JP3984908B2 - Engine combustion chamber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion chamber configured by providing a cavity on a piston top surface of a direct injection diesel engine.
[0002]
[Prior art]
Conventionally, in a combustion chamber of a direct injection type diesel engine, a cavity is provided on the top surface of a piston to constitute a combustion chamber, and the injection chamber of the injection nozzle faces the inside of the combustion chamber so that air flows such as swirl and squish The spray sprayed from the injection nozzle collides with the wall surface of the combustion chamber and diffuses, and the fuel is mixed with the air and burned.
In such a combustion chamber, a plurality of injection holes are provided in the fuel injection nozzle to increase the number of sprays in order to increase the efficiency of air utilization by diffusing fuel over a wide area, and to improve fuel consumption and smoke. Increasing and spraying radially toward the side wall of the cavity and staggered in the vertical direction, or forming the side wall of the cavity into a stepped shape. For example, in the technique shown in Patent Document 1, the shape of the cavity is a reentrant type in which the opening of the cavity is narrowed and expanded toward the outside in the cylinder radial direction toward the lower side. A plurality of arc strips are provided on the inner surface in the vicinity to constitute a stepped combustion chamber.
[0003]
[Patent Document 1]
JP-A-9-32560 [0004]
[Problems to be solved by the invention]
By the way, when the area of the opening part of the cavity is narrow as in the technique shown in Patent Document 1, the thermal load is increased, causing a problem in durability. Therefore, when durability is important, the thermal load is reduced by increasing the area of the opening of the cavity. As a means for increasing the area of the opening, for example, a valve recess is provided along with the cavity on the top surface of the piston.
However, at present, the valve recess is used as a combustion chamber to perform sufficient combustion, and the stepped shape combustion chamber cannot be used effectively, and the optimal combustion chamber shape is still identified. Not. Therefore, experiments are repeated to specify the shape of the combustion chamber, and the development period tends to be prolonged.
Therefore, the present invention aims to increase the combustion efficiency by effectively utilizing the step-shaped combustion chamber, and particularly to reduce nitrogen oxides.
[0005]
[Means for Solving the Problems]
The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.
[0006]
That is, in the first aspect of the present invention, in the configuration in which a cavity is provided on the piston top surface of the direct injection diesel engine, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity, the cavity is at least in the vertical direction. Forming a recess in two stages, forming a recess recessed downward on the bottom surface of the second recess from the bottom, and expanding the first recess from the bottom radially outward to form a recess. A vertical surface is formed on the top of the substrate.
[0007]
According to a second aspect of the present invention, in the configuration in which a cavity is provided on the piston top surface of the direct injection diesel engine, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle injects into the cavity, the cavity is at least two steps in the vertical direction. Forming a recess on the bottom surface of the second-stage recess from the bottom, and forming a recess by expanding the first-stage recess from the bottom outward in the radial direction. The angle is set to −25 degrees to 0 degrees, and a vertical surface is formed on the upper portion of the depression.
[0008]
According to a third aspect of the present invention, in the configuration in which a cavity is provided on the piston top surface of a direct injection diesel engine, a fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle injects into the cavity, the cavity is at least in two stages in the vertical direction. Forming a recess on the bottom surface of the second-stage recess from the bottom, and forming a recess by expanding the first-stage recess from the bottom outward in the radial direction. An angle is set to −25 degrees to 0 degrees, a vertical surface is formed at the upper portion of the depression, and a range in which fuel is injected from the fuel injection nozzle to the valve recess side wall on the swirl start side is set to 1 of the angle θBv between adjacent valve recess centers. / 4.
[0009]
According to a fourth aspect of the present invention, in the configuration in which the piston top surface cavity of the direct injection diesel engine is provided, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle injects into the cavity, the cavity is at least in two stages in the vertical direction. A recess is provided to form a recess recessed downward on the bottom surface of the second recess from the bottom, and the first recess from the bottom is expanded radially outward to form a recess. The radius of curvature of the recess Is D (cylinder radius) / 24 or more, a vertical surface is formed at the top of the recess, and the radius of curvature of the corner between the bottom surface of the first recess from the bottom and the protrusion surface of the protrusion formed at the center of the cavity Is D / 60 or more.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the invention will be described.
FIG. 1 is a side sectional view of a combustion chamber according to the present invention, FIG. 2 is an enlarged sectional view of a main part in FIG. 1, and FIG. 3 is a plan view of the combustion chamber.
