VEHICLE"

TECHNICAL FIELD

The present invention relates to a noise reducing system for a tracked vehicle and a tracked vehicle, for example for grooming ski runs.

BACKGROUND ART

In general, a tracked vehicle comprises at least one track, which extends along a direction of travel of the vehicle and that, in turn, comprises a rubber belt and a plurality of bars transverse to the direction of travel of the vehicle. In addition, the tracked vehicle comprises a chassis and a cab coupled to the chassis. The cab is connected to the chassis by elastic elements configured to dampen the vibrations caused by the tracks and which propagate to the cab.

One drawback of the known art is that when the tracked vehicle moves along the direction of travel, the transverse bars of the track create vibration on the chassis having a frequency correlated to the speed of travel. This vibration is transmitted from the chassis to the cab and, in certain frequency ranges, these vibrations can be quite annoying for the driver and create noise in the cab that reduces driving comfort for the driver of the tracked vehicle.

DISCLOSURE OF INVENTION

One object of the present invention is to provide a noise reducing system for a tracked vehicle, the tracked vehicle comprising a cab and at least one track that extends along a direction of travel of the vehicle and comprises at least a plurality of bars transverse to the direction of travel and preferably made of metal, the noise reducing system comprising a control unit and an acoustic wave emitter connected to the control unit for being controlled by the control unit, the noise reducing system comprising an acoustic input and being configured to emit an acoustic equalisation wave, phase shifted with respect to the noise and determined on the basis of the acoustic input, to reduce the noise, in particular the noise generated by the tracks .

Thanks to the present invention, the noise reducing system, once installed on the tracked vehicle, more specifically inside the cab, ensures driving comfort for the driver because the noise generated by the tracks and perceived by the driver is reduced. Furthermore, the noise reducing system has the advantage of being installable on the tracked vehicle both in the production phase of the tracked vehicle and afterwards, on already existing tracked vehicles as a retrofit. Another advantage of the noise reducing system is its adaptability to the noise created by the tracks of the tracked vehicle. In fact, the characteristics of the noise created by the tracks are only determinable after the tracked vehicle has been assembled and cannot be determined beforehand, when designing the tracked vehicle, because it is very complex to calculate how vibration will be transmitted from the tracks to the cab and what will be the resonant frequencies of the cab. In fact, the vibrations that create noise that is annoying for the driver are mainly those that have a frequency corresponding to one or more oscillating modes of the cab and/or which coincide with the resonant frequencies of the cab. When it is found that the noise transmitted into the cab is not bearable for the driver, the noise reducing system consequently enables reducing the noise of the tracked vehicle without the need to redesign the cab or the tracks.

According to a preferred embodiment, the noise reducing system comprises a microphone that defines the acoustic input and is connected to the control unit to provide a first signal correlated to the noise to the control unit. According to a preferred embodiment, the control unit is configured to emit the acoustic equalisation wave on the basis of the phase of the first signal to reduce the noise.

According to a preferred embodiment, the control unit is configured to emit the acoustic equalisation wave on the basis of the amplitude of the noise detected through the first signal.

According to a preferred embodiment, the control unit is configured to emit the acoustic equalisation wave on the basis of the frequency of the noise detected through the first signal.

According to another preferred embodiment, the noise reducing system comprises a second input to receive a second signal correlated to the speed of travel of the tracked vehicle, the noise reducing system being configured to emit the acoustic equalisation wave on the basis of the second signal to reduce the noise, and preferably to define the frequency or the frequency and amplitude of the acoustic equalisation wave on the basis of the second signal.

According to another preferred embodiment, the noise reducing system comprises a third input to receive a third signal correlated to the speed in revolutions of an engine of the tracked vehicle, the noise reducing system being configured to emit an acoustic equalisation wave on the basis of the third signal to reduce the noise, and preferably to define the frequency of the acoustic equalisation wave on the basis of the third signal.

According to another preferred embodiment, the noise reducing system comprises a fourth input to receive a fourth signal correlated to a signal of a radio system, the sound reducing system being configured to emit the acoustic equalisation wave on the basis of the fourth signal so as not to reduce the audibility of the radio system. According to another preferred embodiment, the noise reducing system comprises a memory comprising a plurality of pairs of values, wherein each pair of values comprises a speed value of the tracked vehicle and a frequency value of the acoustic equalisation wave associated with the speed value, the control unit being connected to the memory and being configured to define the frequency of the acoustic equalisation wave on the basis of one of the pairs of values selected on the basis of the second signal .

According to another preferred embodiment, the noise reducing system comprises a memory comprising a plurality of sets of three values, wherein each set of three values comprises a speed value of the tracked vehicle and a frequency value and amplitude value of the associated acoustic equalisation wave, the control unit being connected to the memory and being configured to define the frequency of the acoustic equalisation wave on the basis of one of the sets of three values selected on the basis of the second signal.

According to another preferred embodiment, the acoustic wave emitter is configured to emit acoustic equalisation waves within the frequency range from 0 to 100 Hz, preferably from 0 to 50 Hz.

According to another preferred embodiment, the acoustic wave emitter is a loudspeaker, in particular of the subwoofer type, having a capacity of at least 20 litres of air.

Another object of the present invention is to provide a tracked vehicle that reduces the drawbacks of the known art.

According to the present invention, a tracked vehicle is provided that comprises a cab, at least one track that extends along a direction of travel of the vehicle and comprises a plurality of bars transverse to the direction of travel and preferably made of metal, a chassis connected to the tracks and to the cab, and a noise reducing system according to any of claims 1 to 11; the noise reducing system is preferably housed inside the cab.

According to a preferred embodiment, the tracked vehicle comprises a speed detector, the noise reducing system being connected to the speed detector to receive the speed value of the vehicle via the second signal.

According to another preferred embodiment, the tracked vehicle comprises an engine speed sensor, the noise reducing system being connected to the engine speed sensor to receive the engine speed value via the third signal.

According to another preferred embodiment, the tracked vehicle comprises a radio system, the noise reducing system being connected to the radio system to receive a fourth signal associated with the radio system.

According to another preferred embodiment, the plurality of transverse bars are spaced from one another by a given pitch, the noise reducing system being configured to define the frequency of the acoustic equalisation wave on the basis of the given pitch; the pitch is preferably in the range from 100 mm to 160 mm, more preferably from 118 mm to 144 mm.

According to another preferred embodiment, the tracked vehicle comprises an elastic system configured to connect the cab to the chassis to dampen vibrations from the chassis, the elastic system preferably comprising a silent block and/or a gas spring.

According to another preferred embodiment, the cab comprises a roof and a compartment obtained in the roof and inside the cab, the noise reducing system being housed in the compartment. According to another preferred embodiment, the tracked vehicle comprises a door, and the acoustic wave emitter is housed in the door .

According to another preferred embodiment, the cab comprises a driver's seat and a rear panel behind the driver's seat, with the acoustic wave emitter housed in the rear panel.

BRIEF DESCRIPTION OF THE DRAWINGS

According to another preferred embodiment, the acoustic wave emitter is part of the radio system of the tracked vehicle. Other characteristics and advantages of the present invention will become clear from the description that follows of a non- limitative embodiment, with reference to the accompanying drawings, in which:

- Figure 1 is a side elevation view, with parts removed for clarity, of a tracked vehicle made in accordance with the present invention;

- Figure 2 is a block diagram of a noise reducing system for the tracked vehicle in Figure 1;

- Figure 3 is a table comprising a plurality of sets of three values stored in a memory of the noise reducing system in Figure 2 ; and

- Figure 4 is a table of an alternative embodiment to that in Figure 3 and comprises a plurality of pairs of values stored in a memory of the noise reducing system in Figure 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to Figure 1, reference numeral 1 indicates, as a whole, a tracked vehicle for grooming ski runs and configured to move along a direction of travel D. The tracked vehicle 1 comprises a chassis 2, two tracks 3, an engine 4 for generating mechanical energy, two mutually independent drive wheels 5 respectively coupled to the tracks 3 and the engine 4 to transfer mechanical energy from the engine 4 to the tracks 3, a cab 9, an elastic system 11 that couples the cab 9 to the chassis 2, and a noise reducing system 20 housed inside the cab 9. Furthermore, the two drive wheels 5 and the tracks 3 are coupled to the chassis 2.

