DE102009020784B4 - Method for standardizing a device for monitoring tire pressure, method and device for monitoring tire pressure - Google Patents

Abstract

Method for standardizing a device for monitoring the tire pressure of a motor vehicle, comprising the following steps:
a) measuring the individual wheel rotation speeds of all wheels of a motor vehicle at at least one substantially constant vehicle speed and determining the torque applied at the at least one constant vehicle speed as the standardisation torque,
b) Determination of proportionality factors by which the individual wheel rotation speeds must be multiplied in order to obtain the same speed variables for all wheels of the motor vehicle at the standardisation torque,
c) Multiple measurement of the wheel rotation speeds when torques are present within a specified torque range, which includes torques whose magnitude differs from the standardization torque, and multiplication of the measured wheel rotation speeds by the corresponding proportionality factors in order to obtain corresponding torque-dependent speed variables for the individual wheels,
d) determining standardization diagonal values (SDEL) from the speed variables determined in step c), whereby a standardization diagonal value is the sum of the speed variables of the front left wheel and the rear right wheel with the sum of the relates the speed variables of the front right wheel and the rear left wheel to each other,
(e) determining the slope of a fictitious straight line fitted to the points obtained by plotting the standardisation diagonal values (SDEL) against the corresponding torque values or against the difference (ΔT) between the corresponding torque values and the standardisation torque, and
f1) Establishing at least one warning threshold, which, if exceeded by a diagonal value determined during vehicle operation, generates a warning signal depending on the gradient of the fictitious straight line.

Description

The invention relates to a method for standardizing a device for monitoring the tire air pressure of a motor vehicle and to methods and devices for monitoring the tire air pressure.

There are known methods for monitoring tire pressure in motor vehicles. These methods evaluate the wheel rotational speeds, which differ when the tire pressure deviates from the norm because the rolling radius of the wheel changes with changing air pressure. For this purpose, for example, a parameter is evaluated that relates the speeds of the individual wheels to one another. Known methods calculate a corresponding diagonal value that relates the sum of the speed variables of the front right wheel and the rear left wheel to the sum of the speed variables of the front left wheel and the rear right wheel and, in particular, is proportional to the difference between this sum. Such a diagonal value is zero if the wheel rotational speeds are the same for all wheels. If the value deviates from zero or its absolute value exceeds a predetermined limit, a signal can be output indicating an irregularity.

A device for carrying out such a tire monitoring method has sensors that measure the individual wheel rotation speeds.

If a tire loses air, the corresponding wheel rotates faster to accommodate the smaller rolling radius. On the other hand, if a tire is replaced, for example, it usually has a thicker tread and thus a larger rolling radius and a lower wheel rotation speed. If, for example, at least one tire differs from the others ("mixed tire setup"), its rolling radius will usually differ from that of the others. This leads to different wheel rotation speeds at a constant vehicle speed and while driving straight ahead, even if the air pressure of the individual tires is the same.

If, for example, the vehicle user has changed the air pressure or fitted a new tire, the system must be re-standardized to establish reference values for the individual wheel rotation speeds under known conditions.

Therefore, after a change in the tire system, e.g. triggered by the user, a standardization process is initiated in which the wheel rotation speeds are measured and fictitious proportionality factors are determined which are selected in such a way that, after multiplication with the respective wheel rotation speeds determined under normal conditions, they result in the same speed variables for all wheels, so that different rolling radii - e.g. in the case of mixed tires - are compensated.

Such a standardization process is advantageously carried out at a substantially constant speed, where no or only a small amount of drive torque is transferred to the wheels. This results in a torque suitable for standardization ("standardization torque").

Even if different tire types or tire brands are mounted on the drive axle, with such a low standardization torque the slip differences are limited and the diagonal value is only slightly affected.

