JPS6122123B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for reducing harmful components in the exhaust gas of an internal combustion engine.

[Conventional technology]

In recent internal combustion engines that use gasoline as fuel, purification of unburned harmful components such as HC and CO in the exhaust gas is done using methods such as those described in Japanese Patent Application Laid-Open No. 51-5411. By supplying secondary air to the exhaust system, unburned harmful components are oxidized and purified using this secondary air. As described in Japanese Patent No. 52-47130, NOx generation is reduced by circulating a portion of the exhaust gas back into the intake system.

[Problem that the invention seeks to solve]

However, when secondary air is supplied to the exhaust system in this way, the oxidation reaction in the exhaust system is captured and the unburned components of the exhaust gas become particularly large during engine deceleration or when the car is driven down a long downhill slope. This increases the occurrence of afterburn in the exhaust system.

On the other hand, when part of the exhaust gas is returned to the intake system for the purpose of reducing NOx in the exhaust gas, the exhaust gas returned to the intake system should be in an inert state with less combustion components. In addition to supplying secondary air to the exhaust system, when part of the exhaust gas is recirculated to the intake system, a part of the secondary air supplied to the exhaust system from the secondary air supply passage. but,
Since it is mixed with the exhaust gas that is recirculated to the intake system, the inertness of the exhaust gas that is recirculated to the intake system is lowered, and the effect of reducing NOx by recirculating the exhaust gas to the intake system is reduced.

An object of the present invention is to solve the above-mentioned problem when secondary air is supplied to the exhaust system and a part of the exhaust gas is recirculated to the intake system.

[Means for solving problems]

For this reason, the present invention connects a secondary air supply passage to a specific exhaust passage from each exhaust passage from each cylinder in a multi-cylinder internal combustion engine, or to a collective junction of the exhaust passages or downstream from this, while In an internal combustion engine, an exhaust gas recirculation passage is provided between the system and the intake system to recirculate part of the exhaust gas to the intake system. A heat storage material for the oxidation reaction of unburned components is provided at a portion upstream of the connection portion of the supply passage, while a specific exhaust passage among the exhaust passages from each cylinder is provided with a heat storage material downstream of the heat storage material and The exhaust gas recirculation passage is connected to a portion upstream of the connection portion of the secondary air supply passage.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, reference numeral 1 indicates a multi-cylinder engine having a first cylinder 2 and a second cylinder 3, and reference numeral 4 in the drawings indicates a carburetor 5 attached to the side of the engine 1. Reference numerals 6 and 7 indicate exhaust passages connected to exhaust ports 8 and 9 in each cylinder 2 and 3 of the internal combustion engine 1, respectively.

Each of the exhaust passages 6 and 7 merges into one main exhaust passage 10 and is connected to an exhaust gas purification device 21 such as a catalytic converter or a thermal reactor. The exhaust passage is provided with a secondary air supply hole 11 at a portion slightly upstream of the confluence of the two exhaust passages 6 and 7 (however, in the drawing, the secondary air supply hole 11 is provided in the exhaust passage 6 of the first cylinder 2). ), and the tip of the secondary air supply hole 11 is an air cleaner (not shown).
A secondary air supply passage 13 of an appropriate length, which opens to an atmospheric communication point and is equipped with a check valve 12, is connected,
A check valve 12 opens and closes in response to the pulsation of exhaust gas in both exhaust passages 6 and 7 to suck and supply secondary air. In this case, the secondary air supply hole 11 may be provided at the joint of both exhaust passages 6 and 7 or at the main exhaust passage 10 after the joint of both exhaust passages 6 and 7, and the secondary air may be supplied thereto. good.

Further, in one of the exhaust passages 6 and 7, a recirculation exhaust gas extraction hole 14 is provided at a location upstream of the secondary air supply hole 11 by an appropriate distance (however, the drawing shows (This shows a case where a recirculated exhaust gas take-off hole 14 is provided in the exhaust passage 7 of the second cylinder 3). An exhaust gas recirculation passage 18 is provided with an exhaust gas recirculation control device consisting of a control valve 16 and an exhaust pressure regulating valve 17. , a part of the exhaust gas is returned to the intake system, and in this case, the secondary air supply hole 1
1 is located in the main exhaust passage 10, the recirculated exhaust gas take-off hole 14 may be provided at the confluence of both the exhaust passages 6 and 7.

In addition to the above configuration, the present invention provides that the secondary air supply hole 11 is provided in both the exhaust passages 6 and 7.
On the more upstream side and the recirculated exhaust gas outlet hole 1
A heat storage material 20 for oxidizing unburned components in the exhaust gas is provided at a location further upstream from the exhaust gas.

