JPH0336070Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Advantages] This invention relates to a structure for mounting a spark plug with a built-in heater and a plug cap.

[Prior art and its problems] For example, in the case of a spark plug for an internal combustion engine, a heater for generating heat is attached around the ignition leg of an insulator, and the insulator is heated by the combustion of fuel injected into the cylinder during operation. The idea is to burn off the carbon attached to the surface. In this case, the lead-out wire from the heater needs to be fixed as a contact on the outer peripheral surface of the insulator of the spark plug and connected to the power supply terminal. These contacts and terminals may be connected by soldering or by bolts embedded in the insulator of the spark plug.

However, those that use soldering may start to melt due to the high heat they receive during use, making it difficult to expect a reliable connection between the terminal and the contact, and those that use bolts may cause damage to the outside. There is an inconvenience that a protrusion occurs and the cap cannot be properly attached to the plug due to the resulting snag.

This idea was made in an attempt to solve the above problems, and its purpose was to ensure the connection of the spark plug with a built-in heater to the heater, and also to make it possible to install the plug cap without any problems. To provide an excellent mounting structure for a spark plug with a built-in heater and a plug cap.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a cylindrical metal shell having an outer electrode projecting into the combustion chamber of an internal combustion engine, and a ignition leg facing the combustion chamber. an insulator disposed concentrically within the metal shell, and an upper end protruding above the metal shell and forming a high voltage terminal; a center electrode forming a spark gap between the electrode and the lower end of the electrode; a metal terminal formed in a ring shape on the outer peripheral surface of the upper end below the high voltage terminal; and a metal terminal provided mainly on the firing leg; A ignition plug with a built-in heater, which has one end connected to the metal shell, the other end connected to the metal terminal, and a heater that generates heat in the ignition leg when energized, and a connecting metal fitting at the mounting position of the high voltage terminal. It is composed of a tube-shaped core portion having a cylindrical shape and a cylindrical elastic rubber that is attached to the lower end of the core portion and makes elastic contact with the outer periphery of the upper end portion of the insulator, and has a ring-shaped contact point that comes into contact with the metal terminal when installed. In order to supply electricity to the heater and the center electrode, a plug cap was adopted, each of which contained a lead wire and a high-voltage electric wire that were electrically connected to the contact and the connecting fitting.

[Operations and effects of the invention] Due to the action of the elastic rubber of the seal part, the contact point and the metal terminal come into firm contact when installed, and power can be reliably supplied to the heater that generates heat in the firing leg.

[Embodiment] An embodiment of this invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a cylinder head of an engine, and this cylinder head 1 is provided with a vertical hole 2 that communicates with an internal combustion chamber 1a. 3
A spark plug is disposed in a vertical hole 2, and this spark plug includes a metal shell 5 having an outer electrode 4 projecting into the combustion chamber 1a. An insulator 6 is disposed concentrically within the metal shell 5, and its upper end protrudes upward to form a high-voltage terminal 6a. Reference numeral 7 denotes a center electrode, which is disposed concentrically within the insulator 6, and whose lower end forms a spark gap G with the outer electrode 4. A heater 8 for generating heat is attached to the firing leg 6b of the insulator 6 via a conical insulating layer 9, one end is grounded to the metal shell 5, and the other end is attached to the outer peripheral surface of the insulator 6. It is connected to the attached ring-shaped metal terminal 10. This heater 8 generates heat when energized, and is used to burn the conductive material and remove carbon and the like adhering to the surface of the firing legs 6b of the insulator 6 during operation. Reference numeral 11 designates the inner core of the cap 12, which is tube-shaped and has a conductor 11a such as a high-voltage wire or winding wire stretched inside, and is connected to a high-voltage terminal 6a of the insulator 6 via a connecting fitting 11b. It is connected to the. The outer periphery of the inner core 11 is covered with a tube-shaped outer core 13 , and the lower end of the outer core 13 is positioned to cover the upper half of the insulator 6 . A cylindrical rubber seal part 14 is attached to the lower end outer circumference of the outer core part 13, and a part of the inner circumferential surface is in elastic contact with the outer circumference of the insulator 6 in a sealed state. An open annular copper contact 15 is buried in the inner peripheral surface of the seal portion 14, and the inner peripheral side of the contact 15 contacts the terminal 10 and is electrically connected. This connection state is made strong and reliable due to the elastic contact of the seal portion 14 with the insulator 6. A lead wire 16 for power supply is integrally formed from one end side of this open-type annular contact 15 and extends upward.

