JPH0640904Y2 - Exhaust device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust system for an internal combustion engine.

(Prior Art) Each cylinder is equipped with two intake valves and two exhaust valves,
There is known an internal combustion engine designed to achieve high output (see Japanese Patent Publication No. 47-17967, etc.) (Problems to be solved by the invention) By the way, in such an internal combustion engine, by increasing the number of valves, Although the intake charge efficiency and the like are improved, the pressure charge pulsation generated during exhaust discharge may adversely affect the intake charge efficiency and the scavenging efficiency depending on operating conditions.

That is, if the exhaust valve is closed when the reflected wave of the exhaust blowout pressure (blowdown pressure) at the exhaust port is negative pressure,
Exhaust gas in the cylinder flows out to the exhaust pipe efficiently. However, if the exhaust valve is closed slowly and the reflected wave is closed when the reflected wave is positive pressure (engine low / medium speed range, etc.), the exhaust gas in the cylinder is good. Therefore, the residual gas increases without being discharged.

Therefore, even if a plurality of intake valves and exhaust valves are provided, there is a problem that the scavenging efficiency and intake charging efficiency are reduced depending on operating conditions, and a predetermined engine output cannot be obtained.

As shown in FIG. 3, the resonance pipes 3 and 4 are connected to the exhaust manifolds 1 and 2 connected to the exhaust ports, and the resonance pipes 3 and 4 are connected.
By providing a partition plate 5 that moves by the exhaust pressure between 4 and by making the lengths of the resonance pipes 3 and 4 variable, a high scavenging effect is obtained in the entire operating range by utilizing the exhaust inertia, that is, the exhaust pulsation. Although there is such a method (see Japanese Utility Model Application Laid-Open No. 57-193026), this requires a variable mechanism in the exhaust system, which is expensive and has a problem in durability, which makes it difficult to realize.

The present invention aims to provide an exhaust system that solves such problems.

(Means for Solving the Problems) The present invention relates to an internal combustion engine having a plurality of exhaust valves and a plurality of exhaust ports for each cylinder, and a plurality of exhaust pipes corresponding to the plurality of exhaust ports are provided in different cylinders. To form a plurality of exhaust systems, a catalyst is installed in each exhaust system, and the length of each passage from the end face of each exhaust valve to the catalyst is made different in the same cylinder.

(Function) Exhaust gas flows out to each exhaust system by opening the exhaust valve,
Since the path length from the exhaust valve end face to the corresponding catalyst differs and the vibration system changes, a phase difference occurs in the pressure wave of the exhaust gas in each exhaust system. That is, due to this phase difference, the exhaust blowout pressure immediately after the opening of the exhaust valve is substantially reduced, and the reflected wave of the blowout pressure is weakened, so that the reflected wave is prevented from adversely affecting the scavenging.

(Embodiment) FIG. 1 shows an embodiment in which the present invention is applied to a four-cylinder engine, in which 10 is a cylinder head and 11 to 14 are combustion chambers of each cylinder.

Further, 15a, 15b to 18a, 18b are intake valves, 19a, 19b to 22a, 2
2b is an intake port connected to each intake valve 15a, 15b to 18a, 18b, 23a, 23b to 26a, 26b is an exhaust valve, 27a, 27b to 30a, 30b
Is an exhaust port connected to each exhaust valve 23a, 23b to 26a, 26b.

Then, exhaust pipes 31a, 31b to 34a, 34b are connected to the exhaust ports 27a, 27b to 30a, 30b, respectively, and these exhaust pipes are in different cylinders and a group of exhaust pipes 31a to 34a, and the exhaust pipe 31.
The exhaust pipes 31a to 34a and 31b to 34b are respectively grouped into groups b to 34b, and two exhaust systems 35A and 35B are formed.

In this case, the exhaust pipes 31a to 34a and 31b to 34b are smoothly connected to the corresponding main exhaust pipes 36a and 36b of the exhaust systems 35A and 35B arranged on the side of the cylinder head 10 through predetermined curved pipe portions. Is
They are collected via main exhaust pipes 36a and 36b, respectively.

