JPH0148378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion chamber for a direct injection internal combustion engine having a main combustion chamber having a concave portion at the top of a piston.

Conventionally, the combustion chamber of a general direct injection internal combustion engine has a first
As shown in the side sectional view in the figure and the plan view in Figure 2,
A trodile type piston 1 is used, which has a main combustion chamber with a recess 2 at the top.If the diameter d of the recess 2 is increased for the same cylinder inner diameter D, the amount of water from the nozzle of the fuel injection valve 3 increases. The fuel spray travel distance l increases indirectly, and the spray travel distance l ₁ < l ₂ , whereas the exhaust odor level at low speed and low load is as follows for the same effective compression ratio ε as shown in Figure 3. It becomes good, and is improved by further increasing the effective compression ratio ε.

In FIG. 2, θ indicates the spread angle of the fuel spray from each nozzle, and arrow S indicates the swirl direction.

Increasing the above effective compression ratio ε means that the piston 1
In addition, increasing the diameter d of the recess 2 reduces the squishing speed in inverse proportion to d/D.

As a result, the main combustion chamber volume ratio and squishing speed decrease, resulting in a significant decrease in the maximum output P _s as shown in Figure 4. Improving the effective compression ratio ε is achieved by
Reduces maximum output at high loads.

In other words, in order to completely burn the small amount of fuel injected at low speed and low load in a direct injection internal combustion engine in the recess 2 of the piston 1 and improve the exhaust odor, it is necessary to increase the effective compression ratio ε and expand the spray reach l. is necessary.

If this is done in a conventional trodile-shaped combustion chamber, it is possible to reduce the irritating odor of the exhaust, but at high speeds and high outputs, the high compression ratio and the extended spray reach cause premature ignition of the fuel, and the squishing force is reduced. As a result, the combustion period becomes longer and maximum power, exhaust color, and fuel consumption worsen.

As a companion to the above, Japanese Patent Publication No. 51-29242 and Japanese Patent Publication No. 51-29242 concerning the combustion chamber of direct-injection diesel engines,
In the inventions of No. 29243 and Japanese Patent Publication No. 51-29244, the fuel spray is not applied to the corner of the main combustion chamber of the recessed part, but is applied to a straight part and reflected. Since the ratio r/R to the collision radius from 0 to 0.075, r is always smaller than R.

If the curvature r is small, the fuel spray will accumulate after collision, slowing down the evaporation rate, prolonging combustion, and deteriorating the performance. In addition, residues in the fuel will accumulate, further deteriorating the above-mentioned performance.

In addition, as in the invention of Utility Model Application Publication No. 168729/1983 regarding the combustion chamber structure and the invention of Japanese Patent Publication No. 16881/1983 regarding the combustion chamber of a diesel engine, attempts have been made to curve the impact surface of the fuel spray to a small extent or to scatter it by reflection. When a small amount of fuel is injected at low force, the injection speed is very low compared to when it is under high load, and there is almost no reflection.As a result, unburnt fuel accumulates on the wall that was set up to reflect it, generating unburned or unnatural gas. do,
It has the disadvantage of emitting a pungent exhaust odor.

Furthermore, Utility Model Application Publication No. 57-107821 regarding the combustion chamber of a diesel engine, and Utility Model Application Publication No. 55-4515 and Utility Model Application Publication No. 1983 concerning the combustion chamber of a direct injection diesel engine.
In the famous invention of No. 139631, a small amount of spray is completely combusted in compressed air at low force.
Considering the shape of the concave part, there is a drawback that the brake is applied to the swirl during compression, and in reality, the spray does not flow due to the swirl.
In the invention of No. 139631, since the curvature of the inner wall of the fuel collision part is small, unburned fuel does not spread during a small amount of spraying, emitting unburned gas, and the opening area is large relative to the piston area, reducing the squishing force. Another disadvantage is that the airflow in the recess due to swirl decreases during compression.

Therefore, the present invention solves the above-mentioned conventional drawbacks, and
This was done with the aim of improving the irritating odor of the exhaust from direct-injection internal combustion engines at low speeds and low power, as well as improving maximum output, exhaust color, fuel efficiency, etc. when running at high speeds and high outputs.

