Note: Descriptions are shown in the official language in which they were submitted.
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SPARK PLUG WITH END PART
The invention relates to a spark plug according to the
preamble of Patent Claim 1.
Such spark plugs are known from WO 2009/059339 Al.
It is the aim of the invention to simplify the production
of such spark plugs, especially with regard to the avoidance of
complex components which are complicated to manufacture and with
regard to the construction of the spark plug from simply
producible parts. This is especially of importance for mass
production.
Furthermore, the electrical properties of such
spark plugs are to at least correspond to those of comparable
spark plugs, if not surpassing these properties.
Accordingly,
an optimum current conduction over the individual ground
electrodes is to be ensured. Finally, the spark characteristics
are to be improved, preferably by optimizing the conductivity
and the heat dissipation from the ignition surfaces, in order to
achieve better stability.
These aims are achieved in a spark plug of the type
referred to in the introduction having the features which are
cited in the characterizing part of Claim 1. The
end part
extends the spark plug housing and it allows the electrode
arrangement to be of a short and compact design. Heat
dissipation from the electrodes, current distribution,
resistance to corrosion and ignition reliability are therefore
significantly improved. An
essential reason for this lies in
the shorter overall height or in the proximity of the electrodes
to the insulating body.
It is advantageous if the ground electrode carrier, as seen
perpendicularly to the longitudinal axis of the spark plug, has
a smaller distance from the centre electrode than the inner
surface of the wall of the chamber and supports at least one
finger-like ground electrode with an ignition surface which lies
at the height level of the ignition surface of the centre
electrode in the chamber, or if the ground electrode carrier, as
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seen perpendicularly to the longitudinal axis of the spark plug,
has a greater distance from the centre electrode than the outer
surface of the wall of the chamber and supports at least one
finger-like ground electrode which extends through a recess in
the wall into the chamber, wherein the ignition surface of the
ground electrode lies at the height level of the ignition
surface of the centre electrode in the chamber. A compact
electrode construction, which can be produced in a simple manner
and can be installed on the end part, is thereby achieved.
The arrangement of the ground electrodes on a separate
carrier ensures a uniform current conduction over the ground
electrodes. Since the ground electrode carrier is arranged at a
distance from the wall of the chamber, the ground electrodes and
the ground electrode carrier represent a system which is
independent with regard to the current and heat conduction from
the wall of the chamber. This enables a simple readjustment of
the ground electrodes and the application-induced electrode
consumption can be easily corrected. On
account of the
possibility of manufacturing the ground electrode carrier and
the ground electrodes independently, especially as a one-piece
component, and locating these on the end part, significant
production-related advantages ensue.
Furthermore, as a result
of the fact that the ground electrodes can be manufactured
together with the ground electrode carrier as a one-piece
component, and that a gap exists between the ground electrode
carrier and the wall of the chamber, improved heat dissipation
from the ignition electrodes to the end part and to the spark
plug housing is achieved. The
special shape of the ground
electrodes and their arrangement provide further advantages with
regard to an improved ignition performance and screening or
flow-through of the chamber, even if the height of the
electrodes which are arranged on the end part is smaller than in
the case of comparable conventional spark plugs.
An especially simple manufacture with a stable construction
of the spark plug is achieved as a result of the special shape
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of the ground electrode carrier. The ground electrode carrier,
having a cylindrical ring-shaped cross section, can be adjusted
in a simple manner at a circumferentially constant distance from
the outer surface of the wall of the chamber so that defined
conditions with regard to combustion and current conduction are
created. Furthermore, the construction and the installation of
the spark plug are simplified since the cylindrical ring-shaped
ground electrode carrier and also the chamber having a
cylindrical ring-shaped cross section can be seated in a simple
manner upon the end part and fastened there. This advantageous
fastening is achieved if the ground electrode carrier and the
wall are supported by the end part which is arranged on the
combustion chamber-side end region of the spark plug housing.
The ground electrode carrier can be formed with a thread on its
inner wall surface or else can have a smooth surface, the same
applying to the wall of the chamber.
Either the ground
electrode carrier or the wall of the chamber are screwed onto
the respective projecting end shoulders of the end part and/or
are fixed in their position by means of welding, or these
components are pushed onto the end part, with a seating which is
accurate as possible, and fixed in their desired position,
especially by means of welding.
