JPH0240262Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention is directed to the combustion chamber structure of an engine, particularly to the combustion chamber of a four-valve engine that is equipped with two intake valves and two exhaust valves per cylinder. Regarding structure.

(Prior Art) A four-valve engine, which has two intake valves and two exhaust valves per cylinder, has been put into practical use as an engine for automobiles and the like. According to this engine, the intake air filling efficiency and the exhaust efficiency are improved, and the combustion state is improved, thereby realizing high output of the engine.

In this type of engine, in order to obtain good flame propagation after ignition throughout the combustion chamber, the ignition must be ignited in the center of the four valves arranged in a square shape with respect to the combustion chamber. It is necessary to place plugs, but it is necessary to place two intake valves and one exhaust valve each.
When driving with an overhead camshaft, 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. As a result, the spark plug and the camshaft may interfere with each other, or the camshaft may interfere with the installation and removal of the spark plug, resulting in poor engine serviceability. Therefore, it is conceivable to arrange the spark plug in an inclined manner, as in the engine disclosed in, for example, Japanese Unexamined Patent Publication No. 57-102506. In other words, as shown in FIGS. 5 and 6, two intake valves 2,
2 and two exhaust valves 3, 3 are arranged in a square shape,
In addition, in the configuration in which one camshaft 4 is disposed above the center of the combustion chamber 1, the spark plug 5 is arranged in an inclined manner between the two exhaust valves 3, and the ignition part 5a at the tip thereof is arranged in an inclined manner. It is located in the center of the combustion chamber 1, and its upper part 5b faces 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 upper part 5b of the spark plug 5 is located between the camshaft 4 and the upper ends of the stem parts of the exhaust valves 3, 3.
The spark plug 5 is constructed directly below the shaft 7 of the spark plug 5.
In order to enable attachment and detachment of the spark plug 5, the rocker arm shaft 7 is divided into two parts for each rocker arm 6, and a space A 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.
In particular, if this configuration is applied to a multi-cylinder engine, a large number of rocker arm shafts will be required, and the mounting structure will become extremely complicated. Therefore, it is conceivable to arrange the spark plug 5 so that the angle of inclination with respect to the horizontal plane is small, so that the upper part 5b of the plug 5 faces outward from the side of the cylinder head. The ignition part 5a of the ignition plug 5 and the ceiling surface 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 surface 8, or exists around the ignition part 5a. Since the amount of air-fuel mixture is insufficient, the flame does not grow well in the initial stage of ignition.

To solve the above-mentioned problem when the spark plug is arranged in an inclined manner in a four-valve engine, a cavity is provided near the ignition part of the spark plug at the center of the ceiling surface of the combustion chamber.
It is conceivable to prevent heat from escaping from the ignition part to the ceiling surface at the time of ignition, and to allow the flame generated in the ignition part to grow within this space, thereby obtaining good flame growth in the initial stage of ignition. However, even in this case, there is the problem of how to uniformly and quickly propagate the initial ignition flame that has grown within the cavity throughout the combustion chamber.

(Purpose of the invention) The present invention addresses the above-mentioned actual situation regarding four-valve engines. By providing a cavity in the vicinity of the ignition part of the spark plug at the center of the surface, the flame can grow well in the vicinity of the ignition part at the initial stage of the ignition part, and the flame can be spread quickly and uniformly throughout the combustion chamber. Let it spread,
The aim is to realize an engine of this type with excellent combustion performance.

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

That is, in a four-valve engine in which each cylinder is provided with two intake valves and two exhaust valves, and the tip of the spark plug insertion hole is opened in the center of the combustion chamber, the spark plug insertion hole is A cavity is provided in the opening in the upper surface of the combustion chamber, and a plurality of grooves are provided in the upper surface of the combustion chamber radially extending from the cavity. Specifically, this groove is formed radially from the cavity to avoid the opening of the intake and exhaust ports on the upper surface of the combustion chamber, but the groove is formed radially from the cavity to avoid the opening of the intake and exhaust ports on the upper surface of the combustion chamber. The flame at the initial stage of the ignition part is led out from inside the cavity to the surrounding area, and has the effect of quickly propagating throughout the combustion chamber.

(Effect of the invention) According to the above configuration, by providing a cavity around the ignition part of the spark plug in the combustion chamber of the four-valve engine, the ignition part of the plug and the ceiling surface of the combustion chamber are connected. A space will exist between the two, and this space will reduce the escape of heat to the ceiling surface when the spark plug ignites, and the air-fuel mixture will exist evenly around the entire periphery of the ignition part of the spark plug. This allows the flame generated by ignition to grow well within the cavity.

The flame within this cavity is propagated not only downward into the combustion chamber but also toward the outer periphery of the upper part of the combustion chamber by a plurality of grooves extending radially from the cavity on the ceiling surface of the combustion chamber. As a result, the flame is uniformly and rapidly propagated throughout the combustion chamber, and the air-fuel mixture is completely combusted in a short time. In this way, the growth and propagation of the flame from ignition of the air-fuel mixture by the spark plug are performed reliably and favorably, resulting in excellent combustibility.

