Information
-
Patent Grant
-
6676468
-
Patent Number
6,676,468
-
Date Filed
Friday, November 2, 200122 years ago
-
Date Issued
Tuesday, January 13, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Reichard; Dean A.
- Estrada; Angel R.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 445 7
- 445 49
- 313 141
- 313 142
- 228 160
- 228 155
- 228 159
-
International Classifications
-
Abstract
In producing a spark plug including a central electrode having a first chip including noble metal and an earth electrode having a second chip including the noble metal, a spark gap being disposed between the first and second chips, a chip including the noble metal. The chip is welded to an end of the central electrode and to an end of the earth electrode. The welded chip is cut to form the first and second chips and the spark gap.
Description
BACKEARTH OF THE INVENTION
1. Field of the Invention
This invention relates to a method of producing a spark plug including a central electrode having a first chip including a noble metal and an earth electrode having a second chip including the noble metal to have a gap between said first and second chips.
2. Description of the Prior Art
Spark plugs using a noble metal chip at the end of their central electrode to provide a spark gap are known. The use of a noble metal provides a long effective life. U.S. Pat. Ser. No. 5,107,168 discloses a spark plug in which a platinum or platinum alloy attachment member is attached to its central electrode to provide a longer effective life.
In such a prior art spark plug, the bonding process of the noble metal chips to the central electrode and the earth electrode is complicated because positioning of the noble metal chips is required for respective electrodes. Moreover, if there are a plurality of earth electrodes, the welding operation is more complicated because several noble chips must be positioned and bonded.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a superior method of producing a spark plug.
According to the present invention, a first aspect of the present invention provides a method of producing a spark plug including a central electrode having a first chip including noble metal and an earth electrode having a second chip including said noble metal, a spark gap being disposed between said first and second chips, comprising the steps of: preparing a chip including said noble metal; welding said chip to an end of said central electrode and to an end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
According to the present invention, a second aspect of the present invention provides a method of producing a spark plug including a central electrode having a first chip including noble metal and a plurality of earth electrodes, each having a second chip including said noble metal, spark gaps being provided between said first chip and second chips, comprising the steps of: preparing a chip including said noble metal; welding said chip to an end of said central electrode and to ends of said earth electrodes; and cutting said welded chip to form said first chip and said second chips with said spark gaps.
According to the present invention, a third aspect of the present invention provides a method of producing a spark plug including a central electrode having a first chip including noble metal and a tubular metal housing with an earth electrode having a second chip including said noble metal, a spark gap being provided between said first and second chips, comprising the steps of: preparing a chip including said noble metal having a hole of which opening size corresponds to a cross-sectional size of an end of said central electrode, an outline size of said chip corresponding to distance between said end of said central electrode and an end of said earth electrode; fitting said end of said central electrode to said hole; placing said earth electrode on an end of said tubular metal housing such that said chip is supported by contact with said end of said earth electrode; welding said fitted chip to said end of said central electrode and to said end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
According to the present invention, a fourth aspect of the present invention provides a method of producing a spark plug including a central electrode having a first chip including noble metal and a tubular metal housing having a plurality of earth electrodes, each earth electrode having a second chip including said noble metal, spark gaps being disposed between said first and second chips, comprising the steps of: preparing a chip including said noble metal; welding said chip to an end of said central electrode; placing a unit member including a plurality of said earth electrodes on one end of said housing such that ends of said earth electrodes are supported by contact with a surface of said chip to position said unit member; welding said unit member to said housing; welding ends of said earth electrodes to said chip; and cutting said welded chip to form said first chip and said second chips with said spark gaps.
According to the present invention, a fifth aspect of the present invention provides a method of producing a spark plug including a central electrode having a first chip including noble metal and having a circular plate shape and an earth electrode having a second chip including said noble metal and having a ring shape surrounding said first chip, a spark gap being disposed between said first and second chips, comprising the steps of: preparing a circular plate chip including said noble metal; welding said circular plate chip to an end of said central electrode and to an end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
In the fifth aspect, said earth electrode is formed to have one open dome.
In the fifth aspect, said earth electrode is formed to have a plurality of earth electrodes which are arranged to surround said first chip.
In the first, second, fourth, and fifth aspects, said chip has a positioning hole, said method further comprising the step of inserting said end of said central electrode into said positioning hole before welding.
In the first, second, fourth, and fifth aspects, an opening size of said hole is determined in accordance with a cross-sectional size of an end of said central electrode, said method further comprising the step of fitting said end of said central electrode to said hole.
In the first to fifth aspects, if it is assumed that a distance across said spark gap is G, a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in said earth electrode resulted by said step of welding and a surface of said earth electrode is L
1
, and a minimum distance between a discharging surface of said second chip defining said spark gap and a second surface of a second welding portion in said central electrode resulted by said step of welding and a surface of the central electrode is L
2
, said L
1
and L
2
are greater than a sum of said G and 0.3 mm.
In the first to fifth aspects, said welded chip is cut by either of discharge process, laser cutting, or wire cutting.
