JP2001525529A - Sheath type glow plug - Google Patents

Abstract

(57) [Summary] A sheath-type glow plug (10) disposed in a combustion chamber of an air-compression-type internal combustion engine has a tubular plug casing (11). In the direction hole (12) a glow pin (16) is fixed with a sealing action for part of its length. Between the longitudinal bore (12) and the glow pin (16) a ring gap (21) is provided in the lower defined area facing the combustion chamber, which serves for thermal insulation between the plug casing and the glow pin. Is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheath-type glow plug disposed in a combustion chamber of an air-compression-type internal combustion engine, according to the first aspect of the present invention.

In known sheath-type glow plugs of this type, the ring gap between the glow pin and the plug casing has a cylindrical shape on the combustion chamber side of the glow pin and the plug casing with a constant diameter in the press-fit region. It is formed by holes. This hole is characterized by a diameter that is larger than the press-fit diameter of the glow pin.

[0003] The sheath-shaped glow plug according to the invention, which is constructed as described in the characterizing part of claim 1, provides sufficient insulation of the glow pin at a corresponding ring gap depth and thus ensures the desired heating characteristics. Have the problem of doing In relation to the so-called overhang value, i.e. in relation to the free length of the glow pin from the lower edge of the plug casing to the tip of the heating element, relative to the standard glow pin whose geometry and heating characteristics remain the same, The depth can be adapted to the overhang. as a result,
By simply changing the depth of the ring gap, a high variety of parts or components of the plug casing can be obtained.

[0004] The significant advantages provided by the sheath-type glow plug according to the present invention include the following. That is, in the sheath-type glow plug according to the invention, the ring gap is correspondingly stepped in the area of the press-fit, unlike the prior art,
This is achieved by a glow pin with an enlarged diameter and a plug casing with a non-stepped diameter. This makes it possible to reduce the number of plug casings whose geometry merely depends on the depth of the ring gap to one casing which can be universally used for this purpose. At the same time, standard glow pins having a geometry that remains the same can still be used, and such standard glow pins are used to produce the desired ring gap depth,
It is pushed into the plug casing to the appropriate depth.

[0005] The formation of the ring gap by the stepped glow pins in the area of the press-fit results in an increase in the press-fit diameter of the glow pins relative to the prior art press-fit diameter. This increase in diameter increases the structural space available for sealing the glow pin. The increase in diameter in this area will reduce the required deformation rate in the glow tube and the pushed seal. As a result, the risk of crack formation in the seal member during hammering of the glow pin for forming the shape is significantly reduced.

Description of Embodiment Next, an embodiment of the present invention will be described with reference to the drawings.

[0007] The sheath-shaped glow plug 10 comprises an elongated cylindrical casing 11, which has a conical enlarged portion 13 in the middle toward the upper end.
Is provided. The hole 12 has a ring-shaped step 15 formed slightly below the enlarged portion 13. The diameter of the hole 12 on the step 15 is such that the diameter of the hole 12 is smaller than the area 12 A following the hole 12. Is somewhat smaller than the diameter at. A glow pin 16 is arranged in the casing 10, and a tip 17 of the glow pin 16 enters the combustion chamber of the internal combustion engine. The joint between the glow pin and the plug casing is conventionally configured as a press fit 12A with a fixed hole diameter on the combustion chamber side. The projection value V of the glow pin of the sheath-type glow plug is defined as the distance between the tip of the heating element and the inspection diameter (Pruefdurchmesser) in the sealing cone of the plug casing.

Since the structure of the sheath-type glow plug is not important for the present invention,
I will not touch any more. The sheath-type glow plug is preferably press-fitted in the bore 12. The glow coil arranged in the glow tube of the glow pin is not shown here. The connection pins 18 projecting from the plug casing 11 serve to supply power to the glow coil. The connecting pin 18 is fixed in the tubular upper region of the glow pin 16 by means of a radially pressed sealing member 20. The seal member 20 seals the glow pin 16 between the glow tube and the connection pin 18 from the surroundings. Ring-shaped step portion 1 in casing 11
5 functions to prevent the glow pin 16 together with the connection pin 18 from being pushed upward from the casing 11 at the time of high pressure in the internal combustion engine. At the upper edge of the glow pin 16, a seal member 20 is provided between the glow tube and the connection pin 18 to seal the heating body to the surroundings.

