JPH07301417A - Heating wire of glow plug - Google Patents

Abstract

PURPOSE:To obtain a heating wire which enhances the uniform and quick heating properties of a ceramic heating element of a glow plug. CONSTITUTION:A metallic wire is bent at a middle bend part 23 and formed into a U-shape so that the arms of the U-shape are kept from contacting, both ends are arranged parallel and connected to a power source to form a pair of straight lead parts 21 and 21a. The part adjacent to the middle bend part 23 is coiled with the lead part 21 as the coil axis to form double heating elements 22 and 22a which are slightly shifted each other toward the coil axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-regulating glow plug for assisting vaporization and ignition of liquid fuel at the time of starting a diesel engine or the like, and more particularly to a heating wire of a glow plug embedded inside a ceramic molded product. is there.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional glow plug mounted on a diesel engine or the like has a structure in which a heating wire 2 is embedded in a ceramic heating element 1. That is, the ceramic heating element 1 is joined to the metal protective cylinder 3 fitted to the tip or the bottom of the metal plug body 4 having the screw portion 4a by the metallizing joining method or the like at the fitting portion 3a. The ceramic heating element 1 is arranged so as to face the pre-combustion chamber of the engine, and contributes to the ignition and combustion of fuel. The heating wire 2 embedded in the ceramic heating element 1 has one end 2b connected to the electrode rod 8 via the base 5, the terminal 6 and the spiral resistance wire 7, and the other end 2a via the protective tube 3. It is connected to the metal plug body 4.

The electrode rod 8 is screwed into an insulating lid 12 fitted to the base end of the metallic plug body 4, and is fastened by a nut 13 screwed into the screw portion 8a. The resistance wire 7 is inserted into the protective cylinder 9 fitted to the metal plug body 4, and the inner space is filled with the insulator 10. The resistance value of the resistance wire 7 increases as the temperature rises due to energization, and the current to the heating wire 2 is reduced to prevent the heating wire 2 from overheating.

In the conventional glow plug described above, in order to make the heating wire 2 embedded in the ceramic heating element 1, the ceramic heating element 1 is divided into a pair of half-moon shaped sections as shown in FIG. It is composed of a body 1a, and a heating wire 2 is sandwiched between a pair of divided bodies 1a, and sintered by a hot press method. Therefore, the distance (indicated by an arrow) between the heating wire 2 and the outer surface 1b of the ceramic heating element 1 becomes uneven,
There has been a problem that the outer surface 1b of the ceramic heating element 1 is not uniformly and quickly heated.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a glow plug heating wire in which the uniform heating property and the rapid heating property of the ceramic heating element are improved.

[0006]

In order to achieve the above object, the structure of the present invention is such that one metal wire is bent in a U-shape from an intermediate bent portion so as not to contact each other, and both end sides are aligned in parallel. Forming a pair of straight lead portions connected to the power source, and winding a portion adjacent to the intermediate bent portion in a spiral shape having the lead portion as a winding axis so as to be slightly offset from each other in the winding axis direction. The heavy heat generating part is formed.

[0007]

The spiral heating part of the heating wire made of tungsten, tungsten alloy, etc. contacts the inner surface of the elongated cup-shaped outer cylinder made of ceramics, so the distance between the heating part of the heating wire and the outer surface of the outer cylinder is the same. Equal to direction. Therefore,
The heat-generating portion of the heat-generating wire covers the entire circumference and heats the outer surface of the outer cylinder quickly and uniformly.

[0008]

1 is a front sectional view of a glow plug having a heating wire according to the present invention, and FIG. 2 is an enlarged plan sectional view taken along line 2A-2A of FIG. In the glow plug according to the present invention, the electrode rod 42 is provided at the base end portion or the upper end portion of the cylindrical metal plug body 47, and the ceramic heating element 30 is provided at the tip end portion or the lower end portion.
, The lower end of the electrode rod 42 is supported by an annular insulator 48 inside the metal plug body 47, and is connected to one end of the heating wire 20 of the ceramic heating element 30. The metal plug main body 47 has a threaded portion 47b formed at an intermediate portion, which is fastened to a threaded hole in a wall portion of a pre-combustion chamber of an engine by engaging a tool with a hexagonal head portion 47a, and a ceramic heating element 30 at a lower end. Is projected into the pre-combustion chamber. Electrode rod 42
Has a threaded portion 42a at its upper end, and is screwed into the inside of an insulating cylinder 46 made of Bakelite or the like, and then fitted into the upper end portion of the metal plug body 47. The flange 46a at the upper end of the insulating cylinder 46 is reinforced by the metal ring 45, and is superposed on the head portion 47a of the metal plug body 47, and by the nut 43 screwed to the screw portion 42a via the insulating seat plate 44. It is concluded. In the ceramic heating element 30, the outer cylinder 31 is fitted to the lower end portion of the metal plug body 47, and the fitting portion is joined by a metallizing method or the like.

According to the present invention, the ceramic heating element 30.
Is a double heating wire 20 formed by molding a metal wire of tungsten, a tungsten alloy or the like inside a slender cup-shaped outer cylinder 31 made of dense silicon nitride that has been fired in advance, and preferably a double heating wire. 20 is coated or fleshed with ceramics 32 in advance so that they do not contact each other, and then inserted, and the inner space of the outer cylinder 31 is filled with powdery or slurry ceramics 32 having no shrinkage upon firing, It is baked and integrated at a predetermined temperature (for example, 1200 to 1500 ° C.).

