JP2001115843A - Combustion chamber for direct injection diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber for a direct injection Diesel engine injecting fuel from a fuel injection nozzle, sufficiently mixing the fuel with air and generating an almost uniform mixture, and capable of performing almost uniform combustion in a combustion chamber total unit. SOLUTION: An annular hollow part injected with fuel from a fuel injection nozzle is provided in a combustion chamber wall surface, an opening bore of a combustion chamber opening part is set smaller than a maximum diameter in the annular hollow part and larger than a combustion chamber wall surface diameter in a combustion chamber bottom part side from the annular hollow part, and a central protrusion part of a height and diameter preventing collision of fuel injected from the fuel injection nozzle is provided in a combustion chamber bottom part. A flat part is provided between the annular hollow part and the combustion chamber wall surface in its downward. An annular protrusion part applying a chamfer is provided in the combustion chamber opening part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a combustion chamber of a direct injection diesel engine.

[0002]

2. Description of the Related Art In a combustion chamber of a conventional direct injection diesel engine indicated by a broken line in FIG. 5, injected fuel and air are hardly mixed, and a highly concentrated air-fuel mixture stagnates near the bottom of the combustion chamber, causing combustion. It is difficult to perform even and uniform combustion by fully utilizing the entire volume of the chamber. As a result, black smoke, nitrogen oxides, and the like are easily generated.

[0003]

Accordingly, in the present invention, the fuel injected from the fuel injection nozzle is sufficiently mixed with the air to generate a substantially uniform mixture, and the combustion is substantially uniform throughout the combustion chamber. It is an object of the present invention to provide a combustion chamber of a direct injection diesel engine capable of performing the following.

[0004]

Means for Solving the Problems To solve the above problems,
Therefore, in the invention of claim 1, the direct injection diesel engine
In the combustion chamber, fuel is injected from the fuel injection nozzle to the combustion chamber wall.
An annular recess into which the fuel is injected, and the opening of the combustion chamber opening
The diameter of the annular recess is smaller than the maximum diameter of the annular recess.
Set to be larger than the diameter of the combustion chamber wall at the bottom of the combustion chamber from the bottom
And the fuel injected from the fuel injection nozzle does not collide.
A central projection of diameter and diameter was provided at the bottom of the combustion chamber. Claim
According to a second aspect of the present invention, there is provided a direct injection diesel engine of the first aspect.
In the invention of the combustion chamber, the fuel is injected from the fuel injection nozzle
The volume of the combustion chamber below the central axis of the fuel is V _LAnd full compression
V_CThen V_L/ V_C≤ 0.0088 x injection angle
Degree (θ)-0.8341 (θ: [deg])
I met it. According to the third aspect of the present invention, the first aspect
In the invention of the combustion chamber of the direct injection type diesel engine,
Between the combustion chamber wall below the recess and the annular recess
A flat portion was provided. According to the fourth aspect of the present invention, the direct
In the invention of the combustion chamber of the injection type diesel engine, the combustion chamber
The distance from the bottom to the annular recess on the combustion chamber wall
h_TwoIf the combustion chamber depth is H, 0.1 <h_Two/ H <0.
5 was satisfied. In the invention of claim 5,
In the combustion chamber of the direct injection diesel engine according to the invention of claim 1
The combustion chamber opening diameter is d₁The maximum diameter of the annular recess
d_TwoAnd combustion chamber diameter d_ThreeThen d_Three<D₁<D_TwoNaruseki
I met the clerk. In the invention of claim 6, claim 1
In the combustion chamber of the direct injection diesel engine of the invention of the invention,
An annular projection with a chamfer at the opening of the combustion chamber was provided. Contract
According to the invention of claim 7, in the direct injection type diesel engine of the invention of claim 1,
In the combustion chamber of the Selle engine, the bottom of the combustion chamber and the central projection
Were connected by a smooth curved surface. According to the invention of claim 8,
Item 1. The combustion chamber of the direct injection diesel engine according to the invention of Item 1.
And the height of the central projection is h_ThreeThen h_Two<H_ThreeNaruseki
I met the clerk.

