DE102009006705B4 - Method for detecting wear on a tread of at least one tire of a vehicle - Google Patents

Abstract

Method for detecting wear on a tread of at least one tire (12; 14; 16; 18) of a vehicle (10) with the steps: - determining a load condition of the vehicle (10), - determining a change in the load on the at least one tire (12; 14; 16; 18) depending on the determined loading condition of the vehicle (10) and determining a change in the wear on the tread of the at least one tire (12; 14; 16; 18) depending on the determined change in the load on the at least one tire (12; 14; 16; 18), characterized by the further steps: - determining a height profile of a route covered by the vehicle (10), - determining a change in the load on the at least one tire (12; 14; 16; 18) depending on the determined height profile and determining a change in the wear on the tread of the at least one tire (12; 14; 16; 18) depending on the determined change in the load on the at least one tires (12; 14; 16; 18).

Description

The invention relates to a method for detecting wear on a tread of at least one tire of a vehicle according to the preamble of claim 1.

There are different types of vehicles for moving and transporting goods and people: watercraft, land vehicles, aircraft, spacecraft and combinations of each other. In particular, the land vehicles such. B. cars, trucks and trailers, as well as the landing gear of aircraft have wheels. The individual wheel usually includes a rim and a tire attached to it, usually filled with compressed air. The wheels are excited to turn and/or braked, so that the vehicles roll on the wheels over a corresponding surface or roadway and/or are braked. The area of the tire that rolls over the vehicle's surface is called the tread. There are tires that have a specially designed profile on the tread. More generally, one can speak of a wear layer on the tread. The wear, which is referred to here as wear and tear, is caused by the friction on the vehicle substrate that occurs when rolling. In particular, this means that the tread depth continuously decreases while driving. This acceptance is permitted until a critical value is reached at which driving safety is significantly impaired.

The tread depth can be measured mechanically, but due to the dimensions of tread depths of only a few millimeters, this requires high accuracy and short measuring intervals in the case of advanced wear. This is labour- and personnel-intensive. There is also a risk that the measurement will simply be forgotten. There are also various ways of automatically detecting the tread depth, which, however, require additional sensors and built-in parts. If no additional sensors are to be installed, one can simply assume average wear per 1,000 km. Such (estimated) wear and tear is referred to below as basic wear.

For example off DE 60 2004 010 398 T2 or off DE 10 2005 052 476 A1 a method according to the preamble of claim 1 is known, according to which the wear of the tires of a vehicle is determined on the basis of the forces to be transmitted by the respective tire, preferably in the three directions of a Cartesian coordinate system, namely in the longitudinal direction of the vehicle and in its vertical axis direction and in its transverse direction, is appreciated.

The present invention is based on the object of further increasing the accuracy of such a known method, which in particular (also=the loading condition of the vehicle - and thus the power transmission in the vertical axis direction of the vehicle) is taken into account.

According to the invention, this object is achieved with a method according to claim 1 . Advantageous developments of the solution according to the invention are the subject matter of the dependent claims.

According to the invention, a method is created for detecting the wear on a tread of at least one tire of a vehicle based on the steps of determining a loading condition of the vehicle, determining a change in the load on the at least one tire as a function of the determined loading condition of the vehicle and determining a Change in the wear on a tread of the at least one tire as a function of the determined change in the load on the at least one tire. In addition, a height profile of a route covered by the vehicle is now determined and a change in the load on the at least one tire is determined as a function of the height profile determined, and a change in the wear on a tread of the at least one tire is determined as a function of the determined change in the load of the at least one tire.

The load and thus the wear of the at least one tire are essentially dependent on braking and acceleration while driving. The more and the larger the differences in altitude covered, the greater the effect of braking and accelerating the vehicle. The weight of the vehicle then becomes more relevant since it acts as an inertial mass and leads to an additional load on the at least one tire. The determination of the height profile in the method according to the invention provides very simple data that take this fact into account.

As a further development of the proposed method, it can be provided that the route covered and/or the elevation profile is recorded and evaluated using a satellite-supported position determination system (in particular GPS (= Global Positioning System)). Otherwise, the height profile could be determined more laboriously by installing an additional sensor and the distance traveled by evaluating the data from the odometer. However, it is simpler, according to the invention, to use the map material used in navigation to include the data of the satellite-based positioning system. This has the great advantage that the distance covered and the elevation profile can be determined at the same time. Furthermore, this measured value is wheel-independent.

