JPH0689773A - Ignition device with series gap - Google Patents

Abstract

PURPOSE:To provide an ignition device equipped with a series gap, which is free from influence of corona degradation of the casing outer surface even during long time service and which does not cause reduction of the effect against smoking in ignition. CONSTITUTION:A discharge tube 10 to form a series gap is arranged inside a cylindrical casing 5 made of an insulative rigid member. High voltage from a high tension cable 3 is supplied to an ignition plug through this discharge tube. A groove is furnished over the circumference on that outside surface of the casing where the discharge tube 10 is positioned, having a specified width and a depth approx. half the thickness of the casing 5, and silicon rubber 16 is fitted in this groove.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device with a series gap used for an ignition device of an automobile engine or the like.

[0002]

2. Description of the Related Art An ignition device in an automobile engine or the like is designed to apply a high voltage to a spark plug to generate a spark, but in order to prevent misfire due to smoldering of the spark plug, it is connected in series with the spark plug. A so-called series gap ignition device having a discharge gap has been proposed.

For example, an ignition device with a series gap shown in Japanese Patent Application No. 2-325388 has a cylindrical casing 5 made of unsaturated polyester resin, PBT or the like, as shown in FIG. A connection terminal 2 for a spark plug is provided inside the tip of the casing 5, and a female terminal 2'for fitting a discharge electrode terminal 7'of a discharge tube 10 to the rear end portion of the connection terminal 2. It is arranged. Further, a resistor 12 is connected to the other discharge electrode terminal 8'of the discharge tube 10 via a female intermediate connection terminal 11 on both ends, and a high voltage cable 3 is connected to the rear end of the resistor 12.
The cable terminal 4 coupled to the end portion of is fitted and connected.

Further, the connection terminal 2, the discharge tube 10, the intermediate connection terminal 11, the resistor 12 and the like are covered with a coating layer 13 molded with an adhesive silicon rubber,
The conductive parts are insulated. A positioning clamp 14 is attached to keep the terminal 4 of the high-voltage cable 3 in the axial position of the casing 5, and an air gap 15 is formed between the outer surface side of the covering layer 13 and the inner surface side of the casing 5. .

This ignition device with a series gap not only prevents the occurrence of smoldering during ignition as described above, but also covers the discharge tube 10 and the like with a coating layer 13, so that a creeping discharge around the discharge tube 10 occurs. Since it does not occur, and the deterioration of the function due to repeated thermal shock and external force does not easily occur, it has high reliability.

[0006]

However, even in the above-mentioned ignition device with a series gap, the use of the ignition device with a series gap for a long period of time causes deterioration of insulation resistance and deterioration of surface water repellency due to corona deterioration due to corona discharge on the casing outer surface. Then, the capacitance between the cathode and the anode of the discharge tube increases from the initial set value, the plug potential rises, and the effect of ignition on smoldering may be reduced.

An object of the present invention is to provide an ignition device with a series gap in which the influence of corona deterioration on the outer surface of the casing does not appear even after long-term use and the effect on ignition smolder is not reduced.

[0008]

According to the present invention, a discharge tube forming a series gap is arranged inside a cylindrical casing made of an insulating rigid member, and a high voltage from a high voltage cable is ignited through the discharge tube. In the ignition device with a series gap for supplying to the plug, a groove is provided over the outer surface portion of the casing within a width where both electrodes of the discharge tube are located, and silicon rubber is fitted into the entire groove. Is characterized by.

The ignition device with a series gap according to the present invention is characterized in that the width of the groove is at least 0.5 mm or more.

Further, according to the present invention, a discharge tube forming a series gap is arranged inside a cylindrical casing made of an insulating rigid member, and a high voltage from a high voltage cable is supplied to the spark plug through the discharge tube. In the ignition device with a series gap, from one end of the casing to a position beyond the position of the electrode near the one end of the discharge tube,
The outer surface of the casing is covered with silicone rubber.

Furthermore, the ignition device with a series gap according to the present invention is characterized in that the portion beyond the position of the electrode is at least 1 mm or more.

[0012]

When the ignition device with a series gap having the above structure is used for many years, the outer surface of the casing around both electrodes of the discharge tube is corona-degraded by corona discharge, and the insulation resistance of the surface is lowered. However, since a groove is provided around the outer surface portion of the casing within the width in which both electrodes of the discharge tube are located, and a silicone rubber that does not deteriorate the insulation performance for a long period of time is fitted in the entire groove, the casing Even if the insulation resistance of the outer surface decreases, the electrostatic capacitance between the electrodes of the discharge tube through the outer surface of the casing does not change from the initial state because the silicone rubber enters in series, and the capacitance between the electrodes of the discharge tube as a whole is the same. The capacitance does not increase. Therefore, the ignition device with a series gap according to the present invention does not cause smoldering of ignition even after long-term use.

