FR3028214A1 - METHOD FOR AUTOMATICALLY SUSTING THE SENSORS OF A TIRE PRESSURE CONTROL SYSTEM - Google Patents

Abstract

The invention aims to reduce the power consumption of the wheel sensors by taking into account their activity while retaining all the information. To do this, the invention proposes to automate the action of specific operating modes from the measurements made. One form of implementation of the method according to the invention uses three modes of activity state, a standby mode (100) and a standard mode (200), this standard mode consisting of non-rolling modes (210) and rolling (220). Switching (F1; F3) from standby mode (100) to non-rolling mode (210) and then to rolling mode (220) are triggered if the pressure (Pv) changes from atmospheric pressure (Patm) to a value greater than one threshold (Ps), whereas the acceleration (Av) remains lower than a minimum acceleration (Amin) and then, respectively, as soon as an acceleration (Anr) is greater than this threshold acceleration (As). Conversely, the rolling mode (220) switches (F6) first to the non-rolling mode (210) when an acceleration (Ar) is less than the minimum acceleration (Amin), and then can switch (F4) to the standby mode (100) if the acceleration (Anr) remains below the minimum acceleration for a duration (Ds).

Description

The invention relates to a method of automatically stopping the wheel sensors of a tire pressure control system (TPMS system, acronym for "lyre Pressure Monitoring System" in English terminology) of a motor vehicle .

Nowadays, vehicle wheels integrate multifunction sensors into modules. These modules are called "wheel units" when attached to the rim of the wheel. Alternatively, these modules can be attached directly to the inner face of the tire. These wheel sensors periodically provide basic parameter measurements of each tire - pressure, temperature, acceleration - to a central processing unit located in the vehicle. These measurements can then be exploited in targeted applications, in particular: the location of the wheels to control the pressure of the tire corresponding to each localized wheel, the overload and wear detections of the tires, the automatic learning of the sensors or tracking the position of the sensors themselves. The measurements, made by dedicated probes, are converted and transmitted to a microprocessor integrated in the central processing unit via transmitter / receiver devices equipped with antennas and a CAN bus. All the means used (probes, central unit, communication network via transmitters / receivers) form a tire pressure monitoring system, conventionally known under the name TPMS system (acronym for "Tire Pressure Monitoring System"). in English terminology). The digital data provided by the wheel sensors to the central processing unit reflect successive levels of variation. From these values, the central processing unit can develop, after filtering and sampling, signals of pressure, temperature, wear and / or overload for transmission to the on-board computer of the vehicle. An important aspect of the use of TPMS systems relates to the reduction of energy consumption. Indeed, these systems, which use wireless communication means for long periods of time, are powered by energy sources of limited capacity, for example batteries or inductive generators. Consumption reduction circuits are known.

Thus, in the TPMS system of patent EP 1 985 472, a voltage regulator and a capacitor are connected to a measurement unit. The average current consumed by the voltage regulator is decreased by providing for activating and deactivating the voltage regulator at predetermined time intervals. The capacitor is then respectively charged and discharged so that, when the regulator is deactivated, the unit of measure is supplied by the capacitor; the average consumption of the voltage regulator is therefore reduced. This solution is based on an energy saving by the use of a capacitor; this gain is low and the reduction in consumption is not optimized.

Furthermore, patent EP 2 150 424 proposes to modulate the data flow, formed by a processing circuit from the measurements of a pressure sensor of a TPMS system, between 2 logical states 1 and 0. Only the data corresponding to logic state 1 are transmitted through a PLL circuit (phase locked loop). The power supply is thus suppressed for the data of the logic state 0, which makes it possible to reduce the power consumption. The solution recommended by this patent EP 2 150 424 only transmits the active data of the pressure sensor from a certain intensity level. However, it is generally useful to be able to follow the evolution of the measurements from zero, in order to deduce the state of the tires and transmit the warning signals in time.

