Method and system for tyre pressure surveillance for vehicles with anti-blocking systems (ABS systems)

0001The invention relates to a method for monitoring tire pressure and to a tire pressure monitoring system.

0002Safety and reliability are central factors in automotive technology. The tire pressure plays an important role here; Tire pressure loss has been found to be a major factor in road accidents. 85% of punctures are the result of a gradual loss of pressure. A correctly set tire pressure also ensures optimal driving comfort in terms of rolling noise, vertical impact and transverse joint sensitivity at all times.

0003For example, it is off <nplcit id="ncit0001" npl-type="s"><text>ATZ 102 (200) 11, p. 950 ff</text></nplcit>. known to measure the tire pressure directly by means of pressure sensors on two- or three-axle vehicles. The pressure sensors are attached to the tire and rotate with the wheel. The pressure sensors have a high-frequency transmitter (HF transmitter), which transmits the measured pressure values ​​to a receiver in the motor vehicle, which signals pressure losses to the driver. This procedure works both when the vehicle is moving and when it is stationary. Since this is a purely measuring method, the costs are relatively high, especially if all wheels are sensed.

0004It is also from the magazine <nplcit id="ncit0002" npl-type="s"><text>ATZ 94 (1992), pages 336-340</text></nplcit>, <patcit id="pcit0001" dnum="EP0489562A"><text>EP-A-0 489 562</text></patcit>, <patcit id="pcit0002" dnum="EP0489563A"><text>EP-A-0 489 563</text></patcit> and <patcit id="pcit0003" dnum="EP0607690A"><text>EP-A-0 607 690</text></patcit> known to indirectly monitor the tire pressure with the help of the wheel sensors of anti-lock braking systems (ABS systems). The tire pressure affects the rolling circumference of the wheel. The wheel rotation speed determined with the help of the wheel sensors of the ABS system depends on the rolling circumference of the wheel. If the wheel rotation speed of a wheel changes when driving straight ahead and without braking relative to the reference speed of the other wheels or another wheel, this is an indication of a change in the rolling circumference of the wheel in question as a result of a loss of pressure in the tire or for a detachment of tire parts on the tire circumference or for represents a change in loading, with each change in the rolling circumference being interpreted as a change in pressure. These known methods are relatively imprecise and can only detect relatively large and suddenly occurring pressure changes.

0005Through the <patcit id="pcit0004" dnum="DE19807880A"><text>DE-A-198 07 880</text></patcit> A method for monitoring the tire air pressure of wheels of a motor vehicle is known, in which the slip and the associated tire circumferential force are recorded in the form of respective tire circumferential force-slip measured value pairs for at least one driven wheel while driving. An evaluation computer determines a compensation curve for these recorded measured value pairs, specifically in the form of a linear regression level, since the functional relationship between tire circumferential force and slip is assumed to be linear in the micro-slip range considered in the known method, in which slip values ​​less than about 2% are used. The offset value of the determined compensation curve with respect to the zero point in the tire circumferential force-slip characteristic map is then determined, and the associated wheel radius ratio between at least one non-driven and one driven wheel is concluded from this offset value, and the relative tire air pressure of the wheels is determined from this. The relative tire air pressure is determined in a motor vehicle with wheels driven on the first axle and wheels not driven on a second axle both for the same-sided as well as for the diagonally opposite wheel pairs. It is also provided that the absolute tire air pressure on at least one wheel is measured directly and used as a reference pressure value for the relative tire air pressure value determined for at least one other wheel.

0006The invention is therefore based on the object of specifying a method and system for monitoring tire pressure which is inexpensive and reacts more sensitively to slight and gradual pressure losses.

0007This object is achieved by the embodiments of the invention specified in patent claims 1 and 7. Advantageous developments of the invention are specified in the subclaims.

