JPH0791313A - Cylinder head of flat head combustion chamber type two cycle engine - Google Patents

Abstract

PURPOSE:To provide the cylinder head of a flat head combustion chamber type two cycle engine, in which the improvement of scavenging efficiency can be compatible with the enlargement of a compression ratio in a combustion chamber. CONSTITUTION:An intake port 2, an exhaust port 3, and a sub-combustion chamber 4 are formed in a cylinder head of a flat head combustion chamber type overhead valve engine, and an air intake outlet of the intake port 2 and an exhaust inlet 31 of the exhaust port 3 are opened in the undersurface 1A of the cylinder head 1 facing a main combustion chamber 10 through a valve-spaced part 5. Steps are provided on the undersurface 1A of the cylinder head to open-form an intake circulating frontage 25 and an exhaust circulating frontage 35. On the inner end faces of the respective circulating frontages 25, 35, an intake valve seat-mouthpiece 22 and an exhaust-valve seat-mouthpiece 32 are provided flush with each other. The effective cross-sectional area of each of the circulating frontages 25, 35 is formed to be narrower on, the side of the valve-spaced part 5, and the effective cross-sectional area of each of the respective circulating frontages 25, 35 is formed to be wider away from the valve- spaced part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head improved from a flat-head type combustion chamber type overhead valve engine for a two-cycle engine, and more particularly to a cylinder head capable of increasing the compression ratio of the combustion chamber to improve combustion performance. It is provided.

[0002]

2. Description of the Related Art In recent years, a two-cycle engine has been attracting attention as a fuel-efficient, low-pollution, small-sized, and noise-reduction type engine in the future, reflecting an increase in environmental awareness. However, in the flat-head type combustion chamber type overhead valve engine as shown in FIG. 4, a two-cycle engine has not existed in the past. In the cylinder head 1 of this flat head type combustion chamber type overhead valve engine, when the intake valve 12 and the exhaust valve 13 are simultaneously opened,
Most of the intake air passes through the gap near the intervalve portion 5, and the intake air inlet 21
Since the intake air passes through from the exhaust outlet 31 to the exhaust outlet 31 and is exhausted from the exhaust inlet 31, the scavenging efficiency is remarkably reduced, so that it was not used as a cylinder head of a two-cycle engine. In FIG. 4, reference numeral 2 is an intake port 2, 3 is an exhaust port, 5 is an intervalve portion 5, 22 is an intake valve washer, and 32 is an exhaust valve washer.

On the other hand, a hemispherical combustion chamber type overhead valve engine has two
As a cylinder head improved for a cycle engine, the one shown in FIG. 6 <Publication “Motor fan” 1989.7 page 119> is conventionally known. In addition,
The cylinder head shown in FIG. 5 is the one before improvement. In this cylinder head, when the intake valve 112 and the exhaust valve 113 are opened simultaneously, half of the intake air A passes through the gap of the intervalve portion 105.
That is, the intake air A passes directly from the intake inlet 121 to the exhaust outlet 131 and is discharged from the exhaust inlet 131, so that the scavenging efficiency is significantly reduced. Therefore, in order to eliminate the above-mentioned difficulty, in the cylinder head shown in FIG.
5a is provided so that the intake air A flows from the intake air inlet 121 to the exhaust air outlet 13
It is configured to prevent passing through to 1. Reference numeral 114 in FIGS. 5 and 6 is a piston.

[0004]

Although the cylinder head of FIG. 6 further promotes the scavenging efficiency, it is premised on a hemispherical combustion chamber type two-cycle engine, and therefore, for example, a flat head type as shown in FIG. It cannot be directly applied to a combustion chamber type cylinder head. Further, the compression ratio cannot be sufficiently increased in the hemispherical combustion chamber. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a cylinder head of a flat-head combustion chamber type two-cycle engine that can improve both scavenging efficiency and increase the compression ratio of the combustion chamber. It is an issue.

