JP2000045778A - Combustion chamber for cylinder fuel injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the combustion performance while preventing the eccentric transmission of the frame inside of a combustion chamber by reducing the angle of inclination of an exhaust side head surface so as to come close to the virtual flat surface crossing the center axis of a cylinder, and raising the height position of an end of the combustion chamber in an exhaust side top surface in response to the change of the angle. SOLUTION: An intake side head surface 19 and an exhaust side head surface 22 are obliquely provided so as to cross each other at a position near the center axis 23 of a cylinder, and the top surface shape of a piston 8 is determined corresponding to the lower surface shape of the cylinder head. In this case, angle of inclination of the exhaust side head surface 22 is set small so as to come close to the virtual flat surface crossing the center axis 23 of the cylinder, and height position of an end of a combustion chamber of the exhaust side top surface 25 of the piston 8 is raised in response to the change of the angle. An intake stroke is completed and the piston 8 starts to be raised, and the fuel injection is started when the piston 8 achieves the predetermined position, mixing of the fuel and the air is performed at an early time, and the combustion is performed well so as to improve the motive power performance.

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 direct injection engine, and belongs to a technical field in which the shape of the combustion chamber is improved.

[0002]

2. Description of the Related Art An intake head surface is formed by an intake valve lower surface of a cylinder head and a lower surface of an intake valve itself, and an exhaust head surface is formed by an exhaust valve lower surface of a cylinder head and an exhaust valve itself. The head surface is arranged so as to intersect near the cylinder center axis, and the piston has an intake-side top surface corresponding to the intake-side head surface and an exhaust-side top surface corresponding to the exhaust-side head surface almost matching both head surfaces. Formed as the shape of the piston top surface, a combustion chamber is formed by providing a recess extending from the intake side top surface to a part of the exhaust side top surface, and fuel is injected into the combustion chamber from the vicinity of the cylinder bore. Are known in various ways.

[0003] Japanese Patent Application Laid-Open No. 9-317, which is of the type described above and which is considered to be the closest to the present invention.
There is a technology disclosed in Japanese Patent No. 474. FIG. 7 is a longitudinal sectional side view showing this, in which an intake port 2 and an exhaust port 3 are formed in a cylinder head 1, and their openings are offset in the direction of the cylinder center axis. This offset amount is indicated by a symbol L. Each of the ports 2 and 3 is provided with an intake valve 4 and an exhaust valve 5, respectively, which are opened and closed by a valve operating mechanism (not shown). The cylinder head 1 is integrated with a cylinder block 6, and a piston 8 is provided in a cylinder 7. A combustion chamber 9 is formed between the top surface of the piston 8 and the lower surface of the cylinder head 1. The combustion chamber 9 is provided at a position facing the intake valve 4, and a curved concave portion 10 forming the combustion chamber 9 extends near the exhaust valve 5.

[0004] Due to the presence of the above-mentioned offset L, the wall surface 11 is formed near the intake valve 4 and the right end of the concave portion 10 is set at a higher position (this position is indicated by a symbol P). Therefore, a recessed space 12 is formed by the wall surface 11 and the right end of the recess 10, and the electrode 13 of the spark plug faces the recessed space 12. The fuel injection into the combustion chamber 9 is performed by the intake valve 4
The injection nozzle 14 is opened at the end of the combustion chamber 9.

In this prior art, gasoline from the injection nozzle 14 is sufficiently vaporized while moving along the recess 10 and stagnates in the space 12 at a high concentration. Is fired. Therefore,
The liquid fuel does not adhere to the electrode 13 and "smoldering" of the electrode is prevented. And the recess 10
Since the right end position is high, there is a function that fuel stagnation in the combustion chamber 9 is good and abnormal leaning is prevented.

[0006]

As described above, this prior art has a considerable advantage. However, since the offset L is indispensable and the bottom surface of the cylinder head is irregularly shaped such that it has a wall surface 11. There are the following problems. That is, since the flame growing from the electrode 13 is blocked by the wall 11, the propagation of the flame to the intake valve 4 is delayed even when the piston 8 is moving down, and the propagation of the flame to the exhaust valve 5 is smaller than the propagation to the exhaust valve 5. As a result, combustion becomes unbalanced. Such an imbalance does not cause a serious problem at a low load.However, at a high load, the air-fuel efficiency is set to a rich side. Normal combustion cannot be obtained, and the intended output cannot be obtained.

From the viewpoint of compacting the cylinder head, the size of the vertical thickness of the cylinder head becomes large to set the offset L, which is disadvantageous in downsizing the engine. Further, since the vertical position of the intake valve 4 and the exhaust valve 5 is shifted due to the offset L, a special design change is required for installing a valve operating mechanism such as a camshaft, a rocker arm, and a valve spring. Disadvantageous.

