JPS632006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device that improves the flow of exhaust gas to an oxygen sensor.

[Conventional technology]

In current exhaust purification systems, an exhaust manifold with a catalytic converter is installed, in which the catalytic converter is placed directly below the exhaust manifold, in order to prevent the warm-up performance of the catalytic converter from being degraded due to heat loss in the middle of the exhaust passage. It tends to be used.
This exhaust manifold with catalytic converter is usually
The exhaust manifold has an expansion chamber with an enlarged passage cross-sectional area, and ports of the exhaust manifold open from the left and right sides of the expansion chamber. A heat control valve is attached to the opening of one port to the expansion chamber, and the exhaust gas whose flow is switched by the heat control valve is transferred to the bottom wall of the riser section provided at the exact center of the intake manifold. Since it is designed to lead to the back side, the expansion chamber is offset from the center of the riser part of the intake manifold, and therefore the expansion chamber is offset to the opposite side from the port where the heat control valve is installed. Of the left and right ports of the exhaust manifold, the port on the side to which the heat control valve is attached has a longer pipe length than the port on the other side to which the heat control valve is not attached. On the other hand, since the oxygen sensor is provided with its element portion extending into the expansion chamber, the flow of exhaust gas from the left and right ports opening into the expansion chamber, which are disposed off-center, toward the oxygen sensor becomes asymmetrical.

[Problem that the invention seeks to solve]

In the above, the flow of exhaust gas flowing into the expansion chamber from the port on the side where the heat control valve is installed (the port with the longer pipe length) has a large flow resistance and the flow velocity decreases, making it difficult to reach the oxygen sensor. . Therefore, the oxygen sensor is strongly affected by the exhaust gas flowing in from the short port on the side where the heat control valve is not installed, making it difficult to control the purification of exhaust gas from all cylinders evenly. become.

An object of the present invention is to improve the contact between the exhaust gas flowing into the expansion chamber from the port on the side where the heat control valve is attached to the oxygen sensor, and to perform more accurate exhaust gas purification control.

[Means for solving problems]

According to the present invention, the above problems are solved by the following exhaust gas purification device.

First Invention An expansion chamber is provided in the exhaust manifold eccentrically from the center of the exhaust manifold, ports of the exhaust manifold are opened from left and right sides of the expansion chamber, and an oxygen sensor is disposed in the expansion chamber with its element part extending into the expansion chamber. At the same time, the opening to the expansion chamber of the port with the longer length among the left and right ports of the exhaust manifold, which have different lengths due to the eccentricity of the expansion chamber, is connected to the exhaust gas from the port when in the open position. In an exhaust gas purification device equipped with a heat control valve that allows the flow of exhaust gas from the port to flow directly into the expansion chamber and, when in the closed position, directs the flow of exhaust gas from the port along the back surface of the bottom wall of the riser part of the intake manifold and then flows into the expansion chamber. , the port with the longer pipe length on the side where the heat control valve is installed has a passage cross-sectional area of the opening to the expansion chamber smaller than the port with the shorter pipe length on the other side, and the element part of the oxygen sensor in the expansion chamber. The exhaust gas is located at a position where, when the heat control valve is in the open position, the flow of exhaust gas flowing into the expansion chamber through the longer port on the side where the heat control valve is attached hits. Purification device.

Second invention: An expansion chamber is provided in the exhaust manifold eccentrically from the center of the exhaust manifold, ports of the exhaust manifold are opened from the left and right sides of the expansion chamber, and an oxygen sensor is disposed in the expansion chamber with its element portion extending into the expansion chamber. Also, the flow of exhaust gas from the port when in the open position is at the opening to the expansion chamber of the longer port of the left and right ports of the exhaust manifold, which have different pipe lengths due to the eccentricity of the expansion chamber. In an exhaust gas purification device equipped with a heat control valve that allows the flow of exhaust gas from the port to flow directly into the expansion chamber when in the closed position, the exhaust gas flows from the port along the back surface of the bottom wall of the riser part of the intake manifold and then flows into the expansion chamber. The port with the longer pipe length on the side where the heat control valve is installed has a smaller passage cross-sectional area at the opening to the expansion chamber than the port with the shorter pipe length on the other side, and The installation position is such that when the heat control valve is in the open position, the exhaust gas flowing into the expansion chamber through the longer port on the side where the heat control valve is installed is directly exposed to the flow of exhaust gas, and the heat control valve is also installed. An exhaust gas purification device characterized in that a sub-chamber is provided in the twin-pipe convergence part of the port with the longer pipe length on the side where the pipes are removed, upstream of the heat control valve.