[0005]

In order to solve the above-mentioned problems, the means adopted by the invention as defined in claim 1 is a cylinder head 1 of a flat-head type combustion chamber type overhead valve engine E in which an intake port 2 and an exhaust port are provided. 3 and an auxiliary combustion chamber 4 are formed, and an intake outlet 21 of the intake port 2 and an exhaust inlet 31 of the exhaust port 3 are opened through the intervalve portion 5 on the lower surface 1A of the cylinder head 1 facing the main combustion chamber 10. , An intake valve washer 22 is provided at the intake outlet 21, and an exhaust valve washer 32 is provided at the exhaust inlet 31.
A flat head configured such that the intake outlet 21 is opened and closed by the intake valve 12 and the exhaust inlet 31 is opened and closed by the exhaust valve 13, and the valve shafts 12a and 13a of the intake valve 12 and the exhaust valve 13 are mounted in parallel. In a cylinder head of a combustion chamber type overhead valve engine, a step is formed on the lower surface 1A of the cylinder head to form an intake flow passage 25 and an exhaust flow front 35, respectively. The intake valve washer 22 and the exhaust valve washer 32 are provided so as to be flush with each other.
The gist is that the effective cross-sectional area of each of the flow openings 25 and 35 is formed to be narrower as the distance from the intervalve portion 5 increases.

In the cylinder head of the flat head type combustion chamber type overhead valve engine having the combustion chamber 4, the means adopted by the invention according to claim 2 is the intake valve washer 22.
The gist of the present invention is that a baffle plate member 26 that narrows the intake outlet 21 is provided near the intervalve portion 5.

In the cylinder head of the flat head type combustion chamber type overhead valve engine having the combustion chamber 4, the means adopted by the invention according to claim 3 is closer to the intervalve portion 5,
The gist of the invention is that a thick wall portion of the cylinder head located above the exhaust valve washer 32 is integrally formed with a baffle portion 36 that narrows the exhaust outlet 31.

Further, the means adopted by the invention described in claim 4 is the main part of the exhaust valve 13 in the cylinder head of the flat head type combustion chamber type two-cycle engine described in any one of claims 1 to 3. Top surface 13b facing the combustion chamber 10
Is formed into a smooth convex surface.

[0009]

The operation and effect of the present invention is as follows. By appropriately setting the size of the auxiliary combustion chamber 4 of the cylinder head 1, the compression ratio of the entire combustion chamber can be set large. Further, the intake air passage 25 and the exhaust air passage 35, which are formed by forming a step on the lower surface 1A of the cylinder head, have a narrow effective cross-sectional area near the intervalve portion 5, and each of the air passage 25 and Since the effective cross-sectional area of 35 is wide, even if the intake valve 12 and the exhaust valve 13 are opened at the same time, the intake air A
The exhaust gas B and the exhaust gas B do not pass through the gap close to the intervalve portion 5, and most of the intake air A and the exhaust gas B pass through the positions of the intake air passage opening 25 and the exhaust air passage opening 35 away from the intervalve area 5, respectively. That is, the intake air A does not pass directly from the intake inlet 21 to the exhaust outlet 31 and is discharged from the exhaust inlet 31. As a result, both the improvement of the scavenging efficiency and the increase of the compression ratio of the combustion chamber can be achieved, and the combustion performance of the two-cycle engine can be improved.

According to the second aspect of the invention, in the cylinder head of the flat-head type combustion chamber type overhead valve engine having the combustion chamber 4, the intake outlet 21 is provided near the intervalve portion 5 of the intake valve washer 22. Since the baffle member 26 for narrowing is provided, even if the intake valve 12 and the exhaust valve 13 are opened at the same time, the intake air A does not pass through the gap near the inter-valve portion 5 of the intake air inlet 21, and most of the intake air A is taken in by the intake air inlet 21. Pass the position away from the intervalve portion 5 of. That is, the intake air A does not pass directly from the intake inlet 21 to the exhaust outlet 31 and is discharged from the exhaust inlet 31. As a result, both the improvement of the scavenging efficiency and the increase of the compression ratio of the combustion chamber can be achieved, and the combustion performance of the two-cycle engine can be improved.

