JPS6018588Y2 - Combustion chamber of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention primarily relates to improvements in the combustion chamber of a direct injection internal combustion engine.

Conventionally, in a combustion chamber 8 as shown in the conventional example shown in FIG. 1, which has been widely used in direct injection internal combustion engines, a recess 8A is provided on the upper surface of the piston 2 that slides up and down on the inner surface of the liner 1. Cylinder head 4 facing this combustion chamber 8
An intake valve 5, an exhaust valve 6, and a fuel valve 7 (or a spark plug) are arranged on the side, and a combustion chamber 8 is constituted by these.

Here, the liner 1 is fitted into a cylinder block 9, and a gasket 10 is inserted between the cylinder block 9 and the cylinder head 4.

Therefore, a recess 3A with a depth of 11 is provided on the upper surface of the piston 2 and corresponds to the intake valve 5, and a recess 3A with a depth of 11 is provided between the top of the piston 2 and the combustion surface of the cylinder head 4.
A top clearance indicated by □ is provided, and the intake valve 5 is provided on the cylinder head 4 side by a depression amount indicated by 13.

Further, a recess 3B having a depth of 15 is provided on the upper surface of the piston 2 as a recess for the exhaust valve 6, and the exhaust valve 6 is further sunk toward the cylinder head 4 by an amount of recess shown as 14.

The intake valve 5 and the exhaust valve 6 are opened and closed by the rotation of a crank (not shown). If T1 bottom dead center is indicated by L, the intake valve 5 closes at point A, which is 40' to 50° after bottom dead center, and opens at point B, where angle θS before top dead center T is 15° to 20°. The part indicated by angle S is the period during which the intake valve 5 is open.

Further, the exhaust valve 6 opens at a point 45° to 50° before the bottom dead center, and the angle θ after the bottom dead center T.

is closed at point C between 15° and 20°, and the portion indicated by angle E is the period during which the exhaust valve 6 is open.

Therefore, during the period in which the angle S indicating the period in which the intake valve 5 is open and the angle E indicating the period in which the exhaust valve 6 is open overlap, both the intake valve 5 and the exhaust valve 6 are open. It becomes almost symmetrical with respect to the dead center T.

Further, FIG. 3 shows the relationship between the crank angle θ and an intake valve lift diagram 31 passing through point B where the intake valve 5 is open and an exhaust valve lift diagram E1 passing through point C where the exhaust valve 6 is closed. , if a line Pd indicating the displacement of the piston 2 is expressed, the amount of overlap between this line Pd and the intake valve lift diagram S1 is 1.
6, and the difference obtained by subtracting the overlap amount 16 from the depth 11, top clearance 12, and sinking amount 13 of the recess 3A shown in Fig. 1, Δ1 = 11 + 1 □ + 12 - 16
is always greater than zero.

Therefore, during combustion in the combustion chamber 8, each valve is sunk toward the cylinder head 4 by a sunk amount of 13 and 14, respectively, and is further sunk to a depth of 1. and 1
．． Due to the presence of recesses 3A and 3B, the squish force when air is forced into the recess 8A of the combustion chamber 8 is weak.
The drawback was that good combustion could not be obtained.

In addition, since the squish force is weak, if the fuel injection timing of the fuel valve 7 is advanced in order to lengthen the combustion time and improve the combustion, the combustion before top dead center T will become more intense and the maximum pressure in the cylinder will increase. This has the drawbacks of lower mechanical efficiency and increased generation of nitrogen oxides.

Therefore, in order to eliminate the above-mentioned conventional drawbacks, the present invention increases the squish force around the top dead center of the piston during combustion in the combustion chamber of a direct injection internal combustion engine to obtain good combustion and to reduce the maximum cylinder pressure. The purpose of this is to reduce the amount of nitrogen oxides generated.

