JP2017162742A - Spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly fix a hollow cylindrical AC power applied electrode in an AC power superimposed type spark plug.SOLUTION: A spark plug includes an ignition voltage applied electrode and an AC power applied electrode. The distal end surface of the AC power applied electrode is positioned closer to a distal end side than the distal end surface of the ignition voltage applied electrode. The distal end surface of the AC power applied electrode, an outer peripheral surface of a rear end portion of a central electrode, and an inner surface of a shaft hole of an insulator are sealed by a glass seal portion.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an AC power superimposing type spark plug having an ignition voltage application electrode and an AC power application electrode.

  A spark plug used for an internal combustion engine generally includes a cylindrical metal shell, a cylindrical insulator disposed in an inner hole of the metal shell, and a tip of the insulator inserted into a shaft hole of the insulator. A center electrode projecting from the outside, a terminal fitting inserted into the shaft hole of the insulator and projecting outside from the rear end of the insulator, one end joined to the front end side of the metal shell, and the other end of the spark discharge gap And a ground electrode opposite to the center electrode. The center electrode and the terminal fitting are electrically connected by a conductive glass seal portion provided in the shaft hole of the insulator.

  In recent years, in order to improve fuel consumption and emissions, there has been a demand for enhanced spark plug ignition performance. As means for enhancing the ignition performance, an AC power superposition type spark plug that supplies a large amount of AC power after the occurrence of a spark has been proposed (Patent Documents 1 and 2). In the AC power superimposing type spark plug, in order to supply power from an external power source to the center electrode, an electrode for applying AC power is separately provided in addition to the terminal fitting. At the time of ignition, first, a high voltage is applied from the high voltage power source to the terminal fitting to generate a spark, and when the spark is generated, a large amount of AC power is supplied from the AC power source to the AC power application electrode. As a result, since the spark is strengthened by the AC power supplied after the spark is generated, the ignition performance is greatly improved. In this AC power superposition type spark plug, the AC power application electrode is often mounted as a pipe-shaped (hollow cylindrical) conductive member.

JP 2009-170324 A JP 2012-219748 A

  By the way, the spark plug has a severe use environment such as vibration and thermal cycle of the internal combustion engine, so that the parts of the spark plug are firmly bonded to each other so that the soundness can be maintained even under these environments. It is required to have.

  However, in the AC power superimposing type spark plug, since it is difficult to fix the hollow cylindrical AC power application electrode in the spark plug, there is a problem in the durability of the spark plug. Therefore, a technique for firmly fixing a hollow cylindrical AC power application electrode in an AC power superimposed type spark plug has been desired.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, an insulator having an axial hole extending in the axial direction, a center electrode that is inserted into the axial hole and protrudes to the outside from the tip of the insulator, An ignition voltage application electrode that is inserted into the shaft hole including a terminal metal part protruding from the rear end to the outside, a metal shell that accommodates the insulator, one end joined to the front end side of the metal metal, and the other end A ground electrode facing the center electrode through a spark discharge gap, and a hollow cylindrical AC power application arranged so as to surround the ignition voltage application electrode and a rear end portion of the center electrode in the shaft hole. An electrode, and a conductive glass seal portion that seals and electrically connects between the center electrode and the ignition voltage application electrode and between the center electrode and the AC power application electrode in the shaft hole. A spark plug with It is. In this spark plug, the front end surface of the AC power application electrode is located on the front side of the front end surface of the ignition voltage application electrode, and the front end surface of the AC power application electrode and the rear end portion of the center electrode And the inner surface of the shaft hole of the insulator are sealed by the glass seal portion.
According to the spark plug described above, the front end surface of the AC power application electrode, the outer peripheral surface of the rear end portion of the center electrode, and the inner surface of the shaft hole of the insulator are sealed by the glass seal portion. The power application electrode can be firmly fixed.

(2) In the spark plug, it is assumed that at least a part of the outer surface of the tip portion of the AC power application electrode and the inner surface of the shaft hole of the insulator are sealed by the glass seal portion. Also good.
According to this configuration, since the gap between the outer surface of the tip portion of the AC power application electrode and the inner surface of the shaft hole of the insulator is sealed by the glass seal portion, the hollow cylindrical AC power application electrode is further strengthened. Can be fixed.

