DE10318168A1 - Motor vehicle tire deformation detection system comprises magnetic field sensors, one or more magnetic encoder tracks attached to the tire and wheel and signal processing electronics that filter out alternating components - Google Patents

Abstract

Arrangement for detection of deformations of magnetically coded motor vehicle tires using at least two magnetically sensitive elements placed at fixed positions on the vehicle relative to the tire axis and at least one tire magnetic track. The element output signals are processed by a signal processing unit with the following steps: signal amplification to the same value; signal multiplication; signal filtering to remove frequencies double the signal frequency following multiplication; supply of the remaining direct current component as a measure of tire deformation to a vehicle control unit.

Description

The invention relates to a device for detecting magnetically coded vehicle tires according to the preamble of Claim 1.

Magnetic rotary encoders can be used in general when a device rotates, from Win angle-dependent electrical measurement signals. The known Rotation position sensor "vehicle tires" contains one layer made of magnetizable material as code carrier. In these Layer is made along a track by means of a magnetic head Magnetization changes or transitions registered. The Inscribed code pattern shows permanent magnetic areas or poles, with alternately arranged, preferably striped north and south poles (N, S). This pattern is one or more sensed magnetic field sensitive elements. The elements are in Distance rigidly arranged to the poles or areas, whereby they are facing the poles or areas of the code carrier. The Strip-like magnetic areas or poles are like this chose that with the help of the elements and one of them assigned evaluation electronics a statement about the angle of rotation is possible with respect to a predetermined reference position.

From WO 96/10505, DE 196 26 843 A1, WO 97/44673 are pneumatic tires in tire sidewalls of a motor vehicle embedded magnetizable layers known for Read out the pattern using magnetoresistive sensors. It are therefore preferably more regulated applications Systems with brake intervention ABS, ASR, ESP provided, especially those systems that have a deformation of Tire rubber under load for measuring or determining forces or Use torques. A process that is called Side Wall Torsion Sensor (SWT) 'is known in DE- A1 44 35 160 described. DE-A1 44 35 160.7 proposed to determine the longitudinal and transverse forces the phase shift of a magnetically encoded tire two wheel speed signals to measure and simultaneously over Air gap deformations and the changing ones Signal amplitudes towards the size of lateral accelerations conclude. In the rubber of the sidewall of the tire is one permanent magnetic track made of alternating stripes North / south polar areas integrated into a ring conclude. Is the rolling tire braked or accelerates, the side wall twists slightly. The strenght the twist is perpendicular to one another by two arranged magnetic field sensitive elements or sensors the time delay of the zero crossings of their signal voltages recorded, which results from the fact that the upper and the lower zone of the permanent magnetic stripes against each other move when the side wall twists. After this Delay in the zero crossings also becomes the duration of the subsequent complete signal period measured. Right away thereafter, by dividing the duration of the time delay of zero crossings through the duration of the complete Signal period a sample value of the temporal Phase angle change calculated. The number of samples per Wheel rotation (corresponding to approx. 2 m travel path) is based on the number of North / south pole pairs of the encoder track of the tire sidewall limited. Through the serial acquisition of the partial measurements the subsequent calculation of the phase shift with the pole pitch errors shown on the sensors Encoder track affected. This aberration increases with increasing Air gap increases considerably and leads to an undesirable "Inaccuracy" of the measured variable sought. Combined with the small number of samples per revolution is achievable accuracy of the phase measurement limited.

The present invention is therefore based on the object the phase angle continuously and without the disadvantages of to determine time-serial measurement.

This object is achieved by the features of Claim 1 solved.

Advantageous further developments are in the subclaims specified.

According to the invention, the task is solved in a generic device by the following steps:
Determination of 4 signals at the same time, offset by λ / 4 of a period, with at least one sine and one cosine value being detected by the elements, amplification of the amplitudes of the signals with an unchanged phase position to the same value
Multiplying the signed signals in a multiplier with one another, filtering the signal in a low-pass filter in order to suppress AC components in the frequency range equal to or greater than twice the frequency, based on one of those signals which have come to multiplication after the signal processing, and supplying the remaining DC component as a measure for the deformation of the sidewall of the tire into a vehicle control system.

It is advantageous that the magnetic field sensitive elements opposite a tire sidewall with a coding a regular sequence of uniform stripe-shaped Areas of alternating north / south poles always in at least two Organized groups work together.

It is also advantageous that at least two groups of magnetic field sensitive elements in the radial direction with each other, but at the same time by a quarter the length of one North / South pole pair of the regular sequence of North / south pole pairs are offset from each other.

