Information
-
Patent Grant
-
6360706
-
Patent Number
6,360,706
-
Date Filed
Friday, March 3, 200024 years ago
-
Date Issued
Tuesday, March 26, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 169 PH
- 123 169 PA
- 123 143 C
- 123 633
- 123 634
- 123 635
- 439 126
- 439 127
- 439 128
-
International Classifications
-
Abstract
An interface device for interfacing a pencil coil to a spark plug is provided. The interface device comprises a substantially C-shaped spring adapted to mechanically and electrically engage a pencil coil shield and also adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield. Also provided is a pencil coil shield assembly for interfacing a pencil coil to a spark plug. The pencil coil shield assembly comprises a substantially cylindrical pencil coil and a spring. The substantially cylindrical pencil coil shield is adapted to surround the pencil coil. The spring is mechanically and electrically engaged with the pencil coil shield and is adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield. The interface device and/or pencil coil shield assembly can be configured to reduce RFI from the secondary current winding currents of a pencil coil. In addition, each can be manufactured using inexpensive and uncomplicated manufacturing and installation techniques, and using starting materials and parts that are relatively inexpensive. Also provided is a method of reducing RFI from secondary winding currents of a pencil coil by, among other things, electrically connecting the substantially cylindrical shield to a low voltage terminal of a secondary winding of the pencil coil, and electrically connecting the substantially cylindrical shield to a spark plug ground of a spark plug associated with the pencil coil.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shield and spring interface to a spark plug from a pencil coil.
2. Discussion of the Related Art
A typical automotive ignition system includes a spark plug, for each combustion chamber of an engine, at least one ignition coil and at least one device adapted to selectively charge the coil(s) and cause the energy stored in the coil(s) to be discharged through the spark plugs in a timed manner so that a spark is generated and ignition of a fuel-air mixture in each combustion chamber occurs at a specified timing.
Recent technological advances have made it more practical and desirable to provide each combustion chamber (or cylinder) with its own dedicated coil, and to provide each coil in a relatively compact configuration at the top of each combustion chamber's spark plug. Such coils are customarily referred to as “pencil coils”. The diameters of such pencil coils enable at least a portion of the coil to extend into the spark plug well on the typical engine, thereby providing efficient use of the limited space therein.
Pencil coils typically are equipped with a conductive shield. The conductive shield surrounds the pencil coil and tends to reduce radio frequency interference (RFI) from the coil. A significant source of RFI, however, is the electrical current path from the secondary winding. In the typical pencil coil arrangement, the spark plug is grounded to the engine and the return path for the electrical current in the secondary winding to the low voltage terminal of the secondary winding is through components located outside of the shield. The secondary winding current flowing through the components located outside of the shield provides a significant source of RFI. Thus, despite the presence of the shield, the typical pencil coil arrangement does not eliminate a significant portion of the RFI caused by the secondary winding current.
There is consequently a need in the art for way of reducing the RFI caused by the secondary winding current. Since it is desirable to keep costs and complexity to a minimum, there is a need in the art for a way of reducing this RFI without significantly increasing the cost, time, or complexity of the ignition system or the manufacturing and/or installation processes associated therewith.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to overcome the foregoing problems and/or to satisfy at least one of the aforementioned needs by providing a shield and spring interface to a spark plug from a pencil coil.
To achieve this and other objects and advantages, the present invention provides an interface device for interfacing a pencil coil to a spark plug. The interface device comprises a substantially C-shaped spring adapted to mechanically and electrically engage a pencil coil shield and also adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.
Also provided by the present invention is a pencil coil shield assembly for interfacing a pencil coil to a spark plug. The pencil coil shield assembly comprises a substantially cylindrical pencil coil and a spring. The substantially cylindrical pencil coil shield is adapted to surround the pencil coil. The spring is mechanically and electrically engaged with the pencil coil shield and is adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.
The present invention also provides a pencil coil shield assembly for interfacing a pencil coil to a spark plug, the assembly comprising a substantially cylindrical pencil coil shield adapted to surround the pencil coil and means mechanically engaged to the pencil coil shield, for electrically connecting the pencil coil shield with a spark plug ground.
Advantageously, the foregoing interface device and/or pencil coil shield assemblies can be configured to reduce RFI from the secondary current winding currents of a pencil coil. In addition, each can be manufactured using inexpensive and uncomplicated manufacturing and installation techniques, and using starting materials and parts that are relatively inexpensive.
