Method for adjusting the air pressure in a vehicle wheel

Abstract

The method involves adjusting the air pressure in a wheel having : a rim (5); a tyre (6) defining, together with the rim (5), a chamber (7) of air that can be pressurized; a compressor (21) having an inlet and an outlet; a reservoir (22) carried by the rim (5), pneumatically connected to the outlet to receive compressed air from the compressor (21) and to the chamber (7) to transfer air to the chamber (7); and a battery (24) to supply electric power; the method involves adjusting the pressure in the chamber (7) by flows of air from the chamber (7) to the reservoir (22) and vice versa, in response to a signal indicative of the air pressure in the chamber (7) to achieve a reference value; the reference value is defined as a function of the grip conditions of the wheel (3), which are estimated using a weather map and a geolocation system, at least when the vehicle (1) is in motion.

Description

[0001] "METHOD FOR ADJUSTING THE AIR PRESSURE IN A VEHICLE WHEEL"

[0002] DESCRIPTION

[0003] TECHNICAL SECTOR

[0004] This invention relates to a method for adj usting air pressure in a vehicle wheel .

[0005] In particular, this invention relates to a vehicle in which the wheel has a power supply battery, a reservoir, a motorised compressor for trans ferring air into this reservoir, and an adj ustment valve that is controlled so as to manage an air flow from the reservoir to the chamber defined by the tyre .

[0006] PRIOR ART

[0007] In order to adj ust the internal pressure in tyres , solutions are known with a centralised on-vehicle architecture having a single reservoir and a single compressor, controlled by a special control unit to be activated and feed compressed air into this reservoir . The reservoir is then connected to the wheels via respective conduits fitted with valves , which are also controlled by the above-mentioned control unit to adj ust the flow of compressed air : these valves are switched to inflate the tyre or discharge air from it to the outside environment .

[0008] In addition, another valve pneumatically connects the compressor to the reservoir so that the two components can be isolated when required .

[0009] Compared to this type of centralised solution, it is preferable to adopt inflation and deflation systems that are arranged directly on the wheel , to reduce the number of components , reduce the space required on board the vehicle , and avoid passages of compressed air between a fixed part , that is , the vehicle body, and a rotating part , that is , the wheel .

[0010] In the context of these decentralised solutions , document EP0621144 discloses an example where a two-way compressor is provided on the wheel , which trans fers air between the air chamber in the tyre and an additional annular chamber, integrated in the wheel rim and defining a reservoir for storing air . Another example disclosed by EP0621144 involves the use of a one-way compressor and an additional pneumatic line , which connects the tyre ' s air chamber with the rim ' s integrated annular reservoir, in parallel with the compressor . A valve then manages the passage of air through this line to inflate the tyre . In both these solutions , to adj ust the pressure in the tyre , air is exchanged between the air chamber and the reservoir integrated into the rim, without contamination by external air .

[0011] There is a need to perfect this type of solution in order to guarantee optimal grip conditions for the wheels when the vehicle is in motion . In this context, it is necessary to take into account that the grip conditions may change as a function of variations in the load on the vehicle, especially when these variations are comparatively large.

[0012] In particular, there is a need to find a solution that is versatile, that is, suitable for different types of vehicles, such as goods vehicles, which may be subject to significant load variations (for example, from empty to a full load) .

[0013] At the same time, as is well known, the grip conditions also tend to vary depending on road conditions, for example between dry and wet road surface conditions. Therefore, there is a need to adapt the internal pressure of the tyres to these conditions, so that any increase in pressure set as a result of an increase in load being detected is not detrimental to the safety of the vehicle while driving.

[0014] More generally, there is a need to refine the known solutions, trying to take into account a number of factors that may occur in actual driving conditions.

[0015] One purpose of this invention is, thus, that of meeting the need described above, preferably in a simple and / or effective and / or cost-effective way.

[0016] SUMMARY OF THE INVENTION

[0017] The aforementioned purpose is achieved with the method for adjusting air pressure in a vehicle wheel as defined in claim 1 .

[0018] The dependent claims define particular embodiments of the invention .

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a better understanding of this invention, preferred embodiments will be described below, by way of non- limiting example , with reference to the accompanying drawings , wherein :

[0021] - Figure 1 is a schematic view from above of a vehicle according to this invention;

[0022] - Figure 2 shows , in perspective and with parts removed for clarity, a wheel of the vehicle in Figure 1 ;

[0023] - Figure 3 is a radial direction view of the wheel in Figure 2 ;

[0024] - Figures 4 and 5 are diagrams relating to the operation of a system that is provided on the wheel , to adj ust the air pressure in the wheel itsel f ;

[0025] - Figure 6 illustrates graphs of an operating example , in which the air pressure inside the wheel is adj usted by taking into account the vertical load on the wheel detected by a sensor ;

[0026] - Figure 7 illustrates a control logic of the adj ustment method according to the precepts of this invention;

[0027] - Figure 8 illustrates graphs of an additional operating example , in which the air pressure inside the wheel is adj usted by taking into account the vertical load detected on the wheel , according to the precepts of this invention; and

[0028] - Figure 9 illustrates a logic for estimating wheel grip conditions according to the precepts of this invention .

