JPS6160966B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides an auxiliary combustion chamber within the main combustion chamber that communicates with the auxiliary combustion chamber through a torch hole, and develops combustion in the lean air-fuel mixture within the main combustion chamber by the torch flame ejected from the auxiliary combustion chamber. The present invention relates to an internal combustion engine with a sub-combustion chamber.

In order to reduce harmful substances in the exhaust gas of gasoline engines, it is effective to increase the excess air ratio of the intake air mixture to achieve lean combustion. In this type of engine, combustion is developed using a torch flame from an auxiliary combustion chamber, and engines with this type of auxiliary combustion chamber have a rich mixture in the auxiliary combustion chamber and a lean mixture in the main combustion chamber. There are two types: a complex mixture type that takes air into both the sub-combustion chamber and the main combustion chamber, and a single-air mixture type that takes in a lean mixture with the same air-fuel ratio into both the sub-combustion chamber and the main combustion chamber. In order to improve the performance, it is necessary to ensure that the ignition combustion of the lean mixture by the torch flame progresses throughout the main combustion chamber, and to complete the combustion of the entire lean mixture early. This is especially necessary in the case of a single mixture type, where the flame strength is weaker than that of a complex mixture type.

Therefore, Japanese Patent Application Laid-Open No. 54-52205 as a prior art proposes to form a main combustion chamber on the lower surface of the cylinder head with a recess that surrounds both the intake port opening and the exhaust port opening with respect to the main combustion chamber. On the other hand, in an internal combustion engine with an auxiliary combustion chamber, the cylinder head is provided with an auxiliary combustion chamber that communicates with the main combustion chamber through a torch hole. is formed to surround the main combustion chamber, a squish flow from the squish area generates a swirl or vortex within the main combustion chamber, and the synergistic effect of this swirl or vortex and the torch flame Therefore, it is proposed to achieve rapid combustion of lean air-fuel mixture.

However, the top surface of the piston here is a flat surface, and the contact area between the squishing flow from the squishing area and the piston top surface is long, and the squishing flow is considerably decelerated by contact with the piston top surface. At the same time, since the piston is cooled so that the heat is taken away, not only is the effect of promoting combustion of lean air-fuel mixture by the squish flow low, but also the torch flame ejected from the torch hole into the main combustion chamber is Since the flat top surface directed the flame toward the periphery of the main combustion chamber, the influence of the torch flame on the lean mixture in the main combustion chamber was also reduced.

In this type of internal combustion engine with a sub-combustion chamber, the present invention reduces deceleration of the squish flow and cooling loss by providing a recess in the top surface of the piston, and directs the squish flow to the center of the main combustion chamber. At the same time, the influence of the torch flame from the torch hole in the auxiliary combustion chamber can be exerted near the center of the main combustion chamber in relation to the recess provided on the top surface of the piston, resulting in a lean mixture. This further increases the rapid burning of Qi.

Therefore, in the present invention, the main combustion chamber is recessed in the lower surface of the cylinder head so as to surround both the intake port opening and the exhaust port opening with respect to the main combustion chamber, and the main combustion chamber is recessed in the cylinder head so as to surround both the intake port opening and the exhaust port opening. A sub-combustion chamber is provided that communicates with the combustion chamber through a torch hole, and a squish area for the top surface of the piston is formed on the lower surface of the cylinder head so as to surround the main combustion chamber. In an internal combustion engine with a combustion chamber, a recess having a relatively shallow depth and having a flat bottom surface and a conical inclined surface from the bottom surface toward the top surface of the piston is formed in the top surface of the piston, and the recess is formed in the top surface of the piston. The diameter of the conical inclined surface relative to the top surface of the piston is made smaller than the inscribed circle of the squish area around the main combustion chamber, and the torch flame from the torch hole in the auxiliary combustion chamber is It is configured to face the conical inclined surface in the recess.

Below, we will explain the drawings of the embodiment when applied to a single mixture type engine. In the drawings, 1 is a cylinder block, 2 is a cylinder head, 3 is a piston that reciprocates within the cylinder bore 4 of the cylinder block 1, and 5 is a cylinder head. A spherical or polyspherical main combustion chamber is formed by recessing the lower surface of the cylinder head 2, and 6 is an intake valve 7 for inhaling a lean air-fuel mixture into the main combustion chamber 5.
8 indicates an intake port with an exhaust valve 9, and 8 indicates an exhaust port with an exhaust valve 9, and the main combustion chamber 5 has an opening to the main combustion chamber 5 of the intake port 8 and an opening of the exhaust port 8 to the main combustion chamber 5 by its circumferential contour 24. This main combustion chamber 5 is formed to surround both openings to the chamber 5.
The cylinder head 2 inside has an intake port 6.
A pre-chamber cup 11 is located approximately midway between the exhaust port 8 and the exhaust port 8 and is eccentric from the center of the cylinder bore 4.
A fitting hole 10 is formed at an angle with respect to the axis of the cylinder bore 5, and a sub-chamber cup 11 is fitted into the fitting hole 10 to form a sub-combustion chamber 12 therein. At 12, an electrode 14 of a spark plug 13 screwed onto the cylinder head 2 is visible.

