DE10349617A1 - Detecting apparatus for tire deformation of vehicle tire, has signal processor which provides signal indicating tire deformation based on difference between tire pressure at first time and tire pressure at second time - Google Patents

Abstract

The detecting apparatus has a tire pressure sensor for sensing a tire pressure. A signal processor provides a signal indicating the tire deformation based on a difference between the tire pressure at a first time and the tire pressure at a second time. An Independent claim is also included for a method for detecting a tire information of vehicle tire.

Description

The The present invention relates to apparatus and method for Detecting a rotation of a wheel, in particular a vehicle wheel is.

In modern vehicles use a plurality of vehicle subsystems, for example, depending on be activated by a vehicle motion state. In the vehicle subsystems For example, they may be tire pressure sensors that arranged in a tire and powered by a battery. Preferably, such systems are therefore activated only then when the vehicle is set in motion to use energy lower and thus more cost-effective to realize electronic systems.

at Tire pressure monitoring systems become tire pressure sensors in the tires installed in the vehicle in order, preferably during vehicle movement, to the tire pressures the respective wheels to measure and, for example, to a central evaluation unit to send. For this purpose, in an interior of the wheel, for example, a sensor installed with a high frequency transmitter. Located in the vehicle a recipient, which evaluates the radio frequency data transmitted by the wheel and the driver over informed the current tire pressure. The sensor (a module) in the The bike is usually powered by a battery, for example ten To keep for years. The module may therefore only send if this necessary, d. H. when the vehicle is in motion. For this Reason will be additional in the wheel module Used sensors that detect a vehicle movement.

To the Detecting a movement of the vehicle, centrifugal force sensors can be used become. Here, by a rotation of the wheel, a centrifugal force exercised on the module. By evaluating the centrifugal force can now be determined whether the wheel is moving, whether the movement is permanent or whether the wheel is in hibernation. The centrifugal force sensors can either be mechanical or electrical. When a mechanical solution is z. B. compressed a spring of a small weight, which For example, an electrical contact closes. adversely However, this approach has a short life as with increasing Always use the spring return forces become smaller. A disadvantage of this approach is further that the electrical Contacts are mechanically closed. This can lead to contact problems come when z. B. the contacts are oxidized or z. B. due a possible Spring deflection a contact contact resistance gets too big.

at the electrical solution Various acceleration sensors are used, such. B. piezoelectric sensors in which due to a mechanical Deformation an electrical signal is delivered, which on the Wheel movement indicates. However, the disadvantages of this concept are the high costs, both by the piezoelectric components as also caused by the complex evaluation electronics.

To the Activating the tire pressure sensors may further include activation systems, So-called wakeup systems are used. It will be from one arranged in a wheel well transmitter to be installed in the wheel module a receiver Activation signals sent out. Does the recipient get in the wheel module a request signal (request signal) from the vehicle has been sent, the wheel module sends the print data from the wheel to the vehicle. However, a disadvantage of this approach is that in the wheel module a complicated receiver must be installed. On the one hand This increases system costs. On the other hand, they increase thereby the system running costs, as the receiver in the wheel module persists Energy needed to be able to receive the activation signal at any time. This reduces the life of the module. Further, a battery greater capacity needed around the needed To deliver energy. Furthermore, a transmitter that is in the Vehicle is installed to wake the module in the wheel, expensive and consuming to integrate into the vehicle systems.

To the Activation of the tire pressure sensor may further include a pressure curve in be analyzed by the wheel. When driving away change for example, the temperature and pressure in the wheel tire. These change can be evaluated by a logic integrated, for example, in the sensor which activates the transmitter. The disadvantage here is that the sensor constantly measures pressure and temperature. This creates a increased Power consumption, by a larger, and therefore more expensive, battery must be covered. Furthermore If the technology required for this is complex and parameter-dependent, then so the existence stable system behavior not in every vehicle situation guaranteed is. This is the case, for example, if dependent on a road surface and from a driving behavior, the pressure differences large and fast-variable are so that the Evaluation logic does not reach a stable state, which can lead to that this For example, system does not respond. This leads to the further disadvantage that such Systems are not sure.

It The object of the present invention is an efficient concept to provide for detecting a rotation of a wheel.

These The object is achieved by the device for detecting a rotation of a Wheel according to claim 1 or by a tire pressure sensor system according to claim 6 or by a A method of detecting a rotation of a wheel according to claim 7 or by a method for detecting a tire pressure in a Rotation of a wheel according to claim 8 or solved by a computer program according to claim 9.

