JPH08158938A - Head gasket of engine - Google Patents

Abstract

PURPOSE: To adjust compression ratio using a head gasket, while preventing enlargement of a squish area and reverse tumbling. CONSTITUTION: A hole 22 is opened in a form matching a combustion chamber 3a. A circular squish-area-forming recess 25 leading to a cylinder bore 2a is formed in the lower surface of a head gasket. A mask for intake air that is blocked by a squish area and by the beveled portions of inlet valves 15, 16 and forced toward the outer periphery of the combustion chamber is formed in the head gasket 7. Thus compression ratio can be varied by varying the thickness of the head gasket without requiring a cylinder head to be replaced, resulting in cost reduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine head gasket interposed between a cylinder body and a cylinder head.

[0002]

2. Description of the Related Art Conventionally, when changing the compression ratio of an engine, the shape of the piston head and the shape of the recess for forming the combustion chamber of the cylinder head have been changed. For this reason, in an engine that uses a lightweight piston with a recessed central portion as the piston, engine control should be performed when the piston is replaced with a flat head to improve durability. The cylinder head was replaced with a deeper one for the combustion chamber forming recess so that the compression ratio would not change significantly so that the same operation could be performed.

[0003]

However, in adjusting the compression ratio, replacing the cylinder head with another one as described above causes a problem that the cost becomes too high. Although it is conceivable to make the head gasket thicker as another method of changing the compression ratio, merely changing the thickness causes a problem in combustion as described below.

If the head gasket is made thick, the vertical width of the squish area formed between the cylinder body and the cylinder head becomes unnecessarily large.
Squish makes it impossible to accelerate combustion.

When the intake air flows into the combustion chamber, the flow direction may be changed so that a part of the intake valve hits the umbrella portion of the intake valve toward the outer peripheral side of the combustion chamber. If the upper and lower widths of the above are expanded, it becomes difficult to regulate the flow of intake air toward the outer peripheral side of the combustion chamber. As a result, when a cylinder head configured to generate tumble of intake air in the cylinder by flowing the intake air from the opening on the combustion chamber side of the intake passage to the exhaust valve side in the combustion chamber, the cylinder head is moved to the outer peripheral side of the combustion chamber. The flow of intake air causes a tumble in which the turning direction is opposite to that of the tumble. That is, if the tumble consisting of the intake air flow from the opening on the intake valve side toward the exhaust valve side is a forward tumble, the forward tumble is weakened by the reverse tumble whose turning direction is opposite to that.

The present invention has been made in order to solve such a problem, and changes the shape of the combustion chamber forming recess of the cylinder head while preventing the squish area from being enlarged and the occurrence of reverse tumble. The purpose is to be able to adjust the compression ratio without.

[0007]

A head gasket for an engine according to the present invention has a portion corresponding to a combustion chamber opened in a shape substantially the same as the opening shape of a combustion chamber forming recess in a cylinder head, and is on the cylinder body side. On the bottom,
The squish area forming recess is formed so as to be continuous with the wall surface of the cylinder hole.

[0008]

By inserting the head gasket according to the present invention between the cylinder body and the cylinder head, the squish area is formed with the head gasket as its peripheral wall and top wall. Further, since the wall surface of the opening portion in the head gasket is substantially the extension portion of the combustion chamber forming concave portion of the cylinder head on the cylinder body side, it blocks the intake air flowing toward the outer peripheral side of the combustion chamber when it hits the umbrella portion of the intake valve. It works as a mask.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 1 is a vertical cross-sectional view of an engine using a head gasket according to the present invention, FIG. 2 is a cross-sectional view showing an enlarged main part in FIG. 1, and FIG. 3 is a cross-sectional view showing an enlarged central intake valve part in FIG. 4 and 5 are bottom views of the cylinder head as seen from the cylinder body side, in which the broken position of FIG. 1 is indicated by the line II. Figure 5
FIG. 6 is a bottom view of the head gasket as seen from the cylinder body side.

In these drawings, 1 is a water-cooled multi-cylinder engine, 2 is a cylinder body of the engine 1, 3 is a cylinder head, 4 is a piston, 5 is a connecting rod connected to the piston 4 via a piston pin 6. Is. A head gasket 7 according to the present invention is interposed between the cylinder body 2 and the cylinder head 3.

