JP2018021540A - Multi-valve type combustion chamber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber of a four-cycle engine where combustion at an air-fuel mixture portion facing an exhaust valve is hard to cause knocking.SOLUTION: A multi-valve type combustion chamber is configured such that a squish area space 8, a first exhaust valve 9, a first ignition plug 4, a first intake valve 11, a second intake valve 12, a second ignition plug 5 and a second exhaust valve 10 are installed in this order in a peripheral direction along an inner periphery of a cylinder. Two bottom surfaces of the two exhaust valves and a virtual cross section 15 intersect with each other. With temperature reduction action due to lowering of a piston during a combustion stroke, temperature rise of part of air-fuel mixture moving to the squish area space 8 is restricted.SELECTED DRAWING: Figure 3

Description

The present invention relates to an improvement in knocking resistance of a spark ignition type 4-cycle engine.

Many of the combustion chambers of a spark ignition type 4-cycle engine have two exhaust valves and two intake valves. Hereinafter, a combustion chamber having two exhaust valves and two intake valves is referred to as a four-valve combustion chamber. The engine of Patent Document 1 is also the four-valve combustion chamber.
In the four-valve combustion chamber, two exhaust valves are installed adjacent to the inner periphery of the cylinder. The exhaust valve becomes hot as the load increases. The combustion rate of the air-fuel mixture that has been heated to the exhaust valve increases. For this reason, at the time of overload, there is a risk of causing knocking due to rapid combustion of a large amount of the air-fuel mixture in contact with the heated exhaust valve. For this reason, the compression ratio and knock resistance of the four-valve combustion chamber are limited.
The present author examined the diameter of the bottom face of the exhaust valve and the bottom face of the intake valve when the diameter of the cylinder of the four-valve combustion chamber was 86 mm.
The diameter of the bottom face of many exhaust valves was set from 27 mm to 30 mm. The diameter of the bottom face of many intake valves was set from 32 mm to 34 mm. The diameter of the bottom surface of many intake valves was set to about 115% of the diameter of the bottom surface of the exhaust valve.
Therefore, the cylinder central axis is located at a point slightly deviated to the intake valve side from the exhaust valve.
In Patent Document 1 shown in FIG. 9, one spark plug is installed near the center of the combustion chamber, the intake valve is located closer to the cylinder center axis than the exhaust valve, and the two exhaust valves are located on the inner periphery of the cylinder. It is installed adjacent to.
In Patent Document 4 shown in FIG. 12, one spark plug is installed near the center of the combustion chamber, and two exhaust valves are installed adjacent to the inner periphery of the cylinder.

In Patent Document 2 shown in FIG. 10 and Patent Document 3 shown in FIG. 11, two spark plugs are installed adjacent to the inner periphery of the cylinder, an exhaust valve, a spark plug, and an intake valve are installed in series, and the center of the cylinder The shaft is located away from the two exhaust valves.
In Patent Document 5 shown in FIG. 13, one spark plug is installed near the center of the combustion chamber, and three exhaust valves are installed away from the inner periphery of the cylinder.
In-cylinder injection internal combustion engine JP2009-41397A (P2009-41397A) Combustion chamber structure of multi-ignition engine JP-A-2000-8943 (P2000-8943A) In-cylinder injection engine JP 2008-138605 (P2008-138605A) 4-cycle engine Japanese Patent Application No. 2015-255509 (P2015-255509A) Japanese Patent No. 5909307 (JP, P5909307)

An object of the present invention is to provide a four-cycle engine in which combustion of the air-fuel mixture facing the exhaust valve hardly causes knocking.