In the first to fifth aspects, said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
In the first to fifth aspects, said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
BRIEF DESCRIPTION OF THE DRAWINGS
The object and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1
is a side elevation view, partly in cross section, of a multi-electrode type of spark plug according to the invention;
FIG. 2A
is an enlarged side elevation view of a spark discharging portion according to the invention and
FIG. 2B
shows a plan view of the spark discharging portion;
FIG. 2C
is a further enlarged side elevation view of the spark discharge portion according to the invention;
FIGS. 3A
to
3
C are sectional side elevation views illustrating the producing process according to a first embodiment;
FIGS. 4A and 4B
are plan views of the central electrode illustrating a cutting process according to the first embodiment;
FIGS. 5A
to
5
C are sectional side elevation views illustrating a modified producing process according to the first embodiment;
FIG. 6
is a graphical drawing showing the relation of distance L with a misfiring rate with sample spark plugs according to the invention;
FIGS. 7A and 7B
are sectional side elevation views of the discharge portion of the spark plug according to a second embodiment illustrating the producing process;
FIG. 7C
is a plan view of the discharge portion of the spark plug according to the second embodiment illustrating the producing process;
FIGS. 8A
to
8
D are sectional side elevation views of the discharge portion of the spark plug illustrating the successive production process conditions according to a third embodiment;
FIGS. 9A
to
9
D are sectional side elevation views of the discharge portion of the spark plug illustrating the successive production process conditions according to a fourth embodiment;
FIG. 10A
is a plan view of the discharge portion of the spark plug according to a fifth embodiment;
FIG. 10B
is a sectional side elevation view taken on the line B—B in
FIG. 10A
;
FIG. 10C
is a perspective view of a circular plate chip according to the fifth embodiment;
FIG. 10D
is a sectional side elevation view of the discharge portion of the spark plug according to modification in the fifth embodiment;
FIG. 10E
is a plan view of the discharge portion according to modification in the fifth embodiment;
FIG. 11A
is a plan view of the discharge portion of a further modification of the discharge portion shown in
FIGS. 10D and 10E
;
FIG. 11B
is a sectional side elevation view taken on the line E—E in FIG.
11
A:
FIG. 12A
is a side elevation view of a discharge portion in a modification wherein the number of the earth electrode is only one;
FIG. 12B
is a plan view of a discharge portion in another modification and
FIG. 12C
is a side elevation view of the portion shown in
FIG. 12B
, wherein the number of the earth electrodes is two;
FIG. 12D
is a plan view of a discharge portion of still another modification, wherein the number of the earth electrodes is three;
FIGS. 13A and 13B
are side elevation views of the discharge portions, wherein discharge surfaces are modified;
FIGS. 14A and 14B
are plan views of the discharge portions, wherein the shape of the noble metal member is modified;
FIGS. 15A
to
15
C are sectional side elevational views of the discharge portion of a further modification, wherein the shape of the noble metal member is modified; and
FIG. 15D
is a sectional side elevation view of the discharge portion illustrating a modified noble metal member having a groove.
The same or corresponding elements or parts are designated with like references throughout the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The spark plug according to this embodiment is used for ignition in a vehicle engine for example.
FIG. 1
shows a side elevation view, partly in cross section, of a multi-electrode type of spark plug S
1
according to the invention. This spark plug S
1
is screwed in a threaded hole in an engine block (not shown) with a threaded portion
10
a.
FIG. 2A
shows an enlarged side elevation view in cross section of a spark discharging portion and
FIG. 2B
shows the plan view.
The multi-electrode type of spark plug S
1
includes a tubular metal housing
10
having an inner hole
36
therein and has the thread portion
10
a
for mounting on the engine block. The housing
10
supports an insulator
20
made of alumina ceramics (Al
2
O
3
) or the like in the inner hole
36
of the housing
10
. An end
21
of the insulator
20
is exposed to the space at one end
11
of the housing
10
.
The insulator
20
supports the central electrode
30
in an axial hole
22
thereof, so that the housing
10
supports the central electrode
30
with insulation. An end
31
of the central electrode
30
is extended from the end
21
of the insulator
20
. The central electrode
30
includes an inner material and an outer material around the inner material. The inner material includes a metallic material having superior heat conductivity such as Cu. The outer material includes a metallic material having a superior heat resistance and a superior corrosion resistance such as Ni group alloy. In this embodiment, the central electrode
30
has a cylindrical shape.
At one end
11
of the housing
10
, a plurality of earth electrodes
40
are fixed to the housing
10
at their one ends
41
by means of welding or the like such that the earth electrodes surround the end
31
of the central electrode
30
. These earth electrodes
40
include a Ni alloy or Fe alloy or the like. In this embodiment, each of the earth electrodes
40
has a post shape of which section is a rectangular and is bent at the intermediate portion thereof to direct the other end
42
of the earth electrode
40
opposite to one end
11
of the housing
10
toward the end
31
of the central electrode
30
.
These earth electrodes
40
are arranged at the opposite positions on the circular shape of the end
11
, so that the central electrode chip
50
on the center electrode
30
is arranged between these earth electrodes
40
with spark gaps
70
.
