JPH0814051A - Combustion chamber for overhead valve type engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of so-called blow-by phenomenon from an intake port to an exhaust port at a low cost and to reinforce a revolving flow in an axial direction formed in a cylinder chamber. CONSTITUTION:A cylinder head 2 is arranged above a cylinder block 1. A spacer 22 is arranged between the cylinder block 1 and the cylinder head 2 and a combustion chamber 6 is arranged in such a manner to extend through the portion, fronting on a cylinder chamber 4, of a spacer 22. An intake port 7 and an exhaust port 8 formed in the cylinder head 2 are opened fronting on the combustion chamber 6. A partition wall 23 is formed in the combustion chamber 6 of the spacer 22 and between the intake port 7 and the exhaust port 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber of an overhead valve engine in which an intake / exhaust port provided in a cylinder head is opened to face the combustion chamber, and more specifically, a partition wall is formed between the intake / exhaust port. Regarding the combustion chamber.

[0002]

BACKGROUND OF THE INVENTION Generally, in an overhead valve engine, a cylinder head is arranged above a cylinder block, a combustion chamber is provided above a cylinder chamber formed in the cylinder block, and an intake port and an exhaust port formed in the cylinder head are provided. It opens to face the combustion chamber. On the other hand, in a two-cycle engine, the intake valve and the exhaust valve simultaneously open during scavenging. Therefore, when the overhead valve engine is applied to a two-stroke engine, there is a problem that a so-called blow-through phenomenon is likely to occur, in which fresh air or air-fuel mixture flowing from the intake port immediately escapes to the exhaust port.

[0003]

In order to prevent this blow-through phenomenon, there is a conventional overhead valve two-cycle engine in which a partition wall is formed between an intake valve and an exhaust valve as shown in FIG. Publication "Nikkei Mechanical" 1991.1
2.9 Page 54 >>.

That is, this overhead valve type two-cycle engine
(E) is provided with a step on the bottom surface (53) of the cylinder head (52) arranged above the cylinder block (51),
The intake port (54) and the exhaust port (55) are formed in (52), the intake port (54) is opened in the upper bottom surface (56), and the exhaust port (55) is opened in the lower bottom surface (57). Each of them faces the combustion chamber (58), and the step portion constitutes a partition wall (59). In the figure, reference numeral (60) is a scavenging port, (61) is an intake valve, (62) is an exhaust valve, (63) is a spark plug, (64) is a fuel injection device, and (65) ) Indicates a supercharger, respectively.

According to the above-mentioned prior art, since the intake port (54) is closed on the exhaust port (55) side by the partition wall (59), the intake air flowing from the intake port (54) is different from the exhaust port (55). It flows from the opposite side into the lower cylinder chamber, and the exhaust port (5
There is no danger of getting out of 5) immediately.

[0006]

However, in the above prior art, since the exhaust port (55) is open to the lower bottom surface (57), there is no partition wall around the exhaust port (55), The gas in the cylinder chamber easily flows out from the peripheral edge of the exhaust port (55) on the intake port (54) side. As a result, the intake air that has flowed into the cylinder chamber from the intake port (54) is exhausted.
It is easy to immediately flow out from (55), and there is a possibility that the above-mentioned blow-in phenomenon of intake air may still occur.

Moreover, in the above-mentioned conventional technique, a step is required to be formed on the expensive cylinder head in order to form the partition wall (59), which cannot be implemented at a low cost.

Further, since the partition wall (59) closes a part of the intake port (54) and thus becomes an intake resistance, it is necessary to modify the partition wall according to the engine specifications in consideration of the balance between the scavenging efficiency and the intake resistance. is there. That is, since a low-speed engine has a small amount of intake air per unit time, even if the range along the intake port and the exhaust port of the partition wall is widened to surely guide the intake air into the lower cylinder chamber, the engine output decreases. There is no fear of On the other hand, in the case of a high-speed engine, the amount of intake air is large and the swirl flow in the cylinder axis direction is strong. The intake air can be reliably guided into the lower cylinder chamber even if it is kept high. In the above prior art, when modifying the partition wall according to the specifications of the engine,
There is a problem that an expensive cylinder head has to be modified and cannot be easily implemented.

According to the present invention, in a combustion chamber of an overhead valve engine, a so-called blow-through phenomenon in which gas immediately escapes from an intake port to an exhaust port can be reliably and inexpensively prevented, and an axial direction formed in a cylinder chamber can be prevented. An object of the present invention is to provide a combustion chamber that can enhance the swirling flow of the.

