Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L17/00—Devices or apparatus for measuring tyre pressure or the pressure in other inflated bodies
  • G01L17/005—Devices or apparatus for measuring tyre pressure or the pressure in other inflated bodies using a sensor contacting the exterior surface, e.g. for measuring deformation

Definitions

• the invention relates to a method and a device for checking the filling pressure in a tire of a vehicle, in particular a rolling vehicle.
• the tire inflation pressure of a motor vehicle is of great importance for road safety, vehicle comfort and handling, fuel consumption and tire wear.
• a tire inflation pressure that is not adapted to the load can considerably impair the directional stability and the driving stability and thus the safety of the vehicle, cause noticeable additional fuel consumption and lead to a significant reduction in the service life of the tires.
• the test of the tire inflation pressure is an integral part of the regular motor vehicle service. These are now subject to a very large time interval. However, the tire inflation pressure should be checked regularly every 2 weeks and in addition to special loads such as a long journey at high speed and / or heavy luggage.
• the control of the tire pressure is the discipline of the driver. At present, a manual check of the tire pressure at service stations and workshops is possible, but this is cumbersome.
• the tire pressure control recommended by the tire manufacturers often takes place much less frequently or not at all. It would therefore be advantageous if the tire inflation pressure e.g. would be controlled automatically on the approach to a gas station with a tester.
• a method for checking the tire inflation pressure with a pressure gauge to be adapted is assigned to the direct tire inflation pressure test when the vehicle is stationary and is known, for example, from FR 2 852 907 A3.
• methods of direct tire inflation pressure testing are known, which are carried out both stationary and rolling vehicle.
• one or more sensors are provided on the valve (JP 3 141 838 U) or within the tire (DE 19 630 015 A1, US 2008/0133081 A1), which continuously monitor the tire inflation pressure. If the tire inflation pressure exceeds or falls below a threshold value, a warning is displayed to the vehicle driver and / or a warning signal sounds.
• these sensors are often inaccurate and expensive.
• the tire pressure can be derived from the tire footprint and the contact force of the individual force sensors within the tire contact surface or the differences in measured contact force between the individual force sensors, i. from characteristic differences in the pressure distribution within the tire contact surface.
• force sensor matrices are expensive on the one hand because the sensors must be arranged over a sufficiently large area.
• they are susceptible to destruction and incorrect measurements when they are designed as pressure-sensitive measuring films, since they are exposed when rolling mechanical transverse loads by starting and braking and by the fall of the wheels and the toe of the wheel axle.
• Tire footprint (Latschbreite) can be detected.
• the length of the tire contact patch (lathe length), which is also necessary for determining the tire contact patch, additionally requires determination of the speed of the motor vehicle.
• the speed is determined from the rise and fall of the signal generated as the tire rolls over the force sensor line.
• a contact rail is arranged in the direction of travel in front of the force sensor line in order to determine the driving speed in cooperation with the force sensor line.
• a method for indirect tire inflation pressure test on rolling vehicle using individual force sensors is known from WO 1998/052008 A1.
• Piezoelectric sensors generate a voltage due to a force acting on them.
• the waveform of the voltage signal in the crossing has a dependent on the tire inflation pressure characteristic, which is additionally dependent on the wheel load of the motor vehicle and on the speed of the crossing.
• the method provides to determine the speed from the known distance of the two sensor cables, to estimate the wheel load from the amplitude of the voltage signal and to apply appropriate corrections, which are stored in a database.
• DE 197 05 047 A1 discloses a method for measuring the tread depth of a tire, in which the tire tread is subjected to laser light.
• US 2009/0290757 discloses a method in which a three-dimensional profile of the object is generated from image data of an object and the three-dimensional profile of the object is analyzed in order to detect anomalies of the object.
• a tire rolls over a glass plate and a camera below the glass plate records images of the tire. This arrangement is not well suited for use in the harsh environment of road traffic because of wear, contamination and risk of damage to the glass plate but rather reserved for laboratory use.
