JPS5857078A - Igniter of engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of abnormal combustion while positively burning residual gas near an exhaust valve by providing a plasma sparking plug close to the exhaust valve in an igniter equipped with the plasma sparking plug. CONSTITUTION:A plasma sparking plug 8 is provided at a position close to an exhaust valve V for opening and shutting the exhaust 7 of a cylinder head 4 having an air intake 6 and the exhaust 7. This sparking plug 8 is constituted such that after high voltage is firstly applied between a central electrode 9 and side electrode 10 to break the insulation of a discharging space, plasma gas is injected from a jet 13 into a combustion chamber 5 while applying low voltage between the both electrodes 8, 9. And said sparking plug 8 is connected to a plasma sparking circuit 14 comprising a high voltage generating circuit 15 for supplying spark discharge energy to the plasma sparking plug 8 and a low voltage generating circuit 19 for supplying plasma spark energy to the sparking plug 8.

Description

[Detailed description of the invention] The present invention relates to an ignition device for an engine.

Conventionally, the spark plug of an engine has been placed close to an intake port into which fresh air flows in order to improve the ignitability of the air-fuel mixture. On the other hand, residual gas with poor combustibility inevitably remains near the exhaust port, and carbon, etc. adhering to the combustion chamber in this area becomes an ignition point, causing the residual casing to self-ignite, resulting in abnormal combustion such as knocking. There is.

In order to solve the above-mentioned problem, it may be possible to provide a spark plug near the exhaust port, but an ordinary spark plug has poor ignition performance and could not be put to practical use.

As a result of studies on the above points, the present inventors found that plasma ignition plugs that have been proposed in recent years (Japanese Unexamined Patent Publication No. 55-9658) have a much better combustion rate than conventional ignition plugs, and therefore It has been found that normal ignitability can be obtained even if the device is placed near the mouth.

The present invention was made based on the above-mentioned knowledge, and a plasma ignition plug is provided in a position close to the exhaust pulp to actively burn the residual gas near the exhaust pulp, thereby preventing the occurrence of abnormal combustion due to the residual gas. The purpose of the present invention is to provide an engine ignition device that prevents ignition.

Next, the present invention will be explained with reference to drawings which are embodiments.

1 and 2 show a first embodiment of the present invention, in which 1 is a cylinder of a reciprocating engine in which a piston 2 is reciprocated within a cylinder 3 to obtain rotational output, and -4 is a combustion chamber 5.
The cylinder head defines the upper part of the cylinder head. Reference numerals 6 and 7 are an intake port and an exhaust port provided in the cylinder head 4, and both of them are filled with conventionally known intake pulp (not shown) and exhaust pulp V. As is clear from FIG. 2, 8 is a plasma ignition plug attached to the cylinder head 4 at a position close to the exhaust pulp V with its tip facing the combustion chamber 5. This plasma ignition plug 8 is well known, and includes a center electrode 9 and side electrodes 10 having threads cut on the outer periphery, which are partitioned by an electrically insulating material 11 such as ceramic to form a discharge space 12 inside. After first applying a high voltage between electrodes 9 and 10 to cause dielectric breakdown of the discharge space 12, a low voltage is applied between both electrodes 9 and 10 to inject plasma gas from the nozzle hole 13 into the combustion chamber 5. It has become.

Reference numeral 14 denotes a plasma ignition circuit, which includes a high voltage generation circuit 15 that supplies spark discharge energy to the plasma ignition plug 8, and a low voltage generation circuit 19 that supplies plasma spark energy to the plasma ignition plug 8. As in the conventional spark ignition device, the high voltage generating circuit 15 is connected to a power supply, which is a power source, to a secondary coil 16 consisting of a key switch SW connected in series to an IJE, a secondary coil 16a, and a secondary coil 16b. One end of the coil 16b is connected to the plasma ignition plug 8 of each cylinder by a distributor 18 via a diode D1, and the low voltage generating circuit 19 is connected to the power source E.
Or a DC/DC converter 20 that is connected to a separate independent power supply and boosts the power supply voltage to about 3KV.
, a resistor connected in parallel thereto, and a capacitor C, and are connected to each plasma ignition plug 8 via diodes D2 to D5.

