A system for increasing the grip of a vehicle on snow or ice

Abstract

Disclosed herein is a system (1; 10; 30; 40) for increasing the grip of a vehicle on snow or ice, including - a storage unit (2) of a grip promoting agent, - a dispensing unit (4) comprising at least a first and a second injector (6) configured for the injection of said grip promoting agent onto a right tread (RT) and a left tread (LT) of a right wheel (R) and a left wheel (L) of an axle of the motor vehicle, in particular at a position in front of each tread in relation to a direction of travel of the vehicle, - a supplier of the grip promoting agent from the storage unit (2) to the injections (6) of the dispensing unit (4). There is moreover described a method for controlling an intervention of said system.

Description

[0001] A system for increasing the grip of a vehicle on snow or ice

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the Invention

[0004] The present invention refers to systems for assisting the traction in motor vehicles. Specifically, the invention was developed with reference to the assistance to traction on snowy or icy grounds.

[0005] Prior Art

[0006] The Applicant has already developed and proposed anti-aquaplaning systems for vehicles, based on the inj ection of liquid in front of the tread of the front wheels of a motor vehicle, wherein the inj ected liquid is drawn from the tank for windshield washer fluid of the motor vehicle. An example of said systems is described in the Italian Industrial Invention Patent Application n. 102014902296915.

[0007] Remaining in the field of said systems, the Applicant has also proposed diagnostic systems of the contact condition between a tyre and the ground, in the Italian Industrial Invention Patent Applications 102021000017588 and 102022000021216. Said methods are adapted, i. a., to discriminate the type of road surface the vehicle is travelling on.

[0008] As is commonly known, snowy and icy grounds are among the most challenging road surfaces as regards the grip of a motor vehicle. Under given conditions, also the best-equipped vehicle (winter tyres, four-wheel drive, etc. ) may not attain the grip necessary for the start or for maintaining the control of said vehicle. In this respect, it would be desirable to have a system to temporarily create - generally speaking, as a function of the intended manoeuvre - improved grip conditions, particularly when low grip conditions of the vehicle aredetected and / or when the vehicle implements one of the aforementioned methods developed by the Applicant, and when the method deduces the presence of an icy or snowy road surface.

[0009] Obj ect of the Invention

[0010] The invention aims at solving the technical problems outlined in the foregoing. Specifically, the obj ect of the invention consists in temporarily increasing the grip of a vehicle on a snowy or icy road surface, and in implementing the intervention in an effective and repeatable fashion.

[0011] Summary of the Invention

[0012] The obj ect of the invention is achieved by means of a system and a method having the features set forth in the claims that follow, which form an integral part of the technical disclosure provided herein with relation to the invention.

[0013] Brief Description of the Figures

[0014] The invention will now be described with reference to the annexed Figures, which are provided by way of non-limiting example only and wherein:

[0015] - Figure 1 is a schematic representation of a system for increasing the grip according to a first embodiment of the invention,

[0016] - Figures 2 and 3 are sectional representations of a component of the system of Figure 1, in two different operating conditions,

[0017] - Figure 2 is a schematic representation of a system for increasing the grip according to a second embodiment of the invention,

[0018] Figure 5 is a sectional representation of a component of the system of Figure 4,

[0019] - Figure 6 is a sectional representation of a known anti-aquaplaning system developed by the Applicant, - Figure 7 is a schematic representation of a systemfor increasing the grip according to a third embodiment of the invention, comprising in particular a configuration combined with the system of Figure 6, - Figure 8 is a schematic representation of a system for increasing the grip according to a fourth embodiment of the invention, comprising in particular a configuration combined with the system of Figure 6, - Figure 9 is a schematic representation of a system for increasing the grip according to a fifth embodiment of the invention, comprising in particular a configuration combined with the system of Figure 6, and - Figures 10 and 12 show implementation aspects of the method according to the invention.

[0020] Detailed Description

[0021] Reference 1 in Figure 1 generally denotes a system for increasing the grip of a vehicle on snow or ice according to a first embodiment of the invention.

[0022] In the present and in other embodiments, the system 1 includes:

[0023] - a storage unit 2 of a grip promoting agent (in the following, for the sake of brevity, simply denoted as "storage unit 2"),

[0024] - a dispensing unit 4, comprising at least a first and a second inj ector, denoted with the reference 6, and configured for the inj ection of liquid onto the ground at a position in front of, respectively, a right tread RT and a left tread LT of a right wheel R and of a left wheel L of an axle of the motor vehicle,

[0025] - a supplier of the grip promoting agent from the storage unit 2 to the inj ectors 6, which in the embodiment of Figure 1 comprises a propellant within the storage unit 2.

[0026] In each embodiment of the invention, the grip promoting agent comprises one of the following:

[0027] i) PVS, which corresponds to a composite coatingformulation based on water-based polymers, e. g. polyvinyl alcohol (PVA), incorporating silicon nanoparticles having such a grain size as to make the agent sprayable. This sprayable - and thus inj ectable -coating forms a hydrophilic film having nanometric roughness on the tread.

[0028] ii) Wax (es): they comprise natural / synthetic polar solvents. Such a solution may form a sticky and hydrophobic film on the tread surface, which can withstand low temperatures.

[0029] iii) Resin: it comprises natural resin ( for example pine resin) and solvents. It may form a very sticky film on the tread surface, which is adapted to make the snow stick on the tread in order to increase the coefficient of friction and the traction.

[0030] Preferably, each inj ector 6 comprises an electrically actuated valve 8, fluidically connected upstream of an inj ection end thereof, in such a way as to open or close the passage of the flow rate of grip promoting agent through the injector 6 itself. Each electrically actuated valve is configured to selectively enable the transit of grip promoting agent towards the inj ection end of the inj ector 6 (since each valve 8 may be arranged internally to the inj ector 6). Therefore, each valve is adapted to be controlled in such a way as to acquire a closed position, in which the transit is blocked, and an open position in which the transit is enabled.

[0031] Moreover, preferably, the presence of a control unit CU is envisaged, which is configured to transmit and receive a pressure signal SP from a pressure sensor PS arranged downstream of the storage unit 2, a signal S8 for opening or closing of the valves 8 (in the present case, except if the valves admit a closed-loop control, the signal is generally only transmitted by the unitCU). The unit CU is moreover configured to receive and transmit an interface signal SNW from and to a data network of the vehicle, e. g. the CAN network.

[0032] It should be kept in mind that, generally speaking, the dispensing unit 4 is installed at least at a drive axle of the motor vehicle (either the front axle or the rear axle, or even both of them); therefore, it is also possible to instal it at a rear axle, i. e. with the first and the second inj ector 6 being configured to inj ect the grip promoting agent on the right tread and on the left tread of a right wheel and of a left wheel of a rear axle of the motor vehicle and / or of a front axle of the motor vehicle. The inj ection takes place at a position in front of each tread in a direction of forward motion of the vehicle, in such a way as to anticipate the inj ection of the grip promoting agent onto a corresponding portion of the tread, before such portion contacts the road surface. The supplier is configured to deliver a flow rate of grip promoting agent from the storage unit 2 towards each inj ector 6, and the inj ectors 6 are configured to inj ect the respective flow rate of grip promoting agent on the tread LT or RT of the wheel with which they are associated so that, as the rotation continues, the contact between the tread and the ground is mediated by the layer of grip promoting agent inj ected onto the tread, thus creating improved grip conditions which would not be achieved by means of a simple interaction between the tread and the road surface, with no intermediary agent. The inj ectors 6 must not necessarily be actuated in such a way as to inj ect the grip promoting agent at the same time. In other words, the valves 8 are not necessarily switched to the open position at the same time. It is possible to inj ect the grip promoting agent on one tread only, if only the latter is detected to be incurring grip problems.Referring to Figures 2 and 3, in the present embodiment wherein the storage unit 2 of the grip promoting agent includes a pressurised container containing said grip promoting agent, and wherein the supplier includes a pressurised gaseous propellant stored inside said pressurised container, the storage unit 2 is conveniently implemented as a cylinder or spray bottle which is connected by a quick coupling Q to the hydraulic circuit that implements the fluid communication of the storage unit 2 with the inj ectors 6. The quick coupling Q comprises a recess Q1 - which is functionally a female element - provided with an inner thread, and a threaded bushing Q2 provided with an outer thread, engageable with the inner thread of the recess Q1. The threaded bushing Q2 is rigidly connected to the body of the cylinder or spray bottle which defines the storage unit 2.

[0033] Within the bushing Q2 there is arranged a cup element Q3, to which a suction pipe Q4 is attached which extends within the volume of the cylinder or spray bottle which forms the storage unit 2. Within the cup element there is arranged a shutter Q6, which is elastically contrasted by a spring Q7. Figure 2 shows a rest position, wherein the shutter Q6 is kept abutted on a gasket GK, arranged between the cup element Q3 and the bushing Q2, by means of the same spring Q7. A spigot Q8, arranged internally to the recess Q1 and coaxially with an outlet OUT in fluid communication with the injectors 6, partially penetrates within the cup element Q3 and reaches the position shown in Figure 2, which corresponds to a condition preparatory for a stable coupling between the cylinder or spray bottle which defines the storage unit 2 and the recess Q1.

[0034] Referring to Figure 3, when the cylinder or spray bottle which defines the storage unit 2 is coupled withthe recess QI, the spigot Q8 further penetrates in the cup element, displacing the shutter Q3 with respect to the gasket GK, thereby enabling the transit of the grip promoting agent through the outlet OUT, driven by the pressure forces of the propellant which acts as a supplier and which in turn is located within the same cylinder or spray bottle. The grip promoting agent fills the interior of the cup element Q3, and reaches the outlet OUT through an opening with radial axis on the spigot Q8.

[0035] In the present embodiment, the user of the system may refill the reserve of grip promoting agent by simply buying a new pressurised canister or spray bottle to be coupled into the recess Q1. The installation and the removal are extremely simple, since they only involve screwing or unscrewing the bushing Q2 on the canister or spray bottle into or out of the recess Q1.

[0036] Referring to Figure 4 and Figure 5, reference 10 identifies a second embodiment of the system according to the invention. The system 10 is identical to the system 1 with the exception of the storage unit, which in the present case is denoted with the reference 12. Instead of the pressurised container (a cylinder or spray bottle) which defines the storage unit 2, the storage unit 12 includes a cartridge 14 with deformable wall, containing the grip promoting agent and being connected in a separable manner and in fluid communication with an outlet OUT in fluid communication with the inj ectors 6 of the dispensing unit 4. The storage unit 12 moreover comprises an enclosure 16 with rigid wall, which is arranged externally to and which contains the cartridge 14 with deformable wall, so as to define a volume VI 6 therebetween. The enclosure 16 comprises a fluid inlet 18, configured for the inlet of fluid (a gas - for example air - or a liquid) into the volume V16 betweenthe enclosure 16 and the cartridge 14 with deformable wall, and for the deformation of the cartridge by means of the expansion of the volume VI 6 for the ej ection of the grip promoting agent from the cartridge 14 through the outlet (OUT). In the present embodiment, the supplier includes the inlet of fluid into the volume V16 between the enclosure and the cartridge 14 with deformable wall. Preferably, referring to Figure 5, the enclosure 16 may be disassembled, and comprises a cup 16A which is (e. g. threadingly) coupled with a disc 16B on which the outlet OUT is arranged. Within the disc 16B, at a position corresponding to the outlet OUT, the cartridge 14 is applied by means of a guide 14A which is fixed to the cartridge 14 and which comprises a threaded end 14B which engages a corresponding inner thread on the disc 16B. The configuration shown in Figure 5 is also known as "bag in valve", and corresponds to a system wherein the propelling action is provided from the outside (specifically from the outlet 18 ), and wherein the consumable material is stored in a cartridge which is not pressurised. In comparison with the storage unit 2, the storage unit 12 simplifies the replacement of the consumable material and makes it safer, since it eliminates the need of pressurisation. For the rest, the operation completely corresponds to the system 1, the only difference being due to the operation of the supplier, which is not automatic as in the storage unit 2, but requires the delivery of fluid to the volume VI 6 so as to ej ect the grip promoting agent through the outlet OUT.

[0037] However, it is to be noted that the embodiment as per Figures 4 and 5 - i. e. an embodiment which does not require a permanent pressurisation of the tank containing the grip promoting agent, may be implemented also by using a pump as the supplier of the grippromoting agent, which in this case is contained in a first tank. Thus, the pump is configured to draw the grip promoting agent from the first tank and to deliver the grip promoting agent to the inj ectors 6 of the dispensing unit 4.

[0038] The following Figures 6 to 9 show embodiments of the invention wherein the system for increasing the grip of a vehicle on snow or ice according to the invention is combined with an anti-aquaplaning system e. g. as per document 102014902296915. Said anti-aquaplaning system is schematically shown in Figure 6, and it includes a second storage tank (22) for an operating liquid, such as pure water or a mixture of water, a windshield washer fluid and an anti-foaming agent,

[0039] - a pump 24 configured to draw operating liquid from the second storage tank 22 and to deliver the operating liquid to a respective dispensing unit comprising at least a third inj ector and a fourth inj ector - both denoted with reference 26 - configured to inj ect liquid towards the ground G at a position in front of, respectively, a right tread RT and a left tread LT of a right wheel R and a left wheel L of the same axle of the motor vehicle to which the inj ectors 6 of the system according to the invention for increasing the vehicle grip on snow or ice are associated. Preferably, a storage tank 28 is arranged branched with respect to the discharge of the pump 24.

[0040] Similarly to the dispensing unit 4, upstream of each inj ector 26 - specifically upstream of an inj ection end thereof - there is arranged an electrically actuated valve 29 which controls the transit of operating liquid through the inj ection end of the corresponding inj ector 26. In the same way as the valves 8, the valves 29 are configured to selectively enable the transit of operating liquid towards the inj ection end of theinj ector 26 (since each valve 29 may be arranged inside the inj ector 26). Therefore, each valve 29 may be controlled so as to acquire a closed position, in which the transit is blocked, and an open position, in which the transit is enabled.

[0041] In such embodiments, which feature a combination of the system for increasing the grip on snow or ice and of the anti-aquaplaning system 20, the pump 24 of the antiaquaplaning system 20 also performs the function of supplying the system for increasing the grip of the vehicle on snow or ice.

[0042] Generally speaking, the connection between the hydraulic circuits of the anti-aquaplaning system and of the system for increasing the grip of the vehicle on snow or ice according to the invention will be described with reference to the following Figures 7 to 9.

[0043] Referring to Figure 7, reference 30 denotes a third embodiment of the system for increasing the grip according to the invention, hydraulically connected to the anti-aquaplaning system 20. The system 30 is identical to the systems 1, 10, but the storage unit includes a first tank 32 containing the grip promoting agent. The circuit also comprises a second tank 22 containing the operating liquid of the anti-aquaplaning system 20, wherein the tanks 20 and 32 are separated tanks in fluid communication with a suction port of the pump 24 through a first selection valve 24 / 1 configured to alternately enable a drawing of grip promoting agent from the first tank 32 by the pump 24, in a first operating condition, and a drawing of operating liquid from the second tank 22 by the pump 24, in a second operating condition. A second selection valve 24 / 2 is configured to alternately enable a discharge of grip promoting agent towards the inj ectors 6 of the system 30 for increasing the vehicle grip on snow or ice, when thefirst selection valve 24 / 1 is in the first operating condition, and a discharge of operating liquid towards the injectors 26 of the anti-aquaplaning system 20, when the first selection valve 24 / 1 is in the second operating condition. Optionally, a storage tank 36 may be installed branched from the hydraulic line extending from the valve V24 / 2 to the dispensing unit 4.

[0044] Referring to Figure 8, reference 40 denotes a fourth embodiment of the system for increasing the grip according to the invention, hydraulically connected to the anti-aquaplaning system 20. The system 40 is identical to the system 30, except for the fact that the first tank 32 containing the grip promoting agent and the second tank 22 containing the operating liquid of the anti-aquaplaning system 20 are one and the same tank (therefore, the reference now becomes 22+32 ), and the grip promoting agent also performs the function of (and therefore is) the operating liquid of the antiaquaplaning system 20. For this reason, there is only one selection valve V24 (instead of the valves V24 / 1 and V24 / 2 ) arranged downstream of the discharge port of the pump 24, for alternately supplying the grip promoting agent to the injectors 6 of the system 40, in a first operating condition, and to the injectors 26 of the antiaquaplaning system 20, in a second operating condition.

[0045] Referring to Figure 9, it shows a further combination of the system according to the invention with the anti-aquaplaning system 20, which in the present instance is based on the system 10. In the present embodiment, the hydraulic connection with the antiaquaplaning system 20 is implemented only with a driving function: specifically, downstream of the discharge of the pump 24 there is arranged a three-way valve V12 comprising an inlet in fluid communication with the discharge of the pump 24, a first outlet in fluidcommunication with the injectors 26 of the system 20, and a second outlet which can be selectively opened for the transit of the operating liquid delivered to the discharge of the pump 24, and which is in fluid communication with the inlet 18 on the enclosure 16. In other words, the selection valve V12 is configured to supply the operating liquid to the injectors 28 of the anti-aquaplaning system in a first operating condition, and to the fluid inlet port 18 of the enclosure 16 with rigid walls of the storage unit 12. The supply to the two users may be exclusive (either the one or the other) or may envisage a combination (both the one and the other). In the present embodiment, the flow rate processed by the pump 24 and delivered to the storage unit 12 serves the only purpose of ejecting the grip promoting agent from the cartridge 14 towards the injectors 6. In the embodiments relating to the systems of Figures 7 and 8, it is to be noted that the respective ej ection pressures of the grip promoting agent and of the anti-aquaplaning liquid will be different; therefore, the circuit will require the presence of a pressure relief valve, specifically in order to limit the pressure within the system 30, 40, since the inj ection pressure of the inj ectors of the antiaquaplaning system 20 (approx. 140 bar) is significantly higher than the injection pressure (few bars) with which the system 30, 40 operates.

[0046] The operation of the system 1, 10, 30, 40 according to the invention will now be further described with reference to Figures 10, 11, 12 which show, by way of example, an intervention of the system 1, 10, 30, 40 in conditions of a start from standstill of the vehicle with low or no grip on at least one drive wheel ( for the sake of simplicity, the instance of a front-wheel drive will be taken into consideration). The wheels of thevehicle are identified by the references FL ( front left), FR ( front right), RL (rear left) and RR (rear right).

[0047] Whatever the embodiment of the present invention under consideration, the invention defines a method for activating the system for increasing the grip 1, 10, 30, 40 (considered individually or in combination with the anti-aquaplaning system 20) which includes:

[0048] - receiving information of the presence of snow or ice on the ground G on which the vehicle is located - verifying whether a rotational speed of one or more wheels of the vehicle is compatible with a speed of advancement VS of said vehicle V and / or with an evolution of the speed of advancement VS of said vehicle V,

[0049] - activating the system for increasing the grip 1, 10, 30, 40 by commanding, with respect to each wheel for which an incompatibility is detected between the rotational speed and the speed of advancement VS of the vehicle V and / or the evolution of the speed of advancement VS of the vehicle V, an injection of grip promoting agent towards the respective tread for a time dependent on the rotational speed itself.

[0050] In more detail, verifying whether the rotational speed ωFL, ωFR, ωRL, ωRR of one or more wheels FL, FR, RL, RR of the vehicle is compatible with a speed of advancement VS and / or with the evolution of the speed of advancement (VS) of the vehicle itself includes:

[0051] - verifying whether the value of rotational speed ωFL, ωFR, ωRL, ωRR of one or more drive wheels FL, FR, RL, RR of the vehicle is different from a zero value when the speed of advancement VS of the vehicle V has a zero value,

[0052] - verifying whether the rotational speed (ωFL, ωFR, ωRL, ωRR) of one or more wheels (FL, FR, RL, RR) of the vehicle and / or a rate of time evolution of the rotational speed ωFL, ωFR, ωRL, ωRR of one or more wheels FL, FR,RL, RR of the vehicle is compatible with a rate of time evolution of the speed of advancement VS of the vehicle V (i. e. with an acceleration of the vehicle).

[0053] Such aspects will be detailed in the following with reference to the manoeuvre exemplified in Figures 10 to 12.

[0054] As described in the foregoing, the activation of the intervention of the system according to the invention is determined by an item of information coming from external control logics, which item of information is available on a data network of the vehicle and indicates the presence of snow or ice on the ground G on which the vehicle is located. By way of example only, such an item of information may derive from the set of the following conditions (whereof the last condition may be considered as optional, since it is connected with the movement of the vehicle, and as such it cannot be used in the case - for example - of an intervention of the system 1, 10, 30, 40 according to the invention with the vehicle starting from a standstill).

[0055] A first condition, which will be denoted as Cl in the following, corresponds to a temperature of the external environment equal to or lower than 0°C. A second condition, denoted as C2 in the following, corresponds to an item of information about the colour of the road surface, specifically a frequency of the light reflected by the road surface and acquired by a camera on board the vehicle ( for example a camera belonging to an ADAS (Advanced Driver Assistance System) ). Snow and ice emit reflected light within a given frequency band, and therefore the presence thereof on the road surface may be ascertained easily and conveniently.

[0056] A third condition, which however may be ascertained only if the vehicle V is in motion, corresponds to one of the deductions of the diagnostic process of theinteraction condition between the wheel and the ground as described in the Italian Industrial Invention Patent Applications 102021000017588 and 102022000021216 in the name of the same Applicant. Such methods are adapted to discriminate the type of ground on which the vehicle is driving (see for example Figures 14 and 15 of the 102021000017588 Application, and the related description) as a function of an additional force acting on the vehicle, of an estimate of the coefficient of friction and of the slipping of the wheels.

[0057] Considering the manoeuvre schematically shown in Figures 10 to 12, which corresponds to a start from standstill, the evolution thereof starts in the condition shown in Figure 9, wherein the speed of advancement VS of the vehicle is zero (VS = 0), and the same is true for the rotational speeds ωFL, ωRL, ωRR of the wheels FL, RR, LR, whereas the rotational speed ωFR is greater than zero. The vehicle has a front-wheel drive, and thus the drive wheels are FR and FL. Moreover, it is assumed that the conditions Cl and C2 are verified, and thus the environmental temperature is equal to or lower than 0°C, and the light reflected by the ground G is within the frequency interval which is associated with snow or ice. This means that the wheel FR is slipping, due to a lack of grip deriving from the presence of snow or ice on the ground G. In such conditions, in the method according to the invention, the angular speed ωFR must be considered as incompatible with the speed of advancement VS of the vehicle, because if it were compatible also the angular speed ωFR would be zero.

[0058] As a consequence, the system 1, 10, 30, 40 is activated, preferably by inj ecting the grip promoting agent only towards the tread of the wheel FR. This takes place by opening the valve 8 upstream of thecorresponding inj ector 6 for a time t sufficient to cover the whole surface of the tread. Specifically, the time t is determined based on the relation: t = k·(2π / ω), wherein:

[0059] ω is the rotational speed of the wheel

[0060] k is a constant of calibration depending on the ejection characteristics of the grip promoting agent in each of the systems 1, 10, 30, 40. Indeed, it may be necessary to apply the grip promoting agent for a time t longer than would be necessary to cover a single revolution of the tread, in such a way as to increase the thickness of the applied substance.

[0061] This leads to the condition shown in Figure 11, wherein the wheel FR has recovered grip thanks to the grip promoting agent injected by the system 1, 10, 30, 40, and the rotational speed ωFR has fallen to zero. However, this has led to an increase of the torque requested by the wheel FR and, given the presence of a differential connecting the wheels FR and FL, this also leads to an increase of the torque which is transmitted to the wheel FL. This increase may temporarily cause a grip loss of the wheel FL, such condition being shown in Figure 11 wherein the speed of advancement VS of the vehicle is zero (VS = 0), and the same is true for the rotational speeds ωFR, ωRL, ωRR of the wheels FR, RR, LR, whereas the rotational speed ωFL is greater than zero. In such conditions, in the method according to the invention, the angular speed ωFL is to be considered incompatible with the speed of advancement of the vehicle VS, since if it were compatible also the angular speed ωFL would be equal to zero. The system 1, 10, 30, 40 is therefore activated, preferably by injecting the grip promoting agent only towards the tread of the wheel FL (in this case, the time t is calculated as a function of ωFL). This restores the grip of the wheel FL inconditions of a torque transmitted to the wheels FL and FR which has already increased since the former grip restoration of the wheel FR. Therefore, the vehicle V has grip and torque sufficient to start moving, thus reaching the condition of Figure 12 wherein ωFR, ωFL, ωRR, ωRL are all greater than zero, in the same way as VS, and are all compatible with VS (thus, the slip value of each wheel is minimum or zero).

[0062] While further exemplifying the method according to the invention, the case will be considered of a braking manoeuvre with an excessive stopping distance, due to the grip loss of one or more wheels on snow or ice. In this case, the wheels losing grip are not necessarily the drive wheels, since the braking dynamics depends more on the weight distribution and on the load transfer of the vehicle.

