JP2001115893A - Cylinder head structure of multicylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly guide exhaust gas and to improve exhaust efficiency. SOLUTION: Combustion chambers 5 are laterally disposed at intervals of an equal distance with a central axis Lo extending through the center of the central combustion chamber 5 in the direction of a cylinder train of a cylinder head 3 and nipped therebetween, and the shapes of each exhaust port 7 extending from each combustion chamber 5, a collection part 7b where the exhaust ports 7 are collected together, and a passage running from the collection part 7b to a discharge port 7c are formed in a symmetrical shape with the central axis Lo nipped therebetween. Since the exhaust passage of each cylinder is formed in a symmetrical shape with the central axis Lo nipped therebetween, an exhaust balance is excellent and exhaust efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head structure of a multi-cylinder engine in which exhaust ports extending from respective cylinders are gathered in a cylinder head.

[0002]

2. Description of the Related Art Generally, an exhaust port formed in a cylinder head of a multi-cylinder engine is disclosed in
As disclosed in JP-A-2009-943 and JP-A-6-58120, they are gathered in an exhaust pipe via an exhaust manifold connected to a side surface of a cylinder head.

[0003] Since the catalyst provided in the exhaust pipe is activated by receiving exhaust heat, in order to activate the catalyst at an early stage, the temperature must be lowered until exhaust gas reaches the catalyst. It is desirable to suppress.

In order to improve the exhaust efficiency, it is desirable to suppress the turbulence of the exhaust gas so that the exhaust gas is guided smoothly.

[0005]

However, the exhaust manifold has a relatively large heat capacity, and the exhaust gas temperature decreases due to heat absorption when the exhaust gas passes through the exhaust manifold. Therefore, the exhaust manifold is connected to the downstream side. It is difficult to activate the catalyst interposed in the exhaust pipe at an early stage.

Further, there is a problem that the exhaust balance tends to be disturbed due to the variation of the passage length until the exhaust gas is collected in the exhaust pipe by the exhaust manifold, and the exhaust efficiency is reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can suppress the temperature drop of the exhaust gas and realize the early activation of the catalyst, and can guide the exhaust gas smoothly and improve the exhaust efficiency. It is an object to provide a cylinder head structure of a multi-cylinder engine.

[0008]

In order to achieve the above object, according to the present invention, there is provided a cylinder head for a multi-cylinder engine in which exhaust ports extending from respective cylinders are gathered in a cylinder head and communicate with an exhaust pipe. The overall shape of the exhaust port is bilaterally symmetrical about an axis perpendicular to the crankshaft direction, and a flat elliptical shape is formed on the downstream side from the exhaust port assembly extending from each cylinder. It is characterized by having.

That is, according to the first aspect of the present invention, the overall shape of the exhaust ports assembled in the cylinder head is bilaterally symmetrical with respect to the axis orthogonal to the crankshaft direction.
In addition, by making the downstream side from the gathering portion of the exhaust ports extending from each cylinder into a flat elliptical shape, the exhaust balance is improved, and the exhaust gas can be smoothly guided to the exhaust pipe side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a schematic view of the engine, FIG. 2 is a sectional view taken along the line II-II of FIG. 3, FIG. 3 is a plan view of the cylinder head viewed from the combustion chamber side, and FIG. 4 is a lower side view of FIG.

Reference numeral 1 in FIG. 1 denotes a multi-cylinder engine. In this embodiment, a horizontally opposed 6-cylinder engine is shown.
(LH, R
H) The cylinder head 3 is provided in the bank. still,
Reference numeral 4 denotes a crankshaft disposed at the center of the cylinder block 2.

Since the cylinder heads 3 provided in both banks are symmetrical, only the structure of the cylinder head 3 on the LH bank side will be described below.
The same reference numerals are given to the configuration of the cylinder head on the bank side, and the description is omitted.

As shown in FIG. 3, the surface of the cylinder head 3 facing the cylinder block 2 is
The combustion chambers 5 are arranged at equal intervals. In addition, an intake port 6 and an exhaust port 7 are formed in the cylinder head 3 corresponding to each combustion chamber 5, and the intake port 6 and the exhaust port 7 are separated by partition walls 8 and 9 near the combustion chamber 5. It is branched into a pair of branch ports 6 a and 7 a and faces the combustion chamber 5.

Reference numeral 10 denotes a valve guide section through which an intake valve 10a and an exhaust valve 10b (see FIG. 1) for opening and closing the branch ports 6a and 7a are inserted.

The upstream side of each intake port 6 formed in the cylinder head 3 is led to an air chamber (not shown) via an intake manifold 11 and is assembled.

Each exhaust port 7 is connected to the cylinder head 3.
Inside the cylinder head 3, they are gathered immediately upstream of the discharge port 7 c opened on the lower surface of the cylinder head 3. The discharge port 7c is opened in a flange portion 3a formed on the lower surface of the cylinder head 3, and a dual exhaust pipe 1 with a front catalyst 12 interposed in the flange portion 3a.
3 are connected.

As shown in FIG. 1, the dual exhaust pipe 13
Extend from the cylinder heads 3 of both banks and are gathered in a rear exhaust pipe 15 in which a sub-muffler 14a and a main muffler 14b are interposed. In addition, a rear catalyst 16 is interposed in the gathering portion of the rear exhaust pipe 15.