As shown in FIG. 3, the heating wire 20 is made of a metal wire made of tungsten and having a wire diameter of about 0.2 mm.
Bend from 3 into a U shape and align both ends in parallel so that they do not touch each other to form a double line. A portion of the double wire adjacent to the intermediate bent portion 23 is spirally wound to form heat generating portions 22 and 22a having a required length and a winding diameter, and both end sides are extended straight to obtain a required length. The lead portions 21 and 21a are formed. The heat generating portions 22 and 22a have the same winding diameter and pitch. As shown in FIGS. 1 and 2, the heating wire 20 is inserted so that the spiral heating portions 22 and 22 a are in contact with the inner surface of the outer cylinder 31, and the lead portion 21 passing through the axis of the outer cylinder 31 is connected to the electrode rod 42. , And the lead portion 21a is connected to the metal ring 49 fitted to the metal plug body 47.

In the above structure, the electrode rod 42 is a terminal (for example, + terminal) of the power source battery by a conductor wire (not shown).
On the other hand, the metal plug body 47 is connected to the terminal (for example, the negative terminal) of the power source battery via the vehicle body. At the time of starting the engine, the electrode rod 42 and the lead portion 2 are removed from the power source battery.
1a, heat generating parts 22a and 22, lead part 21, metal ring 4
9. When the metal plug body 47 is energized, the heat generating portion 2
The ceramic heating elements 30 protruding into the pre-combustion chamber heat and ignite the fuel.

The heat generating portions 22, 22a of the heat generating wire 20 are in contact with the inner surface of the thin outer cylinder 31, and the heat generating portions 22, 22a heat the outer surface of the outer cylinder 31 quickly and uniformly over the entire circumference. Therefore, ignition of the fuel can be obtained within a short time. Exothermic line 2
The electric resistance of the heat generating parts 22 and 22a of 0 increases as the temperature increases, limiting the current flowing to the heat generating parts 22 and 22a, and the temperature required for the heat generating parts 22 and 22a to ignite fuel (for example, about 900 ° C.). Prevent over.

Since the outer cylinder 31 made of silicon nitride as the ceramics is filled with the non-shrinkable ceramics 32, the outer cylinder 31 and the internal ceramics 32 are sintered together, and there is a risk that the outer cylinder 31 and the internal ceramics 32 are cracked at the time of firing or energization. No, heating line 20
Is embedded between the outer cylinder 31 and the ceramics 32 without a gap, so that the heat conductivity from the heating wire 20 to the outer cylinder 31 is excellent.

As shown in FIG. 4, in the heating wire 20, the middle portion of the pair of lead portions 21 and 21a is spirally wound around the lead portion 21a as a winding axis, and is slightly offset in the winding axis direction. The resistor portions 24 and 24a are separately formed, and the resistor portion 2
4, 24a may be arranged inside the metal plug body 47. That is, the heat generating wire 20 limits the current flowing to the heat generating portions 22 and 22a and prevents the heat generating portions 22 and 22a from being overheated.
It is molded away from the spiral heating portions 22 and 22a by 25a.

[0015]

As described above, according to the present invention, one metal wire is bent in a U-shape from the intermediate bent portion so as not to come into contact with each other, and both ends are aligned in parallel and connected to the power source straight.
A pair of lead portions are formed, and a portion adjacent to the intermediate bent portion is spirally wound around the lead portion as a winding axis to form a double heating portion that is slightly biased from each other in the winding axis direction. It is easy to insulate the heating wires from each other and to insert them into the outer cylinder, and the heat generating part can be arranged so as to contact the inner surface of the outer cylinder, thus heating the outer surface of the outer cylinder quickly and uniformly. it can.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view of a glow plug including a heating wire according to the present invention.

2 is a plan sectional view taken along the line 2A-2A in FIG.

FIG. 3 is a front view of a heating wire of a glow plug according to the present invention.

FIG. 4 is a front view of a metal wire of a glow plug according to a modified embodiment of the present invention.

FIG. 5 is a front sectional view of a conventional glow plug.

6 is a cross-sectional plan view taken along the line 6A-6A in FIG.

[Explanation of symbols]

20: Heat generating wires 21, 21a: Lead portions 22, 22
a: Heat generating part 23: Intermediate bending part

Claims (3)

[Claims] 1. A metal wire is bent in a U-shape from an intermediate bent portion so as not to come into contact with each other, and both ends are aligned in parallel to form a pair of straight lead portions connected to a power source. A heating wire for a glow plug, characterized in that a portion adjacent to the intermediate bent portion is spirally wound around the lead portion as a winding axis to form a double heating portion slightly offset from each other in the winding axis direction. . 2. A resistance part that is slightly deviated in the winding axis direction from each other is formed by winding an intermediate part of the pair of lead parts in a spiral shape having the lead parts as a winding axis. Glow plug heating wire. 3. The heating wire of the glow plug according to claim 1, wherein the metal wire is tungsten or a tungsten alloy.