JPH0634583Y2 - Combustion chamber of direct injection diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a combustion chamber of a direct injection diesel engine,
In particular, it relates to a combustion chamber of a direct injection diesel engine in which a pre-combustion chamber communicating with the main combustion chamber is provided at the top of the piston.

[Prior Art] Man-M type, toroidal type, reentrant type, etc. are known as those in which the top of the piston is recessed to form the combustion chamber of a direct injection diesel engine, but combustion of swirl, squish, etc. There is a proposal (Japanese Utility Model Publication No. 55-73518) in which a protrusion is provided in the combustion chamber in order to stabilize the air flow in the chamber or eliminate the dead space.

As shown in FIG. 5, in this proposal, a bar-shaped protrusion b is erected at substantially the center of the combustion chamber a, and among the wall surfaces partitioning the combustion chamber a, from the outer peripheral end d of the bottom face c. While forming up to the side surface e with an arc surface having an appropriate radius of curvature R,
The upper part of the side surface e is formed by a surface composed of a tangent line contacting the arc.

With this configuration, the mixing of the spray and the air is promoted, and combustion without smoke and HC is obtained.

On the other hand, a pre-combustion chamber type diesel engine in which fuel is not directly injected into the combustion chamber but is injected into the auxiliary combustion chamber (pre-combustion chamber) is also widely used.

As shown in FIG. 6, in a conventional engine of this type, a cylinder head f is provided with a pre-combustion chamber i communicating with a cylinder g through a small passage h, and a combustion injection nozzle j is connected to the pre-combustion chamber i.
The fuel is injected by projecting inward. Since this method has almost no ignition delay, it is characterized by preventing rapid combustion (combustion noise).

[Problems to be Solved by the Invention] However, in the above proposal, although desired air mixing can be obtained under high-speed operating conditions (high load), low speed or idle (low load) In the above, there was a problem that the penetration force of the spray was poor, the mixing with the air was insufficient, and the combustion became a discharge of a large amount of smoke and HC.

On the other hand, in the pre-combustion chamber type, even at low speed, since the spray is burned in the pre-combustion chamber i and then reaches the cylinder g through the communication hole h, the above problem does not occur. However, comparing both formulas during high speed operation,
The direct injection type has the great advantages of high output and low fuel consumption, and a combustion chamber having a structure that makes use of these advantages has been desired.

Therefore, in view of the above circumstances, the present invention was devised to provide a combustion chamber of a direct injection diesel engine in which the generation of smoke and HC is suppressed even during low speed operation.

[Means for Solving Problems] According to the present invention, a protrusion is provided substantially in the center of the main combustion chamber formed by recessing the piston top, and a pre-combustion chamber facing the combustion injection nozzle is formed on the protrusion. A communication hole is provided between the combustion chamber and the main combustion chamber in the piston radial direction that coincides with the injection direction of the fuel injection nozzle during high speed operation.

[Operation] During high-speed operation (high load), the communication hole guides the spray from the fuel injection nozzle to the main combustion chamber. The main combustion chamber ignites and burns this spray. At this time, the protrusions generate a predetermined air flow to promote mixing with the air. During low speed operation (low load), the spray is sprayed into the pre-combustion chamber,
Is ignited.

Thereafter, the flame and gas enter the main combustion chamber through the communication hole, and the combustion is completed.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 and 2 show an embodiment of a combustion chamber of a direct injection type diesel engine according to the present invention, in which a main combustion chamber 3 formed by recessing a top portion 2 of a piston 1 is known. Is provided with a pre-combustion chamber 5. And between the pre-combustion chamber 5 and the main combustion chamber 3,
A communication hole 6 formed in the piston radial direction is provided to connect them.

The main combustion chamber 3 has a bottom surface 7 and an outer surface 8 which are curved so that the spray A can be diffused into a predetermined state, and the inner side of the main combustion chamber 3 is formed by a protrusion 4 that is erected approximately at the center. It is partitioned and formed in an annular shape when viewed from above.

