JP2683108B2 - Seeds glow plug - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sheath glow plug used in a diesel engine.

[Prior Art] A conventional sheath glow plug includes a tubular metal shell formed of a low carbon steel, a stainless tube inserted into the metal shell, and a center electrode inserted into the tube and the metal shell. And an iron-chromium screw resistance wire connected between the tip of the center electrode and the inner bottom of the tube, and magnesia filled in the tube.

[Problems to be Solved by the Invention] However, in the conventional sheath glow plug, even if the tube generates heat, it is difficult for the heat to be transmitted to the surroundings, and it takes a long time for the temperature of the surrounding air containing the fuel to reach the ignition point. ,
There was a drawback that it took a long time to complete the explosion.

An object of the present invention is to provide a seed glow plug which has excellent ignitability to fuel and can shorten the time until the engine complete explosion.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a metal tubular metal shell, a heat-resistant metal tube mounted in the tubular metal shell with a tip protruding. A center electrode coaxially arranged in the heat-resistant metal tube and the tubular metal shell while maintaining electrical insulation, and an electric heating element connected between the tip of the center electrode and the inner bottom of the heat-resistant metal tube, In a sheath glow plug comprising an insulating powder filled in the heat-resistant metal tube, a rear end portion of the sheath glow plug is held in the tubular metal shell by abutting the heat-resistant metal tube, and the tip portion of the tubular main body is held. A structure was adopted in which the heat-resistant metal tube was surrounded by a heat-resistant metal cap having a plurality of ventilation holes formed on the outer circumference so as to project from the tip of the metal fitting and form a gap with the heat-resistant metal tube.

[Operation and Effect of Invention] (Operation) (1) When power is supplied between the metal shell and the center electrode, the electric heating element generates heat, and this heat is transmitted to the heat-resistant metal tube through the insulating powder and the temperature of the tube rises. .

In particular, since the gap is formed between the heat-resistant metal cap and the heat-resistant metal tube protruding from the tip of the tubular metal shell, the temperature rise of the heat-resistant metal tube is not hindered, and the temperature rising characteristics are good.

(2) The heat of the heat-resistant metal tube is mainly transferred to the heat-resistant metal cap by conduction, and the heat-resistant metal cap becomes hot. Further, the air in the gap receives heat radiation from both the heat-resistant metal tube and the heat-resistant metal cap, and the heat-resistant metal cap makes it difficult for the air to flow, so that the heat is efficiently conducted and the heat is quickly transferred into the gap. A hot air layer is formed on the surface.

(3) Fuel is injected in the form of mist. Most of the fuel hits the refractory metal cap, and the fuel obtains latent heat of vaporization and vaporizes.

(4) The vaporized fuel enters the interior through the ventilation hole and touches the high temperature air layer or the wall surface of the heat resistant metal tube to be ignited.

(Effect) Since a gap is formed in the entire area between the refractory metal cap protruding from the tip of the tubular metal shell and the refractory metal tube, the temperature of the tip of the refractory metal tube is not hindered by the refractory metal cap, Good temperature rise characteristics of the tube.

Further, the fuel hits the refractory metal cap, vaporizes and enters the inside through the ventilation hole, and comes into contact with the high temperature air layer and the wall surface of the refractory metal tube for ignition. In other words, since the vaporized fuel is in contact with the high temperature air layer and the heat-resistant metal tube, the contact efficiency is good, and the seed glow plug has an excellent fuel ignitability and a short time until the engine complete explosion.

[Embodiment] An embodiment of the present invention will be described with reference to FIG.

The sheath glow plug A includes a tubular metal shell 1, a tube 2 inserted into a tip portion 11 of the tubular metal shell 1, a center electrode 3 inserted into the tube 2, and a center electrode 3. A metal cylinder with a vent hole 61 having a bottom 72, the heating coil 4 being connected between the tip surface 31 of the tube 2 and the inner bottom 21 of the tube 2, and the insulating powder 5 filled in the tube 2. 6 surrounds the tip 22 of the tube 2.

The tubular metal shell 1 is formed of carbon steel, and the outer wall thereof is metal-plated if necessary. Mounting screw 12 on the outer circumference
And a hexagonal part 13 is provided. Further, a groove 14 for mounting the tube 2 is bored in the tip portion 11 of the tubular metal shell 1, and a conical seat surface 17 for keeping airtightness with the engine side is provided around the tip of the groove 14. ing.

The tube 2 (outer diameter 6 mm, wall thickness 0.6 mm) is made of heat-resistant stainless steel and has a bottomed cylindrical shape.

The center electrode 3 is formed of a conductive metal, and the tube 2
Also, it is inserted coaxially with the tubular metal shell 1 with electrical insulation. The tip portion 32 that is fitted into the tube 2 has a small diameter.

The heating coil 4 is formed by winding an iron chrome wire (wire diameter 0.3 mm) by screwing (winding diameter 3 mm).

The insulating powder 5 is a magnesia ceramic powder having electric insulation. Incidentally, 51 is an insulating packing.