Provision can be made for the forming of two concentrically
disposed cylindrical end shoulders on the end part, of which the
inner end shoulder, if applicable, projects beyond the outer end
shoulder in the direction of the combustion chamber, wherein the
ground electrode carrier, together with the ground electrodes
which penetrate the walls, is seated, pushed or screwed on the
outer end shoulder and/or fastened by means of spot welding or
seam welding, as applicable, and the wall of the chamber is
seated, pushed or screwed on the inner end shoulder and/or
fastened by means of spot welding or seam welding, as
applicable, or wherein the wall of the chamber is seated, pushed
or screwed on the outer end shoulder and/or fastened by means of
spot welding or seam welding, as applicable, and the ground
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electrode carrier, which lies at a distance from the inner
surface of the wall, is seated, pushed or screwed on the inner
end shoulder and/or fastened by means of spot welding or seam
welding, as applicable.
It is advantageous if the end part is formed in one piece
with the wall, wherein the ground electrode carrier is seated,
pushed or screwed onto the end part and/or fastened by means of
spot welding or seam welding, as applicable, or if the end part
is formed in one piece with the ground electrode carrier,
wherein the wall, which encompasses the ground electrode carrier
at a distance, is seated, pushed or screwed onto the end part
and/or fastened by means of spot welding or seam welding, as
applicable.
In this way, the production of the spark plug is simplified
and the spark plug housing is extended with the same overall
length of the spark plug. With the same overall length of the
spark plug, better heat dissipation from the ground electrode
and from the wall into the spark plug housing ensues and the
risk of spontaneous ignitions is reduced.
In principle, the ground electrode carrier could
additionally also be fastened on the combustion chamber-side end
region of the spark plug housing.
Advantages in relation to production ensue if the ground
electrode carrier, as seen perpendicularly to the longitudinal
axis of the spark plug, has in section at least partially
circular cross section or is formed by a cylindrical ring and/or
if the at least one ground electrode and the ground electrode
carrier are formed in one piece or are interconnected by means
of welding.
With regard to the thermal endurance of the spark plug, it
is advantageous if through-openings are formed in the wall for
passage of the combustion gas.
For the function of the spark plug, advantages ensue if the
ground electrode carrier supports one, three or five ground
electrodes and/or if the ground electrodes are arranged on the
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ground electrode carrier in a distributed manner around the
centre electrode at equal distances from each other and/or if
each of the ground electrodes, which project from the ground
electrode carrier, has a rectangular or cylindrical ring
5 segment-like cross section, at least in sub-sections of its
longitudinal extent and/or if the spark gap is formed between
surface regions of the ground electrode and of the centre
electrode which extend parallel to the longitudinal axis and lie
opposite one another.
A simple construction ensues if a male thread is formed in
each case on the two concentrically disposed end shoulders of
the end part and if a female thread, matched to the respective
male thread, is formed in each case on the inner wall surface of
the wall and/or on the inner wall surface of the ground
electrode carrier and/or if the ground electrode carrier and the
cylindrical ring-shaped wall are arranged concentrically to each
other, forming the prespecified gap and possibly a height
offset, and/or if the cylindrical wall and/or the ground
electrode carrier is pushed on the respective end shoulder and
fastened there by means of welding.
For the construction of the spark plug/ especially with
regard to current conductivity and heat conductivity or heat
dissipation, it is advantageous if a number of preferably
parallel extending slots, extending parallel to the direction of
the longitudinal axis of the spark plug, are formed in the wall,
through which slots the ground electrodes are guided into the
interior of the chamber, wherein the slots, if necessary, extend
from the combustion chamber-side end face of the wall up to the
level region of the end face of the end part.
If the ground electrodes are located outside the wall and
project through the longitudinal slots into the chamber which is
bounded by the wall, the ground electrodes have a screening
effect and a certain desired circulation of the gas can be
maintained between the ground electrodes and the adjacent slot
surfaces, contributing to the cooling of the electrodes. As a
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result, an excessive accumulation of heat is avoided and
spontaneous combustions are counteracted.
In the case of the spark plug according to the invention,
it is a special embodiment of a screened spark plug.