Also provided by the present invention is a method of reducing RFI from secondary winding currents of a pencil coil. The method comprises the steps of providing a substantially cylindrical shield around a pencil coil, electrically connecting the substantially cylindrical shield to a low voltage terminal of a secondary winding of the pencil coil, and electrically connecting the substantially cylindrical shield to a spark plug ground of a spark plug associated with the pencil coil.
Still other objects, advantages, and features of the present invention will become more readily apparent when reference is made to the accompanying drawing and the associated description contained therewith.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a partially cross-sectional, fragmentary view of an interface device in a pencil coil shield assembly, according to a preferred embodiment of the present invention, wherein the pencil coil is shown schematically.
FIG. 2
is a cross-sectional top view of a spring according to another preferred embodiment of the present invention.
FIG. 3
is a cross-sectional view of a modified pencil coil shield and a spring according to a preferred embodiment of the present invention.
FIG. 4
is a cross-sectional view of the modified pencil coil shield and spring of
FIG. 3
, taken along line IV—IV in FIG.
3
.
FIG. 5
is a perspective view of the modified pencil coil shield shown in FIG.
3
.
FIG. 6
is a partially cross-sectional, fragmentary view of a spark plug, at least one spring in tab form, and a pencil coil shield, according to an alternative embodiment of the present invention.
FIG. 7
is a partially cross-sectional view of the spark plug, the springs in tab form, and the pencil coil shield of
FIG. 6
, taken along line VII—VII of FIG.
6
.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1
illustrates an interface device
10
for interfacing a pencil coil
12
(shown schematically) to a spark plug ground
14
, according to a preferred embodiment of the present invention. While the pencil coil
12
is shown schematically in
FIG. 1
, it is understood that the physical location of the pencil coil
12
is inside a pencil coil housing, the bottom
15
of which is shown in FIG.
1
.
The interface device
10
includes a substantially C-shaped spring
16
. The C-shaped spring
16
is adapted to mechanically and electrically engage a pencil coil shield
18
and is also adapted to make electrical contact with the spark plug ground
14
while the spring
16
remains mechanically and electrically engaged with the pencil coil shield
18
.
The spark plug ground
14
in
FIG. 1
is a conventional spark plug ground. It has a hexagonally shaped feature
20
that can be engaged by a conventional spark plug wrench. Installation of the spark plug
22
is performed by applying the wrench to the hexagonally shaped feature
20
and turning the hexagonally shaped feature
20
using the wrench. After installation, the wrench is removed and the pencil coil assembly
24
is mounted over the spark plug
22
so that the high voltage terminal
26
(shown schematically) of the spark plug
22
engages a high voltage terminal
28
(shown schematically) of the pencil coil assembly
24
and so that the pencil coil shield
18
surrounding the pencil coil
12
also surrounds the upper portion of the spark plug
22
.
As shown in
FIG. 1
, the spring
16
can have radially inward protuberances
30
adapted to mechanically and electrically engage the spark plug ground
14
. The protuberances
30
shown in
FIG. 1
are about 180 degrees from one another about the circumference of the spring
16
.
As shown in
FIG. 2
, the protuberances
30
preferably are located near distal ends
32
of the spring
16
and are spaced apart from one another by about 210 degrees about the circumference of the substantially C-shaped spring
16
. When measured across a gap
34
between the distal ends
32
of the spring
16
, these protuberances
30
are about 150 degrees apart. This 210/150-degree arrangement of the protuberances
30
advantageously limits variance in deflection of the spring
16
to less than about 4% when the substantially hexagonal feature
20
of the spark plug ground
14
is a perfect (equilateral) hexagon. In particular, one protuberance
30
is located in the middle of a side
38
of the hexagon whenever the other protuberance
30
is located at an apex
40
.
Preferably, the substantially C-shaped spring
16
is made from sheet metal that has been reconfigured to provide the C-shape of the spring
16
. Each of the protuberances
30
can be defined by a radially inward bend in the sheet metal. The spring
16
, in this regard, can be manufactured in a relatively inexpensive and uncomplicated manner. While the spring
16
preferably is made of steel, it is understood that other conductive materials can be used.
The substantially C-shaped spring
16
preferably has a diameter substantially equal to an outside diameter of the shield
18
. This allows the spring
16
to be mounted securely and conveniently to a portion
42
of the outside major surface
44
of the shield
18
. That portion
42
of the shield's outside major surface
44
therefore bears against the major inside surface
48
of the spring
16
. The shield
18
preferably has openings
50
aligned with the protuberances
30
, through which the protuberances
30
extend to make contact with the spark plug ground
14
.
