Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
  • G01P3/489—Digital circuits therefor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
  • G01P3/487—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by rotating magnets

Definitions

• the invention relates to a method according to the preamble of claim 1 and a device according to the preamble of claim 3.
• Devices for wheel speed detection in motor vehicles are known in principle. They consist of an encoder and a sensor that magnetically scans this encoder via an air gap.
• the encoder is a machine element that is mechanically connected to the rotating ring of a wheel bearing and carries an incremental angular scale.
• the angular scale is designed as an integer sequence of magnetically alternating areas of different effectiveness, which form a circular encoder track. It is common to use gears, ferromagnetic perforated disks or permanently magnetized structures as encoders, e.g. magnetized wheel bearing seals.
• the sensor reacts to the periodic change of tooth / gap or hole / bridge or north / south pole with a periodic electrical signal that depicts the incremental angle division as a voltage or current curve over time.
• Induction coils, magnetoresistive bridges and Hall elements are used as sensor components, some of which are operated in combination with additional electronic circuits. It is common to refer to sensors as “active sensors” when they need a power supply to operate them and as “passive” sensors when they, like induction coils, do not need an additional power supply to operate them.
• EP-A 0 922 230 (P 8775) describes an arrangement for detecting the rotational behavior of a rotating encoder, with a sensor module the following function group.
• pen contains: A sensor element based on the magnetoresistive effect, a controllable current source that delivers an impressed current that represents the rotational behavior, and a modulator that controls the current source as a function of signals from the sensor element.
• the sensor module is magnetically coupled to the encoder.
• the output signal is a signal representing the rotational behavior with superimposed status and / or additional signals.
• the status signals include information about the direction of rotation.
• WO 99 49322 (P 9352) describes an interface in which the direction of rotation information and its validity are contained as 2-bit information within an 8-bit word which is sent after each speed pulse.
• Active sensor elements based on the Hall effect are also known (TLE 4942, Infineon Technologies, Kunststoff), in which not only the speed but also the information about the direction of rotation is transmitted in coded form. Here, the signal changes between 2 current levels. The time interval between the rising flanks signals the wheel speed, while the direction of rotation is encoded over different pulse durations.
• each of the exclusive-or-linked sensory channels contributes an individually fluctuating pulse duty factor to the overall signal, which increases the jitter for the operation of modern brake controllers inadmissibly.
• the ECU requires significantly more effort than with conventional sensors in which the signal frequency follows the encoder frequency. Conventionally, it is evaluated from the rising to the rising edge and from the falling to the falling edge in order to determine the wheel speed. This avoids jitter errors caused by an asymmetrical duty cycle.
• the present invention thus aims to use one sensor per encoder angular period, e.g. North / south pole pair, tooth / gap, to generate a signal with twice the period number.
• the aim of the invention is to double the spatial frequency of incremental scales that are read by means of sensors via a field coupling.
• the invention is used in particular in the detection of linear path and / or angular displacements or the detection of associated movement speeds or speeds in the motor vehicle industry.
• two or more magnetoelectric transducers which are effective at the same time and are mutually offset are used, the spatial offset (spatial phase) of which is shown as a signal phase angle when the encoder is moved.
• the generation of such a phase shift is required to implement the present invention.
• the encoder has a sequence of alternating permanent magnetic north / south pole areas, which in particular have the same dimensions and form an encoder track closed to a circle.
• the encoder can also comprise a series of alternating ferromagnetic zones and magnetically non-conductive zones.
• the teeth and gaps then usually have the same dimensions and form an encoder track closed to a circle.
• the encoder therefore consists of a sequence of teeth and gaps made of a ferromagnetic material.
• a ruler can also be provided as the encoder, in which the said areas are lined up. It is also possible that the teeth and gaps are lined up so that they form a rack.