It is advantageous for ignition and heat dissipation if a
ignition surface carrier, which is preferably guided radially
through the slot into the interior of the chamber, projects from
the section which extends parallel to, and outside of, the wall
and/or if a connecting piece, which preferably extends parallel
to the direction of the longitudinal axis of the spark plug,
follows the circumferential extent of the wall and partially
closes off the slot or is at least partially arranged in the
slot space, projects from the ignition surface carrier in the
direction of the combustion chamber and, if applicable,
terminates there in the same plane with the end face of the wall
and/or if the section of the ground electrode which projects
from the ground electrode carrier is located outside the
circumferential region of the wall in front of the slot. As a
result of this freeing of the wall, the wall can be cooled in a
better way by means of the gas which is to be combusted.
In a preferred embodiment, it is provided that the centre
electrode has a number of radially outwardly projecting,
preferably centrally symmetrically formed, electrodes which in
their respective end region have an ignition surface, opposite
which in each case lies an ignition surface of a ground
electrode. A
simplified production and exact ignition
performance ensue if an encompassing annular groove, which
adjoins the insulation-side end of the ignition surfaces of the
centre electrode, is formed on this centre electrode.
An advantageous embodiment of the end part provides that
the end part, which is seated upon the end region of the spark
plug housing, is of a rotationally symmetrical, preferably
cylindrical ring-shaped, design and is arranged centrally to the
longitudinal axis of the spark plug and extends the spark plug
housing on the combustion chamber side in form of an
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intermediate piece and/or that the end part, by its combustion
chamber-side end region, encompasses the base section of the
centre electrode.
A constructionally simpler and operationally more reliable
construction ensues if the end part is connected to the spark
plug housing by means of welding and/or screwing, and/or if the
end part encompasses the base of the centre electrode and the
insulating body, forming a gap.
Fig. 1 shows a schematic longitudinal section through an
embodiment of a spark plug according to the invention. Figs. 2a
and 2b shows embodiments of a centre electrode. Fig. 3 shows a
perspective view of a spark plug according to the invention.
Fig. 4a shows a possible embodiment of a spark plug without an
end part. Fig. 4b shows an embodiment of a spark plug with a
seated attached end part. Fig. 4c shows a spark plug according
to the invention with a seated end part which is constructed in
one piece with the wall of the chamber, wherein the ground
electrode carrier is welded on this end part.
Figs. 5 and 6
show embodiments of spark plugs in which the ground electrodes
or the ground electrode carrier are, or is, located inside the
wall on an end part or are connected to the end part in one
piece. Figs. 7 to 9 show embodiments of spark plugs with an end
part which is seated on the spark plug housing and with a
prechamber encompassing electrodes.
Figs. 10 and 11 show a
spark plug with an annular sleeve which is arranged between the
end part and the prechamber.
In the following text, the invention is exemplarily
explained in more detail with reference to the drawing.
Fig. 1 shows a spark plug for use in an internal combustion
engine, especially for an Otto gas engine. A spark plug housing
2 is supported by an insulating body 1, wherein a centre
electrode base 3a is enclosed by, or projects from, the
insulating body 1. Seated on this centre electrode 3a base of
the spark plug is the centre electrode 3 which has at least one
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ignition surface 12. The ignition surfaces 12 lie on discharging
projections of the centre electrode 3.
For the forming of at least one spark gap 12, provision is
made for at least one ground electrode 4 which is supported by a
ground electrode carrier 6. The ground electrodes 4 are
advantageously arranged on the ground electrode carrier 6 in a
distributed manner around the centre electrode 3 at equal
distances from each other. The
ground electrode carrier 6 is
supported on an end part 60, which is seated upon the spark plug
housing 2, or is fastened on this end part.
As is apparent from Fig. 1, the ground electrodes 4 project
in each case from the ground electrode carrier 6 in the form of
a finger with a section 41 and are fastened, preferably welded,
on the carrier 6. The ground electrode 4 and the carrier 6 can
be constructed as a one-piece component, if applicable. The
combustion chamber-side end region or the ignition surface 26 of
the ground electrode 4 lie on an ignition surface carrier 51 and
extend parallel to the longitudinal axis A of the spark plug or
parallel to the facing ignition surface 12 of the centre
electrode 3. The spark gap 13 is formed between the oppositely
disposed ignition surfaces 26, 12 of the ground electrode 4 and
of the centre electrode 3. These ignition surfaces 26, 12 can
preferably be coated with noble metal or noble metal alloys in
the form of strips or small plates.