(3) In the spark plug, a distance between the tip surface of the AC power application electrode and a portion of the center electrode facing the tip surface of the AC power application electrode along the axial direction is 0. It is good also as what is 2 mm or more.
According to this configuration, since the axial distance between the tip surface of the AC power application electrode and the center electrode is 0.2 mm or more, and is sealed by this partial glass seal portion, the hollow cylindrical AC power The application electrode can be more firmly fixed.

(4) In the spark plug, a portion facing the inner surface of the tip portion of the AC power application electrode and the inner surface of the tip portion of the AC power application electrode in the central electrode along a radial direction perpendicular to the axial direction. The distance between and may be 0.2 mm or more.
According to this configuration, the radial distance between the inner surface of the front end portion of the AC power application electrode and the center electrode is 0.2 mm or more, and this portion is sealed by the glass seal portion, so that it has a hollow cylindrical shape. The AC power application electrode can be more firmly fixed.

(5) In the spark plug, the tip portion of the AC power application electrode may have a through hole or a slit penetrating from the inner surface to the outer surface of the tip portion of the AC power application electrode.
According to this configuration, the through hole or slit at the tip of the AC power application electrode is sealed by the glass seal portion, so that the hollow cylindrical AC power application electrode can be more firmly fixed.

(6) The spark plug further includes a cylindrical insulating member inserted between the outer surface of the ignition voltage application electrode and the inner surface of the AC power application electrode in the shaft hole, and the glass seal portion is A front end seal portion at a front end of the glass seal portion; a rear end seal portion at a rear end of the glass seal portion; and the front end seal portion and the rear end seal portion disposed between the front end seal portion and the rear end seal portion. A resistance portion having an electric resistance larger than that of the rear end seal portion, and the front end surface of the cylindrical insulating member includes a front end surface of the ignition voltage application electrode and a front end surface of the AC power application electrode in the axial direction. The distal end portion of the tubular insulating member may be sealed by the distal end seal portion.
According to this configuration, even when the cylindrical insulating member is inserted between the outer surface of the ignition voltage application electrode and the inner surface of the AC power application electrode, the distal end portion of the cylindrical insulating member is sealed by the distal end seal portion. Since it is attached, both the AC power application electrode and the cylindrical insulating member can be firmly fixed.

  In addition, this invention can be implement | achieved in various aspects, for example, can be implement | achieved with the form of the manufacturing method of a spark plug and a spark plug.

Explanatory drawing which shows the ignition system utilized by embodiment. FIG. 2 is a cross-sectional view showing the overall configuration of the spark plug according to the first embodiment. The figure which expands and shows the front-end | tip part of the alternating current power application electrode of 1st Embodiment, and the rear-end part of a center electrode. The figure which expands and shows the front-end | tip part of the alternating current power application electrode of 2nd Embodiment, and the rear-end part of a center electrode. Sectional drawing which shows the dimension of the sample of the spark plug which has the characteristic part of 1st Embodiment and 2nd Embodiment. The figure which shows an example of the preferable shape of the front-end | tip part of an alternating current power application electrode. The figure which shows the other example of the preferable shape of the front-end | tip part of an alternating current power application electrode. Sectional drawing which shows the whole structure of the spark plug of 3rd Embodiment. The figure which expands and shows the glass seal part of 3rd Embodiment. Explanatory drawing which shows the assembly process of the spark plug of 3rd Embodiment.

  FIG. 1 is an explanatory diagram showing an ignition system 300 used in an embodiment of the present invention. The ignition system 300 includes a spark plug 100, an ignition high voltage power supply 210, and a high power supply AC power supply 220. The ignition high voltage power supply 210 applies a high voltage for ignition to the spark plug 100 to generate a spark in the spark discharge gap g. The high power supply AC power supply 220 supplies high power AC power to the spark plug 100 after the occurrence of a spark. As a result, since the spark is strengthened by the AC power supplied after the spark is generated, the ignition performance is greatly improved.

  FIG. 2 is a cross-sectional view showing the overall configuration of the spark plug 100 as the first embodiment of the present invention. The lower side (ignition part side) of FIG. 1 is called the front end side of the spark plug 100, and the upper side (terminal side) is called the rear end side. The spark plug 100 includes an insulator 10, a center electrode 20, an ignition voltage application electrode 30, a metal shell 40, a ground electrode 50, an AC power application electrode 60, and a glass seal portion 70.

