Field of application of the invention

The present invention applies to the field of endothermic engines, also referred to as "internal combustion" engines.

As is known, endothermic engines include one or more combustion chambers in which a fuel undergoes a controlled combustion in the presence of oxygen in order to convert the thermal energy released with the combustion into mechanical energy. A further combustion of the fuel can be undesirably triggered in one or more points of the combustion chamber preliminarily or simultaneously with said controlled combustion. Said undesired and uncontrolled combustion is known as "detonation" and can be caused by multiple factors, such as the fuel reaching too high temperatures in the combustion chamber (e.g., due to the wear of the mechanical components interacting in the chamber).

Detonations compromise, sometimes irreparably, the operation of an endothermic engine. This is the reason why significant efforts are made when studying and/or designing an endothermic engine, in an attempt to avoid the onset of detonations.

More precisely, when a new endothermic engine is developed, the efforts to avoid detonations from being triggered in a combustion chamber usually focus on the design of the mechanical components involved in the combustion. How- ever, when the engine being developed has particularly high performance (such as engines equipping vehicles racing in the so-called "Formula 1", for example), it is not possible to predict where detonations could occur in the combustion chamber based on design alone. Therefore, in these cases, the detection of detonations needs to occur empirically. In other words, an engine is driven and deliberately brought to operating conditions such as to trigger at least one detonation in order to estimate the position, in the combustion chamber, of the detonation onset point and therefore study how to modify the mechanical component (or mechanical components) potentially responsible for triggering the detonation.

The estimation of the position of the detonation trigger point is usually carried out by applying a plurality of piezometric sensors to the combustion chamber. Said sensors are applied to the combustion chamber so that the sensors are hit by the vibrations caused by a detonation in a direct manner and not by propagation through the walls of the combustion chamber. For this purpose, the sensors are preferably applied to the walls of the combustion chamber and suitable holes are made in said walls so as to put the sensors in communication with the interior of the combustion chamber. The sensors convert the vibrations caused by a detonation into electrical pulses which are acquired by a processing unit and communicated to skilled technicians. The latter, based on the position of the piezoelectric sensors, attempt to interpret the signals of electrical nature acquired by the processing unit in order to estimate the position of the detonation onset point in the combustion chamber. By way of example, referring to an Otto- cycle endothermic engine (petrol engine), three or four piezoelectric sensors are usually applied to the combustion chamber at the level of the so-called "cylinder-head gasket" and a further sensor of the aforesaid type is housed in a hole close to the spark plug.

However, piezoelectric sensors must be used during an operation of the engine at very high engine speeds. In addition, piezometric sensors have a very short sampling time and the propagation speed of detonations is only presumed. For the aforesaid reasons, the estimation of the position of the detonation trigger point in a combustion chamber is approximate. Given the above, the present invention relates to a method of creating a system adapted to recognize the occurrence of a detonation in a combustion chamber of an endothermic engine, as well as, upon the occurrence of a detonation, to attempt to estimate the position of the detonation trigger point. The present invention further relates to a system obtainable by implementing said method, for detecting detonations in a combustion chamber of an endothermic engine.

Overview of the prior art

The Applicant is not aware of any system adapted to recognize the occurrence of a detonation in a combustion chamber and to attempt to estimate the position of the detonation trigger point, nor is the Applicant aware of any method of creating a system of the aforesaid type (i.e. , a system for detecting detonations in a combustion chamber of an endothermic engine adapted to recognize the occurrence of a detonation in a combustion chamber, as well as to attempt to estimate the position of the detonation trigger point).

Objects of the invention

It is the object of the present invention to overcome the aforesaid drawbacks by indicating a method of creating a system for detecting possible detonations in a combustion chamber of an endothermic engine adapted to recognize the occurrence of a detonation in a combustion chamber, as well as to attempt to estimate the position of the detonation trigger point.

Summary and advantages of the invention

The present invention relates to a method of creating a system for detecting at least one detonation triggered in a combustion chamber of an endothermic engine, said method comprising the following steps: a) providing:

• a plurality of piezoelectric sensors applicable to said combustion chamber, said sensors being adapted to:

- convert any vibrations experienced by said sensors into signals of electrical nature and to - emit said signals of electrical nature;

• a processing unit electrically connected to said sensors to acquire signals of electrical nature emitted by them, said processing unit being adapted to determine features, at least of amplitude and/or frequency, possessed by signals of electrical nature acquired by it;

• a database accessible by said processing unit and adapted to contain both information concerning said features possessed by signals of electrical nature and information concerning features of a different nature (i.e. , not possessed by signals of electrical nature), said processing unit being adapted to enter (i.e., store) in said database information concerning said features determined by it and possessed by signals of electrical nature; b) applying said sensors to said combustion chamber with said endothermic engine off, so that said sensors are adapted to convert at least (the) vibrations experienced by said sensors due to a detonation possibly occurring in said combustion chamber into signals of electrical nature; c) providing:

• a casing including at least one concave wall delimiting:

- a cavity and

- at an edge thereof, an opening for accessing said cavity;

• an amount of exploding material housed in said cavity, said exploding material being adapted to detonate, a detonation of said exploding material resulting in a propagation of an explosive front from said cavity towards the exterior of the latter, passing through said opening, the propagation direction of each point of said explosive front with respect to said casing depending on the shape of said wall and said opening, the propagation speed of each point of said explosive front with respect to said casing depending on the composition of said exploding material; • a trigger preferably in contact with said exploding material and adapted to trigger a detonation of said exploding material, said casing, together with said exploding material, being housable in said combustion chamber; d) housing said casing, together with said exploding material, in said combustion chamber; e) operating said trigger so as to trigger a detonation of said exploding material, said sensors converting vibrations experienced by them upon the occurrence of said detonation into signals of electrical nature; f) acquiring, by means of said processing unit, said signals of electrical nature into which said sensors, at step e), converted said vibrations experienced by them upon the occurrence of said detonation, determining, by means of said processing unit, said features possessed by said signals of electrical nature into which said sensors, at step e), converted said vibrations experienced by them upon the occurrence of said detonation, entering (i.e., storing) in said database, by means of said processing unit, information concerning said features determined by said processing unit and possessed by said signals of electrical nature into which said sensors, at step e), converted said vibrations experienced by them upon the occurrence of said detonation and entering (i.e., storing) in said database information (corresponding to said "information concerning features of a different nature") concerning:

• the position in which said casing, at step d), was housed in said combustion chamber together with said exploding material;

• the orientation, in said combustion chamber, of said wall and said opening of said casing;

• the shape of said wall and said opening of said casing;

• the composition of said exploding material, associating said information (concerning the four features listed above) with said information concerning said features determined by said processing unit at step f) and possessed by said signals of electrical nature into which said sensors, at step e), converted said vibrations experienced by them upon the occurrence of said detonation.

The operation of entering in the database information concerning the position in which the casing was housed in the combustion chamber, the orientation, in the combustion chamber, of the wall and the opening of the casing, the shape of the wall and the opening of the casing, and the composition of the exploding material, is preferably carried out by a person; g) repeating steps c) to f) at least once so that at each repetition of steps c) to f):

• at step d), said casing is housed in said combustion chamber in a different position from the position in which said casing is housed in said combustion chamber in each of the other repetitions of steps c) to f) and/or

• at step d), said casing is housed in said combustion chamber with said wall and said opening oriented in a different manner from how said wall and said opening of said casing are oriented when said casing is housed in said combustion chamber in each of the other repetitions of steps c) to f) and/or

• the shape of said wall and/or said opening of said casing provided at step c) is different from the shape of said wall and/or said opening of said casing provided at step c) in each of the other repetitions of steps c) to f) and/or

• the composition of said exploding material provided at step c) is different from the composition of said exploding material provided at step c) in each of the other repetitions of c) to f); h) ordering said processing unit not to access said database anymore so that, upon the occurrence of a detonation in said combustion chamber following the present step:

• said sensors convert vibrations experienced by them upon the occur- rence of said detonation following the present step into signals of electrical nature,

• said processing unit acquires said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said detonation following the present step and

• said processing unit determines said features possessed by said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said detonation following the present step but

• information concerning said features determined by said processing unit and possessed by said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said detonation following the present step, are not entered in said database by said processing unit; i) developing a computer program (such as an expert system, for example), or a set of mutually interacting computer programs, connected to both said processing unit, so that the latter can communicate to said program said features determined by it and possessed by signals of electrical nature possibly acquired by it following step h), and said database, so that the latter is accessible from said program and training said program, using said information contained in said database and concerning said features determined by said processing unit and possessed by signals of electrical nature emitted by said sensors prior to step h), to recognize the possible occurrence of, i.e. , detect, a detonation in said combustion chamber following step h), from said features determined by said processing unit, possessed by signals of electrical nature emitted by said sensors due to said detonation occurred following step h) and acquired by said processing unit, and communicated by the latter to said program, said program being developed so as to have access to information concern- ing the shape of said combustion chamber.

