U.S. patent number 3,872,338 [Application Number 05/381,758] was granted by the patent office on 1975-03-18 for spark plug.
Invention is credited to Bernard Wax.
United States Patent |
3,872,338 |
Wax |
March 18, 1975 |
SPARK PLUG
Abstract
A spark plug in which the points are covered by a non-conducting
material and in which a space between the non-conducting material
constitutes the spark gap for ignition of a fuel mixture. In
certain embodiments of the invention the spark plug has electrodes
constructed and arranged to produce a plurality of sparks during
each firing cycle of the plug.
Inventors: |
Wax; Bernard (Succasunna,
NJ) |
Family
ID: |
23506247 |
Appl.
No.: |
05/381,758 |
Filed: |
July 23, 1973 |
Current U.S.
Class: |
313/130; 313/141;
313/123 |
Current CPC
Class: |
H01T
13/39 (20130101) |
Current International
Class: |
H01T
13/39 (20060101); H01t 013/20 (); H01t
013/46 () |
Field of
Search: |
;313/118,141,130,128,141.1,130,131
;123/169E,169EL,169P,169PA,169PB,169PH |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Brody; Alfred L.
Attorney, Agent or Firm: Jurick; Rudolph J.
Claims
Having now described the invention what I desire to protect by
letters
1. A spark plug comprising,
a. a core of insulating material carried by a metal shell,
b. a main electrode carried by said core,
c. a ground electrode connected to said shell and having an end
portion spaced from an end portion of the main electrode to form a
spark gap
d. a non-conducting ceramic material covering the said end portion
of the ground electrode, and
e. a non-conducting ceramic material covering the said end portion
of the main electrode and spaced from the covering on the end
portion of the
2. A spark plug as recited in claim 1, wherein the said
non-conducting material is a high temperature glass.
Description
BACKGROUND OF THE INVENTION
In use, the electrodes of a spark plug are subjected to electric
and chemical erosion which not only limits the useful life of the
plug but, also, necessitates frequent cleaning of the electrode
tips and adjustment of the spark gap length. Various arrangements
have been proposed to overcome this problem.
U.S. Pat. No. 2,391,455, issued Dec. 25, 1945 to Franz R. Hensel
discloses a spark plug in which the electrodes are made of various
metal compositions having a high tensile strength and increased
resistance to gaseous attack at high temperatures.
U.S. Pat. No. 1,515,866, issued Nov. 18, 1924 to L. F. Martin,
discloses spark plug electrodes having tips plated with a metal
having a high heat conductivity and providing a non-oxidizable
surface.
The arrangements heretofore proposed for solving the problem of
erosion of spark plug electrodes result in varying degrees of
improved operating results as they are directed to decreasing the
rate at which erosion takes place. However, they do not completely
solve the problem as the spark for ignition of the fuel mixture
jumps directly between two metal surfaces or points.
In a spark plug made in accordance with this invention, the ends of
the electrodes across which the spark is generated are encased in a
high temperature, non-conducting material, thereby eliminating
electric and chemical erosion of the electrode ends, which results
in a long operating life.
SUMMARY OF THE INVENTION
A spark plug having electrodes for connection to a source of
ignition voltage, the electrodes having spaced tips imbedded in an
electrical insulating material. An air gap is provided in the
insulating material, which gap constitutes the spark gap for
ignition of a fuel mixture. In specific embodiments of the
invention, the spark plug includes more than two electrodes having
tips imbedded in an insulating material, thereby to provide a
plurality of sparks during each firing cycle of the plug.
An object of this invention is the provision of spark plug having
electrodes constructed and arranged to eliminate erosion thereof
during use.
An object of this invention is the provision of a spark plug in
which the spark for ignition of a fuel mixture is generated across
an air gap defined by spaced non-conducting materials.
An object of this invention is the provision of a spark plug having
electrodes for providing a plurality of sparks during each firing
cycle of the plug, each of the electrodes having tips covered with
non-conducting material.
