JPH0579324A - Exhaust purifying device - Google Patents

Abstract

(57) [Summary] [Purpose] Purifies exhaust gas at low temperature with a simple structure. [Structure] In an exhaust system 11 of an internal combustion engine, a starting catalyst 12 that operates even when the exhaust gas temperature is low and a main catalyst 13 that is activated when the exhaust gas temperature becomes high are provided in parallel. The starting catalyst 12 is arranged on the exhaust gas mainstream side 14 and the main catalyst 13 is arranged on the sidestream side 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art Recently, catalysts have been used to purify harmful substances contained in exhaust gas from internal combustion engines such as automobiles. The catalyst is usually composed of a carrier having a large number of cells (gas flow holes), an active component (platinum, palladium, rhodium, etc.) impregnated (supported) on the surface of the carrier, and an additive component (promoter, stabilizer, etc.). It is housed in a predetermined container and is installed in the exhaust system of the internal combustion engine. And C which is a harmful component in the exhaust gas
O, HC, by oxidation and reduction of NO _X, is intended to be converted to harmless substances.

However, this catalyst has a drawback in that the reaction efficiency is poor at the time when the exhaust gas is at a low temperature, such as at the time of starting or after a long idling, and the catalyst is not substantially purified. As a countermeasure against this, for example, as shown in FIG. 5, a configuration is proposed in which a heater 3 with a catalyst is provided immediately upstream of a catalyst 2 (catalyst converter) housed in a container 1 (“heater with catalyst and control thereof”). Method ”, JP-A-3-31510). With this configuration, until the catalyst is fully activated,
The heater 3 is set in an upright state so as to block the exhaust gas flow G, and the entire catalyst is activated early.

[0004]

There are various proposals similar to the above-mentioned proposals (for example, actual Kaihei 3-
No. 10022 gazette, Japanese Utility Model Laid-Open No. 3-17227 gazette,
Etc., all of which require a control mechanism for appropriately operating the heater, a drive mechanism for performing an up-and-down motion, and the like, which causes a problem that the device becomes complicated.

Further, in the case of a diesel engine, a particulate trap may be used as a purifying means, but a high temperature is required for regeneration, and there is a similar problem.

Therefore, in view of the above circumstances, the present invention was devised to provide an exhaust gas purification apparatus capable of purifying exhaust gas at a low temperature period with a simple structure.

[0007]

SUMMARY OF THE INVENTION According to the present invention, an exhaust system of an internal combustion engine is provided with a starting purifying means that operates even when the exhaust gas temperature is low and a main purifying means that operates when the exhaust gas temperature becomes high. The purifying means for startup is arranged on the mainstream side of the exhaust gas, and the main purifying means is arranged on the substream side.

The starting purifying means can be constituted by a purifying means having a heat capacity smaller than that of the main purifying means. Further, the starting purifying means may be a starting catalyst using a heat-resistant and corrosion-resistant metal foil as a carrier, and the main purifying means may be a main catalyst using ceramics as a carrier.

[0009]

With the above structure, the starting purifying means purifies most harmful components of the exhaust gas when the exhaust gas is at a low temperature.

[0010]

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

FIG. 1 shows a first embodiment of an exhaust emission control device according to the present invention. This exhaust purification device
An exhaust system 11 of an internal combustion engine is provided with a starting catalyst 12, which is a purifying means for starting that operates even when the exhaust gas temperature is low, and a main catalyst 13, which is a main purifying means that is activated when the temperature becomes high, in parallel. , The starting catalyst 12 is the exhaust gas mainstream side 14
In addition, the main catalyst 13 is arranged on the side of the sidestream 15.

The exhaust system 11 is formed by an exhaust pipe 16 connected to an exhaust port (not shown) of the engine, and a diameter of the exhaust pipe 16 is enlarged to interpose a starting catalyst 12. A branch pipe 17 attached at a branch angle of about 90 degrees is provided at a position upstream of the starter catalyst 12, and a main catalyst 13 is provided at an enlarged diameter portion of the branch pipe 17. That is, the straight exhaust pipe 16 defines the exhaust gas mainstream side 14 and the branch pipe 17 defines the substream side 15. And the main catalyst 13
Has a durable structure capable of obtaining the same high reaction efficiency as in the past, and the starting catalyst 12 has the same structure as the main catalyst 13, but is formed as a catalyst having a smaller volume and a smaller heat capacity. ..

Therefore, when the exhaust gas temperature is low at the time of start-up, idling, etc., the flow rate is small and the kinetic energy of the exhaust gas G can be utilized, so most of the exhaust gas G flows to the starting catalyst 12, Further, since it is on the mainstream side 14, the exhaust gas temperature drop in the pipeline is minimized, and even when the temperature is low, the heat capacity is small and the reaction temperature reaches a predetermined reaction temperature rapidly. Exhaust gas is purified at low temperatures that have been left unattended. When the load on the engine causes the exhaust gas G to reach a high temperature, the gas flow rate also increases, so the pressure increases due to the resistance on the side of the starting catalyst 12 so that a large amount of the exhaust gas G flows to the main catalyst 13 on the side of the sidestream 15. Become. Further, this configuration is extremely simple and does not require any control device or drive device, and can be a simple device.

