JPS6341531Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention consists of a plurality of exhaust pipes, and the exhaust gas discharged from at least two sets of exhaust ports is separated from each other at the exit end or near the exit. The present invention relates to an exhaust manifold in which an oxygen sensor is provided on an internal partition wall that is formed to lead to the exhaust manifold.

Hereinafter, the type of exhaust manifold in which exhaust gas is separated by an internal partition wall as described above will be referred to as a dual-type exhaust manifold.

(Technical background of the invention) Conventionally, in an air-fuel ratio control method that detects the air-fuel ratio using an oxygen sensor installed in the exhaust manifold and performs feedback control, it is important to determine whether the exhaust gas discharged from each cylinder hits the oxygen sensor or not. It is well known that the air-fuel ratio has a large influence on the air-fuel ratio controllability, and the smaller the difference in the strength of gas per cylinder between the cylinders of the engine, the better the controllability is. Good gas coverage means that the gas exhausted from a certain cylinder has a good effect on the oxygen sensor, and specifically, the volume of gas flowing around the oxygen sensor out of the exhaust gas from that cylinder is large. That's what it means.

In the case of a dual type exhaust manifold, as shown in FIG. 1, a sensor louver is installed at a position indicated by a broken line R in the figure on a partition wall 1 that separates the interior of the exhaust manifold, and an oxygen sensor is fixed within this sensor louver.

FIG. 2 is a partial perspective view of the oxygen sensor mounting section. As can be seen from this figure, a rectangular notch 1a is formed in the partition wall 1, and a mounting hole 1b is bored in the outer wall of the exhaust manifold opposite to this notch 1a. From this mounting hole 1b, the notch 1a
A cylindrical sensor louver 2 with a plurality of holes inside.
The oxygen sensor 3 housed inside is inserted, and the flange 2a integrated with the sensor louver 2 is fixed to the exhaust manifold, so that the oxygen sensor 3 is also fixed. In addition, 6 in FIG. 1 is a monolith catalyst, which oxidizes or reduces toxic nitrogen oxides, carbon oxides, etc. contained in the exhaust gas, thereby rendering them harmless.

In the conventional exhaust manifold shown in FIG. 1, the exhaust collection parts 3a and 3b are completely separated by the partition wall 1 up to the outlet end.
A pressure difference occurs due to pulsation between the two, and within the oxygen sensor louver, the flow of gas exchange as shown by the arrow X in FIG. 1 is dominant. Therefore, the exhaust gas from each cylinder is exchanged in substantially the same way, and the difference between the cylinders in terms of gas per oxygen sensor is relatively small, indicating good air-fuel ratio sensing. However, when the exhaust gas flow rate increases due to changes in engine speed, load, etc.
Gradually, gas exchange began to take place in the flow shown by arrow Y in Figure 1, and the exhaust gas directly hit the oxygen sensor louver in the cylinder, where the gas contact became stronger.
Air-fuel ratio controllability may deteriorate.

3 and 4 are a plan view and a front view showing a conventional exhaust manifold. In such an exhaust manifold, the first cylinder 100 and the fourth cylinder 40 are
0 and the exhaust collecting part 10, the second cylinder 200 and the third cylinder
As shown in FIG. 4, the exhaust gas collecting section 9 of the cylinder 300 is separated by a partition wall 1 up to the outlet end, and the oxygen sensor 3 is attached to the middle of the partition wall 1. In such a configuration, due to the shape of the exhaust manifold, the mounting conditions of the oxygen sensor, etc., as shown in FIG. Although it is small, it was found that as the rotational speed increases, the gas contact of the second cylinder 200 becomes stronger, and conversely, the third cylinder 300 becomes weaker, and the difference between the cylinders tends to increase. Furthermore, the fifth
The figure shows the case where the engine torque is constant at 2.0Kgm. In the figure, A indicates the rotation speed of 1000 rpm, B indicates 2000 rpm, and C indicates 3000 rpm.

If there is a difference in the strength of the gas, one possible way to improve this is to change the shape of the exhaust manifold itself or change the oxygen sensor mounting position, but this is not possible due to cost and mounting constraints. Close to. For example, as shown in FIG. 17, the abutting end of the internal partition wall 1 with the oxygen sensor 3 may be bent and its extension line may be deviated from the center of the oxygen sensor 3; A configuration in which the oxygen sensor mounting position is shifted from the center of the internal partition wall 1 as shown in FIG. Adjusting the gas per cylinder for only one cylinder is difficult and requires dimensional accuracy, which is impractical.

(Purpose of the invention) In view of the above points, the present invention aims to equalize the degree of influence of the exhaust gas discharged from each cylinder on the oxygen sensor among the cylinders.

(Embodiments of the invention) Hereinafter, embodiments of the invention will be described based on the drawings.

FIG. 6 shows a first embodiment of the present invention. As you can see from this diagram, the first cylinder 100 and the fourth cylinder 400
and the exhaust gas collecting section 10, and the second cylinder 200
The third cylinder 300 and the third cylinder 300 join together at the exhaust collecting section 9. The exhaust gas collecting parts 9 and 10 are separated by a partition wall 1, and the partition wall 1 extends to the exhaust manifold outlet as in the conventional example shown in FIG. This partition wall 1 is provided with a notch 1a similar to the conventional example shown in FIG. 2, and a mounting hole 1b is provided in the outer wall of the exhaust manifold opposite to this notch 1a. Then, the notch 1a is opened from this mounting hole 1b.
Oxygen sensor 3 housed inside sensor louver 2
is fixed. Note that the exhaust manifold is made of cast iron or the like, and the partition wall 1 is also integrally molded together with the exhaust manifold.

