JPH0730909Y2 - Piston combustion chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a combustion chamber of a piston of an internal combustion engine, particularly a direct injection diesel engine.

(Prior Art) Conventionally, there is known an internal combustion engine that burns fuel inside an engine to directly heat air and reciprocally moves a piston by its expansion to perform work. Diesel engines with good compression ratio and good thermal efficiency are often used. The piston of this diesel engine and its vicinity are constructed as shown in FIG. In the figure, a piston 1 is arranged in a cylinder space formed by a cylinder liner 5, and the piston 1 is slidable in the cylinder space. A combustion chamber (also referred to as a cavity) 2 is formed in the upper portion of the piston 1, and the combustion chamber forms a substantially cylindrical hollow portion. A cylinder head 4 is provided above the combustion chamber 2 and the cylinder liner 5.
Is mounted, and the cylinder head 4 is provided with an injector 3. Then, the piston 1 is slid upward to compress and heat the intake air high, and at that time, light oil (fuel) is injected from the injector 3 toward the combustion chamber 2 to spontaneously ignite.

(Problems to be Solved by the Invention) By the way, in the injector 3, for example, when a vortex (also called swirl) formed between the piston 1 and the cylinder head 4 is extremely strong, As a countermeasure, as shown in FIG. 5, the injector 3
May be inclined with respect to the axis of the piston 1. However, with this configuration, as shown in FIG. 5, the axis 3a of the injector 3 and the injection port of the injector 3
Angles 6a, 6B ... 6X formed by the respective axes 6a, 6b ... 6x
The larger the b ... θx, the smaller the spray amount. That is, in the explanation with reference to FIG. 5, since there is a magnitude relation of θd> θa, the spray amount on the shaft center 6d side is smaller than that on the shaft center 6a side. Here, the unknown number X represents the number of nozzles. However, as described above, despite that the spray amount is different for each injection port, if the shape of the combustion chamber with which the spray is in contact is a substantially cylindrical hollow portion, the formation of each spray flame will be different. As a result, there has been a problem that the mixing and combustion are not sufficiently performed, and the performance is not improved on the target. Particularly in the above case in which the injector 3 is inclined,
The tip of the injector 3 is the axial center of the piston 1 (the combustion chamber 2
Often, it is not on the axis, and this tendency is further promoted.

It is an object of the present invention to provide a combustion chamber of a piston that forms uniform spray flames regardless of the difference in injection amount of each injection port, improves combustion efficiency, and improves performance.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

(Means for Solving Problems) In order to achieve the above-mentioned object, the combustion chamber of the piston of the present invention has the axial center of the piston as the axis, and the number of the nozzles is equal to the direction of the virtual divided surface. The wall surface of the cavity has an axial center whose direction coincides with the axial center of the piston on the direction surface, and is cut out in an arc shape which becomes larger toward the bottom surface, and the cutout portion substantially coincides with the spray direction. It is characterized in that the capacity of the notch corresponding to the nozzle is made smaller as the angle formed by the axis of the injector and the axis of the nozzle becomes larger.

(Effect) According to the present invention, the inner wall of the combustion chamber in the spray direction is notched, but it is made smaller as the volume of the notch and the angle between the axis of the injector and the axis of the nozzle are increased. A uniform spray flame is formed regardless of the difference in the spray amount.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a top view of a piston showing an embodiment of the present invention, and FIG.
The figure is a sectional side view of FIG.

The difference between the combustion chamber of the piston of this embodiment and that of the prior art is that, as shown in FIGS. 1 and 2, the inner wall of the combustion chamber 12 in the spray direction is notched, and the notches 12a, 12b, 12c are formed. , 12d are made smaller as the angles θa, θb, θc, θd formed by the axis 3a of the injector 3 and the axes 6a, 6b, 6c, 6d of the nozzles 6A, 6B, 6C, 6D become larger. It is a point. Where θa, θb, θc,
The magnitude relationship of θd is θa <θb <θc <θd. Further, although the injection ports 6B and 6C are not shown in the drawing, the injection port 6B is provided in the clockwise direction of 90 ° of the injection port 6A, while the injection port 6C is provided in the 90 ° clockwise direction of the injection port 6D. . The cutouts 12a, 12b, 12c, 12d are evenly divided by the number of their injection ports with the shaft center 1a of the piston 1 as the shaft center, that is, in the present embodiment, are divided into four equal parts (Fig. 1). 7A, 7B, 7C, 7D in the direction of 7A, 7B, 7C, 7D
Shaft center 12A, 12 whose direction matches the shaft center 1a of piston 1 on D
B, 12C, 12D as an axis, is a notch in the shape of an arc that becomes larger toward the bottom, the notch 12a, 12b, 12c,
The direction of 12d substantially coincides with and opposes the spray direction. Then, the axial center 12 at the bottom of each notch 12a, 12b, 12c, 12d
The size relationship among the notched arcs R1, R2, R3, R4 with A, 12B, 12C, 12D as the center of axis is R1>R2>R3> R4. Further, the depth h1, which is the depth of the horizontal depression in the bottom surface of each notch 12a, 12b, 12c, 12d.
The size relationship of h2, h3, and h4 is h1>h2>h3> h4.

That is, the size relationship between the volumes (capacities) of the cutouts 12a, 12b, 12c, 12d is 12a>12b>12c> 12d, and the shaft center 3a of the injector 3 and the shafts of the injection ports 6A, 6B, 6C, 6D are the same. The larger the angles θa, θb, θc, and θd formed by the cores 6a, 6b, 6c, and 6d, the smaller the volume of the notch formed at the opposing position of the spray. The arcs shown by imaginary lines in FIG. 1 indicate the points of intersection between the bottom of the combustion chamber and the downward extension of the tapered arc surface.