• a method of testing the tire inflation pressure of a rolling vehicle comprises the steps of determining the length of the tire footprint in the direction of travel, determining the wheel load of the tire to be tested, and inferring the tire inflation pressure from the length of the tire footprint and the wheel load.
• the force sensor bar outputs a signal that is a function of the load acting on the force sensor bar as a whole.
• the evaluation unit is designed to close the tire inflation pressure from the signal curve of the output signal of the force-sensing beam which it outputs when rolling over with the tire to the evaluation unit.
• the method and the device are suitable for carrying out an examination of the tire inflation pressure in areas with low driving speeds of motor vehicles, for example at driveways to service stations, workshops or parking spaces, and to immediately give a corresponding indication, for example by a multicolored traffic light, to the motor vehicle driver ,
• the invention provides a solution which is widely applicable and comfortable for the driver.
• the influence of the wheel load on the tire footprint can be taken into account. and errors in determining tire inflation pressure resulting from changes in wheel load can be avoided or at least reduced.
• the tire inflation pressure can thus be determined with high accuracy.
• the force sensor bar is designed to output a single (total) signal which is a function of the total load acting on the force sensor beam, and in particular the force sensor bar has no matrix structure which is designed to track the load across the width To measure the tire, the force sensor bar is robust and simpler and thus cheaper to produce than the previously used force sensor rows or - matrices.
• a device according to the invention can be installed in the roadway or in a flat drive over threshold, which is arranged on the roadway.
• the invention has a sufficiently high accuracy for indirect testing of the tire inflation pressure on the rolling vehicle.
• the method includes determining if the tire inflation pressure is within a predetermined range. Tires with insufficient tire inflation pressure (relevant to safety!) Can thus be detected with high probability.
• the method includes determining tire inflation pressure.
• the tire inflation pressure can thus be determined easily and conveniently for the driver.
• the method includes using a wheel load dependent correlation function that describes the relationship between the length of the tire footprint and the tire pressure.
• the correlation function may be a linear or a non-linear correlation function.
• correlation coefficients which are dependent on the wheel load and, if applicable, the tire type and which are calculated, for example, beforehand and then stored for later use, can be used.
• a wheel load dependent correlation function With a wheel load dependent correlation function, a relationship between the length of the. Can be easily and with sufficient accuracy
• Tire contact patch and the inflation pressure of the tire are produced.
• the method includes evaluating the time course of an output signal of at least one force sensor beam overrun by a tire of the vehicle to determine the length of the vehicle
• the method may include analyzing significant time points in the waveform and determining the vehicle speed and the length of the vehicle
• the method includes evaluating the timing of an output of at least one force sensor beam overrun by a tire of the vehicle to determine the wheel load of the wheel.
• the method may include analyzing significant times and force signals in the waveform and using them to determine the wheel load. In this way, the wheel load of the wheel can be reliably determined.
• the method includes measuring the tread depth of the tire and taking it into account when calculating the length of the tire footprint.
• the accuracy of the measurement can be increased because errors resulting from deviations of the tread depth from a predetermined value can be avoided or at least reduced.
• the method includes the lengths of
• Figures 1 a and 1 b show the dependence of the length of the tire contact patch from the tire inflation pressure and the wheel load for two different types of tires at three different wheel loads.
• Figures 2a and 2b show the relationships between the tire pressure and the length of the tire footprint for two different wheel loads for different tire types and tire dimensions.
• Figures 3a and 3b show the recommended tire pressure of vehicles of different car vehicle classes for different loading conditions.
• FIG. 3c shows a classifier with four state classes.
• Figure 4 shows a schematic representation of an embodiment of a device for testing the tire inflation pressure.
• FIG. 5 shows an exemplary embodiment of an overflow channel with integrated testing device.
• FIG. 6 shows a test cover of an overflow channel in the top view.
• FIGS. 7a and 7b show a schematic representation of a measuring arrangement according to the invention with a wheel rolling from left to right over a force sensor bar.
