Source: https://patents.google.com/patent/EP1255260B1/en
Timestamp: 2020-07-09 11:41:00
Document Index: 618132192

Matched Legal Cases: ['art 17', 'arts 17', 'art 17', 'arts 17', 'art 17', 'arts 17', 'art 17', 'arts 17', 'arts 17', 'arts 17', 'art 17', 'art 17', 'arts 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17']

EP1255260B1 - Stick-type ignition coil having improved structure against crack or dielectric discharge - Google Patents
EP1255260B1
EP1255260B1 EP02015929A EP02015929A EP1255260B1 EP 1255260 B1 EP1255260 B1 EP 1255260B1 EP 02015929 A EP02015929 A EP 02015929A EP 02015929 A EP02015929 A EP 02015929A EP 1255260 B1 EP1255260 B1 EP 1255260B1
EP02015929A
EP1255260A1 (en
Naruhiko Inayoshi
1997-02-14 Priority to JP3040397 priority Critical
1997-02-14 Priority to JP3040497 priority
1997-02-14 Priority to JP3040397 priority
1997-04-28 Priority to JP11083697 priority
1997-06-30 Priority to JP17394797 priority
1997-08-07 Priority to JP21362697 priority
1997-08-08 Priority to JP21494397 priority
1997-08-08 Priority to JP9214943A priority patent/JPH10289831A/en
1997-08-08 Priority to JP21494097 priority
1997-08-08 Priority to JP21494097A priority patent/JP3484938B2/en
1997-08-08 Priority to JP21494197A priority patent/JP3587024B2/en
1997-08-08 Priority to JP21493997 priority
1997-08-08 Priority to JP21494197 priority
1997-12-25 Priority to JP9357143A priority patent/JPH11111547A/en
1997-12-25 Priority to JP35714397 priority
1997-12-25 Priority to JP35701197A priority patent/JP3573250B2/en
1997-12-25 Priority to JP35701197 priority
1998-02-13 Priority to EP98102541A priority patent/EP0859383B1/en
2002-11-06 Publication of EP1255260A1 publication Critical patent/EP1255260A1/en
2007-01-24 Publication of EP1255260B1 publication Critical patent/EP1255260B1/en
2007-10-23 First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=27581929&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP1255260(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
239000000615 nonconductor Substances 0.000 claims description 23
229920001971 elastomers Polymers 0.000 description 18
The present invention relates to an ignition coil for an engine according to the preamble of claim 1 and, more particularly, to a stick-type ignition coil to be fitted directly in the plug hole of an internal combustion engine.
As an ignition coil, a stick-type ignition coil is known. It has a rod-shaped central core disposed in a housing, and a primary coil and a secondary coil wound respectively on a primary spool and a secondary spool made of resin. Resin is filled in the housing of the ignition coil as an electric insulator. The insulator not only provides electric insulation among individual members in the housing but also fills clearances between wires of the coils thereby to restrict movements or breakage of the coils which may arise from engine vibrations. As the insulator, a thermosetting resin such as epoxy is used in consideration of the heat resistance. The ignition coil further has a permanent magnet attached to at least one of the two longitudinal ends of the central core to raise a voltage to be supplied to a spark ignition plug.
In this type of ignition coil, the central core contacts with not only the resin insulator but also a case member such as a spool enclosing the outer circumference of the central core. The central core and the resin insulator or the case member, as having different thermal expansion coefficients, may repeat expansions and contractions as the surrounding temperature rises and falls. Then, the resin insulator or the case member, as contacting with the central core, especially the resin insulator or the case member contacting the longitudinal end corners of the central core, may crack which results in defective electric insulation.
If the central core and the resin insulator or the case member are caused to repeat the expansions and the contractions by the change in the temperature, the central core is caused to receive a load in the radial direction and in the longitudinal direction from the resin insulator and the case member by the difference in the thermal expansion coefficient. Especially when the central core receives the load in the longitudinal direction, the magnetic permeability of the core may drop causing the magneto-striction which disable generation of a required high voltage.
In another ignition coil disclosed in JP-U-59-30501, although not a stick-type, the corners of the core are covered by over-coating the surface of the core with an elastomer. This prevents the corners of the core and the insulator made of epoxy resin from coming into direct contact with each other and suppresses the cracks in the epoxy resin in the vicinity of the corners of the core. This over coating is not applicable to the stick-type ignition coil, because the stick-type is so regulated in its external diameter as to match the internal diameter of the plug hole.
A further ignition coil is disclosed in JP-A-58 122 713.
A generic ignition coil is known from EP-A-0 388 146. The ignition coil comprises a central core assembly including a rod-shaped core, a primary coil and a secondary coil wound coaxially on an outer periphery of the core, a primary spool around which the primary coil is wound, a secondary spool around which the secondary coil is wound, and a resin insulator filled around the core.
