WO2011027369A1

WO2011027369A1 - Security system for the control of a vehicle engine

Info

Publication number: WO2011027369A1
Application number: PCT/IT2009/000394
Authority: WO
Inventors: Massimiliano Luciani; Giuseppe Fonti
Original assignee: Know How S.R.L.
Priority date: 2009-09-01
Filing date: 2009-09-01
Publication date: 2011-03-10

Abstract

A security system (10) to control the operation of an engine (22) vehicle (50) is described. The security system comprises a contact sensor (11 ) adapted to generate an analogue signal (S3) indicating the proximity of at least part of a chin strap (4) of a safety helmet (1 ) to the chin of a driver of the vehicle or indicating the proximity of at least part of a seat belt for a vehicle to the body of the driver. The security system further comprises an analog-to-digital converter (12) adapted to receive the analogue signal and to generate therefrom a digital signal (SN) and comprises a controller (13) adapted to elaborate the digital signal and to generate therefrom an enable signal (Sen) for enabling the operation of the vehicle engine.

Description

Security system for the control of a vehicle engine

FIELD OF THE INVENTION

The present invention relates to the field of a security system. Still more in particular, the invention concerns a security system to control the operation of the engine of a vehicle.

BACKGROUND OF THE INVENTION

It is important to check that a safety helmet has been correctly fastened to the head of a driver of a vehicle, for example in a crash helmet for a motorcycle.

It is known from a PCT application (of the same applicant) having publication nb. WO 2005/110138 a security system installed in the safety helmet and in the motorcycle for checking that the safety helmet has been correctly put on the head of the rider driving the motorcycle and for controlling therefrom the connection of the motorcycle power supply to the ignition system. This is achieved by a security system including a sensor arranged inside the shell of the safety helmet (see sensor 15 in Fig.1 and 2) and/or including a mechanical switch arranged in the locking block of the chin strap (see the locking block 6 of the chin strap in Fig.1 and 2A).

The chin strap of the security system disclosed in the above PCT application has the disadvantage that the mechanical switch in the chin strap can provide a false indication that the chin strap has been fastened under the rider's chin, because the chin strap is not fastened correctly or because the chin strap can be fastened also if the safety helmet has not been put on the rider's head; for example, the chin strap can be fastened under the chin but is not sufficiently tensioned (in other words, the chin strap is long) or the chin strap can be even fastened with the safety helmet far from the rider's head.

SUMMARY OF THE INVENTION

The present invention relates to a security system to control the operation of the engine of a vehicle as defined in claim 1 and in the preferred embodiments described in the dependent claims 2 to 12. Another object of the invention is to provide a safety helmet for a vehicle as defined in claim 13 and in the preferred embodiment described in the dependent claim 14.

A further object of the invention is to provide a seat belt for a vehicle as defined in claim 15.

The invention has the following advantages:

- the security system enables the operation (for example, the start) of the vehicle engine only when the chin strap is correctly fastened to the chin of the driver of the vehicle or when the seat belt is correctly fastened to the body of the driver;

- the security system has a better sensitivity compared to prior art security systems;

- the implementation of the security system is simple and cheap;

- the security system also provides an antitheft functionality.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 schematically shows a safety helmet and a motorcycle including a security system according to the invention.

Fig.2 schematically shows a security system for a safety helmet according to a first embodiment of the invention.

Fig.3A and 3B schematically show a security system for a safety helmet according to a second embodiment of the invention.

Fig.4A and 4B schematically show a security system for a safety helmet according to a third embodiment of the invention.

Fig.5 schematically shows a security system for a safety helmet according to a fourth embodiment of the invention.

Fig.6A and 6B schematically show two possible implementations of an head sensor for the security system according to the fourth embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to Fig.1 , it shows schematically a safety helmet 1 and a motorcycle 50 including a security system 10 according to the invention. The safety helmet 1 includes a chin strap for fastening the safety helmet 1 to the head of the driver of a vehicle. Specifically, the chin strap includes strips 3, 4 having a variable length and fixed at one side to the shell 7 of the safety helmet 1 ; the chin strap also includes a clasp 5 and a locking block 6 arranged at the other end of strips 3 and 4 respectively, wherein the clasp 5 engages the locking block 6 for fastening the strips 3, 4 under the chin of the driver (in other words, for fastening the chin strap), so that the safety helmet 1 is fastened to the head of the driver.

