JPS6282223A - Whirl-chamber type diesel engine - Google Patents

Abstract

PURPOSE:To secure favorable combustion as well as to reduce the discharge of HC and smoke, by installing a dish-form concave part in a range almost all over the whole sphere of the top face of a piston, while opening a nozzle hole in an almost tangential direction of this dish-form concave part. CONSTITUTION:A whirl chamber 3 adjoining a fuel injection nozzle 4 to an engine cylinder head 10 is installed. This whirl chamber 3 and a main chamber 2 are interconnected with each other via a nozzle hole 15. A dish-form concave part (cavity) 14 is installed in a range almost all over the whole sphere of the top face of a piston 12. The nozzle hole 15 is opened in an almost tangential direction of this dish-form cavity 14. Thus, favorable combustion is secured and the discharge of HC and smoke is sharply reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to improvements in swirl chamber diesel engines.

(Prior art) A swirl chamber type combustion chamber is known as a combustion chamber suitable for high-speed diesel engines, and one type of this type, as shown in Figures 3 and 4, has been proposed and used (actual Showa 58-1
(See Publication No. 80327).

To explain this, during the compression stroke of the engine, the piston 1
The pressure in main chamber 2 and swirl chamber 3 increases due to the rise in .

The temperature becomes high (the fuel is pushed into the vortex chamber 3 and a vortex is generated, and fuel is injected from the fuel injection nozzle 4 installed in the vortex chamber 3 near compression top dead center).

This fuel is ignited in the swirl chamber 3, turns into a flame, and flows into the main chamber cavity 6, which is formed in a cloverleaf shape, from the injection port 5 together with the unburned fuel.

Within the main chamber cavity 6, the flame and unburned fuel flow along the trench portion 7, collide with the branch portion 8 of the crowbar cavity 6, and are split into two directions. Then, the branched flame and unburned fuel are diffused along the arc of the crowbar cavity 6, and combustion proceeds while taking in fresh air from the main chamber 2.

In addition, 9 is a cylinder block, 10 is a cylinder head,
11 is a glow plug.

(Problem to be Solved by the Invention) However, in this case, the flame and unburned fuel, that is, the jet jet, spouted into the cavity 6 are split into two directions from the trench portion 7 at one end by the crowbar cavity 6. Since it is diffused, mixing with air is quick in this direction of diffusion, but in the region (2) on both sides of the trench portion 7, the flow due to wraparound etc. is weak, so it is difficult to expect sufficient mixing with air.

Therefore, in the region (2), the air utilization rate is poor, so combustion is delayed, and as a result, the amount of HC (hydrocarbon) and smoke emissions may increase, especially at high loads when the amount of fuel injection is large.

This invention aims to solve these problems.

(Means for Solving the Problems) This invention provides a swirl chamber type diesel engine in which a swirl chamber with a fuel injection nozzle facing the engine shilling head is provided, and the swirl chamber and the main chamber are communicated through a nozzle. In this method, a dish-shaped recess is provided over almost the entire top surface of the piston, and the nozzle opening is opened in a substantially tangential direction of the dish-shaped recess.

(Function) Therefore, the flame and fuel from the vortex chamber are vigorously ejected from the nozzle in the tangential direction of the dish-shaped recess and form a strong swirling flow within the dish-shaped recess, making it difficult to mix with the air in the main chamber. It is sufficiently accelerated to ensure good combustion.

(Embodiment) FIGS. 1(A) and 1(B) show an embodiment of the present invention, in which the top surface of the piston 12 has a circumference of a predetermined thickness. ! ! 1
A dish-shaped recess (cavity) 14 cut out to a predetermined depth is provided on almost the entire surface except for 3.

Then, the nozzle 15 that communicates the main chamber 2 and the swirl chamber 3 opens in a substantially tangential direction of the dish-shaped cavity 14.
A nozzle 15 is formed.

In this case, when the swirl chamber 3 is constructed by press-fitting the hot plug 16 into the shilling head 10 as shown in the figure, the hot Set the position of the plug 16. Further, the nozzle port 15 is set to face approximately in the tangential direction of the cavity 14 and approximately at the midpoint between the center of the dish-shaped cavity 14 and the peripheral wall 13 .

In addition, the same reference numerals are given to the same parts as in FIG. 3 regarding other configurations.

With this configuration, the jet consisting of the flame and unburnt fuel in the vortex chamber 3 ignited near the top dead center of Enkun's compression flows from the nozzle 15 to the main chamber 2 as shown by the arrow (A).
It ejects forcefully in the tangential direction to the dish-shaped cavity 14. And this jet flows into a dish-shaped cavity 14
It performs a strong rotational movement inside.

Therefore, the mixing and diffusion of the jet and the air in the dish-shaped cavity 14 is sufficiently promoted by the swirling flow, and the unburned fuel is quickly combusted.

Therefore, there is no partial delay in combustion as in conventional examples, and as a result, good combustion can be ensured even under high loads, and HC and smoke emissions can be significantly reduced. becomes.

Note that since the jet is blocked by the peripheral wall 13 of the dish-shaped cavity 14, it is prevented from reaching the sill wall and burning (oxidizing) the oil adhering to the sill wall.

By the way, when such a dish-shaped cavity 14 is provided, the compression ratio is lower than that of the conventional example, but the lower the compression ratio, the more the friction loss (bumping loss) during the compression stroke is reduced, so this can be compensated for. .

Note that FIG. 2 shows another embodiment of the present invention, in which the inner side of the peripheral wall 18 of the dish-shaped cavity 17 is inclined.

In this way, when the jet turns, air will not remain in the corner 20 between the peripheral wall 18 and the bottom surface 19 of the dish-shaped cavity 17, and this air can also be effectively used for combustion. Of course, this corner 20 and the corner 21 in the embodiment described above may be formed into a curved shape.

(Effects of the Invention) As described above, in the present invention, a dish-shaped recess is provided on the top surface of the piston, and a nozzle communicating with the vortex chamber is opened in a substantially tangential direction of the dish-shaped recess. This has the effect that the mixing and diffusion of unburned fuel and air in the jet is sufficiently accelerated, thereby ensuring good combustion and significantly reducing the amount of HC and smoke emissions.

[Brief explanation of drawings]

FIGS. 1(A) and 1(B) are a plan view of essential parts showing an embodiment of the present invention and a cross-sectional view taken along the line a-a including the shilling head side, and FIG. 2 is another embodiment of the present invention. FIGS. 3 and 4 are a cross-sectional view of a conventional example and a plan view of a main part thereof. 2... Main chamber, 3 vortex chamber, 4... Fuel injection! r:/
: 1: Tadakan 4-112, 10-- Nrisokehe, )-' 12-- and Ostone 14--Concave part (caheity) 15- Uta mouth

Claims (1)

[Claims] In a swirl chamber type diesel engine, in which a swirl chamber with a fuel injection nozzle facing the engine cylinder head is provided, and the swirl chamber and the main chamber are communicated through a nozzle, a dish-shaped recess is formed on the top surface of the piston over almost the entire area. In addition to providing
A swirl chamber type diesel engine characterized in that the nozzle opening is opened in a substantially tangential direction of the dish-shaped recess.