0008The method for tire pressure monitoring has the advantage that, due to the counting of the distance covered in each case, only a few conversion steps are required when using conventional wheel sensors from ABS systems, in particular fewer conversion steps than with the known methods, and as a result greater calculation accuracy can be achieved, in particular with Use of digital computers. A smaller number of conversion steps has the advantage that fewer roundings are made in the course of the calculation, and fewer decimal places are neglected in the calculation. Using the invention, this can advantageously be achieved by simply counting the distance pulses emitted by the wheel sensors, which are generated in proportion to the distance traveled.

0009According to advantageous developments of the invention, the counted distances of the individual wheels are added to each other diagonally with respect to the wheel arrangement on the vehicle, and an detection of an undesired tire pressure state takes place if the diagonal sums differ from one another by more than a predetermined limit value. In addition, the counted distances are monitored in several monitoring cycles, with the detection of an undesired tire pressure condition taking place when the deviations in the diagonal totals exceed a total limit value that is defined for all monitoring cycles. This can further improve the accuracy and sensitivity in the detection of undesired tire pressure conditions.

0010In the embodiment of claim 7, the invention proposes a combination of direct tire pressure measurement with the aid of pressure sensors of a tire pressure measurement system and indirect tire pressure determination by measuring the variables dependent on the rolling circumference, such as wheel rotation speed and distance traveled, by means of wheel sensors of an existing ABS system. This makes it possible to replace pressure sensors of the tire pressure measurement system with ABS wheel sensors and / or to use the ABS control device also for evaluating the measurement signals of the tire pressure measurement system, as a result of which components and costs can be saved without impairing the reliability and safety of tire pressure monitoring. The actual tire pressures determined using the pressure sensors support the values ​​indirectly determined using the ABS system.

0011The invention will be explained in more detail below with reference to the accompanying drawing, in which several exemplary embodiments of the invention are shown.

0012Show it<dl id="dl0001"><dt>Fig. 1-9</dt><dd>different exemplary embodiments of the tire pressure monitoring device according to the invention in three-axle vehicles,</dd><dt>Fig. 10</dt><dd>1 shows a block diagram of an ABS control device with an integrated control unit of a tire pressure measurement system,</dd><dt>Fig. 11</dt><dd>a block diagram of a device for route determination and</dd><dt>Fig. 12</dt><dd>a diagram in which the by a counting register of the facility <figref idref="f0011">Fig. 11</figref> counted number of periods depending on the distance is shown.</dd></dl>

0013Identical components in the figures of the drawing are provided with the same reference symbols.

0014The drawing shows schematically in the <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009">Fig. 1-9</figref> 3-axle vehicles 4 equipped with anti-lock protection systems (ABS systems) 2 and tire pressure measurement systems 12. The following explanations also apply accordingly to vehicles with (2 + n) axles with n ≥ 0, ie also for 2-axle vehicles. The ABS systems and tire pressure measurement systems are combined to form a tire pressure monitoring system.

0015The three-axle vehicles 4 each have a first axle A1, which is the front axle here and has a right front wheel A1r and a left front wheel A1l, a second axle A2, which is the drive axle here and has right twin wheels A2r and left twin wheels A2l, and a third Axis A3, which has right twin wheels A3r and left twin wheels A3l.

0016Instead of the twin tires, there can of course also be single tires.

0017The ABS systems 2 comprise an ABS control unit 6 and a CAN interface 8. The wheels of at least one of the three axles A1, A2, A3 are schematically represented by wheel sensors and brake pressure modulators 25, 26, 27, 28, 29, represented by a common block. 30 assigned. The ABS control unit 6 determines the wheel rotation speed or the distance traveled from the signals from the wheel sensors. A change in the rolling radius due to a loss of tire pressure is recognized by an increasing wheel rotation speed or a decreasing distance and is shown to the driver on a display 10. Influences due to special situations, such as cornering, acceleration, deceleration, high speed, wheel load (load) and abrasion, on the rolling radius and thus on the wheel rotation speed or on the distance covered are compared by suitable axle, side and / or diagonal comparisons of the wheel rotation speed or distance and / or comparisons with threshold values ​​are compensated.