[Effect]

In the exhaust gas purification device of the first invention, when the heat control valve is in the open position, the back side of the bottom wall of the riser part is not bypassed to enter the expansion chamber through the longer port on the side where the heat control valve is installed. The flow of the exhaust gas flowing in as it is is increased in flow velocity by the small passage cross-sectional area of the port, and directly hits the element portion of the oxygen sensor, improving the exhaust gas performance of the oxygen sensor.

In the exhaust gas purification device of the second aspect of the invention, in addition to the effects described above in the exhaust gas purification device of the first aspect, the effect of the auxiliary chamber can be achieved. By providing an auxiliary chamber, the exhaust gases flowing individually through the twin pipes are mixed in the auxiliary chamber, and this mixed exhaust gas is sped up and flows into the expansion chamber, improving the oxygen concentration detection accuracy of the oxygen sensor. can be further enhanced.

〔Example〕

Preferred embodiments of the exhaust purification device of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an exhaust purification device according to the first aspect of the present invention applied to a four-cylinder engine,
#1, #2, in order from one end to the other in the left and right direction.
A device is shown having an exhaust manifold with four exhaust ports, which will be referred to as #3 and #4 exhaust ports. In the figure, reference numeral 1 denotes an exhaust manifold, which has an expansion chamber 2 with an enlarged passage cross-sectional area, which is eccentric from the center of the exhaust manifold in the left-right direction. An oxygen sensor 3 is disposed in the center of the expansion chamber 2 with its element portion 3a extending into the expansion chamber 2. A catalytic converter 4 is disposed directly below the expansion chamber 2, and an element portion 3a of the oxygen sensor 3 is located upstream of the center of the catalytic converter 4.

The exhaust manifold 1 has #1 and #2 exhaust ports 5, 6 separated from each other by a separator 7.
and a curved passage section 13 consisting of a single passage connected downstream of the double tube section 8, curved toward the expansion chamber 2, and extending toward the expansion chamber 2.
In FIG. 1, there is a twin-tube section 12 consisting of a port opening from the right side into the expansion chamber 2, #3 and #4 exhaust ports 9 and 10 separated from each other by a separator 11, and a downstream of the twin-tube section 12. A port opening into the expansion chamber 2 from the left side in FIG. We are prepared. Therefore, both curved passage portions 13 and 14 of both ports open into the expansion chamber 2 at the center of the exhaust manifold 1 from the left and right sides in FIG. However, the left and right ports have different pipe lengths due to the eccentricity of the expansion chamber 2 from the center of the exhaust manifold, and one port has a longer pipe length than the other port. The portions of the curved passages 13 and 14 immediately downstream of the twin tube sections 8 and 12 do not have the separators 7 and 11, so they form a twin tube gathering section where the independent exhaust ports of each twin tube section come together. ing. Reference numeral 14a indicates a double tube gathering portion of the curved passage portion 14.

At the port opening to the expansion chamber 2 of the curved passage section 14 of the port with the longer pipe length, which in the illustrated example is connected to the #3 and #4 exhaust ports 9 and 10, there is a A heat control valve 15 is mounted so as to be rotatable about an axis 16, which takes a closed position indicated by a chain double-dashed line and an open position indicated by a broken line in the figure during warm-up. Reference numeral 17 denotes a riser section, which is disposed directly below the bottom wall of the riser section of the intake manifold (not shown), so that it is located at the center of the exhaust manifold 1 in the left-right direction. The reason why the expansion chamber 2 and the catalytic converter 4 directly below it are eccentric from the center of the exhaust manifold is to ensure that exhaust gas flows smoothly between the heat control valve 15 and the bottom wall of the intake manifold riser section when the heat control valve 15 is in the closed position. This is to ensure that the heat flows into the expansion chamber 2, and the expansion chamber 2 is arranged to be biased toward the port opposite to the port to which the heat control valve 15 is attached with respect to the center of the exhaust manifold. There is. Therefore, the port on the side where the heat control valve 15 is attached has a longer pipe length than the port on the other side.