It is understood, however, that the invention is not limited to such mounting of the spring
16
. To the contrary, the spring
16
can be provided with a diameter substantially equal to the inside diameter of the shield
18
and can be mounted to the inside surface
54
of the shield
18
. Regardless of which mounting configuration is used, it is preferred that the interconnection between the spring
16
and shield
18
be reinforced or otherwise integrated, for example, by welding.
The combination of the shield
18
and the spiring
16
advantageously provides a pencil coil shield assembly
60
that is capable of interfacing the pencil coil
12
to the spark plug
22
. In the resulting assembly
60
, the shield
18
is adapted to surround the pencil coil
12
, and the spring
16
is mechanically and electrically engaged with the pencil coil shield
18
and is adapted to make electrical contact with the spark plug ground
14
while the spring
16
remains mechanically and electrically engaged to the pencil coil shield
18
.
Preferably, the shield
18
is electrically connected to a low voltage terminal
62
of the secondary winding
64
of the pencil coil
12
so that a return path for a secondary winding current is established from the spark plug ground
14
, through the spring
16
, through the shield
18
, and into the low voltage terminal
62
, whenever the spring
16
makes electrical contact with the spark plug ground
14
. This advantageously provides a more direct return path for the secondary winding current than arrangements that rely solely on an indirect return path through the engine and its associated components. This more direct path advantageously provides a significant reduction in RFI from the secondary winding current of the pencil coil
12
.
With reference to
FIGS. 3-5
, the pencil coil shield
18
can be modified so that it includes a main substantially cylindrical body
70
and a ring-shaped spring mount
72
. The ring-shaped spring mount
72
is connected to the substantially cylindrical body
70
by an extension
74
of the body
70
. Preferably, the ring-shaped spring mount
72
is coaxially arranged with respect to the substantially cylindrical body
70
. This modified shield
18
advantageously can be manufactured in a relatively inexpensive and uncomplicated manner from sheet metal, such as steel, that is reconfigured to provide the illustrated shape. In particular, the sheet metal can be stamped and then rolled into the shape shown in
FIGS. 3-5
. The lateral ends
76
that are brought together during the rolling process, then can be welded to one another. Other manufacturing techniques and conductive materials also can be used.
In the exemplary embodiment of
FIGS. 3-5
, the spring
16
is engaged to the spring mount
72
and preferably is welded thereto. The spring
16
is substantially C-shaped and has its protuberances
30
spaced about 180 degrees apart from one another about the circumference of the spring
16
. The openings
50
in the ring-shaped spring mount
72
are correspondingly aligned. The protuberances
30
therefore can extend through the openings
50
and can mechanically and electrically engage the spark plug ground
14
(shown in FIG.
1
).
Preferably, the openings
50
in the spring mount
72
are arranged in the aforementioned 210/150 degree configuration, and the protuberances
30
of the spring
16
are arranged in a corresponding manner. The resulting arrangement advantageously limits variance in deflection of the spring
16
to less than 4% when the substantially hexagonal feature
20
of the spark plug ground
14
is a perfect (equilateral) hexagon.
With reference to
FIG. 6
, an alternative embodiment of the spring
16
is provided in the form of at least one tab
80
that extends down from the shield
18
and then in a substantially radially inward direction to make electrical contact with a spark plug ground
14
. The tab
80
can be welded or otherwise integrated with the shield
18
. Preferably, each tab
80
is substantially hook-shaped. While
FIG. 6
shows a two-piece tab structure, wherein one portion
82
of each tab
80
is integral with the shield
18
, and the other hookshaped portion
84
is welded thereto, it is understood that one-piece or other alternative tab structures can be used.
Multiple tabs
80
preferably are provided. One tab
80
, for example, can be provided for each apex
40
of a hexagonally shaped feature
20
of the spark plug ground
14
.
The tabs
80
desirably are spaced apart from one another symmetrically about a circumference of the shield
18
. Preferably, the tabs
80
are arranged with respect to one another about the shield
18
in such a way that, when the spring
16
is applied to a spark plug ground
14
that has a generally hexagonal shape and in such a way that one of the tabs
80
engages an apex
40
of the generally hexagonal shape, others of the tabs
80
also engage other apexes
40
of the generally hexagonal shape.
