JPS617584A - Ignition plug - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] field] The present invention relates to improving the heat resistance of spark plugs.

[Prior Art] In a resistor-containing spark plug for preventing radio noise, as shown in FIG. 6, the inner cavity of the cylindrical main metal shell 1 is divided by a stepped portion 24 in the middle, with a small diameter at the tip and a large diameter at the rear end. An insulator 2 having a shaft hole with a diameter of 100 mm is fitted into the first inner cavity step 21 of the metal shell 1 via a packing 100, and is engaged with the step in a small diameter hole 25 at the tip of the shaft hole of the insulator 2. Center electrode 3 with a flange 31
is fitted, a terminal electrode is fitted along the rear end, an electric resistor 70 is inserted in the middle part, and a glass sealing layer 60 is provided. In this spark plug, the center electrode 3 is loosely fitted into a small diameter hole 25 at the tip of the insulator to prevent damage to the insulator 2 due to heat dissipation, and the heat received by the center electrode tip from the combustion chamber of the engine is Heat is radiated in the following order: center electrode flange → glass seal → gasket → insulator → mounting bracket → cylinder head, but improving heat resistance is a problem because the heat transfer distance is large and heat conduction is poor.

[Objective] An object of the present invention is to provide a spark plug that is excellent in heat removal from a center electrode and has improved heat resistance.

[Structure of the Invention] The spark plug of the present invention includes a metal shell and an insulator having a shaft hole that is fitted into the inner cavity of the metal shell and has a small diameter at the tip and a large diameter at the rear end through a step. a body, and a flange portion that engages with the stepped portion of the shaft hole at the rear end, the tip of which protrudes from the insulator and is fitted into the small diameter hole of the shaft hole, and the flange portion engages with the stepped portion. a fixed center electrode, a terminal electrode whose rear end protrudes from the rear end of the insulator and is fitted into a large diameter hole of the shaft hole, and a terminal electrode provided between the center electrode and the terminal electrode of the shaft hole. In a spark plug formed by a conductive glass seal or a resistor sandwiched between the glass seal and the resistor, a local part extending from the step to the tip of the shaft hole has a diameter larger than the small diameter hole between the center electrode and the conductive glass seal. The structure is such that an annular gap is provided and a glass seal layer is formed in this annular gap.

[Effects of the invention] 1) By providing a glass seal layer between the tip of the flange of the center electrode and the insulator, a portion of the heat received by the center electrode from the combustion chamber of the engine is transferred to the center electrode→ The heat is transferred in the order of the glass seal layer and the insulator, increasing the width of heat transfer and improving the heat resistance of the plug.

2) By changing the size and shape of the glass seal layer, heat resistance can be adjusted depending on the purpose of use, and variations in heat resistance can be reduced and stabilized.

3) By providing the glass seal layer, the effect of preventing leakage of combustion gas is increased.

[Example] Next, a spark plug of the present invention will be described based on an example shown in the drawings.

In FIG. 1, 1 indicates a metal shell, 2 an insulator, and 3 a center electrode.

The main metal fitting 1 includes a threaded end portion 1A formed with a mounting screw 11 for screwing the spark plug of the present invention into a combustion chamber when the engine is installed, and an intermediate barrel having a large diameter through a gasket seat surface 12. It has a cylindrical shape consisting of a portion 1B and a hexagonal bolt-shaped rear end portion 1C, and the outer electrode 4 is welded to the tip, and the tip is bent inward to form the discharge side end of the center electrode 3. A discharge gap A is formed facing the portion 3a.

The insulator 2 has a cylindrical shape made of electrically insulating ceramic ceramic such as alumina, and has a tapered tip leg 2A with a small outer diameter exposed to the combustion chamber, and a tapered tip leg 2A that extends from the tip leg 2A through a step 21 to a middle outer diameter. The formed intermediate body part 2B, the collar part 2D formed with a large outer diameter through the stage 22 from the body part 2B, and the stage 2 from the collar part 2D.
The rear end portion 2C with a middle and outer diameter extended at 3 has a cylindrical shape and has an axial hole in the center. This shaft hole has a small-diameter hole 25 at the tip and a large-diameter hole 26 at the rear end, which are separated by a step 24, and a large-diameter hole larger than the small-diameter hole 25 in the range of 2 to 5 ml from the step 24 to the tip. An annular gap 27 having a smaller diameter than 26 was provided, and a glass seal layer 5 was provided within the annular gap. In this insulator, the distal end portions 2e of the distal leg portion 2A, body portion 2B, collar portion 2D, and rear end portion 2C are fitted into the metal shell 1, and a metal gasket 10 is inserted into the step 21.
0, the gap 15 between the insulator tip 2e and the rear end 1C of the metal shell 1C is filled with, for example, known talcum, and the rear end of the metal shell 1 is inserted inward through the metal ring 101. The metal shell 1 is fitted into the metal shell 1 by hard caulking or heat caulking.

