JPH0223686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic converter for exhaust gas purification used in vehicles such as automobiles, and particularly relates to a catalytic converter for purifying exhaust gas used in vehicles such as automobiles. This relates to the supplied catalytic converter for purifying exhaust gas.

The oxidation catalyst, which converts harmful unburned components such as HC and CO in the exhaust gas into harmless components, works effectively in an oxidizing atmosphere. Therefore, the catalytic converter for exhaust gas purification that has the oxidation catalyst is installed inside the converter case. It has a secondary air introduction pipe for introducing secondary air into the converter case upstream of the oxidation catalyst bed. The secondary air inlet pipe of a catalytic converter for exhaust gas purification is generally installed in the converter case so that the distribution of secondary air is uniform in one cross section of the converter case so that the entire catalyst bed can operate effectively. It has an extending portion that extends through a part of the wall portion, extends into the converter case, and terminates within the converter case, and the extending portion is provided with a plurality of secondary air introduction holes. Secondary air is supplied into the converter case from each of the secondary air introduction holes.

If secondary air is introduced into the converter case from the secondary air introduction pipe due to exhaust pulsation, the amount of secondary air supplied is determined by the flow of the secondary air supply system including the secondary air introduction pipe. affected by resistance,
It is known that the amount of secondary air supplied increases as the diameter of the pipe member constituting the pipe line increases. However, an increase in the diameter of the tube member results in an increase in the space required for arranging the secondary air supply device, and this has various restrictions and limits.

In view of this, the present inventors conducted a detailed experimental study on the flow of secondary air in a catalytic converter for exhaust gas purification having a secondary air introduction pipe as described above, and found that the secondary air supply Among the pipes constituting the system, if the pipe diameter of at least the terminal end of the extending portion of the secondary air introduction pipe in the converter case is increased, the pipe diameters of the pipe members of other parts will be increased. It has been found that at least the amount of secondary air supplied increases.

This is because the area near the end of the secondary air introduction pipe is more affected by reflected waves in the pipe than other parts, so the flow resistance is greater than in other parts. This problem can be eliminated or reduced by increasing the cross-sectional area of the passage, and as the diameter of the secondary air introduction pipe inside the converter case increases, the problem can be solved or reduced by increasing the cross-sectional area of the passage. The reduction in the cross-sectional area of the exhaust passage increases the flow rate of exhaust gas flowing through this area, which increases the negative pressure acting on the secondary air introduction hole and increases the suction of secondary air into the converter. This is thought to be because.

SUMMARY OF THE INVENTION In view of the above-described circumstances, an object of the present invention is to provide a catalytic converter for exhaust gas purification having an improved secondary air introduction structure so as to increase the amount of secondary air supplied into the converter case.

The present invention provides a catalytic converter for exhaust gas purification as described above, in which at least the terminal end side of the extending portion of the secondary air introduction pipe has a larger cross-sectional shape than the portion penetrating the converter case. This is achieved by a catalytic converter for exhaust gas purification in which at least a portion of the plurality of secondary air introduction holes are provided in the shaped portion.

According to this structure, at least the terminal end side of the extending portion of the secondary air introduction pipe inside the converter case has a larger cross-sectional shape than other portions, thereby reducing the flow resistance of the extending portion. At the same time, the flow velocity of the exhaust gas inside the converter case increases in the area where the secondary air introduction pipe is installed, and as a result, the amount of secondary air introduced into the converter case increases. The secondary air introduction pipe has a large cross-sectional shape only in its extended part, and the cross-sectional shape of the part that penetrates the converter case is not enlarged. There is no need to change the structure of the part that penetrates the pipe, and there is no need to increase the space for installing the secondary air supply device.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a plan view showing one embodiment of a catalytic converter for purifying exhaust gas according to the present invention, and FIG. 2 is a sectional view taken along the line - in FIG. 1.

In these figures, 1 indicates a converter case, which is composed of a combination of an upper half 2 and a lower half 3, and has an inlet flange with an exhaust gas inlet 4 at one end. member 5,
Each of them also has an outlet flange member 7 with an exhaust gas outlet 6 at the other end. Inside the converter case 1, there are a three-way catalyst bed 8 and an oxidation catalyst bed 9, each of which is composed of a monolithic catalyst, as viewed from the flow of exhaust gas flowing inside the converter case 1 from the exhaust gas inlet 4 toward the exhaust gas outlet 6. are installed in series.
The converter case 1 has a cavity (exhaust gas passage) 10 between a three-way catalyst bed 8 and an oxidation catalyst bed 9.