The DE 103 03 492 A1 Describes a method for monitoring the condition of the tires on the wheels of a motor vehicle. First, individual wheel speeds of all wheels are measured at at least one essentially constant vehicle speed. Proportionality factors are then determined, by which the wheel speeds are multiplied to obtain identical speed variables for all wheels of the motor vehicle. Furthermore, wheel speeds are measured at torques within a predetermined torque range. The measured wheel speeds are multiplied by the associated proportionality factors to obtain corresponding torque-dependent speed variables for the individual wheels. Based on the speed variables, respective diagonal values are determined that relate a sum of the speed variables of the front left wheel and the rear right wheel to the sum of the speed variables of the front right wheel and the rear left wheel. If the gradient of a straight line fitted to the points obtained by plotting the diagonal values against the associated torque values exceeds a predetermined threshold, a warning signal is generated.

In the DE 101 30 127 A1 a method according to a related technology is described.

The DE 44 00 913 B4 also describes a method intended for monitoring the condition of the tires on the wheels of a motor vehicle.

In the DE 100 58 097 A1 A method for detecting tire pressure loss is described.

The DE 10 2005 031 485 A1 also describes such a procedure.

In the DE 199 37 596 A1 A method for diagnosing tires according to a related technology is described.

Furthermore, the WO 2004/058519 A1 A method for improving an indirect tire pressure detection system by defining and using a permissible tire pressure monitoring range that depends on the torque and lateral acceleration of a vehicle.

The object of the present invention is to provide methods for standardizing a device for monitoring the tire pressure of a motor vehicle, as well as methods and devices for monitoring the tire pressure that can also take acceleration or deceleration situations into account during standardization. In particular, this should also be possible with mixed tires.

This object is achieved by methods for standardization having the features of claim 1 or claim 2. With regard to the methods and devices for monitoring tire air pressure, the object is achieved by claims 10 or 11, or 13 or 14, respectively. Subclaims are each directed to preferred embodiments.

In a first method for standardizing a device for monitoring the tire pressure of a motor vehicle, the individual wheel rotational speeds of all wheels of a motor vehicle are first measured at at least one substantially constant vehicle speed, and the torque present at this vehicle speed is defined as the standardization torque. The standardization torque can be defined, for example, using a standard torque line stored in a memory chip. To determine the standard torque line, for example, the drive torques required to maintain a given speed are measured for a new vehicle type.

Proportionality factors are determined in the manner described, by which the individual wheel rotation speeds would have to be multiplied in order to obtain the same speed variables for all wheels of the motor vehicle at the standardization torque.

The standardization torque can also be essentially zero, for example, if the measurement is taken while the vehicle is rolling freely, e.g., with the clutch engaged. It can also be measured at several essentially constant vehicle speeds, and a corresponding average value can be determined.

According to the invention, it is particularly provided that, in addition to this standardization for a standardization torque, an additional standardization process is included in the standardization method, which takes into account the influence of higher wheel torques and is also applicable to mixed tires, where increased slip differences can therefore occur.

For this purpose, wheel rotational speeds are measured several times when torques are present within a specified torque range, which includes torques whose magnitude differs from the standardization torque. The wheel rotational speeds measured in this way are multiplied by the proportionality factors determined during the first part of the standardization process to obtain torque-dependent speed variables for the individual wheels. From these speed variables, a standardization diagonal value SDEL can be determined for each wheel. This value relates the sum of the speed variables of the front left wheel and the rear right wheel to the sum of the speed variables of the front right wheel and the rear left wheel. A fictitious straight line can then be assumed that is fitted to the points created by plotting these standardization diagonal values SDEL against the respective torque values or the difference between the corresponding torque values and the standardization torque, and the gradient of this straight line can be determined.

In the first standardization method according to the invention, a warning threshold is set depending on the gradient of this fictitious straight line. If this threshold is exceeded, a warning signal is generated by a diagonal value DEL determined during vehicle operation. For example, a warning signal can be sent to the driver indicating an irregularity. The setting of the warning threshold depending on the gradient of the fictitious straight line takes into account differences in slip, e.g. due to different tire brands, which have a greater influence on the diagonal values in acceleration or deceleration situations than with a low wheel torque, which was defined, e.g., as a standardization torque.

