JP2015069924A - Ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine capable of lowering a charge potential of a dielectric body surface at a power supply side of an ignition plug, of suppressing generation of streamer discharge at the outside of a combustion chamber, and of achieving excellent durability and stable ignition.SOLUTION: An ignition plug 100 includes at least a shaft-like center electrode 10, a dielectric body 20, a housing 3, and a ground electrode 30, and comprises a discharge space 40 sectionalized between the center electrode 10 and the ground electrode 30 at the inside of a combustion chamber 81, a dielectric body head part 23, and a center electrode terminal part 12. Between a part where the dielectric body head part 23 is exposed from a cap part 62, and the housing 3, an insulating layer 50 is provided so as to be tightly bonded to a part or all of these surfaces over the whole periphery. The insulating layer 50 has a diameter larger than that at a part where the cap part 62 of the dielectric body head part 23 is attached.

Description

  The present invention relates to an ignition device for an internal combustion engine, and is particularly effective in an ignition device using barrier discharge.

Recently, fuel efficiency, for the purpose of CO2 reduction, small, development of high efficiency engines to achieve high output and low NO _X is promoted. A high-efficiency engine has a high supercharging and high compression, and the fuel concentration of the air-fuel mixture may be lean, so it is difficult to ignite with spark ignition.
In order to burn such a difficult-ignition internal combustion engine with high efficiency, an ignition device having a high combustion speed and excellent ignitability is desired.

  Patent Document 1 includes a first electrode, a second electrode surrounding the first electrode, and a dielectric covering either the first electrode or the second electrode, and the dielectric is either A barrier for an internal combustion engine that can generate a barrier discharge at any discharge gap regardless of the in-cylinder gas density by making the discharge gap between the other electrode different depending on the position in the longitudinal direction of the electrode. A discharge device is disclosed.

JP 2010-37949 A

However, in the barrier discharge device as disclosed in Patent Document 1, when a high-frequency high voltage is applied to the barrier discharge plug in order to obtain a high output, depending on the operating conditions of the internal combustion engine, the center electrode insulated by a dielectric is used. Impedance formed in the discharge space in the combustion chamber is larger than the impedance formed outside the combustion chamber between the housing and the housing, and a barrier discharge is generated outside the combustion chamber, not in the discharge gap on the combustion chamber side. It turns out that there is a fear.
If a barrier discharge occurs outside the combustion chamber, it results in significant energy loss, which may lead to misfires, and may also cause wiring burnout.

  Therefore, in view of such circumstances, the present invention provides an insulating layer on the power source side of the spark plug to lower the charging potential on the surface of the dielectric, suppresses the occurrence of streamer discharge outside the combustion chamber, and achieves stable ignition. An object is to provide an ignition device for an internal combustion engine that is realized.

In the ignition device (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g) of the present invention, spark plugs (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g), a high energy power source (70, 70g) for supplying electric energy to the spark plug (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g), and the power source (70, 70g) ) And the spark plug (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g)), and the spark plug (100, 100a, 100b). , 100c, 100d, 100e, 100f, 100g)
At least an axial center electrode (10), a cylindrical dielectric (20) holding the center electrode (10), and holding the dielectric (20) and fixing to the internal combustion engine (8) A cylindrical housing (3, 3g) and a ground electrode (30, 30g) extending to the housing (3, 3g), inside the combustion chamber (81) of the internal combustion engine (8) The discharge space (40, 40g) partitioned between the center electrode (10) and the ground electrode (30) and the dielectric (20) are exposed from the housing (3) to the power supply side, and have the cap. The dielectric head (23) to which the cap part (62) of the cord (60) is attached, and the center electrode (10) are exposed from the dielectric head (23) to the power source side, and the cord with cap ( 60) through the high energy power supply (70, 70g) A center electrode terminal portion (12) connected to the dielectric head portion (23) between the portion of the dielectric head portion (23) exposed from the cap portion (62) and the housing (3). Insulating layers (50, 50a) that are in close contact with part or all of the surface over the entire circumference and have a diameter larger than that of the portion of the dielectric head (23) to which the cap portion (62) is attached. , 50b, 50c, 50d, 50e, 50f).

