WO2010046242A2

WO2010046242A2 - Coaxial connector and receptacle

Info

Publication number: WO2010046242A2
Application number: PCT/EP2009/063118
Authority: WO
Inventors: Dean Russel Hudson
Original assignee: Delphi Technologies, Inc.
Priority date: 2008-10-21
Filing date: 2009-10-08
Publication date: 2010-04-29
Also published as: WO2010046242A3

Abstract

Connection system (10) for the connection of a coaxial cable (14) to an electric apparatus (2), suitable to be used for the connection of a generator (1) to a resonator (2) of an ignition system of an internal combustion engine, comprising a receptacle (12) to be attached to the end portion (66) of the coaxial cable (14) and a connector (16) to be attached to the electric apparatus (2), the receptacle (12) and the connector (16) comprising a first spring loaded retainer latch device (36) in order to retain the connector (16) inside the receptacle (12), the receptacle (12) comprising a coaxial recess (54) for fitting a coaxial connector plug (56), characterized in that the first latch device (36) is arranged in a groove (58) inside the coaxial recess (54) of the receptacle (12) to cooperate with the outer coaxial surface (60) of the connector plug (56) in order to retain the connector (16) inside the receptacle (12) when connected.

Description

Coaxial connector and receptacle

TECHNICAL FIELD

The present invention relates generally to a coaxial connector and receptacle for the connection of a coaxial cable to a resonator which can be used in the ignition system of an internal combustion engine.

BACKGROUND OF THE INVENTION

The traditional ignition system consists of a sparkplug acting as an electrical feed into a combustion chamber of a gasoline engine, providing concentrated thermal energy release, in the form of a spark, to initiate the combustion. A conventional transformer is used, incorporating electronics to condition and to feed energy from the electrical network in vehicles (Battery, Generator).

Future direct injection combustion systems are targeting stratified fuel injection, promising significant fuel reduction at low speed and partial load. These stratified gasoline mixtures tend to be difficult to ignite with existing ignition systems, mostly because of the limited energy and the very local distribution of the released heat of the spark itself.

Alternatives are intelligently controlled resonance structures which allow emitting heat over larger space, constant over time, and at extended time compared to existing ignition systems. These systems require at minimum, the resonance structure, and a driving generator.

As shown on figure 1 , a resonance based ignition system comprises of a resonator (2), a generator (1) and heat release interface (3). The resonance structure may be operated beneficially under ISM (Industrial Scientific and Medical) radio bands, which were originally reserved internationally for the use of RF electromagnetic fields for industrial, scientific and medical purposes other than communications. Beneficial but not exclusive are the following ISM frequencies: 13,56MHz, 27,12MHz, 40,68MHz.

A coaxial cable is connected to the resonator thanks to a connection system comprising a receptacle attached to the coaxial cable and a connector attached to the resonator. An existing connection system is shown on figure 2. Such a connection system is cumbersome, comprises a lot of different components, and is not suitable for being used in harsh vibrating environments.

It is an objective of the present invention to provide an improved connection system in a simple and cost-effective way.

SUMMARY OF THE INVENTION

In order to reach the above mentioned objective, the present invention provides a connection system for the connection of a coaxial cable to an electric apparatus, suitable to be used for the connection of a generator to a resonator of an ignition system of an internal combustion engine, comprising a receptacle to be attached to the end portion of the coaxial cable and a connector to be attached to the electric apparatus, the receptacle and the connector comprising a first spring loaded retainer latch device in order to retain the connector inside the receptacle, the receptacle comprising a coaxial recess for fitting a coaxial connector plug, characterized in that the first latch device is arranged in a groove inside the coaxial recess of the receptacle to cooperate with the outer coaxial surface of the connector plug in order to retain the connector inside the receptacle when connected. This new arrangement provides more reliability and more robustness, as well as more compactness.

The connection system according to the present invention is suitable but not limited to high frequency (f~27MHz), high power applications (5kW peak). It is particularly suitable for harsh vibrating environments like automotive under- hood. The contact resistance should be as low as possible, the current carry capability about IOOA (peak) at 27MHz.

Thanks to the invention, the packaging length of the whole connection assembly is shorter than standard systems currently available. Additionally, least electromagnetic radiation shall escape this coupling to outside environment. According to other advantageous features of the present invention:

- the groove is annular and the first latch device comprises a first canted coil spring which is mounted in the annular groove;

- the connector plug comprises a mating groove on its outer surface into which the first canted coil spring is compressed when the receptacle and the connector are connected;

- the connector plug comprises a tubular end portion to be inserted axially in the recess of the receptacle such as to extend radially between the first canted coil spring and an end portion of the coaxial cable;

- the end portion of the coaxial cable is provided with a retaining ferrule in electric contact with the metallic shield of the coaxial cable, and the retaining ferrule extends axially beyond the first canted coil spring towards the connector;

- the connector plug is made of conductive material connected to the ground and it comprises an inner annular groove wherein a second canted coil spring is mounted in order to be compressed radially against an outer electrically conductive surface of the coaxial cable which is connected to the shield of the coaxial cable;

- the retaining ferrule free end is provided with a braid ring and the inner annular groove is facing radially the braid ring such that the second canted coil spring is compressed against the braid ring, said retaining ferrule and said braid ring being electrically conductive;

- an annular seal is arranged between the inner surface of the receptacle and the outer surface of the connector plug and, when connected, said annular seal is located axially near the opening of the receptacle;

- the electric apparatus comprises a center electrode to be connected to the center core of the coaxial cable, said center electrode comprising a tubular portion with an inner annular groove provided with a third canted coil spring, said canted coil spring bearing radially against a portion of the center core when connected in order to ensure good electrical connection.

