Information
-
Patent Grant
-
6580202
-
Patent Number
6,580,202
-
Date Filed
Friday, May 18, 200123 years ago
-
Date Issued
Tuesday, June 17, 200321 years ago
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Inventors
-
Original Assignees
-
Examiners
- Patel; Ashok
- Phinney; Jason
Agents
-
CPC
-
US Classifications
Field of Search
US
- 313 115
- 313 141
- 313 142
- 313 136
- 313 145
- 123 169 E
- 123 169 EL
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International Classifications
-
Abstract
A spark plug with a metallic housing (10) is proposed, which has an insulator (11) embedded in the housing (10), in which a rod-shaped internal conductor device is disposed. The internal conductor device has a contact pin (13), a current-limiting erosion resistor (17), and a central electrode (14). A sealing material (16) secures the central electrode (14) in a sealed fashion in the insulator (11). The temperature resistant sealing material (16) essentially contains at least one metallic component and at least one ceramic component with a low thermal expansion, wherein the metallic component has a melting temperature that is higher than the operating temperature.
Description
BACKGROUND OF THE INVENTION
The invention relates to a spark plug. Sealing materials are used for tightly fusing a central electrode into an insulator of the spark plug.
A spark plug of the type that defines the species is known, for example, from DE 22 45 403 in which the sealing material for tightly fixing the central electrode in the insulator is comprised of a mixture of a glass as a meltable component and graphite and/or powdered carbon black as an electrically conductive component. Moreover, it is also known to use copper or iron as conductive powdered materials. When the mixture in the insulator is melted, the glass softens as a result of which a contact pin and a central electrode become embedded in the insulator upon fusing. The thermal stability of the fusing, however, is limited because the glass is only sufficiently low viscosity for the fusing at temperatures far above the transformation temperature, while the application limit for the fusing is limited by the transformation temperature of the glass (softening of the fusing, decomposition of the fusing by means of ion transport in the electrical field).
SUMMARY OF THE INVENTION
Has the advantage that the sealing material has a higher thermal stability. The proposed metal-ceramic sealing material has a definite melting point and a narrow melting interval, as a result of which the sealing material can be loaded until just below the melting temperature of the metal used. As a result, the distance between the temperature of the fusing and the operating temperature is considerably reduced. This also permits the sealing material to be used in the vicinity of the tip of the insulator base. As a result, it is possible to use the sealing material for nail-shaped platinum electrodes, which have only a slight axial expansion at the tip of the insulator base.
A particularly temperature stable sealing material is achieved if the metallic component is 20 to 40 volume % and the ceramic component is 60 to 80 volume %.
BRIEF DESCRIPTION OF THE DRAWINGS
Three exemplary embodiments of the invention are shown in the drawings and will be described in detail in the subsequent description.
FIG. 1
is a sectional depiction of a spark plug,
FIG. 2
shows the combustion chamber end of a second embodiment of the spark plug, and
FIG. 3
shows the combustion chamber end of a third embodiment of the spark plug.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The spark plug shown in
FIG. 1
is comprised of an insulator
11
, which is crimped in a gas-tight manner into a metallic housing
10
, wherein the rotationally symmetrical axes of the housing
10
and the insulator
11
are congruent. The insulator
11
has an insulator bore
12
in which are disposed an internal conductor device with a contact pin
13
, a connection-end contact packet
15
, an erosion resistor
17
, a temperature resistant sealing material
16
, and a central electrode
14
. A ground electrode
18
is also embodied on the housing
10
. The central electrode
14
and the ground electrode
18
protrude into a combustion chamber that is not shown.
The sealing material
16
and the contact packet
15
have the task of sealing the erosion resistor
17
against the penetration of oxygen during the fusing process and during operation of the spark plug. The contact packet
15
also has the task of fixing the contact pin
13
in the insulator bore
12
. In addition to the sealing action, the sealing material
16
has the same task in relation to the central electrode
14
. Due to its proximity to the combustion chamber, the sealing material
16
is subjected to a significantly higher thermal load than the contact packet
15
.
In order to assure the appropriate thermal stability, the sealing material is essentially comprised of a metallic component and a ceramic component. The metallic component is comprised of at least one metal powder and/or at least one powder of a metal alloy, wherein the melting temperature of the metallic component is above the operating temperature of the spark plug of 900° C., for example. In order to not thermally overload the spark plug during the fusing of the sealing material
16
, it is logical if the melting temperature of the metallic component is below 1000° C. A ceramic powder with a low thermal expansion is suitable as the ceramic component, for example mullite, sillimanite, AlN, Si
3
N
4
, silica glass, or similar ceramic materials, or a mixture of these materials.