  According to the present invention, the dielectric of the spark plug (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g) is formed by the insulating layer (50, 50a, 50b, 50c, 50d, 50e, 50f). The discharge space is not formed between the head (23) and the housing (3), the charged potential of the surface is lowered, and the barrier discharge on the power source side is suppressed, thereby preventing the combustion chamber (81). It has been found that internal discharge can be reliably performed, and energy loss can be reduced and wiring burnout can be prevented.

The half sectional view showing the whole outline of ignition device 100 in a 1st embodiment of the present invention. Sectional drawing of the principal part showing the effect of the ignition device 100 of the present invention Half sectional view showing the general outline and problems of a conventional ignition device 100z shown as a comparative example Sectional drawing of the principal part for demonstrating the problem of the conventional ignition device 100z shown as a comparative example FIG. 1 is a cross-sectional view showing a molding stage on the left side of the drawing and a state after molding on the left side in the manufacturing method of the ignition device of FIG. 1 is a sectional view showing a molding stage on the left side of the drawing and a state after molding on the left side in another manufacturing method of the ignition device of FIG. Sectional drawing which shows the principal part which shows the modification 100a of the ignition device in 1st Embodiment Sectional drawing which shows the principal part which shows the other modification 100b similarly Sectional drawing which shows the principal part which shows the other modification 100c similarly Sectional drawing which shows the principal part which similarly shows other modification 100d Sectional drawing of the principal part of the ignition device 100e shown as the 2nd Embodiment of this invention Sectional drawing of the principal part of the modification 100f of 2nd Embodiment Sectional drawing of the principal part of the ignition device 100g in the 3rd Embodiment of this invention.

With reference to FIG. 1, FIG. 2, the outline | summary of the ignition device 1 in the 1st Embodiment of this invention and the effect of this invention are demonstrated.
The ignition device 1 in the present embodiment applies a predetermined high-frequency voltage from a spark plug 100 provided in the engine block 80 in the internal combustion engine 8 and a high-frequency AC power supply 70 provided as a high-energy power source for supplying electric energy to the spark plug 100. By doing so, barrier discharge is performed in the discharge space 40 partitioned into the spark plug 100, and the air-fuel mixture introduced into the combustion chamber 81 of the internal combustion engine 8 is ignited.

The spark plug 100 according to the present embodiment covers at least the columnar center electrode 10, the bottomed cylindrical dielectric 20 that holds the center electrode 10 inside while covering the tip of the center electrode 10, and the dielectric 20. A dielectric housing 20 is provided at the distal end of the housing 3 and includes a dielectric 20 and an annular ground electrode 30 disposed coaxially with a predetermined discharge space 40 therebetween. An insulating layer 50 that covers the entire surface of the housing 3 and a part of the surface of the dielectric head 23 where the dielectric 20 is exposed from the housing 3 to the power supply side while covering the caulking portion 33 to be formed. It is provided.
The insulating layer 50 in the present embodiment is made of an insulating resin molded body that is molded by an after-mentioned method using an insulating resin such as an epoxy resin, and is formed in a cylindrical shape.
The thickness _{T 50} of the insulating layer 50 is set to be more than 15% of the outer diameter [phi] D ₂₃ of the dielectric head 23.
Furthermore, in this embodiment, the thickness T ₅₀ of the insulating layer 50 is set to 25% or less of the outer diameter φD ₂₃ of the dielectric head 23 so that the hexagonal portion 32 can be screwed.
For example, if the thread diameter of the spark plug 100 is M12, the thickness of the dielectric head 23 is a 12mm, the thickness _{T 50} of the insulating layer 50, 2 mm or more, it is desirable to 3mm or less.

The center electrode 10 is made of a highly conductive material formed in a columnar shape, and the center electrode central shaft portion 11 and the center electrode terminal portion 12 are connected to the base end side (power supply side).
The center electrode terminal portion 12 is connected to a high energy power source 70 through a cord 60 with a cap.
The cap-attached cord 60 has a terminal portion 61 that engages with the center electrode terminal portion 12 at the front end of a transmission line connected to the high energy power source 70, and a dielectric head 23 that elastically holds the dielectric head portion 23 so as to cover the periphery thereof. It is comprised by the bottom cylindrical cap part 62. FIG.
The center electrode 10 may be made of a nickel alloy having high conductivity and excellent heat resistance, or a combination of a highly conductive material such as copper.

