DE19744611A1 - Sensor for detecting tire condition in motor vehicle - Google Patents

Abstract

The sensor measures the separation (a,a') between the inner wall of the tire tread, and the rim (FG), at one or more points within the internal space defined by the tire and rim. The variation in this separation is detected during running of the tire and used to determine the spring deflection (f) of the tire. The variation in separation may be measured with respect to wheel rotation angle or time.

Description

Sensors for automotive technology, with whose help In Formations about the parameters of the tires and their diverse Relationship to the road can be gained, increasingly at Be interpretation. Such sensors are of particular interest, which measure continuously while the vehicle is traveling (e.g. tire pressure) and when irregularities occur (Air pressure loss) warn and / or in addition the measured Values as important parameters for control systems of the vehicle (e.g. chassis, brake and drive control) hand off. Based on the information such Sensor supplies can with the help of this control system driving conditions (e.g. speeds) can be prevented if the tires are not optimal or improper stood risky. Especially with a view to future Expecting facilities with the help of which the tire pressure select r can be changed during operation, can be based on such sensors the tire pressure to the current driving condition be adjusted. For example, lower pressure could be one improved comfort when driving slowly and better grip Allow on a smooth surface, but higher pressure gün increased fuel consumption and reduced tire wear when driving fast.

Tire pressure sensors are used in various places tet, for example with arrangements in which one with pressure acted upon membrane by their deformations coil cores ver pushes or the capacitance of a capacitor is detuned. Close The use of micromechanical (kapa citing or piezoresistive) pressure sensor. The problem of measuring Value transfer from the rotating wheel to the body is common  solved in that a variable with the measured variable resistance is part of a resonance circuit, the resonance fre quenz with the help of a (mounted on the axle or body side ten) The contact coil is queried by the rotating wheel without contact that can.

In addition, using the coupling coils listed above additional electrical energy to supply the sensor ger electronic circuits are transmitted. In this case can also be one prepared by the electronic circuit Measured variable via the coupling coils or by radio contactless Body can be transferred. For this contactless transfer The supply of information and energy are diverse arrangements according to inductive, capacitive, electromagnetic or opti State of the art principles anyway. In addition, known the suggestions, passive radio interrogable surface world to use len pressure sensors as tire pressure sensors (Pohl et alii, wireless measurement of tire air pressure with passive SAW sensors, Sensor 97, conference proceedings Vol. 1, pp. 89-94). Still on more conclusive are sensors which are inserted into the tires themselves are built and, in addition to the tire pressure, many things Stress and deformation states in dynamic operation grasp. Such sensors were made using Hall elements (Breuer et alii, ATZ) or with very inexpensive capacitive Transducer arrays (wobschall, capacitance-type elastomer-based Three-axis Force Sensor, Sensor 97, Proceedings Vol. 2, pp. 13-18) realized.

The object of the invention is a particularly efficient, mon inexpensive and easy to manufacture sensor, which the meets the above requirements. The tasks are solved with the features of claim 1, further out Events of the invention emerge from the subclaims.  

The basic idea of the present invention is, in particular with the aid of an ultrasound echo sounder mounted in the rim of the wheel, consisting of an ultrasound transducer or an ultrasound transducer arrangement (hereinafter referred to as transducer or transducer arrangement) and an electronic operating and evaluation circuit within the tire to measure and evaluate the distance a between the rim and the tread of the tire opposite the inner surface of the tire continuously in static and dynamic driving. In particular, the change in distance Δa caused by the “deflection” f (= change Δr in the wheel radius r at the measuring point) and its dynamic course

f (Φ, v, t,...) = -Δa (Φ, v, t,...) = -Δr (Φ, v, t,...)

depending on the wheel rotation angle Φ, the speed v, the time t, and evaluated by other relevant variables become.

The deflection f is the statement for the correct tire pressure stronger than the pressure p itself, because the optimal tire pressure may vary depending on the axle load. The invention according to the evaluation of the deflection derived statement about the Tire pressure can then be less than optimal or even fall recognize tire pressure if this for a medium load charge state of the vehicle would be correct, but not with one any heavy load. Accordingly rich evaluation of deflection f and and its display (or derived quantities) is a further embodiment of the present invention. The preferably with ultrasound Guided measurement has the particular advantage of being easily off evaluation of the terms and the possibility of other important  parameters such as the speed of sound and the like. to eat.

