EP3118952A1 - Ignition plug - Google Patents

Abstract

A spark plug has a center electrode (8) and an outer electrode (11) separated by an electrode gap (10). The center electrode (8) and the outer electrode (11) have a height (Hm, Ha), the height (Ha) of the outer electrode (11) being Ha> = 0, 8 * Hm + 2 * Smax and <= 1, 2 * Hm + 2 * Smax, and where Hm is the height of the center electrode (8) and Smax is the width of the maximum allowable electrode gap (10).

Description

The invention relates to a spark plug having a center electrode and an outer electrode separated by an electrode gap, the center electrode and the outer electrode having a height.

Such a spark plug is for example from the Austrian patent application A 141/2015 known.

When the center electrode and outer electrode are used within the scope of the description and claims of this invention, it does not necessarily mean that the center electrode in the spark plug must be located farther in the space and the ground or outer electrode must be farther outboard, albeit in preferred embodiments of the invention can be true. Rather, the terms center electrode and outer electrode are to be understood as meaning that the center electrode forms the plus pole and the outer electrode forms the ground electrode or the minus pole, irrespective of their specific position or orientation on the spark plug.

As a rule, a spark occurs at the shortest distance between the center electrode and the outer or ground electrode. Each spark causes erosion on both electrodes. To reduce this erosion, precious metals and precious metal alloys are used. Furthermore, the removal is lower the colder the electrode is. Normally, spark plugs are manufactured with a spark gap of 0.2 mm to 0.35 mm. With the wear of the spark plug it increases. At about 0.6 mm to 0.8 mm, the required ignition voltage is too large and you have to adjust or replace the spark plug. It has been found that the ground electrode wears much faster than the center electrode.

The invention has for its object to extend the life of spark plugs.

ist, wobei Hm die Höhe der Mittelelektrode und Smax die Breite des maximal zulässigen Elektrodenspalts ist.This problem is solved with a spark plug of the beginning mentioned type in that the height of the outer electrode $$\mathrm{Ha}>=0.\mathrm{8th}*\left(\mathrm{Hm}+2*\mathrm{smax}\right)\mathrm{and}<=1.2*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)$$

where Hm is the height of the center electrode and Smax is the width of the maximum allowable electrode gap.

The invention is based on the concept that with an increase in the volume fraction of the ground electrode, the life of a spark plug can be increased essentially. However, since the volume fraction can not be increased in the direction of the distance between the electrodes, since this would increase the electrode gap or ignition gap to an unacceptable extent as the burnup increases, the volume fraction is increased according to the invention by the height. On the other hand, an excessive increase in the height does not lead to a further extension of the life to a corresponding extent, which results in an upper limit for the height of the outer electrode. Furthermore, the costs for the noble metals or noble metal alloys to be used in the electrodes must also be taken into account.

In a preferred embodiment, the height of the outer electrode $$\mathrm{Ha}>=0.9*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)\mathrm{and}<=1.1*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)\mathrm{,}$$

This dimensioning represents an even better compromise between the possible increase in the service life and the use of materials.

In a further preferred embodiment of the invention, the outer electrode consists in the direction of its height of two parts, which optionally have a distance from each other.

These embodiments offer not only a manufacturing advantage in that the outer electrode of noble metal or a noble metal alloy can be made in two parts, but also the advantage that there is an improved mixture accessibility in the region of the electrode gap, whereby the ignition effect can be improved.

In the context of the invention, it is assumed that the center electrode forms the positive pole and the outer electrode forms the negative pole, which will be the case for the vast majority of spark plugs. However, the invention can also be used for the opposite case in that the center electrode forms the negative pole and the outer electrode forms the positive pole, in which case the center electrode has the greater height in comparison to the outer electrode.

Further preferred embodiments of the invention are the subject of the remaining dependent claims.

Fig. 1

eine Zündkerze im Bereich der Elektroden, wobei die Größenverhältnisse der Elektroden dem Stand der Technik entsprechen,

Fig. 2

eine erste Ausführungsform einer Zündkerze gemäß der Erfindung im Bereich der Elektroden,

Fig. 3

das Verschleißbild einer zweiten Ausführungsform einer Zündkerze gemäß der Erfindung und

Fig. 4

eine Stirnansicht der Zündkerze von Fig 2 bis 3.

Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. It shows:

Fig. 1

a spark plug in the region of the electrodes, wherein the size ratios of the electrodes correspond to the prior art,

Fig. 2

a first embodiment of a spark plug according to the invention in the region of the electrodes,

Fig. 3

the wear pattern of a second embodiment of a spark plug according to the invention and

Fig. 4

an end view of the spark plug of 2 to 3 ,

Fig. 1 shows the front part of a spark plug, wherein the size ratios of the electrodes correspond to the prior art. A non-current-conducting insulator 1, preferably made of ceramic, separates a spark plug housing 2 and a rod electrode 4 extending along a central axis 3 structurally and electrically from one another. To install the spark plug as intended, located in the front region on the spark plug housing 2, a spark plug thread 5. In a stepped portion 6 of the Spark plug housing 2, a support plate 7 is attached to a ground electrode 1. At the rod electrode 4, a center electrode 8 is fixed. The ground electrode 9 or outer electrode 9 and the center electrode 8 are made of high-quality electrode material, for example IrRh.

