JP2516093Y2 - Exhaust device for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust system for an internal combustion engine, and more particularly to an exhaust system for a horizontal V-type internal combustion engine or a horizontally opposed internal combustion engine.

[Conventional technology]

In a vehicular internal combustion engine, each cylinder is divided into two banks, and each bank is arranged in a V-shape with the crankshaft as the center, or a horizontal type with the crankshaft centered horizontally. In an opposed internal combustion engine, an exhaust system that purifies exhaust gas from two banks in front and rear by a catalytic converter and guides it to a silencer requires a structure that minimizes pressure loss of exhaust gas and improves exhaust gas purification performance. .

In the conventional exhaust system of this type, a catalyst is separately provided in each exhaust passage connected to the front bank and the rear bank,
A structure in which one of the two catalysts is housed in the same container with the other on the outer periphery of the center, and the exhaust gas from the rear bank is guided to the catalyst in the center Is known (Japanese Utility Model Publication No. 63-98425). In this type, relatively high temperature exhaust gas is introduced from the front bank to the catalyst on the outer peripheral side through a short exhaust passage to accelerate the temperature rise of the catalyst on the outer peripheral side and accelerate the activation, and also the catalyst in the central portion. Exhaust gas from the rear bank introduced into the engine is relatively low in temperature due to heat release due to the long exhaust passage.However, by supplying heat from the outer catalyst to the central catalyst, the central catalyst It is intended to accelerate the activation of the exhaust gas and improve the purification characteristics of the exhaust gas from the rear bank.

[Problems to be solved by the device]

However, in the above conventional exhaust system, the lengths of the first exhaust passage extending from the front bank to the outer peripheral catalyst and the second exhaust passage extending from the rear bank to the central catalyst are not equal. However, there is a problem in that the respective exhaust characteristics cannot be made equal, and the catalyst warm-up property and exhaust pressure loss are not uniform.

An exhaust device having an equal length exhaust pipe structure has been conventionally known (Japanese Utility Model Laid-Open No. 62-67921), but this one has a structure in which the exhaust pipe of the rear bank is temporarily returned to near the front oil pan. Therefore, the total exhaust pipe length must be increased,
For this reason, the catalytic converter arranged under the floor of the vehicle has a poor warm-up property, and sufficient exhaust gas purification performance cannot be obtained.

The present invention has been made in view of the above points, and a merging portion is provided at the lower center of the internal combustion engine by providing a catalytic converter at the rear end of an equal-length exhaust passage connected to each of the front and rear banks. It is an object of the present invention to provide an exhaust system for an internal combustion engine that can improve exhaust gas purification performance and reduce exhaust pressure loss by connecting to the exhaust gas.

[Means for solving the problem]

According to the present invention, a merging portion for connecting both axial lines of first and second exhaust pipes, which are provided in front and rear banks of a horizontally-disposed V-type or horizontally-opposed internal combustion engine, so as to match each other, is provided at a substantially central lower portion of the internal combustion engine. In the exhaust system for an internal combustion engine, the first and second exhaust pipes are arranged so that the lengths of the first and second exhaust pipes to the confluence are equal to each other.
First and second catalytic converters are provided at respective rear end portions of the first and second exhaust pipes, and the exhaust outlets of the first and second catalytic converters are connected to each other at substantially right angles by the merging portion to form a combined exhaust pipe. The structure is commonly connected to.

[Action]

In the present invention, the exhaust gas from the front and rear banks is
And the second exhaust pipes separately flow into the first and second catalytic converters so as to face each other, but smoothly merge after facing each other at the merging portion due to the cell direction of the catalyst carrier of the catalytic converter. Guided to the combined exhaust pipe.

Further, since the first and second catalytic converters are located in the substantially central lower part of the internal combustion engine together with the confluence part, the catalytic converter is sufficiently upstream of the exhaust gas as compared with the conventional exhaust device in which the catalytic converter is provided under the vehicle floor. Since the converter is located and the relatively high temperature exhaust gas flows into the first and second catalytic converters, the catalyst warm-up property is good. Moreover, since the exhaust gas from each of the front and rear banks flows into the merging portion while touching the exhaust outlet side catalyst carrier of the catalyst converter on the opposite bank side, warming up of the catalytic converter on the opposite bank side can be assisted.

