GB2193804A

GB2193804A - Combustion sensing device

Info

Publication number: GB2193804A
Application number: GB08629263A
Authority: GB
Inventors: Roy Haworth; Michael Frederick Russell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1986-01-25
Filing date: 1986-12-08
Publication date: 1988-02-17
Also published as: FR2594545A1; DE3700731C2; GB8629263D0; IT8622770A0; JPS62179617A; DE3700731A1; GB2193804B; US4825689A; JPH07107497B2; IT1213421B; FR2594545B1; GB8601842D0

Description

GB2193804A 1

SPECIFICATION form.

According to the invention a sensing device Sensing device for attachment to an internal combustion en gine whereby an electrical signal can be ob This invention relates to a sensing device 70 tained indicative of combustion of fuel in a whereby an electrical signal indicative of the combustion space of the engine comprises in combustion of fuel in a combustion space of combination, a tubular body part adapted to an internal combustion engine can be ob- be secured within an opening in the wall of tained. the combustion space, a radiation conductive Various forms of such device are known 75 element extending within a bore defined by such for example as radiation responsive de- the tubular member, a sealing lining located vices which are responsive to the radiation between the surface of said element and the emitted by the burning fuel, pressure respon- wall of the bore, said lining acting to retain sive devices which are responsive to the in- the element in the bore and to prevent egress crease in pressure which occurs in the com- 80 of gases from the combustion space, and a bustion space following ignition of the fuel sensor mounted at the end of the element and ionisation sensing devices which are re- which is remote from the combustion space ih sponsive to the free ions in the flame front in use, said sensor being responsive to the radi the combustion space. ation transmitted by the element, the other The present invention is concerned with ra- 85 end of the element in use, being exposed to diation responsive devices. It is known to ob- the combustion space.

serve and indeed to photograph the fuel com- An example of a sensing device in accor- bustion process within an engine combustion dance with the invention will now be de space through a quartz window formed in the scribed with reference to the accompanying wall of the combustion space. Observation in 90 drawing which is part sectional side elevation this manner over an extended period of engine of the device shown mounted in the wall of a use does however become more difficult due cylinder head of an engine.

to the deposition of soot on the window and Referring to the drawing there is indicated at the possible damage to the surface of the 10 a tubular body part which is formed from window exposed to the combustion space. It 95 metal and which has a screw threaded portion is nevertheless possible to locate a suitable 11 formed on its peripheral surface for en sensor behind the window and this will, for an gagement with complementary screw threads initial period of engine use, provide a signal formed in an opening 12 in the cylinder head indicative of the start of combustion of fuel. 13 of the engine. The opening 12 at its inner A more advanced system is known from 100 end communicates with a combustion space United States patent specification 4461170 in 14 of a reciprocating piston engine and adja which a sensor is associated with a fuel injec- cent the inner end of the opening the latter is tion nozzle which supplies fuel to the combus provided with a tapered step 15 which is en tion space. The sensor is connected by means gaged by a complementary step on the per of a light transmitting path which may corn- 105 ipheral surface of the body part to establish a prise a bundle of optical fibres, to a fuel sup- gas tight seal.

ply gallery of the nozzle and from which the The body part has an enlarged head portion nozzle outlet extends. The outlet is controlled 16 upstanding from which is a hollow flange by the valve member of the nozzle so that.in 17.

addition to its normal function it also acts as 110 The body part defines a bore 18 which a switch to isolate the sensor and in particular opens into the combustion chamber 14 when the end of the light transmitting path remote the body part is secured within the opening from the sensor, from the combustion space and which is provided at its end adjacent the except when fuel is being delivered to the combustion space with a step 19. The step space. The aforesaid problems of deposition 115 19 is engaged by one end of a radiation con of soot and damage are therefore overcome. ductive element 20 and this extends through However, the outlet from the nozzle is ex- the bore into a chamber 21 which is bounded tremely small so that the amount of light en- by the flange 17. In order to secure the ele tering the light path will be very small and this ment within the bore and also to provide a requires that the sensor must be responsive 120 seal between the surface of the element and to the small amount of light and the associ- the wall of the bore, a lining 20A is provided ated amplifiers must provide sufficient amplifi- which is formed from a visco-elastic material cation to enable effective use to be made of such as a silicone rubber. Besides providing the signal. In addition, the light sensitive path the retaining and sealing action, the lining has must be sealed against the very high fuel 125 the very important function of protecting the pressure which will exist in the fuel supply element 20 against engine vibration, damping gallery during injection of fuel. any vibration which occurs in the element, and The object of the present invention is to also insulating the element against mechanical provide a sensing device of the radiation re- shock which may occur for example during sponsive type in a simple and convenient 130 the fitting of the sensing device to the engine.