The invention also provides a receptacle and a connector to be used in said connection system.

Other advantages will be explained in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- figure 1 is a bloc-diagram showing a resonance based ignition system; - figure 2 is a cross-sectional view showing an existing connection system with conventional terminal interfaces;

- figure 3 is a cross-sectional view showing a connection system comprising a receptacle, a coaxial cable, and a connector according to a preferred embodiment of the invention;

- figure 4 is a cross-sectional view showing an alternative housing configuration to the receptacle of figure 3 mounted on the end portion of the coaxial cable;

- figure 5 is a perspective view showing the receptacle and the coaxial cable of figure 4;

- figure 6 is a cross-sectional view showing the connector of figure 3 and the centre electrode of the resonator;

- figure 7 is a perspective view showing the connector and the centre electrode of the resonator of figure 6; - figure 8 is a cross-sectional view showing the connection system as mounted on the upper end of the resonator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The connection system according to the present invention will be described in connection with an example application of a resonance based ignition system.

A resonance based ignition system comprises a resonator 2, a generator 1 and a heat release interface 3, as shown on figure 1. The present invention is based on the part of the circuit between the generator 1 and the resonator 2 mating the two together with a firm and robust connection through a connection system and coaxial cable.

Figure 3 and 8 show the connection system 10 according to a preferred embodiment of the invention. It comprises a receptacle 12 fixed to the end portion of the coaxial cable 14, as shown in details on figure 4 and 5, and it comprises a connector 16 to be fixed on the upper end 18 of the resonator 2, or ignition coil, as shown in details on figures 6 to 8.

The coaxial cable 14 is of standard form, consisting of a center core or conductor 20, a dielectric insulator layer 22, a metallic shield or braid 24, and a plastic jacket 26. The cable 14 is inserted into a receptacle housing 28 and trimmed to accept a retaining ferrule 30 and a braid ring 32. Advantageously, the receptacle 12 is then over molded, or flexible rubber 34 is inserted, to make the assembly fixed to the coaxial cable 14. A first spring loaded terminal interface or spring loaded retaining latch 36 is then inserted as shown on the figures.

The retaining latch 36 is made up of a spring 38 in the form of a donut. The turns are canted, and compression forces are perpendicular to the centreline of the spark plug or main axis Al which distorts the coil spring 38 in a radial direction, but does not change the height of the coil spring 38. The advantages of this interface are: that it maintains a near constant force around the mating groove in the connector 16. It allows the spring 38 to compensate for out of round mating surfaces thus accuracy of the mating parts are not of major priority. It compensates for a wide temperature variation without significant change in form. It has a good resistance to vibration under dynamic loads. It is easily connected and disconnected, capable of many connect and disconnect cycles. The spring loaded retainer latch 36 can be designed to accommodate a given push-on pull-off load.

An example of a spring loaded retainer latch using a canted coil spring is disclosed in document US 2005/0212218, which is incorporated by reference. The above receptacle 12 is then attached to its mating connector 16 with a predetermined push-on force. The centre electrode 40 of the ignition coil 2 enters a terminal ferrule having a tubular end portion 42 that houses a terminal interface 44 with a third canted coil spring 45 mounted in a inner annular groove 43. At the same time the braid ring 32 of the receptacle 12 contacts with an earth terminal interface 46 comprising a second canted coil spring 47. Both these terminal interfaces 44, 46 are made up of a spring 45, 47 in the form of a donut. The turns are canted, and compression forces are perpendicular to the main axis Al which distorts the coil spring terminal 44, 46 in a radial direction, but does not change the height of the coil spring terminal 44, 46. The advantages of these conductive interfaces 44, 46 are that it maintains a near constant force. It allows the spring to compensate for out of round mating surfaces thus accuracy of the mating parts are not of major priority. It compensates for a wide temperature variation without significant change in form. It maximizes contact with mating surfaces offering a reliable, and durable conductive interface. It has a good resistance to vibration under dynamic loads. It is easily connected and disconnected, capable of many connect and disconnect cycles.

The upper end of the center electrode 40 comprises a tubular portion 42 wherein the lower end or free end of the conductor 20 of the coaxial cable 14 is inserted. The third canted coil spring 45 bears radially against a portion of the center core 20 to ensure good electrical connection.

An example of an electrical connector using a canted coil spring is disclosed in document WO 2006/124969 which is incorporated by reference. The spring loaded retainer latch 36 of the receptacle 12 then snaps into a mating annular groove 48 of the connector 16. At the same time an o-ring seal 50 of the connector 16 seals against dust and moisture. Short circuiting is avoided by the use of a PTFE insulating bush 52 assembled into the connector 16.