• the areas have the same dimensions and are introduced as an encoder track closed into a circle in the side wall of a pneumatic tire, so that this encoder for a side wall torsion sensor known per se ("side wall Torsion "sensor, hereinafter SWT sensor) can be used.
• side wall Torsion sensor a side wall Torsion sensor known per se
• SWT sensor side wall Torsion sensor
• the number of north / south pole pairs closed in a circle on the sidewall of the tire is in particular exactly 24.
• Preferred uses are in the field of known electronically controlled brake systems (ABS, ASR, ESP, etc.) or in control systems for chassis control (chassis systems), for example with angular position transmitters, motorized adjusting devices, electrical articulation devices etc.
• ABS electronically controlled brake systems
• ASR ASR
• ESP ESP
• chassis control chassis control
• the use of the invention is particularly preferred for the detection of wheel speeds in motor vehicles, very particularly preferred for those which are integrated with wheel bearings.
• Another preferred use is in the field of SWT sensors.
• Fig. 10 different embodiments for housed sensor modules.
• an encoder la, lb or lc is optionally provided in the arrangement according to the invention, which interacts via a magnetic coupling 2 with an active sensor 3, which in turn sends 4 wheel speed signals to an electronic control device 5 via an electrical current interface.
• encoders are generally referred to herein e which are constructed as incremental scale embodiment of machine elements.
• Angular scales are primarily used to explain the invention, however, all designs apply equally to linear path scales or rulers.
• the angle scale la consists of an integer sequence of similar areas of alternating magnetic north and south poles, which form an encoder track closed to a circle.
• the encoder lb is a windowed ferromagnetic disc and the encoder lc is a steel gear.
• the three encoders listed represent the multitude of such encoder variants.
• the encoder is mechanically connected to the rotating ring of the wheel bearing and the magnetic field strength curve of the encoder track is scanned magnetically via the air gap 2 by the stationary active sensor (arrow M).
• a "active" sensor is generally referred to as a measuring sensor that requires an external electrical energy supply for its operation.
• the encoder rotates at the angular velocity ⁇ .
• the magnetically sensitive transducer 9 is technically designed in such a way that either only the angular speed (wheel speed) or additionally the direction of rotation of the wheel (sign of the angular speed) can be derived from its converter signals.
• Both pieces of information are fed to a modulator 6a, which uses them to generate a coded signal which is used to control a current source 6b which sends a coded signal current via the electrical connection 4 to the input stage 7 of the control device 5.
• a demodulation stage 8 Downstream of the input stage is a demodulation stage 8, in which the angular velocity and direction of rotation are recovered as separate information.
• those elements which contain magnetoelectric transducers based on XMR effects are preferably used as sensor elements. Sensors with transducers based on the AMR effect are particularly preferably used (see VDI Technology Center, Dusseldorf, Technology Analysis Magnetism, Volume 2). Of course, other magnetoelectric transducers can also be used according to the invention, such as transducers with Hall elements in particular.
• the arrangement in FIG. 2 consists of a sensor module 10 which interacts with a control device 5 via a two-wire interface 12 and at the same time interacts with a magnetized encoder 11 via a magnetic interface 2.
• the control device 5 supplies the sensor module with electrical energy via a voltage VB and receives the signal current J s .
• the signals Si and S 2 are separated in a signal processing stage 14 reinforced (SCI, SC2) and then fed to an accounting stage 15.
• the allocation level contains two channels.
• SUM and DIF are then amplified separately in two similar amplifier stages with switching hysteresis 16, 17.
• the amplification factors are chosen so high that a compromise between maximum steep zero crossings and a minimum of interference due to the offset offset is set.
• the partial signals are combined via an OR circuit 18 and fed to a modulator 6a with signal current source 6b, so that a defined signal current protocol can be generated. As will be shown later with reference to FIG.
• the signal composed of SUM and DIF has the advantageous property that largely independent of the module, an overall signal with a pulse duty factor of 1: 1 is always generated, which increases in the usual way from the ECU rising edge and from falling to falling edge can be evaluated and thus the desired frequency doubling is achieved.