2 GB2193804A 2 The element can be formed from quartz hav-

Claims

ing flame polished end surfaces. It is only CLAIMS necessary to break the

rod to the required 1. A sensing device for attachment to an length and to anneal the ends thereof in a internal combustion engine whereby an electri flame. 70 cal signal can be obtained indicative of com- Mounted on the end, of the element which bustion of fuel in a combustion space of the lies within the chamber 21 is a sensor 22 and engine comprising in combination, a tubular this conveniently is a photo-diode or diodes, body part adapted to be secured within an which has its light ' opening facing the end of opening in tho wall of the combustion space, the element. The diode is cemented to the 75 a radiation conductive element extending end of the element but in carrying out the within a bore defined by the tubular member, cementing process care must be taken to en- a sealing lining located between the surface of sure that no cement is deposited on the end said element and the wall of the bore, said surface of the rod and a fillet type of joint is lining acting to retain the element in the bore preferred as is illustrated. 80 and to prevent egress of gases from the com- An end cap 23 is provided to close the end bustion space, and a sensor mounted at the of the chamber 21, the cap being in screw end of the element which is remote from the thread engagement with the flange 17. The combustion space in use, said sensor being cap also mounts an electrical connector plug responsive to the radiation transmitted by the generally indicated at 24 which is connected 85 element, the other end of the element in use, to the terminals of the diode by means of being exposed to the combustion space.

insulated conductors. Following assembly the 2. A device according to Claim 1 in which chamber 21 may be filled with potting com- said lining is formed from a visco-elastic ma pound and the threads between the end cap terial whereby the lining also acts to cushion and flange locked with a suitable locking com- 90 the elenent against vibration and shock.

pound. 3. A device according to Claim 2 in which In order to minimise soot deposition on the said material is a silicone rubber.

end of the element which is presented to the 4. A device according to Claim 1 in which combustion space, it is essential to ensure the other end of said element is located that the end of the element is recessed below 95 against a step defined in the bore.

the wall of the combustion space. If the dis- 5. A device according to Claim 1 in which tance is too great then cleaning of the end of said sensor is cemented to the one end of the element by the natural scrubbing action of said element.

the gas within the combustion space will be 6. A device according to Claim 5 in which lost. On the other hand if the distance is too 100 said sensor comprises a photo-diode having a small there is a risk of deposition of soot. light opening facing the end of the element.

The actual distance between the end of the 7. A device according to Claim 5 or Claim 6 element and the wall of the combustion space in which a fillet type of joint is provided be may lie between 3 mm and- 12 mm depending tween the end of the element and the sensor.

on the design of the combustion space. The 105 8. A device according to Claim 1 in which inner end of the opening 12 may be posi- said element is formed from quartz the ele tioned close to the path of the fuel spray ment having flame polished end surfaces.

within diesel combustion chamber providing 9. An internal combustion engine including a the end of the element is set back as men- _sensing device as claimed in Claim 1 in which tioned above. 110 the tubular body part is located in the opening The sensor 22 has been described as a so that the other end of the element is set photo diode and this may be sensitive to vis- back from the entrance to the opening from ible or infra-red light. It may however be the combustion space by a distance within the formed from a pyro-electric material and it range 3-12 mm.

may comprise a more complex semi-conductor 115 10. A sensing device for attachment to an device, a low mass thermocouple or some internal combustion engine whereby an electri other device capable of sensing electromag- cal signal can be obtained indicative of corn netic radiation which is given off during the bustion of fuel in a combustion space of the combustion process. In the case where the engine comprising the combination and ar sensor is responsive to infra-red, the element 120 rangement of parts substantially as hereinbe may be formed from silicon. fore described with reference to the accom- The signal obtained from the sensing device panying drawing.

can be processed in any convenient form of processing circuit to provide a number of sig- CLAIMS nals representative of combustion. For 125 New claims or amendments to claims filed on example, it is possible to obtain a signal in- 25-2-1987.

dicative of the start of combustion and further Superseded claims 1-10.

signals since the sensor is observing the corn- New or amended claims:- 19 bustion process in its entirety, signals indica- 1. A sensing device for attachment to an tive of the level of combustion. 130 internal combustion engine whereby an electri- 3 GB2193804A 3 Cal signal can be obtained indicative of com bustion of fuel in a combustion space of the engine comprising in combination, a tubular body part adapted to be secured within an opening in the wall of the combustion space, a radiation conductive element extending within a bore defined by the tubular member, a sealing lining located between the surface of said element and the wall of the bore, said lining being formed from a visco-elastic ma terial and acting to retain the element in the bore, to prevent egress of gases from the combustion space and to cushion the element against vibration and shock, and a sensor mounted at the end of the element which is remote from the combustion space in use, said sensor being responsive to the radiation transmitted by the element, the other end of the element in use, being exposed to the combustion space.
2. A device according to Claim 1 in which said material is a silicone rubber.
3. A device according to Claim 1 in which the other end of said element is located against a step defined in the bore.
4. A device according to Claim 1 in which said sensor is cemented to the one end of said element.
5. A device according to Claim 4 in which said sensor comprises a photo-diode having a light opening facing th ' e end of the element.
6. A device according to Claim 4 or Claim 5 in which a fillet type of joint is provided be tween the end of the element and the sensor.
7. A device according to Claim 1 in which said element is formed from quartz the ele ment having flame polished end surfaces.
8. An internal combustion engine including a sensing device as claimed in Claim 1 in which the tubular body part is located in the opening so that the other end of the element is set back from the entrance to the opening from the combustion space by a distance within the range 3-12 mm.
9. A sensing device for attachment to an internal combustion engine whereby an electri cal signal can be obtained indicative of com bustion of fuel in a combustion space of the engine comprising the pombination and ar rangement of parts substantially as hereinbe fore described with reference to the accom panying drawing.

Published 1988 at The Patent office, state House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

Printed by Burgess & Son (Abingdon) Ltd. Con, 1/87.