In any of the foregoing embodiments, the shield
18
can be connected to a low voltage terminal
62
of the pencil coil
12
to provide a significantly more direct return path for the secondary winding current. As indicated above, this more direct return path provides a significant reduction in RFI from the secondary winding current. The reduction in RFI, in turn, permits the use of a lower spark plug resistance. A lower spark plug resistance provides a corresponding increase in the ignition system's efficiency. Yet another benefit of the more direct return path for the secondary winding current relates to the wiring needs of the engine. In particular, the more direct current path may provide a reduction in the number of wires needed in the wiring harness associated with the engine.
The present invention thus provides, among other things, a method of reducing RFI from secondary winding currents of a pencil coil
12
. Generally, the method comprises the steps of providing a substantially cylindrical shield
18
around a pencil coil
12
, electrically connecting the substantially cylindrical shield
18
to a low voltage terminal
62
of a secondary winding
64
of the pencil coil
12
, and electrically connecting the substantially cylindrical shield
18
to the spark plug ground
14
of the spark plug
22
associated with the pencil coil
12
.
Preferably, the step of electrically connecting the substantially cylindrical shield
18
to the spark plug ground
14
is performed using a spring
16
(e.g., one of the springs
16
described above) so that a direct return path for the current in the secondary winding
64
is established from the spark plug ground
14
, through the spring
16
, through the shield
18
, and into the low voltage terminal
62
, whenever the spring
16
makes electrical contact with the spark plug ground
14
.
The step of electrically connecting the substantially cylindrical shield
18
to the spark plug ground
14
can be performed on a hexagonal feature
20
of the spark plug ground
14
. Preferably, this step is performed in such a way that spring variance in deflection is limited to less than about 4% during any axial rotation of the shield
18
. Use of the aforementioned 210/150-degree arrangement is one way of providing such a limit on the spring's variance of deflection.
While the dimensions of the spring
16
and shield
18
in the foregoing embodiments will depend to some extent on the spark plug ground
14
dimensions and the diameter of the pencil coil
12
, there arc certain standard dimensions that are well known in the art. One standard dimension, for example, relates to the distance from one apex
40
of a hexagonally shaped feature
20
on the spark plug ground
14
to the opposite apex
40
. A standard value for this distance is about 17.7 millimeters. Therefore, if the spring
16
has its protuberances
30
positioned 180 degrees apart from one another, the spring should urge its protuberances
30
toward a position where there is less than 17.7 millimeters between the protuberances
30
. A common pencil coil dimension also permits the shield
18
to have an outside diameter of about 20 millimeters. The diameter of the spring
16
can be provided accordingly, and in a manner dependent upon whether the spring
16
will engage the outside surface
44
or inside Surface
54
of the shield
18
. Still other standard dimensions for the spring
16
and spring mount
72
can be derived from alternative standard dimensions of the shield
18
, of the pencil coil
12
and of the spark plug ground
14
.
While the present invention has been described with reference to certain preferred embodiments and implementations, it is understood that various modifications and variations will no doubt occur to those skilled in the art to which this invention pertains. These and all other such variations which basically rely of the teachings through which this disclosure has advanced the art are properly considered within the scope of this invention.
Claims
- 1. An interface device for interfacing a pencil coil to a spark plug comprising:a substantially C-shaped spring adapted to mechanically and electrically engage a pencil coil shield and also adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.
- 2. The interface device of claim 1, wherein said spring has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground.
- 3. The interface device of claim 2, wherein the protuberances are spaced apart from one another by about 210 degrees about the circumference of the substantially C-shaped spring.
- 4. The interface device of claim 2, wherein the protuberances are located near distal ends of the substantially C-shaped spring.
- 5. The interface device of claim 4, wherein the protuberances are located near distal ends of the substantially C-shaped spring and are spaced apart from one another by about 210 degrees about the circumference of the substantially C-shaped spring.
- 6. The interface device of claim 2, wherein the substantially C-shaped spring is made from sheet metal that has been reconfigured to provide the C-shape of the spring.
- 7. The interface device of claim 6, wherein each of the protuberances is defined by a radially inward bend in the sheet metal.
- 8. The interface device of claim 1, wherein the substantially C-shaped spring has a diameter substantially equal to an inside or outside diameter of the shield.
- 9. A pencil coil shield assembly for interfacing a pencil coil to a spark plug comprising:a substantially cylindrical pencil coil shield adapted to surround a pencil coil; a spring mechanically and electrically engaged with the pencil coil shield and adapted to make electrical contact with a spark plug ground while the spring remains mechanically and electrically engaged to the pencil coil shield.
- 10. The pencil coil shield assembly of claim 9, wherein said spring is substantially C-shaped and has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground.