At the end
31
of the central electrode
30
, a central electrode chip (discharge member)
50
comprising noble metal or a noble metal alloy is bonded by laser welding or the like to an end surface of the end
31
which is perpendicular to the axis AX. On the other hand, an earth electrode chip (discharge member)
60
having a post shape consisting of noble metal or a noble metal alloy is bonded to the other end
42
of each earth electrode
40
. The central electrode chip
50
and respective earth electrode chips
60
form spark gaps
70
therebetween with a distance G.
Each of the central electrode chip
50
and the earth electrode chips
60
mainly includes Pt or Ir and at least one of Rh (rhodium), Pt, Ru (ruthenium), Pd (palladium), and W (tungsten) is added thereto.
In operation, at least one of gaps
70
develops discharge which ignites the fuel-air mixture in the combustion chamber (not shown). This generates a flame core which grows and expands in the combustion chamber.
This embodiment features in providing and producing the central electrode chip
50
and the earth electrode chips
60
. So, these points are mainly argued in this embodiment, and description about other basic methods of producing the spark plug S
1
are omitted.
FIGS. 3A
to
3
C are sectional side elevation views illustrating the producing process.
FIGS. 4A and 4B
are plan views of the central electrode
50
illustrating a cutting process.
At first, an assembly in which the insulator
20
, the central electrode
30
, and the earth electrode
40
are fixed to the housing
10
, is prepared, and a noble metal member
80
for the central electrode chip
50
and the earth electrode chips
60
are prepared.
The noble metal member
80
has a size defined by the other end
42
of the earth electrodes
40
. That is, the noble metal member
80
is a square plate of which length of the side substantially agrees with distance D between the other ends of the earth electrodes facing to each other. The thickness t of the square plate agrees with difference between the height H
1
of the other ends
42
of the earth electrodes
42
and the height H
2
of the central electrode
30
(
31
) from the end
11
of the housing
10
. The noble metal member
80
is fit into the space between the other ends
42
of the earth electrodes
40
as shown in
FIG. 3A
until the bottom surface of the noble metal member
80
seats on the top surface of the end
31
of the central electrode
30
as shown in FIG.
3
B. Then, the noble metal member
80
contacts with the top surface of the end
31
of the central electrode
30
and the end surfaces of the other ends
42
of the earth electrodes
40
.
In this condition, the noble metal member
80
is welded to other ends
42
of the earth electrodes
40
and to the end
31
of the central electrode
30
by laser welding or resistance welding or the like (chip welding process).
Next, portions of the welded noble metal member
80
are cut between the other ends
42
and the ends
31
of the central electrode
30
on the planes P in parallel to the axis AX and perpendicular to an axis AX
1
of the other end
42
of the earth electrode
40
to produce the spark gaps
70
(cutting process). More specifically, the noble metal member
80
is cut along the dashed lines by either of discharge process, laser cutting, or wire cutting as shown in FIG.
4
B. During this process, the width of cutting is made equal to the gap distance G by adjusting the unit for the cutting process. Accordingly, as shown in
FIG. 4A
, the noble metal member
80
is cut to provide the central electrode chip
50
and the earth electrode chips
60
with spark gaps
70
. The corners
80
a
of the noble metal member
80
are cut off.
FIGS. 5A
to
5
C shows sectional side elevation views illustrating a modification process of producing the central electrode chip
50
and the earth electrode chips
60
in the first embodiment.
This producing process is substantially the same as that shown in
FIGS. 4A
to
4
C. The difference is that the noble metal plate
80
′ has a positioning hole
81
at its center to provide accurate, easy positioning. The diameter D
1
of the positioning hole
81
substantially agrees with the diameter D
2
of the end
31
of the central electrode
30
for positioning. Moreover, the diameter (opening size) D
1
of the positioning hole
81
may be slightly smaller than the diameter (cross-sectional area) D
2
of the end
31
of the central electrode
30
to fit the end
31
to the positioning hole
81
. In other words, the diameter or the opening size D
1
of the positioning hole
81
is determined in accordance with the diameter (the cross-sectional area) D
2
of the end
31
of the central electrode
30
in order to provide (press-) fitting. This temporarily fixes the noble metal plate
80
′ to the end
31
of the central electrode
30
because of the fitting of the noble metal plate
80
′ into the end
31
of the central electrode
30
in addition to the positioning with the positioning hole
81
. The positioning hole
81
is a through hole in this embodiment. However, the positioning hole
81
may be a non-through hole. In this case, the end
31
of the central electrode
30
is inserted into the positioning hole
81
with or without fitting.
With the producing method according to the first embodiment, the number of processes in bonding, i.e., the number of processes of bonding and accompany processes can be reduced. Particularly, the number of the positioning processes of the noble metal plate
80
or
80
′ is reduced from five to one if the number of the earth electrode is four, so that the efficiency in producing the spark plug is increased. Moreover, the positioning is made accurate, and the dispersion in positioning can be reduced. Moreover, this process automatically provides parallelism between the central electrode chip
50
and respective earth electrode chips
60
without any special process.
This process is not limited to the multi-earth electrode type of spark plugs but is applicable to the spark plugs having a single central electrode and a single earth electrode.