[0063] In order to determine the need of an intervention event of the system 1, 10, 30, 40 in such conditions, it is necessary to proceed to additional verifications beside the conditions Cl, C2, C3 (which in the present case are always verified, since the vehicle is moving). Specifically, a braking manoeuvre with an excessive stopping distance may be identified by verifying the following further conditions:

[0064] Condition C4: activation of a brake pedal (a condition which may be defined as a function of a pressure threshold in the braking system or of a position threshold of the brake pedal)

[0065] Condition C5: VS > 0 (also in this case it is possible to define a speed interval wherein the activation of the system 1, 10, 30, 40 may be requested, e. g. if VS is comprised between 10 and 50 Km / h, whereas above 50 Km / h the system 1, 10, 30, 40 may be deactivated with a subsequent warning to the driver).

[0066] Condition C6: the rate of time evolution of thespeed of advancement VS is lower than an expected rate of time evolution (i. e., the deceleration of the vehicle is lower than expected, which can be defined in combination with the pressure exerted on the brake pedal, due to grip loss).

[0067] If all conditions C1-C6 are verified, the invention envisages a measurement of the average rotational speed of the front wheels ωFL and ωFR and, based on the respective values, the respective activation times t_FL (for the front left wheel) and t_FR (for the front right wheel) are established according to the relation set forth in the foregoing, thus

[0068] t_FL = k·(2π / ωFL)

[0069] t_FR = k·(2π / ωFR)

[0070] Preferably, as regards the braking manoeuvres, the constant of calibration k is mapped differently with respect to the manoeuvres of a start from a standstill, in such a way as to compensate for the effects of the events which take place during the braking manoeuvre itself. In more detail, the mapping of the constant k for the braking manoeuvres aims at ensuring the application of a desired thickness of grip promoting agent on one or more treads, taking into account that the anti-lock braking system ABS will tend to cause an oscillation of the rotational speed of the wheels. Moreover, it should be noted that, during a braking manoeuvre, the intervention may be extended to nondriving wheels, for example in order to limit yaw events with car drifting.

[0071] Thanks to the system 1, 10, 30, 40 and the method according to the invention it is therefore possible to temporarily increase the grip of a vehicle on a snowy or icy road surface, and to implement the intervention inan effective and repeatable manner. Moreover, the possibility is given of a synergistic integration with an anti-aquaplaning system, thereby achieving a full driving safety in any condition of the road surface.

[0072] Of course, the implementation details and the embodiments may amply vary with respect to what has been described and illustrated herein, without departing from the extent of the present invention as defined in the annexed claims.

Claims

CLAIMS1. A system ( 1; 10; 30; 40) for increasing the grip of a vehicle on snow or ice, including- a storage unit (2 ) of a grip promoting agent, - a dispensing unit (4) comprising at least a first and a second injector (6) configured for the injection of said grip promoting agent onto a right tread RT and a left tread LT of a right wheel R and a left wheel L of an axle of a motor vehicle, in particular in front of each tread in relation to a direction of travel of the vehicle,- a supplier of the grip promoting agent from the storage group (2) to the injectors (6) of the dispensing unit (4).

2. The system ( 1 ) according to claim 1, wherein said storage group includes a pressurised container containing said grip promoting agent, and wherein said supplier includes a pressurised gaseous propellant stored inside said pressurised container.

3. The system ( 10) according to claim 1, wherein said storage unit includes a cartridge with deformable wall containing said grip promoting agent and connected in a separable manner and in fluid communication with an outlet (OUT) of the injectors (6) of the dispensing unit (4), and further includes a enclosure with rigid wall arranged externally to and containing said cartridge with deformable wall so as to define a volume therebetween, the enclosure comprising a fluid inlet configured for the inlet of fluid into the volume between the enclosure and the cartridge with deformable wall and for the deformation of the cartridge by expansion of said volume for the ejection of said agent from the cartridge through said outlet (OUT),said supplier including the inlet of fluid into the volume between the enclosure and the cartridge withdeformable wall.

4. The system (30) according to claim 1, wherein said storage unit includes a first tank (32; 22+32 ) containing that grip promoting agent, and wherein said supplier includes a pump (24 ) configured to draw said grip promoting agent from said tank (32; 22+32 ) and to deliver said grip promoting agent to the injectors of said dispensing unit.

