JPS61142321A - Construction of combustion chamber in engine - Google Patents

Abstract

PURPOSE:To well perform ignition or the like of a mixture by an ignition plug, by opening the point end of an insertion hole of the ignition plug in a cylinder head to the central part of a combustion chamber while forming in this opening part a semispherical cavity having a predetermined diameter. CONSTITUTION:An engine 10 opens to a ceiling wall 16a of its combustion chamber 16 four intake and exhaust ports 17, 18 in total in openings 17a, 18a. Here a point end part 36a of an insertion hole 36 of an ignition plug 37, provided in a cylinder head 13, is opened to a position, surrounded by each opening 17a, 18a of each port 17, 18 in a bottom surface 13a of the cylinder head 13, that is, the central part in the roof-shaped ceiling wall 16a of the combustion chamber 16. And the point end part 36a is formed in a semispherical cavity in a contour larger than the hole size of an internal thread part 36c, for screwing the ignition plug 37, successively placed to the upper of the part 36a. In this way, ignition of mixture by the ignition plug 37 or growth and propagation or the like of a flame in the beginning of the ignition can be well performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the combustion chamber structure of an engine, particularly for one cylinder.
The present invention relates to a combustion chamber structure of a four-valve engine equipped with two intake valves and two exhaust valves.

(Prior Art) Four-valve engines, each having two intake valves and two exhaust valves per cylinder, have been put into practical use as engines for automobiles and the like. According to this engine, the intake air filling efficiency and exhaust efficiency are improved, and the combustion condition is improved.
High engine output is achieved.

By the way, in this type of engine, in order to obtain good flame propagation after ignition throughout the combustion chamber,
It is necessary to place the spark plug in the center of four valves arranged in a square shape with respect to the combustion chamber, but when two intake valves and two exhaust valves are each driven by one overhead camshaft. In this case, the camshaft passes above the center of the combustion chamber, so if the spark plug is placed in the center of the combustion chamber, the camshaft will be located directly above it. Therefore,
The spark plug and the camshaft interfere with each other, or the camshaft obstructs the installation and removal of the spark plug, resulting in poor engine serviceability. Therefore, for example, JP-A-57-
It is conceivable to arrange the spark plug in an inclined manner as in the engine disclosed in Japanese Patent No. 102506. In other words,
As shown in FIGS. 5 and 6, for one combustion chamber 1, 21
In a configuration in which a 11il intake valve 2.2 and two exhaust valves 3.3 are arranged in a square shape, and one camshaft 4 is arranged above the center of the combustion chamber 1, the spark plug 5 is The ignition part 5 at the tip is arranged in an inclined manner between the two exhaust valves 3, 3.
a at the center of the combustion chamber 1, and the upper part 5b
is made to face obliquely upward from the side of the camshaft 4. According to this, good ignitability can be obtained, and interference between the spark plug 5 and the camshaft 4 can be avoided. However, in this engine, the spark plug 5 is arranged approximately parallel to the exhaust valves 3, 3, so that the upper part 5b of the plug 5 is between the camshaft 4 and the upper end of the stem portion of the exhaust valve 3.3. rocker arm 6 that straddles
．． It will be located directly below the axis 7 of 6, and therefore,
In order to enable the installation and removal of the spark plug 5, the rocker arm shaft 7 is divided into two parts for each rocker arm 6.6, and a space is provided above the spark plug 5. Therefore,
According to this engine, two rocker arm shafts on the exhaust valve side are required for each cylinder, and especially when this configuration is applied to a multi-cylinder engine, a large number of rocker arm shafts are required, and their installation is difficult due to the structure. etc. become significantly more complicated.

In order to avoid such a problem, the spark plug 5 may be mounted such that the angle of inclination with respect to the horizontal plane is small, so that the upper portion 5b of the plug 5 faces outward from the side of the cylinder head. However, in this case, the ignition part 5a of the spark plug 5 and the ceiling wall 8 of the combustion chamber 1 come close to each other, and when the plug 5 is ignited, heat escapes from the ignition part 5a to the ceiling wall 8, or the ignition part Since the amount of air-fuel mixture existing around 5a is insufficient, the flame does not grow well at the initial stage of ignition.

(Object of the Invention) The present invention is intended to address the above-mentioned situation regarding four-valve engines, and is intended to address the above-mentioned circumstances regarding four-valve engines, and specifically to apply spark plugs to four-valve engines in which the ignition part of the spark plug is located in the center of the combustion chamber. In an engine arranged in an inclined manner, by improving the structure near the ignition part of the ignition plug in the center of the ceiling wall of the combustion chamber, it is possible to improve the ignition of the air-fuel mixture by the ignition plug or the growth and propagation of the flame at the initial stage of ignition. The purpose is to realize an engine with excellent combustibility as this type of engine.

(Structure of the Invention) The combustion chamber structure of the engine according to the present invention is characterized in that it is structured as follows to achieve the above object.