The cylinder head 3 is the same as an engine using a lightweight piston (not shown), and an intake port 8 and an exhaust port 9 are formed for each cylinder, and a cylinder bore 2a of the cylinder body 2 is formed. A concave portion 3a for forming a combustion chamber is formed in a portion corresponding to. An intake port 8 serving as an intake passage and an exhaust port 9 serving as an exhaust passage are formed so as to open in the recess 3a. A spark plug 10 is attached to the center of the recess 3a.

Each of the intake port 8 and the exhaust port 9 is opened on the side surface of the cylinder head 3 and extends from this opening toward the combustion chamber. The intake port 8
As shown in FIG. 4, three branch passages (a right branch passage 11, a central branch passage 1) are provided in the middle of a portion of the cylinder head 3 that opens to the side surface of the cylinder head 3 and a portion that opens to the recess 3a.
2 and the left branch passage 13). Reference numeral F in FIG. 4 denotes a fuel injection valve, and this fuel injection valve F
Has a structure in which fuel is injected into the intake port 8 in a substantially conical shape within a range indicated by a chain double-dashed line f in FIG. Further, as shown in FIG. 1, the branch passages 11 to 13 are formed substantially linearly from the upstream side to the vicinity of the opening on the concave portion 3a side, and are formed so that the bent portions are reduced. The exhaust port 9 is branched into two branch passages 9a and 9b.

The openings of these branch passages on the side of the recess 3a are opened and closed by the intake valves 14 to 16 and the exhaust valves 17 and 18, respectively. Intake valves 14-16
The exhaust valves 17 and 18 are configured to be opened and closed by a conventionally known valve operating device 21 having an intake cam shaft 19 and an exhaust cam shaft 20.

The piston 4 is formed such that the central portion of the top surface thereof is slightly recessed and the head portion thereof is substantially flat. That is, the piston 4 is formed such that the distance from the top surface to the piston pin 6 is larger than that of the lightweight piston, and the durability is higher than that of the lightweight piston. The shape of the top surface of the lightweight piston is shown by a chain double-dashed line P in FIG.

The head gasket 7 is made of a stainless material, and an opening hole 22 corresponding to the combustion chamber is opened for each cylinder as shown in FIG. Reference numeral 23 denotes a through hole through which a head bolt (not shown) for fixing a cylinder head is inserted.
Reference numeral 4 is a cooling water hole for passing engine cooling water. In addition, the cylinder body 2, the cylinder head 3, the piston 4
Is made of aluminum alloy.

The opening hole 22 has a shape substantially the same as that of the combustion chamber forming recess 3a in the cylinder head 3. That is, the three intake valves 11 to 1
Umbrella portion 11a of each of the three and two exhaust valves 14 and 15
Extension portions 22a to 2 extending from the outer peripheral side to the vicinity of
2e is formed in series.

On the lower surface of the head gasket 7 on the cylinder body 2 side, there is formed a squish area forming recess 25 which is continuous with the hole wall surface of the cylinder bore 2a. The squish area forming recess 25 is formed by recessing the lower surface of the head gasket 7 into a circle centered on the cylinder axis. The inner diameter of the recess 25 is set to be slightly larger than the inner diameter of the cylinder bore 2a.

Further, the thickness of the head gasket 7 is set so that the compression ratio is substantially equal to that of an engine using a lightweight piston having a top surface shape shown by a chain double-dashed line P in FIG. That is, it is formed thicker than a head gasket used for a lightweight piston engine.

In the engine 1 thus constructed, the intake air flowing into the cylinder through the three branch passages 11 to 13 is, as shown by an arrow I in FIGS. 2 and 3,
Most of the branch passages 11 to 13 pass between the opening and the umbrella portions 14a to 16a of the intake valves 14 to 16 due to the branch passages 11 to 13 being formed substantially linearly in the vicinity of the opening on the concave portion 3a side. It linearly and obliquely flows into the cylinder. That is,
Most of the intake air is from the opening to the exhaust valve 1 from the center of the cylinder.
As a result, the tumble in the clockwise direction in FIGS. 1 to 3 occurs in the cylinder due to the inflow to the 7 and 18 sides.

