Method for standardizing a device for monitoring tire pressure, method and device for monitoring tire pressure

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 standardisation diagonal values (SDEL) from the speed variables determined in step c), whereby a standardisation 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 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 standardization of a device for monitoring the tire air pressure of a motor vehicle and to methods and devices for monitoring the tire air pressure.Methods for monitoring the tire air pressure for motor vehicles are known, which for monitoring perform an evaluation of the wheel rotational speeds, which differ in the case of an air pressure of a tire deviating from the standard, because the rolling radius of the wheel also changes with changing air pressure. For this purpose, for example, a parameter is evaluated which relates the speeds of the individual wheels to one another. Known methods for this purpose calculate a corresponding diagonal value, which relates the sum of speed variables of the front right wheel and of the rear left wheel to the sum of the speed variables of the front left wheel and of the rear right wheel, and is in particular proportional to the difference of this sum. Such diagonal value is zero when the wheel rotational speeds are the same for all wheels. If the value deviates from zero or its absolute value exceeds a predetermined limit value, a signal can be output which indicates an abnormality.An apparatus for carrying out such a tire monitoring method has sensors which measure the individual wheel rotational speeds.If a tire loses air, the corresponding wheel rotates more quickly to accommodate the lower rolling radius. If, on the other hand, a tire is exchanged, for example, then the tire generally has a stronger profile and thus a larger rolling radius and a lower wheel rotational speed. If, for example, at least one tire differs from the other tires ( "Mischbereifung"), its rolling radius generally differs from that of the other tires. This leads to different wheel speeds of rotation at constant vehicle speed and straight-ahead travel, even if the air pressure of the individual tires is the same.Thus, if, for example, the user of the motor vehicle has made a change in the air pressure or, for example, a new tire has been mounted, the system must be re-standardized in order to establish reference values for the individual wheel rotational speeds under known conditions.After a change of the tire system, a standardization process is therefore initiated, e.g. triggered by the user, in which the wheel rotational speeds are measured and fictitious proportionality factors are defined, which are selected such that after multiplication with the respective wheel rotational speeds determined under normal conditions they result in the same speed variables for all wheels, so that different rolling radii-e.g. during mixed ripening-are compensated.Such a standardization process is advantageously carried out at a substantially constant speed, at which no or no large drive torque is transmitted to the wheels. There is then a torque suitable for standardization ("standardization torque").Even if different types of tires or tire manufactures are mounted on the drive axle, the slip differences remain within limits and the diagonal value is only slightly influenced at such a low standardization torque.DE 103 03 492 A1 describes a method for monitoring the tire state at wheels of a motor vehicle. First, individual wheel rotational speeds of all wheels are measured at at least a substantially constant vehicle speed. Thereafter, proportionality factors are defined by which the wheel rotational speeds are multiplied in order to obtain the same speed variables for all wheels of the motor vehicle. Further, wheel rotational speeds are measured at torques within a predetermined torque range. The measured wheel speeds of rotation are multiplied by the associated proportionality factors to obtain corresponding torque-dependent speed variables for the individual wheels. The speed variables are used to determine respective diagonal values which relate a sum of the speed variables of the front left wheel and of the rear right wheel to the sum of the speed variables of the front right wheel and of the rear left wheel. If the gradient of a straight line, which is adapted to the points which arise by applying the diagonal values against the associated torque values, exceeds a predefined threshold value, a warning signal is generated.DE 101 30 127 A1 describes a method according to a related technology.DE 44 00 913 B4 likewise describes a method which is provided for monitoring the tire state at wheels of a motor vehicle.DE 100 58 097 A1 describes a method for detecting a tire pressure loss.DE 10 2005 031 485 A1 likewise describes such a method.DE 199 37 596 A1 describes a method for diagnosing tires according to a related technology.Furthermore, WO 2004 / 058519 A1 describes a method for improving an indirectly measuring tire pressure detection system, in which an admissible tire pressure monitoring range, which depends on the torque and on the lateral acceleration of a vehicle, is defined and used.The object of the present invention is to specify methods for standardization of a device for monitoring the tire air pressure of a motor vehicle and methods and devices for monitoring the tire air pressure, which methods and devices can also take account of acceleration or deceleration situations during standardization. In particular, this should also be possible in the case of mixed processing.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 the tire air pressure, the object is achieved by claims 10 or 11 or 13 or 14, respectively. Dependent claims are directed in each case to preferred embodiments.In a first method for standardization of a device for monitoring the tire air 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 applied at this vehicle speed is defined as a standardization torque. The standardization torque can be established, for example, with the aid of a standard torque line which is stored in a memory chip. For determining the standard torque line, for example, in the case of a new vehicle type, the drive torques necessary for maintaining a respective speed are measured.Proportionality factors are defined in the manner described by which the individual wheel rotational 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 substantially equal to zero, for example, if measurement is made, for example, when the vehicle is rolling freely, i.e., when the clutch is engaged. It can also be measured at a plurality of substantially constant vehicle speeds and a corresponding mean value can be determined.According to the invention, it is provided in particular that, in addition to this standardization at a standardization torque, an additional standardization process is also included in the method for standardization, which takes into account the influence of higher wheel torques and is also applicable to mixed processing, in which slippage differences can thus occur to an increased extent.For this purpose, wheel rotational speeds are measured multiple times in the presence of torques within a predefined torque range which comprises torques whose magnitude differs from the standardization torque. The wheel speeds of rotation thus measured are multiplied by the proportionality factors determined during the first part of the standardization process, so that torque-dependent speed variables for the individual wheels are obtained. From these speed variables, a standardization diagonal value SDEL can be determined in each case, which relates the sum of the speed variables of the front left wheel and of the rear right wheel to the sum of the speed variables of the front right wheel and of the rear left wheel in each case. A fictitious straight line can then be assumed, which is adapted to the points which arise by plotting these standardization diagonal values SDEL against the respective torque values or the difference between the associated torque values and the standardization torque, and the gradient of this straight line can be determined.In the first method according to the invention for standardization, a warning threshold value is defined as a function of the gradient of this fictitious straight line, a warning signal being generated when said warning threshold value is exceeded by a diagonal value DEL-determined during vehicle operation. Thus, for example, a warning signal can be emitted to the motor vehicle driver that an abnormality is present. The determination of the warning threshold value as a function of the gradient of the fictitious straight line takes into account slip differences, for example due to different tire manufactures, which in acceleration or deceleration situations has a greater influence on the diagonal values than in the case of a low wheel torque, which was determined as a standardization torque, for example.The setting of different warning thresholds for different slopes of the fictitious straight line ensures that even in the case of a tyre in which a tyre differs from the three other tyres, a corresponding warning signal is only output if a tyre air pressure drop has actually also taken place in one of the tyres. If, due to a tire in which one tire is different from the three other tires, the slip differences in the acceleration or deceleration operation differ greatly, the DEL value determined in this way is also influenced. It is therefore advantageous to adapt the warning threshold in order to avoid unauthorized output of a warning signal.In a second method according to the invention, the slope of a corresponding fictitious straight line is likewise determined as described. In the second method according to the invention, a tire air pressure monitoring range is defined in a coordinate system spanned by the torque and the lateral acceleration as a function of the gradient of the fictitious straight line, in which a tire air pressure monitoring can be carried out. In this case, the coordinate system does not have to be directly spanned by the torque and the lateral acceleration, but alternatively also by values which are directly associated with these parameters, such as the acceleration or deceleration of the motor vehicle with the respective torque, for example.The second method according to the invention ensures that the tire air pressure monitoring can only take place in a region of this fictitious coordinate system in which reliable measurement is possible, wherein in particular possible slip differences are also taken into account, for example by a non-uniform tire formation, which can have an influence at higher torques.It is particularly advantageous if the first and the second method according to the invention are combined for standardization, i.e. both a warning threshold value and a tire air pressure monitoring range are established from the gradient of the fictitious straight line.It is particularly advantageous if the standardization diagonal value in the standardization torque and / or the standardization diagonal values in the measurements of the wheel rotational speeds in the presence of torques within a predefined torque range is selected as proportional to the difference of 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: wherein 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.Expediently, for the torque range in which the measurements of the wheel rotational speeds are made, it is selected such that the magnitude of the torques differ from the standardization torque value by more than a lower torque difference limit value and less than an upper torque difference limit value.The fictitious straight line, the slope of which is determined for further processing, can be determined in a simple and nevertheless accurate manner using the least squares method.In the method according to the invention for standardization, the warning threshold value or the tire air pressure monitoring range is determined as a function of the gradient of the fictitious straight line. In this case, for example, ranges can be defined for the gradient which are separated from one another by corresponding gradient limit values and for which different rules are defined for determining the respective warning threshold value or the respective tire air pressure monitoring range. In particular, for example, an individual warning threshold value or an individual tire air pressure monitoring range can be established for each of the gradient ranges.In a first method according to the invention for monitoring the tire air pressure for motor vehicles, a method according to the invention for standardization is carried out. During operation of the motor vehicle, the wheel rotational speeds of the wheels of the motor vehicle are then measured and multiplied by the associated proportionality factors which have been established during the standardization method. In this way, the corresponding current speed variables for the individual wheels are determined.Preferably according to the same formula with which the diagonal values SDEL have been determined 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 output if a diagonal value DEL determined in this way exceeds the warning threshold value established during the method for standardization.In a second method according to the invention for monitoring the tire air pressure, it is first checked whether the torque corresponding to the current speed variables and the lateral acceleration lie in the tire air pressure monitoring range which was established in a corresponding method for standardization. A warning signal is generated when the diagonal value DEL exceeds a warning threshold value set in a standardization method, and the torque and lateral acceleration corresponding to the current speed variables are in an allowable tire air pressure monitoring range.Devices according to the invention for monitoring the tire air pressure comprise sensors for measuring the wheel rotational speeds of the four wheels of the motor vehicle. For example, ABS sensors can be used for this purpose, which are present for measuring the wheel rotational speeds for an anti-lock brake system.The apparatuses 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.The invention is explained in detail on the basis of the appended figures by way of example. Figure shows FIG. 1 shows a diagram in which standardization diagonal values SDEL are plotted against the difference ΔT between associated torque values and the standardization torque, FIG. 2 shows a corresponding diagram for a differently composed tire set, FIG. 3 shows the tire air pressure monitoring region for a first gradient region of a straight line corresponding to FIG. 1 or FIG. 2, FIG. 4 shows the tire air pressure monitoring area for a second gradient range, FIG. 5 shows the tire air pressure monitoring area for a third gradient range; and FIG. 6 shows the tire air pressure monitoring area for a fourth gradient range.The figures represent the relationships only by way of example for a selected configuration and are explained in the following description of an embodiment of the method procedure.Setting of the Proportionality Factors:For example, after a new tire has been mounted or an air pressure check or correction has been made, standardization is initiated by the vehicle operator via a corresponding input device on the dashboard. In a torque range with relatively low torques and at a relatively constant vehicle speed (only 70 Nm at 80 km / h, for example), sixty measured values of the respective wheel rotational speeds of all four wheels are then recorded by a control and evaluation device of the tire air monitoring device. This can be done, for example, with the sensors of an anti-lock brake system that are already present. For this purpose, a corresponding driving situation is waited for or actively initiated by the control and evaluation device. The torque applied in each case is referred to below as "standardization torque".For each wheel, the wheel rotational speed at the standardization torque can thus be determined, for example, by averaging from the sixty measured values.The torque associated with the respective vehicle speed can be read, for example, from a standard torque line which has been determined in advance. For this purpose, for example, in the case of a new vehicle type, a plurality of test series having different configurations are driven and the torque is measured at different vehicle speeds. The measurement curve determined from this can be stored in a memory chip of the vehicle and then serves as a standard torque line which enables the determination of the standardization torque at the selected speed.The method according to the invention does not exclude that for different speed ranges in which the standardization is to take place, different standardization torques are assumed, which however are also read from the standard torque line.The calculation of corresponding standardization diagonal values according to the above-mentioned formula should result in relatively small values, since the wheel rotational speeds should not differ significantly even in the case of different tyres, given the only small applied torque, and slip differences due to different tyres should therefore have little influence.A greater deviation above a predefined threshold value would, on the other hand, already indicate an air pressure drop in one of the tires.The control and evaluation device determines proportionality factors which take account of possible deviations on the basis of the wheel rotational speeds measured at the standardization torque. Such deviations can arise, for example, if the profile of the individual tires is not of the same magnitude and, insofar, the rolling radius of the individual wheels is different. The proportionality factors are chosen such that, at the standardization