WO2001012966A1

WO2001012966A1 - Combustion chamber of direct injection diesel engine

Info

Publication number: WO2001012966A1
Application number: PCT/JP2000/005320
Authority: WO
Inventors: Keiichiro Yuzaki; Michihiko Hara; Katsuhiko Nagakura
Original assignee: Yanmar Diesel Engine Co., Ltd.
Priority date: 1999-08-13
Filing date: 2000-08-09
Publication date: 2001-02-22
Also published as: TW444099B

Abstract

A combustion chamber (100) of a direct injection diesel engine capable of sufficiently mixing fuel (2) injected from a fuel injection nozzle (1) with air to produce approximately uniform mixture so that approximately a uniform combustion can be performed in the entire area of the combustion chamber, wherein an annular recessed part (6) having a combustion chamber wall surface (9) onto which the fuel (2) is injected from the fuel injection nozzle (1) is provided, an opening diameter (d1) of a combustion chamber opening part (3) is set smaller than the maximum diameter (d2) of the annular recessed part (6) and larger than a diameter (d3) of a combustion chamber wall surface nearer a combustion chamber bottom part (5) than the annular recessed part (6), a center projected part (7) with a height (h3) and a diameter (d5) that do not allow the fuel (2) injected from the fuel injection nozzle (1) to collide is provided at the combustion chamber bottom part (5), a flat part (4) is provided between the combustion chamber wall surface (9) lower than the annular recessed part (6) and the annular recessed part (6), and a chamfered annular projected part is provided on the combustion chamber opening part (3).

Description

Description Direct combustion diesel engine combustion chamber Technical field

The present invention relates to a structure of a combustion chamber of a direct injection diesel engine. Background art

In the combustion chamber of the conventional reentrant direct injection diesel engine shown by the broken line in FIG. It is difficult to perform unbiased and uniform combustion by making full use of the entire volume of the combustion chamber. As a result, black smoke, nitrogen oxides, and the like are easily generated. Disclosure of the invention

(Technical problem to be solved by the invention)

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

In the early stage of combustion, when the fuel collides with the combustion chamber wall, the kinetic energy of the fuel promotes splitting and evaporation on the combustion chamber wall to diffuse the fuel into the space near the combustion chamber wall. It is an object of the present invention to provide a combustion chamber structure that can mix fuel and air satisfactorily by swirling (air flow) in the combustion chamber in the latter stage of combustion. (How to solve it)

According to the first aspect of the present invention, an annular recessed portion through which fuel is injected from a fuel injection nozzle is provided on a wall of the combustion chamber, and the opening diameter of the opening of the combustion chamber is smaller than the maximum diameter of the annular recessed portion and the combustion chamber is larger than the annular recessed portion. Set the diameter of the center of the combustion chamber wall larger than the bottom wall diameter so that the fuel injected from the fuel injection nozzle does not collide. Provided at the bottom.

In the invention of claim 2, a plurality of annular recesses are provided in the combustion chamber of the direct injection diesel engine of the invention of claim 1.

According to the third aspect of the present invention, in the combustion chamber of the direct injection diesel engine according to the first or second aspect of the present invention, a flat portion is provided between the wall of the combustion chamber below the annular recess and the annular recess. Provided.

According to the invention of claim 4, in the combustion chamber of the direct injection diesel engine according to any one of claims 1 to 3, combustion below the center axis of the fuel injected from the fuel injection nozzle is performed. Assuming that the chamber volume is V _I ^ and the total compression volume is V _C , VLZV _C ≤ 0. 0088 X injection angle (Θ)-0.834 1 (Θ [deg]). According to the invention of claim 5, in the combustion chamber of the direct injection diesel engine according to any one of claims 1 to 3, the distance from the bottom of the combustion chamber to the annular recess provided on the wall of the combustion chamber is reduced. Assuming that h ₂ and the depth of the combustion chamber are H, 0.1 <l ₂ / H and 0.5.

In the invention of claim 6, claim 1及至claimed in the combustion chamber of a direct-injection Ishiki diesel engine of the invention according to any one of claims 3, a combustion chamber opening diameter dp annular recess portion maximum diameter d _2, the combustion chamber When the diameter as d _3, and a (1 district ₃ (1 ₁ <3 _2.

According to a seventh aspect of the present invention, in the combustion chamber of the direct injection diesel engine according to any one of the first to third aspects of the invention, an annular projection having a chamfered opening in the combustion chamber is provided.

In the invention of claim 8, in the combustion chamber of the direct injection diesel engine according to any one of claims 1 to 3, the bottom of the combustion chamber and the central projection are connected by a smooth curved surface.