A part of the outer peripheral surface of the dielectric 20, a base end side base 21 provided by expanding the base end side of the dielectric 20, and an inner periphery of an annular ground electrode 30 opened so as to face the combustion chamber 81 A substantially cylindrical discharge space 40 is defined by the surface.
A part of the center electrode 10 covered with the dielectric 20 is exposed from the tip of the ground electrode portion 30 and protrudes into the combustion chamber 81.

The dielectric 20 is formed in a substantially bottomed cylindrical shape using a highly heat-resistant dielectric material such as alumina or zirconia, and covers the tip of the center electrode 10.
A dielectric base 21 is formed on the base end side of the dielectric 20 and partitions the discharge space 40 together with the ground electrode 30.
In the present embodiment, an example is shown in which the dielectric barrier discharge plug is configured to face the ground electrode 30 with the tip of the center electrode 10 covered with the dielectric 20, but the center electrode 10 and the ground electrode are shown. Any one of the pair of electrodes 30 may be covered with a dielectric, and not only one electrode but also both electrodes may be covered with a dielectric.

On the base end side of the dielectric base portion 21, a part of the outer periphery is formed so as to have a large diameter, and a dielectric expanded diameter portion 22 that is caulked and fixed is formed by the housing 3.
Between the dielectric expanded-diameter portion 22 and the caulking portion 32, a known sealing member such as a powder molded body in which an annular metal seal, talc, etc. are formed in a substantially cylindrical shape is interposed, Airtightness is secured.

A dielectric head portion 23 is formed on the proximal end side of the dielectric expanded diameter portion 22 and is exposed from the housing 3.
A part of the dielectric head 23 is formed in a corrugated shape in which concave and convex surfaces are alternately arranged, and the creeping distance between the electrode terminal portion 12 and the housing 3 is increased.

The housing 3 is formed in a substantially cylindrical shape using a known metal material such as iron, nickel, and stainless steel.
A substantially annular ground electrode 30 is formed extending to the front end side of the housing 3 and exposed in the combustion chamber 81.
The discharge space 40 is partitioned between the dielectric 20 and a screw portion 31 for fixing to the engine block 80 is formed on the outer peripheral surface.
A hexagonal portion 32 for screwing the screw portion 31 is formed on the outer periphery on the proximal end side of the screw portion 31.
Further, a caulking portion 33 that holds the enlarged diameter portion 22 of the dielectric 20 is formed on the base end side.
The housing 3 has both a function as a housing for fixing the spark plug 100 to the engine block 80 and a function for electrically grounding the ground electrode 30 extending at the tip of the housing 3 to the engine block 80. ing.

In the present invention, the insulating layer 50 is formed so as to cover the caulking portion 33 that is closest to the central electrode central shaft portion 21.
In addition to the electrical resistance outside the combustion chamber (impedance Z _AR + Z ₂₃ + Z ₁₃ (= R _AR // C _AR + R ₂₃ // C ₂₃ + R ₁₃ // C ₁₃ )), the presence of the insulating layer 50 makes it possible The electrical resistance (impedance Z ₅₀ (= R ₅₀ // C ₅₀ )) increases, the voltage drop increases accordingly, and the potential difference between the surface of the insulating layer 50 and the surface of the housing 3 decreases.
Further, since the insulating layer 50 is in close contact with the surface of the housing 3 and a part of the surface of the dielectric head 23 where the dielectric 20 is exposed from the housing 3, the surface of the housing 3 and the dielectric head 23 are No discharge space is formed between the surface.
In addition, since the insulating layer 50 is interposed between the center electrode terminal portion 12 and the housing 3, the distance between the extended surfaces is also increased.
For this reason, the electrical resistance (synthesis) of the discharge space 40 in the combustion chamber 81 between the center electrode 10 and the housing 30 insulated by the dielectric 20 due to the operating conditions (for example, high load, lean combustion, etc.) of the internal combustion engine 8. Even if the impedance Z ₄₀ + Z ₂₀ ) increases, the electric resistance (synthetic impedance Z _AR + Z ₅₀ + Z ₂₃ + Z ₁₃ ) formed outside the combustion chamber does not exceed, so that barrier discharge hardly occurs outside the combustion chamber. Stable ignition can be realized.