According to the third aspect of the present invention, in the cylinder head of the flat head type combustion chamber type overhead valve engine having the combustion chamber 4, the exhaust valve washer 3 is provided near the intervalve portion 5.
Since the baffle portion 36 that narrows the exhaust outlet 31 is integrally formed in the thick portion of the cylinder head located on the upper side of 2,
Even if the intake valve 12 and the exhaust valve 13 are opened at the same time, the exhaust gas does not pass through the gap close to the intervalve portion 5 of the exhaust gas inlet 31, and most of the exhaust gas passes through the exhaust gas inlet 31 at a position away from the intervalve portion 5.
That is, the intake air A does not pass directly from the intake inlet 21 to the exhaust outlet 31 and is discharged from the exhaust inlet 31. As a result, both the improvement of the scavenging efficiency and the increase of the compression ratio of the combustion chamber can be achieved, and the combustion performance of the two-cycle engine can be improved.

According to a fourth aspect of the present invention, in the cylinder head of the flat-head type combustion chamber type two-cycle engine according to any one of the first to third aspects, the exhaust valve 13 is provided.
Since the top surface 13b facing the main combustion chamber 10 is formed as a smooth convex surface, the smooth outflow of exhaust gas is promoted. As a result, the scavenging efficiency can be further improved and the combustion performance of the two-cycle engine can be improved.

[0013]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. FIG. 1A is a longitudinal sectional view of a cylinder head of a flat-head type combustion chamber type two-cycle engine, and FIG. 1B is a lower surface of a cylinder head lower surface 1A of FIG. FIG. 2 is a vertical cross-sectional view of a main part of a flat-head type combustion chamber type two-cycle engine to which the present invention is applied.

The flat-head type combustion chamber type two-cycle engine E shown in FIG. 2 is a diesel engine diverted to a water-cooled two-cycle gas engine. As shown in FIGS. 1A and 1B and FIG. 2, the cylinder head according to the present invention has an intake port 2, an exhaust port 3 and a sub-combustion chamber 4 formed in a cylinder head 1 and a main combustion chamber 10 formed therein. Lower surface 1 of cylinder head 1 facing
The intake outlet 21 of the intake port 2 and the exhaust inlet 31 of the exhaust port 3 are opened at A via the intervalve portion 5, and the intake outlet 2
1, an intake valve washer 22 is provided, an exhaust valve washer 32 is provided at the exhaust inlet 31, the intake outlet 21 is opened and closed by the intake valve 12, and the exhaust inlet 31 is opened and closed by the exhaust valve 13. 12 and each valve shaft 12a, 13a of the exhaust valve 13
Are installed in parallel. In FIG. 2, reference numeral 6 is a cylinder block, 4a is a spark plug, 4b is a fuel gas supply device, and the spark plug 4a is provided in the auxiliary combustion chamber 4.
The gas discharge port of the fuel gas supply device 4b is exposed.

The lower surface 1A of the cylinder head 1 is formed with an intake airflow opening 25 and an exhaust airflow opening 35 with steps. The intake valve washer 22 and the exhaust valve washer 3 are respectively provided on the inner end surfaces of the respective circulation fronts 25 and 35.
2 are provided flush with each other, and the intake airflow front 25 and the exhaust airflow front 35 are offset in a direction away from the centers (valve axis) of the intake air inlet 21 and the exhaust air outlet 31.
The effective cross-sectional area of each of the flow openings 25 and 35 is narrowed near the valve portion 5, and the effective cross-sectional area of each of the flow openings 25 and 35 is increased as the distance from the valve portion 5 increases.

That is, even if the intake valve 12 and the exhaust valve 13 are opened at the same time, the intake air A and the exhaust air B do not pass through the gap close to the intervalve portion 5, and most of the intake air A and the exhaust air B are the intake airflow front 25 and the exhaust air, respectively. It passes through a position of the flow front 35 away from the valve portion 5. That is, the intake air does not pass directly from the intake inlet 21 to the exhaust outlet 31 and is discharged from the exhaust inlet 31. As a result, both the improvement of the scavenging efficiency and the increase of the compression ratio of the combustion chamber can be achieved, and the combustion performance of the two-cycle engine can be improved.

A baffle plate member 26 is attached to the intake valve washer 22 near the valve portion 5. The baffle plate member 26 is for narrowing the gap of the intake inlet 21 close to the valve portion 5, and most of the intake air A passes through the position away from the valve inlet 5 of the intake inlet 21. As a result, the intake inlet 2
Inlet A passes directly from 1 to exhaust outlet 31 and exhaust inlet 31
It will not be discharged more.