The center electrode 3 is made of a nickel-based alloy such as Ni-3i-Cr-A1 or Ni-Qr-Fe containing a small amount of manganese, chromium, aluminum, silicon, etc., and has a copper core sealed inside. A rod-shaped member having a large outer diameter flange 31 is formed at the end thereof, and the flange 31 is inserted into the shaft hole of the insulator 2 so that the end on the tIi side protrudes from the tip leg 2A of the insulator. It is locked to the stepped portion 24.

The center electrode 3 in the shaft hole of the insulator 2 is placed on the shaft hole stepped portion 24 by fitting a glass ring for forming a glass seal layer 5 in advance directly under the flange thereof, or A glass material is coated by thermal spraying or the like and similarly inserted into the shaft hole.

Next, the conductive glass seal powder 6, the resistor powder 7, and the conductive glass seal powder 6 are respectively filled on the flange 31, the terminal electrodes 8 are inserted, and heat is applied to soften and melt the glass. The terminal electrode is pressed and sealed integrally within the shaft hole, and at the same time, the glass material is also melted to form the annular gap 27.
A glass seal layer 5 is formed inside. The material for the glass sealing layer 5 may be the same material with a composition ratio of 1 as the conductive glass sealing material (mixture of metal powder and glass powder), a material with less metal powder, or only glass.
Furthermore, an appropriate amount of ceramic powder may be mixed into these to match the thermal expansion suitability.

2 and 3 show other embodiments of the present invention, in which a plurality of vertical grooves 32 are provided on the outer periphery of the flange 31 of the center electrode 3, and FIGS. The figure shows still another embodiment of the present invention, in which the vertical groove 32 shown in FIG.
Instead, a spiral groove is formed on the outer periphery of the flange 31 of the center electrode 3. This vertical groove 32 or spiral groove 33 is also used as a flow path for forming the glass seal layer 5 within the annular gap 27, and is also useful for increasing the fixing strength of the center electrode. The glass seal layer 5 is manufactured as follows. That is, in the embodiments shown in FIGS. 2 and 4, the center electrode 3 is inserted into the small diameter hole 25 of the shaft hole of the insulator 2, and the flange 3 is
1 to the stepped portion 24, conductive glass seal powder 6
, resistor powder 7 and conductive glass seal powder 6 are sequentially filled and hot pressed through terminal electrodes, and at this time S
The electrically conductive glass seal powder 6 passes through the groove into the annular gap 27.
The glass seal layer 5 is formed by fluid filling into the glass seal layer 5.

[Brief explanation of drawings]

FIG. 1 is a side view including a partial cross section of a spark plug showing one embodiment of the present invention, and FIGS. 2 and 3, and 4 and 5 are top views showing other embodiments of the present invention. FIG. 6 is a partial side sectional view illustrating another configuration of the flange of the center electrode, and FIG. 6 is a partial side front view of a conventional spark plug of the same type as the present invention. In the figure 1... Metal shell 2... Insulator 3... Center electrode 5... Glass seal H6... Conductive glass seal powder 7... Resistor powder 8... Terminal electrode
24...Step part 25...Small diameter hole 2G...Large diameter hole 27...Annular gap 31...Flame part 32...Vertical groove 33...Spiral groove Fig. 1 Fig. 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1) A metal shell, an insulator fitted into the inner cavity of the metal shell, and having a shaft hole with a small diameter at the front end and a large diameter at the rear end through a step, and The center has a flange that engages with the step of the shaft hole at the end, the tip protrudes from the insulator and is fitted into the small diameter hole of the shaft hole, and the flange is locked to the step. an electrode, a terminal electrode whose rear end protrudes from the rear end of the insulator and is fitted into a large diameter hole of the shaft hole, and a conductive glass provided between the center electrode of the shaft hole and the terminal electrode. In a spark plug formed by a seal or the glass seal sandwiching and sealing a resistor, an annular gap is provided between the central electrode and the diameter larger than the small diameter hole in a local part extending from the stepped portion of the shaft hole to the tip;
A spark plug characterized in that a glass seal layer is formed in this annular gap. 2) The spark plug according to claim 1, wherein a plurality of longitudinal grooves or spiral grooves are formed on the outer periphery of the center electrode flange. 3) The length of the glass seal layer is 2 to 5 mm from the step of the shaft hole.
The spark plug according to claim 1, characterized in that the spark plug is formed in the range of mm.