In addition, as shown particularly clearly in FIG. 2, the longer port on the side where the heat control valve 15 is attached (the port having the curved passage section 14) has a narrower passage cross-sectional area at the opening to the expansion chamber 2. It is being In other words, the curved passage section 14 is the double pipe section 1
2, the passage cross-sectional area is wider than the cross-sectional area of each port of the twin-tube part 12, so the twin-tube assembly part 14a also functions as a sub-chamber with an enlarged passage cross-sectional area. It is narrowed down as it approaches the expansion chamber 2, and is maximally narrowed at the opening to the expansion chamber 2.

In the exhaust purification device configured as described above, exhaust gas flows from the left and right ports of the exhaust manifold 1 through the expansion chamber 2 to the catalytic converter 4. Heat control valve 1 after engine warm-up
5 is in the open position, the exhaust gas flowing through the curved passage section 14 of the longer port on the side where the heat control valve 15 is attached flows directly into the expansion chamber 2 without detouring to the riser section 17 side. However, at this time, since the curved passage section 14 of the port is constricted, the flow velocity increases there, and the directivity is also strengthened, making it easier for the flow to reach the element section 3a of the oxygen sensor 3. In other words, even though the heat control valve installation side port has a long pipe length, the flow velocity of the exhaust gas passing through it increases, so it is better to contact the element part 3a of the oxygen sensor 3, and the pipe length on the other side is short. The exhaust gas from the other port is equalized to the element portion 3a of the oxygen sensor 3. For this reason,
The oxygen concentration detection accuracy of the oxygen sensor 3 is improved.

Note that the exhaust gas flowing from the twin tube section 12 into the curved passage section 14 is temporarily expanded at the twin tube gathering section 14a, so its flow velocity is reduced, and the exhaust gas flows through each exhaust port 9, 10 of the twin tube section 12. This improves the mixing of incoming exhaust gas. That is, the firing order of each cylinder is #1, #3, #4, #2 cylinder,
Immediately after the inflow of exhaust gas from #3 exhaust port 9, the incoming exhaust gas from #4 exhaust port 10 mixes with the still remaining exhaust gas from #3 exhaust port 9 which previously entered. #4 exhaust port 1
After exhaust gas flows in from #0 cylinder, #2 exhaust gas flows in, and after exhaust gas flows in from #1 cylinder, exhaust gas flows in from #3 exhaust port 9. Since the residual amount of exhaust gas from the #4 exhaust port 10 is small, it is normally difficult to mix it sufficiently with the exhaust gas that previously flowed in from the #4 exhaust port 10.
Since the flow velocity is reduced in , a part of the exhaust gas that previously flowed in from the #4 exhaust port 10 still remains in the twin pipe collecting portion 14a, and the exhaust gases are mixed well. Therefore, the exhaust gas flowing in from the curved passage section 14 is directed to the #3 or #4 exhaust port 9, 1.
The effect of either one of 0 is reduced accordingly, which works synergistically with the increase in flow rate, helping to improve the oxygen concentration detection accuracy of the oxygen sensor 3.

Next, a preferred embodiment of the exhaust purification device according to the second aspect of the present invention will be described with reference to FIGS. 3 and 4. However, in the second invention, parts that are similar to the first invention are given the same reference numerals as in FIG. 2, and the explanation thereof is omitted, and only the parts that are different from the first invention will be explained.

In Figure 3, heat control valve 1
A sub-chamber 18 formed to enlarge the cross-sectional area of the passage is provided in the twin-tube convergence part 14a of the curved passage part 14 of the port with the longer tube length on the side where the tube 5 is attached. This auxiliary chamber 18 is provided on the passage wall on the lower side of the exhaust manifold along which the exhaust gas from the #4 exhaust port 10 flows, and extends from a position directly below the #4 exhaust port 10 to a position directly below the #3 exhaust port 9. It is formed over a period of time. Note that the subchamber 18 may also be formed in the curved passage portion 13 of the port with the shorter pipe length.

Further, FIG. 4 shows another embodiment according to the second invention, and in this embodiment, the auxiliary chamber 18 is provided with a #3 exhaust port 9 on the passage wall on the lower surface side of the curved passage portion 14. It is formed near the position directly below.

