JPH094456A - Combustion chamber of 3-valve overhead valve diesel engine - Google Patents

Abstract

(57) [Summary] [Purpose] To improve exhaust efficiency in a 3-valve overhead valve diesel engine. [Structure] Two intake valves 4 and one exhaust valve 5 are provided in a cylinder head. An exhaust recess 8 is provided on either the piston head 7 or the lower surface of the cylinder head. The exhaust recessed portion 8 includes the exhaust valve 5 in plan view and includes two intake valves 4 and 4
Shape to spread toward. The volume center of the exhaust recess 8 is displaced from the center of the piston 6 toward the exhaust valve 5 side. As a result of the formation of the exhaust concave portion 8, exhaust gas is concentrated and smoothly discharged around the exhaust valve 5 in the exhaust stroke, so that exhaust efficiency is improved. Therefore, the exhaust gas does not stay in the combustion chamber, the inflow of the intake air becomes smooth, and the charging efficiency of the engine is improved.

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 a three-valve overhead valve diesel engine equipped with two intake valves and one exhaust valve, and enhances exhaust efficiency to increase engine charging efficiency. Provided is one that can prevent overheating of the exhaust wall peripheral wall.

[0002]

BACKGROUND OF THE INVENTION Generally, a diesel engine may be provided with two intake valves in order to perform intake efficiently, but the exhaust valve is (1) a sub-chamber diesel engine with a sub-chamber mouthpiece. Since it fits on the lower surface of the cylinder head, there is not enough space for two exhaust valves. (2) In a four-valve engine provided with two exhaust valves in addition to two intake valves, the structure of the cylinder head becomes complicated. (3) When two exhaust valves are provided, the partition wall between the exhaust valves is easily overheated and has a thin wall. Due to the above reasons, the number is limited to one and may be configured as a three-valve overhead valve diesel engine.

The present invention is directed to the combustion chamber of this three-valve diesel engine, and its basic structure is as shown in FIGS. 1 to 6, in which a cylinder head 2 is assembled above a cylinder 1 and the cylinder head 2 is attached to the cylinder head 2. A type in which two intake valves 4 and one exhaust valve 5 are provided, and the piston head 7 of the piston 6 fitted in the cylinder 1 faces the intake valve 4, the exhaust valve 5 and the cylinder head lower surface 3. Is.

[0004]

2. Description of the Related Art As a conventional technique of this type, two intake valves 4 and 4 are provided in one half of the cylinder head 2 around the combustion chamber, and the diameter of the intake valve 4 is slightly larger than the other half. The exhaust valve 5 is generally provided.

[0005]

In the above prior art, since there is only one exhaust valve 5 above all, some of the exhaust gas tends to stay in the combustion chamber, which is not sufficient in terms of smooth exhaust of the exhaust gas. .

If smooth exhaust is not performed, intake air cannot smoothly flow into the combustion chamber, and the charging efficiency of the engine, fuel consumption, or output is adversely affected. Further, when the high-heat exhaust gas stays, the inclined peripheral wall portion of the exhaust port is likely to be overheated, which may cause cracks or thermal strain. The present invention is a three-valve overhead valve diesel engine,
The technical issue is to improve exhaust efficiency.

[0007]

Means for achieving the above object will be described below with reference to FIGS. 1 to 6 showing an embodiment. That is, the first aspect of the present invention is, in the combustion chamber of the three-valve overhead valve diesel engine having the basic structure, the exhaust recess 8 in either the piston head 7 or the cylinder head lower surface 3.
When the piston 6 is viewed from the cylinder head 2 in a plan view, the exhaust recess 8 includes the entire exhaust valve 5 and expands toward the two intake valves 4 and the exhaust recess 8
The center of the volume of is displaced from the center of the piston 6 toward the exhaust valve 5 side.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the exhaust recess 8 is formed in an inclined shape that is deeper as it approaches the exhaust valve 5 and shallower as it approaches the intake valve 4.

The exhaust concave portion 8 spreads toward the intake valve 4, which includes the case where the intake valve 4 is partially included and the case where the intake valve 4 is included.
Is a concept that includes both the case where the intake valve 4 is not included and the case where the intake valve 4 is not included. The overhead valve diesel engine E is
Includes both direct injection type and sub chamber type.

[0010]

[Action]

(1) In the present invention 1, since the exhaust recess 8 is provided on either the piston head 7 or the cylinder head lower surface 3,
The distance between the exhaust port and the piston head 7 is greatly expanded by the amount corresponding to the depression of the concave portion 8, and the exhaust gas is smoothly discharged from the exhaust port. Moreover, since the exhaust concave portion 8 includes the entire exhaust valve 5 and is formed so as to spread toward the two intake valves 4 and 4, the exhaust gas is likely to concentrate around the exhaust valve 5 in the exhaust stroke. Moreover, since the volume center of the exhaust recess 8 is deviated from the center of the piston 6 toward the exhaust valve 5, the exhaust concentration around the exhaust valve 5 becomes more efficient.

