JPS5852327Y2 - Combustion chamber structure of internal combustion engine - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a combustion chamber structure of an internal combustion engine.

In many conventional internal combustion engines, which generate a swirling flow inside the combustion chamber that swirls along the inner circumferential wall of the cylinder head that forms the combustion chamber, the electrodes of the cylinder head and the spark plug are attached almost at the end surface. The spark plugs are arranged so as to be located in the same plane.

However, in such a spark plug arrangement, the electrode is attached because the center electrode insulator, which protrudes from the end face and surrounds the center electrode of the spark plug, is directly exposed to the swirling flow. The liquid fuel adheres to the insulator, and the adhering liquid fuel is burned, and carbon is deposited on the center electrode insulator.

When carbon is deposited in this manner, the ignition current leaks from the center electrode through the deposited carbon, resulting in a decrease in ignition energy, and thus there is a problem in that good ignition cannot be obtained.

To solve this problem, a groove is formed on the inner wall of the cylinder head and the spark plug is placed in the groove so that the discharge gap of the spark plug draws in from the inner wall of the cylinder head. Not only is it not possible to ensure good ignition due to insufficient scavenging air, but also it is difficult to sufficiently increase the combustion rate because the flame kernel does not ride on the swirling flow and grow rapidly immediately after ignition.

The object of the present invention is to provide an internal combustion engine that can achieve a sufficiently high combustion rate and ensure stable and good ignition.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 and 2, 1 is a cylinder block, 2 is a piston that can reciprocate within the cylinder block 1 and has a flat top surface 2a, and 3 is a cylinder head fixed on the cylinder block 1. , 4 is piston 2
and a bathtub-shaped combustion chamber formed between the cylinder head 3,
5F'i intake valve, 6 an intake port, 7 an exhaust valve, 8 an exhaust port, and 9I/i a spark plug, respectively.

The cylinder head 3I/i has a substantially flat inclined inner wall surface portion 3a forming the top surface of the combustion chamber 40, and an intake valve 5 and an exhaust valve 7 are arranged on this inclined inner wall surface portion 3a.

On the other hand, a raised portion 10 having a flat bottom surface 3b is formed on the inner wall surface of the cylinder head on the opposite side of the ignition plug 9 with respect to the inclined inner wall surface portion 3a. Moon-shaped flat squish area A
is formed.

Further, the cylinder head inner wall surface portion 3c on which the spark plug 9 is disposed is formed into a substantially flat inclined surface, and a groove 11 is formed on this inclined inner wall surface portion 3c.

As shown in FIG. 2, the groove 11 is located closer to the exhaust valve 7 than to the intake valve 5.

As shown in FIGS. 1 and 3, the electrodes of the ignition plug 9 are attached to a ground electrode 13 mounted on the end face 12, and a center electrode 15 forming a discharge gap 14 between the ground electrode 13 and the ground electrode 13. The center electrode 15 is surrounded by an insulator 16 except for its tip.

It can be seen from FIGS. 1 and 3 that the tip of the insulator 16 protrudes outward from the end surface 12 where the electrode is attached, but is recessed from the cylinder head inclined inner wall surface portion 3c.

It can also be seen that, conversely, the discharge gap 14 protrudes into the combustion chamber 4 from the cylinder head inclined inner wall surface portion 3c.

As shown in Fig. 2, the intake port 6 (/'i combustion chamber 4
Therefore, during the intake stroke, the air-fuel mixture introduced into the combustion chamber 4 from the intake port 6 through the intake valve 5 flows as shown by the arrow in FIG. A swirling flow is generated within the combustion chamber 4.

As shown in FIG. 3, the inner wall surface of the groove 11 in the cross section along the flow direction of this swirling flow is formed from a part of a sphere having a radius r centered on the discharge gap 14.

Further, as shown in FIG. 3, in this embodiment, the electrode is attached so that the distance between the end face 12 and the inclined inner wall surface portion 3c of the cylinder head is 4 mg or more, and the electrode is attached to the end face 12 and the tip face of the insulator 16. The distance d between them is set to 2 nm or more.

