EP0620947B1

EP0620947B1 - Ignition coil assembly and method of manufacture thereof

Info

Publication number: EP0620947B1
Application number: EP92922627A
Authority: EP
Inventors: Philip Charles Chapekis; Cherry Lee Theresa Green; Robert Laurence Hancock; James Paul Morris; Rebecca Anne Mulrooney; James Peretick; Gregg Michael Stefansky
Original assignee: Ford Werke GmbH; Ford France SA; Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Werke GmbH; Ford France SA; Ford Motor Co Ltd; Ford Motor Co
Priority date: 1991-12-23
Filing date: 1992-10-30
Publication date: 1996-07-10
Anticipated expiration: 2012-10-30
Also published as: CN1255583A; EP0620947A1; WO1993013533A1; CN1074732A; DE69212166T2; DE69212166D1; CN1050173C

Abstract

An ignition coil assembly (2) for an internal combustion engine including an ignition coil housing (4) having integrally moulded mounting members (6, 8, 10) arranged on the outer perimeter of the housing (4) in non-interfering relationship with the internal coil/core assembly components. C-Shaped laminated cores (20) are encased entirely within the ignition assembly housing material or encased in an elastomer such as a rubber modified polypropylene and inserted into the housing assembly. The ignition coil assembly (2) provides for use either in an internal combustion engine with a distributor-based or distributor-less ignition system.

Description

This invention relates to an ignition coil assembly for internal combustion engines.
Current conventional ignition coil assemblies for internal combustion engines, in particular those for vehicular applications, include a sizable steel laminated core and associated primary and secondary coil assemblies encased within a fairly thin electrically insulating thermoplastic housing. To mount or permanently fix the coil assembly to the engine or its environs, it is known to provide mounting holes through the core, and sometimes through the surrounding housing also, as is shown in U.S. Patent No. 4,763,094. This limits the options for placement of the coil assembly within the engine compartment. Specifically, the ignition coil assemblies mentioned above must be mounted on grounded surfaces to eliminate the possibility of electric shock. Further, it has been noted that the differences in thermal expansion coefficients between the housing and laminated core may give rise to stresses in the housing that can affect the waterproof integrity of the assembly and/or lead over time to the propagation of hairline fractures within the housing.
In instances where the core laminations would otherwise be externally exposed, such as in the four tower coil design shown in U.S. Patent No. 4,763,094, it is also know to provide a soft water-proof layer of insulating tape or like material placed across the inner exposed surfaces of the C-shaped laminated cores. This is an expensive procedure to implement in actual mass production of the ignition coil assemblies. Utilisation of the water-proof tape also necessitates adding another operation to the manufacture of the ignition coil assembly on the production assembly line.
EP-A-0 395 513; EP-A-0 395 511 and EP-A-0 253 939 describe typical ignition coil assemblies. In EP-A-0 253 939 the sides of the primary core member locate directly in a keyway in the housing. However due to the effects of differing coefficients of expansion of the core and the housing, a tight fit of the core in the housing keyway could cause cracking of the housing during thermal cycling or during extended periods at elevated temperatures. EP-A-0 253 939 discloses the use of a compressible element (30) in order to overcome expansion problems which may affect the waterproof integrity of the assembly.
The present invention is directed to all the foregoing concerns. Further, the present invention is directed to providing flexibility of manufacturing techniques to allow the same basic coil design to be used for distributor-based and distributorless ignition systems.
Ignition coil assemblies of the prior art are dedicated by design to either distributor or distributorless ignition systems. Distributorless ignition systems typically require high voltage output terminals equal in number to the number of cylinders of the particular engine, for example, a 4-cylinder engine would require a four tower ignition assembly like that disclosed in U.S. Patent No. 4,763,094. This dedication to a particular ignition assembly design requires respective dedication of the production assembly line machinery to distributor or distributorless production systems.
In view of the foregoing, this invention contemplates providing an ignition coil assembly for internal combustion engines having increased overall reliability and precluding any possibility of water ingress to the internal components of the ignition coil and prevents poor performance of the coil assembly while increasing overall reliability.
The invention further contemplates an ignition coil assembly having a housing completely enshrouding the primary and secondary coil assemblies and core member and including integrally moulded mounting members arranged on the outer perimeter of the housing in non-interfering relationship with the internal coil/core assemblies.
The ignition coil assembly embodying the present invention is claimed in claim 1.
By making relatively minor modifications in the design and manufacture of the ignition coil assembly embodying the invention both distributor-based and distributorless ignition systems may be provided.
The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective, partially sectioned, partially exploded view of an ignition coil assembly according to one embodiment of the invention;
Figure 2 is a side, partially sectioned, exploded view of the ignition coil assembly shown in Figure 1 and with potting material and high voltage towers removed;
Figure 3 is a perspective view of a C-shaped laminated core totally encased in a rubber insulation material according to the embodiment shown in Figures 1 and 2;
Figure 4 is a perspective view of a four tower ignition coil assembly of the prior art;
Figure 5 is an enlarged, perspective, partially exploded view of the primary bobbin, primary coil, primary terminals and primary terminal receptacle of the present invention as shown in Figure 1;
Figure 6 is a sectioned side view taken along lines 6-6 of Figure 5 and illustrating the insulation displacement terminal and a portion of the primary coil inserted within;
Figure 7 is a perspective, exploded view of an alternative embodiment of the present invention showing a primary connector assembly and a bypass electrical connection utilised in a distributor-type ignition coil assembly;
Figure 8 is a segmented top view of an alternative embodiment of the primary connector assembly illustrating a bypass electrical connection and the dovetail locking and receiving sections; and
Figure 9 shows an example in partial cross-section wherein the core is moulded within the coil assembly housing.