The aim of the invention is precisely to reduce the power consumption of the wheel sensors by taking into account the activity of these sensors in order to optimize this reduction in consumption while preserving all the information deductible from the measurements provided by the sensors. To do this, the invention proposes to automate the consideration of the operating modes of the wheel sensors from the measurements made by these sensors. More specifically, the subject of the present invention is a method for automatically stopping the wheel sensors of a TPMS system for controlling the tire pressure of the corresponding wheels of a vehicle, in which the wheel sensors periodically provide a signal to a tire. central processing unit of corresponding wheel tire parameter measurements, namely at least pressure and acceleration parameters. This method consists in switching the operation of a wheel sensor between at least two activity status modes, by switching from a so-called "standard" mode of operation of the vehicle to a rest mode called "standby" when no acceleration, greater than or equal to a predefined minimum acceleration value, is measured for the corresponding tire for a duration greater than or equal to an acceleration measurement threshold duration. The acceleration is then measured according to a period of substantially longer duration in standby mode than in standard mode. The method also includes switching each wheel sensor from the standby mode to the standard mode as soon as a corresponding acceleration measurement of the tire is greater than or equal to a predefined threshold acceleration value and a measurement of the corresponding tire pressure is simultaneously greater than or equal to a predefined threshold pressure value. Under these conditions, the power consumption is reduced because the power consumption in standby mode is substantially lower than that in the standard mode of operation of the wheel sensors, which also induces an increase in the life of these sensors. Thus, in the standby mode, the operational activities of the wheel sensors are suspended except for the automatic monitoring of the wake-up conditions defined above and which trigger, when they are satisfied, the switch to the standard mode of the sensors.

Advantageously, the invention remains compatible with all the current hardware and software architectures of wheel sensors of TPMS systems. According to preferred embodiments: the standard mode comprises a so-called "non-rolling" mode and a so-called "rolling" mode, the non-rolling mode being introduced in the standard mode to be interposed between the rolling mode and the standby mode, so that the rolling mode can first switch to the non-rolling mode as soon as a corresponding acceleration measurement of the tire is less than or equal to said predefined minimum acceleration value, then the non-rolling mode may switch to standby mode when the acceleration remains below or equal to this predefined minimum acceleration value, for a period of time equal to the acceleration measurement threshold duration or if a measurement of the corresponding tire pressure is substantially equal to the atmospheric pressure, the acceleration simultaneously being less than or equal to said minimum acceleration value; inverse switching from standby mode to non-rolling mode and then to rolling mode can be triggered when a pressure measurement changes from a value substantially equal to the atmospheric pressure to a value greater than or equal to said threshold pressure value, while the acceleration measurement remains less than or equal to said minimum acceleration value and then, respectively, as soon as an acceleration measurement is greater than said threshold acceleration value; - Switching modes between the standard mode and the standby mode and the reverse switching of a wheel sensor can further be conditioned by a comparison between a set of successive tire pressure measurement variations of the sensor wheel considered and a reference pressure variation, during the same duration as that of the acceleration measurements, said switching mode being triggered when each value of said set of variations is substantially less than the reference variation and the inverse switching when at least the one of said values of said set is substantially greater than said reference variation; the threshold acceleration value is defined by a choice between an acceleration value adapted to the seasonal driving conditions of the vehicle, a servocontrol to a minimization calculation on a set of acceleration measurements taken during a suitable time period, and / or incorporating a fixed value that can be revised according to the type of use of the vehicle; the reference pressure variation is equal to a variation value greater than the pressure variation of the tire when the vehicle is stationary for a predefined period; - the acceleration measurement threshold duration is defined by a choice between a duration value adapted to seasonal conditions and the integration of a fixed duration; the threshold pressure value is equal to a value measured at the beginning of the vehicle's movement, and the acceleration is measured with a period chosen between two to six times longer in the standby mode than in the rolling mode. Other data, characteristics and advantages of the present invention will appear on reading the following nonlimited description, with reference to the appended figures which represent, respectively: FIG. 1, the block diagram of an exemplary unit wheel comprising a device for controlling a wheel sensor adapted to implement the method according to the invention; FIG. 2, an exemplary flowchart for defining the different modes of activity state of the wheel sensor - standby, non-rolling, rolling - and switching between these modes as a function of conditions on the pressure values. , acceleration and duration according to the method of the invention; and FIGS. 3a to 3c, examples of three diagrams of successive commutations between modes of activity state of a wheel sensor, in association with pressure and acceleration values of the corresponding wheel sensor.

