JPH02267314A - Combustion chamber for direct injection diesel engine - Google Patents

Abstract

PURPOSE:To create dynamic swirls so as to improve combustion efficiency by guiding squish flow created in proximity to the top dead point of a piston by offset blades so as to flow into a cavity while swirling. CONSTITUTION:The crown 17 of a piston 15 is provided with a cavity 21 formed being recessed from the upper surface 17a of the crown 17. The crown 17 is further provided with numerous slit grooves 23 formed in such a way as to be released to the upper surface 17 and the inner flank 21a of the cavity 21, as well as offset in relation to the center axis O of the cavity 21. Numerous blades 25 are protrusively provided, in opposition to the respective slit grooves 23, at the lower surface of a cylinder head 5. When the piston 15 reaches the proximity of the top dead point and squish is generated in the ring space between the crown part upper surface 17a and the cylinder head 5, each blade 25 is inserted into the slit groove 23 so as to divide the ring space, and the squish flow A is then pushed out from the divided space and flows into the cavity 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to a combustion chamber of a direct injection diesel engine equipped with a swirl generation mechanism within the combustion chamber.

(Prior Art) Direct injection type diesel engines have less intake throttling loss than pre-chamber types, but because it is difficult to obtain dynamic air flow within the combustion chamber, combustion performance tends to deteriorate. For this reason, in many cases, to compensate for this, the swirl is locally strengthened and fuel is injected there.

As a combustion chamber equipped with such a swirl generation mechanism,
Conventionally, for example, there are devices shown in FIGS. 6 and 7 (see Japanese Patent Laid-Open No. 129716/1983). In the drawings, reference numeral 101 indicates a cylinder block, 103 indicates a cylinder head, 105 and 107 indicate an intake valve and an exhaust valve mounted on the cylinder head 103, respectively, and 111 indicates a piston, which form a combustion chamber 100. FIG. 6 shows a case where the piston 111 is approximately at the top dead center.

The piston 111 has an upper surface 113 of its crown 113.
A substantially short cylindrical cavity 115 is formed which is open to a. A plurality of slit grooves 117 (four in this example) are formed in the crown 113 and open on the upper surface 113a and the inner surface 115a of the cavity.The center line of each slit groove 117 is aligned with the cavity. 1
An offset is provided to avoid the center axis 0 of 15.

With the above configuration, when the piston 111 approaches the top dead center during the compression stroke, the air compressed between the flat round upper surface 113a and the cylinder head 103 becomes a strong squish flow and flows into the cavity 115.
This squish flow also flows into each slit groove 117 and is ejected from the inner surface 115a of the cavity. Slit groove 1
17 is provided with an offset as described above, the ejected airflow is guided by the upper surface 115a and swirls, creating a swirl along with the squish flow that has flowed into the cavity 115. Therefore, when fuel is injected into the cavity 115 from the fuel injection valve 109 at this time, the fuel mist droplets are combusted while being dispersed along with the swirl, thereby improving combustion performance.

Further, as a conventional combustion chamber equipped with a swirl generating mechanism, there are those shown in FIGS. 8 and 9 (see Japanese Patent Laid-Open No. 107812/1983).

That is, FIG. 9 is a top view of the piston, and a short cylindrical cavity 115 is formed in the crown upper surface 113a of the piston 111. Around the cavity 115, for example, three plate-shaped curved protrusions 121 made of ceramic are fixed by screws 119, and between these adjacent protrusions 121, the cavity 115 is inserted from the outer edge 113b of the crown upper surface 113a. The spiral that leads to 123
It is formed.

FIG. 8 is a bottom view of the cylinder head side of this combustion chamber, and a ring 131 made of ceramic is fixed to the cylinder head 103 with screws 129. The ring 131 is formed with a ring portion 131a and a protruding portion 131b that respectively correspond to the outer edge 113b of the crown upper surface 113a and the spiral groove 123 on the piston 111 side.

With the above configuration, when the piston 111 approaches the dead center, each protruding piece 121 is inserted into the ring 131, and the air around the protruding piece 121 is transferred to the ring part 131a of the ring 131 and the protruding part 13.
1b, this air is injected into the cavity 115 from the swirl 123 and generates a swirl within the cavity 115.