  The insulator 10 has an axial hole extending in the direction of the axis O. In the shaft hole of the insulator 10, the rear end portion of the center electrode 20, the rod-like conductive portion 34 that is the tip portion of the ignition voltage application electrode 30, the hollow cylindrical AC power application electrode 60, and the glass seal portion 70. And is housed.

  The center electrode 20 is fixed in the insulator 10 while being inserted into the shaft hole of the insulator 10. The front end portion of the center electrode 20 protrudes outward from the front end of the insulator 10 and forms a spark discharge gap g so as to face the front end portion of the ground electrode 50.

  The ignition voltage application electrode 30 is an electrode that receives an ignition high voltage from the ignition high voltage power supply 210. The ignition voltage application electrode 30 includes a terminal fitting portion 32 that protrudes to the outside from the rear end of the insulator 10 and a rod-shaped conductive portion 34 that is housed in the shaft hole of the insulator 10.

  The metal shell 40 is a metal member that houses the insulator 10. When the main metal fitting 40 is screwed to an engine block (not shown) by a male screw portion (not shown) on the outer periphery of the front end portion of the main metal fitting 40, the main metal fitting 40 is electrically grounded via the engine block.

  One end (base end portion) of the ground electrode 50 is joined to the tip end side of the metal shell 40, and the other end (tip end portion) faces the tip end portion of the center electrode 20 through the spark discharge gap g. . The intermediate portion of the ground electrode 50 has a curved shape so that the tip of the ground electrode 50 faces the tip of the center electrode 20.

  The AC power application electrode 60 is an electrode that receives a large amount of AC power from the AC power supply 220 for supplying a large power after a spark is generated in the spark discharge gap g. The AC power application electrode 60 is a hollow cylindrical (pipe-shaped) electrode arranged so as to surround the periphery of the rear end portion of the center electrode 20. The inner surface of the rear end portion of the AC power application electrode 60 is in contact with the outer surface of the rod-shaped conductive portion 34 of the ignition voltage application electrode 30 in the shaft hole of the insulator 10, and both are electrically connected here. Yes. In the first embodiment, the AC power supply 220 for supplying high power is connected to the terminal fitting 32 of the ignition voltage application electrode 30 and connected to the AC power application electrode 60 through the ignition voltage application electrode 30. The front end surface 60 f of the AC power application electrode 60 is located on the more front end side of the spark plug 100 than the front end surface 30 f of the ignition voltage application electrode 30.

  The glass seal portion 70 seals a gap or a space between the center electrode 20 and the ignition voltage application electrode 30 and between the center electrode 20 and the AC power application electrode 60 in the shaft hole of the insulator 10. At the same time, it is a conductive member that electrically connects them. The glass seal portion 70 is formed by filling a seal member powder containing glass powder such as borosilicate soda glass and conductive member powder such as metal powder into the insulator 10 and then firing the same.

  FIG. 3 is an enlarged view of the region 3 in FIG. 2, and shows the periphery of the front end portion 62 of the AC power application electrode 60 and the rear end portion 22 of the center electrode 20. The shaft hole of the insulator 10 is divided into a small diameter shaft hole portion 12 on the front end side and a large diameter shaft hole portion 14 on the rear end side, and a reduced diameter portion 16 is formed therebetween. . The center electrode 20 has a large-diameter portion 24 having a larger outer shape than the rear end portion 22 on the front end side (lower side in FIG. 3) of the rear end portion 22. At the time of manufacturing the spark plug 100, the center electrode 20 is positioned by pressing the large diameter portion 24 against the reduced diameter portion 16 of the insulator 10. If the outer diameter of the rear end portion 22 of the center electrode 20 is larger than the inner diameter of the small-diameter shaft hole portion 12 of the insulator 10, the large-diameter portion 24 may be omitted.