According to a development of the invention, deviations from the symmetry of the deflection curve Δf (Φ, v, t,...), ins especially measured with ultrasound, used to measure the force of the tire with the surface to evaluate at for example recognizing black ice or slippery road surface. Out Further evaluations of the deflection course are also from Condition of use of the tire and other relevant tire and Road parameters derived for display and control purposes. Model ideas about tires and their ver keep in mind while driving.

These sizes are particularly expected for the future Systems that allow tire pressure while driving to change, of great importance because it is the feedback he possible whether the respective tire condition of the driving style, the Speed, vehicle condition, road conditions etc. are set correctly accordingly.

Since a constant sound velocity c cannot be assumed when measuring the distance a, the influence of sound velocity is compensated for, according to a further embodiment, preferably by additional measurement of the distance of the b of a reference reflector mounted at a known distance from the sensor. Regardless of the value of the speed of sound, the following applies to the measured transit times, t _m to the measuring point and t _r to the reference:

a = bt _m / t _r .

The determination of the reference term is carried out neither in the main beam, for example by a reference reference used wire bracket - or similar - determined or  by means of a reference reflector in a secondary sound path (also Existing suitable areas would be in line with the Erfin usable as reference reflectors). This side sound path can be done by redirecting a small portion of the into the main ultrasound emitted by means of a small Deflecting mirror are sonicated or with the help of a wall learn, which through appropriate constructive design (e.g. Attaching a bevel), a small portion of their sound in send the specified direction to the reference reflector. The Sound emission for reference measurement can also be done simultaneously or take place sequentially on a different carrier frequency. By Determining the distance to the reference reflector is in the sense this configuration can be achieved that measurement echo and Referen zecho are sufficiently separated in time so that egg ne simultaneous evaluation of both echoes made possible in a simple manner light becomes.

In the sense of a further embodiment, the in particular as Complete sensor or at least ultrasonic sensor Parts like the ultrasonic transducer (s) in one in the rim already existing or used specifically for this purpose brought indentation or bead to be attached. Through compact Design of the sensor arrangement and by choosing the installation location is the transducer or sensor assembly from damage to the Tire mounting protected. Also cover plates, Guard bars and similar arrangements for mechanical protection (e.g. perforated cover plates). Preferably the sensor also mounted so that the sound radiation initially essentially tangential to the rim and only then ßend brought in a radial direction by a deflecting mirror becomes. In this way, a lead is achieved, which in particular especially the measurement with so-called monostatic converters (i.e. a and the same converter for sending and receiving) if the measuring and reference distances are smaller than  so-called blind area of the sensor. It can also through groove tion of a reflective edge of this deflecting mirror or by introducing an interruption in the mirror surface (e.g. through a hole or a groove) a stable reference reflector can be realized.

As transducers preferably come with an acoustic adjustment layered piezoceramic transducers in question, the preferred Frequency range is 0.2. . . 1 Mhz Are also well suited electrostatic converter. The converters are in their frequency behave as well as their directional diagram to their up adapted, for example by a high level of sharpness or by forming a side lobe for reference measurement outside of the main beam. Small aperture transducers are manufactured according to ei ner further embodiment with the help of concave mirrors (even sometimes also used as a deflecting mirror) with little additional opening wall with high directional sharpness. By covering the rim inside with an ultrasound absorbing covering faster decay of vagabond ultrasound signals and so that faster and more accurate measurements can be achieved.

According to a further embodiment of the invention a micromechanical ultrasound transceiver (or a micromechanical ultrasound transceiver transducer arrangement tion) and in particular with an integrated one Circuit executed electronic circuit (ASIC) monoli integrated. In addition to functional improvements (better signal-to-noise ratio, etc.), above all, an efficient Production achieved in large quantities. The low dir effect due to the small aperture, which is in such Walkers from the small space available on the According to a further embodiment, the chip can Invention by using a focusing concave mirror he  be significantly improved (see above).