It is an object of the present invention to further develop an ignition coil according to the preamble of claim 1 such that the occurrence of cracks is suppressed.
According to the invention, this object is achieved by an ignition coil having the features of claim 1.
According to the invention, it is not only possible to suppress the occurrence of cracks but also a dielectric breakdown caused by a change in the surrounding temperature.
The ingnition coil has a separating member to preferably separate the spool and a resin insulator from each other so that the spool and the resin insulator disposed inside and outside of the separating member can expand/contract separately from each other with a change in temperatures. Thus, the spool and the resin insulator are prevented from cracking in a peripheral part on which large force is liable to act.
The object, features and advantages of the present invention will become more apparent from the following detailed description with reference to the embodiments shown in the accompanying drawings. In the drawings:
Fig. 1 is a longitudinal sectional view showing an ignition coil according to the first comparative example;
Fig. 2 is a sectional view showing a cylindrical member used in the first comparative example;
Fig. 3 is an enlarged sectional view showing one end portion of the ignition coil according to the first comparative example, the one portion being designated by a circle III in Fig. 1;
Fig. 4 is an enlarged sectional view showing the other end portion of the ignition coil according to the first comparative example, the other portion being designated by a circle IV in Fig. 1;
Fig. 5 is a longitudinal sectional view showing an ignition coil according to the second comparative example;
Fig. 6 is an enlarged sectional view showing one end portion of the ignition coil according to the third comparative example;
Fig. 7 is an enlarged sectional view showing the other end portion of the ignition coil according to the third comparative example;
Fig. 8 is an enlarged sectional view showing one end portion of an ignition coil according to the fourth comparative example;
Fig. 9 is an enlarged sectional view showing the other end portion of the ignition coil according to the fourth comparative example;
Fig. 10 is a sectional view showing an ignition coil according to the fifth comparative example;
Fig. 11 is an enlarged sectional view showing a low voltage side of the ignition coil according to the fifth comparative example;
Fig. 12 is a sectional view showing a high voltage side of the ignition coil according to the fifth comparative example;
Fig. 13 is an enlarged sectional view showing the low voltage side of an ignition coil according to a sixth comparative example;
Fig. 14 is an enlarged sectional view showing the low voltage side of an ignition coil according to a seventh comparative example;
Fig. 15 is an enlarged sectional view showing the low voltage side of an ignition coil according to a modification of the seventh comparative example ;
Fig. 16 is a transverse sectional view showing an ignition coil according to the first embodiment of the invention;
Fig. 17 is an enlarged sectional view of a part of the ignition coil according to the first embodiment, the view being taken along a line XVII-XVII in Fig. 16;
Fig. 18 is a front view showing a primary spool used in the first embodiment;
Fig. 19 is a perspective view showing a film on the primary spool used according to a variation of the first embodiment;
Fig. 20 is a perspective view showing the film on the primary spool according to another variation of the first embodiment;
Fig. 21 is a transverse sectional view showing an ignition coil according to the second embodiment of the invention;
Fig. 22 is an enlarged sectional view showing a part of the ignition coil according to the second embodiment, the view being taken along XXII-XXII in Fig. 21;
Fig. 23 is a longitudinal sectional view showing an ignition coil according to the third embodiment of the invention;
Fig. 24 is a transverse sectional view showing a coil wire of a primary coil before winding according to the third embodiment.
The ignition coil 10 has a cylindrical housing 11 made of a resin, in which an accommodating chamber 11a is formed to accommodate a central core assembly 13, a secondary spool 20, a secondary coil 21, a primary spool 23, a primary coil 24 and an outer core 25. The central core assembly 13 is comprised of a core 12, and permanent magnets 14 and 15 arranged at the two longitudinal ends (top and bottom) of the core 12. An epoxy resin 26 filled in the accommodating chamber 11a infiltrates between the individual members of the ignition coil 10 to ensure the electric insulations among the members as a resin insulating material.
The cylindrical member 17 is integrally formed into a cylindrical tube shape, as shown in Fig. 2. The cylindrical member 17 is comprised of a cylindrical part 17a, annular or ring parts 17b and 17c formed at the two longitudinal ends (top and bottom) of the cylindrical part 17a and having through holes 18 formed at their centers, and angled parts 17d formed at corners between the cylindrical part 17a and the annular parts 17b and 17c. As shown in Figs. 3 and 4, the cylindrical part 17a covers the outer circumference of the central core assembly 13, the annular parts 17b and 17c cover the portions of the two longitudinal end faces of the central core assembly 13, and the angled parts 17d cover the end corners of the permanent magnets 14 and 15 or the two end corners of the central core assembly 13. The annular parts 17b and 17c are made thicker than the cylindrical part 17a to function as a second buffer member. The through holes 18 are made diametrically smaller than the permanent magnets 14 and 15 so that the core 12 and the permanent magnets 14 and 15 are fitted into the cylindrical member 17 by expanding diametrically the through holes 18.