  The front end surface 60 f of the AC power application electrode 60 and the rear end surface 24 e of the large diameter portion 24 of the center electrode 20 are separated along the axial direction of the spark plug 100, and the gap is sealed by the glass seal portion 70. It is worn. Further, a radial direction perpendicular to the axial direction (axis O shown in FIG. 2) is also formed between the outer peripheral surface of the rear end portion 22 of the center electrode 20 and the inner surface of the axial hole (large-diameter axial hole portion 14) of the insulator 10. In the direction from the outer peripheral side to the outer peripheral side), and the gap is also sealed by the glass seal portion 70. In other words, the front end surface 60 f of the AC power application electrode 60, the rear end surface 24 e of the large diameter portion 24 of the center electrode 20, the outer peripheral surface of the rear end portion 22 of the center electrode 20, and the inner surface of the shaft hole of the insulator 10. Are sealed by the glass seal portion 70. As described above, the large-diameter portion 24 of the center electrode 20 can be omitted. Also in this case, the front end surface 60f of the AC power application electrode 60, the outer peripheral surface of the rear end portion 22 of the center electrode 20, It is preferable that the inner surface of the shaft hole of the insulator 10 is sealed by the glass seal portion 70. In this way, the tip 62 of the AC power application electrode 60 can be firmly fixed.

  In the first embodiment, the inner surface of the front end portion 62 of the AC power application electrode 60 and the outer peripheral surface of the rear end portion 22 of the center electrode 20 are separated from each other along the radial direction, and the gap is made of glass. It is sealed by the seal part 70. As a result, the front end portion 62 of the AC power application electrode 60 and the rear end portion 22 of the center electrode 20 can be more firmly fixed by the glass seal portion 70. However, when the gap between the inner surface of the front end portion 62 of the AC power application electrode 60 and the outer peripheral surface of the rear end portion 22 of the center electrode 20 is small, it may not be sealed with the glass seal portion 70.

  There is a gap between the outer peripheral surface of the large diameter portion 24 of the center electrode 20 and the inner surface of the shaft hole of the insulator 10, and this gap is also sealed by the glass seal portion 70. However, the gap between the outer peripheral surface of the large-diameter portion 24 of the center electrode 20 and the inner surface of the shaft hole of the insulator 10 may not be sealed by the glass seal portion 70.

  As described above, in the spark plug 100 of the first embodiment, the front end surface 60f of the AC power application electrode 60, the outer peripheral surface of the rear end portion 22 of the center electrode 20, and the shaft hole (large-diameter shaft hole) of the insulator 10. The inner surface of the part 14) is sealed with a glass seal part 70. As a result, the tip 62 of the AC power application electrode 60 can be firmly fixed, and the durability of the spark plug 100 is improved.

  FIG. 4 is a view showing the periphery of the front end portion 62 of the AC power application electrode 60 and the rear end portion 22 of the center electrode 20 in the second embodiment. In the second embodiment, the outer surface of the distal end portion 62 of the AC power application electrode 60 and the inner surface of the shaft hole (large-diameter shaft hole portion 14) of the insulator 10 are separated from each other. The second embodiment is the same as the first embodiment except that it is sealed by the glass seal portion 70. In this way, it is possible to more firmly fix the tip 62 of the AC power application electrode 60.

  Note that a gap between the outer surface of the tip portion 62 of the AC power application electrode 60 and the inner surface of the shaft hole (large diameter shaft hole portion 14) of the insulator 10 is formed on the outer surface of the tip portion 62 of the AC power application electrode 60. It may be formed over the entire circumference, or a gap may be formed in only a part of the entire circumference. The latter configuration may occur, for example, when a protrusion is provided on a part of the entire circumference of the outer surface of the tip 62 of the AC power application electrode 60. In this manner, the glass seal portion 70 seals between at least a part of the outer surface of the tip portion 62 of the AC power application electrode 60 and the inner surface of the shaft hole (large diameter shaft hole portion 14) of the insulator 10. It is preferable that

FIG. 5 is a cross-sectional view showing the dimensions of a spark plug sample having the features of the first embodiment and the second embodiment described above. This sample has the following dimensions.
(1) Inner diameter D1 of large-diameter shaft hole 14 of insulator 10: φ4.0 mm
(2) Outer diameter D2 of the tip portion of the ignition voltage application electrode 30: φ2.0 mm
(3) Outer diameter D3 of AC power application electrode 60: φ3.8 mm
(4) Inner diameter D4 of AC power application electrode 60: φ3.0 mm
(5) Length L of the rear end 22 of the center electrode 20: 2.3 mm
(6) Outer diameter D5 of rear end 22 of center electrode 20: φ2.5 mm
(7) Radial distance d1: 0.25 mm between the inner surface of the AC power application electrode 60 and the center electrode 20
(8) Distance G in the axial direction between the front end surface 60f of the AC power application electrode 60 and the rear end surface 24e of the large diameter portion 24 of the center electrode 20: 0 <G ≦ 0.5 mm