That is, the present invention provides a direct injection internal combustion engine having a main combustion chamber with a concave portion at the top of the piston, in which the concave portion is provided with an air flow from the center of the nozzle to the wall surface on which the fuel spray of fuel injected from each nozzle of the fuel injection valve collides. distance
L ₁ is 0.25 to 0.35 times the inner diameter of the cylinder, and a fuel collision wall surface corresponding to the fuel spray spread angle θ = 18° to 25° is formed in accordance with the number of nozzles,
The distance between these fuel collision walls is set at a distance L ₂ from the nozzle center that is 0.7 to 0.9 times the distance L ₁ above, and the curvature of the inner wall surface on the swirl inflow side is r ₁ and the curvature of the inner wall surface on the swirl outflow side is curvature r. Continuously forming the recess in a pinwheel shape with an intermediate wall surface having a curvature _r2 larger than ₁ ,
In addition, the bottom of the main combustion chamber is made deep so that the injected fuel does not touch the bottom, and the height of the bottom between other injected fuels is increased.There is a polyhedral pyramid-shaped convex part that is the same as the number of fuel valve nozzles. In addition, a partial shelf is formed at the upper part of each wall surface on which the fuel spray collides.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a side sectional view showing a combustion chamber of a direct injection internal combustion engine in Embodiment 1 of the present invention, and
FIG.
In this direct injection internal combustion engine, the recess 2 is shaped like a wall surface 2A on which the fuel spray injected from each nozzle of the fuel injection valve 3 collides with the spread angle θ=18° to 25°. As shown in the plan view of the main part in Fig. 7, the distance L ₁ from the center No. of the nozzle to the wall it collides with is L 1 = L ₁ =
(0.25~0.35)×D, fuel collision wall 2A
are formed corresponding to the number of injection ports of the fuel injection valve 3.

Next, the distance between the four fuel collision walls 2A is set to a distance _L2 from the nozzle center No. corresponding to _0.7 to 0.9 times the distance L1 from the nozzle center No.
The inner wall surface on the swirl inflow side has a curvature r ₁ and the inner wall surface on the swirl outflow side has a curvature r ₂ larger than the curvature r _1.It is formed by an intermediate wall surface 2B, and the surface 2A on which the fuel spray collides with the intermediate wall surface 2B. are continuously formed into a pinwheel shape.

Furthermore, in this embodiment, the bottom of the recess 2 in the main combustion chamber is formed to have a low height so that the injected fuel sprays do not touch each other, and the waste portions between the fuel sprays are filled. A polyhedral pyramid-shaped convex portion 2C having the same number of nozzles as shown in FIG. 8 is formed with a raised bottom height.

In the recess 2 formed in the shape of a windmill in this way, the swirl shown in the S direction in FIG.
The fuel film after collision flows smoothly and is formed on the inner wall of the piston, which reduces the opening area relative to the piston surface area and prevents the squishing force from decreasing.

As mentioned above, the nozzle center No. on the inner wall surface of the recess 2
By setting the distances L ₁ and L ₂ from L ₂ /L ₁ =0.7 to 0.9, the arrow E in FIG.
A vortex as shown in is generated, which promotes the mixing of fuel spray and air, and also improves the utilization of air by flowing out onto the upper surface of the piston.

Note that the position of the center point of the curvature _r1 is not limited to the first embodiment shown in FIG. 7, and may coincide with the center of the injected fuel spray as shown in the second embodiment shown in FIG. good.

Next, in the present invention, in the recess 2 formed in the shape of a windmill as described above, a small shelf 5 whose width b corresponds to 1 to 3% of the cylinder inner diameter D is provided at the upper part of each wall surface on which the fuel spray collides. They are formed partially to prevent collision fuel from initially flowing out into the gap on the upper surface of the piston 1.

That is, as shown in the enlarged plan view of the shelf-equipped recess in FIG. 11, after the collision fuel spray is slightly blown away by the swirl S, the part beyond the shelf-equipped section C is defined as the shelf-less section d without the shelf 5. As a result, the partially combusted gas can easily flow out from the shelfless part d into the gap on the top surface of the piston 1 as shown by the arrow, improving the air utilization efficiency and increasing the engine output. .