The operation of entering in the program information concerning the shape of said combustion chamber is preferably carried out by a person; j) training said program, using said information (both concerning features possessed by signals of electrical nature and concerning features of a different nature) contained in said database and entered therein prior to step h), to attempt to estimate, upon the occurrence of a detonation in said combustion chamber following step h), the position, in said combustion chamber, of the trigger point of said detonation occurred following step h), from said features determined by said processing unit, possessed by signals of electrical nature emitted by said sensors due to said detonation occurred following step h) and acquired by said processing unit, and communicated by the latter to said program, so that, said program, upon the occurrence of a detonation in said combustion chamber following step h) and from said features determined by said processing unit, possessed by signals of electrical nature emitted by said sensors due to said detonation occurred following step h) and acquired by said processing unit, and communicated by the latter to said program:

• recognizes that a detonation occurred following step h) and

• attempts to estimate the position, in said combustion chamber, of the point at which said detonation that occurred following step h) was triggered based on the similarity between:

- said features determined by said processing unit, possessed by said signals of electrical nature emitted by said sensors due to said detonation occurred following step h) and acquired by said processing unit, and communicated by the latter to said program and

- said features of signals of electrical nature, related information are contained (i.e., were stored in the repetitions of steps c) to f)) in said database and were entered therein prior to step h), and using the information, contained in said database and entered therein prior to step h), associated with said information concerning said features determined by said processing unit and possessed by signals of electrical nature emitted by said sensors prior to step h) (i.e., using the information concerning, in the repetitions of steps c) to f), respectively, the positions in which the casings were housed in the combustion chamber, the orientation, in the combustion chamber, of the wall and opening of the casings, the shape of the wall and the opening of the casings and the composition of the exploding materials); k) upon the occurrence of a detonation in said combustion chamber following step h):

• if said program is capable of estimating the position, in said combustion chamber, of the point at which said detonation that occurred following step h) was triggered, communicating to a user of the method of the invention the detection of said detonation occurred following step h) and said position,

• if, conversely, said program is not capable of estimating the position, in said combustion chamber, of the point at which said detonation that occurred following step h) was triggered:

- communicating to said user the detection of said detonation occurred following step h) and the failed estimation of the position, in said combustion chamber, of the point at which said detonation that occurred following step h) was triggered,

- ordering said processing unit to access said database again so that upon the occurrence of another detonation in said combustion chamber: said sensors convert vibrations experienced by them upon the occurrence of said another detonation into signals of electrical nature, said processing unit acquires said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said another detonation, said processing unit determines said features possessed by said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said another detonation and information concerning said features possessed by said signals of electrical nature into which said sensors converted vibrations experienced by them upon the occurrence of said another detonation, is entered in said database by said processing unit;

- repeating said method from step g), but skipping step i), said system comprising said sensors, said processing unit, said database, said casing of each of the repetitions of steps c) to f), said exploding material of each of the repetitions of steps c) to f), said trigger of each of the repetitions of steps c) to f), and said program.

Incidentally, since at step e), a controlled detonation is triggered when the endothermic engine is not operating, said detonation causes vibrations of the piezoelectric sensors to such an extent that, also repeating steps c) to f) a single time, the program, at step i), learns to detect a detonation, i.e., to recognize the occurrence of a detonation.

Should, at step k), the system obtained by implementing the method of the invention recognize the occurrence of (i.e., detect) a detonation, but is not capable of estimating the position of the trigger point thereof, the training of the program at step i) is resumed.

Incidentally, although the system obtained by implementing the method of the invention is based on a trained program with the engine off, it is however adapted to recognize the occurrence of a detonation and attempt to estimate the trigger point thereof with the engine running because the vibrations to which the piezoelectric sensors are subjected during the operation of an endothermic engine without the occurrence of detonations give rise to easily recognizable signals of electrical nature which are substantially cyclically repeated. The components of the signals of electrical nature associated with the operation of the endothermic engine in the absence of detonations are thus easily excludable from the processing unit before sending the features mentioned above to the computer program.

The information contained in the database of the system obtained by implementing the method of the invention and concerning features, determined by the processing unit, of signals of electrical nature emitted by the piezoelectric sensors and acquired by the processing unit, substantially correspond to electrical-nature "behavior patterns" of said sensors acquired by causing controlled detonations (i.e. , with the engine off and by means of the aforesaid casings, exploding materials, and triggers) in the combustion chamber towards which the method is implemented. More precisely, for each controlled detonation, the processing unit stores in the database features of the electrical signals emitted by the piezoelectric sensors due to said detonation. As specified above, said features are associated with information concerning the controlled detonation. In light of this, when the method of the invention is to be used to test a combustion chamber of an endothermic engine empirically, first the piezoelectric sensors are to be applied to the combustion chamber (e.g., in an Otto cycle engine, as already occurs in the prior art, at the cylinder-head gasket level and close to the spark plug) and multiple controlled detonations are to be triggered, preferably in points of the combustion chamber judged as potentially critical by skilled technicians. An electrical-nature behavior pattern identifying the response of the sensors to the detonation is stored in the database for each of said controlled detonations. The patterns stored in the database are then used to train the computer program, e.g., an expert system. The latter, based on the behavior similarities between the patterns stored in the database, first learns to recognize the occurrence of a detonation. The expert system, upon the occurrence of a detonation, looks to see if the set of features of the electrical signals acquired by the processing unit corresponds to one of the behavior patterns, or to a combination of said patterns, stored in the database of the system obtained by implementing the method of the invention. If yes, the occurred detonation corresponds to one of the controlled detonations triggered to train the expert system. The latter thus communicates the detonation trigger point (corresponding to the position of the casing located in the combustion chamber during one of the repetitions of steps c) to f)).

If no, the expert system attempts to estimate the position of the detonation trigger point based on the information contained in the database (i.e. , the electricalnature behavior patterns of the piezoelectric sensors and the information associated therewith, respectively, and concerning, in the repetitions of steps c) to f), respectively, the positions in which the casings were housed in the combustion chamber, the orientation, in the combustion chamber, of the wall and the opening of the casings, the shape of the wall and the opening of the casings, and the composition of the exploding materials).

If the expert system is not capable of estimating the position of the detonation trigger point, the expert system communicates to a user of the system obtained by implementing the method of the invention that a detonation occurred but that it was not possible to estimate the position of the trigger point. In this case, the training of the expert system is resumed after repeating steps c) to f) at least once. If, conversely, the expert system is capable of estimating the position of the detonation trigger point, the expert system communicates to said user that a detonation occurred and the position of the detonation trigger point in the combustion chamber (e.g., by means of a monitor).

Other innovative features of the present invention are disclosed in the description below and mentioned in the dependent claims.

According to an aspect of the invention, said trigger includes:

• at least one resistor being crossable by an electric current, said resistor preferably being in contact with said exploding material;

• at least a first and a second cable, each of which being crossable by an electric current, each of said cables comprising a first end and a second end opposite to said first end, each of said cables being connected to said resistor at said first end so that said resistor can be crossed, from said first end of said first cable to said first end of said second cable, by an electric current when said electric current crosses said first cable, when said resistor is reached by an electric current crossing said first cable, said electric current crossing said resistor and reaching said second cable to then cross the latter, said resistor being adapted a be heated due to the Joule effect when it is crossed by an electric current, said resistor, when heated due to the Joule effect, being adapted to give heat to said exploding material, said resistor being adapted to be heated due to the Joule effect to a sufficient extent so that the amount of heat given by said resistor to said exploding material is such as to trigger a detonation of said exploding material;

• generator means connected to each of said cables at the respective second end of the latter, said generator means being adapted to ensure that said first cable and, from the latter, by means of said resistor, said second cable, are crossed by a sufficiently strong electric current so that said resistor is heated due to the Joule effect to a sufficient extent so as to trigger a detonation of said exploding material.

According to another aspect of the invention, at step d), said casing is housed in said combustion chamber so that said casing, at a portion of the wall thereof, is in contact with a metal wall at least partially delimiting said combustion chamber, said wall of said casing being made of metal at least at said portion thereof, said trigger comprising:

• at least one cable being crossable by an electric current, said cable comprising a first end and a second end opposite to said first end, said cable, at said first end or at a stretch of said cable closer to said first end than to said second end, being connected to said casing, at said wall portion of the latter, so that said wall portion of said casing is reachable by an electric current when said electric current crosses said cable, when said casing, at said wall portion of the latter, is reached by an electric current crossing said cable, said current reaching said metal wall delimiting said combustion chamber by crossing said wall portion of said casing, said wall portion of said casing being adapted to be heated due to the Joule effect when it is crossed by an electric current, said wall portion of said casing, when heated due to the Joule effect, being adapted to give heat to said exploding material, said wall portion of said casing being adapted to be heated due to the Joule effect to a sufficient extent so that the amount of heat given by said wall portion of said casing to said exploding material is such as to trigger a detonation of said exploding material;

• generator means connected to said cable at said second end and adapted to ensure that said cable is crossed by a sufficiently strong electric current so that said wall portion of said casing is heated due to the Joule effect to a sufficient extent so that the amount of heat given by said wall portion of said casing to said exploding material is such as to trigger a detonation of said exploding material.

Advantageously, according to this aspect of the invention, it is the aforesaid wall portion of the casing to act as a resistor adapted to trigger the detonation. In addition, according to this aspect of the invention, the use of a single cable is sufficient since the current which reaches the casing crosses the metal from which the walls delimiting the combustion chamber are made.

