JPH0419987A - Ignition plug equipped with heater - Google Patents

Abstract

PURPOSE:To enhance the strength and voltage withstand property of an insulator as well productivity of an ignition plug by sintering a heater independently of an insulator, and providing the heater on a tubular heater element mounted on the surface of a long leg portion. CONSTITUTION:A heater element 10 in which a heater 14 is mounted is formed by sintering independently of an insulator 3 and is then mounted to the long leg portion 8 side of the insulator 3 formed by sintering independently of the heater element 10. As a result, productivity of the insulator 3 becomes excellent. Since the insulator 3 is sintered while not having the heater 14, the insulator 3 can be sintered at high temperatures as is a normal ignition plug not having the heater 14. As a result, the strength and voltage withstand property of the insulator 3 are heightened as compared with conventional insulators sintered simultaneously with heaters. Furthermore, mounting of the sintered heater element 10 to the sintered insulator 3 reduces the probability that the insulator is cracked or damaged when the heater element 10 is mounted thereto.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to internal combustion engines that are equipped with a heater that generates heat when energized in the long leg portion, and that prevents contamination around the long leg portion, and that uses non-ignitable fuel. This invention relates to a spark plug with a heater that is used to improve low-temperature starting performance.

[Prior art] As an example of a conventional spark plug with a heater,
The technique disclosed in Japanese Patent No. 239 is known.

This technique provides a ceramic heater on the insulator by wrapping a mixed paste of metal powder and ceramic powder around the long legs of the insulator and sintering it together with the insulator.

In this manner, conventional heaters have been constructed by attaching an unsintered ceramic heater to an unsintered insulator, and then sintering the ceramic heater simultaneously to integrate the heater into the insulator.

[Problems to be Solved by the Invention] However, since the sintering temperature of an insulator sintered together with an unsintered ceramic heater is matched to that of the ceramic heater, the sintering temperature becomes low. As a result, an insulator provided with a heater has lower strength and voltage resistance than a spark plug without a heater.

In addition, the work of attaching an unsintered ceramic heater to an unsintered insulator is likely to cause cracks or damage to the insulator or ceramic heater because both are soft, resulting in poor productivity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark plug with a heater that has high insulating strength and voltage resistance, and has excellent productivity.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following technical means.

The ignition plug with a heater includes a center electrode to which a high voltage is applied, an insulator that insulates and holds the center electrode, and a cylindrical metal shell that holds the insulator. A heater that generates heat when energized is installed in the section.

The heater is sintered and formed separately from the insulator, and is provided in a cylindrical heater element that is attached to at least the surface of the long leg portion.

[Operation and Effects of the Invention] The heater is sintered and formed separately from the insulator as a heater element, and then attached to the long leg portion of the insulator which is also sintered and formed separately from the heater element.

In this way, since the insulator is sintered without a heater, the sintering temperature of the insulator can be made higher than when the insulator is sintered with a heater.

As a result, the strength and voltage resistance of the insulator are higher than those of conventional insulators that are co-sintered with the heater.

Furthermore, since the sintered heater element is attached to the sintered insulator, the probability of cracking or damage occurring when the heater element is attached can be suppressed to a low level.

Also, compared to attaching an unsintered soft ceramic heater to a conventional unsintered soft insulator,
Good workability.

As a result, the heater-equipped spark plug of the present invention has excellent productivity.

[Embodiment] Next, an embodiment of the heater-equipped spark plug of the present invention will be described with reference to the drawings.

(Configuration of Example) FIG. 1 shows a sectional view of a spark plug 1 with a heater.

The heater-equipped spark plug 1 includes a center electrode 2 to which a high voltage is applied, an insulator 3 that insulates and holds the center electrode 2, and a cylindrical metal shell 4 that holds the insulator 3.

The center electrode 2 is a heat-resistant metal body (for example, nickel alloy) that protrudes from the insulator 3 in the ignition part 5, and is electrically connected to a high voltage connection terminal 6 to which a high voltage is applied from an ignition device (not shown). There is.

The insulator 3 is a ceramic sintered body made of alumina or the like, and includes a body part 7 held by the metal shell 4, a long leg part 8 having a smaller diameter than the body part 7 on the side of the ignition part 5 from the body part 7, and a high voltage cord. It consists of a head 9 which is covered with a cap. In addition, the body part 7
A flange portion 7a is formed on the head 9 side of the holder 7a so as to protrude over the entire circumference.

The insulator 3 also includes a heater element 10 shown in FIG.
Equipped with The heater element 10 is a cylindrical ceramic sintered body that is sintered and formed separately from the insulator 3 and attached to the leg length 8 side of the insulator 3. Large diameter part 1″L.

and a small diameter part 12 which is smaller in diameter than the large diameter part 11 and which is attached around the leg length part 8. A stepped portion 13 is formed between the large diameter portion 11 and the small diameter portion 12.