In the shape of FIG. 5, a plurality of samples with the distance G as a parameter was created, and a durability test was performed under the following conditions.
-Thermal cycle: 200 cycles of thermal cycles were performed by holding the temperature at -40 ° C and 200 ° C for 5 minutes, respectively, and changing the temperature between -40 ° C and 200 ° C in 2 hours.
-Damage load measurement: After the thermal cycle, the upper part of the AC power application electrode 60 was pulled to measure the load at which the damage occurred.

Table 1 shows the results of this durability test.

  As can be understood from the test results, in order to strengthen the sealing and improve the durability, the gap between the front end surface 60f of the AC power application electrode 60 and the rear end surface 24e of the large-diameter portion 24 of the center electrode 20 is improved. The distance G in the axial direction is preferably 0.2 mm or more, and this portion G is preferably sealed with the glass seal portion 70. The rear end surface 24e of the large-diameter portion 24 of the center electrode 20 corresponds to “a portion facing the front end surface 60f of the AC power application electrode 60 along the axial direction”.

  In FIG. 5, the radial distance d1 between the inner surface of the AC power application electrode 60 and the outer peripheral surface of the rear end portion 22 of the center electrode 20 is set to 0.25 mm. With respect to the role of fixing the front end portion 62 of the electrode 60, the same function as the axial distance G between the front end surface 60f of the AC power applying electrode 60 and the rear end surface 24e of the large diameter portion 24 of the center electrode 20 is achieved. Presumed to have. Therefore, in order to strengthen the sealing and improve the durability, the radial distance d1 between the inner surface of the AC power application electrode 60 and the outer peripheral surface of the rear end portion 22 of the center electrode 20 is also 0.2 mm or more. It is preferable that this portion is sealed with a glass seal portion 70. The outer peripheral surface of the rear end portion 22 of the center electrode 20 corresponds to “a portion of the center electrode 20 facing the inner surface of the front end portion 62 of the AC power application electrode 60 along the radial direction perpendicular to the axial direction”. .

  FIG. 6 is a diagram illustrating an example of a preferable shape of the distal end portion 62 of the AC power application electrode 60. The AC power application electrode 60 has a slit 64 penetrating from the inner surface to the outer surface at the tip 62. If such a slit 64 is provided, the slit 64 is sealed by the glass seal portion 70, so that the AC power application electrode 60 can be more firmly fixed. The number of slits 64 can be set to an arbitrary value of 1 or more, but it is preferable to provide a plurality of slits 64. In particular, it is preferable to provide a plurality of slits 64 at equal intervals along the outer periphery of the tip 62 of the AC power application electrode 60.

  FIG. 7 is a diagram illustrating another example of a preferable shape of the distal end portion 62 of the AC power application electrode 60. The AC power application electrode 60 has a through-hole 66 penetrating from the inner surface to the outer surface at the tip 62. If such a through-hole 66 is provided, the through-hole 66 is sealed by the glass seal portion 70, so that the AC power application electrode 60 can be more firmly fixed. The number of through holes 66 can be set to an arbitrary value of 1 or more, but it is preferable to provide a plurality of through holes 66. In particular, it is preferable to provide a plurality of through holes 66 at equal intervals along the outer periphery of the tip 62 of the AC power application electrode 60.

Table 2 shows the result of the durability test on the spark plug sample using the AC power application electrode 60 having the slit 64 shown in FIG. As the AC power application electrode 60, one having six slits 64 having a width of 1 mm and an axial length of 2 mm provided at equal intervals was used. Other dimensions of the sample were the same as those in FIG. 5 described above, and the value of the distance G was set to less than 0.05 mm. The durability test was performed under the same conditions as in Table 1 above.

  As can be understood from the test results, if the slit 64 is formed at the tip portion 62 of the AC power application electrode 60, the AC power application electrode 60 can be more firmly fixed. In addition, it is estimated that the through-hole 66 shown in FIG. 7 has the same effect.

