CA1156732A - High tension coil assembly - Google Patents
High tension coil assemblyInfo
- Publication number
- CA1156732A CA1156732A CA000367448A CA367448A CA1156732A CA 1156732 A CA1156732 A CA 1156732A CA 000367448 A CA000367448 A CA 000367448A CA 367448 A CA367448 A CA 367448A CA 1156732 A CA1156732 A CA 1156732A
- Authority
- CA
- Canada
- Prior art keywords
- bobbin
- high tension
- coil assembly
- tension coil
- primary winding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F5/00—Coils
- H01F5/02—Coils wound on non-magnetic supports, e.g. formers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/02—Casings
- H01F27/022—Encapsulation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
- H01F27/306—Fastening or mounting coils or windings on core, casing or other support
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F38/00—Adaptations of transformers or inductances for specific applications or functions
- H01F38/12—Ignition, e.g. for IC engines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F5/00—Coils
- H01F5/02—Coils wound on non-magnetic supports, e.g. formers
- H01F2005/022—Coils wound on non-magnetic supports, e.g. formers wound on formers with several winding chambers separated by flanges, e.g. for high voltage applications
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Insulating Of Coils (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
"A HIGH TENSION COIL ASSEMBLY"
A high voltage coil assembly in which a bobbin of a primary winding is interposed, in the vicinity of the both ends thereof, between an iron core and a casting made of an insulating synthetic resin, where the primary winding as well as a secondary winding and auxiliary elements are covered by the casting to be fixedly supported and to ensure insulation. The bobbin of the primary winding is made of a thermoplastic resin so that the shape thereof slightly changes when heat from the windings is applied thereto. Deformation of the bobbin prevents stress from being applied to the casting, where stress occurs due to the difference in thermal expansion and contraction coefficients between the iron core and the casting.
"A HIGH TENSION COIL ASSEMBLY"
A high voltage coil assembly in which a bobbin of a primary winding is interposed, in the vicinity of the both ends thereof, between an iron core and a casting made of an insulating synthetic resin, where the primary winding as well as a secondary winding and auxiliary elements are covered by the casting to be fixedly supported and to ensure insulation. The bobbin of the primary winding is made of a thermoplastic resin so that the shape thereof slightly changes when heat from the windings is applied thereto. Deformation of the bobbin prevents stress from being applied to the casting, where stress occurs due to the difference in thermal expansion and contraction coefficients between the iron core and the casting.
Description
115~73~
TITLE
"A HIGH TENSION COIL ASSE~LY"
FIELD OF THE INVENTION
This invention generally relates to a high ten-sion coil assembly, which is used as an ignition coil for generating a high voltage in response to a primary low voltage to supply a spark plug or plugs with the high voltage to ignite an air/fuel mixture in an engine of a motor vehicle or the like, and more par~ticularly, the present invention relates to such a high tension coil ---having a structure that primary and secondary windings are embedded in a casting made of a resin.
BACKGROUND OF THE INVENTION
Recently, automobile parts are required to have excellent performance and durability, and to be compact in size. Following this tendency ignition coils of resin-casting type are widely adopted, where resin-casting type means that primary and secondary windings and other auxiliary parts or members are embedded in a casting made of an insulating synthetic resin which is superior in view of heat-resistant, coronaproof and insulating characteristics.
However, such a resin-casting type high tension coil suffers from cracks which occur due to the difference -- 1 -- ~
in expansion and contraction coefficients between various members. Namely, heat is generated when a high tension coil operates so that the temperature of the high ten-sion coil assembly rises when operated, and on the other hand, the temperature falls when deenergized. Since the high tension coil repeats high and low temperature con-ditions, the casting made of an insulating resin material receives a stress so that cracks are apt to occur in the casting. Especially, when the casting is fixedly connected to an iron core which is placed at the center of the coil windings, cracks readily occur aIthough such an arrangement of fixed connection is desirable for im-proving vibrationproof characteristic, buzzproof char-acteristic and for reducing the size. Although there is another conventional high tension coil in which the casting is spaced from the iron core by the bobbin of the primary winding, stress is also applied via the bobbin to the casting to result in occurrence of cracks. Cracks which occur in the resin-casting may cause the coils to break or burn out and may cause the electrical insulating characteristic to deteriorate so that the life of such ~ch B a resin-casting type high tension coil assembly is shorter than that of other type coil assemblies.
For the above reason, a structure such that an iron core is assembled after a casting is formed has to be adopted hitherto, and therefore, the manufacturing process requires an additional step, and when such a high tension coil assembly having such a structure is used, special countermeasures against vibrations and buz have to be taken.