Although the determination of the deflection and ih res course (over time and wheel rotation angle), especially with Ultrasound, which is itself very meaningful, i.e. H. diverse Describe measurements describing tire and road parameters len, provides the determination of further tire-related sizes such as the tire temperature, pressure and density of the in the tire closed air additional important sizes. In the sense of Another embodiment of the invention results in the determination of Ratio of change in deflection and change in Pressure (and / or temperature and / or density) Notes about at for example spring properties of the tire. One with the invent according to the sensor measured strong increase in tire temperature ratur is another indication that something is wrong with the tire is not okay. It is particularly advantageous if the determination of the additional sizes mentioned by a detail Lated evaluation of the anyway in the sensor according to the invention contained information is made possible and thus to this No further sensors are required for this purpose.

According to a further embodiment of the invention to determine the acoustic impedance Z (Z = ρ.c) or Density ρ of the air in the tire is the amplitude of the Echoes or the impedance of the transducers or the decay of the sen dewandlers can be evaluated. With increasing density of the air the efficiency-bandwidth product of the converters increases, which are usually not well adapted to air. Since the Speed of sound is only weakly dependent on pressure, and is also determined from the running time on the reference route, can measure the temperature of the air in the tire from the measured Speed of sound can be determined (unless you do it prefers to use its own temperature sensor, which especially in the case of an integrated electronic circuit  is easy to implement). Thus, one can be wide Ren design according to the determined density and the measured Temperature also the pressure can be determined. With constructive Design as a closed converter can micromechanically re alized ultrasonic transducer according to a further embodiment can also be used for direct pressure measurement by the static deformation of the sound-emitting membrane such a transducer arrangement is detected.

In the sense of a configuration for a tire-specific precise re evaluation of the measured tire values can design and type-determined basic parameters of the tires in the sensor or into the system using the sensor data preferably using electrically readable data carriers (e.g. Cards with magnetic stripes and the like.). In particular, re on data carriers connected to the tire such as e.g. B. bar codes or embossed patterns in the tire surface or surface wave identification components and the like., be used. The use of the parameters entered in this way for Evaluation algorithms, possibly fuzzy algorithms or by Inclusion of the sensor results in self-learning systems (Neural networks etc.) corresponds to a further embodiment the invention.

The course of the measuring cycles in time and / or in relation to the wheel According to the invention, the angle of rotation is to be coordinated so that it is to be determined wheel angles / times at which deflection takes place starts and in particular reaches its maximum value, a measurement the deflection takes place. To determine this Radwin existing wheel sensors can be used; but it also corresponds to a further inventive feature design, the results of previous ultrasound measurements to use to determine the said times, d. H. With Using the measurements to synchronize their further sequence.  

In addition, it is also possible to change the chronological order of the Measurements against fixed values of the wheel rotation angle to make the deflection particularly fine to scan stroboscopically. Due to irregular measuring periods the measuring cycles can be nested, i.e. H. it new measuring cycles can be started before the Signals from previous cycles have completely subsided. This allows the mean measurement period to be shortened considerably.

The measurement of the distance a according to the invention, in particular with ultrasound, is useful not only in the area of the wheel rotation angle in which the deflection takes place, but during the entire wheel revolution. This enables a number of further configurations, as described below:
A reference value for the deflection is obtained by measuring the tightly sprung part of the tire or by averaging over several such values.

These measured values (or mean values) are themselves pressure-dependent and can make an additional statement about the tire pressure, abnormally condition and the like. deliver.

Circumferential vibrations of the tire, as in high driving speed and driving comfort and driving safety adversely affect and cause higher noise things can be measured directly in operation.

