JPH0774631B2 - Ignition device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention is an ignition device capable of preventing smoldering and fouling caused by adhesion of a conductive substance such as creeping discharge type plug carbon used in an internal combustion engine and improving ignitability. Regarding

[Conventional technology]

In high-power engines such as outboard motors and racing engines, in order to prevent engine damage and porcelain cracking of the insulator caused by preignition of the spark plug, the insulator is not provided with the leg part of the ignition part and the center electrode is used. A full creeping discharge type plug is used in which an annular creeping discharge gap is formed along the end face of the insulator between the metal shell forming the ground electrode and the tip inner wall. As described above, since the insulator does not have the ignition leg, carbon is liable to smolder and stain, and the contact with the mixed gas is poor, resulting in poor ignition performance.

Therefore, in order to improve the stain resistance and ignitability of the above-mentioned full creeping discharge type plug, the present inventors have shown that the end face 2e of the ignition portion of the insulator 2 has a hemispherical shape or a mortar shape as shown in FIGS. A recess 2f is provided, and a tip 3a of the center electrode 3 having a small diameter is disposed at the bottom 2h of the recess, and between the center electrode tip 3a, the recess 2f and the inner wall 1d of the metal shell tip. Although the creeping discharge type plug having the creeping discharge gap 4 or the gap 4 and the air gap 5 has been already proposed, it was necessary to take measures against the following problems.

[Problems to be solved by the invention]

That is, even in the above-mentioned creeping discharge type plug, depending on the engine, it is necessary to further improve the ignitability as well as the carbon adhering to the end surface and the recessed portion of the insulator to cause smoldering and stains. It is an object of the present invention to provide an ignition device having further improved stain resistance and ignition resistance.

[Means for solving problems]

The features of the present invention include a metal shell provided with an engine mounting screw, an insulator housed and fixed so as to abut against a tip step surface of an inner cavity of the metal shell, and a hemispherical or mortar-shaped insulator on the end face of the ignition part of the insulator. An annular flat surface that is horizontal in the axial direction is provided on the dent and the outer circumference of the dent, and the tip of the center electrode having a diameter of 0.2 to 1.8 mm is arranged at the bottom of the dent, and the center electrode tip is provided. A creeping discharge plug formed by forming a creeping discharge gap between the recess and the flat surface and the inner wall of the tip of the metal shell, and a voltage rising time in the discharge waveform of the creeping discharge plug is 10 μs or less and Discharge duration is 1m
It is combined with an ignition power source of s or more.

[Action]

According to the present invention, as in the case of the above-mentioned structure, the spark discharge glides on the recess of the insulator and the flat surface of the end face of the ignition portion by using the creeping discharge type plug and the ignition power source having the voltage rise time of the discharge waveform of 10 μs or less. It is possible to reliably remove carbon etc. that have adhered due to the fact that the discharge duration is set to 1 ms or longer, and the formation of the flat surface causes sparks to jump away from the surface of the insulator, causing air discharge. Occurs, the cooling effect of the spark is reduced, and the mixture is easily touched, so that the ignitability of the plug can be further improved.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of a creeping discharge type plug used in the present invention, 10 is a creeping discharge type plug of the present invention, and a metal shell having an engine mounting screw at the tip thereof The step portion 2a of the ceramic insulator 2 made of high alumina or the like is housed by abutting on the tip step bearing surface 1b of the inner cavity 1a of 1 and the upper end peripheral edge 1c of the metal shell 1 is crimped by a known crimping method. It is fixed. This insulator 2 has a small diameter hole 2b through which the small diameter tip portion 3a of the center electrode 3 is inserted, an intermediate hole 2c and a large diameter hole 2d for sealing material sealing, and the ignition portion of the small diameter hole 2b. End face
A mortar-shaped or hemispherical recess 2f is formed in the central portion of 2e so as to widen the tip, and an annular flat surface 2g that is horizontal in the axial direction is provided on the outer periphery of the recess 2f. The bottom of this recess
The center electrode tip portion 3a is arranged in 2h so as to be the same as or slightly protrudes from the bottom surface. The tip peripheral edge 3b of the center electrode tip portion 3a and the tip inner wall 1d forming the ground electrode of the metal shell 1d. And a creeping discharge gap 4 passing through the recess 2f and the flat surface 2g therebetween is formed. Further, 6 is a conductive glass sealing material, and 7 is a resistor. The center electrode is inserted into the shaft hole of the insulator 2, and the resistor 7 is sandwiched by the conductive glass sealing material 6 to be integrated with the terminal electrode 8. It is sealed to. The diameter A of the center electrode tip 3a is 0.2 to 1.8 mm.
φ is preferable from the viewpoint of stain resistance, and if it is 0.2 mmφ or less, it is disadvantageous in terms of wear resistance, and if it exceeds 1.8 mmφ, stain resistance deteriorates. The depth B of the recess is preferably 0.5 mm or more, the diameter C of the opening of the recess is preferably 1.5 A (0.3 mmφ) or more, and the depth B is 0.4.
If it is less than mm, the ignitability is poor and the diameter C of the opening is 0.
If the thickness is 3 mm or less, the ignitability also deteriorates. Further, it is preferable that the dimension D of the flat surface is 0.3 mm or more because sparks jump from the surface of the insulator to improve ignitability.