The wheel unit 1 of the block diagram of FIG. 1 is implanted in the wheel rim of each tire of a vehicle (not shown). Such a wheel unit 1 consists mainly of a microcontroller 10 for managing the measurements provided by a wheel sensor 20 comprising pressure probes 21, acceleration 22 and temperature probes 23. The measurements are periodically supplied according to a setting made by counters 14 in connection with a reference clock 15. The periods of transmission of the measurements to the microcontroller 10 and between the microcontroller 10 and a central processing unit 30 of a TPMS system (not shown) are adjusted according to modes of operation. state of activity of the vehicle, as will be detailed below. The microcontroller 10 transmits pressure, acceleration and temperature data via a radiofrequency RF transmission module "E" RF to the central processing unit 30 of the TPMS system that equips the vehicle. Conversely, this central processing unit 30 transmits LF low frequency control data (initials of "Low Frequency" in English terminology) to the microcontroller 10. These control data are received by an M2 LF reception module. "R" in conjunction with the microcontroller 10 to set and store values of periods of measurement or communication. The switching conditions between the activity status modes, defined by the central processing unit 30, are also stored in the microcontroller 10. These switching conditions are adjustable by receiving control data from the controller. CPU 30 via the M2 module. The supply of electrical energy for the power-up of the probes 21 to 23, the microcontroller 10 and the transmission / reception modules Ml, M2, is provided by a stack 40, the duration of which must be optimized. life by reducing consumption. To do this, the invention then provides for the intervention of at least two modes of specific activity state of the pressure sensors 21 and acceleration 22 of each wheel sensor 20. FIG. 2 illustrates an example of a flowchart for defining the three modes of activity state of the wheel sensor 20 and switching between these modes, namely the idle modes 100, non-rolling 210, and rolling 220, the rolling and non-rolling modes constituting a standard mode 200. These activity status modes are defined in the central processing unit 30. Each activity status mode is defined by specific measuring periods of pressure, acceleration and temperature. a tire by the probes 21 to 23 (Figure 1), as well as specific periods of transmission / reception by the modules Ml, M2. Depending on the mode, it is also expected that measurements or communications are not made.

Thus, in the standby mode 100, only the measurements of pressure P, and of acceleration A, are activated with relatively long periods Tp and TA, respectively every 10 minutes and every minute in the example, these measurements making it possible to follow the wake up conditions for switching (arrow F1) to non-rolling mode 210. In this standby mode 100, the other measuring or transmission means are not used (period T.): the temperature measurements T, the pneumatic and E emissions, RF waves or R receptions, LF waves are disabled in order to best reduce power consumption. In practice, this standby mode 100 corresponds to the spring storage of the tire of flexible rubber called "winter tire", the pressure P, the tire storage is then substantially close to the atmospheric pressure Pm, for example less than 110 kPa. In the non-rolling mode 210, all the measurements and the communications can, in principle, be on alert, the pressure and the acceleration being measured over shorter periods than in the idle mode 100: in the example, the Pnr tire pressure is measured every 4 seconds and its Anr acceleration every 16 seconds. Thus, in the non-rolling mode 210, the measurement period of the acceleration Anr is approximately 4 times shorter than in the standby mode 100 and, in general, the ratio between these measurement periods can be between 2 and 6 times . Furthermore, the temperature Tnr is measured once per hour (TT period equal to 1 hour), the emission E, -, r is performed every 6 hours (period TE equal to 6 h) and the reception Rnr is listened to all the 2 seconds (period TR equal to 2 s). Advantageously, in order to further reduce the electrical consumption, the acceleration measurements Anr and temperature Tnr as well as listening to the reception Rnr of waves LF are only active if the measured pressure Pnr remains greater than or equal to a value threshold pressure Ps, equal to 1.2 bar (120 kPa) in the example. In the case where the tire pressure Pnr falls below the value of the pressure Ps, an alert is advantageously provided to warn the driver of the presence of a tire 30 which loses its load. When in rolling mode 220, it is planned to activate, in principle, all the measurements (pressure Pr, acceleration Ar, temperature Tr and emission Er) - as in the case of the non-rolling mode 210 - except listening to reception LF Rr waves which is deleted (period TR.) because, in rolling mode 220, no external control is compatible with the operation of a mobile wheel unit.