Further, a heater 14 that generates heat when energized is embedded inside the small diameter portion 12. This heater 14 is, for example, a ring-shaped metal heater made of a high-melting point metal (chromium, platinum, or an alloy containing these as main components), but for example, the small diameter portion 12 is entirely or partially made of ceramic mixed with metal powder. It may be formed using a ceramic heater manufactured by.

Further, the large diameter portion 11 has two parts for energizing the heater 14.
Book wiring 15 and 16 are buried. In addition, large diameter part 1
The two wires 15 and 16 in the large diameter portion 11 are respectively connected to heater energizing electrodes 17 and 18 provided at opposite positions at the ends of the large diameter portion 11 .

The metal shell 4 includes a threaded portion 19 that is screwed into the engine, a bolt portion 20 having a hexagonal cross section, and this bolt portion 20.
It is composed of a cylindrical portion 21 extending around the collar portion 7a of the insulator 3.

An inner periphery protrusion 23 is provided on the intermediate inner periphery of the threaded portion 19 against which the stepped portion 13 of the insulator 3 is pressed via the backing 22.
are provided all around.

Further, the end of the cylindrical portion 21 is provided with a caulking portion 25 for caulking the flange portion 7a via a caulking ring 24 and fixing the insulator 3 to the metal shell 4 with the heater element 10 attached.

Furthermore, an outer electrode 26, which faces the center electrode 2 with a spark gap in between, is fixed to the end of the threaded portion 19 by a joining method such as welding.

Furthermore, heater energization terminals 27 and 28 are attached to opposing positions of the cylindrical portion 21. The heater energizing terminals 27 and 28 are metal bodies that come into contact with the heater energizing electrodes 17 and 18 of the heater element 10 on their inner surfaces, and are arranged so that they are not electrically connected to the nine-piece musical instrument 4.
It is attached to the metal shell 4 via the insulator 3. Note that the heater energization terminals 27 and 28 are connected to a heater energization cord provided on a high voltage cord (not shown).

(Operation of the embodiment) Next, the operation of the heater-equipped spark plug 1 will be briefly explained.

When the heater energizing terminals 27 and 28 are energized via a high voltage cord (not shown), the heater 1 embedded in the small diameter portion 12 of the heater element 1o attached around the long leg portion 8 is activated.
4 is energized via heater energizing electrodes 17 and 18 and wiring 15 and 16.

When the heater 14 is energized, it generates heat and burns off the carbon attached around the long leg portion 8. Alternatively, it improves the low-temperature startability of an internal combustion engine that uses a fuel that is difficult to ignite.

(Effects of Example) The heater element 1o containing the heater 14 is sintered and formed separately from the insulator 3, and then attached to the long leg portion 8 side of the insulator 3, which is sintered and formed separately from the heater element 10. be done. That is, since the insulator 3 is sintered and formed without the heater 14, the insulator 3 can be designed and manufactured with the same specifications as a normal spark plug without the heater 14. As a result, the productivity of the insulator 3 is excellent.

Furthermore, since the insulator 3 is sintered without the heater 14, the insulator 3 can be sintered at a high temperature similar to that of a normal spark plug without the heater 14. As a result, the strength and voltage resistance of the insulator 3 are higher than those of conventional insulators that are co-sintered with the heater.

Furthermore, since the sintered heater element 10 is attached to the sintered insulator 3, the probability that cracks or damage will occur when the heater element 10 is attached can be suppressed to a low level.

Furthermore, compared to the conventional case of attaching an unsintered soft ceramic heater to an unsintered soft insulator, the installation is easier and the workability is better. As a result, the heater-equipped spark plug 1 of the present invention has excellent productivity.

(Modification) In the above embodiment, an example was shown in which the heater was energized through the metal shell, but the heater may be energized by wiring buried in the insulator.

Alternatively, one of the heater current supply terminals may be grounded to the metal shell.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the ignition plug with a heater, and a perspective view of the heater element. In the figure: 1...Spark plug with heater 3...Insulator 8...Long leg portion 10...Heater element 14...Heater Figure 2 shows H2...Center electrode 4...Metal shell

Claims (1)

[Claims] 1) A center electrode to which a high voltage is applied, an insulator that insulates and holds the center electrode, and a cylindrical metal shell that holds the insulator, the insulator In the ignition plug with a heater, the long leg portion of the heater is provided with a heater that generates heat when energized, wherein the heater is formed by sintering separately from the insulator, and is attached to at least a surface of the long leg portion. An ignition plug with a heater, characterized in that it is provided in a shaped heater element.