  FIG. 8 is a cross-sectional view showing the overall configuration of the spark plug 100a of the third embodiment. In the spark plug 100a of the third embodiment, the cylindrical insulating member 80 is inserted between the AC power application electrode 60 and the rod-like conductive part 34 of the ignition voltage application electrode 30, and the glass seal part 70 is at the tip. The point which contains the seal part 71, the rear-end seal part 72, and the resistance part 73 differs from 2nd Embodiment, and another structure is the same as 2nd Embodiment. Since the AC power application electrode 60 and the ignition voltage application electrode 30 are insulated by the cylindrical insulating member 80, the insulator 10 is used when the spark plug 100a is mounted on the engine block (not shown). The AC electrode 222 for applying AC power to the AC power application electrode 60 is installed outside the AC electrode 222. The AC electrode 222 and the AC power application electrode 60 are capacitively coupled with the insulator 10 interposed therebetween. When AC power is applied to the AC electrode 222 from the AC power supply 220 for supplying large power, the AC electrode 222 is passed through the AC electrode 222. AC power is supplied to the AC power application electrode 60. However, the AC power supply 220 may be connected to the AC power application electrode 60 via another wiring path not shown in FIG. 8 without using the AC electrode 222. The structure of 3rd Embodiment other than these is the same as 2nd Embodiment.

  FIG. 9 is an enlarged view showing the glass seal portion 70 of the spark plug 100a of the third embodiment. As described above, the glass seal portion 70 is disposed between the center electrode 20 and the ignition voltage application electrode 30 in the shaft hole of the insulator 10 and seals the space or gap therebetween. And the ignition voltage application electrode 30 and between the center electrode 20 and the AC power application electrode 60 are electrically connected. The glass seal portion 70 according to the third embodiment is disposed between the front end seal portion 71 at the front end, the rear end seal portion 72 at the rear end, and the front end seal portion 71 and the rear end seal portion 72. And a resistance portion 73 having a larger electrical resistance than the portion 71 and the rear end seal portion 72. The front end seal portion 71, the rear end seal portion 72, and the resistance portion 73 can be formed by firing a glass seal member powder containing glass powder such as sodium borosilicate glass and conductive member powder such as metal powder. . The resistance portion 73 is configured as a portion having a higher electrical resistance than the front end seal portion 71 and the rear end seal portion 72. The electric resistance of the resistance portion 73 can be adjusted as appropriate by adjusting the material and content of the conductive member. By providing the resistance part 73 in the glass seal part 70, high frequency noise can be reduced.

  The distal end surface 80 f of the cylindrical insulating member 80 exists in a position between the distal end surface 30 f of the ignition voltage application electrode 30 and the distal end surface 60 f of the AC power application electrode 60 in the axial direction. The distal end portion of the cylindrical insulating member 80 is sealed by the distal end seal portion 71. In this way, not only the AC power application electrode 60 but also the cylindrical insulating member 80 can be firmly fixed, so that the durability of the spark plug is improved.

  FIG. 10 is an explanatory diagram showing an assembly process of the spark plug 100a of the third embodiment. In the step (a), the cylindrical insulating member 80 is inserted into the pipe-shaped AC power application electrode 60. In the step (b), the center electrode 20 is first inserted into the tip of the insulator 10, and then the set of the AC power application electrode 60 and the cylindrical insulating member 80 assembled in the step (a) is inserted. In the step (c), the front end seal portion powder 71p, the resistance portion powder 73p, and the rear end seal portion powder 72p are filled in this order using the center hole of the cylindrical insulating member 80. In the step (d), the ignition voltage application electrode 30 is inserted into the central hole of the cylindrical insulating member 80, and the front end seal portion powder 71p, the resistance portion powder 73p, and the rear end seal portion powder 72p are compressed in the axial direction. In the step (e), the glass seal portion 70 is fired while compressing the tip seal portion powder 71p, the resistance portion powder 73p, and the rear end seal portion powder 72p in the axial direction using the ignition voltage application electrode 30. The subsequent steps are the same as the ordinary spark plug manufacturing steps, and the description thereof is omitted. In addition, the manufacturing process of the spark plug of 1st Embodiment or 2nd Embodiment is the same as that of FIG. 10 except the point which does not use the cylindrical insulating member 80. FIG.