FIG. 2 shows another embodiment based on the first embodiment, in which the exhaust gas G is supplied to the main flow side 14 and the side flow side 15 at the branch portion 18 where the branch pipe 17 is connected. A switching valve 19 for guiding only one of the two is provided.
The switching valve 19 is provided with, for example, a temperature sensor 20 provided on the upstream side of the branch portion 18, and a controller 21 that operates the switching valve 19 according to the detected value of the temperature sensor 20,
When the exhaust gas G reaches a predetermined high temperature, the switching valve 19 closes the exhaust pipe 16 which is the mainstream side 14 at the branch portion 18. That is, the starting catalyst 12 is protected from the high-temperature exhaust gas G and the operating time is reduced to compensate for the lack of durability and the like.

Further, as shown in FIG. 2, the starting catalyst 12 of the first embodiment may be provided with a heater 22. The heater 22 does not need to have a large size as in the conventional case, and may be any one that supplementally heats the starting catalyst 12 when the exhaust gas temperature is low.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, the exhaust pipe 31
The catalyst housing chamber 32 is formed by appropriately expanding the diameter of a part of the inside of the catalyst housing chamber 32, and the inside of the catalyst housing chamber 32 is partitioned by a partition plate 33 into a shaft center portion 34 and a peripheral portion 35. Therefore, the shaft center portion 34 corresponds to the mainstream side 14, and the peripheral portion 35 corresponds to the sidestream side 15. A starter catalyst 36 having a small heat capacity is formed on the axial portion 34, and a main catalyst 37 is formed on the peripheral portion 35. A switching valve 38 is provided at the front end portion of the exhaust gas flow G of the partition plate 33, which serves as the inlet of the main flow side 14, and the exhaust gas G
When the temperature becomes high, the flow to the mainstream side 14 is blocked and the starting catalyst 36 is protected.

With this structure, purification of exhaust gas at a low temperature is achieved with a simple structure that does not require a branch pipe in addition to a heater. Other functions and effects are similar to those of the first embodiment.

Although the catalyst having a smaller volume than the main catalyst is shown as the starting catalyst in the above embodiments, the present invention is not limited to this, and the heat capacity may be made different by changing the material and structure of the carrier. .. For example, heat resistance of stainless steel etc.
A starting catalyst using a corrosion-resistant metal foil as a carrier and a main catalyst using ceramics as a carrier may be arranged in parallel.

Further, FIG. 4 shows an example for a diesel engine in the modified embodiment of FIG. 1, in which filters 41 and 42 for particulate trap are used as an exhaust gas purifying means.
Is provided. With this configuration, it is possible to remove harmful substances such as soot in the exhaust gas at the time of startup, and prevent deterioration of the visibility and adverse effects on the human body.

[0021]

In summary, according to the present invention, the following excellent effects are exhibited.

A purifying means for starting which operates even when the exhaust gas temperature is low or the gas flow rate is low, and a high temperature or
Since the main purification means that operates when the amount of gas becomes large is provided in parallel, the starting purification means is arranged on the exhaust gas mainstream side, and the main purification means is arranged on the sidestream side, the exhaust gas temperature can be reduced with a simple configuration. Exhaust gas can be purified even in low season.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a first embodiment of an exhaust emission control device according to the present invention.

FIG. 2 is a side sectional view showing another embodiment of FIG.

FIG. 3 is a side sectional view showing a second embodiment of the present invention.

FIG. 4 is a side sectional view showing a modified example of FIG.

FIG. 5 is a side sectional view showing a conventional exhaust emission control device.

[Explanation of symbols]

 11 Exhaust System 12 Starting Catalyst (Starting Purifying Means) 13 Main Catalyst (Main Purifying Means) 14 Exhaust Gas Main Flow Side 15 Subflow Side

Claims (3)

[Claims] 1. An exhaust system of an internal combustion engine is provided with, in parallel, a starting purifying unit that operates even when the exhaust gas temperature is low and a main purifying unit that operates when the exhaust gas temperature becomes high. An exhaust gas purification device, wherein the main purification means is arranged on the side of the sidestream of exhaust gas. 2. The exhaust emission control device according to claim 1, wherein the starting purification means is a purification means having a heat capacity smaller than that of the main purification means. 3. The starting purification means is a starting catalyst using a heat-resistant / corrosion-resistant metal foil as a carrier, and the main purification means is a main catalyst using ceramics as a carrier. Exhaust gas purification device described.