[0011]
The combustion chamber of the direct injection diesel engine of the present invention will be described with reference to FIGS.
In a direct injection type diesel engine, a cavity 2 and a valve recess 3 are provided on the top surface of a piston 1 that is slidably fitted into a cylinder 10, and the cavity 2 is provided at the center of the piston top surface 1a. The fuel is injected into the cavity 2 from the fuel injection nozzle 7 disposed on the outer peripheral portion and disposed above the center of the piston 1 in plan view. The cavity 2 is provided by forming recesses 21 and 22 deeply in two steps from the periphery in the vertical direction to the center, and is formed continuously with the valve recess 3 so that the diameter becomes wider and shallower toward the piston top surface 1a. A stepped combustion chamber 5 is formed.
[0012]
In the combustion chamber 5, the swirl 20 is formed by the intake air introduced into the cylinder 10 from the intake port 28 in the intake process, and the squish is formed in the cavity 2 by the piston top surface. Utilizing this, air and fuel are mixed in the combustion chamber 5.
[0013]
Further, a protrusion 6 bulging upward is formed at the center of the bottom surface of the cavity 2, and the injection nozzle 7 protrudes into the combustion chamber 5 from a cylinder head (not shown) above the protrusion 6. ing. At the lower end portion of the injection nozzle 7, a plurality of injection holes are arranged at substantially equal intervals around the nozzle axis, and the respective injection holes are arranged in a staggered manner in the vertical direction toward the wall surface of the combustion chamber 5. It is comprised so that it may inject radially. In this embodiment, three jets are made in a range of 90 degrees in a plan view in FIG. 3, and 12 jets are jetted from the total jet nozzles 7. Explaining in the range of 1/4, the first spray 41 is sprayed to the swirl front side of the side wall 3a of the valve recess 3 in a plan view, and sprayed from the upper part of the second-stage recess 21 from the bottom toward the valve recess 3 in a side view. The The second spray 42 is sprayed slightly toward the rear side of the valve recess 3 from the center of the valve recess 3 in plan view and toward the side wall surface of the recess 21 in side view. The third spray 43 is sprayed on the lower side of the second spray 42 in a plan view and toward the side wall surface of the first-stage recess 22 on the lower side in a side view.
[0014]
As shown in FIG. 2, the combustion chamber 5 is composed of a first combustion chamber 5 a and a second combustion chamber 5 b that spread around the injection nozzle 7. In the cross-sectional view of FIG. 2, the first combustion chamber 5 a is located above the line connecting the injection center O 1 of the injection nozzle 7, the lower 22 (first from the bottom) recess 22, and the boundary between the lower second recess 21. The space in the cavity 2 is used. In other words, the first combustion chamber 5a is defined by adding the space between the valve recess 3 and the recess 22 in the second stage from the bottom, the center O1 of the injection nozzle 7, and the top surface of the piston. A space below the first combustion chamber 5a is defined as a second combustion chamber 5b. That is, in the cross-sectional view of FIG. 2, the inside of the cavity 2 below from the line connecting the injection center O1 of the injection nozzle 7, the boundary portion between the lower portion (first step from the bottom) and the second step portion from the bottom. The space is a second combustion chamber 5b.
[0015]
In the first combustion chamber 5a, the valve recess 3 has a valve recess for an intake valve and a valve recess for an exhaust valve, and is provided on the outer periphery of the piston top surface 1a. Two are arranged for intake and exhaust respectively. As shown in FIG. 3, the side wall 3a of the valve recess 3 is formed in such a shape that the piston center side expands in a plan view, and the fuel injected from the injection nozzle 7 is diffused radially outward along the valve recess side wall 3a. Let Here, the fuel is injected toward the swirl start end side of the valve recess side wall 3a (first spray 41), and the range in which the first spray 41 is injected is approximately 1 / of the angle θBv between adjacent valve recess centers. 4 is configured. This makes it possible to promote fuel diffusion using the swirl 20. Thus, when the fuel injected from the injection nozzle 7 collides with the valve recess side wall 3a, as shown by the arrow in FIG. 3, the fuel is diffused in the valve recess 3 and spreads to every corner, and the mixing of fuel and air is promoted. .