For high-resolution distance measurement, it is also in the sense of a Embodiment of the invention, the phase of received ultrasound Evaluate "bursts". Another continuous according to the invention Liche scanning is done by measuring the phase of reception signals of continuously transmitted ultrasound waves enable light (Doppler evaluation, possibly complex), distance Clarity is due to frequency modulation of the transmitted signal additionally reachable (FM-CW-Doppler) and alternate  operation between pulsed and continuous signals (Model-based Doppler evaluation with pulsed measurement known reflective objects) possible. From the spectra the Doppler signals can also make relevant statements about dynami processes are derived. Another embodiment According to the invention, the deflection and its course also by integrating (summing) the Doppler phase ver shift continuously and with high range resolution be true.

While the ultrasonic transducer is inside the tire electronics circuit can also be found outside the. The connection between these two parts can be made through an airtight passage through the rim wall. It is also an advantageous alternative to combine the electronics to be installed inside the tire with the ultrasonic transducer. For Connection with external parts of the Sen according to the invention sensor arrangement, such as a wheel-side coupling coil or to touch generally to a wheel-side coupling element seamless information and energy transmission will continue an airtight implementation of an electrical connection if you don't, another invention thank accordingly, prefers the electronic circuit through to interrogate the tire wall by radio. An advantageous th further embodiment of the invention can be carried out the electrical query signals or the power supply a suitably designed tire valve, the Accordingly, the cap can be used as an electrical connection be carried out constructively.

For the contactless transmission of operating energy (to the sensor), control signals and measurement results, at least one transmission element (e.g. a coupling coil) must be provided on the wheel side and a corresponding transmission element on the axle side or the body side. The transmission should take place between such a pair of transmission elements. There are many possibilities for this: inductive, capacitive or optical transmission as well as radio connection. The transmission elements can be placed in many different ways (see Fig. 3).

The measurement of the distance between the rim and that of the tread opposite surface on the inside of the tire in the sense of the invention also by means of other non-contact from level sensors. As such come opti, for example cal sensors or sensors in which the Ab Position determination with the help of electromagnetic waves or fel the or with the help of capacitive or inductive functional principles pien takes place in question. In particular, the inside can do this the tire with suitable surface finishes, paints, functional coatings (e.g. with conductive lacquers, lacquers with fer Romagnetic particles and the like.) Apply more suitable Parts (e.g. metal foils, printed coils and the like), Application of (in particular optical) patterns in a suitable manner Marked or structured in a way. Advantage of optical Sensors is their high measuring speed and their insensitivity sensitivity to the influences of the trapped in the tire air.

The invention and its further development are illustrated by the figures further explained.

Fig. 1 shows the cross-sectional drawing of a wheel consisting of rim FG and tire RF. RF 'denotes the tire deformed under the wheel load, VL the valve and VK the valve cap. The diameter of the unloaded wheel is specified with A, with r the radius at the point at which the loaded wheel rests on the ground (road surface).

The deflection of the wheel, the measurement of which is the subject of the present invention, is marked with f. The following applies (f = A / 2-r). With d _L is the thickness of the tire on the tread, it is assumed to be approximately constant during rolling. The distance between the rim well and the opposite inside of the tire is denoted by a in the case of the non-sprung tire and a 'in the sprung-in tire.

In Fig. 2 tire sensors according to the invention are shown, each a variant in the upper and lower part of the wheel. In the lower part, W represents the ultrasonic transducer arrangement (individual transducer or several transducers) attached to the rim in the inner part of the tire. This transducer arrangement is connected to the electronic circuit E of the sensor by a connecting line V through the rim by means of a bushing Df. The ultrasound main beam 1 emitted by the transducer arrangement strikes at point F on the point opposite the running surface in the interior of the tire. The echo signal 2 reflected in the direction of the transducer arrangement reaches the transducer arrangement after a distance that is proportional to the distance and is evaluated by means of the electronic circuit. In addition, an ultrasound signal 3 is emitted on a side path to the reference reflector R _r , which is attached at a known distance, and the reference echoes 4 which are thereby caused are used to eliminate the influence of the variable speed of sound or to measure the air temperature inside the tire. The variants in the upper part of FIG. 2 include transducer arrangement W 'together with the electronic circuit E' inside the tire, the reference reflector R _r (could be a wire bracket, for example) is at least partially in the main ultrasound beam 1 '. The measurement echo 2 'and the reference echo (not shown) come one after the other in time so that they can be evaluated one after the other without further teres. The connecting lines V 'and V''are carried out by the valve, in particular V''through the valve cap, and connect the arrangement within the tire to the outside with the rim, which (circuit) arrangements are preferably used for the transmission of measured values and operating energy can serve. Of course, parts of the upper Va riante can be combined with parts of the lower variant in any meaningful way in the sense of the invention.