A Apparatus for detecting a rotation of a wheel according to the invention comprises one in the Wheel arranged device for detecting the earth's magnetic field, a Means for detecting a change in the detected magnetic field, a rotation of the wheel based on the detected change capture.

According to one Another aspect of the present invention comprises a tire pressure system according to the invention for detecting a tire pressure in a rotation of a wheel activatable tire pressure sensor for detecting the tire pressure, wherein the activatable tire pressure sensor is designed to generate an activation signal to receive, and, in response to the activation signal to the To detect tire pressure, and a device for detecting the rotation of the wheel based on a change in the detected earth's magnetic field.

Of the The present invention is based on the finding that a rotation a wheel based on a change in the detected geomagnetic field can be done. According to the invention, the first Earth magnetic field detected, the detected Geomagnetic field in the form of a signal, for example a voltage, can be issued. Is the earth's magnetic field by a in the Rad arranged means for detecting, for example by a magnetic field sensor, detected, so the sensor output signal is variable when moving the wheel because dependent on from the movement and from a sensor position the detected earth magnetic field changes. On the basis of this change of the detected earth magnetic field Now, for example, an activation signal can be delivered, for example, activates a tire pressure sensor.

by virtue of the change of the sensor output, which is a change in the detected geomagnetic field characterized, in addition to a pure detection of rotation, also detects their speed become. For example, if the wheel is rotating at a constant speed, so embraced the sensor output signal vibrates at a frequency that depends on the rotational speed. Will this frequency now recorded, it may indicate the rotational speed, or, alternatively, be closed to the vehicle speed.

Becomes For example, for detecting the earth's magnetic field, a magnetic field sensor used, so is an amplitude of the signal supplied by the sensor in a change of the detected Geomagnetic field, for example in the form of an induced voltage, dependent from the rate of change. The rate of change hangs again due to the law of induction of the rotational speed, or in other words, depending on the speed of the vehicle.

One Advantage of the present invention is that a rotational movement a wheel of, for example, a wheel sensor in which the device according to the invention is installed, can be detected. This is particularly energy efficient, because no signals are actively received or transmitted. Rather, it is the already permanently existing geomagnetic field exploited. The change caused by the wheel rotation of the detected Earth's magnetic field already indicates a Radrotation.

One Another advantage of the present invention is that for detecting a wheel rotation does not use mechanically deformable sensors become. Compared with the traditional concepts, the device according to the invention therefore a higher one Lifespan as well as lower costs.

One Another advantage of the present invention is to be seen in that the Structure of the device according to the invention easy. The inventive device for detecting the geomagnetic field, for example, as a simple Magnetic field sensor, such as a coil can be formed. In addition to a reduction in complexity is achieved so that, compared with known concepts of the prior art, the system cost can be lowered further.

One Another advantage of the present invention can thus be seen that the inventive approach not just used for a pure detection of a rotation can be. Rather, it is also possible from the change of the detected magnetic field to a vehicle speed or to a change to close it.

preferred embodiments The present invention will be described below with reference to FIG the enclosed drawings closer explained. Show it:

1 a block diagram of a device according to the invention for detecting a rotation of a wheel according to a preferred embodiment;

2A an embodiment of an embodiment of the inventive device for detecting the earth's magnetic field, front view;

2 B the embodiment 3A , Side view;

3 a measurement result;

4 another measurement result; and

5 an embodiment of a tire pressure sensor system according to the invention; and

6 a further embodiment of an apparatus for detecting a rotation of a wheel.

1 shows a block diagram of an inventive device for detecting a rotation of a wheel according to a first embodiment.

In the 1 The device shown comprises a device 101 for detecting the earth's magnetic field. The device 101 for detecting the geomagnetic field has an output at which a detection signal can be output. With the exit of the institution 101 for detecting the geomagnetic field is a device 103 coupled to detect a change in the detected magnetic field. The device 103 to detect the change has an exit 105 on which a signal can be output that indicates the change in the detected magnetic field.

The following is the operation of the in 1 illustrated structure explained.