The high energy power supply 70 applies an alternating high voltage (for example, VP _-P : 5 kV to 50 kV) having a predetermined frequency (for example, 1 kHz to 1 MHz) between the center electrode 10 and the ground electrode 30.

With reference to FIG. 3 and FIG. 4, the structure of a conventional ignition device 1z shown as Comparative Example 1 and its problems will be described.
In addition, in order to make the difference from the present invention easy to understand, the same components as those in the above embodiment are denoted by the same reference numerals, and different portions are denoted by z as a branch number.
In the ignition device 1z shown as the comparative example 1, the ignition plug 100z is not formed with the insulating layer 50 which is the main part of the present invention, and the caulking portion 33z and the dielectric head portion 23z are exposed to the atmosphere. It has become.
Depending on the operating conditions of the internal combustion engine 8 (for example, high load, lean combustion, etc.), the electric resistance (impedance Z _AR + Z ₂₃ + Z ₁₃ ) outside the combustion chamber between the center electrode 10 insulated by the dielectric 20 and the housing 30 In other words, the electrical resistance (synthetic impedance Z ₄₀ + Z ₂₀ ) of the discharge space 40 in the combustion chamber 81 is increased, and a barrier discharge may be generated outside the combustion chamber instead of the discharge gap on the combustion chamber side.
In particular, electric field concentration occurs in the caulking portion 33z, which is the most proximal side of the housing 3z, and the shoulder portion 231z where the linear portion of the dielectric head portion 23z and the corrugated portion are switched, and barrier discharge occurs during this time.
When a barrier discharge occurs outside the combustion chamber, there is a significant energy loss, which may lead to misfires, and may also cause wiring burnout.
The cap portion 62 covering the dielectric head portion 23z is also an electrical insulator, but only elastically covers the dielectric head portion 23z and is not completely adhered.
For this reason, even if the cap part 62 covers the entire dielectric head 23z, it is inevitable that a gap is formed between the inner peripheral surface of the cap part 62 and the surface of the dielectric head 23z. This becomes a discharge space and a barrier discharge is generated.

Here, a method of forming the insulating layer 50, which is a main part of the present invention, will be described.
The insulating layer 50 in the present invention can use a known resin molding method, and may be formed using any known resin molding method such as potting molding, injection molding, or transfer molding.
By molding using an insulating resin, the surface of the housing 3 and the surface of the dielectric head 23 can be brought into a completely intimate contact with the insulating layer 50.
With reference to FIG. 5A, an example of a specific method for manufacturing the spark plug 100 which is a main part of the ignition device 1 shown in FIG. 1 will be described.
The pre-molding spark plug 100PRE before forming the resin insulating layer 50 is formed through a known process similar to a general spark discharge spark plug or a conventional barrier discharge spark plug.
By forming the insulating layer 50 using the potting mold Mp on this, the spark plug 100 which is the main part of the present invention can be formed.
The potting mold Mp is formed in a cylindrical shape with a cavity CV (50) for forming the insulating layer 50 inside, and a sealing surface is formed in contact with the housing 3 to prevent resin leakage during molding. Yes.
As shown on the left side of the figure, the potting die Mp is moved in the axial direction in a state where the axis of the pre-molding ignition plug 100PRE and the axis of the potting die Mp are aligned, and the sealing surface is moved to the housing 3 The well-known potting resin RSNp such as epoxy is poured into the cavity CV (50).
When the resin RSN in the cavity CV (50) is solidified, the potting mold Mp is moved in the axial direction, and the spark plug 100 on which the insulating layer 50 is formed is taken out.

With reference to FIG. 5B, the other manufacturing method of the ignition device 1 is demonstrated.
In the present embodiment, it is possible to move in the direction orthogonal to the axial direction of the spark plug 100 by using the split mold Ms divided into two or three.
In the split type Ms, the cavity CV (50) for forming the insulating layer 50 and the surface of the housing 3 and the surface of the dielectric head 23 are in close contact with the resin RSN in the cavity CV (50). A sealing surface is formed to prevent leakage.
As shown on the left side of the figure, the split mold Ms is brought into close contact with the pre-molding ignition plug 100PRE from the side surface, and the cavity from a predetermined gate G provided in the split mold Ms in a state where the split mold Ms is clamped. CV (50) is filled with mold resin RSNm and solidified.
As shown on the right side of the figure, the spark plug 100 on which the insulating layer 50 is formed can be taken out by retracting the split mold Ms in the side surface direction.
In the present embodiment, a known mold resin RSNm such as a thermoplastic resin or a thermosetting resin can be used.

