JPH0716009Y2 - Pipe exhaust manifold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a pipe exhaust manifold used for an exhaust system of an automobile.

[Conventional technology]

Exhaust manifolds installed in automobiles are roughly divided into two types.

One is that the engine capacity is relatively small at 1000-1600cc,
It is an exhaust manifold mounted on a small passenger car called a popular car, and it has to be housed in a small engine room and the cost must be low. E
The exhaust gas discharged from each of the cylinders P _{1 to} P _{4 is} collected immediately after and is discharged from one discharge pipe C.

This exhaust manifold is compact and can be manufactured at low cost, while the exhaust manifolds EP _1- E
The exhaust gas emitted from P ₄ interferes with each other, resulting in a reduction in engine output.

However, this type of mass-produced car has a small body and is not a car in which driving performance is deeply pursued. Therefore, from the standpoint of economic efficiency, it is said that such an exhaust manifold is acceptable.

However, this exhaust manifold is difficult to use in so-called sports cars and the like in terms of running performance.

The other is an exhaust manifold that is installed in so-called sports cars, where the engine capacity is large at 2000cc or more and driving performance is particularly important.

In this exhaust manifold, a relatively long pipe is attached to each cylinder and they are gathered on the downstream side.

Conventionally, as this type of pipe exhaust manifold, for example, the one disclosed in Japanese Utility Model Laid-Open No. 61-152719 is known.

This will be described based on the exhaust device shown in FIG. In the figure, 1 is an engine, and a pipe exhaust manifold 3 is attached to each cylinder (not shown) through a head flange 2.

This pipe-made exhaust manifold 3 is constructed by connecting four manifold tubes 4 to two collecting pipes 5 on the downstream side with two manifold tubes 4 as one unit.

At this time, for each manifold tube 4, the combination of the manifold tubes 4 and the tube length are determined so that the exhaust gases from the explosions from the cylinders do not interfere with each other.

The two collecting pipes 5 connected to the downstream side of the pipe exhaust manifold 3 are connected to the two front tubes 7 via the flange 6. Further, the two front tubes 7 are joined together by a single collecting pipe 8 on the downstream side and are connected to the inflow portion of the catalytic converter 9. By sequentially connecting the cylinders in this manner, the exhaust gases from the cylinders are prevented from interfering with each other and the deterioration of engine performance is prevented as much as possible. Further, an exhaust system (not shown) having a muffler is connected to the downstream side of the catalytic converter 9.

When the exhaust gas is discharged from each cylinder of the engine 1, the exhaust device configured as described above causes the exhaust gas to flow through the corresponding manifold tubes 4 so as not to interfere with each other. It is sent to the catalytic converter 9 via the front tube 7 and the collecting pipe 8, where it is subjected to a predetermined purification treatment, and then discharged to the atmosphere via a downstream exhaust system.

[Problems to be solved by the invention]

However, since the pipe-made exhaust manifold 3 in the above-mentioned exhaust device prevents mutual interference of exhaust gas from each cylinder, the length of the manifold tube 4 per cylinder is long and the total surface area is large. , The heat dissipation effect is large, and the exhaust gas temperature is too low, the catalytic converter 9
Activity deteriorates. Further, since the manifold tube 4 has a complicated shape, it is difficult to attach a heat shield plate having a heat insulating effect. Further, when the engine is started, the pipe exhaust manifold 3 absorbs heat until it warms up, so in cold regions, winter, or when the outside air temperature is low,
There is a problem that the catalytic converter 9 cannot be sufficiently heated and the performance of the catalytic converter 9 is poor.

[Purpose of device]

The present invention has been made to solve such a conventional problem, and an object thereof is to prevent a temperature decrease in a pipe portion of an exhaust manifold which has no choice but to provide a pipe portion and accelerate catalyst ignition, An object of the present invention is to provide a pipe-made exhaust manifold capable of preventing a decrease in temperature of exhaust gas as much as possible and enhancing catalytic activity in a main converter.

[Means for solving problems]

The pipe exhaust manifold according to the present invention is a pipe exhaust manifold in which a long manifold tube per cylinder and a large total surface area are attached to each cylinder of an engine. A layer is formed.

[Function of device]

In the present invention, when exhaust gas is exhausted from each cylinder of the engine and sent to each manifold tube, CO, HC, NOx etc. in the exhaust gas are provided on the inner surface of each manifold tube for catalyst coating. It comes into contact with the bed and is subjected to a cleaning action by the catalyst. The exhaust gas flowing inside due to the reaction heat at this time is sent to the downstream catalytic converter without lowering its temperature. Also, because a catalyst coating layer is provided inside each manifold tube,
The catalyst coating layer forms a heat insulating layer and does not lower the temperature of the exhaust gas flowing down.

[Example of device]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Incidentally, the pipe exhaust manifold according to the present invention has an engine mounted on the upstream side and a catalytic converter mounted on the downstream side, like the conventional exhaust system shown in FIG. ,
Only the essential parts of the device will be described.

