Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
  • B60C23/06—Signalling devices actuated by deformation of the tyre, e.g. tyre mounted deformation sensors or indirect determination of tyre deformation based on wheel speed, wheel-centre to ground distance or inclination of wheel axle
  • B60C23/061—Signalling devices actuated by deformation of the tyre, e.g. tyre mounted deformation sensors or indirect determination of tyre deformation based on wheel speed, wheel-centre to ground distance or inclination of wheel axle by monitoring wheel speed

Definitions

• the invention relates to a method for detecting pressure losses in vehicle tires, a reference value being formed from signals which represent the wheel speeds of a plurality of vehicle wheels, a pressure loss being inferred from a comparison of a currently determined reference value with at least one comparison value if the currently determined one Reference value the comparison value over or falls below.
• the correction factors are determined depending on the driving situation, so that the effects of possible wheel speed deviations due to longitudinal or lateral acceleration, due to cornering and the associated eventuality Oversteer or understeer of the vehicle or due to different slip values due to different friction coefficients on the left and right side of the lane are taken into account.
• this object is achieved by the detection of pressure losses in vehicle tires using at least one reference value which is formed by dividing the sums of two signals representing the wheel speeds.
• the reference values can be formed as follows, for example:
• Ref3 (T vl + T hl ) / (T vr + T hr ).
• the size T x can advantageously be determined here as the signal representing the rotational speed of the wheel with the embodiment of the method according to claim 2.
• Numerical problems in determining the reference values are advantageously minimized with the method according to the invention.
• two quantities are summed up that have almost the same value. Differences only appear in some places after the decimal point, which can result in first problems.
• the difference between these two sums is formed in the prior art. As stated, the two sums have pretty much the same value. In any case, deviations from these two sums are already inaccurate. If the difference is subsequently formed from these two variables, any inaccuracies increase again significantly, so that the difference determined can possibly no longer be used as a numerical value.
• the reference values make the sums of two signals representing the wheel speeds formed, with two of these sums being divided.
• the numerical problems are advantageously minimized because, with the method according to the invention, it is no longer necessary to add two almost equal sizes in subsequent steps and then to subtract the sums.
• the signals representing the wheel speeds of the individual vehicle wheels are obtained by individually starting the time measurement of the individual wheels after a common start signal with the respectively following flank of the wheel concerned and individually for each wheel after expiry of a complete or partial number of wheel revolutions for all wheels is completed.
• a common start signal with the respectively following flank of the wheel concerned and individually for each wheel after expiry of a complete or partial number of wheel revolutions for all wheels is completed.
• this inaccuracy is advantageously minimized by the position of the sensor wheel relative to the sensor being exactly fixed at the beginning and at the end of the measurement. In the case of a sensor wheel with 48 teeth, this makes a 1 / 48th of a turn at the beginning and at the end of the measurement.
• the number of wheel revolutions is specified as a function of the vehicle speed.
• the number of wheel revolutions can be an integer. It is also possible to specify a non-integer number of wheel revolutions.
• the measurement then ends with the flank of a tooth other than the tooth with which the measurement was started. In order to start the measurement exactly with one flank and to be able to end exactly with the flank of another tooth, it is necessary to determine the part of the revolutions that is no longer completed according to the number of teeth on the sensor wheel.
• the measurement can be done individually for each wheel.
• a general start signal is output. After this start signal, the measurement is started individually for each wheel when the corresponding flank of the tooth of the sensor wheel has been recognized.
• a certain flank of a tooth can be recognized, for example, because a tooth gap is provided at one point on the sensor wheel in order to be able to recognize the absolute angular position of the sensor wheel. Based on this gap, the recognized teeth can be "counted” and thus individually recognized.
• the at least one comparison value can be predetermined by adding or subtracting an offset to the mean value of the reference value if a quality measure of the scatter of the mean values does not exceed a certain value and / or if the determined maximum and minimum values of the Reference values by no more deviate as a certain value from the mean of the reference values.