The device 101 for detecting the geomagnetic field includes, for example, a magnetic field sensor, for. B. a Hall sensor or a coil. The magnetic field sensor detects the (permanent) earth magnetic field. If the device according to the invention is installed, for example, in a wheel, the detected earth magnetic field, which is output in the form of a magnetic field sensor signal (detection signal), changes during a rotational movement of the wheel. Includes the device 101 for detecting the geomagnetic field, for example, the already mentioned coil as a magnetic field sensor, a voltage is induced during movement of the wheel in the coil, which is already outputable as the detection signal. Due to the law of induction, the voltage induced in the coil is influenced by the number of coil turns, by the cross-sectional area of the same through the earth's magnetic field, and by a rate of rotation, ie rate of change. If the already mentioned coil is used as a geomagnetic field sensor, a wheel rotation or a vehicle movement can already be detected or detected on the basis of a presence of a coil output signal, which may be the detection signal directly. However, the approach according to the invention applies to any magnetic field sensors, since these provide a variable output signal (detection signal) as a function of a position and of a change in the same with respect to the earth's magnetic field lines.

The inventive device 101 For detecting the earth's magnetic field may include, for example, a preamplifier to amplify the sensor output signal and to output the amplified sensor output signal as the detection signal.

Regardless of whether the detection signal comprises the amplified sensor output signal or whether the detection signal is already directly the sensor output signal, the device is 101 designed to detect the earth's magnetic field in principle to provide a detection signal that characterizes the change of the detected geomagnetic field. It should be noted that the term "change in the detected earth's magnetic field" does not refer to the change in the earth's magnetic field itself, but due to a movement, the detected earth's magnetic field changes due to a momentary wheel position.

As already mentioned, the device according to the invention can 101 for detecting the geomagnetic field provide the detection signal, which in addition to a presence of a rotation also includes information about a speed of the vehicle. For example, the device provides 101 for detecting the earth's magnetic field, a detection signal having a dependent on the change of the detected geomagnetic field amplitude and / or frequency. For example, if the magnetic field sensor is in the form of a coil, the detection signal, which is based on the coil output signal, has a sinusoidal profile whose frequency and amplitude are proportional to the rotational speed of the wheel, and thus to the speed of the car.

The detection signal becomes the device 103 for detecting the change of the detected magnetic field.

The device 103 For example, to detect the change may be a sensor that already has a presence of the detection signal or a presence of a change of the detection signal for the mere detection of the rotation of the wheel. Such a detector may, for example, be a transistor controlled by the detection signal, which, for example, closes a circuit in the presence of the detection signal, so that a current flowing through the transistor indicates the rotation of the wheel. If, on the other hand, a change in the detection signal is used to detect the wheel rotation, then this change can be detected, for example, by generating a signal indicating the change. For this purpose, for example, a subtraction of the instantaneous detection signal from a reference detection signal can be performed, wherein the reference detection signal reproduces the detection signal in the rest position of the wheel. Alternatively, a subtraction of the current detection signal from an earlier detection signal may be performed to detect the change.

Should the device 103 however, in order to detect, in addition to the pure wheel rotation detection, also a statement about a rotational speed, the device according to the invention can 103 for detecting means for evaluating the detection signal or for evaluating the change of the detection signal to detect based on one of the rotational speed indicative features, such as amplitude and / or frequency of the detection signal, the rotational speed of the wheel or its change. As already mentioned, the detection signal has an amplitude and / or frequency dependent on the change of the detected earth magnetic field. Based on the amplitude and / or frequency, the in 1 not shown means for evaluating the associated rotational speed of the wheel or a vehicle speed, which depends on the rotational speed of the wheel proportionally.

In 2A an embodiment of a realization of a geomagnetic field sensor in the form of a coil is shown in plan view. 2 B shows a side view of in 2A illustrated arrangement.

In 2A is a coil 201 , with, for example 200 Turns, on a breadboard 203 assembled. Like it out 2A respectively. 2 B it can be seen, the inventive design of a geomagnetic sensor is simple and inexpensive. Already with this simple approach can be changes of the coil 201 detect detected geomagnetic field in the form of the coil signal.

3 shows a measurement result, wherein in the measurement the in 2A and 2 B shown arrangement was used as geomagnetic sensor. The coil was connected via an amplifier to an oscilloscope and rotated by 180 degrees by hand. This rotation by hand should simulate a rotation of the wheel. Due to the earth's magnetic field and the movement of the coil in the earth's magnetic field, a voltage was induced, which indicates the change of the detected geomagnetic field. The voltage curve 301 has a first section 303 during which the spool has not been moved, whereby a resting state of a wheel has been simulated. The rotation of the coil produced a signal pulse 305 whose amplitude is determined by the in 3 dashed horizontal line 307 is marked. The measured amplitude is about 50 uV for a total pulse duration of 0.2 seconds.