As mentioned above, according to the modification in the first embodiment, the positioning hole
81
for positioning the noble metal plate
80
′ is formed at the center thereof, that is, a position corresponding to the end
31
of the central electrode
30
. This improves the efficiency in assembling process of the noble metal plate
80
′. Moreover, making the diameter of the positioning hole
80
′ slightly smaller than that of the end
31
of the central electrode
30
provides temporal fixing the noble metal plate
80
′ to the end
31
of the central electrode
30
by fitting with easiness, so that the efficiency in assembling process of the noble metal plate
80
′ is further improved.
Moreover, in this embodiment, it is favorable that the noble metal plate
80
or
80
′ is cut by a discharge process, laser cutting, or wire cutting to provide fine cutting surfaces.
In this embodiment, the distance from on of the central electrode chip
50
and the earth electrode chip
60
to the other is controlled. It is assumed that a distance from the discharge surface of one of the central electrode chip
50
and the earth electrode chip
60
to a welding portion
61
or a base material including the earth electrode
40
or the central electrode
30
is L, it is favorable that L is greater than sum of the spark gap distance G and 0.3 mm. That is, L ≧(G+0.3) mm. The inventors experimentally provide this relation.
FIG. 2C
shows an enlarge side elevation view of the discharge portion for illustrating this relation more specifically. If it is assumed that a distance across the spark gap is G, a minimum distance between a discharging surface
54
of the central electrode chip
50
defining the spark gap
70
and a surface
63
of a first welding portion
61
in the earth electrode
40
resulted by welding and a surface
62
of the earth electrode is L
1
(L), and a minimum distance between a discharging surface
64
of the earth electrode chip
60
defining the spark gap
70
and a surface
53
of a second welding portion
51
in the central electrode
30
resulted by welding and a surface
52
of the central electrode
30
is L
2
(L), L
1
and L
2
are greater than a sum of said G and 0.3 mm.
FIG. 6
is a graphical drawing showing the relation of distance L with a misfiring rate with sample spark plugs. The sample spark plugs are prepared in accordance with the above-mentioned process, and the noble metal member includes an Ir alloy including 90% Ir and 10% Rh by weight (hereinafter, this alloy is referred to as Ir-10Rh). The spark gap distance G is varied from 0.3 mm to 0.8 mm to vary L, and the misfiring rate, i.e., the rate of discharge to the base material or the welding portion
50
a
or
60
a
is measured with respect to the total.
The sample spark plug S
1
is fixed and ignition discharge is generated in the condition that the combustion chamber is pressed up to 0.6 MPa.
As shown in
FIG. 6
, in the case that the gap distance G is 0.3 mm, no misfiring occurs if the distance L is equal to or greater than 0.5 mm. That is, all discharges are made only between the central electrode chip
50
and the earth electrode chip
60
in this condition.
In the case that the gap distance G is 0.5 mm, no misfiring occurs if the distance L is equal to or greater than 0.8 mm. That is, all discharges are made only between the central electrode chip
50
and the earth electrode chip
60
in this condition.
In the case that the gap distance G is 0.8 mm, no misfiring occurs if the distance L is equal to or greater than 1.1 mm. That is, all discharges are made only between the central electrode chip
50
and the earth electrode chip
60
in this condition. Accordingly, it is favorable that L (L
1
and L
2
) is greater than sum of the spark gap distance G and 0.3 mm. Thus, the distance L and the gap distance G are determined to prevent misfiring. This reduces burn-off in the base material or the welding portion
51
or
61
. This prevents the central electrode chip
50
and the earth electrode chips
60
from being disconnected.
As mentioned above, the first embodiment provides a method of producing a spark plug including the central electrode
30
having the central electrode chip
50
including noble metal and the earth electrode
40
having the earth electrode chip
60
including the noble metal, a spark gap
70
being disposed between the central electrode chip
50
and the earth electrode chip
60
, comprising the steps of: preparing the chip (noble metal member)
80
including the noble metal; welding the chip
80
to an end
31
of the central electrode
30
and to an end
42
of said earth electrode
40
; and cutting the welded chip
80
to form the central electrode chip
50
and the earth electrode chip
60
and the spark gap
70
.
SECOND EMBODIMENT
The spark plug according to a second embodiment is provided substantially in the same manner as that of the first embodiment. The difference is that the central electrode chip
50
is fixed independently, and on the other hand, earth electrode chips
60
are providing by bonding a unit noble metal member
90
to the earth electrodes
40
and by cutting the noble metal member
90
to provide respective earth electrode chips
60
.
FIGS. 7A and 7B
show sectional side elevational views of the discharge portion of the spark plug according to the second embodiment illustrating the producing process.
FIG. 7C
shows a plan view of the discharge portion of the spark plug according to the second embodiment illustrating the condition where the unit noble metal member
90
is welded before cutting.
This producing method is applicable only to a multi-earth electrode type of spark plug. That is, as shown in
FIG. 1
, a plurality of earth electrodes are provided such that the earth electrodes
40
surround the central electrode
30
.
At first, the central electrode chip
50
is welded as shown in FIG.
7
A. Next, the noble metal member
90
having a square frame shape including respective earth electrode chips
60
is prepared. The noble metal member
90
is welded to respective earth electrodes
40
as shown in
FIGS. 7B and 7C
. This provides spark gaps
70
between the central electrode chip
50
and portions of the noble metal member
90
. Next, the noble metal member
90
is cut along the dashed lines in
FIG. 7C
such that respective earth-side chips
60
are provided.
