JPS59218328A - Direct-injection type diesel engine - Google Patents

Abstract

PURPOSE:To improve output and torque as greately as possible, and reduce emission of smoke and carbon monoxide, etc., by providing a combustion chamber formed with a projection at a bored portion on a top surface of a piston, and forming an inclined surface on a lower end surface of a cylinder head. CONSTITUTION:A cavity-like combustion chamber 3 is formed on a top surface of a piston 1, and a projection 5 is formed at a substantially central portion of a botom 4. A squish deflector 10 is formed with an annular projection 11 at a periphery of a lower end portion thereof, and the annular projection 11 is formed with an inclined surface 12 at a lower end thereof. A squish collides with the annular projection 11 and flows along the inclined surface 12 into the combustion chamber 3. Subsequently, the squish rises from the bottom 4 and along an inner side wall 14 to form a convection. Further, a vertical component of the squish and a horizontal component of a swirl are combined with each other in the combustion chamber 3 to form a steric toroidal flow. Thusly, it is possible to improve output and torque as greatly as possible.

Description

Detailed Description of the Invention [Technical Field of the Invention 1] The present invention relates to a direct injection diesel engine, and in particular to a direct injection diesel engine that effectively forms a vortex of compressed air within a combustion chamber to promote mixing of compressed air and fuel. The present invention relates to a direct injection diesel engine that completely burns fuel to improve output and torque as much as possible, and also contributes to reducing smoke and carbon oxide emissions.

[Technical background of the invention and its problems] Generally, in a direct injection diesel engine, screws 1 to
When the engine reaches near top dead center, fuel is injected directly into the combustion chamber from the injection nozzle. At this time, in order to sufficiently mix the fuel and compressed air, the combustion chamber is configured to generate a vortex flow of compressed air. That is, as shown in FIG. 1, the top surface of the piston a is depressed into a hollow shape approximately at the center thereof, and the bottom C of the depression is projected upward to form a protrusion d. The combustion chamber e is configured by the combustion chamber e.

By the way, when the piston a rises to compress the air in the cylinder f, a compressed air flow (hereinafter referred to as squish) flows from the outside in the radial direction of the cylinder chamber to the inside.
In the combustion chamber e, a vortex of compressed air (hereinafter referred to as a swirl) that flows along the circumferential direction around the protrusion d and swirls in a plane is generated (this swirl is generated in advance by the intake port). >, fuel is injected from the injection nozzle h to the area where this swirl is occurring.

In this way, the above-mentioned squish and swirl act as important factors in order to sufficiently mix the fuel and compressed air within the combustion chamber e.

To explain in more detail how squish occurs, the air in the cylinder chamber 9 is compressed and flows as the piston a rises, and the flow velocity reaches its maximum at about 10 degrees before the top dead center at the crank angle. It flows from the outside in the radial direction in the cylinder chamber g to the inside in the gap between the top surface of the cylinder head a and the lower end surface j of the cylinder head i. Therefore, the squish collide with each other just above the combustion chamber e, but the cylinder chamber g
Since the squish does not have a velocity component in the axial direction, it is not possible to sufficiently increase the flow velocity of the squish that is diverted into the combustion chamber e after the collision. Therefore, only the swirl mainly acts on the mixing of the fuel and compressed air in the combustion chamber e, and the effect of the squish is not sufficiently exhibited. For this reason, complete combustion of the fuel is not performed sufficiently, and the amount of smoke, carbon oxide, etc., emitted cannot be sufficiently suppressed. There was also the problem that sufficient output and torque could not be obtained.

Furthermore, as shown in Fig. 2, a combustion chamber shape is known in which the diameter of the combustion chamber e is extremely narrowed to increase the flow velocity of squish flowing into the combustion chamber e. When the gas expands from the combustion chamber e and flows into the cylinder chamber g, there is a problem in that heat loss is large and sufficient output cannot be obtained.

[Object of the Invention] The present invention has been devised in view of the above problems and to effectively solve them.

The purpose of the present invention is to combine the axial component of the cylinder caused by the squish with the swirl generated within the combustion chamber to create a three-dimensional toroidal flow (a spiral that continues in an annular manner in the circumferential direction while convecting vertically within the combustion chamber). Direct injection that promotes the mixing of compressed air and fuel by forming a swirling flow, completely combusts the fuel, and improves output and torque as much as possible, while also contributing to reducing emissions of smoke, carbon oxide, etc. The objective is to provide a type diesel engine.

[Embodiments of the Invention] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 shows a combustion chamber of a direct injection diesel engine according to the present invention.