The outer surface of the casing covered with silicone rubber from one end of the casing to a position beyond the position of the electrode near the one end of the discharge tube is a casing around both electrodes of the discharge tube. Corona discharge is unlikely to occur on the outer surface, and the water repellency of the silicone rubber hinders the adhesion of water and makes it difficult to form an electrical conduction path. Do not let

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those described in the related art will be designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows a first embodiment of the present invention. As shown in the figure, the ignition device 1 with a series gap according to the present embodiment is substantially the same as the ignition device with a series gap shown in the prior art, except that the discharge tube 10 is located. The outer peripheral surface of the casing 5 is provided with a groove having a predetermined width and a depth of about half the thickness of the casing 5, and the silicone rubber 16 is fitted into the groove.

The capacitance C ₁ between the electrodes (between the positive and negative electrodes) of the discharge tube 10 in the new state of the conventional series gap ignition device shown in FIG. 11 is as shown in FIG. The total of the electrostatic capacitance C _H and the electrostatic capacitance C _{A that} wraps around between the discharges 10, that is, C ₁ = C _H + C _A.

Next, by using this ignition device with a series gap for a long period of time, a conductive portion due to corona deterioration is formed on the outer surface of the casing 5 where the discharge tube 10 is located to form an electric conduction path, or the surface is roughened. When the water repellency disappears, the capacitance C ₂ between the electrodes is the sum of the capacitance C _H of the discharge tube 10 and the capacitance C _A of the wraparound outside the discharge 10 as shown in FIG. In addition, two capacitances Cα between both electrodes and the conductive portion are added in series via the conductive portion to add a capacitance Cα / 2. That is, C ₂ = C _H + C _A + C α / 2 ..., And the capacitance increases.

Therefore, the silicone rubber 1 is not deteriorated for a long period of time.
By 6, the electrostatic capacitance C ₃ between the two electrodes in the case of blocking the conductive sites generated in the casing 5 the outer surface, as shown in FIG. _{8, C 3 = C H +} C A + 1 / (2 / Cα + 1 / Cβ ) ...
・, Note that Cβ represents the capacitance of the conductive portion on the outer surface of the casing 5 which is blocked by the silicone rubber 16.

By comparing the equations, Cα / 2> 1 / (2
/ Cα + 1 / Cβ) always holds, so
It can be seen that the capacitance increases less than the formula capacitance.
Light Further, for example, when Cβ → 0, 1 / (2 / Cα +
1 / Cβ) → 0 and discharge tube 10 after long-term use
On the outer surface of the casing 5 where
Even if a conductive part is formed, the electrostatic discharge between the electrodes of the discharge tube 10
Capacity is initial C₁= C _H+ C_AWill be maintained,
The smaller Cβ is, that is, it is blocked by the silicone rubber 16.
It was found that the longer the non-conductive part formed by
It

FIG. 9 shows the relationship between the length of the non-conductive portion and the capacitance between both electrodes of the discharge tube 10 and the plug potential. As shown in the figure, when the length of the non-conductive portion is increased, the capacitance is rapidly reduced at the first stage, and after a certain length or more, the rate of change becomes small and the state becomes saturated. This is also clear from the above equation. Similar results are obtained for the plug potential, and the branch point of the abrupt change is at the length of the non-conductive portion of about 0.5 mm.

The relationship between the plug potential and the abnormal spark occurrence probability is that, as the plug potential is increased, the abnormal spark occurrence probability is zero up to a certain potential, but as the plug potential is increased above the potential, abnormalities occur. The probability of sparks increases, and idling and drivability deteriorate. It has been experimentally found that the maximum potential at which the probability of abnormal spark occurrence is zero is about 1.3 kV. Therefore, it is necessary to set the plug potential to 1.3 kV or less, and when this is applied to the graph of FIG. 9, it corresponds to a branch point of a sudden change. Therefore, the length of the non-conducting portion on the outer surface of the casing 5 needs to be 0.5 mm or more.