SU~ARY OF THE INVENTION
The present invention has been developed in order to remove the above-mentioned disadvantages and drawbacks inherent to the conventional high tension coil of resin-casting type.
It is, therefore, a primary object of the present invention to provide a high tension coil of resin-casting type in which occurrence of cracks in the resin-casting is prevented.
Another object of the present invention is to provide a high tension coil of resin-casting type which has an excellent vibrationproof characteristic.
A further object of the present ivnention is to provide a high tension coil of resin-casting type which does not suffer from buz.
n V ~ nt~ ' A still further object of the present ivncntio~
is to provide a high tension coil of resin-casting type which is simple in construction so that it is easy to manufacture the same.
A yet further object of the present invention is to provide a high tension coil of resin-casting type which has a long life.
In accordance with the present invention, a bobbin, on which a primary winding is wound, has a longi-tudinal length which is longer than the length of thecoil of the primary winding so that the primary winding is wound around the bobbin in such a manner that both ends of the coil are respectively spaced from the both ends of the bobbin. The bobbin of the primary winding is assembled with an iron core in such a manner that the bobbin surrounds a middle portion of the iron core.
A secondary winding is wound via an insulator, such as a second bobbin or the like, on the primary winding.
The combination of the primary and secondary windings is covered by a resin-casting in such a manner that the inner most portions of the resin-casting abut against the bobbin of the primary winding at places in the vi-cinity of the ends thereof. In other words, the end portions, which may be referred to as margin portions, of the bobbin of the primary winding are sandwiched between the iron core and the resin-casting. The bobbin of the primary winding is made of a thermoplastic resin so that deformation of the bobbin, especially at the margin portions, occurs when heat is applied thereto.
Because of the deformation of the bobbin, undesirable stress is prevented from transmitting to the resin-casting when various members or elements of the high tension coil assembly expand or contract.
BRIEF DESCRIPTIJn O L o~ ~b These and other objects and features of the present invention will be more readily apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings in which:
Fig. 1 is a partially cross-sectional front view of an embodiment of the high tension coil according to the present invention;
Fig. 2 is side view of the embodiment shown in Fig. l;
Fig. 3 is a front view of a combination of an iron core and a first bobbin both shown in Fig. l; and Fig. 4 is a side view of the combination shown in Fig. 3, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 and Fig. 2 illustrate an ignition coil for an automobilé engine as an embodiment of the high tension coil assembly according to the present invention, and the inner structure of the ignition ciol is further shown in Fig. 3 and Fig. 4. The ignition coil comprises an iron core 1 which is made of a lamination of silicon steel plates, a first bobbin 2 made of an insulating material, a primary winding 3 wound around the first bobbin 2, a second bobbin 4 made of an insulating material, a secondary winding 5 wound around the second bobbin 4, and a casting 8 made of an insulating synthetic resin. The first bobbin 2 is made of a thermoplastic resin, such as nylon, and is fixedly disposed around the iron core 1 in such a manner that both ends of the iron core 1 are projecting beyond both ends of the first bobbin 2. Namely, the first bobbin 2 and the iron core 1 are telescopically engeged so that only the middle portion of the iron core 1 is covered. The primary winding 3 wound around the periphery of the first bobbin 2 has first and second lead wires (not shown) at both ends thereof and the first lead wire is electrically connected to the iron core 1, while the second lead wire is connected to a terminal 7.
The first bobbin 2 has first and second flange portions 21 and 21' (see Fig. 3) which define the location of the primary winding 3. In detail, the first flange portion 21 is spaced by a given distance from the first end of the first bobbin 2, while the second flange portion 21' is spaced by a given distance from the second end of the first bobbin 2. A portion 22 of the first bobbin 2 defined between the first end and the first flange portion 21 is referred to as a first margin portion, and another portion 22' defined between the second end and the second flange portion 21' is referred to as a second margin portion. With this arrangement, the primary winding 3 is wound around the periphery of the first bobbin 2 in such a manner that the primary winding 3 is spaced from the both ends of the first bobbin 2. The first bobbin
TITLE
"A HIGH TENSION COIL ASSE~LY"
FIELD OF THE INVENTION
This invention generally relates to a high ten-sion coil assembly, which is used as an ignition coil for generating a high voltage in response to a primary low voltage to supply a spark plug or plugs with the high voltage to ignite an air/fuel mixture in an engine of a motor vehicle or the like, and more par~ticularly, the present invention relates to such a high tension coil ---having a structure that primary and secondary windings are embedded in a casting made of a resin.