Note that the heat storage material 20 may be a catalyst such as a granular catalyst or a honeycomb catalyst or monolith catalyst as long as it promotes the oxidation reaction of unburned components, or a material with a heat storage effect such as ceramic, metal fiber, or metal rod. Any heat storage material 20 may be used, and it is preferable to provide the heat storage material 20 in a location close to the combustion chamber of each cylinder 2, 3, such as in the exhaust port 8, 9 of each cylinder 2, 3.

By the way, if the throttle valve is fully closed when decelerating or going down a slope, the amount of fresh air that can be sucked in is small, resulting in poor scavenging and a large amount of burned gas remaining in the combustion chamber, which can lead to misfires. The gas containing a large amount of unburned gas is discharged into the exhaust system. Then, for the exhaust gas in such a state, as described above, secondary air is supplied to one of the exhaust passages 6 and 7 from each cylinder, or the exhaust gas is supplied to the joint of both exhaust passages 6 and 7 or to the main exhaust passage. In the case of supplying secondary air to the exhaust passage 10, the exhaust gas with many unburned lines and a large amount of secondary air are actively mixed within the exhaust system, and this flows through each exhaust passage 6, 7 and the main exhaust. This results in so-called afterburn, where the fuel suddenly explodes and burns inside the passage 10.

The present invention provides a heat storage material 2 for oxidation reaction of unburned components in each exhaust passage 6, 7 from each cylinder 2, 3 of an internal combustion engine 1, at a site upstream from a secondary air supply point.
0 is provided for each cylinder, so even if the amount of unburned components in the exhaust gas from each cylinder increases due to a misfire,
These unburned components are reduced by an oxidation reaction at a portion of the heat storage material 20 before joining with the secondary air, and the secondary air is supplied and mixed with this in a state where the unburned components are reduced. 6, 7 and the main exhaust passage 10 are reduced to a lean range where afterburn does not occur.
In addition, during normal operation, the exhaust gas from each cylinder is
First, the unburned components undergo an oxidation reaction at the heat storage material 20, and then secondary air is supplied and mixed therewith, and then further oxidized in the exhaust gas purification device 21, and the unburned components are oxidized and purified in two stages. It is done across the board.

Furthermore, the exhaust gas that is returned to the intake system is taken out from a part downstream of the heat storage material 20 and upstream of the secondary air supply point, and the exhaust gas in this part is returned to the previous heat storage material. In addition to reducing unburned components, since it does not contain secondary air, inert exhaust gas can be returned to the intake system.

[Action/effect of the invention]

As described above, the present invention provides a heat storage material in the exhaust passages from each cylinder in a multi-cylinder internal combustion engine upstream of the secondary air supply section to these exhaust passages, thereby supplying secondary air. Since the unburned components in the exhaust gas before mixing can be reduced by the heat storage material, it is possible to prevent the occurrence of afterburn when the internal combustion engine is decelerating or when the car is going downhill.
During normal operation, the purification rate of unburned components can be improved by the two-stage purification action of the oxidation reaction of unburned components by the heat storage material and the oxidation reaction by secondary air. By extracting the recirculating exhaust gas from a region upstream of the secondary air supply point and downstream of the heat storage material, unburned components contained in the exhaust gas recirculating to the intake system are removed from the This can be reduced by using a heat storage material, and it is also possible to avoid mixing secondary air into this recirculated exhaust gas, allowing highly inert exhaust gas to be recirculated to the intake system. This allows the reduction effect to be further increased.

[Brief explanation of the drawing]

The drawings are diagrams showing embodiments of the invention. 1... Engine, 2, 3... Cylinder, 8, 9... Exhaust port, 4... Intake manifold, 5... Carburetor, 6, 7
...Exhaust passage, 10...Main exhaust passage, 11...Secondary air supply hole, 13...Secondary air supply passage, 14...Recirculation exhaust gas take-out hole, 18...Exhaust gas recirculation passage.

Claims (1)

[Claims] 1. A secondary air supply passage is connected to a specific exhaust passage from each exhaust passage from each cylinder in a multi-cylinder internal combustion engine, or to a collective junction of the exhaust passages or downstream from this, while connecting the exhaust system and the intake system. In an internal combustion engine comprising an exhaust gas recirculation passage for recirculating part of the exhaust gas to the intake system between the cylinders, each exhaust passage from each cylinder has a connecting portion for the secondary air supply passage. A heat storage material for the oxidation reaction of unburned components is provided in a region further upstream, while a specific exhaust passage from each cylinder is provided downstream of the heat storage material and supplied with the secondary air. 1. A device for reducing harmful components in exhaust gas of an internal combustion engine, characterized in that the exhaust gas recirculation passage is connected to a portion upstream of a connection portion of the passage.