JPS643785Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a heat shield for a swirl chamber type diesel engine.

Some conventional swirl chamber type diesel engines have adopted a so-called pinto nozzle, which is equipped with a sub-nozzle that performs injection prior to the main nozzle in order to improve startability. Since the fuel injected from the auxiliary nozzle is rapidly combusted within the vortex chamber, there is a problem in that the pressure rise becomes high and the noise and vibration of the engine become large.

In order to solve this problem, a swirl diesel engine and its heat shield as shown in FIGS. 1 and 2 have been devised.

That is, a whirlpool chamber 3 is formed by the mouthpiece and the cylinder head 2, and a so-called pinto type injection nozzle 6, which has a main nozzle hole 4 and a sub-nozzle hole 5 facing the whirlpool chamber 3, has a heat shield 7. A recess 8 for a fuel reservoir is formed in the wall portion of the heat shield 7 that is attached to the cylinder head 7 through the heat shield 7 and in contact with the fuel f injected from the sub-nozzle hole 5 of the heat shield 7. By storing a portion of the fuel, evaporation of a portion of the fuel is delayed and combustion is slowed, thereby preventing evaporation and rapid combustion of the fuel, and controlling noise and vibration of the engine.

Note that 9 indicates a glow plug, 10 a cylinder block, and 11 a piston.

The engine and its heat shield shown in FIGS. 1, 2, and 3 have the effect of preventing fuel evaporation and rapid combustion and suppressing engine noise and vibration. When the amount of C deposited increased and eventually the recess 8 was filled with carbon C as shown in FIG. 3, the effect of providing the recess was significantly reduced and HC increased.

The present invention is a whirlpool type diesel engine which eliminates the above-mentioned defects of the engine and its heat shield shown in Figs. 1 and 2, prevents rapid evaporation and combustion of fuel, and reduces noise and vibration. It provides a heat shield.

Examples of the present invention are shown in Figs. 4, 5, and 6 below.
The diagram will be explained.

Note that parts that are the same as those in FIGS. 1 and 2 are given the same reference numerals.

FIG. 4 shows the first embodiment of the present invention.
Reference numeral 12 denotes a heat shield according to the present invention, whose flange 13 is seated on the shoulder 2a of the cylinder head 2, and a pinto type injection nozzle 6 having a main nozzle hole 4 and a sub-nozzle hole 5 is attached thereto. .
The heat shield 12 has an inlet portion 14a on the upper wall surface 12a facing the sub-nozzle hole 5 of the injection nozzle 6, and an outlet portion 14b on the inner wall surface 12b facing the vortex S direction in the swirl chamber 3. A communication hole 14 is formed therein.

Therefore, when the fuel f is injected from the auxiliary nozzle hole 5, some of the fuel reaches the upper wall surface 1 of the heat shield 12.
When it comes into contact with 2a, it scatters and evaporates, causing combustion. On the other hand, some of the other fuel enters the communication hole 1 from the inlet portion 14a.
4 will be introduced.

Here, the velocity distribution of the airflow flowing in from the outlet portion 14b using the dynamic pressure of the vortex S in the vortex chamber 3 is maximum at the center of the communication hole 14, and as it approaches the peripheral wall surface portion 14c. Therefore, among the fuel injected toward the communication hole 14 as described above, the fuel introduced near the peripheral wall surface 14c of the communication hole 14 adheres to the peripheral wall 14c of the communication hole 14 and evaporates. is delayed. Therefore, slow combustion is performed, pressure rise is suppressed, and combustion noise and engine vibration are reduced. On the other hand, the fuel injected toward the vicinity of the center of the communication hole 14 flows through the communication hole 1 due to the vortex S that reaches its maximum from several degrees before top dead center (crank angle) where injection is performed to top dead center.
4, the introduction into the communication hole 14 is suppressed, thereby restricting the filling of carbon C near the center of the communication hole 14, and also preventing the generation and increase of HC.

FIG. 5 shows a second embodiment of the present invention, in which a communicating hole 14A of a heat shield 12 is narrowed midway to form a narrowed portion 14d.

In this way, by forming the constricted portion 14d, the inflow of the air flow into the communication hole due to the vortex S is relaxed, so the amount of fuel f introduced into the communication hole is slightly increased, and the amount of fuel f introduced into the communication hole is increased. Since the amount of fuel that adheres and whose evaporation is delayed increases slightly, combustion takes place more slowly, which has the effect of further reducing combustion noise and engine vibration.

FIG. 6 shows a third embodiment of the present invention, in which the outlet portion 14e of the communication hole 14B of the heat shield 12 is widened toward the end.

By expanding the outlet portion 14e toward the end, the inflow of air flow due to the vortex S increases, so that filling of carbon near the center of the communication hole 14B is further restricted, and HC is generated and increased. It also has the effect of preventing more damage.

Further, by combining the second embodiment and the third embodiment, it is possible to provide a heat shield for a swirl chamber type diesel engine which is excellent in both effects.

As described above, according to the present invention, it is possible to provide an ideal heat shield for a swirl chamber type diesel engine, which prevents sudden fuel evaporation and combustion and suppresses engine noise and vibration without the problems of carbon buildup or increased HC.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a fuel injection nozzle portion showing a conventional example, Fig. 2 is an enlarged view of the same main part, Fig. 3 is an explanatory diagram of the same main part, and Fig. 4 is a first embodiment of the present invention. FIG. 5 is an enlarged view of the main parts of the second embodiment of the present invention, and FIG. 6 is an enlarged view of the main parts of the third embodiment of the invention. 1...Best, 2...Cylinder head, 3...Swirl chamber,
4... Main nozzle hole, 5... Sub-nozzle hole, 6... Injection nozzle, 7...
Heat shield (in the conventional example), 8... recessed portion,
12...Heat shield (in the present invention), 1
4, 14A, 14B...Communication hole, 14d...Inlet part,
14b... Outlet part, 14c... Surrounding wall surface part, 14d... Throttle part, 14e... Outlet part expanded in a shape that widens toward the end.

Claims (1)

[Claims for Utility Model Registration] 1. An injection nozzle equipped with a main nozzle hole and a sub-nozzle hole is attached to a cylinder head via a heat shield so as to face a swirl chamber, and fuel is injected from the sub-nozzle hole. A heat shield for a swirl chamber type diesel engine, characterized in that a communicating hole is formed in the heat shield that comes into contact with the heat shield, with an inlet portion facing the sub-nozzle hole and an outlet portion facing the vortex direction. 2. A heat shield for a swirl chamber type diesel engine according to claim 1, wherein the communication hole is provided with a constriction portion. 3. A heat shield for a swirl chamber type diesel engine according to claim 1, wherein the exit portion of the communication hole is expanded in a shape that widens toward the end.