[0005]

FIG. 1 shows a combustion chamber 100 of a direct injection type diesel engine embodying the present invention.
FIG. In FIG. 1, the combustion chamber 100 is formed on the top surface (upper end surface) 90 a of the piston 90. The wall 9 of the combustion chamber 100 is provided with an annular recess 6 having a maximum diameter of d ₂ . Between the annular recess portion 6 and the wall 9 is provided with a flat portion 4 of a width d _4. The opening 3 of the combustion chamber 100 is chamfered. The chamfer may be formed on a slope, but a rounded shape is more preferable than a slope. The bottom 5 is provided with a central projection 7 having a height h ₃ and a diameter d ₅ . The central projection 7 and the bottom 5 are connected by a smooth curved surface 8.

The fuel 2 is injected from the fuel injection nozzle 1, and the injection angle θ is set so that the fuel 2 collides with the annular recess 6. The distance d ₃ <between the opening diameter d ₁ of the opening 3, the diameter d _{3 of the} wall surface 9, and the maximum diameter d ₂ of the annular recessed portion 6.
There is a relationship d ₁ <d ₂ .

As shown in FIG. 2A, the fuel 2 is injected from the fuel injection nozzle 1 toward the annular recess 6.
As shown in FIG. 2B, the fuel 2 that has collided with the annular concave portion 6 is miniaturized into the fuel 2b by the collision. afterwards,
As shown in FIG. 2C, the atomized fuel 2b spreads in the combustion chamber 100, is further atomized by the swirl (air flow) into the fuel 2c, and mixes well with air.

Thereafter, although not shown, the piston 90
Descends, the mixture flows out of the combustion chamber 100 to the squish area 95, and the uniformly mixed fuel 2c burns.

[0009] As shown in FIG. 3, the total volume which the piston 90 is formed by the piston 90 and the cylinder 91 when it reaches the top dead center to a total compression volume V _C, the fuel injection nozzle as shown in FIG. 4 Assuming that the volume of the area below the center axis 2a of the fuel 2 injected from the fuel cell 1 (on the bottom 5 side) is the volume _VL and the injection angle of the fuel 2 is θ, V is such that the following expression (1) is satisfied. Set _C , _VL and θ. V _L / V _C ≦ 0.0088 × θ−0.8341 (1) (θ [deg])

In order to satisfy equation (1), V _C , V _L and θ
Is set in the combustion chamber 10 at the beginning of combustion.
Within 0, the fuel and air are well mixed, and in the later stage of combustion, uniform combustion can be performed in the entire compression volume V _C.

FIG. 5 is a schematic sectional view comparing a cross section of a conventional combustion chamber indicated by a broken line with a cross section of the combustion chamber 100 of the present invention (the invention of claims 1 to 8) indicated by a solid line.

[0012] Combustion chamber 100, expand the opening portion 3 as indicated by arrow A ₁ in comparison with the conventional combustion chamber radially outward,
Narrowing the wall 9 as shown by arrow A ₂ radially inward, and further expand the annular recess 6 as shown by arrow A ₃ radially outward.

FIG. 6 is a graph showing the relationship between the fuel injection angle θ and the volume ratio V _L / V _{C in} the conventional combustion chamber and the combustion chamber 100 of the present invention.

As shown in FIG. 6, the graph of the combustion chamber 100 is located below the graph of the conventional combustion chamber, and the graph of the combustion chamber 100 is represented by the following equation (1). Therefore, the above equation (1) shows a hatched portion in FIG. 6, and good combustion can be performed by setting V _C , _VL and θ within the range of the hatched portion.

