JPH02149720A - Combustion chamber of engine - Google Patents

Abstract

PURPOSE:To make it possible to materialize a compact combustion chamber without knocking by setting the squish area formed along the peripheral edge of a cylinder bore in such a way that its suction port side becomes larger than its exhaust port side. CONSTITUTION:No.1 dome 5a and No.2 dome 5b having a diameter larger than the dome 5a are formed around the suction port 8 and exhaust port 9 of a cylinder head side engine combustion chamber 5, respectively. Squish areas, located outside each dome 5a, 5b and formed along the peripheral edge of a cylinder bore 3, are set in such a manner that a suction side squish area 7a becomes larger than an exhaust side squish area 7b. Since the setting sufficiently enhances the combustion speed of the suction side fuel-air mixture with a lower temperature, the combination of the two sets of domes 5a, 5b makes it possible to materialize a compact shape for the combustion chamber 5 by drawing it close to a spherical form as much as possible. The setting also allows to obtain a high efficiency without knocking.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of a combustion chamber of an engine.

(Prior Art) For example, as shown in Japanese Unexamined Patent Publication No. 57-198315, regarding the structure of an engine combustion chamber, two dome parts (
By combining circular concave surfaces), the engine combustion chamber becomes nearly spherical and compact, while a squirrel unit is formed on the outer periphery of these domes to form a squish during the compression or expansion stroke. Some have a spherical combustion chamber structure.

In this way, two sets of dome parts are formed around the intake port and the exhaust port, respectively, and the shape of the engine combustion chamber is approximated to a spherical shape. In addition to this, a squish region is formed around each dome as described above, and flame propagation is made more effective by squishing during the compression stroke or by reverse squishing during the expansion stroke. By increasing the speed, the combustion performance of the engine will be sufficiently improved, and the combustion state will be stabilized, especially in the engine low load region where the intake air flow rate is small and the intake flow rate is low, and the engine will become leaner. It is also possible to perform burn-out operation.This also has the advantage of improving fuel efficiency.

(Problem to be solved by the invention) However, as in the conventional technology, there are two
In the case where a sub-spherical combustion chamber shape is formed by combining two sets of dome parts (circular concave surfaces) and a squish area is provided on the outer periphery of each dome part, first, in the above conventional technology, one part on the intake side than on the exhaust side is formed.・The -mu part (spherical combustion chamber) is formed larger. Therefore, in the case of such a structure, the squish zone on the intake side inevitably becomes narrower, while the squish zone on the exhaust side becomes wider. As a result, the combustion performance of the air-fuel mixture on the intake side, where the intake air temperature is inherently low, deteriorates (
On the intake side, the amount of squish generated decreases, so the flame propagation speed decreases). Furthermore, in the case of the configuration of the prior art described above, it is impossible to expand the intake side skin area as long as the structure of the engine combustion chamber is made compact. Therefore, there is a problem that knocking is relatively easy to occur under high loads.

(Means for Solving the Problems) The present invention solves the above problems, realizes a compact engine combustion chamber, secures a sufficient squish area on the intake side, and ensures sufficient flame propagation. This was done for the purpose of increasing the speed, and is used on the cylinder head side of an engine that is equipped with a squish formation means to improve combustion performance by forming a squish in the engine combustion chamber during the compression stroke. A first dome part around the intake port of the engine combustion chamber,
A second dome portion having a larger diameter than the first dome portion is formed around the same exhaust port, and is located outside each of these dome portions and is formed at the periphery of the cylinder bore. This is characterized in that the squish area is set to be larger on the intake port side than on the exhaust port side.

(Function) In the case of the combustion chamber structure of the engine of the present invention described above, the exhaust side dome portion (dome-shaped combustion chamber) is formed to have a larger diameter than the intake side dome portion (dome-shaped combustion chamber). The squish zone on the intake side becomes wider, making it possible to obtain a sufficient squish-no-yu effect during the compression stroke or expansion stroke, and increasing the flame propagation speed of the low-temperature intake-side mixture to improve combustion performance. You will be able to improve your

(Effect of the invention) Therefore, according to the structure of the combustion chamber of the engine of the present invention,
As mentioned above, by ensuring a particularly wide squish area in the dome-shaped combustion chamber on the intake side,
As a result, the combustion speed of the konai gas can be sufficiently increased, and by combining the two dome sections, the shape of the engine combustion chamber can be made as close to a spherical shape as possible, making the engine combustion chamber more compact. Therefore, it becomes possible to provide a highly efficient engine that does not cause knocking.