In this process, it is also possible that after bonding the noble metal member
90
to the earth electrodes
40
, the central electrode chip
50
is welded to form the spark gaps
70
.
According to this embodiment, in the multi-earth electrode type of spark plug, the noble metal member
90
is welded to respective earth electrodes
40
and then, the noble metal member
90
is cut to provide the earth electrode chips
60
, so that the number of process for bonding, particularly, positioning the earth electrode chips can be reduced. This improves the efficiency in producing the spark plug.
In this embodiment, the positioning hole may be formed in the central electrode chip
50
to fit it into the end
31
of the central electrode
30
. Moreover, it is favorable that the relation L≧(G+0.3) mm is established.
THIRD EMBODIMENT
The spark plug according to a third embodiment is provided substantially in the same manner as that of the first embodiment. The difference is that the earth electrodes are attached and welded after fitting the noble metal member
100
having a positioning hole
101
.
FIGS. 8A
to
8
D are sectional side elevation views of the discharge portion of the spark plug illustrating the successive production process conditions.
At first, as shown in
FIG. 8A
, the noble metal member
100
having a positioning hole
101
is prepared. The end
31
of the central electrode
30
is inserted and fitted into the positioning hole
101
to support the noble metal member
100
. The noble metal member
100
has the same structure as the noble metal member
80
′ in the second embodiment. That is, the diameter of the positioning hole
101
is determined in accordance with the diameter of the end
31
of the central electrode
30
, and its outer diameter is determined in accordance with the position and size of the earth electrodes
40
.
Next, as shown in
FIG. 8B
, the one end
41
of each earth electrode
40
is placed on the one end
11
of the housing
10
such that the surface of the other end
42
of the earth electrode
40
contacts with the noble metal member
100
to support the earth electrode
40
. In this condition, one ends
41
of the earth electrodes
40
are welded to one end
11
of the housing
10
.
Next, as shown in
FIG. 8C
, the fitting portion between the end
31
of the central electrode and the noble metal member
100
, and the contacting portion between the noble metal member
100
and the other ends
42
of the earth electrodes
40
are welded.
Next, the noble metal
100
is cut to provide the spark gaps
70
with chips
50
and
60
being remained as shown in FIG.
8
D. This provides the spark plug S
1
shown in
FIG. 1
too.
According to the third embodiment, the bonding process can be effected at a high efficiency similarly to the first embodiment because the noble metal member
100
including the resultant chips
50
and
60
is welded and then, cut to provide the spark gap
70
.
In this embodiment, the accuracy in producing the spark gaps
70
is favorably provided by cutting the noble metal member
100
similarly to the first embodiment. Moreover, it is favorable that the relation L≧(G+0.3) mm is established. Furthermore, this embodiment is applicable to the spark plug having a single central electrode and a single earth electrode.
Moreover, this embodiment improves the efficiency in bonding the earth electrodes
40
because the end
31
of the central electrode
30
is fitted into the positioning hole
101
to temporarily support the noble metal member
100
, and the earth electrodes
40
are placed using the noble metal member
100
as a spacer for supporting the earth electrodes
40
, which makes the welding process easier and provides a stable welding result.
FOURTH EMBODIMENT
The spark plug according to a fourth embodiment is provided substantially in the same manner as that of the first embodiment. The difference is that a plurality of earth electrodes
40
are formed in a unit and is attached to the one end
11
of the housing at the same time. That is, a plurality of earth electrodes
40
are connected by a connecting member
46
. For this, this embodiment is applicable only to the spark plugs having a plurality of earth electrodes.
FIGS. 9A
to
9
D are sectional side elevation views of the discharge portion of the spark plug illustrating the successive production process conditions according to the fourth embodiment.
At first, as shown in
FIG. 9A
, a work including the central electrode
30
supported by the insulator
20
and the noble metal member
110
having a positioning hole
111
is prepared. The end
31
of the central electrode
30
is inserted and fitted into the positioning hole
111
to support the noble metal member
110
. The noble metal member
110
has the same structure as the noble metal member
80
′ in the second embodiment. That is, the diameter of the positioning hole
111
is determined in accordance with the diameter of the end
31
of the central electrode
30
, and its outer diameter is determined in accordance with the position and size of the earth electrodes
40
in the unit member
45
. The noble metal member
110
is welded to the end
31
of the central electrode
30
.
Next, as shown in
FIG. 9B
, the unit member
45
including a plurality of earth electrodes
40
connected to each other by the connecting member
46
is prepared. The connecting member
46
has a ring shape corresponding to the ring shape of the one end
11
of the housing
10
.
The central electrode
30
to which the noble metal member
110
is bonded is assembled in the housing
10
with the insulator
20
.
Place the unit member
45
on the one end of the housing
10
such that the other ends
42
of the earth electrodes
40
contact with the noble metal member
110
to support the earth electrodes
40
as shown in FIG.
9
C.
Next the contacting portions between the noble metal member
110
and the other ends
42
of a plurality of the earth electrodes
40
and the contacting portions between one ends
41
of the respective earth electrodes
40
and the one end
11
of the housing
10
are welded as shown in FIG.