In the figure, 10 is a pipe exhaust manifold,
There is a hole for each cylinder of the engine, and a head flange 11 attached to the engine and this head flange
Four manifold tubes 12 each having a long length per cylinder and a large total surface area, which are attached so as to communicate with each of the 11 holes, and two manifold tubes 12 at the downstream side of the four manifold tubes 12 Two collecting pipes 13 connected as
And a flange 14 attached to the downstream side of the two collecting pipes 13. A front tube 16 is connected to the flange 14 via a flange 15.

For example, as shown in FIG. 2, the manifold tube 12 has a catalyst coating layer 17 formed therein.

The catalyst coating layer 17 is formed as follows, for example. First, the manifold tube 12 is formed of ferritic stainless steel containing aluminum (for example, Fe-20Cr-5Al) and heated to heat the alumina whiskers 18
To generate. Next, a washcoat layer 19 is formed on the alumina whiskers 18, and the washcoat layer 19 is formed.
A catalyst 20 such as platinum is supported in 19. As the catalyst supporting means, the catalyst 20 is supported in the wash coat layer 19 by accumulating or pouring the catalyst solution into the manifold tube 12.

The operation and effect of the pipe-made exhaust manifold according to the present embodiment thus configured will be described.

When the engine is started and exhaust gas is discharged from each cylinder, the exhaust gas flows down through the corresponding manifold tube 12. At this time, CO, HC, NOx, etc. in the exhaust gas come into contact with the catalyst coating layer 17 and heat is generated by the catalyst. The heat generated heats the inside of the manifold tube 12. When the exhaust gas continuously discharged from the engine flows down in the thus heated manifold tube 12, the amount of heat taken by the manifold tube 12 becomes extremely small, and the decrease in the temperature of the exhaust gas is suppressed. It

Therefore, the exhaust gas whose temperature drop is suppressed in this way is
When it is sent to the catalytic converter located on the downstream side, the catalytic activity in the catalytic converter is enhanced, and the exhaust gas is sufficiently purified.

In particular, even when it is difficult to purify exhaust gas with a catalytic converter, such as immediately after the engine is started, in winter, in cold regions, when the outside air temperature is low, or the exhaust system is not warmed up sufficiently. Even when the exhaust gas temperature is suppressed from decreasing, the performance of the catalytic converter can be exhibited early.

Further, even if the length of the manifold tube 12 per cylinder is long and the total surface area is large as in the present embodiment, the catalyst coating layer 17 provided inside suppresses a decrease in exhaust gas temperature. Naturally, the performance of the catalytic converter can be exhibited early.

Further, since the catalyst coating layer 17 also functions as a heat insulating layer, even if the manifold tube 12 has a complicated shape as in the present embodiment, it is possible to exert a heat shield effect without attaching a heat shield plate. You can

In the above example, the catalyst coating layer 17 was formed by using ferritic stainless steel containing aluminum, but not limited to this, for example, aluminum is vapor-deposited in a stainless tube, and a wash coat layer is formed on this. Further, it may be formed by a method of supporting a catalyst in the washcoat layer.

Further, the catalyst coating layer 17 may be provided over the entire length from the manifold tube 12 to the collecting pipe 13 or a part of the manifold tube 12 or only the collecting pipe 13 as in the above-mentioned embodiment.

[Effect of device]

As described above, according to the present invention, in the exhaust manifold made of pipe, in which each cylinder of the engine has a manifold tube having a long length and a large total surface area per cylinder, a catalyst coating is applied to the inner surface of the manifold tube. Since the layers are formed, the exhaust gas temperature does not decrease from the engine to the catalytic converter, and good catalyst activity in the catalytic converter can be obtained. Even if the exhaust manifold has a complicated shape, the heat insulating effect can be easily obtained. There is an advantage that the catalytic converter can be downsized.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention, and FIG.
FIG. 3 is an enlarged view of part A in the figure, FIG. 3 is a side view showing a conventional example,
FIG. 4 is a side view of an exhaust device using a conventional pipe exhaust manifold. 10 ... Pipe exhaust manifold, 11 ... Head flange, 12 ... Manifold tube, 13 ... Collecting pipe, 16 ... Front tube, 17 ... Catalyst coating layer, 18 ... Whiskers, 19 ... Washcoat layer , 20 ...
…catalyst.

Claims (3)

[Scope of utility model registration request] 1. An exhaust manifold made of pipe, in which a long manifold tube per cylinder and a large total surface area are attached to each cylinder of an engine, and a catalyst coating layer is formed on the inner surface of the manifold tube. An exhaust manifold made of pipe. 2. A manifold tube comprising aluminum-containing ferritic stainless steel, whiskers formed on its inner surface, a washcoat layer provided on the whiskers, and a catalyst supported on the washcoat layer. The exhaust manifold made of pipe according to claim 1, which is a utility model registration claim. 3. A manifold tube made of ferritic stainless steel, aluminum is vapor-deposited on the inner surface of the manifold tube, a wash coat layer is provided on the aluminum layer, and a catalyst is supported on the wash coat layer. The exhaust manifold made of pipe according to claim 1 of the new model registration claim.