In the invention of claim 9, in a combustion chamber of a direct-injection Ishiki diesel engine of the invention according to any one of claims 1及至claim 3, when the height of the central projections and h _3, h ₂ rather h ₃ And

In the combustion chamber of the direct injection diesel engine according to the tenth aspect of the present invention, the opening diameter of the combustion chamber is set to be smaller than that of the inside of the combustion chamber, and the annular shape is formed on the wall of the combustion chamber within a range where fuel is injected from the fuel injection nozzle. Of the fuel injected from the fuel injection nozzle A central projection that has a height that does not collide and that can change the direction of fuel flow so that the fuel that collides with the combustion chamber wall surface and proceeds from the combustion chamber wall surface to the center of the combustion chamber along the bottom of the combustion chamber is directed upward. Was provided at the bottom of the combustion chamber.

According to the invention of claim 11, in the combustion chamber of the direct injection diesel engine of the invention of claim 10, the injection axis of the fuel injected from the fuel injection nozzle is set to be above the wall projection. .

According to the invention of claim 12, in the combustion chamber of the direct injection type diesel engine of the invention of claim 10 or claim 11, a concave portion having an annular and smooth surface is provided above the wall projection. The wall projection and the depression are smoothly connected to each other, so that the path of the fuel that collides with the combustion chamber wall is divided into two directions: the cylinder head side and the combustion chamber bottom side.

According to the invention of claim 13, in the combustion chamber of the direct injection type diesel engine of the invention of claim 12, the angle formed by the tangent to the depression in the wall projection and the candy line is 45 to 90 degrees. Was set within the range.

According to the invention of claim 14, in the combustion chamber of the direct injection diesel engine of the invention of claim 10, a value obtained by dividing the height from the bottom of the combustion chamber to the wall projection by the depth of the combustion chamber is 0.3. It was set in the range from 0.5 to 0.5.

According to a fifteenth aspect of the present invention, in the combustion chamber of the direct injection type diesel engine according to the thirteenth aspect or the fifteenth aspect, the opening diameter of the opening of the combustion chamber, the inner diameter of the combustion chamber, and the maximum diameter of the hollow portion are provided. In order of increasing.

According to the invention of claim 16, in the combustion chamber of the direct injection diesel engine of the invention of claim 10, in the combustion chamber, the bottom of the combustion chamber and the central projection are connected to each other with a smooth curved surface. The combustion area of fuel in the central part was reduced.

According to a seventeenth aspect of the present invention, in the combustion chamber of the direct injection diesel engine according to the tenth aspect, the height of the central projection from the bottom of the combustion chamber is higher than the height of the wall projection from the bottom of the combustion chamber. .

The invention according to claim 18 is characterized in that, in the combustion chamber of the direct injection diesel engine according to the invention according to claim 10, the combustion chamber depth and the screw are set so that the value obtained by dividing the combustion chamber depth by the biston diameter is smaller than 0.2. The size of the ton diameter was set. (Effective effect than conventional technology)

If the cylinder diameter D (piston diameter) is small, it is difficult for the injected fuel and air to mix. However, in the invention of claim 1, sea urchin I indicated by the arrow A have A ₂ and A ₃ in FIG. 5, narrowed bottom 5 side of the combustion chamber 1 0 0 radially inwardly, and the opening 3 and the annular rather pot As shown in Fig. 2, even when the cylinder diameter is relatively small, the atomized fuel 2 collides with the annular recess 6 so that the particles of the fuel 2 are dispersed even when the cylinder diameter is relatively small. Splitting and evaporation can be promoted. Therefore, the swirl (air flow) generated in the combustion chamber 100 can mix the fuel and air satisfactorily to generate a uniform mixture. Further, as shown in FIG. 2 (c), in the latter stage of the combustion, the air-fuel mixture flows out of the combustion chamber 100 to the squish area 95, and the uniformly mixed fuel 2c burns, and the exhaust smoke The density can be improved. By providing an annular depression 6 on the wall of the collision part of the fuel 2, the flow of fuel to the bottom 5 is suppressed in the initial stage of combustion, and the mixing with air is suppressed to suppress the combustion of fuel. Can be suppressed. In addition, since the depression 6 suppresses the diffusion of the air-fuel mixture to the bottom 5 in the latter stage of the combustion, the highly concentrated fuel does not stay in the bottom 5 and the exhaust smoke concentration is improved. As described above, the invention of claim 1 can exert a remarkable effect particularly on the improvement of combustion of an engine having a relatively small cylinder diameter (50 to 150 mm).