• the comparison values are advantageously determined when it is established on the basis of the determined data that only slight fluctuations in the reference values occur.
• the reference values are 1 when driving straight ahead without acceleration. It can also be checked whether the reference values do not deviate from the value 1 by more than a certain threshold.
• the quality measure for the scatter can be calculated from the filtered and unfiltered values and can be, for example, the standard deviation.
• one or more measured values of the rotational speed can be recognized with a large deviation, which are certainly not comparatively due to noise from the sensor, since the effects of the noise have been filtered out by the low-pass filtering.
• This is advantageously a 1st order low-pass filter.
• a comparison value is not formed if there are too large differences in the values from which the comparison value is to be formed.
• This advantageously suppresses the formation of a comparison value if, due to the driving conditions, the wheel speeds of the wheels have different values, as can be the case, for example, when cornering.
• a quality measure e.g. B. the standard deviation
• a first set of measured values and a second set of measured values are formed, comparative values being formed as a function of the maximum value and the minimum value of the reference values if, for the two sets of measured values, the maximum values of the reference values, the minimum values of the Reference values and the respective arithmetic mean of the reference values of the two sets do not differ from one another by more than predetermined specific amounts and the quality measure of the scatter does not exceed a certain value.
• the comparison values are adapted to the extent of the fluctuations in the reference values.
• the method according to claim 5 is used to check whether the fluctuations in the reference values are nevertheless stable at an elevated level. The comparison values are then determined depending on the fluctuations.
• the accuracy requirements can thus be gradually adapted to the manufacturing tolerances and deviations due to the driving conditions.
• the value of the offset can amount to 0.5 per mille.
• the predetermined amount can be in the order of 0.1 per mille, the further predetermined amount also in the order of 0.1 per mille.
• the multiple of the quality measure can advantageously be four times the quality measure.
• the comparison values are determined depending on the axis.
• comparison values as reference points in steps of 30 km / h to 50 km / h.
• the comparison value whose speed is closest to the current speed can then be used, for example, or it is also possible to interpolate between two comparison values of the next lower and the next higher speed.
• the determined values are stored when the journey is interrupted and read out again after the journey begins again.
• the stored values are at least the comparison values.
• a reset button is actuated when changing a wheel.
• the air pressure in the tire is completely different compared to the previously mounted wheel.
• the comparison values are therefore advantageously redefined when a wheel has been changed. If necessary, this can also take place if the air pressure in the tire has been checked, which can be recognized by removing the protective cap of the valve.
• a manually operable reset button is provided.
• the vehicle driver can also determine the comparison values again, for example if the tire air pressure has been checked and refilled accordingly. This can reduce the effort with regard to switches or sensors. It is then up to the user of the vehicle to provide initialization when a wheel has been changed or when air has been refilled.
• the formation of the reference values is interrupted when certain threshold values of the longitudinal acceleration, lateral acceleration and / or wheel acceleration are exceeded.
• the formation of the reference values is interrupted when a brake intervention takes place.
• a brake intervention can be recognized, for example, when an ABS system responds or when an active brake intervention takes place in a traction slip system. This can also be derived from the brake light switch, which also responds to braking where the wheel slip is significantly less.
• the method according to the invention thus advantageously shows that one or more comparison values are only determined if it can be derived from the measured values that are determined that this also makes sense.
• the comparison value is continuously recalculated or possibly discarded, there is the advantage that wheel speeds which have already been falsified due to changed tire pressure are no longer included in the comparison value.
• the speeds of the wheels, which have already suffered a pressure loss are also included in the comparison values are included, the faulty wheel speed influences the comparison value by which this wheel is to be recognized as faulty.
• the comparison value is thus continuously redetermined, so that faulty wheel speeds also lead to a faulty comparison value.
• the detection of pressure losses is only possible with a time delay.