The pre-chamber cup 11 includes a substantially hemispherical head 15 that projects into the main combustion chamber 5 and a cylindrical fitting part 16 that fits tightly into the fitting hole 10 and projects into the main combustion chamber 5. The head 15 has three large, medium and small torch holes 1 for communicating the auxiliary combustion chamber 12 and the main combustion chamber 5.
7, 18, 19 are drilled, and a large diameter torch hole 17
passes through the lower part of the approximate center of the intake valve 7 toward the top surface 21 of the piston 3 as shown by the dotted line arrow 20, and the medium-diameter torch hole 18 passes approximately at the center of the exhaust valve 9 as shown by the solid line arrow 22. piston 3 through the bottom of
The small-diameter torch hole 19 is oriented toward the top surface 21 of the piston 3 substantially directly below the pre-chamber cup 11, as shown by the dash-dotted arrow 23.

The circumferential contour 24 of the main combustion chamber 5 has an intrusion 25 between the intake valve 7 and the exhaust valve 9, between the intake valve 7 and the pre-chamber cup 11, and between the pre-chamber cup 11 and the exhaust valve 9, respectively. , 26, 27, squish areas 29, 30, 3
1 is formed.

On the other hand, in the center of the top surface 21 of the piston 3, a relatively shallow recess 33 having a relatively shallow and flat bottom surface 32 is provided. This recess 33
is formed into a conical inclined surface 34 connected to the top surface 21 of the piston 3 at an appropriate angle θ, and its diameter d is set to the top surface 21 of the piston 3.
The diameter of each squish area 29, 30, 31 is made smaller than the diameter of the inscribed circle of each squish area 29, 30, 31 so that it extends slightly further into the main combustion chamber 5 than each squish area 29, 30, 31.

The squishing flow from each of the squishing areas 29, 30, and 31 occurs most strongly at about 20 degrees before the top dead center of the piston 3 during the upward compression stroke, and flows toward the center along the top surface 21 of the piston 3. .

In this case, when there is no recess 33 in the center of the top surface 21 of the piston 3, each squish flow flows over a long distance along the top surface 21 of the piston 3,
In other words, since it is in contact with the top surface of the piston for a long time,
Not only is this accompanied by a cooling loss of the compressed lean mixture, but the flow velocity of each squish flow is considerably reduced. Area 2
The squish flow from 9, 30, and 31 does not directly hit the center of the top surface of the piston, and the distance it flows along the top surface of the piston is shortened, so the cooling loss of the compressed lean mixture is small and high. The temperature is maintained at a constant temperature, and there is little deceleration of flow velocity due to long contact with the top surface of the piston. On the other hand, the recess 33
The diameter d of each squeeze area 29, 30, 3
In other words, the top surface 21 of the piston 3 is smaller than the diameter of the inscribed circle of the piston 3.
0 and 31 into the main combustion chamber 5, each squish flow is connected to each squish area 2.
By pushing up the top surface of the piston in the portion extending from 9, 30, 31 into the main combustion chamber 5, the flow is directed slightly upward as shown by the arrow in FIG. The swirl or vortex of the lean mixture in 5 becomes particularly strong in the center of the main combustion chamber 5, flows violently at high temperature, and is ignited by the torch flame from the auxiliary combustion chamber 12. The combustion of the lean mixture in the main combustion chamber 5 is strongly developed in the center.

Uniformly generating swirl or vortex caused by the squishing flow from each squishing area over the entire area of the main combustion chamber is good for improving combustion efficiency and suppressing knocking, but As a result, the combustion heat is radiated from the entire surface of the main combustion chamber, cylinder bore, and piston top surface, increasing the cooling loss of combustion heat.However, in the present invention, as described above, the main combustion Since the swirl or vortex in the center of the chamber becomes particularly intense and the combustion in the center becomes stronger, cooling loss of combustion heat can be reduced without impairing reliable combustion throughout the lean mixture. This reduction in cooling loss of combustion heat can provide the advantage of reducing fuel consumption, that is, increasing fuel consumption rate.

In addition, a recess 33 is provided in the center of the top surface 21 of the piston 3.
When the peripheral part of the recess 33 is stepped down from the top surface, a vortex is generated in the stepped part by the squish flow, and therefore separation of the squish flow becomes worse. Although the upward tendency and flow velocity of the squishy flow are weakened, if the periphery of the recess 33 is formed into an inclined surface 34 that slopes down at an appropriate angle θ with respect to the piston top surface 21, no vortex flow is generated at that location. The separation of the squish flow is improved, the upward tendency and velocity of the squish flow are not weakened, and the above-mentioned effects are increased.