As mentioned above, during the intake stroke, a swirling flow K that flows along the cylinder head inclined inner wall surface portion 3c is generated in the combustion chamber 4, but this cylinder head inclined inner wall surface portion 3c extends horizontally in a substantially flat shape. The swirling air-fuel mixture passes over the groove 11 without directly colliding with the center electrode insulator 16.

In this way, the liquid fuel contained in the air-fuel mixture is prevented from directly colliding with the insulator 16 and depositing on the insulator 16.

As a result, the carbon produced by the combustion of this liquid fuel does not accumulate on the insulator 16, so there is no danger that the ignition current will flow from the center electrode 15 through the carbon to a shallow part, and thus the air-fuel mixture Since sufficient ignition energy can be given, stable ignition can be ensured.

On the other hand, during the compression stroke, the air-fuel mixture is pushed into the groove 11 by the compression action of the piston 2, but at this time, the air-fuel mixture contains 1
In some cases, liquid fuel may adhere to the insulator 16.

However, this adhered liquid fuel is a small amount, and this small amount of liquid fuel is burned and the insulator 16
Even if a small amount of carbon is deposited on the electrode, since the insulator 16 and the electrode attachment protrude from the end face 12, the carbon is burned out by the ignition flame, so there is no risk of the ignition current being shallow.

On the other hand, as described above, since the discharge gap 14 of the spark plug 9 protrudes beyond the cylinder head inclined inner wall surface portion 3c, the discharge gap 14 is directly exposed to the swirling flow K during the intake stroke.
The discharge gap 14 is thus well scavenged by the suction mixture.

Then, when ignition occurs at the end of the compression stroke, the discharge gap 14
The flame kernel formed in the combustion chamber 4 rapidly spreads inside the combustion chamber 4 on the swirling flow K, and as a result, the combustion speed can be greatly increased.

Furthermore, as described above, the inner wall surface of the groove 11 is formed from a part of a sphere with a radius r centered on the discharge gap 14, but if this radius r is made too large, the swirling flow K will directly collide with the insulator 16. On the other hand, if this radius r is made too small, the ignition flame will not reach the insulator 161, making it impossible to burn out the carbon deposited on the insulator 16.

Therefore, as shown in FIG. 3, this radius r is equal to the discharge gap 1
It is preferable that the distance from 4 to the peripheral end of the end face 12 be approximately equal to the distance from which the electrode is attached.

As described above, according to the present invention, it is possible to prevent the ignition current from flowing shallowly while ensuring good scavenging of the discharge gap, thereby making it possible to obtain stable ignition. Since it can be grown, the burning rate can be increased.

[Brief explanation of drawings]

1 is a side sectional view of the internal combustion engine according to the present invention taken along the line I-I in FIG. 2, FIG. 2 is a bottom view of the cylinder head taken along the line Figure 3 is the ■− of Figure 1.
■It is a sectional view taken along the line. 2...Piston, 4...Combustion chamber, 5.
...Intake valve, 7...Exhaust valve, 9...
...Spark plug, 11...Concave groove, 12...
Electrode mounting is on the end face, 13... Ground electrode, 15...
...Center electrode, 16...Insulator.

Claims (1)

[Scope of utility model registration request] For an internal combustion engine in which the inner circumferential wall surface of a cylinder head forming a combustion chamber has a flat inner circumferential wall surface portion, and a swirling flow that swirls along the flat inner circumferential wall surface portion is generated in the combustion chamber, the above-mentioned A groove is formed on the flat inner circumferential wall of the cylinder head, and the tip of the center electrode insulator that protrudes from the end face and surrounds the center electrode is retracted from the flat inner wall of the cylinder head to form the groove. A combustion chamber structure for an internal combustion engine, wherein an ignition plug is disposed within the groove so that a discharge gap formed between the center electrode and the ground electrode protrudes beyond the flat inner peripheral wall surface of the cylinder head.