JPH0422088A - Spark plug with heater - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the electrification failure of a heater due to the oxidation of an electrification passage by providing a small diameter tube part on the side where a plug cap is covered, and preparing an electrificating terminal, electrifying the heater, to each of plane parts provided on parts facing the small diameter tube part. CONSTITUTION:A plug cap 9 of a part covering a tube part 22 has a hollow patt having the inner periphery of an oval cross section, and electrifying contact terminals 38 and 39, connected to power source wiring 34 or earth wiring 35, are provided on faced surfaces 36 and 37 inserted in plane parts 23 and 24 of the tube part 22. Electrifying contact terminals 38 and 39 and electrifying terminals 25 and 26 are electrically connected by covering a spark plug 1 with a heater with the plug cap 9, and a heater 15 can be electrified via electrifying electrodes 18 and 19 and wiring 16 and 17 from the power source wiring 34 and the earth wiring 35. This can eliminate the exposure of a contact part to an engine exhaust gas to restrain the occurrence of electrification failure due to the oxidation of the electrification passage of the heater 15.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a heater that generates heat when energized in the long leg portion, and is used to prevent contamination around the long leg portion, and for internal combustion engines that use ignition-resistant fuel. This invention relates to a spark plug with a heater that is used to improve low-temperature starting performance.

[Prior Art] A heater in a heater-equipped spark plug is provided in a long leg portion of an insulator, and a means for energizing the heater will be described below. In the conventional energizing means of a heater, a positive electrode serving as a power source is provided on an insulator or a metal shell, and is connected to a lead wire provided on a plug cap. Further, the negative electrode of the heater is connected to the metal shell, and is grounded by fastening the metal shell to the engine.

Note that the negative electrode of the heater and the metal shell are connected through a backing placed between the insulator and the metal shell.

[Problems to be Solved by the Invention] However, the backing may be provided to prevent air-fuel mixture or combustion gas from blowing between the insulator and the metal shell from the side of the long leg disposed inside the engine combustion chamber. be. The backing is therefore exposed within the engine combustion chamber.

As a result, oxidation and corrosion are likely to occur at the contact portion between the backing and the insulator, and at the contact portion between the backing and the metal shell, and there is a possibility that the negative electrode of the heater may cause a conduction failure.

An object of the present invention is to provide a spark plug with a heater that can reliably energize the heater.

[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 insulator is provided with an energizing electrode that energizes the heater, on an inner periphery of and facing the metal shell that holds the insulator.

Further, the metal shell includes a cylindrical portion that has a smaller diameter than the hexagonal portion and covers the current-carrying electrode, on a side on which the plug cap is covered than the hexagonal portion for tightening the metal shell. The cylindrical portions each have a flat portion at opposing positions, and each of the flat portions is provided with a current-carrying terminal electrically connected to the current-carrying electrode and insulated from the metal shell.

[Operation and Effects of the Invention] The present invention provides a cylindrical portion having a smaller diameter than the hexagonal portion on the side covered by the plug cap than the hexagonal portion, and each of the flat portions provided on the opposing portions of the cylindrical portion. is equipped with an energizing terminal for energizing the heater. In other words, the current supply path of the heater does not include a portion disposed in the combustion chamber as in the conventional case.

As a result, the occurrence of heater energization failures due to oxidation of the heater's energization path can be suppressed compared to the prior art.

[Example] Next, an example 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 central fii 2 is a heat-resistant metal body (for example, a nickel alloy) that protrudes from the insulator 3 at the ignition part, and has a high voltage connection terminal 6 to which a high voltage is applied from an ignition device (not shown) via a high voltage cable 5. electrically connected to.

The insulator 3 is a ceramic sintered body such as alumina, and includes a body 7 held by the metal shell 4, a long leg portion 8 with a smaller diameter than the body 7 on the ignition part side of the body 7, and a plug cap 9. It consists of a head 10 that is covered with a head. Note that a flange portion 7a is formed on the head portion 10 side of the body portion 7 so as to protrude over the entire circumference.

The insulator 3 also includes a heater element 11 . The heater element 11 is a cylindrical ceramic sintered body that is sintered separately from the insulator 3 and installed on the leg length 8 side of the insulator 3. Large diameter portion 12 and large diameter portion 1 attached around leg length portion 8
A small diameter portion 13 having a smaller diameter than 2 is provided. A stepped portion 14 is formed between the large diameter portion 12 and the small diameter portion 13.

Further, a heater 15 that generates heat when energized is embedded inside the small diameter portion 1B. This heater 15 is, for example, a ring-shaped metal heater.
All or part of 3 may be formed by a ceramic heater made of ceramic mixed with metal powder. In addition, the large diameter portion 12
There are two wires 16.1 for energizing the heater 15.
7 are buried. Note that the two wires 16 and 17 in the large diameter portion 12 are respectively connected to current-carrying electrodes 18 and 19 provided at opposing positions at the ends of the large diameter portion 12.

The metal shell 4 includes a threaded portion 20 that is screwed into the engine, and a hexagonal portion 21 having a hexagonal cross section as shown in FIG.
, a cylindrical portion 22 having a smaller diameter than the hexagonal portion 21 and provided on the side covered by the plug cap 9.

