DE10318168B4 - Device for detecting deformations on magnetically encoded vehicle tires - Google Patents

Abstract

A device for detecting deformations on magnetically coded vehicle tires, comprising at least two magnetic field sensitive elements (6, 7) which are mounted at different distances to the tire rotation axis stationary on the vehicle and with at least one magnetic track of the vehicle tire (1) cooperate, wherein the same time λ4 of a period offset signals of the elements (6, 7) in an electronic function group (17, 29) are evaluated, wherein in each case at least one sine and a cosine value (A · sin (ω · t), B · cos (π · t + φ)) are detected by the elements (6, 7) as first signals, characterized in that the electronic function group (17, 29) comprises: amplifiers (11a, 11b) for forming second signals by amplifying the amplitudes (A, B) of the first signals with unchanged phase position ((sin (ω * t), cos (π * t + φ)) to an equal value (C), a multiplier (14) for forming a third signal by multiplying the C · sin (ω · t), C · cos (π · t + φ)), a low-pass filter (15) for filtering the third signal C²2 [sinφ + ...

Description

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

With rotary magnetic encoders can generally win in a rotating movement of a device, dependent on the rotation angle electrical measuring signals. The known rotary position sensor "vehicle tire" contains a layer of magnetizable material as a code carrier. Magnetization changes or transitions are written into this layer by means of a magnetic head along a track. The inscribed code pattern has permanent magnetic areas or poles, with alternately arranged, preferably strip-shaped, north and south poles (N, S). This pattern is scanned by one or more magnetic field sensitive elements. The elements are arranged rigidly at a distance from the poles or areas, facing the poles or areas of the code carrier. The strip-shaped magnetic areas or poles are chosen so that a statement about the angle of rotation with respect to a predetermined reference position is possible with the help of the elements and an evaluation electronics associated therewith.

From the WO 96/10505 A1 , of the DE 196 26 843 A1 , of the WO97 / 44673 A1 In the tire sidewalls of a motor vehicle pneumatic tire embedded magnetizable layers are known which use magnetoresistive sensors for reading the pattern. There are therefore preferably applications in the field of regulated systems with brake intervention ABS, ASR, ESP provided, in particular those systems that use a deformation of tire rubber under load for the measurement or determination of forces or torques. A method known by the term "Side Wall Torsion Sensor (SWT)" is disclosed in U.S.P. DE-A1 44 35 160 described. In the DE-A1 44 35 160 It is proposed to measure the phase shift of two wheel speed signals for determining longitudinal and transverse forces on a magnetically encoded tire and at the same time to conclude the magnitude of lateral accelerations via air gap deformations and the thus variable signal amplitudes. In the rubber of the sidewall of the tire, a permanent magnetic track of strip-shaped alternating north / south polar areas is integrated, which form a ring. If the rolling tire is braked or accelerated, the side wall slightly twists. The strength of the twist is detected by two vertically superimposed magnetic field-sensitive elements or sensors on the time delay of the zero crossings of their signal voltages, which arises because the upper and lower zones of the permanent magnetic strips move against each other when the side wall twists. After the time delay of the zero crossings, the duration of the subsequent complete signal period is also measured. Immediately afterwards, by dividing the duration of the time delay of the zero crossings by the duration of the complete signal period, a sampling value of the temporal phase angle change is calculated. The number of samples per wheel revolution (corresponding to approx. 2 m travel) is limited to the number of north / south pole pairs of the encoder track of the tire sidewall. Due to the serial acquisition of the partial measurements, the subsequent calculation of the phase shift is associated with the pole pitch error of the encoder track mapped to the sensors. This aberration increases considerably with increasing air gap and leads to an undesirable, inaccuracy 'of the desired measurement. In conjunction with the small number of samples per revolution, the achievable accuracy of the phase measurement is limited.

pamphlet DE 100 05 552 C1 discloses a device for detecting deformations on magnetically coded vehicle tires. For this purpose, the vehicle tire has an outer encoder structuring arranged in a tire side surface and an inner encoder structuring located radially further inward than the first encoder structuring. In addition, there is provided a vehicle-mounted sensing device cooperating with the encoder structures for outputting signals which comprise at least one outer sensor element cooperating radially with the outer encoder structure, at least one middle sensor element located radially further inwardly relative to the outer sensor element and at least one radially further inner surface relative to the middle sensor element internal sensor sensor has cooperating inner sensor element. The encoder structures and the arrangement of the sensor elements are also matched to one another such that a circumferential force acting on the tire and at the same time a contact or normal force acting on the tire can be detected.