According to the invention of claim 2, a plurality of annular concave portions (the annular concave portion 6 and the concave portion 10 and the curved surface 11 in FIG. 8, and the annular concave portion 6 and the second concave portion 15 in FIG. 10) are provided. Thereby, the traveling direction of the fuel that collides with the wall surface (annular concave portion 6) and flows toward the bottom portion 5 can be directed toward the center of the combustion chamber. Therefore, fuel does not need to stay near the small bottom 5 of the swirl. Also, by providing the central projection 7, the flow of fuel to the center of the combustion chamber where swirl is reduced can be prevented, and the fuel can be mixed well with air in a large swirl region to achieve uniformity. Since a mixture can be generated, good combustion can be performed. Therefore, the amount of generated nitrogen oxides and black smoke can be reduced. By providing a plurality of annular recesses, a remarkable effect can be obtained particularly when the injection pressure of the fuel 2 from the fuel injection nozzle 1 is high or when the amount of injection per unit time is large. In the invention of claim 3, since the flat portion 4 (FIG. 1) is provided between the annular recess 6 and the wall surface 9, the flow of fuel to the bottom 5 can be suppressed, and the exhaust smoke concentration is improved. Can be

In the invention of claim 4, the generation of the initial combustion by setting the V have V _c and Θ so as to satisfy the equation (1), according to claim 1及至nitrogen oxides than combustion chamber of the invention of claim 3 In the later stage of combustion, the exhaust smoke concentration can be further reduced. Therefore, good combustion can be performed from the initial combustion period to the later combustion period.

In the invention of claim 5, the distance from the bottom 5 to the annular recess 6 Equation (2) (0. 1 < h 2 / H <0. 5) and so as mixing was defined that the bottom 5 does not proceed By suppressing the fuel diffusion, the exhaust smoke concentration (S d) can be reduced as shown in FIG.

In the invention of claim 6, as shown in FIG.

By defining each dimension to be dz, it is possible to appropriately adjust the flow of the fuel from the inside of the combustion chamber 100 to the squish area 95. In other words, in the early stage of combustion, fuel 2 mixes well with air in the region of large swirl (the region occupied by the mixture 2c in Fig. 2 (c)) to produce an air-fuel mixture 2c. The volume V of the air-fuel mixture 2c including the squish area 95 shown in FIG. Since combustion prevails the entire, it is possible to perform uniform and good combustion in volume product V _c whole.

According to the invention of claim 7, 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 in, and fuel and air can be mixed well. Therefore, good combustion can be obtained.

In the invention of claim 8, by connecting the bottom portion 5 and the central projection portion 7 with a smooth curved surface 8 as shown in FIG. 1, it is possible to prevent the swirl (air flow) from attenuating. Therefore, an environment in which fuel and air are easily mixed is maintained, and the air-fuel mixture can be satisfactorily burned.

In the invention of claim 9, by a height h ₃ of the central projection portion 7 as shown in Figure 1 is set higher than the height h ₂ of the annular Kubo body section 6, the combustion chamber along the bottom 5 1 0 0 The direction of travel of the fuel traveling radially inward can be directed to the upper part of the combustion chamber, so that the combustion and the air can be easily mixed and good combustion can be performed.

According to the tenth aspect of the present invention, by providing the wall surface projection 21 on the wall surface 9 as shown in FIG. 11, good combustion can be obtained during the entire combustion period. By providing the wall projection 21, the kinetic energy of the injected fuel 2 itself causes the fuel 2 to be divided and spread into the bottom 5 side and the upper side (opening 3 side). Mixing can be promoted. By providing the central projection 7, the swirl can promote the mixing of fuel and air even in the later stage of combustion.

According to the invention of claim 11, by setting the center line 2a of the fuel 2 to be higher than the wall projection 21 and spraying the fuel 2 on the wall 9, the rate at which the fuel splits up and down is reduced. Thus, the fuel and air in the combustion chamber 100 can be mixed more favorably.

According to the invention of claim 12, by providing the annular concave portion 6 as shown in FIG. 11, a part of the fuel 2 colliding with the wall surface 9 can be guided to the opening 3 side (cylinder head side). Thus, the fuel can be diffused evenly in the peripheral region except the region above the central projection 7 in the combustion chamber 100.

According to the invention of claim 13, the angle で formed by the tangent of the annular recess 6 and the vertical line in the wall projection 21 shown in FIG. 11 is set in the range of 45 ° to 9 °. As a result, the fuel and the air are satisfactorily mixed, and good combustion can be performed, and the exhaust color can also be improved.

In the invention of claim 1 4, the height from the bottom 5 to the wall projections 2 1 and h _2, 0. 3 <h ₂ / H rather 0. To meet the 5 the relationship of the fuel Yakishitsu depth as H As a result, good combustion can be performed, and the exhaust color also becomes good.