- 11. The pencil coil shield assembly of claim 10, wherein the protuberances are spaced apart from one another by about 210 degrees about the circumference of the spring.
- 12. The pencil coil shield assembly of claim 10, wherein the protuberances are located near distal ends of the spring.
- 13. The pencil coil shield assembly of claim 12, wherein the protuberances are located near distal ends of the spring and are spaced apart from one another by about 210 degrees about the circumference of the spring.
- 14. The pencil coil shield assembly of claim 10 wherein the spring is made from sheet metal that has been reconfigured to provide the C-shape of the spring.
- 15. The pencil coil shield assembly of claim 14, wherein each of the protuberances is defined by a radially inward bend in the sheet metal.
- 16. The pencil coil shield assembly of claim 9, wherein the spring is substantially C-shaped and has a diameter substantially equal to an inside or outside diameter of the shield, the spring being arranged with respect to the shield so that a portion of a major surface of the shield bears against a major surface of the spring.
- 17. The pencil coil shield assembly of claim 16, wherein said major surface of the shield is an outer surface of the shield and said major surface of the spring is an inside surface of the spring.
- 18. The pencil coil shield assembly of claim 17, wherein said spring has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground; andwherein the shield has openings aligned with the protuberances, through which said protuberances extend to make contact with a spark plug ground.
- 19. The pencil coil shield assembly of claim 9, wherein said shield is electrically connected to a low voltage terminal of a secondary winding of a pencil coil so that a return path for a secondary winding current is established from a spark plug ground, through the spring, through the shield, and into the low voltage terminal, when the spring makes electrical contact with the spark plug ground.
- 20. The pencil coil shield assembly of claim 9, wherein said pencil coil shield includes a main substantially cylindrical body and a ring-shaped spring mount that is connected to the substantially cylindrical body by an extension of the body.
- 21. The pencil coil shield assembly of claim 20, wherein said spring is engaged to the ring-shaped spring mount.
- 22. The pencil coil shield assembly of claim 20, wherein said ring-shaped mount is coaxially arranged with respect to the substantially cylindrical body.
- 23. The pencil coil shield assembly of claim 20, wherein said spring is substantially C-shaped and has radially inward protuberances adapted to mechanically and electrically engage a spark plug ground; andwherein the ring-shaped mount of the shield has openings aligned with the protuberances, through which said protuberances extend to make contact with a spark plug ground.
- 24. The pencil coil shield assembly of claim 9, wherein said spring, is provided in the form of at least one tab that extends from the shield in a substantially radially inward direction to make electrical contact with a spark plug ground.
- 25. The pencil coil shield assembly of claim 24, wherein said at least one tab is substantially hook-shaped.
- 26. The pencil coil shield assembly of claim 24, wherein said at least one tab comprises a plurality of tabs spaced apart from one another symmetrically about a circumference of the shield.
- 27. The pencil coil shield assembly of claim 26 wherein said plurality of tabs are arranged with respect to one another about the shield in such a way that, when said spring is applied to a spark plug ground that has a generally hexagonal shape and in such a way that one of the tabs engages an apex of the generally hexagonal shape, others of said tabs also engage other apexes of the generally hexagonal shape.
- 28. A pencil coil shield assembly for interfacing a pencil coil to a spark plug comprising:a substantially cylindrical pencil coil shield adapted to surround a pencil coil; means mechanically engaged to the pencil coil shield, for electrically connecting the pencil coil shield with a spark plug ground.
- 29. A method of reducing RFI from secondary winding currents of a pencil coil, said method comprising the steps of:providing a substantially cylindrical shield around a pencil coil; electrically connecting the substantially cylindrical shield to a low voltage terminal of a secondary winding of the pencil coil; and electrically connecting the substantially cylindrical shield to a spark plug ground of a spark plug associated with the pencil coil.
- 30. The method of claim 29, wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed using a spring so that a direct return path for a secondary winding current is established from the spark plug ground, through the spring, through the shield, and into the low voltage terminal, when the spring makes electrical contact with the spark plug ground.
- 31. The method of claim 30, wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed on a hexagonal portion of the spark plug ground.
- 32. The method of claim 31, wherein said step of electrically connecting the substantially cylindrical shield to a spark plug ground is performed in such a way that spring variance in deflection is limited to less than 4% during any axial rotation of the shield.
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Date |
Kind |
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A |
5014656 |
Leptich et al. |
May 1991 |
A |
5351670 |
Buma et al. |
Oct 1994 |
A |
5794603 |
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Aug 1998 |
A |