JPS6318126A - Direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To accelerate fuel-air mixture by forming in a piston an introducing hole for injecting compressed air in opposition to fuel which is injected to the wall of a combustion chamber concavely provided on the top of the piston from a multi-injecting hole nozzle so as to prevent injected oil from adheving to the inner wall. CONSTITUTION:On the top of a piston 1, is formed, in shape of a recess, a combustion chamber 2 which is gradually reduced in the diameter of its inner wall 3 from its bottom part 4 side toward the opening 6 of the top surface 5 of the piston 1 and formed approximately in a large diametral size in its lngitudinal section. On the upper cylinder head in a approximately center part of said combustion chamber 2, a multi-injecting nozzle 8, which is provided with four injecting holes 9, for injecting and supplying fuel toward the inner wall 3 of the combustion chamber 2 is provided, and fuel spray F from each injecting hole 9 is led to make diagonal collision from the upper direction with a corner part 7 for forming the inner wall 3. And an introducing hole 10 of compressed air for diffusing fuel spray F more is formed so as to open at the corner part 7 of the combustion chamber 2, and the compressed air produced during a compression stroke is injected to the corner part 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a direct injection type diesel engine, and particularly to a direct injection type diesel engine that improves combustion by promoting turbulence of vortices generated in a combustion chamber. Regarding diesel engines.

[Prior art] In general, direct injection Q'J type diesel-like combustion engines have a combustion chamber installed at the top of the piston that disturbs the combustion chamber with a strong squish flow to promote the mixing of fuel and air and improve combustion. There is a reentrant type combustion chamber shown in FIGS. 3 and 4 that can introduce such a strong squish flow into the combustion chamber.

As shown in the figure, this reentrant combustion air is created by sequentially reducing the diameter of the inner wall of the combustion chamber a from the bottom C side toward the opening e side of the piston top surface d, thereby increasing the diameter of the opening e. The area of the top surface d of the piston is widened to generate a strong squish flow V near TDC at the end of the compression stroke.

[Problems to be Solved by the Invention] However, in this way, when the diameter of the opening e of the combustion chamber a is narrowed and the bottom C side is enlarged, or in the endrunt-shaped combustion chamber a, the diameter is conversely narrowed. Therefore, it is difficult to introduce a strong swirl flow S into the combustion chamber a, and the vortex generated by introducing the squish flow ■ generated during the compression stroke into the combustion chamber a is
Although strong turbulence is obtained near the opening 0, it is weakened at the corner f connecting the bottom C of the combustion va and the inner circumferential job, and as a result, it is difficult to generate strong turbulence at the corner f. Therefore, when fuel is injected from the fuel injection nozzle Q toward the corner f, the fuel adheres to the corner f due to the condition that the penetration force of the spray F is strong in the case of a direct injection type. This causes a problem in that a sufficient air-fuel mixture cannot be generated and the flame is inhibited from entering the corner f, resulting in an increase in the amount of smoke generated. The problem with this problem is that when atmospheric salt and cooling water temperature are low, or when atmospheric salt and cooling water temperature are at room temperature but at idle or under light load, the wall temperature is high enough to evaporate the fuel. As a result, the ignition delay period becomes longer at low temperatures and light loads, and a large amount of unburned fuel is generated in the corner f of the combustion chamber a, which deteriorates combustibility. This not only caused the generation of IC and blue-white smoke, but also induced a decrease in output.

Incidentally, a part of the unburned fuel in the combustion chamber is injected into the cylinder chamber from the top surface of the piston through a combustion gas passage provided at the top of the piston, and combusted in the cylinder chamber. There is a direct injection diesel engine piston.

[Means for Solving the Problems] The present invention provides a multi-nozzle in the combustion chamber formed at the top of the piston, and the inner wall of the combustion chamber facing each of the nozzles faces the fuel sprayed from the nozzles. A direct injection diesel engine is constructed by forming an introduction hole through which air compressed in the cylinder chamber is ejected during the compression stroke.

[Function] At the end of the compression stroke, fuel is injected from the multi-nozzle to a predetermined position toward the inner wall of the combustion chamber. On the other hand, compressed air in the cylinder chamber that has been compressed during the compression stroke is ejected into the combustion chamber through the introduction hole. The injection port of the introduction hole is opened at the destination of the injected fuel and faces almost opposite to the RFI injection fuel, so the ejected air flow collides with the injected fuel with force and prevents the injected fuel from reaching the injected fuel. causes strong turbulence in the area. As a result, the injected fuel is prevented from adhering to the inner wall near its destination, and is sufficiently stirred with the air to promote mixture vaporization, thereby suppressing the generation of unburned fuel.

[Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a combustion chamber 2 is recessed in the top of the piston 1. This combustion chamber 2 has an inner wall 3 whose diameter is gradually reduced from the bottom 4 side toward the opening 6 side of the piston top surface 5, and the longitudinal section is formed into a trapezoidal shape. A combustion chamber 2 is formed, and the opening 6 side is narrowed with respect to the diameter of the bottom portion 4, and the bottom wall surface 4a and the inner wall surface 3a are connected by an arcuate curved surface 7a, and a corner portion 7 is formed there. ing. Further, a swirl flow S that swirls in one direction is introduced into the combustion chamber 2 during the intake stroke, which is generated at the intake bow 1 to the intake bow.