The multi-valve combustion chamber of this application is the combustion chamber of a spark ignition piston type 4-cycle engine.
This application has three aspects.
One combustion chamber at the time of compression top dead center according to the first aspect of the present application has the following characteristics.
The squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second spark plug, and the second exhaust valve are arranged in the order described in the circumferential direction along the upper end of the inner periphery of the cylinder. It is installed on the cylinder head side wall of the combustion chamber.
The center of the first bottom surface, which is the bottom surface of the first exhaust valve, is located between the first spark plug and the squish area space. The center of the second bottom surface, which is the bottom surface of the second exhaust valve, is located between the second spark plug and the squish area space.
The central axis of the cylinder is located on the virtual cross section. The virtual cross section virtually bisects the combustion chamber.
Two of the first bottom surface and the second bottom surface virtually intersect with the virtual cross section.

The combustion chambers of the second and third aspects of the present application differ from the first aspect in the number of intake valves, and the other elements are the same as in the first aspect. The difference from the first aspect will be described below.
In the combustion chamber of the second aspect, the squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second intake valve, the second spark plug, and the second exhaust valve are Installed on the cylinder head side wall surface of the combustion chamber in the order described in the circumferential direction along the upper end of the inner periphery of the cylinder.
In the combustion chamber of the third aspect, the squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second intake valve, the third intake valve, the second spark plug, and the first Two exhaust valves are installed on the cylinder head side wall surface of the combustion chamber in the order described in the circumferential direction along the upper end of the inner periphery of the cylinder.

Knock resistance is improved by the following first and second actions.
The first action will be described.
The center of the bottom surface of the first exhaust valve is located between the first ignition bragg and the squish area space. That is, the squish area space is located in a straight extension extending from the first spark plug to the center of the bottom surface of the first exhaust valve.
The center of the bottom surface of the second exhaust valve is located between the second ignition bragg and the squish area space. That is, the squish area space is located in a straight extension extending from the second spark plug to the center of the bottom surface of the second exhaust valve.
For this reason, when the flame propagates from the first ignition bragg toward the bottom surface of the first exhaust valve and when the flame propagates from the second ignition bragg toward the bottom surface of the second exhaust valve, A part of the unburned air-fuel mixture facing the bottom surfaces of the two exhaust valves is moved to the squish area space and compressed in the squish area space.
Then, the air-fuel mixture portion moved to the squish area space is cooled by touching the wall surface having a temperature lower than that of the exhaust valve.
Also, the lowering amount of the piston during the combustion stroke is a value close to the top dead center interval in the cylinder central axis direction of the squish area space. For this reason, the volume of the squish area space increases rapidly due to the lowering of the piston during the combustion stroke.
As a result, the temperature increase due to the compression of the air-fuel mixture portion moved to the squish area space is limited by the large temperature lowering effect due to the increase in the volume of the squish area space.
Therefore, a rapid increase in pressure is unlikely to occur during the combustion stroke due to the combustion of the air-fuel mixture in the squish area space.

The second function will be described.
Part of the squish flow that flows away from the squish area space at the end of the compression stroke moves to a region facing the bottom surfaces of the two exhaust valves.
The temperature of the air-fuel mixture in the squish area space is lower than the temperature of the air-fuel mixture portion facing the bottom surface of the exhaust valve.
Then, the temperature at the start of combustion of the air-fuel mixture facing the bottom surface of the exhaust valve decreases. Then, the rapid increase of the combustion pressure value is limited, and the knocking resistance is improved.