That is, in a four-valve engine in which each cylinder is provided with a 2WA intake valve and two exhaust valves, and in which the tip of the spark plug insertion hole is opened in the center of the combustion chamber on the lower surface of the cylinder head, the above-mentioned ignition A capity is provided at the frontage of the plug insertion hole to the combustion chamber. This capity has a hemispherical shape with a diameter larger than the diameter of the female threaded portion for plug screwing formed at the end of the opening side of the spark plug insertion hole, and the ignition portion of the spark plug is an abbreviation of this hemispherical capity. centered. Therefore, a hemispherical space centered on the ignition section is created between the ignition section and the ceiling wall of the combustion chamber.

(Effects of the Invention) According to the above configuration, in the combustion chamber of a four-valve engine, there is a hemispherical shape between the ignition part of the spark plug and the ceiling wall of the combustion chamber, with the ignition part approximately at the center. Since there is a space of The flame generated by this will grow from the ignition part to the entire surrounding area. As a result, the growth and propagation of the flame at the initial stage of ignition are performed well, and in combination with the arrangement of the above-mentioned ignition part in the center of the combustion chamber, the ignition plug is arranged in an inclined shape as in the embodiment described in the description of the good combustion condition. This can be applied not only to engines where the spark plug is installed vertically to the bottom surface of the cylinder head, but also to engines where the spark plug is installed in an inclined manner. The hemispherical shape makes it possible to provide a large volume of space around the ignition part of the spark plug without causing interference between the cavity and the openings of the intake and exhaust boats located around it.

(Example) Examples of the present invention will be described below. Note that this embodiment relates to a four-valve, one-overhead camshaft engine.

As shown in FIG. 1.2, the engine 10 has a cylinder block 11 in which a plurality of cylinders are arranged in a row, and a cylinder head 13 installed on the upper surface of the block 11 via a gasket 12. A combustion chamber 16 is defined by the inner peripheral surface of the cylinder 14 in the block 11, the upper surface of the piston 15 fitted into the cylinder 14, and the lower surface 13a of the cylinder head 13. Here, the combustion chamber 16 has a vent roof type combustion chamber in which a ceiling wall (lower surface of the cylinder head) 16a is recessed in the shape of a roof. The cylinder head 13 also includes two intake boats 17 and 17 that communicate with the combustion chamber 16 from one side surface 13b.
Two exhaust boats 18.18 are provided which communicate with the combustion chamber 16 from the other side 13G, and each of these boats has an opening 17a, 17a,
18a, two intake valves 19 that open and close 18a, respectively.
19 and two exhaust valves 20,20. A stem portion 19a extends above these eight valves.

19a, 20a, and 20a project upward from the upper surface 13d of the cylinder head 13, and have spring retainers 21, 21, 22, and 22 fixed to their upper ends, respectively, and each stem portion 19 on the upper surface 13d of the cylinder head 13.
Between the spring seat portions 23, 23, 24, and 24 formed on the protruding portions of the valves 19, 19, 20, and 20a, there are valve springs 25 that bias each valve 19, 19, 20, and 20 in the closing direction, respectively. .25.26.26 is installed.

On the other hand, a single camshaft 27 extending in the direction of the crankshaft of the engine 10 is disposed at a position sandwiched between the intake valve 19.19 and the exhaust valve 20.20 at the center of the upper part of the cylinder head 13. . The journal portions 27a...2.7a of the camshaft 27 are connected to bearing walls 28...28 which are provided upright between adjacent cylinders at the center of the upper surface of the cylinder head 13 and at both ## parts of the head, and to each bearing wall. 28...28 and bearing caps 30...30 fixed using two bolts 29, 29, respectively. Between the journal parts 27a, 27a, two intake cams 27b, 27b for one cylinder and two exhaust cams 27C, 27C are arranged for one cylinder.
is formed. Two rocker arm shafts 31.32 are installed in parallel on both sides of the upper part of the camshaft 27, and two intake valve rocker arms 33.32 for each cylinder are connected to these shafts 31.32. 33 and an exhaust valve rocker arm 34, 34 are swingably supported,
Both ends of each rocker arm 33.33.34.34 correspond to the cams 27b, 27b, 270.27cc7) and the stem portions 19a, 19a, 20a of the intake and exhaust valves.

20a, the eight valves 19, 19 are opened via the rocker arms 33, 33, 34, 34 by the rotation of the camshaft 27 in synchronization with the crankshaft.
．． 20.20 is opened and moved at a predetermined timing. Here, the rocker arm shafts 31, 32 are fixed to the upper surface of the bearing cap 30 by the bolts 29...29 using presser members 35...35.