Referring now to Figures 1, 2 and 3, an ignition coil assembly 2 of the present invention includes a housing 4 having a plurality of identical mounting members 6, 8 and 10 all disposed on the exterior of the housing and moulded integrally with the housing. Elongated metal bushings 12 are positioned within the centre of the mounting members to facilitate secure mounting of the ignition coil assembly within the engine compartment.
A dove tail receiving section 14 is also integrally moulded onto the outside of the housing. The dove tail receiving section 14 securely receives and holds in place a corresponding dove tail locking section 16 configured on the primary connector assembly. The legs 18 on each side of locking section 16 are in slip fit engagement with and within the respective channels of the receiving section 14.
A steel laminated C-shaped core 20 is located within the housing. Core 20 is provided with an inner open cavity 22 within which is nested primary and secondary coil assemblies designated 24 and 26, respectively. The secondary coil assembly 26 includes bobbin 28. A coil 30 is wound around bobbin 28 with the ends of the coil terminating at the secondary terminal boxes 32. The secondary coil end portions are soldered to the secondary terminals 34 which are press fit into the secondary terminal boxes 32.
Referring now to Figures 1, 2 and 5, the primary coil assembly 24 is seen to comprise a laminated I-shaped core 36 moulded within a bobbin 38. A primary terminal receptacle 40 is an integrally moulded part of the bobbin 38 at one end thereof and includes a terminal seat portion 42. A second seat 44 extends from the bobbin 38 at its other end. Each seat 42,44 is adapted to mate with a first inner recess 46 and a second inner recess 48, respectively, formed on the core 20 as shown in Figure 3.
For assembly purposes, to assure the coil assembly is oriented properly within the case, the seats 42,44 are laterally offset from one another as are the recesses 46,48. Thus, each functions as a piece orientation feature just as the key and keyway 52,54, respectively of the core and housing, as explained in detail below.
Figure 3 shows a laminated C-shaped core 20 encased in a rubber modified polypropylene shell 50. The C-shaped laminated core is adapted to be received and slip fit inside the lower portion of the housing. The rubber modified polypropylene 50 such as sold by A Schulman, Inc. (USA) under the trademark PolytropeR (specification Nos. TPP 503, 504, 514, 517 and 524) and also sold by Advanced Elastomeric Systems (USA) under the trademark SantopreneR and VistaflexR (TPR), specification Nos. 123-60 and 9203-54W900, respectively, is a preferred encasement material because it acts as a compliant, compressible, stress-relief layer between the metal C-core 20 and the housing 4. The surface chemistry of the encasement material must be non-bonding or non-reactive with the housing and potting material to allow for movement of the materials with respect to one another as well as provide relief from the effects of differing coefficients of expansion of the various materials. This non-bonding chemistry prevents cracking during thermal cycling or during extended time periods at elevated temperatures that ignition coil assemblies are commonly subject to.
A keyway 52 is positioned inside an inner portion of the housing 4 and a mateable key 54 is provided on the outside portion of the core and adapted to engage the keyway 52 of the housing 4.
As shown in Figures 5 and 6, the primary bobbin 38 also has disposed above the primary terminal seat 42 a primary terminal receptacle 40 which is configured to receive a pair of insulation displacement terminals 56. A coil 58 is wound around the bobbin 38 with the terminating ends 60 of the coil 58 placed within the insulation displacement terminals 56 and confined within pairs of oppositely disposed, inverted V-shaped slots 62.
The terminating ends 60 of the primary coil 58 thus extend the length of the cavity within which the displacement terminal resides. The terminals 56 are U-shaped and include a spring biasing arm 64 which engages the leads 60. The terminals 56 are held in the cavity by burrs 66 on the sides of the terminals 56. Thus when the insulation displacement terminals 56 are positioned inside the primary terminal receptacle cavity 68, the terminal will be wedged in place against the sidewalls 68 of the cavity. Each insulation displacement terminal 56 includes inverted V-shaped slots 62 or coil receiving openings such that when the terminal is forced down into cavity 70 the primary coil terminating ends 60 will be engaged.