• FIG. 8 shows two curves of the signal of the measured force as a function of time during rolling of a vehicle wheel via a force sensor bar.
• FIG. 9 describes the analysis of a signal course, as shown in FIG.
• Figure 10 shows the relative change in the length of the tire footprint at maximum allowable tread wear with respect to a new tire as a function of tire inflation pressure.
• Figure 1 1 shows the tire inflation pressure as a function of the length of
• Tire contact patch for a new tire and for a tire with a maximum permitted worn tire tread It is known that the length L of the tire footprint of a tire 2 is dependent on the tire inflation pressure p of the tire 2 and the wheel load F resulting from the current load condition of the motor vehicle.
• the characteristic of this dependency varies between different tire types or types.
• FIGS. 1 a and 1 b show this dependency by way of example for two different tire types ("165/70 R 14" and "225/55 R 17 Runfiat") for three different wheel loads F of 2000 N, 2500 N and 3000 N, respectively. Looking at the different tire types with the same wheel load F, a set of curves results, which can be approximated by a suitable correlation function.
• FIGS. 2a and 2b The relationships between the tire pressure p and the length L of the tire contact surface for wheel loads F of 3500 N (FIG. 2a) and 4000 N (FIG. 2b) are shown by way of example for different tire types and tire dimensions in FIGS. 2a and 2b.
• FIGS. 3a and 3b show the results for the front axle (FIG. 3a) and rear axle (FIG. 3b).
• FIGS. 3a and 3b show the results for the front axle (FIG. 3a) and rear axle (FIG. 3b).
• optimum tire inflation pressure is not exceeded by more than 12% below and not more than 18%, a fuel consumption of less than 1% and a tire life of more than 95% can be expected. If the tire pressure shows greater deviations from the optimum value, a disproportionately higher fuel consumption and a disproportionately reduced service life are the result.
• FIGS. 3a and 3b the corresponding boundary lines for the pressure deviations described and which can be justified for practical reasons are shown as solid lines above and below the correlation function (dashed line).
• Tire pressure p and wheel load F represent two dimensions of the condition classifier.
• Tire contact patch is determined by analyzing the signals of the load beam 3 and then the tire pressure p with the corresponding, of the wheel load dependent correlation coefficients A, and B, from the length L of the
• the relevant wheel 2 can then be associated with these two parameters of a state condition Z, the tire pressure p.
• FIG. 3c shows by way of example a classifier with the described four status classes Z1, Z2, Z3, Z4 for a passenger car. It is also possible to define the state classes Z1, Z2, Z3, Z4 differently and / or to reduce or increase their number. For example, trucks and buses are specific
• FIG. 4 shows a possible embodiment of a device 1 for testing the
• a complete device 1 includes at least two force sensor beam 3, one for each side of the vehicle, each with a in the direction of travel R of the motor vehicle extending width b.
• the force sensor bars 3 are connected via electrical connection cables 9 or wirelessly to a measuring and evaluation unit 4.
• the measuring and evaluation unit 4 is via electrical connection cable 9 or wirelessly connected to a display unit 6 and optionally to a server 8.
• the width b of the force sensor beam 3 in the direction of travel R and the measuring frequency f m of the measuring and evaluation unit 4 is known.
• a table with the wheel load-dependent correlation coefficients Ai, Bi described above is stored in the measuring and evaluation unit 4.
• the measuring and evaluation unit 4 is designed for the precise detection and storage of the signals which are emitted by the force sensor bars 3 during each passage of a tire 2.
• the measuring and evaluation unit 4 is equipped with a computer unit of a memory unit and an evaluation software to perform an analysis of the force waveforms, a check of the plausibility of the measurement results, a calculation of the vehicle speed v, the wheel load F, the length L of
• Tire bearing surface and the tire pressure p of each tire 2 an evaluation of the relative deviation of the lengths L of the tire contact patch or the tire inflation pressures p of the tires 2, which are mounted on a common axis, and finally a classification of the tire inflation pressure p in predefined condition classes Z1, Z2 , Z3, Z4 as a final condition assessment.
