GB2280549A - Impedance-load connector for spark plug - Google Patents

Description

1 2280549 A TERMINAL WITH AN INTEGRATED RESISTOR

The present invention relates. to the general technical field of electrical connection between a conductor and equipment for producing or using electricity.

More particularly, the present invention relates to electrical connection means between conductors and members or accessories for producing or using electricity and forming parts of internal combustion engines, and preferably, but not exclusively, of spark ignition engines. In the above technical field, a feed harness is connected by means of endpieces or terminals to equipment for producing or using electricity such as a coil, a distributor, or spark plugs. In general, on either side of an intermediate link portion each terminal includes: a branch for crimping to an electric cable; and a branch for connecting with a complementary terminal on the equipment for producing or using electricity. 20 In addition to its primary function of conducting high tension, the feed harness must also be designed to avoid creating interfering disturbances that could upset the reception of radio signals in the environment of the equipment for producing or using electricity, e. g. inside or outside a vehicle.

To this end, various different types of antiinference devices have been proposed in the state of the art for the purpose of fitting to feed harnesses.

Patent CH-344 871 proposes an electrical circuit element enabling at least two electrical components to be electrically connected together, e.g. conductor wires or connection terminals. The electrical components are clamped, at least in part, in an assembly body made of a material that is flexible and resilient and that serves to keep the parts resiliently in contact with one another. In one embodiment, the assembly body includes a central cavity in which a two-lead device is engaged for 2 limiting interference currents and having two conductor leads penetrating into two end cavities. One of the cavities is designed to receive the terminal pin of a spark plug, while the other cavity receives a conductive cable whose core is made up of strands between which one of the leads of the two-lead device is inserted.

The above circuit element does not give satisfaction in practice, for the following reasons. The assembly body which must be made of a material that is flexible and resilient to enable the electrical components to be engaged therein is unsuitable for ensuring that such electrical components are held together mechanically in a manner that is reliable and long lasting. It turns out to be impossible to control the state of the electrical contacts that are made in the end cavities between the leads of the two- lead device and the components to be connected together. As a result the electrical components are randomly positioned inside the ass ly body. Furthermore, the resilient nature of the assembly body allows relative displacement between the components to be connected together, in particular when they are subjected to mechanical stress or vibration.

Another solution has been proposed in patent FR 2 112 694 which describes a connection device for an anti-interference cable having a terminal. The connection device includes a resistor having one end placed in contact with a determined length of metal wire spiral-wound between an insulating core and an outer insulating sheath. The resistor is embedded in overmolding in order to leave one end projecting for being folded back against the overmolding so as to receive the terminal which is associated therewith by crimping.

Practical implementation of such a device leads to the observation that random electrical contact appears between the resistor and the cable because of the impossibility of controlling the state of the connection.

0 3 Mechanical stress, even in small amounts, imposed on the cable cause the cable to slide relative to the device so that electrical connection is no longer established reliably. Furthermore, crimping the terminal onto the tab of the resistor frequently leads to the tab breaking. The greater the hardness of the encapsulating material, the more frequent such breakage. Using an encapsulating material of smaller hardness allowing it to absorb stresses created during crimping means that an effective mechanical connection cannot be achieved between the terminal and the resistor.

It can also be seen that such a device requires various manufacturing stages to be implemented, namely: engaging one of the tabs of the resistor between the core and the insulating sheath of the cable; encapsulating the resistor mounted on the cable; disposing the other tab of the resistor over the encapsulation; and crimping the terminal onto the folded tab. Such operations are difficult or impossible to automate. Furthermore, the manufacturing method requires the entire cable and device to be handled In order to perform the crimping operation. As a result the cost of manufacturing such a connection is high.

The prior art thus shows that there remains a problem of obtaining a genuine electrical connection terminal suitable for limiting interference current while still allowing connections to be established that are electrically and mechanically reliable and long lasting between two conductive elements, and whose integrity can easily be verified.

The invention thus seeks to provide a connection terminal suitable for remedying the above problem and whose design makes it possible to limit assembly operations, thereby reducing manufacturing costs.

To achieve the above objects, the connection device is of the type comprising:

4 an electrically conductive two-lead device having an impedance suitable for limiting of interference current; and a protective dielectric case surrounding the conductive two-lead device.

According to the invention, the connector constitutes a connection terminal provided with a crimping branch for crimping onto an electrical cable and a connection branch for connection to a complementary terminal, the crimping branch and the connection branch being fixed and electrically connected to the conductive two-lead device via extensions of the branches that are embedded, at least in part, in the dielectric case.

Various other characteristics appear from the following description given with reference to the accompanying drawings which show embodiments and implementations of the invention by way of non-limiting example.

Figure 1 is a partially cutaway perspective view showing a first variant embodiment of a connection terminal of the invention. Figure 2 is a view analogous to Figure 1 showing another variant embodiment of a connection terminal of the invention. 25 In the embodiment shown in Figure 1, the connection device of the invention constitutes an electrical connection terminal given overall reference 1. The terminal comprises a "crimping" branch 2 for crimping onto an electrical conductor 3 as represented by chain- dotted lines, and in a preferred example it forms a portion of an ignition harness for an internal combustion engine. The crimping branch 2 comprises a portion 4 of substantially semi-cylindrical section which is extended by two crimping tabs 5 suitable for folding over and pressing down so as to clamp onto the conductive core 3, thereby providing mechanical strength and indirectly establishing electrical contact.