The cylindrical portion 22 extends further around the flange portion 7a of the insulator 3 than the hexagonal portion 21, and covers one current-carrying electrode 18.

At opposing positions around the cylindrical part 22, there are flat parts 2, respectively.
3.24 is formed, and as shown in FIG. 3, the cross section has a substantially oval shape. This plane portion 23.24 is provided with energizing terminals 25.26.

The current-carrying terminals 25 and 26 are metal bodies that come into contact with the current-carrying electrodes 18 and 19 on their inner surfaces, and are attached to the metal shell 4 via an insulating material 27 so as not to be electrically connected to the metal shell 4. It is being

An inner periphery protrusion 29 is provided on the intermediate inner periphery of the threaded portion 20 against which the stepped portion 14 of the insulator 3 is pressed via the backing 28.
are provided all around.

Further, the end of the cylindrical portion 22 is provided with a caulking portion 31 for caulking the flange portion 7a via a caulking ring 30 and fixing the insulator 3 to the metal shell 4 with the heater element 11 attached.

Furthermore, an outer electrode 32, which faces the center electrode 2 with a spark gap in between, is fixed to the end of the threaded portion 20 by a joining method such as welding.

Next, the plug cap 9 attached to the heater-equipped spark plug 1
Explain.

The plug cap 9 is placed over the head 10 and the cylindrical portion 22, and is made of an insulating material such as rubber or plastic. This plug cap 9 is provided at the end of the high voltage cable 5 that is connected to the ignition device, and when the plug cap 9 is attached to the heater-equipped spark plug 1, the end of the high voltage cable 5 is exposed to high voltage. Contact with the connection terminal 6.

A heater 1 is installed in opposing parts around the plug cap 9.
In order to energize 5, power supply wiring I! ! 34 and a ground wiring 35. The plug cap 9 that covers the cylindrical portion 22 has a hollow portion whose inner periphery is approximately oval in cross section, as shown in FIG.
4, with opposing surfaces 36, 37 which fit into each other. Each opposing surface 36, 37 is provided with a contact terminal 38, 39 for energization connected to the power supply wiring 34 or the ground wiring 35.

These energizing contact terminals 38.3 are connected to the energizing terminals 25 by placing the plug cap 9 on the heater-equipped spark plug 1.
．． It is electrically connected to 26.

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

By covering the heater-equipped spark plug 1 mounted on the engine with the plug cap 9, the three energizing contact terminals 38 and three energizing terminals 25 and 26 are electrically connected. As a result, the power supply wiring 34 and the ground wiring 35 provided on the plug cap 9 are connected to the contact terminals 38, 39, 25, 26, the electrodes 18, 19, and the wiring 16.
．． The heater 15 becomes energized via the heater 17 .

When the heater 15 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 engines that use fuel that is difficult to ignite.

(Effects of Example) The portions where the current-carrying terminals 25, 26 and the current-carrying electrodes 18, 19 come into contact are closer to the head 10 than the backing 28.

That is, this contact part is not exposed to the exhaust gases of the engine combustion chamber. Therefore, the occurrence of failure in energization of the heater 15 due to oxidation of the energization path of the heater 15 can be suppressed compared to the prior art.

Simply place the plug cap 9 over the heater ignition plug,
The heater 15 can now be energized. Note that if the plug cap 9 is not fitted, it is unclear which of the energizing terminals 25 and 26 the power supply wiring 34 and the ground wiring 35 will be connected to, but the heater 15 will not be energized regardless of which terminal it is connected to. Since it is possible, no problem will occur.

The energizing terminals 25.26 of the heater-equipped spark plug 1 and the energizing contact terminals 38.3 of the plug cap 9 can be designed with simple shapes. Therefore, the manufacturing cost of the heater-equipped spark plug 1 and the plug cap 9 can be kept low.

(Modification) In the above embodiment, the heater is provided in a heater element formed separately from the insulator, but it may be provided integrally with the insulator.

Further, the power supply wiring may be embedded within the plug cap.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the ignition plug with heater, Figure 2 is A of Figure 1.
-A cross-sectional view taken along line A, and a cross-sectional view taken along line B-B. In the figure 1... Spark plug with heater 2... Center electrode 4... Metal shell 9... Plug cap 18.19... Electrode for energizing 22... Cylinder part 25.26... For energizing Terminals in Figure 3 are shown in Figure 1: 3...Insulator 8...Long leg portion 15...Heater 21...Hexagonal portion 23.24...Plane portion

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 heater-equipped ignition plug, in which a heater that generates heat when energized is provided on a long leg portion of the heater, the insulator is disposed on the inner periphery of the metal shell holding the insulator at a position facing the heater. The metal shell includes a cylindrical part that covers the current-carrying electrode and has a diameter smaller than that of the hexagonal part on a side where the plug cap is covered with a hexagonal part for tightening the metal shell. In addition, the cylindrical portion has planar portions at opposing positions, and each of the planar portions is provided with a current-carrying terminal electrically connected to the current-carrying electrode and insulated from the metal shell. Spark plug with heater.