(Problems to be Solved by the Invention) However, such conventional combustion chambers have the following drawbacks.

First, in the case of the one shown in FIGS. 6 and 7, the slit groove 11
7 becomes a dead volume with respect to the cavity 115, so that the slit groove cannot be made very large in order to reduce the engine output. As a result, the squish flow passing through this slit groove is restricted, so that the swirl flow cannot be strengthened as desired.

In addition, in the case of FIGS. 8 and 9, the piston 111
As the ring approaches the top dead center, the space around the protruding piece 121 is filled with the ring 131, so the dead volume described above can be suppressed to a small amount. However, on the other hand, the air in the space cannot directly flow into the cavity 115, and while the air circulates around the protrusion 121 and is ejected from the spiral groove 123, the turbulence component due to the squish is reduced. Therefore, the swirl generated within the cavity 115 is less active within the cavity 115, leading to a decrease in the dispersibility of the fuel mist droplets.

Therefore, an object of the present invention is to impart a strong swirl to the squish flow without attenuating it as much as possible.

[Structure of the Invention] (Means for Solving the Problems) The means of the present invention for solving the problems described above is such that the piston constituting one end of the combustion chamber has a cavity that is open on the top surface of its crown, and a cavity in the cavity. It has a plurality of slit grooves that are open on the inner surface and the top surface of the crown and are offset from the center axis of the cavity. A vane plate that can be inserted into these slit grooves is provided.

(Function) According to this means, when the piston rises and approaches the top dead center, the plurality of vanes provided on the cylinder head side are inserted into the slit grooves opened on the top surface of the crown, so that the top surface of the crown and The space between the cylinder head and the cylinder head is divided into a plurality of spaces, and in this state, the air within these spaces forms a strong squish flow. Since the slit grooves and the corresponding vanes are offset from the center axis of the cavity, the above squish flow is guided by the soundboard and swirls while the screw lower reaches the top dead center. It flows into the Lord 11 Bitey. As a result, a highly active swirl is generated within the cavity.

On the other hand, since the inner plate enters the slit groove and fills the slit space, it is possible to significantly eliminate the dead volume for the cavity, and furthermore, the air removed from the slit groove can flow into the cavity. Since it is ejected from the side, this helps create a swirl.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

Similar to those shown in FIGS. 6 and 7, the combustion chamber 1 includes a cylinder block 3, an intake valve 7. A cylinder head 5 to which an exhaust valve 9, a fuel injection valve 10, etc. are attached, and a piston 1
5, and FIG. 1 shows the state when the piston 15 is approximately at the top dead center.

The crown 17 of the piston 15 has a short cylindrical chitopity 21 recessed from approximately the center of its upper surface 17a. Three straight slit grooves 23 are formed in the crown 17 and open on the upper surface 17a and the inner surface 21a of the cavity 21. These slit grooves 23
are arranged axially symmetrically with respect to the central axis 0 of the cavity 21, avoiding the opposing portions of the intake valve 7 and the exhaust valve 9, and are provided with an off-hit so that these slit grooves 23 are not directed toward the central axis W; AO. It is.

On the other hand, each slit groove 23 is provided on the lower surface of the cylinder head 5.
Three soundboards 25 are provided protrudingly facing each other. and,
When the piston 15 reaches near the top dead center and a strong squish occurs, the upper edge of the slit groove 23 reaches the lower edge of the soundboard 25, and after that, the vane plate 25 is inserted into the slit groove 23 with a suitable amount of play and then rises. The mutual dimensional relationship is determined so that the lower edge approaches the bottom surface of the slit groove 23 at the dead center.

Therefore, when the piston 15 reaches the vicinity of the top dead center and a strong squish occurs in the annular space between the crown upper surface 17a and the cylinder head 5, each vane plate 25 closes to the slit groove 2.
3 and divides the annular space into three. When the piston 15 continues to rise, the squish flow is pushed out from the divided space and is swirled as shown by arrow A by the offset sound boards 25, and flows directly into the main pit 21. As a result, a dynamic swirl S rich in turbulent flow components based on squish is generated within the cavity.