As mentioned above, the exhaust gas from the second cylinder 200 is more likely to directly hit the sensor louver 2 than from other cylinders, so the bank 11 is provided at the edge of the notch 1a of the partition wall 1 on the second cylinder 200 side. The embankment 11 acts as a barrier to prevent exhaust gas from the second cylinder 200 from directly hitting the sensor louver 3. The longitudinal length of this embankment 11 is equal to the length of the sensor louver 3, and as shown in FIG. As shown in FIG. 7b, a notch 1a for mounting an oxygen sensor is formed.

This embankment portion 11 is shown in FIG. 8 in a partial perspective view. As can be seen from this figure, a bank 11 is formed at the opening edge of the notch 1a provided in the partition wall 1.

With the above configuration, even if the flow rate of exhaust gas from the second cylinder 200 increases, the embankment 11 acts as a barrier and does not directly hit the sensor louver 3, so direct gas exchange is avoided. Since the gas exchange based on the pressure difference between the exhaust gas collection parts 9 and 10 is always dominant, the difference in gas per cylinder between the cylinders can be made small regardless of the engine operating conditions. This effect is shown in FIG. In the manifold before the improvement, as shown in FIG. 5, the gas contact in the second cylinder was strong and that in the third cylinder was weak, but as in this embodiment, the bank 11 was moved against the oxygen sensor 3. By providing it on the second cylinder 200 side, as shown in Fig. 9, the gas contact of the second cylinder is weakened to the average, and the gas contact of the third cylinder is also improved, making the gas contact of each cylinder uniform as a whole. Can be done. Incidentally, Fig. 9 shows when the engine torque is constant at 2.0 kgm, and in the figure, A indicates the engine rotation speed is 1000 rpm, B indicates 2000 rpm, and C indicates 3000 rpm.

FIG. 10 shows a second embodiment of the present invention. In this exhaust manifold, compared to the above-mentioned exhaust manifold, the internal partition wall 1 does not completely separate the exhaust collecting part,
As shown in FIG. 11, this is an exhaust manifold in which the partition wall 1 extends only up to the middle of the exhaust collecting part. In such an exhaust manifold, arrow Y in Figure 1
Direct gas exchange of exhaust gas as shown in is predominant, and there is a strong tendency for gas to come into contact with the sensor louver 2 from the second cylinder 200 and the third cylinder 300, which are the cylinders where the gas directly hits the sensor louver 2. Therefore, according to its strength,
Embankment portion 11 that protrudes toward the second and third cylinder sides of the internal partition wall
a and 11b are formed to suppress gas contact. The effect is shown in FIG. D in the figure is the conventional one,
E shows the result of the present embodiment, and it can be seen that the present embodiment has a much greater effect than the conventional one.

In the above embodiment, a case where the exhaust gas from the second cylinder 200 is strong and a case where the exhaust gas from the second cylinder 200 and the third cylinder 300 are strong are shown. If the exhaust gas from the engine is strongly hit, it is sufficient to provide embankments 11 on the first cylinder 100 and second cylinder 200 sides, respectively, as shown in FIG. In addition, the first cylinder 100 and the third cylinder 30
If the exhaust gas from zero is strong, it is sufficient to provide embankments 11 on the first cylinder 100 and third cylinder 300 sides, respectively, as shown in FIG. If the exhaust gas from 400 is strong, the first cylinder 100,
The embankment portion 11 may be provided on the second cylinder 200 and third cylinder 400 sides. Alternatively, as shown in FIG. 15, a bank may be provided on each cylinder side to adjust the amount of exhaust gas from each cylinder.

Note that the specific shape of the embankment portion 11 is not limited here, but as long as it has a shape that covers the oxygen sensor 3, its effect will be recognized. In addition, the embankment 11
The standard length in the longitudinal direction is the length of two sensor louvers, but there is no limit to the length.

(Advantages of the Invention) As described above, by using the exhaust manifold of the present invention, the degree of influence of the exhaust gas discharged from each cylinder on the oxygen sensor can be made uniform, and good air-fuel ratio control can be performed.

[Brief explanation of the drawing]

Figures 1 to 5 show conventional examples. Figure 1 is a longitudinal sectional view of a conventional dual-type exhaust manifold, Figure 2 is a partial perspective view showing the oxygen sensor mounting part, and Figure 3 is a diagram of the exhaust manifold. A plan view, FIG. 4 is a front view of the exhaust manifold, FIG. 5 is a diagram showing the strength of each cylinder exhaust gas hitting the oxygen sensor in a conventional exhaust manifold, and FIGS. Fig. 6 is a plan view, Fig. 7 is a diagram showing the method of creating the embankment, Fig. 8 is a perspective view of the main part, and Fig. 9 is a diagram showing the flow of exhaust gas from each cylinder to the oxygen sensor. Figures 10 to 12 show the strength of the hit, and Figures 10 to 12 show the second embodiment of the present invention. Figure 10 is a plan view, Figure 11 is a front view, Figure 12 is a diagram showing the effect, and Figure 13 14, 15, and 16 are detailed views of main parts of other embodiments, and FIGS. 17 and 18.
19 are detailed views of main parts showing a conventional example. DESCRIPTION OF SYMBOLS 1... Partition wall, 3... Oxygen sensor, 9, 10... Exhaust collection part, 11... Embankment part.

Claims (1)

[Scope of utility model registration request] an exhaust gas collection section where a plurality of exhaust pipes gather; a partition wall that partitions and separates the exhaust gas collection section; an oxygen sensor provided on the partition wall that detects the oxygen concentration in the exhaust gas; and an oxygen sensor provided on the partition wall that detects the oxygen concentration in the exhaust gas. An exhaust manifold having an embankment that reduces the amount of exhaust gas.