Setting different warning thresholds for different gradients of the fictitious straight line ensures that, even with a tire configuration in which one tire differs from the other three tires, a corresponding warning signal is only issued if a tire pressure drop has actually occurred in one of the tires. If the slip differences during acceleration and deceleration differ significantly due to a tire configuration in which one tire differs from the other three tires, the resulting DEL value will also be affected. It is therefore advantageous to adjust the warning threshold to avoid the unauthorized issuance of a warning signal.

In a second method according to the invention, the gradient of a corresponding fictitious straight line is also determined as described. In the second method according to the invention, a tire pressure monitoring range is defined, depending on the gradient of the fictitious straight line, in a coordinate system spanned by the torque and the lateral acceleration, in which tire pressure monitoring can be performed. The coordinate system does not have to be spanned directly by the torque and the lateral acceleration, but can alternatively be defined, for example, by values directly related to these parameters, such as the acceleration or deceleration of the motor vehicle with the respective torque.

The second method according to the invention ensures that the tire pressure monitoring can only take place in an area of this fictitious coordinate system in which a reliable measurement is possible, whereby in particular possible slip differences, e.g. due to non-uniform tires, are also taken into account, which can have an influence at higher torques.

It is particularly advantageous if the first and second methods according to the invention are combined for standardization, i.e. both a warning threshold value and a tire pressure monitoring range are determined from the gradient of the fictitious straight line.

It is particularly advantageous if the standardization diagonal value for the standardization torque and/or the standardization diagonal values for the wheel rotation speed measurements when torques are present within a predetermined torque range are selected as proportional to the difference between the sums of the respective speed variables of the front right wheel and the rear left wheel and the sum of the speed variables of the front left wheel and the rear right wheel, particularly expediently according to the following rule: $$\text{SDEL}=\text{K}*\left\{\left[\text{FL}+\text{RR})-\left(\text{FR}+\text{RL}\right)\right]\text{/}\left(\text{FL}+\text{FR}+\text{RL}+\text{RR}\right)\right\},$$ where FL, FR, RR and RL correspond to the speed variables of the front left wheel, the front right wheel, the rear right wheel and the rear left wheel, respectively, and K is a fixed multiplication factor.

It is expedient to select the torque range in which the wheel speed measurements are made so that the magnitude of the torques differs from the standardization torque value by more than a lower torque difference limit and less than an upper torque difference limit.

The fictitious straight line, whose gradient is determined for further processing, can be determined in a simple yet accurate way using the method of least squares.

In the standardization method according to the invention, the warning threshold or tire pressure monitoring range is determined depending on the gradient of the fictitious straight line. For example, gradient ranges can be defined that are separated from each other by corresponding gradient thresholds and for which different rules are defined for determining the respective warning threshold or tire pressure monitoring range. In particular, an individual warning threshold or tire pressure monitoring range can be defined for each of the gradient ranges.

In a first method according to the invention for monitoring tire pressure for motor vehicles, a standardization method according to the invention is implemented. During operation of the motor vehicle, the wheel rotation speeds of the motor vehicle's wheels are measured and multiplied by the corresponding proportionality factors determined during the standardization process. In this way, the corresponding current speed variables for the individual wheels are determined.

Preferably, using the same formula used to determine the diagonal values SDEL for standardization, a diagonal value DEL is now determined from the current speed variables.

In the first method according to the invention for monitoring the tire air pressure, a warning signal is issued when a diagonal value DEL determined in this way exceeds the warning threshold value determined during the standardization process.

In a second method for monitoring tire pressure according to the invention, it is first checked whether the torque and lateral acceleration corresponding to the current speed variables are within the tire pressure monitoring range defined by a corresponding standardization procedure. A warning signal is generated if the diagonal value DEL exceeds a warning threshold defined by a standardization procedure and the torque and lateral acceleration corresponding to the current speed variables are within an approved tire pressure monitoring range.

Devices according to the invention for monitoring tire pressure include sensors for measuring the wheel speeds of the four wheels of the motor vehicle. For example, ABS sensors, which are used to measure wheel speeds for an anti-lock braking system, can be used for this purpose.