[0010]

Means for achieving the above object will be described below with reference to FIGS. 1 to 4 showing an embodiment. That is, according to the present invention, the cylinder head (2) is arranged above the cylinder block (1), and the combustion chamber (6) is provided above the cylinder chamber (4) formed in the cylinder block (1). Intake port (7) and exhaust port formed in 2)
In the combustion chamber of the overhead valve engine in which (8) and (8) are opened facing the combustion chamber (6), a spacer (22) is arranged between the cylinder block (1) and the cylinder head (2), The combustion chamber (6) is located at a portion of the spacer (22) facing the cylinder chamber (4).
And a partition wall (23) is formed between the intake port (7) and the exhaust port (8) in the combustion chamber (6) of the spacer (22).

[0011]

Since the exhaust port side is closed by the partition wall at the opening peripheral edge of the intake port, the intake air flows in from the side opposite to the exhaust port and is guided into the lower cylinder chamber, and the gas in the cylinder chamber is the peripheral edge of the exhaust port opening. Of these, the air is mainly discharged from the side opposite to the intake port.

Moreover, since the partition wall is formed in the combustion chamber of the spacer, the range along the intake port and the exhaust port of the partition wall can be easily changed by replacing the spacer without modifying the cylinder head. it can.

Further, a heat point is apt to be generated in the partition wall which closes a part of the peripheral edge of the opening of the intake port and the exhaust port. However, when the cooling liquid passage is formed in the partition wall, the cooling liquid passage cools the partition wall. Therefore, the generation of heat points is suppressed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a vertical sectional front view of the periphery of a combustion chamber of an overhead valve two-cycle gas engine, FIG. 2 is a vertical sectional side view of the periphery of a cylinder head, and FIG. It is a partially broken plan view.

As shown in FIGS. 1 and 2, the overhead valve type two-cycle gas engine (E) includes a cylinder block (1).
Cylinder head (2) and head cover (3) are placed in this order above the cylinder to form a cylinder chamber in the cylinder block (1).
A piston (5) is vertically movable in (4), and a combustion chamber (6) is provided above the cylinder chamber (4).

An intake port (7) and an exhaust port (8) are formed in the cylinder head (2), and both ports (7.8) are opened so as to face the combustion chamber (6). The intake valve (10) and the exhaust valve (11) are attached to the respective valves, and the intake / exhaust valves (10, 11) are opened / closed by the valve mechanism (12).
Reference numeral (13) indicates a cylinder liner.

As shown in FIG. 2, a sub-chamber (14) is recessed in a dome shape at one end of the lower surface of the cylinder head (2) so as to communicate with the inside of the cylinder chamber (4). A spark plug (15) is screwed onto the inner wall of the sub chamber (14), a linear fuel injection path (16) is formed inside the position where the spark plug (15) is screwed, and a fuel injection nozzle is provided at the upper end. (17) is installed. The injection port (18) of the fuel injection nozzle (17) faces the sub chamber (14) and the combustion chamber (6) above the cylinder chamber (4) through the fuel injection passage (16).

A head jacket (19) is formed in the cylinder head (2) around the sub chamber (14) and the intake / exhaust ports (7.8), and a water jacket formed in the cylinder block (1). It communicates with (20) through a water hole (21).

Cylinder block (1) and cylinder head
An aluminum spacer (22) is arranged between the spacer (22) and (2), and a combustion chamber (6) is transparently provided at a portion of the spacer (22) facing the cylinder chamber (4). The thickness of the spacer (22) is set to be approximately equal to the valve lift of the intake / exhaust valve (10/11). The spacers (22) are not limited to those made of metal such as aluminum or iron, but may be made of a material such as ceramics, but if they are made of the same material as the cylinder block, they will experience thermal expansion between the cylinder block and the cylinder block. It has excellent durability because there is little difference between the two and strain is less likely to occur.

In the combustion chamber (6) of the spacer (22), as shown in FIGS. 1 and 3, an intake port (7) and an exhaust port (7) are provided.
A partition wall (23) is formed between the partition wall and (8), and a cooling liquid passage (24) is formed in the partition wall (23) to communicate with the water hole (21). Reference numeral (25) indicates a bolt insertion hole, and reference numeral (26) indicates a push rod insertion hole.

The function of the combustion chamber of the overhead valve type engine of the first embodiment will be described. Intake valve by actuation of valve mechanism (12)
When pushing down (10), the intake port (7) opens. However, since the thickness of the spacer (22) is set to be approximately equal to the valve lift of the intake valve (10), a certain range (on the exhaust port (8) side of the opening peripheral edge of the intake port (7) ( R) is a partition
Blocked by (23). Therefore, intake air is exhaust port
It flows into the cylinder chamber (4) from the side opposite to (8) and is guided downward. Further, the exhaust port (8) is also closed on the intake port (7) side of the opening peripheral edge by the partition wall (23),
The exhaust gas after combustion is mainly discharged from the side opposite to the intake port (7). As a result, the swirling flow in the cylinder axis (L) direction is strengthened, and the scavenging efficiency is improved.

