Tyre pressure monitoring system

The invention relates to a method for carrying out the Assignment of the wheel position to air pressure control devices in an air pressure control system of a motor vehicle, which, inter alia, the following components has:<ul><li>a number of wheels, wherein each wheel of a Air pressure control device is associated with that for Sending an individual identifier to a Central processing unit is capable of</li><li>a central processing unit, in which the allocation of the identifier an air pressure control device to the wheel position for each wheel is saved</li></ul>wherein the allocation of the air pressure control devices to the wheel positions is effected as follows:<ul><li>Switching on a mapping mode</li><li>Transmission of individual identifiers of 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 central processing unit</li><li>Off the mapping mode and operating the Air pressure control system in a Pressure monitoring mode.</li></ul>

The invention further relates to an air pressure control system of a motor vehicle.

Proper adjustment of the air pressure of Motor vehicle wheels with respect to different Aspects important. A hand, a too high or a too low air pressure in increased tire wear, so that the vehicle tires need to be replaced prematurely, which causes unnecessary costs. On the other hand holds in particular to a lower air pressure a significant Security risk in itself because it increased flexing of causing tire walls, resulting in a strong increase in temperature the motor vehicle tire leads. Consequently, taking the strength of the tire flanks clear on what a "Bursting" of the motor vehicle tire and thus particularly in lead high speeds to serious traffic accidents can.

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

DE 42 05 911 A1 is an air pressure control system known, on the one hand, the method features of the preamble of claim 1, and also, the subject features of the preamble of claim 7, and in which each tire of the motor vehicle each have a Air pressure control device is assigned. Each Air pressure control device transmits at regular Intervals a measured pressure signal with a individual identification to a central unit. The transmission is an individual identifier along with the pressure signal especially important because in the DE 42 05 911 A1 known air pressure control system without contact data from Tires are received from the motor vehicle. It must therefore for example, be ruled out that, for example in a traffic jam received air pressure data of an adjacent motor vehicle be and based on these data to misreporting to the Motor vehicle driver comes. This is achieved by the individual IDs made possible since the tire of another Motor vehicle naturally different individual identifiers send. In the central unit value pairs are of the form (Identifier of the air pressure control device / wheel position) for saved each wheel of the motor vehicle, so that by corresponding comparison in the central unit it it can be concluded that identification with the corresponding Pressure signal from which wheel position of the motor vehicle is sent. A deviation of the transmitted pressure signal of a value assigned to a wheel position is the shown motor vehicle driver by the central unit, so that this may take appropriate measures.

comments show that the DE 42 05 911 A1 known air pressure control system only works properly can work if the central unit assignments (Identifier of the air pressure control device / wheel position) correctly stored. Accordingly, must on the one hand be ensured that this assignment during the Operation of the motor vehicle does not change and, secondly, has a new assignment after each tire change on the motor vehicle be made. To these two constraints to enough is known from DE 42 05 911 A1 Air pressure control system a manually operated switch provided the reversible only at standstill of the motor vehicle is and the air pressure control system after a tire change of a pressure monitoring mode in a mapping mode transferred. In the mapping mode finds an assignment of the new motor vehicle tires with the new contained therein Air pressure control devices to the wheel positions held, for example, the fact that the intensity of each of the air pressure control devices the transmitted signals from the Wheel positions associated receivers is measured and each emitted by an air pressure control device signal the Wheel position of the vehicle tire is assigned to which it produces the highest signal intensity (For example, the signal intensity of the Air pressure control device, in the front tires left, is, at the receiver at its largest, the is wheel position front associated links, so that a can be determined corresponding mapping). The corresponding allocations are in the central unit stored. After completion of the assignment of the switch in turn, converted mauell, so that the air pressure control system is back in his pressure monitoring mode.

is by the providence of the manually operated switch ensures that the assignment during operation of the motor vehicle does not change, since the switch of the Motor vehicle can not be recovered. However, there is the risk that the manual switching from the Druchküberwachungsmoduns in the mapping mode after a tire change forgotten and that a new assignment in the central unit is not stored. In this case, the Air pressure control system no longer functional and to 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 after a flat tire, etc., performed.

The invention is based on the object, a method of Implementation of the allocation of the air pressure control devices to provide to the wheel positions, which the above-described Vulnerability excludes. The invention is also the Object of an air pressure control system for carrying out the process of creating.

In a method of the type mentioned is the Task according to the characterizing features of claim 1 solved in that<ul><li>before or at Commissioning of the motor vehicle, the assignment mode is automatically switched to the pressure monitoring mode.</li><li>the allocation of the air control devices to carried wheel positions during operation of the motor vehicle and that</li><li>after completion of assignment, the assignment mode will be closed automatically.</li></ul>

A switch on the mapping mode when commissioning the Motor vehicle, for example, by turning on the done ignition or upon actuation of the starter. The Assignment of the individual air pressure control devices to the Wheel positions can be, for example, made as it above in connection with DE 42 05 911 A1 has been explained. Below is explained in detail, as the assignment can be done alternatively.

According to the independent product claim 7 is the task at an air pressure control system of the type explained achieved in that the air pressure control system in such a way is adapted to<ul><li>before or during commissioning of the motor vehicle, the assignment mode the pressure monitoring mode is automatically switched on and that</li><li>after completion of assignment, the assignment mode automatically switched off and the air pressure control system operated exclusively in the pressure monitoring mode is.</li></ul>

To carry out the switching operations contains the central processing unit the air pressure control system preferably includes a microprocessor, in each of which a subroutine for the pressure monitoring mode and the mapping mode is saved. By Switching on the ignition of the motor vehicle, the Subprogram "allocation mode" is called and executed. Here is the subprogram "allocation mode" the Subprogram "pressure monitoring mode" turned on and in a "break" of the subroutine "pressure monitoring mode" processed. This is possible because only in Intervals, eg approximately every 30 seconds pressure values ​​to the are received and evaluated by the central unit and between the transmissions referred breaks arise. A connection of the mapping mode to the Pressure monitoring mode is particularly advantageous because then the pressure monitoring mode at zugeschaltetem Mapping mode at least still extreme pressure deviations the vehicle driver can be reported that a could lead hazard. Here, in favor of Safety of the motor vehicle misreporting due to the still failure to assignment accepted. After Assignment is the subprogram "allocation mode" switched off and only the subroutine "Pressure monitoring mode" performed.

The basic idea of ​​the invention is the fact that the Assignment of the air pressure control devices to the Wheel positions is carried out in the operation of the vehicle. The invention makes the simple se knowledge advantage that the operation of the vehicle, a tire change can not be carried out so that a tire changing during the last-aside of the motor vehicle in any Case is detected. This simple se knowledge Allowed Automation of the method and thus has the Invention in the opposite direction as 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 a manual switchover from a pressure monitoring mode deleted in a mapping mode. By the The method according to the invention is further the safety of significantly increased motor vehicle, as in a automatically performing the method, a switch on the Mapping mode can not be forgotten. Another Advantage of the invention lies in the fact that in the automatic carrying out the process operating errors are excluded by an operator. After all is by automating the process of the Ease of use of the air pressure control system increases.

According to one embodiment of the invention according to claim 2 the method each time the Motor vehicle performed. This ensures that one between the last shutdown and the next startup the motor vehicle owned by a tire change detected in any case and a new assignment of the new in the Tires contained air pressure control devices to Wheel positions is carried out.

According to an alternative embodiment of the invention according to claim 3, the process is always performed, when the automotive vehicle is longer than a predetermined time period resting. A predetermined period of time, for example, be detected by a timer in the central unit. Of the Advantage of this embodiment is the fact that the method not after each closure of the motor vehicle is carried out, but only if the duration of the closure exceeds a predetermined period. Prefers the predetermined time period is selected so long that, within this period changing a tire is excluded. As such a period can, for example, about 5 - 30 mins get accepted. The advantage of this embodiment to see that a new association, only relatively rarely is carried out and thus, in most cases even at Driving off the current assignment in the central unit is stored.

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

Here, here and below with sufficient understanding agreement that the measured values ​​up to Inequalities metrologically unavoidable match and thus a clear allocation possible is. The advantage of this development especially in seen that to dispense with complex Radhausantennen can that in the known from DE 42 05 911 A1 Allocation method are necessary to the signal intensities emitted by the air pressure control devices to measure signals with sufficient accuracy, whereby the Air pressure control system is cheaper.

It has been shown that a measurement on "Wheel-specific variables" is based, in a fairly short Period must be carried out because of the motor vehicle wheels various reasons almost always custom measurements present. Suitable measured variable has, for example, Wheel speed (turns / time) or each of these variables from which the Wheel speed can be derived, proved that both of the sensors, the air pressure control devices to are associated with, as well as sensors that each wheel of the Motor vehicle are permanently assigned, are measured. The Wheel speed of the individual wheels of the motor vehicle differs, for example when cornering, but also when driving straight ahead are already, for example due different wear or due to Manufacturing tolerances, individual wheel speeds before that for an allocation of the air pressure control devices to the Wheel positions are sufficient.

Suitable sensors, the air pressure control devices to be assigned and the detection of wheel speed serve, have for example magnetic field sensors, Centrifugal force sensors, gravity sensors and accelerometers proved. Particularly suitable have proven gravity sensors in which a small mass in a piezoelectric element acting a raddrehsynchrone generated charge displacement. For example, in a such element always by the applied pressure a charge displacement generated when a tire of the Motor vehicle and thus the element contained in it the Ground contact point of the tire passes. The number of Charge transfer cycles produced is in an evaluation circuit the sensor are counted. Simultaneously with The aid of a timer contained in the evaluation circuit the time measured. The wheel speed (revolutions / time) may in the evaluation will now be determined by established is the number of turns the wheel corresponding to the Sensor made in a fixed, predetermined period or whichever of a fixed number of Revolutions is needed.

As sensors that measure wheel speed and the individual the Wheels of the vehicle are permanently assigned, can For example, the sensors of an antilock braking system be used, which in any case in many motor vehicles is present, so that additional sensors are not needed will.

As an alternative to the wheel speeds, by the first and second measuring devices, the noise, the Vibration behavior or the tire temperature at the individual vehicle wheels are measured. has Again it turned out that the relevant variables a "Sufficient individuality" exhibit. To measure the these sizes are known, appropriate sensors, so that these sensors are not to be explained here in detail.

In summary, it should be noted that by the The method according to the invention, the allocation of Air pressure control devices to the wheel positions be carried out automatically. This is impossible that a tire change is not detected because the method directly after each start-up or always is performed when the vehicle is standstill for so long that changing a tire could be carried out.

Further advantages and an exemplary embodiment of the invention are 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, the has an air pressure control system. The air pressure control system contains, inter alia, air pressure control devices 6a to 6d, of which one in each of the tires of the Motor vehicle wheels 2a to 2 d included, (eg in Tire rubber or in or on the valve) or of which each is associated with a one tire, for example, by appropriate Positioning and attachment to the rim. The Air pressure control devices 6a to 6d include a Stations, to the the by means of which they data Air pressure control devices 6a to 6d associated Receivers 8a to 8d can transmit without contact. About that , the air pressure control devices 6a to 6d have explained via sensors 16a to 16d whose function later becomes. The receivers 8a transmit to 8d of the Air pressure control devices 6a to 6d received data over transmission paths 12a to 12d to a central unit 10th The receivers 8a to 8d can also through a single Receiver to be replaced, for example, in the CPU 10 is arranged and the signals of all Air pressure control devices 6a to 6d receives. In this Case, the transmission paths 12a to 12d of the Receivers 8a to 8d be dispensed to the central unit. In the simplest case, the receiver 8a to 8d and the only receivers designed as receiving antennas.

The air pressure control system includes all the sensors 16a to 16d sensors 4a to 4d are fixed to the motor vehicle and in each case one wheel 2a to 2d of the vehicle fixed assigned. The sensors 4a to 4d are over Transmission paths 14a to 14d also with the central unit 10 in connection.

In the following, the operation of the Luftdruckontrollsystems explained. before or during commissioning automatically the mapping mode of the air pressure control system switched on. This can, for example, done that by switching on the ignition in a microprocessor CPU 10 a subprogram "allocation mode" is called, which is then "processed" and the Mapping controls. In the mapping mode, both of the sensors 16a to 16d, the air pressure control devices to are assigned to 6d 6a, as also of the Sensors 4a to 4d variables that the in operation Motor vehicle at least temporarily for each vehicle wheel 2a to 2d of the vehicle are individually added and evaluated in the CPU 10th Hereinafter For example, it is assumed that this is the Wheel speed of the individual vehicle wheels 2a to 2d is and the sensors 16a to 16d and 4a to 4d accordingly as Speed ​​sensors are formed. By the sensors 16a 16d measured wheel speeds, along with the individual identifiers of the air pressure control devices 6a to 6d and the pressure values ​​and possibly other measurements to the the receivers 8a to 8d and from there via the transmission paths 12a to 12d transmitted to the central unit 10th In the CPU 10 therefore lie 2a for each vehicle wheel 2d value pairs of the form (a unique identifier Air pressure control device / wheel) before, which of these pairs of values ​​is not yet known, from which wheel position have been transmitted from them.

The measured by the sensors 4a to 4d wheel speeds over transmission paths 14a to 14d also on the CPU 10 transmits. Since the sensors 4a to 4d the individual wheels 2a to 2d of the vehicle permanently assigned are, "pointing" 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 of the front left Motor vehicle wheel 2a sends, etc.).

In the central unit 10 all of the sensors 16a to 16d of the air pressure control devices 6a to 6d provided Wheel speeds with all of the sensors 4a to 4d transmitted wheel speeds compared. A fixed allocation an air pressure control device 6a through 6d to a wheel position is then carried out in the central unit when the measured by a sensor 16a to 16d wheel with that of one of the sensors 4a to 4d measured wheel speed sufficient exactly. The corresponding assignment (individual Identification of air pressure control device / wheel position) is then stored in the central unit 10 (for example, If a match of the measured wheel speeds, when the temperature measured by the sensor 16a of the wheel speed with the sensor 4a measured wheel speed is compared; the CPU "setting" that the corresponding measured Wheel speeds of the vehicle wheel 2a front left originate, since the sensor 4a this wheel position front left fixed assigned. Accordingly, the CPU 10 assigns of the air pressure control device 6a übermittelteindividuelle withdrawing wheel position Left Front the motor vehicle wheel to 2a and stores them. A similar procedure with the other wheel positions. Are this way all relevant assignments created and saved, the assignment is completed, and the assignment mode is automatically released. This can for example, again be done by following the Storage of the assignments the subroutine "Allocation mode" of a microprocessor of the central unit 10 will leave.

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 of the medium Value in each clip the wheel rpm and the last Number in brackets in each case the pressure mean. The CPU 10 "looking" not at first, of which Wheel position which values ​​range comes. In addition, access of the speed sensors 4a to 4d, the measured wheel the central processing unit 10, namely, in this case, for example, 98 by the sensor 4a, 113 of the sensor 4c, 105 from the sensor 4b, and 122 by the sensor 4d. The central unit 10 "prophesy" because of the fixed assignment of the sensors 4a to 4d to the Wheel positions that the rotation speed 98, to the wheel front left 2a the speed 113 on the wheel 2c front right, the speed 105 on the wheel 2b rear left and the rotational speed of 122 to the wheel 2d was measured right rear. By comparing the Air pressure control devices 6a to 6d measured wheel speeds with the values ​​measured by the sensors 4a to 4d can wheel speeds, the CPU 10 is now the individual identifications K_i, I = 1 ... 4 assign the wheel positions, particularly in this example, the following assignments meet: (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" 2d of the wheel), because at the corresponding wheels the best match between the independently measured Radrehzahlen there. The corresponding Assignments are stored in the central unit 10 and in the Pressure monitoring mode used. Can a unique not carried out mapping based on the measured values are, for example, because two or more wheels 2a to 2d of the Sensors 4a are measured to 4d same wheel speeds, so the mapping mode is continued until this is possible.

Through the pressure values ​​transmitted in the assignment mode is only then trigger an alert when a particular 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 are individual Identifiers together with measured pressure values ​​and, if necessary further measurements and values ​​of the wheel speed to the Receivers 8a to 8d and transmitted from there to the CPU 10 passed. In the central unit 10 be the transferred individual identifiers with the compared with stored identifiers and compliance is determined, from which wheel position the individual ID has been sent with the corresponding pressure value. The wheel speeds of the CPU 10 in the pressure monitoring mode not evaluated. Should the submitted Pressure value or one of the other variables in any of Motor vehicle wheels 2a to 2d in an inadmissible way by a predetermined value, this is the motor vehicle driver reported, so that it can take appropriate action. Example: From the Luftdruckontrollvorrichtungen 6a through 6d are in turn the value series of the form (K₁; 150; 1.5); (K₂; 153; 2.0); (K₃; 149; 2.2); (K₄; 147; 2.2) to the central unit 10 transmitted. Based on the stored assignments (Supra.), The CPU 10 determine that the first Values ​​range from the wheel position "front left", the second Values ​​range from the wheel position "front right", the third Values ​​range from the wheel position "rear left" and the fourth transmitted value series from the wheel position "Rear Right" was because the corresponding individual identifiers in the values ​​transmitted range and stored assignment at These specified wheel positions coincide. The Central unit 10 can now detect that the pressure of 1.5 bar on to the wheel position "front left" the pressure of 2.0 bar the wheel position "front right" and the pressure of 2.2 each to the wheel positions "Rear Left" and "Rear Right" was measured. Optionally, a warning issued , when one of the measured air pressures from a different predetermined value. In the example, a issued warning because the air pressure of 1.5 bar at the Wheel position is too low "Left Front".

LIST OF REFERENCE NUMBERS

<dl tsize="9" 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>