The periods of pressure measurement (TP), temperature (TT) and emission Er (TE) are of standard type in rolling mode 220: 4 seconds for the pressure Pr, 16 seconds for the acceleration Ar, 64 seconds for the temperature Tr, while the emission Er is transmitted every 6 hours (period TE equal to 6 hours).

As in the non-rolling mode 210, it is advantageous not to provide for the activation of the acceleration measurements Ar and of temperature Tr, as well as of the reception receiver Rr, as if the measured pressure Pr remains greater than or equal to the threshold pressure value P. The switching (arrow F1) of the idle mode 100 to the non-rolling mode 210 occurs when a tire pressure measurement P exceeds said value substantially close to atmospheric pressure, here the value of 110 kPa to reach a value at least equal to the threshold pressure value Ps equal to 1.2 bar in the example. Acceleration A remains close to zero in this switching, that is to say less than or equal to a minimum acceleration value An ,, here equal to 8g.

Conversely, switching from the non-rolling mode 210 to the standby mode 100 (arrow F2) takes place in the event of inactivation of the vehicle, detected by acceleration measurements Anr less than or equal to the minimum acceleration value An ,,, equal to 8g, for a long period of time DA greater than or equal to a threshold duration Ds, equal to 10 days in the example illustrated.

This passage of modes also occurs when a measurement of the tire pressure Pnr is substantially close to the atmospheric pressure Patm, for example less than 110 kPa, the acceleration remaining less than or equal to 8g. Moreover, the switching between the non-rolling mode 210 and the rolling mode 220 (arrow F3) is triggered as soon as an acceleration measurement Anr is greater than a threshold acceleration value As, equal to 9g in the example . And the reverse switching from the rolling mode 220 to the non-rolling mode 210 (arrow F4) is performed as soon as an acceleration measurement Ar is less than or equal to the minimum acceleration value Amin, equal to 8g in the example. Alternatively, it is possible to dispense with the non-rolling mode 210 and the standard mode 200 is then reduced to only rolling mode 220. The direct switching conditions (arrow F5) of the standby mode 100 to the rolling mode 220 then accumulate by coherent transition, those defined above between the idle modes 100, non-rolling 210 and rolling 220, namely: as soon as an acceleration measurement A, of the corresponding tire is greater than or equal to the threshold acceleration value As here 9g, and a measurement of the pressure P, of the corresponding tire is simultaneously greater than or equal to the threshold pressure value Ps, equal to 1.2 bar in the example.

Conversely, to switch directly from the rolling mode 220 to the standby mode 100 (arrow F6), it suffices that no acceleration Ar is greater than or equal to the minimum acceleration value Amui, predefined at 8g in the example, for a duration DA at least equal to the threshold duration Ds, here equal to 10 days.