Further, in the above process, the air in the slit grooves 23 is pushed out by the soundboard 25 and ejected from the inner surface 21a of the cavity 21 in the same direction as the arrow A, which promotes the formation of the swirl S. Since the slit groove 23 is almost filled with the vane plate 25 in the vicinity of the top dead center, the volume of the cavity 21 is not unnecessarily increased during mixing and combustion of fuel mist droplets.

Furthermore, since this embodiment is a system that generates swirl by the squish flow in the combustion chamber, it is not necessary to generate swirl by an intake port such as a helical port in the intake stroke. As a result, a straight intake port with low intake resistance can be used, improving intake air filling efficiency and increasing output.

FIGS. 3 and 4 show an embodiment in which the present invention is applied to a four-valve type combustion chamber.

In addition, the parts having substantially the same functions as those of the above-mentioned embodiment include:
The symbols used in FIGS. 1 and 2 will be used to omit redundant explanations.

The cylinder head 5 has two intake valves 7 and two exhaust valves 9.
are installed in almost equiangular relationship.

Crown 1 of piston 15 in which cavity 21 is formed
7, -F24 intake and exhaust valves 7 and 9 are respectively formed with offset slit grooves 23 in the same manner as in the above-mentioned embodiment, and these slit grooves 23 are in contact with the crown upper surface 17a. It is open to the cavity inner surface 21a.

On the other hand, a vane plate 25 facing the slit groove 23 is integrally formed on the lower surface of each intake valve 7 and exhaust valve 9. The dimensional relationship between the slit groove 23 and the inner plate 25 is the same as in the embodiment described above. In order to maintain the above-mentioned opposing relationship, the intake and exhaust valves 7 and 9 are prevented from rotating.

FIG. 5 shows an example of the above-mentioned rotation prevention means, which is a valve fitted to the cylinder head 5 to support the valve shaft 7a (9a) of the intake (exhaust) valve 7 (9). Guide 31
A slot groove 33 is formed on both sides of the upper end of the valve shaft 7a (9
In a), a cockbin 35 is fitted in the diametrical direction, and both ends of the cockbin 35 are engaged in the slot grooves 33.

The operation of this embodiment is almost the same as that of the previous embodiment, and when the intake and exhaust valves 7.9 are lowered and opened, the piston 15 is located lower than this and is retracted. , the two do not interfere with each other.

[Effects of the Invention] As explained above, according to the configuration of the present invention, a strong squish flow generated in the vicinity of top dead center is guided by the offset vane and flows into the cavity while rotating. Therefore, a dynamic swirl containing many turbulent flow components is generated within the cavity. Therefore, when fuel is injected into the cavity, the fuel droplets and air actively mix with each other, thereby significantly improving combustion performance. Further, since the vane plate enters the slit groove at the top dead center, the dead volume of the cavity is eliminated by forming the slit groove, and deterioration of combustion is prevented.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a combustion chamber according to an embodiment of the present invention;
2 is a top view of the piston in FIG. 1, FIG. 3 is a vertical sectional view of a combustion chamber according to another embodiment of the invention, FIG. 4 is a top view of the piston in FIG. 3, and FIG. 5 is a top view of the piston in FIG. v in Figure 3
- ■ Cross-sectional view, Figure 6 is a vertical cross-sectional view of the combustion chamber according to the conventional example,
FIG. 7 is a top view of the piston in FIG. 6, FIGS. 8 and 9 are views for explaining a combustion chamber according to another conventional example, FIG. 8 is a bottom view of the cylinder head, and FIG. is a top view of the piston. 1... Combustion chamber 5... Cylinder head 1
5... Piston 17... Crown 17a.
... Crown upper surface 21 ... Capity 23 ... Slit groove 25 ... Vane plate agent Patent attorney 3
Hidekazu Yoshikazu Figure 2 Figure 4 Figure 3 Figure 5 Figure 7

Claims (1)

[Claims] A piston constituting one end of a combustion chamber has a cavity that is open to the top surface of its crown, and a plurality of slit grooves that are open to the inside surface of the cavity and the top surface of the crown and that are offset from the center axis of the cavity. have,
A combustion chamber for a direct injection diesel engine, characterized in that a blade plate that can be inserted into the slit groove near the top dead center of the piston is provided on the cylinder head side constituting the other end of the combustion chamber.