The security system 10 includes a contact sensor, which is indicated in Fig.1 with a dotted area 11 ; the implementation of the contact sensor 11 will be described more in detail afterwards. The contact sensor 11 is a sensor adapted to detect the proximity of at least part of the strip 4 to the chin of the driver. Proximity of the strip 4 to the chin of the driver means that the chin of the driver approaches or touches the at least part of the strip 4: in the first case, the distance between the at least part of the strip 4 and the chin is smaller than a defined value (for example, one centimetre) but there is no physical contact between the at least part of the strip 4 and the chin of the driver, while in the second case there is a physical contact between the at least part of the strip 4 and the chin of the driver.

The contact sensor 11 is attached to the strip 4 internally (as shown schematically in Fig.1 with the dotted area of the contact sensor 11 ) or externally. For example, the strip 4 includes two pieces of fabric sewed each other and the contact sensor 11 is arranged inside the strip 4, between the two pieces of fabric; alternatevely, the contact sensor 11 is attached externally to the strip 4 (for example, it's sewed or glued to one of the two pieces of fabric).

The contact sensor 11 can also be attached to the strip 3 (instead of the strip 4).

Advantageously, the contact sensor 11 is attached to both the strip 3 and the strip 4, thus providing more security. The security system 10 further includes a security device 8. Fig.1 shows that the security device 8 is arranged inside the shell 7 of the safety helmet 1 (this is indicated in Fig.1 with a broken line). Moreover, the security device 8 is attached to the internal surface of the shell 7 (that is, to the surface which is in contact with the head of the driver) and is connected to the contact sensor 11 with a cable 33.

Alternatevely, the security device 8 can be arranged externally to the shell 7 and is attached to the external surface of the shell 7.

Alternatevely, the security device 8 can also be arranged into the locking block 6 or into the clasp 5.

The motorcycle 50 includes another part of the security system 10; specifically, the other part of the security system 10 is included into a control device 51 mounted on the motorcycle 50, as indicated schematically in Fig.1.

Referring to Fig.2, it shows more in detail the part of the security system 0 included into the security device 8 and into the strip 4 and it shows more in detail the part of the security system 10 included into the control device 51 mounted on the motorcycle 50.

As indicated above, the contact sensor 11 is a sensor adapted to detect the proximity of the strip 4 of the chin strap of the safety helmet 1 to the chin of the driver and thus the contact sensor 11 will be indicated with "chin strap contact sensor" 1 1 .

The chin strap contact sensor 11 includes an output terminal adapted to generate an analogue signal S_a indicating the proximity of at least part of the strip 4 to the chin of the driver. For example, the analogue signal S_a is a voltage signal which indicates that the at least part of the strip 4 is in the proximity of the chin of the driver when the value of the voltage signal S_a is greater than a threshold indicated with "activation threshold" of the chin strap contact sensor 1 1. The chin strap contact sensor 1 1 is connected to the security device 8 with the cable 33.

The security device 8 includes: - an analog-to-digital converter 12 having an input terminal for receiving the analogue signal S_a and having an output terminal for generating a digital signal S equal to the digital conversion of the analogue signal S_A;

- a controller 13 having an input terminal for receiving the digital signal S_N and having an output terminal for generating an enable signal S_en- The controller

13 is adapted to elaborate the digital signal SN and to generate therefrom the enable signal S_en over its output terminal. For example, in the case wherein the controller 13 is such to receive a value of the digital signal SN equal or greater than the digital conversion of the activation threshold of the chin strap contact sensor 1 1 , the controller 13 is such to generate the enable signal S_en having a high logic value (that is, a logic value ): the enable signal S_en with the high logic value is taken into account for enabling the operation of the engine 22 of the motorcycle 50, as it will be described more in detail afterwards. Operation of the engine 22 includes both the phase of the start of the engine 22 and the subsequent phase wherein the engine 22 is running. In the case wherein the controller 13 is such to receive a value of the digital signal SN smaller than the digital conversion of the activation threshold of the chin strap contact sensor 1 1 , the controller 13 is such to generate the enable signal S_en having a low logic value (that is, a logic value Ό'): the enable signal S_en with the low logic value is taken into account for disabling the operation (for example, the start) of the engine 22 of the motorcycle 50, as it will be described more in detail afterwards;

- a transmitter 14 having an input terminal for receving the enable signal S_en and having an output terminal for transmitting a transmitted signal S^; the transmitter 14 has the function to convert the enable signal S_en into the transmitted signal Stx which has voltage values which are suitable for the transmission over a communication channel 40 (for example, a radio communication channel) connecting the transmitter 14 to a receiver 52.

Fig.2 also shows that the motorcycle 50 includes a power source 20 (for example, a battery), an engine 22 and an ignition system 21 for the engine 22 and shows that the security system 10 includes a switch 54 connected between the power source 20 and the ignition system 21 and controlled by a switch signal S_sw.

The switch 54 has a closed position and an open position and the switch signal S_sw controls the switch 54 between the closed and the open position; specifically, the switch signal S_sw configures the switch 54 in the closed position wherein the power supply 20 is connected to the ignition system 21 in order to allow the operation (for example, the start) of the engine 22 of the motorcycle 50, or the switch signal S_sw configures the switch 54 in the open position wherein the power supply 20 is disconnected from the ignition system 21 in order to block the operation (for example, the start) of the engine 22 of the motorcycle 50.

The control device 51 includes:

- the receiver 52 having an input terminal for receiving a received signal from the communication channel 40 and having an output terminal for generating a signal S1 . The receiver 52 has the function to convert the received signal S_rx into the signal S1 which is suitable for the processing by another controller 53;

- the other controller 53 having an input terminal for receiving the signal S1 and having an output terminal for generating the switch signal S_sw- The other controller 53 is adapted to elaborate the signal S1 and to generate therefrom the switch signal S_sw for the configuration of the switch 54 between the closed and the open position;

- the switch 54 having an input terminal connected to the power source 20, having an output terminal connected to the engine 22 and having a control terminal for receiving the switch signal S_sw for controlling the connection of the input terminal to the output terminal.

It will be described hereinafter the functionality of the security system 10. The safety helmet 1 is put on the head of the motorcycle's rider, which fastens the chin strap so that at least part of the strip 4 is in the proximity of the chin of the rider.

The chin strap contact sensor 1 1 detects that the at least part of the strip 4 is in the proximity of the chin of the rider by generating on its output terminal the analogue signal S_a having a first analogue value, for example greater than the activation threshold of the chin strap contact sensor 11.

The analog-to-digital converter 12 receives on its input terminal the first analogue value, performs the conversion of the first analogue value into a first digital value and generates on its output terminal the digital signal S_N having the first digital value.

The controller 13 receives on its input terminal the digital signal SN having the first digital value and generates on its output terminal the enable signal S_en having an high logic value; for example, the controller 13 performs a comparison between the first digital value of the digital signal S_N and the digital conversion of the activation threshold of the chin strap contact sensor 1 1 , and detects that the first digital value is greater or equal than the digital conversion of the activation threshold.

The transmitter 14 receives on its input terminal the enable signal S_en having the high logic value and transmits over the communication channel 40 the transmitted signal Stx having an high logic value with a voltage value suitable for the communication channel 40.

The receiver 52 receives on its input terminal from the communication channel 40 the received signal Srx having an high logic value, converts the high logic value of the received signal into an high logic value and transmits over its output terminal the signal S1 having the high logic value.

The controller 53 receives on its input terminal the signal S1 having the high logic value and generates on its output terminal the switch signal S_sw having an high logic value.

The switch 54 receives on the control terminal the switch signal S_sw having the high logic value and connects the output of the power source 20 to the input of the ignition system 21 : this connection enables the operation (for example, the start) of the engine 22 of the motorcycle 50.

Advantageously, the chin strap contact sensor 1 1 is a capacitive sensor having a variable capacitance (and thus it's indicated hereinafter with "chin strap capacitive sensor"), that is the chin strap capacitive sensor (indicated in

Fig.3A with 111 , for distinguishing with respect to the contact sensor 1 1 of Fig.2) is equivalent to a capacitor able to detect the proximity of at least part of the strip 4 to the chin of the driver by detecting a change of the value of the capacitance of the capacitive sensor (for example, the capacitance value increases) when the at least part of the strip 4 is in the proximity of the chin of the driver; in this case, the analogue signal S_a' generated by the chin strap capacitive sensor 111 is the capacitance value of the chin strap capacitive sensor 111. For example, in the case wherein the capacitance value increases when the at least part of the strip 4 is in the proximity of the chin of the driver, the analogue signal S_a is the capacitance value which indicates that the at least part of the strip 4 is in the proximity of the chin of the driver when the capacitance value S_a is greater than the activation threshold of the chin strap capacitive sensor 111.

Referring to Fig.3A, it shows a security system according to a second embodiment of the invention, including the chin strap capacitive sensor 111. The chin strap capacitive sensor 111 is attached internally to the strip 4 of the safety helmet 1. The implementation of the chin strap capacitive sensor 111 is shown in Fig.3B and will be described afterwards.

The security system is indicated in Fig.3A with 110 for distinguishing with respect to the security system 10 of Fig.2; the security system 110 is included into the strip 4 and into the security device 8 which is inside the safety helmet 1 (like the first embodiment).

The blocks of Fig.3A with the same reference numbers of Fig.2 have equal or similar functionality.

The security system 110 of the second embodiment has the following differences with respect to the security system 10 of the first embodiment:

- the chin strap capacitive sensor 111 includes an input/output terminal for receving a square wave excitation signal S_e and for transmitting an analogue signal S_a' having a function similar to the analogue signal S_a, that is the analogue signal S_a' indicates the proximity of at least part of the strip 4 to the chin of the driver;

- the security device 8 includes a multiplexer 116 having an input/output terminal for receiving the analogue signal S_a' from the chin strap capacitive sensor 111 and for transmitting a square wave signal S_e to the chin strap capacitive sensor 1 11 , having an output terminal for transmitting the analogue signal S_a' to the analog-to-digital converter 12 and having an input terminal for receiving the square wave excitation signal S_e;

- the security device 8 includes a signal source 1 15 adapted to generate the square wave excitation signal S_e (having for example a frequency of 250 Khz).

Fig.3B shows the implementation of the chin strap capacitive sensor 1 1 1. The chin strap capacitive sensor 1 11 is equivalent to a capacitor having a first plate implemented on a metal trace 131 of a printed circuit board 130, while the second plate of the capacitor is the chin of the driver (the rider) of the vehicle (the motorcycle), wherein the chin of the driver is electrically equivalent to a connection to ground. Therefore the capacitance of the chin strap capacitive sensor 111 is such to change its value when the chin is in the proximity of at least part of the strip 4.

The shape of the printed circuit board 130 and of the metal trace 131 is substantially rectangular: for example, the length of one side of the metal trace 131 is about 65,5 mm and the length of the other side of the metal trace 131 is about 21 mm.

The chin strap capacitive sensor 1 1 1 further includes a portion 132 of the metal trace 131 for generating the analogue signal S_a'. Fig.3B also shows a coaxial cable having an inner cable 133 and a shield 134 and electrically connected from one side to the printed circuit board 130 and from the other side to the multiplexer 1 16 of the security device 8: specifically, the inner cable 133 is welded to the portion 132 and the shield 134 is welded to the metal trace 131. The use of shield 134 in the electrical connection between the chin strap capacitive sensor 11 1 and the multiplexer 1 16 in the security device 8 has the advantage to minimize noise pickup in the chin strap capacitive sensor 1 1 1.

Preferably, the metal trace 131 is copper.

Advantageously, the thickness of the metal trace 131 is smaller or equal to 35 μιη and the thickness of the printed circuit board 130 is smaller or equal to 150 μιτι, so that the chin strap capacitive sensor 111 is flexible and sufficiently resistent to the bending which occurs in the strip 4.

Moreover, said flexibility allows to have a larger chin strap capacitive sensor 111 inside the strip 4 (even large like the entire area of the strip 4) without being damaged, thus improving the sensitivity of the chin strap capacitive sensor 111 (and of the security system 110). In fact, the capacitance has an ambient value, that is a capacitance value measured when the chin is not in the proximity of the strip 4: when the chin is in the proximity of at least part of the strip 4, the capacitance value (for example) increases to a value greater than the capacitance ambient value. The capacitance ambient value can change depending on the environment conditions, for example by increasing the value: in this case wherein the chin is in the proximity of at least part of the strip 4, a large chin strap capacitive sensor 111 is able to detect a significant increase of the capacitance value greater than the capacitance ambient value (which has increased), so to allow a correct activation of the chin strap capacitive sensor 111.

The functionality of the security system 110 is similar to the functionality of the security system 10.

The signal source 115 generates the square wave excitation signal S_e. The multiplexer 116 receives the square wave excitation signal S_e and transmits the square wave excitation signal S_e to the chin strap capacitive sensor 111.

The chin strap capacitive sensor 111 receives the square wave excitation signal S_e which charges the first plate 131 of the chin strap capacitive sensor 111.

The safety helmet 1 is put on the head of the motorcycle's rider, which fastens the chin strap so that at least part of the strip 4 is in the proximity of the chin of the rider: the second plate of the chin strap capacitive sensor 111 is connected to ground, so that the value of the capacitance of the chin strap capacitive sensor 111 changes.

The chin strap capacitive sensor 111 detects that the at least part of the strip 4 is in the proximity of the chin of the rider by generating on its output terminal the analogue signal S_a' having a second analogue value, for example greater than the activation threshold of the chin strap capacitive sensor 111.

The multiplexer 116 receives from the chin strap capacitive sensor 111 the analogue signal S_a' having the second analogue value and transmits to the analog-to-digital converter 12 the analogue signal S_a' having the second analogue value.

The analog-to-digital converter 12 receives on its input terminal the second analogue value, performs the conversion of the second analogue value into a second digital value and generates on its output terminal the digital signal S_N having the second digital value.

The controller 13 receives on its input terminal the digital signal SN having the second digital value and generates on its output terminal the enable signal S_en having an high logic value; for example, the controller 13 performs a comparison between the second digital value of the digital signal S_N and the digital conversion of the activation threshold of the chin strap capacitive sensor 111 , and detects that the second digital value is greater or equal than the digital conversion of the activation threshold.

The transmitter 14 receives on its input terminal the enable signal S_en having the high logic value and transmits over the communication channel 40 the transmitted signal St having an high logic value with a voltage value suitable for the communication channel 40.

Referring to Fig.4A, it shows a security system according to a third embodiment of the invention, wherein the chin strap contact sensor 211 is a capacitive sensor having a variable capacitance (like the chin strap capacitive sensor 111 of Fig.3A and 3B and thus it's indicated with "chin strap capacitive sensor" 211 ), that is the chin strap capacitive sensor 211 is a capacitor able to detect the proximity of at least part of the strip 4 to the chin of the driver by detecting a change of the value of the capacitance of the chin strap capacitive sensor 211 (for example, the capacitance value decreases) when the at least part of the strip 4 is in the proximity of the chin of the driver; in this case, the analogue signal S_a" generated by the chin strap capacitive sensor 211 is the capacitance value of the chin strap capacitive sensor 21 1 . The chin strap capacitive sensor 21 1 is attached internally to the strip 4.

The security system is indicated in Fig.4A with 210 for distinguishing with respect to the security system 10 of Fig.2 and 1 10 of Fig.3A; the security system 210 is included into the strip 4 and into the security device 8 which is inside the shell 7 of the safety helmet 1 (like in the first and in the second embodiment).

The blocks of Fig.4A with the same reference numbers of Fig.2 have equal or similar functionality.

The security system 210 of the third embodiment has the following differences with respect to the security system 10 of the first embodiment:

- the chin strap capacitive sensor 21 1 includes an output terminal for transmitting an analogue signal S_a" to the analog-to-digital converter 12 and includes an input terminal for receiving a square wave excitation signal S_e', wherein the analogue signal S_a" indicates the proximity of at least part of the strip 4 to the chin of the driver;

- the security device 8 includes a signal source 215 adapted to generate the square wave excitation signal S_e' (having for example a frequency of 250 Khz).

Fig.4B shows the implementation of the chin strap capacitive sensor 21 1 .

The chin strap capacitive sensor 21 1 is a capacitor having a first plate implemented on a first metal trace 231 of a printed circuit board 230 and having a second plate implemented on a second metal trace 233 of the printed circuit board 230. The capacitance of the chin strap capacitive sensor 21 1 is such to change its value when the chin of the driver is in the proximity of at least part of the strip 4, because the chin is such to interfere with the electrical field between the first plate 231 and the second plate 233 of the chin strap capacitive sensor 21 1 and part of the field lines of the electrical field are shunted to ground through the chin of the driver.

The first metal trace 231 and the second metal trace 233 have an interdigitized shape, as shown schematically in Fig.4B: this has the advantage to improve the sensitivity of the chin strap capacitive sensor 21 1 (and thus of the security system 210).

The chin strap capacitive sensor 21 1 further includes a portion 234 (shown also in Fig.4A) of the metal trace 233 for receiving the square wave excitation signal S_e' from the signal source 215 and includes a portion 232 (shown also in Fig.4A) of the metal trace 231 for generating the analogue signal S_a".

Preferably, the first metal trace 231 and the second metal trace 233 are copper.

Advantageously, the thickness of the first metal trace 231 and of the second metal trace 233 are smaller or equal to 35 μητι and the thickness of the printed circuit board 230 is smaller or equal to 150 μιτι, so that the chin strap capacitive sensor 21 1 is flexible and sufficiently resistent to the bending which occurs in the strip 4.

The functionality of the security system 210 is similar to the functionality of the security system 10.

The signal source 215 generates the square wave excitation signal S_e'. The chin strap capacitive sensor 21 1 receives the square wave excitation signal S_e', which generates an electrical field between the first plate 231 and the second plate 233 of the chin strap capacitive sensor 21 1.

The safety helmet 1 is put on the head of the motorcycle's rider, which fastens the chin strap so that at least part of the strip 4 is in the proximity of the chin of the rider: the chin of the driver interferes with the electrical field between the first and the second plate of the chin strap capacitive sensor 21 1 , so that the value of the capacitance of the chin strap capacitive sensor 21 1 changes.

The chin strap capacitive sensor 21 1 detects that the at least part of the strip 4 is in the proximity of the chin of the rider by generating on its output terminal the analogue signal S_a" having a third analogue value greater than the activation threshold of the chin strap capacitive sensor 211 .

The analog-to-digital converter 12 receives on its input terminal the third analogue value, performs the conversion of the third analogue value into a third digital value and generates on its output terminal the digital signal SN having the third digital value.

The controller 13 receives on its input terminal the digital signal S having the third digital value and generates on its output terminal the enable signal S_en having an high logic value; for example, the controller 13 performs a comparison between the third digital value of the digital signal SN and the digital conversion of the activation threshold of the chin strap capacitive sensor 211 , and detects that the third digital value is greater or equal than the digital conversion of the activation threshold.

Referring to Fig.5, it shows a security system 310 for a safety helmet 1 according to a fourth embodiment of the invention, wherein the blocks of Fig.5 with the same reference numbers of Fig.1 have equal or similar functionality. The security system 310 further includes a contact sensor 311 arranged inside the shell 7 of the safety helmet 1 and attached to the shell 7: the contact sensor 311 is adapted to detect the proximity of at least part of the shell 7 to the head of the driver in order to check that the safety helmet 1 has been put on the head of the driver (thus the contact sensor 311 is indicated with "head contact sensor" 311 ). For example, the head contact sensor 311 is such to generate an analogue signal S_a'" which is a voltage signal indicating that at least part of the shell 7 of the safety helmet 1 is in the proximity of the head of the driver when the value of the voltage signal S_a'" is greater than a threshold indicated with "activation threshold" of the head contact sensor 311.

The security device 8 includes an analog-to-digital converter 312 having a first input terminal for receiving the analogue signal S_a from the chin strap contact sensor 11 and having a second input terminal for receiving the analogue signal S_a'" from the head contact sensor 311 ; the analog-to-digital converter 312 includes an output terminal for generating serially the digital signal SN equal to the digital conversion of the analogue signal S_A and a second digital signal SN" equal to the digital conversion of the analogue signal S_A'".

The controller 13 has an input terminal for receiving serially the digital signal S_N and the second digital signal SN" and has an output terminal for generating the enable signal S_EN. The controller 13 is adapted to elaborate the digital signal S_N and the second digital signal SN" and to generate therefrom the enable signal S_EN over its output terminal. For example, in the case wherein the controller 13 is such to receive the digital signal S_N equal or greater than the digital conversion of the activation threshold of the chin strap contact sensor 11 and to receive also the second digital signal S_N" equal or greater than the digital conversion of the activation threshold of the head contact sensor 311 , the controller 13 is such to generate the enable signal S_EN having a high logic value (that is, a logic value ): the enable signal S_EN with the high logic value is taken into account for enabling the operation (for example, the start) of the engine 22 of the motorcycle 50, as explained in the first embodiment of the invention. In the case wherein the controller 13 is such to receive the digital signal S_N smaller than the digital conversion of the activation threshold of the chin strap contact sensor 11 or to receive the second digital signal S_N" smaller than the digital conversion of the activation threshold of the head contact sensor 311 , the controller 13 is such to generate the enable signal S_EN having a low logic value (that is, a logic value Ό'): the enable signal S_EN with the low logic value is taken into account for disabling the operation (for example, the start) of the engine 22 of the motorcycle 50, as explained in the first embodiment of the invention.

The security system 310 has the advantage to provide more safety because two sensors (11 , 311 ) are used for checking that the safety helmet 1 has been correctly put on the head of the driver, by checking the proximity of both the chin and of the head, as explained above.