For the fastening of the ground electrode carrier 6 on the
end part 60, it is provided that the end part 60 has two
concentrically lying, cylindrical end shoulders 17, 18, of which
the inner end shoulder 17 projects beyond the outer end shoulder
18 in the direction of the combustion chamber. The
ground
electrode carrier 6 is seated, pushed or screwed on the outer
end shoulder 18 and/or, if applicable, fastened by means of
welding, especially spot welding or seam welding, and a wall 8,
which forms a chamber 5 which is open on the combustion chamber
side, is seated, pushed or screwed on the inner end shoulder 17
and/or, if applicable, fastened by means of welding, especially
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spot welding or seam welding. The
internal dimensions of the
wall 8 and of the ground electrode carrier 6 are matched to the
respective external dimensions of the end shoulders 17, 18. The
wall 8 forms a screen or shield or an open chamber and the spark
plug according to the invention can also be referred to as a
screened spark plug.
The ground electrode carrier 6, and especially also the
section 41, of each of the ground electrodes 4 which project
from the ground electrode carrier 6 are arranged at a distance
from the outer surface 7 of the wall 8 of the chamber 5,
possibly offset downwards in the direction of the spark plug
housing 2 in relation to the centre electrode 3. This distance
is provided in order to ensure a defined or uninfluenced current
flow in the ground electrode carrier 6.
Furthermore, as a
result of the distance 21, as already explained above, a
distinct or defined heat dissipation from the ground electrodes
4 to the spark plug housing 2 is made possible.
Shown in Fig. 1 is a spark plug with a cylindrical ring-
like wall 8 which circumferentially encompasses the centre
electrode 3. Variations of the shape of such walls or chambers
can also be provided.
A simple construction and a simple production of the parts
ensue if the wall 8 of the swirl chamber 5, which is open on the
combustion chamber side, and the ground electrode carrier 6
have, at least in sections, a circular cross section, or are
formed in each case by a cylindrical ring.
Through-openings 10 can be formed in the wall 8 for passage
of the gas.
Each finger-like ground electrode 4 is advantageously
offset from the ground electrode carrier 6 towards the centre
electrode 3 in the form of an ignition surface carrier 51,
forming a section 41 extending parallel to the wall 8, and
terminates in front of the centre electrode 3. To
this end,
slots 50 are formed in the wall 8. The width of these slots 50
basically corresponds to the width of the section 41 or slightly
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exceeds this width.
These slots 50 basically extend over the
entire height of the wall 8, that is to say they extend
especially from a region of the wall 8 which lies approximately
at the level of the end face of the end part 60 and terminate on
5 the combustion chamber-side end face of the wall 8. The offset
radially extending ignition surface carrier 51 of the ground
electrode 4 extends through this slot 50 in the direction of the
centre electrode 3. A
connecting piece 52, which extends
parallel to, or in the direction of, the longitudinal axis A of
10 the spark plug, adjoins the ignition surface carrier 51 which
extends from the section 41 radially through the slot 50 into
the interior of the chamber 5. The connecting piece 52 follows
the circumferential extent of the wall 8 and in this region at
least partially closes off the slot 50 or lies preferably inside
the slot 50. This
connecting piece 52 projects from the
ignition surface carrier 51 in the direction of the combustion
chamber and terminates with the end face of the wall 8 and
contributes to controlled gas circulation.
As is apparent from Figs. 2 and 3, the centre electrode 3
has three centrally symmetrically arranged ignition surfaces 12,
opposite which in each case lies an ignition surface 26 of a
ground electrode 4.
Adjacent strips 40 consisting of a noble metal alloy can be
applied to or fused onto the radially outwardly pointing surface
regions 12 of the centre electrode 2 and/or onto the surfaces 26
of the respectively opposite ground electrodes 4 which face the
centre electrode 3.
Instead of directly applied or fused on
noble metal alloy strips 40 according to Fig. 2a, the noble
metal alloy can also be applied to or welded onto or fused onto
projecting regions 48 of the cylindrical part of the centre
electrode 3 in the form of small noble metal plates 40', which
regions 48 are formed by projections which are welded on or
moulded on in one piece.