0018The tire pressure measurement system 12 has wheel electronics 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 for each wheel of at least one of the three axles, which is arranged in or on the tire and as essential components a sensor, a Signal processing stage, an RF transmitter stage and a battery as an energy source. Instead of supplying energy via a battery, external supply of energy is also possible using transponder technology. The wheel electronics form a unit with the respective tire inflation valve, which is mounted on the rim. The sensor has a pressure sensor measuring the pressure in the tire and a device for recording measured values ​​and processing signals. The sensor controls a digital module, in which the RF transmission stage is integrated, which sends the measured data to a receiver / evaluation unit 42, possibly with a CAN interface 44, for example in the 433 MHz range. Each wheel electronics has its own identifier, which is also transmitted when it is transmitted. The respective set tire pressure is initialized by the driver or the system uses target pressures that are stored for the vehicle types in question, the system checking the set pressures for plausibility. The system detects a wheel change or change with regard to position on the vehicle. A decrease in tire pressure - both when the vehicle is at a standstill and while driving - is indicated to the driver by the receiver / evaluation unit 42 on the display 10.

0019The <figref idref="f0001">Fig. 1</figref> schematically shows a tire pressure monitoring system that uses a 6-channel ABS system 2, which has wheel sensors and brake pressure modulators (shown as common blocks 25, 26, 27, 28, 29, 30) on all three axes, and a tire pressure measuring system 12 with ten Has wheel electronics 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, each wheel of each axle having wheel electronics. The ABS system for the indirect determination of tire pressures and the tire pressure measurement system work in parallel and independently.

0020The <figref idref="f0002">Fig. 2</figref> shows a tire pressure monitoring system that uses a 4-channel ABS system and is different from the system <figref idref="f0001">Fig. 1</figref> differs in that only four sensors and four brake pressure modulators 25, 26, 27, 28 are provided for the first and second axes A1 and A2 and that the third axis is not sensed for the ABS control, but is controlled indirectly. The direct pressure measurement by the tire pressure measuring system 12 takes place as in the system<figref idref="f0001">Fig. 1</figref> on all wheels on all axles. When executing after<figref idref="f0002">Fig. 2</figref> two ABS wheel sensors and two ABS pole wheels are saved.

0021The <figref idref="f0003">Fig. 3</figref> shows schematically a tire pressure monitoring system in which the ABS system used for tire pressure monitoring as in <figref idref="f0002">Fig. 2</figref> has four sensors and four brake pressure modulators 25, 26, 27, 28, on the first and second axes A1 and A2. Unlike the embodiments according to the<figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref> wheel electronics 33, 34, 35, 36, 37, 38, 39, 40 of the tire pressure measuring system 12 are provided only for the twin wheels of the second and third axles A2 and A3. No wheel electronics are provided on the wheels of the front axle A1. It is also different from the<figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref> the receiver / evaluation unit 42 of the tire pressure measurement system 12 is integrated in the housing of the ABS control unit, the ABS computer also taking over the evaluation of the measurement signals of the wheel electronics. The wheel sensors and wheel pole wheels are thus saved on the third axis and wheel electronics on the first axis, and those in the embodiments according to FIGS<figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref> separate evaluation device and CAN interface as well as the separate housing of the tire pressure measuring system. In this embodiment there is a diagonal comparison of the sum of the wheel rotation speeds or distances of the right front wheel A1r and the left wheel of the second axis A21 with the sum of the wheel rotation speeds or distances of the left front wheel A1l and the right wheel of the second axis A2r. If the tire pressure drops, the speed of the wheel in question will increase compared to the other wheels or the distance traveled will decrease accordingly. Positive values ​​then mean, for example, when comparing the speed, reduced pressure on the right front wheel A1r or left wheel A2l of the second axis; negative values ​​mean reduced pressure on the left front wheel A1l or on the right wheel A2r of the second axle.

0022The diagonal comparison over the wheel rotation speed or distance of the wheels of the first and second axles replaces the pressure sensors on the first axle.

0023The diagonal comparison largely compensates for curve effects. The absolute tire pressures determined by the wheel pressure sensors support the results from the diagonal comparison.