With reference to FIG. 6A, a modified example 100a of the ignition device in the first embodiment of the present invention will be described.
In the following embodiments, the same components as those in the above embodiments are denoted by the same reference numerals, and alphabetic branch numbers are added to the characteristic portions of the respective embodiments. Therefore, description of common portions is omitted. The explanation will focus on the characteristic part.
In the present embodiment, a large-diameter portion 24 is formed by enlarging a part of the dielectric head portion 23 a in the outer diameter direction, and the insulating layer 50 a is filled between the large-diameter portion 24 and the hexagonal portion 32 of the housing 3. Is formed.
By providing the large diameter portion 24 integrally with the dielectric head portion 23, it is possible to increase the voltage drop width from the center electrode middle shaft 11 to the surface of the large diameter portion 24 and to prevent the occurrence of barrier discharge outside the combustion chamber. It becomes possible.
Moreover, since the resin-made insulating layer 50a is formed between the large diameter portion 24 and the surface of the housing 3, a voltage drop can be achieved between them and the occurrence of barrier discharge can be prevented.
Further, if the entire dielectric head 23 exposed from the housing 3 is made thick, the housing 3 cannot be caulked.
However, as in the present embodiment, a part of the dielectric head 23a is thickened, and after the housing 3 is caulked, the insulating layer 50a is formed by using a resin, so that the housing 3 is substantially separated from the housing 3. The same effect as that obtained by thickening the entire exposed dielectric head portion 23a can be exhibited.
In addition, since the salt surface distance between the center electrode terminal portion 12 exposed from the dielectric head portion 23a and the housing 3 is increased and the insulation resistance is increased, it is possible to prevent electric discharge between them.

With reference to FIG. 6B, another modification 100b will be described. In the present embodiment, the insulating layer 50b is formed in a folded shape having a hollow portion 51 on the inner side, so that in addition to the same effect as that of the ignition device 1, creeping up to the surface of the dielectric head 23 exposed from the housing 3 is achieved. By increasing the distance, it is possible to prevent the occurrence of barrier discharge outside the combustion chamber more one-phase.
Further, the provision of the cavity 51 can be expected to reduce the material cost of the insulating layer 50b.

With reference to FIG. 6C, another modification 100c will be described.
In the embodiment, the example in which the insulating layer 50 is formed so as to be able to be screwed by the hexagonal portion 32 of the housing 3 has been shown. However, as shown in this figure, the outer periphery of the housing 3 is entirely covered. Anyway.
However, the insulating layer 50c in the present embodiment is provided with a hexagonal portion 52 for screwing and fixing the spark plug 100c to the engine block 80.
In the present embodiment, it is desirable to use a fiber reinforced resin to which glass fiber or the like is added so that the hexagonal portion 52 has sufficient strength against the tightening torque.
In the present embodiment, since the insulating layer 50c covers the entire housing 3, the potential difference between the surface of the insulating layer 50c and the surface of the dielectric head 23 is reduced, so that the housing 3 and the dielectric 23 can be reduced. Barrier discharge is less likely to occur with the surface.

With reference to FIG. 6D, another modified example 100d in the present embodiment will be described. In this modification, a large dielectric diameter portion 24d is formed by reducing the inner diameter toward the inside at a position facing the caulking portion 33, and the insulation distance from the central electrode central shaft portion 11d is increased. The charging voltage on the surface of the thick dielectric portion 24d is lowered to make it difficult for barrier discharge outside the combustion chamber to occur.
Also in the present embodiment, by forming the resin insulating layer 50d, one-phase barrier discharge outside the combustion chamber is less likely to occur.
However, in this embodiment, since the large dielectric diameter portion 24d is formed, the insulating layer 50d can be made smaller than that in the first embodiment.