Fig. 3 shows schematically some ways to contact the wheel-bound sensor (as shown in Fig. 2) contactless with axially or body-connected transmission devices to transmit measured values, control signals and operating energy. Here are Ü _R , Ü ' _R ,. . ., Ü '''' _R wheel-bound transmission devices and Ü _A , Ü ' _A , Ü'' _A , Ü''' _A the corresponding axle-side and Ü '' _K and Ü '''' _K the corresponding body-side transmission Counterparts. 5 and 5 'identify radio transmission paths, 5 ' connects in particular a wheel-side transmission unit placed inside the tire with an external counterpart. AR is used to denote a possibly sound absorbing covering.

Reference list

f deflection
a, a 'Distance between the rim well and the opposite inner wall of the tire, not compressed and compressed
Δa change of a
b Distance to reference reflector
Φ wheel rotation angle
v speed
c speed of sound
t time
z acoustic impedance
ρ density
tm, tr transit time of the measurement signal or the reference signal
FG rim
RF, RF 'tires, dto. In the sprung condition
VL valve
VK valve cap
A wheel diameter
r Distance between wheel axis and road surface (wheel radius)
d _L

Thickness of the tire wall on the tread
W, W 'ultrasonic transducer, ultrasonic transducer arrangement
E, E 'electronic circuit
V-V '' electrical connection cable
F, F 'impact point d. Measuring beam

1

;

2nd

Ultrasonic measuring beam; Measurement echo
R _r

, R ' _r

, Reference reflectors

3rd

;

4th

Ultrasound reference beam; Reference echo
Ü _R

-Ü _R

'''' coupling elements on the wheel side
Ü _A

-Ü _A

'''' Axial coupling elements
Df implementation
Ü _K

'', T _K

'''' Body-side coupling elements
AR sound absorbing surface

Claims (38)

1. Sensor or sensor system for recording the tire condition of vehicles, in which:

• the distance between the tire inner wall on the tread and the rim is measured at one or more points in the tire interior formed by the tire and rim;
• - The change in this distance during the Reifenabrol lens detected and ver used to determine the deflection of the tire.