(Example) Hereinafter, an example of the present invention will be described. still,
This embodiment relates to a 4-valve, 1-overhead camshaft engine.

As shown in FIGS. 1 and 2, an engine 10 has a cylinder block 1 in which a plurality of cylinders are arranged in a row.
1, and a cylinder head 13 installed on the upper surface of the block 11 via a gasket 12,
The inner peripheral surface of the cylinder 14 in the cylinder block 11, the upper surface of the piston 15 fitted in the cylinder 14, and the lower surface 13a of the cylinder head 13.
A combustion chamber 16 is defined by these. Here, the combustion chamber 16 has a ceiling surface (lower surface of the cylinder head) 16a.
It is said to be a pent-roof type combustion chamber with a recessed roof. Further, in this embodiment, the upper surface 15a of the piston 15 is also connected to the ceiling surface 16 of the combustion chamber 16.
It is said to be a pent roof type similar to a, and
A combustion recess 15b serving as a main combustion chamber is formed in the center of the upper surface 15a of the piston 15, and when the piston 15 reaches near the top dead center during the compression stroke, the piston upper surface 15a and the combustion chamber ceiling surface 1
6a, squish flowing into the combustion recess 15b is generated.

The cylinder head 13 is provided with two intake ports 17, 17 that communicate with the combustion chamber 16 from one side surface 13b, and two exhaust ports 18, 18 that communicate with the combustion chamber 16 from the other side surface 13c. In addition, the combustion chamber 1 of each of these ports
Two intake valves 19, 19 and two exhaust valves 20, 20 are provided, which open and close openings 17a, 17a, 18a, 18a to the engine 6, respectively. In addition, stem portions 19a, 19 extending above each of these valves
a, 20a, 20a are spring retainers 21, 21, 22, which protrude upward from the upper surface 13d of the cylinder head 13 and are fixed to the upper end thereof, respectively.
22, and spring seat portions 23, 2 formed at the protruding portions of the respective stem portions 19a, 19a, 20a, 20a on the upper surface 13d of the cylinder head 13.
3, 24, 24, each valve 19, 1
Valve springs 25, 25, 26, and 26 are installed to bias valves 9, 20, and 20 in the closing direction, respectively.

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 valves 19, 19 and the exhaust valves 20, 20 at the center of the upper part of the cylinder head 13. . Journal portion 27a of this camshaft 27...27a
The bearing wall 2 stands between adjacent cylinders at the center of the upper surface of the cylinder head 13 and at both ends of the cylinder head 13.
8...28 and a bearing cap 30...30 fixed to each bearing wall 28...28 using two bolts 29, 29, respectively. , 1 between the adjacent journal parts 27a...27a of the camshaft 27.
Two intake cams 27b, 27b and two exhaust cams 27c, 27c for each cylinder are formed. Two rocker arm shafts 31 and 32 are installed in parallel on both sides of the upper part of the camshaft 27, and two rocker arm shafts 33 and 33 for intake valves are mounted on these shafts 31 and 32, respectively, for each cylinder. Exhaust valve rocker arms 34, 34 are swingably supported, and each rocker arm 33, 33, 34, 3
Cams 27b, 27b, 27 corresponding to both ends of 4
c, the circumferential surface of 27c and the stem portion 19a of the intake/exhaust valve,
The rocker arms 33, 3 are in contact with the upper ends of the rocker arms 33, 20a, respectively, so that the rocker arms 33, 3 are rotated by the rotation of the camshaft 27 in synchronization with the crankshaft.
3, 34, 34 through each valve 19, 19, 20,
20 is adapted to be opened and moved at a predetermined timing. Here, the Rocker arm shafts 31, 3
2 is a holding member 35 on the upper surface of the bearing cap 30...
...35 and are fixed by the bolts 29...29.

In addition to the above configuration, the cylinder head 13 is provided with a spark plug insertion hole 36, into which a spark plug 37 is installed. This insertion hole 3
6 is two exhaust ports 18, 1 in each cylinder.
It is provided in an inclined manner so as to intersect the exhaust valves 20, 20 between 8 and 8, and its tip 36a is located at a position surrounded by the openings 17a, 17a, 18a, 18a of each port on the lower surface 13a of the cylinder head 13, i.e. The hole 36 is opened at the center of the roof-like ceiling surface 16a of the combustion chamber 16, and the rear end 36b of the hole 36 is connected to one side surface 13 of the cylinder head 13.
Opening 18 of exhaust port 18, 18 at c
b, 18b, and the spring seat portion 24 of the exhaust valve 20, 20 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 head 24 and the head 13.

However, as shown in FIGS. 3 and 4, the tip 36a of the spark plug insertion hole 36 that opens in the ceiling surface 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. The ceiling surface 16a is
Four grooves 36d...36d are formed extending from the cavity 36a in all directions between the respective valve seat mounting recesses 17', 17', 18', and 18'. When the male threaded part 37a of the spark plug 37 is screwed into the female threaded part 36c of the spark plug insertion hole 36, the ignition part 37 at the tip of the plug 37
b is located inside the hemispherical cavity 36a.