[0029] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0030] In Figure 1 , the reference number 1 indicates a vehicle as a whole . The vehicle 1 has a chassis 2 and four wheels 3 , connected to the chassis 2 via respective suspensions 4 .

[0031] The vehicle 1 also has a control unit 25 . The control unit 25 is , for example , a microprocessor . According to the preferred embodiment illustrated, the control unit 25 is arranged on the wheel 3 .

[0032] With reference to Figures 2 and 3 , the wheel 3 has an axis 17 , coinciding, in use , with its rotation axis , and comprises a rim 5 and a tyre 6 ( illustrated in dashed lines and in a simpli fied way) , fitted on the rim 5 so as to define , together with the latter, a chamber 7 that is filled with air and can be pressuri zed from the outside through a valve 14 . The valve 14 , a known type , is general ly brought to a relative fixed position by the rim 5 .

[0033] In particular, the rim 5 has an outer annular wall 16 , which radially delimits the chamber 7 and is shaped to comprise an intermediate portion 8 and two shoulders 9 arranged at oppos ite axial ends of the rim 5 . These shoulders 9 protrude radially outwards from the intermediate portion 8 ; furthermore , at the shoulders 9 , the wall 16 defines two concave areas 10 that are shaped so as to couple the tyre 6 beads , in a sealed manner, according to shapes and techniques that are known and not described in detail . In addition, again according to configurations that are already known, the intermediate portion 8 of the wall 16 is shaped so as to define an annular channel 11 , forming part of the chamber 7 and connected to the areas 10 via respective portions 12 and 13 of the wall 16 . In particular, the portion 13 has a flared shape , for example a truncated cone shape , which diverges from the channel 11 towards the corresponding axial end of the rim 5 ; more speci fically, the portion 12 has a smaller axial extension than the portion 13 ; in use , the portion 13 is axially facing the body of the vehicle 1 on which the wheel 3 is mounted, while the portion 12 is axially facing the outside of the vehicle 1 , that is , towards an axial end of the rim 5 provided with spokes 15 .

[0034] According to one aspect of this invention, the wheel 3 comprises a system 20 for adj usting the pressure in the chamber 7 automatically, to keep it as close as possible to a predetermined reference value ( setpoint ) during use ( that is , during vehicle 1 travel ) .

[0035] The system 20 is supported on the wheel 3 and rotates together with the rim 5 around the axis 17 during use .

[0036] The system 20 comprises at least one motorised compressor 21 , at least one reservoir 22 defining at least one chamber with a substantially fixed volume , separated from the chamber 7 and the external environment ; and at least one battery 24 for supplying electric power to the electric motor of the compressor 21 .

[0037] According to one aspect of this invention, for the individual wheel 3 , the control unit 25 controls the electric motor in response to command signals emitted wirelessly by an emitter (not illustrated) placed in a fixed position on board the vehicle 1 , and / or in response to operations performed by a control strategy stored in a memory forming part of the same control unit 25 .

[0038] The architecture illustrated by Figures 1 , 2 and 3 is , therefore , decentralised, as the system 20 is mounted on each of the wheels 3 of the vehicle 1 and has no pneumatic and / or electrical connections to the fixed parts of the vehicle 1 .

[0039] Speci fically, the control unit 25 is configured to drive the compressor 21 motor and then activate the latter, for example in response to a control signal and / or a reference signal provided by the instrument panel of the vehicle 1 , to send pressurised air from the chamber 7 to the reservoir 22 , but not vice versa . According to a preferred embodiment , the compressor 21 is actually one-way, that is , it is constructed and assembled so that it can only convey a flow of air in one direction ( from the chamber 7 to the reservoir 22 ) .

[0040] The system 20 also comprises a solenoid valve , shown in Figure 3 in a simpli fied manner with the reference number 26 , which switches under the control of the control unit 25 between a closed and an open configuration, in order to allow a flow of air from the reservoir 22 to the chamber 7 , that is , in the opposite direction to that imposed by the compressor 21 .

[0041] In other words , the control unit 25 controls the compressor 21 and the solenoid valve 26 to adj ust the pressure in the chamber 7 by making air flow from the chamber 7 to the reservoir 22 and vice versa, in response to a pressure signal indicating the air pressure in the chamber 7 to reach the reference value mentioned above .

[0042] In order to detect the air pressure within the chamber 7 , the system 20 comprises a pressure sensor . The pressure sensor can be of a known type , usually referred to as a TPMS and usually installed at the valve 14 . The control unit 25 interacts with this sensor to receive readings of the pressure values inside the chamber 7 . In particular, the control unit 25 , being arranged on the wheel 3 , communicates with the sensor wirelessly or in wired mode . According to one embodiment of this invention, the vehicle 1 has a respective sensor 29 connected with each wheel 3 . Each sensor 29 is a known sensor ( therefore , it will not be described in detail below) configured to measure , directly or indirectly, the vertical load acting on the corresponding wheel 3 .