BACKGROUND OF THE INVENTION
Recently, automobile parts are required to have excellent performance and durability, and to be compact in size. Following this tendency ignition coils of resin-casting type are widely adopted, where resin-casting type means that primary and secondary windings and other auxiliary parts or members are embedded in a casting made of an insulating synthetic resin which is superior in view of heat-resistant, coronaproof and insulating characteristics.
However, such a resin-casting type high tension coil suffers from cracks which occur due to the difference -- 1 -- ~
in expansion and contraction coefficients between various members. Namely, heat is generated when a high tension coil operates so that the temperature of the high ten-sion coil assembly rises when operated, and on the other hand, the temperature falls when deenergized. Since the high tension coil repeats high and low temperature con-ditions, the casting made of an insulating resin material receives a stress so that cracks are apt to occur in the casting. Especially, when the casting is fixedly connected to an iron core which is placed at the center of the coil windings, cracks readily occur aIthough such an arrangement of fixed connection is desirable for im-proving vibrationproof characteristic, buzzproof char-acteristic and for reducing the size. Although there is another conventional high tension coil in which the casting is spaced from the iron core by the bobbin of the primary winding, stress is also applied via the bobbin to the casting to result in occurrence of cracks. Cracks which occur in the resin-casting may cause the coils to break or burn out and may cause the electrical insulating characteristic to deteriorate so that the life of such ~ch B a resin-casting type high tension coil assembly is shorter than that of other type coil assemblies.
For the above reason, a structure such that an iron core is assembled after a casting is formed has to be adopted hitherto, and therefore, the manufacturing process requires an additional step, and when such a high tension coil assembly having such a structure is used, special countermeasures against vibrations and buz have to be taken.
SU~ARY OF THE INVENTION
The present invention has been developed in order to remove the above-mentioned disadvantages and drawbacks inherent to the conventional high tension coil of resin-casting type.
It is, therefore, a primary object of the present invention to provide a high tension coil of resin-casting type in which occurrence of cracks in the resin-casting is prevented.
Another object of the present invention is to provide a high tension coil of resin-casting type which has an excellent vibrationproof characteristic.
A further object of the present ivnention is to provide a high tension coil of resin-casting type which does not suffer from buz.
n V ~ nt~ ' A still further object of the present ivncntio~
is to provide a high tension coil of resin-casting type which is simple in construction so that it is easy to manufacture the same.
A yet further object of the present invention is to provide a high tension coil of resin-casting type which has a long life.
In accordance with the present invention, a bobbin, on which a primary winding is wound, has a longi-tudinal length which is longer than the length of thecoil of the primary winding so that the primary winding is wound around the bobbin in such a manner that both ends of the coil are respectively spaced from the both ends of the bobbin. The bobbin of the primary winding is assembled with an iron core in such a manner that the bobbin surrounds a middle portion of the iron core.
A secondary winding is wound via an insulator, such as a second bobbin or the like, on the primary winding.
The combination of the primary and secondary windings is covered by a resin-casting in such a manner that the inner most portions of the resin-casting abut against the bobbin of the primary winding at places in the vi-cinity of the ends thereof. In other words, the end portions, which may be referred to as margin portions, of the bobbin of the primary winding are sandwiched between the iron core and the resin-casting. The bobbin of the primary winding is made of a thermoplastic resin so that deformation of the bobbin, especially at the margin portions, occurs when heat is applied thereto.
Because of the deformation of the bobbin, undesirable stress is prevented from transmitting to the resin-casting when various members or elements of the high tension coil assembly expand or contract.
BRIEF DESCRIPTIJn O L o~ ~b These and other objects and features of the present invention will be more readily apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings in which:
Fig. 1 is a partially cross-sectional front view of an embodiment of the high tension coil according to the present invention;
Fig. 2 is side view of the embodiment shown in Fig. l;
Fig. 3 is a front view of a combination of an iron core and a first bobbin both shown in Fig. l; and Fig. 4 is a side view of the combination shown in Fig. 3, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 and Fig. 2 illustrate an ignition coil for an automobilé engine as an embodiment of the high tension coil assembly according to the present invention, and the inner structure of the ignition ciol is further shown in Fig. 3 and Fig. 4. The ignition coil comprises an iron core 1 which is made of a lamination of silicon steel plates, a first bobbin 2 made of an insulating material, a primary winding 3 wound around the first bobbin 2, a second bobbin 4 made of an insulating material, a secondary winding 5 wound around the second bobbin 4, and a casting 8 made of an insulating synthetic resin. The first bobbin 2 is made of a thermoplastic resin, such as nylon, and is fixedly disposed around the iron core 1 in such a manner that both ends of the iron core 1 are projecting beyond both ends of the first bobbin 2. Namely, the first bobbin 2 and the iron core 1 are telescopically engeged so that only the middle portion of the iron core 1 is covered. The primary winding 3 wound around the periphery of the first bobbin 2 has first and second lead wires (not shown) at both ends thereof and the first lead wire is electrically connected to the iron core 1, while the second lead wire is connected to a terminal 7.
