JPH0752332Y2 - Spark ignition engine combustion chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a combustion chamber of an internal combustion engine, in particular, a spark ignition engine.

[Conventional technology]

An example of a combustion chamber of a conventional spark ignition engine is shown in FIG. FIG. 3 (a) is a plan view of the cylinder head (view seen in a direction perpendicular to the cylinder axis), FIG. 3 (b),
(C) is a BB sectional view and a CC sectional view of FIG. 3 (a), respectively. FIG. 3 shows an example of a multi-valve engine with two intake and two exhaust valves, where 1 is a cylinder head, 2 is a piston,
3 is a cylinder liner, 4 is a spark plug, 5 is an intake valve, 6 is an exhaust valve, 7 is an intake port, 8 is an exhaust port, and 9 is a combustion chamber space.

In order to increase the output of the spark ignition engine, in order to increase the intake air-fuel mixture amount and reduce the pumping loss in the intake and exhaust strokes, a plurality of intake and exhaust valves are provided as shown in FIG. It is trying to increase. In FIG. 3, the intake valve,
An example of a four-valve system with two exhaust valves each is shown. In the combustion chamber of such a system, a large amount of air-fuel mixture is sucked in and exhausted sufficiently, and it is ignited by a spark plug arranged in the center of the combustion chamber to burn by flame propagation and flame propagation. Since the distance is short and uniform, fast combustion is obtained and high output is obtained.

[Problems to be solved by the device]

However, in the multi-valve engine as shown in FIG. 3, the lower surfaces of the plurality of intake / exhaust valves and the inner surface 1a of the cylinder head 1 are configured substantially in the same plane due to the constraint condition of the valve system configuration, and the valve area is reduced. In order to make it large, the surfaces 1a are installed so as to be inclined, and the piston top surface 2a is flat. As a result, in FIG. 3 (a), in the BB cross section through the center of each of the intake valve 5 and the exhaust valve 6,
As shown in FIG. (B), the inner surfaces 1a of the cylinder heads on both sides of the spark plug are inclined, and the depth H'from the head lower surface 1b, which is the tightening surface of the cylinder head 1, becomes farther away from the spark plug 4. Since the combustion chamber height H (that is, the thickness of the combustion chamber space) is reduced because it is decreased, the B-
In the cross section CC, which is perpendicular to the cross section B, the inner surface 1a of the cylinder head is a horizontal straight line as shown in FIG. 3 (c), and the depth H'from the lower surface 1b of the head is constant, so that the height of the combustion chamber is increased. It is a so-called pentroof type combustion chamber in which H (that is, the thickness of the combustion chamber space) does not change. Therefore, the flame propagation speed from the spark plug has different values depending on the direction.

In the flame propagation theory of gasoline engine, the flame propagation velocity is affected by the change of the spatial shape. That is, when the thickness of the space does not change, the flame velocity v _f
Is almost constant and propagates. However, when the thickness decreases as shown in Fig. 2 (b), the flame propagation speed accompanying the decrease in thickness.
When v _f increases and conversely the thickness increases as shown in FIG. 2 (c), the flame propagation velocity v _f decreases as the thickness increases. Therefore, in the conventional combustion chamber, as shown by the equal flame propagation time line t in FIG. 4, the flame propagates in the direction in which the combustion chamber height H decreases in the BB cross section, but at a right angle to this. On the cross-section in the C-C direction where the thickness of the combustion chamber does not change, flame propagation is relatively delayed, and although the geometric flame propagation distance is uniform, the flame propagation is substantially delayed (see FIG. 4). (A hatched portion) is formed, and knocking occurs in this region, resulting in hindering output improvement.

The object of the present invention is to solve the problems of the conventional device, to equalize flame propagation in the combustion chamber, to avoid knocking of unburned gas in a region where flame propagation is delayed, and to increase the output of a spark ignition engine. Providing a combustion chamber.

[Means for Solving the Problems] A combustion chamber of a spark ignition engine according to the present invention has a spark plug for air-fuel mixture ignition in a central portion of a cylinder head, and an inner surface of the cylinder head is provided with a spark plug of the cylinder head. In one vertical section passing through, the depth from the lower surface of the head decreases as it approaches the cylinder liners on both sides from the spark plug position, and in other vertical sections orthogonal to the vertical section of the cylinder head, In a spark ignition engine horizontally formed so that the depth from the lower surface of the head does not change, the top surface of the piston is located in the direction in which the inner surface of the cylinder head is horizontal from the central portion facing the spark plug. It is not an inclined straight plane extending in the direction of the cylinder liners on both sides, and the inclined straight plane is most depressed at the central portion and is close to the outer peripheral cylinder liner. It is characterized in that it is formed so as to become higher in accordance with the above, and in the direction in which the inner surface of the cylinder head is inclined, the inclined straight plane is horizontal.

[Action]

With the above-described configuration, the height of the combustion chamber in the direction in which the lower surface of the cylinder head inclines decreases with increasing distance from the spark plug, and the intersection of the plane including the intake valve lower surface and the plane including the exhaust valve decreases. The combustion chamber height in the linear direction, that is, the direction in which the inner surface of the cylinder head is horizontal, decreases as the distance from the spark plug increases, and the flame propagation speed in the intersecting direction increases, so that the flame propagation in the entire combustion chamber is increased. It is possible to equalize and eliminate the region where flame propagation is delayed and knocking is likely to occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1, 1A and 2.

