JPS648170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark ignition internal combustion engine that promotes turbulence in a compressed air-fuel mixture near the ignition part of a spark plug to stabilize combustion.

Conventionally, there are systems that utilize squish (compression vortex) to enhance turbulence in compressed air-fuel mixtures and improve combustion. However, the ignition part of the spark plug is located deep in the combustion chamber formed by a recess formed in the cylinder head, while the squish region is formed by the top surface of the piston and the bottom surface of the cylinder head. Therefore, the squish flow (mixture air flow) pushed out from the squish area near the top dead center of the piston flows along the top surface of the piston, and this squish flow does not flow directly to the ignition section. Therefore, in the conventional system, the turbulence of the entire compressed air-fuel mixture increases on average due to squishing, but the turbulence near the ignition part becomes unstable.
The flow velocity near this ignition part was likely to fluctuate from cycle to cycle. Irregular combustion, which is generally a particular problem in 4-cycle engines, is different from the irregular combustion peculiar to 2-stroke engines, and is affected by cycle-by-cycle fluctuations in flame propagation speed, and especially by fluctuations in flame propagation speed immediately after ignition. It is considered a thing. Therefore, if the turbulence of the air-fuel mixture near the ignition part changes from cycle to cycle, the flame propagation speed immediately after ignition will also vary greatly, making irregular combustion more likely to occur. This tendency becomes particularly noticeable when using a lean mixture where the flame propagation speed becomes low, making it difficult to improve fuel efficiency.

Therefore, by forming a small hole in the cylinder head that directly guides the air-fuel mixture compressed in the squish region to the ignition part, the flame propagation speed immediately after ignition is increased and fluctuations in the flame propagation speed from cycle to cycle are suppressed. was proposed by the same applicant (for example, see Utility Model Application No. 138300/1983). However, in this case, not only is the process of forming a small hole in the cylinder head complicated, but also there is a problem in that incomplete combustion products such as carbon are likely to accumulate in the small hole.

This invention was developed in view of the above circumstances, and it guides the squish flow to the ignition part of the ignition plug and suppresses cycle-by-cycle fluctuations in turbulence in the vicinity of the ignition part immediately after ignition, thereby stabilizing combustion and achieving lean mixing. To provide a spark ignition internal combustion engine that can be operated with air, is easy to manufacture, and is less likely to accumulate incomplete combustion products.

In order to achieve such an object, the present invention has a squish area formed between the top surface of the piston and the bottom surface of the cylinder head, and an ignition plug disposed at a position biased toward the squish area of the cylinder head. and a convex portion provided on the top surface of the piston so as to be located below the firing portion,
The squishing flow pushed out from the squishing region near the top dead center of the piston is guided to the firing portion by the flow guide surface formed by the convex portion. The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a side sectional view showing an embodiment of the present invention;
FIG. 2 is a plan view of the top surface of the piston, and in this FIG. 2, members on the cylinder head side are shown by imaginary lines. In these figures, numeral 10 is a cylinder body, 12 is a piston that slides vertically within the cylinder body 10, and 14 is a cylinder head. A recess 16 facing the piston 12 is formed in the cylinder head 14, and a substantially wedge-shaped combustion chamber 18 is formed by the recess 16. As shown in FIG. 2, the opening of the recessed hole 16 is formed into a substantially circular shape, and the length of this circular shape in the long axis direction is equal to that of the piston 1.
The diameter is approximately the same as that of 2. Therefore, between the top surface 20 of the piston and the bottom surface 22 of the cylinder head, two skid areas 2 are provided so as to sandwich the recess 16.
4 and 26 are formed. An intake valve 28 and an exhaust valve 30 are provided on the upper wall surface of the recess 16, and communicate with an intake passage 32 and an exhaust passage (not shown), respectively. These intake valves 28 and exhaust valves 30 are opened and closed at predetermined timings by a known valve operating mechanism.

34 is an ignition plug, and its ignition part 36 is arranged so as to be directed between the intake valve 28 and the exhaust valve 30 from the deeper side wall of the recess 16, that is, the side wall on the squish area 24 side. There is. Therefore, the firing section 36 is disposed at a position biased toward one squish region 24 side.

A convex portion 38 located below the firing portion 36 is formed on the top surface 20 of the piston. As shown in FIG.
The side slope 40 serves as a flow guide surface. That is, the flow guide surface 40 deflects the squish flow pushed out from the squish area 24 obliquely upward near the top dead center of the piston 12 and guides it toward the ignition section 36 .

Next, the operation of this embodiment will be explained. The air-fuel mixture sucked in during the suction process is compressed as the piston 12 rises during the compression process, and electrical ignition occurs in the ignition section 36 at a predetermined crank angle before the top dead center of the piston 12. A flame kernel is formed between the electrodes of the ignition section 36 by this electric spark. As the piston 12 approaches the top dead center, the squeezing area 24,2
The air-fuel mixture of No. 6 is pushed out into the recess 16, and the flow of this pushed-out air-fuel mixture, that is, the squishy flow, generates strong turbulence within the combustion chamber 18. At this time, the squishing flow pushed out from the squishing region 24 on the spark plug 34 side is guided by the flow guide surface 40 of the convex portion 38 and flows to the ignition portion 36 . Since the squishing flow from the squishing region 24 is forcibly guided to the ignition section 36 in this way, there is little variation in the air-fuel mixture flow rate from cycle to cycle in the vicinity of the ignition section 36. This squish flow causes the flame already formed in the ignition part 36 to grow and spread into the combustion chamber 18. This flame propagates at high speed due to the strong turbulence of the air-fuel mixture within the combustion chamber 18, and completes combustion. Since the convex portion 38 of the piston top surface 20 is violently hit by high-speed, high-temperature combustion gas, incomplete combustion products such as carbon are not deposited. Note that since the convex portion 38 is formed integrally with the piston 12, it is easy to manufacture.

As described above, in this invention, the ignition part of the ignition plug is disposed at a position biased toward the squeezing area, a convex part is provided on the top surface of the piston so as to be located below the ignition part, and a convex part is formed by the convex part. By the flow guiding surface,
Since the structure is configured so that the squish flow pushed out from the squish region near the piston top dead center is guided to the ignition section, the turbulence of the air-fuel mixture near the ignition section, that is, the flow velocity, hardly changes from cycle to cycle at the crank angle immediately after the ignition timing. I won't. Therefore, the flame propagation speed immediately after ignition near the ignition part becomes less likely to fluctuate from cycle to cycle, making it possible to stabilize combustion and prevent irregular combustion. Furthermore, when the air-fuel mixture is diluted, the flame propagation speed decreases and combustion becomes unstable, but according to the present invention, asymmetric combustion is less likely to occur, making it possible to dilute the air-fuel mixture, thereby improving fuel efficiency. I can do it. Furthermore, since the convex portion forming the flow guiding surface is formed on the top surface of the piston, machining is facilitated, and incomplete combustion products are not deposited.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention;
FIG. 2 is a plan view of the piston. 14... Cylinder head, 20... Piston top surface, 22... Cylinder head bottom surface, 24... Squeeze area, 34... Spark plug, 36... Firing part,
38...Convex portion, 40...Driving surface.

Claims (1)

[Claims] 1. A squish area formed between the top surface of the piston and the bottom surface of the cylinder head, a firing part of the spark plug disposed at a position offset toward the squeeze area of the cylinder head, and a squish area located below the firing part. a convex portion provided on the top surface of the piston, and a flow guide surface formed by the convex portion guides the squish flow pushed out from the squish area near the top dead center of the piston to the firing portion. Features a spark ignition internal combustion engine.