Connector plug for connecting an ignition coil to a spark plug

Abstract

A connector plug is described for connecting an ignition coil to a spark plug, comprising an electrical conductor, which has a first end for contacting the ignition coil and a second end for contacting the spark plug, and a protective tube, which surrounds the electrical conductor. In accordance with this disclosure it is proposed that the protective tube has a predetermined bending point with a reduced bending stiffness.

Claims

1. A connector plug for connecting an ignition coil to a spark plug, comprising: an electrical conductor having a first end configured for contacting the ignition coil and a second end configured for contacting the spark plug; and a protective tube surrounding the electrical conductor; wherein the protective tube has a predetermined bending point with a reduced bending stiffness; further wherein the protective tube has a plurality of reinforcement ribs extending in a longitudinal direction thereof, and wherein the predetermined bending point comprises a recess in one or a plurality of the reinforcement ribs.

2. The connector plug in accordance with claim 1, wherein one or more of the reinforcement ribs has no recess for reducing the bending stiffness.

3. The connector plug in accordance with claim 2, wherein the protective tube has four reinforcement ribs, wherein two opposing reinforcement ribs have a predetermined bending point comprising a recess, and two reinforcement ribs have no recess.

4. The connector plug in accordance with claim 1, wherein the width of the recess, measured in the longitudinal direction of the reinforcement ribs, is equal to or greater than the width of the reinforcement ribs measured transversely to their longitudinal direction.

5. The connector plug in accordance with claim 4, wherein the width of the recess measured in the longitudinal direction of the reinforcement ribs is not more than three times the width of the reinforcement ribs measured in their longitudinal direction.

6. The connector plug in accordance with claim 1, wherein the outer surface of the protective tube is closed in the vicinity of the predetermined bending point.

7. The connector plug in accordance with claim 1, wherein the protective tube has a section at a distance from the predetermined bending point in which its wall thickness is increased around its periphery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 shows an example of embodiment of an inventive connector plug;

(3) FIG. 2 shows the connector plug shown in FIG. 1 in a curved state;

(4) FIG. 3 shows another example of embodiment of a protective tube for a connector plug;

(5) FIG. 4 shows a detail of FIG. 3; and

(6) FIG. 5 shows a cross-sectional view of the protective tube shown in FIG. 3 in a curved state.

DESCRIPTION

(7) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(8) The connector plug 10 shown in FIG. 1 is used to connect an ignition coil to a spark plug of an internal combustion engine. For this purpose, the upper end 1 of the connector plug 10 in the figures is connected to the ignition coil, and the lower end 2 in the figures is connected to the spark plug. The connector plug 10 contains an electrical conductor 8 (shown schematically in FIG. 5), for example in the form of a metallic coil spring, which is surrounded by a protective tube 3, and in operation connects the high-voltage contact of an ignition coil to the terminal contact of a spark plug in an electrically conducting manner. The protective tube 3 can be seen in FIGS. 1 and 2, and may be made of silicone, for example. A further example of embodiment of the protective tube 3 is shown in FIGS. 3 to 5.

(9) The protective tube 3 has a plurality of reinforcement ribs 4, which, located side by side around its circumference, extend parallel to its longitudinal direction. In the example of embodiment of FIGS. 1 and 2, the reinforcement ribs 4 extend over the majority of the protective tube 3, for example over three quarters of its length or more. The reinforcement ribs increase the mechanical load-bearing capacity of the protective tube 3, and are preferably dimensioned such that they can support the connector plug 10 on a cylinder head bore of an engine. In addition, the space between the reinforcement ribs 4 facilitates air exchange in the cylinder head bore. At least one of the said reinforcement ribs 4 has a predetermined bending point formed by at least one recess 5.

(10) The protective tube 3 can, for example, have four reinforcement ribs 4, wherein two of the said reinforcement ribs 4 each have predetermined bending points located opposite each other and formed by a recess 5. The two reinforcement ribs 4 located in between them have no recesses in the corresponding position. If the protective tube 3 is curved, one of the said two recesses 5 forming a predetermined bending point is then located on the inside of the curve and the opposing recess 5 is located on the outside of the curve. The recess 5 on the inside of the curve avoids compressive stresses in the reinforcement rib 4. The recess 5 located on the outside of the curve avoids tensile stresses in the corresponding reinforcement rib 4. The reinforcement ribs 4 without recesses located between the said two reinforcement ribs 4 with recesses 5 are only slightly affected by the curvature shown in FIG. 2 and therefore do not require any recesses 5.

(11) In the example of embodiment shown, the recesses 5 have a rectangular shape, but can also be of a different shape, for example they can be wedge-shaped or U-shaped.

(12) At a distance from the predetermined bending points formed by the recesses 5, the protective tube 3 has a section 6 with an increased wall thickness. The increased wall thickness can be thickened up to the height of the reinforcement ribs, as shown in FIG. 1, but can also protrude beyond, or be thinner than, the outer diameter of the reinforcement ribs, so that reinforcement ribs can also be formed in region 6. In this manner, the mechanical stability of the protective tube 3 can be improved. In section 7 of the protective tube 3 containing the recesses 5, the wall thickness between the reinforcement ribs 4 can be significantly reduced so as to save material and facilitate the bending of the protective tube 3.

(13) The recesses 5 of the reinforcement ribs 4 are preferably not so deep that an opening is thereby created in the protective tube 3. The recesses 5 of the reinforcement ribs 4 are preferably approximately as deep as the height of the reinforcement rib. The remaining wall thickness must be thick enough to provide the necessary protection and insulation.

(14) The width of the recess 5 or recesses 5 measured in the longitudinal direction of the reinforcement ribs 4 is preferably as large as, or larger than, the width of the reinforcement ribs 4 measured transversely to their longitudinal direction, but is not more than three times the width of the reinforcement ribs 4.

(15) The width of the recess (measured at rib height) may approach zero on the outer radius of the bend; a narrow slot or cut may be sufficient, as the recess diverges during bending. The recess is preferably slightly wider, so that a bending radius can form at the base of the recess. On the inside of the bend, the width of the recess should be dimensioned so that, during bending, the inner walls of the recess do not come into contact with each other, or only with a low contact pressure.

(16) Only a single recess 5 is shown in FIG. 1. However, a plurality of recesses 5 can also be provided on a reinforcement rib 4.

(17) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SYMBOLS

(18) 1 End of connector plug adjacent to ignition coil 2 End of connector plug adjacent to spark plug 3 Protective tube 4 Reinforcement rib 5 Recess 6 Protective tube section 7 Protective tube section 8 Electrical conductor 10 Connector plug