The devices according to the invention have an evaluation and control device which is connected to the sensors and is configured to carry out the method steps according to the invention.

• 1 ein Diagramm, in dem Standardisierungsdiagonalwerte SDEL gegen die Differenz ΔT zugehöriger Drehmomentwerte und des Standardisierungsdrehmoments aufgetragen sind,
• 2 ein entsprechendes Diagramm für einen anders zusammengesetzten Reifensatz,
• 3 den Reifenluftdrucküberwachungsbereich für einen ersten Steigungsbereich einer Gerade entsprechend 1 oder 2,
• 4 den Reifenluftdrucküberwachungsbereich für einen zweiten Steigungsbereich,
• 5 den Reifenluftdrucküberwachungsbereich für einen dritten Steigungsbereich, und
• 6 den Reifenluftdrucküberwachungsbereich für einen vierten Steigungsbereich.

The invention is explained in detail using an example in the accompanying figures.

• 1 a diagram in which standardization diagonal values SDEL are plotted against the difference ΔT of corresponding torque values and the standardization torque,
• 2 a corresponding diagram for a differently composed set of tires,
• 3 the tire pressure monitoring area for a first gradient area of a straight line corresponding 1 or 2 ,
• 4 the tire pressure monitoring area for a second gradient range,
• 5 the tire pressure monitoring area for a third gradient range, and
• 6 the tire pressure monitoring area for a fourth gradient range.

The figures only represent the conditions as examples for a selected configuration and are explained in the following description of a design of the process.

Determination of proportionality factors:

For example, after a new tire has been fitted or an air pressure check or adjustment has been carried out, the driver initiates a standardization process using a corresponding input device on the dashboard. In a torque range with relatively low torques and at a relatively constant vehicle speed (e.g., only 70 Nm at 80 km/h), a control and evaluation device of the tire pressure monitoring system then records, for example, sixty measured values of the respective wheel speeds of all four wheels. This can be done, for example, using the sensors already present in an anti-lock braking system. For this purpose, the control and evaluation device waits for a corresponding driving situation or actively initiates it. The torque applied in each case is referred to below as the "standardization torque."

For each wheel, the wheel rotation speed at the standardization torque can be determined, for example, by averaging the sixty measured values.

The torque corresponding to a given vehicle speed can be determined, for example, from a pre-determined standard torque curve. For example, several test series with different configurations are run on a new vehicle model, and the torque is measured at different vehicle speeds. The resulting measurement curve can be stored in a memory chip in the vehicle and then serves as a standard torque curve, which allows the standardization torque to be determined at the selected speed.

The method according to the invention does not exclude the assumption of different standardization torques for different speed ranges in which the standardization is to take place, which, however, are also read from the standard torque line.

The calculation of corresponding standardization diagonal values according to the formula given above: $$\text{SDEL}=\text{K}*\left\{\left[\text{FL}+\text{RR})-\left(\text{FR}+\text{RL}\right)\right]\text{/}\left(\text{FL}+\text{FR}+\text{RL}+\text{RR}\right)\right\}$$ should result in relatively small values, since the wheel rotation speeds should not differ significantly even with different tires in view of the small applied torque and slip differences due to different tires should therefore have little influence.

On the other hand, a larger deviation above a predefined threshold would already indicate a drop in air pressure in one of the tires.

Based on the wheel speeds measured at the standardization torque, the control and evaluation system determines proportionality factors that account for possible deviations. Such deviations can arise, for example, if the profiles of the individual tires are not the same and, therefore, the rolling radius of the individual wheels is different. The proportionality factors are selected such that, at the standardization torque, speed parameters are obtained by multiplying the proportionality factors by the wheel speeds, which are equal to one another. If the speed parameters determined in this way are substituted for the values FL, RR, FR, and RL used in the above formula, a standardization diagonal value SDEL of zero results for the journey at the standardization torque.