2. Sensor / sensor system according to claim 1, in which the course of this change in distance depending on the wheel Angle of rotation and / or the time and / or other parameters is evaluated. 3. Sensor according to claim 1 or 2, in which at least one non-contact Ab attached to the rim level sensor is provided. 4. Sensor / sensor system according to claim 1, 2 or 3, in which at least one ultrasonic distance attached to the rim sensor is arranged. 5. Sensor / sensor system according to claim 1, 2 or 3, in which at least one distance sensor attached to the rim an optical operating principle is used. 6. Sensor / sensor system according to claim 4, in which the term to a Refe attached at a known distance renzreflektor is measured and to correct the measuring distance Is used.   7. Sensor / sensor system according to claim 4, in which from the measured transit time at a known distance brought reference reflector determined the speed of sound becomes. 8. Sensor / sensor system according to claim 7, in which from the measured speed of sound the temperature of the Tire trapped air is determined. 9. Sensor / sensor system according to claim 7, in which from the amplitude of the echo signal from the reference reflector and / or the amplitude of other echoes on the acoustic imp danz and / or the density and / or the pressure in the tire closed air is determined. 10. Sensor / sensor system according to claim 7, 8 and 9, in which determine the pressure of the air trapped in the tire values of acoustic impedance, speed of sound and Temperature is calculated. 11. Sensor / sensor system according to claim 1, 2, 3, 4 or 5, at the from the form of the functional course of the change in Einfe change over time or over the angle of rotation of the tire condition characterizing parameters can be derived. 12. Sensor / sensor system according to claim 1, 2, 3, 4 or 5, at the from the form of the functional course of the change in Einfe change over time or over the angle of rotation of the tire bahn contact characterizing parameters can be derived. 13. Sensor / sensor system according to claim 1, 2, 3, 4 or 5, at the  from the symmetry of the functional course of the change in Deflection over time or over the angle of rotation of the force conclusion between tire and road surface is determined. 14. Sensor / sensor system according to claim 13, wherein from the adhesion, statements about grip of the road and stripped over slippery road surface and presence of black ice be tested. 15. Sensor / sensor system according to claim 13 and / or 14, in which From the determined adhesion, statements about the grip of the Roadway are derived perpendicular to the direction of travel. 16. Sensor / sensor system according to claim 13 and / or 14, in which the determined adhesion or the statements about grip automatic braking or drive control systems be fed. 17. Sensor / sensor system according to claim 13 and / or 14 and / or 15 where the determined adhesion or the statements about grip automatic steering correction across the road tur or driving stability control systems are supplied. 18. Sensor / sensor system according to claim 1, 2, 3, 4 or 5, at the from local slopes of the functional course of the change the deflection over time or over the angle of rotation parameters that characterize the use of the tire become. 19. Sensor / sensor system according to claim 1, 2, 3, 4 or 5, at the from local slopes of the functional course of the change  the deflection over time or over the angle of rotation the Al parameters that characterize the tire the. 20. Sensor / sensor system according to claim 4, in which at least one ultrasonic transducer as a micromechanical mem branch converter is executed. 21. Sensor / sensor system according to claim 20, in which at least one ultrasonic transducer simultaneously as a pressure transducer mer is executed. 22. Sensor / sensor system according to claim 20 or 21, in which one or more ultrasonic transducers together with an inte electronic circuit monolithically integrated on a chip are free. 23. Sensor / sensor system according to claim 20 or 21, in which one or more ultrasonic transducers together with an inte electronic circuit as a multichip arrangement are. 24. Sensor / sensor system according to claim 5, in which one or more optical, especially in integrated optics executed, elements together with an integrated electrical Electronics circuit are monolithically integrated on a chip. 25. Sensor / sensor system according to claim 5, in which one or more optical, especially in integrated optics executed, elements together with an integrated electrical Electronics circuit are designed as a multi-chip arrangement. 26. Sensor / sensor system according to claim 4 or 5, in which

• - The ultrasound or light emission is arranged almost tangentially to the rim and
• - A deflection mirror is provided for deflection in the radial direction.

27. Sensor / sensor system according to claim 4 or 5, in which a beam-focusing mirror is arranged. 28. Sensor / sensor system according to claim 26, in which a deflecting mirror arranged with a beam-focusing effect is. 29. Sensor / sensor system according to at least one of claims 1 to 5, at which for the sensor and the sensor evaluating systems gave way parameters of the tire on one supplied with the tire machine-readable data carriers are provided. 30. Sensor / sensor system according to at least one of claims 1 to 5, at which for the sensor and the sensor evaluating systems gave way The parameters of the tire are linked to the tire which structure is provided. 31. Sensor / sensor system according to at least one of claims 1 to 5, at which the distance between the tire inner wall on the tread and the rim at points not in contact with the road or Wheel angles is measured. 32. Sensor / sensor system according to claim 31, in which a reference value for the deflection from the measured distances or whose course is determined. 33. Sensor / sensor system according to claim 31, in which  from the measured distances and changes in scope over time vibrations of the tire can be determined. 34. Sensor / sensor system according to claim 31, in which a tire condition statement from the measured distances is leading. 35. Sensor / sensor system according to claim 4 or 5, in which Means are provided which change the distance evaluate the Doppler modulation that occurs. 36. Sensor / sensor system according to claim 26, 27 or 28, in which a reflective edge of the mirror as a reference reflection gate is arranged. 37. Sensor / sensor system according to claim 26, 27 or 28, in which a disturbance on the surface of the mirror as a reference reflection gate is arranged. 38. Sensor / sensor system according to claim 26, 27 or 28, in which at least one reference reflector with the mirror a structural Unity.