JPH04136415A - Auxiliary combustion chamber type diesel engine - Google Patents

Abstract

PURPOSE:To accelerate the diffusion into a main combustion chamber by projectingly installing a projection whose inclination angle for the edge surface increases gradually an the edge surface of a piston and increasing the volume increase speed in a main combustion chamber during the lowering of the piston larger on the part having a gentle inclination on the projecting aslant surface than that on the part having a sharp inclination. CONSTITUTION:A projection 21 whose inclination on an aslant surface is sharp at the center part and becomes gentle gradually toward the peripheral part is projectingly installed at the center at the upper edge part of a piston 2, and the upper edge of the projection 21 is set close to a subcombustion chamber 3. Inside the subcombustion chamber 3, a fuel injection nozzle 31 for jetting fuel and a glow plug 32 for assisting the ignition of fuel on the engine start, etc., are arranged. Since the volume increase speed in a main combustion chamber during the lowering of the piston is made larger on the part having a gentle inclination on the aslant surface of the projection than that on the part having a sharp inclination, the reverse skewish flow speed in the partial combustion gas is accelerated, and the difsusion to the main combustion chamber is accelerated, and the discharge quantity of black smoke is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sub-combustion chamber type diesel engine in which air and partially combusted gas are well mixed in the main combustion chamber.

(Prior art) In a conventional sub-combustion chamber type diesel engine, the amount of air in the sub-combustion chamber during compression is approximately 50% of the total air amount in the combustion chamber.
It is set so that The fuel injected into the sub-combustion chamber at the end of the compression stroke mixes with the air in the sub-combustion chamber and starts combustion, so the inside of the sub-combustion chamber becomes high temperature and high pressure.6 Combustion gas in the sub-combustion chamber Partially burned gas, which is a mixture of unburned gas and unburned gas, is injected into the main combustion chamber through the nozzle hole, mixed with the air in the main combustion chamber, and continues combustion. Note that when combustion continues in the main combustion chamber, the piston is in the process of descending, and therefore the volume of the main combustion chamber is in the process of expanding, so that the combustion temperature is maintained at a low temperature.

As mentioned above (because only 50% of the total air is filled in the auxiliary combustion chamber where fuel is injected, the equivalence ratio C in the auxiliary combustion chamber is the ratio of fuel to the amount of air), and in the main combustion chamber Since the combustion of N continues at a low temperature, the N
The generation of Ox is suppressed and the amount of NOx contained in the exhaust gas is significantly reduced.

(Problem H to be solved by the invention) In such a conventional sub-combustion chamber type diesel engine,
When the piston rises, the air in the main combustion chamber flows into the sub-combustion chamber as a squish flow, but when the piston descends, there is almost no reverse squish flow from inside the sub-combustion chamber to the main combustion chamber, and the air inside the sub-combustion chamber Combustion gas and air in the main combustion chamber are mixed only by ejection of partially combusted gas accompanying combustion in the auxiliary combustion chamber.

Therefore, the time required for mixing the air and the partially combusted gas in the main combustion chamber becomes long, and combustion may stop in an incomplete combustion state. As a result, the amount of black smoke contained in the exhaust gas increases, and the output and efficiency of the engine decrease.

The present invention has been made in view of the above points, and it shortens the mixing time of air and partially combusted gas in the main combustion chamber, suppresses the amount of black smoke emission, and reduces the amount of black smoke emitted. The aim is to provide a combustion chamber type diesel engine.

(Means for Solving the Problems) According to the present invention, a projection having a slope provided on an end surface of a piston and having a slope whose inclination angle with respect to the end surface gradually increases; an inner end surface of the cylinder forming a main combustion chamber with a constant thickness between the slope and the slope at a point position, and a nozzle hole provided at a position facing the top of the protrusion and communicating the sub-combustion chamber with the main combustion chamber. It is possible to provide a sub-combustion chamber type diesel engine having the following features.

(Function) In the auxiliary combustion chamber type diesel engine of the present invention, the volume increase rate of the main combustion chamber when the piston descends is greater in the part where the slope of the protrusion provided on the piston is gentler than in the steep part. Therefore, the reverse squish flow velocity of the partially combusted gas is accelerated, and its diffusion into the main combustion chamber is promoted.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an embodiment of an engine according to the present invention.