(2) In the second aspect of the invention, since the exhaust recess 8 is formed in an inclined shape that becomes deeper as it approaches the exhaust valve 5, the center of volume of the exhaust recess 8 is further displaced toward the exhaust valve 5 side. ,
Exhaust gas is likely to concentrate around the exhaust valve 5 and is discharged smoothly, and the concentration of exhaust gas around the exhaust valve 5 can be promoted by the action of the inclined surface of the exhaust recess 8.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a plan view of a piston head of a three-valve vertical overhead valve diesel engine showing Embodiment 1, FIG. 2 is a vertical cross-sectional view of the intake valve and the exhaust valve of the diesel engine, and FIG.
FIG. 4 is a vertical cross-sectional view of the sub-chamber and the vicinity of the intake valve of the diesel engine, and FIG. 4 is a perspective view of the piston head.

As shown in FIG. 3, a cylinder head 2 is assembled above the cylinder 1 of the overhead valve subchamber diesel engine E, and a piston 6 is fitted in the cylinder 1 so as to be vertically movable. The sub chamber mouthpiece 10 is engaged with the cylinder head lower surface 3 of the cylinder head 2 which faces the piston 6, and the fuel injection nozzle 12 is placed above the subchamber 11 (specifically, the swirl chamber) in the subchamber mouthpiece 10. The sub chamber 11 is communicated with the main combustion chamber 16 through the injection hole 15.

Further, two intake ports 13 and one exhaust port 14 are opened in the cylinder head 2, and two intake valves 4.4 are attached to the intake ports 13 and 13 and the exhaust port 14 is provided.
A single exhaust valve 5 is provided to each of the above-mentioned valves so that the piston head 7 faces the intake valve 4, the exhaust valve 5 and the cylinder head lower surface 3 to form a three-valve overhead valve diesel engine. The diameter of the exhaust valve 5 is slightly larger than that of the intake valve.

As shown in FIGS. 1 to 4, two valve recesses 17 and 18 are formed on one half side of the piston head 7, and a substantially fan-shaped exhaust recess 8 is formed on the other half side. The valve recesses 17 and 18 are arranged to face the intake valves 4 and 4 on the cylinder head 2 side, and the exhaust recess 8 is arranged to face the exhaust valve 5. The exhaust recess 8 is formed by the exhaust valve 5.
Also serves as the valve recess 19 facing the.

As shown in FIG. 1, when the piston 6 is viewed from the cylinder head 2 in a plan view, the exhaust recessed portion 8 includes the exhaust valve 5 as a ratchet 8a and includes the entire exhaust valve 5.
It is formed so as to expand in a fan shape toward these intake valves 4 so as to include a part of the two intake valves 4. In addition, as shown in FIGS. 2 and 4, the exhaust recess 8 is formed in an inclined shape that becomes deeper as it approaches the exhaust valve 5 and shallower as it approaches the intake valve 4 (however, it is formed at the same depth. It is also possible), but the volume center of the exhaust recess 8 is located between the center of the piston 6 and the center of the exhaust valve 5 in plan view.
As shown in FIGS. 1 to 4, since the exhaust recess 8 includes a part of the intake valve 4 in a plan view, the tip 8b of the exhaust recess 8 has two valve recesses 17 and 18 and a part thereof. They overlap.

Therefore, the function of the combustion chamber of the three-valve vertical subchamber diesel engine of the first embodiment will be described. First, since the exhaust recess 8 provided in the piston head 7 is formed in a fan shape that spreads toward the two intake valves 4 and 4 by using the exhaust valve 5 as a kameme, the exhaust is exhausted to the vicinity of the exhaust valve 5. Concentrate more smoothly and efficiently. Secondly, the distance between the exhaust port 14 and the piston head 7 can be increased by the amount corresponding to the depression of the exhaust concave portion 8, and the exhaust gas can be discharged smoothly. Thirdly, since the volume center of the exhaust recess 8 is displaced from the center of the piston 6 toward the exhaust valve 5 side, exhaust gas is likely to concentrate around the exhaust valve 5 in the exhaust stroke, and is efficiently discharged from the exhaust port 14. To be done.
Fourthly, since the exhaust recess 8 is formed in an inclined shape that becomes deeper as it approaches the exhaust valve 5, the concentration of exhaust gas around the exhaust valve 5 is further promoted by the action of this inclined surface.