With reference to FIG. 7A, the ignition device 100e shown as the 2nd Embodiment of this invention is demonstrated.
In the above-described embodiment, the configuration in which the resin insulating layer 50 is provided so as to cover at least the crimped portion 33 that is the base end side end of the housing 3 to prevent the occurrence of barrier discharge outside the combustion chamber has been described. In this embodiment, a sealed space 801e is provided on the outer periphery of the spark plug 100e, and an insulating layer is formed in the space, such as mineral oil, alkylbenzene, polybutene, alkylnaphthalene, methylpolyallylmethane, alkyldiphenylethane, and silicone oil. By filling the insulating oil 50e, an air layer serving as a discharge space is eliminated, and a barrier discharge is not generated between the surface of the housing 3 and the surface of the dielectric head 23.
In the present embodiment, the plug hole 801e of the engine block 80e is used as a sealed space.
In the present embodiment, after the spark plug 100e is fixed in the plug hole 801e, the insulating oil 50e is injected so as to cover at least the crimp part 33 of the housing 3, the plug cap part 62 is attached, and the plug hole 801e is attached. Is sealed with a hole cap 802 and a seal member 803.
Also in the present embodiment, it is possible to prevent the occurrence of barrier discharge outside the combustion chamber, as in the first embodiment.

A modification 100f of the second embodiment will be described with reference to FIG. 7B.
In this modified example, the insulating oil 50e is not directly poured into the plug hole 801e as in the ignition device 1e, but a rubber insulating oil cup 90 disposed in the plug hole 801f is used. The difference is that the inside of the hole 801f is not contaminated by the insulating oil 50f.
The insulating oil cup 90 is formed in a cylindrical shape made of an elastic member such as oil-resistant rubber, and when the folded portion 91 provided at the tip elastically presses the hexagonal portion 32 of the housing 3 to inject the insulating oil. In addition, the structure does not leak into the plug hole 801f.
In this modification, after the ignition plug 100f is mounted and fixed in the plug hole 801f, the insulating oil cup 90 is mounted, and the insulating oil 50f is injected into the insulating oil cup 90, whereby the caulking portion 33 of the housing 3 is inserted. And an air layer between the surface of the dielectric head 23 and the barrier discharge outside the combustion chamber can be prevented.

With reference to FIG. 8, the ignition device 1g in the 3rd Embodiment of this invention is demonstrated.
In the embodiment, as the spark plug 100, an arc is generated in the discharge space 40 by applying a high-frequency voltage between the ground electrode 30 and the insulated center electrode 10 in which the tip of the center electrode 10 is covered with the dielectric 20. Although an example in which the present invention is applied to ignite an air-fuel mixture introduced into a combustion chamber by performing a so-called barrier discharge that generates a streamer discharge without discharge is shown, in the present embodiment, A long-axis-shaped center electrode 10g held by a cylindrical dielectric 30g and a distal end side of a cylindrical housing 3 holding the dielectric 30 are bent into an L shape and bent into an L-shape. While using the electrode pair directly opposed type plug 100g which has a ground electrode 30g opposed to the tip and is directly opposed to the electrode pair, which is generally used as a spark discharge type spark plug. By increasing the frequency of the applied high voltage (e.g., above 1 kHz), by switching the polarity of the applied voltage before the transition to the arc discharge, a point which is adapted to generate a streamer discharge is different to the discharge space 40 g.
Also in the present embodiment, by providing the insulating layer 50g so as to cover the caulking portion 33 of the housing 3, the occurrence of barrier discharge outside the combustion chamber can be suppressed and the energy can be reduced as in the ignition device 1 in the above embodiment. Can be used efficiently to achieve stable ignition.

The present invention is not limited to the above-described embodiments, and these embodiments can be combined and used in a superimposed manner.
In addition, the present invention applies a high voltage between a center electrode whose tip is covered with a dielectric and a grounding electrode facing each other with a predetermined discharge space, in particular, using a high frequency AC power source as a high energy power source. However, it is suitable for an ignition device that generates a barrier discharge and ignites an air-fuel mixture introduced into a combustion chamber of an internal combustion engine, but is not necessarily limited to a barrier discharge. You may form an insulating layer as shown in the said embodiment between the housing of a normal spark discharge plug, and the insulator head part exposed from a housing using a power supply.
By providing the spark discharge plug with the insulating layer of the present invention, corona discharge at the insulator head can be suppressed and durability can be improved.