5. The system (30) according to any of the preceding claims, including in combination an antiaquaplaning system including:- a second storage tank for an operating liquid (22 )- a pump (24 ) configured to draw operating liquid from said second storage tank, and- a respective dispensing unit (28, 29) comprising at least a third and a fourth injectors (28) configured for the injection of liquid towards the ground (G) at a position in front of, respectively, a right tread (RT) and a left tread (LT) of a right wheel (R) and a left wheel (L) of the same axle of the motor vehicle to which the injectors of the system (30) for increasing the vehicle grip on snow or ice are associated,wherein the pump (24 ) of the anti-aquaplaning system (20) provides the supplier of the system (30) for increasing the grip of the vehicle on snow or ice.

6. The system (30) according to claim 5, wherein the first tank (32 ) containing the grip promoting agent and the second tank (22 ) containing the operating fluid of the anti-aquaplaning system (20) are separate tanks in fluid communication with a suction port of said pump (24 ) by means of a first selection valve (24 / 1 ) configured to alternatively enable a drawing of grip promoting agent from the first tank (32 ) by said pump (24 ) in a first operating condition and a drawing ofoperating fluid from the second tank (22 ) by said pump (24 ) in a second operating condition, and wherein a second selection valve (24 / 2 ) is also configured to alternately enable a delivery of grip promoting agent to the injectors (6) of the system (30) for increasing the vehicle grip on snow or ice when the first selection valve (24 / 1) is in the first operating condition and a delivery of operating fluid to the injectors (26) of the anti-aquaplaning system (20) when the first selection valve (24 / 1) is in the second operating condition.

7. The system (40) according to claim 5, wherein the first tank (32 ) containing the grip promoting agent and the second tank (22 ) containing the operating liquid of the anti-aquaplaning system (20) are the same tank, and in wherein said grip promoting agent is said operating liquid of the anti-aquaplaning system,and further wherein a selection valve is arranged downstream of a discharge port of said pump (24 ) to alternately supply the grip promoting agent to the injectors (6) of the system (40) for increasing the vehicle grip on snow or ice in a first operating condition, and to the injectors (28) of the antiaquaplaning system in a second operating condition.

8. The system ( 10) according to claim 5, comprising a selection valve (V12 ) downstream of a discharge port of said pump (24 ) to alternately supply the operating fluid to the injectors (28) of the anti-aquaplaning system in a first operating condition, and to the fluid inlet of the enclosure with rigid wall of the storage unit ( 12 ) of the system ( 10) for increasing the vehicle grip on snow or ice.

9. A method for the activation of a system ( 1; 10; 30; 40) for increasing the grip of the vehicle on snow or ice according to any of the above claims, including:- receiving information (Cl, C2, C3) of snow or iceon the ground (G) on which the vehicle is located- verifying whether a rotational speed (wFL, wFR, wRL, wRR) of one or more wheels (FL, FR, RL, RR) of the vehicle is compatible with a speed of advancement (VS) of the vehicle itself and / or with an evolution of the speed of advancement (VS) of the vehicle itself,- activating the system for increasing the vehicle grip (1, 10, 30, 40) by commanding, with respect to each wheel (FL, FR, RL, RR) for which an incompatibility is detected between the rotational speed (ωFL, ωFR, ωRL, ωRR) and the speed of advancement of the vehicle (VS) and / or the evolution of the speed of advancement of the vehicle, an injection of grip promoting agent towards the respective tread for a time (T) dependent on the rotational speed (ωFL, ωFR, ωRL, ωRR) itself.

10. The method according to claim 9, wherein said verifying whether the rotational speed (ωFL, ωFR, ωRL, ωRR) of one or more wheels (FL, FR, RL, RR) of the vehicle is compatible with a speed of advancement (VS) of the vehicle itself includes:- verifying whether the rotational speed (ωFL, ωFR, ωRL, ωRR) of one or more drive wheels (FL, FR, RL, RR) of the vehicle is different from a zero value when the speed of advancement of the vehicle has a zero value, - verifying whether the rotational speed (ωFL, ωFR, ωRL, ωRR) of one or more wheels (FL, FR, RL, RR) of the vehicle and / or a rate of time evolution of the rotational speed (ωFL, ωFR, ωRL, ωRR) of one or more wheels (FL, FR, RL, RR) of the vehicle is compatible with a rate of time evolution of the vehicle speed of advancement.

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