JPS60147526A - Direct-injection type diesel engine - Google Patents

Abstract

PURPOSE:To lower a noise level in a simplified structure, by forming a main combustion chamber and a swirl chamber in the head of piston and providing a cylinder head with a fuel nozzle having two nozzle holes formed therethrough, while at the same time reducing the diameter of nozzle bore for the swirl chamber and increasing the diameter of nozzle bore for the main combustion chamber. CONSTITUTION:While a main combustion chamber 2 and a swirl chamber 3 are formed at the head 11 of piston 1, a hot plug 5 having an opening 31 is secured to the upper surface of swirl chamber 3. A cylinder head is in turn provided with a fuel nozzle 7 having two nozzle holes 71, 72 formed therethrough. While the swirl chamber 3 has its nozzle bore 71 reduced in diameter, the main combustion chamber 2 selects a larger diameter for its nozzle bore 72. This arrangement permits the nozzle hole 71 to inject a fuel from it while a fresh air is swirling inside the swirl chamber 3, so that a fuel- air mixture is ignited and burnt in an optimum manner. Then, a flame is injected from inside the swirl chamber 3 to the main combustion chamber 2, igniting and burning a fuel injected from the nozzle bore 72 to the wall surface 22 of main combustion chamber 2. In this way, the cylinder can lower its maximum internal pressure, and thereby achieving a purpose as desired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a direct injection diesel engine, and more particularly to a combustion chamber of a diesel engine.

[Prior Art] Conventionally, the combustion chamber in a direct injection diesel engine has a flat cylinder head and a piston crown shape as shown in Fig. 1 (a), (b), (c), or something similar. is widely known. However, since these combustion chambers inject all of the fuel into one combustion chamber, there is a large amount of premixed combustion due to the cheap combustion of fuel during the ignition delay period, and the rate of increase in pressure within the cylinder is extremely high. They had the disadvantages of being high and making noise.

Furthermore, there is a known technology that improves thermal efficiency by increasing the compression ratio, but on the other hand, the problem arises that the maximum pressure increases due to the adoption of a high compression ratio, making the noise even louder. was.

Furthermore, in order to improve the above problems,
As shown in Publication No. 13911M, etc., a convex part is installed on the cylinder head to provide an auxiliary combustion chamber, and nozzles are installed in each of the main and auxiliary combustion chambers to adjust the timing of combustion in the auxiliary combustion chamber to the main combustion chamber. Techniques to make the combustion chamber faster than the combustion chamber are also known.However, in these techniques, the auxiliary combustion chamber is formed by a combination of the shapes of the cylinder head and piston crown, so it is difficult to manufacture, and the combustion chamber operates in a different system. There were problems such as the need to provide similar nozzles.

[Object of the Invention] The object of the present invention is to improve the above-mentioned drawbacks and problems, and to provide a direct injection diesel engine that is easy to manufacture since only the top of the piston is processed, operates with only one nozzle, and has low noise. It is about providing.

[Configuration of the Invention] In order to achieve the above-mentioned object, the configuration of the present invention is such that a main combustion chamber and a swirl chamber are provided at the top of the piston, a fuel nozzle having two injection holes is provided in the cylinder head, and a swirl chamber is provided at the top of the piston. It is characterized by having smaller nozzle holes on the side and larger nozzle holes on the main combustion chamber side.

[Fruit Example] An embodiment of the present invention will be described based on FIGS. 2 to 4.

At the top 11 of the piston 1, a main combustion chamber 2 and a swirl chamber 3 are provided. The vortex chamber 3 has a smaller volume than the main combustion chamber 2, and has a spherical shape so that mixing vortex is likely to occur. A hot plug 5 having an opening 31 is fixed to the upper surface of the swirl chamber 3 with a mounting screw 51.

The hot plug 5 is made of a heat-resistant material with good heat retention, and is inclined with respect to the cylinder head 6.
It extends from the opening 31 of the swirl chamber 3 to the edge 21 of the main combustion chamber 2 .

The main combustion chamber 2 has a bowl shape with a large opening at the top, and burns most of the fuel.

A fuel nozzle 7 having two injection holes 71 and 72 is installed in the cylinder head 6.
1 , 72 faces the swirl chamber 3 and the main combustion chamber 2 .

The nozzle holes 71 on the swirl chamber 3 side are small, and the nozzle holes 72 on the main combustion chamber 2 side are large. There are also few.

The injection direction is set so that the nozzle hole 71 on the swirl chamber 3 side is attached to the wall surface of the hot plug hole 31), and the nozzle hole 72 on the main combustion chamber 2 side is set so that the fuel adheres to the wall surface 22 of the main combustion chamber 2. do.

Next, the operation of this embodiment will be explained. As the piston 1 rises, fresh air flows into the hot plug hole 31 and a vortex is created in the vortex chamber 3. When the piston 1 further rises and approaches top dead center, fuel is injected from the injection hole 71 of the fuel nozzle 7 into the vortex, but the vortex stirs the fuel and mixes it well, reducing the ignition delay. and immediately ignites and burns. Note that the presence of the hot plug 5 makes ignition even better.

On the other hand, the nozzle hole 72 of the fuel nozzle 7 is located on the side 22 of the main combustion chamber 2.
The injected fuel vaporizes immediately after adhering to the n''! surface 22, but because it is rich, it is not in a state that leads to combustion. The pressure becomes higher than the pressure inside the main combustion chamber 2, and flame jets out at high speed toward the main combustion chamber 2, stirring the fuel A on the main wall surface 22,
Combustion occurs in the main combustion chamber 2 due to the propagation of fire and flame from the swirl chamber 3.

Therefore, the timing of combustion in the swirl chamber 3 and the combustion in the main combustion chamber 2 are shifted, resulting in two-stage combustion, so the maximum pressure in the cylinder (A) is lower than that of the conventional engine, as shown in Figure 4. It is lower than the maximum pressure (b), resulting in smooth and quiet combustion.

[Effects of the Invention] As described above, the present invention first performs combustion in a swirl chamber,
This is a 2-stage combustion in which combustion is then carried out in the main combustion chamber.
Compared to conventional engines, the maximum pressure in the cylinder is lower, and the rise in pressure in the cylinder becomes gentler and smoother, resulting in less engine noise.Furthermore, two chambers are provided at the top of the piston. Since the configuration is simple, it is easy to design and manufacture, and since only one fuel nozzle is required, effects such as the simplification of the injection device can also be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional piston crown, Fig. 2 is a sectional view of an embodiment of the present invention, Fig. 3 is a view taken along the line I-I in Fig. 2, and Fig. 4 is a crank angle view. It is a figure showing the relationship between and pressure. DESCRIPTION OF SYMBOLS 1...Piston, 2...Main combustion chamber, 3...Swirl chamber, 6...Cylinder head, 7...Fuel nozzle, 11
...Top of the piston. Figure 1 (a) City) (C) Figure 2 Ikura #I/IJl

Claims (1)

[Claims] A main combustion chamber and a swirl chamber are provided at the top of the piston, and a fuel nozzle with two injection holes is provided in the cylinder head, with the injection hole on the swirl chamber side being small and the injection hole on the main combustion chamber side being large. Features a direct injection diesel engine.