[0016]
Further, as shown in FIG. 2, the side wall 3a of the valve recess 3 is inclined by an inclination angle θ1 so as to open outward from the vertical direction (parallel to the axis of the piston) in a side view. The inclination angle θ1 is set to a value within a range of 3 degrees to 15 degrees. Therefore, it is diffused upward and outward. Further, the top surface 1a on the outer periphery of the piston is inclined so as to be lowered toward the center of the piston, and an inclination angle θ2 that extends downward from the piston top surface 1a (perpendicular to the axial center line of the piston) is 1 degree to 1 °. It is formed to have a value within a range of 3 degrees. When the corner portion 31 between the valve recess side wall 3a and the piston top surface 1a is formed in an arcuate curved surface, and the value of the radius of curvature of the corner portion 31 is a cylinder radius D, the value is equal to or greater than D / 60. It is comprised so that. Hereinafter, the cylinder radius is assumed to be D.
Further, the corner portion 32 between the valve recess side wall 3a and the valve recess bottom surface 3b is also formed in an arcuate curved surface, and the value of the curvature radius of the corner portion 32 is set to D / 60 or more.
In this way, the fuel injected from the injection nozzle 7 is prevented from being caught from the inside of the combustion chamber 5 to a region where the relation to the combustion outside the cylinder diameter is small.
[0017]
The valve recess bottom surface 3b is formed as an inclined surface that rises by an inclination angle θ3 outward in the cylinder radial direction. The inclination angle θ3 is a value within a range of 1 degree to 3 degrees. And the corner | angular part 33 between this valve recess bottom face 3b and the side wall 21a of the recessed part 21 of the 2nd step | paragraph from the bottom is formed in an arc-shaped curved surface, and the value of the curvature radius of this corner | angular part 33 is D / 60 or more It is comprised so that.
Thereby, after the fuel injected from the injection nozzle 7 collides with the side wall 21a of the second-stage recess, it flows along the corner portion 33 and is diffused to reach every corner of the valve recess 3, and the fuel and air are mixed. Mixing is promoted.
[0018]
Further, the side wall 21a of the recess 21 in the second step from the bottom is inclined by an inclination angle θ4 so as to open outward from the vertical direction in a side view. The inclination angle θ4 is a value within a range of 3 degrees to 10 degrees. Therefore, the reach distance of the fuel injected from the injection nozzle 7 to the wall surface is extended, and the fuel colliding with the wall surface is diffused to reach every corner in the first combustion chamber 5a, thereby mixing the fuel and air. Is promoted.
On the other hand, a recess 21b that is recessed downward is formed on the bottom surface of the horizontal portion of the second-stage recess 21 from the bottom. In such a configuration, when the fuel injected from the injection nozzle 7 collides with the side wall 21a of the second-stage recess 21 and flows downward along the side wall 21a and reaches the recess 21b, the fuel is shown in FIG. As shown by the arrows in FIG. 6, since the fuel is diffused to the lower side of the cylinder center, collision between sprays can be reduced and the fuel diffusion effect can be increased. Therefore, it is possible to prevent the fuel injected from the fuel injection nozzle 7 from the bottom into the second-stage recess 21 from being mixed with the fuel injected in different directions and overlapping to prevent the deterioration of combustion. .
[0019]
Further, in the second combustion chamber 5b, a depression 22b is provided by expanding downward from the upper and lower center of the side wall 22a of the recess 22 in the first stage from the bottom downward in the cylinder radial direction, and the value of the radius of curvature of the depression 22b is set. In addition to a value equal to or greater than D / 24, the angle θ5 of the side wall 22a expanding outward in the radial direction is set to a value in the range of −25 degrees to 0 degrees.
Thereby, while being able to extend the reach distance to the wall surface of the fuel injected toward the side wall 22a of the recessed part 22 of the 1st step | paragraph from the injection nozzle 7, the scorch effect can be increased. Further, since the fuel reaching the side wall 22a is diffused to the piston center side by the recess 22b as shown by an arrow in FIG. 2, collision between sprays can be reduced.
[0020]
Further, in the side wall 22a of the recess 22 in the first step from the bottom, a vertical surface 22c is formed on the upper portion of the recess 22b to increase the scuffing effect. However, as the length of the vertical surface 22c increases. The scuffing effect can be further increased.
[0021]
Further, a horizontal portion 22d is formed on the bottom surface on the outer peripheral side of the first-stage recess 22 from the bottom, and the horizontal portion 22d is configured to promote the evaporation of the injected fuel.