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

This object is achieved by the features of claim 1.

Advantageous developments are specified in the subclaims.

According to the invention the object is achieved in a generic device by the following steps:
Determine from simultaneous to λ / 4 a period offset signals, wherein in each case at least one sine and a cosine value is detected by the elements, amplifying the amplitudes of the signals at an unchanged phase position to an equal value
Multiplying the signed signals in a multiplier with each other, filtering the signal in a low-pass filter to suppress AC components in the frequency range equal to or more than twice the frequency with respect to one of the signals multiplied after signal conditioning and supplying the remaining DC component as a measure of the deformation of the sidewall of the tire to a vehicle control system.

It is advantageous that the magnetic field-sensitive elements with respect to a tire sidewall with a coding of a regular sequence of uniform strip-shaped areas of alternating north / south poles always divided into at least two groups interact with each other.

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

Furthermore, it is expedient for the group of magnetic-field-sensitive elements to be composed of two subgroups which are offset from one another by one spatial distance or one spatial phase which does not exceed one-eighth the length of a north / south pole pair of the regular sequence of north / south pole pairs. In this case, the subgroups comprise means with which at least two independent sub-signals S1 = A * sin (ω * t) and S2 = -A * sin (π * t + Φ) and S1 '= B * cos (ω * t) and S2 = -B · cos (π · t + Φ) are generated. In an electronic functional unit of the sub-signals S1 and S2 or S1 'and S2' each have a signal sum and a signal difference are formed, which are connected to an OR gate in each case to a common signal with twice the frequency of one of the sub-signals.

According to a further embodiment, it is advantageous that the sub-signals are fed at twice the frequency of an electronic function group, as in connection with 3 or 5 is described in more detail.

In order to improve the signal processing, it is expedient that the magnetic field sensitive elements are modular with the post-processing electronic circuits. The magnetic field-sensitive elements are combined with the post-processing electronic circuits in a plurality of housed units. The output signal is fed to an electronic controller of a vehicle.

In order to improve a driving dynamics controller, it is advantageous that the signals of the magnetic field sensitive elements are processed by electronic circuits so that in addition to a signal for imaging the deformation of the side wall simultaneously a continuous signal for imaging the distance of the side wall is generated and that both output signals be continuously fed to an electronic controller.

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

It is expedient that at least one group of magnetic-field-sensitive elements reads the coding of the pneumatic tire and at least one second group reads the coding of the pulse generator of a wheel speed sensor for ABS systems.

It is also advantageous that the groups of magnetic field-sensitive elements are arranged radially perpendicular to one another, while the sampled magnetic encoder tracks are magnetized to each other at intervals of one quarter of a magnetic period.

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

Show it:

1 a pneumatic tire with sidewall encoding and encoder in the wheel bearing

2 a section of the 1 with a deformation of the encoder track

3 a block diagram of the device

4 an embodiment of the phase determination on the pneumatic tire

5 an embodiment with amplitude measurement

6 a device for spatial frequency doubling

7 an embodiment of the invention with spatial frequency doubling

8th An embodiment of a trained as a unit sensor

9 an embodiment using a wheel speed sensor

10 an operative scheme of a low pass implementation according to 3

11 an alternative device in the 1 and 2 schematically shown sidewall encoding

1 shows a pneumatic tire with magnetic sidewall encoding 1 , consisting of an integer series of alternating north / south poles (N, S). The tire is part of a vehicle wheel 2 with another 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 detection for regulated brake systems.

2 shows stripe-shaped permanent magnetic areas 5 the encoded sidewall 1 that deform under load 5 ' , These are two magnetic field-sensitive elements, the sensors 6 . 7 present, which are mutually offset, but at the same time by a quarter of the length of a north / south pole pair against each other, near the ends of the magnetized strips and the location-dependent magnetic field of the encoder track 10 to capture. They produce by their arrangement to each other a sinusoidal 8a and a cosinusoid 9a electrical signal voltage. When twisting the side wall 1 under load, this initial state changes in a changed mutual phase position 8b . 9b to a phase angle deviation, which is to be measured continuously according to the invention.