[0043] In particular, the sensor 29 is configured to detect the vertical load acting on the wheel 3 , at least when the vehicle 1 is in motion . Advantageously, the sensor 29 is placed at the suspension 4 , which connects the wheel 3 to the chassis 2 of the vehicle 1 . For example , considering a spring suspension and a shock absorber, the sensor 29 is a known sensor that measures the spring deformation or travel or the shock absorber travel to then determine the vertical load acting on the suspension .

[0044] Being positioned on the suspension, the sensor 29 is preferably connected wirelessly to communicate with the control unit 25 , preferably arranged on the edge of the wheel , as schematically shown in Figure 3 with a dotted arrow . Alternatively or in combination with this connection, the sensor 29 is connected to communicate with an electronic control unit on board the vehicle , which is fixed and centralised, that is , in common for all wheels o f the same vehicle 1 .

[0045] According to one aspect of this invention, the electronic control unit 25 (or the centralised electronic unit) is configured to receive, from the sensor 29, an input signal indicating the detected vertical load, and vary the reference value according to the input signal.

[0046] In other words, the electronic control unit 25 adj usts / determines the pressure setpoint, depending on the vertical load acting on the wheel 3.

[0047] The control logics implemented in the electronic control unit 25 (and / or the control signals coming from the control unit fixed on board the vehicle 1) are configured so as to inflate and deflate the chamber 7, that is, to adjust the air pressure inside it, with such quantities / pressures of air that optimise grip to the ground during use, depending also on the type of ground or according to a driver's command that indicates this type (for example, on mud or sand the pressure should be reduced, while on asphalt the pressure should be greater to reduce rolling resistance) .

[0048] As mentioned above, the air in the chamber 7, previously supplied from outside through the valve 14, is pumped by the compressor 21 and transferred to the reservoir 22 in order to reduce the pressure, that is, to deflate the tyre 6, as shown in Figure 4.

[0049] Similarly, by controlling the solenoid valve 26 that is placed at the outlet of the reservoir 22, a flow of air can pass from that reservoir 22 (at a higher pressure) to the chamber 7 ( at a lower pressure ) , and thus the pressure in the chamber 7 increases . : In other words , the tyre 6 is inflated, as shown in Figure 5 .

[0050] The microprocessor 25 is preferably configured with appropriate control logics to carry out diagnostics of the whole system 20 and then transmit information relating to any mal functions and / or information relating to adj ustment and stand-by steps between two successive adj ustments to the electronic control unit on board the vehicle 1 ( and then to the instrument panel in the passenger compartment ) .

[0051] The system 20 also comprises a device (not shown) for recharging the battery 24 . In particular, this device is of the induction type and / or is arranged on an external surface of the wheel 3 to be coupled to the mains power supply, or to a vehicle 1 power supply device ( for example , a cigarette lighter device ) , only when the vehicle 1 is stationary . Other charging systems can still be envisaged, for example by using the very rotation of the wheel 3 to generate power for the battery 24 .

[0052] I f the vehicle 1 is equipped with a conventional tyre 6 repair kit in the event of a puncture , the components of the system 20 must be appropriately chosen to be compatible with the chemicals ( for example , a mixture of water, latex and ethylene glycol ) used in such repair kits .

[0053] With reference to the graphs in Figures 4 and 5 , mentioned above, the pressure in the reservoir 22 increases more than the pressure in the chamber 7 decreases, with the same amount of air entering and respectively leaving, because the volumes in the reservoir 22 are smaller than in the chamber 7, and the pressure in the reservoir 22 is much higher than that in the chamber 7.

[0054] Figure 4 shows what happens during deflation: in the first graph starting from the top, it can be seen that the pressure in the chamber 7 decreases, for example from 3 bar to 1.5 bar, while the pressure in the reservoir 22 (third graph) increases, for example from 3 bar to 20 bar, that is, to a relatively high value. This happens when the compressor 21 is driven (second graph) , as mentioned above. At the same time, the solenoid valve 26 remains in an inactive condition, that is, closed (fourth graph) .

[0055] Therefore, the compressed air from the compressor 21 preferably reaches the reservoir 22 without switching any valves, but just by actuating the compressor 21.

[0056] During inflation, as shown in the first graph from the top in Figure 5, it can be seen that the pressure in the chamber 7 increases to the desired setpoint, for example 3 bar, due to the flow from the reservoir 22. At the same time, the compressor 21 remains switched off (second graph in Figure 5) and the reservoir 22 pressure (third graph) decreases, for example from 20 bar to 3 bar. Returning to the control logics , it should be repeated that these are implemented either in the microprocessor 25 or in a fixed control unit , on board the vehicle 1 , communicating with the microprocessor 25 wirelessly, as mentioned above .

[0057] These control logics , when executed, are configured to adj ust the pressure in the chamber 7 in response to a pressure signal provided by the above-mentioned pressure sensor and reach a pre-set reference value ( setpoint ) . This reference value can also be defined, i f necessary, on the basis of the vehicle 1 and / or road conditions .

[0058] In addition, as mentioned above , pressure regulation in the chamber 7 is preferably also performed in response to the vertical load signal provided by the sensor 29 by adj usting the reference value or pressure setpoint .

[0059] Advantageously, the change in the reference value , in response to the load changes detected by the sensors 29 , only occurs when the vehicle is in motion, for example at a speed above a given threshold value , greater than zero .

[0060] In this way, at low speeds ( that is , manoeuvring speeds where grip is of little importance ) or when the vehicle is stationary, when loading and unloading can take place , the pressure setpoint remains constant and, therefore , there is no adj ustment .

[0061] In addition, the control strategies are calibrated so as to intervene by changing the pressure setpoint only if the detected load variation (compared to a previously measured value) is greater than a given deviation or tolerance (possibly set as a percentage of the vehicle's maximum load value) , for example considered relevant to the grip conditions. This avoids irrelevant or negligible interventions of the system 20 and, thus, reduces the overall number of compressor 21 starts.

[0062] In addition, the vehicle 1 preferably comprises control (or consensus) means, indicated in the diagram in Figure 7 by reference number 30, which are manually operable and, when activated, enable and disable the system 20, that is, the variation of the reference value as a function of the load. In other words, the driver can activate the system 20 for pressure regulation via, for example, a switch in the instrument panel.

[0063] A control logic implemented in the electronic control unit 25, and illustrated schematically by the diagram in Figure 7, preferably provides input (for example, from the driver) via the control means 30, which cause the activation (enabling) or deactivation (disabling) of the system 20 for pressure adjustment. If the system 20 is switched on (output V at block 31) , and if the vehicle is switched on and is moving above a given speed, preferably greater than zero, that is, in "running" mode (output V at block 32) , a check is then done that at least one intervention condition is fulfilled (block 34) , in particular:

[0064] - if the load variation detected by the sensors 29 exceeds a given tolerance / threshold / displacement (for example, 50 kg per wheel) , as described above; and

[0065] - if this load variation persists for longer than a given interval (for example 10 seconds) .

[0066] If this intervention condition is actually met, then a new pressure setpoint is set corresponding to the new load detected (block 35) , whereby the system 20 commands a pressure change in the chamber 7 to reach the new setpoint (block 36) .

[0067] As long as the system 20 is active and the vehicle is on and moving, the load conditions are continuously monitored, so the cycle described above for blocks 34, 35, 36 is repeated.

[0068] In the event that the vehicle 1 is below a given speed (output X at block 32) or the system 20 is disabled (output X at block 31) , the pressure is not regulated. Instead, the pressure value reached in the previous cycle is kept constant .

[0069] In a manner not illustrated in the diagram in Figure 7, in response to driver input on the control means 30 and prior to performing checks at block 34, the pressure setpoint can preferably be automatically raised to a stored default value, that is, to a nominal value.

[0070] Similarly, if it is verified that the adjustment system 20 has been disabled (output X at block 31) , the pressure setpoint is preferably reset to the nominal value (block 39a) and the pressure is adjusted accordingly (block 39b) .

[0071] Two non-limiting examples of the embodiments just described will now be considered.

[0072] Considering Figure 6 and Figure 8: the first graph from the top illustrates the pressure variation in the chamber 7; the second graph from the top illustrates an example of the operating mode of the vehicle 1, "Running" if in motion and "Stationary" if stationary; the third graph from the top shows an example of load variation of the vehicle 1; and the fourth graph from above shows the status of the adjustment system 20, "Off", if deactivated, and "On", if activated. Below, reference will be made to the graphs according to the numbering just explained, starting from the top-down.

[0073] In Figure 6, while the vehicle 1 is in motion (Running mode, second graph) , the driver activates the adjustment system 20 (On mode, fourth graph) .

[0074] Specifically, in the non-limiting example illustrated, when the vehicle 1 is started up (switches to Running mode) , the adjustment system 20 is not immediately activated by the driver (it remains in Off mode, as illustrated in the fourth graph from the top ) ; therefore , the pressure is not adj usted, as illustrated in the first graph, and remains constant ( for example , equal to 1 . 5 bar, indicated as "Low" ) .

[0075] With the system 20 activated, the vertical load (which had previously been increased, with the vehicle 1 stationary, in the instant of the third graph) is measured .

[0076] For example , a vertical load equal to the total permissible weight of the vehicle 1 ( GVW or Gross Vehicle Weight , which corresponds to the unladen weight of the vehicle 1 plus the maximum load that the vehicle 1 can carry) is measured .

[0077] In particular, in this discussion, it is assumed that the load variations have a stepwise pattern, that is , they are instantaneous for simplicity of discussion, and the load of the vehicle 1 varies for loading or unloading operations with the vehicle 1 stationary .

[0078] The load change detected, when the system 20 is activated, is higher than a predefined threshold value , so that the reference value or pressure setpoint is adj usted to a new value ( indicated by "Optimal pressure" in the first graph) in order to increase , due to the increased vertical load on the wheel 3 .

[0079] In the speci fic case illustrated, the reference value is set at 3 bar (value indicated as "High" ) .

[0080] As a result , the pressure in the chamber 7 is adj usted to track and reach the reference value. In this specific case, since it is a pressure increase, the adjustment system 20 makes air flow from the reservoir 22 to the chamber 7, in the manner described above.

[0081] According to the particular example illustrated, the pressure-raising step lasts a few seconds.

[0082] Then, in the example shown, in the instant t2, the vehicle 1 comes to a halt (switches from Running mode to Stationary mode) and, at the same time, there is an initial decrease in the load, in which the acting load changes from the maximum GVW to an intermediate value.

[0083] Between the instant t2and instant t3, despite the load change, the reference value is kept constant as the vehicle 1 is stationary. In this way, no adjustment is made to the pressure setpoint, so the previously set pressure value is kept constant.

[0084] Then, in the instant t3, just before the vehicle 1 is put back into motion, a second load decrease occurs, for example, to a minimum value (indicated by Ip) , corresponding to the starting load. Even in this case, the load variation exceeds the predetermined threshold or tolerance, so that it can trigger the system 20.

[0085] In the instant t3, the vehicle 1 is set in motion again and, therefore, the pressure setpoint is actually changed from this instant. As the load is lowered, the pressure setpoint is lowered to a new value , called the "new set point" . The pressure is then adj usted to be lowered to this new value , causing air to flow from the chamber 7 to the reservoir 22 via the compressor 21 . In the particular example shown, the pressure lowering step lasts about one minute .

[0086] In the example in Figure 8 , the vehicle 1 is started (Running) from a standstill ( Stationary) ( second graph) , and after an interval of time the driver activates the adj ustment system 20 ( On mode , fourth graph) .

[0087] Even in this case , the adj ustment system 20 is not immediately activated by the driver and, therefore , the pressure is not adj usted and remains constant ( equal to an initial value Pi ) .

[0088] When the system 20 is activated, the pressure is first adj usted by setting the pressure setpoint to a nominal value NP .

[0089] Subsequently, the system 20 waits for an interval of time for stabilising the load on the wheel 3 .

[0090] The stabilisation time interval is preferably equal to or greater than 10 seconds . Generally, the stabilisation time depends on the characteristics of the system 20 and the wheels 3 . For example , the time may vary depending on the responsiveness of the system and / or pressure sensors .

[0091] Once it is stabilised, the vertical load (which had previously been changed with the vehicle 1 stationary, in the instant t4in the third graph) is measured . In particular, the vertical load was increased up to the permissible total weight of the vehicle 1 ( GVW) , as in the case above and under the same simpli fying assumptions .

[0092] The load variation detected, relative to the nominal value NP, is greater than the threshold tolerance that has been predefined, whereby the system 20 sets a new, optimal , pressure setpoint corresponding to the load detected, in order to implement the adj ustment strategy .

[0093] In other words , the optimal reference value indicated with "OP ' in the first graph is set .

[0094] As a result , the pressure in the chamber 7 is adj usted to track and reach this reference value . In this speci fic case , since it is a pressure increase , the adj ustment system 20 makes air flow from the reservoir 22 to the chamber 7 , in the manner described above .

[0095] Then, in the example shown, in the instant t5, the vehicle 1 comes to a halt ( switches from Running mode to Stationary mode ) and there is an initial decrease in the load, in which the acting load changes from the maximum GVW to an intermediate value .

[0096] Between instant t5and instant t6, despite the load change , the reference value is kept constant as the vehicle 1 is stationary . In this way, no adj ustment is made to the pressure and the previously set pressure value is kept constant .

[0097] In the instant t6the vehicle is restarted (Running) and due to the load decrease that had previously occurred ( exceeding the threshold tolerance ) , a new optimal reference value is set ("0P2" ) .

[0098] In the instant t7, for example , the system 20 is disabled, whereby the system 20 automatically returns the pressure setpoint to the nominal value (NP ) , from which a corresponding pressure adj ustment follows . As a result of this deactivation, despite the subsequent changes in load and vehicle state ( graphs 2 and 3 ) , no pressure adj ustment is carried out , as can be seen from the first graph .

[0099] According to this invention, as anticipated, the control logics implemented in the electronic control unit 25 ( and / or control signals from the fixed control unit on board the vehicle 1 ) are configured to adj ust the pressure setpoint and, thus , vary the air pressure inside the chamber 7 according to grip conditions estimated for the wheels 3 on the road surface on which the vehicle 1 travels .

[0100] In other words , these control logics , when executed, are configured to adj ust the pressure in the chamber 7 in response to a pressure signal provided by the pressure sensor 29 and reach a reference value ( setpoint ) that is set according to the estimated grip conditions for the wheels 3 . The method for adj usting the air pressure in the wheel 3 comprises the step of adj usting, via the electronic control unit 25 , the pressure in the chamber 7 by making air flow from the chamber 7 to the reservoir 22 and vice versa, in response to a pressure signal indicating the air pressure in the chamber 7 to reach a reference value defined according to the grip conditions of the wheel 3 , which are estimated by means of at least one weather map acquired in real time (block 41 in Figure 9 ) and by means of a geolocation system (block 42 in Figure 9 ) , at least when the vehicle 1 is in motion .

[0101] Therefore , the electronic control unit 25 ( or the centralised electronic control unit ) is configured to receive an input signal indicating the grip conditions of the wheels of the vehicle 1 , and vary the pressure reference value according to the input signal .

[0102] The grip conditions are estimated based on the road conditions (wet , dry, snow, ice , etc . ) that , in turn, are determined based on the weather conditions at the current position of the vehicle 1 .

[0103] The grip conditions are estimated in real time .

[0104] For this purpose , the vehicle 1 comprises the geolocation system, mentioned above , for example a GPS device with an antenna (block 42 in Figure 9 ) , to determine or detect the coordinates of the position of the vehicle 1 in real time .

[0105] The vehicle 1 also comprises a receiving device with an additional antenna (block 41 in Figure 9 ) to which the weather map is transmitted, for example from a weather station . Alternatively, the weather maps are provided by an application or service to which the driver is subscribed, accessible via, for example , the internet .

[0106] Speci fically, the current position of the vehicle 1 is detected via the geolocation device 42 , and this information, together with the weather maps acquired in real time (block 41 ) , is provided to a calculation block 46 of the control unit 25 , which determines the weather condition indicated on the weather map at the current position of the vehicle 1 that has been detected / determined . In other words , when the current position of the vehicle 1 is known, the weather conditions at that position are determined in real time .

[0107] Based on the weather information, as mentioned above , the road conditions are determined, that is , whether the vehicle is travelling in dry, wet , icy, or snowy conditions , etc .

[0108] From the road conditions , it is possible to estimate the friction coef ficient and, thus , the level of grip on the section the vehicle 1 is travelling over, and while the vehicle 1 is travelling, via a dedicated calculation block

[0109] 44 of the control unit 25 . In addition, it is also possible to use information on the type of road surface ( asphalt , dirt , gravel , etc . ) that the vehicle 1 is driving on to estimate the level of grip . This type of road surface is determined from the current position of the vehicle 1 , for example by means of an appropriate database or navigation maps (block 43 ) , which correlate the road being driven on with the type of land or surface that this road consists of . For example , such databases or navigation maps are stored in the vehicle 1 , or provided via a remote service , such as an internet service .

[0110] In addition, the wheel 3 pressure value detected by the pressure sensor, for example installed in the valve 14 , and / or the load detected by the sensor 29 , are provided to the calculation block 44 for the grip estimation .

[0111] According to one embodiment , information from a vehicle 1 braking system control system (block 45 in Figure 9 ) is also advantageously taken into account when estimating wheel 3 grip conditions , for example information on deceleration obtained in response to a given braking command, detection of wheel lock, etc . This information, in fact , is an indication of the friction between the wheel and the ground on which the vehicle 1 is moving, and is preferably used as a correction tool on the previous estimate calculated using the weather map and the current position of the vehicle 1 .

[0112] In the embodiment illustrated in Figure 7 , after activating the adjustment system (block 31) , an initial check is done on the grip conditions (block 33) and, if the estimated grip conditions are satisfactory (that is, they exceed a pre-set threshold value) , a check is done on the load variation (block 34) . If both conditions are verified, the new optimal pressure value is determined (block 35) and tracked (block 36) .

[0113] With regard to the verification of the grip conditions at block 33, as mentioned above, a threshold grip value is defined in advance: if the estimated grip is lower than this value (output X at block 33) , that is, the level of grip is not satisfactory, the pressure of the chambers 7 is reduced to a predetermined pressure value in order to bring the grip conditions to an acceptable level. In particular, an acceptable pressure setpoint is set (block 38a) and this setpoint is tracked (block 38b) .

[0114] By way of example, if the information on the weather conditions is of heavy rain and the road travelled has a slippery surface, the grip conditions may not be satisfactory, that is, not compatible with the threshold value. In this case, the vertical load conditions are not checked at block 34, but the pressure of the chambers 7 is reduced to a value appropriate to the safety of the vehicle 1.

[0115] Several reference grip levels of the wheels 3 can preferably be stored in advance, instead of a single threshold value, for example low, medium and good, in order to adjust the pressure in different ways.

[0116] When estimating the grip at block 44, other factors can also be taken into account, including the type of vehicle 1, the number of wheels 3, and the tyre's state of wear.

[0117] If the grip conditions are compatible with the predefined threshold value (output V at block 33) , the verification is carried out according to the vertical load conditions (block 34) , as indicated above.

[0118] In particular, if the load-dependent intervention conditions are met (output V at block 34) , referring to the graph in Figure 7, a new optimal pressure setpoint is estimated and tracked based on vertical load conditions (blocks 35 and 36) , as previously described.

[0119] According to one embodiment, a check is done of the slope of the road (block 40 in Figure 7) travelled by the vehicle 1, before checking and adjusting the pressure according to the load, that is, before the checks at block 34. The slope of the road actually affects the distribution of the vertical load on the wheels 3. Specifically, rear and front wheels could be loaded differently, both uphill and downhill .