Such raised regions 48 can also be
formed on or attached to the ground electrodes 4 and to which,
or onto which, noble metal alloy, possibly in the form of small
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noble metal plates, is applied, or welded or fused. On the side
of the ignition surfaces 12 which is remote from the combustion
chamber or directly beneath the projections 48 of the centre
electrode 3, an encompassing annular groove 61 can be formed.
This annular groove 61 represents a defined boundary of the
ignition surfaces 12 and makes the welding on and application of
small noble metal plates and/or strips 40, 40' easier.
The wall 8 of the chamber 5 and/or the ground electrodes 4
and/or the ground electrode carrier 6 are manufactured from
nickel-based alloy and/or high-temperature high-grade steel
and/or hot corrosion resistant metal alloys with good thermal
conductivity. The wall 8 can also be manufactured from brass.
For the production and the operation of the spark plugs, it
has proved to be advantageous if the number of ground electrodes
4 is uneven or if the ground electrodes 4 do not lie opposite
each other with regard to the centre axis of the centre
electrode 3. As a result, the application of noble metal alloys
upon the ground electrodes 4 which project from the carrier 6
becomes possible in a simple manner.
The slot 50 which is provided makes necessary maintenance
operations or readjustments easier.
The ground electrode carrier 6 and the wall 8 of the
chamber 5 are connected in an electrically conducting manner to
the spark plug housing 2. The centre electrode 3 is connected
to the centre electrode base 3a of the spark plug, preferably by
means of welding. The centre electrode base 3a is guided in the
insulating body 1 and is electrically insulated towards the
spark plug housing 2 by means of the insulating body 1.
The ground electrodes 4 are designed in such a way that the
section 41 extends basically in a straight line and parallel to
the wall 8 without deflection and preferably has a constant
cross-sectional shape over this longitudinal extent. The
transition from the ground electrode carrier 6 to the section 41
can extend in a rounded manner.
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Shown in Fig. 4a is a known spark plug. The length of the
spark plug housing 2 is represented by L, wherein on the
combustion chamber-side end region of the spark plug 2 the
ground electrode carrier 6 and the wall 8 are mounted, or
fastened, especially by means of welding, on corresponding
shoulders 17, 18 of the spark plug housing 2. In
the case of
the spark plug according to the invention according to Fig. 4b,
the end part 60, in the form of an intermediate ring, is seated,
for example pushed or screwed and, if applicable, fastened by
means of spot welding or seam welding, on the combustion
chamber-side end region of the spark plug housing 2. This end
part 60 serves for extending the spark plug housing 2. This end
part 60 supports a shoulder 18 on which the ground electrode
carrier 6 is fastened and/or welded and furthermore supports a
shoulder 17 which supports the wall 8. Resulting from this,
therefore, is a length Li of the spark plug housing 2 and seated
end part 60 which is greater that the length L. As a result,
the parts which are required for the ignition, specifically the
ground electrode 4 and the wall 8, can be of shorter design and
the distance B between the wall 8 and the stem or section 41 of
the ground electrode can be of longer design. As a result, heat
dissipation and ignition reliability are improved.
In the case of the embodiment of the spark plug according
to Fig. 4c, the wall 8 is formed in one piece with the end part
60, which is fastened on the combustion chamber-side end region
of the spark plug housing 2. A shoulder 64, on which the end
part 60 is seated, screwed and, if applicable, fastened by means
of seam welding or spot welding, can be formed on the spark plug
housing. The ground electrode carrier 6 is seated, especially
welded, on the end part 60. The ground electrode carrier 6 can
be seated on a shoulder 18 of the end part 60 and fastened there
by means of welding.
The dark arrows, which are directed towards the
longitudinal axis A of the spark plug, represent possible weld
seams or weld spots with which the end part 60 and/or the ground
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electrode carrier 6 and/or the wall 8 can be welded to the
respective components which support them.
The spark plug which is shown in Figs. 5 and 6 basically
has the same construction as the spark plugs which are shown in
the other figures except for the modification that the ground
electrodes 4 or the ground electrode carrier 6 are to be located
inside the wall 8, in fact at a distance from the inner surface
19 of the wall 8 in the direction of the centre electrode 3. A
spark plug housing 2 is supported by the insulating body 1,
wherein a centre electrode base 3a, upon which the centre
electrode 3 is seated, projects from the insulating body 1. The
ground electrodes 4, which are arranged around the centre
electrode 3, are supported by a ground electrode carrier 6 which
is seated on an end shoulder 17 of the end part 60 and, if
applicable, is fastened thereto by means of welding. The wall 8
is seated on a further shoulder 18 and, if applicable, is
fastened by means of welding. The
ground electrode carrier 6
and the ground electrodes 4 lie at a distance D away from the
inner surface 19 of the wall 8. As a result, a current-wise and
heat dissipation-wise separation of the ground electrodes 4 from
the wall 8 ensues and the heat can be satisfactorily dissipated
via the end part 60 or an exact and reliable current conduction
can be carried out via the end part 60.
