JPS6115208Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of an exhaust manifold in an internal combustion engine that reduces exhaust gas emissions by improving feedback control performance in a feedback control type exhaust gas purification device using a catalytic converter. .

In order to send exhaust gas with an optimum air-fuel ratio to the exhaust gas purifying catalytic converter, an O ₂ sensor is installed in a general exhaust system to perform feedback control of the air-fuel ratio A/F. However, in the case of a multi-cylinder engine, the A/F of a certain cylinder is detected and the result is applied to all cylinders, so it is difficult to perform feedback control on the exhaust gas of all cylinders. It's hard to say. That is, since the cylinders A to F are not uniform, for example, if the exhaust gas in the specific cylinder is lean and the other cylinders are rich (this can actually happen), the lean signal of the specific cylinder Based on this, in order to make the A/F appropriate, the overall A/F is controlled to the rich side. In this case, needless to say, the other cylinders will shift further to the rich side. As a result, the overall exhaust gas flowing into the catalytic converter becomes richer than the optimum A/F required for catalytic purification, resulting in a significant reduction in purification efficiency.

In order to solve this problem, the present invention detects the average A/F of the exhaust gas of each cylinder, thereby eliminating the difference in measured A/F between cylinders as a whole. The purpose is to always send exhaust gas at the optimum A/F to maximize its purification efficiency.

This will be explained below with reference to the drawings.

According to the present invention, the exhaust passages 1, 2, 3, and 4, which are fixed to the engine body (not shown) by the flanges 9a, 9b, and 9c, respectively carry exhaust gas from each cylinder No. 1 to No. 4. It is sent to two independent merging passages 5 and 6. That is, the passages 1 and 4 become the merging passage 5, and
The passages 2 and 3 are respectively merged into a merging passage 6. As shown in FIG. 2, these passages 1, 4 and 2, 3 merge tangentially at the entrances of the respective merging passages 5, 6. As a result, the confluence passage 5
, exhaust gas (arrows) from passages 1 and 4 flows into the merging passage 6, and exhaust gas from passages 2 and 3 swirls into the merging passage 6, so that exhaust gas from the passages 1 and 4 flows into the merging passage 5. Also, the exhaust gases from passages 2 and 3 are effectively mixed within passage 6, respectively.

The center axis of each exhaust passage is oriented so as not to pass through the center of the merging passages 5 and 6, as shown in FIG.

Further, according to the present invention, the O ₂ sensor 10 is mounted on the passage wall so as to face both the merging passages 5 and 6. As a result, the exhaust gas from the passages 1, 2, 3, and 4 always comes into contact with this common O ₂ sensor 10 provided between the merging passages 5 and 6.

Thus, according to the present invention, all the exhaust gas from each cylinder hits the O ₂ sensor 10, so the average A/F of the engine can be detected by this O ₂ sensor. This average A/F is equivalent to the A/F of the exhaust gas flowing into the three-way catalytic converter (not shown) installed in the exhaust pipe (not shown) fixed to the flange 7, so It is possible to control the A/F so that the purification rate of the three-way catalytic converter is the highest while canceling out variations in the A/F. Therefore,
With this three-way catalytic converter,
It can effectively reduce HC, CO, and NOx.
Furthermore, since the O ₂ sensor is provided at the exhaust gas confluence (inside the exhaust manifold), the warm-up performance of the O ₂ sensor does not deteriorate compared to the conventional O ₂ sensor placed inside the exhaust pipe. Although it is possible to place the _O2 sensor in the exhaust pipe downstream of the exhaust manifold from the point of view of measuring the average A/F with no variation between cylinders, the reason why this is not done in this invention is because the A/F
This is because it is intended not only to make the temperature uniform, but also to improve the warm-up performance of the above-mentioned O ₂ sensor. In other words, in order to quickly bring the O ₂ sensor to its active temperature range (in other words, improve warm-up performance), it is desirable to place the O ₂ sensor at a position that is as high as possible in the exhaust temperature, that is, as close to the engine as possible. Therefore, in the present invention, the O ₂ sensor is placed in the exhaust manifold upstream of the exhaust pipe.

In this way, according to the present invention, it is possible to improve the controllability of the air-fuel ratio without reducing the warm-up performance of the O ₂ sensor.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the entire exhaust manifold according to the present invention, and FIG. 2 is a plan view of the passage seen from the - line direction in FIG. 1, 2, 3, 4...exhaust passage, 5, 6...merging passage, 10...O ₂ sensor.

Claims (1)

[Scope of utility model registration request] A plurality of exhaust passages extending from each cylinder intersect each other tangentially and merge into several merging passages, and a single O ₂ sensor is installed on the passage wall of these merging passages so as to face each merging passage. Exhaust manifold featuring: