GB2254969A - Electro mechanical linkage - Google Patents

Abstract

A system for providing measurements of temperature, pressure and other physical parameters by means of transducers mounted in a hostile, rapidly moving environment such as that found in the vicinity of the pistons in an internal combustion engine, such measurements being highly desirable in the design and development of such engines. An electromechanical linkage is provided to route transducer wires across reciprocating components to a suitable location for onward transmission to a central data collecting apparatus. The hot junctions of thermocouples are mounted in a piston crown and the wires (18) led to a fixed disc (206) within a gudgeon pin (200). Soldered connections (14) are made to flexible wires (20) linking to connections (16) at a movable disc (208). Temperature conduction around wires (20) is enhanced by liquid or paste. Wires (22) lead through a rotatable T-tube to be led at (22) along a conrod to a transmitter. Bearings/anchors (212, 210, 204) can be linked by rods, for stability. <IMAGE>

Description

TRANSDUCER-TRANSMITTER ELECTROMECHANICAL LINKAGE The present invention relates to apparatus used in the design and testing of, for example, internal combustion engines. The apparatus provides an electromechanical linkage to enable transducer measurements to be made on rapidly moving parts of the engine, for example the piston.

It is desirable during the design of internal combustion engines to effect measurements of physical parameters such as temperature and pressure at specific locations in the cylinders-, particularly on the piston itself.

Such measurements are extremely difficult to make in a reliable manner, largely due to the difficulty of routing the wires to such transducers across rapidly moving components, such as the piston to conrod interface. A known technique is to provide a transmitter module to sample the physical data being collected by one or more transducers, the transmitter then transmitting that data to a receiver located in a more convenient location, for example, on the engine block.

The vicinity of the piston / conrod interface has been determined to be an unsuitable location for such transmitters due to the very high temperatures to which they will be subjected, and due to the effect that the mass of the transmitter will have on the balance of such a rapidly moving part. It will be appreciated that if severe modifications to the engine design are required to install such equipment, there is a danger that the measurements will be made on apparatus that is not representative of the engine design under test.

A suitable location for the transmitter for such measurement systems has been identified as the big end of the conrod, where the angular motion of the conrod on the crankshaft at this point can further be used to enable the transmitter to derive power from an inductive link.

The present invention is directed to provide the necessary reciprocating linkage for wiring connecting, for example, one or more transducers housed within the piston, and the transmitter mounted on the conrod, passing via the gudgeon pin. A problem of known systems is that signal carrying wires subjected to the extremes of repetitive flexing or reciprocating action possibly thousands of times per minute last only a few minutes under such conditions as found at the piston to conrod interface of an internal combustion engine.

It is an object of the present invention to provide an improved electromechanical linkage for a piston engine. The present invention provides in one aspect a reciprocating electromechanical linkage for electrically coupling an electronic signal generating means to a corresponding electronic signal receiving means, said linkage being operative to pass one or more signal carrying wires from a piston through to a connecting rod via a rotationally mounted connecting member mounted within a gudgeon pin.

According to another aspect, the present invention provides an electromechanical linkage for a piston engine comprising a fixed plate member, a rotationally mounted plate member, a flexible electrical link between the fixed and rotating plate members, tube means rigidly attached to the rotationally mounted member for attachment of an electrically conducting wire, in which the wire is electrically continuous across the fixed plate, the flexible link, the rotationally mounted plate member and within the tube means.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a schematic block diagram of the electronic system according to the present invention, Figure 2 shows schematically in elevational cross-section a conrod-piston assembly appropriate for locating the present invention, Figure 3 is a cross section through an embodiment of the present invention mounted inside a gudgeon pin.

Figure 4 is a cross section through a further embodiment of the present invention mounted inside a gudgeon pin.

The present invention is described in detail according to a particular embodiment incorporating a thermocouple as the transducer effecting the measurements, and in this context the hot junction end of the thermocouple is equated with the signal generating means, and the cold junction end of the thermocouple is associated with the signal receiving means, ie. where the transducer measurement of voltage corresponding to temperature is received. It will be evident that the principle underlying the present invention is readily applicable to a wide variety of transducers, such as pressure sensors and strain sensors.