Here, the outer diameter d3 of the lead wire 16 is 0.5 mm to 2.0 mm as shown in FIG.
The distance d2 between the ends of the terminal 5 is 0 to 1.0 mm, and the difference d1 between the inner radius R2 of the contact 15 and the outer radius R1 of the terminal 10 has a tolerance range of -0.3 mm to +0.3 mm. It is set so that it becomes zero. In this case, the contact 15 is preferably integrally molded at the time of molding the seal portion 14, and the contact 15 is
It is preferable to configure the inner peripheral side of 5 to be slightly exposed to the outside. Note that 17 is a rubber plug provided in the vertical hole 2 to seal between the vertical hole 2 and the outer core 13 of the cap 12.

According to the above configuration, since the terminal 10 is formed on the insulator 6 side and the contact 15 is formed on the seal part 14 side, the seal part 14 does not interfere with the plug, unlike the conventional one using a bolt. It can be installed without any
Moreover, as the contact 15 automatically comes into contact with the terminal 10 and is electrically connected with this installation,
Unlike the conventional case where solder is used as a fixing member, there is no risk of melting, and a reliable connection can be obtained regardless of whether heat is generated.

Further, since the annular contact 15 is configured to concentrically contact the annular terminal 10, the cap 12 is rotationally displaced relative to the insulator 6, and there is no need to perform positioning, and the cap 12 is simply fitted and bonded. This will suffice, and the two will definitely come into contact with each other as a result of this attachment. Therefore, the mounting operation becomes easy, and practical effects such as no failure to connect can be obtained.

In the above embodiment, the contacts 15 and the lead wires 16 are made of copper, but they may be made of other metals such as gold, silver, or a heat-resistant alloy. The same holds true for the terminals 10, and the point is that these terminals, contacts, and lead wires only need to be made of a material with good electrical conductivity. Also, contact 1
5 and the lead wire 16 are not limited to round wires, but may have a rectangular cross section.

It goes without saying that the present invention can be applied to any type of internal combustion engine, such as a single overhead camshaft or a double overhead camshaft.

In addition, various changes may be made in the specific implementation without departing from the gist of the invention.

[Brief explanation of the drawing]

FIG. 1 is an overall vertical sectional view, and FIG. 2 is a schematic diagram showing the length relationship of main parts. In the figure, 1... cylinder head, 3... spark plug, 4... outer electrode, 5... metal shell, 6... insulator, 6b... firing leg, 7... center electrode, 8...
...Heater, 10...Metal terminal, 14...Seal portion, 15...Contact.

Claims (1)

[Claims for Utility Model Registration] (a) A cylindrical metal shell with an outer electrode protruding into the combustion chamber of an internal combustion engine, an ignition leg facing the combustion chamber, and a high-voltage terminal protruding above the metal shell. an insulator disposed concentrically within the metal shell; and an insulator disposed concentrically within the insulator to provide a spark gap between the outer electrode and the lower end of the electrode. a metal terminal formed in a ring shape on the outer circumferential surface of the upper end below the high voltage terminal; and a metal terminal provided mainly on the firing leg, with one end connected to the metal shell and the other end connected to the metal shell. (b) a tube-shaped core portion having a connecting fitting disposed at a mounting position with the high-voltage terminal; and a sealing part made of a cylindrical elastic rubber attached to the lower end of the core part and making elastic contact with the outer periphery of the upper end of the insulator, and provided with a ring-shaped contact point that comes into contact with the metal terminal when installed, To energize the heater and center electrode,
A mounting structure for a spark plug with a built-in heater and a plug cap, each comprising a plug cap carrying a lead wire and a high-voltage electric wire inside, each of which is electrically connected to the contact and the connecting fitting.