1 1 The crimping branch 3 is connected via an intermediate link portion 6 to a "connection" branch 7 for connection to a complementary terminal 8 represented by chain-dotted lines in the drawing. The complementary terminal 8 may be carried, in particular, by a coil or a distributor in an ignition system for a spark ignition engine such as those fitted to motor vehicles. Alternatively the complementary terminal may be the terminal pin of a spark plug. The branch 7 is preferably of the substantially tubular type comprising a portion 7a that is resiliently deformable in the radial direction to facilitate fitting, installing, securing, and electrically connecting the terminal to the complementary terminal 8 which may be of the male type or of the female type. The resiliently deformable portion 7a is made up of two tabs 9a.

The link portion 6 is constituted by an electrically conductive two-lead device 10 which is connected directly and electrically to the crimping branch 2 and to the connection branch 7. The device has an electrical impedance that is suitable for limiting interference current. In the example shown In Figure 1, the device 10 is corstituted by a resistor whose two terminal leads 11 and 12 are connected to assembly tabs or connections 13 and 14 respectively carried by the crimping branch 2 and by the connection branch 7. For example, the tab 13 is made from a segment extending the portion 4 of the crimping branch 2 and it is partially rolled up so as to constitute a tubular sleeve for receiving the lead 11 of the resistor. Similarly, assembly tab 14 is formed, for example, from two similar tabs 14a which are attached to portion 7a ofthe connection branch 7. The tabs 14a are folded and pressed down so as to clamp onto lead 12 of the resistor 10.

Naturally, the resistor 10 may be fixed to the crimping branch 2 and to the connection branch 7 by connection means other than those described above. For 6 example, the resistor 10 may be fixed and connected to the branches 2 and 7 by soldering. In the example shown, the way the branches 2 and 7 are connected to the resistor 10 gives rise to a terminal that is angled in shape. A terminal of the invention could naturally have some other general shape, for example it could be straight.

According to the invention, the link portion 6 is also constituted by a dielectric case 16 surrounding the resistor 10 and at least part of the assembly tabs 13 and 14. The dielectric case 16 is preferably formed by encapsulating or overmolding an insulating material onto the resistor 10 and the assembly tabs 13 and 14 of the branches 2 and 7. In this way, the branches 2 and 7 project from the case 16, thereby making it easy to connect them to the respective associated parts. A cap (not shown) may naturally be applied to the terminal as a whole so as to protect the various component parts of the terminal.

Thus, by the presence of the resistor, the terminal of the invention serves to limit interference currents flowing in the cable, thereby obtaining an anti Interference terminal. The resistance of the electrical component 10 preferably lies in the range 1 kohms to 5 kohms.

The terminal 1 constitutes an Independent element that provides both electrical connection and also mechanical connection that Is reliable between two electrical parts. The case 16 provides mechanical strength between the crimping branch 2 and the connection branch 7, with the extensions thereof, i.e. the assembly tabs 13 and 14 being embedded in the overmolded case 16. The resistor 10 is thus electrically connected to and securely fastened to the branches 2 and 7. The terminal of the invention also has the advantage of being capable of being manufactured with a limited number of assembly operations, thus reducing its manufacturing cost.

J 7 Figure 2 shows a variant embodiment of the invention in which the electrically conductive two-lead device of the link portion 6 is constituted by a body 18 that is made of a material that provides given electrical impedance for the purpose of limiting interference currents. By way of example, the body 18 may be made of a semiconductive insulating material. The body 18 is preferably partially reinforced by two reinforcing tongues 19 that are mounted therein without coming into contact with each other, respectively extending the portion 4 of the crimping branch 2 and the portion 7a of the connection branch 7. The reinforcing tongues or extensions 19 include shapes 20 that are mutually angularly offset to enhance retention of the body 18 on the branches 2 and 7 and to reduce contact resistance to a minimum. It should be observed that the body 18 can thus be obtained by being overmolded or encapsulated onto the reinforcing tongues 19. The body 18 may be protected by a dielectric case 16 as described when describing the embodiment shown in Figure 1.

The Invention Is not limited to the examples described and shown and various modifications can be made thereto without going beyond the ambit of the Invention.

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Claims (8)

1. An electrical connector comprising an electrically conductive two-lead device having an impedance suitable for limiting the flow of interfering current, and a protective dielectric case surrounding the conductive twolead device, characterized in that the connector constitutes a connection terminal provided with a crimping branch for crimping onto an electrical cable and a connection branch for connection to a complementary terminal, the crimping branch and the connection branch being fixed and electrically connected to the conductive two-lead device via extensions of the branches that are embedded, at least in part, in the dielectric case.

2. A connector according to claim 1, in which the conductive two-lead device is constituted by a resistor whose two terminals are connected to tabs respectively extending the crimping branch and the connection branch.

3. A connector according to claim 1, in which the conductive two-lead device is constituted by a body made of a material providing a given electrical impedance for eliminating interference.

4 1 9 4. A connector according to claim 3, in which the body is carried by two reinforcing tongues mounted without making contact with each other and extending the crimping branch and the connection branch.

5. A connector according to claim 4, in which the reinforcing tongues include portions that are mutually angularly offset to enhance retention in the body and to reduce contact resistance.

6. A connector according to claim 4 or claim 5J. in which the body is overmolded or encapsulated on the reinforcing tongues.

7. A connector according to claim 1, in which the dielectric case is overmolded on the conductive two-lead device.

8. An electrical connector substantially as herein described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.