The tracked vehicle 1 may comprise a group of work devices 7, shown with broken lines. The group of work devices 7 may comprise a shovel, a cutter and a winch.

The elastic system 11 is configure to dampen the vibrations transmitted from the chassis 2 to the cab 9 and comprises silent blocks and/or gas springs.

Each track 3 extends along the direction of travel D and comprises a rubber belt 13 and a plurality of bars 15 transverse to the direction of travel D, arranged along the rubber belt 13 and spaced from one another by a given pitch P. The transverse bars are made of metal. In one preferred non-limitative embodiment of the present invention, the pitch P is preferably in the range from 100 mm to 160 mm. More preferably, the pitch P in the range from 118 mm to 144 mm.

In the non-limitative embodiment of the present invention shown in the accompanying figures, the track 3 comprises a cleat arranged on each transverse bar 15.

The cab 9 comprises a driver's seat 10 for accommodating a driver U and a roof 16.

In addition, the cab 9 comprises a compartment 18 inside the cab 9 and made in the roof 16. In other words, the compartment 18 is obtained on the side of the roof 16 facing the inside of the cab 9.

Referring to Figure 2, the tracked vehicle 1 comprises a speed detector 19 configured to detect the speed of travel of the tracked vehicle 1 and to emit a speed signal SV correlated to the speed of travel of the tracked vehicle 1.

Furthermore, the tracked vehicle 1 comprises an engine speed sensor 17 configured to emit an engine speed signal Sn correlated to the speed in revolutions of the engine 4.

In addition, the tracked vehicle 1 comprises a radio system 14 installed in the cab 9 and comprising a receiver unit 14a and speakers 14b. The radio system 14 has the purpose of providing infotainment for the driver U through music, radio news and/or other services. In addition, the radio system 14 could comprise a radio communications system usable by the driver U to communicate via a radio frequency system, in which case the radio system comprises a microphone. The radio communications system can be of the citizen band (so-called CB) type, which uses a radio frequency band around 27 MHz. In another embodiment, the radio communications system could be of the type that uses the VHF or UHF frequency bands.

The receiver unit 14a is connected to the speakers 14b and sends a signal SA to the speakers 14b.

Referring to Figure 2, the noise reducing system 20 comprises a control unit 21 and an acoustic wave emitter 22 connected to the control unit 21 for being controlled by the control unit 21.

In greater detail, the noise reducing system 20 comprises a microphone 23 that defines an acoustic input of the noise reducing system 20. The microphone 23 is connected to the control unit 21 by an input 21a of the control unit 21 and provides a signal SR to the control unit 21 that is correlated to the detected noise. The microphone 23 is housed inside the cab 9 near to the driver's seat 10 so as to detect the noise perceived by the driver U.

The noise reducing system 20 is connected to the speed detector 19 to receive the value of the speed of travel of the tracked vehicle 1. In greater detail, the control unit 21 comprises an input 21b to receive the speed signal SV from the speed detector 19.

Referring to Figures 2 and 3, the control unit 21 comprises a memory 24 in which a plurality of sets of three values V, f and A, are stored. Each set of three values VI, fl, Al ; V2, f2, A2 ;

Vn, fn, An, comprises a speed value V of the tracked vehicle 1 and a frequency value f and amplitude value A of an acoustic equalisation wave associated with each other. In an alternative embodiment of the present invention, the control unit 21 comprises a memory 24 in which a plurality of sets of three value groups V, f and A are stored. Each set of three value groups VI, fl, Al; V2, f2, A2 ; Vn, fn, An, comprises a speed value V of the tracked vehicle 1 and a group of frequency values f and a group of amplitude values A of an acoustic equalisation wave associated with each other. In greater detail, the group of frequency values f comprises the frequency values of the various components of the noise frequency spectrum. The group of amplitude values A comprises the amplitude values of the various components of the noise frequency spectrum.