According to a further advantageous development, a method is created in which a temperature of the at least one tire is recorded and evaluated when determining the change in wear on the tread of the at least one tire. If the tire heats up while driving, the air pressure increases, consequently the diameter also increases, the contact area or the tread of the tire decreases, and wear and tear decreases. The temperature has an influence on the wear of the tyre. If the temperature is not available as a measured value to be taken into account, a sole measurement can ideally be used, e.g. B. at the beginning of the first trip after a longer period (z. B. overnight).

The influence of the loading condition of the vehicle on the load on the tire and thus on the wear on the tread of the tire when the vehicle is driving will now be discussed in more detail. A changed load condition changes the contact area of the tire and the radius of the wheel, measured up to the contact area. The change has the following effect: If the load increases compared to a specified base value, the contact patch increases and the radius decreases. This increases the number of revolutions of the tire. This leads to higher wear. If the load decreases, the contact area becomes smaller and the radius larger. The number of revolutions of the tire decreases. This leads to less wear. This interaction can be mapped mathematically, making it possible to determine or identify a limit value for tire wear more precisely. The above-mentioned (only estimated) basic wear is thus specified by a load-dependent wear.

In this case, the loading state of the vehicle can be determined by evaluating sensor values of a level control system. This means that no new or additional sensor has to be installed to determine the load status, because many vehicles already have a level control system with appropriate sensors for detecting the load status. This simple solution can save considerable costs.

For example, the loading status of the vehicle can be determined by evaluating sensor values of an altitude sensor of a headlamp leveling system of the vehicle. Here, too, no new or additional sensor has to be installed to determine the load status, since the level indicator for the headlight range control is already present in many vehicles. Significant costs can also be saved with this simple solution.

wobei:

p =

Endwert der Profiltiefe (= verbleibende Profiltiefe) des mindestens einen Reifens,

p0 =

Anfangswert der Profiltiefe des mindestens einen Reifens bei Initialisierung,

x0 =

Anfangswert der Strecke des Fahrzeugs bei Initialisierung,

ω0 =

Anfangswert des aufsummierten Winkels des mindestens einen Reifens bei Initialisierung,

k =

Korrekturfaktor bzgl. Beladungszustand, k = 1 bei Initialisierung des Systems, k > 1 bei Zuladung, k < 1 bei Gewichtsreduktion,

x =

Endwert der zurückgelegten Strecke des Fahrzeugs, und

ω =

Endwert des aufsummierten Winkels des mindestens einen Reifens.

According to an advantageous development, a method is created in which a correction factor k is determined from the sensor values for calculating a remaining profile depth—only by way of example without considering a height profile of a route covered—using the following formula: $$p=p_0-\frac{\left(\frac{x_0}{2\pi \frac{{\omega }_0}{360°}}-k\cdot \frac{x}{2\pi \frac{\omega }{360°}}\right)}{1000}$$

whereby:

p =

Final value of the tread depth (= remaining tread depth) of at least one tire,

p0 =

Initial value of the tread depth of at least one tire during initialization,

x0 =

initial value of the distance of the vehicle at initialization,

ω0 =

initial value of the total angle of the at least one tire upon initialization,

k =

Correction factor for load status, k = 1 when initializing the system, k > 1 for additional load, k < 1 for weight reduction,

x =

Final value of the distance traveled by the vehicle, and

ω =

Final value of the accumulated angle of the at least one tire.

This formula is used to calculate the tread depth p that remains when a distance x is covered. The loading condition of the vehicle is taken into account here by the correction factor k. When the method according to the invention is initialized, k=1 is set (=initial value).

Loading the vehicle increases the pressure on the at least one tire, ie the compression of the tire increases compared to the initial value. As a result, the radius of the tire decreases solely due to the increase in compression due to loading, the total angle increases. The decrease in radius by increasing compression however, is greater than the resulting increase in tire wear. To compensate for this, a correction factor k is introduced, which must have a value greater than 1 when loading.

In contrast, when the vehicle is unloaded, the pressure on the at least one tire decreases, i.e. the compression of the tire decreases compared to the initial value. As a result, the radius of the tire increases solely due to the compression reduction due to unloading, the added angle decreases. However, the increase in radius from compression reduction is greater than the resulting reduction in tire wear. To compensate for this, the correction factor k is used, which must have a value less than 1 when discharging. In summary, k is greater than 1 (k>1) when loading or increasing the weight, and less than 1 (k<1) when unloading or reducing the weight. Without taking into account the correction factor k, one would have to ensure that the vehicle's loading condition was always the same for all measurements. This would involve additional effort and is often not feasible in reality.