It is also appropriate that the group Magnetic field sensitive elements consist of two sub-groups put together by a local distance or a local phase are offset by one eighth the length of one North / South pole pair of the regular sequence of North / South pole pairs do not exceed. The include Subgroups means, each with at least two independent partial signals S1 = A.sin (ω.t) and S2 = -A.sin (ω.t + Φ) and S1 '= B.cos (ω.t) and S2 = -B.cos (ω.t + Φ) be generated. In an electronic functional unit become from the partial signals S1 and S2 or S1 'and S2' respectively a signal sum and a signal difference formed with an OR gate with a common signal twice the frequency of one of the partial signals are connected.

According to a further embodiment, it is advantageous for the partial signals to be fed at double frequency to an electronic function group, as is described in more detail in connection with FIG. 3 or FIG. 5.

To improve signal processing, it is advisable to that the magnetic field sensitive elements with the post-processing electronic circuits modular are. The elements sensitive to magnetic fields are included the post-processing electronic circuits in summarized several housed units. The The output signal is an electronic controller of a vehicle fed.

It is to improve a driving dynamics controller advantageous that the signals of the magnetic field sensitive elements be prepared by electronic circuits so that next to a signal to represent the deformation of the Sidewall simultaneously a continuous signal for imaging the distance of the side wall is generated and that both Output signals continuously an electronic controller be fed.

It is advantageous that the groups of magnetic field sensitive elements with at least two different ones Interact encoder tracks.

It is useful that at least one group magnetic field sensitive elements reads the coding of the tire and at least one second group encoding the Pulse generator of a wheel speed sensor for ABS systems reads.

It is also advantageous that the groups Magnetic field-sensitive elements arranged radially vertically one above the other are, while the scanned magnetic encoder tracks in the Distance of a quarter of a magnetic period from one another are magnetized.

An embodiment of the invention is in the drawing shown and will be described in more detail below.

Show it:

Fig. 1 shows a pneumatic tire with side wall encoding and encoder in the wheel bearing

Fig. 2 shows a detail of Fig. 1 with a deformation of the encoder track

Fig. 3 is a block diagram of the device

Fig. 4 shows an embodiment of the phase determination on the pneumatic tire

Fig. 5 shows an embodiment with amplitude measurement

Fig. 6 shows a device for doubling the spatial frequency

Fig. 7 shows an embodiment according to the invention with spatial frequency doubling

Fig. 8 shows an embodiment of a sensor designed as a structural unit

Fig. 9 shows an embodiment using a wheel speed sensor

Fig. 10 3 Figure 11 is an alternative means of schematically illustrated in FIGS. 1 and 2 encoding sidewall according to a knitting diagram of a low-pass realization Fig..

Fig. 1 shows a pneumatic tire with magnetic sidewall encoding 1 , consisting of an integer sequence of alternating north / south poles (N, S). The tire is part of a vehicle wheel 2 with a further magnetized encoder 3 , the z. B. can be designed as a magnetized wheel bearing seal. This second encoder also follows the rotation of the wheel in the direction ω. It is usually used for conventional wheel speed measurement for controlled brake systems.

Fig. 2 shows strip-shaped permanent magnetic areas 5 of the encoded side wall 1 , which deform 5 'under load. For this purpose, two magnetic field-sensitive elements, the sensors 6 , 7 are present, which are mutually offset, but at the same time offset by a quarter of the length of a north / south pole pair, are arranged near the ends of the magnetized strips and detect the location-dependent magnetic field of the encoder track 10 . Their arrangement in relation to each other generates a sinusoidal 8a and a cosine 9a electrical signal voltage. When the side wall 1 is twisted under load, this initial state changes into a changed mutual phase position 8 b, 9 b by a phase angle deviation which is to be measured continuously according to the invention.

Fig. 3 shows the scheme of the device for carrying out the method with the encoder track 10, which at the angular velocity ω at the sensors 6, is moved past. 7 As described above, the signals A.sin (ω.t) and B.cos (ω.t + φ) are produced, which are each routed to a similar, separately controllable amplifier 11 a, 11 b. The different amplitudes A, B are separately amplified or weakened with respect to a reference voltage 12 by regulators 13 a, 13 b in such a way that signals of the same amplitude C but unchanged phase relationship to one another arise at the outputs of 11 a and 11 b. These signals C.sin (ωt) and C. cos (ωt + φ) are fed to a four-quadrant multiplier 14 or a comparable functional unit, multiplied with one another and the result passed through a controllable low-pass filter 15 . The low-pass filter 15 suppresses the AC voltage component, proportional sin (2ωt + φ), resulting from the multiplication, so that essentially a DC voltage component, proportional k.sinφ, remains which, due to the small angular range present, can be viewed in proportion to the phase shift φ. The sensors 6 , 7 arranged offset by λ / 4 of a magnetic encoder period have the purpose of generating the term sinφ or of avoiding a term cosφ; because it should be exploited that the sine reacts to positive / negative phase shifts (ie braking or acceleration) with an associated changing sign, whereas the cosine function, in contrast, always delivers positive results and is therefore ambiguous and unusable. The cut-off frequency of the low pass 15 can be varied in a voltage-controllable manner. For this purpose, the frequency ω is determined from one of the two channels and z. B. converted via a frequency / voltage converter 16 into a control voltage that controls the low pass. A more detailed description of the voltage control of the low-pass filter 15 is described in more detail in connection with FIG. 10.