Next, second to fifth embodiments of the present invention will be described. The same parts as those described in the section of the prior art or the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

A second embodiment is shown in FIG.
As shown in the drawing, a groove having a substantially semicircular cross section is provided on the outer surface of the casing 5 within the width where both electrodes (the positive and negative electrodes) of the discharge tube 10 are located, and the groove is made of silicon rubber. The ring 17 is fitted. As a result, similar to the case of the first embodiment, the effect of blocking the conductive part formed by corona inferiority can be obtained, and the workability can be improved.

A third embodiment is shown in FIG.
The outer surface of the casing 5 where both electrodes (the positive and negative electrodes) of the discharge tube 10 are located is provided with a groove having a substantially semicircular cross section, and an O-ring 17 made of silicon rubber is fitted into the groove. The same effect as the second embodiment can be obtained.

FIG. 4 shows a fourth embodiment.
As shown in the figure, the outer surface of the casing 5 is covered with a lower cap 18 made of silicon rubber by 5 mm or more above the lower electrode position of the discharge tube 10. As a result, the corona deterioration of the surface of the casing 5 can be prevented, and the water repellency can be maintained, so that the formation of the electric conduction path due to the adhesion of moisture can be prevented and the workability can be improved.

FIG. 5 shows a fifth embodiment.
As shown in the figure, the outer surface of the casing 5 is covered with an upper cap 19 made of silicone rubber by 5 mm or more below the upper electrode position of the discharge tube 10. As a result, corona deterioration of the surface of the casing 5 can be prevented, water repellency can be maintained, and workability can be improved.

FIG. 10 shows the relationship between the position where the lower cap 18 and the upper cap 19 shown in FIGS. 4 and 5 cover the surface of the casing 5 and the plug potential, which is apparent from the drawings. In either case, the plug potential is 1.
In order to store the voltage within 3 kV, it is necessary to cover the lower cap 18 and the upper cap 19 by 1 mm or more from the electrode position of the discharge tube 10.

[0028]

As described above, according to the present invention,
Silicon rubber blocks the electrical conduction path of the conductive part caused by corona deterioration on the outer surface of the casing, so the electrostatic capacitance between both electrodes of the discharge tube does not increase, and even when the spark plug is ignited even after long-term use. No smoldering occurs. Further, in the case where a predetermined position on the outer surface of the casing is covered with a lower cap or an upper cap made of silicon rubber, water adhesion can be prevented by the water repellency of the silicon rubber, and an electric conduction path can be prevented from being formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

FIG. 6 is a diagram for explaining the capacitance between both electrodes of the discharge tube in a new state.

FIG. 7 is a diagram illustrating the electrostatic capacitance between both electrodes of the discharge tube during long-term use.

FIG. 8 is a diagram for explaining the electrostatic capacitance between both electrodes of the discharge tube in the present embodiment.

FIG. 9 is a diagram for explaining the relationship between the length of the formed non-conductive portion and the capacitance between both electrodes of the discharge tube.

FIG. 10 is a diagram showing the relationship between the tip position of the upper cap or the lower cap covering the outer surface of the casing and the plug potential.

FIG. 11 is a cross-sectional view of a conventional ignition device with a series gap.

[Explanation of symbols]

 1 Series Ignition device with a gap 3 High-voltage cable 5 Casing 10 Discharge tube 16 Silicon rubber 17 O-ring (silicon rubber) 18 Lower cap (silicon rubber) 19 Upper cap (silicon rubber)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yoji Suzuki, 252, Kawashimada, Gotemba, Shizuoka Prefecture, Yazaki Parts Co., Ltd. 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (4)

[Claims] 1. An ignition with a series gap, wherein a discharge tube forming a series gap is arranged inside a cylindrical casing made of an insulating rigid member, and a high voltage from a high-voltage cable is supplied to the ignition plug through the discharge tube. In the device, a series gap ignition is provided in which a groove is provided around the outer surface portion of the casing within a width where both electrodes of the discharge tube are located, and silicon rubber is fitted into the entire groove. apparatus. 2. The ignition device with a series gap according to claim 1, wherein the width of the groove is at least 0.5 mm or more. 3. A spark having a series gap, in which a discharge tube forming a series gap is arranged inside a cylindrical casing made of an insulating rigid member, and a high voltage from a high voltage cable is supplied to the spark plug through the discharge tube. In the device, an ignition device with a series gap, characterized in that an outer surface of the casing is covered with silicone rubber from one end of the casing to a position beyond a position of an electrode near the one end of the discharge tube. 4. The ignition device with a series gap according to claim 3, wherein the portion beyond the position of the electrode is at least 1 mm or more.