• the measuring and evaluation unit 4 also controls the display unit 6, which is provided for outputting the test results, and optionally the transmission of the test results to a higher-order server 8.
• Tire bearing surface and the wheel load F is possible, is defined by the measuring frequency f m , the crossing speed v and the width b of the load beam.
• the width b of the load bar should be greater than 70 mm.
• the measuring and evaluation unit 4 can be equipped with a plausibility algorithm, which uses the time profile of the output data of the force sensor bars 3 to distinguish between a person and a vehicle and thus avoids erroneous measurement results.
• the described device 1 is extended by an additional sensor or contact switch 10. This additional sensor 10 is suitable for detecting a vehicle approaching the device 1.
• the additional sensor or contact switch 10 is connected to the measuring and evaluation unit 4 and triggers the start of the measuring and evaluation unit 4 shortly before the passage of a vehicle via the device 1.
• a device 20 for measuring the tread depth of the tire 2 is arranged in each case.
• the 20 for measuring the tread depth can also be arranged in the direction of travel R in front of the force sensor beam 3 and are optional, d. not absolutely necessary for the realization of the method according to the invention for determining the tire inflation pressure.
• the use of the results of measuring the tread depth to improve the measurement results for the tire inflation pressure will be described below.
• the device 1 can be conveniently integrated into a crossover channel 12, as is known and proven from road construction.
• FIG. 5 shows an exemplary embodiment with such an overflow channel 12 in cross section.
• FIG. 6 shows a special cover 14 for an overflow channel 12 with an integrated arrangement of a force sensor beam 3 for measuring the length L of the tire contact patch and the wheel load on a vehicle side in the plan view.
• the force sensor bars 3 are each in a recess of the lid 14 of
• Overflow channel 12 mounted so that their surface depending on the embodiment of the force sensor beam 3, if necessary, only after the completion of the increase in force flush with the upper edge of the lid 14 and thus to the road surface.
• the gap between the lid 14 and the force sensor bar 3 is circumferentially filled with a suitable elastomer 16 with sufficient thickness to permanently prevent the ingress of moisture, dust and coarse dirt. It is advantageous to provide a positive connection between the recess in the cover 14 and the elastomer 16 and between the elastomer 16 and the force sensor bar 3.
• the lid 14 and the force sensor bar 3 may be provided with a corresponding shape (e.g., groove or grooves).
• the physical properties and the layer thickness of the elastomer 16 are to be dimensioned so that the release force of the force sensor beam 3 sufficient is small, in order to ensure reliable triggering of the force sensor beam 3 even in small and light vehicles with low wheel load.
• the physical properties of the elastomer 16 could be considered in the algorithm for determining the length L of the tire footprint and the wheel load F with a correction term.
• a calibration of the force sensor beam 3 at the end of the manufacturing process can be performed.
• the result of the calibration is then stored for each connected force sensor bar 3 in the measuring and evaluation unit 4 and taken into account in the later analysis of the measured force signal curves.
• the device 20 for measuring the tread depth of the tire 2 is arranged.
• Each recess in the lid 14 is provided with an aperture 18 (e.g., a bore) for passing the electrical connection cables 9 from the force sensor bar 3 to the measurement and evaluation unit 4.
• This can also be integrated in the overflow channel 12.
• An assembly of the measuring and evaluation unit 4 on the side wall 13 of the overflow channel 12 protects the measuring and evaluation unit 4, for example. backwater accumulating at the bottom of the overflow channel 12.
• FIGS. 7a and 7b show a schematic representation of a measuring arrangement according to the invention with a wheel or tire 2 rolling from left to right over the force sensor bar 3.
• the tire 2 touches for the last time with its tire footprint the entire force sensor beam 3 and at time t4 the trailing edge of the tire footprint touches the last time the tire contact patch Force sensor bar 3.