[0008]

[Other prior arts and their problems] Japanese Patent Application Laid-Open No. Hei 8-310354 discloses a type having no offset L as shown in FIG.
The technique disclosed in Japanese Patent Application Laid-Open Publication No. H10-26095 is known, and has a structure as shown in FIG. Parts having the same functions as those in FIG. 7 are denoted by the same reference numerals in FIG. 6, and detailed description is omitted. Since this type is a symmetrical pen-to-lobe type having no offset L as described above, the problem described with reference to FIG. 7 can be avoided, but another problem occurs when the point P is low. . That is, the injected fuel does not sufficiently stay in the concave portion 10 and is also ejected to the right of the point P and adheres to the cylinder bore indicated by reference numeral 15. Such adhesion of fuel causes dilution of the lubricating oil, and the fuel denoted by reference numeral 15 and the fuel in the vicinity thereof become unburned, and as a result, hydrocarbon (H
C) is inconvenient for reduction. In addition, poor fuel stagnation in the concave portion 10 causes the fuel concentration in the vicinity of the electrode 13 not to be an appropriate value, and thus makes it difficult to obtain stable ignition and combustion. In addition, the included angles A and B between the intake valve 4 and the exhaust valve 5
Are almost the same.

[0009]

SUMMARY OF THE INVENTION The present invention has been provided to solve the problems described with reference to FIGS. 7 and 6 as described above. The intake-side head surface is formed by the lower surface of the intake valve itself and the lower surface of the intake valve itself, and the exhaust-side head surface is formed by the lower surface of the cylinder head on the exhaust valve side and the lower surface of the exhaust valve itself. The piston has a piston top surface shape such that the intake side top surface corresponding to the intake side head surface and the exhaust side top surface corresponding to the exhaust side head surface almost coincide with both head surfaces. In the type in which a recess is provided in a form extending from the intake side top surface to a part of the exhaust side top surface to form a combustion chamber, and fuel is injected into the combustion chamber from the vicinity of the cylinder bore,
The inclination angle of the exhaust-side head surface is reduced so as to approach an imaginary plane perpendicular to the cylinder center axis centering around the cylinder center axis, and the height of the end of the combustion chamber at the top surface of the exhaust side corresponding to this angle change. It is characterized by its raised position. Therefore, the height position of the end portion of the combustion chamber can be increased without the above-described problem.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment shown in FIGS. 1 to 5 will be described, but illustration of an intake valve and an exhaust valve is omitted in FIGS. FIG. 7 in each drawing of the embodiment.
Parts having the same functions as those of FIG. 6 and those of FIG. 6 are denoted by the same reference numerals in these figures, and detailed description thereof is omitted. FIG. 2 is a plan view of the cylinder head 6 turned upside down and viewed in a plan view. 19 are formed. The intake valve side lower surface 17 and the lower surface 18 form a substantially flat intake side head surface 19. An exhaust-side head surface 22 is formed by the exhaust valve-side lower surface 20 of the cylinder head and the lower surface 21 of the exhaust valve 5 itself. Exhaust valve side lower surface 20
The lower surface 21 forms a substantially flat exhaust-side head surface 22. The intake-side head surface 19 and the exhaust-side head surface 22 are arranged so as to intersect near the cylinder center axis 23, and the two surfaces 19 and 22 are inclined as shown in FIG.

The top surface shape of the piston is determined so as to conform to the lower surface shape of the cylinder head as described above. The shape of the piston top surface 26 is formed so that the intake side top surface 24 with respect to the intake side head surface 19 and the exhaust side top surface 25 with respect to the exhaust side head surface 22 substantially match the two head surfaces 19 and 22. As shown in FIG. 3, the piston top surface 26 is provided with some depressions 27 and 28 in order to avoid interference with the intake valve 4 and the exhaust valve 5. This embodiment is a four-valve engine as shown in FIG. Recess 10
3 extends from the intake side top surface 24 to a part of the exhaust side top surface 25 in a state of extending in the diameter direction of the piston 8 as shown in FIG. The injection nozzle 14 is installed near the cylinder bore 16 in the same manner as described above.

FIG. 5 illustrates the gist of the present invention. The state shown by the two-dot chain line shows the shape before the improvement in FIG. 6, and reference numeral 22 'denotes the exhaust side head surface having the same inclination angle as that in FIG. Exhaust side top surface 2 shown by two-dot chain line
5 'is the same inclination angle as FIG. Here, the inclination angle of the exhaust-side head surface 22 ′ is changed from the position shown by the two-dot chain line
The height of the exhaust-side top surface 25 at the end of the combustion chamber is raised to correspond to the imaginary plane 29 orthogonal to 3. That is, by changing the angle of the intake-side head surface from the position 22 'to the position 22,
The exhaust-side top surface can also change the angle from the position 25 'to the position 25. Thereby, the height position P at the end of the combustion chamber can be increased to a higher P 'position. This height increase is indicated by the symbol H.

