Ignition coil cassette having epoxy anchored bushings

The present invention relates to automotive engine ignition coil cassettes, and more particularly to a bushing installation methodology therefor.

Ignition coil cassettes used for automotive applications are constructed of plastic with epoxy potting, and include metallic bushings through which mounting bolts pass for mounting the ignition coil cassette to a mounting surface.

As shown at FIGS. 1 through 3 , the current practice is to provide an automotive engine ignition coil cassette 10 with metallic bushings 12 therefor. The bushings 12 have an irregularity 14 , such as a knurl, a hole, or an undercut 14 ′ for being anchored relative to the casing by interfacing with plastic. The bushings 12 are, according to one methodology of the prior art, overmolded with plastic 16 seatably into a cylindrical bushing seat 18 which is coextensive with the bushing. Alternatively according to a second methodology of the prior art, the bushings 12 are ulrasonically inserted by pressing into position at the respective bushing seats 18 .

Plastic overmolding of the bushing represents an expensive extra production step. On the other hand, ultrasonic insertion, while eliminating the plastic overmolding step, can potentially cause damage to the ignition coil cassette.

Accordingly, what is needed is a process by which bushings may be installed into an ignition coil cassette without the cost associated with the plastic overmolding installation process, and without the potential for damage associated with the ultrasonic insertion process.

The present invention is an ignition coil cassette having bushings retained by an irregularity of the bushings being encased by epoxy potting, rather than by the plastic interfacing methodologies utilized in the prior art. As a result, the process by which the bushings are installed into the ignition coil cassette avoids the cost associated with the overmolding installation process, and further avoids the potential for damage associated with the ultrasonic insertion process.

The bushing according to the present invention is metallic, having a hollow cylindrical configuration, wherein adjacent one end thereof is an irregularity. The irregularity may be, for example, an undercut, a knurl, or a protrusion. The ignition coil cassette has a plastic casing having a plurality of bushing seats formed therein, one bushing seat, respectively, for each bushing. Each bushing seat is a cylindrical passage through the casing defined by a cylindrical wall, the length of which being less than the length of the bushing such that when the bushing is pressed thereinto, the irregularity is exposed, free of the cylindrical wall.

Operatively, each bushing is pressed into its respective bushing seat in the plastic casing of the ignition coil cassette such that the irregularity thereof does not enter into the bushing seat. Advantageously, a protuberant irregularity may serve as a bushing locating stop when the irregularity abuts the upper surface of the cylindrical wall. Thereafter, epoxy is potted into the void above the bushing seat, surrounding and anchoring the exposed portion of the bushing, including the irregularity thereof, so as to thereby anchor the bushing with respect to the casing.

Accordingly, it is an object of the present invention to provide an ignition coil cassette having bushings which are anchored by an irregularity thereof engaging epoxy potting.

It is an additional object of the present invention to provide a method for installing bushings into an ignition coil cassette, wherein the bushings are anchored by epoxy potting.

These and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.

FIG. 1A is a plan view of a prior art ignition coil cassette having bushings therefor installed.

FIG. 1B is a partly sectional view of the prior art ignition coil cassette, seen along line 1 B— 1 B of FIG. 1 A.

FIG. 2A is a sectional view of a prior art plastic overmolded bushing.

FIG. 2B is a sectional view of a prior art bushing.

FIG. 3 is a partly side view of an ignition coil cassette according to the present invention, wherein bushings therefor are at an initial stage of installation.

FIG. 4 is a partly sectional side view, as in FIG. 3 , wherein now the bushings have been pressed into their respective bushing seats.

FIG. 5 is a partly sectional side view as in FIG. 4 , wherein now the bushings have been anchored by epoxy potting according to the present invention.

FIG. 6 is a detail, perspective view of a bushing having a first form of irregularity seated in its respective bushing seat and anchored by epoxy potting according to the present invention.

FIG. 7A is a detail, perspective view of a bushing having a second form of irregularity seated in its respective bushing seat and anchored by epoxy potting according to the present invention.

FIG. 7B is a partly sectional view, seen long line 7 B— 7 B of FIG. 7 A.

