JPH0765503B2 - Exhaust manifold structure of engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold structure of an engine, and more particularly to an exhaust manifold structure of a multi-cylinder engine having an exhaust passage portion independently connected to each cylinder.

(Prior art and its problems) In a multi-cylinder engine, the exhaust gas becomes high temperature and high pressure at high speed and high load, the passage resistance of the exhaust gas becomes large, and the exhaust gas efficiency decreases, so that the intake charging efficiency decreases. Will end up. Further, there is a fear that the aging of the exhaust manifold and the exhaust purification device arranged in the exhaust passage downstream thereof may be accelerated.

Therefore, the present applicant has previously proposed an exhaust manifold structure for solving the above problem (Japanese Patent Application No. 61-123742).
issue).

This is one in which the exhaust passages of the exhaust manifold that are independently connected to the exhaust ports of each cylinder are made to communicate with each other by a communication passage. The exhaust passage portions to be connected are connected to each other through the communication passage to reduce the exhaust temperature, while preventing exhaust interference.

By the way, when connecting the independent exhaust passages of the exhaust manifold with a plurality of communicating passages in this way, the communicating passages have the same length and diameter to have the same capacity, and the exhaust pressure decrease degree and the heat dissipation effect are improved. It is necessary to make the degrees approximately the same. That is, if the degree of exhaust pressure reduction / heat radiation effect is different, the exhaust efficiency is different between the cylinders communicating with each communication passage, and the combustion state is different.

However, if all the communication passages are concentrated on one of the upper side and the lower side of the exhaust passage portion, the exhaust communication passages interfere with each other, which causes a problem in that the arrangement is restricted. In addition, if it is installed on the upper side, the bonnet is restricted, and if it is installed on the lower side, there is not enough space between itself and the engine body. is expected.

(Object of the Invention) In view of the circumstances as described above, an object of the present invention is to provide an exhaust manifold structure of an engine capable of achieving equalization of the capacities of respective communication passages with a compact structure.

(Structure of the Invention) In the engine exhaust manifold structure according to the present invention, the exhaust passage portions that are independently connected to the exhaust ports of the respective cylinders are divided into a plurality of groups of the same number, and the exhaust passage portions are mutually arranged for each group. A communication passage is provided to communicate with each other, and some of these communication passages are arranged on the upper side of the exhaust passage portion and the rest are arranged on the lower side of the exhaust passage portion. It is possible to install the communication passage in a compact manner by effectively utilizing the space around the engine without being restricted by the bonnet or the like, without interfering with each other.

(Embodiment of the Invention) The first and second illustrated exhaust manifolds are applied to a four-cylinder engine.
The piston 3 is arranged in each of the cylinders # 1 to # 4 formed in the cylinder, and the cylinder head 4 includes each of the cylinders # 1 to # 4.
Intake / exhaust ports 5 and 6 are formed for each, and intake / exhaust valves 8 and 9 are provided between the intake / exhaust ports 5 and 6 and the combustion chamber 7.
Are installed respectively. Each exhaust port 6 is connected to an exhaust pipe 10 on the downstream side via an exhaust manifold 11.

The exhaust manifold 11 is the exhaust port 6 of each cylinder # 1 to # 4.
The four exhaust passages 11a to 11d that are connected so that the upstream ends thereof are independently connected to each other and the downstream ends are communicated with each other, and the exhaust passage portions 11a and 11d that are communicated with the cylinders # 1 and # 4, respectively. And a communication passage 12 that communicates with the exhaust passage portions 11b and 11c that communicate with the cylinders # 2 and # 3, respectively.
It is composed of 13 and. One communication passage 12 is arranged above the exhaust manifold 11, the other communication passage 13 is arranged below the exhaust manifold 11, and both communication passages are arranged.
The connecting portions of 12 and 13 with the exhaust passage portions 11a to 11d are provided on substantially the same line from the exhaust port, and the passage lengths are set to be substantially the same so that the capacities of both the communication passages 12 and 13 are substantially equal. I am doing it. Further, the communication passage 13 is fixed to the cylinder block 2 by a bracket 14.

According to the exhaust manifold configured as described above, for example, the exhaust gas discharged from the cylinder # 1 or # 4 is discharged through the exhaust passage portion 11a or 11d and the exhaust passage portion 11d through the communication passage 12. Alternatively, the gas flows to the protector 51 side 11a and is discharged from here. Similarly, for the cylinders # 2 and # 3, the exhaust gas is exhausted from the exhaust path portions 11b and 11c by the communication path 13. Therefore, the exhaust passage cross-sectional area is substantially expanded and the passage resistance is reduced. As a result, the exhaust pressure is lowered and the exhaust temperature is lowered, so that the exhaust efficiency is improved, so that the intake charging efficiency is improved and the fuel efficiency at high speed can be improved. Further, since the capacities of the communication passages 12 and 13 are made substantially equal, the degree of decrease in exhaust pressure and the degree of heat radiation effect become substantially equal, and each cylinder # 1 to # 1.
It is possible to suppress variations in the combustion state in # 4. Further, the communication passage 13 is fixed to the cylinder block 2 by a bracket 14, and exhaust heat is transmitted to the cylinder block 2 side via the bracket 14, and both the communication passages 12 and 13 are formed in upper and lower spaces of the exhaust manifold 11. That is, since they are arranged in different space portions, the heat radiation effect can be further enhanced, and the capacities of both passages 12 and 13 can be made uniform with a compact structure.

Further, exhaust passage portions 11a to 11d connected by the communication passages 12 and 13 are connected.
Cylinders # 1 and # 4, # 2 and # 3 that are not adjacent to each other in the exhaust stroke
Since they are connected to each other, it is possible to prevent exhaust interference.

Although the present embodiment is applied to a 4-cylinder engine, it goes without saying that it can also be applied to other multi-cylinder engines such as 6 cylinders.

(Effects of the Invention) According to the exhaust manifold structure of the engine according to the present invention, it is possible to make the capacities of the plurality of communication passages equal to each other with a compact structure, and to reduce the exhaust pressure and the heat radiation effect of each communication passage. Equal and can be improved. Therefore, it is possible to prevent variations in combustion among the cylinders, suppress torque fluctuations, improve charging efficiency, and further improve fuel efficiency at high speeds.

[Brief description of drawings]

FIG. 1 is a perspective view of a four-cylinder engine to which an embodiment of an exhaust manifold structure according to the present invention is applied, and FIG. 2 is a cross-sectional view of a main part thereof. 6 ... Exhaust port 11 ... Exhaust manifold 11a to 11d ... Exhaust passage section 12/13 ... Connection path

Claims (1)

[Claims] 1. An exhaust manifold structure for an engine, wherein an upstream end is independently connected to an exhaust port of each cylinder and an exhaust passage portion is assembled so that the downstream ends communicate with each other. The passages are divided into a plurality of groups of the same number, and a communication passage that connects the exhaust passages to each other is provided for each group, and some of these communication passages are arranged above the exhaust passage and the rest are exhaust passages. The exhaust manifold structure of the engine, which is arranged on the lower side of the section.