• FIG. 3 shows an application variant of FIG. 2 for vehicle tires with an encoder-like magnetized side wall, such as are used for so-called side wall torsion sensors (SWT sensors), for example according to DE 196 20 582 (P 8700).
• SWT sensors side wall torsion sensors
• Alternating strip-shaped north / south pole areas are introduced into the side wall of the tire 19, which close to form an annular encoder track.
• the encoder track is scanned by two magnetically sensitive sensors arranged one above the other.
• An air gap of approx. 40 mm must be set between the side wall and the sensor for practical operation. This is currently achieved with a pole pair number of 24.
• the sensor principle shown can meet this need.
• FIG. 4a explains the signal technology background of the invention using the example of a magnetoresistive bridge 21, under which a magnetized encoder track 22 is moved past.
• the four bridge resistors 23, 24, 25 and 26 are largely identical except for their direction of action with respect to the magnetic vector of the encoder.
• the respective effective direction is identified by the symbols (+) and (-) and mean an increase or decrease in the bridge resistance under the same field direction, so that the development of the partial voltages Si and S 2 can be seen.
• FIG. 5 shows a simple analog circuit for realizing the invention.
• two aggressive resistive full bridges 27, 28 are used, the signals of which are processed in the same way via the instrumentation amplifiers 29, 30 and are then fed to both a summing amplifier 31 and a differential amplifier 32 at the same time.
• the output signals SUM and DIF are fed to an OR gate 33, so that the desired frequency-doubled signal can be tapped at output 34.
• the signals of the electromagnetic partial transducers Wi, W 2 from FIG. 4 can also be processed via corresponding instrumentation amplifiers 29, 30 and then fed to both a summing amplifier 31 and a differential amplifier 32.
• the output signals of these two amplifiers are then also fed to an OR gate 33, at whose output 34 the desired frequency-doubled signal can be tapped.
• 6 shows examples of transducer arrangements and their effective mutual displacement ⁇ , which can be used according to the invention.
• 6a shows two separate areas of a Hall arrangement.
• 6b shows three separate areas of a Hall arrangement, the middle area being assigned to the two outer areas.
• FIG. 6c symbolizes a magnetoresistive bridge, the spatial phase ⁇ of which arises from the spatial distance between the two bridge branches.
• 6d shows a magnetoresistive bridge structure with three bridge branches, the middle bridge branch being assigned to the two outer bridge branches.
• 6e shows two separate full bridges, the spatial phase ⁇ of which arises from the distance between the centers of the bridges.
• the electromagnetic partial transducers Wi, W 2 and their spatial offset ⁇ are preferably realized against each other by two or three separate areas of a Hall arrangement.
• the electromagnetic partial transducers W i # W 2 and their spatial offset ⁇ from one another are realized by the distance between two or three bridge branches of a magnetoresistive bridge 53 or 54 are .
• the sensor-active partial transducers are preferably those types which are constructed with magnetoresistive conductor structures, to which a Barber pole structure is additionally applied.
• the electromagnetic partial transducers (Wi, W 2 ) and their spatial offset ⁇ from one another are realized by the center distance between two magnetoresistive bridges 55.
• FIG. 7 shows an embodiment of the invention with digital offset compensation 35 of the two partial signals from the converters Wi and W 2 .
• the digital offset compensation enables a very high amplification of the signals SUM and DIF and therefore a particularly high quality of the 90 ° phase shift.
• offset compensation takes place via an electronic functional unit 35, which alternately feeds the signals from SCI and SC2 via a multiplexer (MUX) to the digital offset compensation stage (DOC).
• MUX multiplexer
• DOC digital offset compensation stage
• the output signals SCI and SC2 are then essentially pure AC signals.