[0120] The pressure adjustment (blocks 34, 35, 36) preferably only takes place on roads with a slope (for example an average slope for a given time interval) less than or equal to a threshold value. Consider the inclination of the ground in relation to a plane parallel to the horizon as the average slope %. In particular, this threshold value can be 8%.

[0121] Specifically, if the slope is greater than the threshold value (output X at block 40) , vertical load adjustment is not carried out. If, on the contrary, the slope is below the threshold value (output V at block 40) , the check at block 34 is carried out.

[0122] In the case just described, the vehicle 1 comprises a slope detection sensor. This sensor could be a gyroscope, or an inclinometer. Alternatively, the slope of roads could be determined on the basis of the position detected thanks to the geolocation device (GPS) , thanks to navigation maps or databases configured to provide information on the road the vehicle 1 travels.

[0123] According to an embodiment not illustrated, the pressure regulation of the chamber 7 can only be carried out according to the grip conditions estimated at block 33, without taking into account changes in vertical load (that is, without performing the operations at blocks 34, 35 and 36) .

[0124] In this case, in particular, having defined a grip threshold value in advance, if the estimated grip (from block 44) is lower or higher than this value, the pressure setpoint of the chambers 7 is decreased and, respectively, increased. That is, the pressure is reduced if the grip is unsatisfactory, for example in wet conditions, and restored to a nominal value if the grip is satisfactory, for example in dry conditions.

[0125] As an example, consider an event with a change in the estimated grip conditions of the vehicle 1, while the vehicle 1 is in motion (Running mode) , for example at a speed greater than a certain threshold speed greater than zero, with the adjustment system 20 having been activated (On mode) , for example by the driver.

[0126] According to a non-limiting example, the event could be, at the beginning, a very strong thunderstorm starting with clear weather conditions, with the same road surface.

[0127] Having verified that the adjustment system 20 is active and the vehicle 1 is in motion, according to the estimated grip conditions the adjustment system 20 adjusts the pressure in the chamber 7 to reach an optimal value determined according to the actual grip conditions.

[0128] In the example given, the presence of rain (typically) reduces grip, and, therefore, the pressure in the chambers 7 is decreased, reducing the pressure setpoint.

[0129] The adjustment is preferably carried out whenever a change in the grip conditions occurs, when the adjustment system 20 is active, and the vehicle 1 in motion. In other words , in response to a change in grip conditions , an optimal reference value is set and tracked by making air flow from the reservoir 22 to the chamber 7 and vice versa .

[0130] In the absence of an event and / or i f the adj ustment system 20 is not active and / or the vehicle 1 is below a predetermined limit speed, the pressure value is kept constant .

[0131] I f the vehicle 1 is stationary, despite changing grip conditions , for example due to adverse weather conditions , the reference value is preferably kept constant . In other words , no pressure adj ustment takes place when the vehicle 1 is stationary .

[0132] In the instant when the vehicle 1 is set in motion again, the pressure setpoint is enabled to vary again to a new setpoint value . The pressure is then adj usted to reach this new value , causing air to flow from the chamber 7 to the reservoir 22 , or vice versa, via the compressor 21 , in response to the weather conditions detected on the weather map and, preferably, in response to any load changes .

[0133] It is also poss ible to adj ust the pressure of the chamber 7 according to other factors .

[0134] Preferably, when adj usting the pressure according to the load on each wheel 3 , it may be important to bear in mind that the pressure di f ference between the various wheels must not exceed a predetermined limit value , so as not to jeopardise the safety of the vehicle 1.

[0135] In this regard, a load-dependent pressure adjustment could also lead to widely differing inflation pressures for the various wheels, in the event of a load imbalance on the same vehicle 1. It is therefore preferable to define a threshold in terms of the maximum pressure difference between the wheels, beyond which the pressure adjustment must be interrupted. In particular, this maximum difference can be equal to 0.5 bar. Block 35, which is responsible for setting the pressure setpoint on each wheel 3, is then configured, by means of appropriate verification and / or control strategies, to also respect this maximum pressure difference between the various wheels 3.

[0136] In addition to the conditions described above, other parameters can also be taken into account when adjusting the pressure, for example the air temperature inside the chamber 7 or the state of tyre wear, as well as the tyre type.

[0137] From the above, it is clear that optimal wheel grip conditions are guaranteed for the vehicle 1 during movement.

[0138] In particular, optimal grip conditions are achieved by taking into account various factors external and internal to the vehicle 1, when adjusting the flows of the compressor 21 and / or the solenoid valve 26. Among these factors, the main one is the grip conditions of the ground estimated on the basis of the weather conditions and, advantageously, the type of road the vehicle drives on too.

[0139] A pressure adjustment based on a grip estimate is particularly advantageous when combined with the load-based pressure adjustment, as it has priority over the latter and prevents any increase in pressure due to an increase in load from compromising safety in the event of poor grip due to bad weather conditions.