3 shows the scheme of the device for carrying out the method with the encoder track 10 with the angular velocity ω at the sensors 6 . 7 is moved past. As described above, the signals A.sup.in (.omega.t) and B.times.cos (.omega.t + .phi.), Which each have a similar, separately controllable amplifier, are generated 11a . 11b be guided. The different amplitudes A, B are compared to a reference voltage 12 by regulator 13 . 13b separately so amplified, or weakened, that at the outputs of 11a and 11b Signals of the same amplitude C but unchanged phase relationship to each other arise. These signals C · sin (ωt) and C · cos (ωt + φ) become a four-quadrant multiplier 14 or supplied to a comparable functional unit, multiplied together and the result via a controllable low-pass filter 15 directed. The low pass 15 suppresses the alternating voltage component resulting from the multiplication, proportionally sin (2ωt + φ), so that substantially a DC component, proportional k · sinφ, remains, which can be considered proportional to the phase shift φ as a result of the present small angular range. The offset by λ / 4 a magnetic encoder period arranged sensors 6 . 7 have the purpose to generate the term sinφ, or to avoid a term cosφ; because it should be exploited that the sine responds to positive / negative phase shifts (ie braking or acceleration) with associated sign, while the cosine function in contrast always gives positive results and therefore ambiguous and unusable. The cutoff frequency of the low pass 15 is voltage controllable changeable. For this purpose, the frequency ω is determined from one of the two channels and z. B. via a frequency / voltage converter 16 turned into a control voltage that controls the low pass. A more detailed description of the voltage control of the low-pass filter 15 will be in contact with 10 described in more detail.

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

5 shows an embodiment of the device according to 3 with the difference of the amplitude measurement. The control signals of the partial amplitudes 19 . 20 be in the functional unit 21 weighted and next to the phase information 22 as amplitude information 23 to the ECU 18 sent. The amplitude signal 21 is a measure of air gap changes of the sensors relative to the tire sidewall, e.g. As a measure of lateral acceleration, which act on the vehicle.

6 shows a device for spatial frequency doubling, according to 7 can be used according to the invention. In the sensor module 24 is a magnetoelectric converter, which is composed of two components W1 and W2, which are offset by the distance Φ against each other, and which act so that the rotary encoder 25 , two signals S1 = A · sin (ωt) and S2 = A · sin (ωt + φ) are generated. The signals S1 and S2 are amplified in separate signal processing stages (SC1 / SC2) and then fed to a billing stage. The billing 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 in the second channel. SUM and DIF are then separately amplified in two identical amplifier stages and combined via an OR circuit (OR) to form a common signal S3. The signal S3 has twice the frequency of S1 or S2.

7 shows an embodiment under inventive use of this method of spatial frequency doubling. There are two of these before too 6 described sensory doubler 27 . 28 present, around λ / 4 against each other offset an encoded tire sidewall 1 scan. In this case, the subgroups W1, W2 and W1 ', W2' respectively generate at least two independent sub-signals S1 = A * sin (ω * t) and S2 = -A * sin (π * t + φ) and S1 '= B * cos (ω · t) and S2 = -B · cos (π · t + Φ). The doublers 27 . 28 form from the sub-signals S1 and S2 or S1 'and S2' each have a signal sum and a signal difference, which are each connected to an OR gate to a common signal with twice the frequency of one of the sub-signals. The output signals of this doubler 27 . 28 become the functional unit 17 or 29 fed as they are to the 3 . 4 or 5 are described properly.

8th schematically shows the embodiment of a sensor or sensor module. The previously described functional units, doubler 27 . 28 . 29 generate the analog phase signal in an A / D converter 31 is converted to analog / digital and a bus driver 32 is supplied. In an advantageous embodiment, it is a CAN bus connection 33 to the ECU 18 , The functional units 27 to 32 are to a sensor module 30 summarized.

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

10 shows an exemplary embodiment of the operating scheme of a low-pass filtering, as in the in 3 can be used or performed described device. That at the entrance 40 pending signal C² / 2 [sinφ + sin (2πt + φ)] becomes on two paths 41 . 42 a differential amplifier 43 fed to the output 44 the desired signal result φ can be tapped. For this purpose is in the path 41 an amplifier 45 introduced with DC coupling and into the path 42 an amplifier 46 with AC coupling 47 , in chain with a controllable phase shifter 48 , brought in. The working range of the phase shifter and u. U. also the gain of the amplifier 46 be from a control unit 48 set. This control unit measures the frequency of the sensory subchannels, such as 3 described, and generates an associated control signal. It is within the meaning of the invention that the required control parameters are stored as numbers coded in an electronic allocation table.

11 shows an alternative arrangement with two separate encoder tracks 52 . 53 on the sidewall of a pneumatic tire.