In the invention of claim 15, as shown in FIG. 11, the opening diameter of the opening 3 of the combustion chamber 300 is set to (^, the maximum diameter of the annular recess 6 is d ₂ , When diameter (inner diameter of the wall 9) and d _3, since the set each size so as to satisfy dd ₃ <d ₂ the relationship can be fuel and air to perform good combustion are well mixed, the exhaust Color is good.

In the invention of claim 16, as shown in FIG. 11, the bottom 5 and the central projection 7 are slid. The connection by the kana curved surface 8 reduces the combustion area of the fuel in the center of the combustion chamber where the air flow due to swirl is relatively small, and the air flow due to the swirl mixes fuel and air in the periphery of the combustion chamber where the air flow is relatively large. The combustion is promoted, so that good combustion can be performed and the exhaust color is also improved.

By a low height h ₃ of the central projection portion 7 fuel in the invention of the force according to claim 1 7 will proceed to the center of the combustion chamber portion past the central projection portion 7, h ₂ <h _3, the central projecting portion The fuel traveling along the side wall of 7 can be directed upward of the combustion chamber, and can be burned in a region where fuel and air are easily mixed, so that good combustion can be obtained.

According to the invention of claim 18, since the combustion chamber depth H is shallow, the air in the entire combustion chamber can be used for combustion. By setting the H / D to 0.2, the fuel and air are mixed well, the combustion is improved, and the exhaust color is also improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view of a combustion chamber of a direct injection diesel engine according to the first, third and ninth aspects of the present invention.

Figure 2 relates to claims 1 to 9. (A) is a schematic sectional view of the combustion chamber immediately before the fuel collides with the annular recess. (B) is a schematic cross-sectional view showing a state in which the fuel colliding with the annular hollow part is 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 cross-sectional view of the combustion chamber showing the total compression volume when the piston reaches the top dead center.

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

FIG. 5 is a schematic cross-sectional view comparing the shape of a conventional combustion chamber with the shape of the combustion chamber according to the first aspect of the present invention.

FIG. 6 shows 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 aspect of the present invention. FIG. 7 is a graph showing the relationship between the depth of the combustion chamber, the distance from the bottom of the annular recess, and the exhaust smoke concentration.

FIG. 8 is a schematic sectional view of a combustion chamber of a direct injection diesel engine according to the second aspect of the present invention.

FIG. 9 relates to a combustion chamber according to the second aspect of the present invention. (A) is a schematic sectional view of the combustion chamber immediately before the fuel collides with the annular recess. (B) is a schematic cross-sectional view showing a state in which the fuel colliding with the annular hollow part is being spread 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. 10 is a schematic sectional view of a combustion chamber of another direct injection diesel engine according to the second aspect of the present invention.

FIG. 11 is a schematic sectional view showing a combustion chamber of a direct injection diesel engine to which the invention of claim 10 is applied.

FIG. 12 relates to a combustion chamber of a direct injection diesel engine according to the tenth aspect of the present invention. (A) is a schematic sectional view showing a combustion chamber structure of a direct injection type diesel engine until fuel injected from a fuel injection nozzle collides with a wall surface. (B) is a schematic cross-sectional view of the combustion chamber showing a state in which fuel is separated at the protrusion. (C) is a schematic sectional view of the combustion chamber in which the paths of the separated fuels are indicated by arrows.

FIG. 13 is a schematic cross-sectional view of the combustion chamber of the direct injection diesel engine according to the tenth aspect of the present invention, showing another shape of the wall surface projection. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic cross-sectional view of a combustion chamber 100 of a direct injection diesel engine in which the inventions of claims 1, 3 to 9 are implemented. 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 1 0 0, the maximum diameter is provided with a circular recess 6 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. This chamfer may be formed with a slope, but a rounded shape is more preferable than a slope. Bottom 5 to a height h _3, Ru Oh provided with a central protrusion 7 of the diameter d _5. The central projection 7 and the bottom 5 are connected by a smooth curved surface 8. 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 diameter d 3 of the wall surface 9 and the maximum diameter d ₂ of the annular recess 6 have a relationship d ₃ <d <d ₂ . As shown in FIG. 2 (a), the fuel 2 is injected from the fuel injection nozzle 1 toward the annular recess 6. As shown in FIG. 2 (b), the fuel 2 that has collided with the annular recess 6 is atomized into fuel 2b by the collision. Thereafter, as shown in FIG. 2 (c), the finely divided fuel 2b spreads in the combustion chamber 100, and is confused with air by swirl (air flow) to generate a mixture 2c. .