The planar shape of this shelf 5 is as shown in FIG.
It is formed with a curvature R along the direction, and its cross-sectional shape has an acute corner as shown in Fig. 12, or a curvature as shown in Example 3 of Fig. 13.
It may be formed in any way, such as having a rounded corner of R ₁ .

In the case of a shelf with a shelf 5 as described above,
The diagram in FIG. 14 shows the performance of the maximum pipe pressure Pmax and the exhaust color Sd corresponding to the injection timing in the case of no shelf without the shelf 5, and the effects of the shelf are shown.

In an internal combustion engine having a combustion chamber configured as described above, when a small amount of fuel is sprayed at low power, the shelf 5
The fuel spray does not come into contact with the shelf 5, and the blue white smoke and pungent odor are improved as in the case without the shelf 5, but
When a large amount of fuel collides with the wall surface during high output of the engine and is slightly blown away by the swirl S, the shelf 5 prevents the fuel spray from spreading upward due to the collision and stays within the recess 2.

Therefore, as shown in the 14th diagram, the effect of the squishing force is obtained, and the initial outflow of the colliding fuel to the upper surface of the piston 1 is prevented, even when the maximum cylinder pressure Pmax is suppressed by retarding the spray timing. There is very little deterioration in exhaust color.

Next, in Embodiment 4 shown in FIG. 16, which is a plan view of the main part in FIG. A partial shelf 5 is provided at the upper part of the wall surface, and a tapered part 6 at an angle dθ is formed on the wall surface slightly downstream of the shelf 5 in the flow direction of the swirl S so that the gas can easily flow to the upper surface of the piston 1. There is.

By forming such a shelf 5 and tapered part 6, a part of the impinging jet of fuel does not flow out onto the upper surface of the piston 1 when the engine is under high power, and is evaporated by the subsequent swirl S while being evaporated into the recessed part 2. The fuel burns from the inside, and the fuel adhering to the inner wall of the recess 2 is gasified and flowed away, flowing out from the tapered part 6 to the upper surface of the piston 1 and being completely combusted.

Therefore, even if the maximum cylinder pressure at which the spray timing is delayed is low, the unused gas is combusted, resulting in a good exhaust color, clean combustion, and an internal combustion engine with excellent high output performance. .

Next, a side sectional view of the main part of the piston in Fig. 17, Fig. 18 which is a plan sectional view of the piston 1 in Fig. 17, and Fig. 19 which is an enlarged plan sectional view of the main part in Fig. Embodiment 5 of the invention is a combustion chamber of a direct injection internal combustion engine having almost the same configuration as Embodiments 1 to 4, and the same parts are indicated by the same part numbers, but the differences are the same as in Embodiment 1. The glow plug 10 is disposed on the upstream side of the wall surface 2A in the direction of the swirl shown by the arrow S on which the fuel spray F of the combustion chamber of the recess 2 collides.

The glow plug 10 is provided so as to be inclined at an angle α to the upper surface of the piston 1, as shown in FIG. 17, and is also provided slightly upstream of the swirl S from the center of the fuel spray F, as shown in FIG. 18.

By arranging the glow plug 10 at such a position, the glow plug 10 is
By generating the turbulence shown by X on the downstream side of swirl S, which is marked with , mixing with fuel injection F is promoted, it is possible to improve engine startability, and improve high-load performance, especially exhaust color. This can improve low-power combustion.

In particular, in the case of a combustion chamber consisting of a concave portion 2 formed in the shape of a windmill as in the present invention, the distance L ₁ from the nozzle center No. to the wall surface with which the fuel spray F collides is larger than in the case of a conventionally shaped concave portion. As a result, the glow plug 10 can be moved away from the nozzle center No., making it easy to install the glow plug 10. Furthermore, related to this, since the spray reach distance from the nozzle center No. to the glow plug 10 is large, ignition is good and starting is easy. Improves sex and low power combustion.