The ignition brags of Patent Document 1 and Patent Document 4 are located slightly on the exhaust valve side from the cylinder center axis. In Patent Literature 1 and Patent Literature 4, the outer periphery of the bottom surface of the exhaust valve is located away from the virtual cross section shown in the present application. In this case, the center axis of the crankshaft is located in the virtual cross section.
The outer circumferences of the bottom surfaces of the two exhaust valves are adjacent to the inner circumference of the cylinder.
Therefore, there is no wide space between the straight reaching point from the spark plug through the center of the bottom surface of the exhaust valve to the inner periphery of the cylinder and the outer periphery of the bottom surface of the exhaust valve. For this reason, a large squish area area similar to the present application cannot be formed.
Therefore, in these engines, when the flame propagates from the ignition plug toward the bottom surface of the exhaust valve, most of the air-fuel mixture facing the bottom surface of the exhaust valve is caused by the expansion of the burned gas to face the bottom surface of the exhaust valve. Compressed in the area facing the bottom surface of the exhaust valve without moving from the area.
The mixture portion compressed in the region facing the bottom surface of the exhaust valve is heated by touching the exhaust valve.
Therefore, the engine of patent document 1 and patent document 4 cannot perform the 1st and 2nd effect | action of this application.
Patent Document 2 and Patent Document 3 have two spark plugs installed adjacent to the inner periphery of the cylinder. The other ignition brags are located on the exhaust valve side of the cylinder central axis. For this reason, the outer periphery of the bottom surface of the exhaust valve is located away from the virtual cross section shown in the present application. In this case, the center axis of the crankshaft is located in the virtual cross section.
Therefore, in Patent Document 2 and Patent Document 3, a large squish area area similar to that of the present application is formed in the vicinity of a straight line reaching from the spark plug located near the center to the inner periphery of the cylinder through the center of the bottom surface of the exhaust valve. Can not. In addition, most of the air-fuel mixture facing the bottom surface of the exhaust valve is not moved from the region facing the bottom surface of the exhaust valve due to the expansion of the burned gas near the ignition brag located near the center. Therefore, in patent document 2 and patent document 3, the effect by the 1st and 2nd effect | action of this application is limited small.
Patent Document 5 has three exhaust valves and three squish area spaces, one spark plug near the center of the combustion chamber, and the number of exhaust valves and squish area spaces is different.
In addition, the arrangement of the exhaust ports in Patent Document 5 is more complicated than in this application. For these reasons, the cost of the cylinder head of Patent Document 4 is higher than that of the present application.

The effect by this invention is demonstrated.
By improving the knocking resistance, the present invention can achieve a high compression ratio.
The thermal efficiency is improved by increasing the compression ratio.

The first embodiment will be described with reference to FIGS.
The engine of the first embodiment is a spark ignition type 4-cycle engine.
Two spark plugs, one intake valve, and two exhaust valves are installed in one combustion chamber of the engine.
In one combustion chamber at the time of compression top dead center, a squish area space 8, a first exhaust valve 9, a first spark plug 4, a first intake valve 11, a second spark plug 5, and a second exhaust valve 10 are provided in a cylinder. 1 are installed on the wall surface of the combustion chamber 3 on the cylinder head side in the order described in the circumferential direction along the upper end of the inner periphery of the combustion chamber 3.

The first embodiment has the following first feature.
In FIG. 1, the squish area space 8 is indicated by a collection of points.
The center of the first bottom surface, which is the bottom surface of the first exhaust valve 9, is located between the first spark plug 4 and the squish area space 8. The center of the second bottom surface, which is the bottom surface of the exhaust valve 10, is located.
That is, the squish area space 8 is located in a straight line extending from the first spark plug 4 to the center of the bottom surface of the first exhaust valve 9, and a straight line connecting the second spark plug 5 to the center of the bottom surface of the second exhaust valve 10. The squish area space 8 is located in the extended portion.
By the first feature, the first action is performed. The first feature is shared by all embodiments.

