Tyre pressure monitoring system

The invention relates to a method for carrying out the allocation of the wheel position to air pressure control devices in an air pressure monitoring system of a motor vehicle, which has among others the following components:<ul><li>a number of wheels, wherein each wheel is associated with an air pressure control device which is for emitting an individual identification to a central unit capable of</li><li>a central processing unit, is the allocation (identifier of the air pressure control device / wheel position) is stored for each wheel wherein the allocation of the air pressure control devices to the wheel positions is carried out as follows:<ul><li>Switching on a mapping mode</li><li>Sending the individual identifiers of the air pressure control devices</li><li>Evaluation in the central unit, which individual identifier sent from which wheel position </li><li>Storing the determined assignment in the central unit</li><li>Off the mapping mode and operate the air pressure control system in a pressure monitoring mode.</li></ul></li></ul> The invention further relates to an air pressure monitoring system of a motor vehicle.

Proper adjustment of the air pressure of vehicle wheels is important with regard to different aspects. On the one hand, too high or too low air pressure leads to increased tire wear, so that the vehicle tires need to be replaced prematurely which causes unnecessary costs. On the other hand especially prone to a lower air pressure a significant security risk in itself, as it causes increased flexing of the tire wall, resulting in a strong increase in temperature of the motor vehicle tire. Consequently, the strength of the tire walls from clear what can lead to a "burst" of the motor vehicle tire and therefore particularly at high speeds to serious traffic accidents.

For the above reasons, the air pressure of automobile tires must be checked regularly, which is often neglected by the motor vehicle driver, for various reasons. Therefore, air pressure control systems have already been developed that each wheel associated contain an air pressure control device that automatically measure the air pressure of automobile tires and at least a critical deviation from a desired air pressure reported to the motor vehicle driver. The air pressure control devices can be, for example vulcanized or glued into the tire or on or in the valve or on or attached in the rim. Corresponding embodiments are known.

DE 42 05 911 A1 an air pressure control system is known in which each tire of the vehicle in each case an air pressure control device is assigned. Each air pressure control device periodically transmits a measured pressure signal together with an individual identification to a central unit. The transmission of an individual identifier, together with the pressure signal is therefore particularly important because without contact with the air pressure control system is known from DE 42 05 911 A1 data is transmitted from the tire to the motor vehicle. It must be excluded, therefore, for example, that for example, be received in the ram air pressure data of an adjacent vehicle and there is misreporting to the motor vehicle driver based on these data. This is made possible by the individual identifiers because the tires of another vehicle naturally send other individual identifiers. In the central unit value pairs of the form (identifier of the air pressure control device / wheel position) are stored for each wheel of the motor vehicle, so that can be closed by appropriate comparison in the central unit on which identification is sent with the corresponding pressure signal from which wheel position of the motor vehicle. A deviation of the transmitted pressure signal from a value assigned to a wheel position is the motor vehicle driver by the central unit display so that it can take appropriate measures.

comments show that the can 42 05 911 A1 known air pressure control system can only function from DE properly if the central unit assignments (identifier of the air pressure control device / wheel position) are stored properly. Accordingly, on the one hand it must be ensured that this mapping does not change during operation of the motor vehicle and on the other hand a new assignment after each tire change must be made to the motor vehicle. To satisfy these two conditions, a manually operated switch is provided in the air pressure control system is known from DE 42 05 911 A1, which is reversible only at standstill of the motor vehicle and converts the air pressure control system after a tire change of a pressure monitoring mode in a mapping mode. In the mapping mode a mapping of the new motor-vehicle tires with the included therein new air pressure control devices to the wheel positions takes place, for example, characterized in that the intensity of the signals transmitted by each air pressure control devices assigned to the wheel positions of receivers is measured, and each emitted from a air pressure control device signal from the wheel position of the is motor vehicle tire assigned to which it produces the highest signal intensity (for example, the signal intensity of the air pressure control device, which is on the front left tire, be at the receiver is greatest, is assigned to the wheel position front left, so that a corresponding allocation can be found ). The corresponding allocations are stored in the central unit. After completion of the assignment of the switch will turn, converted mauell, so that the air pressure control system is again in its pressure monitoring mode.