As shown in Figs. 1 and 3, the secondary spool 20 is arranged on the outer circumference of the cylindrical member 17 and is molded of a resin material into such a bottomed cylinder as is closed at the longitudinal end side of the permanent magnet 15. The secondary coil 21 is wound on the outer circumference of the secondary spool 20, and a dummy coil 22 is further wound by one turn on the higher voltage side of the secondary coil 21. The dummy coil 22 connects the secondary coil 21 and a terminal plate 40 electrically. Since the secondary coil 21 and the terminal plate 40 are electrically connected through not a single but the dummy coil 22, the surface area of the electrically connected portion between the secondary coil 21 and the terminal plate 40 is enlarged to avoid the concentration of electric field at the electrically connected portion.
The outer core 25 is mounted on the outer circumference side of the primary coil 24. The outer core 25 is provided by winding a thin silicon (Si) steel sheet into a cylindrical shape but does not connect the starting end and the terminal end of the winding to leave a gap in the longitudinal direction. The outer core 25 has a longitudinal length from the outer circumference position of the permanent magnet 14 to the outer circumference position of the permanent magnet 15 to form a magnetic circuit.
In the first comparative example, however, the outer circumference of the central core assembly 13 and the end corners of the permanent magnets 14 and 15 are covered with the cylindrical member 17 which is an elastic member so that the outer circumference of the central core assembly 13 and the end corners of the permanent magnets 14 and 15 are prevented from coming into direct contact with the secondary spool 20 and the epoxy resin 26. Even if the central core assembly 13 and the secondary spool 20 or the epoxy resin 26 having different thermal expansion coefficients repeat expansions and contractions in accordance with the temperature change, moreover, the cylindrical member 17 can elastically deform to absorb the difference in the thermal expansion coefficients. As a result, the cracks are prevented around the outer circumference of the central core assembly 13 and especially at the secondary spool 20 and the epoxy resin 26 in the vicinity of the two end corners of the central core assembly 13, where the cracks might otherwise be liable to occur, so that the electric discharge between the high voltage side and the central core assembly 13 can be prevented. This makes it possible to apply the desired high voltage to the ignition plug.
The thermal expansion coefficient of the cap 19, the secondary spool 20 and the epoxy resin 26 is different from or larger than that of the central core assembly 13 comprised of the core 12 and the permanent magnets 14 and 15. As the temperature lowers, therefore, the cap 19, the secondary spool 20 and the epoxy resin 26 contact to activate a force to contract the central core assembly 13 in the radial direction and in the longitudinal direction. Especially when the force is applied in the longitudinal direction of the central core assembly 13, a magneto-striction to lower the magnetic permeability of the core 12 may occur to lower the voltage to be generated in the secondary coil 21. Since the central core assembly 13 is covered at its outer circumference with the cylindrical part 17a and partially at its two longitudinal ends with the annular parts 17b and 17c thicker than the cylindrical member 17, however, this cylindrical member 17 is elastically deformed to buffer the forces to be received by the central core assembly 13 in the radial direction and in the longitudinal direction so that no magneto-striction occurs in the core 12. As a result, the desired high voltage can be applied to the ignition plug.
The permanent magnets 14 and 15 are arranged in the first comparative example at the two longitudinal ends of the core 12, but the permanent magnet may be arranged at only one end of the core 12.
In the second comparative example shown in Fig. 5, no the permanent magnets are arranged at the two longitudinal ends of the core 12, but the core 12 itself provides the central core assembly 13. The core 12 is covered partially at the outer circumference, at the two end corners and at the two longitudinal end faces with the cylindrical member 17.
In the second comparative example, too, the cracks can be prevented around the outer circumference of the core 12 and especially at the secondary spool 20 and the epoxy resin 26 in the vicinity of the two end corners of the core 12, where the cracks might otherwise be liable to occur, so that the electric discharge between the high voltage side and the central core assembly 13 can be prevented. As a result, the desired high voltage can be applied to the ignition plug.