Thereafter, although not shown, the gas mixture 2 c and piston 9 0 descends flows out into the squish area 9 5 from the combustion chamber 1◦ within 0, prevailing on the total compression volume V _c to be described later (FIG. 3) It burns uniformly.

As shown in FIG. 3, the total volume formed by the piston 90 and the cylinder 91 when the piston 90 reaches the top dead center is defined as the total compression volume _Vc , as shown in FIG. Assuming that the volume of the area below the center axis 2a of fuel 2 injected from the fuel injection nozzle 1 (bottom 5 side) is the volume and the injection angle of the fuel 2 is Θ, the following equation (1) is obtained. Set V _c , ^ and 0 to satisfy.

V _L / V _C ≤ 0.0 0.88 X 0-0.0.8 3 4 1 (1) (Θ [deg])

By setting the v _c, V _L and Θ so as to satisfy the equation (1), in the initial combustion and the fuel and air are well mixed in the combustion chamber 1 0 within 0, also Oite combustion late it can perform uniform combustion in all compression volume V _c.

FIG. 5 is a schematic cross-sectional view comparing a cross section of a conventional combustion chamber indicated by a broken line with a cross section of a combustion chamber 100 of the present invention (invention of claim 1, claim 3 to claim 8) indicated by a solid line. It is. Combustion chamber 1 0 0, compared with the conventional combustion chamber widened openings 3 as indicated by an arrow A toward the outside radius direction, narrowing to the wall 9 radially inward as indicated by arrow A _2, and expanding the annular recessed portion 6 radially outward as further shown by the arrow a _3.

FIG. 6 is a graph showing the relationship between the fuel injection angle における and the volume ratio _VL / Vc in the conventional combustion chamber and the combustion chamber 100 of the present invention.

As shown in Fig. 6, the graph of combustion chamber 100 is lower than that of the conventional combustion chamber. And the graph of the combustion chamber 100 is represented by 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, the depth of the combustion chamber 100 is defined as H, and the annular recess is formed from the bottom 5.

When the distance to 6 (height of the annular recess portion 6) and h _2, by setting the H and h ₂ so as to satisfy the following equation (2), good fuel and air in the combustion chamber 100 And good combustion can be performed.

0.1 h h ₂ / H <0.5 (2)

7 is a graph showing the relationship between h ₂ ZH and the exhaust smoke density relative value (S d) (degree). As shown in FIG. 7, if the general value of h ₂ ZH is 0.1 Power et 0.5 of within range (the range satisfying formula (2)), the relative value of the exhaust smoke density is zero. 8 or less.

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.

For the respective dimensions in FIG. 1, for example, numerical values in the following ranges can be adopted.

Cylinder diameter (piston diameter) D = 50 ~: 1 50 [mm]

Combustion chamber opening diameter d = 25 to 77 [mm]

Maximum diameter d ₂ of annular recess 6 = 28 to 84 [mm]

Diameter of wall 9 (combustion chamber diameter) d ₃ = 24 to 75 [mm]

Flat part 4 width d ₄ = 0.1 to 2 [mm]

Diameter d ₅ of central projection 7 = 9 to 27 [mm]

Combustion chamber depth H = 8 ~ 28 [mm]

Height of annular recessed part 6 h ₂ = 3 ～; 1 2 [mm]

The height h ₃ = 4~l ₃ of the central protrusion 7 [mm]

Total compression volume V _c = 5,000 to 180,000 [mm ³ ]

Volume of the area below the central axis 2a V _L = 2,200 ~: 100,000 [mm ³ ]

Injection angle θ = 1 4 5 ~; 16 0 [d eg]

FIG. 8 is a schematic sectional view of a combustion chamber 200 of a direct injection diesel engine according to the second aspect of the present invention. In the combustion chamber 200 of FIG. 8, the same components as those of the combustion chamber 100 of FIG. 1 are denoted by the same reference numerals.

The wall 9 of the combustion chamber 2 0 0, annular recess 6 of the largest diameter d _2, is provided with a recess 1 0 diameter d _6. An annular protrusion 12 is formed between the annular concave portion 6 and the concave portion 10. A curved surface 11 is formed between the wall surface 9 and the concave portion 10. 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. There is a relationship d ₃ <dd ₂ between the opening diameter d of the opening 3 d the diameter d 3 of the wall surface 9 and the maximum diameter d ₂ of the annular recess 6. As shown in FIG. 9 (a), the fuel 2 is injected from the fuel injection nozzle 1 toward the annular recess 6. As shown in FIG. 9 (b), the fuel 2 that has collided with the annular recess 6 is atomized into fuel 2b by the collision. Thereafter, as shown in FIG. 9 (c), the finely divided fuel 2b spreads in the combustion chamber 100, and is mixed with air by swirl (air flow) to generate an air-fuel mixture 2c. .