The first bobbin 2 has first and second flange portions 21 and 21' (see Fig. 3) which define the location of the primary winding 3. In detail, the first flange portion 21 is spaced by a given distance from the first end of the first bobbin 2, while the second flange portion 21' is spaced by a given distance from the second end of the first bobbin 2. A portion 22 of the first bobbin 2 defined between the first end and the first flange portion 21 is referred to as a first margin portion, and another portion 22' defined between the second end and the second flange portion 21' is referred to as a second margin portion. With this arrangement, the primary winding 3 is wound around the periphery of the first bobbin 2 in such a manner that the primary winding 3 is spaced from the both ends of the first bobbin 2. The first bobbin
2 has an outwardly projecting portion 23 connected to the first flange po~tion 21.
In order to assemble the first bobbin 2 with the iron core 1, the first bobbin may be formed centering the iron core 1 to be integrally assembled. If desired, however, the iron core 1 may be inserted under pressure in the center hole of the first bobbin 2 which has been premanufactured.
The second bobbin 4 has a recess for receiving the above-mentioned projecting portion 23, at one end thereof, so thàt the second bobbin 4 is stationarily positioned with respect to the first bobbin 2. In detail, the inner surface of the second bobbin 4 is arranged to abut against the periphery of the first and second flange portions 21 and 21' respectively. The second bobbin 4, which functions as an insulator between the primary and secondary windings 3 and 5, has spiral grooves on the outer surface thereof so that the secondary winding 5 is wound around the periphery of the second bobbin 4 in the form of a sectional winding. The second bobbin 4 has first and second supporting portions 44 and 44' which extend outwardly from the end portions thereof. These supporting portions 44 and 44' are used to support a 5 ~ high tension ~vdc 6 which is arranged in parallel with the iron core 1. The secondary winding 5 has first and second lead wires (not shown) at both ends thereof, and the first lead wire is electrically connected to the terminal 7, while the second lead wire is electrically connected to 7 conductor portion of the above-mentioned ~ d high tension eo~ 6.
-The first bobbin 2 further comprises a terminal-supporting portion 24 which projects outwardly, and the above-mentioned terminal 7 is fixedly supported by the terminal-supporting portion 24. The terminal 7 is spaced by a given distance from the iron core 1 to be insulated from the iron core 1.
The resin-casting 8 is placed to cover the above-ventioned first and second bobbins 2 and 4, the primary and secondary windings 3 and 5, a portion of the high J æc~d tension~a~e 6. However, this does not mean that the entire body of the first bobbin 2 is enclosed by the casting 8. Namely, the casting 8 is formed in such a manner that the inner most portions thereof abut against the outer or peripheral portion of the first bobbin 2 in the vicinity of the first and second end portions of the first bobbin 2. Namely, the inner most portions of the casting 8 are in contact with the first and second margin portions 22 and 22'. With this arrangement, the first S and second end surfaces 81 and 81', which respectively extend radially from the margin portions 22 and 22' of the first bobbin 2, are in planes which intersect the margin portions 22 and 22' respectively. In other words, the longitudinal length of the resin-casting 8 measured along the inner most portion thereof is not greater than the longitudinal length of the first bobbin 2 so that the first and second margin portions 22 and 22' respect-ively project in the longitudinal direction of the iron core 1 beyond the first and second end surfaces 81 and 81'.
The casting 8 is formed by a well known injection molding technique so that all spaces between the elements are filled with the insulating material. As a result, the first and second bobbins 2 and 4, the primary and secondary windings 3 and 5, and a portion of the high . ~ l æ~d tension csde 6 are respectively embedded in the resin-casting 8. A heat-resistant insulating material having a coronaproof characteristic should be used for the casting 8. Therefore, an insulating synthetic resin, such as a polyester resin, an epoxy resin, a butadiene resin, is added with an inorganic filler, such as silica powder, and with a hardener to provide a raw material. The raw material is mixed by stirring, and then the raw material is debubbled. The raw material prepared in this way is vapor injected into a mold (not shown), and then the injected material is hardened or set to become the above-mentioned casting 8.
Although, it is not mentioned in the above, a suitable grommet 9 made of an elastic material, such as rubber, is provided to surround a portion of the high ~ /~d 10 ~ tension ca~e 6 before the casting 8 is formed. With the provision of the gromment 9 airtightness is improved, I~J
while an external force applied via the high tension codo 6 is prevented from transmitting to the casting 8 so that occurence of cracks is preventable.