Furthermore, when determining the change in the wear of the at least one tire, a total angle of the at least one tire can be recorded and evaluated. The accumulated angle is derived from the speed of the vehicle and/or from measurement data from wheel speed sensors.

Furthermore, when a wheel is mounted on the vehicle, an initial tread depth of the at least one tire can be determined and used as an initial value for the step of determining a change in wear on the tread of the at least one tire. In this way, the initial tread depth of each tire can be taken into account individually.

A limit value or threshold value for a minimum permissible profile depth can also be defined and stored. Reaching the limit value is checked when determining the change in wear on the tread of the at least one tire. When the limit value is approached and/or when the limit value is reached, a signal can be triggered by a notification device. This notification signal can, for example, notify the driver inside the vehicle by means of a light-emitting diode. This increases driving safety and optimizes the utilization of the at least one tire by allowing a change to be controlled in a targeted and timely manner. It is also particularly advantageous if a notification, in particular by telematics, is sent directly to a location that looks after the vehicle. This location is particularly advantageous for an associated service workshop. With the information about the need to replace the tires, the workshop employees can react accordingly, e.g. B. Inform the vehicle owner, order the appropriate tires and mount them at the next workshop appointment. This is particularly advantageous for large fleets, e.g. B. at municipal or municipal vehicle fleets, at bus companies or at vehicle rental companies. Since there is no longer any need for ongoing manual checks of all vehicles, this approach makes work much easier and saves costs. The safety aspect should not be forgotten either.

In other words, vehicles are generally subject to wear and tear during operation. Moving parts and their operating materials, such as brakes, oil, etc. are particularly affected by this. Individual components are already subject to wear monitoring, which uses a suitable mechanism to indicate the resulting need for service when certain defined limit values, such as wear, aging, etc. are reached.

There is currently no automated mechanism integrated into the vehicle for detecting the state of wear of tires or determining the wear on the tread of at least one tire of a vehicle that would count on the remaining tread depth and the associated possible remaining mileage of the tire until it is reached a (legal) wear limit or a threshold value of the minimum permissible tread depth. Only with such an automated detection would it be possible to include tires or at least one tire in a wear detection and report it to a suitable place for correction. This location can be in the vehicle or else a location that looks after the vehicle, preferably a workshop.

With a system that uses existing or continuously available data such as GPS position, speed, tire air pressure, wheel speed sensors and, if necessary, an initial tread depth that was stored once when the wheels were mounted, the remaining tread depth can be determined continuously or in regular cycles. When defined and stored threshold values are reached, a notification is sent to a responsible location, preferably via a telematic connection, in order to inform them of the upcoming need to change the tires.

• - Durch eine Erwärmung des Reifens während der Fahrt erhöht sich der Luftdruck. Folglich nimmt auch der Durchmesser zu, die Aufstandsfläche des Reifens nimmt ab. Sofern die Temperatur nicht als Messwert zur Berücksichtigung verfügbar ist, erfolgt die Messung idealerweise z. B. zu Beginn der ersten Fahrt nach einer längeren Standzeit, vorzugsweise über Nacht.
• - Durch einen veränderten Beladungszustand verändern sich die Aufstandsfläche und der Radius des Reifens. Dieser Umstand fließt durch einen Korrekturfaktor k in die Berechnung ein. Der Korrekturfaktor wird durch Verwerten von Sensorwerten, die zur Bestimmung des Beladungszustandes dienen können, vorzugsweise von Niveauregulierung und/oder Höhenstandsmesser für Leuchtweitenregulierung, ermittelt. Bei Initialisierung des Systems wird k = 1 gesetzt. Bei Zuladung ergibt sich ein Wert k > 1, bei Gewichtsreduktion k < 1.
• - Wesentlichen Einfluss auf die Genauigkeit der Messung hat die Genauigkeit der zur Ermittlung der Profiltiefe genutzten Strecke. Einen räderunabhängigen Messwert erhält man durch Nutzung von GPS, optimiert durch Einbeziehen des in der Navigation genutzten Kartenmaterials. Bei einer Messung der Streckenlänge ist das Höhenprofil zu berücksichtigen.

