JPS6224010Y2 - - Google Patents

Description

[Detailed Description of the Invention] In a conventional direct fuel injection diesel engine, the combustion chamber thereof was constructed as shown in FIG. That is, a cavity c called a bathtub type is formed as a combustion chamber on the upper surface of the piston b which is slidably fitted into the cylinder liner a, and as the piston b descends, the intake valve d opens and the new air flows through the intake passage e. The intake port shape of the intake passage e is formed in a spiral shape, a tangential shape, or the like so that air flows into the cylinder liner a while creating a swirl.

In the combustion chamber configured in this way, the incoming fresh air enters the compression stroke while maintaining a swirl motion, and when the piston b approaches top dead center, most of the fresh air is forced into the cavity c. and obtain even faster swirl rotation speed.

Fuel is injected into the swirl air compressed to high temperature and high pressure in the form of a spray from the fuel valve f into the cylinder liner a as shown in the figure, and is stirred by the swirl to form an air-fuel mixture, which is ignited and combusted. The pressure increases and piston b is pushed down,
Rotational force is generated in a crank (not shown) via a connecting rod (not shown), and when the piston b reaches near the bottom dead center, the exhaust valve g opens and combustion gas is discharged through the exhaust hole h.

In the above process, the swirl in the cylinder liner a or the cavity c generally has a velocity distribution as shown in FIG. 3, and moves close to a so-called rigid body vortex. For this reason, the injected fuel spray is well stirred during fuel injection, but during the combustion after injection, in the latter half of the diffusive combustion period, the fuel and gas rotate as one at the same speed, causing agitation. is not done enough.

For this reason, in conventional combustion chambers, the combustion rate in the latter stages of combustion does not increase, resulting in a prolonged combustion period.
It was not possible to obtain high thermal efficiency.

In addition, even in the conventional toroidal combustion chamber as shown in FIG. 2, the swirl in the combustion chamber similarly becomes a rigid vortex, so the combustion rate in the latter stages of combustion does not increase and the combustion period becomes longer.

The present invention relates to a direct fuel injection internal combustion engine that eliminates the above-mentioned drawbacks, and is a direct injection internal combustion engine that generates a swirl in a cavity recessed in the upper surface of a piston and injects fuel into the swirl. In the engine, a plurality of air guide protrusions are arranged on the bottom surface of the cavity from the side wall of the cavity toward the center and inclined with respect to the radial direction, and each inner end of each of the air guide protrusions is arranged at an angle with respect to the radial direction. The arrangement is such that an inscribed circle is drawn at the center of the bottom surface, and the upper edges of each of the air guide protrusions are lowered from the side wall to the inner end so that the distance from the top surface of the piston is gradually increased. It is characterized in that the air guiding protrusions are formed to be large in size and the swirl on the side wall portion is deflected toward the inscribed circle, and the purpose thereof is to The object of the present invention is to provide a direct fuel injection type internal combustion engine that can greatly shorten the combustion period by improving the combustion rate in the diffusion combustion region in the latter stage.

The present invention provides a direct fuel injection internal combustion engine that generates a swirl in a cavity recessed in the upper surface of a piston and injects fuel into the swirl, as described above, in which a plurality of air guides are provided on the bottom surface of the cavity. The projection is arranged from the side wall of the cavity toward the center and inclined with respect to the radial direction,
Each inner end of each of the air guiding protrusions is arranged to draw an inscribed circle at the center of the bottom surface, and the upper edge of each of the air guiding protrusions is lowered from the side wall to the inner end. However, since the distance from the top surface of the piston is gradually increased and the swirl on the side wall portion is deflected toward the inscribed circle by each of the air guiding protrusions, the air is generated within the cavity. The part of the swirl of the rigid body vortex is
The high-velocity swirl on the side wall of the cavity is deflected toward the center of the cavity by each of the air guide protrusions, and together with the formation of an inscribed circle by each inner end of each air guide protrusion, the gas flow velocity at the center of the cavity is reduced. In other words, the turbulence is significantly increased, the mixing of combustion is greatly improved, and the remaining part of the swirl is sufficiently stirred by the deflected flow even in the later diffusion combustion period during combustion after the end of injection, and the combustion rate is improved. As a result, the combustion period is significantly shortened and extremely high thermal efficiency is achieved. Furthermore, in the present invention, since the height of each of the air guiding protrusions decreases toward the center of the cavity, the swirl at the outer peripheral portion (side wall portion) inside the cavity, that is,
A high flow rate air portion is efficiently flowed between each of the air guide protrusions, and the amount of deflected flow and kinetic energy inside each air guide protrusion are significantly increased, significantly improving fuel agitation efficiency. At the same time, the combustion efficiency is increased and high thermal efficiency is achieved.

Hereinafter, the present invention will be described with reference to the embodiment shown in FIGS. 4 to 6. On the upper surface of a piston 2 with a radius of Rcyl, which is slidably fitted into a cylinder liner 1, a bathtub-shaped combustion chamber with a radius of approximately Rc is provided. A cylindrical cavity 3 is recessed in the cylinder head 4.
Although not shown, intake valves and intake passages similar to conventional ones,
An exhaust valve, an exhaust passage, etc. are provided, and a fuel valve 5 is disposed opposite to the center of the cavity 3.