By providing the manually operated switch ensures that the mapping does not change during operation of the motor vehicle, since the switch of the motor vehicle can not be recovered. However, there is a danger that the manual switching from the Druchküberwachungsmoduns forgotten in the mapping mode after a tire change and that a new assignment in the central unit is not stored. In this case, the air pressure control system is no longer functional and an excessively low pressure is no longer reported. The safety of the motor vehicle is then limited German light. This risk is particularly high when the tire change from one untrained person, for example, of the motor vehicle driver is to have a flat tire, etc., performed.

The invention has for its object to provide a method of performing the mapping of air pressure control devices to the wheel positions, which excludes the above-described security risk. The invention further has for its object to provide an air pressure control system for implementing the method.

In a method of the type mentioned, the object according to the characterizing features of claim 1 is achieved in that<ul><li>automatically switching on the allocation mode before or during commissioning of the motor vehicle</li><li>the assignment of the air control devices to the wheel positions during operation of the motor vehicle and that</li><li>will be closed automatically after completion of assignment of the mapping mode.</li></ul> A switch on the mapping mode during commissioning of the motor vehicle can be done for example by switching on the ignition or when operating the starter. The allocation of individual air pressure control devices to the wheel positions can for example be carried out as it has already been explained above in connection with DE 42 05 911 A1. Below is explained in detail how the assignment can be done alternatively.

According to the independent product claim 7, the object is achieved with an air pressure control system of the type explained by the fact that the air pressure control system is designed such that<ul><li>it is automatically switched to the allocation mode before or during commissioning of the motor vehicle and that</li><li>after completion of assignment, the assignment mode can be switched off automatically and the air pressure control system can only be operated in a pressure monitoring mode.</li></ul>

To perform the switching operations, the central unit of the air pressure control system preferably includes a microprocessor, in each of which a subroutine for the Drusküberwachungsmodus and the mapping mode is saved. By switching on the ignition of the vehicle is the subprogram "allocation mode" is called and executed. In this case, the subprogram "allocation mode" subroutine "pressure monitoring mode" enabled and are processed in a "break" of the subroutine "pressure monitoring mode". This is possible because only at intervals, for example, are received approximately every 30 seconds pressure values ​​to the central unit and evaluated by the latter and caused the said intervals between transmissions. A connection of the mapping mode to the pressure monitoring mode is particularly advantageous, since then the pressure monitoring mode at zugeschaltetem mapping mode at least still extreme pressure deviations can be reported to the motor vehicle driver, which could result in a hazard. This misreporting due to the not yet performed assignment to be accepted in favor of the safety of the motor vehicle. Once the assignment is the subprogram "allocation mode" is turned off and only performed the subprogram "pressure monitoring mode".

Alternatively, it is also possible, when carrying out the subroutine "mapping mode" disable the subroutine "pressure monitoring mode", and to switch on again after the assignment.

The basic idea of ​​the invention is the fact that the allocation of the air pressure control devices will be made to the wheel positions during operation of the motor vehicle. The invention makes the simple se insight that the operation of the vehicle, a tire change can not be performed, so that a tire change during the last shutdown of the motor vehicle is definitely detected. This simple se knowledge allows automation of the process and therefore, the invention in the opposite direction than the initially cited prior art.

The advantages achieved with the invention are particularly seen in the fact that the process is carried out automatically and thus eliminates manual switching of a pressure monitoring mode in a mapping mode. The inventive method the safety of the motor vehicle is also considerably increased, since an automatic carrying out the process a turn on the mapping mode can not be forgotten. Another advantage of the invention is the fact that during the automatic execution of the process eliminates operator error on the part of an operator. Finally, it is increased by the automation of the method of the ease of operation of the air pressure control system.

According to one embodiment of the invention according to claim 2, the method is carried out at each start of the motor vehicle. This ensures that a final between the closure and the next time the motor vehicle owned by tire changes detected definitely and a new allocation of the air pressure control devices contained in the new tire is performed to the wheel positions.

According to an alternative embodiment of the invention according to claim 3, the procedure is always carried out when the motor vehicle is stopped for more than a predetermined period of time. A predetermined period of time can be detected for example by a timer in the central unit. The advantage of this embodiment is the fact that the procedure is not performed after each shutdown of the motor vehicle, but only if the duration of the closure exceeds a predetermined period. Preferably, the predetermined period is chosen so long that within this period a tire change is excluded. As such a period, for example, about 5 - will be accepted for 30 minutes. The advantage of this embodiment is the fact that a new allocation is only rarely carried out and therefore in most cases already upon boarding the current assignment is stored in the central unit.