That is, the present invention provides a direct injection type combustion chamber having a recessed combustion chamber 8 in the upper part of the piston 2, in which a surface corresponding to the umbrella parts of the intake valve 5 and an exhaust valve 6 on the upper surface of the piston 2 and a surface not corresponding thereto. are formed on the same continuous surface, and the intake valve 5 is arranged so that the lower surface of its umbrella almost coincides with the combustion surface on the cylinder head 4 side, and the exhaust valve 6 is arranged so that the lower surface of its umbrella is on the cylinder head 4 side. Amount of sinking from the combustion surface of 1. The exhaust valve closing timing C' is set to 10° to 50° after the piston top dead center T, and the intake valve opening timing B' is set to 10° to 50° after the piston top dead center T. It is configured by setting the angle from 5° to 100 after T.

Embodiments of the present invention will be described below with reference to the drawings.
The same parts and parts as in the conventional example shown in the figures through FIG. 3 are indicated by the same part numbers and the same symbols.

First, the combustion chamber 8 in the embodiment of the present invention shown in FIG. 4 has almost the same structure as the combustion chamber 8 in the conventional example shown in FIG. This eliminates the need to form the recesses 3A and 3B that were conventionally provided corresponding to the umbrella portions of the intake valve 5 and the exhaust valve 6. Therefore, the depth of the recess 3A shown in the conventional example in FIG. The recess 3B indicated by the length 11 and the depth 15 are both zero.

In addition, the intake valve 5 is arranged so that the lower surface of its umbrella almost coincides with the combustion surface on the cylinder head 4 side.
The amount of sinking of the intake valve 5 toward the cylinder head 4 side, shown as
13=0±0.1 to 0.2TIrIn.

Furthermore, in the present invention, as shown in the chart showing the opening and closing timing of the intake and exhaust valves in FIG. 5, the intake valve 5 has an angle θ5 after the top dead center T of 5
The exhaust valve 6 is set to open at a point B' which is 10' from the top dead center T, and closed at a point C' where the angle θE after the top dead center T is 10° to 20°.

As described above, in the embodiment of the present invention in which the combustion chamber 8 is formed and the opening and closing timings of the intake valve 5 and the exhaust valve 6 are set, the crank angle θ and the intake valve passing through B' with the intake valve 5 open In FIG. 6 showing the relationship between the lift diagram S1 and the exhaust valve lift diagram E1 passing through the point C' where the exhaust valve 6 is closed, if a diagram Pd indicating the displacement of the piston 2 is represented, this diagram Pd The amount of overlap between this and the exhaust valve lift diagram El is 17,
The top clearance is 1° and the depression amount of the exhaust valve 6 is 1. The difference obtained by subtracting the overlap amount 17 from Δl
=I□+14-1□ is always greater than zero.

Therefore, to compare and explain the combustion chamber 8 of the present invention and the conventional combustion chamber 8 shown in FIG. In the schematic plan view of the combustion surface of the cylinder head 4 in the conventional example shown in FIG. 7, this occurs in the shaded area SK excluding the recess 8A, recess 3A of the intake valve 5, and recess 3B of the exhaust valve. , in the embodiment of the present invention, the eighth
In the figure, since the combustion surface of the cylinder head 4 and the lower surface of the cap of the intake valve 5 match, squish also occurs at the cap of the intake valve 5, which is indicated by the diagonal line SK'.

Therefore, as shown in FIG. 9, in which the horizontal axis represents the crank angle θ and the vertical axis represents the squish force F, the squish force diagram Fs2 in the embodiment of the present invention is different from the conventional squish force diagram F8□. In the figure, both the squish force shown in the positive direction and the reverse squish force shown in the negative direction increase.

Furthermore, in FIG. 10, where the horizontal axis represents the crank angle θ centered on the top dead center T of the piston 2, and the vertical axis represents the maximum in-cylinder pressure pmax, the fuel injection timing is advanced from the top dead center T. In contrast to the diagram Sd1 showing the exhaust color Sd in the combustion chamber 8 of the conventional example on the vertical axis, the fuel injection timing is changed from the conventional example as shown by the line group d2 showing the exhaust color in the combustion chamber 8 of the embodiment of the present invention. Even if it is delayed from the example, good combustion can be obtained and the maximum in-cylinder pressure pmax can be lowered by Δpmax.