A secondary air introduction pipe 11 is attached to the converter case 1. The secondary air introduction pipe 11 has a penetrating portion 12 that passes through a through hole 3a provided in the lower half 3 of the converter case 1, and a hole 10 that crosses the exhaust gas flow flowing through the hole. The extending portion 13 extends in the direction of the converter case 1 and terminates in the converter case 1, and the extending portion 13 has a penetrating portion 12.
The pipe diameter, that is, the cross-sectional shape is larger than that of the pipe. In this embodiment, the portion having a large cross-sectional shape as described above constitutes a large portion of the extension portion 13 on its terminal end side. The secondary air introduction pipe 11 is fixed to the lower half body 3 at a portion passing through the through hole 3a, and the tip of the extending portion 13 is supported by a stay member 14 attached to the lower half body 3. The tip opening (terminus) is closed by a stay member 14. Secondary air introduction pipe 1
A plurality of secondary air introduction holes 15 are bored in the peripheral wall of the portion of the converter case 1 located inside the converter case 1 . The secondary air introduction hole 15 opens toward the upstream side of the exhaust gas flow at a predetermined angle with respect to the exhaust gas flow. By setting the opening direction of the secondary air introduction hole 15 in this manner, the distribution of secondary air within the converter case is improved. If a more detailed explanation of this is required, please refer to Utility Model Application No. 56-94717 (Utility Model Publication No. 61-2265) filed by the same applicant as the present applicant.
Please refer to

The secondary air introduction holes 15 are all secondary air introduction holes 1
5, and most of them are provided in the portion of the extending portion 13 that has a large cross-sectional shape. The opening diameter of this secondary air introduction hole 15 is
1/ of the inner diameter of the extension portion 13 on which it is provided.
It is preferable that the ratio is about 2 to 1/3; if the ratio is more than 1/2, the distribution of secondary air in the converter case will deteriorate, and if the ratio is less than 1/3, , this becomes a flow resistance and reduces the amount of secondary air supplied.

As mentioned above, the extension portion 1 of the secondary air introduction pipe 11
By expanding the cross-sectional shape of 3,
In particular, the amount of secondary air supplied due to exhaust pulsation increases.

FIG. 3 shows the secondary air supply characteristics due to exhaust pulsation. In this glass, A indicates the secondary air supply characteristics of the catalytic converter for exhaust gas purification according to the present invention as in the above embodiment, and B indicates the conventional type in which the extending portion 13 has the same passage cross-sectional area as the penetrating portion 12. The secondary air supply characteristics of the catalytic converter for exhaust gas purification are shown respectively. In addition, in the test for collecting this data, the number, size, arrangement position, shape, and penetration of the secondary air introduction pipe of the secondary air supply introduction hole were compared between the one according to the present invention and the conventional one. The tube diameters of the portions 12 were made the same, and only the tube diameters of the extension portions 13 were made different. Furthermore, the outer diameter of the penetrating portion 12 is
The outer diameter of the extension portion 13 was 25.9 mm. As is clear from this graph, when looking at the amount of secondary air supply, especially in the normal engine speed range,
The catalytic converter for exhaust gas purification according to the present invention is more numerous than the conventional catalytic converter for exhaust gas purification.

In the catalytic converter for exhaust gas purification according to the present invention, at least the terminal end side of the extending portion of the secondary air introduction pipe located inside the converter case is enlarged in cross-sectional shape. When the amount increases, there is no need to increase the size of the exhaust gas purifying catalytic converter, and there is no need to increase the size, weight, and material costs of the members constituting the secondary air supply system. Furthermore, in the catalytic converter for exhaust gas purification according to the present invention, it is only necessary to enlarge the cross-sectional shape of the extending portion of the secondary air introduction pipe.
If the amount of secondary air supply remains the same as before, other parts of the secondary air supply system can be constructed with smaller parts than before, compared to conventional products with equivalent performance. This will result in economical effects due to the reduction in material and weight, as well as increased design freedom and productivity as a result of saving space when mounted on vehicles.

Although the present invention has been described above in detail with reference to specific embodiments, it is understood that the present invention is not limited thereto and that various embodiments are possible within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the catalytic converter for purifying exhaust gas according to the present invention, FIG. 2 is a sectional view taken along the line - in FIG. It is a graph showing characteristics with respect to numbers. 1...Converter case, 2...Upper half, 3
... lower half, 4 ... exhaust gas inlet, 5 ... inlet flange member, 6 ... exhaust gas outlet, 7 ... outlet flange member, 8 ... three-way catalyst bed, 9 ... oxidation catalyst bed, 10 ...Empty part, 11...Secondary air introduction pipe, 12...Penetration part, 13...Extension part, 14
...Stay member, 15...Secondary air introduction hole.

Claims (1)

[Claims] 1. A converter case, an extending portion extending through the converter case, extending into the converter case, and terminating within the converter case, the extending portion having a plurality of secondary air introduction holes. In a catalytic converter for exhaust gas purification having a secondary air introduction pipe, at least the terminal end side of the extending portion has a larger cross-sectional shape than the portion penetrating the converter case, and the larger cross-sectional shape portion A catalytic converter for purifying exhaust gas, wherein at least a portion of the plurality of secondary air introduction holes are provided in the catalytic converter.