In addition to the above configuration, a spark plug insertion hole 36 is provided in the cylinder head 13, and a spark plug 37 is inserted into the hole 36.
is installed. This insertion hole 36 is located between the two exhaust boats 18.18 in each cylinder with the exhaust valve 20.2.
The distal end 36 is provided in an inclined manner so as to intersect with
a is opened at a position surrounded by the openings 17a, 17a, 18a, and 18a of each boat on the lower surface 13a of the cylinder head 13, that is, at the center of the roof-like ceiling wall 16a of the combustion chamber 16, and the hole 36 The rear end 36b is the opening 18b of the exhaust boat 18.18 on one side 13C of the cylinder head 13.

18b, and an exhaust valve 2 on the upper surface 13d of the head 13.
It is opened so as to face the upper outer side of the head 13 from between the spring seat portions 24 and 24 having a diameter of 0.20 mm.

However, as shown in Fig. 3.4, the tip 36a of the spark plug insertion hole 36 opened in the ceiling wall 16a has a hemispherical diameter larger than the hole diameter of the female threaded portion 36c for threading the spark plug that continues above the tip 36a. It is said to be a shaped cavity. . Then, when the male threaded portion 37a of the spark plug 37 is screwed into the female threaded portion 360 of the spark plug insertion hole 36, the ignition portion 37b at the tip of the plug 37 is positioned approximately at the center of the hemispherical cavity 36a. It has become.

According to the above configuration, in the engine 10 in which a total of four intake/exhaust boats 17a, 17a, 18a, 18a are opened in the ceiling wall 16a of the combustion chamber 16, the ignition part 37b at the tip of the spark plug 37 is connected to the combustion chamber 16. By being located in the upper center of the combustion chamber 16, the flame of the air-fuel mixture ignited by the spark plug 37 can be propagated throughout the combustion chamber 16. Especially in the initial stage of ignition, the spark plug 3
The ignition part 37b of No. 7 is located approximately at the center of a hemispherical cavity 36a formed on the ceiling 116a of the combustion chamber 16, and the space between the ignition part 37b and the ceiling wall 16a is filled with air-fuel mixture (
Since the space is provided, the flame generated in the ignition part 37b grows not only below the combustion chamber 16 but also uniformly all around the combustion chamber 16. Furthermore, since the ignition section 37b is separated from the ceiling wall 16a of the combustion chamber 16 by an appropriate distance, the escape of the heat of the flame generated at the ignition section 37b toward the ceiling wall 16a is reduced. This also results in better ignitability of the air-fuel mixture, and better flame growth and propagation. This improves the intake and exhaust efficiency by providing two intake and exhaust valves 19, 19, 20, and 20, and improves the efficiency by locating the ignition part 37b of the spark plug 37 in the center of the combustion chamber 16. Coupled with the improvement in flame propagation throughout the combustion chamber 16, excellent combustibility is obtained, and output performance, fuel efficiency, exhaust performance, etc. are improved.

Particularly in the present invention, by making the shape of the cavity 36a hemispherical, the openings 17a, 17a, 18a, 18 of the intake and exhaust boat as shown in FIG.
Valve seat mounting recesses 17', 17 provided in a.
' , 18' , 18' without causing interference,
It becomes possible to secure a sufficient volume of the cavity 36a. In other words, when the spark plug insertion hole is provided in an inclined shape, if a cavity with a large volume is provided at the tip opening, the cavity and the valve seat mounting recess will interfere, but if the cavity is made in a hemispherical shape. By doing so, a large cavity volume can be obtained without this interference occurring.

In this embodiment, the rear end 36b of the spark plug insertion hole 36 is the opening 18b of the exhaust port 18.18 on the side surface 13C of the cylinder head 13.

18b and the spring seat portion 24 of the exhaust valve 20.20.
Since the spark plug 37 is opened between the spark plug 37 and the
It is possible to attach and remove the exhaust valve from the outside of the valve operating mechanism 38 for the exhaust valve on the side of the cylinder head 13 without being obstructed by the valve operating mechanism 38.

[Brief explanation of drawings]

Figures 1 to 4 show embodiments of the present invention. Figure 1 is a vertical sectional view of the cylinder head and its surroundings taken at the center of the combustion chamber, and Figure 2 is a cross-sectional view taken along line IF-IF in Figure 1. FIG. 3 is a bottom view of the cylinder head, and FIG. 4 is a vertical cross-sectional view of the main part of the cylinder head taken along line IV--IV in FIG. 3. FIG. 5.6 is a longitudinal sectional front view and a lateral plan view of a cylinder head and its surroundings, showing a conventional example. 13... Cylinder head, 16... Combustion chamber, 36.
...Insertion hole, 36a... Capity, 36c... Female thread part, 37... Spark plug.

Claims (1)

[Claims] (1) In an engine equipped with two intake valves and two exhaust valves for one cylinder, the tip of the spark plug insertion hole in the cylinder head is opened in the center of the combustion chamber, and the tip of the spark plug insertion hole in the cylinder head is opened in the center of the combustion chamber. A combustion chamber structure for an engine, characterized in that a hemispherical cavity having a diameter larger than the diameter of a female screw portion for threading a spark plug in an insertion hole is provided.