Consideration of higher torques:

The wheel speeds for each wheel are then additionally measured when larger torques are present, for example, during acceleration or deceleration. For example, measured values in a range of 50 Nm to 150 Nm difference from a standardized torque are useful. Again, 60 measured values are taken.

The respective standardization diagonal value SDEL is determined for each measured value using the formula given above. The multiplication factor K is set to one in each case.

If the values SDEL determined in this way are plotted against the difference between the respective torque and the standardization torque, a diagram corresponding to the 1 The differential values are in the range from 50 to 150 Nm and from -150 to -50 Nm, respectively. The SDEL values plotted on the vertical axis are dimensionless and plotted in arbitrary units. A straight line can be drawn through the measurement points using the least squares method, and the gradient can be determined, as shown in 1 The gradient in this example is -0.000032.

The example of 1 comes from a set of tires where all four tires are the same.

For a set of tires where one tire is, for example, younger than the others and therefore has a stronger profile, a different straight line with a greater gradient results due to the slip differences, which have a greater influence at higher torques, as shown in 2 The gradient in this example is -0.000811.

The gradient determined in this way is used in the further procedure as follows:

Selecting the settings:

The absolute value of the determined gradient is compared with specified gradient limits. These gradient limits are determined in advance, for example, based on the vehicle type and tire type (e.g., winter or summer tires). For example, in the units chosen for this example in this description (here and in the following, 1/(Nm)), a first gradient limit can be 200 · 10 ^-6 , a second gradient limit can be 500 · 10 ^-6 , and a third gradient limit can be 1000 · 10 ^-6 .

Depending on the gradient range or the two gradient limit values between which the absolute value of the determined gradient lies, different “settings” are selected.

These different “settings” differ in particular with regard to a warning threshold and a tire pressure monitoring range in which tire pressure monitoring can be meaningfully carried out.

Selecting the warning threshold:

A warning threshold fulfills the following function: During vehicle operation, the speed of the respective wheels is measured continuously or at regular intervals and multiplied by the proportionality factors previously determined when the standardization torque is applied as described above in order to obtain current speed variables FL, FR, RL and RR, which correspond to the wheel rotation speeds of the front left wheel, the front right wheel, the rear left wheel and the rear right wheel. Using these current speed variables, a diagonal value is then determined using the following formula: $$\text{DEL}=\text{K}*\left\{\left[\text{FL}+\text{RR})-\left(\text{FR}+\text{RL}\right)\right]\text{/}\left(\text{FL}+\text{FR}+\text{RL}+\text{RR}\right)\right\}$$

If a DEL value determined in this way exceeds a warning threshold, a warning signal is issued to the driver that an irregularity has occurred, in particular, for example, a drop in air pressure in one of the tires.

Depending on whether the absolute value of the gradient determined during standardization operation as described is above or below a respective gradient limit value, the threshold values are adjusted. If these values are exceeded, a warning signal is issued to the driver by means of a diagonal value determined during vehicle operation.

If the amount of gradient in the selected units is, for example, in a range between 0 and 200 · 10 ^-6 , a normal preset warning threshold applies, and if this threshold is exceeded, a warning signal is triggered by the DEL value measured during vehicle operation.

For example, if the gradient determined during standardization is between 200 · 10 ^-6 and 500 · 10 ^-6 , it can be assumed that mixed tires are present. However, the gradient is not so different that the warning threshold would need to be adjusted.

If the gradient determined during the standardization process is between 500 · 10 ^-6 and 1000 · 10 ^-6 , the warning threshold is set to, for example, 120% of the normal warning threshold. This ensures that even with larger slip differences due to different tires, a warning signal is only triggered if an additional irregularity actually occurs, for example, if a tire pressure drop occurs.

If the gradient learned during the standardization process exceeds 1000 10 ^-6 , the warning threshold is set to, for example, 130% of the normal warning threshold. With such a determined gradient, it can be assumed that one tire differs from the other three tires, and raising the warning threshold ensures that, despite the resulting larger slip differences, a warning signal is not unjustifiably issued, indicating a tire pressure drop in one tire when no such tire pressure drop actually exists.