When the high tension coil assembly operates, namely, when the primary winding 3 is energized, the high tension coil assembly gets hot due to the heat emitted mainly from the primary winding 3. On the contrary, when the high tension coil does not operate, no heat is emitted so that the temperature drops to the outside air temper-ature. Therefore, hot and cool conditions repeat to cause each element of the high tension coil asse~bly to expand and contract in accordance with each coefficient of thermal expantion. Since the coefficient of thermal expansion of the iron core 1 is considerably different from that of 11567~2 the casting 8, there is a remarkable difference in the amount of expansion and contraction between these two members.
In accordance with the present inVentiOn, however, as described in the above, the resin-casting 8 is spaced from the iron core 1 by means of the first bobbin 2.
Namely, the resin-casting 8 is not in direct contact with the iron core 1. This means that the first bobbin 2, especially the margin portions 22 and 22' thereof function as buffers. In detail, the above-mentioned difference in the amount of expansion and contraction i-s absorbed by the thermoplasticity and therefore, hy the de-formation of the first bobbin 2 which is made of a thermo-plastic resin. With this arrangement a great stress is not applied to the resin-casting 8, and therefore, occur-rence of cracks is effectively prevented. As a result, the resin-casting 8 is capable of maintaining its func-tions, namely all elements are securely supported to prevent the occurrence of buz, while desired electrical insulation is kept.
As shown in the drawings, each of the above-mentioned margin portions 22 and 22' has upper and lower projections 25, 25', 26 and 26' which project in the longitudinal direction of the first bobbin 2. The upper projections 25 and 25' are respectively abut against one 11~6732 side of the lamination of the iron core 1, while the lower projections 26 and 26' respectively abut against the other side of the lamination. Since the lamination of the iron core 1 tends to expand and contract along the side to side derection, i.e. the vertical direction in Fig. 4, rather than bottom to top direction, i.e. the horizontal direction in Fig. 4, it is preferable to arrange the above-mentioned upper and lower projections 25, 25' 26 and 26' on both sides of the lamination of the iron core 1 for effectively absorbing the difference in expansion and contraction-between the iron core 1 and the casting 8.
In the above-described embodiment, although the second bobbin 4 is provided to insulate the primary and secondary windings 3 and 5 from each other, such a bobbin is not necessarily needed if a suitable insulator, such as a sheet of insulating film is placed around the primary winding 3. Furthermore, the high tension ~ 6 is not necessarily needed to be embedded in the resin-casting 8.
Namely, a suitable terminal may be provided to establish an electrical connection between an external high tension d ~e~e and the secondary winding 5. The above-mentioned flange portions 21 and 21', the projecting portion 23, the terminal-supporting portion 24 may be omitted if desired.
Summarizing the structure of the high tension coil according to the present invention, the first bobbin 2, around which the primary winding is wound, is sand-wiched between the iron core 1 and the resin-casting 8 at the margin portions 22 and 22', where the first bobbin 2 is made of a thermoplastic resin, and has margin portions 22 and 22' in the vicinity of ~he end portions thereof, which margin portions 22 and 22' are not covered by the primary winding 3.
From the foregoing description, it will be under-stood that the present invention provides various advan-tages which could not be attained by the conventional high tension coils of resin-casting type. The above-described embodiment is just an example, and therefore, it will be apparent for those skilled in the art that many modifications and variations may be made without departing from the spirit of the instant invention.
In order to assemble the first bobbin 2 with the iron core 1, the first bobbin may be formed centering the iron core 1 to be integrally assembled. If desired, however, the iron core 1 may be inserted under pressure in the center hole of the first bobbin 2 which has been premanufactured.
The second bobbin 4 has a recess for receiving the above-mentioned projecting portion 23, at one end thereof, so thàt the second bobbin 4 is stationarily positioned with respect to the first bobbin 2. In detail, the inner surface of the second bobbin 4 is arranged to abut against the periphery of the first and second flange portions 21 and 21' respectively. The second bobbin 4, which functions as an insulator between the primary and secondary windings 3 and 5, has spiral grooves on the outer surface thereof so that the secondary winding 5 is wound around the periphery of the second bobbin 4 in the form of a sectional winding. The second bobbin 4 has first and second supporting portions 44 and 44' which extend outwardly from the end portions thereof. These supporting portions 44 and 44' are used to support a 5 ~ high tension ~vdc 6 which is arranged in parallel with the iron core 1. The secondary winding 5 has first and second lead wires (not shown) at both ends thereof, and the first lead wire is electrically connected to the terminal 7, while the second lead wire is electrically connected to 7 conductor portion of the above-mentioned ~ d high tension eo~ 6.