As described above, the combustion chamber of the present invention is a direct injection type combustion chamber having a recessed combustion chamber 8 on the upper part of the piston 2, and has a surface corresponding to the umbrella parts of the intake valve 5 and the exhaust valve 6 on the upper surface of the piston 2. Forming surfaces that do not correspond to them into the same continuous surface,
In addition, the intake valve 5 and the lower surface of its umbrella are arranged so as to substantially match the combustion surface on the cylinder head 4 side, and the exhaust valve 6
The valve is sunk so that the lower surface of the umbrella has a sunken amount of 14 from the combustion surface on the cylinder head 4 side, and the exhaust valve closing timing C' is set from 10° to 20° after the top dead center T of the piston. and set the intake valve opening timing B' to 5 after the top dead center T of the piston.
Since the direct injection internal combustion engine to which the combustion chamber of the present invention is applied has the squish force increased from 10° to 100°, the squish force is increased compared to the conventional example, and good combustion can be achieved.

In addition, since the air moving (squish) force that promotes combustion is large, the mixing of fuel and air is expanded, and the peak of its occurrence is just past the top dead center of combustion, so it is possible to delay the fuel injection timing compared to conventional methods. This has the effect of obtaining good combustion and reducing the maximum pressure in the cylinder, and is effective in reducing the generation of nitrogen oxides and the like in the exhaust gas.

In particular, in this invention, the intake valve opening timing B' is after the top dead center T of the piston, so the residual gas around the top dead center of the piston exhaust stroke is exhausted through the exhaust valve and exhaust port. This has the advantage that the amount of intake air decreases little.

The present invention is mainly applicable to a gasoline or diesel type four-stroke direct injection internal combustion engine equipped with a combustion chamber having one intake valve and one exhaust valve, or a combustion chamber having two intake valves and one exhaust valve. It can be effectively applied to

[Brief explanation of drawings]

Figure 1 is a side sectional view of the main part of the combustion chamber of a conventional direct injection internal combustion engine, Figure 2 is a chart showing the opening and closing timing of the intake and exhaust valves in Figure 1, and Figure 3 is the crank angle in Figure 1. And suck,
An exhaust valve lift diagram and a diagram showing the relationship with piston displacement, FIG. 4 is a sectional side view of the main part of the combustion chamber of a direct injection internal combustion engine according to an embodiment of the present invention, and FIG. ,
A chart showing the exhaust valve opening/closing timing, Fig. 6 is a diagram showing the relationship between the crank angle, intake and exhaust valve lift diagrams and piston displacement in Fig. 4, and Fig. 7 is a diagram showing the relationship between the cylinder head of the conventional example in Fig. 1. 8 is a schematic plan view of the combustion surface of the cylinder head of the embodiment of the present invention shown in FIG. 4, and FIG. 9 is a schematic plan view of the combustion surface of the cylinder head of the embodiment of the invention shown in FIG. A diagram showing the relationship between the crank angle and the squish force in an actual example, and FIG. 10 shows the maximum cylinder pressure in the combustion chamber, exhaust color, and crank in the conventional example in FIG. 1 and the embodiment of the present invention in FIG. 4. FIG. 3 is a diagram showing the relationship with angle. 2... Piston, 3A, 3B... Recess, 4... Cylinder head, 5... Intake valve, 6... Exhaust valve, 8... Combustion chamber,
8A...Concavity, T...Top dead center, 13,
1.・・・・・・Amount of sinking.

Claims (1)

[Scope of utility model registration request] In a direct injection type combustion chamber having a recessed combustion chamber 8 at the top of the piston 2, an intake valve 5 and an exhaust valve 6 on the top surface of the piston 2 are provided.
The surfaces corresponding to the respective umbrella portions and the surfaces not corresponding to them are formed into the same continuous surface, and the intake valve 5 is arranged so that the lower surface of the umbrella substantially coincides with the combustion surface on the cylinder head 4 side. At the same time, the exhaust valve 6 is provided with a valve depression so that the lower surface of its umbrella has a depression amount of 14 from the combustion surface on the cylinder head 4 side, and the exhaust valve closing timing C' is set to 100 minutes after the top dead center T of the piston. The combustion chamber of an internal combustion engine is configured such that the intake valve opening timing B' is set at 5° to 10° after the top dead center T of the piston.