Therefore, first, a high voltage of about 50 KV is applied from the high voltage generating circuit 15 via the distributor 18 between the center electrode 9 and the side electrodes 10 of the plasma ignition plug 8 to generate a spark, and then both @ The low voltage from the low voltage generating circuit 19 applied between the caps 9 and 10 causes the discharge space 12 dielectrically broken by the spark to maintain an absent center state, thereby increasing the high temperature and high pressure generated within the discharge space 12. Plasma gas is ejected from the nozzle hole 13 into the combustion chamber 5. As mentioned above, this plasma-like gas is at high temperature and pressure, so it burns not only the residual gas remaining near the exhaust valve V but also other air-fuel mixtures, allowing the residual gas to self-ignite and completely eliminating abnormal combustion. can be prevented.

3 and 4 show a second embodiment of the present invention, in which the air-fuel mixture taken into the combustion chamber 5 from the intake port 6 is swirled in the circumferential direction of the combustion chamber 5 to improve combustibility. The present invention is applied to an improved combustion chamber structure.

That is, a guide wall 21 is provided protruding into the combustion chamber 5 from the vicinity of the intake port 6 on the wall surface of the cylinder head 4.
First, an annular intake valve seat (not shown) fitted in the intake port 6 is formed to protrude into the combustion chamber 5 along a part of the outer periphery;
In addition, during the intake stroke, the first guide surface 22a is formed so that the intake air from the intake port 6 rotates in the circumferential direction of the combustion chamber 5 (in the direction of the arrow X in FIG. 3), and the exhaust lower is bottomed. a second guide surface 22b facing an annular exhaust valve seat (not shown) and protruding into the combustion chamber 5 to swirl the air-fuel mixture in the circumferential direction of the combustion chamber 5 during the compression stroke; Guide surface 22a
and a third guide surface 22C connected to the second guide surface 22b.
and has. A plasma ignition plug 8 similar to that in the first embodiment is attached to the second guide surface 22b, particularly to the edge portion 22d facing the exhaust lower in the vicinity of the exhaust lower. Residual gas may accumulate in the vicinity where the plasma ignition plug 8 is provided, and the edge portion 22d may have an ignition point different from that of the ignition plug, causing abnormal combustion as described above. A plasma ignition plug 8 is installed in the engine to burn residual gas during normal ignition to prevent abnormal combustion throughout the year.

As is clear from the above explanation, according to the present invention, a plasma ignition plug with a good combustion speed is provided in a position close to the exhaust pulp where residual gas that causes abnormal combustion in the engine is most likely to accumulate. It is possible to completely prevent abnormal combustion such as knocking due to self-ignition of NFF storage gas.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the engine ignition system according to the present invention, FIG. 1 is a sectional view of the combustion chamber and a plasma ignition circuit diagram, and FIG. 2 is a view from inside the combustion chamber. 3 and 4 show the second embodiment, FIG. 3 is a front view of the cylinder wall seen from inside the combustion chamber, and FIG. 4 is a front view of the cylinder wall as seen from the combustion chamber. FIG. 1...Cylinder, 6...Intake port, 7...Exhaust port, 8...
...Plasma ignition device.

Claims (1)

[Claims] (1) A plasma ignition plug having a discharge space formed by surrounding the ignition gap between the positive and negative electrodes with an electrical insulating material;
An engine ignition device comprising a plasma ignition circuit that supplies plasma energy to the plasma ignition plug and performs plasma ignition by spouting plasma-like gas generated in a discharge space into a combustion chamber, wherein the plasma ignition plug An ignition device for an engine, characterized in that it is provided in a position close to an exhaust pulp.