Thereafter, although not shown, mixing the mixture the piston 9 0 descends combustion chamber 1 in 0◦ flows into the squish area ₉ 5, the total compression volume V _c (see V _c of FIG. 3) Qi 2c is prevalent and burns.

FIG. 10 is a schematic sectional view of another combustion chamber 201 according to the second aspect of the present invention. The configuration of the combustion chamber 201 in FIG. 10 is such that a second recess 15 is provided in place of the concave portion 10 and the curved surface 11 in the combustion chamber 200 shown in FIG. Only the point that an annular projection 20 is formed between the second concave portions 15 is different from the configuration of the combustion chamber 200 in FIG.

The fuel flowing downward from the annular recess 6 (bottom 5 side) changes its traveling direction from the bottom 5 direction to the central projection 7 at the second recess 15. Therefore, the fuel does not reach the bottom 5 where the swirl (air flow) is small, and mixes well with air in the region where the swirl is large (the region corresponding to the region occupied by the mixture 2c in FIG. 9 (c)). To form a mixture, and the mixture spreads over the entire compressed volume (the area corresponding to this in Fig. 3). Burn.

Fig. 8 shows a combustion chamber with two annular recesses 6 and a second recess 15 in Fig. 10, and Fig. 10 shows a combustion chamber with two annular recesses and a second recess 15 respectively. Three or more recesses may be provided.

In FIG. 8, for each dimension, for example, numerical values in the following ranges can be adopted.

Cylinder diameter (piston diameter) D = 50 to 150 [mm]

Combustion chamber opening diameter d = 25 to 77 [mm]

Maximum diameter d ₂ of annular recess 6 = 28 to 84 [mm]

Diameter of wall 9 (combustion chamber diameter) d ₃ = 24 to 75 [mm]

Diameter d ₅ of central projection 7 = 9 to 2 7 [mm]

Concave 10 diameter d ₆ = 25 to 76 [mm] (1 mm more than d ₃ )

Combustion chamber depth H = 8 ~ 28 [mm]

Height of annular recess 6: h ₂ = 2 to: 1 1 [mm]

The height of the central projection portion _{7 h 3 = 4~ 1 3 [} mm]

Total compression volume V _c = 5,000 or more: 180,000 [mm ³ ]

Volume of the area below the central axis 2a V _L = 2,200 ~: L 00,000 [mm

³ ]

Injection angle θ = 145 to 160 [d e g]

FIG. 11 is a schematic cross-sectional view of a combustion chamber 300 of a direct injection diesel engine according to the invention of claims 10 to 18. In FIG. 11, only characteristic portions of the combustion chamber 300 according to the tenth to eighteenth aspects are shown.

The annular wall surface 9 of the combustion chamber 300 is provided with an annular wall surface projection 21. An annular recess 6 is provided above the wall projection 21, and the wall projection 21 and the annular recess 6 are smoothly connected. An opening 3 is provided at the upper end of the wall surface 9. The opening diameter of the opening 3 is set to be smaller than the diameter d _{3 of the} wall surface 9 (the inner diameter of the combustion chamber 300).

A central projection 7 is provided on the bottom 5 of the combustion chamber 300. Central protrusion 7 is raised in the center of the combustion chamber 3 00, a height h _3, the height h ₄ of the wall projections 2 1 And does not collide with the fuel 2 injected from the fuel injection nozzle 1. The size of the diameter d ₅ so that the fuel 2 which is the fuel injection nozzle 1 forces et injection does not collide with the central projection portion 7 is set. Further, the central projection 7 and the bottom 5 are connected by a smooth curved surface 8.

In the combustion chamber 300 thus formed, the fuel 2 injected from the fuel injection nozzle 1 collides with the wall 9 while spreading in the form of a mist, but as shown by a dashed line in FIG. The injection direction of the fuel injection nozzle 1 is set so that the injection center axis 2 a of the fuel 2 is located above the wall projection 21.

The fuel 2 (FIG. 12 (a)) injected from the fuel injection nozzle 1 collides with the wall surface 9 provided with the wall surface projection 21 and the annular recess 6. The fuel 2 colliding with the wall 9 is separated into two paths by the wall projection 21 as shown in FIG. 12 (b), one of which is upward along the annular recess 6 (opening 3). Side), the other along the wall 9 and the bottom 5 towards the center of the combustion chamber 300.

Some of the fuel going upward passes through the opening 3 to the squish area 95, and the rest diffuses in the combustion chamber 300. In addition, the fuel heading toward the center smoothly changes its course upward on the curved surface 8 as shown in FIG. 12 (c), and rises along the wall surface of the central projection 7.