In this arrangement or these size ratios according to the prior art, the outer electrode 9 has a height Ha, which is in most cases the same size or possibly slightly larger than the height Hm of the center electrode 8 to account for the increased wear of the ground electrode 1 ,

The two electrodes 8, 9 are separated from each other by an electrode gap 10, which increases with increasing wear of the center electrode 8 and in particular the outer electrode 9 until it reaches a maximum value at which the ignition voltage rises above a permissible value and the spark plug is then revised or must be exchanged.

In Fig. 2 is an electrode assembly according to the invention is shown, in which the height Hm of the center electrode 8 over the prior art is unchanged, the height Ha of the outer electrode 11, however, is greater than the height Ha of the outer electrode 9 of the prior art.

The spark plug is in the illustrated embodiment of Fig. 2 and 3 dimensioned so that Hm = 0.4mm and Smax = 0.8mm, so that for Ha = 2mm and for $$\mathrm{Ha}/\left(\mathrm{Hm}+2*\mathrm{Smax}\right)=\left(0.4+2*0.\mathrm{8th}\right)=1\mathrm{results}\mathrm{,}$$

In the preferred embodiment according to Fig. 2 the outer electrode 11 consists of two parts 11a, 11b. The two parts 11a, 11b can abut one another directly. However, it is preferred if the two parts 11a, 11b as in Fig. 2 shown in the direction of the longitudinal axis 3 of the spark plug have a distance from each other, as in the gap 12 between the Both parts 11a, 11b fuel mixture can get, so that the ignition can be improved.

The two parts 11a, 11b are mounted on a support plate 7 made of a lower-quality material, wherein the support plate 7 may have a not dargestellen projection which extends into the gap 12 and which forms an assembly aid for the two parts 11a, 11b, by defines the distance between the two parts 11a, 11b.

It would also be possible to use two spaced-apart support plates, one for each part 11a, 11b of the outer electrode 11, which gives a further improved mixture accessibility in the region of the electrode gap 10, whereby the ignition effect can be further improved.

In Fig. 3 an embodiment of the spark plug according to the invention is shown, in which the outer electrode 11 consists only of a single, annular part.

In Fig. 3 It can be seen that in the spark plug according to the invention a wear pattern with a spark gap 10 results, which has on the side of the outer electrode 11 an arcuately curved end wall. Due to the increased height Ha of the outer electrode 11, however, a higher material reserve is given, wherein the height Ha is limited to a level at which a significant extension of the life is to be expected, however, the increased costs due to the higher mass of high-quality electrode material in reasonable Limits are kept.

In Fig. 4 is an end view of the spark plugs shown with an annular spark gap 10, which in all variants of Fig. 1 to 3 is the same, since according to the invention, only the height of the annular outer electrode 11 has been changed.

In the spark plug according to the invention, the electrode gap but also be executed as a polygon. In general, the geometry of the spark plug according to the invention or the electrodes is not limited to a particular design, but the invention can be used in all types of spark plugs and therefore also in spark plugs, in which the electrodes are not in the broadest sense annular around the longitudinal axis or center electrode of the spark plug but are also arranged in other directions or levels.

In particular, it is conceivable to use the inventive dimensioning of the spark plug in those types in which a single center electrode with, for example, rectangular or round face of a single center electrode with, for example, rectangular or round face opposite or two or more such electrode pairs are present in a single spark plug wherein the position of the end face with respect to the longitudinal axis of the spark plug is not essential to the invention.

In the case of electrodes having a round end face, the diameter of the electrodes corresponds to the height Ha, Hm according to the invention. The height of the electrodes can furthermore be measured not only in the direction of the longitudinal axis 3 but also transversely thereto.

Claims (11)

A spark plug having a center electrode (8) and an outer electrode (11) separated by an electrode gap (10), the center electrode (8) and the outer electrode (11) having a height (Hm, Ha), characterized in that the height (Ha) of the outer electrode (11) $$\mathrm{Ha}>=0.\mathrm{8th}*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)\mathrm{and}<=1.2*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)$$

where Hm is the height of the center electrode (8) and Smax is the width of the maximum allowable electrode gap (10). Spark plug according to Claim 1, characterized in that the center electrode (8) and the outer electrode (11) are arranged symmetrically in the direction of their height (Hm, Ha). Spark plug according to claim 1 or 2, characterized in that the height (Ha) of the outer electrode (11) $$\mathrm{Ha}>=0.9*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)\mathrm{and}<=1.1*\left(\mathrm{Hm}+2*\mathrm{Smax}\right)\mathrm{is}\mathrm{,}$$

is. Spark plug according to one of claims 1 to 3, characterized in that the electrode gap (10) is formed polygonal. Spark plug according to one of claims 1 to 3, characterized in that the electrode gap (10) is annular. Spark plug according to one of claims 1 to 5, characterized in that the outer electrode (11) on a support plate (7) is mounted. Spark plug according to one of claims 1 to 6, characterized in that the outer electrode (11) in the direction of their height (Ha) consists of two parts (11a, 11b). Spark plug according to Claim 7, characterized in that the two parts (11a, 11b) are at a distance from each other. Spark plug according to claim 7 or 8, characterized in that the two parts (11a, 11b) are mounted on separate carrier plates. Spark plug according to one of claims 1 to 9, characterized in that the spark plug has a longitudinal axis (3) and that the height (Hm, Ha) in the direction of the longitudinal axis (3) is measured. Spark plug according to one of claims 1 to 9, characterized in that the spark plug has a longitudinal axis (3) and that the height (Hm, Ha) is measured transversely to the longitudinal axis (3).

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