Therefore, in a direct-injection internal combustion engine to which the combustion chamber of the present invention is applied, in order to completely burn a small amount of fuel in compressed air at low speed and low power, it is necessary to reduce the spray reach by using an appropriate effective compression ratio. Furthermore, when a large amount of fuel is applied to the collision area at high speeds and high forces, part of the collision jet does not flow into the gap on the top surface of the piston. In addition, the inner wall has a gentle shape so that the swirl of the suction swirl flows smoothly in a film-like manner on the inner wall surface downstream, and the inlet side has a shape that prevents unnecessary swirl from occurring in the swirl flowing into the injected fuel.

In addition, some unburned evaporated gas flows out from the inner wall downstream of the swirl after the fuel collision to the upper surface of the piston, improving the utilization of air on the upper surface of the piston.

As a result, the maximum output at high speeds and high loads increases, and the exhaust color and fuel efficiency are improved.

Note that the present invention is mainly effectively applied to direct injection diesel engines.

[Brief explanation of drawings]

Figure 1 is a side sectional view of the combustion chamber of a conventional direct injection internal combustion engine, Figure 2 is a plan view of Figure 1, and Figure 3 is the level of exhaust odor, effective compression, and spray in the combustion chamber of Figure 1. Figure 4 is a diagram showing the relationship between the maximum output, effective compression ratio, and spray travel distance in the combustion chamber of Figure 1, and Figure 5 is a diagram showing the relationship between the maximum output and effective compression ratio in the combustion chamber of Figure 1, and the spray travel distance. 6 is a side sectional view showing the combustion chamber of a direct injection internal combustion engine, FIG. 6 is a plan sectional view in the - direction of FIG. 5, FIG.
The figure is a plan sectional view showing the bottom of the recess shown in Fig. 5, and Fig. 9 is a plan sectional view showing the vortex generated in the recess shown in Fig. 5.
FIG. 10 is a plan sectional view of the concave portion of the combustion chamber in Embodiment 2 of the present invention, FIG. 11 is an enlarged plan view of the main part of the recess shown in FIG. 6, and FIG. 12 is a side sectional view of the main part of FIG. 11. , FIG. 13 is a side cross-sectional view of the main part of the combustion chamber recess in Example 3 of the present invention, and FIG. 14 is a comparison of the combustion chamber with a shelf of the present invention with that without a shelf, and shows the exhaust color and maximum in-cylinder pressure. Diagrams showing the improvement effect, FIG. 15 is a plan view of the main part of the recessed part of the combustion chamber in Example 4 of the present invention, FIG. 16 is a side sectional view of the main part of FIG. 15, and FIG.
The figure is a sectional side view of the main part of the combustion chamber concave portion of the piston in Embodiment 5 of the present invention, and FIG. 18 is a -
FIG. 19 is an enlarged plan sectional view of the main part near the glow plug in FIG. 18. 1...Piston, 2...Recess, 2A...Wall surface,
2B...Intermediate wall surface, 5...Shelf, D...Cylinder inner diameter, _L1 , _L2 ...Distance, No...Nozzle center, _r1 , _r2
……curvature.

Claims (1)

[Claims] 1 In a direct-injection internal combustion engine that has a main combustion chamber with a recess at the top of the piston, the distance L ₁ from the center of the nozzle to the wall surface on which the fuel spray of fuel injected from each nozzle of the fuel injection valve collides with the recess is defined as Fuel collision walls that are 0.25 to 0.35 times the cylinder inner diameter and that correspond to a fuel spray spread angle θ = 18° to 25° are formed in accordance with the number of nozzles, and the distances between these fuel collision walls are The distance L ₂ from the center of the nozzle is set to 0.7 to 0.9 times ₁ , and the curvature of the inner wall surface on the swirl inflow side is r ₁ and the curvature r ₂ is larger than the curvature r ₁ of the wall surface on the swirl outflow side. , the recess is formed in the shape of a windmill, and the bottom of the main combustion chamber is deep so that the injected fuel does not touch the bottom, and the number of fuel valve nozzles is increased so that the height of the bottom between other injected fuels is increased. A pyramid-shaped convex portion of the same polyhedron is provided, and further,
A combustion chamber for a direct injection internal combustion engine, characterized in that a partial shelf is formed at the top of each wall surface on which fuel spray collides.