Then, the catalysts 38a, 3 housed in predetermined cases 37a, 37b as exhaust emission control devices on the downstream sides of the respective exhaust systems 35A, 35B.
Together 8b it is interposed, so that the catalyst 38a corresponding from the end surface of the exhaust valve in each this same cylinder, path length l _a to 38b, is l _b differ, the exhaust pipe 31 a to 34, 31B～34
The lengths of b and the main exhaust pipes 36a, 36b are determined.

In addition, these lengths are for both exhaust systems 35A and 35B when exhaust is exhausted.
It is selected so as to cause a predetermined phase difference in the inner pressure wave.

With such a configuration, when the exhaust valve (for example, 24a, 24b) of the cylinder that has completed the combustion process is opened, the exhaust gas in the cylinder is exhausted from the exhaust valves 24a, 24b through the exhaust ports 28a, 28b to the exhaust systems 35A, 35B, but in this case the passage length from the end face of the exhaust valve 24a to the catalyst 38a is short.
In A, the vibration cycle of the pressure wave of the exhaust becomes short, whereas in the exhaust system 35B where the passage length from the end face of the exhaust valve 24b to the catalyst 38b is long, the vibration cycle of the pressure wave of the exhaust becomes long.

Therefore, a phase difference occurs in the pressure wave between the exhaust system 35A side and the exhaust system 35B side, and this phase difference substantially reduces the exhaust blowout pressure immediately after the opening of the exhaust valves 24a, 24b and reflects the exhaust blowout pressure. The waves also weaken.

Here, FIG. 2 shows the experimental results of the blowout pressure and the reflected wave when the passage length from the end face of the exhaust valve to the corresponding catalyst is the same or different (invention), as shown in FIG. It has been confirmed that the blowing pressure and the reflected wave are weakened.

Further, in the present invention, since a phase difference is generated between the exhaust systems 35A and 35B connected to the exhaust valves 23a and 23b to 26a and 26b, the blowout pressure and the reflected wave are weakened regardless of the operating conditions.

Therefore, irrespective of the low, medium and high speed range of the engine, when the exhaust valves 23a, 23b to 26a, 26b are closed, it is prevented that the reflected wave of the blowout pressure adversely affects the scavenging. Efficiency can be secured, and engine output can be improved in all operating ranges.

In addition, although the embodiment has been described with reference to the one provided with two exhaust valves and two exhaust ports, a device provided with three or more exhaust valves is also applicable.

As described above, according to the present invention, in an internal combustion engine having a plurality of exhaust valves for each cylinder, each passage length from the end face of each exhaust valve to the corresponding catalyst of each exhaust system in the same cylinder. The exhaust blowout pressure and its reflected wave can be weakened because the vibration system of each exhaust system is changed, and therefore, the adverse effect of the reflected wave on the scavenging can be prevented, and high scavenging efficiency and intake charging efficiency can always be obtained. It can be secured and the engine output can be improved in the entire operating range.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a pressure characteristic diagram of exhaust gas, and FIG. 3 is a configuration diagram of a conventional example. 23a, 23b ~ 26a, 26b ... Exhaust valve, 27a, 27b ~ 30a, 30b ...
Exhaust port, 31a, 31b to 34a, 34b ... Exhaust pipe, 35A, 35B
...... Exhaust system, 38a, 38b …… Catalyst.

Claims (1)

[Scope of utility model registration request] 1. In an internal combustion engine having a plurality of exhaust valves and a plurality of exhaust ports for each cylinder, a plurality of exhaust pipes corresponding to the plurality of exhaust ports are collected in different cylinders to form a plurality of exhaust systems. An exhaust system for an internal combustion engine, wherein the exhaust system is formed, a catalyst is installed in each exhaust system, and each passage length from each exhaust valve end face to the catalyst is different in the same cylinder.