The torch holes 17, 18, and 19 in the head 15 of the subchamber cup 11 are bored in the directions described above, but among the torch holes, the large diameter torch hole 17 and the medium diameter torch hole 18 are The ejected torch flame is directed toward the lower part of the intake valve 7 and the lower part of the exhaust valve 9, respectively, and toward the inclined surface 34 around the recess 33 in the center of the top surface 21 of the piston 3.

In this way, when the torch flame from the torch hole is directed toward the inclined surface 34, the torch flame hits the inclined surface 34 and is deflected so as to spread in the lateral direction with respect to the axial direction of the torch flame. The area where the torch flame can affect the lean mixture can be increased in the direction toward the center of the main combustion chamber 5 instead of in the direction around the main combustion chamber 5, which improves the ignition combustibility for the lean mixture. and rapid completion of combustion can be significantly improved.

In this case, if the depth of the recess 33 formed in the top surface 21 of the piston 3 is deep, the center of the main combustion chamber 5 will be further away from the sub-combustion chamber 12 below, and each torch hole 17, 18, 19 The torch flame from the main combustion chamber 5
However, in the present invention, the depth of the recess 33 formed in the top surface 21 of the piston 3 is compared. In addition to making the target shallow, the bottom surface 32 is formed to be a flat surface, so that the center of the main combustion chamber 5 is further away from the sub-combustion chamber 12 downward, which means that the torch flame from each torch hole 17, 18, 19 is This makes it possible to avoid slowing down the speed when passing approximately the center of the main combustion chamber 5. In other words, the depth of the recess 33 is set to such an extent that the squish flow does not come into contact with the center of the top surface 21 of the piston 3. In addition, the inclination angle θ of the conical inclined surface 34 in the recess 33 should be determined taking into consideration both the separation property of the squish flow and the drift of the torch flame.

According to experiments, in the case of the internal combustion engine of the illustrated embodiment, the depth of the recess 33 is 1.5-2.5 mm, and the depth of the recess 33 is 1.5 to 2.5 mm.
The appropriate inclination angle θ of No. 4 was 10 to 40 degrees.

As described above, according to the present invention, a relatively shallow recess having a flat bottom surface and a conical inclined surface extending from the bottom surface toward the top surface of the piston is formed in the top surface of the piston. By making the diameter of the conical inclined surface relative to the top surface of the piston smaller than the inscribed circle of the squish area around the main combustion chamber, the torch flame from the auxiliary combustion chamber passes approximately through the center of the main combustion chamber. The squish flow can be diverted to the center of the main combustion chamber without reducing the speed during combustion, making it possible to strengthen the swirl or vortex at the center of the main combustion chamber, and to reduce the temperature at the center of the main combustion chamber. By configuring the torch hole in the auxiliary combustion chamber so that the torch flame from the torch hole heads toward the conical inclined surface in the recess, the torch flame can be maintained at a high temperature by using the recess. This allows the area of influence to be increased to the center of the main combustion chamber.

As a result, according to the present invention, as described above, the speed of the torch flame from the auxiliary combustion chamber when passing through the approximate center of the main combustion chamber is not reduced, and the swirl or vortex at the center of the main combustion chamber is not reduced. The temperature in the center of the main combustion chamber can be maintained at a high level.
and the ability to increase the area of influence of the torch flame to the center of the main combustion chamber by using the recess, together significantly improve reliable and rapid combustion of lean mixtures. This has the effect of reducing engine fuel consumption.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main parts of the engine, FIG. 2 is a sectional view shown in FIG. 1, FIG. FIG. 2 is an enlarged cross-sectional view of FIG. 2; 1...Cylinder block, 2...Cylinder head,
4...Cylinder bore, 3...Piston, 5...Main combustion chamber, 6...Intake port, 7...Intake valve, 8...Exhaust port, 9...Exhaust valve, 11...Subchamber cup, 12...Subcombustion chamber, 13...Spark plug , 17, 18, 19... Torch hole, 29, 30, 31... Squeeze area, 21
...piston top surface, 33...recess, 34...slanted surface.

Claims (1)

[Claims] 1. A main combustion chamber is recessed in the lower surface of the cylinder head so as to surround both the intake port opening and the exhaust port opening for the main combustion chamber, and a torch hole is formed in the main combustion chamber in the cylinder head. An internal combustion engine with a sub-combustion chamber that communicates with the main combustion chamber through the main combustion chamber, and a squish area for the top surface of the piston is formed on the lower surface of the cylinder head so as to surround the main combustion chamber. In the top surface of the piston, a recess having a relatively shallow depth having a flat bottom surface and a conical inclined surface from the bottom surface toward the top surface of the piston is formed, and a conical shape in the recess is formed. The diameter of the inclined surface relative to the top surface of the piston is made smaller than the inscribed circle of the squish area around the main combustion chamber, and the torch hole in the auxiliary combustion chamber is set so that the torch flame from the torch hole reaches the recess. An internal combustion engine with auxiliary combustion characterized by being configured to face a conical inclined surface.