The control unit 21 is configured to define an acoustic equalisation wave able to reduce the noise; in particular, the acoustic equalisation wave has the same waveform as the acoustic noise wave that it wished to compensate and is phase shifted with respect to the acoustic noise wave by 180°. To this end, the control unit 21 defines a compensation signal SC to send to the acoustic wave emitter 22 to emit the acoustic equalisation wave to reduce the noise.

The control unit 21 determines the frequency f and amplitude A of the acoustic equalisation wave and of the compensation signal SC on the basis of the value of the speed of travel V detected by the speed detector 19. In greater detail, the control unit 21 derives the frequency f and amplitude A of the acoustic equalisation wave from the set of three values V, f and A that has the speed value V equal to the detected speed value. The control unit 21 thus selects one of the sets of three values V, f and A on the basis of the speed signal SV and determines the frequency f and amplitude A of the compensation signal SC from the frequency value f of the selected set of three values V, f and A.

In addition, the control unit 21 determines the phase of the equalisation wave on the basis of the acoustic input signal. In greater detail, the noise reducing system 20 detects the noise via the microphone 23 that determines the SR signal, and the control unit 21 derives the phase of the SR signal and determines the phase of the compensation signal SC so that the acoustic equalisation wave is phase shifted 180° with respect to the detected acoustic noise wave.

In this way, the acoustic equalisation wave defined by the compensation signal SC will reduce the noise perceived by the driver U.

In another embodiment shown in Figure 4, the memory 24 stores a plurality of pairs of values V, f. Each pair of values VI, fl; V2, f2; Vn, fn, comprises a speed value V of the tracked vehicle 1 and a frequency value f of an acoustic equalisation wave paired with the speed value V. In this embodiment, the control unit 21 determines the frequency f of the acoustic equalisation wave and of the compensation signal SC on the basis of the value of the speed of travel V detected by the speed detector 19. In greater detail, the control unit 21 derives the frequency f of the acoustic equalisation wave from the pair of values V and f that has the speed value V equal to the detected speed value. The control unit 21 thus selects one of the pairs of values V and f on the basis of the speed signal SV and determines the frequency f of the compensation signal SC from the frequency value f of the selected pair of values V and f. The control unit 21 determines the phase and amplitude A of the equalisation wave on the basis of the acoustic input signal. In greater detail, the noise reducing system 20 detects the noise via the microphone 23 that determines the SR signal, and the control unit 21 derives the phase of the SR signal and the amplitude of the SR signal and determines the phase of the compensation signal and the amplitude of the compensation signal SC so that the acoustic equalisation wave is phase shifted 180° with respect to the detected acoustic noise wave and has an amplitude A equal to the noise that it is wished to cancel.

In an alternative embodiment of the present invention, the control unit 21 comprises a memory 24 in which a plurality of pairs of value groups V and f are stored. Each pair of value groups VI, fl; V2, f2; Vn, fn, comprises a speed value V of the tracked vehicle 1 and a group of frequency values f paired with the speed of travel value V. In greater detail, the group of frequency values f comprises the frequency values of the various components of the frequency spectrum of the noise that occurs at a given speed V and which it is wished to cancel.

In an alternative and preferred embodiment of the present invention, the control unit 21 calculates the frequency f of the compensation signal on the basis of the speed of travel V and the given pitch P. In greater detail, the control unit 21 calculates the frequency f of the compensation signal SC on the basis of the speed signal SV and the given pitch P. In particular, the control unit 21 calculates the frequency f of the compensation signal SC on the basis of a first function that is a function of the speed signal SV and the given pitch P. Furthermore, in this embodiment, the control unit 21 determines the phase and amplitude of the equalisation wave on the basis of the acoustic input signal. In greater detail, the control unit 21 determines the phase of the compensation signal SC and the amplitude A of the compensation signal SC from the SR signal so that the acoustic equalisation wave is phase shifted 180° with respect to the detected acoustic noise wave and has an amplitude equal to the noise.