According to another aspect of the invention, said wall of said casing is entirely made of metal.

Advantageously, according to this aspect of the invention, even if it is only said wall portion of said casing to be crossed by an electric current, the heat developed due to the Joule effect upon the passage of an electric current is propagated to the whole casing.

According to another aspect of the invention, said wall of said casing comprises a base opposite to said opening, and a side "sub-wall" extending from said base to said edge, said cable being wound around said wall of said casing at said side sub-wall, at step d), said casing being housed in said combustion chamber so that said casing is in contact with said metal wall at least partially delimiting said combustion chamber, at said base, said wall portion of said casing comprising said base and a part of said side sub-wall at which (part) said cable is wound around said casing.

Incidentally, according to this aspect of the invention, the wall of the casing comprises a first portion corresponding to the aforesaid base and a second portion corresponding to the aforesaid side sub-wall. The above is equivalent to asserting that the casing comprises a base opposite to the aforesaid opening, and a side wall extending from the base to the aforesaid edge.

Advantageously, according to this aspect of the invention, it is substantially the whole casing to be crossable by an electric current, and thus heatable due to the Joule effect.

The invention also relates to a system obtainable by implementing the method disclosed above.

Brief description of the drawings

Further objects and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments thereof and from the accompanying drawings, merely provided by way of non-limiting explanation, in which:

- figure 1 shows a diagrammatic straight section of a combustion chamber of an endothermic engine towards which the method of the invention is implemented;

- figure 2 shows a diagrammatic perspective view of a group of elements adapted, as a whole, to simulate a controlled detonation and to be used by implementing the method of the invention;

- figure 3 shows a diagrammatic perspective view of a variant of the group of elements in figure 2.

Detailed description of some preferred embodiments of the invention

Hereinafter in the present description, a figure may also be shown with reference to elements not expressly indicated in that figure but in other figures. The scale and proportions of the various elements depicted do not necessarily correspond to the real ones.

Figure 1 shows a combustion chamber 1 of an endothermic engine, by way of example an Otto-cycle endothermic engine. The invention relates to a method of creating a system adapted to recognize the occurrence (i.e. , to detect) a det- onation in chamber 1 , as well as, upon the occurrence of a detonation in chamber 1 , to attempt to estimate the position, in chamber 1 , of the trigger point of said detonation.

First, a plurality of piezoelectric sensors 2 applicable to chamber 1 needs to be provided. As is known, the sensors 2 are adapted to convert any vibrations experienced by them into signals of electrical nature and to emit said signals of electrical nature. The sensors 2 are electrically connected to a processing unit 3 adapted to acquire the signals of electrical nature emitted by the sensors 2. Unit 3 is also adapted to determine specific features, at least concerning the amplitude and/or frequency, possessed by the signals of electrical nature emitted by the sensors 2 and acquired by it. Unit 3 can access a database 4 adapted to contain both information concerning the aforesaid features possessed by signals of electrical nature and information concerning features of a different nature. Unit 3 is adapted to enter (i.e., to store), in database 4, information concerning the aforesaid features determined by it and possessed by signals of electrical nature acquired by it.

The sensors 2 are to be applied to chamber 1 with the endothermic engine, to which chamber 1 belongs, off (i.e., not running). The sensors 2 are to be applied to chamber 1 so as to be capable of converting at least the vibrations experienced by them due to a detonation possibly occurred in chamber 1 into signals of electrical nature. In light of the above, a detonation in chamber 1 causes vibrations of the sensors 2, which vibrations are converted by the latter into signals of electrical nature acquired by the unit 3. By way of example, a plurality of sensors 2 can be applied at the cylinder-head gasket level. As mentioned above, the sensors 2 are applied to the combustion chamber 1 preferably so that the sensors 2 are hit by the vibrations caused by a detonation occurring in chamber 1 , in a direct manner and not by propagation through the walls of chamber 1 . For this purpose, the sensors 2 are preferably applied to the walls of chamber 1 and suitable holes are made in said walls so as to put the sensors 2 in communication with the interior of chamber 1 .

In addition to the sensors 2, the processing unit 3 and the database 4, the method of the invention includes providing a device 6 (corresponding to the "group of elements" mentioned in the "Brief description of the drawings"), shown in figure 2 and adapted to simulate, inside chamber 1 , a controlled detonation, i.e. , a detonation the trigger of which is controllable and the direction of which as well as the propagation speed of the explosive front (i.e., the expansion front of the detonation reaction) can preferably be estimated. Device 6 comprises a casing 7 including at least one concave wall 8 delimiting a cavity, and at an edge 9 thereof, an opening 10 for accessing said cavity. Device 6 further comprises an amount of exploding material 11 housed in the aforesaid cavity. The exploding material 11 is adapted to detonate, and a detonation of the material 11 results in a propagation of the explosive front from the cavity of casing 7 towards the exterior of the latter through the opening 10. The propagation direction of each point of the explosive front with respect to casing 7 depends on the shape of the wall 8 and opening 10. The propagation speed of each point of the explosive front with respect to casing 7 depends on the composition of the material 11. Finally, device 6 comprises a trigger 12 preferably in contact with the material 11 and adapted to trigger a detonation of said material 11. The casing 7, together with the material 11 , have dimensions such as to be housable in chamber 1 .

As shown in figure 2, the wall 8 of casing 7 preferably comprises a preferably circular base 13 opposite to the opening 10, also preferably circular in shape, and a preferably cylindrical side "sub-wall" 14 extending from base 13 to edge 9. The latter is preferably arranged parallel to base 13. In light of the above, casing 7 is preferably substantially shaped as a cylinder without one of the two bases. Incidentally, the wall 8 of casing 7 preferably comprises a first portion corresponding to base 13 and a second portion corresponding to the side subwall 14. The above is equivalent to asserting that casing 7 comprises a base 13 opposite to opening 10 and a side wall 14 extending from base 13 to edge 9.

Trigger 12 comprises at least one resistor 15 being crossable by an electric current and preferably in contact with the material 11 . More preferably, the resistor 15 is housed in the cavity of casing 7 and is immersed into the material 11. Trigger 12 further comprises a first and a second cable 16 and 17, each of which being crossable by an electric current. Each of the cables 16 and 17 comprises a first end 16a and 17a, respectively, and a second end 16b and 17b, respectively, opposite to end 16a or 17a. Each of the cables 16 and 17 is connected to resistor 15 at the end 16a or 17a so that the resistor 15 is crossable, from end 16a to end 17a, by an electric current when the latter crosses the cable 16, for example. When the resistor 15 is reached by an electric current crossing the cable 16 (approaching resistor 15), said electric current crosses the resistor 15 and reaches the cable 17 to then cross the latter (away from resistor 15). Resistor 15, when crossed by an electric current, is heated due to the Joule effect and gives heat to the material 11 (in which it is preferably immersed). Resistor 15 is adapted to be heated due to the Joule effect to a sufficient extent so that the amount of heat given by the resistor 15 to the material 11 is such as to trigger a detonation of said material 11. Trigger 12 also comprises means adapted to circulate an electric current in the cables 16 and 17. More precisely, trigger 12 preferably comprises a current generator 18 connected to each of the cables 16 and 17 at the end 16b or 17b. The generator 18 is adapted to ensure that cable 16 and, from the latter, by means of resistor 15, cable 17 are crossed by a sufficiently strong electric current so that the resistor

15 is heated due to the Joule effect to a sufficient extent so as to trigger a detonation of the material 11 . The wall 8 of casing 7 is preferably polymeric and the cables 16 and 17 reach resistor 15 from outside the casing 7 preferably by passing through the side sub-wall 14 at a respective through hole.

Returning to the description of the method of the invention, once the device 6 has been provided, the casing 7 needs to be housed in chamber 1 together with the material 11 . Since the generator 18 is located outside chamber 1 , the cables

16 and 17 need to be brought out from the latter. This is not a problem since, as mentioned above, the method of the invention is implemented towards a combustion chamber of an endothermic engine when it is not running. In order to bring the cables 16 and 17 out from chamber 1 , it is sufficient, by way of example, to make a through hole in a wall delimiting the chamber 1. Once casing 7 together with the material 11 has been housed in chamber 1 , the trigger 12 is operated so as to trigger a (controlled) detonation 19 of the material 11. The sensors 2 vibrate due to said detonation 19 and convert the experienced vibra- tions into signals of electrical nature. Said signals are acquired by unit 3. Therefore, the latter determines the above-mentioned features possessed by said signals of electrical nature and enters (i.e., stores) information concerning said features in database 4. The set of information stored in database 4 by unit 3 and concerning the features determined by unit 3 and possessed by the signals of electrical nature emitted by the sensors 2 following the detonation 19 and acquired by unit 3 substantially corresponds to the electrical-nature behavior pattern of the sensors 3 associated with the detonation 19. In order to identify the detonation which allowed determining said pattern, the latter is associated, in database 4, with information (corresponding to the previously mentioned "information concerning features of a different nature") concerning the position in which the casing 7 was housed in chamber 1 , the orientation, in chamber 1 , of the wall 8 and the opening 10 of casing 7, the shape of the wall 8 and the opening 10 of casing 7, and the composition of the material 11 . The operation of entering in database 4 the above-listed information associated with the aforesaid electrical-nature behavior pattern of the sensors 2 is preferably carried out by a person.