The display areas arranged to the right of the diagram 308 indicate the operating mode of the measuring instrument used.

As has already been mentioned, in a continuous rotation of the wheel instead of in 3 pulse produced a sinusoidal signal (a sine wave). The frequency and amplitude of this signal is proportional to the speed of the car due to the law of induction. In this case, the signal form can be received and evaluated with the aid of a suitable evaluation unit in order, for example, to supply an activation signal which "wakes up" a wheel pressure sensor If, for example, the car moves at 50 km / h, a frequency of the associated detection signal is approximately 10 Hz.

Due to the field strength of the geomagnetic field (about 50 μTesla), a coil is preferably used according to the present invention for detecting the geomagnetic field, since the geomagnetic field has a comparable high field strength. For example, the maximum permissible magnetic field of a monitor at a distance of 0.5 m is only 200 nTesla. The magnetic field of a 10 A conductor is also only 200 nTesla at a distance of 1 m. The two above comparison values are thus by the factor 250 under the given geomagnetic field strength.

In the 3 measured amplitude of about 50 mV, however, may be too low, depending on the sensitivity of the evaluation devices connected to the coil. For example, this problem can be solved be increased by a sensitivity of a low-frequency receiver (LF receiver) receiving the voltage by a predetermined factor, for example by a factor of 7. The power consumption would increase only minimally, for example by about 1%. A change in the sensitivity of the low-frequency receiver, which receives and evaluates the detection signal (coil signal), can already be performed during a design phase of the low-frequency receiver cost-neutral.

However, according to another embodiment of the present invention, a higher signal amplitude can be achieved if the magnetic field sensor used to detect the earth's magnetic field is set in further rotation in addition to the wheel rotation. For example, this has the in 1 illustrated device 101 means for detecting the earth's magnetic field means for setting the earth's magnetic field sensor in a further rotation to obtain a detected based on the change of the detected geomagnetic field detection signal having a higher amplitude than an amplitude of a detection signal upon deactivation of the means for moving the earth's magnetic field sensor in the other Rotation or in the absence of the latter.

Based on the concept described above for obtaining a better detection signal, a measurement was performed, the result of which in 4 is shown.

The measurement (the test) was performed with the in 2A or in 2 B shown coil with a normal 125 kHz transponder coil for a tire pressure measurement system (TPMS).

4 shows a voltage curve 501 , the one impulse 403 wherein the pulse 403 has an amplitude determined by the in 4 illustrated vertical dashed line 505 is clarified.

This in 4 recorded signal 401 was achieved by a rotation of the coil at about 2 Hz. With a rotation of the coil or the wheel with 2 × 7 = 14 Hz, the signal level would be 500 μVp, so that detection is easily possible. This corresponds to a speed of the car of about 50 km / h. This in 4 signal was amplified by a factor of 50,000 by a preamplifier. The signal on the coil has an amplitude of 70 μvp. The amplitude of the signal was measured via a preamplifier. The displayed voltage is therefore higher. The sensitivity of the conventional TPMS 125 kHz low-frequency receiver is 500 μVp, ie the signal shown above would be too low by a factor of 7 if no rotation of the coil according to the invention had been carried out.

at The measurement discussed above has used a coil already now for other functions are used in TMPS modules, for example as a 125kHz LF antenna (LF = low frequency). This serves for transmission of data on a frequency of 125kHz. So this antenna can used twice: as a 125kHZ antenna and as a geomagnetic sensor, which leads to a cost saving. Other magnetic field sensors would be much more expensive, which their use in mass production as questionable appears.

To the Displacement of the magnetic field sensor in the further rotation, for example an electrically driven motor can be used, which is the magnetic field sensor rotates about an axis, so that the rotation of the wheel and the further rotation of the magnetic field sensor superimpose that this Detection signal the already mentioned desirable higher Having amplitude.

In 5 is an embodiment of a tire pressure sensor system according to the invention represents.

This in 5 shown tire pressure sensor system has an activatable tire pressure sensor 501 , the one entrance 503 and an exit 505 having.

This in 5 illustrated tire pressure sensor system has a device 507 for detecting the earth's magnetic field. The device 507 has an exit 509 on, with which a facility 511 is coupled to detect the change of a detected geomagnetic field. The device 511 for detecting has an output 513 on that with the entrance 503 the activatable tire pressure sensor 501 is coupled.