〔Example〕

1 and 2 are respectively a front view and a bottom view of an embodiment of an exhaust system for an internal combustion engine according to the present invention, in which the same components are designated by the same reference numerals. In both figures, reference numeral 1 denotes a horizontal V-type internal combustion engine for a vehicle, which has multiple cylinders, and each cylinder is arranged in two banks. The two banks are a front bank 2a located in the front direction of the vehicle in which the internal combustion engine 1 is mounted and a rear bank 2b located in the rear direction.
The front bank 2a is connected to the front end of the first exhaust pipe 3a, and the rear bank 2b is connected to the front end of the second exhaust pipe 3b.

The first exhaust pipe 3a is bent rearward so that the rear end portion 3a ₁ is located near the lower center of the internal combustion engine 1.
Is connected to the exhaust inlet of the mixed flow catalytic converter 4a. Further, as the second exhaust pipe 3b is bent forward, a rear end portion 3b ₁ are located near the bottom center of the internal combustion engine 1, and, spaced apart opposed to the rear end 3a ₁ of the first exhaust pipe 3a And is connected to the exhaust inlet of the second mixed flow catalytic converter 4b.

An oil pan 5 is arranged in the lower center of the internal combustion engine 1, and a recess 6 is formed in a part of the bottom surface of the oil pan 5 as shown in FIG. In the recess 6, the first
Also, the second mixed flow type catalytic converters 4a, 4b are arranged, and the merging portion 7 for connecting the exhaust outlets of these mixed flow type catalytic converters 4a, 4b at a substantially right angle is also arranged in the recess 6.
The other end of the merging portion 7 is connected to a silencer (not shown) via a merging exhaust pipe 8.

In this embodiment, the first and second exhaust pipes 3a and 3b have the same length, and the mixed flow catalytic converters 4a and 4b are arranged substantially in the lower center of the internal combustion engine 1.

Next, the main part of this embodiment will be described in more detail. FIG. 3 is a front view of an embodiment of the main part of the present invention, the left half of which is shown in cross section. In the figure, the first mixed flow catalytic converter 4a is configured such that a catalyst carrier 12a is provided between a front bank exhaust inlet 10a and an exhaust outlet 11a.
2a is arranged so as to be inclined by an angle θ with respect to the axis of the conduit extending from the front bank exhaust inlet 10a to the catalyst carrier 12a. Similarly, in the second mixed flow catalytic converter 4b, the catalyst carrier 12b has an angle θ between the rear bank exhaust inlet 10b and the exhaust outlet 11b.
It is arranged to be inclined.

The exhaust outlets 11a and 11b are joined at a merging portion 7 at a substantially right angle and connected to the merging portion exhaust outlet 13. The catalyst carrier 12
The gas passages in front of and behind a and 12b are formed by a half press sheet metal welding structure.

A sectional view of the catalyst carrier 12b taken along the line AA in FIG. 3 is shown in FIG. As shown in FIG. 4, the catalyst carrier 12b has a metal carrier catalyst structure in which a honeycomb structure 16 made of, for example, a Fe—Cr—Al heat-resistant alloy is enclosed in an elliptic cylindrical steel outer cylinder 15. ing. The catalyst carrier 12a also has the same structure as the catalyst carrier 12b.

Next, the operation of this embodiment will be described. As an example,
If it is applied to a V-type 6-cylinder vehicle internal combustion engine,
Since the explosion order is normally alternating between the front bank 2a and the rear bank 2b, the exhaust gas flowing from the front bank 2a through the first exhaust pipe 3a to the front bank exhaust inlet 10a in FIG.
Exhaust gas flowing from the rear bank 2b through the second exhaust pipe 3b into the rear bank exhaust inlet 10b of FIG. 3 alternately flows at every crank angle of 120 ° C.

The exhaust gas flowing into the front bank exhaust inlet 10a flows into the catalyst carrier 12a at an incident angle (90 ° −θ) as shown in FIG. 3, where harmful components in the exhaust gas are oxidized or decomposed, As the exhaust gas is purified, the flow direction is changed and flows out from the exhaust outlet 11a to reach the merging portion 7. At this time, the exhaust gas also hits the exhaust outlet 11b side portion of the catalyst carrier 12b and reaches the merging portion 7.

Here, since the catalyst carrier 12a is provided so as to be inclined with respect to the flow direction of the inflowing exhaust gas, the catalyst carrier 12a
The exhaust gas inlet area of the is substantially increased. For this reason,
The flow velocity of the exhaust gas passing through the inside of the catalyst carrier 12a decreases in inverse proportion to the increase of the flow passage area, and the flow resistance proportional to the square of the flow velocity significantly decreases, so that the pressure loss of the catalyst carrier 12a is small.