According to a development of the invention according to claim 4, the allocation of the air pressure control devices to the wheel positions in the mapping mode is as follows:<ul><li>at each wheel of the vehicle size is with the first measuring devices, one of which is associated with each one of the corresponding air pressure control device of the respective tire measured, which takes at least temporarily, for each wheel of the motor vehicle a characteristic value</li><li>the same size is measured at each wheel of the motor vehicle with the second measuring devices, each of which is stationary and a wheel position associated fixed to the motor vehicle, wherein the allocation of the second measuring devices to the wheel positions of the central unit is known</li><li>the values ​​measured by the first measuring devices sizes are received together with the individual identifications of the air pressure control devices to the central unit</li><li>the values ​​measured by the second measuring devices values ​​are also transmitted to the central unit, so that present in the central unit value pairs of the form (measured value / wheel position)</li><li>the values ​​measured by the first measuring means values ​​are compared with the gemessenenen of the second measuring devices values, wherein in sufficient conformity of the measured values ​​concluded that the transmitted together with the first measured value identifier belongs to the wheel position at the second of a measuring device a measured value was measured with sufficient agreement as a first measuring device</li><li>the resulting allocation (identifier of the air pressure control device / wheel position) is stored in the central unit.</li></ul>

Here, here and understand below with sufficient consensus that the measured values ​​correspond to measurement technology to unavoidable disparities and thus an unambiguous assignment is possible. The advantage of this development is to be seen particularly in the fact that can be dispensed with elaborate Radhausantennen that are necessary in the allocation method known from DE 42 05 911 A1 to measure the signal intensities of the light emitted from the air pressure control devices signals with sufficient accuracy, whereby the air pressure control system is cheaper.

It has been shown that a measurement that is based on "individual wheel sizes", is carried out in a fairly short period of time, as present on the vehicle wheel for various reasons almost always custom measurements. As suitable measured variable has, for example, the wheel speed (turns / time) or each of these variables from which the wheel speed can be derived, have proven both of the sensors which are assigned to the air pressure control devices, as well as sensors that each wheel of the motor vehicle are permanently assigned to be measured. The wheel speed of each wheel of the motor vehicle is different, for example, when cornering, but also in straight driving are already, for example due to different wear or due to manufacturing tolerances, individual wheel speeds before, which are sufficient for an allocation of the air pressure control devices to the wheel positions.

Suitable sensors which are assigned to the air pressure control devices and are used to measure the wheel speed, for example, magnetic field sensors, centrifugal sensors, gravity sensors and accelerometers have been found. Particularly suitable gravity sensors have proven, in which a small mass generates a raddrehsynchrone charge displacement in a piezoelectric element acting. For example, a charge transfer is in such an element always by the applied pressure generated when a tire of the vehicle and thus the element contained in it passes through the ground contact point of the tire. The number of charge transfer cycles produced is counted in an evaluation circuit of the sensor. Simultaneously, the time is measured with the aid of a timer contained in the evaluation circuit. The wheel speed (revolutions / time) can be determined in the evaluation now, by determining how much revolutions has made the wheel with the corresponding sensor in a fixed, predetermined period or which period for a fixed number of required revolutions.

As sensors which measure the wheel speed and which are permanently assigned to the individual wheels of the motor vehicle, for example, the sensors of an antilock braking system may be used, which is already present in many vehicles, so that additional sensors are not needed.

Alternatively, the wheel speeds may be measured by the first and second measuring devices and the noise, the oscillation behavior or the tire temperature at the individual vehicle wheels. Again, it has been shown that the relevant variables have a "sufficient individuality". To measure these sizes corresponding sensors are known, so that these sensors are to be explained here in detail.

In summary, it should be noted that the allocation of the air pressure control devices to the wheel positions is carried out automatically by the inventive method. This is impossible for a tire change is not detected, since the process is carried out immediately after each start-up or whenever the vehicle standstill for so long that a tire change could be carried out.

Further advantages and an exemplary embodiment of the invention will be explained in connection with the following figure, which shows a motor vehicle with an air pressure control system.