9
C.
Next, as shown in
FIG. 9D
, the noble metal member
110
is cut to provide the spark gaps
70
. This provides the spark plug S
1
shown in
FIG. 1
also.
According to the fourth embodiment, the bonding process can be effected at a higher efficiency than the third embodiment because the unit member
45
including a plurality of earth electrodes
30
is temporarily fixed to the housing
10
at the same time.
In this embodiment, it is also favorable that the relation L≧(G+0.3) mm is established.
FIFTH EMBODIMENT
FIG. 10A
is a plan view of the discharge portion of the spark plug S
2
according to a fifth embodiment.
FIG. 10B
is a sectional side elevation view taken on the line B—B in FIG.
10
A. This spark plug S
2
is obtained by modifying the shape of the discharge portion of the spark plug shown in FIG.
1
.
The spark plug S
2
includes one central electrode
30
and earth electrodes (four earth electrodes in this embodiment) are bonded such that the earth electrodes
40
surround the central electrode
30
. A central electrode chip
50
is bonded to the central electrode
30
, and a ring chip
85
is bonded to respective earth electrodes
40
. The inner surface of the ring chip
85
faces the central electrode chip
50
to form a spark gap
70
.
The fifth embodiment provides a method of producing the spark plug S
2
shown in
FIGS. 10A and 10B
.
FIG. 10C
is a perspective view of a noble metal member used for the spark plug S
2
.
At first, a noble metal member
120
having a circular plate shape is prepared. The noble metal member
120
corresponds to the central electrode chip
50
, the ring chip
85
, and the cut portion as the spark gap
70
.
Next, the noble metal member
120
is placed on the end
31
of the central electrode
30
between the other ends
42
of the earth electrodes
40
. Next, the noble metal member
120
is welded to the end
31
of the central electrode
30
and welded to respective the other ends
42
of the earth electrodes
40
.
Next, the noble metal member
120
is cut to provide the central electrode chip
50
and the ring chip
85
with the spark gap
70
. The above-mentioned process provides the spark plug S
2
shown in
FIGS. 10A and 10B
.
According to the fifth embodiment, the spark plug S
2
is produced by welding the noble metal member
120
having a circular plate shape to the central electrode
30
and the earth electrodes
40
and by cutting the noble metal member
120
to provide the central electrode chip
50
and the ring chip
85
with the spark gap
70
, so that the number of processes for producing the spark plug S
2
can be reduced. That is, the efficiency of producing the spark plug is improved.
In this embodiment, the spark gap
70
can be provided accurately due to cutting similarly to the first embodiment. Moreover, the positioning hole
121
may be provided in the noble metal member
120
. Furthermore, in this embodiment, it is also favorable that the relation L≧(G+0.3) mm is established.
In
FIGS. 10A and 10B
, a plurality of earth electrodes
40
are provided and welded to all earth electrodes
40
. However, only one earth electrode
40
having a circular shape surrounding the central electrode
30
may be used.
FIGS. 10D and 10E
show this example.
FIG. 10D
is a plan view of the discharge portion of this example.
FIG. 10E
is a sectional side elevation view taken on the line C—C in FIG.
10
A. The earth electrode is formed to have an open dome
40
′. The ring chip
85
is welded to the center edge of the open dome
40
′.
FIG. 11A
is a plan view of the discharge portion of modification of the discharge portion shown in
FIG. 10D and 10E
.
FIG. 11B
is a sectional side elevation view taken on the line E—E in FIG.
11
A. After forming the spark plug as shown in
FIGS. 10A and 10B
, the ring chip
85
may cut in the radial directions as shown in
FIG. 11A
to provide segmented earth electrode chips
60
. In other words, this embodiment is not subjected to limitation of the number of earth electrodes
40
.
OTHER MODIFICATIONS
In the embodiments without limitation in the number of earth electrodes
40
out of the above-mentioned embodiments, there are modifications in accordance with the number of the earth electrodes as shown in
FIGS. 12A
to
12
D.
FIG. 12A
is a side elevational view of a discharge portion in modification wherein the number of the earth electrode
40
is only one.
FIG. 12B
is a plan view of a discharge portion in another modification and
FIG. 12C
is a side elevation view of this portion, wherein the number of the earth electrodes is two.
FIG. 12D
is a plan view of a discharge portion of still another modification, wherein the number of the earth electrodes is three.
In each of the above-mentioned modifications, the noble metal member is welded to the central electrode
30
and to at least an earth electrode
40
, and then, the noble metal member is cut at least a portion between the central electrode and at least an earth electrode to provide at least a spark gap. This is applicable to the spark plug having more than four earth electrodes also.
Moreover, the discharge surfaces of both chips facing to each other may have various shapes even if both discharge surfaces have parallelism therebetween. That is, the discharge surfaces may be slant surfaces as shown in FIG.
13
A and may be uneven surfaces as shown in FIG.
13
B.
Moreover, if the noble metal member
80
having a square top surface is cut as shown in
FIG. 4A
, there are useless portions at corners. However, using another noble metal member having a top surface of a cross shape (not shown) provides no useless portions.
Further, the noble metal member
80
may have slits
80
b
, at the cutting places as shown in
FIG. 14A
to improve the efficiency in the cutting process.