Next, exhaust gas flows into the rear bank exhaust port 10b,
Similar to the above, this exhaust gas is purified by the catalyst carrier 12b, flows out from the exhaust outlet 11b with little pressure loss, and reaches the merging portion 7 while also touching the exhaust outlet 11a side portion of the other catalyst carrier 12a. Thereafter, the same operation as above is repeated. Then, the exhaust gas combined at the merging portion 7 is discharged from the merging portion exhaust outlet 13 to the merging exhaust pipe 8 shown in FIGS. 1 and 2.
Is discharged to

Thus, in the present embodiment, the mixed flow catalytic converter 4
Since the a and 4b are arranged in the recess 6 of the oil pan 5 sufficiently upstream from the underfloor of the vehicle, the exhaust gas from each of the front bank 2a and the rear bank 2b has a small amount of heat release and is in a high temperature state. As it flows into the mixed flow type catalytic converters 4a, 4b as it is,
Since the catalyst carriers 12a and 12b have good warm-up properties, and the exhaust gas to the merging portion 7 hits the exhaust outlet side of the other catalyst carrier on the bank side, the part is also warmed up. Since the carriers 12a and 12b are sufficiently activated, good exhaust gas purification performance can be obtained.

Also, the rear bank exhaust inlet 10a and the rear bank exhaust inlet 1
The exhaust gases flowing into 0b face each other at the time of inflow, but do not face each other in the merging portion 7 due to the cell direction of the catalyst carriers 12a and 12b and join at a substantially right angle, so that the exhaust gases do not collide and interfere with each other. The pressure loss is minimized because the pressure loss of the catalyst carriers 12a and 12b is smoothly guided to the merging portion exhaust outlet 13, and as described above.

Furthermore, since the exhaust pipes 3a and 3b are of equal length, and the explosion order alternates between the front bank 2a and the rear bank 2b, the pulsation of sound pressure due to the explosion alternates with the confluent exhaust pipe 8. The exhaust noise resulting from the deviation of the sound pressure pulsation can be minimized because it flows into and is rectified.

Further, since the mixed flow type catalytic converters 4a, 4b have an aggregate structure, they can be compactly installed in the confluence portion 7, and thus a relatively large capacity catalyst can be mounted.

It should be noted that the present invention is not limited to the above-described embodiment, but can be applied to a horizontally opposed internal combustion engine instead of the V internal combustion engine 1, for example.

[Effect of device]

As described above, according to the present invention, the exhaust gas from the front bank and the exhaust gas from the rear bank are not opposed to each other at the merging portion depending on the cell direction of the catalyst carrier of the catalytic converter, and then smoothly flow to the merging exhaust pipe. Since it is guided, exhaust pressure loss can be reduced, and the catalytic converter is located substantially in the lower center part of the internal combustion engine, and the exhaust gas from the front and rear banks also flows to the exhaust outlet side part of the catalytic converter on the other bank side. By bringing them into contact with each other, the warming-up property of the catalyst carrier is remarkably improved as compared with the conventional one, so that the exhaust gas purification performance can be remarkably improved as compared with the conventional one.

[Brief description of drawings]

1 and 2 are a front view and a bottom view, respectively, of an embodiment of the present invention, and FIG. 3 is a half-cut front view and a front view of an embodiment of an essential part in FIGS. 1 and 2. FIG. 4 is a sectional view taken along the line AA in FIG. 1 ... V type internal combustion engine, 2a ... front bank, 2b ... rear bank, 3a ... first exhaust pipe, 3b ... second exhaust pipe, 4a ...
... 1st mixed flow catalytic converter, 4b ... 2nd mixed flow catalytic converter, 7 ... merge part, 8 ... merged exhaust pipe, 12a,
12b ... Catalyst carrier.

Claims (1)

(57) [Scope of utility model registration request] 1. A merging portion for connecting both axial lines of first and second exhaust pipes provided in front and rear banks of a horizontal V-type or horizontally-opposed internal combustion engine so as to be aligned with each other is approximately at the center of the internal combustion engine. An exhaust system for an internal combustion engine, which is arranged at a lower portion and has a structure in which the lengths of the first and second exhaust pipes to the confluence are equal to each other, wherein the rear end portions of the first and second exhaust pipes are An internal combustion engine having a structure in which first and second catalytic converters are provided, and the exhaust outlets of the first and second catalytic converters are coupled to each other at substantially right angles by the confluence portion and are commonly connected to a confluent exhaust pipe. Exhaust system.