1st Example has the structure for forming the squish area space 8 larger than the conventional 4-valve combustion chamber. This configuration is the second feature.
The central axis of the cylinder 1 is located on the virtual cross section 15. The virtual cross section 15 virtually bisects the combustion chamber.
In FIG. 1, the bottom surface of the first exhaust valve 9, the bottom surface of the second exhaust valve 10, and the virtual cross section 15 are positioned so as to overlap each other. That is, the virtual cross section 15 virtually intersects the two bottom surfaces of the first bottom surface that is the bottom surface of the first exhaust valve 9 and the second bottom surface that is the bottom surface of the second exhaust valve 10.
Then, the bottom surface of the first exhaust valve 9 and the bottom surface of the second exhaust valve 10 are located closer to the central axis of the cylinder 1 than the conventional four-valve combustion chamber. Then, a 1st wall surface spreads and the squish area space 8 larger than the conventional 4-valve combustion chamber can be formed.
The first feature is enhanced by the second feature.
Further, the smaller the distance in the cylinder central axis direction between the two bottom surfaces of the bottom surface of the first exhaust valve 9 and the second exhaust valve 10 and the top surface portion of the piston 2, the more in contact with the bottom surfaces of the two exhaust valves. A large amount of air-fuel mixture flows into the squish area space 8, and the first action is enhanced.
The virtual cross section 15 is limited to the plane on which the central axis of the cylinder 1 is located, but is not limited to the plane on which the central axis of the crankshaft is located.
When the center axis of the crankshaft is located on the virtual cross section 15, the direction of the exhaust port of the first exhaust valve 9 and the direction of the intake port of the first intake valve 11 are opposite. The direction of the exhaust port of the second exhaust valve 10 is opposite to the direction of the intake port of the first intake valve 11.
The diameter of the bottom surface of the first intake valve 11 is set larger than the diameters of the two bottom surfaces of the first exhaust valve 9 and the second exhaust valve 10.

The squish area space 8 will be described.
The squish area space 8 is located adjacent to the bottom surface of the first exhaust valve 9 and the bottom surface of the second exhaust valve 10.
The distance at the top dead center of the squish area in the direction of the center axis of the cylinder is the minimum distance at which the upper surface of the piston 2 and the bottom surface of the exhaust valve do not collide when carbon accumulates on the wall surface of the combustion chamber 3.
An example of the above interval is shown. When the piston stroke is set to less than 90mm, it is a narrow interval of around 1mm. However, when the stroke of the piston is set to 90 mm or more, the interval can be set to about 1.5 mm. The interval is not limited to the above example.
The second spark plug 5 is indicated by a dotted line on the far side in the direction perpendicular to the cross-section indicated by the oblique lines in FIG.
Moreover, the 1st exhaust valve 9, the squish area space 8, and the 1st spark plug 4 exist in the near side in the direction perpendicular | vertical to the cross section of FIG. However, the first exhaust valve 9 and the first spark plug 4 are not shown in FIG.

The second embodiment will be described with reference to FIGS.
In the second embodiment, only differences from the first embodiment will be described.
In the combustion chamber of the second embodiment, two spark plugs, two intake valves, and two exhaust valves are installed.
The squish area space 8, the first exhaust valve 9, the first spark plug 4, the first intake valve 11, the second intake valve 12, the second spark plug 5, and the second exhaust valve 10 are at the upper end of the inner periphery of the cylinder 1. Along the circumferential direction, the cylinder head side wall surfaces of the combustion chamber 3 are installed in the order described.
The diameter of the bottom surface of the first intake valve 11 and the diameter of the bottom surface of the second intake valve 12 are set to the same value as the diameter of the bottom surface of the first exhaust valve 9 or smaller than the diameter of the bottom surface of the first exhaust valve 9. The Similarly, the diameter of the bottom surface of the first intake valve 11 and the diameter of the bottom surface of the second intake valve 12 are the same value as the diameter of the bottom surface of the second exhaust valve 10 or a value smaller than the diameter of the bottom surface of the second exhaust valve 10. Set to
That is, the diameter of the bottom surface of the intake valve of the second embodiment is set smaller than the diameter of the bottom surface of the intake valve of the conventional four-valve combustion chamber.