Further, in the thick portion of the cylinder head located near the intervalve portion 5 and above the exhaust valve washer 32,
The baffle portion 36 is integrally formed. This disturbing meat part 3
Reference numeral 6 is for narrowing the exhaust outlet 31, and most of the exhaust B passes through the position of the intake inlet 21 away from the intervalve portion 5. This prevents the intake air A from passing through the intake air inlet 21 to the exhaust air outlet 31 and being discharged from the exhaust air inlet 31. A member similar to the baffle plate member 26 attached to the intake valve washer 22 may be attached to the exhaust valve washer 32, but the exhaust valve washer 32 causes thermal strain due to exhaust heat. Therefore, it is not appropriate to attach a baffle plate member to this. On the other hand, when the baffle portion 36 is formed integrally with the thick portion of the cylinder head, the cylinder head 1 itself is cooled by the head jacket 1b, so that there is no adverse effect of thermal distortion.

The top surface 13b of the exhaust valve 13 which faces the main combustion chamber 10 is formed into a smooth convex surface. This is to promote smooth outflow of exhaust gas. As shown in FIG. 2, an intake air inlet 7 is provided on the side surface of the cylinder block 6, and the intake port 2 and the intake air inlet 7 are connected to an intake passage 8 including a supercharger 9 to introduce the intake air. Mouth 7 is piston 1
4 is moved to the bottom dead center position L to open and introduce the intake air A into the cylinder 11. As a result, the scavenging efficiency is further improved, and the combustion performance of the two-cycle engine is improved.

The operation of the engine according to the above embodiment will be described below. FIG. 3 is a time chart in a two-cycle engine, where U is the top dead center position of crankshaft rotation, and L is the bottom dead center position. In this figure, the combustion explosion process is shown between F and A, and the exhaust valve 13 opens at the end point A of this combustion explosion process, and the intake valve (not shown) opens continuously at the point B to shift to the scavenging process. . In this scavenging step, the exhaust gas B is forcibly discharged from the exhaust port 3 by the intake air A supercharged by the supercharger 9. When the piston 14 further reaches the bottom dead center position L, the intake air inlet 7 is opened, and the similarly supercharged intake air A is introduced from the intake air inlet 7 to promote scavenging. Next, the exhaust valve 13 is closed at point C, the intake valve 12 is subsequently closed at point D, and thereafter the compression process is started. During this compression process (somewhere appropriate)
At point E, the fuel gas is injected into the auxiliary combustion chamber 4. This air-fuel mixture is ignited by the spark plug 4a at point F immediately before the end of the compression process, and moves to the combustion and explosion process.

The present invention is not limited to the gas engine shown in the above embodiment, but can be applied to a gasoline engine, an engine having no intake inlet 7, and a premix engine other than the cylinder injection type. . Further, in the above embodiment,
For the sake of convenience of description, the cylinder head including the intake air passage 25, the exhaust air passage 35, the baffle plate member 26, and the baffle portion 36 has been described, but as described in claims 1 to 3, they may be provided independently of each other. good.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 (A) is a longitudinal cross-sectional view of a main part of a cylinder head for a flat-head type combustion chamber type two-cycle engine, and FIG. 1 (B) is a cylinder of FIG. 1 (A). It is a bottom view of the lower surface of the head as seen from below.

FIG. 2 is a longitudinal sectional view of a main part of a flat-head type combustion chamber type two-cycle engine according to an embodiment of the present invention.

FIG. 3 is a time chart in the two-cycle engine according to the embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of a main part of a cylinder head of a flat-head combustion chamber type overhead valve engine.

FIG. 5 is a longitudinal cross-sectional view of a main part of a cylinder head of a hemispherical combustion chamber type overhead valve engine according to a conventional example.

FIG. 6 is a vertical cross-sectional view of a main part of a cylinder head for a hemispherical combustion chamber type two-cycle engine according to a conventional example.