The figure shows a motor vehicle having wheels 2a to 2d that has an air pressure control system. The air pressure control system includes, inter alia, air pressure control devices 6a to 6d, one of which is respectively contained in the tires of motor vehicle wheels 2a to 2 d, (eg in the tire rubber, or in or on the valve) or one of which is respectively associated with a tire, for example by appropriate positioning and attachment to the rim. The air pressure control devices 6a to 6d include a transmitter, by means of which it to the air pressure control devices 6a to 6d associated receiver 8a to 8d can transmit data without contact. In addition, the air pressure control devices 6a to 6d include sensors 16a to 16d, whose function will be explained later. The receivers 8a to 8d transmit the data received from the air pressure control devices 6a to 6d data over transmission paths 12a to 12d to a central unit 10. The receivers 8a to 8d can also be replaced by a single receiver, which is arranged for example in the central unit 10 and the signals all air pressure control devices 6a to 6d receives. In this case, to omit the transmission paths 12a to 12d by the receivers 8a to 8d to the central unit. In the simplest case, the receiver 8a-8d and the only recipient are formed as receiving antennas.

The air pressure control system includes sensors 16a to 16d in addition to the sensors 4a to 4d, which are attached to the motor vehicle and each having a wheel 2a to 2d of the vehicle assigned. The sensors 4a to 4d are over transmission paths 14a to 14d also with the central unit 10 in connection.

Hereinafter, the operation of the Luftdruckontrollsystems will be explained. Prior to or at the start of the mapping mode of the air pressure control system is switched on automatically. This can occur, for example, that 10 a subprogram "allocation mode" is invoked by switching on the ignition in a microprocessor of the central unit, which is then "processed" and controls the assignment. In the assignment mode, both of the sensors 16a to 16d, which are the air pressure control devices assigned 6a to 6d, was added as well as by the sensors 4a to 4d measured variables, which are in the operation of the vehicle at least at times for each individual vehicle wheel 2a to 2d of the motor vehicle and evaluated in the CPU 10th In the following example it is assumed that this is the wheel speed of the individual vehicle wheels 2a to 2d and the sensors 16a to 16d and 4a formed correspondingly to 4d as speed sensors. The measured by the sensors 16a to 16d wheel speeds are transmitted together with the individual identifications of the air pressure control devices 6a to 6d and the pressure values, and optionally further measured values ​​to the receivers 8a to 8d and from there via the transmission paths 12a to 12d to the central unit 10th In the central unit 10 thus lie on each vehicle wheel 2a to 2d value pairs of the form (individual identifier of an air pressure control device / wheel), which of these pairs is not yet known, have been from which wheel position sent from them.

The measured by the sensors 4a to 4d wheel speeds are also transmitted via the transmission paths 14a to 14d to the central unit 10th Since the sensors 4a to 4d the individual wheels 2a to 2d of the vehicle permanently assigned, "looking", the central processing unit, to which wheel position the corresponding wheel speed has been measured (due to the fixed assignment facing the central unit 10, for example, that the sensor 4a, the wheel speed the front left wheel motor vehicle 2a sends, etc.).

In the central unit 10 all wheel speeds 6a transmitted from the sensors 16a to 16d of the air pressure control devices to 6d with all information provided by the sensors 4a to 4d wheel speeds are compared. A fixed assignment of an air pressure control device 6a to 6d to a wheel position is then made in the central unit, if the temperature measured by a sensor 16a to 16d with the wheel speed measured by one of the sensors 4a to 4d wheel speed coincides sufficiently accurately. The corresponding assignment (individual identifier of an air pressure control device / wheel position) is then stored in the central unit 10 (for example, is a match of the measured wheel speeds before, when the temperature measured by the sensor 16a wheel speed is compared with that of the sensor 4a measured wheel speed; the central processing unit " note "that the respective measured wheel submitted by the vehicle wheel 2a front left, since the sensor is 4 this wheel position associated with the front left fixed. Accordingly, allocates the CPU 10 the übermittelteindividuelle of the air pressure control device 6a withdrawing wheel position left front of the motor vehicle wheel 2a and stores this from. A similar procedure with the other wheel positions. Are this way created and saved all relevant assignments, the assignment is completed, and the assignment mode is automatically released. this may for example again be done by the after storing the mappings subprogram "allocation mode" of a microprocessor of the central unit 10 is left.