Determination of the tire pressure monitoring range:

In addition, a range is defined within which tire pressure monitoring can be meaningfully performed, depending on the gradient determined during the standardization process. This takes into account that, for example, a meaningful measurement is not possible if the lateral acceleration is too high, and under certain conditions, if the forward acceleration or deceleration is too high. The critical values for the forward acceleration or deceleration and the lateral acceleration can also depend on the tire type, i.e., whether one tire differs from the other three tires, which is reflected in the gradient of the fictitious straight line determined during standardization.

3 indicates such a range, as selected, for example, when the absolute value of the gradient of the fictitious straight line determined during the standardization process lies between 0 and 200 10 ^-6 in the units chosen for this example in this description (here and in the following 1/(Nm)). The measurement of wheel speeds and the resulting determination of the DEL values are permitted only within the hatched area. For greater lateral acceleration or greater forward torque, the measurement is not performed.

3 shows that a measurement is always carried out if the lateral acceleration is less than a first lateral acceleration limit value A ₁ , which is e.g. 0.05 g (g = acceleration due to gravity). If the lateral acceleration is more than a second limit value B ₁ (e.g. 0.2 g), no measurement is permitted at all. Otherwise, measurements would only be permitted if the magnitude of the torque T and the magnitude of the lateral acceleration are in a range formed by the triangle spanned by the values A ₁ , B ₁ and C ₁ , where C ₁ in this example is e.g. 80 Nm.

In 4 The shaded area shows the range for which tire pressure measurements are permitted when the absolute value of the gradient of the fictitious straight line, which was established during the standardization process, lies between 200 10 ^-6 and 500 10 ^-6 . It is clear here that there is an upper limit C ₂ of, in this example, 60 Nm; if exceeded due to the torque applied to the drive axle, no wheel speed measurement is permitted. The upper limit for lateral acceleration B ₂ can, for example, be 0.2 g.

The 5 and 6 show corresponding ranges for a fictitious gradient determined during standardization with a magnitude of 500 · 10 ^-6 to 1000 · 10 ^-6 or greater than 1000 · 10 ^-6 . The limit values C ₃ and B ₃ or C ₄ and B ₄ can, for example, have the same numerical values as the limit values C ₂ and D ₂ , which are selected for a gradient magnitude between 200 · 10 ^-6 and 500 · 10 ^-6 .

Taken together, the following situation arises for the example described:

If the absolute value of the gradient determined during standardization in the units chosen for this example in this description (here and in the following 1/(Nm)) is between 0 and 200 · 10 ^-6 , the warning threshold, above which a warning signal is triggered by the diagonal value DEL, is left unchanged, e.g. at a value that was set at the factory assuming four identical tires.

Measurements of wheel rotation speeds for calculating the diagonal value DEL during normal vehicle operation for monitoring tire pressure are only permitted in an area defined by the hatched area of the 3 results.

If the absolute value of the gradient of the fictitious straight line is determined during the standardization process to be between 200 10 ^-6 and 500 10 ^-6 , the warning threshold remains unchanged. However, the tire pressure monitoring range is adjusted according to the 4 selected, ie with different limit values C ₂ and B ₂ . In particular, this results in only a limited range for forward acceleration or deceleration.

If the absolute value of the determined gradient of the fictitious straight line is determined to be between 500 × 10 ^-6 and 1000 × 10 ^-6 , the warning threshold, which, if exceeded by the DEL value during vehicle operation, triggers a warning signal, is set to 120% of the normal warning threshold. A corresponding warning signal is therefore only issued if the DEL value deviates significantly from zero. In this example, the tire pressure monitoring range within which tire pressure monitoring can be performed remains unchanged compared to the gradient range between 200 × 10 ^-6 and 500 × 10 ^-6 .

If the gradient learned during the standardization process is greater than 1000 · 10 ^-6 , the warning threshold is increased again, e.g., to 130%. The tire pressure monitoring range is also left unchanged in this example, meaning that the limit values C ₄ and B ₄ are set equal to the limit values C ₂ and B ₂ .