(Example) FIGS. 1 to 4 show the combustion chamber structure of an engine according to an example of the present invention.

First, Figure 1 shows the longitudinal cross-sectional structure of the combustion chamber of the engine.
In the figure, reference numeral 1a denotes a cylinder block, and lb denotes a cylinder head located at the upper part of the cylinder block la, which is integrally provided through a gasket 2, and forms a predetermined engine and non-cylinder together with the cylinder block la.

- Seven cylinder bores 3 having a predetermined diameter and a predetermined length are formed inside the cylinder block la (note that water jackets and the like are omitted in the drawings to simplify the explanation).

Further, the surface of the lower surface of the cylinder head tb that corresponds to the cylinder bore 3 is a first dome portion that mutually separates two areas, an intake side 4a and an exhaust side 11b, as shown in FIGS. 1 and 2, for example. A child spherical engine combustion chamber 5 is formed of a (circular concave surface) 5a and a second dome portion (circular concave surface) 5b.

As shown in FIG. ) r
The diameter (same) r of the second dome portion 5b is formed to be a predetermined larger diameter than +, and when viewed from above, it is deformed into a daruma shape from the intake side 4a to the exhaust side 4b. Also, on the outer circumferential side of both dome areas, there are squish areas 7a, 7 that are wide on the intake side 4a and relatively narrow on the exhaust side 4b.
It forms b. The squish areas 7a, 7b
The function is to increase the flame propagation speed and improve the combustion performance by forming a compression vortex particularly in this region during the engine compression stroke. Additionally, the squish region acts to increase the flame propagation speed by forming a reverse squish during the expansion stroke.

Further, numeral 8 is an intake port, and 9 is an exhaust port. The intake port 8 is configured with two sets of ports, a main port 8A and a swirl port (secondary port) 8B, and a shutter valve IO for opening and closing the main port 8A is provided on the main port 1-8A side. It is being The shutter valve 10 closes, for example, in a low-speed, low-load region, and allows a high flow rate into the engine combustion chamber 5 only from the swirl port 8B, and moreover, is smaller than the protrusion 13 of the dome portion 5b of the large-diameter exhaust pipe 2. By flowing the injected fuel along the circumferential direction toward the inner circumferential surface part 14 on the inner side (downstream side), the injected fuel is atomized well, and the mixing of the fuel and air is made good. By combining it with a double injection stem, it is possible to effectively stratify the air-fuel mixture in the combustion chamber.

As a result, combustibility is improved as much as possible to compensate for the drop in engine torque in the low-speed, low-load region, and fuel efficiency is improved.

On the other hand, when the operating condition of Entsuno becomes high speed and high load,
The shutter valve IO is wide open and the intake port 8
The overall diameter of the intake passage is enlarged to supply a sufficient amount of intake air with low intake resistance and to improve output in response to engine high speed and high load conditions.

Further, reference numeral 11 denotes a fuel injector that is configured to have the above-mentioned timed injection function, which injects fuel in synchronization with the intake stroke of the engine, for example.

The fuel injector 11 has a direction from the connecting portion between the main intake port 8A and the intake manifold 12 continuous to the main intake port 8A, which is the same as the inflow direction of the swirl flow above the path as shown in FIG. The injection direction is set so that the fuel is synchronously injected outward from the position of the electrode portion 15a of the spark plug 15 (radially outward of the dome portion 5b). As a result, the fuel injected in the latter half of the engine intake stroke by the timed injection in synchronization with the engine intake stroke rides on the swirl flow formed by the swirl port 8B and directly hits the electrode portion 15a of the spark plug 15. Instead, they are gathered near the electrode portion 15a of the spark plug 15.

As a result, especially the electrode part of the spark plug 15! The mixture concentration near 5a becomes rich and the ignitability improves. This effect is combined with the relationship between the installed position of the pilot spark plug 15 and the upstream and downstream angles of the installed portion to achieve a more effective effect.

On the other hand, the two-leg spark plug 15 is, for example, the exhaust side pipe 2.
The installation wall angle θ with respect to the head mating surface (the surface of the gasket 2) of the combustion chamber wall on the downstream side of the swirl is the wall surface angle on the upstream side of the swirl, as shown in FIG. The downstream wall angle (curvature R,) θ is larger than (curvature R,) θ1 (θ,〉θ,
).