1 is an engine body, and a piston 2 is disposed inside the engine body 1. A protrusion 21 is provided at the center of the upper end of the piston 2 . The slope of the protrusion 21 is steep at the center and gradually becomes steeper toward the periphery. Note that this figure shows a case where the piston 2 is at the top dead center position, and the main combustion chamber is formed to have a constant thickness.

3 is an auxiliary combustion chamber, and a fuel injection nozzle 31 that injects fuel into the auxiliary combustion chamber 3 and a glow plug 32 that assists in igniting the fuel at the time of starting the engine, etc. are disposed.

Next, the operation of the engine with the above configuration will be explained.

FIG. 2 is a diagram showing a state in which the piston 2 is in the middle of its descent.

The internal volume of the main combustion chamber increases as the piston 2 descends, but since the slope of the upper end surface of the piston 2 is not constant, the rate of increase in the internal volume varies depending on the location within the main combustion chamber.

The portion indicated by a in FIG. 2 is a portion where the upper end surface of the piston 2 has a gentle slope and is in a nearly horizontal state. On the other hand, the part indicated by b has a steep slope and is almost vertical.

As is clear from Fig. 2, the rate of increase in internal volume is different between section a, where the slope is gentle, and section a, where the slope is steep.
The rate of increase in internal volume is higher in section a where the slope is gentler.

In addition, the slope of the upper end surface of the piston 2 is steep near the nozzle hole that communicates with the sub-combustion chamber 3, and becomes gentler as it moves away from the nozzle hole, so the reverse squish flow flows toward the part with a gentler slope. It is accelerated and diffused into the main combustion chamber.

By the way, although the embodiment in which the protrusion is provided at the center of the upper end surface of the piston has been described above, the location where the protrusion is provided is not limited to the center of the upper end surface of the piston.

FIG. 3 is a sectional view showing the structure of an engine in another embodiment.

4 is a piston, and the upper end of the piston 4 is provided with a protrusion 41 that is eccentric around the periphery. A sub-combustion chamber 5 is provided in a portion corresponding to the protrusion 41.

The slope of the protrusion 41 is steepest in the vicinity of the nozzle hole, and becomes gentler toward the right in the figure, that is, as it moves away from the nozzle hole.

Therefore, as the piston 4 descends, the reverse squish flow from the auxiliary combustion chamber 5 is accelerated to the right in the figure and diffused into the main combustion chamber.

Although the embodiments of the present invention have been described in detail above, various different embodiments can be easily constructed without departing from the spirit of the invention, and therefore, the present invention is not limited to any limitations other than those set forth in the claims. , and is not limited to any particular implementation.

(Effects of the Invention) As explained above, according to the present invention, the volume increase rate of the main combustion chamber when the piston descends is slower in the part where the slope of the protrusion provided on the piston is steeper than in the part where the slope is steeper. Because of the large size, the reverse squish flow velocity of the partially combusted gas is accelerated, the diffusion into the main combustion chamber is promoted, and therefore the mixing time of the air and the partially combusted gas in the main combustion chamber is shortened.
It is possible to provide a sub-combustion chamber type diesel engine in which the amount of black smoke emission is suppressed and the output and efficiency do not decrease.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of one embodiment of the engine according to the present invention, FIG. 2 is a diagram showing the state in which the piston 2 is in the middle of its descent, and FIG. 3 is the structure of the engine in another embodiment. FIG. 1... Engine body, 2... Piston, 3...
Sub-combustion chamber, 4... Piston, 5... Sub-combustion chamber, 21
...Protrusion, 41...Protrusion.

Claims (2)

[Claims] (1) A constant thickness exists between a protrusion provided on the end face of the piston and having a slope whose inclination angle with respect to the end face gradually increases, and the slope that faces the slope forming the protrusion and is located at the top dead center position of the piston. an inner end surface of the cylinder forming the main combustion chamber;
A sub-combustion chamber type diesel engine, comprising a nozzle hole provided at a position facing the top of the protrusion and communicating the sub-combustion chamber with the main combustion chamber. (2) The auxiliary combustion chamber type diesel engine according to claim (1), wherein the protrusion is provided at the center of the end surface of the piston.