[Explanation of symbols]

E ... Engine, 1 ... Cylinder head, 1A ...
Lower surface of cylinder head, 2 ... intake port, 3 ... exhaust port, 4 ... auxiliary combustion chamber, 10 ... main combustion chamber,
12 ... Intake valve, 12a ... Intake valve shaft, 13 ...
Exhaust valve, 13a ... Exhaust valve shaft, 13b ... Exhaust valve top surface, 21 ... Intake inlet, 22 ... Intake valve washer, 25 ... Intake flow front, 26 ... Baffle plate member,
31 ... Exhaust outlet, 32 ... Exhaust valve washer, 35 ...
Exhaust flow frontage, 36 ... Baffle meat part.

Claims (4)

[Claims] 1. A flat head combustion chamber type overhead valve engine (E) having a cylinder head (1) having an intake port (2), an exhaust port (3) and an auxiliary combustion chamber (4) formed therein, 10) the lower surface (1) of the cylinder head (1) facing
In A), the intake port (21) of the intake port (2) and the exhaust port
The exhaust inlet (31) of (3) is opened via the intervalve portion (5), the intake valve washer (22) is provided at the intake outlet (21), and the exhaust valve washer (22) is provided at the exhaust inlet (31). 32), and the intake outlet (21) is the intake valve (12) and the exhaust inlet (31)
Are configured to be opened and closed by the exhaust valve (13) respectively, and each valve shaft (12a) of the intake valve (12) and the exhaust valve (13)
In a cylinder head of a flat-head type combustion chamber type overhead valve engine configured by mounting (13a) in parallel, a step is formed on the lower surface (1A) of the cylinder head to form an intake flow front (25) and an exhaust flow front (35). Are formed respectively, and the intake valve washer (22) and the exhaust valve washer (32) are provided flush with the back end surfaces of the flow fronts (25) (35),
The effective cross-sectional area of each flow front (25) (35) is narrowed near the valve interval (5), and the effective cross-sectional area of each flow front (25) (35) is widened as the distance from the intervalve (5) increases. A cylinder head of a flat-head type combustion chamber type two-cycle engine characterized by the above. 2. A flat head type combustion chamber type overhead valve engine (E) having a cylinder head (1) formed with an intake port (2), an exhaust port (3) and a sub combustion chamber (4). 10) the lower surface (1) of the cylinder head (1) facing
In A), the intake port (21) of the intake port (2) and the exhaust port
The exhaust inlet (31) of (3) is opened via the intervalve portion (5), the intake valve washer (22) is provided at the intake outlet (21), and the exhaust valve washer (22) is provided at the exhaust inlet (31). 32), and the intake outlet (21) is the intake valve (12) and the exhaust inlet (31)
Are configured to be opened and closed by the exhaust valve (13) respectively, and each valve shaft (12a) of the intake valve (12) and the exhaust valve (13)
In a cylinder head of a flat-head type combustion chamber type overhead valve engine configured by mounting (13a) in parallel, the intake outlet (21) is narrowed toward the intervalve portion (5) of the intake valve washer (22). A cylinder head for a flat-head type combustion chamber type two-cycle engine, which is additionally provided with a baffle plate member (26). 3. An intake port (2), an exhaust port (3) and an auxiliary combustion chamber (4) are formed in a cylinder head (1) of a flat head type combustion chamber type overhead valve engine (E), and a main combustion chamber ( 10) the lower surface (1) of the cylinder head (1) facing
In A), the intake port (21) of the intake port (2) and the exhaust port
The exhaust inlet (31) of (3) is opened via the intervalve portion (5), the intake valve washer (22) is provided at the intake outlet (21), and the exhaust valve washer (22) is provided at the exhaust inlet (31). 32), and the intake outlet (21) is the intake valve (12) and the exhaust inlet (31)
Are configured to be opened and closed by the exhaust valve (13) respectively, and each valve shaft (12a) of the intake valve (12) and the exhaust valve (13)
In a cylinder head of a flat head type combustion chamber type overhead valve engine configured by mounting (13a) in parallel, a cylinder head meat located above the exhaust valve washer (32) near the intervalve portion (5). A cylinder head of a flat-head type combustion chamber type two-cycle engine, characterized in that a baffle portion (36) for narrowing an exhaust outlet (31) is integrally formed in a thick portion. 4. The top surface (13b) of the exhaust valve (13) facing the main combustion chamber (10) is formed into a smooth convex surface, according to any one of claims 1 to 3. Cylinder head of a flat head type combustion chamber type two cycle engine.