A third embodiment will be described with reference to FIG.
In the third embodiment, only differences from the second embodiment will be described.
In the combustion chamber of the third embodiment, two spark plugs, three intake valves, and two exhaust valves are installed.
The squish area 8, the first exhaust valve 9, the first spark plug 4, the first intake valve 11, the second intake valve 12, the third intake valve 13, the second spark plug 5, and the second exhaust valve 10 are connected to the cylinder 1. Are installed on the cylinder head side wall surface of the combustion chamber 3 in the order described in the circumferential direction along the upper end of the inner circumference.
A second intake valve 12 is installed between the first intake valve 11 and the third intake valve 13.
Three diameters of the three bottom surfaces of the first intake valve 11, the second intake valve 12, and the third intake valve 13 are two diameters of the two bottom surfaces of the first exhaust valve 9 and the second exhaust valve 10. Is set to a smaller value.

A fourth embodiment will be described with reference to FIGS. 6, 7 and 8. FIG.
In the first to third embodiments, the sum of the outer circumferences of the bottom surfaces of the intake valves is smaller than that of the conventional four-valve combustion chamber, and the maximum torque is reduced.
In order to improve this problem, the fourth embodiment adds the following configuration to the first to third embodiments.
A fourth intake valve 16 is added between the first exhaust valve 9 and the second exhaust valve 10. A fourth intake valve 16 is added next to the first exhaust valve 9 and the second exhaust valve 10. The fourth intake valve 16 is installed adjacent to the inner periphery of the cylinder 1. The fourth intake valve 16 is installed facing the squish area space 8. That is, the first exhaust valve 9, the fourth intake valve 16, and the second exhaust valve 10 are located in a row.
As a result, the sum of the circumferences of the intake valves is increased and the torque is improved as compared with the first to third embodiments.
Further, the exhaust manifold of the first exhaust valve 9 and the exhaust manifold of the second exhaust valve 10 are not assembled into one, but two exhaust manifolds are installed independently.

A fifth embodiment will be described.
The fifth embodiment adds the following configuration to the second embodiment and the embodiment shown in FIG.
The opening timing of the second intake valve 12 is set before the exhaust top dead center, and the closing timing of the first exhaust valve 9 is set after the exhaust top dead center. The opening period of the second intake valve 12 and the opening period of the first exhaust valve 9 overlap in the vicinity of the exhaust top dead center.
Then, the second exhaust valve 10 is closed by the exhaust top dead center.
The opening timing of the first intake valve 11 is set in the vicinity of the closing timing of the first exhaust valve 9.
Then, the length of the scavenging passage from the second intake valve 12 to the first exhaust valve 9 can be set long, the overlap period can be set long, and the scavenging effect is improved. Improvement of knocking resistance and scavenging effect are compatible.

A sixth embodiment will be described.
In the sixth embodiment, the following configuration is added to the third embodiment and the embodiment shown in FIG.
The opening timing of the second intake valve 12 and the opening timing of the third intake valve 13 are set before the exhaust top dead center, and the closing timing of the first exhaust valve 9 is set after the exhaust top dead center. The valve opening period of the second intake valve 12, the valve opening period of the third intake valve 13, and the valve opening period of the first exhaust valve 9 overlap in the vicinity of the exhaust top dead center.
The closing timing of the second exhaust valve 10 and the opening timing of the first intake valve 11 are set in the same manner as in the fifth embodiment.
Then, the length of the scavenging passage from the second intake valve 12 to the first exhaust valve 9 and the length of the scavenging passage from the third intake valve 13 to the first exhaust valve 9 can be set longer, and the scavenging effect is improved.

The top view of the combustion chamber of 1st Embodiment which looked at the cylinder head lower surface from the piston upper surface. The vertical sectional view of the combustion chamber of 1st Embodiment cut | disconnected by the vertical cross section containing the straight line which connects the center of the bottom face of a 1st intake valve, and a cylinder central axis. The top view of the combustion chamber of 2nd Embodiment which looked at the cylinder head lower surface from the piston upper surface. The vertical sectional view of the combustion chamber of 2nd Embodiment cut | disconnected by the vertical cross section containing the straight line which connects the center of the bottom face of a 2nd exhaust valve, and the center of the bottom face of a 2nd intake valve. The top view of the combustion chamber of 3rd Embodiment which looked at the cylinder head lower surface from the piston upper surface. The top view of the combustion chamber of 4th Embodiment which extended the 4th intake valve to the structure of 1st Embodiment. The top view of the combustion chamber of 4th Embodiment which added the 4th intake valve to the structure of 2nd Embodiment. The top view of the combustion chamber of 4th Embodiment which extended the 4th intake valve to the structure of 3rd Embodiment. FIG. 9 is a diagram corresponding to FIG. The figure equivalent to FIG. 1 (A) of patent document 2. FIG. The figure equivalent to FIG. 4 of patent document 3. FIG. The figure equivalent to FIG. FIG. 1 of Patent Document 5.

DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Piston 3 ... Combustion chamber 4 ... 1st spark plug 5 ... 2nd spark plug 6 ... Virtual cross section 7 which bisects a combustion chamber 7th 4. Intake valve 8 ... Squish area 9 ... First exhaust valve 10 ... Second exhaust valve 11 ... First intake valve 12 ... Second intake valve 13 ... Third intake valve

Claims (5)

In one combustion chamber at the compression top dead center of a spark ignition type 4-cycle engine,
The squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second spark plug, and the second exhaust valve are arranged in the order of the combustion chambers in the order described in the circumferential direction along the upper end of the inner periphery of the cylinder. Installed on the cylinder head side wall,
The center of the first bottom surface, which is the bottom surface of the first exhaust valve, is located between the first spark plug and the squish area space, and the second exhaust valve is located between the second spark plug and the squish area space. The center of the second bottom surface, which is the bottom surface, is located,
A central axis of the cylinder is located on a virtual cross section, and the virtual cross section virtually bisects the combustion chamber;
The multi-valve combustion chamber characterized in that the virtual cross section virtually intersects with the first bottom surface and the second bottom surface. In one combustion chamber at the compression top dead center of a spark ignition type 4-cycle engine,
The squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second intake valve, the second spark plug, and the second exhaust valve are listed in the circumferential direction along the upper end of the inner periphery of the cylinder. Installed on the cylinder head side wall of the combustion chamber,
The center of the first bottom surface, which is the bottom surface of the first exhaust valve, is located between the first spark plug and the squish area space, and the second exhaust valve is located between the second spark plug and the squish area space. The center of the second bottom surface, which is the bottom surface, is located,
A central axis of the cylinder is located on a virtual cross section, and the virtual cross section virtually bisects the combustion chamber;
The multi-valve combustion chamber characterized in that the virtual cross section virtually intersects with the first bottom surface and the second bottom surface. In one combustion chamber at the compression top dead center of a spark ignition type 4-cycle engine,
The squish area space, the first exhaust valve, the first spark plug, the first intake valve, the second intake valve, the third intake valve, the second spark plug, and the second exhaust valve are circumferentially along the upper end of the inner periphery of the cylinder. Are installed on the cylinder head side wall surface of the combustion chamber in the order described in
The center of the first bottom surface, which is the bottom surface of the first exhaust valve, is located between the first spark plug and the squish area space, and the second exhaust valve is located between the second spark plug and the squish area space. The center of the second bottom surface, which is the bottom surface, is located,
A central axis of the cylinder is located on a virtual cross section, and the virtual cross section virtually bisects the combustion chamber;
The multi-valve combustion chamber characterized in that the virtual cross section virtually intersects with the first bottom surface and the second bottom surface. A fourth intake valve is installed facing the squish area space;
The multi-valve combustion according to any one of claims 1 to 3, wherein the first exhaust valve, the fourth intake valve, and the second exhaust valve are connected to each other. Room. The opening timing of the second intake valve is set before exhaust top dead center,
The closing timing of the first exhaust valve is set after exhaust top dead center,
The valve opening period of the second intake valve and the valve opening period of the first exhaust valve overlap each other in the vicinity of the exhaust top dead center. The multi-valve combustion chamber described in 1.

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