FIG. 14B
shows the view of the discharge portion after cutting.
FIGS. 15A
to
15
C show a further modification. The central electrode
31
and the earth electrodes
40
are made to have the same height along the axis AX from the one end of the housing
10
. A noble metal plate
80
c
having a size covering all earth electrodes
40
is placed on the end
31
of the central electrode
30
and the other ends
42
of the earth electrodes
40
as shown in FIG.
15
A. Next, the noble metal plate
80
c
is welded to the central electrode
30
and to the other ends
42
of the earth electrodes
40
as shown in FIG.
15
B. Next, the noble metal plate
80
c
is cut to provide the central electrode chip
50
and the earth electrode chips
60
with spark gap
70
as shown in FIG.
15
C. Moreover, the noble metal member
80
d
may have grooves
49
at the cutting places to make the cutting process easy as shown in FIG.
15
D.
In the second embodiment, the noble metal chip
50
may have the positioning hole.
In the above-mentioned embodiments, each welded chip
80
,
80
′, or
120
is cut by either of discharge process, laser cutting, or wire cutting.
Claims
- 1. A method of producing a spark plug including a central electrode having a first chip including noble metal and an earth electrode having a second chip including said noble metal, a spark gap being disposed between said first and second chips, comprising the steps of:preparing a chip including said noble metal; welding said chip to an end of said central electrode and to an end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
- 2. The method as claimed in claim 1, wherein said chip has a positioning hole, said method further comprising the step of inserting said end of said central electrode into said positioning hole before welding.
- 3. The method as claimed in claim 2, wherein an opening size of said hole is determined in accordance with a cross-sectional size of an end of said central electrode, said method further comprising the step of fitting said end of said central electrode to said hole.
- 4. The method as claimed in claim 1, wherein, L1 and L2 are greater than a sum of G and 0.3 mm where G is a distance across said spark gap, L1 is a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in said earth electrode resulting from said step of welding and a surface of said earth electrode and L2 is a minimum distance between a discharging surface of said second chip defining said spark gap and a second surface of a second welding portion in said central electrode resulting from said step of welding and a surface of the central electrode.
- 5. The method as claimed in claim 1, wherein said welded chip is cut by either of a discharge process, laser cutting, or wire cutting.
- 6. The method as claimed in claim 1, wherein said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
- 7. The method as claimed in claim 1, wherein said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
- 8. The method as claimed in claim 1, wherein said chip is single and welded both to said end of said center electrode and said end of said earth electrode and then is cut at an intermediate position thereof so as to form said first and second chips and said spark gap.
- 9. The method as claimed in claim 1, wherein said central electrode and said earth electrode are formed to have the same height along the axis of said central electrode from one end of a housing supporting said central electrode and said earth electrode with a size covering said ends of said central electrode and said earth electrode, said method further comprising the step of placing said chip on said ends of said central electrode and said earth electrode before the step of welding, wherein said chip has a groove at a cutting place for the step of cutting, further comprising the step of forming a groove at a cutting place in step of cutting.
- 10. The method as claimed in claim 1, wherein said central electrode is supported by a housing and wherein said central electrode and said earth electrode are formed having the same height along the axis of said central electrode from one end of said housing supporting said central electrode, and wherein said earth electrode is of a size covering said ends of said central electrode and said earth electrode, and wherein said method further comprises the steps of:placing said chip on said ends of said central electrode and said earth electrode before the step of welding, and forming a groove at a cutting place on said chip in during said step of cutting such that said chip has a groove at a cutting place at the time of cutting.
- 11. A method of producing a spark plug including a central electrode having a first chip including noble metal and a plurality of earth electrodes, each having a second chip including said noble metal, spark gaps being provided between said first chip and second chips, comprising the steps of:preparing a chip including said noble metal; welding said chip to an end of said central electrode and to ends of said earth electrodes; and cutting said welded chip to form said first chip and said second chips with said spark gaps.
- 12. The method as claimed in claim 11, wherein said chip has a positioning hole, said method further comprising the step of inserting said end of said central electrode into said positioning hole before welding.
- 13. The method as claimed in claim 12, wherein an opening size of said hole is determined in accordance with a cross-sectional size of an end of said central electrode, said method further comprising the step of fitting said end of said central electrode to said hole.
- 14. The method as claimed in claim 11, wherein, L1 and L2 are greater than a sum of G and 0.3 mm where G is a distance across said spark gap, L1 is a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in each of said earth electrodes resulting from said step of welding and a surface of each of said earth electrodes, and L2 is a minimum distance between a discharging surface of each of said second chips defining said spark gap and a second surface of a second welding portion in said central electrode resulting from said step of welding and a surface of the central electrode.
- 15. The method as claimed in claim 11, wherein said welded chip is cut by either of a discharge process, laser cutting, or wire cutting.
- 16. The method as claimed in claim 11, wherein said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
- 17. The method as claimed in claim 8, wherein said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
- 18. The method as claimed in claim 11, wherein said chip is single and welded to said end of said center electrode and said end of said earth electrodes and then is cut at intermediate positions thereof so as to form said first chip and said second chips and said spark gap.