According to the above configuration, the ceiling surface 16 of the combustion chamber 16
A total of 4 intake and exhaust ports 17a, 17a, 1
In the engine 10 with openings 8a and 18a,
Since the ignition part 37b at the tip of the ignition plug 37 is located at the center of the upper part of the combustion chamber 16, the flame of the air-fuel mixture ignited by the ignition plug 37 propagates well throughout the combustion chamber 16. . Especially in the early stage of ignition, the spark plug 3
A cavity 36a is formed around the ignition part 37b of No. 7, and a space filled with the air-fuel mixture is provided between the ignition part 37b and the ceiling surface 16a, so that the flame generated in the ignition part 37b is Combustion chamber 16
The ignition portion 37b will grow evenly around the entire circumference, not just below, and since the ignition portion 37b will be separated from the ceiling surface 16a of the combustion chamber 16 by an appropriate distance, the ignition portion 37b will grow evenly. The escape of flame heat to the ceiling wall 16a side is reduced,
This also improves the ignitability of the air-fuel mixture and the growth of the flame within the cavity 36a.

In addition, in this embodiment, as shown in FIG. 4, the piston 15 during the compression stroke of the engine
When the engine reaches near the top dead center, the air-fuel mixture flows into the combustion recess 15b from the gap X between the upper surface 15a of the piston 15 and the ceiling surface 16a of the combustion chamber 16, as shown by arrows a and a. However, the flow a caused by this squishing becomes an extremely strong flow at the end of the compression stroke, and the spark plug 37 ignites during the period when this strong flow is occurring. Therefore, if the ignition part 37b of the spark plug 37 is plunged into the flow a, the growth of the flame generated at the ignition part 37b at the time of ignition will be hindered, which will eventually cause the flame to misfire. However, since the ignition part 37b of the spark plug 37 is located inside the hemispherical cavity 36a, the ignition part 37b is protected from the flow a caused by the squish, and therefore the ignition of the spark plug 37 is prevented. No deterioration in ignitability or misfires occur during times of fire.

However, the flame that grows inside the hemispherical cavity 36a is propagated downward from inside the cavity 36a to the combustion chamber 16.
In that case, there are grooves 36 in all directions from the cavity 36a.
Since the grooves 36d...36d are provided, the flame within the cavity 36a is also propagated toward the combustion recess 15b or the outer periphery of the combustion chamber 16 through these grooves 36d...36d. Therefore,
The flame generated inside the cavity 36a is
Propagates quickly and evenly throughout the combustion chamber 16,
In addition to ensuring ignition by providing the cavity 36a, the ignition of the air-fuel mixture in the combustion chamber 16 of this type of engine 10 allows for good growth and propagation of the flame, so that the air-fuel mixture is completed in a short period of time. As a result, excellent combustibility can be obtained.

According to this embodiment, the air-fuel mixture is well mixed by the squish generated within the combustion recess 15b of the piston 15, and the flame generated within the cavity 36a is mixed within the combustion recess 15b. The generated air-fuel mixture is well propagated throughout the combustion chamber 16 by the flow, and even better combustibility can be ensured. In addition, in this embodiment, the shape of the cavity 36a is hemispherical, so that the valve seat mounting recesses 17 provided at the openings 17a, 17a, 18a, 18a of the intake and exhaust ports are formed as shown in FIG. ',17',
It becomes possible to secure a sufficient volume of the cavity 36a without causing interference with the cavities 18' and 18'. In other words, if the spark plug insertion hole is provided in an inclined shape and 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. As a result, a large cavity volume can be obtained without this interference occurring.

In this embodiment, the spark plug insertion hole 36
The rear end portion 36b is connected to the side surface 13 of the cylinder head 13.
Opening 18 of exhaust port 18, 18 at c
b, 18b and the spring seat portions 24, 24 of the exhaust valves 20, 20, the spark plug 37 can be inserted from the outside of the exhaust valve valve mechanism 38 on the side of the cylinder head 13. It becomes possible to attach and detach without being obstructed by the valve mechanism 38.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment 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 longitudinal sectional view of the cylinder taken along the line shown in Figure 1. FIG. 3 is a cross-sectional plan view of the head alone, FIG. 3 is a bottom view of the cylinder head alone, and FIG. 4 is an enlarged longitudinal sectional view of the main parts around the combustion chamber. 5 and 6 are 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, 1
6a... Combustion chamber top surface (ceiling surface), 36... Insertion hole,
36a...Cavity, 36c...Female thread part, 3
6d...Groove, 37...Spark plug.

Claims (1)

[Scope of utility model registration request] 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 at the center of the upper surface of the combustion chamber, and the opening is connected to the upper surface of the combustion chamber. What is claimed is: 1. A combustion chamber structure for an engine, comprising: a cavity formed by recessing the cavity upward; and a plurality of grooves extending radially from the cavity on the upper surface of the combustion chamber.