There is a swirl (air flow) in the combustion chamber 300, and the swirl is more active in the periphery (closer to the wall 9) than in the center of the combustion chamber 300. Therefore, mixing of fuel and air is performed better in the peripheral part than in the central part. By providing the central projection 7, the fuel can be convected in a region where the air flow is large, so that the air and the fuel are mixed well, and as a result, the combustion is performed well. In addition, the larger the radius of the curved surface 8 is, the narrower the central area of the combustion chamber 100 is, and the more the air is distributed in the peripheral area where the air flow is large, so that the air and the fuel are mixed well. It will be easier for you.

In a conventional reentrant combustion chamber, rich fuel accumulates in the vicinity of the bottom of the combustion chamber, whereas in the combustion chamber 300 of the invention of claim 10, the wall projection 21 and the annular recess 6 provide the fuel. Since the fuel 2 is dispersed up and down and the fuel is distributed in the places where the air flow due to the swirl is large, the fuel and the air are mixed well. If the angle Θ] formed between the tangent of the recess 6 and the vertical line in the wall projection 21 shown in Fig. 11 is within the range of 45 to 90 degrees, the fuel and air are mixed well. Good combustion can be performed, and the exhaust color also becomes good.

Instead of the wall projection 21 in FIG. 11, wall projections 22 and 23 shown in FIG. 13 may be provided. At this time, by setting the angle theta ₂ formed by the straight line and the vertical line connecting the wall surface protrusion 22 and 23 within the range of 45 to 90 degrees, the fuel and air are engaged satisfactorily mixed perform good combustion The exhaust color can be good.

Also, the height from the bottom portion 5 as shown in the first 1 FIG from the wall projections 2 1 and h _4, the combustion chamber depth and H, a 0. 3 <h ₄ ZH rather 0.5 the relationship When satisfied, the fuel and air are well mixed and good combustion can be performed, and the exhaust color is also good. Further, when the height h ₃ of the central projection portion 7 is greater than the height h ₄ of the wall surface protrusion 21, the fuel proceeds toward the center along the bottom 5 may proceed to further center from the central protrusion 7 Therefore, the traveling direction can be changed upward, and the fuel can be prevented from traveling to the central region of the combustion chamber where the air flow is relatively small.

Assuming that the diameter of the opening 3 is d ₂ , the maximum diameter of the annular recess 6 is d ₂ , and the internal diameter of the combustion chamber 300 (the diameter of the wall 9) is d ₃ .

When the diameters are set so as to satisfy the relationship of ds, the fuel and the air can be mixed well and good combustion can be performed, and the exhaust color can be improved.

Also, assuming that the depth of the combustion chamber 300 is H and the diameter of the piston 90 is D, the depth H of the combustion chamber 300 and the piston diameter D are set so as to satisfy the relationship of HZ D <0.2. However, the fuel and the air are mixed well, and good combustion can be performed, and the exhaust color also becomes good.

In FIG. 11, for each dimension, for example, numerical values in the following ranges can be adopted.

Cylinder diameter (piston diameter) D = 50 to 150 [mm]

Combustion chamber opening diameter d = 21 to 64 [mm]

Maximum diameter d ₂ of the annular recess 6 = 25 to 75 [mm]

Diameter of wall 9 (combustion chamber diameter) d ₃ = 24 to 72 [mm]

Diameter of central projection 7 d _ε = 8 to 24 [mm] Combustion chamber depth H = 7 to 24 [mm]

The height h of the central projection portion _{7 3 = 3~ 1 0 [mm} ]

Height of wall projection 2 1 h ₄ = 2.5 to 9 [mm]

Injection angle S i A S S O [d e g]

In FIG. 13, the value of the angle θ ₂ can adopt a numerical value in the following range.

Angle Θ ₂ = 45 ～ 90 [deg] Possibility of industrial use

INDUSTRIAL APPLICABILITY The present invention can be generally applied to a combustion chamber of a reentrant direct injection diesel engine.

Claims

The scope of the claims

1. Ring-shaped recesses in which the fuel injection Nozunore (1) Power et al fuel (2) is injected (6) provided in the combustion chamber wall surface (9), the opening diameter of the combustion chamber opening (3) to (d ₃₎ The diameter of the annular recess is smaller than the maximum diameter (d ₂ ) and the bottom of the combustion chamber is smaller than the annular recess (6).

(5) Set to be larger than the combustion chamber wall diameter (d ₃ ) on the side, and the height (h ₃ ) and the center of the diameter (d ₅ ) at which the fuel (2) injected from the fuel injection nozzle (1) does not collide A combustion chamber for a direct-injection diesel engine, characterized in that a projection (7) is provided at the bottom (5) of the combustion chamber.