The following is the functionality of in 5 explained arrangement explained.

The activatable tire pressure sensor 501 is for example installed in a wheel. As already mentioned, in order to achieve low energy consumption, it is advantageous to activate the tire pressure sensor, if necessary. This is the case, for example, when the vehicle is set in motion to forward the tire pressures to the driver as safety-related information. For activation (wakeup), the activatable tire pressure sensor 501 the entrance 503 to which the activation signal (wakeup signal) can be applied. After activation measures the activatable tire pressure sensor, the tire pressure in the respective tire and as a result provides tire pressure measurements on the output 505 , The tire pressure measurements can be sent to an in 5 not shown central Auserteeinheit be sent by means of a transmitter, the transmitter is for example a radio transmitter.

To activate the activatable tire pressure sensor, however, it is necessary to recognize when the vehicle is being set in motion. For this purpose, the device according to the invention for detecting a rotation of a wheel can advantageously be used, as already described in connection with the in 1 illustrated embodiment has already been presented.

The device for detecting the rotation, consisting of the device 507 for detecting the earth's magnetic field and the device 511 to detect a change in the same supplies via the output 513 the activation signal to the input 503 the activatable tire pressure sensor 501 can be applied. To illustrate this concept, the output is 513 the device 511 to detect with the input 503 coupled to the activatable tire pressure sensor. It should be noted, however, that this coupling represents only a signal coupling. The exit 513 For example, it can be galvanically connected to the input 503 be coupled. This can be realized, for example, by the activation signal is supplied via, for example, a line to the activatable tire pressure sensor. This is advantageous if both the activatable tire pressure sensor 501 as well as the inventive device for detecting the rotation, for example, integrated on a chip and are arranged as a whole in a wheel. Alternatively, however, it is also conceivable that the device 511 for detecting the activation signal to the activatable tire pressure sensor 501 using a radio transmitter.

Regardless of the form in which the activation signal the activatable tire pressure sensor 501 reached is the activatable tire pressure sensor 501 configured to receive the activation signal and, in response to the activation signal, to detect the tire pressure.

This in 5 shown tire pressure sensor system based on that to an activation of the tire pressure sensor 501 the earth's magnetic field is used as a reference for a movement. When the wheel starts to move, it changes from that of the device 507 for detecting the earth magnetic field detected magnetic field sensor detected magnetic field. As a result, a wakeup of the module is triggered and the tire pressure (tire pressure measurements) transmitted via high-frequency carrier to the vehicle.

Instead of the known static magnetic field sensors, such as e.g. a Hall sensor or a magnetoresistive sensor, can, as it has already been mentioned is preferred, a simple coil can be used. Through the rotation of the wheel becomes in the coil due to the permanent earth magnetic field Induced voltage.

In 6 another embodiment of a tire pressure sensor system according to the present invention is shown.

This in 6 shown system comprises a coil 601 whose inputs are equipped with a low-frequency receiver 603 (LF receiver) are coupled. The LF receiver 603 also serves as an activation signal generator (wakeup generator). The LF receiver 603 has an output connected to a logic circuit 605 is coupled.

The logic circuit 605 has a first connection 607 and a second connection 609 on. With the first connection 607 the logic circuit 605 is a pressure sensor 611 coupled (pressure sensor). With the second connection 601 the logic circuit 605 is a transmitter 613 (Transmitter) coupled. The transmitter 613 has an output with which an antenna 615 is coupled.

This in 6 illustrated embodiment of a tire pressure sensor is used in its entirety in a wheel tire. The sink 601 serves as a low-frequency magnetic field motion sensor for detecting the movement (rotation) of the wheel. Due to the wheel rotation of the coil is induced an alternating voltage whose instantaneous direction by the in 6 indicated arrow is indicated. The voltage signal is from the generator 603 receive, with the generator 603 is formed to generate from the induced voltage signal, a signal indicative of a wheel rotation, or which characterizes a wheel rotation with respect to the rotational speed. The generator 603 provides as an output signal to the logic circuit 605 , which contains information about whether the wheel has been set in motion or what is the current wheel speed.