Moreover, above the approximate center of the combustion chamber 2, a multi-nozzle nozzle 8 that is attached to a cylinder head (not shown) and injects fuel into the combustion chamber 2 is disposed. This multi-nozzle nozzle 8 has four nozzles 9 facing the inner wall 3 of the combustion chamber 2 and having four nozzles 9 for injecting fuel at regular intervals at predetermined positions. The fuel sprays F injected from them with a phase of 90° to each other in the horizontal plane are directed downwards to impinge on the cope part 7. Therefore, the fuel spray F from each nozzle 9 collides with the corner portion 7 forming the inner wall portion 3 obliquely from above and flows down in the downstream direction of the swirl flow S.

Furthermore, the corner portion 7 of the combustion chamber 2 is provided with the multi-nozzle 8.
A compressed air introduction hole 10 is provided to further diffuse the fuel spray F that is injected from the fuel spray and flows down into the swirl flow S. The introduction hole 10 is provided diagonally through the top of the piston to communicate the corner part 7 with the cylinder chamber 11 above the piston top surface 5, and one end on the side of the jet nozzle 12 is connected to the corner part 7 of the combustion chamber 2. It is opened in the curved surface 7a of the facing inner wall portion 3,
The inlet 13 at the other end is opened at the top surface 5 of the piston, and the compressed air generated in the cylinder chamber 11 during the compression stroke is transferred to the combustion chamber 1.
The turbulent flow T is generated in the vicinity of the corner 7 in the combustion chamber 2 by ejecting it to the corner 7 inside the combustion chamber 2.

Further, the axis of the introduction hole 10 on the side of the injection port 12 faces downwardly to the arrival part of the fuel spray F, that is, the corner part 7, and is in the horizontal plane direction with respect to the fuel spray F injected from the multi-nozzle nozzle 8. The air jets are formed along the tangential direction of the corner portion 7 so as to face each other, and the air jet jetted from the jet port 12 is directed between the curved surface 7a of the corner portion 7 of the combustion chamber 2 and the bottom wall surface 4a.
The turbulent flow T is generated at the corner portion 7 by being guided by the squish flow 2 and interacting with the squish flow 2 introduced from the opening 6.

In a direct injection diesel engine configured in this way,
At the end of the compression stroke, air compressed within the cylinder chamber 11 is ejected through the introduction hole 10 to the corner 7 within the combustion chamber 2, creating a strong turbulent flow T there. This turbulent flow T collides with the fuel spray F injected and supplied from the multi-nozzle 8 at the end of the compression stroke, stirring it, and the fuel adheres to the reaching part (the curved surface 7a of the corner part 7). This prevents the fuel from becoming atomized and promotes evaporation and diffusion to increase the air utilization rate, form a sufficient mixture in the part 7, and this mixture flows in a swirl flow. It flows downstream.

Further, since the same number of introduction holes 10 are provided according to the number of fuel sprays F injected from the multi-nozzle 8, it is possible to prevent unburned fuel from being generated in the corner portion 7.
Ignition timing delay is shortened and uniform and good combustion can be achieved.・For this reason, it is possible to reduce the occurrence of smoke (black smoke, blue-white smoke) and UC, and improve output, and it is possible to improve the reduction of smoke and HC and increase of output, especially at low temperatures and light loads. become.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects are achieved.

(1) Opposing the fuel injected from the multi-nozzle toward the wall of the combustion chamber, an introduction hole is provided on the inner wall of the area where the fuel spray reaches, through which air compressed in the cylinder chamber is ejected. It is possible to prevent the injected fuel from adhering to the inner wall surface in the vicinity of the reaching portion, and it is also possible to increase the air utilization rate and promote the mixture vaporization of air and fuel.

(2) Therefore, it is possible to prevent unburned fuel from being generated in the area where the fuel reaches, and to prevent smoke (black smoke, blue-white smoke) and HC.
It is possible to achieve uniform and good combustion by reducing the occurrence of carbon and improve output.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the top of a piston showing a preferred embodiment of the present invention, FIG. 2 is a plan view thereof, and FIGS. 3 and 4 are a side sectional view and a plan view showing a conventional example. In the figure, 1 is a piston, 2 is a combustion chamber, 3 is an inner wall part, 4 is a bottom part, 5 is a piston top surface, 6 is an opening, 7 is a corner part, 8
1 is a multi-spout nozzle, 9 is a spout, 10 is an introduction hole, 11 is a cylinder chamber, 12 is a spout, and 13 is an introduction port.

Claims (5)

[Claims] (1) A multi-nozzle is provided in the combustion chamber formed at the top of the piston, and the air compressed in the cylinder chamber during the compression stroke is placed on the inner wall of the combustion chamber where each nozzle faces, facing the fuel sprayed from these nozzles. A direct-injection diesel engine characterized by having an introduction hole for ejecting. (2) The introduction hole is formed at the top of the piston with its introduction port opened at the top surface of the piston and its ejection port opened at the inner wall of the combustion chamber. Direct injection diesel engine. (3) The direct injection diesel engine according to claim 2, wherein the combustion chamber is formed by decreasing the diameter of the inner wall of the chamber from the bottom side toward the opening of the top surface of the piston. institution. (4) The direct injection type according to claim 2 or 3, wherein the multi-nozzle has each nozzle opened toward a corner connecting the inner wall and the bottom of the combustion chamber. diesel engine. (5) The direct injection diesel engine according to claim 3 or 4, wherein the introduction hole has an ejection port formed along a tangential direction of the corner portion.