In the third comparative example shown in Figs. 6 and 7, the cylindrical member 17 made of rubber to act as the first buffer member is comprised of the cylindrical part 17a, an angled part 17b and a bottom disc part 17c acting as a second buffer member, and is shaped into a bottomed cylindrical shape, as closed at the bottom longitudinal end side of the permanent magnet 15. The cylindrical part 17a covers the outer circumference of the central core assembly 13, the annular angled part 17b covers the end corner of the permanent magnet 15, and the disc part 17c covers the bottom end face of the permanent magnet 15. The cylindrical member 17 is extended upwardly at the side of the permanent magnet 14 over the end face of the permanent magnet 14. A plate member 17e made of rubber to act as the first buffer member and the second buffer member is formed into a disc shape separate from the cylindrical member 17 and has a larger diameter than the permanent magnet 14. The end corner of the permanent magnet 14 is covered with the cylindrical member 17 and the plate member 17e, and the longitudinal top end face of the permanent magnet 14 is covered with the plate member 17e. Moreover, this plate member 17e effects a sealing between the cap 19 acting as the case member and the permanent magnet 14 so that the epoxy resin 26 will not enter the central core assembly 13.
In the third comparative example, too, the cracks can be prevented around the outer circumference of the central core assembly 13 and especially at the secondary spool 20 and the epoxy resin 26. in the vicinity of the two end corners of the central core assembly 13, where the cracks might otherwise be liable to occur, so that the electric discharge between the high voltage side and the central core assembly 13 can be prevented. As a result, the desired high voltage can be applied to the ignition plug.
As a result of the elastic deformations of the cylindrical member 17 and the plate member 17e, moreover, the forces for the central core assembly 13 to receive in the radial direction and in the longitudinal direction are buffered to establish no magneto-striction in the central core assembly 13. As a result, the desired high voltage can be applied to the ignition plug.
The first buffer member is comprised of the cylindrical member 17 and the plate member 17e, and the cylindrical member 17 is formed into the bottomed cylindrical shape having no longitudinal end face at its longitudinal top end, so that the first buffer member can be easily provided.
In the fourth comparative example shown in Figs. 8 and 9, the cylindrical member 17, as made of rubber to act as the first buffer member, is comprised of the cylindrical part 17a, the angled part 17b and the annular part 17c, and is formed into a cylindrical tube shape. The cylindrical part 17a covers the outer circumference of the central core assembly 13, the annular angled part 17b covers the end corner of the permanent magnet 15, and the annular part 17c covers a portion of the longitudinal bottom end face of the permanent magnet 15. The cylindrical part 17a extends to the circumferential side of the permanent magnet 14, but its end portion falls short of the top end face of the permanent magnet 14.
Plate members 17f and 17g made of rubber to act as the second buffer member are formed into a circular shape separate from the cylindrical member 17. The plate members 17f and 17g are made radially smaller than the permanent magnets 14 and 15 and are in abutment against the longitudinal end faces of the permanent magnets 14 and 15, respectively.
As shown in Fig. 8, the end corner of the permanent magnet 14 is surrounded by a space 100 and is kept out of contact with any member. Moreover, the plate member 17f effects a sealing between the cap 19 as the case member and the permanent magnet 14 so that the epoxy resin 26 will not enter the central core assembly 13.
In the fourth comparative example, the end corner of the permanent magnet 14 confronts the space 100, and the end corner of the permanent magnet 15 is covered with the cylindrical member 17, so that the two longitudinal end corners of the central core assembly 13 are out of contact with the secondary spool 20 and the epoxy resin 26. Since the outer circumference of the central core assembly 13 is covered with the cylindrical part 17a, moreover, even if the central core assembly 13 and the secondary spool 20 or the epoxy resin 26 having different thermal expansion coefficients repeat expansions and contractions in accordance with the temperature change, the cracks are prevented around the outer circumference of the central core assembly 13 and especially at the secondary spool 20 and the epoxy resin 26 in the vicinity of the two end corners of the central core assembly 13, where the cracks might otherwise be liable to occur, so that the discharge between the high voltage side and the central core assembly 13 can be prevented. This makes it possible to apply the desired high voltage to the ignition plug.
As a result of the elastic deformations of the plate members 17f and 17g, moreover, the forces for the central core assembly 13 to receive in the radial direction and in the longitudinal direction are buffered so that the magneto-striction will not occur in the central core assembly 13. Thus, the desired high voltage can be applied to the ignition plug. Moreover, the plate member 17f as the second buffer member acts as the seal member between the end face of the permanent magnet 14 and the cap 19 so that the number of parts and the number of assembling steps are reduced.