When the angle of the exhaust-side head surface 22 is reduced in this manner, the exhaust valve is also displaced toward the upright side in accordance with the angle, so that B '<B, A' =
A, and inevitably A '>B'.

In the embodiment described above, the angle change is given only to the exhaust-side head surface and the exhaust-side top surface. However, the relative angle between the exhaust-side head surface and the intake-side head surface is made constant, and Even if an angle change is given to the head surface, the height H can be secured. This is not shown, but is included in the concept of the present invention.

The operation of the embodiment will be described. In principle, fuel injection is started when the intake stroke ends and the piston 8 starts to rise and the piston comes to a predetermined position. At this time, since the height position of the end of the combustion chamber is increased by the height increase H, the fuel is sufficiently contained in the cavity of the combustion chamber 9. When the load is high, the fuel injection start time is set to a considerably early time, for example, 360 degrees BTDC, and the mixture with the air or the vaporization is sufficiently exhausted early in the in-cylinder airflow. Therefore, the fuel liquid does not adhere to the inner surface of the cylinder as described with reference to FIG.

On the other hand, when the load is low, the fuel injection start timing is set at a considerably late timing, for example, 70 degrees BTDC, and the injected fuel tends to go directly to the opposite surface of the injection nozzle, that is, the location denoted by reference numeral 15 in FIG. However, such a fuel behavior is prevented by the height increase H. Therefore, even with a lean fuel generally set at a low load, the amount of fuel retained in the combustion chamber 9 increases, so that the ignitability is good and the generation of HC due to the unburned state as described above. The amount can also be significantly reduced.

[0017]

According to the present invention, the suction and suction of the prior art can be achieved.
Since the method does not require the offset arrangement of the exhaust valve, it is possible to smoothly spread the flame over the entire area without installing a special projection in the combustion chamber. Therefore, uneven flame propagation does not occur in the combustion chamber, and expected power performance can be obtained under favorable combustion. Furthermore, since there is no offset as described above, an increase in the thickness of the cylinder head can be minimized, and there is no need to make any special design change of the valve operating mechanism, which is advantageous in terms of rationalization such as common use of parts. It is.

As described above, since the height of the end of the combustion chamber is increased in response to the reduction of the inclination angle of the exhaust-side head surface, the modification to be applied to the lower surface of the cylinder head and the top surface of the piston is extremely small. It can be scaled and is therefore very advantageous in retrofitting existing engines.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing an embodiment of the present invention.

FIG. 2 is a plan view illustrating a lower surface of a cylinder head.

FIG. 3 is a plan view showing a piston top surface.

FIG. 4 is a side view of a piston.

FIG. 5 is a longitudinal sectional side view showing the present invention in principle.

FIG. 6 is a longitudinal sectional side view of the prior art.

FIG. 7 is a vertical sectional side view showing another conventional technique.

[Explanation of symbols]

 Reference Signs List 1 cylinder head 17 intake valve side lower surface 18 lower surface of intake valve itself 19 intake side head surface 20 exhaust valve side lower surface 21 lower surface of exhaust valve itself 22 exhaust side head surface 23 cylinder center axis 8 piston 24 intake side top surface 25 exhaust side top Surface 10 Recess 9 Combustion chamber 16 Cylinder bore 14 Injection nozzle 29 Virtual plane P 'Height position of combustion chamber end

Claims (1)

[Claims] An intake-side head surface is formed by an intake valve-side lower surface of a cylinder head and a lower surface of an intake valve itself, and an exhaust-side head surface is formed by an exhaust valve-side lower surface of a cylinder head and an exhaust valve itself. The head surface is arranged so as to intersect near the cylinder center axis, and the piston has an intake-side top surface corresponding to the intake-side head surface and an exhaust-side top surface corresponding to the exhaust-side head surface almost matching both head surfaces. Formed as the shape of the piston top surface, a combustion chamber is formed by providing a recess extending from the intake side top surface to a part of the exhaust side top surface, and fuel is injected into the combustion chamber from the vicinity of the cylinder bore. The inclination angle of the exhaust-side head surface is reduced so as to approach an imaginary plane perpendicular to the cylinder center axis centering on the vicinity of the cylinder center axis, and the exhaust-side head surface is adjusted to correspond to this angle change. A combustion chamber of a direct injection engine, characterized in that a height position of an end portion of the combustion chamber surface is increased.