2. The combustion chamber of a direct-injection diesel engine according to claim 1, wherein a plurality of the annular recesses (6) are provided.

3. The direct injection diesel engine according to claim 1, wherein a flat portion (4) is provided between the combustion chamber wall (9) below the annular recess (6) and the annular recess (6). Combustion chamber of the ladle engine.

4. If the volume of the combustion chamber below the center axis (2a) of the fuel (2) injected from the fuel injection nozzle (1) is V _L and the total compression volume is V _c , then V _L ZV _c The combustion chamber of a direct injection diesel engine according to any one of claims 1 to 3, wherein the injection angle is ≤0.008 8 injection angle (6)-0.834 1 (: [deg]).

5. combustion chamber bottom (5) h ₂ a distance to the annular recess portion provided in the combustion chamber wall surface (9) (6) from the combustion chamber depth and H, 0. 1 rather h ₂ / H <0 The combustion chamber of a direct injection diesel engine according to any one of claims 1 to 3, wherein the combustion chamber is:

6. combustion chamber opening diameter (^, the annular recess portion maximum diameter d _2, the combustion chamber diameter If you and d _3, to one of d ₃ <d <claim 1及至claim 3 is d ₂ The combustion chamber of the direct injection diesel engine described.

7. The combustion chamber of a direct injection diesel engine according to any one of claims 1 to 3, wherein the combustion chamber opening (3) is provided with an annular protrusion chamfered.

8. The combustion chamber of a direct injection diesel engine according to any one of claims 1 to 3, wherein the bottom (5) of the combustion chamber and the central projection (7) are connected by a smooth curved surface (8).

9. The height of the central projections and h _3, h ₂ <h. Claim 1 to Claim 3 The combustion chamber of a direct injection diesel engine described in any of the above.

10. is set to be smaller than the combustion chamber opening diameter (combustion chamber diameter dj (d _3), the combustion chamber wall surface in a range of fuel injection nozzle (1) Power et al fuel (2) is injected (9) An annular wall projection (2 1) is provided, which has a height (h ₃ ) that does not collide with the fuel (2) injected from the fuel injection nozzle (1) and collides with the combustion chamber wall (9). Wall

From (9), a central projection (7) with a height (h ₃ ) that can change the direction of the fuel so that the fuel that travels toward the center of the combustion chamber along the bottom of the combustion chamber (5) is directed upward is attached to the combustion chamber. The combustion chamber of a direct injection diesel engine, which is provided at the bottom (5).

11. The direct injection diesel engine according to claim 10, wherein the injection center axis (2a) of the fuel (2) injected from the fuel injection nozzle (1) is set above the wall projection (21). / Combustion chamber of the engine.

12. A curved concave portion (6) having an annular and smooth surface is provided above the wall projection (21), and the wall projection (21) is smoothly connected to the annular depression (6). The direct injection according to claim 10 or 11, wherein the path of the fuel that has collided with the combustion chamber wall surface (9) is divided into two directions, an opening (3) side and a combustion chamber bottom (5) side. -Type diesel engine combustion chamber structure.

13. The direct injection method according to claim 12, wherein the angle formed by the tangent of the annular recess (6) and the vertical line in the wall projection (21) is set within a range of 45 degrees to 90 degrees. Diesel engine combustion chamber structure.

14. The value obtained by dividing the height (h ₄ ) from the bottom of the combustion chamber (5) to the wall projection (21) by the depth of the combustion chamber (H) was set in the range of 0.3 to 0.5. The combustion chamber structure of the direct injection diesel engine according to claim 10.

1 5. opening diameter (dj of the combustion chamber opening (3), combustion chamber diameter (d _3), in claim 1 3 or claim 14 which increases in the order of annular rather Bomi portion maximum diameter (d ₂₎ The combustion chamber structure of the direct injection diesel engine described.

16. In the combustion chamber (300), the combustion area of fuel in the center of the combustion chamber was reduced by connecting the bottom (5) of the combustion chamber and the central projection (7) with a smooth curved surface (8). A combustion chamber structure for a direct injection diesel engine according to claim 10.

1 7. Adjust the height (h ₃ ) of the central projection (2 1) from the bottom of the combustion chamber (5) to the bottom of the combustion chamber. A combustion chamber structure for a direct injection type Diesel engine mounting serial to claim 10 which is higher than the wall projections (21) of the height (h ₄₎ from Part (5).

18. The combustion chamber depth (H) and the piston diameter (D) were set so that the value obtained by dividing the combustion chamber depth (H) by the piston diameter (D) was less than 0.2. A combustion chamber structure for a direct injection diesel engine according to claim 10.