JPS6120261Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion chamber, and particularly to a combustion chamber for a direct injection diesel engine.

The above-mentioned combustion chamber for a diesel engine generally consists of a cavity formed at the top of a piston, and is roughly classified into shallow dish, deep dish, and spherical shapes depending on the shape of the cavity.

Among these shapes, the deep-dish type combustion chamber is said to be suitable for automobile engines in terms of output performance, exhaust characteristics, fuel efficiency, noise characteristics, durability, etc. In fact, it is used in many automobile engines.

This deep-dish type combustion chamber is further divided into closed chamber types such as the Saura type combustion chamber and open chamber types such as the toroidal type combustion chamber, each of which has its own advantages and disadvantages. There is.

That is, the closed chamber type has better exhaust performance, especially smoke characteristics, than the open chamber type, but has worse fuel efficiency.

This is due to the presence or absence of a restriction in the opening of the cavity.In an open chamber type without this restriction, the opening does not provide any resistance when air flows into the combustion chamber or combustion gas flows out from it. In the case of a closed chamber type in which an aperture is provided with a diaphragm, the aperture creates a large resistance and deteriorates fuel efficiency. Furthermore, when fuel is injected into the combustion chamber, since the opening is narrowed in the closed chamber type, the spray is preferably injected below this opening and dispersed inside the combustion chamber, but it is hardly scattered to the outside. However, in the open chamber type, since there is no throttle in the opening, it is impossible to prevent some of the spray from scattering outside the combustion chamber, and the spray may come into contact with the lower surface of the cylinder head or the cylinder liner. Since smoke is generated, the smoke characteristics are deteriorated.

The present invention has been developed in view of these points, and is based on the idea that the inner wall of a deep-dish open chamber type combustion chamber for a direct injection diesel engine is provided with large and small holes with respect to the axial direction of the combustion chamber. By providing an undercut portion with two types of curvature radii and also forming a pocket portion with two types of curvature radii, large and small, in the radial direction, it is possible to improve the appearance of a closed chamber type combustion chamber. The aim is to have these advantages as well.

One embodiment of the present invention shown in the drawings will be described in detail below. In FIG. 1, 10 is a piston, and a deep-dish-shaped cavity 11 is formed at the top of the piston, and a combustion chamber 12 is formed here. A fuel injection nozzle 13 is positioned approximately at the center of the combustion chamber 12, so that fuel spray 15 can be radially injected toward the cavity inner wall 14. Note that the arrow S in the figure indicates the direction of swirl.

The inner wall 14 has an undercut portion 16 formed with two different radii of curvature, r and R, as shown in an enlarged view in FIG. , Q, and the spray 15 injected from the nozzle 13 flows into the pocket part 17.
The scattering direction is appropriately controlled by the undercut portion 16 and the pocket portion 17.

That is, in the direction of the axis C of the combustion chamber 12, the undercut portion 16 is located between the geometrical center J of the spray 15 and the inside wall W of the cavity foundation shown by the dotted line in the figure, as shown in FIG. A point X1 near the intersection of
and a first profile 18 formed with a radius of curvature r determined in consideration of the geometrical diffusion of the spray 15 in the direction of the axis C in the vicinity of the intersection; It has a contour defined by a second profile 19 centered on a certain point X2 near a line L passing through point X1 and perpendicular to the combustion chamber axis C, and having a radius of curvature R larger than the radius of curvature r; The first profile 18 is recessed by a maximum depth T with respect to the inner wall W of the foundation.
falls relatively steeply relative to the cavity opening 20, and the second profile 19 smoothly communicates with the lower inner cavity wall 21.
In this case, the opening 20 as well as the lower inner wall 21
All approximately coincide with the cavity foundation inner wall W.

Of course, the undercut portion 16 configured in this manner is, as is clear from FIG.
It is formed over the entire circumference of the cavity 11 immediately below the point 0. Then, the undercut portion 1
6, pocket portions 17 are formed in four places (in line with the fact that the nozzle 13 sprays four sprays 15), and the pocket portions 17 are formed in the direction of the axis C. is smoothly connected to the undercut 16.

On the other hand, with respect to the radial direction of the combustion chamber 12, the pocket portion 17 is located at a point X3 near the intersection of the center J and the base inner wall W, as shown in FIG.
with a radius of curvature q determined by securing a depression with a depth t further than the maximum depth T and taking into consideration the geometrical radial diffusion of the spray 15 near the intersection point. The hemispherical third profile 22 formed is centered at a certain point X4 on a line M passing through the center point X3 and perpendicular to the combustion chamber axis C, and has a radius of curvature Q larger than the radius of curvature q. Partially spherical fourth profile 2 formed by
3, and is formed such that a third profile 22 is located on the upstream side of the swirl S, and a fourth profile 23 is located on the downstream side of the swirl S. In contrast to the sudden drop in the profile, the fourth profile 23 is relatively smoothly connected to the inner wall 14.

As described above, the undercut portion 16 formed by combining the first and second profiles 18 and 19 formed with radii of curvature r and R is provided directly below the opening portion 20 over the entire circumference of the cavity 11, and A hemispherical third profile with curvature radii q and Q and a partially spherical fourth profile are formed at the collision site of the spray 15.
In the combustion chamber of the present invention including the pocket portion 17 formed by combining the profile with the pocket portion 17, the scattering of the spray 15 is controlled in the following manner.

