JPS60221622A - Fixing method of external connecting terminal in glow plug - Google Patents

Abstract

PURPOSE:To prevent the loosing in radial direction by a method wherein an insulating member supporting an external connecting terminal is formed of an insulating body and a metal pipe surrounding the insulating body, and the buckling deformation is produced on the metal pipe. CONSTITUTION:An insulating member 13 is used for attaching an external connecting terminal 14 on the rear end part of a holder 12. An insulating body 31 holds the external connecting terminal 14 interposed in the inside of a metal pipe 30. The insulating member 13 is formed of the metal pipe 30 and the insulating body 31. That is, the buckling deformation of the metal pipe 30 is produced by using the insulating member 13 formed of the metal pipe 30 and the insulating body 31. Thereby, the loosing for a holder caused by the temperature change produced at the utilizing of only synthetic resin insulating body can be prevented, the mechanical strength between the insulating member and the holder can be improved, also the airtight properties can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glow plug for preheating the inside of a cylinder of a diesel engine, and more particularly to a method for fixing an external connection terminal in a glow plug.

[Conventional technology]

Generally, in a diesel engine, a method is used in which a glow plug is provided in the cylinder and heated by passing an electric current through the glow plug to raise the temperature of the combustion chamber and improve the startability of the engine. As a glow plug like this,
There are so-called sheathed heaters, in which a coiled heating wire is embedded in a heat-resistant metal sheath filled with heat-resistant insulating powder, and heater rods in which a resistor is embedded in a ceramic material, etc. ing.

By the way, in this type of glow plug, various heater rods are held at the tip of a hollow metal holder, and an external connection terminal is attached to the rear end of this holder, and the tip of the external connection terminal and A structure in which the rear end of the heater rod is connected to the heater rod by a conductive wire is known. In such a glow plug, in order to maintain insulation between the external connection terminal and the holder, an insulating member made of synthetic resin fixed to the outer periphery of the distal end thereof is inserted from the rear end opening of the holder, and the external connection terminal is connected to the holder. A method was adopted in which the holder was fixed to the holder by caulking the periphery of the opening.

[Problem that the invention seeks to solve]

However, with devices formed by this method, the external connection terminal is locked at the periphery of the holder opening that is caulked to the insulating member, so it is prevented from coming off in the axial direction, but the insulation does not close in the radial direction. There is a problem in that the difference in thermal expansion coefficient between the member and the holder creates a gap between them, causing them to loosen.

In other words, in this type of glow plug, the insulating member is generally made of thermosetting resin, but in this case, care must be taken when using the glow plug for a long period of time due to the large difference in ambient temperature. If this happens, some heat shrinkage will occur in the insulating member, which is a molded product. this is,
This can be easily understood from the difference in ambient temperature between when a diesel engine using this type of glow plug is running and when it is stopped.

On the other hand, the metal holder side also expands due to the influence of temperature changes, but the amount of expansion is small and does not compensate for the amount of contraction of the insulating member mentioned above.As a result, a gap is created between the two and the outside This causes the connection terminal to become loose in the radial direction.

Therefore, in the case of using insulating members made of synthetic resin,
When screwing a wiring terminal or the like to the external connection terminal, the external connection terminal itself rotates and cannot be fixed, which is undesirable in terms of strength. In particular, such rotation may cause the conductive wire connecting the external connection terminal and the heater rod to become twisted or the connection portion to come off. Also, if a gap occurs between the insulating member and the holder opening,
It is not possible to maintain the airtightness of the conductor wiring space in the holder mentioned above, and water, oil, etc. may enter and corrode the electrical connection parts, which is a problem in terms of performance as a glow plug. isn't it.

[Failure to solve the problem]

The present invention has been made to solve such problems, and the insulating member that holds the external connection terminal is formed of an insulator and a metal pipe surrounding the insulator, and after the insulating member is fitted into the holder, The metal pipe is caused to buckle by caulking its rear end side with the periphery of the opening of the holder with a high pressure.

[Effect]

The buckling deformation of the metal pipe creates a strong bond between the shield holder and the insulator, which absorbs thermal shrinkage due to internal stress.

〔Example〕

FIGS. 1 and 2 show an embodiment of a glow plug for a diesel engine in which the present invention is implemented. In these figures, the glow plug shown as a whole by the reference numeral 10 has a resistor embedded therein that generates heat when energized. A heater rod 11 made of a ceramic material and a substantially tubular metal holder 12 that holds the heater rod 11 at its tip end are provided. An external connection terminal 14 is fixed, and this external connection terminal 14 is connected to the rear end of the heater rod 11 via a conductive wire 15.

Reference numerals 16 and 17 denote metal coating layers formed on the outer periphery of the central portion, the outer periphery of the rear end, and the end surface of the heater rod 11, which are connected to both ends of the resistor embedded in the heater rod 11 through lead portions. connected. The metal coating layer 16 in the center is connected to the holder 12 side via a reinforcing metal tube 18 fitted to its outer periphery.
A terminal cap 19 is placed on the rear end side and connected to the conductive wire 15.

The rear end side of the external connection terminal 14 is a screw portion, and an insulating washer 20. Natsu 21. Spring washer 22. A washer 23 and a nut 24 for tightening the external lead 5 are screwed together, and these members connect the external connection terminal 14.
is electrically connected to the battery terminals. The holder 12 is attached by screwing a threaded portion 25 formed on the outer periphery of the holder 12 into a threaded hole formed in the cylinder head of the engine.