In another alternative embodiment of the present invention, the input 21b of the speed signal SV is omitted and the control unit 21 determines the phase, frequency f and amplitude A of the equalisation wave on the basis of the phase of the SR signal, the frequency of the SR signal and the amplitude of the SR signal. In greater detail, the control unit 21 performs a fast Fourier transform (FFT) on the SR signal and derives the frequency f and amplitude A of the noise component it is wished to cancel. In an alternative embodiment, the control unit 21 derives the frequencies f and amplitudes A of the components of the noise spectrum from the fast Fourier transform.

The control unit 21 defines the compensation signal SC on the basis of the detected frequency f, the detected amplitude A and the detected phase, all detected via the microphone 23.

In one preferred embodiment, the noise reducing system 20 is connected to the engine speed sensor 17 to receive the engine speed value of the engine 4. In this embodiment, the noise reducing system 20 comprises an input 21c to receive the engine speed signal Sn, which is correlated to the speed in revolutions of the engine 4 of the tracked vehicle 1. The control unit 21 is configured to define the acoustic equalisation wave also on the basis of the engine speed signal Sn to reduce the noise. In particular, the control unit 21 defines the frequency f of the compensation signal SC on the basis of the engine speed signal Sn.

In one preferred embodiment, the noise reducing system 20 is connected to the radio system 14 to receive the SA signal and has an input 21d to receive the SA signal. The control unit 21 determines the compensation signal SC also on the basis of the SA signal so as not to equalise the SA signal. In other words, the SA signal, which is also detected via the microphone 23, is not equalised by the control unit 21. In greater detail, by excluding the frequencies and/or the phase deriving from the SA signal from the compensation process, the control unit 21 will emit a compensation signal SC that will not have a component equal to and in antiphase with the SA signal. In this way, the noise reducing system 20 does not reduce the audibility of the radio system 14 for the driver U.

In all the embodiments, the acoustic equalisation wave has a frequency ranging from 0 to 100 Hz, preferably from 0 to 50 Hz. In consequence, the acoustic wave emitter 22 is configured to emit acoustic waves in the frequency range 0 to 100 Hz, preferably 0 to 50 Hz. To this end, the acoustic wave emitter 22 is a speaker, more specifically of the subwoofer type, having a capacity of at least 20 litres of air. In particular, the acoustic wave emitter is housed in the compartment.

In the embodiment shown in Figure 1, the noise reducing system 20 is housed in the compartment 18. This characteristic has the advantage that it is not necessary to redesign the cab 9 to insert the noise reducing system 20 or the acoustic wave emitter 22 and, in consequence, the noise reducing system 20 can be applied to already existing tracked vehicles 1 as a retrofit.

In one embodiment, not shown in the accompanying figures, the speakers 14b of the radio system 14 define the acoustic wave emitter 22, and the control unit 21 consequently provides the compensation signal SC to the radio system 14. The radio system 14 emits the acoustic equalisation wave via the speaker 14b on the basis of the compensation signal SC received from the control unit 21.

In one embodiment, not shown in the accompanying figures, the cab comprises a door and the acoustic wave emitter is housed in the door.

In one embodiment, not shown in the accompanying figures, the cab comprises a rear panel located behind the driver's seat, with the acoustic wave emitter housed in the rear panel.

Thanks to the present invention, the tracked vehicle 1 offers excellent driving comfort for the driver U, who does not perceive the noise caused by the tracks 3. Furthermore, thanks to the present invention, the noise reducing system 20 can be installed in already existing tracked vehicles 1, thereby increasing comfort for the driver U. This characteristic allows having a system that is easy to install and not having to redesign the entire tracked vehicle 1 when it is found that the tracked vehicle 1 generates noise in the cab 9 that is not bearable by a driver U.

Furthermore, it is evident that the present invention also covers embodiments not described in the detailed description and equivalent embodiments that fall within the scope of the appended claims.