To implement the method of the invention, at least another device 6 needs to be provided and a second controlled detonation is to be triggered in chamber 1 , repeating the above-listed operations, so as to obtain a second electrical-nature behavior pattern of the sensors 2 associated with information identifying said second detonation. Preferably, the trigger of a controlled detonation is not only repeated a single time, but a plurality of times.

The behavior patterns obtained are to be generated from mutually different detonations. For this purpose, for each controlled detonation triggered in chamber 1 :

• The casing 7 is housed in chamber 1 in a different position from the position in which the casing 7 is housed in chamber 1 in each of the other controlled detonations and/or

The casing 7 is housed in chamber 1 with the wall 8 and the opening 10 oriented in a different manner from how the wall 8 and the opening 10 of casing 7 are oriented, when the casing 7 is housed in chamber 1 , in each of the other controlled detonations and/or

• the shape of the wall 8 and/or the opening 10 of casing 7 is different from the shape of the wall 8 and/or the opening 10 of casing 7 in each of the other programmed detonations and/or

• the composition of the material 11 is different from the composition of the material 11 in each of the other programmed detonations.

After storing, in database 4, multiple electrical-nature behavior patterns of the sensors 2 associated with information identifying the controlled detonations which allowed the determination thereof, respectively, ordering unit 3 not to access database 4 anymore is required, for example by disconnecting it from the latter, so that upon the occurrence of a (new) detonation in chamber 1 , the signals of electrical nature emitted by the sensors 2 due to said detonation, are acquired by unit 3 and the latter determines the features possessed by said signals without however any information concerning said features being entered in database 4. Incidentally, following the "disconnection" of unit 3 from database 4, since new electrical-nature behavior patterns are not entered in database 4, information identifying the detonations which allowed determining said patterns are not entered in database 4 either.

After ordering unit 3 not to access database 4 anymore, a computer program 20 needs to be developed, preferably an expert system, or a set of mutually interacting computer programs, connected to both unit 3, so that the latter can communicate to the program 20 the features determined by it and possessed by signals of electrical nature possibly acquired by unit 3 after being disconnected from database 4, and said database 4 so that the latter is accessible from program 20. By using the electrical-nature behavior patterns contained in database 4 (i.e., using the information concerning the features, determined by unit 3, of the signals of electrical nature emitted by the sensors 2 and acquired by unit 3 prior to the "disconnection" of the latter from database 4), the program 20 is trained to recognize the possible occurrence of (i.e., to detect) a detonation in chamber 1 (after the disconnection of unit 3 from database 4) from the features determined by unit 3, possessed by the signals of electrical nature emitted by the sensors 2 due to said detonation occurred after the disconnection of unit 3 from database 4 and acquired by unit 3, and communicated by the latter to the program 20. Incidentally, program 20 "knows" the shape of chamber 1. The program 20 is thus developed so as to have access to information concerning the shape of chamber 1 .

By using the information contained in database 4 (i.e., not only the electricalnature behavior patterns of the sensors 2 but also the information associated therewith, respectively, and concerning, for each of said patterns, the position in which the casing 7 was housed in chamber 1 , the orientation, in chamber 1 , of the wall 8 and the opening 10 of casing 7, the shape of the wall 8 and the opening 10 of casing 7, and the composition of the material 11 ), the program 20 is also trained to attempt to estimate, upon the occurrence of a detonation in chamber 1 after the disconnection of unit 3 from database 4, the position, in chamber 1 , of the trigger point of said detonation occurred after the disconnection of unit 3 from database 4, from the features determined by unit 3, possessed by the signals of electrical nature emitted by the sensors 2 due to said detonation occurred after the disconnection of unit 3 from database 4 and acquired by unit 3, and communicated by the latter to the program 20.

In light of the above, program 20, upon the occurrence of a detonation in chamber 1 after the disconnection of unit 3 from database 4 and from the features determined by unit 3, possessed by the signals of electrical nature emitted by the sensors 2 due to said detonation occurred after the disconnection of unit 3 from database 4 and acquired by unit 3, and communicated by the latter to the program 20, recognizes that a detonation occurred (after the disconnection of unit 3 from database 4) and attempts to estimate the position, in chamber 1 , of the point at which said detonation occurred after the disconnection of unit 3 from database 4 was triggered based on the similarity (i.e., the level of existing similarity) between:

• the features determined by unit 3, possessed by the signals of electrical nature emitted by the sensors 2 due to said detonation occurred after the dis- connection of unit 3 from database 4 and acquired by unit 3, and communicated by the latter to the program 20 and

• one or more electrical-nature behavior patterns of the sensors 2 contained in database 4 and using the information contained in database 4 associated with said behavior patterns (i.e., using the information concerning, for the respective behavior patterns, the positions in which the casings 7 were housed in chamber 1 , the orientation, in chamber 1 , of the wall 8 and the opening 10 of the casings 7, the shape of the wall 8 and the opening 10 of the casings 7, and the composition of the materials 11 used).