[0022]
Further, the protrusion 6 formed so as to rise upward in the center of the bottom surface of the cavity 2 has the highest center portion and is formed in a substantially conical shape so as to descend outward in the cylinder radial direction. The upper end 6a of the projection 6 is formed in an arcuate curved surface in a cross-sectional view, and is formed so that the value of the radius of curvature of the upper end 6a is not less than D / 24. Therefore, in the combustion chamber 5, the spray flow smoothly flows and collision between the sprays is prevented.
Further, the corner 34 of the portion of the protrusion 6 where the slope that descends from the upper end 6a in the outer circumferential direction and the slope that rises from the bottom of the concave portion 21 (horizontal portion 22d) from the bottom toward the upper end 6a intersects. It is formed into a curved surface having a circular arc shape in cross section, the value of the radius of curvature of the corner portion 34 is set to a value of D / 60 or more, and the bending angle of the slopes on both sides of the corner portion 34 formed in the middle portion of the slope of the projection 26 θ6 is set to a value in the range of 90 degrees to 145 degrees. Thereby, it is possible to prevent the spray flow of the fuel mixed with air from flowing along the slope and being caught in the vicinity of the injection nozzle 7.
[0023]
Further, the combustion chamber volume Vs of the first-stage recess 22 (second combustion chamber 5b) from the bottom and the combustion chamber volume (first combustion chamber) above the second-stage recess 21 (first combustion chamber 5a) from the bottom. 5a (volume Vm + valve recess volume Vv), and the nozzle area (discharge area of the third spray 43) As from the bottom of the fuel injection nozzle 7 to the first recess 22 (second combustion chamber 5b) The relationship between the ratio of the nozzle area (discharge area Am of the second spray 42 + discharge area Av of the first spray 41) upward from the second-stage recess 21 (first combustion chamber 5a) is as follows: The combustion chamber volume of the combustion chamber 5 and the nozzle area of the fuel injection nozzle 7 are easily determined.
(Am + Av) / As = (1.5-2.5) (Vm + Vv) / Vs
Therefore, since the volume of the combustion chamber 5 or the nozzle diameter of the injection nozzle 7 can be easily determined, there is no need to repeat the experiment to determine the shape of the combustion chamber as in the prior art, and the development period is shortened. be able to.
[0024]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0025]
That is, according to a first aspect of the present invention, there is provided a structure in which a cavity is provided on a piston top surface of a direct injection diesel engine, a fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity. Forming a recess in two stages in the direction, forming a recess recessed downward on the bottom surface of the second recess from the bottom, expanding the first recess from the bottom radially outward to form a recess, Since a vertical surface was formed at the top of the depression,
The injected fuel can be diffused in the recess. Further, the spray reach distance in the cavity of the fuel injected from the injection nozzle can be extended, and the squish effect is increased. Furthermore, collision between sprays can be prevented. Therefore, the step-shaped combustion chamber is effectively utilized, mixing of air and fuel is promoted, and combustion efficiency is increased.
In particular, the amount of nitrogen oxides generated can be reduced.
[0026]
According to a second aspect of the present invention, in a configuration in which a cavity is provided on the piston top surface of a direct injection diesel engine, a fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle injects the cavity into the cavity. A recess is formed at the stage, a recess recessed downward is formed on the bottom surface of the second recess from the bottom, and a recess is formed by expanding the first recess from the bottom radially outward. Since the angle to be -25 degrees to 0 degrees, and a vertical surface was formed on the top of the depression,
The injected fuel can be diffused in the recess. The spray reach distance in the cavity of the fuel injected from the injection nozzle can be extended, the squish effect can be increased, and the diffusion from the bottom to the first recess can be promoted. Furthermore, collision between sprays can be prevented. Therefore, the step-shaped combustion chamber is effectively utilized, mixing of air and fuel is promoted, and combustion efficiency is increased.
In particular, the amount of nitrogen oxides generated can be reduced.