The above-stated and other objects and advantages of the invention
will become apparent from the following description when taken with
the accompanying drawings. It will be understood, however, that the
drawings are for purposes of illustration and are not to be
construed as defining the scope or limits of the invention,
reference being had for the latter purpose to the claims appended
hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings wherein like reference characters denote like parts
in the several views:
FIG. 1 is a side elevational view of a single gap spark plug made
in accordance with one embodiment of this invention, certain parts
being shown in section;
FIG. 2 is a fragmentary cross-sectional view showing a single gap
spark plug made in accordance with another embodiment of this
invention;
FIG. 3 is a bottom plan view showing a two-gap spark plug made in
accordance with another embodiment of this invention, certain parts
being broken away;
FIG. 4 is a fragmentary, cross-sectional view taken along the line
4--4 of FIG. 3;
FIG. 5 is a fragmentary, cross-sectional view of a three-gap spark
plug made in accordance with another embodiment of this
invention;
FIG. 6 is a bottom plan view of a two-gap spark plug made in
accordance with still another embodiment of this invention; and
FIG. 7 is a fragmentary, cross-sectional view taken along the line
7--7 of FIG. 5.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1, the spark plug comprises a core 10 made of an
insulating material, a metal shell 11 provided with a threaded
portion 12, and a center electrode 13 terminating in a terminal 14
for connection of the plug to the ignition system of an internal
combustion engine. The core has a conical end portion 15 which is
spaced from the threaded portion of the shell. In a conventional
spark plug, the center electrode 13 has a bare tip projecting from
the core portion 15 and a bare ground electrode 16 having one end
welded to the threaded shell portion 12 and the other end spaced
from the exposed tip of the center electrode. The spacing between
these two electrodes constitutes the normal air gap across which a
spark is generated for ignition of a fuel mixture. In accordance
with this invention, the center electrode tip is encased in a
non-conducting coating identified by the numeral 17. Similarly, all
or a major portion of the ground electrode 16 is encased in a
non-conducting coating identified by the numeral 18. The
non-conducting coatings may be formed by applying a ceramic paste
or a high temperature glass over the electrode tips. In either
case, the coating material is subjected to suitable high
temperature, thereby to fuse the material to the electrodes. The
two coatings are spaced apart to form an air gap (a). When a
voltage of suitable magnitude is applied to the spark plug, a spark
will jump from the center electrode 13, through the insulator
coating 17, across the air gap (a), through the insulator coating
18, and to the ground electrode 16. The insulator coatings, which
may be relatively thin, prevent chemical and electrical erosion of
the electrode points.
In the FIG. 2 embodiment of the invention, the lower end of the
center electrode 20 is encased in the conical portion 15 of the
insulating core of the spark plug and the ground electrode 21 is
covered with a non-conducting coating 22. The air gap (b)
constitutes the spark gap for ignition of the fuel mixture.
A double-gap spark plug is shown in FIGS. 3 and 4. Here, the
conical core portion 15 has two, cylindrical projections 24 and 25
extending therefrom. The lower portion of the center electrode 26
is offset with a tip 27 encased within the projection 24. The
neutral electrode comprises a metal piece 28 encased within the
projection 25. The ground electrode 29 is encased in a
non-conducting coating 30. When the plug is fired, two sparks, in
series, jump across the air gaps (c) and (d).
A triple-gap spark plug made in accordance with this invention is
shown in FIG. 5. In this arrangement, the conical portion 15, of
the core 10, has a helical groove 32 formed in the peripheral
surface thereof. A first, generally-helical neutral electrode 33 is
positioned in the helical groove and has a tip 34 spaced from the
tip 35 of the center electrode, said tips 34 and 35 being encased
within non-conducting coating 36 and 37, respectively. A second
neutral electrode 38 is positioned in the helical groove. One end
of the neutral electrode 38 is spaced from the end of the neutral
electrode 33, and the other end of the neutral electrode 38 is
spaced from the ground electrode 39 welded to the threaded portion
12 of the spark plug case. The portions of the neutral electrodes
33 and 38 which are disposed in the helical groove are covered with
a ceramic paste as indicated by the reference numerals 40 and 41,
which paste is then heat cured and maintains these electrodes in
fixed position on the supporting core portion 15. It will be noted
that the ceramic paste extends somewhat beyond the proximate ends
of the two neutral electrodes. More specifically, these proximate
ends of the neutral electrodes are completely encased with the
ceramic but the ceramic is parted to form the air gap (e). That end
of the neutral electrode 38 which is proximate to the ground
electrode 39 also is completely encased in the ceramic. When a
firing voltage is applied to the spark plug, three sparks, in
series, will jump across the air gaps (f), (e) and (g).
FIGS. 6 and 7 show a two-gap spark plug made in accordance with
another embodiment of this invention. A neutral electrode 43 is
imbedded in a tubular member 44 made of a ceramic or a high
temperature glass, said member 44 including a radially-extending
leg 45 which is cemented in a diametrical slot formed in the end of
the core 46. The center electrode 47 has a tip 48 extending toward
the neutral electrode, which tip is encased within a non-conducting
coating 49. The ground electrode 50 is welded to the threaded
portion 12 of the spark plug shell and has a tip spaced from the
neutral electrode, said tip being encased in a non-conducting
coating 51. In this particular construction, the two spark gaps (h)
and (i) are well spaced from each other. Also, the spark gaps lie
on opposite sides of the tubular member 44 which serves as a
combustion deflector. When the spark plug is installed on an
internal combusion engine, initial ignition of the compressed fuel
mixture takes place at the spark gap (h). Although measured in
milliseconds, some period of time is required for combustion to
take place in those areas of the fuel mixture which are remote from
the point of initial ignition. The spacing of the spark gaps and
the action of the deflector provide a sufficient time delay so that
an ignitable fuel mixture is present at the spark gap (i) when the
second spark occurs across such gap. The net result is a more
complete combustion of the fuel which provides increased power to
the piston of the engine with a corresponding reduction in
pollutants exhausted into the atmosphere.
The coating of the electrode tips with a high temperature
non-conducting material eliminates chemical and electrical erosion
of the tips, whereby the electrodes may be made of an inexpensive
base metal. Also, accumulated carbon deposits on the non-conductor
surfaces can be removed easily and does not necessitate a
re-adjustment of the effective spark gap length, as is the case
when the eroded surface is removed from the tips of conventional
electrodes.
* * * * *