- 19. A method of producing a spark plug including a central electrode having a first chip including noble metal and a tubular metal housing with an earth electrode having a second chip including said noble metal, a spark gap being disposed between said first and second chips, comprising the steps of:preparing a chip including said noble metal having a hole of which opening size corresponds to a cross-sectional size of an end of said central electrode, an outline size of said chip corresponding to distance between said end of said central electrode and an end of said earth electrode; fitting said end of said central electrode to said hole; placing said earth electrode on an end of said tubular metal housing such that said chip is supported by contact with said end of said earth electrode; welding said fitted chip to said end of said central electrode and to said end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
- 20. The method as claimed in claim 19, wherein L1 and L2 are greater than a sum of G and 0.3 mm where G is a distance across said spark gap, L1 is a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in said earth electrode resulting from said step of welding and a surface of each of said earth electrodes, and L2 is a minimum distance between a discharging surface of said second chip defining said spark gap and a second surface of a second welding portion in said central electrode resulting from said step of welding and a surface of the central electrode.
- 21. The method as claimed in claim 19, wherein said welded chip is cut by either of discharge process, laser cutting, or wire cutting.
- 22. The method as claimed in claim 19, wherein said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
- 23. The method as claimed in claim 19, wherein said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
- 24. A method of producing a spark plug including a central electrode having a first chip including noble metal and a tubular metal housing having a plurality of earth electrodes, each earth electrode having a second chip including said noble metal, spark gaps being provided between said first chip and second chips, comprising the steps of:preparing a chip including said noble metal; welding said chip to an end of said central electrode; placing a unit member including a plurality of said earth electrodes on one end of said housing such that ends of said earth electrodes are supported by contact with a surface of said chip to position said unit member; welding said unit member to said housing; welding ends of said earth electrodes to said chip; and cutting said welded chip to form said first chip and said second chips with said spark gaps.
- 25. The method as claimed in claim 24, wherein said chip has a positioning hole, said method further comprising the step of inserting said end of said central electrode into said positioning hole before welding.
- 26. The method as claimed in claim 25, wherein an opening size of said hole is determined in accordance with a cross-sectional size of an end of said central electrode, said method further comprising the step of fitting said end of said central electrode to said hole.
- 27. The method as claimed in claim 24, wherein, L1 and L2 are greater than a sum of G and 0.3 mm where G is a distance across said spark gap, L1 is a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in each of said earth electrodes resulting from said step of welding and a surface 62 of each of said earth electrodes, and a minimum distance between a discharging surface of each of said second chips defining said spark gap and a second surface of a second welding portion in said central electrode resulting from said step of welding and a surface of the central electrode.
- 28. The method as claimed in claim 24, wherein said welded chip is cut by either of discharge process, laser cutting, or wire cutting.
- 29. The method as claimed in claim 24, wherein said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
- 30. The method as claimed in claim 24, wherein said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
- 31. A method of producing a spark plug including a central electrode having a first chip including noble metal and having a circular plate shape and an earth electrode having a second chip including said noble metal and having a ring shape surrounding said first chip, a spark gap being provided between said first and second chips, comprising the steps of:preparing a circular plate chip including said noble metal; welding said circular plate chip to an end of said central electrode and to an end of said earth electrode; and cutting said welded chip to form said first and second chips and said spark gap.
- 32. The method as claimed in claim 31, wherein said earth electrode is formed to have one open dome.
- 33. The method as claimed in claim 31, wherein said earth electrode is formed to have a plurality of earth electrodes which are arranged to surround said first chip.
- 34. The method as claimed in claim 31, wherein said chip has a positioning hole, said method further comprising the step of inserting said end of said central electrode into said positioning hole before welding.
- 35. The method as claimed in claim 34, wherein an opening size of said hole is determined in accordance with a cross-sectional size of an end of said central electrode, said method further comprising the step of press-fitting said end of said central electrode to said hole.
- 36. The method as claimed in claim 31, wherein L1 and L2 are greater than a sum of G and 0.3 mm where G is a distance across said spark gap, L1 is a minimum distance between a discharging surface of said first chip defining said spark gap and a first surface of a first welding portion in said earth electrodes resulting from said step of welding and a surface 62 of said earth electrodes, and L2 is a minimum distance between a discharging surface of said second chip defining said spark gap and a second surface of a second welding portion in said central electrode resulting from said step of welding and a surface of the central electrode.
- 37. The method as claimed in claim 31, wherein said welded chip is cut by either of discharge process, laser cutting, or wire cutting.
- 38. The method as claimed in claim 31, wherein said noble metal mainly includes Pt and further includes at least one of Ir, Rh, Ru, Pd, Ni, and W.
- 39. The method as claimed in claim 31, wherein said noble metal mainly includes Ir and further includes at least one of Pt, Rh, Ru, Pd, Ni, and W.
- 40. The method as claimed in claim 31, wherein said chip is single and welded both to said end of said center electrode and said end of said earth electrodes and then is cut at an intermediate position thereof so as to form said first and second chips and said spark gap.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-337835 |
Nov 2000 |
JP |
|
US Referenced Citations (20)
Foreign Referenced Citations (1)
Number |
Date |
Country |
A-3-34283 |
Feb 1991 |
JP |