Further, the intake air whose flow direction is changed to the outer peripheral side (the side opposite to the exhaust valve) by hitting the umbrella portions 14a to 16a of the intake valves 14 to 16 when flowing into the cylinder (indicated by an arrow Ia in FIG. 3). (Shown) is an extension part 22a-22 of the head gasket 7 located laterally of the umbrella parts 14a-16a.
The flow is regulated by c. For this reason, if the clockwise tumble is the forward tumble in FIGS. 1 to 3, it is difficult to generate the reverse tumble in which the turning direction is opposite to the forward tumble.

On the other hand, at the end of the compression stroke, when the piston 4 rises to the top dead center as shown in FIG. 1, squish is generated from the squish area forming recess 25 between the piston 4 and the head gasket 7. As a result, high speed combustion using squish is performed.

Therefore, by interposing the head gasket 7 according to the present invention between the cylinder body 2 and the cylinder head 3, the squish area is formed with the head gasket 7 as its peripheral wall and top wall. Even when the lightweight piston type cylinder head 3 is adopted in the engine 1 that uses the piston 4 having a substantially flat head, the head gasket 7 can be formed thick and the compression ratio can be substantially the same.

Moreover, since the wall surface of the opening hole 22 in the head gasket 7 is substantially the extension of the combustion chamber forming recess 3a of the cylinder head 3 on the cylinder body side, it hits the intake valves 14 to 16 to the outer peripheral side of the combustion chamber. It comes to function as a mask that blocks the inhaled air. Therefore, in adjusting the compression ratio by forming the head gasket 7 thick as described above, the forward tumble composed of the clockwise intake air flow in FIGS. 1 to 3 is formed by the reverse tumble in which the swirling direction is the opposite direction. Less likely to be weakened.

[0024]

As described above, in the engine head gasket according to the present invention, the portion corresponding to the combustion chamber is opened to have a shape substantially the same as the opening shape of the combustion chamber forming recess in the cylinder head, and to be connected to the cylinder body side. Since a recess for forming a squish area that is continuous with the wall surface of the cylinder hole is formed on the lower surface, the squish area inserts the head gasket between the cylinder body and the cylinder head. Will be formed as. Moreover, since the wall surface of the opening in the head gasket is substantially an extension of the combustion chamber forming recess of the cylinder head on the cylinder body side, it blocks the intake air flowing toward the outer peripheral side of the combustion chamber by hitting the umbrella portion of the intake valve. It works as a mask.

Therefore, since the head gasket according to the present invention substantially constitutes a part of the combustion chamber forming recess in the cylinder head, the combustion chamber of the cylinder head can be changed by changing the thickness of the head gasket. The compression ratio can be changed without changing the shape of the forming recess. Therefore, when changing a lightweight piston having a recessed head portion to a highly durable piston having a substantially flat head portion, the thickness of the head gasket according to the present invention is set so that the compression ratio becomes substantially equal. By
Since it is not necessary to replace the cylinder head, the cost can be reduced. As a result, it is possible to obtain a plurality of types of engines using one type of cylinder head.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an engine using a head gasket according to the present invention.

FIG. 2 is a cross-sectional view showing an enlarged main part in FIG.

FIG. 3 is an enlarged sectional view showing a central intake valve portion in FIG.

FIG. 4 is a bottom view of the cylinder head as viewed from the cylinder body side.

FIG. 5 is a bottom view of the head gasket as viewed from the cylinder body side.

[Explanation of symbols]

1 ... Engine, 2 ... Cylinder body, 2a ... Cylinder bore, 3 ... Cylinder head, 3a ... Combustion chamber forming recess, 4
... piston, 7 ... head gasket, 14-16 ... intake valve, 22 ... opening hole, 22a-22e ... extension part, 25 ... squish area forming recess.

Claims (1)

[Claims] 1. In a head gasket of an engine interposed between a cylinder body and a cylinder head, a portion corresponding to the combustion chamber is opened with a shape substantially the same as the opening shape of a combustion chamber forming recess in the cylinder head. A head gasket for an engine, characterized in that a squish area forming recess that is continuous with a wall surface of a cylinder hole is formed on a lower surface of the cylinder body side.