A combustion chamber 3 is formed in the top surface 2 of the piston 1 in the shape of a cavity by recessing the piston 1 to a substantially medium extent. A protrusion 5 is formed on the bottom 4 of the combustion chamber 3 at a substantially medium flame level and protrudes upward.

A fuel injection nozzle 8 has a nozzle tip 9 exposed on the lower end surface 7 of the cylinder head 6 facing the substantially medium flame of the combustion chamber 3. The injection nozzle 8 is fixed within the cylinder head 6, and around the nozzle tip 8 there is a squish deflector 10 that is press-fitted into the lower end surface 7 of the cylinder head 6 in the form of a plug.
is provided, and its outer periphery is surrounded along the circumferential direction.

The squish deflector 10 has an annular protrusion 11 formed at the lower end of its periphery, so that when the squish deflector 10 is fitted into the cylinder head 6, the annular protrusion 11 protrudes below the lower end surface 7 of the cylinder head 6. It is composed of The annular protrusion 11 is formed into a tapered shape with its outer peripheral side narrowed downward, and is formed into an inclined surface 12 so that squish colliding with this surface is deflected downward.
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The circumferential side surface 13 of the protrusion 5 in the combustion chamber 3 described above is formed to draw a curve that widens towards the end as an outline line so that the squish whose direction is changed by the inclined surface 12 flows along this to form a spiral flow. Been (Xru)

Next, the operation of the present invention will be explained.

As the piston 1 rises, the air in the cylinder chamber 13 is compressed and flows from the peripheral edge of the cylinder chamber 13 toward the center, forming a squish.

The flow velocity increases as the piston 1 rises, and reaches its maximum at a position approximately 10 degrees before the top dead center of the crank angle.

The squish collides with the annular protrusion 11 of the squish deflector 10 and is diverted downward along the inclined surface 12, but flows into the combustion chamber 3 while maintaining its flow velocity. The squish further descends along the circumferential side 15 of the protrusion 5 and rises from the bottom 4 of the combustion chamber 3 along the inner wall 14, forming vertical convection. In addition, a swirl is formed in the combustion chamber 3 that rotates in a plane along its circumferential direction, and the component in the vertical plane of the squish and the component in the horizontal plane of the swirl are combined to form a three-dimensional toroidal flow (helical swirling flow).
is formed.

When fuel is injected into the combustion chamber 3 where a toroidal flow is formed, the mixing of compressed air and fuel is promoted dramatically compared to a flat swirl, so the fuel is completely combusted, resulting in smoke and - Generation of carbon oxide, etc. is suppressed to a minimum. .

Furthermore, the combustion gas can easily expand from the inside of the combustion chamber 3 to the cylinder chamber 13, resulting in low heat loss and high output and large torque.

Incidentally, as shown in FIG. 4, the lower end surface 7 of the cylinder head 6 may be formed by casting into a curved shape having a gentle slope that gradually descends toward the upper center of the combustion chamber 3.

Effects of the Invention] As is clear from the above description, the present invention exhibits the following excellent effects.

(1) Squish and swirl can be effectively combined, and an effective toroidal flow can be formed within the combustion chamber.

(2) Mixing of compressed air and fuel can be promoted as much as possible.

(3) Output and torque can be improved as much as possible.

(4) Emissions of smoke, carbon oxide, etc. can be reduced.

(5) The structure is simple and can be easily adopted.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a conventional example of a direct injection diesel engine, FIG. 2 is a side sectional view showing another conventional example of a direct injection diesel engine, and FIG. 3 is a direct injection diesel engine according to the present invention. FIG. 4 is a side sectional view showing another embodiment of the direct injection diesel engine according to the present invention. In the figure, 1 is the piston, 2 is its top surface, 3 is the combustion chamber,
4 is the bottom, 5 is the protrusion, 6 is the cylinder bed,
7 is its lower end surface, 11 is an annular projection, 12 is an inclined surface, 1
3 is a cylinder chamber. Patent applicant Nobuo Kinuya, patent attorney representing Isuzu Motors Co., Ltd.

Claims (2)

[Claims] (1) The piston has a combustion chamber in which the top surface of the piston is depressed into a hollow shape, and a protrusion projecting upward from the bottom of the depression is formed approximately in the center of the depression; The direction of the compressed air flowing from the outside in the cylinder chamber toward the center of the combustion chamber is changed between the lower end surfaces of the cylinder head facing the cylinder head, and the vortex flow is turned into a spiral swirl flow. A direct injection type diesel engine, characterized in that a slope is formed on the lower end surface of the cylinder l ped to form an inclined surface. (2) The direct injection diesel engine according to claim 1, wherein the inclined surface is formed by an annular projection projecting downward from the lower end surface of the cylinder head facing the center of the combustion chamber.