As shown in FIG. 3, the center axis Lo extending through the center of the combustion chamber 5 located at the center in the cylinder row direction and extending in a direction orthogonal to the cylinder row direction (the direction of the crankshaft 4) is centered. The exhaust ports 7 communicating with the combustion chambers 5 at both ends in the cylinder row direction are formed in a symmetrical shape, and a pair of branch ports 7a constituting the exhaust port 7 communicating with the central combustion chamber 5 are formed by a central axis Lo. It is formed in a symmetrical shape with the partition wall 9 formed above interposed therebetween.

An exhaust port 7 extending from each combustion chamber 5
Are gathered and a discharge port 7c located on the downstream side of the gathering portion 7b is formed in a symmetrical shape with respect to the center axis Lo.

As shown in FIGS. 3 and 4, from the collecting portion 7b to the discharge port 7c, at least a pair of branch ports 7a extending from the central combustion chamber 5 can be directly looked at. Is formed in a horizontally long flat elliptical shape. The exhaust ports 7 extending from the combustion chambers 5 at both ends in the cylinder row direction to the collecting portion 7b are guided to the collecting portion 7b at a gentle inclination so as to avoid collision of exhaust gas against the wall surface. I have.

Next, the operation of the present embodiment having the above configuration will be described. Exhaust gas discharged from the combustion chamber 5 at the center of the cylinder row passes through a pair of branch ports 7a defined by the partition wall 9, is joined at the collecting portion 7b, and is guided to the discharge port 7c. The passage from the gathering portion 7b to the discharge port 7c is formed in a flat elliptical shape that allows the pair of branch ports 7a communicating with the central combustion chamber 5 to be directly looked into, so that the passage resistance is small. The exhaust gas discharged from the central combustion chamber 5 can be smoothly guided toward the discharge port 7c without generating turbulence.

Exhaust gas exhausted from the combustion chambers 5 at both ends in the cylinder row direction passes through the exhaust ports 7 and is guided to the collecting portion 7b. Since the exhaust port 7 is guided to the collecting portion 7b at a gentle inclination capable of avoiding collision of the exhaust gas with the wall surface, turbulent flow generated in the exhaust gas when passing through the exhaust port 7 is generated. It is suppressed and the exhaust gas can be guided smoothly.

Further, the exhaust ports 7 communicating with the combustion chambers 5 at both ends in the cylinder row direction, a pair of branch ports 7a communicating with the combustion chamber 4 at the center of the cylinder row, and a discharge portion 7b collecting the exhaust ports 7 are formed. Since the shape of the passage leading to the port 7c is formed symmetrically with respect to the center axis Lo, the exhaust balance is good and the exhaust efficiency is improved.

Further, since the exhaust ports 7 communicating with the respective combustion chambers 5 are gathered in the cylinder head 3, an exhaust manifold is not required, the number of parts can be reduced, and the assembly work can be simplified. it can.

Further, since the exhaust manifold having a relatively large heat capacity is eliminated, the temperature of the exhaust gas flowing to the dual exhaust pipe 13 is prevented from lowering. Particularly, in the warm-up operation after the cold start, the catalysts 12 and 16 are used. Can be activated at an early stage, and exhaust emission can be improved.

The present invention is not limited to the above-described embodiment, and the engine to be employed is not limited to the horizontally opposed engine, but may be any of a V-type engine and an in-line engine.
Also, if there are a plurality of cylinders in each cylinder row, if there are a plurality of cylinders in each cylinder row, an exhaust port formed for each cylinder, an aggregation section in which each exhaust port is gathered, about the center axis Lo in the cylinder row direction, and By making the shape of the passage from the collecting portion to the discharge port symmetrical, the same operation and effect as in the present embodiment can be obtained.

[0027]

As described above, according to the first aspect of the present invention, the entire shape of the exhaust ports assembled in the cylinder head is symmetrical with respect to the axis orthogonal to the crankshaft direction. Because it was formed, the exhaust balance was improved, and furthermore, the downstream side from the gathering portion of the exhaust ports extending from each cylinder was formed into a flat elliptical shape, so that the passage resistance was reduced and the exhaust gas could be guided smoothly, Exhaust efficiency is improved.

Further, since the exhaust ports of each cylinder are assembled in the cylinder head, an exhaust manifold is not required, the number of parts can be reduced, and the assembling operation can be simplified.

Further, since the exhaust manifold having a relatively large heat capacity is eliminated, it is possible to directly connect the exhaust pipe to the cylinder head, and it is possible to supply exhaust gas with a suppressed temperature drop to the catalyst. Exhaust emission can be improved by early activation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an engine.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a plan view of the cylinder head viewed from the combustion chamber side.

FIG. 4 is a bottom view of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-cylinder engine 3 Cylinder head 4 Crankshaft 7 Exhaust port 7b Collecting part 13 Dual exhaust pipe (exhaust pipe) 15 Rear exhaust pipe (exhaust pipe) Lo Center axis (orthogonal axis)

Claims (1)

[Claims] 1. A cylinder head structure for a multi-cylinder engine in which exhaust ports extending from respective cylinders are gathered in a cylinder head and communicate with an exhaust pipe. A cylinder head structure for an engine, wherein the engine has a symmetrical shape with respect to an orthogonal axis, and a flat elliptical shape on the downstream side from a collection portion of the exhaust ports extending from each cylinder.