FIG. 1 is a combustion chamber shape diagram of an embodiment, FIG. 1A is a plan view of a cylinder head, and FIGS. 1B and 1C are sectional views taken along line BB and CC of FIG. It is a figure. FIG. 1A is a top perspective view of the piston, and FIG. 2 is a change diagram of the flame propagation velocity depending on the flame propagation space shape.

In FIG. 1, 1 is a cylinder head, 2 is a piston, 3
In the cylinder liner, the combustion chamber space 9 is formed. Further, a spark plug 4 is provided on the upper surface of the center of the combustion chamber of the cylinder head 1. In a multi-valve engine with improved high-speed performance, the lower surface of multiple intake valves and the lower surface of exhaust valves are configured to be approximately on the same plane due to the constraint conditions of the valve system configuration, and each valve is inclined to have a large valve area. Has been installed. Therefore, the plane including the lower surface of the intake valve 5 and the plane including the lower surface of the exhaust valve 6 intersect at a straight line. Such a combustion chamber is called a pent roof type combustion chamber 9. The inner surface (combustion chamber surface) 1a of the cylinder head in the combustion chamber 9 is inclined to both sides with the spark plug 4 sandwiched in the cross section taken along the line BB in FIG. 1 (b). The depth H'from the head lower surface 1b, which is the tightening surface of the piston, is reduced, and the top surface 2a of the piston in the direction of the cross section BB is horizontal as shown in FIG. 1 (b). Even if there is, the height H of the combustion chamber becomes smaller toward the outer peripheral side.

In the present invention, the shape of the top surface 2a of the piston 2 is as shown in FIG. 1 (c) in the CC direction in which the inner surface 1a of the cylinder head is horizontal without inclination as shown in FIG. 1 (c). To
The central portion 21 facing the spark plug 4 is the lowest, and the spark plug 4
It is composed of _two inclined straight planes 2a ₁ and 2a ₂ which are inclined so as to become higher as they get closer to the cylinder liner 3. As a result, the inner surface 1a of the cylinder head
Also in the horizontal direction (CC direction), the height H of the combustion chamber becomes smaller toward the outer peripheral side.

In addition, in FIG. 1 (b), 2b is an inclined straight plane of the piston.
Notches are formed on the outer sides of 2a ₁ and 2a ₂ so as not to interfere with the inner surface 1a of the inclined cylinder head.

Next, the operation of the above embodiment will be described.

In the pentroof type combustion chamber of the present invention, the height of the combustion chamber in the direction in which the lower surface of the cylinder head inclines in the past decreases with distance from the spark plug in the same manner as in the conventional case, and the height of the combustion chamber (space thickness) in the conventional case decreases. The piston top surface 2a in the direction of the line of intersection (the direction of the cross section C-C in FIG. 1) of the plane including the lower surface of the intake valve and the plane including the lower surface of the exhaust valve, in which there is no change and the flame propagation is relatively delayed, is made into two inclined straight lines. Since the height H of the combustion chamber is reduced as the distance from the spark plug 4 is increased by forming a concave shape including the planes 2a ₁ and 2a ₂ , the flame propagation speed in that direction increases and the relative flame propagation delay occurs. Can be prevented, and flame propagation in the entire combustion chamber can be equalized.

[Effect of device]

Since the present invention is configured as described above, flame propagation in the combustion chamber can be equalized, self-ignition or knocking of unburned gas in a region where flame propagation is delayed can be avoided, and output can be increased.

[Brief description of drawings]

1 and 2 relate to the present invention, FIG. 1 (a) is a plan view showing the configuration of the combustion chamber on the cylinder head side, and FIG. 1 (b) is a sectional view taken along the line BB in FIG. FIG. 1 (c) is a sectional view taken along the line CC of FIG. 1, FIG. 1A is a perspective view of the upper portion of the piston, and FIG.
The figure shows the state of change in flame propagation velocity due to the flame propagation space shape. Fig. 2 (a) shows the case where the space shape does not change, Fig. 2 (b) shows the case where the space gradually narrows, and Fig. 2 (c). When the space is gradually widened, FIGS. 3 to 4 are conventional examples, FIG. 3 is the corresponding diagram of FIG. 1, and FIG. 4 is a flame propagation situation diagram of the conventional example. 1 ... cylinder head, 1a ... inner surface of cylinder head,
2 ...... piston, 2a _1, 2a ₂ ...... inclined face, 3 ...... cylinder liner, 4 ...... spark plug, 5 ...... intake valve, 6 ...... exhaust valve, 7 ...... intake port, 8 ...... exhaust port , 9 ... Combustion chamber space.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Nakagawa 1-1 1-1 Atsunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute (72) Hirohiko Iwamoto 5-33-8 Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) Inventor Shinichi Murata 5-3-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) Reference JP 62-67222 (JP, A) Actual development Sho 62 -72437 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A cylinder head has a spark plug for igniting an air-fuel mixture, and an inner surface of the cylinder head in a vertical cross section (a cross section along a cylinder axis) passing through the spark plug of the cylinder head. Are inclined so that the depth (H ') from the lower surface of the head decreases as they approach the cylinder liners on both sides from the spark plug position, and in other vertical cross sections orthogonal to the vertical cross section of the cylinder head,
In a spark ignition engine horizontally formed so that the depth (H ') from the lower surface of the head does not change; the top surface of the piston faces the spark plug in a direction in which the inner surface of the cylinder head is horizontal. The cylinder head is formed as an inclined straight plane extending from the central portion toward both sides of the cylinder liner, and the inclined straight plane is most depressed in the central portion and becomes higher as it approaches the outer peripheral cylinder liner. The combustion chamber of the spark ignition engine, wherein the inclined straight plane is formed to be horizontal in a direction in which the inner surface of the element is inclined.