The system of the invention, obtained by implementing the method of the invention, comprises the sensors 2, the unit 3, the database 4, the device 6 (and thus the casing 7, the material 11 and the trigger 12 included in device 6) used in each controlled detonation, and the program 20.

Upon the occurrence of a detonation in chamber 1 after the disconnection of unit 3 from database 4, the occurrence of the detonation is communicated to a user of the method of the invention. If the program 20 is capable of estimating the position, in chamber 1 , of the point at which the detonation was triggered, said position is communicated to the aforesaid user. If, conversely, the program 20 is not capable of estimating the position, in chamber 1 , of the point at which the detonation was triggered:

• the detection of a detonation and the failed estimation of the position of the point in which the detonation was triggered is communicated to the aforesaid user,

• unit 3 is ordered to access database 4 again so that, upon the occurrence of another detonation in chamber 1 :

- the sensors 2 convert vibrations experienced by them upon the occurrence of said another detonation into signals of electrical nature,

- the unit 3 acquires the signals of electrical nature into which the sensors 2 converted vibrations experienced by them upon the occurrence of said another detonation, - the unit 3 determines the aforesaid features possessed by the signals of electrical nature into which the sensors 2 converted vibrations experienced by them upon the occurrence of said another detonation and

- the electrical-nature behavior pattern of the sensors 2 associated with said another detonation (i.e., information concerning the aforesaid features possessed by the signals of electrical nature into which the sensors 2 converted the vibrations experienced by them upon the occurrence of said detonation) is entered by unit 3 in database 4,

• repeating the training of the program 20 related to the estimation of the position of the detonation trigger point, after triggering at least another controlled detonation.

Figure 3 shows a device 21 which is an alternative to device 6 (and therefore which could belong to the system of the invention in place of the device 6). Device 21 differs from device 6 in that the wall 8 of casing 7 is at least partially made of metal. More precisely, in implementing the method of the invention using device 21 , the casing 7 of device 21 is housed in chamber 1 so that said casing, at a portion 22 of (its own) wall 8, is in contact with a metal wall at least partially delimiting chamber 1 . The wall 8 of the casing 7 of device 21 is made of metal at least at portion 22. The latter preferably includes the base 13 of wall 8. Unlike the trigger 12 of device 6, the trigger 12 of device 21 can comprise a single cable 23 being crossable by an electric current and comprising a first end 23a and a second end 23b opposite to end 23a. Cable 23, preferably at the end 23a or at a stretch of said cable 23 closer to the end 23a than to the end 23b, is connected to the casing 7 of device 21 at least at portion 22 so that said portion 22 is reachable by an electric current when said electric current crosses the cable 23. More precisely, when the casing 7 of device 21 , at the portion 22, is reached by an electric current crossing cable 23 (approaching the end 23a), said current reaches the aforesaid metal wall delimiting the chamber 1 by crossing the portion 22.

The latter is heated due to the Joule effect when it is crossed by an electric current. When heated due to the Joule effect, portion 22 gives heat to the material 11 . More precisely, portion 22 is adapted to be heated due to the Joule effect to a sufficient extent so that the amount of heat given to the material 11 is such as to trigger a detonation of said material 11 . In light of the above, the resistor 15 is not present in device 21 since it is the portion 22 of the wall 8 of casing 7 to act as a resistor adapted to trigger a detonation of the material 11. The trigger 12 of device 21 preferably comprises a current generator 24 connected to cable 23 at the end 23b and adapted to ensure that cable 23 is crossed by a sufficiently strong electric current so that the portion 22 is heated due to the Joule effect to a sufficient extent so that the amount of heat given to the material 11 is such as to trigger a detonation of said material 11 . Incidentally, the use of a single cable 23 in the trigger 12 of device 21 is sufficient since the current reaching casing 7 crosses the metal from which the walls delimiting the chamber 1 are made.

Preferably, the wall 8 of the casing 7 of device 21 is entirely made of metal. In this case, cable 23 is preferably wound around the side sub-wall 14 of the casing 7 of device 21. Therefore, in this case, the portion 22 comprises the base 13 and a part of side sub-wall 14 at which (part) the cable 23 is wound around casing 7.

Based on the description provided for a preferred embodiment, it is obvious that some changes may be made by those skilled in the art without departing from the scope of the invention as defined by the following claims.