Fig. 4 shows an advantageous embodiment of the arrangement on a wheel 2 with pneumatic tires. The feed lines of the two sensors 6 , 7 are connected to a housing unit 17 which is designed as a structural unit and which contains electrical circuits which physically implement the functionalities of the device described for FIG. 3. The output signal is fed to the electronic control (ECU) 18 of a brake system.

FIG. 5 shows an embodiment variant of the device according to FIG. 3 with the difference of the amplitude measurement. The control signals of the partial amplitudes 19 , 20 are weighted in the functional unit 21 and, in addition to the phase information 22, are sent to the ECU 18 as amplitude information 23 . The amplitude signal 21 is a measure of changes in the air gap of the sensors with respect to the tire sidewall, e.g. B. a measure of lateral accelerations that act on the vehicle.

FIG. 6 shows a device for doubling the spatial frequency, which according to FIG. 7 can be used according to the invention. In the sensor module 24 is a magneto-electric transducer which is composed of two components W1 and W2, which are mutually offset by the distance Φ, and act to ω in the rotating encoder 25, two signals S1 = A.sin (. t) and S2 = A.sin (ω.t + Φ) are generated. The signals S1 and S2 are amplified in separate signal processing stages (SC1 / SC2) and then fed to an accounting stage. The allocation level contains two channels. The partial signal sum SUM = S1 + S2 is formed in the first channel and the partial signal difference DIF = S1 - S2 is formed in the second channel. SUM and DIF are then separately amplified in two identical amplifier stages and combined to form a common signal S3 via an OR circuit (OR). The signal S3 has twice the frequency of S1 or S2.

Fig. 7 shows an embodiment according to the invention under use of this method the spatial frequency doubling. There are two of these sensory doublers 27 , 28 described above for FIG. 6, which scan an encoded tire sidewall 1 offset from one another by λ / 4. The subgroups W1, W2 and W1 ', W2' each generate at least two independent partial signals S1 = A.sin (ω.t) and S2 = -A. sin (≙.t + Φ) and S1 '= B.cos (ω.t) and S2 = -B.cos (≙.t + Φ). The doublers 27 , 28 each form a signal sum and a signal difference from the partial signals S1 and S2 or S1 'and S2', which are each connected with an OR gate to form a common signal at twice the frequency of one of the partial signals. The output signals of these doublers 27 , 28 are fed to the functional unit 17 or 29 , as described for FIGS. 3, 4 or 5.

Fig. 8 shows the embodiment schematically a sensor or sensor module. The previously described functional units, doublers 27 , 28 , 29 generate the analog phase signal, which is converted analog / digital in an A7D converter 31 and fed to a bus driver 32 . In an advantageous embodiment, it is a CAN bus connection 33 to the ECU 18 . The functional units 27 to 32 are combined to form a sensor module 30 .

FIG. 9 schematically shows an embodiment similar to FIG. 8 with the difference that a wheel speed sensor 34 is used in cooperation with a single sensor on the tire sidewall 1 . The arrangement has the advantage that the wheel speed signal can be generated very precisely. The two sensors are set on their associated encoder tracks so that they have the required magnetic spatial phase difference of λ / 4 from one another in the normal state, which is described in more detail in connection with FIG. 2.

FIG. 10 shows, as an exemplary embodiment, the operating diagram of low-pass filtering, as can be used or carried out in the device described in FIG. 3. The signal C ^2/2 [sinφ + sin (2 ≙t + φ)] present at the input 40 is fed on two paths 41 , 42 to a differential amplifier 43 , from whose output 44 the desired signal result φ can be tapped. For this purpose, an amplifier 45 with a DC coupling is introduced into the path 41 and an amplifier 46 with an AC coupling 47 , in a chain with a controllable phase shifter 48 , is introduced into the path 42 . The working area of the phase shifter and u. U. also the gain of the amplifier 46 are set by a control unit 48 . This control unit measures the frequency of the sensory subchannels, as described for FIG. 3, and generates an assigned control signal therefrom. It is in the sense of the invention that the required control parameters are stored as numbers coded in an electronic allocation table.