As shown in FIG. 1, when the depth of the combustion chamber 100 is H, and the distance from the bottom 5 to the annular recess 6 (height of the annular recess 6) is h ₂ , the following equation (2) is obtained. By setting H and h ₂ so as to satisfy
Within 0, the fuel and the air mix well, and good combustion can be performed. 0.1 <h ₂ /H<0.5 (2)

FIG. 7 is a graph showing the relationship between h ₂ / H and the relative value (degree) of exhaust smoke density. As shown in FIG. 7, in general, when the value of h ₂ / H is in the range of 0.1 to 0.5 (within a range satisfying the expression (2)), the exhaust smoke concentration is equal to or less than the allowable value of 0.8. Becomes

In the combustion chamber 100 described above, good combustion can be obtained regardless of the injection pressure of the fuel 2 injected from the fuel injection nozzle 1 and the injection amount per unit time.

[0018]

When the cylinder diameter, according to the present invention (piston diameter D) is small, difficult to mix with the injected fuel and air, but in the invention of claim 1, as indicated by arrow A ₁ to A ₃ in FIG. 5, Since the bottom 5 side of the combustion chamber 100 was narrowed inward in the radial direction, and the opening 3 and the annular recess 6 were expanded radially outward,
Even when the cylinder diameter is relatively small, the atomized fuel 2 collides with the annular recess 6 to promote the fragmentation and evaporation of the fuel 2 particles, and the swirl (air flow) generated in the combustion chamber 100 causes the fuel to flow. The air-fuel mixture is satisfactorily mixed with the air to generate an air-fuel mixture. In the later stage of the combustion, the air-fuel mixture further flows out of the combustion chamber 100 to the squish area 95, and the uniformly mixed fuel 2c burns, thereby reducing the exhaust smoke concentration. Can be good.

An annular recess 6 is formed on the wall of the collision portion of the fuel 2.
Is provided so that the bottom 5
The generation of nitrogen oxides can be suppressed by suppressing the flow to the air and suppressing the combustion of the fuel by suppressing the mixing with the air. In addition, since the hollow portion 6 suppresses the diffusion of the air-fuel mixture to the bottom portion 5 in the latter stage of the combustion, the exhaust smoke density is improved. As described above, the invention of claim 1 can exert a remarkable effect particularly in improving combustion of an engine having a relatively small cylinder diameter.

According to the second aspect of the present invention, V _L , V _C and θ are set so as to satisfy the expression (1).
As compared with the combustion chamber of the invention, the generation of nitrogen oxides can be further reduced in the early stage of combustion, and the exhaust smoke concentration can be further reduced in the latter stage of combustion.

According to the third aspect of the present invention, since the flat portion 4 is provided between the annular concave portion 6 and the wall surface 9, the flow of the fuel to the bottom portion 5 can be suppressed, and the exhaust smoke density is improved. .

According to the fourth aspect of the present invention, the distance from the bottom 5 to the annular concave portion 6 is defined so as to satisfy 0.1 <h ₂ /H<0.5 (formula (2)), and the mixing does not proceed. By suppressing the diffusion of the fuel to the bottom part 5, the exhaust smoke density can be reduced.

According to the fifth aspect of the present invention, by defining d ₃ <d ₁ <d ₂ , the outflow of fuel from the combustion chamber 100 to the squish area 95 can be appropriately adjusted. That is, in the initial combustion suppresses the outflow of the squish area 95 of the fuel in the combustion late mixture mixed with air, and burned flows out into the squish area 95 as spread over the entire volume V _c shown in FIG. 3 So the volume V
_c Uniform and good combustion can be performed over the entire area.

According to the sixth aspect of the present invention, the opening 3 is formed by an annular projection directed inward in the radial direction, and since the annular projection is chamfered, the air resistance is reduced, and the air flows into the combustion chamber 100 during the compression stroke. Can easily flow, and the fuel and air can be mixed well. Therefore, good combustion can be obtained.

According to the seventh aspect of the present invention, by connecting the bottom portion 5 and the central projection portion 7 with a smooth curved surface, the swirl (air flow) is not attenuated, so that an environment in which fuel and air are easily mixed is provided. Thus, the mixture can be satisfactorily burned.