Further, a plurality of air guide protrusions 6 are arranged on the bottom surface of the cavity 3 at intervals in the circumferential direction, and each air guide protrusion 6 extends from the side wall of the cavity 3 toward the center and has a radius Rc. The inner ends of each air guiding protrusion 6 are arranged to draw an inscribed circle with radius r at the center of the bottom surface. The upper edges (α-α' line) of the projections 6 are made lower from the side wall of the cavity toward the inner end, and the distance from the top surface of the piston 2 is gradually increased (see FIG. 5). Each air guide protrusion 6 deflects the swirl of the cavity side wall toward the inscribed circle.

As shown in FIG. 4, with respect to the circumferential (X-Y) flow of the swirl inside the cavity 3, the upper edge (α-α' line) of each air guide protrusion 6 is arranged at an angle as shown in the figure. Y-Y between each air guiding protrusion 6 and 6
The tilted arrangement facilitates deflection of the swirl.

Since the embodiment shown in FIGS. 4 to 6 is constructed as described above, fresh air drawn into the cylinder liner 1 through the intake passage (not shown) is
It flows in the circumferential direction (X-X) to generate a rigid body vortex swirl, but the piston 2 rises and reaches the end of the compression stroke, and most of the gas in the cylinder liner 1 is forced into the cavity 3. and circumferential direction (X-
The flow of
The gas inside cavity 3 is sufficiently stirred.

This stirring effect becomes stronger as the engine speed increases, as the swirl speed increases.

Therefore, when there is a large amount of combustion after fuel injection, such as in a high-speed engine, the stirring effect appears significantly, increasing the combustion rate in the latter stages of combustion and shortening the combustion period.
The thermal efficiency of the engine is significantly improved, and smoke generation is reduced, which is effective in reducing pollution.

In the embodiment shown in FIGS. 4 to 6, the surface of the air guide protrusion 6 is formed into a gently curved surface, but as shown in FIGS. 7 to 8, the crest of the wave looks like it is about to collapse. The air guide protrusions 7 and 8 may be formed in a shape or in a shape with both side surfaces rising parallel to each other as shown in FIGS. 9 and 10, and as shown in FIGS. 4 to 6. It is possible to achieve substantially the same effects as the embodiment shown in .

Further, in the embodiments shown in FIGS. 4 to 10, the present invention was applied to a bathtub type combustion chamber cavity, but as shown in FIGS. 11 to 15, a toroidal type combustion chamber cavity 9 was applied. Four air guide protrusions 10 having a cross-sectional shape substantially similar to the air guide protrusions 6 shown in FIGS. 4 to 6 may be installed on the bottom wall of the cavity 9 at equal intervals in the circumferential direction. , the same embodiment can also provide the same effects as the previous embodiment.

In the embodiments described above, the cavities 3,
Although a plurality of air guiding protrusions 6, 10 are installed on the bottom wall of the cavities 3, 9, on the side walls of the cavities 3, 9, the air guiding protrusions 6, 10 are installed in the center of the cavities 3, 9 over part or the entire length of the range from the bottom wall to the top edge of the side walls. A plurality of guide protrusions formed in a direction drawing an inscribed circle on the bottom surface may be protruded at equal intervals in the circumferential direction, and the cavity 3,
Air guiding protrusions may be provided on both the bottom wall and the side wall of 9.

[Brief explanation of the drawing]

Figure 1 is a vertical side view of a direct fuel injection diesel engine with a conventional bathtub-type combustion chamber, Figure 2 is a vertical side view of a direct fuel injection diesel engine with a conventional toroidal combustion chamber, and Figure 3 is a vertical side view of a direct fuel injection diesel engine with a conventional toroidal combustion chamber. The figure is an explanatory diagram illustrating the swirl velocity distribution in the combustion chamber in these engines, and FIG.
5 is a vertical cross-sectional view taken along the line V-V in FIG. 4, FIG. 6 is a cross-sectional view taken along the - line in FIG. 4, and FIG. 7 is a cross-sectional view taken along the line - in FIG. 6
FIG. 8 is a cross-sectional view similar to that shown in the figure, FIG. 8 is a cutaway slope view of the main part, FIG. Fig. 11 is a plan view of the main part of another embodiment, Fig. 12 is a vertical sectional view taken along the line XII-XII in Fig. 11, Fig. 13 is a cutaway perspective view of the main part, 14
The figure is a plan view illustrating the operation of the same embodiment, and FIG. 15 is a cutaway perspective view of the main part thereof. 1...Cylinder liner, 2...Piston, 3...
...Cavity, 4...Cylinder head, 5...Fuel valve, 6, 7, 8, 10...Air guide projection, 9
... Cavity.

Claims (1)

[Scope of utility model registration request] In a direct fuel injection internal combustion engine that generates a swirl in a cavity recessed in the upper surface of a piston and injects fuel into the swirl, a plurality of air guiding protrusions are provided on the bottom surface of the cavity from the side wall of the cavity. The air guiding protrusions are arranged to be inclined toward the center and in the radial direction, and each inner end of each of the air guiding protrusions is arranged to draw an inscribed circle at the center of the bottom surface, and each of the air guiding protrusions The upper edge of each protrusion is made lower from the side wall to the inner end, and the distance from the top surface of the piston is gradually increased, so that the swirl of the side wall portion is caused by each of the air guiding protrusions. A direct fuel injection type internal combustion engine, characterized in that the fuel is deflected toward the inscribed circle.