JPS6339378Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of the combustion chamber of a direct injection diesel engine.

In a conventional direct injection diesel engine, as shown in FIG.
The fuel injected from the fuel injection nozzle 4 into the combustion chamber 3 is mixed in the combustion chamber 3 by a swirl flow and a squish flow to form a proper air-fuel mixture, which is then compressed and ignited. Since the spray A collides with the peripheral wall 5, it flows back into the cavity 7 as shown by arrow B due to the so-called reverse squish flow that occurs when the piston 1 is displaced downward from the top dead center. I will do it. However,
The temperature of this cavity 7 and its vicinity is quite low, unlike that inside the combustion chamber 3, so the cavity 7
There was a problem in which the combustion of the fuel that entered the tank deteriorated and was emitted as black smoke.

This invention was devised in view of the above,
The main feature is that the peripheral wall of the corner of the combustion chamber is formed so as to be inclined from the bottom surface of the combustion chamber toward the top surface toward the center of the combustion chamber, and that the spray is injected toward the peripheral wall of the corner. According to the present invention, the sprayed fuel temporarily stagnates in the acute-angled space formed by the inclined surface and the bottom surface, and as a result, the spray rises upward along the peripheral wall of the combustion chamber and reaches the piston at approximately the top dead center position. The fuel does not escape into the gap formed between the top and the cylinder head, and therefore the combustion of fuel in the gap, which is considered to be a low-temperature area, is avoided, and the generation of black smoke due to unburned fuel is greatly reduced. This has the effect of reducing the amount of black smoke generated during warm-up operation, especially in winter.

The present invention will be explained below based on the embodiment shown in FIGS. 2 and 3. Reference numeral 8 refers to the opening edge of the top surface 2' of the combustion chamber 3 formed in a planar circular shape, and 9, indicated by a broken line, indicates the bottom surface 10 of the combustion chamber 3. A bottom circumferential wall having a rectangular planar shape forming the outermost side of the swirl is formed to be concentric with and circumscribed to the circular shape forming the top opening edge. Reference numeral 12 denotes a peripheral wall that defines the outermost part of the swirl, and when a plane including the vertical center line C is rotated around the same center line, the peripheral wall 12 rotates each intersection of the plane and the top surface 2' and the bottom surface 10, respectively. It is formed by connecting straight lines. Therefore, D, E, where the bottom surface 10 and the top surface 2' are circumscribed,
The peripheral wall 12 at F, G has a vertical surface portion 13,
The peripheral walls of the corners 14 to 17 have sloped surface portions 11 that slope toward the center of the combustion chamber 3 from the bottom surface to the top surface.
That is, the vertical cross section of the peripheral wall 12 from the part where the circular shape of the combustion chamber opening and the polygonal shape of the bottom surface touch to the corner part changes continuously from a state parallel to the center line C to a straight inclined surface 11 in a straight line. It is formed to have a curved surface. Further, the injection holes of the fuel injection nozzle 4 are directed toward the peripheral walls of the corners 14 to 17.

Since this embodiment has the above-mentioned configuration, when the sprayed fuel is injected from the nozzle 4 toward the corners 14 to 17, the spray is directed along the inclined surface 14 in the direction of the arrow H, as clearly shown in FIG. However, since the upward flow into the cavity 7 due to reverse squishing is restricted, the generation of smoke can be suppressed. Furthermore, since the flow speeds of the fuel flowing into the combustion chamber 3 through the vertical surface section 13 and the inclined surface section 11 are different, if the atomized fuel is stirred by the swirl in this state, the stirring efficiency will be increased. As a result, combustion characteristics are improved. Furthermore, since the peripheral wall 12 is formed into a smooth curved surface, it has the effect of suppressing swirl attenuation.

In the above embodiment, the bottom surface is square, but it may be triangular or pentagonal.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional device, Fig. 2 is a top plan view of a combustion chamber in an embodiment of the present invention, and Fig. 3 is a top plan view of a combustion chamber in an embodiment of the present invention.
The figure is a sectional view taken along the - line in FIG. 2. 3; Combustion chamber, 2; Top, 2'; Top surface, 8; Opening edge, 9; Bottom peripheral wall, 10; Bottom surface, 14-17; Corners.

Claims (1)

[Scope of utility model registration request] The top opening of the combustion chamber recessed in the top of the piston is formed into a circular planar shape, and the bottom surface of the combustion chamber is formed into a planar polygonal shape that is concentric with and circumscribed to the circular shape. A peripheral wall defining the outermost side is formed by connecting each intersection of the top surface and the bottom surface with a straight line when a plane including the vertical center line of the combustion chamber is rotated around the same center line, Furthermore, the peripheral wall at the corner of the polygonal shape is formed into the linear inclined surface that slopes from the bottom surface to the top surface toward the center of the combustion chamber, and from the part where the circular shape and the polygonal shape touch, The vertical cross section of the peripheral wall is formed to be a curved surface that changes continuously from being parallel to the center line to forming a straight line to the inclined surface, and the spray from the fuel injection nozzle is directed toward the corner of the peripheral wall. A combustion chamber of a diesel engine characterized by being configured to once produce an injection.