The logic circuit 605 generated on the basis of the generator signal at the output of the generator 603 a signal that the sensor 611 activated. The tire pressure sensor 611 then measures the tire pressure, with the measured tire pressure values back to the logic circuit 605 be sent, so that a signal can be generated, the at For example, by a central evaluation unit, which is arranged in a vehicle, can be interpreted. The output signal of the logic circuit 605 gets to the transmitter 613 Posted. At the transmitter 613 For example, it may be a radio transmitter that generates a high-frequency signal from the antenna 615 can be sent to the already mentioned central processing unit. At the transmitter 613 For example, it could be a Bluetooth transmitter.

Like it out 6 As can be seen, the earth's magnetic field according to the invention is used for detecting the rotation of a wheel in tire pressure monitoring systems in order to generate a wake-up signal. As is clear from the above, the geomagnetic field strength is sufficient to use even simple coils for detecting the earth's magnetic field. This also implies that coils already used in finished tire pressure systems, which are used, for example, as the already mentioned 125kHz LF antennas or 125kHz tansponder coils, can also be used to simultaneously wake-up based on utilizing the change in the detected earth magnetic field to produce. This can be taken into account at a low cost already during production of the module. According to the invention fall in this case, no additional external components, so that the wakeup signal can be generated cost neutral.

at The 125kHz transponder coil may be, for example, a Transponder coil 5315TC of the company Coilcraft act.

Depending on the circumstances can inventive method be implemented in hardware or in software. The implementation can be on a digital storage medium, especially a floppy disk or CD with electronically readable control signals, the so can interact with a programmable computer system that the corresponding Procedure executed becomes. Generally, the invention thus also consists in a computer program product with program code stored on a machine-readable carrier to carry out the respective method according to the invention, when the computer program product runs on a computer. In in other words Thus, the invention can be considered as a computer program with a program code to carry out the process can be realized when the computer program is up a computer expires.

101

Facility for detecting the earth's magnetic field

103

Facility to detect a change of the seized

th magnetic field

105

output

201

Kitchen sink

203

Breadboard

301

voltage curve

303

first Section of the voltage curve 301

305

pulse

307

amplitude

308

display areas

401

voltage curve

403

pulse

405

amplitude

501

activatable Tire pressure sensor

503

entrance

505

output

507

Facility for detecting the earth's magnetic field

509

output

511

Facility to detect a change of the seized

th magnetic field

513

output

601

Kitchen sink

603

Low frequency receiver

605

logical circuit

607

first Connection

609

second Connection

611

Tire pressure sensor

613

transmitter

615

antenna

Claims (9)

Device for detecting a rotation of a wheel, having the following features: a device arranged in the wheel ( 101 . 507 ) for detecting the earth's magnetic field; and a facility ( 103 . 511 ) for detecting a change in the detected earth magnetic field to detect a rotation of the wheel based on the detected change. Device according to claim 1, in which the device ( 101 . 507 ) for detecting the geomagnetic field comprises a magnetic field sensor. Device according to Claim 2, in which the magnetic field sensor comprises a coil ( 201 ). Device according to one of claims 2 or 3, in which the device ( 101 . 507 ) for detecting the earth 's magnetic field further comprises means for displacing the magnetic field sensor into a further rotation in order to detect a change in the detected earth magnetic field based detection signal having a higher amplitude than an amplitude of a detection signal upon deactivation of the means for moving the magnetic field in the further rotation. Device according to one of claims 1 to 4, wherein the device ( 101 . 507 ) for detecting the geomagnetic field is provided to provide a detection signal having an amplitude and / or frequency dependent on the change in the detected geomagnetic field, the device ( 103 . 511 ) for detecting comprises means for evaluating to detect a rotational speed of the wheel based on the amplitude and / or frequency. Tire pressure sensor system for detecting a tire pressure during a rotation of a wheel, comprising: an activatable tire pressure sensor ( 501 . 611 ) for detecting the tire pressure, wherein the activatable tire pressure sensor ( 501 . 611 ) is configured to receive an activation signal and, in response to the activation signal, to detect the tire pressure; and a device for detecting the rotation of the wheel according to one of claims 1 to 5, wherein the means for detecting the rotation of the wheel is adapted to supply the activation signal. Method for detecting a rotation of a wheel with the following steps: Detecting the earth's magnetic field; detect a change of the detected Earth's magnetic field; and Capture the rotation of the wheel based on the detected change of the detected Earth's magnetic field. Method for detecting a tire pressure in a Rotation of a wheel with the following steps: Capture the Tire pressure responsive to an activation signal; Produce the activation signal by the method according to claim 7. Computer program with a program code for carrying out the Process according to claim 7 or 8 when the program runs on a computer.