Advantageously, the head contact sensor 311 is a capacitive sensor having a variable capacitance (and thus it's indicated with "head capacitive sensor" 311 ), that is the head capacitive sensor 311 is equivalent to a capacitor able to detect the proximity of at least part of the shell 7 to the head of the driver by detecting a change of the value of its capacitance (for example, the capacitance value increases) when the at least part of the shell 7 is in the proximity of the head of the driver; in this case, the analogue signal S_a'" generated by the head capacitive sensor 31 1 is the capacitance value of the head capacitive sensor 31 1 . For example, in the case wherein the capacitance value increases when the at least part of the shell 7 is in the proximity of the head of the driver, the analogue signal S_a"' is the capacitance value which indicates that the at least part of the shell 7 is in the proximity of the head of the driver when the capacitance value S_a'" is greater than the activation threshold of the head capacitive sensor 31 1 .

Fig.6A shows the implementation of the head capacitive sensor 31 1 , which is equivalent to a capacitor having a first plate implemented on a metal trace 331 of a printed circuit board 330. The functionality of the head capacitive sensor 31 1 of Fig.6A is similar to the functionality of the chin strap capacitive sensor 1 1 1 of Fig.3B, with the difference that the second plate of the capacitor is the head of the driver, wherein the head of the driver is electrically equivalent to a connection to ground. Therefore the capacitance of the head capacitive sensor 31 1 is such to change its value when at least part of the shell 7 is in the proximity of the head of the driver.

The shape of the printed circuit board 330 and of the metal trace 331 is substantially square: for example, the length of the side of the square of the metal trace 331 is about 64 mm.

The head capacitive sensor 31 1 further includes a portion 332 of the metal trace 331 for generating the analogue signal S_a'". Fig.6A also shows a coaxial cable having an inner cable 333 and the shield 334 and electrically connected from one side to the printed circuit board 330 and from the other side to the security device 8: specifically, the inner cable 333 is welded to the portion 332 and the shield 334 is welded to the metal trace 331 . The use of shield 334 in the electrical connection between the head capacitive sensor 31 1 and the security device 8 has the advantage to minimize noise pickup in the head capacitive sensor 31 1 .

Preferably, the metal trace 331 is copper. Advantageously, the thickness of the metal trace 331 is smaller or equal to 35 μιη and the thickness of the printed circuit 330 board is smaller or equal to 150 μητι, so that the head capacitive sensor 31 1 is flexible and sufficiently resistent to the bending which occurs in the shell 7.

Fig.6B shows another implementation of the head capacitive sensor indicated with 41 1 (for distinguishing with respect to the implementation of the head capacitive sensor 311 ), which is a capacitor having a first plate implemented on a first metal trace 431 of a printed circuit board 430 and having a second plate implemented on a second metal trace 433.

The functionality of the head capacitive sensor 41 1 of Fig.6B is similar to the functionality of the chin strap capacitive sensor 211 of Fig.4B, with the difference that the head of the driver replaces the chin of the driver. Therefore the capacitance of the head capacitive sensor 41 1 is such to change its value when at least part of the shell 7 is in the proximity of the head, because the head is such to interfere with the electrical field between the first plate 431 and the second plate 433 of the head capacitive sensor 411 and part of the field lines of the electrical field are shunted to ground through the head of the driver.

The first metal trace 431 and the second metal trace 433 have an interdigitized shape, as shown schematically in Fig.6B: this has the advantage to improve the sensitivity of the head capacitive sensor 41 1 (and thus of the security system 310).

The head capacitive sensor 411 further includes a portion 434 of the metal trace 433 for receiving a square wave excitation signal (similar the square wave excitation signal S_e' of the third embodiment) and includes a portion 432 of the metal trace 431 for generating an analogue signal S_a'" (similar to the analogue signal S_a" of the third embodiment).

Preferably, the first metal trace 431 and the second metal trace 433 are copper.

Advantageously, the thickness of the first metal trace 431 and of the second metal trace 433 are smaller or equal to 35 pm and the thickness of the printed circuit board 430 is smaller or equal to 150 pm, so that the head capacitive sensor 411 is flexible and sufficiently resistent to the bending which occurs in the shell 7.