• FIG. 8 shows by way of example two curves of the signal for the measured force (y axis) as a function of time (x axis) during rolling of a vehicle wheel 2 via a force sensor bar 3, wherein different tire inflation pressures are used. tire p 2 different lengths L of the tire footprint result.
• the signal profile is analyzed with regard to significant points in time.
• a first time measurement takes place.
• a second time measurement follows when the force curve at time t2 in a constant, maximum force F max passes, ie when the tire 2 has covered the path of the beam width b and rests on the entire width b of the force sensor beam 3 on this.
• time t3 Further time measurements are taken when the rear region of the tire contact patch leaves the force sensor beam 3 (time t3), recognizable at the transition from the constant force to the force drop Fr 2 , and when the tire 2 touches the force sensor beam 3 for the last time (time t4) and the measured Force F is again equal to the initial value measured before the tire 2 first touched the force sensor beam 3 (t ⁇ t1).
• Nr-1, Nm, Nr 2 of the measured values between the previously identified times t1, t2, t3, t4 can be automatically determined.
• Nr- 1 and Nr 2 indicate the number of measured values during the force increase (t1 ⁇ t ⁇ t2) or during the force drop (t3 ⁇ t ⁇ t4).
• these values can be used to calculate the pass speed v, the length L R of the tire contact patch and the wheel load F R :
• No. 2 can be used instead of Nr- ⁇ . If the values for v, L R and F R are calculated both from Nr- 1 and from No. 2 , an over-determination results. Such over-determination offers the possibility to increase the accuracy. In addition, the over-determination offers the possibility to correct the results, for example, by recognizing and taking into account possible speed changes by accelerating or braking when passing over the force sensor beam 3, whereby the accuracy is also increased.
• the measurement with a corresponding message to the driver can be declared invalid if the changes in speed exceed a predetermined limit and meaningful evaluation of the measurement results is no longer possible.
• the vehicle first travels with the front tire 2 and then with the rear tire 2 via the force sensor beam 3.
• the lengths L of the tire footprints and the wheel loads F of all wheels 2 of a vehicle can be determined almost simultaneously.
• the corresponding correlation coefficients A and B can be taken and with these correlation coefficients and the tire contact patch length L R determined as described above the tire pressure p r of the wheel 2 Approximate:
• the correlation coefficients A, and B are determined by interpolation between the adjacent correlation coefficients A n and A ( n + i ) and B n and B (n + 1) determined.
• the correlation coefficients of several adjacent wheel load stages eg A (n- i ) , A n , A (n + 1) and A (n + 2) as well as B (n-1) , B n , B can also be included in a nonlinear interpolation process 5 (n + 1) and B (n + 2) are included in the interpolation process.
• the tire pressure p With the tire pressure p R approximately calculated in this way and the wheel load F R approximately determined by means of a condition classifier previously described in connection with FIG. 3 c, the tire pressure p can be evaluated and evaluated by the measuring system in the sense of a diagnosis.
• FIG. 10 shows the relative change AL (y-axis) of the length of the tire contact patch at maximum permissible tire wear (minimum permissible tread depth) relative to the new tire as a function of the tire inflation pressure p (x-axis).
• the relative change AL in the length of the tire contact patch is shown here as the average of several different tires 2 and additionally as an average of a plurality of wheel load stages.
• the averaging of the wheel load stages was chosen because the influence of the wheel load on the change AL in the length of the tire contact patch is significantly less than the influence of the tire pressure p.
• FIG. 10 therefore, the dominant dependence of the wear-related change AL on the length of the tire contact patch from the tire pressure p is shown.
• the length L of the tire footprint is affected up to 10% of the tread depth or tire wear.
• FIG. 10 shows that the accuracy of the previously described indirect tire pressure test can be considerably improved by taking account of the tread depth.
• FIG. 11 illustrates this potential for improvement using the example of a tire under examination. In FIG. 11, with the wheel load F remaining the tire inflation pressure p (y-axis) as a function of the length L of the tire contact surface (x-axis) for a new tire (right curve) and a tire worn to the permissibility limit (left) Curve).
