JPH0422087A - Spark plug with heater - Google Patents

Abstract

PURPOSE:To improve heating efficiency in a leg length part with a heater with the escape of heat generated with the heater to a principal fitting restrained by forming a packing, for fixing an insulating body insulatingly retaining an electrode and the principal fitting holding the insulating body, with a material having heat resistance and low heat conductivity. CONSTITUTION:A packing 22 is a ring formed with a material, having heat resistance and low heat conductivity, for preventing the escape of the heat of a leg length part 8 to a principal fitting 4, and is imposed between the different level part 13 of an insulating body 3 and the inner peripheral projection of the principal fitting 4. Ceramic fiber such as glass fiber, Mn, and Ti, etc., are cited as material for the packing 22. This can improve hating efficiency heating the leg length part 8 with a heater 14, and the temperature-rise ratio and the temperature of the leg length part 8 better than before by using the heater 14 having the same calorific value as usual.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug with a heater, which has a long leg portion that is equipped with a heater that generates heat when energized.

[Prior Art] A spark plug with a heater is equipped with a heater that generates heat when energized around or inside the long legs, and is used to prevent contamination around the long legs and for internal combustion engines that use hard-to-ignite fuel. It is used to improve low-temperature startability.

On the other hand, the long leg portion and the metal shell around the long leg portion are exposed to the combustion chamber of the internal combustion engine. For this reason, packing is arranged on the long leg side between the metal shell and the insulator to prevent air-fuel mixture or combustion gas from blowing through between the metal shell and the insulator. Conventionally, this packing has been made of heat-resistant materials with high thermal conductivity, such as copper and iron, in order to improve heat transfer from the long legs.

[Problems to be Solved by the Invention] However, in conventional spark plugs with heaters, when the heater is energized and generates heat, the rate at which the heat generated by the heater escapes to the metal shell through the packing with high thermal conductivity is low. It gets expensive.

For this reason, in the conventional spark plug with a heater, the heating efficiency with which the heater heats the long leg portion is low. As a result, in order to raise the temperature of the long leg portions, a heater with a large amount of heat must be used, which poses a problem in that power consumption is large when the heater is energized.

An object of the present invention is to provide a spark plug with a heater that suppresses the heat generated by the heater from escaping to the metal shell and improves the heating efficiency of the long leg portion by the heater.

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

The heater-equipped spark plug 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. Further, the insulator and the metal shell are fixed via packing. Further, the long leg portion of the insulator is provided with a heater that generates heat when energized.

The packing is made of a material that is heat resistant and has low thermal conductivity.

[Operations and Effects of the Invention] By forming the packing from a material with low thermal conductivity, the amount of heat transmitted from the long leg portion to the metal shell via the packing is reduced compared to the conventional case.

In other words, when the heater is energized and generates heat, it is possible to suppress the heat generated by the heater from escaping to the metal shell via the packing compared to the conventional method.

As a result, the heating efficiency with which the heater heats the long leg portion is higher than before, and if a heater with the same calorific value as the conventional heater is used, the temperature rise rate of the long leg portion and the temperature of the long leg portion will be lower than before. It gets expensive.

Furthermore, the amount of heat generated by the heater can be reduced if the same performance as the conventional one is obtained. Therefore, power consumption of the heater can be suppressed.

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

(Refinement of Examples) 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 protruding 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). ing.

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 head 9 and protrudes over the entire circumference.

The insulator 3 also includes a heater element 10 . The heater element 10 is formed separately from the insulator 3 and is a cylindrical ceramic sintered body attached to the long leg portion 8 side of the insulator 3. A diameter portion 11 and a small diameter portion 12 having a smaller diameter than the large diameter portion 11 arranged around the long leg portion 8 are provided.6 And between the large diameter portion 11 and the small diameter portion 12, a stepped portion 13 is formed. There is. In addition, the small diameter portion 12 includes a heater 1 that generates heat when energized.
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).
For example, part or all of the small diameter portion 12 may be formed of a ceramic heater made of ceramic mixed with metal powder.

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 one threaded portion that is screwed into an engine (not shown), a bolt portion 20 having a hexagonal cross section, and a cylindrical portion 21 extending from the bolt portion 20 around the collar portion 7a of the insulator 3. has been done.

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 packing 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 holding the insulator 3 with the metal shell 4.

Furthermore, an outer electrode 26, which faces the center electrode 2 with a spark gap in between, is fixed to one end of the threaded portion 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 connected via the insulator 3 so as not to be electrically connected to the metal shell 4. It is attached to the main metal fitting 4. Note that the heater energization terminals 27 and 28 are connected to a heater energization cord provided on a high voltage cord (not shown).

The packing 22 is a ring made of a material that is heat resistant and has low thermal conductivity in order to prevent heat from the long leg portion 8 from escaping to the metal shell 4. and the inner peripheral protrusion of the metal shell 4. Specifically, the thermal conductivity applicable to the packing 22 is 0.10 cal/ct sec'c or less,
Examples of such materials include ceramic fibers such as glass fibers, Mn, and Ti.

(Operation of Example) Next, FIG. 2 shows the change in temperature of the long leg portion 8 when the heater 14 is energized.

Solid line A indicates that the packing 22 is made of Ti. Moreover, solid line B is a conventional technology shown for reference, and copper is used as the packing material. The packing 22 used in the solid line A and the packing used in the solid line B have the same shape and the same dimensions, and the other experimental conditions are the same.9 (Effects of Example) As shown in Figure 2. The present invention indicated by solid line A was applied to -
When the heater 14 is energized, the ignition plug 1 with the tab 1 heats the long leg portion 8 more quickly and to a higher temperature than the solid line B of the prior art.

As a result, when the heater-equipped spark plug 1 is used for the purpose of burning off carbon attached to the long leg portion 8, the carbon can be sintered quickly and reliably, and the ignitability of the spark plug can be improved.

Further, when the heater-equipped spark plug 1 is used for the purpose of improving low-temperature startability of an internal combustion engine that uses a fuel that uses difficult-to-ignite fuel, it is possible to quickly bring the internal combustion engine into a state where it can be started.

Furthermore, if the performance of the heater 14 is the same as the conventional one, the amount of heat generated by the heater 14 can be reduced.

As a result, power consumption can be reduced and, for example, when used in a car, the electrical load on the battery can be kept small.

(Modification) In the above embodiment, an example was shown in which the heater was formed separately as a heater element and was mounted around the long leg portion, but the heater may be provided directly on the long leg portion.

In that case, the heater may be on the surface of the long leg portion or may be embedded inside the long leg portion.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the ignition plug with a heater, and FIG. 2 is a graph showing the relationship between the temperature of the long leg portion and time when the heater is energized. In the diagram: 1. - Evening spark plug 2. Center electrode 3.. Insulator 4. Metal shell 8.. Long leg part
14... Heater 22... Packing

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 and the metal shell are fixed via a packing, and the heater-equipped spark plug is provided with a heater that generates heat when energized in the long leg portion of the insulator, wherein the packing is heat resistant and heat conductive. An ignition plug with a heater characterized in that it is formed of a material with a low heat exchange rate.