The metal tube 6 is made of heat-resistant stainless steel made of the same material as the tube 2, the rear end portion 62 has the same inner diameter as the tube 2, and the tip portion 63 protruding from the tip of the tubular metal shell 1 is the tube 2 Has a slightly larger inner diameter.

The plurality of ventilation holes 61 are formed on the tip end 63 side of the metal cylinder 6. The rear end portion 62 has a size that fits exactly in the groove 14.

Next, a manufacturing method (main part) of the sheath glow plug B will be described.

(1) The outer wall of the rear end portion 62 of the metal tube 6 is brazed to the groove 14 of the tubular metal shell 1.

(2) The insulating powder 5 is enclosed, the heating coil 4 is attached, and the tube assembly in which the center electrode 3 is inserted is pressed into the tubular metal shell 1.

The center electrode 3 of the tube assembly is fixed to the tubular metal shell 1 in the hexagonal portion 13 by a fixing member (not shown) for electrical insulation.

(3) The insulating plate 15, the center electrode fixing nut 16, and the lead wire mounting nut (not shown) are mounted on the rear end side of the center electrode 3 to complete the process.

Next, the startability comparison test of the sheath glow plug A and its function and effect will be described.

The startability comparison test was carried out by mounting the seed glow plug A and the comparative product on a vehicle equipped with a swirl chamber engine and setting the environmental temperature to -25 ° C. The result is shown in FIG.
The horizontal axis of the graph in FIG. 2 is the current passage time, and the vertical axis is the engine speed.

The comparative product is the sheath glow plug A with the metal cylinder 6 removed.

The time required for the initial explosion is 3 seconds for the comparative product and 1 second for the sheath glow plug A. The time until complete explosion is 55 seconds for the comparative product, whereas it is 40 seconds for the invention product. For this reason, the use of the sheath glow plug A improves the ignitability of the fuel and reduces the time required for the engine to fully explode by 15
It can be shortened by about a second.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the sheath glow plug B of this embodiment, instead of the metal cylinder 6, a bottomed cylinder 7 with a vent hole 71 made of the same material as the metal cylinder 6 is used, and a gap is similarly provided between the inner diameter of the tip portion 74 and the tube 2. Is formed.

The bottomed cylinder 7 is inserted by inserting the tube assembly into the tubular metal shell 1 by press fitting and then press fitting it into the groove 14.

The sheath glow plug B of this embodiment is easy to manufacture because the bottom end 72 can be easily hit to press the rear end portion 73 into the groove 14.

In addition, since the air flow in the swirl chamber does not enter from below the bottomed cylinder 7, the high temperature air layer is excellently retained, and the engine startability is slightly better than that of the sheath glow plug A.

 The present invention includes the following embodiments in addition to the above embodiments.

The material of the tube 2 may be Hastelloy (trademark) or the like, the outer diameter is preferably 3 mm to 6 mm, the wall thickness is 0.4 mm to 1.2 mm, and the tip may be tapered.

b. The heating coil 4 may be made of nichrome, nickel, tungsten, molybdenum, etc., and the wire diameter is 0.2m.
It is preferable that m to 0.6 mm and the winding diameter be 2 mm to 4 mm, and the winding pitch may be different. Further, as the heating coil 4, iron chromium or nichrome having a constant resistance temperature coefficient may be used, and a control coil such as nickel or iron having a positive high resistance temperature coefficient may be connected in series to the heating coil. .

c. The shape, size, number and position of the ventilation holes 61, 71 may be arbitrary.

d. The material of the metal cylinder 6 and the bottomed cylinder 7 may be heat-resistant metal, and the gap between the metal cylinder 6 and the bottomed cylinder 7 and the tube 2 may be arbitrary. The rear end of 7 may be welded to the tube 2.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a sheath glow plug according to an embodiment of the present invention, and FIG. 2 is a graph showing the results of a startability comparison test of the glow plug. FIG. 3 is a partial sectional view of a sheath glow plug according to a second embodiment of the present invention. In the figure, A, B ... Sheath glow plug, 1 ... Cylindrical metal shell, 2 ... Tube (heat-resistant metal tube), 3 ... Center electrode, 4 ... Heating coil (electric heating element), 5 ... Insulation Powder, 6 ... Metal cylinder (heat-resistant metal cap), 7 ... Bottomed cylinder (heat-resistant metal cap), 22 ... Tip (metal tube), 62, 73 ... Rear end, 70 ... Tip, 61, 71 ... Ventilation holes

Claims (1)

(57) [Claims] 1. A tubular metal shell made of metal, a heat-resistant metal tube mounted in the tubular metal shell with a tip protruding, and a heat-resistant metal tube coaxially and electrically insulated from the metal shell. A center electrode disposed so as to be kept; an electric heating element connected between the tip of the center electrode and the inner bottom of the heat-resistant metal tube; and an insulating powder filled in the heat-resistant metal tube. In the sheath glow plug, the rear end of the sheath glow plug contacts the heat-resistant metal tube and is held in the tubular metal shell, and the tip portion projects from the tip of the tubular metal shell to form a gap with the heat-resistant metal tube. As described above, the sheath glow plug is characterized in that the heat-resistant metal tube is surrounded by a heat-resistant metal cap having a plurality of ventilation holes on the outer circumference.