FIGS. 2 and 3 show the extent of the ring gap 21 between the plug casing and the glow pin, which is important for the invention. This ring gap 21 is realized between a fixed press-fit diameter of the plug casing on the combustion chamber side and a glow pin having a reduced outer diameter inside the plug casing. In this case, step 1
The combustion chamber-side region of the glow pin below 6B has a diameter 16C smaller than the diameter of the press-fit region 12A.

FIG. 2, in particular, shows the arrangement of a sheath-type glow plug according to the invention in a plug housing for producing a ring gap depth R1. FIG. 3 shows the arrangement of a sheath-type glow plug according to the invention in a plug housing for producing a ring gap depth R2. The sheath-type glow plugs shown in FIGS. 2 and 3 can have the same geometry and heating characteristics, ie different to achieve different ring gap depths (here R1> R2) and thus different A standard sheath glow plug can be used to achieve an overhang (here V1 <V2). The ring gap depth and the protrusion value can be achieved by pushing the standard sheath glow plug into the press-fitting of the casing 11 at a suitable depth.

[Brief description of the drawings]

FIG. 1 is a partially sectional view showing the entire sheath type glow plug.

FIG. 2 is an enlarged view showing a ring gap region indicated by X in FIG. 1;

FIG. 3 is an enlarged view showing a ring gap region indicated by X in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Sheath type glow plug, 11 Casing, 12 holes, 13 Enlarged part, 15 steps, 16 Glow pin, 18 Connection pin, 20 Seal member

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] November 18, 1999 (November 18, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Steffen Schott Schwieberdingen Germany Stuttgarter Strasse 69/2

Claims (7)

[Claims] 1. A sheath type glow plug (10) arranged in a combustion chamber of an air compression type internal combustion engine, wherein a metal tubular plug casing (11) is provided. ), A glow pin (16) is sealingly fixed for part of its length in a longitudinally extending bore (12), and furthermore a connection arranged partly in the glow pin and serving for power supply. A pin (18) is provided, at least partially defining a ring gap (21) between the glow pin (16) and the plug casing (11), the ring gap (21) being used for combustion of the plug casing. In the form extending from the chamber-side end, the ring gap (21) has a reduced-diameter region (16A) at the glow pin (16C).
). A sheath-type glow plug characterized by being formed by: 2. Different ring gap depths (R1, R2) and protrusion values (V
3.) The sheath-type glow plug according to claim 1, wherein the glow plug can be realized by changing the depth of pushing of the glow pin into the press fitting of the plug casing in the single standard glow pin having the same geometry and heating characteristics. 3. In order to achieve different ring gap depths (R1, R2), only one standard plug casing can be used, in which case the press fit and the ring gap of the plug casing are reduced. , Having a constant diameter towards the combustion chamber or an arbitrary diameter step of constant geometry.
The described sheath-type glow plug. 4. The glow pin (16) in which the diameter variation at the ring edge (16B) has an arbitrary geometrical configuration, wherein the glow pin is positioned such that the diameter step is located inside the plug casing. Being pushed into the casing,
The sheath-type glow plug according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the area of the enlarged diameter of the glow pin (16) requires only a small deformation rate of the glow tube inside the plug casing.
The sheath-shaped glow plug according to any one of claims 1 to 4. 6. The sheath-shaped glow plug according to claim 1, wherein the diameter step of the glow pin is formed by hammering, rolling, drawing or cold pressing. 7. A ring edge (15) formed inside the plug casing, said ring edge (15) being slightly smaller than the outer diameter of the glow pin (16) in this region. 7. The sheath-shaped glow plug according to any one of items 1 to 6.