0024The <figref idref="f0004">Fig. 4</figref> shows an embodiment of the tire pressure monitoring system according to the invention, which differs from the corresponding system <figref idref="f0003">Fig. 3</figref> differs in that wheel electronics 31, 32 are provided on the wheels A1r and A1l of the first axis instead of on the wheels of the second axis A2. The advantage over the embodiment according to<figref idref="f0003">Fig. 3</figref> It can be seen that the load / empty ratio on the first axle, the front axle, is lower than on the second axle, so that changes in the rolling radius due to changes in loading are not as noticeable on the first axle as on the second axle or on the third axis.

0025The <figref idref="f0005">Fig. 5</figref> shows an embodiment that differs from the embodiments of the <figref idref="f0003">Fig. 3</figref> and <figref idref="f0004">4</figref> differs in that the direct pressure measurement is only carried out on the twin tires of the third axis A3. A support of the indirect pressure determination via the diagonal comparison of the wheels of the first and second axles by the direct pressure measurement on the third axle can be carried out here due to the spatial proximity of the second and third axles to one another. Due to the close proximity, it can be assumed that the wheel speeds or Wheel rotational speeds of the wheels on the second and third axes are essentially identical and the speed values ​​of the second axis can thus be transferred to the third axis.

0026The <figref idref="f0006">Fig. 6</figref> shows an embodiment of the tire pressure monitoring system in which wheel sensors 25, 26, 27, 28, 29, 30 of the ABS system 2 are provided on the wheels of all three axles A1, A2, A3. A direct tire pressure measurement via wheel electronics 31, 32 is provided in a cost-saving manner only on the first axle A1, the front axle or steering axle. Unlike the embodiments according to the<figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref> In this embodiment, not individual wheels, but diagonal sums of the wheel speed signals or the distances of all sensed axles are compared with one another. This largely compensates for the effects of curves.

0027The following diagonal differences are formed in the speed comparison, where v means the speed: <maths id="math0001"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">1</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0001.tif" /></maths><maths id="math0002"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">2</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0002.tif" /></maths><maths id="math0003"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">3</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0003.tif" /></maths>

0028The evaluation of the diagonal difference formation gives the following:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="34mm" /><colspec colnum="3" colname="col3" colwidth="34mm" /><colspec colnum="4" colname="col4" colwidth="25mm" /><thead><row><entry align="center" valign="top"><b>Diagonal difference 1</b></entry><entry align="center" valign="top"><b>Diagonal difference 2</b></entry><entry align="center" valign="top"><b>Diagonal difference 3</b></entry><entry align="center" valign="top"><b>Reduced pressure</b></entry></row></thead><tbody><row><entry align="right">positive</entry><entry align="right">0</entry><entry align="right">positive</entry><entry align="center">A1r</entry></row><row><entry align="right">negative</entry><entry align="right">0</entry><entry align="right">negative</entry><entry align="center">A1l</entry></row><row><entry align="right">negative</entry><entry align="right">positive</entry><entry align="right">0</entry><entry align="center">A2r</entry></row><row><entry align="right">positive</entry><entry align="right">negative</entry><entry align="right">0</entry><entry align="center">A2l</entry></row><row><entry align="right">0</entry><entry align="right">negative</entry><entry align="right">negative</entry><entry align="center">A3r</entry></row><row><entry align="right">0</entry><entry align="right">positive</entry><entry align="right">positive</entry><entry align="center">A3l</entry></row></tbody></tgroup></table></tables>

0029These diagonal total comparisons therefore provide the possibility of realizing a wheel-associated low pressure display.