The magnetized areas are equally large strips that have been magnetized offset by a quarter of a north / south pole period against each other. The magnetically sensitive sensors 50 . 51 are arranged one above the other in a radial line. The signal processing takes place in the same way as described for the various figures. The required sine / cosine spatial phase shift is now generated by the offset of the two encoder patterns against each other.

Claims (12)

Device for detecting deformations on magnetically coded vehicle tires, comprising at least two magnetic field-sensitive elements ( 6 . 7 ) mounted at different distances to the tire rotation axis stationary on the vehicle and with at least one magnetic track of the vehicle tire ( 1 ), with the same time, um λ / 4 a period offset signals of the elements ( 6 . 7 ) in an electronic function group ( 17 . 29 ), wherein in each case at least one sine and one cosine value (A · sin (ω · t), B · cos (π · t + φ)) of the elements ( 6 . 7 ) are detected as first signals, characterized in that the electronic function group ( 17 . 29 ) comprises: amplifiers ( 11a . 11b ) for forming second signals by amplifying the amplitudes (A, B) of the first signals with an unchanged phase position ((sin (ω * t), cos (π * t + φ)) to an equal value (C), a multiplier ( 14 ) for forming a third signal by multiplying the signed second signals (C * sin (ω * t), C * cos (π * t + φ)) with each other, a low-pass filter ( 15 ) for filtering the third signal C² / 2 [sinφ + sin (2πt + φ)] to suppress AC components in the frequency range equal to or greater than twice the frequency with respect to one of the second signals (C ·sin (ω ·t), C ·cos (π ·t + φ)) and supplying the remaining DC component k · sinφ as a measure of the deformation of the sidewall of the vehicle tire to a vehicle control system ( 18 ). Device according to Claim 1, characterized in that the magnetic-field-sensitive elements ( 6 . 7 ) against a tire sidewall ( 1 ) with a coding of a regular sequence of uniform strip-shaped areas ( 5 ) alternating north / south poles (N, S) into at least two groups ( 5 . 6 . 7 ; 50 . 51 . 52 . 53 ) interact with each other articulated. Device according to claim 1 and 2, characterized in that at least two groups of magnetic field sensitive elements ( 6 . 7 ) in the radial direction with each other, but at the same time by a quarter of the length of a north / south pole pair of the regular sequence of north / south pole pairs are offset from each other. Device according to claim 2 or 3, characterized in that the groups of magnetic field-sensitive elements ( 6 . 7 ) consists of two sensory active subgroups ( 24 ; 27 . 28 ), which are offset from each other by a spatial distance or by a spatial phase Φ, which does not exceed one-eighth of the length of a north / south pole pair of the regular sequence of north / south pole pairs. Device according to claim 4, characterized in that the subgroups ( 24 ; 27 . 28 ) Comprise means with which at least two independent sub-signals S1 = A * sin (ω * t) and S2 = -A * sin (π * t + φ) and S1 '= B * cos (ω * t) and S2 = -B · cos (π · t + Φ). Device according to claim 5, characterized in that an electronic functional unit ( 24 ) is provided, which forms from the sub-signals S1 and S2 or S1 'and S2' each have a signal sum and a signal difference, which are each connected to an OR gate to a common signal with double frequency of one of the sub-signals. Device according to claim 6, characterized in that the sub-signals with double frequency of the electronic function group ( 17 or 29 ). Device according to claim 1 to 5, characterized in that the magnetic field sensitive elements ( 6 . 7 ) are combined with the post-processing electronic circuits in several housed units and the output signal is fed to an electronic controller. Device according to Claims 1 to 6, characterized in that the signals of the magnetic field-sensitive elements ( 6 . 7 ) are processed by electronic circuits so that in addition to a signal for imaging the deformation of the side wall simultaneously a continuous signal for imaging the distance of the side wall is generated and that both output signals are continuously fed to an electronic controller. Device according to Claims 2 to 7, characterized in that the groups of magnetic-field-sensitive elements ( 50 . 51 ) with at least two different encoder tracks ( 52 . 53 ) interact. Device according to claim 2 to 8, characterized in that at least one group of magnetic field sensitive elements ( 6 . 7 ) reads the coding of the vehicle tire and at least a second group reads the coding of the encoder of a wheel speed sensor for ABS systems. Device according to Claims 2 and 4 to 8, characterized in that the groups of magnetic field-sensitive elements ( 50 . 51 ) are arranged radially perpendicular to one another while the sampled magnetic encoder tracks ( 52 . 53 ) are magnetized to each other at a distance of one quarter of a magnetic period.

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