  As described above, in the third embodiment, the cylindrical insulating member 80 is inserted between the outer surface of the ignition voltage application electrode 30 and the inner surface of the AC power application electrode 60, and the tip portion of the cylindrical insulating member 80. Is sealed by the tip seal portion 71, so that the AC power application electrode 60 and the cylindrical insulating member 80 can be firmly fixed. As a result, the durability of the spark plug can be improved.

Modifications The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the scope of the invention.

・ Modification 1:
As the spark plug, spark plugs having various configurations other than those shown in FIGS. 2 and 8 can be applied to the present invention.

DESCRIPTION OF SYMBOLS 10 ... Insulator 12 ... Small diameter axial hole part 14 ... Large diameter axial hole part 16 ... Reduced diameter part 20 ... Center electrode 22 ... Rear end part of the center electrode 20 24 ... Large diameter part 24e of the central electrode 20e ... Large diameter part 24 Rear end surface 30 ... Ignition voltage application electrode 30f ... Front end surface of ignition voltage application electrode 30 ... Terminal metal part of ignition voltage application electrode 34 ... Bar-shaped conductive part of ignition voltage application electrode 30 ... Metal metal 50 ... Ground electrode 60 ... AC power application electrode 60f ... tip surface of AC power application electrode 60 62 ... tip part of AC power application electrode 60 64 ... slit 66 ... through hole 70 ... glass seal part 71 ... tip seal part 71p ... tip seal part powder 72 ... Rear end seal part 72p ... Rear end seal part powder 73 ... Resistance part 73p ... Resistance part powder 80 ... Cylindrical insulating member 80f ... Front end surface of cylindrical insulating member 80 100, 100a ... Spark plug 2 0 ... igniting high voltage power supply 220 ... large power supply for the AC power supply 222 ... AC electrodes 300 ... ignition system

Claims (6)

An insulator having an axial hole extending in the axial direction; a center electrode that is inserted into the axial hole and projects outward from a tip of the insulator; and a terminal fitting that projects outward from a rear end of the insulator. An ignition voltage application electrode inserted into the shaft hole, a metal shell for housing the insulator, one end joined to the front end side of the metal shell, and the other end facing the center electrode via a spark discharge gap A ground electrode, a hollow cylindrical AC power application electrode disposed so as to surround the rear end of the ignition voltage application electrode and the center electrode in the shaft hole, and the center electrode in the shaft hole; In a spark plug comprising: a conductive glass seal portion that seals and electrically connects between the ignition voltage application electrode and between the center electrode and the AC power application electrode,
The front end surface of the AC power application electrode is located on the front side of the front end surface of the ignition voltage application electrode,
A spark plug, wherein a front end surface of the AC power application electrode, an outer peripheral surface of a rear end portion of the center electrode, and an inner surface of a shaft hole of the insulator are sealed by the glass seal portion. The spark plug according to claim 1,
The spark plug is characterized in that a gap between at least a part of the outer surface of the tip portion of the AC power application electrode and the inner surface of the shaft hole of the insulator is sealed by the glass seal portion. The spark plug according to claim 1 or 2,
The distance between the tip surface of the AC power application electrode and the portion of the center electrode facing the tip surface of the AC power application electrode along the axial direction is 0.2 mm or more. Spark plug to do. The spark plug according to any one of claims 1 to 3,
The distance between the inner surface of the tip of the AC power application electrode and the portion of the center electrode facing the inner surface of the tip of the AC power application electrode along the radial direction perpendicular to the axial direction is 0. Spark plug characterized by being 2 mm or more. The spark plug according to any one of claims 1 to 4,
The spark plug, wherein the tip of the AC power application electrode has a through hole or a slit that penetrates from the inner surface to the outer surface of the tip of the AC power application electrode. The spark plug according to any one of claims 1 to 5, further comprising:
A cylindrical insulating member inserted between the outer surface of the ignition voltage application electrode and the inner surface of the AC power application electrode in the shaft hole;
The glass seal portion is disposed between a front end seal portion at a front end of the glass seal portion, a rear end seal portion at a rear end of the glass seal portion, and the front end seal portion and the rear end seal portion. A leading end seal portion and a resistance portion having a larger electrical resistance than the rear end seal portion, and
The distal end surface of the cylindrical insulating member exists in a position between the distal end surface of the ignition voltage application electrode and the distal end surface of the AC power application electrode in the axial direction.
A spark plug, wherein a tip end portion of the cylindrical insulating member is sealed by the tip seal portion.

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