Another embodiment of the creeping discharge type plug used in the present invention may have the structure shown in FIG. That is, the difference from this embodiment of this plug is that the metal shell 1
An annular protrusion 1e that protrudes from the tip surface is provided at the tip forming the ground electrode, and an air gap 5 is formed between the protrusion 1e and the flat surface 2g of the end face of the insulator ignition part. Yes, sparks are dented 2f from the tip peripheral edge 3b of the center electrode tip 3a.
This is a creeping discharge type plug that discharges to the inner wall 1f of the metallic shell protruding portion 1e through the creeping discharge gap 4 and the air gap 5. The dimension F of the air gap 5 is preferably 0.2 to 1.2 mm, and if it is 0.2 mm or less, the effect of improving the ignitability cannot be obtained.
If it is 1.2 mm or more, the discharge voltage increases, which is not preferable.

Next, such a creeping discharge type plug 10 is used in the ignition device shown in FIG. In the figure, 11 is an ignition power supply having a discharge duration of 1 ms or more.A full-thruster unit 12 is used, and although the full-thruster unit is not shown, a pulse generator that determines the ignition timing, amplifies the pulse and turns on the power transistor. It is composed of an amplifier circuit and a switching circuit for OFF control, and the output of this full-transmission unit is connected in series to the primary side coil of the ignition coil 13 and the secondary side high voltage is passed through the high voltage diode 14 to the creeping discharge. Connected to the mold plug 10. 15 is a CDI ignition power source whose discharge waveform voltage rise time is 10 μs or less.
Ignition coil 18 via converter 16 and CDI unit 17
High-voltage diode 19 connected to the secondary side high voltage
Is similarly connected to the creeping discharge type plug 10 via
The CDI ignition power source 15 forms a parallel circuit with the ignition power source 11 and superimposes a secondary output on the plug 10. 20 is a battery electrode.

In the ignition device of the present invention, the diameter of the tip of the center electrode is set to a small diameter (0.2 to 1.8 mmφ), which is arranged at the bottom of the recess of the end face of the insulator ignition part, and is particularly horizontal to the outer periphery of the recess in the axial direction. By forming an annular flat surface, it has the effect of improving stain resistance and ignitability, but when these become a problem depending on the engine, the voltage rise of the discharge waveform used as the ignition power source in the creeping discharge type plug is further increased. The spark resistance of the capacity component of the CDI ignition power source whose time is 10 μs or less can further improve the stain resistance, and following this spark discharge, when the engine speed is 2000 rpm or less, the induction component with a discharge duration of 1 ms or more is superimposed. Moreover, spark jumping on the flat surface causes air discharge, which reduces the cooling effect of the spark, makes it easier to touch the air-fuel mixture, and is expected to have a synergistic effect of further improving ignitability.

The ignition power source is not limited to the non-contact type of the above-mentioned embodiment, but a contact switching type ignition power source and a CDI power source may be combined, in short, the voltage rising time and the discharge duration time satisfy the above numerical values. If

〔The invention's effect〕

The ignition device of the present invention having the above-described structure has a center electrode tip diameter of 0.2 to 1.8 mm in such a creeping discharge plug in an engine in which a problem arises in stain resistance and ignitability in such a creeping discharge plug. At the same time, an annular flat surface that is horizontal in the axial direction is provided on the outer circumference of the dent, and sparks are jumped between the dent and the flat surface to cause air discharge. Furthermore, the voltage rise time is 10 μs or less and the discharge duration is By combining with an ignition power source having 1 ms or more, a more remarkable synergistic effect can be obtained with respect to improvement of stain resistance and ignitability. Further, since the spark jumps due to the formation of the flat surface, it has an effect of reducing electric breakdown (channeling phenomenon) of the insulator surface due to the spark. For the reason, the combination of the conventional full creepage discharge type plug and the ignition power source of the present invention is effective in the stain resistance and the ignitability, but the engine continues to malfunction in the idle continuous operation at the rich air-fuel ratio of -10 ° C. It has been confirmed that the ignition resistance of the ignition device of the present invention is completely inferior in the stain resistance test in time and the ignition test in the start test of -20 ° C.

[Brief description of drawings]

FIGS. 1 and 2 show one embodiment of a creeping discharge type plug used in the present invention. FIG. 1 is a sectional view of the main part of the plug, and FIG. 2 is a diagram showing the ignition part of FIG. Sectional drawing, FIG. 3 is a sectional view of an ignition part of a creeping discharge type plug showing another embodiment used in the present invention, and FIG. 4 is a circuit diagram showing an ignition device of the present invention. 1 ... Metal shell, 1a ... Lumen, 1b ... Tip step seat surface, 1d ...
… Tip inner wall, 2… Insulator, 2e …… Firing part end face, 2f…
Recess, 2g ... flat surface, 2h ... bottom, 3 ... center electrode, 3a
…… Tip part, 4 …… Creeping discharge gap, 5 …… Air gap, 10
…… Creepage discharge type plug, 11 …… Ignition power supply, 15 …… CDI ignition power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Sugimoto 14-18 Takatsuji-cho, Mizuho-ku, Nagoya, Aichi Nihon Special Ceramics Co., Ltd. (56) Reference JP-A-63-500970 (JP, A)

Claims (1)

[Claims] 1. A metal shell equipped with an engine mounting screw, an insulator housed and fixed so as to abut on a tip step seat surface of an inner cavity of the metal shell, and a hemisphere or a mortar on the end face of the ignition part of the insulator. A concave shape and an annular flat surface that is horizontal in the axial direction are provided on the outer circumference of the concave shape, and the tip portion of the center electrode having a diameter of 0.2 to 1.8 mm is arranged at the bottom of the concave portion, and the center electrode tip is formed. A creeping discharge type plug formed by forming a creeping discharge gap between the concave portion and the flat surface and the inner wall of the end of the metal shell, and a voltage rising time of 10 μs or less in the discharge waveform in the creeping discharge type plug. And the duration of discharge is 1ms
An ignition device characterized by being combined with the above ignition power source.