Now, according to the present invention, in the glow plug having the above-described configuration, the insulating member 13 for attaching the external connection terminal 14 to the rear end of the holder 12 is interposed inside the metal pipe 30 and the external connection terminal 14 and an insulator 31 that holds the insulator 14. That is, the insulating member 13 formed by such a metal pipe 3° and the insulator 31
By buckling and deforming the metal pipe 30, it is possible to prevent the metal pipe 30 from loosening against the holder due to temperature changes, which occurs in the case of only conventional synthetic resin insulators, and to prevent the metal pipe 30 from becoming loose between the insulating member and the holder. It is characterized by its improved mechanical strength and ability to maintain airtightness.

To explain this in detail, as shown in FIG. 3, the insulating member 13 includes an insulator 31 made of a synthetic resin material etc. that is integrally fixed to the outer circumference of the tip end of the external connection terminal 14, and It is integrated by press-fitting a metal pipe 30 so as to surround it.

At this time, knurling or the like is applied to the outer circumferential surface of the tip side of the external connection terminal 14 and the inner circumferential surface of the metal pipe 30 as shown in the figure, which can be effective in increasing the bonding strength between them.

Furthermore, when molding the insulator 31, the metal pipe 3o may also be placed in the mold together with the external connection terminal 14 to perform so-called insert molding.

In short, it is sufficient that the insulator 31 holding the external connection terminal 14 is interposed within the metal pin 30 and these are integrated. Of course, the length of the metal pipe 3o in the axial direction is
It is set substantially equal to the insulator 31.

On the other hand, a fitting hole 32 into which the insulating member 13 is fitted is formed at the rear end of the holder 12, and a locking step 33 for locking the tip of the insulating member 13 is provided at the tip of the fitting hole 32 in the circumferential direction. is formed. A through hole 34 is formed in the holder 12 in communication with the fitting hole 32, and an internal space is formed in which a conductive wire 15 and the like connected to the heater rod 11 are disposed.

Although the above-mentioned fitting hole 32 is formed with an inner diameter substantially equal to the outer diameter of the metal pipe 3o, strict dimensional accuracy is not required. Also, the length from the stepped portion 33 of this fitting hole 32 to the open end side is the length of the metal pipe 30 in the axial direction)
is also set slightly shorter.

The insulating member 13 thus formed is inserted into the fitting hole 3 from the rear end opening of the holder 12 together with the external connection terminal 14.
2, and its tip is locked to the stepped portion 33. Next, the insulating member 13 is fixed to the holder 12 by caulking the rear end side opening periphery 35 of the holder 12 to the rear end side of the insulating member 13 with a high pressure.

Therefore, the metal pipe 3 constituting the insulating member 13
0 is pressurized by a high pressure between the step portion 33 and the opening periphery 35, which causes buckling deformation in the axial direction, as shown in FIG. A deformation occurs as shown in . In such a state, the outer circumference of the metal pipe 30 is firmly pressed against the inner circumference of the fitting hole 32 of the holder 12, and the inner circumference of the metal pipe 30 is in contact with the insulator 31.
The metal pipe 30 and the insulator 31 are pressed into contact with each other and are mechanically strongly connected, and a large internal stress is generated in the metal pipe 30 and the insulator 31. That is, the metal pipe 30 is connected to the holder 12 and the insulator 31.
Because the material undergoes buckling deformation within a limited space, a large internal stress is generated, and this is maintained in an accumulated state.

Therefore, even if the insulator 31 shrinks slightly due to a large change in ambient temperature, the amount of deformation will be absorbed by the internal stress of the metal pipe 3°, and there will be no problem of loosening. airtightness is also maintained.

For example, when using a metal pipe 3o with a wall thickness of 0.75 mm, it has been confirmed through experiments that the high pressure required to obtain the above-mentioned effects is approximately 1.5 to 2.0. There is.

As explained above, according to the present invention, the insulating member that holds the external connection terminal at the open end of the holder is formed of an insulator and a metal pipe surrounding the insulator, and the tip side of the insulating member is attached to the step inside the holder. The metal pipe was inserted into the holder so as to be locked, and then the metal pipe was buckled by caulking the periphery of the opening of the holder on the rear end side with a high pressure, and internal stress was generated in the metal pipe and the insulator. Because it is a metal pipe that has undergone buckling deformation, the inner wall of the holder and the insulator are firmly connected, ensuring mechanical strength that is unaffected by ambient temperature changes, and maintaining internal airtightness. I can do it. Further, since it can be easily carried out using a press machine without requiring a special processing machine or the like, it has the advantage that it can be manufactured at low cost.

[Brief explanation of drawings]

The figure shows an embodiment of a glow plug to which the present invention is applied,
FIG. 1 is an exploded perspective view showing the general structure of the entire glow plug, FIG. 2 is a longitudinal side view showing its assembled state, and FIG. 3 is an exploded perspective view showing an enlarged view of the characteristic terminal unit.
Figure 4 is an enlarged view of the main part. No. 10... Glow plug, 11... Heater rod, 1
2..11@Holder, 13.e++.Insulating member, 14.
...External connection terminal, 30...Metal pipe, 311
1...Insulator, 32...Life/fitting hole, 33...
Stepped portion, 35...periphery of opening.

Claims (1)

[Claims] An insulating member (13) interposed between the holder (12) and the external connection terminal (14) is composed of an insulator (31) integrally fixed to the external connection terminal (14) and a metal pipe (31) surrounding the insulator (31). This insulating member (13) is fitted into the opening (32) of the holder (12) to form a metal pipe (30).
The tip of the metal pipe (0) is locked to the step (33) in the holder, and the rear end is caulked to the opening periphery (35) of the holder (12) with high pressure from the axial direction. (
30) A method for fixing an external connection terminal in a glow plug, the method comprising buckling and deforming the external connection terminal.