In this case, the partition wall (23) is close to the intake valve (10) and the exhaust valve (11), but the water jacket (20) is placed in the cooling liquid passage (24) formed in the partition wall (23). Since the cooling water is circulated to effectively cool the partition wall (23), it is possible to suppress the occurrence of heat points and reliably prevent premature ignition.

Further, the spacer (22) is replaced with another spacer having a different range (R) along the intake port (7) and the exhaust port (8) of the partition wall (23), so that the engine specifications for high speed can be improved. It can be divided into an engine and a low speed engine.

In the first embodiment, the combustion chamber of the vertical engine in which the cylinder axis (L) is vertical has been described, but the present invention is an inclined engine in which the cylinder axis is inclined, or the cylinder axis is in the horizontal direction. It can also be applied to the combustion chamber of a horizontal engine located at. Further, the present invention is not limited to the two-cycle gas engine, and can be applied to any combustion chamber as long as it is an overhead valve type engine, and can be applied to a combustion chamber of a diesel engine or a gasoline engine as well as a four-cycle engine.

Further, in the first embodiment, the cylinder head
Although the combustion chamber of the engine in which the sub chamber (14) is formed in (2) has been described, the present invention can be applied to the combustion chamber of an engine having no sub chamber. That is, FIG. 4 shows Example 2 and is a plan view of a spacer when applied to a combustion chamber of a premixed gasoline engine.

In the second embodiment, the combustion chamber of the spacer (22) is
The partition wall (23) formed in (6) is provided with an ignition plug insertion hole (27), and cooling liquid passages (24) are formed on both sides of the ignition plug insertion hole (27). 24 ・ 24) is connected to one water hole (21) at one end, and intake / exhaust ports
Both cooling liquid passages (24, 24) are joined between (7, 8), and the other end of the joined cooling liquid passages (24) is communicated with the other water hole (21).

[0027]

Since the present invention is constructed and operates as described above, it has the following effects.

(B) Since the partition wall is formed between the intake port and the exhaust port, it is possible to prevent the blow-through phenomenon and reliably guide the intake air into the lower cylinder chamber. Moreover, since the gas in the cylinder chamber is discharged from the side of the opening peripheral edge of the exhaust port opposite to the intake port, the swirling flow in the cylinder axial direction can be strengthened, and the dispersion of the air-fuel mixture can be improved and combustion performance can be improved. When applied to a 2-cycle engine, the scavenging efficiency can be improved.

(B) Since the partition wall is formed in the combustion chamber of the spacer, there is no need to process the expensive cylinder head itself, and the cost can be reduced. In addition, the spacer can be selected as an intake port or an exhaust port of the partition wall. It is possible to easily create a high-speed engine and a low-speed engine separately by changing the range along the line.

(C) When the cooling liquid passage is formed in the partition wall, the cooling liquid passage cools the partition wall, so that it is possible to suppress the occurrence of heat points and reliably prevent premature ignition.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of the vicinity of a combustion chamber of an overhead valve two-cycle gas engine, showing a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional side surface around a cylinder head according to the first embodiment.

FIG. 3 is a partially cutaway plan view of the spacer according to the first exemplary embodiment.

FIG. 4 is a plan view of a spacer according to a second exemplary embodiment.

FIG. 5 is a vertical cross-sectional side view of an overhead valve type two-cycle engine showing a conventional technique.

[Explanation of symbols]

 1 ... Cylinder block, 2 ... Cylinder head, 4 ... Cylinder chamber, 6 ... Combustion chamber, 7 ... Intake port, 8 ... Exhaust port, 22 ... Spacer, 23 ... Partition wall, 24 ... Coolant passage.

Claims (2)

[Claims] 1. A cylinder head (2) is arranged above a cylinder block (1), and a combustion chamber (6) is provided above a cylinder chamber (4) formed in the cylinder block (1). In the combustion chamber of the overhead valve engine in which the intake port (7) and the exhaust port (8) formed in () are opened to face the combustion chamber (6), the cylinder block (1) and the cylinder head (2) Place the spacer (22) between the cylinder chamber of this spacer (22).
A combustion chamber (6) is provided in a region facing (4), and a partition wall (23) is provided between the intake port (7) and the exhaust port (8) in the combustion chamber (6) of the spacer (22). A combustion chamber of an overhead valve engine characterized by being formed. 2. The combustion chamber for an overhead valve engine according to claim 1, wherein a cooling liquid passage (24) is formed in the partition wall (23).