In the foregoing first to fourth comparative examples, at least one of the outer circumference and the two longitudinal end corners of the central core assembly 13 is covered with the buffer member such as the cylindrical member 17, and the other is either covered with the cylindrical member 17 or made to be surrounded by the space. As a result, the secondary spool 20 and the epoxy resin 26 having the thermal expansion coefficient different from that of the central core assembly 13 are prevented from contacting with the outer circumference and the two end corners of the central core assembly 13, and the difference in the thermal expansion coefficients is absorbed by the elastic deformation of the buffer member. As a result, even if the central core and the secondary spool 20 or the epoxy resin 26 having different expansion coefficients repeat expansions and contractions in accordance with the temperature change, the cracks are prevented around the outer circumference of the central core and especially at the secondary spool 20 and the epoxy resin 26 in the vicinity of the two longitudinal end corners of the central core, where the cracks might otherwise be liable to occur. Thus, the discharge between the high voltage side in the ignition coil and the central core or the low voltage side can be prevented, as might otherwise occur along the cracks, so that the desired high voltage can be applied to the ignition plug.
Moreover, the outer circumference of the central core assembly 13 is covered with the cylindrical member 17, and the two longitudinal end faces of the central core assembly 13 are covered with either the cylindrical member 17 or the plate members 17e, 17f, 17g acting as the buffer member. Even if the secondary spool 20 or the epoxy resin 26 having the thermal expansion coefficient different from that of the central core are expanded or contracted together with the central core assembly 13 as the temperature changes, the cylindrical member 17 and the plate members 17e, 17f, 17g are elastically deformed to buffer the forces to be received by the central core assembly 13 in the radial direction and in the longitudinal direction are buffered. As a result, no magneto-striction will be caused in the central core assembly 13 so that the desired high voltage can be applied to the ignition plug.
Although the cylindrical member 17 and the plate members 17e, 17f, 17g are molded of rubber, the cylindrical member 17 and the plate members 17e, 17f, 17g can be molded of an elastomer resin, and the cylindrical member 17 can be insert-molded to have the central core assembly 13 integrally therein. Alternatively, the central core assembly 13 may be inserted into the cylindrical member 12 which is molded of the elastomer resin.
In the fifth comparative example shown in Fig. 11 and 12, at the end portion of the primary spool 23, as located at the low voltage side of the secondary coil 21, there is formed a flange 23a which is bulged radially outward and which has a fitting portion 23b formed to have an L-shaped section for fitting a ring member 50a therein.
The inner circumference corners of the two longitudinal end portions of the outer core 25 are covered with ring members 50b and 50a which are made of rubber to act as angled members. The inner circumference of the end portion of the outer core 25, as located at the high voltage side of the secondary coil 21, is covered with the ring member 50, whereas the inner circumference corner of the end portion of the outer core 25, as located at the low voltage side of the secondary coil 21, is covered with the ring member 51. As shown in Fig. 11, the ring member 50a is fitted in the fitting portion 23b which is formed in the flange 23a. Before the ring member 50a is fitted in the fitting portion 23b, the internal diameter of the ring member 50a is set to be slightly smaller than the external diameter of the outer circumference of the fitting portion 23b. As a result, the elastic force of the ring member 50a acts upon the fitting portion 23b inward in the radial direction.
(1) The ring member 50b is fitted in one end portion of the outer core 25, and this outer core 25 is inserted from the side of the ring member 50b into the transformer portion 11b having the high voltage terminal 41 and the spring 42. The ring member 50b is retained by the retaining portion 13a of the transformer portion 11b, as shown in Fig. 12, to regulate the stroke of insertion of the outer core 25.
(2) The coil assembly, as constructed of the central core assembly 13, the permanent magnets 14 and 15, the secondary spool 20, the secondary coil 21, the primary spool 23 having the ring member 50a fitted in the fitting portion 23b, and the primary coil 24, is inserted into the outer core 25. The ring member 50a is fitted in the fitting portion 23b by the radially inward elastic force so that it is less likely to get out of place from the fitting portion 23b. The ring member 50a is retained on the inner circumference corner of the end portion of the outer core 25 so that the stroke of insertion of the coil assembly is regulated.
(3) The cap is fitted on the transformer portion 11b, and the epoxy resin is poured from the opening 12a of a cap 31.
In the assembling procedure described above, the coil assembly including the outer core 25 may be inserted into the transformer portion 11b by assembling the outer core 25 with the coil assembly, and then by covering the inner circumference corner of the end portion of the outer core 25 at the low voltage side in advance with the ring member 51.
Here, the epoxy resin 26 has a larger thermal expansion coefficient than that of the outer core 25 made of a silicon steel sheet. If the inner circumference corners of the two end portions of the outer core 25 are not covered with the ring members 50b and 50a but are in direct contact with the epoxy resin 26, the ring members 50b and 50a and the epoxy resin 26 repeat the expansions and contractions as the temperature changes, so that cracks will occur in the epoxy resin 26 contacting with the inner circumference corners of the two end portions of the outer core 25. If the cracks occur in the epoxy resin 26 contacting with the inner circumference corners of the two end portions of the outer core 25, a discharge may occur through the cracks between the dummy coil 22, the terminal plate 40 or the high voltage terminal 41 at the high voltage side of the secondary coil 21 or the high voltage side and the outer core 25 or the low voltage portion. With this discharge between the high voltage portion and the low voltage portion, the voltage to be applied to the ignition plug drops so that the desired high voltage cannot be applied to the ignition plug.