Referring to figure 1, a thermocouple is mounted partly inside the body of a piston 20, such that the hot junction 12 of the thermocouple is operative to measure the crown temperature of the piston at a specific location. The thermocouple wires 18 are connected to the input terminals 14 of a linkage unit 25. Multistranded copper wires 20, which may be PTFE coated to withstand high temperatures, are used within the linkage unit 25 to connect the input terminals 14 to output-terminals 16. The thermocouple wires 22 are then continued from these output terminals to a cold junction 24 at an 8-way differential multiplexer unit 30.

It will be appreciated that in order for the thermocouple to function correctly, it is essential that the input terminals 14 and output terminals 16 of the linkage unit 25 be at approximately the same temperature.

The multiplexer unit 30 may have a number of thermocouple or other transducer inputs 32, 34 also connected to its inputs, and these transducer wires may be fed through the same linkage unit 25 as the thermocouple. In a preferred embodiment, the multiplexer unit 30 is capable of scanning 5 transducer inputs and several internal calibration signals. Scanning rates of, for example, up to 10kHz are possible.

The output of 8-way differential multiplexer unit 30 is connected via line 36 to the input of amplifier unit 40, the output of which is sent via line 42 to the input of a 10-bit analogue to digital converter 50. The digitised signals are then fed to transmitter unit 60 via line 52, and are transmitted via aerial 62 on an UHF link to receiver unit 80. The receiver signals can then be decoded and passed to a signal processing computer 90.

The units 30, 40, 50, 60, form a single transmitter module 75, and may all be powered by inductive link power supply 70 operating at, for example, 450kHz, power being transferred for approximately one quarter of a revolution of the engine, and being stored on board to allow continuous operation.

Figure 2 shows a simplified diagram of a piston / conrod / crankshaft assembly showing suitable locations for the components as described above. A piston 20 is constrained within cylinder 100 in known manner. The thermocouple hot junction 12 is mounted close to the crown of the piston for monitoring temperatures of combustion, the thermocouple wires 18 being passed down to one end of a gudgeon pin 200 described in greater detail later. The gudgeon pin has the linkage unit 25 mounted inside it, and is prevented from rotating by pin 112. Steel tube 220 carries thermocouple wires 22 out of the gudgeon pin in a radial direction, and allows wires 22 to be attached to the conrod 120 to run down the length of the conrod to transmitter module 75, which is fixed to the big end of the conrod by suitable means.

The inductive link power supply 70 is able to derive power for the transmitter module each time the crankshaft 130 passes the induction link 140, which passes into and out of the plane of the drawing.

Referring now to figure 3, there is shown an adapted gudgeon pin 200, into one end of which is mounted an aluminium fixed anchoring point 204 through which is mounted a tube 202 for carrying thermocouple wires 18 from the hot junction 12 mounted in or on the piston. The thermocouple wires 18 are terminated at a fixed disc 206, where soldered connections 14 are made to multi-stranded PTFE coated copper wires 20. These wires 20 pass across to a rotating disc 208, where they are connected to the thermocouple cable 22 by soldered connections 16. Rotating disc 208 is mounted in a fixed manner onto steel tube T-piece 220 which is rotatably mounted inside gudgeon pin 200 by means of two PTFE bearings 210, 212. The T-piece 220 and rotating disc 208 are rotatable only through sufficient angle to accommodate the normal motion of the conrod by means of a slotted aperture in the gudgeon pin.The thermocouple wires 22 are passed through the steel tube T-piece 220 from the rotating disc 208 to where they can be passed down the length of the conrod 120 to the transmitter module 75.

Referring now to figure 4, a further embodiment of the adapted gudgeon pin 200 is shown. In this particular embodiment, there are two spacing bars 225, 226 passing through the PTFE bearings 210, 212, and through the fixed aluminium anchoring point 204, the spacing bars being provided to improve the rigidity and stability of the linkage, particularly during assembly. The multi-stranded PTFE coated copper wires 20 are routed closer together, and close to the central axis of the linkage further reducing the strain upon these wires.

The linkage unit 25 is designed to be sited at a point of minimum movement of the wires, this movement being most detrimental to the longevity of the wire linkage under normal operation of the engine.