torque, speed parameters arise from the multiplication of the proportionality factors by the wheel rotational speeds which are equal to one another. When the speed parameters thus obtained are used for the values FL, RR, FR and RL used in the above formula, a standardization diagonal value SDEL of zero is obtained for running at the standardization torque.Consideration of Higher Torques:The wheel rotational speeds for the individual wheels are then additionally measured when torques of greater magnitude are present, i.e. for example in acceleration or deceleration situations. Here, for example, measured values in a range from 50 Nm to 150 Nm difference from a standardization torque are expedient. Again, sixty measured values are taken, for example.For the respective measured values, the respective standardization diagonal value SDEL is determined according to the above-mentioned formula. The multiplication factor K is selected here to be 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 FIG. 1 is obtained, for example. The SDEL values plotted on the vertical axis are dimensionless and are plotted in arbitrary units. A straight line can be placed through the measurement points according to the least squares method and the gradient determined, as is shown in FIG. 1. The slope is -0.000032 in this example.The example of FIG. 1 originates from a tire set in which all four tires are the same.For a set of tires in which one tire is, for example, more recent than the other tires and thus has an even stronger profile, a different straight line with a greater gradient in terms of amount results due to the slip differences, which have a stronger influence at larger torques, as is illustrated in FIG. 2. The slope in this example is -0.000811.The slope thus determined is used in the further method as follows:Selection of Settings:The absolute value of the ascertained gradient is compared with predefined gradient limit values. These gradient limit values are defined in advance, for example, according to the type of vehicle and type of tyres (for example winter or summer tyres). For example, in the units selected for this example in this specification (here and hereinafter 1 / (Nm)), a first slope threshold may be 200·10 -6 a second slope threshold may be 500·10 -6 and a third slope threshold may be 1000·10 -6.Depending on the gradient range or between which two gradient limit values the absolute value of the determined gradient lies, different "settings" are selected.These different settings differ in particular with regard to a warning threshold value and to a tire air pressure monitoring range in which tire air pressure monitoring can be carried out in a meaningful manner.Selection of Warning Threshold:A warning threshold value thereby fulfils the following function. During vehicle operation, the speeds of the respective wheels are continuously or periodically measured and multiplied by the proportionality factors previously determined upon application of the standardization torque as described to obtain actual speed variables FL, FR, RL and RR corresponding to the wheel rotational speeds of the front-left wheel, the front-right wheel, the rear-left wheel and the rear-right wheel, respectively. With these current speed variables, a diagonal value is then determined according to the following formula:If a DEL value determined in this way exceeds a warning threshold, a warning signal is output to the vehicle driver that an abnormality is present, 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 the standardization operation as described lies above or below a respective gradient limit value, the threshold values are adapted, when they are exceeded by a diagonal value determined during the vehicle operation, a warning signal is output to the motor vehicle driver.If the magnitude of the gradient in the selected units is, for example, in a range between 0 and 200·10 -6, a normal preset warning threshold applies, when this warning threshold is exceeded, a warning signal is triggered by the DEL value measured during vehicle operation.If the amount of the slope determined during standardization is between 200·10 -6 and 500·10 -6, for example, it is indeed to be assumed that a mixed frost is present. Nevertheless, the gradient does not deviate so much that the warning threshold would have to be adapted.If the amount of the slope determined during the standardization process is between 500·10 -6 and 1000·10 -6, the warning threshold is set to 120% of the normal warning threshold, for example. This ensures that even in the case of relatively large slip differences owing to different tyres a warning signal is only triggered if there is actually an additional irregularity, that is to say if, for example, a tyre air pressure drop occurs on a tyre.When the amount of the slope learned during the standardization process is over 1000·10 -6 the warning threshold is set to 130% of the normal warning threshold, for example. It is to be assumed with such a determined gradient that a tire differs from the three other tires, and the increase in the warning threshold ensures that, despite the greater differences in slip resulting therefrom, a warning signal will not be output in an unauthorized manner, which would indicate a drop in tire air pressure in a tire, even though such a drop in tire air pressure does not exist.Setting of tire air pressure monitoring range:In addition, a range is defined as a function of the value of the gradient determined during the standardization process, in which range tire air pressure monitoring can be carried out in a meaningful manner. It is taken into account here that, for example, in the case of too great a lateral acceleration and under certain conditions, even in the case of too great a forward acceleration or deceleration, a reasonable measurement is not possible. The critical values for the forward acceleration or deceleration and the lateral acceleration can likewise depend on the tire, i.e. whether, for