The first spring loaded retainer latch device 36 is aimed at retaining the connector 16 inside the receptacle 12. The receptacle 12 comprises a coaxial cylindrical recess 54 for fitting a coaxial connector plug 56. The first canted coil spring 38 is arranged in an annular groove 58 inside the coaxial recess 54 and said spring 38 cooperates with the outer coaxial surface 60 of the connector plug 56 in order to retain the connector 16 inside the receptacle 12 when connected. The connector plug 56 comprises a mating annular groove 62 on its outer surface 60 into which the first canted coil spring 38 is compressed radially when the receptacle 12 and the connector 16 are connected.

According to a preferred embodiment, the connector plug 56 comprises a tubular end portion 64 to be inserted axially in the recess 54 of the receptacle 12 such as to extend radially between the first canted coil spring 38 and an end portion 66 of the coaxial cable 14.

The retaining ferrule 30 is in electric contact with the metallic shield 24 of the coaxial cable 14 and the retaining ferrule 30 extends axially beyond the first canted coil spring 38 towards the connector 16. Advantageously, the connector plug 56 comprises an inner annular groove 68 wherein the second canted coil spring 47 is mounted in order to be compressed radially against the electrically conductive outer surface of the braid ring 32. The connector plug 56 is made of electrically conductive material and is placed at the ground potential. Consequently, the earth terminal interface 46 connects electrically the metallic shield 24 of the coaxial cable 14 to the ground through the retaining ferrule 30, the braid ring 32, and the second canted coil spring 47 which is in electrical contact with the connector plug 56.

According to a preferred embodiment, the o-ring seal 50 is arranged between the inner surface of the receptacle 12 and the outer surface of the connector plug 56 such that, when connected, said o-ring seal 50 is located axially near the opening of the recess 54.

Claims

1. Connection system (10) for the connection of a coaxial cable (14) to an electric apparatus (2), suitable to be used for the connection of a generator (1) to a resonator (2) of an ignition system of an internal combustion engine, comprising a receptacle (12) to be attached to the end portion (66) of the coaxial cable (14) and a connector (16) to be attached to the electric apparatus (2), the receptacle (12) and the connector (16) comprising a first spring loaded retainer latch device (36) in order to retain the connector (16) inside the receptacle (12), the receptacle (12) comprising a coaxial recess (54) for fitting a coaxial connector plug (56), characterized in that the first latch device (36) is arranged in a groove (58) inside the coaxial recess (54) of the receptacle (12) to cooperate with the outer coaxial surface (60) of the connector plug (56) in order to retain the connector (16) inside the receptacle (12) when connected.

2. Connection system (10) according to claim 1, characterized in that the groove (58) is annular and in that the first latch device (36) comprises a first canted coil spring (38) which is mounted in the annular groove (58).

3. Connection system (10) according to claim 2, characterized in that the connector plug (56) comprises a mating groove (62) on its outer surface (60) into which the first canted coil spring (38) is compressed when the receptacle (12) and the connector (16) are connected.

4. Connection system (10) according to claim 2 or 3, characterized in that the connector plug (56) comprises a tubular end portion (64) to be inserted axially in the recess (54) of the receptacle (12) such as to extend radially between the first canted coil spring (38) and the end portion (66) of the coaxial cable (14).

5. Connection system (10) according to claim 4, characterized in that the end portion (66) of the coaxial cable (14) is provided with a retaining ferrule (30) in electric contact with the conductive shield (24) of the coaxial cable (14), and in that the retaining ferrule (30) extends axially beyond the first canted coil spring (38) towards the connector (16).

6. Connection system (10) according to claim 4 or 5, characterized in that the connector plug (56) is made of conductive material connected to the ground and it comprises an inner annular groove (68) wherein a second canted coil spring (47) is mounted in order to be compressed radially against an outer electrically conductive surface (32) of the coaxial cable (14) which is connected to the shield (24) of the coaxial cable (14).

7. Connection system (10) according to claim 6, characterized in that the retaining ferrule (30) is provided with a braid ring (32) and in that the inner annular groove (68) is facing radially the braid ring (32) such that the second canted coil spring (47) is compressed against the braid ring (32), said retaining ferrule (30) and said braid ring (32) being electrically conductive.

8. Connection system (10) according to anyone of the preceding claims, characterized in that an annular seal (50) is arranged between the inner surface of the receptacle (12) and the outer surface of the connector plug (56), and in that, when connected, said annular seal (50) is located axially near the opening of the receptacle (12).

9. Connection system (10) according to anyone of the preceding claims, characterized in that the electric apparatus (2) comprises a center electrode (40) to be connected to the center core (20) of the coaxial cable (14), said center electrode (40) comprising a tubular portion (42) with an inner annular groove (43) provided with a third canted coil spring (45), said canted coil spring (45) bearing radially against a portion of the center core (20) when connected in order to ensure good electrical connection.

10 Receptacle (12) to be used in the connection system (10) according to any of the preceding claims.

11. Connector (16) to be used in the connection system (10) according to any of claims 1 to 9.