• reference values are compared with previously determined comparison values, so that a pressure loss can be recognized without delay.
• an optical and / or acoustic warning signal can be issued.
• Fig. 3 the reset of the determined values.
• step 101 the wheel speed signals of the individual wheels are initially recorded in step 101.
• step 102 it can then be checked whether there is no driving condition that does not appear to make sense when forming the reference values.
• a driving condition For example, the longitudinal acceleration of the vehicle, the lateral acceleration of the vehicle and / or the wheel acceleration of at least one wheel of the vehicle may exceed certain threshold values.
• Such a driving condition can also consist of a brake intervention.
• This can be recognized, for example, by responding to an anti-lock braking system, traction control with brake intervention and / or by evaluating the brake light switch. This can also be done when system faults are detected, such as sensor errors.
• step 103 in which at least one reference value Ref1, Ref2, Ref3 is formed from the measured times.
• the reference values can be formed as follows, for example:
• Ref l (T vl + T hr ) / (T vr + T hl )
• Ref 3 (T vl + T hl ) / (T vr + T hr ).
• the signal representing the speed can advantageously be used for the period of time which was required for a predetermined number of wheel revolutions.
• One or more of these reference values can be used in combination for the further method.
• the signal representing the speed of the wheel is advantageously obtained with improved accuracy with the aid of a time measurement according to the representation according to claims 2 and 3 and the associated description in the introduction to the description. A repetition of these components of the application is not given here because the procedure describes this procedure with sufficient clarity.
• An unfiltered value is determined and a value that has been subjected to low-pass filtering. This is advantageously a 1st order low-pass filter.
• step 103 it is checked in step 103 whether the currently determined filtered reference value is greater than the previously determined maximum value of the filtered reference values. If this is the case, the currently determined filtered reference value is stored as the maximum value of the filtered reference values.
• step 103 It is also checked in step 103 whether the currently determined filtered reference value is smaller than the previously determined minimum value of the filtered reference values. If this is the case, the currently determined filtered reference value is stored as the minimum value of the filtered reference values.
• step 103 the mean value of the unfiltered reference values and the associated quality measure are continuously determined from the unfiltered reference value.
• a transition then takes place to step 104, in which it is checked whether a certain number of reference values has already been determined.
• the method is initially ended until a number of reference values which corresponds to the determined number have been determined during further runs of the method.
• step 104 If it has been determined in step 104 that a certain number of reference values have already been determined, a transition is made to step 105.
• step 105 it is checked whether the difference between the maximum values and minimum values of the filtered reference values determined in step 103 is smaller than a first threshold value. It is also checked whether the quality measure of the unfiltered reference values is less than a second threshold value.
• the corresponding values are deleted (mean value, quality measure, maximum value and minimum value). If the deviation was too large, this may have been due to unfavorable driving conditions (accelerations, cornering). An attempt is then still made to determine reference values at which the corresponding conditions for specifying a comparison value are met.
• step 106 in which comparison values are determined by averaging the reference values and adding or subtracting an offset.
• FIG. 2 shows a sequence of a method for determining the comparison values. The first steps in this method are identical to the steps in FIG. 1.
• step 201 the wheel speed signals of the individual wheels are initially recorded.
• step 202 it can then be checked whether there is no driving condition that does not make it sensible to form the reference values.
• a driving condition can consist, for example, in that the longitudinal acceleration of the vehicle, the lateral acceleration of the vehicle and / or the wheel acceleration of at least one wheel of the vehicle exceed certain threshold values.
• Such a driving condition can also consist of a brake intervention. This can be recognized, for example, by responding to an anti-lock braking system, traction control with brake intervention and / or by evaluating the brake light switch.
• step 203 in which at least one reference value Ref1, Ref2, Ref3 is formed from the measured wheel speeds.
• the reference values can be formed as follows, for example:
• Ref l (T vl + T hr ) / (T vr + T hl )
• Ref 3 (T vl + T hl ) / (T vr + T hr ).
• the signal representing the speed of the wheel is advantageously obtained with improved accuracy in accordance with the representation according to claims 2 and 3 and the associated description in the introduction to the description.
• An unfiltered value is determined and a value that has been subjected to low-pass filtering. This is advantageously a 1st order low-pass filter.
• this step 203 it is also checked whether the currently determined filtered reference value is greater than the previously determined maximum value of the filtered reference values. If this is the case, the currently determined filtered reference value is stored as the maximum value of the filtered reference values.
• step 203 It is also checked in step 203 whether the currently determined filtered reference value is smaller than the previously determined minimum value of the filtered reference values. If this is the case, the currently determined filtered reference value is stored as the minimum value of the filtered reference values. In this step 203, the mean value of the unfiltered reference values and the associated quality measure are continuously determined from the unfiltered reference value.
• step 204 in which it is checked whether a further predetermined number of reference values has already been determined, i.e. whether a complete sample of reference values was recorded.
• step 205 in which it is checked whether the maximum value of the filtered reference values of the currently recorded sample does not deviate from the maximum value of the filtered reference values of the last stored sample by more than a predetermined amount. Furthermore, in step 205 it is checked whether the minimum value of the filtered reference values of the currently recorded sample does not deviate from the minimum value of the filtered reference values of the last stored sample by more than a predetermined amount.
• step 206 it is checked whether the mean value of the unfiltered reference values of the current sample deviates by no more than a certain amount from the mean value of the unfiltered reference values of the last stored sample. Furthermore, in this step 206 it is checked whether the mean value of the unfiltered reference values of the current sample plus and minus a multiple of the quality measure within the range defined by the upper limit value and the lower their limit is given. This multiple can be four times, for example.
• an upper limit value is defined in step 207 by adding an offset value to the maximum value of the filtered reference values of the current sample.
• a lower limit is determined by subtracting an offset value from the minimum value of the filtered reference values of the current sample.
• step 208 If one of the checks in step 205 or 206 indicated that the deviations of the values in the current sample were too large, a transition is made to step 208 in which the corresponding values of the current sample (mean value, quality measure of the unfiltered reference values, maximum value and Minimum value of the filtered reference values of the current sample) can be saved for comparison with future recorded samples.
• FIG. 2 The method shown in FIG. 2 is advantageously used where the method according to FIG. 1 does not lead to success.
• the method according to FIG. 2 is then used to check whether the deviations of the reference values, which prevent comparison values from being determined by the method according to FIG. 1, are stable to the extent that comparison values can be determined according to the method from FIG. 2.
• Figure 3 shows the check of the reset of the corresponding values. This should be done, for example, when the wheel has been changed or air has been refilled. This can be monitored with appropriate switches or sensors. It is also possible to provide a manually operated reset switch.
• step 301 If the check in step 301 shows that a reset is to take place, then a transition is made to step 302 in which the reset is carried out. All saved values (upper and lower limit value, comparison value, quality measure, maximum value and minimum value) are set to 0.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Measuring Fluid Pressure (AREA)
• Regulating Braking Force (AREA)

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Citations (6)

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• 1997
  • 1997-05-23 DE DE19721480A patent/DE19721480A1/de not_active Withdrawn
• 1998
  • 1998-05-19 WO PCT/EP1998/002937 patent/WO1998052780A1/de not_active Ceased
  • 1998-05-19 JP JP54994598A patent/JP4297983B2/ja not_active Expired - Fee Related
  • 1998-05-19 EP EP98928292A patent/EP0983154B1/de not_active Expired - Lifetime
  • 1998-05-19 DE DE59811289T patent/DE59811289D1/de not_active Expired - Lifetime
  • 1998-05-19 US US09/424,205 patent/US6439045B1/en not_active Expired - Fee Related

Patent Citations (6)

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