The invention can also be applied to a seat belt for a vehicle (for example, a car). In this case, a contact sensor (preferably, a capacitive sensor) is attached to at least a part of the seat belt which is (when the seat belt is fastened) in the proximity of the body of the driver, for example in the proximity of the breast of the driver or in the proximity of the waist of the driver. In this case, part of the security system (similar to the sensor 4 and to the device 8 of Fig.2) is included into the seat belt and another part of the security system (similar to the control device 51 of Fig.2) is included into the vehicle. Therefore the security system mounted on the seat belt and in the vehicle enables the operation (for example, the start) of the engine of the vehicle only when the seat belt is fastened correctly, by detecting the proximity of at least part of the safety belt to a part of the body of the driver.

Claims

1 . Security system (10) to control the operation of an engine (22) of a vehicle (50), the system comprising:

- a contact sensor (1 1 ) adapted to generate an analogue signal (S_a) indicating the proximity of at least part of a chin strap (4) of a safety helmet (1 ) to the chin of a driver of the vehicle or indicating the proximity of at least part of a seat belt for a vehicle to the body of the driver;

- an analog-to-digital converter (12) adapted to receive the analogue signal and to generate therefrom a digital signal (SN);

- a controller (13) adapted to elaborate the digital signal and to generate therefrom an enable signal (S_en) for enabling the operation of the vehicle engine.

2. Security system according to claim 1 , wherein the contact sensor is a capacitive sensor (1 1 1 , 21 1 ) having a variable capacitance and is adapted to generate the analogue signal indicating a change of the value of the capacitance when the at least part of the chin strap is in the proximity of the chin of the driver or the at least part of the seat belt is in the proximity of the body of the driver.

3. Security system according to claim 2, wherein the capacitive sensor includes at least one plate implemented on at least one respective metal trace

(131 ) of a printed circuit board (130).

4. A security system according to claim 3, wherein the capacitive sensor (21 1 ) includes two plates implemented on two metal traces (231 , 233) with an interdigitized shape.

5. Security system according to claims 3 or 4, wherein the thickness of the metal trace is smaller or equal to 35 μητι and the thickness of the printed circuit board is smaller or equal to 150 pm.

6. Security system according to at least one of claims 3 to 5, wherein the shape of the metal trace is substantially rectangular with one side of about 65,5 mm and the other side of about 21 mm.

7. Security system according to at least one of claims 3 to 6, wherein the size of the printed circuit board is substantially equal to the size of a strip (4) of the chin strap.

8. Security system (310) according to at least one of the previous claims, the system further including another capacitive sensor (31 1 ) having a variable capacitance and adapted to generate another analogue signal (S_a'") indicating a change of the value of the capacitance when at least part of the shell (7) of the safety helmet is in the proximity of the head of the driver,

wherein the analog-to-digital converter is further adapted to receive the other analogue signal and to generate therefrom another digital signal (S_N"), wherein the controller is adapted to elaborate the digital signal and the other digital signal and to generate therefrom the enable signal for enabling the operation of the vehicle engine.

9. Security system according to claim 8, wherein the other capacitive sensor includes two plates implemented on two metal traces with an interdigitized shape.

10. Security system according to at least one of the previous claims, further including a transmitter (14) adapted to transmit the enable signal to the vehicle over a communication channel (40).

1 1 . Security system according to at least one of the previous claims, wherein the controller is adapted to generate the enable signal for enabling the connection of the power supply (20) of a motorcycle (50) to the ignition system (21 ) of the motorcycle engine (22).

12. Security system according to at least one of the previous claims, wherein the controller is adapted to generate the enable signal for enabling the starting of the vehicle engine.

13. Safety helmet (1 ) for a vehicle, the safety helmet including:

- a chin strap (3, 4, 5, 6) comprising a strip (4) having at least in part attached a contact sensor (1 1 , 1 1 1 , 21 1 ) adapted to generate an analogue signal (S_a) indicating the proximity of at least part of the strip (4) to the chin of a driver of the vehicle;

- a security device (8) including an analogue-to-digital converter adapted to receive the analogue signal and to generate therefrom a digital signal (SN) and including a controller adapted to elaborate the digital signal and to generate therefrom an enable signal (S_en) for enabling the operation of a vehicle engine;

- a cable (33) adapted to connect the contact sensor to the security device.

14. Safety helmet according to claim 13, wherein the security device is arranged inside the shell (7) of the safety helmet or is arranged externally to the shell.

15. Seat belt for a vehicle, the belt having at least in part attached a contact sensor (11 , 111 , 211 ) adapted to generate an analogue signal (S_a) indicating the proximity of at least part of the belt to the body of a driver of the vehicle.