As shown in Fig. 6, the ground electrodes 4 can also
project from a ground electrode carrier 6 which is formed in one
piece with the end part 60. In this case, the wall 8 is seated
upon the end part 60 upon the shoulder 18 and, if necessary,
fastened there by means of welding. Also in the case of this
embodiment, an electrode arrangement of shorter construction is
achieved, with which the conduction of heat and current is
favourably influenced.
Also in this case, the end part 60
encompasses the combustion chamber-side end region of the
insulating body 1 and/or the base part of the electrode 3 which
is remote from the combustion chamber. As a result of the one-
piece design of the end part 60 and the ground electrode carrier
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6, or with the ground electrodes 4, a simplified production of
the spark plug ensues since only the wall 8 needs to be seated
on and, if applicable, welded onto the one-piece component which
is formed by the ground electrodes 4 and the end part 60.
It is also possible to provide other types of fastening for
the end part 60 on the spark plug housing 2 or for the wall 8
and/or the ground electrode carrier on the end part 60 and/or on
the spark plug housing 2, for example by pressing. In any case,
the end part 60 is not seated upon the tapering insulating body.
The parts are necessarily spaced apart for insulation reasons.
The end part 60 encompasses the end region of the insulating
body 1 at a distance.
By one piece, it is primarily to be understood that the
respective component, or components, does not have, or do not
have, a welded or soldered connection and is, or are, formed
from the same material, or exists, or exist, as a single non-
assembled part or is, or are, formed from the same component.
Spark plugs with open chambers 5 are shown in Figs. 1 to 6.
Spark plugs with prechambers 5' are shown in Figs. 7 to 9. The
number of through-openings 10 which are formed in the chambers 5
and prechambers 5' and their shape or position, is selectable or
is determined by the application of the spark plug.
Shown in Fig. 7 is an embodiment of a spark plug according
to the invention, in which the ground electrode carrier 6, as in
Fig. 6, is formed in one piece with the end part 60. The end
face of the end part 60 which is remote from the combustion
chamber is seated on a shoulder 61 of the spark plug housing 2.
In particular, this region of the end part 60, as represented by
55 in Fig. 8, can be welded to the spark plug housing 2. On its
outer circumference the spark plug housing 2 carries a thread 51
by means of which is can be screwed into an engine block. It is
provided that the end part 60 has an annular shape and by the
inner surface of its end region which is remote from the
combustion chamber and/or by its end face which is remote from
the combustion chamber is connected to the spark plug housing 2
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or is seated upon this, preferably upon a shoulder 61.
Furthermore, it can be provided that the end region of the end
part 60 which is remote from the combustion chamber externally
encompasses an end region 64 of the spark plug housing 2 which
5 is close to the combustion chamber, or is connected to its outer
wall surface, forming a gap 56, if necessary. The
annular gap
56 can be formed between the end region 56 of the spark plug
housing 2 and the end region of the end part which is remote
from the combustion chamber.
10 The insulating body 1, which encompasses the centre
electrode base 3a and supports the electrode arrangement 3 or
the individual electrodes of the centre electrode 3, is inserted
into the spark plug housing 2 using a seal 52.
The end part 60, by means of a shoulder 58, supports the
15 wall 8 of a prechamber 5' which covers the electrodes, i.e. the
centre electrode 3 and the ground electrodes 4 and also the
ground electrode carrier 6.
Corresponding through-openings 10
are formed in the prechamber 5'.
A gap 53 is recessed in each case between the ground
electrodes 6 which project from the end part 60 and the inner
surface of the wall 8 so that the current distribution and heat
dissipation are defined.
It is furthermore provided that the ground electrode
carriers 6 project from the end part 60 in the region, or at the
level, in which or at which the end face of the wall 8 which is
remote from the combustion chamber is connected to the end part
60 or at which the shoulder 58 lies.