[0027]
According to a third aspect of the present invention, there is provided a structure in which a cavity is provided on the piston top surface of a direct injection diesel engine, a fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity. A recess is formed at the stage, a recess recessed downward is formed on the bottom surface of the second recess from the bottom, and a recess is formed by expanding the first recess from the bottom radially outward. An angle of -25 degrees to 0 degrees is formed, a vertical surface is formed on the upper portion of the depression, and a range in which fuel is injected from the fuel injection nozzle to the valve recess side wall on the swirl start side is set to an angle θBv between adjacent valve recess centers. Since it was configured to 1/4,
The injected fuel can be diffused in the recess. The spray reach distance in the cavity of the fuel injected from the injection nozzle can be extended, and collision between the sprays can be prevented. In addition, the squish effect is increased, and diffusion to the first recess from the bottom can be promoted. Furthermore, the diffusion of fuel can be promoted by utilizing the valve recess wall surface. Therefore, the step-shaped combustion chamber is effectively utilized, mixing of air and fuel is promoted, and combustion efficiency is increased.
As a result, in particular, the amount of nitrogen oxides generated can be reduced.
[0028]
According to a fourth aspect of the present invention, in the configuration in which the piston top surface cavity of the direct injection type diesel engine is provided, the fuel injection nozzle is arranged above the piston center, and the fuel injection nozzle injects into the cavity, the cavity is at least in two stages in the vertical direction. A recess is formed on the bottom surface of the second-stage recess from the bottom, and a recess is formed by expanding the first-stage recess from the bottom outward in the radial direction. The curvature of the recess The radius is D (cylinder radius) / 24 or more, a vertical surface is formed at the top of the recess, and the curvature of the corner between the bottom surface of the first recess from the bottom and the protrusion surface of the protrusion formed at the center of the cavity Since the radius was set to D / 60 or more,
The squish effect is increased and the injected fuel can be diffused in the recess. In addition, the spray reach distance from the injection nozzle to the cavity side wall can be extended, and collision of sprays can be prevented. Further, it is possible to prevent the injected fuel from being caught in the vicinity of the fuel injection nozzle. Therefore, the step-shaped combustion chamber is effectively utilized, mixing of air and fuel is promoted, and combustion efficiency is increased.
As a result, in particular, the amount of nitrogen oxides generated can be reduced.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a combustion chamber according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part in FIG.
FIG. 3 is a plan view of a combustion chamber.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piston 2 Cavity 21 The recessed part 21b of the 2nd step from the bottom 22 The recessed part 22b of the 1st step from the bottom 22b The recessed part 22c Vertical surface

Claims (4)

In the configuration in which a cavity is provided on the piston top surface of the direct injection diesel engine, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity.
The cavity is provided with a recess formed in at least two stages in the vertical direction,
Form a dent recessed downward on the bottom of the second recess from the bottom,
The first step from the bottom expands radially outward to form a recess,
A combustion chamber of an engine, wherein a vertical surface is formed on an upper portion of the recess. In the configuration in which a cavity is provided on the piston top surface of the direct injection diesel engine, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity.
The cavity is provided with a recess formed in at least two stages in the vertical direction,
Form a dent recessed downward on the bottom of the second recess from the bottom,
The first step from the bottom expands radially outward to form a recess,
The spreading angle is -25 degrees to 0 degrees,
A combustion chamber of an engine, wherein a vertical surface is formed on an upper portion of the recess. In the configuration in which a cavity is provided on the piston top surface of the direct injection diesel engine, the fuel injection nozzle is disposed above the center of the piston, and the fuel injection nozzle is injected into the cavity.
The cavity is provided with a recess formed in at least two stages in the vertical direction,
Form a dent recessed downward on the bottom of the second recess from the bottom,
The first step from the bottom expands radially outward to form a recess,
The spreading angle is -25 degrees to 0 degrees,
Forming a vertical surface at the top of the depression;
A combustion chamber of an engine, wherein a range in which fuel is injected from the fuel injection nozzle to a valve recess side wall on the swirl start side is configured to be ¼ of an adjacent valve recess center angle θBv. In the configuration in which the piston top surface cavity of the direct injection type diesel engine is provided, the fuel injection nozzle is arranged above the piston center, and the fuel injection nozzle is injected into the cavity.
The cavity is provided with a recess formed in at least two stages in the vertical direction,
Form a dent recessed downward on the bottom of the second recess from the bottom,
The first step from the bottom expands radially outward to form a recess,
The radius of curvature of the depression is D (cylinder radius) / 24 or more,
Forming a vertical surface at the top of the depression;
A combustion chamber of an engine, characterized in that a radius of curvature of a corner between a bottom surface of the first recess from the bottom and a projection surface of a projection formed in the center of the cavity is set to D / 60 or more.

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