A mixture of 30 volume % tin bronze powder and 7.0 volume % mullite has turned out to be a suitable composition of the sealing material
16
which, with a thermal expansion coefficient of 8.4*10
−6
K
1
, for example, is largely adapted to the thermal expansion coefficient of the insulator. In order to improve the adhesion of the metal phase to the ceramic filler, an active solder, e.g. AgTi solder, can be used as the metallic component.
A second exemplary embodiment of the spark plug can be inferred from FIG.
2
. This embodiment uses a nail-shaped platinum electrode
21
, which is for example sintered into the insulator
11
. The platinum electrode
21
cooperates, for example, with 2 or 4 ground electrodes
22
. In this embodiment, the insulator bore
12
is embodied as stepped. Starting from the platinum electrode
21
, a first bore section
24
, a second bore section
25
, and a third bore section
26
are embodied one after the other, wherein the diameter of the first bore section
24
is smaller than the bore diameter of the second bore section
25
, and the diameter of the third bore section
26
is greater than the diameter of the second bore section
25
. In the exemplary embodiment according to
FIG. 2
, the contact pin
13
and the contact packet
15
are disposed in the third bore section
26
. At the end oriented toward the combustion chamber, the contact packet
15
is adjoined by the erosion resistor
17
, which extends essentially inside the second bore section
25
. The sealing material
16
is disposed between the erosion resistor
17
and the platinum electrode
21
, and consequently is disposed inside the first bore section
24
. The sealing material
16
has the composition described in the first exemplary embodiment.
A third exemplary embodiment of a spark plug can be inferred from
FIG. 3
in which, by contrast with the embodiment according to
FIG. 2
, an additional electrically conductive contact packet
28
is disposed between the erosion resistor
17
and the sealing material
16
. The contact packet
28
extends, for example, from the second bore section
25
into the third bore section
26
. However, it can also assume any other position; the only thing that must be assured is that the erosion resistor
17
and the sealing material
16
retain their function. The additional contact packet
28
, which is preceded by the sealing material
17
viewed from the combustion chamber, does not thereby have to possess the high thermal stability of the sealing material
16
. Therefore the additional contact packet
28
can be comprised of a composition which corresponds, for example, to the composition of the contact packet
15
oriented toward the connection end. Compositions of this kind are, for example, a mixture of glass and graphite and/or carbon black, wherein small amounts of powdered aluminum can be contained in the mixture.
Claims
- 1. A spark plug, comprising a metallic housing; an insulator embedded in said housing; a rod-shaped internal conductive device disposed in said insulator, said conductor device having a contact pin, a current-limiting erosion resistor, and a central electrode, said central electrode being fused in said insulator by a temperature resistant sealing material, said sealing material essentially containing at least one metallic component and at least one ceramic component with a low thermal expansion, said metallic component having a melting temperature that is higher than an operating temperature and lower than 1000° C., wherein said metallic component is 20-40 volume percent, and said ceramic component is 60-80 volume percent.
- 2. A spark plug as defined in claim 1, wherein said metallic component is composed of a material selected from a group consisting of at least one metal, at least one metal alloy, and both.
- 3. A spark plug as defined in claim 1, wherein said metallic component is a material selected from the group consisting of tin bronze, and active solder, and a mixture of both.
- 4. A spark plug as defined in claim 3, wherein said active solder is an AgTi solder.
- 5. A spark plug as defined in claim 1, wherein said ceramic component is a material selected from the group consisting of mullite, sillimanite, AlN, Si3N4, sillicaglass, and a mixture of these materials.
- 6. A spark plug as defined in claim 1, wherein said sealing material has a thermal expansion coefficient which is adjustable by a composition ratio of said metallic component and said ceramic component.
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 53 844 |
Nov 1998 |
DE |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/DE99/03622 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO00/31843 |
6/2/2000 |
WO |
A |
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4400643 |
Nishio et al. |
Aug 1983 |
A |
4414483 |
Nishio et al. |
Nov 1983 |
A |
5310373 |
Treiber et al. |
May 1994 |
A |
Foreign Referenced Citations (1)
Number |
Date |
Country |
22 45 403 |
Mar 1974 |
DE |