According to the invention, the following are or can be taken into account:

• - If the tire heats up while driving, the air pressure increases. As a result, the diameter also increases and the contact area of the tire decreases. If the temperature is not available as a measured value to be taken into account, the measurement should ideally be carried out, e.g. B. at the beginning of the first trip after a longer period of rest, preferably overnight.
• - The contact area and the radius of the tire change when the load is changed. This circumstance is included in the calculation through a correction factor k. The correction factor is determined by evaluating sensor values that can be used to determine the load status, preferably from level control and/or height gauge for headlight range control. When the system is initialized, k=1 is set. A value of k > 1 results when the vehicle is loaded, and k < 1 when the weight is reduced.
• - The accuracy of the route used to determine the tread depth has a significant influence on the accuracy of the measurement. A wheel-independent measured value is obtained by using GPS, optimized by including the map material used in navigation. When measuring the route length, the elevation profile must be taken into account.

• - in der optimalen Ausnutzung der Reifen, indem gezielt und rechtzeitig ein Wechsel gesteuert werden kann,
• - in der Erhöhung der Fahrsicherheit durch Warnen bzw. Erinnern von Fahrer und einer Fahrzeug betreuenden Stelle,
• - darin, dass keine zusätzlichen Hardwarekosten für die Umsetzung im Fahrzeug erforderlich sind, und
• - in der Erfassung von Reifen als Verschleißteil und Information eines Händlers über den Erneuerungsbedarf, dadurch in der erhöhten Kundenbindung und Sicherung des Service- und Teileumsatzes.

The advantages of the solution according to the invention are

• - in the optimal utilization of the tires, in that a change can be controlled in a targeted and timely manner,
• - in increasing driving safety by warning or reminding the driver and a vehicle-supervising body,
• - in that no additional hardware costs are required for implementation in the vehicle, and
• - in recording tires as wearing parts and informing a dealer about the need for replacement, thereby increasing customer loyalty and securing service and parts sales.

Reference List

10

vehicle

12

tires

14

tires

16

tires

18

tires

20

vehicle underground

22

driving direction

Claims (5)

Method for detecting the wear on a tread of at least one tire (12; 14; 16; 18) of a vehicle (10) with the steps: - determining a load condition of the vehicle (10), - determining a change in the load on the at least one tire (12; 14; 16; 18) depending on the determined loading condition of the vehicle (10) and - determining a change in the wear on the tread of the at least one tire (12; 14; 16; 18) depending on the determined change in the load on the at least one tire (12; 14; 16; 18), characterized by the further steps: - determining a height profile of a distance covered by the vehicle (10), - determining a change in the load on the at least one tire (12; 14; 16; 18) depending on the determined height profile and determining a change in the wear on the tread of the at least one tire (12; 14; 16; 18) depending on the determined change in the load on the at least a tire (12; 14; 16; 18). procedure after claim 1 , The distance traveled and the elevation profile being recorded and evaluated by using a satellite-supported positioning system. procedure after claim 1 or 2 , wherein when determining the change in wear on the tread of the at least one tire (12; 14; 16; 18) a temperature of the at least one tire (12; 14; 16; 18) is detected and evaluated. Method according to one of the preceding claims, wherein when determining the loading condition of the vehicle (10) there is an evaluation of sensor values of a level control and/or a level indicator of a headlight range control of the vehicle (10). procedure after claim 4 , characterized in that a correction factor k is determined from the sensor values, which is suitable for calculating a remaining profile depth, without taking into account a height profile of a route covered, with the following formula: $$p=p_0-\frac{\left(\frac{x_0}{2\pi \frac{{\omega }_0}{360°}}-k\cdot \frac{x}{2\pi \frac{\omega }{360°}}\right)}{1000}$$

where: p = final value of the tread depth (= remaining tread depth) of the at least one tire (12; 14; 16; 18), p ₀ = initial value of the tread depth of the at least one tire (12; 14; 16; 18) upon initialization, x ₀ = initial value of the route of the vehicle (10) during initialization, ω ₀ = initial value of the total angle of the at least one tire (12; 14; 16; 18) during initialization, k = correction factor with regard to the load status, k = 1 during initialization of the system, k>1 with payload, k<1 with weight reduction, x=final value of the distance covered by the vehicle (10) and ω=final value of the total angle of the at least one tire (12; 14; 16; 18).

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