In the fifth comparative example, however, the inner circumference corners of the two end portions of the outer core 25 are covered with the ring members 50b and 50a made of rubber, so that they are prevented from contacting directly with the epoxy resin 26. Moreover, the difference in the expansion coefficient between the outer core 25 and the epoxy resin 26 can be absorbed by the elastic deformations of the ring members 50b and 51. As a result, no crack occurs in the epoxy resin 26 in the vicinity of the inner circumference corners of the two end portions of the outer core 25 so that the discharge can be suppressed between the high voltage side of the secondary coil 21, i.e., the dummy coil 22, the terminal plate 40 or the high voltage terminal 41 and the outer core 25. As a result, the desired high voltage can be applied to the ignition plug.
Moreover, the ring member 50a can be fitted in the fitting portion 23b of the primary spool 23 so that the ring member 50a is less likely to come out of the primary spool 23 when this primary spool 23 is inserted into the outer core 25. As a result, the assemlability of the ring member 50a is improved to reduce the number of Assembling steps.
(Sixth Comparative Example)
In the sixth comparative example, at the end portion of a primary spool 27, as located at the low voltage side of the secondary coil 21, there is formed the flange 23a, in which an annular groove 27b is formed as the fitting portion for fitting the ring member 50c as the angled member. When the ring member 50c is fitted in the annular groove 27b, its longitudinal motion is regulated so that the ring member 50c is less likely to get out of position when the primary spool 27 is inserted into the outer core 25. As a result, the assembly of the primary spool 27 having the ring member 50c fitted therein is further facilitated to reduce the number of assembling steps. The inner circumference corner, as located at the high voltage side of the secondary coil 21, of the end portions of the outer core 25 is covered with the ring member 50b as in the fifth comparative example.
In the fifth and the second comparative examples described above, the ring member as the angled member covers the inner circumference corners of the two longitudinal end portions of the outer core 25 thereby to prevent the epoxy resin 26 from coming into direct contact with the inner circumference corners of the two end portions of the outer core 25. As a result, the cracks are suppressed in the epoxy resin 26 in the vicinity of the inner circumference corners of the two end portions of the outer core 25 due to the temperature change. By making the ring members of an elastic material such as rubber, moreover, the difference in the expansion coefficient between the outer core 25 and the epoxy resin 26 is absorbed by the elastic deformation of the ring members so that the cracks are made further less likely to occur. As a result, the discharge between the high voltage side of the secondary coil 21 or the high voltage portion such as the dummy coil 22, the terminal plate 40 or the high voltage terminal 41 and the outer core 25 or the low voltage portion can be suppressed to apply the desired high voltage to the ignition coil. On the other hand, not the whole surface of the outer core 25 but only the inner circumference corner of its end portion is covered with the ring member so that the radius of the ignition coil is not enlarged.
(Seventh Comparative Example)
In the seventh comparative example, the inner circumference corner of the end portion of the outer core 25 is not covered with the ring member, but the end portion of the primary spool 23, as located at the low voltage side of the secondary coil 21, is extended longer in the longitudinal direction than the outer core 25. Moreover, the flange 23a, as formed at the end portion of the primary spool 23 at the low voltage side of the secondary coil 21, is more extended in the radial direction than the end portion of the outer core 25 thereby to cover the end portion of the outer core 25. The inner circumference corner of the end portion of the outer core 25, as located at the high voltage side of the secondary coil 21, is covered with the ring member 50b (not shown) as in the fifth comparative example.
In the seventh comparative example, the cracks, if caused in the epoxy resin 26 in the vicinity of the corner of the end portion of the outer core 25, are shielded by the flange 23a so that they become less likely to extend. As a result, the cracks fail to reach the electric wires connecting the secondary coil 21 and the primary coil 24, and the terminals which are arranged in the ignition coil, so that the electric wires can be prevented from being broken by the cracks. Moreover, the discharge is suppressed through the cracks between the high voltage side of the secondary coil or the high voltage terminal and the outer core 25 so that the desired high voltage can be applied to the ignition plug.
In a modification of Fig. 15, the end portion of the outer core 25 is held in contact with and covered with the flange 23a of the primary spool 23. Since the inner circumference corner of the end portion of the outer core 25 hardly contacts with the epoxy resin 26, the cracks are prevented from occurring in the epoxy resin 26, and the cracks, if caused in the epoxy resin 26 in the vicinity of the inner circumference corner of the end portion of the outer core 25, can be prevented from extending.