FIG. 8A is a sectional view of a bushing having a third form of irregularity according to the present invention.

FIG. 8B is a partly sectional view, seen along line 8 B— 8 B of FIG. 8 A.

FIG. 9A is a sectional view of a bushing having a fourth form of irregularity according to the present invention.

FIG. 9B is a side view, seen along line 9 B— 9 B of FIG. 9 A.

FIG. 9C is a partly sectional view, seen along line 9 C— 9 C of FIG. 9 B.

FIG. 10 is a detail, perspective view of a bushing having the fourth form of irregularity seated in its respective bushing seat and anchored by epoxy potting according to the present invention.

Referring now to the Drawing, FIGS. 3 through 6 depict an installation methodology for providing an ignition coil cassette 100 with bushings 102 according to the present invention.

Firstly, the ignition coil cassette 100 is fabricated, including a plastic casing 104 . The plastic casing 104 includes a plurality of bushing seats 106 , each composed of a cylindrical wall 106 W passing entirely through the casing. The cylindrical wall 106 W is truncated at its upper end 106 U, having a bushing seat length L.

A metallic bushing 102 is provided for each bushing seat, respectively. Each bushing 102 is in the form of a hollow cylinder, having an irregularity 108 formed generally adjacent a first end 102 F thereof. The length L′ of the bushing is longer than that of the bushing seat length L, such that when the bushing is pressed into its respective bushing seat 106 , the irregularity is exposed, free of the cylindrical wall 106 W. The irregularity 108 shown is that of an annular undercut 108 ′, but may be otherwise configured, as will be discussed hereinbelow.

In operation, as shown by FIGS. 3 through 6 , each bushing 102 is pressed into its respective bushing seat 106 , wherein a second end 102 S of each bushing 102 enters firstly into its respective bushing seat. Once seated, as shown at FIG. 2 , each bushing 102 has an exposed portion 102 E above the upper end 106 U of the cylindrical wall 106 W, wherein the exposed portion includes the irregularity 108 . As shown at FIG. 5 , an epoxy 112 is placed into a cup-shaped void 110 surrounding the exposed portion 102 E of each of the bushings 102 , respectively. The epoxy 112 is a potting which, when in a liquid state, fluidly conforms with respect to the irregularity 108 such that when it solidifies, it provides a hardened interfering interface with respect to the irregularity 108 . As a result, the bushings 102 are anchored to the epoxy. Since the epoxy 112 is, itself, attached to the casing 104 at the cup shaped well 110 , the bushing 102 is thereby attached to the casing.

As mentioned hereinabove, the irregularity 108 of the bushings 102 may have configurations other than an annular undercut 108 ′ as shown at FIGS. 3 through 6 . For example, FIGS. 7A and 7B depict a bushing 102 ′ having an irregularity 108 in the form of an annular knurl 108 ″. Further for example, FIGS. 8A and 8B depict a bushing 102 ″ having an irregularity 108 in the form of an annular protuberance 108 ′″. For yet another example, FIGS. 9A through 9C depict a bushing 102 ′″ having an irregularity 108 in the form of a knobular protuberance 108 ″″. It is to be understood that the irregularity 108 may assume any suitable configuration which ensures an interfering interface with respect to the epoxy 112 which thereby anchors the bushing to the casing in the manner hereinabove discussed.

An advantage of a protuberant irregularity 108 ′″, 108 ″″ is that the protuberance may serve to provide definite location of the bushing 102 ″, 102 ′″ with respect to the cylindrical wall 106 W of the bushing seat 106 . In this regard, as the bushing 102 ″, 102 ′″ is pressed downwardly into its respective bushing seat 106 , the protruding aspect of the protuberant irregularity 108 ′″, 108 ″″ positively abuts the upper end 106 U of the cylindrical wall 106 W precisely when the bushing is correctly seated with respect to the bushing seat 106 , as representatively shown at FIG. 10 (which depicts, by way of example, the irregularity 108 ′″). Of course, if the annular knurling would be protuberant, then it could suffice as a location stop, as well.

To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.