As shown in Figure 6, the primary coil terminating ends 60 extend through both the primary terminal receptacle 40 and the insulation displacement terminals 56. As the coil receiving opening 62 is brought down upon the primary coil end portion 60, the insulation material deposited entirely along on the primary coil 58 is shaved off and direct electrical contact is made between the primary coil terminating ends 60 and the insulation displacement terminal 56.
The primary connector assembly 74 as shown in Figures 1 and 2 is made of an electrically insulating material. It has an electrode insulation segment 76 and a receptacle portion 78. Electrode insulation segment 76 is constructed to overlap a lip portion 80 of the housing 4 and extend down into the housing. Leg 18 is spaced from the receptacle portion 78 to provide a gap 82 slightly greater in width than the thickness of the housing such that the connector assembly will slip over the housing until the lip 80 engages the connector assembly at the bend 84. As earlier described the primary connector assembly 74 also includes a dove tail locking section 14 for use in affixing the primary connector assembly to the housing. Whereas the gap 82 retains the assembly 74 from outward separation from the housing, the locking section 14, specifically channel members 86 preclude relative lateral displacement.
As shown in Figure 7, electrical leads 88 and 90 travel through the electrode insulation segment 76 and the receptacle portion 78. The electrical leads 88,90 have at their end portions, openings 92,94 which facilitate a direct electrical connection between the end portion of the electrical leads 88,90 and the primary coil 58.
As is conventional lead 88 receives ignition system control data from an onboard ignition control system and second primary connector assembly electrical lead 90 receives 12 volt input from the vehicle battery system.
To assemble the coil assembly 2, the primary coil assembly 24 is inserted within secondary coil assembly 26. Separately the core 20 is inserted within housing 4. Then the combined coil assembly 24,26 is placed within the cavity 22 of core 20 such that primary terminal seats 42 and extension seat 44 of the primary bobbin 38 rest within recesses 46 and 48, respectively of C-shaped core 20. The secondary coil assembly 26 and the primary coil assembly 24 are thus supported within the inner open cavity 22 of the C-shaped laminated core 20.
Towers 96 are then threaded into secondary terminals 34. A moulding resin 98 is subsequently introduced into the inner portion of the housing after all components have been assembled and the moulding resin covers and electrically insulates the entire ignition coil assembly.
Figures 7 and 8 show an alternative embodiment of the present invention adapting an ignition coil assembly suitable for use with a distributorless ignition system to an ignition ccil assembly suitable for use with a distributor-based ignition system. Removal of one high voltage tower 96 and the addition of a slightly modified primary connector assembly effectively transforms the ignition coil assembly to a distributor type coil for use in a conventional internal combustion engine. Specifically, the modified primary connector assembly of this embodiment utilises a bypass member 108 which connects the secondary terminal 34 to the second electrical lead 88 which is the positive terminal of the primary coil. Electrical lead 88 is at low voltage, i.e. 12 volts for the conventional 12 volt system and thus provides a virtual ground. Fastening screw 110 secures bypass electrical connection 108 to terminal 34.
Figure 9 shows a further example wherein the core 20 is moulded entirely within the inner and outer walls 100,102 of the housing. The core 20 entirely encased within the housing is provided with a first inner recess 104 and a second inner recess 106 adapted to mate with the terminal seat portion 42 and the second seat 44 of the bobbin 38. The corresponding position of the inner recesses is identical to that shown in Figure 3. According to the invention, a rubber coated core, not shown, is insert moulded between the inner and outer walls of the assembly housing 2.