All terminals within the linkage unit 25 are coated with high temperature epoxy for added rigidity, and all electrical joints are kept as close to one another as possible in order to minimise the temperature differences across the additional metallurgic junctions introduced into the thermocouple. The use of copper conducting materials further assists in the reduction of temperature differences. The multi-stranded copper wire has been found to be sufficiently robust to be subjected to the reciprocating action for some considerable time without failure, whereas single core thermocouple wire is known to survive only a very short time in such an environment.

In a further embodiment, the cavity containing the multi-stranded PTFE coated copper wires 20 between discs 206 and 208 is filled with a suitable liquid or paste to enhance temperature conduction.

It has been determined that a considerable number of multistranded PTFE coated copper wires can be simultaneously passed across the linkage unit 25, this number being only constrained by the dimensional requirements of the gudgeon pin, and the size of wiring required for the transducers.

It will further be evident that the connections made at input 14 and output 16 of the linkage unit 25 are not necessary in the event that the transducer wires can be constructed from suitable wire along the entire length, to include sections of wire 18 and 22. The embodiment previously described permits the use of thermocouple sensors having single stranded, application specific metal wires (for instance a type J thermocouple), which wires are not suitable for the crossing of linkage unit 25.

It will be readily apparent to one skilled in the art that many modifications and variations can be made to this electromechanical link without departing from the spirit or scope of the present invention.

Claims (17)

1. An electromechanical linkage for a piston engine comprising a fixed plate member (206), a rotationally mounted plate member (208), a flexible electrical link (20) between the fixed and rotating plate members, tube means (220) rigidly attached to the rotationally mounted member for attachment of an electrically conducting wire (22), in which the wire is- electrically continuous across the fixed plate, the flexible link, the rotationally mounted plate member and within the tube means.

2. A linkage as in claim 1 wherein the rotationally mounted plate member and the fixed plate member have electrical connections attached for enabling a first wire to be connected to a second wire at said fixed plate member, said second wire being connected at said rotationally mounted plate member to a third wire, said third wire being carried away from said rotationally mounted plate member by said tube means.

3. A linkage as in claim 2 wherein the first and third wires are of one type, and the second wire is a multi-stranded, electrically insulated type.

4. A linkage as in any preceding claim, wherein the linkage carries a plurality of wires, each electrically insulated from one another.

5. A linkage as in any preceding claim wherein the wire from the fixed plate end is connected to a transducer.

6. A linkage as in any preceding'claim wherein the wire from the rotationally mounted plate end is connected to a radio transmitter module.

7. A linkage as in claim 3 wherein the first and third wires are of two different metals.

8. A linkage as in any preceding claim wherein said fixed and rotationally mounted plate members are each supported by a bearing, said bearings mounted within a metallic cylinder, said fixed and rotationally mounted plate members being enclosed in a volume defined by the metallic cylinder and the bearings.

9. A linkage as in claim 8 wherein the volume is filled with a heat conducting liquid or paste.

10. A reciprocating electromechanical linkage for electrically coupling an electronic signal generating means to a corresponding electronic signal receiving means, said linkage being operative to pass one or more signal carrying wires from a piston through to a connecting rod via a rotationally mounted connecting member mounted within a gudgeon pin.

11. A linkage as in claim 10 wherein the electronic signal generating means is the hot junction end of a thermocouple, and the electronic receiving means is the cold junction end of a thermocouple.

12. A linkage as in claim 10 wherein the electronic signal generating means is a pressure transducer.

13. A linkage as in claim 10 wherein the electronic signal receiving means comprises a multiplexer, an amplifier, an analogue-digital converter and a radio transmitter.

14. A linkage as in claim 13 wherein the electronic receiving means includes an inductive link power supply capable of receiving power from an induction link attached to another part of the engine, said receiving means moving in close proximity to said another part of the engine.

15. A linkage as in claim 8 or 9 wherein the bearings are linked by one or more spacing bars.

16. A linkage as in claim 8, 9 or 15 wherein one or more of the bearings are manufactured from PTFE.

17. A linkage substantially as described herein, with reference to the accompanying drawings.