0030As an example, the aforementioned formation of diagonal differences is also shown below for a four-axle vehicle, although only three diagonal differences are to be formed for a four-axle vehicle: <maths id="math0004"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">1</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0004.tif" /></maths><maths id="math0005"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">2</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">4</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">4</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0005.tif" /></maths><maths id="math0006"><math display="block"><mi>Diagonal difference</mi><mspace width="1em" /><mn mathvariant="normal">3</mn><mo mathvariant="normal">:</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">4</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub></mfenced><mo mathvariant="normal">-</mo><mfenced><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">l</mi></mrow></msub><mo mathvariant="normal">+</mo><msub><mi mathvariant="normal">v</mi><mrow><mi mathvariant="normal">A</mi><mo>⁢</mo><mn mathvariant="normal">4</mn><mo>⁢</mo><mi mathvariant="normal">r</mi></mrow></msub></mfenced></math><img file="EP1236588B1_D0006.tif" /></maths><tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="34mm" /><colspec colnum="3" colname="col3" colwidth="34mm" /><colspec colnum="4" colname="col4" colwidth="25mm" /><thead><row><entry align="center" valign="top"><b>Diagonal difference 1</b></entry><entry align="center" valign="top"><b>Diagonal difference 2</b></entry><entry align="center" valign="top"><b>Diagonal difference 3</b></entry><entry align="center" valign="top"><b>Reduced pressure</b></entry></row></thead><tbody><row><entry align="right">positive</entry><entry align="right">0</entry><entry align="right">positive</entry><entry align="center">A1r</entry></row><row><entry align="right">negative</entry><entry align="right">0</entry><entry align="right">negative</entry><entry align="center">A1l</entry></row><row><entry align="right">negative</entry><entry align="right">0</entry><entry align="right">0</entry><entry align="center">A2r</entry></row><row><entry align="right">positive</entry><entry align="right">0</entry><entry align="right">0</entry><entry align="center">A2l</entry></row><row><entry align="right">0</entry><entry align="right">negative</entry><entry align="right">0</entry><entry align="center">A3r</entry></row><row><entry align="right">0</entry><entry align="right">positive</entry><entry align="right">0</entry><entry align="center">A3l</entry></row><row><entry align="right">0</entry><entry align="right">negative</entry><entry align="right">negative</entry><entry align="center">A4r</entry></row><row><entry align="right">0</entry><entry align="right">positive</entry><entry align="right">positive</entry><entry align="center">A4l</entry></row></tbody></tgroup></table></tables>

0031In principle, any difference formation in which at least one axis of a diagonal difference is included in another diagonal difference leads to a unique wheel assignment. A fourth diagonal difference is required from a five-axis model.

0032The absolute tire pressures measured on the first axle with the aid of wheel electronics 31 and 32 support the diagonal total comparison.

0033The embodiment according to <figref idref="f0006">Fig. 6</figref> has particular advantages when using external tire pressure sensors, which can remain on the vehicle when changing complete wheels. It is then not necessary to enter the wheel identification of the pressure sensor into the electronics using a suitable diagnostic device each time the wheel is changed. The use of wheel electronics to measure the absolute tire pressures only on the first axle (front axle or Steering axle) also has the great advantage that the expensive tire pressure sensors on the second and third axles can be omitted. Otherwise, one would have to build double tire pressure sensors on the twin tires or one would have to connect two tire inflation connections using tubes, screw connections and T-pieces.

0034By measuring the absolute pressure on the wheels of the first axle, the other two axles can be compared more reliably. In the diagonal total comparisons, the pressure measurement on the first axis can assume that at least two values ​​are related to the absolute pressure level, which would not be the case if only ABS wheel sensors were used, so that cost-effective, reliable and safe tire pressure monitoring can be implemented is.

0035The <figref idref="f0007">Fig. 7</figref> and <figref idref="f0008">8</figref> show embodiments of the invention, which differ from the embodiment <figref idref="f0006">Fig. 6</figref> distinguish by measuring the absolute tire pressure on two axles, namely on the wheels of the first axle A1 and on the wheels of the second axle A2 (<figref idref="f0007">Fig. 7</figref>) and on the wheels of the first axis A1 and on the wheels of the third axis A3 (<figref idref="f0008">Fig. 8</figref>). Although this means a greater structural effort compared to the embodiment<figref idref="f0006">Fig. 6</figref>; however, there is greater support for the results from the diagonal comparisons.