According to the eighth aspect of the present invention, the height h ₃ of the central projection 7 is set higher than the height h ₂ of the annular recessed portion, so that the height h ₃ of the center recessed portion 7 extends radially inward of the combustion chamber 100 along the bottom 5. The traveling direction of the traveling fuel can be directed to the upper side of the combustion chamber, so that the combustion and the air can be easily mixed, and good combustion can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a combustion chamber according to claims 1 to 8;

FIG. 2 (a) is a schematic cross-sectional view of a combustion chamber immediately before fuel collides with an annular recess. (B) is a schematic cross-sectional view showing a state in which the fuel colliding with the annular hollow portion is in the middle of spreading into the combustion chamber. (C) is a schematic sectional view showing a state in which the finely divided fuel has spread into the fuel chamber.

FIG. 3 is a schematic sectional view of a combustion chamber showing a total compression volume when a piston reaches a top dead center.

FIG. 4 is a schematic sectional view showing a region below a central axis of fuel to be injected in FIG. 3;

FIG. 5 is a schematic sectional view comparing the shapes of a conventional combustion chamber and the combustion chambers according to the first to eighth aspects of the present invention.

6 is a graph showing the relationship between the ratio of the volume shown in FIG. 4 to the volume shown in FIG. 3 and the fuel injection angle in the conventional combustion chamber and the combustion chamber according to the first to eighth aspects of the present invention.

FIG. 7 is a graph showing the relationship between the distance from the bottom of the annular depression to the depth of the combustion chamber and the exhaust smoke concentration.

[Explanation of symbols]

1 fuel injection nozzle 2 injection fuel 2a injection fuel central axis 3 opening 4 flat portion 5 a bottom 6 annular recess 7 central projection portion 8 curved 9 walls 90 the piston 100 combustion chamber d ₁ opening opening diameter d ₂ annular recess maximum diameter d ₃ wall diameter d ₄ flats width H combustion chamber depth h ₂ annular recess height h ₃ central projections height θ fuel injection angle V _C total compression volume V _L combustion chamber lower volume

Claims (8)

[Claims] An annular recess for injecting fuel from a fuel injection nozzle is provided on a wall surface of a combustion chamber, and an opening diameter of the opening of the combustion chamber is smaller than the maximum diameter of the annular recess and is closer to the bottom of the combustion chamber than the annular recess. A combustion chamber for a direct injection diesel engine, wherein the combustion chamber is set to have a diameter larger than a wall diameter of the combustion chamber and a central projection having a height and a diameter at which fuel injected from a fuel injection nozzle does not collide is provided at the bottom of the combustion chamber. 2. The volume of the combustion chamber below the central axis of the fuel injected from the fuel injection nozzle is _VL , and the total compression volume is V _C.
Then, V _L / V _C ≦ 0.0088 × injection angle (θ) −
2. The combustion chamber of a direct injection diesel engine according to claim 1, wherein 0.8341 (θ: [deg]). 3. The combustion chamber of a direct injection diesel engine according to claim 1, wherein a flat portion is provided between a wall surface of the combustion chamber below the annular hollow portion and the annular hollow portion. 4. When the distance from the bottom of the combustion chamber to the annular recess provided in the wall of the combustion chamber is h ₂ , and the depth of the combustion chamber is H,
_2. The combustion chamber of a direct injection diesel engine according to claim 1, wherein 0.1 <h2 / H <0.5. 5. When the opening diameter of the combustion chamber is d ₁ , the maximum diameter of the annular recess is d ₂ , and the diameter of the combustion chamber is d ₃ , d ₃ <d ₁ <d _2.
The combustion chamber of a direct injection diesel engine according to claim 1, wherein 6. The combustion chamber of a direct injection diesel engine according to claim 1, further comprising an annular projection having a chamfered opening in the combustion chamber. 7. The combustion chamber of a direct injection diesel engine according to claim 1, wherein the bottom of the combustion chamber and the central projection are connected by a smooth curved surface. 8. Assuming that the height of the central projection is h ₃ , h ₂ <
combustion chamber of direct-injection diesel engine according to claim 1 which is h _3.