The centre electrode 3 is designed in such a way that the
combustion chamber-side end of the centre electrode 3 terminates
with the end of the centre electrode base 3a or does not project
beyond the combustion chamber-side end of the centre electrode
base 3a or that the electrodes 4 and/or ignition plates 24 which
are supported by the centre electrode 3 and/or the electrodes 4
and/or ignition plates 24 which are supported by the ground
electrodes 6 do not project beyond the combustion chamber-side
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end of the centre electrode base 3a on the combustion chamber
side. As a result, a short, compact design of the electrodes is
achieved, with which the heat transfers and current distribution
are advantageously influenced.
Shown in an embodiment of a prechamber spark plug according
to Fig. 8 are weld seams 55 which are to be advantageously
applied and with which the spark plug housing 2 can be connected
to the end part 60 or with which the end part 60 can be
connected to the wall 8 of the prechamber 5'. Such weld seams
55 can also be used in order to connect the centre electrode 3
to the centre electrode base 3a.
In principle, the gap 53 could even be omitted or the inner
surface of the wall 8 could bear against the outwardly
orientated surface of the ground electrode carrier 6 or be
connected to this. The
forming of a gap 53, however, brings
defined heat and current conditions.
Shown in Fig. 9 is a prechamber spark plug in which the
chamber 5' has a different shape from the chamber 5' of the
spark plugs according to Figs. 7 and 8. In
comparison to Fig.
8, the electrode arrangement 3 does not additionally project
beyond the electrode base 3a on the combustion chamber side, as
is the case with the spark plug according to Fig. 8. It is
apparent in the case of the spark plug according to Fig. 8 that
the end part 60 has a greater height than the end part 60 of the
spark plugs which are shown in Figs. 7 and 9. In
Fig. 8, the
centre electrode 3 projects beyond the centre electrode base 3a
so that the result is a higher electrode construction or a
higher construction of the end part 60 with the ground electrode
carriers 6 which are supported by it.
Figs. 10 and 11 show a spark plug in which the spark plug
housing 2 is extended on the combustion chamber side by a sleeve
70 which supports the prechamber 5'.
Fig. 10 shows a spark plug in which the prechamber 5' is
not supported directly by the spark plug housing 2 but supported
indirectly by using, or applying, an intermediate piece 70.
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This intermediate piece 70 is connected to the outer wall of the
spark plug housing 2, or is supported by this, and the
combustion chamber-side end region of the intermediate piece 70
supports the prechamber 5', or is connected to the wall 8 of the
prechamber 5', for example by means of welding.
For the production of such a spark plug, a thread, which
possibly exists on the spark plug housing 2, can be turned out
and the cylindrical intermediate piece can be fitted onto the
thereby prepared spark plug housing 2 and be fastened by means
of welding, especially spot welding or laser welding. As is
apparent from Figs. 10 and 11, it is provided that the
combustion chamber-side end region of the intermediate piece 70
encompasses the electrodes of the spark plug or the centre
electrode base 3a and also the insulating body 1. It
is
advantageous in this case if a gap 53 is recessed between the
intermediate piece 70 and the ground electrode carrier 6 in
order to realise the heat dissipation and the current flow in a
defined manner. The seating of the intermediate piece 70 upon
the spark plug housing 2 is carried out after installing the
electrodes on the centre electrode base 3a and after installing
the end part 60 together with the ground electrode carrier 6 on
the spark plug housing 2.
The thread 51 which is formed on the outer wall surface of
the intermediate piece 70 is designed in such a way that the
spark plug can be screwed into an engine block.
The intermediate piece 70 can be seated upon a shoulder 71
of the spark plug housing 2 or located upon this. To this end,
a shoulder base 72 is formed on the intermediate piece 70 and
can also serve as a carrier for a sealing ring 74 which is
provided if necessary. A seal 52 is provided between the spark
plug housing 2 and the insulating body 1. Furthermore, seating
of the insulating body or of the spark plug housing 2, or the
connecting of these two components, is carried out via a socket
component 73.
CA 02826807 2013-08-08
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The prechamber 5' does not project beyond the intermediate
piece 70, as seen radially to .the longitudinal axis of the spark
plug.
Furthermore, the wall 8 of the prechamber 5' is
advantageously free of a thread.