The pre-combustion chamber 5 faces the fuel injection nozzle 9 provided above the protrusion 4 and is provided in a substantially spherical shape, and the upper opening 10 thereof promotes the occurrence of squish, In addition, the tip end side of the injection nozzle 9 is appropriately narrowed so that it can enter the pre-combustion chamber 5. Further, the pre-combustion chamber 5 has a shape and a volume such that the pre-combustion chamber 5 receives the spray A from the fuel injection nozzle 9 and burns it at the time of low speed operation, like the sub chamber of the conventional pre-combustion chamber type diesel engine. Have

In this embodiment, four communication holes 6 are formed, which corresponds to the number of injection holes 11 provided in the fuel injection nozzle 9.
It is located radially from the center when viewed from above, facing the injection hole 11. Further, the vertical position thereof is formed substantially from the middle position to the high position of the partition wall 12 of the protrusion 4 that separates the pre-combustion chamber 5 and the main combustion chamber 3. At this position, during the high speed operation, the spray A, which is to be injected at a predetermined timing, that is, when the piston 1 rises to the position just before the top dead center L of the backward movement, is applied to the outer surface 8 of the main combustion chamber 3. The range of injection hole movement during the injection is matched so as to lead to. Therefore, the communication hole 6 has a vertically long shape having an appropriate width when viewed from the side. Further, the lower end of the communication hole 6 is positioned above the injection position so that the spray A does not enter the communication hole 6 when the top dead center L of the piston 1 which is the injection timing during low speed operation is reached. .

Next, the operation of this embodiment will be described.

When the engine is operating at high speed, the fuel injection nozzle 9
Injects fuel before the piston 1 reaches the top dead center L. The injected fuel is atomized, passes through the communication hole 6, hits the outer surface 8 of the main combustion chamber 3, and is mixed with the air which is appropriately diffused and compressed, and burned. At this time, the protrusion 4
Generates stable swirl and squish, and promotes mixing.

As shown in FIG. 3, at the time of low speed operation, the fuel injection nozzle 9 causes the fuel injection nozzle 9 to move when the piston 1 almost reaches the top dead center L.
Inject fuel. The spray A is injected into the pre-combustion chamber 5,
Is ignited. When the pressure in the pre-combustion chamber 5 rises due to combustion, the flame and the combustion gas flow into the main combustion chamber 3 from the communication hole 6 as shown by the arrow B as shown in FIG. 4, and the combustion is completed. To be done. That is, it operates similarly to the conventional pre-combustion chamber type diesel engine.

Thus, since ignition is performed in the pre-combustion chamber during low-speed operation, known low noise, low HC, and low smoke combustion can be obtained. Further, at the time of high speed operation, the fuel is injected directly into the main combustion chamber, so that low fuel consumption and high output can be obtained. Further, since the pre-combustion chamber of the present invention is provided at the top of the piston, there is no heat loss due to the cooling water of the cylinder head, and the startability does not deteriorate.

Although the pre-combustion chamber has a spherical shape in this embodiment, it may have another shape as long as the spray can be appropriately ignited at a low speed. In FIG. 1 or FIG. 3, the injection direction from the fuel injection nozzle is substantially horizontal, but the injection direction at that time is slightly downward so that the fuel is surely injected into the pre-combustion chamber at low speed. You may form. Further, the injection amount at this time may be adjusted according to the volume of the pre-combustion chamber to deal with HC generation due to excessive combustion supply.

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

A pre-combustion chamber with a communication hole that guides the spray to the main combustion chamber only during high-speed operation (high load) is formed on the protrusion provided in the main combustion chamber, so it is a direct injection type at high speed and a pre-combustion chamber type at low speed. By functioning as a combustion chamber of the engine, it is possible to obtain a direct-injection diesel engine that achieves low smoke, low HC, and low noise combustion regardless of operating conditions.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a combustion chamber of a direct injection type diesel engine according to the present invention, FIG. 2 is a plan view thereof, and FIGS. 3 and 4 are vertical sectional views showing its action. Figure,
FIG. 5 is a longitudinal sectional view showing a combustion chamber of a conventional direct injection diesel engine, and FIG. 6 is a longitudinal sectional view showing a combustion chamber of a conventional pre-combustion chamber diesel engine. In the figure, 2 is the piston top, 3 is the main combustion chamber, 4 is the protrusion,
Reference numeral 5 is a pre-combustion chamber, 6 is a communication hole, and 9 is a fuel injection nozzle.

Claims (2)

[Scope of utility model registration request] 1. A main combustion chamber formed by denting the top of a piston is provided with a protrusion at a substantially central portion thereof, and a pre-combustion chamber facing a fuel injection nozzle is formed on the protrusion, the pre-combustion chamber and the main combustion chamber. A combustion chamber of a direct injection diesel engine, characterized in that a communication hole in the piston radial direction corresponding to the injection direction of the fuel injection nozzle at the time of high speed operation is provided between and. 2. The combustion chamber of a direct injection diesel engine according to claim 1, wherein the pre-combustion chamber is formed into a substantially spherical shape.