[0140] In addition, it is clear that the illustrated solution is versatile, that is, suitable for different types of vehicles, such as goods trucks, which can be subject to significant load variations (for example, from empty to a full load) , or agricultural vehicles, which have to cope with very different types of terrain and weather conditions.

[0141] Other advantages are then clear for a person skilled in the art on the basis of the above.

[0142] Lastly, it is clear that modifications may be made to the vehicle 1 according to this invention, and variants produced thereto, without, however, departing from the scope of protection defined by the attached claims.

[0143] For example, in the embodiment shown, the vehicle 1 has four wheels; according to some variants, the vehicle 1 may have more or fewer than four wheels.

[0144] Furthermore, the manner in which air is transferred from the reservoir 22 to the chamber 7 during inflation of the wheel 3 could take place in different ways, for example by exploiting the passage defined by the compressor 21 itsel f

[0145] ( and excluding any solenoid valve 26 ) .

[0146] In addition, the sensor 29 can be placed on a vehicle 1 component other than the suspension to detect the load . Finally, the weather map may not be transmitted by the vehicle 1 , but remain with a remote service . In this case , the vehicle 1 transmits its current position, determined via the geolocation system, to that service in order to obtain the weather condition and / or directly the road conditions (wet , dry, snow, etc . ) being travelled over wirelessly in response , and then estimate the grip conditions via block 44 .

Claims

CLAIMS1.- A method for adjusting air pressure in a wheel (3) on a vehicle (1) ; the wheel comprising: a rim (5) ; a tyre (6) defining, together with the rim (5) , a chamber (7) that is filled with air and can be pressurized; at least one compressor (21) having an inlet, pneumatically connected to the chamber (7) and an outlet; at least one reservoir (22) carried by the rim (5) , pneumatically connected to said outlet to receive compressed air from said compressor (21) and adapted to be pneumatically connected to said chamber (7) to transfer air to said chamber (7) ; and at least one battery (24) to supply electric power; the method comprising the step of adjusting, using an electronic control unit (25) , the pressure in said chamber (7) by flows of air from the chamber (7) to the reservoir (22) and vice versa, in response to a pressure signal indicative of the air pressure in said chamber (7) to achieve a reference value; wherein said reference value is defined as a function of the grip conditions of the wheel (3) , which are estimated by at least one weather map and using a geolocation system, at least when the vehicle (1) is in motion.2.- The method according to claim 1, in which the grip conditions of the wheel (3) are estimated by- determining a current position of the vehicle using saidgeolocation system,- determining, on said weather map, a weather condition corresponding to the determined current position;- estimating road conditions of the road travelled by the vehicle (1) based on the determined weather condition.3.- The method according to claim 1 or 2, wherein the grip conditions are also estimated based on information provided by a control system of a braking system.4.- The method according to any one of the preceding claims, wherein the weather map is acquired in real time by the vehicle.5.- The method according to any one of the preceding claims, wherein the change in the reference value occurs exclusively when the vehicle (1) is in motion, at a speed above a given threshold value, greater than zero.6.- The method according to any one of the preceding claims and comprising a step of verifying whether an enable / disable command has been provided to enable / disable the reference value change.7.- The method according to any one of the preceding claims and comprising the steps of detecting, using a sensor (29) , a vertical load acting on the wheel (3) ; receiving, from said sensor (29) , a further input signal indicative of the detected vertical load; and varying said reference value according to said further input signal if the estimated gripconditions meet a given threshold condition (33) .8.- The method according to claim 7, wherein varying the reference value in response to the additional input signal occurs only when the slope of the road travelled by the vehicle (1) is less than a given threshold value, greater than zero.9.- The method according to claim 8, wherein the change in the reference value in response to the further input signal occurs exclusively when a load difference greater than a given threshold value, greater than zero, is detected.10.- The method according to claim 9, wherein the change in the reference value in response to the further input signal occurs exclusively if said load difference persists for a time greater than a given interval, greater than zero.11.- A vehicle (1) comprising:(A) at least one wheel (3) comprising: a rim ( 5 ) , a tyre (6) defining, together with said rim (5) , a chamber (7) that is filled with air and can be pressurized; a system (20) for adjusting the air pressure in said chamber (7) ; said system comprising: a) at least one compressor (21) having an inlet, pneumatically connected to said chamber (7) and an outlet ; b) at least one reservoir (22) carried by said rim(5) , pneumatically connected to said outlet to receive compressed air from said compressor (21) and capable of being pneumatically connected to said chamber (7) to transfer air to said chamber ( 7 ) ; and c) at least one battery (24) to supply electrical power;B) an electronic control unit (25) configured to adjust the pressure in said chamber (7) by flows of air from said chamber (7) to said reservoir (22) and vice versa, in response to a pressure signal indicative of the air pressure in said chamber to achieve a reference value; wherein said electronic control unit (25) is configured to perform the method of any one of the preceding claims.12.- The vehicle according to claim 11, wherein the electronic control unit (25) is arranged on board the wheel (3) and receives said input signal wirelessly.13.- The vehicle according to claim 11 or 12, and comprising control means that are manually operable by a user and, when operated, enable and / or disable the variation of said reference value.

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