Examples of successive commutations between the three modes of activity state 100, 210 and 220 of a wheel sensor 20 (FIG. 1) are illustrated by the diagrams of FIGS. 3a to 3c as a function of time "t" and by connection with acceleration values "A" and pressure "P" of the corresponding tire. The first diagram (FIG. 3a) illustrates the sequence of "standard" state modes involving the non-rolling 210 and rolling 220 modes. In this diagram, the "P" pressure of the tire remains greater than the pressure value. threshold Ps (1.2 bar) and its acceleration "A" has four successive sequences: a sequence Si in which the acceleration "A" is less than the minimum acceleration Amui of 8g; A sequence S2 with acceleration values in general greater than the threshold acceleration value As of 9g, and a sequence S3 during which the acceleration "A" again appears lower than Amin, and an S4 sequence. in which the acceleration "A" rapidly reaches a value greater than the threshold acceleration value A. Under these conditions, the state modes follow one another in the following manner according to the sequences: the sequences Si and S3 correspond to the non-rolling mode 210 since the acceleration "A" is less than Amin and therefore close to zero and the pressure 25 "P" greater than the threshold value Ps (and not the standby mode which is defined with a tire pressure close to atmospheric pressure); and the sequences S2 and S4 relate to the rolling mode 220 since the pressure "P" and the acceleration "A" have values greater than the threshold values, respectively Ps (120 kPa) and As (9g). The diagram of FIG. 3b generally presents the pressure "P" and the acceleration "A" of the tire, respectively with a value close to the atmospheric pressure Pat (less than 110 kPa) and a value lower than the minimum value Amin. (8g) in a central sequence (S7), framed by pressure values "P" and acceleration "A" higher than the threshold values of activity Ps and As 35 (respectively 120 kPa and 9g). Thus, this diagram comprises four sequences S4 to S8 corresponding to the following state modes: in sequences S5 and S8: the pressure "P" and the acceleration "A" being greater than the threshold values P, and A, (respectively 120 kPa and 9g), these sequences relate to rolling mode 220; in sequence S6: the pressure "P" remaining greater than the threshold value P, of 120 kPa and the acceleration being less than the minimum value Amin of 8 g, the state mode corresponds to the non-rolling mode 210; and in sequence S7: the values of the pressure "P" and the acceleration "A" being minimal, respectively close to the atmospheric pressure Patm (less than 110 kPa) and lower than the minimum acceleration value Amin (8g ), the state mode goes into standby mode 100. The third diagram of FIG. 3c is also divided into four sequences S9 to S12. In this diagram, the pressure "P" of the tire of the wheel unit remains greater than the threshold value Ps (120 kPa) while its acceleration "A" follows the same profile as in the diagram of FIG. 3b, namely a minimum value in the central sequences S10 and S11 (less than the Amin acceleration, ie 8g in the example) framed by values greater than the threshold value A, (equal to 9g in the example) in the extreme sequences S9 and S12 . Under these conditions, the state modes follow one another as follows: in sequences S9 and S12: as for the sequences S5 and S8 of FIG. 3b, the pressure "P" and the acceleration "A" being greater than threshold values P, and A, (respectively 120 kPa and 9g), these sequences S9 and S12 relate to the rolling mode 220; and in sequences S10 and S11: the acceleration "A" decreasing to a value lower than the minimum value Amin (here 8g), the rolling mode 220 of the sequence S9 switches to non-rolling mode 210 since, simultaneously, the pressure remains above the operational threshold value P, (120 kPa in the example); the conditions do not vary substantially for a period DA equal to the threshold duration D, extending over 10 days, the non-rolling mode 210 switches to the standby mode 100 to the flow of this duration D, 10 days.

The invention is not limited to the embodiments described and shown. Other diagrams can illustrate the sequence of different activity state modes from a flowchart illustrating switching between activity status modes, such as that of Figure 2 or equivalent. Thus, the switching of modes between one of the standard modes and the standby mode, or respectively the inverse switching, can be subject to an additional condition from a comparison between a set of variations and a reference variation, for example. example of 0.5 bar (50 kPa) for a given time for example 1 day. The mode switches are then triggered when a value or a determined number of values is substantially lower, respectively greater than the reference variation, the difference being for example 0.3 bar (30 kPa). The reference pressure variation may be adjusted with respect to a ceiling variation value, this ceiling variation being able to be the pressure variation of the tire when the vehicle is stationary for a given duration, for example for at least 15 minutes. It is also possible to introduce other intermediate activity state modes by setting more specific conditions on the measurement and communication periods or by adding other more stringent conditions for switching between the state modes of carrying state. on other parameters, for example the temperature or the wear of the tire. Furthermore, the threshold acceleration value As or, respectively, of the threshold duration Ds may be dictated by an adaptation to the type of tire according to the model of the vehicle and / or the meteorological / seasonal driving conditions, for example between 1 , 2 bar (110 kPa) and 2 bar (200 kPa) or, respectively, between 3 and 20 days. In addition, the threshold acceleration value As may also result from servocontrolling a minimization calculation of a set of acceleration measurements taken during a given time period when the vehicle is traveling, for example between 10 minutes and 10 minutes. one o'clock. Alternatively, a fixed value can be used, this fixed value can advantageously be revised depending on the type of use of the vehicle. In addition, the threshold pressure value ID may be that measured at the beginning of movement of the vehicle, for example 100 meters in order to use the current value, adapted to the type of tire.