• the approximate calculation of the tire pressure p from the measured length L of the tire footprint and wheel load F would, in the present example, result in a tire pressure p inflated by 0.2 to 0.5 bar using the correlation coefficients of a new tire for a worn tire. This can be avoided by measuring the tire tread according to the invention and correcting the measured length L of the tire footprint based on the measured tire tread.
• An extended test method therefore additionally includes measuring the tread depth on each tire.
• a known profile depth measuring device is used, which as such is not the subject of the present invention.
• the measured length L of the tire footprint is corrected with the measured tread depth, and the previously described approximate calculation of the tire pressure p is performed from the corrected length of the tire footprint.
• This step comprises the following sub-steps, the tire pressure p R calculated in the previous method according to formula (5) being designated as the provisional tire pressure p RV :
• a wear-related change dL length L of the tire contact patch is calculated.
• the statistical relationship between the tire pressure p and a mean change dL length L of the tire contact patch per mm profile wear is used in the form of a correlation function. This relationship can be derived from the data of the relationship shown in FIG.
• the corrected length L RK of the tire contact patch is calculated from the measured length L R of the tire contact patch, the length correction dL and the measured tread depth T R as follows:
• T max is the maximum tread depth of a new tire. Again, summer and winter tires usually have different values to use.
• the limitation to new tires on the one hand reduces the effort required to determine the wheel load tables and on the other hand contributes to an improvement in the accuracy of the approximately calculated tire inflation pressure.
• Another test criterion for the tire inflation pressure p represents the demand of the tire and vehicle manufacturers that the inflation pressures p of all tires 2 must be the same on one axle, whereas the inflation pressures p of the tires 2 between the front and rear axles may well differ. Since tire replacement always involves the use of tires 2 of the same type during vehicle use, the measurement of the length L of the tire footprint or the approximately calculated tire inflation pressures p gives an additional possibility of differences in the tire inflation pressure p between the left and the right tire 2 of an axle with relatively high accuracy.
• Tire contact areas of the two tires 2 mounted on an axle or the relative difference ⁇ between the two tire inflation pressures p of the tires 2 of an axle must not exceed a defined limit of x% of the smaller of the two values.
• this limit can also refer to the larger of the two values or to the mean.
• a method for the indirect testing of the tire pressure on a vehicle axle comprises in the extended variant the following method steps:
• Classifier for one of, for example, four state classes Z1, Z2, Z3, Z4 and thus evaluation of the tire pressure p RK of each individual wheel 2.
• the method steps for a two-axle vehicle include the above-described method steps 1 to 8 for the front axle and immediately thereafter the same method steps 1 to 8 for the rear axle.
• the process steps 9 and 10 are performed simultaneously for all wheels of the vehicle.
• the profile depth and / or a traffic light color coupled to the evaluation of the tread depth for each tire can also be displayed on the display unit.
• the evaluation of the tread depth is carried out with the legally prescribed minimum tread depth and a defined value for the warning of heavily worn tires with only a small remaining service life. If the measured tread depth falls below the warning value, then the traffic light color "yellow”, if the minimum profile depth falls below the traffic light color "red” and otherwise the traffic light color "green”.
• step 1 If the method is carried out without the profile depth correction, the detection and storage of the tread depth and step 6 "Correcting the length L of the tire contact patch" are omitted in step 1.

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• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Tires In General (AREA)
• Measuring Fluid Pressure (AREA)

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• 2012
  • 2012-04-05 DE DE201210205694 patent/DE102012205694A1/de not_active Withdrawn
• 2013
  • 2013-03-19 WO PCT/EP2013/055709 patent/WO2013149825A1/de active Application Filing
  • 2013-03-19 IN IN7815DEN2014 patent/IN2014DN07815A/en unknown
  • 2013-03-19 CN CN201380018741.6A patent/CN104204756B/zh not_active Expired - Fee Related
  • 2013-03-19 EP EP13710420.4A patent/EP2834610A1/de not_active Withdrawn

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