Therefore, due to the above-mentioned timed injection, a portion of the relatively rich air-fuel mixture that has effectively ridden the swirl flow as described above flows into the spark plug 15 as shown by the arrow (a) in the figure. ! The spark plug 1 rotates near the X pole part 15a.
The particles remain near the electrode portion 15a of No. 5 in a stratified state for a predetermined period of time. Therefore, as a result, the above-mentioned effect of improving ignitability can be more effectively improved.

Next, reference numeral 20 denotes a piston fitted into the cylinder bore 3 via a piston ring 20a so as to be vertically slidable. The piston 20 is vertically movably supported by a connecting rod 22 via a piston pin 21, and the piston head upper surface 23 has a concave groove in the opposite direction corresponding to the shape of the combustion chamber 5 on the cylinder head side. The first dome portion 21a and the second dome portion 21b are formed to intersect with each other. This, together with the dome structure on the cylinder head side, forms a combustion chamber structure that is nearly spherical as a whole, allows easy generation of swirl and squish, and allows for a compact engine shape. Moreover, in this case, as described above, the first dome portion 5a on the cylinder head side and the first dome portion 5a on the piston head side
Since both the dome portions 21a have smaller diameters than the second dome portions 5b and 21b, the engine combustion chamber can secure a particularly wide squish area in the intake side 4a region where the air-fuel mixture temperature is low. This makes it possible to sufficiently improve the combustion rate in this region. As a result, it is possible to make the shape of the engine combustion chamber compact and increase the degree of uniformity while sufficiently improving combustion performance, making it possible to provide a highly efficient engine that does not cause knocking. Furthermore, in this case, the first and second piston head 23 side
The protrusion 24 on the downstream side of the swirl formed at the intersection between the dome portions 21a and 21b is located downstream of the swirl far from the spark plug 15 (in front of the dome on the intake side where the air-fuel mixture temperature is low). , spark plug 15 as described above.
The stratified air mixture flow ignited through the downstream protrusion 2
4, the air is further agitated to form a disordered air motion due to tumble air motion, and the combustion performance (combustion speed) of the end gas zone located far from the spark plug 15 is further greatly improved. As a result, the combustion performance of the entire engine combustion chamber is greatly improved, and the lean burn performance is further improved.

In addition, as mentioned above, the first and second dome parts 5 a
, 5b merely indicates the radius of the circular plane of the opening of each dome portion 5a, 5b. Therefore, the curvature R,, r
The radius of the sphere defining t may be larger on the first dome portion 5b side. The relationship between them is determined solely by the relationship between the spherical cut planes.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the structure of a combustion chamber of an engine according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. Figure 3 is an enlarged cross-sectional view of the spark plug mounting part of the same embodiment structure (Figure 2B-
FIG. 4 is a plan view showing the shape of the upper surface of the piston head in the same embodiment structure. La...Cylinder block ib...Cylinder head 2...Gasket 3...Cylinder bore 4a...Intake side 4b...Exhaust side 5...Combustion chamber 5a...First dome part 5b...Second dome part 7a...Intake side squish region 7b...Exhaust side squish region 8...Intake port 8A... - Main port 8B... Swirl port 9... Exhaust port 10... Shutter valve 20... Piston 21a... First dome part 21b... Second dome part 23・ ・Top part of piston helad Fig. 3

Claims (1)

[Scope of Claims] 1. In an engine that is equipped with squish forming means and is configured to improve combustion performance by forming squish in the engine combustion chamber during the compression stroke, the engine is equipped with squish forming means that forms a squish in the engine combustion chamber during the compression stroke to improve combustion performance. A first dome part and a second dome part having a larger diameter than the first dome part are formed around the same exhaust port, and are located outside of each dome part and formed along the periphery of the cylinder bore. A combustion chamber for an engine, characterized in that a squish area is set to be larger on an intake port side than on an exhaust port side. 2. In addition to the squish forming means, a swirl generating means is further provided, and the first dome part and the second dome part of the cylinder head side combustion chamber are formed in a mutually intersecting state, On the other hand, corresponding to the dome shape of the combustion chamber on the cylinder head side, on the piston head side, a first dome part and a second dome part, which are made of concave surfaces in the opposite direction, intersect with each other and swirl downstream. The combustion chamber of an engine according to claim 1, characterized in that it is formed with a protrusion for generating turbulent flow.