-The first bobbin 2 further comprises a terminal-supporting portion 24 which projects outwardly, and the above-mentioned terminal 7 is fixedly supported by the terminal-supporting portion 24. The terminal 7 is spaced by a given distance from the iron core 1 to be insulated from the iron core 1.
The resin-casting 8 is placed to cover the above-ventioned first and second bobbins 2 and 4, the primary and secondary windings 3 and 5, a portion of the high J æc~d tension~a~e 6. However, this does not mean that the entire body of the first bobbin 2 is enclosed by the casting 8. Namely, the casting 8 is formed in such a manner that the inner most portions thereof abut against the outer or peripheral portion of the first bobbin 2 in the vicinity of the first and second end portions of the first bobbin 2. Namely, the inner most portions of the casting 8 are in contact with the first and second margin portions 22 and 22'. With this arrangement, the first S and second end surfaces 81 and 81', which respectively extend radially from the margin portions 22 and 22' of the first bobbin 2, are in planes which intersect the margin portions 22 and 22' respectively. In other words, the longitudinal length of the resin-casting 8 measured along the inner most portion thereof is not greater than the longitudinal length of the first bobbin 2 so that the first and second margin portions 22 and 22' respect-ively project in the longitudinal direction of the iron core 1 beyond the first and second end surfaces 81 and 81'.
The casting 8 is formed by a well known injection molding technique so that all spaces between the elements are filled with the insulating material. As a result, the first and second bobbins 2 and 4, the primary and secondary windings 3 and 5, and a portion of the high . ~ l æ~d tension csde 6 are respectively embedded in the resin-casting 8. A heat-resistant insulating material having a coronaproof characteristic should be used for the casting 8. Therefore, an insulating synthetic resin, such as a polyester resin, an epoxy resin, a butadiene resin, is added with an inorganic filler, such as silica powder, and with a hardener to provide a raw material. The raw material is mixed by stirring, and then the raw material is debubbled. The raw material prepared in this way is vapor injected into a mold (not shown), and then the injected material is hardened or set to become the above-mentioned casting 8.
Although, it is not mentioned in the above, a suitable grommet 9 made of an elastic material, such as rubber, is provided to surround a portion of the high ~ /~d 10 ~ tension ca~e 6 before the casting 8 is formed. With the provision of the gromment 9 airtightness is improved, I~J
while an external force applied via the high tension codo 6 is prevented from transmitting to the casting 8 so that occurence of cracks is preventable.
When the high tension coil assembly operates, namely, when the primary winding 3 is energized, the high tension coil assembly gets hot due to the heat emitted mainly from the primary winding 3. On the contrary, when the high tension coil does not operate, no heat is emitted so that the temperature drops to the outside air temper-ature. Therefore, hot and cool conditions repeat to cause each element of the high tension coil asse~bly to expand and contract in accordance with each coefficient of thermal expantion. Since the coefficient of thermal expansion of the iron core 1 is considerably different from that of 11567~2 the casting 8, there is a remarkable difference in the amount of expansion and contraction between these two members.
In accordance with the present inVentiOn, however, as described in the above, the resin-casting 8 is spaced from the iron core 1 by means of the first bobbin 2.
Namely, the resin-casting 8 is not in direct contact with the iron core 1. This means that the first bobbin 2, especially the margin portions 22 and 22' thereof function as buffers. In detail, the above-mentioned difference in the amount of expansion and contraction i-s absorbed by the thermoplasticity and therefore, hy the de-formation of the first bobbin 2 which is made of a thermo-plastic resin. With this arrangement a great stress is not applied to the resin-casting 8, and therefore, occur-rence of cracks is effectively prevented. As a result, the resin-casting 8 is capable of maintaining its func-tions, namely all elements are securely supported to prevent the occurrence of buz, while desired electrical insulation is kept.
As shown in the drawings, each of the above-mentioned margin portions 22 and 22' has upper and lower projections 25, 25', 26 and 26' which project in the longitudinal direction of the first bobbin 2. The upper projections 25 and 25' are respectively abut against one 11~6732 side of the lamination of the iron core 1, while the lower projections 26 and 26' respectively abut against the other side of the lamination. Since the lamination of the iron core 1 tends to expand and contract along the side to side derection, i.e. the vertical direction in Fig. 4, rather than bottom to top direction, i.e. the horizontal direction in Fig. 4, it is preferable to arrange the above-mentioned upper and lower projections 25, 25' 26 and 26' on both sides of the lamination of the iron core 1 for effectively absorbing the difference in expansion and contraction-between the iron core 1 and the casting 8.