In the seventh comparative example and its modification, the inner circumference corner of the end portion of the outer core 25, as covered with the primary spool, is not covered with the ring member. However, the end portion of the outer core 25, as covered with the ring member, is further covered with the ring member, which is covered with the flange of the primary spool.
On the other hand, the inner circumference of the end portion of the outer core 25 at the high voltage side of the secondary coil is not covered with the ring member 50b but may be covered with the flange of the primary spool or the outer spool. When the secondary coil 21 is arranged around the outer circumference of the primary coil 24, too, the inner circumference corners of the end portions of the outer core 25 at the low voltage side and the high voltage side of the secondary coil are not covered with the ring members but may be covered with the flange of the secondary spool. If the inner circumference corner of the end portion of the outer core 25 at the high voltage side of the secondary coil is not covered with the ring member, the cracks may occur in the epoxy resin 26 in the vicinity of the inner circumference corner of the end portion of the outer core 25 thereby to establish the discharge between the high voltage side of the secondary coil 21 and the outer core 25. However, the cracks, if any, are shielded by the flange of the secondary spool or the outer spool and are suppressed from any extension so that the discharge can be suppressed between another high voltage portion and the outer core 25. Moreover, the electric wires, if any at the high voltage side of the secondary coil, can be prevented from breaking.
In the above comparative examples thus far described, the ring member to come into contact with the corner of the end portion of the outer core 25 can be prevented from any damage by rounding the same end portion corner by chamfering it by the indenting or machining method. When the end portion of the corner of the outer core 25 is not covered with the ring member, too, the cracks can be suppressed in the epoxy resin 26 in the vicinity of the end portion corner of the outer core 25.
In the first embodiment shown in Figs. 16 and 17, the primary spool 23 is disposed on the outer periphery of the secondary coil 21 and is formed of a resin material. A thin film 51 as a separating member made of PET (polyethylene terephthalate) for example is wrapped around the outer periphery of the primary spool 23 shown in Fig. 18. The primary coil 24 is wound around the outer periphery of the thin film 51. The thin film 51 may be wrapped by overlapping a wrap end 51a as shown in Fig. 19 or by leaving a gap 51b as shown in Fig. 20. The thin film 51 formed of PET adheres less with both of the primary spool 23 and epoxy resin 26. Accordingly, the primary spool 23 and the primary coil 24 can expand/contract separately without restraining each other when the primary spool 23 and the primary coil 24 whose thermal expansion coefficients differ expand/contract as the surrounding temperature changes.
In the above first embodiment, the thin film 51 interposed between the primary spool 23 and the primary coil 24 adheres less with the epoxy resin 26 which has infiltrated between coil wires of the primary coil 24 and the primary spool 23. Accordingly, when each member of the ignition coil 10 expands/contracts as the ambient temperature changes, (1) the members on the inner periphery side of the thin film 51, i.e., the primary spool 23, the secondary coil 21, the secondary spool 20, the central core assembly 13 and the epoxy resin 26 on the inner periphery side of the thin film 51 and (2) the members on the outer periphery side of the thin film 51, i.e., the primary coil 24, the outer core 25, the housing 11 and the epoxy resin 26 on the outer periphery side of the thin film 51 expand/contract separately from each other bordering on the thin film 51. Thereby, the force which acts on each other when the inner and the outer peripheral parts of the thin film 51 expand/contract is divided by the thin film 51. Accordingly, the force which acts on the inner peripheral part which is otherwise liable to receive the greater force than the outer peripheral part when they expand/contract is reduced, so that the distortion of the inner peripheral part is reduced. For instance, because the distortion of the secondary spool 20 as a member composing the inner peripheral part is reduced, it is possible to prevent the secondary spool 20 from cracking in low temperature when the toughness of the secondary spool 20 drops. Thereby, it is possible to prevent the electric discharge from occurring between the coil wires composing the secondary coil 21 along the crack which might otherwise be caused in the secondary spool 20 and to prevent the electric discharge between the secondary coil 21 and the central core assembly 13 as well as the dielectric breakdown between the secondary coil 21 and the central core assembly 13 from occurring. Accordingly, desired high voltage is generated by the secondary coil 21 and the high voltage causes the ignition plug to generate a good spark.
In the second embodiment shown in Figs. 21 and 22, the thin film 51 is interposed between the primary coil 24 and the outer core 25. Although the position of the thin film 51 is different from that in the first embodiment, the force which acts on each other when the inner and outer peripheral parts expand/contract bordering on the thin film 51 is divided by the thin film 51 in the same manner as in the first embodiment. Accordingly, it is possible to prevent the member, e.g., the secondary spool 20, composing the inner peripheral part from cracking and to prevent dielectric breakdown within the ignition coil 10.