The inventive method for checking tire pressure using the inventive method for standardization thus makes it possible to take into account, for example, different tires that lead to different slip behavior during acceleration and deceleration. This involves adjusting the limit value; if exceeded by the diagonal value, a warning signal is issued indicating a drop in tire pressure. Furthermore, the tire pressure monitoring range, which depends on the forward torque and lateral acceleration and indicates the value range within which tire pressure monitoring is reasonably possible, is adjusted.

List of reference symbols

T

torque

ΔT

Torque difference

SDEL

Diagonal value in standardization

DEL

Diagonal value during vehicle operation

LB

Lateral acceleration

A1, B1, B2, B3, B4

Lateral acceleration value

C1, C2, C3, C4

Forward acceleration values

Claims (15)

Method for standardizing a device for monitoring the tire pressure of a motor vehicle, comprising the following steps: a) measuring the individual wheel rotational speeds of all wheels of a motor vehicle at at least one substantially constant vehicle speed and defining the torque present at the at least one constant vehicle speed as the standardization torque, b) defining proportionality factors by which the individual wheel rotational speeds must be multiplied in order to obtain the same speed variables for all wheels of the motor vehicle at the standardization torque, c) multiple measurement of the wheel rotational speeds when torques are present within a predetermined torque range, Torques whose magnitude differs from the standardization torque, and multiplying the measured wheel rotational speeds by the associated proportionality factors to obtain corresponding torque-dependent speed variables for the individual wheels, d) respective determination of standardization diagonal values (SDEL) from the speed variables determined in step c), wherein a standardization diagonal value relates the sum of the speed variables of the front left wheel and the rear right wheel to the sum of the speed variables of the front right wheel and the rear left wheel, e) determining the gradient of a fictitious straight line that is fitted to the points obtained by plotting the standardization diagonal values (SDEL) against the associated torque values or against the difference (ΔT) between the associated torque values and the standardization torque, and f1) specifying at least one warning threshold value, upon exceeding which a warning signal is generated by a diagonal value determined during vehicle operation, in Dependence of the gradient of the fictitious straight line. A method for standardizing a device for monitoring the tire pressure of a motor vehicle, comprising the following steps: a) Measuring the individual wheel rotational speeds of all wheels of a motor vehicle at at least one substantially constant vehicle speed and defining the torque present at the at least one constant vehicle speed as the standardization torque; b) Defining proportionality factors by which the wheel rotational speeds must be multiplied in order to obtain identical speed variables for all wheels of the motor vehicle at the standardization torque; c) Multiple measurement of the wheel rotational speeds when torques are present within a predetermined torque range, which includes torques whose magnitude differs from the standardization torque, and multiplying the measured wheel rotational speeds by the associated proportionality factors to obtain corresponding torque-dependent speed variables for the individual wheels; d) Determining standardization diagonal values (SDEL) from the speed variables determined in step c), wherein a standardization diagonal value is the sum of the speed variables in each case. of the front left wheel and the rear right wheel with the sum of the speed variables of the front right wheel and the rear left wheel, e) determining the gradient of a fictitious straight line fitted to the points obtained by plotting the standardization diagonal values (SDEL) against the corresponding torque values or the difference (ΔT) between the corresponding torque values and the standardization torque, and f2) defining at least one tire pressure monitoring area in a coordinate system spanned by the torque (T) or a quantity clearly related thereto and the lateral acceleration (LB), in which tire pressure monitoring can be carried out, depending on the gradient of the fictitious straight line. Method for standardizing a device for monitoring the tire pressure of a motor vehicle with the features of Claims 1 and 2 . Standardization procedure according to one of the Claims 1 until 3 , where the standardization diagonal values (SDEL) are determined according to the following formula: $$\text{SDEL}=\text{K}*\left\{\left[\text{FL}+\text{RR})-\left(\text{FR}+\text{RL}\right)\right]\text{/}\left(\text{FL}+\text{FR}+\text{RL}+\text{RR}\right)\right\},$$ where FL, FR, RR and RL correspond to the speed variables of the front left wheel, the front right wheel, the rear right wheel and the rear left wheel, respectively, and K is a fixed multiplication factor. Standardization procedure according to one of the Claims 1 until 4 , in which the torque range in which the measurements in step c) are carried out includes torques whose magnitude differs from the standardization torque value by more than a lower torque difference limit and less than an upper torque difference limit. Standardization procedure according to one of the Claims 1 until 5 , in which in step e) the fictitious straight line is determined using the least squares method. Standardization procedure according to one of the Claims 1 until 6 , in which m gradient ranges are defined, separated by (m - 1) gradient limits. Procedure for standardization according to Claim 7 , insofar as it is directly or indirectly Claim 1 depends on which, in step f1), gradient limits are defined at which Individual warning thresholds can be selected if the absolute value of the gradient is exceeded or not reached. Procedure for standardization according to Claim 7 , insofar as it is directly or indirectly Claim 2 depends on which, in step f2), gradient limit values are defined, and if the absolute value of the gradient is exceeded or undershot, individual tyre pressure monitoring ranges are defined. Method for monitoring tyre pressure for motor vehicles, in which the following steps are carried out: A1) Carrying out a standardisation procedure with the characteristics of the Claim 1 or one of the Claims 3 until 9 , insofar as it is directly or indirectly Claim 1 depends, B1) measuring the wheel rotational speeds of the wheels of the motor vehicle and multiplying the measured wheel rotational speeds by the associated proportionality factors in order to determine the corresponding current speed variables for the individual wheels, C1) determining a diagonal value (DEL) from the current speed variables, wherein the diagonal value relates the sum of the current speed variables of the front left wheel and the rear right wheel to the sum of the current speed variables of the front right wheel and the rear left wheel, D1) generating and outputting a warning signal if the diagonal value (DEL) determined in this way exceeds a warning threshold value determined in step f1). Method for monitoring tire pressure, comprising the following steps: A2) Carrying out a standardization procedure with the characteristics of the Claim 3 or one of the Claims 4 until 9 , insofar as it is directly or indirectly Claim 3 depends, B2) measuring the wheel rotational speeds for the wheels of the motor vehicle and multiplying the measured wheel rotational speeds by the associated proportionality factors in order to determine the corresponding current speed variables, C2) determining a diagonal value (DEL) from the current speed variables, wherein the diagonal value relates the sum of the current speed variables of the front left wheel and the rear right wheel to the sum of the current speed variables of the front right wheel and the rear left wheel, D2) checking whether the torque (T) and the lateral acceleration (LB) corresponding to the current speed variables are within the tire pressure monitoring range defined in step f2), E2) generating and outputting a warning signal if the diagonal value (DEL) exceeds a warning threshold defined in step f1) if the check in step D2) had a positive result. Method for monitoring tire pressure according to one of the Claims 10 or 11 , where the diagonal value (DEL) is determined according to the following formula: $$\text{DEL}=\text{K}*\left\{\left[\text{FL}+\text{RR})-\left(\text{FR}+\text{RL}\right)\right]\text{/}\left(\text{FL}+\text{FR}+\text{RL}+\text{RR}\right)\right\},$$ where FL, FR, RR and RL correspond to the current speed variables of the front left wheel, the front right wheel, the rear right wheel and the rear left wheel, respectively, and K is a fixed multiplication factor. Device for monitoring the tyre pressure for motor vehicles, with - sensors for measuring the wheel rotation speeds of the four wheels of the motor vehicle, and - an evaluation and control device which is connected to the sensors and for carrying out the steps of the method of Claim 10 configured using the sensor signals. Device for monitoring the tyre pressure for motor vehicles, with - sensors for measuring the wheel rotation speeds of the wheels of the motor vehicle, and - an evaluation and control device which is connected to the sensors and for carrying out the steps of Claim 11 configured using the sensor signals. Device for monitoring tyre pressure for motor vehicles, with the features of Claims 13 and 14 .