In the above-described embodiment, although the second bobbin 4 is provided to insulate the primary and secondary windings 3 and 5 from each other, such a bobbin is not necessarily needed if a suitable insulator, such as a sheet of insulating film is placed around the primary winding 3. Furthermore, the high tension ~ 6 is not necessarily needed to be embedded in the resin-casting 8.
Namely, a suitable terminal may be provided to establish an electrical connection between an external high tension d ~e~e and the secondary winding 5. The above-mentioned flange portions 21 and 21', the projecting portion 23, the terminal-supporting portion 24 may be omitted if desired.
Summarizing the structure of the high tension coil according to the present invention, the first bobbin 2, around which the primary winding is wound, is sand-wiched between the iron core 1 and the resin-casting 8 at the margin portions 22 and 22', where the first bobbin 2 is made of a thermoplastic resin, and has margin portions 22 and 22' in the vicinity of ~he end portions thereof, which margin portions 22 and 22' are not covered by the primary winding 3.
From the foregoing description, it will be under-stood that the present invention provides various advan-tages which could not be attained by the conventional high tension coils of resin-casting type. The above-described embodiment is just an example, and therefore, it will be apparent for those skilled in the art that many modifications and variations may be made without departing from the spirit of the instant invention.
Claims (14)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A high tension coil assembly for generating a high voltage in response to a low voltage excitation, comprising:
(a) an iron core;
(b) a thermoplastic resin bobbin disposed around said iron core such that both ends of said iron core project beyond said bobbin;
(c) a primary winding wound around said bobbin so as to be spaced from both ends of said bobbin;
(d) an insulator placed around said primary winding;
(e) a secondary winding wound around said insulator;
and (f) an insulating synthetic resin molding structure for covering said bobbin, primary winding, insulator and secondary winding, said molding structure being spaced from said iron core by said bobbin which is covered by said molding structure in such a manner that each of the ends of said bobbin is exposed so that said bobbin is capable of expanding in the axial direction of said iron core when said bobbin is heated by heat generated by said high tension coil assembly.
(a) an iron core;
(b) a thermoplastic resin bobbin disposed around said iron core such that both ends of said iron core project beyond said bobbin;
(c) a primary winding wound around said bobbin so as to be spaced from both ends of said bobbin;
(d) an insulator placed around said primary winding;
(e) a secondary winding wound around said insulator;
and (f) an insulating synthetic resin molding structure for covering said bobbin, primary winding, insulator and secondary winding, said molding structure being spaced from said iron core by said bobbin which is covered by said molding structure in such a manner that each of the ends of said bobbin is exposed so that said bobbin is capable of expanding in the axial direction of said iron core when said bobbin is heated by heat generated by said high tension coil assembly.
2. A high tension coil assembly as claimed in Claim 1, wherein said iron core comprises a lamination of iron plates.
3. A high tension coil assembly as claimed in Claim 1, wherein said bobbin comprises first and second flange portions for defining the location of said primary winding, said first and second flange portions being respectively spaced from the ends of said bobbin.
4. A high tension coil assembly as claimed in Claim 1, wherein said bobbin comprises a terminal-supporting por-tion, which projects outwardly, for supporting a terminal.
5. A high tension coil assembly as claimed in Claim 1, wherein said insulator comprises a second bobbin placed around said bobbin of said primary winding.
6. A high tension coil assembly as claimed in Claim 5, wherein said bobbin of said primary winding comprises an outwardly projecting portion for stationarily supporting said second bobbin.
7. A high tension coil assembly as claimed in Claim 6, wherein said second bobbin comprises a recess at the inner surface thereof for receiving said projecting portion of said bobbin of said primary winding.
8. A high tension coil assembly as claimed in Claim 5, wherein said second bobbin comprises spiral grooves on the peripheral surface thereof, said secondary winding is wound around said second bobbin in the form of a sectional winding.
9. A high tension coil assembly as claimed in Claim 5, wherein said second bobbin comprises supporting portions which outwardly extend for supporting a portion of a high tension lead to which said second winding is electrically connected.
10. A high tension coil assembly as claimed in claim 9, wherein said portion of said high tension lead is embedded in said casting.
11. A high tension coil assembly as claimed in Claim 10, further comprising a grommet placed around a portion of said high tension lead, said gromment being made of an elastic material.
12. A high tension coil assembly as claimed in Claim 1, wherein said thermoplastic resin used for said bobbin of said primary winding is nylon.