In the device having the above configuration, the exhaust gas flowing from the #4 exhaust port 10 into the twin-tube collecting part 14a has a reduced velocity in the twin-tube collecting part 14a due to the presence of the subchamber 18, and A portion of the gas remains in the vicinity and mixes well with the exhaust gas from the #3 exhaust port 9 that flows in next. As in the case of the first invention, this well-mixed exhaust gas is throttled at the inlet of the expansion chamber 2 to increase its flow velocity, touches the element portion 3a of the oxygen sensor 3, and flows downward into the catalytic converter 4. It flows. Therefore, antechamber 1
The presence of No. 8 further promotes mixing of exhaust gases.

〔Effect of the invention〕

When using the exhaust gas purification device of the present invention, the passage cross-sectional area of the opening to the expansion chamber of the longer port on the side where the heat control valve is attached to the exhaust manifold is the passage cross-sectional area of the port on the other side. Since it is made smaller, it is possible to improve the exhaust gas flow to the element part of the oxygen sensor, improve the oxygen concentration detection accuracy of the oxygen sensor, and improve the exhaust purification control performance. In addition, by adding a sub-chamber to the longer port on the side where the heat control valve is installed, in addition to the above effects, the oxygen concentration detection accuracy of the oxygen sensor is further improved by improving the mixing performance of exhaust gas. It also has the effect of being able to do this.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a part of the exhaust purification device according to the first invention in cross section, FIG. 2 is a front view of the device shown in FIG. 1, and FIG. FIG. 4 is a front view of another embodiment of the exhaust gas purification device according to the second invention of the present invention. DESCRIPTION OF SYMBOLS 1... Exhaust manifold, 2... Expansion chamber, 3... Oxygen sensor, 8, 12... Twin pipe part, 13, 14... Curved passage part, 14a... Twin pipe collection part, 15... Heat control valve, 18... Sub-chamber.

Claims (1)

[Claims] 1. An expansion chamber is provided in the exhaust manifold eccentrically from the center of the exhaust manifold, ports of the exhaust manifold are opened from the left and right sides of the expansion chamber, and an oxygen sensor is provided in the expansion chamber with its element portion extended into the expansion chamber. and at the opening to the expansion chamber of the port with the longer tube length among the left and right ports of the exhaust manifold, which have different tube lengths due to the eccentricity of the expansion chamber,
When in the open position, the flow of exhaust gas from the port flows directly into the expansion chamber.When in the closed position, the flow of exhaust gas from the port flows along the bottom wall of the riser part of the intake manifold and then flows into the expansion chamber. In an exhaust gas purification system equipped with a heat control valve, the passage cross-sectional area of the opening to the expansion chamber is made smaller for the port with the longer pipe length on the side where the heat control valve is installed than the port with the shorter pipe length on the other side. The location of the oxygen sensor element in the expansion chamber is adjusted so that when the heat control valve is in the open position, the exhaust gas flows into the expansion chamber through the longer port on the side where the heat control valve is installed. An exhaust purification device characterized by being located in a position where 2. An expansion chamber is provided in the exhaust manifold eccentrically from the center of the exhaust manifold, ports of the exhaust manifold are opened from the left and right sides of the expansion chamber, and an oxygen sensor is disposed in the expansion chamber with its element part extending into the expansion chamber, and the expansion chamber is arranged eccentrically from the center of the exhaust manifold. Of the left and right ports of the exhaust manifold, which have different pipe lengths due to the eccentricity of the chamber, the exhaust gas flow from the port is expanded as is when it is in the open position, to the opening to the expansion chamber of the port with the longer pipe length. In an exhaust purification system equipped with a heat control valve that directs the flow of exhaust gas from the port along the back surface of the bottom wall of the riser part of the intake manifold and then flows into the expansion chamber when the exhaust gas is in the closed position, the heat control valve The passage cross-sectional area of the opening to the expansion chamber is made smaller for the port with the longer tube length on the side where the is installed than the port with the shorter tube length on the other side, and the location of the oxygen sensor element in the expansion chamber. When the heat control valve is in the open position, the exhaust gas flowing into the expansion chamber through the longer port on the side where the heat control valve is installed is directly exposed to the flow of exhaust gas, and the position on the side where the heat control valve is installed is the same. An exhaust gas purification device characterized in that an auxiliary chamber is provided at the twin-pipe collection part of the longer port on the upstream side of the heat control valve.