example, a tire differs from the three other tires, which is reflected in the gradient of the fictitious straight line determined during standardization.FIG. 3 shows such a range as is selected, for example, if the magnitude of the slope of the fictitious straight line defined during the standardization process in the units selected for this example in this description (here and below 1 / (Nm)) is between 0 and 200·10 -6. Only within the shaded area is the measurement of the wheel rotational speeds permitted and the determination of the DEL values resulting therefrom permitted. With greater lateral acceleration or with greater forward torque, the measurement is not carried out.FIG. 3 shows that a measurement is performed in any case when the lateral acceleration is less than a first lateral acceleration limit value A 1, which is, for example, 0.05 g (g=ehear acceleration). If the lateral acceleration is more than a second limit value B 1( e.g. 0.2 g), no measurement is allowed at all. Otherwise, measurements would only be permitted if the magnitude of torque T and the magnitude of lateral acceleration are in a range formed by the triangle spanned between values A 1, B 1 and C 1 where C 1 in this example is, for example, 80 Nm.In Figure 4, the area for which measurements of tire air pressure are permitted is shown shaded when the absolute amount of the slope of the fictitious straight line established during the standardization process is between 200·10 -6 and 500·10 -6. Here it is clear that there is an upper limit value C 2 of 60 Nm in this example, which, when exceeded by the torque applied to the drive axle, does not permit measurement of the wheel rotational speeds. The upper limit value for the lateral acceleration B 2 can be 0.2 g again, for example.FIGS. 5 and 6 show corresponding regions for a fictitious slope determined during standardization, having an amount of 500·10 -6 to 1000·10 -6 or greater than 1000·10 -6. The limit values C 3 and B 3 and. Here, C 4 and B 4 may have the same numerical values as the limit values C 2 and D 2, which are selected at a slope amount between 200·10 -6 and 500·10 -6 for example.Taken together, the following situation arises for the example described:If the absolute value of the gradient determined during standardization in the units selected for this example in this description (here and below 1 / (Nm)) is between 0 and 200·10 -6, the warning threshold, at the crossing of which a warning signal is triggered by the diagonal value DEL, is left unchanged, i.e. for example at a value which was set at the factory under the assumption of four identical tires.Measurements of the wheel rotational speeds for calculating the diagonal value DEL during normal vehicle operation for monitoring the tire air pressure are permitted only in a range indicated by the hatched portion of FIG. 3.If the absolute value of the slope of the fictitious straight line is determined in the standardization process to be between 200·10 -6 and 500·10 -6 the warning threshold remains unchanged. However, the tire air pressure monitoring range is selected according to FIG. 4, i.e., with other limit values C 2 and B 2. In particular, this results in only a limited range being permitted for the forward acceleration or deceleration.If the absolute value of the ascertained slope of the fictitious straight line is determined to be between 500·10 -6 and 1000·10 -6 then the warning threshold, when exceeded by the DEL value during vehicle operation, a warning signal is output, is set to 120% of the normal warning threshold. Only when the DEL value deviates from zero is a corresponding warning signal therefore output. In this example, the tire air pressure monitoring range in which tire air pressure monitoring can be performed is left unchanged from the gradient amount range between 200·10 -6 and 500·10 -6.If the amount of the slope taught during the standardization process is greater than 1000·10 -6, the warning threshold is increased once again, e.g. to 130%. The tire air pressure monitoring range is also left unchanged in this example, i.e., the limit values C 4 and B 4 are selected to be equal to the limit values C 2 and B 2 respectively.The method according to the invention for checking the tire air pressure using the method according to the invention for standardization therefore makes it possible to take account of, for example, different tires which lead to different slip behavior during acceleration and deceleration. In this case, on the one hand, the limit value is adapted, when it is exceeded by the diagonal value, a warning signal is output, which indicates a drop in tire air pressure. On the other hand, the tire air pressure monitoring range, which is dependent on the forward torque and the lateral acceleration and specifies in which value range tire air pressure monitoring is usefully possible, is adapted.List of reference charactersT torque ΔT torque difference SDEL diagonal value in standardization DEL diagonal value during vehicle operation LB lateral acceleration A 1, B 1, B 2, B 3, B 4 lateral acceleration value C 1, C 2, C 3, C 4 forward acceleration values

Claims