0036The <figref idref="f0009">Fig. 9</figref> shows an embodiment of the invention, completely according to the embodiment <figref idref="f0001">Fig. 1</figref> corresponds with the exception that a diagonal sum comparison according to the embodiments according to <figref idref="f0006 f0007 f0008">Fig. 6-8</figref> is carried out.

0037The <figref idref="f0010">Fig. 10</figref> shows schematically the integration of the receiver / evaluation device 42 of the tire pressure measurement system 12 in the ABS control unit 6 of the ABS system 2. In a common housing, the ABS control unit 6, the HF receiver 42 of the tire pressure measurement system 12, is a stand-by micro Controller 50 and a CAN interface 8 used in common for both systems. The standby controller is always ready to receive the signals from the wheel electronics, even when the vehicle is parked, since the wheel electronics constantly send measured pressure values. This design is in the embodiments of the tire pressure monitoring device according to the invention<figref idref="f0003 f0004 f0005 f0006 f0007 f0008">Fig. 3-8</figref> intended. Reference numerals 25, 25 'and 10 and 31-40 schematically denote an ABS wheel sensor, an ABS control valve, a display and wheel electronics of the tire pressure measuring system.

0038Based on <figref idref="f0011">11 and 12</figref> A device for determining the route is to be explained in more detail. Voltages emitted by wheel sensors 25, 26, 27, 28 are filtered by input circuits 60 and converted into square-wave signals, the half or full period of which are evaluated by at least one microcontroller 62. Multiple micro-controllers can be used. For better understanding, only one micro controller is drawn in the drawing. The functions required for anti-lock protection / traction control (ABS / ASR) are referred to as period measurement and speed calculation.

0039According to the invention, a parallel path determination is provided, which represents a counting register, the value of which is increased with each zero crossing of the sensor voltage. The distance can thus be determined in a simple manner by counting the periods of the sensor signals.

0040If the micro-controller 62 only evaluates whole periods or multiples thereof, the distance counter (counting register) is only increased with each corresponding zero crossing. If the micro-controller should choose between these options depending on the speed, it is advantageous to choose the increase corresponding to the multiple of a half-period. The number of zero crossings depends on the tire roll circumference and the number of teeth on the flywheel. The numerical values ​​are continuously evaluated by a comparator 64 or only when the counting register with the highest count number reached overflows.

0041Example: With a rolling circumference of 3,425 mm and a pole wheel with 100 teeth, each zero crossing represents a distance of 17.125 mm. B. 1 km, the counted values ​​are compared with each other. As a digitally simple measure, the evaluation of the count values ​​achieved can be triggered when the count value leads to an overflow of the count register. With 16-bit counter registers, the overflow occurs when the numerical value 65,535 (2nd¹⁶ - 1) is increased. 65,535 + 1 is zero since the 17th digit of the binary number is not available, see Representation in the diagram according to<figref idref="f0011">Fig. 11</figref>. The count 2¹⁶ = 65,536 corresponds to 1.122 km. This results in a resolution of 1/65536 corresponding to 0.0015%.

0042Studies have shown that the wheel speed increases by approx. 0.5% per bar pressure loss. This means that the period and thus the distance of a tooth decreases by approx. 0.5% per bar. Since 100 teeth represent the rolling circumference of the tire, this is also reduced by said value. In this example, the above-mentioned favorable resolution (measuring accuracy) is greater by a factor of 328 than the influence of the pressure reduction to be measured (per bar).

0043The counting results achieved are weighted. As is usual with ASR threshold calculation, the difference between wheels with the same side is rated higher than wheels with the same axis or diagonally arranged.

0044The route determination can be interrupted or canceled and restarted, e.g. B. when an unsteady driving situation is detected such as anti-lock protection control, traction control, cornering or driving at low speed.

0045The device according to the invention for determining the route operates independently of the speed. No further effort is necessary to either improve the speed calculation or to strongly filter the result in order to eliminate short-term fluctuations. The measurement inaccuracies, such as rounding errors, are not taken into account when calculating the speed. The distance traveled by the wheel is determined directly without the need for a different calculation. The determined distance forms an integral, so that fluctuations of individual periods, z. B. by bumps in the road, have no influence.