JP2003314357A - Cylinder head structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the cooling property of the vicinity of a combustion chamber by improving cylinder head structure. <P>SOLUTION: A cylindrical plug tower portion 5 mounted with an ignition plug of a cylinder head 1 is formed in a manner that its sectional area at a section perpendicular to a center shaft increases gradually toward an upper deck 6 side from a combustion chamber side. Accordingly, since the sectional area of a path close to the combustion chamber requiring cooling of a water jacket 7 is assured and the flow speed of cooling water increases, the thermal conductivity to the cooling water increases and the cooling property is improved. Also, unlike a partition or a rib, since it does not block the flow of the cooling water by facing the flow perpendicularly, the increase of the flow resistance of the cooling water is prevented and the increase of the driving force of a water pump is prevented. Also, stagnation on the partition or the back side of the rib does not occur. <P>COPYRIGHT: (C)2004,JPO

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 an internal combustion engine, and more particularly to a technique for improving cooling performance.

[0002]

2. Description of the Related Art Conventionally, as a cylinder head structure of an internal combustion engine, a partition wall is provided so as to close a water jacket passage in an upper portion of a cylindrical plug tower portion into which a spark plug is inserted and mounted, so that a heat load is high. There is one in which cooling water is concentratedly distributed to the lower part of the plug tower portion (combustion chamber side) to improve cooling performance (Japanese Patent Laid-Open No. 9-326).
No. 32).

[0003]

However, the above-described conventional cylinder head structure has a problem that the flow resistance of the cooling water is significantly increased, the shape of the cylinder jacket becomes complicated, and the manufacturing becomes difficult. The present invention has been made by paying attention to such a conventional problem, and has a simple shape that does not impair manufacturability, and an internal combustion engine that has improved cooling performance while suppressing an increase in cooling water flow resistance. An object of the present invention is to provide a cylinder head structure.

[0004]

Therefore, in the invention according to claim 1, the cylindrical plug tower portion into which the ignition plug of the cylinder head is inserted is cut off inside the outer peripheral wall in a cross section perpendicular to the central axis. It is characterized in that the area is formed so as to smoothly increase from the combustion chamber side toward the upper deck side.

According to the first aspect of the present invention, the cross-sectional area of the passage of the water jacket around the plug tower portion is reduced toward the upper deck side away from the combustion chamber where the need for cooling is reduced, so that the cooling water is cooled. Since the passage cross-sectional area is secured on the side closer to the combustion chamber where cooling is highly required while increasing the flow velocity, the heat transfer coefficient to the cooling water is increased and the cooling performance is improved.

Further, unlike a partition wall or rib, it does not obstruct the flow of the cooling water at right angles to each other, and it is possible to suppress an increase in the cooling water flow resistance and an increase in the driving force of the water pump. No stagnation occurs on the back side of the rib. Also, when the cooling water flows from the upstream side and hits the plug tower part, the cooling water hits the upper deck side smoothly along the outer wall of the plug tower part formed so that the cross-sectional area decreases toward the combustion chamber side. Since it is guided to the combustion chamber side, the flow resistance is reduced, the flow velocity is further increased, and the cooling performance is improved.

Further, since the internal space of the plug tower portion also expands toward the upper deck side, the process of assembling the spark plug on the seat surface is simplified, and the spark plug detachability is improved. The invention according to claim 2 is characterized in that the rate of change of the cross-sectional area is large on the upper deck side and small on the combustion chamber side.

According to the second aspect of the present invention, the cross-sectional area of the water jacket passage can be further reduced on the upper deck side. Therefore, the cooling water flow velocity on the combustion chamber side can be further increased to enhance the cooling performance. As well as
Since the plug tower portion is smoothly connected to the upper deck, the flow of cooling water can be smoothly directed to the combustion chamber side to further reduce the flow resistance.

The invention according to claim 3 is characterized in that the upstream side portion of the cross-sectional area in the cooling water flow direction is formed to be larger than the downstream side portion. According to the invention of claim 3, the direction of the cooling water from the upper deck side of the plug tower portion to the combustion chamber side direction is further promoted, and the cooling of the outer wall of the combustion chamber is promoted.

The invention according to claim 4 is characterized in that the plug tower portion is formed so that the wall thickness in the cooling water flow direction increases smoothly from the combustion chamber side toward the upper deck side. . According to the invention of claim 4, the cross-sectional area of the water jacket passage can be further reduced on the upper deck side, the cooling water flow velocity on the combustion chamber side can be further increased, and the cooling performance can be enhanced. In addition, by reducing the thickness of the combustion chamber side where the heat load is high,
The heat dissipation can also be improved.

The invention according to claim 5 is characterized in that the change rate of the wall thickness of the plug tower portion is large on the upper deck side and small on the combustion chamber side. According to the invention of claim 5, the effect described in claim 4 is further promoted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows cylinder heads # 3 and # 4 of an in-line four-cylinder engine according to an embodiment of the present invention.
2 shows a cross section near the cylinder, FIG. 2 is a vertical cross section taken along line AA of FIG. 1, FIG. 3 is a vertical cross section taken along line BB of FIG.
Shows a vertical section taken along the line CC of FIG. 1, respectively.

As shown in FIG. 2, an outer wall 2 of a combustion chamber, an outer wall 3 of an intake port, an outer wall 4 of an exhaust port, and an outer wall 5a of a plug tower 5 for mounting an ignition plug (not shown) in an internal space are provided in a cylinder head 1. A water jacket 7 is formed which is surrounded by the cylinder head upper deck 6.
Then, as shown in FIGS.
Is formed such that the substantially circular cross-sectional area in a cross section perpendicular to the central axis smoothly decreases from the upper deck side toward the combustion chamber side.