The cutouts 12a, 12b, 12c, 12d form the arcs R1, R2, R
Insert a conical cutter having 3, R4 as a bottom arc into a conventional combustion chamber that forms a substantially cylindrical cavity as shown by the phantom line in Fig. 2, with the axial center of each cutter facing the wall surface. It is formed by cutting and moving on the virtual dividing plane.

According to the combustion chamber of this embodiment configured as described above,
The following effects can be obtained.

That is, the inner wall of the combustion chamber in the spray direction is notched, and the capacity of the notch is made smaller as the angle between the axis of the injector and the axis of the injection port becomes larger, that is, the contact of the spray amount Since the notch portion of the wall surface has the larger notch volume, the spray amount decreases as the angle θ formed by the axis 3a of the injector 3 and the axis of each nozzle of the injector 3 increases. It is possible to eliminate the irregular formation of each spray flame caused by the above characteristic, that is, all spray flames can be formed uniformly and the combustion efficiency is improved.

Further, according to the combustion chamber 12 of this piston, each notch 12
Since a, 12b, 12c, and 12d are formed such that the arcuate notches gradually increase from the upper part to the bottom part of the combustion chamber, the fuel spray is formed in the gap between the upper part of the piston 1 and the lower surface of the cylinder head 4. 9 (see Fig. 2), it is difficult to move to the bottom of the combustion chamber, and most of it is guided to the bottom of the combustion chamber, and the circumferential length of the side wall circumference becomes long, so the development of fuel spray to the center of the combustion chamber Thus, the air-fuel mixture can be collected in the side wall portion (notch portion) of the combustion chamber where the air flow velocity is high, and the fuel and air can be mixed well and combustion can be performed.

Next, a second embodiment will be described.

The difference between the combustion chamber of the second embodiment and that of the first embodiment is that, as shown in FIG. 3, the notches 13a, 13b, 13
Change the volume of c, 13d only by the size of the notched arcs R1, R2, R3, R4 with the shaft center 13A, 13B, 13C, 13D as the shaft center, and the lateral recess depths h1, h2, This is a point where h3 and h4 are all set to the same depth h.

It goes without saying that even if the combustion chamber 13 is configured in this way, the same effects as those of the previous embodiment can be obtained.

Next, a third embodiment will be described.

The difference between the combustion chamber of the third embodiment and that of the first embodiment is that, as shown in FIG. 4, the notches 14a, 14b, 14
Change the volume of c, 14d by the depth of the recesses h1, h2, h3, h4 in the lateral direction, and cutout arcs R1, R2, R3, R4 with the axes 14A, 14B, 14C, 14D as the axes. This is a point where all the sizes are the same circular arc R.

Even if the combustion chamber 14 is configured in this way, it is of course possible to obtain the same effects as those of the first embodiment, and it is not necessary to provide cutters each having an arc corresponding to the cutout portion.
Since it becomes possible to cut with one cutter, the manufacturing cost can be reduced, and the ends of the notches (14P, 14Q in FIG. 4) can be changed to the first and second embodiments. Since they can be separated from each other, flame interference between adjacent ones can be prevented.

Although the invention made by the inventor has been specifically described based on the embodiments, the invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the number of injection holes of the injector is four, but the number is not limited to four.

The above-described embodiment is applicable to all the fuel chambers that receive fuel spray from the injectors arranged at an inclination, and is particularly effective when two or more injectors are provided.

(Effect of the Invention) As described above, according to the present invention, the larger the angle between the axis of the injector and the axis of the injection port, the smaller the volume of the notch corresponding to the injection port. , A uniform spray flame is formed regardless of the difference in the spray amount of each injection port, the combustion efficiency is improved, and the combustion chamber of the piston is improved.

[Brief description of drawings]

1 is a top view of a piston showing an embodiment of the present invention, FIG. 2 is a side sectional view of FIG. 1, FIG. 3 is a top view of a piston showing a second embodiment of the present invention, and FIG. FIG. 5 is a top view of a piston showing a third embodiment of the present invention, and FIG. 5 is a cross-sectional view of a piston of a diesel engine showing a conventional technique and a main part in the vicinity thereof. 1 ... Piston, 1a ... Piston axis, 2, 12, 13, 14 ... Combustion chamber, 3 ... Injector, 3a ... Injector axis, 6A, 6
D ... Nozzle, 6a, 6d ... Nozzle axis, 7A, 7B, 7C, 7D ... Virtual dividing plane, 12A-12D, 13A-13D, 14A-14D ... Notch part axis, 12
a to 12d, 13a to 13d, 14a to 14d ... Notch, R, R1, R2, R3, R
4 ··· Arc, θa, θd… Angle formed by the axis of the injector and the axis of the injection port.

Claims (1)

[Scope of utility model registration request] 1. In a combustion chamber of a piston having a substantially cylindrical hollow portion which receives fuel spray from an injector nozzle arranged obliquely, the axis of the piston is taken as an axis and the number of the nozzles is equal. The wall surface of the hollow portion in the direction of the divided virtual dividing surface has an axial center whose direction coincides with the axial center of the piston on the directional surface, and is cut out in an arc shape that becomes larger toward the bottom surface, The notches are arranged so as to face each other substantially in the spray direction, and the larger the angle between the axis of the injector and the axis of the injection port, the smaller the volume of the notch corresponding to the injection port. Combustion chamber of the piston.