Also in the second embodiment, the fuel injection pump for supplying the pressurized fuel to the fuel injection nozzle 31 or the timing of regeneration of the catalyst-equipped filter 21 is determined, and the fuel injection nozzle 31 and the fuel are ejected. It goes without saying that a control device (9) for sending a control signal to the injection pump and the like are also provided as in the first embodiment.

[0026]

The exhaust gas purifying apparatus for an internal combustion engine according to the present invention has the advantages that the structure is simple and the system can be easily downsized, and additionally supplied unburned fuel passes through the filter. There is no risk that emission will be released into the atmosphere to deteriorate emissions, and that the catalyst supported on the filter will not deteriorate, and the particulates deposited on the filter will be incinerated evenly over the entire area of the filter, It has the feature that it is played back.

[Brief description of drawings]

FIG. 1A is a vertical cross-sectional view of a filter according to a first embodiment, and FIG. 1B is a diagram showing a temperature distribution and an activation temperature distribution in the AA cross section together.

FIG. 2 is a perspective view showing the structure of the filter of the first embodiment.

FIG. 3 is a system configuration diagram showing an entire exhaust particulate purifying apparatus for an internal combustion engine, including a conventional technique.

FIG. 4 is a vertical cross-sectional view for explaining the problems of the conventional technique.

FIG. 5 is a vertical cross-sectional view showing the main parts of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Fuel pump 3 ... Fuel line 4 ... Injector 5 ... Exhaust pipe line 6 ... Catalytic particulate matter filter 8 ... Check valve 9 ... Control device 10 ... Exhaust particulate purification device (prior art) 11 ... Cylindrical body 14 ... Differential Pressure Sensor 20 ... Exhaust Particle Purification Device (First Embodiment) 21 ... Catalyst Filter 22 ... Center Part 23 ... Outer Part 30 ... Exhaust Particle Purification Device (Second Embodiment) 31 ... Fuel Injection Nozzle

Claims (3)

[Claims] 1. A catalyst-equipped filter which is provided in an exhaust pipe from an internal combustion engine to collect particulates in exhaust gas and which carries a catalyst on itself, and an amount of particulates deposited on the catalyst-equipped filter. According to the control means for determining the regeneration time of the filter with catalyst and outputting a control signal for regeneration at the regeneration time, and receiving the control signal output from the control means, the upstream side of the filter with catalyst A fuel injection means for injecting and supplying fuel to be oxidized by the catalyst carried by the catalyst with a catalyst, and the filter with a catalyst has a catalyst with a high activation temperature and an activation temperature of At least two types of catalysts, low catalysts, are loaded, a catalyst with a relatively high activation temperature is arranged in the central part, and a catalyst with a relatively low activation temperature is arranged in the outer peripheral part. An exhaust gas purification apparatus for an internal combustion engine, which is characterized by being installed. 2. Carrying at least two kinds of catalysts, a catalyst having a high activation temperature and a catalyst having a low activation temperature,
In particular, for an exhaust gas purification apparatus for an internal combustion engine, characterized in that a catalyst having a relatively high activation temperature is arranged in the central portion and a catalyst having a relatively low activation temperature is arranged in the outer peripheral portion. Filter with catalyst. 3. Carrying at least two kinds of catalysts, a catalyst having a high activation temperature and a catalyst having a low activation temperature,
In particular, a catalyst for an exhaust gas purification device of an internal combustion engine, characterized in that a catalyst having a relatively high activation temperature is arranged in a central portion and a catalyst having a relatively low activation temperature is arranged in an outer peripheral portion. Carrier.