Further, as shown in FIG. 3, since the cross-sectional area of the water jacket 7 on the combustion chamber side 7a is secured and the cross-sectional area of the upper deck side 7b is reduced, the combustion chamber requiring more cooling. The flow velocity of the cooling water on the side 7a increases, and the cooling of the outer wall 2 of the combustion chamber is promoted. As shown in FIG. 4, in the present embodiment, the cooling water flows from the front of the engine to the rear, but the cooling water that collides from the front of the engine with the upper deck side 5b of the outer wall of the plug tower section 5 is Since the flow flows in the direction of the combustion chamber side 5c of the plug tower portion 5 along the shape of 5, the flow velocity of the cooling water on the combustion chamber side 5c is further increased, and the cooling of the outer wall 2 of the combustion chamber is promoted.

Further, in addition to the present embodiment, the cross-sectional area of the water jacket is small even when the direction of the flow of the cooling water is in the direction of the engine intake side-exhaust side or in the direction oblique to the longitudinal direction of the engine. It is clear that the same effect can be obtained because the size is smoothly reduced from the combustion chamber side to the upper deck side. Further, as shown in FIGS. 2 to 4, since the internal space 5d of the plug tower portion 5 which is the installation space for the spark plug expands toward the upper deck side, the assembly process of the spark plug assembly seat surface 5g is simplified. , The spark plug detachability is improved.

Furthermore, in this embodiment, the rate of change in the cross-sectional area of the plug tower 5 is large on the upper deck side,
Since the wall thickness is made smaller on the combustion chamber side, and the wall thickness is made larger on the upper deck side and smaller on the combustion chamber side (see FIG. 3), the passage cross-sectional area of the water jacket 7 is made larger on the upper deck side 7b. It can be reduced more greatly.

As a result, the cooling water flow velocity on the combustion chamber side 7a can be further increased to enhance the cooling performance.
Since the plug tower portion 5 is smoothly connected to the upper deck 6, the flow of cooling water can be smoothly directed to the combustion chamber side 7a to further reduce the flow resistance. Further, by reducing the wall thickness on the side of the combustion chamber where the heat load is high, heat dissipation can be improved.

5 to 7 show a second embodiment, FIG. 5 is a vertical cross section taken along line AA of FIG. 1, and FIG. 6 is B of FIG.
A vertical section taken along line -B, and Fig. 7 show a vertical section taken along line CC of Fig. 1, respectively. As shown, plug tower section 5
Has a substantially conical shape, but the same basic effects as those of the first embodiment can be obtained, and the cross-sectional shape is simple, so that the manufacturing is easy.

FIG. 8 shows a third embodiment, which is indicated by B in FIG.
-The longitudinal section which follows the B line is shown. As shown in the figure, the upstream side 5e of the cooling water in the plug tower portion 5 in the flow direction and the other side 5
The expansion ratio of the cross-sectional area of the plug tower portion 5 to the upper deck 6 side differs from that of f. That is, the enlargement ratio of the upstream side 5e is set to be larger than that of the other side 5f, whereby the upper deck side 5b of the plug tower portion 5 to the combustion chamber side 5f.
The direction of the cooling water in the c direction is further promoted, and the combustion chamber outer wall 2
Cooling is accelerated.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view of a cylinder head common to each embodiment of the present invention in the vicinity of # 3 and # 4 cylinders.

FIG. 2 is a vertical sectional view taken along the line AA of FIG. 1 in the first embodiment.

FIG. 3 is a vertical cross-sectional view taken along the line BB of FIG. 1 in the first embodiment.

FIG. 4 is a vertical cross-sectional view taken along the line CC of FIG. 1 in the first embodiment.

FIG. 5 is a vertical sectional view taken along the line AA of FIG. 1 in the second embodiment.

FIG. 6 is a vertical sectional view taken along the line BB of FIG. 1 in the second embodiment.

FIG. 7 is a vertical cross-sectional view taken along the line CC of FIG. 1 according to the second embodiment.

FIG. 8 is a vertical cross-sectional view taken along line BB of FIG. 1 in the third embodiment.

[Explanation of symbols]

1 cylinder head 2 Outer wall of combustion chamber 3 Outer wall of intake port 4 Outer wall of exhaust port 5 Plug tower section 5a External wall of plug tower 5b Upper deck side of plug tower section 5c Plug tower, combustion chamber side 5e upstream of plug tower flow direction 6 upper deck 7 water jacket 7a Water jacket combustion chamber side 7b Upper deck side of water jacket

Claims (5)

[Claims] 1. A cylindrical plug tower portion to which a spark plug of a cylinder head is attached is formed so that a cross-sectional area in a cross section perpendicular to a central axis smoothly increases from a combustion chamber side toward an upper deck side. A cylinder head structure for an internal combustion engine characterized by the above. 2. The cylinder head structure for an internal combustion engine according to claim 1, wherein the rate of change of the cross-sectional area is large on the upper deck side and small on the combustion chamber side. 3. The cylinder head structure for an internal combustion engine according to claim 1, wherein the upstream side portion of the cross-sectional area in the cooling water flow direction is formed to be larger than the downstream side portion. . 4. The thickness of the plug tower portion in the cooling water flow direction is formed so as to smoothly increase from the combustion chamber side toward the upper deck side.
The cylinder head structure for an internal combustion engine according to claim 4. 5. The cylinder head structure for an internal combustion engine according to claim 4, wherein the rate of change in wall thickness of the plug tower portion is set to be large on the upper deck side and small on the combustion chamber side.