Method for standardization of a device for monitoring the tire air pressure of a motor vehicle, having 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 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 in the presence of torques within a predefined torque range which comprises torques whose magnitude differs from the standardization torque, and multiplication of the measured wheel rotational speeds with the associated 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), respectively, wherein a standardization diagonal value relates the sum of the speed variables of the front left wheel and of the rear right wheel to the sum of the speed variables of the front right wheel and of the rear left wheel, respectively, e) determining the gradient of a fictitious straight line, which is adapted to the points that are produced by applying the standardization diagonal values (SDEL) to the associated torque values or to the difference (ΔT) between the associated torque values and the standardization torque, and f1) defining at least one warning threshold value, at the exceed of which a warning signal is produced by a diagonal value determined during vehicle operation, depending on the slope of the fictitious straight line.Method for standardization of a device for monitoring the tire air pressure of a motor vehicle, having 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 standardization torque, b) defining proportionality factors with which the 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 in the presence of torques within a predefined torque range which comprises torques whose magnitude differs from the standardization torque, and multiplication of the measured wheel rotational speeds with the associated 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), respectively, wherein a standardization diagonal value relates the sum of the speed variables of the front left wheel and of the rear right wheel to the sum of the speed variables of the front right wheel and of the rear left wheel, respectively, e) determining the gradient of a fictitious straight line, which is adapted to the points that arise by applying the standardization diagonal values (SDEL) against the associated torque values or the difference (ΔT) between the associated torque values and the standardization torque, and f2) defining at least one tire air pressure monitoring range in a coordinate system defined by the torque (T) or a variable and the lateral acceleration (LB) which is unambiguously associated therewith, in which coordinate system tire air pressure monitoring can be carried out, as a function of the gradient of the fictitious straight line.Method for standardization of a device for monitoring the tire air pressure of a motor vehicle having the features of Claims 1 and 2.Standardization method according to one of Claims 1 to 3, in which the standardization diagonal values (SDEL) are determined according to the following formula: SDEL = K * { [ FL + RR ) - ( FR + RL ) ] / ( FL + FR + RL + RR ) }, in which FL, FR, RR and RL correspond to the speed variables of the front-left wheel, of the front-right wheel, of the rear-right wheel and of the rear-left wheel, respectively, and K is a fixed multiplication factor.Standardization method according to one of Claims 1 to 4, in which the torque range in which the measurements are carried out in step c) comprises torques whose magnitude differ from the standardization torque value by more than a lower torque difference limit value and less than an upper torque difference limit value.Standardization method according to one of Claims 1 to 5, in which, in step e), the fictitious straight line is determined using the least squares method.Standardization method according to one of Claims 1 to 6, in which m gradient ranges are defined which are separated from one another by (m - 1) gradient limit values.Method for standardization according to Claim 7, insofar as it is directly or indirectly dependent on Claim 1, in which slope limit values are defined in step f1), individual warning threshold values being selected when the absolute value of the slope exceeds or falls below said threshold values.Method for standardization according to Claim 7, insofar as it is directly or indirectly dependent on Claim 2, in which gradient limit values are established in step f2), at the overshooting or undershooting of which individual tyre air pressure monitoring ranges are established by the absolute value of the gradient.A method for monitoring tire air pressure for motor vehicles, comprising the following steps being carried out: A1) carrying out a standardization method having the features of claim 1 or one of claims 3 to 9 insofar as it depends directly or indirectly on claim 1, 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 of the rear right wheel to the sum of the current speed variables of the front right wheel and of the rear left wheel, to one another, D1) generating and outputting a warning signal when the diagonal value (DEL) thus determined exceeds a warning threshold value determined in step f1).Method for monitoring the tire air pressure, comprising the following steps: A2) carrying out a standardization method with the features of claim 3 or one of claims 4 to 9, insofar as it is directly or indirectly dependent on claim 3, 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 of the rear right wheel to the sum of the current speed variables of the front right wheel and of the rear left wheel, D2) checking, whether the torque (T) and the lateral acceleration (LB) corresponding to the current speed variables are in the tire air pressure monitoring range set in step f 2), E 2) generating and outputting a warning signal when the diagonal value (DEL) exceeds a warning threshold set in step f 1), if the check in step D 2) had a positive result.Method for monitoring the tyre air pressure according to either of Claims 10 and 11, in which the diagonal value (DEL) is determined according to the following formula: DEL = K * { [ FL + RR ) - ( FR + RL ) ] / ( FL + FR + RL + RR ) }, in which 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 tire air pressure for motor vehicles, having - sensors for measuring the wheel rotational speeds of the four wheels of the motor vehicle, and - an evaluation and control device which is connected to the sensors and is configured to carry out the steps of the method of claim 10 using the sensor signals.Device for monitoring the tire air pressure for motor vehicles, having - sensors for measuring the wheel rotational speeds of the wheels of the motor vehicle, and - an evaluation and control device which is connected to the sensors and is configured to carry out the steps of claim 11 using the sensor signals.Device for monitoring the tire air pressure for motor vehicles, having the features of claims 13 and 14.

Images