• This method of direction detection is known per se from SAE Technical Paper # 2000-01-0082, Stefan Pusch, but not in connection with the uses according to the invention. It is also a preferred counter tand the invention to combine the known method of direction detection described in this paragraph with the method and apparatus of the present invention.
• FIG. 9 shows proposals according to the invention for implementing data protocols for the sensor variants described.
• the time profile of an encoder track gear for example, is shown in partial image 9a.
• 9d shows an advantageous signal current protocol, the two amplitudes J and J M of which follow the change in amplitude of the encoder track at twice the frequency.
• 9c shows a signal current protocol with the current levels J L , J M and J H.
• the pulse sequence J H denotes twice the encoder frequency. This is followed by a pause and then 9-bit additional information.
• the pulse length t p is also valid for the length of the pause and the length of the bits in the additional information.
• the time period t p is particularly advantageously in the range of approximately 50 ⁇ s.
• the direction of rotation information is encoded in the additional information.
• 9b shows the proposal according to the invention of a simple protocol with the current levels J L , J M and J H for coding the speed and direction of rotation. While the pulse interval represents the speed, the direction of rotation is coded in the signal levels J M and J H.
• the modulator 6a shown in FIGS. 1 and 2 therefore preferably generates, in combination with the signal current source 6b also shown in these figures, a signal current protocol 56 which has two different amplitudes J L and J M which, at twice the frequency, cause an encoder track change 59 (see drawing 9a ) ) consequences.
• the modulator 6a in combination with the signal current source 6b generates a signal current protocol 57 which has three different amplitudes J L , J M and J H , which follow an encoder track change 59 at four times the frequency, the signal pattern also including the wheel speed information further additional information, including the direction of rotation, are encoded.
• the modulator 6a in combination with the signal current source 6b, generates a signal current protocol 58 which has three different amplitudes J L , J M and J H , which follow an encoder track change 59 at four times the frequency, the amplitudes J M and J H is differentiated between two directions of rotation.
• the three signal current amplitudes J L , J M and J H are expediently around 7 mA, 14 mA and 28 mA.
• the pulse duration t p of the wheel speed information 57 or 58 is also advantageously about 50 ⁇ s.
• FIG. 10 shows embodiments of housings and biasing magnets as can be used advantageously in combination with the invention.
• Partial images 10a), b) and c) show embodiments with magnets 37, 38 and 39 of different sizes.
• the magnets can also differ from one another in the direction of magnetization.
• the magnetoelectric transducers Wi and W 2 are accommodated in the housing part 40; the entire electronic circuit for processing the converter signals is accommodated in the housing part 41 with the two-wire output 42.
• FIG. 10d shows an embodiment in which both transducers and electronic see circuits are housed in a common housing 44. According to the invention, SOI technology is used here.
• the device is integrated in a one-piece housing 44, which accommodates both the sensor-active partial transducers Wx and W 2 and the necessary electronic circuits for signal processing up to the two-wire output 42.
• the housing shapes in sub-images a) to c) are usually used in the field of wheel speed sensors. The same also applies to the implementation of the current interfaces according to FIGS. 9c and 9d. See also PHILIPS DATA HANDBOOK SC17, page 234 ff. And page 170 ff.

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• 2003
  • 2003-04-16 US US10/510,856 patent/US7170280B2/en not_active Expired - Fee Related
  • 2003-04-16 DE DE10391610T patent/DE10391610D2/de not_active Expired - Lifetime
  • 2003-04-16 JP JP2003584737A patent/JP4410566B2/ja not_active Expired - Fee Related
  • 2003-04-16 WO PCT/EP2003/003947 patent/WO2003087845A2/de active Application Filing
  • 2003-04-16 CN CNB03808466XA patent/CN100439921C/zh not_active Expired - Fee Related
  • 2003-04-16 EP EP03720477A patent/EP1499901A2/de not_active Withdrawn
  • 2003-04-16 KR KR10-2004-7016612A patent/KR20040102113A/ko active IP Right Grant

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