That is, in the direction of the combustion chamber axis C, there are an undercut portion 16 with a depth T and a pocket portion 17 with a depth t.
, the center J of the spray 15 is located at the center point X1, X of the first and third profiles 18, 22.
3, and the profile 18,
The radii of curvature r and R of the spray 15 are set in consideration of the diffusion of the spray 15 in the direction of the axis C.
is securely held by the profiles 18 and 22, and is prevented from scattering in the direction of the opening 20. Furthermore,
The spray 15 smoothly flows down along the second profile 19 with a large radius of curvature R and reaches the lower inner wall 2.
1 to the bottom center of the combustion chamber, where it can be conveniently mixed with the center of the combustion chamber and air.

Also, regarding the radial direction, as mentioned above,
The spray 15 is reliably held in the third profile 22, and then flows along the fourth profile 23, is suitably guided in the direction of the swirl S, and can be mixed conveniently with the air in the center of the combustion chamber. can. Since the profile 22 is relatively steeply depressed with respect to the inner wall 14 of the cavity, the swirl S is disturbed in this part, as shown by the small arrow V in FIG. This further promotes mixing with.

As described above, according to the combustion chamber of the present invention, although it is an open chamber type combustion chamber, by forming the undercut portion 16 and the pocket portion 17 with appropriate profiles as described above, it can be made into a closed chamber type combustion chamber. The generation of smoke is suppressed by skillfully creating an effect similar to the throttling effect of the opening 20 seen in the figure, and the spray 15 is further guided and diffused toward the center of the bottom of the combustion chamber and in the radial direction. Since certain air can be used effectively, output performance, fuel efficiency, etc. are further improved. Furthermore, since the opening 20 in the present invention is not narrowed in any way, it does not have the disadvantages of a closed chamber combustion chamber, and can take advantage of the inherent advantages of an open chamber combustion chamber. It can be done.

For example, the center point X1 of the radius of curvature r is placed near the intersection of the center J and the inner wall W, and the center point X2 of the radius of curvature R is placed on the perpendicular line L passing through the center point X1. However, this does not mean that these (including center points X3 and X4) are placed here in a strict sense, but that they may be slightly moved within the scope of the technical idea of the present invention. It does not prevent Also, the radius of curvature R or Q needs to be larger than the radius of curvature r or q, but according to experiments, 1.5r<R<3r,
1.8q<Q<4q, q≦r, etc., and t<
It is important to set it to T. Furthermore, the thickness R of the opening 19 is 0.7r<in relation to the radius of curvature r.
It is advisable to set t<1.5r. It is also effective to make the profile of the pocket portion 17 in the direction of the axis C similar to the profiles 18 and 19 of the undercut portion 16.

[Brief explanation of the drawing]

FIG. 1 is a top view of a piston showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. 2. 10... Piston, 11... Cavity, 12
... Combustion chamber, 13 ... Nozzle, 14 ... Inner wall,
15...Spraying, 16...Undercut part, 17
... Pocket portion, 18, 19, 22, 23 ... Profile, 20 ... Opening.

Claims (1)

[Scope of utility model registration request] A deep-dish open chamber combustion chamber 12 for a direct injection diesel engine that injects spray 15 radially directly toward the cavity inner wall 14 from a fuel injection nozzle 13 located approximately at the center thereof.
In this step, an undercut portion 16 recessed by a depth T is formed around the entire circumference of the cavity inner wall 14 directly below the cavity opening 20, and pocket portions 17 corresponding to the number of sprays 15 are inserted into the undercut portion 16. The undercut portion 16 has a center point X1 near the intersection of the geometric center J of the spray 15 and the base circle side wall W of the cavity 11. A first profile 18 formed with a radius of curvature r determined in consideration of the geometrical diffusion of the spray 15 near the intersection, and a first profile 18 that passes through the center point X1 and is aligned with the axis C of the combustion chamber. A second profile 19 having a center point X2 near a perpendicular line L and having a radius of curvature R larger than the radius of curvature r, and having a maximum depth T in the direction of the axis C. The first profile 18 is relatively steeply depressed with respect to the cavity opening 20, and the second profile 19 smoothly communicates with the lower inside wall 21 of the cavity, while the undercut portion 16 Pocket part 1 with a shape roughly similar to the outline
7 is smoothly connected to the undercut portion, and the pocket portion 17 is connected to the center J and the inner wall W.
The radius of curvature q is set at a certain point X3 near the intersection with and a third profile 22 formed with a certain point X4 on a line M passing through the center point X3 and perpendicular to the axis, and having a radius of curvature Q larger than the radius of curvature q. The combustion chamber has a contour in the radial direction consisting of four profiles 23, and the third profile 22 is positioned upstream of the fourth profile 23 with respect to the swirl direction of the swirl S. The fourth profile 22 is relatively steeply depressed from the inside wall 14 of the cavity, and the fourth profile 23 is smoothly connected to the inside wall 14.
A combustion chamber in which substantially the entire amount of the spray 15 is received by the pocket portion 17 and is guided by the pocket portion 17 and the undercut portion 16 so that it can be widely diffused within the combustion chamber.