Abstract:
An embodiment of a control method for a vehicle which is provided with a number of wheels, each of which comprises a tire and at least a disc brake of a braking system; the control method includes the step of sensing the current temperature of at least one component of a respective wheel by means of at least one sensor; determining, in a step of engineering and setting up, at least one first predetermined threshold value indicating the minimum temperature from which the component of wheel shows its maximum efficiency; comparing the current temperature of the component of wheel with the first predetermined threshold value; and signaling to the driver when the current temperature of the component of wheel is lower than the first predetermined threshold value.

Description:
PRIORITY CLAIM 
     The present application claims the benefit of Italian Patent Application Serial No. BO2008A000510, filed Aug. 6, 2008, which application is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     An embodiment of the present invention relates to a control method for a vehicle. 
     An embodiment of the present invention is advantageously applied to an automobile, to which explicit reference will be made in the following description without a loss in generality. 
     BACKGROUND 
     An automobile has four wheels, each of which comprises a tire and a brake disc of a braking system. In general, the performance offered by the rotary components of each wheel, i.e., tire and brake disc, depends on the current temperature of the rotary components themselves; the subordination of the performance of the rotary components of each wheel according to their current temperature is very apparent in sports automobiles, in which particular materials are used (e.g., carbon-ceramic alloys for brake discs or high-grip compounds in tire treads), which provide a very high performance in relatively narrow temperature ranges. 
     In order to avoid an excessive overheating of the rotary components of each wheel (with a consequent very apparent performance decay), it has been suggested to install a monitoring and control system of the temperature of tires and/or brake discs in an automobile. In particular, the known monitoring and control systems signal through a display placed on the dashboard of the automobile itself when the brake discs and/or tires have reached temperatures higher than a safety limit value and so as to jeopardize their correct operation and determine unsafe driving conditions of the automobile. An example of a monitoring and control system is provided in patent application US2007295072A1, and which is incorporated by reference, in which a monitoring and control system of the temperature of tires of an automobile is described, which system comprises a plurality of wireless-type sensors, which are arranged inside the tires themselves and, in particular, are embedded in the tire tread. 
     However, the known monitoring and control systems are not able to provide complete information on the actual efficiency of the rotary components of each wheel, i.e., of the tire and brake disc of each wheel, to the driver of a high-performance sports automobile. 
     SUMMARY 
     An embodiment of the present invention is a control method and device for an automobile, which are free from the above-described drawbacks while being cost-effective and simple to be implemented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described with reference to the accompanying drawings illustrating a non-limitative embodiment thereof, in which: 
         FIG. 1  is a diagrammatic, plan view of an automobile implementing a control method according to an embodiment of the present invention; and 
         FIG. 2  shows a detail of an embodiment of an indicator instrument of the automobile in  FIG. 1  on an enlarged scale. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , numeral  1  indicates as a whole an automobile provided with four wheels  2  (two front wheels and two rear drive wheels) and comprising a front internal combustion engine  3 , which produces a driving torque that is transmitted to the rear wheels  2  by means of a driveline  4 . 
     Automobile  1  is provided with a braking system  5  having four brake discs  6 ; two discs  6  are arranged inside a respective front wheel  2  and two discs  6  are arranged inside a respective rear wheel  2 . Each disc  6  is coupled to a respective caliper  7 , which is controlled by a brake pedal  8  arranged in a passenger compartment of the automobile  1  and operated by the driver. 
     Automobile  1  further comprises a control device  9  of the automobile  1  itself, which is provided with a control unit  10  connected both to the braking system  5  and to the wheels  2 . In particular, the control unit  10  is adapted to sense and store the working temperature value of brake discs  6  and tires  11  of the front and rear wheels  2  by means of a sensing device  12  of the temperatures, which comprises a plurality of sensors  13  coupled to the tires  11  and a plurality of sensors  14  coupled to the brake discs  7 . It has indeed been observed that the performance provided by automobile  1  and the wear of tires  11  and braking system  5 , respectively, are strongly affected by the working temperatures reached by the tires  11  themselves and by the disc brakes  6 . 
     Each sensor  13  is embedded in the tread for sensing the working temperature of a respective tire  11  and is of the wireless and battery-less type. Thereby, the sensor  13  does not require any connection wires to the control unit  10  and is able to work without the presence of an energy supplying battery, because it is self-powered by means of the motion of the tire  11  itself. In this case, the sensors  13  could be piezoelectric sensors, which comprise a series of crystals the property of which is to generate an electrical charge proportional to the force applied during the motion of the tire  11  when subjected to mechanical stress. 
     The wear of the braking system  5  depends on the working temperature reached by the brake discs  6 , which is sensed by means of the sensors  14 . Furthermore, the same amount of dissipated energy generates a different wear according to the conditions of use, and in particular wear is much higher during a high-performance use of the automobile  1 , in which the temperatures reached by the brake discs  6  are substantially high as compared to the use under normal conditions. It is worth emphasizing that the possibility of controlling the working temperatures of the braking system  5  may be very important, because it has been demonstrated that the braking power of the automobile  1  when cold is considerably lower than the braking power under normal conditions of operation; this reduction is substantially high and equal to about 30% of the braking power. A step of warming up the braking system  5  may thus be needed, the duration of which was simply determined, until now, by the driver. 
       FIG. 2  partially shows the onboard instrumentation  15  of a dashboard  16 , comprising an indicator device  17  of the working temperatures of the braking system  5  and wheels  2 . The indicator device  17  is illuminated by a light source (not shown), connected to the control unit  10 , and adapted to signal, in use, when the braking system  5  and the wheels  2  have reached an optimal working temperature. 
     In particular, the sensors  13  and  14  periodically sense the temperatures of tire  11  and brake disc  6 , respectively, and the control unit  10  is intended to compare the sensed temperature value with a pair of predetermined threshold values. These values represent the bounds of a temperature range characterizing the optimal operation of the automobile  1 . First, the control unit  10  compares the sensed temperature with a threshold value T min ; if the sensed temperature is lower, the control unit  10  is set up to send a signal to the driver through the indicator device  17 . Instead, if the sensed temperature is higher than the threshold value T min , the control unit  10  compares the sensed temperature with the threshold value T max . If the sensed temperature is higher than the threshold value T max , the control unit  10  is set up to send a signal to the driver through the indicator device  17  also in this case. The indicator device  17  is not illuminated in the time range in which the working temperatures are kept within the range between the two threshold values T min  and T max . As soon as the sensed temperatures are no longer within this optimal operating range, the control unit  10  sends a signal to the driver by lighting up the light source (not shown) and illuminating the indicator device  17 . Alternatively, the control unit  10  may send a signal to indicate the working temperatures are within range, or may send a first signal to indicate an out-of-range condition and a second signal to indicate an in-range condition. 
     In use, when the automobile  1  is started, the light source (not shown) is turned on to be able to inform the driver that both brake discs  6  and tires  11  are cold, i.e., have not reached the threshold value T min  and prudence is thus recommended to allow the components of the automobile  1  to reach an optimal working temperature at which they may provide their maximum performance. Instead, when the light source (not shown) is turned off, it means that the step of warming up has ended and all the brake discs  6  and tires  11  have reached a temperature such that safe driving conditions of the automobile  1  are determined. 
     As shown in  FIG. 1 , automobile  1  is further provided with a passenger compartment in which there are the dashboard  16  (partially shown in  FIG. 2 ), the brake pedal  9  for controlling the braking system  5 , and a selection device  18 , usually named “joystick”, which allows the driver to communicate the desired driving mode of the automobile  1  to the control unit  10  (e.g., sporty driving on a race track, normal driving on a road open to the public, driving on wet road, etc.). 
     The selection device  18  may take, for example, five different positions, each corresponding to a given dynamic behavior of the automobile  1  and to which five different threshold values T min  and five different threshold values T max  correspond. The bounds and amplitude of the temperature range which determine the optimal operating conditions of the automobile are thus variable according to the position taken by the selection device  18 , so as to be able to optimize different parameters depending on the driver&#39;s choice (e.g., comfort or performance of the automobile  1 ). 
     In particular, the selection device  18  comprises a rotary switch  19 , which may take the five different positions and is connected to the control unit  10 . According to the driver&#39;s choice, i.e., to the position taken by the rotary switch  19 , the control unit  10  varies the intervention parameters of the various electronic devices (such as, for example, ABS, ESP, etc.) so as to make the dynamic behavior of the automobile  1  as close to the driver&#39;s wishes as possible; in other words, the control unit  10  is set to control some parameters including, for example, suspension adjustment, stability and traction control, etc. Furthermore, according to the position taken by the rotary switch  19 , the control unit  10  is set to compare the working temperatures sensed by the sensors  13 ,  14 , with the respective threshold values T min  and T max  in order to establish if the sensed working temperatures are within the optimal operation range. 
     Since drivers often estimate their driving skills incorrectly, in particular they usually tend to overestimate them, the control unit  10  is set to limit the performance of the automobile  1  according to the conditions of braking system  5  and wheels  2 , i.e., according to the working temperatures sensed by the sensors  13  and  14 . 
     Being connected to a plurality of sensors distributed inside the automobile, including the sensors  13  and  14 , the control unit  10 , which supervises the operation of the active parts of automobile  1 , is able to limit the performance of the automobile  1  according to the working temperatures sensed by the sensors  13  and  14 , and in particular until the sensed temperature are at least equal to the threshold value T min . Thereby, if the drivers overestimates their conditions or do not correctly evaluate the conditions of the road on which they are traveling, the performance of the automobile  1  will thus be such to ensure safer driving conditions until the braking system  5  and the tires  11  have reached a working temperature within the optimal operating range. 
     In the automobile  1  shown in  FIG. 1 , each wheel  2  is provided with a respective sensor  13  for sensing the working temperature of the tire  11 , and a respective sensor  14  for sensing the working temperature of the brake disc  6 . According to a further embodiment (not shown in the figures), the front wheels  2  of the automobile  1  are provided with a temperature sensing device  12  only, i.e., with a respective sensor  13  for sensing a working temperature of the tire  11  and with a respective sensor  14  for sensing the working temperature of the brake disc  6 . This embodiment may be applied because it helps to contain costs while allowing to control the temperatures of the rotary components of the front wheels  2 , which are the most stressed both during the step of braking and during the step of steering. 
     According to a further embodiment (not shown in the figures), the above-described control method is implemented on a motorcycle for signaling when the optimal working temperature of tires and brakes is reached; also in this case, the front wheel only, or alternatively both the wheels of the motorcycle are provided with the temperature sensing device, i.e., with a respective sensor for sensing the working temperature of the tire, and with a respective sensor for sensing the working temperature of the brake disc. 
     According to a further embodiment (not shown in the figures), the control unit  10  of the control device  9  is set to estimate the temperature value of tires  11  and brake discs  7  through a thermal balance model. The model includes evaluating and balancing the energy contribution of a plurality of parameters (such as for example external temperature, radiation index, drift angle, etc.) in order to be able to correctly estimate the correct temperature of tires  11  and brake discs  7 . 
     It is worth underlining that, according to this further embodiment, the control device does not require the presence of sensors  13  and  14  coupled to the tires  11  and brake discs  7 , respectively, because, through the thermal balance model, the control unit  10  is set to self-estimate the temperature of these components and a physical connection of the control unit  10  itself both to the braking system  5  and to the wheels  2  is no longer needed. 
     Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the embodiments described above many modifications and alterations. Particularly, although one or more embodiments have been described with a certain degree of particularity, it should be understood that various omissions, substitutions, and changes in the form and details as well as other embodiments are possible. Moreover, it is expressly intended that specific elements and/or method steps described in connection with any disclosed embodiment may be incorporated in any other embodiment.