13. A high tension coil assembly as claimed in Claim 1, wherein said casting is made of one of a polyester resin, an epoxy resin, and a butadiene resin, said resin being added with an inorganic filler and a hardener before injected in a mold.
14. A high tension coil assembly as claimed in Claim 1, wherein each of said ends of said bobbin projects axially beyond the ends of said molding structure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16997079A JPS5693309A (en) | 1979-12-26 | 1979-12-26 | High-tension coil |
| JP54-169970 | 1979-12-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1156732A true CA1156732A (en) | 1983-11-08 |
Family
ID=15896180
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000367448A Expired CA1156732A (en) | 1979-12-26 | 1980-12-23 | High tension coil assembly |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5693309A (en) |
| CA (1) | CA1156732A (en) |
| DE (1) | DE3048803C2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6208231B1 (en) | 1997-02-14 | 2001-03-27 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US6930583B2 (en) | 1997-02-14 | 2005-08-16 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58158425U (en) * | 1982-04-15 | 1983-10-22 | 阪神エレクトリツク株式会社 | molded ignition coil |
| DE3217754A1 (en) * | 1982-05-12 | 1983-11-17 | Robert Bosch Gmbh, 7000 Stuttgart | Ignition coils for the ignition systems of internal-combustion engines |
| DE3309986A1 (en) * | 1983-03-19 | 1984-09-20 | Robert Bosch Gmbh, 7000 Stuttgart | Ignition coil for ignition systems of internal-combustion engines |
| KR860001409B1 (en) * | 1983-06-10 | 1986-09-23 | 니혼엑스란 고오교오 가부시끼가이샤 | Preparation method of bead phase polymer |
| FR2593962B1 (en) * | 1986-01-24 | 1989-03-03 | Ducellier & Cie | CLOSED CIRCUIT IGNITION COIL |
| FR2602087B2 (en) * | 1986-07-23 | 1989-04-07 | Ducellier & Cie | CLOSED CIRCUIT IGNITION COIL |
| EP0230811B1 (en) * | 1986-01-24 | 1992-06-03 | Valeo Electronique | Ignition coil with a closed magnetic circuit |
| FR2627548B1 (en) * | 1988-02-19 | 1993-06-18 | Marchal Equip Auto | IGNITION COIL, PARTICULARLY FOR IGNITION OF INTERNAL COMBUSTION ENGINES |
| FR2641038B1 (en) * | 1988-12-23 | 1994-02-11 | Marchal Equip Automobiles | |
| DE69414862T2 (en) * | 1993-08-26 | 1999-04-29 | Ford-Werke Ag, 50735 Koeln | METHOD FOR PRODUCING A IGNITION COIL ARRANGEMENT |
| US5861791A (en) * | 1995-06-21 | 1999-01-19 | Brunswick Corporation | Ignition coil with non-filtering/non-segregating secondary winding separators |
| EP1225603A3 (en) * | 1997-05-23 | 2002-08-28 | Hitachi, Ltd. | Ignition coil for use in engine and engine having plastic cylinder head cover |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3394331A (en) * | 1966-06-02 | 1968-07-23 | Texaco Inc | Winding having a two turn conductive strip therearound |
| US3546647A (en) * | 1969-08-08 | 1970-12-08 | Eltra Corp | Electric coil construction |
| DE2346346C2 (en) * | 1973-09-14 | 1982-06-09 | Robert Bosch Gmbh, 7000 Stuttgart | Ignition transformer for generating high-voltage pulses, in particular ignition armatures |
| NL159223C (en) * | 1973-10-10 |
-
1979
- 1979-12-26 JP JP16997079A patent/JPS5693309A/en active Granted
-
1980
- 1980-12-23 CA CA000367448A patent/CA1156732A/en not_active Expired
- 1980-12-23 DE DE19803048803 patent/DE3048803C2/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6208231B1 (en) | 1997-02-14 | 2001-03-27 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US6525636B1 (en) | 1997-02-14 | 2003-02-25 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US6930583B2 (en) | 1997-02-14 | 2005-08-16 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US6977574B1 (en) | 1997-02-14 | 2005-12-20 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US6995644B2 (en) | 1997-02-14 | 2006-02-07 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US7068135B1 (en) | 1997-02-14 | 2006-06-27 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
| US7071804B2 (en) | 1997-02-14 | 2006-07-04 | Denso Corporation | Stick-type ignition coil having improved structure against crack or dielectric discharge |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3048803A1 (en) | 1981-10-01 |
| DE3048803C2 (en) | 1983-11-10 |
| JPS5693309A (en) | 1981-07-28 |
| JPS5739041B2 (en) | 1982-08-19 |
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