Claims (8)

REVENDICATIONS1. A method of automatically stopping the wheel sensors (20) of a TPMS system for controlling the tire pressure (P) of the corresponding wheels of a vehicle, wherein the wheel sensors (20) periodically supply a unit central processing unit (30) of corresponding wheel tire parameter measurements, namely at least pressure parameters (P; Pv, Pnr, Pr) and acceleration parameters (A; Av, Anr, Al), characterized in that what it consists in switching the operation of a wheel sensor (20) between at least two activity status modes (100, 200; 100, 210, 220), while passing from a mode of operation said standard (200; 210, 220) of the vehicle to a so-called idle rest mode (100) when no acceleration (Ar, Anr), greater than or equal to a predefined minimum acceleration value (Amin), is measured for the corresponding tire for a duration greater than or equal to a threshold duration of my ure of acceleration (De), the acceleration (Ar, Anr) being then measured according to a period of substantially longer duration in standby mode (100) than in standard mode (200; 210, 220), and in that it consists in switching each wheel sensor (20) from the standby mode (100) to the standard mode (200; 210; 220) as soon as an acceleration measurement (Au) of the tire corresponding is greater than or equal to a predefined threshold acceleration value (As) and a measurement of the pressure (Pu) of the corresponding tire is simultaneously greater than or equal to a predefined threshold pressure value (Ps). The automatic standby method according to claim 1, wherein the standard mode (200) comprises a non-rolling mode (210) and a rolling mode (220), the non-rolling mode (210) being introduced. in the standard mode (200) for interposing between the rolling mode (220) and the standby mode (100), so that the rolling mode (220) switches (F6) first to the non-rolling mode (210). ) as soon as an acceleration measurement (Ar) of the corresponding tire is less than or equal to said predefined minimum acceleration value (Amin), then the non-rolling mode (210) switches (F4) to the standby mode (100). ) when the acceleration (Anr) remains less than or equal to this predefined minimum acceleration value (Amin), for a period of time equal to said acceleration measurement threshold time (De) OR if a pressure measurement ( Pnr) of the corresponding tire is substantially equal to the atmospheric pressure (Patm), the acceleration (Anr) being simultaneously lower than or equal to said minimum acceleration value (Amin), and wherein inverse commutations (F1; F3) from the standby mode (100) to the non-rolling mode (210) and then to the rolling mode (220) are triggered when a pressure measurement (Pu) changes from a value substantially equal to the atmospheric pressure (Patm) to a value greater than or equal to said threshold pressure value (Pe), while the acceleration measurement (Au) remains less than or equal to said minimum acceleration value and then, respectively, as soon as an acceleration measurement (Anr) is greater than said threshold acceleration value (As). An automatic standby method according to any one of the preceding claims, wherein the mode switching (F2) between the standard mode (200) and the idle mode (100) and the inverse switching (F1) of a wheel sensor (20) are further conditioned by a comparison between a set of successive tire pressure measurement variations of the respective sensor wheel (20) and a reference pressure variation, for the same duration as that of the acceleration measurements (A; A ', Anr, Ar), said mode switching (F2) being triggered when each value of said set of variations is substantially less than the reference variation and the inverse switching (F1) when at least one of said values of said set is substantially greater than said reference variation. An automatic standby method according to any one of the preceding claims, wherein the threshold acceleration value (As) is defined by a choice between a value adapted to the seasonal driving conditions of the vehicle, a servo to a minimization calculation on a set of acceleration measurements (Ar) taken during a suitable period of time, and / or the integration of a fixed value that can be revised according to the type of use of the vehicle. 20 The automatic standby method according to claim 3, wherein the reference pressure variation is equal to a variation value greater than the pressure variation of the tire when the vehicle is stationary for a predefined period of time. An automatic standby method according to any one of the preceding claims, wherein the acceleration measurement threshold duration (De) is defined by a choice between a duration value adapted to seasonal conditions and the integration of a fixed duration. An automatic standby method according to any one of the preceding claims, wherein the threshold pressure value (Ps) is equal to a value measured at a start of vehicle travel. An automatic standby method according to any one of the preceding claims, wherein the acceleration (A; A ', Ar, Anr) is measured with a period selected from two to six times longer in idle mode (100 ) than in standard mode (200; 210, 220).