Although the PET thin film 51 is used as the separating member in the first and second embodiments, it is possible to form a separating member by applying PET as a separating material on the primary spool 23. Instead of PET, silicone, wax or the like may be used as the separating material to be applied on the primary spool 23. Further, a plurality of thin films may be disposed at a plurality of sections.
In the third embodiment shown in Fig. 23, the housing 11 of the ignition coil 10 has a first housing (transformer portion) 11a and a second housing (plug portion) 11c, and the connector 30 formed by inserting a plurality of terminals 30a is provided at an opening on the low voltage side of the first housing 11b. An electronic igniter circuit 66 as the switching circuit is provided within the ignition coil 10.
a central core assembly (13) including a rod-shaped core (12);
a primary coil (24) and a secondary coil (21) wound coaxially on an outer periphery of the core (12);
a primary spool (23) around which the primary coil (24) is wound and a secondary spool (20) around which the secondary coil (21) is wound; and
a resin insulator (26) filled around the core (12),
characterized by an adherence reducing thin film separating member (51) surrounding the core,
wherein an inner peripheral part of the ignition coil existing radially inside of the separating member (51) and an outer peripheral part of the ignition coil existing radially outside of the separating member (51) are separated to expand /contract separately from each other without restraining each other.
The ignition coil of claim 1, wherein:
the separating member (51) is interposed between the primary spool (23) and the primary coil (24).
The ignition coil of claim 2, wherein:
the primary spool (23) functions also as the separating member (51).
the primary spool (23) is pasted with a separating material.
the primary coil (24) is pasted with a separating material.
the primary coil (24) has a wire material (72) covered by a material which hardly adheres with the resin insulator (26).
The ignition coil of claim 1, further comprising:
an outer core (25) disposed radially outside of the primary coil (24), wherein the separating member (51) is disposed between the primary coil (24) and the outer core (25).
The ignition coil of any of claims 1 to 7, wherein the primary coil (24) is disposed radially outside of the secondary coil (21).
an outer core (25) disposed around the primary coil (24) and the secondary coil (21) and having an inner peripheral surface which is separated from a member in contact with the inner peripheral surface of the outer core (25) to expand/contract separately.
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1998-02-13 ES ES02015927T patent/ES2275785T3/en not_active Expired - Lifetime
1998-02-13 EP EP98102541A patent/EP0859383B1/en not_active Expired - Lifetime
1998-02-13 ES ES02015928T patent/ES2275786T3/en not_active Expired - Lifetime
1998-02-13 ES ES98102541T patent/ES2221085T3/en not_active Expired - Lifetime
1998-02-13 EP EP04003282A patent/EP1426985B1/en not_active Expired - Lifetime
1998-02-13 ES ES02015929T patent/ES2280458T3/en not_active Expired - Lifetime
1998-02-13 EP EP02015929A patent/EP1255260B1/en not_active Expired - Lifetime
1998-02-13 DE DE69824215T patent/DE69824215T8/en active Active
1998-02-13 EP EP02015928A patent/EP1255259B1/en not_active Expired - Lifetime
1998-02-13 EP EP02015927A patent/EP1253606B1/en not_active Expired - Lifetime
2000-08-09 US US09/635,137 patent/US6525636B1/en not_active Expired - Lifetime
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EP1253606B1 (en) 2007-01-17
US7071804B2 (en) 2006-07-04
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EP1255259B1 (en) 2006-11-29
DE69824215T8 (en) 2006-06-22
EP1255259A1 (en) 2002-11-06
DE69824215D1 (en) 2004-07-08
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EP1426985A3 (en) 2004-06-23
EP0859383A2 (en) 1998-08-19
EP1426985B1 (en) 2011-10-26
ES2280458T3 (en) 2007-09-16
EP0859383B1 (en) 2004-06-02
EP1255260A1 (en) 2002-11-06
ES2275786T3 (en) 2007-06-16
ES2221085T3 (en) 2004-12-16
EP0859383A3 (en) 1998-09-23
EP1253606A1 (en) 2002-10-30
DE69824215T2 (en) 2005-07-07
EP1426985A2 (en) 2004-06-09
ES2275785T3 (en) 2007-06-16
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2002-11-06 AC Divisional application: reference to earlier application
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Opponent name: BERU AG
2010-05-19 R26 Opposition filed (corrected)
2010-06-16 R26 Opposition filed (corrected)
Opponent name: BORGWARNER BERU SYSTEMS GMBH
2014-08-06 27O Opposition rejected