Fig. 11 shows an alternative arrangement with two separate encoder tracks 52, 53 on the side wall of a tire.

The magnetized areas are strips of equal size that were magnetized offset from one another by a quarter of a north / south pole period. The magnetically sensitive sensors 50 , 51 are arranged one above the other in a radial line. The signal processing takes place in an unchanged manner, as described for the various figures. The required sine / cosine spatial phase shift is now generated by the offset of the two encoder patterns.

Claims (12)

1. Device for detecting deformations on magnetically coded vehicle tires, with at least two magnetic field-sensitive elements ( 6 , 7 ), which are stationary at different distances from the tire rotation axis on the vehicle and interact with at least one magnetic track of the vehicle tire ( 1 ), the output signals or output information of the elements ( 6 , 7 ) are evaluated or processed in a signal processing unit, characterized by the steps:
Determination of simultaneous signals offset by 4 of a period, with at least one sine and one cosine value (A.sin (ω.t), B.cos (≙.t + φ)) being recorded by the elements,
Amplifying the amplitudes (A, B) of the signals with the phase position unchanged ((sin (ω.t), cos (≙.t + φ)) to the same value (C),
Multiplying the signed signals (C.sin (ω.t), C.cos (≙.t + φ)) in a multiplier ( 14 ),
Filtering the signal C ^2/2 [sinφ + sin (2 ≙t + φ)] in a low-pass filter (TP) by AC components in the frequency range equal to or greater than twice the frequency, based on one of the signals (C.sin (ω.t) To suppress C.cos (≙.t + φ)) and
Supply of the remaining DC component k.sinφ, as a measure of the deformation of the sidewall of the tire to a vehicle control system. 2. Device according to claim 1, characterized in that the magnetic field-sensitive elements ( 6 , 7 ) with respect to a tire side wall ( 1 ) with a coding from a regular sequence of uniform strip-shaped areas alternating north / south poles (N, S) in at least two groups (5 , 6, 7; 27, 5 28; 50, 51, 52, 53). 3. Device according to claim 1 and 2, characterized in that at least two groups of the magnetic field-sensitive elements ( 6 , 7 ) in the radial direction with each other, but at the same time offset by a quarter of the length of a north / south pole pair of the regular sequence of north / south pole pairs , 4. Device according to claim 1 to 3, characterized in that the groups of magnetic field-sensitive elements ( 6 , 7 ) are composed of two sensor-active subgroups ( 24 ; 27 , 28 ) which are offset from one another by a spatial distance or by a spatial phase Φ that does not exceed one eighth the length of a north / south pole pair in the regular sequence of north / south pole pairs. 5. Device according to claim 4, characterized in that the subgroups ( 24 ; 26 , 27 ) comprise means with which at least two independent partial signals S1 = A.sin (ω.t) and S2 = -A.sin (≙. t + Φ) = and S1 '= B. cos (ω.t) and S2 = -B.cos (≙.t + Φ). 6. Device according to claim 4 or 5, characterized in that an electronic functional unit ( 24 ) is provided which each form a signal sum and a signal difference from the partial signals 51 and 52 or S1 'and S2', with an OR gate are each connected to a common signal at twice the frequency of one of the sub-signals. 7. Device according to claim 5 or 6, characterized in that the partial signals with double frequency of the electronic function group ( 17 or 29 ) are supplied. 8. Device according to claim 1 to 5, characterized characterized in that the magnetic field sensitive elements with the postprocessing electronic circuits in several housed units are combined and that Output signal fed to an electronic controller becomes. 9. Device according to claim 1 to 6, characterized characterized that the signals of the magnetic field sensitive Elements so prepared by electronic circuits that in addition to a signal to represent the Deformation of the side wall at the same time a continuous Signal for mapping the distance of the side wall is generated and that both output signals are continuous be supplied to an electronic controller. 10. Device according to claim 1 to 7, characterized characterized that the groups of magnetic field sensitive Elements with at least two different ones Interact encoder tracks. 11. The device according to claim 1 to 8, characterized characterized in that at least one group is sensitive to magnetic fields Elements of the tire reading and coding at least one second group encoding the pulse generator of a wheel speed sensor for ABS systems reads. 12. The device according to claim 1, 2 and 4 to 8, characterized characterized that the groups are more sensitive to magnetic fields Elements are arranged radially vertically one above the other, while the scanned magnetic encoder tracks in the Distance of a quarter of a magnetic period are magnetized to each other.