DESCRIPTION OF SYMBOLS 1 Ignition apparatus 100 Spark plug 10 Center electrode 11 Center electrode center shaft part 12 Center electrode terminal part 20 Dielectric 201 Conductive film (potential adjusting means)
21 Dielectric Bottom 22 Dielectric Expanding Portion 23 Dielectric Head 3 Housing 30 Ground Electrode 31 Screw Portion 32 Hexagonal Portion 33 Caulking Portion 40 Discharge Space 50 Resin Molding Portion (Insulating Means)
60 Cord 61 with Cap 61 Input Terminal 62 Plug Cap 70 High Energy Power Supply 8 Internal Combustion Engine 80 Engine Block 801 Plug Hole 81 Combustion Chamber 82 Piston

Claims (7)

Spark plugs (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g) provided in the internal combustion engine (8) and the spark plugs (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g) With a high energy power source (70, 70g) for supplying electric energy to the power source, and a cap for connecting the power source (70, 70g) and the spark plug (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g)) An ignition device comprising a cord (60),
The spark plug (100, 100a, 100b, 100c, 100d, 100e, 100f, 100g)
At least an axial center electrode (10), a cylindrical dielectric (20) holding the center electrode (10), and holding the dielectric (20) and fixing to the internal combustion engine (8) Including a cylindrical housing (3, 3g) and a ground electrode (30, 30g) extending to the housing (3, 3g),
A discharge space (40, 40g) partitioned between the center electrode (10) and the ground electrode (30) inside the combustion chamber (81) of the internal combustion engine (8);
A dielectric head (23) on which the dielectric (20) is exposed from the housing (3) to the power supply side and a cap portion (62) of the cord (60) with the cap is mounted;
The center electrode terminal portion (10) is exposed to the power source side from the dielectric head (23) and connected to the high energy power source (70, 70g) via the cap-attached cord (60). 12), and
The dielectric head (23) is in close contact with a part or all of these surfaces between the part exposed from the cap part (62) and the housing (3). An insulating layer (50, 50a, 50b, 50c, 50d, 50e, 50f) having a diameter larger than that of the portion where the cap portion (62) of the dielectric head (23) is mounted is provided. Ignition device (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g)   The ignition device according to claim 1, wherein the high energy power source (70, 70g) is a high-frequency AC power source.   Insulating resin molded body (50, 50a, 50b, 50c, 50d) molded so that the insulating layer (50, 50a, 50b, 50c, 50d, 50e) covers the periphery of the dielectric head (23) , A large diameter part (24) integrally provided by expanding a part of the dielectric head (23a), and insulating oil (50e, 50f) injected so as to cover the periphery of the dielectric head (23) The ignition device according to claim 1 or 2, wherein the ignition device is a combination thereof. The spark plug is
Dielectric barrier discharge plugs (100, 100a, 100b, 100c, 100d, 100e, 100f) in which one or both of the center electrode (10) and the ground electrode (30) are covered with the dielectric (20). The ignition device (1, 1a, 1b, 1c, 1d, 1e, 1f) according to any one of claims 1 to 3   The spark plug exposes the tip of the center electrode (10g) from the dielectric (20g) to the inside of the combustion chamber (81) and the ground electrode (30g) to the tip of the center electrode (10g). The ignition device according to any one of claims 1 to 3, wherein the ignition device is a direct-to-electrode spark plug (100g) opposed to each other, and the high-energy power source is a high-frequency AC power source (70g) having a frequency of 1 kHz or more. (1g) The thickness (T ₅₀ ) of the insulating layer (50, 50a, 50b, 50c, 50d, 50e, 50f) is 15% or more of the outer diameter (φD ₂₃ ) of the dielectric head (23). The ignition device according to any one of 1 to 5 (1, 1a, 1b, 1c, 1d, 1e, 1f, 1g) The thickness (T ₅₀ ) of the insulating layer (50, 50a, 50b, 50d) is 25% or less of the outer diameter (φD ₂₃ ) of the dielectric head (23). Ignition device described in (1, 1a, 1b, 1d, 1g)

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