Claims

An ignition coil assembly for an ignition system suitable for use in an internal combustion engine comprising: a housing (4) made of an electrical insulating material and provided with at least one mounting member (6,8,10) integrally formed with said housing (4), said one mounting member (6,8,10) having a through-bore adapted to receive a fastener (12) for securing said housing (4) to a support, and said one mounting member (6,8,10) being located on the outside of said housing (4); an electromagnetic core assembly located within said housing (4) and comprising at least one primary core member (20), a primary coil assembly (24), and a secondary coil assembly (26), characterised in that (a) one of said housing (4) and said primary core member (20) is provided with an elongate keyway (52) and the other of said housing (4) and said primary core member (20) is provided with an elongate key (54) mateable to said elongate keyway (52) for positioning said primary core member (20) within said housing (4) and (6) said primary core member (20) is completely encased by a compliant, compressible, stress-relief layer (50) whereby the primary core member (20) and the housing (4) may move relative to each other during any thermal cycling of the ignition coil assembly during use.
An ignition coil assembly as claimed in claim 1 in which the stress-relief layer (50) is of rubber-modified polypropylene.
An ignition coil assembly as claimed in either claim 1 or claim 2 wherein the primary core (20) is C-shaped and has an inner open cavity (22); the secondary coil assembly (26) comprises a secondary bobbin (28) located within said inner open cavity (22) of said primary core (20) and having a pair of secondary terminals (34), a secondary coil (30) wound on said secondary bobbin (28) and connected to said secondary terminals (34); the primary coil assembly (24) comprises a second laminated I-shaped, core (36), a primary bobbin (38) encasing said second core and a primary coil (58); said primary bobbin (38) being located within said secondary bobbin (28) and having a pair of primary terminals (56); said primary coil (58) being wound on said primary bobbin (38) and connected to said primary terminals (56); the ignition coil assembly further comprises a primary connector assembly (74) having a pair of electrical leads (88,90) engaging said primary terminals (56) and providing a virtual ground for one of said secondary terminals (34) by electrically coupling it to one of said electrical leads within said connector assembly.
An ignition coil assembly as claimed in claim 3 wherein said housing (4) is provided with a lip portion (80) and said primary connector assembly is made of an electrical insulating material having a receptacle portion (78) and an electrode insulation segment (76); said electrode insulation segment (76) traversing said lip portion (80) and extending down into the housing (4).
A method of manufacturing and assembly from a single production line an ignition coil assembly for internal combustion engine system which can alternatively be used in a system requiring (i) a distributor for time distribution of the coil voltage output to a particular combustion cylinder and (ii) distributing ignition coil output directly to a designated combustion cylinder ignition device, the ignition coil assembly being as claimed in claim 1 and where in the secondary coil assembly (26) comprises a secondary bobbin (28) having two secondary tower terminals (96), a secondary coil (30) wound on secondary bobbin (28) and connected to said two tower secondary terminals (96); the primary coil assembly (24) comprises a second core (36), a primary bobbin (38) encasing said second core (36) and having a pair of primary terminals (56), and a primary coil (58) wound on said bobbin (38) and connected to said primary terminals (56); the ignition coil assembly further comprises either a first primary connector having a pair of electrical leads adapted to engage said primary terminals (56) and means for providing a virtual ground for the secondary coil by connecting it to one of said electrical leads, or a second primary connector having a pair of electrical leads adapted to engage said primary terminals (56), said method comprising:
connecting said first primary connector to said primary terminals (56) and to one of said secondary terminals (34,96) when said ignition coil assembly is used as a distributor-based ignition system;

connecting said second primary connector to said primary terminals (56) when said ignition coil assembly is used for an internal combustion engine using an ignition system distributing ignition coil output directly to a designated combustion cylinder.