As a result, in the exhaust stroke, the exhaust gas is effectively concentrated around the exhaust valve 5 and discharged smoothly, so that the exhaust efficiency is improved. Therefore, the exhaust gas does not stay in the combustion chamber and the intake air flows in smoothly, so that the charging efficiency, fuel consumption, or output of the diesel engine E is improved. Further, since high-heat exhaust gas does not stay, it is possible to prevent overheating of the inclined peripheral wall portion of the exhaust port 14 and prevent cracks and thermal distortion.

5 and 6 show a second embodiment of the present invention,
In place of the first embodiment in which the exhaust recess 8 is provided in the piston head 7, it is provided in the lower surface 3 of the cylinder head. That is, as shown in FIG. 5, the exhaust valve 5 is included in its entirety, and
The exhaust recess 8 is formed in a substantially circular shape so as to include a part of the intake valves 4 and 4. As shown in FIG. 6, the exhaust recess 8 has the same depth from the exhaust valve 5 to the intake valve 4. It is set (however, it is possible to incline deeply toward the exhaust valve 5 as in the first embodiment).

Since the exhaust recess 8 is arranged on the lower surface 3 of the cylinder head, the exhaust recess 8 is formed so as not to come into contact with the sub chamber mouthpiece 10. Reference numeral 20 indicates a cylinder bore assumed on the cylinder side.

As described above, in the present invention, the exhaust recess 8 is formed.
Is characterized in that it includes the entire exhaust valve 5 and spreads toward the intake valve 4. Therefore, the present invention is not limited to the first and second embodiments in which the tip 8b of the exhaust recess 8 partially overlaps the intake valve 4, Although the exhaust recess 8 extends to the periphery of the intake valve 4, the exhaust recess 8 may be formed so as not to include the intake valve 4. Further, the present invention is applicable regardless of a direct injection type diesel engine or a sub chamber type (not limited to a swirl type) diesel engine.
Further, the present invention is not limited to the vertical overhead valve diesel engine and is also applied to a horizontal overhead valve diesel engine in which the cylinder bores are arranged sideways.

[0022]

【The invention's effect】

(1) In the first aspect of the present invention, since the exhaust concave portion is formed, the exhaust gas is effectively concentrated around the exhaust valve and smoothly discharged in the exhaust stroke, so that the exhaust efficiency is improved. Therefore, the exhaust gas does not stay in the combustion chamber, the inflow of the intake air becomes smooth, and the charging efficiency of the engine, fuel consumption, or output is improved. Further, since the high-heat exhaust gas does not stay, it is possible to prevent overheating of the inclined peripheral wall portion of the exhaust port and prevent cracks and thermal distortion.

(2) According to the second aspect of the present invention, the exhaust recess is formed to have a deeper slope as it gets closer to the exhaust valve, so that the concentration and discharge of the exhaust gas around the exhaust valve can be promoted more smoothly. The effect of is further improved.

[Brief description of drawings]

FIG. 1 is a plan view of a piston head of a three-valve vertical overhead valve diesel engine showing a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view around an intake valve and an exhaust valve of the diesel engine.

FIG. 3 is a vertical cross-sectional view of a sub-chamber and an intake valve of the same diesel engine.

FIG. 4 is a perspective view of the piston head.

FIG. 5 is a view equivalent to FIG. 1 showing a second embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a sub-chamber and an exhaust valve of a three-valve vertical overhead valve diesel engine according to the second embodiment.

[Explanation of symbols]

1 ... Cylinder, 2 ... Cylinder head, 3 ... Cylinder head lower surface, 4 ... Intake valve, 5 ... Exhaust valve, 6 ... Piston, 7 ...
Piston head, 8 ... Exhaust recess, E ... 3-valve overhead valve diesel engine.

Claims (2)

[Claims] 1. A cylinder head above the cylinder (1).
Assemble (2) and install two intake valves on the cylinder head (2).
(4.4) and one exhaust valve (5) are provided, and the piston head (7) of the piston (6) fitted inside the cylinder (1) is an intake valve.
(4), in the combustion chamber of a three-valve overhead valve diesel engine facing the exhaust valve (5) and the lower surface (3) of the cylinder head, exhaust gas to either the piston head (7) or the lower surface (3) of the cylinder head. When the piston (6) is viewed in plan from the cylinder head (2) by providing the concave portion (8) for the
The exhaust recess (8) includes the entire exhaust valve (5) and expands toward the two intake valves (4, 4), and the exhaust recess (8)
A combustion chamber of a three-valve overhead valve diesel engine, wherein the center of volume of (8) is displaced from the center of piston (6) to the side of exhaust valve (5). 2. The exhaust according to claim 1, wherein the exhaust recess (8) is formed in an inclined shape that is deeper as it approaches the exhaust valve (5) and shallower as it approaches the intake valve (4). Valve-type overhead valve Diesel engine combustion chamber.