Example: Of the four air pressure control devices 6a to 6d reach the central unit 10, the series of values ​​(K₁; 100; 2.0); (K₂; 115; 2.0); (K₃; 105; 2.2); (K₄; 120; 2.2), where K_i i = 1 ... 4 respectively the identifier, the average value of the wheel rpm and the last value in the parentheses each represent in each bracket printing. The central unit 10 "looking" not at first, from which wheel position which values ​​range comes. In addition, access of the speed sensors 4a to 4d, the measured wheel speeds to the central unit 10, namely in this case, for example, 98 by the sensor 4a, 113 of the sensor 4c, 4b and 105 from the sensor 122 from the sensor 4d. The central unit 10 "looking" because of the fixed allocation of the sensors 4a to 4d to the wheel positions, that the speed of 98 on the wheel 2a front left, the speed 113 on the wheel 2c front right, the speed 105 2b to the left rear wheel and the speed was 122 measured at the wheel 2d rear right. By comparing the values ​​measured by the air pressure control devices 6a to 6d with the wheel speeds measured by the sensors 4a to 4d wheel speeds, the central unit 10 can now that the individual identifiers K_i, I = 1 ... 4 assign the wheel positions, especially in this example, make the following assignments: (K₁; Wheel position "front left" of the wheel 2a); (K₂; Wheel position "front right" of the wheel 2c); (K₃; Wheel position "rear left" wheel 2b); (K₄; Wheel position "rear right" of the wheel 2d), there exists at the corresponding wheels, the best match between the independently measured Radrehzahlen. The corresponding allocations are stored in the central unit 10 and used in the pressure monitoring mode. May an unambiguous assignment based on the measured values ​​can not be carried out, for example because 2a to 2d are measured by the sensors 4a to 4d same wheel speeds of two wheels or more, so the mapping mode is continued until this is possible.

Through the pressure values ​​transmitted in the assignment mode, a warning is triggered only when a certain minimum pressure value of 1.2 for example is below bar.

In pressure monitoring mode, the air pressure control system works as known. That is, by the air pressure control devices 6a to 6d individual identifiers together with the measured pressure values, and optionally further measuring values ​​as well as values ​​of the wheel speed is transmitted to the receivers 8a to 8d and passed on from there to the central unit 10th In the central unit 10, the transmitted individual identifiers with the stored tags are compared and when a match is determined, from which wheel position the individual identifier is sent with the corresponding pressure value. The wheel speeds of the CPU 10 in the pressure monitoring not evaluated mode. Should the transmitted pressure value or one of the other variables on one of the vehicle wheels 2a to 2d in an impermissible manner from a predetermined value, this is reported to the motor vehicle driver, so that it can take appropriate action. Example: From the Luftdruckontrollvorrichtungen 6a through 6d are wiederrum value series of the form (K₁; 150; 1.5); (K₂; 153; 2.0); (K₃; 149; 2.2); (K₄; 147; 2.2) transmitted to the Central Unit 10th Because the stored assignments (supra.), The central processing unit to determine 10 that the first set of values ​​from the wheel position "front left", the second series of values ​​from the wheel position "front right", the third set of values ​​from the wheel position "rear left" and the fourth series of values ​​transmitted from the wheel position "rear right" because the corresponding individual identifiers in the transmitted values ​​range and stored assignment in these specified wheel positions coincide. The central unit 10 can determine now that the pressure of 1.5 bar at the wheel position "front left" the pressure of 2.0 bar at the wheel position "front right" and the pressure of 2.2 in each of the wheel positions "Rear Left "and" Rear right was "measured. Optionally, a warning may be issued if one of the measured air pressures deviates from a predetermined value. In the example, a warning is issued because of the air pressure of 1.5 bar at the wheel position is "Front L" too low.

LIST OF REFERENCE NUMBERS

<dl id="dl0001" compact="compact"><dt>2a - 2d</dt><dd>motor vehicle wheel</dd><dt>4a - 4d</dt><dd>, The wheel position sensor is permanently assigned</dd><dt>6a - 6d</dt><dd>Air pressure control device with sensor</dd><dt>8a - 8d</dt><dd>receiver</dd><dt>10</dt><dd>central processing unit</dd><dt>12a - 12d</dt><dd>Transmission of receiver 8a - 8d to the central unit 10</dd><dt>14a - 14d</dt><dd>Transmission of sensor 4a - 4d to the central unit 10</dd><dt>16a - 16d</dt><dd>Sensors of the air pressure control devices 6a - 6d</dd></dl>